Fausto Calderazzo: Pioneer in Mechanistic Organometallic Chemistry

Review pubs.acs.org/Organometallics

Fausto Calderazzo: Pioneer in Mechanistic Organometallic Chemistry Peter M. Maitlis*,† and Daniela Belli Dell’Amico‡ †

Department of Chemistry, The University of Sheffield, Sheffield S3 7HF, U.K. Dipartimento di Chimica e Chimica Industriale, Università di Pisa, via Moruzzi 3, I-56124 Pisa, Italy

‡

ABSTRACT: A biographical sketch of Fausto Calderazzo (deceased June 1, 2014) is presented. This is followed by personal tributes from former co-workers and colleagues around the world that emphasize not only his seminal contributions to organometallic chemistry but also his scientific ingenuity, knowledge, and integrity, which inspired those who worked with him.

■

His first research related to an organic chemistry problem, but he became strongly influenced by his teacher, the outstanding inorganic chemist, Luigi Sacconi (Figure 2), who was, at that time, Assistant Professor of Physical Chemistry in Florence. Under Sacconi’s guidance, he started his career in organometallic chemistry.

BIOGRAPHICAL SKETCH OF FAUSTO CALDERAZZO Early Days: First Researches (1953−1956). Fausto Calderazzo (Figure 1) passed away quite suddenly, on June

Figure 1. Fausto Calderazzo in November 2006.

1, 2014, aged 84, at his home in Pisa, Italy. He was one of the great pioneers of organometallic chemistry, and a founding member of the group of brilliant Italian chemists of the 20th century who made such enormous contributions to both synthesis and mechanistic studies. Fausto was born in Parma, on March 8, 1930, where his father served in the Italian army. After finishing high school, he was undecided whether to study chemistry or medicine, but he finally decided on the former since he felt it would be easier to find a job as a chemist. Accordingly, he enrolled for the Laurea (Italian first degree, approximately equivalent to a bachelor’s degree) at the University of Florence, where he graduated in 1952. © XXXX American Chemical Society

Figure 2. Prof. Luigi Sacconi; University of Florence.

Sacconi not only was a good teacher and an excellent organizer but also had an exceptional instinct for choosing interesting and worthwhile topics for his students. He also appreciated the importance of writing up his work promptly and had already published some significant papers in the Journal of the American Chemical Society.1 Received: November 26, 2014

A

dx.doi.org/10.1021/om5011963 | Organometallics XXXX, XXX, XXX−XXX

Organometallics

Review

pentadienyl- and η6-arene- organo-transition metal compounds that were being published around this time by Geoffrey Wilkinson at Imperial College, London, and by Ernst-Otto Fischer at the Technische Hochschule in Munich4. Several routes to Cr(CO)6, of varying degrees of difficulty, were known, and he chose one starting from the easily accessible tris(acetylacetonato)chromium, with magnesium as reductant, and iodine as promoter, in pyridine, under an atmosphere of CO (Scheme 2). This was experimentally

In his very perceptive published interview article with Fausto, entitled “Celebration of Inorganic Lives”, Rinaldo Poli remarked that, when Fausto started his chemistry degree program in November 1947, the wartime shortages that still remained meant that only simple experiments using inexpensive materials were possible in the teaching laboratories.2 Far from creating a problem, this actually proved to be an advantage since it meant that the students had to think carefully about their experiments and did not carry out the tasks required automatically without understanding the underlying reasons. Fausto completed his research project with Sacconi for the Laurea degree on nickel hydrazide complexes in July 1952. Although he was then ready to practice his chemical knowledge, he first had to spend 18 months as a conscript on his military service in the far south of Italy. By December 1953, he was free of his commitments to the Italian army and could resume his chemistry studies (Figure 3).

Scheme 2. A New Synthesis of Cr(CO)6

simpler than other routes, such as the one that required first the synthesis of dicyclopentadienylchromium, followed by its carbonylation. Since Fausto’s route had substantial novel features, it was published in the Journal of the American Chemical Society.5 Many details of the early work on metal carbonyls are contained in an extensive review by Calderazzo, Ercoli, and Natta.6 The availability of Cr(CO)6 led to studies of its reactivity, which showed that three of the CO ligands were readily substituted, by benzene and other arenes (Scheme 3): the resultant half-sandwich complexes showed a chemistry analogous to that of the well-known cyclopendienylmanganese tricarbonyl CpMn(CO)3.7 Scheme 3. Reaction of Cr(CO)6 with Arenes

Mechanistic Studies (1959−1960). Fausto also carried out mechanistic studies on the carbonyl complexes. The first was on the isotopic exchange beween 14CO and Cr(CO)6, which was found to be first order in [Cr] and zero order in [CO] with an activation energy of ca. 79 kJ/mol.8 These data also allowed direct comparisons with the reactivities of other carbonyl complexes, such as those studied by Basolo and Wojcicki.9 As his mechanistic carbonyl work needed special equipment not available in Milan at that time, Fausto had first to design the necessary apparatus and then had to teach the laboratory glassblower how to make the gas buret that was needed for his measurements. Fausto later reported that these first mechanistic studies, at the Polytechnic Institute of Milan during the period 1954− 1960, were carried out with considerable help from Pino and Ercoli in Natta’s group. Natta himself was also very supportive, but since he was extremely busy developing his polymerization work with Montecatini, the industrial group that sponsored him, he was not able to devote much time to helping Fausto. In fact, Fausto was much encouraged by Fred Basolo from Northwestern University in the USA, who happened to be spending a Sabbatical term in Rome. Basolo’s influence was clearly important since Fausto then went on to carry out the mechanistic studies on the alkyl migration reaction (with Klaus Noack) for which he became justly famous (see below). In 1955, Piero Pino moved from the Milan Polytechnic to the University of Pisa as Professor of Industrial Organic Chemistry. He tried to persuade Fausto to accompany him, but

Figure 3. Fausto when he was a young researcher.

He was invited to join the research group of Giulio Natta at the Polytechnic Institute of Milan, where he became part of the team that included Adolfo Quilico, Piero Pino, Raffaele Ercoli, Franco Piacenti, and Paolo Chini. The work of this stellar group of researchers was to have a considerable impact on the development of organometallic and catalytic chemistry. Hydroformylation and Metal Carbonyls (1954−1959). By 1954, organometallic chemistry had become the main focus of Fausto’s work and he began studies of the stoichiometric cobalt promoted hydroformylation reaction (Scheme 1).3 Scheme 1. Stoichiometric Reaction of Alkenes with Dicobalt-Octacarbonyl and Hydrogen

To carry out his studies, he needed some carbonyl complexes. Although the Milan laboratory was well equipped for high pressure work, no one had expertise with low-valent air-sensitive materials, and thus, Fausto first had to develop routes to compounds such as chromium hexacarbonyl. This work was also spurred on by the studies on η5-cycloB


Organometallics

Review

conditions than vanadium.13 Their work was published at the same time as a paper that appeared in Organometallics by John Ellis from Minnesota, who also reported tantalum carbonyls.14 The importance of these studies is emphasized by the fact that several groups were working in the area, an ultimate goal being to devise new metal-catalyzed routes to organic oxygenate compounds from simple readily available precursors and carbon monoxide. A Year with Al Cotton (July 1960−September 1961). In 1959, John Waugh from MIT visited Fausto’s lab. He was impressed by the work, and he encouraged Fausto to consider spending some time in the USA. F. Albert Cotton, then at MIT in Cambridge, Mass, was able to help Fausto to enter for an Alfred P. Sloan Fellowship that allowed him to take a Sabbatical leave in his lab at MIT. The project chosen for Fausto’s work was an extension of the discovery made earlier by Coffield at the Ethyl Corporation in Detroit of the reversible “insertion” of carbon monoxide into the Mn−C bond of alkyl-manganese pentacarbonyl complexes (Scheme 5).15 Such “insertions” were key steps in many carbonylation reactions, and Fausto decided to use his gas buret to measure the thermodynamic parameters. The work was published in a paper that appeared in the first volume of the newly launched ACS journal Inorganic Chemistry.16 At the end of his Sabbatical, Fausto returned to the Polytechnic of Milan, where he continued his studies on the chemistry of vanadium hexacarbonyl and on the carbonylation of alkyl-manganese pentacarbonyls. Cyanamid European Research Institute (1963−1968). In 1963, Fausto moved to Switzerland to join the Inorganic Synthesis Group at the Cyanamid European Research Institute (CERI) in Geneva (Figure 6). Fausto was appointed Director of the group in 1965, a position he held until 1968. Since several other scientists of the Institute left over the next couple of years, Fausto was able to make some new appointments, in particular of Carlo Floriani, a graduate of the University of Milan, and François L’Eplattenier, who had graduated from the ETH in Zurich. In Geneva, Fausto established a close working relationship with the crystallographer Erwin Weiss, who was initially the Institute Director, but who later left to take up the Chair at the University of Hamburg in Germany. Another collaborator was the IR spectroscopist Klaus Noack, with whom Fausto had a very valuable partnership. Using 13C labeling, they succeeded in showing that the key carbon−carbon bond forming step in the reaction of CO with Mn(CO)5Me involved a migration rather than a simple insertion as had previously been suggested. The subtle details of the experiment are summarized (Scheme 6).17 In Geneva, Fausto also studied aspects of the chemistry of ruthenium and osmium pentacarbonyls and the homogeneous ruthenium-catalyzed reduction of nitrobenzene.18 Moreover, he began to explore the chemistry of Schiff-base metal complexes focusing on cobalt and iron derivatives.19 His chemical curiosity led him to become attracted by the chemistry of the lanthanides, where he prepared some organometallic derivatives of ytterbium, and also began writing Annual Surveys of the lanthanide and actinide literature. These contributions were some of the first systematic studies of f-block organometallic chemistry. Fausto stayed in Geneva until 1968, when he returned to Italy as Professore Ordinario (Full Professor) at the Institute of General and Inorganic Chemistry of the University of Pisa.

Fausto was unable to do so at that time and only moved to Pisa much later, in 1967. While he was working at the Milan Polytechnic, Fausto also had a close friendship with Paolo Chini, who was developing his amazing synthetic and structural studies of polynuclear metal carbonyls (“cluster complexes”) at the neighboring Inorganic Chemistry Institute of the University of Milan. Fausto later suggested that an important impetus that led to Chini’s discoveries was the finding by Natta and Ercoli of the so-called “negative pressure effect” of CO on the rate of cobaltcatalyzed hydroformylation and the investigation of the Co2(CO)8/Co4(CO)12 equilibrium.10 Vanadium Carbonyl (1959−1960). Their success with the chromium reactions then prompted Fausto and his coworkers to investigate the behavior of other neighboring metals. They soon found that tris(acetylacetonato)vanadium or VCl3 also reacted with CO under pressure in the presence of pyridine and an electropositive metal (Scheme 4). Scheme 4. Synthesis of V(CO)6

The product of the reaction was particularly interesting since a neutral vanadium carbonyl would be expected to be di- (or poly-) nuclear. In fact, the material that was first isolated by Angel Alberola from Spain, who spent some time with Fausto, was the anionic hexacarbonylvanadate(−I) [V(CO)6]¯. He was then able to convert this into the neutral, black, monomeric, and paramagnetic V(CO)6, which had a low spin d5 electronic configuration. The monomeric structure (Figure 4) was

Figure 4. V(CO)6 molecular structure.

confirmed by Corradini, who carried out a single-crystal X-ray diffraction study. The novel and exciting discovery of the first paramagnetic metal carbonyl was presented by Natta in a paper to the Accademia dei Lincei in 1959 (Figure 5), and a paper in the Journal of the American Chemical Society followed very shortly thereafter.11 Virtually at the same time, Pruett and Wyman working at the Union Carbide laboratory in South Charleston, West Virginia, obtained a similar vanadium carbonyl material by a different route.12 However, they claimed it to be dinuclear and diamagnetic, V2(CO)12, until further investigations showed that it was identical to the correctly formulated V(CO)6 that Fausto’s group had made. Much later, in 1982, following up this work, the Calderazzo group found that niobium was carbonylated under even milder C


Organometallics

Review

Figure 5. Photocopy of the abstract of the presentation of V(CO)6 to the Accademia Nazionale dei Lincei.

attracted many talented Ph.D. students, who soon fulfilled their initial promise; they included Rinaldo Poli, Ulrich Englert, Paolo Biagini, Antonio Belforte, Ulrich Baisch, Peter Strasser, and Walter Baratta, to mention only a few of those who later also became well-known in their own right. Fausto and his group widened their studies on other metal− ligand combinations, paying special attention to the periodic trends. They compared complexes where the same coordination sphere was maintained while the metal center was varied, and also complexes where the metal center and part of its coordination sphere were kept constant, while the donor atom of one type of ligand was varied within a group. Novel Syntheses: Gold, Platinum, and Palladium Complexes. The work on the halo-carbonyls of the late transition metals (Pd, Pt, Au) led to the characterization of a novel Au(I)−Au(III) mixed valence gold chloride, Au4Cl8, which was formed in the course of the reductive carbonylation of Au2Cl6 (Scheme 7 and Figure 8),20 and the discovery of which is described below in Daniela Belli’s personal tribute. New syntheses of halocarbonyls of platinum(II) were developed21 and a study of the carbonylation of PdCl2 provided the first neutral chloro-carbonyl complex of palladium(II), which was characterized as Pd2Cl4(CO)2 (Scheme 8).22 Pd2Cl4(CO)2 was analogous to the known platinum complex Pt2Cl4(CO)2, but the carbonyl ligands in the palladium dimer were found to be cis (Figure 9). Moreover, Pd2Cl4(CO)2 did not react further with CO and was not stable under a reduced partial pressure of carbon monoxide, because of an equilibrium with β-PdCl2, the molecular hexanuclear form of palladium dichloride (Figure 10).23 The thermodynamic parameters of

Scheme 5. Co Insertion into the Mn−C Bond of Mn(Co)5Me

Figure 6. Fausto (third from right) at the Cyanamid European Research Institute (1967).

1968 Onward: General and Inorganic Chemistry at the University of Pisa. The research group that Fausto set up in 1968 on his arrival in Pisa became very successful and productive with numerous collaborators, including Carlo Floriani, Giuseppe Fachinetti, Dario Vitali, Daniela Belli, Marco Pasquali, Fabio Marchetti, Guido Pampaloni, and Luca Labella (group photograph in Figure 7). The group also D


Organometallics

Review

Scheme 6. Insertion or Migration Was the Question? Fausto’s Subtle 13C Labeling Studies Showed that Migration Occurred

Scheme 8. Synthesis of Pd2Cl4(CO)2

Figure 9. Molecular structure of Pd2Cl4(CO)2.

the equilibrium were determined, and the Pd−CO bond energy in the compound was evaluated.

Figure 7. Researchers of the inorganic chemistry section in Pisa on the roof of the Department (2000). From left: Marco Pasquali, Fausto Calderazzo, Piero Leoni, Guido Pampaloni, Dario Vitali, Tiziana Funaioli, Fabio Marchetti, Daniela Belli, Mauro Isola, Luca Labella, Marino Cavazza.

Scheme 7. Reductive Carbonylation of Au2Cl6 with the Intermediate Formation of Au4Cl8 Figure 10. Molecular structure of Pd6Cl12.

As these noble metal halo-carbonyl complexes showed unusually high CO stretching vibrations, Fausto proposed, on the basis of their spectroscopic and other properties, that the πback-donation from the metal to the carbon monoxide was negligible.24 Several years later, studies by Aubke in Canada and Strauss in the USA, and their colleagues, on the so-called “nonclassical metal carbonyls” have confirmed his proposal.25 Early Transition Metal Chemistry. Fausto’s researches on early transition metal carbonyls led to the synthesis of salts containing the hexacarbonyl-niobate and -tantalate anions ([M(CO)6]−; M = Nb, Ta) under mild conditions (Scheme

Figure 8. Molecular structure of Au4Cl8.

E


Organometallics

Review

9)26 and the stabilization of niobium(0) and tantalium(0) in mixed metal clusters containing silver (Figure 11).27 Scheme 9. Synthesis of M(CO)6]−; M = Nb, Ta

Figure 12. Molecular structure of Nb[η2-C2Me2)(η6-C6H4F)2B(C6H4F)2.

the halides in the majority of cases. This group included complexes of both metallic and nonmetallic elements of the sand p-groups, the d-block transition and f-block lanthanide and actinide metals. Many of the complexes were structurally characterized by Xray studies. The preparation and single-crystal structure determinations of a series of tetranuclear isotypic lanthanide carbamates allowed the determination of the size of the lanthanide contraction along the series by accurately measuring the metal−oxygen bond distances of neutral complexes, with the same types of ligand and the same coordination number and geometry (illustrated in Scheme 12 and Figures 13 and 14.31

Figure 11. Ag3Ta3(CO)12(dmpe)3 molecular structure.

Scheme 12. Synthesis of Ln4(O2CNiPr2)12

These studies were also extended using arene complexes. The bis-mesitylene-vanadium(0) complex, V(η 6 -1,3,5Me3C6H3))2, previously prepared by Fausto at CERI, turned out to be a useful precursor for the preparation of both inorganic and organometallic compounds of V(II) and V(III). For this reason, V((η6-1,3,5-Me3C6H3))2 was considered by the industrial company Enichem ANIC to be of potential commercial interest and a procedure was patented, which allowed its production in large amounts (10 kg) in substantially quantitative yields starting from VCl3 (Scheme 10).28 Scheme 10. Synthesis of V(η6-1,3,5-Me3C6H3)2

The Pisan group also synthesized the novel complexes Nb(η6-1,3,5-Me3C6H3)2 (Scheme 11),29 and niobium(I) Scheme 11. Synthesis of Nb(η6-1,3,5-Me3C6H3)2 Figure 13. Molecular structure of the isotypic complexes [Ln4(O2CNiPr2)12].

complexes containing the tetra-phenylborate anion acting as a 12-electron donor30 (Figure 12) . This route is at present the only synthesis other than one using an MVS technique. Carbon Dioxide Chemistry. As CO2 was a readily available starting material for reactions, and one favored for environmental reasons, Fausto and his research team also carried out important syntheses involving carbon dioxide chemistry. They synthesized N,N-dialkylcarbamato complexes of a number of elements under mild conditions using secondary amines, CO2, and suitable precursors of the selected element,

In the course of their study of the equilibria involved in the systems NHR2/CO2 (Scheme 13), the N,N-dibenzyl carbamic acid was synthesized and characterized (Figure 15).32 This compound is the only member of the family of the often cited, but elusive, carbamic acids that has been isolated and structurally defined. Since they are very reactive toward reagents showing Brønsted acidity, the N,N-dialkylcarbamato complexes have been used as precursors in inorganic synthesis. Thus, for F


Organometallics

Review

Figure 14. Graphs of Ln−O bond distances in [Ln4(O2CNiPr2)12] versus atomic number showing the lanthanide contraction. Figure 16. Molecular structure of the isotypic [M 8 (μ 4 O)2(O2CNiPr2)12] complexes; M8 = Mn8, Fe8, Co8, Ni6Zn2.

Scheme 13. The System NHR2/CO2

Figure 17. Molecular structure of [Ti8(μ2-O)8(O2CNEt2)16]. Figure 15. Molecular structure of N,N-dibenzyl-carbamic acid.

Scheme 15. Grafting of Metal Ions onto Surfaces of Materials Showing Brønsted’s Acidity

example, they were used to make the unusual μ-oxo metal clusters that were easily obtained via partial hydrolysis of the carbamate clusters (Scheme 14 and Figures 16 and 17).33 These compounds have also been used to load metal ions onto the surfaces of materials that show Brønsted acidity, such as silica (Scheme 15).34 Scheme 14. Synthesis of μ-Oxo Cluster Complexes of the First Transition Metal Series

Fausto’s extensive work on the chemistry of the alkylcarbamato complexes led to an invitation to write a review of the field, which was published in Chemical Reviews.35 Epilog: Fausto’s Legacy. In addition to his research work, Fausto was an excellent teacher, and many students from Pisa University and from the neighboring prestigious Scuola Normale Superiore benefited from his tutelage. He was a demanding but also a helpful and caring tutor, and his students greatly enjoyed his clear lessons and his optimistic nature. G


Organometallics

Review

Many testimonials to the quality of his teaching, both in the lab and at the blackboard, as well as the love he inspired are provided by the many tributes from colleagues and former students that are collected in the Tributes section and, in particular, by the personal accounts written by his colleagues, Professors Belli, Pampaloni, Macchioni, and Poli. Fausto was a frequent and much sought-after speaker at chemistry conferences. He also arranged and organized many symposia both in Italy and abroad, which were well-acclaimed. In 2000, a symposium in his honor was organized in Pisa (Trends in Transition Metal Chemistry: Towards the Third Millennium) to celebrate his 70th birthday (Figure 18). The meeting was attended by a great number of Italian and foreign scientists and friends.

Figure 19. Posthumous award by SCI to Fausto (September 2014).

Figure 18. Fausto on the occasion of the meeting celebrating his 70th birthday, with his wife, Roberta, and Maria Sacconi.

He received several awards in the course of his career, including the “Medaglia Miolati” in Inorganic Chemistry (1988), the “Medaglia del Gruppo di Chimica Organometallica della Società Chimica Italiana”, the “Medaglia Sacconi” (1998), and the International award “Ultimo Novecento, Pisa 2000 nel mondo”. In 1999, he was honored by election as a Socio of the Accademia dei Lincei, and in 2006, he was appointed Emeritus Professor of the University of Pisa. In May 2014, Fausto was told that he would be honored in September with the Societa Chimica Italiana award in the course of the SCI National Meeting: he was very pleased and was planning to be present at the meeting. Unfortunately, however, Fausto passed away before he could receive the Award, and at the awards ceremony, on September 7, 2014, the medal (Figure 19) was formally presented to his former coworker, Dr. Fabio Marchetti, for transfer to Fausto’s family. As a person, Fausto was a very talented and friendly, but extremely modest, man. He was not pompous and had no vanity. His normal attire for both work and social events included a very loosely knotted tie around his neck and, most important, a large bag of indeterminate color, shape, and contents that he always carried slung over his shoulder (Figure 20). Fausto was happily married to Roberta for many years. Sadly, Roberta died a few days after Fausto, on August 3, 2014. Their son, Gianluca, survives them, as does Marco, Fausto’s son by his earlier marriage, to Silvia.

Figure 20. From the left: F. A. Cotton, F. Calderazzo, G. Wilkinson, E. O. Fischer, W. Beck, J. Chatt, W. Hieber (Ettal Conference in honor of Wolfgang Hieber, 1974).

Italian colleagues Daniela Belli Dell’Amico (University of Pisa, Italy) Guido Pampaloni (University of Pisa, Italy) Alberto Albinati (University of Milan, Italy) Gino Busetto (University of Bologna, Italy) Valerio Zanotti (University of Bologna, Italy) Rinaldo Poli (University of Bourgogne, Dijon, France) Marta Catellani (University of Parma, Italy) Alceo Macchioni (University of Perugia, Italy) Friends f rom many countries Peter Maitlis (University of Sheffield, U.K.) Howard Alper (University of Ottawa, Canada Fred Basolo (Northwestern University, IL, USA; 1920− 2007) Martin Bennett (Australian National University, Canberra, Australia) Robin Clark (University College, London, U.K.) John Ellis (University of Minnesota, USA) Gerhard Erker (University of Muenster, Germany)

■

PERSONAL TRIBUTES TO FAUSTO CALDERAZZO A Selection of Tributes from Colleagues and Friends Is Given Below. H


Organometallics

Review

in the lab, I found a black suspension in my flask. I was very disappointed, and I could not understand what had happened. I checked if there had been a mistake with the solvent, but its smell was unmistakably that of the thionyl chloride. Therefore, water could not have been responsible for what had occurred. I went to the office of the Professor and I told him my misadventures. He came to the lab, observed the black suspension in the flask, and said: “I don’t know what it is, but it must be an interesting product.” Although the black color led us to fear a decomposition, a more careful inspection showed that the solid was fine, as it was a microcrystalline product composed of lustrous needles. Elemental analysis and X-ray diffraction studies revealed that we were dealing with a new gold chloride, the mixed valence tetranuclear Au4Cl8. In the course of the preparation of AuCl(CO) on a larger scale, it happened that the amount of CO in the flask was not sufficient to complete the reaction and the partial reduction of Au(III) to Au(I) had created the conditions for the formation of the mixed valence gold chloride. At the time, Fausto and I often discussed the characteristics of the platinum(II) and gold(I) chlorocarbonyls, in particular the high energy of their CO stretching vibrations, which were even greater than that of uncoordinated CO, and also about their reactivity towards some Lewis bases, such as water or secondary amines, that proceeded with attack at the CO carbon atom. A simple explanation could be that the back-donation from the metal to carbon monoxide was less or absent in these complexes. Although I was convinced of this interpretation of the experimental data, I was reluctant to write it up in an article, out of respect of the long-accepted description of the metal− CO bond based on σ-donation and π-back-donation. He convinced me that, in science, it is always possible to question even well-agreed models if some data are not well explained by them. We, therefore, submitted a paper discussing this point and described the platinum(II) and gold(I) chlorocarbonyls as “atypical”. Subsequently, in the period 1990−2010, several interesting papers appeared in the literature reporting other metal carbonyl complexes characterized by CO stretching vibrations at very high wave numbers and with such a high reactivity of the coordinated CO towards nucleophiles that extremely acidic solvents were required to prepare and handle them. At the beginning of the 1980s, Fausto suggested that I should undertake a study of the system PdCl2/CO, as there were some controversies in the literature about the existence of palladium(II) chlorocarbonyls. By operating in SOCl2 as solvent to ensure the absence of water, the dinuclear Pd2Cl4(CO)2 was obtained and characterized. This complex at room temperature appeared to decompose, both in SOCl2 and in the solid state. Fausto and I discussed this problem and decided to carry out some experiments to understand if the decomposition was due to a partial reduction of the metal or to a loss of CO. Thus, he suggested that I should study the equilibrium between PdCl2 and CO, which had to be carried out under a high pressure of CO. He gave me a lot of support in designing the experiments, since it was not easy to work under pressure in thionyl chloride as solvent in a stainless-steel autoclave. Slowly, helped by discussion and by adjusting the conditions and the procedures step-by-step, we were able to measure the equilibrium constants of the process at various temperatures and to derive the thermodynamic parameters, which allowed us to determine the Pd−CO bond energy in the compound.

Pablo Espinet (University of Valladolid, Spain) Malcolm Green (Oxford University, U.K.) Brian James (University of British Columbia, Vancouver, Canada) Karel Mach (J. Heyrovsky Institute of Physical Chemistry, Prague, Czech Republic) David Milstein (Weizmann Institute of Science, Rehovot, Israel) Ilya Moiseev (Russian Academy of Sciences, Moscow, Russia) Luis Oro (University of Zaragoza, Spain) Helmut Werner (University of Wuerzburg, Germany) Daniela Belli Dell’Amico (University of Pisa, Italy). This commemoration of Fausto Calderazzo’s work in chemistry gives me the opportunity to describe some details of the experiments that I carried out, initially as a student and later as a co-worker. My researches began with the Laurea thesis work that I undertook under his supervision, where my first task was the synthesis of platinum carbonyls, and hopefully of the unknown platinum tetracarbonyl, Pt(CO)4. I remember that, on my first day, the Professor (for me Fausto has been always “The Professor”) accompanied me to a local bank in order to withdraw from a safe-deposit box the large platinum crucible that the Institute of Inorganic Chemistry had placed there. I became responsible for this precious vessel, which also had in part to be the source of my chemistry. The large crucible weighed about 50 g and had very thin walls. We took about 30 g to build two new small crucibles, while from the remainder, we periodically cut some pieces with a pair of scissors and attacked them with aqua regia to produce the platinum salts used as precursors. In the course of my work, I prepared some chlorocarbonyls of platinum(II): the colorless cis-PtCl2(CO)2 and the orange trans-Pt2(μ-Cl)2Cl2(CO)2, according to Schutzenberger’s method, starting from platinum black treated at high temperature with a mixture of chlorine and CO. I soon realized that these complexes were very sensitive to moisture and that the traditional solvents, even if carefully dried, were not able to avoid the fortuitous presence of traces of water. The reaction of these complexes with water produced black sticky solids. I discussed this problem with the Professor and he suggested that I should try thionyl chloride as solvent. I was initially astonished, because I was accustomed to consider thionyl chloride as a rather aggressive reagent, not as a solvent. However, at the same time, I had to recognize that it would be an excellent water scavenger. In fact, it worked very well and its use allowed us to handle without problems not only chlorocarbonyls of platinum(II) but also those of platinum(IV) and of other noble metals. Some months later, a convenient new method for the preparation of AuCl(CO) was developed starting from the hydrated HAuCl4, operating in SOCl2. The reaction was run initially under dinitrogen, up to the formation of the red Au2Cl6, and subsequently under CO. The synthesis proceeded smoothly, and nice pearly crystals of the gold carbonyl were obtained in high yields. The gold carbonyl was also very sensitive to moisture, yielding violet or black decomposition products. On one occasion, I decided to prepare a large quantity of AuCl(CO). When the conversion of the hydrated HAuCl4 to Au2Cl6 was complete, I filled the flask with CO and stirred the red mixture overnight. The following morning, when I arrived I


Organometallics

Review

homoleptic, niobium or tantalum hexacarbonyl were unsuccessful: niobium(0) and tantalum(0) hexacarbonyls are still elusive.

Later on, we found that the PdCl2 crystalline phase in equilibrium with the chlorocarbonyl was the beta modification, Pd6Cl12 whose structure was solved by single-crystal X-ray diffraction measurements. We were able to grow single crystals of the hexanuclear chloride exploiting the equilibrium we had studied. A solution of the palladium chlorocarbonyl in SOCl2 was prepared, initially under CO, and the partial pressure of carbon monoxide was slowly decreased. The crystallographic study on the carbonyl product confirmed that it was a dinuclear chlorobridged complex and established that we were dealing with the cis isomer, cis-Pd2(μ-Cl)2Cl2(CO)2. By contrast, the dimeric platinum analog is the trans-isomer. I have tried, in this account, to give some details of my research activity and the relationships that Fausto had with his co-workers and the atmosphere that was consequently created. Fausto was always available and his door was always open, both in a literal and a metaphorical way: there were no barriers between him and researchers who wanted to discuss with him, no matter if they were students, Ph.D.’s or professors. Moreover, the discussions were very democratic and he made a point of stimulating the co-worker to express any doubts and to propose new solutions. He was always keen to hear other interpretations of the data by his co-workers and taught his group members informally to debate the current research being presented by the other researchers, emphasizing also the uncertainties we had, in order to evaluate the data just obtained and also to seek advice about how to solve some scientific or technical problems. I was always amazed by the elegant simplicity of the proposals and suggestions that he made in the course of our discussions, a style that accompanied all his activities. The scientific dialogues I had with him remain as moments of intellectual delight, and I thank him very much for his teaching. Guido Pampaloni (University of Pisa, Italy). It is an honor to participate in this issue of Organometallics commemorating Professor Fausto Calderazzo: he was an honest man and un grande maestro of chemical science. I had the pleasure of working with Fausto for many years, first, as a laureando in Chemistry and, later, as a member of his research group in Pisa. I remember that, when I applied to join his team, he had just come back from the 26th IUPAC Congress in Tokyo, where his attention was captured by metal complexes of N4 macrocycles. The topic of my experimental thesis (Synthesis and Carbonylation Reactions of Iron(II) Phthalocyanine), was probably quite far from his thoughts at the time, but he became interested due to the curiosity he had about every field of chemistry. Some years later, I started to investigate the carbonylation reactions of metal halides and to study the reactivity of low-valent early transition metal carbonyl and arene complexes. The research on hexacarbonylmetalates(−I) of group 5 elements led to some new procedures for their synthesis and some new reactions. Thus, a new process was devised for the synthesis of V(CO)6, consisting of a one-electron oxidation of Na[V(CO)6] with hydrogen chloride in pentane at ca. −70 °C.36 We also showed that, under the same experimental conditions, the hexacarbonylmetalates Na[M(CO)6], of niobium and tantalum (M = Nb, Ta), only underwent twoelectron oxidations to the halocarbonyls of the metal in the oxidation state (+1) of formula [M2(μ-Cl)3(CO)8]− (Scheme 16 and Figure 21). All our efforts to isolate a neutral,

Scheme 16. One- and Two-Electron Oxidations of Group 5 Hexacarbonyl Metalates(−1)

Figure 21. X-ray structure of [H(tetrahydrofuran)2 ][Nb 2 (μCl)3(CO)8].

Right from the beginning of his career, Fausto was in close contact with the Italian chemical industry, especially Eni, the petrochemical company. One day, a group of Eni researchers asked Fausto if he could help them find a simple way to prepare large amounts of solid solutions of titanium and vanadium halides. The problem was discussed at a meeting in the small library of the Inorganic Chemistry Section of the old Dipartimento di Chimica e Chimica Industriale in Pisa. During the presentation of the problem by the Eni researchers, Fausto looked at me and said: “Dovrebbe far reagire il vanadio esacarbonile con TiCl4; funzionerà!” (If one were to react V(CO)6 with TiCl4, that should do it!) He was right! The two substances immediately reacted with evolution of carbon monoxide and afforded an amorphous solid that caught fire on exposure to air. The composition corresponded to the formula VTiyCl4y, where y depended on the Ti/V molar ratio used (eq 1). V(CO)6 + y TiCl4 → VTi yCl4y + 6CO

(1)

The first step, and probably the easiest, was overcome, but we then had to tackle the problem of preparing large amounts of vanadium hexacarbonyl, which is a greenish-black material with an unpleasant odor, similar to that of Co2(CO)8 (di colore verde-nero e di odore caratteristico, ingrato, simile a quello del dicobalto ottacarbonile). As it is sensitive to light, heat, moisture, and oxygen, it must be stored in the dark at low temperature; if not, a beautiful vanadium mirror appears on the walls of the sealed tube, which is then dangerous as it is full of carbon monoxide under presssure! Unfortunately, although we had solved the synthesis problem, V(CO)6 required too many precautions to be used as a starting material on an industrial scale. Fausto’s time at the European Cyanamid European Research Institute in Geneva and his superb memory for experimental details helped us to revisit his synthesis of the very much easier to handle, bis(mesitylene) vanadium, V(η6-mesH)2 (mesH = 1,3,5-Me3C6H3),37 a compound that had previously been J


Organometallics

Review

Scheme 19. Reactivity of M(η6-mesH)2; M = V, Nba

obtained in low yields by a modification of the Fischer−Hafner procedure (Scheme 17). Scheme 17. Synthesis of V(η6-mesH)2 via Aqueous Alkaline Procedure

The new synthesis was a two-step process where the first step (the V(III) → V(I) reduction) works only in the presence of a large excess of the reductant. Fausto suggested that we should change the polarity of the medium and use a large excess of aluminum as a reducing agent. The idea was good, and the collaboration with the Eni researchers succeeded in producing V(η6-mesH)2 in almost quantitative yield from VCl3 on a kilogram scale; see Scheme 18.38 Scheme 18. One-Pot Synthesis of V(η6-mesH)2

a

mesH = 1,3,5-Me3C6H3; acac = acetylacetonato anion; hfacac = hexafluoroacetylacetonato anion.

The same procedure was also applied to the synthesis of the bis-mesitylene derivatives of niobium(0),39 chromium(0), and molybdenum(0).38 This preparation still represents the only synthetic route to a niobium(0) derivative in gram quantities that does not require the use of an MVS technique. The procedure, and some of its variants, were patented,40 as was the use of V(η6-mesH)2 for the preparation of solid solutions of vanadium and titanium halides.41 Fausto’s simple, ingenious, and fundamental suggestions allowed the chemistry of arene derivatives of early transition metals to be expanded in several important ways: (i). The low-valent bis(η6-arene) compounds represented a useful entry into the chemistry of the corresponding metals in nonaqueous systems (Scheme 19).42 Thus, some of the halides obtained by such low temperature routes proved to be much more reactive than the commercial ones. (ii). The niobium(I) bis-arene derivatives (Scheme 20A) included the first example of a tetraarylborate anion behaving as a 12-e donor. The complex was prepared by thermal decomposition of [Nb(η6-mesH)2L][BAr4] (L = CO, alkyne; Scheme 20B).43 (iii). Although the procedure described in Scheme 18 could not be used for the preparation of the bis-arene derivatives of group 4 elements, tantalum or of tungsten, the experience acquired on the oxidation of group 5 bisarenes, and the paucity of data on the reactivity of group 4 metals bis-arenes, encouraged us to explore further. Thus, one of our graduate students spent 3 months in the Inorganic Chemistry Laboratory of Malcolm Green (Oxford, U.K.) and came back to Pisa with two sealed tubes containing some grams of very precious Ti(η6C6H6)2 and Ti(η6-1,3,5-iPr3C6H3)2, prepared by the MVS technique. Treatment of a toluene solution of Ti(η6-

1,3,5-iPr3C6H3)2 with [FeCp2]BAr4 afforded the orange, paramagnetic cation [Ti(η6-1,3,5-iPr3C6H3)2]+ (Scheme 21), representing the first fully characterized titanium(I) derivative.44 Fausto’s great curiosity had produced another interesting result. Alberto Albinati (University of Milan, Italy), Luigi Busetto (University of Bologna, Italy), Valerio Zanotti (University of Bologna, Italy). The outstanding scientific contributions of Fausto Calderazzo to chemistry have been extensively described in special issues of journals in the fields of inorganic and organometallic chemistry. Particularly important were the interview with Fausto, by Rinaldo Poli2 and the special issues of the same journal45 dedicated to Fausto on the occasion of his 80th birthday and edited by Guido Pampaloni. Less emphasized, but no less important, is the contribution that Fausto made to the growth of inorganic chemical research in Italy by his unrivaled success in stimulating discussions, collaborations, and the drawing together of research groups with different competences, within the national community of inorganic researchers. This increased the overall research quality and competitiveness at the international level. The opportunity to launch the first large gatherings of inorganic chemists in Italy stemmed from the funding possibilities offered by MURST (the Italian Ministry for University and Research) in the early 90s. The Bologna group had the privilege of hosting the preparatory meetings that were held at the Faculty (now Department) of Industrial Chemistry, and were attended by about a hundred scientists. By virtue of Calderazzo’s outstanding reputation and his convincing arguments, the participants all agreed to join in a research project entitled “Chemical Reactivity and Catalysis”. This program, which comprised 62 active groups from 26 Italian Universities, was funded on three occasions. In the course of the program, K


Organometallics

Review

Scheme 20. Synthesis of Niobium(I) Derivatives by Oxidation of Nb(η6-mesH)2a

a

mesH = 1,3,5-Me3C6H3.

Scheme 21. Synthesis of [Ti(η6-1,3,5-iPr3C6H3)2]BAr4 and X-ray Structure of [Ti(η6-1,3,5-iPr3C6H3)2]B(p-C6H4F)4

and scientific curiosity helped to make the seminars more and more relevant. For younger researchers, it was a very stimulating experience, and they were encouraged to participate in the Discussion Arena. Usually, the Bologna meetings were held on Fridays and Saturdays or during the winter holidays in order not to take up precious research time, and this corresponded to Fausto’s own approach. The results of these new initiatives and the enthusiasm of all the participants convinced Fausto to found the “Interuniversity Consortium for Chemical Reactivity and Catalysis”, which was approved by the Ministry MIUR in 1994 and is still a very active organization. Fausto’s efforts to improve and stimulate the consortium of

Fausto was able to suggest and coordinate new research lines and to promote close cooperation among the various groups. Progress in the implementation of the project was monitored by periodic meetings held in Bologna. The participants all came together to discuss their results and to highhlight the new developments. The atmosphere in the first meetings was exciting: Fausto chaired the discussions and invited each research-unit coordinator to present their results at the blackboard: no transparencies or PowerPoint presentations were allowed. The talks and discussions went on from early morning to late afternoon, with just a very short break for lunch. Fausto’s inexhaustible energy, unrivaled competence, L


Organometallics

Review

highlight my feelings for him, as a scientist, and also as a human being. His most useful lessons were, at least for me, the need to observe carefully, to analyze deeply using all available information, and to find the simplest possible solution to problems, even those that might appear complex at first sight. During my stay initially as a Laurea and then as a doctoral student in his group, he took pleasure in dropping by once or twice a day, carefully observing with me the appearance of the compounds and of the solutions I was working on. He analyzed the significance of these observations and proposed modified experimental conditions and new experiments. I was most impressed by the ingenuity of some of the apparently trivial suggestions, such as a simple change of solvent, and their strong impact on the results. For instance, I needed to carry out several experiments using [MnX(CO)4]2 (X = Br, I) as starting material, but the literature preparation by thermal decarbonylation of [MnX(CO)5] was low yielding, presumably because of the high temperature (100−120 °C) that was required and which led to partial disproportionation to MnX2 and [Mn2(CO)10]. This was shown by identification of the latter compound in the supernatant by IR spectroscopy. Fausto proposed that we use isopropyl ether as solvent, and indeed, the resultant stabilization of the decarbonylated [MnX(CO)4] intermediate accelerated the reaction, while the lower boiling point minimized decomposition. The weak coordinating power of the ether did not hamper the formation of the dihalo-bridged product, which could be isolated in excellent yield and in pure form. The new procedure was later published in Inorganic Syntheses.46 The most spectacular example of this type of ingenuity was probably the synthesis of late transition metal carbonyl derivatives, notably of platinum, palladium, and gold, which Daniela Belli accomplished at that time. The low energy of the d electrons in these metals allows only a very weak backbonding to CO, which is, therefore, highly electrophilic. Consequently, the products are extremely sensitive to moisture, particularly in the case of Pd(II), while O2 sensitivity is not a major issue. Thus, the simple and ingenious solution to the problem was to carry out the syntheses in thionyl chloride as solvent, allowing the hydrated halide salts to be used directly as precursors. The products also remained protected from moisture during the workup, which could even be done in air in certain cases!47 This methodology also led to the isolation and characterization of one of the most beautiful molecules I have ever seen, [Au4Cl8], which contains two Au(I) and two Au(III) centers in their preferred linear and square planar coordination environments.20b To my mind, this has been a major contribution to inorganic chemistry. Of course, Fausto Calderazzo is mostly known for landmark contributions in carbonyl chemistry: on the nature of [V(CO)6], and on the mechanism of the “CO insertion” process in [Mn(CH3)(CO)5]. However, those landmark discoveries were already part of history when I was a student with him. The lessons I learned from Fausto have been invaluable in my career: for instance, the synthesis of MoCl3(thf)3 was optimized by a solvent switch from MeCN to Et2O during the first step of the MoCl5 reduction.48,49 Fausto Calderazzo as a man was equally admirable. I remember his chief traits as being kind, humble, sensitive,

research groups continued during the following years and successfully influenced changes in the funding policy of MURST. Between 1998 and 2004, Fausto successfully coordinated a new national research project in chemistry. As Catalysis had become a low priority key word in Italy, Fausto’s lifelong interest in the relationships between the properties of the elements and their reactivities led to a new research topic: “New strategies for the control of reactions: interactions of molecular f ragments with metallic sites in non conventional species”. As requested by MIUR, the number of research units and participants involved were drastically reduced, with more specific targets and duties allocated to each unit; however, the spirit of cooperation of the early years survived. Regular scientific meetings continued to be held in Bologna, and a new generation of young researchers was trained. By then, Fausto had become more accommodating to the point of allowing slides and PowerPoint presentations. The most remarkable change in these meeting, however, was the presence of a “foreign referee” who co-chaired the meeting; thus presentations and discussions were given in English. Fausto invited many distinguished scientists in the field, including Peter Maitlis, David Milstein, and Hans-Jörg Grutzmacher, to be our guests. In particular, Peter acted as a referee for most of our meetings, which contributed to the research standard of the network. It is interesting to recall that Fausto, as the scientific coordinator, always kept a very open mind and never let his own enthusiasms prevail in the research groups. Indeed, he encouraged an approach covering a wide spectrum of interests, topics, and expertise without emphasizing applied over fundamental research. He only discriminated between “good and bad research”; in that, he was inflexible in requiring that any result should be of high quality and based on reliable and carefully documented experimental data. Obviously, he was pleased when interesting work was reported during the meetings, but he was much more excited when unclear and intriguing results were presented, looking for possible interpretations. That was his style: his lectures, rather than reporting remarkable, but final results, often contained more questions than answers and focused on still open questions and topics for which he was working hard to get a better understanding After his retirement, the network he had created (which was composed of chemists at the universities of Bari, Bologna, Florence, Messina, Milan, Naples, Perugia, Pisa, and Venice) continued, and Fausto, as Emeritus Professor at the University of Pisa, continued to inspire new fields of investigation as well as helping to assess the progress of the projects. Among the various research topics he suggested, based on his own investigations, it is worth mentioning his effort in promoting the study of “weak interactions” and their role in determining the chemical reactivity of metal−ligand fragments. Indeed, the most recent research programs that were coordinated by the Bologna and then by the Milan groups were based on these ideas. For all of us, Fausto was a mentor and a friend who made doing science together a pleasure and who taught us the excitement of doing science. He will be sorely missed by his friends and colleagues. Rinaldo Poli (CNRS, Laboratoire de Chimie de Coordination, Toulouse, France). My Maestro is no more. Fausto Calderazzo was for me a wonderful teacher, a source of inspiration, and a point of reference. The following lines M


Organometallics

Review

could also have been found, particularly to locate the anion position with respect to that of the cation. After my Ph.D., I spent more than 2 years at the ETH of Zürich as a postdoctoral in the research groups of Paul Pregosin and Luigi Venanzi, learning how advanced multinuclear and multidimensional NMR spectroscopy can structurally characterize organometallic complexes in solution. When I went back to Perugia as a researcher, I had still in my mind the unsolved problem of obtaining structural information on ion pairs, but I had a lot of new NMR tools in my pocket to face such a challenge. I also realized that ion pairing had a strong influence on several other important reactions in addition to the CO migratory insertion.53 Our initial results on the structures of ion pairs were obtained by applying 1H− NOESY and 19F, 1H−HOESY NMR techniques to the investigation of M(II)-carbonyl compounds bearing bi- and tridentate nitrogen ligands similar to those used in my Ph.D. work in order to better differentiate all the coordination sites.54 Financial support for the work came from the Italian National Projects coordinated by Fausto Calderazzo. Since the project ran over quite a long period of time (1995−2012), we held about two meetings per year where we presented our achievements. On those occasions, I could appreciate the breadth and depth of Fausto’s knowledge and also his scientific curiosity and constructive criticisms. He always showed interests in my studies and encouraged me to explore indepth the potential and limitations of my NMR methods. I remember that, at one meeting where I presented the utilization of NOE NMR techniques to investigate ion pairs,55 Fausto had invited Peter Maitlis as external referee. After my 20 min oral presentation, Fausto and Peter bombarded me with questions for almost an hour. That was really a little hard but a stimulating and instructive experience! Another feature of the personality of Professor Calderazzo was his “originality”. At our meetings, he did not want us to use transparencies or (even less) PowerPoint presentations to illustrate our results. All the student presenters, including myself, complained about this, but we could not change Fausto’s mind. I now think he was right because writing on the blackboard provides the opportunity to construct the logical thread of the discourse, even though it was rather difficult for me when I had to draw 19F, 1H−HOESY spectra! I am proud to have been able to interact with such a great scientist, and such a source of inspiration, as Fausto Calderazzo. We have lost our undisputed leader, but the Italian organometallic community will continue to grow thanks to the school that he founded. Peter Maitlis (University of Sheffield, U.K.). I was devastated to hear of the passing of Fausto Calderazzo: Fausto and I were close friends for nearly 50 years. I first visited Fausto in August 1968 when he was working at the Cyanamid European Research Institue (CERI) in Geneva. A year or so later, when we lived in Canada, he came and stayed with us and gave an excellent lecture at McMaster University in Hamilton. After his lecture, we all drove over to see a play at the Shakespeare Theatre in Stratford, Ontario. I do not remember which play it was, but I do recall that we picnicked in the theater gardens and ate huge Bing cherries that Fausto loved. As I followed his outstanding chemistry very closely, I heard him speak at many meetings. In 1971, on the occasion of the International Conference on Organometallic Chemistry in Moscow, when we were both invited speakers, Fausto and I

and optimistic. Although his ways drew some mixed responses from the local community, this was inevitable in a competitive research environment, but over many years, I never heard anything but words of praise for him as a scientist and as a human being from colleagues abroad where I have long lived. His friends and admirers include some of the most influential scientists of our generation, including G. Wilkinson, F. A. Cotton, F. Basolo, J. Halpern, W. A. Herrmann, P. M. Maitlis, M. L. H. Green, and I. I. Moiseev, some of whom did not always get along very well with each other. It is also noteworthy that he enjoyed the admiration and friendship of J. E. Ellis, probably his fiercest competitor in low-valent carbonyl chemistry. The symposium that I helped organize on the occasion of his 70th birthday drew to Pisa the crème de la crème of inorganic and organometallic chemists worldwide. He followed with interest, though discretely, the careers of his pupils both at the scientific and the personal level, as it clearly transpired during our subsequent encounters and through discussions with those closest to him. Fausto was an outstanding man, a scholar, and a gentleman, my Maestro, whom I will sorely miss. Marta Catellani (University of Parma, Italy). Fausto Calderazzo was a scientist of exceptional ability with an abiding curiosity and interest in understanding why and how chemical reactions happen. By profound and constant questioning, he succeeded in providing clear, simple, and elegant explanations to numerous problems. Paradigmatic to me are the mechanistic studies on the carbonylation reactions of methylmanganese pentacarbonyl with labeled CO. Reading his papers taught me a lot of organometallic chemistry. Alceo Macchioni (University of Perugia, Italy). I am particularly pleased to contribute to the special issue of Organometallics dedicated to the memory of Fausto Calderazzo. He was undoubtedly the most prominent Italian organometallic chemist of the last decades and one of the most important worldwide. At the same time, Fausto was a scientist with a crystalline intellectual honesty who provided an important reference point for many generations of young chemists. Although I had not the opportunity to collaborate directly with Fausto, his innovative ideas strongly affected my initial studies and indirectly delineated my more recent research activity. One of his most important achievements concerned the understanding of the CO migratory insertion reaction into metal carbon bonds..17c He elegantly demonstrated that, in Mn(CO)5Me, it was the alkyl group that migrates, rather than the CO that inserts, by an in-depth IR spectroscopic study based on selective isotopic labeling of complexes with 13CO.17a My Ph.D. research project, supervised by Giuseppe Cardaci, was an investigation of the kinetics and thermodynamics of the migratory insertion of CO and CNR in M(II)−organometallic complexes (M = Fe, Ru, and Os). This was a subject strongly inspired by the studies of Calderazzo on the CO migratory insertion. A complication was introduced in our studies largely by the presence of a rather labile M−I bond, which opened an alternative reaction pathway, involving the initial ionization of that bond,50 followed by a migratory insertion that was either accelerated or retarded by the interaction of the anion with the carbon atom bearing a partial positive charge.51 Such interactions were assumed to occur within an intimate ion pair.52 Several kinetic studies supported that hypothesis, but I would have been much more satisfied if structural evidence N


Organometallics

Review

such complex earlier. These three occasions of our research requiring that we carefully study some of your papers, have made me a believer in your elegant work.” Howard Alper (University of Ottawa, Canada). Fausto Calderazzo was a great scientist who made splendid contributions to chemistry. Excellence was his signature in everything. I always treasured his genuinely warm personality and generosity of spirit. He inspired his students and his more experienced colleagues, both Italian and foreign, and we all learned so much from him. May his memory be a blessing. Martin Bennett (Australian National University, Canberra, Australia). I used to visit Pisa regularly because I collaborated on arene-Ru chemistry with Paolo Pertici in Piero Salvadori’s group, but I always had a talk and sometimes a meal with Fausto during my visit. I had the greatest respect for his knowledge and insight. He was one of those rather rare people who made important contributions to the chemistry of the elements at both ends of the d-block series. Robin Clark (University College, London, U.K.). Fausto I liked very much both as a person and as a scientist. My favorite story is that, on visiting him in Pisa about 15 years ago to lecture, I told him that I had spoken there previously. I was surprised to find that he kept on the wall in the corridor outside his office the names of all visiting lecturers to the Inorganic Department in Pisa, together with the titles of their lectures. I easily found my name and the lecture title there, as well as the exact date, sometime in the 1960s. It was nice to be reminded of the event. John Ellis (University of Minnesota, USA). I am so sad to hear of the passing of a wonderful friend. When I was a graduate student, Fausto taught me nearly all I knew about metal carbonyl chemistry through his gold mine of information in the chapter (coauthored by R. Ercoli and G. Natta) entitled “Metal Carbonyls: Preparation, Structure, and Properties” in the monograph Organic Syntheses via Metal Carbonyls, Volume 1, edited by Wender and Pino.56 About 30 years later, I had an opportunity to meet the Maestro of Organometallic Chemistry at the University of Pisa for the first time and to see his laboratory where so many fabulous discoveries had been made over the years. It was also a special treat to meet his associates, Daniella Belli Dell’Amico and Guido Pampaloni, who helped to bring so many of Fausto’s dreams to fruition. I feel that, if I had not been able to “stand on the shoulders” of Fausto Calderazzo, a true giant, whatever success I have had in metal carbonyl and metal arene chemistry would have been much diminished. We will all miss him greatly! Gerhard Erker (University of Mü nster, Germany). It is so sad to know that Fausto Calderazzo is not among us anymore. I had not seen him personally for many years, but he had a substantial influence on my early work in organometallic chemistry. I first met him in Pisa at an early stage of my independent academic career, and from then on, I greatly admired his beautiful work. I will always remember him as a great scientist and a very friendly wonderful person. Pablo Espinet (University of Valladolid, Spain). Fausto Calderazzo is certainly one of the people who will remain forever in the history of Organometallic Chemistry. I want to present my respects and admiration to one of the founders of the modern chemistry that I was reading as a student in the mid-sixties. I met him at a meeting in 2000, when he gave me regards for Rafael Usón. Although he was by then already no longer young, he looked and sounded very strong, as strong as I, a chemist of the next generation, found his chemistry.

took some time off to explore the Kremlin, with its green and gold domed churches, and even visited a Berioska Dollar store, closed to most Russians. A visit to Sardinia in 1973 to participate in a conference at the BP Research Center near Santa Margherita di Pula was also interesting as it also shone a light into chemical economics. We met one group of researchers who were charged with converting a carbohydrate (food) into fuel, while another was engaged in researching the conversion of hydrocarbon fuel into animal feeds. However, my strongest memories are of Fausto showing me how to gather pine nuts (pinoli) from the trees at the roadside and, equally important, to appreciate the marvelous local cheese (pecorino sardo), a liking that has always remained with me until now. There was also the occasion when Fausto, his wife, Roberta, and their son, GianLuca, accompanied Vanna and Paolo Chiusoli (the very distinguished organometallic chemist from Parma), my wife Marion, and myself, to a small restaurant in Rome, Sor’Ella, to celebrate after an election at the Accademia Lincei. The house specialty was a Gorgonzola pizza, but Fausto contented himself, as always, with a plate of simply cooked vegetables. Although Fausto’s tastes in food became somewhat ascetic, he always made sure that everyone around his table ate plentifully of the best. Fausto also invited me on many occasions to Bologna to help moderate the oral “examinations” of students in Chemistry, which were taken under the auspicies of the Italian government agency, MIUR or PRIN. They spoke about their current researches, which also allowed them to practice their English. The 20 min presentations were usually followed by 10 min of discussion where Fausto and I were encouraged to ask many hard-hitting questions. The students answered impeccably, and we all learned much from these exchanges. On these occasions, I usually stayed in the hostel of the Collegio Erasmus in Bologna. The Collegio had been a monastery, and on one occasion, I found the steep stairs rather difficult. Fausto saw my problem and, without a word, took my arm and guided me safely down. That small incident exemplifies Fausto: he was strong, kind, and thoughtful, and very much “no nonsense”if help was needed, he would give it, without being asked and without expecting thanks. He was a marvelous and kind man, a superb scientist, and a unique and magnifent friend. I miss him greatly. Fred Basolo (Northwestern University, IL, USA; 1920− 2007). Rinaldo Poli recollected that, on the occasion of Fausto’s 70th Birthday celebration in 1990, Fred Basolo wrote, “I would be delighted to attend your Birthday celebration but my health makes it impossible to travel. Fausto, I am pleased to see you being honored as a deserving person and as an outstanding inorganic chemist.” “I recall we first met when you were doing research with the famous Natta group. Later I read about your showing V(CO)6 is not a dimer, but a 17-e monomer. This interested us and we demonstrated that it undergoes CO exchange orders of magnitude faster than does the similar 18-e Cr(CO)6.” “Our scientific paths crossed on two other occasions. Once, when we discussed the migratory methyl insertion reaction of CH3Mn(CO)5. You then did a careful detailed job on the system and showed that our facts were wrong, but our suggested mechanism seemed OK.” “The other time our research paths crossed was when we prepared a series of monomeric cobalt dioxygen complexes, only to find in the literature that you had already prepared one O


Organometallics

Review

David Milstein (Weizmann Institue of Science, Rehovot, Israel). It was with great sadness that I learned of the passing of Fausto Calderazzo. I always admired Fausto, not only for his scientific leadership but also as a warm, generous, and friendly person. We met several times, including once at his home in Pisa, where I had the pleasure to meet his wife, Roberta, and son, GianLuca. We had common scientific interests, and even applied together for a grant. I was honored to contribute a paper to a special issue of the Journal of Organometallic Chemistry that marked his 70th birthday.60 His work on metal carbonyls, in particular his classic studies on the CO migratory insertion into metal−carbon bonds, was undoubtedly an important landmark in organometallic chemistry, which I have taught at our Institute for many years. Fausto was a caring person; in one of his e-mails to me in 2004, he wrote, “I hope this finds you in good shape and in full activity, in spite of the political situation in your country, which I am following constantly, in the hope that everything is going to become quieter.” I will greatly miss him. May he rest in peace. Ilya Moiseev (Distinguished Member of the Russian Academy of Sciences, Moscow, Russia). In 1980, Eni S.p.A. (Ente Nazionale Idrocarburi, the Italian Gas and Oil Company) organized a colloquium in Castel Gandolfo near Rome with the aim of bringing together Italian and Russian chemists for discussions on topics of mutual interest. I was invited to lecture on the first Pd(I) carbonyl complex which had been synthesized and characterized in my group by the late Tatiana Stromnova.61 I was pleased and proud to have been invited to speak at this prestigious meeting and that is was where I first met Professor Fausto Calderazzo. He had already established a worldwide reputation for both his synthetic and mechanistic studies on metal carbonyl complexes. A prolific contributor to the fields of coordination chemistry, organometallic, and bioinorganic chemistry, Fausto published over 400 papers, and supervised many Ph.D. students. Another occasion when our research paths crossed was when we made a series of monomeric cobalt dioxygen complexes, only to find from the literature that Fausto had already prepared such a complex earlier. These two occasions indicated that we needed to read Fausto’s papers very carefully and made me an admirer of his elegant work. In 1991, he suggested that I should submit a paper on the catalysis of hydroperoxide decomposition to Gazzetta Chimica Italiana, where it was published under his guidance (Hydrogen Peroxide Decomposition catalyzed with Vanadium(V) Compounds in Trifluoroacetic Acid Solution).62 Fausto was not only Editor-in-Chief, he was also extremely patient and kind and helped me with putting it into a good colloquial format. I enjoyed visiting his cosy home in Pisa on many occasions, and the memories of the hospitality of his wife, Roberta, are very much alive. Many chemists around the world now miss a good and gentle friend and teacher. Luis A. Oro (University of Zaragoza, Spain). The scientific community was shocked to hear that Fausto Calderazzo passed away. Fausto’s kind and modest personality was combined with intellectual rigor, great clarity of expression, and broad interests, both personal and scientific. He visited Zaragoza several times, and it was always a real pleasure to learn from him. Fausto Calderazzo will always be remembered for his

A later connection was on the occasion of a 1 day symposium to celebrate the retirement of Professor Alberola, the “catedrático” of organic chemistry in Valladolid (now deceased). I represented our university and gave one of the four invited lectures dedicated to him with the title, “C’era una volta a Milano” (Once upon a time in Milan). It was about the discovery of V(CO)6 since it was Alberola who first made this famous molecule during his postdoc with Natta and Calderazzo.57 Malcolm Green (University of Oxford, U.K.). Fausto Calderazzo was a leader from the earliest days of organotransition metal chemistry. Over the years, starting in about1960, we met at scientific conferences, and I attended two of these at Pisa where Fausto Calderazzo was the Chairman. I collaborated with him in the development of bisarene titanium chemistry. As a scientist and as a man, I greatly respected him, and he was excellent company. He also assisted me on one occasion by offering advice to a Canadian-born student, of Italian parents, who was a postgraduate student of mine in Oxford. He visited Professor Calderazzo to seek advice on entering an academic career in Italy. Fausto was a great help, and the young man concerned is now a Professor at UniversityCollege, London. Brian James (University of British Columbia, Vancouver, Canada). I met Fausto Calderazzo at one of the legendary Sheffield-Leeds Organometallic/Catalysis meetings during the 1970s, but I became aware of his name a few years earlier through my early days of teaching mechanisms of inorganic/ organometallic chemistry, specifically on the topic of insertion reactions of CO. The publications and patents of Calderazzo and Floriani from their work at Cyanamid in Geneva attracted much attention in the 60s and early 70s, and mutual interests in activation of CO, O2, and H2 eventually led me to a 5-month sabbatical at the University of Pisa in the summer of 1979, with funding from a NATO-Professorship, thanks to Fausto’s support. The visit remains highly memorable for me, my wife, and our four children (then 7−16 years old), both socially and, for me, scientifically. Fausto arranged accommodation, behind the Teatro Verdi in the center of the city, and a carboy (∼demijohn) of local Chianti wine arrived at the same time that we did! The stay in Pisa has resulted in Italy being the second favorite country for all my family members. In fact, I did my last experimental bench work in Calderazzo’s lab and there is one multiauthored paper that reports on the study of carbonyl derivatives of Fe(II)phthalocyanato species.58 I last met Fausto in 2008, again in Pisa; he seemed the same as 35 years previouslyhard working, exceptionally generous with his time, enjoying life, and making life enjoyable for others. Karel Mach (J. Heyrovsky Institute of Physical Chemistry, Prague, Czech Republic). This news is sad, indeed. Professor Calderazzo will be missed by many people because he was a gentle and kind man and an excellent chemist who did beautiful and original titanium chemistry. I met him at the 16th Polish-German Colloquy on Organometallic Chemistry in 1987 in Tuczno, where we arranged cooperation in research on the catalysis of alkyne cyclo-trimerization by (arene)titanium(II) complexes, which Helena Antropiusova and I were studying by electronic absorption spectroscopy. This very pleasant work resulted in a joint paper,59 with which we were very pleased. P


Organometallics

Review

(14) Dewey, C. G.; Ellis, J. E.; Fjare, K. L.; Pfahl, K. M.; Warnock, G. F. P. Organometallics 1983, 2, 388. (15) Coffield, T. H.; Closson, R. D.; Kozikowski, J. J. . Org. Chem. 1957, 22, 598. (16) Calderazzo, F.; Cotton, F. A. Inorg. Chem. 1962, 1, 30. (17) (a) Noack, K.; Calderazzo, F. J. Organomet. Chem. 1967, 10, 101. (b) Noack, K.; Ruch, M.; Calderazzo, F. Inorg. Chem. 1968, 7, 345. (c) Calderazzo, F. Angew. Chem., Int. Ed. 1977, 16, 299. (18) (a) L’Eplattenier, F.; Calderazzo, F. Inorg. Chem. 1967, 6, 2092. (b) L’Eplattenier, F.; Calderazzo, F. Inorg. Chem. 1968, 7, 1290. (b) L’Eplattenier, F.; Matthys, P.; Calderazzo, F. Inorg. Chem. 1970, 9, 342. (19) (a) Floriani, C.; Puppis, M.; Calderazzo, F. J. Organomet. Chem. 1968, 12, 209. (b) Calderazzo, F.; Floriani, C. Chem. Commun. 1968, 417. (c) Floriani, C.; Calderazzo, F. J. Chem. Soc. A 1969, 946. (20) (a) Belli Dell’Amico, D.; Calderazzo, F.; Marchetti, F.; Merlino, S.; Perego, G. Chem. Commun. 1977, 31. (b) Belli Dell’Amico, D.; Calderazzo, F.; Marchetti, F.; Merlino, S. J. Chem. Soc., Dalton Trans. 1982, 2257. (21) Belli Dell’Amico, D.; Calderazzo, F. Gazz. Chim. Ital. 1979, 109, 99. (22) (a) Calderazzo, F.; Belli Dell’Amico, D. Inorg. Chem. 1981, 20, 1310. (b) Belli Dell’Amico, D.; Calderazzo, F.; Zandonà, N. Inorg. Chem. 1984, 23, 137. (23) Belli Dell’Amico, D.; Calderazzo, F.; Marchetti, F.; Ramello, S. Angew. Chem., Int. Ed. Engl. 1996, 35, 1331. (24) Calderazzo, F.; Belli Dell’Amico, D. Pure Appl. Chem. 1986, 58, 561. (25) (a) Aubke, F.; Wang, C. Coord. Chem. Rev. 1994, 137, 483. (b) Lupinetti, A. J.; Frenking, G.; Strauss, S. H. Angew. Chem., Int. Ed. 1998, 37, 2113. (26) (a) Calderazzo, F.; Englert, U.; Pampaloni, G.; Pelizzi, G.; Zamboni, R. Inorg. Chem. 1983, 22, 1865. (b) Calderazzo, F.; Pampaloni, G. J. Organomet. Chem. 1983, 250, C33. (27) (a) Calderazzo, F.; Pampaloni, G.; Englert, U.; Strähle, J. Angew. Chem., Int. Ed. Engl. 1989, 28, 471. (b) Calderazzo, F.; Pampaloni, G.; Englert, U.; Strähle, J. J. Organomet. Chem. 1990, 383, 45. (28) Calderazzo, F.; Pampaloni, G.; Masi, F.; Moalli, A.; Invernizzi, R. (ENIChem ANIC S.p.A.). Process for Producing Vanadium Arenes. U.S. Patent 4,980,491, 1990. (29) (a) Calderazzo, F.; Pampaloni, G.; Rocchi, L.; Strähle, J.; Wurst, K. Angew. Chem., Int. Ed. Engl. 1991, 30, 102. (b) Calderazzo, F.; Pampaloni, G.; Rocchi, L.; Strähle, J.; Wurst, K. J. Organomet. Chem. 1991, 413, 91. (30) (a) Calderazzo, F.; Englert, U.; Pampaloni, G.; Rocchi, L. Angew. Chem., Int. Ed. Engl. 1992, 31, 1235. (b) Calderazzo, F.; Pampaloni, G.; Rocchi, L.; Englert, U. Organometallics 1994, 13, 2592. (31) (a) Abram, U.; Belli Dell’Amico, D.; Calderazzo, F.; Della Porta, C.; Englert, U.; Marchetti, F.; Merigo, A. Chem. Commun. 1999, 2053. (b) Baisch, U.; Belli Dell’Amico, D.; Calderazzo, F.; Labella, L.; Marchetti, F. Eur. J. Inorg. Chem. 2004, 1219. (32) Aresta, M.; Ballivet-Tkatchenko, D.; Belli Dell’Amico, D.; Bonnet, M. C.; Boschi, D.; Calderazzo, F.; Faure, R.; Labella, L.; Marchetti, F. Chem. Commun. 2000, 1099. (33) (a) Belli Dell’Amico, D.; Calderazzo, F.; Labella, L.; MaichleMössmer, C.; Strähle, J. Chem. Commun. 1994, 1555. (b) Abram, U.; Belli Dell’Amico, D.; Calderazzo, F.; Kaskel, S.; Labella, L.; Marchetti, F.; Rovai, R.; Strähle, J. Chem. Commun. 1997, 1941. (c) Belli Dell’Amico, D.; Calderazzo, F.; Marchetti, F.; Pampaloni, G. Met. Clusters 1999, 209. (34) (a) Abis, L.; Belli Dell’Amico, D.; Calderazzo, F.; Caminiti, R.; Garbassi, F.; Ianelli, S.; Pelizzi, G.; Robino, P.; Tomei, A. J. Mol. Catal. 1996, 108, L113. (b) Abis, L.; Belli Dell’Amico, D.; Busetto, C.; Calderazzo, F.; Caminiti, R.; Ciofi, C.; Garbassi, F.; Masciarelli, G. J. Mater. Chem. 1998, 8, 751. (c) Abis, L.; Belli Dell’Amico, D.; Busetto, C.; Calderazzo, F.; Caminiti, R.; Garbassi, F.; Tomei, A. J. Mater. Chem. 1998, 8, 2855. (d) Abis, L.; Armelao, L.; Belli Dell’Amico, D.; Calderazzo, F.; Garbassi, F.; Merigo, A.; Quadrelli, E. A. J. Chem. Soc., Dalton Trans. 2001, 2704.

exemplary work on organometallic chemistry and homogeneous catalysis. Helmut Werner (Universität Wü rzburg Am Hubland, Würzburg, Germany). “Fausto was without a doubt one of the standard-bearers of organometallic chemistry in Italy. Although I knew Fausto very well, I had not heard of his death before. My last contact with him related to my book, “Landmarks in Organo-Transition Metal Chemistry”, published in 2008.” [Ich schicke Dir beiliegend ein Photo und einen kurzen Text zu dem geplanten Nachruf f ür Fausto. Ich wusste nichts von seinem Tod, kannte ihn aber recht gut, wobei mein letzter Kontakt im Zusammenhang mit meinem Buch “Landmarks in OrganoTransition Metal Chemistry” zustande kam. Er war zweifellos einer der Bannerträger der metallorganischen Chemie in Italien. ] Helmut Werner also contributed the photo included in the Biography as Figure 20. The picture was taken at the 1974 Ettal Symposium on Metal Carbonyl Chemistry, and shows some of the great men of carbonyl chemistry: (l. to r.) front row: F. Calderazzo (Pisa, Italy), E. O Fischer, (Munich TU, Germany), and, with stick, W. Hieber (Munich TU, Germany); second row: F. A. Cotton (MIT, USA), G. Wilkinson (Imperial College, London, U.K.), W. Beck (University of Munich, Germany), and J. Chatt (Sussex University, U.K).

■ ■

AUTHOR INFORMATION

Notes

The authors declare no competing financial interest.

ACKNOWLEDGMENTS We gratefully acknowledge the very valuable help given by our colleague Fabio Marchetti in the preparation of the cover and of the majority of the figures and schemes for this article. We also thank Rinaldo Poli for much of the basic information about Fausto’s early career.

■

REFERENCES

(1) Sacconi, L. J. Am. Chem. Soc. 1952, 74, 4503. (2) Poli, R. Coord. Chem. Rev. 1999, 188, 1. (3) Pino, P.; Ercoli, R.; Calderazzo, F. Chim. Ind. (Milan, Italy) 1955, XXXVII, 782. (4) Interestingly and significantly, Natta, Fischer, and Wilkinson were all awarded Nobel Prizes: Natta in 1963 (for his studies in metalcatalyzed polymerization, shared with Karl Ziegler), while Wilkinson and Fischer shared the chemistry prize in 1973 for their work on cyclopentadienyl and arene metal complexes. Wilkinson was also knighted by Queen Elizabeth II for his achievements. (5) Natta, G.; Ercoli, R.; Calderazzo, F.; Rabizzoni, A. J. Am. Chem. Soc. 1957, 79, 3611. (6) Calderazzo, F.; Ercoli, R.; Natta, G. In Organic Syntheses via Metal Carbonyls; Wender, I., Pino, P., Eds.; Interscience - Wiley: New York, 1968. (7) Natta, G.; Ercoli, R.; Calderazzo, F. Chim. Ind. (Milan, Italy) 1958, XL, 287. (8) Paiaro, G.; Calderazzo, F.; Ercoli, R. Gazz. Chim. Ital. 1960, 90, 1486. (9) (a) Wojcicki, A.; Basolo, F. J. Inorg. Nucl. Chem. 1961, 17, 77. (b) Basolo, F.; Wojcicki, A. J. Am. Chem. Soc. 1961, 83, 520. (c) Wojcicki, A.; Basolo, F. J. Am. Chem. Soc. 1961, 83, 525. (10) See also: Piacenti, F.; Calderazzo, F.; Bianchi, M. Organometallics 1997, 16, 4235. (11) Ercoli, R.; Calderazzo, F.; Alberola, A. J. Am. Chem. Soc. 1960, 82, 2966. (12) Pruett, R. L.; Wyman, J. E. Chem. Ind. (London) 1960, 119. (13) Calderazzo, F.; Pampaloni, G.; Pelizzi, G. J. Organomet. Chem. 1982, 233, C41. Q


Organometallics

Review

(35) Belli Dell’Amico, D.; Calderazzo, F.; Labella, L.; Marchetti, F.; Pampaloni, G. Chem. Rev. 2003, 103, 3857. (36) (a) Calderazzo, F.; Pampaloni, G.; Vitali, D. Gazz. Chim. Ital. 1981, 111, 455. (b) Calderazzo, F.; Castellani, M.; Pampaloni, G.; Zanazzi, P. F. J. Chem. Soc., Dalton Trans. 1985, 1989. (37) Calderazzo, F. Inorg. Chem. 1964, 3, 810. (38) Calderazzo, F.; Invernizzi, R.; Marchetti, F.; Masi, F.; Moalli, A.; Pampaloni, G.; Rocchi, L. Gazz. Chim. Ital. 1993, 123, 53. (39) Calderazzo, F.; Pampaloni, G.; Rocchi, L.; Strähle, J.; Wurst, K. J. Organomet. Chem. 1991, 413, 91. (40) (a) Calderazzo, F.; Pampaloni, G.; Masi, F.; Moalli, A.; Invernizzi, R. (ENIChem ANIC S.p.A.). Process for Producing Vanadium Arenes. U.S. Patent 4,980,491, 1990. (b) Calderazzo, F.; Pampaloni, G.; Rocchi, L.; Moalli, A.; Masi, F.; Invernizzi, R. (to ENIMont ANIC S.r.l.). Improved Process for Producing Vanadium Arenes. U.S. Patent 5,093,508, 1992. (41) Calderazzo, F.; Pampaloni, G.; Masi, F.; Moalli, A.; Invernizzi, R. (to ENIChem ANIC S.p.A.). Catalyst Component for the Polymerization and the Copolymerization of Ethylene with Alpha-Olefins. U.S. Patent 4,987,111, 1991. (42) (a) Calderazzo, F.; De Benedetto, G. E.; Pampaloni, G.; Maichle-Moessmer, C.; Strähle, J.; Wurst, K. J. Organomet. Chem. 1993, 451, 73. (b) Calderazzo, F.; De Benedetto, G. E.; Englert, U.; Ferri, I.; Pampaloni, G.; Wagner, T. Z. Naturforsch. 1996, 51b, 506. (c) Calderazzo, F.; Englert, U.; Pampaloni, G.; Volpe, M. J. Organomet. Chem. 2005, 690, 3321. (43) (a) Calderazzo, F.; Pampaloni, G.; Rocchi, L.; Strähle, J.; Wurst, K. J. Organomet. Chem. 1991, 413, 91. (b) Calderazzo, F.; Pampaloni, G.; Rocchi, L.; Englert, U. Organometallics 1994, 13, 2592. (44) Calderazzo, F.; Ferri, I.; Pampaloni, G.; Englert, U.; Green, M. L. H. Organometallics 1997, 16, 3100. (45) Coord. Chem. Rev. 2010, 254, 5−6. A Tribute to Fausto Calderazzo on the Occasion of His 80th Birthday. (46) Calderazzo, F.; Poli, R.; Vitali, D. Inorg. Synth. 1985, 23, 32. (47) Belli Dell’Amico, D.; Calderazzo, F. Gazz. Chim. Ital. 1979, 109, 99. (48) Stoffelbach, F.; Saurenz, D.; Poli, R. Eur. J. Inorg. Chem. 2001, 2699. (49) Maria, S.; Poli, R. Inorg. Synth. 2014, 36, 16. (50) Bellachioma, G.; Cardaci, G.; Macchioni, A.; Reichenbach, G. Inorg. Chem. 1992, 31, 3018. (51) Bellachioma, G.; Cardaci, G.; Macchioni, A.; Reichenbach, G. Inorg. Chem. 1992, 31, 63. (52) (a) Bellachioma, G.; Cardaci, G.; Macchioni, A.; Reichenbach, G. Gazz. Chim. Ital. 1991, 121, 101. (b) Bellachioma, G.; Cardaci, G.; Macchioni, A.; Reichenbach, G. J. Organomet. Chem. 1992, 427, C37. (53) Macchioni, A. Chem. Rev. 2005, 105, 2039. (54) (a) Bellachioma, G.; Cardaci, G.; Macchioni, A.; Reichenbach, G.; Terenzi, S. Organometallics 1996, 15, 4349. (b) Macchioni, A.; Bellachioma, G.; Cardaci, G.; Gramlich, V.; Rüegger, H.; Terenzi, S.; Venanzi, L. M. Organometallics 1997, 16, 2139. (55) Macchioni, A. Eur. J. Inorg. Chem. 2003, 195. (56) Wender, I., Pino, P., Eds. Organic Synthesis via Metal Carbonyls; Wiley: New York, 1968; Vol. 1. (57) Ercoli, R.; Calderazzo, F.; Alberola, A. J. Am. Chem. Soc. 1960, 82, 107. (58) Calderazzo, F.; Frediani, S.; James, B. R.; Pampaloni, G.; Reimer, K. J.; Sams, J. R.; Serra, A. M.; Vitali, D. Inorg.Chem. 1982, 21, 2302. (59) Calderazzo, F.; Marchetti, F.; Pampaloni, G.; Hiller, W.; Antropiusová, H.; Mach, K. Chem. Ber. 1989, 122, 2229. (60) J. Organomet. Chem. 2000, 593−594. (61) Moiseev, I. I.; Stromnova, T. A.; Vargaftik, M. N.; Mazo, G. J.; Kuz’mina, L. G.; Struchkov, Y. T. J. Chem. Soc., Chem. Commun. 1978, 27. (62) Moiseeva, N. I.; Gekhman, A. E.; Moiseev, I. I. Gazz. Chim. Ital. 1992, 122, 187.

R


Fausto Calderazzo: Pioneer in Mechanistic Organometallic Chemistry

Recommend Documents