Infrared Photodissociation Spectroscopic and Theoretical Study of

Subscriber access provided by CORNELL UNIVERSITY LIBRARY

Article

Infrared Photodissociation Spectroscopic and Theoretical Study of Heteronuclear Transition Metal Carbonyl Cluster Cations in the Gas Phase Hui Qu, Fanchen Kong, Guanjun Wang, and Mingfei Zhou J. Phys. Chem. A, Just Accepted Manuscript • DOI: 10.1021/acs.jpca.6b08310 • Publication Date (Web): 29 Aug 2016 Downloaded from http://pubs.acs.org on September 4, 2016

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

The Journal of Physical Chemistry A is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

The Journal of Physical Chemistry

Infrared Photodissociation Spectroscopic and Theoretical Study of Heteronuclear Transition Metal Carbonyl Cluster Cations in the Gas Phase Hui Qu, Fanchen Kong, Guanjun Wang, Mingfei Zhou* Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysts and Innovative Materials, Fudan University, Shanghai 200433, China. E-mail: [email protected] Abstract Heteronuclear transition metal carbonyl cluster cations FeM(CO) 8+ (M=Co, Ni and Cu) and MCu(CO)7+ (M=Co and Ni) are produced via a laser vaporization supersonic cluster ion source in the gas phase, which are each mass-selected and studied by infrared photodissociation spectroscopy in the carbonyl stretching frequency region. Their geometric and electronic structures are established by comparison of the experimental spectra with those derived from density functional theoretical calculations. The FeM(CO)8+ (M = Co, Ni, Cu) complexes are determined to have eclipsed (CO)5Fe-M(CO)3+ structures, while the MCu(CO)7+ (M = Co, Ni) ions are characterized to have staggered (CO)4M-Cu(CO)3+ structures. Natural bonding orbital analysis indicate that the positive charge is mainly distributed on the M(CO) 3 fragment; The metal-metal interaction involves an -type (OC)4,5MM(CO)3+ dative bonding.

1

ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 28

Introduction Transition metal carbonyl cluster complexes play an important role in organometallic chemistry and catalysis, which can also serve as appropriate models in understanding metal-metal and metal-ligand bonding.1-4 The direct interactions between different transition metals have caught an upsurge of interest for many years.5,6 The synergy effects of two or more different transition metals in the chemical processes are expected to be the reason of high catalytic performance for heteronuclear transition metal complexes.7 There have been voluminous reports on heteronuclear transition metal carbonyl complexes. 8-12 In order to stabilize the hetero metal-metal bond, carbonyls can act as bridging ligands, which are divided into different categories, including but not limited to bridging and semi-bridging.7 Previous studies on heteronuclear transition metal carbonyls have focused mainly on the neutral complexes. Charged complexes have received much less attention. The electron density distribution in FeCo(CO)8- containing a semibridging carbonyl was determined through experimental X-ray diffraction and quantum chemical computations.13 The metal-metal interaction in FeCo(CO)8- was also studied using the interacting quantum atoms approach. 14 A delocalized covalent bond is found to occur, involving the metals and the carbonyls, and the semi-bridged carbonyl provided more stability than bridged and terminal carbonyls, but the global stability mainly originates from the Coulombic attraction between the metals and the oxygens.14 Photoelectron velocity-map imaging and theoretical studies of heteronuclear metal carbonyls CuNi(CO)n- (n = 2-4) indicate that the carbonyl groups are preferentially bonded to the nickel atom. When the nickel center satisfies the 18-electron configuration, the copper atom starts to adsorb additional CO molecules. 15 Heteronuclear iron−copper carbonyl cluster anions 2


Page 3 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


CuFe(CO)n- (n=4-7) have been studied by infrared photodissociation spectroscopy. 16 These cluster anions are characterized to have (OC) 4Fe−Cu(CO)n−4 structures, each involving a C3v symmetry Fe(CO)4- building block with the iron center possessing the most favored 18-electron configuration. Recently, infrared photodissociation spectroscopy has been successfully employed in studying homonuclear transition metal carbonyl cation complexes in the gas phase.17-24 However, there is no spectroscopic report on hetero dinuclear transition carbonyl cation complexes in the gas phase. In the present paper, heteronuclear carbonyl cluster cations in the form of FeM(CO)8+ (M=Co, Ni and Cu) and MCu(CO)7+ (M=Co and Ni) are produced in the gas phase. The cations are each mass-selected and studied by infrared photodissociation spectroscopy. The geometric and electronic structures are assigned by comparison of the experimental spectra with simulated spectra derived from density functional calculations. Experimental and Computational Methods The infrared photodissociation spectra of the heteronuclear transition metal carbonyl cluster cations were measured using a collinear tandem time-of-flight mass spectrometer. The experimental apparatus has been described in detail previously.25,26 The cations were produced in a Smalley-type laser vaporization supersonic cluster ion source using a mixed metal target, which was prepared by pressing the mixtures of metal powders. The 1064 nm fundamental of a Nd:YAG laser (Continuum, Minilite II) was used to vaporize the rotating metal target. The laser beam with 10-20 mJ/pulse is focused by a lens with a focal length of 300 mm. The hetero-dinuclear transition metal carbonyl complexes were produced from the laser vaporization process in expansions of helium gas seeded with 10% CO using a pulsed valve at about 0.8 MPa backing pressure. After free expansion, the cation complexes were skimmed and 3



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 28

analysed using a Wiley-McLaren time-of-flight mass spectrometer. The cations of interest were each mass selected and decelerated into the extraction region of a second collinear time-of-flight mass spectrometer, where they were dissociated by a tunable IR laser. The fragment and parent cations were reaccelerated and mass analysed by the second time-of-flight mass spectrometer. The fragment and parent ions were detected with a dual microchannel plate detector. The mass signals were amplified with a broadband amplifier and digitized and transferred to a computer. Infrared photodissociation spectra were obtained by monitoring the relative yield of fragment ions as a function of the dissociation IR laser wavelength. Typical spectra were recorded by scanning the dissociation laser in steps of 2 cm-1 and averaging over 300 laser shots at each wavelength. The tunable infrared source is generated by a KTP/KTA/AgGaSe2 optical parametric oscillator/amplifier system (OPO/OPA, Laser Vision) pumped by a Continuum Powerlite 8000 Nd:YAG laser. The laser pulse energies range from 0.6-1.0 mJ per pulse in the range of 1600–2200 cm-1. The infrared laser is loosely focused by a CaF2 lens. The wavenumber of the OPO laser is calibrated by a photoacoustic spectrum of CO gas. In order to verify the assignments of the experimentally observed vibrational spectra, density functional theory (DFT) calculations were performed with the Gaussian 09 program. 27 Geometry optimizations without symmetry constraints were carried out using the B3LYP functional28,29 with the 6-311+G(d) basis sets for all atoms.30,31 Harmonic vibrational frequencies were calculated at the B3LYP level and are scaled by a factor of 0.97 according to previous report.32,33 The zero-point energies were derived. Results and Discussion The mass spectra of carbonyl cluster cations produced by the laser vaporization supersonic 4


Page 5 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


cluster ion source depend strongly on the parameters of the ion source such as vaporization laser power, He and carbon monoxide stagnation pressures, and timing. In the present study, the mass spectra are recorded at the experimental conditions that favor the formation of saturate coordinated carbonyl species. A typical mass spectrum of carbonyl cations produced by laser vaporization of a mixed Fe/Co target in the m/z range of 170-400 is shown in Figure 1. The spectrum is composed of strong mass peaks of mononuclear carbonyl cations Fe(CO) 5+ and Co(CO)5+ as well as dinuclear carbonyl cations Fe2(CO)n+ (n=8 and 9), Co2(CO)8+ and FeCo(CO)8+ as labeled in the spectrum. The peak intensities of iron carbonyl cations are always larger than those of the cobalt carbonyl cations. The relative intensities do not represent the proportion of the two metals in the mixture, as the stability of their carbonyl cations are not the same. The preferred formation of iron carbonyls can be rationalized that the iron- carbonyl bond strength is larger than that of cobalt. 34,35 The mass spectra with the other mixed targets are shown in Figures S1-S4 of Supporting Information. Similar to the Fe/Co spectrum, dinuclear carbonyl cations in the form of FeNi(CO)8+, FeCu(CO)8+, CoCu(CO)7+ and NiCu(CO)7+ are observed to be the most intense heteronuclear carbonyl cation peaks in the mass spectra. In each spectrum, the isotopic splitting of iron, nickel and copper can clearly be resolved with their relative intensities in general matching the natural abundance isotopic distributions. The heteronuclear carbonyl cluster cations including FeM(CO)8+ (M=Co, Ni and Cu) and MCu(CO)7+ (M=Co and Ni) are each mass-selected and subjected to infrared photodissociation. For each cluster, only the mass peak corresponding to the most abundance isotopomer is selected. We were not able to obtain the infrared spectrum of CoNi(CO) 7+, as it is overlapped by the 59Ni58Ni(CO)7+ cation in the mass spectrum. When the IR laser is on resonance with the 5



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 6 of 28

CO stretching of the cluster cations, photofragmentation takes place via the loss of one CO ligand. FeCo(CO)8+ The infrared photodissociation spectrum of FeCo(CO)8+ is shown in Figure 2. The infrared spectrum consists of five bands centered at 2072, 2092, 2122, 2144 and 2172 cm-1 (Table 1). The dissociation efficiency is about 8% at 2122 cm-1. These bands all are above 2000 cm-1, indicating that they are originated from terminally bonded carbonyl ligands. Geometric optimizations were performed on various possible structures for FeCo(CO)8+. The three most stable structures are shown in Figure 2. All structures have triplet ground state without symmetry. The first two isomers each has five carbonyls bonded on the iron center and three carbonyls on the cobalt center. The first structure with almost C s symmetry involving two eclipsed carbonyl ligands (eclipsed structure a) is the most stable one among these isomers. The second structure (b) with a staggered carbonyl arrangement is 9.2 kcal/mol higher in energy than the most stable eclipsed structure (a). The third isomer (c) with four carbonyls on both metal centers is 10.5 kcal/mol higher in energy than the most stable structure. The simulated spectra are compared with the experimental spectrum in Figure 2. Apparently, the simulated spectrum of structure (a) matches the experimental one better than that of the other structures. Therefore, the experimentally observed FeCo(CO) 8+ cation can be confidentially assigned to the eclipsed structure (a), which is quite similar to the most stable structure of Fe2(CO)8+,20 but is very different from that of Co2(CO)8+.21 The Co2(CO)8+ cation has been characterized to involve a bridging CO ligand.21 The FeCo(CO)8+ cation without symmetry has eight CO stretching modes, which are IR active. Only five bands are observed due to band overlap. The 2072 cm-1 band can be assigned to the nearly degenerate antisymmetric stretching modes of the 6


Page 7 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


equatorial CO ligands of the Fe(CO)5 fragment. The 2092 cm-1 band is mainly the axial CO ligand of the Fe(CO)5 fragment. The 2122 cm-1 band is attributed to the nearly degenerate antisymmetric stretching modes of the Co(CO)3 fragment. The remaining two bands are due to the symmetric stretching modes. FeNi(CO)8+ The infrared photodissociation spectrum of FeNi(CO)8+ is shown in Figure 3. Five bands centered at 2066, 2092, 2108, 2141 and 2174 cm-1 are observed, which are originated from terminally bonded carbonyl ligands. The 2140 cm-1 band is asymmetric, suggesting the involvement of more than one vibrations. The parent ions can be depleted by about 10% via the loss of one CO ligand at 2140 cm-1. Three stationary points were found which are close in energy, as shown in Figure 3. The first two structures each has five carbonyls on the iron center and three carbonyls on the nickel center. The first structure (a) with an eclipsed conformation is almost isoenergetic with the second structure with a staggered CO arrangement (the eclipsed structure is 0.1 kcal/mol less stable than the staggered structure). The third structure (c) has a C2v geometry with evenly distributed carbonyl ligands. This structure is 0.9 kcal/mol higher in energy than the first structure. As shown in Figure 3, the simulated vibrational spectrum of the first structure matches the experimental spectrum better than those of the other two structures, therefore, the experimentally observed FeNi(CO)8+ cation can be assigned to the eclipsed (OC)5Fe-Ni(CO)3+ structure. Based on theoretical calculations, the 2066, 2092, and 2108 cm-1 bands are assigned to the carbonyl stretching vibrations of the Fe(CO)5 fragment (Table 1). FeCu(CO)8+ The infrared spectrum of FeCu(CO)8+ is shown in Figure 4, which consists of five well-resolved bands centered at 2064, 2100, 2142, 2172 and 2188 cm-1. The parent ion has 7



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 28

a maximum depletion of about 20% at the dissociation IR laser wavenumber of 2064 cm-1. Only one stable structure was located from geometric optimization starting with various possible structures. As shown in Figure 4, it has an eclipsed (CO)5Fe-Cu(CO)3 structure with a closed-shell singlet ground state. The simulated vibrational spectrum is in perfect agreement with the experimental one. The 2064, 2100 and 2142 cm-1 bands are mainly originated from the five carbonyls on the iron center, while the 2172 and 2188 cm-1 bands are carbonyl stretching vibrations of the Cu(CO)3 fragment. CoCu(CO)7+ The infrared spectrum of CoCu(CO)7+ (Figure 5) consists of six well-resolved bands at 2046, 2070, 2102, 2148, 2180 and 2196 cm-1, which are originated from terminally bonded carbonyl ligands. The cation was predicted to have a staggered (CO)4Co-Cu(CO)3 structure without symmetry. The eclipsed structure is not a minimum. The simulated vibrational spectrum is in perfect agreement with the experimental one. The 2046, 2070, 2102 and 2148 cm-1 bands are assigned to the CO stretching vibrations of the Co(CO)4 fragment, while the 2180 and 2196 cm-1 bands are attributed to the antisymmetric and symmetric stretching modes of the Cu(CO)3 fragment. NiCu(CO)7+ The infrared spectrum of NiCu(CO)7+ has five bands at 2086, 2120, 2166, 2194 and 2212 cm-1. Only one stable structure was found starting with different structures. It has a closed-shell singlet ground state with a staggered (CO)4Ni-Cu(CO)3 structure. The 2086, 2120 and 2166 cm-1 bands belong to the carbonyl stretching vibrations of the Ni(CO)4 subunit. The 2086 and 2120 cm-1 bands are due to the doubly degenerate antisymmetric stretching and the symmetric stretching modes of the three equatorial CO ligands of the C3v Ni(CO)4 fragment. The 2166 cm-1 band is attributed to the vibration of the axial CO ligand of the Ni(CO)4 8


Page 9 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


fragment. The 2194 and 2212 cm-1 bands are attributed to the antisymmetric and symmetric stretching modes of the Cu(CO)3 group. Discussion On the basis of above discussion, the three FeM(CO) 8+ (M=Co, Ni and Cu) cations are determined to have metal-metal bonded (OC)5Fe-M(CO)3+ structures each involving a square pyramid Fe(CO)5 subunit with C4v symmetry. Natural population analysis indicates that the positive charge and the unpaired electrons are largely located on the M(CO)3 subunit (Table 2). Therefore, the FeM(CO)8+ cations can be viewed as being formed via the interactions between the neutral Fe(CO)5 fragment and the M(CO)3+ fragment. The Fe(CO)5 neutral has been determined to be building blocks for the homoleptic Fe2(CO)8+, Fe2(CO)9+ and Fe3(CO)12+ cluster cations.20 As shown in Figure 7, the HOMO of square pyramid Fe(CO)5 is primarily an iron 3d orbital in character that comprises some metal to CO  back bonding. It serves as the primary donation orbital, which can interact with an unoccupied  type molecular orbital of the M(CO)3+ groups. The C3v symmetry M(CO)3+ fragments have triplet, doublet and singlet ground states for Co, Ni and Cu, respectively. The singly occupied orbitals (SOMO) of Co(CO)3+ and Ni(CO)3+ are metal-based 3d orbitals, while the lowest unoccupied molecular orbital (LUMO) is predominantly metal-based sp(σ) hybrid orbital that comprises notable metal to CO backdonation. This LUMO serves as the primary acceptor orbital for donation from the Fe(CO)5 fragment (Figure 7). Accordingly, the Fe–M bond in these cluster cations can roughly be regarded as a weak -type dative single bond. The 18-electron Fe(CO)5 neutral serves as a two-electron donor in these cation complexes, with the Co, Ni and Cu centers having 16, 17 and 18 valence electrons, respectively. The Fe-M bond distance is predicted to be 2.643, 2.735 and 2.793 Å, increases monotonically from Co to Cu. In concert, the bond 9



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 28

dissociation energy decreases from 24.9 kcal/mol for Co, to 15.0 kcal/mol for Ni and to 11.4 kcal/mol for Cu (Table 2). The CoCu(CO)7+ and NiCu(CO)7+ cations are characterized to have metal-metal bonded (OC)4M-Cu(CO)3+ structures with the positive charge largely located on the Cu(CO) 3 moiety (Table 2). Thus, both cations can be regarded as being formed via the interactions between the M(CO)4 neutral fragment and the Cu(CO)3+ cation fragment. The NiCu(CO)7+ cation has nearly C3 symmetry involving a C3v symmetry Ni(CO)4 neutral fragment and a C3v symmetry Cu(CO)3+ fragment. The Ni(CO)4 neutral has a closed-shell singlet ground state with the nickel center having the most favorable 18-electron configuration, while the copper center in Cu(CO)3+ has only 16 valence electrons. The bonding interactions between Ni(CO)4 and Cu(CO)3+ come mainly from the donation of the doubly occupied HOMO orbital of Ni(CO)4 to the LUMO orbital of Cu(CO)3+. As shown in Figure 7, the HOMO of Ni(CO)4 is primarily a hybrid of the Ni 3dz2, 4s, and 4p orbitals, which comprise notable metal to the equatorial CO ligands  backdonation. The resulting Ni-Cu  bonding orbital is doubly occupied, and thus, the Ni-Cu bond can be regarded as a formal single bond. In this regard, the NiCu(CO)7+ cation has a completed coordination sphere with both the nickel and copper centers having the 18-electron configurations. The bonding in CoCu(CO)7+ is slightly different from that of NiCu(CO)7+. The Co(CO)4 neutral is one electron less than Ni(CO)4 and has a doublet ground state with C3v symmetry.36 If CoCu(CO)7+ exhibits the same bonding situation as NiCu(CO)7+, the bonding interaction between the C3v Co(CO)4 fragment and the C3v Cu(CO)3+ fragment should result in only a one-electron Co-Cu bond. In fact, the CoCu(CO)7+ cation is determined to have Cs symmetry involving a C2v symmetry neutral Co(CO)4 fragment. As shown in Figure 10


Page 11 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


7, the highest doubly occupied orbital of C2v symmetry Co(CO)4 is involved in bonding with Cu(CO)3+ in forming a formal Co-Cu dative single bond. Although the C2v structure Co(CO)4 is predicted to be 5.7 kcal/mol less stable than the C3v structure, Co(CO)4 binds preferentially through the C2v structure in forming a strongly bonded CoCu(CO)7+ cation complex. The metal-carbonyl bonding can be explained using the Dewar-Chatt-Duncanson (DCD) model, which involves a combination of -type donation from the CO HOMO (5) into empty -type orbitals on the metal, and  back donation from the filled metal d orbitals into the antibonding 2* orbitals of CO.2,17,36 Electrostatic polarization also plays important role in metal carbonyl cation complexes.37-39 The effects of these bonding interactions on the vibrational frequencies of CO ligands are well documented. Both the  donation and charge-induced polarization lead to a blue shift in the CO stretching frequency, whereas  back-bonding weakens the C-O bond leading to a red-shift. As listed in Table 1, the vibrational frequencies mainly originated from the M(CO) 3 fragments in FeM(CO)8+ (M=Co, Ni and Cu) and MCu(CO)7+ (M=Co and Ni) are blue-shifted compared to the isolated CO stretching (2143 cm-1). These frequencies are only slightly lower than the corresponding vibrations of isolated M(CO)3+ cations, but are significantly blue-shifted from those of isolated neutral M(CO)3 complexes.36,40,41 In concert, the vibrational frequencies of the Fe(CO) 5 and M(CO)4 (M=Co, Ni) fragments are slightly blue-shifted from those in isolated Fe(CO)5 and M(CO)4 (M=Co, Ni) neutral complexes.36 These observations are in accord with the bonding analysis that the charge is mainly distributed on the M(CO)3 fragments. The present study together with recent investigations on other dinuclear transition metal carbonyl complexes provide some valuable information on the structure and bonding of 11



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 28

transition metal carbonyl ion complexes. These results suggest that metal−metal multiple bonding is not favorable in the coordination saturated or near saturated dinuclear carbonyl ion complexes.18-24,42 When the dinuclear metal carbonyl ion complexes have odd number of electrons that are not able to satisfy the 18-electron configuration of both metal centers, the complexes prefer to form asymmetric structures to satisfy the 18-electron configuration of one metal center. In this regard, the Fe(CO)5 neutral fragment is determined to be a common building block in both homonuclear and heteronuclear cation complexes such as Fe 2(CO)8+, Fe2(CO)9+ and the FeM(CO)8+ (M=Co, Ni and Cu) cation complexes reported in this study;20 while the Fe(CO)4 - anion is a common building block in the homonuclear and heteronuclear anion complexes.16,42 These building blocks exhibit high stability due to strong metal-CO bonding. Conclusions Hetero dinuclear transition metal carbonyl cation complexes in the form of FeM(CO)8+ (M=Co, Ni and Cu) and MCu(CO)7+ (M=Co and Ni) are produced in the gas phase via pulsed laser vaporization supersonic expansion. These cations are observed to be the most intense heteronuclear carbonyl cation species in the mass spectra. The cations are each mass-selected and their infrared spectra are measured by infrared photodissociation spectroscopy in the carbonyl stretching frequency region. The geometric and electronic structures are assigned by comparison of the experimental spectra with simulated spectra derived from density functional calculations at the B3LYP/6-311+G(d) level. The experimentally observed FeM′(CO)8+ (M′ = Co, Ni, Cu) complexes are determined to have eclipsed (CO) 5Fe-M(CO)3 structures, which can be regarded as being formed through the interactions between a Fe(CO) 5 fragment and a 12


Page 13 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


M′(CO)3+ fragment. While the MCu(CO)7+ (M = Co, Ni) ions are determined to have staggered (CO)4M-Cu(CO)3 structures, which The FeM(CO)8+ (M = Co, Ni, Cu) complexes are determined to have eclipsed (CO)5Fe-M(CO)3+ structures, while the MCu(CO)7+ (M = Co, Ni) ions are characterized to have staggered (CO)4M-Cu(CO)3+ structures. Natural bonding orbital analysis indicate that the positive charge is mainly distributed on the M(CO) 3 fragment, therefore, these complexes can be regarded as being formed through the interactions between a neutral Fe(CO)5 or M(CO)4 (M=Co, Ni) fragment and a M(CO)3+ (M=Co, Ni, Cu) fragment. The metal-metal interaction involves an -type (OC)4,5MM(CO)3+ dative bonding. Acknowledgment We gratefully acknowledge financial support from National Natural Science Foundation (Grant No. 21433005) and Ministry of Science and Technology of China (2013CB834603 and 2012YQ220113-3). Supporting Information The mass spectra, calculated geometries, vibrational frequencies and intensities, and complete ref. 27. This material is available free of charge via the Internet at http://pubs.acs.org. References (1) Pauling, L. C. Metal-Metal Bond Lengths in Complexes of Transition Metals. Proc. Natl. Acad. Sci. USA, 1976, 73, 4290-4293. (2) Frenking, G.; Fröhlich, N. The Nature of the Bonding in Transition-Metal Compounds. Chem. Rev. 2000, 100, 717–774. (3) Hughes, A. K.; Wade, K. Metal–Metal and Metal–Ligand Bond Strengths in Metal Carbonyl Clusters. Coord. Chem. Rev. 2000, 197, 191–229. (4) Macchi, P.; Sironi, A. Chemical Bonding in Transition Metal Carbonyl Clusters: 13



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 28

Complementary Analysis of Theoretical and Experimental Electron Densities. Coord. Chem. Rev. 2003, 238-239, 383-412. (5) Sappa, E; Tiripicchio, A; Braunstein, P. Selective Metal-Ligand Interactions in Heterometallic Transition-Metal Clusters. Coord. Chem. Rev. 1985, 65, 219-284. (6) Eisenhart, R. J.; Clouston, L. J.; Lu, C. C. Conﬁguring Bonds Between First-Row Transition Metals. Acc. Chem. Res. 2015, 48, 2885−2894. (7) Komiya, S. Synthesis, Reaction and Catalysis of Heterodinuclear Organoplatinum or Palladium Complexes Having M–M' and M–C Bonds Without M–M' Connecting Ligand. Coord. Chem. Rev. 2012, 256, 556-573. (8) Bruce, M. I. Organometallic Cluster Complexes of the Transition Metals. In Organometallic Chemistry. Abel, E. W. Royal Society of Chemistry, 1996, Vol. 25, pp 203-211. (9) Humphrey, M. G.; Cifuentes, M. P. Organo-Transition Metal Cluster Complexes. In Organometallic Chemistry. Green, M. Royal Society of Chemistry, 2005, Vol. 32, pp 214-263. (10) Sappa, E; Tiripicchio, A; Braunstein, P. Alkyne-Substituted Homo- and Heterometallic Carbonyl Clusters of the Iron, Cobalt, and Nickel Triads. Chem. Rev. 1983, 83, 203-239. (11) Ervin, K. M. Metal-Ligand Interactions: Gas-Phase Transition Metal Cluster Carbonyls. Int. Rev. Phys. Chem. 2001, 20, 127-164. (12) Housecroft, C. E. Metal−Metal Bonded Carbonyl Dimers and Clusters. Oxford University Press: Oxford, U.K. 1996. (13) Macchi, P.; Garlaschelli, L.; Sironi, A. Electron Density of Semi-Bridging Carbonyls. 14


Page 15 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Metamorphosis of CO Ligands Observed via Experimental and Theoretical Investigations on [FeCo(CO)8]-. J. Am. Chem. Soc. 2002, 124, 14173-14184. (14) Tiana, D.; Francisco, E.; Macchi, P.; Sironi, A.; Martin P. A. An Interacting Quantum Atoms Analysis of the Metal−Metal Bond in [M2(CO)8]n Systems. J. Phys. Chem. A. 2015, 119, 2153−2160. (15) Liu, Z. L.; Xie, H.; Qin, Z. B.; Fan, H. J.; Tang, Z. C. Structural Evolution of Homoleptic Heterodinuclear

Copper-Nickel

Carbonyl

Anions

Revealed

Using

Photoelectron

Velocity-Map Imaging. Inorg. Chem. 2014, 53, 10909-10916. (16) Zhang, N.; Luo, M. B.; Chi, C. X.; Wang, G. J.; Cui, J. M.; Zhou, M. F. Infrared Photodissociation Spectroscopy of Mass-Selected Heteronuclear Iron−Copper Carbonyl Cluster Anions in the Gas Phase. J. Phys. Chem. A. 2015, 119, 4142−4150. (17) Ricks, A. M.; Reed, Z. E.; Duncan, M. A. Infrared Spectroscopy of Mass-Selected Metal Carbonyl Cations. J. Mol. Spectrosc. 2011, 266, 63-74. (18) Zhou, X. J.; Cui J. M.; Li Z. H.; Wang, G. J.; Liu, Z. P.; Zhou, M. F. Carbonyl Bonding on Oxophilic Metal Centers: Infrared Photodissociation Spectroscopy of Mononuclear and Dinuclear Titanium Carbonyl Cation Complexes. J. Phys. Chem. A. 2013, 117, 1514-1521. (19) Zhou, X. J.; Cui, J. M.; Li, Z. H.; Wang, G. J.; Zhou, M. F. Infrared Photodissociation Spectroscopic and Theoretical Study of Homoleptic Dinuclear Chromium Carbonyl Cluster Cations with a Linear Bridging Carbonyl Group. J. Phys. Chem. A. 2012, 116, 12349-12356. (20) Wang, G. J.; Cui, J. M.; Chi, C. X.; Zhou, X. J.; Li, Z. H.; Xing, X. P.; Zhou, M. F. Bonding in Homoleptic Iron Carbonyl Cluster Cations: A Combined Infrared 15



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 28

Photodissociation Spectroscopic and Theoretical Study. Chem. Sci. 2012, 3, 3272-3279. (21) Cui, J. M.; Zhou, X. J.; Wang, G. J.; Chi, C. X.; Li, Z. H.; Zhou, M. F. Infrared Photodissociation Spectroscopy of Mass Selected Homoleptic Cobalt Carbonyl Cluster Cations in the Gas Phase. J. Phys. Chem. A. 2014, 118, 2719-2727. (22) Cui, J. M.; Wang, G. J.; Zhou, X. J.; Chi, C. X.; Li, Z. H.; Liu, Z. P.; Zhou, M. F. Infrared Photodissociation Spectra of Mass Selected Homoleptic Nickel Carbonyl Cluster Cations in the Gas Phase. Phys. Chem. Chem. Phys. 2013, 25, 10224-10232. (23) Cui, J. M.; Zhou, X. J.; Wang, G. J.; Chi, C. X.; Liu, Z. P.; Zhou, M. F. Infrared Photodissociation Spectroscopy of Mass Selected Homoleptic Copper Carbonyl Cluster Cations in the Gas Phase. J. Phys. Chem. A 2013, 117, 7810-7817. (24) Cui, J. M.; Xing, X. P.; Chi, C. X.; Wang, G. J.; Liu, Z. P.; Zhou, M. F. Infrared Photodissociation Spectra of Mass-Selected Homoleptic Dinuclear Palladium Carbonyl Cluster Cations in the Gas Phase. Chin. J. Chem. 2012, 30, 2131-2137. (25) Wang, G. J.; Chi, C. X.; Cui, J. M.; Xing, X. P.; Zhou, M. F. Infrared Photodissociation Spectroscopy of Mononuclear Iron Carbonyl Anions. J. Phys. Chem. A 2012, 116, 2484-2489. (26) Wang, G. J.; Chi, C. X.; Xing, X. P.; Ding, C. F.; Zhou, M. F. A Collinear Tandem Time-of-Flight Mass Spectrometer for Infrared Photodissociation Spectroscopy of Mass-Selected Ions. Sci. China Chem. 2014, 57, 172-177. (27) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, G.; Scalmani, J. R.; Barone, V.; Mennucci, B.; Petersson, G. A.; et al. Gaussian 09, revision A.2; Gaussian, Inc.: Wallingford, CT, 2009. 16


Page 17 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(28) Becke, A. D. Density-Functional Exchange-Energy Approximation with Correct Asymptotic Behavior. Phys. Rev. A. 1988, 38, 3098-3100. (29) Lee, C. T.; Yang, W. T.; Parr, R. G. Development of the Colle-Salvetti Correlation-Energy Formula into a Functional of the Electron-Density. J. Phys. Chem. 1988, 37, 785-789. (30) McLean, A. D.; Chandler, G. S. Contracted Gaussian Basis Sets for Molecular Calculations. I. Second Row Atoms, Z=11–18. J. Chem. Phys. 1980, 72, 5639-5648. (31) Krishnan, R.; Binkley, J. S.; Seeger, R.; Pople, J. A. Self-Consistent Molecular Orbital Methods. XX. A Basis Set for Correlated Wave Functions. J. Chem. Phys. 1980, 72, 650-654. (32) Sinha, P.; Boesch, S. E.; Gu, C.; Wheeler, R. A.; Wilson, A. K. Harmonic Vibrational Frequencies: Scaling Factors for HF, B3LYP, and MP2 Methods in Combination with Correlation Consistent Basis Sets. J. Phys. Chem. A. 2004, 108, 9213-9217. (33) Assefa, M. K.; Devera, J. L.; Brathwaite, A. D.; Mosley, J. D.; Duncan, M. A Vibrational Scaling Factors for Transition Metal Carbonyls. Chem. Phys. Lett. 2015, 640, 175-179. (34) Goebel, S.; Haynes, C. L.; Khan, F. A.; Armentrout, P. B. Collision-Induced Dissociation Studies of Co(CO)x+, x=1-5-Sequential Bond Energies and the Heat of Formation of Co(CO)4. J. Am. Chem. Soc. 1995, 117, 6994-7002. (35) Schultz, R. H.; Crellin, K. C.; Armentrout, P. B. Sequential Bond Energies of Fe(CO)x+ (x=1-5)-Systematic Effects on Collision Induced Disssociation Measurements. J. Am. Chem. Soc. 1991, 113, 8590–8601. (36) Zhou, M. F.; Andrews, L.; Bauschlicher, C. W. Jr. Spectroscopic and Theoretical Investigations of Vibrational Frequencies in Binary Unsaturated Transition-Metal Carbonyl 17



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 28

Cations, Neutrals, and Anions. Chem. Rev. 2001, 101, 1931-1961. (37) Goldman, A. S.; Krogh-Jespersen, K. Why Do Cationic Carbon Monoxide Complexes Have High CO Stretching Force Constants and Short CO Bonds? Electrostatic Effects, Not σ Bonding. J. Am. Chem. Soc. 1996, 118, 12159−12166. (38) Lupinetti, A. J.; Frenking, G.; Strauss, S. H. Nonclassical Metal Carbonyls. Angew. Chem. Int. Ed. 1998, 37, 2113−2116. (39) Chen, M. H.; Zhang, Q. N.; Zhou, M. F.; Andrada, D. M.; Frenking, G. Carbon Monoxide Bonding With BeO and BeCO3: Surprisingly High CO Stretching Frequency of OCBeCO3. Angew. Chem, Int. Ed. 2015, 54, 124-128. (40) Ricks, A. M.; Bakker, J. M.; Douberly, G. E.; Duncan, M. A. Infrared Spectroscopy and Structures of Cobalt Carbonyl Cations, Co(CO) n+(n=1−9). J. Phys. Chem. A 2009, 113, 4701-4708. (41) Brathwaite, A. D.; Reed, Z. D.; Duncan, M. A. Infrared Photodissociation Spectroscopy of Copper Carbonyl Cations. J. Phys. Chem. A 2011, 115, 10461-10469. (42) Chi, C. X.; Cui, J. M.; Li, Z. H.; Xing, X. P.; Wang, G. J.; Zhou, M. F. Infrared Photodissociation Spectra of Mass Selected Homoleptic Dinuclear Iron Carbonyl Cluster Anions in the Gas Phase. Chem. Sci. 2012, 3, 1698−1706.

18


Page 19 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 1. Comparison of the Experimental Vibrational Frequencies (cm-1) of the MM(CO)n+ Complexes to The Calculated Ones at the B3LYP/6-311+G(d) Level (Scaled by a Factor of 0.97, the IR Intensities are Listed in Parentheses in km/mol). Complex Exptl. Calcd. 2072 2068 (881), 2071 (881), 2078 (11) 2092 2102 (177) + 2125 (712), 2126 (710) FeCo(CO)8 2122 2144 2136 (836) 2172 2169 (63) 2066 2053 (1049) 2092 2069 (32), 2078 (855) + FeNi(CO)8 2108 2099 (153) 2140 2131 (824), 2138 (725), 2149 (451) 2174 2177 (141) 2064 2060 (987), 2063 (1065), 2070 (75) 2100 2093 (187) + FeCu(CO)8 2142 2133 (716) 2172 2165 (444), 2166 (429) 2188 2188 (133) 2046 2044 (1174) 2070 2071 (159) 2102 2109 (464) CoCu(CO)7+ 2148 2138 (697) 2180 2170 (418), 2172 (376) 2196 2192 (134) 2086 2075 (790), 2075 (789) 2120 2105 (134) + NiCu(CO)7 2166 2151 (486) 2194 2182 (364), 2182 (364) 2212 2202 (104)

19



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Table 2. The M-M Bond Distances (in Angstroms), the Natural Charges and the Dissociation Energies (in kcal/mol, Dissociate to M(CO)4or5 + M(CO)3+, zero point energy corrected) of the MM(CO)n+ Complexes. M Represents the Metal with Smaller Atomic Number, While M is the Metal with Larger Atomic Number. Natural Charge NBO Group Charge M−M Complex De Distance M M(CO)4or5 M(CO)3 M -24.9 FeCo(CO)8+ 2.643 -2.214 -0.211 0.342 0.658 + -15.0 FeNi(CO)8 2.735 -2.180 -0.198 0.336 0.664 + -11.4 FeCu(CO)8 2.793 -2.182 -0.115 0.311 0.689 + -9.5 CoCu(CO)7 2.778 -1.051 -0.141 0.324 0.676 + -5.9 NiCu(CO)7 2.840 -1.141 -0.047 0.231 0.769

20


Page 20 of 28

Page 21 of 28

0.5 +

Fe(CO)5

0.4 +

Co(CO)5

Intensity

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


0.3

+

FeCo(CO)8 + Co2(CO)8 + Fe2(CO)8

0.2

+

Fe2(CO)9

0.1 +

Fe(CO)6

+

Co(CO)6

0.0 200

250

300

350

400

m/z

Figure 1. Mass spectrum of carbonyl cluster cation complexes formed from pulsed laser vaporization of an iron-cobalt mixed metal target in an expansion of helium seeded by carbon monoxide.

21



30 3

25

20

Intensity

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 28

(c) C1, A, E=10.5

3

(b) C1, A, E=9.2

15 3

10

(a) C1, A, E=0.0

5

0 1800

1900

2000

2100

Wavenumber / cm

2200

-1

Figure 2. The experimental (black) and simulated (red) vibrational spectra of the FeCo(CO)8+ cation complex in the carbonyl stretching frequency region. The simulated spectra are obtained from scaled harmonic vibrational frequencies and intensities for the three most stable structures calculated at the B3LYP/6-311+G(d) level.

22


Page 23 of 28

40

2

30

Intensity

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(c) C2v, A, E=0.9

2

20

(b) Cs, A, E=-0.1

2

10

(a) C1, A, E=0.0

0 1800

1900

2000

2100

Wavenumber / cm

2200

2300

-1

Figure 3. The experimental (black) and simulated (red) vibrational spectra of the FeNi(CO)8+ cation complex in the carbonyl stretching frequency region. The simulated spectra are obtained from scaled harmonic vibrational frequencies and intensities for the three most stable structures calculated at the B3LYP/6-311+G(d) level.

23



40

30

Intensity

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 28

20

10

0 1800

1900

2000

2100

Wavenumber / cm

2200

2300

-1

Figure 4. The experimental (black) and simulated (red) vibrational spectra of the FeCu(CO)8+ cation complex in the carbonyl stretching frequency region. The simulated spectrum is obtained from scaled harmonic vibrational frequencies and intensities for the most stable structure calculated at the B3LYP/6-311+G(d) level.

24


Page 25 of 28

20

15

Intensity

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


10

5

0 1800

1900

2000

2100

Wavenumber / cm

2200

2300

-1

Figure 5. The experimental (black) and simulated (red) vibrational spectra of the CoCu(CO)7+ complex in the carbonyl stretching frequency region. The simulated spectrum is obtained from scaled harmonic vibrational frequencies and intensities for the most stable structure calculated at the B3LYP/6-311+G(d) level.

25



10

8

6

Intensity

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 28

4

2

0 1800

1900

2000

2100

Wavenumber / cm

2200

2300

-1

Figure 6. The experimental (black) and simulated (red) vibrational spectra of the NiCu(CO)7+ cation complex in the carbonyl stretching frequency region. The simulated spectrum is obtained from scaled harmonic vibrational frequencies and intensities for the most stable structure calculated at the B3LYP/6-311+G(d) level.

26


Page 27 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60




+

Co(CO)3+ LUMO

Fe(CO)5 HOMO



+

Cu(CO)3+ LUMO

Co(CO)4 HOMO

CoCu(CO)7+ HOMO



+

Ni(CO)4 HOMO

FeCo(CO)8+ HOMO

Cu(CO)3+ LUMO

NiCu(CO)7+ HOMO

Figure 7. Plots of the pivotal molecule orbitals of the pairwise orbital interactions between Fe(CO)5 or M(CO)4 (M=Co , Ni) and the M(CO)3+ (M=Co, Ni, Cu) fragment in the FeM(CO)8+ and MCu(CO)7+ complexes.

27



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

TOC graphic

1800

1900

2000

2100

2200

2300

-1

Wavenumber / cm

28


Page 28 of 28

Infrared Photodissociation Spectroscopic and Theoretical Study of

Recommend Documents