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Dec 13, 2017 - ABSTRACT: The metalation of 1,2-bis(anilino)ethane with excess KH leads to the formation of the potassium complex. [(thf)3K2{1 ...
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Article Cite This: Organometallics XXXX, XXX, XXX−XXX

1,2-Bis(anilido)ethane Complexes of Calcium and Potassium: Synthesis, Structures, and Catalytic Activity Steffen Ziemann, Sven Krieck, Helmar Görls, and Matthias Westerhausen* Institute of Inorganic and Analytical Chemistry, Friedrich Schiller University Jena, Humboldtstraße 8, D-07743 Jena, Germany S Supporting Information *

ABSTRACT: The metalation of 1,2-bis(anilino)ethane with excess KH leads to the formation of the potassium complex [(thf)3K2{1,2-(PhN)2C2H4}] (1). Complex 1 quantitatively reacts with anhydrous CaI2 in THF yielding insoluble KI and dinuclear [(thf)5Ca2{1,2-(PhN)2C2H4}2] (2) after crystallization from a mixture of THF and hexane. Addition of N,N,N′,N′′,N′′′,N′′′-hexamethyltriethylenetetraamine (hmteta) yields [(hmteta)Ca{1,2-(PhN)2C2H4}] (3). The complexes 1 and 2 proved to be inactive as catalysts in hydroamination reactions of diphenylbutadiyne with secondary amines. However, a mixture of 1 and 2 (K:Ca ratio of 2:1) mediated the addition of N-methyl-aniline and 1,2-bis(anilino)ethane to one of the CC triple bonds of diphenylbutadiyne. Addition of 18-crown-6 ether (18C6) leads to the formation of the sparingly soluble potassium complex [{(18C6)K}2{1,2-(PhN)2C2H4}] (5) and the insoluble calcium complex [(18C6)Ca{1,2(PhN)2C2H4}] (6). The calciate-mediated hydroamination reaction is regiocontrolled, but E- and Z-isomeric addition products are observed, regardless of whether the reaction is performed at daylight or in the dark. If toluene is used as solvent for this sblock metal-mediated hydroamination catalysis, (Z,Z)-1,4,5,8,9,12-hexaphenyl-5,8-diazadodeca-3,9-diene-1,11-diyne (Z,Z-8) precipitates, allowing isolation and characterization of this isomer. In solution, this compound isomerizes upon irradiation yielding an equilibrium between (Z,Z)-, (E,Z)- and (E,E)-isomers. The determination of the crystal structures of (Z,Z)- and (E,E)-1,4,5,8,9,12-hexaphenyl-5,8-diazadodeca-3,9-diene-1,11-diyne unequivocally allows the assignment of the NMR parameters to specific isomers.

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INTRODUCTION Hydroamination reactions represent an atom-economic procedure to add N−H bonds to unsaturated organic compounds such as alkenes and alkynes (Scheme 1).1,2 However, this

groups), strong Lewis acidity, and highly heteropolar Ae−N bonds (comparable to alkali ions).3,5−7 The most beneficial alkaline earth metal (Ae) is calcium due to its global abundance and availability, nontoxicity, and inexpensiveness. Therefore, several research groups investigated the suitability of calcium complexes as hydroamination catalysts.3,4 By avoiding the struggle with the disadvantageous entropic effect, the intramolecular hydroamination was investigated much more intensely yielding azaheterocycles.8 Diverse calcium complexes with Ca−N bonds have been studied; however, in most cases the intermolecular alkaline earth metal-mediated hydroamination reaction requires activated alkenes or alkynes.9 Often, mononuclear calcium bis(amides) are not sufficient to promote intermolecular hydroamination procedures and the more reactive calciates have to be applied, mainly as their soluble potassium salts. Thus, hydroamination of diphenylbutadiyne with secondary anilines requires dipotassium tetrakis(amino)calciate. The resulting CC double bonds are inert toward calcium-mediated hydroamination. The calciate K2[Ca{N(H)Dipp}4] (Dipp = C6H3-2,6-iPr2) represents an estab-

Scheme 1. Schematic Hydroamination via Addition of N−H Bond across CC Triple Bond

reaction requires a catalyst to overcome the electrostatic repulsion between a strong Lewis base (secondary or primary amine) and an electron-rich CC or CC multiple bond. The energy difference of the N−H bond and the CC/CC multiple bonds is quite large, which also hinders this entropically disadvantageous addition reaction. Recently, the catalytic properties of alkaline earth metal compounds3,4 have been explored because the ions of these elements promise advantageous properties such as availability of d-orbitals (they are isoelectronic to the ions of the scandium and titanium © XXXX American Chemical Society

Received: December 13, 2017

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of both amino functionalities occurred smoothly, and a yield of isolated crystalline compound 1 of 80% was achieved. This potassium complex quantitatively underwent a metathesis reaction with anhydrous CaI2 in THF yielding insoluble KI and dinuclear [(thf)5Ca2{1,2-(PhN)2C2H4}2] (2) after crystallization from a mixture of THF and hexane. DOSY spectra show that this complex is mononuclear in [D8]THF solution. On the basis of our experience that N,N,N′,N′′,N′′′,N′′′hexamethyltriethylenetetraamine (hmteta) acts as a strong donor17 stabilizing cisoid calcium complexes, we also added this tetradentate amino base and obtained [(hmteta)Ca{1,2(PhN)2C2H4}] (3) as shown in Scheme 2. Molecular Structures. The molecular structure and atom numbering scheme of dinuclear [(thf)3K2{1,2-(PhN)2C2H4}] (1) is depicted in Figure 1. In the asymmetric unit, the potassium atoms bind to both amide bases with bond lengths between 286.3(2) and 288.9(2) pm. Furthermore, the K atoms are bound each to one terminal tetrahydrofuran molecule, and a third thf ligand occupies a bridging position between K1 and K2. Regardless of the coordination mode the K−O distances

lished calcium-based catalyst whereas the potassium amide as well as the calcium bis(amide) were not catalytically active.10,11 Bidentate amides seem to be favorable for the calciummediated hydroamination catalysis because a cis-arrangement of the amido functionalities is enforced which ensures an “open” coordination site that, of course, might be saturated by other Lewis bases such as ether or amine molecules or via aggregation of these complexes. These calcium complexes are most commonly prepared via a metathetical approach from potassium amide and calcium iodide. First attempts to prepare such a potassium calciate remained unsuccessful because a double deprotonation of 1,2-bis(neopentylamino)benzene with potassium bases failed.12 Only dilithium13 as well as mixed lithium/potassium12 and lithium/calcium derivatives14 have been described so far. In addition, it has been demonstrated that metalation of 1,2-di(anilino)benzene can yield paramagnetic radical species with unique properties.15 We were interested in a straightforward synthesis of dipotassium bis(amides) in order to metathetically transfer a 1,2-bis(anilido)ethane base to calcium. In addition, diphenylamides proved to be less reactive than N-alkyl-anilides11 or even dialkylamides.16 Therefore, we chose 1,2-bis(anilino)ethane as the basis of our investigations.

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RESULTS AND DISCUSSION Synthesis. The deprotonation of 1,2-bis(anilino)ethane with [(thf)2Ca{N(SiMe3)2}2] in tetrahydrofuran failed, and therefore, the metathetical approach had to be chosen. In a heterogeneous reaction, excess of potassium hydride was reacted with 1,2-bis(anilino)ethane in tetrahydrofuran (THF) at room temperature. Evolution of hydrogen gas and a pale yellow color of the reaction mixture was indicative of the deprotonation reaction according to Scheme 2. After removal of excess KH, the potassium complex [(thf) 3 K 2 {1,2(PhN)2C2H4}] (1) was isolated. The double deprotonation Scheme 2. Synthesis of the s-Block Metal Amides [(thf)3K2{1,2-(PhN)2C2H4}] (1), [(thf)5Ca2{1,2(PhN)2C2H4}2] (2), and [(hmteta)Ca{1,2-(PhN)2C2H4}] (3)a

a

Figure 1. Molecular structure and numbering scheme of [(thf)3K2{1,2(PhN)2C2H4}] (1, top). The ellipsoids represent a probability of 30%, and H atoms are neglected for clarity reasons. The formation of a strand structure in the crystalline state is realized by intermolecular K− N bonds (bottom). The color code is identical but the atoms are shown as balls with arbitrary radii. Selected bond lengths (pm): K1− O1 275.7(2), K1−O2 280.2(2), K1−N1 286.9(2), K1−N2 286.3(2), K1−N2′ 295.7(2), K2−O2 276.7(2), K2−O3 278.0(2), K2−N1 288.9(2), K2−N2 287.7(2), K2−N1′ 287.0(2), N1−C1 145.4(2), N1−C9 135.4(2), N2−C2 145.4(2), N2−C3 135.1(2), C1−C2 151.9(3).

thf = tetrahydrofuran; hmteta = hexamethyltriethylenetetraamine. B

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Ca{1,2-(PhN)2C2H4}] (3) is presented in Figure 3. In order to discuss intramolecular steric strain, the structure of [(hmteta)-

vary between 275.7(2) and 280.2(2) pm. The N−CPh bond lengths are 10 pm smaller than those to the ethylene backbone suggesting charge delocalization into the phenyl substituents. These dinuclear units are linked by additional K−N bonds to neighboring complexes, thus forming a strand structure in the crystalline state. Dinuclear [(thf)5Ca2{1,2-(PhN)2C2H4}2] (2) crystallizes with two crystallographically independent molecules A and B. The molecular structure and atom numbering scheme of molecule A is shown in Figure 2. The central feature is a four-

Figure 3. Molecular structure and numbering scheme of [(hmteta)Ca{1,2-(PhN)2C2H4}] (3). The ellipsoids represent a probability of 30%. H atoms are omitted for the sake of clarity. Selected bond lengths (pm): Ca1−N1 238.4(3), Ca1−N2 236.1(3), Ca1−N3 259.6(3), Ca1−N4 261.5(4), Ca1−N5 269.9(4), Ca1−N6 266.8(4), N1−C1 145.7(5), N1−C9 136.2(5), N2−C2 145.8(4), N2−C3 135.8(5).

CaI2] (4) was determined (see Supporting Information), being a different modification of the already reported structure.17c Again this hmteta base enforces a cisoid arrangement of the iodide ions in complex 4 (Ca−I 308.99(7) and 310.20(7) pm). The Ca−N distances vary between 252.2(3) and 257.3(3) pm with the smaller values for the terminal amino groups. Due to enhanced steric pressure in [(hmteta)Ca{1,2-(PhN)2C2H4}] (3) the Ca−N distances to the neutral tetradentate hmteta base are elongated (Ca−N between 259.6(3) and 269.9(3) pm). Electrostatic attraction between the alkaline earth ion and the amide functionalities leads to significantly shorter Ca1−N1 and Ca1−N2 bonds of 238.4(3) and 236.1(3) pm. As observed for the dinuclear s-block metal derivatives 1 and 2, the N−CPh bonds are approximately 10 pm shorter than the N−C bonds to the ethylene backbone. The 1,2-bis(phenylamido)ethane ligands act as strong chelate bases that can squeeze ether ligands out of the coordination spheres of cations. Therefore, the amido functionalities occupy bridging positions between two metal ions if steric protection by strong multidentate bases (such as hmteta as in 3) is missing. Because the potassium ions are captured between the N atoms of the chelating 1,2-bis(phenylamido)ethane ligand, there are no significant π-interactions between the potassium cation and the phenyl groups. Catalysis Studies. For comparison reasons, we tested the catalytic activity of [(thf)3K2{1,2-(PhN)2C2H4}] (1) and [(thf)5Ca2{1,2-(PhN)2C2H4}2] (2) in the intermolecular hydroamination of diphenylbutadiyne with N-methyl-aniline in tetrahydrofuran. Both complexes are unable to mediate the addition of the N−H bonds to the alkyne functionality. In order to enhance the reactivity, heterobimetallic complexes were prepared by a 2:1 mixture of 1 and 2 in THF (K:Ca ratio of 2:1). The NMR spectra verified that these complexes react

Figure 2. Molecular structure and numbering scheme of [(thf)5Ca2{1,2-(PhN)2C2H4}2] (2). The ellipsoids represent a probability of 30%. Only one hydrogen atom is shown to clarify the short contact to Ca2A. The asymmetric unit consists of two molecules A and B. Only molecule A is depicted. Selected bond lengths (pm) of molecule A [molecule B]: Ca1−O1 241.3(3) [240.5(3)], Ca1−O2 244.0(3) [242.9(3)], Ca1−O3 239.0(3) [244.5(3)], Ca1−N1 242.3(3) [241.8(3)], Ca1−N2 257.3(3) [258.2(3)], Ca1−N3 246.2(3) [241.9(3)], Ca2−O4 240.6(3) [238.9(3)], Ca2−O5 243.6(2) [243.7(3)], Ca2−N1 277.0(3) [280.4(3)], Ca2−N2 244.4(3) [246.1(3)], Ca2−N3 246.7(3) [247.5(3)], Ca2−N4 237.1(3) [238.2(3)]; agostic bonds (pm): Ca1−C2 305.5(4) [308.5(4)], Ca2−C1 302.0(4) [302.0(4)], Ca2−C15 315.1(4) [313.9(4)]; nonbonding contact (pm): Ca1−Ca2 332.2(1) [332.5(1)].

membered Ca1−N2−Ca2−N3 ring with two different bis(phenylamido)ethane ligands, the other amido functionalities (N1 and N4) bind terminally to the calcium atoms. The coordination spheres of both alkaline earth metals differ significantly. The atom Ca1A binds to three thf ligands (Ca− O distances between 239.0(3) and 244.0(3) pm), whereas Ca2A is coordinated by only two ether molecules (Ca−O 240.6(3) and 243.6(3) pm). The free coordination site is occupied by an agostic interaction to the ethylene moiety of the bis(phenylamido)ethane backbone (Ca2A···C1A 302.0(4) pm). Other slightly larger Ca···C contacts are observed as well (Ca1A···C2A 305.5(4) pm, Ca2A···C15A 315.1(4) pm), demonstrating the constrictions in this dinuclear complex. As expected, the tetradentate hmteta ligand ensures the formation of mononuclear complexes with hexa-coordinate calcium centers. As reported earlier,17 this hmteta base enforces a cisoid arrangement of the remaining two ligands. The molecular structure and atom numbering scheme of [(hmteta)C

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due to the large coordination number of the metal ions K1 and K2. The molecular structure of the calcium complex 6 is shown in Figure 5. Despite the large coordination number of eight, the Ca−N bond lengths are comparable to those of complex 3 with a hexa-coordinate calcium center.

with each other presumably forming a dipotassium calciate as had been observed earlier with other amido groups.10e The NMR spectra of 1, 2, and the 2:1 mixture (yielding a K:Ca ratio of 2:1) are depicted in the Supporting Information. In this mixture, neither 1 nor 2 are observed, but a dynamic complex equilibrium can be detected. However, we were unable to crystallize any potassium calciate complex from this reaction solution. Furthermore, the 13C{1H} NMR spectra of these solutions also demonstrated that the mixture of 1 and 2 yielded new yet structurally unknown complexes. During recrystallization efforts of a dipotassium calciate, best described as K2Ca{1,2-(PhN)2C2H4}2, a heterobimetallic complex with an oxide-centered Ca4 square with the formula sum of [{(thf)3K}2Ca4{1,2-(PhN)2C2H4}4(μ4-O)] was isolated (see Supporting Information).18 In this side product (which formed presumably via hydrolysis due to inadvertently introduced traces of moisture), the potassium ions are coordinated to the π-systems of the aryl groups (see Supporting Information). This finding supports the assumption that calciate anions might be present in solution with potassium ions bound to the outer sphere of the complex. Therefore, we intended to capture the potassium ions with 18-crown-6 (18C6) to isolate a solvent-separated ion pair, consisting of ligated potassium ions and a calciate counteranion. However, addition of this crown ether led to formation of sparingly soluble homometallic [{(18C6)K} 2 {1,2(PhN)2C2H4}] (5) which precipitated as a microcrystalline powder. Single crystals were obtained upon cooling of the mother liquor. In the supernatant solution, amidocalcium species are enriched. However, a pure 18-crown-6 ether adduct was not obtained as a comparison with the calcium complex [(18C6)Ca{1,2-(PhN)2C2H4}] (6) (prepared via ether substitution of [(thf)5Ca2{1,2-(PhN)2C2H4}2] (2) with 18-crown6) showed. The structure of this potassium complex is depicted in Figure 4. The K−N bond lengths are slightly smaller than observed for complex 1, but the average K−O distances (K1− O 293.0, K2−O 293.3 pm), varying between 281.6(1) (K2− O8) and 308.0(1) pm (K2−O11), are larger than observed in 1

Figure 5. Molecular structure and numbering scheme of [(18C6)Ca{1,2-(PhN)2C2H4}] (6). The ellipsoids represent a probability of 30%. H atoms are omitted for clarity reasons. Selected bond lengths (pm): Ca1−N1 238.9(5), Ca1−N2 238.0(4), Ca1−O1 259.3(4), Ca1−O2 261.1(4), Ca1−O3 257.2(4), Ca1−O4 256.5(4), Ca1−O5 261.5(4), Ca1−O6 248.1(4), N1−C1 146.4(6), N1−C9 135.5(6), N2−C2 144.9(7), N2−C3 135.6(7).

The 2:1 mixture of 1 and 2 in THF showed catalytic activity and promoted the singular addition of N-methyl-aniline to diphenylbutadiyne yielding well-known10 1,4-diphenyl-1-(Nmethyl-anilino)but-1-ene-3-yne. In a typical procedure, 3 mol % of K2Ca{1,2-(PhN)2C2H4}2 was added to a 1:1 mixture of Nmethyl-aniline and diphenylbutadiyne in THF. As also observed in earlier studies with the precatalyst [K2Ca{N(H)Dipp}4] (Dipp = 2,6-diisopropylphenyl),10 an E/Z mixture formed with a ratio of approximately 0.7:0.3 (Scheme 3, Table 1). Very similar results were also obtained for a mixture of 2 with KN(Me)Ph (K:Ca ratio of 2:1). Furthermore, an excess of Nmethyl-aniline also did not lead to a 2-fold addition of the amine to diphenylbutadiyne. These encouraging findings prompted us to test the catalytic activity of the homometallic complexes of potassium (1) and calcium (2) for the reaction of diphenylbutadiyne with 1,2di(anilino)ethane in THF. Again, these s-block metal complexes showed no catalytic activity under these reaction conditions. This observation is in agreement with former studies for the catalytic addition of N-alkyl-anilines across diphenylbutadiyne requiring mixed metal complexes such as K2[Ca{N(H)Dipp}4].10 Therefore, a 2:1 mixture of [(thf)3K2{1,2-(PhN)2C2H4}] (1) and [(thf)5Ca2{1,2-(PhN)2C2H4}2] (2) was prepared in THF and added to a 1:1 mixture of diphenylbutadiyne and 1,2di(anilino)ethane at room temperature. This reaction was monitored by 1H NMR spectroscopy in the region between 3.5 and 6 ppm because in this window the resonances of the alkenyl-hydrogen atoms and of the ethylene backbone can easily be observed. The reaction mixture was hydrolyzed to inactivate the catalyst, and then the 1H NMR spectrum was recorded to determine the molar ratio of the hydroamination products (see Scheme 4). Reduction of the volume of the hydrolyzed reaction mixture and crystallization at low temper-

Figure 4. Molecular structure and numbering scheme of [{(18C6)K}2{1,2-(PhN)2C2H4}] (5). The ellipsoids represent a probability of 30%. H atoms are omitted for the sake of clarity. Selected bond lengths (pm): K1−N1 283.5(2), K2−N2 282.5(2), N1−C1 145.2(2), N1−C9 134.0(2), N2−C2 145.4(2), N2−C3 134.1(2). D

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Organometallics Scheme 3. Catalytic Hydroamination of Diphenylbutadiyne with N-Methyl-aniline, Using the Precatalysts K2Ca{1,2(PhN)2C2H4}2 or [K2Ca{N(H)Dipp}4]

Scheme 4. Products of the Calciate-Mediated Hydroamination of Diphenylbutadiyne with 1,2Di(anilino)ethane (red) in THF at Room Temperaturea

a

The top row shows the E- and Z-isomers of the 1:1 (7), the bottom row the E,E-, E,Z-, and Z,Z-isomers of the 2:1 hydroamination products 8; see text.

In order to raise the yield of 1,4,5,8,9,12-hexaphenyl-5,8diazadodeca-3,9-diene-1,11-diyne (8) the s-block metal-mediated catalytic hydroamination of diphenylbutadiyne with 1,2di(anilino)ethane was repeated in toluene (Figure 6). In the beginning, the products with a 1:1 ratio of 1,2-(PhNH)2C2H4 to diphenylbutadiyne (E-7 and Z-7) formed; then the concentration decreased because the 1:2 products (Z,Z-8, E,Z-8 and E,E-8) formed. In this aromatic hydrocarbon solvent, Z,Z-8 was only sparingly soluble, and pure Z,Z-8 precipitated during the catalytic addition reaction (yield of isolated Z,Z-8: 69%); whereas, the supernatant reaction solution contained the isomeric mixture of Z,Z-8, E,Z-8, and E,E-8 (ratio of approximately 2:5:3). Performance of this catalyzed hydroamination procedure in concentrated solution enhanced the yield of Z,Z-8. Recrystallization from toluene or toluene/THF mixtures gave crystals of the isomers Z,Z-8 and E,E-8; however, an isolation of pure E,E-8 failed.

atures yielded yellow single-crystals of (Z,Z)-1,4,5,8,9,12hexaphenyl-5,8-diazadodeca-3,9-diene-1,11-diyne (Z,Z-8) with a diphenylbutadiyne/1,2-di(anilino)ethane ratio of 2:1 with a poor yield of only 5%. In agreement with former hydroamination studies, the resonances in this NMR range can be assigned to Z,Z-8 (5.75 ppm), Z,E-8 (5.73 and 5.18 ppm), and E,E-isomeric 8 (5.12 ppm) with an intensity ratio of approximately 4:4:2. Recrystallization led to an enrichment of the Z,Z-isomer of 8 in the crystalline phase. The components at 5.29 and 5.82 ppm can be assigned to the E and Z isomers, respectively, of 1,4-diphenyl-1-(N-phenyl−phenylaminoethylamino)but-1-ene-3-yne (7) with a diphenylbutadiyne/ 1,2-di(anilino)ethane ratio of 1:1. In Scheme 4, all these products are depicted. Again, species with doubly hydroaminated diphenylbutadiyne fragments were not observed.

Table 1. Catalytic Hydroamination of Diphenylbutadiyne with N-Methylaniline and 1,2-Di(anilino)ethane in THF with Different Catalysts at Room Temperature or under Reflux Conditions reaction HN(Me)Ph + PhCC−CCPh

PhN(H)C2H4N(H)Ph + PhCC−CCPh

catalyst (ratio), load

t [h]

temp [°C]

conv.a [%]

E:Z

2, 1.5 mol-% 1/2 (2:1), 1.5 mol-% K2[Ca{N(H)Dipp}4], 5 mol-%b KN(Me)Ph/2 (4:1), 1.5 mol-% 1, 10 mol-% 1, 10 mol-% 2, 2.5 mol-% 1/2 (2:1), 3 mol-%c K2[Ca{N(H)Dipp}4], 6 mol-% KN(Me)Ph/2 (4:1), 1.5 mol-%

72 26 6 3 150 10 23 20 31 24

r.t. r.t. r.t. r.t. r.t. reflux reflux r.t. reflux r.t.

0 35 92 100 0 0 0 100 0 0

63:37 61:39 65:35 E,E-: E,Z-: Z,Z-8, 24:37:39 -

a

Conversion was determined by integration of the o-Ph signal of diphenylbutadiyne via 1H NMR spectroscopy (7.56 ppm, CDCl3). bSee references 10a and 10b. cByproducts are E- and Z-isomers of PhCC−CHC(Ph)−N(Ph)C2H4N(H)Ph (7) being the 1:1 addition product of diphenylbutadiyne and 1,2-bis(anilino)ethane. E

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from pure Z,Z-8. In a light-protected NMR tube in the dark, the isomerization process is extremely slow. After removal of the light protection, isomerization took place as observed earlier. Whereas the ratio of the isomers of 8 was nearly not affected by the solvent, the wavelength of the irradiation had a strong influence on the isomer distribution. At wavelengths between 365 and 440 nm, the isomer E,Z-8 was the major component with an increasing wavelength leading to an increasing ratio of E,E-8 to Z,Z-8. At 480 nm the isomer E,E-8 represents the major component (Figure 8).

Figure 6. Decrease of the starting diamine 1,2-(PhNH)2C2H4 (blue) and increase of the 1:1 products (E-7 and Z-7; black) and the delayed increase of the 1:2 products (Z,Z-8, E,Z-8 and E,E-8; red); the starting solution showed molarities of 0.0435 M for 1,2-(PhNH)2C2H4 and 0.0884 M for diphenylbutadiyne.

During characterization and isolation of pure Z,Z-8 at daylight, isomerization occurred yielding again a mixture of all possible isomers of 8. In the beginning, the isomer E,Z-8 formed until an equilibrium between all possible isomers was observed (Figure 7). Thermal and photochemical isomerization

Figure 8. Dependency of the distribution of the isomers Z,Z-8 (black), E,Z-8 (red), and E,E-8 (blue) on the wavelength of irradiation in CDCl3.

The molecular structure and atom numbering scheme of (Z,Z)-1,4,5,8,9,12-hexaphenyl-5,8-diazadodeca-3,9-diene-1,11diyne (Z,Z-8) is depicted in Figure 9. The asymmetric unit contains two half centrosymmetric molecules A and B; because of far-reaching similarity, only molecule B is depicted. The nitrogen atoms are in distorted trigonal planar environments.

Figure 7. Isomerization of Z,Z-8 (black) at 480 nm in chloroform and formation of E,Z-8 (red) and E,E-8 (blue).

of vinylamines and related compounds (like amides, amidines, enamines, anilines) has already been studied and represents a well-known reaction behavior.19−21 To clarify if the catalytic addition was stereoselective and isomerization occurred after hydroamination in a second step or if the catalytic hydroamination lacked stereoselectivity, we repeated the catalytic addition of 1,2-di(anilino)ethane across diphenylbutadiyne in the dark; again, an isomeric mixture formed verifying that the sblock metal-mediated hydroamination was regioselective but not stereoselective. This finding is in agreement with former sblock metal-mediated hydroamination reactions.10 Furthermore, we studied the isomerization of pure Z,Z-8 in CDCl3 and [D8]THF at daylight. In both solvents, a rather similar isomeric distribution is observed after 2 weeks starting

Figure 9. Molecular structure and atom numbering scheme of (Z,Z)1,4,5,8,9,12-hexaphenyl-5,8-diazadodeca-3,9-diene-1,11-diyne (Z,Z-8). The ellipsoids represent a probability of 30%. H atoms are not shown for clarity reasons. The asymmetric unit contains two half molecules A and B, only the complete molecule B is depicted. Selected bond lengths (pm) of molecule A [molecule B]: C1−C1′ 150.8(3) [150.1(3)], N1−C1 146.1(2) [146.2(2)], N1−C2 141.1(2) [140.7(2)], N1−C8 140.3(2) [140.4(2)], C8−C9 134.7(2) [135.0(2)], C8−C18 148.6(2) [148.5(2)], C9−C10 142.4(3) [142.4(2)], C10−C11 119.9(2) [120.0(2)], C11−C12 143.2(3) [143.3(2)]. F

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Organometallics The N−C bond lengths to the sp2 hybridized atoms are approximately 5 pm smaller than those to the ethylene backbone with sp3 hybridized carbon atoms. The but-1-en-3yne moieties show insignificant conjugation and characteristic C−C bond lengths for single, double, and triple bonds are observed. The molecular structure and atom numbering scheme of (E,E)-1,4,5,8,9,12-hexaphenyl-5,8-diazadodeca-3,9-diene-1,11diyne (E,E-8) is depicted in Figure 10. This centrosymmetric

Scheme 5. Simplified Representation of the Proposed Catalytic Cycle Showing the Hydroamination Including an Explanation for the E/Z Isomerism via Rearrangement of an Unobserved Intermediate Cumulene Speciesa

Figure 10. Molecular structure and atom numbering scheme of centrosymmetric (E,E)-1,4,5,8,9,12-hexaphenyl-5,8-diazadodeca-3,9diene-1,11-diyne (E,E-8). The ellipsoids represent a probability of 30%. H atoms are not shown for clarity reasons. Atoms generated by inversion symmetry are marked with the letter A. Selected bond lengths (pm): C1−C1′ 153.0(6), N1−C1 147.0(4), N1−C2 139.0(4), N1−C18 144.3(4), C2−C3 135.0(4), C2−C12 149.4(4), C3−C4 141.7(4), C4−C5 120.5(4), C5−C6 142.9(4).

a

See also Scheme S1 in the Supporting Information.

contrast, the precursor complexes 1 and 2 alone are unable to initiate this addition reaction. This heterobimetallic complex K2Ca{1,2-(PhN)2C2H4}2 of unknown structure is more reactive than the approved heterobimetallic K2[Ca{N(H)Dipp}4] which crystallizes without ether coligands. In the presence of catalytic amounts of complex K2Ca{1,2-(PhN)2C2H4}2, 1,2-bis(anilino)ethane only adds once to diphenylbutadiyne yielding an (E,E)-, (E,Z)-, and (Z,Z)-isomeric mixture of 1,4,5,8,9,12-hexaphenyl5,8-diazadodeca-3,9-diene-1,11-diyne (8); the other CC triple bond is not hydroaminated under these reaction conditions. The ratio of these isomers can be influenced by the choice of solvent. Whereas E,E-8 and E,Z-8 are highly soluble in toluene, Z,Z-8 is only sparingly soluble in this hydrocarbon. This behavior and the fact that isomerization occurs at daylight allow to isolate analytically pure Z,Z-8. The calciate-mediated hydroamination of diphenylbutadiyne with 1,2-di(anilino)ethane is regioselective but lacks stereoselectivity.

molecule crystallizes with half a molecule in the asymmetric unit; symmetry-dependent atoms are marked with the letter A. The bond lengths of Z,Z-8 and E,E-8 are comparable as one would expect because both isomers lack steric strain or hindrance.

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CONCLUSIONS In comparison to K2[Ca{N(H)Dipp}4], which crystallizes as an ether-free complex, the above-discussed K 2 Ca{1,2(PhN)2C2H4}2 is significantly more reactive. Thus, the hydroamination of diphenylbutadiyne with 1,2-bis(anilino)ethane can be initiated by K2Ca{1,2-(PhN)2C2H4}2 whereas K2[Ca{N(H)Dipp}4] was inactive in this catalytic hydroamination. However, the intermediate species during the catalytic cycle are unknown as is the molecular structure of K2Ca{1,2-(PhN)2C2H4}2 in the solid phase. Whereas K2[Ca{N(H)Dipp}4] can be stored in an inert gas atmosphere, the isolated crystalline precursor compounds 1 and 2 slowly desolvate and freshly prepared stock solutions were used for our catalytic investigations. In contrast to 1,2-bis(neopentylamido)benzene, the deprotonation of 1,2-bis(anilino)ethane succeeds with KH in tetrahydrofuran yielding [(thf)3K2{1,2-(PhN)2C2H4}] (1), whereas the transamination with [(thf)2Ca{N(SiMe3)2}2] fails. Nevertheless, the metathesis reaction of 1 with CaI2 in THF leads to the formation of crystalline [(thf)5Ca2{1,2(PhN)2C2H4}2] (2) after removal of excess of KH and addition of hexane. Addition of tetradentate hmteta yields mononuclear [(hmteta)Ca{1,2-(PhN)2C2H4}] (3). In all these s-block metal complexes, the bis(amide) ligand acts as a chelate forming fivemembered cycles with the metal atoms. A 2:1 mixture of [(thf)3K2{1,2-(PhN)2C2H4}] (1) and [(thf)5Ca2{1,2-(PhN)2C2H4}2] (2) mediates the addition of N−H bonds to alkynes yielding alkenylamines (Scheme 5). In

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EXPERIMENTAL SECTION

General Remarks. All manipulations were carried out under an inert nitrogen atmosphere using standard Schlenk techniques. The solvents were dried over KOH and subsequently distilled over sodium/benzophenone under a nitrogen atmosphere prior to use. Deuterated solvents were dried over sodium, degassed, and saturated with nitrogen. The yields given are not optimized. 1H and 13C{1H} NMR spectra were recorded on Bruker AC 400 and AC 600 spectrometers. Chemical shifts are reported in parts per million relative to SiMe4 as external standards. The residual signals of the deuterated solvents [D8]THF and CD2Cl2 were used as internal standards for 1H and 13C{1H} NMR experiments. Purity was controlled 1H NMR spectroscopically and/or by titration of the metal content. Combustion analyses gave no reliable results due to the enormous reactivity toward moisture and air, and therefore, in many cases only determination of metal content was feasible after integration of the 1H NMR spectrum to determine the ether content of the sample. Specific amounts of the potassium-based catalysts were dissolved in anhydrous THF and aliquots of these freshly prepared G

DOI: 10.1021/acs.organomet.7b00890 Organometallics XXXX, XXX, XXX−XXX

Article

Organometallics

46.4 (N(CH3)2/hmteta), 43.6 (N(CH3)/hmteta). IR (cm−1): 3041 (vw), 2944 (w), 2765 (m), 1582 (m), 1544 (w), 1536 (w), 1485 (s), 1462 (s), 1390 (w), 1353 (w), 1307 (s), 1276 (m), 1172 (m), 1158 (m), 1143 (m), 1093 (m), 1058 (m), 1036 (m), 1020 (m), 976 (s), 942 (m), 923 (m), 892 (m), 839 (m), 821 (w), 785 (m), 745 (vs), 694 (s), 637 (m), 611 (w), 594 (w), 519 (m), 469 (m), 439 (m), 413 (m). Metal content for [(hmteta)1.9Ca{1,2-(PhN)2C2H4}] (688.12 g/mol): calcd: Ca 5.82; found: Ca 5.54 Preparation of a Stock Solution of K2Ca{1,2-(PhN)2C2H4}2 in THF. A solution of [(thf)3K2{C2H4-1,2-(N−C6H5)2}] in THF (c = 0.133 M, 15.6 mL, 2.07 mmol) was slowly added to a stirred suspension of calcium iodide (0.304 g, 1.03 mmol) in 10 mL of THF. After stirring for 20 h at ambient temperature, the mixture was filtered over diatomaceous earth to give a greenish yellow solution. Concentration: 0.040 M (ref to calcium). Synthesis of (18C6)2K2{1,2-(PhN)2C2H4} (5). An aliquot of a 0.0625 M stock solution of 1 in THF (5 mL, 0.31 mmol) was treated dropwise with 18C6 (6.5 mL of a 0.0973 M solution in THF, 0.63 mmol) at r.t. The product 5 readily precipitated as an off-white solid after a few hours at r.t. This solid was collected, washed twice with 4 mL of n-hexane and dried in vacuo (0.08 g, 0.09 mmol, 15%). 1H NMR (400.13 MHz, [D8]THF, 297 K): δ [ppm] 6.77 (t, 3JH,H = 7.5 Hz, 4H, Ar-H), 6.25 (d, 3JH,H = 8.0 Hz, 4H, Ar-H), 5.94 (t, 3JH,H = 7.1 Hz, 2H, Ar-H), 3.52 (s, 36H, CH2 {18c6}), 3.13 (s, 4H, CH2). 13 C{1H} NMR (100.61 MHz, CDCl3, 297 K): δ [ppm] 157.5 (i-C), 129.3 (m-C), 113.2 (o-C), 109.3 (p-C), 71.2 (CH2 {18c6}), 48.3 (CH2). IR (cm−1): 3501 (vw), 3050 (vw), 2883 (m), 2728 (w), 1598 (w), 1581 (w), 1502 (w), 1487 (w), 1470 (m), 1350 (s), 1317 (w), 1285 (w), 1246 (m), 1101 (vs), 1039 (s), 960 (s), 836 (m), 748 (m), 722 (m), 693 (m), 652 (w), 528 (w), 505 (m). Metal content for [(18C6)1.5K2{1,2-(PhN)2C2H4}] (684.96 g/mol): calcd: K 11.41; found: K 10.82. Synthesis of (18C6)Ca{1,2-(PhN)2C2H4} (6). An aliquot of a 0.058 M stock solution of (thf)nCa{1,2-(PhN)2C2H4} in THF (5 mL, 0.29 mmol) was treated dropwise with 18C6 (3 mL of a 0.0973 M solution in THF, 0.29 mmol) at r.t. Product 6 solidifies as colorless crystals out of a green solution after 2 days at r.t. The crystals were collected, washed twice with 2 mL of n-hexane and dried in vacuo (0.02 g, 0.04 mmol, 14%). This solid is insoluble in THF or hydrocarbons, and therefore, no NMR data can be provided. IR (cm−1): 3370 (vw), 3025 (vw), 2861 (m), 2751 (w), 1599 (m), 1584 (m), 1528 (w), 1485 (m), 1449 (m), 1428 (m), 1337 (m), 1314 (s), 1253 (m), 1199 (w), 1170 (m), 1107 (s), 1086 (s), 1070 (s), 1055 (s), 1013 (m), 973 (s), 933 (s), 867 (m), 837 (m), 825 (m), 804 (m), 784 (m), 748 (s), 733 (s), 693 (vs), 626 (m), 519 (s). Elemental Anal. (C26H38N2O6Ca, 514.68 g/mol): Calcd: C 60.68, H 7.44, N 5.44; found: C 59.31, H 7.49, N 5.61. Synthesis of Z,Z-1,4,5,8,9,12-Hexaphenyl-5,8-diazadodeca3,9-diene-1,11-diyne (Z,Z-8). Diphenylbutadiyne (0.41 g, 2.03 mmol) and 1,2-dianilinoethane (0.21 g, 0.99 mmol) were dissolved in 10 mL of toluene before 1.2 mL of the K/Ca amide mixture (0.05 mmol) was added at r.t. The solution was stirred for 3 days at ambient temperature, as an off-white solid began to precipitate out of the brown reaction mixture. After an additional 3 days at r.t., the mixture was filtrated. The solid, which was washed with n-pentane and dried in vacuo, was found to be (Z,Z)-8 (0.43 g, 0.69 mmol, 69%). mp: 222− 224 °C (dec.). Elemental Anal. (C46H36N2, 616.81 g/mol): Calcd: C 89.58, H 5.88, N 4.54. Found: C 89.30, H 5.89, N 4.76. MS (EI, [m/z (%)]): 616 (10) [M]+, 414 (40) [1,2-(PhNH)2C2H4 + PhCC−C CPh]+, 308 (100) [1/2 M]+ or [M]2+, 202 (20) [PhCC−C CPh]+. 1H NMR (400.13 MHz, CDCl3, 297 K): δ [ppm] 7.48 (dd, 3 JH,H = 7.7 Hz, 4JH,H = 1.7 Hz, 4H, Ar-H), 7.34 (m, 6H, Ar-H), 7.14 (m, 6H, Ar-H), 7.06 (t, 3JH,H = 8.0 Hz, 4H, Ar-H), 6.92 (dd, 3JH,H = 8.1 Hz, 4JH,H = 1.4 Hz, 4H, Ar-H), 6.78 (d, 3JH,H = 7.9 Hz, 4H, Ar-H), 6.75 (t, 3JH,H = 7.3 Hz, 2H, Ar-H), 5.73 (s, 2H, C = CH), 4.05 (s, 4H, CH2). 13C{1H}-NMR (100.61 MHz, CDCl3, 297 K): δ [ppm] 153.4 (C1), 147.3 (C18), 138.5 (C11), 131.3, 129.2, 128.9, 128.8, 128.1, 127.8, 127.7, 123.6, 119.6, 117.3, 100.3 (C2), 99.1 (C3), 87.9 (C4), 48.3 (C17); see Supporting Information for numbering scheme. IR (cm−1): 3021 (vw), 2954 (vw), 2899 (vw), 2189 (vw), 1596 (w), 1584

solutions were added as catalysts to the reaction mixtures. This procedure allowed to easily add definite amounts of precatalyst to the substrates under strictly anaerobic and anhydrous conditions. All substrates were purchased from Sigma-Aldrich, Merck, or Alfa Aesar and used without further purification. Synthesis of [(thf)3K2{1,2-(PhN)2C2H4}] (1). A stirred suspension of potassium hydride (0.170 g, 4.24 mmol) in 8 mL of THF was treated dropwise with 1,2-dianilinoethane (0.220 g, 1.04 mmol) solved in 8 mL of THF, which causes a vigorous formation of hydrogen gas and a yellow stain. The mixture was stirred for 24 h at 34 °C until gas development was complete and filtered. After the concentration was doubled, the solution was stored at −20 °C for three and at −60 °C for 2 days to yield yellow crystals of 1, which were decanted, washed with THF, and dried in vacuo. Yield: 0.419 g (0.83 mmol, 80%). mp: 254−269 °C (color change to red), 287 °C (red melt, dec.). 1H NMR (300.19 MHz, [D8]THF, 299 K): δ [ppm] 6.71 (t, 3JH,H = 7.7 Hz, 4H, m-H), 6.10 (d, 3JH,H = 7.9 Hz, 4H, o-H), 5.64 (t, 3JH,H = 6.9 Hz, 2H, pH), 3.62 (m, 9H, thf), 3.08 (s, 4H, CH2), 1.78 (m, 9H, thf). 13C{1H}NMR (100.61 MHz, [D8]THF, 297 K): δ [ppm] 161.60 (i-C), 130.41 (m-C), 112.11 (o-C), 105.00 (p-C), 67.57 (thf), 53.06 (CH2), 25.49 (thf). IR (cm−1): 3416 (vw), 3052 (vw), 2945 (vw), 2748 (vw), 1573 (m), 1529 (vw), 1513 (vw), 1481 (m), 1441 (w), 1334 (m), 1310 (s), 1264 (m), 1170 (m), 1145 (w), 1080 (w), 1052 (w), 1012 (w), 970 (s), 914 (w), 832 (w), 743 (vs), 692 (vs), 631 (w), 515 (m). Metal content for [(thf)1.5K2{1,2-(PhN)2C2H4}] (396.65 g/mol): calcd: K 19.71; found: K 20.05. Synthesis of [(thf) n Ca{1,2-(PhN) 2 C 2 H 4 }]. A solution of [(thf)3K2{1,2-(PhN)2C2H4}] (1), freshly prepared from 1,2-dianilinoethane (0.636 g, 2.99 mmol) and potassium hydride (0.490 g, 12.21 mmol) in 30 mL of THF, was slowly added to a stirred suspension of calcium iodide (0.878 g, 2.99 mmol) in 25 mL of THF at r.t. After stirring for 24 h at ambient temperature, the mixture was filtered over Celite to give a yellow solution. Concentration: 0.054 M. This solution was used to grow single crystals of [(thf)2.5Ca{1,2-(PhN)2C2H4}]2 (2) and of [(hmteta)Ca{1,2-(PhN)2C2H4}] (3). Synthesis of [(thf)2.5Ca{1,2-(PhN)2C2H4}]2 (2). A 6 mL portion of the [(thf)nCa{1,2-(PhN)2C2H4}] solution (0.33 mmol) was concentrated to approximately 1.5 mL and carefully layered with 0.9 mL of nhexane. The slightly turbid solution was stored for 2 days at r.t. and for two additional days at −20 °C, which resulted in the growth of colorless crystals of 2 which were collected, washed three times with 1.5 mL of n-hexane and dried under vacuum. Yield: 0.090 g (0.209 mmol, 64%). Dec. above 276 °C without melting. 1H NMR (400.13 MHz, [D8]THF, 297 K): δ [ppm] 6.80 (t, 3JH,H = 7.6 Hz, 4H, m-H), 6.60 (d, 3JH,H = 8.0 Hz, 4H, o-H), 6.05 (t, 3JH,H = 6.9 Hz, 2H, p-H), 3.62 (m, 11H, THF), 3.50 (s, 4H, CH2), 1.77 (m, 11H, THF). 13 C{1H} NMR (100.61 MHz, [D8]THF, 297 K): δ [ppm] 161.4 (i-C), 129.1 (m-C), 115.4 (o-C), 110.7 (p-C), 68.4 (thf), 50.5 (CH2), 26.5 (thf). IR (cm−1): 3415 (vw), 3042 (w), 2973 (w), 2870 (w), 2793 (w), 1586 (s), 1551 (w), 1536 (w), 1511 (w), 1482 (s), 1451 (m), 1412 (vw), 1301 (m), 1263 (s), 1218 (m), 1177 (m), 1150 (w), 1087 (w), 1027 (m), 975 (m), 893 (m), 878 (m), 857 (m), 837 (m), 796 (w), 747 (vs), 692 (vs), 663 (m), 638 (w), 612 (w), 595 (w), 511 (m), 432 (s). Metal content for [(thf)1.5Ca{1,2-(PhN)2C2H4}] (358.53 g/mol): calcd: Ca 11.18; found: Ca 10.75. Synthesis of [(hmteta)Ca{1,2-(PhN)2C2H4}] (3). A 6 mL portion of the [(thf)nCa{1,2-(PhN)2C2H4}] solution (0.33 mmol) was concentrated to approximately 3 mL and carefully layered with 1 mL of n-hexane. To this layer, 0.7 mL of HMTETA was added dropwise and the resulting solution was stored at r.t. for 6 days and after further concentration for 2 days at 5 °C. The thus formed colorless crystals of 3 were collected, washed three times with 2 mL of n-hexane and dried in vacuo. Yield: 0.070 g (0.146 mmol, 45%). Dec. above 206 °C without melting. 1H NMR (300.19 MHz, [D8]THF, 297 K): δ [ppm] 6.80 (t, 3JH,H = 7.5 Hz, 4H, m-H), 6.60 (d, 3JH,H = 8.0 Hz, 4H, o-H), 6.05 (t, 3JH,H = 6.9 Hz, 2H, p-H), 3.50 (s, 4H, CH2), 2.44− 2.30 (m, 15H, CH2/hmteta), 2.20 (s, 8H, N(CH3)/hmteta), 2.16 (s, 16H, N(CH3)2/hmteta). 13C{1H} NMR (100.61 MHz, [D8]THF, 297 K): δ [ppm] 161.4 (i-C), 129.2 (m-C), 115.4 (o-C), 110.7 (p-C), 59.1 (CH2/hmteta), 57.6 (CH2/hmteta), 57.5 (CH2/hmteta), 50.5 (CH2), H

DOI: 10.1021/acs.organomet.7b00890 Organometallics XXXX, XXX, XXX−XXX

Article

Organometallics (w), 1565 (m), 1485 (m), 1441 (w), 1373 (m), 1335 (w), 1303 (w), 1276 (w), 1243 (w), 1208 (m), 1184 (w), 1148 (m), 1069 (w), 1038 (w), 1021 (w), 998 (w), 965 (w), 915 (w), 886 (w), 848 (vw), 804 (vw), 755 (vs), 690 (s), 616 (w), 558 (m), 532 (m), 492 (w), 460 (w), 439 (w), 417 (w). Crystal Structure Determinations. The intensity data for the compounds were collected on a Nonius KappaCCD diffractometer using graphite-monochromated Mo Kα radiation. Data were corrected for Lorentz and polarization effects; absorption was taken into account on a semiempirical basis using multiple-scans.22−24 The structures were solved by direct methods (SHELXS)25 and refined by full-matrix least-squares techniques against F02 (SHELXL-97).25 The hydrogen atoms of the compounds 1 (with exception of thf molecules) and Z,Z8 (with exception of the disordered phenyl ring C18A to C23A) and the hydrogen atoms bonded to C1 and C3 for E,E-8 were located by difference Fourier synthesis and refined isotropically. All other hydrogen atoms were included at calculated positions with fixed thermal parameters. All nondisordered, non-hydrogen atoms were refined anisotropically.25 The crystal of 2 was a nonmerohedral twin. The twin law was determined by PLATON25 to (0.524, −0.041, −0.476) (0.0, −1.0, 0.0) (−1.524, 0.041, −0.524). The contribution of the main component was refined to 0.748(1). Crystallographic data as well as structure solution and refinement details are summarized in Table S1 in the Supporting Information. XP26 and POV-Ray27 were used for structure representations.

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ni, A., Grützmacher, H., Eds.; Wiley-VCH: Weinheim, 2001; Chapter 4, pp 91−141. (2) (a) Huang, L.; Arndt, M.; Gooßen, K.; Heydt, H.; Gooßen, L. J. Chem. Rev. 2015, 115, 2596−2697. (b) Nishina, N.; Yamamoto, Y. Top. Organomet. Chem. 2012, 43, 115−144. (c) Reznichenko, A. L.; Hultzsch, K. C. Top. Organomet. Chem. 2011, 43, 51−114. (3) Harder, S. Chem. Rev. 2010, 110, 3852−3876. (4) (a) Hill, M. S.; Liptrot, D. J.; Weetman, C. Chem. Soc. Rev. 2016, 45, 972−988. (b) Crimmin, M. R.; Hill, M. S. Top. Organomet. Chem. 2013, 45, 191−242. (c) Barrett, A. G. M.; Crimmin, M. R.; Hill, M. S.; Procopiou, P. A. Proc. R. Soc. London, Ser. A 2010, 466, 927−963. (5) Coles, M. P. Coord. Chem. Rev. 2015, 297−298, 2−23. (6) (a) Westerhausen, M.; Langer, J.; Krieck, S.; Glock, C. Rev. Inorg. Chem. 2011, 31, 143−184. (b) Westerhausen, M. Coord. Chem. Rev. 1998, 176, 157−210. (c) Westerhausen, M. Trends Organomet. Chem. 1997, 2, 89−105. (7) Torvisco, A.; O’Brien, A. Y.; Ruhlandt-Senge, K. Coord. Chem. Rev. 2011, 255, 1268−1292. (8) (a) Romero, N.; Roşca, S.-C.; Sarazin, Y.; Carpentier, J.-F.; Vendier, L.; Mallet-Ladeira, S.; Dinoi, C.; Etienne, M. Chem. - Eur. J. 2015, 21, 4115−4125. (b) Liu, B.; Roisnel, T.; Carpentier, J. F.; Sarazin, Y. Chem. - Eur. J. 2013, 19, 2784−2802. (c) Wixey, J. S.; Ward, B. D. Chem. Commun. 2011, 47, 5449−5451. (d) Wixey, J. S.; Ward, B. D. Dalton Trans. 2011, 40, 7693−7696. (e) Mukherjee, A.; Nembenna, S.; Sen, T. K.; Sarish, S. P.; Ghorai, P. K.; Ott, H.; Stalke, D.; Mandal, S. K.; Roesky, H. W. Angew. Chem., Int. Ed. 2011, 50, 3968−3972. (f) Arrowsmith, M.; Crimmin, M. R.; Barrett, A. G. M.; Hill, M. S.; Kociok-Köhn, G.; Procopiou, P. A. Organometallics 2011, 30, 1493− 1506. (g) Neal, S. R.; Ellern, A.; Sadow, A. D. J. Organomet. Chem. 2011, 696, 228−234. (h) Crimmin, M. R.; Arrowsmith, M.; Barrett, A. G. M.; Casely, I. J.; Hill, M. S.; Procopiou, P. A. J. Am. Chem. Soc. 2009, 131, 9670−9685. (i) Barrett, A. G. M.; Crimmin, M. R.; Hill, M. S.; Hitchcock, P. B.; Kociok-Köhn, G.; Procopiou, P. A. Inorg. Chem. 2008, 47, 7366−7376. (j) Panda, T. K.; Hrib, C. G.; Jones, P. G.; Jenter, J.; Roesky, P. W.; Tamm, M. Eur. J. Inorg. Chem. 2008, 2008, 4270−4279. (k) Crimmin, M. R.; Casely, I. J.; Hill, M. S. J. Am. Chem. Soc. 2005, 127, 2042−2043. (9) (a) Brinkmann, C.; Barrett, A. G. M.; Hill, M. S.; Procopiou, P. A. J. Am. Chem. Soc. 2012, 134, 2193−2207. (b) Liu, B.; Roisnel, T.; Carpentier, J.-F.; Sarazin, Y. Angew. Chem., Int. Ed. 2012, 51, 4943− 4946. (10) (a) Younis, F. M.; Krieck, S.; Al-Shboul, T. M. A.; Görls, H.; Westerhausen, M. Inorg. Chem. 2016, 55, 4676−4682. (b) Younis, F. M.; Krieck, S.; Görls, H.; Westerhausen, M. Dalton Trans. 2016, 45, 6241−6250. (c) Younis, F. M.; Krieck, S.; Görls, H.; Westerhausen, M. Organometallics 2015, 34, 3577−3585. (d) Glock, C.; Younis, F. M.; Ziemann, S.; Görls, H.; Imhof, W.; Krieck, S.; Westerhausen, M. Organometallics 2013, 32, 2649−2660. (e) Glock, C.; Görls, H.; Westerhausen, M. Dalton Trans. 2011, 40, 8108−8113. (11) Glock, C.; Görls, H.; Westerhausen, M. Chem. Commun. 2012, 48, 7094−7096. (12) Ziemann, S.; Krieck, S.; Görls, H.; Westerhausen, M. Z. Z. Anorg. Allg. Chem. 2015, 641, 2140−2146. (13) Danièle, S.; Drost, C.; Gehrhus, B.; Hawkins, S. M.; Hitchcock, P. B.; Lappert, M. F.; Merle, P. G.; Bott, S. G. J. Chem. Soc., Dalton Trans. 2001, 3179−3188. (14) Hitchcock, P. B.; Lappert, M. F.; Wei, X.-H. Dalton Trans. 2006, 1181−1187. (15) Robinson, S.; Davies, E. S.; Lewis, W.; Blake, A. J.; Liddle, S. T. Dalton Trans. 2014, 43, 4351−4360. (16) Glock, C.; Görls, H.; Westerhausen, M. Inorg. Chim. Acta 2011, 374, 429−434. (17) (a) Langer, J.; Köhler, M.; Görls, H.; Westerhausen, M. Chem. Eur. J. 2014, 20, 3154−3161. (b) Langer, J.; Al-Shboul, T. M. A.; Younis, F. M.; Görls, H.; Westerhausen, M. Eur. J. Inorg. Chem. 2011, 2011, 3002−3007. (c) Langer, J.; Krieck, S.; Fischer, R.; Görls, H.; Westerhausen, M. Z. Anorg. Allg. Chem. 2010, 636, 1190−1198.

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.organomet.7b00890. Spectra of new compounds, irradiation experiments, crystallographic and refinement data (PDF) Accession Codes

CCDC 1497243−1497247 and 1580152−1580154 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/ data_request/cif, or by emailing [email protected]. uk, or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Fax: +49 3641 948132. ORCID

Matthias Westerhausen: 0000-0002-1520-2401 Author Contributions

The manuscript was written through contributions of all authors. They have given approval to the final version of the manuscript. Funding

We appreciate the financial support of the Fonds der Chemischen Industrie (Verband der Chemischen Industrie e.V., FCI/VCI, Frankfurt/Main, Germany). Notes

The authors declare no competing financial interest.

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REFERENCES

(1) (a) Taube, R. In Applied Homogeneous Catalysis with Organometallic Compounds: A Comprehensive Handbook; Cornils, B., Herrmann, W. A., Eds.; Wiley-VCH: Weinheim, 2000; Chapter 2.7, pp 507−520. (b) Brunet, J. J.; Neibecker, D. In Catalytic Heterofunctionalization: From Hydroamination to Hydrozirconation;TogI

DOI: 10.1021/acs.organomet.7b00890 Organometallics XXXX, XXX, XXX−XXX

Article

Organometallics (18) Ziemann, S.; Krieck, S.; Gö r ls, H.; Westerhausen, M.unpublished results.Z. Anorg. Allg. Chem.2015641214010.1002/ zaac.201500521 (19) Gilli, G.; Bertolasi, V.; Bellucci, F.; Ferretti, V. J. Am. Chem. Soc. 1986, 108, 2420−2424. (20) Ferretti, V.; Bertolasi, V.; Gilli, P.; Gilli, G. J. Phys. Chem. 1993, 97, 13568−13574. (21) Zilberg, S.; Haas, Y. Photochem. Photobiol. Sci. 2003, 2, 1256− 1263. (22) Hooft, R. COLLECT, Data Collection Software; Nonius B.V.: Netherlands, 1998. (23) Otwinowski, Z.; Minor, W. In Methods in Enzymology, Vol. 276, Macromolecular Crystallography; Carter, C. W., Sweet, R. M., Eds.; Academic Press: New York, 1997; Part A, pp 307−326. (24) Sheldrick, G. M. Acta Crystallogr., Sect. A: Found. Crystallogr. 2008, A64, 112−122. (25) Spek, A. L. Acta Crystallogr., Sect. D: Biol. Crystallogr. 2009, D65, 148−155. (26) XP; Siemens Analytical X-ray Instruments Inc: Karlsruhe, Germany, 1990; Madison, WI, 1994. (27) POV-Ray, Persistence of Vision Raytracer; Australia, Victoria, 2007.

J

DOI: 10.1021/acs.organomet.7b00890 Organometallics XXXX, XXX, XXX−XXX