Mononuclear dpp-Bian Gallium Complexes: Synthesis, Crystal

Apr 6, 2015 - Treatment of (dpp-Bian)Ga–Ga(dpp-Bian) (1) (dpp-Bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) with iodine gives ...
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Mononuclear dpp-Bian Gallium Complexes: Synthesis, Crystal Structures, and Reactivity toward Alkynes and Enones Igor L. Fedushkin,*,† Olga V. Kazarina,† Anton N. Lukoyanov,† Alexandra A. Skatova,† Natalia L. Bazyakina,† Anton V. Cherkasov,† and Eftimios Palamidis‡ †

G.A. Razuvaev Institute of Organometallic Chemistry of Russian Academy of Sciences, Tropinina str. 49, 603950 Nizhny Novgorod, Russian Federation ‡ Institut für Chemie der Technischen Universität Berlin, Straβe des 17. Juni 135, 10623 Berlin, Germany S Supporting Information *

ABSTRACT: Treatment of (dpp-Bian)Ga−Ga(dpp-Bian) (1) (dpp-Bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) with iodine gives (dpp-Bian)Ga(I)−Ga(I)(dpp-Bian) (2), which reacts in situ with K(C 5 H 4 CH 2 CH 2 NMe 2 ) (KCp Do ) or K(OCH 2 CH 2 NMe 2 ) (KORDo) to produce the monomeric species (dpp-Bian)GaCpDo (3) and (dpp-Bian)GaOR Do (4), respectively. Complex 3 reacts with PhCCH to give the paramagnetic derivative (dpp-Bian)Ga(CCPh)2 (5), while compound 4 is inert toward this alkyne. In contrast, monomeric (dppBian)Ga(S2CNMe2) (6) reacts with PhCCH and HCCH to give the cycloaddition products [dpp-Bian(PhC CH)]Ga(S2CNMe2) (7) and [dpp-Bian(HCCH)]Ga(S2CNMe2) (8). The related compounds [dpp-Bian(MeCCC(O)OMe)]Ga(S2CNMe2) (9) and [dpp-Bian(CH2CHC(Me)O)]Ga(S2CNMe2) (10) have been obtained in the reactions of complex 6 with methyl 2-butynoate and methyl vinyl ketone, respectively. New complexes have been characterized by 1H NMR (3, 4, and 7−10) and ESR (5) spectroscopy; their molecular structures have been established by single-crystal X-ray analysis. The catalytic activity of complex 6 in the hydroamination and hydroarylation of alkynes has been examined.

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INTRODUCTION

Scheme 1. Reactivity of Magnesium and Gallium Complexes of the dpp-Bian Dianion toward Phenylacetylene

Since 2003 we elaborate an approach to the main-group metal complexes, which may emulate specific reactivity of coordination and organometallic compounds of transition metals. The main instruments used to reach the goal were redox-active ligands that may undergo reduction or oxidation by a substrate while still coordinated to a redox-inactive metal. In our laboratory we use 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-Bian), which in addition to its bulkiness and rigidity is redox-active, as demonstrated by the four-step reduction of dpp-Bian with sodium.1 Group 22 and 133 metal complexes of the dpp-Bian dianion serve well as reducing agents toward different substrates: in the course of the reactions the dpp-Bian dianion is oxidized to the monoanion. The metal bound to dpp-Bian controls the course of reactivity of the latter. For example, the reaction of (dpp-Bian)Mg(THF)3 with PhCCH proceeds as acid−base interaction (Scheme 1),4 while the reaction between (dpp-Bian)Ga−Ga(dpp-Bian) (1) and PhCCH affords a cycloaddition product (Scheme 1).5 It is worth mentioning that addition of PhCCH to compound 1 is reversible: at room temperature the phenylacetylene adduct is stable, whereas raising the temperature to 70 °C leads to full elimination of the alkyne, thereby affording the starting materials. Thus, the complex of a typical non transition metal − compound 1 − binds the π system in a reversible manner as transition metals do. © 2015 American Chemical Society

Cycloaddition of alkynes is also observed with aluminum dpp-Bian species: e.g., (dpp-Bian)AlEt(Et2O)6 and (dppReceived: January 1, 2015 Published: April 6, 2015 1498

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Organometallics Bian)Al−Al(dpp-Bian).7 According to our observations the aluminum dpp-Bian complexes are in general more reactive toward alkynes in comparison to the gallium analogues. For example, complex 1 is inert toward PhCCMe, while (dppBian)Al−Al(dpp-Bian) binds this alkyne to form stable monoas well as bis-adducts. The ability of complex 1 to “coordinate” PhCCH allows hydroamination and hydroarylation of the latter with anilines in the presence of 1 as catalyst.8 The catalytic activity of compound 1 in the hydroamination of phenylacetylene with aromatic amines is comparable to the activity of transition-metal-based systems.9 On the other hand, the catalytic activity of aluminum dpp-Bian species in the reactions between PhCCH and anilines is much lower in comparison to that of complex 1.7 In order to determine whether other gallium complexes of the dpp-Bian dianion are reactive toward alkynes, we intended to prepare mononuclear gallium derivatives of the dpp-Bian dianion. Here we report on the synthesis and characterization of the desired gallium complexes. We show that the mononuclear gallium species (dpp-Bian)GaCpDo (3), (dpp-Bian)GaORDo (4), and (dppBian)Ga[S2CNMe2] (6) are reactive toward alkynes. Furthermore, we demonstrate that conjugated enones (e.g., methyl vinyl ketone) can also be involved in cycloaddition reactions with main-group-metal complexes of redox-active ligands. Preliminary data on the catalytic activity of compound 6 in the reactions of phenylacetylene with some anilines are also presented.

Scheme 2. Synthesis of Compounds 3 and 4

Scheme 3. Reaction of Compound 3 with Phenylacetylene

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RESULTS AND DISCUSSION Synthesis and Characterization of Compounds 3−5 and 7−10. An exchange reaction between (dpp-Bian)Ga(I)− Ga(I)(dpp-Bian) (2) and cyclopentadienylpotassium KCpDo (CpDo = C5H4CH2CH2NMe2) in toluene is accompanied by a redox process, which is manifested by a color change of the reaction mixture from red-brown to blue-green. This process involves an intramolecular electron transfer from the metal− metal bond to the dpp-Bian radical anionic ligands. The reaction product is a mononuclear cyclopentadienyl gallium stabilized by a dpp-Bian dianion (dpp-Bian)GaCpDo (3) (Scheme 2). The related alkoxide (dpp-Bian)GaORDo (4) was prepared similarly by reacting complex 2 with KORDo (ORDo = OCH2CH2NMe2) (Scheme 2). Air- and moisturesensitive complexes 3 and 4 have been isolated in good yields as dark crystals from diethyl ether and toluene, respectively. Unexpectedly, the reaction of compound 3 with phenylacetylene does not afford a cycloadduct similar to that formed in the reaction of 1 with PhCCH (Scheme 1). In the course of the reaction the solution changes its color from deep blue, typical for the dpp-Bian dianion, to cherry red, indicative for the formation of the radical anion of dpp-Bian. The product, the bis(alkynyl)gallium species (dpp-Bian)Ga(CCPh)2 (5), was isolated in high yield from hexane (Scheme 3). We suggest that the reaction proceeds in several steps involving protonation of the Cp ligand and evolution of the dihydrogen from PhCCH under reduction of the latter with dpp-Bian dianion. Due to the presence of the dpp-Bian radical-anion, complex 5 reveals a well-resolved ESR signal (Figure 1). Its hyperfine structure is caused by the coupling of an unpaired electron to two pairs of protons (99.98%, I = 1/2, μN = 2.7928),10 to two equivalent 14N nuclei (99.63%, I = 1, μN = 0.4037),10 and to gallium magnetic isotopes 69Ga (60.11%, I = 3/2, μN = 1.8507) and 71Ga (39.89%, I = 3/2, μN = 2.56227).10

Figure 1. ESR spectrum of compound 5 at 290 K in toluene: (a) experimental; (b) simulated, AN = 0.512 mT (2 × 14N), AH = 0.089 mT (2 × 1H), AH = 0.095 mT (2 × 1H), AGa = 1.614 mT (1 × 69Ga), AGa = 2.050 mT (1 × 71Ga), g = 2.0026.

Addition of 1 mol equiv of PhCCH to a solution of complex 4 in toluene at 20 °C does not result in a color change. However, within 18 h the reaction mixture turned red-brown. Attempts to isolate the product of this reaction failed. Nevertheless, the 1H NMR spectrum of the reaction mixture consists of signals that might be assigned to the cycloadduct 1499

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NMR spectrum of compound 8 consists of only three septets (2 H + 1 H + 1 H) and six doublets (3 H + 3 H + 6 H + 3 H + 3 H + 6 H), which arise from the iPr groups of the aryl substituents. This spectral pattern indicates nonequivalence of two methine protons as well as of the protons of four methyl groups in one iPr2C6H3 substituent (δ 3.39 (1 H), 3.36 (1 H), 1.38 (3 H), 1.31 (3 H), 1.16 (3 H), and 1.10 (3 H) ppm). According to the X-ray crystallography (vide infra) the nitrogen atom bonded to this iPr2C6H3 substituent in compound 8 is not involved in coordination to the gallium atom, whereas the second iPr2C6H3N fragment is coordinated to gallium. One can suggest that at 363 K the nitrogen atom (sp3) in the latter undergoes fast (in NMR time scale) umbrella-like inversion, which resulted in equivalent methine protons. The methyl groups of two iPr substituents remain in unequal pairs due to the restricted rotation around the Me2(H)C−C(Ar) bonds. Thus, the isopropyl groups of the second iPr2C6H3N fragment produce one septet (δ 3.49 (2 H) ppm) and two doublets (δ 1.23 (6 H) and 0.64 (6 H) ppm). One of the important conclusions made on the basis of the 1H NMR spectroscopic data is that in solution no elimination of acetylene takes place from complex 8 when it is heated, at least up to 363 K. In contrast, at 363 K in toluene the adduct between digallane 1 and acetylene, 1·2HCCH, undergoes complete dissociation to 1 and HCCH. On the other hand, the phenylacetylene adduct 1·2PhCCH is completely converted to digallane 1 and phenylacetylene already at 343 K. This observation allows making another qualitative conclusion: acetylene forms more stable adducts with dppBian main-group-metal complexes in comparison to phenylacetylene. In contrast to our expectation the reaction of complex 6 with an active alkyne such as methyl 2-butynoate does not proceed instantly upon mixing the reagents, as happened in the case of compound 1. The reaction proceeds within several hours and results in yellow crystals of the complex [dpp-Bian(MeC CC(O)OMe)]Ga(S2CNMe2) (9) (Scheme 6), which were isolated from toluene in 64% yield.

between 4 and PhCCH. Treatment of the earlier reported dithiocarbamate (dpp-Bian)Ga(S2CNMe2) (6)2f with phenylacetylene in toluene resulted in a color change from deep blue to red greyish. With changing temperature the color of this toluene solution varies in the same way as the solution containing the cycloadduct of 1 and PhCCH: blue above 90 °C, red below −30 °C. Again isolation of a crystalline product was not achieved. However, addition of phenylacetylene (10 mol equiv) to crystalline 6 dissolved in toluene-d8 in an NMR tube resulted in a 1H NMR spectrum, which indicates the formation of [dpp-Bian(PhCCH)]Ga(S2CNMe2) (7) at low temperature (Scheme 4). Scheme 4. Reaction of Compound 6 with Phenylacetylene

The asymmetry of the ligand in complex 7 causes nonequivalence of the four methine protons and of the eight methyl groups of the four isopropyl substituents. In the 1H NMR spectrum of compound 7 (in situ in the NMR tube) the methine protons give rise to four septets (δ 4.34 (1 H), 3.71 (1 H), 3.69 (1 H), and 3.32 (1 H) ppm) and the methyl groups of the isopropyl substituents appear as eight doublets (δ 1.68 (3 H), 1.67 (3 H), 1.63 (3 H), 1.29 (6 H), 1.25 (3 H), 1.11 (3 H), and 0.01 (3 H) ppm), which overlap partially. The protons of the (CH3)2N group of the dithiocarbamate ligand produce a singlet at δ 2.02 ppm. The presence of an excess of phenylacetylene in the sample is manifested by a singlet of the acetylenic proton at δ 2.65 ppm. Increasing the temperature to 333 K results in the 1H NMR spectrum (see the Supporting Information), which points out elimination of phenylacetylene from compound 7. The resulting complex 6 reveals one septet (δ 3.94 (4 H) ppm) and two doublets (δ 1.42 (12 H), 1.18 (12 H) ppm) that correspond to four equivalent isopropyl substituents. The reaction of (dpp-Bian)Ga(S2CNMe2) (6) with HC CH gave the adduct [dpp-Bian(HCCH)]Ga(S2CNMe2) (8) (Scheme 5).

Scheme 6. Reaction of Compound 6 with Methyl 2Butynoate

Scheme 5. Reaction of Compound 6 with Acetylene

The 1H NMR spectrum of product 9 (see the Supporting Information) proves the presence of the asymmetric amidoimino ligand. The spectrum consists of four septets (δ 4.11 (1 H), 3.71 (1 H), 3.54 (1 H), and 3.33 (1 H) ppm) and eight doublets (δ 1.56 (3 H), 1.54 (3 H), 1.52 (3 H), 1.47 (3 H), 1.23 (3 H), 1.13 (3 H), 1.09 (3 H), and 0.09 (3 H) ppm) that arise from nonequivalent isopropyl groups of the dpp-Bian fragment. The singlet signals at δ 3.68 (3 H) and 1.90 (3 H) ppm correspond to the methyl group of the alkyne fragment, whereas the signal at δ 2.09 (6 H) indicates the presence of a S2CN(CH3)2 ligand. The lattice DME molecule gives rise to two signals at δ 3.33 and 3.12 ppm.

Due to the broadening of the signals in the 1H NMR spectrum of compound 8 in toluene at 293 K interpretation of the spectrum is difficult. Increasing the temperature leads to sharpening of the resonances. At 363 K the 1H NMR spectrum of compound 8 reveals an unusual set of the signals that, however, can be well assigned (see the Supporting Information). In contrast to all the earlier reported adducts of alkynes and dpp-Bian group 13 metal complexes the 1H 1500

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at δ 1.27 (12 H) and 1.07 (12 H) ppm. However, at 333 K compound 10 is still present in solution (10 → 6 + MVK; Keq = 0.137). Molecular Structures of 3−5 and 8−10. The new complexes have been characterized by X-ray crystallography. The molecular structures of 3−5 and 8−10 are depicted in Figures 3−8, respectively. Compounds 3 and 4 represent

Looking for other organic substrates that could add in a reversible manner to complex 6, we switched to conjugated enones. Treatment of complex 6 with benzylideneacetone (BA) or methyl vinyl ketone (MVK) resulted in a color change from deep blue to red-brown over several hours at ambient temperatures. In the case of BA we failed to isolate any individual product, whereas with MVK the cycloaddition product [dpp-Bian(CH2CHC(Me)O)]Ga(S2CNMe2) (10) was isolated in the form of orange crystals (Scheme 7). Scheme 7. Reaction of Compound 6 with Methyl Vinyl Ketone

In contrast to the case for the alkynes, MVK adds to complex 6 in a 1,4-fashion resulting also in a Ga−O bond in addition to the C−C bond. Upon rising the temperature in a THF solution compound 10 eliminates MVK and results in starting compound 6. However, as can be seen from UV−vis as well as 1 H NMR spectroscopic data (see the Supporting Information), even at 90 °C the elimination process is far from complete. The absorption spectra of a solution of complex 10 in THF at different temperatures together with the spectrum of pure complex 6 (dashed line) are depicted in Figure 2.

Figure 3. Molecular structure of compound 3. Thermal ellipsoids are drawn at the 30% probability level. Hydrogen atoms are omitted. Selected bond lengths (Å) and angles (deg): Ga−N(1) 1.918(2), Ga− N(2) 1.909(2), Ga−C(37) 1.993(3), Ga−N(3) 2.081(2), N(1)−C(1) 1.391(3), N(2)−C(2) 1.392(3), C(1)−C(2) 1.367(3); N(1)−Ga− N(2) 90.61(9), N(1)−Ga−C(37) 113.6(1), N(2)−Ga−C(37) 129.8(1), C(37)−Ga−N(3) 96.39(8).

Ga(III) complexes of a dpp-Bian dianion with the metal atoms tetrahedrally coordinated. The bond lengths Ga−N(1) and Ga−N(2) in 3 (average 1.913 Å) and in 4 (average 1.890 Å) are in good agreement with those in other four-coordinate gallium(III) complexes of the dpp-Bian dianion: for instance, in

Figure 2. Temperature dependence of the electronic absorption spectrum of complex 10 in THF. For comparison the UV−vis spectrum of compound 6 is presented as a dashed line.

At 278 K adduct 10 reveals the absorption with the maximum at ca. 550 nm. When the temperature is raised, the intensity of this absorption gradually decreases with a concurrent increase of the absorption in the long-wave region, thus indicating the formation of compound 6. The elimination process is reversible; lowering the temperature back to 278 K leads to restoration of the initial spectral image. These data are consistent with 1H NMR spectroscopy. In the 1H NMR spectrum of complex 10 at 233 K (see the Supporting Information) the methyl groups of iPr substituents give rise to doublet signals located at δ 1.35 (6 H), 1.29 (3 H), 1.12 (3 H), 1.04 (3 H), 1.01 (3 H), 0.26 (3 H), and 0.14 (3 H) ppm. Raising the temperature leads to a decrease in the intensities of these signals with simultaneous increase of the intensities of signals that belong to complex 6, as for instance, two doublets

Figure 4. Molecular structure of compound 4. Thermal ellipsoids are drawn at the 30% probability level. Hydrogen atoms are omitted. Selected bond lengths (Å) and angles (deg): Ga−O 1.8307(9), Ga− N(1) 1.893(1), Ga−N(2) 1.887(1), Ga−N(3) 2.0490(9), N(1)−C(1) 1.400(1), N(2)−C(2) 1.393(2), C(1)−C(2) 1.380(2); N(1)−Ga− N(2) 91.04(4), O−Ga−N(3) 87.95(4). 1501

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Figure 7. Molecular structure of compound 9. Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms are omitted. Selected bond lengths (Å) and angles (deg): Ga−N(1) 1.886(2), Ga− C(38) 1.963(2), Ga(1)−S(1) 2.3044(6), Ga(1)−S(2) 2.3638(6), N(1)−C(1) 1.482(3), N(2)−C(2) 1.268(3), C(1)−C(2) 1.576(2), C(1)−C(37) 1.568(3), C(37)−C(38) 1.340(3); N(1)−Ga−C(38) 90.75(9), S(1)−Ga−S(2) 77.77(2).

Figure 5. Molecular structure of compound 5. Thermal ellipsoids are drawn at the 30% probability level. Hydrogen atoms are omitted. Selected bond lengths (Å) and angles (deg): Ga−N(1) 1.967(2), Ga− N(2) 1.981(2), Ga−C(37) 1.917(2), Ga−C(45) 1.932(2), N(1)− C(1) 1.335(3), N(2)−C(2) 1.324(2), C(1)−C(2) 1.426(3); N(1)− Ga−N(2) 85.40(7), C(37)−Ga−C(45) 116.81(9).

Figure 8. Molecular structure of compound 10. Thermal ellipsoids are drawn at the 30% probability level. Hydrogen atoms are omitted. Selected bond lengths (Å) and angles (deg): Ga−O 1.8360(7), Ga− N(1) 1.8658(8), Ga−N(2) 2.2215(8), Ga−S(1) 2.3576(3), Ga−S(2) 2.4412(3), N(1)−C(1) 1.460(1), N(2)−C(2) 1.286(1), C(1)−C(2) 1.543(1), C(1)−C(37) 1.565(1), C(37)−C(38) 1.507(1), C(39)−O 1.356(1), C(38)−C(39) 1.342(2); O(1)−Ga−N(1) 111.91(3), O(1)−Ga−N(2) 95.20(3), N(1)−Ga−N(2) 82.61(3), S(1)−Ga− S(2) 75.224(9).

Figure 6. Molecular structure of compound 8. Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms are omitted. Selected bond lengths (Å) and angles (deg): Ga−N(1) 1.8695(7), Ga−C(38) 1.947(1), Ga−S(1) 2.3279(2), Ga−S(2) 2.3730(3), N(1)−C(1) 1.469(1), N(2)−C(2) 1.272(1), C(1)−C(2) 1.560(1), C(1)−C(37) 1.542(1), C(37)−C(38) 1.338(1); N(1)−Ga−C(38) 91.41(4), S(1)−Ga−S(2) 77.358(9).

complex 4 (1.8307(9) Å) is the shortest among all related compounds containing the Me2NCH2CH2O ligand. The dianionic character of dpp-Bian in 3 and 4 is evident from the bond lengths within both metallacycles. Thus, the C(1)− N(1) and C(2)−N(2) bonds in 3 and 4 (average 1.391 and 1.396 Å, respectively) are much longer than those bonds in free dpp-Bian (both 1.282(4) Å)14 as well as in the dpp-Bian radical anion, for instance in complex 5 (vide infra). Crystallographic data obtained for compound 5 are in agreement with ESR spectroscopic data and prove the presence of the dpp-Bian radical anion. The C−N bonds in 5 (1.335(3) and 1.324(2) Å) are longer than those in free dpp-Bian but shorter than those in the dpp dianion in 3 and 4. Ga−N distances in 5 (average 1.974 Å) are also remarkably longer in comparison to those values in 3 (average 1.913 Å) and 4 (average 1.890 Å). The Ga−C(sp) bond lengths in 5 (average

6 (average 1.877 Å)2f and in (dpp-Bian)GaI(Py) (average 1.896 Å).11 In complex 3 the Cp ligand is η1-coordinated to the gallium atom. The latter is bonded to the carbon atom positioned next to the donor substituent. It is part of a sixmembered metallcycle, which has a “chair” conformation. The Ga−C(CpDo) bond in complex 3 (1.993(3) Å) is in good agreement with those bonds in CpDoGaX2 (X = Cl, Br, I, CH3) (average 2.021 Å).12 To date several gallium complexes with a Me2NCH2CH2O ligand (RDoO) have been reported.13 These can be divided into two series: complexes with one or two RDoO ligands. In contrast to the case for 4 all of the monoligand species represent dimers with bridging oxygen atoms, [X2Ga(μ-ORDo)]2 (X = H,13a Cl,13e Me,13a Et13c). Monomeric complexes are limited to the two five-coordinated species (RDoO)2GaX (X = Cl,13d Et13b). The Ga−O bond in 1502

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Organometallics 1.924 Å) are comparable with Ga−N(amido) distances in compounds 3 and 4 but are significantly shorter than the Ga− C(sp3) bond in complex 3 (1.993(3) Å). As expected, an increase of the Ga−N bond lengths on going from 3 and 4 to 5 resulted in a decrease of the bite angles (3, 90.6°; 4, 91.0°; 5, 85.4°). The molecular structures of compounds 8−10 are quite different from those of complexes 3−5. In the latter complexes dpp-Bian acts as a symmetric chelating ligand independent of whether the dpp-Bian acts as a dianion (3 and 4) or a monoanion (5). An attachment of unsaturated organic molecules in 8−10 across the C−N−Ga section resulted in an asymmetric ligand system, which comprises amido, imino, and carbyl functions. The gallium five-membered metallacycles 1,2-azagalols observed in 8−10 are rather unique and, as far as we know, have not yet been reported. Coupling of dpp-Bian with acetylene, methyl 2-butynoate, or methyl vinyl ketone makes the C(1) atom in 8−10 chiral. Unit cells in each case contain R and S enantiomers in pairs (8, Z = 2; 9, Z = 8; 10, Z = 8). In 9 two enantiomers represent crystallographically independent molecules. In 8 and 9 gallium atoms are tetrahedrally coordinated, while in 10 the metal coordination environment is best described as trigonal bipyramidal. In all three compounds the Ga−N(1) bond lengths are close to each other. In addition, the Ga− C(38) bonds in 8 and 9 (1.947(1) and 1.963(2) Å) are of the same magnitude but ca. 0.1 Å longer than the Ga−N(1) bonds. As one may expect in complex 10 among the Ga−N, Ga−S, and Ga−O bonds the last is the shortest bond (1.8360(7) Å). Due to the lesser constraints in the seven-membered metallacycle in 10 in comparison to those in the five-membered metallacycles in 8 and 9 the atom N(2) in 10 can be involved in the coordination to gallium, thus occupying one of the axial positions in the bipyramid along with atom S(2). In addition, the difference in Ga−S bond lengths in 10 is more pronounced in comparison to that in compounds 8 and 9. Test of Catalytic Activity of 6 in Reactions of Phenylacetylene with Anilines and 1-Naphthol. Being inspired by the catalytic activity of compound 1 in the hydroamination and hydroarylation of alkynes by aromatic amines,6 we examined the catalytic properties of complex 6 in those reactions. All of the catalytic tests were performed with 4 mol % of complex 6 relative to the substrates (1:1 molar ratio) in C6D6 in an NMR tube. Conversion of the substrates to the products was estimated by 1H NMR spectroscopy. The results are summarized in Table 1. In the presence of 2 mol % of complex 1 an equimolar mixture of PhCCH and 4-chloroaniline was quantitatively converted to the hydroamination product within a few hours at 110 °C.6 In contrast, in the presence of 4 mol % of complex 6 the yield of the corresponding imine (Table 1, entry 1) reached only 25% within 2 days. With simple aniline complex 6 exhibits almost no catalytic activity (Table 1, entry 2), while in the presence of complex 1 (2 mol %) PhCCH reacts with PhNH2 to give a >99% yield of the expected imine within 16 h.6 As with 1, the reaction between phenylacetylene and 1aminonaphthalene in the presence of 6 affords both a hydroamination and a hydroarylation product. First, an overall conversion of the reagents using 6 as catalyst reached only 25% after more than 100 h (cf. 100% conversion in the presence of 1 within 12 h). Second, in the presence of 1 phenylacetylene reacts with 1-aminonaphthalene, resulting in a 1:1 mixture of hydroamination and hydroarylation products.

Table 1. Reactions of Phenylacetylene with Anilines and 1Naphthol Catalyzed by Complex 6

With bulky anilines (Table 1, entries 4 and 5) complex 6 does not serve as catalyst at all, while in the presence of compound 1 phenylacetylene reacts with 2-methoxy-5-chloroaniline to give the corresponding imine in 98% yield within 50 h. Similar to the case for complex 1 compound 6 catalyzes hydroarylation of phenylacetylene with 1-naphthol. Initially the reaction rate is rather good: in 7 h conversion of the reagents reached 40%. However, in the course of the next 163 h the conversion grew only by another 10%. In the presence of 1-naphthol deactivation of catalyst 6 probably takes place. We also tried a Diels−Alder reaction between phenylacetylene and MVK in the presence of complex 6 as catalyst. No reaction was observed at room temperature over 24 h. At 100 °C MVK polymerized in the presence of 6 with 74% conversion within 144 h. Thus, we conclude that in comparison with digallane 1 the mononuclear gallium complex supported by the dianionic dpp-Bian ligandcompound 6is not efficient enough as catalyst for the addition of anilines to phenylacetylene. One of the reasons for that is coordinative saturation of 6 as well as of its adduct with phenylacetylene, compound 7. Although the molecular geometry of the latter was not determined by a single-crystal X-ray analysis, one may expect that adduct 7 represents, like other adducts between 6 and alkynes, a four- or even five-coordinate gallium complex. 1503

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Precipitated KCl was filtered off. Crystallization from mother liquor gave 4·1.5C7H8 as deep blue prismatic crystals (0.46 g, 58%). Mp: 283−287 °C dec. IR (Nujol): 1919 w, 1858 w, 1802 w, 1786 w, 1670 m, 1656 m, 1642 w, 1614 w, 1603 w, 1592 m, 1578 w, 1519 s, 1496 w, 1439 s, 1361 m, 1341 s, 1326 s, 1266 m, 1254 m, 1211 w, 1192 w, 1186 w, 1137 w, 1103 m, 1081 s, 1058 w, 1031 m, 1022 w, 1000 w, 944 s, 938 s, 925 s, 909 m, 885 s, 835 m, 815 s, 806 m, 798 m, 780 m, 766 vs, 762 vs, 731 vs, 695 s, 683 w, 651 w, 624 s, 592 w, 569 m, 550 w, 535 w, 517 w, 494 w, 465 s cm−1. 1H NMR (400 MHz, C6D6, 293 K): δ 7.27 (m, 8 H, iPr2C6H3), 6.86 (dd, 2 H, Ar, J = 8.0 and 7.0 Hz), 6.23 (d, 2 H, Ar, J = 6.7 Hz), 4.10 (sept, 2 H, CH(CH3)2, J = 6.8 Hz), 3.85 (sept, 2 H, CH(CH3) 2, J = 6.5 Hz), 3.57 (s, 6 H, OCH2CH2N(CH3)2), 3.47 (t, 2 H, CH2CH2N(CH3)2, J = 5.3 Hz), 1.59 (t, 2 H, CH2CH2N(CH3)2, J = 5.3 Hz), 1.49−1.07 (m, 24 H, CH(CH3)2). Anal. Calcd for C50.50H62GaN3O (796.75): C, 76.12; H, 7.84; N, 5.27. Found: C, 76.83; H, 7.67; N, 5.15 (dpp-Bian)Ga(CCPh)2 (5). Phenylacetylene 0.24 g (2.4 mmol) was added to a toluene solution (30 mL) of complex 3, which was obtained in situ as described above using 0.5 g (1.0 mmol) of dppBian. Within 4 h at 80 °C the reaction mixture turned from blue-green to red-brown. A solid left after evaporation of toluene was dissolved in hexane (30 mL). Concentration of the hexane solution (20 mL) afforded red-brown cubic crystals of 5·Et2O (0.55 g, 79%). Mp: 185 °C. IR (Nujol): 2144 s, 1947 w, 1879 w, 1825 w, 1804 w, 1738 w, 1676 w, 1595 m, 1543 s, 1480 s, 1428 s, 1364 m, 1350 w, 1323 s, 1256 s, 1213 s, 1186 m, 1150 m, 1111 w, 1080 w, 1070 w, 1057 w, 1040 w, 1026 w, 951 w, 935 w, 914 w, 893 m, 877 w, 823 s, 804 s, 787 w, 773 s, 766 s, 756 s, 690 s, 669 m, 640 w, 615 w, 592 w, 573 m, 565 m, 547 m, 536 m, 493 w, 459 s cm−1. X-ray-quality crystals of compound 5 were obtained from diethyl ether. Anal. Calcd For C56H60GaN2O (846.78): C, 79.43; H, 7.14; N, 3.31. Found: C, 79.57; H, 7.18; N, 3.14. [dpp-Bian(PhCCH)]Ga(S2CNMe2) (7). To a solution of (dppBian)GaS(S)CNMe2·C7H8 (0.783 g, 1 mmol) in toluene was added phenylacetylene (0.2 g, 0.22 mL, 2 mmol). The reaction mixture turned from deep blue to red-brown. Then toluene was completely evacuated and the solid was washed with n-hexane. 1H NMR (400 MHz, toluene-d8, 233 K): δ 7.70 (s, 1 H, [−C(C6H5)CH−]), 7.40− 6.65 (m, 6 H, Ar; 12 H, 4 × C6H3iPr2, 5 H, [−C(C6H5)CH−]), 4.34 (sept, 1 H, CH(CH3)2, J = 6.5 Hz), 3.71 (sept, 1 H, CH(CH3)2), J = 6.8 Hz), 3.69 (sept, 1 H, CH(CH3)2), J = 6.8 Hz), 3.32 (sept, 1 H, CH(CH3)2, J = 6.5 Hz), 2.02 (s, 6 H, S2CN(CH3)2), 1.68 (d, 3 H, H(CH3)(CH3), J = 6.8 Hz), 1.67 (d, 3 H, H(CH3)(CH3), J = 6.8 Hz), 1.63 (d, 3 H, H(CH3)(CH3), J = 6.8 Hz), 1.29 (d, 6 H, 2 × H(CH3)(CH3), J = 6.5 Hz), 1.25 (d, 3 H, H(CH3)(CH3), J = 6.8 Hz), 1.11 (d, 3 H, H(CH3)(CH3), J = 6.8 Hz), 0.01 (d, 3 H, H(CH3)(CH3), J = 6.8 Hz). [dpp-Bian(HCCH)]Ga(S2CNMe2) (8). To a solution of 6·C7H8 (0.39 g, 0.5 mmol) in DME (20 mL) was added gaseous acetylene (16 mL, 0.7 mmol) at −78 °C. The reaction mixture was warmed to ambient temperature. Over 18 h the reaction mixture turned from deep blue to red-brown. Crystallization from mother liquor gave yellow crystals of 8·DME (0.09 g, 32%). Mp: 123 °C dec. IR (Nujol): ν 2675 w, 1925 w, 1660 s, 1618 w, 1589 w, 1542 s, 1456 vs, 1402 m, 1323 w, 1316 w, 1302 w, 1249 s, 1207 m, 1189 w, 1171 w, 1137 w, 1105 s, 1043 w, 1007 m, 976 m, 936 w, 917 s, 875 w, 853 m, 830 m, 818 w, 797 s, 777 vs, 756 s, 732 s, 660 w, 648 m, 621 w, 603 m, 572 s, 550 w, 541 m, 516 w, 499 w, 470 s, 456 m cm−1. 1H NMR (400 MHz, toluene-d8, 363 K): δ 7.75 (d, 1 H, −CHCH−, J = 13.5 Hz), 7.44 (d, 1 H, Ar, J = 8.0 Hz), 7.38 (d, 1 H, Ar, J = 8.3 Hz), 7.29 (t, 2 H, Ar, J = 9.0 Hz), 7.22−6.92 (m, 6 H, Ar), 6.87 (d, 1 H, Ar, J = 6.5 Hz), 6.76 (d, 1 H, Ar, J = 7.0 Hz), 6.55 (d, 1 H, −CHCH−, J = 13.8 Hz) 3.49 (br sept, 2 H, CH(CH3)2), 3.39 (sept, 1 H, CH(CH3)2, J = 6.8 Hz), 3.36 (sept, 1 H, CH(CH3)2, J = 6.8 Hz), 2.59 (s, 6 H, S2CN(CH3)2), 1.38 (d, 3 H, CH(CH3)(CH3), J = 6.8 Hz), 1.31 (d, 3 H, CH(CH3)(CH3), J = 6.5 Hz), 1.23 (d, 6 H, CH(CH3)2, J = 6.8 Hz), 1.16 (d, 3 H, CH(CH3)(CH3), J = 6.8 Hz), 1.10 (d, 3 H, CH(CH3)(CH3), J = 7.0 Hz), 0.64 (d, 6 H, CH(CH3)2, J = 6.3 Hz). Anal. Calcd for C45H58GaN3O2S2 (806.78): C, 66.99; H, 7.25; N, 5.21. Found: C, 67.12; H, 7.31; N, 5.08.

CONCLUSION In conclusion, we have prepared new monomeric gallium complexes with rigid the bis-amido ligand dpp-Bian: cyclopentadienyl and alkoxide derivatives 3 and 4, respectively. In contrast to our expectation, the reaction of complex 3 with PhCCH does not afford a cycloaddition product but proceeds with oxidation of the dpp dianion to give the radical anion, resulting in (dpp-Bian)Ga(CCPh)2 (5). In contrast, the gallium complex with a bis-amido ligand (dpp-Bian)Ga(S2CNMe2) (6) reacts with alkynes as well as with methyl vinyl ketone to give cycloadducts 7−10. Comparison of the catalytic properties of complex 6 to those of (dpp-Bian)Ga−Ga(dppBian) (1) has shown a lower activity of the former complex in the reactions between phenylacetylene and anilines. This can be explained by a less labile coordination sphere of gallium metal in compound 6 due to the presence of the two chelating ligands dpp-Bian and dithiocarbamate.

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EXPERIMENTAL SECTION

General Remarks. Compounds 1−10 are sensitive to air and moisture. Therefore, all manipulations concerning their preparation and identification were carried out under vacuum using glass ampules. The solvents 1,2-dimethoxyethane, diethyl ether, hexane, and toluene were dried over sodium/benzophenone and condensed under vacuum in the reaction flasks just prior to the syntheses. Benzene-d6, toluened8, and THF-d8 (all from Aldrich) were dried over sodium/ benzophenone at ambient temperature and condensed just prior to use under vacuum into the NMR tubes, which contained already the samples that should be analyzed. Phenylacetylene, methyl vinyl ketone, and methyl 2-butynoate (all from Aldrich) were placed over sodium metal just prior to use and then condensed under vacuum in the reaction flasks. The IR spectra were recorded on a FSM-1201 spectrometer and the 1H NMR spectra on Bruker DPX-200 and Bruker Advance III 400 spectrometers. Compound 1 was prepared reacting metallic gallium (excess) and dpp-Bian (0.5 g, 1.0 mmol) in toluene at reflux.5 Toluene solutions of compound 1 were used in situ for the preparation of compound 2 as described recently.11 Compound 2 was also used in situ for the preparation of complexes 3 and 4. The yields of 3 and 4 were calculated on dpp-Bian, which was used for the syntheses of 1. 6·C7H8 was prepared and isolated according to a literature procedure.8 Synthesis of (dpp-Bian)GaCpDo (3). To a suspension of complex 2 (prepared as described above) in toluene (30 mL) was added 0.17 g (1.0 mmol) of K(C5H4CH2CH2NMe2) with stirring. The ampule was sealed off and heated to 80 °C. Within 3 h the reaction mixture turned from red-brown to blue-green. Colorless solid (KI) was filtered off. The residual solid left after evaporation of the solvent from the bluegreen solution was dissolved in diethyl ether (40 mL) at reflux. Crystallization at 0 °C resulted in blue-green crystals of 3·0.5Et2O (0.31 g, 50%). Mp: 190 °C. IR (Nujol): 1590 w, 1541 m, 1520 s, 1435 s, 1354 m, 1329 s, 1256 s, 1209 w, 1182 w, 1161 w, 1134 w, 1117 m, 1080 w, 1057 w, 1042 w, 1026 w, 1001 w, 960 w, 922 s, 901 m, 887 m, 845 w, 825 w, 810 m, 802 m, 764 s, 731 m, 711 w, 677 w, 671 w, 646 w, 634 w, 621 w, 594 w, 549 w, 538 w, 517 w, 439 w cm−1. 1H NMR (200 MHz, C6D6, 293 K): δ 7.33 (m, 3 H, C5H4), 7.25 (m, 6 H, iPr2C6H3), 7.14 (d, 2 H, Ar, J = 8.2 Hz), 6.92 (pst, 2 H, Ar, J = 8.2 Hz), 6.77 (s, 1 H, CH-Ga), 6.21 (d, 2 H, Ar, J = 8.2 Hz), 3.71 (br s, 4 H, CHMe2), 3.35 (q, 2 H, (CH3CH2)2O), 2.37−2.10 (m, 4 H, Me2NCH2CH2), 2.05 (s, 6 H, (CH3)2N), 1.41 (br s, 12 H, CH(CH3)2), 1.19 (br s, 12 H, CH(CH3)2), 1.11 (t, 3 H, (CH3CH2)2O). Anal. Calcd for C47H59GaN3O0.50 (743.69): C, 75.90; H, 8.00; N, 5.65. Found: C, 75.73; H, 7.94; N, 5.78. Synthesis of (dpp-Bian)GaORDo (4). To a suspension of complex 2 (prepared as described above) in toluene (30 mL) was added 0.13 g (1.0 mmol) of K(OCH2CH2NMe2). The reaction mixture was stirred at ambient temperature until both substances dissolved completely. Within 12 h the mixture turned from red-brown to deep blue. 1504

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[dpp-Bian(MeCCC(O)OMe)]Ga(S2CNMe2) (9). To a solution of 6·C7H8 (0.47 g, 0.59 mmol) in DME (15 mL) was added 0.083 g (0.85 mmol) of methyl 2-butynoate by condensation under vacuum at −78 °C. A change in the color of the reaction mixture from deep blue to light brown within several hours was accompanied by formation of yellow crystals of complex 9·0.25 DME. Yield: 0.43 g (64%). Mp: >150 °C dec. IR (Nujol): 1959 w, 1933 w, 1860 w, 1687 vs, 1657 s, 1617 w, 1590 m, 1582 m, 1548 s, 1430 m, 1404 m, 1365 m, 1347 w, 1327 m, 1317 s, 1250 vs, 1216 vs, 1186 m, 1136 w, 1109 m, 1044 s, 1035 s, 1019 m, 979 s, 952 m, 933 m, 883 w, 850 s, 835 s, 819 w, 802 s, 790 vs, 783 vs, 762 s, 755 s, 696 w, 631 w, 615 w, 593 w, 571 w, 546 m, 525 w, 489 w, 463 m cm−1. 1H NMR (200 MHz, benzene-d6, 298 K): δ 7.38−6.82 (m, 11 H, Ar), 6.73 (d, 1 H, Ar, J = 7.1 Hz), 4.11 (sept, 1 H, CH(CH3)2, J = 6.7 Hz), 3.71 (sept, 1 H, CH(CH3)2, J = 7.1 Hz), 3.68 (s, 3 H, CH3−CHC(O)OCH3), 3.54 (sept, 1 H, CH(CH3)2, J = 6.7 Hz), 3.33 (sept, 1 H, CH(CH3)2, J = 7.1 Hz), 3.31 (s, 4 H, DME, 2 × CH2OCH3) 3.12 (s, 6 H, DME, 2 × CH2OCH3), 2.09 (s, 6 H, S2CN(CH3)2), 1.9 (s, 3 H, CH3−CHC(O)OCH3), 1.56 (d, 3 H, H(CH3)(CH3), J = 6.7 Hz), 1.54 (d, 3 H, CH(CH3)(CH3), J = 6.7 Hz), 1.52 (d, 3 H, CH(CH3)(CH3), J = 6.7 Hz), 1.47 (d, 3 H, CH(CH3)(CH3), J = 6.8 Hz), 1.23 (d, 3 H, CH(CH3)(CH3), J = 6.7 Hz), 1.13 (d, 3 H, H(CH3)(CH3), J = 6.8 Hz), 1.09 (d, 3 H, CH(CH3)(CH3), J = 7.0 Hz), 0.09 (d, 3 H, CH(CH3)(CH3), J = 7.0 Hz). Anal. Calcd for C45H54.5GaN3O2.5S2 (811.26): C, 66.62; H, 6.77; N, 5.18. Found: C, 66.07; H, 7.12; N, 5.29. [dpp-Bian(CH2CHC(Me)O)]Ga(S2CNMe2) (10). To a solution of 6·C7H8 (0.56 g, 0.71 mmol) in DME (15 mL) was added 0.05 g of MVK (0.73 mmol) by condensation at −78 °C. Within 18 h at 20 °C the reaction mixture turned from deep blue to red-brown. Compound 10 crystallized from mother liquor in form of orange-brown crystals. Yield: 0.32 g (59%). Mp: >150 °C dec. IR (Nujol): 1929 w, 1869 w, 1805 w, 1646 vs, 1597 w, 1588 w, 1530 s, 1488 w, 1435 m, 1396 m, 1315 m, 1251 s, 1231 w, 1207 w, 1179 s, 1140 w, 1102 m, 1084 m, 1058 w, 1040 m, 1008 m, 985 s, 959 w, 937 m, 926 m, 903 w, 885 w, 868 w, 841 s, 835 s, 821 w, 802 vs, 782 vs, 765 vs, 692 m, 652 s, 636 w, 573 s, 545 m, 530 w, 514 w, 497 w, 468 s, 460 m cm−1. 1H NMR (400 MHz, THF-d8, 233 K): δ 8.00 (d, 1 H, Ar, J = 8.3 Hz), 7.69 (d, 1 H, Ar, J = 8.3 Hz), 7.41−7.17 (m, 7 H, Ar), 7.13 (dd, 1 H, Ar, J = 8.3 and 7.0 Hz), 6.29 (d, 1 H, Ar, J = 7.0 Hz), 6.04 (d, 1 H, Ar, J = 7.0 Hz), 4.34 (sept, 1 H, CH(CH3)2, J = 6.5 Hz), 3.94 (d, 1 H, CH2−CH C(Me)−O), J = 4.3 Hz), 3.76−3.65 (m, 2 H, CH(CH3)2), 3.43−3.36 (m, 1 H, CH(CH3)2), 3.43 (s, 6 H, S(S)CN(CH3)2), 3.16 (d, 1 H, CH2−CHC(Me)−O), J = 17.8 Hz), 3.10−2.94 (m, 2 H, CH(CH3)2, 1 H, CH2−CHC(Me)−O), 1.92 (m, 1 H, CH2− CHC(Me)−O)), 1.35 (d, 6 H, 2 × CH(CH3)(CH3), J = 6.5 Hz), 1.29 (d, 3 H, CH(CH3)(CH3), J = 6.5 Hz), 1.12 (d, 3 H, CH(CH3)(CH3), J = 6.8 Hz), 1.04 (d, 3 H, CH(CH3)(CH3), J = 6.5 Hz), 1.01 (d, 3 H, CH(CH3)(CH3), J = 6.5 Hz), 0.26 (d, 3 H, CH(CH3)(CH3), J = 6.5 Hz), 0.14 (d, 3 H, H(CH3)(CH3), J = 6.8 Hz). Anal. Calcd for C43H52GaN3OS2 (760.72): C, 67.89; H, 6.89; N, 5.52. Found: C, 68.01; H, 6.83; N, 5.64. Single-Crystal X-ray Structure Determination. The X-ray density data for 3−5 and 8−10 were collected on Bruker Smart Apex (3, 9) and Agilent Xcalibur E diffractometers (4, 5, 8, 10) with graphite-monochromated Mo Kα radiation (λ = 0.71073 Å), using the ω-scan technique. The structures were solved by direct methods and were refined on F2 using the SHELXTL15 and Crysalis Pro16 packages. All non-hydrogen atoms in 3−5 and 8−10 and H(37) and H(38) atoms in 10 were found from Fourier syntheses of electron density and were refined anisotropically. All other hydrogen atoms in 3−5 and 8− 10 were placed in calculated positions and were refined in the “riding model” with Uiso(H) = 1.2Ueq (Uiso(H) = 1.5Ueq for the hydrogen atoms in CH3 groups) of their parent atoms. SADABS17 and ABSPACK (Crysalis Pro)16 were used to perform area-detector scaling and absorption corrections. For crystal data and details of data collection and structure refinement see the Supporting Information. CCDC 1037186 (3), 1037187 (4), 1037188 (5), 1037189 (8), 1037190 (9), and 1037191 (10) contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via ccdc.cam.ac.uk/community/requestastructure.

Article

ASSOCIATED CONTENT

S Supporting Information *

Figures, a table, and CIF files giving NMR spectra as well as crystal data of compounds 4 and 7−10. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*E-mail for I.L.F.: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by the Russian Science Foundation (grant 14-13-01063). REFERENCES

(1) (a) Fedushkin, I. L.; Skatova, A. A.; Chudakova, V. A.; Fukin, G. K. Angew. Chem. 2003, 115, 3416−3420. Angew. Chem., Int. Ed. 2003, 42, 3294−3298. (b) Fedushkin, L. L.; Khvoinova, N. M.; Piskunov, A. V.; Fukin, G. K.; Hummert, M.; Schumann, H. Russ. Chem. Bull. 2006, 55, 722−730. (2) (a) Fedushkin, I. L.; Skatova, A. A.; Cherkasov, V. K.; Chudakova, V. A.; Dechert, S.; Hummert, M.; Schumann, H. Chem. - Eur. J. 2003, 9, 5778−5783. (b) Fedushkin, I. L.; Skatova, A. A.; Lukoyanova, A. N.; Chudakova, V. A.; Dechert, S.; Hummert, M.; Schumann, H. Russ. Chem. Bull. 2004, 53, 2751−2762. (c) Fedushkin, I. L.; Skatova, A. A.; Hummert, M.; Schumann, H. Eur. J. Inorg. Chem. 2005, 1601−1608. (d) Fedushkin, I. L.; Makarov, V. M.; Rosenthal, E. C. E.; Fukin, G. K. Eur. J. Inorg. Chem. 2006, 827−832. (e) Fedushkin, I. L.; Chudakova, V. A.; Hummert, M.; Schumann, H. Z. Naturforsch., B 2008, 63, 161− 168. (f) Fedushkin, I. L.; Nikipelov, A. S.; Skatova, A. A.; Maslova, O. V.; Lukoyanov, A. N.; Fukin, G. K.; Cherkasov, A. V. Eur. J. Inorg. Chem. 2009, 3742−3749. (3) Fedushkin, I. L.; Lukoyanov, A. N.; Fukin, G. K.; Hummert, M.; Schumann, H. Russ. Chem. Bull. 2006, 55, 1177−1183. (4) Fedushkin, I. L.; Khvoinova, N. M.; Skatova, A. A.; Fukin, G. K. Angew. Chem. 2003, 115, 5381−5384. Angew. Chem., Int. Ed. 2003, 42, 5223−5226. (5) Fedushkin, I. L.; Nikipelov, A. S.; Lyssenko, K. A. J. Am. Chem. Soc. 2010, 132, 7874−7875. (6) Fedushkin, I. L.; Moskalev, M. V.; Baranov, E. V.; Abakumov, G. A. J. Organomet. Chem. 2013, 747, 235−240. (7) Fedushkin, I. L.; Moskalev, M. V.; Lukoyanov, A. N.; Tishkina, A. N.; Baranov, E. V.; Abakumov, G. A. Chem. - Eur. J. 2012, 18, 11264− 11276. (8) Fedushkin, I. L.; Nikipelov, A. S.; Morozov, A. G.; Skatova, A. A.; Cherkasov, A. V.; Abakumov, G. A. Chem. - Eur. J. 2012, 18, 255−266. (9) (a) Dabb, S. L.; Messerle, B. A. Dalton Trans. 2008, 6368−6371. (b) Shaffer, A. R.; Schmidt, J. A. R. Organometallics 2008, 27, 1259− 266. (c) Shi, Y.; Ciszewski, J. T.; Odom, A. L. Organometallics 2002, 21, 5148. (10) Emsley, J. The Elements; Clarendon Press: Oxford, U.K., 1991. (11) Fedushkin, I. L.; Skatova, A. A.; Dodonov, V. A.; Chudakova, V. A.; Bazyakina, N. L.; Piskunov, A. V.; Demeshko, S. V.; Fukin, G. K. Inorg. Chem. 2014, 53, 5159−5170. (12) Jutzi, P.; Bangel, M.; Neumann, B.; Stammler, H.-G. Organometallics 1996, 15, 4559−4564. (13) (a) Rettig, S. J.; Storr, A.; Trotter, J. Can. J. Chem. 1975, 53, 58− 66. (b) Basharat, S.; Carmalt, C. J.; King, S. J.; Peters, E. S.; Tocher, D. A. Dalton Trans. 2004, 3475−3480. (c) Basharat, S.; Carmalt, C. J.; Palgrave, R.; Barnett, S. A.; Tocher, D. A.; Davies, H. O. J. Organomet. Chem. 2008, 693, 1787−1796. (d) Basharat, S.; Knapp, C. E.; Carmalt, C. J.; Barnett, S. A.; Tocher, D. A. New J. Chem. 2008, 32, 1513−1518. (e) Knapp, C. E.; Pugh, D.; McMillan, P. F.; Parkin, I. P.; Carmalt, C. J. Inorg. Chem. 2011, 50, 9491−9498. 1505

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Organometallics (14) Fedushkin, I. L.; Chudakova, V. A.; Fukin, G. K.; Dechert, S.; Hummert, M.; Schumann, H. Russ. Chem. Bull. 2004, 53, 2744−2750. (15) Sheldrick, G. M. SHELXTL v.6.12, Structure Determination Software Suite; Bruker AXS, Madison, WI, USA, 2000. (16) CrysAlis Pro; Agilent Technologies Ltd., Yarnton, U.K., 2011. (17) Sheldrick, G. M. SADABS v.2.01, Bruker/Siemens Area Detector Absorption Correction Program; Bruker AXS, Madison, WI, USA, 1998.

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