75522-33-7Relevant academic research and scientific papers
Preparation and reaction chemistry of trimethylsilyl derivatives of tantalum. X-ray structures of d0 (η5-C5Me5)Ta(SiMe3)Cl 3 and d1 (η5-C5Me5)Ta(SiMe3)(PMe 3)Cl2
Arnold, John,Shina, David N.,Tilley, T. Don,Arif, Atta M.
, p. 2037 - 2044 (2008/10/08)
The preparation of Cp*Ta(SiMe3)Cl3 (1, Cp* = η5-C5Me5) from Cp*TaCl4 and Al(SiMe3)3·OEt2 is reported. Compound 1 is converted to the derivatives Cp*Ta(SiMe3)(OR)Cl2 (2, R = SiMe3; 3, R = CMe3) upon treatment with KOSiMe3 or LiOCMe3, respectively. Reaction of 1 with MeMgBr (3 equiv) produces Cp*Ta(SiMe3)Me3 (4). Donor ligands induce reductive elimination of Me3SiCl from 1. In the case of alkyne addition, the resulting tantalum (III) products are Cp*Ta(RC≡CR′)Cl2 (R = R′ = Me3Si, Ph, Me; R = Ph, R′ = H). When the incoming ligand is PMe3, it appears that an initially formed tantalum(III) product reacts with starting material to afford the tantalum(IV) silyl Cp*Ta(SiMe3)(PMe3)Cl2 (8) and Cp*TaCl4(PMe3) via a series of redox transformations. Complexes 1 and 8 have been structurally characterized. Dark green crystals of 1 belong to space group P21/c with unit cell dimensions a = 15.133 (2) A?, b = 8.522 (2) A?, c = 14.157 (1) A?, β = 91.923 (1)°, V = 1824.7 (5) A?3, and Z = 4. The final R value refined against 1959 data was 3.84%. The paramagnetic d1 silyl 8 also crystallizes in the monoclinic space group P21/c with a = 13.3309 (14) A?, b = 10.3770 (10) A?, c = 16.1017 (25) A?, β = 94.061 (10)°, V = 2221.8 (8) A?3, and Z = 4. The final R value for 2494 data was 1.54%. Both structures exhibit a four-legged piano-stool geometry with noncrystallographic Cs symmetry. The Ta(IV)-Si bond in 8, 2.642 (1) A?, is slightly shorter than the Ta(V)-Si bond in 1, 2.669 (4) A?. These distances are discussed with respect to electron density at the transition-metal center and Ta-Si π-bonding.
