Cleavage of Formamidinate Ligands on a TaTa Double Bond: Formation of H x CNAryl ( x = 0 and 1) and Arylimido-Bridged Complexes
1997; American Chemical Society; Volume: 36; Issue: 5 Linguagem: Inglês
10.1021/ic9611507
ISSN1520-510X
AutoresF. Albert Cotton, L.M. Daniels, C.A. Murillo, Xiaoping Wang,
Tópico(s)Synthesis and characterization of novel inorganic/organometallic compounds
ResumoThree complexes which resulted from the C−N bond cleavage reactions of formamidinate anions, [ArNC(H)NAr]-, have been synthesized and structurally characterized. The reaction of N,N'-diphenylformamidinate, DPhF-, with (Me2S)Cl2Ta(μ-Me2S)(μ-Cl)2TaCl2(SMe2) (abbreviated as Ta2Cl6(SMe2)3) in the presence of Zn metal produces the CNPh-containing dinuclear compound (η2-DPhF)2Ta(μ-NPh)(μ-η2-CNPh)Ta(η2-DPhF)2·C7H8, 1·C7H8. By using DTolF- and Na/Hg as reducing agent, the isolated product is (η2-DTolF)Ta(μ-NTol)(μ-η2-CNTol)(μ-DTolF)2Ta(η2-DTolF)·1.5C6H14, 2·1.5C6H14, where DTolF- = N,N'-di(p-tolyl)formamidinate. Both 1 and 2 are isolated in low yields. There is a formal single bond between the tantalum atoms which are bonded to intact formamidinate ions as well as the two fragments which result from the cleavage of a formamidinate ligand, namely arylimido (NAr2-) and (CNAr). In the absence of a reducing agent, the reaction of LiDTolF and Ta2Cl6(SMe2)3 produces Cl2(η2-DTolF)Ta(μ-NTol)(μ-η2, η2-HCNTol)Ta(η2-DTolF)2, 3, in high yield. In addition to the tolylimido group, a tolylformimidoyl fragment (HCNTol) binds to the tantalum atom through both carbon and nitrogen atoms in a η2,η2 mode. Because of this and the relatively long C−N bond distance (1.42(1) Å), the ligand can be formulated as [HCNTol]3-. Thus the tantalum atoms in 3 have a formal oxidation state of +5, which precludes the presence of a metal-metal bond. Crystal data for 1·C7H8: monoclinic, I2/a, a = 19.437(2) Å, b = 15.587(1) Å, c = 20.401(1) Å, and β = 97.840(6)°. Crystal data for 2·1.5C6H14: triclinic, P1̄, a = 13.990(2) Å, b = 15.841(1) Å, c = 19.442(4) Å, α = 98.98(1)°, β = 104.07(1)°; γ = 109.59(1)°. Crystal data for 3: monoclinic, P21/n, a = 17.962(3) Å, b = 15.539(4) Å, c = 19.973(3) Å, β = 90.126(7)°.
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