Portal de Periódicos da CAPES

nido -Metalloborane Complexes: Synthesis and Structural Characterization of μ 2 ,η 4 -Hexahydrodiboratotetrakis( N , N‘ -diarylformamidinato)ditantalum(III), Aryl = p -Tolyl and Phenyl. The First Structurally Characterized Complexes Containing the μ 2 ,η 4 -B 2 H 6 2- Ligand

1996; American Chemical Society; Volume: 118; Issue: 20 Linguagem: Inglês

10.1021/ja954087d

1943-2984

F. Albert Cotton, L.M. Daniels, C.A. Murillo, Xiaoping Wang,

Organoboron and organosilicon chemistry

The nido-metalloborane complexes Ta2(μ2,η4-B2H6)(DTolF)4·2Et2O, 1, DTolF- = [(p-tolyl)NCHN(p-tolyl)]-, and Ta2(μ2,η4-B2H6)(DPhF)4·Et2O, 2, DPhF- = [phenylNCHNphenyl]-, are formed as the products of tantalum pentachloride with lithium borohydride followed by the addition of LiDTolF or LiDPhF. Complexes 1 and 2 are the first structurally characterized compounds in which two metal atoms that are bonded to each other are also bridged by an hexahydroborate ligand through four B−H−M three-center bonds in a symmetric bonding mode. The Ta−Ta distances are 2.725(1) Å in 1 and 2.728(1), 2.736(1) Å in 2. Crystallographic data are as follows: compound 1, P1̄, a = 15.197(3) Å, b = 15.675(2) Å, c = 16.449(6) Å, α = 102.50(1)°, β = 99.04(1)°, γ = 117.10(2)°, and Z = 2; compound 2, P1̄ with a = 11.547(5) Å, b = 20.03(1) Å, c = 24.934(8) Å, α = 107.60(1)°, β = 100.86(2)°, γ = 95.65(2)°, and Z = 4. In these molecules there are two ArNC(H)NAr- ligand corrdinated in a chelating manner to each of two tantalum atoms. These two Ta(DTolF)2 or Ta(DPhF)2 fragments are united by a TaTa bond (ca. 2.73 Å), and a B2H6 unit lies across the bond forming two B−H−Ta bridge bonds to each tantalum atom. The B2H6Ta2 moiety constitutes a B2Ta2 nido-metalloborane, formally similar to B4H10.