Carbonylcobalt(I) complexes. The crystal and molecular structure of [Co(CO)(dppm) 2]ClO 4

Abstract

New anionic carbonylcobalt(I) complexes [X 2Co(CO) 2(PPh 3)](PR 4) (X=Cl, PR 4 = PBzPh 3 (I); X = Br, PR 4 = PEtPh 3 (II)) have been prepared by reduction of the cobalt(II) halides with NaBH 4 in the presence of PPh 3 and the phosphonium salt PR 4X. Cleavage of halide bridges in dimeric or polymeric [XCo(PPh 3) 2] n and [XCo(PPh 3)] n gives the neutral dicarbonyl derivatives XCo(CO) 2PPh 3) 2. Treatment of ClCo(CO) 2(PPh 3) 2 with alkylating agents gives the known σ- and η- organocobalt(I) derivatives, and reactions with TIClO 4 in the presence of various amounts of different mono- and bi-dentate phosphines give the cationic tricarbonyl [Co(CO) 3(PPh 3) 2] +, dicarbonyl [Co(CO) 2(PMePh 2) 3] + and monocarbonyl [Co(CO)L 4] + complexes (L 4 = 4P(OMe) 3, 2 dppe and 2dppm). The dppm complex crystallizes in the monoclinic space group P2 1/ c with a 17.895(6), b 10.751(2), c 24.687(4) Å, β 98.92(1)°, and D calc 1.35 g cm −3 for Z = 4. A final R value of 0.077 ( R w = 0.061), based on 2656 observed reflections, was obtained. The cobalt atom exhibits a distorted trigonal bipyramidal geometry. The perchlorate anion is severely disordered or freely rotating.