Carbonylcobalt(I) complexes. The crystal and molecular structure of [Co(CO)(dppm)2] ClO4

Abstract

New anionic carbonylcobalt(I) complexes [X2Co(CO)2(PPh3)](PR4) (X=Cl, PR4 = PBzPh3 (I); X = Br, PR4 = PEtPh3 (II)) have been prepared by reduction of the cobalt(II) halides with NaBH4 in the presence of PPh3 and the phosphonium salt PR4X. Cleavage of halide bridges in dimeric or polymeric [XCo(PPh3)2]n and [XCo(PPh3)]n gives the neutral dicarbonyl derivatives XCo(CO)2PPh3)2. Treatment of ClCo(CO)2(PPh3)2 with alkylating agents gives the known σ- and η- organocobalt(I) derivatives, and reactions with TIClO4 in the presence of various amounts of different mono- and bi-dentate phosphines give the cationic tricarbonyl [Co(CO)3(PPh3)2]+, dicarbonyl [Co(CO)2(PMePh2)3]+ and monocarbonyl [Co(CO)L4]+ complexes (L4 = 4P(OMe)3, 2 dppe and 2dppm). The dppm complex crystallizes in the monoclinic space group P21/c with a 17.895(6), b 10.751(2), c 24.687(4) Å, β 98.92(1)°, and Dcalc 1.35 g cm−3 for Z = 4. A final R value of 0.077 ( Rw = 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.