Synthesis and reactivity of (R)(eta(1)-C(5)Me(5))P=Co(CO)(3)

The synthesis of compounds (2,4,6-(t)Bu(3)C(6)H(2)O)(eta(1)-C(5)Me(5))P = Co(CO)(3) (6a) and {Co[mu-P(2,4,6-Me(3)C(6)H(2))(eta(1)-C(5)Me(5))]-(CO)(2)}(2)(Co = Co) (8) on treatment of (R)(eta(1)-C(5)Me(5))P(Cl) (3a: R = 2,4,6-(t)Bu(3)C(6)H(2)O; 3b: R = 2,4,6-Me(3)C(6)H(2)) with Na[Co(CO)(4)] (4) or Co-2(CO)(8) (5) is described. The reaction sequence for the formation of compound 8 is discussed. The X-ray structural analyses of compounds 6a and 8 are reported. Crystals of 6a are triclinic, space group <P(1)over bar>, with a = 912.4(5), b = 936.4(5), c = 2078(1) pm, alpha = 87.42(5), beta = 84.87(4), gamma = 64.51(4)degrees, V = 1594(1) x 10(6) pm(3) and Z = 2. Dinuclear 8 crystallizes in the monoclinic space group P2(1)/c, with a = 868.7(5), b = 1370.2(9), c = 3616(2) pm, beta = 93.46(5)degrees, V = 4297(4) x 10(6) pm(3) and Z = 4. Compound 6a contains a phosphorus atom in a trigonal-planar environment, which is part of a phosphorus-cobalt double bond unit. Compound 8 features a planar Co2P2 core with a cobalt-cobalt double bond; the C(5)Me(5) and 2,4,6-Me(3)C(6)H(2) groups are arranged in pairs on the same side of the Co2P2 unit.