REACTIVITY OF A (ETA(5)-PHOSPHOLYL)COBALT DICARBONYL COMPLEX - SYNTHESIS OF [CO-2(ETA(5)-(PC4H2BU2)-BU-T)(2)(CO)(2)] AND O-2(ETA(5)-(PC4H2BU2)-BU-T)(2)(MU-CHCO2ET)(CO)(2)]

Thermolysis of 2,2',5,5'-tetra-tert-butyl-1,1'-biphosphole with Co-2(C O)(8) gives good yields of (2,5-di-tert-butylphospholyl)dicarbonylcoba lt (1), a compound which provided access to a range of cobalt phosphol yl complexes. Thermolysis with trimethylphosphite produced C12H20PCo(C O)P(OMe)(3) (2), while photolysis with 1,3-cyclohexadiene and 1,5-cycl ooctadiene gave the corresponding complexes C12H20PCo(diene) (3, 4). I n the absence of a donor ligand, a metal-metal doubly bridged dimer 6 was obtained; this reacted classically with ethyl diazoacetate to give the bridging complex {C12H20PCo(CO)}(2)(mu-CHCO2Et) (7). Prolonged he ating of 1 with 3-hexyne in xylene gave the cyclotrimerization product C6Et6; an initial attempt to prepare pyridines by cocyclization of Pr CN with PhC=CH gave the cyclobutadiene complex C12H20PCo(1,2-C4H2Ph2) (5).