ORGANOMETALLIC CLUSTERS WITH FACE-CAPPING ARENE LIGANDS .5. C-H ACTIVATION AND FORMATION OF A MU-3-ARENE COMPLEX - COMPETING REACTIONS DURING ASSEMBLY OF (CPCO)3 CLUSTER COMPLEXES WITH VINYLBENZENES AS LIGANDS

A number of ring-substituted styrenes R(C6H4)C2H3 (R = CH3, F) reacts with [CpCo(C2H4)2] (1) to give both the cluster complexes [(CpCo)3{mu3-eta2:eta2:eta2-(C6H4R)C2H3}] [2a (R=p-CH3), 2c (R = m-F), 2d (R = p-F)] with CO3 face-capping arenes and [(mu2-H)(mu3-H)(CpCo)3{mu3-1-sigma: 2-sigma:eta2-HCC(C6H4R)}] [7a (R = p-CH3), 7b (R = o-F), 7c (R = m-F), 7d (R = p-F)] with CO3 face capping alkynes derived from dehydrogenation of the vinyl group. The X-ray structure analysis of 7a confirms the 1-sigma:2-sigma: eta2 coordination of the bridging alkyne ligand. In solution the complexes 7 are fluxional and exhibit migration of the alkyne and hydride ligands on the CO3 cluster.