CYCLOOCTADIENYL COMPLEXES OF MOLYBDENUM - SYNTHESIS AND ETA(5)-]ETA(3) HAPTICITY INTERCONVERSION

The cyclooctadienylmolybdenum complexes [MoBr(CO)(2)(NCMe)(2)(eta(3)-2.5-C8H11)] and [MoBr(CO)(2)(NCMe)(2)(eta(3)-2.4-C8H11)]. accessible by reaction of [Mo(CO)(2)(NCMe)(3)] with bromocyclooctadienes. have been found to be precursors to the pentahapto-bonded complexes [Mo(CO)(2)(L-L)(eta(2),eta(3)-2,5-C8H11)](+) [L-L=Ph(2)PCH(2)PPh(2) (dppm) (crystallographically characterised) or Ph(2)PCH(2)CH(2)PPh(2)] and [Mo(CO)(2)(dppm)(eta(5)-C8H11)](+); the reactivity of the last three complexes towards eta(5)-->eta(3) hapticity conversion at the dienyl ligand is controlled by the bonding mode of the cyclooctadienyl ligand and the identity of L-L.