Dalton communications. Cyclooctadienyl complexes of molybdenum: synthesis and η5→η3hapticity interconversion

Abstract
The cyclooctadienylmolybdenum complexes [MoBr(CO)2(NCMe)23-2,5-C8H11)] and [MoBr(CO)2(NCMe)23-2,4-C8H11)], accessible by reaction of [Mo(CO)3(NCMe)3] with bromocyclooctadienes, have been found to be precursors to the pentahapto-bonded complexes [Mo(CO)2(L–L)(η23-2,5-C8H11)]+[L–L = Ph2PCH2PPh2(dppm)(crystallographically characterised) or Ph2PCH2CH2PPh2] and [Mo(CO)2(dppm)(η5-C8H11)]+; the reactivity of the last three complexes towards η5→η3 hapticity conversion at the dienyl ligand is controlled by the bonding mode of the cyclooctadienyl ligand and the identity of L–L.