SUBSTITUTION-REACTIONS OF A MU-THIOETHER LIGAND IN DINUCLEAR CYCLOPENTADIENYLMOLYBDENUM COMPLEXES

The thermal reaction of the thioether-bridged complex [(CpMo)(2)(S2CH2 )(mu-SMe)(mu-SMe(2))]-OTf(1) with electron donors leads to the elimina tion of dimethyl sulfide and the formation of structures which incorpo rate new ligands into the dimer. For example, reaction of 1 with exces s LiCl results in the formation of (CpMo)(2)(S2CH2)(mu-SMe)(mu-Cl) (2) , which has been isolated and characterized by an X-ray diffraction st udy. Dimers with mu-bromide and with mu-eta(2)-alkyne ligands have als o been prepared by thioether substitution reactions and characterized spectroscopically. The reaction of 1 with two-electron donors led to t he formation of dimers with new terminal ligands of the formula [(CpMo L)(2)(S2CH2)(mu-SMe)]OTf with L = (t)BuNC (6a), C6H5CH2NC (6b), and CO (7). The X-ray diffraction study of one isomer of 7 established that the cation contained cis carbonyl ligands and an equatorial configurat ion for the methanethiolate substituent. The complexes with terminal i socyanide ligands are thermally stable, but the complex with carbon mo noxide ligands undergoes ligand exchange reactions at high temperature s. The potential reactivity of the carbonmonoxide ligands in 7 with nu cleophiles and with oxidants has been explored. For example, the react ion of 7 with Me(3)NO in acetonitrile solution results in the loss of one carbonyl ligand and the formation of [CpMo(CO)(S2CH2)(mu-SMe)(MeCN )MoCp]OTf (9), a potential precursor to coordinatively unsaturated com plexes.