MOLYBDENUM COMPLEXES WITH TRIDENTATE NS2 LIGANDS - SYNTHESIS, CRYSTAL-STRUCTURES AND SPECTROSCOPIC PROPERTIES

Reaction of the new tridentate NS, ligands 2-HSC6H4C(Me)=NNHC(S)SCH2Ph (H2L1), 2-HSC6H4C(Me)=NNHC(S)NHCPh3 (H2L2), 2-HSC6H4CH=NNHC(S)NHCPh3 (H2L3) and 1-Ph-3-Me-5-HS-C3N2-CH=NNC(SH)-NHCPh3 (H2L4) with dioxomoly bdenum(VI) precursors yielded mononuclear molybdenum(VI) complexes [Mo O2(L-1)(pic)] 1 (pic = 4-methylpyridine), [MoO2L2(MeOH)]. 2.25 MeOH 2 and the dinuclear molybdenum(v) complexes [Mo2O3L23]. 3CH(2)Cl(2) 3 an d [Mo2O3L24] 4. The molecular structures of 1-3 were determined by sin gle-crystal X-ray analysis. Complexes 1 and 2 each consist of a centra l cis-MoO2 unit with a mer co-ordinating tridentate dianionic ligand a nd one neutral donor molecule completing the octahedral environment of molybdenum(VI). Complex 3 exhibits an anti-Mo2O3 group co-ordinated b y two mer chelating ligands. The symmetry-related molybdenum(v) centre s are in a square pyramidal environment. Infrared, NMR and MS studies evidenced a comparable structure for 4. The reduction of the dioxomoly bdenum(VI) compounds 1 and 2, achieved by addition of phosphines like PPh3, also leads to dinuclear mu-oxo-bridged complexes. The reverse ox idations of the oxomolybdenum(v) complexes are restricted by the natur e of the ligand and the oxidizing agents.