Dioxomolybdenum(VI) Complexes with Ene-1,2-dithiolate Ligands: Synthesis, Spectroscopy, and Oxygen Atom Transfer Reactivity

摘要

New dioxomolybdenum(VI) complexes, (Et4N)(Ph4P)[(MoO2)-O-VI(S2C2(CO2Me)(2))(bdt)] (2) and (Et4N)(Ph4P)[(MoO2)-O-VI-(S2C2(CO2Me)(2))(bdtCl(2))](4)(S2C2(CO2Me)(2) = 1,2-dicarbomethoxyethylene-1,2-ditholate, bdt = 1,2-benzenedithiolate, bdtCl(2) = 3,6-dichloro-1,2-benzenedithiolate), that possess at least one ene-1,2-dithiolate ligand were synthesized by the reaction of their mono-oxo-molybdenum(IV) derivatives, (Et4N)(2)[(MoO)-O-IV(S2C2(CO2Me)(2))(bdt)] (1) and (Et4N)(2)[(MoO)-O-IV(S2C2(CO2Me)(2))(bdtCl(2))] (3), with Me3NO. Additionally, the bis(ene-1,2-dithiolate)(MoO2)-O-VI complex, (Et4N)(Ph4P)[(MoO2)-O-VI(S2C2(CO2Me)(2))(2)] (6), was isolated. Complexes 2, 4, and 6 were characterized by elemental analysis, negative-ion ESI mass spectrometry, and IR spectroscopy. X-ray analysis of 4 and 6 revealed a Mo-VI center that adopts a distorted octahedral geometry. Variable-temperature H-1 NMR spectra of (CD3)(2)CO Solutions of the (MoO2)-O-VI complexes indicated that the Mo centers isomerize between Delta and Lambda forms. The electronic structures of 2, 4, and 6 have been investigated by electronic absorption and resonance Raman spectroscopy and bonding calculations. The results indicate very similar electronic structures for the complexes and considerable pi-delocalization between the (MoO2)-O-VI and ene-1,2-dithiolate units. The similar oxygen atom transfer kinetics for the complexes results from their similar electronic structures.