Dioxo–Molybdenum(VI) Complexes with Ene–12–dithiolate Ligands: Synthesis Spectroscopy and Oxygen Atom Transfer Reactivity

摘要

New dioxo–molybdenum(VI) complexes, (Et4N)(Ph4P)[Mo^VIO2(S2C2(CO2Me)2)(bdt)] (>2) and (Et4N)(Ph4P)[Mo^VIO2(S2C2(CO2Me)2)(bdtCl2)] (>4) (S2C₂(CO₂Me)₂ = 1,2–dicarbomethoxyethylene–1,2–ditholate, bdt = 1,2–benzenedithiolate, bdtCl₂ = 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[Mo^IVO(S₂C₂(CO₂Me)₂)(bdt)] (>1) and (Et₄N)₂[Mo^IVO(S₂C₂(CO₂Me)₂)(bdtCl₂)] (>3), with Me₃NO (). Additionally, the bis(ene–1,2–dithiolate)Mo^VIO₂ complex, (Et₄N)(Ph₄P)[Mo^VIO₂(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 ¹H NMR spectra of (CD₃)₂CO solutions of the Mo^VIO₂ complexes indicated that the Mo centers isomerize between Δ and Λ 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 π–delocalization between the Mo^VIO₂ and ene–1,2–dithiolate units. The similar oxygen atom transfer kinetics for the complexes results from their similar electronic structures.Designation and Abbreviation of Complex Structures