Bromination of molybdenum carbonyls revisited: oxo complexes and routes to new materials chemistry

Abstract

The use of in situ[{MoBr(µ-Br)(CO)₄}₂] led to considerably improved preparations of [MoBr₂(CO)₃(PPh₃)₂] for which the rate of decarbonylation to [MoBr₂(CO)₂(PPh₃)₂] is greatly increased by refluxing under reduced pressure (15–20 mmHg). Attempts to prepare [MoBr₂(CO)₂{P(C₆H₁₁)₃}₂] by Br₂ addition to cis- or trans-[Mo(CO)₄{P(C₆H₁₁)₃}₂] led to [HP(C₆H₁₁)₃][Mo(O)Br₄L][L = OP(C₆H₁₁)₃ or H₂O]. The OP(C₆H₁₁)₃ complex may be used as a catalyst for the epoxidation of cyclohexene or for the addition of singlet oxygen to α-terpinene (1-isopropyl-4-methylcyclohexa-1,3-diene). The species [HP(C₆H₁₁)₃][Mo(O)Br₄{OP(C₆H₁₁)₃}] was adsorbed onto sodium montmorillonite in a new type of reaction for sodium montmorillonite involving multiple abstractions of NaBr from the complex anion. In solution [HP(C₆H₁₁)₃][Mo(O)Br₄{OP(C₆H₁₁)₃}] also decomposes to crystalline [Mo(O)₂Br₂{OP(C₆H₁₁)₃}₂] which is monoclinic, space group C2/c[a= 27.15(5), b= 8.486(8), c= 18.49(2)Å, β= 110.94(7)°].