Bond isomerism, formation of heterocyclic cationic complex, and insertion into the tantalum-fluorine bond in the reaction of TaF5 with MeNCO in CH2Cl2

Abstract

The reaction of tantalum pentafluoride with methyl isocyanate in dichloromethane was studied by 19F NMR and IR spectroscopy. The reaction was found to give bond isomers TaF5L, in which methyl isocyanate (L) is coordinated in the monodentate mode via N or O atom, and the heterocyclic cation [(μ-F)(μ-MeNCO)(TaF4)2]n+(n=1,2). On storage of the reaction mixture, a signal in the C-F bond region appears in the spectrum and other new signals appear, which were assigned to the formation of O- and N- bonded isomers of pentafluoro complex of tantalum with aminocarboxylic acid fluoride anions [FC(O)N(Me)TaF5]− and [N{Me)C(F)OTaF5]−, which can be considered as insertion of MeNCO into the Ta-F bond. The IR spectroscopy data support these assumptions.