Reactions of [ReN(Cl)(Me 2PhP) 2(HEt 2tcb)] with Lewis Acids. Synthesis, Characterization and Structures of [Re(NBBr 3)Br 2(Me 2PhP) 3], [Re(NGaCl 3)Cl(Me 2PhP) 2(H 2Et 2tcb)][GaCl 4] and [Re{NB(C 6F 5) 3}Cl(Me 2PhP) 2(HEt 2tcb)] (H 2Et 2tcb= N,N-diethylthiocarbamoylbenzamidine)

Abstract

Reactions of [ReN(Cl)(Me 2PhP) 2(HEt 2tcb)] (HEt 2tcb −= N,N-diethylthiocarbamoylbenzamidinate, Me 2PhP=dimethylphenylphosphine) with Lewis acidic compounds such as BBr 3, (C 6F 5) 3B or gallium(III) chloride yield nitrogen-bridged binuclear complexes with covalent bonds between the nitrido ligand and boron or gallium. The reactions go along with activation of the transition metal centre which can lead to ligand re-arrangements and reactions with solvent molecules. The reaction with BBr 3 results in cleavage of the bonds to the chelating ligand. [Re(NBBr 3)Br 2(Me 2PhP) 3] was isolated as the only product with a nitrido bridge. The bis-chelate [ReN(HEt 2tcb) 2] was formed as a side-product. Upon formation of a nitrido bridge to GaCl 3 the first co-ordination sphere of rhenium is retained. The co-ordinated thiocarbamoylbenzamidinate, however, undergoes protonation and is bonded as a neutral, bidentate ligand in the product [Re(NGaCl 3)Cl(Me 2PhP) 2(H 2Et 2tcb)][GaCl 4]. In [Re{NB(C 6F 5) 3}Cl(Me 2PhP) 2(HEt 2tcb)], which can be obtained in good yield from the reaction of [ReN(Cl)(Me 2PhP) 2(HEt 2tcb)] with (C 6F 5) 3B, the co-ordination environment of the metal remains essentially unchanged. X-ray structural studies on the products suggest that the strong structural trans influence of the terminal nitrido ligand in the starting complex decreases significantly as a consequence of the formation of the N–B/Ga bonds. The rhenium–nitrogen multiple bond distances, however, remain almost unchanged.