The nature of the bridging nitrido ligand. Synthesis and reactivity of heterobimetallic nitrido-bridged compounds

Abstract

Heterobimetallic nitrido-bridged compounds (R 3SiO) 3VNM(CO)(PPh 3) 2 (R  Me or Et and M  Ir or Rh) and (Me 3SiO) 3VNRh(PPh 3) 3 have been synthesized by condensation reactions between vanadium silylimido compounds, V(NSiR 3)(OSiR 3) 3, and group VIII metal fluorides, MF(L)(PPh 3) 2. Oxidative addition of small molecules (MeI, O 2, H 2) to the iridium(I) of (R 3SiO) 3VNIr(CO)(PPh 3) 2 occurs, producing iridium(III) compounds in which the VNIr interaction is retained. In contrast, however, the nitrido linkages in (Me 3SiO) 3VNM(L)(PPh 3) 2 are readily cleaved by silylating reagents (ClSiMe 3, ClSiEt 3, HSiEt 3), producing V(NSiR 3)(OSiMe 3) 3 and a group VIII metal chloride or hydride product. Comparison of the reactivity and spectroscopic data among the nitrido-bridged compounds and with related iridium(I) and rhodium(I) complexes suggests that the nitrido-bridged compounds are best viewed as adducts in which anionic [(R 3SiO) 3VN:] − acts as a simple two-electron donor to the 14-electron cationic [M(L)(PPh) 2] + fragment.