Synthetic and fluxional behaviour of M(1,5 cyclooctadiene)(tripod)+BF4− (M = Rh Ir; Tripod = HC(PPh2)3)

Abstract The complexes M(1,5 cyclooctadiene)(HC(PPh 2 ) 3 ) + BF 4 − (M = Rh, Ir) have been synthesized characterized. The 31 P 1 H NMR spectra show that in the ground-state structure the tripod ligand forms a bidentate chelate with the metal, the third phosphorus atom remaining uncoordinated. However, VTNMR studies show a rapid exchange process to be occurring at room temperature causing equilibration of all the phosphorus nuclei as well as the vinylic and methylenic protons of the diene ligand. An associative intramolecular exchange mechanism is proposed.