Dihydride versus dihydrogen complex; the photochemical reaction of [(η⁵;-C₅H₅)M(CO)₄](M = V, Nb and Ta) with hydrogen in solution at both cryogenic and room temperatures

Abstract

UV photolysis of [cpM(CO)4](cp =η5-C5H5; M = V, Nb and Ta) and H2has been studied by IR spectroscopy both in n-heptane solution at 25 °C and in liquid Xenon solution at –110 to –45 °C; for V, the reaction leads to formation of the non-classical complex [cpV(CO)3(η2-H2)] while, for Ta, the dihydride [cpTa(CO)3H2] is formed; for Nb, there is a temperature dependent equilibrium between the classical [cpNb(CO)3H2] and non-classical [cpNb(CO)3(η2-H2)] compounds, which presents an unusual opportunity to study the formation of these species using nanosecond Time-resolved IR spectroscopy (TRIR).