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).