An investigation into the photochemical reactions of M(η⁵-C₅H₅)-(CO)₄ and M(η⁵-C₉H₇)(CO)4 (M = Nb or Ta) with H₂ and N₂ in polyethylene matrices and liquid xenon at low temperature

The photolysis of MCp′(CO)4 (Cp′ = Cp or indenyl; M = Mb or Ta) in polyethylene (PE) matrices at low temperature under a high pressure of reactant gas led to formation of a wide range of photoproducts. Under an inert atmosphere (helium), NbCp′(CO)₃ and NbCp′(CO)₂ are observed following irradiation of the parent tetracarbonyl. However, only TaCp′(CO)₃ is observed for the analogous reactions of the corresponding tantalum compounds. Similarly, NbCp′(CO)₃(N2) and NbCp′(CO)₂ (N2)2 are seen following irradiation of NbCp′(CO)4 under a high pressure of N2, whereas only TaCp′(CO)₃(N2) was observed following irradiation of TaCp′(CO)4. Under hydrogen, the classical dihydride TaCp′(CO)₃H2 is formed following irradiation of TaCp′(CO)4. The non-classical dihydrogen complex Nb(C9H7)(CO)₃(r|2-H2) is formed following irradiation of Nb(C9H7)(CO)4. NbCp(CO)4 forms both the classical hydride and non-classical dihydrogen complex. Using a high pressure-low temperature cell, the thermal reaction of TaCp′(CO)₃(N2) with hydrogen to form TaCp′(CO)₃H2 was observed. Preliminary room temperature studies suggest that Ta(C9H7)(CO)₃H2 is ca. 50 times more reactive than TaCp(CO)₃H2 in PE.