Coordination of Some Simple Molecules onto W(CO)5 in the Gas Phase

In the gas phase at room temperature, the coordination process of NH3, C2H4, CF4, SF6, and Xe onto “naked” W(CO)5, selectively prepared by pulsed 355-nm laser photolysis of W(CO)6, was investigated by laser-based time-resolved infrared absorption spectroscopy. W(CO)5 reacted with these reactant gases, except for CF 4 and SF6, to make a simple coordination complex, W(CO)5(L), where L is NH3, C2H4, or Xe. The bimolecular rate constants for these reactions were (5.6 ± 0.6) × 106 Torr−1 s−1 for W(CO)5 + NH3, (2.8 ± 0.5) × 106 Torr−1 s−1 for W(CO)5 + C2H4, and (1.0 ± 0.3) × 105 Torr−1 s−1 for W(CO)5 + Xe. W(CO)5Xe was unstable owing to its weak interaction with the coordinatively unsaturated tungsten center, the unimolecular decomposition rate of which was about 1.0 × 105 s−1, but W(CO)5(NH3) and W(CO)5(η2-C2H4) were stable under our experimental conditions. The band shifts of C–O stretching modes observed in the coordination of NH3 as a typical σ-donor, C2H4 as a typical π-acceptor, and Xe as a weak σ-donor could interpreted by MO considerations.