Interaction of alkanes with unsaturated metal centers. 2. Complexes of

J . Am. Chem. SOC.1990, 112, 2530-2536

2530

Interaction of Alkanes with Unsaturated Metal Centers. 2. Complexes of Alkanes and Fluoroalkanes with W(CO)5 in the Gas Phase' Carl E.

Yo-ichi Ishikawa,2bPeter A. Hackett,* and David M. Rayner*

Contribution from the Laser Chemistry Group, Division of Chemistry, National Research Council Canada, 100 Sussex Drive, Ottawa, Ontario KIA OR6,Canada. Received August 23, 1989

Abstract: Time-resolved infrared spectroscopy has been used to study the interaction of a range of open-chain, cyclic, and fluorine-substituted alkanes with the 16-electronspecies W(CO),. W(CO), forms reversible complexes with all the unsubstituted at 300 K, increases with carbon alkanes studied except CH4. The equilibrium constant Kp = [W(CO),L]/([W(CO),]p(L)), number from 610 100 atm-' in ethane to 5200 1600 atm-I in n-hexane, and from 1300 f 400 atm-' in cyclopropane to 7300 f 2000 atm-' in cyclohexane. Binding energies have also been obtained through temperature studies. They are in the range 7-1 1 kcal mol-', again increasing with the size of the alkanes. In the case of CH,, a binding energy 5 13.29#