Chemistry of phosphido-bridged dimolybdenum complexes. Part 4. Reactions of [Mo2(η5-C5H5)2(µ-H)(µ-PR2)(CO)4](R = Ph or Me) with dienes

Abstract

The photochemical reactions of [Mo₂(η⁵-C₅H₅)₂(µ-H)(µ-PR₂)(CO)₄](R = Ph or Me) with allene, 1,3-butadiene, 2-methyl-1,3-butadiene, and 1,3-cyclohexadiene have been studied. In each of these reactions allyl complexes of general formula [Mo₂(η⁵-C₅H₅)₂(µ-PR₂)(η³-allyl)(CO)₃] are obtained as major products. The ¹H n.m.r. spectra of these allyl complexes indicate that they exist in solution as an equilibrium mixture of exo and endo isomers. In the reactions with 1,3-butadiene the allyl complexes are accompanied by very low yields of other species which are assigned the formula [Mo₂(η⁵-C₅H₅)₂O(µ-vinyl)(µ-PR₂)(CO)] on the basis of spectroscopic evidence. The reaction of [Mo₂(η⁵-C₅H₅)₂(µ-H)(µ-PMe₂)(CO)₄] with allene gives as a major product, in addition to the allyl species, the complex [Mo₂(η⁵-C₅H₅)₂{µ-σ:η²-C(Me)=CH₂}(µ-PMe₂)(CO)₃].