Formation of α, ω-dienes upon photooxidation of alkenyl carbyne complexes

Abstract

Photolysis of the alkenyl carbyne complexes ( η 5–C 5H 5)(CO){P(OMe) 3}Mo≡CCH 2(CH 2) n CHCH 2 ( n=2 ( 1b), 3 ( 1c) and 4 ( 1d)) in CHCl 3 results in the formation of the corresponding α, ω-dienes CH 2CH(CH 2) n CHCH 2. Also produced are the dichloromolybdenum carbynes ( η 5–C 5H 5)Cl 2{P(OMe) 3}Mo≡C–CH 2(CH 2) n CHCH 2 ( n=2 ( 8b), 3 ( 8c), and 4 ( 8d)). Both sets of products arise following the generation of highly reactive 17-electron complexes via photochemical electron transfer from 1b– d to the solvent. These radical cations either undergo H-abstraction at the carbyne carbon followed by H-shift to form the dienes or they undergo exchange of Cl − for the CO ligand and Cl-abstraction at the metal to yield 8b– d. The product ratios reflect partitioning of the 17-electron species between reactivity at the metal center vs. the carbyne carbon.