Photochemical reactions of allyl and crotyl halides with cyclopentadienyl-chromium, -molybdenum and -tungsten complexes

[MoCl(CO) 3 (η 5 -C 5 H 5 )] on photolysis with allyl or crotyl halides C 5 H 4 RX gives Mo IV complexes [MoX 2 (CO)(η 3 -C 3 H 4 R)(η 5 -C 5 H 5 )] (R = H, X = Cl, Br, I; R = Me, X = Cl, Br). [WCl(CO) 3 (η 5 -C 5 H 5 )] under similar conditions gives trihalides [WX 3 (CO) 2 (η 5 -C 5 H 5 )] (X = Cl, Br) on reaction with C 3 H 5 Cl and C 3 H 5 Br while [WCl(CO) 3 (η 5 -C 5 H 4 SiMe 3 )] and [CrI(CO) 3 (η 5 -C 5 H 5 )] react with allyl chloride to give [WCl 3 (CO) 2 (η 5 -C 5 H 4 SiMe 3 )] and [CrCl 2 (η 5 -C 5 H 5 )] respectively.