Syntheses and Chemistry of the diynyl Complexes M(CCCCH)(CO)3(η-C5H5) (M = MO, W):: Crystal Structures of W(CCCCSiMe3)(CO)3 (η-C5H5), W{CCC[CH=C(CN)2]=C(CN)2}(CO)3(η-C5H5), and cis-W(CCPh)(CO)2(PPh3)(η-C5H5)

Reactions of buta-1,3-diyne with appropriate metal halides, carried out in the presence of CuI in NHEt2, have given high yields of M(C=CC=CH)(CO)(n)Cp [M = W (1-W), Mo (1-Mo), n = 3; M = Fe, n = 2 (2)]. Complex 1-W was metalated with LiNPr2i; subsequent reactions with SiClMe3 or PClPh2 gave W(C=CC=CR)(CO)(3)Cp [R = SiMe3 (3) or P(O)Ph-2 (4)] in modest to high yield. Coupling of 1 with iodoarenes, catalyzed by a mixed Cu-I-Pd-0 catalyst, gave M(C=CC=CAr) (CO)(3)Cp [M = W, Ar = Ph (5-W), tol (6), C6H4OMe-4 (7), C6H4CO2Me-4 (8); M = Mo, Ar = Ph (5-Mo)]. Oxidative coupling of 1 (CuCl-tmed-O-2) gave {M(CO)(3)Cp}(2) (mu-C-8) [M = W(9-W), Mo (9-Mo)]. Addition of tetracyanoethene to 1-W occurred at the C=C triple bond further from the metal atom, to give W{C=CC[=C(CN)(2)]CH=C(CN)(2)}(CO)(3)Cp (10). Substitution of CO by PPh3 was difficult, but the Me3NO-induced reaction with 5-W afforded cis-W(C=CC=CPh)(CO)(2)(PPh3)Cp (11) in low yield. The X-ray crystal structures of 3 and 10, together with that of cis-W(C=CPh)(CO)(2)(PPh3)Cp (12), are reported.