Phosphorus-Substituted η1-Vinylidene Tungsten Complexes: Synthesis and Cyclization

Abstract

Reaction of a dilute solution of LiC⋮CP(C6H5)2 (5) with the tungsten carbonyl complex (η5-Cp)(CO)2(NO)W (1a) afforded at −30 °C after protonation the bimetallic complexes [{(Ph2P)HCC}(NO)(η5-Cp)W−W(η5-Cp)(NO)(CO){CCH(PPh2)}] (8a,b). It could be shown that prior to the formation of 8a,b the η1-vinylidene complex (η5-Cp)(CO)2(NO)WCCH(PPh2) (7) is formed as an intermediate, which reacts with an additional η1-vinylidene complex 7 present in the solution to give the observed products by losing 1 mol of carbon monoxide. The η1-vinylidene complex 7 and its analogous derivative (η5-Cp)(CO)2(NO)WCCH(PMes2) (10; Mes = 2,4,6-trimethylbenzene) are stable in solution at −60 °C and could be identified by spectroscopic methods. The η1-vinylidene complexes 7 and 10 are trapped with (η5-Cp)(CO)2(NO)WCCHR (R = H (12a), C6H5 (12b), CH3C6H4 (12c)) to give the corresponding bimetallic complexes 13a−c and 14a−c. A different mode of reaction is observed, when the acetylide 5 is treated with a concentrated solution of tungsten carbonyl complex 1a. Here after protonation the eight-membered bimetallic complex 15 is obtained. The crystal structures of bicyclic complexes 8a, 11, and 13a as well as the monocyclic complex 15 are reported.