Phosphorus-substituted η1-vinylidene tungsten complexes: Synthesis and cyclization

Reaction of a dilute solution of LiC≡CP(C 6 H 5 ) 2 (5) with the tungsten carbonyl complex (η 5 -Cp)(CO) 2 (NO)W (la) afforded at -30 °C after protonation the bimetallic complexes [{(Ph 2 P)HC=C}(NO)(η 5 -Cp)W-W(η 5 -Cp)(NO)(CO){C=CH(PPh 2 )}] (8a,b). It could be shown that prior to the formation of 8a,b the η 1 -vinylidene complex (η 5 -Cp)(CO) 2 (NO)W=C=CH-(PPh 2 ) (7) is formed as an intermediate, which reacts with an additional η 1 -vinylidene complex 7 present in the solution to give the observed products by losing 1 mol of carbon monoxide. The η 1 -vinylidene complex 7 and its analogous derivative (η 5 -Cp)(CO)2(NO)W=C=CH(PMes2) (10; Mes = 2,4,6-trimethylbenzene) are stable in solution at -60 °C and could be identified by spectroscopic methods. The η 1 -vinylidene complexes 7 and 10 are trapped with (η 5 -Cp)-(CO) 2 (NO)W=C=CHR (R = H (12a), C 6 H 5 (12b), CH 3 C 6 H 4 (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 la. 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.