New synthesis of μ-allenylidene complexes from dimolybdenum carbenium ions crystal structure of [Mo( η5-C 5H 5)(CO) 22( μ, η2-CCC 6H 10)

Abstract

A selective abstraction of the acetylenic proton of cationic allynyl complexes [MoCp(CO) 2 2( μ- η 2, η 3-HCCCR 1R 2)][BF 4](Cp η 5-C 5H 5) by using the acetylide LiCCC(CH 3)CH 2 gives rise to allenylidene complexes [Cp 2Mo 2(CO) 4( μ, η 2-CCCR 1R 2)] ▪R 2 = C 6H 5 ( 6c). Compounds 3b and 4b exist as two isomers while for 6c the formation reaction is stereoselective. The crystal structure of [Cp 2Mo 2(CO) 4( μ, η 2-CCC 6H 10)] ( 1b) has been determined.