Alkylidenes binuclear

Addition of 2 eq HC1 to (22) in ether produced a thermally unstable bis(alkylidene) complex, which upon addition of excess PMe3 generated binuclear (41). The bridging alkylidyne ligands of (41) exhibited inequivalent Ta—C bond lengths of 2.073(6)-2.099(6) A and 1.922(6)-1.942(7) A, consistent with the different nature of the Ta centers.73,74... 

A binuclear calixarene-supported niobium-alkylidyne complex ((42) Scheme 32) was prepared by deprotonation of a mononuclear alkylidene species (14).36 The chemistry of calixarene-supported species containing metal-carbon bonds has been reviewed.37... 

The synthesis of an alkylidene bridged binuclear titanium complex (Scheme 654 Section 4.05.5) has been described and its use in ethylene polymerization in the presence of MAO was investigated.1081... 

Other, less acidic alcohols show no reaction, while phenol derivatives result in the formation of dineopentyl derivatives. Finally, binuclear molybdenum alkylidenes are obtained by reaction of a Schrock carbene with a.cu-dienes such as divi-nylbenzene or with octatetraene [91]. 

Herrmaim and co-workers first reported on the synthesis of mononuclear as well as binuclear NHC-based ruthenium alkylidenes [235] (Scheme 5.17). 

The introduction of bridged binuclear complexes, the so-called Tebbe reagents, to achieve alkylidene transfer to carbonyl species was a useful discovery. However, developments of these systems such that substituted examples could also be prepared was necessary. Recently, substituted alkylidene-bridged zirconium reagents have been prepared and briefly examined as suitable transfer reagents. ... 

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