Alkylidyne-metals

The chemistry of CR fragments ligating metal centers has been a topic of considerable interest since the discovery of the first alkylidyne-metal complexes in E.O. Fischer s Laboratory in 1973 (1). These ligands have been implicated in Fischer-Tropsch reactions (2) and in alkyne metathesis (5). Moreover, the isolation of stable compounds containing carbon-metal triple bonds completed the matrix of bond types represented here ... 

Physical and Theoretical Studies of Alkylidyne Metal Complexes. 228... 

Alkylidyne-metal complexes have traditionally been divided into two categories, according to the oxidation state of the metals, in a manner directly analogous to the classification of the very large number of known alkylidene-metal species (19a,b). Hence Fischer-type alkylidyne complexes involve metals in low oxidation states, while Schrock-type complexes generally involve more electropositive metals with higher oxidation states (13). However, the properties of some of the numerous carbyne-metal complexes that have been characterized since the early days have in many cases blurred the distinction between the two classes (12a). 

The addition of Lewis base substrate molecules to solutions containing alkylidyne-metal species prior to treatment with acid introduces a new dimension in the protonation reactivity of these complexes. This was... 

A. Protonation of Mixtures Containing Two Distinct Alkylidyne-Metal Complexes... 

Several types of dimetal product have been obtained by this method. Thus, treatment of equimolar mixtures of the (alkynyl-alkylidyne)metal complexes 4g or 4h and the alkylidyne(carbaborane)metal salts la or lb, with HBF4-Et20 in the combinations shown in Scheme 7, yields the compounds 45 (44). In these products, the icosahedral cage from the precursors 1 adopts the form familiar from protonation reactions described... 

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