Triruthenium anionic clusters

Examples of O-alkylation have also been demonstrated for triruthenium and triosmium anionic clusters, as well as the tetrairon cluster Fe CO)] - (31-33). This reaction has considerable promise as an entry into many different methylidyne complexes through the replacement of the OR" group, eq. 20 (38). 

The synthetically useful dianions [M3(CO)u]2- were first isolated by Shore and co-workers as the Ca2+ (M=Ru) and the K+ (M=Os) salts by the reduction of M3(CO)12 using alkali metal benzophenone solutions in THF.1 [Ru3(CO) J2 reacts with Ru3(CO) 2 to form the higher nuclearity clusters [Ru4(CO)13]2- and [Ru6(CO)i8]2- but the triruthenium anion can be obtained in high purity by slowly adding triruthenium dodecacarbonyl to an excess of reducing solution using vacuum-line techniques.2 Vacuum-line syntheses of both dianions have been described in detail.1... 

Even if the electrochemical behaviour of this cluster is presently unknown, it has been reported that it undergoes, chemically, a first one-electron reduction to the corresponding monoanion [ (C2 — Bu JRujfCO jHg]-, and a second one-electron addition, which causes declustering of the central Hg metal (with formation of triruthenium anions) [168]. 

Reaction between the arachno-[B3H8 ] anion and complex 1 gives the arachno four-vertex complex 140 in 66% yield (92,97). Treatment of 140 with closo-[Bl0Hw]2 in refluxing ethanol affords as the major product (32%) the unexpected triruthenium decaboron double-cluster compound 141, which has been analyzed by single-crystal X-ray diffraction (97). 

In the cases of [Ru3(CO)i2] and [Ru4H4(CO)i2], which have very unstable anion radicals, Lewis base substitution reactions are stoichiometric rather than catalytic in the reducing agent (167) dppe and the triruthenium cluster give [Ru3(CO)io(dppe)J, [Ru3(CO)n(dppe)], or [ Ru3(CO)n 2(/u.-dppe)], depending on the relative stoichiometries of the reactants (168). Complexes such as [Ru3(CO)uL] and [Ru4H4(CO)uL] [L = PPh2CH2CH2Si(OEt)3], precursors to surface-anchored species, have also been prepared by reductively induced substitution reactions (169). 

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