The Chemistry of Organosamarium(II) and Related Complexes

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This project in the Inorganic, Bioinorganic and Organometallic Chemistry Program deals with the organometallic chemistry of the lanthanide metals, especially samarium. Organosamarium complexes have been shown by the Principal Investigator to be unusually powerful reducing agents which have the advantage of being soluble in a number of common organic solvents, in which they effect a variety of highly unusual transformations of organic molecules. Further studies of these complexes are expected both to define better their utility as synthetic reagents and to provide an understanding of their chemical reactivity. The objective of this project is to determine the factors which control the special reactivity of organolanthanide(II) complexes, especially of organosamarium(II) complexes. Of special interest is a series of related Sm(II)-mediated reactions in which carbon-carbon double or triple bonds, or nitrogen-nitrogen double bonds, are activated and reacted with CO to give significantly transformed products. These will provide excellent opportunities to probe the principles of Sm(II) reactivity and therefore will be studied in detail. This chemistry will be extended to C-C bond cleavage reactions and the use of Sm(II)-generated dihaptoacyl complexes to effect cyclization of straight-chain alkyls. The effect of the Lewis acid center on Sm(II) reactions will be examined by studying reductive transformations using an external reductant in the presence of bis(pentamethylcyclopentadiene)- bis(THF)samarium(III) and bis(pentamethylcyclopentadiene)- (THF)europium(II). The results of these experiments, together with studies of methods for effecting reductive Sm-O bond cleavage, are expected to lead to reductive transformation systems which are catalytic in samarium. The synthesis of reactive bridged bimetallic Sm(II) reagents will be explored also, as will the chemical consequences of the unusual bent structure of the bis(pentamethylcyclopentadiene)samarium(II) in the activation of alkenes by this reagent.