Bis(diphenylphosphino)Alkane / Co(II)/Tetrahydroborate and Cyanotrihydroborate Reactions: Formation of Unusual Bis(diphenylphosphino)methane Complexes and the Influence of Carbon Monoxide |
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| Authors: | D. J. Elliot D. G. Holah A. N. Hughes S. Maciaszek J. D. Thompson V. R. Magnuson |
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| Affiliation: | 1. Department of Chemistry , Lakehead University , Thunder Bay, Ontario , Canada , P7B 5E1;2. Department of Chemistry , University of Minnesota-Duluth , Duluth , Minnesota , 55812 , U.S.A. |
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| Abstract: | Abstract Reactions between Co(II), bis(diphenylphosphino)methane (dppm) and either NaBH4 or NaBH3CN have been studied. They follow pathways which are in marked contrast to those followed by Ph2P(CH2)nPPh2 (n=2?6) in the presence of NaBH4 in which the final product is normally CoH(phosphine)2 although binuclear BH4-bridged complexes may sometimes be obtained. The products obtained with dppm are Co2X3(dppm)2 (X=Cl,Br) (I), CoCl(dppm)3 (II), {CoHX(dppm)2}Y (X=Cl, Br, I, BH3CN; Y=Cl,BH3CN,BPh4,Clo4) (III), and Co2H2(dppm)3 (IV). While a binuclear A-frame structure can be proposed for the Co(I)-Co(II) species (I), crystal twinning has so far prevented an X-ray determination. However, X-ray studies on (II) and (IV) have shown that (II) contains tetrahedral Co(I) to which one chloro and three monodentate dppm ligands are attracted while (IV) is a binuclear species containing bridging dppm ligands and two terminal hydrides. The compounds (III) are octahedral Co(III) complexes. Possible mechanisms for the formation of these in strongly reducing environments will be discussed. |
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