Production of Ni(I) complexes from reactions between Ni(II) and NaBH 4 in the presence of triphenylphosphine and some bidentate phosphines

Abstract

The reactions between a variety of Ni(II) compounds and NaBH 4 have been studied in the presence of triphenylphosphine (P) and the bidentate phosphines 1,2-bis(diphenylphosphino)-ethane (diphos), bis(diphenylphosphino)methane (dppm), and cis-1,2-bis(diphenylphosphino)-ethylene (vpp). In ethanol, NiCl 2 •6H 2 O, P, and NaBH 4 give [Ni(BH 4 )P 3 ]2 while NiX 2 P 2 X = Cl, Br, I) and NaBH 4 produce Ni(BH 4 )P 1 . 5 . Further reactions of the former complex leading to [Ni 2 P 6 ](PF 6 ) 2 and [NiP 4 ](PF 6 ) have been studied. Reactions of Ni(ClO 4 ) 2 •6H 2 O, P, and NaBH 4 produce Ni(ClO 4 )P 3 and [NiP 4 ](ClO 4 ). The bidentate phosphines, Ni(ClO 4 ) 2 •-6H 2 O and NaBH 4 in ethanol all lead to quite different products. For example, with diphos, Ni(II) is stabilized and [HNi(diphos) 2 ](ClO 4 ) is formed, but with the other two bidentate phosphines, reduction occurs. With dppm, [Ni 2 (dppm) 4 ](ClO 4 ) 2 is produced, while vpp produces [Ni(vpp) 2 ](ClO 4 ). Physical properties, possible structures, and suggested mechanisms of reduction are discussed.