Production of Ni(I) complexes from reactions between Ni(II) and NaBH₄ in the presence of triphenylphosphine and some bidentate phosphines

Abstract

The reactions between a variety of Ni(II) compounds and NaBH4 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, NiCl2•6H2O, P, and NaBH4 give [Ni(BH4)P3]2 while NiX2P2 X = Cl, Br, I) and NaBH4 produce Ni(BH4)P1.5. Further reactions of the former complex leading to [Ni2P6](PF6)2 and [NiP4](PF6) have been studied. Reactions of Ni(ClO4)2•6H2O, P, and NaBH4 produce Ni(ClO4)P3 and [NiP4](ClO4). The bidentate phosphines, Ni(ClO4)2•-6H2O and NaBH4 in ethanol all lead to quite different products. For example, with diphos, Ni(II) is stabilized and [HNi(diphos)2](ClO4) is formed, but with the other two bidentate phosphines, reduction occurs. With dppm, [Ni2(dppm)4](ClO4)2 is produced, while vpp produces [Ni(vpp)2](ClO4). Physical properties, possible structures, and suggested mechanisms of reduction are discussed.

Preparation and characterization of a new series of Cr(II) hydroborates

“…The Cr-Cr distance (Crl-Crl = 1.844(2) A) is among the shortest formed in this type of complex and places 5b in the family of the supershort quadruply bonded dichromium species (21) donor atoms (N4-C8-N4 = 121.3(8)", N2-C2-N3 = 12 1.1(6)") are similar to those of the dimeric compound Cr,(CyNCHNCy),. The structural features of 1, 2, 3, and 5 compare well with those of other q-BH, complexes of different transition metals described in the literature (22).…”

Titanium(III) tetrahydroborates. Preparation and crystal structure of Ti(BH4)3(PMe3)2 containing an unusual Ti.cntdot..cntdot..cntdot.H.cntdot..cntdot..cntdot.B agostic interaction

“…More recently, examples of unusual bridging geometries with short M-B contacts involving tetrahydroborate groups have been observed in the dimeric transition-metal complex [Ru2(BH4)H2(tripod)2+] and the tetrahedral cluster Fe3(BH4)H(CO)9. 36,37 Other examples of BH4groups bridging between transition metals have been reported, [38][39][40][41] but in all cases it is difficult to assess the extent of direct bonding between the metal atom and boron. In any event, none of these molecules possesses a side-on B-H bonding mode closely analogous to that found in the Ti(BH4)3(PR3)2 system.…”

Preparation, Crystal Structures, and Spectroscopic and Redox Properties of Nickel(II) Complexes Containing Phosphane–(Amine or Quinoline)‐Type Hybrid Ligands and a Nickel(I) Complex Bearing 8‐(Diphenylphosphanyl)quinoline

“…Reduction of Ph 2 Pqn complex 3 with Zn powder [22] in acetonitrile afforded a dark red solution, from which a dark red precipitate could be isolated on addition of deaerated water. As the cyclic voltammogram of this product (in acetonitrile) was almost identical to that of complex 3, it was assumed to be the corresponding Ni I complex of [Ni(Ph 2 Pqn) 2 ]BF 4 (5).…”