Generation of metal formyl complexes using nickel and platinum hydrides as reducing agents

The five-coordinate nickel hydride complex [Ni(dmpe)₂H]PF₆ (1) [dmpe = 1,2-bis-(dimethylphosphino)ethane] was synthesized by protonation of Ni(dmpe)₂ with NH₄PF₆. The platinum analog, [Pt(dmpe)₂H]PF₆ (2), and [Pt(depe)₂H]PF₆ (3) [depe = 1,2-bis(diethylphospnino)ethane] were synthesized by reduction of the corresponding Pt(II) complexes with NaBH₄ on alumina. Complexes 1 and 3 can also be synthesized electrochemically. Reduction of Ni-(dmpe)₂ ²⁺ by two electrons in the presence of ammonium ion generates 1, and reduction of Pt(depe)₂ ²⁺ in methanol or wet acetonitrile produces 3. These hydrides react with a variety of cationic metal carbonyl complexes to produce known metal formyl complexes. The structure of 3 was determined by X-ray diffraction. Complex 3 crystallizes in a monoclinic unit cell with P2₁/c symmetry with a = 14.258 (4) Å, b = 9.648 (3) Å, c= 21.898 (5) Å, β = 91.17 (2)°, V = 3011.7 (14) ų, Z = 4, and d_calcd = 1.662 g/cm³. Full-matrix least-squares refinement converged with residuals R = 4.52% and R_w = 5.90%.