Reactions of 6,6?-bis(nido-decaboranyl) oxide and 6-hydroxy-nido-decaborane with dihalogenobis(phosphine) complexes of nickel, palladium, and platinum, and some related chemistry; nuclear magnetic resonance investigations and the crystal and molecular structures of bis(dimethylphosphine)-di--(2,3,4-?3-nido-hexaboranyl)-diplatinum(Pt?Pt), [Pt2(-?3-B6H9)2(PMe2Ph)2], and of 2,4-dichloro-1,1-bis(dimethylphenylphosphine)-closo-1-nickeladecaborane, [(PhMe2P)2NiB9H7Cl2]