Preparation and Reactions of a Half-Sandwich Dicarbollyl Nickel(II) Complex Containing a Dimethylamino Pendent Group

The dicarbollylamino nickel complex [(η 5:η 1-C2B9H10-CH2NMe2)Ni(PPh3)] (3), in which the ligating amino group is connected to the dicarbollyl ligand, was prepared by the treatment of the lithium salt of Dcab N H [nido-7-NMe2CH2-7,8-C2B9H11]1- (2) with NiCl2(PPh3)2 in THF. Ligand substitution at 3 with a variety of mono- or bidentate ligand systems has been studied. The intramolecularly coordinated dicarbollylamino nickel complex 3 reacted with soft donor ligands, such as PEt3 and CNBu t , at the metal center to provide substituted bis(ligand) nickel complexes with an uncoordinated amino side group [(η 5-C2B9H10CH2NMe2)Ni(PPh3)(L)] (L = PEt3 (4a); CNBu t (4b)). However, 3 reacted with bidentate ligands, such as dpe (bis(diphenylphosphino)ethane) and bipy (2,2‘-bipyridine), to give nickel complexes with a coordinated amino group [(η 5:η 1-C2B9H10-CH2NMe2)Ni(L−L)] (L−L = dpe (5a); bipy (5b)) after removal of the phosphine ligand. In particular, the tert-butylisocyanide complex 4b reacted with the methyl iodide to provide exclusive formation of a deaminated species [(η 5-C2B9H10CH2PPh3)Ni(CNBu t )(I)] (6). All of these new compounds have been isolated in good yield and characterized by IR and NMR spectroscopies. In addition, the solid state structures of 3, 5b, and 6 were characterized by single-crystal X-ray analyses.