Preparation and reactions of a half-sandwich dicarbollyl nickel(II) complex containing a dimethylamino pendent group

The dicarbollylamino nickel complex [(eta (5):eta (1)-C2B9H10-CH2NMe2)Ni(PP h3)] (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 [nid o-7-NMe2CH2-7,8-C2B9H11](1-) (2) with NiCl2(PPh3)(2) in THF. Ligand substit ution at a with a variety of mono- or bidentate ligand systems has been stu died. The intramolecularly coordinated dicarbollylamino nickel complex 3 re acted with soft donor ligands, such as PEt3 and CNBut, at the metal center to provide substituted bis(ligand) nickel complexes with an uncoordinated a mino side group [(eta (5)-C2B9H10CH2NMe2)Ni(PPh3)(L)] (L = PEt3 (4a); CNBut (4b)). However, 3 reacted with bidentate ligands, such as dpe (bis(dipheny lphosphino)ethane) and bipy (2,2'-bipyridine), to give nickel complexes wit h a coordinated amino group [(eta (5):eta (1)-C2B9H10-CH2NMe2)Ni(L-L)] (L-L = dpe (5a); bipy (5b)) after removal of the phosphine ligand. In particula r, the tert-butylisocyanide complex 4b reacted with the methyl iodide to pr ovide exclusive formation of a deaminated species [(eta (5)-C2B9H10CH2PPh3) Ni(CNBut)(I)] (6). All of these new compounds have been isolated in good yi eld 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.