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

The dicarbollylamino nickel complex [(η5:η1-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 DcabNH [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 CNBut, at the metal center to provide substituted bis(ligand) nickel
complexes with an uncoordinated amino side group [(η5-C2B9H10CH2NMe2)Ni(PPh3)(L)] (L
= PEt3 (4a); CNBut (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 [(η5:η1-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 [(η5-C2B9H10CH2PPh3)Ni(CNBut)(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.