Half-Sandwich Iron(II) and Ruthenium(II) Complexes with the Dicarbollylamino Ligand System

The syntheses of half-sandwich iron(II) complexes [(η5:η1-C2B9H10-CH2NMe2)FeL2] (L =
CO (4a), CNBut (4b), PMe3 (4c), 1,5-cycloctadiene (cod) (4d)) are reported, and the structure
of 4a has been established by an X-ray diffraction study. The complex 4a adopts a
characteristic three-legged “piano stool” structure with the iron atom η5-coordinated on one
side by a nido o-carboranyl group and the other by the dimethylamino group and two CO
ligands. Thus, treatment of the lithium salt of DcabHN [nido-7-NMe2CH2-7,8-C2B9H11]1- (2)
with FeCl2(THF)n in THF affords solutions of the labile species [(η5:η1-C2B9H10-CH2NMe2)Fe(THF)2] (3), which readily reacts with CO, CNBut, PMe3, and cod, yielding the species
4a−d. In particular, the η4-bonding mode of the cycloctadienyl group to the metal of complex
4d is displaced in the reaction with CNBut and PMe3, yielding 4b and 4c, respectively. [Ru(CO)3Cl2]2 reacts with the lithium salt of 2 in THF to give [(η5:η1-C2B9H10-CH2NMe2)Ru(CO)2] (5), having a molecular structure closely related to that of 4a, as confirmed by an
X-ray diffraction study. Further decarbonylation reaction of 5 with Me3NO was carried out
in acetonitrile solution to give the corresponding monosubstituted complex [(η5:η1-C2B9H10-CH2NMe2)Ru(CO)(NCMe)] (6).