Half-sandwich iron(II) and ruthenium(II) complexes with the dicarbollylamino ligand system

The syntheses of half-sandwich iron(II) complexes [(eta (5):eta (1)-C2B9H10-CH2NMe2)-Fe(THF)(2)] (3) 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 eta (5)-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 DcabH(N) [nido-7-NMe2CH2-7,8-C2B9H11](1-) (2) with FeCl2(THF)(n) in THF affords solutions of the labile species [(eta (5):eta (1)-C2B9H10-CH2NMe2)-Fe(THF)(2)] (3), which readily reacts with CO, CNBul, PMe3, and cod, yielding the species 4a-d. In particular, the eta (4)-bonding mode of the cycloctadienyl group to the metal of complex 4d is displaced in the reaction with CNBul and PMe3, yielding 4b and 4c, respectively. [Ru(CO)(3)Cl-2](2) reacts with the lithium salt of 2 in THF to give [(eta (5):eta (1)-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 [(eta (5):eta (1)-C2B9H10CH2NMe2)Ru(CO)(NCMe)] (6). (6).