Synthesis and Reactivity of the 9- and 10-Vertex Iron−Monocarborane Anions [7,7,7-(CO)₃-<i>c</i><i>loso</i>-7,1-FeCB₇H₈]^- and [6,6,6,10,10,10-(CO)₆-<i>c</i><i>loso</i>-6,10,1-Fe₂CB₇H₈]^-

The reagent [NBun4][closo-1-CB7H8] reacts with [Fe3(CO)12] in THF at reflux temperatures to give the anion [7,7,7-(CO)3-closo-7,1-FeCB7H8]-, isolated as the [N(PPh3)2]+ salt (1a). Further heating with excess [Fe3(CO)12] inserts a second {Fe(CO)3} fragment to yield [6,6,6, 10,10,10-(CO)6-closo-6,10,1-Fe2CB7H8]-, also isolated as its [N(PPh3)2]+ salt (2). Compounds 1a and 2 react with [CuCl(PPh3)]4 and Tl[PF6] to yield the bi- and trimetallic complexes [6,7,9-{Cu(PPh3)}-6,9-(μ-H)2-7,7,7-(CO)3-closo-7,1-FeCB7H6] (4) and [7,10-{Cu(PPh3)}-7-(μ-H)-6,6,6,10,10,10-(CO)6-closo-6,10,1-Fe2CB7H7] (5), respectively. Compound 2 with Ag[PF6] and PPh3 fails to give the analogous Ag−Fe2CB7 species, but instead under oxidative conditions one {Fe(CO)3} moiety is removed from the anion of 2 and the anion of 1a is isolated as the [Ag(PPh3)3]+ salt (1b). The bimetallic species [6,7,9-{Ag(PPh3)}-6,9-(μ-H)2-7,7,7-(CO)3-closo-7,1-FeCB7H6] (6) is also obtained. Treatment of 2 with CF3SO3H in donor solvents L yields the zwitterionic B-substituted compounds [6,6,6,10,10,10-(CO)6-7-L-closo-6,10,1-Fe2CB7H7] (L = SMe2 (7), THF (8)). The former of these products reacts with SMe2 in the presence of Me3NO to yield the doubly substituted species [6,6,10,10,10-(CO)5-6,7-(SMe2)2-closo-6,10,1-Fe2CB7H7] (9), while the latter with the nucleophile PEt3 undergoes THF ring opening to yield [6,6,6,10,10,10-(CO)6-7-{O(CH2)4PEt3}-closo-6,10,1-Fe2CB7H7] (12).