Synthesis and Reactivity of the 9- and 10-Vertex Iron−Monocarborane Anions [7,7,7-(CO)3-closo-7,1-FeCB7H8]-and [6,6,6,10,10,10-(CO)6-closo-6,10,1-Fe2CB7H8]-

The reagent [NBu n 4 ][ closo -1-CB 7 H 8 ] reacts with [Fe 3 (CO) 12 ] in THF at reflux temperatures to give the anion [7,7,7-(CO) 3 - closo -7,1-FeCB 7 H 8 ] -, isolated as the [N(PPh 3 ) 2 ] + salt ( 1a ). Further heating with excess [Fe 3 (CO) 12 ] inserts a second {Fe(CO) 3 } fragment to yield [6,6,6, 10,10,10-(CO) 6 - closo -6,10,1-Fe 2 CB 7 H 8 ] -, also isolated as its [N(PPh 3 ) 2 ] + salt ( 2 ). Compounds 1a and 2 react with [CuCl(PPh 3 )] 4 and Tl[PF 6 ] to yield the bi- and trimetallic complexes [6,7,9-{Cu(PPh 3 )}-6,9-( μ -H) 2 -7,7,7-(CO) 3 - closo -7,1-FeCB 7 H 6 ] ( 4 ) and [7,10-{Cu(PPh 3 )}-7-( μ -H)-6,6,6,10,10,10-(CO) 6 - closo -6,10,1-Fe 2 CB 7 H 7 ] ( 5 ), respectively. Compound 2 with Ag[PF 6 ] and PPh 3 fails to give the analogous Ag−Fe 2 CB 7 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(PPh 3 ) 3 ] + salt ( 1b ). The bimetallic species [6,7,9-{Ag(PPh 3 )}-6,9-( μ -H) 2 -7,7,7-(CO) 3 - closo -7,1-FeCB 7 H 6 ] ( 6 ) is also obtained. Treatment of 2 with CF 3 SO 3 H in donor solvents L yields the zwitterionic B-substituted compounds [6,6,6,10,10,10-(CO) 6 -7-L- closo -6,10,1-Fe 2 CB 7 H 7 ] (L = SMe 2 ( 7 ), THF ( 8 )). The former of these products reacts with SMe 2 in the presence of Me 3 NO to yield the doubly substituted species [6,6,10,10,10-(CO) 5 -6,7-(SMe 2 ) 2 - closo -6,10,1-Fe 2 CB 7 H 7 ] ( 9 ), while the latter with the nucleophile PEt 3 undergoes THF ring opening to yield [6,6,6,10,10,10-(CO) 6 -7-{O(CH 2 ) 4 PEt 3 }- closo -6,10,1-Fe 2 CB 7 H 7 ] ( 12 ).