A FERRACARBORANE ANALOG TO [FP]- - SYNTHESIS AND REACTIONS OF [CLOSO-3,3-(CO)2-3,1,2-FEC2B9H11]2-

Reduction of [closo-3,3,3-(CO)3-3,1,2-FeC2B9H11] (1) with 2 equiv of sodium naphthalide affords the high-yield synthesis of a formal iron (0) ferracarborane dianion [closo-3,3-(CO)2-3,1,2-FeC2B9H11]2- (3), as monitored by B-11 NMR spectroscopy. Complex 3 serves as a nucleophile in a variety of alkylation, acylation, and metalation reactions to yield ferracarborane anions of the type [closo-3,3-(CO)2-3-L-3,1,2,-FeC2B9H11]-(4, L = CH3; 5, L = CH2C6H5; 6, L = COCH3; 7, L = SnC6H5). The molecular structure of [N(C2H5)4][7] has been determined by X-ray diffraction techniques. Compound 7 crystallized in the triclinic space group P1BAR with a = 11.209 (1) angstrom, b = 13.026 (1) angstrom, c = 13.595 (1) angstrom, alpha = 79.959 (3)-degrees, beta = 84.143 (3)-degrees, gamma = 66.060 (2)-degrees, V = 1785 angstrom-3, and Z = 2. In situ reactions of 3 with allyl and methyallyl chloride followed by subsequent loss of CO induced by ultraviolet radiation, resulted in the isolation of the corresponding eta-3-allyl derivatives, [closo-3-CO-3-(eta-3-CH2CRCH2)-3,1,2-FeC2B9H11]-(8, R = H; 9, R = CH3). The structure of 8 as the PPN+ salt was also elucidated by single-crystal X-ray diffraction and found to crystallize in the monoclinic space group P2(1)/m with a = 9.1250 (7) angstrom, b = 25.011 (2) angstrom, c = 18.517 (2) angstrom, beta = 91.328 (3)-degrees, V = 4225 angstrom 3, and Z = 4 (two crystallographically different half-anions and one cation in the asymmetric unit). Migratory insertion of alkyls was demonstrated in the preparation of [closo-3-CO-3-COCH3-3-P(CH3)3-3,1,2-FeC2B9H11]-(10) by heating 4 and excess P(CH3)3 in THF for 7 days at the reflux temperature. A single-crystal X-ray diffraction study of [PPN][10] is reported. Complex 10 crystallized in the triclinic space group P1BAR with a = 10.086 (4) angstrom, b = 15.390 (6) angstrom, c = 17.027 (7) angstrom, alpha = 112.636 (8)-degrees, beta = 96.647 (8)-degrees, gamma = 100.206 (9)-degrees, V = 2351 angstrom 3, and Z = 2. The closo 12-vertex icosahedral geometry composed of a polyhedral FeC2B9-d6 framework and pseudooctahedral coordination exhibited by the iron atom are common structural features displayed by all three of the ferracarboranes that were characterized crystallographically.