SYNTHESIS OF COMPLEXES FE2(NO)4(MU-SR)(MU-NHR') BY THE SEQUENCE REDUCTION-ALKYLATION OF FE2(NO)4(MU-SR)2

Reduction of Fe2(NO4(mu-SR)2 (2, R = Me, Et, or t-Bu) with two equivalents of each of MBEt3H, MB(s-Bu)3H (M = Li, Na, or K), NaBH4, KH, or Na affords green, very air-sensitive anionic complexes M2[Fe2(NO)4(mu-SR)2] ((M+)2(3). The formulation of 3 is based on quantitative measurement of H2 released in the reaction of 2 (R = Me) with LiBEt3H and on conductivity, IR, and H-1 NMR studies of solutions of (M+)2(3). When only 1 equivalent of MBEt3H or MB(s-Bu)3H is used for reduction of 2, a different anionic product, tentatively formulated as M[HFe2(NO)4(mu-SR)2] (M+ 4) is obtained. Both 3 and 4 react with excess R'I (R' = Me, Et, or CH2Ph) to yield 2, Fe2(NO)4(mu-SR)(mu-SR)(mu-NHR') (or Fe2(NO)4(mu-SR)(mu-NHEt) if 3 or 4 was obtained by reduction of 2 with MBEt3H) (5, R = Me or Et), and Fe2(NO)4(mu-I)2. The mixed-bridge complexes 5 were characterized by a combination of elemental analysis, EI mass spectrometry, and IR and H-1 and C-13 NMR spectroscopy. The mechanism of their formation is considered.