Proton reactivity of butterfly oxo and sulfide clusters and structural characterization of HFe3Mn(CO)(10)(dmpm)(mu(4)-O)

Phosphine substitution for CO in the butterfly oxo cluster [Fe3Mn(CO)(12)(m u(4)-O)](-) (1) produces the bis-phosphine clusters [Fe3Mn(CO)(10)(PR3)(2)( mu(4)-O)](-) (R = OCH3 (2a), CH3 (2b)) and [Fe3Mn(CO)(10)(dmpm)(mu(4)-O)](- ) (3). In the presence of the strong acid, HSO3CF3, the oxo cluster 1 is no t protonated, 3 is protonated at the Fe-Fe backbone of the butterfly, and [ Fe3Mn(CO)(12)(mu(4-)S)](-) (5) loses CO and Mn upon protonation to yield H2 Fe3(CO)(9)(mu(3)-S) and a manganese containing by-product. The structure of the protonated cluster HFe3Mn(CO)(10)(dmpm)(mu(4)-O) (4), determined by si ngle-crystal X-ray diffraction, compared with its parent, 1, compound 4, ha s elongated metal-metal bonds, a smaller dihedral angle (111 degrees compar ed to 113 degrees), and shorter wingtip metal-to-ore ligand distances. Addi tionally, the carbonyl ligands on 4 shift to accommodate the hydride ligand on the hinge iron metals and the bidentate phosphine ligand spanning the h inge and wingtip iron atoms. The butterfly clusters were characterized by H -1 NMR, variable temperature C-13 NMR, P-31 NMR, and infrared spectroscopy. Crystal data for 4: monoclinic (Cc), a = 7.917(2), b = 18.541(2), c = 16.1 96(I) Angstrom, beta = 95.41(1)degrees, Z = 4, R (R-w) = 0.022 (0.024). (C) 2000 Elsevier Science S.A. All rights reserved.