Molybdenum tricarbonyl complexes of tricyclic trisaminomethane derivatives; synthesis and structural studies

Abstract

Reactions of the trisaminomethanes, 1 (R = H) and 2 (R = Me), with cycloheptatrienyl molybdenum tricarbonyl afforded their respective molybdenum tricarbonyl complexes; 3 and 4. Structures of these products have been determined by X-ray diffraction studies. Complex 3 crystallizes in the monoclinic space group P2 1/ m with a = 7.7364(6), b = 12.505(1), c = 7.774(1) Å, β = 107.70(1)°, Z = 2, μ(Mo- K α) = 0.90 mm −1. Its molybdenum coordination sphere features unusually small ligand bite angles (NMoN) of 57.7(1)–58.0(1)°. The unique bridgehead methinyl hydrogen was not located, but its existence has been confirmed by IR and solid-state NMR spectroscopy. Complex 4 crystallizes in the orthorhombic space group Pcmn with a = 7.7537(2), b = 12.3176(4), c = 15.6563(7) Å, Z = 4, μ(Mo- K α) = 0.87 mm −1. Similarly, pinched NMON angles of 58.8(1)° are observed. Significantly, the methyl to bridgehead carbon bond is shortened by 0.04 Å relative to the free ligand value, consistent with a reduced negative hyperconjugation upon complexation.