Perfluormethyl-Element-Liganden, XXXIV* 55Mn-NMR-Untersuchungen an Zweikernkomplexen des Typs Mn2(CO)8E(CF3)2Y (E = P, As; Y = Hal und E' R; E' = S, Se, Te)

Abstract

Abstract Dinuclear complexes of the type {(CO)4Mn}μ-E(CF3)2, μ-Y {Mn(CO)4} (E = P, As; Y = Cl, Br, I; SR, SeR , TeR , with R varying over a wide range of inductive, mesomeric and steric properties) have been investigated by 55Mn NMR spectroscopy. The NMR signals cover the range of -415 to -1450 ppm (relative to aqueous KMnO4); half-widths are between 400 and several thousand Hz. The 55Mn - 31P one-bond coupling is usually unresolved, an exception being the complex with two P(CF3)2 bridges [J(MnP) = 152 Hz], The temperatur gradient for δ(55Mn) is 1.2 ppm/deg. Shielding of the 55Mn nucleus is discussed with respect to δ and π bonding effects and the polarizability (electronegativity) of the bridging functions. With Y = SP(CF3)2 and SeP(CF3)2, five-ring system s with two inequivalent manganese sites are formed, which give rise to two 55Mn NMR signals, the sharper resonance for the site of higher symmetry [Mn{P(CF3)2}2] lying at -1750 ppm.