NEW STUDIES ON 2 OLD SANDWICH COMPOUNDS - CYCLOPENTADIENYLMANGANESE BENZENE AND CYCLOPENTADIENYLMANGANESE BIPHENYL

The sandwich complexes CpMn(C6H6) (1) and CpMn(C6H5-Ph) (2) have been characterized by X-ray structure analyses. The description of 1 involved a model of disordered ring ligands; the distance between the ring centers (327 pm) has been found to be intermediate between the ring-ring distances of ferrocene (332 pm) and dibenzenechromium (323 pm). In 2 the manganese atom stands closer to the center of the six-membered (154.6 pin) than to that of the five-membered ring (174.8 pm); the planes of the two phenyl moieties of the biphenyl ligand are twisted by 24.4-degrees in the crystal. Displacement of the benzene ring in 1 by the two-electron ligands L = CO, PMe3 and P(OMe)3 gives halfsandwich compounds CpMnL3 (3a-c). The metallation of 1 by (n)butyl-lithium in the presence of tetramethylethylenediamine (tmeda) leads to a 1,1'-dilithiated intermediate (C5H4Li)Mn(C6H5Li) (4) which, after reaction with trimethylelement chlorides, Me3E-Cl (E = Si, Ge, Sn, Pb), or diorganyl dichalcogenides, MeE-EMe and PhE-EPh (E = S, Se), gives 1,1'-disubstituted derivatives of 1. The new sandwich compounds (C5H4-R)Mn(C6H5-R') (R = R' = SiMe, (5a), GeMe3 (5b), SnMe3 (5c), PbMe3 (5d), SMe (6a) and SeMe (6b)) have been studied in benzene solution by H-1, C-13, Si-29, Se-77, Sn-119 and Pb-207 NMR spectroscopy, and the NMR data have been compared with those of the corresponding ferrocene derivatives, Fe(C5H4-R)2.