Zeitschrift für Naturforschung B · 1983 · 38 citations · 0 references
Natural SciencesChemistryInorganic ChemistryNuclear ChemistryOrganic ChemistryCoordination ChemistryHeterocyclic ChemistryHeterocyclic CompoundsMolecular SymmetryTransition Metal ChemistryTransition Metal ComplexesMagnetic Exchange In Transition Metal CompoundsMagnetic Exchange InteractionsMetal-metal InteractionsParamagnetic CentersParamagnetic ComplexesParamagnetic Nmr SpectroscopyParamagnetic SpeciesX-ray Spectral Analysis
Reaction of chromocene with chloroform yields [Cp 2 Cr] + [CpCrCl 3 ] - (2) which is transformed to trans-[CpCrCl 2 ] 2 (3 a) on heating and to a mixture of cis/trans-[CpCrCl 2 ] 2 (3 b/a) on standing in chloroform. 2 and 3a/b have been characterized by paramagnetic 1 H and 13 C NMR yielding the first spectra of the chromocenium cation and the halfsandwich type [CpCrX 2 L] n- . For comparison, CpCrCl 2 (pyridine) (4) has been studied; the NMR data of 4 and [CpCrC 3 ] - indicate that both are electronically similar. An X-ray analysis shows one isomer of 3 to be the trans-compound. Its chromium and bridging chlorine atoms constitute a square with a metal-metal distance of 336.2 pm. Magnetic exchange is established for 3 a by temperature dependent NMR studies. The X-ray results suggest superexchange to be the dominating mechanism.