Dirhodium(II) carboxylate complexes as building blocks. Synthesis of dimeric species as connectors for macrocycles

Two complexes of the form (AcO)2Rh2LRh2(OAc)2 in which two Rh24+ units are covalently linked have been prepared by reaction of Rh2(OAc)4 with bischelating tetracarboxylate ligand L=(−O2CC(Me)2O))2PhPh(OC(CH3)2CO2−)2 in N,N-dimethylaniline. A crystal structure of the major (kinetic) product showed, unexpectedly, that it contained two 14 membered chelate rings, with the isomeric minor (thermodynamic) product having two 12 membered chelate rings.