Dirhodium(II) carboxylates as building blocks.: Synthesis and structures of cis-chelate complexes

Dirhodium tetracarboxylate complexes (C)Rh-2(OAc)(2) and (C)(2)Rh-2, where C is a chelating dicarboxylate of general form meta-C6H4(OC(CH3)(2)CO2-)(2), were prepared by heating Rh-2(OAc)(4) and diacids in N,N-dimethylaniline. The structures of six new complexes with one or two chelate rings were obtained, with pyridine ligands (or in one case N,N-dimethylaniline) co-ordinated to rhodium. The geometries of the molecules are similar, with the aromatic part of the chelate ring tilted out of the plane of the Rh-O cage by 57.5 to 66.6 degrees. The monochelate Rh-2{C6H4(OC(CH3)(2)CO2)(2)-m}(OAc)(2). 2Bu(t)Py ((BuPy)-Py-t=4-tert-butylpyridine) packed in the crystal to generate a hexagonal network of channels of (minimum) diameter 5 Angstrom due to vertical stacking of its axial pyridine ligands. Several other instances of intramolecular CH-pi and intermolecular pi-pi interactions were noted in the packing diagrams. The bischelate Rh-2{Ar(OC(CH3)(2)CO2)(2)-m}(2). PhNMe2, with Ar=4,6-di-tert-butylphenyl, has a polymeric structure displaying a new mode of arene co-ordination. The aromatic ring of the N-bound aniline co-ordinates to a neighbouring dirhodium complex via the para carbon atom with a Rh-C distance of 2.709 Angstrom.