Ferrocenylpyrazolyl bridging rhodium dimers. Crystal structure of [Rh(μ-pzFc)(COD)

Abstract

The ability of pyrazolato ligands to form dinuclear complexes has been used to prepare a family of rhodium(I) complexes of the type [Rh(μ-pz Fc )(L 2 )] 2 (L 2 =2,5-norbornadiene (NBD) ( 1 ); 1,5-cyclooctadiene (COD) ( 2 ); 2CO ( 3 )) containing ferrocenylpyrazolate (pz Fc ) as a bridging ligand. The diolefinic compounds 1 and 2 were obtained as the head-to-tail (H-T) isomer, whereas the tetracarbonyl derivative 3 was formed as a mixture of the head-to-tail (H-T) and head-to-head (H-H) isomers, as deduced by NMR studies in solution. The crystal structure determination of [Rh(μ-pz Fc )(COD)] 2 confirmed its identity as the H-T isomer having the boat conformation for the six-membered Rh(NN) 2 Rh ring in the solid state. Important structural parameters were Rh⋯Rh and Rh⋯H10 distances of 3.189(1) and 2.877 A, respectively, according to the presence of weak intermolecular interactions. Electronic and electrochemical studies were also performed.