Direct Chlorination of Trispyrazolyl Borate Ligands in Tp-Ruthenium Complexes

Trispyrazolyl borate (Tp) ligands are highly modifiable to vary their steric and electronic properties, and the ability to selectively modify them after metal complexation would allow for rapid catalyst diversification. To this end, stable ruthenium complexes TpRu­(cod)­Cl (cod = 1,5-cyclooctadiene) and TpRu­(nbd)Cl (nbd = norbornadiene) were selectively chlorinated at the 4-positions of the Tp pyrazole rings in high yields to afford Tp^ClRu­(cod)Cl and Tp^ClRu­(nbd)­Cl. The chlorinated complexes could then undergo diene ligand exchange to afford phosphine complexes Tp^ClRu­(phosphine)­Cl and Tp^ClRu­(phosphine)­Cl₂. Complexes were characterized via NMR spectroscopy, X-ray crystallography, UV–vis spectroscopy, and cyclic voltammetry