Variations in the Coordination Sphere of Ruthenacyclic Carbamoyl Complexes: Mapping Their Suitability for Direct Conjugation

The reactivity of a series of ruthenacyclic carbamoyl derivatives 4x, which are structural mimics of the [Fe]-hydrogenase metal cofactor, have been assessed in relation to their suitability for direct conjugation onto peptides. Substitution of a bromido ligand is specific for thiolates and selenolates, offering direct conjugation and precise control of the conjugation site. The ligand trans to the carbamoyl moiety is labile and, in certain solvents, may be uncoordinated. Steric effects from substitution at the 6-position of the aminopyridyl ring, or of the thiolato ligand in the thiolated derivatives, influence isomerization and dimerization, as well as efficacy and selectivity in catalytic organosilane hydrolysis.