Guanidinates as Alternative Ligands for Organometallic Complexes

For decades, ligands such as phosphanes or cyclopentadienyl ring derivatives have dominated Coordination and Organometallic Chemistry. At the same time, alternative compounds have emerged that could compete either for a more practical and accessible synthesis or for greater control of steric and electronic properties. Guanidines, nitrogen-rich compounds, appear as one such potential alternatives as ligands or proligands. In addition to occurring in a plethora of natural compounds, and thus in compounds of pharmacological use, guanidines allow a wide variety of coordination modes to different metal centers along the periodic table, with their monoanionic chelate derivatives being the most common. In this review, we focused on the organometallic chemistry of guanidinato compounds, discussing selected examples of coordination modes, reactivity and uses in catalysis or materials science. We believe that these amazing ligands offer a new promise in Organometallic Chemistry.

The chemistry of guanidinate complexes of the platinum group metals

In this Perspective article, recent advances in the chemistry of platinum group metal complexes containing mono- and dianionic guanidinate ligands, i.e. [(RN)2C-NR2]- and [(RN)2C[double bond, length as m-dash]NR]2-, respectively, are presented. Synthetic and structural aspects, reactivity studies, and applications of these compounds are discussed.

Probing the factors that influence the conformation of a guanidinato ligand in [(η5-C5Me5)M(NN)X] (NN = chelating N,N′,N′′-tri(o-substituted aryl)guanidinate(1−); X = chloro, azido and triazolato)

The conformational difference illustrated is ascribed to a subtle repulsive interaction between the o-Cl substituent of two proximal aryl rings in the guanidinate ligand.