The coordination chemistry of guanidines and guanidinates

Species containing the Y-shaped CN, unit have recently attracted increasing attention as electronically and sterically flexible ligands. Neutral guanidines [(R2N)(2)C=NR], guanidinates(-1) [(RN)(2)CNR2](-) and guanidinates(2-) [(RN)(2)C=NR](2-) are capable of exhibiting a variety of coordination modes and a range of donor properties leading to compatibility with a remarkably wide range of metal ions from all parts of the periodic table. The coordination chemistry of these species is reviewed up to July 2000, and aspects of their electronic structures and metal-ligand bonding characteristics discussed. (C) 2001 Elsevier Science B.V. All rights reserved.