Monodentate ligands, transition metal structural studies

The use of bulky monodentate m-terphenyl ligands in the stabilisation of d-block organometallic compounds is surveyed. Importantly, these ligands have facilitated the isolation of hitherto unknown species containing low-coordinate centres and metal-metal multiple bonds. This review reports on these advances with emphasis on the synthesis, structural characterisation and, where possible, reactivity studies of complexes featuring metal-carbon bonds between m-terphenyl ligands and the transition metals. 

The study of the molecular structure of thiocyanato complexes is interesting in view of the variety of coordinated forms and the occurrence of bridging structures. The ability of the thiocyanate ion to form complexes with d and f transition elements in a mono (M-NCS, M-SCN) or bidentate (M-NCS-M) coordination has been extensively investigated. In the majority of reported cases however, the NCS group is coordinated to the metal as a monodentate ligand. 

---