Ligands N-heterocyclic

Versatile supramolecular helicatedmetal complexes with N-heterocyclic ligands 97CRV2005. 

Isolation and characterization of stereoisomers in di- and trinuclear complexes with N-heterocyclic ligands 98CSR185. 

The surprising stability of N-heterocyclic carbenes was of interest to organometallic chemists who started to explore the metal complexes of these new ligands. The first examples of this class had been synthesized as early as 1968 by Wanzlick [9] and Ofele [10], only 4 years after the first Fischer-type carbene complex was synthesized [2,3] and 6 years before the first report of a Schrock-type carbene complex [11]. Once the N-heterocyclic ligands are attached to a metal they show a completely different reaction pattern compared to the electrophilic Fischer- and nucleophilic Schrock-type carbene complexes. 

N-heterocycles are a class of neutral ligands with strong coordination affinity to many metal ions. Since a number of neutral N-donors ligands are available, a wide range of oxo-centered triruthenium complexes with various N-heterocyclic ligands have been prepared through axial ligand substitution. By judicious selection of the N-heterocyclic type and modification of the substituents with different electronic and steric effects, the electronic, redox, and spectroscopic properties in these oxo-centered triruthenium derivatives are controllable. 

Polydentate NHC ligands have provided numerous new compounds [19]. Chelate-N-heterocyclic ligands also allow the fine-tuning of topological properties such as steric hindrance, bite angles, chirahty and fluxional behavior. In the case of Ir—chelate—NHC compounds, most of the data that have been reported were obtained as an extension of investigations into their rhodium analogues [19, 20]. 

Table 4 Complexes of Zirconium(IV) and Hafnium(IV) Halides with N-heterocyclic Ligands...

Zirconium and hafnium cyanate, thiocyanate, and selenocyanate complexes that contain N-heterocyclic ligands are discussed in Sections 32.4.2.5.iii, 32.4.2.5.iv and 32.4.2.5.V. 

Table 10 Some Complexes of N-Heterocyclic Ligands with Actinide(IV) Compounds...

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