Cyclometallated complexes synthesis

S. Lamansky, P. Djurovich, D. Murphy, F. Abdel-Razzaq, H.-E. Lee, C. Adachi, P.E. Burrows, S.R. Forrest, and M.E. Thompson, Highly phosphorescent te-cyclometalated iridium complexes synthesis, photophysical characterization, and use in organic light emitting diodes, J. Am. Chem. Soc., 123 4304—4312 (2001). 

Dinuclear cyclometallated complexes are usually prepared starting from the metal chloride and the cyclometallating ligand (Figure 5, top). The same type of synthesis can be used to prepare cyclometallated complexes of high nuclearity. As an example, the recently reported synthesis of a hexanuclear cyclometallated complex is shown in Figure 5, bottom. ... 

Figure 5. (a) Metal chlorides can react with simple cyclometalating ligands to give dinuclear cyclometallated complexes, (b) Schematic representation of the synthesis of a hexanuclear complex containing cyclometallated units. ... 

Heterocycles can coordinate to transition metals by either electron donation from ligand to metal. The former most commonly occurs via the heteroatom, although binding through a ring carbon atom has often been observed, most notably in cyclometallated complexes (84MI7). 7r-coordination almost always requires the metal ion to be in a low oxidation state and can utilize either all or part of the 77-system. Thus any given heterocycle will have a number of coordination modes open to it and synthesis of the metal complex can result in isolation of the kinetic product. 

Lamansky, S. Djurovich, P. Murphy, D. Abdel-Razzaq, F. Lee, H.-E. Adachi, C Burrows, B. E. Forrest, S. R. (2001). Highly Phosphorescent Bis-Cyclometalated Iridium Complexes Synthesis, Photophysical Characterization, and Use in Organic Light Emitting Diodes. Journal of American Chemical Society, Vol. 123, pp. 4304-4312. 

The method of synthesis of these bis-cyclometallated complexes with tridentate ligands (pincers) is again by transmetallation of the di-lithiated ligand ... 

Some synthetic problems, as for example, the systematic synthesis of multiple-cyclometallated species, especially tris-cyclometallated complexes, remain open. 

Exchange of one ligand in a metallacycle by another ligand has been observed in Pd(II) complexes dissolved in acidic solution [74]. Synthesis of a cyclometallic complex comprising six-membered metallacycles from species containing five-membered metallacycles has been achieved in this way. 

Constable, E.C. Eeese. T.A. Tocher, D.A. Polynuclear 7E intermediates in the synthesis of cyclometallated complexes and molecular structure of (2-pyridylphenyl)mer-cury(II) chloride tetramer. J. Chem. Soc., Dalton Trans. 

Scheme 4.2 Synthesis of the cyclometalated complexes 16-18. (I) Na[AuCUl, MeCN/H20, rt Oi)...

Metallacycles are also featured in Chapters 2 and 3 of this volume. Cobalt- and nickel-based metallacycles are key cataljrtic intermediates in Transition-Metal-Catalyzed Cycloaddition Reactions of Bicy-clo[2.2.1]heptadienes by Professor Mark Lautens and Dr. William Tam of the University of Toronto (Chapter 2). The high sttain energy of norbomadiene makes possible many of the interesting processes covered in this informative chapter. It is followed by a comprehensive review of the State of the Art in Selective Hetero- and Carbocyclic Synthesis Mediated by Cyclometallated Complexes ... 

Heating [Ir(acac)3] with 2-phenylpyridine (Hppy) affords the tris-cyclometallated complex [Ir(ppy)3],392 and the synthesis of other complexes of the ppy ligand have also been reported.393,394 cyclometallated benzoquinoline Ir complex was shown to be an active catalyst for the H/D exchange of alcohols with D2.395 2.3 The Nickel Triad... 

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