Abstract
We have developed a selective low-temperature synthesis of fac and mer tris-cyclometalated Ir(III) complexes. The chloro-bridged dimers [Ir(C∧N)2Cl]2 (C∧N = cyclometalating ligand) are cleaved in coordinating solvents like acetonitrile to give neutral Ir(C∧N)2(NCCH3)Cl species which in turn are reacted with AgPF6 to give hexafluorophosphate salts of the bis-acetonitrile species [Ir(C∧N)2(NCCH3)2]PF6 for C∧N = 2,2′-thienylpyridine (thpy) and 2-phenylpyridine (ppy). These bis-acetonitrile complexes are excellent starting materials for the synthesis of tris-Ir(III) complexes. The complexes of the general formula fac-Ir(C∧N)3 were synthesized with the ligands thpy and ppy at 100°C in o-dichlorobenzene from the corresponding [Ir(C∧N) 2(NCCH3)2]PF6 complexes. The reaction of [Ir(C∧N)2(NCCH3)2]-PF 6 with thpy at room temperature did not give the expected tris complex but instead gave [Ir(thpy)2(N,S-thpy)]PF6, with the third chelating ligand complexed through the sulfur atom of the thiophene ring. [Ir(thpy)2Cl]2, [Ir(ppy)2Cl]2, Ir(thpy)2(NCCH3)Cl, [Ir(thpy)2(NCCH 3)2]PF6, [Ir(ppy)2(NCCH 3)2]PF6, and [Ir(thpy)2(N,S-thpy)] PF6 were structurally characterized by X-ray crystallography. Additionally, hydroxy-bridged dimers, [Ir(C∧N)2(OH)]2, were synthesized as starting materials for the selective synthesis of mer-Ir(C∧N)3 complexes at 100°C in o-dichlorobenzene. A mechanism is proposed that may account for the selectivity observed in the formation of the mer-Ir(C∧N)3 and fac-Ir(C∧N)3 isomers in previous studies and the studies presented here.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 7800-7809 |
| Number of pages | 10 |
| Journal | Inorganic Chemistry |
| Volume | 46 |
| Issue number | 19 |
| DOIs | |
| State | Published - Sep 17 2007 |