Preparation of Capped Octahedral OsHC₆ Complexes by Sequential Carbon-Directed C–H Bond Activation Reactions

Abstract

A synthetic procedure based on sequential C-directed C-H bond activation reactions is reported for the preparation of capped octahedral OsHC6-complexes. Reactions of the dimer [OsCl2(η 6-p-cymene)]2 (1) with PhMeLAgI (MePhL = 1-phenyl-3methyl-1H-benzimidazolylidene (PhMeBIm), 1-phenyl-3,5,6-trimethyl-1H-benzimidazolylidene (PhMeBIm *)) afford OsCl2(η 6-pcymene)(PhMeL) (L = BIm(2), BIm * (3)), which undergo cyclization to give OsCl{κ 2-C,C-(MeL-C6H4)}(η 6-p-cymene) (L = BIm (4), BIm * (5)) by stirring in dichloromethane suspensions of Al2O3. Complexes 4 and 5 exchange the anion with AgOTf (OTf = CF3SO3). In acetonitrile, at 75ºC, the resulting OTf-derivatives Os(OTf){κ 2-C,C-(MeL-C6H4)}(η 6-p-cymene) (L = BIm (6), BIm * (7)) release the arene to yield the tetra(solvento) compounds [Os{κ 2-C,C-(MeL-C6H4)(CH3CN)4]OTf (L = BIm (8), BIm * (9)). Complexes 8 and 9 react with PhMeLAgI to coordinate a second NHC ligand. The generated species Os{κ 2-C,C-(MeL-C6H4)(PhMeL)(CH3CN)3]OTf (L = BIm (10), BIm * (11)), containing a C,C-chelate NHC-C6H4 ligand and a monodentated NHC group, exist as a mixture of mer (a and b) and fac (c) acetonitrile isomers. The X-ray diffraction structure of 10c reveals aromaticaromatic interactions between the N-phenyl substituent of the monodentated NHC group and aromatic rings of the chelate ligand. The π-π stacking has been analyzed by means of DFT calculations by using the AIM approach. Treatment of 10 and 11 with [PhMeLH]I, in the presence of an excess of Et3N leads to the capped octahedral target compounds OsH{κ 2-C,C-(MeL-C6H4)}3 (L = BIm (12), BIm * (13)), as a result of the coordination of a third NHC group and the orthometalation of the N-phenyl substituents of the second and third NHC ligands. 1 H NMR, 13 C{1H} APT and 1 H-1 H NOESY NMR spectra utilized for the characterization of all the complexes and centroids calculation of complex 10c (PDF). Crystallographic data for compounds 4, 8, 10c, and 12 (CIF). Cartesian coordinates of calculated compound (XYZ).

Osmium(II) Complexes Containing a Dianionic CCCC-Donor Tetradentate Ligand

“…Scheme 5 summarizes the procedure used. Addition of one equivalent of dppbz to dichloromethane solutions of the tetra(solvento) complexes [Os{κ 2 -C,C-(MeL-C 6 H 4 )}(CH 3 CN) 4 ]OTf (L = BzIm (9), BzIm* (10)), recently reported by us, 36 produces the replacement of two acetonitrile molecules by a bidentate ligand to afford after 12 h the di-…”

Recent Advances in Synthesis of Molecular Heteroleptic Osmium and Iridium Phosphorescent Emitters

“…They were obtained according to Scheme 13, starting from the tetrakis(solvento) complexes 45 and 46 via a two steps procedure. [39] These compounds initially react with 1,2-bis-(diphenylphosphino)benzene in dichloromethane to afford 47 and 48. The subsequent treatment of dimethylformamide solutions of 47 and 48 with the iodide salts of 1-phenyl-3-methyl-1H-benzimidazolium and 1-phenyl-3methyl-1H-5,6-dimethyl-benzimidazolium, in the presence of 10 equiv.…”

Cyclometalated Osmium Compounds and beyond: Synthesis, Properties, Applications

“…Intermediate 98 forms first followed by the metalation of the phenyl group in the presence of Al 2 O 3 . Piano-stool mono -cyclometalated complex 99 is the final product ( Figure 20 ) [ 77 ]. It takes two days for triazolium silver salts to react with [Os(η 6 -C 6 H 6 )(μ-Cl)Cl] 2 to give structurally similar complex 100 after treatment with KPF 6 [ 78 ].…”

“…Imidazolium complex 99 can be converted to a complex with four acetonitrile ligands 105 , which undergoes a second transmetalation with the organosilver compound to give 106 . The latter affords tris -cyclometalated complex 107 as shown in Figure 22 [ 77 ].…”