95274-87-6Relevant academic research and scientific papers
Pyrazolyl-bridged iridium dimers. 7. Synthesis and properties of bridge-substituted analogues of [Ir(COD)(μ-pz)]2 (pzH = pyrazole), the mixed-bridge complex [Ir2(COD)2(μ-pz)(μ-fpz)] (fpzH = 3,5-bis(trifluoromethyl)pyrazole), and the mixed-metal dimer [IrRh(COD)2(μ-pz)2]. Crystal ...
Bushnell, Gordon W.,Fjeldsted, D. O. Kimberley,Stobart, Stephen R.,Zaworotko, Michael J.,Knox, Selby A. R.,Macpherson, Kirsty A.
, p. 1107 - 1114 (2008/10/08)
Full title: Pyrazolyl-bridged iridium dimers. 7. Synthesis and properties of bridge-substituted analogues of [Ir(COD)(μ-pz)]2 (pzH = pyrazole), the mixed-bridge complex [Ir2(COD)2(μ-pz)(μ-fpz)] (fpzH = 3,5-bis(trifluoromethyl)pyrazole), and the mixed-metal dimer [IrRh(COD)2(μ-pz)2]. Crystal and molecular structures of bis(cyclooctadiene)bis(μ-3-phenyl-5-methylpyrazolyl)-diiridium(I) (dissymmetric isomer) and bis(cyclooctadiene)bis(μ-3,4,5-trimethylpyrazolyl)diiridium(I). Fifteen diiridium(I) complexes [Ir(COD)(μ-L)]2 (2-16) (COD = cycloocta-1,5-diene) related to the prototypal compound [Ir(COD)(μ-pz)]2 (1, pzH = pyrazole) have been synthesized by Cl displacement by LH from [Ir(COD)(μ-Cl)]2 (L = 4-methylpyrazolyl (2), 3-methylpyrazolyl (3), 3,5-dimethylpyrazolyl (4), 3,5-diphenylpyrazolyl (5), 3-phenyl-5-methylpyrazolyl (6), 3-(trifluoromethyl)-5-methylpyrazolyl (7), 3,5-bis(trifluoromethyl)pyrazolyl (8), 3,4,5-trimethylpyrazolyl (9), 3,5-dimethyl-4-bromopyrazolyl (10), indazolyl (11), 3-(heptafluoropropyl)-5-tert-butylpyrazolyl (12), 3-(trifluoromethyl)-5-phenylpyrazolyl (13), 4-chloropyrazolyl (14), 4-iodopyrazolyl (15), and 4-nitropyrazolyl (16)). The products have been characterized by 1H and 13C NMR spectroscopy and UV/visible absorption spectrophotometry and have been subjected to study by cyclic voltammetry. Among complexes incorporating unsymmetrically substituted bridging ligands, dimers 3, 7 and 11 exist as diastereoisomeric mixtures, while for 6 one diastereomer predominates and 12 and 13 appear to be formed as single isomers. The predominant diastereomer of compound 6 has been identified as the dissymmetric isomer (C2 molecular symmetry); monoclinic, of space group P21/n with a = 13.690 (4) A?, b = 14.617 (4) A?, c = 15.749 (10) A?, and β = 96.42 (4)0, in which the Ir2 separation = 3.079 (2) A?. Intramolecular nonbonding approach to within 2.2 A? of hydrogen atoms attached to opposing terminal COD ligands has been identified in crystals of compound 9, triclinic, of space group P1, a = 11.116 (4) A?, b = 13.502 (5) A?, c = 11.006 (4) A?, α = 105.45 (4)0, β = 62.16 (3)0, and γ = 110.07 (4)0, in which the Ir2 separation is 3.096 (1) A?. A marked increase in E1/2 is observed compared with the parent compound 1 accompanying either 3,5 or 4 substitution with electron-withdrawing groups (CF3 or NO2) of the bridging pyrazolyl unit. Synthesis of the mixed-bridge analogue [Ir(COD)(μ-pz)(μ-fpz)Ir(COD)] (17) and of the mixed-metal complex [RhIr(COD)2(μ-pz)2] (18) is described, and stability and NMR properties of both these products are reported.
