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Redox Chemistry, Acid Reactivity, and Hydrogenation Reactions of Two-Electron Mixed Valence Diiridium and Dirhodium Complexes

Redox Chemistry, Acid Reactivity, and Hydrogenation Reactions of Two-Electron Mixed Valence Diiridium and Dirhodium Complexes

Thomas S Teets, Timothy R Cook, Brian D McCarthy, Daniel G Nocera

Inorg Chem. 2011 Jun 6;50(11):5223-33.

PMID: 21557564

Abstract:

The syntheses and reaction chemistry of two electron mixed-valence diphosphazane-bridged dirhodium and diiridium complexes M(2)(0,II)(tfepma)(2)(CN(t)Bu)(2)Cl(2) [M = Rh (1), Ir (2); tfepma = MeN[P(OCH(2)CF(3))(2)](2), CN(t)Bu = tert-butyl isocyanide] are described. 1 and 2 undergo addition and two-electron oxidation and reduction chemistries. In the presence of CN(t)Bu, the addition product with the stoichiometry M(2)(0,II)(tfepma)(2)(CN(t)Bu)(3)Cl(2) [M = Rh (3), Ir (3)] is generated; in the presence of 1 equiv of CN(t)Bu and 2 equiv of bis(pentamethyl-cyclopentadienyl)cobalt(II), 1 and 2 are reduced to furnish M(2)(0,0)(tfepma)(2)(CN(t)Bu)(3) [M = Rh (5), Ir (6)], which feature both four- and five-coordinate M(0) centers. Complexes 1, 2, 5, and 6 all possess coordinatively unsaturated square planar M(0) centers that are reactive: (1) 2 reacts with PhICl(2) to produce Ir(2)(II,II)(tfepma)(2)(CN(t)Bu)(2)Cl(4) (7); (2) protonation of 2 with HX yields Ir(2)(II,II)(tfepma)(2)(CN(t)Bu)(2)Cl(2)HX [X = Cl(-) (8), OTs(-) (9)]; (3) protonation of 5 with HOTs produces [Rh(2)(I,I)(tfepma)(2)(CN(t)Bu)(3)(μ-H)](OTs); and (4) the reversible hydrogenation of 2 proceeds smoothly, furnishing the cis-dihydride complex Ir(2)(II,II)(tfepma)(2)(CN(t)Bu)(2)(H)(2)Cl(2) (11). Substitution of tfepma in 2 with bis(diphenylphsophino)methane (dppm) yields the orthometalated complex Ir(2)(II,II)(dppm)(PPh(o-C(6)H(4))CH(2)PPh(2))(CN(t)Bu)(2)Cl(2)H (12). The X-ray crystal structures of 11 compounds are presented and discussed, and spectroscopic characterization by multinuclear and variable temperature NMR provides details about solution structures and in some cases the formation of isomeric products. The electronic spectra of the new complexes are also described briefly, with absorption and emission features derived from the bimetallic core.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP1277436	Bis(cyclopentadienyl)cobalt(II)		1277-43-6	Price

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