Metal-to-ligand charge-transfer spectra of some chloro-bridged complexes of rhodium(I) and iridium(I)

Abstract

Electronic absorption and magnetic circular dichroism (MCD) spectra are reported for the chloro-bridged dimers [RhCl(CO)2]2, [RhCl(COD)]2, [RhCl(NBD)]2, and [IrCl(COD)]2 (COD = 1,5-cyclooctadiene; NBD = norbornadiene) in dichloromethane solution. Absorption spectra are also reported for the less stable [RhCl(C2H4)2]2, [RhCl(COT)2]2, and [IrCl(COT)2]2 (COT = cyclooctene) complexes. Spectra at 77 K were also obtained for [RhCl(CO)2]2 and several of the olefin complexes in glassy EPA or methylcyclohexane/pentane solution. Dissolution of [RhCl(CO)2]2, [RhCl(COD)]2, [RhCl(NBD)]2, and [IrCl(COD)]2 in acetonitrile gives a bridge-cleavage reaction, and spectral data are reported for the monomeric products [RhCl(CO)2(CH3CN)], [RhCl(COD)(CH3CN)], [RhCl(NBD)(CH3CN)], and [IrCl(COD)(CH3CN)]. The intense bands observed in the visible and near-ultraviolet regions of the spectra of all these complexes are assigned as metal-to-ligand charge-transfer (MLCT) transitions from occupied metal d orbitals to low-energy ligand * orbitals. Detailed spectral assignments are presented, and comparisons are made between the chloro-bridged complexes and related monomeric complexes.

A general approach to mono- and bimetallic organometallic nanoparticles

“…Pleasingly, the resulting Ir-ONPs showed an absorption maximum at 446 nm, similar to that observed for the COD complex (3) (451 nm) (Fig. 1c), 34 while the absorption maximum seen for complex 2 at 420 nm disappeared; strongly supporting the occurrence of binding events of 1,5-hexadiene units to Ir(I). UV measurements were also extended to the Rh-ONPs with similarly positive results (vide infra).…”

A Remarkable Family of Rhodium Acetonitrile Compounds Spanning Three Oxidation States and with Nuclearities Ranging from Mononuclear and Dinuclear to One-Dimensional Chains

“…The salt [Rh(CO) 2 (MeCN) 2 ][BF 4 ], originally isolated from CO trapping of a Rh III intermediate generated by photochemical irradiation of [Rh 2 (MeCN) 10 ][BF 4 ] 4 , has been explored as a possible precursor for the unknown monovalent acetonitrile cation [Rh I (MeCN) 4 ] + . A rational, high-yield synthesis of [Rh(CO) 2 (MeCN) 2 ][BF 4 ] is conveniently performed by abstraction of chloride ions from Rh 2 (μ-Cl) 2 (CO) 2 by AgBF 4 in acetonitrile . Upon treatment with diethyl ether or evaporation of the solvent, the yellow solution of ( 6 ) produces a dark blue solid.…”

Rh NMR studies of organometallic rhodium(I) derivatives

“…To obtain resolved 13C specrra it was necessary to lower the temperature to 223K and, in some cases, the exchange process was not completely stopped (26,28,29). Compound 24 gave a very broad signal.…”