Stoichiometric and Catalytic Reactions Involving Si−H Bond Activations by Rh and Ir Complexes Containing a Pyridylindolide Ligand

Abstract

New rhodium and iridium complexes containing the bidentate, monoanionic 2-(2′-pyridyl)indolide (PyInd) ligand were prepared. The bis(ethylene) complex (PyInd)Rh(C 2 H 4 ) 2 (3) reacted with triethylsilane at 60 °C to produce the 16-electron Rh(V) bis(silyl)dihydride complex (PyInd)RhH 2 (SiEt 3 ) 2 (4). Both 3 and 4 catalyzed the chloride transfer reaction of chlorobenzene and Et 3 SiH to give Et 3 SiCl and benzene in the absence of base. In the presence of LiN i Pr 2 , catalytic C-Si coupling was observed, to produce Et 3 SiPh. Analogous Ir complexes of the type (PyInd)IrH 2 (SiR 3 ) 2 , where R 3 ) Et 3 (6a), Me 2 Ph (6b), Ph 2 Me (6c), or Ph 3 (6d), were not catalytically active in this chloride transfer chemistry. The molecular structure of 6c, determined by X-ray crystallography, may be described as having a highly unusual bicapped tetrahedral geometry. DFT calculations indicate that this distortion is associated with the d 4 electron count and the presence of highly trans-influencing silyl ligands. The reaction of 6a with PMe 3 (5 equiv) produced (PyInd)IrH(SiEt 3 )(PMe 3 ) 2 (7), while the reaction with PPh 3 (1 equiv) generated a mixture of isomers that was converted to (PyInd)IrH(SiEt 3 )(PPh 3 ) (8) upon heating in benzene at 80 °C. Complexes 7 and 8 exhibit regular octahedral and distorted square pyramidal geometries, respectively.

C–C σ complexes of rhodium

“…(54)(55)(56). Both pathways are consistent with a small negative value for ⌬S ‡ in as much as the transition state is ordered but does not require a significant amount of structural reorganization to achieve it.…”

Dehydrogenative Coupling of a Tertiary Silane Using Wilkinson's Catalyst

“…The most conventional used method for the production of high molecular weight polysilanes is the Wurtz‐type condensation of halosilanes in the presence of alkali metals , . The transition metal‐catalyzed Si–Si bond formation has also been thoroughly studied aiming to obtain selective catalysts active under softer reaction conditions . Early transition metal (Group 4) catalysts have been most intensively studied because of their higher catalytic activity, whereas late transition metal complexes, such as Wilkinson's catalyst, can exhibit competing catalytic activities between homodehydrocoupling and substituent redistribution reactions.…”

“…For early transition metal catalysts a mechanism based on successive, concerted, 4‐center transition states is accepted,, whereas for late transition metal catalysts the proposed mechanism consists of consecutive oxidative addition/reductive elimination cycles . Nevertheless, in the later case, the possibility of a mechanism involving σ‐bond metathesis steps has also been considered , , . Furthermore, most recently the dehydrocoupling of primary and secondary silanes, where silylene intermediates could be involved,, has been proposed.…”

Synthesis, characterization and photophysical study of a series of neutral isocyano rhodium(I) complexes with pyridylindolide ligands

“…Reactions of [Rh(cod)Cl] 2 with the corresponding pyridylindole ligands in the presence of triethylamine in CH 2 Cl 2 at room temperature gave the rhodium(I) complex precursors [Rh(cod) (X-pyind)]. With the complex precursors, the bidentate 1,5-cyclooctadiene (cod) ligand could be readily replaced by substituted phenylisocyanide via the ligand substitution reactions with two mole equivalents of isocyanide ligands in THF solution at room temperature to afford the target complexes 1e10 [22,31,35]. After recrystallization from the slow diffusion of diethylether vapor into the concentrated dichloromethane or acetone solution of the complexes, analytically pure complexes isolated as yellow to yellowish green crystalline solids were obtained.…”

“…2-Acetylpyridine, 2,4,6-tribromoaniline, 2,4,6-trichloroaniline, 4-bromo-2,6-dimethylaniline, 1,5-cyclooctadiene (cod), formic acid, phosphoryl chloride, phosphorus pentoxide and triethylamine were obtained from Aldrich Chemical Company and used as received. Rhodium(III) chloride hydrate was obtained from Strem Chemical Inc. [Rh(cod)Cl] 2 was synthesized from the reaction between rhodium(III) chloride and cod according to a literature procedure [22,35]. Substituted phenylisocyanide ligands, CNC 6 H 2 (CH 3 ) 2 -2,6-Br-4, CNC 6 H 2 Cl 2 -2,4-OCH 3 -6, CNC 6 H 2 Br 3 -2,4,6, CNC 6 H 2 Cl 3 -2,4,6 were prepared from the corresponding substituted formamides according to the synthetic methodology reported by Ugi et al [23e26].…”