High throughput screening arrays of rhodium and iridium complexes as catalysts for intramolecular hydroamination using parallel factor analysis

Abstract

Parallel factor analysis (PARAFAC) was used to analyze data from the high throughput screening of an array of organometallic rhodium and iridium complexes as catalysts for the intramolecular hydroamination of 2-(2-phenylethynyl)aniline to give 2-phenylindole. The progress of the hydroamination reactions was monitored using UV-visible spectroscopy. The overlapped UV-visible spectra of the mixture of starting material, product and solvent in the samples taken at different times were deconvoluted using PARAFAC. Unique PARAFAC models led to close approximations of the actual UV-visible spectra of the compounds in the mixture. The performance of the catalysts was then compared by estimating the final concentration of the starting material and product using PARAFAC loadings. A library of 63 complexes generated in situ was examined in a single experiment using this methodology. The complexes were generated from combinations of seven ligands (bis(N-methyl2-imidazolyl)methane, bis(1-pyrazolyl)methane, 1,10-phenanthroline, N,N′-bis(p-tolyl)diazabutadiene, N,N′-bis(p-tolyl)1,2-dimethyldiazabutadiene, N,N′-bis(mesityl)1,2-dimethyldiazabutadiene and bis(2,4,6-trimethylphenylimino)acenapthene) and nine metal precursors ([Ir(COD)Cl]₂ (COD = 1,5-cyclooctadiene), [Ir(CO)₂Cl]_n, [Ir(COE)₂Cl]₂, [IrCp*Cl₂]₂ (Cp* = 1,2,3,4,5-pentamethylcyclopentadiene), [Rh(COD)Cl]₂, [Rh(CO)₂Cl]₂, [Rh(COE)₂Cl]₂, [RhCp*Cl₂]₂ and [RhCpCl₂]₂) (Cp = cyclopentadiene)). The proposed method can be used for the fast screening of arrays of metal complexes for identifying effective catalysts, providing information that can augment traditional methods used for the analysis of catalyzed reactions.