The reactions of Rh2(CO)4Cl2 with 1,5-cyclooctadiene and tetramethylallene. A combined in-situ vibrational spectroscopies, spectral reconstruction and DFT study

Reactions of Rh2(CO)4Cl2 with 1,5-cyclooctadiene (COD) and tetramethylallene (TMA) were performed separately in anhydrous hexane under argon atmosphere. Multiple perturbations of Rh2(CO)4Cl2, COD and TMA were also performed during the reactions. These two reactions were monitored by in-situ FTIR (FIR and MIR) and/or Raman spectroscopies and the collected spectra were further analyzed with BTEM family of algorithms. DFT calculations were performed to identify the organometallic species present. The known diene complex Rh2(CO)2Cl2(η4-C8H12) and a new allene complex Rh2(CO)3Cl2(η2-C7H12) were formed as the two primary organo-rhodium products. Their pure component spectra were reconstructed in the three characteristic regions of 200–680, 800–1360, and 1500–2200 cm−1. Their relative concentrations were also obtained by the least square fitting of the carbonyl region 1500-2200 cm−1. The present contribution shows the usefulness of combining in-situ spectroscopic measurements, BTEM analysis and DFT spectral prediction in order to analyze organometallic reactions at high dilution and identify the reaction products.