Solution Thermochemistry of Organometallic Compounds Using Photoacoustic Calorimetry: Enthalpies of Ligand Exchange, Metal-Ligand Bonds, and Metal-Solvent Interactions

Abstract

This article discusses the application of photoacoustic calorimetry (PAC) to the study of organometallic compounds. Studies include the determination of the enthalpy of CO substitution on M(CO)6 (M = Cr, Mo, W) by heptane, CO substitution on Cr(CO)6 by amines (piperidine, n-butylamine, di-n-butylamine, tri-n-butylamine) and by weakly coordinating solvents (alkane, aromatic, and chlorocarbon solvents), and CO substitution on various metal carbonyls (M(CO)6 (M = Cr, Mo, W), η6-C6H6Cr(CO)3, and η5-CpMn(CO)3 (Cp = cyclopentadienyl)) by triethylsilane. From known metal-CO bond energies estimates of metal-ligand bond energies are calculated. The relation of structure and bond energies is discussed. PAC was also used to investigate the quantum yields of photosubstitution of each metal carbonyl in perfluorodecalin (PFD). In each case the quantum yield decreased a result attributed to the weak metal-PFD interaction. The PAC studies provide insight into the behavior of organometallic species, and the mechanistic significance of these results is considered.KeywordsQuantum YieldMetal CenterBond EnergyActivation EnthalpyActivation EntropyThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.