Experimental Raman spectra of dilute and laser-light-sensitive [Rh 4(CO)9(-CO)3] and [(4- η2-3-hexyne)Rh4(CO)8(-CO)2]. Comparison with theoretically predicted spectra

Abstract

The reaction of [Rh4(CO)9(-CO)3] with 3-hexyne to form the butterfly cluster [(4-η2-3- hexyne)Rh4(CO)8(-CO)2] was monitored via in-situ Raman spectroscopy using an NIR laser source, at room temperature and under atmospheric argon using n-hexane as solvent. The collected raw spectra were deconvoluted using band-target entropy minimization (BTEM). The pure component mid-Raman spectra of the [Rh4(CO)9(-CO) 3] and the butterfly cluster [(4-η2-3- hexyne)Rh4(CO)8(-CO)2], were reconstructed with a high signal-to-noise ratio. Full geometric optimization and Raman vibrational prediction were carried out using DFT. The experimental and predicted Raman spectra were in good agreement. In particular, the far-Raman vibrational modes in the region 100-280 cm-1 provided characterization of the metal-metal bonds and direct confirmation of the structural integrity of the polynuclear frameworks in solution. © The Royal Society of Chemistry 2006.