Experimental Raman spectra of dilute and laser-light-sensitive [Rh4(CO)9(µ-CO)3] and [(µ4-η2-3-hexyne)Rh4(CO)8(µ-CO)2]. Comparison with theoretically predicted spectra

Abstract

The reaction of [Rh₄(CO)₉(µ-CO)₃] with 3-hexyne to form the butterfly cluster [(µ₄-η²-3-hexyne)Rh₄(CO)₈(µ-CO)₂] was monitored viain-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(µ-CO)₃] and the butterfly cluster [(µ₄-η²-3-hexyne)Rh₄(CO)₈(µ-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.