The Determination of the Chemical Bonds in Some Metal-Carbyne Complexes by Structural Studies

Abstract

Metal carbyne complexes (XMCR3 where X = Cl, Br ; M = W, Cr ; R = CH3, CD3, C6H5, C6D5) were studied by both experimental techniques (IR, polarised Raman spectroscopy, X-Ray and neutron diffraction) and theoretical methods (ab initio and semi-empirical calculations). The vibrational spectra show that a conjugation effect (or hyperconjugation effect in the case of the methylcarbynes) exists in these compounds. Moreover, the temperature-dependant spectra of the partially deuterated derivative (R = CHD2) show that two conformers due to a librational effect of the methyl group exist above 100 K. The electronic deformation density using combined X-ray and neutron diffraction data and a multipolar atom model also demonstrates this conjugation effect. The comparison of the experimental and ab-initio electronic deformation density maps shows a very good agreement and proves that both experimental and theoretical results are reliable for such complexes.