Spectroscopic properties of conjugated metalcarbon multiple bonds: synthesis and absorption spectra of the “dialkylidynes” (RO) 3WCCW(OR) 3 (OR = OCMe 3, OCMe 2CF 3, OCMe 2Et)

Abstract

“Dialkylidyne” (μ-dicarbido) complexes (RO) 3WCCW(OR) 3 (Or = OCMe 3, 1; OCMe 2CF 3, 2; OCMe 2Et, 3) have been synthesized. A single crystal X-ray diffraction study performed on the t-butoxy complex 1 demonstrates that the molecule exists in staggered D 3d form in the solid state at − 50°C. Complex 1 cyrstallizes in the rhombohedral space group R 3 , a = 11.301(4) Å, α = 52.93(3)°, Z = 1. Data were collected in the ω−2θ mode and refined to R = 0.039 and R w = 0.055. Absorption spectra of 1–3 in 2-methylpentane show a surprisingly large number of transitions as compared to the alkylidyne Me 3CCW(OCMe 3) 3 and the triply bonded dimer W 2(OCMe 3) 6; while assigning the bands is not currently feasible due to the three-fold symmetry of the molecules, these observations suggest that the π clouds in 1–3 are conjugted in the excited state rather than localized.