An enormous vibrational motion: the gas-phase structure of dimethyl-bis(methoxyethynyl) germanium†
Abstract
The structure of C angles of the two methoxyethynyl fragments in the molecule are computed to deviate by up to 4° from the linear arrangement. As a consequence of low-frequency large-amplitude vibrational motion the experimental structure of these fragments without applying vibrational corrections deviates considerably from linearity, while the structure corrected for vibrational effects using the harmonic approximation and taking into account a non-linear transformation between internal and Cartesian coordinates (rh1) shows closer agreement with theory. The main experimental structural parameters of
C)mean, 122.8(2) pm; r(C–O)mean, 138.9(3) pm; ΔCO =
r(Cmethyl–O)
−
r(Cethynyl–O), 14.5(2) pm, r(C–H)mean, 109.1(4) pm; ∠(X–C–H)mean
(X = Ge,O), 109(1)°; ∠Cethynyl–Ge–Cethynyl, 108.1(4)°; ∠Cmethyl–Ge–Cmethyl, 113.4(5)°; ∠Ge–C
C, 163(1)°; ∠C
C–O, 176(2)°; ∠C–O–C, 115.2(6)°;