Liquid‐ and solid‐state (CP‐MAS) multinuclear magnetic resonance study of some 2,5‐dihydro‐1,2,5‐oxoniastannaboratoles—carboncarbon coupling constants, 1J(13C13C), in organometallic‐substituted alkenes

Abstract

AbstractDerivatives of 2,5‐dihydro‐1,2,5‐oxoniastannaboratoles were studied by multinuclear magnetic resonance both in the liquid (11B, 13C, 29Si, 119Sn NMR) and solid state (13C, 29Si, 119Sn CP/MAS NMR). Together with the results of the x‐ray analysis of the 4,5,5‐triethyl‐2,5‐dihydro‐1,2,2‐trimethyl‐3‐phenyl‐1,2,5‐oxoniastannaboratole‐tetrahydrofuran adduct (1‐THF) (space group P21/c) the NMR data [chemical shifts and coupling constants J(119SnE) (E = 13C, 29Si, 119Sn)] allowed the assessment of structural features in solution and in the solid state (e.g. the weakened coordinative Sn‐O interactions in 1‐THF in solution). The 1J(13C13C) values in 4,5,5‐triethyl‐2,5‐dihydro‐1,2,2‐trimethyl‐3‐trimethylsilyl‐ and ‐3‐trimethylstannyl‐1,2,5‐oxoniastannaboratole and in some non‐cyclic alkenes bearing organometallic substituents were measured using INEPT experiments based on 3J(13C1H) long‐range coupling constants. In the presence of one boryl‐ and two stannyl groups the magnitude of 1J(13C13C) values is reduced to ca. 30 Hz. A positive sign for 2J(119Sn117Sn) in 2‐diethylboryl‐1,1‐bis(trimethylstannyl)but‐1‐ene was determined by 2D 13C1H and 2D 119Sn‐H heteronuclear shift correlations. Scalar 13C11B and 119Sn‐11B coupling has been observed for the first time in 119Sn CP‐MAS NMR spectra.