Liquid‐ and solid‐state (CP‐MAS) multinuclear magnetic resonance study of some 2,5‐dihydro‐1,2,5‐oxoniastannaboratoles—carboncarbon coupling constants, ¹<i>J</i>(¹³C¹³C), in organometallic‐substituted alkenes

Abstract

Abstract Derivatives of 2,5‐dihydro‐1,2,5‐oxoniastannaboratoles were studied by multinuclear magnetic resonance both in the liquid ( 11 B, 13 C, 29 Si, 119 Sn NMR) and solid state ( 13 C, 29 Si, 119 Sn 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 P 2 1 / c ) the NMR data [chemical shifts and coupling constants J ( 119 SnE) (E = 13 C, 29 Si, 119 Sn)] 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 1 J ( 13 C 13 C) 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 3 J ( 13 C 1 H) long‐range coupling constants. In the presence of one boryl‐ and two stannyl groups the magnitude of 1 J ( 13 C 13 C) values is reduced to ca. 30 Hz. A positive sign for 2 J ( 119 Sn 117 Sn) in 2‐diethylboryl‐1,1‐bis(trimethylstannyl)but‐1‐ene was determined by 2D 13 C 1 H and 2D 119 Sn‐H heteronuclear shift correlations. Scalar 13 C 11 B and 119 Sn‐ 11 B coupling has been observed for the first time in 119 Sn CP‐MAS NMR spectra.