Carbon‐13/carbon‐12 isotope effects on ¹¹⁹Sn nuclear shielding

Abstract

Secondary "C/"C isotope effects (As') over one bond on the '"Sn nuelear shielding have been determined for 42 organotin compounds. Changes in the magnitude and sign of As' are related to the nature of the carbon atom and the nature of the other substitnents at the tin atom. In addition to the rotational and vibrational effects connected with the Sn--"C bond itself, Asi is affected by the bonding of tin to the other substitnents. In the case of polar bonds this leads to deshieiding of the tin atom in the heavy isotopomer, which compensates the shielding effect normally associated with heavy isotopic substitntion. Therefore, the magnitnde of As' valnes and of the Sn-C bond distances are not related in a simple manner. A relationship exists between J(lfgsnwC) and As' in alkynyltin compounds. The As'(=C/l2C) values for "Si and 207Pb shielding in some representative organo-silanes and -plnmbanes are reported for comparison.

Reactions of 3‐(Diethylboryl)stannoles with Isocyanates

“…[6] and in CDCl 3 at 296 K (1b); n J 119Sn,13C in Hz in brackets; isotope-induced chemical shifts 1 ∆ 12/13 C( 119 Sn) in ppb in braces with a negative sign for the shift of the more heavy isotopomer to lower frequency. [24] [b] Taken from ref. [24] (in CDCl 3 ).…”

Molecular structures of organotin tropolonato complexes with tin coordination numbers 5–7, seen by single‐crystal x‐ray diffraction and solid‐ and solution‐state 119Sn NMR

“…1 With the advent of high-field NMR spectrometers, further NMR parameters such as isotope-induced chemical shifts can be measured in solution with sufficient accuracy, frequently at the natural abundance of the respective isotopes. Replacement of 12 C by 13 C leads to values of isotopeinduced chemical shifts 1  12/13 C( 119 Sn) of either sign in 119 Sn NMR spectra, 2 which was not predicted by the theory of secondary isotope effects. 3,4 Although 1  12/13 C( 119 Sn) data are relatively easy to obtain, they still receive scant attention.…”

“…Here we consider somewhat less rigid molecular structures with tin CN > 4, derived from organotin moieties and the tropolonato ligand (trop) (1-3) (Scheme 1). According to X-ray diffraction results the tin atom is six-coordinate in Me 2 Sn(trop) 2 (2a) with a distorted octahedral coordination and a cis-like arrangement of the methyl groups. 7 For compounds of this type, a solution structure with trapezoidal bipyramidal character has been proposed.…”

“…119 Sn NMR spectroscopy is being increasingly used in the solid state as well as in solution, in addition to routine solution-state 1 H or 13 C NMR of the organic moieties of the ligands, in particular with respect to J-coupling constants, e.g. 2 119 Sn NMR data provide a link between the molecular structure in the solid state and in †Dedicated to Professor Robin K. Harris on the occasion of his 65th birthday.…”

Ferrocenylethynyltin Compounds – Characterization and Reactivity towards Triethylborane

“…[5][6][7] This indicates that the ferrocenyl group does not exert a special influence on the bonding situation in the Sn-CϵC-Fc fragment. 119 Sn{ 1 H} NMR spectrum (refocused INEPT [25] ; 186.5 MHz) of ferrocenylethynyl(trimethyl)tin (1; 5 % in CDCl 3 at 296 K; acquisition time 5 s, repetition delay 2.5 s; 64 transients).…”