Sn-NMR Spectra

A phenomenological study was performed to determine the effect of solvent on Sn NMR spectra of these organoraetallic polymers. Samples were dissolved in chloroform, benzene, n-hexane, acetone, tetrahydrofuran, methanol, and pyridine. The Sn NMR spectra in these solvents are given in Figure 1. The appearance and location of the H Sn resonance changes drastically over the range of selected solvents. The chemical shift moves upfield in the order chloroform, benzene, n-hexane, acetone, tetrahydrofuran, pyridine, and methanol. The amount of structural information and, conversely, the broadening of the resonance increases in the same order with methanol and pyridine reversed. 

Figure 1. l Sn nmr spectra of 10% w/v poly(TBTM/MMA) in several solvents. From the top chloroform, benzene, n-hexane, acetone, tetrahydrofuran, methanol, and pyridine. 

H, P and Sn NMR spectra have been obtained for the cyclic triorganotin dithiophosphinate (313), its 2,2-di-/cr/-butyl-substituted homologue and their complexes with HMPT <86JOM(309)273>. 

The study of H, B, C and Sn NMR spectra (which included through-space F- H and F- C spin-spin couplings) of 4,5-diethyl-2,2,3-trimethyl-l-(o-trifluoromethylphenyl)-2,5-dihydro-17/-1,2,5-azastannaborole, the first representative of the series, allowed atropisomerism owing to hindered rotation around the A-aryl bond to be observed <87ZN(B)l9i>. 

Fig. 13 Sn NMR spectra of SngXF (left) [23] SngPbxF (right). Reprinted with permission [23, 28]. Copyright 1986 American Chemical Society...

Solid state CP/MAS Sn NMR spectra are fully in accord with these changes in the anions. The Sn resonance shifts upheld in the solid state versus that in solution by ca... 

The bicyclic distannates 108a and 108b were formed presumably as partial hydrolysis products by the reaction of Sn(EDT)2 with the corresponding amine . The Sn NMR spectra of 107 and 108a in MeCN show single resonances in the range —15 to —82 ppm that are consistent with their five-coordinated tin structures in solution. 

The Sn NMR spectra of triorganotin(IV) adducts exhibit a single absorption typical of four- to five-coordinate central tin atom. For example, the signals for (l-BzIm)Me3SnCl... 

In solution, the tin centers in 225 and 226 are also pentacoordinated, as indicated by an increase of the 7( Sn— C) value in the NMR spectra and the high-field shift of the Sn resonance in the Sn NMR spectra (Table 43). Besides, the H and NMR spectra of chiral 225b show two resonances for the diastereotopic NMc2 group, indicating the absence of pyramidal inversion of the nitrogen . ... 

In most stannocanes the pentacoordination state of the tin atom is retained in solution. This was confirmed by the high-field shifts of the signals of these compounds in the Sn NMR spectra compared to model tetracoordinated compounds. This is confirmed by the increase in the coupling constants 7( Sn—for the equatorially bonded carbon atoms in a TBP arrangement as in 4,6-dicarbastannocanes and also by the coupling constants 7( Sn—D) (D = (Tables 60 and 61). NMR studies not only answer... 

The significant upfield chemical shifts of dihalides 568-570 in the Sn NMR spectra in CDCI3 (about —195 to —336 ppm), and IR data in CHCI3 are indicative of hexacoor-dination of the tin atom, i.e. of the presence of the two bidentate chelate ligands and two monodentate ligands " " . 

Solid-state NMR and " Sn NMR spectra are being more frequently reported as the technique becomes more generally available. The combined use of X-ray crystallography, and solution and solid-state NMR spectra enables comparisons to be made between stractures in the... 

Application of triorganostannyl enolates to organic synthesis was investigated on O-stannyl and C-stannyl enolates. " Sn NMR spectra showed that tribntylstannyl enolate is a mixture of both enolate kinds at lower temperatnre. The O- to C-stannyl enolate ratio is temperature-dependent and it was confirmed to be reversible. 

For complexes with nonsymmetric methylglyoxime, the nonequivalence of capping tin atoms was detected. The Sn NMR spectra of the nonsymmetric (HDEA)2[FeMm3(SnHala)2] methylgly-... 

The " Sn NMR spectra confirm the observations made for the highly populated species M. H and Sn spectra reveal identical patterns in C6D6 and CDCI3 and display strong but perfectly reversible temperature dependence (Figures 15a to 15c). 

Figure 17 Spectral expansions of " Sn NMR spectra recorded at 93.2 MHz of 1 in CDCI3 solution at room temperature. Bold dots represent "y(" Sn," /" Sn) coupling satellites, open circles represent V( Sn," Sn) coupling satellites, open triangles represent /(" Sn, Q satellites and asterisks represent resonances from further unidentified minor species. The main resonances of M, mj and m2 are vertically out of scale. M, m, m2 and m3 represent the four spedes observed at room temperature, as identified from the spectral data. (Reproduced with permission from ref. 17)...

Fipire 10 111.9 MHz solid state CP/MAS " Sn NMR spectrum of an 1,2,5-oxoniastannaboratole (adapted with permission from Ref. [26]). The expansion of the centre bands (mark by arrows) reveals a resolv pattern according to V(" n"B)=S5 10Hz which is not resolved in the " Sn NMR spectra of solutions of the same compound. The " /" Sn satellites (asterisks), corrcspondng to V(Sn,Sn) 1930 Hz, are also readily observed. Since this parameter should be sensitive even to small structural changes, it aiq)eaTS that the solid state structure differs little from the structure in solution /( n, n)=20S0Hz)... 

It is a common situation in organotin chemistry that one or two chlorine atoms are directly bonded to tin. In solution state Sn NMR spectra the presence of the quadrupolar nuclei is usually reflected by just a moderate... 

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