Fourier transform NMR studies of organometallic compounds. II—synthesis and NMR spectroscopy of propenyl and isopropenyl derivatives of silicon and lead

Isomeric mixtures of compounds Me_nM(CH?CHMe)_4?n (M=Si, Pb; n=0?3) have been prepared and studied, as well as pure Me₃M(CMe?CH₂) and mixtures containing propenyl isopropenyl residues bonded to silicon and lead. ¹H, ¹³C, ²⁹Si and ²⁰⁷Pb NMR data are presented; as previously observed for the corresponding tin compounds, the ²⁹Si and ²⁰⁷Pb shifts for the Me₃MC₃H₅ isomers can be used to calculate the shifts expected for the other isomers; while for lead the agreement is good, calculated and observed values for silicon diverge with decreasing n due, at least in part, to steric factors.     

Synthesis and reactivity of ω-haloalkyltin compounds

ω-Haloalkyltin trihalides, X(CH₂)_nSnX₃ (n ≧ 3; X = halogen) can readily be prepared in high yields by the direct reaction of stannous halides with α,ω-dihaloalkanes, catalysed by trialkylantimony compounds. The compounds are versatile starting materials for the synthesis of a variety of ω-functionallysubstituted organotin compounds R_3-mX_mSn(CH₂)_n Y (R = alkyl, phenyl; m = 0-3; X = Cl, Br, O; Y = Br, NMe₂, NEt₂, COOH, CHOHR, R₃Sn). ¹H-NMR spectral data for a series of such compounds are presented. The trends observed in the chemical shifts and the ¹¹⁹Sn—methyl proton coupling constants of Me_3-m Br_mSn(CH₂)_nBr (m = 0-3; n = 3-5) are discussed in terms of inductive effects. Intramolecular coordination between the ω-bromine atom and tin could not be demonstrated.     

Quantitative estimation of trans-1,4 and cis-1,4 isomers in polychloroprene by high-resolution NMR

In the ¹H-NMR spectrum of polychloroprene dissolved in C₆D₆, the ?CH proton signal was separated into two triplet peaks. These triplet signals were assigned to the ?CH proton in the trans-1,4 and cis-1,4 isomers by measurement of ¹H-NMR spectra of 3-chloro-1-butene and a mixture of trans- and cis-2-chloro-2-butene as model compounds for the 1,2, trans-1,4 and cis-1,4 isomers. In ¹H-NMR spectra (220 Mcps) of polychloroprene dissolved in C₆D₆, two triplet signals were separated completely from which the relative concentrations of trans-1,4 and cis-1,4 isomers could be obtained quantitatively.     

119Sn NMR Spectra of Some Carbohydrate Organotin Derivatives

Abstract

The ¹¹⁹Sn NMR spectra of several sugar-tin derivatives were recorded. The geometric and steric isomers of all of the organotin derivatives studied were easily differentiated by ¹¹⁹Sn NMR. The appropriate ¹¹⁹Sn resonances are: ca - 50 ppm for trans and ?60 ppm for cis vinyltin derivatives (1-3), ca 16 ppm for allyltins 4-6, and ca ?32 ppm for tin-carbinols 9 and 11. When the hydroxyl group in carbinol 9 was converted to an O-acetyl group, the chemical shift of ¹¹⁹Sn was shifted to ?22 ppm.     

The preparation and 119Sn and 19F NMR spectra of some trifluoromethylphenyltin(IV) compounds

The preparation of a series of new trifluoromethylphenyltin(IV) compounds, Bu_nSn(C₆H₄CF₃-3)_4-n, (C₆H₄CF₃-3)SnCl₃, (C₆H₄CF₃-2)SnCl₃, and some related adducts with 2,2¹-bipyridyl and 1,10-phenanthroline, is described. ¹¹⁹Sn and ¹⁹F chemical shifts have been determined, together with values of J(¹¹⁹Sn=F) and ³J(¹¹⁹Sn=H_itortho), and the possibility of a “through space” tinfluorine coupling mechanism is also discussed.     

Studies on C-heterocyclic tin compounds. The synthesis and spectral characterization of some thienyl tetraorganotin(IV) compounds

The synthesis of a series of tetraorganotin(IV) compounds containing selectively the 2-thienyl, 3-thienyl, 5-methyl-2-thienyl, 5-t-butyl-2-thienyl, 4-methyl-2-thienyl and 3-(2-pyridyl)-2-thienyl groups [L], of formula R_4-nSn[L]_n (R = Ph, p-tolyl, Me, cyclopentyl, cyclohexyl; n = 1–4) is reported. Features of structural interest deduced from ^119mSn Mössbauer and NMR (¹³C and ¹¹⁹Sn modes) spectra are considered.     

A proton NMR investigation of metalmetal bonding in trimethyltin-aluminium, -gallium, -indium and -thallium organometallic compounds

Proton NMR data for the Group III methyl derivatives, MMe₃ and LiMMe₄ are compared with NMR data for the novel tin—Group III-metal bonded species, Li[Me₃SnMMe₃] (M  Al, Ga, In and Tl) and for Li[(Me₃Sn)_n-TlMe_4?n] (n = 0 to 4), reported here for the first time.The presence of tinmetal bonding in these derivatives is established by the observed tin-across-metal coupling constants and for the thallium derivatives by the additional observation of thallium-across-tin coupling.The variation in the magnitudes of ²J(SnCH), ²J(TlCH), ³J(SnMCH) and ³J(TlSnCH) are reported as a function of M and as a function of the number of Me₃Sn groups bond to thallium in the [(Me₃Sn)_nTIME₄?_n]^?anions. Proposals concerning the factors governing the changes in these coupling constants and the chemical shifts are presented.     

Tin-element exchange: Formation and multinuclear NMR characterisation of mixtures of the type C(SnMe3)n(MMe3)4-n (M = Si,Pb; n = 0–3)

Treatment of tetrakis(trimethylstannyl)methane with one equivalent of methyllithium followed by one equivalent of Me₃MCl gives mixtures of the type C(SnMe₃)_n(MMe₃)_4-n (M = Si, Pb; n = 0?3), which have been characterised by multinuclear (¹³C, ²⁹Si, ¹¹⁹Sn, ²⁰⁷Pb) NMR. The main component (ca. 40%) is in each case (Me₃Sn)₃ CMMe₃, but considerable amounts of the other tetrametallamethanes are also present.     

Tin Tetrachloride Adducts with Arylphosphoramidates: A Multinuclear (31P, 19F,and 119Sn) NMR Characterization in Solution

Abstract

The synthesis of octahedral complexes [SnCl₄L₂] (L = R₂NP(O)(OCH₂CF₃)(O-p-tolyl): R₂N = Me₂N (1), Et₂N (2), CH₂(CH₂CH₂)₂N (3), and O(CH₂CH₂)₂N (4), or L = R₂NP(O)(OCH₂CF₃)(O-p-PhNO₂): R₂N = Me₂N (5), Et₂N (6), and O(CH₂CH₂)₂N (7) is described. The new adducts have been characterized by multinuclear (³¹P, ¹⁹F, ¹¹⁹Sn) NMR, IR spectroscopy, and elemental analyses. The solution NMR data show the presence of a mixture of cis and trans isomers. The structure of the complexes in solution was further confirmed by ¹¹⁹Sn NMR spectra, which display a triplet for each isomer, indicating an octahedrally coordinated tin center. The effects of the nature of R and Ar substituents on the donor ability of the P=O group in the ligands R₂NP(O)(OCH₂CF₃)(OAr) were investigated on the basis of ¹¹⁹Sn NMR chemical shifts and used to classify these ligands according to their Lewis basicity.     

Substituent chemical shifts of the organotin moiety in compounds of the type RSnMenCl3 − n (n = 0 to 3; R = n-alkyl)

The ¹³C and ¹¹⁹Sn NMR spectra of 33 organotin compounds of the type RSnMe_nCl_{3 ? n} and related types are discussed. The substituent effects of the groups SnMe₃, SnMe₂Cl, SnMeCl₂ and SnCl₃ (and of some related groups) on the carbon chemical shifts in the alkyl group R have been determined; the SnMe₃ group causes a small upfield shift of the carbon attached to it, while the other groups cause downfield shifts. The shifts show a monotonic change on replacing methyl groups in Me₃Sn by chlorine atoms. The effects on carbons further removed from the tin atom are discussed. Variation in R causes little change in ⁿJ(Sn? C) or δ(¹¹⁹Sn).     

Proton NMR spectra and structure of chlorotin(IV) ternary complexes of 8-quinolinol and its 5,7 dichloro and 2 methyl-5,7 dichloro derivatives

The low temperature ¹H NMR spectra in d-chloroform of the ternary complexes bis-(8-quinolinato) tin(IV) dichloride, bis-(5,7 dichloro-8-quinolinato) tin(IV) dichloride, and bis-(2 methyl-5,7-dichloro-8-quinolinato) tin(IV) dichloride have been obtained. The spectra showed that for the three complexes, only two configurations were appreciably populated, their free energy differences being equal to 0.28, 0.08 and ?0.04 kcal/mol respectively. The proton chemical shifts, the ¹H-¹H coupling constants and some of the ¹H-¹¹⁹Sn coupling constants have been obtained for each complex in the two configurations. An approximate computation of chemical shifts, including aromatic ring magnetic anisotropies and electric effects from polar groups, allowed the identification of the two configurations as the cis-cis-trans and the cis-trans-cis (with respect to Cl, N and O atoms), the former being the more populated one.     

29Si NMR spectra of methylphenylcyclotri-and -tetrasilazanes

²⁹Si NMR spectra of various methylphenyl-substituted cyclotri- and -tetrasilazanes, composed of different combinations of the units d = Me₂SiNH, d^ph = MePhSiNH and d = Ph₂SiNH, have been investigated. For most of the compounds having more than one asymmetric centre, the spectra of both the individual isomers and their mixtures have been studied, and the signals of the individual isomers have been assigned. The effect of a different arrangement of phenyl groups in the rings, and the influence of the stereochemistry of the isomers on the ²⁹Si chemical shifts in cyclotri- and -tetrasilazanes have been studied. The ²⁹Si chemical shifts in cyclotrisilazanes are additive and can be represented as the sum of increments corresponding to the number and positions of the phenyl groups in the rings. In these compounds, the spatial structure of the isomers does not exert any noticeable effect on the spectra. On the contrary, chemical shifts are not simply additive in cyclotetrasilazanes: a pronounced stereochemical dependence is apparent.     

Multinuclear two-dimensional NMR: Assignments of natural abundance polypeptide 13C, 1H and 15N chemical shifts and demonstration of isomer interconversion

The polypeptide carbobenzoxy-glycyl-L -prolyl-L -leucyl-L -alanyl-L -proline (0.2 M in DMSO-d₆) was investigated using ¹³C, ¹H and ¹⁵N NMR in natural abundance at 4.7 tesla. The existence of cis–trans-Gly-Pro and -Ala-Pro bonds permits up to four isomers, and all four were observed (in a 60:30:7:3 ratio). ¹³C shifts of the proline β-CH₂ resonances are consistent only with the 60% form being trans–trans. The 30% form is either trans–cis or cis–trans (order as above) and was tentatively assigned as cis-trans on the basis of relaxation behavior. Refocused INEPT studies aided the ¹³C assignments. The ¹⁵N data were obtained using both NOE and INEPT excitation, with signals evident for the three major isomers. The spectra were analysed by starting from the ¹³C data, which were assigned based on known regularities in peptide spectra. A ¹³C? ¹H heteronuclear two-dimensional chemical shift correlation experiment allowed direct assignment of proton shifts for major and minor isomers. The NH proton shifts were assigned by running a homonuclear two-dimensional chemical shift correlation experiment and noting the correlation with the previously assigned α-CH protons. The ¹⁵N resonances were then assigned from a ¹⁵N? ¹H heteronuclear two-dimensional chemical shift correlation experiment, relating the ¹⁵N signals directly to the NH proton resonances. Isomer interconversion between the two major isomers was demonstrated by performing a magnetization transfer homonuclear 2D experiment. Off-diagonal intensity was noted relating the major and minor isomer alanine NH proton, as well as for the major and minor isomer leucine NH protons.     

The regio- and stereospecific synthesis of diarylpropenyllithium compounds from dimethylamino- and dimethylaminomethyl-substituted diarylacetylenes via transmetallation reactions involving diarylpropenylmagnesium and -tin compounds

Dimethylamino- and dimethylaminomethyl-substituted diarylacetylenes were prepared by the Pd(PPh₃)₄-catalyzed coupling reaction of dimethylamino- and dimethylaminomethyl-substituted aryl halides with arylacetylenes.Reaction of the asymmetric diarylacetylenes with methylmagnesium bromide in the presence of NiCl₂(PPh₃)₂ gave stereo- and regio-selectively cis addition products in which the aryl group bearing the built-in ligand (Me₂N or Me₂NCH₂) and the magnesium atom are bonded to the same unsaturated carbon atom. The E-diarylpropenylmagnesium bromides were converted in two successive transmetallation steps into the corresponding E-triphenyltin and Z-lithium compounds with retention of configuration. Depending on the type of solvent, complete inversion of configuration was observed for the Z-diarylpropenyllithium compounds. From the E-lithium compounds the corresponding Z-diarylpropenyltriphenyltin compounds were prepared (Scheme 1).Retention of configuration in the series of transmetallation reactions has unambiguously been established by comparison of the ¹¹⁹Sn¹H, ¹³C¹H and ¹¹⁹Sn¹³C coupling constants observed in the ¹H and ¹³C NMR spectra of the configurationally pure stereoisomeric pairs.     

29Si and 13C NMR spectra of permethylpolysilanes

²⁹Si, ¹³C and ¹H NMR spectra are reported for the series of linear permethylpolysilanes Me(SiMe₂)_nMe where n = 1 to 6, for the cyclic permethylpolysilanes (Me₂Si)_n where n = 5 to 8, and for a few related compounds. For linear polysilanes the ²⁹Si and ¹³C chemical shifts can be accurately calculated from simple additivity relationships based on the number of silicon atoms in α, β, γ and δ positions. Adjacent (α) silicon atoms lead to upfield shifts in the ²⁹Si and ¹³C resonances, whereas more remote silicon atoms lead to downfield shifts. The ²⁹Si chemical shifts of the polysilane chains are linearly related to the ¹³C shifts of the carbon atoms attached to the silicon. The ²⁹Si and ¹³C resonances of the cyclic silanes deviate from this relationship. Ring current effects arising from σ delocalization are suggested as an explanation for the deviations. Proton-coupled ²⁹Si NMR spectra are reported for Me₃SiSiMe₃ and for (Me₂Si)_n, n = 5 to 7.     

Stereochemistry of organophosphorus cyclic compounds—II : Stereospecific synthesis of cis- and trans 2-halogeno-2-oxo-4-methyl-1,3,2-dioxaphosphorinans and their chemical transformations

cis- and trans-2-Chloro-2-oxo-4-methyl-1,3,2-dioxaphosphorinans have been obtained by stereospecific reactions of diastereomerically pure 2-methoxy-4-methyl-1,3,2-dioxaphosphorinans or 2-hydrogen-2-oxo-4-methyl-1,3,2-dioxaphosphorinans with chlorine and sulphuryl chloride, respectively. Similarly, the action of the corresponding brominating agents on isomeric phosphites and phosphonates afforded pure cis- and trans-2-bromo-2-oxo-4-methyl-1,3,2-dioxaphosphorinans. It has been shown that halogenolysis proceeds with retention of configuration at the P atom. On the basis of the ¹H- and ³¹P-NMR spectra conformation of the halogenoanhydrides obtained has been discussed briefly.It has been also found that model nucleophilic substitution reactions occur with inversion of configuration at the P atom in the cyclic halogenoanhydrides.     

Synthesis and multinuclear NMR data of the ferrocenes (Me3Ecp)2Fe (E = C,Si, Ge,Sn, Pb)

The substituted cyclopentadienyl anions Me₃Ecp⁻ with E = C, Si, Ge, Sn, Pb have been prepared from either the mono- or disubstituted cyclopentadienes, including the hitherto unknown (Me₃Pb)₂C₅H₄. Representative examples have been characterized by ¹³C NMR spectroscopy. Treatment with iron(II) chloride yielded the ferrocenes (Me₃Ecp)₂Fe, which have been investigated by ¹H, ¹³C, ²⁹Si, ¹¹⁹Sn, and ²⁰⁷Pb NMR spectroscopy. ¹³C¹³C coupling and selective proton decoupling were used for the assignment of the ¹³C and ¹H signals. The shifts δ(¹³C) reflect the electron-releasing or -withdrawing power of the substituents Me₃E, but the isotope shifts ¹Δ¹³C(i)(¹³C(j)) do not show a similar trend. There is evidence that δ(¹¹⁹Sn) and δ(²⁰⁷Pb) are influenced by the coordination. The analysis of the coupling constants reveals that ¹J(¹³C(1)¹³C(2/5)) varies with the electronegativity of E. Because of the small range (4.5–5.0 Hz) of ¹J(⁵⁷Fe¹³C) the effect of E is apparent only when E = C is replaced by E = Si. As for the coupling between E and ¹³C or ¹H, the square root of the reduced coupling constant K is related linearly to the atomic number of E; exceptions are ¹K(²⁰⁷Pb¹³C).     

Tin(IV) Chloride Complexes of β-Chlorovinyl Aldehydes: A Multinuclear Nmr Characterization in Solution

Abstract

The reaction of SnCl₄ with β-chlorovinyl aldehydes in anhydrous dichloromethane gave a series of octahedral complexes of the general formula SnCl₄·2L (L = aldehyde). The adducts have been characterized in solution using multinuclear (¹H, ¹³C, and ¹¹⁹Sn) NMR and IR spectroscopy. Solution NMR studies show that the complexes undergo rapid ligand dissociation at ambient temperature. Ligand exchange is slowed significantly at low temperature, such that, in most of the complexes, it is possible to identify both the cis and trans isomers with predominance of the cis form. The magnitude of the metal-ligand interaction was estimated on the basis of ¹¹⁹Sn NMR chemical shifts and used to classify the aldehydes studied according to their Lewis basicity.     

NMR study of the spatial structure of synthetic pyrethroids

The spatial isomers of the new synthetic analogs of ethyl permithrinic ether and permethrin were investigated by NMR (¹H, ¹³C, DEPT (distortionless enhancement by polarization transfer), COSY (correlation spectroscopy), CHCORR (heteronuclear (C, H) shift correlation spectroscopy), ROESY (rotating-frame Overhauser effect spectroscopy)). Several tendencies were revealed in the ¹H and ¹³C chemical shifts of the α atoms of the substituents in the 2nd and 3rd positions of the cyclopropane ring. For substituents cis-orientated relative to the ester group, the spectra show a paramagnetic shift of the ¹H signals and the diamagnetic shift of the ¹³C signals relative to the trans-orientated substituents. The ¹H and ¹³C chemical shifts of the α atoms of the substituents in the 2nd and 3rd positions of the cyclopropane ring permit an unambiguous determination of the stereochemistry of ethyl permethrinic ether and permethrin analogs.     

13C and 119Sn NMR spectra of some tribenzyltin(IV) compounds

The ¹³C and ¹¹⁹Sn NMR spectra of some tribenzyltin(IV) compounds and their complexes in coordinating and non-coordinating solvents have been studied. The δ(¹¹⁹Sn) chemical shifts and coupling constants ¹J(¹¹⁹Sn, ¹³C) clearly depend on the coordination number of the central tin atom and the geometry of its coordination polyhedra. Approximate ranges of the characteristic values of both the NMR parameters were determined for various configurational types of tribenzyltin compound. The ¹³C and ¹¹⁹Sn NMR parameters found are indicative of a distinct interaction between the polarized σ(SnC) bond and adjacent π-electron system of the aromatic ring(s).