Dainis Dakternieks

Phosphorus-31 and tin-119 NMR studies on tin(IV) halides and their adducts

Abstract Tin-119 NMR spectra have been recorded for SnX4 (X = Cl, Br, I) and mixtures thereof. All fifteen possible SnClxBryIz (x + y + z = 4) species were observed. Tin-119 NMR spectra were observed for SnX−5 and SnX2−6 (X = Cl, Br) and for an equimolar mixture of SnCl2−6 and SnBr2−6 which gave all ten possible isomers of [SnClxBr6−x]2− in the statistical distribution. Phosphorus-31 and tin-119 NMR spectra were observed for SnX4(PBu3)2 (X = Cl, Br) and a mixture gave all six possible trans phosphine isomers in the statistical distribution. [SnX5(PBu3)]− (X = Cl, Br) species show some disproportionation, although the [SnX5(PBu3)]− ion is the dominant species in solution. A mixture of [SnCl5(PBu3)]− and [SnBr5-(PBu3)]− gave a complex mixture in solution, but all twelve isomers of the [SnCl5Br5−x(PBu3)]− series were identified. The well known pairwise additivity model fits well within the tetrahalide or hexahalide anion series and it is shown that the chemical shift of tin both tetrahedral and octahedral environments may be predicted from a single set of interaction parameters if geometrical factors are taken into account. The same interaction parameters are of use in identifying the mixed tin halide-phosphine complexes.

Tin-119 NMR studies on some adducts of tin(IV) halides

Abstract Tin-119 and phosphorus-31 NMR spectra have been recorded for SnCI 4 L 2 , SnBr 4 L 2 (L = tributylphosphine oxide) and mixtures thereof. The compound SnCl 4 L 2 exists predominantly as the trans L 2 isomer with a small proportion of the cis L 2 isomer also present in solution whereas SnBr 4 L 2 appears to be present only as the trans L 2 isomer. In the mixed solution all the trans snCI x Br 4−x L 2 species are observed. The anionic complexes [SnCI 5- L] − and [SnBr 5 L] − both show slight dissociation in solution to SnX 4 L 2 and [SnX 6 ] 2− (X = CI, Br). The tin-199 NMR spectrum of an equimolar mixture of [SnCI 5 L] − and [SnBr 5 L] − shows ten of the possible twelve [SnCI x Br 5-x L] − species. In contrast, SnX 4 L 2 (L′ = acetone; X = CI, Br) exist predominantly as cis L′ 2 isomers. A 1:1 mixture of the complexes in dichloromethane solution at −50 °C shows average tin-119 resonances for each stoichiometry of mixed halo species cis SnCI x Br 4-x L′ 2 . Subsequent cooling to −100 °C slows intramolecular processes sufficiently to enable observation and identification of most of the individual geometric isomers of each stoichiometry. The anionic complexes [SnCI 5 L′ − and [SnBr 5 L′ − show no appreciable dissociation in dichloromethane solution and the tin-119 spectrum of a 1:1 mixture of these compounds at −100 °C shows only six resonances corresponding to various [SnCI x Br 5-x L′] − species without distinguishing between individual isomers of each stoichiometry. Cooling to −100 °C enables identification of some of these isomers. The pairwise additivity model, using previously established interaction parameters, was used to assign all isomers species observed in the tin-119 spectra of these systems.

The preparation, spectral studies, and the crystal structure of dimethylbis(O-ethylxanthato)tin(IV)

Tin-119 NMR data indicate that the tin atom in (CH 3 ) 2 Sn(S 2 COC 2 H 5 ) 2 is four co-ordinated in dichloromethane solution. However, single crystal X-ray analysis shows the tin atom to be six co-ordinated in the solid state in which the bidentate xanthate ligands display gross asymmetry in their mode of co-ordination to the tin. The crystals are molecular and there is no association between neighbouring molecules. The unit cell of Me 2 Sn(exa) 2 is orthorhombic, Pnma, a = 14.165(1), b = 7.675(9), c = 13.977(2) A with Z = 4. The structure was refined by conventional least squares methods with final R 0.041 and R w 0.043 for 1229 unique reflections with 1 ⩾ 2σ(I).

Tin-119 NMR studies of alkyl and aryl haloxanthates of tin(IV): The crystal and molecular structure of diphenyl(O-isopropylxanthato)chlorotin(IV)

Tin-119 NMR data are reported for the two series of compounds of the type R2Sn(S2COR′)2 and R2SnX(S2COR′) [where R = CH3, C6H5, R′ = C2H5, i-C3H7, and X = Cl, Br]. In solution both types of compounds appear to have a coordination number less than six. The crystal structure of o2SnCl(S2CO-i-C3H7) shows that the tin atom is penta-coordinated in a distorted trigonal bipyramidal environment. The iprxa ligand coordinates the tin atom with asymmetric SnS bonds of 2.450(2) and 2.826(1) A. The unit cell of o2SnCl(S2CO-i-C3H7) is monoclinic, P21/c, a = 12.206(4), b = 10.825(3), c = 19.374(3) A and β = 133.32(2)°, Z = 4. The structure was refined by conventional least squares methods with final values of R 0.038 and Rw 0.042 for 3112 unique reflections.

Phosphorus-31, platinum-195 and lead-207 NMR studies on some platinum-lead bonded compounds

Abstract Phosphorus-31, platinum-195 and lead-207 nuclear magnetic resonance studies have been carried out on a series of complexes of the type cis -Pt(PPh 3 ) 2 (R)(PbR 2 R′) and trans -Pt(PBu 3 ) 2 (PbR 3 ) 2 (R  Ph, 4-MePh, 4-MeOPh, 4-ClPh, 4-FPh; R′  R, Br, I). Lead-platinum coupling constants, 1 J ( 207 Pb- 195 Pt), range between 14.5 kHz and 18.5 kHz with the trans compounds having the smaller coupling constants. Variation of the phenyl group substituents has only a small effect on the lead chemical shift and virtually no effect on the other NMR parameters. However, variation of the substituents directly bonded to the lead atom significantly effects the 207 Pb chemical shift and causes corresponding, but weaker, effects in the other spectral parameters. Second order heteronuclear coupling effects between platinum-195 and lead-207 are observed for all the complexes and this is the first time that second order coupling has been observed between different elements. Phosphorus-31, 195 Pt and 207 Pb NMR spectra have been used to confirm the identity of the intermediate cis -Pt(PPh 3 ) 2 (Ph)(Pb 2 Ph 5 ) observed during the preparation of cis -Pt(PPh 3 ) 2 (Ph)(PbPh 3 ).

Phosphorus-31 and mercury-199 NMR studies of some mercury(II) complexes containing tricyclohexylphosphine and tributylphosphine

Abstract Phosphorus-31 and mercury-199 NMR measurements are reported for a series of mercury(II) complexes HgX2[P(c-C6H11)3][PBu3] (where X = O3SCF3, ClO4, NO3, CF3COO, CH3COO, Cl, Br, I, SCN, CN) in dichloromethane solution. The two bond coupling 2J(P′P) of these asymmetric complexes decrease with increasing coordination ability of the anion and range between 198 Hz and 85 Hz. Data are also presented for Hg(O3SCF3)2[P(c-C6H11)3]2, Hg(O3SCF3)2[PBu3]n (n = 2, 3, 4) which imply that the perchlorate anion may be more strongly involved in coordination to mercury, in solution, than the trifluoromethylsulphonate anion.

Phosphorus-31, tin-119 and platinum-195 NMR studies on some platinum(II)-tin bonded compounds

Abstract Phosphorus-31, tin-119 and platinum-195 NMR spectra have been measured for three series of compounds; cis -Pt(PPh 3 ) 2 (Ph)(Z) where Z = SnPh 3 , SnPh 2 Cl, SnPhCl 2 , SnCl 3 , SnPh 2 Br, SnPhBr 2 , SnPh 2 I, SnPh 2 NCS, SnPh 2 SPh and SnPh 2 SCH 2 Ph; cis / trans -Pt(PPh 3 ) 2 (Cl)(Q) where Q = SnMe 2 Cl, SnBu 2 Cl, Sn(t-Bu) 2 Cl, SnMeCl 2 , SnBuCl 2 and SnPhCl 2 ; and cis / trans -Pt(PPh 3 ) 2 (Br)(Y) where Y = SnMe 2 Br, SnBu 2 Br, SnMeBr 2 , SnBuBr 2 , SnPhBr 2 . The 195 Pt resonances cover a range of 450 ppm and the 119 Sn resonances a range of 300 ppm, with 1 J (Pt- 119 Sn) varying between 7 and 20 kHz. Plots of 1 J (Pt-P trans ) against 1 J (Pt- 119 Sn) are approximately linear, indicating that the platinum-tin bond is predominantly σ in character.

Tin-119 and carbon-13 NMR studies on tin(IV) xanthates

Abstract Tin-119 NMR spectroscopy of solutions containing Sn(exa)4 and Sn(isopropxa)4 establishes the existence of the mixed xanthates Sn(exa)n(i-propxa)4−n. Furthermore, evidence is obtained for the existence of mono-, di-, and trihaloxanthates in solutions of appropriate mixtures of the tetraxanthates, dihaloxanthates and tetrahalides. The xanthate ligands undergo temperature dependent monodentate-bidentate exchange about the tin atom which determines the nature of the complexes observed in the various mixtures.

Phosphorus-31 and cadmium-113 NMR studies of some cadmium(II) complexes containing tricyclohexylphosphine and tributylphosphine

Abstract Phosphorus-31 and cadmium-113 NMR spectroscopy has been used to study the interaction between tertiary phosphines (P(c-C6H11)3 and PBu3) and Cd(O3SCF3)2, Cd(ClO4)2, Cd(CF3COO)2 and Cd(SCN)2 salts in solution. the NMR data imply the formation in solution of novel 1:1 adducts CdX2(phos) (X = O3SCF3, ClO4, CF3COO, phos = P(c-C6H11)3, PBu3) in which there is substantial interaction between the anions and cadmium. Data are also presented for mixed phosphine complexes CdX2[P(c-C6H11)3][PBu3] (X = O3SCF3, ClO4, NO3, CF3COO, CH3COO, Cl, Br, I, SCN). The two bond coupling constants 2J(P′P) of these mixed phosphine complexes decrease as the coordination ability of the anion increases and cover the narrow range from 95 Hz to 66 Hz.

STUDIES OF SOME MERCURY(II) AND CADMIUM(II) COMPLEXES WITH DICYCLOHEXYLPHOSPHINE AND (1-(DICYCLOHEXYLPHOSPHINO))-N-PHENYLTHIOFORMAMIDE

Abstract Dicyclohexylphosphine, HPcycl 2 , reacts with mercury(II) and cadmium(II) halides to give isolable 1:1 adducts HgX 2 (HPcycl 2 ) (X = Cl, Br, I), CdX 2 (HPcycl 2 ) (X = Br, I) and 1:2 adducts HgX 2 (HP-cycl 2 ) 2 , CdX 2 (HPcycl) 2 (X = Cl, Br, I). The 1:2 adducts HgX 2 (HPcycl 2 ) 2 react in solution with additional HPcycl 2 to give 1:3 adducts HgX 2 (HP-cycl 2 ) 3 whereas the corresponding CdX 2 (HPcycl 2 ) 2 do not react further with HPcycl 2 .Both mercury(II) and cadmium(II) 1:1 adducts react with halide ion to give anionic [MX 3 HPcycl 2 ] − (M = Hg, Cd) species in solution. The ligand (1-(dicyclohexylphosphino))-N-phenylthioformamide, LH, (LH = (C 6 H 11 ) 2 PC(S)N(H)C 6 H 5 ) reacts with mercury(II) halides to give isolable 1:1 and 1:2 adducts, [HgX 2 (LH)] 2 and HgX 2 (LH) 2 , in which coordination of the ligand occurs only through the phosphorus atom. There is no evidence for the addition of a third LH to mercury but the 1:1 adducts react with halide ion to give anionic [HgX 3 LH] − species. The 1:2 adducts HgX 2 (HPcycl 2 ) 2 and CdX 2 (HPcycl 2 ) 2 react in solution with C 6 H 5 NCS to form the corresponding MX 2 (LH) 2 complexes. NMR data imply formation in solution of dimeric [CdX 2 (LH)] 2 compounds in which LH acts as a bridging ligand bonding through sulphur and phosphorus. Mixed ligand species HgX 2 (HPcycl 2 )(LH) and CdX 2 (HPcycl 2 )(LH) are also identified in solution. Phosphorus-31, cadmium-113 and mercury-199 NMR spectra were used to characterise new species in solution. There is no evidence for phosphido formation in any of the systems investigated in this study.