Nicola A. Davies

The effects of interplay between quadrupolar, dipolar and shielding tensors on magic-angle spinning NMR spectra: shapes of spinning sidebands

The shapes of spinning sidebands for 13C magic-angle spinning spectra of solids affected by residual dipolar splittings to 14N are found to be spinning-speed dependent. Simple theory for the case of co-axial tensors indicates that centreband splittings at low spinning speeds yield values of xD (x and D are quadrupolar and dipolar coupling constants respectively) directly. The case of the cyanide carbon resonances for the coordination polymer [[ttilde](CH3)3Pb∼4Ru(CN)6]∞ is considered in detail. Computer simulations of the sideband bandshapes fit the experimental results well. The quadrupole coupling constants for the three cyanide nitrogen sites lie in the range -1·9 to -2·5 MHz. The shielding anisotropy for the cyanide carbon giving the highest-frequency resonance is found to be Δσ = ± 350 ppm.

Unprecedented N–E Bond Cleavage (E=Sn, Pb) by R4N+ Ions (R=nBu, nPr): Formation, Architecture, and Multinuclear Magnetic Resonance Spectroscopy of Novel Supramolecular [(R4N)(Me3E)2M(CN)6⋅H2O] Assemblies (M=Fe, Co)

Hydrogen bonds of the two types O−H⋅⋅⋅N and C−H⋅⋅⋅N (shortest C⋅⋅⋅N contact: 317.3 pm) seem to dictate the supramolecular architecture of novel host–guest systems involving nBu4N+, Me3Sn+, [M(CN)6]3− and H2O as primary building blocks (1:2:1:1). The multinuclear (13C, 15N, 59Co, 119Sn) solid-state NMR spectrum of M = Co corroborates very well with the X-ray structure for M = Fe (right: host without guest cations).

Self-assembly of [Cu(CN)4]3− ions with cationic {Me3Sn}+ or {Me2Sn(CH2)3SnMe2}2+ fragments in the presence of a nBu4N+ template

Abstract As described earlier, solutions of nBu4NCl and K3[Cu(CN)4] react with Et3SnCl to zeolite-like [(Bu4N)(Et3Sn)2Cu(CN)4] (1), but with Me3SnCl exclusively to [(Bu4N)(Me3Sn)Cu2(CN)4] (2), the crystal structure of which is reported here for the first time. The nBu4N+ guest ions of 2 are accommodated between planar, negatively charged layers, wherein three-coordinated Cu(I) ions are interlinked by CN and CN·SnMe3·NC bridges (2:1). The slightly modified new homologue of 2: [(nBu4N){Me2Sn(CH2)3SnMe2}0.5Cu2(CN)4] (3), displays an almost identical powder X-ray diffractogram as 2 and, moreover, surprisingly similar solid-state NMR spectra for the nuclei 13C, 15N and 119Sn. A three-dimensional host framework is postulated to encapsulate the nBu4N+ guest of 3, the Sn atoms of adjacent layers being therein tied pair-wise together by trimethylene tethers, (CH2)3. For further comparison, the solid-state NMR data of the new coordination polymer [{Me2Sn(CH2)3SnMe2}0.5Au(CN)2] (5) are also presented.

The organometallic double metal cyanide [(Me2Sn)3{Co(CN)6}2·6H2O]. A three-dimensional framework of infinite, stapled ribbons

Abstract The admixture of aqueous Me2SnCl2–Me3SnCl solutions to solutions of K3[Co(CN)6] in the molar ratios 3:0:2 and 1:1:1, respectively, affords precipitates of [(Me2Sn)3{Co(CN)6}2·6H2O] (1) and [(Me2Sn)(Me3Sn)Co(CN)6] (2). Another synthesis of 2 is based upon the bromination of [(Me3Sn)3Co(CN)6] in MeOH. The crystal structure analysis of 1 reveals stacks of infinite planar ribbons built up of trans-Me2Sn(μ-NC)4 and trans-Me2Sn(μ-NC)2(OH2)2 units as well as of trans-Co(CN)2 fragments with terminal CN-ligands. Sn←OH2⋯(NC)2 hydrogen bonds interlink adjacent ribbons. Multinuclear (13C, 15N, 59Co, 119Sn) CPMAS solid-state NMR studies of 1 suggest some intra-ribbon dynamics, and help in proposing both a plausible architecture for anhydrous 2 and a better understanding of the nature of another precipitate 5 resulting from the admixture of a Me2SnCl2/Me3SnCl solution to a solution of K4[Fe(CN)6] (1:2:1).

Novel organotin-functionalized, polymeric transition metal cyanides: From Me3Sn- to Me2Sn(CH2) 3SnMe2 spacers

Abstract The two new compounds [Me2Sn(CH2)3SnMe21.5Co(CN)6], 1, and [Me2Sn(CH2)3SnMe22Mo(CN)8], 2, have been prepared and compared with their notional ‘parent’ systems [(R3Sn)3Co(CN)6] (R = Me, Et, nBu) and solvent-free [(Me3Sn)4M(CN)8] (M = Mo, W) respectively. Results of extensive spectroscopic (i.e. IR/Raman as well as multinuclear CP MAS NMR) studies and of X-ray powder diffractometry suggest that the crystal structures of 1 and 2 involve three-dimensional networks notably different from those of their ‘parent’ systems. The probably regular, pairwise linkage of two CNSnMe2CH2 ligand fragments by a third CH2 group even appears to ‘improve’ the local symmetry of the respective M(CN)k building block (k = 6 or 8) and simplifies the corresponding asymmetric units.

Tin-119 NMR spectroscopic studies of some six-coordinate complexes R2SnCl2·2L and R2SnCl2·L′ (R = Me or Ph; L = py; L′ = bipy or phen)

Abstract Solid-state cross-polarization magic-angle spinning 119Sn NMR spectra have been obtained for six adducts of dimethyl- or diphenyl-tin dichloride. Shielding tensor components as well as isotropic chemical shifts are presented and discussed. The shielding anisotropies provide some evidence that the pyridine adducts are all-trans, in contrast to the other compounds. Some solution-state 119Sn NMR data are also given.

[Ni(CN)2 · 2Me3SnCN · (nBu4N)OH]: a layered, supramolecular assembly containing the earlier described, macrocyclic building block [{(Me3Sn)2OH}2{μ-(NC)2Ni(CN)2}2]2−

Abstract The crystal structure of [(nBu4N){(Me3Sn)2OH}{Ni(CN)4}][Ni(CN)2 · 2Me3SnCN · (nBu4N)OH] (1), the formal 1:1-addition product of polymeric [(Me3Sn)2Ni(CN)4][Ni(CN)2 · 2Me3SnCN] and (nBu4N)OH, has been revisited at 153 K. Owing to the presence of distinct (Me3Sn)2OH · · ·NC hydrogen bonds, infinite, negatively charged layers containing cyclic [{(Me3Sn)2OH}2{μ(NC)2Ni(CN)2}2]2− units alternate with layers of nBu4N+ ions. CPMAS solid-state NMR spectra (13C, 15N, 119Sn) strongly support nonsymmetric building blocks with exceedingly weak SnN bonds.

Motion in solid organotin(IV) coordination polymers: a two-dimensional exchange magic angle spinning 13C NMR study

Solid-state 13C CP MAS NMR studies of compounds [(Me3Sn)4M(CN)6]∞ with M = Fe, Ru and Os, using variable temperature, show that the trigonal bipyramidal arrangements at Sn are undergoing internal rotation about the N-Sn-N axes with lifetimes of the order of 0.5 s at moderately lowered temperature.