Conformational dependence of through-space tellurium-tellurium spin-spin coupling in peri-substituted bis(tellurides).

Three related series of peri-substituted bis(tellurides) bearing naphthalene, acenaphthene and acenaphthylene backbones (Nap/Acenap/Aceyl(TeY)2 (Nap = naphthalene-1,8-diyl N; Acenap = acenaphthene-5,6-diyl A; Aceyl = acenaphthylene-5,6-diyl Ay; Y = Ph 1; Fp 2; Tol 3; An-p- 4; An-o- 5; Tp 6; Mes 7; Tip 8) have been synthesised and their solid-state structures determined by X-ray crystallography. Molecular conformations were classified as a function of the two C9-C-Te-C(Y) dihedral angles (θ); in the solid all members adopt AB or CCt configurations, with larger Te(aryl) moieties exclusively imposing the CCt variant. Exceptionally large J((125)Te,(125)Te) spin-spin coupling constants between 3289-3848 Hz were obtained for compounds substituted by bulky Te(aryl) groups, implying these species are locked in a CCt-type conformation. In contrast, compounds incorporating smaller Te(aryl) moieties are predicted to be rather dynamic in solution and afford much smaller J values (2050-2676 Hz), characteristic of greater populations of AB conformers with lower couplings. This conformational dependence of through-space coupling is supported by DFT calculations.

Crystal structure of 2-phenyl-2λ(4),3-ditellura-tetra-cyclo-[5.5.2.0(4,13).0(10,14)]tetra-deca-1(12),4,6,10,13-pentaen-2-ylium tri-fluoro-methane-sulfonate.

In the title compound, C18H13Te2 (+)·CF3O3S(-), the Te(II) atom of the cation and one O atom of the tri-fluoro-methane-sulfonate counter-ion form a close-to-linear Te-Te-O system, with a Te-Te-O angle of 172.3 (1)° and a Te-O distance of 2.816 (5) Å, which may suggest the presence of a three-centre-four-electron (3c-4e) bond. Secondary Te⋯O inter-actions [3.003 (4) and 3.016 (4) Å], involving the second Te(II) atom of the binuclear mol-ecule, are also noted, resulting in a supra-molecular layer in the bc plane.

S-alkylation of soft scorpionates.

The alkylation reactions of soft scorpionates are reported. The hydrotris(S-alkyl-methimazolyl)borate dications (alkyl = methyl, allyl, benzyl), which were prepared by the reaction of Tm(Me) anion and primary alkyl halides, have been isolated and structurally characterised. The reaction is, however, not universally successful. DFT analysis of these alkylation reactions (C=S versus B-H alkylation) indicates that the observed outcome is driven by kinetic factors. Extending the study to incorporate alternative imine thiones (mercaptobenzothiazole, bz; thiazoline, tz) led to the structural characterisation of di[aquo-µ-aquohydrotris(mercaptobenzothiazolyl)boratosodium], which contains sodium atoms in the κ(3)-S,S,S coordination mode. Alkylation of Na[Tbz] and Na[tzTtz] leads to decomposition resulting in the formation of the simple S-alkylated heterocycles. The analysis of the species involved in these reactions shows an inherent weakness in the B-N bond in soft scorpionates, which has implications for their use in more advanced chemistry.