Organomercury(II) and tellurium(II) compounds with the "pincer" ligand 2,6-[O(CH2CH2)2NCH2]2C6H3--stabilization of an unusual organotellurium(II) cationic species

N-Coordinated tellurenium(II) and telluronium(IV) cations: synthesis, structure and hydrolysis

A set of N-coordinated tellurium(II) compounds containing either C,N-chelating ligands CNR (where CN = 2-(RNCH)C6H4, R = tBu or Dipp; Dipp = 2,6-iPr2C6H3) or N,C,N pincer ligands NCNR (where NCN = 2,6-(RNCH)2C6H4, R = tBu or Dipp) were synthesized. In the case of C,N-chelated compounds, the reaction of CNDippLi with Te(dtc)2 (where dtc = Et2NCS2) in a 1 : 1 molar ratio smoothly provided the carbamate CNDippTe(dtc) which upon treatment with 2 eq. of HCl provided the chloride CNDippTeCl. In contrast, the analogous conversion of NCNRLi with Te(dtc)2 surprisingly furnished ionic bromides [NCNRTe]Br as a result of the exchange of dtc by Br coming from nBuBr present in the reaction mixture. Furthermore, the reaction of CNDippTeCl or [NCNRTe]Br with silver salts AgX (X = OTf or SbF6) provided the expected tellurenium cations [CNDippTe]SbF6 and [NCNRTe]X. To further increase the Lewis acidity of the central atom, the oxidation of selected compounds with 1 eq. of SO2Cl2 was examined yielding stable compounds [CNtBuTeCl2]X and [NCNtBuTeCl2]X. The oxidation of the Dipp substituted compounds proved to be more challenging and an excess of SO2Cl2 was necessary to obtain the oxidized products [CNDippTeCl2]SbF6 and [NCNDippTeCl2]SbF6, which could solely be characterized in solution. Compounds [CNtBuTeCl2]OTf and [NCNtBuTeCl2]OTf were shown to undergo a controlled hydrolysis to the corresponding telluroxanes. All compounds were studied by multinuclear NMR spectroscopy in solution and for selected compounds solid state 125Te NMR spectroscopy and single-crystal X-ray diffraction analysis were performed. The Lewis acidity of the studied cations was examined by the Gutmann-Beckett method using Et3PO as the probing agent. The Te-N chalcogen bonding situation of selected compounds has also been examined computationally by a set of real-space bonding indicators.

Structure of a diorganotelluroxonium(IV) cation, {[2,6-(CH2NMe2)2C6H3Te(μ-O)]2}2+, with the tri-chlorido-(dimethyl sulfoxide)-platinum(II) anion

In the title salt, di-μ-oxido-bis-{2,6-bis-[(di-methyl-amino)-meth-yl]phenyl-κC ¹}tellurium(-IV) bis[tri-chlorido-(dimethyl sulfoxide-κS)platinate(II)], (C₂₄H₃₈N₄O₂Te₂)[PdCl₃(C₂H₆OS)]₂, which crystallizes in the triclinic space group P , each Te atom is in a distorted five-coordinated TeO₂N₂C square-pyramidal geometry (τ values of 0.026 and 0.001) with the C atoms of the phenyl rings occupying the apical positions. The phenyl rings in the [C₂₄H₃₈N₄O₂Te₂]²⁺ cation are in a cis arrangement to enable this species to participate in Te⋯Cl cation-anion inter-actions. There are also C-H⋯O inter-actions involving the dimethyl sulfoxide ligands and numerous cation-anion and anion-anion C-H⋯Cl inter-actions, which link the ions into a complex three-dimensional array.

Reaction of imidazoline-2-selone derivatives with mesityltellurenyl iodide: a unique example of a 3c-4e Se→Te←Se three-body system embedding a tellurenyl cation

1,2-Bis(3-methyl-4-imidazolin-2-selone)ethane was used to stabilize the first example of an authentic mesityltellurenyl cation, [MesTe]⁺, as a charge transfer adduct featuring a 3c-4e Se→Te←Se three-body system.

Reactivity of bis[{2,6-(dimethylamino)methyl}phenyl]telluride with Pd(ii) and Hg(ii): isolation of the first Pd(ii) complex of an organotellurenium cation as a ligand

The first complex of an organotellurenium cation as a ligand with Pd(ii) is reported.

Synthesis and structure of an aryl-tellurenium(II) cation; [4-tert-butyl-2,6-bis-(1-pentyl-1H-benz-imidazol-2-yl-κN3)phenyl-κC1]tellurium(II) (1,4-dioxane)tri-iodido-mercurate(II)

In the title salt, (C34H41N4Te)[HgI3(C4H8O2)], the aryl-tellurenium [C34H41N4Te]+ cations and [HgI3(dioxane)]- anions are linked by a short inter-action between the Te atom and one of the I-atom donors of the anion, as well as through weak C-H⋯I inter-actions. The geometry around the Te atom is T-shaped with the coordination comprising a C atom of the central aromatic ring and two N atom donors of the benzimidazolyl moiety. The Te-N bond lengths are almost equal [2.232 (3) and 2.244 (3) Å], while the Te-C bond length is 2.071 (4) Å. The N-Te-N bond angle is 150.68 (11)°. The HgII atom of the anion is coordinated by iodide ions from three sides and the fourth coordination site is occupied by an O atom of the solvent mol-ecule (dioxane). Thus, it attains a trigonal-pyrimidal geometry, with O-Hg-I angles ranging of 90.76 (8) and 96.76 (7)° and I-Hg-I angles ranging from 112.41 (1) to 125.10 (1)°. The cations and anions are involved in numerous weak π-π stacking inter-actions involving both the central phenyl ring and two inversion-related benzimidazole moieties, which propagate in the a-axis direction. In addition, there are numerous C-H⋯I inter-actions between the cations and anions, which link them into a complex three-dimensional array.

Synthesis and structure of arylselenium(ii) and aryltellurium(ii) cations based on rigid 5-tert-butyl-1,3-bis-(N-pentylbenzimidazol-2′-yl)benzenes

The transmetalation reactions of mercury precursor, [^Pentyl(N^C^N)HgCl] (19) with selenium and tellurium halides led to isolation of air stable NCN pincer based arylselenium(ii) and aryltellurium(ii) cations due to facile ionization of Se/Te halogen bond.

Crystal structure of {2,6-bis-[(di-methyl-amino)-meth-yl]phenyl-κ3N,C1,N'}(bromido/chlorido)-mercury(II)

In the mol-ecular structure of the title compound, {2,6-bis-[(di-methyl-amino)-meth-yl]phenyl-κ3N,C1,N'}[bromido/chlorido-(0.30/0.70)]mercury(II)-{2,6-bis-[(di-methyl-amino)-meth-yl]phenyl-κ3N,C1,N'}[bromido/chlorido-(0.24/0.76)]mer-cury(II) (1/1), [HgBr0.30Cl0.70(C12H19N2)]·[HgBr0.24Cl0.76(C12H19N2)], there are two mol-ecules in the asymmetric unit of formula LHgX {L = 2,6-bis-[(di-methyl-amino)-meth-yl]phenyl and X = Cl/Br}. In each mol-ecule, the halide site is mixed Cl/Br, with occupancies of 0.699 (7):0.301 (7) and 0.763 (7):0.237 (7), respectively. The two mol-ecules are linked into dimers by a combination of Hg⋯Hg [Hg⋯Hg = 3.6153 (3) Å] and C-H⋯Cl and C-H⋯π inter-actions.

N-Heterocyclic carbene stabilized parent sulfenyl, selenenyl, and tellurenyl cations (XH+, X = S, Se, Te)

NHC-stabilized parent sulfenyl (H–S⁺), selenenyl (H–Se⁺) and tellurenyl (H–Te⁺) cations have been achieved by treatment of NHC chalcogen adducts with trifluoromethanesulfonic acid.

Synthesis, characterization, and ligand behaviour of a new ditelluroether (C10H7)Te(CH2)4Te(C10H7) and the concurrently formed ionic [(C10H7)Te(CH2)4]Br

The reaction of 1-naphthyl bromide with n-butyl lithium, elemental tellurium, and 1,4-dibromobutane in THF affords both (C₁₀H₇)Te(CH₂)₄Te(C₁₀H₇) (1) and [(C₁₀H₇)Te(CH₂)₄]Br (2) in good yields. 1 is preferentially formed at low temperatures and is a rare example of a structurally characterized ditelluroether in which the tellurium atoms are bridged by a hydrocarbon chain. In the solid state, 1 shows secondary bonding TeTe interactions, which connect the molecules into layers which are further linked to 3-dimensional frameworks by TeH hydrogen bonds. [(C₁₀H₇)Te(CH₂)₄]Br (2) is formed concurrently during the synthesis of 1 and is the main product, when the reaction is carried out at room temperature. The revPBE/def2-TZVPP calculations of the reaction profiles indicate that the formation of 2 is somewhat more favourable than that of 1. Furthermore, at room temperature the activation energy for the formation of 2 is lower than that of 1. At low temperatures the activation energy of the reaction leading to 1 is lower than that to 2, which is consistent with the synthetic observations. When 1 was treated with CuBr, [Cu₂(μ-Br)₂{μ-(C₁₀H₇)Te(CH₂)₄Te(C₁₀H₇)}₂] (3) was formed. It crystallizes as two polymorphs (3a) and (3b) in which both the packing and the conformation of the ditelluroether ligands are different. The reaction of 1 with HgCl₂ produces [(C₁₀H₇)Te(CH₂)₄]₂[HgCl₄]·CH₂Cl₂ (4·CH₂Cl₂) and that of 1 with CuCl₂ affords [(C₁₀H₇)Te(CH₂)₄]Cl (5). 2 and 5 are isomorphous.

Selone-stabilized aryltellurenyl cations

Controlled bromination of a diarylditelluride, R2Te2 (R = 2,6-dimethylphenyl) (6) in dichloromethane led to the formation of a Te(II)-Te(IV) mixed-valent tellurenyl bromide, RBr2TeTeR (7). A further reaction of 7 with 1,3-dibutylbenzimidazolin-2-selone, C15H22N2Se (L) (9), produced the first selone adduct of the 2,6-dimethylphenyltellurenyl cation with the 2,6-dimethylphenyltellurium dibromide anion, [(2,6-Me2C6H3)Te(L)](+)[(2,6-Me2C6H3)TeBr2](-) (10). The red colored cationic adduct 10 is not stable in acetonitrile and disproportionated to give the selone adduct of 2,6-dimethylphenyltellurenyl bromide, [(2,6-Me2C6H3)Te(L)Br] (11b) and bis(2,6-dimethylphenyl)tellurium dibromide, [(2,6-Me2C6H3)2TeBr2], (13). The metathesis reaction of 11b with AgBF4 produced a stable dark red colored selone adduct of the 2,6-dimethylphenyltellurenyl cation with the BF4(-) anion, [(2,6-Me2C6H3)Te(L)](+)BF4(-) (15). The selone adducts of aryltellurenyl halides, i.e. [(2,6-Me2C6H3)Te(L)X] (X = Cl, Br, I) (11a-11c), have been synthesized by a one-pot reaction of 6 with an equimolar mixture of 9 and 1,3-dibutylbenzimidazolin-2-dihaloselones, C15H22N2SeX2 (14a-14c). Triphenylphosphine (PPh3), when treated with [(2,6-Me2C6H3)Te(L)X] (11a-11c), substitutes selone from the adduct to afford the triphenylphosphine adducts of aryltellurenyl halides, [(2,6-Me2C6H3)Te(PPh3)X] (16a-16c).

Activity of antifungal organobismuth(III) compounds derived from alkyl aryl ketones against S. cerevisiae: comparison with a heterocyclic bismuth scaffold consisting of a diphenyl sulfone

A series of hypervalent organobismuth(III) compounds derived from alkyl aryl ketones [XBi(5-R'C₆H₃-2-COR)(Ar)] was synthesized to investigate the effect of the compounds’ structural features on their antifungal activity against the yeast Saccharomyces cerevisiae. In contrast to bismuth heterocycles [XBi(5-RC₆H₃-2-SO₂C₆H₄-1'-)] derived from diphenyl sulfones, a systematic quantitative structure-activity relationship study was possible. The activity depended on the Ar group and increased for heavier X atoms, whereas lengthening the alkyl chain (R) or introducing a substituent (R') reduced the activity. IBi(C₆H₄-2-COCH₃)(4-FC₆H₄) was the most active. Its activity was superior to that of the related acyclic analogues ClBi[C₆H₄-2-CH₂N(CH₃)₂](Ar) and ClBi(C₆H₄-2-SO₂tert-Bu)(Ar) and also comparable to that of heterocyclic ClBi(C₆H₄-2-SO₂C₆H₄-1'-), which was the most active compound in our previous studies. Density function theory calculations suggested that hypervalent bismuthanes undergo nucleophilic addition with a biomolecule at the bismuth atom to give an intermediate ate complex. For higher antifungal activity, adjusting the lipophilicity-hydrophilicity balance, modeling the three-dimensional molecular structure around the bismuth atom, and stabilizing the ate complex appear to be more important than tuning the Lewis acidity at the bismuth atom.

Tin and Mercury Compounds Supported by a Bulky Organometallic Ligand Incorporating a Pendant Guanidine Functionality

The structure of a triclinic form of the organolithium derivative LiR, R = C(SiMe3)2(SiMe2{hpp}) (1) (hppH = 1,3,4,6,7,8,-hexahydro-2H-pyrimido[1,2-a]pyrimidine) comprises dimers [1]2 held together by Li···H3C interactions like those in the polymeric structure [1]∞ of the previously described orthorhombic form. Compound 1 reacts with the chlorides MCl2 (M = Hg or Sn) to give compounds HgRCl (2) or SnRCl (3), which have been characterised by NMR spectroscopy and X-ray crystallography. The structural parameters and conformations of the metallacycles MRLn are compared with those in related compounds containing bulky organosilicon ligands with pendant nitrogen donors. Compound 3 reacts with Li[P{H}Ar*] (Ar* = 2,4,6-tBu3C6H2) to give the crowded phosphanide SnR(P{H}Ar*) (4).

1,4-Bis{[hydroxy(phenyl)phosphoryl]methyl}piperazine-1,4-diium tetrachloridocadmate(II) dihydrate and the cobaltate(II) analogue

The reaction of aminophosphinic acid with CdCl2·2.5H2O or CoCl2·6H2O in concentrated hydrochloric acid yielded the isostructural compounds 1,4-bis{[hydroxy(phenyl)phosphoryl]methyl}piperazine-1,4-diium tetrachloridocadmate(II) dihydrate, (C18H26N2O4P2)[CdCl4]·2H2O, (I), and 1,4-bis{[hydroxy(phenyl)phosphoryl]methyl}piperazine-1,4-diium tetrachloridocobaltate(II) dihydrate, (C18H26N2O4P2)[CoCl4]·2H2O, (II). The asymmetric unit of each contains two half dications, both located on crystallographic centres of inversion, a tetrachloridometallate(II) dianion and two solvent water molecules. The residues are linked into two-dimensional layers in the ab plane by O-H···O hydrogen bonds.