α,ω-Bis(trichlorostannyl)alkanes: unravelling the hydrolysis pathway to organotin-oxo oligomers

New α,ω-bis(trichlorostannyl)alkanes, Cl₃Sn(CH₂)_nSnCl₃ [n = 3-5, 8], have been synthesized via tin-phenyl bond cleavage reactions on α,ω-bis(triphenylstannyl)alkanes, Ph₃Sn(CH₂)_nSnPh₃ [n = 3-5, 8], using either SnCl₄ or concentrated hydrochloric acid. Some key missing links, (H₂O)Cl₃Sn(CH₂)₃SnCl₃(H₂O) (1a) and (H₂O)₂Cl₃Sn(CH₂)₃SnCl₃(H₂O)₂ (6), in the hydrolysis pathway of organotin trichlorides were identified. Crystal structures of the nonassociated di-tin compounds (H₂O)Cl₃Sn(CH₂)₃SnCl₃(H₂O) (1a) and (H₂O)₂Cl₃Sn(CH₂)₃SnCl₃(H₂O)₂ (6, isolated as the 18-crown-6 cocrystal acetonitrile solvate) as well as the polymeric hydrolysis product [H₂O(OH)Cl₂Sn(CH₂)₃SnCl₂(OH)H₂O·₂H2O]_n (7·2H₂O) are reported.

Octabutyl-1k2C,2k2C,3k2C,4k2C-di-µ3-oxo-1:2:3k3O;2:3:4k2O-di-µ2-phenoxy-1:2k2O;3:4k2O-diphenyoxy-1kO,4kO-tetratin(IV)

The dimeric title compound, tetrabutyldiphenoxydistannoxane, [Sn₄(C₄H₉)₈(C₆H₅O)₄O₂], adopts a ladder-type structure, featuring an almost planar inorganic framework with three four-membered Sn₂O₂ rings and four coplanar phenoxy groups.

A dimeric tellurastannoxane carbonate cluster, tetra-tert-butyl-di-µ3-carbonato-tetrakis-[4-(N,N-dimethylamino)phenyl]di-µ-oxo-ditelluriumditin chloroform tetrasolvate

The title compound, [Sn₂Te₂(C₄H₉)₄(CO₃)₂O₂(C₈H₁₀N)₄]·4CHCl₃ or [(p-Me₂NC₆H₄)₂TeOSn^tBu₂CO₃]₂·4CHCl₃, contains an almost planar centrosymmetric inorganic Sn₂Te₂O₈C₂ core and hypercoordinated Sn and Te atoms. The structure features four secondary intramolecular Te...O contacts.

Solvent-controlled assembling by hydrogen bridges and halogen-halogen interactions of novel organotin oxo clusters

The crystal structure of the novel methylene-bridged tetraorganodistannoxane {[Ph(HO)SnCH₂Sn(I)Ph]O}₄ (1) depends on the solvent it is crystallised from and is controlled by hydrogen bridges and interhalogen interactions.

Crystal structure of (13S*,13aR*)-2,3-dimethoxy-13-hydroxy-13a-methyl-8-oxo-5,6,13,13a-tetrahydro-8H-dibenzo[a,g]quinolizine, C20H21NO4

C₂₀H₂₁N0_4, monoclinic, P12₁/cl (No. 14), a = 7.521(2) Å,
b = 23.257(2) Å c = 9.784(2) Å, ß= 95.57(2)°, V = 1703.3 ų,
Z = 4, R_gt(F) = 0.060, wR_ref(F²) = 0.183, T = 293 K.

The utility of hypercoordination and secondary bonding for the synthesis of a binary organoelement oxo cluster

A strategy for the preparation of the otherwise difficult to obtain binary organometallic oxides containing two heavy main group elements is described and exemplified by the synthesis of [(p-MeOC₆H₄)₂Te(OSnt-Bu₂OH)₂]₂.

Organotin-oxo clusters

This thesis reports on the development and expansion of reliable synthetic di-and multi-tin precursors for the assembly of oligomeric organotin-oxo compounds in which the shape, dimension and tin nuclearity can be controlled. The reaction of polymeric diorganotin oxides, (R2SnO)m (R = Me, Et, n-Bu, n-Oct, c-Hex, i-Pr, Ph), with saturated aqueous NH4X solutions (X = F, Cl, Br, I, OAc) in refluxing 1,4-dioxane afforded in high yields dimeric tetraorganodistannoxanes, [R2(X)SnOSn(X)R2]2, and in a few cases diorganotin dihalides or diacetates, R2SnX2. This method appears to be particularly good for the synthesis of halogenated tetraorganodistannoxanes but a less suitable method for the preparation of dicarboxylato tetraorganodistannoxanes. Identification of [R2(OH)SnOSn(X)R2]2 (R = n-Bu; X = Cl, Br) and [R2(OH)SnOSn(X)R2][R2(X)SnOSn(X)R2] suggest a serial substitution mechanism starting from [R2(OH)SnOSn(OH)R2]2. A series of α, ω -bis(triphenylstannyl)alkanes, [Ph3Sn]2(CH2)n (n = 3-8, 10, 12) and some of their derivatives were synthesised and characterised. These α, ω-bis(triphenylstannyl)alkanes, [Ph3Sn]2(CH2)n were converted to the corresponding halides [R(Cl)2Sn]2(CH2)n (R = CH2SiMe3) and subsequently to the polymeric oxides {[R(0)Sn]2(CH2)n}m. Reaction of {[R(O)Sn]2(CH2)n}m with [R(Cl)2Sn]2(CH2)n. (n = 3, n' = 4 and n = 4, n' = 3) in toluene at 100°C results in a mixture of symmetric and asymmetric double ladders, where different spacer chain lengths (n and n') provide the source of asymmetry. The coexistence at high temperature of separate 119Sn NMR signals belonging to symmetric and asymmetric double ladders suggests an equilibrium that is slow on the 119Sn NMR time scale and the position of which is temperature dependent. However, 119Sn NMR spectroscopic experiments of {[R(0)Sn]2(CH2)3}m with [R(Cl)2Sn]2(CH2)n for longer spacers (n - 5, 6, 8, 10, 12) reveal that molecular self-assembly of symmetric spacer-bridged di-tin precursors of equal chain length is preferred over asymmetric species. An ether-bridged di-tin tetrachloride [R(Cl)2Sn(CH2)3]2O (R = CH2SiMe3) and its corresponding polymeric oxide {[R(O)Sn(CH2)3]2O}m were synthesised and characterised. Reaction of [R(Cl)2Sn(CH2)3]2O with {[R(O)Sn(CH2)3]2O}m results in a unique functionalised double ladder {{[RSn(Cl)](CH2)3O(CH2)3[RSn(Cl)]}O}4 whose structure in the solid state was determined by X-ray analysis. Identification of tetrameric functionalised double ladder as well as dimeric and monomeric species suggest the existence of an equilibrium in solution. The feasibility of the functionalised double ladder to form host-guest complexes with a variety of metal cations is investigated using electrospray mass spectrometry (ESMS). Evidence for such complexes is found only for sodium cations. The reaction between {[R(O)Sn]2(CH2)n}m (n = 3, 4, 8, 10) and triflic acid is described. The initial formed products [RSn(CH2)nSnR](OTf)4 are easily hydrolysed. For n = 3, self-assembly leads to a discrete double ladder type structure, {{[RSn(OH)](CH2)3[RSn(H2O)]}O}44OTf, which is the first example of a cationic double ladder. For n ≥ 3, hydrolysis gives polymeric products, as demonstrated by the crystal structure of {[(H2O)(OH)RSn]2(CH2)4-2OTf2H2O}m. Two spacer-bridged terra-tin octachlorides [R(Cl)2Sn(CH2)3Sn(Cl)2]2(CH2)n (R = CH2SiMes; n = 1, 8) and their corresponding polymeric oxides {[R(O)Sn(CH2)3Sn(O)]2(CH2)n}m were successfully synthesised and characterised. Attempts were made to synthesise quadruple ladders from these precursors. Reactions of [R(Cl)2Sn(CH2)3Sn(Cl)2]2CH2 with {[R(O)Sn(CH2)3Sn(O)]2CH2}m or (Y-Bu2SnO)3 result in, mostly insoluble, amorphous solids. Reactions of [R(Cl)2Sn(CH2)3Sn(Cl)2]2(CH2)8 with {[R(O)Sn(CH2)3Sn(O)]2(CH2)8}m or (t-Bu2SnO)s result in new tin-containing species which are presumably oligomeric. The synthesis of a series of alkyl-bridged di-tin hexacarboxylates [(RCO2)3Sn]2(CH2)n (n = 3, 4; R = Ph, c-C6H11, CH3, C1CH2) is also reported. The hydrolysis of these compounds is facile and complex. There appears to be no correlation between spacer chain length and hydrolysis product. However, the conjugate acid strength of the carboxylate does appear to be important. In general only insoluble amorphous polymeric organotin-oxo compounds were obtained.

Solubility and Stability of cytochrome c in hydrated ionic liquids : effect of oxo acid residues and kosmotropicity

Hydrated ionic liquids (ILs) were prepared by adding appropriate amounts of water to hydrophilic ILs. Some hydrated ILs show excellent solubilizing ability for proteins, keeping the basic properties of ILs. The solubility of cytochrome c (cyt c) depended on the structure of the component ions. When component anions have oxo acid residues, the resulting hydrated ILs solubilize cyt c quite well. In such hydrated ILs, the structure and activity of cyt c is influenced by the kosmotropicity of the component ions. We synthesized ILs from various ions having different kosmotropicity, including dihydrogen phosphate (dhp), dibutylphosphate, acetate, lactate, and methanesulfonate as anions. The activity of the dissolved cyt c depends on the permutations of kosmotropicity of the component ions. cyt c shows no structural change and retains its activity when dissolved in the hydrated choline dhp, which is an excellent combination of chaotropic cation and kosmotropic anion. Furthermore, cyt c dissolved in the hydrated choline dhp remained in a native state and was active after 18 months of storage at room temperature.

Hexameric isopropyloxotin acetate chloroform tetrasolvate

The molecular structure of the centrosymmetric hexanuclear title compound, [ⁱPrSn(O)(O₂CCH₃)]₆·4CHCl1₃ or [Sn₆O₆(C₃H₇)₆(C₂H₃O₂)₆]·4CHCl₃, adopts the `drum' motif, in which two (ⁱPrSnO)₃ caps are linked via six ^μ₃-oxo atoms and six acetate groups. The Sn atoms are in distorted octahedral environments, defined by a CO₅ donor set for each of the three independent Sn atoms.

Hexameric trimethylsilylmethyloxotin acetate, [(Me3SiCH2)Sn(O)(OAc)]6

The centrosymmetric hexanuclear title compound, hexa-^μ₂-acetato-hexa-^μ₃-oxo-hexakis[(trimethylsilylmethyl)tin], [Sn₆O₆(C₂H₃O₂)₆(C₄H₁₁Si)₆], adopts a 'drum' structure in which two [(Me₃SiCH₂)SnO]₃ caps are linked to each other via six ^μ₃-O atoms and six bidentate bridging acetate groups. A CO₅ donor set defines a distorted octahedral environment for each of the three independent Sn atoms.

The first spacer-bridged tetraorganodistannoxanes with a mixed double ladder structure

The reaction of Me₃SiCH₂Cl₂Sn(CH₂)₃SnCl₂Ph (6) with (tBu₂SnO)₃ gave a statistical mixture of the corresponding tetraorganodistannoxanes whereas the reaction of the spacer-bridged ditin tetrachlorides RCl₂Sn(CH₂)₄SnCl₂R (3, R = Me₃CCH₂; 4, R = Me₂CHCH₂; 10, R = Me₃SiCH₂) with the polymeric spacer-bridged ditin oxides [R(O)Sn(CH₂)₄Sn(O)R]_n (7, R = Me₂CHCH₂; 8, R = Me₃CCH₂; 11, R = Me₃SiCH₂) provided the mixed double ladder compounds {[R(Cl)Sn(CH₂)₄Sn(Cl)R][R(Cl)Sn(CH₂)₄Sn(Cl)R']O₂}₂ (9, R = Me₃CCH₂, R' = Me₂CHCH₂; 12, R = Me₃CCH₂, R' = Me₃SiCH₂) in almost quantitative yield. In solution, 9 and 12 are in equilibrium with their corresponding dimers, as was evidenced by ¹¹⁹Sn NMR spectroscopy, molecular mass determination, and electrospray mass spectrometry. The molecular structures of 9 and 12 were established by single crystal X-ray diffraction.

Chromium(III)-docosahexaenoic acid complex : synthesis and characterization

Supplements containing chromium in its trivalent oxidation state [Cr(III)] are used by diabetic patients to improve their glucose and insulin levels and omega-3 fatty acids are also beneficial for people with insulin resistance or diabetes. It seemed very useful to combine chromium(III) and omega-3 functional entities into single molecules. Here we synthesized and characterized a chromium cis-4,7,10,13,16,19-docosahexaenoic acid (DHA) complex, one of the two main components of the heterogeneous chromium(III) fish oil omega-3 concentrate products. Ethyl cis-4,7,10,13,16,19-docosahexaenoate was hydrolyzed with sodium hydroxide, and the generated salt was reacted in situ with chromium(III) chloride hexahydrate and converted into an oxo-centred trinuclear chromium(III) complex. A study of the DHA–chromium(III) complex by liquid chromatography/tandem mass spectrometry/(LC/MS/MS) is reported in this work. The data suggest a triaqua-μ3-oxohexakis-μ-docosahexaenoatotrichromium(1+), [Cr3O(C22H31O2)6(H2O)3]+, core structure.

Evaluation of novel hyphodermin derivatives as glycogen phosphorylase a inhibitors

The lipophilicity, permeability, solubility, polar surface area and ‘rule-of-five’ properties were assessed, using QikProp v2.5 (Schrödinger, Inc.) and ALOGPS 2.1 calculations, for 25 Hyphodermin derivatives. These compounds obeyed the ‘rule-of-five’, and the calculated physicochemical values were generally within desired limits. All compounds were tested against Glycogen Phosphorylase a (GPa). Four phenyl and benzyl substituted 2-oxo-hexahydro and tetrahydrobenzo[cd]indole carboxylic acids were identified as novel inhibitors of GPa with estimated IC50 values in the range 0.8–1.3 mM. Molecular modelling of these novel inhibitors was used to obtain the main structural features of this class of molecule for future structure–activity relationship studies.