Water-soluble luminescent platinum(II) complexes for guanine quadruplex binding.

A family of 16 platinum(II) complexes was synthesized with the aim of obtaining water-soluble luminescent coordination compounds for guanine quadruplex (G4) binding. The complexes share a common tridentate N^N^C-donor ligand (based on 2-phenyl-6-(1-1,2,3-triazol-4-yl)pyridine) bearing different substituents for solubilization, and an additional monodentate ancillary ligand (either phenylacetylide or 3-(trimethylammonium)prop-1-yne-1-ide). Single-crystal X-ray diffraction analyses confirm that the substituents do not interfere with the central planar core of the complexes required for π stacking interactions with the DNA.

Regioselective Formal β-Allylation of Carbonyl Compounds Enabled by Cooperative Nickel and Photoredox Catalysis.

The Tsuji-Trost reaction between carbonyl compounds and allylic precursors has been widely used in the synthesis of natural products and pharmaceutical compounds. As the α-C-H bond is far more acidic than the β-C-H bond, carbonyl compounds undergo highly regioselective allylation at the α-position and their β-allylation is therefore highly challenging. This innate α-reactivity conversely hampers diversity, especially if the corresponding β-allylation product is targeted.

Aspects of Phosphaallene Chemistry: Heat-Induced Formation of 1,2-Dihydrophosphetes by Intramolecular Nucleophilic Aromatic Substitution and Photochemical Generation of Tricyclic Phosphiranes.

3H-Phosphaallenes are accessible on a new and facile route and show a fascinating chemical behavior. The thermally induced rearrangement of Mes*P═C═C(H)R' (R' = Bu, Ad) afforded by C-H activation, isobutene elimination, and C-C and P-H bond formation bicyclic 1-benzo-dihydrophosphetes () with PC heterocycles. DFT calculations suggest a mechanism with intramolecular nucleophilic aromatic substitution and replacement of an alkyl group by the nucleophilic α-C atom of the phosphaallene.

Structure and reactivity of an Al/P-based frustrated Lewis pair bearing relatively small substituents at aluminium.

Reaction of MesP─C≡C─Ph (Mes = mesityl) with dineopentylaluminium hydride afforded by hydroalumination a geminal Al/P-based frustrated Lewis pair (FLP; ). Its steric shielding is relatively low, and its reactivity in various secondary reactions is less hindered by steric repulsion than observed for related compounds having bulkier groups attached to aluminium. FLP yielded adducts with MeC─NCO or benzaldehyde via the formation of Al-O and P-C bonds.

Functionalized alkynyl-chlorogermanes: hydrometallation, Ge-Cl bond activation, Ge-H bond formation and chlorine-tert-butyl exchange via a transient germyl cation.

Treatment of alkynyl-arylchlorogermanes ArylnGe(Cl)(C[triple bond, length as m-dash]C-(t)Bu)3-n (n = 1, 2) with HM(t)Bu2 (M = Al, Ga) yielded mixed Al or Ga alkenyl-alkynylchlorogermanes via hydrometallation reactions. Intramolecular interactions between the Lewis-basic Cl atoms and the Lewis-acidic Al or Ga atoms afforded MCGeCl heterocycles. The endocyclic M-Cl distances were significantly lengthened compared to the starting compounds and indicated Ge-Cl bond activation.

Hydroalumination of alkynyl-aminophosphines as a promising tool for the synthesis of unusual phosphines: P-N bond activation, a transient phosphaallene, a zwitterionic AlP2C2 heterocycle and a masked Al/P-based frustrated Lewis pair.

Treatment of the new alkynyl-chlorophosphine, Mes-P(Cl)-C ≡ C-CMe3, with LiNR2 afforded various unprecedented aminophosphines, Mes-P(NR2)-C ≡ C-CMe3, which showed a fascinating diversity in their reactivity towards H-Al(t)Bu2. NMe2 and NEt2 derivatives yielded the hydroalumination products Mes-P(NR2)-C(Al(t)Bu2) = C(H)-CMe3 which have an Al-N and an activated P-N bond. Elimination of aluminium amide yielded the transient 3H-phosphaallene, Mes-P = C = C(H)-CMe3, which finally afforded a five-membered AlP2C2 heterocycle with an Al-P bond and two exocyclic C = C bonds.

Cooperative Ge-N Bond activation in aluminium-functionalised aminogermanes and spontaneous imine elimination via an intermediate germyl cation.

Hydrometallation of iPr2 N-Ge(CMe3 )(C≡C-CMe3 )2 with H-M(CMe3 )2 (M=Al, Ga) affords alkenyl-alkynylgermanes in which the Lewis-acidic metal atoms are not coordinated by the amino N atoms but by the α-C atoms of the ethynyl groups. These interactions result in a lengthening of the Ge-C bonds by approximately 10 pm and a comparably strong deviation of the Ge-CC angle from linearity (154.3(1)°).

Hydrometallation of amino-trialkynylsilanes--intramolecular M-N interactions (M = Al, Ga) and potential activation of Si-N bonds.

Hydrometallation of a pyrrolidyl functionalised trialkynylsilane, H8C4N-Si(C≡C-CMe3)3, with equimolar quantities of H-M(CMe3)2 (M = Al, Ga) resulted in the formation of mixed alkenyl-dialkynylsilanes (3a, 3b) which have a Lewis-acidic Al or Ga atom in the geminal position to the Si atom and form four-membered M-N-Si-C heterocycles by a strong interaction of the amine N atoms with the Lewis-acidic metal atoms. This interaction results in a concomitant lengthening and weakening of the Si-N bonds. Dual hydrometallation afforded alkynyl-dialkenylsilanes (4a, 4b) with two Lewis-acidic metal atoms.

Hydroalumination of a chlorotrialkynylsilane: spontaneous stepwise 1,3-dyotropic rearrangement via an intermediate silyl cation.

A new functionalised alkynylsilane, Cl-Si(CC-CMe3 )3 (3), was obtained by a facile multistep synthesis. Treatment of 3 with equimolar quantities of the hydrides H-M(CMe3 )2 (M=Al, Ga) gave the mixed alkenyl-di(alkynyl)silanes, in which the chlorine atom adopts a bridging position between the aluminium and silicon atoms. Dual hydrogallation of 3 resulted in the formation of a di(alkenyl)-alkynylsilane containing two gallium atoms, one of which is coordinated to the chlorine atom, and the second is bonded to the α-carbon atom of the remaining alkynyl group.

Formation of isostructural solid solutions in 2,6-disubstituted N-phenylformamides and N-phenylthioamides.

In order to investigate possible isostructural solid solutions of disubstituted N-phenylformamides and thioamides, we have studied the re-crystallization of pairs of compounds selected from 2,6-difluoro-N-phenylformamide (I), 2,6-dichloro-N-phenylformamide (II), 2,6-dimethyl-N-phenylformamide (III), 2,6-dichloro-N-phenylthioamide (IV), 2,6-dimethyl-N-phenylthioamide (V), 2,6-diisopropyl-N-phenylformamide (VI) and 2,6-diisopropyl-N-phenylthioamide (VII). For single-component 2,6-disubstituted-N-phenylformamides only the trans form occurs in the pure crystal, while for thioamides the cis form occurs, with only one exception. By forming solid solutions of pairs of these molecules the resulting structures all adopt similar N-H.

The missing link in the coordination chemistry of hydrazines--a hydrazinetriide [N-N(Me)](3-) anion coordinated to five Al atoms.

The heptanuclear aluminium-nitrogen cage compound [(AlMe(2))(4)(AlMe)(3)(NHNMe)(3)(N-NMe)(OMe)] contains the unique hydrazinetriide fragment [N-N(Me)](3-) stabilized by coordination to five Al atoms. It was synthesised by thermolysis of the sesqui-hydrazide Al[(μ-NH-NHMe)(2)AlMe(2)](3) in refluxing toluene in the presence of a small quantity of methanol.

Vinylgallium and alkyllithium compounds: transmetalation and generation of oligolithium cages.

Vinylgallium compounds [C(6)H(6-n){(H)C=C(SiR(2) R')-GaR''(2)}(n ] (3, R=Ph, Me; R'=Ph, Me; R''=tBu, Et; n=1, 2) are easily accessible by hydrogallation of the corresponding alkynylbenzene derivatives with H-GaCl(2) and subsequent reaction with alkyllithium derivatives. Treatment of 3 with an excess amount of tert-butyl- or ethyllithium yielded by transmetalation and ortho-deprotonation of the aromatic rings the unprecedented solvent-free oligolithium cluster compounds [{(C(6)H(4)Li)HC=C(SiPh(3))Li}(2)(tBuLi)(2)] (4), [{(C(6)H(4)Li)HC=C(SiPh(2)Me)Li}(4)] (5) and [{(C(6)H(3)Li){HC=C(SiMe(3))Li}(2)}(3)] (6) in moderate yields. Their solid-state structures revealed the presence of unique molecular lithium clusters with 6, 8, or 9 lithium atoms that may be derived from two edge-sharing Li(4) tetrahedra (4), three Li(4) tetrahedra in a chain joined by two common edges (5) or a tricapped trigonal prism of lithium atoms (6).

Aluminum, gallium, and indium hydrazides and the generation of oligonuclear element-nitrogen cages: molecular intermediates on the way to element nitrides.

Organoelement aluminum, gallium, and indium hydrazides, [R(2)ENHN(H)R'](2) (E = Al, Ga, In), are easily available from the corresponding trialkylelement compounds, ER(3), and hydrazines, H(2)NN(H)R', via elimination of the respective hydrocarbons. Their diverse molecular structures are derived from four-, five-, or six-membered element-nitrogen heterocycles. Their stepwise thermolysis under carefully controlled conditions was shown to proceed along one of several different well-defined routes.

Oligonuclear gallium nitrogen cage compounds: molecular intermediates on the way from gallium hydrazides to gallium nitride.

Gallium hydrazides are potentially applicable as facile starting compounds for the generation of GaN by thermolysis. The decomposition pathways are, however, complicated and depend strongly on the substituents attached to the gallium atoms and the hydrazido groups. This paper describes some systematic investigations into the thermolysis of the gallium hydrazine adduct Bu(t)(3)Ga←NH(2)-NHMe (1a) and the dimeric gallium hydrazides [R(2)Ga(N(2)H(2)R')](2) (2b, R = Bu(t), R' = Bu(t); 2c, R = Pr(i), R' = Ph; 2d, R = Me, R' = Bu(t)) which have four- or five-membered heterocycles in their molecular cores.

Synthesis of a GaN cage compound with a hydrazinetetraide fragment, [N-N]4-, stabilised by six gallium atoms.

Thermolysis of the bicyclic gallium hydrazide [(GaMe(2))(4)(NH-NMe)(NH-NHMe)(2)] (1) yielded the unique cage compound [(GaMe)(4)(GaMe(2))(4)(N(2))(NH-NMe)(4)] (2). Compound 2 contains a remarkable hydrazinetetraide moiety, [N-N](4-), as the central structural motif which is stabilised by coordination to six gallium atoms.

Gallium-gallium bonds as efficient templates for the generation of a large cage containing twelve gallium atoms.

Treatment of the digallium compound R(2)Ga-GaR(2) [R = CH(SiMe(3))(2)] with benzotriazol-5-carboxylic acid afforded a large cage-like compound in which six Ga-Ga bonds are bridged by six trifunctional ligands. The central cavity encapsulated a THF molecule which cannot be removed in vacuo and does not show exchange with a large excess of the solvent.

Two polymorphs of N-(2,6-difluorophenyl)formamide.

The structures of two distinct polymorphic forms of N-(2,6-difluorophenyl)formamide, C(7)H(5)F(2)NO, have been studied using single crystals obtained under different crystallizing conditions. The two forms crystallize in different space groups, viz. form (Ia) in the orthorhombic Pbca and form (Ib) in the monoclinic P2(1) space group.

A heterocyclic organogallium peroxide with two dialkylgallium groups bridged by a peroxide dianion.

Treatment of Li[H2GaR2] [R=CH(SiMe3)2] with the hydrogen peroxide adduct (H2O2)2.DABCO (DABCO=diazabicyclooctane) afforded a heterocyclic digallium peroxide, [R2Ga(micro,eta1,eta1-O2)(micro-OH)GaR2]Li(DABCO) (2), in which two dialkylgallium groups are bridged by an oxidizing peroxo and a hydroxo ligand.

N-(2,6-Dibromophenyl)formamide.

In the crystal structure of the title compound, C(7)H(5)Br(2)NO, molecules related by translation are linked through N-H...

cis/trans Isomerism of hydroalumination and hydrogallation products-reflections on stability and rearrangement mechanism.

Treatment of (silylalkynyl)benzenes with (Me(3)C)(2)Ga-H afforded stable cis-addition products, for example, (Me(3)C)(2)Ga-C(SiMe(3))=C(H)-C(6)H(5) (1), while spontaneous cis/trans rearrangement was observed for sterically less shielded gallium hydrides. The corresponding trans-di(tert-butyl)gallium compounds (13, 14) were obtained by the reaction of C(6)H(6-n)[C(H)=C(SiMe(3))GaCl(2)](n) (11, 12) with LiCMe(3). In contrast, spontaneous isomerization took place upon reaction of (Me(3)C)(2)Al-H with phenyltrimethylsilylethyne.

The in vitro antitumour activity of novel, mitochondrial-interactive, gold-based lipophilic cations.

In this study we compared the effects of two previously described antimitochondrial gold complexes, that is, [A] [Au(dppe)(2)]Cl and [B] [Au(d4pype)(2)]Cl with two novel lipophilic cations, that is, [C] [Au(dpmaaH(2))(dpmaaSnMe(2))]Cl and [D] [Au(dpmaaSnMe(2))(2)]Cl as antimitochondrial agents. The results of this study indicate that [C] and [D] have intermediate partition coefficients and exhibited a selective uptake by cells. They exhibited a higher selectivity for the various cell lines than [A] but were more cytotoxic than [B].

Cocrystal of cis- and trans-N-phenylformamide.

N-Phenylformamide, C(7)H(7)NO, crystallizes with two molecules in the asymmetric unit which have different conformations of the formylamino group, one being cis and the other trans. This is the first example of an arylformamide crystal containing both conformational isomers and it may thus be considered a cocrystal of the two conformers. The two molecules in the unit cell are linked through N-H.

Tris(2-pyridyl)phosphine oxide: how C-H.O and C-H.N interactions can affect crystal packing efficiency.

Tris(2-pyridyl)phosphine oxide, (I), C(15)H(12)N(3)OP, is isomorphous with tris(2-pyridyl)phosphine. Because of a combination of C-H.O and C-H.

2,2'-Bipyridinium(1+) bromide monohydrate.

In the crystal structure of 2,2'-bipyridinium(1+) bromide monohydrate, C(10)H(9)N(2)(+).Br(-).H(2)O, the cation has a cisoid conformation with an intramolecular N-H.

An N-lithio-indole from the reaction of LiCH(TMS)2 and PhNC.

The reaction of LiCH(TMS)2 with phenyl isocyanide PhNC has unexpectedly led to the N-lithio-indole derivative 1, that has been fully characterised including its X-ray crystal structure determination.