2-Acetylpyridine- and 2-benzoylpyridine-derived thiosemicarbazones and their antimony(III) complexes exhibit high anti-trypanosomal activity

Complexes [Sb(2Ac4oClPh)Cl₂] (1), [Sb(2Ac4oFPh)Cl₂] (2), [Sb(2Ac4oNO₂Ph)Cl₂] (3), [Sb(2Bz4oClPh)Cl₂] (4), [Sb(2Bz4oFPh)Cl₂] (5) and [Sb(2Bz4oNO₂Ph)Cl₂] (6) were obtained with 2-acetylpyridine-N(4)-ortho-chlorophenyl thiosemicarbazone (H2Ac4oClPh) and its N(4)-ortho-fluor (H2Ac4oFPh) and N(4)-ortho-nitro (H2Ac4oNO₂Ph) analogues, and with the corresponding 2-benzoylpyridine-derived thiosemicarbazones (H2Bz4oClPh, H2Bz4oFPh, H2Bz4oNO₂Ph). The studied compounds are excellent inhibitors of Trypanosoma cruzi growth. H2Bz4oClPh and complexes (4) and (1) were the most trypanosomicidal.Upon coordination of H2Ac4oClPh to antimony(III) in 1, the therapeutic index (TI) goes from 10.58 to 14.35. However, the best values of TI were found for H2Bz4oClPh (TI = 1240) and H2Ac4oNO₂Ph (TI = 773). Structure-activity relationship (SAR) studies did not allow the establishment of correlations between the anti-trypanosomal activity and physico-chemical parameters, but correlations were found between the cytotoxicities and physico-chemical properties.     

Increasing the antibacterial activity of gallium(III) against Pseudomonas aeruginosa upon coordination to pyridine-derived thiosemicarbazones

Reaction of N(4)-phenyl-2-formylpyridine thiosemicarbazone (H2Fo4Ph), N(4)-phenyl-2-acetylpyridine thiosemicarbazone (H2Ac4Ph) and N(4)-phenyl-2-benzoylpyridine thiosemicarbazone (H2Bz4Ph) with gallium nitrate gave [Ga(H2Fo4Ph)₂](NO₃)₃ (1), [Ga(2Ac4Ph)₂]NO₃ (2) and [Ga(2Bz4Ph)₂]NO₃ (3). In all complexes coordination of the thiosemicarbazone via the N_py–N–S chelating system occurs. In 1 the thiosemicarbazone acts as a neutral ligand while in 2 and 3 the ligand is anionic. Upon slow diffusion of 2 in DMSO [Ga(2Ac4Ph)₂]NO₃·DMSO (2a) was formed. The crystal structure of 2a was determined. Upon coordination the antibacterial activity of both gallium and thiosemicarbazones against Pseudomonas aeruginosa significantly increases.     

Manganese(II) complexes with N-methyl-4-nitrobenzaldehyde, N-methyl-4-nitroacetofenone,and N-methyl-4-nitrobenzophenone thiosemicarbazone: Investigation of in vitro activity against Trypanosoma cruzi

Thiosemicarbazones are known to be active against different pathogenic microorganisms including Trypanosoma cruzi, the etiological agent of Chagas disease. In the search for new therapeutic drugs against this illness, the complexes [Mn(H4NO₂Fo4M)₂Cl₂] (1), [Mn(H4NO₂Ac4M)₂Cl₂] (2) and [Mn(H4NO₂Bz4M)₂Cl₂] (3) of N⁴-methyl-4-nitrobenzaldehyde thiosemicarbazone (H4NO₂Fo4M), N⁴-methyl-4-nitroacetophenone thiosemicarbazone (H4NO₂Ac4M) and N⁴-methyl-4-nitrobenzophenone thiosemicarbazone (H4NO₂Bz4M) were obtained and screened in vitro against bloodstream and intracellular forms of T. cruzi. H4NO₂Fo4M, H4NO₂Ac4M and their Mn(II) complexes displayed poor effect on bloodstream trypomastigotes, with IC₅₀ values ranging from 68 to >200 μM. However, although H4NO₂Bz4M was also not active, its corresponding Mn(II) complex presented high effect on this T. cruzi form, with an IC₅₀ value of 19 μM. The effect of complex (3), against trypomastigotes of T. cruzi supports further in vitro as well as in vivo studies.     

Tin(IV) complexes obtained by reacting 2-benzoylpyridine-derived thiosemicarbazones with SnCl4 and Ph2SnCl2

Reaction of 2-benzoylpyridine thiosemicarbazone (H2Bz4DH, HL1) and its N(4)-methyl (H2Bz4Me, HL2) and N(4)-phenyl (H2Bz4Ph, HL3) derivatives with SnCl₄ and diphenyltin dichloride (Ph₂SnCl₂) gave [Sn(L1)Cl₃] (1), [Sn(L1)PhCl₂] (2), [Sn(L2)Cl₃] (3), (4) [Sn(L3)PhCl₂] (5) and [Sn(L3)Ph₂Cl] (6). Infrared and ¹H, ¹³C and ¹¹⁹Sn NMR spectra of 1-3, 5 and 6 are compatible with the presence of an anionic ligand attached to the metal through the N_py-N-S chelating system and formation of hexacoordinated tin complexes. The crystal structures of 1-3, 5 and 6 show that the geometry around the metal is a distorted octahedron formed by the thiosemicarbazone and either chlorides or chlorides and phenyl groups. The crystal structure of 4 reveals the presence of and trans [Ph₂SnCl₄]²⁻.     

Antimony(V) catecholato complexes based on 4,5-dialkylsubstituted o-benzoquinone. The spectroscopic and electrochemical studies. Crystal structure of [Ph4Sb][Ph2Sb(4,5-Cat)2]

Triphenylantimony(III) and triethylantimony(III) readily react with 4,5-(1,1,4,4-tetramethyl-butane-1,4-diyl)-o-benzoquinone to form catecholato complexes R₃Sb(4,5-Cat) (R = Ph (1), Et (2); 4,5-Cat is dianionic 4,5-(1,1,4,4-tetramethyl-butane-1,4-diyl)-catecholate). In polar solvents (CHCl₃, acetone) complex 1 transforms easily to ionic complex compound [Ph₄Sb]⁺[Ph₂Sb(4,5-Cat)₂]⁻ (3) with diphenyl-bis-[4,5-(1,1,4,4-tetramethyl-butane-1,4-diyl)-catecholato]antimony(V) complex anion. Complexes were characterized by IR, ¹H, ¹³C NMR spectroscopy, cyclic voltammometry. Molecular structure of 3·CHCl₃ was confirmed by X-ray analysis. Cyclic voltammometry of 1 and 3 shows that both complexes undergo reversible one-electron oxidation to quite stable paramagnetic o-semiquinonato species [Ph₃Sb(4,5-SQ)]⁺ and [Ph₂Sb(4,5-SQ)(4,5-Cat)] (0.75 and 0.49 V in CH₂Cl₂ vs. Ag/AgCl/KCl, respectively).     

Oxidative addition reaction of o-quinones to triphenylantimony: novel triphenylantimony catecholate complexes

New catecholate Sb(V) complexes triphenyl(3,6-di-tert-butylcatecholato)antimony(V) Ph₃Sb(3,6-DBCat) (1) and triphenyl(perchloroxanthrenecatecholato)antimony(V) Ph₃Sb(^OXCat_Cl) (2) were synthesized by the oxidative addition reaction of corresponding o-quinones (3,6-di-tert-butyl-o-benzoquinone and perchloroxanthrenequinone-2,3) with triphenylantimony. Catecholates 1 and 2 can alternatively be synthesized by reacting the appropriate thallium catecholate with triphenylantimony dichloride. The oxidative addition reaction of an equimolar ratio of 4,4′-di-(3-methyl-6-tert-butyl-o-benzoquinone) and triphenylantimony yielded 4-(2-methyl-5-tert-butyl-cyclohexadien-1,5-dion-3,4-yl)-(3-methyl-6-tert-butyl-catecholato)triphenylantimony(V) Ph₃Sb(Cat-Q) (3); in the case of a 1:2 molar ratio, complex 4,4′-di-[(3-methyl-6-tert-butyl-catecholato)triphenylantimony(V)] Ph₃Sb(Cat-Cat)SbPh₃ (4) resulted. Complexes 1-4 were characterized by IR- and ¹H NMR spectroscopy. Molecular structures of 1, 2 and 4 were determined by X-ray crystallography to be a distorted tetragonal-pyramidal.     

Synthesis and structure of highly substituted pyrazole ligands and their complexes with platinum(II) and palladium(II) metal ions

Reaction of 3-methoxycarbonyl-2-methyl- or 3-dimethoxyphosphoryl-2-methyl-substituted 4-oxo-4H-chromones 1 with N-methylhydrazine resulted in the formation of isomeric, highly substituted pyrazoles 4 (major products) and 5 (minor products). Intramolecular transesterification of 4 and 5 under basic conditions led, respectively, to tricyclic derivatives 7 and 8. The structures of pyrazoles 4a (dimethyl 2-methyl-4-oxo-4H-chromen-3-yl-phosphonate) and 4b (methyl 4-oxo-2-methyl-4H-chromene-3-carboxylate) were confirmed by X-ray crystallography. Pyrazoles 4a and 4b were used as ligands (L) in the formation of ML₂Cl₂ complexes with platinum(II) or palladium(II) metal ions (M). Potassium tetrachloroplatinate(II), used as the metal ion reagent, gave both trans-[Pt(4a)₂Cl₂] and cis-[Pt(4a)₂Cl₂], complexes with ligand 4a, and only cis-[Pt(4b)₂Cl₂] isomer with ligand 4b. Palladium complexes were obtained by the reaction of bis(benzonitrile)dichloropalladium(II) with the test ligands. trans-[Pd(4a)₂Cl₂] and trans-[Pd(4b)₂Cl₂] were the exclusive products of these reactions. The structures of all the complexes were confirmed by IR, ¹H NMR and FAB MS spectral analysis, elemental analysis and Kurnakov tests.     

Synthesis and characterisation of six Fe(II or III), Co(II) or Zr(IV) complexes containing the ligand [CH(SiMe2R)P(Ph)2NSiMe3] (R = Me, NEt2) and of [Co{N(SiMe3)C(Ph)C(H)P(Ph)2NSiMe3}2]

The C,N-(trimethylsilyliminodiphenylphosphoranyl)silylmethylmetal complexes [Fe(L)₂] (3), [Co(L)₂] (4), [ZrCl₃(L)]·0.83CH₂Cl₂ (5), [Fe(L)₃] (6), [Fe(L′)₂] (7) and [Co(L′)₂] (8) have been prepared from the lithium compound Li[CH(SiMe₂R)P(Ph)₂NSiMe₃] [1a, (R = Me) {≡ Li(L)}; 1b, (R = NEt₂) {≡ Li(L′)}] and the appropriate metal chloride (or for 7, FeCl₃). From Li[N(SiMe₃)C(Ph)C(H)P(Ph)₂NSiMe₃] [≡ Li(L″)] (2), prepared in situ from Li(L) (1a) and PhCN, and CoCl₂ there was obtained bis(3-trimethylsilylimino- diphenylphosphoranyl-2-phenyl-N-trimethylsilyl-1-azaallyl-N,N′)cobalt(II) (9). These crystalline complexes 3-9 were characterised by their mass spectra, microanalyses, high spin magnetic moments (not 5) and for 5 multinuclear NMR solution spectra. The X-ray structure of 3 showed it to be a pseudotetrahedral bis(chelate), the iron atom at the spiro junction.     

Synthesis and reactivity of rhodium fluoro complexes

[RhH(CO)(PPh₃)₂] (1) reacts with Et₃N·3HF to give the fluoro compound [RhF(CO)(PPh₃)₂] (2). In a comparable reaction [RhF(PEt₃)₃] (5) has been obtained from [RhH(PEt₃)₃] (3) or [RhH(PEt₃)₄] (4) with substoichiometric amounts of Et₃N·3HF in THF. If the latter reaction is carried out in benzene, the complexes 5, cis-mer-[Rh(H)₂F(PEt₃)₃] (6) and cis-fac-[Rh(H)₂F(PEt₃)₃] (7) are obtained. Treatment of 5 with HCl in ether effects the generation of [RhCl(PEt₃)₃] (8) and the bifluoride compound [Rh(FHF)(PEt₃)₃] (9), which can be converted into 5 in the presence of Et₃N and Cs₂CO₃. Treatment of 5 with HSiR₂Ph (R=Ph, Me) leads to the formation of 3 and the rhodium(III) silyl complexes fac-[Rh(H)₂(SiR₂Ph)(PEt₃)₃] (10: R=Ph, 11: R=Me).     

Synthesis,characterization, crystal structures, in vitro and in vivo antitumor activity of palladium(II) and zinc(II) complexes with 2-formyl and 2-acetyl pyridine N(4)-1-(2-pyridyl)-piperazinyl thiosemicarbazone

The present paper includes synthesis and spectral characterization of the novel prepared palladium(II) and zinc(II) complexes with 2-formyl pyridine N(4)-1-(2-pyridyl)-piperazinyl thiosemicarbazone, HFo4Npypipe, 1 and the 2-acetyl pyridine N(4)-1-(2-pyridyl)-piperazinyl thiosemicarbazone, HAc4Npypipe, 2. The Pd(II) complexes [PdCl(Fo4Npypipe)], 3, [PdCl(Ac4Npypipe)], 4 and the Zn(II) complexes [ZnCl₂(Fo4Npypipe)], 5 and [ZnCl₂(Ac4Npypipe)], 6 have been characterized by elemental analyses and spectroscopic studies. The crystal structure of the complexes [PdCl(Fo4Npippy)], 3 and [PdCl(Ac4Npippy)], 4, have been solved by single-crystal X-ray diffraction. The electronic, IR, UV/Vis, and NMR spectroscopic data of the complexes are reported. The results of the cytotoxic activity of 1–6 have been evaluated in vitro against the cells of three human cancer cell lines: MCF-7, T24, A-549 and a mouse L-929 (a fibroblast-like cell line cloned from strain L). For selected compounds 2 and 6 the acute toxicity and antitumor activity were evaluated on leukemia P388-bearing mice. The Zn(II) compounds 5 and 6 are considered as agents with potential antitumor activity, and can therefore be candidates for further stages of screening in vitro and/or in vivo.     

Aminobis(phenolate)s of imidomolybdenum(VI) and -tungsten(VI)

The reactions of trans-[MoO(ONO^Me)Cl₂] 1 (ONO^Me = methylamino-N,N-bis(2-methylene-4,6-dimethylphenolate) dianion) and trans-[MoO(ONO^tBu)Cl₂] 2 (ONO^tBu = methylamino-N,N-bis(2-methylene-4-methyl-6-tert-butylphenolate) dianion) with PhNCO afforded new imido molybdenum complexes trans-[Mo(NPh)(ONO^Me)Cl₂] 3 and trans-[Mo(NPh)(ONO^tBu)Cl₂] 4, respectively. As analogous oxotungsten starting materials did not show similar reactivity, corresponding imido tungsten complexes were prepared by the reaction between [W(NPh)Cl₄] with aminobis(phenol)s. These reactions yielded cis- and trans-isomers of dichloro complexes [W(NPh)(ONO^Me)Cl₂] 5 and [W(NPh)(ONO^tBu)Cl₂] 6, respectively. The molecular structures of 4, cis-6 and trans-6 were verified by X-ray crystallography. Organosubstituted imido tungsten(VI) complex cis-[W(NPh)(ONO^tBu)Me₂] 7 was prepared by the transmetallation reaction of 6 (either cis or trans isomer) with methyl magnesium iodide.     

Effect of ortho-substituents on the stereochemistry of 2-(o-substituted phenyl)-1H-imidazoline-palladium complexes

Palladium complexes composed of [Pd(Ln)₂Cl₂] (n = 1, 2, 3, 4, 6), [L5a]₂[PdCl₄] and [Pd(L5b)₂], where L1 = 4,5-dihydro-2-phenyl-1H-imidazole (=2-phenyl-1H-imidazoline), L2 = 2-(o-fluorophenyl)-1H-imidazoline, L3 = 2-(o-methylphenyl)-1H-imidazoline, L4 = 2-(o-tert-butylphenyl)-1H-imidazoline, L5a = 2-(o-hydroxyphenyl)-1H-imidazolinium, L5b = 2-(1H-imidazolin-2-yl)phenolate, and L6 = 2-(o-methylphenyl)-1H-imidazole, were synthesized. Molecular structures of the isolated palladium complexes were characterized by single crystal X-ray diffraction analysis. The effect of ortho-substituents on the phenyl ring on trans-chlorine geometry was noted for complexes [Pd(L1)₂Cl₂] 1a and 1b, [Pd(L2)₂Cl₂] 2 and [Pd(L6)₂Cl₂] 6, whereas cis-chlorine geometry was observed for [Pd(L3)₂Cl₂] 3 and [Pd(L4)₂Cl₂] 4. PdCl₂ reacts with 2-(o-hydroxyphenyl)-1H-imidazoline in DMF to give [L5a]⁺ and [L5b]^- so that [L5a]₂[PdCl₄] 5a and [Pd(L5b)₂] 5b were obtained. In complex 5b, as an N,O-bidentate ligand, two ligands L5b coordinated with the central Pd(II) ion in the trans-form. The coordination of PdCl₂ with 2-(o-hydroxyphenyl)-1H-imidazolines in solution was investigated by NMR spectroscopy.     

Ruthenium(III) and iridium(III) complexes with nicotine

A new chloride-dimethylsulfoxide-ruthenium(III) complex with nicotine trans-[Ru^IIICl₄(DMSO)[H-(Nicotine)]] (1) and three related iridium(III) complexes; [H-(Nicotine)]trans-[Ir^IIICl₄(DMSO)₂] (2), trans-[Ir^IIICl₄(DMSO)[H-(Nicotine)]] (3) and mer-[Ir^IIICl₃(DMSO)(Nicotine)₂] (4) have been synthesized and characterized by spectroscopic techniques and by single crystal X-ray diffraction (1, 2, and 4). Protonated nicotine at pyrrolidine nitrogen is present in complexes 1 and 3 while two neutral nicotine ligands are observed in 4. In these three inner-sphere complexes coordination occurs through the pyridine nitrogen. Moreover, in the outer-sphere complex 2, an electrostatic interaction is observed between a cationic protonated nicotine at the pyrrolidine nitrogen and the anionic trans-[Ir^IIICl₄(DMSO)₂]^¯ complex.     

Hydro- and chloro-substituted silyl- and silyl-η-amido-η-tetramethylcyclopentadienyl titanium complexes

Chlorosilyl-cyclopentadienyl titanium precursors [Ti(η⁵-C₅Me₄SiMeXCl)Cl₃] (X=H 2, Cl 3) were prepared by reaction of TiCl₄ with the trimethylsilyl derivatives of the corresponding cyclopentadienes. Methylation of these compounds with MgClMe under appropriate conditions afforded the methyl complexes [Ti(η⁵-C₅Me₄SiMe₂R)XMe₂] (R=H, X=Cl 5, Me 6; R=X=Me 7). Reactions of 2 and 3 with two equivalents of LiNH^tBu afforded the ansa-silyl-η-amido compounds [Ti{η⁵-C₅Me₄SiMeX(η¹-N^tBu)}Cl₂] (X=H 8, Cl 9). Methylation of 8 gave [Ti{η⁵-C₅Me₄SiMeH(η¹-N^tBu)}Me₂] 10. Complex 9 was also obtained by reaction of 8 with BCl₃, whereas the same reaction using alternative chlorinating agents (TiCl₄, HCl) resulted in deamidation to give 2, which was also converted into 3 by reaction with BCl₃. All of the new compounds were characterized by NMR spectroscopy and the molecular structures of 2 and 4 were determined by X-ray diffraction methods.     

Ruthenium and rhodium nitrosyl complexes containing dichalcogenoimidodiphosphinate ligands

Interaction of [Ru(NO)Cl₃(PPh₃)₂] with K[N(R₂PS)₂] in refluxing N,N-dimethylformamide afforded trans-[Ru(NO)Cl{N(R₂PS)₂}₂] (R = Ph (1), Prⁱ (2)). Reaction of [Ru(NO)Cl₃(PPh₃)₂] with K[N(Ph₂PSe)₂] led to formation of a mixture of trans-[Ru(NO)Cl{N(Ph₂PSe)₂}₂] (3) and trans-[Ru(NO)Cl{N(Ph₂PSe)₂}{Ph₂P(Se)NPPh₂}] (4). Reaction of Ru(NO)Cl₃ · xH₂O with K[N(Ph₂PO)₂] afforded cis-[Ru(NO)(Cl){N(Ph₂PO)₂}₂] (5). Treatment of [Rh(NO)Cl₂(PPh₃)₂] with K[N(R₂PQ)₂] gave Rh(NO){N(R₂PQ)₂}₂] (R = Ph, Q = S (6) or Se (7); R = Prⁱ, Q = S (8) or Se (9)). Protonation of 8 with HBF₄ led to formation of trans-[Rh(NO)Cl{HN(Prⁱ₂PS)₂}₂][BF₄]₂ (10). X-ray diffraction studies revealed that the nitrosyl ligands in 2 and 4 are linear, whereas that in 9 is bent with the Rh–N–O bond angle of 125.7(3)°.     

Syntheses, structures and intermolecular interactions of tetraorganoammonium, -phosphonium and -stibonium dimethyl- and diphenyltetrahaloantimonates

The syntheses and spectroscopic (NMR, MS) investigations of the antimonates [Ph₄P]⁺[Me₂SbCl₄]⁻ (1), [Me₄Sb]⁺[Me₂SbCl₄]⁻ (2), [Et₄N]⁺[Ph₂SbCl₄]⁻ (3), [Bu₄N]⁺[Ph₂SbCl₄]⁻ (4), [Me₄Sb]⁺[Ph₂SbCl₄]⁻ (5), [Et₃MeSb]⁺[Ph₂SbCl₄]⁻ (6), [Et₄N]⁺[Ph₂SbF₄]⁻ (7) and [Et₄N]⁺[Ph₂SbBr₄]⁻ (8) are reported. Halogen scrambling reactions of Et₄NBr or Ph₄EBr (E = P, Sb) with R₂SbCl₃ (R = Me, Ph) produce mixtures of compounds from which crystals of [Et₄N]⁺[Ph₂SbBr_1.24Cl_2.76]⁻ (9), [Et₄N]⁺[Ph₂SbBr_2.92Cl_1.08]⁻ (10) or [Ph₄Sb]⁺[Me₂SbCl₄]⁻ (11) were isolated. The crystal and molecular structures of 1 and 3-11 are reported.     

Syntheses, characterizations and crystal structures of new organoantimony(V) complexes with heterocyclic (S, N) ligand

Eight new organoantimony(V) complexes with 1-phenyl-1H-tetrazole-5-thiol [L¹H] and 2,5-dimercapto-4-phenyl-1,3,4-thiodiazole [L²H] of the type R_nSbL_5 − n (L = L¹: n = 4, R = n-Bu 1, Ph 2, n = 3, R = Me 3, Ph 4; L = L²: n = 4, R = n-Bu 5, Ph 6, n = 3, R = Me 7, Ph 8) have been synthesized. All the complexes 1-8 have been characterized by elemental, FT-IR, ¹H and ¹³C NMR analyses. Among them complexes 2, 6 and 8 have also been confirmed by X-ray crystallography. The structure analyses show that the antimony atoms in complexes 2 and 6 display a trigonal bipyramid geometry, while it displays a distorted capped trigonal prism in complex 8 with two intramolecular Sb?N weak interactions. Furthermore, the supramolecular structure of 2 has been found to consist of one-dimensional linear molecular chain built up by intermolecular C-H?N weak hydrogen bonds, while a macrocyclic dimer has been found in complex 6 linked by intermolecular C-H?S weak hydrogen bonds with head-to-tail arrangement. Interestingly, one-dimensional helical chain is recognized in complex 8, which is connected by intermolecular C-H?S weak hydrogen bonds.     

Syntheses, crystal structures and DFT studies of [Me3EM(CO)5] (E = Sb, Bi; M = Cr, W), cis-[(Me3Sb)2Mo(CO)4], and [Bu3BiFe(CO)4]

Syntheses of [Me₃SbM(CO)₅] [M = Cr (1), W (2)], [Me₃BiM(CO)₅] [M = Cr (3), W (4)], cis-[(Me₃Sb)₂Mo(CO)₄] (5), [^tBu₃BiFe(CO)₄] (6), crystal structures of 1-6 and DFT studies of 1-4 are reported.     

Synthesis, spectroscopy and structures of palladium(II) and platinum(II) complexes containing mercapto-o-carborane

The reactions of [M₂Cl₂(μ-Cl)₂(PMe₂Ph)₂] with mercapto-o-carboranes in the presence of pyridine afforded mono-nuclear complexes of composition, [MCl(SCb°R)(py)(PMe₂Ph)] (M = Pd or Pt; Cb° = o-C₂B₁₀H₁₀; R = H or Ph). The treatment of [PdCl₂(PEt₃)₂] with PhCb°SH yielded trans-[Pd(SCb°Ph)₂(PEt₃)₂] (4) which when left in solution in the presence of pyridine gave another substitution product, [Pd(SCb°Ph)₂(py)(PEt₃)] (5). The structures of [PdCl(SCb°Ph)(py)(PMe₂Ph)] (1), [Pd(SCb°Ph)₂(PEt₃)₂] (4) and [Pd(SCb^oPh)₂(py)(PEt₃)] (5) were established unambiguously by X-ray crystallography. The palladium atom in these complexes adopts a distorted square-planar configuration with neutral donor atoms occupying the trans positions. Thermolysis of [PdCl(SCb°)(py)(PMe₂Ph)] (2) in TOPO (trioctylphosphine oxide) at 200 °C gave nanocrystals of TOPO capped Pd₄S which were characterized by XRD pattern and SEM.     

Introduction of a phosphorus ylide moiety into [η-(ω-hydroxy)alkenyl]chromium(0) carbene complexes with Ph3PCCO and consecutive Wittig alkenations with 2-alkynals. Part 12: the chemistry of metallacyclic alkenylcarbene complexes

Ketenylidenetriphenylphosphorane, Ph₃PCCO (2), reacts selectively with the ω-hydroxy group of the alkene-carbene complexes (OC)₄CrC(η²-NMeCH₂CHCHCH₂OH)R¹ (1) (R¹=Me: (1a); Ph: (1b)) to give the acyl ylide terminated complexes (OC)₄CrC[(4,5-η²)-NMeCH₂CHCHCH₂O(O)C-CHPPh₃]R¹ (3) (R¹=Me: (3a); Ph: (3b)). Complexes 3 undergo Wittig alkenation reactions with aldehydes such as 2-alkynals, R²-CC-CHO (R²=H, SiMe₃, Ph), to give the corresponding 4Z, 9E-dien-11-ynes (OC)₄CrC[(4,5-η²)-NMeCH₂CHCHCH₂O(O)C-CHCH-CC-R²]R¹ (4-6) (R¹=Me, R²=H, SiMe₃, Ph: (4a-6a); R¹=Ph, R²=H, SiMe₃, Ph: (4b-6b)). All complexes were characterized in solution by one- and two-dimensional NMR spectroscopy (¹H, ¹³C, ²⁹Si, ³¹P, ¹H/¹H COSY, ¹³C/¹H HETCOR, ³¹P/³¹P EXSY).