Vanadium complexes with 2-pyridineformamide thiosemicarbazones: In vitro studies of insulin-like activity

Reaction of VOCl₂ with 2-pyridineformamide thiosemicarbazone (H2Am4DH) and its N(4)-methyl (H2Am4Me), N(4)-ethyl (H2Am4Et) and N(4)-phenyl (H2Am4Ph) derivatives in ethanol gave as products [VO(H2Am4DH)Cl₂] (1), [VO(H2Am4Me)Cl₂] · 1/2HCl (2), [VO(H2Am4Et)Cl₂] · HCl (3) and [VO(2Am4Ph)Cl] (4). Upon the dissolution of 1-4 in water, oxidation immediately occurs with the formation of [VO₂(2Am4DH)] (5), [VO₂(2Am4Me)] (6), [VO₂(2Am4Et)] (7) and [VO₂(2Am4Ph)] (8). The crystal and molecular structures of 5 and 6 were determined. Complexes 5-8 inhibited glycerol release in a similar way to that observed with insulin but showed a low enhancing effect on glucose uptake by rat adipocytes.     

Reactivity of platina-β-diketones towards chelating nitrogen and sulfur donors: formation of acyl(hydrido)platinum(IV) and acyl(chloro)platinum(II) complexes

The platina-β-diketone [Pt₂{(COMe)₂H}₂(μ-Cl)₂] (1) was found to react with chelating N,N-ligands 2(R^′NCR)C₅H₄N (R/R^′=Ph/OH, H/Ph, Me/Ph) to form acyl(hydrido)platinum(IV) complexes [Pt(COMe)₂Cl(H){2-(R^′NCR)C₅H₄N}] (R/R^′=Ph/OH 2a; H/Ph 2b; Me/Ph (2c)). Reactions of complex 1 with chelating S,S- and N,S-donors (RS-CH₂-CH₂-SR, 2-(RSCH₂)C₅H₄N, R=Et, Ph, t-Bu) afforded acyl(chloro)platinum(II) complexes [Pt(COMe)Cl(RSCH₂CH₂SR)] (R=Et, 3a; Ph, 3b; t-Bu, 3c) and [Pt(COMe)Cl{2-(RSCH₂)C₅H₄N}] (R=Et, 4a; Ph, 4b; t-Bu, 4c), respectively. All complexes were fully characterized by microanalysis, IR and NMR (¹H, ¹³C) spectroscopy. Furthermore, molecular structures of complexes 3b and 4b were determined by single-crystal X-ray diffraction analyses revealing close to square-planar configuration. In complex 4b the acetyl ligand is trans to pyridine N atom (configuration index SP-4-2). The reactions are discussed in terms of consecutive oxidative addition and reductive elimination reactions.     

N(4)-Tolyl-2-acetylpyridine thiosemicarbazones and their platinum(II,IV) and gold(III) complexes: cytotoxicity against human glioma cells and studies on the mode of action

Complexes [Au(2Ac4oT)Cl][AuCl₂] (1), [Au(H_py2Ac4mT)Cl₂]Cl·H₂O (2), [Au(H_py2Ac4pT)Cl₂]Cl (3), [Pt(H2Ac4oT)Cl]Cl (4), [Pt(2Ac4mT)Cl]·H₂O (5), [Pt(2Ac4pT)Cl] (6) and [Pt(L)Cl₂OH], L = 2Ac4mT (7), 2Ac4oT (8), 2Ac4pT (9) were prepared with N(4)-ortho- (H2Ac4oT), N(4)-meta- (H2Ac4mT) and N(4)-para- (H2Ac4pT) tolyl-2-acetylpyridine thiosemicarbazone. The cytotoxic activities of all compounds were assayed against U-87 and T-98 human malignant glioma cell lines. Upon coordination cytotoxicity improved in 2, 5 and 8. In general, the gold(III) complexes were more cytotoxic than those with platinum(II,IV). Several of these compounds proved to be more active than cisplatin and auranofin used as controls. The gold(III) complexes probably act by inhibiting the activity of thioredoxin reductase enzyme whereas the mode of action of the platinum(II,IV) complexes involves binding to DNA. Cells treated with the studied compounds presented morphological changes such as cell shrinkage and blebs formation, which indicate cell death by apoptosis induction.     

Iron Se-bonded mono-selenocarbonates CpFe(CO)2SeCO2R: the first selenocarbonate complexes

The reactivity of the iron selenide complex (μ-Se)[CpFe(CO)₂]₂ toward chloroformates, ROCOCl, has been studied and the products CpFe(CO)₂SeCO₂R [R=Me (1), Et (2), iso-Bu (3), Ph (4), 2-C₆H₄Cl (5), 4-C₆H₄Cl (6), and 4-C₆H₄NO₂ (7)] have been obtained. The novel complexes, 1-7, have been characterized by elemental analyses, IR and ¹H NMR spectroscopy. The solid state structure of CpFe(CO)₂SeCO₂Et, 2, was determined by an X-ray crystal structure analysis.     

Synthesis, characterizations, and crystal structures of triorganotin(IV) derivatives with areneseleninic acids

Six new triorganotin(IV) complexes, [R₃Sn(O₂SeC₆H₄Cl)]_n (R = Me 1; Ph 2), [R₃Sn(O₂SeC₆H₄Me)]_n (R = Me 3; Ph 4), [R₃Sn(O₂SeC₆H₄Bu)]_n (R = Me 5; Ph 6) have been synthesized by the reaction of 4-chlorobenzeneseleninic acid, p-Tolueneseleninic acid, and 4-tert-butylbenzeneseleninic acid with triorganotin(IV) chloride in the presence of sodium ethoxide. All of the complexes were characterized by elemental analysis, FT-IR, NMR (¹H, ¹³C, and ¹¹⁹Sn) spectroscopy, and X-ray crystallography. Crystal structures show that all of the complexes exhibit 1D infinite chain structures which are generated by the bidentate oxygen atoms and the five-coordinated tin centers.     

Syntheses and structures of vinyl and aryl derivatives of carbonyl halide iron complexes

cis,trans-Fe(CO)₂(PMe₃)₂(p-Y-C₆H₄)X [X=Br, Y=H (4a), MeO (4b), Cl (4c), F (4d), Me (4e); X=I, Y=H (5); X=Cl, Y=H (6)] and cis,trans-Fe(CO)₂(PMe₃)₂(σ-CHCH₂)X [X=Br (7); X=I (8); X=Cl (9)] are prepared by reacting dihalide complexes cis,trans,cis- Fe(CO)₂(PMe₃)₂X₂ [X=Br (1), X=I (2), X=Cl (3)] with Grignard reagents p-Y-C₆H₄-MgBr (Y=H, OMe, Cl, F, Me) or CH₂CH-MgBr and with lithium reagents PhLi, CH₂CH-Li. With both reagents, the reaction proceeds following two parallel pathways: one is the metallation reaction which yields alkyl derivatives, the other affords 17 electron complexes [Fe(CO)₂(PMe₃)₂X] via monoelectron reductive elimination. The influence of the halides and organometallic reagents on the yield of the metallation reaction is discussed. The solution structure of the complexes is assigned on the basis of IR and ¹H, ¹³C, ¹⁹F, ³¹P NMR spectra. The solid state structure of complexes 4a, 5 and 6 is determined by single crystal X-ray diffractometric methods.     

Synthesis and characterization of CpMCl(PR3)(S or W-η-butadienesulfonyl) compounds of rhodium and iridium

A metathesis reaction of [Cp^∗MCl₂(PR₃)] [M = Rh, R = Ph (1), Me (3); M = Ir, R = Ph (2), Me (4)] takes place in the presence of potassium butadienesulfinate (SO₂CHCHCHCH₂)K (9) to afford the mononuclear compounds [Cp^∗M(Cl)(PR₃)(η¹-SO₂CHCHCHCH₂)] [M = Rh, R = Ph (11S), (11W); M = Rh, R = Me (13S), (13W)] and [M = Ir, R = Ph (12S); M = Ir, R = Me (14S), (14W)] under different reaction conditions. The addition of PR₃ (R = Ph, Me) to Cp^∗Ir(Cl)[(1,2,5-η)-SO₂CHCHCHCH₂] (7) affords the corresponding iridium isomers 12S, 12W and 14S, in a non-selective reaction, along with the corresponding dichloride compounds 2 or 4. The ¹H and ¹³C{¹H} NMR data are consistent with the butadienesulfonyl ligands coordinated exclusively through the sulfur atom, and they show the presence of two isomers, described as the S and W conformers, which can be isolated separately. There is clear evidence that these isomers correspond to the kinetic and thermodynamic derivatives, respectively.     

The first 1,3,2-diazabora-[3]ferrocenophanes - molecular structures and dynamic behaviour in solution

Dilithiated 1,1^′-bis(trimethylsilylamino)ferrocene (1) reacts with aminoboron dihalides (2) X₂B-N(R^′)R [X=Br, R^′=R=Et (2a); X=Cl, R^′=Me, R=CH₂Ph (2b), X=Cl, R^′=Et, R=Ph (2c)] to give 2-amino-1,3,2-diazabora-[3]ferrocenophanes (3a-c) for the first time. The steric constraints exerted by the [3]ferrocenophane unit and the presence of the N-SiMe₃ groups cause rather different B-N bonding situations in these tri(amino)boranes. The boron atom has the choice between three nitrogen atoms for BN(pp)π bonding: in the cases of 3a and 3b, it prefers the NEt₂ and the N(Me)CH₂Ph group, respectively, over the N-SiMe₃ groups, whereas in 3c the N(Et)Ph group appears to be the weaker π-donor. This can be concluded from the X-ray structural analyses carried out for 3a and 3c, and from the low temperature ¹H, ¹³C, and ²⁹Si NMR spectra of 3a-3c.     

Triorganotin(IV) complexes of Schiff base derived from 6-amino-2-mercaptobenzothiazole: Synthesis, characterization and X-ray crystal structures

Nine triorganotin(IV) complexes of the type R₃SnL (L = L1 R = Me 1, Ph 2, PhCH₂3; L = L2 R = Me 4, Ph 5, PhCH₂6; L = L2 R = Me 7, Ph 8, PhCH₂9) have been obtained by reaction of new Schiff base HL1, HL2 or HL3 with triorganotin(IV) chloride in the presence of sodium ethoxide. All the complexes 1-9 were characterized by elemental, IR and NMR spectra analyses. Except for complexes 3, 4, 6, 9, the others were also characterized by X-ray crystallography diffraction analyses, which revealed that complexes 1, 2, 5, 7, 8 were four coordinated and displayed a capped tetrahedron.     

Synthesis, characterization and crystal structures of the organotin(IV) compounds with the Schiff base ligands of pyruvic acid thiophene-2-carboxylic hydrazone and salicylaldehyde thiophene-2-carboxylic hydrazone

A series of organotin (IV) compounds of the type [R₃SnL]₂, R is Me (1), Bu (2), [R₂SnL]₂, R is Ph (3), Me (4), Bu (5), L is pyruvic acid thiophene-2-carboxylic hydrazone, and R₂SnL, R is Me (6), Bu (7), Ph (8), L is salicylaldehyde thiophene-2-carboxylic hydrazone have been synthesized in 1:1 molar ratio. All compounds were characterized by elemental analysis, IR, ¹H NMR, ¹³C NMR and ¹¹⁹Sn NMR spectra. The crystal structure of compounds 1, 3, 4, 8 have been determined by X-ray single crystal diffraction analyses, study found that the compounds 1 and 3 are rendered one-dimensional chain structure and the tin atoms are five-coordinated in a distorted trigonal-bipyramidal geometry. The compound 4 has a dimeric structure and the central tin atom is rendered seven-coordinate in a distorted pentagonal-bipyramid configuration. While the compound 8 is a monomer in which the tin atom adopts five-coordinated in distorted trigonal-bipyramidal geometry.     

Synthesis and reactivity with amines of new diiron alkynyl methoxy carbene complexes

The new diiron alkynyl methoxy carbene complexes [Fe₂{μ-CN(Me)(R)}(μ-CO)(CO){C(OMe)CCR′}(Cp)₂]⁺ (R = 2,6-Me₂C₆H₃ (Xyl), R′ = Tol, 3a; R = Xyl, R′ = Ph, 3b; R = Xyl, R′=Buⁿ, 3c; R = Xyl, R′=SiMe₃, 3d; R = Me, R′ = Tol, 3e; R = Me, R′ = Ph, 3f) are obtained in two steps by addition of R′CCLi (R′ = Tol, Ph, Buⁿ, SiMe₃) to the carbonyl aminocarbyne complexes [Fe₂{μ-CN(Me)(R)}(μ-CO)(CO)₂(Cp)₂]⁺ (R = Xyl, 1a; Me, 1b), followed by methylation of the resulting alkynyl acyl compounds [Fe₂{μ-CN(Me)(R)}(μ-CO)(CO){C(O)CCR′}(Cp)₂] (R = Xyl, R′ = Tol, 2a; R = Xyl, R′ = Ph, 2b; R = Xyl, R′ = Buⁿ, 2c; R = Xyl, R′ = SiMe₃, 2d; R = Me, R′ = Tol, 2e; R = Me, R′ = Ph, 2f). Complexes 3 react with secondary amines (i.e., Me₂NH, C₅H₁₀NH) to give the 4-amino-1-metalla-1,3-dienes [Fe₂{μ-CN(Me)(R)}(μ-CO)(CO){C(OMe)CHC(R′)(NMe₂)}(Cp)₂]⁺ (R = Xyl, R′ = Tol, 4a; R = Xyl, R′ = Ph, 4b; R = Me, R′ = Ph, 4c) and [Fe₂{μ-CN(Me)(Xyl)}(μ-CO)(CO){C(OMe)CHC(Tol)(NC₅H₁₀)}(Cp)₂]⁺, 5. The addition occurs stereo-selectively affording only the E-configured products. Analogously, addition of primary amines R′NH₂ (R′ = Ph, Et, Prⁱ) affords the 4-(NH-amino)-1-metalla-1,3-diene complexes [Fe₂{μ-CN(Me)(Xyl)}(μ-CO)(CO){C(OMe)CHC(R)(NHR′)}(Cp)₂]⁺ (R = Ph, 6a; Et, 6b; Prⁱ, 6c). In the case of 6a, only the E isomer is formed, whereas a mixture of the E and Z isomers is present in the case of 6b,c, with prevalence of the latter. Moreover, the two isomeric forms exist under dynamic equilibrium conditions, as shown by VT NMR studies. Complexes 6 are deprotonated by strong bases (e.g., NaH) resulting in the formation of the neutral vinyl imine complexes [Fe₂{μ-CN(Me)(Xyl)}(μ-CO)(CO){C(OMe)CHC(NR)(Tol)}(Cp)₂] (R = Ph, 7a; Et, 7b; Prⁱ, 7c); the reaction can be reverted by addition of strong acids. X-ray crystal structures have been determined for 3a[CF₃SO₃] · Et₂O, 4c[CF₃SO₃], 6a[BF₄] · CH₂Cl₂, 6c[CF₃SO₃] · 0.5Et₂O and 7a · CH₂Cl₂.     

Reaction of R(Ph)SnCl2(R=Me, Et) with 2,6-diacetylpyridine bis(thiosemicarbazone) (H2DAPTSC): the crystal structures of [Me(Ph)Sn(HDAPTSC)]Cl · 1.25 MeOH and [Et(Ph)Sn(H2DAPTSC)]Cl2 · MeOH · H2O

The reactions of Me(Ph)SnCl₂ and Et(Ph)SnCl₂ with 2,6-diacetylpyridine bis(thiosemicarbazone) (H₂DAPTSC) afforded the complexes [Me(Ph)Sn(HDAPTSC)]Cl · 1.25MeOH (1) and [Et(Ph)Sn(H₂DAPTSC)]Cl₂ · MeOH · H₂O (2), respectively. Single-crystal X-ray crystallography showed that in both complexes the ligand, monodeprotonated in 1 and neutral in 2, is S(1),S(2),N(3),N(4),N(5)-coordinated, and the coordination geometry around the metal can be described as a distorted pentagonal bipyramid with the aryl and alkyl groups in axial positions. ¹H and ¹¹⁹Sn NMR studies of solution in DMSO suggest that 2 dissociates completely in this solvent, while 1 evolves to the new complex [Me(Ph)Sn(DAPTSC)], with release of H₂DAPTSC and Me(Ph)SnCl₂. These conclusions were also supported by conductivity measurements.     

Bis(pyrazolyl) palladium(II), platinum(II) and gold(III) complexes: Syntheses, molecular structures and substitution reactions with l-cysteine

A series of pyrazolyl palladium(II), platinum(II) and gold(III) complexes, [PdCl₂(3,5-R₂bpza)] {R = H (1), R = Me (2), bpza = bis-pyrazolyl acetic acid}, [PtCl₂(3,5-R₂bpza)] {R = H (3a), R = Me (4)}, [AuCl₂(3,5-R₂bpza)]Cl {R = H (5a), R = Me (6a)} and [PdCl₂(3,5-R₂bpzate)] {R = Me (7)} have been synthesised and structurally characterised. Single crystal X-ray crystallography showed that the pyrazolyl ligands exhibit N^N-coordination with the metals. Anticancer activities of six complexes 1-6a were investigated against CHO cells and were found to have low activities. Substitution reactions of selected complexes 1, 2, 3a and 5a with l-cysteine show that the low anticancer activities compounds and that the rate of substitution with sulfur-containing compounds is not the cause of the low anticancer activities.     

Synthesis and reactivity of five- and six-coordinate hydrido(vinyl) iridium(III) complexes

The reaction of the dihydrido iridium(III) precursor [IrH₂(Cl)(PiPr₃)₂] (5) with internal alkynes RCC(CO₂Me) (R = Me, CO₂Me) afforded the five-coordinate hydrido(vinyl) complexes [IrH(Cl){(E)-C(R)CH(CO₂Me)}(PiPr₃)₂] (6, 7), via insertion of the alkyne into one of the IrH bonds. Compounds 6 and 7 are also accessible by careful hydrogenation of the alkyne iridium(I) derivatives trans-[IrCl{RCC(CO₂Me)}(PiPr₃)₂] (9, 10), the latter being prepared from in situ generated trans-[IrCl(C₈H₁₄)(PiPr₃)₂] and RCC(CO₂Me). UV irradiation of 6 (R = CO₂Me) led to the formation of the isomer [IrH(Cl){κ²(C,O)-C(CO₂Me)CHC(OMe)O}(PiPr₃)₂] (3) having the vinyl ligand coordinated in a bidentate fashion. While 6 reacted with acetonitrile and CO to afford the six-coordinate iridium(III) compounds [IrH(Cl){(E)-C(CO₂Me)CH(CO₂Me)}(L′)(PiPr₃)₂] (11, 12), treatment of 6 with LiC₅H₅ gave the half-sandwich-type complex [(η⁵-C₅H₅)IrH{(E)-C(CO₂Me)CH(CO₂Me)}(PiPr₃)] (13) by, the loss of one PiPr₃. The reaction of 3 with CO under pressure resulted in the formation of [IrH(Cl){(Z)-C(CO₂Me)CH(CO₂Me)}(CO)(PiPr₃)₂] (14) in which, in contrast to the stereoisomer 12, the two CO₂Me substituents are trans disposed.     

Synthesis and structures of aryloxo- and binaphthoxogermanium(IV) alkyl iodide complexes

The germanium(II) aryloxide complexes (S)-[Ge{O₂C₂₀H₁₀-(SiMe₂Ph)₂-3,3′}{NH₃}] (1) and [Ge(OC₆H₃Ph₂-2,6)₂] (2) react with either Bu^tI or MeI to yield the corresponding germanium(IV) compounds (S)-[Ge{O₂C₂₀H₁₀-(SiMe₂Ph)₂-3,3′}{Bu^t}{I}] (3), (S)-[Ge{O₂C₂₀H₁₀-(SiMe₂Ph)₂-3,3′}{Me}{I}] (4), [Ge(OC₆H₃Ph₂-2,6)₂(Bu^t)(I)] (5), and [Ge(OC₆H₃Ph₂-2,6)₂(Me)(I)] (6). Compound 6 reacts with 2,6-diphenylphenol to yield [Ge(OC₆H₃Ph₂-2,6)₃(Me)] (7), while 3-5 do not. The X-ray crystal structures of 3-5 and 7 were determined, and 3-5 represent the first structurally characterized germanium(IV) species having germanium bound to both oxygen and iodine.     

Synthesis and characterization of sterically hindered tris(pyrazolyl)borate Ni complexes

Addition of KTp^Ph2 to a solution of NiX₂ (X = Cl, Br, NO₃, OAc and acac) or NiBr(NO)(PPh₃)₂ in THF yields the structurally characterized series [NiCl(Hpz^Ph2)Tp^Ph2] (1) and [NiXTp^Ph2] (X = Br 2, NO 3, NO₃4, OAc 5 and acac 6) including the first example of a tris(pyrazolyl)borate nickel nitrosyl complex. IR spectroscopy confirms that all the Tp^Ph2 ligands are κ³ coordinated and that the NO ligand in 3 is linearly bound. Electronic spectra are consistent with four- or five-coordinate species in solution. NMR spectroscopic studies indicate that the complexes are paramagnetic, with the exception of 3. This is confirmed by magnetic susceptibility studies, which suggest that complexes 1, 2 and 4-6 are paramagnetic with two unpaired electrons. X-ray crystallographic studies of 5 reveal a distorted trigonal bipyramidal nickel centre with a symmetrically coordinated acetate ligand.     

Synthesis and structure of products of interaction of H[AuCl4] with H2DMG and pyridine

Two complexes of gold of the compositions [Au(DMG)ClPy] (1) and [AuCl₂Py₂][AuCl₄] · 2[AuCl₃Py] (2), where H₂DMG was dimethylglyoxime, were synthesized as the products of interaction of H[AuCl₄] · 4H₂O with H₂DMG in the presence of pyridine and characterized by X-ray structural analysis. It was shown that depending on the synthetic conditions, the final product represents a molecular complex 1 or an ionic complex 2, in the latter one the charged and neutral species being combined via Au?Cl or Au?Au interactions.     

Diiron and diruthenium aminocarbyne complexes containing pseudohalides: stereochemistry and reactivity

Acetonitrile is easily displaced from [Fe₂{μ-CN(Me)(R)}(μ-CO)(CO)(MeCN)(Cp)₂][SO₃CF₃] (R = 2,6-Me₂C₆H₃ (Xyl) (1a); Me (1b)) upon stirring in THF at room temperature in the presence of [NBu₄][SCN]. The resulting complexes trans-[Fe₂{μ-CN(Me)(R)}(μ-CO)(CO)(NCS)(Cp)₂] (R = Xyl (trans-2a); Me (trans-2b)) are completely isomerised to cis-[Fe₂{μ-CN(Me)(R)}(μ-CO)(CO)(NCS)(Cp)₂] (R = Xyl (cis-2a); Me (cis-2b)) when heated at reflux temperature. Similarly, the complexes cis-[M₂{μ-CN(Me)(R)}(μ-CO)(CO)(NCO)(Cp)₂] (M = Fe, R = Me (4a); M = Ru, R = Xyl (4b); M = Ru, R = Me (4c)) and cis-[M₂{μ-CN(Me)(R)}(μ-CO)(CO)(N₃)(Cp)₂] (M = Fe, R = Xyl (5a); M = Fe, R = Me (5b); M = Ru, R = Xyl (5c)) can be obtained by heating at reflux temperature a THF solution of [M₂{μ-CN(Me)(R)}(μ-CO)(CO)(MeCN)(Cp)₂][SO₃CF₃] (M = Fe, R = Xyl (1a); M = Fe, Me (1b); M = Ru, R = Xyl (1c); M = Ru, R = Me (1d)) in the presence of NaNCO and NaN₃, respectively. The reactions of 5 with MeO₂CCCCO₂Me, HCCCO₂Me and (NC)(H)CC(H)(CN) afford the triazolato complexes [M₂{μ-CN(Me)(R)}(μ-CO)(CO){N₃C₂(CO₂Me)₂}(Cp)₂] (M = Fe, R = Xyl (6a); M = Fe, R = Me (6b); M = Ru, R = Xyl (6c)), [M₂{μ-CN(Me)(R)}(μ- CO)(CO){N₃C₂(H)(CO₂Me)}(Cp)₂] (M = Fe, R = Me (7a); M = Ru, R = Xyl (7b)) and [Fe₂{μ-CN(Me)(Xyl)}(μ-CO)(CO){N₃C₂(H)(CN)}(Cp)₂] (8), respectively. The asymmetrically substituted triazolato complexes 7-8 are obtained as mixtures of N(1) and N(2) bonded isomers, whereas 6 exists only in the N(2) form. Methylation of 6-8 results in the formation of the triazole complexes [Fe₂{μ-CN(Me)(Xyl)}(μ-CO)(CO){N₃(Me)C₂(CO₂Me)₂}(Cp)₂][CF₃SO₃] (9), [M₂{μ-CN(Me)(R)}(μ-CO)(CO){N₃(Me)C₂(H)(CO₂Me)}(Cp)₂][CF₃SO₃] (M = Fe, R = Me (10a); M = Ru, R = Xyl (10b)) and [Fe₂{μ-CN(Me)(Xyl)}(μ-CO)(CO){N₃(Me)C₂(H)(CN)}(Cp)₂][CF₃SO₃], 11. The crystal structures of trans-2b, 4b · CH₂Cl₂, 5a, 6b · 0.5CH₂Cl₂ and 8 · CH₂Cl₂ have been determined.     

Synthesis, characterization and cytotoxic properties of platinum(II) complexes containing the nucleosides adenosine and cytidine

Cytidine (cyt) and adenosine (ado) react with cis-[L₂Pt(μ-OH)]₂(NO₃)₂ (L = PMe₃, PPh₃) in various solvents to give the nucleoside complexes cis-[L₂Pt{cyt(− H),N³N⁴}]₃(NO₃)₃ (L = PMe₃, 1),cis-[L₂Pt{cyt(− H),N⁴}(cyt,N³)]NO₃ (L = PPh₃, 2), cis-[L₂Pt{ado(− H),N¹N⁶}]₂(NO₃)₂ (L = PMe₃, 3) and cis-[L₂Pt{ado(− H),N⁶N⁷}]NO₃ (L = PPh₃, 4). When the condensation reaction is carried out in solution of nitriles (RCN, R = Me, Ph) the amidine derivatives cis-[(PPh₃)₂PtNH=C(R){cyt(− 2H)}]NO₃ (R = Me, 5a; R = Ph, 5b) and cis-[(PPh₃)₂PtNH=C(R){ado(− 2H)}]NO₃ (R = Me, 6a: R = Ph, 6b) are quantitatively formed. The coordination mode of these nucleosides, characterized in solution by multinuclear NMR spectroscopy and mass spectrometry, is similar to that previously observed for the nucleobases 1-methylcytosine (1-MeCy) and 9-methyladenine (9-MeAd). The cytotoxic properties of the new complexes, and those of the nucleobase analogs, cis-[(PPh₃)₂PtNH=C(R){1-MeCy(− 2H)}]NO₃ (R = Me, 7a: R = Ph, 7b), cis-[(PPh₃)₂PtNH=C(R){9-MeAd(− 2H)}]NO₃ (R = Me, 8a: R = Ph, 8b) have been investigated in a wide panel of human cancer cells. Interestingly, whereas the Pt(II) nucleoside complexes (1-4) did not show appreciable cytotoxicity, the corresponding amidine derivatives (7a, 7b, 8a, 8b, 5b, and 6b) exhibited a significant in vitro antitumor activity.     

An efficient route to substituted 1-silacyclopent-2-enes and 1-silacyclohex-2-enes via consecutive 1,2-hydroboration and 1,1-organoboration

The reaction of alkyn-1-yl(vinyl)silanes R₂Si(CCR¹)CHCH₂ [R = Me (1), Ph (2); R¹ = ^tBu (a), Ph (b), SiMe₃ (c)] with 9-borabicyclo[3.3.1]nonane in a 1:1 ratio affords the 1-silacyclopent-2-ene derivatives 4a-c (R = Me) and 5a-c (R = Ph) as a result of selective intermolecular 1,2-hydroboration of the vinyl group, followed by intramolecular 1,1-organoboration of the alkynyl substituent. The analogous reaction sequence converts the alkyn-1-yl(allyl)dimethylsilanes 3a,c into the 1-silacyclohex-2-ene derivatives 7a,c. All reactions were monitored by ²⁹Si NMR spectroscopy and the structural assignment of the final products was based on multinuclear magnetic resonance data (¹H, ¹¹B, ¹³C and ²⁹Si NMR). The molecular structure of 6a was determined by X-ray analysis.