Crystal and solution structures of di-n-butyltin(IV) complexes of 5-[(E)-2-(4-methoxyphenyl)-1-diazenyl]quinolin-8-ol and benzoic acid derivatives: En route to elegant self-assembly via modulation of the tin coordination geometry

Reactions of ⁿBu₂SnCl(L¹) (1), where L¹ = acid residue of 5-[(E)-2-(4-methoxyphenyl)-1-diazenyl]quinolin-8-ol, with various substituted benzoic acids in refluxing toluene, in the presence of triethylamine, yielded dimeric mixed ligand di-n-butyltin(IV) complexes of composition [ⁿBu₂Sn(L¹)(L^2-6)]₂ where L² = benzene carboxylate (2), L³ = 2-[(E)-2-(2-hydroxy-5-methylphenyl)-1-diazenyl]benzoate (3), L⁴ = 5-[(E)-2-(4-methylphenyl)-1-diazenyl]-2-hydroxybenzoate (4), L⁵ = 2-{(E)-4-hydroxy-3-[(E)-4-chlorophenyliminomethyl]-phenyldiazenyl}benzoate (5) and L⁶ = 2-[(E)-(3-formyl-4-hydroxyphenyl)-diazenyl]benzoate (6). All complexes (1-6) have been characterized by elemental analyses, IR, ¹H, ¹³C and ¹¹⁷Sn NMR and ¹¹⁹Sn Mössbauer spectroscopy and their structures were determined by X-ray crystallography, complemented by ¹¹⁷Sn CP-MAS NMR spectroscopy studies in the solid state. The crystal structure of 1 reveals a distorted trigonal bipyramidal coordination geometry around the Sn-atom where the Cl- and N-atoms of ligand L¹ occupy the axial positions. In complexes 2-5, the molecules are centrosymmetric dimers in which the Sn-atoms are connected by asymmetric μ-O bridges through the quinoline O-atom to give an Sn₂O₂ core. The differences in the Sn-O bond lengths within the bridge range from 0.28 to 0.48 Å, with the longer of the Sn-O distances being in the range 2.56-2.68 Å and the most symmetrical bridge being in 5. The carboxylate group is almost symmetrically bidentate coordinated to the tin atom in 5 (Sn-O distances of 2.327(2) and 2.441(2) Å), unlike the other complexes in which the distance of the carboxylate carbonyl O-atom from the tin atom is in the range 2.92-3.03 Å. The structure of 5 displays a more regular pentagonal bipyramidal coordination geometry about each tin atom than in 2-4. In contrast, the centrosymmetric dimeric structure of 6 involves asymmetric carboxylate bridges, resulting in a different Sn₂C₂O₄ motif. The Sn-O bond lengths in the bridge differ by about 0.6 Å, with the longer distance involving the carboxylate carbonyl O-atom (2.683(2) and 2.798(2) Å for two molecules in the asymmetric unit). The carboxylate carbonyl O-atom has a second, even longer intramolecular contact to the Sn-atom to which the carboxylate group is primarily coordinated, with these Sn?O distances being as high as 3.085(2) and 2.898(2) Å. If the secondary interactions are considered, all the di-n-butyltin(IV) complexes (2-6) display a distorted pentagonal bipyramidal arrangement about each tin atom in which the n-butyl groups occupy the axial positions.     

Synthesis and characterization of bis[dicarboxylatotetraorganodistannoxane] units involving 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoic acids: An investigation of structures by X-ray diffraction, NMR, electrospray ionisation MS and assessment of in vitro cytotoxicity

Reactions of 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoic acids (LHH′, where the aryl group is an R-substituted phenyl ring such that for L¹HH′: R = H; L²HH′: R = 2′-CH₃; L³HH′: R = 3′-CH₃; L⁴HH′: R = 4′-CH₃; L⁵HH′: R = 4′-Cl; L⁶HH′: R = 4′-Br) with ⁿBu₂SnO in a 1:1 molar ratio yielded complexes of composition {[ⁿBu₂Sn(LH)]₂O}₂. The complexes have been characterized by ¹H, ¹³C, ¹¹⁹Sn NMR, ESI-MS, IR and ^119mSn Mössbauer spectroscopic techniques in combination with elemental analyses. The crystal structures of {[ⁿBu₂Sn(L¹H)]₂O}₂ (1), {[ⁿBu₂Sn(L⁴H)]₂O}₂ (4), {[ⁿBu₂Sn(L⁵H)]₂O}₂ (5) and {[ⁿBu₂Sn(L⁶H)]₂O}₂ (6) were determined. The compounds are centrosymmetric tetranuclear bis(dicarboxylatotetrabutyldistannoxane) complexes containing a planar Sn₄O₂ core in which two μ₃-oxo O-atoms connect an Sn₂O₂ ring to two exocyclic Sn-atoms. The four carboxylate ligands display two different modes of coordination where both modes involve bridging of two structurally distinct Sn-atoms. The solution structures were confirmed by ¹¹⁹Sn NMR spectroscopy by observing two tin resonances in compounds 1, and 4-6. The observed difference between the two tin resonances was about 3 ppm while the differences in ¹³C resonances were even smaller. Compounds {[ⁿBu₂Sn(L²H)]₂O}₂ (2) and {[ⁿBu₂Sn(L³H)]₂O}₂ (3) undergo a very complex exchange processes in deuteriochloroform solution. The in vitro cytotoxic activity of compounds 1 and 4 against WIDR, M19 MEL, A498, IGROV, H226, MCF7 and EVSA-T human tumour cell lines is reported.     

Diphenyltin(IV) complexes of the 5-[(E)-2-(aryl)-1-diazenyl]quinolin-8-olates: Synthesis and multinuclear NMR, Sn Mössbauer, electrospray ionization MS, X-ray characterization and assessment of in vitro cytotoxicity

A series of cis-bis{5-[(E)-2-(aryl)-1-diazenyl]quinolinolato}diphenyltin(IV) complexes have been synthesized and characterized by ¹H, ¹³C, ¹¹⁹Sn NMR, ESI-MS, IR and ^119mSn Mössbauer spectroscopic techniques in combination with elemental analysis. The structures of a ligand L⁶H (i.e., 5-[(E)-2-(4-ethoxyphenyl)-1-diazenyl]quinolin-8-ol) and three diphenyltin(IV) complexes, viz., Ph₂Sn(L¹)₂ · (CH₃)₂CO (1), Ph₂Sn(L⁴)₂ (4) and Ph₂Sn(L⁵)₂ (5) (L = 5-[(E)-2-(aryl)-1-diazenyl]quinolin-8-ol: aryl = phenyl - (L¹H); 4′-methylphenyl - (L⁴H) and 4′-bromophenyl - (L⁵H)) were determined by single crystal X-ray diffraction. In general, the complexes were found to adopt a distorted cis-octahedral arrangement around the tin atom. These complexes retain their solid-state structure in non-coordinating solvent as evidenced by ¹¹⁹Sn NMR spectroscopic results. The in vitro cytotoxicity of 1 is reported and compared with Ph₂Sn(Ox)₂ (Ox = deprotonated quinolin-8-ol) against seven well characterized human tumor cell lines.     

Dibenzyltin(IV) complexes of the 5-[(E)-2-(aryl)-1-diazenyl]quinolin-8-olates: Synthesis and an investigation of structures by X-ray diffraction, solution and solid-state tin NMR, Sn Mössbauer and electrospray ionization MS

A series of cis-bis{5-[(E)-2-(aryl)-1-diazenyl]quinolinolato}dibenzyltin(IV) complexes have been synthesized by reacting sodium salts of 5-[(E)-2-(aryl)-1-diazenyl]quinolin-8-ol (LH) and dibenzyltin dichloride. These complexes have been characterized by ¹H, ¹³C, ¹¹⁹Sn NMR, ESI-MS in solution and by IR and ^119mSn Mössbauer, ¹¹⁷Sn CP-MAS NMR spectroscopy in solid state. In addition, the structures of three of the dibenzyltin(IV) complexes, viz., Bz₂Sn(L²)₂ (2), Bz₂Sn(L³)₂ (3), and Bz₂Sn(L⁵)₂ (5) (L = 5-[(E)-2-(aryl)-1-diazenyl]quinolin-8-ol: aryl = 4′-methylphenyl- (L²H), 4′-methoxylphenyl- (L³H) and 4′-bromophenyl- (L⁵H)) were determined by single-crystal X-ray diffraction. In general, the complexes were found to adopt a distorted cis-octahedral arrangement around the tin atom in both solution and solid state.     

Synthesis and characterization of the first diorganotin(IV) complexes containing mixed arylazobenzoic acids and having skew trapezoidal bipyramidal geometry

Three diorganotin(IV) complexes of the type, [R₂Sn(L^aH)(L^bH)] (R = ⁿBu or Me and, L^aH and L^bH are two different 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoate residues; a: aryl = 4′-Cl-(held constant) and b: aryl = 4′-Me or 4′-Br) have been prepared either by reacting ⁿBu₂SnO, L^aHH′ and L^bHH′ (1:1:1) in anhydrous toluene or by reacting Me₂SnCl₂, L^aHNa and L^bHNa (1:1:1) in anhydrous methanol. The products were characterized by microanalysis, IR, NMR (¹H, ¹³C, ¹¹⁹Sn) and ^119mSn Mössbauer spectroscopy. A full characterization of the structures of the complexes [ⁿBu₂Sn(L^aH)(L^bH)] (1 and 2) and [Me₂Sn(L^aH)(L^bH)] (3) in the solid state were accomplished by single crystal X-ray crystallography. These complexes were found to adopt the usual dicarboxylato structural type with a skew-trapezoidal bipyramidal arrangement around the tin atom.     

Re-visiting of 5-[(E)-2-(aryl)-1-diazenyl]-quinolin-8-ol with tweaking of Sn-Ph groups: Synthesis, spectroscopic characterization and X-ray crystallography

Reactions of sodium 5-[(E)-2-(aryl)-1-diazenyl]quinolin-8-olates (LH, where the aryl group is an R-substituted phenyl ring such that for L¹H: R = H; L²H: R = 2′-CH₃; L³H: R = 3′-CH₃; L⁴H: R = 4′-CH₃; L⁵H: R = 4′-OCH₃ and L⁶H: R = 4′-OC₂H₅) with Ph₃SnCl in a 1:1 molar ratio yielded complexes of composition Ph₃SnL. The complexes have been characterized by ¹H, ¹³C, ¹¹⁹Sn NMR, IR and ^119mSn Mössbauer spectroscopic techniques in combination with elemental analyses. The crystal structures of Ph₃SnL¹ · 0.5C₆H₆ (1), Ph₃SnL² (2), Ph₃SnL⁵ · C₆H₆ (5) and Ph₃SnL⁶ · 0.5C₆H₆ (6) were determined. The results of the X-ray studies indicated that the benzene solvated compounds 1, 5 and 6 are distorted square pyramid, with one of the phenyl C atoms in the apex while the ligand arrangement around central Sn atom in 2 is distorted trigonal-bipyramidal, with a phenyl C and the oxinato N atoms in axial positions.     

Di-n-octyltin(IV) complexes with 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoic acid: Syntheses and assessment of solid state structures by Sn Mössbauer and X-ray diffraction and further insight into the solution structures using electrospray ionization MS, Sn NMR and variable temperature NMR spectroscopy

Reactions of 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoic acids (LHH′, where the aryl group is an R-substituted phenyl ring such that for L¹HH′: X = H; L²HH′: X=2′-OCH₃; L³HH′: X = 3′-CH₃; L⁴HH′: X = 4′-CH₃; L⁵HH′:X = 4′-Cl) with ⁿOct₂SnO in 2:1 and 1:1 molar ratios have been investigated. Two types of complexes, ⁿOct₂Sn(LH)₂ and {[ⁿOct₂Sn(LH)]₂O}₂, were isolated and they have been characterized by ¹H, ¹³C, ¹¹⁹Sn NMR, ESI-MS, IR and ^119mSn Mössbauer spectroscopic techniques in combination with elemental analyses. The crystal structures of ⁿOct₂Sn(L¹H)₂ (1), {[ⁿOct₂Sn(L²H)]₂O}₂ (3) and {[ⁿOct₂Sn(L³H)]₂O}₂(4) were determined. The mononuclear complex 1 was found to adopt a skew-trapezoidal bipyramidal arrangement around the tin atom while 3 and 4 are centrosymmetric tetranuclear bis(dicarboxylatotetrabutyldistannoxane) complexes containing a planar Sn₄O₂ core in which two μ₃-oxo O-atoms connect an Sn₂O₂ ring to two exocyclic Sn-atoms. The solution structures were confirmed by ¹¹⁹Sn NMR spectroscopy by observing one tin resonance in compound 1 and two tin resonances in {[ⁿOct₂Sn(L⁵H)]₂O}₂ (5). {[ⁿOct₂Sn(L²H)]₂O}₂ (3) and {[ⁿOct₂Sn(L³H)]₂O}₂ (4) undergo very complex exchange processes in deuteriochloroform solution, which has been confirmed by variable temperature ¹H NMR spectroscopy. The cleavage of the most labile bond in the molecule was studied by ESI mass spectrometry.     

Self-assembly of diorganotin(IV) 2-{[(E)-1-(2-oxyaryl)alkylidene]amino}acetates: An investigation of structures by X-ray diffraction, solution and solid-state tin NMR, and electrospray ionization MS

The diorganotin(IV) compounds, [Me₂SnL²(OH₂)]₂ (1), [ⁿBu₂SnL²(OH₂)]₂ (2), [ⁿBu₂SnL¹]₃ · 0.5C₃H₆O (3), [ⁿBu₂SnL³]₃ · 0.5C₆H₆ (4) and [Ph₂SnL³]_n · 0.5C₆H₆ (5) (L = carboxylic acid residue, i.e., 2-{[(E)-1-(2-oxyaryl)alkylidene]amino}acetate), were synthesized by treating the appropriate diorganotin(IV) dichloride with the potassium salt of the ligand in anhydrous methanol.The reaction of Ph₂SnL² (L = 2-{[(E)-1-(2-oxyphenyl)ethylidene]amino}acetate) with 1,10-phenanthroline (Phen) yielded a 1:1 adduct of composition, [Ph₂SnL²(Phen)] (6).The crystal structures of 1-6 were determined.The crystal of 1 is composed of centrosymmetric dimers of the basic Me₂SnL²(OH₂) moiety, where the two Sn-centres are linked by two asymmetric Sn-O?Sn bridges involving the carboxylic acid O atom of the ligand and a long Sn?O distance of 3.174(2) Å.The dimers are further linked into columns by hydrogen bonds.The coordination geometry about the Sn atom is a distorted pentagonal bipyramid with the two methyl groups in axial positions.The structure of 2 is similar.The same Sn atom coordination geometry is observed in compound 3, which is a cyclic trinuclear[ⁿBu₂SnL¹]₃ compound. Each Sn atom is coordinated by the phenoxide O atom, one carboxylate O atom and the imino N atom from one ligand and both the exo- and endo-carboxylate O atoms (mean Sn-O(exo): 2.35 Å; Sn-O(endo): 2.96 Å) from an adjacent ligand to form the equatorial plane, while the two butyl groups occupy axial positions. Compound 4 was found to crystallize in two polymorphic forms. The Sn-complex in both forms has a trinuclear [ⁿBu₂SnL³]₃ structural motif similar to that found in 3. In compound 5, distorted trigonal bipyramidal Ph₂SnL³ units are linked into polymeric cis-bridged chains by a weak Sn?O interaction (3.491(2) Å) involving the exocyclic O atom of the tridentate ligand of a neighboring Sn-complex unit. This interaction completes a highly distorted octahedron about the Sn atom, where the weakly coordinated exocyclic O atom and one phenyl group are trans to one another. In contrast, a monomeric distorted pentagonal bipyramidal geometry is found for adduct 6 where the Sn-phenyl groups occupy the axial positions. The solution and solid-state structures are compared by using ¹¹⁹Sn NMR chemical shift data. Compounds 1-6 were also studied using ESI-MS and their positive- and negative-ions mass fragmentation patterns are discussed.     

Synthesis, characterization, cytotoxic activity and crystal structures of tri- and di-organotin(IV) complexes constructed from the β-{[(E)-1-(2-hydroxyaryl)alkylidene]amino}propionate and β-{[(2Z)-(3-hydroxy-1-methyl-2-butenylidene)]amino}propionate skeletons

Reactions of potassium β-{[(E)-1-(2-hydroxyaryl)alkylidene]amino}propionates (L¹HK-L³HK) and potassium β-{[(2Z)-(3-hydroxy-1-methyl-2- butenylidene)]amino}propionate (L⁴HK) with R₃SnCl (R = Ph and ⁿBu) and ⁿBu₂SnCl₂ yielded complexes of composition Ph₃SnL¹H (1), Ph₃SnL²H (2), Ph₃SnL⁴H (3), ⁿBu₃SnL¹H (4), and {[ⁿBu₂Sn(L²H)]₂O}₂ (5) and {[ⁿBu₂Sn(L³H)]₂O}₂ (6), respectively. These complexes have been characterized by ¹H, ¹³C, ¹¹⁹Sn NMR, ESI-MS, IR and ^119mSn Mössbauer spectroscopic techniques in combination with elemental analyses. The crystal structures of 1, 4, 5 and 6 were determined. In the solid state, compound 1 is a one-dimensional polymer built from SnPh₃ moieties bridged by single carboxylate ligands, but two alternating modes of bridging are present along the polymeric chain. Compound 4 is also a one-dimensional polymer built from SnBu₃ moieties bridged by the two carboxylate O-atoms of a single ligand, but only one mode of bridging is present. Di-n-butyltin compounds 5 and 6 are centrosymmetric tetranuclear bis(dicarboxylatotetrabutyldistannoxane) complexes containing a planar Sn₄O₂ core in which two μ₃-oxo O-atoms connect an Sn₂O₂ ring to two exocyclic Sn-atoms. The four carboxylate ligands display two different modes of coordination where both modes involve bridging of two Sn-atoms. The solution structures were predicted by ¹¹⁹Sn NMR spectroscopy. The in vitro cytotoxic activity of compound 5 against WIDR, M19 MEL, A498, IGROV, H226, MCF7 and EVSA-T human tumor cell lines is reported.     

Synthesis, characterization and crystal structures of polymeric and dimeric triphenyltin(IV) complexes of 4-[((E)-1-{2-hydroxy-5-[(E)-2-(2-carboxyphenyl)-1-diazenyl]phenyl}methylidene)amino]aryls

The triphenyltin(IV) complexes of 4-[((E)-1-{2-hydroxy-5-[(E)-2-(2-carboxyphenyl)-1-diazenyl]phenyl}methylidene)amino]aryls (aryls = 4-CH₃, 4-Br, 4-Cl, 4-OCH₃) have been synthesized and characterized by ¹H-, ¹³C-, ¹¹⁹Sn-NMR, ESI mass spectrometry, IR and ^119mSn Mössbauer spectroscopic techniques in combination with elemental analysis. The crystal structures of a representative carboxylate ligand (aryl = 4-CH₃) and three Sn complexes, viz., polymeric (Ph₃Sn[O₂CC₆H₄{NN(C₆H₃-4-OH(C(H)NC₆H₄X-4))}-o])_n (X = Me (1) and Br (2)) and dimeric (Ph₃Sn[O₂CC₆H₄{NN(C₆H₃-4-OH(C(H)NC₆H₄X-4))}-o])₂ (X = OMe (4)) complexes are reported. The coordination environment in each complex is trigonal bipyramidal trans-Ph₃SnO₂. A single zwitterionic carboxylate ligand bridges adjacent Sn atoms via the carboxylate and phenoxide O atoms.     

A contribution to 1-azapentadienylmetal chemistry: Si, Sn(II), Fe(II) and Co(II) complexes

Complexes of three related 1-azapentadienyl ligands [N(SiMe₂R¹)C(Bu^t)(CH)₃SiMe₂R]⁻, abbreviated as L (R = Bu^t, R¹ = Me), L′ (R = Me = R¹), and L″ (R = Bu^t = R¹), are described. The crystalline compounds Sn(L)₂ (1), Sn(L′)₂ (2), [Sn(L′)(μ-Cl)]₂ (3) and [Sn(L″)(μ-Cl)]₂ (4) were prepared from SnCl₂ and 2 K(L), 2 K(L′), K(L′) and K(L″), respectively, in thf. Treatment of the appropriate lithium 1-azapentadienyl with Si(Cl)Me₃ yielded the yellow crystalline Me₃Si(L) (5) and the volatile liquid Me₃Si(L′) (6) and Me₃Si(L″) (7), each being an N,N,C-trisilyldieneamine. The red, crystalline Fe(L)₂ (8) and Co(L′)₂ (9) were obtained from thf solutions of FeCl₂ with 2 Li(L)(tmeda) and CoCl₂ with 2 K(L′), respectively. Each of 1-9 gave satisfactory C, H, N analyses; 6 and 7 (GC-MS) and 1, 2, 8 and 9 (MS) showed molecular cations and appropriate fragments (also 3 and 4). The ¹H, ¹³C and ¹¹⁹Sn NMR (1-4) and IR spectra support the assignment of 1-4 as containing Sn-N(SiMe₂R¹)-C(Bu^t)(CH)₃SiMe₂R moieties and 5-7 as N(SiMe₃)(SiMe₂R¹)C(Bu^t)(CH)₃SiMe₂R molecules; for 1-4 this is confirmed by their X-ray structures. The magnetic moments for 8 (5.56 μ_B) and 9 (2.75 μ_B) are remarkably close to the appropriate Fe and Co complex [M{η³-N(SiMe₃)C(Bu^t)C(H)SiMe₃}₂]; hence it is proposed that 8 and 9 have similar metal-centred, centrosymmetric, distorted octahedral structures.     

Synthesis, characterizations and crystal structures of di-n-butyltin(IV) complexes with heteroatomic (N, O or S) acid

Two types of di-n-butyltin(IV) complexes {[ⁿBu₂Sn(O₂CR)]₂O}₂ · L 1-4 and ⁿBu₂Sn(O₂CR)₂Y 5-8 (when L=H₂O, R=2-pyrazine 1; L=0, R=2-pyrimidylthiomethylene 2, 1-naphthoxymethylene 3; L=C₆H₆, R=2-naphthoxymethylene 4; when Y=H₂O, R=2-pyrazine 5; Y=0, R=2-pyrimidylthiomethylene 6, 1-naphthoxymethylene 7, 2-naphthoxymethylene 8) have been prepared in 1:1 or 1:2 molar ratios by reactions of di-n-butyltin oxide with the heteroatomic (N, O or S) carboxylic acids. The complexes 1-8 are characterized by elemental, IR, ¹H and ¹³C NMR spectra. And except for complexes 6 and 7, the complexes 1-5 and 8 are also characterized by X-ray crystallography diffraction analyses, which reveal that the tin atom of complex 5 is seven-coordinated, while the complexes 1-4 and 8 are all hexa-coordinated. The nitrogen atom of the aromatic ring in complexes 1 and 5 participates in the interactions with the Sn atom.     

Chiral self-assembly of triorganotin complexes: Syntheses, characterization, crystal structures and antitumor activity of organotin(IV) complexes containing (R)-(+)-methylsuccinic acid, (S)-(+)-methylglutaric acid and l-(−)-malic acid ligands

Six new chiral triorganotin(IV) complexes, {(R₃Sn)₂[C₃H₆(COO)₂]}_n (R = Me: 1; Bu: 2), {(R₃Sn)₂[C₄H₈(COO)₂]}_n (R = Me: 3; Bu: 4), and {(R₃Sn)₂[C₂H₄O(COO)₂]}_n (R = Me: 5; Bu: 6) have been prepared by treatment of (R)-(+)-methylsuccinic acid, (S)-(+)-methylglutaric acid and l-(−)-malic acid, with the corresponding R₃SnCl (R = Me, Bu) and sodium ethoxide in methanol. All the complexes were characterized by elemental analysis, FT-IR, NMR (¹H, ¹³C, ¹¹⁹Sn) spectroscopy and TGA. Except for 3, all of the complexes were also characterized by X-ray crystallography. The structural analyses reveal that complexes 1 and 5 have 2D network structures in which (R)-(+)-methylsuccinic acid and l-(−)-malic acid act as tetradentate ligands coordinated to trimethyltin(IV) ions. Complexes 2 and 4 have 3D metal-organic framework structures in which the deprotoned acids serve as tetradentate ligands. Complex 6 adopts a 1D zigzag chain structure and forms a 2D supramolecular framework through intermolecular C-H?O interactions. In addition, the antitumor activities of complexes 1-6 have been studied. We also have measured the specific rotation of the chiral dicarboxylic acids and the organotin derivatives.     

Structure of N,C,N-chelated organotin(IV) fluorides

The set of starting tri-, di- and monoorganotin(IV) halides containing N,C,N-chelating ligand (L^NCN = {1,3-[(CH₃)₂NCH₂]₂C₆H₃}⁻) has been prepared (1-5) and two compounds structurally characterized ([L^NCNPh₂Sn]⁺I₃⁻ (1c), L^NCNSnBr₃ (5)) in the solid state. These compounds were reacted with KF with 18-crown-6, NH₄F or L^CNnBu₂SnF to give derivatives containing fluorine atom(s). Triorganotin(IV) fluorides L^NCNMe₂SnF (2a) and L^NCNnBu₂SnF (3a) revealed monomeric structural arrangement with covalent Sn-F bond both in the coordinating and non-coordinating solvents, except the behaviour of 3a that was ionized in the methanol solution at low temperature. The products of fluorination of L^NCNSnPhCl₂ (4) and 5 were described by NMR in solution as the ionic hypervalent fluorostannates or the oligomeric species reacting with chloroform, methanol or moisture to zwitterionic monomeric stannate L^NCN(H)⁺SnF₄⁻ (5c), which was confirmed by XRD analysis in the solid state.     

Interaction of 2-(2′,6′-dialkylphenylazo)-4-methylphenols with iridium. C-H activation and migration of alkyl group

Reaction of 2-(2′,6′-diethylphenylazo)-4-methylphenol (L²) with [Ir(PPh₃)₃Cl] afforded two organoiridium complexes 3 and 4 via C-H bond activation of an ethyl group in the arylazo fragment of the L² ligand. In both the complexes the azo ligand binds to iridium as a dianionic tridentate C,N,O-donor. Two triphenylphosphines and a hydride (in the case of complex 3) or chloride (in the case of complex 4) are also coordinated to the metal center. A similar reaction of [Ir(PPh₃)₃Cl] with 2-(2′,6′-diisopropylphenylazo)-4-methylphenol (L³) yielded another organoiridium complex 5, where migration of one iso-propyl group from its original location (say, the 2′ position) to the corresponding third position (say, the 4′ position) took place through C-C bond activation. In this complex the modified azo ligand binds to iridium as a dianionic tridentate C,N,O-donor. Two triphenylphosphines and a hydride are also coordinated to the metal center. The structures of complexes 3 and 4 have been optimized through DFT calculations. The structure of complex 5 has been determined by X-ray crystallography. All the complexes show characteristic ¹H NMR signals and intense transitions in the visible region. Cyclic voltammetry on all the complexes shows an oxidation within 0.66-1.10 V vs SCE, followed by a second oxidation within 1.15-1.33 V vs SCE and a reduction within −0.96 to −1.07 V vs SCE.     

Synthesis, crystal structure and biological activities of four novel tetranuclear di-organotin(IV) carboxylates

Four complexes: [Bu₂(L₁)SnOSn(L₁)Bu₂]₂ (1), [Bu₂(L₂)SnOSn(L₂)Bu₂]₂ (2), [Bu₂(L₃)SnOSn(L₃)Bu₂]₂ (3), and [Bu₂(L₄)SnOSn(L₄)Bu₂]₂ (4), (HL₁ = 2-(4-methylbenzoyl)benzoic acid, HL₂ = 2-(2,4-diethylbenzoyl)benzoic acid, HL₃ = 2-(4-chlorobenzoyl)benzoic acid, HL₄ = 2-(4-isopropylbenzoyl)benzoic acid) have been prepared and structurally characterized by means of elemental analysis and vibrational, ¹H NMR and FT-IR spectroscopies. The crystal structures of all complexes have been determined by X-ray crystallography. Three distannoxane rings are present to the dimeric tetraorganodistannoxane of planar ladder arrangement. Each structure is centro-symmetric and features a central rhombus Sn₂O₂ unit with two additional tin atoms linked at the O atoms. Complex 1 exhibited good antibacterial and antitumor activities and have a potential to be used as drugs.     

Syntheses and structures of iron carbonyl complexes derived from N-(5-methyl-2-thienylmethylidene)-2-thiolethylamine and N-(6-methyl-2-pyridylmethylidene)-2-thiolethylamine

The reaction of N-(5-methyl-2-thienylmethylidene)-2-thiolethylamine (1) with Fe₂(CO)₉ in refluxing acetonitrile yielded di-(μ₃-thia)nonacarbonyltriiron (2), μ-[N-(5-methyl-2-thienylmethyl)-η¹:η¹(N);η¹:η¹(S)-2-thiolatoethylamido]hexacarbonyldiiron (3), and N-(5-methyl-2-thienylmethylidene)amine (4). If the reaction was carried out at 45 °C, di-μ-[N-(5-methyl-2-thienylmethylidene)-η¹(N);η¹(S)-2-thiolethylamino]-μ-carbonyl-tetracarbonyldiiron (5) and trace amount of 4 were obtained. Stirring 5 in refluxing acetonitrile led to the thermal decomposition of 5, and ligand 1 was recovered quantitatively. However, in the presence of excess amount of Fe₂(CO)₉ in refluxing acetonitrile, complex 5 was converted into 2-4. On the other hand, the reaction of N-(6-methyl-2-pyridylmethylidene)-2-thiolethylamine (6) with Fe₂(CO)₉ in refluxing acetonitrile produced 2, μ-[N-(6-methyl-2-pyridylmethyl)-η¹ (N_py);η¹:η¹(N); η¹:η¹(S)-2-thiolatoethylamido]pentacarbonyldiiron (7), and μ-[N-(6-methyl-2-pyridylmethylidene)-η²(C,N);η¹:η¹(S)-2- thiolethylamino]hexacarbonyldiiron (8). Reactions of both complex 7 and 8 with NOBF₄ gave μ-[(6-methyl-2-pyridylmethyl)-η¹(N_py);η¹:η¹(N);η¹:η¹(S)-2-thiolatoethylamido](acetonitrile)tricarbonylnitrosyldiiron (9). These reaction products were well characterized spectrally. The molecular structures of complexes 3, 7-9 have been determined by means of X-ray diffraction. Intramolecular 1,5-hydrogen shift from the thiol to the methine carbon was observed in complexes 3, 7, and 9.     

Synthesis, structural characterization and reactivity of new tin bridged ansa-bis(cyclopentadiene) compounds: X-ray crystal structures of Me2Sn(C5Me4R-1)2 (R = H, SiMe3)

The organo-tin compounds, Me₂Sn(C₅H₄R-1)₂ (R = Me (1), Prⁱ (2), Bu^t (3), SiMe₃ (4)) and Me₂Sn(C₅Me₄R-1)₂ (R = H (5), SiMe₃ (6)), were prepared by the reaction of Me₂SnCl₂ with the lithium or sodium derivative of the corresponding cyclopentadiene. Compounds 1-6 have been characterized by multinuclear NMR spectroscopy (¹H, ¹³C, ¹¹⁹Sn). In addition the molecular structures of 5 and 6 were determined by single crystal X-ray diffraction studies. The transmetalation reaction of 1-6 with ZrCl₄ or [NbCl₄(THF)₂] gave the corresponding metallocene complexes in high yields.     

Hypervalent triphenyl and diphenyl tin coordination compounds derived from 2-(1H-benzimidazol-2-yl)phenol

Reactions of 2-(1H-benzimidazol-2-yl)phenol (1) and SnPh₃Cl, SnPh₂Cl₂ and SnCl₄ were investigated. One tetracoordinated triphenyltin(IV) compound: triphenyltin-2-(1H-benzimidazol-2-yl)phenolate] (3) and its adducts: [O → Sn] dimethylsulfoxide triphenyltin-[2-(1H-benzimidazol-2-yl)phenolate] (4), [O → Sn] aqua triphenyltin-[2-(1H-benzimidazol-2-yl)phenolate] (5) [O → Sn] ethanol triphenyltin-[2-(1H-benzimidazol-2-yl)phenolate] (6), [N → Sn] pyridine triphenyltin-[2-(1H-benzimidazol-2-yl)phenolate] (7), where 1 acts as a monodentate ligand bound through the phenol oxygen, were obtained. In the pentacoordinated compounds 4-7, the tin atom has tbp geometry. The three phenyl groups are in equatorial positions, whereas the benzimidazole and the Lewis base are in apical positions. Two hexacoordinated tin compounds: diphenyltin-bis[2-(1H-benzimidazol-2-yl-κN)phenolate-κO] (8), dichlorotin-bis[2-(1H-benzimidazol-2-yl-κN)phenolate-κO] (9) bearing two bidentate ligands are reported. The coplanar ligands in 8 and 9 form six membered rings by oxygen and nitrogen coordination. The tin geometry is all-trans octahedral. In 8 the two phenyl groups, and in 9 the two chlorine atoms are perpendicular to the plane of the ligands. Compounds were identified in solution mainly by ¹H, ¹³C and ¹¹⁹Sn NMR and in the solid state by X-ray diffraction analysis.     

Synthesis, structural characterization, and initial electroluminescent properties of bis-cycloiridiated complexes of 2-(3,5-bis(trifluoromethyl)phenyl)-4-methylpyridine

A series of bis-cyclometalated Ir(III) complexes (8-10, 12, 15, 17, 19, 21, 23, 25, 28, 29 and 33) bearing two chromophoric N^∧C cyclometalated ligands derived from 2-(3,5-bis(trifluoromethyl)phenyl)-4-methylpyridine (1) and a third nonchromophoric ligand has been synthesized. A palladium-catalyzed cross-coupling reaction between 2-chloro-4-methylpyridine (2) and 3,5-bis(trifluoromethyl)phenylboronic acid (3) was used to prepare 2-(3,5-bis(trifluoromethyl)phenyl)-4-methylpyridine (1). Cyclometalation of (1) by IrCl₃ was carried out in (MeO)₃PO, with the formation of chloro-bridged dimer [N^∧C]₂Ir(μ-Cl)₂Ir[C^∧N]₂ (8). Reaction of (8) with lithium 2,4-pentanedionate, lithium 2,2,6,6-tetramethyl-heptane-3,5-dionate (13), dipivaloyltrimethylsilylphosphine (14), 2,2-dimethyl-6,6,7,7,8,8,8-heptafluoro-3,5-octadione (16), 1,1,1,3,3,3-hexafluoro-2-pyridin-2-yl-propan-2-ol (18), 1,1,1,3,3,3-hexafluoro-2-pyrazol-1-ylmethyl-propan-2-ol (20), 2-diphenylphosphanylethanol (22), and 1-diphenylphosphanylpropan-2-ol (24), afforded octahedral iridium complexes 9, 12, 15, 17, 19, 21, 23 and 25, respectively. Complex 10, which contains three different ligands (L₁ = N^∧C of 1; L₂ = N^∧C of 4,4′-dimethyl-[2,2′]bipyridinyl 4; L₃ = O^∧O of 2,4-pentanedione), and complex 11, which contains no cyclometalated ligands (L₁ = 4; L₂ = L₃ = Cl; L₄ = O^∧O of 2,4-pentanedione) were also isolated as minor products in a one-pot reaction between a 94:5 mixture of 1 and 4, IrCl₃ and lithium 2,4-pentanedionate. Reaction of 8 with diphenylphosphanylmethanol (27) in 1,2-dichloroethane unexpectedly led to complexes 28 and 29. The reactions of 8 with benzoylformic acid resulted in the formation of hydroxyl-bridged dimer [N^∧C]₂Ir(μ-OH)₂Ir[C^∧N]₂ (33). According to X-ray analyses, Ir-to-Ir distances in the crystal cell increase from 6.86 Å for 10 to 13.31 Å for 33. The angle theta, which represents the twisting of two cyclometalated C-Ir-N planes relative to each other, varies from 97.5° for 21 to 90.76 for complex 28. OLED devices were fabricated from several Ir complexes and preliminary results are discussed.