A 3D supramolecular network of cobalt(II)(bis(4-pyridyl)ethylene) with terephthalate dianions

A three dimensional supramolecular network, {[Co(bpee)(H₂O)₄] · (tp) · 2(H₂O)}_n (1) [bpee = trans-1,2 bis(4-pyridyl)ethylene; tp = terephthalate dianion] has been synthesized and characterized by X-ray single crystal structure, magnetic measurement and thermal analysis. The structure determination reveals that the cobalt(II) ions, bridged by bpee and coordinated by four water molecules, give rise to covalently linked 1D polymeric chain. The parallel chains get involved in H-bonding with tp resulting in a 3D architecture. Upon heating 1, which is pink in color, transforms to [Co(bpee)(tp)] (1a, blue). The deaquated species (1a) reverts on keeping in humid atmosphere. Low temperature magnetic data indicate weak antiferromagnetic coupling.     

Synthesis and structural determination of new octaethylporphyrin iron(III) complexes containing cyanamide derivatives as axial ligand

The reactions of heme, [OEPFeCl] where OEP is the dianion of octaethylporphyrin, with phenylcyanamide (pcyd) ligands have been studied. Four new porphyrin complexes, [OEPFe(L)] (L = pcyd (2), 2-Clpcyd (3), 2-Mepcyd (4), 2,4-Me₂pcyd (5)), have been isolated and characterized by spectroscopic methods. ¹H NMR spectroscopy reveals that the species [OEPFe(L)] are paramagnetic and iron is five-coordinate. The structure of [OEPFe(pcyd)] (2) has been determined by X-ray diffraction analysis. The four Fe-N, bond distances have average values of 2.062 Å. The average displacement of the iron(III) atom from the mean porphinato core is 0.45 Å. Electrochemical of [OEPFe(L)] (L = pcyd (2), 2-Clpcyd (3), 2-Mepcyd (4), 2,4-Me₂pcyd (5)) have been studied by cyclic voltammetry.     

Synthesis and characterization of two new metal-organic materials based on In/btec

Two new metal-organic materials, In(2,2′-bipy)(btec)_0.5Cl (1) and In₂(phen)₄(Hbtec)₂ (2) (btec = 1,2,4,5-benzenetetracarboxylate, 2,2′-bipy = 2,2′-bipyridyl, phen = 1,10-phenanthroline) have been synthesized under mild hydrothermal condition. Their structures were determined by single-crystal X-ray diffraction and further characterized by X-ray powder diffraction, thermogravimetric analysis, IR, fluorescence spectroscopy, inductively coupled plasma (ICP) and elemental analysis. The structural analysis reveals that compound 1 exhibits a novel wavelike 2D layer with unusual contorted rhombic grids, while compound 2 possesses dinuclear In₂(phen)₄(Hbtec)₂ complex molecules. It is noteworthy that their structures finally extend to the higher dimensional supramolecular framework structures through the π-π stacking interactions of N-donor ligands. Additionally, these two compounds show strong fluorescence in the solid state at room temperature.     

Syntheses and characterization of 3D heterometallic (3d-4f) metal-organic frameworks: Reversible de- and rehydration performance and magnetic properties

By the “metalloligand” strategy, two new 3d-4f heterometallic metal-organic frameworks (MOFs), {[Ln₂Cu₃(IDA)₆] · 1.5H₂O}_n [Ln = Tb (1) and Dy (2); H₂IDA = iminodiacetate acid], had been prepared. X-ray crystal structure analyses show that 1 and 2 possess of 3D frameworks with highly ordered 1D channels along the c axis. The highly stable skeleton and reversible de- and rehydration performance of 1 are demonstrated by thermogravimetric and powder X-ray diffraction analyses, and a low temperature magnetic study of 2 reveals a weak ferromagnetic interaction between the metal ions.     

Structural and magnetic characterization of one-dimensional oxalato-bridged metal(II) complexes with 4-amino-3,5-bis(2-pyridyl)-1,2,4-triazole ligand: A supramolecular open-framework

A new family of one-dimensional oxalato-bridged metal(II) complexes with formula {[M(ox)(abpt)]·4H₂O}_n [M^II = Mn (1), Fe (2), Co (3), Zn (4); ox = oxalate dianion; abpt = 4-amino-3,5-bis(2-pyridyl)-1,2,4-triazole] has been synthesized and chemically, structurally and magnetically characterized. The crystal structures of compounds 2-4 have been solved by single crystal X-ray diffraction, whereas complex 1 has been studied by means of X-ray powder diffraction methods. All of them are isomorphous and crystallize in the triclinic space group P. The metal atoms are bridged by bis-bidentate oxalate anions forming zig-zag chains in which bidentate chelating abpt ligands complete the octahedral O₄N₂ donor set. The crystal structures show an open-framework that contains rectangular channels in which easily removable hydrogen bonded ribbons of water molecules are located. The occurrence of antiferromagnetic intrachain interactions for compounds 1-3 was determined by cryomagnetic susceptibility measurements.     

Synthesis, and characterization of cobalt(III) complexes with Schiff bases derived from 2-hydroxynaphthaldehyde, (naph)2dien and (naph)2dpt, and monodentate amine ligands: Crystal structure, spectral and redox properties

Two series of complexes of the type [Co^III{(naph)₂dien}(amine)]BPh₄ {(naph)₂dien = bis-(2-hydroxy-1-naphthaldimine)-N-diethylenetriamine dianion, and amine = piperidine (pprdn) (1), pyrrolidine (prldn) (2), pyridine (py) (3), N-methylimidazole (N-MeIm) (4)}, and [Co^III{(naph)₂dpt}(amine)]BPh₄ {(naph)₂dpt = bis-(2-hydroxy-1-naphthaldimine)-N-dipropylenetriamine dianion, and amine = piperidine (pprdn) (5), 3-methylpyridine (3-Mepy) (6)} have been synthesized and characterized by elemental analyses, IR, UV-Vis, and ¹H NMR spectroscopy. The crystal structures of (2) and (6) have been determined by X-ray diffraction. The redox potentials of the central cobalt ion show a relatively good correlation with the σ-donor ability of the axial ligands. The spectroscopic and electrochemical properties of these complexes are also influenced by the mutual steric hindrance between the pentadentate Schiff base and the ancillary ligands.     

Copper(II) complexes derived from tripodal tris[(2-ethyl-(1-pyrazolyl)]amine

Three mono-nuclear copper(II) complexes [Cu(tepza)X]ClO₄ (X = Cl, 1; X = NCS, 2; X = dca, 3) and two dinuclear bridging complexes [Cu₂(tepza)₂(μ-C₄O₄)](ClO₄)₂·H₂O(4) and [Cu₂(tepza)₂(μ-C₅O₅)](ClO₄)₂(5) where tepza = tris[2-ethyl(1-pyrazolyl)]amine, dca = dicyanamide, C₄O₄²⁻ = 3,4-dihydroxycyclobut-3-ene-1,2-dionate (squarate dianion) and C₅O₅²⁻ = 4,5-dihydroxycyclopent-4-ene-1,2,3-trionate (croconate dianion) were synthesized and structurally characterized by IR and UV-Vis spectroscopy as well as by single X-ray crystallography. In the solid state, the geometry of copper(II) centers in these complexes are as follows: close to SP in 2, distorted TBP in 3, predominant SP in 4, and distorted octahedral in 5, whereas in solution distorted SP geometry was generally found. The squarato and the croconato dianions in complexes 4 and 5 are bridging the two copper(II) centers in cis-bis-monodentate and bis-bidentate bonding modes, respectively. Magnetic susceptibility measurements at variable temperatures (2-300 K) reveal the weak antiferromagnetic coupling in the two bridging dinuclear complexes 4 (J = −24.9 cm⁻¹) and 5 (J = −3.1 cm⁻¹).     

Non-linear optically active zinc and cadmium p-pyridinecarboxylate coordination networks

Non-centrosymmetric 1D and 3D coordination networks [Zn(L)₂(H₂O)]₂ · CH₃CN · 3H₂O (1), and [Cd_2.5(L)₅] · EtOH · 5H₂O (2), have been synthesized hydro(solvo)thermally between Zn(II) or Cd(II) ions and methyl 4-[2-(4-pyridyl)ethenyl]cinnamate (L-Me), respectively. X-ray single-crystal diffractions studies show that 1 adopts a caterpillar-shaped 1D chain structure, while 2 has a complicated 3D structure formed by linking cadmium-carboxylate chains with the L ligands. Both face-to-face and edge-to-face π-π interactions between the L ligands are key to the polar arrangement of the L ligands in 1. The dipole moments of all the L ligands have on the other hand essentially cancelled out in 2, and the polar axis is defined by the cadmium-carboxylate chains. Consistent with their polar structures, powder second harmonic generation measurements indicate that 1 and 2 exhibit powder SHG intensities of 75 and 20 versus α-quartz, respectively.     

Dinuclear terephthalato-bridged nickel(II) complexes. Structural characterization and magnetic properties

The dinuclear terephthalato-bridged nickel(II) complexes [Ni₂(cyclen)₂(μ-tp)](ClO₄)₂ (1) [Ni₂(trpn)₂(μ-tp)(H₂O)₂](ClO₄)₂ (2) and [Ni₂(3,3,3-tet)₂(μ-tp)(H₂O)₂](ClO₄)₂ · 2H₂O (3), where tp = terephthalate dianion, cyclen = 1,4,7,10-tetraazacyclododecane, trpn = tris(3-aminopropyl)amine and 3,3,3-tet = 1,5,9,13-tetraazatridecane, were synthesized and structurally characterized by X-ray crystallography. Their magnetic susceptibilities were also determined at variable temperatures over the range 2-300 K. The structures of these complexes consist of μ-tp bridging two Ni(II) centers in a bis(bidentate) bonding fashion in 1 and in bis(monodentate) bonding fashion in 2 and 3. The coordination geometry around the Ni(II) ions in these compounds has a distorted octahedral geometry with four nitrogen atoms from the amine ligand (cyclen, trpn or 3,3,3-tet) and two coordinated oxygen atoms supplied by the chelated carboxylate group of the bridged terephthalate ligand in 1, and by one tp-carboxylate-oxygen in 2 and 3. The sixth coordination site in the last two complexes 2 and 3 is achieved via an oxygen atom from a coordinated water molecule. The intradimer Ni…Ni distances in these complexes are 10.740, 11.428 and 11.537 Å for 1, 2 and 3, respectively. The electronic spectra of the complexes in aqueous solutions are in complete agreement with the assigned X-ray geometry around the Ni(II) centers. Also, the analysis of the infrared spectral data for the ν(COO⁻) stretching frequencies of the tp-carboxalato groups reveals the existence of the bis(bidentate) and bis(monodentate) coordination modes for the bridged terephthalate ligand in 1, 2 and 3, respectively. Despite the different coordination modes of the tp bridging ligand in these complexes, they all exhibit very weak antiferromagnetic coupling. The coupling constants J were found to be −2.2, −0.6 and −1.5 cm³ K mol⁻¹ for the complexes 1, 2 and 3, respectively. The structural and magnetic results of 1-3 are discussed in relation to the other related published μ-terephthalato dinuclear Ni(II) compounds.     

Five-coordinate cobalt(II) complexes of tris(2-pyridylmethyl)amine (TPA): Synthesis, structural and magnetic characterization of a terephthalato-bridged dinuclear cobalt(II) complex

The cobalt(II) complexes [Co(TPA)Cl]ClO₄ (1), [Co(TPA)Br]ClO₄ (2), [Co(TPA)(H₂O)]Cl(ClO₄) (3) and [Co₂(TPA)₂(μ-tp)](ClO₄)₂ · 2H₂O (4) (TPA = tris(2-methylpyridyl)amine and tp = terephthalate dianion) were synthesized and structurally characterized by UV-vis and IR spectroscopy. The molecular structures of complexes 1 and 4 were determined by X-ray crystallography and their magnetic properties were measured over the temperature range 2-300 K. The coordination geometry around the central Co(II) in these compounds has a distorted trigonal bipyamidal geometry with four nitrogen atoms from the TPA ligand and the fifth coordination site is occupied by Cl⁻ ion in 1, Br⁻ ion in 2, coordinated oxygen atom from H₂O in 3 and by an oxygen atom supplied by the carboxylate group of the bridged terephthalato ligand in 4. The visible spectra of the complexes 1-3 in MeOH show strong distortion toward tetrahedral geometry. For complex 4, analysis of the infrared spectral data for the ν(COO⁻) stretching frequencies of the tp-carboxalato groups reveals the existence of the bis(monodentate) coordination mode for the bridged tp. X-ray data for 1 and 4 show that the former is mononuclear while the latter is dinuclear. The electronic spectrum of 4 in MeOH is in complete agreement with the assigned X-ray geometry around the Co(II) centers. The magnetic behavior of the mononuclear complex 1 is indicative of a high-spin compound with zero-field splitting. The best fit was obtained with ∣D∣ = 7.3 cm⁻¹, g = 2.25. The dinuclear complex 4 exhibits weak antiferromagnetic coupling with a coupling constant J = −0.8 cm⁻¹. The magnetic properties and the structural parameters of 4 are discussed in relation to the other related μ-terephthalato dinuclear Co(II) compounds. The geometry of the coordination sphere around 4 is unique - the CSD compilation listing only one other compound with such a geometry around the dinuclear Co(II) complex and its composition is far different from that in 4. However, they share a common feature of having a weakly antiferromagnetic coupling between Co(II) centers.     

Dinuclear fumarato- and terephthalato-bridged copper(II) complexes: Structural characterization and magnetic properties

The dinuclear dicarboxylato-bridged copper(II) complexes [Cu₂(TPA)₂(μ-tp)](ClO₄)₂ · H₂O (1), [Cu₂(TPA)₂(μ-fum)](ClO₄)₂ · 2H₂O (2) and [Cu₂(pmedien)₂(μ-fum)(H₂O)₂](ClO₄)₂ (3) (tp = terephthalate dianion, fum = fumarate dianion, TPA = tris(2-pyridylmethyl)amine and pmedien = N,N,N′,N″,N″-pentamethyldiethylenetriamine) were synthesized and structurally characterized by X-ray crystallography. The structures of the TPA complexes 1 and 2 consist of μ-tp or μ-fum bridging two Cu(II) centers in a bis(monodentate) bonding fashion. The coordination geometry around the Cu(II) ions in these compounds has a distorted trigonal bipyamidal geometry, TBP with four nitrogen atoms from the TPA ligand and a coordinated oxygen atom supplied by the carboxylate group of the bridged dicarboxylato ligand. Complex 3 has a distorted square pyramidal geometry achieved by the three N-atoms of the pmedien, one fum-carboxylate-oxygen and by an oxygen atom from a coordinated water molecule. The intradimer Cu…Cu distances in these complexes are 11.078(3), 8.663(4) and 9.520(3) Å for 1, 2 and 3, respectively. The electronic spectra of the complexes in aqueous solutions are in complete agreement with the assigned X-ray geometry around the Cu(II) centers. Also, analysis of the infrared spectral data for the ν(COO⁻) stretching frequencies of the tp-carboxalato groups reveals the existence of the bis(mondentate) coordination mode for the bridged dicarboxylato ligands in compounds 1 and 2. The susceptibility measurements at variable temperature over the 2-300 K range are reported. For 1-3, it has been observed slight antiferromagnetic coupling with J values of −0.8, −3.0 and −2.9 cm⁻¹, respectively.     

Syntheses, structures and magnetic properties of three 1-D chain metal-nitroxide coordination polymers bridged by e,e-trans-1,4-cyclohexanedicarboxylate

Three new one-dimensional (1-D) chain metal-nitroxide complexes of the formula [M(NIT4Py)₂(e,e-trans-1,4-chdc)(H₂O)₂]_n (M = Co(II) 1, Ni(II) 2 and Zn(II) 3; NIT4Py = 2-(4′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide and 1,4-chdc = 1,4-cyclohexanedicarboxylate dianion) have been synthesized and characterized structurally as well as magnetically. The X-ray crystal structure analyses of complexes 1, 2 and 3 reveal that they are isostructural. Three complexes all crystallize in neutral 1-D chains where metal-nitroxide units [M(NIT4Py)₂(H₂O)₂] are linked by the linear 1,4-cyclohexanedicarboxylate dianion. The 1,4-chdc completes the segregation and only possesses the e,e-trans-conformation, although there are both cis- and trans-isomers in the raw material. The magnetic measurements show that complexes 1 and 2 both exhibit weak antiferromagnetic interactions between the metal ions and the nitroxides.     

X-ray powder and single crystal structures of two unprecedented families of bpca-based 1-D magnetic chains (Hbpca = bis(2-pyridylcarbonyl)amine)

Two unprecedented families of bpca-based mono-dimensional complexes Cu(bpca)(X) (X = CN, 1; N₃, 2) and [Cu_1 − xFe_x(bpca)](ClO₄) (x = 0, 3; 0.23, 4) were synthesised. The structure of 1 was solved ab initio from X-ray powder diffraction data and refined by Rietveld methods. The complexes 3-4 were characterised by X-ray single crystal diffraction. In 1 the cyano ligand coordinates the metal centres, the Cu centres forming a zigzag 1-D chain along the (0 0 1) direction, while in 3-4, the bpca ligand itself acts as the link towards the metal ions which are arranged in a linear 1-D chain running parallel to the (0 0 1) direction. An infrared spectroscopy study confirmed these coordination modes. The magnetic properties of both chain families were studied. 1-2 do not show significant magnetic interactions, whereas the magnetic behaviour for 3-4 suggests dominant antiferromagnetic interactions between the metal ions within the chains. The magnetic behaviour of 3 was analysed using the Padé approximation of the Bonner-Fisher model for S = 1/2 antiferromagnetic chains. The J value was estimated as 10 K.     

Syntheses, structures and magnetic properties of two new metal complexes based on a pyridyl-diphosphonate ligand

Two new first-raw transition metal diphosphonate complexes, namely, {[Ni₃([hpyedpH)₂(H₂O)₄]·(H₂O)₂}_n (1) and [Mn[hpyedpH₂](H₂O)]_n (2), based on a multidentate ligand 1-hydroxy-2-(3-pyridyl)-ethylidene-1,1-diphosphonic acid (hpyedpH₄) have been synthesized under hydrothermal reaction and structurally characterized by single-crystal X-ray diffraction, IR spectroscopy and element analyses. The data reveals that complex 1 is a 2D layer structure, whereas the complex 2 possesses a 1D motif. The powder X-ray diffraction (PXRD) patterns for complexes 1 and 2 were collected as well, which match well with the ones calculated from their single-crystal structure data. Magnetic measurements show that complex 1 is a ferrimagnet with T_c = 5.0 K. Magnetic studies of complex 2 indicate antiferromagnetic behavior.     

Synthesis and characterization of ether-derivatized aminophosphines and their application in C-C coupling reactions

Four new bis(phosphino)amine ligands (Ph₂P)₂N-C₆H₃-R, where R = 3,5-OMe (1), 2,5-OMe (2), 2,4-OMe (3) or 3,4-OMe (4), were prepared via aminolysis of the corresponding dimethoxyanilines with 2 equiv. of diphenylphosphine chloride in the presence of triethyl amine. Oxidation of these ligands with aqueous H₂O₂, elemental S₈ or Se powder afforded the corresponding chalcogen oxides 1a-4a, sulfides 1b-4b and selenides 1c-4c in good yields. Reaction of 1-4 with [MCl₂(cod)] (M = Pt, Pd; cod = cycloocta-1,5-diene) in equimolar ratios afforded cis-[MCl₂{(Ph₂P)₂N-C₆H₃-R}] (M = Pt; R = 3,5-OMe 1d, R = 2,5-OMe 2d, R = 2,4-OMe 3d, and R = 3,4-OMe 4d. M = Pd; R = 3,5-OMe 1e, R = 2,5-OMe 2e, R = 2,4-OMe 3e, and R = 3,4-OMe 4e). Similarly, reaction of [Cu(CH₃CN)₄]PF₆ with the 1-4 in 1:2 ratio gave [Cu{(Ph₂P)₂N-C₆H₃-R}₂]PF₆ (R = 3,5-OMe 1f, 2,5-OMe 2f, 2,4-OMe 3f and 3,4-OMe 4f). All new compounds were fully characterized by spectroscopy and elemental analysis and the molecular structures of seven representative compounds were determined by single-crystal X-ray crystallography. In addition, the palladium complexes were investigated as pre-catalysts in C-C coupling reactions.     

Palladium(II) complexes obtained from 3,4-bis(cyanamido)cyclobutane-1,2-dione dianion

Three palladium(II) complexes have been synthesized, using 3,4-bis(cyanamido) cyclobutane-1,2-dione dianion (3,4-bis(cyanamido)squarate or 3,4-NCNsq²⁻): [Pd(en)(3,4-NCNsq)] · 1.5H₂O (1) (en=1,2-diaminoethane), [Pd(en)(3,4-(NC(O)NH₂)sq)] · 0.5H₂O (2) and K₃Na[Pd₂(3,4-(NCN)₂sq)₄] · 5H₂O (3). Complex 1 has been characterized by elemental analysis, IR and ¹³C NMR spectroscopies. Complexes 2 and 3 have been characterized by single-crystal X-ray diffraction. In complex 2, the unusual hydration of the cyanamido ligand was observed, it proceeds in the coordination sphere of the palladium and leads to a chelating urea squarate ligand. Complex 3 is an anionic dinuclear complex containing four bridging cyanamido squarate ligands. In complexes 2 and 3, the 3,4-NCNsq²⁻ ligand (hydrated or not) is, for the first time, coordinated to the metal atom by the two amido nitrogen atoms, either in a chelating mode (complex 2) or in a bridging mode giving a short Pd ? Pd distance of 2.8866(15) Å (complex 3). Electrochemical studies in acetonitrile and dmf solutions have been performed on complexes 1 and 3.     

Synthesis, crystal structures and characterization of three novel complexes with N-[2-(2-hydroxybenzylideneamino)ethyl]-4-methyl-benzene-sulfonamide as ligand

Reaction of the N-tosyl-ethylenediamine and salicylaldehyde forms a new sulfonamide Schiff base N-[2-(2-hydroxybenzylideneamino)ethyl]-4-methyl-benzene-sulfonamide (H₂L). Three novel complexes constructed from H₂L, namely, [M(HL)₂] · xH₂O (M = Cu, x = 0 for 1, M = Ni, x = 0 for 2 and M = Zn, x = 1 for 3) have been prepared and characterized via X-ray single-crystal diffraction, elemental analysis, X-ray powder diffraction (XRPD), FT-IR, UV-Vis, TGA and photoluminescence measurements. Complex hydrogen bonds, C-H···π and π-π stacking interactions lead 1-3 to present 1-D, 2-D and 3-D supramolecular architectures, respectively.     

Synthesis, structure and luminescence of a new series of rigid-flexible lanthanide coordination polymers constructed from benzene sulfonic acid and glutaric acid

A new series of rigid-flexible lanthanide coordination polymers, namely, [Eu(BSA)(glu)(H₂O)₂]·H₂O (Ln = Eu(1), Sm(2), Ce(3), Pr(4), Nd(5)); H₂glu = glutaric acid, HBSA = benzene sulfonic acid), have been constructed by a solution synthesis method from the self-assembly of the lanthanide ions (Ln³⁺) with the flexible aliphatic dicarboxylate glutaric and the rigid aromatic benzene sulfonic acid. All of them were characterized by elemental analysis, IR spectroscopy, and single-crystal X-ray diffraction. X-ray single crystal analyses reveal that they crystallize in monoclinic, space group P2₁/n, possessing 2D net-structures. In addition, the phase purities of the bulk samples were identified by X-ray powder diffraction. The thermogravimetric analysis of 1 and photoluminescent properties of 1 and 2 were investigated in detailed.     

Mononuclear single helices of lanthanum(III) and europium(III). Metal dependent diastereomeric excess

Using the 1:2 condensate of benzildihydrazone and 2-acetylpyridine as a tetradentate N donor ligand L, LaL(NO₃)₃ (1) and EuL(NO₃)₃ (2), which are pale yellow in colour, are synthesized. While single crystals of 1 could not be obtained, 2 crystallises as a monodichloromethane solvate, 2·CH₂Cl₂ in the space group Cc with a = 11.7099(5) Å, b = 16.4872(5) Å, c = 17.9224(6) Å and β = 104.048(4)°. From the X-ray crystal structure, 2 is found to be a rare example of monohelical complex of Eu(III). Complex 1 is diamagnetic. The magnetic moment of 2 at room temperature is 3.32 BM. Comparing the FT-IR spectra of 1 and 2, it is concluded that 1 also is a mononuclear single helix. ¹H NMR reveals that both 1 and 2 are mixtures of two diastereomers. In the case of the La(III) complex (1), the diastereomeric excess is only 10% but in the Eu(III) complex 2 it is 80%. The occurrence of diastereomerism is explained by the chiralities of the helical motif and the type of pentakis chelates present in 1 and 2.     

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.