Novel heteroligand complexes of Co(II), Cu(II), Ni(II) and Mn(II) formed by 2,2′-dipyridyl or 1,10-phenanthroline and phosphortriamide ligands: Synthesis and structure

This paper presents examples of mixed-ligand Co(II), Cu(II), Ni(II) and Mn(II) complexes, with a distorted octahedral coordination geometry, with 2,2′-dipyridyl or 1,10-phenanthroline and phosphortriamide ligands. The complexes of the general type ML₂·Lig (where M = Co(II), Cu(II), Ni(II), Mn(II); L⁻ = {Cl₃C(O)NP(O)R₂}⁻ (R = NHBz, NHCH₂CHCH₂, NEt₂); Lig = 2,2′-dipyridyl or 1,10-phenanthroline) were synthesised and characterised by means of X-ray diffraction, IR and UV–Vis spectroscopy. The phosphortriamide ligands are coordinated via oxygen atoms of phosphoryl and carbonyl groups involved in six-membered metal cycles. The additional ligands 2,2′-dipyridyl or 1,10-phenanthroline are coordinated to the central atom, forming five-membered cycles.     

Magnetism and crystal structures of CuMn and CuNi ordered bimetallic chains

The syntheses, crystal structures and magnetic properties of the new bimetallic compounds {CuL_α[Ni(NCS)₄(H₂O)₂]} (1) and {CuL_α[Mn(NCS)₄(H₂O)₂]} (2), where L = N-dl-5,12-dimethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene, are reported. Both structures consist of well-separated and magnetically equivalent layers which are composed of thiocyanate-bridged Cu(II)–Mn(II) or Cu(II)–Ni(II) binuclear units and create infinite polymeric zig-zag-like chains in the crystal lattices. The [Ni(NCS)₄(H₂O)₂] and [Mn(NCS)₄(H₂O)₂] molecular fragments have a distorted octahedral symmetry. The geometry of the Cu(II) unit is octahedral with the apical positions occupied by bridging thiocyanate ligands and the basal ones by four nitrogen atoms from the macrocyclic ring. The shortest intramolecular M–M distances are: 6.342 Å (Cu–Ni) and 6.421 Å (Cu–Mn). Magnetic susceptibility and magnetization measurements for the examined compounds have been carried out over the range 1.8–300 K. The data suggest antiferromagnetic interactions through the thiocyanate bridge. Finally, the magnitudes of the Cu(II)–M(II) interactions (M = Ni and Mn) have been compared and qualitatively rationalised.     

Syntheses and X-ray structures of Cu(II) and Zn(II) complexes of N,N′-dibenzyl-(R,R)-1,2-diaminocyclohexane and application to nitroaldol reaction

Chiral Cu(II) and Zn(II) complexes with N,N′-dibenzyl-(R,R)-1,2-diaminocyclohexane ligands were synthesized and characterized. X-ray crystal structures of these complexes reveal that Cu complex has the distorted square-planar geometry and the Zn one has the nearly tetrahedral pattern. The coordination of metals to the chiral diamine ligand leads to a 5-membered metallaheterocycle of (S,S)-configuration of nitrogen atoms. Their asymmetric catalytic activities to nitroaldol reaction of benzaldehyde and nitromethane were examined. The difference of the geometry around metals leads to the opposite preferential configuration of alcohol products using these chiral complexes as asymmetric catalysts in the presence of triethylamine or diisopropylethylamine.     

Synthesis,structure, spectroscopic,magnetic and electrochemical studies of a rare syn–anti acetate-bridged copper(II) complex

The structure, spectroscopy and electrochemical properties of a novel dinuclear copper(II) complex, [{Cu(phen)₂}₂(μ-CH₃COO)][PF₆]₃ where phen = 1,10-phenanthroline, is reported. The crystal structure contains two independent Cu(II) ions, with different geometry around each copper center, which are bridged by an acetate anion. The acetate-bridged ligand shows a syn–anti coordination mode with a trigonal bipyramidal geometry for the Cu(1) center and a distorted square-based pyramidal geometry for the Cu(2) center. The angular structural index parameter τ for Cu(1) and Cu(2) is 0.9 and 0.33, respectively. The copper(II) atoms display a different geometry with a N₄O chromophore group and with Cu–O distances of 1.993(5)–1.996(5) Å and Cu–N distances which vary from 1.980(5) to 2.161(6) Å. The intra Cu…Cu separation is 4.9904(5) Å. The effective magnetic moment (μ_eff) of the complex was measured by the Evans method. The cyclic voltammogram of [{Cu(phen)₂}₂(μ-CH₃COO)][PF₆]₃ shows two waves at positive potential which are assigned to the two Cu(II/I) reduction couples.     

Crystal structure,spectroscopy and magnetism of a dinuclear strongly antiferromagnetically coupled N-oxido-bridged Cu(II) compound with 2,2′-bipyridine-1,1′-dioxide (bpdo) as a ligand; [Cu2(bpdo)2Br4]

A new dinuclear compound, [Cu₂(bpdo)₂Br₄], (in which bpdo = 2,2′-Bipyridine-1,1′-dioxide), has been synthesized and fully characterized, including the X-ray and the magnetic susceptibility. Each copper(II) ion in the dinuclear compound has a distorted square pyramidal geometry with the basal plane formed by two oxygen atoms of two ligand molecules which are bridging between the Cu ions with Cu–O distances of 2.021(2) and 2.039(2) Å and two bromide atoms with Cu–Br distances of 2.3577(6) and 2.3665(7) Å. The fifth position is occupied by a non bridging oxygen atom of a ligand with a Cu–O distance of 2.197(2) Å. The distance between the Cu ions is 3.334 Å, while the Cu–O–Cu angle is 110.37(9)°. The magnetic susceptibility measurements (from 5 to 350 K) agree with a very strong antiferromagnetic interaction with a large singlet–triplet splitting (J) of −905 cm⁻¹. At high T (above 250 K) a triplet powder EPR is observed.     

Crystal structure and magnetic properties of the 1D bimetallic thiocyanate bridged compound: {(CuL1)[Co(NCS)4]}(L1 = N-rac-5,12-Me2-[14]-4,11-dieneN4)

The synthesis, crystal structure and magnetic properties are reported for the new bimetallic compound {(CuL₁)[Co(NCS)₄]} where L₁ = N-rac-5,12-dimethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene. The complex forms a one-dimensional zig-zag coordination polymer along the crystallographic c axis, with Co(II) and Cu(II) ions connected via thiocyanate bridges. The Co(II) centre in the [Co(NCS)₄] fragment approximates a distorted tetrahedral symmetry. The Cu(II) geometry is a distorted tetragonal bipyramid with the apical position occupied by the bridging thiocyanate ligand and the basal ones by the four nitrogen atoms from the macrocyclic ring. The polymer chain nearest Cu(1)?Co(1) distances are 6.4152(9) and 6.0988(9) Å and the nearest Cu(1)?Co(1) interchain distances are 6.8609(9), 6.9628(9) and 6.0336(10) Å. The magnetization measurements for the examined compound have been carried out over the range 1.8–300 K. This data suggest ferromagnetic interactions through the thiocyanate bridge.     

Co(II), Ni(II) and Zn(II)-orotate complexes with N-methylimidazole: Synthesis, crystal structures and antimicrobial activities

Three Co(II), Ni(II) and Zn(II) complexes of orotate with the N-methylimidazole ligand were synthesized and characterized by means of elemental and thermal analysis, magnetic susceptibilities, IR, UV-Vis spectroscopic and antimicrobial activity studies. The crystal structures of [Co(HOr)(H₂O)₂(Nmeim)₂]₃·H₂O (1), [Ni(HOr)(H₂O)₂(Nmeim)₂] (2) and [Zn(HOr)(H₂O)(Nmeim)₂] (3) were determined by the single crystal X-ray diffraction technique (H₃Or = orotic acid and Nmeim = N-methylimidazole). In complexes 1 and 2, the Co(II) and Ni(II) ions have distorted octahedral geometries with two Nmeim, one orotate and two aqua ligands. Complex 3 has a distorted trigonal bipyramidal geometry with two N-methylimidazole, one orotate and one aqua ligands. In the complexes, the orotate is coordinated to the metal(II) ions through the deprotonated nitrogen atom of the pyrimidine ring and the oxygen atom of the carboxylate group as a bidentate ligand. The complexes form a three-dimensional framework by hydrogen bonding, C-H?π and π?π stacking interactions. The MIC values of the complexes against selected microorganisms were determined to be in range 300-2400 μg/mL.     

Redox-active metal(II) complexes of sterically hindered phenolic ligands: Antibacterial activity and reduction of cytochrome c. Part II. Metal(II) complexes of o-diphenol derivatives of thioglycolic acid

The synthesis and physico-chemical characterization of Fe(II) and Mn(II) complexes of 2-[4,6-di(tert-butyl)-2,3-dihydroxyphenylsulfanyl]acetic acid (HL^I) and 2-[4,6-di(tert-butyl)-2,3-dihydroxyphenylsulfinyl]acetic acid (HL^II) were carried out. The investigation of the molecular and electronic structure of Cu(II), Ni(II), Zn(II), Fe(II) and Mn(II) complexes has been performed within the density functional theory (DFT) framework. The computed properties were compared to the experimental ones, and molecular structures of the compounds were proposed based on the array of spectral data and quantum chemical calculations. Antibacterial activity of the Fe(II) and Mn(II) complexes was evaluated in comparison with Cu(II), Co(II), Ni(II) and Zn(II) complexes and three standard antibiotics; it was found to follow the order: (1) Сu(L^I)₂ > Mn(L^I)₂ > HL^I > Ni(L^I)₂ > Zn(L^I)₂ > Fe(L^I)₂ > Co(H₂O)₂L^I; (2) Cu(L^II)₂ > Сo(L^II)₂ > Ni(L^II)₂ > Mn(H₂O)₂(L^II)₂ > Fe(L^II)₂ > HL^II > Zn(L^II)₂; their reducing ability (determined electrochemically) followed the same order. Spectrophotometric investigation was carried out in order to estimate the rate of the reduction of bovine heart сytochrome c with the ligands and their metal(II) complexes. The complexes Сu(L^I)₂, Mn(L^I)₂ and Co(L^II)₂ with the high reducing ability were found to be characterized by the highest rates of Cyt с reduction. NADPH:cytochrome P450-reductase had no substantial effect on the rate of сytochrome c reduction with HL^I and HL^II ligands.     

Synthesis and crystal structure of manganese(II) complexes with high-denticity ligands derived from azacrowns

The hepta- and octa-dentate ligands N,N′-bis(2-aminobenzyl)-1,10-diaza-15-crown-5 (L¹) and N,N′-bis(2-aminobenzyl)-1,10-diaza-18-crown-6 (L²), respectively, form stable mononuclear Mn(II) complexes. Spectrophotometric titrations performed in acetonitrile solution indicate the formation of mononuclear Mn(II) complexes with both ligands, and no evidence for the formation of binuclear complexes was obtained. The optimal architecture of L¹ allows it to impose the less usual pentagonal bipyramidal geometry on the Mn(II) guest, and the X-ray crystal structure of [Mn(L¹)](ClO₄)₂ shows that the Mn(II) ion is deeply buried in the receptor cavity, coordinated to the seven available donor atoms, with the perchlorate anions remaining outside the metal coordination sphere. In spite of its higher denticity, the receptor L² is unable to form the expected binuclear complexes. The X-ray crystal structure of [Mn(L²)](NO₃)₂ consists of the [Mn(L²)]²⁺ cation and nitrate anions involved in hydrogen-bonding interactions with the aniline groups. In [Mn(L²)]²⁺ the metal ion is also placed in the crown hole, but as a result of the large size of the macrocyclic cavity only six of the eight available donor atoms of the receptor form part of the Mn(II) coordination sphere, with the Mn(II) ion found in a distorted octahedral coordination environment.     

Synthesis, spectral and biological studies of nitrogen–sulphur donor macrocyclic ligands and their transition metals complexes

Mn(II), Co(II), Ni(II) and Cu(II) complexes have been synthesized with 22 and 24 membered tetramide macrocyclic ligands viz; 1,9,12,20-tetraaza-2,8,13,19-tetraone-5,16-dithiacyclodocosane [L¹] and 1,9,13,21-tetraaza-2,8,14,20-tetraone-5,17-dithiacyclotetracosane [L²] and characterized by elemental analysis, molar conductance, magnetic susceptibility measurements, mass, IR, electronic EPR spectral studies and electrochemical properties. The molar conductance of all the complexes in DMSO solution is corresponding to 1:2 electrolyte. Thus these complexes may be formulated as [M(L′)]Cl₂ [where M = Mn(II), Co(II), Ni(II) and Cu(II) L′ = L¹ and L²]. On the basis of spectral studies a distorted octahedral geometry has been assigned for all the complexes. The ligands and their complexes were also screened in vitro against two pathogenic fungi (F. moniliformae and R. solani) to assess their growth inhibiting potential.     

Spectroscopy and stereochemistry of the optically active copper(II), cobalt(II) and nickel(II) complexes with Schiff bases N,N′-(1R,2R)-(−)-1,2-cyclohexylenebis(3-methylbenzylideneiminato) and N,N′-(1R,2R)-(−)-1,2-cyclohexylenebis(5-methylbenzylideneiminato)

Schiff bases obtained from N,N′-(1R,2R)-1,2-cyclohexanediamine and 2-hydroxy-3-methylbenzaldehyde, 2-hydroxy-5-methylbenzaldehyde, have been used as ligands for copper(II), cobalt(II) and nickel(II). The complexes were characterized with UV–Vis, circular dichroism (CD), infrared, diamagnetic and paramagnetic ¹H NMR spectroscopy. CD spectra revealed exciton coupled π→π* transitions. Assignments of LMCT and d–d transitions in CD spectra of Ni(II), Co(II) and Cu(II) complexes is proposed. CD data are characteristic for central ion tetrahedral distortion from the planarity and λ conformation of the cyclohexane ring. ¹H NMR of Ni(II) complexes exhibited significant coordination shifts of CHN and ring protons which are in the closest proximity to Ni(II). The ¹H NMR paramagnetic spectra of Co(II) complexes revealed the most upfield shifted resonance at −60 ppm assigned to CHN and −28 ppm to hydrogen atom at C(5′) of the phenyl ring. Results of spectral analyses suggest central ions in a distorted square-planar geometry with N₂O₂ chromofore group.     

Coordination behaviour of Schiff base 2-acetyl-2-thiazoline hydrazone (ATH) towards cobalt(II), nickel(II) and copper(II)

The synthesis and characterization of Co(II), Ni(II) and Cu(II) complexes of 2-acetyl-2-thiazoline hydrazone (ATH) are reported. Elemental analysis, IR spectroscopy, UV–Vis–NIR diffuse reflectance and magnetic susceptibility measurement, as well as, in the case of copper complex EPR spectroscopy, have been used to characterize the complexes. In addition, the structure of [NiCl₂(ATH)₂] (2) and [{CuCl(ATH)}₂(μ-Cl)₂] (3) have been determined by single crystal X-ray diffraction. In all complexes, the ligand ATH bonds to the metal ion through the imine and thiazoline nitrogen atoms. X-ray data indicates that the environment around the nickel atom in 2 may be described as a distorted octahedral geometry with the metallic atom coordinated to two chlorine atoms, two thiazoline nitrogen atoms and two imino nitrogen atoms. With regard to 3, it can be said that its structure consists of dimeric molecules in which copper ions are bridge by two chlorine ligands. The geometry about each copper ion approximates to a distorted square pyramid with each copper atom coordinated to one thiazoline nitrogen atom, one imine nitrogen atom, one terminal chlorine ligand and two bridge chlorine ligands. In compound 3, magnetic susceptibility measurements in the temperature range 2–300 K show an intradimer antiferromagnetic interaction (J = −7.5 cm⁻¹).     

Redox-active antifungal cobalt(II) and copper(II) complexes with sterically hindered o-aminophenol derivatives

Co(II) complexes with 4,6-di(tert-butyl)-2-aminophenol (HL^I) and 2-anilino-4,6-di(tert-butyl)phenol (HL^II) have been synthesized and characterized by means of physico-chemical methods. The compounds HL^I and HL^II coordinate in their singly deprotonated forms and behave as bidentate O,N-coordinated ligands; their low-spin Co(II) complexes are characterized by CoN₂O₂ coordination modes and square planar geometry. Both the free ligands and their Co(II) and Cu(II) complexes (we have produced and characterized the latter before) exhibit a pronounced antifungal activity against Aspergillus niger, Fusarium spp., Mucor spp., Penicillium lividum, Botrytis cinerea, Alternaria alternata, Sclerotinia sclerotiorum, Monilia spp., which in a number of cases is comparable with that of Nystatin and Terbinafine or even higher. The reducing properties of the ligands and their metal(II) complexes, as well as their antifungal activities, were found to decrease in the order: Cu(L^I)₂ > Cu(L^II)₂ ? Co(L^I)₂ > Co(L^II)₂ > HL^I > HL^II.     

Synthesis,Characterization and Spectral Studies of Triethanolamine Complexes of Metal Saccharinates. Crystal Structures of [Co(TEA)2](SAC)2 AND [Cu2(μ-TEA)2(SAC)2]·2(CH3OH)

The novel transition metal saccharinate complexes of triethanolamine (TEA) have been synthesized and characterized by elemental analyses, magnetic moments, UV-Vis and IR spectra. Mn(II), Co(II), Ni(II), Zn(II), Cd(II) and Hg(II) form mononuclear complexes of [M(TEA)₂](SAC)₂, where SAC is the saccharinate ion, while the Cu(II) complex is dimeric. The TEA ligand acts as a tridentate N,O,O'-donor ligand and one ethanol group is not involved in coordination. The SAC ion does not coordinate to the metal ions and is present as the counter-ion in the Mn(II), Co(II), Ni(II), Zn(II), Cd(II) and Hg(II) complexes, but coordinates to the Cu(II) ion as a monodentate ligand. The crystal structures of the [Co(TEA)₂](SAC)₂ and [Cu₂(μ-TEA)₂(SAC)₂]·2(CH₃OH) complexes were determined by single crystal x-ray diffraction. The Co(II) ion has a distorted octahedral coordination by two TEA ligands. The Cu(II) complex crystallizes as a dimethanol solvate and has doubly alkoxo-bridged centrosymmetric dimeric molecules involving two tridentate triethanolaminate (deprotonated TEA) and two monodentate SAC ligands. The geometry of each Cu(II) ion is a distorted square pyramid. Both crystal structures are stabilized by hydrogen bonds to form a three-dimensional network.     

Synthesis and structure determination of Co(HNCN)2 and Ni(HNCN)2

Well-crystallized cobalt and nickel hydrogencyanamide, Co(HNCN)₂ and Ni(HNCN)₂, were synthesized from the corresponding ammonia complexes [M(NH₃)₆]²⁺ under aqueous cyanamide conditions. The X-ray and neutron powder data evidence the orthorhombic system and space group Pnnm. The cell parameters for Co(HNCN)₂ are a=6.572(1), b=8.805(2), c=3.267(1) Å, and Z=2; for the isotypic Ni(HNCN)₂, the cell parameters arrive at a=6.457(1), b=8.768(2), c=3.230(1) Å. The octahedral coordinations of the metal ions are marginally squeezed, with interatomic distances of 4×Co-N=2.134(5) Å, 2×Co-N=2.122(9) Å, and 4×Ni-N=2.133(6) Å, 2×Ni-N=2.035(11) Å. The HNCN⁻ units appear as slightly bent (177.5(2)° for Co(HNCN)₂ and 175.7(2)° for Ni(HNCN)₂) and exhibit cyanamide shape character due to triple- and single-bond C-N distances (1.20(2) vs. 1.33(2) Å for Co(HNCN)₂ and 1.15(2) vs. 1.38(2) Å for Ni(HNCN)₂). The infrared vibration data compare well with those of the three existing alkali-metal hydrogencyanamides.     

Syntheses, crystal structures and spectral properties of three chiral complexes [M((R, R)-et-pybox)Cl2] (M=Zn and Mn) and [Ni((R, R)-et-pybox)(H2O)2Cl]Cl

Three chiral complexes: [M((R, R)-et-pybox)Cl₂] (M=Zn, 1, and Mn, 2) and [Ni((R, R)-et-pybox)(H₂O)₂Cl]Cl (3) ((R, R)-et-pybox is C₂-symmetric 2,6-bis[4′-(R)-ethoxyoxazolin-2′-yl]pyridine) have been synthesized and characterized by elemental analysis, IR, UV, TG and single-crystal X-ray diffraction. Single-crystal X-ray diffraction analyses show that 1 is isostructural to 2, the obtained complexes are of isolated mononuclear and the metal atoms of 1 and 2 have distorted trigonal bipyramidal coordination environment. A feature of interest is noted in the unit cell of 3, there exist two types of molecules, which similarly have a distorted octahedral geometry but only slightly differ in the orientation of the coordinated atoms to the central Ni atom. These two types of molecules interact with each other by O–H···Cl hydrogen bonds, giving rise to one-dimensional ribbon structure.     

Hydrothermal synthesis, thermal, structural, spectroscopic and magnetic studies of the Mn5−xCox(HPO4)2(PO4)2(H2O)4 (x=1.25, 2, 2.5 and 3) finite solid solution

The Mn_5−xCo_x(HPO₄)₂(PO₄)₂(H₂O)₄ (x=1.25, 2, 2.5, 3) finite solid solution has been synthesized by mild hydrothermal conditions under autogeneous pressure. The phases crystallize in the C2/c space group with Z=4, belonging to the monoclinic system. The unit-cell parameters obtained from single crystal X-ray diffraction are: a=17.525(1), b=9.0535(6), c=9.4517(7) Å, β=96.633(5) ° being R1=0.0436, wR2=0.0454 for Mn75Co25; a=17.444(2), b=9.0093(9), c=9.400(1) Å, β=96.76(1) ° being R1=0.0381, wR2=0.0490 for Mn60Co40; a=17.433(2), b=8.9989(9), c=9.405(1) Å, β=96.662(9) ° being R1=0.0438, wR2=0.0515 for Mn50Co50 and a=17.4257(9), b=8.9869(5), c=9.3935(5) Å, β=96.685(4) ° being R1=0.0296, wR2=0.0460 for Mn40Co60. The structure consists of a three dimensional network formed by octahedral pentameric entities (Mn,Co)₅O₁₆(H₂O)₆ sharing vertices with the (PO₄)³⁻ and (HPO₄)²⁻ tetrahedra. The limit of thermal stability of these compounds is, approximately, 165 °C, near to this mean temperature the phases loose their water content in two successive steps. IR spectra show the characteristic bands of the water molecules and the phosphate and hydrogen-phosphate oxoanions. The diffuse reflectance spectra are consistent with the presence of MO₆ octahedra environments in slightly distorted octahedral geometry, except for the M(3)O₆ octahedron which presents a remarkable distortion and so a higher Dq parameter. The mean value for the Dq and B-Racah parameter for the M(1),(2)O₆ octahedra is 685 and 850 cm⁻¹, respectively. These parameters for the most distorted M(3)O₆ polyhedron are 825 and 880 cm⁻¹, respectively. The four phases exhibit antiferromagnetic couplings as the major magnetic interactions. However, a small spin canting phenomenon is observed at low temperatures for the two phases with major content in the anisotropic-Co(II) cation.     

Synthesis, structure and physical properties of Ru ferrites: BaMRu5O11 (M=Li and Cu) and BaM′2Ru4O11 (M′=Mn, Fe and Co)

The synthesis, structure, and physical properties of five R-type Ru ferrites with chemical formula BaMRu₅O₁₁ (M=Li and Cu) and BaM′₂Ru₄O₁₁ (M′=Mn, Fe and Co) are reported. All the ferrites crystallize in space group P6₃/mmc and consist of layers of edge sharing octahedra interconnected by pairs of face sharing octahedra and isolated trigonal bipyramids. For M=Li and Cu, the ferrites are paramagnetic metals with the M atoms found on the trigonal bipyramid sites exclusively. For M′=Mn, Fe and Co, the ferrites are soft ferromagnetic metals. For M′=Mn, the Mn atoms are mixed randomly with Ru atoms on different sites. The magnetic structure for BaMn₂Ru₄O₁₁ is reported.     

Preparation and structural characterization of nickel(II), cobalt(II), zinc(II) and tin(IV) complexes of the isatin Schiff bases of S-methyl and S-benzyldithiocarbazates

The molecular structures of the isatin Schiff bases of S-methyldithiocarbazate (Hisasme) and S-benzyldithiocarbazate (Hisasbz) have been determined by X-ray diffraction and their complexes of general formula [ML₂]·n(solvate) [M = Co²⁺, Ni²⁺, Zn²⁺; L = anionic forms of Hisasme or Hisasbz; solvate = DMF, DMSO; n = 1, 2] and [Sn(L)Ph₂Cl]·nMeOH (n = 0, 1) have been synthesized and characterized by a variety of physicochemical techniques and X-ray diffraction. The bis-ligand complexes, [Ni(isasbz)₂]·2DMSO and [Co(isasme)₂]·DMF have a six-coordinate, distorted octahedral geometry with the two uninegatively charged tridentate ONS ligands coordinated to the metal ions meridionally via the amide O-atoms, the azomethine nitrogen atoms and the thiolate sulfur atoms. By contrast, the crystal structure of [Zn(isasbz)₂]·2DMF shows a four-coordinate distorted tetrahedral geometry with the two Schiff bases coordinated as NS bidentate ligands via the azomethine nitrogen atoms and the thiolate sulfur atoms. Steric constraints of the rigid tridentate ligands lead to unusual ‘pseudo-coordination’ of the O-donors which occupy sites close to the metal but too distant to be considered as true coordinate bonds.The crystal structures of the tin(IV) complexes [SnLPh₂Cl]·nMeOH (L = isasme and isasbz; n = 0, 1) also show that the Schiff bases act as monoanionic bidentate NS chelating agents coordinating the tin(IV) ion via the azomethine nitrogen atoms and the thiolate sulfur atoms, the tin atom in each complex is five-coordinate with a highly distorted geometry intermediate of square pyramidal and trigonal bipyramidal. Again Sn?O contacts are weak and do not qualify as coordinate bonds.     

Metal-betaine interactions. Part XII

Two copper(II) complexes of pyridine betaine (C₅H₅N⁺CH₂COO^–; pyBET) were prepared and characterized by X-ray crystallography. In [Cu(pyBET)(H₂O₂)₂(SO₄)]_n (1), each Cu (II) atom is in a distorted square-pyramidal environment surrounded by a carboxylato oxygen atom [1.944(5) Å], two oxygen atoms [1.921 (5) basal, 2.268(5) apical Å] from different sulfato groups, and two aqua ligands [1.944(4) Å]. The primary coordination sphere is extended into a zigzag chain through sulfato bridging linkages, and hydrogen bonding involving the aqua ligands generates a three-dimensional network. [Cu(pyBET)(H₂O)₂Cl₂]·H₂O (2) features a discrete metal complex with its distorted square-pyramidal coordination sites occupied by a carboxylato oxygen atom [2.000(2) Å], two aqua ligands [1.968(3) Å], and two chloro ligands [2.266(1), 2.469(1) Å] of which one is apical. The lattice water molecules form hydrogen bonds with the aqua and chloro ligands to yield a layer structure.