Pseudo-octahedral Coordination Sphere Research Articles

Crystal structure of bis-{3-(3-bromo-4-methoxyphenyl)-5-[6-(1H-pyrazol-1-yl)pyridin-2-yl]-1,2,4-triazol-3-ato}-iron(II) methano-l disolvate.

The unit cell of the title compound, [FeII(C17H12BrN6O)2]·2MeOH, consists of a charge-neutral complex mol-ecule and two independent mol-ecules of methanol. In the complex mol-ecule, the two tridentate ligand mol-ecules 2-[5-(3-bromo-4-meth-oxy-phen-yl)-4H-1,2,4-triazol-3-yl]-6-(1H-pyrazol-1-yl)pyridine coordinate to the FeII ion through the N atoms of the pyrazole, pyridine and triazole groups, forming a pseudo-octa-hedral coordination sphere around the central ion. In the crystal, neighbouring asymmetric mol-ecules are linked through weak C-H(pz)⋯π(ph) inter-actions into chains, which are then linked into layers by weak C-H⋯N/C inter-actions. Finally, the layers stack into a three-dimensional network linked by weak inter-layer C-H⋯π inter-actions between the meth-oxy groups and the phenyl rings. The inter-molecular contacts were qu-anti-fied using Hirshfeld surface analysis and two-dimensional fingerprint plots, revealing the relative contributions of the contacts to the crystal packing to be H⋯H 34.2%, H⋯C/C⋯H 25.2%, H⋯Br/Br⋯H 13.2%, H⋯N/N⋯H 12.2% and H⋯O/O⋯H 4.0%. The average Fe-N bond distance is 1.949 Å, indicating the low-spin state of the FeII ion. Energy framework analysis at the HF/3-21 G theory level was performed to qu-antify the inter-action energies in the crystal structure.

Crystal structure of bis{3-(3,4-dimethylphenyl)-5-[6-(1H-pyrazol-1-yl)pyridin-2-yl]-4H-1,2,4-triazol-4-ido}iron(II) methanol disolvate

As a result of the high symmetry of the Aea2 structure, the asymmetric unit of the title compound, [FeII(C18H15N6)2]·2MeOH, consists of half of a charge-neutral complex mol-ecule and a discrete methanol mol-ecule. The planar anionic tridentate ligand 2-[5-(3,4-di-methyl-phen-yl)-4H-1,2,4-triazol-3-ato]-6-(1H-pyrazol-1-yl)pyridine coordinates the FeII ion meridionally through the N atoms of the pyrazole, pyridine and triazole groups, forming a pseudo-octa-hedral coordination sphere of the central ion. The average Fe-N bond distance is 1.955 Å, indicating a low-spin state of the FeII ion. Neighbouring cone-shaped mol-ecules, nested into each other, are linked through double weak C-H(pz)⋯π(ph') inter-actions into mono-periodic columns, which are further linked through weak C-H⋯N'/C' inter-actions into di-periodic layers. No inter-actions shorter than the sum of the van der Waals radii of the neighbouring layers are observed. Energy framework analysis at the B3LYP/6-31 G(d,p) theory level, performed to qu-antify the inter-molecular inter-action energies, reproduces the weak inter-layer inter-actions in contrast to the strong inter-action within the layers. Inter-molecular contacts were qu-anti-fied using Hirshfeld surface analysis and two-dimensional fingerprint plots, showing the relative contributions of the contacts to the crystal packing to be H⋯H 48.5%, H⋯C/C⋯H 28.9%, H⋯N/N⋯H 16.2% and C⋯C 2.4%.

Anion Binding Based on Hg3 Anticrowns as Multidentate Lewis Acidic Hosts.

We present herein a combined structural and computational analysis of the anion binding capabilities of perfluorinated polymercuramacrocycles. The Cambridge Structural Database (CSD) has been explored to find the coordination preference of these cyclic systems toward specific Lewis bases, both anionic and neutral. Interaction energies with different electron-rich species have been computed and further decomposed into chemically meaningful terms by means of energy decomposition analysis. Furthermore, we have investigated, by means of the natural resonance theory and natural bond orbital analyses how the orbitals involved in the interaction are key in determining the final geometry of the adduct. Finally, a generalization of the findings in terms of the molecular orbital theory has allowed us to understand the formation of the pseudo-octahedral second coordination sphere in linear Hg(II) complexes.

Zn and Ni complexes of pyridine-2,6-di-carboxyl-ates: crystal field stabilization matters!

Six reaction products of ZnII and NiII with pyridine-2,6-di-carb-oxy-lic acid (H2Lig1), 4-chloro-pyridine-2,6-di-carb-oxy-lic acid (H2Lig2) and 4-hy-droxy-pyridine-2,6-di-carb-oxy-lic acid (H2Lig3) are used to pinpoint the structural consequences of crystal field stabilization by an incomplete d shell. The pseudo-octa-hedral ZnII coordination sphere in bis-(6-carb-oxy-picolinato)zinc(II) trihydrate, [Zn(C7H4NO4)2]·3H2O or [Zn(HLig1)2]·3H2O, (1), is significantly less regular than that about NiII in the isostructural compound bis-(6-carb-oxy-picolinato)nickel(II) trihydrate, [Ni(C7H4NO4)2]·3H2O or [Ni(HLig1)2]·3H2O, (2). The ZnII complexes poly[(4-chloro-pyridine-2,6-di-carboxyl-ato)zinc(II)], [Zn(C7H2ClNO4)] n or [Zn(Lig2)] n , (3), and poly[[(4-hy-droxy-pyridine-2,6-di-carboxyl-ato)zinc(II)] monohydrate], {[Zn(C7H3NO5)]·H2O} n or {[Zn(Lig3)]·H2O} n , (4), represent two-dimensional coordination polymers with chelating and bridging pyridine-2,6-di-carboxyl-ate ligands in which the coordination polyhedra about the central cations cannot be associated with any regular shape; their coordination environments range between trigonal-bipyramidal and square-pyramidal geometries. In contrast, the corresponding adducts of the diprotonated ligands to NiII, namely tri-aqua-(4-chloro-pyridine-2,6-di-carboxyl-ato)nickel(II), [Ni(C7H2ClNO4)(H2O)3] or [NiLig2(OH2)3)], (5), and tri-aqua-(4-hy-droxy-pyridine-2,6-di-carboxyl-ato)nickel(II) 1.7-hydrate, [Ni(C7H3NO5)(H2O)3]·1.7H2O or [NiLig3(OH2)3)]·1.7H2O, (6), feature rather regular octa-hedral coordination spheres about the transition-metal cations, thus precluding the formation of analogous extended structures.

Analysis of Magnetic Anisotropy and the Role of Magnetic Dilution in Triggering Single-Molecule Magnet (SMM) Behavior in a Family of CoII YIII Dinuclear Complexes with Easy-Plane Anisotropy.

Three new closely related CoII YIII complexes of general formula [Co(μ-L)(μ-X)Y(NO3 )2 ] (X- =NO3- 1, benzoate 2, or 9-anthracenecarboxylato 3) have been prepared with the compartmental ligand N,N',N''-trimethyl-N,N''-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylenetriamine (H2 L). In these complexes, CoII and YIII are triply bridged by two phenoxide groups belonging to the di-deprotonated ligand (L2- ) and one ancillary anion X- . The change of the ancillary bridging group connecting CoII and YIII ions induces small differences in the trigonally distorted CoN3 O3 coordination sphere with a concomitant tuning of the magnetic anisotropy and intermolecular interactions. Direct current magnetic, high-frequency and -field EPR (HFEPR), frequency domain Fourier transform THz electron paramagnetic resonance (FD-FT THz-EPR) measurements, and ab initio theoretical calculations demonstrate that CoII ions in compounds 1-3 have large and positive D values (≈50 cm-1 ), which decrease with increasing the distortion of the pseudo-octahedral CoII coordination sphere. Dynamic ac magnetic susceptibility measurements indicate that compound 1 exhibits field-induced single-molecule magnet (SMM) behavior, whereas compounds 2 and 3 only display this behavior when they are magnetically diluted with diamagnetic ZnII (Zn/Co=10:1). In view of this, it is always advisable to use magnetically diluted complexes, in which intermolecular interactions and quantum tunneling of magnetism (QTM) would be at least partly suppressed, so that "hidden single-ion magnet (SIM)" behavior could emerge. Field- and temperature-dependence of the relaxation times indicate the prevalence of the Raman process in all these complexes above approximately 3 K.

Synthesis, spectroscopic studies, thermal analyses, biological activity of tridentate-coordinated transition-metal complexes [M(L)X2] and crystal structure of [ZnBr2(2,6-bis(tert-butylthiomethyl)pyridine)

A new terdentate acyclic pincer ligand, 2,6-bis( tert -butylthiomethyl)pyridine (tbtmp), was synthesized and reacted with several complexes of iron, zinc, nickel, cobalt, and copper. The ligand and its coordination compounds were characterized using elemental analysis, infrared, 1 H- and 13 C-NMR-spectroscopy, thermal analyses, plus—for the Zn complex—single-crystal X-ray diffractometry. The structure of [Zn(L)Br 2 ] was solved in the tetragonal crystal system, chiral space groups P4 1 2 1 2 and P4 3 2 1 2 (No. 92 and No. 96, a = 947.2(1) pm, c = 2265.2(5) pm), revealing five-fold coordination of the metal atoms. According to spectroscopy, all complexes share the same coordination environment around the metal atoms, consisting of two halide anions and a sulfur-methylene-pyridine-methylene-sulfur entity; tbtmp acts as a tridentate ligand with the pyridine N atom and both tert -butylthio S atoms coordinating to the metal ions (NS2). The analysis results indicate that the metal ions are coordinated as distorted pseudo-bipyramids, LMX 2 , with the chelate ligand meridionally arranged. One of the complexes contains ethanol as an additional ligand, resulting in a pseudo-octahedral coordination sphere [Ni(L)Cl 2 EtOH]. The latter was obtained in the form of green crystals, which turn into a red powder with loss of the ethanol molecule. Fe (III), Co(II), Ni(II) and Cu(II) metal complexes [M(L)Cl 2 ] were screened for their antibacterial activity against B. subtilis G(+) and Escherichia coli G(−) bacteria, and fungus ( Candida albicans and Aspergillus flavus ).

{Ru(CO)x}-core complexes with selected azoles: Synthesis, X-ray structure, spectroscopy, DFT analysis and evaluation of cytotoxic activity against human cancer cells

The reaction of [RuII2(CO)6Cl2], 1, in methanol with azoles affords complexes that contain the fac-{RuII(CO)3}2+-core. The complexes presented in this paper have the general formula fac-[RuII(CO)3Cl2L], with a molecule L of imidazole (IM), 2, or N-methyl-imidazole (MIM), 3, as a ligand in the pseudo-octahedral coordination sphere that is completed by two chlorido ligands cis to each other. The compounds show an appreciable solubility in water (up to ca 1g/L) at 25°C, and are well soluble in other solvents, such as alcohol, acetone, dicholoromethane, dimethylsulfoxide, and in mixtures of solvents. In the case where water is present in the medium (10% v/v or higher), significant dissociation of the Ru–N bond that is trans to a carbonyl ligand occurs, and a series of substitutions and other types of reactions may take place afterwards, depending on the reactants and the applied experimental conditions. The synthesis and isolation of single crystals of 2 was performed by reacting the starting dimer 1 with 1-acetylimidazole in alcohol medium. DFT structure simulations/optimizations were carried out at Becke3lyp level of theory by using several basis sets up to 6-311++G∗∗ for C, H, Cl, N and O atoms, and the Lanl2DZ pseudo-potential for Ru. In vitro cytotoxicity tests for 2, 3 and fac-[RuII(CO)3Cl2(THZ)] (THZ=1,3-thiazole), 4, showed IC50 values mostly in the range 100–200μM in CH1 (ovarian carcinoma) and SW480 (colon carcinoma) cell lines. ESI-MS studies revealed the ability of these complexes to link the model proteins Lysozyme and Cytochrome c and similar binding patterns are highlighted; interestingly, protein binding is accompanied by a partial release of the original ligands. Fragments of the type [RuII(CO)2]2+ or [RuII(CO)]2+ are found associated to the proteins.

First example of a 1:1 vanadium(IV)–citrate complex featuring the 2,2′-bipyridine co-ligand: Synthesis, X-ray crystal structure and DFT calculations

An unprecedented 1:1:1 complex [VO(bipy)(cit[H]H)]·1.5H2O was obtained from the reaction of vanadium(III) chloride, 2,2′-bipyridine (bipy), and citric acid (cit[H]H3) in methyl alcohol/water. The citrate anion (cit[H]H)2− chelates the metal centre as a tridentate ligand via the unusually protonated α-alcoholic group, and two oxygen atoms from the α- and one β-carboxylate groups, the other β-carboxylic acid group remaining uncoordinated. A pseudo-octahedral coordination sphere is completed by a bidentate bipy unit. The electronic nature of this complex is investigated by means of DFT calculations.

Phenylcyanamidoruthenium Scorpionate Complexes

Nine [Ru(Tp)(dppe)L] complexes, where Tp is hydrotris(pyrazol-1-yl)borate, dppe is ethylenebis(diphenylphosphine), and L is (4-nitrophenyl)cyanamide (NO(2)pcyd(-)), (2-chlorophenyl)cyanamide (2-Clpcyd(-)), (3-chlorophenyl)cyanamide (3-Clpcyd(-)), (2,4-dichlorophenyl)cyanamide (2,4-Cl(2)pcyd(-)), (2,3-dichlorophenyl)cyanamide (2,3-Cl(2)pcyd(-)), (2,5-dichlorophenyl)cyanamide (2,5-Cl(2)pcyd(-)), (2,4,5-trichlorophenyl)cyanamide (2,4,5-Cl(3)pcyd(-)), (2,3,5,6-tetrachlorophenyl)cyanamide (2,3,5,6-Cl(4)pcyd(-)), and (pentachlorophenyl)cyanamide (Cl(5)pcyd(-)), and the dinuclear complex [{Ru(Tp)(dppe)}(2)(μ-adpc)], where adpc(2-) is azo-4,4-diphenylcyanamide, have been prepared and characterized. The crystal structures of [Ru(Tp)(dppe)(Cl(5)pcyd)] and [{Ru(Tp)(dppe)}(2)(μ-adpc)] reveal the Ru(II) ion to occupy a pseudooctahedral coordination sphere in which the cyanamide ligand coordinates to Ru(II) by its terminal nitrogen atom. For both complexes, the cyanamide ligands are planar, indicating significant π mixing between the cyanamide and phenyl moieties as well as the azo group in the case of adpc(2-). The optical spectra of the nominally ruthenium(III) species [Ru(Tp)(dppe)L](+) were obtained through spectroelectrochemistry measurements and showed an intense near-IR absorption band. Time-dependent density functional theory calculations of these species revealed that oxidation of the ruthenium(II) species led to species where partial oxidation of the cyanamide ligand had occurred, indicative of noninnocent character for these ligands. The spin densities reveal that while the 3-Clpycd species has substantial Ru(II)(3-Clpycd(0)) character, the Cl(5)pycd species is a much more localized ruthenium(III) complex of the Cl(5)pycd monoanion. Some bond order and charge distribution data are derived for these ruthenium(III) species. The near-IR band is assigned as a quite complex mixture of d-d, 4d(π) to L(NCN) MLCT, and L(NCN) to Ru 4d LMCT with even a scorpionate ligand component. Spectroelectrochemistry was also performed on [{Ru(Tp)(dppe)}(2)(μ-adpc)] to generate the mixed-valence state. The intense intervalence transition that is observed in the near-IR is very similar to that previously reported for [{Ru(trpy)(bpy)}(2)(μ-adpc)](2+), where trpy is 2,2':6',2"-terpyridine and bpy is 2,2'-bipyridine, and by analogy identifies [{Ru(Tp)(dppe)}(2)(μ-adpc)](+) as a delocalized mixed-valence complex.

Mono- and di-nuclear nickel(II) complexes with mixed N/S-donor ligands: Syntheses, structures and physical properties

Two new Ni(II) complexes are reported with tridentate thiosemicarbazone ligands derived from Schiff-base condensation with phenylthiosemicarbazide. Complex 1, a novel dinuclear Ni(II) complex of a SNS ligand synthesized by reaction with 2,2′-dithiodibenzaldehyde (DTDB), adopts a butterfly-type structure in which thiolates derived from DTDB reside in the bridging positions. Complex 2-(NO3)2, a mononuclear Ni(II) complex of a NNS ligand synthesized by reaction with pyridine carboxaldehyde features two ligands spanning three meridional positions on the pseudo-octahedral coordination sphere of the Ni(II) center. The thiosemicarbazone-S is coordinated to the Ni(II) center in 1 in the deprotonated anionic thiolate-S form, while the neutral thione-S is present in 2-(NO3)2. To the best of our knowledge complex 1 is the first example of a dinuclear bis(thiolate)-bridged Ni(II) complex with NS3 coordination involving a thiosemicarbazide moiety.

Alkynyl Ti–M complexes with M = Cd and Hg: Synthesis, characterization, and reaction chemistry

The synthesis and properties of heterobimetallic Ti–Cd complexes of type {[Ti](μ-η 1:η 2–C CR) 2}CdX 2 ([Ti] = Ti(η 5–C 5H 4SiMe 3) 2; R = SiMe 3: 3a, X = Cl; 3b, X = Br; 3c, X = I; R = Fc: 3d, X = Br; Fc = Fe(η 5–C 5H 4)(η 5–C 5H 5) is reported. These compounds were accessible by treatment of [Ti](C CR) 2 ( 1a, R = SiMe 3; 1b, R = Fc) with the cadmium salts CdX 2 ( 2a, X = Cl; 2b, X = Br; 2c, X = I) in a 1:1 M ratio in diethyl ether. Dissolving, for example, 3b in tetrahydrofuran afforded coordination polymer [Cd(μ-Br) 2(thf) 2] n ( 4) along with the tweezer molecule 1a. Treatment of 3b with two equiv of LiC CFc ( 5) gave {[Ti](μ-η 1:η 2–C CSiMe 3) 2}Cd(C CFc) 2 ( 6) which eliminated at ambient temperature the all-carbon buta-1,3-diyne FcC C–C CFc ( 7) producing 1a and elemental Cd. The same reaction behavior was observed, when 2b was reacted with 5. The thus obtained bis(alkynyl) cadmium complex Cd(C CFc) 2 ( 8) is redox-active at low temperature producing 7 and Cd(0). When mercury halides HgX 2 ( 9a, X = Cl; 9b, X = Br) are used, then the titanocene dihalides [Ti]X 2 ( 10a, X = Cl; 10b, X = Br) together with Me 3SiC C–C CSiMe 3 ( 11) and Hg(0) were formed. Nevertheless, mercury acetylides were available by treatment of Hg(OAc) 2 ( 12) with HC CFc ( 13) in a 1:2 M ratio. Thus obtained Hg(C CFc) 2 ( 14) gave with [CuBr] ( 15) coordination polymer [{Hg(η 2-C CFc) 2}(Cu 2(μ-Br) 2] n ( 16), while with [AgPF 6] oxidation of the ferrocenyl moieties took place affording dicationic [Hg(C CFc) 2] 2+ ( 18). The structures of 3b and 4 in the solid state are reported. Compound 3b shows the typical characteristics for heterobimetallic organometallic π-tweezer complexes with cadmium in a tetrahedral environment, while 4 corresponds to a one-dimensional coordination polymer in which the Cd(II) ions are linked in a edge-sharing fashion by bromide bridges in the pseudo-equatorial plane. The appropriate tetrahydrofuran molecules are completing the pseudo-octahedral coordination sphere at cadmium. The cyclic voltammogram of 14 is reported showing a single reversible redox event at E 0 = 0.108 V with Δ E p = 76 mV indicating that there is no communication between the Fc termini along the mercury acetylide unit.

Iron and cobalt complexes of 2,6-diacetylpyridine-bis(R-thiosemicarbazone) (R = H, phenyl) showing unprecedented ligand deviation from planarity

The syntheses, characterization, and single-crystal X-ray crystal structures are reported for four complexes of iron and cobalt with the pentadentate ligands, 2,6-diacetylpyridinebis(thiosemicarbazone) (H 2L 1) and 2,6-diacetylpyridinebis(phenylthiosemicarbazone) (H 2L 2), including a cobalt dimer displaying a deviation from planarity which is unprecedented for this class of ligands and allows the ligand to occupy five positions of a pseudo-octahedral coordination sphere. This dimer reacts with KCN to produce a mononuclear complex of relevance to the active site of cobalt nitrile hydratase.

Chloro[2,2'-[(1S,2S)-1,2-diphenyl-1,2-ethanediylbis(nitrilomethylidyne)]diphenolato-kappa4O,N,N',O'](ethanol-kappaO)manganese(III).

The crystal structure of the title compound, [MnCl(C(28)H(22)N(2)O(2))(C(2)H(6)O)], has been determined at 173 (2) K in the non-centrosymmetric space group P2(1)2(1)2(1). The asymmetric unit contains two molecular units. An intermolecular O-H.Cl hydrogen bond is formed between the OH group of an ethanol molecule coordinated to the Mn atom and the coordinated Cl(-) anion, and so polymeric chains of Mn-containing fragments are formed [O-H.Cl = 3.1281 (16) and 3.1282 (15) A]. The Mn atoms have a pseudo-octahedral coordination sphere, with the four donor atoms of the Schiff base forming an equatorial plane [Mn-O distances are 1.8740 (13), 1.8717 (13), 1.8749 (13) and 1.8823 (13) A, and Mn-N distances are 1.9868 (15), 1.9910 (14), 1.9828 (15) and 1.9979 (14) A]. The axial positions are occupied by an ethanol molecule [Mn-O distances of 2.3069 (15) and 2.3130 (15) A] and a Cl(-) ligand [Mn-Cl distances of 2.5732 (6) and 2.5509 (6) A].

Coordination polymers based on cadmium(ii) pyridine complexes: synthesis, range of existence, and structureDedicated to Prof. Dr. G. E. Herberich on the occasion of his 65th birthday.

A series of nine new cadmium compounds of formal composition [Cd(μ-X)2py2] (X = Cl, Br, I; py = 3,5-disubstituted pyridine ligands with methyl, chloro, and bromo substituents) were synthesized and characterized by single crystal X-ray diffraction. Only for the combination of the sterically most demanding ligands, namely I and 3,5-dimethylpyridine, is a mononuclear tetrahedral complex obtained; in all other eight cases one-dimensional coordination polymers are found. In these chains cadmium(II) cations are linked in an edge-sharing fashion by halogen bridges in their pseudoequatorial plane, with terminal pyridine ligands completing the pseudo-octahedral coordination sphere. In all polymers the distance between neighboring Cd atoms corresponds to the shortest lattice constant: metal⋯metal separations systematically depend on both bridging and terminal ligands and range between 3.77 and 4.14 Å. This intermetal distance and the coordination mode of the donor ligands are found to be correlated. Five of the Cd chain polymers adopt the structure type found for [Zn(μ-Cl)2py2]∞. In addition to previous work the zinc derivatives [ZnX2(3,5-Me2py)2] (X = Cl, Br) were investigated for comparison and shown to be mononuclear.

Synthetic, Structural and Vibrational Spectroscopic Studies in Bismuth(III) Halide/N,N′-Aromatic Bidentate Base Systems. I Large-Cation (2,2′-Bipyridinium and 1,10-Phenan- throlinium) Salts of Polyhalobismuthate(III) Ions

Syntheses and room-temperature single-crystal X-ray studies are recorded for a variety of salts of cations derived from protonated 2,2′-bipyridine and 1,10-phenanthroline (bpyH+ and phenH+) with polyhalobismuthate(III) anions. ‘[(phenH)(phenH2)(H2O)2] [BiCl6]’ is triclinic, P-1, a 9·791(1), b 9·338(3), c 8·311(3) Å, α 73·46(3), β 69·71(2), γ 86·36(2)°, Z = 1; conventional R on |F| was 0·027 for No 4852 independent ‘observed’ (I > 3σ(I)) reflections. [BiCl6]3- is closely octahedral, accompanied by an interesting protonation/hydrogen-bonding array among the other moieties. The latter comment applies also to ‘[(phenH2)(H2O)][BiCl5](∞|∞)’, monoclinic, P2/c, a 8·388(1), b 12·004(1), c 17·146(3) Å, β 98·26(1)°, Z = 4, R 0·047 for No 2670, the anion array being a one-dimensional polymer with bridging chlorine atoms occupying cis sites in the pseudo-octahedral coordination sphere of the bismuth. [bpyH2]4 [Bi4Cl20] is monoclinic, P21/c, a 14·228(4), b 14·217(2), c 16·254(4) Å, β 110·14(2)°, Z = 2, R 0·045 for No 2777; in the novel centrosymmetric tetramer, the four bismuth atoms are bridged into a square array by four linearly coordinated halogen atoms at the centres of the edges, a pair of these lying cis in the pseudo-octahedral coordination sphere of each bismuth. [bpyH]3 [Bi2Cl9] is triclinic, P-1 a 19·288(7), b 14·251(3), c 7·644(3) Å, α 75·02(2), β 80·15(3), γ 72·76(2)°, Z = 2, R 0·072 for No 3600, the two pseudo-octahedrally coordinated bismuth atoms being bridged by three chlorine atoms on a mutual octahedral face, [Cl3Bi(µ-Cl)3BiCl3]3-. [phenH] [BiCl4](∞|∞),H2O is triclinic, space group P-1, a 12·119(7), b 10·169(6), c 7·247(4) Å, α 69·30(4), β 75·05(4), γ 77·92(5)°, Z = 2, R 0·035 for No 2348. The anion is a one-dimensional polymer, successive metal atoms being bridged by pairs of chlorine atoms lying cis in the pseudo-octahedral coordination sphere. [bpyH]4 [Bi2I10] is monoclinic, P21/n, a 13·426(4), b 14·396(6), c 14·539(5) Å, β 101·31(3)°, Z = 2, R 0·11 for No 1862; the anion is of the form [I4Bi(µ-I)2BiI4]4- with quasi-octahedral bismuth. [bpyH] [BiI4](∞|∞) is monoclinic, C2/c, a 12·442(5), b 18·41(2), c 7·714(2) Å, β 92·80(3)°, Z = 4, R 0·080 for No 850, with a polymeric one-dimensional anion comparable to that in [phenH] [BiCl4](∞|∞),H2O. The structure of the 2,6-dimethylpyridinium salt of [BiCl6]3- is also recorded, as its acetonitrile solvate; triclinic, P-1, a 15·025(2), b 10·357(3), c 9·964(1) Å, α 83·14(2), β 89·32(1), γ 86·61(2)°, Z = 2, R 0·046 for No 3601; there is also an isomorphous bromide, and also an isostoichiometric bromide modelled as monoclinic, Cm, a 18·128(6), b 10·348(2), c 10·241(2) Å, β 121·31(3)°, Z = 2, R 0·050 for No 1379. Bands in the far-infrared and Raman spectra due to the v(BiCl) modes are assigned in [(phenH)(phenH2)(H2O)2] [BiCl6] and [bpyH2]4 [Bi4Cl20], and are discussed in relation to the structures of the complexes.

Tetrachloro[2-(phenylamino)pyridinato]titanate(IV) with a 2-(Phenylamino)pyridinium Counterion

The title salt, 2-(Phenylamino)pyridinium tetrachloro[2(phenylamino)pyridinato-N,N′]titanate(IV), (C11H11N2)[TiCl4(C11H9N2)], is a product of the reaction of titanium tetrachloride and 2-(phenylamino)pyridine. The coordinated deprotonated aminopyridine forms a four-membered chelate ring. Titanium has a pseudo-octahedral coordination sphere. A second 2-(phenylamino)pyridine residue behaves as a proton acceptor and is a counterion in the solid state.

Reaction of Ketones with 1,4-Diaza-1,3-diene Zirconium and Hafnium Complexes: First Example of a 1,3-Dipolar Cycloaddition Reaction of 1,4-Diaza-1,3-diene Complexes of Early Transition Metals.

The novel complexes M[O(R)PhCH{CH=N(tBu)}N(tBu)](2) [M = Zr, R = Me (4a), R = Ph (4b) and M = Hf, R = Me (5a), R = Ph (5b)] have been prepared in almost quantitative yield by reaction of (tBu-DAD)(2)Zr (1) and (tBu-DAD)(2)Hf (2) [tBu-DAD = (tBu)N=CHCH=N(tBu)] with 2 equiv of the ketones MeCOPh (3a) or PhCOPh (3b). The reaction proceeds via a 1,3-dipolar cycloaddition of the C=O bond across the M-N-C unit of the DAD complexes. The molecular structures of the complexes 4a and 5b have been determined by a single-crystal X-ray diffraction study (4a, triclinic, space group P&onemacr;; a = 10.395(2) Å, b = 10.865(2) Å, c = 16.842(3) Å, alpha = 93.80(3) degrees, beta = 99.84(3) degrees, gamma = 106.12(3) degrees, V = 1787.4(6) Å(3), Z = 2, R1 = 0.035 (wR2 = 0.101) for 6963 reflections with I > 2sigma(I); 5b, monoclinic, space group P2(1)/c, a = 19.961(4) Å, b = 10.482(2) Å, c = 20.150(4) Å, beta = 91.30(1) degrees, V = 4215(1) Å(3), Z = 4, R1 = 0.036 (wR2 = 0.097) for 4650 reflections with I > 2sigma(I)). The metal atoms in 4a and 5b adopt a pseudooctahedral coordination sphere consisting of four nitrogen and two oxygen atoms. The distortion is a consequence of the [2.2.1] bicyclic structure of the newly formed tridentate ligands which are not able to span three regular octahedral positions.

Cationic titanium(IV) complexes via halide abstraction from [Ti(C5H5)Cl3]: crystal and molecular structure of [Ti(C5H5)(MeCN)5][SbCl6]3·2MeCN

Treatment of [Ti(cp)Cl3](cp =η5-C5H5) with SbCl5 as chloride abstractor in acetonitrile provided hexachloroantimonate(V) salts of [Ti(cp)Cl2]+, [Ti(cp)Cl]2+ and [Ti(cp)]3 + respectively. With 1 : 1 stoichiometry red-brown crystals of [Ti(cp)Cl2(MeCN)3][SbCl6]1 are obtained and with 1 : 2 stoichiometry light blue crystals of [Ti(cp)Cl(MeCN)4][SbCl6]22. Complete removal of chloride ion from [Ti(cp)Cl3] requires a six-fold excess of SbCl5 when purple-blue crystals of [Ti(cp)(MeCN)5][SbCl6]33 can be isolated. These products were characterised by analytical and spectroscopic (IR, 1H NMR) data and, in the case of 3, by a crystal structure determination. Proton NMR studies indicate the presence of intermediate halide-bridged [Ti(µ-Cl)2Sb] species in solution during the sequential halide abstractions 1→2→3. Crystals of complex 3, obtained as the bis(solvate) from recrystallisation in acetonitrile, are monoclinic and X-ray structural analysis confirmed the formulation. The crystal structure [space group Cc, a= 19.650(4), b= 19.182(4), c= 12.958(3)A, β= 91.612(3)°, Z= 4, R= 0.0386, R′= 0.0406] shows discrete cations and anions and a pseudo-octahedral co-ordination sphere for the TiIV. A significant trans influence of the cyclopentadienyl ligand affects Ti–N bond lengths in the complex.

The Crystal and Molecular structure of trans-Dichlorobis(1,3-Diaminopropan-2-ol)cobalt(III) Chloride

A single-crystal X-ray structure determination of the title compound is reported. The compound crystallizes in the space group P1 with a 7.273(1), b 8.525(2), c 12.358(3) �, α 80.03(3),β 75.38(2), γ 65.06(2)� and Z 2. The final R value for 3318 reflections was 0.041. The structure consists of two independent trans- dichlorobis (l,3-diaminopropan-2-ol)cobalt(III) cations and chloride ions interconnected by a hydrogen bonding network. The axial Co-Cl bonds in the pseudo-octahedral coordination sphere are shorter than those in the coordination sphere of the copper(II) analogue. The compression is clearly related to the simultaneous flattening of the rings.

Circular Dichroism Spectra and Their Relation to Asymmetric Distortion of Some Dimeric Molybdenum(V) Complexes Containing Optically Active Amino Carboxylate

Abstract Circular dichroism (CD) spectra of fifteen kinds of μ-X-μ-Y-bis(oxomolybdenum(V)) complexes, where X=Y=O, X=O and Y=S, and X=Y=S, containing optically active ligands such as (S)-cysteinate, its alkyl esters, (R)-penicillaminate (R-pen), (S)-histidinate, and (R)-propylenediaminetetraacetate, give two distinctive peaks with opposite signs at ca. 26000 and 33000 cm−1 in various media including KBr disks. Close examination of the known X-ray structural data of eight complexes indicated that the pseudo-octahedral coordination sphere of two molybdenum(V) ions are asymmetrically twisted around the Mo–Mo axis. The direction of such a twist for the complexes containing the ester ligands and R-pen, is opposite to that for the complexes with other ligands. The former and latter complexes give positive and negative, and negative and positive CD peaks at ca. 26000 and 33000 cm−1, respectively. Thus the CD signs of the two peaks are related to the asymmetric distortion around the Mo–Mo axis.