Di- and trinuclear complexes derived from hexakis(2-pyridyloxy)cyclotriphosphazene. Unusual P-O bond cleavage in the formation of [{(L'CuCl)2(Co(NO3)}Cl] (L' = N3P3(OC5H4N)5(O))

Hexakis(2-pyridyloxy)cyclotriphosphazene (L) is an efficient multisite coordination ligand which binds with transition metal ions to produce dinuclear (homo- and heterometallic) complexes [L(CuCl)(CoCl3)], [L(CuCl)(ZnCl3)], [L(CoCl)(ZnCl3)], and [L(ZnCl2)2]. In these dinuclear derivatives the cyclophosphazene ligand utilizes from five to six nitrogen coordination sites out of the maximum of nine available sites. Further, the spacer oxygen that separates the pyridyl moiety from the cyclophosphazene ring ensures minimum steric strain to the cyclophosphazene ring upon coordination. This is reflected in the near planarity of the cyclophosphazene ring in all the dinuclear derivatives. In the dinuclear heterobimetallic derivatives one of the metal ions [Cu(II) or Co(II)] is hexacoordinate and is bound by the cyclophosphazene in a eta5-gem-N5 mode. The other metal ion in these heterobimetallic derivatives [Co(II) or Zn(II)] is tetracoordinate and is bound in an eta(1)-N(1) fashion. In the homobimetallic derivative, [L(ZnCl2)2], one of the zinc ions is five-coordinate (eta3-nongem-N3), while the other zinc ion is tetracoordinate(eta2-gem-N2). The reaction of L with CuCl2 followed by Co(NO3)2.6H2O yields a trinuclear heterobimetallic complex [{(L'CuCl)2Co(NO3)}Cl] [L' = N3P3(OC5H4N)5(O)]. In the formation of this compound an unusual P-O bond cleavage involving one of the phosphorus-pyridyloxy bonds is observed. The molecular structure of [{(L'CuCl)2Co(NO3)}Cl] [L' = N3P3(OC5H4N)5(O)] reveals that each of the two the P-O-cleaved L' ligands is involved in binding to Cu(II) to generate the motif L'CuCl. Two such units are bridged by a Co(II) ion. The coordination environment around the bridging Co(II) ion contains four oxygen (two P-O units, one chelating nitrate) and two nitrogen atoms (pyridyloxy nitrogens).     

Syntheses and structures of isoindoline complexes of Zn(II) and Cu(II): an unexpected trinuclear Zn(II) complex

Deprotonation of the tridentate isoindoline ligand 1,3-bis[2-(4-methylpyridyl)imino]-isoindoline, 4'-MeLH, and reaction with hydrated zinc(II) perchlorate produces an unexpected trinuclear Zn(II) complex, [Zn(3)(4'-MeL)(4)](ClO(4))(2).5H(2)O (1), whereas reaction with hydrated copper(II) perchlorate in methanol produces the expected mononuclear product, [Cu(4'-MeL)(H(2)O)(2)]ClO(4) (2). X-ray diffraction shows that the trinuclear Zn(II) complex (1) contains a linear zinc backbone, and the arrangement of ligands about the outer chiral zinc(II) atoms is helical. The two terminal zinc ions exhibit approximate C(2) site symmetry, with tetrahedral coordination by two pyrrole and two pyridyl nitrogen atoms of the potentially tridentate isoindoline ligands. The central zinc ion exhibits approximate tetrahedral symmetry, with coordination by four pyridyl nitrogen atoms of four different isoindoline ligands. Pyridyl-pyrrole intramolecular pi-stacking interactions contribute to the stability of the trinuclear cation. The structure of the mononuclear copper(II) complex cation in 2 is best described as a distorted trigonal bipyramid. The isoindoline anion binds Cu(II) in both axial positions and one of the equatorial positions; water molecules occupy the other two equatorial positions.     

Dinuclear versus tetranuclear cluster formation in zinc(II) nitrate/di-2-pyridyl ketone chemistry: synthetic, structural and spectroscopic studies

The use of di-2-pyridyl ketone, (py)2CO, in zinc(II) nitrate chemistry has yielded a dinuclear complex and a cationic tetranuclear cluster. The 1:1 Zn(NO3)2.4H2O/(py)2CO reaction system in EtOH gives [Zn2(NO3)2{(py)2C(OEt)O}2].0.5H2O (1.0.5H2O), whereas the same reaction system in MeCN yields [Zn4(NO3)3{(py)2C(OH)O}4(H2O)](NO3) (2). The monoanionic derivatives of the hemiacetal and the gem-diol forms of di-2-pyridyl ketone have been derived from the ZnII-mediated addition of solvent (EtOH, H2O involved in MeCN) on the carbonyl group of (py)2CO. Each (py)2C(OEt)O- ion functions as an eta1:eta2:eta1:mu2 ligand in 1.0.5H2O chelating the two ZnII atoms through the 2-pyridyl nitrogen atoms and the common bridging, deprotonated oxygen atom; one asymmetric chelating nitrate completes six coordination at each metal center. The tetranuclear cluster cation of 2 has a cubane topology with the ZnII ions and the deprotonated oxygen atoms from the four eta1:eta3:eta1:mu3 (py)2C(OH)O- ligands occupying alternate vertices. Three monodentate nitrates and one aqua ligand complete the sixth coordination site at the metal ions. The two complexes have been characterized by IR and far-IR spectroscopies. Characteristic bands are discussed in terms of the known structures and the coordination modes of the nitrato ligands. Upon excitation at 371 nm, complex 2 displays blue photoluminescence in the solid state at room temperature with two emission maxima at 430 and 455 nm.     

Phenolate and phenoxyl radical complexes of Co(II) and Co(III)

The new phenol-imidazole pro-ligands (R)LH react with Co(BF(4))(2).6H(2)O in the presence of Et(3)N to form the corresponding [Co(II)((R)L)(2)] compound (R = Ph (1), PhOMe (2), or Bz (3)). Also, (Bz)LH, reacts with Co(ii) in the presence of Et(3)N and H(2)O(2) to form [Co(III)((Bz)L)(3)](4). The structures of 1.2.5MeCN, 2.2DMF, 3.4MeOH, and 4.4DMF have been determined by X-ray crystallography. 1, 2, and 3 each involve Co(II) bound to two N,O-bidentate ligands with a distorted tetrahedral coordination sphere; 4 involves Co(III) bound to three N,O-bidentate ligands in a mer-N(3)O(3) distorted octahedral geometry. [Co(II)((R)L)(2)](R = Ph or PhOMe) undergo two, one-electron, oxidations. The products of the first oxidation, [1](+) and [2](+), have been synthesised by the chemical oxidation of 1 and 2, respectively; these cations, formulated as [Co(II)((R)L*)((R)L)(2)](+), comprise one phenoxyl radical and one phenolate ligand bound to Co(II) and are the first phenoxyl radical ligand complexes of tetra-coordinated Co(II). 4 undergoes two, one-electron, ligand-based oxidations, the first of which produces [4](+), [Co(III)((Bz)L*)((Bz)L)(2)](+). Unlike [1](+) and [2](+), product of the one-electron oxidation of [Co(II)((Bz)L)(2)], [3](+), is unstable and decomposes to produce [4](+). These studies have demonstrated that the chemical properties of [M(II)((R)L*)((R)L)(2)](+)(M = Co, Cu, Zn) are highly dependent on the nature of both the ligand and the metal centre.     

Two one-dimension copper(II) coordination polymers based on imine-based bidentate Schiff-base ligand: synthesis, crystal structure and luminescent properties

Two new one-dimension copper(II) coordination polymers [CuL(2)(NCS)(2)](n) (1) and [CuL(2)(NO(3))(2)](n) (2) (L=(C(5)H(4)N)C(CH(3))=N-N=(CH(3))C(C(5)H(4)N)) have been synthesized and characterized by IR, elemental analysis, TG technique and X-ray crystallography. Each Cu(II) atom has a distorted octahedral N(6) (1) or N(4)O(2) (2) environment with four pyridyl N atoms from four ligands and two N atoms from two NCS(-) anions for polymer 1 or two O atoms from two NO(3)(-) anions for polymer 2, respectively. A pair of bis-monodentate bridging ligands links two Cu(II) centers to form one dimension chain structure containing bimetallic 22-membered macrometallacyclic rings. 1D chain is held together with its neighboring ones via C-H?S hydrogen bonds for 1 and C-H?O hydrogen bonds, C-H?π interactions for 2 to form a 3D supramolecular structure, respectively. The luminescent properties of the polymers 1 and 2 were investigated in the solid state at room temperature.     

Syntheses and X-ray characterization of metal complexes with the pentadentate thiosemicarbazone ligand bis(4-N-methylthiosemicarbazone)-2,6-diacetylpyridine. The first pentacoordinate lead(II) complex with a pentagonal geometry

In this paper we describe the electrochemical synthesis and characterization of new neutral manganese, iron, cobalt, nickel, copper, zinc, cadmium and lead complexes with the ligand bis(4-N-methylthiosemicarbazone)-2,6-diacetylpyridine, H4DAPTsz-Me. X-Ray structures of [Mn(H2DAPTsz-Me)(EtOH)2] 1, [Pb(H2DAPTsz-Me)] 3 and [Zn(H2DAPTsz-Me)]2.EtOH.2H2O 4, were also determined. In these complexes the ligand behaves as bis-deprotonated and SNNNS pentadentate. In the manganese complex the metal is heptacoordinated, in a distorted pentagonal-bipyramidal environment, with the N3S2 donor set of the ligand in the pentagonal girdle and two solvent molecules occupying the axial positions. In the lead complex 3 the metal is pentacoordinated, bound exclusively to the five donor atoms of the ligand, as a consequence of the existence of "inert pair effect". The bishelical zinc complex 4 shows each zinc atom with different coordination geometry, one octahedrally six-coordinate while the other is distorted tetrahedrally four-coordinate.     

Exploring the effect of metal ions and counteranions on the structure and magnetic properties of five dodecanuclear Co(II) and Ni(II) clusters

We present the synthesis, characterization of the structures, and magnetic properties of five isostructural dodecanuclear coordination clusters of Ni(II) and Co(II): [Co(12)(bm)(12)(NO(3))(O(2)CMe)(6)(EtOH)(6)](NO(3))(5) (1), [Ni(12)(bm)(12)(NO(3))(O(2)CMe)(6)(H(2)O)(3)(EtOH)(3)](NO(3))(5)·2H(2)O (2), mixed-metal composition (Ni/Co 1:1) [Co(6)Ni(6)(bm)(12)(NO(3))(O(2)CMe)(6)(NO(3))(5) (3), and [M(12)(bm)(12)(NO(3))(O(2)CMe)(6)(EtOH)(6)](ClO(4))(5) (M=Co (4), Ni (5)), in which Hbm=(1H-benzimidazol-2-yl)methanol. They consist of analogous structural cores that are constructed by three cubanes (M(4)O(4)) that surround the templating nitrate and bridging auxiliary acetate and the directing ligands bm. They have different magnetic behaviors. Whereas there is the absence of the out-of-phase ac susceptibility (χ') for the Ni(II)-based compounds 2 and 5, the Co(II)-containing compounds 1, 3, and 4 have prominent χ' signals that exhibit frequency dependence, which indicates slow magnetic relaxation behavior above 1.8 K. In particular, the larger perchlorate counterions in 4 further change the overall correlation interaction between clusters, thus leading to an enhanced blocking temperature for the less-symmetrical 4 (pseudo-C(3)) relative to 1 and 3 (true C(3)). Interestingly, electrospray ionization mass spectrometry (ESI-MS) indicates that the three dodecanuclear clusters of 1-3 retain their compositions in solution. The mixed-metal cluster cores of 3 are formed based on the nature of the interchangeability between metal centers in solution.     

基于4H-1,2,4-三氮唑-4-乙酸配体的两个新的过渡金属配位聚合物的合成、结构与性质(英文)

用水热方法合成了两个新的配位聚合物[Co(trza)](1)和[Ni(trza)(H2O)2](2)(Htrza=4H-1,2,4-三氮唑-4-乙酸).单晶X-射线衍射结构分析表明:化合物1和2具有二维(2D)层状结构.在1中,Co(II)离子采用六配位方式,分别与来自两个不同配体(trza)上的两个氮原子和四个羧基氧原子配位,形成八面体配位聚合物,每个羧基以二齿桥联方式连接两个Co原子,形成1D链,这些一维链进一步与唑环上的N原子形成2D层状结构.在2中,中心Ni(II)离子采用同样的配位模式形成八面体配位聚合物,与1不同的是:来自两个配体阴离子(trza)上的两个羧基氧原子分别被两个配位水分子所取代,且配体上的羧基氧原子采用的是单齿配位模式.化合物1的变温磁化率测定表明了金属间弱的反铁磁相互作用.此外,两个配位聚合物的IR光谱、热稳定性以及化合物1的磁性质也被测定.     

Syntheses, structures, and photoluminescence properties of metal(II) halide complexes with pyridine-containing flexible tripodal ligands

Seven coordination compounds, [Zn(L3)Cl2] . MeOH . H2O (1), [Mn(L3)2Cl2] . 0.5EtOH . 0.5H2O (2), [Cu3(L2)2Cl6] . 2DMF (3), [Cu3(L2)2Br6] . 4MeOH (4), [Hg2(L4)Cl4] (5), [Hg2(L4)Br4] (6), and [Hg3(L4)2I6] . H2O (7), were synthesized by the reactions of ligands 1,3,5-tris(3-pyridylmethoxyl)benzene (L3), 1,3,5-tris(2-pyridylmethoxyl)benzene (L2), and 1,3,5-tris(4-pyridylmethoxyl)benzene (L4) with the corresponding metal halides. All the structures were established by single-crystal X-ray diffraction analysis. In complexes 1 and 2, L3 acts as a bidentate ligand using two of three pyridyl arms to link two metal atoms to result in two different 1D chain structures. In complexes 3 and 4, each L2 serves as tridentate ligand and connects three Cu(II) atoms to form a 2D network structure. Complexes 5 and 6 have the same framework structure, and L4 acts as a three-connecting ligand to connect Hg(II) atoms to generate a 3D 4-fold interpenetrated framework, while the structure of complex 7 is an infinite 1D chain. The results indicate that the flexible ligands can adopt different conformations and thus can form complexes with varied structures. In addition, the coordination geometry of the metal atom and the species of the halide were found to have great impact on the structure of the complexes. The photoluminescence properties of the complexes were investigated, and the Zn(II), Mn(II) and Hg(II) complexes showed blue emissions in solid state at room temperature.     

Synthesis and Crystal Structure of a Novel 1D Magnesium(II) Coordination Polymer Constructed by L-Cysteic Acid

A novel coordination polymer [Mg(L)(H2O)2]·H2O] (LH2 = L-cysteic acid) has been synthesized and characterized by elemental analysis, IR and single-crystal X-ray diffraction. The crystal crystallizes in orthorhombic system, space group P212121, with a = 5.962(3), b = 11.224(6), c = 13.664(7) , V = 914.3(8) 3, Z = 4, Mr = 245.50, Dc = 1.783 g/cm3, μ = 0.445 mm–1, flack parameter = 0.32(16), F(000) = 512, the final R = 0.0458 and wR = 0.1172 for 1578 observed reflections with I > 2σ(I). The Mg(II) atom shows an octahedral geometry defined by two carboxyl O atoms from two different L-cysteic acid ligands, one carboxyl O atom and one amino N atom from the adjacent ligand, and two aqua ligands. The Mg(II) atoms are bridged by L-cysteic acid ligands, leading to a 1D infinite zigzag chain. In the structure there are extensive hydrogen bonds, through which the complex completes its 3D framework structure.     

Syntheses and characterization of six coordination polymers of zinc(II) and cobalt(II) with 1,3,5-benzenetricarboxylate anion and bis(imidazole) ligands

Six new coordination polymers, namely [Zn1.5(BTC)(L1)(H2O)2].1.5H2O (1), [Zn3(BTC)2(L2)3] (2), [Zn3(BTC)2(L3)1.5(H2O)].H2O (3), [Co6(BTC)4(L1)6(H2O)3].9H2O (4), [Co1.5(BTC)(L2)1.5].0.25H2O (5), and [Co4(BTC)2(L3)2(OH)2(H2O)].4.5H2O (6), where L1 = 1,2-bis(imidazol-1-ylmethyl)benzene, L2 = 1,3-bis(imidazol-1-ylmethyl)benzene, L3 = 1,1'-(1,4-butanediyl)bis(imidazole), and BTC = 1,3,5-benzenetricarboxylate anion, were synthesized under hydrothermal conditions. In 1-6, each of L1-L3 serves as a bidentate bridging ligand. In 1, BTC anions act as tridentate ligands, and compound 1 shows a 2D polymeric structure which consists of 2-fold interpenetrating (6, 3) networks. In compound 2, BTC anions coordinate to zinc cations as tridentate ligands to form a net with (64.82)2(86)(62.8)2 topology. In compound 3, BTC anions act as tetradentate ligands and coordinate to zinc cations to form a net with (4.62.83)2(8.102)(4.6.83.10)2 topology. In compound 5, each BTC anion coordinates to three Co cations, and the framework of 5 can be simplified as (64.82)2(62.82.102)(63)2 topology. For 4 and 6, the 2D cobalt-BTC layers are linked by bis(imidazole) ligands to form 3D frameworks. In 6, the Co centers are connected by micro3-OH and carboxylate O atoms to form two kinds of cobalt-oxygen clusters. Thermogravimetric analyses (TGA) for these compounds are discussed. The luminescent properties for 1-3 and magnetic properties for 4-6 are also discussed in detail.     

Steric effects on uranyl complexation: synthetic, structural, and theoretical studies of carbamoyl pyrazole compounds of the uranyl(VI) ion

New bifunctional pyrazole based ligands of the type [C(3)HR(2)N(2)CONR'] (where R = H or CH(3); R' = CH(3), C(2)H(5), or (i)C(3)H(7)) were prepared and characterized. The coordination chemistry of these ligands with uranyl nitrate and uranyl bis(dibenzoyl methanate) was studied with infrared (IR), (1)H NMR, electrospray-mass spectrometry (ES-MS), elemental analysis, and single crystal X-ray diffraction methods. The structure of compound [UO(2)(NO(3))(2)(C(3)H(3)N(2)CON{C(2)H(5)}(2))] (2) shows that the uranium(VI) ion is surrounded by one nitrogen atom and seven oxygen atoms in a hexagonal bipyramidal geometry with the ligand acting as a bidentate chelating ligand and bonds through both the carbamoyl oxygen and pyrazolyl nitrogen atoms. In the structure of [UO(2)(NO(3))(2)(H(2)O)(2)(C(5)H(7)N(2)CON {C(2)H(5)}(2))(2)], (5) the pyrazole ligand acts as a second sphere ligand and hydrogen bonds to the water molecules through carbamoyl oxygen and pyrazolyl nitrogen atoms. The structure of [UO(2)(DBM)(2)C(3)H(3)N(2)CON{C(2)H(5)}(2)] (8) (where DBM = C(6)H(5)COCHCOC(6)H(5)) shows that the pyrazole ligand acts as a monodentate ligand and bonds through the carbamoyl oxygen to the uranyl group. The ES-MS spectra of 2 and 8 show that the ligand is similarly bonded to the metal ion in solution. Ab initio quantum chemical studies show that the steric effect plays the key role in complexation behavior.     

Poly[[aqua(μ7‐ethylenediaminetetraacetato)dicadmium(II)] monohydrate]

The title compound, {[Cd₂(C₁₀H₁₂N₂O₈)(H₂O)]·H₂O}_n, consists of two crystallographically independent Cd^II cations, one ethylenediaminetetraacetate (edta) tetraanion, one coordinated water molecule and one solvent water molecule. The coordination of one of the Cd atoms, Cd1, is composed of five O atoms and two N atoms from two tetraanionic edta ligands in a distorted pentagonal–bipyramidal coordination geometry. The other Cd atom, Cd2, is six‐coordinated by five carboxylate O atoms from five edta ligands and one water molecule in a distorted octahedral geometry. Two neighbouring Cd1 atoms are bridged by a pair of carboxylate O atoms to form a centrosymmetric [Cd₂(edta)₂]⁴⁻ unit located on the inversion centre, which is further extended into a two‐dimensional layered structure through Cd2—O bonds. There are hydrogen bonds between the coordinated water molecules and carboxylate O atoms within the layer. The solvent water molecules occupy the space between the layers and interact with the host layers through O—H...O and C—H...O interactions.     

Poly[bis(μ‐4‐benzoyl‐1‐isonicotinoylthiosemicarbazide‐κ2N:S)dichloridocadmium(II)]

The asymmetric unit of the title complex, [CdCl₂(C₁₄H₁₂N₄O₂S)₂]_n, consists of one Cd^II ion located on the crystallographic inversion centre, one 4‐benzoyl‐1‐isonicotinoylthiosemicarbazide ligand and one chloride ligand. The central Cd^II ion adopts a distorted octahedral coordination geometry formed by two pyridyl N atoms of two ligands, two S atoms of two other ligands and two chloride ligands. The thiosemicarbazide ligands act as bridges, linking the metal ions into a two‐dimensional layered structure parallel to the bc plane. Intermolecular N—H...O hydrogen bonds and C—H...π interactions exist between adjacent layers.     

Synthesis and Crystal Structure of Cobalt(II) Complex [Co(H2O)2(bpe)(OAc)2](4,4''-dpdo

The reaction of Co(OAc)2 with bpe and 4,4'-dpdo in an aqueous-alcohol solution affords the formation of red crystals of [Co(H2O)2(bpe)(OAc)2](4,4'-dpdo (bpe = trans-1,2-bis(4- pyridyl)ethylene, 4,4'-dpdo = 4,4'-dipyridyl N,N'-oxide). The molecular and crystal structures were determined by single-crystal X-ray diffraction. The crystal is of triclinic, space group P with a = 7.6146(9), b = 8.6691(11), c = 10.344011 A, α = 88.311(3), β = 76.992(3), γ = 75.809(3)°, V = 644.7613 A3, Z = 1, C26H28CoN4O8, Mr = 583.45, Dc = 1.503 g/cm3, μ = 0.724 mm-1, F(000) = 303, T = 223(2) K, the final R = 0.0477 and wR = 0.1177 for 3199 observed reflections with I > 2σ(I). In the crystal the cobalt atom is six-coordinated by oxygen atoms from two carboxylic molecules, two nitrogen atoms from the bpe ligands and two water molecules, completing an octahedral geometry. The structure of the title complex consists of neutral chains containing cobalt(II) ions bridged by mutually trans bpe molecules. The adjacent chains are connected through weak hydrogen bonds to form a two-dimensional structure.     

具有梯形结构钴(Ⅱ)配位聚合物的合成及晶体结构

Co(NO₃)₂, N-carbazolyacetic acid and 4,4′-bipyridyl can give rise to a novel coordination polymer [CO₂(Cabo)₂(NO₃)₂(4,4′-bipy)₂]_n using a fritted U-tube. Single crystal X-ray diffraction displays in the complex, each Co(Ⅱ) is six-coordinated by two N atoms from different 4,4′-bipyridyl ligands, two O atoms of the bridge from two N-carbazolyacetic acid and two O atoms of one nitrate anion to form a distorted octahedral. Two O atoms of the carboxyl group act as bridge to link two Co(Ⅱ) atoms. The resulting structure is a ladder polymer. CCDC: 211713.     

Diacetatobis(2‐amino­benzothia­zole‐κN)cobalt(II)

The title complex, [Co(C₂H₃O₂)₂(C₇H₆N₂S)₂], contains a Co centre with a slightly distorted tetra­hedral coordination geometry, involving two acetate ligands and two N atoms from the thia­zole moiety [Co—O = 2.0025 (14) and 1.9953 (16) Å, and Co—N = 2.0524 (18) and 2.0568 (18) Å]. The inter­planar angle between the two benzothia­zole moieties is 77.86 (3)°. The amine groups, acting as donors, participate in intra‐ and inter­molecular N—H⋯O hydrogen bonds, with N⋯O distances in the range 2.806 (2)–2.857 (2) Å.     

Synthesis of the new ligand bis[3-(2-pyrazinyl-pyrazol-1-yl) dihydroborate,and the crystal structures of its complexes with thallium(I) and lead(II)

Reaction of 3-(2-pyrazinyl)pyrazole with KBH₄ in a 21:1 ratio afforded the new ligand bis3, 2, 1dihydroborate [L]⁻a bis(pyrazolyl)borate in which each pyrazolyl ring is functionalised with a pyrazin-2-yl group at the C³ position[L]⁻ is therefore a potentially chelating tetradentate ligand with two externally-directed N atoms (the pyrazinyl N⁴ atoms) which are available for additional metal–ion bindingleading to eg coordination polymers The crystal structure of [TlL] shows it to be a simple mononuclear complex with the Tl(I) ion coordinated in the N₄ binding pocket of the ligandand the externally-directed N atoms involved only in intermolecular N H–C hydrogen-bonding interactions The two Tl–N bonds to the pyrazolyl N² atoms (average length 270 Å) are much shorter than the bonds to the pyrazinyl N¹ atoms (average length 305 Å) also there is an obvious gap in the apical position of the metal–ion coordination sphere characteristic of a stereochemically active lone pair The crystal structure of [PbL₂] Et₂O shows that the Pb(II) centre is nine-coordinate with two tetradentate chelating ligands and the ninth donor being a pyrazinyl N⁴ atom from an adjacent complex unit The molecules therefore form infinite one-dimensional chains in the crystal via bridging pyrazinyl groups The coordination geometry about the Pb(II) ions is approximately capped square antiprismatic with no obvious gap in the coordination sphere suggesting that the lone pair is stereochemically inactive.     

Bis(ketopyrrolyl) complexes of Co(II) stabilised by trimethylphosphine ligands

2-Formylpyrrole and 2-acetylpyrrole were deprotonated with NaH to give the corresponding Na salts 1a and 1b, respectively. The reactivity of these salts towards cobalt chloride compounds was studied. The resulting new bis(ketopyrrolyl) Co(II) 19-electron complexes [Co(kappa(2)N,O-2-NC4H3C(R)=O)2(PMe3)2] (R = H 2a, and Me 2b) were characterised by single crystal X-ray diffraction, to show an octahedral geometry with the PMe3 ligands in trans positions to each other, and two bidentate ketopyrrolyl ligands occupying the remaining coordination positions in a transoid conformation. Powder and solution magnetic susceptibility measurements together with EPR and UV/Vis/NIR spectra revealed a low-spin ground state (dz2, S = 1/2) for Co(II) in these compounds. Analysis of the EPR superhyperfine couplings suggested that the longer distances (z axis) of the hexacoordinate Co coordination sphere are occupied by the keto-O atoms of the bidentate ligand, leaving the pyrrolyl N and the phosphine P atoms within the equatorial plane. This is confirmed by means of DFT calculations, which also indicate that the most thermodynamically stable isomers are low-spin (S = 1/2) complexes with coordination geometries corresponding to the molecular structures obtained by X-ray crystallography.     

Proton and anion control of framework complexity in copper(II) complex structures derived from 2-(hydroxymethyl)pyridine

Three copper(II) complexes derived from 2-(hydroxymethyl)pyridine (LH) have been synthesised and a comparative X-ray investigation of their respective crystal structures undertaken. In the absence of added base, LH reacts with copper(II) chloride or nitrate to yield the five-coordinate [Cu(LH)₂Cl]Cl and six-coordinate [Cu(LH)₂(NO₃)₂] species. In the chloro complex the coordination geometry is distorted trigonal bipyramidal, with the pyridyl nitrogens occupying the axial position and two hydroxyl oxygens from the bidentate ligands together with a chloro group occupying the equatorial sites. The structure of the nitrate species, published previously, has been reinvestigated at low temperature in order to specify the weak interactions in the crystal; it contains two molecules of bidentate LH bound trans in the equatorial plane while monodentate nitrato ligands occupy the axial sites. In each of these complexes the hydroxyl protons act as hydrogen bond donors, interacting with the non-coordinated chloride anion in [Cu(LH)₂Cl]Cl and the coordinated nitrato groups in [Cu(LH)₂(NO₃)₂] to form bridged, hydrogen-bonded, copper(II)-organic arrays in each case; offset face-to-face π-stacking in the latter produces a two dimensional structure. Further weak CH?Cl, CH?O interactions stabilise both arrangements. The X-ray structure of the complex [Cu(L)₂] · 4H₂O containing the deprotonated ligand is also described. The presence of the latter results in the above hydrogen bonding arrangements being ‘switched off’ and instead a new two-dimensional network involving bridging tetrameric water clusters hydrogen bound to adjacent ligand hydroxo groups to give extended sheets is generated; offset face-to-face π-stacking occurs between sheets to yield a three dimensional array.