Synthesis and structures of three triphosphonate compounds containing d10 transition metal ions

Three new triphosphonate compounds, [Zn(APTPH₄)(2,2′-bipy)(H₂O)]?·?2H₂O (1), [Cd(APTPH₄)(2,2′-bipy)(H₂O)]?·?2H₂O (2), and [Zn(APTPH₄)(phen)₂]?·?phen?·?4H₂O (3) (APTPH₆?=?1-aminopropane-1,1,3-triphosphonic acid, 2,2′-bipy?=?2,2′-bipyridine, phen?=?1,10-phenanthroline), are synthesized by a low-temperature hydrothermal method. Compounds 1 and 2 are isomorphous, both one-dimensional (1D) coordination polymers expanded into three-dimensional (3D) supramolecular structures by hydrogen bonds and π–π stacking interactions. Compound 3 is a molecular complex and forms a 3D network through an S-shaped water hexamer. Crystal data for 1: Triclinic, space group P 1, a?=?6.6814(5)?Å, b?=?10.0929(7)?Å, c?=?15.438(2)?Å, α?=?81.544(2)°, β?=?79.066(2)°, γ?=?82.278(2)°, Z?=?2; for 2: Triclinic, space group P 1, a?=?6.9380(8)?Å, b?= 10.043(2)?Å, c?=?15.681(2)?Å, α?=?81.357(2)°, β?=?78.510(2)°, γ?=?81.902(2)°, Z?=?2; Crystal data for 3: Triclinic, space group P 1, a?=?12.540(2)?Å, b?=?12.596(2)?Å, c?=?14.997(2)?Å, α?=?100.795(2)°, β?=?113.328(2)°, γ?=?101.358(2)°, Z?=?2.     

Reactivity of scandium terminal imido complexes towards metal halides

Reactions of scandium terminal imido complexes with CuI and [M(COD)Cl](2) (M = Rh, Ir) show two interesting reaction patterns, and the formed heterobimetallic complexes have intriguing structural features and show promising catalytic properties.     

2,2'-Biphosphinines and 2,2'-bipyridines in homoleptic dianionic Group 4 complexes and neutral 2,2'-biphosphinine Group 6 d(6) metal complexes: octahedral versus trigonal-prismatic geometries

The geometric and electronic structure of formally d(6) tris-biphosphinine [M(bp)(3)](q) and tris-bipyridine [M(bpy)(3)](q) complexes were studied by means of DFT calculations with the B3LYP functional. In agreement with the available experimental data, Group 4 dianionic [M(bp)(3)](2-) complexes (1P-3P for M=Ti, Zr, and Hf, respectively) adopt a trigonal-prismatic (TP) structure, whereas the geometry of their nitrogen analogues [M(bpy)(3)](2-) (1N-3N) is nearly octahedral (OC), although a secondary minimum was found for the TP structures (1N'-3N'). The electronic factors at work in these systems are discussed by means of an MO analysis of the minima, MO correlation diagrams, and thermodynamic cycles connecting the octahedral and trigonal-prismatic limits. In all these complexes, pronounced electron transfer from the metal center to the lowest lying pi* ligand orbitals makes the d(6) electron count purely formal. However, it is shown that the bp and bpy ligands accommodate the release of electron density from the metal in different ways because of a change in the localization of the HOMO, which is a mainly metal-centered orbital in bp complexes and a pure pi* ligand orbital in bpy complexes. The energetic evolution of the HOMO allows a simple rationalization of the progressive change from the TP to the OC structure on successive oxidation of the [Zr(bp)(3)](2-) complex, a trend in agreement with the experimental structure of the monoanionic complex. The geometry of Group 6 neutral complexes [M(bp)(3)] (4P and 5P for M=Mo and W, respectively) is found to be intermediate between the TP and OC limits, as previously shown experimentally for the tungsten complex. The electron transfer from the metal center to the lowest lying pi* ligand orbitals is found to be significantly smaller than for the Group 4 dianionic analogues. The geometrical change between [Zr(bp)(3)](2-) and [W(bp)(3)] is analyzed by means of a thermodynamic cycle and it is shown that a larger ligand-ligand repulsion plays an important role in favoring the distortion of the tungsten complex away from the TP structure.     

Metal Derivatives of 1,3‐Imidazolidine‐2‐thione with Divalent d10 Metal Ions (Zn–Hg) : Synthesis and Structures

Reactions of divalent Zn‐Hg metal ions with 1,3‐imidazolidine‐2‐thione (imdtH₂) in 1 : 2 molar ratio have formed monomeric complexes, [Zn(η¹‐S‐imdtH₂)₂(OAc)₂] ( 1 ), [Cd((η¹‐SimdtH₂)₂I₂] ( 2 ), [Cd(η¹‐S‐imdtH₂)₂Br₂] ( 3 ), and [Hg(η¹‐S‐imdtH₂)₂I₂] ( 4 ). Complexes 1 – 4 , have been characterized by elemental analysis (C, H, N), spectroscopy (IR, ¹H, NMR) and x‐ray crystallography ( 1 ‐ 4 ). Hydrogen bonding between oxygen of acetate and imino hydrogen of ligand, {N(2)–H(2C)···O(2)^#} in 1 , ring CH and imino hydrogen, {C(2A)–H(2A)···Br(2)^#} in 3 have formed H‐bonded dimers. Similarly, the interactions between molecular units of complexes 2 and 4 have yielded 2D polymers. The polymerization occurs via intermolecular interactions between thione sulfur and imino hydrogen, {N(2)–H(2)···S(1)^#}, imino hydrogen and the iodine atom, {NH(1)···I(2)^#} in 2 and imino hydrogen – iodine atom {N(2A)–H(2A)···I(2)} and I···I interaction in 4 . Crystal data: [Zn(η¹‐S‐imdtH₂)₂(OAc)₂] ( 1 ), C₁₀H₁₈N₄O₄S₂Zn, orthorhombic, Pbcn, a = 9.3854(7) Å, b = 12.4647(10) Å, c = 13.2263(11) Å; V = 1547.3(2) ų, Z = 4, R = 0.0280 [Cd((η¹‐S‐imdtH₂)₂I₂] ( 2 ), C₆H₁₂CdI₂N₄S₂, orthorhombic, Pnma, a = 13.8487(10) Å, b = 14.4232(11) Å, c = 7.0659(5) Å; Z = 4, V = 1411.36(18) ų, R = 0.0186.     

Luminescent metal complexes of d6, d8 and d10 transition metal centres

This highlight focuses on various luminescent complexes with different transition metal centres of d(6), d(8) and d(10) electronic configurations. Through the systematic study on the variation of ligands, structural and bonding modes of different metal centres, the structure-property relationships of the various classes of luminescent transition metal complexes can be obtained. With the knowledge and fundamental understanding of their photophysical behaviours, their electronic absorption and luminescence properties can be fine-tuned. Introduction of supramolecular assembly with hierarchical complexity involving non-covalent interactions could lead to research dimensions of unlimited possibilities and opportunities. The approach of "function by design" could be employed to explore and exploit the potential applications of such luminescent transition metal complexes for future development of luminescent materials.     

Synthesis and Structural Characterization of Metal Complexes of 2‐Formylpyrrole‐4N‐ethylthiosemicarbazone (4 EL1) and 2‐Acetylpyrrole‐4N‐ethylthiosemicarbazone (4 EL2)

The reactions of ⁴N‐ethyl‐2‐[1‐(pyrrol‐2‐yl)methylidene(hydrazine carbothioamide ( 4 EL₁ ) and ⁴N‐ethyl‐2[1‐(pyrrol‐2‐yl)ethylidene(hydrazine carbothioamide ( 4 EL₂ ) with Group 12 metal halides afforded complexes of types [M(L)₂X₂] (M = Zn, Cd; L = 4 EL₁, 4 EL₂; X = Cl, Br, I; 1 – 6 , 14 – 19 ) and [M(L)X₂] (M = Hg; L = 4 EL₁, 4 EL₂; X = Cl, Br, I; 7 – 9 , 20 – 22 ). In addition, reaction of 4 EL₁ with salts of Cu^II, Ni^II, Pd^II and Pt^II afforded compounds of type [M(4 EL₁–H)₂] ( 10 – 13 ). The new compounds were characterized by elemental analysis, FAB mass spectrometry, IR and electronic spectroscopy and, for sufficiently soluble compounds, ¹H, ¹³C and, when appropriate, ¹¹³Cd or ¹⁹⁹Hg NMR spectrometry. The spectral data suggest that in their complexes with Group 12 metal cations, both thiosemicarbazones are neutral and S‐monodentate; and for [Zn(4 EL₁)₂I₂] ( 3 ), [Cd(4 EL₁)₂Br₂] ( 5 ) and [Hg(4 EL₁)Cl₂]₂ ( 7 ) this was confirmed by X‐ray diffractometry. By contrast, in its complexes with Cu^II and Group 10 metal cations, 4 EL₁ is monodeprotonated and S,N‐bidentate, as was confirmed by X‐ray diffractometry for [Ni(4 EL₁–H)₂] ( 11 ) and [Pd(4 EL₁–H)₂] ( 12 ).     

Reactivity of cationic decamethylmetallocene complexes towards ketones

Reaction of decamethylmetallocene cations [Cp∗₂M]⁺ (M = Sc, Ti, V) with acetone and benzophenone resulted in the formation of the corresponding acetone adducts [Cp∗₂M(OCMe₂)_n]⁺ (M = Sc, n = 2; M = Ti, n = 1; M = V, n = 1) and benzophenone adducts [Cp∗₂M(OCPh)]⁺. The stoichiometry of these adducts is determined by both the electronic configuration of the metal center as well as steric pressure imparted by the large Cp∗-ligands. In addition, the M-O-C angle is controlled by the number of free valence orbitals of the Cp∗₂M unit.     

Pyridine-type complexes of transition metal halides

Formation of nitrogen ligated complexes of types NiL₆X₂, NiL₄X₂, NiL₂X₂ and NiL₁X₂ (whereL=pyridine, 2-, 3- and 4-methyl-pyridine andX=F, Cl, Br, I) have been studied by traditional preparative methods, i.e. from solutions and by solid-gas phase chemisorption. Quaternary mixed complexes were obtained by chemisorption from heated intermediates. The complexes thus formed were further analysed by simultaneous TG-DTG-DTA. Effects of the ligands on stoichiometry and thermal properties of the complexes are discussed.     

1D Coordination Polymers from Zinc(II) and Cadmium(II) Halides and 2,2′‐Dithiobis(pyridine N‐oxide): Isostructurality and Structural Diversity

Group 12 halides and 2,2′‐dithiobis(pyridine N‐oxide) (dtpo) form the crystalline the 1D coordination polymers [ZnX₂(μ‐dtpo‐κ²O:O′)]_n [X = Cl ( 1 ), Br ( 2 ), I ( 3 )], [Cd₃(μ‐Cl)₄Cl₂(μ‐dtpo‐κ²O:O′)₂(CH₃OH)₂]_n ( 4 ), [(CdBr₂)₂(μ₃‐dtpo‐κ³O,O:O′)₂(H₂O)₂]_n ( 5 ), and [(CdI₂)₂(μ‐dtpo‐κ²O:O′)₃]_n ( 6 ) in methanol. The compounds were structurally characterized by single‐crystal X‐ray analysis. Compounds 1 – 3 represent an isomorphous series of single‐stranded coordination polymers, whereas the Cd^II derivatives are structurally diverse. The metal nodes in 4 and 5 are trinuclear and dinuclear cadmium clusters, respectively. In 4 and 5 , the metal nodes are linked into double‐stranded 1D coordination polymers by two dtpo bridging ligands. Compound 6 contains mononuclear CdI₂ units as nodes and can be viewed as an alternating copolymer of CdI₂(μ‐dtpo‐κ²O:O′)₂ and CdI₂(μ‐dtpo‐κ²O:O′) entities. Owing to the disulfide moiety, the dtpo bridging ligand inevitably exhibits an axially chiral angular structure. The dtpo ligand adopts various coordination modes through the pyridine N‐oxide oxygen atoms.     

Reactivity of molecular dioxygen towards a series of isostructural dichloroiron(III) complexes with tripodal tetraamine ligands: general access to mu-oxodiiron(III) complexes and effect of alpha-fluorination on the reaction kinetics

We have synthesized the mono, di-, and tri-alpha-fluoro ligands in the tris(2-pyridylmethyl)amine (TPA) series, namely, FTPA, F(2)TPA and F(3)TPA, respectively. Fluorination at the alpha-position of these nitrogen-containing tripods shifts the oxidation potential of the ligand by 45-70 mV per added fluorine atom. The crystal structures of the dichloroiron(II) complexes with FTPA and F(2)TPA reveal that the iron center lies in a distorted octahedral geometry comparable to that already found in TPAFeCl(2). All spectroscopic data indicate that the geometry is retained in solution. These three isostructural complexes all react with molecular dioxygen to yield stable mu-oxodiiron(III) complexes. Crystal structure analyses are reported for each of these three mu-oxo compounds. With TPA, a symmetrical structure is obtained for a dicationic compound with the tripod coordinated in the kappa(4)N coordination mode. With FTPA, the compound is a neutral mu-oxodiiron(III) complex with a kappa(3)N coordination mode of the ligand. Oxygenation of the F(2)TPA complex gave a neutral unsymmetrical compound, the structure of which is reminiscent of that already found with the trifluorinated ligand. On reduction, all mu-oxodiiron(III) complexes revert to the starting iron(II) species. The oxygenation reaction parallels the well-known formation of mu-oxo derivatives from dioxygen in the chemistry of porphyrins reported almost three decades ago. The striking feature of the series of iron(II) precursors is the effect of the ligand on the kinetics of oxygenation of the complexes. Whereas the parent complex undergoes 90 % conversion over 40 h, the monofluorinated ligand provides a complex that has fully reacted after 30 h, whereas the reaction time for the complex with the difluorinated ligand is only 10 h. Analysis of the spectroscopic data reveals that formation of the mu-oxo complexes proceeds in two distinct reversible kinetic steps with k(1) approximately 10 k(2). For TPAFeCl(2) and FTPAFeCl(2) only small variations in the k(1) and k(2) values are observed. By contrast, F(2)TPAFeCl(2) exhibits k(1) and k(2) values that are ten times higher. These differences in kinetics are interpreted in the light of structural and electronic effects, especially the Lewis acidity at the metal center. Our results suggest coordination of dioxygen as an initial step in the process leading to formation of mu-oxodiiron(III) compounds, by contrast with an unlikely outer-sphere reduction of dioxygen, which generally occurs at negative potentials.     

Two coordination polymers based on 2,2′-biimidazoles and d10 metal ions: syntheses,structures, and luminescence

Two d¹⁰ metal coordination polymers, [Zn(µ-Me₂biim)Cl₂] _n (1) and [Cd₃(MeHbiim)₂(1,4-BDC)₃] _n (2) (Me₂biim?=?N,N′-dimethyl-2,2′-biimidazole, MeHbiim?=?N-methyl-2,2′-biimidazole, 1,4-BDC?=?1,4-benzenedicarboxylate), were synthesized under hydrothermal conditions and characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis, and single-crystal X-ray crystallography. Complex 1 features an infinite neutral zigzag 1-D chain. Interchain hydrogen-bonding interactions further extend the 1-D arrangement to generate a 2-D supramolecular architecture. Complex 2 features a 3-D coordination polymer with α-Po net topology, based on linear trinuclear {Cd₃O₁₄N₄} clusters. Both complexes have high thermal stability and exhibit strong luminescence at room temperature.     

Synthesis,Crystal Structures and Spectrothermal Characterization of a Heptacoordinated Dimeric Salicylato Cadmium(II) Complex with 2,2′‐Azobispyridine (abpy), (µ‐abpy)[Cd(Hsal)2(abpy)]2

µ‐2,2′‐Azobispyridinebis[2,2′‐azobispyridinesalicylato(O)salicylato(O,O′) cadmium(II)], (µ‐abpy)[Cd(Hsal)₂(abpy)]₂ ( I ) was synthesized and characterized by IR and UV/ Vis spectroscopy, thermal analysis, and X‐ray diffraction techniques. Two abpy ligands and two salicylato ligands coordinate to the Cd²⁺ ion in a monocapped trigonal‐prismatic arrangement. The capping atom is the N3 atom. One of the two abpy ligands behaves as a “s‐frame” bridging ligand and adopts a s‐cis/ E/ s‐cis conformation, whereas the other one adopts as a s‐cis/ E/ s‐trans conformation. One of the two salicylato ligands acts as a monodentate ligand, which coordinates with the carboxylate oxygen atom, whereas the other one adopts bidentate coordination through two carboxylate oxygen atoms. The hydroxy groups of salicylato ligands, which coordinate in a monodentate fashion, are disordered over two positions, with occupancies of 0.52 for group A and 0.48 for group B. The decomposition reaction takes place in the temperature range 20–1000 °C under nitrogen. Thermal decomposition of the title complex proceeds in two stages.     

Novel Octahedral Bis[2‐(1‐aziridinyl)ethanol‐κ2N,O] Complexes of Cobalt(II)

The synthesis and molecular structure of trans‐{bis[(acetato‐κO)‐(2‐(1‐aziridinyl)ethanol‐κ²N,O)]}cobalt(II) ( 4 ) and cis‐{bis[chlorido‐(2‐(1‐aziridinyl)ethanol‐κ²N,O)]}cobalt(II) ( 5 ) is reported. Both neutral chelate complexes are prepared from the corresponding Co^II salt [CoX₂; X = OAc ( 1 ), Cl ( 2 )] and 2‐(1‐aziridinyl)ethanol (azolH, 3 ) in dry dichloromethane. A third, ionic complex, cis‐{bis[aqua‐(2‐(1‐aziridinyl)ethanol‐κ²N,O)]}cobalt(II) diacetate ( 6 ) is formed from 4 in the presence of water and could be crystallized from aqueous dichloromethane. In all cases, 2‐(1‐aziridinyl)ethanol is coordinating as bidentate chelate ligand by the nitrogen and oxygen atom of the aziridinyl and hydroxy moiety. After purification, the compounds have been fully characterized using IR spectroscopy and FAB⁺‐MS. The single‐crystal X‐ray structure analysis revealed a distorted octahedral geometry for all complexes with either trans ( 4 ) or cis ( 5 , 6 ) configuration.     

Syntheses and crystal structures of bis(4-dimethylaminopyridine) group 12 trifluoroacetates — M(OCOCF3)2·2DMAP (M=Zn, Cd, Hg)

Bis(4-dimethylaminopyridine) group 12 trifluoroacetates—M(OCOCF₃)₂·2DMAP (M=Zn, Cd, Hg) were prepared in quantitative yields from the anhydrous metal trifluoroacetates and DMAP. All compounds crystallize in the triclinic space group (no. 2) with two molecules per unit cell. While Zn(OCOCF₃)₂·2DMAP is built up by well-separated tetrahedral units exhibiting strongly covalent ZnO bonds to monodentate trifluoroactate groups, Cd(OCOCF₃)₂·2DMAP and Hg(OCOCF₃)₂·2DMAP form dimeric units. The metal centers are distorted octahedrally surrounded by two axial DMAP ligands, two ionic bridging and one chelating trifluoroacetate group.     

Energy analysis of metal-metal bonding in [RM-MR] (M = Zn, Cd, Hg; R = CH3, SiH3, GeH3, C5H5, C5Me5)

The metal-metal bonds of the title compounds have been investigated with the help of energy decomposition analysis at the DFT/TZ2P level. In good agreement with experiment, computations yield Hg-Hg bond distance in [H₃SiHg-HgSiH₃] of 2.706 Å and Zn-Zn bond distance in [(η⁵-C₅Me₅)Zn-Zn(η⁵-C₅Me₅)] of 2.281 Å. The Cd-Cd bond distances are longer than the Hg-Hg bond distances. Bond dissociation energies (-BDE) for Zn-Zn bonds in zincocene −70.6 kcal/mol in [(η⁵-C₅H₅)₂Zn₂] and −70.3 kcal/mol in [(η⁵-C₅Me₅)₂Zn₂] are greater amongst the compounds under study. In addition, [(η⁵-C₅H₅)₂M₂] is found to have a binding energy slightly larger than those in [(η⁵-C₅Me₅)₂M₂]. The trend of the M-M bond dissociation energy for the substituents R shows for metals the order GeH₃ < SiH₃ < CH₃ < C₅Me₅ < C₅H₅. Electrostatic forces between the metals are always attractive and they are strong (−75.8 to −110.5 kcal/mol). The results demonstrate clearly that the atomic partial charges cannot be taken as a measure of the electrostatic interactions between the atoms. The orbital interaction (covalent bonding) ΔE_orb is always smaller than the electrostatic attraction ΔE_elstat. The M-M bonding in [RM-M-R] (R = CH₃, SiH₃, GeH₃, C₅H₅, C₅Me₅; M = Zn, Cd, Hg) has more than half ionic character (56-64%). The values of Pauli repulsions, ΔE_Pauli, electrostatic interactions, ΔE_elstat, and orbital interactions, ΔE_elstat are larger for mercury compounds as compared to zinc and cadmium.     

Syntheses and Characterization of Zinc,Cadmium, and Mercury(II) Complexes with N‐(2‐pyridyl)carbonylaniline (L), X‐ray Crystal Structure of [Hg(L)(SCN)2]

The reaction of N‐(2‐pyridyl)carbonylaniline (L) with Zn(NO₃)₂, CdCl₂, and Hg(SCN)₂ gives the following complexes: [Zn(L)₂](NO₃)₂, [Cd(L)₂Cl₂], and [Hg(L)(SCN)₂]. The new complexes were characterized by elemental analyses and IR‐, ¹H‐, ¹³C‐NMR spectroscopy. The crystal structure of the [Hg(L)(SCN)₂] was determined by single crystal X‐ray analysis. The monomeric complex is built up of a Hg(SCN)₂ unit with one N‐(2‐pyridyl)carbonylaniline (L) ligand coordinated to the Hg atom via the ring pyridinic nitrogen atom and the carbonyl oxygen atom forming a five‐membered chelate ring. The Hg atom has a distorted tetrahedral environment. There is π‐π stacking interaction between the parallel aromatic rings belonging to adjacent chain as planar species in which the mean molecular planes are close to parallel and separated by a distance of ～ 3.5Å, close to that of the planes in graphite. The coordinated N‐(2‐pyridyl)carbonylaniline (L) molecule is involved in hydrogen bonding acting as hydrogen‐bond donors with S and N atoms from SCN^— ligand as potential hydrogen‐bond acceptors. There is a shortest intermolecular contacts between the S and N atoms. The hydrogen bonding and shortest intermolecular contacts between the S and N atoms yields infinite chains parallel to the crystallographic vector c. Each molecule is bonded to two neighbors.     

An investigation of Hartree-Fock calculations on some d 8 and d 10 transition metal nitrosyls

Ab initio Hartree-Fock calculations have been performed on some systems involving a metal atom and a single nitrosyl group. These reveal a large splitting of the d-orbital energies. The importance of these in influencing the bonding picture is discussed and a method is introduced for the analysis of the contributions to individual Fock matrix elements. The source of the energy splitting is found to have its origin in the distribution of electron density on the metal atom rather than the electrostatic ligand field.     

Syntheses,structures, photoluminescence,and theoretical studies of a novel class of d10 metal complexes of 1H-[1,10]phenanthrolin-2-one

A novel asymmetric monosubstituted 1,10-phenanthroline, Hophen.0.5 H(2)O (1, Hophen=1H-[1,10]phenanthrolin-2-one), was generated by a facile route, and a novel class of crystalline, d(10)-metal, monomeric or oligomeric complexes of this ligand, namely [Hg(ophen)(2)].4 H(2)O.CH(2)Cl(2) (2), [Cd(3)Cl(ophen)(5)].1.5 H(2)O.2 CH(2)Cl(2) (3), and [Zn(4)O(ophen)(4)(OAc)(2)].4H(2)O.2 CH(2)Cl(2) (4), were obtained by means of liquid diffusion, and were characterized by X-ray crystallography and photoluminescence studies. Complex 1 exhibits a hydrogen-bonded dimeric structure, 2 is a neutral monomeric complex, 3 has a trinuclear structure with the ophen ligand acting as a bridge through the ketone groups, and 4 features a tetranuclear Zn(4)O core that is consolidated further by bridging ophen and acetate ligands. All the complexes display photoluminescent properties in the blue/green region. The photoluminescent mechanisms were investigated by means of molecular orbital calculations, which showed that the photoluminescent properties are ligand-based and can be tuned upon ligation to different metal ions.