Alexander N. Chernega

1,2,4-Triazolyl-Carboxylate-Based MOFs Incorporating Triangular Cu(II)-Hydroxo Clusters: Topological Metamorphosis and Magnetism

Bifunctional 1,2,4-triazole-carboxylate ligands, an achiral 1,2,4-triazol-4-yl-acetic acid (trgly-H) and a chiral (d)-2-(1,2,4-triazol-4-yl)-propionic acid (d-trala-H), derived from the corresponding α-amino acid precursors revealed unique binding abilities in the construction of Cu(II)-coordination polymers composing discrete triangular [Cu3(μ3-OH)] clusters. A related series of MOFs, [Cu3(μ3-OH)(trgly)3(SO4)]·2H2O (1a), [Cu3(μ3-OH)(trgly)3(H2O)3]SO4·16H2O (1b), Cu3(μ3-OH)(d-trala)3(ClO4)0.5](ClO4)1.5·1.5H2O (2), was prepared, and their crystal structures were determined by means of X-ray diffraction. Being singly deprotonated, the organic ligands act as multidentate μ3- or μ4-donors using tr and -COO(-) moieties. The generated [Cu3(μ3-OH)(tr)3] cluster core is primarily supported by three [-N-N-] triazole heterocycles in a basal plane and tripodal-assisted μ3-anions (SO4(2-): 1a; ClO4(-): 2) capping the axial faces. The carboxylate groups join the units into either two-dimensional (2D) layer (1a, 2) or 3D zeolite-like networks (1b). Compound 1b represents the topology of α-Po (pcu: 4(12).6(3)) and crystallizes in the noncentrosymmetric space group I4̅3m, in which the six-connected [Cu3(μ3-OH)] clusters and trgly self-assemble in an open-channel cubic array possessing ∼56% solvent-accessible volume. Upon slight thermal treatment (∼60 °C), the structure irreversibly shrinks to the nonporous 2D motif 1a that belongs to a uninodal (3,6) network type. In structure 2 (space group R32), due to the [-N-N-] triazole and 1,3-bidentate carboxylate binding mode, each organic ligand bridges three metal clusters affording cross-linking of two adjacent layers with the same (3,6) topology. The resultant 3,9-c net is novel and can be categorized as two-nodal with point symbol {4(18).6(18)}{4(2).6}3. Spin frustration and antisymmetric exchange effects, resulting in abnormally low g values in the S = 1/2 states, were observed in the magnetic properties and the EPR spectra.

Ag(I)/V(V) heterobimetallic frameworks generated from novel-type {Ag2(VO2F2)2(triazole)4} secondary building blocks: a new aspect in the design of SVOF hybrids.

A series of new silver(I)-containing MOFs [Ag(2)(tr(2)ad)(2)](ClO(4))(2) (1), [Ag(2)(VO(2)F(2))(2)(tr(2)ad)(2)]·H(2)O (2), [Ag(2)(VO(2)F(2))(2)(tr(2)eth)(2)(H(2)O)(2)] (3), and [Ag(2)(VO(2)F(2))(2)(tr(2)cy)(2)]·4H(2)O (4) supported by 4-substituted bifunctional 1,2,4-triazole ligands (tr(2)ad = 1,3-bis(1,2,4-triazol-4-yl)adamantane, tr(2)eth = 1,2-bis(1,2,4-triazol-4-yl)ethane, tr(2)cy = trans-1,4-bis(1,2,4-triazol-4-yl)cyclohexane) were hydrothermally synthesized and structurally characterized. In these complexes, the triazole heterocycle as an N(1),N(2)-bridge links either two adjacent Ag-Ag or Ag-V centers at short distances forming polynuclear clusters. The crystal structure of compound 1 is based on cationic {Ag(2)(tr)(4)}(2+) fragments connected in a 2D rhombohedral grid network with (4,4) topology. The neighboring layers are tightly packed into a 3D array by means of argentophilic interactions (Ag···Ag 3.28 Å). Bridging between different metal atoms through the triazole groups assists formation of heterobimetallic Ag(I)/V(V) secondary building blocks in a linear V-Ag-Ag-V sequence that is observed in complexes 2-4. These unprecedented tetranuclear {Ag(2)(VO(2)F(2))(2)(tr)(4)} units (the intermetal Ag-Ag and Ag-V distances are 4.24-4.36 and 3.74-3.81 Å, respectively), in which vanadium(V) oxofluoride units possess distorted trigonal bipyramidal environment {VO(2)F(2)N}¯, are incorporated into 1D ribbon (2) or 2D square nets (3, 4) using bitopic μ(4)-triazole ligands. The valence bond calculation for vanadium atoms shows +V oxidation state in the corresponding compounds. Thermal stability and photoluminescence properties were studied for all reported coordination polymers.

New microporous copper(II) coordination polymers based upon bifunctional 1,2,4-triazole/tetrazolate bridges

A series of Cu(II) coordination polymers, [Cu(μ2-L1)3]PO3F (1), [Cu2(μ2-L1)4(μ4-L1)](NO3)4·2H2O (2), [Cu(μ2-L1)2(μ2-X)]X·12H2O (X = Cl, 3; Br, 4), [Cu4(μ2-OH)2(μ4-L1)3(μ2-L1)2(H2O)2](CF3SO3)6·10H2O (5), [Cu3(μ2-OH)2(μ4-L1)(H2O)2(μ3-SO4)2] (6), [Cu(μ4-L1)(μ2-SO4)]·6H2O (7), [Cu2(μ4-L2)3]Cl·12H2O (8) involving new bifunctional p-phenylene bridged bi(1,2,4-triazole) and mixed 1,2,4-triazole-tetrazolate based ligands (L1= 1,4-phenylene-4,4′-bi(1,2,4-triazole), HL2= 5-(4-[1,2,4]triazol-4-yl-phenyl)-1H-tetrazole) has been prepared under hydrothermal conditions and their structures have been established by means of X-ray diffraction. In crystal structures 1–8, the organic ligands, utilizing two neighboring nitrogen atoms (N1, N2 in triazole (trz) and N2, N3 in tetrazolate), behave either in μ2 or in μ2 + μ4 manner binding the adjacent metal centers or Cu3(μ2-OH)2 clusters into 1D columns (1, 3, 4), 2D zigzag layers (2) and 3D frameworks (5–8). The mutual coplanarity between uncoordinated trz moiety and p-phenylene spacer as well as its radial disposition around the “propeller-like” [Cu2(η2-trz)3] subunits is a crucial factor, which specifically mediates multiple π–π interactions through intercalation of the neighboring Cu(η2-trz)n (n = 2,3) axles, and as a consequence, affording one-dimensional channels with trigonal (1, 2) or rhombic geometry (3, 4). Large rectangular channels have been realized in neutral [Cu(μ4-L1)(μ2-SO4)]n (7) and cationic [Cu2(μ4-L2)3]nn+ (8) frameworks, in which the remaining void space is filled by water molecules and counter anions (Cl−).

One- and two-dimensional coordination polymers of 3,3′,5,5′-tetramethyl-4,4′-bipyrazolyl, a new perspective crystal engineering module

Abstract The coordination polymers based upon new bidentate ligand 3,3′,5,5′-tetramethyl-4,4′-bipyrazolyl (4,4′-bpz) have been prepared and characterized by means of X-ray analysis. In all compounds Ag(4,4′-bpz)NO3·CH3OH (1), Cd(4,4′-bpz)(C3H7OH)(NO3)2 (2), Cd(4,4′-bpz)2(NO3)2 (3), Cu(4,4′-bpz)2(H2O)(BF4)2·0.5C6H5Br (4), and Cu(4,4′-bpz)2(H2O)(HCOO)2·2.5HCONH2 (5) the molecules of bipyrazolyl act as bridging neutral groups and connect two metal atoms at the distances of 9.58–10.25 A. Complexes 1 and 2 exhibit one-dimensional polymeric structure, while compounds 3–5 exist as two-dimensional polymers, containing layers of four-connected coordination nets. In structures 4 and 5 the layers are interlinked by means of hydrogen bonding involving counter anions, which lead to formation of three-dimensional open networks capable of incorporation of hydrophilic (5) or hydrophobic (4) guest molecules. Geometry of coordination polymer in these cases is significantly dominated by the angular structure of 4,4′-bpz ligand, while structure of the coordination net in 3 is very similar for analogues containing linear 4,4′-bipyridine bridges.

Functionalized adamantane tectons used in the design of mixed-ligand copper(II) 1,2,4-triazolyl/carboxylate metal-organic frameworks.

Bistriazoles, 1,3-bis(1,2,4-triazol-4-yl)propane (tr(2)pr) and 1,3-bis(1,2,4-triazol-4-yl)adamantane (tr(2)ad), were examined in combination with the rigid tetratopic 1,3,5,7-adamantanetetracarboxylic acid (H(4)-adtc) platform for the construction of neutral heteroleptic copper(II) metal-organic frameworks. Two coordination polymers, [{Cu(4)(OH)(2)(H(2)O)(2)}{Cu(4)(OH)(2)}(tr(2)pr)(2)(H-adtc)(4)]·2H(2)O (1) and [Cu(4)(OH)(2)(tr(2)ad)(2)(H-adtc)(2)(H(2)O)(2)]·3H(2)O (2), were synthesized and structurally characterized. In complexes 1 and 2, the N(1),N(2)-1,2,4-triazolyl (tr) and μ(3)-OH(-) groups serve as complementary bridges between adjacent metal centers supporting the tetranuclear dihydroxo clusters. The structure of 1 represents a unique association of two different kinds of centrosymmetrical {Cu(4)(OH)(2)} units in a tight 3D framework, while in compound 2, another configuration type of acentric tetranuclear metal clusters is organized in a layered 3,6-hexagonal motif. In both cases, the {Cu(4)(OH)(2)} secondary building block and trideprotonated carboxylate H-adtc(3-) can be viewed as covalently bound six- and three-connected nodes that define the net topology. The tr ligands, showing μ(3)- or μ(4)-binding patterns, introduce additional integrating links between the neighboring {Cu(4)(OH)(2)} fragments. A variable-temperature magnetic susceptibility study of 2 demonstrates strong antiferromagnetic intracluster coupling (J(1) = -109 cm(-1) and J(2) = -21 cm(-1)), which combines for the bulk phase with a weak antiferromagnetic intercluster interaction (zj = -2.5 cm(-1)).

Aliphatic aldehydes in multicomponent syntheses of 4-alkyl-substituted partially hydrogenated quinolines, fused 4H-pyrans, and 2-amino-4-ethyl-5-methylbenzene- 1,3-dicarbonitrile

The Knoevenagel condensation of aliphatic aldehydes with CH acids, malonodinitrile, cyanothioacetamide, cyclohexane-1,3-dione, dimedone, 4-hydroxycoumarin, 3-aminophenol, and N-(cyclohex-1-enyl)-morpholine leads to formation of 4-alkyl-substituted partially hydrogenated quinolines, fused 4H-pyrans, and 2-amino-4-ethyl-5-methylbenzene-1,3-dicarbonitrile. The structure of the latter was proved by the X-ray diffraction data.

4,4′-Bipyrazolyl: new bitopic connector for construction of coordination networks

Abstract New organic bitopic connector 4,4′-bipyrazolyl (bpz) easily forms complexes with metal ions and produces 1, 2 and 3D coordination polymers of different topology. Ten coordination polymers based upon bpz ligand and octahedral metal centers (Zn2+, Cd2+, Cu2+, Co2+) have been prepared and characterized by means of X-ray analysis. In all compounds the bipyrazolyl molecules act as bridging neutral groups and connect two metal atoms at the distances of 9.81–10.34 A. Representative possibilities for the formation of multidimensional metal-organic array include linear chains in [Cu(bpz)(H2O)3(SO4)]·H2O, ‘ladder chains’ in [M(bpz)1.5(H2O)2(NO3)](NO3) (M=Cu, Zn), flat and corrugated square grid layers in 1:2 complexes with cobalt chloride, zinc and cadmium perchlorates and copper trifluoroacetate, parallel/parallel interpenetrated square grid layers in [Cd(bpz)2(NO3)2] and 3D diamondoid net in [Cu(bpz)2(H2O)2](ClO3)2·5H2O. With exception of the latter example the supramolecular architecture of metal-organic polymers may be clearly related with 4,4′-bipyridine derivatives, but more hydrophilic nature of pyrazole nuclei facilitates easy incorporation of different H-bond donors/acceptors—H2O, CH3OH, DMF. The 2D coordination arrays may enclathrate also guest molecules of hydrophilic aromatics that appear to be located between successive coordination layers: [Cu(bpz)2(H2O)2](CF3CO2)2·2H2O·C6H5OH.

Mono(η-cyclopentadienyl)benzamidinato alkyl compounds of titanium and zirconium

The compounds [Zr(η-C5H5){CPh(NSiMe3)2}2Cl], [{Zr(η-C5H5)[CPh(NSiMe3)2]Cl}2{µ-CPh(NSiMe3)2}][{Zr(η-C5H5)[CPh(NSiMe3)2]Cl}2(µ-O)], [Zr(η-C5R5){CPh(NSiMe3)2}(CH2Ph)Cl](R = H or Me), [Zr(η-C5R5){CPh(NSiMe3)2}(CH2Ph)2](R = H or Me) and [M(η-C5R5){CPh(NSiMe3)2}Me2](M = Zr, R = H or Me; M = Ti, R = H have been synthesized and the crystal structures of three of them) determined.

Homo- and hetero-binuclear ansa-metallocenes of the group 4 transition metals as homogeneous co-catalysts for the polymerisation of ethene and propene

Abstract The compounds [M{(CH 2 ) 4 C( η -C 5 H 4 ) 2 }( η -C 5 H 5 )Cl] (M=Zr * , Hf), [M{(CH 2 ) 4 C( η -C 5 H 4 ) 2 }( η -C 5 H 5 )Me] (M=Zr, Hf), [( η -C 5 H 5 )MCl 2 {(CH 2 ) 4 C( η -C 5 H 4 ) 2 }MCl 2 ( η -C 5 H 5 )] (M=Zr, Hf), [( η -C 5 H 5 )ZrCl 2 {(CH 2 ) 4 C( η -C 5 H 4 )( η -C 9 H 6 )}ZrCl 2 ( η -C 5 H 5 )], [( η -C 5 H 5 )MMe 2 {(CH 2 ) 4 C( η -C 5 H 4 ) 2 }MMe 2 ( η -C 5 H 5 )] (M=Zr, Hf), [( η -C 5 H 5 )ZrCl 2 {(CH 2 ) 4 C( η -C 5 H 4 ) 2 }HfCl 2 ( η -C 5 H 5 )], [( η -C 5 H 5 )MCl 2 {(CH 2 ) 4 C( η -C 5 H 4 ) 2 }Rh( η -C 8 H 12 )] (M=Zr * , Hf), [( η -C 5 H 5 )ZrCl 2 {(CH 2 ) 4 C( η -C 5 H 4 ) 2 }TiCl 3 ], [( η -C 5 H 5 )ZrMe 2 {(CH 2 ) 4 C( η -C 5 H 4 ) 2 }HfMe 2 ( η -C 5 H 5 )], [( η -C 5 H 5 )MMe 2 {(CH 2 ) 4 C( η -C 5 H 4 ) 2 }Rh( η -C 8 H 12 )] (M=Zr * , Hf) have been prepared and characterised. * indicates the crystal structure has been determined. Their catalytic properties for ethene and propene polymerisation have been explored.

Syntheses and reactions of ansa-[2,2-bis(η-cyclopentadienyl)propane]-tungsten and -molybdenum compounds

Reaction between [MCl4(dme)](M = W or Mo; dme = 1,2-dimethoxyethane) with Li2[C5H4CMe2C5H4] gave the ansa-bridged metallocene dichlorides [M{(η-C5H4)CMe2(η-C5H4)}Cl2](M = W or Mo). Treatment of these with LiAlH4 or ZnMe2 gave respectively the dihydrides [M{(η-C5H4)CMe2(η-C5H4)}H2](M = W or Mo) and the dimethyl derivatives [M{(η-C5H4)CMe2(η-C5H4)}Me2](M = W or Mo). Treatment of [W{(η-C5H4)CMe2(η-C5H4)}Me2] with HX (X = PhCO2 or NH3l) gave [W{(η-C5H4)CMe2(η-C5H4)}Me(Y)] with Y = PhCO2 or l, respectively. Both of these react with Na[AlH2(OCH2CH2OMe)2] giving the methylhydride [W{(η-C5H4)CMe2(η-C5H4)}Me(H)]. The latter is thermally stable in refluxing benzene. Ultraviolet photolysis of [Mo{(η-C5H4)CMe2(η-C5H4)}H2] in benzene gave the phenylhydride derivative [Mo{(η-C5H4)CMe2(η-C5H4)}Ph(H)]; the corresponding tungsten derivative [W{(η-C5H4)CMe2(η-C5H4)}H2] is not photosensitive. The crystal structures of [W{(η-C5H4)CMe2(η-C5H4)}Cl2], [W{(η-C5H4)CMe2(η-C5H4)}H2], (two modifications) and [Mo{(η-C5H4)CMe2(η-C5H4)}H2] have been determined by X-ray diffraction. The ansa-bridged bis(η-cyclopentadienyl) compounds show marked differences in reactivity compared to non-ansa analogues and this is discussed in terms of the modifications of the electronic structure as a consequence of the ansa bridge.