Expanding the Variety of Zirconium‐based Inorganic Building Units for Metal–Organic Frameworks

Two new zirconium‐based metal–organic frameworks with the composition [Zr₆O₄(OH)₄(OAc)₆(BDC)₃] (CAU‐26) and [Zr₅O₄(OH)₄(OAc)₄(BDC)₂] (CAU‐27) are reported, which were synthesized from acetic acid, a rarely utilized but green and sustainable solvent (BDC^2?: 1,4‐benzenedicarboxylate). Structure determination aided by automated electron diffraction tomography revealed that CAU‐26 is composed of layers of well‐known {Zr₆O₈} clusters interconnected by terephthalate ions. In contrast CAU‐27 exhibits a three‐dimensional structure with a so far unknown type of one‐dimensional inorganic building unit (IBU), which can be rationalized as condensed polyhedron‐sharing chains of {Zr₆O₈} clusters. CAU‐26 occurs as an intermediate of the CAU‐27 synthesis and can be isolated easily, when reaction temperature and time are decreased. We were also able to synthesize two isoreticular derivatives of CAU‐27 with extended linker molecules by implementing 4,4′‐biphenyldicarboxylic acid (H₂BPDC) and 5,5′‐dicarboxy‐2,2′‐bipyridine (H₂BIPY). All materials show high thermal and chemical stability as well as permanent microporosity. The excellent stability of CAU‐27‐BIPY was exploited to synthesize a performant iridium‐supported heterogeneous MOF‐based catalyst for the direct C?H borylation of arenes.     

A three‐dimensional coordination polymer based on the Zn4(μ3‐OH)2 unit: poly[[(μ4‐benzene‐1,4‐dicarboxylato)bis(μ3‐benzene‐1,4‐dicarboxylato)bis(μ3‐hydroxido)bis(1,10‐phenanthroline‐5,6‐dione)tetrazinc] dihydrate]

The title compound, {[Zn₄(C₈H₄O₄)₃(OH)₂(C₁₂H₆N₂O₂)₂]·2H₂O}_n, has been prepared hydrothermally by the reaction of Zn(NO₃)₂·6H₂O with benzene‐1,4‐dicarboxylic acid (H₂bdc) and 1,10‐phenanthroline‐5,6‐dione (pdon) in H₂O. In the crystal structure, a tetranuclear Zn₄(OH)₂ fragment is located on a crystallographic inversion centre which relates two subunits, each containing a [ZnN₂O₄] octahedron and a [ZnO₄] tetrahedron bridged by a μ₃‐OH group. The pdon ligand chelates to zinc through its two N atoms to form part of the [ZnN₂O₄] octahedron. The two crystallographically independent bdc²⁻ ligands are fully deprotonated and adopt μ₃‐κO:κO′:κO′′ and μ₄‐κO:κO′:κO′′:κO′′′ coordination modes, bridging three or four Zn^II cations, respectively, from two Zn₄(OH)₂ units. The Zn₄(OH)₂ fragment connects six neighbouring tetranuclear units through four μ₃‐bdc²⁻ and two μ₄‐bdc²⁻ ligands, forming a three‐dimensional framework with uninodal 6‐connected α‐Po topology, in which the tetranuclear Zn₄(OH)₂ units are considered as 6‐connected nodes and the bdc²⁻ ligands act as linkers. The uncoordinated water molecules are located on opposite sides of the Zn₄(OH)₂ unit and are connected to it through hydrogen‐bonding interactions involving hydroxide and carboxylate groups. The structure is further stabilized by extensive π–π interactions between the pdon and μ₄‐bdc²⁻ ligands.     

Three‐Dimensional MOF‐Type Architectures with Tetravalent Uranium Hexanuclear Motifs (U6O8)

Four metal–organic frameworks (MOF) with tetravalent uranium have been solvothermally synthesized by treating UCl₄ with rigid dicarboxylate linkers in N,N‐dimethylfomamide (DMF). The use of the ditopic ligands 4,4′‐biphenyldicarboxylate ( 1 ), 2,6‐naphthalenedicarboxylate ( 2 ), terephthalate ( 3 ), and fumarate ( 4 ) resulted in the formation of three‐dimensional networks based on the hexanuclear uranium‐centered motif [U₆O₄(OH)₄(H₂O)₆]. This motif corresponds to an octahedral configuration of uranium nodes and is also known for thorium in crystalline solids. The atomic arrangement of this specific building unit with organic linkers is similar to that found in the zirconium‐based porous compounds of the UiO‐66/67 series. The structure of [U₆O₄(OH)₄(H₂O)₆(L)₆] ? X (L=dicarboxylate ligand; X=DMF) shows the inorganic hexamers connected in a face‐centered cubic manner through the ditopic linkers to build up a three‐dimensional framework that delimits octahedral (from 5.4 Å for 4 up to 14.0 Å for 1 ) and tetrahedral cavities. The four compounds have been characterized by using single‐crystal X‐ray diffraction analysis (or powder diffraction analysis for 4 ). The tetravalent state of uranium has been examined by using XPS and solid‐state UV/Vis analyses. The measurement of the Brunauer–Emmett–Teller surface area indicated very low values (Langmuir <300 m² g^?1 for 1 , <7 m² g^?1 for 2 – 4 ) and showed that the structures are quite unstable upon removal of the encapsulated DMF solvent.     

Cube‐like 12‐MC‐4 and Offset Stacked 10‐MC‐3 Metallacrowns: Synthesis,Structure, and Magnetic Properties

Two complexes [Mn^III₄(naphthsao)₄(naphthsaoH)₄] ( 1 ) and [Fe^III₆O₂(naphthsao)₄(O₂CPh)₆] ( 2 ) [naphthsao = 1‐(1‐hydroxy‐naphthalen‐2‐yl)ethanone oxime] were obtained through the reactions of naphthsao ligand and MnCl₂ · 4H₂O or FeCl₃ · 6H₂O in the presence of triethylamine (Et₃N). Their structures were determined by X‐ray single crystal diffraction, elemental analysis, and IR spectra. Complex 1 displays 12‐MC‐4 metallacrown structural type with cube‐like configuration and 2 shows an offset stacked 10‐MC‐3 structural type with the ring connectivity containing Fe–O–C–O–Fe–O–N–Fe–O–N. Magnetic susceptibility measurement reveals the ferromagnetic interactions and field‐induced slow relaxation of the magnetization for 1 , whereas out‐of‐phase signal is not observed for 2 .     

A thermally stable three‐dimensional cobalt(II) coordination polymer based on the V‐shaped ligand 4‐(4‐carboxyphenoxy)isophthalate

A new cobalt(II) coordination polymer (CP), poly[[bis[μ₆‐4‐(4‐carboxylatophenoxy)benzene‐1,3‐dicarboxylato‐κ⁶O¹:O¹:O³:O^3′:O⁴:O^4′]bis(1,10‐phenanthroline‐κ²N,N′)tricobalt(II)] 0.72‐hydrate], {[Co₃(C₁₅H₇O₇)₂(C₁₂H₈N₂)₂]·0.72H₂O}_n, (I), is constructed from Co^II ions and 4‐(4‐carboxyphenoxy)isophthalate (cpoia³⁻) and 1,10‐phenanthroline (phen) ligands. Based on centrosymmetric trinuclear [Co₃(phen)₂(COO)₆] secondary building units (SBUs), the structure of (I) is a three‐dimensional CP with a (3,6)‐connected net and point symbol (4².6)₂(4⁴.6².8⁷.10²). The positions of four [Co₃(phen)₂(COO)₆] SBUs and four cpoia³⁻ ligands reproduce a Chinese‐knot‐shaped arrangement along the ab plane. (I) has been characterized by single‐crystal X‐ray diffraction, IR spectroscopy, powder X‐ray diffraction (PXRD) and thermostability analysis. It shows a good thermal stability from room temperature to 673 K. In addition, the temperature dependence of the magnetic properties was measured.     

Three isotypic polymeric complexes with rare earth cations,but‐2‐enoate anions and 4,4′‐(ethane‐1,2‐diyl)dipyridine and 4,4′‐(ethene‐1,2‐diyl)dipyridine bridging ligands

Three isotypic rare earth complexes, catena‐poly[[aquabis(but‐2‐enoato‐κ²O,O′)yttrium(III)]‐bis(μ‐but‐2‐enoato)‐κ³O,O′:O;κ³O:O,O′‐[aquabis(but‐2‐enoato‐κ²O,O′)yttrium(III)]‐μ‐4,4′‐(ethane‐1,2‐diyl)dipyridine‐κ²N:N′], [Y₂(C₄H₅O₂)₆(C₁₂H₁₂N₂)(H₂O)₂], the gadolinium(III) analogue, [Gd₂(C₄H₅O₂)₆(C₁₂H₁₂N₂)(H₂O)₂], and the gadolinium(III) analogue with a 4,4′‐(ethene‐1,2‐diyl)dipyridine bridging ligand, [Gd₂(C₄H₅O₂)₆(C₁₂H₁₀N₂)(H₂O)₂], are one‐dimensional coordination polymers made up of centrosymmetric dinuclear [M(but‐2‐enoato)₃(H₂O)]₂ units (M = rare earth), further bridged by centrosymmetric 4,4′‐(ethane‐1,2‐diyl)dipyridine or 4,4′‐(ethene‐1,2‐diyl)dipyridine spacers into sets of chains parallel to the [20] direction. There are intra‐chain and inter‐chain hydrogen bonds in the structures, the former providing cohesion of the linear arrays and the latter promoting the formation of broad planes parallel to (010).     

Construction of (3,8)‐connected three‐dimensional cobalt(II) and copper(II) coordination polymers with 1,3‐bis[(1,2,4‐triazol‐4‐yl)methyl]benzene and benzene‐1,3,5‐tricarboxylate ligands

Coordination polymers (CPs) have been widely studied because of their diverse and adjustable topologies and wide‐ranging applications in luminescence, chemical sensors, magnetism, photocatalysis, gas adsorption and separation. In the present work, two coordination polymers, namely poly[(μ₅‐benzene‐1,3,5‐tricarboxylato‐κ⁶O¹:O^1′:O³:O³:O⁵,O^5′){μ₃‐1,3‐bis[(1,2,4‐triazol‐4‐yl)methyl]benzene‐κ³N:N′:N′′}di‐μ₃‐hydroxido‐dicobalt(II)], [Co₂(C₉H₃O₆)(OH)(C₁₂H₁₂N₆)]_n or [Co₂(btc)(OH)(mtrb)]_n, (1), and poly[[diaquabis(μ₃‐benzene‐1,3,5‐tricarboxylato‐κ³O¹:O³:O⁵)bis{μ₃‐1,3‐bis[(1,2,4‐triazol‐4‐yl)methyl]benzene‐κ³N:N′:N′′}tetra‐μ₃‐hydroxido‐tetracopper(II)] monohydrate], {[Cu₄(C₉H₃O₆)₂(OH)₂(C₁₂H₁₂N₆)₂(H₂O)₂]·H₂O}_n or {[Cu₄(btc)₂(OH)₂(mtrb)₂(H₂O)₂]·H₂O}_n, (2), were synthesized by the hydrothermal method using 1,3‐bis[(1,2,4‐triazol‐4‐yl)methyl]benzene (mtrb) and benzene‐1,3,5‐tricarboxylate (btc^3?). CP (1) exhibits a (3,8)‐coordinated three‐dimensional (3D) network of the 3,8T38 topological type, with a point symbol of {4,5,6}₂{4²·5⁶·6¹⁶·7²·8²}, based on the tetranuclear hydroxide cobalt(II) cluster [Co₄(μ₃‐OH)₂]. CP (2) shows a (3,8)‐coordinated tfz‐d topology, with a point symbol of {4₃}₂{4⁶·6¹⁸·8⁴}, based on the tetranuclear hydroxide copper(II) cluster [Cu₄(μ₃‐OH)₂]. The different (3,8)‐coordinated 3D networks based on tetranuclear hydroxide–metal clusters of (1) and (2) are controlled by the different central metal ions [Co^II for (1) and Cu^II for (2)]. The thermal stabilities and solid‐state optical diffuse‐reflection spectra were measured. The energy band gaps (E_g) obtained for (1) and (2) were 2.72 and 2.29 eV, respectively. CPs (1) and (2) exhibit good photocatalytic degradation of the organic dyes methylene blue (MB) and rhodamine B (RhB) under visible‐light irradiation.     

Zirconium Complexes of Two Different Iminopyrrolyl Ligands – Syntheses and Structures

The reaction involving N‐aryliminopyrrolyl ligand, 2‐((p‐Me‐C₆H₃N=CMe)–C₄H₃NH) ( 1a ) (Imp^Me‐H), and Zr(OtBu)₄ in a 2:1 molar ratio in toluene at 90 °C afforded the corresponding bis(iminopyrrolyl) complex of zirconium, [(Imp^Me)₂Zr(OtBu)₂] ( 2a ) having two bidentate iminopyrrole groups in the coordination sphere. In contrast, the bulkier 2‐((2,6‐iPr₂C₆H₃N=CH)–C₄H₃NH) ( 1b ) (Imp^Dipp‐H) and Zr(OtBu)₄ in a 1:1 molar ratio under the same condition yielded the corresponding mono(iminopyrrolyl) complex of zirconium, [(Imp^Dipp)Zr(OtBu)₃(THF)] ( 2b ), which contains only one bidentate iminopyrrole moiety in the coordination sphere. Both complexes were characterized by single‐crystal X‐ray diffraction analysis. The solid‐state structures reveal that the bulky iminopyrrole ligands cause a steric crowding around the zirconium ion along with three tert‐butoxide ligands attached to the central metal atom.     

Solid‐State Structural Transformations and Photoreactivity of 1D‐Ladder Coordination Polymers of PbII

An attempt has been made to design double‐stranded ladder‐like coordination polymers (CPs) of hemidirected Pb^II. Four CPs, [Pb(μ‐bpe)(O₂C‐C₆H₅)₂] ? 2H₂O ( 1 ), [Pb₂(μ‐bpe)₂(μ‐O₂C‐C₆H₅)₂(O₂C‐C₆H₅)₂] ( 2 ), [Pb₂(μ‐bpe)₂(μ‐O₂C‐p‐Tol)₂(O₂C‐p‐Tol)₂] ? 1.5 H₂O ( 3 ) and [Pb₂(μ‐bpe)₂(μ‐O₂C‐m‐Tol)₂(O₂C‐m‐Tol)₂] ( 4 ) (bpe=1,2‐bis(4′‐pyridyl)ethylene), have been synthesised and investigated for their solid‐state photoreactivity. CPs 2 – 4 , having a parallel orientation of bpe molecules in their ladder structures and being bridged by carboxylates, were found to be photoreactive, whereas CP 1 is a linear one‐dimensional (1D) CP with guest water molecules aggregating to form a hydrogen‐bonded 1D structure. The linear strands of 1 were found to pair up upon eliminating lattice water molecules by heating, which led to the solid‐state structural transformation of photostable linear 1D CP 1 into photoreactive ladder CP 2 . In the construction of the double‐stranded ladder‐like structures, the parallel alignment of C?C bonds in 2 – 4 is dictated by the chelating and μ₂‐η²:η¹ bridging modes of the benzoate and toluate ligands. The role of solvents in the formation of such double‐stranded ladder‐like structures has also been investigated. A single‐crystal‐to‐single‐crystal transformation occurred when 4 was irradiated under UV light to form [Pb₂(rctt‐tpcb)(μ‐O₂C‐m‐Tol)₂(O₂C‐m‐Tol)₂] ( 5 ).     

Organic‐inorganic Hybrid Lanthanide‐Silver Heterometallic Coordination Frameworks Constructed from Oxalate and Sulfate Anion: Syntheses,Structures, and Photoluminescent Properties

The first four examples of organic‐inorganic hybrid lanthanide‐silver heterometallic frameworks, namely, [AgLn(μ₅‐C₂O₄)(SO₄)(H₂O)₂] [Ln = Eu ( 1 ) and Sm ( 2 )] and [AgLn(μ₄‐C₂O₄)_0.5(μ₆‐C₂O₄)_0.5(SO₄)(H₂O)] [Ln = Tb ( 3 ) and Dy ( 4 )] based on oxalate and sulfate anions were synthesized by hydrothermal reactions of lanthanide oxide, silver nitrate, oxalic acid and sulfuric acid. All structures contain ladder‐like inorganic lanthanide sulfato chains, which are further connected together through silver atoms by oxalate anions with different coordination behavior (μ₅‐C₂O₄: 1 and 2 , μ₆‐C₂O₄ mixed μ₄‐C₂O₄: 3 and 4 ) to generate two types of 3D networks. The luminescent properties of these compounds were also studied.     

Synthesis,crystal structures and magnetic and electrochemiluminescence properties of three manganese(II) complexes

Three novel complexes, namely, penta‐μ‐acetato‐bis(μ₂‐2‐{[2‐(6‐chloropyridin‐2‐yl)hydrazinylidene]methyl}‐6‐methoxyphenolato)‐μ‐formato‐tetramanganese(II), [Mn₄(C₁₃H₁₁ClN₃O₂)₂(C₂H₃O₂)_5.168(CHO₂)_0.832], 1 , hexa‐μ₂‐acetato‐bis(μ₂‐2‐{[2‐(6‐bromopyridin‐2‐yl)hydrazinylidene]methyl}‐6‐methoxyphenolato)tetramanganese(II), [Mn₄(C₁₃H₁₁BrN₃O₂)₂(C₂H₃O₂)₆], 2 , and catena‐poly[[μ₂‐acetato‐acetatoaqua(μ₂‐2‐{[2‐(6‐chloropyridin‐2‐yl)hydrazinylidene]methyl}‐6‐methoxyphenolato)dimanganese(II)]‐μ₂‐acetato], [Mn₂(C₁₃H₁₁ClN₃O₂)(C₂H₃O₂)₃(H₂O)]_n, 3 , have been synthesized using solvothermal methods. Complexes 1 – 3 were characterized by IR spectroscopy, elemental analysis and single‐crystal X‐ray diffraction. Complexes 1 and 2 are tetranuclear manganese clusters, while complex 3 has a one‐dimensional network based on tetranuclear Mn₄(L¹)₂(CH₃COO)₆(H₂O)₂ building units (L¹ is 2‐{[2‐(6‐chloropyridin‐2‐yl)hydrazinylidene]methyl}‐6‐methoxyphenolate). Magnetic studies reveal that complexes 1 – 3 display dominant antiferromagnetic interactions between Mn^II ions through μ₂‐O bridges. In addition, 1 – 3 also display favourable electrochemiluminescence (ECL) properties.     

Crystal Growth,Single‐Crystal Structure Refinement and Unusual Ligand‐Field Splittings of Lazulite‐Type Oxidephosphates MTi2O2(PO4)2 (M = FeII,CoII, NiII)

Single crystals of oxidephosphates MTi₂O₂(PO₄)₂ [M: Fe (dark red), Co (pinkish red), Ni (green)] with edge‐lengths up to 0.4 mm were grown by chemical vapour transport. FeTi₂O₂(PO₄)₂ and CoTi₂O₂(PO₄)₂ are isotypic to NiTi₂O₂(PO₄)₂. The crystal structure of the latter was previously solved from powder data [FeTi₂O₂(PO₄)₂ (data for CoTi₂O₂(PO₄)₂ and NiTi₂O₂(PO₄)₂ in brackets): monoclinic, P2₁/c, Z = 2, a = 7.394(3) (7.381(6), 7.388(4)) Å, b = 7.396(2) (7.371(5), 7.334(10)) Å, c = 7.401(3) (7.366(6), 7.340(3)) Å, β = 120.20(3) (120.26(6), 120.12(4))°, R₁ = 0.0393 (0.0309, 0.0539) wR₂ = 0.1154 (0.0740, 0.1389), 2160 (1059, 1564) independent reflections, 75 (76, 77) variables]. The single‐crystal study allowed improved refinement using anisotropic displacement parameters, yielded lower standard deviations for the structural parameters and revealed a small amount of cation disordering. Twinning and cation disordering within the structures are rationalized by a detailed crystallographic classification of the MTi₂O₂(PO₄)₂ structure type in terms of group‐subgroup relations. The structure is characterized by a three‐dimensional network of [PO₄] tetrahedra and [M^IITi₂O₁₂] groups formed by face‐sharing of [M^IIO₆] and [TiO₆] octahedra. Electronic absorption spectra of MTi₂O₂(PO₄)₂ in the UV/VIS/NIR region show rather large ligand‐field splittings for the strongly trigonally distorted chromophors [M^IIO₆] (M = Fe, Co, Ni) with interelectronic repulsion parameters beeing slightly smaller than in other phosphates. Interpretation of the spectra within the framework of the angular overlap model reveals a significant second‐sphere ligand field effect of Ti^IV ions on the electronic levels of the Ni^II and Co^II.     

Phosphaniminato‐Acetato‐Cluster von Kupfer und Zink. Kristallstrukturen von [Cu4(NPEt3)2(O2CCH3)6] und [Zn4(NPEt3)2(O2CCH3)6]

Phosphoraneiminato Acetate Cluster of Copper and Zinc. Crystal Structures of [Cu₄(NPEt₃)₂(O₂CCH₃)₆] and [Zn₄(NPEt₃)₂(O₂CCH₃)₆] The anhydrous acetates of copper(II) and zinc react with the silylated phosphaneimine Me₃SiNPEt₃ in dichloromethane at 20 °C forming the mixed phosphoraneiminato acetate clusters [Cu₄(NPEt₃)₂(O₂CCH₃)₆] ( 1 ), which forms emerald crystals, and colourless [Zn₄(NPEt₃)₂ · (O₂CCH₃)₆] ( 2 ). In spite of analogous composition the structures of 1 and 2 are completely different. In the asymmetric unit of 1 three copper atoms of an almost isosceles triangle are linked via two nitrogen atoms of the NPEt₃^– groups to form a trigonal bipyramidal aggregate. One of these three copper atoms is chelated by an acetate group, another one is connected with the fourth copper atom via three μ₂‐O₂C–CH₃ groups. The asymmetric units are associated via a μ₂‐O₂C–CH₃ group and a μ₃‐OC(O)CH₃ group at a time so that infinite chains result. In 2 two zinc atoms are linked via the nitrogen atoms of the two NPEt₃^– groups to form an almost centrosymmetric four‐membered ring. Both nitrogen atoms of the four‐membered ring are connected with another zinc atom each. These zinc atoms again are linked with the zinc atoms of the Zn₂N₂ four‐membered ring via two μ₂‐O₂C–CH₃ groups each and additionally coordinated with a terminal acetate ligand each.     

Topological identification of the first uninodal 8‐connected lsz MOF built from 2,2′‐difluorobiphenyl‐4,4′‐dicarboxylate pillars and cadmium(II)–triazolate layers

Using polynuclear metal clusters as nodes, many high‐symmetry high‐connectivity nets, like 8‐connnected bcu and 12‐connected fcu , have been attained in metal–organic frameworks (MOFs). However, construction of low‐symmetry high‐connected MOFs with a novel topology still remains a big challenge. For example, a uninodal 8‐connected lsz network, observed in inorganic ZrSiO₄, has not been topologically identified in MOFs. Using 2,2′‐difluorobiphenyl‐4,4′‐dicarboxylic acid (H₂L) as a new linker and 1,2,4‐triazole (Htrz) as a coligand, a novel three‐dimensional Cd^II–MOF, namely poly[tetrakis(μ₄‐2,2′‐difluorobiphenyl‐4,4′‐dicarboxylato‐κ⁵O¹,O^1′:O^1′:O⁴:O^4′)tetrakis(N,N‐dimethylformamide‐κO)tetrakis(μ₃‐1,2,4‐triazolato‐κ³N¹:N²:N⁴)hexacadmium(II)], [Cd₆(C₁₄H₆F₂O₄)₄(C₂H₂N₃)₄(C₃H₇NO)₄]_n, (I), has been prepared. Single‐crystal structure analysis indicates that six different Cd^II ions co‐exist in (I) and each Cd^II ion displays a distorted [CdO₄N₂] octahedral geometry with four equatorial O atoms and two axial N atoms. Three Cd^II ions are connected by four carboxylate groups and four trz⁻ ligands to form a linear trinuclear [Cd₃(COO)₄(trz)₄] cluster, as do the other three Cd^II ions. Two Cd₃ clusters are linked by trz⁻ ligands in a μ_1,2,4‐bridging mode to produce a two‐dimensional Cd^II–triazolate layer with (6,3) topology in the ab plane. These two‐dimensional layers are further pillared by the L²⁻ ligands along the c axis to generate a complicated three‐dimensional framework. Topologically, regarding the Cd₃ cluster as an 8‐connected node, the whole architecture of (I) is a uninodal 8‐connected lsz framework with the Schläfli symbol (4²²·6⁶). Complex (I) was further characterized by elemental analysis, IR spectroscopy, powder X‐ray diffraction, thermogravimetric analysis and a photoluminescence study. MOF (I) has a high thermal and water stability.     

Two new cadmium(II) coordination polymers based on bis(1,2,4‐triazol‐1‐yl)alkane ligands and pyrazine‐2,3‐dicarboxylic acid

Assemblies of pyrazine‐2,3‐dicarboxylic acid and Cd^II in the presence of bis(1,2,4‐triazol‐1‐yl)butane or bis(1,2,4‐triazol‐1‐yl)ethane under ambient conditions yielded two new coordination polymers, namely poly[[tetraaqua[μ₂‐1,4‐bis(1,2,4‐triazol‐1‐yl)butane‐κ²N⁴:N^4′]bis(μ₂‐pyrazine‐2,3‐dicarboxylato‐κ³N¹,O²:O³)dicadmium(II)] dihydrate], {[Cd₂(C₆H₂N₂O₄)₂(C₈H₁₂N₆)(H₂O)₄]·2H₂O}_n, (I), and poly[[diaqua[μ₂‐1,2‐bis(1,2,4‐triazol‐1‐yl)ethane‐κ²N⁴:N^4′]bis(μ₃‐pyrazine‐2,3‐dicarboxylato‐κ⁴N¹,O²:O³:O^3′)dicadmium(II)] dihydrate], {[Cd₂(C₆H₂N₂O₄)₂(C₆H₈N₆)(H₂O)₂]·2H₂O}_n, (II). Complex (I) displays an interesting two‐dimensional wave‐like structure and forms a distinct extended three‐dimensional supramolecular structure with the help of O—H...N and O—H...O hydrogen bonds. Complex (II) has a three‐dimensional framework structure in which hydrogen bonds of the O—H...N and O—H...O types are found.     

{[Mn2(μ3‐Tda)2(μ‐H2O)(H2O)2(bipy)]·DMF}n – a 2D Manganese(II) Coordination Polymer involving Six‐membered Binuclear Metallacycle Nodes

The single crystal X‐ray analysis of a novel thiophene‐2,5‐dicarboxylic acid (H₂Tda) Manganese(II) coordination polymer, {Mn₂(μ₃‐Tda)₂(μ‐H₂O)(H₂O)₂(bipy)]·DMF}_n, shows two different types of Mn²⁺‐ions with environment of Mn1O₆ and Mn2O₄N₂, and the complex is a two‐dimensional polymer as a result of bridging (Tda)^2? ligands and by connecting the carboxylate‐ and water‐bridged {Mn₂(μ‐Tda)₂(μ‐H₂O)} nodes.     

Chromium complexes bearing disubstituted organophosphate ligands and their use in ethylene polymerization

The crystal structures of three unusual chromium organophosphate complexes have been determined, namely, bis(μ‐butyl 2,6‐di‐tert‐butyl‐4‐methylphenyl hydrogen phosphato‐κO:κO′)di‐μ‐hydroxido‐bis[(butyl 2,6‐di‐tert‐butyl‐4‐methylphenyl hydrogen phosphato‐κO)(butyl 2,6‐di‐tert‐butyl‐4‐methylphenyl phosphato‐κO)chromium](Cr—Cr) heptane disolvate or {Cr₂(μ₂‐OH)₂[μ₂‐PO₂(OBu)(O‐2,6‐^tBu₂‐4‐MeC₆H₂)‐κO:κO′]₂[PO₂(OBu)(O‐2,6‐^tBu₂‐4‐MeC₆H₂)‐κO]₂[HOPO(OBu)(O‐2,6‐^tBu₂‐4‐MeC₆H₂)‐κO]₂}·2C₇H₁₆, [Cr₂(C₁₉H₃₂O₄P)₄(C₁₉H₃₃O₄P)₂(OH)₂]·2C₇H₁₆, denoted ( 1 )·2(heptane), [μ‐bis(2,6‐diisopropylphenyl) phosphato‐1κO:2κO′]bis[bis(2,6‐diisopropylphenyl) phosphato]‐1κO,2κO‐chlorido‐2κCl‐triethanol‐1κ²O,2κO‐di‐μ‐ethanolato‐1κ²O:2κ²O‐dichromium(Cr—Cr) ethanol monosolvate or {Cr₂(μ₂‐OEt)₂[μ₂‐PO₂(O‐2,6‐ⁱPr₂‐C₆H₃)₂‐κO:κO′][PO₂(O‐2,6‐ⁱPr₂‐C₆H₃)₂‐κO]₂Cl(EtOH)₃}·EtOH, [Cr₂(C₂H₅O)₂(C₂₄H₃₄O₄P)₃Cl(C₂H₆O)₃]·C₂H₆O, denoted ( 2 )·EtOH, and di‐μ‐ethanolato‐1κ²O:2κ²O‐bis{[bis(2,6‐diisopropylphenyl) hydrogen phosphato‐κO][bis(2,6‐diisopropylphenyl) phosphato‐κO]chlorido(ethanol‐κO)chromium}(Cr—Cr) benzene disolvate or {Cr₂(μ₂‐OEt)₂[PO₂(O‐2,6‐ⁱPr₂‐C₆H₃)₂‐κO]₂[HOPO(O‐2,6‐ⁱPr₂‐C₆H₃)₂‐κO]₂Cl₂(EtOH)₂}·2C₆H₆, [Cr₂(C₂H₅O)₂(C₂₄H₃₄O₄P)₂(C₂₄H₃₅O₄P)₂Cl₂(C₂H₆O)₂]·2C₆H₆, denoted ( 3 )·2C₆H₆. Complexes ( 1 )–( 3 ) have been synthesized by an exchange reaction between the in‐situ‐generated corresponding lithium or potassium disubstituted phosphates with CrCl₃(H₂O)₆ in ethanol. The subsequent crystallization of ( 1 ) from heptane, ( 2 ) from ethanol and ( 3 ) from an ethanol/benzene mixture allowed us to obtain crystals of ( 1 )·2(heptane), ( 2 )·EtOH and ( 3 )·2C₆H₆, whose structures have the monoclinic P2₁, orthorhombic P2₁2₁2₁ and triclinic P space groups, respectively. All three complexes have binuclear cores with a single Cr—Cr bond, i.e. Cr₂O₆P₂ in ( 1 ), Cr₂PO₄ in ( 2 ) and Cr₂O₂ in ( 3 ), where the Cr atoms are in distorted octahedral environments, formally having 16 ē per Cr atom. The complexes have bridging ligands μ₂‐OH in ( 1 ) or μ₂‐OEt in ( 2 ) and ( 3 ). The organophosphate ligands demonstrate terminal κO coordination modes in ( 1 )–( 3 ) and bridging μ₂‐κO:κO′ coordination modes in ( 1 ) and ( 2 ). All the complexes exhibit hydrogen bonding: two intramolecular O_phos…H—O_phos interactions in ( 1 ) and ( 3 ) form two {H[PO₂(OR)₂]₂} associates; two intramolecular Cl…H—O_Et hydrogen bonds additionally stabilize the Cr₂O₂ core in ( 3 ); two intramolecular O_phos…H—O_Et interactions and two O…H—O intermolecular hydrogen bonds with a noncoordinating ethanol molecule are observed in ( 2 )·EtOH. The presence of both basic ligands (OH^? or OEt^?) and acidic [H(phosphate)₂]^? associates at the same metal centres in ( 1 ) and ( 3 ) is rather unusual. Complexes may serve as precatalysts for ethylene polymerization under mild conditions, providing polyethylene with a small amount of short‐chain branching. The formation of a small amount of α‐olefins has been detected in this reaction.     

Oxygen‐Atom Transfer Chemistry and Thermolytic Properties of a Di‐tert‐Butylphosphate‐Ligated Mn4O4 Cubane

[Mn₄O₄{O₂P(OtBu)₂}₆] ( 1 ), an Mn₄O₄ cubane complex combining the structural inspiration of the photosystem II oxygen‐evolving complex with thermolytic precursor ligands, was synthesized and fully characterized. Core oxygen atoms within complex 1 are transferred upon reaction with an oxygen‐atom acceptor (PEt₃), to give the butterfly complex [Mn₄O₂{O₂P(OtBu)₂}₆(OPEt₃)₂]. The cubane structure is restored by reaction of the latter complex with the O‐atom donor PhIO. Complex 1 was investigated as a precursor to inorganic Mn metaphosphate/pyrophosphate materials, which were studied by X‐ray absorption spectroscopy to determine the fate of the Mn₄O₄ unit. Under the conditions employed, thermolyses of 1 result in reduction of the manganese to Mn^II species. Finally, the related butterfly complex [Mn₄O₂{O₂P(pin)}₆(bpy)₂] (pin=pinacolate) is described.     

Structural diversity of polynuclear MgxOy cores in magnesium phenoxide complexes

The binuclear complex bis(2,6‐di‐tert‐butyl‐4‐methylphenolato)‐1κO ,2κO‐(1,2‐dimethoxyethane‐1κ²O ,O ′)bis(μ‐phenylmethanolato‐1:2κ²O :O )(tetrahydrofuran‐2κO )dimagnesium(II), [Mg₂(C₇H₇O)₂(C₁₅H₂₃O)₂(C₄H₈O)(C₄H₁₀O₂)] or [(BHT)(DME)Mg(μ‐OBn)₂Mg(THF)(BHT)], (I), was obtained from the complex [(BHT)Mg(μ‐OBn)(THF)]₂ by substitution of one tetrahydrofuran (THF) molecule with 1,2‐dimethoxyethane (DME) in toluene (BHT is O‐2,6‐^t Bu₂‐4‐MeC₆H₄ and Bn is benzyl). The trinuclear complex bis(2,6‐di‐tert‐butyl‐4‐methylphenolato)‐1κO ,3κO‐tetrakis(μ‐2‐methylphenolato)‐1:2κ⁴O :O ;2:3κ⁴O :O‐bis(tetrahydrofuran)‐1κO ,3κO‐trimagnesium(II), [Mg₃(C₇H₇O)₄(C₁₅H₂₃O)₂(C₄H₈O)₂] or [(BHT)₂(μ‐O‐2‐MeC₆H₄)₄(THF)₂Mg₃], (II), was formed from a mixture of Bu₂Mg, [(BHT)Mg(ⁿ Bu)(THF)₂] and 2‐methylphenol. An unusual tetranuclear complex, bis(μ₃‐2‐aminoethanolato‐κ⁴O :O :O ,N )tetrakis(μ₂‐2‐aminoethanolato‐κ³O :O ,N )bis(2,6‐di‐tert‐butyl‐4‐methylphenolato‐κO )tetramagnesium(II), [Mg₄(C₂H₆NO)₆(C₁₅H₂₃O)₂] or Mg₄(BHT)₂(OCH₂CH₂NH₂)₆, (III), resulted from the reaction between (BHT)₂Mg(THF)₂ and 2‐aminoethanol. A polymerization test demonstrated the ability of (III) to catalyse the ring‐opening polymerization of ϵ‐caprolactone without activation by alcohol. In all three complexes (I)–(III), the BHT ligand demonstrates the terminal κO‐coordination mode. Complexes (I), (II) and (III) have binuclear rhomboid Mg₂O₂, trinuclear chain‐like Mg₃O₄ and bicubic Mg₄O₆ cores, respectively. A survey of the literature on known polynuclear Mg_x O_y core types for ArO–Mg complexes is also presented.     

Three‐dimensional hydrogen‐bonded structures in the hydrated proton‐transfer salts of isonipecotamide with the dicarboxylic oxalic and adipic acid homologues

The structures of the 1:1 hydrated proton‐transfer compounds of isonipecotamide (piperidine‐4‐carboxamide) with oxalic acid, 4‐carbamoylpiperidinium hydrogen oxalate dihydrate, C₆H₁₃N₂O⁺·C₂HO₄⁻·2H₂O, (I), and with adipic acid, bis(4‐carbamoylpiperidinium) adipate dihydrate, 2C₆H₁₃N₂O⁺·C₆H₈O₄²⁻·2H₂O, (II), are three‐dimensional hydrogen‐bonded constructs involving several different types of enlarged water‐bridged cyclic associations. In the structure of (I), the oxalate monoanions give head‐to‐tail carboxylic acid O—H...O_carboxyl hydrogen‐bonding interactions, forming C(5) chain substructures which extend along a. The isonipecotamide cations also give parallel chain substructures through amide N—H...O hydrogen bonds, the chains being linked across b and down c by alternating water bridges involving both carboxyl and amide O‐atom acceptors and amide and piperidinium N—H...O_carboxyl hydrogen bonds, generating cyclic R₄³(10) and R₃²(11) motifs. In the structure of (II), the asymmetric unit comprises a piperidinium cation, half an adipate dianion, which lies across a crystallographic inversion centre, and a solvent water molecule. In the crystal structure, the two inversion‐related cations are interlinked through the two water molecules, which act as acceptors in dual amide N—H...O_water hydrogen bonds, to give a cyclic R₄²(8) association which is conjoined with an R₄⁴(12) motif. Further N—H...O_water, water O—H...O_amide and piperidinium N—H...O_carboxyl hydrogen bonds give the overall three‐dimensional structure. The structures reported here further demonstrate the utility of the isonipecotamide cation as a synthon for the generation of stable hydrogen‐bonded structures. The presence of solvent water molecules in these structures is largely responsible for the non‐occurrence of the common hydrogen‐bonded amide–amide dimer, promoting instead various expanded cyclic hydrogen‐bonding motifs.