Anomalous Stoichiometry and Antiferromagnetic Ordering for the Extended Hydroxymanganese(II) Cubes/Hexacyanometalate-Based 3D-Structured [MnII 4 (OH)4 ][MnII (CN)6 ](OH2 )6 ⋅H2 O

The reaction of Mn^II (O₂ CMe)₂ and NaCN or LiCN in water forms a light green insoluble material. Structural solution and Rietveld refinement of high-resolution synchrotron powder diffraction data for this unprecedented, complicated compound of previously unknown composition revealed a new alkali-free ordered structural motif with [Mn^II ₄ (μ₃ -OH)₄ ]⁴⁺ cubes and octahedral [Mn^II (CN)₆ ]^4- ions interconnected in 3D by Mn^II -N≡C-Mn^II linkages. The composition is {[Mn^II (OH₂ )₃ ][Mn^II (OH₂ )]₃ }(μ₃ -OH)₄ ][Mn^II (μ-CN)₂ (CN)₄ ]⋅H₂ O=[Mn^II ₄ (μ₃ -OH)₄ (OH₂ )₆ ][Mn^II (μ-CN)₂ (CN)₄ ]⋅H₂ O, which is further simplified to [Mn₄ (OH)₄ ][Mn(CN)₆ ](OH₂ )₇ (1). 1 has four high-spin (S=5/2) Mn^II sites that are antiferromagnetically coupled within the cube and are antiferromagnetically coupled to six low-spin (S=1/2) octahedral [Mn^II (CN)₆ ]^4- ions. Above 40 K the magnetic susceptibility, χ(T), can be fitted to the Curie-Weiss expression, χ ∝(T-θ)^-1 , with θ=-13.4 K, indicative of significant antiferromagnetic coupling and 1 orders as an antiferromagnet at T_c =7.8 K.

Towards an understanding of the propensity for crystalline hydrate formation by molecular compounds

Hydrates are technologically important and ubiquitous yet they remain a poorly understood and understudied class of molecular crystals. In this work, we attempt to rationalize propensity towards hydrate formation through crystallization studies of molecules that lack strong hydrogen-bond donor groups. A Cambridge Structural Database (CSD) survey indicates that the statistical occurrence of hydrates in 124 molecules that contain five- and six-membered N-heterocyclic aromatic moieties is 18.5%. However, hydrate screening experiments on a library of 11 N-heterocyclic aromatic compounds with at least two acceptor moieties and no competing hydrogen-bond donors or acceptors reveals that over 70% of this group form hydrates, suggesting that extrapolation from CSD statistics might, at least in some cases, be deceiving. Slurrying in water and exposure to humidity were found to be the most effective discovery methods. Electrostatic potential maps and/or analysis of the crystal packing in anhydrate structures was used to rationalize why certain molecules did not readily form hydrates.

Tetra-μ(3)-hydroxido-tetra-kis-[tricarbonyl-rhenium(I)] pyridine tetra-solvate

The title compound, [Re(4)(μ(3)-OH)(4)(CO)(12)]·4C(5)H(5)N, crystallizes with one tetranuclear rhenium(I) cubane-like molecule and four pyridine mol-ecules in the asymmetric unit. The coordination environment of each Re(I) atom is distorted octahedral. Four intra-molecular O-H⋯N and four inter-molecular C-H⋯O hydrogen-bond inter-actions are observed. Relatively strong hydrogen bonds are found between the hydrogen-bond donor (μ(3)-OH) and acceptor (basic N atom of pyridine), with N⋯O distances between 2.586 (10) and 2.628 (10) Å. Inter-cube distances of 9.873 (2) and 12.376 (3) Å are observed.

2:1 cocrystals of homochiral and achiral amino acid zwitterions with Li+ salts: water-stable zeolitic and diamondoid metal-organic materials

Eight 2:1 cocrystals of amino acid zwitterions and Li(+) salts were crystallized from hot water to afford cationic networks based on tetrahedral lithium cations: square grids, an ABW topology net, and diamondoid nets.

Solvent-Dependent Coordination Polymers: Cobalt Complexes of 3,5-Dinitrobenzoic Acid and 3,5-Dinitro-4-methylbenzoic Acid with 4,4‘-Bipyrdine

The synthesis, structure elucidation, and analysis of the self-assembly of Co(II) complexes of 3,5-dinitrobenzoic acid and 3,5-dinitro-4-methylbenzoic acid with 4,4'-bipyridine have been reported. Formation of the complexes and the self-assembly in the three-dimensional structures have been found to be dependent on the solvents (such as acetone, dimethly sulfoxide, etc.) employed for the synthesis of the aggregates. 3,5-Dinitrobenzoic acid forms two coordination polymers, 1a and 1b, from methanol and a mixture of methanol and acetone solvents, respectively, with entirely different recognition patterns. Similarly, 3,5-dinitro-4-methylbenzoic acid also forms two coordination complexes, 2a and 2b, incorporating the solvent of the reaction medium into the crystal lattice. Complex 2a forms a solvated channel structure, whereas 2b gives a bilayered structure, with the layers being separated by solvent of crystallization (dimethyl sulfoxide) molecules. All the complexes have been characterized by single-crystal X-ray diffraction studies. Complexes 1b, 2a, and 2b crystallize in a monoclinic lattice, but 1a adopts a tetragonal lattice. The unit cell dimensions are, for 1a, a = 8.095(1) A, b = 8.095(1) A, c = 46.283 (6) A, alpha = 90 degrees, beta = 90 degrees, and gamma = 90 degrees (space group P4(3)2(1)2, Z = 4), for 1b, a = 22.774(2) A, b = 11.375 (1) A, c = 22.533(2) A, alpha = 90 degrees, beta = 104.15(1) degrees, and gamma = 90 degrees (space group P2(1)/c, Z = 4), for 2a, a = 17.657(6) A, b = 18.709(4) A, c = 21.044(6) A, alpha = 90 degrees, beta = 108.68(3) degrees, and gamma = 90 degrees (space group, C2/c, Z = 8), and, for 2b, a = 11.025(5) A, b = 15.139(4) A, c = 11.443(4) A, alpha = 90 degrees, beta = 97.48(3) degrees, and gamma = 90 degrees (space group P2/n, Z = 2). In all the complexes 1a, 1b, 2a, and 2b, the basic interaction between Co(II) and 4,4'-bipyridine remains the same with the formation of linear Co-N dative bonds, but the carboxylates display various modes of interaction with Co(II). The average Co-N and Co-O distances are 2.161 and 2.108 A, respectively.

The charge-transfer motif in crystal engineering. Self-assembly of acentric (diamondoid) networks from halide salts and carbon tetrabromide as electron-donor/acceptor synthons

Unusual strength and directionality for the charge-transfer motif (established in solution) are shown to carry over into the solid state by the facile synthesis of a series of robust crystals of the [1:1] donor/acceptor complexes of carbon tetrabromide with the electron-rich halide anions (chloride, bromide, and iodide). X-ray crystallographic analyses identify the consistent formation of diamondoid networks, the dimensionality of which is dictated by the size of the tetraalkylammonium counterion. For the tetraethylammonium bromide/carbon tetrabromide dyad, the three-dimensional (diamondoid) network consists of donor (bromide) and acceptor (CBr(4)) nodes alternately populated to result in the effective annihilation of centers of symmetry in agreement with the sphaleroid structural subclass. Such inherently acentric networks exhibit intensive nonlinear optical properties in which the second harmonics generation in the extended charge-transfer system is augmented by the effective electronic (HOMO-LUMO) coupling between contiguous CBr(4)/halide centers.

Preparation and substitution chemistry of [Bu4N]2[W6Cl8(p-OSO2C6H4CH3)6]. A useful precursor for pseudohalide, acetate, and organometallic complexes containing the [W6Cl8](4+) core

The tosylate (p-toluenesulfonate) cluster [Bu4N]2[W6Cl8(p-OSO2C6H4CH3)6] (1) has been prepared and characterized by IR and NMR spectroscopy, elemental analysis, and an X-ray crystal structure. This cluster complex is shown to be a useful starting material for the preparation of pseudohalide clusters, [Bu4N]2[W6Cl8(NCQ)6] (Q = O (2), S (3), and Se (4)), in high yields. Cluster 1 also serves as a precursor to the new cluster compounds: [Bu4N]2[W6Cl8(O2CCH3)6] (5), [Bu4N]2[W6Cl8((mu-NC)Mn(CO)2(C5H5))6] (6), [W6Cl8((mu-NC)Ru(PPh3)2(C5H5))6][ p-OSO2C6H4CH3]4 (7), and [W6Cl8((mu-NC)Os(PPh3)2(C5H5))6][ p-OSO2C6H4CH3]4 (8). X-ray crystal structures are reported for 1, 4, and 5.

[Co(4)O(4)](4+) Cubane Core as a Brønsted Base: Preparation and Properties of [Co(4)O(3)(OH)(O(2)CR)(2)(bpy)(2)](3+) and [Co(4)O(2)(OH)(2)(O(2)CR)(2)(bpy)(2)](4+) Salts

The preparation and properties are described of complexes resulting from the mono- and diprotonation of the [Co(4)O(4)](4+) unit to give products containing [Co(4)O(3)(OH)](5+) and [Co(4)O(2)(OH)(2)](6+), respectively. Treatment of [Co(4)O(4)(O(2)CC(6)H(4)-p-OMe)(2)(bpy)(4)](2+) (bpy = 2,2'-bipyridine) in MeCN with 70% perchloric acid leads to isolation of [Co(4)O(2)(OH)(2)(O(2)CC(6)H(4)-p-OMe)(2)(bpy)(4)](ClO(4))(4) (5) in 61% yield. Treatment of [Co(4)O(4)(O(2)CC(6)H(4)-p-Me)(2)(bpy)(4)](2+) in MeCN with an acidic solution of (NH(4))(3)[Ce(NO(3))(6)] leads to isolation of [Co(4)O(3)(OH)(O(2)CC(6)H(4)-p-Me)(2)(bpy)(4)][Ce(NO(3))(6)] (6) in 96% yield. Complex 5.3MeCN.H(2)O crystallizes in monoclinic space group C2/c with (at -155 degrees C) a = 33.838(8) Å, b = 13.826(3) Å, c = 29.944(7) Å, beta = 98.84(1) degrees, and Z = 8. Complex 6.PhCN.H(2)O crystallizes in orthorhombic space group Pbca with (at -154 degrees C) a = 22.603(4) Å, b = 34.759(6) Å, c = 18.167(3) Å, and Z = 8. The complexes contain [Co(4)O(2)(OH)(2)](6+) (5) and [Co(4)O(3)(OH)](5+) (6) distorted-cubane cores, the sites of protonation being apparent by (i) the approach of ClO(4)(-) or [Ce(NO(3))(6)](3)(-) anions to within hydrogen-bonding distances (O.O approximately 2.7 Å) and (ii) the longer Co-OH(-) bond lengths compared with Co-O(2)(-) bond lengths. Peripheral ligation is provided by chelating bpy and syn,syn-bridging RCO(2)(-) groups. The Co(III) atoms are six-coordinate and approximately octahedral. Solution studies show that the diprotonated species is a strong diprotic acid analogous to H(2)SO(4); the first deprotonation goes to completion, but the monoprotonated species is a weak acid and is in equilibirium with the nonprotonated species. pH studies in aqueous solution yield a pK(a2) value of 3.15 for the second deprotonation. Electronic and (1)H NMR spectra of the diprotonated complexes in various solvents are consistent with the monoprotonated complex being the major species in solution. The combined results demonstrate that the [Co(4)O(4)](4+) core is capable of acting as a Brønsted base, undergoing either one or two protonation reactions.

Metal Complexes of Pyridylphenylisocyanides and Pyridylethynylphenylisocyanides as Building Blocks for Coordination Polymers and Supramolecular Assemblies

The isocyanides 3-(4-pyridylethynyl)phenylisocyanide, 3, 4-(4-pyridylethynyl)phenylisocyanide, 6, 2,6-diisopropyl-4-(4-pyridylethynyl)phenylisocyanide, 9, and 2,6-diisopropyl-4-(4-pyridyl)phenylisocyanide, 11, were prepared. With PdI(2) and PtI(2), these isocyanides form the complexes trans-[MI(2)(CNR)(2)], 12-19 (M = Pd, Pt; CNR = 3, 6, 9, 11). The previously prepared complex trans-[PdI(2)(CNC(5)H(4)N-3)(2)] and trans-[PdI(2)(CNC(6)H(2)-(i-Pr)(2)-2,6-(CC-C(5)H(4)N-4)-4)(2)], 16, combine with copper bis(trifluoroacetylacetonate) in the ratio of 1:2 to form the adducts trans-[PdI(2)(CNC(5)H(4)N-3)(2)].2[Cu(tfacac)(2)].2CH(2)Cl(2), 20, and trans-[PdI(2)(CNC(6)H(2)-(i-Pr)(2)-2,6-(CC-C(5)H(4)N-4)-4)(2)].2[Cu(tfacac)(2)], 21, respectively. The complexes trans-[MI(2)(CNC(6)H(2)-(i-Pr)(2)-2,6-(C(5)H(4)N-4)-4)(2)], 19 (M = Pd) and 20 (M = Pt), react with [Pd(SO(3)CF(3))(2)(dppp)] (dppp = bisdiphenylphosphinopropane) to form the molecular squares [Pd(dppp)(trans-[MI(2)(CNC(6)H(2)-(i-Pr)(2)-2,6-(C(5)H(4)N-4)-4)(2)](4)(SO(3)CF(3))(8), 22 (M = Pd) and 23 (M = Pt). The crystal structure of 20 has been determined by X-ray crystallography. 20: C(34)H(28)Cl(4)Cu(2)F(12)I(2)N(4)O(8)Pd, monoclinic space group, P2(1)/n (No. 14), a = 10.899(3) Å, b = 13.903(1) Å, c = 17.827(6) Å, beta = 105.50(2) degrees, Z = 2, 2618 unique reflections, R = 0.093, R(w) = 0.091.