Lattice Solvent Molecules Research Articles

Reversible Solvatomagnetic Effect in Novel Tetranuclear Cubane-Type Ni4 Complexes and Magnetostructural Correlations for the [Ni4(μ3-O)4] Core

A new family of tetranuclear nickel cube complexes [Ni(4)L(4)(solv)(4)] (1, solv = MeOH; 2, solv = H(2)O; H(2)L = pyrazole-based tridentate {ONO} ligand) has been studied in detail, in particular by X-ray diffraction and superconducting quantum interference device (SQUID) magnetometry. Different solvates 1·H(2)O, 2·4C(3)H(6)O, 2·CH(2)Cl(2), and 2·H(2)O were obtained in crystalline form. Only small structural variations were found for the Ni-O-Ni angles of the [Ni(4)O(4)] cores of those compounds, but these slight variations have dramatic consequences for the magnetic properties. [Ni(4)L(4)(MeOH)(4)]·H(2)O (1·H(2)O) and [Ni(4)L(4)(H(2)O)(4)]·H(2)O (2·H(2)O) can be reversibly interconverted in the solid state by exposure to the respective solvent, MeOH or H(2)O, and this goes along with a switching of the spin ground state from magnetic (S(T) = 4) to diamagnetic (S(T) = 0). Likewise the (irreversible) loss of lattice solvent in [Ni(4)L(4)(H(2)O)(4)]·4C(3)H(6)O (2·4C(3)H(6)O) to give 2·2C(3)H(6)O changes the ground state from S(T) = 4 to S(T) = 0. In view of these dramatic solvatomagnetic effects for the present [Ni(4)L(4)(solv)(4)] complexes, which occur upon extrusion of lattice solvent or facile exchange of coordinated solvent molecules while keeping the robust [Ni(4)O(4)] core intact, a note of care is issued: whenever magnetic data are obtained for powdered material or for crystals that easily loose lattice solvent molecules, the magnetic properties may not necessarily reflect the situation observed in the corresponding single crystal diffraction study. Finally, a thorough analysis of the present series of complexes as well as other {Ni(4)(μ(3)-OR)(4)} cubes reported in the literature confirms that a correlation between the (Ni-O-Ni)(av) bond angle and J in [Ni(4)O(4)] cubane complexes does indeed exist.

Solvent-Dependent Assemblies of Trinuclear Copper Cluster into Variable Frameworks Based on Mixed Ligands of Polyalcohol Amines and Organic Carboxylates

A systematic investigation on solvent-dependent assembly of trinuclear copper cluhster has resulted in eight related coordination polymers: Cu3(teaH2)2(oba)2(MeOH)2 (1), Cu3(teaH2)2(oba)2(EtOH)2 (2), Cu3(teaH2)2(oba)2·(n-PrOH) (3), Cu3(teaH2)2(oba)2 (4), Cu3(teaH2)2(oba)2(H2O)2 (5), Cu3(MedeaH)2(oba)2(MeOH)2 (6), Cu[Cu3(Medea)2(oba)2]·(solvent)x (7), and [Cu3(MedeaH)2(oba)2(H2O)]·(n-PrOH)2 (8) where oba = 4,4′-oxy-bis(benzoate), teaH3 = triethanolamine, and MedeaH2 = N-methyldiethanolamine. In 1–8, the trinuclear copper secondary building units (SBUs) (Cu3) are furnished via the synergistic coordination of two organic ligands with metal centers. The structures of 1–8 exhibit two types of extensible modes (mode I for 1, 2, 3, 7, 8 and mode II for 4, 5, 6) to Cu3 SBUs. Mode I assembles Cu3 SBUs into the one-dimensional (1D) iron-chain-like structure while mode II facilitates the two-dimensional (2D) undulate rectangular (4, 4) connection. Compounds 1 and 2 feature zero-dimensional (0D) molecular structures in which two strong hydrogen-bonding interactions extend its molecular components into 1D chains. Compound 3 comprises 1D chains interspersed by free solvent molecules, whereas compound 4 consists of 2D sheets excluding any solvent molecules. Compound 5 is also made up of 0D molecular structures but uses two classic hydrogen-bonding interactions to form its 2D supramolecular connection. Compound 6 has a 2D network similar to 4. Compound 7 shows an unusual three-dimensional (3D) microporous framework in which a 1D chain is further assembled by extra CuII ions. Compound 8 provides 1D solvated structures with the voids occupied by lattice solvent molecules. The coordination ability of solvent molecules has been established for the underlying factor behind the different assemblies of compounds 1–8. Compounds 5 and 8 from an alcohol/H2O mixture indicate a behavior of selective coordination to the available coordination points of metal centers. The gas sorption property of compound 7 has also been investigated.

Direct Crystallographic Observation of Catalytic Reactions inside the Pores of a Flexible Coordination Polymer

A new flexible porous coordination polymer (PCP), {[Gd(2)(L)(3)(dmf)(4)]·4DMF·3H(2)O}(n) (1), was synthesized under solvothermal condition by reacting [Gd(NO(3))(3)]·6H(2)O with the ligand 2,6,2',6'-tetranitro-biphenyl-4,4'-dicarboxylic acid (H(2)L). Compound 1 had a 3D coordination polymeric structure with two types of 1D channels (A and B) that were occupied by DMF and water molecules. When crystals of 1 were separately exposed to vapors of various aromatic aldehydes, either the lattice or both the lattice and metal-bound solvent molecules were replaced by aldehyde molecules. The aldehyde molecules inside the pores spontaneously underwent cyanosilylation and Knoevenagel condensation reactions upon exposure to vapors of trimethylsilyl cyanide and malononitrile, respectively. These reactions took place at ambient temperature and pressure. Moreover, both the reactants and the products translocated from one cavity to another. The products that occupied the cavity were expunged upon exposure to the vapors of an aldehyde. Because crystallinity was maintained during these chemical transformations, direct crystallographic observation was possible. Herein, we showed that confinement of the reactants inside the void spaces of the PCP led to the products; we also assessed catalytic activities of this PCP in bulk quantities.

New single-molecule magnet based on Mn12 oxocarboxylate clusters with mixed carboxylate ligands, [Mn12O12(CN-o-C6H4CO2)12(CH3CO2)4(H2O)4]·8CH2Cl2: Synthesis, crystal and electronic structure, magnetic properties

A new high symmetry Mn(12) oxocarboxylate cluster [Mn(12)O(12)(CN-o-C(6)H(4)CO(2))(12)(CH(3)CO(2))(4)(H(2)O)(4)]·8CH(2)Cl(2) (1) with mixed carboxylate ligands is reported. It was synthesized by the standard carboxylate substitution method. 1 crystallizes in the tetragonal space group I4(1)/a. Complex 1 contains a [Mn(12)O(12)] core with eight CN-o-C(6)H(4)CO(2) ligands in the axial positions, four CH(3)CO(2) and four CN-o-C(6)H(4)CO(2) in equatorial positions. Four H(2)O molecules are bonded to four Mn atoms in an alternating up, down, up, down arrangement indicating a 1 : 1 : 1 : 1 isomer. The Mn(12) molecules in 1 are self-assembled by complementary hydrogen C-H···N bonds formed with participation of the axial o-cyanobenzoate ligands of the adjacent Mn(12) clusters. The lattice solvent molecules (CH(2)Cl(2)) are weakly interacted with Mn(12) units that results in solvent loss immediately after removal of the crystals from the mother liquor. The electronic structure and the intramolecular exchange parameters have been calculated. Mn 3d bands of 1 are rather broad, and the center of gravity of the bands shifts down from the Fermi level. The overlap between Mn 3d bands and 2p ones of the oxygen atoms from the carboxylate bridges is higher than in the parent Mn(12)-acetate cluster. These changes in the electronic structure provide a significant difference in the exchange interactions in comparison to Mn(12)-acetate. The magnetic properties have been studied on a dried (solvent-free) polycrystalline sample of 1. The dc magnetic susceptibility measurements in the 2-300 K temperature range support a high-spin ground state (S = 10). A bifurcation of temperature dependencies of magnetization taken under zero field cooled and field cooled conditions observed below 4.5 K is due to slow magnetization relaxation. Magnetization versus applied dc field exhibited a stepwise hysteresis loop at 2 K. The ac magnetic susceptibility data revealed the frequency dependent out-of-phase (χ(M)'') signals characteristic of single-molecule magnets.

Aquabis(1,1,1,5,5,5-hexafluoroacetylacetonato)[4′-(4-pyridyl)-2,2′:6′,2′′-terpyridine]ytterbium(III) chloride methanol monosolvate monohydrate

The title compound, [Yb(C5HF6O2)2(C20H14N4)(H2O)]Cl·CH3OH·H2O, adopts an eight-coordinated geometry around the YbIII atom consisting of a 4′-(4-pyrid­yl)-2,2′:6′,2′′-terpyridine (pytpy) ligand, two 1,1,1,5,5,5-hexa­fluoro­acetyl­acetonate (hfac) anions and an aqua ligand. In the solid state, the compound forms supra­molecular chains running along the b-axis via inter­molecular hydrogen bonds between the Yb—OH2 unit and the N-atom donor of the 4-pyridyl pendant of pytpy, with an O⋯N distance of 2.686 (4) Å. A chloride counter-anion and lattice methanol and water solvent mol­ecules occupy a hydro­philic columnar space along the coordination chains. O—H⋯Cl hydrogen bonds occur. The two water molecules and the four trifluoromethyl groups are disordered over two sets of sites, each with different occupancy ratios.

Syntheses, structures and luminescent properties of decorated lanthanide metal-organic frameworks of (E)-4,4′-(ethene-1,2-diyl)dibenzoic acids

The functionalized ligand (E)-4,4′-(1,4-bis(methylthio)but-2-ene-2,3-diyl)dibenzoic acid (H2LS) and four metal-organic frameworks, [M2(LH)3(DMSO)4]·xDMSO (6 and 7 for M = Tb3+, Eu3+ respectively; LH = (E)-4,4′-(ethene-1,2-diyl)dibenzoate) and [M2(LS)3(DMF)2(H2O)2] (8 and 9 for M = Eu3+, Tb3+) have been synthesized and characterized. All four MOFs adopt the anticipated connectivity, but the fold of interpenetration in each MOF crystal varies as a result of different solvent inclusion and ligand functionality. Compounds 6 and 7 contain a large amount of solvent molecules and tend to lose solvent in air. Compounds 8 and 9 are stable crystals without lattice solvent molecules in the crystals; the coordinating solvent molecules can be reversibly removed and replenished with the skeletons intact. All four MOFs show mainly the ligand-based luminescence, while 8 also displays metal-based luminescence.

A new cyanido-bridged [{CL}2(μ-NC)2MoIV(CN)6] pentanuclear complex (L2−=bicompartmental macrocyclic ligand): synthesis, spectral, and structural characterization

An unprecedented pentanuclear hetero-bimetallic complex has been obtained by a self-assembling process between {Cu2L}2+ binuclear cationic units and [Mo(CN)8]4− anions. The compound with the formula [{CL}2(µ-NC)2MoIV(CN)6(CH3OH)1.5(H2O)0.5] · [{CL}2(µ-NC)2MoIV(CN)6(CH3OH)2] · 5H2O · 7.5CH3OH (1) (H2L = binucleating Schiff-base obtained by condensation of 2,6-diformyl-4-methylphenol with 1,3-propylenediamine), 1, crystallizes in P 1 triclinic space group and consists of two pentanuclear species, [{CL}2(µ-NC)2MoIV(CN)6(CH3OH)1.5(H2O)0.5] (A), [{CL}2(µ-NC)2MoIV(CN)6(CH3OH)2] (B) and solvent. In each unit, two {Cu2L}2+ cations are bridged by one octacyanidomolybdate, via two cis-cyanido groups. Non-covalent channel motifs are developed through a complex network of supramolecular interactions (hydrogen bonds, π–π stacking interaction) involving A and B units and lattice solvent molecules.

Effect of Bulkiness on Reversible Substitution Reaction at MnII Center with Concomitant Movement of the Lattice DMF: Observation through Single‐Crystal to Single‐Crystal Fashion

The porous coordination polymer ({[Mn(L)H(2)O](H(2)O)(1.5)(dmf)}(n), 1) (DMF=N,N-dimethylformamide) exhibits variety of substitution reactions along with movement of lattice DMF molecule depending upon bulkiness of the external guest molecules. If pyridine or 4-picoline is used as a guest, both lattice and coordinated solvent molecules are simultaneously substituted (complexes 6 and 7, respectively). If a bulky guest like aniline is used, a partial substitution at the metal centers and full substitution at the channels takes place (complex 8). If the guest is 2-picoline (by varying the position of bulky methyl group with respect to donor N atom), one Mn(II) center is substituted by 2-picoline, whereas the remaining center is substituted by a DMF molecule that migrates from the channel to the metal center (complex 9). Here, the lattice solvent molecules are substituted by 2-picoline molecules. For the case of other bulky guests like benzonitrile or 2,6-lutidine, both the metal centers are substituted by two DMF molecules, again migrating from the channel, and the lattice solvent molecules are substituted by these guest molecules (complex 10 and 11, respectively). A preferential substitution of pyridine over benzonitrile (complex 12) at the metal centers is observed only when the molar ratio of PhCN:Py is 95:5 or less. For the case of an aliphatic dimethylaminoacetonitrile guest, the metal centers remain unsubstituted (complex 13); rather substitutions of the lattice solvents by the guest molecules take place. All these phenomena are observed through single crystal to single crystal (SC-SC) phenomena.

Supramolecular lattice-solvent control of iron(ii) spin transition parameters

We report on the synthesis of spin transition compounds 1, 2 of formula [Fe(L)2](A)2 (where L = 2′,6′-bis(pyrazol-1-yl)-3,4′-bipyridine, A = ClO4−—compound 1; A = BF4−—compound 2) and compound 3 of formula [Fe(L)(LH)](BF4)3·H2O·CH3CN (where LH = 3-(2,6-bis(pyrazol-1-yl) pyridine-4-yl)-pyridinium(+)). Compounds 1, 2 and 3 were characterized by single-crystal X-ray diffraction, ESI-ToF mass spectrometry, 1H NMR and elemental analysis. The single-crystal X-ray diffraction study of the counter anion analogues 1 and 2 reveals almost identical molecular structures without any significant presence of intermolecular interactions. However, in the case of compound 3, the crystal structure reveals supramolecular interactions involving molecular cations, BF4− anions and, most importantly, lattice solvent molecules. The presence of solvent water molecules induces the presence of two different types of hydrogen bonding: (i) water molecules interacting with the fluorine atoms of BF4− anions and (ii) water molecules interconnecting protonated and nonprotonated nitrogens of pyridine-3-yl substituents of neighboring complex cations. These overall hydrogen bonding pattern between the neighboring iron(II) complex cation moieties is responsible for the formation of a one dimensional (1D) hydrogen bonded zig-zag chain. The magnetic investigations elucidate high temperature spin transition behavior for both anion analogues 1 and 2, while compound 3 exhibits a lattice-solvent dependency of the temperature-driven spin transition accompanied with stepwise solvent liberation above room temperature. After complete solvent removal the solvent-free compound 3d, [Fe(L)(LH)](BF4)3, shows an abrupt spin transition accompanied with thermal hysteresis loop; T1/2(↑) = 240 K and T1/2(↓) = 231 K, ΔT1/2 = 9 K. The Ising-like model that includes two vibrational modes has been applied in a direct fitting of magnetic data. The model recovers the temperature evolution of the χT product functions for all compounds under study, involving also compound 3d with the thermal hysteresis.

Isovalent and mixed-valent molybdenum complexes containing Mo V(μ-E)(μ-S 2)Mo V/IV (E = O, S) core units

The reactions of Tp i PrMoO(SR)(NCMe) (Tp i Pr = hydrotris(3-isopropylpyrazolyl)borate) with propylene sulfide in toluene result in the formation of the diamagnetic, isovalent Mo(V) complex, [Tp i PrMo VO] 2(μ-S)(μ-S 2). This complex and its previously reported μ-oxo analog, [Tp i PrMo VO] 2(μ-O)(μ-S 2), react with cobaltocene to produce one-electron-reduced, mixed-valent complexes, [CoCp 2][{Tp i PrMo IV,VO} 2(μ-E)(μ-S 2)] (E = S or O, respectively). All complexes have been isolated and characterized by microanalysis, mass spectrometry, IR and 1H NMR or EPR spectroscopies, and X-ray crystallography. Neutral [Tp i PrMo VO] 2(μ-S)(μ-S 2) exhibits a pseudo- C 2 symmetric structure, with distorted octahedral anti oxo-Mo(IV) centers coordinated by Tp i Pr and linked by μ-sulfido and μ-disulfido ligands. A similar structure is adopted by the anion in mixed-valent [CoCp 2][{Tp i PrMo IV,VO} 2(μ-S)(μ-S 2)]; this compound adopts a hexagonal, supramolecular structure with columns of tight ion-pairs with ( μ - S 2 ) ⋯ CoCp 2 + interactions, interconnected through weaker ( μ - S ) ⋯ CoCp 2 + contacts to three neighboring columns. The structure contains large interstitial voids filled with lattice solvent molecules. EPR investigation of the mixed-valent complexes gave rise to unusually broad signals with no evident hyperfine splitting. The synthesis and characterization of a number of cis-dioxo-Mo(VI) precursors are also reported.

A Cyclometallated (Azobenzene)palladium(II) Complex of 1,4,7‐Trithiacyclononane: Synthesis and Reactivity with Thioether‐Dithiolate Metalloligands, Single‐Crystal X‐ray Diffraction Analyses and Electrochemical Studies

AbstractThe treatment of [{Pd(C6H4N=NC6H5)(μ‐Cl)}2] (5) with AgPF6/NH4PF6 in acetone, followed by the addition of two molar equivalents of 1,4,7‐trithiacyclononane (9S3), gives the deep red complex [Pd(C6H4N=NC6H5)(9S3)][PF6] (6A) in high yield, whereas the direct reaction of 5 with two molar equivalents of 9S3 gives [Pd(C6H4N=NC6H5)(9S3)][Pd(C6H4N=NC6H5)Cl2] (6B) in quantitative yield based on 5. The subsequent reaction of 5 and 6A with the metalloligand [(HMB)RuII{η3‐tpdt}] [3; HMB = η6‐C6Me6, tpdt = S(CH2CH2S–)2] results in displacement of the chloride and 9S3 ligands, respectively, to give the Ru‐Pd heterobimetallic complex [{(HMB)RuII(μ‐η2:η3‐tpdt)}{Pd(C6H4N=NC6H5)}][PF6] (7) in 85 % yield. Similar reactions with the Cp* analogue of 3, namely [(Cp*)RuIII{η3‐tpdt}] (4), give the trinuclear complex [{Cp*RuIII(μ‐η2:η3‐tpdt)}2Pd](PF6)2 (8), in which all the ligands on palladium have been displaced, in a yield of around 80 %. X‐ray diffraction analyses of 6A, 6B and its solvates (6B·H2O and 6B·CHCl3) have shown that short atom–atom interactions between the cation and the counterion and lattice solvent molecules have a significant effect on the bond parameters of the molecules, and 1H NMR spectroscopy indicates that these interactions persist even in solution. The single‐crystal X‐ray structure of 7 has also been determined. Cyclic voltammetry experiments have been performed on 6A, 6B and 7 in CH2Cl2 and CH3CN at GC and Pt electrodes.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Synthesis, characterization, electrochemical and spectroscopic investigation of cobalt(III) Schiff base complexes with axial amine ligands: The layered crystal structure of [Co III(salophen)(4-picoline) 2]ClO 4 · CH 2Cl 2

Cobalt(III) complexes with potentially tetradentate salophen (H 2salophen = N, N′–bis(salicylidene)-1,2-phenylenediamine) as equatorial ligand and with different axial amine ligands (NH 3, cyclohexylamine, aniline, 4-picoline and pyridine) were synthesized and characterized by IR, 1H NMR, elemental analysis. Electronic spectra and electrochemical properties of the complexes were studied in DMF solutions. The lowest energy transitions, which occur between 464.8 and 477 nm, are attributed mainly to the intraligand charge transfer, confirmed by Zindo/S electronic structure calculations. The reduction potentials of Co(III)/Co(II) are more affected than those of Co(II)/Co(I) by the axial amine ligands. The crystal structure of the [Co III(salophen)(4- picoline) 2]ClO 4 · CH 2Cl 2 was determined, indicating that the cobalt(III) center is six coordinated surrounded by the tetradentate salophen ligand and two 4-picoline ligands. The crystal packing of the complex shows a layered structure, in which the perchlorate counter ions and also the lattice solvent molecules are intercalated between the bc planes of the complex cations.

Disorder of lattice solvent molecules in the structure of hexaaqua(μ2-1,2,4,5-benzenetetracarboxylato)-bis(2,2’-dipyridylamine)dinickel(II) hexahydrate DMSO solvate

The crystal structure of the complex [Ni2(btc)(dipya)2(H2O)6]?6H2O?DMSO (btc = tetra-anion of 1,2,4,5-benzenetetracarboxylic acid, dipya = 2,2?-dipyridylamine) was refined in the triclinic system, space group P1, using low temperature (170 K) X-ray diffraction data. The compound consists of binuclear complex entities and lattice solvent molecules making pseudo-layers parallel to the 101 plane and channels parallel to the b-axis. The observed structural features were compared with the previously reported results and formula [Ni2(btc)(dipya)2(H2O)6]?4H2O based on room temperature X-ray diffraction data. A possible arrangement of the disordered lattice solvent molecules located in the structural channels is described and discussed. It is concluded that the layout of these molecules is non-centrosymmetric, although the remaining and main part of the structure is centrosymmetric. .

Magnetostructural Studies on Ferromagnetically Coupled Copper(II) Cubanes of Schiff‐Base Ligands

Three cubane copper(II) clusters, namely [Cu(4)(HL')4] (1), [Cu4L2(OH)2] (2), and [Cu4L2(OMe)2] (3), of two pentadentate Schiff-base ligands N,N'-(2-hydroxypropane-1,3-diyl)bis(acetylacetoneimine) (H3L') and N,N'-(2-hydroxypropane-1,3-diyl)bis(salicylaldimine) (H3L), are prepared, structurally characterized by X-ray crystallography, and their variable-temperature magnetic properties studied. Complex 1 has a metal-to-ligand stoichiometry of 1:1 and it crystallizes in the cubic space group P43n with a structure that consists of a tetranuclear core with metal centers linked by a mu(3)-alkoxo oxygen atom to form a cubic arrangement of the metal and oxygen atoms. Each ligand displays a tridentate binding mode which means that a total of eight pendant binding sites remain per cubane molecule. Complexes [Cu4L2(OH)2] (2) and [Cu4L2(OMe)2] (3) crystallize in the orthorhombic space group Pccn and have a cubane structure that is formed by the self-assembly of two {Cu2L}+ units. The variable-temperature magnetic susceptibility data in the range 300-18 K show ferromagnetic exchange interactions in the complexes. Along with the ferromagnetic exchange pathway, there is also a weak antiferromagnetic exchange between the copper centers. The theoretical fitting of the magnetic data gives the following parameters: J1 = 38.5 and J2 = -18 cm(-1) for 1 with a triplet (S = 1) ground state and quintet (S = 2) lowest excited state; J1 = 14.7 and J2 = -18.4 cm(-1) for 2 with a triplet ground state and singlet (S = 0) lowest excited state; and J1 = 33.3 and J2 = -15.6 cm(-1) for 3 with a triplet ground state and quintet lowest excited state, where J1 and J2 are two different exchange pathways in the cubane {Cu4O4} core. The crystal structures of 2 * 6 H2O and 3 * 2 H2O * THF show the presence of channels containing the lattice solvent molecules.

Single-molecule magnets: control by a single solvent molecule of Jahn-Teller isomerism in [Mn12O12(O2CCH2Bu(t))16(H2O)4

Faster- and slower-relaxing versions of the title Mn12 compound have been obtained in pure forms that crystallize in the same space group and differ only in the identity of one lattice solvent molecule; solvent loss causes isomerization from the faster- to the slower-relaxing form.

Valence-Delocalized Diiron(II,III) Cores Supported by Carboxylate-Only Bridging Ligands

Valence-Delocalized Diiron(II,III) Cores Supported by Carboxylate-Only Bridging Ligands

Octanuclear Lanthanide Sulfido Clusters: Synthesis, Structure, and Coordination Chemistry.

Octanuclear (THF)(8)Ln(8)S(6)(SPh)(12).xTHF clusters (Ln = lanthanide ion) can be isolated from the reactions of Ln(SPh)(3) with elemental S. Complexes have been isolated successfully for Ln = Ce (1), Pr (2), Nd (3), Sm (5), Gd (6), Tb (7), Dy (8), Ho (9), and Er (10). Only the Ce and Sm compounds are intensely colored, due to a relatively low energy f( )(1)-to-d(1) promotion for 1 and a S(2)(-) to Sm charge transfer absorption for 5. The complexes are all thermally unstable with respect to loss of THF at room temperature. The reaction of Sm(SPh)(3) with S in a THF/DME mixture gives thermally unstable (THF)(8)Ln(8)S(6)(SPh)(12).6DME (4). The analogous pyridine (py) complexes (py)(8)Ln(8)S(6)(SPh)(12).xpy (Ln = Nd (11), Sm (12), Er (13)) were also found to desolvate at room temperature. All compounds have been characterized by conventional methods and by low-temperature single-crystal X-ray diffraction. Complete structural analyses have been obtained for compounds 4, 7, 12, and 13, and the structures of the rest were confirmed by unit cell determinations. In each case, the same basic octanuclear framework, with a cube of metal atoms connected by S(2)(-) ligands capping the faces of the cube, and SPh ligands spanning the edges of the cube, is observed. Differences in the structures originate either in the relative orientation of the Ph moieties or in the number and orientations of the lattice solvent molecules. The Ce cluster is isostructural with (THF)(8)Sm(8)Se(6)(SePh)(12), compounds 2 and 3 are isostructural with the previously reported structure of 6, clusters 5 and 8-10 are isostructural with 7, and cluster 11 is isostructural with 12.

Mesitylcopper: Tetrameric and Pentameric

New phases containing tetrameric and pentameric mesitylcopper have been isolated from ether solvents and characterized with single-crystal X-ray diffraction. Mesitylcopper crystallized from toluene, which is a widely used reagent, has been found to contain one lattice solvent molecule. On the basis of these findings and cryoscopic molecular weight determinations, an equilibrium between a tetramer and pentamer in both etheral and aromatic solutions is proposed.

Structures of the multireceptor vaulted cyclidene complexes

The preparations and structures of three vaulted cyclidene complexes are compared with the two previously reported. All show similar structures with large rigid cavities partly closed off by the piperidine risers, illustrating in particular the attractive effect of van der Waals forces resulting in the incorporation of solvent molecules or [PF 6] − ions nesting on the edges of the cavities. However, the detailed geometries vary, according to the nature of the ligand substituents, the metal, the counter-ion and the lattice solvent molecules. These give rise to differing orientations of the capping aromatic rings and the piperidine risers.

Co-ordination chemistry of mixed pyridine–phenol ligands: polynuclear complexes of 6-(2-hydroxyphenyl)-2,2′-bipyridine with NiII, CdII, MnIIand MnIIMnIII

A series of complexes with the N,N,O-terdentate ligand 6-(2-hydroxyphenyl)-2,2′-bipyridine (HL1) has been prepared and structurally characterised. The complexes are [Ni2L12(dmf)2(H2O)2][BPh4]21(dmf = dimethylformamide), [Cd2L12(HL1)(dmf)2][BPh4]22, [Mn4L16][BPh4]23 and [Mn2L13(MeCN)][PF6]24. In the centrosymmetric complex 1 one ligand L1 is associated with each metal but the phenolates are bridging, giving a NiII2(µ-O)2 core; the remaining two co-ordination sites are occupied by H2O and dmf (O-co-ordinated) ligands. In complex 2 one CdII ion is octahedrally co-ordinated by two ligands L1; the two phenolates bridge to the second CdII, whose co-ordination sphere is completed by two dmf ligands and the two pyridyl donors of another equivalent of HL1, whose pendant phenol remains protonated and forms hydrogen-bonding interactions to lattice solvent molecules. Complex 3 in contrast is an unusual example of a linear chain, with a MnII(µ-O)2MnII(µ-O)2MnII(µ-O)2MnII core (where O denotes a bridging phenolate) and highly distorted six-co-ordinate MnII centres: the chain formation is apparently facilitated by the absence of any stereoelectronic preference for the MnII ions which can readily tolerate the distorted geometries. Complex 4 contains a MnII centre, co-ordinated by two ligands L1, and a MnIII centre which shares two phenolates with the MnII and also has a terdentate L1 and a MeCN ligand to complete the co-ordination sphere. The MnIII centre shows Jahn–Teller elongation along one of the axes. The contributions of factors such as the metal oxidation state, the co-ordination modes available to the ligand, and non-covalent interactions (hydrogen bonding, aromatic π-stacking) to the structures of the complexes are discussed.