Selten‐Erd‐Metall‐Koordinationspolymere: Synthesen und Kristallstrukturen von sechs neuen Pimelinaten, [M(Pim)(PimH)(H2O)](H2O) (M = Ce,Pr) und [M2(Pim)3(H2O)4] (M = Tb,Ho, Er,Tm)

Rare‐Earth‐Metal Coordination Polymers: Syntheses and Crystal Structures of Six New Pimelinates, [M(Pim)(PimH)(H₂O)](H₂O) (M = Ce, Pr) and [M₂(Pim)₃(H₂O)₄] (M = Tb, Ho, Er, Tm) The new rare‐earth metal carboxylates [M(Pim)(PimH)(H₂O)](H₂O) (M = Ce ( 1 ), Pr ( 2 )) and [M₂(Pim)₃(H₂O)₄] (M = Tb ( 3 ), Ho ( 4 ), Er ( 5 ), Tm ( 6 )) were prepared from the reaction of pimelinic acid with CeO₂, Pr₆O₁₁, Tb₄O₇, HoCl₃, ErCl₃ and Tm(NO₃)₃, respectively. Their crystal structures were determined by single‐crystal X‐ray diffraction. [M(Pim)(PimH)(H₂O)](H₂O) crystallize in the monoclinic space group P2₁/n (no. 14) with a = 909.6(1), b = 870.6(1), c = 2240.5(2) pm, β = 92.30(1)°, Z = 4 (crystal data for M = Ce). The isostructural pimelinate‐hydrates [M₂(Pim)₃(H₂O)₄] crystallize with orthorhombic symmetry, Pbcn (no. 60), with a = 1392.5(1), b = 902.3(1), c = 2408.8(2) pm, Z = 4 (crystal data for M = Tb). The rare‐earth cations have coordination numbers of 10 ( 1 , 2 ) and 9 ( 3 , 4 , 5 and 6 ), respectively. In the crystal structure of [M(Pim)(PimH)(H₂O)](H₂O) bidentate and tridentate‐bridging carboxylate groups form rather dense structures in which chains are bridged to layers and further to networks. Pimelinic acid molecules fill the channels. In [M₂(Pim)₃(H₂O)₄] tridentate‐bridging carboxylate groups coordinating to two rare‐earth ions lead to dimers that are linked with other dimers to strands. The channels thus formed between the strands are rather small in diameter. They do not contain any non‐coordinated water molecules.     

Tin(II) aminoalkoxides and heterobimetallic derivatives: the structures of Sn6(O)4(dmae)4, Sn6(O)4(OEt)4 and [Sn(dmae)2Cd(acac)2]2

Tin(II) methoxide reacts with N,N′‐dimethylaminoethanol (dmaeH) to yield Sn(dmae)₂ ( 1 ) along with small amounts of the hydrolysis product Sn₆(O)₄(dmae)₄ ( 2 ). The geometrically more regular iso‐structural cage Sn₆(O)₄(OEt)₄ ( 3 ) was obtained as the only tractable product isolated from reaction of 2 and Sb(OEt)₃, while 1 reacted with CdX₂ (X = acac, I) to afford Sn(dmae)₂Cd(acac)₂ ( 4 ) and Sn(dmae)₂CdI₂ ( 5 ). The X‐ray structures of 2, 3 and 4 are reported. Decomposition of 4 under aerosol‐assisted chemical vapour deposition conditions leads to amorphous tin oxide films with no detectable cadmium (i.e. ca < 2% cadmium), rather than a stoichiometric Sn:Cd oxide. Copyright © 2006 John Wiley & Sons, Ltd.     

Selten‐Erd‐Metall‐Koordinationspolymere: Synthese und Kristallstrukturen von fünf neuen Adipinaten, [M2(Adi)3(H2O)4](AdiH2)(H2O)4 (M = La,Nd), [Er(Adi)(H2O)5]Cl(H2O) und [M(Adi)(H2O)5](NO3)(H2O) (M = Gd,Er)

Rare‐Earth‐Metal Coordination Polymers: Synthesis and Crystal Structures of Five New Adipinates, [M₂(Adi)₃(H₂O)₄](AdiH₂)(H₂O)₄ (M = La, Nd), [Er(Adi)(H₂O)₅]Cl(H₂O) and [M(Adi)(H₂O)₅](NO₃)(H₂O) (M = Gd, Er) The new rare‐earth compounds [M₂(Adi)₃(H₂O)₄](AdiH₂)(H₂O)₄ (M = La ( 1 ), Nd ( 2 )), [Er(Adi)(H₂O)₅]Cl(H₂O) ( 3 ) and [M(Adi)(H₂O)₅](NO₃)(H₂O) (M = Gd ( 4 ), Er ( 5 )) were obtained from the reaction of adipinic acid with La(OH)₃·xH₂O, Nd₂O₃, ErCl₃·6H₂O, Gd(NO)₃·xH₂O and Er₂O₃, respectively. Their crystal structures were determined by single‐crystal X‐ray diffraction. The coordination polymers [M₂(Adi)₃(H₂O)₄](AdiH₂)(H₂O)₄ crystallize in the triclinic space group (no. 2) with a = 875.4(1), b = 1000.4(2), c = 1179.0(2) pm, α = 74.70(1), β = 69.85(1), γ = 86.18(2)° and Z = 1 (crystal data for M = La, ( 1 )). The quasi‐isostructural compounds [Er(Adi)(H₂O)₅]Cl(H₂O) ( 3 ) and [M(Adi)(H₂O)₅](NO₃)(H₂O) (M = Gd ( 4 ), Er ( 5 )) crystallize with monoclinic symmetry, space group C2/c (no. 15) with lattice parameters of a = 1231.5(1), b = 1532.6(1), c = 895.4(1) pm, β = 123.44(1)° and Z = 4 (crystal data for ( 3 )). The rare‐earth cations have the coordination numbers 10 ( 1 , 2 ) and 9 ( 3 , 4 and 5 ), respectively. The compounds [M₂(Adi)₃(H₂O)₄](AdiH₂)(H₂O)₄ are constructed of infinite chains of edge‐sharig [MO₈(H₂O)₂] polyhedra that are cross‐linked by adipinic acid molecules to form framework structures. In [Er(Adi)(H₂O)₅]Cl(H₂O) ( 3 ) and [M(Adi)(H₂O)₅](NO₃)(H₂O) (M = Gd ( 4 ), Er ( 5 )) the central cations are bridged by adipinic acid molecules in a bidentate‐chelating manner to positively charged zigzag chains. Between these the counter ions and crystal water molecules are incorporated.     

Drei Heterocubanartige (MII4O4)‐Typ Verbindungen (M = FeII,CoII, NiII)

By reaction of M^IICl₂·x H₂O (M = Fe (x = 4), Co, Ni (x = 6)) and LiOH·H₂O in diethylene glycol (DEG) rod‐like crystals of the composition M^II₄Cl₄(OCH₂CH₂OCH₂CH₂OH)₄ are formed. According to X‐ray diffraction data obtained by both, single crystals and powders, the Co^II and Ni^II compounds crystallize monoclinic with C2/c (Co^II₄Cl₄(OCH₂CH₂OCH₂CH₂OH)₄ ( 1 ): a = 2084.1(4), b = 919.0(2), c = 1754.0(4) pm, β = 124.3(1)°, Z = 4; Ni^II₄Cl₄(OCH₂CH₂OCH₂CH₂OH)₄ ( 2 ): a = 2055.2(4), b = 932.1(2), c = 1727.4(4) pm, β = 125.2(1)°, Z = 4), whereas Fe^II₄Cl₄(OCH₂CH₂OCH₂CH₂OH)₄ ( 3 ) crystallizes tetragonal with (a = 1251.4(2), c = 915.3(2) pm, Z = 2). All compounds exhibit analogous molecular structures which are built of a heterocubane‐type core consisting of four metal ions and four deprotonated oxygen atoms of four coordinated diethylene glycol molecules. Neutrality of charge is realized by additional coordination of four chloride anions. In addition to the structural characterization, the thermal and magnetical properties of the title compounds are investigated in detail.     

Influence of the Monovalent M Cation on the M2+xTh2-xNdx(C2O4)5 nH2O Solid Solution Domain

An optimized fuel cycle option for Generation III/IV systems could be co-management of the minor actinides in an integrated closed fuel cycle. This approach implies separating these actinides from the fission products, and then converting them to solid forms to re-fabricate fresh fuel. Oxalate compounds are well known for this purpose. Co-management process is based on the oxalic co-precipitation of An(IV) and An(III) in a mixed oxalate as, for example, the hexagonal phase, M⁺_2+xAn^IV_2-xAn^III_x(C₂O₄)₅ nH₂O with M⁺ representing a singly-charged cation. A study of the Th-Nd-M⁺ hexagonal oxalate systems has been carried out in order to understand the charge compensation mechanisms implicated in the formation of mixed oxalates systems.     

Metalloxane des Siliciums und Germaniums mit dem 2‐(Dimethylaminomethyl)ferrocenyl‐Liganden (FcN): Darstellung und Molekülstrukturen von (FcN)4M4O4(OH)4(M = Si,Ge), (FcN)6Ge6O8(OH)2 und von (FcN)2Si(OH)2

Metalloxanes of Silicon and Germanium with the 2‐(Dimethylaminomethyl)‐ferrocenyl Ligand (FcN): Synthesis and Molecular Structures of (FcN)₄M₄O₄(OH)₄(M = Si, Ge), (FcN)₆Ge₆O₈(OH)₂ and of (FcN)₂Si(OH)₂ (FcN)₄M₄O₄(OH)₄ · H₂O [FcN = 2‐(dimethylaminomethyl)ferrocenyl, M = Si ( 2 ) und Ge ( 3 )] are prepared by hydrolysis of FcNSiCl₃ or FcNGeCl₃ ( 1 ) in Et₂O in the presence of (NH₄)₂CO₃. The tricyclic compound (FcN)₆Ge₆O₈(OH)₂ ( 4 ) is formed after treatment of the hydrolysis solution of FcNGeCl₃ with CaH₂. (FcN)₂Si(OH)₂ ( 5 ) was sythesized by hydrolysis of (FcN)₂SiCl₂ under similar conditions. Compounds 1 — 5 are obtained as yellow orange crystals, the molecular structures of 1 — 5 were determinated by X‐ray diffraction. 2 and 3 are 8‐membered Si‐O/Ge‐O cycles with one OH and one FcN‐ligand on each Si or Ge atom, respectively. Compound 4 represents a stair‐like tricyclic Ge‐O structure whereas 5 is a discrete Silanediol. 2 — 5 show O‐H···N hydrogene bridges of the OH groups to the nitrogen atoms of the FcN substituents.     

Tetranuclear Complexes with {M4O4} (M = CoII,NiII) Cubane‐Like Core: Synthesis,Crystal Structure,and Magnetic Properties

Two tetranuclear clusters of formula [M₄L₄(HOMe)₄] {H₂L = (E)‐1‐[(2‐(hydroxymethyl)phenylimino)methyl]naphthalen‐2‐ol} [M = Co ( 1 ), Ni ( 2 )] were hydrothermally synthesized by reaction of M(OAc)₂ · 4H₂O with H₂L and NaOH in MeOH. X‐ray crystal structure analysis revealed that complexes 1 and 2 are isostructural. In the core of the structures, four M^II ions and four oxygen atoms occupied alternate vertices of [M₄O₄] cubane. The magnetic property measurements of 1 and 2 revealed that overall ferromagnetic M^II ··· M^II exchange interactions exist in both complexes.     

Das erste Oxatetraphospholan, (PBut)4O

Contributions to the Chemistry of Phosphorus. 244. The First Oxatetraphospholane, (PBu^t)₄O Under suitable conditions, the reaction ot tri‐tertbutylcyclotriphosphane, (PBu^t)₃, with di‐tert‐butylperoxide gives rise to a mixture of 2,3,4,5‐tetra‐tert‐butyl‐1,2,3,4,5‐oxatetraphospholane, (PBu^t)₄O ( 1 ), and 1,2‐di‐tert‐butyl‐1,2‐di‐tert‐butoxidiphosphane, [Bu^t(Bu^tO)P]₂ ( 2 ). Both compounds have been isolated in the pure state. The oxatetraphospholane 1 is a constitutional isomer of 1,2,3,4‐Tetra‐tert‐butyl‐1‐oxocyclotetraphosphane, which has been reported recently [1]. The corresponding reaction of tetra‐tert‐butylcyclotetraphosphane furnishes only small amounts of 1 because of the kinetic stability of (PBu^t)₄. The diphosphane 2 is presumably a secondary product of primarily formed oxocyclotetraphosphanes (PBu^t)₄O_1–4. The NMR parameters of 1 and 2 are reported and discussed.     

Von kleinen Bausteinen zu neuen Poly‐alkoxo‐oxometallat‐Derivaten: Synthese und Strukturaufklärung von K4[VIV12O12(OCH3)16(C4O4)6], Cs10[VIV24O24(OCH3)32(C4O4)12][VIV8O8(OCH3)16(C2O4)] und M2[VIV8O8(OCH3)16(VIVOF4)] (M = [N(nBu)4] bzw. [NEt4])

>From Small Fragments to New Poly‐alkoxo‐oxo‐metalate Derivatives: Syntheses and Crystal Structures of K₄[V^IV₁₂O₁₂(OCH₃)₁₆(C₄O₄)₆], Cs₁₀[V^IV₂₄O₂₄(OCH₃)₃₂(C₄O₄)₁₂][V^IV₈O₈(OCH₃)₁₆(C₂O₄)], and M₂[V^IV₈O₈(OCH₃)₁₆(V^IVOF₄)] (M = [N(nBu)₄] or [NEt₄]) By solvothermal reaction of ortho‐vanadicacid ester [VO(OMe)₃] with squaric acid and potassium or caesium hydroxide the compounds K₄[V^IV₁₂O₁₂(OCH₃)₁₆(C₄O₄)₆] ( 2 ) and Cs₁₀[V^IV₂₄O₂₄(OCH₃)₃₂(C₄O₄)₁₂][V^IV₈O₈(OCH₃)₁₆(C₂O₄)] ( 3 ) could be syntesized. With tetra‐n‐butyl‐ or tetra‐n‐ethylammonium fluoride [N(nBu)₄]₂[V^IV₈O₈(OCH₃)₁₆(V^IVOF₄)] ( 4 ) and [N(Et)₄]₂[V^IV₈O₈(OCH₃)₁₆(V^IVOF₄)] ( 5 ) could be isolated. In 2 and 3 the corners of a tetrahedron or cube resp. are occupied by {(VO)₃(OMe)₄} groups and connected along the edges of the tetrahedron resp. cube by six or twelve resp. squarato‐groups. The octanuclear anions in the compounds 3 , 4 , and 5 are assumedly built up by fragments of the ortho‐vanadicacid ester [VO(OMe)₃]. Around the anions C₂O₄^2— or VOF₄^— these oligormeric chains are closed to a ring . Crystal data: 2 , tetragonal, P4₃, a = 18.166(3)Å, c = 29.165(7)Å, V = 9625(3)ų, Z = 4, d_c = 1.469 gcm^—3; 3 , orthorhombic, Pbca, a = 29.493(5)Å, b = 25.564(4)Å, c = 31.076Å, V = 23430(6)ų, Z = 4, d_c = 1.892 gcm^—3; 4 , monoclinic, P2₁/n, a = 9.528(1)Å, b = 23.021(2)Å, c = 19.303(2)Å, β = 92.570(2)°, V = 4229.8(5)ų, Z = 2, d_c = 1.391 gcm^—3; 5 , monoclinic, P2₁/n, a = 16.451(2)Å, b = 8.806(1)Å, c = 23.812(1)Å, β = 102.423(2)°, V = 3368.7(6)ų, Z = 2, d_c = 1.534 gcm^—3.     

Synthesis,Crystal Structures and Properties of Tetrametallic Complexes: [M2(phen)4(FCA)2](ClO4)2·(H2O)2 (M=Zn or Co,phen=1,10‐phenanthroline,FCA=anion of 3‐ferrocenyl‐2‐crotonic acid)

Two new complexes [Zn₂(phen)₄(FCA)₂](ClO₄)₂·(H₂O)₂ ( 1 ) and [Co₂(phen)₄ (FCA)₂](ClO₄)₂·(H₂O)₂ (2) (FCA=anion of 3‐ferrocenyl‐2‐crotonic acid, phen=1,10‐phenanthroline) have been synthesized, and characterized by elemental analysis, IR, UV‐Vis spectra, thermal analyses, and single‐crystal X‐ray diffraction. Two M(II) (M=Zn or Co) ions are bridged by two FCA anions with syn‐anti bridging ligands, leading to dimeric cores, [M₂(phen)₄(FCA)₂]²⁺, and each M(II) ion is six‐coordinated in a distorted octahedral geometry by two chelate phen ligands and two μ₂‐carboxylate oxygen atoms from two FCA groups. The M(II)…M(II) intradimer distances are 0.4391 and 0.4462 nm in 1 and 2 , respectively. Electrochemical properties of the complexes have been discussed.     

Three New Thioantimonates(V): Solvothermal Syntheses and Crystal Structures of [M(chxn)3]3(SbS4)2·4H2O (M = Ni,Co) and [Co(dien)2][Co(tren)SbS4]2·4H2O

The three new thioantimonates(V) [Ni(chxn)₃]₃(SbS₄)₂·4H₂O ( I ), [Co(chxn)₃]₃(SbS₄)₂·4H₂O ( II ) (chxn is trans‐1,2‐diaminocyclohexane) and [Co(dien)₂][Co(tren)SbS₄]₂·4H₂O ( III ) (dien is diethylenetriamine and tren is tris(2‐aminoethyl)amine) were synthesized under solvothermal conditions. Compounds I and II are isostructural crystallizing in space group C2/c. The structures are composed of isolated [M(chxn)₃]²⁺ complexes (M = Ni, Co), [SbS₄]^3? anions and crystal water molecules. Short S···N/S···O/O···O separations indicate hydrogen bonding interactions between the different constituents. Compound III crystallizes in space group and is composed of [Co(dien)₂]²⁺ and [Co(tren)SbS₄]^? anions and crystal water molecules. In the cationic complex the Co²⁺ ion is in an octahedral environment of two dien ligands whereas in [Co(tren)SbS₄]^? the Co²⁺ ion is in a trigonal bipyramidal coordination of four N atoms of tren and one S atom of the [SbS₄]^3? anion, i.e., two different coordination polyhedra around Co²⁺ coexist in this compound. Like in the former compounds an extended hydrogen bonding network connects the complexes and the water molecules into a three‐dimensional network.     

Syntheses and Crystal Structures of Two New Open‐Framework Tin(II) Phosphates: Sn5O2(PO4)2 and Sn4O(PO4)2

Two new three‐dimensional neutral open‐framework tin(II) phosphates, Sn₅O₂(PO₄)₂ and Sn₄O(PO₄)₂, were synthesized under hydrothermal conditions with different ratio of tin(II) oxalate, phosphoric acid and 4,4′‐diaminodiphenylmethane. Their crystal structures have been solved by single‐crystal X‐ray diffraction methods. Sn₅O₂(PO₄)₂ crystallizes in the space group and contains six‐membered ring and twelve‐membered ring channels running parallel to the b axis. Sn₄O(PO₄)₂ crystallizes in the space group P2₁/n and contains intersecting eight‐membered ring channels. These two compounds have rare trigonal‐planar Sn₃O.     

Synthesis,Crystal Structures and Electrochemical Properties of Complexes [M(ImH)4(tfbdc)(H2O)] (M=Co,Ni)

The title complexes [M(ImH)₄(tfbdc)(H₂O)] ( 1 : M=Co; 2 : M=Ni) (ImH=imidazole, tfbdc=2,3,5,6‐tetrafluoroterephthalate) were synthesized by the reaction of M(OAc)₂·4H₂O, H₂tfbdc and ImH in water solution. The complexes were characterized by elemental analysis, IR spectra, thermogravimetric analysis, cyclic voltammetry and X‐ray single crystal structure analysis. Structural analysis reveals that 1 and 2 possess isostructure: monoclinic, P2₁/c, Z=4. M(II) ion in complexes 1 and 2 has a distorted octahedral geometry coordinated by one oxygen atom from water, one oxygen atom from tfbdc^2? and four nitrogen atoms from ImHs. They are discrete zero‐dimensional molecular complexes. And the adjacent monomeric components are connected by hydrogen bonds to form a supramolecule. Electrochemical properties of the complexes 1 and 2 show that electron transfer of M(II) between M(III) in electrolysis is a quasi‐reversible process.     

Supramolecular Complexes Based on [M(CN)8]4– (M = Mo,W) and Aliphatic Amine CuII Tectons

Three heterometallic supramolecular complexes [Cu₂(pn)₄(Mo(CN)₈)·4H₂O] (pn = diaminopropane) ( 1 ), [Cu₂(pn)₄(W(CN)₈)·4H₂O] ( 2 ) and [Cu₂(1,2‐pn)₄(H₂O) (W(CN)₈)·3H₂O] ( 3 ) have been synthesized and structurally characterized by single‐crystal X‐ray diffraction studies. Complexes 1 – 3 exhibit three different networks. In 1 , the copper(II) ion is pentacoordinate with a distorted square‐pyramidal arrangement and the network is formed by the incorporation of coordinative linkage between the μ₂ bridge of [Mo(CN)₈]^4– and copper(II) ions and hydrogen‐bonding interactions. In 2 , the copper(II) ion exhibits a distorted square‐pyramidal arrangement and the network is formed by the hydrogen bonded trinuclear complexesof [Cu₂(pn)₂(W(CN)₈)]. In 3 , the copper(II) ions show twodifferent distorted octahedral arrangements. The network structure of 3 is formed by the hydrogen‐bonded complex chains of [Cu₂(1,2‐pn)₂(W(CN)₈)].     

Photomagnetic Switching of Heterometallic Complexes [M(dmf)4(H2O)3(μ‐CN)Fe(CN)5]⋅H2O (M=Nd,La, Gd,Y) Analyzed by Single‐Crystal X‐ray Diffraction and Ab Initio Theory

Single‐crystal X‐ray diffraction measurements have been carried out on [Nd(dmf)₄(H₂O)₃(μ‐CN)Fe(CN)₅]?H₂O ( 1 ; dmf=dimethylformamide), [Nd(dmf)₄(H₂O)₃(μ‐CN)Co(CN)₅]?H₂O ( 2 ), [La(dmf)₄(H₂O)₃(μ‐CN)Fe(CN)₅]?H₂O ( 3 ), [Gd(dmf)₄(H₂O)₃(μ‐CN)Fe(CN)₅]?H₂O ( 4 ), and [Y(dmf)₄(H₂O)₃(μ‐CN)Fe(CN)₅]?H₂O ( 5 ), at 15(2) K with and without UV illumination of the crystals. Significant changes in unit‐cell parameters were observed for all the iron‐containing complexes, whereas 2 showed no response to UV illumination. Photoexcited crystal structures have been determined for 1 , 3 , and 4 based on refinements of two‐conformer models, and excited‐state occupancies of 78.6(1), 84(6), and 86.6(7) % were reached, respectively. Significant bond‐length changes were observed for the Fe–ligand bonds (up to 0.19 Å), the cyano bonds (up to 0.09 Å), and the lanthanide–ligand bonds (up to 0.10 Å). Ab initio theoretical calculations were carried out for the experimental ground‐state geometry of 1 to understand the electronic structure changes upon UV illumination. The calculations suggest that UV illumination gives a charge transfer from the cyano groups on the iron atom to the lanthanide ion moiety, {Nd(dmf)₄(H₂O)₃}, with a distance of approximately 6 Å from the iron atom. The charge transfer is accompanied by a reorganization of the spin state on the {Fe(CN)₆} complex, and a change in geometry that produces a metastable charge‐transfer state with an increased number of unpaired electrons, thus accounting for the observed photomagnetic effect.     

Synthesis,Magnetic Properties,and STM Spectroscopy of Cobalt(II) Cubanes [CoII4(Cl)4(HL)4]

Reaction of cobalt(II) chloride hexahydrate with N‐substituted diethanolamines H₂L^2–4 ( 3 ) in the presence of LiH in anhydrous THF leads under anaerobic conditions to the formation of three isostructural tetranuclear cobalt(II) complexes [Co^II₄(Cl)₄(HL^2–4)₄] ( 4 ) with a [Co₄(μ₃‐O)₄]⁴⁺ cubane core. According to X‐ray structural analyses, the complexes 4 a , c crystallize in the tetragonal space group I4₁/a, whereas for complex 4 b the tetragonal space group P$\bar 4$ was found. In the solid state the orientation of the cubane cores and the formation of a 3D framework were controlled by the ligand substituents of the cobalt(II) cubanes 4 . This also allowed detailed magnetic investigations on single crystals. The analysis of the SQUID magnetic susceptibility data for 4 a gave intramolecular ferromagnetic couplings of the cobalt(II) ions (J₁≈20.4 K, J₂≈7.6 K), resulting in an S=6 ground‐state multiplet. The anisotropy was found to be of the easy‐axis type (D=?1.55 K) with a resulting anisotropy barrier of Δ≈55.8 K. Two‐dimensional electron‐gas (2DEG) Hall magnetization measurements revealed that complex 4 a is a single‐molecule magnet and shows hysteretic magnetization characteristics with typical temperature and sweep‐rate dependencies below a blocking temperature of about 4.4 K. The hysteresis loops collapse at zero field owing to fast quantum tunneling of the magnetization (QTM). The structural and electronic properties of cobalt(II) cubane 4 a , deposited on a highly oriented pyrolytic graphite (HOPG) surface, were investigated by means of STM and current imaging tunneling spectroscopy (CITS) at RT and standard atmospheric pressure. In CITS measurements the rather large contrast found at the expected locations of the metal centers of the molecules indicated the presence of a strongly localized LUMO.     

ASb2(SO4)2(PO4) (A = H3O+, K,Rb): Layered Structure Containing Ordered Sulfate and Phosphate Anions

Three compounds ASb₂(SO₄)₂(PO₄) (A = H₃O⁺, K, Rb) were obtained from the reactions of Sb₂O₃, A₂CO₃ (A = Li, Rb) or K₂SO₄ and NH₄H₂PO₄ in H₂SO₄ (98 %) at 220–250 °C. Their structures were determined by single‐crystal X‐ray diffraction. All compounds crystallize in the triclinic space group P$\bar{1}$ (no.2) and are isostructural. The crystal structures consist of two‐dimensional ²_∞[Sb₂(SO₄)₂(PO₄)]^– anionic layers and alkali cations, which are located between anionic layers. The anionic layers are composed of [SbO₄] ψ‐trigonal bipyramids, [SbO₅] ψ octahedra, [SO₄] tetrahedra, and [PO₄] tetrahedra. All compounds are characterized by solid state UV/Vis/NIR diffuse reflectance spectra, FT‐IR spectroscopy, and Raman spectroscopy.     

RbCrIII(C2O4)2·2H2O,Cs2Mg(C2O4)2·4H2O and Rb2CuII(C2O4)2·2H2O: three new complex oxalate hydrates

Rubidium chromium(III) dioxalate dihydrate [di­aqua­bis(μ‐oxalato)­chromium(III)­rubidium(I)], [RbCr(C₂O₄)₂(H₂O)₂], (I), and dicaesium magnesium dioxalate tetrahydrate [tetra­aqua­bis(μ‐oxalato)­magnesium(II)­dicaesium(I)], [Cs₂Mg(C₂­O₄)₂(H₂O)₄], (II), have layered structures which are new among double‐metal oxalates. In (I), the Rb and Cr atoms lie on sites with imposed 2/m symmetry and the unique water molecule lies on a mirror plane; in (II), the Mg atom lies on a twofold axis. The two non‐equivalent Cr and Mg atoms both show octahedral coordination, with a mean Cr—O distance of 1.966 Å and a mean Mg—O distance of 2.066 Å. Dirubid­ium copper(II) dioxalate dihydrate [di­aqua­bis(μ‐oxalato)­copper(II)­dirubidium(I)], [Rb₂Cu(C₂O₄)₂(H₂O)₂], (III), is also layered and is isotypic with the previously described K₂‐ and (NH₄)₂Cu^II(C₂O₄)₂·2H₂O compounds. The two non‐equivalent Cu atoms lie on inversion centres and are both (4+2)‐coordinated. Hydro­gen bonds are medium‐strong to weak in the three compounds. The oxalate groups are slightly non‐planar only in the Cs–Mg compound, (II), and are more distinctly non‐planar in the K–Cu compound, (III).     

Synthesis,Crystal Structure and Magnetic Behaviour of the new Tetrameric Gadolinium Carboxylate [Gd4(OH)4(CF3COO)8(H2O)4] · 2.5 H2O

The novel tetrameric gadolinium(III) compound [Gd₄(OH)₄(CF₃COO)₈(H₂O)₄] · 2.5 H₂O was synthesized and structurally characterized by X‐ray crystallography. The Gd³⁺ ions are bridged by hydroxide ions and carboxylate groups to tetramers with Gd³⁺‐Gd³⁺ distances between 384.2(2) and 388.1(2) pm. The compound crystallizes in the monoclinic space group C2/c (Z = 4). The magnetic behaviour of [Gd₄(OH)₄(CF₃COO)₈(H₂O)₄] · 2.5 H₂O was investigated in the temperature range of 2 to 300 K. The magnetic data of this compound indicate antiferromagnetic interactions (J_ex = ?0.0197 cm^?1).     

Molecular and Crystal Structures of Mononuclear trans‐[Fe(CN)2(tOcNC)4] and trans‐[Mn(CN)(CO)(tOcNC)4] as well as of Cyanide Bridged Coordination Polymers Derived from trans‐[M(CN)2(tOcNC)4] (M = Fe,Ru)

The octahedral complexes trans‐[Fe(CN)₂(^tOcNC)₄] and trans‐[Mn(CN)(CO)(^tOcNC)₄] are produced by the reaction of 2‐isocyano‐2,4,4‐trimethyl‐pentane (tert. octyl‐isocyanide) with the corresponding transition metal carbonyls Fe₂(CO)₉ and Mn₂(CO)₁₀. In contrast to isostructural compounds with less bulky tert.‐butylisocyanide ligands the cyanide groups in trans‐[Fe(CN)₂(^tOcNC)₄] and trans‐[Mn(CN)(CO)(^tOcNC)₄] do not act as hydrogen bond acceptors towards solvent molecules in the crystal structures. In addition, the corresponding cis‐isomers are configurationally unstable. The reaction of trans‐[Fe(CN)₂(^tOcNC)₄] and trans‐[Ru(CN)₂(^tOcNC)₄] with MnCl₂, NiCl₂ and Co(NO₃)₂ ends up in the formation of cyanide bridged coordination polymers. X‐ray structure determinations of the cobalt compounds reveal different molecular structures. Whereas the former produces highly distorted infinite polymeric chains with the nitrate anions still coordinated to the cobalt centers, the latter forms polymers with the cobalt atoms being coordinated by four ethanol molecules to which the anions are bound via hydrogen bond interactions. The coordination geometries around ruthenium and cobalt in this coordination polymer are therefore nearly perfectly octahedral and tetrahedral, respectively. Measurements of the magnetic susceptibility of the coordination polymers at different temperatures are indicative of weak antiferromagnetic coupling of the paramagnetic centers along the polymeric chains.