Synthesis, crystal structure, and magnetic properties of hexanuclear [{MnL2}4{Nb(CN)8}2] and Nonanuclear [{MnL2}6{Nb(CN)8}3] heterometallic clusters (L=bpy, phen)

A hexanuclear cyano-bridged {MnII4NbIV2} cluster (1) bearing 2,2'-bipyridine (bpy) as the blocking ligand at manganese is obtained from the reaction of cis-[MnCl2(bpy)2] and K4[Nb(CN)8]. When the blocking ligand is 1,10-phenanthroline (phen), a nonanuclear cluster {MnII6NbIV3} (2) is obtained. The structure of [{Mn(bpy)2}4{Nb(CN)8}2] has been solved by single-crystal X-ray crystallography, whereas the phen derivative has been confirmed by means of the structure analysis of the corresponding WIV analogue [{Mn(phen)2}6{W(CN)8}3(H2O)2]. Magnetic measurements revealed S=9 and 27/2 spin ground states for these aggregates as a result of antiferromagnetic Nb-Mn interaction with JNb-Mn=-18.1 cm(-1) (1) and -13.6 cm(-1) (2).     

Tetranuclear [{Ni(HL3)}{W(CN)8}]2 square: a case of antiferromagnetic {NiIIWV} interactions

A tetranuclear cyano-bridged [{Ni(HL3)}{W(CN)8}]2 compound in a square geometry was formed by self-assembling of {W(CN)8}3- and {NiL3}2+ (L3=pentadentate ligand). The structure of the compound has been established by single crystal X-ray diffraction. The coordination sphere of the Ni ions is severely distorted with the macrocyclic ligand adopting a facial coordination with only four linkages to the metal center. The N atom of the pendant aminopropyl arm of L3 is no longer coordinated to the metal center but has undergone protonation during the assembling process. Magnetic measurements have revealed an unexpected antiferromagnetic behavior (J=-9 cm(-1)), which has been explained using a microscopic many-body electronic model Hamiltonian, based on DFT results. The many-body model is used to fit both the chiMT versus T and the M versus H plots obtained from experiments.     

First trinuclear paramagnetic transition metal complexes with redox active ligands derived from TTF: Co2M(PhCOO)6(TTF-CH=CH-py)2.2CH3CN, M = CoII, MnII

The first paramagnetic homo- and hetero-metallic trinuclear complexes with redox active ligands derived from TTF are synthesized, the central metal ion has an octahedral coordination sphere while the outer Co(II) ions are in a distorted bipyramidal surrounding, bearing TTF-ligands, the magnetic properties show antiferromagnetic coupling leading to a magnetic ground state.     

Metal-metal bonding in tetracyanometalates (M=PtII, PdII, NiII) of monovalent thallium. Crystallographic and spectroscopic characterization of the new compounds Tl2Ni(CN)4 and Tl2Pd(CN)4

The new crystalline compounds Tl2Ni(CN)4 and Tl2Pd(CN)4 were synthesized by several procedures. The structures of the compounds were determined by single-crystal X-ray diffraction. The compounds are isostructural with the previously reported platinum analogue, Tl2Pt(CN)4. A new synthetic route to the latter compound is also suggested. In contrast to the usual infinite columnar stacking of [M(CN)4]2- ions with short intrachain M-M separations, characteristic of salts of tetracyanometalates of NiII, PdII, and PtII, the structure of the thallium compounds is noncolumnar with the two TlI ions occupying axial vertices of a distorted pseudo-octahedron of the transition metal, [MTl2C4]. The Tl-M distances in the compounds are 3.0560(6), 3.1733(7), and 3.140(1) A for NiII, PdII, and PtII, respectively. The short Tl-Ni distance in Tl2Ni(CN)4 is the first example of metal-metal bonding between these two metals. The strength of the metal-metal bonds in this series of compounds was assessed by means of vibrational spectroscopy. Rigorous calculations, performed on the molecules in D4h point group symmetry, provide force constants for the Tl-M stretching vibration constants of 146.2, 139.6, and 156.2 N/m for the NiII, PdII, and PtII compounds, respectively, showing the strongest metal-metal bonding in the case of the Tl-Pt compound. Amsterdam density-functional calculations for isolated Tl2M(CN)4 molecules give Tl-M geometry-optimized distances of 2.67, 2.80, and 2.84 A for M = NiII, PdII, and PtII, respectively. These distances are all substantially shorter than the experimental values, most likely because of intermolecular Tl-N interactions in the solid compounds. Time-dependent density-functional theory calculations reveal a low-energy, allowed transition in all three compounds that involves excitation from an a1g orbital of mixed Tl 6pz-M ndz2 character to an a2u orbital of dominant Tl 6pz character.     

Metallophilic attractions between d8-d10 heterometallic compounds trans-[Pt(PH3)2(CN)2] and M(PH3)2+ (M=Ag or Cu): Ab initio study

The weak metal-metal interactions of Pt(II)-Ag(I)/Cu(I) have been investigated by ab initio method at MP2 level through the model complexes [trans-Pt(PH3)2(CN)2-M(PH3)2+] (M=Ag,Cu). The calculated interaction energy of 12.9 and 11.5 kcal mol(-1) for [trans-Pt(PH3)2(CN)2-Ag(PH3)2+] and [trans-Pt(PH3)2(CN)2-Cu(PH3)2+] respectively, are in the middle of the van der Waals force and the strong hydrogen bond. The estimated equilibrium separations between Pt and M, r(eq)(Pt-M) (3.32 A for M=Ag and 3.23 A for M=Cu), lie within the region expected for weak metal-metal interaction. The electronic dispersive contributions dominate the weak interaction.     

金属富氮化合物N3MN3(M=Be, Mg, Ca)的量子化学研究

使用密度泛函理论，在B3LYP／6—311＋G^＊水平上，对金属富氮化合物N3MN3（M=Be，Mg，Ca）的两种几何结构进行了理论计算，并对得到的几何结构做了振动频率分析．结果表明，所有几何结构的振动频率都是正的，没有虚频存在，说明这类金属富氮化合物是热力学稳定的，当嵌入金属离子后，M—N之间开始表现出显著的离子性特征，由线形N3某团组成的N3MN3比由三角形N3某团组成的N3MN3更稳定．     

Metal-metal interactions in dinuclear d(8) metal cyanide complexes supported by phosphine ligands. Spectroscopic properties and ab initio calculations of [M(2)(mu-diphosphine)(2)(CN)(4)] and trans-[M(phosphine)(2)(CN)(2)] (M = Pt,Ni)

Structural, spectroscopic properties on the dinuclear [M(2)(dcpm)(2)(CN)(4)] (M = Pt, 1a; Ni, 2a, dcpm = bis(dicyclohexylphosphino)methane) and [M(2)(dmpm)(2)(CN)(4)] (M = Pt, 1b; Ni, 2b, dmpm = bis(dimethylphosphino)methane) and the mononuclear trans-[M(PCy(3))(2)(CN)(2)] (M = Pt, 3; Ni, 4, PCy(3) = tricyclohexylphosphine) and theoretical investigations on the corresponding model compounds are described. X-ray structural analyses reveal Pt.Pt and Ni.Ni distances of 3.0565(4)/3.189(1) A and 2.957(1)/3.209(8) A for 1a/1b and 2a/2b, respectively. The UV-vis absorption bands at 337 nm (epsilon 2.41 x 10(4) dm(3) mol(-)(1) cm(-)(1)) for 1a and 328 nm (epsilon 2.43 x 10(4) dm(3) mol(-)(1) cm(-)(1)) for 1b in CH(2)Cl(2) are assigned to (1)(5d(sigma) --> 6p(sigma)) electronic transitions originating from Pt(II)-Pt(II) interactions. Resonance Raman spectroscopy of 1a, in which all the Raman intensity appears in the Pt-Pt stretch fundamental (93 cm(-)(1)) and overtone bands, verifies this metal-metal interaction. Complexes 1a and 1b exhibit photoluminescence in the solid state and solution. For the dinuclear nickel(II) complexes 2a and 2b, neither spectroscopic data nor theoretical calculation suggests the presence of Ni(II)-Ni(II) interactions. The intense absorption bands at lambda > 320 nm in the UV-vis spectra of 2a and 2b are tentatively assigned to d --> d transitions.     

Novel octatungstate-supported tricarbonyl metal derivatives: {[H2W8O30][M(CO)3]2}8- (M = Mn(I) and Re(I))

Three novel octatungstate-supported tricarbonyl metal derivatives have been synthesized and characterized, which represent the first examples of isopolyoxotungstates-supported carbonyl metal compounds.     

Syntheses and crystal structures of heterometallic complexes [{Cu(en)2}2{Cu(en)2(NH3)}{M4Te4(CN)12}]·5H2O (M = Mo,W)

Evaporation of aqueous ammonia solutions of K₇[Mo₄Te₄(CN)₁₂]·12H₂O or K₆[W₄Te₄(CN)₁₂]·5H₂O, copper(ii) chloride, and ethylenediamine afforded the isostructural heterometallic complexes [{Cu(en)₂}₂{Cu(en)₂(NH₃)}{M₄Te₄(CN)₁₂}]·5H₂O (M = Mo or W), which were characterized by IR and ESR spectroscopy and X-ray diffraction analysis.     

Changes in electronic properties of polymeric one-dimensional {[M(CN)2]-}n (M = Au, Ag) chains due to neighboring closed-shell Zn(II) or open-shell Cu(II) ions

A series of d(10) dicyanometallate polymeric compounds were studied by electronic spectroscopy and density functional theory (DFT) calculations. In these materials, the negatively charged one-dimensional (1D) polymeric chains are linked together by [M(en)(2)](2+) (M = Cu(II) and Zn(II); en = ethylenediamine). More than innocent building blocks, the [M(en)(2)](2+) units offer a possible synthetic way to modify electronic properties of the materials. Through its low energy d-d excited state, the d(9) copper(II) ions offer deactivation pathways for the normally emissive dicyanometallate polymer. Deactivation was shown to be specific to the excited state energy.     

Thermal- and pressure-induced cooperative spin transition in the 2D and 3D coordination polymers {Fe(5-Br-pmd)z[M(CN)x]y} (M=AgI, AuI, NiII, PdII, PtII)

A new family of cyanide-based spin-crossover polymers with the general formula {Fe(5-Br-pmd)z[M(CN)x]y} [M=AgI (1), AuI (2), NiII (3), PdII (4), PtII (5); 5-Br-pmd=5-bromopyrimidine; z=1 or 2, x=2 or 4, and y=2 or 1] have been synthesized and characterized using single-crystal X-ray diffraction (XRD), X-ray powder diffraction (XRPD), magnetic susceptibility measurements, and differential scanning calorimetry (DSC). At 293 K, compound 1 presents the monoclinic space group C2/c, whereas at 120 K, it changes to the monoclinic space group P21/c. At 293 K, the crystal structure of 1 displays an uninodal three-dimensional network whose nodes, constituted of FeII, lie at the inversion center of an elongated octahedron. The equatorial bond lengths are defined by the N atoms of four [AgI(CN)2]- groups belonging to two crystallographically nonequivalent AgI atoms, Ag(1) and Ag(2). They are shorter than those of the axial positions occupied by the N atoms of the 5-Br-pmd ligands. The Fe-N average bond length of 2.1657(7) A is consistent with a high-spin (HS) state for the FeII ions. At 120 K, the crystal structure changes refer mainly to the FeII environment. There are two crystallographically independent FeII ions at this temperature, Fe(1) and Fe(2), which adopt the HS and low-spin (LS) states, respectively. The average Fe-N bond length for Fe(1) [2.174(5) A] and Fe(2) [1.955(5) A] agrees well with the reported magnetic data at this temperature. The spin transition of the FeII ions labeled as Fe(1) is found to be centered at Tc downward arrow=149 K and Tc upward arrow=167 K and accompanied by a drastic change of color from orange (HS) to red (LS). Magnetic susceptibility measurements under applied hydrostatic pressure performed on 1 have shown a linear displacement of the transition to higher temperatures while the hysteresis width remains unaltered in the interval of pressures of 105 Pa to 0.34 GPa. A further increase of the pressure induces the spin transition in the Fe(2) ions, which is completely accomplished at 1.12 GPa (T1/2=162 K). Compounds 1 and 2 are isostructural, but 2 does not exhibit spin-transition properties; the FeII centers remain in the HS state in the temperature range investigated, 5-300 K. Compounds 3-5 are not similar or isostructural with 1. A two-dimensional structure for 3-5 has been proposed on the basis of analytical data and the XRPD patterns. Compounds 3-5 undergo first-order spin transition where the critical temperatures for the cooling (Tc downward arrow) and warming (Tc upward arrow) modes are 170 and 180 K (3), 204 and 214 K (4), and 197 and 223 K (5), respectively. It is worth mentioning the color change from yellow to orange observed in 3-5 upon spin transition. The thermodynamic parameters associated with the spin transition estimated from DSC measurements are DeltaH=6 kJ mol(-1) (1), 11 kJ mol(-1) (3), 16 kJ mol(-1) (4), and 16 kJ mol(-1) (5) and DeltaS=38 J K(-1) mol(-1) (1), 62 J K(-1) mol(-1) (3), 76 J K-1 mol(-1) (4), and 81 J K(-1) mol(-1) (5).     

The synthesis of heteronuclear cluster compounds containing M(PR3) (M = Cu,Ag, or Au; R = alkyl or aryl) units via Group IB metal exchange reactions

Treatment of dichloromethane solutions of the heteronuclear cluster compounds [M₂Ru₄(μ₃-H)₂{μ-Ph₂P(CH₂)₂PPh₂}(CO)₁₂] (M = Cu or Ag) with dichloromethane solutions containing the appropriate quantities of the complex [Ag(NCMe)₄]PF₆ or [AuCl(SC₄H₈)] results in the replacement of either one or both of the Group IB metals M by silver or gold atoms. The products from the Group IB metal exchange reactions are obtained in ca. 65–75% yield.     

Lanthanide-3d cyanometalate chains Ln(III)-M(III) (Ln=Pr, Nd, Sm, Eu, Gd, Tb; M=Fe) with the tridentate ligand 2,4,6-tri(2-pyridyl)-1,3,5-triazine (tptz): evidence of ferromagnetic interactions for the Sm(III)-M(III) compounds (M=Fe, Cr)

A series of cyanide-bridged chain mixed Fe(III)/Ln(III) (Ln=Pr, Nd, Sm, Eu, Gd, Tb) complexes with the tridentate ligand 2,4,6-tri(2-pyridyl)-1,3,5-triazine (tptz) used as a capping group has been prepared. Reactions of tptz and LnCl3 with K3Fe(CN)6 yield a family of air-stable 1-D compounds {[Pr(tptz)(H2O)4Fe(CN)6].8H2O}infinity, {[Nd(tptz)(H2O)4Fe(CN)6].8H2O}infinity, {[Sm(tptz)(H2O)4Fe(CN)6].8H2O}, {[Eu(tptz)(H2O)4Fe(CN)6].6H2O}infinity, {[Gd(tptz)(H2O)4Fe(CN)6].6H2O}infinity, and {[Tb(tptz)(H2O)4Fe(CN)6].8H2O}infinity. Temperature dependent magnetic susceptibility studies of reveal that in , the Sm(III) and Fe(III) ions are ferromagnetically coupled with 3-D ordering occurring below 3.5 K. The appearance of the frequency dependent out-of-phase signal is explained in terms of an ordering with a spin glass-like behavior. To compare the magnetic behavior of with related compounds, {[Sm(tptz)(H2O)4Co(CN)6].8H2O}infinity and {[La(tptz)(DMF)(H2O)3Fe(CN)6].5H2O}infinity, {[Sm(tmphen)(DMF)3(H2O)Fe(CN)6].2H2O}infinity, {[Sm(tmphen)2(H2O)2Fe(CN)6].MeOH.13H2O}infinity and {[Sm(tmphen)2(H2O)2Cr(CN)6].MeOH.9H2O}infinity with 3,4,7,8-tetramethyl-1,10-phenanthroline (tmphen) were also prepared.     

Imidazole Coordinated Sandwich‐type Antimony Poly‐oxotungstates Na9[{Na(H2O)2}3{M(C3H4N2)}3(SbW9O33)2]·xH2O (M=NiII,CoII, ZnII,MnII)

The imidazole covalently coordinated sandwich‐type heteropolytungstates Na₉[{Na(H₂O)₂}₃{M(C₃H₄N₂)}₃‐ (SbW₉O₃₃)₂]·xH₂O (M=Ni^II, x=32; M=Co^II, x=32; M=Zn^II, x=33; M=Mn^II, x=34) were obtained by the reaction of Na₂WO₄·2H₂O, SbCl₃·6H₂O, NiCl₂·6H₂O [MnSO₄·H₂O, Co(NO₃)₂·6H₂O, ZnSO₄·7H₂O] and imidazole at pH≈7.5. The structure of Na₉[{Na(H₂O)₂}₃{Ni(C₃H₄N₂)}₃(SbW₉O₃₃)₂]·32H₂O was determined by single crystal X‐ray diffraction. Polyanion [{Na(H₂O)₂}₃{Ni(C₃H₄N₂)}₃(SbW₉O₃₃)₂}₃]^9? has approximate C_3v symmetry, imidazole coordinated six‐nuclear cluster [{Na(H₂O)₂}₃{Ni(C₃H₄N₂)}₃]⁹⁺ is encapsulated between two (α‐SbW₉O₃₃)^9?, the three rings of imidazole in the polyanion are perpendicular to the horizontal plane formed by six metals (Na‐Ni‐Na‐Ni‐Na‐Ni) in the central belt, and π‐stacking interactions exist between imidazoles of neighboring polyanions with dihedral angel of 60°. The compounds were also characterized by IR, UV‐Vis spectra, TG and DSC, and the thermal decomposition mechanism of the four compounds was suggested by TG curves.     

A family of cyanide-bridged molecular squares: structural and magnetic properties of [{MIICl2}2{CoII(triphos)(CN)2}2].xCH2Cl2, M = Mn, Fe, Co, Ni, Zn

The syntheses, structures, and magnetic properties of a series of tetranuclear cyanide-bridged compounds are reported. This family of molecular squares, [{M(II)Cl2}2{Co(II)(triphos)(CN)2}2] (M = Mn ([CoMn]), Fe ([CoFe]), Co ([CoCo]), Ni ([CoNi]), and Zn ([CoZn]), triphos = 1,1,1-tris(diphenylphosphinomethyl)ethane), has been synthesized by the reaction of Co(II)(triphos)(CN)2 and MCl2 (M = Mn, Co, Ni, Zn) or Fe4Cl8(THF)6 in a CH2Cl2/EtOH mixture. These complexes are isostructural and consist of two pentacoordinate Co(II) and two tetrahedral M(II) centers. The resulting molecular squares are characterized by antiferromagnetic coupling between metal centers that generally follows the spin-coupling model S total = SM(II)1 - SCo1 + SM(II)2 - SCo2. Magnetic parameters for all the complexes were measured using SQUID magnetometry. Additionally, [CoZn] and [CoMn] were studied by both conventional and high-frequency and high-field electron paramagnetic resonance.     

Analogues of the Lavallo-Grubbs compound Fe3(C8H8)3: equilateral, isosceles, and scalene metal triangles in trinuclear cyclooctatetraene complexes M3(C8H8)3 of the first row transition metals (M = Ti, V, Cr, Mn, Fe, Co, and Ni)

The trinuclear derivative Fe(3)(C(8)H(8))(3) was synthesized in 2009 by Lavallo and Grubbs via the reaction of Fe(C(8)H(8))(2) with a bulky heterocyclic carbene. This fascinating structure is the first example of a derivative of the well-known Fe(3)(CO)(12) in which all 12 carbonyl groups have been replaced by hydrocarbon ligands. The density functional theory predicts a structure having a central Fe(3) equilateral triangle with ～2.9 ? Fe-Fe single bonded edges bridged by η(5),η(3)-C(8)H(8) ligands. This structure is close to the experimental structure, determined by X-ray crystallography. The related hypoelectronic M(3)(C(8)H(8))(3) derivatives (M = Cr, V, Ti) are predicted to have central scalene M(3) triangles with edge lengths and Wiberg bond indices (WBIs) corresponding to one formal single M-M bond, one formal double M═M bond, and one formal triple M≡M bond. For Mn(3)(C(8)H(8))(3), both a doublet structure with one Mn═Mn double bond and two Mn-Mn single bonds in the Mn(3) triangle, and a quartet structure with two Mn═Mn double bonds and one Mn-Mn single bond are predicted. The hyperelectronic derivatives M(3)(C(8)H(8))(3) have weaker direct M-M interactions in their M(3) triangles, as indicated by both the M-M distances and the WBIs. Thus, Ni(3)(C(8)H(8))(3) has bis(trihapto) η(3),η(3)-C(8)H(8) ligands bridging the edges of a central approximately equilateral Ni(3) triangle with long Ni···Ni distances of ～3.7 ?. The WBIs indicate very little direct Ni-Ni bonding in this Ni(3) triangle and thus a local nickel environment in the singlet Ni(3)(C(8)H(8))(3) similar to that observed for diallylnickel (η(3)-C(3)H(5))(2)Ni.     

SEM and EDXS analysis of the reaction products of compounds AxM6X8 (A = Tl,K; M = V,Ti; X = S,Se) with I2/CH3CN and H2O

The ternary transition metal chalcogenides A_xM₆X₈ (A=Tl, K; M=V, Ti; X=S, Se) build up a three dimensional framework with large hexagonal channels running parallel to the crystallographic c-axis. The electropositive elements thallium or potassium are confined within these channels. It is possible to remove the Tl or K atoms via a chemical redox reaction with an I₂/CH₃CN solution or with H₂O. Using SEM it is demonstrated that the host matrix “V₆S₈” is only slightly affected by the redox agent. In contrast the host matrix “Ti₆Se₈” of Tl_xTi₆Se₈ reacts with the I₂/CH₃CN solution. The results of the EDXS analyses clearly show that the removal of the electropositive elements proceeds only along the large channels and not through the host matrix.     

Analysis of the spin exchange interactions and the ordered magnetic structures of lithium transition metal phosphates LiMPO4 (M = Mn, Fe, Co, Ni) with the olivine structure

The olivine-type compounds LiMPO4 (M = Mn, Fe, Co, Ni) consist of MO4 layers made up of corner-sharing MO6 octahedra of high-spin M2+ ions. To gain insight into the magnetic properties of these phosphates, their spin exchange interactions were estimated by spin dimer analysis using tight binding calculations and by electronic band structure analysis using first principles density functional theory calculations. Three spin exchange interactions were found to be important for LiMPO4, namely, the intralayer superexchange J1, the intralayer super-superexchange Jb along the b-direction, and the interlayer super-superexchange J2 along the b-direction. The magnetic ground state of LiMPO4 was determined in terms of these spin exchange interactions by calculating the total spin exchange interaction energy under the classical spin approximation. In the spin lattice of LiMPO4, the two-dimensional antiferromagnetic planes defined by the spin exchange J1 are antiferromagnetically coupled by the spin exchange J2, in agreement with available experimental data.