Cyclohexylamine) 2 M(CN) 4 ⋅2C 6 H 6 (M = Cd or Hg)

Two new title compounds have been prepared in powder form. Their spectral data are found to be consistent with the structure foundin Hofmann-T_d-type clathrates.     

An Infrared and Raman Spectroscopic Study of pn-Td-Type dl% -Propylenediaminemetal(II) Tetracyanometallate(II) Benzene Clathrates: M(dl-pn)M'(CN)4.nC6H6 (M = Mn, M' = Zn, Cd or Hg; M = Cd, M' = Cd or Hg; 1≤n≤1.5)

IR spectra of Mn(dl-propylenediamine)M(CN)4.nC6H6 (M = Zn, n = 1.25; M = Cd, n = 1.00 or M = Hg, n = 1.18), and IR and Raman spectra of Cd(dl-propylenediamine)M(CN) 4. 1.5C6H6 (M = Cd or Hg) are reported. The spectral data suggest that the former three compounds are similar in structure to the latter two pn-Td-type clathrates.     

Synthesis,structures, and properties of the niobium and tantalum telluride cubane clusters [M4(μ4-O)(μ3-Te)4(CN)12]6– (M = Nb or Ta)

The new cubane cluster complex K₆[Ta₄(₄-O)(₃-Te)₄(CN)₁₂]·KOH·4H₂O was prepared from a mixture of TaTe₄ and KCN by the high-temperature synthesis followed by crystallization from aqueous solutions. The compound was characterized by cyclic voltammetry, X-ray diffraction analysis, and IR, Raman, and electronic spectroscopy. A comparative study of the clusters [M₄(₄-O)(₃-Te)(CN)₁₂]^6– (M = Nb or Ta) containing the ₄-O ligands was carried out. These clusters are the first molecular chalcogenide cubane complexes of Group V metals.     

An Infrared Spectroscopic Study of Pyrazine- and 4,4′-bipyridyl-Td-type Clathrates: Mn (pyrazine) M(CN)4 benzene (M = Cd or Hg) and Mn (4,4′-bipyridyl) M(CN)4. benzene (M = Zn, Cd or Hg)

The infrared spectra of the title compounds have been reported. The spectral data suggest that the host framework of these compounds are similar to those of the en-T_d-type clathrate compounds. There is good evidence for hydrogen bonding from ligand molecules to benzene molecules as a to hydrogen bond.     

Vibrational Spectroscopic Studies on the Td-Type Clathrates: M(trimethylenediamine)M'(CN)4⋅2C6H6 (M=Mn or Cd, M';=Cd or Hg)

IR spectra of Mn(C3H10N2)M(CN)42C6H6 (M=Cd or Hg),and IR and Raman spectra of Cd(C3H10N2)M(CN)4 2C6H6(M=Cd or Hg) are reported. The spectral data suggest that the former twocompounds are similar in structure to the latter two Td-type clathrates.     

Formation of M(4)Se(4) cuboids (M = As, Sb, Bi) via secondary pnictogen-chalcogen interactions in the co-crystals MX(3)·Se[double bond, length as m-dash]P(p-FC(6)H(4))(3) (M = As, X = Br; M = Sb, X = Cl; M = Bi, X = Cl, Br)

The reactions of the group 15 trihalides, MX(3) (M = As, Sb, Bi; X = Cl, Br), with the phosphine selenide SeP(p-FC(6)H(4))(3) result in the formation of co-crystals of formula MX(3)·SeP(p-FC(6)H(4))(3). No reaction was observed with MI(3) (M = As, Sb, Bi). The structures of MX(3)·SeP(p-FC(6)H(4))(3) (M = As, X = Br 2; M = Sb, X = Cl 3; M = Bi, X = Cl 5; M = Bi, X = Br 6) have been established, and are isomorphous, crystallising in the cubic I23 space group. All the structures feature a primary MX(3) unit, which has three weak secondary MSe interactions to SeP(p-FC(6)H(4))(3) molecules. However, each of these SeP(p-FC(6)H(4))(3) molecules bridges three MX(3) molecules, resulting in the generation of an M(4)Se(4) (M = As, Sb, Bi) distorted cuboid linked by the pnictogen-chalcogen interactions. Four opposing corners of the cuboid are occupied by the M atom (M = As, Sb, Bi) of an MX(3) pyramid, and the other four by the selenium atom of the phosphine selenide.     

All-metal aromatic clusters M4(2-) (M = B, Al, and Ga). Are π-electrons distortive or not?

The π-electrons in benzene, the quintessential aromatic molecule, were previously shown to be distortive, i.e., they prefer localized double bonds alternating with single bonds. It is the σ-electrons that force the double bonds to delocalize, leading to a regular, D(6h) geometry. Herein, we computationally investigate the double-bond localizing or delocalizing propensities of σ- and π-electrons in the archetypal all-metal aromatic cluster Al(4)(2-) and its second- and fourth-period analogs B(4)(2-) and Ga(4)(2-), using Kohn-Sham molecular orbital (MO) theory at BP86/TZ2P in combination with quantitative bond energy decomposition analyses (EDA). We compare the three all-metal aromatic clusters with the structurally related organic species C(4)H(4)(2+), C(4)H(4), and C(4)H(4)(2-). Our analyses reveal that the π-electrons in the group-13 M(4)(2-) molecules have a weak preference for localizing the double bonds. Instead, the σ-electrons enforce the regular D(4h) equilibrium geometry with delocalized double bonds.     

Interactions of M(z)-X complexes (M = Cu, Ag, and Au; X = He, Ne, and Ar; and z = ±1)

The coupled cluster singles and doubles method with perturbative treatment of triple excitations is applied to calculate the potentials of M(z)-X complexes (M = Cu, Ag, and Au; X = He, Ne, and Ar; and z = ±1). The bond functions and the basis set superposition errors are considered to obtain accurate interaction energies. The potential energy curves of all complexes are obtained. The vibrational energy levels and the spectroscopic parameters for these complexes are determined. The analytical potential energy functions are also fitted based on the potential energies.     

Why are the Homoleptic Diyl Complexes M(InR)4 with M = Ni and Pt Stable Compounds while only Ni(CO)4 but not Pt(CO)4 can become Isolated? A Theoretical Study of M(EMe)44 and M(CO)4 (M = Ni,Pd, Pt; E = B,Al, Ga,In, Tl)

The equilibrium geometries and first bond dissociation energies of the homoleptic complexes M(EMe)₄ and M(CO)₄ with M = Ni, Pd, Pt and E = B, Al, Ga, In, Tl have been calculated at the gradient corrected DFT level using the BP86 functionals. The electronic structure of the metal‐ligand bonds has been examined with the topologial analysis of the electron density distribution. The nature of the bonding is revealed by partitioning the metal‐ligand interaction energies into contributions by electrostatic attraction, covalent bonding and Pauli repulsion. The calculated data show that the M‐CO and M‐EMe bonding is very similar. However, the M‐EMe bonds of the lighter elements E are much stronger than the M‐CO bonds. The bond energies of the latter are as low or even lower than the M‐TlMe bonds. The main reason why Pd(CO)₄ and Pt(CO)₄ are unstable at room temperature in a condensed phase can be traced back to the already rather weak bond energy of the Ni‐CO bond. The Pd‐L bond energies of the complexes with L = CO and L = EMe are always 10 — 20 kcal/mol lower than the Ni‐L bond energies. The calculated bond energy of Ni(CO)₄ is only D_o = 27 kcal/mol. Thus, the bond energy of Pd(CO)₄ is only D_o = 12 kcal/mol. The first bond dissociation energy of Pt(CO)₄ is low because the relaxation energy of the Pt(CO)₃ fragment is rather high. The low bond energies of the M‐CO bonds are mainly caused by the relatively weak electrostatic attraction and by the comparatively large Pauli repulsion. The σ and π contributions to the covalent M‐CO interactions have about the same strength. The π bonding in the M‐EMe bonds is less than in the M‐CO bonds but it remains an important part of the bond energy. The trends of the electrostatic and covalent contributions to the bond energies and the σ and π bonding in the metal‐ligand bonds are discussed.     

Syntheses and X-ray Characterization of Novel [M4(H2O)2(XW9O34)2] n− (M=CuII, X=CuII; and M=FeIII, X=FeIII) Polyoxotungstates

Two novel examples of sandwich type heteropolyanions were synthesized and characterized by X-ray crystal structure and elemental analysis as well as infrared spectroscopy. Na₁₃[H₃Cu₄(H₂O)₂(CuW₉O₃₄)₂]39H₂O (1) and Na₉K[Fe₄(H₂O)₂(FeW₉O₃₄)₂]32H₂O (2) were prepared in aqueous solution by reaction of sodium tungstate with Fe^III and Cu^II cations, respectively. 1 crystallizes in the monoclinic space group P2₁/n (a=13.054(3) Å, b=17.729(4) Å, c=20.998(4) Å, =93.50(3)°), while 2 is triclinic, space group P¯1 (a=12.316(2) Å, b=13.716(3) Å, c=14.925(3) Å, =99.36(3)°, =104.21(3)°, =101.55(3)°). Each anion consists of two [XW₉O₃₄] ^n– moieties (X=Fe^III, n=11 (1) and Cu^II, n=12 (2)) which can be described as -B-isomers of the defect Keggin anion. These units are linked via a belt of four Fe^IIIO₆ or Cu^IIO₆ groups. Two transition metal atoms fill their octahedral coordination sphere with one additional water ligand.     

Novel crystal structures of potassium salts of chalcohydroxo cluster complexes [Re6Q8(OH)6]4− (Q = S or Se)

Potassium salts of chalcohydroxo rhenium cluster complexes [Re₆Q₈(OH)₆]^4? (Q = S or Se) with the composition K₄[Re₆S₈(OH)₆]·4H₂O (1) and K₄[Re₆Se₈(OH)₆]·5H₂O (2) are produced by evaporation of the corresponding strongly alkaline aqueous solutions. The composition of the compounds is determined by the single crystal X-ray diffraction study. The compounds crystallize in the triclinic space group P $\bar 1$ with the following unit cell parameters: a = 8.408(2) Å, b = 9.096(2) Å, c = 9.222(2) Å, α = 95.110(4)°, β = 107.085(4)°, γ = 113.026(4)°, V = 603.5(3) ų, Z = 1, d _x = 4.689 g/cm³ (for 1) and a = 8.782(3) Å, b = 9.155(4) Å, c = 9.325(4) Å, α = 105.481(7)°, β = 109.266(6)°, γ = 99.104(6)°, V = 656.6(4) ų, Z = 1, d _x = 5.305 g/cm³ (for 2).     

Correlation between solvatochromism and back-bonding in four isomeric (α-diimine)M(CO)4 complexes,M = Cr,Mo, W

Long-wavelength charge transfer absorption energies of isomeric complexes (bidiazine)M(CO)₄, (bidiazine = 3,3′-bipyridazine, 2,2′- and 4,4′-bipyrimidine, 2,2′-bipyrazine; M = Cr, Mo, W) were measured in various solvents and compared with those for corresponding 2,2′-bipyridine complexes. Linear correlations of energies of absorption maxima with solvent parameters E_MLCT revealed that the solvent dependence Δυ/gDE_MLCT within the bidiazine series increases with decreasing absolute charge transfer transition energy in a given solvent, i.e. with increasing back-donation into the ligand π orbital. Complexes of the most strongly back-bonding ligand, 4,4′-bipyrimidine, thus display by far the most pronounced solvent dependence, with Δυ/gdE_MLCT 4100 cm ⁻¹ for the molybdenum system.     

MAlH4(M=Li,Na)储氢材料*

氢能是一种新型的清洁能源,有望替代碳经济,而氢的储存是氢能应用的关键。近年来,研究集中在具有储氢容量高和可逆性好等优点的固态储氢材料上。许多新型储氢材料不断出现,其中以MAlH₄(M=Li, Na)为代表的金属复合氢化物体系被认为是最有前景的储氢材料之一。本文综述了MAlH₄(M=Li, Na)作为可逆储氢材料的研究现状,主要从吸放氢反应、储氢性能、反应机理、理论计算和存在的问题等方面进行了讨论,并指出其相关发展趋势。     

Synthesis and characterisation of [AgL(μ-PR2)M(CO)5], L= 1,10-phenanthroline or tricyclohexylphosphine; M = Cr,Mo, W

The new heterobimetallic phosphide-bridged compounds [AgL(μ-PR₂)M(CO)₅], (L = 1,10-phenanthroline or tricyclohexylphosphine: M = Cr, M, W) have been prepared from AgO₃SCF₃, M(CO)₅PR₂H and the ligand L in the presence of Et₂NH or MeO⁻ as base, and characterized by ³¹P NMR spectroscopy.     

氧心羧桥异三核过渡金属簇合物[Fe2MO(CH3COO)6Py3].Py(1,M=Mn;2,M=Co;3,M=Ni)和[Fe2MO(CCl3COO)6(THF)3](4,M=Mn;5,M=Co;6,M=Ni)电子光谱的研究

The UV/VIS spectra for pyridine solution of complexes [Fe_2MO(CH_3COO)_6Py_2]·Py and THF solution of complexes Fe_2MO(CCl_3COO)_6(THF)_3 were studied. The d-d transitions were assigned and the ligand field parameters(B,D_q,β) were calculated for the related metal ions according to ligand field theory (Tanabe-Sugano diagram) in terms of O_h symmetry and reasonably good fits were obtained for the calculated and observed frequencies. The calculated results show that (1) the larger the ionic potential for M~(2+) ion, the larger the values of B, D_q for Fe~(3+) ion (2) the ligand field parameters of metal ions vary in parallel with the electronagativity of R in RCOO~-.     

Vibrational spectroscopic study on some Hofmann-Td type clathrates: Ni(4-phenylpyridine)2M(CN)4·2G (M=Cd or Hg, G=1,4-dioxane)

New Hofmann-T(d) type clathrates in the form of Ni(4-Phpy)(2)M(CN)(4)·2G (where 4-Phpy=4-phenylpyridine, M=Cd or Hg and G=1,4-dioxane) have been prepared in powder form and their FT-IR and Raman spectra have been reported. The results suggest that these compounds are similar in structure to the Hofmann-T(d) type clathrates.     

Crystal structures and vibrational spectra ofMSnF6·6H2O(M=Fe,Co, Ni)

Summary Single crystal X-ray structural data (atT=300 K) are reported for CoSnF₆·6H₂O (rhombohedral; R{ie61-1}-C _3i ² ;a=9.735(7) Å,c=10.095(7) Å, =120°;Z=3;R=0.047) and for NiSnF₆· 6H₂O (rhombohedral; R{ie61-2}-C _3i ² ;a=9.697(1)Å,c=10.021(1)Å, =120°;Z=3;R=0.038). The two compounds are isostructural to FeSnF₆·6H₂O. IR and Raman spectroscopic data (atT=300 and 75 K) are reported for hydrated and for partially deuterated samples ofMSnF₆·6H₂O (M=Fe, Co, Ni). Two rather similar (OD) stretching frequencies and one (HDO) bending frequency of isotopically dilute HDO molecules are observed for either of the three compounds, which is consistent with one crystallographically distinct water molecule forming two different, but rather similar O ... F hydrogen bonds.

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Kristallstrukturen und Schwingungsspektren vonMSnF₆·6H₂O (M=Fe, Co, Ni)

Zusammenfassung Die Kristallstrukturen von CoSnF₆·6H₂O (rhomboedrisch; R{ie61-3}-C _3i ² ;a=9.735(7) Å,c=10.095(7) Å, =120°;Z=3;R=0.047) und von NiSnF₆·6H₂O (rhomboedrisch; R{ie61-4}-C _3i ² ;a=9.697(1)Å,c=10.021(1)Å, =120°;Z=3;R=0.038) wurden mittels Röntgen-Einkristalldaten (beiT=300 K) bestimmt. Die beiden Verbindungen sind isostrukturell zu FeSnF₆·6H₂O. IR- und Raman-Spektren vonMSnF₆·6H₂O (M=Fe, Co, Ni) wurden von Proben mit unterschiedlichem Deuterierungsgrad gemessen (beiT=300 und 75 K). Bei allen drei Verbindungen findet man für isotopenverdünnte HDO Moleküle zwei nur geringfügig unterschiedliche (OD)-Valenzfrequenzen und eine (HDO)-Deformationsfrequenz, was mit der Existenz von nur einer Art von Wassermolekülen mit zwei verschiedenen, aber doch sehr ähnlichen O ... F Wasserstoffbrückenbindungen übereinstimmt.

     

Framework polymers based on octahedral chalcocyanide cluster [Re6Q8(CN)6]4−/3− anions (Q = Se, Te) and [Nd(Bipy)n]3+ Complexes (n = 1, 2)

Interaction of salts of the cluster anions {Re [Re₆Q₈(CN)₆]^4?/3? (Q = Se, Te) with Nd salts in the presence of 2,2′-bipyridyl (Bipy) ligand brings about new coordination polymers: Pr ₄ ⁿ N[{Nd(Bipy)(H₂O)₄} {Re₆Se₈(CN)₆}] · 2H₂O (I) (space group C2/c, a = 18.2918(16) Å, b = 14.9972(13) Å, c = 37.513(3) Å, β = 102.046(4)°, V = 10064.2(15) ų, Z = 8), [{Nd(Bipy)₂(H₂O)} {Re₆Se₈(CN)₆}] (II) (space group C2/c, a = 15.8668(3) Å, b = 13.5403(3) Å, c = 20.5189(4) Å, β = 110.135(1)°, V = 4138.89(15) Å₃, Z = 4), and [{Nd(Bipy)(EtOH)(H₂O)₄}{Re₆Te₈(CN)₆}] · EtOH (III) (space group $P\bar 1$ , a = 9.4733(6) Å, b = 12.5326(8) Å, c = 17.2374(11) Å, α = 96.561(2)°, β = 90.310(2)°, γ = 94.876(2)°, V = 4138.89(15) Å₃, Z = 4). The compounds synthesized are characterized by single-crystal X-ray diffraction and IR methods. Compounds I and III have layered (2D) structures, compound II is a framework (3D) polymer.     

Structural,vibrational, and bonding analysis of M2?SiO (M=Li or Ag) using density functional theory

The spectroscopic properties of the M₂ SiO (M=Li or Ag) complexes were studied using density functional theory. It is shown that the global minimum of Li₂ SiO corresponds to a doubly bridged silonyl structure, while that of Ag₂ SiO is a phosgenelike structure. The calculated binding energies of the M₂ SiO complexes relative to M₂+SiO are −47.8 and −4.0 kcal mol⁻¹ for M=Li and Ag, respectively. In the case of Ag₂ SiO, the calculated SiO stretching frequency as well as its isotopic shifts are in good agreement with the experimental data. For Li₂ SiO, the SiO vibrational frequency is calculated to be greatly red‐shifted by 493.4 cm⁻¹ (≈40% of free ν_SiO) upon complexation. According to the natural population analysis, the charge transfer from metal to ligand is 0.79 e⁻ for each Li and is only of 0.15 e⁻ for each Ag. The bonding was also investigated using the topological analysis of the charge density. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 71: 499–503, 1999