Nitrile Cluster Compounds [(M6X12)X2(RCN)4] (M=Nb, Ta; X=Cl, Br; R=Et, n-Pr, n-Bu)

Three new series of mixed-ligand clusters of the [(M₆X₁₂)X₂(RCN)₄] (M=Nb, Ta; X=Cl, Br; R=Et, n-Pr, n-Bu) composition have been prepared. It is supposed that four nitrile molecules and two halogen atoms are coordinated to the terminal octahedral coordination sites of the [M₆X₁₂]²⁺ unit.     

Resonance Raman Spectra of [M(6)X(8)Y(6)](2)(-) Cluster Complexes (M = Mo, W; X, Y = Cl, Br, I)

Resonance Raman spectra of the cubic metal-halide complexes having the general formula [M(6)X(8)Y(6)](2)(-) (M = Mo or W; X, Y = Cl, Br, or I) are reported. The three totally symmetric fundamental vibrations of these complexes are identified. The extensive mixing of the symmetry coordinates that compose the symmetric normal modes expected in these systems is not observed. Instead the "group-frequency" approximation is valid. Furthermore, the force constants of both the apical and face-bridging metal-halide bonds are insensitive to the identity of either the metal or the halide. Raman spectra of related complexes with methoxy and benzenethiol groups as ligands are reported along with the structural data for [Mo(6)Cl(8)(SPh)(6)][NBu(4)](2). Crystal data for [Mo(6)Cl(8)(SPh)(6)][NBu(4)](2) at -156 degrees C: monoclinic space group P2(1)/c; a = 12.588(3), b = 17.471(5), c = 20.646(2) ?; beta = 118.53(1) degrees, V = 3223.4 ?(3); d(calcd) = 1.664 g cm(-)(3); Z = 2.     

Structure and bonding in coinage metal halide clusters M(n)X(n), M = Cu, Ag, Au; X = Br, I; n = 1-6

Ab initio calculations in the framework of density functional theory (DFT) were performed to study the lowest-energy isomers of noble metal halide clusters M(n)Br(n) and M(n)I(n), for M = Cu, Ag, or Au and n = 1-6. For all species, the most stable structures were found to be cyclic arrangements. Calculated bond lengths and infrared frequencies were compared with the available experimental data. The nature of the ionocovalent bonding was characterized. The stability and fragmentation were also investigated. The present work confirms previous observations on the particular stability of the trimer.     

Schwingungsspektren der Clusterverbindungen (M6X)X · 8 H2O,M = Nb,Ta; Xi = CI,Br; Xa = CI,Br, I

Vibrational Spectra of the Cluster Compounds (M₆X₁₂ⁱ) · 8H₂O, M = Nb, Ta; Xⁱ = Cl, Br; X^a = Cl, Br, I IR and, for the first time, Raman spectra at 80 K of the cluster compounds (M₆X)X · 8H₂O; M = Nb, Ta; Xⁱ = Cl, Br; X^a = Cl, Br, I, have been recorded, characterized by typical frequencies of the (M₆X) unit, which are only slightly influenced by the terminal X^a ligands. The most intense line with the depolarisation ≈? 0.2 in all Raman spectra is caused by inphase movement of all atoms and assigned to the symmetric metal-metal vibration v₁, observed for the clusters (Nb₆Cl) at 233–234, for (Nb₆Br) at 186–187, for (Ta₆Cl) at 199–203, and for (Ta₆Br) at 176–179 cm^?1. The IR spectra exhibit in the same series intense bands at 233, 204, 207, and 179 cm^?1, assigned to the antisymmetric metal-metal vibration. The metal-metal frequencies are significantly higher than discussed before. The tantalum clusters show on excitation with the krypton line 647.1 nm in the region of a d–d transition at 645 nm a resonance Raman effect with series of overtones and combination bands. In case of (Ta₆Br) another polarisized band is observed at 229 cm^?1 and assigned to the Ta? Brⁱ vibration v₂. From the progressions of v₁ and v₂ anharmonicity constants of about ?3 cm^?1 are calculated indicating a strong distortion of the potential curves.     

Preparation of Pseudohalidoheptasulfur(+1) Hexafluorometallates S7X+MF−6 (X = CN,OCN, SeCN; M = As,Sb)

The preparation and spectroscopic characterization of S₇X⁺MF^?₆ (X = CN, OCN, SCN, SeCN; M = As, Sb) is reported. The new compounds are formed in analogy to the preparation of halidocycloheptrasulfur(+1) cations from S²⁺₈(MF^?₆)₂ and alkali pseudohalides in So₂ as solvent. Their thermal stabilities decrease with the increasing Pearson hardness of the pseudohalide ligands.     

A coordinatively flexible hexadentate ligand gives structurally isomeric complexes M2(L)X3 (M = Cu,Zn; X = Br,Cl)

Polypyridyl multidentate ligands based on ethylenediamine backbones are important metal‐binding agents with applications in biomimetics and homogeneous catalysis. The seemingly hexadentate tpena ligand [systematic name: N,N,N′‐tris(pyridin‐2‐ylmethyl)ethylenediamine‐N′‐acetate] reacts with zinc chloride and zinc bromide to form trichlorido[μ‐N,N,N′‐tris(pyridin‐2‐ylmethyl)ethylenediamine‐N′‐acetato]dizinc(II), [Zn₂(C₂₂H₂₄N₅O₂)Cl₃], and tribromido[μ‐N,N,N′‐tris(pyridin‐2‐ylmethyl)ethylenediamine‐N′‐acetato]dizinc(II), [Zn₂Br₃(C₂₂H₂₄N₅O₂)]. One Zn^II ion shows the anticipated N₅O coordination in an irregular six‐coordinate site and is linked by an anti carboxylate bridge to a tetrahedral ZnX₃ (X = Cl or Br) unit. In contrast, the Cu^II ions in aquatribromido[μ‐N,N,N′‐tris(pyridin‐2‐ylmethyl)ethylenediamine‐N′‐acetato]dicopper(II)–tribromido[μ‐N,N,N′‐tris(pyridin‐2‐ylmethyl)ethylenediamine‐N′‐acetato]dicopper(II)–water (1/1/6.5) [Cu₂Br₃(C₂₂H₂₄N₅O₂)][Cu₂Br₃(C₂₂H₂₄N₅O₂)(H₂O)]·6.5H₂O, occupy two tpena‐chelated sites, one a trigonal bipyramidal N₃Cl₂ site and the other a square‐planar N₂OCl site. In all three cases, electrospray ionization mass spectra were dominated by a misleading ion assignable to [M(tpena)]⁺ (M = Zn²⁺ and Cu²⁺).     

Ligand dependence of metal-metal bonding in the d(3)d(3) dimers M(2)X(9)(n-) (M(III) = Cr, Mo, W; M(IV) = Mn, Tc, Re; X = F, Cl, Br, I)

The ligand dependence of metal-metal bonding in the d(3)d(3) face-shared M(2)X(9)(n-) (M(III) = Cr, Mo, W; M(IV) = Mn, Tc, Re; X = F, Cl, Br, I) dimers has been investigated using density functional theory. In general, significant differences in metal-metal bonding are observed between the fluoride and chloride complexes involving the same metal ion, whereas less dramatic changes occur between the bromide and iodide complexes and minimal differences between the chloride and bromide complexes. For M = Mo, Tc, and Re, change in the halide from F to I results in weaker metal-metal bonding corresponding to a shift from either the triple metal-metal bonded to single bonded case or from the latter to a nonbonded structure. A fragment analysis performed on M(2)X(9)(3-) (M = Mo, W) allowed determination of the metal-metal and metal-bridge contributions to the total bonding energy in the dimer. As the halide changes from F to I, there is a systematic reduction in the total interaction energy of the fragments which can be traced to a progressive destabilization of the metal-bridge interaction because of weaker M-X(bridge) bonding as fluoride is replaced by its heavier congeners. In contrast, the metal-metal interaction remains essentially constant with change in the halide.     

Structural Variety of Defect Perovskite Variants M3E2X9 (M = Rb,Tl, E = Bi,Sb, X = Br,I)

The compounds Rb₃Sb₂Br₉, Rb₃Sb₂I₉, Rb₃Bi₂Br₉, Rb₃Bi₂I₉, and Tl₃Bi₂Br₉ were synthesized and their crystal structures determined from single crystal X‐ray diffraction data. The compounds Rb₃Sb₂Br₉, Rb₃Sb₂I₉, and Rb₃Bi₂I₉ crystallize in the Tl₃Bi₂I₉ type of structure (space group P2₁/n, no. 14). Rb₃Bi₂Br₉ and Tl₃Bi₂Br₉ crystallize in a new but closely related type of structure (space group P2₁/a, no. 14). Both structure types feature characteristic double layers comprising corner‐sharing EX₆ octahedra. The space groups are set in a way that the stacking direction of the layers is the [001] direction. The group‐subgroup relations to cubic perovskite ABO₃ are discussed. Differences between M₃E₂X₉ types are attributed to distortions of the underlying MX₃ close packing. Depending on the atomic size ratio, the distortions are quantified by an order parameter.     

Molecular Recognition of Amino Acids by Copper(II) Complexes of 6(A),6(X)-Diamino-6(A),6(X)-dideoxy-beta-cyclodextrin (X = B, C, D)

The three regioisomers of beta-cyclodextrin 6-difunctionalized with NH(2) groups (6(A),6(X)-diamino-6(A),6(X)-dideoxy-beta-cyclodextrin, A,X-CDNH(2), X = B, C, or D) were synthesized. Their binary and ternary copper(II) complexes with amino acids were characterized by ESR and electronic spectroscopy. Furthermore, the binary copper(II) complexes were used as eluent in ligand exchange chromatography (LEC), to resolve racemates of unmodified amino acids. HPLC separation of enantiomers of aromatic amino acids was obtained only when the complex [Cu(A,B-CDNH(2))](2+) was used as eluent. The two complexes with the other two regioisomers did not show chiral recognition ability. Circular dichroism (c.d.) spectroscopy studies of the ternary complexes with D- and L-amino acids carried out in the presence and in the absence of 1-adamantanol, suggested a recognition mechanism that involves the cyclodextrin cavity, only in the case of ternary A,B-CDNH(2) complexes.     

Synthesis and Structural Characterization of New Phases in the Cubic M3Te2O6X2 (M = Sr,Ba; X = Cl,Br) Structure Family

Four alkaline earth oxotellurate(IV) halides with common formula M₃Te₂O₆X₂ (M = Sr, Ba; X = Cl, Br) have been prepared as polycrystalline powders and/or in the form of single crystals. All compounds crystallize in the cubic space group Fd$\bar{3}$ m with cell parameters a = 15.9351(4) Å for Sr₃Te₂O₆Cl₂ (single‐crystal X‐ray data), 16.052(5) Å for Sr₃Te₂O₆Br₂ (powder X‐ray data), 16.688(2) Å for Ba₃Te₂O₆Cl₂ (single‐crystal X‐ray data) and 16.8072(3) Å for Ba₃Te₂O₆Br_1.64Cl_0.36 (single‐crystal X‐ray data). The results of the crystal structure analyses reveal a rigid ${3}\atop{{\infty}}$ [M₃Te₂O₆]²⁺ framework which can be described as being composed of regular octahedra of two types of chemically non‐bonded M₆ octahedra that are capped by trigonal pyramidal [TeO₃] anions located above every second face of one of the M₆ octahedra. The halide X^– anions are situated in the voids of the ${3}\atop{{\infty}}$ [M₃Te₂O₆]²⁺ framework. Dependent on the nature of the halogen, the anions show various kinds of occupational disorder which eventually led to a revision of the previous structure model of Ba₃Te₂O₆Cl₂. A comparative discussion with other structures of general formula M₃Ch₂O₆X₂ (M = divalent metal; Ch = Te, Se; X = Cl, Br) is presented.     

Darstellung und spektroskopische Charakterisierung der Fluorphosphonium-Salze X2FPSCH3+MF6− (X = Br,Cl; M = As,Sb) und XF2PSCH3+SbF6− (X = Br,Cl, F)

Preparation and Spectroscopic Characterization of the Fluorophosphonium Salts X₂FPSCH₃⁺MF₆^? (X = Br, Cl; M = As, Sb) and XF₂PSCH₃⁺SbF₆^? (X = Br, Cl, F) The preparation of the fluorophosphonium salts X₂FPSCH₃⁺MF₆^? (X = Br, Cl; M = As, Sb) and XF₂PSCH₃⁺SbF₆^? (X = Br, Cl, F) by methylation of the corresponding thiophosphorylhalides in the system CH₃F/SO₂/MF₅ (M = As, Sb) is reported. The new salts are characterized by their vibrational and NMR spectra.     

The compounds KAs4O6 X (X=Cl,Br, I) and NH4As4O6 X (X=Br,I): Hydrothermal syntheses and structure determinations

The crystal structures of five isotypic hexagonal compounds with general formulaMAs₄O₆ X [M=K, NH₄;X=Cl, Br, I; space group: P622;Z=1] were determined from 370 single crystal X-ray data and refined toR values <0.05. The structure type is characterized by neutral charged [As₂O₃] sheets arranged parallel (00.1). The As atoms of neighbouring two sheets point to each other and the sheets are combined by interlayeredM andX atoms, respectively. TheM atoms are coordinated to twelve oxygen atoms, theX atoms are coordinated to twelve arsenic atoms. In both cases the coordination polyhedron is a hexagonal prism. The compounds were synthesized by thermal treatments of cubic As₂O₃ and potassium or ammonium haloids in a saturated aqueous solution of potassium acetate resp. ammonia [500 K, saturation vapour pressure].

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Die Verbindungen KAs₄O₆ X (X=Cl, Br, I) und NH₄As₄O₆ X (X=Br, I): Hydrothermalsynthese und Strukturbestimmung

Zusammenfassung Die Kristallstrukturen der fünf isotypen hexagonalen Verbindungen mit der allgemeinen FormelMAs₄O₆ X [M=K, NH₄;X=Cl, Br, I; Raumgruppe: P622;Z=1] wurden anhand von 370 Einkristall-Röntgendaten bestimmt und aufR-Werte <0.05 verfeinert. Der Strukturtyp ist ausgezeichnet durch neutrale [As₂O₃]-Schichten, die parallel (00.1) angeordnet sind. Die As-Atome zweier benachbarter Schichten weisen jeweils aufeinander zu, und die Schichten selbst werden durch zwischengelagerteM- bzw.X-Atome verbunden. DieM-Atome werden jeweils von zwölf O-Atomen, dieX-Atome von zwölf As-Atomen umgeben. Das Koordinationspolyeder ist in beiden Fällen ein hexagonales Primsa. Die einzelnen Verbindungen wurden unter Hydrothermalbedingungen aus kubischem As₂O₃ und dem jeweiligen Kalium- oder Ammoniumhalogenid in einer gesättigten wäßrigen Lösung von Kaliumacetat bzw. Ammoniak synthetisiert (500 K, Sättigungsdampfdruck).

     

Synthesis and structures of five-coordinate bis-o-iminobenzosemiquinone complexes M(ISQ-R)2X (X = Cl, Br, I, or SCN; M = CoIII, FeIII, or MnIII)

New five-coordinate complexes Co(ISQ-Prⁱ)₂Cl, Co(ISQ-Me)₂Cl, Co(ISQ-Me)₂I, Co(ISQ-Me)₂(SCN), Mn(ISQ-Prⁱ)₂Cl, and Fe(ISQ-Me)₂Br (ISQ-Prⁱ and ISQ-Me are the 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-and 4,6-di-tert-butyl-N-(2,6-dimethylphenyl)-o-iminobenzosemiquinone radical anions, respectively) were synthesized. The complexes were characterized by UV-Vis and IR spectroscopy and magnetochemistry. The molecular structures of the Fe(ISQ-Me)₂Br and Mn(ISQ-Prⁱ)₂Cl complexes were established by X-ray diffraction. The singlet ground state (S = 0) of the cobalt complexes is caused by antiferromagnetic coupling between the unpaired electrons of the radical ligands (S = 1/2) through the fully occupied atomic orbitals of low-spin cobalt(III) (d⁶, S = 0). The effective magnetic moments of the complexes at 10 K are 0.18 μ_B for Co(ISQ-Prⁱ)₂Cl and 0.16 μ_B for Co(ISQ-Me)₂I. The ground state of the manganese complex is triplet (S = 1). Two unpaired electrons of the o-iminobenzosemiquinone ligands are strongly antiferromagnetically coupled with two of four unpaired electrons of high-spin manganese(III) (d⁴, S = 2). Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 43–51, January, 2006.     

Synthesis and characterization of HC[C(Me)N(C(6)H(3)-2,6-i-Pr(2))](2)MX(2) (M = Al, X = Cl, I; M = Ga, In, X = Me, Cl, I): sterically encumbered beta-diketiminate group 13 metal derivatives

A series of group 13 metal complexes featuring the beta-diketiminate ligand [[(C(6)H(3)-2,6-i-Pr(2))NC(Me)](2)CH](-) (i.e., [Dipp(2)nacnac](-), Dipp = C(6)H(3)-2,6-i-Pr(2)) have been prepared and spectroscopically and structurally characterized. The chloride derivatives Dipp(2)nacnacMCl(2) (M = Al (3), Ga (5), In (8)) were isolated in good yield by the reaction of 1 equiv of Dipp(2)nacnacLi.Et(2)O (2) and the respective metal halides. The iodide derivatives Dipp(2)nacnacMI(2) (M = Al (4), Ga (6), In (9)), which are useful for reduction to afford M(I) species, were made by a variety of routes. Thus, 4 was obtained by treatment of the previously reported Dipp(2)nacnacAlMe(2) with I(2), whereas the gallium analogue 6 was obtained as a product of the reaction of "GaI" with Dipp(2)nacnacLi.Et(2)O, and 9 was obtained by direct reaction of InI(3) and the lithium salt. The methyl derivatives Dipp(2)nacnacMMe(2) (M = Ga (7), In (10)), which are analogous to the previously reported Dipp(2)nacnacAlMe(2), were synthesized by the reaction of GaMe(3) with Dipp(2)nacnacH (1) or by reaction of the indium chloride derivative 8 with 2 equiv of MeMgBr in diethyl ether. The compounds 3-10 exist as colorless, air- and moisture-sensitive crystalline solids. Their X-ray crystal structures feature nearly planar C(3)N(2) arrays in the Dipp(2)nacnac ligand backbone with short C-C and C-N distances that are consistent with a delocalized structure. However, there are large dihedral angles between the C(3)N(2) plane and the N(2)M metal coordination plane which have been attributed mainly to steric effects. The relatively short M-N distances are consistent with the coordination numbers of the metals and the normal/dative character of the nitrogen ligands. The compounds were also characterized by (1)H and (13)C NMR spectroscopy. (1)H NMR data for 7 revealed equivalent methyl groups whereas the spectrum of 10 displayed two In-Me signals which indicated that ring wagging was slow on the (1)H NMR time scale.     

Pnicogen-hydride interaction between FH2X (X = P and As) and HM (M = ZnH, BeH, MgH, Li, and Na)

A pnicogen-hydride interaction has been predicted and characterized in FH(2)P-HM and FH(2)As-HM (M = ZnH, BeH, MgH, Li, and Na) complexes at the MP2/aug-cc-pVTZ level. For the complexes analyzed here, P(As) and HM are treated as a Lewis acid and a Lewis base, respectively. This interaction is moderate or strong since, for the strongest interaction of the FH(2)As-HNa complex, the interaction energy amounts to -24.79 kcal/mol, and the binding distance is equal to about 1.7 ?, much less than the sum of the corresponding van der Waals radii. By comparison with some related systems, it is concluded that the pnicogen-hydride interactions are stronger than dihydrogen bonds and lithium-hydride interactions. This interaction has been analyzed with natural bond orbitals, atoms in molecules, electron localization function, and symmetry adapted perturbation theory methods.     

Mechanism of CO exchange on cis-[M(CO)2X2]- complexes (M=Rh,Ir;X=Cl, Br, or I)

The CO exchange on cis-[M(CO)2X2]- with M = Ir (X = Cl, la; X = Br, 1b; X = I, 1c) and M = Rh (X = Cl, 2a; X = Br, 2b; X = I, 2c) was studied in dichloromethane. The exchange reaction [cis-[M(CO)2X2]- + 2*CO is in equilibrium cis-[M(*CO)2X2]- + 2CO (exchange rate constant: kobs)] was followed as a function of temperature and carbon monoxide concentration (up to 6 MPa) using homemade high gas pressure NMR sapphire tubes. The reaction is first order for both CO and cis-[M(CO)2X2]- concentrations. The second-order rate constant, k2(298) (=kobs)[CO]), the enthalpy, deltaH*, and the entropy of activation, deltaS*, obtained for the six complexes are respectively as follows: la, (1.08 +/- 0.01) x 10(3) L mol(-1) s(-1), 15.37 +/- 0.3 kJ mol(-1), -135.3 +/- 1 J mol(-1) K(-1); 1b, (12.7 +/- 0.2) x 10(3) L mol(-1) s(-1), 13.26 +/- 0.5 kJ mol(-1), -121.9 +/- 2 J mol(-1) K(-1); 1c, (98.9 +/- 1.4) x 10(3) L mol(-1) s(-1), 12.50 +/- 0.6 kJ mol(-1), -107.4 +/- 2 J mol(-1) K(-1); 2a, (1.62 +/- 0.02) x 10(3) L mol(-1) s(-1), 17.47 +/- 0.4 kJ mol(-1), -124.9 +/- 1 J mol(-1) K(-1); 2b, (24.8 +/- 0.2) x 10(3) L mol(-1) s(-1), 11.35 +/- 0.4 kJ mol(-1), -122.7 +/- 1 J mol(-1) K(-1); 2c, (850 +/- 120) x 10(3) L mol(-1), s(-1), 9.87 +/- 0.8 kJ mol(-1), -98.3 +/- 4 J mol(-1) K(-1). For complexes la and 2a, the volumes of activation were measured and are -20.9 +/- 1.2 cm3 mol(-1) (332.0 K) and -17.2 +/- 1.0 cm3 mol(-1) (330.8 K), respectively. The second-order kinetics and the large negative values of the entropies and volumes of activation point to a limiting associative, A, exchange mechanism. The reactivity of CO exchange follows the increasing trans effect of the halogens (Cl < Br < I), and this is observed on both metal centers. For the same halogen, the rhodium complex is more reactive than the iridium complex. This reactivity difference between rhodium and iridium is less marked for chloride (1.5: 1) than for iodide (8.6:1) at 298 K.     

(M4H3X)2B2O2: hydrometal complexes (M = Ni, Mg) containing double tetracoordinate planar nonmetal centers (X = C, N)

Geometrical optimizations and electronic structural analyses of the -O(2)B(2)- bridged hydrometal complexes (M(4)H(3)C)(2)B(2)O(2) and (M(4)H(3)N)(2)B(2)O(2)(2+) (M = Ni, Mg) containing double tetracoordinate planar nonmetals (TPN) have been performed using the density functional theory at the B3LYP/6-311+G(d,p) level. Theoretical evidence of the possibility of double TPN centers coexisting in one planar molecule is presented.