Structural diversity of 1,2,4-diazaphospholide complexes with alkali metals

Treatment of H[3,5-Ph2dp] (Hdp = 1H-1,2,4-diazaphosphole) with nBuLi or KH, or the reaction of K[3,5-tBu2dp] with an excess amount of O2, afforded the dimeric species [(eta2,eta1-3,5-Ph2dp)Li(THF)2]2 and the polymeric complexes [(eta2:eta4-3,5-Ph2dp)K(Et2O2]n, and [[(eta2:eta5-3,5-tBu2dp)K(THF)][eta2(N,N)-eta3(O,P,O)-3,5-tBu2dp-(O,O)O2K]]n, respectively.     

Cube-type nitrido complexes containing titanium and alkali/alkaline-earth metals

Treatment of [[Ti(eta(5)-C(5)Me(5))(mu-NH)](3)(mu(3)-N)] with alkali-metal bis(trimethylsilyl)amido derivatives [M[N(SiMe(3))(2)]] in toluene affords edge-linked double-cube nitrido complexes [M(mu(4)-N)(mu(3)-NH)(2)[Ti(3)(eta(5)-C(5)Me(5))(3)(mu(3)-N)]](2) (M = Li, Na, K, Rb, Cs) or corner-shared double-cube nitrido complexes [M(mu(3)-N)(mu(3)-NH)(5)[Ti(3)(eta(5)-C(5)Me(5))(3)(mu(3)-N)](2)] (M = Na, K, Rb, Cs). Analogous reactions with 1/2 equiv of alkaline-earth bis(trimethylsilyl)amido derivatives [M[N(SiMe(3))(2)](2)(thf)(2)] give corner-shared double-cube nitrido complexes [M[(mu(3)-N)(mu(3)-NH)(2)Ti(3)(eta(5)-C(5)Me(5))(3)(mu(3)-N)](2)] (M = Mg, Ca, Sr, Ba). If 1 equiv of the group 2 amido reagent is employed, single-cube-type derivatives [(thf)(x)[(Me(3)Si)(2)N]M[(mu(3)-N)(mu(3)-NH)(2)Ti(3)(eta(5)-C(5)Me(5))(3)(mu(3)-N)]] (M = Mg, x = 0; M = Ca, Sr, Ba, x = 1) can be isolated or identified. The tetrahydrofuran molecules are easily displaced with 4-tert-butylpyridine in toluene, affording the analogous complexes [(tBupy)[(Me(3)Si)(2)N]M[(mu(3)-N)(mu(3)-NH)(2)Ti(3)(eta(5)-C(5)Me(5))(3)(mu(3)-N)]] (M = Ca, Sr). The X-ray crystal structures of [M(mu(3)-N)(mu(3)-NH)(5)[Ti(3)(eta(5)-C(5)Me(5))(3)(mu(3)-N)](2)] (M = K, Rb, Cs) and [M[(mu(3)-N)(mu(3)-NH)(2)Ti(3)(eta(5)-C(5)Me(5))(3)(mu(3))-N)](2)] (M = Ca, Sr) have been determined. The properties and solid-state structures of the azaheterometallocubane complexes bearing alkali and alkaline-earth metals are discussed.     

Synthesis, structures and stabilities of thioanisole-functionalised phosphido-borane complexes of the alkali metals

Treatment of the secondary phosphine {(Me(3)Si)(2)CH}PH(C(6)H(4)-2-SMe) with BH(3)·SMe(2) gives the corresponding phosphine-borane {(Me(3)Si)(2)CH}PH(BH(3))(C(6)H(4)-2-SMe) (9) as a colourless solid. Deprotonation of 9 with n-BuLi, PhCH(2)Na or PhCH(2)K proceeds cleanly to give the corresponding alkali metal complexes [[{(Me(3)Si)(2)CH}P(BH(3))(C(6)H(4)-2-SMe)]ML](n) [ML = Li(THF), n = 2 (10); ML = Na(tmeda), n = ∞ (11); ML = K(pmdeta), n = 2 (12)] as yellow/orange crystalline solids. X-ray crystallography reveals that the phosphido-borane ligands bind the metal centres through their sulfur and phosphorus atoms and through the hydrogen atoms of the BH(3) group in each case, leading to dimeric or polymeric structures. Compounds 10-12 are stable towards both heat and ambient light; however, on heating in toluene solution in the presence of 10, traces of free phosphine-borane 9 are slowly converted to the free phosphine {(Me(3)Si)(2)CH}PH(C(6)H(4)-2-SMe) (5) with concomitant formation of the corresponding phosphido-bis(borane) complex [{(Me(3)Si)(2)CH}P(BH(3))(2)(C(6)H(4)-2-SMe)]Li (14).     

Molecular structure of 3-aminobenzoic acid complexes with alkali metals

The vibration (FT-IR, FT-Raman), electronic (UV-Vis) and NMR (1H and 13C) spectra for 3-aminobenzoic acid and its alkali metal salts were recorded. The influence of lithium, sodium, potassium, rubidium and cesium on the electronic system of the 3-aminobenzoic acid was studied. The assignment of the vibration spectra was done. Characteristic shifts of band wavenumbers and changes in band intensities along the metal series were observed. Good correlation between the wavenumbers of the vibrational bands in the IR and Raman spectra for 3-aminobenzoates and ionic potential, electronegativity, atomic mass and affinity of metal cations were found. The chemical shifts of protons (1H NMR) and carbons (13C NMR) in the series of studied alkali metals were also observed. Optimized geometrical structures of studied compounds were calculated by ab initio and density functional methods.     

The coordination properties of aminobenzoate ligands in complexes with alkali metals

The crystal structures of sodium 4-amino-2-hydroxybenzoate dihydrate [NaL·2H₂O, L?= C₆H₃(NH₂)(OH)COO] and potassium 2-aminobenzoate monohydrate [KL*·H₂O, L*?=?C₆H₄(NH₂)COO] were determined by X-ray diffraction methods. The compound NaL·2H₂O crystallizes in the monoclinic system, space group P2₁/c with a?=?8.820(2), b?=?14.632(3), c?=?6.948(2)?Å, β?=?97.88(3)°. The structure consists of sodium ion pairs joined together by tridentate 4-amino-2-hydroxybenzoate moieties creating a polymeric chain. In the metal centres, two water molecules bridge the sodium atoms. Five oxygen atoms and one nitrogen atom form a distorted octahedral environment. The compound KL*·H₂O crystallizes in the monoclinic system, space group P2₁/c with a?=?14.684(3), b?=?7.618(2), c?=?7.512(2)?Å, β?=?96.95(3)°. The structure consists of octacoordinated potassium atoms bonded with three water molecules and five carboxylate oxygen atoms. Water molecules appear as bridging ligands. The 2-aminobenzoate ligand acts as a pentadentate ligand with the molecular network stabilized by hydrogen bonds. Among the polymeric chains in both structures appear noncovalent interactions of type N?H···X.     

Alkali metal complexes: Complexes of alkali metals with quinaldinic acid

Complexes having the general formula ML.HL, where M = Na, K, Rb or Cs and HL = quinaldinic acid, have been obtained. The isolation of adducts in the solid state appeared to be favoured by increase in atomic radius, and hence decrease in ionisation potential of the metal. Attempts to synthesise similar adducts of picolinic acid N-oxide and quinaldinic acid N-oxide did not succeed. Complexes have been characterised by elemental analyses, thermal, IR spectral and solution studies. Our findings suggest that pK value of the ligands cannot be regarded a dominant factor in the synthesis and isolation of alkali metal complexes.     

Field-evaporation mass spectroscopy applied to crown ether complexes with alkali and alkaline-earth metals

Field evaporation from solution has been used to detect crown-ether 15K5 and 18K6 coordination compounds formed with Na⁺, K⁺, Cs⁺, Ba²⁺ and Ca²⁺ in aqueous solution, both hydrated and unhydrated; the Ca²⁺·18K6·(H₂O)_n (n=0, 1, 2,...) compounds have been observed before. 18K6 present in the solution greatly increases the yields of 18K6 compounds with the dissociation products from Ba(NO₃)₂. The detection limits for 15K5 and 18K6 combined with Na⁺, K⁺, and Cs⁺ are approximately the same at 10^–7 g.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 24, No. 2, pp. 239–242, March–April 1988.     

On the solubility of lanthanum oxide in molten alkali fluorides

The solubilities of lanthanum oxide in LiF, NaF, KF and eutectic melt LiF-NaF-KF (46.5 mole% LiF; 11.5 mole% NaF and 42.0 mole% KF) were measured in order to find the suitable electrolyte for electrodeposition of lanthanum. Solidus-liquidus lines were obtained by the method of thermal analysis. The solubility of lanthanum oxide in alkali fluorides is rather low and decreases in the order LiF>NaF>KF. It was found that lanthanum oxide reacts with the components of the melt. LaOF and alkali metal oxide are formed during dissolution of La₂O₃ in the melt.     

The minimal energy conformations of o-benzosemiquinone anion radicals in the solvents containing the alkali metals and the alkali earth metals

The minimal energy conformations of o-benzosemiquinone anion radicals in the solvents containing the alkali metals and the alkali earth metals were calculated by using the INDO method and the molecular geometry adjusting method. Our previous calculations of o-benzosemiquinone anion radical in the lithium ion solution showed that the total energy of the minimal energy conformation in the case of the assignment |A₃| > |A₄| were lower by approximately 320 kcal/mol than that in the case of the assignment |A₃| > |A₄|. Therefore, the calculations of the minimal energy conformations of o-benzosemiquinone anion radicals in the metal ion solutions were carried out in the cases of the assignment |A₃| > |A₄|. The conformations in both assignments A₃ < A₄ < 0 and (A₃ < 0 < A₄ and |A₃| > |A₄|) were calculated. Although the metal ions were not explicitly contained in the molecular geometries, the minimal energy conformations are considered to be close to the real minimal energy conformations of o-benzosemiquinone anion radicals in the metal ion solutions. The C? O bond lengths has a good positive rank correlation with the stabilities of o-benzosemiquinone radicals in the divalent metal ion solutions and the bond angles ∠C₃C₄H₄ had a good negative rank correlation with those stabilities.     

Synthesis of pyroperoxoniobates of the alkali metals

Conclusions A new method for obtaining pyroperoxoniobates of the alkali metalswith the composition(Na, K)₄Nb₂O₁₁ · 2H₂O has been developed.The solid salts (Na, K)₄Nb₂O₁₁ · 2H₂O are stable above 100°. They decompose completely 300° with the formation of pyro salts having the composition (Na, K)₄Nb₂O₇ of reagent purity.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1281–1283, July, 1966.     

Ansa-tris(allyl) complexes of alkali metals: tripodal analogues of cyclopentadienyl and ansa-metallocene ligands

Alkali metal complexes of two types of ansa-tris(allyl) ligand are reported; a monoanionic ansa-tris(allyl) ligand containing tin(II) is formally valence isoelectronic to the cyclopentadienyl ligand and a trianionic ansa-tris(allyl) ligand containing silicon(IV) is formally valence isoelectronic to an ansa-metallocene ligand; the potential wider use of these tripodal ligands in coordination chemistry is discussed.