Showing papers in "Polyhedron in 1985"

Abstract: B Electronic effects 904 (a) Dipole moments 904 (b) Inductive effects 906 (c) Stabilization of a positive charge in zor /?-position 907 (d) Stabilization of a negative charge in c(or /?-position 909 (e) Basic&y of benzylic protons vs aromatic protons 911 (f) Metallation 912

Abstract: INTRODUCTION. 1802 TERMINAL CS LIGANDS-PREPARATIVE METHODS 1802 i. Direct reaction of CS 1802 ii. Preparations using heteroallenes 1802 iii. Preparations using [Cl(X)CS] (X = Cl or OR) and [Cl,C*SR] ........ 1810 iv. Preparations via dichlorocarbene or chlorocarbyne complexes ........ 1811 v. Modification of thiocarbonyl complexes 1812 (a) Cr triad. 1812 (b) Mntriad 1813 (c) Fe triad 1814 (d) Cotriad. 1816

Abstract: 17 O (40.7 MHz) and 183 W (12.5 MHz) NMR spectra of aqueous Na 10 [H 2 W 12 O 42 ]·27H 2 O ( 1 ), Na 6 [W 7 O 24 ]·14H 2 O ( 2 ) and (NH 4 ) 6 [Mo 7 O 24 ]· n H 2 O solutions, as well as of 2, 1 and 0.1 M Na 2 WO 4 and 2 M Li 2 WO 4 solutions acidified up to P = 0.5, 1 and 1.14 have been measured. The composition of the W 7 O 24 6− anion remains unchanged ( 2 ), its structure being similar to that of Mo 7 O 24 6− 183 W NMR spectrum shows three resonances with the chemical shifts + 269.2, −98.8 and −178.9 ppm relative to WO 4 2− and intensity ratio 1:4:2. “Paratungstate A” produced during polycondensation of WO 4 2− at P ⩽ 1.17 is identical with heptatungstate W 7 O 24 6− . The [H 2 W 12 O 42 ] 10− 183 W NMR spectrum in the acidified 2 M Li 2 WO 4 solution has four resonances with the chemical shifts in the range - 105–145 ppm and intensity ratio 1:2:1:2. As suggested by NMR data, the H 2 W 12 O 42 10− ⇌ W 7 O 24 6− transformations occur, which depend upon concentration and temperature.

Abstract: Sixteen complexes of general formula R2SnL2 and R2(L)SnOSn(L)R2 (where L = N-acetyl-L-leucine or N-acetyl-L-phenylalanine) R = CH3, C2H5, n-C4H9, or n-C8H17) have been prepared by interaction between the ligand and R2SnO in 2:1 or 1:1 molar ratio. The complexes were characterized by IR, 1H NMR and 119Sn Mossbauer spectroscopy. All the 2:1 complexes are assigned six-coordinate, distorted octahedral geometry with chelating carboxylate groups, while the 1:1 complexes have oxygen-bridged binuclear five-coordinate, trigonal-bipyramidal configurations. The amido −CO and −NH groups are hydrogen bonded in the solid state.

Abstract: The 1,3-dipolar cycloreversion pathway of the pentazole anion (N 5 − ) to the azide anion (N 3 − ) plus dinitrogen (N 2 ) has been investigated using ab initio methods. At the MP4SDQ/6–31 + G* level of theory plus zero-point energy contributions, the pentazole anion is predicted to lie at 31 kcal mol −1 above the N 3 − + N 2 system but the energy barrier for decomposition is 22 kcal mol −1 . This indicates that the pentazole anion could be isolated in an inert matrix at low temperature. Comparison between extended Huckel calculations on the (N 5 )M(CO) 3 and (C 5 H 5 )M(CO) 3 complexes (with M = Fe 2+ , Mn + and Cr) suggests that the N 5 − complexes would be formed if the fragments could be brought together. Predicted vibrational frequencies of the N 5 − anion are also reported.

Abstract: The X-ray photoelectron spectra of 14 complexes of Al3+, Cr 3+, Fe3+, Co3+ and Cu2+ with 3-X-2,4-pentanedione (X = H, Cl, Br) were determined to analyse the nature of metal-ligand bonding in these complexes. The trend in the position of np photoelectron lines of X-group with a change of metal ion was decided by the relative contribution of metal-toligand and ligand-to-metal charge transfer. The analysis of the satellites in the M(2p3/2) and M(2p1/2) spectra suggested that the metal-ligand bond in the chromium(III) complex had higher covalent character than that in the iron(III) complex. The satellite separations in the O(1s) spectra of M(3-Xptdn)3 were in the range 4.0-4.8 eV: these satellites were assigned to a shake-up transition of Lπ → Lπ* character. The O(1s) spectra of Fe(3-Xptdn)3 and A1(3-Xptdn)3 displayed an additional strong peak to higher energy than that of the main peak (δE = 2.1–3.1 eV) when the samples of complexes were bombarded with argon ions for a longer time.

Abstract: The nature of the 8-quinolinato ligand in various forms has been examined by 15N, 13C and 119Sn NMR spectroscopy, with evidence also from electronic spectroscopy. These forms include 8-quinolinol (HQ), 8-quinolinate, the 8-hydroxyquinolinium ion, O- and N-methyl derivatives, 8-methoxyquinoline (MeQ), the zwitterionic N-methylquinolinium-8-olate and the N-methylquinolinium ion, and the chelating ligand in organotin(IV) complexes. The 15N shift from MeQ to HQ affords a measure of the intramolecular hydrogen bonding in HQ. The 15N shifts and 2J(15N1H) couplings afford criteria of chelation, and the O- and N-methyl compounds provide useful reference points for its assessment. Evidence for chelation is demonstrated in three groups of compounds, [SnR2Q2] (R = Me, Et, Bun, Octn or Ph), [SnR3Q] (R = Me, Et, Bun or Ph) and [SnR2ClQ] (R = Me, Et, Bun or Octn), the 15N and 119Sn shielding increasing from the [SnR3Q] to the [SnR2Q2] compounds.

Abstract: The diamagnetic Roussin esters Fe 2 (SR) 2 (NO) 4 readily underwent exchange with thiols R′SH to yield Fe 2 (SR′) 2 (NO) 4 : the exchange was faster in polar, coordinating solvents where paramagnetic, mononuclear complexes of types [Fe(NO) 2 (solvent) 2 ] + and Fe(NO) 2 (SR)(solvent) were formed. With the corresponding thiolate anions RS - , the esters Fe 2 (SR) 2 (NO) 4 formed the mononuclear complexes [Fe(SR) 2 (NO) 2 ] - , which were fully characterised by EPR spectroscopy for R = H, Me, Et, i -Pr, t -Bu and PhCH 2 : assignments of hyperfine couplings were confirmed by use of 15 N. With Fe 2 (SR) 2 (NO) 4 and a different set of thiolate anion, R′S - , in excess, thiol exchange occurred to give [Fe(SR′) 2 (NO) 2 ] - . A mechanism for formation of Fe 2 (SR′) 2 (NO) 4 from Fe 2 (SR) 2 (NO) 4 has been proposed. The paramagnetic mononuclear complexes [Fe(SR) 2 (NO) 2 ] were also readily formed from the diamagnetic clusters [Fe 4 S 3 (NO) 7 ] - and Fe 4 S 4 (NO) 4 , together with [Fe(SR) 3 (NO)] - , and additionally from [Fe(CO) 3 NO] - . [Fe(SMe) 2 (NO) 2 ] - . was found to be a precursor of isolable Fe 2 (SMe) 2 (NO) 4 , and [Fe(SH) 2 (NO) 2 ] - to be the common precursor of both Roussin′s red anion [Fe 2 S 2 (NO) 4 ] - and Roussin's black anion [Fe 4 S 3 (NO) 7 ] - interconvertible by appropriate adjustment of pH. The nitrosyl groups in these complexes were freely labile, and mononitrosyliron and dinitrosyliron fragments were readily interconvertible: FE(NO) fragments were favoured by the dimethyldithiocarbamate ligand (Me 2 NCS 2 ) and Fe(NO) 2 fragments by thiolate ligands, RS - , regardless of the origin of the Fe(NO) x ( x = 1,2) fragment: both mono- and dinitrosyliron complexes persisted with [( i -PrO) 2 S 2 ] - as ligand. Isotopic labelling showed the occurrence of rapid exchange of nitrogen between nitrosyl ligands and added nitrite in Fe(NO)(S 2 CNMe 2 ) 2 and [Fe(SR) 2 (NO) 2 ] -

Abstract: The hydrides [MH(O2CCF3)(CO)(PPh3)2] (M = Ru or Os) react with disubstituted acetylenes PhCCPh and PhCCMe to afford vinylic products [M{C(Ph)CHPh}(O2CCF3)(CO)(PPh3)2] and [M{C(Ph)CHMe}(O2CCF3)(CO) (PPh3)2]/[M{C(Me)CHPh}(O2CCF3)(CO)(PPh3)2] respectively Acidolysis of these products with trifluoroacetic acid in cold ethanol liberates cis-stilbene and cis-PhHCCHMe respectively thus establishing the cis-stereochemistry of the vinylic ligands The complexes [M(O2CCF3)2(CO)(PPh3)2] formed during the acidolysis step undergo facile alcoholysis followed by β-elimination of aldehyde to regenerate the parent hydrides [MH(O2CCF3)(CO)(PPh3)2] and thereby complete a catalytic cycle for the transfer hydrogenation of acetylenes The molecular structure of the methanol-adduct intermediate, [Ru(O2CCF3)2(MeOH)(CO)(PPh3)2] has been determined by X-ray methods and shows that the coordinated methanol is involved in H-bonding with the monodentate trifluoroacetate ligand [MEO-H---OC(O)CF3; OO = 254 A] The hydrides [MH(O2CCF3)(CO) (PPh3)2]react with 1,4-diphenylbutadiyne to afford the complexes [M{C(CCPh)CHPh} (O2CCF3)(CO)(PPh3)2] The ruthenium product, which has also been obtained by treatment of [RuH(O2CCF3)(CO)(PPh3)2] with phenylacetylene, has been shown by X-ray diffraction methods to contain a 1,4-diphenylbut-1-en-3-yn-2-yl ligand The osmium complexes [Os(O2CCF3)2(CO)(PPh3)2], [OsH(O2CCF3)(CO)(PPh3)2] and [Os{C(CCPh)CHPh}(O2CCF3)(CO)(PPh3)2] all serve as catalysts for the oligomerisation of phenylacetylene Acetylene reacts with [Ru(O2CCF3)2(CO)(PPh3)2] in ethanol to afford the vinyl complex [Ru(CHCH2)(O2CCF3)(CO)(PPh3)2]

Abstract: The coordination mode of a commercial chelating ion-exchange resin, ES 467, containing aminomethylphosphonic acid groups anchored on a macroporous styrenedivinylbenzene copolymer, with several metal ions, such as chromium(III), cobalt(II), nickel(II), copper(II) and zinc(II) has been studied with the aid of IR, ligand field and ESR spectra. The chelating group of ES 467, aminomethylphosphonic acid, appears to bind different metal ions mainly through oxygen atoms of the phosphonic acid group, though, in the case of those species containing low-loading of metal ions, the secondary amine nitrogen atom also appears to take part in coordination. Most of the metal ions studied seem to be present as six-coordinated species in the polymeric matrix, whereas cobalt(II) species show electronic spectra which are consistent with the presence of both four-coordinated (tetrahedral) and six-coordinated (octahedral) structures of these species. The distribution coefficients for cobalt(II), nickel(II), copper(II) and zinc(II) have been determined and it appears that the resin ES 467 binds copper(II) ions selectively. An attempt has been made to find a possible relationship between the selectivity of the chelating resin and the stereochemistry of the adsorbed metal ions.

Abstract: 3,3′-Dicarbomethoxy-2,2′-bipyridyl(DCMB)reacts with K2MCl4(M = Pd,Pt) to give M(DCMB)Cl2 and with RhCl3 to give the cis-[Rh(DCMB)2Cl2]+ ion. Attempts to prepare the tris (DCMB) complex with Rh(III) and analogous Co(III) complexes were unsuccessful.

Abstract: The salts [(C2H5)3NH]2[M4(SC6H5)10] (M = Zn, Cd) can be prepared by the electrochemical oxidation of the metal in an acetonitrile solution of triethylamine and benzenethiol. An X-ray crystal structure determination shows that the anion consists of a tetrahedron of metal atoms, each carrying a terminal -SC6H5 ligand, and connected to the three other metal atoms by bridging > SC6H5 groups. The results are compared with those for similar compounds reported in the literature.

Abstract: The nature of 2/1 Cl/Se and Br/Se stoichiometric mixtures in acetonitrile has been studied by UV-visible and Raman spectroscopy. For both mixtures the selenium dihalide has been shown to be the predominant species in solution, although there are other species present in equilibrium with the dihalide, according to 3SeCl2 = Se2Cl2 + SeCl4 2SeBr2 = Se2Br2 + Br2 as demonstrated by both techniques. The Raman spectra of SeCl2 and SeBr2 are given. Force constant calculations show that the bonds in the dihalides are the strongest SeCl and SeBr bonds known.

Abstract: The synthesis of the novel ligand 2,2,7-trimethyl-3,5-octanedione, H(tod), is described, as well as the preparation of some of the transition metal and lanthanide complexes containing the anion of this unsymmetrical beta-diketone ligand. The structure of Cu(tod)2 has been determined by X-ray crystallography to be square-planar with the isobutyl groups cis to each other. Thermogravimetric analyses indicate that several of these metal complexes are volatile and thermally stable compounds. Metal complexes containing this ligand also show unusually high solubilities in non-polar solvents such as n-hexane. The properties of these compounds indicate that they may be useful for vapour-plating of metals, as fuel additives, and in other applications.

Abstract: Complexes of copper(II) with 2-(acetylamino)benzoic acid, 2-(benzoylamino) benzoic acid, 2-(aminocarbonyl)benzoic acid, 2-[(phenylamino)carbonyl]benzoic acid, 2-[(1-naphthalenylamino)carbonyl]benzoic acid, 2-[(2-aminophenylamino)carbonyl]benzoic acid, 2-aminobenzanilide, 2(aminobenzoyl)benzoic acid, maleanilic acid and malea-1-naphthalanilic acid have been prepared and characterized by chemical analyses, molar conductivity, magnetic susceptibility measurements, thermal data, IR, electronic and ESR spectra. The visible and ESR spectral studies of these complexes (except those of maleanilic acid and malea-1-naphthalanilic acid) indicate that they are monomeric having either square planar or distorted octahedral geometry around Cu(II). The Cu(II) complexes of maleanilic acid and malea-1-naphthalanilic acid have been tentatively assigned dimeric structures. From the ESR spectra of Cu(II) complexes various parameters have been calculated.

Abstract: Some five- and six-coordinated di- and tri-n-butyl tin(IV) complexes of the type Bu2SnL, Bu2SnL2 and Bu3SnL (where L is the anion of a monofunctional bidentate or bifunctional tridentate Schiff base) have been synthesized and characterised on the basis of microanalyses, molecular weight determinations, IR, NMR (1H, 13C, 119Sn) and 119Sn Mossbauer spectroscopy. These complexes are highly active towards bacteria.

Abstract: The reaction of [Bzo2Me4[14]hexaenato(2−)N4]Ni(II) and [Bzo2Me2Ph2[14]hexaenato(2−)N4]Ni(II) with benzoyl chloride leading to mono- and disubstituted derivatives is reported. The condition of the reliable demetalation of γ,γ′-dibenzoylated complexes by means of gaseous HCl are described. The Cu(II) complexes are synthesized from free ligands. All new compounds are characterized by elemental analysis, IR, 1H NMR and MS data.

Abstract: Metal(II) complexes of N-(thiophene-2-carboxamido)salicylaldimine (H2TCS) of types M(H2TCS)2Cl2 [M = Ni, Cu and Zn], M(HTCS)Cl [M = Co, Ni and Cu], M(HTCS)2 [M = Mn, Fe, Co, Ni, Cu and Zn], M(TCS)·xH2O [M = Mn, Co and Ni, x = 2; M = Cu, x = 0], Ni(TCS)py2 and Cu(TCS)py have been prepared. Elemental analyses, molar conductance, magnetic moment, electronic, IR and ESR spectral studies have been used to characterize these complexes. The different modes of chelation of the ligand and the stereochemistry of the complexes are discussed.

Abstract: (C6F5)3Sb has been found to react with interhalogens and halo-pseudohalogens, IX(X = Cl, Br, N3 and NCO), pseudohalogen (SCN), and elemental sulphur to give oxidative addition products (I–VI). (C6F5)3SbS(VI) may also be prepared by the reaction of (C6F5)3SbCl2 with H2S. Metathetical reactions of (C6F5)3SbCl2 with appropriate metallic salts yield covalent pentacoordinate disubstituted products (V, VII–XII) of the general formula, (C6F5)3SbY2 (Y = NCS, NCO, −ONCMe2, −ONCMePh −NCO(CH 2 ) 2 C O and p-NO2C6H4OCO). Treatment of (C6F5)3SbCl2 with aqueous NaN3 gives the binuclear oxo-bridge compound, [(C6F5)3SbOSb(C6F5)3](N3)2·(III) and (IV) are also accessible by displacement reaction of (I) or (II) with the corresponding metallic salt. Molecular weight, conductance measurements, and IR spectra on the new organoantimony(V) derivatives have been obtained. Reductive cleavage reactions of (C6F5)3SbS with hexaaryldileads, Ar6Pb2(Ar = Phenyl, p-tolyl) produce (C6F5)3Sb and the corresponding bis(triaryllead) sulphide but treatment of (C6F5)3SbX2(X = NCO, Cl) with Ar6Pb2 gave Ar4Pb and Ar2PbX2 together with (C6F5)3Sb. (C6F5)3SbCl2 and bis(triorganotin)sulphides undergo exchange of anionic groups.

Abstract: The synthesis of a new class of two-dimensional triazole compounds is described, including the crystal structure of [Co(NCS)2(btr)2]H2O [btr stands for 4,4′-bis-1,2,4-triazole (C4H4N6)]. Crystals are monoclinic, space group C2/c, a = 11.159(1) A, b = 13.047(4) A, c = 12.993(3) A, β = 91.81(2)°, Z = 4. The structure has been solved by Fourier and direct methods and refined by full-matrix least squares to R = 0.0229, Rw = 0.0283. The structure consists of layers of six-coordinated cobalt atoms, each having two trans-oriented N-bonded thiocyanate groups [CoNCS 2.098(2) A] and linked together in the equatorial plane by single bridges of btr to a two-dimensional network. The btr ligand coordinates through its N(1) and N(1′) atoms [CoN 2.128(1) and 2.142(1) A]. The intralayer CoCo distance is 9.207(2) A, and the inter-layer CoCo distance is 8.584(1) A. The magnetic susceptibilities of the compound and of the isostructural nickel and iron compounds are discussed. The iron compound exhibits a high-spin-low-spin crossover at liquid-nitrogen temperatures, as shown by magnetic susceptibility.

Abstract: Determinations of the [Ti(IV)]/[Ti(III) ratio in solutions of titanium(IV) chloride equilibrated with H2(g), at 25°C in 3 M (Na)Cl ionic medium, have indicated the predominance of the Ti(OH)22+ species in the concentration ranges 0.5 ⩽ [H+] ⩽ 2 M and 1.5 x 10−3 ⩽ [Ti(IV)] ⩽ 0.05 M. From the equilibrium data the reduction potential has been evaluated Ti(OH)22+ + 2 H+ + e ⇋ Ti3+ + 2H2O, EoH = (7.7 ± 0.6) x 10−3 V. The acidification reactions of Ti(OH)22+ were also studied in 12 M(Li)Cl medium at 25°C by measuring the redox potential of the Ti(IV)/Ti(III) couple as a function of [H+]. The potentiometric data in the acidity range 0.3 ⩽ [H+] ⩽ 12 M have been explained by assuming Ti4+ + e ⇋ Ti3+, Eo = 0.202 ± 0.002 V Ti4+ + H2O ⇋ TiOH3+ + H+, log Ka1 = 0.3 ± 0.01 Ti4+ + 2H2O ⇋ Ti(OH)22+ + 2H+, log Ka1Ka2 = 1.38 ± 0.05.

Abstract: New rhodium(III), iridium(III), palladium(II) and platinum(II) dithiocarbamate complexes of the types M(Rdtc)3 and M(Rdtc)2 (Rdtc = 2-, 3- and 4-methylpiperidine dithiocarbamate) have been prepared and characterized by chemical analyses, conductance measurements, electronic and IR spectral studies, magnetic measurements and thermal analyses (TG and DTG techniques). From the electronic absorption spectra the values of the ligand field parameters were determined; the nephelauxetic parameters are indicative of a strong covalency in the metal-ligand bond. All the complexes here reported are diamagnetic and nonconducting both in the solid state and in DMF solution.

Abstract: Tetratomic tetrahedral main-group clusters have four or six (but not five) skeletal pairs, an exception to the ( n + 1) rule for closo clusters. A general group-theoretical criterion, based on the pairing principle in Stone's tensor surface harmonic (TSH) theory, is presented for symmetry-induced departures from the ( n + 1) rule. A count of ( n + 2) or n skeletal pairs is forced by symmetry for: (i) T - or T d -clusters with an odd number of sets of four equivalent cage atoms, and (ii) C m or C mv ( m ⩾ 3) clusters with an odd number of cage atoms on the C m -axis. Three such cases, B n H n or B n H n 4− , are found among the hypothetical supraicosahedral closo boranes proposed by Brown and Lipscomb ( n = 16,19 or 22). Extended Huckel calculations show that the TSH pattern applies to the whole series of closo boranes ( n \ 24). Charges of + 4, −8 and −2 are discussed for a very large B 32 H 32 q cluster.

Abstract: The extraction of Cu(II) with 1-phenyl-3-methyl-4-acyl-5-pyrazolone (HA), in different organic solvents has been studied. The extraction mechanism of Cu(II) and the composition of the extracted species has been determined. Cu(II) was extracted as CuA2, or in the presence of TOPO, as CuA2TOPO. The extraction constants do not change regularly with increasing the length of acyl chain in the 1-phenyl-3-methyl-4-acyl-5-pyrazolone derivatives. The effect of the temperature on the extraction of Cu(II) has also been investigated.

Abstract: As a part of a systematic study of the synergic extractions of metals with mixtures of acidic chelating extractants and lipophilic anion-exchangers (B, X with X − 6 inorganic anion), the extractions of M  Cd and Zn from perchlorate, nitrate and sulphate media with 1-phenyl-3-methyl-4-benzoyl-pyrazol-5- one (HL) and tri- n -octylammonium salts (TOAH.X) or aliquat 336 (TOMA.X) in toluene have been investigated. Three key equilibria describe the extractions: (a) M 2+ +2 HL ⇌ ML 2 +2H + . (b) B.X + HL ⇌ B.L +H + +X − with B efficiency TOMA 4 3 4 . (c) ML 2 + B.L ⇌ B.ML 3 with B efficiency toma > TOAH and Ni ∼ Co > Cd > ZN. As a consequence of the conflicting orders of efficiencies of TOMA and TOAH in equilibria b and c, TOAH.X is a better synergic extractant from perchlorate medium than TOMA.X whereas the inverse is observed from nitrate and sulphate media. Equilibrium c is independent of the inorganic anions. Constants of equilibria a, b and c are given. B.ML 3 species are not extracted in 1-octanol.

Abstract: The complexes Ga2X4 · 2L (L = pyridine, 3-methylpyridine, 4-methylpyridine, morpholine, 1,4-thioxane, 1,4-dithiane, tetrahydropyran, tetrahydrofuran, tetrahydrothiophene and dimethylsulphide) have been prepared. Vibrational spectra indicate that they all contain GaGa bonds and this is confirmed for Ga2Cl4 · 2pyridine by a crystal structure determination which shows it to be isostructural with the bromide analogue. We were unable to synthesize complexes of stoichiometry Ga2X4 · 4L which had previously been reported.