Bromo Complexes Research Articles

Palladium-catalysed cross-coupling reactions of ruthenium bis-terpyridyl complexes: strategies for the incorporation and exploitation of boronic acid functionality

The palladium catalysed Miyaura cross-coupling reactions of 4′-(4-bromophenyl)-2,2′:6′,2″-terpyridine (tpy-ϕ-Br) and 4′-bromo-2,2′:6′,2″-terpyridine (tpy-Br) with bis(neopentyl glycolato)diboron (B2neo2) lead to the first reported examples of boronate ester-substituted terpyridine ligands, L1 and L2. Ligand L1, which incorporates a benzene ring between the terpyridine group and the boron, reacts with transition metals such as iron and ruthenium to generate complexes containing the analogous boronic acid-substituted terpyridine L3. The heteroleptic complex [Ru(ttpy)L3]2+ has also been prepared by an analogous cross-coupling reaction of the bromo complex [Ru(ttpy)(tpy-ϕ-Br)]2+ with B2neo2 (ttpy = 4′-tolyl-2,2′:6′,2″-terpyridine). The structurally related complex [Ru(ttpy)L4]2+ (L4 = terpyridine-4′-boronic acid) could not be prepared, either directly from L2 or from [Ru(ttpy)(tpy-Br)]2+, apparently due to competitive hydrodeboration and solvolysis. The complex [Ru(ttpy)L3]2+ reacts with aryl halides under standard palladium-catalysed Suzuki–Miyaura cross-coupling conditions to generate more elaborate 4′-aryl-substituted terpyridyl complexes. Cross-coupling has also been achieved by reaction of [Ru(ttpy)(tpy-Br)]2+ with an arylboronic acid. The photophysical properties of [Ru(ttpy)L3]2+ are shown to be largely typical of ruthenium bis-terpyridyl complexes.

A specific interaction of dihalogeno complexes of zinc(II) with 1,10-phenanthroline in N,N-dimethylformamide

The zinc(II) ion preferentially forms tetrahedral four-coordinate dihalogeno complexes [ZnX2(DMF)2] (X = Cl, Br, I) in N,N-dimethylformamide (DMF), while formation of the ZnX+ complex is strongly suppressed. The zinc(II) ion also binds bidentate 1,10-phenanthroline to form octahedral six-coordinate complexes preferentially. On the basis of these facts, interaction of the [ZnX2(DMF)2] complex with 1,10-phenanthroline has been investigated in DMF by potentiometry, titration calorimetry and spectrophotometry at 298 K. Thermodynamic parameters of the formation of binary zinc(II) halogeno and 1,10-phenanthroline complexes in DMF have been studied in advance in the previous and present works, respectively. It is found that 1,10-phenanthroline binds to the [ZnX2(DMF)2] complex to form ZnX2(phen) and ZnX2(phen)2 in all the halide systems. Formation of ZnX2(phen)2, according to ZnX2 + 2phen = ZnX2(phen)2, is significantly enhanced in the order Cl ΔH°(Br)>ΔH°(I). This is unusual because the Zn(II)–DMF bond within [ZnX2(DMF)2] is expected to be stronger in the order Cl<Br<I, suggesting that a specific interaction operates between 1,10-phenanthroline and the halide ion. Formation enthalpy and entropy values for reaction, ZnX2 + phen = ZnX2(phen), also show unusual behavior, suggesting the iodide complex is five-coordinated as [ZnX2(phen)(DMF)] with one coordinating DMF molecule, while the chloro and bromo complexes are four-coordinated without coordinating solvent molecule. Complexation of zinc(II) with thiocyanate ions and 1,10-phenanthroline has also been investigated.

Monomeric and Dimeric Cyclooctyne-Stabilized Complexes of Copper(I)1

The syntheses and structures of cyclooctyne halogeno copper(I) complexes are described. The dimeric compounds [CuX(cyclooctyne)]2 (5: 5a, X = Cl; 5b, X = Br; 5c, X = I) are formed by reaction of equimolar amounts of cyclooctyne and copper(I) halide. X-ray structure analyses of all three compounds 5 show the copper(I) ion in a trigonal-planar coordination with bridging halide ligands. The complexes 5 react with an excess of cyclooctyne to give the monomeric bis(alkyne) complexes [CuX(cyclooctyne)2] (7: 7a, X = Cl; 7b, X = Br; 7c, X = I). Here, the three X-ray structure determinations prove that two η2-coordinated alkyne ligands are bound to a monomeric copper(I) halide unit. The reaction of the bromo complex 5b with 3,3,6,6-tetramethyl-l-thia-4-cycloheptyne (S-alkyne) affords the first mixed-alkyne copper complex [(cyclooctyne)CuBr2Cu(S-alkyne)] (9). Compound 9 forms dinuclear molecules in solution but a polymeric bent chain in the solid state (X-ray structure determination), in which one copper remains in a trigonal-planar environment and the other copper has a tetracoordinated structure.

A Structurally Characterised Pair of Dicobalt(III) Peroxo/Superoxo Complexes withC2-Symmetrical Tetrapodal Pentadentate Amine Ligands, and Some Reactivity en route

The tetrapodal pentaamine ligand 2,6-bis(1′,3′-diamino-2′-methylprop-2′yl)pyridine (pyN4, 1) provides square-pyramidal coordinated cobalt(II) building blocks, which have been used in the synthesis of the singly-bridged dicobalt(III) µ2-η1:η1-peroxo and superoxo complexes [(1)Co−O2−Co(1)]4+/5+, isolated as the chloride, bromide, and mixed chloride/dithionate and bromide/dithionate salts. The peroxo complex is accessible by the classical route involving oxygenation of [(pyN4)CoII], but has also been obtained from a cobalt(III) precursor in air, which implies that the pentaamine 1 acts as a multi-electron reductant. Oxidation of the peroxo complex with chlorine generated in situ from an HCl/H2O2 mixture (H2O2 derived from partial peroxo complex hydrolysis) generates the superoxo complex. Both cations have highly symmetrical solid state structures, locked in transoid Co−O−O−Co conformations by two pairs of intramolecular hydrogen bonds. Each involves two protons in the equatorial Co(NH2R)4 plane of one half of the molecule and the bridge oxygen atom in the other half. A significant difference between the two structures is the orientation of the O2 bridge, which is coplanar with the pyridine rings of the coordination caps in the peroxo complex and at right angles in the superoxo complex. The reactivities of the complexes in acidic and basic media have been explored, and the mononuclear bromo complex [(1)CoBr]2+ was isolated in one of the products. Dithionite, intended as an external reducing agent in the reaction of Na3[CoIII(CO3)3] with 1, instead yields the S-sulfito complex cation [(1)Co(SO3)]+, by disproportionation of S2O42− to give SO32− and S2−. All complexes have been characterised by 1H, 13C NMR, IR, Raman, UV/Vis, and EPR spectroscopy (as applicable), elemental analysis and X-ray structure determination, and the cyclic voltammetry parameters of the peroxo/superoxo pair of complexes have been determined.

Complexes of heterocyclic thiones and Group 12 metals: Part 3. Preparation and characterisation of 1:2 complexes of mercury(II) halides with 1-methylimidazoline-2(3 H)-thione: the crystal structures of [(HgX 2)(1-methylimidazoline-2(3 H)-thione) 2] (X=Cl, Br, I) at 160 K

The stoichiometric addition (1:2 metal–ligand) of aqueous alcoholic solutions of the metal salts to similar solutions of 1-methyl-imidazoline-2(3 H)-thione (1-meimz2SH) generated crystalline complexes of general formula, [HgX 2(1-meimz2SH) 2] (X=Cl, Br, I), in good yield. The chemical formulae of the complexes have been characterised by elemental chemical analysis. Infrared and 13C NMR spectra indicated the presence of the thione form of the heterocyclic ligands in the complexes, as well as their thione–sulfur ligating character. X-ray crystal structure analyses have been performed on the three complexes. The metal in the chloro complex occupies a crystallographic two-fold axis which bisects the SHgS angle. The bromo and iodo complexes occupy general positions, but one of the ligands is disordered in the bromo complex. All of the complexes are mononuclear with the four-coordinate metals possessing distorted tetrahedral geometry. The extent of the distortion is indicated by the angles at the metal which range from 93.71(7) to 127.73(7)°. Metal–sulfur distances range from 2.4514(14) to 2.571(3) Å. Metal–halogen distances range from 2.5984(13) Å (chloro) through 2.641(3) and 2.647(3) Å (bromo) to 2.7866(11) and 2.8047(9) Å (iodo). Hydrogen bonds, involving the thioamide hydrogen (NH) and halogen atoms are exclusively intramolecular in the chloro complex, but both intramolecular and intermolecular in the bromo and iodo complexes.

Synthesis and Characterisation of Tetraphenylarsonium Halochromates

Tetraphenylarsonium halochromate (halo=fluoro, chloro and bromo) complexes are synthesised and characterised by spectral and thermal studies. The effect of ionic size and electronegativity of halide ions on the infrared spectra, X-ray emission spectra, activation energy of the first decomposition step and thermal stability of the complexes are investigated. The complexes possess tetragonal unit cell with a=b=12.93 A and c=7.68 A.These complexes decompose in two exothermic stages. Cleavage of one Ph-As bond to give triphenylarsine and reduction of Cr(VI) to Cr(III) occur simultaneously. First step mass loss corresponds to the loss of two phenyl halide molecules and 3/2 moles of oxygen. The overall kinetics of the first step is described by diffusion controlled reaction mechanism with a function g(α)=[1−(1−α)1/2]. The second step decomposition is due to the further degradation of triphenylarsine. The final product is Cr2O3.

Mercury(II) compounds with 1,3-imidazole-2-thione and its 1-methyl analogue. Preparative and NMR spectroscopic studies. The crystal structures of di-μ-iodo-bis[iodo(1,3-imidazolium-2-thiolato- S)mercury(II)], bis[bromo(1,3-imidazolium-2-thiolato- S)]mercury(II) and bis[μ-(1- N-methyl-1,3-imidazole-2-thiolato- S)]mercury(II)

A series of mercury(II) compounds of the empirical formulae HgX 2L, and HgX 2L 2 (X=Cl −, Br −, I −, SCN −; L=imtH 2, meimtH; imtH 2=1,3-imidazole-2-thione, meimtH=1-methyl-1,3-imidazole-2-thione) has been obtained by the reaction of mercury(II) salts and 1,3-imidazole-2-thione and 1-methyl-1,3-imidazole-2-thione, respectively. Mercury(II) acetate yields HgL 2 complexes where L=imtH −, meimt −. The isolated compounds have been characterised by elemental chemical analysis, IR and 1H and 13C NMR spectroscopy. Complexation effects on chemical shifts in 1H and 13C spectra were shown to be a reliable probe for distinguishing HgX 2L and HgX 2L 2 complexes. In the former molecules the thione carbon (C-2) is shielded up to 3.0 ppm and the thioamide protons (NH) are deshielded up to 0.5 ppm, as compared to the corresponding atoms in the latter molecules. In all complexes the 13C complexation shift at C-2 decreases with decreasing electronegativity of the halogen atom (X), indicating the corresponding increase in π-character of the C-2–S bond. The crystal structures of HgI 2(imtH 2), HgBr 2(imtH 2) 2 and Hg(meimt) 2 have been determined by X-ray diffractometry and revealed S-bound imtH 2 in the iodo and bromo complex, while in Hg(meimt) 2 the ligand acts as bridging with stronger S and weaker N bonds.

X-Ray Absorption Fine Structure (XAFS) Studies on Cobalt(II) Bromo Complexes in Acetic Acid Solutions

Abstract X-Ray absorption fine structure (XAFS) studies were performed for cobalt(II) bromo complexes prepared for the ratio Br/Co from 0.0 to 4.0 and for their oxidized complexes with ozone in acetic acid solvent. The multivariate curve resolution method indicates the existence of two kinds of chemical species both before and after the oxidation. Before oxidation, the two species are cobalt(II) acetate and tetrahedral cobalt(II) complex coordinated by Br. The oxidized sample with ozone consists of cobalt(II) acetate and trinuclear cobalt(III) complex; however, cobalt(III) complexes including Br are not detected. The rate of the change from the cobalt(II) complex coordinated by Br to the trinuclear cobalt(III) complex is lower than that from cobalt(II) acetate complex. This indicates that the tetrahedral cobalt(II) complex coordinated by Br is more difficult to be oxidized than the octahedral cobalt(II) acetate complex.

Geometrical Preferences in Bis(dithiocarbamato)tin(IV) Complexes: X-Ray Structure of cis-I2Sn[S2CN(C2H5)2]2 and Theoretical Investigations

The geometry of cis-l2Sn[S2CN(C2H5)2]2 is confirmed by single crystal X-ray analysis; the spectral data of the complex resemble those of the bromo complex and PM3 calculations on octahedral complexes of the type XYSn[S2CN(C2H5)2]2 reveal that their geometrical preferences depend upon the electron availability on the monodentate ligands X or Y.

Geometrical Preferences in Bis(dithiocarbamato)tin(IV) Complexes: X-Ray Structure of cis-I2Sn[S2CN(C2H5)2]2 and Theoretical Investigations

The geometry of cis-I2Sn[S2CN(C2H5)2]2 is confirmed by single crystal X-ray analysis; the spectral data of the complex resemble those of the bromo complex and PM3 calculations on octahedral complexes of the type XYSn[S2CN(C2H5)2]2 reveal that their geometrical preferences depend upon the electron availability on the monodentate ligands X or Y.

Synthesis and reactions of the rhenium fulvene complexes [Re(η6-C5Me4CH2)(CO)2(C6F4R)] (R = F or CF3): products derived from initial C–F activation

The UV irradiation of [Re(η5-C5Me5)(CO)3] in the presence of C6F6 effected intermolecular C–F and intramolecular C–H activation generating [Re(η6-C5Me4CH2)(CO)2(C6F5)] 1a in two isomeric forms. In the major isomer the CH2 group lies trans to the C6F5 group both in solution and in the crystal. In the minor isomer the CH2 lies cis to the C6F5 group. A similar reaction with C6F5CF3 generates [Re(η6-C5Me4CH2)(CO)2(C6F4CF3)] 1b in four isomeric forms. In the major form the CF3 group is in the 4 position and the CH2 group lies trans to the C6F4CF3 group. The other three isomers are formed by rotation of the η6-C5Me4CH2 ligand as above, by placing the CF3 at the 3 position, and by a combination of the two. Complex 1a reacted with PMe3 to form the zwitterionic complex [Re(η5-C5Me4CH2PMe3)(CO)2(C6F5)] and with MeO– to form the anion [Re(η5-C5Me4CH2OMe)(CO)2(C6F5)]–, isolable as the NEt4+ salt. The reaction of 1a with HX (X = Cl or Br) generated cis-[Re(η5-C5Me5)(CO)2(C6F5)X] initially. More prolonged reaction led to the trans isomers. On reaction with HI, only the trans isomer was formed. Reaction of 1a with HBF4 in Et2O in the presence of MeCN led to formation of the salt [Re(η5-C5Me5)(CO)2(C6F5)(NCMe)]+[BF4]–. The halogens Cl2, Br2 and I2 reacted to form (halogenomethyl)tetramethylcyclopentadienyl complexes trans-[Re(η5-C5Me4CH2X)(CO)2(C6F5)X] (X = Cl, Br or I). The bromo complex has been characterized crystallographically.

Effects of anions on the solid state structures of linear gold(I) complexes of the type (o-xylyl isocyanide)gold(I) (monoanion)

The preparation, spectroscopic, and structural characterization of four gold(I) complexes, (o-xylylNC)AuX with X as I, Br, Cl or CN, are reported. Each crystallizes in a unique, solvent-free form with varying aurophilic interactions between the linear, two-coordinate molecules. Thus, (o-xylylNC)AuCl forms a simple dimer, while the bromo and iodo analogs form slightly kinked chains with extended Au· · ·Au· · ·Au· · · units. The bromo complex differs from the iodo complex due to the fact that an independent, non-interacting (o-xylylNC)AuBr unit lies off to the side of the linear chain. The structure of (o-xylylNC)AuCN consists of a complex grid which involves kinked chains of gold atoms cross linked by another aurophilically connected triad of gold centers. The complexes are all luminescent at room temperature in solution and in the solid state.

Study of the aqueous reactions of K[Pt(Ph 2SO)Cl 3] with nitrile ligands and crystal structures of N(C 4H 9) 4[Pt(Ph 2SO)Cl 3], N(C 2H 5) 4[Pt(Ph 2SO)Br 3] and cis-Pt(Ph 2SO)(C 3H 5CN)Cl 2

The aqeuous reactions of K[Pt(Ph 2So)Cl 1] with nitriles were studied in different conditions of pH, mainly by 195Pt and 1H NMR. At normal pH (≈ 2.4), the ligands RCN have produced the neutral complexes Pt(Ph 2SO)(RCN)Cl 2. For acetonitrile, only the cis isomer was obtained, while for other nitriles a mixture of the two isomers was formed. The 195Pt NMR spectra of the compounds were measured. The signals of the cis isomers were observed around −3040 ppm, while those of the trans isomers were found around − 3180 ppm. The study has shown that the first product formed is the trans isomer, which then isomerizes partially to the cis compounds. The 195Pt NMR spectra of the products obtained in neutral medium (pH adjusted to ∼ 7 with NaOH) have shown several signals depending on the nitrile. Dimeric species of the type Pt(Ph 2SO)Cl(μ-NHC(R)O 2Pt(Ph 2SO)Cl are suggested to exist in solution. Head-to-head and head-to-tail isomers are probably formed. The crystal structures of N(C 4H 9) 4[Pt(Ph 2SO)Cl 3] ( I), N(C 2H 5) 4[Pt(Ph 2SO)Br 3] ( II) and cis-Pt(Ph 2SO)(C 3H 5CN)Cl 2 ( III) were determined. The chloro ionic complex is triclinic, P-1, with a = 10.674(2), b = 11.424(2), c = 13.731(2) A ̊ , α = 89.54(1), β = 83.27(1), γ = 80.48(1)°, Z = 2 rmand R = 0.042, while the bromo complex is monoclinic, P2 1/ n, with a = 11.258(3), b = 19.425(4), c = 11.590(2) A ̊ , β = 102.62(2)°, Z = 4 and R = 0.053 . Crystal III is orthorhombic, space group P2 12 12 1, a = 9.532(3), b = 11.787(2), c = 15.464(4) A ̊ , Z = 4 and R = 0.031 . The compound is the cis isomer. For crystal I, the PtCl bond in trans position to the sulfoxide is 2.312(2) Å, while the cis bonds are 2.282(2) and 2.299(2) Å. For the bromo compound ( II), the PtBr bonds vary between 2.397(3) and 2.421(3) Å. In crystal III, the PtCl bond located in trans position to the nitrile is considerably shorter (2.269(3) Å) than the PtCl bond in trans position to the sulfoxide ligand (2.311(3) Å). The PtS bond distances vary between 2.201(2) and 2.228(3) Å.

Osmium Alkyl and Silyl Derivatives with Cyclopentadienyl(phosphine) and Pentamethylcyclopentadienyl(phosphine) Ligand Sets

The preparation and characterization of new osmium(II) and osmium(IV) silyl derivatives containing the cyclopentadienyl(phosphine) and pentamethylcyclopentadienyl(phosphine) ligand sets are described. The osmium silyl complexes are prepared by thermal reactions of hydrosilanes with osmium(II) alkyl complexes of the type Cp‘(PR3)2OsCH2SiMe3 (Cp‘ = Cp, R = Ph (4), Me (5); Cp‘ = η5-C5Me5, R = Me (7)), which in turn are available via alkylation of the corresponding bromo complexes. The synthesis of alkyl derivatives of Cp(PR3)2Os (R = Ph, Me) requires the use of dialkylmagnesium reagents, while alkylation of the more electron-rich Cp*(PMe3)2Os system can be achieved using Grignard reagents. Additionally, reaction of Cp(PPh3)2OsBr with AgOTf (Tf = SO2CF3) affords the osmium(II) triflate complex Cp(PPh3)2OsOTf (2), which possesses a labile triflate group. The structure of complex 2 was determined by X-ray crystallography. Similar to their ruthenium analogs, the osmium(II) alkyl complexes 4, 5, and 7 thermally a...

Thermodynamic and Structural Aspects on Solvation Steric Effect in Nonaqueous Solution

Abstract Formation thermodynamics and structure of halogeno and pseudo-halogeno complexes of transition metal(II) and lanthanide(III) ions have been studied in N,N-dimethylacetamide (DMA) and hexamethylphosphoric triamide (HMPA), and compared with those in N,N-dimethylformamide (DMF). Significant differences in the formation thermodynamics and structure among solvents has been explained in terms of a solvation steric effect. A structural survey by EXAFS demonstrates that solvent coordination number of a solvate metal ion is kept unchanged (weak solvation steric effect) or reduced (strong solvation steric effect) when the metal ion is transferred to DMA or HMPA, respectively, from DMF. DMA usually exhibits a weak solvation steric effect. It elucidates that a weak solvation steric effect of DMA is ascribable mainly to a distortion of the M–O–C–N dihedral angle. The solvent effect operates for a complex with a coordination number larger than four in DMF, but it does not for a complex of four-coordination. Lanthanide(III) ions exhibit a specific solvation steric effect, and an outer-sphere bromo complex in DMF changes to an inner-sphere complex in DMA. Besides, the solvent coordination number varies with solvent composition in DMF–DMA mixtures, and the variation manner strongly depends on the metal ion or the ionic radius. HMPA shows a strong solvation steric effect, and halogeno complexation is significantly enhanced in HMPA relative to that in DMF, although HMPA has a stronger electron-pair donating ability. The coordination number is four or five, and the M–O(HMPA) bondlength is significantly shortened.

Structural and biological aspects of copper (II) complexes with 2-methyl-3-amino-(3 H)-quinazolin-4-one

A series of new copper(II) complexes with 2-methyl-3-amino(3 H)-quinazolin-4-one (MAQ) and various anions (Cl −, Br −, ClO 4 −, NO 3 −, SCN −, and SO 4 2−) was prepared. Their structures and properties were characterized by elemental analysis, IR, UV-Vis and ESR spectroscopy, molar conductivity, and magnetic moment measurements. The square-planar complex was only obtained in the presence of perchlorate anion, whereas the five coordinate species, which have a square-pyramidal structure, were obtained for chloro and bromo complexes. In the case of hexa coordinate complexes, in which nitrate, sulphate, or thiocyanate is attached to a copper(II) ion in a 1:2 (metal:ligand) ratio, a distorted octahedral geometry around copper(II) is proposed. The antimicrobial activity of the free ligand and its copper(II) complexes clearly illustrates that the compounds have both an antibacterial and antifungal potency against the organisms tested. In most cases, the complexes were found to be more active than the free ligand, but in some cases, an equal activity was displayed. To further elucidate the biological activity of the complexes, their activities towards active oxygen species, such as H 2O 2 and O 2 −, were investigated. A probable mechanism for the cytotoxic reaction with the different organisms is proposed.

Effect of Platinum(II) Complexes of 4-Methoxy-and 4-Chlorobenzoic Acid Hydrazides on Saccharomyces cerevisiae

This study reports the anti-yeast effect of the 4-methoxybenzoic acid hydrazide (pmbah), 4-chlorobenzoic acid hydrazide (pcbah) and their Pt(II) complexes: cis- [PtL2X2] and cis- [PtL(NH3)Cl2] where L is either pcbah or pmbah and X is Cl, Br or I. MICs of the 4- substituted analogues (20,000-625 microM) are much lower than those of the previously reported benzoic acid hydrazide and 3-methoxybenzoic acid hydrazide. Complex formation results in significant increase of potency which may be due to a change in the mechanism of action, but the MIC (> 400-50 microM) and the IC50 (> 400-1 microM) values show that higher activity of the ligands in the free state does not result in enhanced complex activity. Differences in the potency of iodo-, chloro- and bromo complexes suggest MIC and IC50 values may be in correlation with the stability of the complex, rather than with the activity of the free ligands. Osmotically unstable mutants were more susceptible to the compounds than their parent strains, but differences among the parent strains, but differences among the parent strains were greater.

HPLC of Platinum Metals and Gold Based on Their Bromo Complexes

PtII,IV, PdII, and AuIII can be separated and quantitated by HPLC in the form of ion-associates of their bromo complexes with the cetyltrimethylammonium (CTMA) cation, using the acetonitrile-water 60 : 40 system containing 0.002 mol l-1 CTMA and 0.05 mol l-1 NaBr (pH 3) as the mobile phase and detection at 240 nm. In such circumstances the detection limits for the injection of 20 μl sample are 6.7, 0.4, 0.9, and 4.3 ng for PtII, PtIV, PdII, and AuIII, respectively. Excess Fe3+, Al3+, Mg2+, Ca2+, NO3-, SO42-, and Cl- does not interfere. On-line preconcentration of the PtII,IV bromo complexes on Separon SGX RPS is recommended.

Fischer-type alkylidyne tungsten complexes containing strong π donor ligands

Reaction of [W(CPh)Cl(CO)(PMe 3) 3] ( 1), with NaNC 4H 4, NaNC 8H 6, NaOC 6H 5 and NaSR (R = CMe 3, C 6H 11) in THF afford the alkylidyne tungsten complexes [W(CPh)X(CO)(PMe 3) 3] ( 2a−e), containing pyrrolide, indolide, phenoxide and alkylsulfide ligands, X, respectively. The π donor ligands X occupy the coordination site trans to the alkylidyne ligand. The anionic complexes [NEt 4][W(CPh)X 2(CO)(PMe 3) 2] ( ( 3a) X = NC 4 H 4), (( 3a) X = NC 8 H 6 ), form upon reaction of 1 with 2 equiv. of NaNC 4H 4 and NaNC 8H 6 in THF, followed by metathesis with NEt 4Cl in CH 2Cl 2. Reaction of 1 with the sodium salt of pyrrole-2-carboxaldehydemethylimine affords [W(CPh(NC 4H 3-CHNMe-2)(CO)(PMe 3) 2] ( 4). The solid state structures of complexes 2a and 2e were determined by X-ray crystallography. Complex 2d reacts in THF solution with carbon monoxide to afford cis-[W(CPh)(SCMe 3)(CO) 2(PMe 3) 2] ( 6). In contrast, the analogous bromo complexes [W(CPh)Br(CO)(PMe 3) 3] ( 7) gives under the same conditions an equilibrium mixture of 7 and trans-[W(CPh)Br(CO) 2(PMe 3) 2].

{(CEP) 2Au} +{Au(CN) 2} −]: A compound with gold-gold bonds

Tris(2-cyanoethyl)phosphine (CEP) acts as a phosphorus-donor ligand forming strong metal-phosphorus bonds in several metal complexes. It forms monomeric complexes with AuCl and AuBr, whereas an ionic complex [{(CEP) 2Au} +{Au(CN) 2} −] ( I) was formed with AuCN, presumably as a result of ligand scrambling in solution. The X-ray structure of I revealed mutually perpendicular [(CEP)Au(CEP) + and [(CN)Au(CN)] − ions, with an AuAu separation of 3.279(2) Å. No inter- or intramolecular metal coordination of CN groups was observed. There are two three-coordinated gold atoms per asymmetric unit, with a packing pattern based upon alternating [(CEP) 2Au] + and [Au(CN) 2] − ions. The presence of CN groups in gold complexes of trialkylphosphines appears to be conductive towards ligand scrambling reactions forming ionic complexes, as compared to the monomeric linear species in the case of chloro or bromo complexes.