Four-coordinate Gold Research Articles

Synthesis, X-ray crystallography, and photoluminescence studies of four coordinate gold(I) complexes with the weak Lewis base tri-2-furyl phosphine ligand

The synthesis and structural characterization, and luminescence properties of two new four-coordinate gold(I) complexes containing the monodentate tri-2-furly phosphine is described. The gold(I) center easily accommodates up to four of the phosphine ligands forming a nearly tetrahedral geometry. Formation of four-coordinate gold(I) species is favored mainly due to electronic factors since the cone angle of the ligand is larger than several other alkyl phosphines hitherto unknown to form four coordination. In the complexes the gold center has a nearly regular tetrahedral geometry with an average P–Au–P angle of 109.37°. The crystal structure of [Au(TFP)4]Cl·CH3CN, 3, reveals four phosphine ligands bound to the gold(I) atom as well as free Cl− and CH3CN within the crystal lattice providing a nearly regular tetrahedral geometry with an average P–Au–P angle of 109.4°. The photo-luminescent properties of the complexes are compared with that of the ligand and show ligand centered emission perturbed by the metal coordination. DFT theoretical calculations were also conducted and support the assignment of the spectroscopic data.

Crystallographic and Computational Studies of Luminescent, Binuclear Gold(I) Complexes, AuI2(Ph2P(CH2)nPPh2)2I2(n= 3–6)

Four crystalline dimers of the type, Au(I)(2)(μ-PnP)(2)I(2), where PnP is PPh(2)(CH(2))(n)PPh(2) with n = 3, 4, 5, and 6 have been prepared and characterized by single-crystal X-ray diffraction and by (31)P NMR and infrared spectroscopy. Au(I)(2)(μ-P3P)(2)I(2) and Au(I)(2)(μ-P6P)(2)I(2) are centrosymmetric dimers with the planar Au(I)P(2)I units oriented in antiparallel fashion. Remarkably, noncentrosymmetric Au(I)(2)(μ-P5P)(2)I(2) has its planar Au(I)P(2)I units oriented in parallel manner. Au(I)(2)(μ-P4P)(2)(μ-I)(2) is unique, since it contains four-coordinate gold centers that are bridged by both iodide and diphosphine ligands. All four compounds are luminescent as solids at room temperature. B3LYP, B2PLYP, and spectroscopically oriented configuration interaction (SORCI) calculations have been conducted to give insight into the electronic and geometric structures of the ground and first excited triplet states of the three trigonal-planar complexes. The emission energies for the trigonal planar complexes are more strongly correlated with changes in the Au-I bond length rather than changes in the P-Au-P angle.

Gold(i) and silver(i) complexes containing a tripodal tetraphosphine ligand: influence of the halogen and stoichiometry on the properties. The X-ray crystal structure of two gold(i) dimeric aggregates

Complexes of the type [Au2(micro-PP3)2]X2 [X=Cl (), Br (), I ()], [Ag2(micro-PP3)2](NO3)2 (), Ag(PP3)Cl (), M3(micro-PP3)X3 [M=Au, X=Cl (), Br (), I (); M=Ag, X=NO3 ()] and Au4(micro-PP3)X4 [X=Cl (), Br (), I ()] have been prepared by interaction between gold(I) or silver(I) salts and the ligand tris[2-(diphenylphosphino)ethyl]phosphine (PP3) in the appropriate molar ratio. Microanalysis, mass spectrometry, IR and NMR spectroscopies and conductivity measurements were used for characterization. and are ionic dinuclear species containing four-coordinate gold(i) and four/three coordinate silver(i), respectively. Solutions of behave as mixtures of complexes in a 2:1 [Au2(micro-PP3)X2; X=Cl(), Br(), I()] and 4:1 () metal to ligand ratio. and react with free PP(3) in solution to generate the ionic compounds and , respectively. Complexes and , with four linear PAuX fragments per molecule, were shown by X-ray diffraction to consist of dimeric aggregates via close intermolecular gold(I)gold(I) contacts of 3.270 A () and 3.184 A (). The resultant octanuclear systems have an inversion center with two symmetry-related gold(I) atoms being totally out of the aurophilic area and represent a new form of aggregation compared to that found in other halo complexes of gold(I) containing polyphosphines. The luminescence properties of the ligand and complexes, in the solid state, have been studied. Most of the gold systems display intense luminescent emission at room and low temperature. The influence of the halogen on the aurophilic contacts of compounds with a 4:1 metal to ligand ratio results in different photophysical properties, while and are luminescent complex is nonemissive. The luminescence increases with increasing the phosphine/metal ratio affording for complexes , without aurophilic contacts, the stronger emissions. Silver complexes and are nonemissive at room temperature and show weaker emissions than gold(I) species at 77 K.

Luminescent dinuclear gold complexes of bis(diphenylphosphano)acetylene

We have synthesized a series of dinuclear gold(I) derivatives with the diphosphane bis(diphenylphosphano)acetylene, namely [(AuX) 2(μ-dppa)] (X=Cl, C 6F 5, SC 6F 5, S 2CN(CH 2Ph) 2). X-ray structure determinations for the first three derivatives reveal a linear geometry for the gold centres. There are no intramolecular gold–gold interactions, although for X=Cl intermolecular gold(I)–gold(I) interactions of 3.0694(4) Å lead to an infinite twisted chain; the further presence of C–H⋯Cl contacts leads to a more complex three-dimensional structure. All the derivatives are luminescent in the solid state at low temperature in the range 455–593 nm; most of them are emissive at room temperature in the range 470–598 nm. We have also prepared the dinuclear gold(III) derivative [(Au(C 6F 5) 3) 2(μ-dppa)]. Finally, we have prepared the derivative [(AuCl) 2(μ-dppa) 3], which forms a cage with two tetrahedrically coordinated gold(I) centres at the apical positions bridged by three rigid diphosphane ligands, with a helical twist of 26.2°, and a gold–gold distance of 5.769 Å. The gold(III) and the four-coordinate gold(I) derivatives are not luminescent.

Three- and four-coordinate gold(I) complexes of 3,6-bis(diphenylphosphino)pyridazine: monomers, polymers, and a metallocryptand cage.

The slightly yellow polymeric complexes [Au(2)Cl(2)(P(2)pz)(3)](n), 1 x 6CHCl(3), (P(2)pz is 3,6-bis(diphenylphosphino)pyridazine) and [[Au(2)(P(2)pz)(3)](PF(6))(2)](n), 2, are prepared by the stoichiometric reaction of AuCl(tht) (tht is tetrahydrothiophene) and P(2)pz in either dichloromethane or dichloromethane/methanol, respectively. Addition of 2 equiv of AuCl(tht) to a dichloromethane solution of 1 equiv of P(2)pz generates the simple (AuCl)(2)(P(2)pz) compound, 3. Compound 3 contains nearly linear P-Au-Cl units with intermolecular Au.Au separations of 3.570 A. Au(2)I(2)(P(2)pz)(3), 4, is prepared by reacting excess NaI with 2 in a dichloromethane/methanol mixture. Characterization of 1, 2, and 4 by X-ray crystallography confirms the 2:3 gold/ligand ratio of all three complexes. The coordination polymer 1 maintains a high degree of solvation in the solid-state with three chloroform adducts hydrogen-bonded to the chloride ligand on each gold atom. These chloroform molecules are sandwiched between the two-dimensional polymeric sheets of 1. The crystal structure of 4 reveals an empty, iodide-capped metallocryptand cage with the tetrahedrally distorted gold atoms and the nitrogen atoms on the pyridazine rings directed away from the center of the cavity. No metal ion encapsulation was observed for complex 4. Complex 2 forms one-dimensional arrays of [Au(2)(P(2)pz)(2)](2+) metallomacrocycles connected to each other by a third P(2)pz ligand. The electronic absorption spectra (CH(2)Cl(2)) of 1-4 show broad, nearly featureless absorption bands that tail into the visible with pi-pi bands at 296 nm and discernible shoulders at 314 nm for 2 and 334 nm for 3. Excitation into the low energy band of 2 produces only a modest emission in solution at 540 nm (lambda(ex) 468 nm) and 493 nm (lambda(ex) 403 nm). Under identical conditions, the P(2)pz ligand also emits at 540 and 493 nm.

Metal cluster topology 19. Beyond the auride ion: triangulated gold networks and ethane-like structural units in binary and ternary alkali metal gold intermetallics

The range of known structurally characterized alkali metal gold intermetallics now extends far beyond the simple ‘auride’ derivatives CsAu and RbAu containing the discrete auride ion, Au −, isoelectronic with Hg o. The structurally characterized binary alkali metal gold intermetallics M 2Au 3 (M = K, Rb), Rb 3Au 7 and MAu 5 (M = K, Rb) contain infinite triangulated anionic gold subnetworks which can be constructed from linear sp-hybridized gold atoms linked to each other through multicenter bonding within Au 4 tetrahedra (for RFb 3Au 7), Au 4 butterflies (for M 2Au 3) or Au 5 trigonal bipyramids (for MAu 5). The infinite anionic gold subnetworks in other alkali metal gold intermetallics provide examples of two-coordinate gold in Na 2Au; four-coordinate gold in AeAu 2 (Ae = Ca, Sr), Na 2LiAu 3 and NaAuGe; and six-coordinate gold in MAu 2 (M = Na, K) and NaAuIn 2. More complicated gold structures are found in other sodium-gold-indium ternary intermetallics including in-centered Au 12 and empty Au 6 octahedra in Na 2Au 6In 5 as well as squashed Au 6In pentagonal bipyramids in Na 8Au 11In 6. Many ternary gold intermetallics (E = Ge, In) also contain ethane-like E 2Au 6 units with unbridged EE bonds (e.g., K 4Au 2Ge 2, NuAuGe, and NaAuIn 2) or diborane-like E 2Au 6 units with EE bonds bridged by two gold atoms (e.g., Na 2Au 6In 5).

Four-Coordinate Gold(I), Silver(I), and Copper(I) Complexes with a Large-Span Chiral Ditertiary Phosphine Ligand.

The ligand L = Ph(2)PCH(2)CHEtOPPh(2) (R,S) with two chemically different donor sites and a center of chirality in the middle of the loop connecting the phosphorus atoms has been chosen for the preparation of a series of gold(I), silver(I), and copper(I) complexes. The ligand-to-metal ratio was allowed to vary between 2:1, 1:1, and 1:2. The 1:1 complexes [LAuX](2) with X = Cl, Br, I, and SCN have been found to be components of solution equilibria (in di- or trichloromethane) of various cyclic dinuclear isomers involving also several complexes generated in ligand redistribution processes. However, single crystals (X = Cl, Br) obtained from these solutions are composed solely of centrosymmetrical dimers where the two metal atoms are part of 12-membered rings and are bridged transannularly by two halogen atoms. By symmetry, the metal bridging by the two ligands L follows a head-to-tail pattern and involves a pair of enantiomers of L. The silver compound [LAgClO(4)](2) has an analogous structure with the silver atoms attaining coordination number 4 by perchlorate bridging. The copper complex [LCuCl](2) is a tricyclic binuclear compound where each copper atom is chelated by an individual ligand L and doubly halogen bridged with the second metal atom. The 2:1 complex [L(2)Au]Cl is assigned a bis-chelated structure with the tetracoordinated metal atom as a spiro center of two six-membered rings. The solution (31)P NMR spectra show the presence of various stereoisomers which are readily identified via the strong couplings mediated by the metal center. Only small J(P, P') values would be expected for P-P' coupling along the ligand PCCOP' loops. The spectrum of the dinuclear 1:2 complex L(AuCl)(2) features only two singlet (31)P resonances.

Three- and Four-Coordinate Gold(I) Complexes.

Three- and Four-Coordinate Gold(I) Complexes.

Syntheses and Structural Characterization of Tetrahedral Four-Coordinate Gold(I) Complexes of 1,3,5-Triaza-7-phosphaadamantane. An Example of a Hydrogen-Bond-Directed Supramolecular Assembly.

The synthesis and structural characterization of water-soluble four-coordinate gold(I) complexes containing monodentate phosphine ligands are described. The ligands used are 1,3,5-triaza-7-phosphaadamantane (TPA) and its protonated and methylated derivatives, [HTPA]Cl and [MeTPA]I. Formation of the four-coordinate gold(I) species is favored by the small cone angle of the phosphine (102 degrees ) and its ability to form a hydrogen-bonded network between the nitrogen atoms of the ligand and solvent water molecules. The gold center in all four complexes has a nearly regular tetrahedral geometry with an average P-Au-P angle of 109.5 degrees. [(HTPA)(3)(TPA)Au](PF(6))(4).4H(2)O.CH(3)CN(1) crystallizes in the monoclinic space group P2(1)/c (No. 14) with cell constants a = 20.719(3) Å, b = 15.606(2) Å, c = 17.854(2) Å, beta = 114.03(1) degrees, and Z = 4. Refinement of 4977 reflections and 650 parameters yields R = 0.0396 and R(w) = 0.0500. [(TPA)(4)Au]PF(6).1.5HCl.H(2)O (2), crystallizes in the monoclinic space group C2/c (No. 15) with cell constants a = 33.036(7) Å, b = 11.212(2) Å, c = 31.503(5) Å, b = 137.58(1) degrees, and Z = 8. Refinement of 3835 reflections and 470 parameters yields R = 0.0351 and R(w) = 0.0403. [(TPA)(4)Au]Cl(4).6H(2)O (3) was characterized structurally in the cubic space group Fd&thremacr;m (No. 227) with cell constants a = b = c = 20.020(2) Å and Z = 8. Refinement of 290 reflections and 28 parameters yields R = 0.0624 and R(w) = 0.1291. [(MeTPA)(4)Au](PF(6))(5).2CH(3)CN (4) crystallizes in the monoclinic space group C2/c (No. 15) with cell constants a = 23.337(3) Å, b = 14.855(3) Å, c = 35.317(5) Å, b = 97.95(1) degrees, and Z = 8. Refinement of 7840 reflections and 621 parameters yields R = 0.0493 and R(w) = 0.0698.

Two- and four-coordinate gold(I) complexes of tris(2-(diphenylphosphino)ethyl)phosphine

Treatment of tris(2-(diphenylphosphino)ethyl)phosphine (PP 3 ) with Me 2 -SAuCl produces colorless [Au 2 (μ-PP 3 ) 2 ]Cl 2 . This crystallizes as a dichloroform solvate in the triclinic space group P1. The binuclear ion reacts readily with Me 2 SAuCl to form Au 4 Cl 4 (μ-PP 3 ). Colorless needles of the dichloromethane/ethyl ether solvate of Au 4 Cl 4 (μ-PP 3 ) crystallize in the monoclinic space group P2 1 /n. There are two similar Au 4 Cl 4 (μ-PP 3 ) molecules in the asymmetric unit

197Au Mössbauer spectra of two-, three-, and four-coordinate gold(I) complexes

The 197Au Mössbauer parameters of [Au(PPH 3) n]ClO 4 ( n = 2,3,4) are consistent with linear, trigonal, and tetrahedral two-, three-, and four-coordination for the gold atom. Change in the coordination number gives rise to a very large variation in isomer shift. The four-coordinate complex shows no quadrupole splitting. The near equality of the quadrupole splittings of the other two compounds is rationalised on the basis of simple models.