Multiple Coordination Modes Research Articles

Synthesis, Structures, and Properties of Four Novel Coordination Compounds based on a Flexible Tetrakis(imidazol‐1‐ylmethyl)methane Ligand

AbstractFour coordination polymers, namely, [Zn2(TIYM)(2,6‐PYDC)2]n·n(CH3OH)·3n(H2O) (1), [Cu(TIYM)(2,6‐PYDC)]n·3n(H2O) (2), [Co(TIYM)(2,6‐PYDC)]n·n(CH3OH)·3n(H2O) (3), and [Cd2(TIYM)(2,6‐PYDC)2(H2O)]n·n(H2O) (4) with the flexible N‐containing ligand [tetrakis(imidazol‐1‐ylmethyl)methane (TIYM)] and the N‐containing dicarboxylic acid [2,6‐pyridinedicarboxylic acid (2,6‐PYDC)] were prepared. Compounds 1–4 show various structures because of different N–Ccenter–N angles (θ) of TIYM ligands and changing coordination modes of 2,6‐PYDC. Compounds 1, 2, and 3 display a similar 1D ladder‐like chain, whereas 4 gives a 1D quad‐core lifting platform shaped belt. The structural diversities in 1–4 suggest that the multiple coordination modes or the different freely twist angles of ligands and the presence of different metal atoms play important roles in the resulting structures of the coordination polymers. Furthermore, the solid‐state luminescence properties of 1 and 4, and the magnetic properties of 3 were investigated.

Structurally Diverse Diazafluorene-Ligated Palladium(II) Complexes and Their Implications for Aerobic Oxidation Reactions

4,5-Diazafluoren-9-one (DAF) has been identified as a highly effective ligand in a number of Pd-catalyzed oxidation reactions, but the mechanistic basis for its utility has not been elucidated. Here, we present the complex coordination chemistry of DAF and palladium(II) carboxylate salts. Multiple complexes among an equilibrating mixture of species have been characterized by (1)H and (15)N NMR spectroscopy and X-ray crystallography. These complexes include monomeric and dimeric Pd(II) species, with monodentate (κ(1)), bidentate (κ(2)), and bridging (μ:κ(1):κ(1)) DAF coordination modes. Titration studies of DAF and Pd(OAc)2 reveal the formation of two dimeric DAF/Pd(OAc)2 complexes at low [DAF] and four monomeric species at higher [DAF]. The dimeric complexes feature two bridging acetate ligands together with either a bridging or nonbridging (κ(1)) DAF ligand coordinated to each Pd(II) center. The monomeric structures consist of three isomeric Pd(κ(1)-DAF)2(OAc)2 complexes, together with Pd(κ(2)-DAF)(OAc)2 in which the DAF exhibits a traditional bidentate coordination mode. Replacing DAF with the structurally related, but more-electron-rich derivative 9,9-dimethyl-4,5-diazafluorene (Me2DAF) simplifies the equilibrium mixture to two complexes: a dimeric species in which the Me2DAF bridges the two Pd centers and a monomeric species with a traditional κ(2)-Me2DAF coordination mode. The use of DAF in combination with other carboxylate ligands (CF3CO2(-) or tBuCO2(-)) also results in a simplified collection of equilibrating Pd(II)-DAF complexes. Collectively, the results highlight the ability of DAF to equilibrate rapidly among multiple coordination modes, and provide valuable insights into the utility of DAF as a ligand in Pd-catalyzed oxidation reactions.

A novel octanuclear nickel(II)-molybdenum(VI) heterometallic cluster based on the salicylhydroxamate ligand.

Salicylhydroxamic acid (H3shi) is known for its strong coordination ability and multiple coordination modes, and can easily coordinate to metal cations to form compounds with five- or six-membered rings, as well as mono-, di- and multinuclear compounds with interesting structures having potential applications in organic chemistry, coordination chemistry, and the materials and biological sciences. A novel octanuclear nickel(II)-molybdenum(VI) heterometallic cluster based on the salicylhydroxamate ligand, namely di-μ3-acetato-di-μ2-acetato-di-μ3-hydroxido-di-μ3-oxido-tetraoxidooctakis(pyridine-κN)bis(μ5-salicylhydroxamato)hexanickel(II)dimolybdenum(VI) monohydrate, [Mo2Ni6(C7H4NO3)2(C2H3O2)4O5(OH)2(C5H5N)8]·H2O, (I), was synthesized by the reaction of sodium molybdate, nickel acetate and salicylhydroxamic acid in a dimethylformamide/pyridine/methanol solution at room temperature. The salicylhydroxamate(3-) (shi(3-)), acetate and oxide ligands adopt complicated coordination modes and link six Ni(II) and two Mo(VI) cations into the octanuclear heterometallic cluster. All of the metal cations exhibit octahedral coordination geometries and are connected to each other through the sharing of corners, edges or planes. The heterometallic clusters are further connected to form two-dimensional supramolecular layers through weak C-H...O hydrogen bonds. Studies of the magnetic properties of the title compound reveal antiferromagnetic interactions between the Ni(II) cations.

Mechanism of Subunit Coordination of an AAA + Hexameric Molecular Nanomachine

Simian virus 40 large tumor antigen (LT) is both a potent oncogenic protein and an efficient hexameric nanomachine that harnesses the energy from ATP binding/hydrolysis to melt origin DNA and unwind replication forks. However, how the six subunits of the helicase motor coordinate during ATP hydrolysis and DNA unwinding/translocation is unresolved. Here we investigated the subunit coordination mechanisms “binomial distribution mutant doping” experiments in the presence of various DNA substrates. For ATP hydrolysis, we observed multiple coordination modes, ranging from random and semi-random, and semi-coordinated modes, depending on which type of DNA is present. For DNA unwinding, however, the results indicated a fully-coordinated mode for the natural origin-containing duplex DNA, but a semi-coordinated mode for a pre-existing fork-DNA, providing direct evidence for LT to use potentially different mechanisms to unwind the two types of substrates. The results of this study provide insights into DNA translocation and unwinding mechanisms for LT hexameric biomotor. From the Clinical EditorThe study describes the subunit coordination of simian virus 40 large tumor antigen (LT) showing that multiple mechanisms exist that handle the specific needs of different stages of DNA replication.

ChemInform Abstract: Catalysis by 1,2,3‐Triazole‐ and Related Transition‐Metal Complexes

AbstractReview: 177 refs.

Metalloporphyrinic Framework Containing Multiple Pores for Highly Efficient and Selective Epoxidation

Metalloporphyrin Mn(III)Cl-5,10,15,20-tetrakis(3,5-biscarboxylphenyl)porphyrin, having eight carboxylate groups in multiple coordination modes, connects with paddle-wheel Zn2(COO)4 units for the construction of an interesting porous porphyrinic framework that demonstrates high efficiency and stability upon epoxidation of olefins with excellent substrate size selectivity.

Anthraquinone-based demultiplexer and other multiple operations at the molecular level

Anthraquinone-based chemosensor L with pyridine units as additional functional groups has been found to show pH-dependent multiple coordination modes towards different metal ions (Co2+, Ni2+ and Cu2+). Based on these different absorption changes, this differential colorimetric chemosensor L has found promising applications as a multiple-mode molecular logic system, i.e., OR, three – input NOR, three – input INHIBIT, TRANSFER and 1:2 DEMUX. Anthraquinone based chemosensor L with pyridine units has been used for elaboration of multiple logic gates, viz. OR, three – input NOR, three – input INHIBIT, TRANSFER and 1:2 DEMUX.

Highly enhanced selectivity for the separation of CH4 over N2 on two ultra-microporous frameworks with multiple coordination modes

Two typical ultra-microporous adsorbents namely [Ni3(HCOO)6] and [Co3(HCOO)6] were successfully prepared in a feasible route to scale up using non-corrosive methyl methanoate instead of formic acid. Pure gas and binary gas mixture adsorption equilibria of CH4 and N2 were conducted on the two compounds to evaluate their CH4 adsorption capacities and selectivities against N2. The two compounds exhibit preferential adsorption of CH4 over N2 at 298K in the pressure range 0.1–1.0MPa, and the adsorption selectivities of CH4/N2 mixture are determined to be 6.0–6.5 for [Ni3(HCOO)6] and 5.1–5.8 for [Co3(HCOO)6], respectively. The uniform ultra-micropores and optimal polarizability resulted from multiple coordination modes play the essential roles in their preferential adsorption of CH4 with the highest selectivities up to date, making the two compounds as promising candidates of existing adsorbents for unconventional natural gas upgrading.

Diverse Structural Ag(I) Supramolecular Complexes Constructed from Multidentate Dicyanoisophorone-Based Ligands: Structures and Enhanced Luminescence

Two multidentate ligands containing a delocalized π-electron system, 2-{5,5-dimethyl-3-[2-(pyridin-3-yl)-ethenyl]cyclohex-2-enylidene}propanedinitrile (L1) and 2-{5,5-dimethyl-3-[2-(pyridin-2-yl)-ethenyl]cyclohex-2-enylidene}propanedinitrile (L2), were synthesized. By self-assembly of the ligands with silver(I) salts, six supramolecular complexes, [Ag(L1)(TsO)(H2O)]2(1), {[Ag3(L1)2(H2O)](ClO4)3}n (2), {[Ag(L1)(NO3)]·0.5C6H6}n (3), {[Ag(L2)(NO3)]·0.5C6H6}n (4), [Ag(L2)2](ClO4) (5), and [Ag(L2)2](PF6) (6), with different structures and topologies were obtained. In polymer 2, L1 acts as a tridentate ligand to bind Ag(I) ions to form a one-dimensional (1D) supramolecular structure. However, when the ligands adopt bidentate coordination modes to coordinate with Ag(I) ions through the pyridyl nitrogen atom and one cyano nitrogen atom, the dinuclear supramolecular complex 1, 1D coordination polymer 3, and two-dimensional (2D) coordination polymer 4 were obtained. In 5 or 6, only the pyridyl nitrogen atom of L2 ligand coordinates with the Ag(I) ion to form a mononuclear complex. The multiple coordination modes of the multidentate ligands and the effect of anions and solvents play important roles in the structural and topological diversity. The luminescent properties were investigated. Compared with the ligands, the complexes show superior luminescent properties with red-shifted and enhanced emission as well as longer fluorescence lifetimes, which indicates that they may be good candidates for optical materials.

Assembly of Helicene‐Capped N,P,N,P,N‐Helicands within CuI Helicates: Impacting Chiroptical Properties by Ligand–Ligand Charge Transfer

Combining helicate and helicene chemistry: Pentadentate phosphole-pyridine helicands (see scheme) coordinated to CuI or AgI centers afford configurationally stable double-stranded helicates bearing multiple bridging-phosphane coordination modes. Similarly enantiomerically pure helicene-grafted helicands afford enantiopure helicates.

In situ syntheses, crystal structures and magnetic properties of CuIIand MnIIcoordination assemblies based on a novel heteroalicyclic dicarboxylate tecton and N-donor co-ligands

This work focuses on coordination chemistry of a heteroalicyclic dicarboxylate ligand 5,6-dihydro-1,4-dithiin-2,3-dicarboxylate (L) with transition metals in the presence of N-donor co-ligands. A series of five CuII and MnII coordination complexes with L building blocks and different chelating/bridging co-ligands have been prepared, namely [Cu(L)(phen)]n (1), [Cu(L)(4bpy)(H2O)]n (2), {[Cu2(L)2(μ3-OH)](H2dabco)0.5(H2O)}n (3), {[Mn2(L)(phen)4](H2O)2(ClO4)2}2 (4), and {[Mn2(L)(2bpy)4](2bpy)0.5(ClO4)2}2 (5) (phen = 1,10-phenanthroline, 4bpy = 4,4′-bipyridine, dabco = 1,4-diazabicyclo[2,2,2]octane, 2bpy = 2,2′-bipyridine), in which the ligand L is obtained by an in situhydrolysis reaction of 5,6-dihydro-1,4-dithiin-2,3-dicarboxylic anhydride in the presence of lithium hydroxide. Single-crystal X-ray diffraction reveals that these complexes display a variety of coordination motifs, from the discrete tetranuclear species (4 and 5) to infinite 1-D arrays (1 and 3) and 2-D → 3-D polycatenated architecture (2), which are regulated by the multiple coordination modes of L. Furthermore, the introduction of auxiliary N-heterocyclic ligands plays a critical role in extending the dimensionality of these metallosupramolecular systems via coordination and/or secondary interactions such as hydrogen bonds and aromatic stacking. The magnetic properties and thermal stability of these complexes have also been investigated and discussed in detail.

XAFS Study of Coordination Structure of Cu(L-His)2 in Solution

Multiple coordination modes are present in the CuII-histidine complex in solution and the copper coordination environment varies with pH. In this work, we have investigated the coordination geometry of Cu(His)2 complex using X-ray absorption fine structure (XAFS) analysis. Copper K-edge XAFS spectra were acquired on aqueous Cu2+ samples with histidine at different pH values. The coordination environments were further confirmed by chemically modified histidine. Results show that the caboxylate groups coordinate at acidic condition, while amino and imidazole nitrogens get coordinated at higher pH. For the coordination geometry of Cu(His)2 in solution at physiological pH, the sixfold coordination is preferentially formed, while the fivefold coordination can co-exist in equilibrium.

A homochiral three-dimensional zinc aspartate framework that displays multiple coordination modes and geometries

A homochiral three-dimensional zinc aspartate has been synthesised via reflux and solvothermal methods, which due to the coordinative flexibility of zinc displays three distinct coordination geometries and three coordination modes of aspartic acid to zinc.

Two-dimensional metal–organic frameworks with blue luminescence

Three new isostructural two-dimensional metal-organic frameworks (MOFs), [M(bpydc)(H(2)O).H(2)O](n) where M = Zn (1); Co (2); Ni (3) and the bpydc is 2,2'-bipyridine-5,5'-dicarboxylate), were prepared by various methods such as hydrothermal, ultrasonic and microwave-assisted synthetic methods. Microcrystalline could be obtained by using ultrasonification or microwave irradiation in a short time. Their solid-state structures were revealed by X-ray crystallography. The coordination environment of the metal ions is distorted octahedral geometry. The metal ions are coordinated by two nitrogen atoms from the bipyridyl moiety, two oxygen atoms from one carboxylate in a bidentate manner, one oxygen atom from another carboxylate in a monodentate manner, and one oxygen atom from the aqua ligand. The multiple coordination modes of the bpydc ligand led to a novel topologically interesting two-dimensional sheet structure; a 6-connected uninodal net with Schläfli symbol of 3(3).4(4).5(5).6(2).7. Thermal and luminescence properties of the three MOFs were also investigated. The weight maintained constant in the range 290-342 degrees C for 1, 250-470 degrees C for 2, and 275-470 degrees C for 3 after the initial weight loss related to the dehydration steps. In particular, [Zn(bpydc)(H(2)O).H(2)O](n) (1) displays strong solid state blue luminescence.

Complexation of Uranium(VI) by Gluconate in Acidic Solutions: a Thermodynamic Study with Structural Analysis

Within the pC(H) range of 2.5 to 4.2, gluconate forms three uranyl complexes UO(2)(GH(4))(+), UO(2)(GH(3))(aq), and UO(2)(GH(3))(GH(4))(-), through the following reactions: (1) UO(2)(2+) + GH(4)(-) = UO(2)(GH(4))(+), (2) UO(2)(2+) + GH(4)(-) = UO(2)(GH(3))(aq) + H(+), and (3) UO(2)(2+) + 2GH(4)(-) = UO(2)(GH(3))(GH(4))(-) + H(+). Complexes were inferred from potentiometric, calorimetric, NMR, and EXAFS studies. Correspondingly, the stability constants and enthalpies were determined to be log beta(1) = 2.2 +/- 0.3 and DeltaH(1) = 7.5 +/- 1.3 kJ mol(-1) for reaction (1), log beta(2) = -(0.38 +/- 0.05) and DeltaH(2) = 15.4 +/- 0.3 kJ mol(-1) for reaction (2), and log beta(3) = 1.3 +/- 0.2 and DeltaH(3) = 14.6 +/- 0.3 kJ mol(-1) for reaction (3), at I = 1.0 M NaClO(4) and t = 25 degrees C. The UO(2)(GH(4))(+) complex forms through the bidentate carboxylate binding to U(VI). In the UO(2)(GH(3))(aq) complex, hydroxyl-deprotonated gluconate (GH(3)(2-)) coordinates to U(VI) through the five-membered ring chelation. For the UO(2)(GH(3))(GH(4))(-) complex, multiple coordination modes are suggested. These results are discussed in the context of trivalent and pentavalent actinide complexation by gluconate.

Modeling by Assembly and Molecular Dynamics Simulations of the Low Cu 2+ Occupancy Form of the Mammalian Prion Protein Octarepeat Region: Gaining Insight into Cu 2+-Mediated β-Cleavage

The prion protein has garnered considerable interest because of its involvement in prion disease as well as its unresolved cellular function. The octarepeat region in the flexible N-domain is capable of binding copper through multiple coordination modes. Under conditions of low pH and low Cu 2+ concentration, the four octarepeats (ORs) cooperatively coordinate a single copper ion. Based on the average structure of the PHGG and GWGQ portions of a copper-free OR 2 model from molecular dynamics simulations, the starting structures of the OR 4 complex could be constructed by assembling the repeating structure of PHGG and GWGQ fragments. The resulting model contains a preformed site suitable for Cu 2+ coordination. Molecular dynamics simulations of Cu 2+ bound to the assembled OR 4 model (Cu:OR 4) reveal a close association of specific Trp and Gly residues with the Cu 2+ center. This low Cu 2+-occupancy form of prion protein is redox-active and can readily initiate cleavage of the OR region, mediated by reactive oxygen species generated by Cu +. The OR region is known to be required for β-cleavage, as are the Trp residues within the OR region. The β-cleaved form of the prion protein accumulates in amyloid fibrils. Hence, the close approach of Trp and Gly residues to the Cu 2+ coordination site in the low Cu 2+-occupancy form of the OR region may signal an important interaction for the initiation of prion disease.

General Molecular Mechanics Method for Transition Metal Carboxylates and its Application to the Multiple Coordination Modes in Mono- and Dinuclear Mn(II) Complexes

A general molecular mechanics method is presented for modeling the symmetric bidentate, asymmetric bidentate, and bridging modes of metal-carboxylates with a single parameter set by using a double-minimum M-O-C angle-bending potential. The method is implemented within the Molecular Operating Environment (MOE) with parameters based on the Merck molecular force field although, with suitable modifications, other MM packages and force fields could easily be used. Parameters for high-spin d (5) manganese(II) bound to carboxylate and water plus amine, pyridyl, imidazolyl, and pyrazolyl donors are developed based on 26 mononuclear and 29 dinuclear crystallographically characterized complexes. The average rmsd for Mn-L distances is 0.08 A, which is comparable to the experimental uncertainty required to cover multiple binding modes, and the average rmsd in heavy atom positions is around 0.5 A. In all cases, whatever binding mode is reported is also computed to be a stable local minimum. In addition, the structure-based parametrization implicitly captures the energetics and gives the same relative energies of symmetric and asymmetric coordination modes as density functional theory calculations in model and "real" complexes. Molecular dynamics simulations show that carboxylate rotation is favored over "flipping" while a stochastic search algorithm is described for randomly searching conformational space. The model reproduces Mn-Mn distances in dinuclear systems especially accurately, and this feature is employed to illustrate how MM calculations on models for the dimanganese active site of methionine aminopeptidase can help determine some of the details which may be missing from the experimental structure.

New Examples of Metal Coordination Architectures of 4,4′‐Sulfonyldibenzoic Acid: Syntheses, Crystal Structure and Luminescence

AbstractSeven metal–organic coordination polymers, namely [Cd(sfdb)(phen)2]n·2nH2O (1), [Cd(sfdb)(bpy)2]n·nH2O (2), [Cu(sfdb)(phen)(H2O)]n·0.5nH2O (3), [Zn(sfdb)(bpy)(H2O)]n·0.5nCH3OH (4), [Cd(sfdb)(quin)]n (5), [Cd3(sfdb)2(Hsfdb)2(phen)2]n (6), and [Cd(sfdb)(bpy)]n (7) [H2sfdb = 4,4′‐sulfonyldibenzoic acid, phen = 1,10‐phenanthroline, quin = 2,2′‐biquinoline, bpy = 2,2′‐bipyridine] have been synthesized according to the principles of crystal engineering and structurally characterized by elemental analysis, IR spectroscopy, and single‐crystal X‐ray diffraction analyses. Compounds 1–3 form 1D zigzag chains. Two phen ligands chelate to one cadmium atom in 1, which is rare in similar polymers, while two 2,2′‐bpy ligands coordinate one cadmium atom in 2. The zigzag chains in 3 propagate in two different directions (rotated by 75°) that are assembled by supramolecular forces into an intriguing three‐dimensional network. Complexes 4 and 5 form square‐wave‐like 1D chains, although the results indicate a transformation of 2,2′‐bpy into quin during the course of the hydrothermal synthesis of compound 5. Compound 6 is a 1D grid‐chain based on a linear trinuclear unit, and compound 7 shows a 1D double chain containing 28‐membered rings with sfdb2– ligands as bridges. Weak hydrogen bonding and intra‐ and/or intermolecular π···π stacking contacts in compounds 3–7 link the discrete 1D chains into high‐dimensional supramolecular structures. The sfdb2– ligand displays multiple coordination modes in these seven complexes. Complexes 1, 2, and 4–7 show blue photoluminescence at room temperature. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Multiple coordination modes of hemilabile 3-dimethylaminopropyl chalcogenolates in platinum(II) complexes: Synthesis, spectroscopy and structures

The reactions of N, N-dimethylaminopropyl chalcogenolates with platinum(II) compounds have been carried out and complexes of the types [PtCl(ECH 2CH 2CH 2NMe 2)] 2 ( 1) (E = S ( 1a) and Se ( 1b)), [Pt(ECH 2CH 2CH 2NMe 2) 2] n ( 2) (E = S ( 2a) and Se ( 2b)), [(PtCl 2) 2{(Me 2NCH 2CH 2CH 2E) 2}] n ( 3), [PtX(SeCH 2CH 2CH 2NMe 2)] 2 ( 4) (X = SePh ( 4a) and OAc ( 4b)) and [PtCl(ECH 2CH 2CH 2NMe 2)(PR 3)] n ( 5) (E = S, Se, Te) have been isolated. These complexes have been characterized by elemental analysis, IR, UV–Vis, NMR ( 1H, 13C, 31P, 77Se, 195Pt) spectroscopy and FAB mass spectral data. The structures of [PtCl(SeCH 2CH 2CH 2NMe 2)] 2 ( 1b) and [PtCl(SCH 2CH 2CH 2NMe 2)(PPr 3)] 2 ( 5a) have been established by single crystal X-ray diffraction data. Both the molecules have dimeric structures. In 1b, two platinum atoms are held together by symmetrically bridging Se atoms of the chelating selenolate groups. In 5a, two thiolates form a four-membered Pt 2S 2 bridge with dangling NMe 2 groups.

Syntheses and structures of dinuclear gold(I) dithiophosphonate complexes and the reaction of the dithiophosphonate complexes with phosphines: diverse coordination types.

The dinuclear gold(I) dithiophosphonate complex, [Au(2)(dtp)(2)] (1), where dtp = [S(2)P(R)(OR')](-) with R = p-C(6)H(4)OCH(3); R'= c-C(5)H(9), has been synthesized and its reaction studied with the phosphine ligands PPh(3) and Ph(2)P(CH(2))(n)PPh(2) (n = 1-4). Compound 1 contains two gold atoms homobridged by the anionic dithiophosphonate ligand, forming an eight-membered ring complex in a chair form. After the reaction of 1 with diphosphine ligands, the dinuclear open-ring complexes Au(2)(dppm)(dtp)(2) (2), Au(2)(dppe)(dtp)(2) (3), Au(2)(dppp)(dtp)(2) (4), Au(2)(dppb)(dtp)(2) (5) were formed (dppm = diphenylphosphinomethane; dppe = diphenylphosphinoethane; dppp = diphenylphosphinopropane; dppb = diphenylphosphinobutane). The reaction with dppm is stoichiometry-dependent. Thus, when 1 reacts with 2 equiv of dppm, the ionic complex [Au(2)(dppm)(2)(dtp)]dtp forms. This dtp counterion was exchanged with tetrafluoroborate to yield [Au(2)(dppm)(2)(dtp)]BF(4), the crystallization of which afforded two interconvertible isomers, 6-yellow and 7-white. Reaction of 1 with PPh(3) affords the tetracoordinate mononuclear complex [Au(dtp)(PPh(3))(2)] (8). The molecular structures of 1-8 were confirmed by X-ray crystallography and show multiple coordination modes and geometries. The crystal structures of 1 and its reaction products with dppm (2, 6, 7) show short intramolecular Au.Au aurophilic bonding interactions of 2.95-3.10 A while no intermolecular interactions were discernible. However, reaction products of 1 with longer-chain Ph(2)P(CH(2))(n)PPh(2) ligands, n = 2-4, exhibit structures that lack both intra- and intermolecular Au.Au interactions.