Argentophilic interactions.

The decade 1990-2000 saw a growing interest in aurophilic interactions in gold chemistry. These interactions were found to influence significantly a variety of structural and other physical characteristics of gold(I) compounds. The attention paid to this unusual and counterintuitive type of intra- and intermolecular bonding between seemingly closed-shell metal centers has rapidly been extended to also include silver chemistry.

Coordination chemistry at carbon: the patchwork family comprising (Ph3P)2C, (Ph3P)C(C2H4), and (C2H4)2C.

The revitalized concept of "coordination at carbon" allows relationships between seemingly unrelated families of carbon-centered compounds to be discovered generating fascinating patchwork families of compounds. It is shown how olefins and cyclopropanes can be regarded as donors for carbon acceptors C(1), C(2), and C(3). Through this approach, hydrocarbons such as spiropentane and dicyclopropylidene are found to be counterparts of the bis-ylidic carbodiphosphoranes and the corresponding mixed mono-ylidic systems.

Aurophilic interactions as a subject of current research: an up-date.

Recently accumulated experimental evidence for aurophilic interactions in and between molecular gold(I) compounds and the results of pertinent theoretical calculations are reviewed for the period from 2007 to mid-2011. The influence of the intra- and intermolecular bonding contacts between the closed-shell metal centres, Au-Au, on the molecular and crystal structures, and the consequences of these effects for the chemical and physical properties of gold compounds are summarized for the various classes of mono- and polynuclear systems. The literature survey builds on the contents of previous reviews and relates new experimental and theoretical findings to earlier observations (353 references).

Zintl ions, cage compounds, and intermetalloid clusters of Group 14 and Group 15 elements.

For a long time, Zintl ions of Group 14 and 15 elements were considered to be remarkable species domiciled in solid-state chemistry that have unexpected stoichiometries and fascinating structures, but were of limited relevance. The revival of Zintl ions was heralded by the observation that these species, preformed in solid-state Zintl phases, can be extracted from the lattice of the solids and dissolved in appropriate solvents, and thus become available as reactants and building blocks in solution chemistry. The recent upsurge of research activity in this fast-growing field has now provided a rich plethora of new compounds, for example by substitution of these Zintl ions with organic groups and organometallic fragments, by oxidative coupling reactions leading to dimers, oligomers, or polymers, or by the inclusion of metal atoms under formation of endohedral cluster species and intermetalloid compounds; some of these species have good prospects in applications in materials science.

A briefing on aurophilicity.

There is now compelling experimental evidence for the existence of specific intra- and intermolecular bonding between seemingly closed-shell gold(I) centers (5d10) which manifests itself in all areas of gold chemistry. This "aurophilic interaction", which had not been predicted by conventional valence theory, was found to be associated with binding energies in some cases exceeding even those of strong hydrogen bonds and therefore to be highly significant in co-determining molecular structure and dynamics. In high-level theoretical treatments the attraction is rationalized as a "super van der Waals bonding" based on particularly strong relativistic, dispersion and correlation effects (critical review, 265 references).

Governing the oxidative addition of iodine to gold(I) complexes by ligand tuning.

While several gold(I) complexes of the type (L)AuX (X = Cl, Br) are known to undergo oxidative addition of elemental chlorine and bromine (X2), respectively, to give the corresponding gold(III) complexes (L)AuX3, the addition of iodine to (iodo)gold(I) compounds is strongly ligand-dependent, suggesting a crucial threshold in the oxidation potentials. A systematic investigation of this particular oxidative addition of iodine using a large series of tertiary phosphines as ligands L has shown that both electronic and steric effects influence the course of the reaction. The reactions were followed by 31P NMR spectroscopy and the products crystallized from dichloromethane-pentane solutions.

Aurophilicity-based one-dimensional arrays of gold(I) phenylene-1,3- and -1,4-dithiolates.

Phenylene-1,3-dithiol is converted into a trinuclear gold complex by treatment with 1 equiv of [[(Ph(3)P)Au](3)O](+)BF(4)(-). In the product, the phenylene unit bears one gold thiolate and one di(gold)sulfonium function. These components aggregate into one-dimensional arrays through head-to-tail aurophilic contacts between the two functions.

5-Organyl-5-phosphaspiro[4.4]nonanes: a contribution to the structural chemistry of spirocyclic tetraalkylphosphonium salts and pentaalkylphosphoranes.

Spirocyclic phosphonium salts of the type [(CH(2))(4)P(CH(2))(4)](+) X(-) with X = I(3) (1a), I (1b), picrate (1c), benzoate (1d), and Cl (1e) were prepared from 1,4-diiodobutane and elemental phosphorus followed by metathesis reactions. The crystal structures of 1b and 1c and of 1d(H(2)O) have been determined by X-ray diffraction methods. In the cations of these salts the phosphorus atoms are shared by two five-membered rings in envelop conformations.

Cluster self-assembly of di[gold(I)]halonium cations.

Treatment of gold(I) halide complexes of the type L-Au-X [where L = PPh(3), PEt(3) with X = Cl, Br, I, or L = 2,6-(MeO)(2)C(6)H(3)PPh(2) with X = Cl] with AgSbF(6) in the molar ratio 2:1 in dichloromethane/tetrahydrofuran at -78 degrees C affords high yields of di[gold(I)]halonium salts of the formula [X[Au(PR(3))](2)](+) SbF(6)(-) (2-8). A determination of the crystal structures of the four triarylphosphine complexes (2-4, 8) revealed the presence of novel tetranuclear dications with a highly symmetrical structure (point group S(4)) that arises from self-assembly of the dinuclear monocations through a set of four equivalent aurophilic Au-Au interactions. A comparison with two reference structures of corresponding chloronium perchlorate and bromonium tetrafluoroborate salts with monomeric, dinuclear cations shows that the geometry of the latter is greatly altered on dimerization to optimize the interactions between the closed-shell metal centers (Au: 5d(10)).

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.

Binary Si/N-[4.4]-Spirocycles with Two SiH(2)SiH(2) Loops.

Tetra(alkylamino)silanes Si(NHR)(4) with R = Me, n-Pr, n-Bu, and i-Pr (1a-d) have been prepared via improved methods and characterized by complementary analytical and spectroscopic data. The reaction of 1a-c with 2 equiv of Tf-SiH(2)SiH(2)-Tf (Tf = trifluoromethylsulfonyloxy, "triflate") and triethylamine in toluene gives good yields of the spirocyclic compounds [(SiH(2)NR)(2)](2)Si (2a-c). 2a is obtained as a crystalline, but highly volatile, product (mp 35 degrees C, bp(0.

alpha,alpha'-m-Xylenediylbis(indium dichloride). A Novel Bifunctional Lewis Acid.

Reaction of the di-Grignard compound 1,3-(ClMgCH(2))(2)C(6)H(4) with HgCl(2) yields 1,3-(ClHgCH(2))(2)C(6)H(4) (1), which crystallizes in the orthorhombic space group P2(1)2(1)2(1) with a = 8.494(1), b = 10.859(1), and c = 10.

A Novel Anionic Gold-Indium Cluster Compound: Synthesis and Molecular and Electronic Structure.

The insertion of InBr into the Au-Br bond of [(Ph(3)P)AuBr] in tetrahydrofuran (thf) in the presence of [(CH(2)PPh(2))(2)] (dppe) leads to the formation of an orange complex [(dppe)(2)Au](+)[(dppe)(2)Au(3)In(3)Br(7)(thf)](-), 2. Analytical, spectroscopic, and X-ray structural investigations showed that this product is an anionic analogue of a neutral chloride complex [(dppe)(2)Au(3)In(3)Cl(6)(thf)(3)], 1, prepared recently. Both complexes have an Au(3)In(3) cluster core of approximate C(2)(v)() symmetry with one extremely short Au-Au bond [Au1-Au3 2.

Unusual Ring Systems Containing Indium. Synthesis and Structure of the First Mercuraindacycles.

The mercuraindacycles bis(&mgr;-1,8-naphthalenediyl)mercury(II)(bis(tetrahydrofuran)chloroindium(III)) (5) and bis(&mgr;-1,8-naphthalenediyl)mercury(II)(bis(tetrahydrofuran)bromoindium(III)) (7) are the products of the reaction of indium(I) halides with 1,8-naphthalenediylbis(mercury(II) halides). Their formation involves a partial transmetalation followed by a spontaneous ring closure. Compounds 5 and 7 have been characterized by (1)H, (13)C, and (199)Hg NMR spectroscopy.

A Bifunctional Lewis Acidic Spacer in Self-Assembled Molecular Stairs and Ladders.

Depending on the stoichiometry, diindacycle 1 and pyrazine in THF reversibly form a stair- or a ladderlike self-organized coordination polymer. In both cases, the building blocks are assembled at angles close to 90°.

1,2-Disilanediyl Bis(triflate), F(3)CSO(3)-SiH(2)SiH(2)-O(3)SCF(3), as the Key Intermediate for a Facile Preparation of Open-Chain and Cyclic 1,1- and 1,2-Diaminodisilanes.

Convenient high-yield syntheses for several open-chain and cyclic diaminodisilanes with fully hydrogenated Si-Si linkages are reported. The key intermediate for the preparation of the title compounds, 1,2-bis(((trifluoromethyl)sulfonyl)oxy)disilane (1), reacts with 2 equiv of diethylamine to afford a mixture of the isomers Et(2)NSiH(2)SiH(2)NEt(2) (2a) and (Et(2)N)(2)SiHSiH(3) (2a'). Isopropylamine and 1 give (i)Pr(2)NSiH(2)SiH(2)N(i)Pr(2) (2b) exclusively.

Gold Clustering at the Terminal Functions of Long-Chain Thiols and Amines.

Treatment of 1,6-hexanedithiol with (4)/(3) mol equiv of tris[(triphenylphosphino)aurio(I)]oxonium tetrafluoroborate and sodium tetrafluoroborate affords (n-hexane-1,6-dithiolato)tetrakis-[(triphenylphosphine)gold(I)] bis(tetrafluoroborate) (1). The analogous reactions with beta-mercaptoethylamine, HS(CH(2))(2)NH(2), 1,4-diaminobutane, H(2)N(CH(2))(4)NH(2), and n-butyl- and n-octylamine, CH(3)(CH(2))(n)()NH(2) (n = 3 or 7), give the corresponding penta- (2), hexa- (3), and trinuclear (4, 5) complexes, respectively. The crystal structures of compounds 3 and 5 have been determined by single-crystal X-ray diffraction studies.

Synthesis, X-ray Crystal Structure Determination, and NMR Spectroscopic Investigation of Two Homoleptic Four-Coordinate Lanthanide Complexes: Trivalent ((t)Bu(2)P)(2)La[(&mgr;-P(t)Bu(2))(2)Li(thf)] and Divalent Yb[(&mgr;-P(t)Bu(2))(2)Li(thf)](2)(,)(1).

La(OSO(2)CF(3))(3) reacts with 4 equiv of LiP(t)Bu(2) in tetrahydrofuran to give dark red ((t)Bu(2)P)(2)La[(&mgr;-P(t)Bu(2))(2)Li(thf)] (1). Yb(OSO(2)CF(3))(3) reacts with LiP(t)Bu(2) in tetrahydrofuran in a 1:5 ratio to produce Yb[(&mgr;-P(t)Bu(2))(2)Li(thf)](2) (2) and 1/2 an equiv of (t)Bu(2)P-P(t)Bu(2). Both 1 and 2 crystallize in the monoclinic space group P2(1)/c.