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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)). Weak metallophilic bonding clearly becomes significant only in crystal lattices where anions with a larger ionic radius (SbF(6)(-) vs. BF(4)(-), ClO(4)(-)) reduce the otherwise dominant role of strong interionic Coulomb forces. The results indicate that aurophilic bonding is indeed an ubiquitous, quite dependable mode of intermetallic interactions provided that the right environment is chosen to allow the weak forces to become operative.

Complexes of the type (R3P)AuSCN and (R3P)AuSeCN have been prepared in high yields from the corresponding chlorides (R3P)AuCl by treatment with KSCN or KSeCN, respectively, in a two-phase water/dichloromethane system. Crystal structure determinations revealed discrete monomeric molecules for the isomorphous thiocyanate and selenocyanate compounds with R=2-MeC6H4. For R=iPro there is only weak association into dimers via long Au&z.sbnd;S contacts, but for R3=Me2PhP chain-like polymers are formed via short aurophilic interactions [Au&z.sbnd;Au, 3.2334(2) and 3.2533(2) A˚]. A monoclinic modification of (Ph3P)AuSCN was found, which shows a standard geometry of the molecules. An orthorhombic modification published previously featured a doubtful strongly distorted molecular geometry. All compounds of the type (R3P)AuS/SeCN can be converted into salts with dinuclear cations {[(R3P)Au]2S/SeCN}+Y− on reaction with equimolar quantities of [(R3P)Au]+Y− (Y=BF4, SbF6) as confirmed by analytical and spectroscopic data. The S/SeCN units are found to be bridging the two metal atoms via the S/Se atoms. The tetrafluoroborates are less stable than the hexafluoroantimonates, and all selenocyanate complexes are markedly less stable thermally and more sensitive towards air and moisture than their sulfur counterparts. [Copyright &y& Elsevier]

Treatment of the gold(I) halide complexes LAuCl (where L=PMe3, PEt3, PPh3, PPh2Py) and PP(AuCl)2 [where PP=bis(diphenylphosphino)methane; 1,1′-bis(diphenylphosphino)ferrocene] with 4-amino-2-pyrimidine-thiol (2-SPym-4-NH2) (one or two equivalents as required) in the presence of sodium methoxide provides the corresponding (phosphine)gold(I) thiolate complexes LAu(2-SPym-4-NH2) and PP[Au(2-SPym-4-NH2)]2, respectively. A polyaurated product [(Ph3PAu)2(2-SPym-4-NH2)]BF4 is obtained on treating the thiol with the oxonium complex [(Ph3PAu)3O]BF4. The compounds LAu(2-SPym-4-NH2) (L=PPh3, PPh2Py, PEt3) and [(dppm)Au2(2-SPym-4-NH2)2] have been investigated crystallographically. [Copyright &y& Elsevier]