Manuel Bardají

Structural characterization of silver(I) complexes [Ag(O3SCF3)(L)] (L=PPh3, PPh2Me, SC4H8) and [AgLn](CF3SO3) (n=2–4), (L=PPh3, PPh2Me)

Abstract We have studied the solution and some solid state structures of a series of trifluoromethanesulfonate silver(I) complexes, namely of formula [Ag(O3SCF3)(L)] (L=PPh3, PPh2Me, SC4H8) and [AgLn](CF3SO3) (n=2–4, L=PPh3, PPh2Me). The solution behaviour is as expected for mononuclear silver species, although polynuclear species can not be totally ruled out in non-coordinating solvents. The solid state structures display a wide variety of nuclearities, silver co-ordination numbers and trifluoromethanesulfonate co-ordination modes, depending on the ligand L. Thus, for complexes of empirical formula [Ag(O3SCF3)(L)], the crystal structure of [Ag(O3SCF3)(PPh3)] is a trimer with bridging triflates; the molecular structure of [Ag(O3SCF3)(PPh2Me)] shows tetranuclear complexes with a ‘chair’ geometry, further linked into chains by Ag–phenyl interactions; and [Ag(O3SCF3)(tht)] (tht=SC4H8) crystallizes in infinite chains. For complexes of formula [Ag(O3SCF3)(L)2], the PPh3 derivative is a dimer with two bridging triflates, and the PPh2Me derivative is a monomer.

Azo Isocyanide Gold(I) Liquid Crystals, Highly Birefringent and Photosensitive in the Mesophase

Isocyanide ligands bearing an azo group and one alkoxy chain OC(n)H(2n+1) have been synthesized. They are calamitic liquid crystals for n > 4 and display nematic (n = 8, 12) and SmA (n = 12) mesophases. Their gold(I) compounds [AuX(CNR)] (X = Cl, C(6)F(5); R = C(6)H(4)N horizontal lineNC(6)H(4)OC(n)H(2n+1), n = 4, 8, 12) have been obtained by displacement of a weakly coordinated ligand. The chloro gold(I) compounds exhibit nematic (n = 4) and SmA mesophases, and decompose at temperatures higher than 200 degrees C, before reaching the clearing point. The pentafluorophenyl gold(I) compounds show nematic and SmA (n = 12) mesophases. All the derivatives are photosensitive in solution because of trans to cis isomerization of the azo group under UV light, which reverts photochemically or thermally to the trans isomer. Irradiation in the mesophase also induces isomerization with consequent destabilization of the mesophase to an isotropic liquid; the mesophase is recovered as soon as illumination stops. These azo mesogens show high birefringence values, higher for the linear gold complexes than for the free azo ligand.

Syntheses of dinuclear gold(I) ring complexes containing two different bridging ligands. Crystal structure of [Au2{µ-(CH2)2PPh2}(µ-S2CNEt2)]

The reaction of [Au2{µ-(CH2)2PPh2}2] with [Au2(µ-L–L)2]n+[n= 0, L–L = S2CNMe2, S2CNEt2 or S2CN(CH2Ph)2; n= 2, L–L = Ph2PCH2PPh2(dppm), Ph2P(CH2)2PPh2 or Ph2PNHPPh2] led to heterobridged dinuclear complexes [Au2{µ-(CH2)2PPh2}(µ-L–L)]n+(n= 0 or 1). The same complexes can also be obtained by reaction of [N(PPh3)2][(AuCl)2{µ-(CH2)2PPh2}] with the silver compounds [Ag(S2CNMe2)]6 or [Ag2(OClO3)2(dppm)3] or by reaction of [(AuPPh3)2{µ-(CH2)2PPh2}][ClO4] with [{Au(C6F5)}2(µ-L–L)](L–L = diphosphines or o-Ph2PC5H4N). The structure of [Au2{µ-(CH2)2PPh2}(µ-S2CNEt2)] has been established by X-ray crystallography. Two molecules are bonded through an intermolecular gold–gold interaction, thus forming a linear chain of four gold atoms with Au–Au (intramolecular) 2.867, 2.868, (intermolecular) 2.984 A.

Gold(I) complexes containing the cationic ylide ligand bis(methyldiphenylphosphonio)methylide

Abstract The ylide Ph2PCHPPh2Me can be selectively P-alkylated by MeI or MeO3SCF3 to form the bis(methyldiphenylphosphonio)methylide salts [MePPh2CHPPh2Me]A (AI (1), CF3SO3 (2)). The ylidic carbon shows a weak nucleophilicity and does not give typical reactions with common organic electrophiles, including Wittig type reactions, but it is able to displace tetrahydrothiophene in [AuX(tht)] to give the corresponding C-coordinated gold(I) compounds [Au{CH(PPh2Me)2}X]CF3SO3 (XCl (3), C6F5 (4)). The crystal structure of (4) displays a linear coordination for the gold atom, single PC bond lengths and a PCP angle of 119.1(3)° for the ligand.

Synthesis of 2,4,6-tris(trifluoromethyl)phenyl complexes of gold and thallium

Abstract Reaction of [AuCl(AsPh3)] with [LiFmes] (Fmes=2,4,6-tris(trifluoromethyl)phenyl) leads to the gold(I) complex [Au(Fmes)(AsPh3)], which can be used as precursor to other gold(I) complexes by displacement of AsPh3. Thus, treatment with diphosphines leads to mono- or dinuclear gold(I) complexes, namely [Au(Fmes)(dppm)], [Au(dppe)2][Au(Fmes)2] or [{Au(Fmes)}2(μ-PP)] (PP: bis(diphenylphosphino)methane (dppm), 1,2-bis(diphenylphosphino)ethane (dppe)). X-ray diffraction studies of [{Au(Fmes)}2(μ-PP)] show the expected trans-conformation for dppe but an unexpected gauche conformation for the dppm derivative. There are no short gold–gold contacts. The ionic nature of [Au(dppe)2][Au(Fmes)2] was also established by X-ray methods. Reaction of TlCl3 with [LiFmes] affords [Tl(Fmes)3], which does not react further with gold(I) derivatives to give gold(III) derivatives.

Synthesis and structural characterization of luminescent gold(I) derivatives with an unsymmetric diphosphine

We have synthesised a series of mono-bridged digold(I) derivatives with an unsymmetric diphosphine, namely, [(AuX)2(μ-PiPr2CH2PPh2)] (X = Cl, Br, I, C6F5, S2CN(CH2Ph)2) and the mononuclear gold(III) complex [Au(C6F5)3(PiPr2CH2PPh2)]. X-ray diffraction studies show intramolecular gold(I)–gold(I) interactions of 3.4179(2), 3.1660(2) and 3.0926(3) A, respectively, for X = Cl, Br and C6F5. The pentafluorophenyl derivative emits at 445 nm at room temperature in the solid state; this compound and the halo-derivatives are emissive at low temperature in the range 440–486 nm. We have also prepared doubly-bridged diauracycles, namely, [Au2X2(μ-PiPr2CH2PPh2)2] (X = Cl, Br, I) and [Au2(μ-PiPr2CH2PPh2)2]A2 (A = CF3SO3, ClO4). The crystal structure of the iodo derivative displays three-coordinated gold centres in a T-shaped geometry, with a gold–gold distance of 2.9931(6) A and a gold–iodo distance of 3.0999(6) A, whilst the triflate derivative displays di-coordinated gold centres and a gold–gold distance of 2.9838(5) A. All the derivatives are intensely photoluminescent in the visible range, with the emission maxima between 480 and 513 nm at 298 K and 459–508 nm at 77 K. The emission energies and the gold–gold distances are not directly related.

Acetylenephosphino gold(I) derivatives: structure, reactivity and luminescence properties

We have synthesised the acetylenephosphino gold(I) derivatives, AuX(PPh2CCH) (X = Cl, Br, I, C6F5). X-Ray diffraction studies show that the chloro derivative is a dimer connected by two short hydrogen bonds from the acetylenic hydrogen to chlorine, whilst the iodo derivative is also a dimer because of a gold–gold interaction of 3.0625(9) A. The crystal structure of the pentafluorophenyl derivative shows the presence of intermolecular hydrogen bonds Au⋯H (3.07 A, 143°), also from the acetylenic hydrogen, which link the molecules into chains. The possibility of preparing alkynyl derivatives has been investigated but only complex [Au(C6F5)(PPh2CC)Au(C6F5)][N(PPh3)2] 6 has been obtained in a pure state. Complex 6 luminesces at room temperature in the solid state, and all the complexes are luminescent at 77 K with excitation maxima in the range 292–335 nm and emission maxima between 445 and 533 nm.

Synthesis and electrochemistry of heterobridged gold(I) and gold(II) complexes of pyridine-2-thiolate. Crystal structures of [Au2{µ-(CH2)2PPh2}(µ-C5H4NS)] and [Au2{µ-(CH2)2PPh2}(µ-C5H4NS)Br2]

The reaction of [Au2{µ-(CH2)2PPh2}2] or [Au2(µ-L–L)2][ClO4]2[L–L = dppm (Ph2PCH2PPh2) or dppe (Ph2PCH2CH2PPh2)] with [Aun(µ-C5H4NS)n] led to the heterobridged dinuclear complexes [Au2{µ-(CH2)2PPh2}(µ-C5H4NS)] or [Au2(µ-C5H4NS)(µ-L–L)]ClO4. The structure of [Au2{µ-(CH2)2PPh2}(µ-C5H4NS)] has been established by X-ray crystallography and exhibits a short intermolecular gold–gold distance of 2.8623(7)A, whereas the shortest intermolecular distance is 3.984 A. The complex crystallized in the monoclinic space group P21/n with a= 9.430(2), b= 8.819(2), c= 22.786(5)A, β= 99.08(3)°, Z= 4. Cyclic voltammograms showed that this complex is irreversibly oxidised at a platinum electrode; chemical oxidation with the ferrocenium ion in the presence of halide or pseudohalide ions gave the gold(II) complexes [Au2{µ-(CH2)2PPh2}(µ-C5H4NS)X2](X = Cl, Br, I or SCN). The same derivatives can be obtained by oxidative addition of halogen and/or by subsequent substitution with other halogens or pseudohalogens. The complex [Au2{µ-(CH2)2PPh2}(µ-C5H4NS)Br2] crystallized in the triclinic space group P with a= 14.810(10), b= 14.908(10), c= 17.041(12)A, α= 70.20(5), β= 69.77(5), γ= 89.19(5)°, Z= 6 (at –100 °C). The Au–Au bond lengths in the three independent molecules are 2.564(4), 2.548(4) and 2.547(4)A.

Methyl dithiocarbamate gold(I) and gold(III) complexes. Synthesis and reactivity with amines

Abstract The reaction of several methyl dithiocarbamates {S(MeS)CNHR} (R= p -MeC 6 H 4 , o -MeC 6 H 4 , p -MeOC 6 H 4 and 3,5-Me 2 C 6 H 3 ) with Au(C 6 F 5 )(tht) and Au(C 6 F 5 ) 3 (OEt 2 ) gives the suitable complexes containing S-bonded ligands. Thioacylation of primary amines is reported, through a reaction in the coordinated ligands; the new ligands hold the coordination to the gold atom.

Di- and tetranuclear gold(II) complexes with dithiocarbamate and related ligands. X-ray structure of Au2(μ-CH2PPh2CH2)2(S2CNMe2)2]

Abstract The reaction of [Au 2 (μ-CH 2 PPh 2 CH 2 ) 2 (tht) 2 ](CIO 4 ) 2 or [Au 2 (μ-CH 2 PPh 2 CH 2 ) 2 (PPh 3 )(tht)](CIO 4 ) 2 (tht=tetrahydrothiophene) with various dithiocarbamates gives the cationic or neutral complexes [Au 2 (μ-CH 2 PPh 2 CH 2 ) 2 {S(MeS)CNHR} 2 ](CIO 4 ) 2 , [Au 2 (μ- CH 2 PPh 2 CH 2 ) 2 (PPh 3 ){S(Mes)CNHR}](CIO 4 ) 2 or [Au 2 (μ-CH 2 PPh 2 CH 2 ) 2 (S 2 CNR 2 ) 2 ]. Displacement of tht from [Au 2 (μ-CH 2 PPh 2 CH 2 ) 2 (R′)(tht)](CIO 4 ) (R′=C 6 F 5 or 2,4,6-C 6 F 3 H 2 ) gives new cationic tetranuclear complexes [{Au 2 (μ-CH 2 PPh 2 CH 2 ) 2 (R′)} 2 (μ- S 2 CNR 2 )](CIO 4 ) in which the dithiocarbamate acts as a bridging ligand. The structure of [Au 2 (μ-CH 2 PPh 2 - CH 2 ) 2 (S 2 CNMe 2 ) 2 ] has been established by an X-ray diffraction study and shows that the dithiocarbamate is unidentate.