Isocyanide gold complexes

Liquid-crystalline gold isocyanide complexes [C H2n+iO—(CgELj)—O—C(O)—(Cg H4)—NCAuCl] react with alcohols Cmff2m+iOE[ (n = 10 or 11 m = 2 to 5) to form ZJE isomeric mixtures of carbene complexes [isomerism occurs around the C(carbene)—N bond] with mesomorphic properties and provide the first examples of liquid-crystalline metal-carbene complexes421. The isomers can also be separated, with the E form being slightly more stable than the Z form. 

Hu and Wu showed that the hydration of terminal alk)mes could be efficiently carried out at room temperature when 5 mol% of the gold isocyanide complex XXVIII in combination with 5 mol% of KB(C6Fs)4 was used as the catalyst system. The products were obtained in excellent yields (Scheme 16.49). 

There are scattered reports on isocyanide complexes of other metals including copper and gold, vanadium, and several lanthanides and actinides. 

Gold(I) isocyanide complexes [62, 63] are prepared as shown in Equation 3.1. 

Depending on the R group, this reaction could lead to the formation of gold(I) isocyanide complexes that behave as liquid crystals. Thus, complexes [Au(C6F5) (C = N(QH4)OCioH2i-p)] and [Au(QF5)(C = N(QH4)OCnH2n + rP)] [64] where n = 4, 6, 8, 10 and 12 show this behavior. All of these complexes are mesomorphic and behave as liquid crystals showing a nematic (N) phase when the isocyanide has a... 

The reaction of the gold(I) pentafluorophenyl isocyanide complexes with primary and secondary amines as well as alcohols leads to the corresponding gold(I) [62, 65] carbenes (Table 3.2). The addition of amines leads to the corresponding carbenes... 

Neutral ylide, isocyanide and carbene pentafluorophenyl gold] 111) complexes with the general formulae trans-[Au]C6F5)X2]CH2PR3)[ ]PR3 = PPh3, PPh2Me, PPhMe2),... 

Cyclic carbenes [46] are also described by the addition of a isocyanide to a diamine gold(III) complex (Scheme 3.2). 

Bayon, R., Coco, S., Espinet, P., Fernandez-Mayordomo, C. and Martin-Alvarez, J.M. (1997) Liquid-Crystalline Mono- and Dinuclear (Perhalophenyl) gold(l) Isocyanide Complexes. Inorganic Chemistry, 36(11), 2329-2334. 

Luminescent gold(l) acetylide complexes. Photophysical and photoredox properties and crystal structure of [ Au(C = CPh) 2 (p-Ph2PCH2CH2PPh2)]. Journal of the Chemical Society, Dalton Transactions, 2929-2932 (d) Che, C.-M., Wong, W.-T., Lai, T.-F. and Kwong, H.-L. (1989) Novel luminescent binuclear gold(I) isocyanide complexes. Synthesis, spectroscopy, and X-ray crystal structure of Au2(dmh)(CN)2 (dmb = 1,8-di-isocyano-p-menfhane). Journal of the Chemical Society, Chemical Communications, 243-244. 

As indicated above in chiral mesophases, the introduction of a functional group in mesogenic stmctures offers the opportunity to achieve functional LCs. With this aim, mesomorphic crown-ether-isocyanide-gold(I) complexes (26) have been prepared recently [38]. The derivatives with one alkoxy chain show monotropic SmC mesophases at or close to room temperature. In contrast, the complexes with three alkoxy chains behave as monotropic (n = 4) or enantiotropic (n > 4) LCs. The structure of the mesophases could not be fully eluddated because X-ray diffraction studies in the mesophase were unsuccessful and mesophase characterization was made only on the basis of polarized optical microscopy. These complexes are luminescent not only in the solid state and in solution, but also in the mesophase and in the isotropic liquid state at moderate temperatures. The emission spectra of 26a with n=12 were... 

Omenat, A., Serrano, J.L., Sierra, T., Amabilino, D.B., Minguet, M., Ramos, E. and Veciana, J. (1999) Chiral linear isocyanide palladium(II) and gold(I) complexes as ferroelectric liquid crystals. Journal of Materials Chemistry, 9, 2301-2305. 

Coco, S., Cordovilla, C., Espinet, P., Martm-Alvarez, J. and Munoz, P. (2006) Dinudear gold(I) isocyanide complexes with luminescent properties, and displaying thermotropic liquid crystalline behavior. Inorganic Chemistry, 45, 10180-10187. 

Arias, J., Bardaji, M. and Espinet, P. (2008) Luminescence and Mesogenic Properties in Crown-Ether-Isocyanide or Carbene Gold(I) Complexes Luminescence in Solution, in the Solid, in the Mesophase, and in the Isotropic Liquid State. Inorganic Chemistry, 47, 3559-3567. 

Benouazzane, M., Coco, S., EspineL P., Martm-Alvarez, J. and Barbera J. (2002) Liquid crystalline behavior in gold(I) and silver(I) ionic isocyanide complexes smectic and columnar mesophases. Journal of Materials Chemistry, 12, 691-696. 

Isocyanides RNC have been employed extensively as ligands for gold cations, and gold(i) complexes of the types (RNC)AuX and [(RNC)2Au]+X in particular are legion. As for alkynylgold compounds (Section 4), research activities in this area have several quite obvious reasons, as follows. 

Most gold(i) isocyanide complexes are colorless, crystalline materials, stable in air at room temperature, and soluble in common organic solvents. The compounds have been generally well characterized by IR/Raman and NMR spectroscopy, and crystal structures have been determined for almost a 100 examples. From the spectroscopic and structural data, it has been concluded that gold(i) isocyanides are strong cr-donors and poor 7r-acceptors. 

Diethynyl-pyridine was reacted with 2 equiv. of (Me2S)AuCl to give a gold alkynyl as an insoluble coordination polymer of unknown structure. This product could be dissolved in organic solvents with cBuNG to afford the bis(isocyanide) complex with an angular structure (Scheme 50).214... 

Owing to the good ligand properties of isocyanides for complexation of gold(i), complexes of the type [(RNC)2Au]+X are readily available through a variety of synthetic routes. One new approach is the substitution of organic nitriles. The reaction is carried out in acetonitrile and gives quantitative yields (Equation (43)).2... 

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