Isocyanides alkynyl complexes

ABSTRACT. Alkynes, when activated by an electron-rich d Re, Mo or W phosphinic centre, undergo hydrogen shift reactions (to give, e.g., vinylidene species) or oxidatively add to the metal (forming alkynyl--hydrido or alkynyl complexes). These alkyne-derived products undergo 3-protonation to afford a variety of carbyne-fluoro or -chloro complexes, whereas aminocarbynes are obtained upon 3-electrophilic attack (e.g., by a protic or a Lewis acid) at isocyanides when ligating such metal sites. Mechanistic studies, by stopped-flow spectrophotometry, are also indicated. 

Liquid crystals based on aliphatic isocyanides and aromatic alkynyls (compounds 16) show enantiotropic nematic phases between 110 and 160 °C. Important reductions in the transition temperatures, mainly in clearing points (<100 °C), areobtained when a branched octyl isocyanide is used. The nematic phase stability is also reduced and the complexes are thermally more stable than derivatives of aliphatic alkynes. Other structural variations such as the introduction of a lateral chlorine atom on one ring of the phenyl benzoate moiety or the use of a branched terminal alkyl chain produce a decrease of the transition temperatures enhancing the formation of enantiotropic nematic phases without decomposition. 

In summary, [Au(alkynyl)(CNR)j complexes also show mesomorphic behavior but, in contrast to the halide-isocyanide derivatives, they are thermally less stable and usually decompose before or at the clearing temperatures. This thermal instability is thought to be associated with the gold-(alkynyl) bond and makes these compounds... 

This work was extended to include acetylides (alkynyls) of the type (RNG)Au-G=C-C6H4-/)-C H2 +1, with n — 6-12 (even numbers), and R as above. The compounds were prepared from (tht)AuCl and the alkynes /)-HC=C-C6H4-C H2 +1 in aqueous acetone with soda as a weak base. The resulting insoluble, polymeric alkynylgold(i) complexes were dissolved in an organic solvent by adding equivalent quantities of the isocyanides. All products show distinct transitions from a crystalline to a smectic A phase and finally to the isotropic melts.206... 

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... 

The first polynuclear structures with gold(i) centers coordinated to isocyanide and alkynyl groups were prepared through a novel exchange of alkynyl ligands. This special route became necessary, because the coupling of certain complexes proved elusive (Equation (40)) AuCl complexes of isocyanides with terminal alkynyl groups are subject to decomposition upon treatment with a variety of auxiliary bases. 

Rod-like mononuclear derivatives have been prepared by the reaction of a polymeric alkynyl gold(I) complex with isocyanides. The mesomorphic properties of three types ofgold(I) acetylide complexes, namely, [Au(CC-Ar)(CN-Ar)J, [Au(CC-R)(CN-Ar)J and [Au(CC-Ar)(CN-R)] (Ar = aryl with aliphatic chain, R = alkyl chain), have been systematically examined. 

Platinum complexes (continued) with aryls, thallium adducts, 3, 399 with bis(alkynyl), NLO properties, 12, 125 with bisalkynyl copper complexes, 2, 182-186 with bis(3,5-dichloro-2,4,6-trifluorophenyl), 8, 483 and C-F bond activation, 1, 743 in C-H bond alkenylations, 10, 225 in C-H bond electrophilic activation studies, 1, 707 with chromium, 5, 312 with copper, 2, 168 cyclometallated, for OLEDs, 12, 145 in diyne carbometallations, 10, 351-352 in ene-yne metathesis, 11, 273 in enyne skeletal reorganization, 11, 289 heteronuclear Pt isocyanides, 8, 431 inside metallodendrimers, 12, 400 kinetic studies, 1, 531 on metallodendrimer surfaces, 12, 391 mononuclear Pt(II) isocyanides, 8, 428 mononuclear Pt(0) isocyanides, 8, 424 overview, 8, 405-444 d -cP oxidative addition, PHIP, 1, 436 polynuclear Pt isocyanides, 8, 431 polynuclear Pt(0) isocyanides, 8, 425 Pt(I) isocyanides, 8, 425 Pt(IV) isocyanides, 8, 430... 

Typical modes for the preparation of (l-alkynyl)carbene complexes, as well as spectroscopic and structural data, are briefly summarized. Alkoxy-and amino(l-alkynyl)carbene complexes are available from metal carbonyls and metal isocyanides, respectively. 

Addition of cyclohexyl isocyanide to enol ether 164 derived from addition of phenol to a (l-alkynyl)carbene complex la results in formation of a... 

Recently, the CpNi system was reinvestigated to reveal the system s catalytic activity toward aryl isocyanides [19]. The CpNiR(PPh3) complexes 3a and 5a-c, where R=methyl or alkynyl group, polymerized p- or ra-substitut-ed aryl isocyanides in THF at room temperature (Scheme 9). Alkyl iso-... 

Complexes of this type may contain a variety of orgaiuc residues R, such as alkyl, vinyl, alkynyl or aryl. The neutral donor group L is most commonly a tertiary phosphine or an isocyanide ligand, and polynuclear complexes with bridging polyfunctional donor ligands are also known . From a practical point of view, the series of organogold(I) and isocyanide complexes is of particular interest since some of its members hold promise as precursors for the chemical vapour deposition of gold films. A selection of these and other compounds of the type [RAuL] is presented in Tables 1-3. 

The activation of adequate small unsaturated-C molecules, typically isocyanides or alkyne-derived vinylidenes and alkynyls, towards 3-electrophilic attack by electron-rich group 6 (Mo or W) or 7 (Re) transition metal centres constitutes a convenient and established route for the synthesis of carbyne complexes, which has been discussed in this paper. 

---