Isocyanide-substituted complexes

The isocyanide-substituted complexes can be correspondingly obtained following thermal decarbonylation of the bromotetracarbonyl species with tert-butyl isonitrile to produce the cationic aminocarbyne complex [Cr(=CN Pr2)(CO)(CN Bu)4]. Subsequent treatment with Na[Cp] or K[Tp ] in tetrahydrofuran at 50 °C results in formation of LCr(=CN Pr2)(CO)(CN Bu) (L = Cp or Tp in 61 and 58% yield, respectively). In both reactions the minor product [Cr(=CN Pr2)(CN Bu)5] is formed by a competitive carbonyl-substitution reaction of the tetra(isonitrile) complex with liberated CN Bu. ... 

Lithium 1,2,4-triazolate with [Rh2( j,-Ph2PCH2PPh2)(CO)2( j.-Cl)]PFj. gives the A-framed complex 177 (L=L = CO) (86IC4597). With one equivalent of terf-butyl isocyanide, substitution of one carbon monoxide ligand takes place to yield 177 (L = CO, L = r-BuNC), whereas two equivalents of rerr-butyl isocyanide lead to the product of complete substitution, 177 (L = L = r-BuNC). The starting complex (L = L = CO) oxidatively adds molecular iodine to give the rhodium(II)-rhodium(II) cationic species 178. 

The reactions of nucleophilic reagents with cationic and uncharged metal carbonyl complexes have received much attention in the past, and it is not surprising that these studies have now been extended to isocyanide metal complexes. Different products in these reactions can arise by three general routes these include ligand substitution, reactions involving attack at a ligand, and reduction of the metal complex. All have been observed in reactions with metal isocyanide complexes. 

Ionic LCs are interesting systems because they combine the properties of LCs with those of ionic liquids. Although alkali metal soaps were among the first thermotropic LCs to be systematically studied, ionic liquid crystalline derivatives have been reported less frequently than those based on neutral molecular and macromolecular species [39]. When the halide of [AuX(CNR)] complexes is substituted by a second isocyanide, ionic complexes [Au(CNR)2][Y] [R = C6H40C H2 + i (27a),... 

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... 

Methyl-isocyanide-substituted derivatives of [h -C5H5Fe(CO)3] also undergo photo-substitution, yielding complexes where carbonyl, but not isocyanide, is replaced ... 

Organogold carbene compounds [Au(carbene)(CN) j iR ] can be obtained from com-plexed cyanides [Au(CN)m(C6F5) ] (n = 1 or 3, m = 1 and n = m = 2) by sequential alkylation (to form isocyanide complexes) and nucleophilic attack of amine" . Gold(III) diisocyanides [Au(CNR)2(CgF5)2]+ (R = Ph or p-tolyl), which can also be obtained by isocyanide substitution of ether in [Au(C6F5)2(OEt2)2] > react with hydrazobenzene NH(Ph)NHPh and hydrazine or phenyUiydrazine according to the reactions in Scheme 32 to furnish cyclic bis(carbene) and cyclic carbene-imidoyl compounds . ... 

Typically the desired isocyanide substitution products are obtained in good yield from such reactions. However, a major drawback of this strategy entails the prior preparation and purification of the labile precursor complexes. The transition metal catalyzed substitution of the metal hexacarbonyls [M(CO)e] (M = Cr, Mo, W) by isocyanides has, by way of contrast, proved to be a direct and rapid synthetic route that reliably gives the products [M(C0)6, (CNR)J (n = 1-3) in high yield. We describe here general procedures that illustrate the methods involved and that highlight the synthetic utility of these reactions. 

To further complicate the picture, the related isocyanide-substituted cation, [Os(=Cp-tolyl)(CNp-tolyl)(CO)(PPh3)2], undergoes a fast thermal reaction with HCl as depicted in Scheme 3. The cationic carbene complex produced is converted by treatment with LiEt3BH to the neutral substituted-benzyl complex labelled B in Scheme 3. The overall two-step transformation of A into B is a good example of the conversion of a metal-carbon triple bond to a metal-carbon single bond by sequential addition of "H+ followed by "H-" [11]. 

While the template-stabilized 2-aminoethyl isocyanide ligand in 48 was observed more or less by accident, the directed stabilization of /3-amino functionalized isocyanides is possible at electron-rich metal templates. Isocyanides 35, 41 and 2-nitrophenyl isocyanide form the electron-rich complexes of types 50 and 51. Reduction of the 2-azido or 2-nitro functions leads to the 2-amino-substituted isocyanides in complexes 52 and 53 that are stabilized by M CsNR backbonding and thus undergo no cyclization to the NH,NH-NHC ligands (Scheme 9.16) [64]. 

An isocyanide-substituted iron-platinum complex 26 undergoes Fe-Pt bond cleavage to give 27 upon further treatment with TuNG (Equation (25)). The ease with which the bond was opened was attributed to the dative character of the Fe-Pt bond. 

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