Isocyanide palladium

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. 

Oxidative addition of the silicon-silicon bond of l,l,2,2-tetramethyl-l,2-disilacy-clopentane 2 onto bis(tert-butyl isocyanide)palladium(O) occurred instantaneously to give a six-membered cyclic bis(organosilyl)bis(tert-butyl isocyanide)palladium(II) complex 3a (Scheme... 

A common method for the m situ synthesis of carbene complexes has been via isocyanide complexes, although this method is used less frequently now that free carbenes have been isolated. An example of this approach is the reaction of the (l,l-ethylenedithiolato)(isocyanide)palladium(ii) complexes with NHEt and Reaction of... 

C5 sHs 3CI3F6NO8P, 1,1 -Binaphthylmacrocyclicpolyether (R)-phenylgly-cine methyl ester hexafluorophosphate chloroform, 43B, 426 C60H3 iiN2 2Pd, Tetrakis (methyl isocyanide )palladium( 11) tetrakis-(7,7,8,8-tetracyano-p-quinodimethane) diacetonitrile solvate, 42B, 499... 

The unusual complex tetrakis(tert-butyl isocyanide)di-/i-chloro-di palladium(I) chlorobenzene has been prepared by Otsuka et al The preparation utilized a novel coupling reaction between bis(rert-butyl isocyanide)palladium(O) and cis-bis(rert-butyl isocyanide)dichloro-palladium(II) in cold chlorobenzene. Although the reported yield for the final step of this synthesis was good (70%), the preparation of the precursor bis(tert butyl isocyanide)palladium(O) from (i7 -allylX> cyclopenta-dienyl)palladium is time-consuming and is accomplished in only S0% yield. We have developed a greatly improved preparation of the title complex (chlorobenzene-free), which utilizes readily available Pd(0) and Pd(II) compounds as starting materials, namely bis(dibenzylideneacetone)palladium(0), [Pd(dba)2], and trans-bis(benzonitrile)dichloropalladium(II). In addition, since full details of the preparation of Pd(dba)2 have not been reported, we give a complete account of the preparation here.H... 

Four-membered heterocycles can be formed by the addition of isocyanides to 1,3-dipoles (80AG(E)45) and by the reaction of carbon monoxide with -haloamines, with the aid of palladium catalysis (Scheme 10) (79CC699). 

Trimethylsiloxyphenyl isocyanide enters the cyclization reaction with [MCl2(NCPh)2] (M = Pt, Pd) to yield the homoleptic tetracarbenes 77 (M=Pt, Pd) (97JOM(541)51). Complex 77 (M = Pd) enters an interesting reaction with ammonia to yield the species 78 where two of this benzoxazol-2-ylidene ligands are deprotonated and become C-coordinated benzoxazole moieties, while the other two remain intact. Palladium(II) iodide in these conditions behaves differently yielding the di-Mo-cyanide complex, which in the presence of tetra- -butyl ammonium fluoride gives the dicarbene 79. 

A few isocyanides of palladium and platinum are known in the zerovalent oxidation state. The best characterized compounds involve triangular M3 clusters with M-M bonds. 

Substantially more work has been done on reactions of square-planar nickel, palladium, and platinum alkyl and aryl complexes with isocyanides. A communication by Otsuka et al. (108) described the initial work in this area. These workers carried out oxidative addition reactions with Ni(CNBu )4 and with [Pd(CNBu )2] (. In a reaction of the latter compound with methyl iodide the complex, Pd(CNBu )2(CH3)I, stable as a solid but unstable in solution, was obtained. This complex when dissolved in toluene proceeds through an intermediate believed to be dimeric, which then reacts with an additional ligand L (CNBu or PPh3) to give PdL(CNBu )- C(CH3)=NBu I [Eq. (7)]. 

The addition of cyclohexyl isocyanide to several palladium(II) methyl complexes has proven particularly interesting 169, 170). From... 

Since the initial report on the addition reactions of palladium(II) and platinum(II) isocyanide complexes by Badley et al. (S), a rather substantial number of further examples have been reported. These are summarized in Table II. 

Stone et al. 43, 60, 61) have studied reactions of nickel and palladium isocyanides and a number of fluorocarbons which give a remarkable variety of products. With Ni(CNBu )4 and fluoroolefins [C2F4, (CF3)2C=C(CN)2 and CF2 = CFCF = CF2] themetallocyclic complexes (XXXIV), (XXXV), and (XXXVI) are observed 60,61) the complex Ni(CNBu )2(CjF5), analo-... 

A large amount of the work on palladium isocyanide complexes has been mentioned earlier, in discussions on insertion reactions 30,74,108,169,170) and on addition reactions of coordinated isocyanides 25, 33, 34, 49) the reactions of [Pd(CNBu )2] with oxygen 107) and with various olefins 29, 110) were noted. 

It is possible to replace one isocyanide by triphenylphosphine, or to replace two isocyanides with diphos, giving phosphine analogues of these complexes. These species are not available from analogous reactions of phosphine-palladium(O) and (II) complexes. Reactions with active alkyl halides proceeds with oxidation nitric oxide also oxidizes these complexes. [Eqs. (31, 32)]. 

Cavell KJ, McGuinness DS (2007) Palladium complexes with carbonyl, isocyanide and carbene ligands. In Crabtree RH, Mingos DMP, Canty AJ (eds) Comprehensive organometallic chemistry 111. Elsevier, Amsterdam... 

Coco, S., Cordovdla, C., Donnio, B., Espinet, P., Garda-Casas, M.J. and Gudlon, D. (2008) Self-Organization of Dendritic Supermolecules, Based on Isocyanide-Gold(I), -Copper(l), -Palladium(II), and -Platinum(ll) Complexes, into Micellar Cubic Mesophases. Chemistry - A European Journal, 14, 3544-3552. 

Dixon, K. R. Dixon, A. C. Palladium Complexes with Carbonyl, Isocyanide and Carbene Ligands, In Comprehensive Organometallic Chemistry II A review of the literature 1982-1994 Puddephatt, R. J. Ed., Elsevier, 1995, Vol. 9, p 193. 

The hexakis(methyl isocyanide) dimers, [Pt2(CNMe)6], undergo photolytic cleavage of the Pt—Pt bond to give 15-electron radicals, Pt(CNMe)3.94 Mixtures of platinum and palladium dimers give rise to heteronuclear complexes under photolytic conditions. Mixtures of normal and deuterium-labeled methyl isocyanide complexes reveal that the metal-ligand bonds undergo thermal redistribution.94... 

The indazoline products can also be made directly from the palladium complexes 78 by heating them with the isonitrile in toluene at 120CC.162 They are also formed in dicobalt octacarbonyl-catalyzed reactions of azo-arenes with isocyanides but in this case an alternative reaction pathway leading to indazolo[2,l- ]indazoles (79) is observed (Scheme 96).163 Products of the latter type are formed from sterically hindered isocyanides hence it is likely that in these cases a double metallation is favored over isocyanide insertion into a monometallated species (Scheme 97). 

A few additional Pd-catalyzed schemes have been employed for Ilac type cyclization chemistry. Palladium-phenanthroline complexes were used by the Ragaini group to prepare indoles via the intermolecular cyclization of nitroarenes and alkynes in the presence of carbon monoxide <06JOC3748>. Jia and Zhu employed Pd-catalysis for the annulation of o-haloanilines with aldehydes <06JOC7826>. A one-pot Ugi/Heck reaction was employed in the preparation of polysubstituted indoles from a four-component reaction system of acrylic aldehydes, bromoanilines, acids, and isocyanides <06TL4683>. 

The 2,3-substituted indols are formed via a palladium-catalyzed coupling reaction of aryl halide, o-alkenylphenyl isocyanide, and amine (Equation (122)).481 Oxidative addition of an aryl halide, insertion of both the isonitrile and alkene moieties of o-alkenylphenyl isocyanide, and 1,3-hydrogen migration may form a 7r-allylpalladium species, which is then attacked by an amine to afford an indol. 

A unique bis-silylation system, in which a bis(silyl)palladium intermediate is generated via recombination of two Si-Si bonds, has been developed.8,97 A bis(disilanyl)dithiane reacts with alkynes in the presence of a palladium/ isocyanide catalyst, giving five-membered ring bis-silylation products in high yield with elimination of hexamethyl-disilane (Scheme 14). The recombination, that is, bond metathesis, is so efficient that no product derived from direct insertion of acetylene into the Si-Si bonds of the bis(silyl)dithiane is formed at all. 

Palladium-catalyzed bis-silylation of benzynes has been achieved. Reaction of 2-trimethylsilylaryl triflates with cyclic disilanes in the presence of KF/18-crown-6 affords cyclic bis-silylation products in good yields (Equation (29)). It is crucially important to use the palladium-isocyanide catalyst.99 100... 

Intermolecular bis-silylation of highly strained bicyclopropylidene with hexaorganodisilanes proceeds at 70 °C in the presence of the palladium// r/-alkyl isocyanide catalyst (Equation (34)).102... 

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