Palladium complexes isocyanide

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. 

Addition of distannane to alkenes has been achieved only with strained cyclopropenes (Equation (60)).158 3,3-Disubstituted cyclopropenes undergo highly face-selective distannation in the presence of the palladium-isocyanide complex to afford m-adducts. 

The palladium-isocyanide complex is effective for silastannation of ethoxyethyne, a labile alkyne, to produce (Z)-1-ethoxy-l-silyl-2-stannylethene with high regioselectivity (Equation (106)).253 The regioselectivity observed has also been studied by computation.263... 

Palladium isocyanide complexes react with amines and alcohols to give palladium Carbene Complexes (equation 15) in a reaction that is a nucleophihc attack on the isonitrile carbon. These complexes easily lose a halide if it is trans to the carbene hgand, since the carbene carbon has a high trans influence. The structures of these compounds have the carbene carbon and its two heteroatom groups in one plane, which is perpendicular to the coordination plane of the Pd. 

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-... 

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... 

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>. 

Benzyne, which is generated in situ from 2-(trimethylsilyl)phenyl triflate and KF, acts as an alkyne congener in distannation in the presence of palladium-/ r/-alkyl isocyanide complex.157 A variety of substituted benzyne derivatives inserts into the Sn-Sn bond to give l,2-bis(stannyl)benzenes (Equation (59)). The reaction fails to occur in the presence of other palladium catalysts such as Pd(PPh3)4. 

Tanase, T., Ukaji, H. and Yamamoto, Y. (1995) Dinuclear palladium(l) complexes with isocyanide and N-donor bidentate ligands. /. Chem. Soc., Dalton Trans., 3059-54. 

This compound reacts readily with alkyl isocyanides to give a cluster Pd(CNR)2 ,6 and with bulky alkyl phosphines to give two coordinated palladium(O) complexes.7... 

Chemical routes to palladium(I) and platinum(I) isocyanide complexes have been devised. Addition of CNMe to an aqueous solution of [MC14]2-(M = Pd, Pt) resulted in the rapid formation of [M(CNMe)4]2+ cations, which were isolated as the hexafluorophosphate salts. On standing, however, the cations [M(CNMe)4]2+ slowly converted over 18 hr to [M CNMe ]2 ... 

Activation of two Si—Si bonds in bis(disilanyl)alkanes with palladium(O) bis(tert-alkyl isocyanide) induced the formation of the cyclic bis(silyl)palladium(II) bis(terf-alkyl isocyanide) complexes (100) and disilanes described schematically in Scheme 42. These complexes were found to react with phenylacetylene, affording different amounts of five-membered cyclic products and acyclic products which are derived from the insertion of the alkyne into the general intermediate complex 101 (Scheme 42, equation 54). The bis(silanyl)dithiane palladium complex (102) was isolated and characterized in the solid state the two silicon atoms, the two isocyano carbons and the palladium atom are nearly in a plane with a short cross-ring Si—Si distance of 2.613(2) A, suggesting the possibility of covalently bonded two Si—Si atoms in the four-membered ring. Similar reaction with cyclic disilanes afforded oligomers, and cyclic 20-membered compounds have been prepared in the presence of nitriles248,249. 

J. S. Miller, and A. L. Balch, Preparation and Reactions of Tetrakis(methyl isocyanide) Complexes of Divalent Nickel, Palladium, and Platinum, Inorg. Chem. 11, 2069-2074 (1972). 

Addition reactions of the Si-Si cr-bonds of disilanes 121, 131, and 133 to the C=C bonds of various arynes were found to be promoted by a palladium-1,1,3,3-tetramethylbutyl isocyanide complex. Diverse 1,2-disilylated arenes 130, 132, and 134 were obtained from five-membered and benzo-condensed six-membered cyclic disilanes (Equations 21-23). The H, 13C, and z9Si NMR spectroscopic data as well as X-ray crystallographic analysis were used to confirm the above structures <20050M156>. 

In the reactions of episulfides ring opening usually occurs, as in the reaction between palladium(Il) isocyanide complexes of type 165 (L =... 

Similar insertion reactions have been found for the palladium(II) complex that results from reaction (f), which reacts with o-xylyl-isocyanide to give the triple insertion product, with a five-membered ring including palladium. 

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... 

An X-ray analysis of the air-sensitive crystal of the bis( 1-adamantyl isocyanide)pal-ladacycle complex 3b revealed a square planar structure with two coordinated isocyanide figands on the palladium atom. An addition of phosphine Ugands to a solution of 3 induced reductive elimination of the Si—Si bond to give 1,2-disilacyclopentane 2. Thus, tert-alkyl isocyanide ligand plays a critical role to stabilize bis(organosilyl)palladium(ll) complexes. 

Isocyanides. Several instances for nickel(ii) and palladium(ii) complexes have been suggested. - One interesting feature is that whereas carbon monoxide only inserts once into a given bond, isocyanides can insert repeatedly, providing a potential route for catalytic polymerisation. ... 

Palladium(II) complexes are reduced to Pd(0) complexes in strongly basic medium containing excess of isocyanide ... 

Isocyanide complexes have found numerous applications in organic synthesis and catalysis. Isocyanides undergo polymerization in the presence of many transition metal complexes, for instance, metal carbonyls, metallocenes, cyclopentadienyl carbonyls, nickel(II), palladium(II), and cobalt(II) complexes. Exceptionally high activity is exhibited by nickel and cobalt carbonyls. The resulting polymers are Schiff bases ... 

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