1,3-Cyclopentadiene palladium complex

In 2005, Carretero et al. reported a second example of chiral catalysts based on S/P-coordination employed in the catalysis of the enantioselective Diels-Alder reaction, namely palladium complexes of chiral planar l-phosphino-2-sulfenylferrocenes (Fesulphos). This new family of chiral ligands afforded, in the presence of PdCl2, high enantioselectivities of up to 95% ee, in the asymmetric Diels-Alder reaction of cyclopentadiene with A-acryloyl-l,3-oxazolidin-2-one (Scheme 5.17). The S/P-bidentate character of the Fesulphos ligands has been proved by X-ray diffraction analysis of several metal complexes. When the reaction was performed in the presence of the corresponding copper-chelates, a lower and opposite enantioselectivity was obtained. This difference of results was explained by the geometry of the palladium (square-planar) and copper (tetrahedral) complexes. 

These studies were extended to hydrosilation of cyclopentadiene with trichlorosilane (52). This is most difficult with platinum catalysts. Palladium complexes favored production of 1 1 adducts as a mixture of 3- and 4-trichlorosilylcyclopentene. Nickel complexes produced substantial amounts of 1 2 adducts as trichlorosilyl-substituted 4,7-methylene-4,7,-8,9-tetrahydroindanes, with the exception of nickel tetracarbonyl, which was very active and selectively formed almost exclusively 3-trichlorosi-lylcyclopentene with no 1 2 adduct. 

A palladium complex of tropyne (230) has been prepared by the same method used for 223.86 Interestingly, in contrast to all of the platinum tropyne complexes (223, 226, 235), which are stable at room temperature, the palladium complex is thermally labile, decomposing at -35°C with a half-life of about 3 h. Reactions of 230 with KBEt3H, LiAl(0-f-Bu)3H, HBr, or cyclopentadiene gave only intractable mixtures. 

Stereoselective hydrosilylation of 1,3-cyclopentadiene giving (f )-3-trimethylsilyl-1 -cydopen-tene [(/ )-13] can be achieved using ferrocenylphosphine-palladium complexes as catalysts15. 

A o,jt-bonded alkyl-palladium complex undergoes P-carbon elimination on protonation of the cyclopentadiene ring [79]. 

The hydrosilylation of cyclopentadiene with chlorohydrosilanes catalyzed by a phosphine-palladium complex gives 3-silylpent-l-ene in high yield . 

Asymmetric hydrosilylation of cyclopentadiene and cyclohexa-1,3-diene using chiral phosphine-palladium complexes gives optically active 3-trimethylsilylcyclohex-1-ene after methylation ... 

Asymmetric hydrosilylation of cyclopentadiene and 1,3-cyclohexadiene was performed using chiral phosphine-palladium complexes to give optically active 3-trimethylsilyl-1-cyclopentene95 and 3-trimethylsilyl-l-cyclohexene68, respectively, after methylation (equations 42 and 43). 

C,2H, )N2, Azobenzene, cobalt and palladium complexes, 26 175,176 manganese complex, 26 173 C,2H N, Pyridine, 2-(phenylmethyl)-, palladium complex, 26 208-210 C,2H, P, Phosphine, diphenyl-, manganese complex, 26 158,226-230 ruthenium complex, 26 264 C 2H,2, Toluene, a-2,4-cyclopentadiene-l-yl-, chromium, molybdenum and tungsten hexacaibonyl complexes, 28 148... 

In an alternative route to the prostaglandins from cyclopentadiene, Holton has made use of the technique of so-called carbo-palladation , whereby the two side-chain fragments are attached in sequence to the double bonds of cyclopentadiene via appropriate palladium complexes. Thus treatment of the enamine (58), derived from cyclopentadiene, with lithium tetrachloropalladate and sodium diethylmalonate led to the palladium complex (59) which with di-iso-... 

Ligand-substitution reactions (or nucleophilic attack at the metal) in cyclopentadienyl complexes of palladium have been used to prepare new derivatives. The classical introduction of a cyclopentadienyl moiety by use of TlCp or NaCp and a cationic or halo palladium complex has been employed in the synthesis of complexes [Pd( 7 -Cp)(dppe)]Tf " and PdCp 3-(CHO)C6H3C(H)=NCy. A novel route has been applied that involves deprotonation of cyclopentadiene by a coordinated hydroxyl group to afford the cyclopentadienyl complexes shown in Equation (63). ... 

C2ftH3u02Pd, dihapto-Cyclopentadiene-acetylacetone-palladium complex, 39B, 570... 

In 2005, Yoshida et al. disclosed that distannylation of arynes was accompanied by dimerization of arynes by use of phosphite, ETPO (4-ethyl-2,6,7-trioxa-l-phosphabicyclo[2.2.2]octane), as a ligand for a palladium catalyst to produce diverse 2,2 -bis(trimethylstannyl)biaryls 51 in one step (Scheme 28.19) [25]. The dimerizative insertion into an Sn—Sn a-bond should be initiated by the formation of pallada-cyclopentadiene 52 from the palladium complex and two molar amounts of arynes. 

Yasuda S, Yorimitsu H, Oshima K (2008) Synthesis of aryliron complexes by palladium-catalyzed transmetalation between [CpFe(CO)2l] and aryl Grignard reagents and their chemistry directed toward organic synthesis. Organometallics 27 4025 027 Jonas K, Schieferstein L (1979) Simple route to Li- or Zn-metalated r -cyclopentadien-yliron-olefin complexes. Angew Chem Int Ed Engl 18 549-550... 

Fischer and Werner (218) have reported the preparation of the Pd(0)-olefin complex (cyclopentadiene)( 1,3-cyclohexadiene)palladium-(0). Initially they prepared dimeric (l,3-cyclohexadiene)dichloropal-ladium(II) by reaction of the diene with Pd(CO)Cl2, which was, in turn, reacted with cyclopentadienylpotassium. The red, air-stable, monomeric complex was diamagnetic, soluble in most organic solvents, and had a dipole moment of 2.11 Z) in agreement with the tetrahedral structure (204). 

The [Ir(C6H6)2]+ ion, analogous to the [00(05115)2] + and [Rh(05115)2]+ ions, also has been obtained and investigated as was expected, it showed similar properties. The uncharged complex Ir (05115)2, like Rh(C6H6)2, has not yet been prepared. For palladium and platinum only simple olefin complexes are, as yet, known. Among these there is also a complex of platinous chloride with cyclopentadiene, but physical evidence excludes the possibility of a sandwich structure in this compound (29). 

Diazomethane generateti in the presence of palladium compounds has been shown to undergo addition to the double bond of the norbornene fragment of the cyclopentadiene dimer, e.g. formation of 14 and This was attributed to the formation of a 7t-alkene complex of... 

Recently, a palladium(II) complex with a chiral (S)-BINAP ligand was shown to induce an excellent enantioselectivity in the model reaction of iV-acryloyl-l,3-oxazolidin-2-one with cyclopentadiene. ... 

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