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Issue 12, 1999
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Migratory insertion reactions of norbornene, norbornadiene and 7-oxanorbornene derivatives into the palladium–carbon bond of heterodinuclear Fe–Pd–Acyl complexes. Substrate influence on the Pd coordination sphere and crystal structure of [(OC)3Fe[upper bond 1 start]{µ-Si(OMe)2(O[lower bond 1 start]Me)}(µ-dppa)Pd[upper bond 1 end][lower bond 1 end][upper bond 1 start]{C9H9NO3C([double bond, length half m-dash]O[upper bond 1 end])Me}]

Abstract

[(OC)3Fwe{µ-Si(OMe)2(OMe)}(µ-dppm)Pzd{C(2O)Me}] (1a) (dppm=Ph2PCH2PPh2) to afford the heterodinuclear complexes [(OC)3{(MeO)3Si}Fwe(µ-dppm)Pzdw{C7H10C(2Oz)Me}] (2) and [(OC)3{(MeO)3Si}- Fwe(µ-dppm)Pzdw{C7H8C(2Oz)Me}] (3), respectively. In these insertion products, the alkoxysilyl ligand has become terminally bound whereas a dative bond between the acetyl oxygen and the metal allows the square-planar Pd centre to achieve a 16e configuration, thus resulting in a five-membered Pwd–C–C–C–Oz ring. This chemistry was extended to chiral olefins and when the dppm and dppa complexes 1a,b were reacted with a 9:1 mixture of (±)-(2-cyano-7-oxabicyclo[2.2.1]hept-5-ene-2-endo-yl and -2-exo-yl acetate (4,4′), the stable insertion products [(OC)3Fwe{µ-Si(OMe)2(OMe)}(µ-Ph2PXPPh2)Pzdw{C9H9NO3C(2Oz)Me}] (5a,5a′ X=CH2; 5b,5b′ X=NH) were isolated in high yield. A high stereo- and regioselectivity was found for these metallacarbonylations. Spectroscopic data as well as X-ray diffraction studies show that in contrast to 2 and 3, the µ22-Si–O interaction present in the precursors 1a,b is retained in 5a,b. The Pd atom adopts a pseudo square-pyramidal coordination resulting from an additional weak ketonic interaction with the 5-exo-acetyl group of the 2-endo-acetoxy-2-cyano-7-oxabicyclo[2.2.1]hept-5-exo-yl moiety, which leads to the formation of a five-membered chelate ring. Electronic effects are invoked to account for these different structural features. Under a carbon monoxide atmosphere, CO migratory insertion into the Pd–oxanorbornyl bond of pure 5a,b occurs and leads to the acyl complexes [(OC)3Fwe{µ-Si(OMe)2(OMe)}(µ-Ph2PXPPh2)Pzd{C(2O)C9H9NO3C(2O)Me}] (6a X=CH2; 6b X=NH). These successive insertion reactions constitute the first elementary steps on the way to polyketone chain growth mediated by a bimetallic system.

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Supplementary files


Article type: Paper
DOI: 10.1039/A905842G
New J. Chem., 1999,23, 1215-1222

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    Migratory insertion reactions of norbornene, norbornadiene and 7-oxanorbornene derivatives into the palladium–carbon bond of heterodinuclear Fe–Pd–Acyl complexes. Substrate influence on the Pd coordination sphere and crystal structure of [(OC)3Fe[upper bond 1 start]{µ-Si(OMe)2(O[lower bond 1 start]Me)}(µ-dppa)Pd[upper bond 1 end][lower bond 1 end][upper bond 1 start]{C9H9NO3C([double bond, length half m-dash]O[upper bond 1 end])Me}]

    P. Braunstein, J. Cossy, M. Knorr, C. Strohmann and P. Vogel, New J. Chem., 1999, 23, 1215
    DOI: 10.1039/A905842G

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