Mechanism of Ethylene Oligomerization by the Catalytic System Ni(COD)2 / BF3·OEt2 Modified with Tertiary Phosphines

Gold‐Mediated Isomerization of ­Cyclooctyne to Ring Fused Olefinic Bicycles

“…[54,55] The X-ray structure of 4[SbF 6 ] ( Figure 2) revealed that the gold center adopts an essentially linear coordination geometry with a C (carbene) -Au-(-C≡C-centroid ) angle of 176.7°. The Au-C(carbene) and Au-(-C≡C-centroid ) distances are 2.012 (4) 6 ], they were also synthesized via independent routes using authentic free alkenes bicyclo [3.3.0]oct-1(5)-ene (2) [56,57] and cis-bicyclo-[3.3.0]oct-2-ene (3) [58] (prepared following literature procedures), and (IPr)AuSbF 6 6 ] are rotated by about 79°(average) relative to the carbene Au(N-C-N) planes whereas in 6[SbF 6 ], this angle is about 74°. The structurally authenticated alkenes adducts of (IPr)Au + show a range of such inter-planar angles from essentially coplanar to nearly perpendicular suggesting that the relative alkene orientation is determined largely by steric factors, [37] presumably arising from interaction with methyl hydrogens on the IPr ligand.…”

“…[64] Ni(COD) 2 /BF 3 ·OEt 2 mediated conversion of 1,5-cyclooctadiene to 3 has also been reported. [58] Base mediated routes from 1,5-or 1,3-cyclooctadiene to 3 are available as well. [65] Since one could speculate pathways to ring non-contracted olefins like 1,3-cyclooctadiene and 1,2-cyclooctadiene (an allene) via C-H insertions to 7 (and G rel values for cyclooctyne, 1,3-cyclooctadiene and 1,2-cyclooctadiene are 35.4, 13.6, and 29.8 kcal/mol), we tested the chemistry of 1,3-or 1,5-cyclooctadiene using either gold catalyst or strong acid (100 or 120°C in CHCl 3 ).…”

“…[66] and was dried using 4 Å molecular sieves (see below as well). (IPr)AuCl, [54] (IPr)AuCl 3 , [67] [(SIPr)Au(cyclooctyne)][SbF 6 ], [25] and AgNTf 2 , [68] bicyclo [3.3.0]oct-1(5)-ene, [56,57,69] and cis-bicyclo [3.3.0]oct-2-ene [58] were prepared according to reported procedures. AgSbF 6 was purchased from commercial sources and used as received.…”

Nickel Catalyzed Olefin Oligomerization and Dimerization

“…Additionally, alcohols are presented by Saraev et al as promoters of such Ni(0) systems, making possible the generation of an active Ni­(II) hydride or a coordinatively unsaturated cationic Ni­(I) species, described as being ten-times more active catalysts than the Ni­(II) hydride . On the basis of a related system, Kraikivskii et al proposed that when [Ni­(cod) 2 ] is reacted with BF 3 .Et 2 O, ethylene can be dimerized with a Ni­(I)/Ni­(III) metallacyclic mechanism . Schmidt et al.…”

“…Kraikivskii et al proposed that when [Ni(cod) 2 ] is reacted with BF 3 .Et 2 O, ethylene can be dimerized with a Ni(I)/Ni(III) metallacyclic mechanism 428. Schmidt et al focused on the same [Ni(PPh 3 ) 4 ] -BF 3 .Et 2 O system, but he postulated the presence of a Brønsted acid impurity that could form the catalytically active Ni(II) hydride species 429.…”