Controlled Acrylate Insertion Regioselectivity in Diazaphospholidine- Sulfonato Palladium(II) Complexes

Diazaphospholidine-sulfonato Pd(II) complexes [{.r-P,O-(N-Ar!C214N!P)C6H4S03}PdMe(L)] l-L (L::: dmso, pyridine, hltidine, or Jl-LiCI(solvent)j la: Ar = Ph, Ib: Ar = 2-MeC614, lc: Ar = 2-MeOC6H", Id: Ar ::: 2,4,6-Me3C6H!J le: Ar = 2,6-iPr2C6H3' If: Ar = 2,6-(p-tolyl)2C6H3) were prepared and structurally characterized. The regioselectivity of methyl acrylate (MA) insertion into the Pd-Me bond is entirely inverted from >93% 1,2-insertion for bulky substituents (Id;.,t; yielding the insertion products [(PO)Pd{.r-CP-CH2CHMeC(O)OMe], 12) to the usual electronically controlled 2,l-insertion (>95%) for the less bulky Ar ::: Ph (la, yielding the insertion product [(pAO )Pd{.r-C,O-CHEtC( O)OMe], 11, and fJ-H elinlination product methyl crotonate). DFT studies underline that this is due to a more favorable insertion transition state (2,1favored by 12 k] mor-I over 1,2for la) vs destabilization of the2,i-insertion transition state in Id,e. By contrast, MA insertion into the novel isolated and structurally characterized hydride and deuteride complexes [{ T!-P,O-(N-Ar2C2H4N2P)C6H4S03}PdR(Iutidine)] (Ar = 2,6-iPr2C6H3; ge: R = H, lOe: R::: D) occurs 2,I-selectively. This is due to the insertion occurring from the isomer with the Pdonor and the olefin in trans arrangement, rather than the insertion into the alkyl from the cis isomer in which the olefin is in proxinlity to the bulky diazaphospholidine. la-f are precursors to active catalysts for ethylene polymerization to highly linear polyethylene with M" up to 35 OOOg morI. In copolymerization experiments, notbornene was incorporated in up to 6.1 mol % into the polyethylene backbone. .