Polymorphism of a nickel polymerization catalyst

Highly Active Single-Component Neutral Nickel Ethylene Polymerization Catalysts: The Influence of Electronic Effects and Spectator Ligands

“…The phosphine ligand in the three complexes is situated in the trans position of the N-aryl group, respectively, as in the case of B and α-iminocarboxamide-based benzyl nickel trimethylphosphine complexes . Comparing the Ni−PPh 3 distances of 6b-PPh 3 (2.165(4) Å) (two independent molecules with slightly different bond lengths and angles crystallized in the asymmetric unit, and the average values were used for comparison) with reported complexes bearing similar steric hindrance, we found that the distances are shorter than the nitro-bearing complex 6a (2.1851(11) Å), cyclohexyl-substituted complex [6-CHN(2,6- i Pr 2 C 6 H 3 )-3-Cy-5-Me-C 6 H 3 O-κ 2 - N,O ]Ni(Ph)(PPh 3 ) (2.182(2) Å), phenyl-substituted complex (2.1838(12) Å), and the complex with no substituent in the C3 position (2.1833(5) Å), which implies that the electron-withdrawing group in 6b-PPh 3 may strengthen the Ni−PPh 3 bond and consequently hamper the initiation process. As for 6b- 1 Bz , the wide angles of O1−Ni1−C26 (164.35(11)°) and N1−Ni1−P1 (163.26(7)°) also reveal a slightly distorted square-planar geometry and the trans arrangement of the PMe 3 and N-aryl moieties.…”