Abstract
AbstractNickel(II)‐aryl complexes [(L2)Ni(Ar)Br] bearing either chiral phosphine ligands (L2 = RR‐ or SS‐DIPAMP, Ar = ortho‐anisyl), or a chiral aryl‐group have been prepared, and their structural optical an chiroptical properties have been characterized. Enantiomeric pairs of both catalysts have been used for the asymmetric polymerization of different isocyanides (M1, M2, M3), to give well defined polyisocyanides (P1, P2, P3). Their polymerization behavior has been studied, which confirmed chain‐growth polymerization in all cases. The asymmetric induction has been verified by circular dichroism spectroscopy on enantiomeric pairs of all three polymers.
Highlights
C3/C1: Ar = ortho-anisyl, C3*/C2: Ar = R-/S-1-trimethylsilyloxyethyl)-phenyl, C1: L2 = RR-/ SS-DIPAMP, C2: L2 = DPPE. cod: 1,5-cyclooctadiene were prepared via a modified known procedure (Scheme 2).[34]
We have introduced new nickel precatalysts of the type [(L2)Ni(Ar)Br], bearing either chiral chelating phosphine ligands (RR-/SS-dipamp) (C1) or a chiral aryl-substituent (C2)
Polymerization experiments with the fulvenylfunctionalized M2 showed that both catalysts reliably initiate chain-growth polymerization, and give access to high molecular weight materials (Mn 50–100 kg/mol, degrees of polymerization (DPn) = 100–230)
Summary
Abstract Nickel(II)-aryl complexes [(L2)Ni(Ar)Br] bearing either chiral phosphine ligands (L2 = RR- or SS-DIPAMP, Ar = ortho-anisyl), or a chiral aryl-group have been prepared, and their structural optical an chiroptical properties have been characterized. A similar effect has been observed in the structurally related complex [(dppe)Ni(ortho-anisyl)Br],[34] wherein the anisyl-ring stands at an angle of 88.3 (1) relative to the coordination plane, and the OÁ Á ÁNi-distance (2.871 (2) Å) is smaller than the van-der-Waals radii.
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