Nickel Polymerization Catalysts with Ylide Steering Ligands - Late Transition Metal Polymerization Catalysis - page 7

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1.2.2.1 NiPh(Ph 2 PCHCPhO)(Me 3 PCH 2 )1a
The 13 C{ 1 H} NMR spectrum of 1a displays 16 C resonances, some of which are
split by 31 P couplings, and which can be assigned to a structurally intact C-coordi-
nated ylide ligand, a nickel-bound phenyl ligand, and a chelating bidentate (PO)-li-
gand.

The Intact Ylide Ligand (Me 3 PCH 2 )
The nickel-bound anionic ylide carbon (

13 C=7.2 ppm) is the most strongly
shielded C center of the molecule. Its position signals a negative partial charge.
The four-line pattern stems from a doublet-of-doublets splitting (31 Hz/65 Hz) -
the smaller coupling can be assigned to the ( 31 P 13 C) one-bond interaction. The
size of the two-bond coupling is due to the special trans orientation of an ylide
and a phosphane ligand in a square planar nickel coordination sphere.
In the 1 H-coupled 13 C NMR spectrum each of the 4 lines splits further into a
1 : 2 : 1 triplet through interaction with the two magnetically equivalent directly
bound H atoms, resulting in a 12-line pattern. The 130 Hz ( 13 C 1 H) interaction in-
dicates a pyramidalization of the anionic ylide carbon by coordination on nickel.