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Modified 13C NMR assignments of the aromatic C-2 carbon of poly(2-vinylpyridine) in methanol-G?4 are proposed on the basis of compliance with the necessary statistical relations between pentad sequence intensities. The spectral analysis shows that the C-2 resonance assignments are more complex than previously believed. The relative ordering of the mmrm and mmrr pentad resonances is opposite to previous assignments. Significant overlap between the rmmr and mmrr pentads is found, indicating that the separation of the isotactic and heterotactic triads is not clean. The three syndiotactic pentad resonances could be reliably identified.

The alkylation, silylation and other electrophilic reactions of l-lithio-l,3-bis(2-pyridyl)butane (2a) in THF at -78 "C leads to meso-like products that may be accounted for by intramolecular coordination of Li ion with the penultimate 2-pyridyl group. This is also demonstrated by proton-transfer equilibria between l-lithio-2ethylpyridine and 2a, allowing the determination of the AH and AS of intramolecular chelation in 2a. The AS of chelation is nearly zero, probably as a result of chelation-induced desolvation of Li ion. Surprisingly, however, the corresponding addition of 2-vinylpyridine to 2a and higher P2VPLi homologs in THF is not stereoselective. In toluene at -78 "C the t-BuLi-initiated polymerization of 2-VP is actually somewhat syndiotactic (rr=0.44). The presence in this polymerization of at least one equivalent of t-BuOLi or other tertiary ROLi surprisingly leads to isotactic P2VP. SEC viscometric and other studies indicate that both the P2VPLi-and P2VPLi-ROLi complexes are monomeric in toluene. The stereochemistry is apparently due to a 1 : 1 P2VPLi-ROLi complex that discriminates between the two pro-chiral faces of the anion by preferential coordination of the (ROLi,) moiety to the meso-prochiral face. Isotactic-like addition now occurs by electropbilic attack of 2-VP that is syn with respect to the (ROLi,) 'counter ion.'