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Coordinated experimental and orthogonal space random walk (OSRW) molecular dynamics simulation studies were performed to understand the exceptionally low temperature required for thermal conversion of a poly(phenylenevinylene) (PPV) precursor containing the macromolecular counterion poly(ethylene glycol)-4-nonylphenyl-3-sulfopropyl ether (PEGNOPS). Simulations of this solvent-free system converged for starting points where the backbone was artificially expanded or compressed. In this example of a polymer organized by a polymer, the simulations revealed the ability of PEGNOPS to partially preorder the precursor chain in a conformation that favors the E2 elimination pathway. [ABSTRACT FROM AUTHOR]

Addition of BF3·OEt2 to ethereal solutions of the Ni(ll) β-diketiminates (Me2NN]Ni(F1)(2,4-lutidine) (R = Et (1), Pr (2)) allows the isolation of the neutral β-H agostic monoalkyls (Me2NN]Ni(R) (R = Et (3), Pr (4)). X-ray studies of primary alkyls 3 and 4a reveal acute Ni-Cα-Cβ angles with short Ni-Cβ distances, indicating structures along the β-H elimination pathway. Positional disorder of the alkyl group in the X-ray structure of 4 corresponds to partial (22%) occupancy by the secondary alkyl [Me2NN)Ni(CHMe2) (4b). Variable-temperature NMR spectra of 3 and 4 reveal fluxional behavior that result from β-H elimination, in-plane rotation of the β-CH3 group, and a tetrahedral triplet structure for 3 that were investigated by density functional theory calculations at the Becke3LYP/6-31 G* level of theory without simplifications on the β-diketiminate ancillary ligand. Calculations support low temperature NMR studies that identify the linear β-H agostic propyl isomer 4a as the ground state with the branched β-H agostic isomer 4b slightly higher in energy. NMR studies and calculations show that the β-agostic 3 reluctantly coordinates ethene and that 3 is the ground state for this ethylene oligomerization catalyst. The thermodynamic isotope effect KH/KD = 1.3(2) measured for the loss of 2,4-lutidine from 1 to form β-agostic 3 was also examined by DFT calculations. [ABSTRACT FROM AUTHOR]