Synthesis of (Adamantylmido)vanadium(V)-Alkyl, Alkylidene Complex Trapped with PMe<sub>3</sub>: Reactions of the Alkylidene Complexes with Phenols
dataset
posted on 2015-12-17, 05:58 authored by Kohei Hatagami, Kotohiro NomuraV(CHSiMe<sub>3</sub>)(NAd)(CH<sub>2</sub>SiMe<sub>3</sub>)(PMe<sub>3</sub>)<sub>2</sub> (<b>1</b>, Ad = 1-adamantyl)
has been isolated from V(NAd)(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>3</sub> in the presence of PMe<sub>3</sub> (excess, 12 equiv) upon
heating, and the reaction of <b>1</b> with 2,6-Me<sub>2</sub>C<sub>6</sub>H<sub>3</sub>OH in <i>n</i>-hexane afforded
V(CHSiMe<sub>3</sub>)(NAd)(O-2,6-Me<sub>2</sub>C<sub>6</sub>H<sub>3</sub>)(PMe<sub>3</sub>)<sub>2</sub> (<b>2a</b>); structures
of <b>1</b> and <b>2a</b> have been determined by X-ray
crystallography. Reaction of <b>1</b> with C<sub>6</sub>F<sub>5</sub>OH in C<sub>6</sub>D<sub>6</sub> afforded a mixture of V(CHSiMe<sub>3</sub>)(NAd)(OC<sub>6</sub>F<sub>5</sub>)(PMe<sub>3</sub>)<sub>2</sub> (<b>2b</b>) and V(NAd)(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub>(OC<sub>6</sub>F<sub>5</sub>) (<b>3b</b>) and the PMe<sub>3</sub> adduct (<b>3b</b>-<b>PMe</b><sub><b>3</b></sub>), and the consumption rate of <b>1</b> decreased upon addition of PMe<sub>3</sub> or use of C<sub>6</sub>F<sub>5</sub>OD in place of C<sub>6</sub>F<sub>5</sub>OH, clearly
suggesting that the reaction proceeds via coordination of C<sub>6</sub>F<sub>5</sub>OH and subsequent reaction with the alkylidene or the
alkyl moiety. The catalytic activity in the ring-opening metathesis
polymerization (ROMP) of norbornene by <b>1</b> increased upon
addition of phenol; <b>1</b>-C<sub>6</sub>F<sub>5</sub>OH catalyst
showed a remarkable activity (TOF 20 000 h<sup>–1</sup>), affording high molecular weight polymer with a unimodal molecular
weight distribution. Reactions with <b>2a</b>,<b>b</b> with phenol afforded the bis(phenoxy) complexes, and it has been
suggested that these reactions proceed via coordination of phenol
and subsequent reaction with the alkylidene accompanying phenoxy exchange
on the vanadium.
