Synthesis of (Adamantylmido)vanadium(V)-Alkyl, Alkylidene Complex Trapped with PMe3: Reactions of the Alkylidene Complexes with Phenols
dataset
posted on 2015-12-17, 05:58 authored by Kohei Hatagami, Kotohiro NomuraV(CHSiMe3)(NAd)(CH2SiMe3)(PMe3)2 (1, Ad = 1-adamantyl)
has been isolated from V(NAd)(CH2SiMe3)3 in the presence of PMe3 (excess, 12 equiv) upon
heating, and the reaction of 1 with 2,6-Me2C6H3OH in n-hexane afforded
V(CHSiMe3)(NAd)(O-2,6-Me2C6H3)(PMe3)2 (2a); structures
of 1 and 2a have been determined by X-ray
crystallography. Reaction of 1 with C6F5OH in C6D6 afforded a mixture of V(CHSiMe3)(NAd)(OC6F5)(PMe3)2 (2b) and V(NAd)(CH2SiMe3)2(OC6F5) (3b) and the PMe3 adduct (3b-PMe3), and the consumption rate of 1 decreased upon addition of PMe3 or use of C6F5OD in place of C6F5OH, clearly
suggesting that the reaction proceeds via coordination of C6F5OH and subsequent reaction with the alkylidene or the
alkyl moiety. The catalytic activity in the ring-opening metathesis
polymerization (ROMP) of norbornene by 1 increased upon
addition of phenol; 1-C6F5OH catalyst
showed a remarkable activity (TOF 20 000 h–1), affording high molecular weight polymer with a unimodal molecular
weight distribution. Reactions with 2a,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.
