Synthetic Endeavors toward Titanium Based Frustrated Lewis Pairs with Controlled Electronic and Steric Properties
dataset
posted on 2015-05-26, 00:00 authored by Adrien
T. Normand, Philippe Richard, Cédric Balan, Constantin
G. Daniliuc, Gerald Kehr, Gerhard Erker, Pierre Le GendreA new family of cationic
Ti complexes <b>4</b>′ with
a pendant phosphine of general formula [CpCp<sup>P</sup>TiOAr][BPh<sub>4</sub>] (Cp = η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>; Cp<sup>P</sup> = η<sup>5</sup>-C<sub>5</sub>H<sub>4</sub>(CMe<sub>2</sub>)PR<sub>2</sub>) has been prepared in four steps from 6,6-dimethylfulvene.
These complexes were designed to behave as Ti based frustrated Lewis
pairs (FLPs). The key synthetic step is a reduction–oxidation
sequence from [CpCp<sup>P</sup>TiClOAr] complexes <b>3</b> using lithium phosphide salts as
the reductants and ferricinium tetraphenylborate as the oxidant. Four
complexes have been structurally characterized by X-ray diffraction
and show elongated Ti–P bonds, above 2.60 Å. One complex
(<b>4b</b>′: OAr = 2,6-Me<sub>2</sub>C<sub>6</sub>H<sub>3</sub>; PR<sub>2</sub> = PCy<sub>2</sub>) reacted with benzaldehyde
to form a typical FLP activation product. Complex <b>4b</b>′
also reacted with 2 equiv of <i>trans</i>-chalcone to form
a 10-membered Ti phosphonium macrocycle (<b>6b</b>′)
by extrusion of 6,6-dimethylfulvene.
