Cationic and Neutral Cp*M(NO)(κ<sup>2</sup>‑Ph<sub>2</sub>PCH<sub>2</sub>CH<sub>2</sub>PPh<sub>2</sub>) Complexes of Molybdenum and Tungsten: Lewis-Acid-Induced Intramolecular C–H Activation
Version 2 2017-03-02, 00:00
Version 1 2017-03-02, 17:12
dataset
posted on 2017-03-02, 00:00 authored by Rex C. Handford, Russell J. Wakeham, Brian O. Patrick, Peter LegzdinsTreatment
of CH<sub>2</sub>Cl<sub>2</sub> solutions of Cp*M(NO)Cl<sub>2</sub> (Cp* = η<sup>5</sup>-C<sub>5</sub>(CH<sub>3</sub>)<sub>5</sub>; M = Mo, W) first with 2 equiv of AgSbF<sub>6</sub> in the presence
of PhCN and then with 1 equiv of Ph<sub>2</sub>PCH<sub>2</sub>CH<sub>2</sub>PPh<sub>2</sub> affords the yellow–orange salts [Cp*M(NO)(PhCN)(κ<sup>2</sup>-Ph<sub>2</sub>PCH<sub>2</sub>CH<sub>2</sub>PPh<sub>2</sub>)](SbF<sub>6</sub>)<sub>2</sub> in good yields (M = Mo, W).
Reduction of [Cp*M(NO)(PhCN)(κ<sup>2</sup>-Ph<sub>2</sub>PCH<sub>2</sub>CH<sub>2</sub>PPh<sub>2</sub>)](SbF<sub>6</sub>)<sub>2</sub> with 2 equiv of Cp<sub>2</sub>Co in C<sub>6</sub>H<sub>6</sub> at 80 °C produces the corresponding 18e neutral
compounds, Cp*M(NO)(κ<sup>2</sup>-Ph<sub>2</sub>PCH<sub>2</sub>CH<sub>2</sub>PPh<sub>2</sub>) which have been isolated as
analytically pure orange–red solids. The addition of 1 equiv
of the Lewis acid, Sc(OTf)<sub>3</sub>, to solutions of Cp*M(NO)(κ<sup>2</sup>-Ph<sub>2</sub>PCH<sub>2</sub>CH<sub>2</sub>PPh<sub>2</sub>) at room temperature results in the immediate formation of thermally
stable Cp*M(NO→Sc(OTf)<sub>3</sub>)(H)(κ<sup>3</sup>-(C<sub>6</sub>H<sub>4</sub>)PhPCH<sub>2</sub>CH<sub>2</sub>PPh<sub>2</sub>) complexes in which one of the phenyl substituents
of the Ph<sub>2</sub>PCH<sub>2</sub>CH<sub>2</sub>PPh<sub>2</sub> ligands
has undergone intramolecular orthometalation. In a similar manner,
addition of BF<sub>3</sub> produces the analogous Cp*M(NO→BF<sub>3</sub>)(H)(κ<sup>3</sup>-(C<sub>6</sub>H<sub>4</sub>)PhPCH<sub>2</sub>CH<sub>2</sub>PPh<sub>2</sub>) complexes. In contrast,
B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> forms the 1:1 Lewis acid–base
adducts, Cp*M(NO→B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>)(κ<sup>2</sup>-Ph<sub>2</sub>PCH<sub>2</sub>CH<sub>2</sub>PPh<sub>2</sub>) in CH<sub>2</sub>Cl<sub>2</sub> at room temperature. Upon warming
to 80 °C, Cp*Mo(NO→B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>)(κ<sup>2</sup>-Ph<sub>2</sub>PCH<sub>2</sub>CH<sub>2</sub>PPh<sub>2</sub>) converts cleanly to the orthometalated product Cp*Mo(NO→B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>)(H)(κ<sup>3</sup>-(C<sub>6</sub>H<sub>4</sub>)PhPCH<sub>2</sub>CH<sub>2</sub>PPh<sub>2</sub>), but Cp*W(NO→B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>)(κ<sup>2</sup>-Ph<sub>2</sub>PCH<sub>2</sub>CH<sub>2</sub>PPh<sub>2</sub>) generates a mixture of products whose identities
remain to be ascertained. Attempts to extend this chemistry to include
related Ph<sub>2</sub>PCH<sub>2</sub>PPh<sub>2</sub> compounds have
had only limited success. All new complexes have been characterized
by conventional spectroscopic and analytical methods, and the solid-state
molecular structures of most of them have been established by single-crystal
X-ray crystallographic analyses.
