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Mono and dinuclear rhodium, iridium and ruthenium complexes containing chelating 2,2′-bipyrimidine ligands: Synthesis, molecular structure, electrochemistry and catalytic properties
Auteur(s)
Govindaswamy, Padavattan
Canivet, Jérôme
Štěpnička, Petr
Ludvík, Jiří
Date Issued
2007
Journal
Journal of Organometallic Chemistry, Elsevier, 2007/692/17/3664-3675
Abstract
The mononuclear cations [(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)RhCl(bpym)]<sup>+</sup> (<b>1</b>), [(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)IrCl(bpym)]<sup>+</sup> (<b>2</b>), [(η<sup>6</sup>-p-Pr<i>i</i>C<sub>6</sub>H<sub>4</sub>Me)RuCl(bpym)]<sup>+</sup> (<b>3</b>) and [(η<sup>6</sup>-C<sub>6</sub>Me<sub>6</sub>)RuCl(bpym)]<sup>+</sup> (<b>4</b>) as well as the dinuclear dications [{(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)RhCl}<sub>2</sub> (bpym)]<sup>2+</sup> (<b>5</b>), [{(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)IrCl}<sub>2</sub> (bpym)]<sup>2+</sup> (<b>6</b>), [{(η<sup>6</sup>-p-Pr<sup><i>i</i></sup>C<sub>6</sub>H<sub>4</sub>Me)RuCl}<sub>2</sub> (bpym)]<sup>2+</sup> (<b>7</b>) and [{(η<sup>6</sup>-C<sub>6</sub>Me<sub>6</sub>)RuCl}<sub>2</sub> (bpym)]<sup>2+</sup> (<b>8</b>) have been synthesised from 2,2′-bipyrimidine (bpym) and the corresponding chloro complexes [(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)RhCl<sub>2</sub>]<sub>2</sub>, [(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)IrCl<sub>2</sub>]<sub>2</sub>, [(η<sup>6</sup>-Pr<sup><i>i</i></sup>C<sub>6</sub>H<sub>4</sub>Me)RuCl<sub>2</sub>]<sub>2</sub> and [(η<sup>6</sup>-C<sub>6</sub>Me<sub>6</sub>)RuCl<sub>2</sub>]<sub>2</sub>, respectively. The X-ray crystal structure analyses of [<b>3</b>][PF<sub>6</sub>], [<b>5</b>][PF<sub>6</sub>]<sub>2</sub>, [<b>6</b>][CF<sub>3</sub>SO<sub>3</sub>]<sub>2</sub> and [<b>7</b>][PF<sub>6</sub>]<sub>2</sub> reveal a typical piano-stool geometry around the metal centres; in the dinuclear complexes the chloro ligands attached to the two metal centres are found to be, with respect to each other, cis oriented for <b>5</b> and <b>6</b> but <i>trans</i> for <b>7</b>. The electrochemical behaviour of <b>1–8</b> has been studied by voltammetric methods. In addition, the catalytic potential <b>of 1–8</b> for transfer hydrogenation reactions in aqueous solution has been evaluated: All complexes catalyse the reaction of acetophenone with formic acid to give phenylethanol and carbon dioxide. For both the mononuclear and dinuclear series the best results were obtained (50 °C, pH 4) with rhodium complexes, giving turnover frequencies of 10.5 h<sup>−1</sup> for <b>1</b> and 19 h<sup>−1</sup> for <b>5</b>.
Publication type
journal article
