Novel Counter Ion Effect on the Disruption of the Homobimetallic Anion, (η5-MeCp)Mn(CO)2Mn(CO)5-M+ (M+=Na+, PPN+a) by PR3 (R=C6H5, C2H5, OCH3)

초록

The homobimetallic anion, (η5-MeCp)Mn(CO)<inf>2</inf>Mn(CO)<inf>5</inf> M+ (M+=Na+, PPN+) was disrupted by PR<inf>3</inf> (R=C<inf>6</inf>H<inf>5</inf>, C<inf>2</inf>H<inf>5</inf>, OCH<inf>3</inf>) in THF at various temperatures (r.t. ∼65°C) under the pseudo first order reaction conditions where excess of PR<inf>3</inf> was employed under a nitrogen atmosphere. For the reaction involving PPN+ analog, Mn-Mn heterolytic cleavage occurred, leading to PPN+Mn(CO)<inf>5</inf>- and (η5-MeCp)Mn(CO)<inf>2</inf>PR<inf>3</inf> as products; however, in case of Na+ analog, Na+ seems to play a novel counter ion effect on the disruption reaction by transferring one terminal CO from the Mn(CO)<inf>5</inf> moiety on to the (η5-MeCp)Mn(CO)<inf>2</inf> of the corresponding homobimetallic complex, eventually resulting in Na+Mn(CO)<inf>4</inf>PR<inf>3</inf>- and (η5-MeCp)Mn(CO)<inf>3</inf>. This reaction is of overall first order with respect to [homobimetallic complex] with the activation parameters (ΔH≠=23.0±0.7 kcal/mol, ΔS≠=-8.7±0.8 e.u. for Na+ analog; ΔH≠=28.8±0.4 kcal/mol, ΔS≠=15.7±0.6 e.u. for PPN+ analog reaction).