NOVEL COUNTER ION EFFECT ON THE DISRUPTION OF THE HOMOBIMETALLIC ANION, (ETA(5)-MECP)MN(CO)(2)MN(CO)(5)-M+ (M+=NA+, PPN+A) BY PR3 (R=C6H5, C2H5, OCH3)

The homobimetallic anion, (eta(5)-MeCp)Mn(CO)(2)Mn(CO)(5)(-) M+ (M+ = Na+, PPN+) was disrupted by PR3 (R = C6H5, C2H5, OCH3) in THF at vario us temperatures (r.t. similar to 65 degrees C) under the pseudo first order reaction conditions where excess of PR3 was employed under a nit rogen atmosphere. For the reaction involving PPN+ analog, Mn-Mn hetero lytic cleavage occurred, leading to PPN+Mn(CO)(5)(-) and (eta(5)-MeCp) Mn(CO)(2)PR3 as products; however, in case of Na+ analog, Na+ seems to play a novel counter ion effect on the disruption reaction by transfe rring one terminal CO from the Mn(CO), moiety on to the (eta(5)-MeCp)M n(CO)(2) of the corresponding homobimetallic complex, eventually resul ting in Na+Mn(CO)(4)PR3- and (eta(5)-MeCp)Mn(CO)(3). This reaction is of overall first order with respect to [homobimetallic complex] with t he activation parameters (Delta H-not equal = 23.0 +/- 0.7 kcal/mol, D elta S-not equal = -8.7 +/- 0.8 e.u. for Na+ analog; Delta H-not equal = 28.8 +/- 0.4 kcal/mol, Delta S-not equal = 15.7 +/- 0.6 e.u. for PP N+ analog reaction).