THE SYNTHESIS AND REACTIONS OF RE-I CARBOXYLIC-ACIDS - THE X-RAY STRUCTURE OF FAC-RE(CO)3(DPPP)CO2D.0.5C6D6

The metallocarboxylic acids Re(CO)3(P-P)C(O)OH where (P-P) is either dppe [1,2-bis(diphenylphosphino)ethane] or dppp [1,3-bis(diphenylphosphino)propane] and their deuterio analogs have been prepared from the reaction of [Re(CO)4(P-P)]+ BF4- with NaOH(D) and characterized. Concentrated benzene solutions of the dppp complex deposit the acid as a dimer with 1 mol of solvated benzene and the X-ray crystal structure study of the deuterio dimer acid is reported. The cationic salts, 1, do not react with alcohols unless base is present. However, the acids are immediately esterified when they are dissolved in alcohols by virtue of the acids' spontaneous ionization through acyl-oxygen cleavage to the cation and hydroxyl anion; the latter abstracts a proton to give the conjugate base of the alcohol required for esterification. Solutions of the acids in DMSO undergo slow decarboxylation to the corresponding hydrides; addition of KOH to either DMSO or DMF solutions results in immediate decarboxylation.