Question

(1) what is the chemical driving force for the conversion of Mn(III)(salpn)(AcAc) to the Mn(III)(salpn)(H2O)₂⁺ complex?

Experiment Guide:

[MnIII(salpn)(H2O)2](CF3SO3) In a round bottom flask, to a slurry of 1.5 mmoles MnIII(salpn)(AcAc) (0.65 g) in 15 mL of acetonitrile, add 1.5 mmol of trifluoromethanesulfonic acid (triflic acid, 1.5 ml of a 1.0 M solution in acetonitrile) dropwise.

• Stir 15 minutes, filter if some solid remains, then reduce solvent to about 5 ml by rotary evaporation (do not reduce the solvent too much).

• Transfer concentrated solution/slurry to a 100-250 mL beaker. • Add about 25 ml ether to the solution and collect the solid by vacuum filtration.

• When it is dry, determine the yield.

Answer 1

A variety of Mn(III)salpn complexes as monomeric and dimeric derivatives have been prepared. Acetonitrile solutions of tetragonal complexes such as [Mn(III)(SALPN)(CH3OH)2]ClO4, are unreactive with trifluoromethasulfonic acid unless base is added. In contrast, Mn(III)(salpn)(AcAc), internally carry an equivalent of base (AcAc^-) and react rapidly to form Mn(III)(salpn)(H₂O)₂⁺, the base is required to deprotonate the trifluoromethasulfonic acid prior to reaction. The base is the chemical driving force