RESUMEN
A reaction between the (4,0) isomer of Ru 2(ap) 4Cl and LiC[triple bond]CC5H4N leads to a (3,1) isomer of Ru 2(ap) 4(C[triple bond]CC5H4N) 2 1 (ap = anilinopyridinate anion), whereas a reaction involving the (3,1) isomer of Ru 2(F 3ap) 4Cl and TBACl.H 2O leads to (4,0) Ru 2(F 3ap) 4Cl 2 (F 3ap = 2-(2,4,6-trifluoroanilino)pyridinate anion). To our knowledge, these are the first documented examples for isomeric conversion involving diruthenium compounds with tetracarboxylate-type structures. The structural, electrochemical, and spectroscopic properties of 1 and 2 were examined. The reversible Ru 2 (5+/6+) process of (3,1) [Ru 2(F 3ap) 4Cl] (+) is located at 0.62 V in CH 2Cl 2, 0.1 M TBAP but shifts to 0.29 V upon formation of (3,1) Ru 2(F 3ap) 4Cl 2 in CH 2Cl 2 containing chloride from added TBACl.H 2O and shifts even further to E 1/2 = 0.10 V after generation of (4,0) Ru 2(F 3ap) 4Cl 2 in solution. The 190 mV potential difference between the Ru 2 (6+/5+) redox couples of (3,1) Ru 2(F 3ap) 4Cl 2 and (4,0) Ru 2(F 3ap) 4Cl 2 in chloride-containing media can be compared to a smaller potential difference of only 60 mV between the Ru 2 (6+/5+) redox couples of (3,1) Ru 2(F 3ap) 4Cl and (4,0) Ru 2(F 3ap) 4Cl in CH 2Cl 2 containing 0.1 M tetrabutylammonium perchlorate (TBAP) as supporting electrolyte. The larger Delta E 1/2 in the case of the bis-chloride complexes in solutions containing 0.1 M TBACl.H 2O can be accounted for in large part by structural differences that manifest themselves in different strengths of axial coordination to the Ru 2 (5+) form of the compounds.