Interconversion between (3,1) and (4,0) isomers of Ru2(L)4X complexes where L is 2-anilinopyridinate or 2-(2,4,6-trifluoroanilino)pyridinate anion and X = Cl- or C=CC5H4N-

A reaction between the (4,0) isomer of Ru-2(ap)(4)Cl and LiC CC5H4N leads to a (3,1) isomer of Ru-2(ap)(4)(C CC5H4N)(2) 1 (ap = anilinopyriclinate anion), whereas a reaction involving the (3, 1) isomer of Ru-2(F(3)ap)(4)Cl and TBACl center dot H2O leads to (4,0) Ru-2(F(3)ap)(4)Cl-2 (F(3)ap = 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(3)ap)(4)Cl](+) is located at 0.62 V in CH2Cl2, 0.1 M TBAP but shifts to 0.29 V upon formation of (3,1) Ru-2(F(3)ap)(4)Cl-2 in CH2Cl2 containing chloride from added TBACl center dot H2O and shifts even further to E-1/2 = 0.10 V after generation of (4,0) Ru-2(F(3)ap)(4)Cl-2 in solution. The 190 mV potential difference between the Ru-2(6+/5+) redox couples of (3,1) Ru-2(F(3)ap)(4)Cl-2 and (4,0) Ru-2(F(3)ap)(4)Cl-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(3)ap)(4)Cl and (4,0) Ru-2(F(3)ap)(4)Cl in CH2O2 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 center dot H2O 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.