The reaction of cis-{(η 5 -C 5 H 3 ) 2 (CMe 2 ) 2 }-Ru 2 (CO) 4 Br 2 with naphthalene affords the syn-facial [cis-{(η 5 -C 5 H 3 ) 2 (CMe 2 ) 2 }Ru 2 (μ-η 6 ,η 6 -C 10 H 8 )][OTf] 2 , (2 2+ ), a complex that appears to be two electrons short of the 18electron rule. Density functional theory (DFT) calculations suggest that the Ru atoms satisfy their missing valence by a combination of a weak metal−metal bond and sharing electrons from the central π bond of the naphthalene. The one-electron reduction of 2 2+ yields 2 + , a Class II mixed-valence complex, while the two-electron reduction of 2 2+ causes a hapticity change from η 6 to η 4 on one of the naphthalene rings and yields cis-{(η 5 -C 5 H 3 ) 2 (CMe 2 ) 2 }Ru 2 (μ-η 6 ,η 4 -C 10 H 8 ) (2 0 ), a zwitterionic complex. The DFT calculations predict that the C s isomer of 2 0 is 4.69 kcal/mol lower in energy than the C 2v isomer, which is a transition state. Reaction of cis-{(η 5 -C 5 H 3 ) 2 (CMe 2 ) 2 }Ru 2 (CO) 4 Br 2 with anthracene affords the analogous syn-facial anthracene complex, [cis-{(η 5 -C 5 H 3 ) 2 (CMe 2 ) 2 }Ru 2 (μ-η 6 ,η 6 -C 14 H 10 )][OTf] 2 , (4), and the tetranuclear dianthracene complex, [cis-{(η 5 -C 5 H 3 ) 2 (CMe 2 ) 2 }Ru 2 (μ-η 6 ,η 6 -C 14 H 10 )] 2 [OTf] 4 , (5). 2 2+ , 2 0 , and 5 were structurally characterized by X-ray diffraction.

Palladium(II)‐catalyzed ethoxycarbonylation of aryl bromides with diethyloxalate oxalate is described. Functionalized aromatic esters can be efficiently synthesized with only 0.65 mol % PdCl2(PPh3)2 catalyst under microwave irradiation and without additional ligand. This method illustrates an inexpensive and operationally simple method for the preparation of aromatic esters.magnified image