SPECIFIC SYNTHESIS AND REACTION OF HETEROBRIDGED AND HOMOBRIDGED DIRUTHENIUM CARBONYL-COMPLEXES CONTAINING ONE OR 2 MU-AZOLATO BRIDGES

Diruthenium(I) carbonyl complexes with either hetero- or homobridges, [Ru-2(mu-Pz)(2)(CO)(4)-(HPz)(2)] (1), [Ru-2(mu-Pz')(mu-O(2)CMe)(CO)(4) (HPz')(2)] (2), and [Ru-2(mu-Pz')(2)(CO)(4)(HPz')(2)] (3), can be prep ared specifically. These complexes reached with either nucleophiles or electrophiles to produce selectively only one product. The terminal a zole groups, pyrozole (HPz) or 3,5-dimethylpyrazole (HPz'), of 1-3 are easily replaced by the phosphine ligands to give [Ru-2-(mu-Pz)(2)(CO) (4)(PPh(3))(2)] (4), [Ru-2(mu-Pz')(mu-O(2)CMe)(CO)(4)(PPh(3))(2)] (5), [Ru-2(mu-Pz')(2)(CO)(4)(PPh(3))(2)] (6), and [Ru-2(mu-Pz)(2)(CO)(4)(e ta(1)-dppm)(2)] (7). The mu-acetato bridge is more fragile than the mu -azolato bridge, and only the former bridge of 5 can be replaced by Pz - and SR- to afford [Ru-2(mu-Pz')(mu-Pz)(CO)(4)(PPh(3))(2)] (8) and [R u-2(mu-Pz')(mu-SR)(CO)(4)(PPh(3))(2)] (R = Ph (9), (t)Bu (10)). Heatin g the mixture of 3 with dppm in THF gave a product retaining all the m u-azolato bridges but losing two carbonyls, [Ru-2(mu-Pz')(2)(CO)(2)(mu (1),eta(2)-dppm)(2)] (11), whereas a similar reaction between 1-3 and nitrogen-bidentate ligands gave products retaining all four carbonyls but only one mu-azolato bridge, (mu-L)(mu-CO)(2)(CO)(2)(mu(1),eta(2)-( N-N))(2)](+) (L = Pz, N-N = bpy ([12](+)), phen ([13](+)); L = Pz', N- N = bpy ([14](+)), phen ([15](+))). The electrophilic addition of 4 wi th I-2 produced [Ru-2(mu-Pz)(2)(mu-I)(CO)(4)(PPh(3))(2)][I-3] (16). Th e X-ray structure of this product confirms the cleavage of the Ru-Ru b ond rather than the mu-azolato bridges. However, the mu-azolato and -a cetato bridges, as well as the terminal azole groups, of 1-6 can be ea sily removed by an electrophilc reagent such as Et(3)O(+)BF(4)(-) in t he presence of MeCN to give [Ru-2(CO)(4)-(MeCN)(6)][BF4](2) and [Ru-2( CO)(4)(MeCN)(4)(PPh(3))(2)][BF4](2).