EXTENSIVE SUBSTITUTION, PROTONATION, AND METHOXIDATION REACTIONS OF TRIRUTHENIUM CARBONYL CLUSTERS CONTAINING 2-AMINO-6-METHYLPYRIDINATO (MU-3-AMPY) AS A FACE-BRIDGING LIGAND - X-RAY STRUCTURES OF [RU3(MU-H)(MU-3-AMPY)(CO)7(PPH3)2] AND [RU3(MU-H)2(MU-3-AMPY)(CO2ME)(CO)6(PPH3)2].MEOH

The complex [Ru3(mu-H)(mu-3-ampy)(CO)9] (1) (Hampy = 2-amino-6-methylpyridine) reacts with excess triphenylphosphine to give the disubstituted derivative [Ru3(mu-H)(mu-3-ampy)(CO)7(PPh3)2] (3), which has the phosphorus atoms cis to the bridging amido fragment and cis to the hydride. Complex 3 undergoes protonation with HBF4.OEt2 at one hydride-unbridged Ru-Ru edge to give [Ru3(mu-H)2(mu-3-ampy)(CO)7(PPh3)2]BF4 (4a), in which one PPh3 ligand has moved from cis (in complex 3) to trans (in complex 4a) to the hydride that spans the amido-bridged Ru-Ru edge. The cationic complex [Ru3(mu-H)2(mu-3-ampy)(CO)9]BF4 (2) reacts with 2 equiv of triphenylphosphine to give [Ru3(mu-H)2(mu-3-ampy)(CO)7(PPh3)2]BF4 (4b), in which the PPh3 ligands are cis to the hydrides on the Ru atoms bonded to only one hydride, being therefore an isomer of 4a. The transformation of 4b into 4a can be achieved in refluxing THF. Both 4a and 4b react with an excess of triphenylphosphine to give the trisubstituted derivative [Ru3(mu-H)2(mu-3-ampy)(CO)6(PPh3)3]BF4(5). The reactions of 4a and 5 with potassium methoxide lead to the neutral derivatives [Ru3(mu-H)2(mu-3-ampy)(CO2Me)(CO)6(PPh3)2] (6a) and [Ru3(mu-H)2(mu-3-ampy)(CO2Me)(CO)5(PPh3)3] (7), respectively. These complexes contain a methoxycarbonyl group on the Ru atoms attached to two hydrides. A similar reaction with complex 4b renders a mixture of two isomers (6b, 6c) of 6a. The molecular structures of 3 and 6a have been confirmed by X-ray crystallography. Complex 3: monoclinic, space group P2(1)/c, a = 16.719 (7) angstrom, b = 12.263 (5) angstrom, c = 24.448 (9) angstrom, beta = 108.69 (2)-degrees, and Z = 4. Complex 6a.MeOH: monoclinic, space group P2(1)/n, a = 18.006 (7) angstrom, b = 26.118 (8) angstrom, c = 10.580 (5) angstrom, beta = 90.33 (2)-degrees, and Z = 4. The structures were solved by Patterson and Fourier methods and refined to R = 0.0630 (3) and 0.0461 (6a) and R' = 0.0860 (3) and 0.0624 (6a) for 4278 (3) and 6422 (6a) observed reflections with I > 2-sigma(I).