SYNTHESIS AND REACTIVITY OF DIPHENYLPHOSPHINE DERIVATIVES OF [RU3(MU-H)(MU-3-AMPY)(CO)9] AND [RU3(MU-H)2(MU-3-AMPY)(CO)9][BF4] (HAMPY=2-AMINO-6-METHYLPYRIDINE)

The reactions of [Ru3(mu-H)(mu-3-ampy)(CO)9] (1) (Hampy = 2-amino-6-methylpyridine) with one or two equivalents of PPh2H give the complexes [Ru3(mu-H)(mu-3-ampy)(CO)8(PPh2H)] (3) or [Ru3(mu-H)(mu-3-ampy)(CO)7(PPh2H)2] (4), in which the PPh2H ligands are cis to the bridging NH fragment and cis to the hydride. Complex 3 eliminates hydrogen in refluxing tetrahydrofuran to give the phosphidobridged derivative [Ru3(mu-3-ampy)(mu-PPh2)(mu-CO)2(CO)6] (5), which contains the PPh2 ligand spanning one of the two Ru-Ru edges unbridged by the amido moiety. Under similar conditions, complex 4 gives a separable mixture of two isomers of [Ru3(mu-H)(mu-3-ampy)(mu-PPh2)2(CO)6] in a 5:1 ratio; the major product (6a) has a plane of symmetry, whereas the minor one (6b) is asymmetric. Compound 6a can also be prepared by reaction of 5 with PPh2H. Complexes 3 and 4 undergo protonation with HBF4.OEt2 at an amido-unbridged P-bonded Ru-Ru edge, rendering [Ru3(mu-H)2(mu-3-ampy)(CO)8(PPh2H)][BF4] (7a) and [Ru3(mu-H)2(mu-3-ampy)(CO)7(PPh2H)2]BF4] (8), respectively. Upon reaction with potassium methoxide, the cation 7a regenerates the neutral complex 3, while complex 8 gives a mixture of 4, 6a and 6b. Treatment of the dihydride [Ru3(mu-H)2(mu-3-ampy)(CO)9][BF4] (2) with PPh2H gives [Ru3(mu-H)2(mu-3-ampy)(CO)8(PPh2H)][BF4] (7b), which has the PPh2H ligand cis to the bridging NH moiety and cis to the hydride on the Ru atom bonded to only one hydride, being therefore an isomer of complex 7a. The cation 7b undergoes nucleophilic attack by potassium methoxide to give the neutral methoxycarbonyl derivative [Ru3(mu-H)2(mu-3-ampy)(CO2Me)(CO)7(PPh2H)] (9). Proton and P-31 {H-1} NMR and IR spectra of all the compounds are included and discussed in relation to their structures.