Neutral binuclear and anionic trinuclear rhenium carbonyl complexes containing bridging ligands derived from 2-amino- and 2-mercaptopyridines

The reactions of the nitrile-stabilized complex [Re-3(mu-H)(3)(CO)(11)(MeCN)] (1) and of the unsaturated complex [Re-4(mu-H)(4)(CO)(12)] (2) with 2-amino-6-methylpyridine (Hampy), 2-mercaptopyridine (Hmerpy), and 2-hydroxy-6-methylpyridine (Hhympy) have been studied. Complex 1 reacts slowly with Hampy and Hmerpy (refluxing toluene, 5-7 h) to give the binuclear derivatives [Re-2(mu-ampy)(2)(CO)(6)] (3) and [Re-2(mu-merpy)(2)(CO)(6)] (4), but no reaction is observed between 1 and Hhympy under analogous conditions. Complex 2 reacts with Hampy and Hmerpy (refluxing 1,2-dichloroethane, 10-20 min) to give the trinuclear anionic derivatives [Re-3(mu-H)(3)(mu(3)-ampy)(CO)(9)](-) (5) and [Re-3(mu-H)(3)(mu(3)-merpy)(CO)(9)](-) (6), which have been isolated as pyridinium ([H(2)ampy]5) or triethylammonium ([HNEt3]5, [HNEt3]6) salts. Under analogous conditions, the reaction of 2 with Hhympy gives an inseparable mixture of compounds. The X-ray structures of [HNEt3]5 and [HNEt3]6 confirm that the three edges of the clusters are spanned by hydride ligands, that the ampy (in 5) and merpy (in 6) are attached to the three Re atoms, and that there are hydrogen-bonding interactions in the solid state between some carbonyl oxygen atoms and the NH fragments of the ampy ligand (in 5) and the triethylammonium cation (in 5 and 6).