The reaction of the labile compound [Re-2(CO)(8)(CH3CN)(2)] with trans-1,2-bis(2-pyridyl)ethene (C12H10N2) at room temperature in tetrahydrofuran affords the compounds [Re-2(mu:eta(3)-C12H10N2)(CO)(8)] (1) and the oxidative addition product [Re-2(mu-H)(mu:eta(3)- C12H9N2)(CO)(7)] (2). When the reaction is carried out at temperatures of refluxing tetrahydrofuran, besides compounds 1 and 2, the oxidative addition product [Re-2(mu-H)(mu:eta(4)-C12H9N2)(CO)(6)] (3), the insertion product [Re-2(mu:eta(4)-C12H10N2)(CO)(8)] (4) and [Re-2(mu:eta(6)-C14H18N4)(CO)(6)] (5) are obtained. Compound 5 contains the organic ligand rtct-tetrakis(2-pyridyl)cyclobutandiyl which is derived from a [2 + 2] cycloaddition of 1,2-bis(2-pyridyl)ethene mediated by its coordination to the bimetallic framework. The molecular structures of 1, 2, 4 and 5 were confirmed by X-ray crystallographic studies. (C) 2004 Elsevier B.V. All rights reserved.

The cluster [Os(3)(CO)(10)(MeCN)(2)] reacts readily with azulene in refluxing cyclohexane to give the oxidative addition product [Os(3)(mu-H)(mu(2)-eta'-C(10)H(7))(CO)(10)] 1 which was shown by its X-ray crystal structure to contain the C(5) ring of the azulenyl ligand bonded through a single carbon atom at the 1-position. We propose that the Compound is zwitterionic, with the 7-membered ring a tropylium cation and the 5-membered ring coordinated as a mu-alkylidene to the metal cluster, which carries a formal negative charge. Thermal loss of one CO ligand leads by further oxidative addition to the known cluster [Os(3)(mu-H)(2)mu(3)-eta(1):eta(1):eta(1)-C(10)H(6))(CO)(9)] 2. (C) 2004 Elsevier B.V. All rights reserved.

Carbonylation of the known cluster [Ru-3 (CO)(6)(mu -CO)(mu (3)-eta (5):eta (3):eta (3)-C10H8)] (1) gives the metastable trinuclear derivative [Ru-3(CO)(8)(mu (3)-eta (5):eta (2):eta (1)-C10H8)] (2). On further carboxylation of 1 the stable product [Ru-2(CO)(5)(mu (2)-eta (5):eta (3)-C10H8] (3) is obtained. X-ray diffraction studies and full spectroscopic assignment of 3 show that the azulene ligand is bonded through a pi -Cp to one metal and via a pi -allyl moiety to the other. Compound 3 reacts reversibly with CO to yield, [Ru-2(CO)(6)(mu (2)-eta (5):eta (1)-C10H8] (4), which maintains the pi -Cp bond while the heptadienyl ring contributes to the bonding only through one sigma -C-Ru interaction.