Synthesis, characterization and theoretical studies of new heterometallic carbonyl clusters bridged by 4,4′-dipyridyl unit

Abstract

4,4′-Bipyridine (4,4′-bipy) reacts with the activated cluster [Os 3(CO) 10(NCMe) 2] readily at room temperature to give a mixture of [Os 3(μ-H)(CO) 10(μ-NC 5H 3C 5H 4N)] ( 1) and [Os 3(μ-H)(CO) 10(μ-NC 5H 3C 5H 3N)Os 3(μ-H)(CO) 10] ( 2), the composition of which depends upon the reaction conditions and the ratio of the reactants. The reactivities of the metalloligand precursor 1 with a pendant nitrogen atom towards [W(CO) 5(THF)] and [Re(CO) 5Cl] have been investigated, affording two new heterometallic clusters [Os 3(μ-H)(CO) 10(μ-NC 5H 3C 5H 4N)W(CO) 5] ( 3) and [ReCl(CO) 3{Os 3(μ-H)(CO) 10(μ-NC 5H 3C 5H 4N)} 2] ( 4) in moderate to good yields. Compound 4 can also be prepared from the reaction between [Os 3(CO) 10(NCMe) 2] and [ReCl(CO) 3(4,4′-bipy) 2]. The X-ray crystal structures of compounds 1– 3 have been determined and molecular orbital calculations on these complexes using density functional theory (DFT) method reveal that they all have similar orbitals in the LUMO region. Clusters 1 and 2 have the OsOs σ-bonding orbitals as their HOMO orbitals while cluster 3 has the ‘t 2g’ set orbitals of the W(CO) 5 fragment as the HOMO orbitals.