The First Trimetallic Pd/Tl/Co Carbonyl Cluster, Trigonal [Pd_9{μ_3-TlCo(CO)_3L}(μ_2-CO)_6(μ_3-CO)_3L_6]: Ligand-Stabilization of the Trigonal-Bipyramidal [TlCo(CO)_3L] Entity

摘要

In the course of our exploration of reactivities of carbonyl/phosphine clusters of palladium with thallium(I) complexes, we have isolated approximately 40 % yield) and crystallographically and spectroscopically characterized a remarkable 11-metal-atom pseudo-C_(3v) cluster, [Pd_9{μ_3-TlCo(CO)_3L}(μ_2-CO)_6(μ_3-CO)_3L_6], (L = PEt_3) (1), from reactions of [Pd_4(CO)_5L_4] (2) and/or [Pd_(10)(CO)_(12)L_6] (3) with [TlCo(CO)_4]. Its unusual solid-state molecular geometry was ascertained from a low-temperature X-ray diffractometry study. Cluster 1 furnishes the first crystallographic example of a trigonal-bipyramidal [TlCo(CO)_3L] entity of thallium(I) which in 1 is stabilized as a ligand by tripalladium coordination; otherwise it would be unstable. The only other isolated non-phosphite L derivative of [TlCo(CO)_4] is [TlCo(CO)_3PPh_3], but even this molecular thallium(I) product was found to readily disproportionate into thallium(III) [Tl{Co(CO)_3PPh_3}_3] and thallium metal. Spectroscopic measurements including a multinuclear NMR (~(205,203)Tl, ~(31)P, ~(13)C, ~1H) investigation coupled with solid-state/solution IR and UV/Vis spectra have provided considerable insight concerning the indicated dynamic behavior of the entire [TlCo(CO)_3PEt_3] ligand of 1 in solution.