Synthesis, Structure, and Characterizations of a Heterobimetallic Heptanuclear Complex [Pb₂Co₅(acac)₁₄]

An unusual heterobimetallic volatile compound [Pb₂Co₅(acac)₁₄] was synthesized by the gas phase/solid-state technique. The preparation can be readily scaled up using the solution approach. X-ray powder diffraction, ICP-OES analysis, and DART mass spectrometry were engaged to confirm the composition and purity of heterobimetallic complex. The composition is unique among the large family of lead(tin): transition metal = 2:1, 1:1, and 1:2 β-diketonates compounds that are mostly represented by coordination polymers. The molecular structure of the complex was elucidated by synchrotron single crystal X-ray diffraction to reveal the unique heptanuclear moiety {Co(acac)₂[Pb(acac)₂-Co(acac)₂-Co(acac)₂]₂} built upon bridging interactions of acetylacetonate oxygens to neighboring metal centers that bring their coordination numbers to six. The appearance of unique heptanuclear assembly can be attributed to the fact that the [Co(acac)₂] units feature both cis- and trans-bis-bridging modes, making the polynuclear moiety rather flexible. This type of octahedral coordination is relatively unique among known lead(tin)-3d transition metal β-diketonates. Due to the high-volatility, [Pb₂Co₅(acac)₁₄] can be potentially applied as a MOCVD precursor for the low-temperature preparation of lead-containing functional materials.