A novel bis-β-diketonate ligand stabilizes a [Co(II)8] cage that encapsulates a (μ3-O)⋯H⋯(μ3-O) moiety

New coordination features; a bridging pyridine and the forced shortest non-covalent distance between two CO32−species

“…12 It has now been found that the use of a strong enough base allows removing all the ionisable protons from H 4 L, which facilitates the involvement of the resulting phenolate groups in the coordination. This concept had been proofed previously with the related ligand H 4 L1, featuring an m -phenylene spacer instead of the m -pyridinediyl.…”

“…This ligand had only been used once in the past, also with Co( ii ). 12 On that occasion, the chemistry was performed in the absence of any base, and the result was the formation of a cluster with formula [Co 8 O(OH)(H 2 L) 6 ]NO 3 , which encapsulates a [μ 3 -O···H···μ 3 -O] moiety while the ligand H 4 L was found to retain its phenolic protons upon coordination. We show now that the use of strong basic conditions leads to full deprotonation of H 4 L, which is conducive to the oxidation of some of the Co( ii ) ions to Co( iii ) by atmospheric oxygen.…”

Novel Topologies in Vanadium-bis-β-Diketone Chemistry: A [V4] and a [V6] Metallacyclophane

“…The structural versatility of H4L1 and H4L2 has been emphasized in the Introduction. The former donor has allowed the subtle control of cluster topology and nuclearity [19,40,42], whereas the latter led to the discovery of unexpected structural features [27,28]. Interestingly, all the studied compounds exhibit the ligands in a linear conformation (Scheme 1) with both coordination pockets facing the same direction (syn, syn conformation).…”

“…In this endeavor, the field of coordination chemistry is an inexhaustible spring of tools resulting from the combination of versatile organic scaffolds and the diverse physico-chemical properties of transition and rare-earth metals. In this context, the implementation of judiciously engineered ligands, such as bis-β-diketones [13], has allowed the preparation of abundant families of metallohelicates [14][15][16], linear molecular platforms [17,18], weakly coupled molecular cluster pairs [19,20], metallamacrocycles [21][22][23][24], and cage clusters [25][26][27][28] displaying interesting topologies and unprecedented structural features. However, despite that the vast majority of their coordination entities involve divalent and trivalent 3d metal ions, the chemistry of bis-β-diketone ligands with vanadium remains relatively scarce, especially when considering the diverse reactivity of this metal together with the biological and catalytic importance of its compounds [29][30][31][32][33][34].…”

“…On the other hand, ligand H4L2 has been used exclusively in preparation of Co(II) coordination compounds with some unprecedented features. Employment of the ligand under weakly basic conditions allowed deprotonating only the β-diketone moiety leading to the octanuclear cluster [Co8O(OH)(H2L2)6]NO3, which encapsulates a very rare [μ3-O···H···μ3-O] structural motif [27]. The use of a strong base (TBAOH, NaH) and a coordinating solvent (pyridine) directed the outcome of aerobic analogous reactions towards the unusual tetranuclear [Co4(L2)2(OH)(py)7]NO3 and octanuclear [Co8Na4(L2)4(OH)2(CO3)2(py)10](BF4)2 coordination compounds [28].…”