Iridium-Mediated Regioselective B–H/C–H Activation of Carborane Cage: A Facile Synthetic Route to Metallacycles with a Carborane Backbone

Abstract

One-pot reactions of carborane carboxylic acids (L), [Cp*IrCl2]2, and silver salt are reported, which lead to regioselective B-H or C-H bond activation at ambient temperature in good yields. This process is demonstrated for three carborane (o-, m-, p-) dicarboxylates, and metal-mediated B-H functionalization of a p-carborane derivative is accomplished for the first time. Two metal-induced self-assembly routes to tetra-nuclear metallacycles 3 and 5 were performed through B(4, 7)/H and B(2, 10)/H activation, respectively, and the two metallacycles were found to be stable and to exist in solution as discrete complexes. Different activation modes in the carborane cage were ascribed to the characteristic structure of the products and the electronic density differences. The analogous reaction of o-carborane monocarboxylate with the same metal precursor gave the C-H activation complex 6, indicating that the B-H bond is more stable than the C-H bond in this carborane cage. The selective activation was confirmed by DFT calculation results. In this study, a facile and efficient synthetic route has been developed through specific B-H bond activation to construct carborane-based metallacycles that are unavailable by conventional methods.

Polymer complexes. LXVIII. Spectroscopic studies of supramolecular copper(II) polymeric complexes of biologically active monomer derived from novel sulfa drug

“…Interest in coordination chemistry continues to increase with the preparation of organic/aliphatic ligands containing a variety of donor groups and it is multiplied when the ligands have biological importance . The number and diversity of nitrogen, oxygen and/or sulfur chelating agents used to prepare new coordination and organometallic compounds have increased rapidly during the past few years …”

Iridium-catalysed regioselective borylation of carboranes via direct B–H activation

“…In contrast, transition metal-catalysed B(3,6)-difunctionalization of o -carboranes is much less studied3637, although transition metal promoted B(3)–H activation in o -carboranes has been well documented38394041424344.…”

Heterometallic transition metal clusters and cluster-supported coordination polymers derived from Tp- and Tp*-based Mo(W) sulfido precursors

“…The cage compounds, extensively studied in the last few decades by Fujita, Raymond, Nitschke and others [115][116][117][118][119][120][121][122][123][124][125][126], are a fascinating class of discrete molecular entities capable of altering molecular behavior within the confined space, and termed as 'molecular flasks' by Fujita [127]. The geometrical advantage of Tp and Tp* along with MS 3 Cu 3 (M = Mo, W) in favoring tetrahedral cages may allow us to approach other cage compounds with relative ease.…”