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We present herein anionic borate‐based bi‐mesoionic carbene compounds of the 1,2,3‐triazol‐4‐ylidene type that undergo C−N isomerization reactions. The isomerized compounds are excellent ligands for CoII centers. Strong agostic interactions with the "C−H"‐groups of the cyclohexyl substituents result in an unusual low‐spin square planar CoII complex, which is unreactive towards external substrates. Such agostic interactions are absent in the complex with phenyl substituents on the borate backbone. This complex displays a high‐spin tetrahedral CoII center, which is reactive towards external substrates including dioxygen. To the best of our knowledge, this is also the first investigation of agostic interactions through single‐crystal EPR spectroscopy. We conclusively show here that the structure and properties of these CoII complexes can be strongly influenced through interactions in the secondary coordination sphere. Additionally, we unravel a unique ligand rearrangement for these classes of anionic mesoionic carbene‐based ligands. [ABSTRACT FROM AUTHOR]

Abstract: Bimetallic lithium aluminates and neutral aluminum counterparts are compared as catalysts in hydroboration reactions with aldehydes, ketones, imines and alkynes. Possessing Li–Al cooperativity, ate catalysts are found to be generally superior. Catalytic activity is also influenced by the ligand set, alkyl and/or amido. Devoid of an Al−H bond, iBu2Al(TMP) operates as a masked hydride reducing benzophenone through a β‐Η transfer process. This catalyst library therefore provides an entry point into the future design of Al catalysts targeting substrate specific transformations. [ABSTRACT FROM AUTHOR]

Abstract: A series of heteroleptic monoamido‐monohydrido‐dialkylaluminate complexes of general formula [iBu2AlTMPHLi⋅donor] were synthesized and characterised in solution and in the solid state. Applying these complexes in catalytic hydroboration reactions with representative aldehydes and ketones reveals that all are competent, however a definite donor substituent effect is discernible. The bifunctional nature of the complexes is also probed by assessing their performance in metallation of a triazole and phenylacetylene and addition across pyrazine. These results lead to an example of phenylacetylene hydroboration, which likely proceeds via deprotonation, rather than insertion as observed with the aldehydes and ketones. Collectively, the results emphasise that reactivity is strongly influenced by both the mixed‐metal constitution and mixed‐ligand constitution of the new aluminates. [ABSTRACT FROM AUTHOR]

Calix[4]arenes are versatile ligands that, whilst also serving other purposes, can act as platforms for the synthesis of a wide range of 3 d, 4 f, and 3 d-4 f polymetallic clusters. The empirical metal ion binding rules established for calix[4]arene are closely mirrored by bis-calix[4]arene, a relatively new ligand in which two equivalents of the former are directly tethered at a methylene bridge position. The direct tethering within bis-calix[4]arene gives rise to some structural features that are related to calix[4]arene coordination chemistry, but the prevailing clusters have fascinating new topologies and coordination behaviors. Here, we present the synthesis of a family of new bis-calix[4]arene-supported 3 d-4 f clusters, as well as their structural characterization and magnetic properties. Comparison is drawn with calix[4]arene coordination chemistry, showing logical extension of common structural fragments and cluster capping behaviors upon moving to bis-calix[4]arene. This approach therefore holds great potential for tuning cluster formation and composition at a high level through subsequent ligand alteration. [ABSTRACT FROM AUTHOR]

Calix[4]arenes are versatile ligands capable of forming a wide range of cluster motifs when reacted with 3d, 4for 3d/4fmetal ions. Synthetic modification at the calix[4]arene methylene bridge offers a unique opportunity to explore cluster formation with these alternative building blocks. Here, we present the synthesis of a range of bis-calix[4]arenes that are tethered by alkyl chains, as well as exploratory structural studies into cluster-forming reactions. Single crystals were formed in four cases, and from the X-ray structures elucidated it is possible to conclude that sufficiently long alkyl tethers allow for the formation of established cluster topologies without disruption to the core coordination chemistry. Synthetic modification at the calix[4]arene methylene bridge offers a unique opportunity to synthesise alternative supramolecular building blocks. This paper describes the synthesis of a range of alkyl-tethered bis-calix[4]arenes, as well as exploratory structural studies into polymetallic cluster formation. [ABSTRACT FROM AUTHOR]

A bis-phenolate that has structural similarities to both calix[4]arene and the oxacalix[ n]arenes provides access to a 'butterfly'-like Mn4 cluster in which all metals are in the oxidation state+3. Specific properties of this ligand, in comparison to others in the literature, offer a route to influencing the orientation of the Jahn-Teller axes within this cluster motif, which possesses a rare oxidation state arrangement. [ABSTRACT FROM AUTHOR]

Two new metallaphosphacarboranes have been synthesised from [7, 8- nido-CPB9H11]- by deprotonation followed by treatment with a metal fragment. Starting with [HNMe3][7, 8- nido-CPB9H11] deprotonation and reaction with a source of {(indenyl)Co}2+ affords the η-bonded cobaltaphosphacarborane 3-(η-C9H7)-3,1,2- closo-CoCPB9H10 ( 1) the first 'half-sandwich' 3,1,2-metallaphosphacarborane. The indenyl ligand conformation in 1 ( cisoid between the indenyl bridgehead carbon atoms and cage heteroatoms, with the cage carbon atom lying below the indenyl C-C bond) reveals that the structural trans effect in a phosphacarborane ligand is weakest for carbon and therefore varies in the order B > P > C. Starting with [HNC5H11][7, 8- nido-CPB9H11] deprotonation and reaction with half an equivalent of [Ru( p-cymene)Cl2]2 affords the σ-bonded ruthenaphosphacarborane 8-{Ru( p-cymene)Cl(C5H11N)}-7, 8- nido-CPB9H11 ( 2), the first example of a molecule with a phosphacarborane σ-bonded to a metal to be crystallographically characterised. [ABSTRACT FROM AUTHOR]

Abstract: Methylene-bridged calix[4]arenes have emerged as excellent ligands for polynuclear cluster formation. In this contribution methylene- and oxa-bridged calix[6]arenes have been examined as candidates for cluster formation with cobalt(II) nitrate, affording two markedly different structures. The nature of the structures is highly dependent on the bridging atoms. Reaction of p-tert-butylcalix[6]arene with cobalt(II) nitrate in DMF results in the formation of a coordination polymer in which the calixarene adopts a ‘double-partial’ cone conformation. A similar reaction with p-tert-butyltetrahomodioxacalix[6]arene affords a discrete complex in which a central heteroatom also coordinates to the metal centre, with the calixarene in a ‘double-cone’ conformation. The synthesis and structure of both compounds is presented. [Copyright &y& Elsevier]

The ligand bis(5-tert-butyl-2-hydroxy-3-hydroxymethyl-phenyl)methane, a flexible calix[n]arene analogue, is employed to construct an unusual linear [Ln3] trimer. [ABSTRACT FROM AUTHOR]