Chemical transformations supported by the [Re6(μ3-Se)8]2+ cluster core

Abstract

This Perspective article discusses three interesting chemical transformations promoted by the octahedral [Re 6 (μ 3 -Se) 8 ] 2+ cluster core. These include (1) nucleophilic addition of alcohols to cluster-bound nitrile(s) to produce imino ester complexes; (2) synthesis of cluster-imine complexes with geometric specificity by reacting cluster nitrile solvates with organic azides; and (3) preparation and reactivity studies of carbonyl complexes of the cluster. We found that cluster-bound nitrile ligands were activated toward nucleophilic attack by methanol or ethanol, affording predominantly the Z-configured cluster-imino ester complexes, for which a mechanism evoking bifurcated hydrogen bonding interactions involving both the alcohol OH group and two nearest Se atoms of the cluster core was proposed. When reacted with organic azides, cluster-bound nitrile ligands were displaced and cluster-imine complexes were obtained, presumably through the formation of the corresponding cluster-azide complexes, followed by their photodecomposition. Lastly, cluster complexes featuring all-terminal carbonyl ligands were synthesized. Back-bonding interactions were verified, both experimentally and by computational studies. Their thermal and photo-stabilities were also evaluated, so was their reactivity toward methyl lithium for the eventual making of cluster-carbene catalysts. These findings, together with those by others, portend an exciting, new direction in the chemistry of solid-state type transition metal clusters.

Imines in the Titanium Coordination Sphere: Highly Reactive Titanaaziridines and Larger Titanacycles Formed by Subsequent C–C Coupling Reactions

“…[1,2] The coordination of such a Schiff base to a metal center allows the formation of supramolecular complexes [3] as well as the development of highly potent homogeneous catalysts. [4] Although late transition metals often prefer η 1 -coordination of the imine through the lone pair at the nitrogen atom for donation (Scheme 1, mode I), [5][6][7] the chemistry of the early transition metals, especially in low-valent states, is characterized by the η 2 -coordination mode of the imine ligand (Scheme 1, mode IIa), which implies a metallaaziridine structure (Scheme 1, mode IIb).…”

[Re6(μ3-Se)8]2+ Core-Containing Cluster Complexes with Isonicotinic Acid: Synthesis, Structural Characterization, and Hydrogen-Bonded Assemblies

“…The organic phase was dried over anhydrous MgSO 4 , filtered, and rotovapped to yield an orange solid that was subsequently recrystallized from CH 2 Cl 2 and diethyl ether to afford the product in 71 % yield. Synthesis of trans-[Re 6 (l 3 -Se) 8 …”

“…This compound was prepared by adopting the procedure described above, but using a mixture of trans-[Re 6 (l 3 -Se) 8 This compound was prepared by adopting the procedure described above, but using a mixture of cis-[Re 6 (l 3 -Se) 8 Single Crystal Structure Determination CH 3 CN was also required for cis-P 4 (INA) 2 to fully dissolve. Single crystals were mounted on a 0.15-mm micromount with paratone oil.…”

“…cluster core have been reported [13,14]. Several of these compounds utilize [Re 6 (l 3 -Se) 8 (CN) 6 ] 4-as a linker to build polymeric arrays with direct coordination to secondary metal ions [15][16][17][18][19][20][21][22][23]. Other efforts involve incorporating cluster systems into polymers [24], nanoparticles [25], self-assembly structures [26][27][28], and surfaces [29], all for the purpose of integrating the red/nearinfrared luminescence and redox properties of the cluster for functional materials.…”

“…Protecting ligands, such as triethylphosphine, are used to stabilize the cluster core's reactive sites and provide a route to site-differentiated isomers that can be used for additional studies [4][5][6]. The Lewis acidic core activates cluster-bound ligand(s) thus providing a pathway for possible further chemical transformations of the ligand [7][8][9][10][11][12]. These fundamental properties of the cluster have been well established and current research aims at assessing both the catalytic capabilities of the cluster complexes and using their unique physical and chemical properties for the development of functional materials.…”