Geometrically Specific Imino Complexes of the [Re₆(μ₃‐Se)₈]²⁺ Core‐Containing Clusters

Abstract

The reactions of nitrile complexes of the [Re(6)(μ(3)-Se)(8)](2+) core-containing clusters, [Re(6)(μ(3)-Se)(8)(PEt(3))(n)(CH(3)CN)(6-n)](2+) [n = 5 (1); n = 4, cis- (2) and trans- (3); n = 0 (4)], with organic azides C(6)H(5)CH(CH(3))N(3) and C(6)H(5)CH(2)N(3) produced the corresponding cationic imino complexes of the general formula [Re(6)(μ(3)-Se)(8)(PEt(3))(n)(L)(6-n)](2+) [L = PhN=CHCH(3): n = 5 (5); n = 4, cis- (6) and trans- (7); n = 0 (8) and L = HN=CHPh: n = 5 (9); n = 4, cis- (10) and trans- (11)]. These novel complexes were characterized by NMR spectroscopy ((1)H and (31)P) and single-crystal X-ray diffraction. A mechanism involving the migration of one of the groups on the azido α-C atom to the α-N atom of the azido complex, concerted with the photo-expulsion of N(2), was invoked to rationalize the formation of the imino complexes. Density functional theory (DFT) calculations indicated that due to the coordination with and activation by the cluster core, the energy of the electronic transition responsible for the photo-decomposition of a cluster-bound azide is much reduced with respect to its pure organic counterpart. The observed geometric specificity was rationalized by using the calculated and optimized preferred ground-state conformation of the cluster-azido intermediates.

Borylated Tetrazoles from Cycloaddition of Azide Anions to Nitrilium Derivatives ofcloso-Decaborate Clusters

“…Under the conventional conditions for CA of organic azide to activated nitriles − (2 d, dry EtCN, 100 °C, under Ar) no traces of CA products were observed by high-resolution ESI-MS, while slow degradations of the starting nitrilium derivatives were detected. Similar differences in reactions of activated nitriles with azide ions and organic azides were previously reported for the Re 6 Se 8 clusters bearing nitrile ligands. , The reason for the different behavior of N 3 – and RN 3 toward borylated nitriles is disclosed in the section devoted to theoretical study of the azide cycloaddition in this article.…”

“…Similar differences in reactions of activated nitriles with azide ions and organic azides were previously reported for the Re 6 Se 8 clusters bearing nitrile ligands. 45,46 The reason for the different behavior of N 3 − and RN 3 toward borylated nitriles is disclosed in the section devoted to theoretical study of the azide cycloaddition in this article.…”

Experimental and theoretical studies of the ancillary ligand (E)-2-((3-amino-pyridin-4-ylimino)-methyl)-4,6-di-tert-butylphenol in the rhenium(i) core

“…19 The molecular geometry of the ground states and the oxidized and reduced states were fully optimized employing the BP86 functional. 19 The molecular geometry of the ground states and the oxidized and reduced states were fully optimized employing the BP86 functional.…”

“…All the calculations reported here were carried out in the framework of the density functional theory (DFT) using the Amsterdam Density Functional computational package (ADF2012) via the zeroth order regular approximation (ZORA) Hamiltonian including spin-orbit (SO) relativistic corrections and employing Slater Type Orbitals (STO) basis sets with triple-z accuracy plus one polarization function (TZP) for all the atoms. 19 The molecular geometry of the ground states and the oxidized and reduced states were fully optimized employing the BP86 functional. 20 In all cases, frequency analysis were performed after each geometry optimization, where we obtained non-imaginary frequencies verifying the local minima.…”

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

“…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.…”