Small molecule activation of nitriles coordinated to the [Re6Se8]2+ core: formation of oxazine, oxazoline and carboxamide complexes

[ReH3 (PPh3 )4 ] - A Key Compound in the Rhenium Hydride Chemistry

The chemistry of the rhenium trihydrido complex [ReH₃ (PPh₃ )₄ ] (1) has been reinvestigated. An improved synthesis and the solid-state structure of the compound as well as several reactions are reported. The solid-state structure of 1 is similar to that of [TcH₃ (PPh₃ )₄ ] having a capped-octahedral coordination sphere. The PPh₃ ligands surround the Re atom in a trigonal-pyramidal mode with a short apical Re-P bond (2.300(2) Å) and three longer basal bonds (2.429(2)-2.449(2) Å). Reactions of 1 with monodentate phosphines such as PMe₃ or PBu₃ give the mono-substituted complexes [ReH₃ (PPh₃ )₃ (PMe₃ )] (2) and [ReH₃ (PPh₃ )₃ (PBu₃ )] (3) under retention of the apical PPh₃ ligand and substitution of one of the basal PPh₃ ligands. The stability of the phosphine trihydride complexes decreases in the order PPh₃ >PMe₃ >PBu₃ . Treatment of [ReH₃ (PPh₃ )₄ ] with trityl hexafluorophosphate in CH₃ CN does not result in a hydride abstraction, but gives the tetrahydrido cation [ReH₄ (NCCH₃ )(PPh₃ )₃ ]⁺ (4), while reactions with nitriles give unstable azavinylidene complexes of the composition [ReH₂ (PPh₃ )₃ (NC(H)R)] (5). They are formed by an insertion of the nitrile into a Re-H bond. The solid-state structure of the methyl derivative [ReH₂ (PPh₃ )₃ (NC(H)CH₃ )] (5 a) was determined showing a linear Re-N-C unit with rhenium-nitrogen and nitrogen-carbon double bonds, while the N=CH-C bond is clearly bent with an angle of 124°. Two previously unknown polymorphs of [ReH₅ (PPh₃ )₃ ] were isolated from reactions of 1 with HOC₆ H₃ (CH₃ )₂ and thiourea after prolonged heating in toluene and characterized by IR spectroscopy and X-ray diffraction.

Primary Amine Nucleophilic Addition to Nitrilium Closo-Dodecaborate [B12H11NCCH3]-: A Simple and Effective Route to the New BNCT Drug Design

In the present work, a convenient and straightforward approach to the preparation of borylated amidines based on the closo-dodecaborate anion [B₁₂H₁₁NCCH₃NHR]-, R=H, Alk, Ar was developed. This method has two stages. A nitrile derivative of the general form [B₁₂H₁₁NCCH₃]^- was obtained, using a modified technique, in the first stage. On the second stage the resulting molecular system interacted with primary amines to form the target amidine products. This approach is characterised by a simple chemical apparatus, mild conditions and high yields of the final products. The mechanism of the addition of amine to the nitrile derivative of the closo-dodecaborate anion was studied, using quantum-chemical methods. The interaction between NH₃ and [B₁₂H₁₁NCCH₃]^- ammonia was chosen as an example. It was found that the structure of the transition state determines the stereo-selectivity of the process. A study of the biological properties of borylated amidine sodium salts indicated that the substances had low toxicity and could accumulate in cancer cells in significant amounts.

Soluble Molecular Rhenium Cluster Complexes Exhibiting Multistage Terminal Ligands Reduction

Substitution of terminal halide ligands of octahedral rhenium cluster complexes [Re₆Q₈X₆]^4- in a melt of 4,4'-bipyridine (bpy) led to us obtaining four new compounds with the general formula trans-[Re₆Q₈(bpy)₄X₂] (Q = S or Se; X = Cl or Br) in high yield. In contrast to most of the known molecular rhenium cluster complexes with heteroaromatic terminal ligands, compounds 1-4 are soluble in organic solvents. This made it possible to carry out a detailed characterization of the new compounds both in solids and in solutions. In particular, it was shown that compounds 1-4 in the DMSO solution exhibit four reversible reduction processes. A comparison of the obtained data with the results of DFT calculations of the electronic structure suggests that these processes correspond to two-electron reduction of all four bpy ligands. The reduction potentials are shifted to the positive region compared with the potential of free bipyridine, and the value of the shift depends on the composition of the cluster core. The presence of four transitions also suggests that electronic exchange between terminal ligands in the cis-position is possible. The study of the luminescence of the compounds showed that emission maxima of selenide clusters almost coincide with those of sulfide ones, while luminescence spectra of the complexes with chloride terminal ligands (1 and 3) are slightly blue-shifted relative to the spectra of the complexes with bromide ligands (2 and 4).

Easy Ligand Activation in the Coordination Sphere of Ru inside the [PW11O39]7- Backbone

Irradiation of the Keggin-type [PW₁₁O₃₉{Ru(NO)}]⁴⁻ (Ru-NO) polyoxometalate in CH₃CN results in rapid NO ligand elimination with the formation of [PW₁₁O₃₉{Ru^III(CH₃CN)}]⁴⁻ (Ru-CH₃CN). This complex offers an easy entry into the Ru-based chemistry of the {PW₁₁Ru} complex. Attempts to substitute N₃⁻ for CH₃CN in the presence of an NaN₃ excess lead a variety of products: (i) [PW₁₁O₃₉{Ru^III(N₃)}]⁴⁻ (Ru-N₃); (ii) [PW₁₁O₃₉{Ru^III(N₄HC-CH₃)}]⁴⁻ (Ru-Tz) as a click-reaction product; and (iii) [PW₁₁O₃₉{Ru^II(N₂)}]⁵⁻ (Ru-N₂). UV-VIS, CV, and HR-ESI-MS techniques were used for the reaction monitoring and characterization of the products.

Phosphorescent complexes of {Mo6I8}4+ with triazolates: [2+3] cycloaddition of alkynes to [Mo6I8(N3)6]2−

“Click” reaction of activated alkynes with [Mo₆I₈(N₃)₆]²⁻ produces novel emissive triazolate complexes with the {Mo₆I₈}⁴⁺ cluster core.

Water-soluble Re6-clusters with aromatic phosphine ligands – from synthesis to potential biomedical applications

New hexarhenium clusters exhibit radio- and photoluminescence, have low cytotoxicity, are capable of penetrating into cells and exhibit photodynamic toxicity.

Functionalization of [Re6Q8(CN)6]4− clusters by methylation of cyanide ligands

Methylation of anionic cluster complexes [Re₆Q₈(CN)₆]⁴⁻ with ((CH₃)₃O)BF₄ or CF₃SO₃CH₃ afforded homoleptic isonitrile cluster complexes [Re₆Q₈(CH₃NC)₆]²⁺ (Q = S, Se, Te).