PO23- and AsO3-: Pnictogenide Ligands in the Highly Charged Re4 Cluster Anions [{Re4(PO)3(PO2)}(CN)12]8-, [{Re4As2(AsO)2}(CN)12]8-, and [{Re4(AsO)4}(CN)12]8.

New tetrahedral anionic rhenium cluster complexes [{Re4(PO)3(PO2)}(CN)12]8- (1) and [{Re4As2(AsO)2}(CN)12]8- (2) have been synthesized by the reaction of ReI3 with NaCN and Pred or KCN and Asgray, respectively. Compound 2 was further oxidized by aqueous H2O2 to produce the cluster anion [{Re4(AsO)4}(CN)12]8- (3). The anions contain new pnictogen/oxygen-based ligands, PO23- and AsO3-, which were stabilized by the coordination to the triangular faces of the tetrahedral Re4 metallocluster in µ3-mode. All three compounds were crystallized as either sodium or potassium salts, and their crystal structures were determined by single crystal X-ray diffraction analysis.

23-Electron Octahedral Molybdenum Cluster Complex [{Mo6I8}Cl6].

Photoactive transition metal compounds that are prone to reversible redox reactions are important for myriad applications, including catalysis, optoelectronics, and sensing. This article describes chemical and electrochemical methods to prepare cluster complex (Bu4N)[{Mo6I8}Cl6], a rare example of a 23 e- cluster complex within the family of octahedral clusters of Mo, W, and Re. The low temperature and room temperature crystal structures; electronic structure; and the magnetic, optical, and electrochemical properties of this complex are described.

Facile Substitution of Bridging SO22- Ligands in Re12 Bioctahedral Cluster Complexes.

Selective substitution of µ-SO22- groups by either O2- or Se2- ions occurs upon heating the bioctahedral rhenium cluster complex K6[Re12CS14(µ-SO2)3(CN)6] in air atmosphere or in the presence of a Se source, respectively, manifesting the remarkable lability of SO22- ligands bound to a transition-metal cluster. A series of compounds based on the new mixed-ligand anions, [Re12CS14(µ-O)3(CN)6]6-, [Re12CS14(µ-Se)3(CN)6]6-, and [Re12CS14(µ-O)3(OH)6]6-, were isolated and their solid-state structures were elucidated by single-crystal X-ray diffraction analysis. Along with the previously reported µ-sulfide clusters, the new species constitute a series of rhenium anionic complexes with the common formula [Re12CS14(µ-Q)3L6]6- (Q = O, S, Se, L = CN-; Q = O, S, L = OH-), within which the total charge and number of cluster valence electrons (CVEs) are constant. The article presents insights into the mechanistic and synthetic aspects of the substitution process, and it comprehensively discusses the influence of inner ligand environment on the structure, spectroscopic characteristics, and electrochemical behavior of the novel compounds.

Mixed-metal clusters with a {Re3Mo3Se8} core: from a polymeric solid to soluble species with multiple redox transitions.

Cluster compounds based on a new {Re3Mo3Se8}n core were obtained and studied. The polymeric solid K6[Re3Mo3Se8(CN)4(CN)2/2] (1) containing 24 cluster valence electrons (CVE) was isolated as a result of high-temperature reaction. Water-soluble salts K5[Re3Mo3Se8(CN)6]·11H2O (2) and Cs5[Re3Mo3Se8(CN)6]·H2O (3) were prepared from compound 1. Crystal structures of the diamagnetic compounds 2 and 3 contain a cluster anion [Re3Mo3Se8(CN)6]5- with a 22-electronic core {Re3Mo3Se8}+. Metathesis reaction followed by recrystallization from CH3CN yielded paramagnetic salt (Ph4P)4[Re3Mo3Se8(CN)6]·2CH3CN (4) containing the {Re3Mo3Se8}2+ core with 21 CVE. Cyclic voltammetry of the solution of 4 displayed three quasi-reversible waves with E1/2 = -0.325, -0.818 and -1.410 V vs. Ag/AgCl electrode indicating the presence of [Re3Mo3Se8(CN)6]4-/5-/6-/7- transitions. Electronic structure calculations showed that both mer- and fac-isomers of [Re3Mo3Se8(CN)6]n- clusters undergo great distortion when the number of CVE decreases.

A comparative study of optical properties and X-ray induced luminescence of octahedral molybdenum and tungsten cluster complexes.

Octahedral metal cluster complexes have high potential for biomedical applications. In order to evaluate the benefits of these moieties for combined CT/X-ray luminescence computed tomography, this paper compares photoluminescence, radiodensity and X-ray induced luminescence properties of eight related octahedral molybdenum and tungsten cluster complexes [{M6I8}L6]n (where M is Mo or W and L is I-, NO3-, OTs- or OH-/H2O). This article demonstrates that despite the fact that molybdenum cluster complexes are better photoluminescence emitters, tungsten cluster complexes, in particular (Bu4N)2[{W6I8}I6], demonstrate significantly higher X-ray induced luminescence due to a combination of relatively good photoluminescence properties and high X-ray attenuation. Additionally, photo-degradation of [{M6I8}(NO3)6]2- was evaluated.

Cooperative reduction by Ln(2+) and Cp*(-) ions: synthesis and properties of Sm, Eu, and Yb complexes with 3,6-di-tert-butyl-o-benzoquinone.

The first examples of samarium, europium, and ytterbium complexes with 3,6-di-tert-butyl-o-benzoquinone(3,6-dbbq) in the form of catecholate have been obtained by reactions of the quinone with the corresponding lanthanocenes, [LnCp2*(thf)n] (n = 1 or 2) in solution. In the course of the reactions lanthanide ions lose one or two Cp* ligands, which take part in reduction of a quinone molecule into a catecholate anion (dbcat, 2(-)). As a result of the reactions, Sm and Yb clearly yield dimeric complexes[(LnCp*)2(dbcat)2], where each Ln ion loses one Cp* ligand. Eu forms a trimeric complex [(EuCp*)-(Eu·thf)2(dbcat)3], in which one Eu ion is coordinated by one Cp* ligand, while two Eu ions have lost all Cp* ligands and are coordinated by THF molecules instead. Magnetic properties corroborate the assignment of oxidation states made on the basis of single-crystal X-ray diffraction: all the quinone ligands are present in the catecholate state; both Sm/Yb ions in the dimers are in the +3 oxidation state, whereas the Eu trimer contains two Eu(II) and one Eu(III) ions. Cyclovoltammetry studies show the presence of two reversible oxidation waves for all complexes, presumably concerned with the redox transitions of the dbcat ligands.

Octahedral molybdenum cluster complexes with aromatic sulfonate ligands.

This article describes the synthesis, structures and systematic study of the spectroscopic and redox properties of a series of octahedral molybdenum metal cluster complexes with aromatic sulfonate ligands (nBu4N)2[{Mo6X8}(OTs)6] and (nBu4N)2[{Mo6X8}(PhSO3)6] (where X- is Cl-, Br- or I-; OTs- is p-toluenesulfonate and PhSO3- is benzenesulfonate). All the complexes demonstrated photoluminescence in the red region and an ability to generate singlet oxygen. Notably, the highest quantum yields (>0.6) and narrowest emission bands were found for complexes with a {Mo6I8}4+ cluster core. Moreover, cyclic voltammetric studies revealed that (nBu4N)2[{Mo6X8}(OTs)6] and (nBu4N)2[{Mo6X8}(PhSO3)6] confer enhanced stability towards electrochemical oxidation relative to corresponding starting complexes (nBu4N)2[{Mo6X8}X6].