Platinum based mixed-metal clusters (PtnMm(CO)xLy, M=Ru or Os; n+m=2 to 10 and Ly=other ligands)—Synthesis, structure, reactivity and applications

New Highly Charged Iron(III) Metal-Organic Cube Stabilized by a Bulky Amine

In this work, we report a new octanuclear cluster based on Fe^III and the ligand 1H-imidazole-4,5-dicarboxylic acid, [Et₃NH]₁₂[Fe₈(IDC)₁₂]·10DMF·13H₂O (1), with a metal core containing eight Fe^III connected by only one type of organic ligand. A peak at 573 m/z in the mass spectra of the compound suggests the adduct species {[Fe₈(IDC)₁₂]+8H}^4-. By X-ray photoelectron spectroscopy, the oxidation state of the iron cation was confirmed to be 3+, also identifying the presence of a quaternary nitrogen species, which act as a countercation of the anionic metal core [Fe₈(IDC)₁₂]^12-. Mössbauer spectra recorded at different temperatures show an isomer shift and quadrupole splitting parameters that confirm the existence of only Fe^III-HS in the structure of 1. X-ray analysis reveals that compound 1 crystallizes in the orthorhombic system space group Ibam, confirming a molecular cluster structure with an almost regular cube as geometry, with the Fe^III atoms located at the corners of the cube and connected by μ-1κ² N,O:2κ² N',O‴-IDC^3- bridges. Additionally, the magnetic measurements reveal a weak antiferromagnetic coupling in the Fe₈ ^III coordination cluster (J = -3.8 cm^-1). To the best of our knowledge, 1 is the first member of the family of cubes assembled with 1H-imidazole-4,5-dicarboxylic acid and Fe^III cation, exhibiting high pH stability over a broad pH range, making it an ideal candidate for the design of supramolecular structures and metal-organic frameworks.

Survey of short and long cuprophilic d10–d10 contacts for tetranuclear copper clusters. Understanding of bonding and ligand role from a planar superatom perspective

Polynuclear copper(i) complexes involving d¹⁰–d¹⁰ interactions have been studied to a lesser extent in comparison to their gold counterparts.

Trigonal-bipyramidal and square-pyramidal chromium-manganese chalcogenide clusters, [E2CrMn2(CO)n](2-) (E=S, Se, Te; n=9, 10): synthesis, electrochemistry, UV/Vis absorption, and computational studies

The reactions of E powder (E=S, Se) with a mixture of Cr(CO)6 and Mn2(CO)10 in concentrated solutions of KOH/MeOH produced two new mixed Cr-Mn-carbonyl clusters, [E2CrMn2(CO)9](2-) (E=S, 1; Se, 2). Clusters 1 and 2 were isostructural with one another and each displayed a trigonal-bipyramidal structure, with the CrMn2 triangle axially capped by two μ3-E atoms. The analogous telluride cluster, [Te2CrMn2(CO)9](2-) (3), was obtained from the ring-closure of Te2Mn2 ring complex [Te2Mn2Cr2(CO)18](2-) (4). Upon bubbling with CO, clusters 2 and 3 were readily converted into square-pyramidal clusters, [E2CrMn2(CO)10](2-) (E=Se, 5; Te, 6), accompanied with the cleavage of one Cr-Mn bond. According to SQUID analysis, cluster 6 was paramagnetic, with S=1 at room temperature; however, the Se analogue (5) was spectroscopically proposed to be diamagnetic, as verified by TD-DFT calculations. Cluster 6 could be further carbonylated, with cleavage of the Mn-Mn bond to produce a new arachno-cluster, [Te2CrMn2(CO)11](2-) (7). The formation and structural isomers, as well as electrochemistry and UV/Vis absorption, of these clusters were also elucidated by DFT calculations.

Stepwise construction of manganese-chromium carbonyl chalcogenide complexes: synthesis, electrochemical properties, and computational studies

When trigonal-bipyramidal clusters, [PPN][E(2)Mn(3)(CO)(9)] (E = S, Se), were treated with Cr(CO)(6) and PPNCl in a molar ratio of 1:1:2 or 1:2:2 in 4 M KOH/MeCN/MeOH solutions, mono-Cr(CO)(5)-incorporated HE(2)Mn(3)-complexes [PPN](2)[HE(2)Mn(3)Cr(CO)(14)] (E = S, [PPN](2)[1a]; Se, [PPN](2)[1b]), respectively, were formed. X-ray crystallographic analysis showed that 1a and 1b were isostructural and each displayed an E(2)Mn(3) square-pyramidal core with one of the two basal E atoms externally coordinated with one Cr(CO)(5) group and one Mn-Mn bond bridged by one hydrogen atom. However, when the TMBA(+) salts for [E(2)Mn(3)(CO)(9)](-) were mixed with Cr(CO)(6) in a molar ratio of 1:1 in 4 M KOH/MeOH solutions and refluxed at 60 °C, mono-Cr(CO)(3)-incorporated E(2)Mn(3)Cr octahedral clusters [TMBA](3)[E(2)Mn(3)Cr(CO)(12)] (E = S, [TMBA](3)[2a]; Se, [TMBA](3)[2b]), respectively, were obtained. Clusters 2a and 2b were isostructural, and each consisted of an octahedral E(2)Mn(3)Cr core, in which each Mn-Mn or Mn-Cr bond of the Mn(3)Cr plane was semibridged by one carbonyl ligand. Clusters 1a and 1b (with [TMBA] salts) underwent metal core closure to form octahedral clusters 2a and 2b upon treatment with KOH/MeOH at 60 °C. In addition, 1a and 1b were found to undergo cluster expansion to form di-Cr(CO)(5)-incorporated HE(2)Mn(3)-clusters [HE(2)Mn(3)Cr(2)(CO)(19)](2-) (E = S, 3a; Se, 3b), respectively, upon the addition of 1 or 2 equiv of Cr(CO)(6) heated in refluxing CH(2)Cl(2). Clusters 3a and 3b were structurally related to clusters 1a and 1b, but with the other bare E atom (E = S, 3a; Se, 3b) further externally coordinated with one Cr(CO)(5) group. The nature, cluster transformation, and electrochemical properties of the mixed manganese-chromium carbonyl sulfides and selenides were systematically discussed in terms of the chalcogen elements, the introduced chromium carbonyl group, and the metal skeleton with the aid of molecular calculations at the BP86 level of the density functional theory.

Lead-chromium carbonyl complexes incorporated with group 8 metals: synthesis, reactivity, and theoretical calculations

The trichromium-lead complex [Pb{Cr(CO)5}3](2-) (1) was isolated from the reaction of PbCl2 and Cr(CO)6 in a KOH/MeOH solution, and the new mixed chromium-iron-lead complex [Pb{Cr(CO)5}{Fe(CO)4}2](2-) (3) was synthesized from the reaction of PbCl2 and Cr(CO)6 in a KOH/MeOH solution followed by the addition of Fe(CO)5. X-ray crystallography showed that 3 consisted of a central Pb atom bound in a trigonal-planar environment to two Fe(CO)4 and one Cr(CO)5 fragments. When complex 1 reacted with 1.5 equiv of Mn(CO)5Br, the Cr(CO)4-bridged dimeric lead-chromium carbonyl complex [Pb2Br2Cr4(CO)18](2-) (4) was produced. However, a similar reaction of 3 or the isostructural triiron-lead complex [Pb{Fe(CO)4}3](2-) (2) with Mn(CO)5Br in MeCN led to the formation of the Fe3Pb2-based trigonal-bipyramidal complexes [Fe3(CO)9{PbCr(CO)5}2](2-) (6) and [Fe3(CO)9{PbFe(CO)4}2](2-) (5), respectively. On the other hand, the Ru3Pb2-based trigonal-bipyramidal complex [Ru3(CO)9{PbCr(CO)5}2](2-) (7) was obtained directly from the reaction of PbCl2, Cr(CO)6, and Ru3(CO)12 in a KOH/MeOH solution. X-ray crystallography showed that 5 and 6 each had an Fe3Pb2 trigonal-bipyramidal core geometry, with three Fe(CO)3 groups occupying the equatorial positions and two PbFe(CO)4 or PbCr(CO)5 units in the axial positions, while 7 displayed a Ru3Pb2 trigonal-bipyramidal geometry with three equatorial Ru(CO)3 groups and two axial PbCr(CO)5 units. The complexes 3-7 were characterized spectroscopically, and their nature, formation, and electrochemistry were further examined by molecular orbital calculations at the B3LYP level of density functional theory.

Chromium-manganese selenide carbonyl complexes: paramagnetic clusters and relevance to C=O activation of acetone

The paramagnetic even-electron cluster, [Et(4)N](2)[Se(2)Cr(3)(CO)(10)], was found to react readily with Mn(CO)(5)Br in acetone to produce two unprecedented mixed chromium-manganese selenide carbonyl complexes, [Et(4)N][Me(2)CSe(2){Mn(CO)(4)}{Cr(CO)(5)}(2)] ([Et(4)N][1]) and [Et(4)N](2)[Se(2)Mn(3)(CO)(10){Cr(CO)(5)}(2)] ([Et(4)N](2)[2]). X-ray crystallographic analysis showed that anion 1 consisted of two Se-Cr(CO)(5) moieties, which were further bridged by one isopropylene group and one Mn(CO)(4) moiety. The dianionic cluster 2 was shown to display a Se(2)Mn(3) square-pyramidal core with each Se atom externally coordinated by one Cr(CO)(5) group. The formation of complex 1, presumably via C=O activation of acetone, was further facilitated by acidification of the reaction of [Et(4)N](2)[Se(2)Cr(3)(CO)(10)] with Mn(CO)(5)Br in acetone. Complex 1 readily transformed into 2 upon treatment with Mn(2)(CO)(10) in a KOH/MeOH/MeCN solution. Cluster 2 was a 51-electron species, which readily converted to the known 49-electron cluster [Se(2)Mn(3)(CO)(9)](2-) upon heating and bubbling with CO. Magnetic studies of the even-electron cluster, [Et(4)N](2)[Se(2)Cr(3)(CO)(10)], and the odd-electron species, [Et(4)N](2)[2] and [PPN](2)[Se(2)Mn(3)(CO)(9)], were determined by the SQUID measurement to have 2, 3, and 1 unpaired electrons, respectively. In addition, the nature and formation of complexes 1 and 2 are discussed, and the magnetic properties and electrochemistry of [Se(2)Cr(3)(CO)(10)](2-), 2, and [Se(2)Mn(3)(CO)(9)](2-) were further studied and elucidated by molecular orbital calculations at the PW91 level of density functional theory.

Bimetallic Ru-Cu tellurido complexes: controlled synthesis and electrochemical studies of copper halide-TeRu(5) and Te(2)Ru(4) clusters

When [TeRu(5)(CO)(14)](2-) () was treated with 1 equiv. of CuX (X = Cl, Br, I) in THF, mono-CuX-TeRu(5) clusters [TeRu(5)(CO)(14)CuX](2-) (X = Cl, ; Br, ; I, ) were obtained. Clusters consist of an octahedral TeRu(5) core, in which one triangular Ru(3) plane is capped by a mu(3)-CuX fragment. For CuX (X = Cl, Br), the reaction of complex with 2 equiv. of CuX in THF at room temperature formed Cu(4)X(2)-linked di-TeRu(5) clusters [{TeRu(5)(CO)(14)}(2)Cu(4)X(2)](2-) (X = Cl, ; Br, ), while the same reaction in MeCN at -35 degrees C produced bis-CuX-TeRu(5) complexes [TeRu(5)(CO)(14)(CuX)(2)](2-) (X = Cl, ; Br, ). X-Ray analysis showed that displays a TeRu(5) core with two adjacent Ru(3) triangles each capped by a mu(3)-CuBr ligand while has two TeRu(5) cores that are linked by a mu(6)-Cu(4)Br(2) moiety. Clusters and underwent coupling reactions in THF to yield clusters and , and easily transformed to bis-CuX-Te(2)Ru(4) clusters [Te(2)Ru(4)(CO)(10)(CuX)(2)](2-) (X = Cl, ; X = Br, ) in MeCN. On the other hand, the reaction of with 2 equiv. of CuI in THF directly produced the bis-CuI-Te(2)Ru(4) cluster [Te(2)Ru(4)(CO)(10)(CuI)(2)](2-) (). The nature, stability, stepwise cluster transformation, and electrochemistry of these CuX-incorporated TeRu(5)- and Te(2)Ru(4)-based complexes are discussed systematically. In particular, the effects of CuX and the metal cores (TeRu(5)vs. Te(2)Ru(4)) on the resultant Te-Ru-Cu clusters are further elucidated by molecular orbital calculations at the B3LYP level of the density functional theory.