Preparation, Structure, and Properties of an Anionic Tetrameric Copper Complex Containing a Planar, Eight-Membered Ring Core

Synthesis of a Series of a Few Hydrosulfide Complexes of Cu(I). A μ3-SH-Bridged Rare Cubane-like Tetramer Showing Efficient Catalytic Activity toward Azide-Alkyne Cycloaddition

A cubane-like tetranuclear hydrosulfido complex of Cu(I), [Cu₄(SH)₄(PPh₃)₄] (1), has been synthesized by the reaction of Cu(NO₃)₂·3H₂O, NaSCOPh, and Cu(PPh₃)₂NO₃ and characterized structurally. Complex 1 represents the first example of crystallographically characterized μ₃-SH-bridged cubanoid hydrosulfide. By direct reactions of [(PPh₃)₂Cu(NO₃)] and NaSH, neutral hydrosulfide complexes [Cu(SH)(PPh₃)₂]·C₆H₆ (2), [Cu₂(SH)₂(PPh₃)₃] (3), and [Cu₂(SH)₂(PPh₃)₄] (4) have also been synthesized and structurally characterized. Complex 2 is monomeric with a terminal hydrosulfide ligand. The other two, 3 and 4, are μ₂-SH-bridged unsymmetrical and symmetrical dinuclear complexes, respectively. In the symmetric one (4), both Cu(I) ions are tetrahedrally coordinated while in the unsymmetric one (3), one Cu(I) ion is tetrahedral and the other one has a trigonal-planar coordination geometry. The catalytic activity of a hydrosulfido complex in a "click" azide-alkyne cycloaddition reaction has been explored for the first time, and complex 1 is found to be an efficient catalyst for the regioselective synthesis of glycoconjugate triazoles.

Inter-conversion of 15-MC-5 to 12-MC-4 manganese metallacrowns: structure and bioactivity of metallacrowns hosting carboxylato complexes

Interaction of manganese with salicylhydroxamic ligands (shi) in methanol, in the presence of pyridine, leads to the formation of a series of 15-membered metallacrown (MC) Mn(II)(L)2[15-MCMn(III)N(shi)-5](py)6 or 7, (L=formato, benzoate or alkanoato ligand, py=pyridine). In the absence of pyridine, the Mn(II)(L)2[12-MCMn(III)N(shi)-4](MeOH)6 metallacrown was isolated and structurally characterized. The crystal structure of {[Mn(II)(HCOO)2][(15-MCMn(III)N(shi)-5)(py)7]}.py.1.9CH3OH.H2O (1) contains a neutral 15-membered metallacrown ring consisting of five Mn(III) and five shi(-3) ligands. The 15-membered metallacrown ring is formed by the succession of five structural moieties of the type [Mn(III)-N-O]. The diverse in the configuration (planar or propeller) for the ring Mn(III) ions gives the metallacrown core a bending structure. The crystal structure of {[Mn(II)(C6H5COO)2][(12-MCMn(III)N(shi)-4)(CH3OH)6]}.2CH3OH (2) contains a neutral 12-membered metallacrown ring consisting of four Mn(III) and four shi(-3) ligands. The 12-membered metallacrown ring is formed by the same way of succession of four structural moieties of the type [Mn(III)-N-O], while the presence of a planar only configuration of shi ligands around ring Mn(III) ions gives to the metallacrown core a planar structure. The encapsulated Mn(II) is six and seven-coordinate for (1) and (2), respectively, and is bound to the hydroximate oxygen of the metallacrown core and two oxygen atoms from the carboxylate ligands. Antibacterial screening data showed that, among all the compounds tested, manganese metallacrowns are more active compared to the simple manganese herbicide or carboxylate complexes, with increased efficiency for [15-MCMn(III)N(shi)-5] compared to the analogous [12-MCMn(III)N(shi)-4].

A cationic 24-MC-8 manganese cluster with ring metals possessing three oxidation states [MnII4MnIII6MnIV2(μ4-O)2(μ3-O)4(μ3-OH)4(μ3-OCH3)2(pko)12](OH)(ClO4)3

Reaction of Mn(ClO4)2 with di-pyridyl ketone oxime, (2-py)2C=NOH, gives the novel cluster [Mn(II)4Mn(III)6Mn(IV)2(mu4-O)2(mu3-O)4(mu3-OH)4(mu3-OCH3)2(pko)12](OH)(ClO4)3 1. It is the only example of a 24-MC-8, and the first metallacrown with ring metal ions in three different oxidation states. Magnetic measurements show antiferromagnetic behavior.

Synthesis, Crystal Structure, Magnetic Properties, and EPR of Cu(bp3ca)Br(2).H(2)O (bp3ca = 2,2'-Bipyridine-3,3'-dicarboxylic Acid). Ferromagnetic Interactions via Unsymmetrical Bromide Bridges

Cu(bp3ca)Br(2).H(2)O crystallizes in the triclinic space group P&onemacr; with a = 10.622(2) Å, b = 10.832(2) Å, c = 14.684(2) Å, alpha = 106.13(1) degrees, beta = 105.91(1) degrees, gamma = 102.74(1) degrees, and Z = 2. The asymmetric unit consists of a bis &mgr;-bromo unsymmetrically dibridged dimer which is further linked to its inversion-related partner to form a dimer of dimers. Weak intertetramer contacts are also observed. The magnetic data for this compound were fit to a linear tetramer model to give J(1) = J(3) = -8.69 x 10(-)(3) cm(-)(1), J(2) = 91.52 cm(-)(1), and the intertetramer interaction J' = -1.187 cm(-)(1) with g = 1.93. EPR data are consistent with the magnetic data. This system is compared to its previously reported chloro counterpart, which differs markedly in both structure and magnetic properties.