Reactions involving reductive aggregation of MnO 4− in methanol in the presence of Ce IV and an excess of carboxylic acid have led to the synthesis of structurally related Ce/ Mn clusters, [Ce 3 Mn 5 O 8 (OMe)(O 2 CBu t ) 13 (MeOH)] (1) and [Ce 2 Mn 3 O 5 (O 2 CPh) 9 (MeOH) 3 ] (2), containing at least one {Mn 2 Ce 2 O 4 } cubane unit. The cores of both clusters contain Mn x units separated by three (1) or two (2) Ce IV ions. Fits of variable-temperature, solid-state dc and ac magnetic susceptibility data reveal dominant ferromagnetic interactions within 1 and 2, resulting in the maximum S = 17 / 2 and S = 5 ground state spins, respectively, and thus suggesting significant ferromagnetic (F) interactions between the Mn x units that are ≥6 Å apart and separated by four intervening bonds through diamagnetic Ce IV . Fits of magnetic susceptibility data also revealed unusual long-range F interactions, and this finding was further supported by high-field EPR measurements and simulations. Density functional theory calculations and a Wannier function analysis confirm long-range interactions and indicate a Mn−Ce−Mn superexchange pathway via Mn-d/Ce-f orbital overlap/hybridization

1,3-Di-tert-butyl-imidazolin-2-ylidine-1,1-diphenylphosphinamine (2) was prepared from 1,3-di-tert-butyl-imidazolin-2-imine (1) and chlorodiphenylphosphine. Compound 2 was treated further with elemental sulfur, selenium, and tellurium to afford the corresponding chalcogenide derivatives, 1,3-di-tert-butyl-imidazolin-2-ylidine-P,P-diphenylphosphinothioicamide (4), 1,3-di-tert-butyl-imidazolin-2-ylidine-P,P-diphenyl-phosphinoselenoicamide (5), and 1,3-ditert-butyl-imidazolin-2-ylidine-P,P-diphenyl-phosphinotelluroicamide (6) in good yield. 1,3-Di-tert-butyl-imidazolin-2-ylidine-P,P-diphenylphosphinicamide (3) was obtained by dissolving compound 2 in hydrochloric acid solution in THF. The corresponding borane adduct, 1,3-di-tert-butyl-imidazolin-2-ylidine-P,P-diphenyl-phosphinaminoborane (7) was isolated by the reaction of compound 2 and sodium borohydride in good yield. The molecular structures of compounds 2 and 4-7 were established by X-ray diffraction analyses. To analyse the electronic structure of chalcogenides of imidazolin-2-imine ligands, the protonation energies of the oxygen, sulfur, and selenide derivative of ligand 2 were calculated by means of density functional theory. Finally, the charge distribution in compounds 3, 4, and 5 were determined using natural bond orbital analysis.

One-pot reactions between the [MnO(OCPh)(py)] triangular precursors and either CaBr·xHO or CaCl·6HO, in the presence of salicylhydroxamic acid (shaH), have afforded the heterometallic complexes [MnCa(OCPh)(shi)(HO)(MeCO)] (1) and (pyH)[MnMnCaCl(OCPh)(shi)(py)] (2), respectively, in good yields. Further reactions but using a more flexible synthetic scheme comprising the Mn(NO)·4HO/Ca(NO)·4HO and Mn(OCPh)·2HO/Ca(ClO)·4HO "metal blends" and shaH, in the presence of external base NEt, led to the new complexes (NHEt)[MnMnCa(OEt)(shi)(EtOH)] (3) and (NHEt)[MnCa(CO)(shi)] (4), respectively. In all reported compounds, the anion of the tetradentate (N,O,O,O)-chelating/bridging ligand salicylhydroxime (shi), resulting from the in situ metal-ion-assisted amide-iminol tautomerism of shaH, was found to bridge both Mn and Ca atoms. Complexes 1-4 exhibit a variety of different structures, metal stoichiometries, and Mn oxidation-state descriptions; 1 possesses an overall octahedral metal arrangement, 2 can be described as a MnCa octahedron bound to an additional Mn unit, 3 consists of a Mn "ring" surrounding a Ca atom, and 4 adopts a rectangular cuboidal motif of eight Mn atoms accommodating two Ca atoms. Solid-state direct-current magnetic susceptibility studies revealed the presence of predominant antiferromagnetic exchange interactions between the Mn centers, leading to S = 0 spin ground-state values for all complexes. From a bioinorganic chemistry perspective, the reported compounds may demonstrate some relevance to both high-valent scheme (3) and lower-oxidation-level species (1, 2, and 4) of the catalytic cycle of the oxygen-evolving complex.

A series of FeLn (Ln = La, Gd, Tb, Dy and Ho) and FeY complexes have been synthesized via metal substitution and characterized by single crystal X-ray diffraction. All the molecules are isostructural and have a FeLnO triangular core with the oxygen atom existing as an μ-oxo anion. DC and AC magnetic susceptibility studies were performed on all the molecules. For FeLn (Ln = Gd, La) and FeY, the data were fitted to Van Vleck equations and the magnetic coupling constants were obtained. In all cases, the two Fe(iii) spins were found to be antiparallel to each other in the ground state leaving the heterometal to remain essentially uncoupled.

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