Mononuclear cationic rhodium complexes of dioxygen have been synthesized and characterized. Crystallographic, spectroscopic, and computational results support the conclusion that these complexes are best described as Rh III {O 2 2− } (rhodium(III) peroxo) complexes, in contrast to recently reported neutral analogues that are best described as Rh I { 1 O 2 } adducts. The nature of the ligand trans to the O 2 ligand is crucial in defining the electronic nature of the RhO 2 bonding. It is determined that π-donor ligands such as the halidesin conjunction with sufficient steric bulkcan stabilize the formation of Rh I { 1 O 2 } adducts, whereas stronger field ligands lead to the stabilization of asymmetric O 2 binding that ultimately favors formation of higher coordinate Rh III peroxo species. The factors that control the relative stabilization of Rh III {O 2 2− } versus Rh I { 1 O 2 } species are related to the well-established Dewar−Chatt−Duncanson model that has been successfully used to describe the bonding in isoelectronic transition-metal alkene complexes. The specific factors that control the stabilization of one electromer (resonance structure) over another are explored and discussed in detail.

The synthesis and characterization of the first dipyrrinato-alkali-metal complex is reported herein. The novel reactivity of this lithium complex is demonstrated in the preparation, isolation, and characterization of a heteroleptic zinc(II) complex in high yield.

Thick, tetrasulfide‐functionalized periodic mesoporous organosilica films are presented as chemically specific coatings on long‐period grating (LPG)‐inscribed fiber‐optic waveguides for the direct, parts per billion (ppb)‐level detection of Pb(II) species in solution.

The first series of alkali dipyrrinato complexes is reported, encompassing lithium, sodium, and potassium salts of meso-unsubstituted and meso-aryl-substituted derivatives. By varying the substituents at the meso position, the intermolecular distance between the two nitrogen atoms and thus the k 2 -N,N-bidentate bite angle was altered, as confirmed by comparison of crystallographic structures of dipyrrin free-bases in the solid-state. The mode of bonding varies as the ionic radius of the metal ion increases: solid-state structures reveal lithium to be accommodated in the plane of the dipyrrinato unit, whilst sodium is accommodated out of plane. The reactivity of analogous lithium, sodium, and potassium dipyrrinato complexes increases as the ionic radius of the metal ion increases, in keeping with the concept that the complexes tend towards an increasingly ionic nature as the size of the alkali metal increases.Résumé : On rapporte la préparation de la première série de complexes dipyrrinato alcalins comportant les sels de lithium, de sodium et de potassium de dérivés méso non substitués et méso substitués par des groupes aryles. En faisant varier la nature des substituants en position méso, on modifie la distance intermoléculaire entre les deux atomes d'azote et, en conséquence, l'angle de morsure k 2 -N,N du bidentate, tel que confirmé par une comparaison des structures cristallographiques des bases libres dipyrrines à l'état solide. Le mode de liaison varie avec une augmentation du rayon ionique de l'ion métallique; les structures à l'état solide révèlent que le lithium s'accommode dans le plan de l'unité dipyrrinato alors que le sodium est accommodé hors du plan. La réactivité des complexes analogues du lithium, du sodium et du potassium augmente avec une augmentation du rayon ionique du métal ionique, en accord avec le concept que les complexes tendent vers une nature de plus en plus ionique avec une augmentation de la taille des métaux alcalins.

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