We report here covalent attachment of a catalytically active cobalt complex onto boron-doped, p-type conductive diamond. Peripheral acetylene groups were appended on a cobalt porphyrin complex, and azide-alkyne cycloaddition was used for covalent linking to a diamond surface decorated with alkyl azides. The functionalized surface was characterized by X-ray photoelectron spectroscopy and Fourier transform IR spectroscopy, and the catalytic activity was characterized using cyclic voltammetry and FTIR. The catalyst-modified diamond surfaces were used as "smart" electrodes exhibiting good stability and electrocatalytic activity for electrochemical reduction of CO(2) to CO in acetonitrile solution.

Several tricyclic phenoxasilin and phenazasiline heterocycles were synthesized from the corresponding 2,2‘-dilithio-diphenyl ether or diphenyl amine precursor and silicon tetrachloride (or trichlorosilane) followed by reduction with lithium aluminum hydride [H2SiAr2:  Ar2 = C12H8O (1); Ar2 = C14H12O (2); Ar2 = C13H11N (3); Ar2 = C15H15N (4); Ar2 = C13H9Br2N (5)]. The reactivity of hydrosilanes 1−5 with (Ph3P)2Pt(η2-C2H4) (6) was investigated. At room temperature, mononuclear complexes, (Ph3P)2Pt(H)(SiAr2H) and (Ph3P)2Pt(SiAr2H)2, were generally observed by NMR spectroscopy but were too reactive or unstable to isolate. Dinuclear and in some cases trinuclear Pt−Si-containing complexes were observed as the major products from the reactions. Symmetrical dinuclear complexes, [(Ph3P)Pt(μ-η2-H-SiAr2)]2 (8 and 22, respectively), were produced from the reaction of 1 or 3 with 6. In contrast, reaction of silane 2 with 6 produced a trinuclear complex, [(Ph3P)Pt(μ-SiAr2)]3 (16), as the major product. However, reaction of 4 or 5 with complex 6 produced an unsymmetrical dinuclear complex, [(Ph3P)2Pt(H)(μ-SiAr2)(μ-η2-H-SiAr2)Pt(PPh3)] (26 and 30, respectively), as the major component. The molecular structures of a symmetrical (22) and unsymmetrical dinuclear (30) complex as well as a trinuclear (16) complex were determined by X-ray crystallography.

Doing things by halves: The dimeric compound (Cp'Ni)(2)(μ(2)-Se(2)) (Cp' = 1,2,3,4-tetraisopropylcyclopentadienyl), shown in the scheme, was investigated by using low temperature X-ray crystallography and X-ray absorption spectroscopy. The Se K-edge energy strongly indicates a Se physical oxidation state of -1.5, consistent with an unprecedented two-center/three-electron half-bonded Se(2)(3-) or "subselenide" ion.

Organometallics 2001, 20, 700], have unusual E•••E distances, leading to ambiguities in how to best describe their electronic structure. Three limiting possibilities are considered: case A, in which the compounds contain singly bonded E 2 2− units; case B, in which a threeelectron E∴E half-bond exists in a formal E 2 3− unit; case C, in which two E 2− ions exist with no formal E−E bond. One-electron reduction of 1 and 2 yields the new compounds [Cp* 2 Co][Cp′ 2 Ni 2 E 2 ] (1red: E = S, 2red: E = Se; Cp* = 1,2,3,4,5-pentamethylcyclopentadieyl). Evidence from X-ray crystallography, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy suggest that reduction of 1 and 2 is Ni-centered. Density functional theory (DFT) and ab initio multireference methods (CASSCF) have been used to investigate the electronic structures of 1−3 and indicate covalent bonding of an E 2 3− ligand with a mixed-valent Ni 2 (II,III) species. Thus, reduction of 1 and 2 yields Ni 2 (II,II) species 1red and 2red that bear unchanged E 2 3− ligands. We provide strong computational and experimental evidence, including results from a large survey of data from the Cambridge Structural Database, indicating that M 2 E 2 compounds occur in quantized E 2 oxidation states of (2 × E 2− ), E 2 3− , and E 2 2− , rather than displaying a continuum of variable E−E bonding interactions.

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