Enzymatic immobilization of organometallic species: biosilification of NCN- and PCP-pincer metal species using demosponge axial filaments.

Silicatein protein filaments isolated from marine demosponges have been used to influence the condensation of siloxanes bearing organometallic pincer complexes. The siliceous material is formed under remarkably mild conditions and the organometallic pincer becomes an intrinsic part of the silica. The immobilisation of a metal pincer, which acts as a sensor and initial results on the immobilisation of a pre-catalytic pincer species are reported.

Prototropic rearrangements in cycloheptatrienyl PCP pincer iridium complexes.

When the cycloheptatriene iridium(iii) pincer complex (PCP)Ir(CO)(H)(Cl) (3) (PCP = 2,7-(CH(2)P(t)Bu(2))(2)C(7)H(5)) is treated with the bases NaH, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and lithium 2,2,6,6-tetramethylpiperidide (LiTMP) under various conditions different products are obtained. At elevated temperatures and with DBU or LiTMP as a base the trans dihydride (PCP')Ir(CO)(H)(2) (PCP' = 2-(CHP(t)Bu(2))-7-(CH(2)P(t)Bu(2))C(7)H(4)) (5) is formed where the pi-system extends into one of the phosphine bridges. This compound loses H(2) to give the square-planar iridium(I) carbonyl complex (PCP'IrCO). The dihydride 5 can also rearrange to the new isomeric iridium(I) carbonyl 6 (PCP''IrCO, PCP'' = 2,7-(CH(2)P(t)Bu(2))(2)C(7)H(5)). Thus the two hydrides have moved into the ligand backbone creating a methylene group in the 3-position of the cycloheptatriene ring. Alternatively, 6 is formed by a rearrangement from 6a which differs from 6 by having the methylene group in the 4-position of the cycloheptatriene ring. The iridium(I) carbonyl 6a in turn is made from 3 by treatment with DBU at room temperature. Interestingly, when compound is heated to reflux in THF the hydrogen bound at the metal carbon is shifted to a carbon atom in the cycloheptatriene ring generating a ring methylene group (3a). From this complex HCl is eliminated upon chromatography forming 6 as the final product. Quantum chemical calculations at various levels of theory illustrate the relative energetic stabilities of all iridium complexes.

Variable solid state aggregations in a series of (isocyanide)gold(I) halides with the novel trimethylamine-isocyanoborane adduct.

This paper provides evidence that the degree of aurophilic character and resulting solid state arrangement observed in (isocyanide)gold(I) halides is in part dependent on the nature of halide substituent. In particular, we report here the synthesis of a series of novel (isocyanide)gold(I) halides involving trimethylamine-isocyanoborane, an unusual 'zwitterionic' isocyanide that is comparable to the more familiar methyl isocyanide, but potentially more strongly Lewis basic. The reaction of chloro(dimethyl sulfide)gold(I) and the isocyanoborane species, (RNC)(R =(H3C)3NB(H)2), gives the novel crystalline adduct [(RNC)AuCl] (1). Treatment of 1 in an organic phase with aqueous KBr effected substitution of the chloride to give the bromide analogue [(RNC)AuBr] (2). The structures of 1 and 2 were determined by X-ray crystallography to be isostructural, consisting of a zigzag topology of chains of monomers, where adjacent gold(I) centres interact aurophilically. However, similar reaction of 1 with KI solution affords the unusual and unexpected compound, [(RNC)2Au][AuI2] (3). This iodide 3, is a linear chain polymer of alternating anion, cation units that is formed via ligand redistribution. The complexes 1-3 all fluoresce in the presence of UV light; the fluorescence of 3 being most prevalent at room temperature. The free trimethylamine-isocyanoborane ligand, the dimeric structures of compounds 1,2 and the thermodynamic stabilities of the dimers in the gas phase were studied by density functional and ab initio calculations at various levels of theory. The theoretical results are compared to the corresponding experimental data.

Transition Metal Complexes with the Proton Sponge 4,9-Dichloroquino[7,8-h]quinoline: Highly Twisted Aromatic Systems and an Extreme "Out-of-Plane" Position of the Coordinated Transition Metal Atom.

An extremely high thermal and chemical stability as well as a unique "out-of-plane" position of the metal atom is shown by the first stable transition metal complexes formed with the proton sponge 1 as the ligand. The properties of these complexes await wide application in catalysis and medicine.