Cationic terminal gallylene complexes by halide abstraction: coordination chemistry of a valence isoelectronic analogue of CO and N2.

While N(2) and CO have played central roles in developing models of electronic structure, and their interactions with transition metals have been widely investigated, the valence isoelectronic diatomic molecules EX (E = group 13 element, X = group 17 element) have yet to be isolated under ambient conditions, either as the "free" molecule or as a ligand in a simple metal complex. As part of a program designed to address this deficiency, together with wider issues of the chemistry of cationic systems [L(n)M(ER)](+) (E = B, Al, Ga; R = aryl, amido, halide), we have targeted complexes of the type [L(n)M(GaX)](+). Halide abstraction is shown to be a viable method for the generation of mononuclear cationic complexes containing gallium donor ligands.

Colorimetric fluoride ion sensing by polyborylated ferrocenes: structural influences on thermodynamics and kinetics.

The thermodynamic factors underlying the use of ferroceneboronic esters as electrochemical or colorimetric fluoride ion sensors have been investigated through the synthesis of a range of systematically related derivatives differing in the number/nature of the boronic ester substituents and in the nature of ancillary ligands. Thus, if the shift in electrochemical potential associated with the conversion of one (or more) boronic ester group(s) to anionic boronate(s) on fluoride binding is sufficient to allow oxidation of the resulting host/guest complex by dioxygen, colorimetric sensing is possible. In practice, while monofunctional systems of the type CpFe[eta(5)-C(5)H(4)B(OR)(2)] offer selectivity in fluoride binding, electrochemical shifts in chloroform solution are insufficient to allow for a colorimetric response.

Insertion reactions of dicyclohexylcarbodiimide with aminoboranes, -boryls and -borylenes.

Insertion reactions of dicyclohexylcarbodiimide with aminoboranes and with aminoboryl and -borylene transition metal complexes have been examined as potential routes to new boron-containing ligand systems. Reactions with systems containing two-coordinate boron centres are found to be significantly more facile than those with three-coordinate substrates. Thus, reaction of (dicyclohexylamino)boron dichloride () with dicyclohexylcarbodiimide over 36 h at 50 degrees C generates the (structurally authenticated) guanidinate complex Cy(2)NC(NCy)(2)BCl(2) () via insertion into the BN bond.

Synthesis of polymeric and macrocyclic Lewis acids: influence of backbone on degree of aggregation.

A simple, one-step synthesis of multinuclear Lewis acids can be driven with high selectivity towards either macrocyclic or polymeric arrays by appropriate choice of backbone framework.

Fluoride anion binding by cyclic boronic esters: influence of backbone chelate on receptor integrity.

A systematic investigation of fluoride anion binding properties as a function of chelate backbone has been carried out for ferrocene functionalised boronic esters of the types FcB(OR)2 and fc[B(OR)2]2 [Fc = ferrocenyl = (eta5-C5H5)Fe(eta5-C5H4); fc = ferrocendiyl = Fe(eta5-C5H4)2]. Cyclic boronic esters containing a saturated five- or six-membered chelate ring are readily synthesized from ferrocene, and selectively bind fluoride via Lewis acid/base chemistry in chloroform solution. The resulting complexes are characterized by relatively weak fluoride binding (e.