Biological systems are capable of remarkable control over crystal growth, producing morphologically complex single crystals with curved surfaces. We have previously demonstrated that crystals with identical morphological complexities can be produced synthetically using templating routes. This article provides a detailed investigation into the mechanism of this process, studying the relationship between the chemical environment provided by the template and the structure of the templated particles produced. A range of crystals were precipitated within the confines of macroporous polymer templates whose surface chemistries were varied by oxidation with an oxygen plasma, by modification with adsorbed polyelectrolytes, or by electroless deposition of a thin layer of gold and subsequent functionalization with ω-terminated self-assembled monolayers. The surface chemistry of the template was shown to play a crucial role in determining the structure of templated calcite particles, such that only non-charged surfaces directed the formation of single-crystal particles and polycrystalline particles being produced with negatively charged surfaces. Control of crystal morphologies is clearly fundamental to the development of many new functional materials and devices. This work therefore demonstrates how a templating methodology can provide a general and highly controllable route to synthesizing crystalline materials with defined morphologies and structures.

The synthesis of a new CNC pincer-type ligand based on an N-heterocyclic carbene substituted carbazole is presented. The resulting 3,6-di-tert-butyl-1,8-bis(3-methylimidazolin-2-yliden-1-yl)carbazolide (bimca) is a monoanionic, meridionally coordinating tridentate ligand that was generated in situ by deprotonation of the imidazolium salt (bimca)‚2HI (3a) or (bimca)‚2HBF 4 (3b) and characterized by NMR spectroscopy as the Li complex 4. The successful transmetalation to rhodium upon reaction with [Rh(CO) 2 Cl] 2 yielded Rh(bimca)(CO) (5). This complex shows a very small wavenumber in the IR spectrum for the ν(CO) band, thus indicating strong σ-donor and weak π-acceptor properties of the bimca ligand. The highly nucleophilic character of the Rh(I) center was proven by the formal oxidative addition of methyl iodide to Rh(bimca)(CO) (5), a reaction that proceeded more quickly than with any other Rh(I) complex reported so far. The complex Rh(bimca)(CH 3 )I(CO) (6) as well as Rh(bimca)(CO) (5) were characterized by X-ray crystal structure analyses and show a strong distortion of the CO ligand from the Rh(bimca) plane.

The in situ generated CNC pincer lithium complex [Li(bimca)] (2) (bimca = bis(3-methylimidazolin-2ylidene)carbazolide) reacts with M = Pt(0), Pd(0), and Ni(0) precursors under formal oxidative addition to (bimca)hydrido M(II) complexes 3. This unusual reaction involves proton abstraction that can derive from various sources including the ligand itself. Mechanistic considerations are given. The respective [M(bmica)Cl] complexes 4 have been prepared from the hydrido complexes 3 and subjected to reduction in order to identify a proposed zerovalent anionic [M(bimca)] − complex. In the case of M = Pt, only the (bimca)hydrido Pt(II) complex is observed, whereas, for [Pd(bimca)Cl], a dimeric Pd(0) complex [Pd 2 (bimca) 2 ]K 2 (6) bearing an anionic carbazole moiety is formed in the solid state. NMR DOSY experiments show that, in solution, this dimer dissociates to the monomeric anionic complex [Pd(bimca)] − (5b). We conclude that such anionic zerovalent complexes are plausible intermediates in the synthesis of group 10 metal(II) complexes from the respective metal(0) species with anionic CNC ligands.

An efficient Rh(I)-NHC-pincer catalyst for the highly regioselective Meinwald rearrangement of monoalkylated epoxides into methylketones under mild conditions is presented. The nucleophilic epoxide opening is assisted by Lewis acids.

Metal-to-metal allyl transfer: Using the first structurally characterized rhodium eta(1)-allyl complexes it is shown that the sigma-bound allyl substituent can be transferred from the Rh(III) complex to a Rh(I) complex in a fast equilibrium. This process may account for the decrease in regioselectivity observed in allylic alkylation reactions in which complex 1 is used as a catalyst.