Harm P. Dijkstra

Design of novel Hexametallic Cartwheel Molecules From Persubstituted Benzene Compounds

The cartwheel complexes A are novel, nano-sized hexametallic species available from persubstituted benzenes C(6)[3,5-(CH(2)Y)(2)C(6)H(3)] (Y=NMe(2), P(O)Ph(2), PPh(2), SPh). The molecular structure of A (Y=SPh, ML(n)=PdCl) shows C(3) symmetry with adjacent radial Pd-Pd separations of 7.339(2) and 8.006(2) Å and a diametrically opposed Pd-Pd separation of 15.340(2) Å. Because of their size hexametallic species such as A are potential homogeneous catalysts in organic reactions which can be recovered by nanomembrane filtration techniques.

Acetylene-bridged P,C,P'-Ligands and Corresponding Cyclopalladated Compounds

Bis-‘pincer’-cyclopalladates 1 and 2 containing an ethynediyl- or a butadiynediyl-bridge have been synthesized, characterized and used as precatalysts in the Heck reaction.

Synthesis and self-assembly of giant porphyrin discsElectronic supplementary information (ESI) available: experimental procedures and characterization data, NMR- and UV/Vis-titration data. See http://www.rsc.org/suppdata/cc/b4/b401324g/

A giant porphyrin disc (M(w)= 15 kDa) has been synthesized and its self-assembly behaviour at an interface studied by liquid STM which reveals the presence of huge domains (>400 x 400 nm2) of very well ordered and molecularly resolved columnar stacks.

Conjugated G0 metallo-dendrimers, functionalized with tridentate ‘pincer’-type ligands

Abstract 1,3,5-Tris{3,5-bis[(diphenylphosphino)methyl]phenylethynyl}benzene (1) and hexakis{3,5-bis[(diphenylphosphino)methyl]phenylethynyl}benzene (2) have been synthesized and characterized. Furthermore, 1 was successfully cyclopalladated.

Hexakis(PCP-Platinum and -Ruthenium) Complexes by the Transcyclometalation Reaction and Their Use in Catalysis

Hexakis(PCP-pincer) complexes [C6{PtBr(PCP)}6] (5d) and [C6{RuCl(PCP)(PPh3)}6] (5e) were synthesized via the transcyclometalation (TCM) procedure. Mixing the hexakis(PCHP-arene) ligand 7 with six equivalents of [PtBr(NCN)] (1a) or [RuCl(NCN)(PPh3)] (1b), respectively, resulted in the selective metalation of all PCP-ligand sites and the concomitant formation of six equivalents of the NCHN-arene ligand. This procedure was found to be superior over existing metalation procedures. In addition, hexakisruthenium complex 5e was applied as homogeneous catalyst in the hydrogen transfer reactions of cyclohexanone, acetophenone and benzophenone to the corresponding alcohols. In these reactions, the activity per ruthenium center of 5e was found to be of the same order of magnitude as that of the mononuclear analogue [RuCl(PCP)(PPh3)] 3b, indicating that all ruthenium centers act as independent catalytic sites.

Tethered pincer complexes as recyclable homogeneous catalysts

The utilisation of recyclable pincer complexes in applied catalysis is a vital progression in the field of homogeneous catalysis. This is routed in the high thermal and mechanical stability that most pincer complexes demonstrate. The pincer framework of a tridentate bis-chelating ligand system, with two dative appendages and a direct metal ligand σ-bond, shows higher stability than most other coordination complexes. This is essential to testing immobilisation and recycling methods for homogeneous catalysis. We review herein efforts made towards the efficient immobilisation (heterogenisation) of homogeneous pincer complexes, and their application in a variety of catalytic processes. Recycling of pincer complexes, as described herein, does not display high rates of ligand and metal leaching. The outcome of this is an array of homogeneous catalyst immobilisation techniques which can be probed using pincer complexes.