Multi-Functional Ligand Design: cis- and trans-Spanning multidentate ligands
We are interested in ligand design for metal catalysis. We have worked on alkenes, alkene-phosphine, alkene-phosphine sulfide and phosphinite ligands. We are interested in synergic effects of different types of functionality.
Our work on dibenzylidene acetone (dba) ligands led us to design and prepare a phosphine-variant containing the dba sub-unit. Using a straight-forward synthesis it was possible to prepare dba-phos, as a new ligand. It is a multidentate ligand system, offering several coordination modes toward transition metals. Some examples are given below.
The X-ray crystal structure of dba-phos is shown opposite, here in its s-cis,s-cis-conformation (around dienone moiety). The ligand is flexible and can adopt a range of coordination modes to transition metals.
This work was reported: Chem. Eur. J. 2013, 19, 6034.
A platinum complex showing that the dba-phos ligand can be cis-chelating (at Pt).
A palladium complex showing that the dba-phos ligand can be trans-chelating (at Pd).
The dba-phos ligand will also bridge two palladium centres, see opposite.
The Pd2(dba-phos)2 complex exhibits interesting chemical exchange, which was studied using dynamic NMR spectroscopic methods.