Phosphines as building blocks in coordination-based self-assembly.

Although phosphines have been less widely investigated in coordination self-assembly than have N- and O-donor ligands, interesting and unusual chemistry has been observed from their study in this context. This includes the selective formation of large rings, unsaturated as well as complete coordination cages, solvent- and anion-dependent aggregation, in addition to ring-opening polymerisation to give crystalline or non-crystalline coordination polymers. Important aspects which underpin this chemistry include (i) soft donor character, (ii) pyramidal geometry at the donor atom, (iii) highly bulky and irregular shapes, (iv) the applicability of (31)P NMR spectroscopy, and (v) their relevance to organometallic chemistry and homogeneous catalysis. In this critical review, findings which precede the concept of self-assembly as adopted by synthetic chemists as well as the latest 'supramolecular' chemistry of phosphines are discussed together in an attempt to give the current state of the topic in its historical context. Finally, some aspects and opportunities which may be of interest in the future are suggested (107 references).