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A straightforward high-yield synthesis for the photoinitiator bis(2,4,6-trimethylbenzoyl)phenylphosphane oxide (16, IRGACURE 819) involves: i) the reaction of phenyldichlorophosphane, PhPCl2, with sodium to give [Na2(P2Ph2)(tmeda)]6 (5); ii) protonation of 5 with tert-butanol to give 1,2-diphenyldiphosphane, PhHP-PHPh (12); iii) reduction of 12 by sodium to yield [Na(PHPh)]x (13); iv) protonation of 13 with tert-butanol to give phenylphosphane PhPH2 (14) in excellent yields; v) reaction of 14 with 2,4,6-trimethylbenzoylchloride (MesCOCl) in presence of the NaOt-Bu formed in steps ii and iv to give bis(2,4,6-trimethylbenzoyl)phenylphosphane 7; vi) oxygenation of 7 with 30% aqueous hydrogen peroxide to give the final product 16. This reaction can be performed in toluene with about 4 vol-% of tmeda as an activator in a one-pot synthesis without changing the solvent. The structures determined by X-ray diffraction of the unique hexameric aggregate 5 and 16 are reported.

The reaction of phenyldichlorophosphane, PhPCl2, a commercially important precursor for organophosphorus compounds, with lithium and sodium as reducing metals was re-investigated with the aim to well-characterize the resulting oligophosphandiides, [M2(PnPhn)(solv)x] (M = Li, Na). Experimental conditions for the optimal formation of these compounds were found for both series with M = Li and M = Na and several of these were crystallized and characterized by X-ray diffraction studies. As a result, we find that sodium strongly prefers ion triple structures [M2(PnPhn)(solv)x] over solvent-separated ion pairs, [M(solv)m]+[MPnPhn(solv)n]?, which have a higher tendency to form with M = Li. Also, while [Na2(P4Ph4)(solv)x] retains its structure in thf solution, [Li2(P4Ph4)(solv)x] partially dissociates into the radical anion (Ph2P2).? which is detected by EPR spectroscopy. The knowledge about the structures and the behavior of the alkali metal diphosphandiides allows us to propose a reaction mechanism for their formation.

The dibenzo[a,d]cycloheptatrienyl residue is introduced as platform for the high-yield synthesis of new rigid phosphanes (tropp ligand system) and phosphiranes (BABAR-phos); strained three-membered heterocycles. With tropp as ligands, transition metal complexes with unusual low oxidation states at the metal center could be prepared and isolated. Especially mononuclear paramagnetic rhodium(O) and iridium(O) complexes could be studied in detail. The BABAR-phos compounds show very high thermal and chemical stability, i.e. they are remarkably stable against oxygen, sulfur, strong alkylating agents, and aqueous acid and base. Rhodium(l) complexes with BABAR-phos proved to be highly stable active catalyst precursors for hydroborations.