Protonation of 1,1,3,3,5,5-hexakis(dimethylamino)-lambda(5)-[1,3,5] triphosphinine. Cyclotrimethylenetriphosphinic acid. NMR data, crystal structures, and quantum chemical calculations

Preparation of 1,1,3,3,5,5-hexakis(dimethylamino)-1,2-dihydro-3 lambda(5),5 lambda(5)-[1,3,5]triphosphininium-tetrafluoroborate (3) und 1,1,3,3,5,5-he xakis(dimethylamino)-lambda(5)-[1,3,5]triphssphinanetriium-tris(tetrafluoro borate) (4) from 1,1,3,3,5,5-hexakis(dimethylamino)-1 lambda(5),3 lambda(5) ,5 lambda(5)-triphosphinine 1 and HBF4. O(C2H5)(2) are described. The struc tures of 3 und 4 are elucidated by n.m.r. and X-ray structural analyses. By hydrolysis of 4 with conc. hydrochloric acid 1,3,5-trioxo-1 lambda(5),3 la mbda(5),5 lambda(5)-[1,3,5]triphosphinane-1,3,5-triol (cyclotrimethylene-tr iphosphinic acid) (8) is formed. Neutralisation with NaOH yields its sodium salt 9. 8 and 9 are characterized by their n.m.r. spectra. Quantum chemica l calculations have been investigated for the compounds 1'-4' and the trian ion 9. The systems 1'-4' are distinguished from 1-4 by the size of the liga nds at phosphorus which is reduced from N(CH3)(2) to NH2, respectively. The aims of the calculations are to elucidate hybridisations and molecular str uctures, Lewis or resonance structures, electronic charge distributions and NMR chemical shifts.