Coordination Chemistry and Methylation of Mixed-Substituted Tetraphosphetanes (RP-PtBu) (R=Ph, Py).

Synthesis of mixed-substituted tetraphosphetanes (RP-PtBu) (R=Ph (4), Py (5); Py=2-pyridyl) is achieved from the condensation of dipyrazolylphosphanes RPpyr (R=Py (1), Ph (3); pyr=3,5-dimethylpyrazolyl) as P -building block (R-P) and tBuPH in an equimolar ratio. Compound 5 is of special interest since the presence of two pyridyl-substituents as well as the P -core allows for a rich coordination chemistry with coinage metal salts [Cu(MeCN) ][OTf], Ag[OTf] and in situ formed [Au(tht)][OTf] (tht=tetrahydrothiophene). Both tetraphosphetanes undergo alkylation reaction with MeOTf to give a series of tetraphosphetanium and tetraphosphetanediium triflate salts with additional methylation of the pyridyl-moiety in case of 5 resulting in interesting novel cyclic trications. Harsh reaction condition and an excess of MeOTf converts 5 into the cyclic trication [-P( Py)PMe P( Py)PtBu-] (13 ; Py=1-methylpyridiniumyl) through the elimination of isobutene. This salt undergoes a complicated rearrangement reaction involving a P-P/P-P bond metathesis to form trication [-P(MePy) PtBu-] (17 ) when reacted with Me PPMe .