Coordination Chemistry and Methylation of Mixed‐Substituted Tetraphosphetanes (RP−PtBu)(2) (R=Ph, Py)

Synthesis of mixed‐substituted tetraphosphetanes (RP−PtBu)(2) (R=Ph (4), Py (5); Py=2‐pyridyl) is achieved from the condensation of dipyrazolylphosphanes RPpyr(2) (R=Py (1), Ph (3); pyr=3,5‐dimethylpyrazolyl) as P(1)‐building block (R−P) and tBuPH(2) in an equimolar ratio. Compound 5 is of special interest since the presence of two pyridyl‐substituents as well as the P(4)‐core allows for a rich coordination chemistry with coinage metal salts [Cu(MeCN)(4)][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((Me)Py)PMe(2)P((Me)Py)PtBu‐](3+) (13 (3+); (Me)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)(3)PtBu‐](3+) (17 (3+)) when reacted with Me(2)PPMe(2).