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

Synthesis of mixed-substituted tetraphosphetanes (RP-P t Bu) 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 t BuPH 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)P t Bu-] 3+ ( 13 3+ ; Me Py = 1-methylpyridiniumyl) via the elimination of iso butene. This salt undergoes a complicated rearrangement reaction involving a P-P/P-P bond metathesis to form trication [-P( Me Py) 3 P t Bu-] 3+ ( 17 3+ ) when reacted with Me 2 PPMe 2 .