1,3,5,2,4,6-Triazatriphosphorine,2,2,4,4,6-pentakis(dimethylamino)-2,2,4,4,6,6-hexahydro-6-[[3-[1,3,3,3-tetramethyl-1-[(trimethylsilyl)oxy]disiloxanyl]propyl]amino]-