Tertiary phosphine abstraction from a platinum(II) coordination complex with SeCN-: Crystal and molecular structures of Se=PTA and [Se=PTA-Me]I center dot CH3OH

Reacting [PtCl(PTA)(3)]Cl (PTA = 1,3,5-triaza-7-phosphatricyclo[3.3.1.1(3,7)]decane) with KSeCN in aqueous or MeOH medium results in the abstraction of the PTA ligands to yield Se = PTA. The reaction also proceeds quantitatively by direct reaction of PTA and KSeCN in water or methanol. The methylated PTA ligand, [PTA-Me]I (1-methyl-1-azonia-3,5-diaza-7-phosphatricyclo[3.3. 1.1(3,7)]decane iodide), reacts accordingly with KSeCN, albeit significantly slower. The crystal structure of Se = PTA, 1, and [Se = PTA-Me]I - CH3OH, 2, revealed P = Se bond distances of 2.0991(19) and 2.100(2) angstrom, respectively. The first order phosphorous selenium coupling constants, (1)J(P-Se) (D2O), of 722 and 788 Hz for Se = PTA and [Se = PTA-Me]I, respectively, indicates the latter is significantly less electron rich.