Oxidative addition reactions of nicotinamide based organoselenium compounds on [M(PPh3)4] (M = Pd or Pt): An insight study for the formation of several isolable products

Oxidative addition reactions of [2-NC5H3(3-COR)Se]2 (R = NH2, NHPh, or NHpym (pym = pyrimidine)) with [M(PPh3)4] (M = Pd, Pt) in benzene afforded complexes of the type, [M{η2-SeC5H3(3-COR)N}{SeC5H3(3-COR)N}(PPh3)] (1) (M = Pt, Pd; R = NH2, NHPh, or NHpym). A similar reaction with [2-NC5H3(3-COOH)Se]2 gave an insoluble product which after extraction with dichloromethane gave [M(Cl){SeC5H3(3-COOH)N}(PPh3)2] (2). Compound 2, in methanolic solution is transformed into a dimeric ionic complex, but on prolonged standing in CH2Cl2 or CHCl3 is converted into [M(Cl){η2-SeC5H3(3-COOH)N}(PPh3)]. Treatment of [M(PPh3)4] with [2-NC5H3(3-CONHPh)SeI] initially yielded the expected oxidative addition product [M(I){SeC5H3(3-CONHPh)N}(PPh3)2] (4) which loses a molecule of PPh3 to give [M(I){η2-SeC5H3(3-CONHPh)N}(PPh3)] (5). Both 4 and 5 on prolonged standing in dichloromethane gave several products such as [M(I)(Ph)(PPh3)2] (6), [2-NC5H3(3-CO)SeNH] (9). All the complexes were characterized by elemental analyses and NMR spectroscopy. The molecular structures of [Pt{η2-SeC5H3(3-CONH2)N}{SeC5H3(3-CONH2)N}(PPh3)] (1a), [Pd{η2-SeC5H3(3-CONHPh)N}{SeC5H3(3-CONHPh)N}(PPh3)] (1d), [Pt(I)(Ph)(PPh3)2] (6) and [Pt(Cl0.5I0.5){C5H3(3-CONHPh)N}(PPh3)2]·HCl (7) were established by single crystal X-ray diffraction analyses.