Oxidative addition reactions of nicotinamide based organoselenium compounds on [M(PPh_3)_4] (M = Pd or Pt): An insight study for the formation of several isolable products

摘要

Oxidative addition reactions of [2-NC_5H_3(3-COR)Se] _2 (R = NH2, NHPh, or NHpym (pym = pyrimidine)) with [M(PPh_3)_4] (M = Pd, Pt) in benzene afforded complexes of the type, [M{η~2-SeC_5H_3(3-COR)N}{SeC _5H_3(3-COR)N}(PPh_3)] (1) (M = Pt, Pd; R = NH2, NHPh, or NHpym). A similar reaction with [2-NC_5H _3(3-COOH)Se]_2 gave an insoluble product which after extraction with dichloromethane gave [M(Cl){SeC_5H_3(3-COOH) N}(PPh_3)_2] (2). Compound 2, in methanolic solution is transformed into a dimeric ionic complex, but on prolonged standing in CH _2Cl_2 or CHCl_3 is converted into [M(Cl){η~2-SeC_5H_3(3-COOH)N}(PPh _3)]. Treatment of [M(PPh_3)_4] with [2-NC _5H_3(3-CONHPh)SeI] initially yielded the expected oxidative addition product [M(I){SeC_5H_3(3-CONHPh)N}(PPh _3)_2] (4) which loses a molecule of PPh_3 to give [M(I){η~2-SeC_5H_3(3-CONHPh)N}(PPh _3)] (5). Both 4 and 5 on prolonged standing in dichloromethane gave several products such as [M(I)(Ph)(PPh3)2] (6), [2-NC _5H_3(3-CO)SeNH] (9). All the complexes were characterized by elemental analyses and NMR spectroscopy. The molecular structures of [Pt{η~2-SeC_5H_3(3-CONH_2)N} {SeC_5H_3(3-CONH_2)N}(PPh_3)] (1a), [Pd{η~2-SeC_5H_3(3-CONHPh)N}{SeC _5H_3(3-CONHPh)N}(PPh_3)] (1d), [Pt(I)(Ph)(PPh_3)_2] (6) and [Pt(Cl_(0.5)I _(0.5)){C_5H_3(3-CONHPh)N}(PPh_3) _2]·HCl (7) were established by single crystal X-ray diffraction analyses.