Reactivity of dipyrimidyldiselenides with [M(PPh3)4] and 2-pyrimidylchalcogenolates with [MCl2(diphosphine)] (M = Pd or Pt)

Oxidative addition reactions of {SeC4H(4,6-R)2N2}2 with [M(PPh3)4] (M = Pt or Pd) in benzene afforded complexes of composition, [Pt{SeC4H(4,6-R)2N2}2(PPh3)2] (1) and [Pd{η2-SeC4H(4,6-R)2N2}{SeC4H(4,6-R)2N2}(PPh3)] (3) (R = H or Me). The former when left in solution dissociated to [Pt{η2-SeC4H(4,6-R)2N2}{SeC4H(4,6-R)2N2}(PPh3)] (2) and PPh3. Treatment of [PtCl2(P∩P)] (P∩P = dppe or dppp) and NaEC4H(4,6-R)2N2 (for E/R = Se/H/Me or Te/Me) gave mononuclear complexes [Pt{EC4H(4,6-R)2N2}2(P∩P)] (4 and 6) (R = H or Me, P∩P = dppe or dppp) which on leaving for recrystallization in dichloromethane/CDCl3 solution resulted in trinuclear chalcogenido-bridged complexes [Pt3(μ-E)2(P∩P)3]·2Cl (E = Se or Te) (6). The latter were also formed when [PtCl2(P∩P)] (P∩P = dppe or dppp) was treated with sodium 2-pyrimidyltellurolate. The substitution reactions between [PdCl2(P∩P)] (P∩P = dppe or dppp) and NaEC4H(4,6-R)2N2 (E = Se or Te; R = H or Me) afforded chalcogenido-bridged trinuclear complexes, [Pd3(μ-E)2(P∩P)3]2Cl (7) (P∩P = dppe or dppp). These complexes were characterized by elemental analyses and NMR (1H, 31P, 77Se, 125Te, 195Pt) spectroscopy. The molecular structures of [Pt(SeC4H3N2)2(PPh3)2] (1a) and [Pd{η2-SeC4H3N2}{SeC4H3N2}(PPh3)] (3a) were established by single crystal X-ray diffraction analyses. Metal atom in these complexes acquires a distorted squareplanar configuration.