Coordination chemistry of dinucleating P2N2S ligands: preparation and characterization of cationic palladium complexes

Abstract

The thioethers(4-tert-butyl-2,6-bis((2-(diphenylphosphino)ethylimino)methyl)phenyl)(tert-butyl)sulfane (tBuL³) and (4-tert-butyl-2,6-bis((2-(diphenylphosphino)ethylamino)methyl)phenyl)(tert-butyl)sulfane (tBuL⁴) react readily with [Pd(NCMe)₂Cl₂] to give the dinuclear palladium thiophenolate complexes [(L³)Pd₂(Cl)₂]⁺ (4) and [(L⁴)Pd₂(µ-Cl)]²⁺ (5) (HL³ = 2,6-bis((2-(diphenylphosphino)ethylimino)methyl)-4-tert-butylbenzenethiol, HL⁴ = 2,6-bis((2-(diphenylphosphino)ethylamino)methyl)-4-tert-butylbenzenethiol). The chlorides in 4 could be replaced by neutral (MeCN) and anionic ligands (NCS^–, N₃^–, I^–, CN^–) to give the dinuclear Pd^II complexes [(L³)Pd₂(NCMe)₂]³⁺ (6), [(L³)Pd₂(SCN)₂]⁺ (7), [(L³)Pd₂(N₃)₂]⁺ (8), [(L³)Pd₂(I)₂]⁺ (9), and [(L³)Pd₂(CN)₂]⁺ (10). The acetonitrile ligands in 6 are readily hydrated to give the corresponding amidato complex [(L³)Pd₂(NHCOMe)]²⁺ (11). All complexes were isolated as perchlorate salts and studied by infrared, ¹H, and ³¹P NMR spectroscopy. In addition, complexes 4[ClO₄]·EtOH, 5[ClO₄]₂, 9[ClO₄], 10[ClO₄]·EtOH, and 11[ClO₄]₂·MeCN·MeOH have been characterized by X-ray crystallography. The dipalladium complex 4 was found to catalyse the vinyl-addition polymerization of norbornene in the presence of MAO (methylalumoxane) and B(C₆F₅)₃/AlEt₃.