Cyclometallated complexes of palladium(II) with a C,N,N′ terdentate Schiff base donor ligand. Oxidative addition of an aryl-chlorine bond to palladium(0)

Article abstract of DOI:10.1016/S0022-328X(96)06800-3

Treatment of N-(2-chlorobenzylidene)-N,N′-dimethylethylenediamine, 2-ClC₆H₄C(H)=NCH₂CH₂NMe₂, with tris(dibenzylideneacetone)dipalladium(0) in chloroform gave the oxidative addition cyclometallated product [Pd{C₆H₄C(H)=NCH₂CH₂NMe₂}(Cl)] (1) with the palladium atom bonded to a C,N,N′ terdentate donor ligand. Treatment of 1 with tertiary monophosphines gave the cyclometallated complexes [Pd{C₆H₄C(H)=NCH₂CH₂NMe₂}(Cl(L)] (2: L = PPh₃; 3: L = PEtPh₂; 4: L = PEt₂Ph; 5: L = PEt₃), where the phosphine ligand is either trans to the phenyl carbon atom (2, 3) or trans to the imine nitrogen atom (4, 5). Treatment of 1 with silver perchlorate followed by reaction with tertiary monophosphines gave the cyclometallated complexes [Pd{C₆H₄C(H)=N-CH₂CH₂NMe₂}(L)][ClO₄] (6: L = PPh₃; 7: L = PEtPh₂; 8: L = PEt₂Ph; 9: L = PEt₃). Reaction of 1 with thallium acetylacetonate gave the cyclometallated complex [Pd{C₆H₄C(H)=NCH₂CH₂NMe₂}(H₃CCOCHCOCH₃)] (10). Treatment of 1 with ditertiary diphosphines in a complex 1/diphosphine 2:1 molar ratio gave the dinuclear cyclometallated complexes [{Pd[C₆H₄C(H)=NCH₂CH₂NMe₂](Cl)}₂(L-L)] (11: L-L = trans-Ph₂PCH=CHP-Ph₂; 12: L-L = Ph₂P(CH₂)₃PPh₂; 13: L-L = Ph₂P(CH₂)₄PPh₂), where the phosphorus atom is trans to the phenyl carbon atom. Treatment of 1 with silver perchlorate followed by ditertiary diphosphines in a complex 1/diphosphine 2:1 molar ratio gave the dinuclear cyclometallated complexes [{Pd[C₆H₄C(H)=NCH₂CH₂NMe₂]}₂(L-L)][ClO₄]₂ [14: L-L = trans-Ph₂P-CH=CHPPh₂; 15: L-L = Ph₂P(CH₂)₃PPh₂; 16: L-L = Ph₂P(CH₂)₄PPh₂)]. Reaction of 1 with ditertiary diphosphines in a complex 1/diphosphine 1:1 molar ratio, and silver perchlorate as appropriate, gave the cyclometallated complexes [Pd{C₆H₄C(H)=NCH₂CH₂NMe₂}(Ph₂P(CH₂)₂PPh₂-P,P)][ClO₄] (17), [Pd{C₆H₄C(H)=NCH₂CH₂NMe₂}(Ph₂P(CH₂)₃PPh₂-P,P)][ClO₄] (18), [Pd{C₆H₄C(H)=NCH₂CH₂NMe₂}(cis-Ph₂PCH = CHPPh₂-P,P)][Cl] (19) and [Pd{C₆H₄C-(H)=NCR₂CH₂NMe₂}(Cl)(Ph₂P(CH₂)₄PPh₂-P,P)] (20).