Synthesis and characterization of cyclometallated complexes of palladium(II) and manganese(I) with bidentate Schiff bases

Article abstract of DOI:10.1016/0022-328X(95)05691-H

Treatment of N,N-isophthalylidenebis(cyclohexylamine), 1,3-(CyN = CH)₂C₆H₄ (L²) (Cy = cyclohexyl) with palladium(II) acetate in glacial acetic acid gave after column chromatography the monocyclometallated dimer complex [{Pd[3-(CHO)C₆H₃C(H)=NCy](O₂CMe)}₂] (1) with a free formyl group on each phenyl ring, and a mixture of 1 with the doubly cyclometallated complex [Pd{3-(CyN=CH)C₆H₃C(H)=NCy}(O₂CMe)] (2). Treatment of 1 with cyclohexylamine gave the correspond ing dimer complex [{Pd[3-(CyN=CH)C₆H₃C(H)=NCy](O₂CMe)}₂] (17) with an uncoordinated C=N group on each phenyl ring. Treatment of 1 and 2 with aqueous NaX gave the dimer complexes [{Pd[3-(CHO)C₆H₃C(H)=NCy](X)}₂] (3: X = Cl; 4: X = Br; 5: X = I) and a mixture of 3, 4 or 5 with the doubly cyclometallated complex [Pd{3-(CyN=CH)C₆H₃C(H)=NCy}(X)] (6: X - Cl; 7: X = Br; 8: X = I), respectively. The dicyclometallated iodo complex 8 was isolated pure. Treatment of 3, 4 or 5 with cyclohexylamine in a 1:2 or 1:4 molar ratio gave the cyclometallated complexes [Pd{3-(CHO)C₆H₃C(H)=NCy}(X)(NH₂Cy)] (9: X = Cl; 10: X = Br; 11: X = I) and [Pd{3-(CyN=CH)C₆H₃C(H)=NCy}(X)(NH₂Cy)] (12: X = Cl; 13: X = Br; 14: X = I), respectively; the last three compounds each contain an uncoordinated C=N group. The corresponding bromo and iodo analogues were made similarly. Treatment of 3, 4 or 5 with thallium cyclopentadienyl or thallium acetylacetonate gave the mononuclear complexes [Pd{3-(CHO)C₆H₃C(H)=NCy}(C₅H₅)] (15) and [Pd{3-(CHO)C₆H₃C(H)=NCy}H₃CCOCHCOCH₃)] (16), respectively. Treatment of L² with MnMe(CO)₅ in a 1:1 molar ratio gave the monocyclometallated complex [(OC)₄Mn{3-(CHO)C₆H₃C(H)=NCy}] (18) by cleavage of one C=N bond, whereas treatment of L² with MnMe(CO)₅ in a 1:1.2 molar ratio produced a mixture of the doubly cyclometallated complex 19 and the monocyclometallated complex 20 without cleavage of the C=N bond. Treatment of N,N-terephthalylidenebis(cyclohexylamine), 1,4-(CyN=CH)₂C₆H₄ (L¹) (Cy = cyclohexyl), with MnMe(CO)₅ in a 1:1.2 molar ratio gave a mixture of the monocyclometallated compound [(OC)₄Mn{4-(CHO)C₆H₃C(H)=NCy}] (22) and the monocyclometallated compound [(OC)₄Mn{4-(CyN=CH)C₆H₃C(H)=NCy}] (23); compound 22 was isolated in a pure state.