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

Abstract

Treatment of N, N-isophthalylidenebis(cyclohexylamine), 1,3-(CyNCH) 2C 6H 4 ( L 2 ) (Cy = cyclohexyl) with palladium(II) acetate in glacial acetic acid gave after column chromatography the monocyclometallated dimer complex [{ Pd[3-(CHO)C 6H 3C(H)N Cy](O 2CMe)} 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)C 6H 3C(H)N Cy}(O 2CMe) ] ( 2). Treatment of 1 with cyclohecylamine gave the corresponding dimer complex [{ Pd[3-(CyNCH)C 6H 3C(H)N Cy]O 2CMe)} 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)C 6H 3C(H)N Cy](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)C 6H 3C(H)N Cy}(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)C 6H 3C(H)N Cy}(X)(NH 2Cy) ] ( 9: X = Cl; 10: X = Br; 11: X = I) and [{ Pd[3-(CyNCH)C 6H 3C(H)N Cy}(X)(NH 2Cy) ] ( 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)C 6H 3C(H)N Cy}(C 5H 5) ] ( 15) and [{ Pd[3-(CHO)C 6H 3C(H)N Cy}(H 3CCOCHCOCH 3) ] ( 16), respectively. Treatment of L 2 with MnMe(CO) 5 in a 1 : 1 molar ratio gave the monocyclometallated complex [ (OC) 4 Mn{3-(CHO)C 6H 3C(H)N Cy} ] ( 18) by cleavage of one CN bond, whereas treatment of L 2 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) 2C 6H 4 ( L 1 ) (Cy = cyclohexyl), with MnMe(CO) 5 in a 1 : 1.2 molar ratio gave a mixture of the monocyclometallated compound [ (OC) 4 Mn{4-(CHO)C 6H 3C(H)N Cy} ] ( 22) and the monocyclometallated compound [ (OC) 4 Mn{4-(CyNCH)C 6H 3C(H)N Cy} ] ( 23); compound 22 was isolated in a pure state.