Synthesis and structural characterization of 1′-(diphenylphosphino)ferrocene-1-carboxamide, its corresponding hydrazide, some heterocycles derived from the hydrazide and palladium(II) complexes with these functional phosphinoferrocene ligands

Abstract

Two polar phosphinoferrocene ligands, 1′-(diphenylphosphino)ferrocene-1-carboxamide ( 1) and 1′-(diphenylphosphino)ferrocene-1-carbohydrazide ( 2), were synthesized in good yields from 1′-(diphenylphosphino)ferrocene-1-carboxylic acid (Hdpf) via the reactive benzotriazole derivative, 1-[1′-(diphenylphosphino)ferrocene-1-carbonyl]-1 H-1,2,3-benzotriazole ( 3). Alternatively, the hydrazide was prepared by the conventional reaction of methyl 1′-(diphenylphosphino)ferrocene-1-carboxylate with hydrazine hydrate, and was further converted via standard condensation reactions to three phosphinoferrocene heterocycles, viz 2-[1′-(diphenylphosphino)ferrocen-1-yl]-1,3,4-oxadiazole ( 4), 1-[1′-(diphenylphosphino)ferrocen-1-carbonyl]-3,5-dimethyl-1,2-pyrazole ( 5), and 1-[1′-(diphenylphosphino)ferrocene-1-carboxamido]-3,5-dimethylpyrrole ( 6). Compounds 1 and 2 react with [PdCl 2(cod)] (cod = η 2:η 2-cycloocta-1,5-diene) to afford the respective bis-phosphine complexes trans-[PdCl 2(L-κ P) 2] ( 7, L = 1; 8, L = 2). The dimeric precursor [(L NC)PdCl] 2 (L NC = 2-[(dimethylamino-κ N)methyl]phenyl-κ C 1) is cleaved with 1 to give the neutral phosphine complex [(L NC)PdCl( 1-κ P)] ( 9), which is readily transformed into a ionic bis-chelate complex [(L NC)PdCl( 1-κ 2 O,P)][SbF 6] ( 10) upon removal of the chloride ligand with Ag[SbF 6]. Pyrazole 5 behaves similarly affording the related complexes [(L NC)PdCl( 5-κ P)] ( 12) and [(L NC)PdCl( 5-κ 2 O,P)][SbF 6] ( 13), in which the ferrocene ligand coordinates as a simple phosphine and an O,P-chelate respectively, while oxadiazole 4 affords the phosphine complex [(L NC)PdCl( 4-κ P)] ( 11) and a P,N-chelate [(L NC)PdCl( 4-κ 2 N 3 ,P)][SbF 6] ( 14) under similar conditions. All compounds were characterized by elemental analysis and spectroscopic methods (multinuclear NMR, IR and MS). The solid-state structures of 1⋅½AcOEt, 2, 7⋅3CH 3CN, 8⋅2CHCl 3, 9⋅½CH 2Cl 2⋅0.375C 6H 14, 10, and 14 were determined by single-crystal X-ray crystallography.