Synthesis, coordination and catalytic use of 1-(diphenylphosphino)-1'-carbamoylferrocenes with pyridyl-containing N-substituents
Abstract
Ferrocene phosphinocarboxamides were studied as ligands for palladium. Their structures were determined by X-ray structure analysis from single-ctystal data.
Ferrocene phosphinocarboxamides, 1-(diphenylphosphino)-1'-{N-[(2-pyridyl) methyl]carbamoyl} ferrocene (1) and 1-(diphenylphosphino)-1'-{N-[2-(2- pyridyl) ethyl] carbamoyl} ferrocene (2) were prepared from 1-(diphenylphosphino)- 1'-ferrocenecarboxylic acid and studied as ligands for palladium. Starting with [PdCl2(cod)], the reactions at a 2 : 1 ligand-to-metal ratio gave uniformly the bis- phosphine complexes [PdCl2( L-kappa P)(2)] (3, L = 1; 4, L = 2) whereas those performed at a 1 : 1 ratio yielded distinct products: [PdCl2(1-kappa P-2,N)] (5) with 1 coordinating as a trans-spanning P, N-donor, and the symmetric, P, N-bridged dimer [(mu-2-N,P)(2){PdCl2}(2)] (6), respectively.
The crystal structures of 1, 2, 4 . 4 CHCl3, 5.AcOH, and 6 . 8 CHCl3 as determined by X- ray diffraction showed the compounds to form well de. ned solid-state assemblies through hydrogen bonds. Testing of the phosphinocarboxamides in the palladium-catalysed Suzuki cross-coupling reaction revealed 1 and 2, combined with Pd(OAc)(2) to form efficient catalysts for the reactions of aryl bromides while aryl chlorides coupled only when activated with electron-withdrawing groups.