The first orthopalladation of a primary nitrobenzylamine. Synthesis of chiral cyclopalladated complexes derived from (S)-α-methyl-4-nitrobenzylamine

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Abstract
By refluxing a mixture of (S)-α-methyl-4-nitrobenzylamine and Pd(O2CMe)2(1 : 1) in acetone, complexes (S,S)-[{Pd[C6H3{CH(Me)NH2}-2-NO2-5](µ-X)}2](X = MeCO21a or Cl 1b) are obtained. Complex 1b can also be obtained by treating (S)-α-methyl-4-nitrobenzylamine hydrochloride with Pd(O2CMe)2(1 : 1) in acetone. These complexes are the first orthometallated complexes containing a primary amine with an electron-withdrawing group in the benzene ring. Complex 1a reacted with an excess of NaBr or Nal to give (S,S)-[{Pd[C6H3{CH(Me)NH2}-2-NO2-5](µ-X)}2](X = Br 1c or I 1d). Triphenylphosphine reacted with 1b or 1c to give (S)-[Pd{C6H3[CH(Me)NH2]-2-NO2-5}X(PPH3)](X = Cl 2a or Br 2b). The reaction of complex 1b with AgClO4(1 : 1) and an excess of pyridine (py) gave (S)-[Pd{C6H3[CH(Me)NH2]-2-NO2-5}(py)2]ClO43. Complex 1c reacted with 3 equivalents of RCCR (R = CO2Me) to give a tri-insertion reaction product, the crystal structure of which has been determined: space group P212121, a= 11.0969(14), b= 17.197(2), c= 19.604(3)Å, R(F)= 0.041. The planar co-ordination at palladium is not significantly disturbed by a short contact of 2.600 Å to the C atom of a CO2Me group. A cationic derivative of this complex has also been prepared.