The First Complexes with Two Metallacycles Fused Around a Common Aryl Substituent: “Akimbo” Complexes

Following the reaction sequence i) oxidative addition
of RNHC­(O)­C6H3I2-2,6 (R = Me, Tol)
to [Pd2(dba)3]·dba in the presence of chelating
ligands
N∧N or XyNC (Xy = C6H3Me2-2,6), ii) treatment of the resulting complexes with TlTfO
or Tl­(acac) (acac = acetylacetonato), and iii) insertion of unsaturated
molecules (CO, XyNC, MeO2CCCCO2Me, MeC­(O)­CHCH2) into one of the Pd–Caryl bonds of the
resulting complexes allowed the synthesis of aryldipalladated complexes
containing the ligands L1 = μ-C,C-{C6H3C­(O)­NHR}-2,6, L2 = μ-C,C-{C6H3C­(O)­NHMe}­(CNXy)2-2,6, L3 =
μ-C,O,C-{C6H3C­(O)­NHMe}-2,6,
L4 = μ-C,O,C,N-{C6H3C­(O)­NR}-2,6,
L6 = μ-C,N,C,O-{C6H3C­(O)­NR}-2-(CO)-6,
L7 = μ-C,N,C,O-{C6H3C­(O)­NR}-2-{C­(CO2Me)C­(CO2Me)}-6, L8 = μ-C,N,C,O-{C6H3C­(O)­NR}-2-(CNXy)-6 and two arylmonopalladated
complexes with the ligands L5 = C,O-{C6H4C­(O)­NHMe}-2 and L9 = C,N-{C6H3C­(O)­NTol}-2-{CHCHC­(O)­Me}-6. The complex with
the ligand L7 inserted CO into the second Pd–Caryl bond to give an L10-Pd2 complex (L10 = μ-C,N,C,O-{C6H3C­(O)­NTol}­(CO)-2-{C­(CO2Me)C­(CO2Me)}-6. The dipalladated species
display a different environment for each palladium atom and represent
the first systems containing two 5 + 5, 5 + 6, 5 + 7, or 6 + 7-membered
palladacycles condensed over the central benzamide group. The two
arms of the ligands L4 and L6-L8 and L10 are “akimbo”,
and we coin this name both for the ligands and for the dimetallic
complexes bearing them. The crystal structure of a [{Pd­(N∧N)}2L6]+ complex has been determined.