Stepwise successive insertion of carbon monoxide and allenes into palladium-carbon bonds of complexes containing the rigid bidentate nitrogen ligand bis(p-anisylimino)acenaphthene

Propadiene, 3-methyl-1,2-butadiene (DMA), and 2,4-dimethyl-2,3-pentadiene (TMA) reacted via migratory insertion with both neutral and ionic Pd(R)X(p-An-BIAN) (R = Me (1), C(O)Me (2); X = Cl (a), SO3CF3 (b)) complexes, containing the rigid nitrogen ligand bis(p-anisylimino)acenaphthene (p-An-BIAN), resulting in the novel and stable allylpalladium complexes Pd(eta(3)-C(3)H(4)R)X(p-An-BIAN) (R = Me (3), C(O)Me (6)), Pd(eta(3)-C(5)H(8)R)X(p-An-BIAN) (R = Me (4), C(O)Me (7)), and Pd(eta(3)-C(7)H(12)R)X(p-An-BIAN) (R = Me (5), C(O)Me (8)), respectively (X = Cl (a), SO3CF3 (b)). The neutral complexes 6a and 7a reacted with carbon monoxide to form the acylpalladium complexes Pd(C(O)C3H4C(O)Me)Cl(p-An-BIAN) (9) and Pd(C(O)C5H8C(O)Me)Cl(p-An-BIAN) (10), respectively, while the analogous trifluoromethanesulfonate complexes 6b and 7b were completely inert toward CO. Complexes 9 and 10 reacted again with propadiene and DMA, respectively, to yield the allylpalladium complexes Pd(eta(3)-C3H4C(O)C3H4C(O)Me)Cl(p-An-BIAN) (11) and Pd(eta(3)-C5H8C(O)C5H8C(O)Me)Cl(p-An-BIAN) (12), respectively. Also insertion of norbornadiene in complex 10 was possible, yielding the ionic complex [Pd(C7H8C(O)C5H8C(O)Me)(p-An-BIAN)]Cl (13a), which reacted with AgSO3CF3 to give [Pd(C7H8C(O)C5H8C(O)Me)(p-An-BIAN)]SO3CF3 (13b). The novel complexes 9-12 are the first isolated and fully characterized complexes formed by successive insertion reactions of carbon monoxide and allenes, while 13a is the first isolated complex containing a metal-bonded ter-oligomer of carbon monoxide, an allene, and norbornadiene. The X-ray crystal structure of 7a has been determined and shows a distorted square pyramidal geometry in which the BIAN ligand is bonded to the palladium center in an unusual asymmetric fashion (Pd-N(1)= 2.144(7) Angstrom; Pd-N(2)= 2.600(8) Angstrom).