ORTHOMETALLATED PRIMARY AMINES .2. INSERTION OF INTERNAL ACETYLENES INTO ORTHOPALLADATED ALPHA-METHYLBENZYLAMINE - CRYSTAL-STRUCTURE OF [PD(C(PH)=C(PH)C(PH)=C(PH)C6H4CH(ME)NH2)BR]

The complex [Pd{C6H4CH(Me)NH2}(Me2CO)(2)]ClO4 reacted with diphenylacetylene to give [Pd-2(eta(5)-C5Ph5)(2)(mu-eta(2)-PhC=CPh)]. A pathway for this reaction is suggested. Species related with the postulated intermediates can be isolated starting from [{Pd[C6H4CH(Me)NH2](mu-Br)}(2)] which reacts with disubstituted alkynes (RC=CR, R = CO2Me or Ph) to afford [Pd{C(R)=C(R)C(R)=C(R)C6H4CH(Me)NH2}Br] (R = CO2Me 1a or Ph 1b) through a double insertion pf the alkyne into the Pd-C bond. Complex 1a reacted with 1 equivalent of MeO2CC=CCO2Me to give the tri-insertion reaction product 2. These are the first products of alkyne insertion into a cyclopalladated primary amine. Neutral ligands, such as pyridine (py) or CO, can break the Pd-pi-olefinic bond in 1a to give the corresponding adducts [Pd{C(R)=C(R)C(R)=C(R)C6H4CH(Me)NH2}Br(L)] (R = CO2Me; L = py 3 or CO 4). Complexes 1a and 1b reacted with AgClO4 (1:1) in acetone to afford AgBr and [Pd{C(R)=C(R)C(R)=C(R)C6H4CH(Me)NH2}(solv)]ClO4 (R = CO2Me, solv = H2O 5a; R = Ph, solv = Me2CO 5b). The reaction of complex la with AgClO4 (1:1) and excess of pyridine gave the cationic complex [Pd{C(R)=C(R)C(R)=C(R)C6H4CH(Me)NH2}(py)(2)]ClO4 6 (R = CO2Me). The crystal structure of complex Ib has been determined by X-ray diffraction. The palladium atom is bonded to Br, N, C(1) and to the midpoint of the C(3)-C(4) double bond in a distorted square-planar geometry.