Insertion of Internal Acetylenes into Orthopalladated a- Methyl benzylami ne. Crystal Structure of [ Pd{C( Ph)=C( Ph)C( Ph)=C( Ph)C,H,CH( Me)NH,}Br]

Abstract

The complex [Pd{C,H,CH (Me)NH,}( Me,CO),]CIO, reacted with diphenylacetylene to give [ Pd2(q5- C,Ph,),(p-q2-PhC=CPh)]. A pathway for this reaction is suggested. Species related with the postulated intermediates can be isolated starting from [{Pd[C,H,CH( Me) NH,] (p-Br)},] which reacts with disubstituted alkynes (RCECR, R = C0,Me or Ph) to afford [Pd{C(R)=C(R)C(R)=C(R)C,H,CH- (Me)NH,}Br) (R = C0,Me l a or Ph 1 b) through a double insertion of the alkyne into the Pd-C bond. Complex la reacted with 1 equivalent of MeO,CC=CCO,Me 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-n-olefinic bond in la to give the corresponding adducts [Pd{C(R)=C(R)C(R)=C(R)C,H,CH(Me)NH,}Br(L)] (R = C0,Me; L = py 3 or CO 4). Complexes l a and 1 b reacted with AgCIO, (1 : 1) in acetone to afford AgBr and [Pd{C(R)=C(R)C(R)=C(R)C,H,CH(Me)NH2}(solv)]CI0, (R = CO,Me, solv = H,O 5a; R = Ph, solv = Me,CO 5b). The reaction of complex la with AgCIO, (1 :1) and excess of pyridine gave the cationic complex [Pd{C(R)=C(R)C(R)=C(R)C,H,CH(Me)NH,}(py),]CIO, 6 (R = C0,Me). The crystal structure of complex l b has been determined by X-ray diffraction. The palladium atom is bonded to Br, N, C(l) and to the midpoint of the C(3)-C(4) double bond in a distorted square-planar geometry.