Insertion of One, Two, and Three Molecules of Alkyne into the Pd−C Bond of Ortho-palladated Primary and Secondary Arylalkylamines

Abstract

The ortho-metalated complex [Pd 2 {κ 2 (C,N)-C 6 H 4 CH 2 CH 2 NHMe-2} 2 (μ-Br) 2 ] (1) can be prepared by refluxing a 1:1 mixture of Pd(OAc) 2 and N-methylphenethylamine in acetonitrile, followed by addition of an excess of NaBr. Complex 1 reacts with PPh 3 to give the mononuclear derivative [Pd{κ 2 (C,N)-C 6 H 4 CH 2 CH 2 NHMe-2}Br(PPh 3 )] (2). The cationic complex [Pd{κ 2 (C,N)-C 6 H 4 CH 2 CH 2 NHMe-2}(py) 2 ]-ClO 4 (3) can be obtained by reacting 1 with AgClO 4 and pyridine. The previously reported com- Et (4b)). These dimers react with neutral ligands (L=PPh 3 , t BuNC) in a 2:1 molar ratio to afford the monomeric complexes R=Et (7a), Ph (7b); X=F, R=Et (8a), Ph (8b); X=NO 2 , R=Ph (9)) through a double insertion of the alkyne into the Pd-C bond. Complexes A and D react with PhCtCCO 2 R in molar ratio 1:6-7 to afford a mixture of di-inserted head-to-tail and tail-to-tail isomersR 00 =Ph (12b)). CO further inserts into the Pd-C bond of complexes 7a,b and 8a,b to give the 10-membered palladacycles [Pd 2 {κ 2which contain a cyclopentadienyl unit. Complex 18 reacts with TlOTf and neutral ligands to give [Pd{κ 3 (O, C,N)-OdC(OMe){C 5 (CO 2 Me) 4 }C(CO 2 Me)C 6 H 4 CH 2 NHCH 2 Ph-2}(L)]OTf (L = H 2 O (22), py ( 23)). Reaction of complex A with an excess of 2-butyne for long periods of time affords the coordination derivative 24, probably emerging from tri-insertion of the alkyne into the Pd-C bond, followed by an internal cyclization and β-hydrogen abstraction. When complex G reacts with an excess of 2-butyne and TlOTf, the tri-inserted product 25 is obtained, which also contains a C 5 R 5 unit, although in this case, coordination around the palladium atom is completed by one CdC bond of the cyclopentadienyl unit. The crystal structures of complexes 2, 5a, 6b, 7a, 7b 3 3DMSO, 9, 14a 3 2DMSO, 18, 21, 24, and 25 have been solved by X-ray diffraction. In all these structures, the palladium atom shows a distorted or slightly distorted square-planar environment, except in complex 14a, where Pd(II) exhibits a distorted trigonalbipyramidal geometry.

A kinetico-mechanistic study on the C–H bond activation of primary benzylamines; cooperative and solid-state cyclopalladation on dimeric complexes

“…55 Despite the fact that cyclopalladation of tertiary amines is a long known reaction, 56 and a kinetico-mechanistic study has even been published, 57 cyclometallation of primary amines has received much less attention, even though a general method for their ortho-palladation has been described. 58 Besides this, the elegant isolation of a variety of dinuclear [Pd(AcO)(μ-AcO)L] 2 complexes (L being a primary amine), potential starting materials for the cyclometallated compounds, [59][60][61][62][63] is especially relevant.…”

Sequential Insertion of Alkynes, Alkenes, and CO into the Pd–C Bond of ortho-Palladated Primary Phenethylamines: from η3-Allyl Complexes and Enlarged Palladacycles to Functionalized Arylalkylamines

“…The methyl and phenyl substituents are mutually trans , which requires the isomerization of the first inserted alkyne. This arrangement reduces the steric hindrance between the substituents and is the normal behavior for di-inserted derivatives containing cyclometalated amines …”

“…This arrangement reduces the steric hindrance between the substituents and is the normal behavior for di-inserted derivatives containing cyclometalated amines. 31 …”

Imine Palladacycles: Synthesis, Structural Analysis and Application in Suzuki–Miyaura Cross Coupling in Semi-Aqueous Media

“…Their development has been extended to a rather large variety of metals, especially palladium [ 2 ], and organic ligands, among which Schiff bases, [ 3 ] thiosemicarbazones [ 4 ] and pincer ligands [ 5 ] stand out. The high level of interest in these complexes mainly stems from the high number of applications they provide, such as in metallomesogens [ 6 ], as antineoplastic substances [ 7 , 8 ] and in synthetic chemistry, where they have been used to functionalize aromatic carbons through the insertion reactions of molecules such as CO [ 9 ], alkenes [ 10 ] or alkynes [ 11 ]. In the field of catalysis, after the breakthrough with phosphine palladacycles by Hermann et al [ 12 , 13 , 14 ], a myriad of palladacycles have been used as pre-catalysts in cross-coupling reactions, such as in the work of Suzuki–Miyaura [ 15 , 16 , 17 , 18 , 19 ], Mizoroki–Heck [ 20 ], Negishi [ 21 ] and Sonogashira [ 22 ].…”