The Nitrogen‐Assisted Triphenylphosphine Displacement of Methylpyridine Ligand in Palladium(II) Complex: Crystal Structures of [Pd(PPh₃)²{η1‐C₅H₃N(CH₃)}(Br)] and [Pd(PPh₃)Br]₂{μ,η²‐C₅H₃N(CH₃)}₂

Abstract

Treatment of Pd(PPh3)4 with 2‐bromo‐4‐methylpyridine, C5H3N(CH3)Br, in dichloromethane at −20 °C causes the oxidative addition reaction to produce the palladium complex [Pd(PPh3)2 {η1‐C5H3N(CH3)}(Br)], 2, by substituting two triphenylphosphine ligands. In a dichloromethane solution of complex 2 at room temperature for 3 h, it undergoes displacement of the triphenylphosphine ligand to form the dipalladium complex [Pd(PPh3)Br]2{μ,η2‐C5H3N(CH3)}2, 3, in which the two 4‐methylpyridine ligands coordinated through carbon to one metal center and bridging the other metal through the nitrogen atom. Complexes 2 and 3 are characterized by X‐ray diffraction analyses.

Syntheses, Reactivities, Characterization, and Crystal Structures of Dipalladium Complexes Containing the 1,3-pyrimidinyl Ligand: Structures of [Pd(PPh3)(Br)]2(μ,η2-C4H3N2)2, [Pd(Br)]2(μ,η2-Hdppa)2, and [{Pd(PPh3)(CH3CN)}2(μ,η2-C4H3N2)2][BF4]2

“…The average C-C bond distances (1.370(5)~1.378(5) Å for 3 and 1.374(5)~1.378(5) Å for 8 ) were comparable to that of the C-C double bond (1.38 Å). The average Pd-C and Pd-N lengths of 3 (1.979, 2.090) and 8 (1.964, 2.089) were in accordance with previously reported values [ 7 , 8 , 9 , 10 , 15 ].…”

“…The average C-C bond distances (1.370(5)~1.378(5) Å for 3 and 1.374(5)~1.378(5) Å for 8) were comparable to that of the C-C double bond (1.38 Å). The average 2.090) and 8 (1.964, 2.089) were in accordance with previously reported values [7][8][9][10]15]. 513.6382 813.3314 6b, Å 13.0314 717.0076 1013.7552 6c, Å 17.6646 921.1326 1216.7500 7α, deg 76.958(1) 90 71.6169 9β, deg 77.213 1105.145 280.4954 10γ, deg 71.316 1 Syntheses of syn and anti-isomers of Pd 2 Cl 2 (dpmMe) 2 [16], as well as the phosphine and arsine Pd(I) dimers Pd 2 (dppm) 2 × 2 (X = Cl, Br) and Pd 2 (dam) 2 Cl 2 {dam = bis(diphenylarsino)methane}, were originally provided by Colton and coworkers [16].…”

“…The Pd-Pd bond distance was 3.2008(4) Å in 3 and 3.2275(4) Å in 8, indicating the absence of bonding between the Pd metal atoms. This is consistent with the previously reported structures [Pd(PPh 3 )Br] 2 {μ,η 2 -C 5 H 3 N(OH)} 2 (3.1823(9) Å), [Pd(PPh 3 )Br] 2 {μ,η 2 -C 5 H 3 N(NH 2 )} 2 (3.1925(5) Å) [ 15 ], and [Pd(PPh 3 )Br] 2 {μ,η 2 -C 5 H 3 N(CH 3 )} 2 (3.2254(6) Å), [ 10 ]. The pyrimidinyl nitrogen atoms were thus preferentially bonded, and the triphenylphosphine ligands favored the trans site to the nitrogen donors, which have a lower trans influence.…”

“…Complexes 3 and 8 were dimers, with each pyrimidinyl unit bridging through a carbon atom of the pyrimidinyl group to one palladium metal center and a nitrogen atom to the other palladium metal center, thus forming a six-membered ring with similar boat-form geometry. 6Å), [10]. The pyrimidinyl nitrogen atoms were thus preferentially bonded, and the triphenylphosphine ligands favored the trans site to the nitrogen donors, which have a lower trans influence.…”

“…We recently reported syntheses, reactivities, inter- and intramolecular dissociation, and crystal structures of Pd complexes containing thiocarbarmoyl [ 7 ], oxythiocarbonyl [ 8 ], thiazolinyl [ 9 ], and methylpyridinyl [ 10 ] moieties. These ligands induced the formation of binuclear complexes that were assisted by the nitrogen or sulfur atom of these ligands.…”