Intermediates in the palladium-catalysed reaction of 1,3-dienes Part 8. The reaction of palladium-butadiene complexes with ethyl methylacetoacetate

Synthesis, X-ray crystal structure, and reactivity of Pd2(μ-dotpm)2 (dotpm=bis(di-ortho-tolylphosphino)methane)

“…The Pd1-Pd2 bond distance is 2.8560(6) Å, which is on the long end of the PdPd bond range (2.7611(5)-2.8582(6) Å) found for other Pd 2 (l-P-P) 2 complexes [2,13,18]. Although the Pd-Pd bond distance is too long for a formal Pd-Pd r-bond (2.53-2.77 Å) [20], 1 likely possesses weak d 10 -d 10 Pd(0)-Pd(0) bonding interactions attributed to d-p mixing in the r-bonding orbital that are proposed in its Pd 2 (l-P-P) 2 analogues.…”

“…We further examined the spatial effects of the aromatic substituents in the ligand and found that PdCl 2 (dppm) [13,25,26] reacts with 2 equivalents of n-BuLi in diethyl ether to give orange-red crystals of the known binuclear complex Pd 2 (l-dppm) 3 (Scheme 2) [27][28][29]. Obviously, the dipalladium(0) structure can accommodate three bridging dppm ligands but only two bridging dotpm ligands, because the o-tolyl groups are more sterically demanding.…”

“…Bisphosphine complexes Pd 2 (l-P-P) 2 have been synthesized by a number of different reaction methods [1][2][3][12][13][14][15][16][17][18]. For example, Pd 2 (l-dppm) 2 [3,12] (dppm = bis(diphenylphosphino)methane) has not been isolated, but it is observed in situ from the disproportionation of Pd 2 ClMe(l-dppm) 2 [3], and it has been proposed as an intermediate in the electrolysis of Pd 2 (l-dppm) 3 [12].…”

“…Most of the other Pd 2 (l-P-P) 2 complexes are formed from mononuclear palladium compounds. For example, Pd 2 (l-dippm) 2 (dippm = bis(diisopropylphosphino)methane) is obtained as a byproduct of the catalytic reaction of 1,3-butadiene with ethyl methylacetoacetate in the presence of Pd(g 2 -1,3-butadiene)(dippm); the X-ray structure of Pd 2 (l-dippm) 2 has been obtained [13]. The complex Pd 2 (l-dippe) 2 (dippe = 1,2-bis(diisopropylphosphino)ethane) has been implicated in several reactions [14][15][16][17], but it can be isolated in high yield from the reduction of Pd(dippe)(OAc) 2 by hydrazine [1].…”

Linearly Aligned Metal Clusters: Versatile Reactivity and Bonding Nature of Tetrametal M–Mo–Mo–M Complexes (M = Pt, Pd, Ir, and Rh) Supported by 6-Diphenylphosphino-2-pyridonato Ligand

“…Thus, it was reasonably assumed that the first one-electron oxidation of 34 gave a mixed-valence monocationic species [34] + , where two palladium atoms electrochemically communicated through a Mo 2 unit, and the second one-electron oxidation resulted in the formation of [34] 2+ , i.e., complex 32 in acetonitrile (Scheme 4). 93,94 which have been reported to have unique attractive bonding interaction between two Pd 0 atoms through dp mixed ·-bonding orbitals. …”