1392507-06-0Relevant articles and documents
Preparation, structure, and reactivity of dipalladium(I) complexes containing the carbanion 2-C6F4PPh2: Coexistence of distinct, noninterconverting head-to-head [dipalladium(0/II)] and head-to-tail [dipalladium(I)] species
Bhargava, Suresh K.,Priver, Steven H.,Willis, Anthony C.,Bennett, Martin A.
, p. 5561 - 5572,12 (2020/08/31)
Comproportionation of trans-[Pd(κ2-2-C6F 4PPh2)2] with [PdL4] (L = PPh 3, AsPh3) gives metal-metal-bonded dipalladium(I) complexes [Pd2I(μ-2-C6F4PPh 2)2(L)2] [L = PPh3 (5), AsPh 3 (6)] in which the bridging ligands adopt a head-to-tail arrangement. The corresponding diplatinum(I) complex [Pt2 I(μ-2-C6F4PPh2) 2(PPh3)2] (9) is obtained similarly from [Pt(κ2-2-C6F4PPh2) 2] and [Pt(PPh3)3]. The separations between the metal atoms in the dipalladium(I) complexes [2.5740(3) A (5), 2.5511(3) A (6)] are slightly less than that in the diplatinum(I) complex 9 [2.61179(15) A]. The axial triphenylarsine ligands of 6 are replaced by tert-butyl isocyanide to give the dipalladium(I) complex [Pd2 I(μ-2-C6F4PPh2) 2(CNtBu)2] (7). However, treatment of trans-[Pd(κ2-2-C6F4PPh2) 2] with [Pd(CNtBu)2], generated in situ from a mixture of tert-butyl isocyanide and [Pd(η5-Cp) (η3-allyl)], gives a formally mixed-valent palladium(0)- palladium(II) complex [Pd20/II(μ-2-C6F 4PPh2)2(CNtBu)2] (8), in which the bridging ligands are arranged head-to-head. In contrast, comproportionation of [Pt(κ2-2-C6F 4PPh2)2] with [Pt3(CN tBu)6] gives the diplatinum(I) complex [Pt 2I(μ-2-C6F4PPh2) 2(CNtBu)2] (10) analogous to 7; there was no evidence for the formation of a dinuclear mixed-valent species. Although complexes 7 and 8 are isomers, with similar Pd-Pd separations [2.5803(4) A (7), 2.5580(2) A (8)], they do not interconvert in solution. The diplatinum(I) complex 9 undergoes oxidative addition with iodine to give an A-frame cation, [Pt2(μ-I)(μ-2-C6F 4PPh2)2(PPh3)2] +, isolated as its PF6- salt (11). In contrast, the dipalladium(I) complex 5 eliminates one of the PPh3 ligands when it undergoes oxidative addition with halogens and with methyl iodide, the products being A-frame dipalladium(II) complexes [Pd2X(μ-Y)(μ- 2-C6F4PPh2)2(PPh3)] [X = Y = I (12), Cl (13); X = Me, Y = I (14)]. The metal-metal distances in 11-14 [2.9478(5) A (11), 2.8078(7) A (12), 2.8241(3) A (13), and 2.8013(5) A (14)] are ca. 0.3 A greater than in their dimetal(I) precursors, consistent with a weaker metal-metal interaction in the dimetal(II) complexes. Unexpectedly, reaction of 5 with iodobenzene gives a mononuclear palladium(II) complex, cis-[Pd(κ2C,P-2-C6F 4PPh2)(κC-2-C6F4PPh 2)(PPh3)] (15). This is suggested to be formed by a sequence of (a) oxidative addition of iodobenzene to 5 to give a σ-phenyl complex analogous to the σ-methyl complex 14, (b) a change in the binding mode of one of the 2-C6F4PPh2 ligands from μ- to κ2-, and (c) reductive elimination of tetraphenylphosphonium iodide and loss of Pd(0).
