Preparation, Structure, and Reactivity of Dipalladium(I) Complexes Containing the Carbanion 2-C6F4PPh2: Coexistence of Distinct, Noninterconverting Head-to-Head [Dipal

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• 作者：Suresh K. Bhargava ; Steven H. Priv茅r ; Anthony C. Willis ; Martin A. Bennett
• 刊名：Organometallics
• 出版年：2012
• 出版时间：August 13, 2012
• 年：2012
• 卷：31
• 期：15
• 页码：5561-5572
• 全文大小：593K
• 年卷期：v.31,no.15(August 13, 2012)
• ISSN：1520-6041

文摘

Comproportionation of trans-[Pd(魏²-2-C₆F₄PPh₂)₂] with [PdL₄] (L = PPh₃, AsPh₃) gives metal鈥搈etal-bonded dipalladium(I) complexes [Pd₂^I(渭-2-C₆F₄PPh₂)₂(L)₂] [L = PPh₃ (5), AsPh₃ (6)] in which the bridging ligands adopt a head-to-tail arrangement. The corresponding diplatinum(I) complex [Pt₂^I(渭-2-C₆F₄PPh₂)₂(PPh₃)₂] (9) is obtained similarly from [Pt(魏²-2-C₆F₄PPh₂)₂] and [Pt(PPh₃)₃]. The separations between the metal atoms in the dipalladium(I) complexes [2.5740(3) 脜 (5), 2.5511(3) 脜 (6)] are slightly less than that in the diplatinum(I) complex 9 [2.61179(15) 脜]. The axial triphenylarsine ligands of 6 are replaced by tert-butyl isocyanide to give the dipalladium(I) complex [Pd₂^I(渭-2-C₆F₄PPh₂)₂(CN^tBu)₂] (7). However, treatment of trans-[Pd(魏²-2-C₆F₄PPh₂)₂] with [Pd(CN^tBu)₂], generated in situ from a mixture of tert-butyl isocyanide and [Pd(畏⁵-Cp)(畏³-allyl)], gives a formally mixed-valent palladium(0)鈥損alladium(II) complex [Pd₂^0/II(渭-2-C₆F₄PPh₂)₂(CN^tBu)₂] (8), in which the bridging ligands are arranged head-to-head. In contrast, comproportionation of [Pt(魏²-2-C₆F₄PPh₂)₂] with [Pt₃(CN^tBu)₆] gives the diplatinum(I) complex [Pt₂^I(渭-2-C₆F₄PPh₂)₂(CN^tBu)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鈥揚d separations [2.5803(4) 脜 (7), 2.5580(2) 脜 (8)], they do not interconvert in solution. The diplatinum(I) complex 9 undergoes oxidative addition with iodine to give an A-frame cation, [Pt₂(渭-I)(渭-2-C₆F₄PPh₂)₂(PPh₃)₂]⁺, isolated as its PF₆^{鈥?/sup> 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(渭-Y)(渭-2-C₆F₄PPh₂)₂(PPh₃)] [X = Y = I (12), Cl (13); X = Me, Y = I (14)]. The metal鈥搈etal distances in 11鈥?b>14 [2.9478(5) 脜 (11), 2.8078(7) 脜 (12), 2.8241(3) 脜 (13), and 2.8013(5) 脜 (14)] are ca. 0.3 脜 greater than in their dimetal(I) precursors, consistent with a weaker metal鈥搈etal interaction in the dimetal(II) complexes. Unexpectedly, reaction of 5 with iodobenzene gives a mononuclear palladium(II) complex, cis-[Pd(魏2C,P-2-C₆F₄PPh₂)(魏C-2-C₆F₄PPh₂)(PPh₃)] (15). This is suggested to be formed by a sequence of (a) oxidative addition of iodobenzene to 5 to give a 蟽-phenyl complex analogous to the 蟽-methyl complex 14, (b) a change in the binding mode of one of the 2-C₆F₄PPh₂ ligands from 渭- to 魏2-, and (c) reductive elimination of tetraphenylphosphonium iodide and loss of Pd(0).}