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

作者：Bhargava Suresh K^*; Priver Steven H; Willis Anthony C; Bennett Martin A

来源：Organometallics, 2012, 31(15): 5561-5572.

DOI：10.1021/om300525p

Comproportionation of trans-[Pd(kappa(2)-2-C6F4PPh2)(2)] with [PdL4] (L = PPh3, AsPh3) gives metal metal-bonded dipalladium(I) complexes [Pd-2(1)(mu-2-C6F4PPh2)(2)(PPh3)(2)] [L = PPh3 (5), AsPh3 (6)] in which the bridging ligands adopt a head-to-tail arrangement. The corresponding diplatinum(I) complex [Pt-2(1)(mu-2-C6F4PPh2)(2)(PPh3)(2)] (9) is obtained similarly from [Pt(kappa(2)-2-C6F4PPh2)(2)] and [Pt(PPh3)3]. The separations between the metal atoms in the dipalladium(I) complexes [2.5740(3) angstrom (5), 2.5511(3) angstrom (6)] are slightly less than that in the diplatinum(I) complex 9 [2.61179(15) angstrom]. The axial triphenylarsine ligands of 6 are replaced by tert-butyl isocyanide to give the dipalladium(I) complex [Pd-2(1)(mu-2-C6F4PPh2)(2)((CNBu)-Bu-t)(2)] (7). However, treatment of trans-[Pd(kappa(2)-2-C6F4PPh2)(2)] with [Pd((CNBu)-Bu-t)(2)], generated in situ from a mixture of tert-butyl isocyanide and [Pd(eta(5)-Cp)(eta(3)-allyl)], gives a formally mixed-valent palladium(0) palladium(II) complex [Pd (0/II)(2)(mu-2-C6F4PPh2)(2)((CNBu)-Bu-t)(2)] (8), in which the bridging ligands are arranged head-to-head. In contrast, comproportionation of [Pt(kappa(2)-2-C6F4PPh2)(2)] with [Pt-3((CNBu)-Bu-t)(6)] gives the diplatinum(I) complex [Pt-2(1)(mu-2-C6F4PPh2)(2)((CNBu)-Bu-t)(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) angstrom (7), 2.5580(2) angstrom (8)], they do not interconvert in solution. The diplatinum(I) complex 9 undergoes oxidative addition with iodine to give an A-frame cation, [Pt-2(mu-I)(mu-2-C6F4PPh2)(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(mu-Y)(mu-2-C6P4PPh2)(2)(PPh3)] [X = Y = I(12), Cl (13); X = Me, Y = I (14)]. The metal-metal distances in 11-14 [2.9478(5) angstrom (11), 2.8078(7) angstrom (12), 2.8241(3) angstrom (13), and 2.8013(5) angstrom (14)] are ca. 0.3 angstrom 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(H) complex, cis-[Pd(kappa C-2,P-2-C6F4PPh2)(kappa C-2-C6F4PPh2)(PPh3)] (is).
This is suggested to be formed by a sequence of (a) oxidative addition of iodobenzene to 5 to give a sigma-phenyl complex analogous to

• 出版日期2012-8-13