Synthesis and fluxional behavior of [bis(trialkylphosphine)nickelio]anthracene (alkyl = Et, Bu)
摘要:
The title compounds were prepared from the respective (R3P)2NiCl2 complexes and magnesium-anthracene-(THF)3 (or anthracene in the presence of Mg or C8K). The assignment of the anthracene proton NMR signals using NOE in conjunction with magnetization-transfer techniques is described. The complexes undergo haptotropic rearrangements in which the (R3P)2Ni moiety migrates between the two terminal rings of the coordinated anthracene. The rates of these processes are concentration independent and unaffected by the presence of free anthracene and tris(trialkylphosphine)nickel. Kinetic studies in the temperature range -60 to +70-degrees-C using line shape analysis and spin saturation transfer techniques were carried out. It was found that DELTA-H double-ended-dagger = 13.6 kcal mol-1 and DELTA-S double-ended-dagger = -4.3 eu for the haptotropic rearrangement in 2, and similar values were found for 1. Possible mechanisms are discussed. According to H-1, C-13, and P-31 NMR data, the coordination number between the anthracene and the (R3P)2Ni moiety is 4. However, an equilibrium between two eta(2) structures with DELTA-G double-ended-dagger less-than-or-equal-to 4 kcal mol-1 cannot be ruled out.
Reactions of halogen(2,4,6-tri-tert-butylphenylimino)phosphine complexes with electrophiles and nucleophiies: abstraction or substitution of the halogen
作者:E. Niecke、J. F. Nixon、P. Wenderoth、B. F. Trigo Passos、M. Nieger
DOI:10.1039/c39930000846
日期:——
The structure of the first nickel halogeniminophosphine complex, i.e.(PEt3)2Ni(X–PNAr)2(Ar = 2,4,6-tri-tert-butylphenyl); X = Cl is reported; reactions of this and related compounds with AlCl3 afford the cationic complexes 7–10; the alkyliminophosphine complexes 12 and 13 are obtained by treatment of the chloroiminophosphine complexes 1a and 4a with Grignard reagent.