Solvent dependent anion dissociation limits copper(I) catalysed atom transfer reactions.

نویسندگان

  • Timothy J Zerk
  • Paul V Bernhardt
چکیده

Atom transfer radical addition (ATRA) and polymerisation (ATRP) reactions are commonly catalyzed by copper(I) complexes which react, reversibly, with a dormant alkyl halide initiator (RX) releasing a reactive organic radical R˙. The copper catalyst bears a multidentate N-donor ligand (L) and the active catalyst is simply Cu(I)L. The role of the catalyst in these reactions is to abstract a halogen atom from RX forming the corresponding higher oxidation state species Cu(II)LX. However, in order to perform its catalytic function (in multiple turnovers) the halido ligand must be released from the copper ion en route to regenerating the active catalyst Cu(I)L. In this work we investigate the kinetics of the Cu(I)LX/Cu(I)L equilibrium where L is the tridentate N,N,N',N'',N''-pentamethyl-diethylenetriamine (PMDETA). Using electrochemical analysis we find that the rate of formation of the active catalyst Cu(I)L is strongly dependent on solvent. We demonstrate that both the kinetics and thermodynamics of this simple ligand exchange reaction are critical in the overall reaction pathway.

برای دانلود رایگان متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Proposal for halogen atom transfer mechanism for Ullmann O-arylation of phenols with aryl halides.

A systematic theoretical study on reaction mechanisms for copper(I)-catalyzed C-O coupling of phenols with aryl bromides is reported herein. Through evaluation of the relative concentrations of possible copper species in reaction solution and reactivity study of these copper species with aryl halides in the context of several commonly proposed mechanisms for copper(I)-catalyzed Ullmann reaction...

متن کامل

Time resolved solvent rearrangement dynamics.

Ultrafast pump-probe studies of I2- recombination in size-selected I2- (CO2)n cluster ions demonstrate long time coherent motions in size-selected clusters and the resulting non-statistical energy flow in the cluster. For I2- photodissociated to produce either I- + I or I- + I*, we identify a solvent-driven energy transfer process without a condensed phase counterpart. The mechanism involved is...

متن کامل

The mechanism of the modified Ullmann reaction.

The copper-mediated aromatic nucleophilic substitution reactions developed by Fritz Ullmann and Irma Goldberg required stoichiometric amounts of copper and very high reaction temperatures. Recently, it was found that addition of relatively cheap ligands (diamines, aminoalcohols, diketones, diols) made these reactions truly catalytic, with catalyst amounts as low as 1 mol% or even lower. Since t...

متن کامل

Heavy Atom Substituents as Molecular Probes for Solvent Effects on the Dynamics of Short-lived Triplet Exciplexes

The influence of heavy atom substituents (Br, I) in the electron donor aniline on the electron transfer reaction with thiopyronine triplet is investigated by flash spectroscopy in solvents of different viscosity and polarity. Triplet quenching constants and radical yields are determined. The results are analysed in terms of decay constants of an intermediate triplet exciplex where the heavy ato...

متن کامل

A Theoretical Study on the Structure-Radical Scavenging Activity of Some Hydroxyphenols

Antioxidants are made for the struggle and reconstruction of the damaged cells, because of their ability in destroying the free radicals. On account of their importance, a theoretical procedure was applied for the study of the molecular structure and radical scavenging activity of six hydroxyphenols which have been introduced as antioxidant compounds. All geometry structures were optimized by M...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

عنوان ژورنال:
  • Dalton transactions

دوره 42 32  شماره 

صفحات  -

تاریخ انتشار 2013