Efficient Synthesis of Cu(II)‐N‐Heterocyclic Carbene Complexes in Water and Their Activity Towards Aerobic Alcohol Oxidation.

Ahmad Bhat, Irshad; Avinash, Iruthayaraj; Kumar Sachan, Sharad; Singh, Sadhana; Anantharaman, Ganapathi

The majority of the copper N‐heterocyclic carbene (NHC) complexes contain Cu in a 1 oxidation state. The Cu(II)‐NHC complexes reported so far usually require strict inert atmosphere conditions. In this work, we report a very facile and quantitative preparation of a series of new Cu(II)‐NHC complexes (2 a–c) starting from the inexpensive and readily available Cu(II) salts like Cu(OAc)2 and CuCl2 ⋅ 2H2O with imidazolium salts (1 a–c), wherein 2 b and 2 c were exclusively synthesized in water under aerobic condition. It should be emphasized that this is the first example where Cu(II)‐NHC complexes have been prepared in the aqueous medium. All the complexes have manifested with a heterobidentate C, O chelate type of coordination to Cu(II) centers forming trans‐[Cu(IRpyO)2] (where R=Me, Mes, Dipp) type of complexes where 2 b forms a perfect square planar Cu(II)‐NHC complex. Complexes 2 a–c were evaluated as catalysts for the aerobic oxidation of alcohols.

ALCOHOL oxidation; OXIDATION states; ALCOHOL; CARBENE synthesis; CHELATES

European Journal of Inorganic Chemistry, 2021, Vol 2021, Issue 44, p4560

1434-1948

Academic Journal

10.1002/ejic.202100631