B−C Bond Cleavage of BArFAnion Upon Oxidation of Rhodium(I) with AgBArF. Phosphinite Rhodium(I), Rhodium(II), and Rhodium(III) Pincer Complexes

A rare case of BAr F anion cleavage (BAr F − = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate) by a metal complex is described. Reaction of the Rh(I) dinitrogen complexes 5a, b and 6a, b, based on the phosphinite pincer ligands {C 6 H 4 [OP( t Bu) 2 ] 2 } ( 2 ), with 2 equiv of AgBAr F at room temperature resulted in B−C bond cleavage of one of the BAr F anions and aryl transfer to afford the Rh(III) aryl complexes 7 and 8, respectively. The X-ray structure of 8 revealed a square-pyramidal geometry with a coordinated acetone molecule. The aryl transfer occurred as a result of electrophilic attack by unsaturated Rh(III) on one of the aryl rings of the BAr F anion. Utilizing different solvents yielded the same product, except when CH 3 CN was used, in which case one-electron oxidation took place, yielding complex 9 . Treatment of 6a, b with 1 equiv of AgX (X = BAr F, BF 4, PF 6 ) resulted in a one-electron oxidation to yield the paramagnetic Rh(II) complexes 9 − 11, respectively. Complex 11 was characterized by X-ray diffraction, revealing a mononuclear square-planar Rh(II) complex.