New 3-imidazoline derivatives and their palladium(II) complexes [1]

The protection of the hydroxy group of 1-hydroxy-2.2.4.5.5-pentamethyl-3-im idazoline by a t-butyldimethylsilyl group gives the silane 1 which allows v ia the 4-lithium salt the preparation of 4-substituted derivatives, i.e. a dithio-carboxylic acid (2), a disulfide (3), a phosphane (4) and a thioethe r (5). Oxidation of 4-lithiated 1 yields under C-C coupling an ethylene bri dged bis(3-imidazoline) (6). From these compounds Pd(II) and Pt(II) complex es M(4)(2)Cl-2 (M = Pd, Pt and Pd(5)Cl-2 were prepared and the structure of the dithiocarboxylate chelate complex Pd(2-H+)(2) (7) was determined by X- ray diffraction. Cleavage of the silyl group from 7 gives complex 8 which c an be oxidized to the corresponding diradical (9). Complex 9 was characteri zed by its EPR spectrum. Measurements of the magnetic susceptibility of 9 r eveal strong antiferromagnetic coupling between the two spins at low temper atures.