Models for the Initial Stages of Oxidative Addition : Synthesis, Characterization and Mechanistic Investigation of N1-I2 Organometallic 'Pincer' Complexes of Platinum : X-ray Crystal Structures of [Ptl(C6H3{CH2NMe2}2-2,6)(N1-I2)] and exo-meso-[Pt(N1-I3)(N1-I2)(C6H3{CH2N-(t-Bu)Me}2-2,6)

Abstract

The reaction of I2 with platinum 'pincer' complexes of the general formula [PtI(NCN' ')] (NCN' ' = [C6H3(CH2NRR')2-2,6]-; R = R' = Me or Et; or R = Me, R' = t-Bu) is reported. All three complexes contain an end-on (1) I2 unit, and these compounds represent the only known isolable organometallic species which contain I2 in this bonding motif. These compounds can be envisioned as representing the initial stages of oxidative addition of dihalides to d8 transition metal complexes. The complexes [PtI{C6H3(CH2NMe2)2-2,6}(1-I2)] (1) and exo-meso-[PtI3{C6H3(CH2NMe[t-Bu])2-2,6}(1-I2)] (3b) have been structurally characterized by single-crystal X-ray diffraction methods. Mechanistic and spectroscopic (IR, Raman, NMR, UV/vis) investigations have led to the conclusion that complex 1 is formed via a 1,2-shift of the dihalide from the primary product [Pt(1-I3){C6H3(CH2NMe2)2-2,6}]. The role of the metal-bound halide anion as the point of initial attack of I2 is described. The results of these investigations are discussed in terms of the basic mechanism of oxidative addition and its implications for catalysis.