Models for the Initial Stages of Oxidative Addition. Synthesis, Characterization, and Mechanistic Investigation of η¹-I₂ Organometallic “Pincer” Complexes of Platinum. X-ray Crystal Structures of [PtI(C₆H₃{CH₂NMe₂}₂-2,6)(η¹-I₂)] and exo-meso-[Pt(η¹-I₃)(η¹-I₂)(C₆H₃{CH₂N(t-Bu)Me}₂-2,6)]

The reaction of I 2 with platinum “pincer” complexes of the general formula [PtI(NCN‘ ‘)] (NCN‘ ‘ = [C 6 H 3 (CH 2 NRR‘) 2 -2,6] -; R = R‘ = Me or Et; or R = Me, R‘ = t -Bu) is reported. All three complexes contain an end-on (η 1 ) I 2 unit, and these compounds represent the only known isolable organometallic species which contain I 2 in this bonding motif. These compounds can be envisioned as representing the initial stages of oxidative addition of dihalides to d 8 transition metal complexes. The complexes [PtI{C 6 H 3 (CH 2 NMe 2 ) 2 -2,6}(η 1 -I 2 )] ( 1 ) and exo - meso - [PtI 3 {C 6 H 3 (CH 2 NMe[ t -Bu]) 2 -2,6}(η 1 -I 2 )] ( 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(η 1 -I 3 ){C 6 H 3 (CH 2 NMe 2 ) 2 -2,6}]. The role of the metal-bound halide anion as the point of initial attack of I 2 is described. The results of these investigations are discussed in terms of the basic mechanism of oxidative addition and its implications for catalysis.