20. "Cyclometalation of Dimesitylphosphine in Cationic Pd(II) and Pt(II) Complexes: P-H vs C-H Activation," Michael A. Zhuravel, Navrose S. Grewal, David S. Glueck, Kin-Chung Lam, and Arnold L. Rheingold, Organometallics, 2000, 19, 2882 -2890.

Abstract The cationic complexes [M(dppe)(R)(PHMes₂)][OTf] (M = Pd, R = Me (1), Ph (2); M = Pt, R = Me (3), Et (4), dppe = Ph₂PCH₂CH₂PPh ₂, Mes = 2,4,6-Me₃C₆H ₂, OTf = OSO₂CF₃) were prepared by the reaction of the corresponding M(dppe)(R)(X) (X = Cl, I) with AgOTf and PHMes₂. On standing in THF or CH₂Cl₂ solution the Pd complexes underwent cyclometalation, forming [Pd(dppe)(CH₂C₆H₂(Me)₂PHMes)][OTf] (5). Thermolysis of Pt complexes 3 or 4 gave [Pt(dppe)(CH₂C₆H₂(Me)₂PHMes)][OTf] (6), along with ethylene in the latter case. Reaction of Pt(dppe)(Et)(Cl) with AgOTf generated [Pt(dppe)(H)]₂²⁺, which on treatment with PHMes₂ also yielded 6. Treatment of 1-2 and 3-4 with triflic acid gave 5 and 6, respectively. The cyclometalation of 1 is acid-catalyzed; the intermediacy of [Pd(dppe)(PHMes₂)]²⁺ in these reactions was supported by formation of 5 from sources of the [Pd(dppe)]²⁺ fragment and dimesitylphosphine.