Acceptor Pincer Coordination Chemistry of Platinum: Reactivity Properties of (^CF₃PCP)Pt(L)⁺ (L = NC₅F₅, C₂H₄)

Abstract

Synthetic strategies toward the synthesis of electron-poor pincer complexes (CF3PCP)PtH and (CF3PCP)Pt(η2-H2)+ are described. Metathesis of (CF3PCP)PtCl with hydride reagents does not lead to (CF3PCP)PtH; (CF3PCP)PtCl with KH in tetrahydrofuran (THF) afforded an unusual metallated bimetallic pincer product (CF3PCP)Pt[κ1-C,κ3−P,C,P-2,6-(CHP(CF3)2)(CH2P(CF3)2)-C6H3]PtCl, which has been structurally characterized. Chloride abstraction from (CF3PCP)PtCl or protonolysis of (CF3PCP)PtMe in the presence of H2 gives the structurally characterized hydride-bridged dimer {(CF3PCP)Pt}2(μ-H)+. In the presence of trapping ligands H2O, C2H4, or pentafluoropyridine, the corresponding complexes (CF3PCP)Pt(L)+ (L = H2O, C2H4, NC5F5) are cleanly produced and have been structurally characterized. The C2H4 and NC5F5 adducts may be alternatively prepared by methide abstraction from (CF3PCP)PtMe with Ph3C+B(C6F5)4− in the presence of trapping ligand. Evidence for the transient formation of (CF3PCP)PtH from treatment of (CF3PCP)PtCl or (CF3PCP)Pt(NC5F5)+ with Et3Si+B(C6F5)4− is presented. (CF3PCP)Pt(C2H4)+ serves as a catalyst for ethylene hydrogenation (0.30 turnovers h−1, 70 °C) and hydrosilation with Et3SiH (460 turnovers h−1, RT) and Cl3SiH (5 turnovers h−1, RT). At elevated temperatures, (CF3PCP)Pt(C2H4)+ also exhibits limited ethylene dimerization activity (0.07 turnovers h−1, 155 °C) and 1-butene isomerization (0.9 turnovers h−1, 80 °C).