Synthesis of [(dfepe)Pt(Me)(NC₅F₅)]⁺B(C₆F₅)₄⁻, a Highly Active Ethylene Dimerization Catalyst

The synthesis of cationic adducts (dfepe)Pt(Me)(L)+ (dfepe = (C2F5)2PCH2CH2P(C2F5)2; L = MeCN, CO, C2H4, C5F5N, μ-Cl) are reported. Treatment of (cod)Pt(Me)Cl with AgSbF6 in acetonitrile followed by the addition of dfepe afforded (dfepe)Pt(Me)(CH3CN)+SbF6−. Addition of B(C6F5)3 to (dfepe)Pt(Me)(O2CCF3) in methylene chloride afforded the structurally characterized borane association product (dfepe)Pt(Me)[(O2CCF3)B(C6F5)3] in high yield. Attempts to displace the [(O2CCF3)B(C6F5)3]− anion with donor ligands resulted in loss of borane and regeneration of (dfepe)Pt(Me)(O2CCF3). Addition of the mesitylenium acid (1,3,5-C6H4Me3)+B(C6F5)4− to (dfepe)PtMe2 in methylene chloride at ambient temperatures resulted in chloride abstraction and the precipitation of the chloride-bridged dimeric complex [{(dfepe)Pt(Me)}2(μ-Cl)]+B(C6F5)4−, which has been structurally characterized. In contrast, treatment of (dfepe)PtMe2 with (1,3,5-C6H4Me3)+B(C6F5)4− in pentafluoropyridine at ambient temperature resulted in the precipitation of the structurally characterized pentafluoropyridine adduct [(dfepe)Pt(Me)(NC5F5)]+B(C6F5)4− in good yield. Exposure of [(dfepe)Pt(Me)(NC5F5)]+B(C6F5)4− to 1 atm of CO in o-difluorobenzene gave the carbonyl complex [(dfepe)Pt(Me)(CO)]+B(C6F5)4−. In marked contrast to previously reported platinum systems, [(dfepe)Pt(Me)(NC5F5)]+B(C6F5)4− is a very active ethylene dimerization catalyst at ambient temperature (600 psi ethylene, 22 °C in ortho-difluorobenzene, 150 turnovers h−1). The ethylene adduct [(dfepe)Pt(Me)(η2-C2H4)]+B(C6F5)4− has been spectroscopically characterized at −20 °C

Synthesis of [(dfepe)Pt(Me)(NC₅F₅)]⁺B(C₆F₅)₄⁻, a Highly Active Ethylene Dimerization Catalyst

The synthesis of cationic adducts (dfepe)Pt(Me)(L)+ (dfepe = (C2F5)2PCH2CH2P(C2F5)2; L = MeCN, CO, C2H4, C5F5N, μ-Cl) are reported. Treatment of (cod)Pt(Me)Cl with AgSbF6 in acetonitrile followed by the addition of dfepe afforded (dfepe)Pt(Me)(CH3CN)+SbF6−. Addition of B(C6F5)3 to (dfepe)Pt(Me)(O2CCF3) in methylene chloride afforded the structurally characterized borane association product (dfepe)Pt(Me)[(O2CCF3)B(C6F5)3] in high yield. Attempts to displace the [(O2CCF3)B(C6F5)3]− anion with donor ligands resulted in loss of borane and regeneration of (dfepe)Pt(Me)(O2CCF3). Addition of the mesitylenium acid (1,3,5-C6H4Me3)+B(C6F5)4− to (dfepe)PtMe2 in methylene chloride at ambient temperatures resulted in chloride abstraction and the precipitation of the chloride-bridged dimeric complex [{(dfepe)Pt(Me)}2(μ-Cl)]+B(C6F5)4−, which has been structurally characterized. In contrast, treatment of (dfepe)PtMe2 with (1,3,5-C6H4Me3)+B(C6F5)4− in pentafluoropyridine at ambient temperature resulted in the precipitation of the structurally characterized pentafluoropyridine adduct [(dfepe)Pt(Me)(NC5F5)]+B(C6F5)4− in good yield. Exposure of [(dfepe)Pt(Me)(NC5F5)]+B(C6F5)4− to 1 atm of CO in o-difluorobenzene gave the carbonyl complex [(dfepe)Pt(Me)(CO)]+B(C6F5)4−. In marked contrast to previously reported platinum systems, [(dfepe)Pt(Me)(NC5F5)]+B(C6F5)4− is a very active ethylene dimerization catalyst at ambient temperature (600 psi ethylene, 22 °C in ortho-difluorobenzene, 150 turnovers h−1). The ethylene adduct [(dfepe)Pt(Me)(η2-C2H4)]+B(C6F5)4− has been spectroscopically characterized at −20 °C