Some transition metal complexes derived from mono- and di-ethynyl perfluorobenzenes

Abstract

Transition metal alkynyl complexes containing perfluoroaryl groups have been prepared directly from trimethylsilyl-protected mono- and di-ethynyl perfluoroarenes by simple desilylation/metallation reaction sequences. Reactions between Me₃SiCCC₆F₅ and RuCl(dppe)Cp′ [Cp′ = Cp, Cp*] in the presence of KF in MeOH give the monoruthenium complexes Ru(CCC₆F₅)(dppe)Cp′ [Cp′ = Cp (2); Cp* (3)], which are related to the known compound Ru(CCC₆F₅)(PPh₃)₂Cp (1). Treatment of Me₃SiCCC₆F₅ with Pt₂(μ-dppm)₂Cl₂ in the presence of NaOMe in MeOH gave the bis(alkynyl) complex Pt₂(μ-dppm)₂(CCC₆F₅)₂ (4). The Pd(0)/Cu(I)-catalysed reactions between Au(CCC₆F₅)(PPh₃) and Mo(≡CBr)(CO)₂Tp* [Tp* = hydridotris(3.5-dimethylpyrazoyl)borate], Co₃(μ₃-CBr)(μ-dppm)(CO)₇ or ICCFc [Fc = (η⁵-C₅H₄)FeCp] afford Mo(≡CCCC₆F₅)(CO)₂Tp* (5), Co₃(μ₃-CCCC₆F₅)(μ-dppm)(CO)₇ (6) and FcCCCCC₆F₅ (7), respectively. The diruthenium complexes 1,4-{Cp′(PP)RuCC}₂C₆F₄ [(PP)Cp′ = (PPh₃)₂Cp (8); (dppe)Cp (9); (dppe)Cp* (10)] are prepared from 1,4-(Me₃SiCC)₂C₆F₄ in a manner similar to that described for the monoruthenium complexes 1–3. The non-fluorinated complexes 1,4-{Cp′(PP)RuCC}₂C₆H₄ [(PP)Cp′ = (PPh₃)₂Cp (11); (dppe)Cp (12); (dppe)Cp* (13)], prepared for comparison, are obtained from 1,4-(Me₃SiCC)₂C₆H₄. Spectro-electrochemical studies of the ruthenium aryl and arylene alkynyl complexes 2–3 and 8–13, together with DFT-based computational studies on suitable model systems, indicate that perfluorination of the aromatic ring has little effect on the electronic structures of these compounds, and that the frontier orbitals have appreciable diethynylphenylene character. Molecular structure determinations are reported for the fluoroaromatic complexes 1, 2, 3, 6 and 10.