Chemistry of low-valent metal isocyanide complexes. Part 2. Oxidative reactions of pentakis(t-butyl isocyanide)iron with alkyl, allyl, benzyl, fluoroalkyl, and pentafluorophenyl halides, and with trimethyloxonium tetrafluoroborate and diphenylacetylene. Evidence for isocyanide insertion reactions, and the molecular structure of [Fe(CNBut)3{1–4-η-C(NBut)C(Ph)C(Ph)C(NBut)}]

Abstract

Reaction of [Fe(CNBu^t)₅] with MeI in thf (tetrahydrofuran) affords [[graphic omitted]Bu^t}(CNBu^t)₃], whereas with diethyl ether as solvent the salt [FeMe(CNBu^t)₅]I is formed, which on dissolving in thf is transformed into the former product. Cationic complexes [Fe(CH₂CHCH₂)(CNBu^t)₅]X are formed on reaction of [Fe(CNBu^t)₅] in thf with allyl halides or benzyl bromide. However, EtI, EtBr, PrⁱI, and [Me₃O][BF₄] afford η²-iminoacyl complexes [[graphic omitted]Bu^t}(CNBu^t)₄]X. Reaction of [Fe(CNC₆H₃Me₂-2,3)₅] with MeI or EtI gives [FeI{C(R)N(C₆H₃Me₂-2,3)}(CNC₆H₃Me₂-2,3)₄]. n-Heptafluoropropyl iodide and bromopentafluorobenzene readily react with [Fe(CNBu^t)₅] to give [FeI{CF(CF₃)₂}(CNBu^t)₄] and [Fe(C₆F₅)(CNBu^t)₅]Br respectively. Diphenylacetylene reacts with [Fe(CNBu^t)₅] to give [Fe(CNBu^t)₃{1–4-η-C(NBu^t)C(Ph)C(Ph)C(NBu^t)}], which was structurally identified by a single-crystal X-ray diffraction study. The crystals are monoclinic, space froup P2₁/c, Z= 4 in a unit cell of dimensions a= 9.724(4), b= 42.11(3), c= 11.330(4)Å, β= 113.57(5)7°. The structure has been refined to R= 0.092 (R′= 0.123) for 4 327 reflections to 2.9 ⩽ 2θ⩽ 50.0° at 183 K. The dynamic behaviour of the complex in solution and its mode of formation are discussed.