Di-terf-butylallenylidene Complexes of Iron The synthesis of a tetracarbonyl(di-tert-butylallenylidene)iron(O) complex (1) is reported. It can be transformed to an octacarbonyl-p-(di-tert-butylallenylidene)-diiron(O) compound 2 and reactsthermally to an allenylidenetriiron derivative Fe,(CO)loC3(tBu)2 3. The synthesis of 1 via a trimethylamine oxide-induced substitution of CO with di-tert-butylpropargylate residues is accompanied by the formation of (C0)4Fecomplex 4, which has been characterized by an X-ray analysis.Der Allenylidencarben-Rest fungiert in Ubergangsmetallkomplexen als terminaler Ligand", als p2-bruckenstandiger Zwei-Elektr~nen-~-~) oder als p3-Vier-Elektronendonor '). In Eisensystemen wurden Carbenteilchen terminal gebunden 6, oder wie Methylen-und Vinylidenreste in p2-Bruckenstell~ng~~~) aufgefunden.Zur Erkundung des Bindungsverhaltens von Allenyliden-Fragmenten in Carbonyleisen-Verbindungen wurde ein Darstellungsweg dieser ungesattigten Spezies nach G1. (1)

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The reactivity of a di-tert-butylallenylidene tetracarbonyliron complex (1) and a ,μ-di-tert-butyl-allenylideneoctacarbonyldiiron (2) compound towards triphenylphosphane and pyridine were investigated. The reaction of 1 with PPh3 results in the formation of an ylid complex, di-tert-butylallenylidenetriphenylphosphorane tetracarbonyliron (3). 2 reacts with L = PPh3 with substitution of one or two CO molecules to give (tBu)2C3Fe2(CO)7L 4 and (tBu)2C3Fe2(CO)6L2 5 compounds. Pyridin (py) causes initial displacement of one CO ligand in 2 but subsequent rearrangement results in the formation of 3-t-butyl-4-dimethyl-2-(2-pyridino)pent-2-ene-lylideneheptacarbonyldiiron(0) system (7).