Synthesis and characterization of transition metal stabilized carbocations of the types [Cp∗(CO)2Fe{μ-(CnH2n−1}M(CO)xCp]PF6 (x = 2, M = Fe or Ru; x = 3, M = W, Cp∗ = η5-C5(CH3)5; Cp = η5-C5H5; n = 3–6) and [Cp(CO)2Ru{μ-(CnH2n−1)}W(CO)3Cp]PF6 (n = 3–5) and

The mixed-ligand complexes [Cp∗(CO)2Fe(CH2)nM(CO)xCp] (x = 2, M = Fe or Ru; x = 3, M = W, Cp∗ = η5-C5(CH3)5; Cp = η5-C5H5; n = 3–6), type I, react with one equivalent of the hydride abstractor Ph3CPF6 to give the transition metal-stabilized carbocation complexes [Cp∗(CO)2Fe{μ-(CnH2n−1)}M(CO)xCp]PF6. Similarly the new heterobimetallic complexes [Cp(CO)2Ru{μ-(CnH2n−1)}W(CO)3Cp], type II, react with Ph3CPF6 to give the carbocation complexes [Cp(CO)2Ru{μ-(CnH2n−1)}W(CO)3Cp]PF6. Spectroscopic data show that hydride abstraction selectively takes place from the methylene group β to the metal atom attached to the Cp∗ ligand in type I complexes. In type II complexes, the reaction is totally metalloselective with hydride abstraction occurring at the CH2 β to the ruthenium metal centre. All products have been characterized by IR, 1H,13C NMR spectroscopy and elemental analysis. 1H and 13C NMR data clearly show that in the carbocation complexes one metal is σ-bonded to the alkanediyl carbocation while the other is bonded to the cationic end in a η2-fashion forming a chiral metallacylopropane type structure. The molecular structures of the cationic metallacyclic complexes [Cp∗(CO)2Fe{μ-(C3H5)}Fe(CO)2Cp]PF6 [E.O. Changamu, H.B. Friedrich, M. Rademeyer, Acta Crystallogr., Sect. E 62 (2006) m442.] and [Cp∗(CO)2Fe(μ-C3H5)Ru-(CO)2Cp]PF6 [H.B. Friedrich, E.O. Changamu, M. Rademeyer, Acta Crystallogr., Sect. E 62 (2006) m405.] have been confirmed by single crystal X-ray crystallography and reported elsewhere. The structures of the precursor complexes [Cp∗(CO)2Fe(CH2)3Ru-(CO)2Cp] (1), [Cp∗(CO)2Fe(CH2)5Ru-(CO)2Cp] (2), [Cp∗(CO)2Fe(CH2)5W(CO)3Cp] (3), and [Cp(CO)2Ru (CH2)5W(CO)3Cp] (4), have been confirmed by single crystal X-ray crystallography. The structure of [Cp∗(CO)2Fe(CH2)3Ru(CO)2Cp] is compared with that of its corresponding cationic complex, [Cp∗(CO)2Fe{μ-(C3H5)}Ru(CO)2Cp]PF6.

The complexes [Cp∗(CO)2Fe(CH2)nM(CO)xCp] (n = 3–6, Cp∗ = η5-C5(CH3)5, Cp = η5-C5H5, x = 2, M = Fe or Ru; x = 3, M = W), undergo hydride abstraction selectively from the CH2 β to Cp∗(CO)2Fe to give the cationic metallocycles [Cp∗(CO)2Fe{μ-(CnH2n−1)}M(CO)xCp]PF6 upon reaction with Ph3CPF6. Similarly, [Cp(CO)2Ru(CH2)nW(CO)3Cp] (n = 3–5) undergo hydride abstraction from the CH2 β to Cp(CO)2Ru to give [Cp(CO)2Ru{μ-(CnH2n−1)}W(CO)3Cp]PF6.Figure optionsDownload as PowerPoint slide