A family of bimetallic complexes [Cp(CO)2Fe–CC–Ar– CC–Fe(CO)2Cp] {Cp = C5H5; 6a–g: Ar = C4H2S (a), 3- (C4H9)-C4HS (b), 3-(C16H33)-C4HS (c), C6H4 (d), 2,5-bis- (OC4H9)-C6H2 (e), 2,5-bis(OC8H17)-C6H2 (f), (C6H4)2 (g)} was prepared by the three-step Pd-catalysed extended one-pot (EOP) synthetic protocol from Bu3Sn–CCH, X–Ar–X (X = I, Br) and Cp(CO)2FeI. Complexes 6a,d,g were then exposed to ultraviolet irradiation in the presence of an equivalent amount of 1,2-bis(diphenylphosphanyl)ethane (dppe) to form the corresponding bimetallic complexes [Cp(dppe)Fe–CC– Ar–CC–Fe(dppe)Cp] (7a,d,g). Compounds 6a–g and 7a,d,g were characterised by cyclic voltammetry (CV). The most significant electrochemical information comes from the oxidation of the dppe derivatives. The ∆E° separations between the subsequent reversible waves suggest that the efficiency of the metal–metal electronic coupling decreases in the order 7a 7d 7g. Complexes 7a and 7g were also chemically oxidised with [Fe(Cp*)]2[BF4] {Cp* = C5(CH3)5} and [Fe(Cp)]2[BF4] respectively, and the near infrared (NIR) spectra of the mixed-valence species 7a + and 7g + were recorded. A strong intervalence transition (IT) band was observed only for the radical cation 7a + . While this finding confirms the existence of an electronic interaction between the two termini when a 2,5-thiophene group is present in the spacer, the NIR spectrum of 7g + reveals a reduced efficiency in conveying electrons when the C4H2S moiety is replaced by a 4,4-biphenyl. In order to rationalise and quantify the extent of electronic communication, ruled by geometrical and electronic factors, density functional computational results on selected [Cp (PH3)2Fe] and [Cp(CO)2Fe] binuclear model complexes are reported.

A Joint Experimental and Computational Study on the Electronic Communication in Diethynylaryl Bridged (eta5-C5H5)Fe(eta2-dppe) and (eta5-C5H5)Fe(CO)2 Units.

ORIAN, LAURA;SANTI, SAVERIO;DURANTE, CHRISTIAN;
2006

Abstract

A family of bimetallic complexes [Cp(CO)2Fe–CC–Ar– CC–Fe(CO)2Cp] {Cp = C5H5; 6a–g: Ar = C4H2S (a), 3- (C4H9)-C4HS (b), 3-(C16H33)-C4HS (c), C6H4 (d), 2,5-bis- (OC4H9)-C6H2 (e), 2,5-bis(OC8H17)-C6H2 (f), (C6H4)2 (g)} was prepared by the three-step Pd-catalysed extended one-pot (EOP) synthetic protocol from Bu3Sn–CCH, X–Ar–X (X = I, Br) and Cp(CO)2FeI. Complexes 6a,d,g were then exposed to ultraviolet irradiation in the presence of an equivalent amount of 1,2-bis(diphenylphosphanyl)ethane (dppe) to form the corresponding bimetallic complexes [Cp(dppe)Fe–CC– Ar–CC–Fe(dppe)Cp] (7a,d,g). Compounds 6a–g and 7a,d,g were characterised by cyclic voltammetry (CV). The most significant electrochemical information comes from the oxidation of the dppe derivatives. The ∆E° separations between the subsequent reversible waves suggest that the efficiency of the metal–metal electronic coupling decreases in the order 7a 7d 7g. Complexes 7a and 7g were also chemically oxidised with [Fe(Cp*)]2[BF4] {Cp* = C5(CH3)5} and [Fe(Cp)]2[BF4] respectively, and the near infrared (NIR) spectra of the mixed-valence species 7a + and 7g + were recorded. A strong intervalence transition (IT) band was observed only for the radical cation 7a + . While this finding confirms the existence of an electronic interaction between the two termini when a 2,5-thiophene group is present in the spacer, the NIR spectrum of 7g + reveals a reduced efficiency in conveying electrons when the C4H2S moiety is replaced by a 4,4-biphenyl. In order to rationalise and quantify the extent of electronic communication, ruled by geometrical and electronic factors, density functional computational results on selected [Cp (PH3)2Fe] and [Cp(CO)2Fe] binuclear model complexes are reported.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11577/2467977
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