A Joint Experimental and Computational Study on the Electronic Communication in Diethynylaryl‐Bridged (η⁵‐C₅H₅)Fe(η²‐dppe) and (η⁵‐C₅H₅)Fe(CO)₂ Units

Abstract

A family of bimetallic complexes [Cp(CO)2FeCCArCC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CCH, XArX (X=I,Br) and Cp(CO)2FeI. Complexes 6a,d,g were then exposed to ultraviolet irradiation in presence of an equivalent amount of 1,2-bis(diphenylphosphyne)ethane (dppe) to form the corresponding bimetallic complexes [Cp(dppe)FeCCArCCFe(dppe)Cp] (7a,d,g). Compounds 6a-g and 7a,d,g were characterised by Ciclic 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 6a > 6d > 6g. 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 Charge Transfer band (ICT) was observed only for the radical cation 7a+. While this finding confirms the existence of 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

Metal–Metal Electronic Coupling in syn and anti Stereoisomers of Mixed‐Valent (FeCp)2‐, (RhL2)2‐, and (FeCp)(RhL2)‐as‐Indacenediide Ions

“…Inspection of the pairs of MOs involved in the dominant monoelectronic transitions, that is, HOMOβ–LUMOβ and (HOMO−1)β–LUMOβ, reveals no appreciable MMCT character between the metal centres, as reported recently for other organometallic homobinuclear systems 3k. 19d, 30 These absorptions are better interpreted as allowed electronic transitions between filled and empty delocalised frontier levels (Figure 8 a).…”

“…The difference between the theoretical and the experimental energies is within the tolerance accepted for this kind of analysis on large open‐shell organometallic molecules 3l. 19d, 30, 41, 43…”

“…The choice of this functional was motivated by its successful performance reported in recent studies on electronic coupling in mixed‐valent organometallic complexes 3l. 19d, 30, 41 All‐electron 6‐31G(d,p) basis sets were used for C and H;42a,b Fe was described with Stuttgart relativistic small‐core ECP basis set 42c. This level of theory is abbreviated in the text as B3LYP/SDD,6‐31G(d,p).…”

Electronic Properties of Poly‐Yne Carbon Chains and Derivatives with Transition Metal End‐Groups

“…The last three decades have witnessed a stunning collection of works devoted to the syntheses and characterizations of the redox properties, molecular and electronic structures of a variety of π‐conjugated carbon‐containing units spanning two transition metal organometallic termini Much of the interest for these so‐called molecular organometallic wires has been prompted by the rich redox chemistry of the different metal termini which encompass several transition metal elements such as, non‐exhaustively, Cr, Mn, Fe, Co, Mo, Ru, W, Re, Os, Pt, and Au organometallic fragments . Additionally, the efficiency of diverse linkers allows to convey electronic and magnetic communication between the termini.…”

Electrochemical Study of a Heterobinuclear pyridylvinylidene Complex Cp(CO)2Fe [μ-C=CH(2-C5H4N)]PdI

“…В основе всех этих реакций лежат процессы окислительного присоеди-нения и восстановительного элиминирования [2]. Кроме того, соединения палладия способ-ны катализировать реакции сочетания переходный металл-углерод, что позволяет получать σ-этинильные комплексы переходных металлов, представляющие научный и практический интерес как объекты для получения супрамолекулярных ансамблей в молекулярной электро-нике [5], нелинейной оптике [6,7], а также как прекурсоры придилвинилиденовых комплексов [8] и потенциальные катализаторы электрохимического восстановления протона [9]. Среди известных реакций сочетания, катализируемых комплексами палладия, реакции сочетания металл-углерод являются наименее изученными [10].…”