Heterotrimetallic M−M′−M′′ Transition Metal Complexes Based on 1,3,5-Triethynylbenzene: Synthesis, Solid State Structure, and Electrochemical and UV−Vis Characterization. EPR Analysis of thein SituGenerated Associated Radical Cations

Abstract

The synthesis of a series of complexes with different organometallic building blocks unsymmetrically arranged around the periphery of a 1,3,5-triethynylbenzene core is discussed. They are accessible by diverse consecutive reaction sequences, which allow the introduction of transition metal units such as Fc, [( t Bu 2 bpy)(CO) 3 Re], [(η 5 -C 5 H 5 )(Ph 3 P) 2 Ru], [(η 5 -C 5 H 5 )(Ph 3 P) 2 Os], and trans-[(Ph 3 P) 2 (Cl)Pt] (Fc ) (η 5 -C 5 H 5 )(η 5 -C 5 H 4 )Fe; t Bu 2 bpy ) 4,4′-di-tert-butyl-2,2′-bipyridyl). The solid state structures of five complexes have been determined. The electrochemical behavior of the newly synthesized mono-, heterobi-, and heterotrimetallic assemblies have been studied, showing that there is no significant electronic interaction between the respective metal atoms. UV-vis spectroscopic measurements suggest a weak interaction between the appropriate metal atoms. The associated radical cations were in situ generated by stepwise chemical oxidation and characterized by continuous wave electron paramagnetic resonance (EPR) investigations in X-band performed at low temperatures.

Synthesis, Spectroelectrochemical, and EPR Spectroscopic Studies of Mixed Bis(alkynyl)biferrocenes of the Type (LnMC≡C)(LnM′C≡C)bfc

“…e . (Cp)­(PPh 3 ) 2 Ru–(CC) 2 –Ru­(PPh 3 ) 2 (Cp), (Cp)­(NO)­(PPh 3 )­Re–(CC) 2 –Re­(PPh 3 )­(NO)­(Cp), and (Cp*)­(dppe)­Fe–(CC) 2 -Fe­(dppe)­(Cp*). − Rigid-rod structured molecules featuring redox-active terminal metallocenyl groups have also been extensively studied, since they represent model compounds for molecular wire molecules. ,− In addition, a combination of sandwich and half-sandwich units bridged by linear alkynyl building blocks (CC) n ( n = 0, 1, 2, 3, ...) or other carbon-rich connectivities, including 1,4-diethynyl- or 1,3,5-triethynylbenzene, are known, and their spectro-electrochemical behavior was investigated in detail. ,− In particular, it was found that lengthening of the carbon chain (C 2 to C 8 ) resulted in an increase of the redox potential of the end-grafted ferrocenyl moiety in, for example, Fc–(CC) n –WCp­(CO) 3 (Fc = Fe­(η 5 -C 5 H 4 )­(η 5 -C 5 H 5 ); Cp = η 5 -C 5 H 5 ; n = 1–4) . Metallocenyls also can be incorporated in alkynyl chains, resulting in the formation of (L n MCC)­(L n M′CC)­fc compounds (fc = (η 5 -C 5 H 4 ) 2 Fe; L n M = L n M′; L n M ≠ L n M′; 17-valence-electron half-sandwich or sandwich entities). ,,,− These molecules were prepared to examine the transmission of electronic effects between the appropriate terminal transition metals on the carbon connectivities via the central fc unit.…”

Heteromultimetallic Transition Metal Complexes Based on Unsymmetrical Platinum(II) Bis-Acetylides

“…Due to their active coordination sites, all-carbon ligands, aryldiethynyls, arylethenyls, alkynylthiophenes, etc., are of particular importance in the synthesis of a huge number of rigid-rod-structured carbon-rich π-conjugated homo- and heterometallic transition metal complexes. – Especially, the 1,3,5-triethynylbenzene core allows the design of organometallics that can be extended in three directions. , Hitherto, mainly homotrimetallic systems incorporating, for example, [(R 3 P)Au] and [(η 5 -C 5 Me 5 )(η 2 -dppe)Fe] (dppe = bis(diphenylphosphino)ethane) building blocks exist, while less is known about heterometallic derivatives. , A short while ago, only one example with three different metal-containing building blocks such as Fc, [(η 2 -dppm) 2 OsCl], and (η 2 -dppm) 2 RuCl] (Fc = (η 5 -C 5 H 5 )(η 5 -C 5 H 4 )Fe; dppm = bis(diphenylphosphino)methane) was available . Very recently this family of complexes was enriched by diverse iron, ruthenium, osmium, rhenium, and platinum organometallic termini . One of these molecules is 1-(FcCC)-3-[( t Bu 2 bpy)(CO) 3 ReCC]-5-[ trans -(Ph 3 P) 2 (Cl)PtCC]C 6 H 3 ( t Bu 2 bpy = 4,4′-di- tert -butyl-2,2′-bipyridyl), which can be used as a suitable starting material in the preparation of heterometallic complexes of higher nuclearity .…”

“…Very recently this family of complexes was enriched by diverse iron, ruthenium, osmium, rhenium, and platinum organometallic termini . One of these molecules is 1-(FcCC)-3-[( t Bu 2 bpy)(CO) 3 ReCC]-5-[ trans -(Ph 3 P) 2 (Cl)PtCC]C 6 H 3 ( t Bu 2 bpy = 4,4′-di- tert -butyl-2,2′-bipyridyl), which can be used as a suitable starting material in the preparation of heterometallic complexes of higher nuclearity . The Pt−Cl functionality facilitates the formation of unsymmetrical platinum(II) bis-acetylides and consequently the connection to further organic and organometallic groups, which additionally can possess pendent coordination sites.…”

Probing CH-π(alkyne) interactions in a series of ethynylferrocenes

“…Also, three examples have an inversion dimer based on OFF interactions between the aryl termini. Adding support to the argument for an orthogonal preference for adoption of the CH … p(alkyne) based inversion dimer, there are two dual entries in Table 2 and 3, Entries 3/28 (VOGFIH 45 ) and 8/35 (BAGKEA 49 ). VOGFIH has two unique molecules in the asymmetric unit, that with orthogonal Cp-aryl geometry (86.3u dihedral) forms the compact inversion dimer, the coplanar molecule (3.6u dihedral) does not.…”