Coordinating Tectons: Bimetallic Complexes from Bipyridyl Terminated Group 8 Alkynyl Complexes

Abstract

Bipyridyl appended ruthenium alkynyl complexes have been used to prepare a range of binuclear homometallic ruthenium and heterometallic ruthenium−rhenium complexes. The two metal centers are only weakly coupled, as evinced by IR and UV−vis−near NIR spectroelectrochemical experiments and supported by quantum chemical calculations. The alkynyl complexes of the type [Ru(C Cbpy){L n }] ({L n } = {(PPh 3 ) 2 Cp}, {(dppe)Cp*}, {Cl(dppm) 2 }) undergo reversible one-electron oxidations centered largely on the alkynyl ligands, as has been observed previously for closely related complexes. The homometallic binuclear complexes, exemplified by [Ru(C 2 bpy-κ 2 -N′N-RuClCp)(PPh 3 ) 2 Cp] undergo two essentially reversible oxidations, the first centered on the (C 2 bpy-κ 2 -N′N-RuClCp) moiety and the second on the Ru(CCbpy)(PPh 3 ) 2 Cp fragment, leading to radical cations that can be described as Class II mixed-valence complexes. The heterometallic binuclear complexes [Ru(C 2 bpy-κ 2 -N′N-ReCl(CO) 3 ){L n }] display similar behavior, with initial oxidation on the ruthenium fragment giving rise to a new optical absorption band with Re → Ru(CCbpy) charge transfer character. The heterometallic complexes also exhibit irreversible reductions associated with the Re hetereocycle moiety. ■ EXPERIMENTAL SECTIONGeneral Considerations. All reactions were performed under an atmosphere of high purity argon or nitrogen using standard Schlenk techniques. Reaction solvents either were purified and dried using an Special Issue: Organometallic Electrochemistry

Coordinating Tectons. Experimental and Computational Infrared Data as Tools To Identify Conformational Isomers and Explore Electronic Structures of 4-Ethynyl-2,2′-bipyridine Complexes

“…The bimetallic complexes 12-15 were prepared from the σalkynyl complexes 4 and 5 through coordination of an additional metal center to the bipyridyl moiety of the metallo-ligand in a similar manner to analogous 5-ethynyl-2,2' bipyridine complexes. 18 The heterobimetallic complexes 12 and 14 were prepared through a thermal carbonyl ligand displacement reaction with [ReCl(CO) 5 ]. 92 The homobimetallic complexes 13 and 15 were obtained through reaction of 4 or 5 with [RuCl(COD)Cp] and displacement of the labile 1,5-cyclooctadiene (COD) ligand.…”

“…17-20 A series of bimetallic complexes of the well-studied, bifunctional ligand 5-ethynyl-2,2'-bipyridine were synthesized by this approach, and weak electronic communication was observed between two metal centers across this ligand. 18 Indeed, the electronic interactions between metal termini separated by organic functionality, M-bridge-M', are often investigated in order to define the intramolecular, electron transfer (or wire-like) characteristics of the assembly. [21][22][23][24] Investigations of organometallic complexes in this area have focused on the mixed-valence characteristics of bimetallic complexes derived from bridging moieties such as polyynes, [25][26][27][28] oligo(phenylene)ethynylenes 29 and bis(terpyridine)metal complexes.…”

Clusters as ligands: Synthesis, structure and coordination chemistry of ruthenium clusters derived from 4- and 5-ethynyl-2,2′-bipyridine

“…The bi-functional nature of these compounds makes them ideally suited for the construction of multimetallic systems, and 5-ethynyl-2,2'-bipyridine has found application as a linking unit within the Tinkertoy-based construction of multi-metallic frameworks based on monomolecular nodes [12,13]. Further exploration has revealed the capacity of such ligands to promote weak electronic interactions between the tethered nodes [14].…”

Synthesis and optical properties of cationic cyclopentadienyl iron complexes with diphenylacetylene chromophores

“…These advantageous characteristics are the key elements in the design of organic molecules for optical applications. Some acetylene-connected ferrocene derivatives with charge transfer ability, special redox behavior, electronic properties, and non-linear optical (NLO) properties have been reported [11][12][13][14][15][16][17].…”