Kinetic Pathway Control in the Synthesis of Well‐Defined Ruthenium Coordination Oligomers

TL;DR

This paper describes the synthesis of well-defined ruthenium-based coordination oligomers with precise control over their structure and length.

Contribution

The study introduces a method to kinetically control the synthesis of monodisperse ruthenium coordination oligomers.

Findings

Linear coordination oligomers with defined lengths (n=4 or 5) were synthesized in high purity and yield.

A complex reaction network explains the kinetic pathway selection during synthesis.

Thermodynamic and kinetic factors govern the formation and elongation of the oligomers.

Abstract

Ruthenium complexes with 2,2′‐bipyridine‐6,6′‐dicarboxylate (bda) ligands have emerged as highly potent catalysts for water oxidation. In this context, the accumulation of active Ru centers in macrocyclic arrays or coordination oligomers and polymers has proven to be very beneficial for an enhanced stability under operating conditions and to facilitate surface adhesion in heterogeneous systems. For a better insight into structure–activity relationships though, well–defined systems with a precise control over stoichiometry and constitution are highly desired. Herein, the synthesis and characterization of a series of structurally precise and monodisperse linear coordination oligomers [(Ru(bda))
n

L

n−1
pic
2] (n = 4 or 5, L = 4,4′‐bipyridine or 1,4‐bis‐(pyridine‐4‐yl)benzene derivatives, pic = 4‐picoline), in excellent purity and yields are reported. Based on detailed mechanistic investigations, a complex network of interconnected and competing reactions is proposed that fully explains both the high overall turnover and the kinetic pathway selection between alternative endcapping and dissociation–elongation sequences.

Ru(bda) coordination oligomers with defined length have been prepared from bidentate linkers and pyridine endcaps. While the high yield of the reactions is driven by the thermodynamically favorable formation of strong Ru–pyridine bonds, the oligomer length is kinetically controlled by varying rates for the various dissociation, elongation, and capping steps.© 2025 WILEY‐VCH GmbH

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