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Updated: Feb 15, 2026

Ultrafast Time-resolved Near-IR Stimulated Raman Measurements of Functional π-conjugate Systems
Published on: February 10, 2020
Contiguous multiple π-coordination of π-conjugated polyenes: bonding nature and charge delocalization behaviour of
Mariko Yamane1, Mitsuki Yamashita, Koji Yamamoto
1Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita, Osaka, 565-0871, Japan.
Abstract:
The contiguous multiple π-coordination (CMπC) bonds are formed at the molecular interface between the extended π-conjugated sp2-carbon framework and metal-metal moieties. However, the static properties including the bonding nature of the CMπC bonds have not been well-understood. Here we report the charge delocalization behavior and bonding nature of the polyene-(palladium chain) sandwich clusters. We observed the chain-length dependent 13C NMR chemical shifts of the terminal phenyl groups in [Pdm{Ph(CH[double bond, length as m-dash]CH)m+1Ph}2][B(ArF)4]2 (m = 3, 4, 5, 6), showing the efficient delocalization of positive charge over the polyene ligands. Furthermore, the detailed molecular orbital analysis of several model clusters provides insights into the bonding nature of the μ-η2:(η2:)nη2- and μ-η3:(η2:)nη3-poylene palladium chain sandwich clusters, where the former type is attributed to the corner-sharing Pd array and the latter to the edge-sharing/corner-sharing hybrid Pd array. The analogy of the μ-η3:(η2:)nη3-type with the carbonyl-bridge coordination is discussed. The Pd string in each mode of sandwich chain clusters has a weak M-M bonding interaction.
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