The coordination chemistry of copper is dominated by its monovalent and divalent oxidation states and interplay between the two is central to the role of copper-based homogeneous catalysts. Upon reduction of most copper(II) complexes, which commonly are five coordinate, the coordination number rapidly changes to four or less. This feature is advantageous for atom transfer reactions where single electron transfer is coupled to the association or dissociation of a radical. Although this coupled change in coordination number and oxidation state is central to the mechanism of atom transfer reactions, its importance to catalysis is not widely appreciated. Herein we review the structural chemistry of copper(I) and copper(II) with a range of multidentate N-donor ligands employed in atom transfer radical polymerisation (ATRP). The remarkable resistance of copper(I) to accept more than four donor atoms is illustrated and discussed in the context of both its solid state and solution structures.

铜的配位化学主要由其单价和二价氧化态决定，两者之间的相互作用是铜基均相催化剂作用的关键。在还原通常为五个配位的大多数铜（II）配合物后，配位数迅速变为四个或更少。该特征对于原子转移反应是有利的，在原子转移反应中，单电子转移与自由基的缔合或解离偶联。尽管配位数和氧化态的这种耦合变化是原子转移反应机理的核心，但其在催化中的重要性并未得到广泛的认识。本文中，我们回顾了用于原子转移自由基聚合（ATRP）的一系列多齿N供体配体的铜（I）和铜（II）的结构化学。