High-valent metal–oxo species with multiply-bonded M–O groups have been proposed as key intermediates in many biological and abiological catalytic oxidation reactions. These intermediates are implicated as active oxidants in alkane hydroxylation, olefin epoxidation and other oxidation reactions. For example, [Fe^ivO(porphyrinato^•−)]⁺ cofactors bearing π-radical porphyrinato^•− ligands oxidize organic substrates in cytochrome P450 enzymes, which are common to many life forms. Likewise, high-valent Mn–oxo species are active for H₂O oxidation in photosystem II. The chemistry of these native reactive species has inspired chemists to prepare highly oxidized transition-metal complexes as functional mimics. Although many synthetic Fe–O and Mn–O complexes now exist, the analogous oxo complexes of the late transition metals (groups 9–11) are rare. Indeed, late-transition-metal–oxo complexes of tetragonal (fourfold) symmetry should be electronically unstable, a rule commonly referred to as the ‘oxo wall’. A few late metal–oxos have been prepared by targeting other symmetries or unusual spin states. These complexes have been studied using spectroscopic and theoretical methods. This Review describes mononuclear non-haem Fe–O and Mn–O species, the nature of the oxo wall and recent advances in the preparation of oxo complexes of Co, Ni and Cu beyond the oxo wall.

具有多重键合的 M-O 基团的高价金属-氧代物种已被提议作为许多生物和非生物催化氧化反应中的关键中间体。这些中间体被认为是烷烃羟基化、烯烃环氧化和其他氧化反应中的活性氧化剂。例如，[Fe ^iv O(porphyrinato ^•− )] ⁺带有 π-自由基卟啉基^•−配体的辅因子氧化细胞色素 P450 酶中的有机底物，这对许多生命形式都很常见。同样，高价 Mn-oxo 物种对 H _{2具有活性}光系统 II 中的 O 氧化。这些天然活性物质的化学性质启发了化学家们制备高度氧化的过渡金属配合物作为功能模拟物。尽管现在存在许多合成的 Fe-O 和 Mn-O 配合物，但后过渡金属（第 9-11 族）的类似氧代配合物很少见。事实上，四方（四重）对称的后过渡金属-氧代络合物应该是电子不稳定的，这一规则通常被称为“氧代墙”。已经通过针对其他对称性或不寻常的自旋态制备了一些晚期金属氧代化合物。已经使用光谱和理论方法研究了这些配合物。本综述描述了单核非血红素 Fe-O 和 Mn-O 物种、氧代壁的性质以及在氧代壁外制备 Co、Ni 和 Cu 氧代络合物的最新进展。