Covalent Bonding Between Ir and High-Oxidation State Sb Constrained by Quinoline Scaffolds

From the reaction of a high-valent Sb(V) proligand with
a low-valent
Ir(I) precursor in acetonitrile, a bimetallic Sb–Ir complex
was isolated in which one of the quinoline groups inverted such that
it is N-coordinated to Sb and C-coordinated
to Ir. The new Sb–Ir complex has a unique structure containing
the shortest reported Sb–Ir bond (2.51502(18) Å). Our
combined experimental and computational studies indicate pronounced
covalent character for the Sb–Ir bond. Based on the covalent
bonding, the complex more closely resembles Sb(IV)–Ir(II) species
rather than Sb(V)–Ir(I) and thus results in an Ir center with
poor π-basicity, particularly toward the position trans to Sb.

以高氧化态锑(V)前配体与低氧化态铱(I)前驱体在乙腈中发生反应，成功分离得到一种双金属Sb-Ir配合物；该配合物中一个喹啉基团发生构型翻转，以氮原子配位结合锑、碳原子配位结合铱。该新型Sb-Ir配合物具有独特的分子结构，其Sb-Ir键长为已报道的最短值（2.51502(18) 埃）。我们结合实验与计算的联合研究表明，该Sb-Ir键具有显著的共价特征。基于该共价成键特性，该配合物的氧化态更接近Sb(IV)-Ir(II)物种而非初始的Sb(V)-Ir(I)，由此导致铱中心的π碱性较弱，尤其是在与锑处于反位的配位位点上。