Hart Mason D, Meyers John J, Wood Zachary A, Nakakita Toshinori, Applegate Jason C, Erickson Nathan R, Gerasimchuk Nikolay N, Barybin Mikhail V
Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, KS 66045, USA.
Department of Chemistry & Physics, Clayton State University, 2000 Clayton State Blvd., Morrow, GA 30260, USA.
Molecules. 2021 Feb 12;26(4):981. doi: 10.3390/molecules26040981.
Isocyanoazulenes (CNAz) constitute a relatively new class of isocyanoarenes that offers rich structural and electronic diversification of the organic isocyanide ligand platform. This article considers a series of 2-isocyano-1,3-X-azulene ligands (X = H, Me, COEt, Br, and CN) and the corresponding zero-valent complexes thereof, [(OC)Cr(2-isocyano-1,3-X-azulene)]. Air- and thermally stable, X-ray structurally characterized 2-isocyano-1,3-dimethylazulene may be viewed as a non-benzenoid aromatic congener of 2,6-dimethyphenyl isocyanide (2,6-xylyl isocyanide), a longtime "workhorse" aryl isocyanide ligand in coordination chemistry. Single crystal X-ray crystallographic {Cr-CNAz bond distances}, cyclic voltametric {(Cr)}, C NMR {δ(CN), δ(CO)}, UV-vis {dπ(Cr) → pπ*(CNAz) Metal-to-Ligand Charge Transfer}, and FTIR {ν, ν, k} analyses of the [(OC)Cr(2-isocyano-1,3-X-azulene)] complexes provided a multifaceted, quantitative assessment of the π-acceptor/σ-donor characteristics of the above five 2-isocyanoazulenes. In particular, the following inverse linear relationships were documented: δ(CO) vs. δ(CN), δ(CO) vs. δ(CN), and δ(CO) vs. k force constant. Remarkably, the electron withdrawing capability of the 2-isocyano-1,3-dicyanoazulene ligand rivals those of perfluorinated isocyanides CNCF and CNCF.
异氰基薁（CNAz）构成了一类相对较新的异氰基芳烃，为有机异氰化物配体平台提供了丰富的结构和电子多样性。本文研究了一系列2-异氰基-1,3-X-薁配体（X = H、Me、COEt、Br和CN）及其相应的零价配合物[(OC)Cr(2-异氰基-1,3-X-薁)]。空气和热稳定的、经X射线结构表征的2-异氰基-1,3-二甲基薁可被视为2,6-二甲基苯基异氰化物（2,6-二甲苯基异氰化物）的非苯型芳香类似物，2,6-二甲苯基异氰化物是配位化学中一种长期使用的“主力”芳基异氰化物配体。对[(OC)Cr(2-异氰基-1,3-X-薁)]配合物进行的单晶X射线晶体学{Cr-CNAz键长}、循环伏安法{(Cr)}、碳核磁共振{δ(CN), δ(CO)}、紫外可见{dπ(Cr) → pπ*(CNAz) 金属到配体的电荷转移}以及傅里叶变换红外光谱{ν, ν, k}分析，对上述五种2-异氰基薁的π受体/σ供体特性进行了多方面的定量评估。特别是，记录了以下反比线性关系：δ(CO)与δ(CN)、δ(CO)与δ(CN)以及δ(CO)与k力常数之间的关系。值得注意的是，2-异氰基-1,3-二氰基薁配体的吸电子能力与全氟异氰化物CNCF和CNCF相当。
