Role of Axial Base Coordination in Isonitrile Binding and Chalcogen Atom Transfer to Vanadium(III) Complexes

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• 作者：Subhojit Majumdar ; Julia M. Stauber ; Taryn D. Palluccio ; Xiaochen Cai ; Alexandra Velian ; Elena V. Rybak-Akimova ; Manuel Temprado ; Burjor Captain ; Christopher C. Cummins ; Carl D. Hoff
• 刊名：Inorganic Chemistry
• 出版年：2014
• 出版时间：October 20, 2014
• 年：2014
• 卷：53
• 期：20
• 页码：11185-11196
• 全文大小：557K
• ISSN：1520-510X

文摘

The enthalpy of oxygen atom transfer (OAT) to V[(Me₃SiNCH₂CH₂)₃N], 1, forming OV[(Me₃SiNCH₂CH₂)₃N], 1鈥揙, and the enthalpies of sulfur atom transfer (SAT) to 1 and V(N[t-Bu]Ar)₃, 2 (Ar = 3,5-C₆H₃Me₂), forming the corresponding sulfides SV[(Me₃SiNCH₂CH₂)₃N], 1鈥揝, and SV(N[t-Bu]Ar)₃, 2鈥揝, have been measured by solution calorimetry in toluene solution using dbabhNO (dbabhNO = 7-nitroso-2,3:5,6-dibenzo-7-azabicyclo[2.2.1]hepta-2,5-diene) and Ph₃SbS as chalcogen atom transfer reagents. The V鈥揙 BDE in 1鈥揙 is 6.3 卤 3.2 kcal路mol^鈥? lower than the previously reported value for 2鈥揙 and the V鈥揝 BDE in 1鈥揝 is 3.3 卤 3.1 kcal路mol^鈥? lower than that in 2鈥揝. These differences are attributed primarily to a weakening of the V鈥揘_axial bond present in complexes of 1 upon oxidation. The rate of reaction of 1 with dbabhNO has been studied by low temperature stopped-flow kinetics. Rate constants for OAT are over 20 times greater than those reported for 2. Adamantyl isonitrile (AdNC) binds rapidly and quantitatively to both 1 and 2 forming high spin adducts of V(III). The enthalpies of ligand addition to 1 and 2 in toluene solution are 鈭?9.9 卤 0.6 and 鈭?7.1 卤 0.7 kcal路mol^鈥?, respectively. The more exothermic ligand addition to 1 as compared to 2 is opposite to what was observed for OAT and SAT. This is attributed to less weakening of the V鈥揘_axial bond in ligand binding as opposed to chalcogen atom transfer and is in keeping with structural data and computations. The structures of 1, 1鈥揙, 1鈥揝, 1鈥揅NAd, and 2鈥揅NAd have been determined by X-ray crystallography and are reported.