Fujisawa Kiyoshi, Tateda Akira, Miyashita Yoshitaro, Okamoto Ken-ichi, Paulat Florian, Praneeth V K K, Merkle Anna, Lehnert Nicolai
Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571, Japan.
J Am Chem Soc. 2008 Jan 30;130(4):1205-13. doi: 10.1021/ja075071d. Epub 2008 Jan 8.
Two crystal structures of the mononuclear copper(I)-nitrosyl complexes [Cu(L3)(NO)] (1) and Cu(L3')(NO) (2) with the related coligands L3- (hydrotris(3-tert-butyl-5-isopropyl-1-pyrazolyl)borate) and L3' (tris(3-tert-butyl-5-isopropyl-1-pyrazolyl)methane) are presented. These compounds are then investigated in detail using a variety of spectroscopic methods. Vibrational spectra show nu(N-O) at 1698 cm(-1) and nu(Cu-NO) split at 365/338 cm(-1) for 1, which translates to force constants of 12.53 (N-O) and 1.31 mdyn/A (Cu-NO), respectively. The weak Cu-NO force constant is in agreement with the observed instability of the Cu-NO bond. Interestingly, complex 2 with the neutral coligand L3' shows a stronger N-O bond, evident from nu(N-O) at 1742 cm(-1). This difference is attributed to a true second coordination sphere effect, where the covalency of the Cu(I)-NO bond is not altered. The EPR spectrum of 1 is in agreement with the Cu(I)-NO(radical) electronic structure of the complexes, as obtained from density functional theory (DFT) calculations. In addition, an interesting trend between g parallel(gz) and the Cu-N-O angle is established. Finally, high-quality MCD spectra of 1 are presented and assigned using TD-DFT calculations. Based on the in-depth spectroscopic characterization of end-on bound NO to copper(I) presented in this work, it is possible to determine the binding mode of the Cu-NO intermediate of Cu nitrite reductase studied by Scholes and co-workers (Usov, O. M.; Sun, Y.; Grigoryants, V. M.; Shapleigh, J. P.; Scholes, C. P., J. Am. Chem. Soc. 2006, 128, 13102-13111) in solution as strongly bent (approximately 135 degrees) but likely not side-on.
本文报道了单核铜（I）-亚硝酰配合物[Cu(L3)(NO)]（1）和Cu(L3')(NO)（2）的两种晶体结构，其中配体L3-为氢三（3-叔丁基-5-异丙基-1-吡唑基）硼酸根，L3'为三（3-叔丁基-5-异丙基-1-吡唑基）甲烷。然后使用多种光谱方法对这些化合物进行了详细研究。振动光谱显示，化合物1的ν(N-O)位于1698 cm(-1)，ν(Cu-NO)分裂为365/338 cm(-1)，这分别对应于12.53（N-O）和1.31 mdyn/A（Cu-NO）的力常数。较弱的Cu-NO力常数与观察到的Cu-NO键的不稳定性一致。有趣的是，具有中性配体L3'的配合物2显示出更强的N-O键，这从ν(N-O)位于1742 cm(-1)可以明显看出。这种差异归因于真正的第二配位层效应，其中Cu（I）-NO键的共价性没有改变。配合物1的电子顺磁共振（EPR）光谱与密度泛函理论（DFT）计算得到的配合物的Cu（I）-NO（自由基）电子结构一致。此外，还建立了g平行（gz）与Cu-N-O角之间的有趣趋势。最后，给出了配合物1的高质量磁圆二色性（MCD）光谱，并使用含时密度泛函理论（TD-DFT）计算进行了归属。基于本文对端基结合的NO与铜（I）的深入光谱表征，有可能确定Scholes及其同事（Usov, O. M.; Sun, Y.; Grigoryants, V. M.; Shapleigh, J. P.; Scholes, C. P., J. Am. Chem. Soc. 2006, 128, 13102-13111）研究的亚硝酸铜还原酶的Cu-NO中间体在溶液中的结合模式为强弯曲（约135度）但可能不是侧基结合。
