Fedushkin Igor L, Lukoyanov Anton N, Ketkov Sergey Y, Hummert Markus, Schumann Herbert
G. A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences, Tropinina 49, 603950 Nizhny Novgorod, GSP-445, Russia.
Chemistry. 2007;13(25):7050-6. doi: 10.1002/chem.200700736.
1,2-Bis[(2,6-diisopropylphenyl)imino]acenaphthene) (dpp-bian) stabilizes gallium-gallium and zinc-gallium bonds (compounds 1-3). The compound [(dpp-bian)Ga-Ga(dpp-bian)] (2) was prepared by the reaction of GaCl3 with K3[dpp-bian] and the heterometallic [(dpp-bian)Zn-Ga(dpp-bian)] (3) was prepared by a simple one-pot reaction of [{(dpp-bian)ZnI}(2)] with GaCl3 and K4[dpp-bian]. In contrast to [(dpp-bian)Zn-Zn(dpp-bian)] (1) and 3, compound 2 is ESR silent, thus proving the dianionic character of both dpp-bian ligands. The solution ESR spectrum of 3 reveals the coupling of an unpaired electron with the gallium nuclei (69)Ga and (71)Ga (A((69)Ga)=0.97, A((71)Ga)=1.23 mT), thus confirming the presence of Zn-Ga bonds in solution. According to the results of the X-ray crystal structure analyses the metal-metal bond lengths in 2 (2.3598(3) A) and 3 (2.3531(8) A) are close to that found in 1 (2.3321(2) A). The electronic structures of compounds 2 and 3 were studied by DFT (B3 LYP/6-31G* level). The metal-metal pi bond in 2 is mainly formed by overlap of the p orbitals of Ga in the HOMO and HOMO-1, the latter showing a stronger interaction. The s and p orbitals of Ga overlap in the deeper located HOMO-17 producing a Ga-Ga sigma bond. In contrast to the Zn-Zn bond in 1, which has 95 % s character, the NBO (natural bond order) analysis of 2 reveals 67.8 % s, 32.0 % p, and 0.2 % d character for the Ga-Ga bond. Compound 3 has a doublet electronic ground state. The unpaired electron occupies the alpha HOMO-1 localized at the Zn-containing fragment. The Ga-Zn bond is mainly formed by overlap of the metal orbitals in the alpha HOMO-6 and beta HOMO-5. According to the results of the NBO analysis, the Zn wave functions are responsible for 28.7 % of the Zn-Ga bond, with 96.7 % s, 1.0 % p, and 2.3 % d character.
1,2-双[(2,6-二异丙基苯基)亚氨基]苊烯（dpp-bian）可稳定镓-镓键和锌-镓键（化合物1 - 3）。化合物[(dpp-bian)Ga-Ga(dpp-bian)]（2）通过GaCl₃与K₃[dpp-bian]反应制备，而异金属化合物[(dpp-bian)Zn-Ga(dpp-bian)]（3）通过[{(dpp-bian)ZnI}(2)]与GaCl₃和K₄[dpp-bian]进行简单的一锅法反应制备。与[(dpp-bian)Zn-Zn(dpp-bian)]（1）和3不同，化合物2的电子自旋共振（ESR）无信号，从而证明了两个dpp-bian配体的双阴离子特性。3的溶液ESR谱显示未成对电子与镓核（⁶⁹Ga和⁷¹Ga）的耦合（A(⁶⁹Ga)=0.97，A(⁷¹Ga)=1.23 mT），从而证实了溶液中存在锌-镓键。根据X射线晶体结构分析结果，2（2.3598(3) Å）和3（2.3531(8) Å）中的金属-金属键长与1（2.3321(2) Å）中的相近。通过密度泛函理论（DFT，B3 LYP/6 - 31G*水平）研究了化合物2和3的电子结构。2中的金属-金属π键主要由最高占据分子轨道（HOMO）和HOMO - 1中Ga的p轨道重叠形成，后者显示出更强的相互作用。Ga的s和p轨道在更深的HOMO - 17中重叠形成Ga - Ga σ键。与1中具有95% s特征的Zn - Zn键不同，对2的自然键轨道（NBO）分析表明Ga - Ga键具有67.8%的s特征、32.0%的p特征和0.2%的d特征。化合物3具有双重简并电子基态。未成对电子占据位于含锌片段的α HOMO - 1。Ga - Zn键主要由α HOMO - 6和β HOMO - 5中的金属轨道重叠形成。根据NBO分析结果，Zn波函数对Zn - Ga键的贡献为28.7%，具有96.7%的s特征、1.0%的p特征和2.3%的d特征。
