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首页> 外文期刊>Chemistry: A European journal >Transition-metal complexes of tetrylones [(CO) _5W-E(PPh _3) _2] and tetrylenes [(CO) _5W-NHE] (E=C-Pb): A theoretical study
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Transition-metal complexes of tetrylones [(CO) _5W-E(PPh _3) _2] and tetrylenes [(CO) _5W-NHE] (E=C-Pb): A theoretical study

机译：Tetrylones [（CO）_5W-E（PPh _3）_2]和四甲苯[[CO] _5W-NHE]（E = C-Pb）的过渡金属配合物：理论研究

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Quantum chemical calculations at the BP86/TZVPP//BP86/SVP level are performed for the tetrylone complexes [W(CO) _5-E(PPh _3) _2] (W-1 E) and the tetrylene complexes [W(CO) _5-NHE] (W-2 E) with E=C-Pb. The bonding is analyzed using charge and energy decomposition methods. The carbone ligand C(PPh _3) is bonded head-on to the metal in W-1 C, but the tetrylone ligands E(PPh _3) _2 are bonded side-on in the heavier homologues W-1 Si to W-1 Pb. The W-E bond dissociation energies (BDEs) increase from the lighter to the heavier homologues (W-1 C: D _e=25.1 kcal mol ~(-1); W-1 Pb: D _e=44.6 kcal mol ~(-1)). The W(CO) _5←C(PPh _3) _2 donation in W-1 C comes from the σ lone-pair orbital of C(PPh _3) _2, whereas the W(CO) _5←E(PPh _3) _2 donation in the side-on bonded complexes with E=Si-Pb arises from the π lone-pair orbital of E(PPh _3) _2 (the HOMO of the free ligand). The π-HOMO energy level rises continuously for the heavier homologues, and the hybridization has greater p character, making the heavier tetrylones stronger donors than the lighter systems, because tetrylones have two lone-pair orbitals available for donation. Energy decomposition analysis (EDA) in conjunction with natural orbital for chemical valence (NOCV) suggests that the W-E BDE trend in W-1 E comes from the increase in W(CO) _5←E(PPh _3) _2 donation and from stronger electrostatic attraction, and that the E(PPh _3) _2 ligands are strong σ-donors and weak π-donors. The NHE ligands in the W-2 E complexes are bonded end-on for E=C, Si, and Ge, but side-on for E=Sn and Pb. The W-E BDE trend is opposite to that of the W-1 E complexes. The NHE ligands are strong σ-donors and weak π-acceptors. The observed trend arises because the hybridization of the donor orbital at atom E in W-2 E has much greater s character than that in W-1 E, and even increases for heavier atoms, because the tetrylenes have only one lone-pair orbital available for donation. In addition, the W-E bonds of the heavier systems W-2 E are strongly polarized toward atom E, so the electrostatic attraction with the tungsten atom is weak. The BDEs calculated for the W-E bonds in W-1 E, W-2 E and the less bulky tetrylone complexes [W(CO) _5-E(PH 3) 2] (W-3 E) show that the effect of bulky ligands may obscure the intrinsic W-E bond strength. Opposite bonding trends: Quantum chemical calculations suggest that the bond strength of W-E (E=C-Pb) in the experimentally yet unknown tetrylone complexes W-1 E increases for the heavier Group 14 elements from carbon to lead, whereas the W-E bond in the tetrylene complexes W-2 E becomes weaker for the heavier atoms. The heavier ligands prefer a side-on bonding mode in both series of compounds.
机译：对tetrylone配合物[W（CO）_5-E（PPh _3）_2]（W-1 E）和四甲苯配合物[W（CO）_5进行BP86 / TZVPP // BP86 / SVP级的量子化学计算-NHE]（W-2 E），其中E = C-Pb。使用电荷和能量分解方法分析键合。碳配体C（PPh _3）与W-1 C中的金属正面键合，而四烯酮配体E（PPh _3）_2在较重的同系物W-1 Si至W-1 Pb中侧面键合。 。 WE键离解能（BDEs）从较轻的同系物增加（W-1 C：D _e = 25.1 kcal mol〜（-1）; W-1 Pb：D _e = 44.6 kcal mol〜（-1） ）。 W-1 C中的W（CO）_5←C（PPh _3）_2捐赠来自C（PPh _3）_2的σ孤对轨道，而W（CO）_5←E（PPh _3）_2捐赠E = Si-Pb的侧键结合复合物中的“α”是由E（PPh _3）_2的π孤对轨道（游离配体的HOMO）引起的。对于较重的同源物，π-HOMO能级持续升高，并且杂交具有更大的p特性，这使得较重的替替龙要比较轻的系统更强的供体，因为替替龙具有两个可用于捐赠的孤对轨道。能量分解分析（EDA）结合化学价的自然轨道（NOCV）表明，W-1 E中的WE BDE趋势来自W（CO）_5←E（PPh _3）_2捐赠的增加和静电的增强吸引，并且E（PPh _3）_2配体是强σ供体和弱π供体。对于E = C，Si和Ge，W-2 E络合物中的NHE配体末端相连，而对于E = Sn和Pb，NHE配体末端相连。 W-E BDE趋势与W-1 E配合物相反。 NHE配体是强σ供体和弱π受体。观察到的趋势是由于W-2 E中的原子E上的供体轨道的杂合性比W-1 E中的原子的杂合性大得多，甚至对于重原子而言，杂散性也增加了，因为四甲苯中只有一个孤对轨道可用捐款另外，较重体系W-2 E的W-E键向原子E强烈极化，因此与钨原子的静电吸引较弱。针对W-1 E，W-2 E和体积较小的替替龙复合物[W（CO）_5-E（PH 3）2]（W-3 E）中的WE键计算的BDE表明，较大的配体效应可能会掩盖固有的WE键强度。相反的键合趋势：量子化学计算表明，从碳到铅的第14组较重的元素，实验上未知的tetrylone配合物W-1 E中的WE（E = C-Pb）的键强度增加，而对于重原子，四甲苯配合物W-2 E变得更弱。在两个系列的化合物中，较重的配体都倾向于侧键结合模式。

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