Experimental and Computational Studies of Ruthenium Complexes Bearing Z‑Acceptor Aluminum-Based Phosphine Pincer Ligands

Reaction of [Ru(C6H4PPh2)2(Ph2PC6H4AlMe(THF))H]
with
CO results in clean conversion to the Ru−Al heterobimetallic
complex [Ru(AlMePhos)(CO)3] (1), where AlMePhos
is the novel P–Al(Me)–P pincer ligand (o-Ph2PC6H4)2AlMe. Under
photolytic conditions, 1 reacts with H2 to
give [Ru(AlMePhos)(CO)2(μ-H)H] (2) that
is characterized by multinuclear NMR and IR spectroscopies. DFT calculations
indicate that 2 features one terminal and one bridging
hydride that are respectively anti and syn to the AlMe group. Calculations also define a mechanism
for H2 addition to 1 and predict facile hydride
exchange in 2 that is also observed experimentally. Reaction
of 1 with B(C6F5)3 results
in Me abstraction to form the ion pair [Ru(AlPhos)(CO)3][MeB(C6F5)3] (4) featuring
a cationic [(o-Ph2PC6H4)2Al]+ ligand, [AlPhos]+.
The Ru–Al distance in 4 (2.5334(16) Å) is
significantly shorter than that in 1 (2.6578(6) Å),
consistent with an enhanced Lewis acidity of the [AlPhos]+ ligand. This is corroborated by a blue shift in both the observed
and computed νCO stretching frequencies upon Me abstraction.
Electronic structure analyses (QTAIM and EDA-ETS) comparing 1, 4, and the previously reported [Ru(ZnPhos)(CO)3] analogue (ZnPhos = (o-Ph2PC6H4)2Zn) indicate that the Lewis acidity
of these pincer ligands increases along the series ZnPhos < AlMePhos
< [AlPhos]+.

该数据集描述了配合物[Ru(C6H4PPh2)2(Ph2PC6H4AlMe(THF))H]与一氧化碳反应，实现了对Ru-Al异核双金属配合物[Ru(AlMePhos)(CO)3](1)的清洁转化，其中AlMePhos代表一种新型的P-Al(Me)-P钳式配体(o-Ph2PC6H4)2AlMe。在光化学条件下，1与氢气反应生成[Ru(AlMePhos)(CO)2(μ-H)H](2)，并通过多核核磁共振和红外光谱技术进行表征。密度泛函理论计算表明，2具有一个端基氢化物和一个桥连氢化物，分别与AlMe基团呈反式和顺式。计算还定义了氢气对1的加成机制，并预测了2中的氢化物交换反应，这一预测也得到了实验的证实。1与B(C6F5)3反应导致Me基团被抽象，形成阳离子[(o-Ph2PC6H4)2Al]+配体和[AlPhos]+的离子对[Ru(AlPhos)(CO)3][MeB(C6F5)3](4)。在4中，Ru-Al的距离(2.5334(16) Å)显著短于1中的距离(2.6578(6) Å)，这与[AlPhos]+配体的增强路易斯酸性一致。这一结论得到了观察和计算的νCO伸缩频率在Me抽象过程中的蓝移的证实。通过比较1、4和先前报道的[Ru(ZnPhos)(CO)3]类似物(ZnPhos = (o-Ph2PC6H4)2Zn)的电子结构分析(QTAIM和EDA-ETS)，表明这些钳式配体的路易斯酸性沿着系列ZnPhos < AlMePhos < [AlPhos]+逐渐增强。