Mateu-Campos Juanjo, Gutiérrez-Blanco María, Guillamón Eva, Safont Vicent S, Benet-Buchholz Jordi, Oliva Mónica, Llusar Rosa
Departament de Química Física i Analítica, Universitat Jaume I, Av. Sos Baynat s/n, Castelló de la Plana 12071, Spain.
Institute of Chemical Research of Catalonia - ICIQ, Av. Països Catalans 16, Tarragona 43007, Spain.
Inorg Chem. 2025 Apr 7;64(13):6552-6560. doi: 10.1021/acs.inorgchem.4c05438. Epub 2025 Mar 21.
Methanolysis of hydrosilanes is catalyzed by incomplete cubane-type Mo(μ-S)(μ-S) clusters functionalized with diamino and imidazolyl amino ligands under mild conditions. Silane activation mediated by the air-stable [Mo(μ-S)(μ-S)Cl(ImNH)]Cl (ImNH = (1-methyl-1-imidazol-2-yl)methanamine) ([]Cl) cluster salt has been elucidated through a comprehensive experimental and theoretical study. Our results support the operation of a sulfur-centered mechanism without direct participation of the metals in clear contrast with all previously reported mechanisms catalyzed by transition metal complexes. The reaction proceeds in two steps, with the first one being the rate-determining step. The process starts with the hydrosilane Si-H bond activation, which occurs at one of the bridging sulfur atoms of the Mo(μ-S)(μ-S) cluster unit. This step takes place through a concerted and asynchronous transition state with the participation of one methanol molecule to yield the silyl ether product and a bis(hydrosulfido) intermediate. Analysis of this transition state reveals that its imaginary frequency is basically associated with the silane hydride transfer and the formation of the Si-O bond in agreement with the observed KIE results. The second step consists in the hydrogen release from the bis(hydrosulfido) intermediate, from which the cluster catalyst is recovered. The same mechanism operates for the diamino [MoSCl(en)]Cl (en = ethylenediamine) ([]Cl) and [MoSCl(dmen)] (dmen = N,N'-dimethylethylenediamine) ([]Cl) cluster salts. The calculated free energy barriers for those cluster catalysts agree with the observed catalytic activities, giving further support to our mechanistic proposal.
在温和条件下，用二氨基和咪唑基氨基配体官能化的不完全立方烷型Mo(μ-S)(μ-S)簇催化硅烷的甲醇解反应。通过全面的实验和理论研究，阐明了空气稳定的[Mo(μ-S)(μ-S)Cl(ImNH)]Cl（ImNH = (1-甲基-1-咪唑-2-基)甲胺）（[ ]Cl）簇盐介导的硅烷活化。与之前报道的所有过渡金属配合物催化的机制形成鲜明对比的是，我们的结果支持一种以硫为中心的机制，其中金属不直接参与。反应分两步进行，第一步是速率决定步骤。该过程始于硅烷Si-H键的活化，其发生在Mo(μ-S)(μ-S)簇单元的一个桥连硫原子上。这一步通过一个协同且异步的过渡态进行，有一个甲醇分子参与，生成甲硅烷基醚产物和双（氢硫基）中间体。对这个过渡态的分析表明，其虚频基本上与硅烷氢转移和Si-O键的形成有关，这与观察到的动力学同位素效应（KIE）结果一致。第二步是双（氢硫基）中间体释放氢，从而回收簇催化剂。二氨基[MoSCl(en)]Cl（en = 乙二胺）（[ ]Cl）和[MoSCl(dmen)]（dmen = N,N'-二甲基乙二胺）（[ ]Cl）簇盐也遵循相同的机制。这些簇催化剂的计算自由能垒与观察到的催化活性一致，进一步支持了我们的机理提议。
