Vidal V, Theolier A, Thivolle-Cazat J, Basset JM
Laboratoire de Chimie Organometallique de Surface, UMR CNRS-CPE 9986, 43 Boulevard du 11 Novembre 1918, 69616 Villeurbanne Cedex, France.
Science. 1997 Apr 4;276(5309):99-102. doi: 10.1126/science.276.5309.99.
The silica-supported transition metal hydrides (=Si-O-Si=)(=Si-O-)2Ta-H and (=Si-O-)xM-H (M, chromium or tungsten) catalyze the metathesis reaction of linear or branched alkanes into the next higher and lower alkanes at moderate temperature (25degrees to 200degreesC). With (=Si-O-Si=)(=Si-O-)2Ta-H, ethane was transformed at room temperature into an equimolar mixture of propane and methane. Higher and lower homologs were obtained from propane, butane, and pentane as well as from branched alkanes such as isobutane and isopentane. The mechanism of the step leading to carbon-carbon bond cleavage and formation likely involves a four-centered transition state between a tantalum-alkyl intermediate and a carbon-carbon final sigma-bond of a second molecule of alkane.
二氧化硅负载的过渡金属氢化物（=Si - O - Si=）（=Si - O -）₂Ta - H和（=Si - O -）ₓM - H（M为铬或钨）在中等温度（25℃至200℃）下催化直链或支链烷烃复分解反应生成更高和更低碳数的烷烃。使用（=Si - O - Si=）（=Si - O -）₂Ta - H时，乙烷在室温下转化为丙烷和甲烷的等摩尔混合物。从丙烷、丁烷和戊烷以及支链烷烃如异丁烷和异戊烷中都能得到更高和更低碳数的同系物。导致碳 - 碳键断裂和形成步骤的机理可能涉及钽 - 烷基中间体与第二个烷烃分子的碳 - 碳最终σ键之间的四中心过渡态。
