[(K,Rb)@([2.2.2]crypt)](2)(K,Rb)(4)[Si9W(CO)(4)]center dot 13.4 NH3 - The First Tungsten Functionalized Silicon Zintl Cluster

The reaction between the heteroleptic metal carbonyl complex [W(CO)(4)(tmeda)] ((tmeda)= N,N,N',N'-Tetramethylethane-1,2-diamine) with [Si-9](4-) silicon Zintl clusters in presence of [2.2.2]crypt ([2.2.2]crypt= 4,7,13,16,21,24-Hexaoxa-1,10-diazabicyclo[8.8.8]-hexacosane) in liquid ammonia yielded the compound [(K,Rb)@([2.2.2]crypt)](2)(K,Rb)(4)[Si9W(CO)(4)]center dot 13.4 NH3. The compound was analyzed by single crystal X-ray diffraction and crystallizes in the space group P (1) over bar (a= 11.48390(10) angstrom, b= 19.7383(2) angstrom, c= 19.8983(2) angstrom, alpha = 112.5760(10)degrees, beta = 97.4210(10)degrees, gamma = 95.3760(10)degrees, V= 4079.01(7) angstrom(3)). The compound represents the first group 6 carbonylate-functionalized silicon Zintl cluster. The central moiety is composed of a tricapped trigonal prismatic nine-atom silicon species which coordinates with the lone pair of one capping atom to the tungsten tetracarbonylate, forming a pseudo trigonal bipyramidal carbonylate cluster anion [Si9W-(CO)(4)](6-). The chemical bonding in the new cluster entity is analyzed using theoretical calculations and subsequent analysis using QTAIM and NBO.