The reaction between the heteroleptic metal carbonyl complex [W(CO)4(tmeda)] ((tmeda)=N,N,N′,N′-Tetramethylethane-1,2-diamine) with [Si9]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] ⋅ 13.4 NH3. The compound was analyzed by single crystal X-ray diffraction and crystallizes in the space group urn:x-wiley:00442313:media:zaac202300117:zaac202300117-math-0001 (a=11.48390(10) Å, b=19.7383(2) Å, c=19.8983(2) Å, α=112.5760(10)°, β=97.4210(10)°, γ=95.3760(10)°, V=4079.01(7) Å3). 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.