The Cobalticinium Cation [Co III (η5‐C5H5)2]+: A metal‐organic complex as a novel template for the synthesis of clathrasils

The cobalticinium cation [CoIII(η5‐C5H5)2]+  Cocp2+ is the first metal‐organic complex that acts as a structure‐directing template in the hydrothermal synthesis of microporous solids. Three different clathrasil framework structures – nonasil (NON), octadecasil (AST) and dodecasil 1H (DOH) – crystallize during hydrothermal treatment from the synthesis system SiO2NH4FCocp2PF6H2O at 420–470 K. From infrared, optical and x‐ray absorption (XANES, EXAFS) spectroscopic measurements, it is evident that the cobalticinium cation remains unchanged upon incorporation into the crystallizing silica framework proving its role as a template. Thermal analysis demonstrates that Cocp2+ entrapped in silica frameworks possesses a much higher thermal stability than the cation in simple salts. An X‐ray single‐crystal structure determination of cobalticinium nonasil was performed at 220 K: [Cocp2F]4 · 88 SiO2, orthorhombic, space group Pccn, a = 22.125(2) Å, b = 13.612(3) Å, c = 14.889(2) Å, Z = 1. Each of the large [58612]‐cages of the nonasil structure is occupied by a Cocp2+ cation in staggered conformation which does not show any orientational or rotational disorder but is fixed due to steric confinement and weak CH …︁ O(host) interactions. Fluoride anions that compensate the charge of the Cocp2+ cations reside in half of the small [4158] cages in front of the four‐membered rings. They coordinate to the neighbouring framework atom Si1 (d(Si1F): 1.836(6) Å), causing a distortion of the tetrahedral oxygen environment to a nearly ideal trigonal‐bipyramidal penta‐coordination of Si1.