Organic−Organometallic Crystal Synthesis. 1. Hosting Paramagnetic [(η⁶-Arene)₂Cr]⁺(Arene = Benzene, Toluene) in Organic Anion Frameworks<i>via</i>OH···O and CH···O Hydrogen Bonds

Abstract

The engineering of organic−organometallic crystals based on hydrogen bonding and on shape complementarity is discussed. The crystalline salts [(η 6 -C 6 H 6 ) 2 Cr][(CHD) 4 ] ( 1 ) and [(η 6 -C 6 H 5 Me) 2 Cr][(CHD) 2 ] ( 2 ), in which the paramagnetic cations [(η 6 -C 6 H 6 ) 2 Cr] + and [(η 6 -C 6 H 5 Me) 2 Cr] + are encapsulated within organic anion frameworks derived from 1,3-cyclohexanedione (CHD), have been constructed. The idea of this crystal synthesis stems from the structure of the host−guest cyclamer (CHD) 6 ·(C 6 H 6 ) prepared by Etter et al. ( J. Am. Chem. Soc . 1986, 108, 5871). The crystals are held together by O−H···O hydrogen bonds between the supramolecular [(CHD) 2 ] - ·(CHD) 2 and [(CHD) 2 ] - anions and by C−H···O hydrogen bonds between the anions and the organometallic cations. The hydrated crystalline species [(η 6 -C 6 H 6 ) 2 Cr][OH]·3H 2 O ( 3 ) and [(η 6 -C 6 H 6 ) 2 Cr][CHD]·3H 2 O ( 4 ) have also been prepared and structurally characterized. The crystals are held together by O−H···O as well as C−H···O interactions involving the water molecules. The hydroxide forms a polar crystal structure composed of an ABAB stacking sequence of layers containing OH - groups and water molecules and layers containing [(η 6 -C 6 H 6 ) 2 Cr] + cations distributed in herringbone fashion.