Formation and crystal structures of novel seven-coordinate 15-crown-5 complexes of manganese(II), iron(II) and cobalt(II)

The reactions of Mn(CO)(5)Br, Fe(CO)(5) and Co-2(CO)(8) with HCl(g) in the presence of 15-crown-5 and H2O in toluene have been explored. These reactio ns were promoted with the use of UV radiation and formed liquid clathrates almost immediately upon reaction. For each metal species, oxidation of the metal center from either [+ 1] (for Mn) or [0] (for Fe, Co) to [ +2] occurr ed. For manganese, the Mn-II species [Mn-II(H2O)(2). 15-crown-5] [Br-Cl-] ( 1) was obtained from the liquid clathrate layer in the reaction mixture. Fo r iron the Fe-II species [(FeCl)-Cl-II(H2O) . 15-crown-5] [H2O2+][(FeCl42-) -Cl-II] (2) rapidly formed, and for cobalt the Co-II species [Co-II(H2O) . 15-crown-5]-[H9O4+ ] [ Co-II . 15-crown-5 ] [H9O4+ ] [Co-II(H2O) . 15-crown -5] [(CoCl42-)-Cl-II](4) (3) was deposited from the liquid clathrate layer. It was established by X-ray crystallography that each species contains a s even-coordinate metal center with pentagonal bipyramidal stereochemistry. C omplex 1 is a hydrogen-bonded single-stranded polymer through bridging hali de atoms. Complex 2 has a H5O2+ oxonium ion hydrogen-bonded to the cations and complex 3 has a remarkable H2O-Co2+-H9O4+-Co-2(+)-H9O4+-Co-2(+)-H2O cat ionic chain. (C) 2000 Elsevier Science Ltd. All rights reserved.