The Monomeric Pentacyanocobaltate[II) Anion Preparation and Properties of Thallium(l) Pentacyanocobaltate(II) Donnati M. S. Mosha Inorganic Laboratories, The University, Dares Salaam. Tanzania l'he reversible uptake of molecular hydrogen by aqueous cobalt(l1) saltk in the presence of the cyanide ion first observed by Iguchi ( I ) has prompted extensive studies of this system. Its application incatalytic hydrogenation of organic substrates is the subject of an excellent review by Kwiatek ( 2 ) . Most studies have, for reasons of solubility, been carried out almost exclusivelv in aoueous solutions. However. alcohols (3) and acetic acid(4) ark among a few nonaqueous solvents r e p o d . I n addition, we have recently demonstrated the catalytic hydrogenation of nitrobenzene, benzil, and styrene by this system in liquid ammonia (5). It is now conclusively established (6) that the olive green solutions prepared hy adding excess cvanide to aaueous cohalt(11) salts contain the Ico(CN)~13ion, but its isblation in the soiid state has been reported.&ly in few instances because the ion dimerizes to the violet diamagnetic [C02(CN)lo]G- ion due to its reactivity. Thus, the violet salt K ~ [ C O ~ ( C Ncommonly )~~], referred to as Adamson's salt (7). may be obtained from solutions of cobalt(I1) salts in excess KCN by addition of alcohol. T h e preparation and characterization of the dimeric barium salt Ba3[Col(CN)lo]1 3 H 2 0 has been reported (8.9).Our recent study in which liquid ammonia was used as preparative medium and NH4C N as starting material also led to a dimeric salt ( N H ~ ) ~ [ C O ~ ( C N(5.10). ) I ~ ] T h e isolation of salts containing the monomeric [Co(CN)5I3- ion is described in a few reports. Among these are Lis[Co(CN)5] (4); (Et4N)3[Co(CN)5], ( B U ~ N ) ~ [ C O ( C (3); N ) ~and ] (EtzPrpN)3[Co(CN)s] (Pr = isopropyl) (11). The preparation of a pale green thallium(1) salt described here was carried out in aqueous medium. Experimental Procedure Characterization Methds In this work, infrared spectra were recorded on a Perkin Elmer 257 instrument employing nujol mulls and sodium chloride windows. Diffuse reflectance soectra of oowdered samoles with added maenesium oxide diluent were rut; on a ~nicamSPl00Csoectronho. tometer. R w r n temperature magnctir soiceprihilir~eswere determined by the methud win
