962
JOHN
Inorganic Chemistry
L. BURMEISTER AND MONTHER Y . AL-JANABI COSTRIBUTION FROM
THE
WILLIAMALBERTNOYESCHEMISTRY LABORATORY, UNIVERSITYOF ILLIXOIS, URBANA,ILLINOIS
Selenocyariate Complexes of Cobalt (I1I), Palladium (II), and Platinum (I I)la,b BY JOHN L. BURMEISTER"
AND
MONTHER T. XL-JASABI
Received September 18, 1964 The synthesis and partial characterization, on the basis of infrared spectra, of the new selenocyanate complexes Ka [Co(C S )iNCSe], [Co( CS)NCSe] C1, [Co(KH3)&CSe] ( r\j03)2, [Pd(bipp)(SeCN)2], and [Pt(bipy)(SeCK)2] are reported. The use of the selenocyanate ion as a bridging ligand in the transition state in oxidation-reduction reactions of coordination complexes is discussed. The type of selenocyanate bonding, M-h-CSe or 13-SeCS, in the new complexes is contrasted with that found in similarly constituted thiocyanate complexes.
Introduction Although the behavior of the thiocyanate ion as an ambidentate ligand has been the subject of a number of recent studies, relatively little work has been published concerning the selenocyanate ion, NCSe-. I t , too, has been found to function as an ambidentate ligand, being Se-bonded in complexes of metals of class b char~], acterI2 e . g . , Kz[Pt(SeCN)G] and K s [ H ~ ( S ~ C N )and N-bonded in complexes of metals of class a character, e.g., [ (CH3)qN ]Z [Co (NCSe)4 1 2 - 4 and K3[ Cr (NCSe)6 1 .b A third type of bonding for the selenocyanate ion, as a bridging group, has been reported for AgSeCN,2 Hg[ C O ( N C S ~ ) ~ and ] , ~ , ~[Co(py)(NCSe)z] (py = pyridine) .G The published results indicate a close similarity in the coordination behavior of the thiocyanate and selenocyanate ions. However, selenocyanate-containingcomplexes of the majority of the transition metal ions have not yet been prepared. Furthermore, it remains to be demonstrated whether the presence of other ligands in the coordination sphere of a metal ion can affect the nature of the metal-selenocyanate bond, as has been shown to be the case for several thiocyanate complexe~.~ This paper reports the synthesis and partial characterization of several new coordination complexes of the selenocyanate ion and a study of the use of the selenocyanate ion as a bridging ligand in the transition state in oxidation-reduction reactions of coordination complexes.
prepared according to the method of Turco, et aZ.,4 was added, whereupon the color of the solution changed from reddish yellow to dark red. The solution was filtered, allowing the filtrate to reddish pass directly into 50 ml. of absolute ethanol at 0'. oil formed which, with standing, crystallized t o form a ycllovvbrown solid. T h e solid was isolated by filtration, washed with ethanol and ether, both at O " , and dried i n vacuo over calcium chloride. The complex was found to be stable with respect t o isomerization in the solid state. .4naZ. Calcd. for KsCoCsSsSe: C, 17.52; X, 20.43. Found: C , 18.04; K, 20.86. NCS A \
/
\
\
/
&[(NChCO
CO(CN)~]5H20.- This brown
bridgcd
SCN complex was isolated as the product of the preceding reaction when 0.51 g. (1 mmole) of K2[Hg(SCS)4], prepared according to the method of Turco, et aZ.,4 was used in place of the KZ[Hg(SeCS)I:. A n a l . Calcd. for KICo2CloS10S2H1005: C, 17.44; H, 1.46; S,20.34. Found: C, 17.41; H, 1.14; N , 20.38. [Co(NH3),(CN)NCSe]Cl.-To a solution of 0.48 g. (2 mmoles) of iCo(SHg)g(FT2O)CS;Cl? (prepared according t o the method of Siebertg)in 25 ml. of water was added 0.29 g. ( 2 mmoles) of potassium selenocyanate, followed by 0.5 g. of activated charcoal. The solution was gradually heated t o boiling, then filtered, allowing the filtrate t o pass directly into 50 ml. of absolute ethanol a t 0'. T h e yellow precipitate which formed was isolated by filtration, washed with ethanol and ether, and dried in vacuo over calcium chloride. Aizal. Calcd. for CoSGH1zC2SeC1: C, 8.19; H , 4.12; X, 28.63. Found: C , 8.27; H , 4.95; S , 27.93. [Co(NH,)jNCSe](NOs)2.-Fivemrnoles (1.7 8.) of (Co(KH3)8OSO2](S O s ) % ,prepared according t o the method of I'almer,lo was slowly added to a solution of 4.3 g. (30 inmoles) of potassium selenocyanate in a minimum amount of water. T h e reddish Experimental brown precipitate which formed was removed by filtration and Preparation of Compounds.-Potassium selenocyanate was dried in vacuo over calcium chloride. It was then treated with prepared by the method given in Inorganic Syntheses.* dimethylformamide t o separate the desired product from the red Ks [Co( CN)6NCSe].-This preparation was carried out in a selenium decomposition product. The mixture was filtered and drybox and nitrogen atmosphere. T o a solution of 0.33 g. ( 3 the red filtrate thus obtained was allowed t o stand, covered, for 4 mmoles) of potassium cyanide in 10 ml. of deoxygenated water ~ H Z O . dal-s. Ether was then added, whereupon the precipitation of a a t 0' was added 0.23 g. (1 mmole) of C O ( C ~ H ~ O ~ ) ~ , When pink solid occurred. It was isolated by filtration, washed with dissolution was complete, 0.70 g. (1 mmole) of K2[Hg(SeCN)J, ethanol and ether, and dried in vacuo over calcium chloride. Selenocyanate substitution was not complete, as indicated by (1) (a) Abstracted in part from t h e X S . Thesis of Ll. Y.A , , University of Illinois, 1964; (b) pi-esented a t t h e Fifteenth Delaware Science Symposium, the high value obtained for the nitrogen content. Kewark, Del., Feh. 1965; ( c ) University of Delaware, S e w a r k , Del. Anal. Calcd. for CoN*H&SeOe: N, 30.04. Found: N, (2) A. Turco, C. P e d e , and ivl. Nicolini, Pvoc. Chem. Soc., 213 (1961). 32.16. (3) F. A. Cotton, I). M . L. Goodgame, M. Goodgame, and T. E. Haas, iPd(bipy)(SeCN)*;.-One gram ( 3 rnmoles) of [I'd( bipy)CL! Inorg. Chem., 1, 565 (1962). (4) A. Tui-co, C. P e d e , and M. Sicolini, J . Chrnz. Soc., 3008 (1962). (bipy = 2,2'-bipyridine), prepared according t o thc mcthod of (,5) K. ?vIichelsen. A c t a C h e m . Scn?zd., 17, 1811 (1963). (6) S. &I. Kelson, Pmc. Chem. Soc., 372 (1961). ( 7 ) J,L. Bui-meister a n d F.Basolo, I n o i g . C h e w . , 3 , 1587 (1064), and i-eferences contained therein. (8) G. R. X'aitkins and I
