June 5 , 1964
COMMUNICATIONS TO THE EDITOR
2311
the intense band a t 295.5 mp, which is not characteristic of other pentacyanocobaltate(II1) complexes, is not clear but is believed to be connected with the aromatic component of the complex, since the corresponding alkyl complexes do not exhibit this band. The chemical shifts of the benzyl protons are similar to those obC. E. CASTRO served in CeH6CH2HgC1 (CH2, -1.85; CeH6, -5.86 DEPARTMENT OF NEMATOLOGY p.p.m,from t-butyl alcohol, measured in CDC13). UNIVERSITY OF CALIFORNIA RIVERSIDE, CALIFORNIA Pentacyanoalkylcobaltate( 111) compounds may be RECEIVED APRIL4, 1964 similarly prepared although the study of these has not proceeded as far as that of the benzyl compound. The reaction of CH3I with Co(CN)s3- yields [CH~COPentacyanobenzylcobaltate(II1). A New Series of (CN),I3which has also been obtained, in nearly Stable Organocobalt Compounds pure (-90%) form, as the sodium salt. The ethyl Sir : and n-propyl compounds can be similarly prepared in We wish to report the preparation and characterizasolution although these are less stable than the benzyl tion of a new series of stable, water-soluble organoand methyl analogs and have not as yet been fully cobalt compounds, which are formed by the reduction characterized or recovered in pure form. The ultraof organic halides with pentacyanocobaltate( 11). violet spectrum of [CH3Co(CN)5I3- resembles that of On addition of benzyl bromide to a water-methanol other typical pentacyanocobaltate(II1) complexes, solution containing CoCl2 and NaCN (which react e.g., [Co(CN)sC1I3-, and the band a t 318 mp (whose together to form C O ( C N ) ~ ~in - ) ~the absence of air, counterpart in the benzyl compound presumably is a compound which we are led to formulate as pentaobscured by the tail of the much more intense 295 cyanobenzylcobaltate(II1) is rapidly formed by the mp band) may accordingly be assigned to a (tzg)sreaction (eg)l + (t2g)etransition. This suggests that the ligand field strength of CHI approaches that of CN- (Ama, ~ [ C O * ~ ( C N+ ) ~CBHbCH2Br ]~+ 311 mp for Co(CN)e3--) and is in line with the high [CaH5CHd20111(CN)5] 8+ [ColI1(CN),Br]*- ligand fields exhibited by alkyl ligands in other complexes2 [ C H ~ C O ( C N ) ~reacts ] ~ - with HgC1, to form By fractional precipitation and recrystallization from CH3HgC1and with Iz to form CH31. alcohol solutions, the sodium salt of [CeHsCH2CoThe formation of a binuclear, unsaturated organo(CN)6l3- could be separated from the less soluble salts pentacyanocobalt(II1) complex, [ (CN)6Co-CH=CH of C O ( C N ) ~ B ~ ~c -o, ( c N ) ~ ~ - and , Co(CN)60H3-, C O ( C N ) ~ ] ~by - , a somewhat different route, namely which are by-products of the reaction. Anal. Calcd. the reduction of acetylene by Co(CN)b3-, has previously for N ~ ~ [ C B H ~ C H Z C O. (2C HN z 0) :~ Co, ] 15.3; C, 37.4; been described by Griffith and W i l k i n ~ o n . ~T h e H, 2.9; N, 18.2. Found: Co, 15.8; C, 37.6; H, 3.2; [ C ~ H S C H Z C O ( C N ) anion ~ ] ~ - and its alkyl analogs N, 17.6. The original yield of CeHsCH2Co(CN)s3-, reported here are isoelectronic with the corresponding based on the ultraviolet spectrum of the reaction solustable organomanganese pentacarbonyls, e.g., CH3tion, is estimated to be about 70%. Mn(CO)s; their mode of preparation, described above, Na3 [C~HSCHZCO(CN)S]. 2Hz0 is a yellow, somewhat finds an analogy in the formation of another stable, deliquescent, crystalline salt. I t is soluble in water, water-soluble organometallic complex, [CeHsCHzCr"'methanol, and ethanol and insoluble in ether, acetone, (H20)6l2+, by the reduction of benzyl chloride with or hydrocarbons. Thermal decomposition in vacuo chromium(I1). Finally, reference should be made yields dibenzyl as the organic product. Alkaline to some interesting points of analogy between the aqueous solutions of [ C ~ H S C H ~ C O ( C Nare ) ~ ] stable ~chemistry of C O ( C N ) ~ ~revealed -, here, and that of the in the absence of oxygen and show no immediate rereduced derivatives of vitamin BIZ ( i . e . , vitamins action with NaBH4 or CO. The anion is decomposed B12r and Bizs), including the reactions of the latter slowly by oxygen and rapidly by acids, the course of with alkyl halides and other alkylating agents to form the latter reaction being complex and as yet unresolved. stable alkyl cobalt derivativess The ultraviolet and n.m.r. spectra of [CeHbCHzCoFurther studies on the preparation and characteri(CN)Sl3- are summarized in Table I. The origin of zation of these compounds are in progress. TABLEI Acknowledgment.-Support of this work by the Proton n.m.r. National Science Foundation (Grant No. GP-654) spectra in Dz0 CEN Ultraviolet Chemiand by the National Institutes of Health of the U. S. stretching absorption Group cal Public Health Service (Grant No. GM-10662) is assignshift, frequency, Xmsx (ernax), gratefully acknowledged. ment p.p.m.b Anion cm. --La mu
Acknowledgment.-This work was supported by the National Science Foundation, NSF G19145, and the National Institutes of Health, EF 00079-01, for which the author is grateful. The author wishes to thank Dr. Lyle Gaston for pure samples of D D T and D D D and for helpful analytical advice.
[ C ~ H S C H I C O ( C N ) ~ ] * -2093 f 3
-
*
(CHaCo(CN)s 1 * 2094 3 [ C ~ H S C O ( C N ) ~ I ' - ~ 2094 f 3
295.5 (1.8X 10') 318 ( 2 . 9 X 102)
...
a Measured on the sodium salt in KBr pellet. t-butyl alcohol. Based on impure samples.
(1) A. W. Adamson, J. A m . Chem. Soc., 1 8 , 5710 (1951)
CH2 CeHa CHs CHp CHa
-1.67 -6.01 i-0.70 -0.35 +0.09 Relative t o
(2) J . Chatt and R . G. Haytei, J . Chem. Soc., 772 (1961).
13) W. P. Griffith and G. Wilkinson, ibid., 1629 (1959). (4) F.A. L.Anet and E. Lehlanc, J. A m . Chem. Soc., 79, 2649 (1957). (5) R. Bonnett, Chem. Rev., 63, 573 (1963).
DEPARTMENT OF CHEMISTRY THEUNIVERSITY OF CHICAGO CHICAGO, ILLINOIS60637 RECEIVED APRIL16, 1964
JACK HALPERN JOHN P. MAHER
