2534 CORRESPONDENCE
Inorganic Chemistry
of cuprous oxide and TFAA until water is added. The addition of 4 equiv of water brings about immediate reaction, presumably through the formation of TFA and its dissolution of the Cu(1) ion. Uptake of 1 equiv of carbon monoxide per Cu(1) is rapid and stops sharply. Separation of the crystals of the carbonyl complex from the cooled solution by filtration in a glove bag is necessary, as the indicative blue-green color of Cu(I1) is almost impossible t o avoid. Analysis of the crystals, their infrared spectrum, and
the pumping experiment all support the postulated stoichiometry of Cu + : CO :TFA- : T F A as 1 : 1: 1: 1. That the carbon monoxide is still present in the solventfree crystals prepared by brief pumping is shown by its appearance at 2155 cm-’; the frequency is unshifted from that characteristic of the initially prepared complex. Acknowledgment.-We wish to acknowledge with thanks the very helpful advice of Dr. R. L. -4utrey.
Correspondence On t h e Existence of t h e p-cis Configuration Qf Chelated Ethylenediamine-N,N’-diacetat e
nate (mal) analogs. It is noteworthy that in the p-cis isomers of these complexes the steric interactions postulated for the corresponding diamine analogs are absent. Van Saun and Douglas only found the a-cis isomers for Sir : Co(edda) COX- and related complexes. a However, The use of ethylenediaminediacetate (edda) as a cothey isolated less than 30y0 of the total possible yield, ordinating ligand has been the subject of several recent and it is conceivable that the @-cis isomers still remained papers. These papers concern the preparation, in solution. resolution, and characterization of complexes in which We have prepared a series of edda complexes and are edda acts as a tetradentate ligand and the other two studying the kinetics of their aquation and isomerizapositions in the coordination sphere are occupied by tion. The a-cis and p-cis isomers of Co(edda)COs--, various bidentate groups. Co(edda) (ox)-, Co(edda)(mal)-, Co(edda)(OH&+, and Legg and Cookel distinguished the coordination of Co(edda)C12- have been prepared. A previous nmr edda in the so-called trans configuration from the sostudy showed that in the a-cis isomers the acetate ring called cis configuration by means of nuclear magnetic protons exhibited only one AB quartet but in the p-cis resonance spectroscopy. We feel that complexes with isomers the spectrum was much more complex.’ Our edda in these configurations should be called a-cis and complexes confirm this conclusion. Further support p-cis, respectively, in accord with the nomenclature used of configuration has come from the for our assignment for triethylenetetramine complexes. This enables retention of configuration when the carbonato isomers complexes where edda assumes a planar disposition are aquated with dilute perchloric acid and regenerated about the central metal atom (allowing two unidentate with bicarbonate. These reactions occur with retention ligands t o occupy positions trans to one another) to be as had previously been found in the reactions of related described as trans. Such a compound has been precomplexes.6 pared. The a-cis and @-cis isomers of Co(edda)(OH&i Small amounts of the p-cis isomer of some edda comwere separable by cation-exchange chromatography plexes have been isolated by ion-exchange chromatogand in aqueous solution the p-cis form isomerizes to the raphy.’n2 However, in the systems so far r e p ~ r t e d l - ~ more stable a-cis. However, in contrast to the findthe a-cis isomer appears to have been formed almost ings of Van Saun and Douglas3 and unlike any of the exclusively. This together with an analysis of nmr systems so far in~estigatedl-~, the p-cis isomer of Codata and a consideration of molecular models led Legg (edda)C03is more stable than the a-cis isonier in and Cookel to conclude that edda favored an a-cis conP-cis isomer is thermodynamiaqueous solution. The figuration due to increased “steric interaction between cally favored over the a-cis by about 600 cal/mol. the ligands” in the p-cis isomers. Specifically there (6) F. P. Dwyer, A. M . Sargeson, and I. K. Reid, J . A m . Chenb. Soc., 85, appears t o be a greater interaction between the amine 1215 (1963). protons of ethylenediamine and the protons of edda (7) Support from t h e Petroleum Research Fund ( G r a n t No. 3153.A3) a n d a grant provided for biological and medical research by t h e State of Wsshin the @cis isomer. Our present work has shown that ington Initiative Measure No. 171 IS gratefully acknowledged. the a-cis configuration of edda is not preferred in all l’. J. GARNETT SCHOOL OF CHEMISTRY complexes and in particular in the case of the CoD. W.WATTS THEUNIVERSITY OF WESTERNAUSTRALIA (edda)C03- isomers and their oxalate (ox) and maloNEDLANDS, WESTERNACSTRALIA 6009
(1) (2) Legg, (3) (4) (6)
J. 1. Legg a n d 1). %’. Cooke, Iiioig. Chcm., 4, 1576 (1966). J. 1. Legg, D. W. Cooke, a n d B. E. D o u g h s , ibid., 6, 700 (1967); J. I. Chem. Commuii., 675 (1967). C. W. Van S a u n and B. E. Douglas, I n o i g . C h e m . , 8, 115 (lY69). A. M. Sargeson and G . H. Searle, ibid., 4, 45 (1965). C. F. Liu, ibid.. 3,680 (1964).
DEPARTMEKT OF CHEMISTRY ~ ’ A S H I N G T O XSTATE UNIVERSITY
99163 RECEIVED MAY19, 1969
PULLMAK, U’ASHINGTON
J. IVANLEGG’
