Vol. 8, No.
4,April 1969
&DIKETONE COMPLEXES O F COBALT(II1) 789 the U. S. Atomic Energy Commission, Division of Biology and Medicine, under Contracts AT(30-1)3859 and -3514. Part of the work was performed (by L. E,) a t Westinghouse Research Laboratories.
cyclic, benzyl, and picolyl did not. Derivatives of five- or higher-membered cyclic amines can be classed with the n-alkyl derivatives. Acknowledgment.-This research was supported by
CONTRIBUTION FROM THE DEPARTMENTS OF CHEMISTRY, UNIVERSITY OF MASSACHUSETTS, AMHERST,MASSACHUSETTS 01002, AND TULANE UNIVERSITY, NEW ORLEANS, LOUISIANA70118
p- Diketone Complexes of Cobalt(111).
111. Tris(p-diketona to)cobal t (111) and Bis(acetylacetonato)diaminecobalt(III) Trichelate Species1& BY ROBERT J. YORK,lb WESLEY D. BONDS, J R . , ' ~ BRILLE P. COTSORADIS,'"
AND
RONALD D. ARCHERlbvd
Received October 84, 1068 The two geometrical isomers of tris(2,2-dimethyl-3,5-hexanedionato)cobalt(111) have been prepared, separated chromatographically, and identified by proton magnetic resonance (pmr) spectroscopy. The pmr of a series of bis(acety1acetonato)diaminecobalt(II1) complexes (diamine = ethylenediamine, N,N,N',N'-tetramethylethylenediamine, 2,2'-bipyridine, or 1,lO-phenanthroline) show the importance of both diamagnetic ring anisotropy and external environmental effects. Marked improvements have been made in the synthesis of tris(2,2,6,6-tetramethyl-3,6-heptanedionato)cobalt~III)and tris(l,l,l,5,5,5hexafluoroacetylacetonato)cobalt(III). Electronic and vibrational energy levels are also discussed.
Introduction A detailed study of bis(P-diketonato)cobalt(III) complexes is in progress in this laboratory to determine the u and a ligand field effects on the reaction rates and the reaction stereochemistry of cobalt(II1) complexes. Previous r e p ~ r t have s ~ ~demonstrated ~ ~ ~ ~ the usefulness of sodium dinitr obis (acetylacetonato) cobaltate(II1) for the synthesis of bis(acety1acetonato)cobalt (111) complexes. A series of diamine complexes have been used to study effects on the p-diketone methyl group pmr (proton magnetic resonance) signals. The tris complexes of dhd and thd4 have been prepared for the purpose of spectral correlations in the study of the bis complexes of these ligands now in progress. Co(thd), has been prepared by an alternate method,s but no characterization has been reported. We have increased the yield of the tris complex and spectrally characterized it. The volatility of hexafluoroacetylacetonate complexes makes them particularly useful in chemical research (1) (a) Part 11: B. P. Cotsoradis and R. D. Archer, Inorg. Chem., 6 , 800 (1967); piesented in pait a t 156th National Meeting of the Ameiican Chemical Society, Atlantic City, N. J., Sept 1968; (b) Department of Chemistry, University of Massachusetts, Amherst, Mass. 01002; ( 0 ) Department of Chemistry, Tulane University, New Orleans, La. 70118; (d) t o whom correspondence should be sent. (2) R. D. Archer and B. P. Cotsoradis, Inorv. Chem., 4, 1584 (1965). (3) L. J. Boucher, ibid.,6 , 2162 (1967). (4) Abbreviations used in this paper include: dhd, 2,2-dimethylhexane-3,5-dionato; thd, 2,2,6,6-tetramethylheptane-3,5-dionato; en, ethylenediamine; bipy. 22'-bipyridine; c-phen, 1,lO-phenanthroline; acac, 2,4-pentanedionato; tmed, N,N,N',N'-tetramethylhfa, 1,1,1,5,5,5-hexafluoro-2,4-pentanedionato: ethylenediamine. ( 5 ) G . S. Hammond, D. C. Nonhebel, and C. H. S. Wu, Inorg. Chem., 2 , 73 (1963).
such as gas chromatography6 and mass spectroscopy.' Unfortunately, previously reported methods of preparing the cobalt(II1) c ~ m p l e x *are ~ ~less than satisfactory in terms of either yield (1%)* or safety (90% H20z).g We have achieved the synthesis of C0(1ifa)~in high yield with safe, commercially available reactants and are currently studying the reaction mechanism. Results Syntheses.-As previously reported2s3 treatment of Co@-dik)z(NOz)2- with amines in the presence of activated carbon results in the formation of the diamine derivatives. This procedure has been used to form the N,N,N',N'-tetramethylethylenediamine and 1,lo-phenanthroline derivatives of bis(acety1acetonato)diaminecobalt(II1) perchlorate. The use of Norit A for the synthesis of the heterochelates is important. To illustrate, the reaction of truns-Co(a~ac)~(NO~) 2and ammonia with neutral Norit or Norit FQP produces Co(acac) 3 rather than the cis- and transCo (acac) 2 (NH 3) Z+ species.lo The tris complexes of cobalt(II1) with 2,2-dimethylhexane-3,5-dione and 2,2,6,6-tetraniethylheptane-3,5dione have been prepared in high yield by allowing (6) R. W. Moshier and R. E. Sievers, "Gas Chromatography of Metal Chelates," Pergamon Prees Ltd., London, 1965. (7) S. M. Schildcront, R. G . Pearson, and F. E. Stafford, J . A m . Chcm. Soc., 90, 4006 (1968). ( 8 ) M. Kilner, F. A. Hartman, and A. Wojcicki, Inorg. Chem., 6 , 406 (1967). (9) H. Yeening, W. E. Bachman, and D. M. Wilkinson, J. Gas Chromatog., 5, 248 (1967). (10) S. Golinger, unpublished results.
790 YORK,BONDS, COTSORADIS, AND ARCHER
Inorganic Chemistry
TABLEI sodium hexanitrocobaltate(II1) to react with basic solutions of the diketones. I n order to attain sufficient P R O T O N CHEMICAL SHIFTS FOR BIS(ACETYLACETONATO)COBALT(III) COMPLEXES" solubility for the synthesis of the Co(thd)3 complex, a mixed solvent of ethanol and water was found necessary. CH, proton C H proton Complex Solvent peak positions Ab peak positions The tris complex of hexafluoroacetylacetone, preCHSOD -2.11 0.018d -5.64 viously prepared in low yield by alternate n i e t h ~ d s , ~ , ICo(a~ac)zen]ClO~~ ~ -2.13 has been successfully synthesized by the reaction of CDaOD -2.13 0.022d - 5.64 CoFa and the anhydrous ligand. I n the presence of -2.14 dry powdered sodium fluoride, the reaction rate is 0.018d (CD3)zSO -2.08 -5.61 D20e -2.16 0.008dsf -5.77 markedly increased and the yield is improved. Little, DzOg h,i 0.010 i if any, of the cobalt(I1) p-dilietone complex is formed [Co(acac),tmed]ClO4i CDC13 0.11 -2.09 -5.59 when water is rigorously excluded from the reaction. -2.20 However, a great deal of the reduced product is formed -2.12 CD3OD 0.12 -5.76 in the presence of incompletely dehydrated reagents. -2.24 [ C o ( a c a ~ ) ~ b i p y ] I CD,OD -1.91 0.51 -5.83 Nuclear Magnetic Resonance Spectra.-The pmr -2.42 and I9F magnetic resonance spectra of the new coniCDCI, - 1.93 0.47 -5.32 pounds are listed in Tables I and I1 along with more -2.40 detailed chemical shift data for the previously reported2 -1.91 CHzClz 0.49 k [Co(acac)zen]ClOi and [Co(acac)zbipy]I complexes. -2.40 [Co(acac)2-o-phen]C104 CH2C1zE - 1.86 0.59 k, Improved instrunientation and solvent changes have -2.45 resulted in the observation of a slight splitting in the diketone methyl protons (Figure 1) of the [Co(acac)2en]Chemical shifts, ppm, relative to tetramethylsilane, 500-cps sweep width, saturated solutions, unless otherwise noted. ( 2 1 0 4 complex which had previously been reported t o Methyl splitting. Ethylenediamine CH, protons observed a t show only a single methyl resonance.2 The pinr -2.7 ppm when not obscured by solvent. Splitting measured spectra of the chroniatographed isomers of Co(dhd) 3 at 50-cps sweep width. * Chemical shifts relative to the methyl (Figure 2 ) allow the assignment of fuc and mer strucgroups of sodium 3-trimethylsilyl-1-propanesulfonate.f Splittures.",'* ting obtained by Varian Associates on a precisely tuned Varian A-60 spectrometer. 0 Spectrum obtained on a Varian Model Infrared Spectra.-The vibrational spectra of the HA-100 spectrometer by Varian Associates. Doublet observed. compounds have been recorded in the region from No reference available. 2 N-Methyl peaks of the diamine 4000 to 300 em-l. Tables I11 and IV list the characobserved a t -1.81 and -2.25 ppm; latter overlaps diketonate teristic bands of the new conipounds. Our spectra for methyl signal. Ir Peak obscured by solvent. Methylene the other species are in agreement with those reported chloride is the only solvent which dissolves enough complex to obtain a pmr spectrum. previously, specifically, [Co(acac)2en]C104,2[Co(acac)2b i ~ y ] I [C0(hfa)3],~ ,~ and Hdhd.I3 TABLEI1 Assignments for the coordinated acetylacetonate P R O T O N CHEMICAL SHIFTS' ligand vibrations have been made with reference to the t-Butyl proton Methyl proton CH proton revised assignments of the vibrational bands in Compound peak positions 12eak positions peak positions tris (acetylacetonato) chr oniium (111) using l8Olabeling. l4 Hdhd -1.15 (9) -2.00 (3) -5.60 (1) This places the C=O and C=C vibrations back t o the -2.05 (3)* -5.60 (l)* -1.15 (9)b order recommended by Dismukes, Jones, and Bailar. l 5 -2.16 (3) -5.49 (1) f~c-Co(dhd)a -1.10 (9) Our previous assignments,l, which were based on -2.08) -5.41) me~-Co(dhd)~ - 1.08 \(9)c -2.15 (3) -5.50 (1) Nakanioto's normal-coordinate analysis,'6 should be -I.l01 -2.18 -5.53 revised to agree with Tables I11 and IV. Assignments CO(thd) 3 - 1.09 '(18) ... -5.62 (1) of the o-phenanthroline vibrational modes has been -6.5jd Co (hfa) ... ... made with reference to the work of Schilt and Taylor.'' -6.95e .. See also ref 18-20 for data pertinent to Table 111.
i
(11) (a) R. C. Fay and T. 8 . Piper, J . Am. Chem. Soc., 84, 2303 (1962); (b) R. C. Fay and T. S.Piper, ibid., 85, 500 (1963). (12) (a) R. C. Fay and T. S. Piper, I n o r g . Chem., 3 , 348 (1964); ( b ) R. A . Palmer, R. C. Fay, and T. 9. Piper, ibid., 3,875 (1964). (13) J. Charette and P. TeysEiB, Speclrochm. Acta. 16, 689 (1960). (14) S. Pinchas, B. L. Silver, and J. Laulicht, J . Chem. P h y s . , 46, 1506 (1967). (15) J. P. Dismukes, L. H . Jones, and J. C. Bailar, Jr., J . Phvs. Chem., 65, 793 (1961). (16) I
