C02+.nC02 + C O
-
J. Phys. Chem. 1989, 93, 1197-1203 CO2+-CO.(n -1)C02
+ C02
(5)
At low O2concentration, reaction 5 predominates over reaction 4. Reaction 5 together with reaction 6 contributes the formation of (C0)2+.nC02 and decreases the apparent decay rate of (C0)2+.nC02. Thus, this reaction sequence can explain the O2 C02+.C0.(n - 1 ) C 0 2 + 2C0, C02+.C0.nC02 + C O
-
-
C02+.C0.nC02
(C0)2+.nC02
+ C02
+ C02
(6)
concentration dependence of the apparent bimolecular rate constant of reaction 1. The decrease of apparent kl with the decrease
1197
of O2concentration is explained by reaction IC. As the decrease of rate constant with the decrease of O2 concentration reached 1.8 X lo-" cm3 s-' in Table I, the ionic back reaction IC is estimated to have a rate constant of the order of lo-" cm3 s-l. This value satisfies an estimated value higher than cm3 s-I for the ionic back reaction in the radiolysis of carbon dioxide.I3 Thus, it is deduced that reaction I C or the ionic species, (C0)2+.nC02 (n = 1-4) is responsible for the rapid oxidation of carbon monoxide in the radiolysis of carbon dioxide. Registry No. 02,7782-44-7; C 0 2 , 124-38-9; C O , 630-08-0; CH,, 74-82-8; CzH6, 74-84-0; C3Hs, 74-98-6; n-C4Hlo,106-97-8; n-C6Hk4, 110-54-3.
Resonance Raman and Infrared Studies of Matrix-Isolated Cuo(ethylene), Complexes. Contribution of C2H4/C2D4Mixture to the Structural Analysis Th6rese Merle-MGjean,*.t Sdd Bouchareb,t and Michel Tranquille* Laboratoire de spectroscopie moleculaire et cristalline (U.A. 124), Universite de Bordeaux I, 351 Cours de la Liberation, 33405 Talence Cedex, France (Received: February 29, 1988; In Final Form: June 23, 1988)
Products of cocondensation of copper atoms with either pure ethylene (Et) or ethyleneargon mixtures trapped at 12 K were reinvestigated by IR spectroscopy. The first Raman spectra were obtained. IR spectroscopy indicates that the distribution of complexes in pure ethylene and that in argon matrices are different. Isotopic H/D experimentsstrongly support the formation of the Cu2Et2dimer in addition to the known CuEt,, CuEt,, and CuEt, complexes. In Raman experiments, only complexes of the highest stoichiometries were detected since their visible absorptions led to a resonance Raman enhancement. The stoichiometry can be deduced by an original study of the totally symmetric Raman-active metal-ligand stretching mode ~(CU-C). Finally, the variation of the relative intensities of the lines assigned to different isotopic molecules of identical stoichiometry, on annealing or on laser illumination, was interpreted on the basis of the expected equilibrium constants as shown by statistical thermodynamics.
Introduction Atoms or small molecules formed by sublimation of a metal under vacuum are much more reactive than those found in their bulk form and are well-known to form many interesting complexes with a large variety of ligands even at very low temperatures. These reactions are of great interest in catalysis and organometallic synthesis.'-* Some metal atoms have been demonstrated to react with ethylene (Et) when trapped in cryogenic conditions; resulting complexes have been previously studied by UV-visible, IR, and EPR technique^."^ The use of Raman spectrometry has been demonstrated as powerful in the case of Ni(Et), c o m p l e x e ~ . ' ~ J ~ As the IB group (d'O-s') has an unpaired electron in an open shell, the IB metal-ligand complexes present visible absorption bands unlike complexes obtained from group VIII.'* In this paper, for the first time, we report the Raman spectra of the &(Et), complexes easily obtained from resonance Raman enhancement effect. We also give new information on their I R spectra. Previous studies on the Cu f Et f Ar system have been mainly reported by Kasai et al.I9 and Ozin et aLzoJ' By EPR experiments, using a very dilute matrix, Kasai et al. proposed the formation of Cu(Et), (n = 1, 2) species. Ozin et al., using IR and visible absorption techniques, demonstrated the presence of three binary complexes Cu(Et), (n = 1,2, 3), their abundance depending on the ligand dilution in argon and on the metal concentration. Moreover, quantitative Cu/Et concentration experiments and controlled annealing (30-45 K) of the matrices, containing &(Et), (n = 2, 3) species, provided evidence for a transformation to *To whom correspondence should be addressed. 'Present address: Laboratoire de SpectromCtrieI.R. (U.A. 320), FacultC de Sciences, 123 rue Albert Thomas, 87060 Limoges Cedex, France. *Present address: ENS FZs, BP A34, F b , Morocco.
dimeric Cu2(Et), (n = 4,6) complexes. In the IR study,"P2* the identification of species was mainly done on the basis of the following ligand inkrnal mxles: v ( c e ) , ~ ( C H Z )and , U(CH2).
(1) Timms, P. L.;Turney, T. W. Adv. Orgonomet. Chem. 1977, 15, 53. Timms, P. L. Angew. Chem., Int. Ed. Engl. 1975,14, 273. (2) Pimentel, G. C. Angew. Chem., Int. Ed. Engl. 1975, 14, 199. (3) Skell, P. S.; McGlinchey, M. J. Angew. Chem., Int. Ed. Engl. 1975, 14, 195. (4) Moskovits, M.; Ozin, G. A. Cryochemistry; Wiley: New York, 1976. (5) Kundig, E. P.; Moskovits, M.; Ozin, G. A. Angew. Chem., In?. Ed. Engl. 1975, 14, 292. ( 6 ) Ozin, G . A.; Andrews, M.P.;Nazar, L. F.; Huber,H.X.;Francis, C. G. Coord. Chem. Rev. 1983, 48(3), 203. (7) Davis, S. C.; Klabunde, K. J. J . Am. Chem. SOC.1978, 100, 5973. (8) Ozin, G. A.; Mitchell, S . A. Angew. Chem., Int. Ed. Engl. 1983, 22, 674. (9) Ozin, G. A.; Power, W. J.; Upton, T. H.; Goddard 111, W. A. J . Am. Chem. SOC.1978, 100,4750. (10) Ozin, G. A,; Power, W. J. Inorg. Chem. 1977, 16, 212. (11) Huber,H.; Ozin, G. A.; Power, W. J. Inorg. Chem. 1977, 16, 979. (12) Lee Hanlan, A. J.; Ozin, G. A.; Power, W. J. Inorg. Chem. 1978, 17, 3648. (13) Kasai, P. H.J. Am. Chem. SOC.1983, 105,6704. (14) Kasai, P. H. J . Am. Chem. SOC.1982, 104, 1165. (15) McIntosh, D.; Ozin, G. A. J . Orgonomet. Chem. 1976, 121, 127. (16) Cosse, C. T h b e 3O cycle Bordeaux, 1981. (17) Bouchareb, S. T h h e 3O cycle Bordeaux, 1983. (18) McIntosh, D.; Ozin, G. A,; Messmer, R. P. Inorg. Chem. 1980, 19, 3321. (19) Kasai, P. H.; M c M Jr., D.; Watanabe, T. J . Am. Chem. Soc. 1980, 102, 179. (20) Huber, H.; McIntosh, D.; Ozin, G. A. J . Orgonomet. Chem. 1976, C50, 112. (21) Ozin, G. A,; Huber, H.; McIntosh, D. Inorg. Chem. 1977,16, 3070.
0022-3654/89/2093-1197$01.50/00 1989 American Chemical Society
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The Journal of Physical Chemistry, Vol. 93, No. 4, 1989
Merle-MEjean et al.
We have thus undertaken a new vibrational study on this system in order to determine definitely the stoichiometry of the complexes by looking at the metal-ligand stretching vibrations. Mixed isotopic substitution (CzH4/CzD4),several laser irradiations, and annealing experiments were performed in order to characterize the different species by Raman spectrometry for which v(MC) was easily detected.
Experimental Section Monoatomic copper was generated by heating a niobium ribbon (0.5 mm thickness) wrapped with a copper sheet. Metals used were respectively provided by Goodfellow and Bordeaux-Chimie with at least a 99.9% purity. The ethylene gas was supplied by Air Liquide and its isotopic derivative C2D4 by C.E.A. (95% enrichment). Their purity was at least 99.99%; they were used without additional purification. The furnace used for metal evaporation has been described elsewhere.16 The metal evaporation rate was monitored with a quartz crystal microbalance. Copper or aluminum plates on which metal vapors, ligand, and argon were condensed were cooled to 12 K by means of a closed-cycle helium refrigerator (C.T.I. Cryodyne 21). Cesium iodide windows were used for IR experiments. For Raman studies, radiation shields were built so that the whole surface would receive the ligand-argon mixture; only one-half of it was covered by the metal. IR spectra were recorded on a Perkin-Elmer spectrophotometer (Model 180). Raman spectra were recorded on a Coderg T800 spectrometer; exciting lines were provided by a Spectra Physics argon ion laser or an He-Ne laser for 632.8 nm. In some experiments, the spectrometer was interfaced with a Digital MINC 11 computer in order to improve signal to noise ratio. Infrared Results and Discussion 1 . Presentation of the Infrared Spectra. When copper atoms were condensed with neat CzH4 or C2H4 in argon (1/200, 1/10) at 12 K, the spectra recorded before and after annealing were similar to those published by Ozin et al.;21 for this reason they are not presented here. Metal concentration was kept low enough to prevent aggregation ( 450 nm). 1. Main Raman Results. Raman spectra of cocondensation products of Cu atoms with a C2D4/Ar mixture (1/60) were recorded by using the 514.5- and 632.8-nm exciting lines produced respectively by argon and helium/neon continuous lasers (Figure 3). By comparison with the red excitation, the spectrum recorded by using a green laser line was characterized by the lack of bands associated with free ethylene which however was in great excess in the matrix. The new set of lines was due to the resonance effect of the absorbing complex species. These lines were detected in different spectrum regions corresponding to v(CC), 6(CD2), w(CD,), and v(CuC). The Raman shifts are reported in Table I . We easily identified the intense symmetric vibrations arising from v(CuC) in the low-frequency range; they were not observed in IR spectroscopy. In the 300-cm-' range, two emissions were detected: the highest one decreased on annealing and the lowest one increased at the same time, which indicates the presence of two resonant species. The same order of magnitude of their intensities does not mean that their concentrations were equivalent. (28) Moskovits, M.; Dilella, D. P. Chem. Phys. Lett. 1980, 73(3), 500. (29) Patterson, M. L.; Weaver, M. J. J . Phys. Chem. 1985, 89, 1331.
The Journal of Physical Chemistry, Vol. 93, No. 4, 1989 1201
Matrix-Isolated Cu(ethylene), Complexes a
d
Figure 4. (a) Resonance Raman spectra of the Cu/L/Ar system (1/16/1000) recorded after deposition; 514.5 nm, spectral slit = 4 cm-'. 2, stoichiometry 1-2; 3, stoichiometry 1-3. (b) Experimental and calculated spectra of v(CuC) (stoichiometry 1-3). (c) Experimental and calculated spectra of u(Cu-C) (stoichiometry 1-2).
TABLE 11: Comparison of the K , and K 2 Equilibrium Constants Calculated at Different Temperatures with Intensity Ratios of u(M-C) Components for Cu(ethy1ene)i K2 = I(CUL~)/ K I= I(CuLL')/ temp, K I(CuL',) I(CuL'2) conditions
10 20 30 60
0.15
0.39 0.53 0.73 1.o
25
0.96 0.54
27
1.61 1.9 0.52
Calculated 0.84 1.28 1.73
1.90 1.31 Argon Matrices 2.54 2.4 1.39 N
exp[-(0.72
300
350
crn-'
J
Figure 5. Raman spectra of the Cu-C2D4-C2H4system (1/500/500) in the metal-ligand range: (-) 15 K after deposition; after irradiation by laser beam 632.8 nm, spectral slit = 4 cm-l, P = 20 mW. a, Stoichiometry 1-2; b, stoichiometry 1-3. (..e)
Experimental Pure Ligands
" L = C,H4; L' = C2D,; K2
exp[-(0.72
I
1.so
2.0
I
a
statistical L/L' = 1 after deposition after annealing statistical L/L' = 1.27 after deposition after annealing + laser power 500 mW X
26/T)]; K ,
N
2
X
X 12/01,
Similar studies with C2H4 in argon (1/60) and an isotopic mixture C2H4/CZD4/Ar(1/ 1/60) were performed (Figure 4 and Table 11). In the mixed ligand spectra, a new set of lines appeared for each of the two species assigned to mixed species Cu(C2H4)n(C2D4)m. Annealing gave evidence of the presence of two different species. As no line was detected below 260 cm-I, the frequency of the Cuz, we conclude that only mononuclear complexes were detected in these resonance Raman experiments. Several studies using only pure ethylene matrices were performed and they gave similar results; no other species were detected in these conditions. An increase of metal concentration enhanced the lowest line (b) with respect to the highest component (a) (Figure 5). Such an effect is similar to that obtained on annealing the matrix. We think it would be preferably interpreted as a rearrangement effect on the deposition rather than as a new species with metallic enrichment since bimetallic forms were demonstrated as unable to give Raman enhancement in these conditions. This rearrangement is similar to that obtained in IR experiments; for low deposition rates, we were only able to synthesize the 1-2 complex in pure ethylene. The presence of other species was due to uncontrolled annealing during the deposition. 2. Stoichiometries Deduced from v(CuC) Band Analysis. The metal-ligand modes observed at 350 and 285 cm-' appeared as intense lines (Figure 4), which is not surprising since the corre-
sponding electronic transition is a charge transfer due to the excitation of the copper unpaired electron;6-8 consequently, the v(CuC) vibrational modes are expected to be enhanced by resonance Raman effect. The stoichiometries can be unambiguously determined by CZH4/C2D4mixed isotopic experiments from the relative proportions of C2H4 and C2D4in the mixtures and from the relative intensities of the patterns measured just after deposition (vide infra). The patterns can be easily identified since the frequency shifts are large enough and arise from totally symmetric vibrations. In IR spectrometry, the resulting isotopic pattern is much more difficult to interpret since many modes are degenerate for DZdand D3,, (or D3d)species. In the 380-320-cm-' range, the triplet (369,355, and 343 cm-I) expected for a 1-2 complex was observed: the outer frequencies were those observed in C2H4 and C2D4 matrices; the additional central band arose from the Cu(C2H4)(CZD4)molecule. This triplet has been analyzed using a Lorentzian shape for each band considering the resolution and composition of the C2H4/C2D4 mixture. The comparison between calculated and experimental results is in quite good agreement with the 1-2 assumptions (Figure 4). In the 320-270-cm-' range, the four lines observed are assigned to the 1-3 complex: Cu(C2H4),(C2D4), with m n = 3. The agreement between experimental and computed patterns provides a good support of the assignment (Figure 4b). 3. Dependence of v(CuC) Lines on Annealing and Laser Irradiation. 3.1. Experimental Evidence. Depending on the experimental conditions, we have carefully analyzed the different parameters which influence the equilibrium between on the one hand 1-2 and 1-3 complexes and on the other hand hydrogenated and deuteriated forms. Laser Irradiation Time and Laser Power. A matrix containing 1-3 and 1-2 species irradiated at low laser power and for a long time showed a small decrease of all the signals. Over the same
+
Merle-Mgjean et al.
1202 The Journal of Physical Chemistry, Vol. 93, No. 4, 1989
cLm-l 350
300
Figure 6. Resonance Raman (514.5 nm) and Raman (632.8 nm) spectra of the (a) stoichiometry 1-2 and (b) stoichiometry 1-3 species. Cu/ C2H4/C2D4/Ar = 1/10/8/120; C2H4/C2D4= 1.27. (1) 15 K after deposition; (2) after annealing to 30 K.
time, for each pattern, the ratio of the isotopic components changed in favor of the deuteriated species. Figure 6 presents the effect of laser power leading to a similar intensity change. High laser power (A = 514.5 nm) increased drastically the percentage of 1-3 species. All these effects were irreversible. Thermal Effect. Under annealing, we had to discriminate between changes in argon-diluted matrices (irreversible effect) or in pure matrices (reversible effect). In argon-diluted systems, warm-up increased the 1-3 species with respect to the 1-2 species and enhanced the percentage of deuteriated compounds (Figure 6). In pure matrices, Raman spectra were recorded at different temperatures between 15 and 5 5 K (Figure 7). Up to 46 K, the intensities of the lines assigned to 1-3 species increased and the isotopic ratio in the triplet of the 1-2 complex tended to be 1-2-1. Cooling down the matrix to 15 K, the 1-2 complex became again the predominant species; the isotopic ratio was the same as before the thermal process. 3.2. Interpretation. Results of Laser Power on 1-2 Complexes. After deposition, the intensities associated with the isotopic forms of 1-2 complexes belong to a statistical distribution unstable from a thermodynamical point of view, due to the system constraints during the freezing process. At chemical equilibrium, the most deuteriated species are expected to be the most abundant in the mixture because of their different zero-point energies. In these experiments, an equilibrium shift is observed for all parameters (irradiation time, laser power, or annealing). Statistical thermodynamics gives the relationship between the equilibrium constant K associated with the reaction and the partition functions Z of the molecules, where Z,, Z,, and Z, are respectively the translational, vibrational, and rotational parts. Considering an equimolecular mixture of CzH4 and C2D4, the expression of the equilibrium constant is
KI = [CU(CZH~)(CZD~)] - ztzvzrot exP([cU(czD4)z] z :z :z 'TO,
E)
cm;'
300
Finally, the rotational partition function Zrotdepends on the inverse of the number of symmetry; this number is function of the symmetry of the whole molecule. The mixed isotopic molecule Cu(CzH4)(CzD4)has a lower symmetry than the C U ( C ~ Hor~ ) ~ C U ( C , D ~ species, )~ so we can write ~[CU(CZH~= ) Z'J[Cu(CzD4)z] ] =4 dCu(CzH4)(CzDd] = 2 For the reaction 1, it turns out that K1 =
[Cu(CzH4)(CzD4)1 dCu(CzD4)zI N [cU(czD4)z] ~C~(C~H~)(CZD~)I = 2 exp( -
g)
where AE is only a function of the zero-point energies assuming the potential energy for all the molecules to be the same. Therefore AE = 1/Zh(v(cu(cZH4)(cZD4)) - v(cU(cZp4!2)) = ' / Z h A v . In the same way, for the following equilibrium Cu(CZD4)Z + 2CzH4 * Cu(CZH4)z + 2CZD4 (2) one defines K2 =
The translational partition function Z , depends on the molecular weight square root, e.g.
i3
[Cu(CzH4)zI 0[CU(CzD4)21 2:exp [ C U ( C ~ D ~ )Z ] b[CU(Cz&)z]
--
=
eXP(-
Zt/Zft = [M(CU(C~H~)(C,D~))/M(CU(C~D~)~)]'/~ = 0.974
The vibrational partition function Z, depends on the vibrational frequencies. Since the highest modes are isotopic dependent, we can assume Z , II Zfv.
400
Figure 7. Raman spectra of the (a) stoichiometry 1-2 and (b) stoichiometry 1-3 species, recorded at different temperatures; 632.8 nm, spectral slit = 4 cm-I, P = 20 mW; Cu/C2H4/C2D4;C2H4/C2D4= I .
E)
Table I1 summarizes the calculated values K , and Kz for several experimental conditions. According to the table, it is evident that either irradiation time or laser power effect generates an increase of the matrix temperature and that the change in Raman inten-
Matrix-Isolated Cu(ethylene), Complexes sities has a thermodynamical rather than a photochemical origin. Such temperature differences observed when the sample is maintained onto the laser beam can be due to an absorption effect. These complexes exhibit some electronic absorptions coincident with laser line frequencies permitting resonance spectral enhancement. On annealing, spectra were recorded at different matrix temperatures: the effect described above was also observed even at low laser power. The most puzzling feature is the variation of intensity of all scattered lines when changing the temperature. It appears again that the 1-2 complex seems to be the most stable in pure ethylene matrix; this result is in agreement with those obtained by IR. In fact, the intensities of the Raman emissions depend not only on the complex concentrations but also on the absorption of the incident and scattered beams. These two terms are known to have an opposite effect. If the amount of complexes decreases, laser line absorption decreases too and the term that governs the intensity varying in an exponential way can be the major one. Relative Stabilities of 1-2 and 1-3 Complexes. In dilute matrices, an increasing proportion of the 1-3 species with respect to the 1-2 species was observed on annealing effect or laser power effect; such a behavior is coincident with those observed from IR and UV-visible experiments."-'2 In pure ethylene matrices the 1-3 complex disappeared compared with the 1-2 species; this unexpected result was not metal concentration dependent. Such a behavior can be partially explained by absorption effects on incident and scattered beams. Assuming only two absorbing species, the scattered intensities, I 2 and I,, may be expressed in the following way: I 2 0: c21'(v) exp(-k2c21) I,
a:
c31'(u) exp(-k,c,l)
where I' is the incident beam intensity and ki the absorption coefficient of i species with concentration ciat Y frequency. Even though values of absorption coefficients are unknown, the above experimental results seem to be qualitatively explained by the exponential terms. In fact, from IR studies, the 1-2 species decreases, so c2 decreases and the term (exp[-k2c21]) increases; these two terms compete, and the second becomes preponderant when the absorption coefficient is large. Similarly, according to IR results, the 1-3 species increases on warm-up experiments: this means c3 increases and (exp[-k3c31]) decreases. Therefore, the Raman results indicate that, in both cases, the absorption coefficients k2 and k, are large enough.
Conclusions This new study of the copper-ethylene binary complex confirms the presence of three different species in low metal concentration conditions. Two of them are observed by both IR and Raman spectroscopies, the third being only detected by IR spectroscopy. In pure ethylene matrices, the lowest deposition temperature (12 K) favors the 1-2 complex. On annealing or laser irradiation, this species is transformed in a small amount of 1-3 molecule and particularly a complex in which ethylene is strongly perturbed; we think the complex is a dimeric form of the 1-1 molecule. This
The Journal of Physical Chemistry, Vol. 93, No. 4, 1989 1203 dimeric form is proposed when considering the stability of this compound upon irradiation and annealing and when considering the analysis of the IR spectrum recorded with a C2H4/C2D4 mixture which is completely different from the result obtained with nickel atoms. In concentrated argon containing matrices (IO%), the coexistence of the three species is confirmed but the 1-3 complex is always a minor product. The low-concentration IR studies show the same frequency as reported here for C U ~ ( C ~but H ~we) cannot ~ exclude in this case that this frequency could be due to monomeric Cu(C2H4)complex. The 1-2 and 1-3 structures have been proved unambiguously by studying the resonance Raman spectra in the metal-ligand symmetric stretch region. The patterns obtained with mixed C2H4/C2D4ligand are easily interpreted in terms of stoichiometry. No emission line coming from metal-metal interaction has been observed. The lowest stoichiometry cannot be identified by Raman spectroscopy because this species is highly diluted and does not absorb in the visible range accessible to our lasers. Compared with similar nickel complexes, the 1-2 and 1-3 species have smaller metal-ligand bond frequencies (about 25% less), the corresponding symmetric stretching frequencies lying at 320 and 280 cm-' (vs 420 and 380 cm-l in the nickel). Considering the 2-2 complex, we have observed a similar behavior in the IR spectrum of silver-ethylene. Unfortunately resonance Raman spectra have not yet been obtained. Our IR results from concentrated matrices well agree with similar EPR experiment^'^ assuming Cu2Et2is diamagnetic; consequently, only the 1-2 species can be observed in EPR experiments, the low concentrations of 1-3 complexes making them unobserved. For the copper system, our results are in good agreement with theoretical calculations and EPR experiments which predict a van der Waals complex for Cu(C2H4). This weak complex would be difficult to observe by vibrational spectroscopy because a small frequency shift from ethylene is expected in this case as for surface studies (SERS). In an opposite way, the strong perturbation observed for ethylene in the 2-2 complex demonstrates the extreme ability of unpaired electrons of copper atoms to interact between themselves to give a strongly bonded dimeric form of the weak 1-1 complex. Matrices are known to freeze chemical mixtures out of chemical equilibrium conditions. A careful analysis of the metal stretch vibrations under thermal or irradiation control of an isotopic mixture allows us to observe the system from a statistical to a thermodynamical repartition. Equilibrium constants at the lowest temperatures 'favor the most deuteriated species compared with hydrogenated ones as their zero-point energy is smaller. Acknowledgment. We thank Prof. Martin Moskovits for giving us, through useful discussions, the benefit of his large experience in spectroscopy. This work was partly supported by a grant from NATO (RG 109.82). Registry No. C U ( C ~ H ~60203-83-0; )~, Cu(C2D4)), 117872-79-4; Cu(C2H4)2, 60241-41-0; C U ( C ~ D ~72316-88-2; )~, C U ~ ( C Z H ~117872-80-7; )~, Cu,(C,H,)(C,D,), 117872-81-8; C U Z ( C ~ D ~117872-82-9; )~, CU, 744050-8; C2H4, 74-85-1; C U ( C ~ H ~ ) ~ ( C117872-83-0 ~D~), CU(C~H~)(C~D~)~, 117872-84-1; Cu(C,H,)(C,D,), 117872-85-2; CZD4, 683-73-8.
