摘要:

J. CHEM. SOC. DALTON TRANS. 1984 307 Thermodynamic Studies on the Addition of Molecular Oxygen to Cobalt(ii) Complexes. Part 3.1 The Cobalt(ii)-Tetraethylenepenta- amine-O2 System in Aqueous Solution at 25 "C t Sergio Cabani." Norbert0 Ceccanti, and Paolo Gianni lstituto di Chimica Fisica, Universitd di Pisa, Pisa, Italy Calorimetric measurements have been carried out on the heat evolved when O2 is bubbled into KN03 (0.1 rnol dmP3) aqueous solutions of CO(NO~)~, tetraethylenepenta-amine (tetren) and HCI, or when a C O ( N O ~ ) ~ stock solution is added to a KN03 (0.1 rnol dm-3) aqueous solution of tetren and HCI under both anaerobic (pN2 = 1 atm) or aerobic (po, = 1 atm) conditions. An acceptable agreement is found between the value for the enthalpy change of formation of [Co2L2O2I4+ (L = tetren) when it is obtained through direct measurements of oxygen addition to [CoLI2+ or by using the enthalpy changes relative to the formation of [CoLI2+ and [Co2L2O2I4+ starting from Co2+.The thermodynamic data for the binding of oxygen to complexes of CoI1 with tetren and other linear polyamines are compared and discussed. As a part of a systematic study 'J on oxygen-carrier complexes the thermodynamic aspects of oxygen addition to Co" complexes with tetraethylenepenta-amine (tetren) are con- sidered herein. Tetraethylenepenta-amine is a quinquedentate ligand which with CO" forms complexes capable of adding reversibly molecular oxygen in order to give a singly bridged p-peroxo-compound, [C~,(tetren)~O~]~ + .3-9 For this peroxo- compound spectral studies 4 9 8 have been carried out and the kinetic and equilibrium 5-7*9 data for its formation from [Co- (tetren)12 + and 0, have been reported.But, as far as we know, enthalpy values for the oxygenation reaction are lacking. This paper reports the results of calorimetric measurements on the formation of [C~,(tetren)~O~]~+ from [Co(tetren)12+. Some calorimetric measurements have also been performed on the formation of [Co(tetren)I2+ and [ C ~ ~ ( t e t r e n ) ~ O ~ ] ~ + starting from Co2+, and also on the tetren-H+ system, in order to verify the internal consistency of the results. Experimental Commercial tetren (Strem) was distilled under reduced pressure and precipitated as a hydrochloride by addition of concentrated HCl solution. The pentahydrochloride was recrystallized from aqueous ethanol and its purity checked by elemental analysis. The stock solution of CO(NO~)~ was standardized as p revi o us1 y described. ' A 11 solutions were prepared with deionized water and contained KNOJ (0.1 mol dm-3).The calorimetric measurements were carried out using several methods: (i) by bubbling O2 gas into N2-saturated aqueous solutions containing known amounts of tetren, Co(NO,),, and HCl; (ii) by adding known amounts of cobalt stock solution to aqueous solutions of tetren under both anaerobic (N2 at 1 atm) and aerobic (0, at 1 atm) conditions. Experiments have also been carried out where (iii) known amounts of HCl stock solution were added to aqueous solutions containing tetren and HCI. We determined the heat of dilution of the Co(NOJ2 stock solution in aqueous KNO, (0.I rnol dm ,). The heat of dilution of the HCl stock solution in KNO, (0.1 rnol dm-') was calculated using the data of ref. 10 and by assuming Young's rule to be valid." The heat of solution of O2 gas in aqueous KN03 (0.1 mol dm-3) was assumed to be equal to - 12.06 kJ mol-' (see refs. 1 and 2). The enthalpy of formation of water in the same solvent t Noti-S.1. rrriits eniplojred: atm = 101 325 N m-2, cal = 4.184 J. Table 1. Calorimetric data for the addition of oxygen to [Co- (tetren)]'+ at 25 "C in KN03 (0.1 rnol dm-3) aqueous solution 1 04rnc00/ rnol 4.48 I 4.48 I 4.978 4.978 5.476 5.178 I 04mLo/ rnol 15.66 14.36 14.65 14.05 12.31 8.40 - AHcolL20pL dl PH q r '/J kJ mol-' 7.96 40.75 181.9 8.18 39.96 178.3 8.14 43.18 173.5 8.40 44.06 177.0 7.94 49.00 178.9 8.80 47.53 183.6 -178.9 & 1.5 The experiments were conducted by bubbling 0, into solutions containing mcoo moles of Co", mLo moles of tetren, and whose pH was adjusted to the value given in the third column. pH Refers to the molar concentration of H+ ions.' q r = qobs. - qsoz; qobs. = the heat measured, qso2 = (mco0/2) x 12016 J = the heat of -(2ql/mcoo) = the enthalpy solution of oxygen. * A H c ~ ~ L ~ o ~ ~ ~ ~ = change relative to the reaction 2[CoL]'+ + 02(aq) -+ [Co,- L,O,]*+. Average value of AHcozLzo2c0L; standard deviation Q = [Z (AH, - AR)2/n(rr - I)]*, where n = number of measure- ments. n J = I medium was taken to be equal to -56.57 kJ mol-', as previ- ously reported (in ref. 1 the quoted value of 13 250 cal mo1-l is a misprint for 13 520 cal mol-').The heats measured in experiments (i), (ii), and (iii), corrected for the appropriate dilution or solution heats, are reported in Tables 1, 2, and 3 respectively. The calorimetric apparatus and the procedure followed have been described elsewhere.'J The calorimeter vessel contained ca. 360g of solution ( V = solution volume). The concentration of CO(NO,)~ ranged from 5 x to 1.5 x mol dm-3, and the ratios of tetren : cobalt from 1.5 : 1 to 12 : 1. The pH of the solutions was measured before and after each experiment by means of a Radiometer PHM 84 pH- meter, equipped with a GK 2351 B combined glass electrode, and standardized against known hydrogen-ion concentrations. (Throughout this paper pH refers to the molar concentration of H+ ions.) The formation and stability with time of the oxygenated complex was monitored through spectrophotometric measure- ments (E = 13 980 dm3 mol-' cm-' at h = 308 nm) performed on a Pye-Unicam SP8-150 UV/VIS spectrophotometer.308 J.CHEM. SOC. DALTON TRANS. 1984 Table 2. Calorimetric data for the reaction of Co" with tetren under anaerobic (pNl = 1 atm) and aerobic (pol = 1 atm) conditions [T = 25 "C; aqueous KN03 (0.1 rnol dm-3)] a 1 O'mLo/ rnol 15.66 12.31 15.20 14.65 14.36 14.05 8.40 1 vmHo/ rnol 28.30 16.55 31.00 23.25 23.80 20.25 5.01 Vr/cm3 360.3 369.6 359.9 373.2 355.7 368.6 365.4 PHl 9.05 9.52 8.82 9.28 9.21 9.40 9.97 AH.1 1.81 1 1.360 2.042 1.595 1.664 1.452 0.660 I@mc,ol rnol 4.48 1 5.478 2.987 4.979 4.48 1 4.979 5.178 PHI 7.96 7.96 8.10 8.15 8.18 8.41 8.80 iiH.f 2.532 2.422 2.539 2.405 2.410 2.234 1.565 q '/J 26.99 32.80 18.12 30.25 25.86 30.17 3 1.09 q w dIJ 0.33 1.05 0.17 0.59 0.46 0.75 2.85 qprot 'IJ - 0.27 - 0.86 -0.14 - 0.47 - 0.38 - 0.60 - 2.28 - A H f i kJ mol-' 60.10 59.53 60.56 60.51 57.53 60.29 58.94 AHcoL = -59.64 f 0.41 kJ mol-I 10.05 20.26 360.1 8.83 2.019 2.751 7.15 2.774 39.66 0.21 -0.17 288.0 8.18 10.92 361.8 9.48 1.355 3.658 7.94 2.414 51.67 0.96 -0.76 281.4 16.00 35.03 351.2 8.60 2.190 1.470 8.25 2.410 21.88 0.08 -0.06 297.4 9.57 7.85 365.1 9.88 0.866 5.175 8.65 1.792 75.27 2.30 - 1.87 289.2 8.84 9.22 367.1 9.68 1.074 1.809 9.35 1.329 26.36 0.84 -0.67 289.6 21.92 49.60 343.8 8.49 2.264 1.990 8.09 2.489 29.92 0.04 - 0.05 300.8 11.48 12.38 367.9 9.68 1.103 1.441 9.50 1.252 20.67 0.54 - 0.43 285.4 A H c ~ ~ L , ~ ~ ~ ~ = -290.3 f 2.6 kJ mol-' 0 The experiments were conducted by adding a stock CO(NO~)~ solution (0.4979 rnol dm-3) to a solution containing known amounts of tetren5HC1 and NaOH under Nz or under 02.Initial and final states of the reaction are indicated by subscripts i and f respectively. iiH = (cHO - [H+] f Pw/[H+])/cL*, where P, is the ionic product of water in 0.1 rnol dm-3 aqueous KN03 (1.56 x lo-" molZ dm-6), cH0 the concentration of HCI, [H+] the concentration of hydrogen ion, and cL* the concentration of tetren not involved in complexes with cobalt ion. ' q = qobs. - qdilCo - qsol. The heat of dilution of the CO(NO~)~ solution, qdilco, was determined in separate experiments, qsoa as in Table 1. Heat of formation of water.' Heat effect associated with the redistribution of protons on the ligand molecules, calculated as qprol = -ARHL(riH,( mL,f - i j H , , mL,l); the moles of ligand at the end of each run were taken as those remaining available for protonation equilibria, i.e. mL = mLo - mcoo. ARHL = -45.5 kJ mo1-l (see Table 3). ' AH = -qq,/moles of complex formed, where qr = q - qw - qprot- Standard deviation Q = [C (AH, - AR)'/n(n - I)]*. n j = t 1 Results In the experiments (i) where O2 gas was bubbled into solutions containing [Co(tetren)]'+ no change of pH was observed and therefore no correction for proton redistribution was neces- sary. The heat evolved was therefore corrected only for the heat of solution of 02, 9s0*, calculated by assuming that the number of moles of oxygen dissolved was equal t o the number of moles of oxygenated complex.No correction was intro- duced for the substitution of N2 by 02. The enthalpy change corresponding t o the reaction, i.e. equation ( 1 ) (L = tetren) gave AHcolLlolcoL = - 178.9 f 1.5 kJ mol-' (see Table 1). 2[CoLlZ+ + 02(aq) -+ [ C O ~ L , O ~ ] ~ + In the experiments (ii) carried out in order t o obtain the enthalpy changes corresponding t o reactions (2) or (3) c o 2 + + L - [COL]'+ ( 2 ) 2CO2+ + 2L + 0 2 - [cozL20214+ (3) according t o anaerobic or aerobic experimental conditions respectively, noticeable changes of pH were observed (see Table 2) and corrections for the proton redistribution were necessary.* This was effected by calculating the proton distribution before and after the formation of the complex by using the average number of hydrogens bonded t o tetren, iH (see footnote of Table 2), obtained by direct calculation from experimental data alone, and by using for the enthalpy change in the proton addition to tetren a mean value of ARH, = -45.5 kJ per mole of proton added.This was possible since in the pH range we explored the heat evolved per mole of proton added was almost independent of the number of hydrogens bonded t o tetren (see data of Table 3), also in agreement with the values of AHHlL (i = 1-3) obtained by Paoletti and Vacca.'' For reaction ( 2 ) the value, AHcoL = -59.6 rt 0.4 kJ mol-' was obtained which agrees satisfactorily with the correspond- ing value of - 57.9 kJ mol-' obtained by Paoletti and Vacca,lZ who employed experimental conditions such that the cor- rection for the proton redistribution was reduced t o practic- ally zero.2.6 kJ mol-I was obtained which when combined with the value for AHcoL from ref. 12 (AHcolL2~lcoL = A H ~ o , ~ , ~ l c o - 2AHcoL) produced for reaction (1) a value of AHCO,LpOICoL = - 174.5 & 2.7 kJ mol-'. This value agrees with that obtained in experi- ments (i) by the direct addition of oxygen t o [CoLI2+. A satisfactory internal consistency is therefore attained despite the uncertainty in the equilibrium constants of proton addition to tetren. Table 4 summarizes the more reliable thermodynamic data *The values of the equilibrium constants and heats of reaction reported in the literature for the system tetren-H+ did not yield reliable corrections for the formation of the protonated species of tetren.In effect, the calorimetric data of experiments (ii) (see Table 2) yielded highly variable values of AH,,, or AHCo2L10tCo when the protonation corrections were made using a given set of PHIL ( i = number of protons bonded to L = l-5), and quite different mean values of these enthalpy changes when different sources of @HiL (indicated in parentheses) were utilized: AHcoL (kJ mol-') = - 15.6 f 5.3 (ref. 121, -22.2 t 4.0 (ref. 5 ) , -30.0 & 2.9 (ref. 7), and -65.2 0.9 (ref. 13); (kJ rno1-l) = -206.7 $7 8.9 (ref. 7), - 180.6 h 9.3 (ref. 12), - 192.6 i 7.8 (ref. 5 ) , and -298.4 h 6.6 (ref. 13). Only the data derived from ref. 13 approach the results obtained as described in the text and present an acceptable standard deviation.In all the above calculations we used the values for the enthalpy changes, A H H i L , for proton addition to tetren as reported in ref. 12. These are the only available data. For reaction (3) the value, A H ~ o l ~ 2 ~ l c o = -290.3J. CHEM. SOC. DALTON TRANS. 1984 309 Table 3. Calorimetric data for addition of H+ to tetren at 25 "C in KN03 (0.1 mol dmb3) aqueous solution ' 1 CPmLo/ l @ m H o '1 - A B H L ' 1 mol mol V/cm3 PH AH qobs.d/J qprot 'IJ kJ mol-' 9.86 8.30 368.0 9.89 0.888 - - - 14.30 368.3 9.39 1.465 29.12 26.1 1 45.89 - - - 7.82 8.10 358.5 9.74 1.075 12.10 358.7 9.32 1.562 18.95 17.03 44.72 16.10 358.9 8.81 2.064 19.33 17.99 45.83 20.10 359.1 8.15 2.572 19.33 18.33 46.14 12.66 - - I 13.29 368.5 9.75 1.075 18.29 368.7 9.42 1.457 24.81 22.76 47.06 22.29 368.9 9.14 1.767 19.92 18.66 47.55 28.29 369.2 8.63 2.236 30.08 28.49 47.98 33.29 369.5 8.09 2.630 22.64 21.46 43.02 38.29 369.7 6.32 3.023 22.64 21.51 43.23 - - - 30.7 1 15.54 360.8 10.12 0.530 26.22 361.3 9.78 0.865 49.41 44.85 43.60 -45.5 f 0.6' The experiments were conducted by adding successive amounts of a stock solution of HCI to solutions containing mLo moles of tetren- 5HC1 and mNaOH0 moles of NaOH.' Moles of HCl present in solution mHo = 5mL0 - mNaoH0 + mHCI, where mHC1 is the total moles of HCI added as a titrant. The actual moles of HCI added per single step may be obtained as the difference between two consecutive steps of the titration. Heat effect observed in each step. qprot = qobs. - qdilHC' - qw, where qdllHC' is the heat of dilution of the stock solution of HCl and qw the heat of formation of water from its ions (see Experimental section).' Mean enthalpy of formation of ligand-hydrogen bond calculated as: ARHL = -qpro,/(AfiHmLo) where AtiH is the change of AH in each step. g Average value of AGHL; standard deviation CT = [5 (AH, - Ag)'/n(n - I)]*. See footnote h of Table 2. j = 1 for the reactions occurring in aqueous solutions of Co" and tetren in both anaerobic and aerobic conditions. The mean values of the standard free energy of reaction have been calculated by using all the available equilibrium constant values, with no previous critical evaluation. Discussion The thermodynamic characteristics of the reaction of binding oxygen t o Co"-tetren, in particular the enthalpic effects, are very different from those presented by other oxygen binding reactions.As usual the entropy change is negative and similar in value to that obtained for the binding of O2 t o [Co(en),]'+ (en -= ethylenediamine) (AS = -297 J K-I mol-') or t o [Co(trien)l2+ (trien == triethylenetetra-amine) (AS = - 259 J K-' mol-').I In these latter cases, however, the formation of the double bridge requires thedissociation of one mole of water and consequently a loss of entropy of about 81 J K-' mol-' perhaps only partly balanced by the entrance of the hydroxide ion in the olate complex, [CO~L~O~(OH)]~+. On the basis of these con- siderations, the loss of entropy in the formation of the mono- bridged p-peroxo-Co"-tetren complex, although similar in value, is in effect much larger than that associated with the formation of p-peroxo-p-hydroxo-complexes.This large entropy loss may be only in part attributed to the loss of entropy of the oxygen dissolved in water (ASIOz(aq), 1 mol dm '1 := - 109.2 J K-' mol-I) and in part to the formation of a dimeric compound.* I t seems therefore that some specific effects should also be taken into consideration in order to justify the A S values found for the 0, binding to Co" complexes in aqueous solution. However, only a significant improvement in the determination of equilibrium constants and enthalpy changes would justify a deeper investigation of the causes of the observed entropy loss. More than the entropy, the most peculiar feature of the [ C ~ ~ ( t e t r e n ) ~ O ~ ] ~ + species is the extremely large decrease in enthalpy associated with its formation from [Co(tetren)]'+ and molecular oxygen. This change is much larger than twice the enthalpy change found in the formation of the 1 : 1 mononuclear oxygenated complexes which usually range from -40 to -65 kJ mol-' and are independent of tem- perature and But it is also very large with respect t o the enthalpy changes in the addition of oxygen to [Co(en)J2+ [A~Cu,(en~,Ol(OH~Co(en)r = - 1 16 kJ mol-'1 and [Co(trien)12+ [AHCc,~trien~lO,~OH)Co~trien~ = - 11 1 kJ mol-'1 in order t o form binuclear dibridged p-peroxo-p-hydroxo-complexes.Since the energy spent for the dissociation of one mole of water is reasonably recovered in part in the formation of the hydroxo-bridge, it seems logical to assume a larger stabil- izing enthalpic effect in the addition of O2 to [Co(tetren)l2+ with respect to the formation of the single oxygen bridge in the O2 addition to the en or trien cobalt complex. Such a behaviour is in contrast with the behaviour shown by * The entropy changes for reactions of dimerization of large non- charged molecules in aqueous solution are usually less negative than - 100 J K-' mol-'.For instance, for the dimerization of some dyes A S values from 0 to -34 J K-' mol..' have been rep~rted.'~ For the self-association of some pyrimidine derivatives AS ranges from -30 to -42 J K-' mol-' and the heteroassociation between 2- aminopurine and thymidine produces an entropy decrease, A S = -25 J K-' mo1-1.'6 Only for the base stacking self-association of some purine nucleoside-5'-monophosphates '' and various purine bases are more negative A S values, ranging from -40 to - 100 J K-' mol-', found.The likeness between the dimerization of large non-charged molecules and the association of the charged [Co- (tetren)l2 + species into the binuclear p-peroxo-complex seems to be justified by the fact that the thermodynamic behaviour of large cations, such as tetra-alkylammonium ions, is closer to that of non- ionic than of ionic species.I9 In any case, the interaction between two [Co(tetren)]' + cations and water should not substantially change when the two cations are held together through the oxygen bridge. The main factor responsible for the entropy change in the associ- ation process should be generally related with the decrease of the number of free species with loss of translational and rotational degrees of freedom.3 10 J.CHEM. SOC. DALTON TRANS. 1984 Table 4. Thermodynamic data for the formation of [ C O ~ L ~ O ~ ] ~ + (L = tetren) in KN03 (0.1 mol dm-3) aqueous solution at 25 "C React ion - - Ace/ - AHe/ ASe/ P a kJ mol-' kJ mol-' J K-' mol-I Cot+ + L --+ [COL]2+ (2.7 & 1.3) x lot3 dm3 mol-I 76.6 & 0.8 59.6 f 0.4 57 * 3 57.9 63 2CoZ+ + 2L + 02(aq) --+ [Co2LZO2l4+ (7.2 7) x lo4' dm12 moI4 244.3 f 1.7 290.3 I 2.6 -154 f 1 1 -279 12 -294 f 8 2[CoLl2 + + O,(aq) --t [ C O ~ L ~ O ~ ] ~ + (9.9 f 8) x dm6 mol-21 91.2 .& 1.7 174.5 f 2.7 (9.9 & 8) x 1015 dm6 mol-2J 91.2 & 1.7 178.9 I 1.5 Average values of equilibrium constants. Calculated using refs.5, 7, and 12. This work. From ref. 12. Calculated using refs. 5 and 7. From AHe values of the two preceding reactions. For AH,,, the value -57.9 kJ mol-' was chosen since it was obtained in such conditions that the corrections for proton addition to tetren were not significant. From direct calorimetric measurements of oxygen addition to [CoLl2+ complex. Calculated from values of the two preceding reactions. the parent non-oxygenated complexes of Co". As a matter of fact, the mean values of the enthalpy change per mole of single cobalt-nitrogen bonds in the cobalt complexes able to add molecular oxygen exhibit a trend which is opposite to the trend observed for the peroxo-complexes. Namely, the mean enthalpy changes for the formation of one mole of cobalt-nitrogen bond are: -14.6 kJ mol-I for the Co"-en complex [AHcocen,2 = -58.3 kJ m01-'],~' -11.1 kJ mol-' for the Co"-trien complex [AHcoctrien, = -44.6 k.1 m~l-'],~' and - 1 1.6 kJ mol-' for the Co"-tetren complex [AHcoctctrcn) = -57.9 kJ m01-~].'~ Obviously, many other calorimetric values of enthalpy changes need to be reported, besides those now at our in order to gain a significant picture of the thermodynamic behaviour of oxygen carrier complexes in aqueous solution.Nevertheless, the results obtained so far allow the correction of some points of view, for example that which identifies a particular stabilizing effect in the formation of the olate c ~ m p l e x . ~ ~ * ~ ~ Actually, it is the bonding of O2 in the monobridged complex which is associated with large negative enthalpic effects not observed in the formation of olate p-peroxo-complexes. Curious, but significant, is the finding that the smaller the strength of the cobalt-nitrogen bond in the non-oxygenated complexes, the stronger is the reinforcement of this bond in the oxygenated complexes.It is in fact reasonable to associate the enthalpy change observed in the formation of [ C ~ ~ ( t e t r e n ) ~ O ~ ] ~ + mainly to a reinforce- ment of the cobalt-nitrogen bonding rather than t o a very unusual strength of the cobalt-oxygen bond. In other words, it is reasonable to assume that there is a co-operative effect, increasing the strength of the cobalt-oxygen bond due to a charge transfer from cobalt to oxygen and increasing the strength of the cobalt-nitrogen bond due to a more pro- nounced character of CO"~.It is really a very acceptable hypothesis, even in the absence of relevant experimental data, to attribute an enthalpic nature to the huge increase in stability which the Co"' complexes show compared with the corresponding complexes of Co". Acknowledgements This work was supported by the Minister0 della Pubblica Istruzione (Rome). References 1 Part 2, S. Cabani, N. Ceccanti, G. Conti, and P. Gianni, Gun. Chim. Ital., 1982, 112, 159. 2 S. Cabani, N. Ceccanti, and G. Conti, J. Chem. SOC., Dalton 3 F. Miller, J. Simplicio, and R. G. Wilkins, J. Am. Chem. Soc., 4 Y. Sasaki, J. Fujita, and K. Saito, Bull. Chem. SOC. Jpn., 1971, 5 R. Nakon and A. E. Martell, 1. Inorg. Nucl. Chem., 1972, 14, 6 A. Kufelnicki, S.Petri, and H. Zwirello, Pol. J. Chem., 1978, 7 W. R. Harris, 1. Murase, J. H. Timmons, and A. E. Martell, 8 S. R. Pickens and A, E. Martell, Inorg. Chem., 1980, 19, 15. 9 M. Kodama and E. Kimura, Inorg. Chem., 1980, 19, 1871. Trans., 1983, 1247. 1969, 91, 1962. 44, 3373. 1365. 52, 1337. Inorg. Chem., 1978, 17, 889. 10 V. B. Parker ' Thermal Properties of Aqueous Uni-univalent Electrolytes,' Nut. Bur. Stand. (U.S.) Ref. Data Ser., 2, 1965. 1 I T. F. Young and M. B. Smith, J . Phys. Chem., 1954,58, 716. 12 P. 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Hayes, and K. S. Suslick, J. Am. Chem. SOC., 1978, 100, 2761 ; M. J. Carter, D. P. Rillema, and F. Basolo, ibid., 1974, 96, 392; E. Cesarotti, M. Gullotti, A. Pasini, and R. Ugo, J . Chem. SOC., Dalton Trans., 1977, 757. 21 L. Sacconi, P. Paoletti, and M. Ciampolini, J . Chem. Soc., 1961, 5115. 22 J. H. Timmons, A. E. Martell, W. R. Harris, and I. Murase, Inorg. Chem., 1982, 21, 1525. 23 G. McLendon and A. E. Martell, Coord. Chem. Rev., 1976, 19, 1 . 24 R. D. Jones, D. A. Summerville, and F. Basolo, Chem. Rev., 1979, 79, 139. Received 2nd February 1983 ; Paper 311 52

ISSN:1477-9226    

DOI:10.1039/DT9840000307

出版商:RSC    

年代:1984

数据来源: RSC