Langmuir 1993,9, 2982-2985
2982
A Novel Synthetic Route for Supporting Ruthenium Complexes on Functionalized Silica Gel Sonia M. C. Neiva,t Jose A. V. Santos,t Josh C. Moreira,t Yoshitaka Gushikem,s Helion Vargas) and Douglas W. Franco*J Funda@o Universidade Federal do Piaut, Teresina, PI, Brasil, Instituto de Qutmica, UNESP, Araraquara, SP, B r a d , Instituto de Qutmica, UNICAMP, Campinas, SP, Brasil, Instituto de Fisica Gleb Wataghin, UNICAMP, Campinas, SP, Brasil, and Instituto de Ftsica e Qufmica de SBo Carlos, USP, C.P. 369, 13560-970 SBo Carlos, SP, Brasil Received March 8, 1993. In Final Form: July 9, 199P The immobilizationof the ruthenium moiety Ru(NH3)4SO3by reaction of trans-[Ru(NH3)BOz(Hz0)]2+ with silica gel functionalized with 3-(l-imidazolyl)propylgroups is reported. A 60% surface coveragewas obtained in the proportion of the resulting material [ ~ ~ ( C H ~ ) ~ ~ " - R U ( N H ~ ) The B O ~anchored ]. Ru(11) complex was characterized and ita reactivity investigated. Derivatives of CO, pyrazine, and isonicotinamide have been prepared and characterized by electronic and vibrational spectroscopies, as well as by chemical means. The [di(CH2)3imN-Ru(NH3)4S041C1, obtained through oxidation of the correspondingruthenium(I1) sulfite species,has been characterized and the aquo and the oxalate derivative have been synthesized.
Introduction Immobilization of homogeneous catalysts by anchoring coordination compounds on solid supports is one area of interest in current research on catalysts1*2and electroanalytical c h e m i ~ t r y . ~ * ~ In this paper, a general synthetic route to support ruthenium complexes on silica gel modified with 3(1imidazoly1)propyl groups is presented. The Ru(I1)-imidazole system was chosen for this study on the basis of previous knowledge of the solution chemistry of ruthenium complexess$ and of the preparation and characterization of modified silica gel.7 The Ru(I1) and Ru(II1) centers exhibit a high thermodynamic affinity819for imidazole groups (imN) and, as expected for low spin d6 and dS centers, the bound Ru(11)-imN and Ru(II1)-imN are inert with respect to aquation of the imidazole ligand. Although the related Ru(1V)-imN complex has not yet been isolated, since it is a d4low-pin system, it is expected to behave similarly to the Ru(I1) and Ru(II1) imidazole complexes regarding substitution reactions. Therefore, taking into account the inertness of the ruthenium center in the [=Si(CH~)~~~N-RU(NH~)~(H~O)]~+/~+ systems, leaching of the metal center during chemical processes should be minimal.
* To whom correspondence should be addressed.
+ FundaMo Universidade Federal do Piaul. t Instituto de Qulmica, UNESP. 1 Instituto de Qulmica, UNICAMP.
11 Instituto de FIsica Gleb Wataghin, UNICAMP. 1
Instituto de Flsica e Qulmica de SHo Carlos, USP. Advance ACS Abstracts, September 1,
a Abstract published in
1993. (1) Prignano, A. L:;Trogler, W. C. J.Am. Chem. Soe. 1987,109,3586,
and referencee therein. (2)Rong, D.; Kim, Y.; Mollouk, T. E. Inorg. Chem. 1990,29, 1531. (3) Kalcher, K. Electroanulysie 1990,2, 419. (4) Zaldivar, G. A. P.; Gushikem, Y.; Kubota, L. T. J.Electroanal. Chem. 1991,318,247.
(5) Franco, D. W.; Taube, H. Inorg. Chem. 1978,17, 571. (6) Brown, G.M.; Sutton, J. E.; Taube, H. J. Am. Chem. SOC.1968, 9, 2767. (7) Gushikem, Y.; Moreira, J. C. J. Colloid Interface Sci. 1985, 107, 70. (8) Taube, H. Comments Inorg. Chem. 1981,1, 17. (9) Seddon,E. A.; Seddon,K. R. The Chemistry of Ruthenium, Topics in Inorganic and General Chemistry, Clark, R. J. H., Ed.; Elservier: Amsterdam, 1984.
0743-7463193/2409-2982$04.O0/0
In addition, the properties of the immobilized ruthenium complexes discussed here are expected to be very similar to those of the complexes in solution, since the immobilized complexes studied are separated from the support by more than two carbon atoms.lO Experimental Section Unless otherwiseindicated,all manipulationswere carried out under argon atmosphere, at room temperature, and following conventional techniques.11 All chemicalsused were Aldrich reagentgradeunlessotherwise specified. Doubly distilledwater was used throughoutthis work; RuC&.xHzO was used as the starting material for the synthesis of the ruthenium complexes. The complexes [Ru(NHs)&l)]C12, trans-[Ru(NH3)4(HSOs)~l, and trans-[Ru(NH3)rSO2(H20)1 (CFsSO& were obtainedand characterizedfollowing proceduresthat have been described elsewhere.1213 Silica gel-60 (Merck)with specific surface area of 263 f 6 mz gl,was activated by boiling in 6 M HC1 solution for 24 h and then washed with distilled water until completeremoval of acid had been achieved. The solid was then fiitered off and dried under vacuum at 120 O C for 6 h. Imidazole was also dried under vacuum (=lo-'mmHg) at 120 OC for 3 h. The 3-(l-imidazolyl)propyl groups were bound to the silica gel surface, as previously described' yielding [=si(CH~)iiNl. Synthesis of [ES~(CH~).J~N-RU(NH,)~SO~]C~~. Ruthenium ammines were supported on silica modified with imidazole groups (imN)by reacting 0.20 g of the support with 30 mL of 2.0 X 10-9M ~ ~ ~ ~ ~ - [ R U ( N H ~ ) ~ S O ~ ( Hsolution ~ O ) I (inCaF0.4~ S O ~ ) ~ M NaHC03aqueous solution. The resultingsolid was separated from the solution, washed with 100 mL of 1.0 X 10-9 M HC1, ethanol, and ether, dried, and stored in a Schlenk tube under argon.
Synthesis of [=Si(CHa)&mN-Ru(NH&SO,]Cl. A 0.20-g portion of the [=Si(CH2)3imN-Ru(NH3)4SOz]Clwas added to 30 mL of 1.0 X 10-9MHCl. The supported complex was then oxidized by addition of a stoichiometric amount of 1.9 X 10-9M hydrogen peroxide aqueous solution. Synthesis of [=S~(CH~)P~N-R~(NH~)&]C~Z (L = pyrazine (pz) or isonicotinamide (isn)). A 0.20-g portion of [=SI(CH2)simN-Ru(NHa)&Od]Cl was added to 30 mL of degassed
(lO)Kudryavt'sev, G. V.; Mil'chenko, D. V.; Bemadyuk, S. Z.; Vertinskaya, T. E.; Lisichkin, G.V. Theor. Exp. Chem. 1987,23,658. (11) Shriver, D. F. The Manipulation of Air-Sensitive Compounds, McGraw-Hik New York, 1969; pp 139-162. (12) Voght, L. H.; Katz, J. L.; Wiberley, S. E. Inorg. Chem. 1969,4, 1157. (13) Isied, S.S.;Taube, H. Inorg. Chem. 1974,13, 1545.
0 1993 American Chemical Society
Langmuir, Vol. 9, No. 11, 1993 2983
Ru Complexes on Silica Gel
4.0 20
t
0'
0
50
10.0
15.0
M O
%oOH lm' ) Figure 1. Titration curve for [di(CHz)si"H]Cl
20.0 mL of HCl(6.88 X 10-9M) with 1.07 X
(200 g) in M NaOH.
1.0 x M HC1aqueous solution. A calculated volume of Eu(C104)2acid solution was added dropwise to accomplish the desired reduction. The solid [~i(CHz)3i"-Ru(MI3)4(HzO)lC12was separated from the solution by fiitration in a glovebag, washed with 30 mL of 1.0 X 10-9M HC1, and immediately used in the next step. This solid was added to 50 mL of 0.1 M pz (or isn)aqueoussolution. After 40min, it was separatedby fiitration, washed with ethanol and ether, dried, and stored under nitrogen in a Schlenk tube. Synthesis of [ = J ~ ( C H & ~ N - R U ( N H ~ ) ~ C O ]The C ~ car~. bonyl derivative was obtained as follows: 0.20 g of [=Si(CH2)3imN-Ru(NHs)4(HzO)]Cl~was added to 30 mL of 1.0 X 10-9 M CFsCOOH aqueous solution. The resulting solution was kept under CO atmospherefor 24 h. The solid was then separated by fiitration, washed with ethanol and ether, dried, and stored under nitrogen in a Schlenk tube. Synthesis of [ - J ~ ( C H ~ ) ~ ~ N - R U ( N E L ) , ( H A ~ ~O.)%~gC ~ . portion of [di(CH2)aimN-Ru(NHs)4(H2O)lCl2was added to 50 mL of 1.0 X 10-9M HC1aqueous solution containing H202 in excess (30%)of the required stoichiometricamount to oxidaze Ru(II) to Ru(II1). After 5-10 min the solid was isolated by filtration,washed with 1.0 x 10-9M HClaqueoussolution,ethanol, and ether, dried, and stored in a Schlenk tube. Synthesis of [=Pi(CHz)&uN-Ru(NH~)~C~O~]Cl. A0.20-g portion of [di(CHz)simN-Ru(NH3)r(HaO)]C~was added to 50 mL of oxalic acid saturated solution. The mixture was heated at 40 "C for 12 h. The mixture was then cooled down to room temperature and the resulting solid was isolated by filtration, washed with ethanol and ether, dried, and stored in a Schlenk tube. Elemental Analysis. Nitrogen elemental analysis hae determinated a functionalizationof 6.7 (f0.3) X W m o l g1for the silica gel modified with 3(1-imidazolyl)propylgroups based on the nitrogen content. pK. and Concentration of Ionogenic Groups Determination. The formal pK. and the concentration of ionogenic groups in the silicagel modified with 3(1-imidazolyl)propy1groups were evaluated by pH titration: a weighed sample of functionalized silica (0.10-0.20 g) was suspended in 10 mL of 0.10 M aqueous NaCFsCOO solution. An excess of 6.88 X 10-9 HC1 M, about twice the required amount to protonate all supported N groups calculated on the basis of nitrogen elemental analysis data,was added and followed by back-titration with 1.07 X MaqueousNaOH. A typical titration curveis presented in Figure 1. The numerical calculation of the pK, and concentration of ionogenicgroupswere performed followingstandard procedures." The surface imidazolyl propyl groups density 6 and their average interatomicdistance, 1, have been calculated,16assuming that the imN groups uniformly covers the surface, by applying / ~ , NOis the equations: 6 = N&]Stm and I = ( S & N O N ) ~where (14) Helfferich, F. Ion Exchange; McGraw-Hilk New York, 1961; Chapter IV. (15) Denofre, S.;Gushikem, Y.; Castro, S. C., Kawano, Y. J. Chem. SOC., Faraday Trans. 1993,89,1057.
the amount of i" attached on the surface and N ie the Avogadro's number. Endcapping. Silica gel functionalized with 3(1-imidazolyl)propyl groups was endcapped with trimethylchlorosilane (Aldrich) according to procedures described in the literature.I6 Stability of the Anchored Complex [di(CH&imN-Ru(NHa),(&O)]Cls. Leaching out of the anchored ruthenium complex under different experimentalconditions was evaluated in the following way 0.20 g of the anchored complex was equilibrated with 25 mL of 104 M CFsCOOH aqueous solution (theionicstrength and hydrogen ion concentrationwas previously adjusted). The concentration of ruthenium complex in the aqueousphase was evaluatedby adding isn (0.1M) t o t h e sample and following the amount of trans-[ImN-Ru(NH3)rienI1+and trans-[isn[Ru(NH3)risnl2+formed based on absorbance measurements at 414 nm.13 Ruthenium Analysis. The amount of ruthenium complexes anchored on the functionaliized silica was analysed as follow: the anchored complex (50-100 mg of sample), after previous attack with KOH 2 M (5mL) and NaClO 5% (1mL), was cooled and the volumeadjustedto 25 mL. The rutheniumconcentration was determined by adsorbance measurements at 415 nm, according to the method described by Malouf." The amountof [rSi(CH2)3i"-Ru(NH3)$023Clz formedhae been also determined by measuring the amount of unreacted trans-[Ru(NHs)rSOs(H20)] 2+ formedthroughits conversioninto trans-[Ru(NHs)&Oii12+,as describedbefore.13 Therewas very good agreement between the results obtained from both procedures for amount of the anchored ruthenium complex. Specific Area " m i n a t i o n . specific areas of the silica samples were determined by the BET methodla and using an Equipamentos Cientificos CG-2000 instrument. SulfateDetermination. Determinationof sulfatewas carried out spectrophotometricallyand using the barium chlorinalate method.le The followingsteps were used (a) 20 gof [=Si(CHl)g ~ ~ N - R U ( N H ~ ) ~ was S O added ~ ] C ~to 30 mL of 1.0 X 10-9 M HC1; (b) the supported complex was then oxidized by addition of a stoichiometricamountof hydrogen peroxidesolutionand reduced by adding 8 mL of Eu(I1) solution; (c) the solid was collected by fiitration and washed with 1.0 X 10-9 M HCl until a drop of the fiitrate w p insensitive to a barium nitrate solution; (d) all the filtrate solutions were collected together and the Sodz content was determined. Electronic Spectra. Electronicspectra for the immobilized species were obtained with the solid suspended in CC4 and by photoacoustic measurements. There was very good agreement between n e spectra obtained by both techniques, for each compound. Photoacoustic measurements were carried out at room temperature in the 300-700 nm wavelength range and using an EDT OAS-400photoacoustic spectrometerwith 8O-Hz chopper modulation frequency, 0.032 nm/min band pass, 1s time constant, 0.2 nm/min scan rate, and 30 mV sensitivity. Electronicspectrafor the CC4suspensionswere obtainedwith aHP 8451Adiodearray spectrophotometerusing aO.lO-an path length quartz cell. The A, values were evaluated through Gaussian deconvolution of the absorbance spectral data. Band assignments are suggested based on comparison with available data for similar compounds.2o IR Spectra. Infrared spectra were obtained with a PerkinElmer Model 180 IR spectrophotometer from sample disks containing approximately 12 mg cm-2. The disks were prepared without any dilution of the immobilized complexes with KBr. Electron Paramagnetic Resonance Spectra. Low temperature electron paramagnetic resonance (EPR) spectra were recorded using a Varian E-12 spectrometer,at 6 K and 9.20 GHz. The spectra were digitized and analyzed with a Gateway 2000486/33C microcomputer. (16) Bayer, E.; Albert, K.; Reiners, J.; Nieder, N.; Milller, D. J. Chromatogr. 1983,264,197. (17) Malouf, M. G. Ph.D. Thesis, University of California, Santa Barbara, CA, 1977. (18) Iler, R. K. The Chemistry of Silica; John Wiley & Sons: New York, 1977. (19) Bertolachi, R. J.; Barney, J. E. A n d . Chem. 1957,29,281. (20) Neiva, S. M. C.; Franco, D. W. Manuscript in preparation.
Neiva et al.
2984 Langmuir, Vol.9,No.11,1993 Cyclic Voltammetry. Cyclic voltammetric measurements were carried out with a multifunctional 173/175 PARC system coupled to a Re-0074 X-Y recorder. A conventional threeelectrodeelectrochemicalcell was used. A modified carbon pasta electrode, a platinum wire, and SCE were used as working, auxiliary, and reference electrodes, respectively. Modified carbon paste electrodes were prepared by mixing the desired amount of [=Ci(CHz)ai"l or [=Si(CHz)si"-Ru(NHs)&02]Clz(40%) with graphite powder (56%) and Nujol oil (4%).
Results The pKa of the imidazole groups bonded to the silica gel through the propyl groups was determined to be 6.3f 0.3. There was very good agreement between the PKa found for functionalized silica gel and the one reported (PKa = 6.95)for the equilibrium imNH+ + H 2 0 F? imN + H30+ in aqueous soIution,2' suggesting that the 6 basicity of the ligand has not been significantly affected upon functionalization. The number of ionogenic groups determined by pH titrations was 6.5 (f0.2)X 10-4 mol gl, which essentially is the same as evaluated by nitrogen microanalysis 6.7 (f0.3) X 10-4 mol g'. Within the limits of the experimental error, the PKa and number of ionogenic groups determined for the endcapped and nonendcapped silica gel samplse are the same. Ruthenium tetraamine was supported on silica gel, previously functionalized with imidazole groups (imN), according to the following scheme:
c*taS +0.6 +0.4 ~ 0 . 2
9
0
-0.2
E / V vs SCE Figure 2. Cyclic voltammogram obtained by using the carbon paste modified electrode: [~i(CHz)si"-Ru(NHs)rSOzlCl~ (a%), graphite (56%), and Nujol oil (4%), P = 0.10 (LiNOa); CH+= 1.0 X 10-9 M, 25 'C; scan rate 50 mV/s.
treatment with the coupling reagents.23 The surfacebonded imidazolyl propyl groups density has been calculated as (2.3 f 0.1)X 10ls M-2 and according to the mean distance between two imidazolyl propyl groups estimatedls as 6.6 0.3 A. The specific area of the solid after anchoring the metal complex further decreases to 148 (f8)m2 g'. From the X-ray crystallographic data22 obtained on truns-[Ru(NH3)r(imN)CO12+, it was possible to estimate the minimum distance between two ruthenium centers as 4.0A. On the other hand, the specific area measurements for the [~i(CHz)~imN-Ru(NH3)4(H20)1Clz solid suggests 6.6 A as the average distance between imidazole groups, which is essentially the same distance for two [=Si(CH,),imN] + tr~ns-Ru"(NH~)~SO~(H~0)3~+ imidazolylpropyl groups in the functionalizedsilicabefore 10.40 M N~HCO,aqueous solution the reaction with the ruthenium complex. Therefore, since one metal center is coordinated to only imidazolyl propyl [4i(CH2)3imN-Ru(NH3)4S031 (1) ligand and not all the imidazolyl propyl groups are 4 1.0 X lo4 M HC1 coordinated to Ru(I1) centers, 6.6 A could be considered [4i(CH2)3imN-Ru(NH3)4S021C12 as an estimate of the minimum average distance between two metal centers. As described in the Experimental The supported ruthenium complexes are presumed to be Section, the sulfite complex was converted to the L e i N-bound species since the hydrogen ion concentration of ( C H Z ) ~ ~ ~ N - R U ( N Hform. ~)~S InO the ~ sulfur ~ C ~ dioxide ~ the medium, CH+,was kept below 103 M. According to form, the solid is more stable to oxidation and, therefore, studies22in aqueous solution, the rearrangement of Neasier to handle. The SO2 group can be easily removed bound to C-bound species occurs when CH+is excess 1k2 from the anchored complex by oxidation of the complex M. and further reduction, as illustrated below: Figure 2 shows cyclic voltammograms obtained for a modified carbon paste electrode containing the solid [=Si[~i(CH2)3imN-Ru(NH3)4S021 C1, ( C H ~ ) ~ ~ ~ N - R U ( N HCl2. ~ ) ~As SO ~ ] from the ratio judged 1 H,O,, HCI (1.0 X lo4 M) of areas correspondingto the cathodic and anodic currents, the couple Ru(III)/Ru(II) in the supported complex [=Si(CH2)3i"-Ru(NH3)4S041 C1 (11) exhibits reversible behavior. The measured formal poHCI (1.0 x lod M) 1 tential for the Ru(III)/Ru(II) couple in the supported complex (0.090 f 0.10 V) and for truns-[Ru(NH3)4HS03[4i(CH2)3imN-R~(NH3)4(H20)lC& + SO,% (111) imNl+ (0.060 f 0.10 V) in aqueous solution under the The pyrazine, isonicotinamide,and CO derivatives were same experimental conditions (0.10M LiN03, CH+= 1V obtained by reaction of the supported ruthenium(I1)aquo M, 25 "C) are in good agreement. complex with the desired ligand: The amount of ruthenium complex supported on functionalized silica was found1' to be (3.9 f 0.2)X 10-4 [=Si(CH2)3imN-Ru(NH3)4(H20)l C1, mol gl. This is in good agreement with the immobilization 1 L reported for other cations on the same support.' The specific area of the silica decreases from 263 (*6) [=f3i(CH2),imN-Ru(NH3),L1 C1, + H 2 0 m2 g' to 175 (*6) m2 g' as a consequence of functionReaction of [=S~(CH~)~~~N-RU(NH~)~(H~O)IC~~ with alization with imidazolylpropyl groups. This decrease on H202 yields the corresponding Ru(II1) aquo species. the surface area is probably due to the blocking or The anchored ruthenium salts are stable up to 60 "C. coalescence of the finest pores, observed upon chemical The compounds s t a r t to lose significant amounts water and ammonia a t temperatures higher than 70 "C. (21) Matuszak, C. A.; Matuszak, A. J. J. Chem. Educ. 1976,53,280. (22) Sundberg, R. J.; Bryan, R. F.; Taylor, I. F., Jr.; Taube, H. J. Am. Chem. SOC.1974,96,381.
*
(23) Plicas, L. M. A.; Franco, D. W. Znorg.Chim. Acta 1987,137,265.
Ru Complexes on Silica Gel
Langmuir, Vol. 9, No. 11, 1993 2985 Table I. UV-Visible Absorption Data. for Ruthenium Complexes
v = 9 3 0 GHz
x (nm)b
complexes
T=6K
[mSi(CHa)ai"-Ru(NHs)r(H20)1Ci2 tram-[(i")R~(NHs)r(HzO)I(PFa)2~ [~i(CHa)si"-Ru(NHs)4pzIClz tram-[(i")Ru(NHs)cpzl (PF6)2' [~i(CHa)si"-Ru(NHa)4CO] Clz trans-[(imN)Ru(NHs)rCOl (PF6)Z' [=Si(CHz)simN-Ru(NHs)~sn]Clz tram- [(i")Ru(NHa)&nl (PF&!' [~i(CHz)si"-Ru(NHs)r(HzO)l C11 [=Si(CH2)3i"-Ru(NHs)sCzO41C1 tram-[(imN)Ru(NH~)sCzOrl (PF6)'
a
8
9 10
20 30 40 MAGNETIC FIELD I K Gauss)
50
CC4 suspension. Uncertainty of &6 nm. Reference 20.
a
Figure 3. ESR spectra of [--~(CH~)~~"-RU(NH~)~SO~]C~.
333 302,349 329,425 346,448 292,348 297,340 337,426 342,430 292,342 297,351 302,349
Table 11. Infrared Absorption Frequencies for Some Supported Ruthenium Complexes
The [ ~ S ~ ( C H ~ ) ~ ~ ~ N - R U ( N Hand ~ ) ~[=SiH~OIC~ COZIlpOUndE frequencies,cm-1 ( C H ~ ) ~ ~ ~ N - R U ( N H ~ )ESR &O~ spectra ] C ~ exhibit signals 1564,1514,1443,1408,1343 centered a t g = 2.31 and 2.39,respectively. The signals (imidazole rine vibration) are in the typical region for Ru(II1) compounds and the 1348 (imidazole + 1518,1478,1456,1405, spectra are consistent with the metal center in C4" symmetry. However, as illustrated in Figure 3,the poor nvrazine rim vibration) resolution of the spectra does not allow a better analysis of the ESR spectra. and 1410 (imidazole In agreement with solution s t ~ d i e s ? *the ~ J ~anchored r i m vibrational) sulfate complex [-i(CH2)3i"-Ru(NH3)45041Cl is air(d) [=Si(CH&iiN-Ru(NH~)&nlClz 166%(vco), 1630 (bNHa), 1574,1475,1450,1405, stable and therefore very easy to store. Quantitative 1352 (imidazole + iaonicodetermination of immobilized sulfate as being 3.6 (f0.4) tinemide ring vibration) X 10-4 mol g ' in [--~(CH~)~~~N-RU(NH~)~SO~]C~ is 1678,(vco), 1631,(GNHs), (e) [=S~(CHZ)~~~N-RU(NHS)SCZO~IC~Z 1578,1500,1430,1380 basically the same as the value calculated 3.9 (f0.2)X 10-4 (imidazoleringhbration) mol g' based on the amount of original supported ruthenium complex. These results suggest that significant Table 111. Elemental Ruthenium Analysis in Some amounts of ruthenium are not lost during the chemical Supported Metal Complexes. manipulations. supported metal complex mol of Ru(II)/g of silicab From spectrophotometric measurements of solution[=Si(CH&&nN-Ru(NH&SOa 3.9 x lo-, phase isn, leaching into aqueous solutions of the anchored [ ~ ~ ( C H ~ ) ~ ~ ~ N - R U ( N H ~ ) ~ ( H 3.7 ~ Ox) lo-, IC~~ derivatives [=S~(CH~)~~~N-RU(NH~)~LIC~~ (where L = [=Si(CH2)si"-Ru(NHs)rpe3Cl2 3.6 X lo-, isn, pz, CO, H2O) is less than 0.8% in the pH range 3.5[~i(CH~)simN-Ru(NHs)&nl Cl2 3.6 X l(r 8.5,over a period of 40 h a t 25 OC. [=S~(CH~)~~"-RU(NH~)~CO]CI~ 3.4 x lo-, Two absorption bands are observed for all the complexes According to Malouf's procedure." Uncertainty of A2 X 10-5 studied. One appears in the 245-255 nm region, and as M. judged from the spectra of the support [=Si(CH2)3i"l absorptions were observed a t 1628-1400 cm-' and 1662itself, is probably due to the imidazol internal transition 1352 cm-I, respectively. For the oxalate complex, the (IT). The other is in the 333-349 nm region, and is presence of cis-carbonylwas confirmed by the appearance attributed8i9to a metal-to-ligandcharge transfer transition of an absorption in the 1670-1380 cm-' region. (MLCT), Ru(I1) i". For the pz and isn derivatives, the Ru(I1) pz and The ruthenium contents of the anchored complexes Ru(I1) isn MLCT bands were observed at 439 and 426 synthesized from the same starting [=Si(CHz)ai"-Runm,respectively. The band at 292 nm for the carbonyl (NH3)4SO3)1compound are consistentwith those expected derivative has been assigned to a ligand field transition. using the starting [=Si(CH2)3imN-Ru(NH&S03] comFor the Ru(II1) species C=Si(CH2)3imN-Ru(NH3)4pounds as an internal standard (see Table 111). (H20)ICla and [4i(CH2)3imN-[Ru(NH3hC2041Cl, two The synthetic procedure outlined in the present work absorptions could be identified, one in the 292-297 nm is now being extended to other ruthenium compounds. and the other in the 342-351 nm region of the spectrum. Studies of reactivity and catalytic activity26(isomerization The A, values for the characteristic absorption of the of allyl alcohol to propanaldehyde) and analytical potenimmobilized complexes in UV-visible region of the spectra tialities (sensors for CO and CN-) of these supported are summarized in Table I. species are also in progress. Table I1 shows the main infrared frequencies for the anchored complexes. A very distinct vco absorption was Acknowledgment. The authors thank the agencies observed a t 1938cm-'. This frequency is very close to the FAPESP, CNPq, CAPES-PICD,and PRONAC-CAT from YCO = 1924cm-' reportedMfor [Ru(NH3)&03(PF6)2.This Brazil, for financial support. Professor Younes Ben Taarit suggests that back-bonding in Ru(II)-CO is not strongly and Horacio Mottola are also acknowledged for helping affected by the coordination of the metal center to us in the preparation of this manuscript. imidazole. For the pz and isn complexes, the ring YCN
-
(I
-
-
-
(24)Vollet,D.R.;Moreua,J.C.;Kubota,L.T.;Varella,J.A.;Gushikem, Y . Colloids Surf. 1989,40, 1.
(25)Hartley, F. R.Supported Metal Complexes-A New Generation
of Catalysts; D. Reidel Publishing Co.: Dordrecht, 1984.
