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Anchored manganese and ruthenium porphyrins as catalysts in the decomposition of cyclohexyl hydroperoxide
Journal of Molecular Catalysis, 79 (1993) 153-163 Elsevier Science Publishers B.V., Amsterdam
153
MO37
Anchored manganese and ruthenium porphyrins as catalysts in the decomposition of cyclohexyl hydroperoxide C.B. Hansen, G.J. Hoogers and W. Drenth* Debije Institute,
Department
of Physical Organic Chemistry,
Utrecht
University,
Padualaan 8,
3584 CH Utrecht (Netherlands) (Received
October
1,1992;
accepted
October 26,1992)
Abstract Manganese and ruthenium porphyrins were anchored on to polystyrene beads and silica powder and tested as catalysts in the decomposition of cyclohexyl hydroperoxide. With Mn and Ru porphyrins
anchored
on to polystyrene
approximately
30% of the peroxide
was decomposed
in 2
h, whereas with the porphyrins anchored on to silica, 55 and 66% of the peroxide, respectively, was decomposed. With ruthenium porphyrins anchored on to silica, better results were obtained than with non-anchored ruthenium porphyrins. Experiments with catalysts supported on polystyrene beads showed that in order to obtain a well-defined anchored catalyst, insertion of the metal must be carried out before the catalyst is anchored on to the support. Furthermore, silica powder is preferred to polystyrene beads as supporting material Key words: cyclohexyl thenium;
hydroperoxide;
silica; supported
decomposition;
manganese;
polystyrene;
porphyrins;
ru-
catalysts
Introduction Oxidation of cyclohexane by molecular oxygen to give cyclohexanol and cyclohexanone is an important industrial process. This reaction is used to produce approximately lo6 tons of cyclohexanol annually [ 11. An intermediate in this reaction is cyclohexyl hydroperoxide. As catalyst for the decomposition of this peroxide, a homogeneous cobalt complex is often used. One problem associated with this catalyst is its subsequent separation from the reaction mixture for reuse. Separation is facilitated by anchoring the catalyst to a solid support. For reviews on anchored homogeneous catalysts see ref. 2. We have prepared several metalloporphyrins anchored on to polystyrene beads and on to silica powder and examined their catalytic activity in the decomposition of cyclohexyl hydroperoxide. *Author to whom correspondence
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should be addressed.
Science
Publishers
B.V.
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154
C.B. Hansen et al./J. Mol. Catal. 79 (1993) 153-163
Results and discussion
Synthesis of porphyrins anchored on to polystyrene In the literature, to anchor porphyrins on to polystyrene, several functional groups have been introduced into polystyrene. Chloromethylated polystyrene has been applied in reactions with porphyrins containing a carboxyl, amino or chlorocarbonyl group [ 3 1, and aminopolystyrene in reactions with porphyrins containing a chlorosulfonyl or a chlorocarbonyl group [4]. In the present research, porphyrins containing four carboxyl groups were synthesized. These porphyrins were treated with thionyl chloride and, then, by Friedel-Crafts acylation, anchored on to polystyrene (Fig. 1) [ 31. This route was used to couple three different porphyrins with polystyrene: 5,10,15,20tetrakis (4-carboxyphenyl)porphyrin (H, (tCPP) ) (to give H, ( 1) ), Mn (tCPP ) Cl to give Mn ( 1) and Ru (tCPP ) (CO ) (to give Ru ( 1) ) . After the metal free porphyrin had been anchored, H, ( 1) , manganese was inserted into the porphyrin moiety by treating the beads with Mn ( OAC)~*~ H,O in boiling iV,N-dimethylformamide (DMF) [ 51. In this way catalyst Mn(2) was obtained. When the polystyrene beads of the latter catalyst were cut into halves,
c=o :I 0 polystyrene Fig. 1. Coupling of porphyrins
with polystyrene.
R = COOH / COCI R’ = COOH / CO-C,H,-polystyrene HZ(l) : M = H, MI>(I) : .M= MnCI Ru(l) : M = Ru(C0)
C.B. Hansen et al/J. Mol. Catal. 79 (1993) 153-163
155
TABLE 1 Some properties
of the polystyrene-anchored
Catalyst
Metal (%, w/w)
Nitrogen (% w/w)
Mn(1)” Ru(1)” Mn(2)b Mn(3)” Ru(3)”
0.55 0.13 0.35 0.25 0.19
0.69 < 0.20 0.55
catalysts
“M ( 1) = metallated 5,10,15,20-tetrakis (I-carboxyphenyl)porphyrin bM(2) =5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin anchored tion took place after anchoring. “M(3) ~metallated 5- (4-carboxyphenyl)-10,15,20-triphenylporphyrin powder.
anchored on to polystyrene. on to polystyrene. Metallaanchored
on to silica
it could be seen that the porphyrins were exclusively present at the surface of the polystyrene beads. Some properties of the catalysts are listed in Table 1. Synthesis
of porphyrins
anchored on to silica powder
Silica powder was treated with 3-aminopropyltrimethoxysilane to provide a spacer [6] and, then, {5- (4-carboxyphenyl)-10,15,20-triphenylporphyrinato}manganese or ruthenium was coupled with the spacer uia the carbonyl chloride, yielding catalysts Mn (3 ) and Ru (3 ) , respectively (Fig. 2 ) . The metal contents of these catalysts are presented in Table 1.
functionalized silica Mn(3) : M = MnCl Ru(3) : M = Ru(C0)
rj-H bHz kH* kH2 H,C-O-Si.O-CH3 6 silica
b)H
Fig. 2. Coupling of porphyrins
with silica powder.
156
C.B. Hansen et al./J. Mol. Catal. 79 (1993) 153-163
Results obtained with catalysts anchored on to polystyrene The catalytic activities obtained with the catalysts, Mn ( 1 ), Ru ( 1) and Mn(2) are summarized in Table 2. Remarkable in this table is the enormous difference between the results obtained with the catalysts Mn (1) and Mn (2 ), which may be related to the different ways in which they have been synthesized. Catalyst Mn(2) was synthesized by first anchoring the porphyrin and then inserting the metal, whereas catalyst Mn( 1) was prepared by just the reverse sequence. The much higher activity of catalyst Mn (2 ) is at least partly caused by adsorption of manganese to the beads as is evident from the following experiments. To test the influence on the catalytic activity of refluxing the catalyst in TABLE 2 Results of the decomposition of cyclohexyl hydroperoxide into cyclohexanol and cyclohexanone catalysed by polystyrene anchored porphyrins” Catalyst
Catalyst concentration/ mm01 dn-3b
Peroxide decomposed/%
Ketone formed/%
Alcohol formed/%
Mn(1)” Mn(1)” Mn(1)” Ru( 1)” Mn(2)d
0.1 0.3 0.5 0.1 0.5
26 29 32 28 98
3.6 8.7 13 2.3 76
21 20 15 24 15
“The reactions were performed for 2 h at 25’ C. The decomposed peroxide and the formed products are expressed as mol percentages of the initial peroxide concentration of 150 mmol dme3. bCatalyst concentration=concentration of the metal in mmol dmm3. “M( 1) ~metallated 5,10,15,20-tetrakis(4carboxyphenyl)porphyrin anchored on to polystyrene. dM(2) =5,10,15,20-tetrakis(4carboxyphenyl)porphyrin anchored on to polystyrene. Insertion of the metal took place after anchoring. TABLE 3 Results of the decomposition of cyclohexyl hydroperoxide into cyclohexanol and cyclohexanone catalysed by modified porphyrins and pure polystyrene beads” Entry
Catalyst
Treatmentb
1 2 3 4 5
Mn(1)’ Mn(1)’ Mn( 1)’ Polystyrene beads Polystyrene beads
DMF DMF/Mn(OAc), DMF/Mn(OAc),
Peroxide decomposed/%
Ketone formed/%
Alcohol formed/%
26 30 48 0 38
3.6 8.8 12.8 0 3
21 18 38 0 34
“The reactions were performed for 2 h at 25 oC. The decomposed peroxide and the products formed are expressed as mol percentage of the initial peroxide concentration of 150 mmol dme3. bDMF=refluxinDMFfor 1 night;DMF/Mn(OA~)~=refluxwithMn(OAc),inDMFfor 1 night. ‘M( 1) =metallated 5,10,15,20-tetrakis(I-carboxyphenyl)porphyrin anchored on to polystyrene.
C.B. Hansen et al./J. Mol. Catal. 79 (1993) 153-163
157
DMF in the presence of M~(OAC)~.~ H20, pure polystyrene beads were subjected to this treatment (compare entries 4 and 5 ) . This treatment led to darkening of the polystyrene beads and to catalytic activity. Both findings will be due to adsorption of manganese on the beads. This adsorption has to be the reason why these beads, in contrast to untreated polystyrene beads, exhibit catalytic activity. Adsorption of Mn (OAc), on polystyrene will also occur when the beads contain anchored porphyrins (compare entries 1 and 3). This adsorption will be a reason why the activity of catalyst Mn(2) is much higher than that of catalyst Mn( 1).For catalysts containing porphyrins with carboxy1 groups, in addition to adsorption of manganese on to the beads, formation of manganese carboxylates is possible. Both facts give rise to an increase in catalytic activity. The assumption that the adsorption of manganese on to polystyrene beads leads to an increase in catalytic activity was supported by experiments in which the catalyst was reused. When catalyst Mn (2 ) was applied for a second time, only 60% of the catalytic activity remained, and after a third application only 25% was left. This decrease is probably due to leaching of the manganese adsorbed on to the polystyrene; UV-Vis spectroscopy has shown the loss of manganese porphyrin by breaking the covalent bond between polystyrene and porphyrin to be less than 3%. Leaching of the manganese from the porphyrin ring is unlikely, since manganese is bonded very strongly in the porphyrin moiety. From the results described above the conclusion can be drawn that anchoring of the free-base porphyrin, followed by insertion of the metal, leads to undefined catalysts. Fundamental research on catalysts prepared in this way, is therefore not advisable. Results obtained with catalysts anchored on to silica powder The metalloporphyrin catalysts anchored on to silica powder, Mn (3 ) and Ru( 3), showed relatively high catalytic activity; see Table 4. The anchored TABLE
4
Results of the decomposition of cyclohexyl hydroperoxide catalysed by non-anchored and anchored porphyrins”
into cyclohexanol
and cyclohexanone
Catalyst
Catalyst concentration /mmol dmW3
Peroxide decomposed/%
Ketone formed/%
Alcohol formed/%
Mn(3)b RUG
0.1 0.1
55 66
13 22
37 44
Mn(TPP)Cl Ru(TPP) (CO)
0.1 0.1
87
41
47 11
.34
40
“The reactions were performed for 2 hat 25°C. The decomposedperoxide and the formed products are expressed as mol percentage of the initial peroxide concentration of 150 mmol dmT3. bM(3) zmetallated 5- (4-carboxyphenyl)-10,15,20-triphenylporphyrin anchored on to silica powder.
158
C.B. Hansen
et al.@
Mol. Catal. 79 (1993) 153-163
ruthenium catalyst Ru(3) exhibited even higher activity than the homogeneous Ru(TPP) (CO) (TPP= 5,10,15,20-tetraphenylporphyrin). Furthermore, the finely dispersed powder showed good mechanical properties. In order to obtain more information about the stability of the catalysts anchored on to silica powder, catalyst Ru(3) was reused. Noteworthy is the fact that the catalytic activity, when reusing the catalyst, appeared to be dependent on the method used to separate the catalyst from the reaction mixture. The loss in catalytic activity varied from 23 to 75% depending on whether the catalyst was separated by filtration, washing with cyclohexane and CH,Cl, and drying (23% loss) or whether it was recovered by removing all the volatile components from the reaction mixture at the oil pump (75% loss).
Conclusions The experiments with polystyrene beads showed that in order to obtain a well-defined anchored catalyst, insertion of the metal always has to be carried out before the catalyst is anchored on to the support. The anchored manganese porphyrins showed lower catalytic activity and lower selectivity for the ketone than their homogeneous counterparts, except for the catalyst that was prepared by anchoring followed by metallation, Mn (2); it showed a higher selectivity. Ruthenium porphyrin anchored on polystyrene, Ru ( 1 ), had lower selectivity and lower activity than the homogeneous ruthenium catalyst whereas the catalyst anchored on to silica, Ru (3 ), exhibited higher activity as well as selectivity. It can be concluded that silica powder is a good supporting material for the anchoring of homogeneous catalysts. It exhibits several advantages such as a large surface area and good mechanical properties. Furthermore, silica powder can easily be functionalized and an almost homogeneous distribution of the very small particles in the reaction mixture is obtained. The polystyrene beads used in this research were partly pulverized during the reaction. From the experiments with catalyst Ru(3) in which its stability was tested, it can be concluded that it is easily separated from the reaction mixture and that it can be reused several times. The stability of the anchored ruthenium porphyrins appeared to be much larger than the stability of homogeneous ruthenium porphyrins; the latter are almost completely destroyed within half an hour. The increase in stability by anchoring is probably due to prevention of dimerization of the porphyrin; dimerization leads to destruction of the catalyst [ 71.
Experimental Instrumentation
The ‘H NMR spectra were recorded on Bruker WP 200 or Bruker WP 300 instruments, with the deuterated solvent as internal standard. The UV-Vis
159
C.B. Hansen et al./J. Mol. Catal. 79 (1993) 153-163 TABLE 5 Some properties of the supporting materials support
Specific area/m2 g-’
Pore size/nm
Porosity /cm3 g-’
Particle size/pm
polystyrene beads silica powder
19 390
80
0.21
300-850 30-100
spectra were recorded on a Perkin Elmer 552 or 555 spectrophotometer. The IR spectra were recorded on Perkin Elmer 283 or Perkin Elmer 1800 FTIR spectrophotometers. The FAB mass spectra were obtained using a VG ZAB 2F instrument. Gas chromatography was performed on a Varian 3700 instrument, equipped with a flame ionization detector, using a Chrompack 25% Carbowax 20M on Chromosorb WAW 60-80 mesh (2 m x 2 mm i.d. ) column. Peak areas were measured using a Shimadzu C-3RA electronic integrator. Materials Unless otherwise stated, commercial chemicals were used as received from Aldrich, Janssen or Merck except BaC1,.2 Hz0 which was obtained from UCB Bruxelles and tetrabutylammonium perchlorate which was obtained from Fluka. Some properties of the supporting materials, polystyrene from Aldrich and Silica 239 from Grace, are listed in Table 5. Cyclohexane was distilled from molecular sieves (4 A) under Na. CH,Cl, (kinetic experiments) was dried for 1 week over CaCl,, distilled from CaCl, and stored under N,. HOAc, CHC13, EtOH, MeOH and water were freed from O2 by means of vigorous stirring under reduced pressure (15 mmHg) at room temperature for 1 h, meanwhile repeatedly filling the vessel with N, and reapplying the reduced pressure. Toluene was dried over KOH for 1 week, and distilled from sodium sand under N,. Silica gel (column chromatography, Merck, art. 9385,0.040-0.0063 mm, 230-400 mesh ASTM) was kept under N,. Cyclohexyl hydroperoxide dissolved in cyclohexane was donated by DSM. The concentration was determined by iodometric titration. Every day a fresh Fe (SCN ) 2 solution was prepared by mixing equal volumes of an FeCl, solution and an NH,SCN solution (30 g NH,SCN in 100 cm3 water). The FeCl, solution was obtained by adding an acidified BaCl, solution (0.8 g BaCl,, 50 cm3 water and 2.0 cm3 HCl) to an FeSO,-7 Hz0 solution (1.0 g FeSO,*7 Hz0 in 50 cm3 water) resulting in a white precipitate. After filtration, the FeCl, solution could be used for 10 days [8]. Decomposition reactions The decomposition reactions were carried out in a Schlenk tube thermostated at 25.0 -t 0.2”C. The tube was filled with 10.5 cm3 of a 0.150 mol dmm3 cyclohexyl hydroperoxide solution in cyclohexane/CH,Cl, (20 : 1). Catalyst
160
C.B. Hansen et al/J. Mol. Catal. 79 (1993) 153-163
was added until the metal concentration was 0.1 mmol dme3. The reaction was stirred magnetically (stirring rod 0.5 x 0.7 cm at 1000 rpm). Two samples were taken, the first one, 10.0 mm3, was required for the determination of the cyclohexanol and cyclohexanone concentrations, and the second, 1.0 mm3, was necessary for the determination of the cyclohexyl hydroperoxide concentration. Spectroscopic determination of the cyclohexyl hydroperoxide This procedure is a modification of the procedure of Kolthoff [8]. A Schlenk tube was filled with 10.0 cm3 of toluene/MeOH (7 : 3 v/v), followed by 1.0 mm3 sample, and the tube was shaken. 100 mm3 of the Fe (SCN), solution was added, the tube was shaken and placed for exactly 5 min in a water bath at 50.0 + 0.5 oC and subsequently for 10 min in a water bath at room temperature. The adsorption at 510 nm was measured and compared with a blank. The exact concentration was determined from a calibration curve. In the blank no cyclohexyl hydroperoxide was added. The determination was performed under N,. Gas chromatographic analysis of cyclohexanol and cyclohexanone To 10.0 cm3 of a triphenylphosphine solution in EtOH (12 g dmp3) 5.0 mm3 of 1,l’ -bicyclohexyl (internal standard) was added. To 500 mm3 of the thus prepared solution was added 10.0 mm3 sample. The solution was shaken for a few seconds. Approximately 1 mm3 of this solution was immediately analysed by GLC (temperature programme 115”C, 0 min., 5”C/min., 160°C 0 min.). The measured cyclohexanol concentration had to be corrected for the cyclohexyl hydroperoxide concentration in the sample. Reaction products were identified by comparison with authentic samples and GC-MS. The determination was carried out under a N2 atmosphere. 5,10,15,20-Tetrakis(4-carboxyphenyljporphyrin (H,(tCPP)) This porphyrin was synthesized according to the procedure described by Adler et al. [9]. Because of the hydrophilic character of this porphyrin the purification method was modified. After filtration over a G3 glass frit, the residue was extracted in a Soxhlet apparatus with MeOH during approximately 10 days. The MeOH fraction was cooled and filtered. Since the porphyrin still appeared to be impure, the residue was extracted once more with MeOH in a Soxhlet apparatus. After removal of the MeOH a dark-purple powder was collected. UV-Vis data are in accord with those reported [lo]. IR (KBr, ?/cm-‘): 1690 (s, C=O), 1600 (s), 791 (m). 5-(4-CarboxyphenylJ-10,15,20-triphenylporphyrin (HJmCtPP)) Pyrrole (10.77 g; 160 mmol) was added to a solution of 60.8 g (40 mmol) benzaldehyde and 12.74 g (120 mmol) 4-carboxybenzaldehyde in 550 cm3 propionic acid. After refluxing for 18 h, the mixture was cooled to 4’ C. After two days it was filtered over a G4 glass frit; the purple residue, H,TPP, was dis-
C.B. Hansen et al./J. Mol. Catal. 79 (1993) 153-163
161
carded. The solvent was removed from the filtrate and the purple-black residue extracted in a Soxhlet apparatus with CH,Cl,. The extract was concentrated and placed on a column (450 g silica, fzI,,1,,,=5 cm) and eluted with CHClJMeOH (95 : 5 v/v). After passage of approximately 180 cm3 of eluent, besides H,TPP, some of the desired porphyrin was present in the fractions (TLC, silica, CHCl,/MeOH (95 : 5 v/v), RF (product) = 0.32 ). These fractions were again submitted to wet column chromatography (500 g silica, facolumn =5 cm, CHC13). After passage of approximately 560 cm3 of eluent the fractions contained no more H,TPP. These fractions were collected, concentrated in CHC13, and again submitted to wet column chromatography (450 g silica, = 5 cm). Elution occurred with 2100 cm3 THF/diethyl ether (1: 1 v/ 0 column v), followed by 2000 cm3 MeOH and 1800 cm3 CHCl,/MeOH (95: 5 v/v). Finally, water/THF (1: 2 v/v) was used as eluent and all the water/THF fractions were collected. The THF was removed by rotary evaporation and some HCl added to prevent dissolution of the porphyrin. The porphyrin was extracted from the water with CHC13. The CHC13 was removed by rotary evaporation and, after drying, 1.5 g (5.7% ) of a dark purple powder was collected. ‘H NMR (DMSO-dG, S/ppm): 8.89 (s, 8H, P-pyrrole ), 8.42 (m, 3H, 4-phenyl) , 8.28 (m, 8H, 2,6-phenyl), 7.91 (m, 9H, 3,5-phenyl+ CO,H). UV-Vis (CH,C&, 13/nm (log (e/dm3 mol-1 cm-‘))): 418 (5.46), 514 (4.18), 549 (3.87), 591 (3.80), 649 (3.81). IR (KBr, c/cm-‘): 1690 (s, C=O), 1600 (s), 956 (s), 797 (s), 698 (s). FAB-MS (m/z): 659 (M+). Mn(tCPP)Cl The manganese insertion was performed with Mn (OAc ) 2 in DMF as described in the literature [5]. Because of the hydrophilic character of this porphyrin the purification method was slightly modified. After removal of DMF the remaining powder was dissolved in a solution of NaOH and NaCl in water (1.0 g NaOH and 3.0 g NaCl/lOO cm3). After stirring for 15 min concentrated HCl was added until the porphyrin had precipitated. Filtration over a G2 glass frit and drying yielded the desired product. UV-Vis (MeOH, il/nm (log (E/ dm3 mol-’ cm-‘)): 374 (4.48), 398 (4.49), 413 (4.47), 465 (4.68), 560 (3.88), 593 (3.75). Mn(mCtPP)Cl The metallation procedure for this porphyrin was similar to that used for the metallation of H,(tCPP). UV-Vis (CH&, A/nm (log (e/dm3 mol-’ cm-‘))): 377 (4.29), 399 (4.25), 477 (5.01), 523 (3.58), 579 (3.74), 614 (3.73). Ru(tCPP)(CO) A solution of 0.332 g (0.42 mmol) of 5,10,15,20-tetrakis (4-carboxyphenyl)porphyrin in 70 cm3 of 2-(2-methoxyethoxy)ethanol was heated to 60” C under N,. Subsequently, 1.021 g (1.6 mmol) Ru, (CO) 12was added. After refluxing for 2 days the solvent was removed. The black residue was extracted
162
C.B. Hansen et al./J. Mol. Catal. 79 (1993) 153-163
with pyridine until, after several portions of pyridine, no porphyrin was extracted anymore. Removal of the pyridine yielded 0.38 g of the purple product. 420 (4.84), 517 (3.69), UV-Vis (DMSO, J,/ nm (log (e/dm3 mol-’ cm-‘))): 598 (3.47), 648 (3.37). IR (KBr, D/cm-‘): 2800-3000 (m), 2030 (m), 1945 (s, CO), 1710 (s, C=O), 1605 (m), 1270 (m), 1100 (m). FAB/MS (m/z): 870880 (M+H-CO,+.),800 (M+HPhCO,+.),373,401,429,480 (Ruclusters). Ru(mCtPP)CO After heating a solution of 0.36 g (0.55 mmol) H, (mCtPP) in 80 cm3 decahydronaphthalene to 60” C, 0.670 g (1.05 mmol) of Ru, (CO) 12was added. After 2 h the reaction was complete (TLC, silica, acetone and UV-Vis spectroscopy) and the reaction mixture was cooled for 1 day. After filtration over a G3 glass frit, the product was extracted from the glass frit with acetone. The acetone was removed and the porphyrin was dissolved in toluene. The porphyrin was submitted to column chromatography (150 g silica, facolumn = 3 cm) with toluene to remove the ruthenium salt. Thereafter, acetone, 10 cm3 of 0.1 mol dme3 HCl and MeOH were used successively as eluent to collect the porphyrin. The combined acetone, HCl and MeOH fractions were acidified and, after removal of the solvents, dried. Yield: 0.39 g of a purple powder. UV-Vis (CH,Cl,,A/nm (log (e/dm3 mol-’ cm-‘))): 413 (5.14), 533 (3.99), 567 (3.55). IR (KBr, B/cm-‘: 2061 (s), 2000 (s), 1898 (s, CO), 1689 (m, C=O), 1600 (m), 1005 (s, Ru”N,). FAB-MS (m/z): 786 (M+), 758 (M-CO+). 5,10,15,20-Tetraki.s(4-carboxyphenyl)porphyrins on to polystyrene A procedure slightly modified from those described in the literature and elsewhere [ 111 was used. In 8 cm3 of thionyl chloride 0.31 mmol of 5,10,15,20tetrakis (4-carboxyphenyl)porphyrin was refluxed for 75 min. After addition of 10 cm3 of 1,1,2,2-tetrachloroethane, the excess of thionyl chloride was distilled from the reaction mixture. Then, the mixture was cooled and 1.66 g of polystyrene, 0.66 g of A1C13and 5 cm3 of 1,1,2,2-tetrachloroethane were added. The mixture was refluxed for 2 days. Filtration over a G2 glass frit yielded dark green beads, which were washed with 200 cm3 of CHC13,250 cm3 of MeOH, 200 cm3 of aqueous NaOH solution (50 g dme3) and 100 cm3 1.0 mol drn3 of HCl. Subsequently, they were dried at 100°C under vacuum, which yielded 2.21 g of green balls. Functionalisation of silica powder This reaction was carried out by the procedure described in ref. 6. Dried silica (24.95 g) was refluxed in 140 cm3 of MeOH under N2 atmosphere for 1 h. After addition of 5.40 cm3 (30.9 mmol) of 3-aminopropyltrimethoxysilane the mixture was refluxed for 2 h, and then stirred for 36 h at room temperature. The silica was filtered off and washed with 120 cm3 of MeOH. After drying at 120” C under vacuum 22.92 g modified silica was obtained.
C.B. Hansen et al/J.
Mol. Catal. 79 (1993) 153-163
163
5-(4-Carboxylphenyl)-lO,15,20-triphenylporphyrins on to silica powder In 16 cm3 of thionyl chloride 0.45 mmol of metallated 5-(4-carboxyphenyl)-10,15,20-triphenylporphyrins were refluxed under N, during 2.5 h. After addition of 15 cm3 of 1,1,2,2-tetrachloroethane the thionyl chloride was distilled off. The solution was cooled to room temperature, then 15 cm3 of pyridine and 4.40 g of functionalized silica were added. After stirring for 1 night, the reaction mixture was filtered and the silica was successively washed with 0.1 mol dnP3 of HCl, CHCl, and water until the washings were colourless. After drying at 110” C 4.2 g of the silica was obtained.
Acknowledgements We are particularly grateful to Mr. U.F. Kragten, dr. O.E. Sielcken and Prof. dr. G. van Koten for the useful discussions. We thank DSM for supplies of cyclohexyl hydroperoxide and financial support.
References 1
2
K.U. Ingold, Aldrichim. Acta, 22 (1989) 69. F.R. Hartley (ed.), Supported Metal Complexes, D. Reidel, Dordrecht, 1985; Y. Iwasawa (ed.), Tailored Metal Catalysis, D. Reidel, Dordrecht, 1986; M. Capka, Collect. Czech. Chem. Commun., 55 (1990) 2803. L.D. Rollmann, J. Am. Chem. Sot., 97 (1975) 2132. R.B. KingandE.M. Sweet, J. Org. Chem., 44 (1979) 385. A.D. Adler, F.R. Longo, F. Kampas and J. Kim, J. Znorg. Nucl. Chem., 32 (1972) 2443. T.G. Waddell, D.E. Leyden and M.T. DeBello, J. Am. Chem. Sot., 103 (1981) 5303. A.W. van der Made, R.J.M. Nolte and W. Drenth, Reel. Trau. Chim. Pays-Bas, 109 (1990) 537.
8 9
10 11
R.D. Mair and R.T. Hall, in I.M. Kolthoff and P.J. Elving (eds.), Treatise on Analytical Chemistry, part II, vol. 14, Wiley Interscience, New York, 1971, p. 295. (a) A.D. Adler, F.R. Longo and W. Shergalis, J. Am. Chem. Sot., 86 (1964) 3145; (b) A.D. Adler, F.R. Longo, J.D. Finarelli, J. Goldmacher, J. Assour and L. Korsakoff, J. Org. Chem., 32 (1967) 476. F.R. Longo, M.G. Finarelli and J.B. Kim, J. Heterocycl. Chem., 6 (1969) 927. (a) L.D. Rollmann, J. Am. Chem. Sot., 97 (1975) 2132; (b) B. Markies and A.W. van der Made, unpublished results.
153
MO37
Anchored manganese and ruthenium porphyrins as catalysts in the decomposition of cyclohexyl hydroperoxide C.B. Hansen, G.J. Hoogers and W. Drenth* Debije Institute,
Department
of Physical Organic Chemistry,
Utrecht
University,
Padualaan 8,
3584 CH Utrecht (Netherlands) (Received
October
1,1992;
accepted
October 26,1992)
Abstract Manganese and ruthenium porphyrins were anchored on to polystyrene beads and silica powder and tested as catalysts in the decomposition of cyclohexyl hydroperoxide. With Mn and Ru porphyrins
anchored
on to polystyrene
approximately
30% of the peroxide
was decomposed
in 2
h, whereas with the porphyrins anchored on to silica, 55 and 66% of the peroxide, respectively, was decomposed. With ruthenium porphyrins anchored on to silica, better results were obtained than with non-anchored ruthenium porphyrins. Experiments with catalysts supported on polystyrene beads showed that in order to obtain a well-defined anchored catalyst, insertion of the metal must be carried out before the catalyst is anchored on to the support. Furthermore, silica powder is preferred to polystyrene beads as supporting material Key words: cyclohexyl thenium;
hydroperoxide;
silica; supported
decomposition;
manganese;
polystyrene;
porphyrins;
ru-
catalysts
Introduction Oxidation of cyclohexane by molecular oxygen to give cyclohexanol and cyclohexanone is an important industrial process. This reaction is used to produce approximately lo6 tons of cyclohexanol annually [ 11. An intermediate in this reaction is cyclohexyl hydroperoxide. As catalyst for the decomposition of this peroxide, a homogeneous cobalt complex is often used. One problem associated with this catalyst is its subsequent separation from the reaction mixture for reuse. Separation is facilitated by anchoring the catalyst to a solid support. For reviews on anchored homogeneous catalysts see ref. 2. We have prepared several metalloporphyrins anchored on to polystyrene beads and on to silica powder and examined their catalytic activity in the decomposition of cyclohexyl hydroperoxide. *Author to whom correspondence
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C.B. Hansen et al./J. Mol. Catal. 79 (1993) 153-163
Results and discussion
Synthesis of porphyrins anchored on to polystyrene In the literature, to anchor porphyrins on to polystyrene, several functional groups have been introduced into polystyrene. Chloromethylated polystyrene has been applied in reactions with porphyrins containing a carboxyl, amino or chlorocarbonyl group [ 3 1, and aminopolystyrene in reactions with porphyrins containing a chlorosulfonyl or a chlorocarbonyl group [4]. In the present research, porphyrins containing four carboxyl groups were synthesized. These porphyrins were treated with thionyl chloride and, then, by Friedel-Crafts acylation, anchored on to polystyrene (Fig. 1) [ 31. This route was used to couple three different porphyrins with polystyrene: 5,10,15,20tetrakis (4-carboxyphenyl)porphyrin (H, (tCPP) ) (to give H, ( 1) ), Mn (tCPP ) Cl to give Mn ( 1) and Ru (tCPP ) (CO ) (to give Ru ( 1) ) . After the metal free porphyrin had been anchored, H, ( 1) , manganese was inserted into the porphyrin moiety by treating the beads with Mn ( OAC)~*~ H,O in boiling iV,N-dimethylformamide (DMF) [ 51. In this way catalyst Mn(2) was obtained. When the polystyrene beads of the latter catalyst were cut into halves,
c=o :I 0 polystyrene Fig. 1. Coupling of porphyrins
with polystyrene.
R = COOH / COCI R’ = COOH / CO-C,H,-polystyrene HZ(l) : M = H, MI>(I) : .M= MnCI Ru(l) : M = Ru(C0)
C.B. Hansen et al/J. Mol. Catal. 79 (1993) 153-163
155
TABLE 1 Some properties
of the polystyrene-anchored
Catalyst
Metal (%, w/w)
Nitrogen (% w/w)
Mn(1)” Ru(1)” Mn(2)b Mn(3)” Ru(3)”
0.55 0.13 0.35 0.25 0.19
0.69 < 0.20 0.55
catalysts
“M ( 1) = metallated 5,10,15,20-tetrakis (I-carboxyphenyl)porphyrin bM(2) =5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin anchored tion took place after anchoring. “M(3) ~metallated 5- (4-carboxyphenyl)-10,15,20-triphenylporphyrin powder.
anchored on to polystyrene. on to polystyrene. Metallaanchored
on to silica
it could be seen that the porphyrins were exclusively present at the surface of the polystyrene beads. Some properties of the catalysts are listed in Table 1. Synthesis
of porphyrins
anchored on to silica powder
Silica powder was treated with 3-aminopropyltrimethoxysilane to provide a spacer [6] and, then, {5- (4-carboxyphenyl)-10,15,20-triphenylporphyrinato}manganese or ruthenium was coupled with the spacer uia the carbonyl chloride, yielding catalysts Mn (3 ) and Ru (3 ) , respectively (Fig. 2 ) . The metal contents of these catalysts are presented in Table 1.
functionalized silica Mn(3) : M = MnCl Ru(3) : M = Ru(C0)
rj-H bHz kH* kH2 H,C-O-Si.O-CH3 6 silica
b)H
Fig. 2. Coupling of porphyrins
with silica powder.
156
C.B. Hansen et al./J. Mol. Catal. 79 (1993) 153-163
Results obtained with catalysts anchored on to polystyrene The catalytic activities obtained with the catalysts, Mn ( 1 ), Ru ( 1) and Mn(2) are summarized in Table 2. Remarkable in this table is the enormous difference between the results obtained with the catalysts Mn (1) and Mn (2 ), which may be related to the different ways in which they have been synthesized. Catalyst Mn(2) was synthesized by first anchoring the porphyrin and then inserting the metal, whereas catalyst Mn( 1) was prepared by just the reverse sequence. The much higher activity of catalyst Mn (2 ) is at least partly caused by adsorption of manganese to the beads as is evident from the following experiments. To test the influence on the catalytic activity of refluxing the catalyst in TABLE 2 Results of the decomposition of cyclohexyl hydroperoxide into cyclohexanol and cyclohexanone catalysed by polystyrene anchored porphyrins” Catalyst
Catalyst concentration/ mm01 dn-3b
Peroxide decomposed/%
Ketone formed/%
Alcohol formed/%
Mn(1)” Mn(1)” Mn(1)” Ru( 1)” Mn(2)d
0.1 0.3 0.5 0.1 0.5
26 29 32 28 98
3.6 8.7 13 2.3 76
21 20 15 24 15
“The reactions were performed for 2 h at 25’ C. The decomposed peroxide and the formed products are expressed as mol percentages of the initial peroxide concentration of 150 mmol dme3. bCatalyst concentration=concentration of the metal in mmol dmm3. “M( 1) ~metallated 5,10,15,20-tetrakis(4carboxyphenyl)porphyrin anchored on to polystyrene. dM(2) =5,10,15,20-tetrakis(4carboxyphenyl)porphyrin anchored on to polystyrene. Insertion of the metal took place after anchoring. TABLE 3 Results of the decomposition of cyclohexyl hydroperoxide into cyclohexanol and cyclohexanone catalysed by modified porphyrins and pure polystyrene beads” Entry
Catalyst
Treatmentb
1 2 3 4 5
Mn(1)’ Mn(1)’ Mn( 1)’ Polystyrene beads Polystyrene beads
DMF DMF/Mn(OAc), DMF/Mn(OAc),
Peroxide decomposed/%
Ketone formed/%
Alcohol formed/%
26 30 48 0 38
3.6 8.8 12.8 0 3
21 18 38 0 34
“The reactions were performed for 2 h at 25 oC. The decomposed peroxide and the products formed are expressed as mol percentage of the initial peroxide concentration of 150 mmol dme3. bDMF=refluxinDMFfor 1 night;DMF/Mn(OA~)~=refluxwithMn(OAc),inDMFfor 1 night. ‘M( 1) =metallated 5,10,15,20-tetrakis(I-carboxyphenyl)porphyrin anchored on to polystyrene.
C.B. Hansen et al./J. Mol. Catal. 79 (1993) 153-163
157
DMF in the presence of M~(OAC)~.~ H20, pure polystyrene beads were subjected to this treatment (compare entries 4 and 5 ) . This treatment led to darkening of the polystyrene beads and to catalytic activity. Both findings will be due to adsorption of manganese on the beads. This adsorption has to be the reason why these beads, in contrast to untreated polystyrene beads, exhibit catalytic activity. Adsorption of Mn (OAc), on polystyrene will also occur when the beads contain anchored porphyrins (compare entries 1 and 3). This adsorption will be a reason why the activity of catalyst Mn(2) is much higher than that of catalyst Mn( 1).For catalysts containing porphyrins with carboxy1 groups, in addition to adsorption of manganese on to the beads, formation of manganese carboxylates is possible. Both facts give rise to an increase in catalytic activity. The assumption that the adsorption of manganese on to polystyrene beads leads to an increase in catalytic activity was supported by experiments in which the catalyst was reused. When catalyst Mn (2 ) was applied for a second time, only 60% of the catalytic activity remained, and after a third application only 25% was left. This decrease is probably due to leaching of the manganese adsorbed on to the polystyrene; UV-Vis spectroscopy has shown the loss of manganese porphyrin by breaking the covalent bond between polystyrene and porphyrin to be less than 3%. Leaching of the manganese from the porphyrin ring is unlikely, since manganese is bonded very strongly in the porphyrin moiety. From the results described above the conclusion can be drawn that anchoring of the free-base porphyrin, followed by insertion of the metal, leads to undefined catalysts. Fundamental research on catalysts prepared in this way, is therefore not advisable. Results obtained with catalysts anchored on to silica powder The metalloporphyrin catalysts anchored on to silica powder, Mn (3 ) and Ru( 3), showed relatively high catalytic activity; see Table 4. The anchored TABLE
4
Results of the decomposition of cyclohexyl hydroperoxide catalysed by non-anchored and anchored porphyrins”
into cyclohexanol
and cyclohexanone
Catalyst
Catalyst concentration /mmol dmW3
Peroxide decomposed/%
Ketone formed/%
Alcohol formed/%
Mn(3)b RUG
0.1 0.1
55 66
13 22
37 44
Mn(TPP)Cl Ru(TPP) (CO)
0.1 0.1
87
41
47 11
.34
40
“The reactions were performed for 2 hat 25°C. The decomposedperoxide and the formed products are expressed as mol percentage of the initial peroxide concentration of 150 mmol dmT3. bM(3) zmetallated 5- (4-carboxyphenyl)-10,15,20-triphenylporphyrin anchored on to silica powder.
158
C.B. Hansen
et al.@
Mol. Catal. 79 (1993) 153-163
ruthenium catalyst Ru(3) exhibited even higher activity than the homogeneous Ru(TPP) (CO) (TPP= 5,10,15,20-tetraphenylporphyrin). Furthermore, the finely dispersed powder showed good mechanical properties. In order to obtain more information about the stability of the catalysts anchored on to silica powder, catalyst Ru(3) was reused. Noteworthy is the fact that the catalytic activity, when reusing the catalyst, appeared to be dependent on the method used to separate the catalyst from the reaction mixture. The loss in catalytic activity varied from 23 to 75% depending on whether the catalyst was separated by filtration, washing with cyclohexane and CH,Cl, and drying (23% loss) or whether it was recovered by removing all the volatile components from the reaction mixture at the oil pump (75% loss).
Conclusions The experiments with polystyrene beads showed that in order to obtain a well-defined anchored catalyst, insertion of the metal always has to be carried out before the catalyst is anchored on to the support. The anchored manganese porphyrins showed lower catalytic activity and lower selectivity for the ketone than their homogeneous counterparts, except for the catalyst that was prepared by anchoring followed by metallation, Mn (2); it showed a higher selectivity. Ruthenium porphyrin anchored on polystyrene, Ru ( 1 ), had lower selectivity and lower activity than the homogeneous ruthenium catalyst whereas the catalyst anchored on to silica, Ru (3 ), exhibited higher activity as well as selectivity. It can be concluded that silica powder is a good supporting material for the anchoring of homogeneous catalysts. It exhibits several advantages such as a large surface area and good mechanical properties. Furthermore, silica powder can easily be functionalized and an almost homogeneous distribution of the very small particles in the reaction mixture is obtained. The polystyrene beads used in this research were partly pulverized during the reaction. From the experiments with catalyst Ru(3) in which its stability was tested, it can be concluded that it is easily separated from the reaction mixture and that it can be reused several times. The stability of the anchored ruthenium porphyrins appeared to be much larger than the stability of homogeneous ruthenium porphyrins; the latter are almost completely destroyed within half an hour. The increase in stability by anchoring is probably due to prevention of dimerization of the porphyrin; dimerization leads to destruction of the catalyst [ 71.
Experimental Instrumentation
The ‘H NMR spectra were recorded on Bruker WP 200 or Bruker WP 300 instruments, with the deuterated solvent as internal standard. The UV-Vis
159
C.B. Hansen et al./J. Mol. Catal. 79 (1993) 153-163 TABLE 5 Some properties of the supporting materials support
Specific area/m2 g-’
Pore size/nm
Porosity /cm3 g-’
Particle size/pm
polystyrene beads silica powder
19 390
80
0.21
300-850 30-100
spectra were recorded on a Perkin Elmer 552 or 555 spectrophotometer. The IR spectra were recorded on Perkin Elmer 283 or Perkin Elmer 1800 FTIR spectrophotometers. The FAB mass spectra were obtained using a VG ZAB 2F instrument. Gas chromatography was performed on a Varian 3700 instrument, equipped with a flame ionization detector, using a Chrompack 25% Carbowax 20M on Chromosorb WAW 60-80 mesh (2 m x 2 mm i.d. ) column. Peak areas were measured using a Shimadzu C-3RA electronic integrator. Materials Unless otherwise stated, commercial chemicals were used as received from Aldrich, Janssen or Merck except BaC1,.2 Hz0 which was obtained from UCB Bruxelles and tetrabutylammonium perchlorate which was obtained from Fluka. Some properties of the supporting materials, polystyrene from Aldrich and Silica 239 from Grace, are listed in Table 5. Cyclohexane was distilled from molecular sieves (4 A) under Na. CH,Cl, (kinetic experiments) was dried for 1 week over CaCl,, distilled from CaCl, and stored under N,. HOAc, CHC13, EtOH, MeOH and water were freed from O2 by means of vigorous stirring under reduced pressure (15 mmHg) at room temperature for 1 h, meanwhile repeatedly filling the vessel with N, and reapplying the reduced pressure. Toluene was dried over KOH for 1 week, and distilled from sodium sand under N,. Silica gel (column chromatography, Merck, art. 9385,0.040-0.0063 mm, 230-400 mesh ASTM) was kept under N,. Cyclohexyl hydroperoxide dissolved in cyclohexane was donated by DSM. The concentration was determined by iodometric titration. Every day a fresh Fe (SCN ) 2 solution was prepared by mixing equal volumes of an FeCl, solution and an NH,SCN solution (30 g NH,SCN in 100 cm3 water). The FeCl, solution was obtained by adding an acidified BaCl, solution (0.8 g BaCl,, 50 cm3 water and 2.0 cm3 HCl) to an FeSO,-7 Hz0 solution (1.0 g FeSO,*7 Hz0 in 50 cm3 water) resulting in a white precipitate. After filtration, the FeCl, solution could be used for 10 days [8]. Decomposition reactions The decomposition reactions were carried out in a Schlenk tube thermostated at 25.0 -t 0.2”C. The tube was filled with 10.5 cm3 of a 0.150 mol dmm3 cyclohexyl hydroperoxide solution in cyclohexane/CH,Cl, (20 : 1). Catalyst
160
C.B. Hansen et al/J. Mol. Catal. 79 (1993) 153-163
was added until the metal concentration was 0.1 mmol dme3. The reaction was stirred magnetically (stirring rod 0.5 x 0.7 cm at 1000 rpm). Two samples were taken, the first one, 10.0 mm3, was required for the determination of the cyclohexanol and cyclohexanone concentrations, and the second, 1.0 mm3, was necessary for the determination of the cyclohexyl hydroperoxide concentration. Spectroscopic determination of the cyclohexyl hydroperoxide This procedure is a modification of the procedure of Kolthoff [8]. A Schlenk tube was filled with 10.0 cm3 of toluene/MeOH (7 : 3 v/v), followed by 1.0 mm3 sample, and the tube was shaken. 100 mm3 of the Fe (SCN), solution was added, the tube was shaken and placed for exactly 5 min in a water bath at 50.0 + 0.5 oC and subsequently for 10 min in a water bath at room temperature. The adsorption at 510 nm was measured and compared with a blank. The exact concentration was determined from a calibration curve. In the blank no cyclohexyl hydroperoxide was added. The determination was performed under N,. Gas chromatographic analysis of cyclohexanol and cyclohexanone To 10.0 cm3 of a triphenylphosphine solution in EtOH (12 g dmp3) 5.0 mm3 of 1,l’ -bicyclohexyl (internal standard) was added. To 500 mm3 of the thus prepared solution was added 10.0 mm3 sample. The solution was shaken for a few seconds. Approximately 1 mm3 of this solution was immediately analysed by GLC (temperature programme 115”C, 0 min., 5”C/min., 160°C 0 min.). The measured cyclohexanol concentration had to be corrected for the cyclohexyl hydroperoxide concentration in the sample. Reaction products were identified by comparison with authentic samples and GC-MS. The determination was carried out under a N2 atmosphere. 5,10,15,20-Tetrakis(4-carboxyphenyljporphyrin (H,(tCPP)) This porphyrin was synthesized according to the procedure described by Adler et al. [9]. Because of the hydrophilic character of this porphyrin the purification method was modified. After filtration over a G3 glass frit, the residue was extracted in a Soxhlet apparatus with MeOH during approximately 10 days. The MeOH fraction was cooled and filtered. Since the porphyrin still appeared to be impure, the residue was extracted once more with MeOH in a Soxhlet apparatus. After removal of the MeOH a dark-purple powder was collected. UV-Vis data are in accord with those reported [lo]. IR (KBr, ?/cm-‘): 1690 (s, C=O), 1600 (s), 791 (m). 5-(4-CarboxyphenylJ-10,15,20-triphenylporphyrin (HJmCtPP)) Pyrrole (10.77 g; 160 mmol) was added to a solution of 60.8 g (40 mmol) benzaldehyde and 12.74 g (120 mmol) 4-carboxybenzaldehyde in 550 cm3 propionic acid. After refluxing for 18 h, the mixture was cooled to 4’ C. After two days it was filtered over a G4 glass frit; the purple residue, H,TPP, was dis-
C.B. Hansen et al./J. Mol. Catal. 79 (1993) 153-163
161
carded. The solvent was removed from the filtrate and the purple-black residue extracted in a Soxhlet apparatus with CH,Cl,. The extract was concentrated and placed on a column (450 g silica, fzI,,1,,,=5 cm) and eluted with CHClJMeOH (95 : 5 v/v). After passage of approximately 180 cm3 of eluent, besides H,TPP, some of the desired porphyrin was present in the fractions (TLC, silica, CHCl,/MeOH (95 : 5 v/v), RF (product) = 0.32 ). These fractions were again submitted to wet column chromatography (500 g silica, facolumn =5 cm, CHC13). After passage of approximately 560 cm3 of eluent the fractions contained no more H,TPP. These fractions were collected, concentrated in CHC13, and again submitted to wet column chromatography (450 g silica, = 5 cm). Elution occurred with 2100 cm3 THF/diethyl ether (1: 1 v/ 0 column v), followed by 2000 cm3 MeOH and 1800 cm3 CHCl,/MeOH (95: 5 v/v). Finally, water/THF (1: 2 v/v) was used as eluent and all the water/THF fractions were collected. The THF was removed by rotary evaporation and some HCl added to prevent dissolution of the porphyrin. The porphyrin was extracted from the water with CHC13. The CHC13 was removed by rotary evaporation and, after drying, 1.5 g (5.7% ) of a dark purple powder was collected. ‘H NMR (DMSO-dG, S/ppm): 8.89 (s, 8H, P-pyrrole ), 8.42 (m, 3H, 4-phenyl) , 8.28 (m, 8H, 2,6-phenyl), 7.91 (m, 9H, 3,5-phenyl+ CO,H). UV-Vis (CH,C&, 13/nm (log (e/dm3 mol-1 cm-‘))): 418 (5.46), 514 (4.18), 549 (3.87), 591 (3.80), 649 (3.81). IR (KBr, c/cm-‘): 1690 (s, C=O), 1600 (s), 956 (s), 797 (s), 698 (s). FAB-MS (m/z): 659 (M+). Mn(tCPP)Cl The manganese insertion was performed with Mn (OAc ) 2 in DMF as described in the literature [5]. Because of the hydrophilic character of this porphyrin the purification method was slightly modified. After removal of DMF the remaining powder was dissolved in a solution of NaOH and NaCl in water (1.0 g NaOH and 3.0 g NaCl/lOO cm3). After stirring for 15 min concentrated HCl was added until the porphyrin had precipitated. Filtration over a G2 glass frit and drying yielded the desired product. UV-Vis (MeOH, il/nm (log (E/ dm3 mol-’ cm-‘)): 374 (4.48), 398 (4.49), 413 (4.47), 465 (4.68), 560 (3.88), 593 (3.75). Mn(mCtPP)Cl The metallation procedure for this porphyrin was similar to that used for the metallation of H,(tCPP). UV-Vis (CH&, A/nm (log (e/dm3 mol-’ cm-‘))): 377 (4.29), 399 (4.25), 477 (5.01), 523 (3.58), 579 (3.74), 614 (3.73). Ru(tCPP)(CO) A solution of 0.332 g (0.42 mmol) of 5,10,15,20-tetrakis (4-carboxyphenyl)porphyrin in 70 cm3 of 2-(2-methoxyethoxy)ethanol was heated to 60” C under N,. Subsequently, 1.021 g (1.6 mmol) Ru, (CO) 12was added. After refluxing for 2 days the solvent was removed. The black residue was extracted
162
C.B. Hansen et al./J. Mol. Catal. 79 (1993) 153-163
with pyridine until, after several portions of pyridine, no porphyrin was extracted anymore. Removal of the pyridine yielded 0.38 g of the purple product. 420 (4.84), 517 (3.69), UV-Vis (DMSO, J,/ nm (log (e/dm3 mol-’ cm-‘))): 598 (3.47), 648 (3.37). IR (KBr, D/cm-‘): 2800-3000 (m), 2030 (m), 1945 (s, CO), 1710 (s, C=O), 1605 (m), 1270 (m), 1100 (m). FAB/MS (m/z): 870880 (M+H-CO,+.),800 (M+HPhCO,+.),373,401,429,480 (Ruclusters). Ru(mCtPP)CO After heating a solution of 0.36 g (0.55 mmol) H, (mCtPP) in 80 cm3 decahydronaphthalene to 60” C, 0.670 g (1.05 mmol) of Ru, (CO) 12was added. After 2 h the reaction was complete (TLC, silica, acetone and UV-Vis spectroscopy) and the reaction mixture was cooled for 1 day. After filtration over a G3 glass frit, the product was extracted from the glass frit with acetone. The acetone was removed and the porphyrin was dissolved in toluene. The porphyrin was submitted to column chromatography (150 g silica, facolumn = 3 cm) with toluene to remove the ruthenium salt. Thereafter, acetone, 10 cm3 of 0.1 mol dme3 HCl and MeOH were used successively as eluent to collect the porphyrin. The combined acetone, HCl and MeOH fractions were acidified and, after removal of the solvents, dried. Yield: 0.39 g of a purple powder. UV-Vis (CH,Cl,,A/nm (log (e/dm3 mol-’ cm-‘))): 413 (5.14), 533 (3.99), 567 (3.55). IR (KBr, B/cm-‘: 2061 (s), 2000 (s), 1898 (s, CO), 1689 (m, C=O), 1600 (m), 1005 (s, Ru”N,). FAB-MS (m/z): 786 (M+), 758 (M-CO+). 5,10,15,20-Tetraki.s(4-carboxyphenyl)porphyrins on to polystyrene A procedure slightly modified from those described in the literature and elsewhere [ 111 was used. In 8 cm3 of thionyl chloride 0.31 mmol of 5,10,15,20tetrakis (4-carboxyphenyl)porphyrin was refluxed for 75 min. After addition of 10 cm3 of 1,1,2,2-tetrachloroethane, the excess of thionyl chloride was distilled from the reaction mixture. Then, the mixture was cooled and 1.66 g of polystyrene, 0.66 g of A1C13and 5 cm3 of 1,1,2,2-tetrachloroethane were added. The mixture was refluxed for 2 days. Filtration over a G2 glass frit yielded dark green beads, which were washed with 200 cm3 of CHC13,250 cm3 of MeOH, 200 cm3 of aqueous NaOH solution (50 g dme3) and 100 cm3 1.0 mol drn3 of HCl. Subsequently, they were dried at 100°C under vacuum, which yielded 2.21 g of green balls. Functionalisation of silica powder This reaction was carried out by the procedure described in ref. 6. Dried silica (24.95 g) was refluxed in 140 cm3 of MeOH under N2 atmosphere for 1 h. After addition of 5.40 cm3 (30.9 mmol) of 3-aminopropyltrimethoxysilane the mixture was refluxed for 2 h, and then stirred for 36 h at room temperature. The silica was filtered off and washed with 120 cm3 of MeOH. After drying at 120” C under vacuum 22.92 g modified silica was obtained.
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163
5-(4-Carboxylphenyl)-lO,15,20-triphenylporphyrins on to silica powder In 16 cm3 of thionyl chloride 0.45 mmol of metallated 5-(4-carboxyphenyl)-10,15,20-triphenylporphyrins were refluxed under N, during 2.5 h. After addition of 15 cm3 of 1,1,2,2-tetrachloroethane the thionyl chloride was distilled off. The solution was cooled to room temperature, then 15 cm3 of pyridine and 4.40 g of functionalized silica were added. After stirring for 1 night, the reaction mixture was filtered and the silica was successively washed with 0.1 mol dnP3 of HCl, CHCl, and water until the washings were colourless. After drying at 110” C 4.2 g of the silica was obtained.
Acknowledgements We are particularly grateful to Mr. U.F. Kragten, dr. O.E. Sielcken and Prof. dr. G. van Koten for the useful discussions. We thank DSM for supplies of cyclohexyl hydroperoxide and financial support.
References 1
2
K.U. Ingold, Aldrichim. Acta, 22 (1989) 69. F.R. Hartley (ed.), Supported Metal Complexes, D. Reidel, Dordrecht, 1985; Y. Iwasawa (ed.), Tailored Metal Catalysis, D. Reidel, Dordrecht, 1986; M. Capka, Collect. Czech. Chem. Commun., 55 (1990) 2803. L.D. Rollmann, J. Am. Chem. Sot., 97 (1975) 2132. R.B. KingandE.M. Sweet, J. Org. Chem., 44 (1979) 385. A.D. Adler, F.R. Longo, F. Kampas and J. Kim, J. Znorg. Nucl. Chem., 32 (1972) 2443. T.G. Waddell, D.E. Leyden and M.T. DeBello, J. Am. Chem. Sot., 103 (1981) 5303. A.W. van der Made, R.J.M. Nolte and W. Drenth, Reel. Trau. Chim. Pays-Bas, 109 (1990) 537.
8 9
10 11
R.D. Mair and R.T. Hall, in I.M. Kolthoff and P.J. Elving (eds.), Treatise on Analytical Chemistry, part II, vol. 14, Wiley Interscience, New York, 1971, p. 295. (a) A.D. Adler, F.R. Longo and W. Shergalis, J. Am. Chem. Sot., 86 (1964) 3145; (b) A.D. Adler, F.R. Longo, J.D. Finarelli, J. Goldmacher, J. Assour and L. Korsakoff, J. Org. Chem., 32 (1967) 476. F.R. Longo, M.G. Finarelli and J.B. Kim, J. Heterocycl. Chem., 6 (1969) 927. (a) L.D. Rollmann, J. Am. Chem. Sot., 97 (1975) 2132; (b) B. Markies and A.W. van der Made, unpublished results.