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Synthesis and complexation of tetrakis(diphenylphosphinomethyl)calix[4]arene adopting the 1,3-alternate conformation
Inorganica Chimica Acta 357 (2004) 3895–3901 www.elsevier.com/locate/ica
Synthesis and complexation of tetrakis(diphenylphosphinomethyl)calix[4]arene adopting the 1,3-alternate conformation q Kazuhiro Takenaka, Yasushi Obora, Yasushi Tsuji
*
Catalysis Research Center, Division of Chemistry, Graduate School of Science, Hokkaido University, CREST, Japan Science and Technology Corporation (JST), Kitaku, Sapporo 060-0811, Japan Received 22 March 2004; accepted 27 March 2004 Available online 10 May 2004 Dedicated to Professor Tobin J. Marks on the occasion of his 60th birthday
Abstract Novel upper-rim modified tetraphosphinocalix[4]arenes (5a–b) adopting 1,3-alternate conformation have been synthesized. Reaction of 5,11,17,23-tetrachloromethyl-25,26,27,28-tetrahydroxycalix[4]arene (1) with Ph2 POEt gave 5,11,17,23-tetrakis(diphenylphosphinoylmethyl)-25,26,27,28-tetrahydroxycalix[4]arene (2). Tetra-O-substitution of 2 with n-propyl iodide or benzyl bromide in the presence of K2 CO3 carried out to afford 5,11,17,23-tetrakis(diphenylphosphinoylmethyl)-25,26,27,28-tetrapropoxy-(3a) or -benzyloxycalix[4]arene (3b), whereas di-O-substituted calix[4]arene, 5,11,17,23-tetrakis(diphenylphosphinoylmethyl)-25,27-dipropoxy-26,28-dihydroxycalix[4]arene (4), was obtained exclusively when Na2 CO3 was used as base. Reduction of 3a–b with PhSiHCl2 afforded 5,11,17,23-tetrakis(diphosphinomethyl)-25,26,27,28-tetrapropoxy-(5a) and -tetrabenzyloxycalix[4]arene (5b). 1 H and 13 C NMR analysis reveals that the phosphines (5a–b) and the tetra-O-substituted phosphine oxides (3a–b) adopt 1,3-alternate conformation, while the parent tetrahydroxy-(2) and the di-O-propylated phosphine oxide (4) adopt cone-conformation. The X-ray structure indicates that the calix[4]arene moieties in 4 a pinched-cone conformation in solid state. Complexation of the phosphine ligand (5a) with [RuCl2 (p-cymene)]2 affords the tetranuclear complexes, [{RuCl2 (p-cymene)}2 5a] (6), as 1,3-alternate conformer. Ó 2004 Elsevier B.V. All rights reserved. Keywords: Calix[4]arene; Phosphine; 1,3-Alternate conformation
1. Introduction Calix[4]arenes are macrocyclic compounds having cavity-shaped building block for ion-selective receptors, molecular sensors, highly ordered materials and catalysts through appropriate modification of the edges [1]. Therefore, a number of synthetic procedures for the selective functionalization of calix[4]arenes either at lower- or upper-rim have been developed and considerable attention has been directed for controlling the q
Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.ica.2004.03.037. * Corresponding author. Tel.: +81-11-706-9155; fax: +81-11-7069156. E-mail address: [email protected] (Y. Tsuji). 0020-1693/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2004.03.037
conformation [1,2]. Among the four conformer, that calix[4]arene may adopt (cone, partial cone, 1,2-alternate, and 1,3-alternate) [3], 1,3-alternate conformation in particular attracted significant interest in recent years as extremely selective extractants for large alkali metal cations in possible applications such as nuclear-waste remediation, sensing, and radiopharmacy [4]. On the other hand, it is well-known that the strong coordinating ability of phosphines to transition metals has been utilized in a wide variety of highly selective catalytic reactions [5]. A topic of growing interest deals with the combination of calix[4]arenes and transition metals [6] because the macrocyclic platforms bearing several phosphino groups are powerful tool for construction of multimetal species that contain discrete metal centers near the calix[4]arene cavities. In most
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studies, phosphine moieties are located at the lower-rim of the calix[4]arene scaffold [7], whereas some upper-rim modified phosphine ligands have been reported recently [6a,8]. It is noteworthy that so far no phosphinocalix[4]arenes fixed in 1,3-alternate conformation have been reported. In this paper, we report the first synthesis of upperrim modified tetraphosphinocalix[4]arene ligands adopting 1,3-alternate conformation from tetraphosphinoylcalix[4]arene precursors having cone or 1,3alternate conformations. Furthermore, Ru(II) complex formation with the phosphine ligand is described.
2. Experimental 2.1. General All reactions were performed under an argon atmosphere using Schlenk techniques. Solvents were dried and purified prior to use by standard method [9]. Compound 1 [10] and [RuCl2 (p-cymene)]2 [11] were synthesized according to the literature method. 1 H NMR (400.13 MHz), 13 C{1 H} NMR (100.61 MHz), and 31 P{1 H} NMR (161.98 MHz) spectra were recorded on a Bruker ARX 400 instrument. The 1 H NMR data are referenced relative to residual protiated solvent in CDCl3 at 7.24 ppm. 13 C NMR chemical shifts are reported relative to CDCl3 (77.0 ppm). The 31 P NMR data are given relative to external 85% H3 PO4 . ESI and FD mass spectra were recorded on a JEOL JMS-SX102A instrument at the GC–MS and NMR Laboratory of Faculty of Agriculture, Hokkaido University. Elemental analysis was performed at the Center for Instrumental Analysis of Hokkaido University. 2.2. Preparation of 5,11,17,23-tetrakis(diphenylphosphinoylmethyl)-25,26,27,28-tetrahydroxycalix[4]arene (2) To a solution of 1 [10] (1.96 g, 3.17 mmol) in toluene (100 ml) was added ethyl diphenylphosphinite (6.90 ml, 31.9 mmol), which was refluxed for 6 h. After cooling the reaction mixture, deposited off-white powders were filtered, washed twice with 15 ml of toluene and twice with 20 ml of ether, and then dried under vacuum. Yield: 3.15 g, 78%. M.p.: 189–192 °C. 1 H NMR, CDCl3 , d: 9.87 (s, 4H, OH ), 7.61–7.56 (m, 16H, m-Ph), 7.41–7.31 (m, 24H, o,p-Ph), 6.73 (d, 8H, 4 JHP ¼ 1:4 Hz, m-ArH ), 3.95 (d, 4H, 2 JHH ¼ 13:8 Hz, ArCH2 Ar), 3.34 (d, 8H, 2 JHP ¼ 13:3 Hz, CH2 P(O)Ph2 ), 3.19 (d, 4H, 2 JHH ¼ 13:8 Hz, ArCH2 Ar). 13 C{1 H} NMR, CDCl3 , d: 147.6 (d, 5 JCP ¼ 3:0 Hz, ArC attached to OH), 132.1 (d, 1 JCP ¼ 98:7 Hz, ipso-Ph), 131.7 (d, 4 JCP ¼ 2:3 Hz, p-Ph), 131.1 (d, 3 JCP ¼ 9:1 Hz, m-Ph), 130.6 (d, 3 JCP ¼ 5:0 Hz,
m-ArC), 128.4 (d, 2 JCP ¼ 11:7 Hz, o-Ph), 128.1 (d, JCP ¼ 2:2 Hz, o-ArC), 124.4 (d, 2 JCP ¼ 7:9 Hz, ArC attached to CH2 P(O)Ph2 ), 37.0 (d, 1 JCP ¼ 67:0 Hz, CH2 P(O)Ph2 ), 31.3 (ACH2 Ar). 31 P{1 H} NMR, CDCl3 , d: 30.1. FD-MS: m=z 1281 ([M + H]þ ), 1280 ([M]þ ). Anal. Calc. for C80 H68 O8 P4 H2 O: C, 73.95; H, 5.43. Found: C, 73.62; H, 5.67%.
4
2.3. Preparation of 5,11,17,23-tetrakis(diphenylphosphinoylmethyl)-25,26,27,28-tetrapropoxycalix[4]arene (3a) To a suspension of 3 (1.00 g, 0.78 mmol) and K2 CO3 (0.93 g, 6.7 mmol) in a mixture of THF (25 ml) and MeCN (25 ml) was added n-propyl iodide (1.95 ml, 20.0 mmol). The reaction mixture was refluxed for 2 days. After removal of the solvents, the resulting yellow solids were redissolved in CHCl3 , which was washed twice with 50 ml of 1 N HCl aq. and 50 ml of Na2 S2 O3 aq., and then dried over MgSO4 . The clear filtrate was evaporated to yield yellow solid, which was purified by column chromatography on alumina (Merck, Aluminium oxide 90 active neutral, activity stage I) using CH2 Cl2 /MeOH (50:1) as an eluent. The product was recrystallized from EtOH-n-hexane to give colorless crystals. Yield: 0.82 g, 73%. M.p.: 127–130 °C. 1 H NMR, CDCl3 , d: 7.62–7.56 (m, 16H, m-Ph), 7.49–7.45 (m, 8H, p-Ph), 7.40–7.35 (m, 16H, o-Ph), 6.50 (d, 8H, 4 JHP ¼ 1:7 Hz, m-ArH ), 3.37 (d, 8H, 2 JHP ¼ 13:6 Hz, CH2 P(O)Ph2 ), 3.214 (t, 8H, 3 JHH ¼ 7:3 Hz, OCH2 CH2 CH3 ), 3.206 (s, 8H, ArCH2 Ar), 1.33 (sextet, 8H, 3 JHH ¼ 7:3 Hz, OCH2 CH2 CH3 ), 0.77 (t, 12H, 3 JHH ¼ 7:4 Hz, OCH2 CH2 CH3 ). 13 C{1 H} NMR, CDCl3 , d: 155.6 (d, 5 JCP ¼ 3:5 Hz, ArC attached to OPrn ), 133.4 (d, 4 JCP ¼ 2:7 Hz, o-ArC), 132.5 (d, 1 JCP ¼ 98:1 Hz, ipso-Ph), 131.7 (p-Ph), 131.7 (m-ArC), 131.2 (d, 3 JCP ¼ 9:1 Hz, m-Ph), 128.3 (d, 2 JCP ¼ 11:6 Hz, o-Ph), 123.1 (d, 2 JCP ¼ 8:0 Hz, ArC attached to CH2 P(O)Ph2 ), 72.9 (OCH2 CH2 CH3 ), 37.5 (d, 1 JCP ¼ 67:4 Hz, CH2 P(O)Ph2 ), 36.6 (ArCH2 Ar), 23.3 (OCH2 CH2 CH3 ), 10.5 (OCH2 CH2 CH3 ). 31 P{1 H} NMR, CDCl3 , d: 30.3. FD-MS: m=z 1449 ([M]þ ), 724 ([M]2þ ). Anal. Calc. for C92 H92 O8 P4 H2 O: C, 75.29; H, 6.46. Found: C, 75.30; H, 6.54%. 2.4. Preparation of 5,11,17,23-tetrakis(diphenylphosphinoylmethyl)-25,26,27,28-tetrabenzyloxycalix[4]arene (3b) In the similar manner as 3a and 3b was obtained from 2 (0.85 g, 0.66 mmol), K2 CO3 (0.87 g, 6.29 mmol), and benzyl bromide (2.50 ml, 21.0 mmol) in a mixture of THF (25 ml) and MeCN (25 ml). Yield: 0.82 g, 80%. M.p.: 134–137 °C. 1 H NMR, CDCl3 , d: 7.48–7.28 (m, 52H), 7.09 (d, 8H, 3 JHH ¼ 7:4 Hz), 6.15 (d, 8H, 4 JHP ¼ 1:5 Hz, m-ArH ), 4.62 (s, 8H, OCH2 Ph), 3.19 (s, 8H, ArCH2 Ar), 2.93 (d, 8H, 2 JHP ¼ 13:3 Hz,
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CH2 P(O)Ph2 ). 13 C{1 H} NMR, CDCl3 , d: 154.5, 138.9, 133.6 (d, 4 JCP ¼ 2:6 Hz, o-ArC), 133.0 (d, 3 JCP ¼ 9:1 Hz, m-Ph), 132.5 (d, 1 JCP ¼ 98:1 Hz, ipso-Ph), 131.5 (d, 4 JCP ¼ 2:4 Hz, p-Ph), 131.1 (d, 3 JCP ¼ 9:1 Hz, m-Ph), 131.1 (m-ArC), 128.2 (d, 2 JCP ¼ 11:6 Hz, o-Ph), 128.0, 126.6, 126.3, 123.7 (d, 2 JCP ¼ 8:3 Hz, ArC attached to CH2 P(O)Ph2 ), 70.9 (OCH2 CH2 CH3 ), 37.1 (ArCH2 Ar), 36.6 (d, 1 JCP ¼ 67:1 Hz, CH2 P(O)Ph2 ). 31 P{1 H} NMR, CDCl3 , d: 30.5. FD-MS: m=z 1641([M]þ ), 821 ([M]2þ ). Anal. Calc. for C108 H92 O8 P4 H2 O: C, 78.15; H, 5.71. Found: C, 77.95; H, 5.99%. 2.5. Preparation of 5,11,17,23-tetrakis(diphenylphosphinoylmethyl)-25,27-dipropoxy-26,28-dihydroxycalix[4]arene (4) To a suspension of 2 (0.45 g, 0.35 mmol) and Na2 CO3 (0.33 g, 3.13 mmol) in a mixture of THF (10 ml) and MeCN (10 ml) was added n-propyl iodide (0.94 ml, 9.64 mmol). The reaction mixture was refluxed for 2 days. After removal of the solvents, the resulting yellow solids were redissolved in CHCl3 , which was washed twice with 30 ml of 1 N HCl aq. and 30 ml of brine, and then dried over MgSO4 . The clear filtrate was evaporated to yield yellow solid, which was purified by column chromatography on silica gel (WakosilÒ , C-300) using CH2 Cl2 /MeOH (20:1) as an eluent. The product was recrystallized from EtOH-n-hexane to give colorless crystals. Yield: 0.37 g, 77%. 1 H NMR, CDCl3 , d: 8.24 (s, 2H, OH ), 7.67–7.02 (m, 40H, Ph), 6.69 (br s, 4H, m-ArH ), 6.43 (br s, 4H, m-ArH ), 4.01 (d, 4H, 2 JHP ¼ 12:9 Hz, CH2 P(O)Ph2 ), 3.77 (t, 4H, 3 JHH ¼ 6:2 Hz, OCH2 CH2 CH3 ), 3.48 (d, 4H, 2 JHH ¼ 13:1 Hz, ArCH2 Ar), 3.01 (d, 4H, 2 JHP ¼ 12:9 Hz, CH2 P(O)Ph2 ), 2.82 (d, 4H, 2 JHH ¼ 13:1 Hz, ArCH2 Ar), 1.94 (sextet, 4H, 3 JHH ¼ 7:2 Hz, OCH2 CH2 CH3 ), 1.20 (t, 6H, 3 JHH ¼ 7:4 Hz, OCH2 CH2 CH3 ). 13 C{1 H} NMR, CDCl3 , d: 152.2 (d, 5 JCP ¼ 2:6 Hz, ArC attached to OPrn ), 150.9 (d, 5 JCP ¼ 3:1 Hz, ArC attached to OH), 133.2 (d, 4 JCP ¼ 1:9 Hz, o-ArC), 132.5 (d, 1 JCP ¼ 98:0 Hz, ipso-Ph), 131.8 (d, 1 JCP ¼ 98:8 Hz, ipso-Ph), 131.6 (p-Ph), 131.2 (d, 3 JCP ¼ 9:1 Hz, o-Ph), 130.8 (d, 3 JCP ¼ 9:1 Hz, o-Ph), 130.7 (d, 3 JCP ¼ 4:5 Hz, m-ArC), 130.3 (d, 3 JCP ¼ 3:1 Hz, m-ArC), 128.4 (d, 2 JCP ¼ 11:6 Hz, m-Ph), 128.2 (d, 2 JCP ¼ 11:6 Hz, m-Ph), 128.0 (d, 4 JCP ¼ 1:9 Hz, o-ArC), 127.5 (d, 2 JCP ¼ 7:9 Hz, ArC attached to CH2 P(O)Ph2 ), 120.8 (d, 2 JCP ¼ 8:0 Hz, ArC attached to CH2 P(O)Ph2 ), 78.2 (OCH2 CH2 CH3 ), 37.1 (d, 1 JCP ¼ 68:2 Hz, CH2 P(O)Ph2 ), 37.0 (d, 1 JCP ¼ 66:9 Hz, CH2 P(O)Ph2 ), 31.1 (ArCH2 Ar), 23.4 (OCH2 CH2 CH3 ), 10.8 (OCH2 CH2 CH3 ). 31 P{1 H} NMR, CDCl3 , d: 30.4, 30.3. FD-MS: m=z 1365 ([M + H]þ ), 1364 ([M]þ ), 683 ([M + H]2þ ), 682 ([M]2þ ). Anal. Calc. for C86 H80 O8 P4 2H2 O: C, 73.70; H, 6.04. Found: C, 73.33; H, 6.04%.
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2.6. Preparation of 5,11,17,23-tetrakis(diphenylphosphinomethyl)-25,26,27,28-tetrapropoxycalix[4]arene (5a) To a suspension of 3a (0.50 g, 0.35 mmol) in 20 ml of dry THF was added phenyldichlorosilane (2.10 ml, 14.4 mmol). The reaction mixture was heated at 70 °C for 18 h. Then, to the resulting orange solution was added 12.5 ml of degassed MeOH in order to decompose the residual PhSiHCl2 , which was stirred for 30 min at ambient temperature. The reaction solution was evaporated to yield a deep yellow solution, which was recrystallized from degassed CH2 Cl2 /degassed MeOH. The off-white powders formed were collected by filtration and washed four times with 5.0 ml of degassed MeOH, followed by drying under vacuum. Yield: 0.33 g, 69%. 1 H NMR, CD2 Cl2 , d: 7.41–7.36 (m, 16H, mPh), 7.34–7.29 (m, 24H, o,p-Ph), 6.69 (d, 8H, 4 JHP ¼ 1:0 Hz, m-ArH ), 3.37 (s, 8H, CH2 PPh2 ), 3.37 (t, 8H, 3 JHH ¼ 7:3 Hz, OCH2 CH2 CH3 ), 3.24 (s, 8H, ArCH2 Ar), 1.51 (sextet, 8H, 3 JHH ¼ 7:3 Hz, OCH2 CH2 CH3 ), 0.91 (t, 12H, 3 JHH ¼ 7:4 Hz, OCH2 CH2 CH3 ). 13 C{1 H} NMR, CD2 Cl2 , d : 154.6 (d, 5 JCP ¼ 3:2 Hz, ArC attached to OPrn ), 138.7 (d, 1 JCP ¼ 16:2 Hz, ipso-Ph), 133.0 (d, 4 JCP ¼ 1:6 Hz, o-ArC), 132.4 (d, 2 JCP ¼ 18:4 Hz, o-Ph), 130.3 (d, 3 JCP ¼ 6:8 Hz, m-ArC), 129.2 (d, 2 JCP ¼ 8:9 Hz, ArC attached to CH2 PPh2 ), 128.1 (pPh), 127.9 (d, 3 JCP ¼ 6:4 Hz, m-Ph), 72.8 (OCH2 CH2 CH3 ), 36.0 (ArCH2 Ar), 34.5 (d, 1 JCP ¼ 14:8 Hz, CH2 PPh2 ), 23.1 (OCH2 CH2 CH3 ), 10.1 (OCH2 CH2 CH3 ). 31 P{1 H} NMR, CD2 Cl2 , d: )11.5. FD-MS: m=z 1384 ([M]þ ). Anal. Calc. for C92 H92 O4 P4 CH3 OH: C, 78.79; H, 6.83. Found: C, 78.92; H, 6.80%.
2.7. Preparation of 5,11,17,23-tetrakis(diphenylphosphinomethyl)-25,26,27,28-tetrabenzyloxycalix[4]arene (5b) Similarly, 5b was prepared from 3b (0.60 g, 0.37 mmol) and phenyldichlorosilane (2.30 ml, 15.7 mmol) in THF. Yield: 0.40 g, 70%. 1 H NMR, CD2 Cl2 , d: 7.45– 7.40 (m, 24H), 7.31–7.16 (m, 36H), 6.37 (d, 8H, 4 JHP ¼ 1:0 Hz, m-ArH ), 4.74 (s, 8H, O-CH2 Ph), 3.41 (s, 8H, ArCH2 Ar), 2.79 (s, 8H, CH2 PPh2 ). 13 C{1 H} NMR (CD2 Cl2 ): d 153.7 (d, 5 JCP ¼ 3:2 Hz, ArC attached to OBz), 138.5 (Bz), 138.4 (d, 1 JCP ¼ 15:7 Hz, ipso-Ph), 133.3 (d, 4 JCP ¼ 1:8 Hz, o-ArC), 132.3 (d, 2 JCP ¼ 18:4 Hz, o-Ph), 131.6 (d, 3 JCP ¼ 6:2 Hz, m-ArC), 130.0 (d, 2 JCP ¼ 8:7 Hz, ArC attached to CH2 PPh2 ), 128.0 (p-Ph), 127.79 (d, 3 JCP ¼ 6:6 Hz, m-Ph), 127.76 (Bz), 126.3 (Bz), 126.2 (Bz), 71.1 (OCH2 Ph), 36.8 (ArCH2 Ar), 33.8 (d, 1 JCP ¼ 14:1 Hz, CH2 PPh2 ). 31 P{1 H} NMR, CD2 Cl2 , d: )11.2. FD-MS: m=z 1577 ([M]þ ), 788 ([M]2þ ). Anal. Calc. for C108 H92 O4 P4 CH3 OH: C, 81.32; H, 6.01. Found: C, 81.56; H, 5.99%.
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2.8. Preparation of [{RuCl2 (p-cymene)}4 (5a)] (6) A solution of [RuCl2 (p-cymene)]2 (25.5 mg, 41.6 lmol) in 5.0 ml of CH2 Cl2 was added to a solution of the ligand 5a (28.2 mg, 20.4 lmol) in 5.0 ml of CH2 Cl2 . The resulting red solution was stirred for 3 h at room temperature. The solvent was concentrated under reduced pressure to ca. 2 ml and n-hexane (20 ml) was added to yield a reddish-orange powder. Yield: 53.5 mg, quant. 1 H NMR, CD2 Cl2 , d: 7.55 (br t, 16H, o-Ph, ), 7.40 (br t, 8H, p-Ph, 3 JHH ¼ 7:6 Hz), 7.28 (br t, 16H, oPh, 3 JHH ¼ 7:6 Hz), 5.75 (s, 8H, m-ArH ) 5.20 and 5.07 (2d, AA0 BB0 spin system, 16H, ArH of p-cymene), 3.57 (d, 8H, 2 JHP ¼ 8:4 Hz, CH2 PPh2 ), 2.72 (s, 8H, ArCHAr), 2.63 (t, 8H, 3 JHH ¼ 7:1 Hz, OCH2 CH2 CH3 ), 2.39 (septet, 4H, 3 JHH ¼ 6:9 Hz, p-Me-C6 H4 -CH (CH3 )2 ), 1.79 (s, 12H, p-CH3 -C6 H4 -Pri ), 0.86 (d, 24H, 3 JHH ¼ 6:9 Hz, p-Me-C6 H4 -CH(CH3 )2 ), 0.66 (sextet, 8H, 3 JHH ¼ 7:2 Hz, OCH2 CH2 CH3 ), 0.42 (t, 12H, 3 JHH ¼ 7:5 Hz, OCH2 CH2 CH3 ). 13 C{1 H} NMR, CD2 Cl2 , d: 155.0 (d, 5 JCP ¼ 3:5 Hz, ArC attached to OPrn ), 133.5 (d, 3 JCP ¼ 8:5 Hz, o-Ph), 132.3 (d, 4 JCP ¼ 2:7 Hz, o-ArC), 131.9 (d, 1 JCP ¼ 42:9 Hz, ipsoPh), 130.4 (d, 3 JCP ¼ 3:9 Hz, m-ArC), 129.8 (d, 4 JCP ¼ 1:9 Hz, p-Ph), 127.1 (d, 2 JCP ¼ 9:5 Hz, m-Ph), 126.2 (d, 2 JCP ¼ 12:4 Hz, ArC attached to CH2 PPh2 ), 107.2 (ipso-ArC attached to Pri ), 93.7 (ipso-ArC attached to Me), 89.7 (d, 2 JCP ¼ 4:0 Hz, ArC of p-cymene), 85.1 (d, 2 JCP ¼ 5:3 Hz, ArC of p-cymene), 71.5 (OCH2 CH2 CH3 ), 36.9 (ArCH2 Ar), 29.6 (p-Me-C6 H4 CH(CH3 )2 ), 29.0 (d, 1 JCP ¼ 23:8 Hz, CH2 PPh2 ), 21.9 (OCH2 CH2 CH3 ), 20.8 (p-Me-C6 H4 -CH(CH3 )2 ), 16.7 (pCH3 -C6 H4 - Pri ), 9.6 (OCH2 CH2 CH3 ). 31 P{1 H} NMR, CD2 Cl2 , d: 30.7. ESI-MS: m=z 2629 ([M + H + H2 O]þ ), 2610 ([M]þ ). Anal. Calc. for C132 H148 Cl8 O4 P4 Ru4 : C, 60.73; H, 5.71. Found: C, 60.95; H, 5.91%. 2.9. X-ray structure determination of 4 Prismatic crystals of 4 suitable for X-ray diffraction were obtained by slow evaporation of an ethanolic solution. The data were collected with Mo Ka radiation at )160 °C on a Rigaku Saturn CCD (k ¼ 0:71070 A) area detector with graphite monochromated Mo Ka radiation. An empirical absorption correction was applied. The structure was solved by direct methods using the program S H E L X -97 [12] and expanded using Fourier techniques [13]. Non-hydrogen atoms except some solvent molecules were refined anisotropically. Hydrogen atoms were refined using the riding model. The final cycle of full-matrix least-squares refinement on F 2 was based on 12733 observed reflections (I > 3:0rðIÞ) and 1118 variable parameters. A Sheldrick weighting scheme was used. The maximum and minimum peaks on the final difference Fourier map corresponded to 1.77 and respectively. Neutral atom scattering factors )0.96 e /A,
Table 1 Crystal data and structure refinements for complex 4 Empirical formula Formula weight Temperature (°C) Wavelength (A) Crystal system Space group Unit cell dimensions a (A) b (A) c (A) V (A3 ) Z Dcalc (g cm3 ) l (cm1 ) Crystal size (mm) Maximum 2h (°) Number of reflections collected Unique Parameters Refinements on RðI > 3rðIÞÞ wRðI > 3rðIÞÞ Rint (all data) Goodness-of-fit
C86 H80 O8 P4 5C2 H5 OH 1595.81 )160(1) 0.71070 triclinic P 1 (#2) 14.87(2) 15.575(10) 20.08(3) 4289.7(84) 2 1.235 1.51 0.20 0.10 0.10 55 33592 18616 1118 F2 0.069 0.180 0.031 1.841
were taken from Cromer and Waber [14]. Anomalous dispersion effects were included in Fc [15]. All calculations were performed using the C R Y S T A L S T R U C T U R E crystallographic software package (ver. 3.6) [16]. Details of the crystal data are given in Table 1. 3. Results and discussion 3.1. Synthesis of tetraphosphinoylcalix[4]arene tetraand dialkyl ether (3,4) adopting 1,3-alternate and coneconformations As a precursor of tetraphosphinocalix[4]arenes (5), tetraphosphinoylcalix[4]arenes (3) were prepared as shown in Scheme 1. First, the reaction of 5,11,17,23tetra(chloromethyl)-25,26,27,28-tetrahydroxycalix[4]arene (1) with ethyl diphenylphosphinite afforded 5,11,17,23tetrakis(diphenylphosphinoylmethyl)-25,26,27,28-tetrahydroxycalix[4]arene (2) in 78% yield. The 31 P{1 H} NMR of 2 showed a sole peak at 30.1 ppm assignable to an alkyldiaryl phosphine oxide. FD-MS spectrum of 2 showed the molecular ion peak (m=z ¼ 1280) as the base peak, and purity of the isolated compound was confirmed by elemental analysis. These analytical data indicate that 2 has four Ph2 P(O) groups on calix[4]arene backbone. It is well-known that conformation of calix[4]arenes can be easily evaluated by a 1 H NMR spectrum which shows different splitting patterns for the ArCH2 Ar protons: a pair of doublets for cone, two pairs of doublets for partial cone, a pair of doublets and a singlet for 1,2-alternate, and a single peak for 1,3-alternate conformations [17]. Moreover, de Mendoza and coworkers [18] reported that a signal of 13 C{1 H} NMR
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had cone-conformation as judged by a pair of doublet peaks due to the bridging methylene protons at 4.38 and 3.08 ppm [20].
Scheme 1.
arising from the bridging methylene carbon appears at near 31 ppm when two adjacent aryl groups are in the syn orientation, and near 37 ppm when they are in the anti orientation. Indeed, in 1 H and 13 C{1 H} NMR spectra of 2, the bridging methylene proton resonance appeared as two doublets with a geminal coupling (13.8 Hz) at 3.19 and 3.95 ppm and the bridging methylene carbon resonance afforded a singlet at 31.3 ppm. These data indicated that the parent tetrahydroxy derivative (2) adopted a cone-conformation, which would be stabilized by a circular array of hydrogen bonds involving the four OH groups [1,17,18]. Tetra-O-propylation of 2 with n-propyl iodide and K2 CO3 as a base in THF/MeCN (1:1) took place to give 5,11,17,23-tetrakis(diphenylphosphinoylmethyl)-25, 26,27,28-tetrapropoxycalix[4]arene (3a) in 73% yield (Scheme 1). The 31 P{1 H} NMR spectrum of 3a showed a solitary signal at 30.3 ppm and the FD-MS spectrum provided the molecular ion peak at m=z ¼ 1449. The observed 1 H and 13 C{1 H} NMR chemical shifts of the bridging methylene protons (one singlet at 3.21 ppm) and the bridging methylene carbons (one singlet at 36.6 ppm) revealed that 3 had a 1,3-alternate structure. Similarly, when benzyl bromide was used, the corresponding tetra-O-benzylation product (3b) was obtained in 80% yield as 1,3-alternate conformer. So far, no phosphinoylcalix[4]arenes fixed in 1,3-alternate conformation have been reported. Recently, Kalchenko and coworkers [19,20] reported the synthesis of diphenylphosphinoyl calix[4]arene derivative (3a0 ) as well as its dibutylphosphinoyl analogue (3c0 ) by the reaction of 5,11,17,23-tetra(chloromethyl)-25,26,27,28-tetrapropoxycalix[4]arene with alkyl diphenyl- or alkyl dibutylphosphinite, respectively. Although they did not mention about conformational preferences of 3a0 and 3c0 , the reported 1 H NMR data clearly showed that 3c0
On the contrary, when Na2 CO3 was used instead of K2 CO3 as a base in the reaction of 2 and n-propyl iodide, di-O-propylation took place exclusively to give 5,11,17,23-tetrakis(diphenylphosphinoylmethyl)-25,27dipropoxy-26,28-dihydroxy-calix[4]arene (4) in 77% yield. The 31 P NMR of 4 showed two singlet peaks at 30.4 and 30.3 ppm, and the FD-MS afforded the parent ion peak (m=z ¼ 1364), indicating that the selective diO-alkylation reaction proceeded. The NMR spectra of 4 displayed a pair of doublets at 3.48 and 2.82 ppm due to the bridging methylene protons and a singlet at 31.1 ppm for the corresponding carbons. These data indicated that the di-O-propylated product (4) was frozen into the cone-conformation in solution state. The X-ray crystallographic structure of 4 was shown in Fig. 1. Crystal data and selected atom distances and bond angles of 4 were summarized in Tables 1 and 2. The dihedral angles between the mean plane of the bridging methylene carbons and the aryl rings possessing P1, P2, P3, P4 are 103.38(9)°, 139.02(9)°, 108.34(9)°, and 135.11(9)°, respectively. The O1–O3 distance (4.544 A) is longer than that of O2–O4 (3.023 A) distance. Thus, the compound 4 has a pinched-cone conformation [21] in solid state with two propoxy-connected phenyl rings
Fig. 1. ORTEP drawing of compound 4 with thermal ellipsoids at 50% probability levels and the scheme of atom numbering. Hydrogen atoms are deleted for clarity.
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Table 2 and bond angles (°) for 4 Selected bond lengths (A) Bond length ( A) P(1)–O(5) 1.487(3) P(3)–O(7) 1.490(2) P(1)–C(1) 1.813(3) P(3)–C(3) 1.818(3) C(1)–C(5) 1.510(4) C(3)–C(7) 1.514(5) C(11)–O(1) 1.399(4) C(13)–O(3) 1.388(4)
P(2)–O(6) 1.489(3) P(4)–O(8) 1.505(3) P(2)–C(2) 1.816(4) P(4)–C(4) 1.814(3) C(2)–C(6) 1.515(5) C(4)–C(8) 1.511(4) C(9)–O(1) 1.488(5) C(10)–O(3) 1.440(4)
Bond angles (°) P(1)–C(1)–C(5) 114.3(3) P(3)–C(3)–C(7) 111.5(2) C(11)–O(1)–C(9) 114.8(2) O(5)–P(1)–C(5) 113.3(1) O(6)–P(2)–C(2) 114.1(1)
P(2)–C(2)–C(6) 110.5(3) P(4)–C(4)–C(8) 115.9(3) C(13)–O(3)–C(10) 115.1(3) O(7)–P(3)–C(3) 112.9(2) O(8)–P(4)–C(4) 114.5(2)
standing up and with two hydroxy-connected ones flattened. The distances between phosphine atoms, for P1–P2, 11.189(1) A for P1–P3, 9.512(1) A 8.807(1) A for P1–P4, 9.222(1) A for P2–P3, and 14.793(1) A for P2–P4, are too long for chelating coordination. The cone di-O-propylated phosphine oxide (4) was converted to 1,3-alternate tetra-O-propylated phosphine oxide (3a) in 91% yield by the reaction with K2 CO3 and n-PrI. The conformational flexibility of calix[4]arene derivatives mainly arises from an oxygen-through annulus rotation, which is sterically hindered by bulky alkoxy moiety larger than propoxy [22]. It is known that the conformational outcome is determined in the alkylation step and is strongly dependent on a cation of a base employed [23]. Since it is reported that 1,3-alternate conformers show high affinity for potassium cation [23,24], the conformer distribution would be controlled by the alkali metal cations which act as the metal template in the step where the conformation is immobilized. 3.2. Synthesis of tetraphosphinocalix[4]arene tetrapropyl- and benzyl ether (5) adopting 1,3-alternate conformation Reduction of 3a with PhSiHCl2 in THF was carried out to afford 5,11,17,23-tetrakis(diphenylphosphinoylmethyl)-25,26,27,28-tetrapropoxycalix[4]arene (5a) in 69% yield (Eq. (1)). Similarly, tetrabenzyloxy analogue (5b) was obtained in 70% yield from 3b. In this step, the use of PhSiH3 or Ph2 SiH2 as reducing reagent resulted in considerable formation of undesired PPh2 H as a side product via cleavage of the P–C (benzylic) bond. FDMS spectrum of 5a and 5b exhibited peaks at 1384 and 1577, respectively, displaying the expected isotopic profiles of the corresponding molecular ion. In the 31 P{1 H} NMR spectrum, one sharp signal appeared at )11.5 ppm for 5a and )11.2 ppm for 5b, confirming the expected alkyl diarylphosphine formation. 1 H and 13 C{1 H} NMR spectra of 5 displayed a singlet peak for
the bridging methylene protons at 3.24 ppm (for 5a) or 3.41 ppm (for 5b). A sole peak for the bridging methylene carbons at 36.0 ppm (for 5a) or 36.8 ppm (for 5b) appeared. These results were in full agreement with a 1,3-alternate conformation of compound 5 [17,18]. To the best of our knowledge, compound 5 is the first example of phosphinocalix[4]arene fixed in the 1,3-alternate conformation.
ð1Þ
3.3. Coordinative properties of 1,3-alternate tetraphosphinocalix[4]arene (5a) with Ru(II) complex To investigate the coordinative properties of the novel 1,3-alternate phosphinocalix[4]arene compound (5), complexation with Ru(II) was carried out. The reaction of 5a with 2 equiv. of [RuCl2 (p-cymene)]2 in CH2 Cl2 afforded the tetranuclear ruthenium complex 6 in quantitative yield (Eq. 2). The ESI-MS spectrum of 6 exhibits two intense signals for [M + H + H2 O]þ (m=z ¼ 2629) and [M]þ (m=z ¼ 2610), indicating the tetranuclear structure. The 31 P{1 H} NMR analysis of 6 indicated that all the phosphino moieties coordinated to Ru(II) center were equivalent and showed a resonance at 30.7 ppm, which is very close to that of Ru-mono phoshinocalix[4]arene complex at 30.3 ppm [25]. As expected, each phosphino group in the tetraphosphine 6 served as a monodentate ligand. The 1 H and 13 C{1 H} NMR spectra of 6 showed singlet proton resonance at 2.72 ppm and a singlet carbon resonance at 36.9 ppm assignable to the bridging methylene group. In the NMR spectra, all the four propoxy groups of the calix[4]arene and the four p-cymene groups were equivalent on the NMR time scale. These spectroscopic observations indicated that the compound 6 retained the original 1,3-alternate conformation in solution state.
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4. Supplementary material Complete crystallographic data in CIF format. References [1] (a) C.D. Gutsche, in: J.F. Stoddart (Ed.), Calixarenes Revisited in Monographs in Supramolecular Chemistry, Royal Society of Chemistry, Cambridge, 1998; (b) C.D. Gutsche, in: J.F. Stoddart (Ed.), Calixarenes in Monographs in Supramolecular Chemistry, Royal Society of Chemistry, Cambridge, 1989; (c) V. B€ ohmer, Angew. Chem., Int. Ed. Engl. 34 (1995) 713; (d) S. Shinkai, Tetrahedron 49 (1993) 8933; (e)Calixarenes 2001 Z. Asfari, V. B€ ohmer, J. Harrowfield, J. Vicens, Kluwer, Dordrecht, The Netherlands, 2001; (f)Calixarenes in Action L. Mandolini, R. Ungaro, Imperial College Press, London, UK, 2000. [2] (a) C.D. Gutsche, P.A. Reddy, J. Org. Chem. 56 (1991) 4783; (b) W. Verboom, S. Datta, Z. Asfari, S. Harkema, D.N. Reinhoudt, J. Org. Chem. 57 (1992) 5394; (c) K. Iwamoto, K. Araki, S. Shinkai, J. Chem. Soc., Perkin Trans. 2 (1992) 2109. [3] C.D. Gutsche, L. Bauer, J. Am. Chem. Soc. 107 (1985) 6052. [4] (a) For examples A. Ikeda, S. Shinkai, J. Am. Chem. Soc. 116 (1994) 3102; (b) P.D. Beer, M.G.B. Drew, P.A. Gale, P.B. Leeson, M.I. Ogden, J. Chem. Soc., Dalton Trans. (1994) 3479; (c) J.-a. Perez-Adelmar, H. Abraham, C. Sanchez, K. Rissanen, P. Prados, J. de Mendoza, Angew. Chem. Int. Ed. 35 (1996) 1009; (d) R. Ungaro, A. Arduini, A. Casnati, A. Pocchini, F. Ugozzoli, Pure Appl. Chem. 68 (1996) 1213; (e) Parzuchowski, V. B€ ohmer, S.E. Biali, I. Thondorf, Tetrahedron: Asymmetr. 11 (2000) 2393; (f) A. Ikeda, T. Tsudera, S. Shinkai, J. Org. Chem. 62 (1997) 3568; (g) R.J.W. Lugtenberg, R.J.M. Egberink, J.F.J. Engbersen, D.N. Reinhoudt, J. Chem. Soc., Prekin Trans. 2 (1997) 1353; (h) S. Shimizu, A. Moriyama, K. Kito, Y. Sasaki, J. Org. Chem. 68 (2003) 2187, and references cited therein. [5] (a) J.P. Collman, L.S. Hegedus, J.R. Norton, R.G. Finke, Principles and Application of Organotransition Metal Chemistry, University Science Books, Mill Valley, CA, 1987; (b) L.H. Pignolet (Ed.), Homogeneous Catalysis with Metal Phosphine Complexes, Plenum Press, New York, 1983. [6] (a) K. Takeneka, Y. Obora, L. Jiang, Y. Tsuji, Organometallics 21 (2002) 1158; (b) F. Plourde, K. Gilbert, J. Gagnon, P.D. Harvey, Organometallics 22 (2003) 2862; (c) C. Wieser, C.B. Dielman, D. Matt, Coord. Chem. Rev. 165 (1997) 93, and references cited therein. [7] (a) For selected recent examples C. Dieleman, S. Steyer, C. Jeunesse, D. Matt, J. Chem. Soc., Dalton Trans. (2001) 2508; (b) C. Jeunesse, C. Dieleman, S. Steyer, D. Matt, J. Chem. Soc., Dalton Trans. (2001) 881; (c) F.J. Parlevliet, C. Kiener, J. Fraanje, K. Goubitz, M. Lutz, A.L. Spek, P.C.J. Kamer, P.W.N.M. van Leeuwen, J. Chem. Soc., Dalton Trans. (2000) 1113; (d) C.J. Cobley, D.D. Ellis, G. Orpen, P.G. Pringle, J. Chem. Soc., Dalton Trans. (2000) 1109; (e) C.B. Dieleman, C. Marsol, D. Matt, N. Kyritsakas, A. Harriman, J.-P. Kintzinger, J. Chem. Soc., Dalton Trans. (1999) 4139; (f) P. Faidherbe, C. Wieser, D. Matt, A. Harriman, A. De Cian, J. Fischer, Eur. Inorg. Chem. (1998) 451; (g) Z. Csok, G. Szalontai, G. Czira, L. Kollar, J. Organomet. Chem. 570 (1998) 23.
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[8] (a) For example X. Fang, B.L. Scott, J.G. Watkin, C.A.G. Carter, G.J. Kubas, Inorg. Chim. Acta 317 (2001) 276; (b) I.A. Bagatin, D. Matt, H. Th€ onnessen, P.G. Jones, Inorg. Chem. 38 (1999) 1585; (c) S. Shimizu, S. Shirakawa, Y. Sasaki, C. Hirai, Angew. Chem., Int. Ed. Engl. 39 (2000) 1256; (d) K. Takenaka, Y. Obora, L. Jiang, Y. Tsuji, Bull. Chem. Soc. Jpn. 74 (2001) 1709; (e) F. Hamada, T. Fukugaki, K. Murai, G.W. Orr, J.L. Atwood, J. Incl. Phenom. 10 (1991) 57; (f) J. Gloede, S. Ozegowski, A. K€ ockritz, I. Keitel, Phosphorus, Sulfur, Silicon Relat. Elem. 131 (1997) 141; (g) S. Ozegowski, B. Costisella, J. Gloede, Phosphorus, Sulfur, Silicon Relat. Elem. 119 (1996) 209; (h) C. Wieser-Jeunesse, D. Matt, A. De Cian, Angew. Chem., Int. Ed. Engl. 37 (1998) 2861; (i) M. Vezina, J. Gagnon, K. Villeneuve, M. Drouin, P.D. Harvey, Organometallics 20 (2001) 273; (j) M. Lejeune, C. Jeunesse, D. Matt, N. Kyritsakas, R. Welter, J.P. Kintzinger, J. Chem. Soc., Dalton Trans. (2002) 1642. [9] W.L.F. Armarego, D.D. Perrin, Purification of Laboratory Chemicals, fourth ed., Butterworth-Heinemann, Oxford, 1997. [10] M. Almi, A. Arduini, A. Casnati, A. Pochini, R. Ungaro, Tetrahedron 45 (1989) 2177. [11] M.A. Benett, A.K. Smith, J. Chem. Soc., Dalton Trans. (1974) 233. [12] S H E L X 97: G.M. Sheldrick (1997). [13] D I R D I F 99: P.T. Beurskens, G. Admiraal, G. Beurskens, W.P. Bosman, R. de Gelder, R. Israel, J.M.M. Smits. The D I R D I F -99 program system, Technical Report of the Crystallography Laboratory, University of Nijmegen, The Netherlands. [14] D.T. Cromer, J.T. Waber, in: In International Tables for X-ray Crystallography, 4, Kynoch Press, Birmingham, UK, 1974. [15] J.A. Ibers, W.C. Hamilton, Acta Crystallogr. 17 (1964) 781. [16] (a) Crystal Structure Analysis Package, Rigaku and Rigaku/MSC, 9009 New Trails Dr. The Woodlands, TX 77381, USA, 2000– 2003; (b) D.J. Watkin, C.K. Prout, J.R. Carruthers, P.W. Betteridge, CRYSTALS Issue 10, Chemical Crystallography Laboratory, Oxford, UK, 1996. [17] K. Iwamoto, A. Ikeda, K. Araki, T. Harada, S. Shinkai, Tetrahedron 49 (1993) 9937, and references cited therein. [18] (a) J.O. Magrans, J. de Mendoza, M. Pons, P. Prados, J. Org. Chem. 62 (1997) 4518; (b) C. Jaime, J. de Mendoza, P. Prados, P.M. Nieto, C. Sanchez, J. Org. Chem. 56 (1991) 3372. [19] V. Kalchenko, L. Atamas, O. Klimchuk, V. Rudzevich, Y. Rudzevich, V. Boyko, A. Drapalio, S. Miroshnichenko, Phosphorus, Sulfur, Silicon Relat. Elem. 177 (2002) 1537. [20] V. Torgov, S. Erenburg, N. Bausk, E. Stoyanov, V. Kalchenko, A. Varnek, G. Wipff, J. Mol. Struct. 611 (2002) 131. [21] P.L.H.M. Cobben, R.J.M. Egberink, J.G. Bomer, P. Bergveld, W. Verboom, D.N. Reinhoudt, J. Am. Chem. Soc. 114 (1992) 10573. [22] (a) K. Iwamoto, K. Araki, S. Shinkai, J. Org. Chem. 56 (1991) 4955; (b) K. Araki, K. Iwamoto, S. Shinkai, T. Matsuda, Chem. Lett. (1989) 1747. [23] (a) For example P.D. Beer, M.G.B. Drew, P.A. Gale, P.B. Leeson, M.I. Ogden, J. Chem. Soc., Dalton Trans. (1994) 3479; (b) K. Iwamoto, S. Shinkai, J. Org. Chem. 57 (1992) 7066. [24] (a) A. Ikeda, S. Shinkai, J. Am. Chem. Soc. 116 (1994) 3102; (b) A. Ikeda, S. Shinkai, Tetrahedron Lett. 33 (1992) 7385. [25] I.A. Bagatin, D. Matt, H. Th€ onnessen, P.G. Jones, Inorg. Chem. 38 (1999) 1585.
Synthesis and complexation of tetrakis(diphenylphosphinomethyl)calix[4]arene adopting the 1,3-alternate conformation q Kazuhiro Takenaka, Yasushi Obora, Yasushi Tsuji
*
Catalysis Research Center, Division of Chemistry, Graduate School of Science, Hokkaido University, CREST, Japan Science and Technology Corporation (JST), Kitaku, Sapporo 060-0811, Japan Received 22 March 2004; accepted 27 March 2004 Available online 10 May 2004 Dedicated to Professor Tobin J. Marks on the occasion of his 60th birthday
Abstract Novel upper-rim modified tetraphosphinocalix[4]arenes (5a–b) adopting 1,3-alternate conformation have been synthesized. Reaction of 5,11,17,23-tetrachloromethyl-25,26,27,28-tetrahydroxycalix[4]arene (1) with Ph2 POEt gave 5,11,17,23-tetrakis(diphenylphosphinoylmethyl)-25,26,27,28-tetrahydroxycalix[4]arene (2). Tetra-O-substitution of 2 with n-propyl iodide or benzyl bromide in the presence of K2 CO3 carried out to afford 5,11,17,23-tetrakis(diphenylphosphinoylmethyl)-25,26,27,28-tetrapropoxy-(3a) or -benzyloxycalix[4]arene (3b), whereas di-O-substituted calix[4]arene, 5,11,17,23-tetrakis(diphenylphosphinoylmethyl)-25,27-dipropoxy-26,28-dihydroxycalix[4]arene (4), was obtained exclusively when Na2 CO3 was used as base. Reduction of 3a–b with PhSiHCl2 afforded 5,11,17,23-tetrakis(diphosphinomethyl)-25,26,27,28-tetrapropoxy-(5a) and -tetrabenzyloxycalix[4]arene (5b). 1 H and 13 C NMR analysis reveals that the phosphines (5a–b) and the tetra-O-substituted phosphine oxides (3a–b) adopt 1,3-alternate conformation, while the parent tetrahydroxy-(2) and the di-O-propylated phosphine oxide (4) adopt cone-conformation. The X-ray structure indicates that the calix[4]arene moieties in 4 a pinched-cone conformation in solid state. Complexation of the phosphine ligand (5a) with [RuCl2 (p-cymene)]2 affords the tetranuclear complexes, [{RuCl2 (p-cymene)}2 5a] (6), as 1,3-alternate conformer. Ó 2004 Elsevier B.V. All rights reserved. Keywords: Calix[4]arene; Phosphine; 1,3-Alternate conformation
1. Introduction Calix[4]arenes are macrocyclic compounds having cavity-shaped building block for ion-selective receptors, molecular sensors, highly ordered materials and catalysts through appropriate modification of the edges [1]. Therefore, a number of synthetic procedures for the selective functionalization of calix[4]arenes either at lower- or upper-rim have been developed and considerable attention has been directed for controlling the q
Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.ica.2004.03.037. * Corresponding author. Tel.: +81-11-706-9155; fax: +81-11-7069156. E-mail address: [email protected] (Y. Tsuji). 0020-1693/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2004.03.037
conformation [1,2]. Among the four conformer, that calix[4]arene may adopt (cone, partial cone, 1,2-alternate, and 1,3-alternate) [3], 1,3-alternate conformation in particular attracted significant interest in recent years as extremely selective extractants for large alkali metal cations in possible applications such as nuclear-waste remediation, sensing, and radiopharmacy [4]. On the other hand, it is well-known that the strong coordinating ability of phosphines to transition metals has been utilized in a wide variety of highly selective catalytic reactions [5]. A topic of growing interest deals with the combination of calix[4]arenes and transition metals [6] because the macrocyclic platforms bearing several phosphino groups are powerful tool for construction of multimetal species that contain discrete metal centers near the calix[4]arene cavities. In most
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studies, phosphine moieties are located at the lower-rim of the calix[4]arene scaffold [7], whereas some upper-rim modified phosphine ligands have been reported recently [6a,8]. It is noteworthy that so far no phosphinocalix[4]arenes fixed in 1,3-alternate conformation have been reported. In this paper, we report the first synthesis of upperrim modified tetraphosphinocalix[4]arene ligands adopting 1,3-alternate conformation from tetraphosphinoylcalix[4]arene precursors having cone or 1,3alternate conformations. Furthermore, Ru(II) complex formation with the phosphine ligand is described.
2. Experimental 2.1. General All reactions were performed under an argon atmosphere using Schlenk techniques. Solvents were dried and purified prior to use by standard method [9]. Compound 1 [10] and [RuCl2 (p-cymene)]2 [11] were synthesized according to the literature method. 1 H NMR (400.13 MHz), 13 C{1 H} NMR (100.61 MHz), and 31 P{1 H} NMR (161.98 MHz) spectra were recorded on a Bruker ARX 400 instrument. The 1 H NMR data are referenced relative to residual protiated solvent in CDCl3 at 7.24 ppm. 13 C NMR chemical shifts are reported relative to CDCl3 (77.0 ppm). The 31 P NMR data are given relative to external 85% H3 PO4 . ESI and FD mass spectra were recorded on a JEOL JMS-SX102A instrument at the GC–MS and NMR Laboratory of Faculty of Agriculture, Hokkaido University. Elemental analysis was performed at the Center for Instrumental Analysis of Hokkaido University. 2.2. Preparation of 5,11,17,23-tetrakis(diphenylphosphinoylmethyl)-25,26,27,28-tetrahydroxycalix[4]arene (2) To a solution of 1 [10] (1.96 g, 3.17 mmol) in toluene (100 ml) was added ethyl diphenylphosphinite (6.90 ml, 31.9 mmol), which was refluxed for 6 h. After cooling the reaction mixture, deposited off-white powders were filtered, washed twice with 15 ml of toluene and twice with 20 ml of ether, and then dried under vacuum. Yield: 3.15 g, 78%. M.p.: 189–192 °C. 1 H NMR, CDCl3 , d: 9.87 (s, 4H, OH ), 7.61–7.56 (m, 16H, m-Ph), 7.41–7.31 (m, 24H, o,p-Ph), 6.73 (d, 8H, 4 JHP ¼ 1:4 Hz, m-ArH ), 3.95 (d, 4H, 2 JHH ¼ 13:8 Hz, ArCH2 Ar), 3.34 (d, 8H, 2 JHP ¼ 13:3 Hz, CH2 P(O)Ph2 ), 3.19 (d, 4H, 2 JHH ¼ 13:8 Hz, ArCH2 Ar). 13 C{1 H} NMR, CDCl3 , d: 147.6 (d, 5 JCP ¼ 3:0 Hz, ArC attached to OH), 132.1 (d, 1 JCP ¼ 98:7 Hz, ipso-Ph), 131.7 (d, 4 JCP ¼ 2:3 Hz, p-Ph), 131.1 (d, 3 JCP ¼ 9:1 Hz, m-Ph), 130.6 (d, 3 JCP ¼ 5:0 Hz,
m-ArC), 128.4 (d, 2 JCP ¼ 11:7 Hz, o-Ph), 128.1 (d, JCP ¼ 2:2 Hz, o-ArC), 124.4 (d, 2 JCP ¼ 7:9 Hz, ArC attached to CH2 P(O)Ph2 ), 37.0 (d, 1 JCP ¼ 67:0 Hz, CH2 P(O)Ph2 ), 31.3 (ACH2 Ar). 31 P{1 H} NMR, CDCl3 , d: 30.1. FD-MS: m=z 1281 ([M + H]þ ), 1280 ([M]þ ). Anal. Calc. for C80 H68 O8 P4 H2 O: C, 73.95; H, 5.43. Found: C, 73.62; H, 5.67%.
4
2.3. Preparation of 5,11,17,23-tetrakis(diphenylphosphinoylmethyl)-25,26,27,28-tetrapropoxycalix[4]arene (3a) To a suspension of 3 (1.00 g, 0.78 mmol) and K2 CO3 (0.93 g, 6.7 mmol) in a mixture of THF (25 ml) and MeCN (25 ml) was added n-propyl iodide (1.95 ml, 20.0 mmol). The reaction mixture was refluxed for 2 days. After removal of the solvents, the resulting yellow solids were redissolved in CHCl3 , which was washed twice with 50 ml of 1 N HCl aq. and 50 ml of Na2 S2 O3 aq., and then dried over MgSO4 . The clear filtrate was evaporated to yield yellow solid, which was purified by column chromatography on alumina (Merck, Aluminium oxide 90 active neutral, activity stage I) using CH2 Cl2 /MeOH (50:1) as an eluent. The product was recrystallized from EtOH-n-hexane to give colorless crystals. Yield: 0.82 g, 73%. M.p.: 127–130 °C. 1 H NMR, CDCl3 , d: 7.62–7.56 (m, 16H, m-Ph), 7.49–7.45 (m, 8H, p-Ph), 7.40–7.35 (m, 16H, o-Ph), 6.50 (d, 8H, 4 JHP ¼ 1:7 Hz, m-ArH ), 3.37 (d, 8H, 2 JHP ¼ 13:6 Hz, CH2 P(O)Ph2 ), 3.214 (t, 8H, 3 JHH ¼ 7:3 Hz, OCH2 CH2 CH3 ), 3.206 (s, 8H, ArCH2 Ar), 1.33 (sextet, 8H, 3 JHH ¼ 7:3 Hz, OCH2 CH2 CH3 ), 0.77 (t, 12H, 3 JHH ¼ 7:4 Hz, OCH2 CH2 CH3 ). 13 C{1 H} NMR, CDCl3 , d: 155.6 (d, 5 JCP ¼ 3:5 Hz, ArC attached to OPrn ), 133.4 (d, 4 JCP ¼ 2:7 Hz, o-ArC), 132.5 (d, 1 JCP ¼ 98:1 Hz, ipso-Ph), 131.7 (p-Ph), 131.7 (m-ArC), 131.2 (d, 3 JCP ¼ 9:1 Hz, m-Ph), 128.3 (d, 2 JCP ¼ 11:6 Hz, o-Ph), 123.1 (d, 2 JCP ¼ 8:0 Hz, ArC attached to CH2 P(O)Ph2 ), 72.9 (OCH2 CH2 CH3 ), 37.5 (d, 1 JCP ¼ 67:4 Hz, CH2 P(O)Ph2 ), 36.6 (ArCH2 Ar), 23.3 (OCH2 CH2 CH3 ), 10.5 (OCH2 CH2 CH3 ). 31 P{1 H} NMR, CDCl3 , d: 30.3. FD-MS: m=z 1449 ([M]þ ), 724 ([M]2þ ). Anal. Calc. for C92 H92 O8 P4 H2 O: C, 75.29; H, 6.46. Found: C, 75.30; H, 6.54%. 2.4. Preparation of 5,11,17,23-tetrakis(diphenylphosphinoylmethyl)-25,26,27,28-tetrabenzyloxycalix[4]arene (3b) In the similar manner as 3a and 3b was obtained from 2 (0.85 g, 0.66 mmol), K2 CO3 (0.87 g, 6.29 mmol), and benzyl bromide (2.50 ml, 21.0 mmol) in a mixture of THF (25 ml) and MeCN (25 ml). Yield: 0.82 g, 80%. M.p.: 134–137 °C. 1 H NMR, CDCl3 , d: 7.48–7.28 (m, 52H), 7.09 (d, 8H, 3 JHH ¼ 7:4 Hz), 6.15 (d, 8H, 4 JHP ¼ 1:5 Hz, m-ArH ), 4.62 (s, 8H, OCH2 Ph), 3.19 (s, 8H, ArCH2 Ar), 2.93 (d, 8H, 2 JHP ¼ 13:3 Hz,
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CH2 P(O)Ph2 ). 13 C{1 H} NMR, CDCl3 , d: 154.5, 138.9, 133.6 (d, 4 JCP ¼ 2:6 Hz, o-ArC), 133.0 (d, 3 JCP ¼ 9:1 Hz, m-Ph), 132.5 (d, 1 JCP ¼ 98:1 Hz, ipso-Ph), 131.5 (d, 4 JCP ¼ 2:4 Hz, p-Ph), 131.1 (d, 3 JCP ¼ 9:1 Hz, m-Ph), 131.1 (m-ArC), 128.2 (d, 2 JCP ¼ 11:6 Hz, o-Ph), 128.0, 126.6, 126.3, 123.7 (d, 2 JCP ¼ 8:3 Hz, ArC attached to CH2 P(O)Ph2 ), 70.9 (OCH2 CH2 CH3 ), 37.1 (ArCH2 Ar), 36.6 (d, 1 JCP ¼ 67:1 Hz, CH2 P(O)Ph2 ). 31 P{1 H} NMR, CDCl3 , d: 30.5. FD-MS: m=z 1641([M]þ ), 821 ([M]2þ ). Anal. Calc. for C108 H92 O8 P4 H2 O: C, 78.15; H, 5.71. Found: C, 77.95; H, 5.99%. 2.5. Preparation of 5,11,17,23-tetrakis(diphenylphosphinoylmethyl)-25,27-dipropoxy-26,28-dihydroxycalix[4]arene (4) To a suspension of 2 (0.45 g, 0.35 mmol) and Na2 CO3 (0.33 g, 3.13 mmol) in a mixture of THF (10 ml) and MeCN (10 ml) was added n-propyl iodide (0.94 ml, 9.64 mmol). The reaction mixture was refluxed for 2 days. After removal of the solvents, the resulting yellow solids were redissolved in CHCl3 , which was washed twice with 30 ml of 1 N HCl aq. and 30 ml of brine, and then dried over MgSO4 . The clear filtrate was evaporated to yield yellow solid, which was purified by column chromatography on silica gel (WakosilÒ , C-300) using CH2 Cl2 /MeOH (20:1) as an eluent. The product was recrystallized from EtOH-n-hexane to give colorless crystals. Yield: 0.37 g, 77%. 1 H NMR, CDCl3 , d: 8.24 (s, 2H, OH ), 7.67–7.02 (m, 40H, Ph), 6.69 (br s, 4H, m-ArH ), 6.43 (br s, 4H, m-ArH ), 4.01 (d, 4H, 2 JHP ¼ 12:9 Hz, CH2 P(O)Ph2 ), 3.77 (t, 4H, 3 JHH ¼ 6:2 Hz, OCH2 CH2 CH3 ), 3.48 (d, 4H, 2 JHH ¼ 13:1 Hz, ArCH2 Ar), 3.01 (d, 4H, 2 JHP ¼ 12:9 Hz, CH2 P(O)Ph2 ), 2.82 (d, 4H, 2 JHH ¼ 13:1 Hz, ArCH2 Ar), 1.94 (sextet, 4H, 3 JHH ¼ 7:2 Hz, OCH2 CH2 CH3 ), 1.20 (t, 6H, 3 JHH ¼ 7:4 Hz, OCH2 CH2 CH3 ). 13 C{1 H} NMR, CDCl3 , d: 152.2 (d, 5 JCP ¼ 2:6 Hz, ArC attached to OPrn ), 150.9 (d, 5 JCP ¼ 3:1 Hz, ArC attached to OH), 133.2 (d, 4 JCP ¼ 1:9 Hz, o-ArC), 132.5 (d, 1 JCP ¼ 98:0 Hz, ipso-Ph), 131.8 (d, 1 JCP ¼ 98:8 Hz, ipso-Ph), 131.6 (p-Ph), 131.2 (d, 3 JCP ¼ 9:1 Hz, o-Ph), 130.8 (d, 3 JCP ¼ 9:1 Hz, o-Ph), 130.7 (d, 3 JCP ¼ 4:5 Hz, m-ArC), 130.3 (d, 3 JCP ¼ 3:1 Hz, m-ArC), 128.4 (d, 2 JCP ¼ 11:6 Hz, m-Ph), 128.2 (d, 2 JCP ¼ 11:6 Hz, m-Ph), 128.0 (d, 4 JCP ¼ 1:9 Hz, o-ArC), 127.5 (d, 2 JCP ¼ 7:9 Hz, ArC attached to CH2 P(O)Ph2 ), 120.8 (d, 2 JCP ¼ 8:0 Hz, ArC attached to CH2 P(O)Ph2 ), 78.2 (OCH2 CH2 CH3 ), 37.1 (d, 1 JCP ¼ 68:2 Hz, CH2 P(O)Ph2 ), 37.0 (d, 1 JCP ¼ 66:9 Hz, CH2 P(O)Ph2 ), 31.1 (ArCH2 Ar), 23.4 (OCH2 CH2 CH3 ), 10.8 (OCH2 CH2 CH3 ). 31 P{1 H} NMR, CDCl3 , d: 30.4, 30.3. FD-MS: m=z 1365 ([M + H]þ ), 1364 ([M]þ ), 683 ([M + H]2þ ), 682 ([M]2þ ). Anal. Calc. for C86 H80 O8 P4 2H2 O: C, 73.70; H, 6.04. Found: C, 73.33; H, 6.04%.
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2.6. Preparation of 5,11,17,23-tetrakis(diphenylphosphinomethyl)-25,26,27,28-tetrapropoxycalix[4]arene (5a) To a suspension of 3a (0.50 g, 0.35 mmol) in 20 ml of dry THF was added phenyldichlorosilane (2.10 ml, 14.4 mmol). The reaction mixture was heated at 70 °C for 18 h. Then, to the resulting orange solution was added 12.5 ml of degassed MeOH in order to decompose the residual PhSiHCl2 , which was stirred for 30 min at ambient temperature. The reaction solution was evaporated to yield a deep yellow solution, which was recrystallized from degassed CH2 Cl2 /degassed MeOH. The off-white powders formed were collected by filtration and washed four times with 5.0 ml of degassed MeOH, followed by drying under vacuum. Yield: 0.33 g, 69%. 1 H NMR, CD2 Cl2 , d: 7.41–7.36 (m, 16H, mPh), 7.34–7.29 (m, 24H, o,p-Ph), 6.69 (d, 8H, 4 JHP ¼ 1:0 Hz, m-ArH ), 3.37 (s, 8H, CH2 PPh2 ), 3.37 (t, 8H, 3 JHH ¼ 7:3 Hz, OCH2 CH2 CH3 ), 3.24 (s, 8H, ArCH2 Ar), 1.51 (sextet, 8H, 3 JHH ¼ 7:3 Hz, OCH2 CH2 CH3 ), 0.91 (t, 12H, 3 JHH ¼ 7:4 Hz, OCH2 CH2 CH3 ). 13 C{1 H} NMR, CD2 Cl2 , d : 154.6 (d, 5 JCP ¼ 3:2 Hz, ArC attached to OPrn ), 138.7 (d, 1 JCP ¼ 16:2 Hz, ipso-Ph), 133.0 (d, 4 JCP ¼ 1:6 Hz, o-ArC), 132.4 (d, 2 JCP ¼ 18:4 Hz, o-Ph), 130.3 (d, 3 JCP ¼ 6:8 Hz, m-ArC), 129.2 (d, 2 JCP ¼ 8:9 Hz, ArC attached to CH2 PPh2 ), 128.1 (pPh), 127.9 (d, 3 JCP ¼ 6:4 Hz, m-Ph), 72.8 (OCH2 CH2 CH3 ), 36.0 (ArCH2 Ar), 34.5 (d, 1 JCP ¼ 14:8 Hz, CH2 PPh2 ), 23.1 (OCH2 CH2 CH3 ), 10.1 (OCH2 CH2 CH3 ). 31 P{1 H} NMR, CD2 Cl2 , d: )11.5. FD-MS: m=z 1384 ([M]þ ). Anal. Calc. for C92 H92 O4 P4 CH3 OH: C, 78.79; H, 6.83. Found: C, 78.92; H, 6.80%.
2.7. Preparation of 5,11,17,23-tetrakis(diphenylphosphinomethyl)-25,26,27,28-tetrabenzyloxycalix[4]arene (5b) Similarly, 5b was prepared from 3b (0.60 g, 0.37 mmol) and phenyldichlorosilane (2.30 ml, 15.7 mmol) in THF. Yield: 0.40 g, 70%. 1 H NMR, CD2 Cl2 , d: 7.45– 7.40 (m, 24H), 7.31–7.16 (m, 36H), 6.37 (d, 8H, 4 JHP ¼ 1:0 Hz, m-ArH ), 4.74 (s, 8H, O-CH2 Ph), 3.41 (s, 8H, ArCH2 Ar), 2.79 (s, 8H, CH2 PPh2 ). 13 C{1 H} NMR (CD2 Cl2 ): d 153.7 (d, 5 JCP ¼ 3:2 Hz, ArC attached to OBz), 138.5 (Bz), 138.4 (d, 1 JCP ¼ 15:7 Hz, ipso-Ph), 133.3 (d, 4 JCP ¼ 1:8 Hz, o-ArC), 132.3 (d, 2 JCP ¼ 18:4 Hz, o-Ph), 131.6 (d, 3 JCP ¼ 6:2 Hz, m-ArC), 130.0 (d, 2 JCP ¼ 8:7 Hz, ArC attached to CH2 PPh2 ), 128.0 (p-Ph), 127.79 (d, 3 JCP ¼ 6:6 Hz, m-Ph), 127.76 (Bz), 126.3 (Bz), 126.2 (Bz), 71.1 (OCH2 Ph), 36.8 (ArCH2 Ar), 33.8 (d, 1 JCP ¼ 14:1 Hz, CH2 PPh2 ). 31 P{1 H} NMR, CD2 Cl2 , d: )11.2. FD-MS: m=z 1577 ([M]þ ), 788 ([M]2þ ). Anal. Calc. for C108 H92 O4 P4 CH3 OH: C, 81.32; H, 6.01. Found: C, 81.56; H, 5.99%.
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2.8. Preparation of [{RuCl2 (p-cymene)}4 (5a)] (6) A solution of [RuCl2 (p-cymene)]2 (25.5 mg, 41.6 lmol) in 5.0 ml of CH2 Cl2 was added to a solution of the ligand 5a (28.2 mg, 20.4 lmol) in 5.0 ml of CH2 Cl2 . The resulting red solution was stirred for 3 h at room temperature. The solvent was concentrated under reduced pressure to ca. 2 ml and n-hexane (20 ml) was added to yield a reddish-orange powder. Yield: 53.5 mg, quant. 1 H NMR, CD2 Cl2 , d: 7.55 (br t, 16H, o-Ph, ), 7.40 (br t, 8H, p-Ph, 3 JHH ¼ 7:6 Hz), 7.28 (br t, 16H, oPh, 3 JHH ¼ 7:6 Hz), 5.75 (s, 8H, m-ArH ) 5.20 and 5.07 (2d, AA0 BB0 spin system, 16H, ArH of p-cymene), 3.57 (d, 8H, 2 JHP ¼ 8:4 Hz, CH2 PPh2 ), 2.72 (s, 8H, ArCHAr), 2.63 (t, 8H, 3 JHH ¼ 7:1 Hz, OCH2 CH2 CH3 ), 2.39 (septet, 4H, 3 JHH ¼ 6:9 Hz, p-Me-C6 H4 -CH (CH3 )2 ), 1.79 (s, 12H, p-CH3 -C6 H4 -Pri ), 0.86 (d, 24H, 3 JHH ¼ 6:9 Hz, p-Me-C6 H4 -CH(CH3 )2 ), 0.66 (sextet, 8H, 3 JHH ¼ 7:2 Hz, OCH2 CH2 CH3 ), 0.42 (t, 12H, 3 JHH ¼ 7:5 Hz, OCH2 CH2 CH3 ). 13 C{1 H} NMR, CD2 Cl2 , d: 155.0 (d, 5 JCP ¼ 3:5 Hz, ArC attached to OPrn ), 133.5 (d, 3 JCP ¼ 8:5 Hz, o-Ph), 132.3 (d, 4 JCP ¼ 2:7 Hz, o-ArC), 131.9 (d, 1 JCP ¼ 42:9 Hz, ipsoPh), 130.4 (d, 3 JCP ¼ 3:9 Hz, m-ArC), 129.8 (d, 4 JCP ¼ 1:9 Hz, p-Ph), 127.1 (d, 2 JCP ¼ 9:5 Hz, m-Ph), 126.2 (d, 2 JCP ¼ 12:4 Hz, ArC attached to CH2 PPh2 ), 107.2 (ipso-ArC attached to Pri ), 93.7 (ipso-ArC attached to Me), 89.7 (d, 2 JCP ¼ 4:0 Hz, ArC of p-cymene), 85.1 (d, 2 JCP ¼ 5:3 Hz, ArC of p-cymene), 71.5 (OCH2 CH2 CH3 ), 36.9 (ArCH2 Ar), 29.6 (p-Me-C6 H4 CH(CH3 )2 ), 29.0 (d, 1 JCP ¼ 23:8 Hz, CH2 PPh2 ), 21.9 (OCH2 CH2 CH3 ), 20.8 (p-Me-C6 H4 -CH(CH3 )2 ), 16.7 (pCH3 -C6 H4 - Pri ), 9.6 (OCH2 CH2 CH3 ). 31 P{1 H} NMR, CD2 Cl2 , d: 30.7. ESI-MS: m=z 2629 ([M + H + H2 O]þ ), 2610 ([M]þ ). Anal. Calc. for C132 H148 Cl8 O4 P4 Ru4 : C, 60.73; H, 5.71. Found: C, 60.95; H, 5.91%. 2.9. X-ray structure determination of 4 Prismatic crystals of 4 suitable for X-ray diffraction were obtained by slow evaporation of an ethanolic solution. The data were collected with Mo Ka radiation at )160 °C on a Rigaku Saturn CCD (k ¼ 0:71070 A) area detector with graphite monochromated Mo Ka radiation. An empirical absorption correction was applied. The structure was solved by direct methods using the program S H E L X -97 [12] and expanded using Fourier techniques [13]. Non-hydrogen atoms except some solvent molecules were refined anisotropically. Hydrogen atoms were refined using the riding model. The final cycle of full-matrix least-squares refinement on F 2 was based on 12733 observed reflections (I > 3:0rðIÞ) and 1118 variable parameters. A Sheldrick weighting scheme was used. The maximum and minimum peaks on the final difference Fourier map corresponded to 1.77 and respectively. Neutral atom scattering factors )0.96 e /A,
Table 1 Crystal data and structure refinements for complex 4 Empirical formula Formula weight Temperature (°C) Wavelength (A) Crystal system Space group Unit cell dimensions a (A) b (A) c (A) V (A3 ) Z Dcalc (g cm3 ) l (cm1 ) Crystal size (mm) Maximum 2h (°) Number of reflections collected Unique Parameters Refinements on RðI > 3rðIÞÞ wRðI > 3rðIÞÞ Rint (all data) Goodness-of-fit
C86 H80 O8 P4 5C2 H5 OH 1595.81 )160(1) 0.71070 triclinic P 1 (#2) 14.87(2) 15.575(10) 20.08(3) 4289.7(84) 2 1.235 1.51 0.20 0.10 0.10 55 33592 18616 1118 F2 0.069 0.180 0.031 1.841
were taken from Cromer and Waber [14]. Anomalous dispersion effects were included in Fc [15]. All calculations were performed using the C R Y S T A L S T R U C T U R E crystallographic software package (ver. 3.6) [16]. Details of the crystal data are given in Table 1. 3. Results and discussion 3.1. Synthesis of tetraphosphinoylcalix[4]arene tetraand dialkyl ether (3,4) adopting 1,3-alternate and coneconformations As a precursor of tetraphosphinocalix[4]arenes (5), tetraphosphinoylcalix[4]arenes (3) were prepared as shown in Scheme 1. First, the reaction of 5,11,17,23tetra(chloromethyl)-25,26,27,28-tetrahydroxycalix[4]arene (1) with ethyl diphenylphosphinite afforded 5,11,17,23tetrakis(diphenylphosphinoylmethyl)-25,26,27,28-tetrahydroxycalix[4]arene (2) in 78% yield. The 31 P{1 H} NMR of 2 showed a sole peak at 30.1 ppm assignable to an alkyldiaryl phosphine oxide. FD-MS spectrum of 2 showed the molecular ion peak (m=z ¼ 1280) as the base peak, and purity of the isolated compound was confirmed by elemental analysis. These analytical data indicate that 2 has four Ph2 P(O) groups on calix[4]arene backbone. It is well-known that conformation of calix[4]arenes can be easily evaluated by a 1 H NMR spectrum which shows different splitting patterns for the ArCH2 Ar protons: a pair of doublets for cone, two pairs of doublets for partial cone, a pair of doublets and a singlet for 1,2-alternate, and a single peak for 1,3-alternate conformations [17]. Moreover, de Mendoza and coworkers [18] reported that a signal of 13 C{1 H} NMR
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had cone-conformation as judged by a pair of doublet peaks due to the bridging methylene protons at 4.38 and 3.08 ppm [20].
Scheme 1.
arising from the bridging methylene carbon appears at near 31 ppm when two adjacent aryl groups are in the syn orientation, and near 37 ppm when they are in the anti orientation. Indeed, in 1 H and 13 C{1 H} NMR spectra of 2, the bridging methylene proton resonance appeared as two doublets with a geminal coupling (13.8 Hz) at 3.19 and 3.95 ppm and the bridging methylene carbon resonance afforded a singlet at 31.3 ppm. These data indicated that the parent tetrahydroxy derivative (2) adopted a cone-conformation, which would be stabilized by a circular array of hydrogen bonds involving the four OH groups [1,17,18]. Tetra-O-propylation of 2 with n-propyl iodide and K2 CO3 as a base in THF/MeCN (1:1) took place to give 5,11,17,23-tetrakis(diphenylphosphinoylmethyl)-25, 26,27,28-tetrapropoxycalix[4]arene (3a) in 73% yield (Scheme 1). The 31 P{1 H} NMR spectrum of 3a showed a solitary signal at 30.3 ppm and the FD-MS spectrum provided the molecular ion peak at m=z ¼ 1449. The observed 1 H and 13 C{1 H} NMR chemical shifts of the bridging methylene protons (one singlet at 3.21 ppm) and the bridging methylene carbons (one singlet at 36.6 ppm) revealed that 3 had a 1,3-alternate structure. Similarly, when benzyl bromide was used, the corresponding tetra-O-benzylation product (3b) was obtained in 80% yield as 1,3-alternate conformer. So far, no phosphinoylcalix[4]arenes fixed in 1,3-alternate conformation have been reported. Recently, Kalchenko and coworkers [19,20] reported the synthesis of diphenylphosphinoyl calix[4]arene derivative (3a0 ) as well as its dibutylphosphinoyl analogue (3c0 ) by the reaction of 5,11,17,23-tetra(chloromethyl)-25,26,27,28-tetrapropoxycalix[4]arene with alkyl diphenyl- or alkyl dibutylphosphinite, respectively. Although they did not mention about conformational preferences of 3a0 and 3c0 , the reported 1 H NMR data clearly showed that 3c0
On the contrary, when Na2 CO3 was used instead of K2 CO3 as a base in the reaction of 2 and n-propyl iodide, di-O-propylation took place exclusively to give 5,11,17,23-tetrakis(diphenylphosphinoylmethyl)-25,27dipropoxy-26,28-dihydroxy-calix[4]arene (4) in 77% yield. The 31 P NMR of 4 showed two singlet peaks at 30.4 and 30.3 ppm, and the FD-MS afforded the parent ion peak (m=z ¼ 1364), indicating that the selective diO-alkylation reaction proceeded. The NMR spectra of 4 displayed a pair of doublets at 3.48 and 2.82 ppm due to the bridging methylene protons and a singlet at 31.1 ppm for the corresponding carbons. These data indicated that the di-O-propylated product (4) was frozen into the cone-conformation in solution state. The X-ray crystallographic structure of 4 was shown in Fig. 1. Crystal data and selected atom distances and bond angles of 4 were summarized in Tables 1 and 2. The dihedral angles between the mean plane of the bridging methylene carbons and the aryl rings possessing P1, P2, P3, P4 are 103.38(9)°, 139.02(9)°, 108.34(9)°, and 135.11(9)°, respectively. The O1–O3 distance (4.544 A) is longer than that of O2–O4 (3.023 A) distance. Thus, the compound 4 has a pinched-cone conformation [21] in solid state with two propoxy-connected phenyl rings
Fig. 1. ORTEP drawing of compound 4 with thermal ellipsoids at 50% probability levels and the scheme of atom numbering. Hydrogen atoms are deleted for clarity.
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Table 2 and bond angles (°) for 4 Selected bond lengths (A) Bond length ( A) P(1)–O(5) 1.487(3) P(3)–O(7) 1.490(2) P(1)–C(1) 1.813(3) P(3)–C(3) 1.818(3) C(1)–C(5) 1.510(4) C(3)–C(7) 1.514(5) C(11)–O(1) 1.399(4) C(13)–O(3) 1.388(4)
P(2)–O(6) 1.489(3) P(4)–O(8) 1.505(3) P(2)–C(2) 1.816(4) P(4)–C(4) 1.814(3) C(2)–C(6) 1.515(5) C(4)–C(8) 1.511(4) C(9)–O(1) 1.488(5) C(10)–O(3) 1.440(4)
Bond angles (°) P(1)–C(1)–C(5) 114.3(3) P(3)–C(3)–C(7) 111.5(2) C(11)–O(1)–C(9) 114.8(2) O(5)–P(1)–C(5) 113.3(1) O(6)–P(2)–C(2) 114.1(1)
P(2)–C(2)–C(6) 110.5(3) P(4)–C(4)–C(8) 115.9(3) C(13)–O(3)–C(10) 115.1(3) O(7)–P(3)–C(3) 112.9(2) O(8)–P(4)–C(4) 114.5(2)
standing up and with two hydroxy-connected ones flattened. The distances between phosphine atoms, for P1–P2, 11.189(1) A for P1–P3, 9.512(1) A 8.807(1) A for P1–P4, 9.222(1) A for P2–P3, and 14.793(1) A for P2–P4, are too long for chelating coordination. The cone di-O-propylated phosphine oxide (4) was converted to 1,3-alternate tetra-O-propylated phosphine oxide (3a) in 91% yield by the reaction with K2 CO3 and n-PrI. The conformational flexibility of calix[4]arene derivatives mainly arises from an oxygen-through annulus rotation, which is sterically hindered by bulky alkoxy moiety larger than propoxy [22]. It is known that the conformational outcome is determined in the alkylation step and is strongly dependent on a cation of a base employed [23]. Since it is reported that 1,3-alternate conformers show high affinity for potassium cation [23,24], the conformer distribution would be controlled by the alkali metal cations which act as the metal template in the step where the conformation is immobilized. 3.2. Synthesis of tetraphosphinocalix[4]arene tetrapropyl- and benzyl ether (5) adopting 1,3-alternate conformation Reduction of 3a with PhSiHCl2 in THF was carried out to afford 5,11,17,23-tetrakis(diphenylphosphinoylmethyl)-25,26,27,28-tetrapropoxycalix[4]arene (5a) in 69% yield (Eq. (1)). Similarly, tetrabenzyloxy analogue (5b) was obtained in 70% yield from 3b. In this step, the use of PhSiH3 or Ph2 SiH2 as reducing reagent resulted in considerable formation of undesired PPh2 H as a side product via cleavage of the P–C (benzylic) bond. FDMS spectrum of 5a and 5b exhibited peaks at 1384 and 1577, respectively, displaying the expected isotopic profiles of the corresponding molecular ion. In the 31 P{1 H} NMR spectrum, one sharp signal appeared at )11.5 ppm for 5a and )11.2 ppm for 5b, confirming the expected alkyl diarylphosphine formation. 1 H and 13 C{1 H} NMR spectra of 5 displayed a singlet peak for
the bridging methylene protons at 3.24 ppm (for 5a) or 3.41 ppm (for 5b). A sole peak for the bridging methylene carbons at 36.0 ppm (for 5a) or 36.8 ppm (for 5b) appeared. These results were in full agreement with a 1,3-alternate conformation of compound 5 [17,18]. To the best of our knowledge, compound 5 is the first example of phosphinocalix[4]arene fixed in the 1,3-alternate conformation.
ð1Þ
3.3. Coordinative properties of 1,3-alternate tetraphosphinocalix[4]arene (5a) with Ru(II) complex To investigate the coordinative properties of the novel 1,3-alternate phosphinocalix[4]arene compound (5), complexation with Ru(II) was carried out. The reaction of 5a with 2 equiv. of [RuCl2 (p-cymene)]2 in CH2 Cl2 afforded the tetranuclear ruthenium complex 6 in quantitative yield (Eq. 2). The ESI-MS spectrum of 6 exhibits two intense signals for [M + H + H2 O]þ (m=z ¼ 2629) and [M]þ (m=z ¼ 2610), indicating the tetranuclear structure. The 31 P{1 H} NMR analysis of 6 indicated that all the phosphino moieties coordinated to Ru(II) center were equivalent and showed a resonance at 30.7 ppm, which is very close to that of Ru-mono phoshinocalix[4]arene complex at 30.3 ppm [25]. As expected, each phosphino group in the tetraphosphine 6 served as a monodentate ligand. The 1 H and 13 C{1 H} NMR spectra of 6 showed singlet proton resonance at 2.72 ppm and a singlet carbon resonance at 36.9 ppm assignable to the bridging methylene group. In the NMR spectra, all the four propoxy groups of the calix[4]arene and the four p-cymene groups were equivalent on the NMR time scale. These spectroscopic observations indicated that the compound 6 retained the original 1,3-alternate conformation in solution state.
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K. Takenaka et al. / Inorganica Chimica Acta 357 (2004) 3895–3901
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