THF [IrCl(cod)]2 + 6 P(CH2OH)3 2 [Ir(cod){P(CH2OH)3}3]Cl (1) 1 room temp. Water-soluble iridium and rhodium complexes with tris(hydroxymethyl)phosphine and their catalysis in biphasic hydrogenation and hydroformylation Atsushi Fukuoka,*a† Wataru Kosugi,a Fumiaki Morishita,a Masafumi Hirano,a Louise McCaffrey,b William Hendersonb and Sanshiro Komiya*a a Department of Applied Chemistry, Tokyo University of Agriculture and Technology, Koganei, Tokyo, 184-8588, Japan b Department of Chemistry, University of Waikato, Private Bag 3105, Hamilton, New Zealand Received (in Cambridge, UK) 28th October 1998, Accepted 5th February 1999 Novel water-soluble Ir and Rh complexes with tris(hydroxymethyl) phosphine catalyse the selective hydrogenation of the CNO bond of cinnamaldehyde and the hydroformylation of pent-1-ene both under biphasic conditions.The use of aqueous/organic biphasic systems is attracting growing interest in catalytic reactions by transition metal complexes.1 The biphasic systems have benefits in catalyst separation and recycling, and the reduction or elimination of organic solvents is also advantageous for the development of economical and environmentally friendly processes.The key for such biphasic catalysis is to use water-soluble phosphines as ligands. Since the launch of the commercial propylene hydroformylation process by Ruhrchemie/Rhône-Poulenc,2 sulfonated derivatives of PPh3 such as PPh2(C6H4-m-SO3Na) (TPPMS) and P(C6H4-m-SO3Na)3 (TPPTS) have been widely used as ligands in hydroformylation, hydrogenation, and related reactions catalysed by transition metals.1,3 Tris(hydroxymethyl)phosphine, P(CH2OH)3 (THMP) is a highly water-soluble phosphine and has unique reactivity towards a number of reagents to give functionalised hydroxymethylphosphines. 4 Although many transition metal complexes of THMP are known,5 there are limited examples of catalytic reactions using the THMP complexes. Chatt et al.reported the first examples of THMP complexes of Rh, Pd and Pt; however, these complexes showed low catalytic activities in hydrogenation and hydroformylation of olefins.5a Recently, Pringle and coworkers showed high efficiency of THMP complexes of Pt, Pd and Ni in catalytic hydrophosphination of formaldehyde,6 and biphasic hydrogenation of sorbic acid was reported using THMP complexes of Ru.7 In this study, we have prepared novel THMP complexes of Ir and Rh, and their catalytic performances have been tested for hydrogenation of cinnamaldehyde and hydroformylation of pent-1-ene.Reaction of [IrCl(cod)]2 (cod = cycloocta-1,5-diene) with THMP5c (P/Ir ratio = 3) in THF at room temperature under N2 readily precipitated a white powder, which was purified by recrystallisation from EtOH–Et2O to give [Ir(cod){P- (CH2OH)3}3]Cl 1 in 91% yield [eqn. (1)]. Complex 1 was characterised by analytical and spectroscopic methods.‡ Electrospray mass spectroscopy (ESMS) of 1 in MeOH at a cone voltage of 20 V gave a single peak at m/z 673 due to [Ir(cod)(THMP)3]+ with the same isotope pattern as calculated. In the 31P{1H} NMR of 1 in (CD3)2SO, only a singlet peak was observed at d 217.5, which was shifted lower than free THMP at d 225.7.A variable-temperature NMR study was performed using CD3OD as a solvent. Similarly, only a singlet peak was observed at d 217.6 with a half width of 5 Hz at 20 °C. On cooling to 280 °C, the singlet peak was gradually shifted lower to d 215.7 and slightly broadened (half width 12 Hz), and the NMR spectral change was reversible on warming again to 20 °C.The broadening of the peak suggests that 1 is fluxional in this temperature range. When THMP was added to 1, the peaks of 1 and THMP were independently seen at 20 °C in the 31P{1H} NMR, thus excluding the intermolecular exchange of the ligands. In accordance with the 31P{1H} NMR, the 1H NMR of 1 gave a doublet (JHP 4.5 Hz) due to CH2 of THMP at d 4.12 and a broad peak due to OH at d 5.53, and these peaks were shifted to lower field than those of free THMP [CH2 at d 3.85 (t, J 5.1 Hz) and OH at d 4.68 (q, J 5.1 Hz)]. The 1H NMR data including integrals and elemental analysis also support the formation of five-coordinate complex 1.One might expect that [IrCl(THMP)2]2 or [Ir- (cod)(THMP)2]Cl would also be formed in the reaction of [IrCl(cod)]2 and THMP; however, in the presence of 3 equiv. of THMP complex 1 is exclusively formed. This type of [Ir(cod)L3]+ complex is known for compact phosphines,8a and [Ir(cod)(PMe3)3]Cl was prepared from the reaction of [IrCl- (cod)]2 with 3 equiv. of PMe3.8b Similar reaction of [RhCl(cod)]2 with THMP (P/Rh ratio = 3) in THF at room temperature under N2 gave a complicated mixture, and isolation of products was unsuccessful.On the other hand, the reaction with 4 equiv. of THMP precipitated a yellow powder, and recrystallisation from EtOH–CH2Cl2 gave cis-[RhH2{P(CH2OH)3}4]Cl 2 in 74% yield based on Rh.‡ The formation of the hydride complex was unexpected; however, the presence of Rh–H was confirmed by 1H NMR and IR.In the 1H NMR of 2 in (CD3)2SO, RhH was observed at d211.26 with couplings to Rh and P (JRhH 120.8 Hz, JPH 12.9 Hz), which is characteristic for cis-[RhH2(PR3)4]+.9 In the IR spectrum, nRhH appeared at 2007 cm21. The 31P{1H} NMR gave two doublets of triplets with equal intensity at d 21.2 (JRhP 86, JPP 22 Hz) and 34.9 (JRhP 97, JPP 22 Hz), showing the cis geometry of 2.ESMS and elemental analysis also support the structure of 2. The hydride origin is not clear at this moment. THMP itself is a reactive agent, and the reactions of THMP such as deprotonation and elimination of formaldehyde were reported in the preparation of THMP complexes of Pt6 and Ru.5f Other possible hydride sources are the cod ligand, the solvents (THF, EtOH, Et2O and CH2Cl2), or a trace of water included in the reaction mixture.§ The possibility of cod is excluded, since a quantitative amount of free cod was observed in the reaction of [RhCl(cod)]2 with THMP (P/Rh = 4) in (CD3)2SO.In the 31P{1H} NMR of this reaction, the resonances of 2 and THMP oxide (d 44) were detected, thus suggesting that a trace of water can react with Ru intermediates to give 2 and THMP oxide. When D2O was added to 2 in (CD3)2SO, the Rh–H and OH peaks in 1H NMR were significantly decreased, and the peaks completely disappeared in pure D2O.This result shows a facile † Present address: Catalysis Research Center, Hokkaido University, Sapporo 060-0811, Japan. E-mail: fukuoka@cat.hokudai.ac.jp Chem. Commun., 1999, 489–490 489Ph O Ph OH Ph O Ph H2 OH H2 3 4 5 6 H–D exchange of Rh–H with D2O, indicating that Rh–H has protic character. Hydrogenation of cinnamaldehyde 3 in the biphasic water/ benzene media was performed as a test reaction of the catalysis using complex 1 (Scheme 1).Selective hydrogenation of the CNO bond would give cinnamyl alcohol 4, which is more valuable than hydrocinnamaldehyde 5 from the CNC bond hydrogenation and hydrocinnamyl alcohol 6 from the complete hydrogenation of both the CNO and CNC bonds.3c Under the conditions of 100 °C and 30 atm, with complex 1, the conversion of 3 was 90% and the proportion of 4 : 5 : 6 was 76 : 2 : 22 (Table 1, run 1). At the H2 pressure of 100 atm, the proportion was 88 : 2 : 9, with 99% conversion (run 2).The addition of 5 equiv. of THMP to 1 at 90 atm decreased the conversion to 20%; however, the selectivity of 4 was increased to 97% (run 3). Interestingly, under the conditions of 125 °C and 90 atm in the presence of 5 equiv. of THMP, the conversion was 97% and the proportion of 4 : 5 : 6 was 97 : 2 : 0.3 (run 4). The role of added THMP in the catalytic mechanism is being studied. Rh complex 2 catalysed the biphasic hydroformylation of pent-1-ene to give oxo aldehydes. Under the conditions of 100 °C, CO/H2 20 atm/20 atm, water/benzene 4 ml/4 ml, and substrate/catalyst ratio 90, pent-1-ene was quantitatively converted to hexanal (43% yield) and 2-methylpentanal (57%) in 20 h.In all the catalytic hydrogenation and hydroformylation reactions, the substrates and products were recovered from the benzene layer, and the catalysts were present in the water layer. In order to test the catalyst stability three catalytic runs were repeated, recycling the same water layer containing 1 or 2.No decrease was observed in the reaction rates and product selectivities, showing the reliable stability of THMP complexes 1 and 2. We are grateful to the Asia 2000 Foundation of New Zealand for financial support. Notes and references ‡ Selected data: 1: 1H NMR [300 MHz, (CD3)2SO]: d 2.12 and 2.41 (br, total 8H, cod CH2), 3.90 (br, 4H, cod CHN), 4.12 [d, JPH 4.5 Hz, 18H, P(CH2OH)3], 5.53 [br, 9H, P(CH2OH)3]. 31P{1H} NMR [122 MHz, (CD3)2SO]: d 217.5 (s).ESMS (20 V, MeOH) m/z 673 ([Ir(cod){P- (CH2OH)3}3]+). Mp 115–117 °C (decomp.). Anal. Found: C, 29.05; H, 5.41. Calc. for C17H39O9P3ClIr: C, 28.84; H, 5.55%. Molar electrical conductivity L (MeOH, 24 °C) 9.05 S cm2 mol21. Halogen check (the Beilstein test): positive. Air-stable. Soluble in water, MeOH, EtOH, 2-PrOH, and Me2SO, but insoluble in benzene, hexane, acetone, or CH2Cl2. 2: IR (KBr, cm21) 2007 (nRhH). 1H NMR [300 MHz, (CD3)2SO]: d 211.26 (m, JRhH 120.8, JPH 12.9 Hz, 2H, RhH), 3.91 and 3.99 [d, JPH 4.5 Hz, total 24H, P(CH2OH)3], 5.45 and 5.51 [br, 12H, P(CH2OH)3]. 31P{1H} NMR [122 MHz, (CD3)2SO]: d 21.2 (dt, JRhP 86, JPP 22 Hz, 2P, trans to H), 34.9 (dt, JRhP 97, JPP 22 Hz, 2P, trans to P).ESMS (20 V, MeOH) m/z 601 ([RhH2{P(CH2OH)3}4]+). Mp 145–150 °C (decomp.). Anal. Found: C, 22.48; H, 5.82. Calc. for C12H38O4P4ClRh: C, 22.64; H, 6.02%. L (MeOH, 24 °C) 8.04 S cm2 mol21. Halogen check (the Beilstein test): positive.Stability and solubility are similar to those of 1. § The THF solvent had no contamination of alcohols, which was confirmed by NMR. In the preparation of 2, RhCl(THMP)4 was not observed in the crude product but 2 was already formed in 70–80% yield with other uncharacterised species. 1 B. Cornils and W. A. 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Merola and R. T. Kacmarcik, Organometallics, 1989, 8, 778. 9 R. A. Jones, F. M. Real, G. Wilkinson, A. M. R. Galas, M. B. Hursthouse and K. M. A. Malik, J. Chem. Soc., Dalton Trans., 1980, 511. Communication 8/08350I Scheme 1 Table 1 Biphasic hydrogenation of cinnamaldehyde catalysed by [Ir- (cod){P(CH2OH)3}3]Cl 1a Selectivity (%)d Conv. Run THMP/1b H2 c/atm T/°C of 3 (%) 4 5 6 1 0 30 100 90 76 2 22 2 0 100 100 99 88 2 9 3 5 90 100 20 97 3 0 4 5 90 125 97 97 2 0.3 a Conditions: 1 0.015 mmol, cinnamaldehyde 7.5 mmol, water/benzene = 5 ml/5 ml, reaction time 24 h. b Molar ratio of added THMP to 1. c Initial pressure at room temperature. d (Mol of product)/(mol of converted 3) 3 100. 490 Chem. Commun., 1999, 489–490