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Journal of the Chilean Chemical Society

versión On-line ISSN 0717-9707

J. Chil. Chem. Soc. v.51 n.2 Concepción jun. 2006

http://dx.doi.org/10.4067/S0717-97072006000200008 

 

J. Chil. Chem. Soc., 51, Nº 2 (2006) , pags: 875-878

 

SYNTHESIS AND COORDINATION PROPERTIES OF CHIRAL BIDENTATE P,O-DONOR LIGANDS

 

OSCAR DIAZ, RAUL CONTRERAS AND MAURICIO VALDERRAMA*

Departamento de Química Inorgánica, Facultad de Química, Pontificia Universidad Católica de Chile, Santiago, Chile.


ABSTRACT

Reaction of the chiral compound (S)-(+)-BrCH2CHMeCH2OH with Ph2PK in the presence of lithium diisopropylamide (LDA) and BH3/THF yields the monophosphine (S)-Ph2P(BH3)CH2CHMeCH 2OH(1). The reaction of 1 with ClOSO2Me/Et3N or NaH/MeI gives rise to the formation of the general compound (S)-Ph2P(BH3)CH2CHMeCH 2OR [Cp*IrCl2(PPh2CH2CHMeCH 2OR-P)], which by treatment with pyrrolidine affords (S)-Ph2PCH2CHMeCH2 OR [R = SO2Me (4), Me (6)]. The monophophines 4, 6 and (S)-PPh2CH2CHMeCH2 OH react with [{Cp*IrCl(µ-Cl)}2] to give the neutral compounds [Cp*IrCl2(PPh2CH2CHMeCH 2OR-P)], where only the compound with R = H (7) was fully characterized. Complex 7 reacts with AgBF4 yielding the cationic complex [Cp*IrCl(PPh2CH2CHMeCH2 OH-P,O)]BF4 (8) in which the ligand acts in its bidentate form. Similar synthetic results were obtained using [{Cp*IrI(µ-I)}2] as starting complex .

KEY WORDS : Iridium, chiral ligands, chiral phiosphine, hemilabile ligands.


INTRODUCTION

There has been considerable interest in the synthesis of chelating ligands that contain mixed donor sets. Of particular interest is the behaviour of chelating phosphino- amine, phosphino-ether and phosphino-alcohol ligands, considering that the combination of soft and hard donor atoms can provide free-coordination sites by the decoordination of the most labile bond atoms.1-8 In the use of P,O-donor species, the oxygen donors may be regarded as intramolecular solvent molecules forming only weak metal-oxygen bonds which may be easily cleaved reversibly. For this reason P,O ligands are also called hemilabile chelate ligands.1The formation of empty coordination sites are made available when needed in the course of the catalytic cycles without separation of the oxygen donors from the complex fragment. Examples of this properties were reported by Lindner et al.9 with the phosphino-ether complex [(h2-C6Me6)RuH(P,O)][BF 4], which catalyzes a ring-opening metathesis polymerization, and by Kadyrov, Börner et al.10 with the phosphino-alcohol complex [Rh(cod)(1,4-bis(diphenylphosphino)butane-2,3-diol)]BF 4 which is active in catalytic asymmetric hydrogenation reactions.

Recently, we have described the reaction of the chiral ligand S-Ph2PCH2CHMeCH2OH with the dinuclear complexes [Cp*RhCl2]2 and [(C6Me6)RuCl2] 2, showing that the phophine-alcohol ligand acts as a monodentate P-donor or a bidentate P,O-donor ligand. Also, the stereoselective h2-coordination of the ligand was proved by circular dicroism spectra and by the crystal X-ray structure determination of complex (SRh, SC)- [Cp*RhCl(h2-PPh2CH2 CHMeCH2OH-P,O)]BF4.11,12In this paper we describe the synthesis of new phosphines that contain a chiral carbon chain bonded to an oxygen moiety of formula (S)-Ph2PCH2C*HMeCH2 OR ( R = H, Me, OSO2Me). The reaction of these compounds with the dinuclear complex [Cp*IrX(µ-X)}2] (X = Cl, I) are discussed.

EXPERIMENTAL

General Data.

All reactions were routinely performed under a purified nitrogen atmosphere, by using standard Schlenk-tube techniques. Solvents were dried, distilled, and stored under a nitrogen atmosphere. The starting compound (S)-(-)-3-bromo-2-methyl-1-propanol was purchased from a commercial source. The starting complex [{Cp*IrX(µ-X)}2] (X = Cl, I)13 and the ligand (S)-Ph2PCH2CHMeCH2 OH11 were synthesized according to literature procedures. Carbon and hydrogen analyses were performed using a Fisons EA 1108 microanalyzer. FTIR spectra were recorded on a Bruker Vector-22 spectrophotometer using KBr pellets. 1H(200 MHz), 13C{1H}(50 MHz) and 31P{1H}((81 MHz) NMR spectra were recorded on Bruker AC-200P and Avance-400 spectrometers. Chemical shifts are reported in ppm relative to SiMe4 (1H) and 85% H3PO4 (31P, positive shifts downfield) as internal and external standards, respectively.

Synthesis of (S)-H3BPPh2CH2CH(Me)CH 2OH (1)

To a mixture of potassium diphenylphosphide (39.0 mL, 0.5 mol L-1 in THF; 19.6 mmol) and lithium diisopropylamide (LDA, 14.4 mL, 1.5 mol L-1 in cyclohexane; 21.5 mmol) at 0º C, a solution of (S)-(-)-3-bromo-2-methyl-1-propanol (3 g; 19.6 mmol) in tetrahydrofuran (30 mL) was added dropwise. After stirring the reaction mixture for 1 h at room temperature (r.t.), a solution of BH3 (25 mL, 1.0 mol L-1 in THF; 25 mmol) was added, and the mixture stirred again for 12 h at r.t. The solvent was removed by vacuum and the residue treated with a mixture of water (60 mL) and dichloromethane (100 mL). The organic layer was separated and dried with MgSO4. The solvent was evaporated to give a very viscous pale-yellow oil. Trace amount of Ph2PH [31P{1H} NMR (CDCl3, 295 K) d - 41.2 (s)], was eliminated by heating the mixture at 100 ºC in high vacuum. Yield 4.98 g (96 %). NMR (CDCl3, 295 K): 1H, d 0.91 [d, 3J(HH) = 6.4 Hz, 3H, Me], 2.0-2.1 (m, 2H, CHMe, HCP), 2.5-2.6 (m, 1H, HCP), 3.3-3.5 (m, 2H, H2CO), 7.3-7.6 (m, 10H, Ph). 31P{1H}, d 13.2 (s, br). 13C{1H}, d 18.53 [d, J(PC) = 5.3 Hz, CH3], 28.86 [d, J(PC) = 36.23 Hz, PCH2], 31.87 (s, CMe), 67.80 [d, J(PC) = 9.56 Hz, CH2O].

Synthesis of (S)-H3BPPh2CH2CH(Me)CH 2OSO2Me (2)

To a solution of 1 (3.9 g; 14.3 mmol) and triethylamine (4.4 mL; 32 mmol) in dichloromethane (30 mL) at 40ºC, MeSO2Cl (2.5 mL; 28.6 mmol) was added dropwise. During the addition a white solid was formed. After stirring for 24 h at r.t. the mixture was treated with 50 mL of water. The organic layer was washed several times with water and dried with MgSO4. The solution was evaporated to dryness to give a yellow oil, which was chromatographed on Silica gel 60 using chloroform as eluent. Yield 1.45 g (29 %) of viscous yellow oil. NMR (CDCl3, 295 K): 1H, d 1.03 [d, 3H, 3J(HH) = 6.6 Hz, MeC], 2.1-2.6 (m, 3H, HCMe, CH2CP), 2.93 (s, 3H, MeS), 4.08 [d, 3J(HH) = 4.9 Hz, 2H, H2CO], 7.3-7.8 (m, 10H, Ph). 31P{1H}, d 13.07 (s, br). 13C{1H}, d 18.6 [d, 3J(CP) = 5.9 Hz, CCH3], 28.7 [d, 1J(CP) = 36.0 Hz, PCH2], 29.4 [d, 2J(CP) = 1.8 Hz, CH], 37.2 (s, SCH3), 74.2 [d, 3J(CP) = 8.6 Hz, OCH2].

Synthesis of (S)-BrCH2CH(Me)CH2OSO2 Me (3)

To a solution of (S)-(-)-3-bromo-2-methyl-1-propanol (3 g; 19.6 mmol) and triethylamine (4.4 mL; 32 mmol) in dichloromethane (30 mL) at 40 ºC, MeSO2Cl (2.5 mL; 28.6 mmol) was added dropwise. During the addition a white solid was formed. After stirring for 24 h at r.t. the mixture was treated with 50 mL of water. After removal of the solvent by evaporation, the residue was heated at 100 ºC in high vacuum. Yield 3.27 g of a light brown liquid (72%). NMR (CDCl3, 295 K): 1H, d 1.01 [d, 3H, 3J(HH) = 6.8 Hz, MeC], 2.29 (m, 1H, HC), 2.95 (s, 3H, MeS), 3.38 (m, 2H, H2CBr), 4.08 (m, 2H, CH2O). 13C{1H}, d 15.24 (s, CH3C), 34.70 (s, CH3O), 36.06 (s, CH2Br), 37.08 (s, CH), 71.69 (s, CH2O).

Synthesis of (S)-Ph2PCH2CH(Me)CH2 OSO2Me (4)

The complexes can be prepared by the two methods described below.

(i) To a solution of 2 (560 mg, 1.6 mmol) in THF a large excess of pyrrolidine (10 mL) was added and the mixture heated at reflux 2 h. The solution was evaporated to dryness to give an oil residue, which was dissolved in n-pentane. The solution was filtered through silica gel and evaporated to form a yellow oil. Yield 240 mg (45%)

(ii) To a solution of 3 (1.27 g; 5.5 mmol) in THF (30 mL) at 50 ºC a solution of KPPh2 (11 mL, 0.5 mol L-1 in THF; 5.5 mmol) was added through a syringe. The mixture was stirred at r.t. for 12 h. The solution was evaporated to dryness and the oily residue treated with a mixture of toluene-water (50:50 mL). The organic layer was separated, dried with MgSO4 and evaporated to dryness in high vacuum. Yield 1.7 g (92%).

NMR (CDCl3, 295 K): 1H, d 1.16 [d, 3H, 3J(HH) = 6.2 Hz, MeC], 1.96 (m, 2H, PCH2), 2.25 (m, 1H, HC), 2.95 (s, 3H, MeS), 4.16 (m, 2H, H2CO), 7.2-7.6 (m, 10H, Ph). 31P, d - 22.70 (s). 13C{1H}, d 18.07 (d, 3J(PC) = 9.1 Hz, CH3C), 31.13 (d, 2J(PC) = 14.69 Hz, CH), 32.11 (d, 1J(PC) = 13.74 Hz, CH2P), 37.21 (s, OCH3), 74.70 (d, 3J(PC) = 10.57, CH2O).

Synthesis of (S)-H3BPPh2CH2CH(Me)CH 2OMe (5)

To a 250 mL three-necked, round-bottom flask equipped with a nitrogen inlet adapter, condenser and a septum, sodium hydride (106 mg; 4.39 mmol) and tetrahydrofuran (10 mL) were added. After heating the mixture to 45-50 ºC, a solution of methyl iodide (728 mg; 5.13 mmol) in THF (10 mL) was added via syringe. The septum was changed by a equal-pressure addition funnel, charged with compound 1 (1 g; 3.66 mmol) in THF (10 mL), and the solution was added dropwise for 30 min. During this time evolution of hydrogen was observed. The resulting mixture was refluxed for 30 min. The cooled mixture was treated with water to eliminate the excess of NaH, evaporated to dryness and the solid residue extracted with diethyl ether (2 x 20 mL). Evaporation of solvent gives a pale yellow oil. Yield 560 mg (54%). NMR (CDCl3, 295 K): 1H, d 0.93 [d, 3H, 3J(HH) = 6.5 Hz, MeC], 1.26 (s, 3H, MeO), 1.9-2.2 (m, 3H, HCMe, PCH2), 3.4-3.6 [m, 2H, H2CO], 7.4-7.7 (m, 10H, Ph). 31P{1H}, d 13.32 (s, br). 13C{1H}, d 1.04 (s, OCH3), 18.6 [d, 3J(CP) = 5.5 Hz, CCH3], 28.9 [d, 1J(CP) = 36.1 Hz, PCH2], 31.9 (s, CH), 67.8 [d, 3J(CP) = 9.5 Hz, OCH2].

Synthesis of (S)-PPh2CH2CH(Me)CH2 OMe (6)

A large excess of pyrrolidine (10 mL) was added to compound 5 (560 mg; 2.0 mmol). After heating at reflux for 2h, the mixture was evaporated to dryness to give a yellow oil, which was dissolved in n-pentane. This solution was filtered through Kieselguhr and evaporated to dryness to give a pale yellow oil. Yield 210 mg (45%). NMR (CDCl3, 295 K): 1H, d 1.05 [d, 3J(HH) = 6.6 Hz, 3H, MeC], 1.26 (s, 3H, MeO), 1.8-2.1 (m, 3H, HCH, CH2P), 3.5-3.6 (m, 2H, H2CO), 7.3-7.7 (m, 10H, Ph). 31P{1H}, d - 21.86 (s). 13C{1H}, d 1.04 (s OCH3), 18.3 [d, 3J(CP) = 9.4 Hz, CCH3], 32.7 [d, 1J(CP) = 13.5 Hz, PCH2], 33.6 [d, 2J(CP) = 12.2 Hz, CH], 68.8 [d, 3J(CP) = 9.3 Hz, OCH2].

Synthesis of [Cp*IrCl2(Ph2PCH2CHMeCH 2OH-P)] (7)

(S)-PPh2CH2CHMeCH 2OH (363 mg; 1.4 mmol) dissolved in tetrahydrofuran (10 mL), was added dropwise via syringe to a solution of [{Cp*IrCl(µ-Cl)}2] (539 mg; 0.68 mmol) in dichloromethane (20 mL). After stirring at r.t. for 12 h, the reaction mixture was evaporated to dryness and the solid residue dissolved in CH2Cl2 and chromatographed on Kieselgel (type 60). The orange fraction was eluted with Et2O-CHCl3 (2:3) and evaporated to dryness. The solid residue was dissolved in CH2Cl2 and the complex precipitated adding n-pentane. Yield 551 mg (62%). Anal. Found: C, 46.8; H, 5.2. C26H34Cl2IrOP requires C, 47.6; H, 5.2%. FTIR (KBr, cm-1): n(OH) 3442. NMR (CDCl3, 295 K): 1H, d 0.47 [d, 3H, 3J(HH) = 6.6 Hz, MeC], 1.32 [d, 15H, 4J(HP) = 2.2 Hz, Me-Cp*], 2.44 (m, 2H, CH2P), 3.17 (m, 3H, H2CO, HC), 7.4-7.9 (m, 10H, Ph). 31P{1H}, d 6.43 (s). 31C{1H}, d 5.12 (s, CH3-Cp*), 18.41 [d, 3JCP) = 4.73 Hz, CHCH3,], 32.14 (s, CHCH3), 32.83 [d, J(CP) = 33.46 Hz, PCH2], 68.73 [d, 3J(CP) = 9.26 Hz, OCH2], 92.21 [d, 2J(CP) = 2.72 Hz, MeC(Cp*)].

Synthesis of [Cp*IrI2(Ph2PCH2CHMeCH 2OH-P)] (9)

The complexes can be prepared by the two methods described below.

(i) A solution of complex 7 (163 mg;0.25 mmol) and sodium iodide (150 mg; 1.0 mmol) in acetone (20 mL) was heated under reflux for 4 h. The reaction mixture was cooled to room temperature to give a red-brown solid. Yield 163 mg (78%).

(ii) Workup as described for 7, using [{Cp*IrI(µ-I)}2] (100 mg; 0.09 mmol) and (S)-PPh2CH2CHMeCH2 OH (0.17 mmol) as starting materials. In this case the red-brown solid residue was purified by thin layer chromatography. The fraction was eluted with CHCl3-hexane (4:1), evaporated to dryness, dissolved in CH2Cl2 and the complex precipitated adding n-pentane. Yield 88 mg (62%). FTIR (KBr, cm-1): n(OH) 3451. NMR (CDCl3, 295 K): 1H, d 0,57 [d, 3H, 3J(HH) = 6.6 Hz, MeC], 1,59 [d, 15H, 4J(HP) = 2.08 Hz, Me-Cp*], 2,23 (m, 1H, HC), 2,96 (m, 1H, H2CP), 3,17 [d, 2H, 4J(HP) = 5.8 Hz, H2CO], 3.43.6 (m, 1H, H2CP), 7,45 (m, 6H, Ph), 7,88 (m, 4H, Ph). 31P{1H}, d -14.25 (s),

Synthesis of [Cp*IrX(Ph2PCH2CHMeCH 2OH-P,O)]BF4 [X = Cl (8), I (10)]

TlBF4 (17 mg; 0.06 mmol) was added to a solution of complex 8 or 10 (0.06 mmol) in acetone (20 mL). For complex 8 the reaction mixture was heated under reflux for 4 h and for complex 10 the reaction mixture was stirred at room temperature for 12 h. In both cases the precipitated TlCl formed was removed by filtration through Kieselguhr, the solution obtained evaporated to a small volume and the complex precipitated by adding n-hexane.

Complex 8: Yield 38 mg (36%). FTIR (KBr, cm-1): n(OH) 3423, n(BF4) 1100. NMR (CDCl3, 295 K): 1H, d 0.74 [dd, 3H, 3J(HH) = 6.6 Hz, 4J(PH) = 2.2 Hz, MeC], 1.44 [d, 15H, 4J(HP) = 2.2 Hz, Me-Cp*], 1.8-2.2 (m, 2H, HCP, HC), 2.75 [ddd, 1H, 2J(HH) = 13.0 Hz, 2J(HP) = 6.2 Hz, 3J(HH) = 6.8 Hz, HCP], 3.3-3.5 (m, 1H, HCP), 3.9-4.1 (m, 1H, HCO), 6.1 (m, 1H, HO), 7.4-8.0 (m, 10H, Ph). 31P{1H}, d 0.25 (s).

Complex 10: Yield 17 mg (35%). FTIR (KBr, cm-1): n(OH) 3441, n(BF4) 1100. NMR (CDCl3, 295°K): 1H, d 0.99 [dd, 3H, 3J(HH) = 1.4 Hz, 4J(HP)= 6.8 Hz, MeC], 1.89 [d, 15H, 4J(HP) = 2.6 Hz, CH3-Cp*], 2.2 2.3 (m, 1H, HC), 2.8 3.0 (m, 1H, HCP), 4.32 (dd, 2H, 2J(HH) = 16.8 Hz, 3J(HH) = 10.0 Hz, HCO], 5.1 (m, 1H, HO), 7.4-7.8 (m, 10H, Ph). 31P{1H}, d -7.05 (s).

RESULTS AND DISCUSSION

The phosphine-alcohol compound (S)-Ph2PCH2CHMeCH2 OH was prepared by reaction of (S)-(+)-BrCH2CHMeCH2OH with Ph2PK in tetrahydrofuran solution in the presence of lithium diisopropylamide (LDA).11 The conversion of the hydroxy functionality into an ether or a leaving group without oxidation of the phosphine is quite difficult.14 Therefore, the phosphine moiety was protected through coordination with bornane (BH3) to form the compound (S)-Ph2P(BH3)CH2CHMeCH 2OH (1). The alcohol could then be converted into the mesylate ester (S)-Ph2P(BH3)CH2CHMeCH 2OSO2Me (2) by reaction of 1 with ClSO2Me in the presence of Et3N, or into the ether group by treatment with NaH in tetrahydrofuran and subsequent reaction with methyl iodide to form (S)-Ph2P(BH3)CH2CHMeCH 2OMe (5). The reactions of compounds 2 and 5 with pyrrolidine produce the decoordination of the BH3 group affording the compounds (S)-Ph2PCH2CHMeCH2 OSO2Me (4) and (S)-Ph2PCH2CHMeCH2 OMe (6)

Compound 4 can be prepared alternatively by reaction of (S)-(+)-BrCH2CHMeCH2OH with ClSO2Me to give the corresponding mesylate ether, (S)-Br CH2CHMeCH2OSO2Me (3), which in turn reacts with Ph2PK in tetrahydrofuran in the presence of LDA to yield the compound (S)-Ph2PCH2CHMeCH2 OSO2Me (4). All the attempts to react 2 or 4 with nucleophiles, such as LiCp or NaOMe, to displace the mesylate group, were unsuccessful. In all cases the reactions give rise to uncharacterized oily compounds.

Scheme 1

The synthetic routes for the compounds 1-6 are summarized in Scheme 1. All compounds were isolated as pale-yellow oils and characterized by NMR spectroscopy. Their 1H NMR spectra show the expected doublet resonance assigned to the methyl group bonded to the chiral carbon atom together with the multiplet signals corresponding to CH and CH2 protons of the carbon chain. Moreover, the 13C{1H} spectra show the expected pattern of doublet resonances due to the P-C coupling. These resonances were assigned with the aid of COSY and DEPT experiments, and of reported data.11, 15 The 31P{1H} NMR spectra of the borane compounds show a broad singlet resonance at the range d 13.0-13.5 ppm, that changes to a sharp resonance at d - 21.8-22.7 ppm, when the BH3 is decoordinated. Table 1 lists selected 1H and 31P{1H} spectroscopy data.


The monophosphine compounds (S)-PPh2CH2CHMeCH2 OH, (S)-PPh2CH2CHMeCH2 OSO2Me (4) and (S)-PPh2CH2CHMeCH2 OMe (6) react with the dinuclear complex [{Cp*IrCl(µ-Cl)}2] in dichloromethane solution , in a 2:1 molar ratio, by cleavage of the chloride bridges to give neutral compounds of general formula [Cp*IrCl2(PPh2CH2CHMeCH 2OR-P)], where R = H, O2SMe and Me. Unfortunately, we could only isolate only the complex 7 as pure sample. In the other cases, the analysis of the NMR spectra shows the cleavage of the chloride bridges of the starting iridium complex and the formation of the mononuclear complexes. However, the analytical results of the isolated solids did not agree with the formulation. Reactions are included in Scheme 2.


As expected, the reaction of complex 7 with the stoichiometric amount of thallium tetrafluoroborate in acetone, gave the cationic compound [Cp*IrCl(PPh2CH2CHMeCH2 OH-P,O)]BF4 (8) that contains the neutral monophosphine bound in its bidentate form, resulting a chiral at-metal complex.11,12 All the attempts to synthesized complex 8 by direct reaction of the dimer complex [{Cp*IrCl(µ-Cl)}2] with the monophosphine ligand in the presence of AgBF4, method used to prepare the rhodium analogous, were unsuccssesful.11 In this case the reaction of the dinuclear starting complex with AgBF4 forms the very stable cationic intermediate [{Cp*IrCl}2(µ-Cl)3]BF 416 which does not react quantitatively with the monophosphine ligand at room temperature.

Similar results were obtained using the dimer compound [{Cp*IrI(µ-I)}2]. This complex reacts with the monophosphine ligand to give the neutral complex [Cp*IrI2(PPh2CH2CHMeCH 2OR-P)] (9), which in turn reacts rapidly with TlBF4 at room temperature to give the cationic compound [Cp*IrI(PPh2CH2CHMeCH2 OH-P,O)]BF4 (10).

Complexes 7-10 were isolated as yellow-orange solids and characterized by IR and NMR spectroscopy. Due to the strong tendency of these complexes to retain crystallization solvent, correct analytical results were obtained only for complex 7. The IR spectra of complexes 7 and 9 show a strong absorption band at 3442 and 3451 cm-1, respectively, assigned to the n(OH) moiety. As expected, cationic complexes 8 and 10 exhibit the n(OH) stretching, shifted to lower frequencies (3423 and 3441 cm-1, respectively) relative to neutral complexes, most likely as a consequence of the decrease of the bond order upon coordination. The 1H NMR spectra of complexes 7-10 in CDCl3 exhibit the expected doublets resonances assigned to the methyl of C5Me5 ring together with multiplet signals corresponding to the CH2 and CH protons of the carbon chain. In complexes 7 and 9, the methyl group bound to the asymmetric carbon appears as a doublet signal at d 0.47 and 0.57 ppm, respectively, due to H-H coupling [3J(HH) = 6.6 Hz]. However, for complexes 8 and 10 the methyl group appears as a doublet of doublets at d 0.74 and 0.99 ppm, respectively, due to H-H and P-H couplings [3J(HH) = 6.6 Hz, 4J(PH) = 2.1 Hz]. The 31P{1H} NMR spectra of neutral complexes 7 and 9 show a singlet resonance at d 6.43 and 14,25 ppm, respectively (free ligand: d - 21.9 ppm). For the cationic compounds 8 and 10, the signals are shifted to low field, 0.25 and 7.05, respectively.

CONCLUSIONS

In this paper we have described the synthesis and spectroscopic characterization of new phosphines with chiral oxygen side-chain, so called hemilabile bidentate ligands. These compounds react with the dinuclear complex [{Cp*IrCl(µ-Cl)} 2] to afford the corresponding neutral complexes [Cp*IrCl2(PPh2CH2CHMeCH 2OR-P)], since only the derivative with R = H can be isolated as pure sample. The abstraction of a halide ligand of complex [Cp*IrX2(PPh2CH2CHMeCH 2OR-P)] (X = Cl, I) give the corresponding cationic complex, [Cp*IrX(PPh2CH2CHMeCH2 OH-P,O)]BF4, where the phosphine-alcohol ligand is acting in its bidentate form.

ACKNOWLEDGEMENTS

The authors thank "Fondo de Desarrollo Científico y Tecnológico", (FONDECYT, Project Nº 1020529), Chile, for financial support.

 

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a Measured in CDCl3 at room temperature. Chemical shifts relative to SiMe4 and 85% H3PO4 in D2O as standards. s = Singlet, d = doublet, m = multiplet. All compounds show multiplets in the region d 7.3 - 7.8 ppm corresponding to the phenyl groups of the phosphine.

 

e-mail: jmvelder@puc.cl

 

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