Inorg. Chem. 1993, 32, 4084-4088
4084
Synthesis of New Tetradentate Oligophosphine Ligands Nick Bampos, Leslie D. Field,' Barbara A. Messerle, and Ronald J. Smernik Department of Organic Chemistry, University of Sydney, Sydney 2006, NSW, Australia
Received April 6, 1993 The synthesis of a series of symmetrical and unsymmetrical tripodal tetradentate alkylphosphine ligands is described. M ~ ~ P C H ~ C H ~ P ( C H ~ C H ~was C Hsynthesized ZPM~~) by~the photochemical reaction of (2-(dimethy1phosphino)ethy1)phosphine with excess allyldimethylphosphine, and M~zPCHZCHZCH~P(CHZCHZPM~~)~ was synthesized by the photochemical reaction of (3-(dimethy1phosphino)propyl)phosphine with excess dimethylvinylphosphine. The known ligand P(CH2CH2PMe2)3 was synthesized in a one-step reaction by the photochemical addition of dimethylphosphine (3 equiv) to trivinylphosphine. The tetradentate ligands form one-to-one complexes Fe(PP3)Clz with iron by displacement of weaker phosphine ligands.
atmosphereanddistilled immediately prior touse. NMR solvents (Merck) were used as received without further purification. A number of symmetrical tetradentate tetraphosphine ligands Dimethylphosphine' was prepared by reaction of tetramethyldiphosincluding P ( C H ~ C H ~ C H ~ P M ~ ZP) (~C~H Z C H Z C H ~ P ( C H ~ - phine disulfide6 with tri-n-butylphosphine in the presence of water. (la), Dimethylphosphine is extremely air sensitive and pyrophoric and must be. handled carefully under an atmosphere of argon or nitrogen. Tris[3-(dimethylphosphino)propyl]phosphinel (la) was prepared by the photochemical addition of dimethylphosphine to triallylphosphin~.~ Dimethylthiophosphinic bromide was prepared by the cleavage of tetramethyldiphosphinedisulfidewith bromine.* Dimethylvinylphosphine sulfide was prepared following the procedure of King et a1.* 1 aR=Me 2 aR=Me 3 Reparatkmof T r i s [ 2 - ( d i m e t l 1 y ~ ~ P ) (eC ~H lm ~+ bR=Ph bR=Ph PMq)3 (2a). (i) Preparation of Trivinylpbosphine, (CH&X)Sp. cR=Et Trivinylphosphine was prepared by the reaction of vinylmagnesium bromide with trimethyl phosphite. Vinyl bromide (45 g, 0.42 mol) was condensed into THF (200 mL), and the resulting solution was added CH3)2)S1 (lc), P ( C H ~ C H ~ P M (2a),2 ~ Z ) ~and P(CH2CHzPPh2)s dropwise to a stirred suspension of magnesium turnings (12.0 g, 0.49 (2b)3 have been synthesized and employed as ligands for transition mol) in degassed THF (300 mL). The reaction was initiated with a metal complexation. The ligands with methyl substituents on crystal of iodine and 1,2-dibromoethane (0.5 mL). On completion of the the terminal phosphorus atoms have a relatively small Tolman addition, the mixture was refluxed for 15 min, stirred for 1 h, and filtered cone angle about the terminal phosphorus atom, and these ligands under nitrogen togivea yellow-brown solution ofvinylmagnesiumbromide. should bind exceptionally well to a wide, variety of transition A solution of trimethyl phosphite (14.7 g, 0.12 mol) in dry, deaerated metals.4 In this paper we report an improved synthesis of the ether (100 mL) was added dropwise to the stirred solution of vinylmagligand 2a and the synthesis and properties of the less symmetrical nesium bromide at 0 OC. A saturated, deaerated aqueous solution of ligand systems 3 and 4, where the radial alkyl chains are not all ammonium chloride was added slowly, and the mixture extracted with dry, deaerated ether (2 X 200 mL, 2 X 100 mL). The combined ether equivalent. Removing the symmetry of the tetradentate ligands extracts were concentrated by distillation under 150 mL of a solution of will provide additional information regarding the stereochemistry trivinylphosphine(approximately 0.12 mol) remained. This solution was of the metal complexes they form. useddirectly in the next step without further purification. 31P(1H)NMR (THF/ether): 6 -20.6 (lP, s) ppm. Experimental Section (ii) Prepamtionof T r i S [ Z ( d i m e t h y ~ ) e t h y l ~ h i oP(CH+ e, CH$Mq)3 (2a). A solution of trivinylphosphine (approximately 0.12 General Data. All manipulations were carried out using standard mol) and dimethylphosphine (37.2 g, 0.60 mol) in ether/THF (300 mL) Schlenk or vacuum line methods or in an argon-filled drybox. NMR containing AIBN (100 mg) was irradiated with a medium-prcasure spectra were obtained on a Bruker AMX400 spectrometer. ,IP NMR mercury vapor lamp (125 W) through a quartz immersion well. The spectra (162.0 MHz) were referenced toextemal, neat trimethyl phosphite, entire apparatus was immersed in ethanol cooled to 0-10 OC throughout takenas 140.85 ppmatthe temperaturequoted. IHNMRspectra (400.1 the experiment. A dry ice condenser (cooled to -78 "C) was fitted to MHz) and I3C NMR spectra (100.6 MHz) were referenced to residual the reaction vessel to prevent the escape of volatile dimethylphosphine. solvent resonances. Mass spectra were recorded on an AEI Model MS902 The solution was maintained under an atmosphere of nitrogen, with double-focusingmass spectrometer with an accelerating voltage of 8000 nitrogen occasionally bubbled through to provide mixing. The solution V and using electron impact (EI) ionization with an electron energy of was irradiated for 24 h by which time there was no trivinylphosphine 70 eV and are quoted in the form x (y), where x is the mass to charge remaining (by 3LPNMR). Excess dimethylphosphine and most of the ratio and y is the percentage abundance relative to the base peak. IR ether/THF was removed by distillation, and the remaining ether removed spectra were recorded on a Biorad FT S20/80 spectrometer. Elemental under vacuum, leaving tris[2-(dimethylphosphino)ethyl]phosphine, (h), analyses were performed by the National Analytical Laboratories, as a white crystalline solid (32.0 g, 0.107 mol, 89%), mp 45-46 O C (lit2 Ferntrec Gully, Victoria, Australia. Nitrogen (>99.5%) and argon mp 45-46 "C). 31P(LH)NMR (benzene): 6 -48.6 (3P, d, )Jp-p = 20.7 (>99.5%) were purchased from CIGHYTEC (Australia) and used as Hz, 3 X -P(CH3)2), -19.8 (lP, q, P(CHzCHzP(CH3)z) ppm. obtained. Pentane, tetrahydrofuran (THF), benzene, and diethyl ether were stored over sodium benzophenone ketyl under a dry nitrogen (5) Trenkle, A.; Vahrenkamp, H. 2.Narurforsch., E Anorg. Chem., Org. Chem. 1987,34B, 642. (6) Parshall, G. W. Org. Synrh. 1965, 45, 102. (1) Antberg, M.; Prengel, C.; Dahlenburg, L. Inorg. Chem. 1984,23,4170. (2) vng, R. B.; Cloyd, J. C., Jr. J. Am. Chem. SOC.1974, 97, 53. (7) (a) Jones, W. J.; Davits, W. C.; Bowden, S. T.; Edwards, C.; Davies, V. E.; Thomas,L. H. J. Chem.SOC.1947,1446. (b) Bampos, N.; Field, (3) Kmg, R.B.; Kapoor, R.N.; Saran, M. S.; Kapoor, P. N. Inorg. Chem. L. D.; Hambley, T. W. Polyhedron 1992, 11, 1213. 1971, 10, 1851. (8) Schmutzler, R.Inorg. Synth. 1970, 12, 287. (4) Tolman, C. A. Chem. Rev. 1977, 77, 313.
Introduction
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0020- 166919311332-4084%04.00/0
0 1993 American Chemical Society
Tetradentate Oligophosphine Ligands Preparation of (2-(Dimethylphosphiw)ethyl)bis[3(dimethylphno)p.op~lphospbhre, MQKWC"(CHfl2CHflMe2)2 (3). (i) Prep amtionof Methyl (2-Bromoethyl)pte,BrCH2CHSO(OEt)2 (6). A solution of triethyl phosphite (83.1 g, 0.5 mol) in 1,2-dibromoethane (2817 g, 15.0 mol) was refluxed for 8 h. Excess dibromoethane was removed by distillation, and the residue was fractionally distilled under reduced pressure. Diethyl (2-bromoethyl)phosphonate (6) (1 11.0 g, 0.46 mol, 91%) was collected as a colorlessliquid in the fraction 80-140 "C/2 mmHg. IR Y(CHClp): 1442 m, 1411 w, 1393 m, 1370 w, 1284 s, 1270 s, 1164 m, 1097 m, 1028 s, 971 s, 589 m cm-I. 31P(lH)NMR (CDCI3): 6 25.3 (lP, s). 'H NMR (CDCl3): 6 1.34 (6H, t, 3 J ~ - 6.6 ~ Hz, 2 X -OCH2CH3), 2.39 (2H, dm, 2 J p - ~= 18.9 Hz, -CHzP(O)-), 3.54 (2H, dm, 3Jp-H = 8.5 Hz, -CH2CH2Br), 4.13 (4H, m, 2 X -0CH2CH3). "C('H) NMR (CDCI3): 6 17.3 (2C, d, 3Jc-p = 5.7 Hz, 2 X -OCH2CHp), 24.7 (lC, s, -CH2Br), 31.7 (lC, d, IJc-p = 113.4 Hz, -CH2P(O)-), 62.9 (2C, d, 2 J c p = 7.8 Hz, 2 X -OCH&H3) ppm. MS (EI) m / z 245 (M, 81Br,O S % ) , 243 (M, 79Br,OS%), 219 (14), 217 (14), 191 (25), 189 (25), 173 (21), 171 (21), 165 (71), 138 (62), 109 (loo), 93 (22), 91 (28), 82 (33), 81 (71), 65 (39). High-resolution MS: Calcd for C6H1p038'Br, m / z 245.9799; found, m / z 245.9794. (ii) PreparationofMethylVinylphosphollate,CH~(OEt)2(8). Triethylamine (183 g, 1.81 mol) was added to a solution of diethyl (2bromoethy1)phosphonate(1 11 g, 0.46 mol) in benzene (180 mL), and the mixture was refluxed for 9 h. The reaction mixture was filtered to remove precipitated salts, and excess triethylamine and benzene were removed under vacuum. The residue was distilled under reduced pressure. Diethyl vinylphosphonate (8) was obtained as a colorlessliquid (65.0 g, 0.40 mol, 88%) bp 60-70 "C/0.142 mmHg. IR Y- (CHCl3): 1442 m, 1399 m, 1164 m, 1053 s, 1028 s, 973 s, 597 w cm-I. 31P{lH)NMR (CDCl3): 6 16.3 (lP, s). 'H NMR (CDCl3): 6 1.36 (6H, t, 3 J ~ - 7.1 ~ Hz, 2 X -OCHzCH3), 4.1 (4H, dq, 3 J p - ~= 7.5 Hz, 2 X -OCH2CH3), 6.0-6.35 (3H, overlapping multiplets, -CH=CH2). 13C('H) NMR (CDClp): 6 16.8 (2C, d, 3Jc-p= 6.4Hz, 2 X -OCH2CH3), 62.2 (2C,2Jcp 5.6 Hz, 2 X -OCHzCHp), 126.5 (lC, d,lJC-p 183.9 Hz, -CHCH2), 135.7 (lC, d, ' J c p < 2 Hz, -CHCH2) ppm. MS (EI) m / z 164 (M, O S ) , 163 (4), 137 (44), 136 (31), 120 (15), 119 (18), 109 (81), 93 (la), 92 (30), 91 (loo), 82 (23), 81 (31), 65 (54). High-resolutionMS: Calcd for CsHl3PO3, m / z 164.0602; found, m / z 164.0523. (W) Preparationof Diethyl (Z(Dimethylphphino)ethyI)phphomte, M"QO(OEt)2 (7). A solution of dimethylphosphine (5.0 g, 81 mmol), diethyl vinylphosphonate (10.0 g, 61 mmol), and AIBN (ca. 100 mg) in ether (130 mL) was irradiated for 24 h with a mediumpressure mercury vapor lamp (125 W) using a cooled quartz immersion well fitted with a dry ice condenser. The temperature of the reaction vessel was maintained at 0-10 "C during the irradiation. Ether and excess dimethylphosphine were removed under vacuum (co. 0.1 mmHg), to give crude diethyl (2-(dimethylphosphino)ethyl)phosphonate, (7), as a colorlessair-sensitive oil (13.5 8). The purity of thematerial was >98% by NMR spectroscopy, and it was used without further purification for the preparation of (2-(dimethy1phosphino)ethyl)phosphine. 31P(1H) NMR (benzene-d6): 6 -48.1 (lP, d, I 4 - p = 50.4 Hz, -P(CH&), 30.8 (lP, d, -P(O)-). 'H NMR (benzene-d6): 6 0.96 (6H, d, 2 J p - ~= 2.8 Hz, -P(cH3)2), 1.30 (6H, t, 3 J ~ =- 7.1 ~ Hz, 2 X -OCH&H3), 1.83 (2H, m,-CH2P(CH3)2), 1.97 (2H, m, -CH2P(O)-), 4.17 (4H, m, 2 X -0CH2CH3) ppm. l3C(lH}NMR(benzene-&): 6 14.1 (2C,d, I J p x = 15.3 Hz, -P(CH3)2), 17.3 (2C, d, 3Jp_c = 3.2 Hz, 2 X -OCH2CH3), 23.2 (lC, dd, ' J p x = 1 4 0 . 6 , 2 J p ~ 13.9 = Hz,-CH~P(O)-), 24.9 (IC,dd, ' J p x = 13.7, 2Jp_c = 6.8 Hz,-CH~P(CH~)~), 62.0 (2C, d, ' J p x 6.5 Hz, 2 X -OCH2CH3) ppm. The phosphinophosphonate(7) was characterizedfully as its phosphine sulfide derivative. Sulfur powder (44 mg, 1.4 mmol) was added to a stirred solutionof diethyl (2-(dimethy1phosphino)ethyl)phosphonate (269 mg, 1.38 mmol) in THF (5 mL). The resulting clear solution was filtered and the solvent removed under vacuum to give diethyl (2-(dimethylthiophosphin0)ethyl)phosphonateas a colorlessoil (291 mg, 1.29 m o l , 93%). IR Y- (CHClp): 1443 w, 1413 m, 1370 w, 1290 m, 1164 m, 1098 m, 1031 s, 970 s, 946 s, 577 w cm-I. 31P(1H]NMR (benzene-d6): 6 30.5 66.7 Hz, (lP, bs, Wl/2 185 Hz, -P(S)(CH3)2), 37.0 (lP, d, 'Jp-p -P(O)-). 'H NMR (benzene-&): 6 1.30 (6H, t, 3Jp-H = 7.0 Hz, 2 X -OCHzCH3), 1.44 (6H, br m, -P(S)(CH3)2), 2.22 (2H, br m, -CH2P(S)(CHp)z), 2.36 (2H, m, -CH2P(O)-), 4.16 (4H, m, 2 X -OCH2CH3). IpC('H) NMR (benzene-&): 6 17.2 (2C, d, 3 J G p = 5.9 Hz, 2 x' -OCH2CHp), 19.8 (lC,dd, 'Jc-p= 143.1, ' J c p = 2.7Hz,-CH2P(O)-), 21.0 (2C, d, ' J c p = 54.6 Hz, -P(S)(CHp)2), 28.4 (lC, dd, ' J c p 52.5, 2 J c=~4.8 Hz, -CH2P(S)(CHp)2), 62.9 (2C, d, 2 J c p 6.3 Hz, 2 X -OCH2CH3) ppm. MS (EI) mlz: 258 (M, 5395), 243 (29), 212 (13),
Inorganic Chemistry, Vol. 32, No. 19, 1993 4085 211 (14), 185 (19), 165 (loo), 137 (36), 121 (38), 111 (43), 109 (83), 94 (53), 93 (87), 81 (25), 79 (29), 77 (20), 65 (47), 63 (21). Highresolution MS: Calcd for C & J O ~ P ~ m S ,/ z 258.0608; found, m / z 258.0650. (iv) Preparation of (2-(DimethyIphosphino)ethyl)phosphioe), MQPCH2CHflH2 (5). A solution of diethyl (2-(dimethylphosphino)ethyl)phosphonate (7) (1 1.0 g, 56.4 mmol) in dry ether (50 mL) was added dropwise to a suspension of powdered lithium aluminum hydride (7.0 g, 0.12 mol) in ether (200 mL) while the solution temperature was maintained in the range 0-10 OC. The mixture was stirred at room temperature (48 h) and hydrolyzed by the successive addition of deaerated water (15 mL), deaeratedaqueoussodiumhydroxidesolution(Is%, lOmL),anddeaerated water (15 mL). The resulting slurry was filtered under nitrogen, and the volume was reduced under vacuum to approximately 80 mL. The solution of (2-(dimethy1phosphino)ethyl)phosphine was used without further purification in subsequent reactions. 3IP NMR (ether): 6 -49.7 (IP, d, 'Jp-p = 15.0 Hz, (CH~)ZP(CH~)ZPH~), -130.5 (lP, dt, (CHp)2P(CH&PHz, 'JP-H= 180 Hz) ppm. (v) Preparation of AUyldimethylphphioe SutTide. A solution of allyl bromide (67.0 g, 0.55 mol) in ether (100 mL) was added dropwise to a stirred suspension of magnesium turnings (20.0 g, 0.82 mol) in dry ether (100 mL). The reaction was initiated with a crystal of iodine, and the rate of addition was such that the reaction mixture maintained a gentle reflux during the addition. After the addition was complete, the mixture was filtered under nitrogen to remove excess magnesium. The solution was cooled (0-10 "C), and a solution of dimethylthiophosphinicbromide (48.0 g, 0.27 mol) in ether (60 mL) was added slowly, maintaining the low temperature. The resulting gray slurry was stirred overnight at room temperature and a saturated aqueous solution of ammonium chloride was added carefully, while thesolution temperature was maintained below 10 "C until all solids had dissolved. The ether layer was removed and dried (anhydrous sodium sulfate). The aqueous layer was further extracted with ether (3 X 60 mL). The combined ether extracts were filtered, and the solvent was removed under vacuum to give the crude product which was recrystallized from hexane. Allyldimethylphosphine sulfide was obtained as a white fibrous solid (33.0 g, 0.25 mol, 89%), mp 41-44 "C. IR Y- 1636 m, 1302 m, 1288 m, 1220 w, 1196 m, 1072 m, 992 m, 953 s, 932 s, 917 s, 862 m, 805 m, 755 m, 610 s cm-I. 31P(IH) NMR (CDClp): 6 34.3 (lP, s). 'H NMR (CDCla): 6 1.70 (6H, d, 2 J p - ~ c 12.7 Hz, -P(S)(CH3)2), 2.77 (2H1, dddd, 2 J ~= ~ 15.3, ~3 1 J ~ ~ - =~ 4 7.6, 4 J H ~ - ~ 2 1.4, 3J~1-H3 = 0.9 Hz, -CH2P(S)(CH3)2), 5.23 (1H2, dddd, 4JP-H2 = 5.5, 3JH2-Hyt,cuu) = 17.0, 'JHZ-H,&m) = 1.4 Hz, -CH2CH--CHH), 5.30(1H3,dddd,4Jp-~p= 4 . 8 , ' J ~ > ~ y a s )10.1 = Hz,-CH2CH=CHH), 5.89 (1H4, dddt, 3 P p - ~ 4= 5.6 Hz, -CH2CH=CHH). = 55.2 Hz,-P(S)(CH3)2), '3C('H)NMR (CDClo): 6 20.7 (2C, d, 'JP-M~ 42.0 (IC, d, 'Jp-1332 50.0 €32, -CH2P(CH3)2), 121.3 (IC, d, 3 J p x ~ 2 < 5.0 Hz, -CH2CH=CH2), 129.0 (lC, d, 2 J p ~ 8.5 ~ Hz, -CHzCH=CH2) ppm. Anal. Calcd for C~HIIPS:C, 44.76; H, 8.26. Found: C, 44.8; H, 8.0. (vi) Preparation of Myldimethylphosphiw (9). Allyldimethylphosphine sulfide (32.0 g, 0.24 mol) was suspended in tri-n-butylphosphine (48 g, 0.24 mol), and the mixture was warmed gently (oil bath, 100 "C) while stirring. The solution became homogeneous, and the mixture was heated further (220-260 "C). Allyldimethylphosphine (9)distilled from the mixture and was collected under nitrogen as a colorless air-sensitive liquid (17.3g,0.17mol,71%). 31P(1H)NMR(toluene-d8):6-53.8 (lP, s). IH NMR (toluene-&): 6 0.95 (6H, d, 2 J ~ = 3.4 - ~Hz, -P(S)(CH3)2), ~ 44 J ~ l - ~=2 1.4, 3 J ~ ~ - 0.9 ~p 2.12 (2H1, dddd, 2 J p - ~
