Synthesis of new tetradentate oligophosphine ligands

4084 zyxwvutsr zyxwvuts zy Inorg. Chem. 1993, 32, 4084-4088 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 zyxwvutsrqp zy ~ 0020- 166919311332-4084%04.00/0 0 1993 American Chemical Society zyxwvuts zyxwvutsr zyxwvutsrqp zyxwvutsrqpo zyxwvutsrqponm 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, = 5.5, 3JH2-Hyt,cuu) = 17.0, 'JHZ-H,&m) = 1.4 Hz, -CH2dddd, 4JP-H2 CH--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), 2.12 (2H1, dddd, 2 J p - ~<~2, 3 J ~ ~=-7.7, ~ 44 J ~ l - ~=2 1.4, 3 J ~ ~ - 0.9 ~p Hz, -CH2P(S)(CH3)2), 5.04 (1H2, dddd, 4 J p - ~ 2 3.32, 'J~2-~yt-) = 17.0, 2 J ~ 2 - ~ p b m ) 2.1 Hz, -CH2CH=CHH), 5.10 (1H3, dddd, ' J p 4 3 = 3.0, 3 J ~ 3 - ~ 4=( 10.2 4 Hz, -CHzCH=CHH), 5.84 (1H4, dddt, 3 J p - ~ 4 = 4.7 Hz, -CHzCH==CHH). IsC(IH) NMR (toluene&): 6 13.8 (2C, d, ' J p x = 10.0 Hz, P(s)(CH3)2), 37.6 (lC, d, ' J p x 12.6 Hz, -CH2P(CH3)2), 116.7 (lC, d, 3Jp_c 4.6 Hz, -CH2CH=CH2), 134.6 (lC, d, 2 J p< ~ 2 Hz, -CH2CH=CH2) ppm. (vii) Preparation of ( 2 - ( D i m e t h y l ) e t h y l ) b ~ ~ ( ~ t h y l ) b i s [ 3 - ( d i m e t p ~ o ) p ~ o p y ~ l P hM o w~ ~2 C , l - l f l ( C l - l Z C l W W " e 2 ) (3). 2 The concentration of an ethereal solution of (2-(dimethylphosphino)ethyl)phosphine wasdeterminedby integrationof its 3'PNMR spectrumagainst an internal standard. Allyldimethylphosphine (9) (9.8 g, 0.157 mol) and AIBN (ca. 100 mg) were added to a solution of (2-(dimethy1phosphino)ethy1)phosphine (5) (2.0 g, 14.6 mmol) in ether (80 mL). The solution was irradiated for 50 h with a medium-pressure mercury vapor lamp through a quartz immersion well. The apparatus was fitted with a dry ice condenser, and the reaction well was cooled to 0-10 OC throughout the experiment. The solution was maintained under an atmosphere of zyxwvutsrqpon zyxwvutsr zyxwvutsrqp zyxwvutsrqp zyxwvutsrq zyxwvutsr zyxwvut 4086 Inorganic Chemistry, Vol. 32, No. 19, 1993 Bampos et al. nitrogen, with nitrogen occasionally bubbled through to provide mixing. dd, 2Jc-p = 11.6, 2 J c p 14.8 Hz, -CH2CH2CHr), 61.7 (2C, d, 2 J c p When the reaction was complete NMR), the solvent was removed = 6.4 Hz, 2 X -OCH2CH3) ppm. under vacuum (ca. 0.1 mmHg). Excess allyldimethylphosphine was The phosphino phosphonate (14) was characterized fully as its separated by distillationunder reduced pressure (80-100 "C, 0.5 mmHg) sulfurizedderivative. Diethyl (3-(dimethy1phosphino)propyl)phosphonate leaving (2-(dimethylphosphino)ethyl) bis[3-(dimethylphosphino)propyl] (14) (315.0 mg, 1.31 mmol) was dissolved in THF (4 mL) and sulfur phosphine (3) as a colorless oil (4.5 g, 12.4 mmol, 92%). By 31PNMR powder (42.1 mg, 1.31 mmol) added while stirring. The resulting clear spectroscopy, the residue contains only (2-(dimethylphosphino)ethyl)solutionwas filtered and the solvent removed under vacuum to give diethyl bis[3-(dimethylphosphino)propyl]phosphine,and this was used directly (3-(dimethy1thiophosphino)propyl)phosphonate as a colorless oil (341 in subsequent reaction steps without further purification. 31P(1H)NMR mg, 1.26 mmol, 96%). IR v,, (CHCI,): 1442w, 1413 m,1369 w, 1303 (benzene-&): 6 -54.0 (2P, s, 2 X -CH2CH2CH2P(CH3)2), 4 8 . 6 (lP, w, 1290 m, 1164 m, 1096 m, 1056 s, 1028 s, 981 s, 964 s, 941 s, 912 s, d, 'Jp-p = 19.8 Hz, -PCH2CH2P(CH3)2), -29.1 (lP, d, -PCH2CH2P575 m cm-I. 31P(1H)NMR (benzene-&): 6 29.9 (lP, d, 4Jp-p = 4.0 Hz, (CH3)Z). IH NMR (benzene-&): 6 1.05 (24H, overlapping m, 3 X -P(O)-), 34.2 (lP, d, -P(S)(CH3)2). 'H NMR (benzene-de): 6 1.33 -P(CH3)2), 1.4-1.9 (16H, overlapping m, 8 X -CHr). 13C(1H)NMR (6H, t, 3JH-H 7.1 Hz, 2 X -OCH2CH3), 1.45 (6H, br d, 2 J p - ~= 12.7 15.0 Hz, -P(S)(CH&), 1.88 (2H, m, -CH2P(S)-), 1.93 (2H, td, 2 J p - ~= (benzene-d6): 6 14.8 (2C,d, l J c p = ~~.~Hz,-PCH~CH~P(CH~)~), 17.9, 3 J H - ~ = 7.7 Hz,-CH~P(O)-), 2.20 (2H, m, -CHzCHzCHr), 4.18 (2C, d, ' J c p 13.0 Hz, -PCH&H2CHzP(CH3)2), 23.5 (lC, dd, IJc-p (4H, m, 2 X -OCH2CH,). 13C(lH)NMR (benzene-d6): 6 17.3 (2C, d, 15.6 Hz, -PCHZCH~CH~P(CH~)~), 23.8 (2C, dd, IJc-p = 3Jcp 3Jc-p = 5.7 Hz, 2 X -OCHzCH3), 17.4 (lC, dd, 'Jc-p = 4.8, 2 J c p = 2.3 16.7, 2 J c p = 12.2 Hz, -P(CH2CH2P(CH3)2)2), 28.8 (2C, dd, IJc-p = Hz,-CH2CHzCHr), 21.5 (2C, d, 'Jc-P= 54.3 Hz, -P(s)(CH3)2), 27.3 11.2, 2 J c p = 12.0 Hz, -P(CH2CH2P(CHa)2)2), 29.9 (lC, dd, 'Jc-P = (lC, dd, 'Jc-p = 140.2, 3 J c p = 15.2 Hz, -CHzP(O)-), 35.5 (lC, dd, 15.1, 3 J ~ - p= 11.6 Hz, -PCH2CH2CH2P(CH3)2), 35.0 (lC, dd, 'Jc-p z 2 J ~ - ~ 53.3, 2 J ~ - p= 13.4 Hz, -CHzP(S)-), 62.2 (2C, d, 2 J c p = 6.3 Hz, 2 J ~ - p= 10.9 Hz, -PCH2CH2CH2P(CH&) ppm. 2 X -OCH&Hs) ppm. MS (EI) m / z : 272 (M, 9%), 225 (7), 199 (8), The tetraphosphine (3) was characterized fully as its sulfurized 179 (loo), 151 (23), 123 (53), 109 (13), 93 (21). High-resolution MS: derivative. Sulfur powder (72.7 mg,2.27 mmol)was added to a solution Calcd for CgH2203P2S, m / z 272.0765; found, m / z 272.0739. of 3 (185 mg, 0.57 mmol) in THF (5 mL). A white precipitate formed (E)(3-(Dimeth~lph~~~)~ro~~l)~hosphine, (CH~~PCH~~CHZinstantaneously. The suspension was stirred overnight and filtered, and PH2 (11). A solution of diethyl (3-(dimethy1phosphino)propyl)phosthe residue was recrystallized from hot chloroform. phonate(14) (20.0g,83.3mmol)indryether(70mL)wasaddeddropwise (2-(Dimethy1phosphino)ethyl)bis [3-(dimethylphosphino)propyl]phosto a suspensionof powdered lithium aluminum hydride (12.0 g, 0.33 mol) phine tetrasulfide was obtained as a white solid (240 mg, 52.8 mmol, in dry ether (200 mL) while the solution temperature was maintained in 93%), mp 176-183 "C. IR u,, (KBr) 1458 w, 1412 m, 1290 m, 1232 the range 0-10 OC. The mixture was stirred at room temperature (48 w, 1193 w, 1105 w, 981 s, 944 s, 910 s, 854 w, 744 s cm-l. 31P(1H)NMR h) and hydrolyzed by the successive addition of deaerated water (25 mL), ~ ) ~(2P, ) , d, 'Jp-p (TFA-dl): 6 43.4 (2P, S, - C H ~ C H Z C H ~ P ( S ) ( C H45.1 deaerated aqueoussodiumhydroxide solution (15%,20mL), and deaerated = 53.4 Hz, -P(S)(CH2CHzP(S)(CH3)2)2), 53.5 (lP, d, -P(S)(CH2water (25 mL). The resulting slurry was filtered under nitrogen. By 31P CH2P(S)(CH3)2)2). IHNMR(TFA-dl): 6 1.68-1.79 (18H,overlapping NMR spectroscopy, the ethereal solution contained only (3-(dimethmultiplets, (CH~)ZPCH~CH~CH~P( CHzCHzP(CH3)2)2) , 1.93-2.45 (14H, y1phosphino)propyl)phosphine (>98%), and this solutionwas used directly MS overlapping multiplets, (CH,)~PCH~CHZCH~P(CH~CH~P(CH~)~)~). in subsequent reaction steps without further purification. 31P(1H)NMR (EI)m/z:454(M, 18%),360(24),348 (30),334(8),287(34),267(19), (benzene-&): 6 -139.4 (lP, s, -PH2), -53.7 (lP, s, -P(CH&). IH 199 (20), 181 (48), 167 (8), 135 (90), 121 (31), 93 (loo), 75 (19), 63 NMR (benzene-d6): 8 1.03 (6H, d, 2 J p - ~= 1.0 Hz, -P(CH3)2), 1.36 (20). High-resolutionMS: Calcd for C14H34PG4, m / z 454.0494; found, (2H, m,-CH2P(CH3)2), 1.52 (2H, m,-CHzPH2), 1.67 (2H, m,-CH2CH2m / z 454.0440. CH2-), 2.84 (2H, dm, IJP-H = 190.5 Hz, -PH2). 13C(1H)NMR Preparation of Bis[Z-(dimethylphosphino)ethyl](3-(dimethylphpbi(benzene-&): 6 14.9 (2C, d, I J c p = 14.9 Hz, -P(CH3)2), 16.4 (lC, dd, a o ) p r o ~ ~ l ) ~ h o s ~MezPCHZCHzCHQ(CHZCHQMq)l hiw, (4). 0 )m'Jc-P = 12.0, 3 J ~ - p= 9.5 Hz, -CHzP(CH3)2), 30.3 (lC, dd, IJc-p = 14.3, ethyl AUylphosphonate, CH@Z€ICHQ(O)(OCH2CH3)2 (13). A mix3 J c p = 3.1 Hz, -CH2PH2), 34.2 (lC, dd, 'Jc-p = 10.9, 2Jc-p = 3.9 Hz, ture of triethyl phosphite (40.0 g, 0.24 mol) and allyl bromide (43.7 g, -CH2CH2CH2-) ppm. 0.36 mol) was refluxed for 18 h, after which e x w s allyl bromide was (iv) Preparation of Dimethylvinylphphine SuVde. Vinyl bromide removed by distillation. Diethyl allylphosphonate (13) was purified by (20.0 g, 0.15 mol) was condensed into dry THF (50 mL, kept at 0 "C). distillation under vacuum (63-67 "C/O.Ol mmHg) and obtained as a The solution was added dropwise to a stirred suspension of magnesium colorless liquid (39.8 g, 0.22 mol, 93%). IR vmeX (CHC13): 1443 w, 1367 filings (3.8 g, 0.16 mol) in tetrahydrofuran (100 mL), to which a crystal w, 1163 m, 1096 m, 1051 s, 1029 s, 991 w, 969 s cm-I. 31P(lH)NMR of iodine and 1,2-dibromoethane(2 mL) was added, maintaining a gentle (CDC13): 626.7(1P,s). IHNMR(CDCl3): 6 1.34(6H,m,ZX-OCH2reflux throughout the addition. The resulting Grignard reagent was CH3), 2.63 (2H, m,-CHzCH=CH2), 4.13 (4H, m,2 X -OCH2CH3), filtered under nitrogen to remove unreacted magnesium. The vinyl 5.24 (2H, m,-CH2CH=CH2), 5.82 (lH, m,-CH2CH=CH2). I3C(IH) Grignard reagent had a tendency to solidify at room temperature and NMR (CDCl3): 8 16.9 (2C, d, 3Jp-H = 3.7 Hz, 2 X -OCH2CH3), 32.3 was warmed (40-50 "C) to ensure that the reagent remained in solution. (lC, d, l J p - ~= 138.4 Hz,-CH~CH=CH~),62.4 (2C, d, 2 J ~ = 6.5 - ~Hz, The Grignard reagent was added, dropwise, to a solution of dimeth2 X -OCH2CHj), 120.3 (lC, d, 3Jc-p = 14.2 Hz, -CH2CH=CH2), ylthiophosphinic bromide (32.0 g, 0.18 mol) in THF (50 mL) while the 128.1 (lC, d, 2 J c p = 12.0 Hz, -CHzCH=CHz) ppm. MS (EI) m / z : temperature of the solution was maintained below 5 OC throughout the 178 (M, lo%), 151 ( l l ) , 137 (12), 124 (9), 109 (loo), 81 (83), 65 (22). addition. The resulting slurry was refluxed (30 min) and then cooled (0 High-resolution MS: Calcd for C7H1503P1m / z 178.0759; found, m / z "C), and a saturated solution of ammonium chloride was added carefully. 178.0753. The ether layer was removed and the aqueous layer washed with ether (fi) Diethyl ( ~ ( D i m e ~ Y ~ ~ ) P ~ (m3)-2Y l ) P ~ ~ @(4 X 50 mL). The combined ether extracts weredried (anhydroussodium CH2CHQ(O)(OCH2CH3)2 (14). A solution of diethyl allylphosphonate sulfate) and filtered, and the solvent was removed under vacuum to afford (13) (24.2 g, 0.14mol),dimethylphosphine(8.67 g,0.14mol), and AIBN the crude product as a pale yellow solid,which was purified by sublimation (cu. 100 me) in ether (150 mL) was irradiated with a medium-pressure (100 OC Kugelrohr, 0.1 mmHg). Dimethylvinylphosphinesulfide was mercury vapor lamp (125 W) in a cooled (0-10 "C) quartz photolysis obtained as a white crystalline solid (13.0 g, 0.1 1 mol, 58%), mp 47-51 immersion well, fitted with a dry ice condenser for 28 h. The reaction OC. IR umPx (Nujol): 1289 m, 1262 w, 1017 m,917 s, 860 s, 734 s, 680 was followed by 31P(1H)NMR spectroscopy,and when starting materials s cm-]. 31P(1H)NMR (CDCl3): 6 29.1 (lP, s). lH NMR (CDCl3): 6 werenolonger present, thesolvent and allvolatilephosphines wereremoved 1.71 (6H, d, 2 J p - ~ c= 13.1 Hz, -P(S)(CH3)2), 6.09 (lH, ddd, 2 J p - ~= under vacuum (cu. 0.1 mmHg) to give diethyl (3-(dimethy1phosphino)45.5, 'JH-H(rr.4 = 10.8, 3JH-H&,,,) 2.3 HZ, - C H d m ) , 6.25-6.39 propy1)phosphonate (14) as a colorless oil (30.3 g, 0.13 mol, 93%). 3IP(2H, unresolved multiplet, -CH=CHH). 13C(1H)NMR (CDCl3): 6 (IH)NMR (benzene-&): 6 -54.2 (lP, s, -P(CH&), 30.7 (lP, s, -P(O)22.1 (2C,d,1Jp~=58.3H~,-P(S)(CH3)2),133.3(1C,d,2Jc-p=12.0 ). IH NMR (benzene-&): 6 1.00 (6H, d, 2 J ~= -2.0 ~Hz, -P(C&)2), Hz,-CH=CH2), 133.4 (lC, s, -CH=CH2) ppm. 1.29 (6H, t, )JH-H = 7.0 Hz, 2 X -OCH2CH3), 1.43 (2H, m, (v) Preparation of Dimethylvhylphosphine(12). Dimethylvinylphos-CH2P(CH&), 1.98(2H,m,-CH2CH2CHr), 1.98 (2H,m,-CH2P(O)phine sulfide (10.8 g, 89.9 mmol)was suspended in tri-n-butylphosphine ), 4.17 (4H, m, 2 X -OCH2CH3). I3C{IH)NMR (benzene-&): 6 14.6 (18.2 g, 90.0 mmol) and the mixture warmed gently (oil bath, 100 "C), (2'2, d, 'Jc-p = 14.5 Hz, -P(m3)2), 17.3 (2C, d, 3Jc-p = 3.4 Hz, 2 X with stirring. The soluton became homogeneous, and the mixture was -OCHICH3),20.3 (lC,dd,'Jc-p= 16.0,3J~-p=4.4H~,-CH2P(CHa)2),heated further (160-200 "C). Dimethylvinylphosphine distilled from the mixture and was collected under nitrogen as a colorless air-sensitive 29.5 (lC, dd, ' J e p 139.8, 3 J c p 11.4 Hz, -CHzP(O)-), 34.0 (lC, zyxwvutsrqp zyxwvutsrq zyxwvutsrq zyxwvutsrq Inorganic Chemistry, Vol. 32, No. 19, 1993 4087 Tetradentate Oligophosphine Ligands liquid (bp 7&90 "C) (2.2 g, 25.0 mmol, 28%). 31P{lH)NMR (benzeneScheme I &): 6 -49.6 (lP, s). IH NMR (benzene-&,): 6 1.12 (6H, d, 2 J p - ~ c= 2.8 HZ, -P(cH3)2), 5.7 (IH, ddd, 3 J p - ~ 12.1, ' J H - H ( ~=, ~18.3, ) 2 J ~ - ~= b2.0 mHz, ) -CH=CHH), 5.72 (1H, ddd, 3 J p 4 25.7, 3 J ~ - ~ ( c i s ) ~~.~Hz,-CH~HH),~.~~(~H,~~~,~J~-H=~~.OHZ,-CH~HH). I3C(lH)NMR(benzene-&): 6 14.2 (2C,d, ~Jc-P = 13.1 Hz,-P(CH3)2), 123.9 (lC, d, 2 J c p = 15.7 Hz, -CH=CH2), 144.1 (lC, d, l J c p = 17.6 Hz, -CH=CHz) ppm. (vi) Preparation of Bis[Z(dimethylphosphiw)ethyl](3-(dimetby~b~phiao)propyl)phowhiae,M ~ ~ C H Z C H Q ( C W C W ' M (4).~ )The ~ concentration of an ethereal solution of (3-(dimethylphosphino)propyl)phosphine wasdetermined by integrationof its31PNMRspectrumagainst an internal standard. Dimethylvinylphosphine (12) (3.8 g, 43.1 mmol) and AIBN (ca. 100 mg) were added to a solution of (3-(dimethylphosphin0)propyl)phosphine (11) (1.46 g, 10.8 "01) in ether (50mL). The solution was irradiated for 24 h with a medium-pressure mercury vapor lamp through a quartz immersion well. The apparatus was fitted with adryicecondenser,andthereactionwellwascooledtoO-1OoCthroughout the experiment. The solution was maintained under an atmosphere of nitrogen, with nitrogen occasionally bubbled through to provide mixing. When the reaction was complete (3lP NMR), the solvent plus excess dimethylvinylphosphine were removed under vacuum (ca. 0.1 mmHg) leaving bis[2-(dimethylphosphino)ethyl] (3-(dimethylphosphino)propyl)phosphine (4) as a colorless oil (3.1 g, 9.9 mmol, 94%). By 3IP NMR spectroscopy, the residue contains only bis [2-(dimethylphosphino)ethyl] (3-(dimethy1phosphino)propyl)phosphine (4), and this was used directly in subsequent reaction steps without further purification. 31P(lH]NMR (benzene-&): 6 -54.0 (lP, s, -CH2CH2CH2P(CH3)2), -48.6 (2P, d, 'Jp-p = 20.7 Hz, -P(CH~CH~P(CH~)Z)Z), -24.4 (lP, t, -P(CH2CH2P(CH3)2)2). IH NMR (benzene-d6): 6 1.08 (6H, d, 2 J p - ~ c= 2.6 Hz, -CH2CH2CH2P(CH3)2), 1.08 (12H, d, ~ J P - M 2.7~Hz, -P(CHzCHzP(cH3)2)2), 1S3-1.89 (14H, overlapping m, (CH&PCH2CH2CH2P(CH2CHzP(CH3)2)2). l3C(lH)NMR (benzene-&): 6 14.7 (4C, d, IJc-p 15.4Hz, 2 X -CHzCHzP(CH3)2), 14.9 (2C,d, ' J c p 12.5 Hz,-PCHzCHzCH2P(CH3)2), 23.5 (lC, dd, 'Jc-p 3 J ~ - p= 14.6 Hz, -PCH2CHzCH2P(CH3)2), 23.7 (2C, dd, ' J c p 17.9, 2 J c p = 12.5 Hz, 2 X -CHzCH2P(CH3)2), 28.9 (2C, dd, 1Jc-p = 11.9, 2 J c p = 12.0 Hz, 2 X -CH2CH2P(CH3)2), 29.6 (lC,dd, IJc-p= 16.0, ' J c p = 10.8 Hz,-PCH2CH2CH2P(CHp)2), 35.2 (lC, dd, 2 J ~ - pz 'Jc-P= 11.4 Hz, -PCH2CH2CH2P(CHd2). The tetraphosphine (4) was characterized fully as its phosphine sulfide derivative. Sulfur powder (82.4 mg, 2.57 mmol) was added to a solution of 4 (200 mg, 0.64 mmol) in THF (5 mL). A white precipitate formed instantaneously. The suspension was stirred overnight and the precipitate collected by filtration. Bis[ 2-(dimethy1phosphino)ethyll(3-(dimethy1phosphino)propyl)phosphine tetrasulfide was obtained as a white solid (245 mg, 0.56 mmol, 87%), mp 155-160 "C. IR (KBr) vmPx 1522 w, 1413 m, 1290 m, 1196 m, 1136 s, 947 s, 858 w, 744 s cm-I. 31P(1H)NMR (TFA-dl): 6 47.8 (2P, S, 2 X -CH2CH2CH2P(S)(CHp)2), 49.8 (lP, t, )Jp-p = 57.4 Hz, -P(S)CH2CH2P(S)(CH3)2), 60.5 (lP, d, -P(S)CH~CHZP(S)(CH~)~). IHNMR (TFA-dl): 6 1.741.85 (24H,overlappingmultiplets,3 X-P(S)(CH3)2), 2.00-2.25 (16H, overlapping multiplets, (CH~)ZPCH~CH~P(CH2CH2CH2P(CH3)2)2). MS (EI) m/r: 440 (M, 18%),424 (4), 362 (12), 347 (13), 331 ( 8 ) , 315 (5), 287 (20), 273 (31), 257 (lo), 237 (19), 221 (32), 209 (27), 169 (25), 153 (30), 135 (32), 121 (60), 105 (78), 93 (72). High-resolutionMS: Calcd for C13H32P&, m/z440.0337; found, m / z 440.0323. Scheme I1 //\/PMe2 9 Me2P 10 3 Scheme I11 zyxwvutsrq zyxwvutsrqp J Results and Discussion The photochemical addition of dimethylphosphine across the C=C bond of an alkene is a general synthetic strategy which has been used successfully to introduce the dimethylphosphinoethylfragment into organic compounds. The reaction between triallylphosphine and excess dimethylphosphine has been employed in the one-step assembly of P ( C H Z C H ~ C H ~ P M(la). ~Z)W ~ ~e have found that a similar reaction between trivinylphosphine and dimethylphosphine can be employed to synthesize the ethylenebridged analogue P(CH2CH2PMe2)s ( 2 4 in high yield (Scheme 1). This synthetic approach to 2a is a significant improvement on the previous multistep synthesis: which involved stepwise construction of the tetraphosphine skeleton using a series of Michaeltype additions of phosphides to vinylphosphine sulfides followed by desulfurization.5 The tetradentate ligand 2a was obtained as an air-sensitive low-melting white solid and exhibits two signals in the 31Pspectrum with the central P resonating a t 6 -19.8 ppm and the terminal phosphorus nuclei a t 6 -48.6 ppm. The nonequivalent phosphorus nuclei are coupled (3Jp-p = 20.7 Hz) resulting in quartet and doublet resonances, respectively. N o such coupling is observed between the central and terminal P atoms of the analogous ligand l a with three CH2 groups separating the phosphorus centers. The unsymmetrical ligand systems 3 and 4 were synthesized by a related scheme but required the preliminary assembly of the appropriate primary phosphine and vinylphosphine fragments. The ligand (2-(dimethylphosphino)ethyl)bis[3-(dimethylphosphino)propyl] phosphine (3)was synthesized by the photochemical reaction of (2-(dimethy1phosphino)ethyl)phosphine (5) with 2 equiv of allyldimethylphosphine (9) and obtained as a colorless air-sensitive oil. The reaction proceeds over a period of 24 h, and the intermediate compound (2-(dimethylphosphino)ethyl)(3(dimethy1phosphino)propyl)phosphine (10) is seen to accumulate in the early stages of the reaction by 3lP NMR spectroscopyg (Scheme 11). (2-(Dimethy1phosphino)ethyl)phosphine (5) was synthesized in four steps from dibromcethane and triethyl phosphite (Scheme 111). Diethylvinylphosphonate (8)was synthesized by treatment of diethyl (2-bromoethy1)phosphonate ( 6 ) with base,'O and photochemical addition of dimethylphosphine across the double bond afforded diethyl (2-(dimethy1phosphino)ethyl)phosphonate (7). The phosphino phosphonate (7) has been synthesized previously by the base-catalyzed conjugate addition of dimethylphosphine to the double bond of 8, under reflux conditions.2J1 W e have found the photochemical addition of dimethylphosphine (9) 3lP NMR data for 10 6 -64.7 (lP, dd, ~JP-H = 194 Hz,3Jp-p = 19.7 Hz,-PH-), -53.8 (lP, s, - C H ~ C H ~ C H Z P M4 ~9 ~ . 4) ,(lP, d, -CH2- CH2PMe2). (10) Ford-Moore, A. H.; Williams, J. H.J. Chem. SOC.1947, 1465. (11) King, R. B.; Cloyd, J. C., Jr. J . Am. Chem. SOC.1975,97,46. zyxwvutsrqpon zyxwvutsrqpo zyxwvutsrq - 4088 Inorganic Chemistry, Vol. 32, No. 19, I993 Bampos et al. Scheme V Scheme IV zyx zyxwvutsrq Me,P-H -e(OEt)z Me2PMpEt)z 0 hv 13 I I Me2P MezP 12 10 Me,P*PHz 4 I LiAIH, O l4 zyxwv 11 across a double bond to be an extremely effective and general method for introducing the Me2P group. The tetradentate ligand 3 exhibits three signals in the 31P spectrum with the central phosphorus resonating a t 6 -29.1 ppm and the terminal phosphorus nuclei a t 6 -48.6 and -54.0 ppm. The phosphorus nuclei separated by an ethylene bridge exhibit a resolved 31P-31P coupling (2Jp-p = 19.8 Hz) resulting in two doublet resonances. N o resolved coupling was observed between the phosphorus nuclei separated by the three-carbon bridge. Bis [2-(dimethylphosphino)ethyl](3-(dimethy1phosphino)propy1)phosphine (4) was synthesized by the photochemical reaction of (3-(dimethy1phosphino)propyl)phosphine (11) with 2 equiv of dimethylvinylphosphine (12) (Scheme IV). The reaction proceeds over a period of 24 h, and as was observed in the synthesis of 3, the intermediate compound (2-(dimethylphosphino)ethyl)(3(dimethy1phosphino)propyl)phosphine (10) is seen to accumulate in the early stages of the reaction by 3lP N M R spectroscopy9 (Scheme IV). The tetradentate ligand 4 exhibits three signals in the 31P spectrum with the central phosphorus resonating a t 6 -24.4 ppm and the terminal phosphorus nuclei a t b -45.6 ppm and -54.1 ppm. Again, the phosphorus nuclei separated by an ethylene bridge exhibit well-resolved P-P coupling (2Jp-p = 20.7 Hz) resulting in triplet and doublet resonances, respectively. No coupling was observed between the phosphorus nuclei separated by the three-carbon bridge. ((Dimethy1phosphino)propyl)phosphine (1 1) was synthesized by the photochemical addition of dimethylphosphine to diethyl allylphosphonate (13) followed by reduction of the ester 14 with lithium aluminum hydride (Scheme V). All of the phosphines were characterized as their air-stable phosphine sulfide derivatives. Sulfurization was achieved by stirring the phosphine with a stoichiometric amount of elemental sulfur in T H F . The polyphosphine ligands 3 and 4 resulted in tetrasulfidederivatives which were white, poorly soluble powders. The lower molecular weight phosphine sulfides (derivatives of the phosphino phosphonates 7 and 14) were colorless viscous oils. Metal Complexes. The symmetrical ligand l a forms one-to- one complexes with iron12and ruthenium,13 and the metal centers adopt a pseudooctahedral coordination with the phosphorus donors constrained to four cis coordination sites. A five-coordinate nickel complex incorporating the ligand 2a has also been reported.3 The unsymmetrical ligands 3 and 4 form one-to-one complexes with iron. When mixed with Fe(DPrPE)2C12 [DPrPE = 1,Zbis(dipropylphosphino)ethane], 3 and 4 displace 2 equiv of DPrPE to give diamagnetic 6-coordinate complexes 15 and 16, respecMe 15a Me Me 15b 16 t i ~ e 1 y . l ~The product complexes have not yet been fully characterized; however, 15 exists in solution as an equilibrating mixture of isomers (15a,b) whereas 16 exists as a single unsymmetrical isomer with the two shorter arms of the ligand in cis coordination sites. Full characterization and properties of these complexes will be reported elsewhere. zyxwv Acknowledgment. We gratefully acknowledge financial support from the Australian Research Council, the Australian Government for an Australian Postgraduate Research Award (N.B., R.J.S.), and a Queen Elizabeth I1 Fellowship (B.A.M.). (12) Antberg, M.; Dahlenberg, L. Inorg. Chem. Acfa 1985, 104, 51. (13) Antberg, M.; Dahlenburg, L. Inorg. Chim. Acta 1986, 111, 73. (14) IIPNMR data for 15a (243MHz, toluene-& 300 K): 6 11.4(lP,ddd, 'Jp(.+p(~) = 56.5,ZJpc~)-p(c)= 166.3,'JP(A)-P(D) = 67.1 Hz,PA), 32.5 (lP,ddd, 'Jp(~)-p(c) 45.8,'Jp(~)-ppc~)= 56.5 Hz,PB),49.5 (IP,ddd, 2 J p ( ~ p (= ~ )41.2Hz,Pc),75.6 (lP,ddd, PD). 3'P NMR data for 15b (243MHz, toluene-ds,300 K): 6 8.2(ZP,dd,2Jp(a)-p(B)= 48.8,'JP(A~P C ) = 61.8Hz,PA),67.1 (lP, dt, 'Jp(~)-p(c) = 38.2 Hz,PB),76.4 (IP,At, Pc).3IP NMR data for 16 (162MHz, toluene-ds, 300 K): 6 14.6 (lP, ddd, 'JP(A)-P(B) = 171.2,'JP(A)-P(c~ = 50.0,'JP(A+P(D) 58.3 Hz,PA). 60.1 (lP,ddd, ZJp(~)-p(c)= 45.2, JP(B)-P(D) = 36.9 Hz,PB),76.9 (lP, ddd, z J p ( c b p ( ~ )= 36.9 Hz,Pc), 125.0(lP,ddd, PO).