Organometallics 1985,4, 112-119
112
Metal Vapor Synthesis of (C,Me,),Sm(THF), and (C,Me,Et),Sm(THF), and Their Reactivity with Organomercurial Reagents. Synthesis and X-ray Structural Analysis of (C5Me,)2Sm(C,H5)(THF)t
William J. Evans,*1aqb Ira Bloom,lb William E. Hunter," and Jerry L. Atwood"' Depafiments of Chemistry, University of California, Irvine, Irvine, California 927 17, The University of Chicago, Chicago, Illinois 60637, and University of Alabama, University, Alabama 35486 Received July 17, 1984
The reaction of samarium metal vapor with hexane solutions of C5Me5Hand C5Me4EtHat -110 to -125 "C followed by suitable workup gives (C5Me5),Sm and (C5Me4Et)2Sm,respectively, as well as products which dissolve in THF to give (C5Me5j2Sm(THF), and (CSMe4Et)&3m(THF),, respectively. Evidence is found for hydride- and nitrogen-containing intermediates that decompose to the above compounds upon workup. (C5Me5)$m(THF), reacts with Hg(C6H5), to form (C5Me5I2Sm(C6H5)(THF)that has been characterized by X-ray crystallography. The phenyl complex crystallizes in space group R 1 / c with unit-cell dimensions a = 9.680 (5) A, b = 17.291 (7)A, c = 17.140 (7)A, /3 = 103.78(4)O,and 2 = 4 for D d d = 1.36 g~ m - ~ Least-squares . refinement on the basis of 3308 observed reflections led to a final R value of 0.034. The two C5Me5ring centroids, the phenyl carbon attached to Sm, and the THF oxygen describe a distorted tetrahedral structure around S m in a structure typical of bent metallocene derivatives. Average Sm-C(ring) distances are 2.73 (1)and 2.745 (9)A, the Sm-C(pheny1) distance is 2.511 (8)A, and the Sm-O(THF) distance is 2.511 (4)A.
For many years, the organometallic chemistry of the lanthanide elements centered almost entirely on the +3 oxidation state.2 Several years ago we initiated an investigation of the low oxidation state chemistry of the lanthanides in efforts to develop a more extensive chemistry for these elements.*' Since then, low-valent lanthanide chemistry has become a very active area812 and numerous reports have appeared on both divalent complexes and the formally zerovalent elemental metals. This paper spans both areas. We report here some reactions of elemental samarium in the vapor state with substituted cyclopentadienes that provide some of the most reactive divalent organolanthanide complexes known. The utility of these divalent species in generating trivalent samarium complexes is presented as well as an X-ray crystal structure of one of these trivalent products. A preliminary report of the synthesis of one divalent product has a ~ p e a r e d . ~
Experimental Section The complexes described below are extremely air- and moisture-sensitive. Therefore, all syntheses and subsequent manipulations of these compounds were conducted under nitrogen with the rigorous exclusion of air and water using Schlenk, vacuum line, and glovebox (Vacuum/Atmospheres HE-553 Dri-Lab) techniques. Materials. Pentane and hexane were washed with sulfuric acid, washed with HzO,dried over MgSO,, heated to reflux over LiAlH4,and vacuum transferred. Toluene and THF were distilled from potassium benzophenone ketyl. THF-d8and benzene-d6 were vacuum transferred from potassium benzophenone ketyl. Samarium ingots were obtained from Research Chemicals (Phoenix, AZ) and filed to a silvery finish in the glovebox prior to use. C5Me5Hwas either made by literature methods13 or purchased (Aldrich). C5Me4EtHwas made according to the 1 i t e r a t ~ r e . l ~ ~ Both types of cyclopentadienes were dried over activated 3A molecular sieves and degassed by dynamic vacuum transfer through a trap before use. Diphenylmercury was purchased from Strem and used as received. Trimethylchlorosilane was dried over This paper is dedicated in memory of Earl L. Muetterties, who, in addition to being an outstanding scientist and teacher, was a remarkable human being and an inspiration to all who knew him well. 0276-7333/85/2304-Ol12$01.50/0
4A molecular sieves and degassed by vacuum transfer. n-Butyllithium in hexane was purchased from Aldrich. Physical Measurements. Infrared spectra were obtained as Nujol mulls between NaCl plates in a Barnes Engineering Pres-Lok holder or as KBr pellets in a KBr press sealed from the atmosphere by O-rings and two NaCl plates. The IR spectra were recorded on a Perkin-Elmer 283 spectrometer. 'H NMR spectra were obtained on a Bruker HX270 spectrometer. 13C NMR (1)(a) Alfred P. Sloan Research Fellow. University of California, Irvine. (b) University of Chicago. (c) University of Alabama. (2)Marks, T. J. B o g . Inorg. Chem. 1978,24,51-107. (3)(a) Evans, W.J.; Engerer, S. C.; Neville, A. C. J. Am. Chem. SOC. 1978,100,331-333.(b) Evans, W. J.; Wayda, A. L.; Chang, C. W.; Cwirla, W. M. J. Am. Chem. SOC.1978,100,333-334,(c) Zinnen, H. A.; Evans, W. J.; Pluth, J. J. J. Chem. Soc., Chem. Common. 1980,810-812. (d) Evans, W. J.; Engerer, S. C.; Neville, A. C. J. Chem. SOC.,Chem. Commun. 1979, 1007-1008. (e) Evans, W.J.; Engerer, S. C.; Piliero, P. A.; Wayda, A. L. "Fundamentals of Homogeneous Catalysis"; Tsutsui, M., Ed.; Plenum Press: New York, 1979;Vol. 3, pp 941-952. (f) Evans, W. J.;Engerer, S. C.; Coleson,K. M. J.Am. Chem. SOC.1981,103,6672-6677. (g) Evans, W. J.; Coleson, K. M.; Engerer, S. C. Inorg. Chem. 1981,20, 4115-4119. (h) Evans, W.J. In "The Rare Earths in Modem Science and Technology";McCarthy, G. J., Rhyne, J. J., Silber, H. E., Eds.; Plenum Press: New York, 1982;Vol. 3,pp 61-70. (i) Evans, W. J. J. Organomet.
Chem. 1983,250,217-226. (4)Evans, W. J.; Bloom, I.; Engerer, S. C. J. Catal. 1982, 104, 2008-2014. (5)Evans, W.J.; Bloom, I,; Hunter, W. E.; Atwood, J. L. J.Am. Chem. SOC.1981,103,6507-6508. (6)Evans, W. J.;Bloom, I.; Hunter, W. E.; Atwood, J. L. J. Am. Chem. SOC.1983,105, 1401-1403. (7)Evans, W. J.;Hughes, L. A,; Hanusa, T. P. J. Am. Chem. SOC.1984, 106,4270-4272. (8)Watson, P. L. J. Chem. SOC.,Chem. Commun. 1980, 652-653. (9)(a) Tilley, D. T.; Andersen. R. A.; Spencer, B.; Ruben, H.; Zalkin, A.; Templeton, D. H. Inorg. Chem. 1980,19,2999-3003. (b) Tilley, T. D.; Andersen. R. A. J. Am. Chem. SOC.1982,104,1772-1774. (c) Tilley, T. D.; Andersen, R. A.; Zalkin, A. J.Am. Chem. SOC.1982,3725-3727. (10)Lappert, M. F.; Yarrow, P. I. W.; Atwood, J. L.; Shakir, R.; Holton, J. J. Chem. SOC.,Chem. Commun. 1980,987-988. (11)Deacon, G. B.; Koplick, A. J.; Raverty, W. D.; Vince, D. G. J . Organomet. Chem. 1979,182,121-141 and references therein. (12)(a) Girard, P.; Namy, J. L.; Kagan, H. B. J.Am. Chem. SOC. 1980, 102,2693-2698. (b) Suppe, J.; Danon, L.; Namy, J. L.; Kagan, H. B. J . Organomet. Chem. 1983,250,227-236 and references therein. (13)Threlkel,R. S.;Bercaw, J. E. J. Organomet. Chem. 1977,136,l-5. (14)(a) Feitler, D.; Whitesides, G. M. Inorg. Chem. 1976,15,466-469. (b) Bagnall, K. W.; Behesht, A.; Heatley, F.; Tempest, A. C. J. Less Common Met. 1979,64,267-275.
0 1985 American Chemical Society
Organometallics, Vol. 4, No. I , 1985 113
Synthesis of (C&e5)2Sm(THF)2 a n d (C&e4Et)2Sm(THF)2
Table I. Effect of Temperature and Concentration on the 'H NMR Chemical Shift of (C,Me,),Sm(THF), (ppm) I
1
I
concn, mol/L
C,Me,
CH,CH,CH,CH,O
CH, CH,CH,CH, 0
20 10
0.0736 0.0736 0.0736 0.0736 0.0736 0.0736 0.0736 0.0736 0.0736 0.0736 0.0736 0.0736 0.022 0.038 0.058
2.30 2.25 2.19 2.08 2.04 2.03 2.04 2.06 2.10 2.15 2.22 2.33 2.90 2.62 2.58
15.13 13.87 12.76 9.76 a a
5.16 5.54 6.15 6.76 7.30 7.90 8.42 8.90 9.76 10.94 11.90 12.76
0 -10 -20 - 30 -40 -50 -60 -70 -80 - 90 26 26 26 a
4
temp, "C
a a
a a a a
15.49 16.34 18.17
a
3.52 3.95
Too broad to observe.
spectra were obtained on a Bruker HE90 spectrometer. NIR spectra were recorded in 2-mm cells on a Cary 14 spectrometer. Magnetic susceptibilities were measured on the Bruker HX270 by the method of Evans.15 Gas chromatography for H2,HD, and Dz in gas samples was done on a 6 ft by in. 40/60 mesh 5A molecular sieves column (activated at 300 "C under He) at -160 "C in a Varian Aerograph GC. Gas chromatography for H2 and Nz was conducted on a 6 ft long by 1/4 in. 5A molecular sieves column at 35 "C in a HP3850A GC. Complete elemental analyses were obtained from Analytische Laboratorien, Engelskirchen, West Germany. Complexometric analyses were obtained as previously described.16 Metal Vapor Reactor. The reactor and its method of operation have been previously described.' (C5Me5)2Sm(THF)z.In a typical reaction, Sm metal (4.60 g, 30.6 mol) was vaporized into a 0.246 M C5Me5H/hexanesolution (5.42 g, 39.9 mmol, in 162 mL) in a rotary metal vapor reactor equipped with a 2-L reactor bottom kept at -123 "C over the c o w of 15 min. This generated a yellow, then green, and fiially black matrix. At this point, the reactor rotation rate was slowed to 6'/2 from 7 on the Biichi scale and the matrix was allowed to melt (bath temperature -115 to -117 OC). After the reaction was continued for an additional 25 min under these conditions, the power was turned off and the reactor was evacuated until a pressure of (8-9) X lo4 torr was achieved. The reactor was warmed to room temperature with a water bath and brought into the drybox. The reaction mixture was filtered through a large, fine porosity frit to give a green filtrate (see next section) and a black solid. Successive extractions of the solid with toluene and THF gave the crude product as a purple-brown, THF-soluble material, I. Anal. Calcd for SmC18H320z(Le., (C5Me5)SmH(THF)& Sm, 34.98; C, 50.30; H, 7.26 0,7.44. Found Sm, 35.09; C, 50.28; H, 7.26; 0,7.37 (by difference). Deuterolysis of I gave 0.85 mol/g atm of Sm of gas which was a mixture of HD and D2 in a 1.9:l ratio. Calcd for (C$ie5)SmH(THF),: 1.5 mol/g atm of Sm; HD/D2 = 2:l. Magnetic susceptibility: xMmK= 3400 X 10-e (cf. 4800 X lo4 ( p = 3.4) to 5400 X lo4 ( p = 3.6) for a typical Sm2+species). Recrystallization of I from THF at -78 "C gave purple crystalline material that contained ca.29% Sm and reacted with DzO to form a 1:l mixture of HD/Dz. Further handling in THF lowers the percent of Sm and the amount of HD generated by a sample. A second recrystallization of I generated purple crystals of (C5Me5)2Sm(THF)2,I1 (2.1 g, 3.7 mmol)." X-ray quality crystals were obtained by slowly cooling a THF solution to -47 "C. An X-ray crystal structure s t u d 9 confirmed the formula. Complexometric Anal. Calcd for SmCBH,02: Sm, 26.61. Found Sm, 26.1. Magnetic susceptibility: xMmK= 5390 X lo4; p+ = 3.6 pB. D20 decomposition: 11 (18.8 mg, 0.03 "01) reacted with D20 to produce a gas that was identified by GC as (15) Evans, D. F. J . Chem. Phys. 1969,2003-2005. Becconsall, J. K. Mol. Phys. 1968, 15, 129-139. (16) Atwood, J. L.; Hunter, W. E.; Wayda, A. L.; Evans, W. J. Inorg. Chem. 1981,20,4115-4119. (17) The formal yield baaed on starting Sm is 12%. However, both unreacted Sm metal and CsMesH can be recovered and recycled.
pure D2 (0.014 mmol,93%). IR (KBr): 3100-2725 s, 2705 w, 1440 s, 1370 w, 1240 m, 1210 w, 1080 8,1040 8,950 w, 895 s, 795 m cm-'. 'H N M R (18.8mg/mL; 0.033 M in at 23 "C): 6 2.45 (C&le5), 4.4 (THF), 18 (THF). Table I presents some data on the concentration and temperature dependence of the 'H NMR signals of 11. 13C NMR (0.054 M at 38 "C in C&s, ppm): 6 149.5 ( CH2CH2CH2CH20), 94.6 (4, J = 117 Hz, C&e& 33.4 (t,J = 125 , Hz, CHzCH2CH2CHz0),-73.7 (s, C5Me5). Near-IR-vis (19.6 mg/mL in toluene): charge transfer like absorption with no maximum in the visible region; c 140 at 1100 nm. (C5Me5)2Sm.The green hexane soluble product separated as a filtrate in the Sm/C5Me5Hreaction discussed above was isolated by removing the unreacted C5Me5Hand hexane under dynamic vacuum on the vacuum line. The green residue was washed with pentane to remove a soluble orange-brownbyproduct and a green solid, 111, remained. Anal. Calcd for Sm3NCBOHw: Sm, 35.34; N, 1.10; C, 56.46; H, 7.10. Found: Sm, 35.30; N, 1.05; C, 56.30; H, 6.93. IR (KBr): 3100-2750 s, 1490 w, 1435 s, 1380 m, 1255 w br, 1155 w, 1020 s, 800 w cm-'. When toluene was distilled onto the solid green product and the mixture was allowed to warm to room temperature, gas evolution was observed. Collection of the gas obtained from 247 mg of 111 (0.19 mmol) by Toepler pump gave 0.147 mmol of gas identified by GC as N2 containing
