78
Organometallics 1988, 7, 78-83
Synthesis, Properties, and Multinuclear NMR (lz5Te('H), 13C('H), 'H) Studies of Di- and Polytelluroether Ligands Eric G. Hope, Tim Kemmitt, and William Levason* Department of Chemistry, The Unlversity, Southampton SO9 5NH, U.K. Received April 27, 1987
Convenient syntheses for RTeLi (R = Me or Ph) from RLi and tellurium in tetrahydrofuran at low temperatures are described. The RTeLi react readily with organic dihalides X(CH2),X (X = C1 or Br), the products depending upon the temperature and the carbon chain length (n). Thus at low temperatures CH2C12and C1(CH2),C1produce high yields of RTe(CH2),TeR ( n = 1 or 3), but at room temperature Cl(CH,),Cl ( n = 2 or 3) affords R2Te2and olefin. 1,4-Dihalobutanesgive RzTe and Te(CH2)3CH2, while C1(CH2)&1produced mixtures of &Te, RTe(CH&TeR, and Te(CH2)4CH2.Preparations for RTe(CH&TeR, MeTe(CH&TeMe, and MeC(CH,TeMe)3are described. PhTeLi and C(CH2Br),gave C(CH,TePh),, but MeTeLi unexpectedly gave CHzCHzC(CH2TeMeI2.The products have been characterized by 'H, 13C('H), and lZ6Te('H}NMR and mass spectrometry and by the preparation of derivatives. Trends in the lZ5Te chemical shifts and UT&, 'JTe+, and VTeH coupling constants are discussed and compared with the corresponding 77Sedata of selenium analogues.
.
I
I
Introduction Although the first diorgano telluride Et2Te was made as long ago as 1840,' organotellurium chemistry has developed slowly. Studies were hindered by the low stability of many compounds that were often light and air sensitive and frequently extremely malodorous. Currently organotellurium chemistry is a field of rapidly growing interest2i3with applications in such diverse areas as synthesis,3 new conducting materials: and nuclear medicine: while developments in FT NMR instrumentation have made direct observation of 12Te nuclei relatively straightforward,6 providing a specific and sensitive probe for the tellurium environment. The studies of the ligand properties of organotellurium species still lag well behind those of sulfur and selenium analogue^^-^ and are mainly restricted to R2Te or RTe- species. We were interested in extending our recent studiesgof the coordination chemistry of diselenoethers and 77SeNMR to tellurium analogues, and here we describe attempts to prepare di- and polytelluroether ligands with Me or Ph terminal groups and a variety of carbon backbones. Few compounds of this type have been described,lD-lB and the data on these is very limited. A preliminary account of this work has appeared." (1)Wohler, F. Ann. Chem. 1840,35, 111. (2)Irgolic, K.J The Organic Chemistry of Tellurium; Gordon and Breach New York, 1974. (3)Petai, S., Rappoport, Z.,Eds. The Chemistry of Organic Selenium and Tellurium Compounds;Wiley: New York, 1986;Vol. 1. (4)Miller, J. S.,Ed. Extended Linear Chain Compounds;Plenum: New York, 1982;Vol. 2. (5)Knapp, F. F.,Jr.; Ambrose, K. R.; Callaghan, A. P. J.Nucl. Med. 1980,21, 251; 1980,21,258. (6) Luthra, N. P.; Odom, J. D. In ref 3,pp 189-241. (7) Murray, S. G.; Hartley, F. R. Chem. Reu. 1981,81, 265. (8)Gysling, H.J. In ref 3,pp 679-855. (9)Gulliver, D.J.; Hope, E. G.; Levason, W.; Murray, S. G.; Marshall, G. L. J . Chem. Soc., Dalton Trans. 1985,1265. Gulliver, D. J.;Hope, E. G.; Levason, W.; Murray, S. G.; Marshall, G. L. J. Chem. Soc., Dalton Trans. 1985,2185. Hope, E.G.; Levason, W.; Webster, M.; Murray, S. G. J . Chem. Soc.,Dalton Trans. 1986,1003.Hope, E.G.; Jewiss, H. C.; Levason, W.; Webster, M. J. Chem. Soc., Dalton Trans. 1986, 1479. (10)Petragnani, N.; Toscano, V. G. Chem. Ber. 1970,103, 1652. (11) Seebach, D.;Beck, A. K. Chem. Ber. 1975,108, 314. (12)Petragnani, N.; Schill, G. Chem. Ber. 1970,103, 2271. (13)De Silva, K. G. K.; Monsef-Mirzai, Z.; McWhinnie, W. R. J. Chem. Soc., Dalton Trans. 1983,2143. (14)Pathirana, H. M. K. K.; McWhinnie, W. R. J.Chem. Soc., Dalton Trans. 1986,2003. (15)Jones, C. H.W.; Sharma, R. D. Organometallics 1986,5, 805. (16) Pathirana, H. M. K. K.; McWhinnie, W. R.; Berry, F. J. J. Organomet. Chem. 1986,312, 323.
0276-7333/88/2307-0078$01.50/0
Rssults RTeLi (R = Me, Ph). Solutions of RTeLi in tetrahydrofuran (THF) are very conveniently obtained by an analogous route to MeSeLi,18essentially adding RLi to a frozen mixture of THF and powdered tellurium and allowing the mixture to warm to room temperature. The reaction with MeLi occurs rapidly but that with PhLi is slower and the mixture is stirred at room temperature to complete the reaction. In both cases all the Te dissolves to give a clear yellow solution that is stable under nitrogen. Yields are high in contrast to the PhLi/Se reaction that gives indifferent yields.16 Various other routes to RTe- are knownlg including cleavage of R2Te2with alkali metal/ liquid NH,, with Rongalite (Na02SCH20H)in water, or with N&H,/EtOH, but the syntheses described above avoids the prior synthesis of R2Te2and provides RTeLi in a solvent in which the organic halides are soluble, facilitating further reaction. These RTeLi solutions were treated with the appropriate haloorganic either at ambient temperature or refrozen (-196 "C), the halide was added, and the mixture allowed to thaw (for brevity the latter conditions are referred to as ''frozen RTeLi" subsequently). After hydrolysis, the organic phase was dried and the solvent removed in vacuo. In view of the instability of many organotellurium compounds, 125TeNMR spectra were routinely recorded upon the crude products and upon the pure components after subsequent separations, which provided to be the best way of identifying minor products. RTeLi X(CH,),X Reactions (X = C1, Br, or I; n = 1-6, 10). It is convenient to deal with each dihalide in turn. The reaction of PhTeLi with CH,X, at room temperature or above was reported to give a poor yield of PhTeCH,TePh," but reaction of CH2Cl2or CH,12 with frozen RTeLi gave good yields of RTeCH,TeR (R = Me, 76%; R = Ph, 66%). The lZ5TeNMR spectra of these ditelluromethanes (Table I) are in excellent agreement with the data reported15 for the products of the R2Tez+ CH2Nzreactions. Attempted quaternization with Me1 failed to give pure telluronium salts, but white crystalline tetrachlorides RC1,TeCH2TeRC1,15were readily isolated
+
(17)Hope, E.G.;Kemmitt, T.; Levason, W. Organometallics 1967,6, 206. (18)Drake, J. E.;Hemmings, R. T. J.Chem. SOC., Dalton Trans. 1976, 1730. (19)Reference 2,p 45 and references therein.
0 1988 American Chemical Society
Organometallics, Vol. 7, No. 1, 1988 79
Synthesis of Telluroether Ligands Table I. '?l'e('H) and 'H NMR Data 6(l2STe) MezTe MePhTe MezTez MeTeCH2TeMe MeClzTeCHzTeClzMe MeTe(CHz)3TeMe MezTe(CHz)3TeMez(I)z MeTe(CHz)30H MeTe(CHz),TeMe MeZTe(CH2),TeMez(I)z MeTe(CHz)loTeMe MezTe(CHz)loTeMez(I)z MeC(CHzTeMe)3
. . .
T~(CHZ)~CHZ Te(CHz)4CH~ CHzCH2C(CHzTeMe)z PhzTe PhzTez PhTeCHzTePh PhC12TeCH2TePhC12 PhTe(CH&TePh PhMeTe(CH,),TePhMe(I), PhTe(CH&TePh PhMeTe(CHz)6TePhMe(I)z C(CH2TePh),
0 329 (lit. 329)* 55 (lit. 49) 212 (lit. 213.5)15 836.5 (lit. 834)15 104 494 105 106 426 104.5 418 21 234 210 65 685 (lit. 688) 417 (lit. 420) 584 (lit. 588)16 880 (lit. 858)15 466 609.7, 610.3 468 600.7, 600.5 407
VH) CHzTe
MeTe
others"
2.1 (s) (21.5)
2.6 ( 8 ) (23.5) 1.95 (s) (21.5) 3.05 (s) (27) 1.85 (s) (20) 2.1 (s) (24) 1.9 (8) (20) 1.9 (9) (20) 2.0 (8) (24) 1.9 (9) (21) 2.0 (9) (21) 1.8 (s) (21)
3.4 ( 8 ) (26) 4.75 (9) (22) 2.6 (t) (26) 2.75 (t) 2.7 (t) (24) 2.6 (t) (26) 2.6 (t) 2.6 (t) 2.6 (m) 2.9 (s) (22) 3.2 (t) (25.5) 2.6 (t) (26) 2.85 (s) (25)
1.9 (9) (20)
2.4
(8)
3.75 (9) (21) 4.7 (s) (21) 2.8 (t) (28) 3.0 (t) 2.8 (t) (26) 2.9 (t) 3.2 (8) (23)
(25)
2.3 (s) (25)
2.05 (4) 2.3 (9) 2.0 (q), 3.7 (t), 2.6 (s) 1.4 (m), 1.6 (m) 1.1-1.6 (m) 1.7 (4,1.3 (m) 1.3 (m) 1.2
(8)
2.05 (m) 2.0 (m), 1.6 (m) 0.65
2.15 (9) 2.0 (9) 1.8 (m), 1.3 (m) -2.0 (m)
"The aryl proton resonances at 7.1-7.7 ppm are not listed. bAll literature data from ref 6 unless otherwise indicated
Table 11. 'sCI'H1 NMR Data ( w m ) MeTe -21.5 (158) MezTe -19.9 (178) MezTez -16.7 (163) MePhTe -15.3 (164) MeTeCH2TeMe +29.5 (192) MeClzTeCHzTeClzMe -23.3 (162) MeTe(CHz)3TeMe Me2Te(CHz)3TeMe2(I)z +5.4 (173) -22.7 (160) MeTe(CH&OH -22.8 (163) MeTe(CHATeMe -22.9 (161) MeTe(CH&TeMe -19.6 (180) MeC(CHzTeMe)3
.
Te(CHz)3CHz Te(CHz)4CHz 1 CHzCHzC(CH2TeMeI2 PhzTe PhTeCHzTePhz PhClZTeCH2TePhClz PhTe(CHz)3TePh PhTe(CHz),TePh C(CHzTePh)4
...
... -22.0 (161)
... ... ... ...
c1
-45.7 (206) +43.3 (285) 5.2 (153) 24.6 (150) -1.6 (151) 3.0 (148) 3.4 (146) 21.4 (168) 5.8 (126) -3.6 (131) 16.4 (153) -6.2 (210) 53.9 (266) 10.5 (157) 8.4 (152) 24.9 (178)
33.6 (32) 21.5 (52) 33.8 (38) 31.0 31.9 38.5 35.8 (28) 28.6 (27)
33.2 (32) 31.6 (36) 42.6
from reaction with C12/CC14. 1,2-Dichloro- or dibromoethane and RTeLi gave only RzTe2and ethene, irrespective of the temperature of reaction, consistent with previous r e p ~ r t s , ~and ~ J no ~ iother ~ tellurium species were detected in the 'WTe NMR spectra of the crude products. Similarly at room temperature RTeLi and X(CHJ3X (X = C1 or Br) gave R2Te2and olefin as major products as reported,13J4 but in marked contrast addition of the l,&dihalopropane to frozen RTeLi gave high yields of RTe(CH2)3TeR(R = Ph, 85%; R = Me, 73%)." Once isolated the ligands are quite stable under nitrogen and were recovered unchanged after being heated for several hours at 100 "C. Careful reexamination of the products from the room-temperature synthesis by lH and 125Te(1H) NMR revealed very small amounts of RTe(CHJ3TeR were present, but without prior (20) Pluscec, J.; Westland, A. D. J. Chem. SOC.1965, 5371.
cn
CZ
aromatics ortho
meta, para
112.5 (...)
136.7 (55)
127.0, 129.0
114.7 (...) 116.0 (...) 137.2 (332) 111.7 (280) 111.8 (280) 113.0 (280)
137.8 (54) 137.6 (50) 129.3 (52) 138.2 (56) 138.3 (55) 139.0 (60)
127.5, 129.2 127.8, 128.0 131.4, 133.9 127.3, 129.0 127.4, 128.0 129.3, 128.0
ipso
62.8 31.5 29.4, 29.0, 28.9 28.1 29 17.7, 22.3
31.0
knowledge of the spectral characteristics, it is not surprising that they have not been detected previously. The reaction of frozen MeTeLi with Cl(CH2)4C1gave MezTe and a compound with 6(laTe) 234 identified by its mass (parent ion m/z 186) and 13C(lH)and 'H NMR spectra (Tables I and 11) as the tellurocycle 1. The identity of 1 was confirmed by comparison of the NMR spectra with those of a genuine sample of telluracyclopentane prepared from NazTe and Br(CH2),Br in water.21 Similarly frozen PhTeLi and Br(CH2)4Brgave 1 and Ph2Te (6(lWTe)685), which were easily separated by fractionation in vacuo. However frozen PhTeLi and CI(CH2),Cl gave 1, Ph2Te, and a small amount of a third product with 6(lZ6Te) 474, which is reasonable for a PhTeCH2CH2CH2CH2-moiety (cf. PhTe-n-Bu, 468 (21) Farrar, W. V.; Gulland, J. M.
J. Chem. SOC.1945, 11.
80 Organometallics, Vol. 7, No. 1, 1988
ppm).,, The possibility that this was the desired PhTe(CH,),TePh was however ruled out by the 13C(lH}spectrum which (after elimination of the resonances of 1 and PhzTe) showed four aryl C and four distinct CH, resonances at 6 7.1, 28.8, 34.4, and 43.8 (confirmed as methylene groups by a DEPT experiment). Attempts to separate this product by flash column chromatography on silica failed but from the 13Cresonances especially that at 43.8 ppm and a weak triplet at 3.5 ppm in the 'H spectrum both characteristic of a -CH2C1 group, it was identified as PhTe(CH2)4C1. The data are inconsistent with a cyclic telluronium salt (cf. ref 14 and 23) which would have only two l3C(CHz)resonances and for which @Wre) is expected some ca. 200 ppm to higher frequency. We have been unable to obtain a larger proportion of PhTe(CHJ4C1 by varying the reaction conditions, and it is not present at all if the reaction is carried out >-lo "C. The reactions of frozen RTeLi with C1(CH2)5C1resembled the 1,4-dichlorobutane reactions in that R2Te and the heterocycle telluracyclohexane 2, Te(CHJ4CH2,6(129e)210, were the major products, and these were the only products from the room-temperature reactions. However, at low-temperatures MeTeLi gave two further minor products 6(lWre) 107 and 105 ppm (intensity ratio ca. 1O:l). After removal of most of 2 by distillation, the residue had a 13C11H}spectrum with 6(MeTe) -22.9 and five substantial CH2 resonances 2.5, 28.3,30.8, 31.7, and 44.3 ppm, showing it to be mainly MeTe(CH,),Cl. This was confirmed by the observation of parent ion with the correct isotope pattern at m/z -250 in the mass spectrum. It seems likely that the 6(12Te)105 is due to MeTe(CH,),TeMe, but the yield is too small to allow its isolation. In the PhTeLi/Cl(CH,),Cl reaction minor products with 6(lz5Te)469 and 472 ppm are tentatively identified as PhTe(CH,),Cl and PhTe(CH,),TePh on the basis of similar spectroscopic evidence. The frozen PhTeLi/C1(CHz),C1reaction afforded three tellurium-containingspecies with s(l25Te) 685 (Ph,Te), 468, and 230. Flash column chromatography on a portion of this mixture separated pure Ph,Te and PhTe(CH&TePh (6 4681, while vacuum distillation of another portion yielded PhzTe as the only volatile (
