Organometallics 1995, 14, 4755-4763
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Syntheses and Characterization of Hybrid Bi- and Multidentate Tellurium Ligands Derived from Nfl-Dimethylbenzylamine: Coordination Behavior of Bis[2-((dimethy1amino)methyl)phenyllTelluride with Chromium Pentacarbonyl Rupinder Kaur,? Harkesh B. Singh,*lt and Ray J. Butcher* Departments of Chemistry, Indian Institute of Technology, Powai, Bombay 400 076, India, and Howard University, Washington, DC, 20059 Received April 26, 1 9 9 P
A range of bi- and multidentate tellurium ligands containing both Te and N donor atoms have been synthesized and characterized by multinuclear NMR (lH, 13C, lZ5Te),MS, and single-crystal X-ray diffraction studies. Bidentate ligand 2-NMezCHzCsH4TeMe (4) was obtained from the reaction of 2-NMezCHzC6H4TeLi (3)with MeI. The reaction, in addition to the expected telluride 4, afforded the novel 2-NMezCHzC6H4TeI (5) and the tridentate ligand (2-NMezCHzC6H4)zTe (6) in poor yields. The compound is monomeric with weak intermolecular contacts between the Te and iodine atoms from adjacent molecules. Alternatively, ligand 6 has been obtained by the reaction of 2-NMezCHzCsH4Li (2) and TeIz, and its bonding capabilities have been evaluated. Ligand 6 displaces the THF ligand in Cr(C0)5THF to give the complex Cr(C0)5(2-NMe2CHzCsH4)2Te(13)in which the ligand is bonded only through Te. Reaction of 6 with Cr(CH3CN)3(C0)3also gives the same complex 13. Structures of the free ligand and its complex have been determined. Li and 6 crystallizes in monoclinic space group P21/n with a = 10.2310(10) b = 5.6110(10) ,c = 32.010(3) #? = 97.13”(1),V = 1823.4(4) A3, 2 = 4, D,= 1.443 mg/m3 (Mo K a radiation at 293(2) K). The Te atom is pyramidal, and the Cr-Te distance of 2.6665 (9) is the shortest known. The bidentate ligand 2-NMe~CHzC&TePh (7) has been similarly obtained from 2 by reaction with PhTeBr. Oxidative workup of 3 afforded the ditelluride (2-NMezCHzC6H4)zTez(8). Reaction of 8 with diazomethane gave the telluroether ligand ( ~ - N M ~ ~ C H ~ C ~ H ~(9). T~)ZCHZ Other multidentate ligands of the type (2-NMezCHzC6HsTe)zE (10-12)(E= (CH2)3, S, Se) were obtained by the reaction of Br(CH2)3Br, S, and Se with 3,respectively.
f
A,
A,
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1. Introduction Organotellurium compounds have become increasingly important as versatile reagents in modern organic synthesis.l A well-established method of obtaining a range of otherwise reactive and unstable organotellurium compounds is intramolecular co~rdination.~,~ Intramolecular coordination also provides a very useful method for the synthesis of “hybrid”bi- and multidentate ligands containing “hard” donor atoms such as nitrogen or oxygen in addition to “soft” tellurium. Hybrid organotellurium ligands are important as they offer the prospect of coordination to both hard and soft transition metal centers, giving rise to complexes possessing novel structures and reactivities. In addition they are suitable for the synthesis of heterobimetallic complexes which have applications in homogeneous ~atalysis.~ +
Indian Institute of Technology.
* Howard University.
Abstract published in Advance ACS Abstracts, September 1,1995. (1)(a) Engman, L. Acc. Chem. Res. 1985, 18, 274. (b) Petragnani, N.; Comasseto, J. V. Synthesis 1988,1, 791,897. (c) The Chemistry of Organic Selenium and Tellurium Compounds; Patai, S., Rappoport, Z., Eds.; Wiley: New York, 1986 and 1987; Vols. 1and 2. (d) Irgolic, K. J. In Methods of Organic Chemistry; Klamann, D., Ed.; Georg
Thieme Verlag: Stuggart, 1990; Vol. E12b. (2) Sudha, N.; Singh, H. B. Coord. Chem. Rev. 1994,135/136,469. (3)McWhinnie, W. R. Phosphorous, Sulfur Silicon Relat. Elem. 1992, 67, 107.
Nitrogen donor complexes have a very important role to play in organic ~ynthesis.~ Tellurium ligands incorporating nitrogen donor atoms are well-known1 Although several examples of hybrid tellurium ligands incorporating sp2 nitrogen atoms, e.g., azobenzenes,6 a~omethines,~ and substituted pyridines,8are available in the literature, far fewer examples of organotellurium ligands having sp3 nitrogen are known. Di(o-aminopheny1)ditelluride was one of the first examples of this kind to be synthesized.6 Levason et ~ 1 have . ~reported methyl o-(dimethy1amino)phenyltelluride and related hybrid ligands. Gysling et al.1° have described the preparation of the aryl analog, phenyl o-(diphenylamino)phenyl telluride. Recently Khandelwal et al. have reported telluroamine, bis[(2-aryltelluro)ethyllamine, (4) Hope, E. G.; Levason, W. Coord. Chem. Rev. 1993,122, 109. (5)Togni, A.; Vananzi, L. M. Angew. Chem., Int. Ed. Engl. 1994, 33, 497. (6) (a) Cobbeldick, R. E.; Einstein, F. W. B.; McWhinnie, W. R.; Musa, F. H. J. Chem. Res. 1979, 901(M); 1979, 145W (7) (a)Al-Salim, N.; Hamor, T. A,; McWhinnie, W. R. J . Chem. Soc., Chem. Commun. 1988,453. (b) Minkin, V. I.; Sadekov, I. D’.; Maksimenko, A. A.; Kompan, 0. E.; Struchkov, Yu. T. J . Organomet. Chem. 1991, 402, 331. (c) Wu, Y. J.; Ding, K. L.; Wang, Y.; Zhu, 2.; Yang, L. J. Organomet. Chem. 1994, 468, 13. (8)(a) Hamor, T. A,; Al-Salim, N.; West, A. A.; McWhinnie, W. R. J. Organomet. Chem. 1988, 310, C5. (b) Al-Salim, N.; West, A. A.; McWhinnie, W. R.; Hamor, T. A. J . Chem. Soc., Dalton Trans. 1988, 2363. (9) Kemmitt, T.; Levason, W. Organometallics 1989, 8, 1303. (10)Gysling, H. J.; Luss, H. R. Organometallics 1984, 3, 596.
Q276-7333l95l2314-4755$Q9.QQlQ 0 1995 American Chemical Society
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Organometallics, Vol. 14, No. 10, 1995
and 2-(2-(aryltelluro)ethyl)pyridinetypes of 1igands.ll Examples of organotellurium compounds containing an ortho-amino group12 and a tetradentate tripodal Te,N ligand are also known.13 All the examples mentioned above include ligands which are capable of forming fivemembered rings upon chelation with metals. Very few examples of ligands capable of forming six-membered chelates are known.14-17 This paper discusses the syntheses of a series of bi- and multidentate Te,N ligands capable of forming six-membered rings upon chelation.
2. Experimental Section General Procedures. All reactions were carried out under the exclusion of air and moisture, under a n atmosphere of dinitrogen. Reactions were monitored using TLC techniques. Solvents and Hg were purified by standard techniques.lS All chemicals were of reagent grade and were used as received. The following starting materials were prepared according to literature methods: diphenyl ditelluride,lg Te12,20 cr(co)5THF,21and Cr(C0)3(CH3CN)3.22Melting points were recorded in capillary tubes and are uncorrected. Elemental analyses were performed on a Carbo-Erba model 1106 elemental analyzer. IR spectra were recorded on a Nicolet Impact 400 FT-IR spectrometer. Magnetic resonance spectra, lH (299.94 MHz), 13C (75.42 MHz), and lz5Te(94.75 MHz), were recorded on a Varian VXR 300s spectrometer a t the indicated frequencies. Chemical shifts are cited with respect to SiMer as the internal standard ('H and 13C)and to a 0.3 M solution of Te(S2CNEt2)z in CDC13 as the external standard (125Te).23Positive chemical shifts are downfield from Te(SzCNEt2)z. The assignment of carbons in the 13CNMR spectra are in accordance with the figure.24 125TeNMR spectra were obtained from ca. 20% wlv solutions in CDC13, a t 25 "C. Satisfactory spectra were obtained after ca. 100-10000 transients. Values quoted are using the high-frequency positive convention. Mass spectra were obtained on a Jeol D-300(EI/CI) spectrometer and are reported as mle (ion percent relative intensity). In case of a n isotopic pattern, the value given is for the most intense peak. (11)(a)Singh, A. K.; Srivastava, V.; Khandelwal, B. L. Polyhedron 1990, 9, 495. (b) Singh, A. K.; Srivastava, V.; Khandelwal, B. L. Polyhedron 1990,9, 851. (c) Khalid, A,; Khandelwal, B. L.; Singh, A. K.; Singh, T. P.; Padmanabhan, B. J . Coord. Chem. 1994,31, 19. (12) Al-Rubaie, A. Z.; Al-Salim, N. I.; Al-Jadaan, A. N. J . Organomet. Chem. 1993,443,67. (13)Singh, A. K.; Srivastava, V. J . Coord. Chem. 1990,21, 39. (14) (a)Christiaens, L.; Luxen, A., Evers, M.; Thiabaut, Ph.; Mbuyi, M.; Welter, A. Chem. Scr. 1984, 24, 178. (b) Gornitzka, H.; Besser, S.; Herbst-Irmer, R.; Kilimann, U.; Edelmann, F. T. J . Organomet. Chem. 1992, 437, 299. (c) Detty, M. R.; Friedman, A. E.; McMillan, M. Organometallics 1996, 14, 1442. (15)Maslokov, A. G.; McWhinnie, W. R.; Perry, M. C.; Shaikh, N.; McWhinnie, S. L. W.; Hamor, T. A. J . Chem. SOC.,Dalton Trans. 1993, fil9
(16) Engman, L.; Stern, D.; Pelcman, M.; Andersson, C. M. J . Org. Chem. 1994,59, 1973. (17) Sineh. H. B.: Sudha. N.: West. A. A,: Hamor. T. A. J . Chem. Soc., Da& Trans. '1990, 907. (18) Perrin, D. D.; Armarego, W. L. F.; Perrin, D. R. Purification o f Laboratory Chemicals, 2nd ed.; Pergamon Press: New York, 1980. (19) Haller, W. S.; Irgolic, K. J. J . Organomet. Chem. 1972,38,97. (20)Brauer, G. Handbook of Preparative Inorganic Chemistry, 3rd ed.; Academic Press: New York, 1975. (21) Werner, H.; Prinz, R. Chem. Ber. 1967, 100, 265. (22) Tate, D. P.; Knipple, W. R.; Augl. J. M. Inorg. Chem. 1962, 1 , 433. (23) Zumbulyadis, N.; Gysling, H. J. J . Organomet. Chem. 1980,192, '
183.
u
11
12
Kaur et al. Synthesis of 2-NMezCHzCeH4TeMe (4).14a A stirred solution ofN,N-dimethylbenzylamine 1(1.53 mL, 1.37 g, 10.2 mmol) in dry ether (50 mL) was treated dropwise with a 1.6 M solution of n-butyllithium in hexane (7.5 mL, 12.0 mmol) under N2. On being stirred for 24 h at room temperature, a white slurry of the lithiated product 2 was obtained. Tellurium powder (1.3 g, 10.2 mmol) was added to this under a brisk flow of N2 gas, and stirring continued for additional 3 h until all the tellurium dissolved to give the lithium arenetellurolate 3.17 The reaction mixture was cooled to 0 "C, after which iodomethane (0.64 mL, 1.448 g, 10.2 mmol) was syringed in; stirring continued for 0.5 h, following which the reaction was quenched with water and the aqueous phase was extracted with ether. The ether extracts were dried over anhydrous sodium sulfate, filtered, and concentrated to give a crude reddish-yellow oil. Separation by flash chromatography (SiOz, 100-200 mesh, ethyl acetate) gave four fractions. The first fraction obtained as a yellow oil after evaporation of the solvent in uucuo corresponded to the desired ligand, 4 (1.15 g, 41%). Anal. Calcd for CloH15NTe: C, 43.39; H, 5.43; N, 5.06. Found: C, 42.32; H, 4.60; N, 5.74. lH NMR (CDC13): 6 7.50-7.47 (m, l H , Ar-H), 7.12-7.06 (m, 3H,Ar-HI, 3.44 (s, 2H, CH2), 2.18 (s, 6H, NMe2), 1.83 (9, 3H,TeMe). 13C NMR (CDCl3): 6 119.3 (Ci), 140.4 (Cz), 126.8 (C31, 127.6 (C4), 124.5 (C5), 132.2 (CS), 65.5 ('271, 42.7 (CS, Cg) -17.0 (TeCH3). MS: mle 279 (M+,28), 264 (M+ - CH3,44), 220 (C6H&H&Te, 12), 134 (C6H&H2NMe2,100), 91 (220 - Te, 491, 77 (C&, 5), 58 (CH2NMe2, 9). Synthesis of 2-NMezCHzC&TeI (5). This compound was obtained as a minor product (second fraction after column chromatography) in the preparation of ligand 4 (0.34 g, 8%, mp 162 "C). Anal. Calcd for CgHlZNTeI: C, 27.78; H, 3.12; N, 3.60. Found: C, 27.80; H, 3.18; N, 3.56. 'H NMR (CDC13): 6 8.12-8.08 (m, l H , Ar-H), 7.26-7.20 (m, 2H, Ar-H), 7.087.05 (m, l H , Ar-H), 3.89 (s, 2H, CH2), 2.75 (s, 6H, NMe2). 13C NMR (CDC13j: 6 117.1 (Ci), 138.3 (Cz), 129.2 (C3), 129.3 (C4), 126.3 (C5), 138.4 (CS), 67.4 (C7), 46.8 (C8, Cg). MS: mle 390 (M+,111,263 (M+ - CH3,63), 220 (CsH&H2NTe, 81,134 (C& CHzNMe2, 1001,91 (220 - Te, 95). Synthesis of (2-NMezCHzC&)zTe (6).16Method A. The desired ligand 6 was obtained as a minor product in the preparation of 4 as already described. Separation of the crude oil obtained after reaction, by flash chromatography, gave, aRer removal of the solvent (from the last fraction), light yellow crystals of 6 (0.120 g, 3%, mp 98 "C). Anal. Calcd for C18H24N2Te: C, 54.60; H, 6.07; N, 7.08. Found: C, 54.53; H, 6.24; N, 7.24. 'H NMR data was in full accordance with reported16 values. 13CNMR (CDC13): 6 126.1 (Cl), 143.2 (Cz), 127.6 (C3), 128.7 (c4),126.5 (cd,138.6 (cs), 67.3 (c7),44.3 (CS,c g ) . MS: mle 396 (M', 51,218 (C&Te, 81,179 (81,134 (NMe2CH2C6H4, 1001, 91 (C7H7, 111,58 (CH2NMe2, 2). Method B. To a cooled stirred solution of 2 a t 0 "C was added TeI2 (1.95 g, 5.1 mmol) in the powdered form. The reaction was stirred a t this temperature for 0.5 h. The TeI2 was found t o be consumed completely. Usual workup gave, on removal of solvent in uucuo, yellow crystals of 6. The compound was recrystallized from pentane (1.30 g, 65%). Other analyses are as above. Synthesis of 2-NMezCHzCeWTePh (7). Ligand 7 was prepared by the reaction of 2 with PhTeBr.'O A solution of PhTeBr was prepared in situ by the addition of Br2 (0.82 g, 0.26 mL, 5.1 mmol) in 12 mL of benzene to a -78 "C solution of PhzTez (2.09 g, 5.1 mmol) in 125 mL of dry ether. The solution was stirred for 15 min in a n ice bath, and the resulting suspension of the dark-red PhTeBr was transferred via a cannula to 2 at -78 "C. The solution was then stirred in a n ice bath for 1h and a t room temperature for 0.5 h. The usual workup afforded a pale yellow oil, which crystallized upon cooling to give white crystals of 7. The compound was recrystallized from n-pentane (1.44 g, 42%, mp 77 "C). Anal. Calcd for C15H17NTe: C, 53.16; H, 5.02; N, 4.13. Found: C, 53.21; H, 5.08; N, 4.13. 'H NMR (CDC13): 6 7.90-7.87 (m,
Hybrid Bi- and Multidentate Te Ligands
Organometallics, Vol. 14, No. 10, 1995 4757
Synthesis of ( ~ - N M ~ ~ C H Z C & T (12). ~ ) ~Ligand S~ 12 2H, Ar-H), 7.37-6.88 (m, 7H, Ar-H), 3.52 (9, 2H, CHz), 2.24 was obtained by a n anologous method to that of 11 by addition (s, 6H, NMe2). NMR (CDC13): 6 122.7 (Cd, 140.6 (Cd, of selenium (0.40 g, 5.1 mmol) to 3 (1.6 g, 72%, mp 114 "C). 128.5 (c3),129.1 (c4),125.7 (c5), 134.5 (CS),66.2 (c7),43.7 (C8, Anal. Calcd for Cl8Hz4NzTe2Se: C, 35.87; H, 3.98; N, 4.65. Cg), 120.9 (Clo), 140.3 ( C d , 127.8 (CUI, 129.1 (c13).MS: mle Found: C, 36.18; H, 4.40; N, 4.60. 'H NMR (CDC13): 6 8.21341 (M+,63), 279 (28), 196 (15), 129 (C~HSN, 20), 105 (C7H$T, 8.18 (d, 2H, Ar-H), 7.15-6.97 (m, 6H, AI-H), 3.55 (s, 4H, 341, 86 ( C ~ H Z1001, , 55 (C3H5N, 40). CHz), 2.31 (9, 12H, NMez). I3C NMR (CDC13): 6 119.9 ((211, Synthesis of (2-NMezCHzC&Te)z (8). Tellurolate (3) 139.6 (cz), 126.9 (c3), 127.8 (c4),125.8 (c5),135.5 (0, 65.6 was poured into a beaker, and oxygen was passed through at (C,), 44.3 (C8, Cg). MS: mle 601 (M+, 31, 523 (M+ - Se, 161, a moderate rate for 10 min, after which time water (100 mL) 389 (191,263 (CsH&HzNMezTe, 601,133 ( C ~ H ~ C H Z N M ~ ~ , ~ ~ ) , was added into the beaker and oxygen was passed through 90 (C7H6, 100). for additional 0.5 h. The organic phase was extracted with Synthesis of Cr(C0)5(2-NMezCHzCs)~Te (13). Method ether and washed several times with water. Usual workup A. A solution of Cr(C0)5THFZ1obtained after photolysis of gave a yellow oil, which was flash-chromatographed using Cr(CO)6 (0.096 g, 0.44 mmol) in THF (75 mL) was treated with diethyl ether as the eluant. The yellow fraction obtained was a solution of 6 (0.17 g, 0.44 mmol) in THF (10 mL) at room concentrated and cooled at -20 "C t o give yellow crystals of temperature. The reaction was stirred at room temperature 8. These were filtered, rinsed with ether, and dried under for 0.5 h, after which insoluble green products were separated nitrogen (1.33 g, 50%, mp 87 "C). Anal. Calcd for C18Hz4Nzby filtration over a pad of Celite. The resulting yellow solution Tez: C, 41.28; H, 4.59; N, 5.35. Found: C, 41.36; H, 4.45; N, obtained was concentrated. Hexane (5 mL) was added to the 5.36. 'H NMR (CDC13): 6 8.01-7.98 (d, 2H, Ar-H), 7.15filtrate, and it was cooled to 5 "C to give a yellow powder. The 6.98 (m, 6H, Ar-H), 3.55 (s, 4H, CHZ), 2.30 (8, 12H, NMez). product was recrystallized from hexane t o give 13 as pale 13C NMR (CDCl3): 6 113.0 (Ci), 140.8 (Cz), 128.0 (C3), 127.7 yellow crystals (0.20 g, 78%, mp 97 "C). Anal. Calcd for c23(C4),126.1 (C5), 138.9 (Cd, 66.3 (C7), 43.8 (CS,Cd. MS: mle Hz4NzCr05Te: C, 46.97; H, 4.11; N, 4.76. Found: C, 46.78; 524 (M+,51,262 (CsH4CHzNMezTe, 911,220 ( C ~ H ~ C H Z28), T~, H, 3.81; N, 4.38. 'H NMR (CDC13): 6 7.94-7.91 (d, 2H, Ar91 (220 - Te, 50),77 (C7H7, 179 (15), 134 (C&I~CHZNM~Z,~OO), H), 7.31-7.12 (m, 6H, Ar-H), 3.70, 3.15 (dd, AB system, 4H, CHz, 2 J =~15 ~ Hz), 2.14 (s, 12H, NMez). 13C NMR (CDC13): 41, 58 (CHZNMez, 8). 6 223.7,217.4 (CO-C), 121.4 (Ci), 142.6 (Cz), 128.9 (C3), 129.3 Synthesis of ( ~ - N M ~ ~ C H ~ C ~ H ~ T(9). ~ ) ZTo ( Ca H soluZ) (C4),128.4 (C5), 137.5 (CS), 66.5 (c7),44.6 (CS,cg). IR (hexane) tion of 8 (0.26 g, 0.5 mmol) in dry ether 0 "C was added an v(C0) = 2058 (m), 1946 (s), 1935 cm-'. excess of diazomethane in ether while a brisk flow of nitrogen Method B. A yellow solid of Cr(C0)3(CH3CN)322obtained passed through the reaction flask. The reaction was stirred after thermolysis of Cr(C0)e (0.192 g, 0.88 mmol) in CH&N at this temperature for 3 h. Excess diazomethane was (100 mL) and removal of the solvent in vacuo was refluxed removed by bubbling nitrogen through the solution, and finally for a period of 0.5 h with a solution of 6 (0.34 g, 0.88 mmol) in the ether was removed under vacuo. The resulting yellow oil THF (50 mL). The pale yellow solution obtained was filtered was the desired ligand, 9 (0.26 g, 100%). 'H NMR (CDCL): 6 over Celite, concentrated, and cooled to 5 "C after addition of 7.71-7.68 (d, 2H, Ar-H), 7.17-7.03 (m, 6H, Ar-H), 3.46 (9, hexane (5 mL) to give 13 (0.10 g, 20%). Other analyses are as 4H, CHz), 3.29 (s, 2H, TeCHz),2.18 (s, 12H, NMez). 13CNMR described above. (CDC13): 6 124.1 (Ci), 140.7 (Cz), 128.1 (C3), 127.8 (C4), 125.2 X-ray Structure Determinations of 5,6, and 13. Com(C5),132.5 (Cs), 65.8 ((271,44.3 (Cs, Cg). MS: mle 538 (M+, 2), pound 6 was obtained as brick red hexagonal plates from 394 ( C ~ E H Z ~ N2), Z T258 ~ , (51,220 ( C ~ H ~ C H Z81,179 T ~ , (181,134 dichloromethane-hexane after 1day at -20 "C. Pale yellow ( C ~ H ~ C H Z N Mloo), ~ Z , 91 (220 - Te, 681, 58 (CHzNMez, 35). needles of ligand 6 were obtained from hexane after 2 days by Synthesis of ( ~ - N M ~ ~ C H ~ C ~ H ~(10). T ~ )Addition Z ( C H ~ ) slow ~ evaporation at 5 "C. Yellow parallelopipeds of complex of 1,3-dichloropropane (4.80 mL, 5.76 g, 5.1 mmol) at -196 "C 13 were obtained similarly from hexane after several weeks to 3 followed by usual workup gave yellow oil of the ditelluroat -20 "C. All diffraction measurements were performed on ether ligand 10 (1.38 g, 48%). Anal. Calcd for CZIH~ONZT~Z: an Enraf-Nonius CAD4 diffractometer usin graphite-monoC, 44.52; H, 5.30; N, 5.04. Found: C, 43.42; H, 4.98; N, 4.01. chromated Mo Ka radiation (1 = 0.710 73 1. The unit cell IH NMR (CDC13): 6 7.55-7.51 (d, 2H, Ar-H), 7.25-7.01 (m, was determined from 25 randomly selected reflections using 6H, Ar-H), 3.69, 3.61 (t, 4H, TeCHd, 3.40, 3.42 (9, 4H, CHd, the automatic search index and the least-squares routine. 2.73-2.65 (m, 2H, CCHzC), 2.15, 2.16 (s, 12H, NMez). 13C During data collection, the intensities of four monitor reflecNMR (CDC13): 6 119.1, 119.6 (CI), 138.1, 141.5 (Cz), 127.6, tions showed no decay effects. The structures were solved by 127.7 (c3),128.8, 128.9 (c4), 125.7, 125.8 (c5), 133.5, 133.8 (Cd, direct methods. The analytical scattering factors of Cromer 65.5, 66.7 (C7), 43.6, 43.7 (Cs, Cg), 32.59, 33.9 (CCHzC), 10.0, and Waber25 were used; real and imaginary components of 3.2 (TeCH2). anomalous scattering for the atoms were included in the calculations. All computational work was carried out using Synthesis of (2-NMezCHzCfiTe)zS (11). Dissolution of Siemens programs SHELTXL PLUTO,27and ORTEP.% 3 in THF (150 mL) after removal of ether gave a red-colored Crystal data and numerical details of measurement of intensolution, which was filtered under nitrogen to remove unresity details are given in Table 1. acted tellurium (if any). The filtered solution was collected in a two-necked flask, one end of which was connected to an 3. Results and Discussion Nz gas supply, The reaction mixture was frozen to -78 "C, and sulfur powder was added (0.16 g, 5.1 mmol). All the sulfur Ligand Synthesis and Characterization. Synwas found to react as the reaction mixture slowly attained thesis of the desired ligands 4 and 6-12 w a s acroom temperature to give a yellow solution. Usual workup complished in yields ranging f r o m 40%-75% by the gave, on removal of the solvent, a yellow solid of 11. The organolithium r o u t e (Scheme 1). Orthometalation w a s compound was recrystallized from ether (1.27 g, 45%, mp 122 "C). Anal. Calcd for C18Hz&TezS: C, 38.90; H, 4.32; N, 5.04. (25) Cromer, D. T.; Waber, T. International Tables for X-ray CrystalFound: C, 38.89; H, 4.76; N, 4.88. lH NMR (CDC13): 6 8.23lography; Kynoch Press: Birmingham, England, 1974; Vol. IV. 8.20 (d, 2H, Ar-H), 7.23-7.02 (m, 6H, Ar-H), 3.63 (s, 4H, (26) SHEIXTL PLUS. X-ray Instruments Group, Nicolet Instruments Corp.: Madison, WI 53711, 1983. CHz), 2.36 (s, 12H, NMez). 13C NMR (CDC13): 6 123.6 (Cd, (27)PLUTO-78. Motherwell, S., Clegg, W. Programme for Plotting 139.5 (cz),127.0 (c3),128.0 (c4),125.8 (C5), 133.5 (CS), 65.8 Molecular and Crystal Structures; University of Cambridge: Cam(C7), 44.6 (CS,Cd. MS: mle 552 (M+, 51,526 (M+ - S, 5), 264 bridge, England, 1978. ( C ~ H ~ C H ~ N M20), ~ Z 220 T ~ ,( C ~ H ~ C H Zlo), T ~ ,134 (CsH4CHz(28) ORTEP-11. Johnson, L. K. Report ORNL-5138; Oak Ridge National Laboratory: Oak Ridge, TN, 1976. NMe2, loo), 91 (220 - Te, 22).
d
4758 Organometallics, Vol. 14, No. 10, 1995
Kaur et al.
Table 1. Crystallographic Data and Measurements for 2-"Me2CH2C&TeI (51, (2-NMezCH2CsH4hTe (61, and C ~ ( C O ) ~ ( ~ - " M ~ ~ C H Z(13) C~H~)~T~ empirical formula fw
cryst color and habit cryst size (mm3) cryst syst space group unit cell dimens a b c
(A) (A) (A)
a (deg)
P (deg)
y (deg) volume (A3)
z
density (Mglmm3)(calcd) abs coeff (mm-l) F(000)
temp (K) 0 range for data collcn index ranges no of reflns collcd no. of indpt reflns (Ri,J abs cor max and min transm refinement method no. of datdrestraintslparams goodness-of-fit on F final R indices [I > 2u(1)]
R indices (all data) abs structure param extinction coeff largest diff peak and hole (e A-3)
CsH12NTeI 388.7 red plates 0.53 x 0.45 x 0.15 orthorhombic Pbca
Crystal Data ClsH24N2Te 395.99 pale yellow needles 0.37 x 0.35 x 0.08 monoclinic P21h
10.2310(10) 5.6110(10) 32.010(3) 90 97.13(1) 90 1823.4(4) 4 1.443 1.628 792 Measurement of Intensity Data 293(2) 293(2)2.03-25.00' 3.66-30.00" -12 5 h 5 12 O5h512 -15 5 k 5 0 O s K 6 -1 5 1 5 38 -33 5 1 5 0 3019 5104 3290 2364 0.0175 0.1380 semiempirical from q-scans semiempirical from pscans 1.000 and 0.364 0.967 and 0.711 full-matrix least-squares on F full-matrix least-squares on F 3290/0/112 2845/0/195 1.034 0.961 R1= 0.0339 R1= 0.0344 wR2 = 0.0874 wR2 = 0.0530 R1= 0.0621 R1= 0.0483 wR2 = 0.0911 wR2 = 0.0871
C23H24CrNz05Te 588.04 yellow parallelopipeds 0.65 x 0.55 x 0.15 orthorhombic Cmc21
8.6610(10) 11.1420(10) 23.5780(10) 90 90 90 2275.3(3) 8 2.269 5.281 1424
18.930(4) 9.135(12) 14.181(3) 90 90 90 2452.3(9) 4 1.593 1.667 1168
0.0064(4) 1.270 and -0.888
203(2) 2.15-32.48" O5h528 O5k513 215150 2357 2357 0.0000 NA NA full-matrix least-squares on F 2357101159 1.105 R1= 0.0340 wR2 = 0.0847 R1 = 0.0348 wR2 = 0.0854 0.00 0.0027(4) 4.003 and -1.651
readily accomplished according to the procedure of Klein and HauserZ9to give a solution of aryllithium 2, which was further reacted with finely ground tellurium powder to give lithium arenetellurolate 3. Syntheses of hybrid bidentate ligand 4 was achieved by the reaction of 3 with MeI. Preliminary workup afforded an impure yellow oil, which was purified by column chromatography. Four fractions obtained after column chromatography corresponded t o the desired ligand 4 in 41%yield as an air sensitive yellow liquid, a red solid (8%, which was identified to be 5), unreacted amine, and the known telluride ligand16 6 (3% yield). The reaction was repeated several times to check its reproducibility. The unexpected formation of 5 can be rationalized by the existence of elemental iodine in solution, which upon reaction with 3 affords 5. In a related study 2-[(phenylamino)carbonyllbenzenetellurenyl iodide was obtained by the addition of iodine to the tellurium-containing of 5 is benzanilide-derived lithium d i a n i ~ n Isolation .~~ determined by the strong stabilization of the N-Te-I system to 10-Te-3 tellurane with intramolecular Te-*N links (where N-X-L classification is used).31 The intramolecular coordination was confirmed by the singlecrystal X-ray structure of 5 (vide infra). Reaction of 5 with RLi probably leads to the formation of 6 in minor yield. (29) Klein, K. P.; Hauser, C . R. J . Org. Chem. 1967,32,1479. (30)Engman, L.;Hallberg, A. J . Org. Chem. 1989,54, 2264. (31)Perkins, C. W.; Martin, J. S. J . A m . Chem. SOC.1980,102,1155.
0.0004(2) 0.303 and -0.286
Ligand 7 was obtained by two routes, first by the treatment of 3 with C&Br. A yellow Viscous semisolid was obtained in moderate yield (37%). However, separation of the unreacted amine posed a major problem. Hence, alternatively, ligand 7 was prepared by reaction of 2 with PhTeBr by nucleophilic substitution on tellurium by a carbon nucleophile. The yield in this case was higher (42%) and afforded a crystalline white product. The telluride ligand 6 was obtained in low yields in the preparation of 4. Alternatively, reaction of 2 with TeIz was carried out in the ratio 2:l to yield 6 in excellent yields. This two-step reaction is a direct method and gives better yields compared to the recent literature method.16 The synthesis of 8 , though conceptually simple, proved to be a difficult task in practice. Isolation of the product and its subsequent crystallization depend on the ratio of product and the unreacted amine. It has been observed that less than 10% of unreacted amine favors crystallization. The complete workup procedure, including chromatography using diethyl ether as the solvent, gave, on cooling, a yellow solid of 8 in 50%yield. It is important to use peroxidefree ether for both reaction and purification. While attempts to grow the good quality crystals from various solvents were unsuccessful, slow evaporation of an ethereal solution gave after several days of standing parallelopipeds of 8 from the mother liquor. A method ~ Z ~ ~ involving the reaction of 3 with excess C H ~ C was attempted for 9 (52%); however, the purity was low.
Hybrid Bi-and Multidentate Te Ligands
Organometallics, Vol. 14, No. 10,1995 4759 Scheme 10
( i i i )
P
Legend: (i) n-BuLi, (ii) TeIz, (iii) PhTeBr, (iv) TeO, (v) MeI, (vi) PhBr, (vii) [ O ] ,(viii) CHZNZ,(ix) X(CHz),X, X = C1, Br, (x) E = Se, Te.
Alternatively, 9 was prepared by the reaction of 8 with d i a ~ o m e t h a n ein~ ~100%yield (based on 8). Although the second method involves the preparation of ditelluride and its subsequent reaction with diazomethane, the purity of the product in this case is high. The reaction of 3 with Cl(CH2)&1 gave 10 as a yellow liquid in 48% yield. Minor amounts of RzTe and R2Te2 were also formed (responsible for slightly lower elemental analysis than expected). Insertion of S and Se into the Te-Te bond was achieved by the reaction of 3 with elemental S and Se to give 11 and 12 in good yields (45%and 72%) re~pectively).~~ The 'H and 13C chemical shifts for the tellurium ligands observe a trend that is indicative of M-**N coordination. The NMe2 resonances (lH NMR) in particular are sensitive to the electronegativity of the group attached directly to tellurium. In the 13Cspectra the effect of the M* *Ncoordination is experienced most by the ortho and ipso carbons. The ipso (C1) carbon resonances span the range 113-126 ppm, and the ortho carbon resonances (C2) were in the range (138.3-141.9 ppm) and are the most deshielded. 12TeNMR. The tellurium ligands and derivative 5 show relatively narrow line widths ( < 2 Hz). The chemical shifts are given in Table 2. The lZ5Techemical shifts range 920 ppm, with the signals being both shielded and deshielded with respect t o Te(S2CNEtdz. The signals are deshielded in all cases, however, with (32) Hope, E. G.; Kemmitt, T.; Levason, W.Organometallics 1988, 7, 78. (33) Jones, C. H. W.; Sharma, R. D. Organometallics 1986,5,805.
(34)Kollemann, C.; Obendorf, D.; Sladky, F. Phosphorous Sulfur Relat. Elem. 1988,38,69. (b) Kollemann, C.; Sladky, F. Organometallics 1991,10, 2101.
Table 2. 12qeChemical Shifts for Organotellurium Ligands entry no.
tellurium ligand
lZ5Te (ppm)
2J~e-~ (Hz) 29
-561 358 -289 - 198 -479 not recorded -435, -439 33,28 194 96
respect to TeMe2. The resonance position is very sensitive t o the electron-withdrawing effect of the substituent group. Thus a decrease in chemical shift is observed in going from R = Me to I, with R = Me being most shielded (-561 ppm) and R = I being most deshielded (358 ppm). The proton-coupled spectra for 4 show the presence of a quartet with 2 J ~ e=- 29 ~ Hz, which agrees well with the literature value of a related c o m p ~ u n d .In ~ 10 a set of triplets occurs at -435 and -439 ppm with 2 J ~ eof- 33 ~ and 28 Hz, respectively. This agrees with similar observations made by lH and 13C NMR, indicating, probably, the presence of two distinct isomeric species. Decomposition of 10 occurs slowly in CDCl3 solution, giving peaks for both 6 and 8. For 5,11,and 12 downfield shifts are observed due to deshielding of Te by more electronegative atoms like I, S, and Se. For 11 minor amounts of polysulfides ( ~ 1 % ) such as RTe(Sh-4TeR are detected by 125TeNMR. These appear even more downfield with respect to 11 (125Te= 273, 288, and 298 ppm). Similarly for 12 a minor amount of polyselenide RTe(SehTeR is detected (125Te = 145 ppm). There is no indication of an
Kaur et al.
4760 Organometallics, Vol. 14, No. 10, 1995
"exchange equilibrium phenomenon" as observed for I related compound PhTeSeTePh34b(giving rise to PhTeTePh and PhTeSeSeTeR) as no peaks for the ditelluride were detected by lZ5TeNMR. This indicates the stability of compound 12 as a result of intramolecular coordination. Complexation Reactions. Attempts to displace ligating carbonyls in Cr(C0)Gby the bidentate ligand 4 in THF in a thermal reaction led only to decomposition of the ligand and reprecipitation of Te even under mild conditions (
