Polyhedron 18 (1999) 2609–2615

The synthesis and characterization of isobutylantimony compounds*Alan Berry

Chemistry Division, Code 6174, Naval Research Laboratory, Washington, DC 20375, USA

Received 11 November 1998; accepted 27 May 1999

Abstract

Six new isobutyl derivatives of antimony have been synthesized in good yields, including the five-coordinate i-Bu SbI and the3 2

three-coordinate i-Bu SbI, i-Bu SbBr, i-BuSbBr , i-Bu SbH, and i-BuSbH . The iodides were made from addition of iodine to i-Bu Sb2 2 2 2 2 3

and subsequent thermal decomposition of i-Bu SbI . The bromides were synthesized by thermal exchange reactions of i-Bu Sb with3 2 3

SbBr , and the hydrides from reduction of the bromides with LiAlH . All compounds have been characterized by elemental analysis, IR,3 4

and NMR spectroscopy. 1999 Elsevier Science Ltd. All rights reserved.

Keywords: Organoantimony; Synthesis; NMR; IR

1. Introduction chosen to impart a degree of stability to the hydridesthrough its size, but yet to allow for the possibility of b

Much of the research in main group chemistry in recent hydrogen elimination as a decompostion pathway that wasyears has been driven by the need for new and improved not available to the neopentyl analogs. Results frommaterials. An example of this has been the growth of a previous work led to recommendations of temperatureswide variety of films including metals, semiconductors, from 3278–4278C to deposit InSb in reactions of theoxides, and nitrides by chemical vapor deposition (CVD). neopentyl hydrides with Me In [9], which is also in the3

This in turn has prompted a search for alternative chemical range suggested for the growth of indium antimonideprecursors to grow purer films, more efficiently, and in alloys containing arsenic and bismuth [4,21]. Our objectivesome instances more selectively. Our interest in organoan- has been to synthesize thermally stable antimony pre-timony chemistry has been associated with synthesizing cursors that will allow deposition of more complex materi-new precursors for the growth of antimony-based semi- als such as InAs Sb and InBi Sb at lower tempera-12x x 12x x

conductors. In most of the early deposition work, Me Sb tures.3

[1] and Et Sb [2] were used because of their commercial3

availability, although there was one report of the use of theunstable SbH [3]. Since 1991, the list of antimony 2. Experimental section3

precursors has increased to include a variety of alkyls[4,5], alkyl hydrides [6–9], amino compounds [10], and A high-vacuum system and helium-filled glove boxmore recently SbD [11]. We have focused on the synthesis (Vacuum/Atmospheres Dri-Lab, model HE 43-2) were3

of new, stable organohydrides in view of the success used in this work. Pentane, toluene, and diethyl ether wereobtained with the tertiarybutyl compounds of phosphorus dried with sodium and stored over sodium/benzophenone;[12,13] and arsenic [14,15]. The route to the hydrides has deuterated benzene was dried and stored over Na/K alloy.been through reduction of the corresponding organohalides Tetraglyme was distilled at reduced pressure from sodium/synthesized by redistribution reactions [16–18] or ther- benzophenone and stored in the glove box; isobutylmolysis of triorganoantimony dihalides [19,20]. In this chloride was distilled in vacuo from P O Antimony2 5.

work, the synthesis and characterization of six new iso- trichloride was purchased from Aldrich Chemical andbutylantimony compounds are reported, including the sublimed before use; antimony, magnesium, and lithiumprimary and secondary hydrides. The isobutyl group was aluminum hydride, also purchased from Aldrich, were used

as received. Proton and carbon-13 NMR spectra were*Fax: 11-202-767-3321. recorded on a Bruker AC-300 instrument at 300.13 and

0277-5387/99/$ – see front matter 1999 Elsevier Science Ltd. All rights reserved.PI I : S0277-5387( 99 )00165-5

2610 A. Berry / Polyhedron 18 (1999) 2609 –2615

75.468 Hz, respectively. The proton spectra were refer- formed immediately. After approximately five min, aenced to the residual protic peak of benzene at 7.15 ppm brown/black solid and a light brown suspension wereand the proton-decoupled carbon-13 spectra to the center present. The reactor was placed in an oil bath at 1328C,of the benzene triplet at 128 ppm. Infrared spectra were and after 20 min it contained a wet, black solid. Heatingobtained on a Perkin–Elmer 1430 spectrophotometer as for 4.5 h at 1308–1358C produced a yellow liquid and agases, liquid films between KBr plates, or as 1% com- smaller amount of gray /black solid; further heating at thisponents of KBr pellets. Transmission intensities were temperature for an additional five hours produced littledetermined by the method of Durkin, et al. [22]. Vapor change in appearance. A clear, colorless liquid (0.0806 g)pressures were measured using an MKS capacitance was distilled in vacuo from the reactor at ambient tempera-manometer. Melting points were obtained on a MEL- ture to a trap at 21968C; the infrared spectrum of thisTEMP II from Laboratory Devices USA and are reported material showed evidence for the presence of i-BuBr,uncorrected. Elemental analyses were performed by E1R based on a comparison to the spectrum of a commercialMicroanalytical Laboratory, Parsippany, NJ. sample, and at least one other unidentified compound. A

yellow liquid (2) (1.0867 g, 3.440 mmol, 54.6% yield)2.1. Synthesis of (Me CHCH ) Sb (1) remained in the reactor and was subsequently distilled at2 2 3

26 1608C and 5310 Torr. H NMR (C D ): 0.89(d, 12H,6 6

A Grignard reaction with i-BuMgCl and SbBr was used J56.5 Hz, CH ), 1.82(d, 4.4H, J56.9 Hz, CH ), 1.99(h,3 3 2

to synthesize (1). Isobutylmagnesium chloride was ob- 2.6H, J56.7 Hz, CH); the spectrum also contained peakstained from the vacuum distillation of i-BuCl (9.9936 g, assigned to a small amount (|11%) of (1) at 1.00(d, J56.6

13 1107.96 mmol) in two quantities into a flask containing 30 Hz), 1.40(d, J56.9 Hz). Ch Hj NMR: 38.72 (s,ml of diethyl ether and powdered magnesium (2.7510 g, SbCH CH(CH ) ), 27.21 (s, SbCH CH(CH ) ), 25.66 (s,2 3 2 2 3 2

113.15 mmol). After each addition, the mixture was SbCH CH(CH ) ); peaks due to (1) were observed at2 3 221warmed to ambient temperature with stirring each time, 28.60(s), 28.08(s), and 25.92(s). IR (film, cm ): 2955 vs,

and the subsequent vigorous reaction was cooled period- 2925 m, sh, 2890 m, 2870 m, 1465 m, 1400 w, 1380 w,ically in liquid nitrogen before allowing the final solution 1365 m, 1330 vw, 1310 w, 1165 w, 1090 vw, 1025 vw,to stir at ambient temperature overnight. The flask with the 605 vw. Elemental Anal. Calcd. for C H SbBr: C, 30.42;8 18

gray–black Grignard reagent was connected to a two-neck H, 5.74; Sb, 38.54; Br, 25.30. Found: C, 30.63; H, 5.69;roundbottom flask containing SbCl (5.830 g, 25.56 Sb, 38.31; Br, 25.14.3

mmol), and the apparatus evacuated before adding 20 mlEt O to dissolve the SbCl The solution was cooled to2 3.

2.3. Synthesis of Me CHCH SbBr (3)08C, and the Grignard was added slowly over a period of 2 2 2

20–25 min to yield a thick gray precipitate that was stirredAn exchange reaction between one equivalent of (1) andovernight at ambient temperature. After removing most of

two equivalents of SbBr yielded (3). The addition ofthe ether by vacuum distillation, the remaining gray solid 3

SbBr (2.1452 g, 5.935 mmol) to a 10-ml Pyrex reactorwas extracted four times with 20 ml of dry pentane, and 3

containing (1) (0.8726 g, 2.977 mmol) in the dry boxthe pentane distilled off. The remaining clear, colorless26 produced a bright yellow solid and liquid mixture, whichliquid was further distilled in vacuo at 508C (5310 Torr)

turned black within 5–10 min. After 16 h in an oil bath atusing a short-path still and the distillate collected at1 1358C, the reactor contained a yellow liquid and a small21968C (1) (4.7725 g, 16.283 mmol, 63.7% yield). H

amount of gray solid. Upon cooling the reactor to 21968CNMR (C D ): 1.00(d, 18H, J56.6 Hz, CH ), 1.39(d,6 6 3

and opening, a small amount of noncondensable gas was5.7H, J56.91 Hz, CH ), 1.85(n, 1.8H, J56.6 Hz, CH).213 1 removed. The reactor was warmed to ambient temperature,Ch Hj NMR: 28.78 (s, SbCH CH(CH ) ), 28.18 (s,2 3 2

and a clear, colorless liquid (0.1043 g) was transferred inSbCH CH(CH ) ), 26.00 (s, SbCH CH(CH ) ). IR (film,2 3 2 2 3 221 vacuo to a trap at 21968C. This material was identified ascm ): 2950 vs, 2920 m, 2890 m, 2860 m, 1465 m, 1450

mainly C H based on the following: IR (gas, P514w, sh, 1405 vw, 1375 m, 1360 m, 1325 w, 1310 w, 1205 4 1021vw, 1160 m, 1080 vw, 1020 vw, 955 vw, 915 vw, 750 br, Torr; cm ): 2975s, sh, 2965 vs, 2950 s, 2920 m, 2900 m,

vw, 730 br, vw, 600 vw. sh, 2890 m, 2880 m, 2870 m, sh, 1475 m, 1465 m, 1455 w,1395 w, 1380 w, 1335 vw, 1175 vw. Molecular weight

2.2. Synthesis of (Me CHCH ) SbBr (2) (gas phase)564; for C H 558. The yellow liquid remain-2 2 2 4 1026ing in the reactor was distilled at 528C (5310 Torr) to

An exchange reaction between two equivalents of (1) yield a yellow distillate (3) (2.0629g, 6.091 mmol, 68.2%1and one equivalent of SbBr was used to synthesize (2). yield): H NMR (C D ): 0.72(d, 6H, J56.6Hz, CH ),3 6 6 3

Antimony tribromide (0.7593 g, 2.101 mmol) was added 2.03(m, 0.9H, J56.4 Hz, CH), 2.14(d, 2.3H, J57.1 Hz);in the dry box to (1) (1.2317 g, 4.201 mmol) in a 10-ml the spectrum also contained peaks assigned to a small

13Pyrex reactor equipped with a Kontes glass–Teflon stop- amount (|6%) of (2) at 0.91(d, J56.6 Hz). ChHj NMR:cock. A clear, yellow solution and a light-colored solid 49.95 (s, SbCH CH(CH ) ), 26.83 (s, SbCH CH(CH ) ),2 3 2 2 3 2

A. Berry / Polyhedron 18 (1999) 2609 –2615 2611

25.51 (s, SbCH CH(CH ) ); peaks due to (2) were 2108C trap. A clear, colorless liquid (0.6571 g) collected2 3 2

observed at 38.85(s), 27.27(s), and 25.74(s). IR (film, at 21968C and was identified primarily as i-BuI (3.57121 1cm ): 2955 vs, 2925 m, sh, 2890 m, sh, 2870 m, 1795 mmol) based on the following: H NMR (C D ): 0.72(d, 66 6

vw, 1465 m, 1455 m, sh, 1440 sh, w, 1395 w, 1385 m, H, J56.5 Hz, CH ), 1.32 (n, 0.5 H, J56.4 Hz, CH),3

1365 m, 1330 vw, 1310 w, 1230 vw, 1200 vw, 1175 sh, w, 2.70(d, 1.4 H, J55.9 Hz, CH ). The pattern was identical2

1165 m, 1080 vw, 1015 w, 955 vw, 920 vw, 815 vw, 735 to that reported for i-BuI in CDCl but with solvent shifts321w, 600 vw. Elemental Anal. Calcd. for C H SbBr : C, [23]. IR (gas, P514 Torr; cm ): 2975 vs, 2970 vs, 28804 9 2

14.19; H, 2.68; Sb, 35.95; Br, 47.19. Found: C, 14.40; H, m, 1465 w, 1395 w, sh, 1385 m, 1320 w, 1310 w, 1200 s,2.59; Sb, 35.79; Br, 47.05. 1195 m, sh, 835 w, 740 w, 615 w, 605 w, 485 w.

Molecular weight (gas phase)5191; for C H I,5184. The4 9262.4. Synthesis of (Me CHCH ) SbI (4) yellow liquid was distilled in vacuo at 5582608C (53102 2 3 2

Torr) to yield a clear, bright yellow distillate (5) (1.3558g,1The reaction of (1) with I yielded (4). Iodine (2.6296 3.736 mmol, 97% yield). H NMR (C D ): 0.86(d, 12H,2 6 6

g, 10.361 mmol) was added slowly to a solution of (1) J56.4 Hz, CH ), 1.98(m, 4.8H, J56.6 Hz, CHCH ); the3 2

(2.9907 g, 10.204 mmol) in toluene in a glove box. The spectrum also contained peaks assigned to |3% of (1) atsolution was colorless in the presence of solid I during the 1.00(d, J56.6 Hz), 1.40(d, J57.2 Hz) and an unidentified2

13 1initial stages of addition but was purple with no solid species at 0.61(d, J56.6 Hz). Ch Hj NMR: 33.61 (s,present when the addition was concluded. No change in SbCH CH(CH ) ), 28.38 (s, SbCH CH(CH ) ), 25.54 (s,2 3 2 2 3 2

21appearance was apparent after stirring overnight at ambient SbCH CH(CH ) ). IR (film, cm ): 2950 vs, 2920 m,sh,2 3 2

temperature. The solution was transferred to an H-tube in 2890 m, 2865 m, 1465 m, 1400 w, 1380 m, 1365 m, 1320the dry box and most of the toluene distilled out, producing w, 1310 w, 1160 m, 1085 vw, 1020 w, 955 vw, 920 vw,a light yellow precipitate. Pentane (10 ml) was distilled 770 br, vw, 605 w. Elemental Anal. Calcd. for C H SbI:8 18

into the H-tube, and the solid dissolved. The solution was C, 26.48; H, 5.00; Sb, 33.55; I, 34.97. Found: C, 26.26; H,cooled with liquid nitrogen until a precipitate formed and 4.84; Sb, 33.29; I, 34.85.filtered cold to yield a light yellow precipitate and a yellowfiltrate. This procedure was repeated an additional three

2.6. Synthesis of (Me CHCH ) SbH (6)2 2 2times to obtain a white precipitate (0.9584 g) and a yellowsolid (3.8716 g), which was left after removal of the

The synthesis of (6) was accomplished by the reductionpentane and drying in vacuo at 608C. Total (4): 4.8300 g,

of (2) with LiAlH . A solution of (2) (0.9682 g, 2.66848.831 mmol, 86.5% yield. Sublimation of the yellow solidmmol) in Et O (6 ml) was added during a 10-min period26 2at 708C (5310 Torr) produced an almost colorlessto a mixture of LiAlH (0.173 g, 4.56 mmol) in Et O (64 2sublimate at 08C and no evidence of any other volatileml) at 2408C. Stirring was continued for an additional 30

material. The white precipitate melted at 748–768C, andmin before transferring the volatile materials to a series of1the sublimate at 748–758C. H NMR of white solidtraps at 2408C|21968C as the reactor warmed to ambient

(C D ): 0.88(d, 18H, J56.6 Hz, CH ), 2.55(n, 2.7H,6 6 3 temperature. A clear, colorless liquid collected at 2408C,13 1J56.7 Hz, CH), 3.01(d, 6.0H, J57.0, CH ). Ch Hj2 was further distilled according to RT|08|21968C. TheNMR: 58.28 (s, SbCH CH(CH ) ), 27.11 (s,2 3 2 21968C fraction was distilled according to RT|2458|2SbCH CH(CH ) ), 24.22 (s, SbCH CH(CH ) ). IR (white2 3 2 2 3 2 1968C to yield (6) (0.5250g, 2.215 mmol, 83.0% yield) in21solid, KBr pellet, cm ): 2960 s, 2920 m, 2895 m, 2870

the 2458C trap with a vapor pressure of 1.6 Torr atm, 2730 vw, 2715 vw, 2635 vw, 2620 vw, 1465 s, 1440 w, 126.58C. H NMR (C D ): 0.933, 0.929(d of d, 12H, J56.7,6 6sh, 1400 m, 1385 m, 1365 m, 1325 m, 1205 w, 1180 m, sh,

6.3 Hz, CH ), 1.29(m, 2.0H, CH), 1.77(m, 3.5H, CH ),3 21160 s, 1095 s, 1035 s, 960 w, 945 w, 925 w, 825 m, 775 132.34(q, 0.8H, J55.1 Hz, SbH). ChHj NMR: 28.89 (s,vs, 615 m, 425 w, 400 w, 305 m. Elemental Anal. (white

SbCH CH(CH ) ), 25.62 (s, SbCH CH(CH )(CH );2 3 2 2 3 3solid) Calcd. for C H SbI : C, 26.35; H, 4.98; Sb, 22.26;12 27 2 25.43 (s, SbCH CH(CH )(CH )), 20.92 (s,2 3 3I, 46.41. Found: C, 26.65; H, 5.00; Sb, 22.00; I, 46.39. 21SbCH CH(CH ) ). IR (film, cm ): 2950 vs, 2930 m,sh,2 3 2

2895 m, 2865 m, 1840 s, 1465 m, 1410 w, 1380 m, 13652.5. Synthesis of (Me CHCH ) SbI (5)2 2 2 m, 1325 w, 1310 w, 1205 vw, 1165 m, 1085 w, 1025 w,955 vw, 920 vw, 820 vw, 775 w, 635 vw, 555 vw.The synthesis of (5) was accomplished by the thermalElemental Anal. Calcd for C H Sb: C, 40.55; H, 8.08; Sb,8 19decomposition of (4). Triisobutylantimony diiodide51.37. Found: C, 40.48; H, 8.62; Sb, 51.18.(2.1109 g, 3.860 mmol) was heated at 1058–1108C for 3 h.

Upon cooling to ambient temperature, a yellow liquidremained. The reactor was opened to a series of traps at 2.7. Synthesis of Me CHCH SbH (7)2 2 2

2108C and 21968C under a dynamic vacuum for twohours. Most of the yellow liquid (1.3558 g) remained in The reduction of (3) with LiAlH yielded (7). Iso-4

the reaction flask with a small amount collecting in the butylantimony dibromide (3) (1.3789 g, 4.071 mmol) was

2612 A. Berry / Polyhedron 18 (1999) 2609 –2615

dissolved in 5 ml of tetraglyme and added in small them to completion. Isobutyl bromide and i-C H were4 10

quantities over a 20-min period to a mixture of LiAlH in observed among the minor products recovered in the4

15 ml of tetraglyme in a 50 ml flask at 2158C connected synthesis of (2) and (3), respectively. The presence ofto a vacuum system. The addition resulted in the formation i-BuBr likely occurred from a competing secondary redoxof a yellow–brown color in the reaction mixture. After reaction to form Sb and i-Bu SbBr , with the latter3 2

each addition, the mixture was stirred for about a minute, subsequently decomposing on heating to give i-Bu SbBr2

and the reactor was opened to a series of three traps at (2) and i-BuBr. Since a stoichiometric quantity of i-BuBr21968C and the vacuum pump to remove noncondensable, was not recovered, it would appear this was not the majorpresumably H , and condensable material. Upon complete reaction path to (2). A similar reaction between Et Sb and2 3

addition of (3), the reaction mixture was stirred for an SbBr in a 1:2 ratio at 1008C reportedly gave Et SbBr in3 3 2

additional 15 min at 2158C with the reactor open to the 84% yields instead of EtSbBr [28]. Infrared and NMR2

traps and pump. At this time, no material was collecting in spectra were obtained for both (2) and (3). The IR spectrathe 21968C traps, and the reactor was allowed to warm were very similar to each other, consisting of peaks arisinggradually to ambient temperature; little additional material from the isobutyl group; the Sb–Br stretching vibrations,

21transferred. The volatile, condensable material was frac- which occur between 225–255 cm in SbBr [29], were3

tionated according to RT|2968|21968C, and the 2968C below the cutoff for the 5-mm KBr windows and were not1fraction distilled further by RT|2238|21968C. A clear, observed. In the H spectra, the methylene doublet was

colorless liquid (7) (0.4326 g, 2.392 mmol, 59% yield) shifted downfield with increasing bromine substitution,collected in the 21968C trap. Vapor pressure at 08C57.9 which was attributed to the deshielding nature of the

1Torr. H NMR (C D ): 0.83 (d, 6H, J56.6 Hz, CH ), 1.45 bromine. Furthermore, the methylene protons of (2) ap-6 6 3

(q, 1.8H, J55.4 Hz, CH ), 1.65(o, 0.9H, J56.6Hz, CH), peared to be equivalent unlike those of (Me CCH )SbI,2 3 213 11.83 (t, 1.4H, J55.3 Hz, SbH ). Ch Hj NMR: 29.21 (s, which produced an AB pattern presumably because of a2

SbCH CH(CH ) ), 24.98 (s, SbCH CH(CH ) ), 14.43 (s, higher barrier to inversion caused by the larger neopentyl2 3 2 2 3 221 groups [30]. The spectrum of (3), on the other hand wasSbCH CH(CH ) ). IR (gas, P520 Torr, cm ): 3670 vw,2 3 2

more complex in both the methylene and methine regions2960 vs, 2880 m, 1920 w, sh, 1870 vs, 1830 w, sh, 1470as shown in Fig. 1(a). The low-field peak of the methylenew, 1385 w, 1325 w, 1315 w, sh, 1170 w, 1090 vw, 1030doublet was split into an irregular doublet while the high-vw, 815 w, 785 w, 665 vw, br, 635 vw, br, 575 vw, 550field peak remained comparatively broad (FWHM51.2vw. Elemental Anal. Calcd. for C H Sb: C, 26.56; H,4 11

Hz); the methine region contained a minimum of 15 peaks.6.13; Sb, 67.31. Found: C, 26.48; H, 6.39; Sb, 67.04.The complexity of these areas is believed to be due to anonequivalence of the methylene protons with respect tothe bromine atoms, giving rise to an ABC system. De-

3. Results and discussion shielding from the bromine atoms was also seen in the13downfield shift of the a carbon resonance of the ChHj

Triisobutylantimony (1) was synthesized by the reaction spectra relative to (2) and (1).of SbCl with a Grignard reagent according to published As expected from previous oxidative addition reactions3

procedures [24] to give reasonable yields (63.7%) of a of halogens to tertiary stibines yielding the well-knownclear, colorless liquid that could be distilled at 508C and trialkylantimony dihalides [31], the reaction of (1) with I2

265310 Torr. The infrared and NMR spectra were in good gave the five-coordinate i-Bu SbI (4) as a soluble,3 2

agreement with those found in more recent studies [25,26]. sublimable white solid in good yields. The IR spectrum1In the H NMR spectrum, the methyl groups and the contained bands similar to those observed for the other

methylene protons produced doublets expected for equiva- isobutyl derivatives as well as weak bands at 425, 400, and21lency and for coupling with the methine proton; the 305 cm ; bands in this region have been assigned to

methine proton pattern contained nine lines resulting from MCC deformations in (i-Pr) SbX [32] and an overtone2 3 21equal coupling with the the methyl and methylene protons. of the asymmetric Sb-I stretch in Me SbI [33]. In the H3 2

13The singlet methyl peak in the C spectrum was con- NMR spectrum, the doublet for the methylene protons wassistent with equivalent C atoms in the methyl groups. shifted downfield from the multiplet of the methine proton,

The synthesis of the mono- and dibromides, (2) and (3), presumably from deshielding by the iodine atoms analo-followed the general procedures for the preparation of gous to bromine mentioned above. Furthermore, thePh SbBr [16], PhSbBr [16,17], Cp SbX, and CpSbX methine group multiplet contained the expected nine-line2 2 2 2

(X5Cl, Br, I) [18] by redistribution reactions of 2 /1 and pattern for equal coupling with the methyl and methylene131 /2 molar mixtures of (1) and SbBr . As with previous protons. The methylene carbon peak in the C spectrum3

alkylantimony bromides (Me SiCH ) SbBr [27] and was shifted downfield considerably from (1) as observed in3 2 2

RSbBr (R5Me SiCH [27], Me CCH [6]), a black (Me CCH ) SbI and (Me SiCH ) SbI relative to their2 3 2 3 2 3 2 3 2 3 2 3 2

mixture formed within minutes after combining the reac- respective triorgano compounds [30].tants, and it was necessary to heat the reactions to drive The well-known thermal decomposition of triorganoan-

A. Berry / Polyhedron 18 (1999) 2609 –2615 2613

1Fig. 1. H NMR spectra of: (a) i-BuSbBr ; (b) i-Bu SbI; (c) i-Bu SbH; (d) i-BuSbH .2 2 2 2

timony dihalides to yield the diorganoantimony halides and very similar to that of the mono- and dibromides, (2) and1the organic halides was used to synthesize the monoiodide (3), the H NMR spectrum seen in Fig. 1(b) was more

(5) from (4) [34]. Although the IR spectrum of (5) was complex with a broad methylene peak overlapping the

2614 A. Berry / Polyhedron 18 (1999) 2609 –2615

13 1methine resonance. In the Ch Hj spectrum, the methyl- hydrogen atom; an analogous shift was observed in theene resonance was shifted downfield halfway between that Me CCH compounds [6].3 2

of (1) and (2). A similar reduction of (3) with LiAlH in tetraglyme at4

Reduction of either (2) or (5) with LiAlH in Et O at 2158C was used to synthesize (7). The product was4 2

2408C resulted in good yields (.80%) of the monohy- removed from the reactor soon after being formed todride (6). Like its Me CCH and Me SiCH analogs prevent decomposition in the presence of the reaction3 2 3 2

[6,27], (6) was stable at ambient temperature in Pyrex mixture and was obtained in reasonable yields of nearlycontainers for at least a month with no discoloration and 60%. As expected, the dihydride was more volatile thanwas found to react with Halocarbon vacuum grease. It was (6) with a vapor pressure of 7.9 Torr at 08C, which isslightly more volatile (vapor pressure51.6 Torr) than the comparable to that of 5.5 Torr for Me CCH SbH at 08C3 2 2

neopentyl compound (0.5 Torr) at ambient temperature. [6]. The gas-phase infrared spectrum in Fig. 2(b) contained21The infrared spectrum of the neat liquid shown in Fig. 2(a) an intense band at 1870 cm assigned to the the Sb–H

21 21 1contained a strong absorption at 1840 cm assigned to the stretch, which was 30 cm higher than that of (6). The H21Sb–H stretch; this is 50 cm below that of the Sb-H NMR spectrum shown in Fig. 1(d) was considerably

stretch in SbH [35] and identical to that in simpler than that of (6). This indicated equivalency for the31(Me CCH ) SbH [6]. In the H NMR spectrum shown in methyl groups, the antimony hydrogens, and the methylene3 2 2

Fig. 1(c), the methyl resonance consisted of a doublet of protons, and equal coupling of CH and CH with CH.3 213doublets indicating diastereotopic methyl groups, and the The C spectrum contained the expected three peaks with

antimony hydrogen resonance was a quintet. The remain- the methylene carbon being shifted upfield with respect toing methylene and methine resonances were complex, with that of (6).the former being an irregular twelve-line pattern and thelatter a triplet superimposed on at least six other smaller

13 1peaks. The Ch Hj spectrum contained four singlets 4. Summaryinstead of the three observed in the other isobutyl com-pounds reported here; the two central peaks were assigned We have synthesized six new organoantimony com-to two different methyl groups consistent with the proton pounds, of which two are hydrides of moderate thermalspectrum. The upfield shift of the methylene carbon peak stability that have potential as precursors for the chemicalwith respect to (1) was attributed to the shielding of the vapor deposition of antimony. Both are colorless liquids,

and although only i-Bu SbH was observed to react with2

Halocarbon grease, it is reasonable to assume that i-BuSbH would do likewise. The former is less volatile2

(vapor pressure51.6 Torr at 26.58C) than the latter (vaporpressure57.9 Torr at 08C) and is stable for up to a monthat ambient temperatures in Pyrex containers; the latterappeared to be stable for several days under these con-ditions. The preferred synthesis scheme for the hydridesuses exchange reactions with i-Bu Sb and SbBr to make3 3

the corresponding mono- and dibromides, which aresubsequently reduced. The yields and purity are suffi-ciently high enough (40–50% overall) to make this apractical approach. One alternate path through the five-coordinate i-Bu SbI has been demonstrated for i-Bu SbH3 2 2

where the yields are higher but at the cost of an extra step.

Acknowledgements

This work was supported by the Office of NavalResearch.

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