Organometallics 1995, 14, 1039-1043
1039
Synthesis and Reactivity of Rhenium(II1) Sulfido Bis(acetylene) Iodide Complexes1 Sam K. Tahmassebi and James M. Mayer* Department of Chemistry, University of Washington, Seattle, Washington 98195 Received October 7,1994@ Rhenium(II1) sulfido bidacetylene) iodide complexes, Re(S)I(RC=CR)2 (R = E t (2a);R = Me (2b)),have been synthesized by addition of boron sulfide, B2S3, to the corresponding oxo compounds Re(O)I(RC=CR)z (R = E t (la);R = Me (lb))in methylene chloride. The solidstate structure of 2b contains pseudotetrahedral molecules, with the vertices occupied by sulfur and iodine atoms and the centroids of the acetylenes, very similar to the structure of the oxo precursor lb. The spectral and physical properties of 2 are also quite similar to those of 1. The sulfido complexes are much less stable than their oxo analogs, decomposing at 25 "C over a few days. Reactions occurring at the sulfido ligand of 2 are quite similar to those involving the oxo ligand of 1. However, reagents that replace the iodide ligand in 1 for the most part cause decomposition of the sulfido complexes 2. The sulfido-ethyl complex Re(S)Et(MeCsCMe)z is formed at low temperatures from Re(O)Et(MeC=CMe)z and B2S3 but decomposes within minutes at 25 "C. Crystal data for 2b: C8H12IReS; orthorhombic, Pna21; a = 7.213(1) b = 10.859(2) c = 14.258(2) V = 1116.8(6)Hi3; 2 = 4 .
A,
A,
The chemistry of transition-metal complexes with terminal sulfido ligands (L,M=S) is quite unexplored compared to that of related metal-terminal oxo specie~.~ This ? ~ is especially true of their organometallic chemistry, which is extensive for oxo derivatives4 but is limited to a handful of sulfido complexes: some cyclopentadienylcompounds, two sullido-acetylene complexes, and a few other specie^.^ We have explored the chemistry of rhenium(II1) oxo bis(acety1ene) complexes in some detail, starting from the iodide derivatives Re(O)I(RC=CR)z (R = Et (la);R = Me (lb)h6 The iodide ligand can be converted into hydride, alkyl, acyl, alkoxide, carboalkoxy, carboxylate, and other ligands, including sulfhydryl, -SH. The oxo-sulfhydryl complex Re(O)SH(RC=CR)z does not rearrange to a sulfidoAbstract published in Advance ACS Abstracts, January 15, 1995. (1) Low-Valent Rhenium-Oxo Compounds. 15. Part 14: Reference
@
A,
hydroxide species such as [R~(S)OH(RC=CR)Z],~ though the analogous tautomerization of Re(OXOHXMeCWMel2 occurs within 1 day at ambient temperatures.6d We report here a direct route to sulfido complexes in this system, by replacement of the oxo ligand in 1 with B2S3. The characterization and the reactivity of the resulting rhenium(II1) sulfido bidacetylene) iodide complexes, Re(S)I(RCGCR)2 (R = Et (2a); R = Me (2b)), are discussed.
Results and Discussion The sulfido complexes 2 are rapidly formed on reaction of Re(O)I(RCICR)z (1) with excess boron sulfide, B2S3, in CH2C12 (eq 11.' Analogous reactions with hexn
S
6j. (2) Metal sulfido compounds: (a)Rice, D. k Coord. Chem. Rev. 1978, 25, 199. (b) Muller, A.; Diemann, E.; Jostes, R.; Bogge, H. Angew. Chem., Znt. Ed. Engl. 1981, 20, 934. (c) Muller, A.; Diemann, E. In
Comprehensive Coordination Chemistry; Wilkinson, G., Ed.; Pergamon Press: Oxford, U.K.,1987; Vol. 2; pp 515-550. (3) Metal oxo compounds: (a) Nugent, W. A.; Mayer, J. M. MetalLigand Multiple Bonds; Wiley: New York, 1988. (b) Kochi, J. K.; Sheldon, R. A. Metal-Catalyzed Oxidation of Organic Compounds; Academic Press: New York, 1981. (c) Holm, R. H. Chem. Rev. 1987, 87,1401. Holm, R. H.; Donahue, J. P. Polyhedron 1993,12,571-589. (d) Bottomley, F.; Sutin, L. Adv. Organomet. Chem. 1988,28, 339. (e) Herrmann, W. A. Angew. Chem., Znt. Ed. Engl. 1988,27,1297. (4) See refs 3d,e and 6e for leading references. (5) (a)Morrow, J. R.; Tonker, T. L.; Templeton, T. L. Organometallics 1986,4,745. (b) Tanner, L. D.; Haltiwanger, R. C.; Rakowski-Du Bois, M. Znorg. Chem. 1988,27, 1741. (c) Su,F.-M.; Bryan, J. C.; Jang, S.; Mayer, J. M. Polyhedron 1989, 8, 1261. (d) Ma, Y.; Faller, J. W. Organometallics 1989,8,609. (e) Feng, S. G.; Gamble, A. S.; Templeton, T. L. Organometallics 1989, 8, 2024. (0 Tremel, W.; H o h a n n , R.; Jemmis, E. D. Znorg. Chem. 1989, 28, 1213. (g) Faller, J. W.; Kucharcyzk, R. R.; Ma, Y. Znorg. Chem. 1990,29, 1662. (h) Gelletti, P. F.; Fenrec, D. A.; Keen, F. I.; Brown, T. M. h o g . Chem. 1992,31, 4008. (i)Carney, M. J.;Walsh, P. J.; Hollander, F. J.;Bergman, R. G. Organometallics 1992,11,761. (i) Tatsumi, K.; Inoue, Y.; Kawaguchi, H.; Kobsaka, M.; Nakamura, A.; Cramer, R. E.; Van Doome, W.; Taogoshi, G. J.; Richmann, P. N. Organometallics 1993, 12, 352. (k) Rau, M. S.; Kretz, C. M.; Geoffrey, G. L.; Rheingold, A. L. Organometallics 1993,12,3447. (1) Brunner, H.; Kubicki, M. M.; Leblanc, J.-C.; Moise, C.; Volpato, F.; Wachter, J. J. Chem. SOC.,Chem. Commun. 1993, 851. (m) Shapley, P. A.; Liang, H.-C.; Shuster, J. M.; Schwab, J . J.; Zhang, N.; Wilson, S. R. Organometallics 1994, 13, 3351.
R = Et (la), Me (lb)
R 3: Et (2a), Me (2b)
amethyldisilathiane ([Me3SiIzS) and Lawesson's reagent ([ArP(S)(~-s)12)~ did not give any 2, although addition of trace amounts of water to a mixture of hexamethyl(6) (a) Mayer, J. M.; Thorn, D. L.; Tullip, T. H. J.Am. Chem. SOC. 1985, 107, 7454. (b) Mayer, J. M.; Tulip, T. H.; Calabrese, J. C.; Valencia, E. J.Am. Chem. SOC.1987,109,157. (c) Erikson, T. K G.; Bryan, J. C.; Mayer, J. M. Organometallics 1988,7,1930. (d) Erikson, T. K. G.; Mayer, J. M. Angew. Chem., Znt. Ed. Engl. 1988,27, 1527.
(e) Spaltenstein, E.; Erikson, T. K. G.; Critchlow, S. C.; Mayer, J. M. J.Am. Chem. SOC.1989, 111, 617. (0 Manion, A. B.; Erikson, T. K.
G.; Spaltenstein, E.; Mayer, J. M. Organometallics 1989,8,1871. (g) Spaltenstein, E.; Mayer, J. M. J.Am. Chem. SOC.1991,113,7744. (h) Conry, R. R.; Mayer, J. M. Organometallics 1993, 12, 3179. (i) Tahmassebi, S. IC;C o w , R. R.; Mayer, J. M. J.Am. Chem. SOC.1993, 115,7553. (j) Cundari, T. R.; Conry, R. R.; Spaltenstein, E.; Critchlow, S. C.; Hall, K. A.; Tahmassebi, S. K; Mayer, J. M. Organometallics 1994,13,322. (7) For other examples of the use of BzSs to convert metal-oxo to metal-sulfido groups, see ref 5g and: (a)Young, C. G.; Roberts, S. A.; Ortega, R. B.; Enemark, J. H. J.Am. Chem. SOC.1987,109, 2938. (b)
Eagle, A. A.; Tiekink, E. R. T.; Young, C. G. J. Chem. SOC.,Chem. Commun. 1991,1746.
0276-733319512314-1039$09.0010 0 1995 American Chemical Society
1040 Organometallics, Vol. 14,No. 2, 1995
Tahmassebi and Mayer Table 2. Selected Bond Length and Bond Angle Comparison between Re(S)I(MeC=CMe)l (2b) and Re(O)I(MeC=CMe)z (lb)
Table 1. Crystallographic Data for Re(S)I(MeC=CMe)z (2b) empirical formula fw cryst syst space group a, A
b, A C,
8,
v,A3
Dcdcd, g/cm3
F(000) radiation 28 range, deg no. of rflns collected no. of indep rflns no. of obsd rflns R, % Rw,
%
GOF data-to-paramratio p(Mo Ka), mm-'
CEHIZRR~S 453.3 orthorhombic Pna21 7.213(1) 10.859(2) 14.258(2) 1116.8(6) 2.696 816 Mo K a (1= 0.710 73 A) 2 5 28 5 50 2505 1956 (Rint = 2.43%) 1705 (F > 4~7,~) 2.65 3.90 0.87 17.0:l 13.776
Bond Lengths (A) bond
x=s
x=o
Re-X Re-I Re-C1 Re-C2 Re-C3 Re-C4 c 1-c2 c3-c4 c1-c11 c2-c21 C3-C31 C4-C41
2.082(3) 2.704(9) 2.036(9) 2.035( 10) 2.037( 10) 2.023( 11) 1.274(16) 1.267(16) 1.513(15) 1.487(14) 1.502(16) 1.502(16)
1.697(3) 2.691(1) 2.061(5) 2.038(5) 2.066(5) 2.040(5) 1.278(7) 1.288(7) 1.485(7) 1.494(7) 1.459(7) 1.470(7)
Bond Angles (deg)
C41
I
C31
Figure 1. ORTEP diagram of Re(S)I(MeCrCMe)z(2b).
disilathiane and 1 does slowly form 2,presumably due to the reaction of H2S with 1 (see below, eq 2). After filtration and removal of the volatiles, sublimation a t 50 "C gives pure samples (by NMR) of the sulfido complexes in 4 0 4 0 % yield. The synthesis is touchy, however, and often fails to give any usable product. The 3-hexyne derivative 2a is isolated as a red-orange oil, while the 2-butyne analog 2b is a red solid. The oxo complexes 1 have the same physical properties: ready sublimation a t slightly above room temperature, with the hexyne complex a yellow oil and the butyne complex a yellow solid. Complex 2b crystallizes in an orthorhombic space group (Table 1) upon slow evaporation of a saturated pentane solution. The solid-state structure of 2b reveals isolated pseudotetrahedral molecules (Figure l),with the vertices defined by the sulfur and iodine atoms and (8)(a) Ar = p-methoxyphenyl. Hexamethyldisilathiane has been used to convert metal-oxo to metal-sulfido groups in other systems, for instance: Dorfman, J. R.; Girerd, J. J.; Simhon, E. D.; Stack, T. D. P.; Holm, R. H. Inorg. Chem. 1984,23,4407. (b) Lawesson's reagent has been used to thiate organic carbonyl group^^^-^ and in a t least one instanceEfhas been used in a n attempt to replace the oxo ligand of a metal complex with a sulfido ligand. (c) Scheibye, S.; Pederson, B. W.; Laweason, S. 0.Bull. Soc. Chim. Belg. 1978,87,229.(d)Walter, W.; Proll, T. Synthesis 1979,941.(e) Raucher, S.;Klein, P. Tetrahedron Lett. 1980,21,4061. (f) Housmekerides, C. E.; Ramage, D. L.; Kretz, C. M.; Shontz, J. T.; Pilato, R. S.; Geoffroy, G. L.; Rheingold, A. L.; Haggerty, B. S. Inorg. Chem. 1992,31,4453.
angle
x=s
x=o
X-Re-I X-Re-C1 X-Re -C2 X -Re -C3 X-Re- C4 I-Re-X I-Re-Cl I-Re-C2 I-Re-C3 I-Re-C4 Re-C 1-C 11 Re-C2-C21 Re-C3-C31 Re-C4-C41 Re-Cl-C2 Re-C3-C4 Re-C2-C 1 Re-C4-C3 c 1-c2-c21 C2-Cl-Cll c3-c4-c41 c4-c3-c31
108.31) 117.1(3) 109.0(3) 117.6(3) 105.2(3) 108.5(3) 84.7(4) 120.1(3) 86.4(3) 122.5(3) 144.6(9) 140.8(8) 144.9(8) 142.3(8) 7 1.6(6) 71.2(7) 71.9(6) 72.4(7) 147.2(10) 143.6(10) 145.2(11) 143.3(10)
109.4(1) 114.8(2) 109.1(2) 114.2(2) 108.8(2) 109.4(1) 85.2(1) 119.6(2) 85.2(1) 119.7(2) 144.9(4) 141.3(4) 145.5(4) 142.2(4) 70.8(3) 70.6(3) 72.9(3) 72.8(3) 145.8(5) 144.3(5) 144.9(5) 144.0(5)
the centroids of the acetylene ligands. The structure could also be viewed as a pentagonal pyramid with an apical multiple bond. Both the overall structure and the bond lengths and bond angles of 2b very closely resemble those of lb (Table 2). All of the analogous bond lengths are the same within 3a error bars (except Re=S vs Re=O), and all of the analogous angles are within 4°.6a For instance, the Re-C distances in 2b vary from 2.023(11) to 2.036(9) A, versus 2.038(5)2.066(5) fi in lb. The most significant difference between the two complexes is that the plane described by the four acetylene carbons in the basal plane is more canted in 2b than in lb: the normal to the C4 plane makes an angle of 16.4" with the Re-S bond in 2b vs the analogous angle of 9.3" in lb. The Re-S bond length of 2.082(3) A in 2b is at the short end of the reported range of rhenium-sulfido d i ~ t a n c e s ,from ~ 2.075(4)A in Re(S)(S&9ato 2.126(4)A in [ReS41[NEt41.9b NMR spectra of 2a and 2b indicate C, symmetry in solution, consistent with the geometry found in the solid (9)Rhenium-sulfido structures located using the Cambridge Structural Database: (a) Blower, P. J.; Dilworth, J. R.; Hutchinson, J. P.; Zubieta, J. A. Inorg. Chim. Acta 1982, 65, L225. (b) Muller, A.; Krickemeyer, E.; Bogge, H.; Perk, M.; Rehder, D. Chimia 1986,40, 50. This paper reports the structure of Re(S)(S& similar to that reported in ref 9d but with a longer Re=S bond length of 2.091(4)A. (c) Scattergood, C. D.; Garner, C. D.; Clegg, W. Inorg. Chim.Acta 1987, 132,161. (d) Cotton, F.A,; Kibala, P. A.; Matusz, M. Polyhedron 1988, 7, 83. (e) Massa, M. A.; Rauchfuss, T.B.; Wilson, S. R. Inorg. Chem. 1991,30, 4667.
Organometallics, Vol. 14, No. 2, 1995 1041
Re(III) Sulfido Bis(acety1ene) Iodide Complexes
--.---Re(O)l(EtCsCEth (Is)
-
Scheme 1. Thermochemical Cycle for Conversion of Oxo to Sulfido Complexes
Re((S)I(EtCtCEOl(28)
6000
I(RCCR)zRd
laa
+ H2S +
I(RCCR)zRd
I
1
D(Re=O)
5000 E 4000 "cm-')
I(RCCR)2Re + 0 + HzS
3000
2000 lo00
0 200
300
400
500
600
700
800
h (M.0 Figure 2. UV/vis spectra of Re(S)I(EtC=CEt)a(2a)and Re(O)I(EtC=CEt)z(la)in CHzClz. state for 2b. The NMR spectra of 2a,for instance, show two sets of ethyl resonances, for the ethyl groups proximal and distal to the iodide, with diastereotopic methylene hydrogens (multiplets at 2.71 and 2.96 ppm). The observation of diastereotopic hydrogens indicates that, as observed for the oxo complexes 1,the acetylene ligands are not rotating on the NMR time scale. The IR spectrum of 2a is quite similar to that of la? except that the strong band at 971 cm-l due to the ReGO stretch has been replaced by a band at 531 cm-' that we assign as v(Re=S). The rhenium-sulfido stretch is a t the high end of the range of reported values, 486525 ~ m - l . ~ The W/vis spectra of compounds la and 2a are quite similar (Figure 2). The spectrum of the yellow oxo M in CH2C12) shows two bands species la (4.0 x in the W region along with a shoulder in the visible region (see the Experimental Section for peak positions). The spectrum of the red sulfido complex 2a (4.8 x M in CH2C12) has basically the same features as that of the oxo compound but the bands are weaker and redshifted. The shift to lower energy is presumably due to the weaker metal-sulfur vs metal-oxygen n-bonding. The similarity of the sulfido and oxo complexes, in their structures, physical properties, and spectroscopic data, suggests that their electronic structures are similar as well. The chemical shifts of the alkyne carbons, which reflect the amount of alkyne-to-rhenium n-donation, are close: the resonances for the sulfido complexes are 9 and 13 ppm downfield from the corresponding resonances in the oxo species (compare 6 150.9, 159.3 for 2a vs 6 142.0, 146.3 for la). Thus, the bonding in the sulfido complexes appears t o be similar to that in the oxo species, with a Re+ triple bond and three-electron-donor alkyne ligands.6aJ The small downfield shift of the alkyne carbons may indicate more alkyne n-donation, perhaps t o compensate for poorer n-donation from sulfide as compared with oxide. The same interaction might also account for the slightly lower acetylenic stretch in 2a (1740 cm-l) vs la (1783 cm-l). Formulation as a rhenium-sulfur triple bond is also indicated by the short Re-S distance and the high IR stretching frequencies. The sulfido complexes are substantially less thermally stable than their oxo counterparts. Crystalline 2b decomposes over a few days at room temperature under an inert atmosphere t o uncharacterized black solids, while lb is indefinitely stable on the benchtop. Simi-
--f
I(RCCR),Re
+ H20
D(ReS)
+ S + HzO
larly, solutions of lb can be heated for at least 1 h at 150 "C in xylene solution without significant decomposition but 2a and 2b decompose to black material within 4-5 days in solution at ambient temperatures, without formation of any free alkyne. In the presence of added alkyne, however, solutions of 2 are inert to decomposition even when heated to 80 "C for 1week. Under these conditions the 3-hexyne complex 2a does not undergo ligand exchange in the presence of 2-butyne, indicating that decomposition does not occur by preequilibrium dissociation of alkyne. The lack of alkyne dissociation from 2a at 80 "C contrasts with the slow exchange of alkynes in lb a t this temperature.6a The inhibition of dissociation by added alkyne is puzzling, perhaps indicating that decomposition is autocatalytic or is mediated by an impurity. Consistent with these suggestions, decomposition of 2a is faster in more concentrated solutions. The oxo complex la reacts slowly with H2S in benzene to give the sulfide compound 2a and water (eq 2). This 0
Ill
E*\t*]*I; E& -t
Re
+H~S
-Et\,a*+21 1 Re
+ H~O
(2)
c&6
E& -t
la
2a
reaction is complicated by the further reaction of 2a with H2S t o give a variety of products. The isolated sulfido complex 2a does not react with H2O in benzene solution. These observations suggest that reaction 2 is exothermic (AH .c 01, as there should be little entropic driving force. A thermochemical analysis of the reaction (Scheme 1)suggests that the rhenium-oxo bond is a t most 46 kcal/mol stronger than the rhenium-sulfido bond, since it is 46 kcdmol enthalpically uphill t o convert S H20 to 0 H2S (in the gas phase).1° This estimate assumes that solvation effects are small, which is reasonable in benzene solution. Both the sulfido and the oxo complexes are unreactive toward Al2Se3 and Al2Te3 in THF, CD2C12, MeCN, and MeCND20. We ascribe the lack of reactivity of aluminum reagents to their very low solubility and their more refractory nature compared with B2S3. Complexes 1 and 2 are also unreactive toward aniline, tert-butylamine, or methylamine. They both, however, react with ammonia t o give uncharacterized compounds. The oxo and sulfido complexes 1 and 2 exhibit very similar reactivity toward phosphines, governed by the basicity of the latter reagents. Both la and 2a are unreactive toward PPh3 but react immediately with the more basic PMe3 to form SPMe3 or OPMe3 and a number of uncharacterized species (reactions performed in the presence of added alkyne). The complexes react cleanly with PMePh2 in the presence of added alkyne
+
+
(10)Based on gas phase heats of formation from: JANAF Thermochemical Tables, 3rd ed.; J . Phys. Chem. Ref. Data, Suppl. 1986,14.
1042 Organometallics, Vol. 14, No. 2, 1995
to produce the expected rhenium(1)tris(acety1ene)iodide complexes R ~ I ( R C Z C Rand ) ~ ~the ~ ~corresponding ~ phosphine chalcogenide, identified by NMR (eq 3). It is
R = Me, Et
x=o,s
Tahmassebi and Mayer
complex, as noted for 2 vs 1. The oxo-hydride species Re(0)H(EtCWEt)26eJquickly decomposes in the presence of B2S3 even at low temperatures. Other transition-metal sulfido-alkyl species have been synthesized by exchange of oxide or chloride ligands for sulfide using B2Ss5g or although these are not always succe~sful.'~ In sum, the unusual organometallic sulfido complexes Re(S)I(RC=CR)2have been prepared by replacement of the oxo group in Re(O)I(RC=CR)2 with B2S3. The structure and spectroscopic properties of the sulfido complexes are very similar to those of the oxo precursors, suggesting similar electronic structures. The reactivities of the two species at the chalcogen site are also very similar. However, the reagents that replace the iodide ligand in the oxo compound with other ligands cause the decomposition of the sulfido-iodide complex. Re(S)Et(MeC=CMe)zhas been generated by treatment of the oxo analog with B2S3 a t 240 K, but it decomposes rapidly at ambient temperatures.
surprising that the sulfido complex, with its weaker rhenium-chalcogen bond, exhibits the same reduction chemistry as the related oxo compound. The relative phosphine reactivity, PMe3 > PMePh2 > PPh3, follows the same order as the P-0 bond strengths.3c Reoxidation of rhenium(1) to rhenium(II1) has not been observed: the tris(acety1ene)-triflate complex ReOTf(RCECR)~(triflate = OTf = CF3S03) reduces propylene sulfide t o propylene, but no characterizable rhenium product is observed. The cyclic voltammogram of 2a in MeCN shows Experimental Section irreversible reductions at -1.0 and -2.3 V (vs Ag/Agil Syntheses were performed using standard vacuum line and MeCN). The oxo complex l b is harder to reduce, with glovebox techniques except where noted. Solvents were dried an initial irreversible reduction at -1.5 V, followed by and deoxygenated according to standard methods.13 BZS3, Alza reversible reduction at -2.5 V.ll Reduction of l b Se3, and AlzTe3 were used as received from Alfa. Re(0)Iforms the rhenium(I1) dimer [Re(0)(MeCWMe)212,6g (RCrCR)z (UV/vis data reported below),6f Re(0)Etwhich is responsible for the reversible wave at -2.5 V;ll (MeCWMe)z,6eRe(0)H(EtCWEt)z,6eand ReOTf(RC=CR)36h there is no evidence for analogous sulfido dimers. were prepared as previously described. NMR spectra were Compound 2a also shows two irreversible oxidation taken on a Bruker M 3 0 0 or AC200 spectrometers. lH and I3C chemical shifts are reported in ppm downfield of SiMe4 waves, at +0.2 and +0.5 V. These most likely arise from and are referenced to the solvent peaks; they are reported as the oxidation of the sulfido ligand, since the oxo species 6 (multiplicity, coupling constant, number of protons, assignshow no oxidation waves to the solvent limit. ment). IR spectra were taken on a Perkin-Elmer 1604 FT-IR Much of the rich chemistry of compounds 1 results spectrometer and are reported in cm-l. Mass spectra were from substitution of the iodide ligand.6 Such reactions taken on a Kratos Analytical instrument using the direct inlet are not, however, successful for the sulfido complex. probe method and are reported in m/e units. UV/vis spectra Reagents that exchange the iodide ligand of 1 for other were taken on a Hewlett-Packard 8452A diode array spectroligands, such as NaBH4,12NaBH3CN,12B u ~ S ~ EtzH , ~ ~ photometer, using quartz cells sealed to a Teflon needle valve, Zn,6eT10Et,6cT102CH,6cand AgSbFdpyridine,6bcause and are reported in nm: ,Imm (E, M-l cm-l). The cyclic the decomposition of 2 t o black material. The first four voltammogram of 2a was obtained in CH3CN using a Bioanalytical Systems B/W 100 electrochemical analyzer with iR reagents can also act as reductants, and the observed compensation, a Ag/AgNO&H&N reference electrode, and decomposition is likely due t o the more facile reduction 0.05 M BudNPF6 as the electrolyte. of 2a as compared with la. The last three reagents are Some reactions were performed in sealed NMR tubes and soft Lewis acids, which attack specifically at the iodide followed by the change in their NMR spectra. Reagents and ligand in la. But the sulfido ligand in 2a is also a solvent were added to NMR tubes sealed to a ground glass potential site of attack by Ag+ or T1+, which could lead joint and fitted with a needle valve. The tubes were cooled to to decomposition. However, harder Lewis acids such 77 K, degassed, and sealed with a torch and were thawed as AlMe3, AlCl3, and LiOEt also cause the decomposition under a stream of acetone. of the sulfido complex. The iodide ligand is also Re(S)I(EtC'CEt)z (2a). A mixture of 0.10 g (0.21 mmol) resistant to exchange in the presence of NMe4C1. of Re(O)I(EtC=CEt)z (la)and 0.021 g of BzS3 (0.18 mmol, 0.85 Since direct derivatization of the sulfido complex eq, 2.6 equiv of S) was stirred in 15 mL of CHzClz for 1 h. The appears impractical, we have explored oxolsulfido exsolvent was removed in vacuo, 20 mL of pentane was transferred in, the mixture was filtered, and solvent was removed change on other rhenium(II1) compounds. The oxoagain. Sublimation at 50 "C gave the product as a reddish ethyl complex Re(o)Et(MeC~cMe)2~~ (3b) reacts with orange oil on the probe. Yield: 0.052 g (49%). While 2a (and B2S3 in CD2C12 at 240 K to form the sulfido-ethyl 2b)decomposes within 4 days a t ambient temperatures, they complex Re(S)Et(MeCWMe)a (4b). Complex 4b is can be stored for months in a -11 "C freezer under an inert stable for a few hours a t 240 K but decomposes within atmosphere. lH NMR (C&): 1.10, 1.12 (t, 7 Hz, each 6 H, minutes at room temperature (in contrast to the only CH~CH~CECCHZCH'~); 2.71, 2.96 (m, each 4 H, 50% decomposition of 3b after 21 days at 120 The CH3CHH'C4XX"W"CH'3). l3C(lH} NMR (C&): 13.1, 14.6 characterization of 4b is based on 'H and 13C NMR (CH~CHZC~CCHZC'H~); 25.8, 28.3 (CH~CHZCGCC'H~CH~); spectra at 240 K, which are only slightly shifted from 150.9, 159.3 (CH~CH~CIC'CHZCH~). MS: 510/508, [MI+. IR the spectra of 3b. The acetylenic 13C chemical shifts (Nujol, KBr): 2960, 2360, 1783, 1740 w v(C=C); 1452, 1368, are roughly 10 ppm farther downfield in the sulfido (11)Conry, R. R.; Mayer, J. M. Unpublished results, and ref 6a. (12)Tahmassebi, S. K.; Mayer, J. M. Unpublished results.
(13) (a)Perrin, D. D.; Armarego, W. L. F. Purification ofLaboratory Chemicals, 3rd ed.; Pergamon: New York, 1988. (b) Fieser, L. F.; Fieser, M. Reagents for Organic Synthesis; Wiley: New York, 1967.
Organometallics, Vol.14, No. 2, 1995 1043
Re(III) Sulfido Bis(acety1ene) Iodide Complexes 1295,1253,1060,934,721,531 m v(RerS). UV/vis (CH2C12): 272 (1.8x lo3);298 (1.3x lo3),shoulder; 432 (2.1x 102);524 (74),shoulder. Re(S)I(MeC=CMe)z(2b). Following a procedure analogous to that used for la, 0.050 g (0.11 mmol) of Re(0)I(MeC=CMe)Z (lb), 0.009 g of BzS3 (0.08 mmol, 0.7 equiv, 2 equiv of S), and 15 mL of CHzClz gave 0.021 g (42%) of red solid (2b) after sublimation, pure by NMR. The thermal instability of 2b has prevented us from obtaining suitable analytical data. IH NMR (C6D6): 2.23,2.92 (9, 1 Hz, each 6 H, CH3CECCB3). 13C{lH} NMR (C&): 17.2, 19.3 (CH3CXCH3); 147.0,155.3 (CHsCeC'CH3). MS: 454/452, [MI+.IR (Nujol, KBr): 1720w ~(CEC);1255,1155,1090,1020, 797,720,620,532 m v(Re3S). Re(S)Et(MeCeCMe)z(4b) was formed and characterized in a n NMR tube. Approximately 0.03g (0.09mmol) of Re(0)wee put in a n NMR tube Et(MeCWMe)z (3b)and excess that was sealed to a ground-glass joint and attached to a Teflon needle valve. The tube was cooled to liquid-nitrogen temperature, and CDzCl2 was transferred in. The tube was then sealed with a torch, thawed under a stream of acetone, mixed vigorously, and immersed immediately into a precooled (220 K) NMR probe. The probe was then warmed slightly to 240 K, and the formation of 4b was monitored. Decomposition occurred within minutes at 25 "C. The reaction was repeated at room temperature, and after a brief period when the color of the solution changed to reddish orange, black solids began to deposit. lH NMR (CDZC12,240K): 2.60,2.96(9, 1 Hz, each 6 H, CH&=CCH'3); 1.39 (t, 7 Hz, 3 H, ReCHzCH3); 4.01(9, 7 Hz, 2 H, ReCH2CH3). 13C{'H} NMR (CD2C12, 240 K): 9.3 (ReCHzCH3); 11.9 (ReCHzCH3); 15.9,18.4 (CH&WC'H3); 154.6,158.8 (CH~CSC'CH~). X-ray Structure. of Re(S)I(MeC=CMe)a(2b). Crystals were grown by slow evaporation of a saturated pentane solution of 2b. A red crystal of dimensions 0.1 x 0.15 x 0.2 mm was mounted, using stopcock grease, on an Enraf-Nonius CAD4 difiactometer under a cold (183 K)nitrogen stream. The data were corrected for Lorentz and polarization effects and for absorption using an empirical absorption method 01 = 13.776mm-l). The structure was solved by direct methods
Table 3. Atomic Coordinates ( x 105) and Equivalent Isotropic Displacement Coefficients (A* x 104) for Re(S)I(MeC=CMe)z (2b) X
Re(1) I(1) S(2) C(1) C(2) C(11) C(21) C(3) C(4) C(31) C(41)
13043(5) 10 175(10) -11 105(39) 14 017(109) 19 062(139) 11 859(151) 26 215(157) 35 179(131) 34 ool(144) 47 230(164) 41 926(173)
Y
1362(3) 2 881(7) -6 594(32) 20 091(80) 16 637(99) 32 233(95) 20 298(105) -9 889(109) -7 693(103) -15 737(100) -10472(137)
Z
64 994 83 870(7) 59 768(24) 65 484(92) 57 337(68) 71 763(78) 47 959(73) 67 275(80) 58 571(79) 74 626(81) 49 058(79)
U(eq)* 207(1) 311(2) 398(10) 240(26) 244(30) 343(40) 389(38) 291(35) 260(32) 383(35) 463(46)
a Equivalent isotropic U, defined as one-third of the brace of the orthogonalized Uv tensor.
(SHELX). All non-hydrogen atoms were refined anisotropically, and the hydrogen atoms were fixed by a riding model at 0.96 A. Crystal data are given in Table 1, selected bond lengths and angles are given in Table 2, and atomic coordinates along with equivalent isotropic thermal parameters are given in Table 3. Re(O)I(EtC=CEt)z (la): UV/vis (CH2C12) 234 (6.9x lo3), shoulder; 368 (7.4x lo2);444 (2.2x lo2), shoulder.
Acknowledgment. We are grateful for the help of Dr. David Barnhart with the X-ray structure and Dr. Frazier Nyasulu with cyclic voltammetry. Helpful suggestions from Drs. Seth Brown, Jerry Cook, and Keith Hall are appreciated. We thank the National Science Foundation for financial support. Supplementary Material Available: Tables giving a structure determination summary, anisotropic displacement coefficients, and hydrogen atom coordinates (5 pages). Ordering information is given on any current masthead page.
OM940778R
