Organometallics 1995, 14, 4808-4815
4808
Synthesis and Characterization of Unsymmetric Ferrocene-TerminatedPhenylethynyl Oligomers Cp2Fe--[C=C-C6HJn-X (X = SH,SMe, SOMe, and SO2Me) Richard P. Hsung,? Christopher E. D. Chidsey,*and Lawrence R. Sita*lt Searle Chemistry Laboratory, Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, and Department of Chemistry, Stanford University, Stanford, California 94305 Received May 25, 1995@ The syntheses and full characterization of the titled compounds are described for X = SH and n = 1-3 (la-c), X = SMe and n = 1-4 (2a-d), X = SOMe and n = 1 and 2 (3a,b),and X = SOzMe and n = 1-3 (4a-c). I n addition, the molecular structure of 2b has been determined by crystallographic analysis. Single crystals of 2b are (at 23 "C)monoclinic, space group P21/c, with a = 6.031(2) b = 33.457(12),c = 10.364(4) B = 90.90(3)",V = 2091.2(13)A3, and 2 = 4 (Dcalcd= 1.373 mg m-3; p(Mo Ka) = 0.831 mm-l). The availability of compounds la-c should prove useful for investigating the factors which govern the rate of electron transfer across interfacial barriers such as those presented by self-assembled monolayer (SAM)structures.
A,
A,
Chart 1
Introduction Self-assembled monolayer ( S A M )structured composed of n-alkanethiol derivatives chemisorbed onto gold surfaces and bearing varying amounts of pendant electroactive ferrocene groups have proven to be excellent systems in which factors governing the rate of electron transfer across interfacial barriers can be investigated.2 Accordingly, a natural extension of these studies is to systematically modify the nature of the interfacial barrier and obtain structure-property relationships that can then be used to provide a clearer picture of how structural effects can mediate the electron transfer process. In this regard, we have recently focused our attention on the fabrication, characterization, and investigation of new classes of S A M structures derived from ferrocene-terminated conjugated arenethio1 derivatives of varying conjugation length and, in particular, those derived from the family of ferroceneterminated phenylethynyl oligomers represented by 1 (see Chart 1). At the outset, however, it was recognized that efficient, high-yielding routes to these arylthiol derivatives posed several synthetic challenges, not the least of which was the identification of protocols that would be compatible with the various sites of reactivity in these compounds. Herein we now report a general synthetic scheme that has been successfully employed to provide members of 1 for n = 1-3. In addition, since it was of interest to investigate the redox properties of 'The University of Chicago.
* Stanford University.
Abstract published in Advance ACS Abstracts, September 1,1995. (1) For general reviews of self-assembled monolayers, see: (a) Salen, @
J. D.; Allara, D. L.; Andrade, J. D.; Chandross, E. A.; Garoff, S.; Israelachvili, J.; McCarthy, T. J.;Murray, R. F.; Rabolt, J. F.; Wynne, K. J.; Yu, H. Langmuir 1987, 3, 932. (b) Ulman, A. An Introduction to Ultrathin Organic Films from Lizngmuir-Blodgett to Self-Assembly; Academic Press, Inc.: New York, 1991. (2) For representative papers, see: (a) Chidsey, C. E. D.; Bertozzi, C. R.; Putvinski, T. M.; Mujsce, A. M. J . A m . Chem. SOC.1990, 112, 4301. (b) Chidsey, C. E. D. Science 1991,251,919. (c) Finklea, H. 0.; Hanshew, D. D. J . A m . Chem. SOC.1992,114,3137. (d) Rowe, G. K.; Creager, S. E. J. Phys. Am. Chem. 1994, 98, 5500. (e) Herr, B. R.; 1994, 116, 1157. (0 Carter, M. T.; Mirkin, C. A. J . A m . Chem. SOC. Rowe, G. K.; Richardson, J. N.; Tender, L. M.; Terrill, R. H.; Murray, R. W. J. A m . Chem. SOC.1995,117, 2896.
l:X=SH 2: X = SMe
3: X = SOMe 4 X = S02Me
these new molecular systems, the synthesis and complete characterization of several members of the families of ferrocene-terminated phenylethynyl oligomers represented by 2-4, which possess both the electrondonating methyl sulfide and the electron-withdrawing methyl sulfoxide and methyl sulfone moieties, respectively, are also reported. These latter compounds are of potential interest since a number of ferroceneterminated conjugated oligomeric systems are known to display interesting nonlinear optical proper tie^.^
Results and Discussion
(a)Synthesis. The family of oligomers represented by 2 provided a convenient target toward which various synthetic strategies for the construction of the conjugated phenylethynyl backbones of 1-4 could be explored. In this regard, it was decided that, in addition to a stepwise iterative approach, a more efficient convergent scheme would be considered for the syntheses of the longer oligomers (i.e., for n L 3). As Scheme 1 shows, the synthesis of 2a (n = 1)could be achieved in a straightforward manner through the palladiumcatalyzed Heck coupling reaction of ferrocenylacetylene (5)4 with 4-iodophenyl methyl sulfide (6) to provide 2a in a 91%~ i e l d . ~For - ~ the synthesis of 2b ( n = 21, the (trimethylsilyl)(4-iodophenyl)acetylenederivative 8 was (3)Long, N. J. Angew. Chem., Int. Ed. Engl. 1995, 34, 21 and references cited therein. (4) Rosenblum, M.; Brawn, N.; Papenmeier, J.; Applebaum, M. J . Organomet. Chem. 1966,6,173. (5)For recent reviews of the Heck reaction, see: (a)Heck, R. F. In Comprehensive Organic Synthesis; Trost, B. M., Fleming, I., Eds.; Pergamon Press: New York, 1991; Vol. 4, pp 833-863. (b) Hegedus, L. S. Tetrahedron 1984, 40, 2415. (c) Heck, R. F. Org. React. 1982, 27, 345.
0276-7333/95/2314-4808$09.00/00 1995 American Chemical Society
Organometallics, Vol. 14, No. 10,1995 4809
Ferrocene-Terminated Phenylethynyl Oligomers
Scheme 1"
&
w
91%
Pa
6
5
&
&
99% 9: R=Me3Si J C 10:R=H
2b
99%
87%
+e
&
83%
11: R = M e 3 S i j 12:R=H
99%
1
I
2d
I
I
7
1
13
8 C
14
96%
15
Legend: (a) Pd(PPh&C12 (1.8 mol %), CUI(5.5 mol %), EtzNH, 50 "C, 15-24 h. (b) (i) t-BuLi (2 equiv), EtzO, -78 "C. (ii) 12, -78 to 0 "C, 20 min. (c) TBAF', CH2C12, room temperature, 1.5 h. first prepared in two steps through the coupling of commercially available l-bromo-4-iodobenzenewith (trimethylsily1)acetylene to provide the intermediate aryl bromide 7,* which was then subjected to halogen exchange (80% overall yield of 8 ) (see box in Scheme 1). Coupling of 8 with 5 provided the ferrocene derivative 9, which was then treated with tetrabutylammonium fluoride (TBAF)to remove the trimethylsilyl group and to generate 10 (Scheme 1). Satisfactorily, the subsequent coupling of 10 with the aryliodide 6 proceeded in a high yield (99%) to provide the extended ferrocene-terminated oligomer 2b. (6)For the use of the Heck reaction to prepare a variety of phenylethynyl oligomers, see: (a)Zhang, J.; Pesak, D. J.;Ludwick, J. L.; Moore, J. S. J. Am. Chem. SOC.1994, 116, 4227. (b) Schumm, J. S.; Pearson, D. L.; Tour, J. M. Angew. Chem., Int. E d . Engl. 1994,33, 1360. (7) It has recently been determined that a variety of thiophenol protecting groups (Le., S-methyl, S-benzyl, S-trityl, and S-acetyl) are compatible with the Heck reaction, see: Hsung, R. P.; Babcock, J. R.; Chidsey, C. E. D.; Sita, L. R. Tetrahedron Lett. 1995,36, 4525. (8)Steinmetz, M. G.; Yu,C.; Li, L. J. Am. Chem. SOC.1994, 116, 932.
Through a repetition of the general scheme used to construct compound 2b,longer oligomers of 2 could be produced in a stepwise fashion. Thus, coupling of 10 with the key building block 8 was carried out to provide 11,which was further backbone extended t o obtain 2c ( n = 3) through the "end-capping" of the intermediate 12 via coupling with 6 (Scheme 1). However, due to anticipated solubility limitations imposed by the longer oligomers, a convergent strategy was conceived to provide rapid access to these extended systems. Accordingly, as shown in Scheme 1, another key building block represented by compound 13 was prepared in three steps from 7 (90% overall yield), and coupling of this compound with the ferrocene derivative 12 then directly provided 2d (n = 4)in high yield. Finally, an even shorter route to longer oligomers of 2 was explored that utilizes the building block 15 which can easily be prepared in two steps from 7 (68%overall yield; see box in Scheme 1). Some appreciation of the advantages represented by these latter two convergent approaches for the synthesis of oligomers of 2 can be obtained by
4810 Organometallics, Vol. 14, No. 10, 1995
Hsung et al.
Scheme 2a
FFq-8-
y + = * y 3
n O
&
T+-q$H3 0
CH,
7 6 86 -
7 . -
91%
00 94%
2a: n = l 2b: n = 2 2c: n = 3
4a: n = 1 4b: n = 2 4c: n - 3
3a: n = l 3b: n = 2
a Legend: (a) 2.1 equiv of MCPBA, CH2C12, -50 to -30 "C, 30 min to 20 h. (b) 1.04 equiv of MCPBA, CHzC12, -50 to -30 "C, 30 min to 20 h.
Scheme 3"
5: n = O 10: n = 1 12: n = 2
l a : n = 1; 85% l b n=2;79% I C : n = 3; 94%
17a: n = 1; 83% 17b: n = 2 ; 71% 17c: n = 3; 56%
Legend: (a) 16,Pd(PPhd2C12(1.8mol %), CUI(5.5 mol %), THFNunig's base (l:l), 50 "C,20-40 h. (b) (i) Et2NH or n-BuNH2 (2-5 equiv),CHC13, 50 "C, 15-24 h; (ii) Zn, HOAc, CH2C12, room temperature, 5-35 min. comparing the overall yield of 2c that is derived from 5 by the following approaches: (1)the stepwise approach utilizing 8 and 6 (5 steps, 66%), (2) the convergent approach utilizing 8 and 13 (3 steps, 74%), and (3) the convergent approach utilizing 15 and 6 (2 steps, 78%). Compounds 2a-c could be selectively oxidized to provide several members of the families of sulfoxide and sulfone oligomers represented by 3 and 4, respectively. Hence, as Scheme 2 shows, reaction of 2a with 1.04 equiv of m-chloroperbenzoic acid (MCPBA) in dichloromethane (CH2C12) a t -50 "C cleanly provided the sulfoxide derivative 3a in high yield. Correspondingly, the same reaction of 2a performed with 2.1 equiv of MCPBA generated the sulfone 4a in high yield (93%) and with virtually no side products being detected. Given the anticipated reactivity of the triple bonds, it was somewhat surprising to find that these oxidation reactions proceeded equally well for the longer oligomers of 2. Thus, 2b could be converted to both 3b and 4b (91% and 94% yield, respectively), and compound 2c could be smoothly oxidized to the sulfone derivative 4ca9 For the synthesis of the primary target compounds represented by 1,it was necessary to identify a thiopheno1 protecting group that was both compatible with the Heck reaction and which subsequently could be selectively removed to provide the desired ferrocene arenethiols in high yield. During the course of the present investigations, it was determined that the S-acetyl moiety could adequately meet both of these requirem e n t ~ . ~Accordingly, ,'~ couplings of 5, 10, and 12 with S-acetyl-4-iodobenzenethiol(l6)proceeded in high yields to provide the respective $-acetylated intermediates (9) Due to solubility limitations, oxidation of 2d to the corresponding compounds, 3d and 4d,was not attempted. (10)Recently, Tour and co-workers have also proposed using the S-acetyl group for the synthesis of arenethiols, see: Tour, J. M. Trends Polym. Sci. 1994,2, 332 reference 26.
Table 1. Selected ProDerties of 2-4 I, (nmP Ef(mVIb n
2
3
4
2
4
a b
312 331 345 357
307 330
308 330 336
267 283 287 c
314 299 c
C
d
a Anhydrous tetrahydrofuran (THF) used as the solvent. Cyclic voltammetry was performed using 1mM of substrate in THF (0.1 M (n-Bu)dN-PF6-)at a glassy carbon working electrode, a R counter electrode, and a Ag/Ag+ reference electrode (2' = 298 K, scan rate = 20 mV/s). The femendferrocenium redox couple was observed at 125 mV under identical conditions. Not measured.
17a-c which were then deprotected to generate the corresponding compounds la-c according to Scheme 3. (b) Properties. All the oligomers of 1-4 that were prepared were found to be crystalline or w w solids that could be purified to homogeneity by conventional column chromatography, and analytic and spectroscopic analyses support their structural formulations as shown. Here it can be mentioned that, although these compounds are all fairly robust, solutions of the arenethiols la-c are all prone to oxidize t o the corresponding disulfides unless deoxygenated solvents are employed. From the full spectroscopic characterization of the oligomers of 1-4 shown in Schemes 1-3, several interesting structure-property relationships could be derived. For instance, as Table 1 reveals, the lowest energy transition for the oligomers of 2 was found to increasingly red-shift with increasing chain length. Thus, while compound 2a (n = 1)exhibits a Am= at 312 nm, this value progressively shifts to longer wavelengths in going to 2b (Amm = 331; n = 2) t o 2c (Am= = 345; n = 3) and finally to 2d (A" = 357; n = 4). Similar trends are observed for the oligomers of 3 and 4 as well as for other families of phenylethynyl oligomers.6b
Organometallics, Vol. 14,No. 10,1995 4811
Ferrocene-Terminated Phenylethynyl Oligomers
Table 2. Fractional Coordinates of the Non-Hydrogen Atoms ( x 104) and Equivalent Isotropic Thermal Parameters ( x 10s) for 2ba 945(4) -16341(9) 512(26) 211(30) 2125(28) 3674(31) 2737(26) -1351(32) -1550(30) 485(29) 1974(32) 779(30) -1006(28) -2202(26) -3722(25) -3206(29) -4691(30) -6629(27) -7074(29) -5649(26) -8193(30) -9557(32) -11117(30) -12549(32) -14138(31) -14369(30) -12961(34) - 11342(36) -18067(32)
Fe
S
c1 c2 c3 c4 c5 C6 c7 C8 c9 c10
c11 c12 C13 C14 C15 C16 C17 C18 c19 c20 c21 c22 C23 C24 C25 C26 C27
3072(1) -6giizi 2490(5) 2748(5) 2966(5) 2846(5) 2551(5) 3221(5) 3478(5) 3673(5) 3530(5) 3240(6) 2196(5) 1932(6) 1622(5) 1395(5) llOO(6) 1020(5) 1244(5) 1549(5) 720(6) 488(6) 204(5) 12(6) -263(6) -349(5) -165(6) llO(6) -806(6)
578(3) -36ioi6j 1074(16) 2176(17) 2404( 18) 1489(18) 657(16) -803(18) 228(18) 373(18) -569(18) - 1281(20) 581(16) 252(16) - 123(16) -1208(17) -1622(18) -963(16) 103(17) 560(17) -1401(17) -1738(18) -2147(19) -1277(21) -1717(19) -2986(19) -3826(24) -3425(21) -227% 18)
Table 3. Bond Lengths (A)for 2bayb
c1-c11 C2-C3 c3-c4 c4-c5
2.030(17) 2.033(18) 2.042(18) 2.031(19) 2.052(16) 2.039(19) 2.056(18) 2.039(18) 2.042(19) 2.009(21) 1.644 1.654 1.767(19) 1.784(20) 1.445(24) 1.431(22) 1.433(23) 1.382(24) 1.400(26) 1.422(24)
C6-C7 C6-C10 C7-C8 C8-C9 c9-c10 Cll-c12 C12-Cl3 C13-Cl4 C13-Cl8 C14-Cl5 C15-Cl6 C16-Cl7 C16-Cl9 C17-Cl8 C19-C20 c20-c21 c21-c22 C21-C26 C22-C23 C23-C24
Cnt(l)-Fe-Cnt(PP C(24)-S-C(27) C(2)-C(l)-C(5) C(2)-C(l)-C(ll) C(5)-C(l)-C(ll) C(l)-C(2)-C(3) C(2)-C(3)-C(4) C(3)-C(4)-C(5) C(l)-C(5)-C(4) C(7)-C(6)-C(lO) C(6)-C(7)-C(8) C(7)-C(8)-C(9) C(8)-C(9)-C(lO) C(6)-C(lO)-C(9) C(l)-C(ll)-C(l2) C(ll)-C(l2)-C(l3) C(12)-C(13)-C(14) C(12)-C(13)-C(18) C(14)-C(13)-C(18)
179.2 104.7(9) 106.5(14) 127.1(15) 125.9(15) 109.5(15) 107.3(16) 110.3(16) 106.3(15) 109.9(17) 106.7(16) 109.5(16) 105.5(16) 108.3(17) 174.6(19) 177.5(19) 117.5(15) 121.6(15) 120.9(15)
C(13)-C(14)-C(15) C(14)-C(15)-C(16) C(15)-C(16)-C(17) C(15)-C(16)-C(19) C(17)-C(16)-C(19) C(16)-C(17)-C(18) C(13)-C(18)-C(17) C(16)-C(19)-C(20) C(19)-C(2O)-C(21) C(2O)-C(21)-C(22) C(2O)-C(21)-C(26) C(22)-C(21)-C(26) C(21)-C(22)-C(23) C(22)-C(23)-C(24) S(l)-C(24)-C(23) S(l)-C(24)-C(25) C(23)-C(24)-C(25) C(24)-C(25)-C(26) C(21)-C(26)-C(25)
118.8(16) 121.8(17) 117.9(16) 122.0(16) 120.0(16) 122.9(16) 117.7(15) 176.5(21) 178.1(20) 122.0(18) 120.4(18) 117.818) 120.9(19) 121.1(18) 123.6(15) 118.5(16) 117.9(18) 122.8(21) 119.8(20)
a The numbers in parentheses are the estimated standard deviations in the last significant digit. bAtoms are labeled in agreement with Figure 1. c Cnt(1) is the centroid of the C(l)-C(5) ring, and Cnt(2) is the centroid of the C(6)-C(10) ring.
a The numbers in parentheses are the estimated standard deviations in the last significant digit. Atoms are labeled in agreement with Figure 1.
Fe-C1 Fe-C2 Fe-C3 Fe-C4 Fe-C5 Fe-C6 Fe-C7 Fe-C8 Fe-C9 Fe-C10 Fe-Cnt(1Y Fe-Cnt(2Y S-C24 S-C27 Cl-C2 Cl-C5
Table 4. Bond Angles (deg) for 2bagb
1.378(26) 1.386(27) 1.395(25) 1.420(26) 1.410(27) 1.188(25) 1.433(24) 1.396(24) 1.392(23) 1.395(26) 1.389(25) 1.366(24) 1.446(25) 1.412(24) 1.179(27) 1.398(26) 1.412(28) 1.366(29) 1.400(27) 1.351(28)
a The numbers in parentheses are the estimated standard deviations in the last significant digit. b Atoms are labeled in agreement with Figure 1. Cnt(1) is the centroid of the Cl-C5 ring, Cnt(2) is the centroid of the C6-C10 ring.
Finally, for each of the series, 2-4, the ,A values were observed to be insensitive to solvent polarity. Of primary interest to the planned investigation of electroactive SAMs prepared from 1 are the values of the formal redox potentials, Ef, for the ferrocene moieities of 2a-d. As shown in Table 1,the Ef values for the observed reversible one-electron oxidations of 2a-c are all shifted t o higher oxidation potentials relative to that of ferrocene itself.ll Thus, an Ef value of 267 mV is obtained for 2a which can be compared to the value (11)The cyclic voltammetry of 2d was not performed due to solubility limitations.
of 125 mV recorded for the ferrocene-ferrocenium couple under identical conditions. Interestingly, on going from 2a to the oligomer 2b, one observes an additional 16 mV shift to higher oxidation potential. However, in going from 2b to 2c, there appears to be virtually no change in this parameter and it can be anticipated that 287 mV is very close to the limit expected for longer oligomers of 2. As a final note, the Ef values obtained for the oligomers of 2 can be compared to those observed for the corresponding oligomers of 4 which possess the electron-withdrawing methyl sulfone moiety instead of the methyl sulfide functional group. In this regard, as expected, both 4a,b have Ef values which are shifted to higher oxidation potentials relative to those of 2a,b, respectively (see Table 1). However, it is interesting to observe that in going from 4a to 4b there is a reduction in oxidation potential (AEf = -15 mV) which tends to suggest that the inductive effect of the sulfone moiety is attenuated fairly quickly as the length of the conjugated phenylethynyl backbone in these oligomers increases. (c) Crystallographic Analysis of 2b. In order to obtain structural parameters that might aid in the planned investigations of S A M s derived from 1, the crystallographic analysis of 2b was conducted. Fractional coordinates of non-hydrogen atoms are given in Table 2; bond lengths and bond angles are given in Tables 3 and 4, respectively. As shown by this data and Figure 1, the solid-state structure obtained for 2b reveals few bond length or bond angle distortions. The average C-C bond length within the cyclopentadienyl rings of the ferrocene moiety is 1.407 A, and those of each of the aromatic rings are 1.391 (C13-Cl8) and 1.384 8, (C21-C26), respectively. The lengths of the carbon-carbon triple bonds involved in connecting these three fragments together are 1.188(25) and 1.179(27) A. The two cyclopentadienyl rings are nearly parallel t o one another with the Cnt(l)-Fe-Cnt(a) angle being 179.2' [Cnt(l) is the centroid of the Cl-C5 ring, and Cnt(2) is the centroid of the C6-C10 ring]. Furthermore, as shown in Figure 2, the aromatic ring defined by C13-Cl8 is nearly coplanar with the cyclopentadienyl ring described by Cl-C5, but not with the aromatic ring defined by C21-C26. Finally, the overall length
4812
Hsung et al.
Organometallics, Vol. 14, No. 10, 1995
Figure 1. Molecular structure of 2b with hydrogen atoms omitted for the purpose of clarity.
Figure 2. Different perspective of the molecular structure of 2b. of a single molecule of 2b is approximately 18 A as calculated from the midpoint of the C3-C4 bond to the
S atom.
Experimental Section All reactions were carried out under an atmosphere of nitrogen, and all reagents were obtained from commercial suppliers and used without further purification unless otherwise indicated. Tetrahydrofuran (THF) and diethyl ether (EtzO) were distilled from Na-benzophenone under nitrogen. Methylene chloride and benzene were distilled from calcium hydride under nitrogen. Methanol was dried over activated 4 A molecular sieves prior to use. Thin-layer chromatography (TLC) analysis was performed using EM Science silica gel 60 (F254) plates (0.25 mm), and the eluted plates were observed under a UV detector andor stained with either an aqueous solution of potassium permaganate (KMn04) or an ethanolic solution of phosphomolybdic acid (PMA) followed by heating. Chromatographic purifications were performed by flash chromatography12 on EM Science silica gel (230-400 mesh). 'H NMR spectra were obtained at either 300 or 500 MHz using chloroform-dl as the solvent and tetramethylsilane as an internal reference. 13CNMR spectra were recorded at 75 MHz using chloroform-dl as the solvent. Infrared spectra (cm-l) were recorded either neat or as Nujol mulls, and absorptions are described qualitatively as follows: s, strong; m, medium; w, weak. Low-resolution mass spectra were recorded on a Finnigan 1015 mass spectrometer; high-resolution mass spectra were recorded on a VG 70-250 instrument. Preparation of 4-IodophenylMethyl Sulfide (6). To a solution of 2.03 g (10.0 mmol) of 4-bromophenyl methyl sulfide in 30 mL of EtzO, cooled t o -78 "C was slowly added 11mL of a solution of tert-butyllithium (1.7 M in pentane, 20.0 mmol) dropwise. After the addition was complete, the reaction mixture was stirred for 35-45 min at -78 "C, after which time a solution of 3.05 g (12.0 mmol) of iodine in 75 mL of EtzO, precooled to -78 "C, was added dropwise via a cannula. The mixture was then stirred at -78 "C for 10 min and a t 0 "C for 25 min, whereupon it was poured into 150 mL of saturated aqueous sodium thiosulfite overlaid with 150 mL of EtzO. The (12)Still, W. C.; Kahn, M.; Mitra, A. J.Org. Chem. 1978,43,2923.
ether layer was washed with 2 x 150 mL of saturated aqueous sodium thiosulfite and 2 x 150 mL of saturated aqueous sodium chloride, dried with anhydrous sodium sulfate, and filtered, and the solvents were removed in uucuo to provide 2.78 g of a solid material. The crude product was purified via filtration through a short silica gel column in a 60-,Dfrit funnel (4 x 5 cm; eluent, 9:l hexane/CHzClz solvent mixture) to provide 2.50 g of the desired aryliodide 6 as a colorless solid (99% yield) which rapidly discolors in air. Analytically pure material in the form of white needles was obtained by recrystallization from hexane. Data for 6: mp 37.0-38.0 "C; Rf = 0.30 (9:l hexane/CHzClz); 'H NMR 6 2.44 (9, 3H), 6.94 (d, 2H, J = 8.3 Hz), 7.52 (d, 2H, J = 8.3 Hz); 13CNMR 6 15.6, 89.1, 128.1, 137.6, 138.5; IR (neat) 3037 w, 2970 w, 2955 w, 2912 s, 2852 w, 1471 m, 1425 m, 1383 s, 1116 m, 1093 m, 976 m, 965 m, 803 s; MS (EI) mle (relative intensity) 250 (100) M+, 235 (16), 217 (2), 204 (2), 123 (51,108 (13). General Procedure for Palladium-CatalyzedCoupling Reactions of Alkynes with Aryl Iodides in the Presence of Protected thiol^.^ The appropriate ferrocenyl arylalkyne (0.05-1.7 mmol scale), aryl iodide, Pd(PPh3)~Clz(1.8 mol %), and CUI (5.5 mol %) were dissolved in diethylamine in a Kontes Schlenk flask. The reaction mixture was deoxygenated using the freeze-pump-thaw method (three cycles), and, at the end of the last cycle, the reaction mixture was backfilled with nitrogen and the flask was sealed. The mixture was then stirred at 50 "C for 15-24 h with the progress of the reaction being carefully monitored by TLC analysis (1:l CHZCld hexane). When the reaction was complete, the solvents were removed in uucuo and the desired product was isolated by column chromatography. Preparation of 2a. Compound 5 (104.9 mg, 0.50 mmol) was coupled with 131.2 mg (0.51 mmol) of the aryl iodide 6 according to the general procedure to provide 150.6 mg (91% yield) of the aryl sulfide 2a as an orange-red crystalline material. Data for 2a: mp 149.0-151.0 "C; R f = 0.56 (1:lCHzClfiexane); lH NMR 6 2.48 (s, 3H), 4.21 (brs, 7H), 4.46 (t, 2H, J = 1.6Hz), 7.14(d, 2H, J = 8.1 Hz), 7.34(d, 2H,J = 8.1 Hz); 13C NMR 6 15.5, 68.8, 69.9, 70.1, 71.3, 85.4, 87.1, 120.3, 125.9, 126.9, 131.7; IR (neat) 3101 w,2922 m, 1651 w, 1585 w, 1496 m, 1438 w, 1399 s, 1105 s, 1090 m, 1027 m; UV (THF) (E) L,, 312 nm (27 130); MS (EI) m/e (relative intensity) 332 (100) M+, 317 (21,251 (4),227 (31,195 (4), 166 (9), 152 (41, 121 (6);HRMS mle for ClgHlsFeS, calcd 332.0322, found 332.0313. Preparation of l-(4-Iodophenyl)-2-(trimethylsilyl)ethyne (8). l-(4-Bromophenyl)-2-(trimethylsilyl)ethyne (7)* (1.27 g, 5.0 mmol) was transhalogenated according to the same procedure as that used for the preparation of the aryl iodide 6 to provide 1.47 g (94% yield) of the aryl iodide 8 as a pale yellow solid. Data for 8: mp 56.0-58.0 "C; R f = 0.43 (1:l CH2Clhexane); lH NMR 6 0.24 (s, 9H), 71.3 (d, 2H, J = 7.9 Hz), 7.58 (d, 2H, J = 7.9 Hz); 13C NMR 6 -0.2, 94.4, 95.8, 103.9, 122.6, 133.4, 137.3; IR (neat) 2959 m, 2898 w, 2159 s, 1482 s, 1389 w, 1249 s, 1217 w, 1055 w, 1006 m, 864 8,843 s, 819 s, 760 m; MS (EI)mle (relative intensity) 300 (100)M+,286 (1001, 271 (81, 255 (lo), 173 (13), 154 (84), 143 (541, 128 (20), 117 (16). Preparation of 9. Compound 5 (351.7 mg, 1.68 mmol) was coupled with 504.3 mg (1.68 mmol) of 8 according to the general procedure to provide 577.8 mg (90% yield) of 9 as an
Organometallics, Vol. 14, No. 10,1995 4813
Ferrocene-Terminated Phenylethynyl Oligomers
J = 8.3 Hz), 7.42 (d, 4H, J = 2.7 Hz), 7.45 (brs, 4H); I3C NMR orange-red crystalline material. Data for 9: mp 169.0-170.0 6 15.1, 64.6, 69.0, 69.9, 71.4, 82.2, 82.6, 83.5, 90.6, 90.7, 91.0, "C; R f = 0.09 (1:9 CHzClAexane); 'H NMR 6 0.25 (s,9H), 4.21 120.7, 122.9, 123.2, 124.1, 125.7, 131.2, 131.4, 131.5, 131.6, (brs, 5H), 4.22 (t, 2H, J = 1.8 Hz), 4.46 (t, 2H, J = 1.8 Hz), 131.8, 134.3, 137.4; IR (neat) 2923 m, 2211 m, 1536 s, 1443 7.35 (brs, 4H); 13C NMR 6 -0.1, 64.8, 68.9, 70.0, 71.4, 85.4, m, 1164 w, 1104 m, 1086 w,1027 w, 837 s, 821 s; W (THF) 90.5,95.9, 104,8,122.1, 124.1, 131.3, 131.8; IR(neat) 3179 w, (E): A, 345 nm (67 039); MS (EI) mle (relative intensity) 532 3161 W, 3086 w, 2954 w, 1600 m, 1559 w, 1501 w, 1247 s, 844 (19) M+, 517 (a), 308 (19), 262 (loo), 183 (561,128 (69); HRMS s; MS (EI) mle (relative intensity) 382 (100) M+, 367 (3), 337 mle for C35H24FeS, calcd 532.0948, found 532.0966. (2), 285 (3,246 (3), 210 (3), 184 (16), 159 (2); HRMS mle for Preparation of 14. Compound 7 (506.0 mg, 2.0 mmol) was Cz3HzzFeSi, calcd 382.0840, found 382.0829. desilylated in the same manner as described for the preparaPreparation of 10. To a solution of 524.6 mg (1.37 mmol) tion of 10 to provide 347.2 mg (96% yield) of 14 as a white of 9 in 50 mL of CHzClzwas slowly added 1.51 mL of a solution crystalline material. Data for 14: mp 56.0-58.0 "C; Rf = 0.45 of TBAF (1M in THF) dropwise. The reaction mixture was (1:9 CH2ClAexane); 'H NMR 6 3.10 (s, lH), 7.30 (d, 2H, J = stirred at room temperature for 1.5 h, after which time the 8.4 Hz), 7.41 (d, 2H, J = 8.4 Hz); I3C NMR 6 78.3, 82.6, 121.0, solvents were removed in uucuo. The resulting crude material 123.1, 131.6, 133.5; IR (neat) 3267 s, 2924 w, 1584 m, 1484 s, was then purified via column chromatography (1:9 CHZCld 1468 m, 1396 m, 1267 w, 1068 m, 1010 m, 821 s; MS (EI) mle hexane) to provide 424.0 mg (99%yield) of the desired product (relative intensity) 182 (98) M+ 2, 180 (100) M+, 101 (50), as an orange-red crystalline material. Data for 10 mp 140.075 (29). 141.0 "C; Rf = 0.67 (1:lCH&lz/hexane); 'H NMR 6 3.14 (9, Preparation of 13. Compound 14 (210.0 mg, 1.2 mmol) lH), 4.22 (brs, 5H), 4.23 (t, 2H, J = 1.4 Hz), 4.47 (t, 2H, J = was coupled with 290.1 mg (1.2 mmol) of 6 according to the 1.4 Hz), 7.38 (brs, 4H); I3C NMR 6 64.8, 69.0, 70.0, 71.5, 78.6, general procedure to afford 306.1 mg (95% yield) of the aryl 83.4, 85.3, 90.7, 121.1, 124.5, 131.2, 132.0; IR (neat) 3271 s, bromide intermediate as a white solid [mp 148.0-149.0 "C; 3005 w, 2968 w,2917 w,2842 w,1619 m,1518 m,1381w, Rf = 0.37 (1:9 CHzClAexane); 'H NMR 6 2.48 (s, 3H), 7.15 1040 w; MS (EI) mle (relative intensity) 310 (100) M+ H, (d, 2H, J = 8.4 Hz), 7.32 (d, 2H, J = 8.4 Hz), 7.37 (d, 2H, J = 310 (67) Mf, 253 (6), 227 (2), 190 (9), 163 (31, 156 (6), 152 (31, 8.4 Hz), 7.42 (d, 2H, J = 8.4 Hz); I3C NMR 6 15.3, 88.4, 90.3, 121 (17); HRMS mle for CzoHlrFe, calcd 310.0445, found 122.3, 122.4, 125.8, 131.6, 131.8, 132.9,138.6, 139.7;IR (neat) 310.0453. 2975 w, 2919 m, 2445 m, 1594 m, 1497 m, 1318 s, 821 s; MS Preparation of 2b. Compound 10 (31.0 mg, 0.10 mmol) (EI) mle (relative intensity) 304 (100) M+ 2, 302 (100) M+, was coupled with 25.0 mg (0.10 mmol) of 6 according to the 289 (31), 287 (31), 208 (121, 152 (12); HRMS mle for c15general procedure to provide 43.1 mg (99% yield) of 2b as an H1179BrS,calcd 301.9765, found 301.9767; mle for C I ~ H ~ ~ ~ ~ B ~ S , orange-red crystalline material. Data for 2b: mp 172.0-174.0 calcd 303.9744, found 303,97611. This compound (246.0 mg, "C; R f = 0.56 (1:lCH&lz/hexane); 'H NMR 6 2.49 (s,3H),4.22 0.81 mmol) was then transhalogenated according to the same (brs, 5H), 4.23 (t, 2H, J = 1.6 Hz), 4.48 (t, 2H, J = 1.6 Hz), procedure as that used for the preparation of the aryl iodide 6 7.16 (d, 2H, J = 8.3 Hz), 7.39 (d, 2H, J = 8.3 Hz), 7.40 (brs, to provide 278.0 mg (99%yield) of the desired product 13 as a 4H); I3C NMR 6 15.2, 66.8, 68.9, 70.0, 71.4, 85.5, 89.3, 90.5, white solid. Data for 13: mp 164.0-166.0 "C; R f = 0.70 (1:l 90.8, 119.3, 122.4, 123.7, 125.8, 131.3, 131.4, 131.8, 132.4; IR CHzClz/hexane); 'H NMR 6 2.48 (8, 3H), 7.15 (d, 2H, J = 8.4 (neat) 2958 w, 2921 m, 2872 w, 2858 w, 2362 m, 2344 w, 1513 Hz), 7.18 (d, 2H, J = 8.0 Hz), 7,37 (d, 2H, J = 8.0 Hz), 7.63 (d, s, 1164 w, 1104 w, 1088 m, 835 s, 818 s; U V (THF) (E): A, 2H, J = 8.4 Hz); I3C NMR 6 15.3, 88.5, 94.0, 119.1, 125.8, 331 nm (10 480); MS (EI) mle (relative intensity) 432 (100) 128.2, 128.3, 131.8,133.0,137.5, 139.7;IR(neat) 2985 w, 2976 M+, 417 (23),310 (a), 250 (381,216(19), 193 (a), 121 (8); HRMS w, 2888 w, 1653 m, 1590 m, 1495 m, 1389 m, 819 s; MS (EI) mle for C Z ~ H Z ~calcd F S , 432.0635, found 432.0631. mle (relative intensity) 350 (100) M+, 335 (23), 208 (121, 175 Preparation of 11. Compound 10 (185.0 mg, 0.60 mmol) (121, 112 (8). was coupled with 196.8 mg (0.66 mmol) of 8 according to the Preparation of 2c from the Arylalkyne 10. Compound general procedure to provide 249.7 mg (87%yield) of 11 as an 10 (15.5 mg, 0.050 mmol) was coupled with 17.5 mg (0.050 orange-red crystalline material. Data for 11: mp 191.0-192.0 mmol) of 13 according to the general procedure to provide 22.1 "C; R f = 0.67 (1:lCHzClfiexane); 'H NMR 6 0.26 (s,9H), 4.22 mg (83% yield) of 2c. (9, 5H), 4.23 (t, 2H, J = 1.6 Hz), 4.47 (t, 2H, J = 1.6 Hz), 7.40 (d,4H, J = 1.4H~),7.4l(brs,4H);'~CNMR6-0.1,64.8,69.0, Preparation of 15. Compound 14 (166.7 mg, 0.92 mmol) was coupled with 276.0 mg (0.92 mmol) of 8 according to the 70.0, 71.4,85.5,90.6,90.7,91.2,96.4,104.6,122.0,123.0,123.1, general procedure t o afford 305.6 mg (94% yield) of the aryl 124.1, 131.3, 131.4, 131.5, 131.9; IR (neat) 2955 m, 2927 w, bromide intermediate as a white solid [mp 138.0-139.0 "C; 2202 m, 2155 m, 1517 m, 1252 m, 866 s, 837 s; MS (EI) mle R f = 0.17 (hexane); 'H NMR 6 0.25 (9, 9H), 7.32 (d, 2H, J = (relative intensity) 482 (100)M+, 467 (3), 410 (21, 346 (2), 316 8.4 Hz), 7.39 (brs, 4H),7.43 (d, 2H, J = 8.4 Hz); I3C NMR 6 (2), 234 (23), 185 (2);HRMSmle for C31H&'eSi, calcd 482.1153, -0.1, 82.1, 90.1, 96.5, 104.5, 122.6, 122.7, 122.9, 123.2, 131.3, found 482.1158. 131.7,131.9,133.0; IR (neat) 2959 w, 2157 w, 1500 m, 1254 s, Preparation of 12. Compound 11 (240.5 mg, 0.50mmol) 1244 m, 867 m, 837 s, 821 s, 760 m; MS (EI) mle (relative was desilylated in the same manner as described for the intensity) 354 (33) M+ + 2, 352 (32) M+, 339 (361, 337 (35), preparation of 10 t o provide 204.3 mg (99% yield) of desired 223 (a), 170 (81, 168 (a), 149 (491, 94 (471, 79 (loo)]. This product as an orange red solid. Data for 12: mp 198.0-199.0 compound (52.5 mg, 0.15 mmol) was then transhalogenated "C; R f = 0.26 (1:lCHzClz/hexane);'H NMR 6 3.16 (s, lH), 4.22 according to the same procedure as that used for the prepara(brs, 5H), 4.23 (t, 2H, J = 1.8 Hz), 4.48 (t, 2H, J = 1.8 Hz), tion of the aryl iodide 6 to provide 60.1 mg of a crude material 7.41 (d, 4H, J = 2.0 Hz),7.42 (brs, 4H); 13CNMR 6 64.8, 69.0, consisting of 75% of the desired product 15 and 25% of the 122.0,123.6, 70.0, 71.5, 79.0,83.2,85.5,90.4,90.8,91.3,121.9, dehalogenated side product that could be used without puri124.1, 131.3,131.4, 131.5,132.1; IR (neat) 3265 s, 2985 w, 2201 fication for subsequent palladium-catalyzed coupling reactions. m, 1594 w, 1518 s, 1359 w, 1255 w, 1106 w, 844 s, 821 m; MS Analytically pure 15 was obtained by preparative TLC. Data (EI) mle (relative intensity) 410 (100) M', 352 (71, 289 (23), for 15: mp 148.0-150.0 "C; R f = 0.17 (hexane); 'H NMR 6 205 (19), 121 (36); HRMS mle for CzgHlgFe, calcd 410.0758, 0.25 (9, 9H), 7.18 (d, 2H, J = 8.0 Hz), 7.39 (brs, 4H), 7.65 (d, found 410.0749. 2H, J = ~ . O H Z ) ; ' ~ C N M-0.1,89.0,90.4,91.3,96.2, R~ 104.6, Preparation of 2c from the Arylalkyne 12. Compound 115.5, 122.7, 122.9, 131.2, 131.4, 133.1, 137.6; IR (neat) 2963 12 (41.0 mg, 0.10 mmol) was coupled with 25.0 mg (0.10 mmol) w, 2959 w, 2935 w, 1509 w, 1501 w, 1390 w, 1252 m, 1244 m, of 6 according to the general procedure to provide 46.3 mg (87% 868 w, 837 s, 821 m, 756 w; MS (EI) mle (relative intensity) yield) of the aryl sulfide 2c as an orange-red solid. Data for 400 (18) M+, 385 (171,274 (loo), 259 (loo), 229 (211,130 (63); 2c: mp 227.0-229.0 "C; Rf = 0.55 (1:l CHzClAexane); 'H HRMS mle for C1gH1,ISi, calcd 400.0144, found 400.0140. NMR 6 2.49 (s, 3H), 4.23 (brs, 5H), 4.24 (t, 2H, J = 1.6 Hz), Preparation of the Arylalkyne 11from 5. Compound 4.48 (t,2H, J = 1.6 Hz), 7.22 (d, 2H, J = 8.3 Hz), 7.39 (d, 2H,
+
+
+
4814 Organometallics, Vol. 14, No. 10, 1995 5 (6.6 mg, 0.032 mmol) was coupled with 12.6 mg of 15 (0.032 mmol) according to the general procedure to provide 13.7 mg (90% yield) of 11 as an orange-red solid. Preparation of 2d. Compound 12 (19 mg, 0.046 mmol) was coupled with 19.3 mg (0.046 mmol) of 13 according t o the general procedure to provide 21.8 mg (75% yield) of 2d as an orange-red solid. Data for 2d: mp 225.0-230 "C (decomp); Rf = 0.56 (1:l CHzClz/hexane); 'H NMR 6 2.49 (8, 3H), 4.23 (brs, 5H), 4.24 (t, 2H, J = 1.2 Hz), 4.48 (t, 2H, J = 1.2 Hz), 7.17(d, 2H, J =8.5 Hz), 7.39(d, 2H, J = 8.5Hz), 7.42(d,4H, J = 2.4 Hz), 7.45 (brs, 4H), 7.46 (brs, 4H); IR (neat) 2982 s, 2870 s, 2203 w, 1725 m, 1519 m, 1066 w, 1056 m, 837 s; W (THF) ( E ) : A,, 357 nm (18 101); MS (EI) mle (relative intensity) 632 (2) M+, 547 (21, 520 (31, 506 (161, 454 (291, 430 (18),418 (loo), 410 (61, 379 (421, 370 (8). Preparation of 3a. To a solution of 88.6 mg (0.27 mmol) of 2a in 80 mL of CHzClz cooled to -40 "C was added 46.0 mg (0.27 mmol) of MCPBA. The reaction mixture was stirred at -40 "C for 24 h while the progress of the reaction was monitored closely by TLC analysis (EtzO). After the reaction was complete, the solvents were removed in uucuo to provide a crude product, which was purified by column chromatography to yield 79.7 mg (86% yield) of 3a as an orange-red crystalline material. Data for 3a: mp 156.5-157.5 "C; Rf = 0.12 (EtzO);'H NMR 6 2.74 (s, 3H), 4.25 (brs, 5H), 4.28 (t, 2H, J = 1.7 Hz), 4.52 (t, 2H, J = 1.7 Hz), 7.61 (brd, 4H, J = 1.8 Hz); 13CNMR6 42.9,66.6,69.1,70.0, 71.8,88.1,92.8,123.4, 132.0, 132.2, 141.1; IR (neat) 2929 m, 2922 m, 2884 w, 1590 m, 1414 m, 1054 s, 1050 s, 1000 s, 822 m; UV (THF) ( E ) : A, 272 nm (28 744), 307 nm (33 688); MS (E11 mle (relative intensity) 348 (26) M+, 332 (loo), 317 (281, 285 (91, 251 (61, 226 (6), 211 (3), 195 (8); HRMS mle for ClgHleFeOS, calcd 348.0271, found 348.0251. Preparation of 4a. Compound 2a (16.6 mg, 0.050 mmol) was treated with 2.0 equiv of MCPBA in the same manner as described above for the preparation of 3a to provide 16.9 mg (93% yield) of 4a as an orange-red solid. Data for 4a: mp 142.0-144.0 "C; R f = 0.23 (EtzO); 'H NMR 6 3.07 (9,3H),4.26 (brs, 5H), 4.32 (t, 2H, J = 1.7 Hz), 4.54 (t, 2H, J = 1.7 Hz), 7.64 (d, 2H, J = 8.4 Hz), 7.89 (d, 2H, J = 8.4 Hz); 13CNMR 6 44.5,63.7,69.4, 70.1,71.7,84.3,93.6,127.3,131.9,133.8,138.7; IR (neat) 3029 w, 2923 w, 2206 m, 1608 w, 1591 m, 1310 s, 1146 s, 1087 w, 761 m; U V (THF) ( E ) : Amax 266 nm (14 2311, 308 nm (12 046); MS (EI) mle (relative intensity) 364 (100) M+ 332 (4), 301 (31,285 (30),229 (91,202 (41, 189 (2), 163 (71, 12; (10); HRMS mle for C19H16FeOzS, calcd 364.0220, found 364.0234. Preparation of 3b. Compound 2b (43.2 mg, 0.10 mmol) was treated with 1.0 equiv of MCPBA in the same manner as described above for the preparation of 3a to provide 40.9 mg (91% yield) of 3b as an orange-red solid. Data for 3b: mp 179.0-180.0 "C; R f = 0.14 (EtzO); 'H NMR 6 2.75 (9,3H),4.26 (brs, 5H), 4.27 (t, 2H, J = 1.7 Hz), 4.52 (t, 2H, J = 1.7 Hz), 7.48 (brs, 4H), 7.66 (dd, 4H, J = 5.3, 8.5 Hz); 13CNMR 6 43.9, 64.7, 69.1, 70.0,71.5,85.4,89.6,91.0,91.4, 121.6,123.6, 124.4, 126.1, 131.3, 131.6, 132.3, 145.6; IR (neat) 3115 w, 3089 w, 2972 m, 2935 m, 2381 w, 2352,2251, 2234 w, 1774 m, 1544 m, 1540 m, 1530 m, 1112 m, 1066 s, 856 s, 823 s; UV (THF) (E) , A 330 nm (41 574); MS (EI) mle (relative intensity) 448 (29) M+, 432 (loo), 417 (19), 385 (6), 329 (6), 295 (6), 263 (4), 216 (ll),184 (10); HRMS mle for Cz7HzoFeOS, calcd 448.0584, found 448.0562. Preparation of 4b. Compound 3b (35.7 mg, 0.080 mmol) was treated with 2.0 equiv of MCPBA in the same manner as described above for the preparation of 3a to provide 34.7 mg (94% yield) of 4b as an orange-red solid. Data for 4b: mp 168.0-170.0 "C (decomp);R f = 0.14 (EtzO); 'H NMR 6 3.08 ( s , 3H), 4.26 (brs, 5H), 4.27 (t, 2H, J = 1.9 Hz), 4.52 (t, 2H, J = 1.9 Hz), 7.50 (d, 4H, J = 1.0 Hz), 7.71 (d, 2H, J = 8.4 Hz), 7.93 (d, 2H, J = 8.4 Hz); 13C NMR 6 44.5, 64.7, 69.1, 70.0, 71.5, 85.3, 89.0, 91.3, 93.3, 121.1, 124.8, 127.4, 129.0, 131.4, 131.7, 132.2, 139.6; IR (neat) 2924 w, 1697 w, 1590 w, 1426 m, 1308 s, 1151 s, 1131 s, 840 m, 763 m; U V (THF) ( E ) : A,,
Hsung et al. 330 nm (33 363); MS (EI) mle (relative intensity) 464 (73) M+, 448 (33),432 (loo), 417 (19), 385 (22), 329 (161, 263 (111, 216 (16), 121 (23); HRMS mle for Cz,H20FeOzS, calcd 464.0588, found 464.0540. Preparation of 4c. Compound 2c (29.0 mg, 0.055 mmol) was treated with 2.0 equiv of MCPBA in the same manner as described above for the preparation of 3a to provide 24.6 mg (80%yield) of 4c as an orange-red solid. Data for 4c: mp 153.0-155.0 "C (decomp);R f = 0.08 (EtzO); 'H NMR 6 3.08 (s, 3H), 4.26 (brs, 5H), 4.27 (t, 2H, J = 1.7 Hz), 4.52 (t, 2H, J = 1.7 Hz), 7.48 (d, 4H, J = 1.0 Hz), 7.54 (brs, 4H), 7.71 (d, 2H, J = 8.3 Hz), 7.94 (d, 2 H , J = 8.3 Hz); 13C NMR 6 44.5, 66.8, 69.0, 70.0, 71.5,89.3, 89.5, 90.4, 90.9, 91.7,93.0, 122.0, 123.9, 127.4, 128.9, 130.3, 131.3, 131.5, 131.6, 131.8, 132.3, 133.9, 139.7; IR (neat) 2924 w, 1702 m, 1565 m, 1426 m, 1399 s, 1314 s, 1263 m, 1155 s, 837 s; W (THF) ( E ) Amax 336 nm (21 151); MS (EI) mle (relative intensity) 564 (100) M+, 485 (201, 429 (20), 376 ( l l ) , 364 (111, 318 ( E ) , 218 (26); HRMS mle for C35Hz4Fe0zS, calcd 564.0846, found 564.0820. Preparation of 4-Iodobenzenethiol. To a suspension of 3.02 g (10.0 mmol) of pipsyl chloride in 70 mL of HzO cooled in an ice-bath was cautiously added 12 mL of concentrated sulfuric acid followed by 4.14 g (63 mmol) of zinc dust. The mixture was stirred for 30 min and then refluxed for 6 h. After cooling, the reaction mixture was poured into a mixture of 50 mL of HzO and 50 mL of saturated aqueous ammonium chloride overlaid with 250 mL of EtzO. The aqueous layer was extracted with 2 x 250 mL of EtzO, and the combined organic layers were washed with an equal volume of saturated aqueous sodium chloride, dried with anhydrous sodium sulfate, and then filtered through a pad of silica gel. Upon removal of the solvents in UUCUO, 1.03 g (44% yield) of the desired material was obtained as a white solid [mp 73.0-74.0 "C; Rf = 0.59 (1:l CHzClz/hexane);'H NMR 6 3.43 (s, lH), 7.01 (d, 2H, J = 8.3Hz),7.54(d,2H, J=8.3H~);'~CNMR693.1,129.9,132.1, 139.0; IR (neat) 3190 w, 2922 w, 2382 s, 2336 s, 1468 m, 1384 m, 1099 m, 1005 m, 806 s; MS (EI) mle (relative intensity) 236 (100) M+, 109 (71), 65 (2411. Preparation of S-Acetyl-44odothiophenol(16). To a solution of 730.0 mg (3.1 mmol) of 4-iodobenzenethiol in 50 mL of CHzClz were added 528.9 mg (7.73 mmol) of imidazole and 408.2 pL (4.3 mmol) of acetic anhydride sequentially. The mixture was stirred at room temperature for 15 h, and then the solvents were removed in uucuo. The crude product was purified by column chromatography to provide 701.2 mg (82% yield) of 16 as a white solid material. Data for 16: mp 54.055.0 "C; R f = 0.30 (1:lCHzClz/hexane);'H NMR 6 2.43 (s, 3H), 7.13 (d, 2H, J = 8.4 Hz), 7.74 (d, 2H, J = 8.4 Hz); 13CNMR 6 30.2, 95.9, 127.7, 135.9, 138.3, 193.2; IR (neat) 2929 m, 2903 w, 2851 w, 1696 s, 1466 m, 1382 w, 1120 w, 1116 w, 1006 s, 812 m; MS (EI)mle (relative intensity) 278 (100) M+,236 (loo), 191 (31, 127 (9), 109 (1001, 82 (281, 69 (48). Preparation of 17a. Compound 5 (62.9 mg, 0.30 mmol) was coupled with 83.4 mg (0.30 mmol) of 16 (1.0 equiv) according t o the general procedure except that 10 mL of a 1:l of THFldiisopropylethylamine (Hunig's base) solvent mixture was used instead of diethylamine7 to provide 89.7 mg (83% yield) of 17a as an orange-red crystalline material. Data for 17a: mp 96.0-98.0 "C; R f = 0.22 (1:l CHzClfiexane); IH NMR 6 2.43 ( s , 3H), 4.24 (brs, 5H), 4.26 (t, 2H, J = 1.6 Hz), 4.51 (t, 2H, J=1.6Hz),7.36(d,2H,J=8.2Hz),7.50(d,2H,J=8.2 Hz); 13C NMR 6 30.2, 64.7, 69.0, 70.0, 71.5, 85.1, 90.4, 125.3, 127.1, 131.9, 134.2, 193.7; IR (neat) 2922 m, 2917 w, 1704 s, 1590 s, 1121 m, 1116 m, 1105 m, 1000 w, 945 w, 822 m, 818 m; MS (EI) mle (relative intensity) 360 (100) M+,318 (57), 251 (61, 195 (8),121 (12); HRMS mk for C Z O H I ~ F ~ O calcd S, 360.0271, found 360.0276. Preparation of la. To a solution of 66.5 mg (0.185 mmol) of 17a in 2 mL of chloroform was added 6 mL of diethylamine. The mixture was then stirred at room temperature for 30 min, at which time the solvents were removed in uucuo. The resulting crude material was then purified by column chromatography to provide 38.5 mg (65% yield) of the disulfide of
Ferrocene-Terminated Phenylethynyl Oligomers
Table 6. Crystal, Data Collection, and Refinement Parameters for 2b formula fw color; habit size ("3) cryst syst space group a, A
b, A c,
A
P, deg
volume, A3 2 Dcdcd, mg mW3 temp, "C radiation scan technique p , mm-1 2&,, deg no. of data no. of data in refinement R criteria
CmHzoFeS 432.3 orange prism 0.037 x 0.065 x 0.170 monoclinic P21Ic
6.031(2) 33.457(12) 10.364(4) 90.90(3) 2091.2(13) 4
1.373 23 Mo Ka (graphite-monochromated) w
0.831 45 3109 935 0.083 I > 4dI)
l a as an orange-red solid [mp 173.0-175.0 "C; Rf = 0.58 (1:l CHzClfiexane); 'H NMR 6 4.23 (brs, lOH), 4.25 (t, 4H, J = 1.8 Hz),4.51 (t, 4H, J = 1.8 Hz),7.42 (dd, 8H, J = 8.8, 10.8 Hz); IR (neat) 2924 m, 2917 w, 2363 m, 2335 w, 2330 w, 1494 s, 1395 m, 1162 w, 1105 m, 1025 m, 823 s, 813 s; MS (EI) mle (relative intensity) 634 (2) M+, 382 (2), 318 (loo), 286 (8), 228 (6), 121 (14); HRMS mle for CasHzsFezSz calcd 634.0175, found 634.01401. To a solution of this disulfide in 4 mL of CHzClz were added 2-4 drops of glacial acetic acid and ca. 100 mg of zinc dust. The heterogeneous mixture was then stirred at room temperature for 5 min, after which time the mixture was passed through a pipette-sized silica gel column to provide 37.5 mg (99%yield) of l a as an orange-red solid. Data for la: mp 114.0-115.0 "C; R f = 0.52 (1:lCHzClz/hexane); 'H NMR 6 3.49 (s, lH), 4.24 (brs, 7H), 4.49 (t,2H, J = 1.8 Hz), 7.21 (d, 2H, J = 8.3 Hz), 7.34 (d, 2H, J = 8.3 Hz); 13C NMR 6 64.2, 68.8, 69.9, 71.3, 84.8,88.7, 121.2, 129.0,131.9,136.1;IR (neat) 2928 m, 2924 m, 2919 w, 2557 w, 2547 w, 2358 w, 2362 w, 2219 w, 2206 w, 1592 s, 1497 s, 1399 m, 1100 s, 1093 m, 817 s; MS (EI) mle (relative intensity) 318 (100) M+, 286 (35), 267 (19), 228 (8), 186 (8), 165 (E),149 (23); HRMS mle for ClsH14FeS, calcd 318.0166, found 318.0170. Preparation of 1%. Compound 10 (93.1 mg, 0.30 mmol) was coupled with 83.4 mg (0.30 mmol) of 16 according to the procedure used to prepare 17a t o provide 98.7 mg (71% yield) of 17b as a n orange-red solid. Data for 1%: mp 183-185 "C; R,-= 0.18 (1:l CHzClfiexane); 'H NMR 6 2.44 ( 8 , 3H), 4.26 (brs, 5H), 4.27 (t, 2H, J = 1.6 Hz), 4.51 (t, 2H, J = 1.6 Hz), 7.40 (d, 2H, J = 8.2 Hz), 7.47 (brs, 4H), 7.56 (d, 2H, J = 8.2 Hz);13C NMR 6 30.3, 64.8, 69.0, 70.0, 71.5, 84.6, 85.5, 86.7, 91.0, 121.6, 127.4, 131.3, 131.6, 132.0, 132.4, 134.2, 135.1, 198.8; IR (neat) 3268 w, 3093 w, 3076 w, 2922 w, 1697 s, 1514 m, 1484 s, 1397 w, 1118 w, 1105 m, 828 s; MS (EI) mle (relative intensity) 460 (100) M+, 418 (441, 386 (lo), 295 (71, 209 (61, 121 (10); HRMS mle for C D H ~ O F ~ Ocalcd S , 460.0584, found 460.0575. Preparation of lb. Compound 17b (20.3 mg, 0.044 mmol) was treated according to the procedure used to prepare l a to provide 14.7 mg of an orange-red solid, which is the disulfide (79% yield) [Rf = 0.48 (1:l CHzClfiexane); IH NMR 6 4.25 (brs, 14H), 4.50 (t, 4H, J = 1.7 Hz),7.45 (brs, 8H), 7.47 (brs, 8H); IR (neat) 2923 m, 2916 w, 2363 m, 2335 w, 2331 m, 1490 s, 1390 m, 1160 s, 1105 m, 1025 w, 823 s, 813 s; MS (EI) mle (relative intensity) 834 (1)M+, 693 (11, 490 (161, 466 (loo), 432 (loo), 417 (421,385 (16), 295 (16), 265 (371,216 (26), 149 ( l l ) , 121 (26)]. This disulfide was then treated with acetic acid and zinc dust according to general procedure to provide 14.6 mg (99% yield) of l b as an orange-red solid. Data for lb: mp 141.5-143.5 "C; Rf = 0.42 (1:l CHzClhexane); 'H NMR 6 3.54 (brs, lH), 4.25 (brs, 5H), 4.27 (t, 2H, J = 1.7 Hz),
Organometallics, Vol. 14, No. 10,1995 4815 4.51 (t, 2H, J = 1.7 Hz),7.21 (d, 2H, J = 8.2 Hz), 7.31 (d, 2H, J = 8.2 Hz), 7.45 (brs, 4H); 13C NMR 6 64.9, 69.0, 70.0, 71.5, 85.5, 89.7, 90.4, 90.6, 122.2, 123.9, 127.2, 128.9, 131.3, 131.4, 132.1,136.1; IR (neat) 2920 s, 2851 m, 2558 m, 2490 w, 2202 m, 1598 m, 1515 s, 1105 s, 835 s, 821 s; MS (E11 mle (relative intensity) 418 (100) M+, 386 (2), 328 (2), 295 (31, 263 (3),209 (121, 121 (8);mle for CZ&Il$eS, calcd 418.0479, found 418.0487. Preparation of 17c. Compound 12 (41.0 mg, 0. LO mmol) was coupled with 27.8 mg (0.10 mmol) of 16 according to the procedure used to prepare 17a to provide 31.2 mg (56%) of 17c as an orange-red solid. Data for 17c: mp 193 0-195.0 "C; R f = 0.39 (1:lCHzCldhexane); lH NMR 6 2.42 (s, ;3H),4.22 (brs, 5H), 4.23 (s, 2H), 4.48 (brt, 2H, J = 1.7 Hz), 7.36 (d, 2H, J=s.OHz), 7.42(dd,4H, J=3.0,9.3Hz), 7.46(brs, 4H),7.50 NMR 6 30.3, 66.8, 69.0, 70.0, 71.5, (d, 2H, J = 8.0 Hz); 85.5, 90.5, 90.6, 90.7, 90.8, 91.3, 122.0, 122.8, 123.3, 124.1, 124.3, 128.3, 131.0, 131.3, 131.5, 131.6, 132.2, 134.2, 193.4; IR (neat) 2957 m, 2925 s, 2870 w, 2854 w, 1708 s, 1679 w, 1608 w, 1589 m, 836 s; MS (E11 mle (relative inten,dty) 560 (100) M+, 518 (39), 517 (311,259 (191, 128 (16); HRMS mle for C3sHz4FeOS,calcd 560.0897, found, 560.0920. Preparation of IC. Compound 17c (7 mg, 0.013 mmol) was treated according to the procedure used to prepare l a to provide 6.8 mg (79% yield) of the disulfide as an orange-red solid [ R f = 0.52 (1:lCHzCldhexane); lH NMR 6 4.22 (Ibrs, 5H), 4.23 ( 8 , 2H), 4.48 (brt, 2H, J = 1.7 Hz),7.39 (brs, 4H), 7.42 (brs, 4H), 7.46 (brs, 4H)I. This disulfide was then treated with acetic acid and zinc dust according t o general procedure to provide 6.1 mg (94%yield) of ICas a n orange-red solid. Data for IC: mp 191.0-194.0 "C (decamp); Rf = 0.42 (1:lCHZCld hexane); lH NMR 6 3.50 (s, lH), 4.22 (brs, 5H), 4.23 (blrs,2H), 4.48 (brt, 2H, J = 1.7 Hz), 7.19 (d, 2H, J = 8.0 Hz), 7.34 (d, 2H, J = 8.0 Hz), 7.42 (dd, 4H, J = 1.9, 10.7 Hz), 7.44 (brs, 4H); IR (neat) 2956 m, 2923 s, 2855 m, 2362 m, 2337 rn, 1652 w, 1541 w, 1458 w, 1122 m, 1106 s, 837 m; MS (131) mle (relative intensity) 518 (100) M', 486 (21,365 (31,279 (41,259 (161, 128 (16); mle for C ~ ~ H Z Z Fcalcd ~ S , 518.0782, found 518.0806. Crystal Data for Compound 2b. Crystals suitable for X-ray analysis were obtained from CHzClz/hexane at, 4 "C. Crystallographic data are summarized in Table 5. Single crystals are (at 296 K) monoclinic, space group P2/c, with a = 6.031(2)A, b = 33.457(12)A, c = 10.364(4)A, /3 = 90.90(3)",V = 2091.2(13)A3, and = 4 (&led = 1.373 mg mi3;p(Mo Ka) = 0.831 mm-l). A total of 3109 symmetry-independent reflections having 28(Mo Ka)-= 45" were collected using full w scans on a Siemens P4 rotating anode difiactometer using graphitemonochromated Mo Ka radiation. The structure was isolved by "direct methods" techniques with the SHELXTL PLUS (PC Version) software package. The resulting structural parameters were refined to convergence R (unweighted, based on F') = 0.083 for 935 independent absorption-corrected reflections having 28(Mo Ka) 45" and Z > 4 d I ) with use of full-m atrix least-squares refinement and a structural model that incorporated anisotropic thermal parameters for all non-hydrogen atoms and isotropic thermal parameters for all hydrogen atoms. Hydrogen atoms were included using a riding model with d(C-H) = 0.96 A and U(iso) = 0.8 Az.
Acknowledgment. We thank the National Scitmce Foundation (IBN-9319656) for support of this work and Dr. Joseph W. Ziller, University of California, I n h e , CA, for the crystallographic analysis of 2b. L.R.S. .is a Camille and Henry Dreyfus Teacher-Scholar and a Beckman Young Investigator. SupportingInformation Available: Tables of positional parameters of hydrogen atoms and anisotropic displacement coefficients for 2b and NMR spectra of products 1-4, 6, and 8-17 (26 pages). Ordering information is given on any current masthead page. OM9503914
