J . Am. Chem. SOC.1991, 113, 1619-1626
1619
Ring-Opening Oligomerization of 3,3-Dimethylthietane by a Triosmium Cluster Complex Richard D. Adams* and Michael P. Pompeo Contribution from the Department of Chemistry, Uniaersity of South Carolina, Columbia, South Carolina 29208. Received June 25, I990
Abstract: The complexes Os3(CO),,(SCH2CMe2CH2)(1) and Os3(CO)lo(p-SCH2CMe2CH2) (2) were synthesized by the reactions of 3,3-dimethylthietane (3,3-DMT) with Os3(CO)I,(NCMe)and Os3(CO),o(NCMe)2,respectively. Complex 2 was characterized crystallographically and was found to contain an S-coordinated bridging DMT ligand. Compound 2 reacts with 3,3-DMT at 25 OC to yield the complex Os3(CO)lo[(p-SCH2CMe,CH2)3] (3), which contains an 11-osmio-2,2,6.6,10,10hexamethyl-4,7-dithiaundecanethiolatoligand formed by the ring-opening oligomerization of three 3.3-DMT molecules. Complex 3 was characterized crystallographically and was found to contain a bridging thiolato group and 0-bonded carbon at the termini of thc oligomer and one thioether group coordinated to an open cluster. Compound 1 does not oligomerize 3,3-DMT at 25 O C . When heated to 125 "C, 3 eliminated carbon monoxide and was transformed to two isomers Os,(CO),[(p-SCH,CMe,CH,),I 4 and 5 that contain closed triosmium clusters. Both also contain the same oligomeric grouping of the three 3,3-DMT ligands a5 in 3, but differ in the coordination position of the thiolato bridge. When heated to 120 OC under 650 psi CO, compounds 3 and 5 were converted to Os3(CO),o[p-O=C(CH2CMe2CH2S)3] ( 6 ) ,68% by carbonylation. The C-terminus of the oligomer is functionalized by a C O group that bridges an open edge of the cluster in a p?2-O=C bridging mode. Both thioether groups a:c uncoordinated in 6. Compound 6 is decarbonylated at 68 OC under nitrogen to yield OS,(CO)~[~-O=C(CH~CM~~CH,S)~] (7). 4 6 4 . Compound 7 is similar to 6 except that one of the thioether groups of the oligomer is coordinated. Crystallographic data. For 2: space group P2,/c, a = 14.075 (3) A, b = 22.143 (4) A, c = 14.788 (3) A, p = 108.37 (2)O, Z = 2,3227 reflections, R = 0.046. For 3: apace group Pi,a = 12.025 (3) A, b = 16.596 (4) A, c = 9.738 (2) A, CY = 95.84 ( 2 ) O , p = 108 76 (2)O, y = 79.96 (2)O, Z = 2, 2867 reflections, R = 0.029. For 4: space group Pi,a = 11.102 (2) A, b = 14.724 (3) A, c = 10.767 (2) A, CY = 104.94 (2)O, = 99.19 (I)', y = 72.73 (I)', Z = 2, 3519 reflections, R = 0.023. For 5: space group P2,/n, a = 15.153 (3) A, b = 24.453 (7) A, c = 10.359 (2) A, /3 = 90.58 (2)O, Z = 4, 2801 reflections, R = 0.031. For 6 : space group Pi, a = 9.909 (2) A, b = 20.642 (4) A, c = 9.283 (2) A, CY = 101.30 ( 2 ) O , p = 103.30 (2)O, y = 96.92 (2)O, = 2, 2568 reflections, R = 0.048. For 7: space group P2,/c, a = 12.256 (3) A, b = 12.054 (2) A, c = 23.1 I O (3) A, 0 = 103.53 ( I ) ' , Z = 4, 3049 reflections, R = 0.033.
z
Introduction T h e ring opening of heterocycles containing sulfur is of great interest because it is believed to be a key step in the purification of fossil fuels by the process of hydrodesulfurization.' In this regard strained ring thioethers, such a s thiirane A and thietane
A
0
B, have attracted attention since the release of ring strain in these molecules should lead to more facile carbonsulfur bond cleavage processes. Thiiranes and thietanes undergo facile desulfurization on certain metal surfaces.1b.2 Presently, we are investigating the nature of the ring opening of thiirane and thietanes by metal carbonyl cluster complexes in the hope of establishing the mechanistic features and the importance of metal coordination to this p r o ~ e s s . ~ . ~ W e have now discovered a facile ring-opening oligomerization process involving 3,3-dimethylthietane (3,3-DMT) that appears to be promoted by bridging coordination of the DMT ligand. These results a r e described in this report. Experimental Section General Data. Keagent-grade solvents were stored over 4-A molecular sieves. Octane was distilled from sodium benzophenone ketyl prior to use. The compounds Os,(CO), , N C M q 5 Osl(CO)lo(NCMe)2,6 and 3,3-di( I ) (a) Angelici, R. J. Acc. Chem. Res. 1988, 21, 387. (b) Friend, C. M.; Roberts, J . T. Arc. Chem. Res. 1988, 21, 394. (c) Markel, E. J.; Schrader, G.L.; Sauer. N. N.; Angelici, R. J. J . Catal. 1989, 116, 1 1 . (d) Prins, R.; De Beer, V . H. H.: Somorjai, G. A. Catal. Reu. Sci. Eng. 1989, 31, 1. ( 2 ) (a) Roberts. J. T.;Friend, C. M. J . Am. Chem. SOC.1987, 109,7899. (b) Roberts, J. T.; Friend, C. M. J . Am. Chem. SOC.1987, 109, 3872. ( 3 ) (a) Adams, R. D.; Chen, G.; Sun, S.;Wolfe, T. A. J . Am. Chem. SOC. 1990, 112, 868. (b) Adams, R. D.; Pompeo, M. P. Organometallics 1990, 9, 1718. (4) Adams. R . D.;
Pompeo, M. P. Organomerallics 1990, 9, 265 I .
methylthietane' (DMT) were prepared by the published procedures. All reactions were performed under a nitrogen atmosphere unless specified otherwise. Infrared spectra were recorded on a Nicolet 5DXB FTlR spectrometer. NMR spectra were run on either a Bruker AM-300 or AM-500 spectrometer operating at 300 and 500 MHz, respectively. TLC separations were performed in air on Whatman 0.25-mm silica gel 60-A FZs4plates purchased from Curtin Matheson. Florisil (60-100 mesh) was purchased from Fisher Scientific and silica gel (70-230 mesh, 60 A) was purchased from Aldrich. Elemental analyses were performed by Desert Analytics, Tucson, AZ. Reaction of Os,(CO),,(NCMe) with 3,3-Dimethylthietanea One equivalent ( I I .O pL, 0.098 mmol) of 3,3-DMT was allowed to react with Os3(CO),,(NCMe)(100 mg, 0.109 mmol) in 35 mL of CH,CI, at 25 OC for 5 h. TLC using a 4/1 (v/v) hexane/CH,CI, solvent mixture yielded yellow Os3(CO),,(SCH2CMe2CH,)(1; 46 mg, 48%). Analytical and spectral data for 1. IR uco (cm-I) in hexane: 21 I O (w), 2056 (s), 2036 (s), 2021 (vs), 2010 (m), 2004 (m), 1993 (m), 1977 (m)?1969 (w), 1956 (w). 'H NMR (6 in CDCI,): 3.44 (br, 4 H), 1.35 (s, 6 H). Anal. Calcd: C, 19.59; H, 1.03. Found: C, 20.40; H, 0.98. Reaction of OS,(CO)~~(NCM~), with 3,3-Dimethylthietane. 3,3-DMT (16.0 NL,0.147 mmol) was allowed to react with Os,(CO),,(NCMe)2 ( I 15 mg, 0.123 mmol) in 25 m L of CH2C12at 25 OC for 2 h. The following compounds were separated by TLC using a 9/1 (v/v) hexane/CHZCl2solvent mixture: 1 (20 mg, 16%) and yellow 0s3(C0),,(p-SCH,CMe,CH,) (2; 48 mg, 41%). For 2. IR uco (cm-I) in hexane: 2095 (m), 2038 (sh), 2035 (vs), 2020 (s), 1988 (s), 1969 (m). 'H NMR (6 in CDCI,): 4.04 (s, 2 H), 3.76 (s, 2 H), 1.58 (s, 6 H). Anal. Calcd: C, 18.91; H, 1.06. Found: C, 18.84; H, 0.94. Reaction of 2 with 3,3-Dimethylthietane. When a solution of 2 (30 mg, 0.03 I mmol) in 25 mL of CH2CI2was allowed to react with a IO-fold excess of 3,3-DMT (32 NL) at 25 "C for 14 h , orange Osl(CO)lo[(pSCH,CMe,CH,),] (3; 18 mg, 4970) was obtained along with a small amount of 1 (4 mg) after separation by TLC using a 9/1 ( v / v ) hcxane/CH2CIz solvent mixture. For 3. IR vc0 (cm-I) in hexane: 2105 (m), 2056 (vs), 2024 (s), 2001 (s), 1987 (s), 1975 ( w ) , 1960 (m), 1953 (m), 1940 (m). 'H NMR (6 in CDCI,): 3.44-2.08 ( m , 12 H), 1.33 (s, 3 H), 1.26 (s, 3 H), 1.17 (s, 3 H), 1.10 (s, 3 H), 1.05 (s, 3 H ) , 0.89 ( 5 , 3 H). ( 5 ) Johnson, B. F. G . ; Lewis, J.; Pippard, D. J . Organomet. Chem. 1978. 160, 263. ( 6 ) Aime, S.;Deeming, A. J. J . Chem. Sur., Dalton Trans. 1983, 1809. (7) Searles, S.;Hays, H. R.; Lutz, E. F. J . Org. Chcm. 1962, 27. 2832.
0002~7863/91/1513-1619$02.50/0 Q 199 1 American Chemical Society
1620 J . Am. Chem. Soc.. Vol. 113. No. 5 , 1991
Adums and Pompeo
Table I . Crystallographic Data for Diffraction Studies
comnound r-empiricdl formula fu cryst syst lattice pdrdma
A
5
6
7
triclinic
monoclinic
triclinic
monoclinic
11.102 (2) 14.724 (3) 10.767 (2) 104.94 (2) 99.19 (I) 72.73 ( I ) 1617 ( I ) Pi (NO.2) 2 2.32 I044 I 19.98 23 45.0 3519 352 0.023: 0.025 I .35 0.00 0.50
15.153 (3) 24 453 (7) 10.359 (2)
3838 (2) P21/n (No. 14) 4 2.10 2288 101.18 23 40.0 2801 376 0.03 I ; 0.032 I .52 0.10 0.90
9.909 (2) 20.642 (4) 9.283 (2) 101.30 (2) 103.30 (2) 96.92 (2) 1784 (I) Pi ( N O . 2) 2 2.09 1036 107.68 23 40.0 2568 258 0.048; 0.050 2.30 0.04 1.88
12.256 (3) 12.054 (2) 23.1 I O (3)
s p x c group d value f):,,
