Tetrameric, Allylsulfene, and Ion-Pair Ruthenium Compounds

3694

Organometallics 2010, 29, 3694–3708 DOI: 10.1021/om901107n

Versatile Chemistry of Butadienesulfinate Salts with (Cp*RuCl)4: Tetrameric, Allylsulfene, and Ion-Pair Ruthenium Compounds Brenda A. Paz-Michel,† Felipe J. Gonzalez-Bravo,† Lindsay S. Hernandez-Mu~ noz,† ‡ ,† Ilia A. Guzei, and M. Angeles Paz-Sandoval* †

Departamento de Quı´mica, Centro de Investigaci on y de Estudios Avanzados del IPN, Avenida IPN # 2508, San Pedro Zacatenco, C. P. 07360, D. F., M exico, and ‡Chemistry Department, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706 Received December 22, 2009

Reactions of the tetranuclear (Cp*RuCl)4 (1) with the corresponding butadienesulfinate salts Li[SO2CHdCR0 CHdCHR] [R=R0 =H, (2a); R=H, R0 =Me, (2b); R=R0 =Me, (2c)] in THF result in the formation of tetrameric [Cp*Ru(1,2,5-η-SO2CHdCR0 CHdCHR)LiCl]4 [R = R0 = H, (3); R=H, R0 =Me, (4); R=R0 =Me, (5)] complexes. Compound 5 has been isolated in two pseudopolymorphic crystal forms as 5 in space group P421c and as 5 3 3THF, where there are three molecules of solvated THF per tetramer, in space group I4. Both tetramers occupied a crystallographic 4-foldroto inversion axis. In both structures the tetramer symmetry is S4, and these distorted cubane-like kernel structures are similar to the one found in compound 1. If potassium butadienesulfinates are used in the reaction with 1 instead of lithium salts 2a-c, mononuclear allylsulfene ruthenium compounds [Cp*Ru(1-5-η-SO2CHdCR0 CHdCHR)] [R = R0 = H, (6); R = H, R0 = Me, (7)] are isolated. The analogous compound 8 [R=R0=Me] was prepared directly from addition of water to 5. Compounds 6-8 are the first complexes to contain a dioxo-η5-thiapentadienyl or 1-5-η-butadienesulfonyl ligand, as confirmed by the determination of the structure of 7 by X-ray crystallography. Tetrameric 3-5 and monomeric 6-8 easily interconvert into each other in the presence of H2O and LiCl, respectively. A comparative study of the dissociation of tetramers 1 and 3, in the presence of THF, via dynamic light scattering measurements shows a tendency of 1 to dissociate and favor polydisperse aggregates in THF, whereas in 3 the tetranuclear structure remains essentially preserved. Furthermore, when the mononuclear 6 was studied and compared to 3, only one welldefined peak was observed in each case, with the average aggregate 4:1 radius ratio. This implies that 3 has aggregates 4 times larger than those formed by 6. Cyclic voltammetry confirms the formation of the ion pair [Cp*Ru(1,2,5-η-SO2CHdCHCHdCH2)(5-η-S(O2-Kþ)CHdCHCHdCH2)] (12a-K) from 6 and 2a-K under stoichiometric ratio or directly from 1 and excess of 2a-K. Selective exchange of the counterion occurs for 12a-K in the presence of AgBF4 and n-Bu4NBF4 in THF to afford 12a-Ag and 12a-(n-Bu4N). Compound 6 reacts with a high excess of 2a-Li, under reflux in THF, to yield [Cp*Ru(1,2,5-η-SO2CHdCHCHdCH2)(5-η-S(O2-Liþ)CHdCHCHdCH2)] (12a-Li) and [Cp*Ru(5-η-SO2CHdCHCHdCH2)(5-η-S(O2-Liþ)CHdCHCHdCH2)2] (13a-Li). The equilibrium reaction between analogous 13a-K and 12a-K was studied in solution by means of 1H NMR spectroscopy. HRMS provided evidence of the capacity of the SO2 fragment, in the butadienesulfinate complexes, to afford new aggregation states according to the cations employed. Introduction We have begun to investigate the reactivity of 5,5-dioxo5-thiapentadienide or butadienesulfonyl anions toward transition metals,1,2 once alternative methods for the syntheses of acyclic metallic salts of thiapentadienyl, sulfinylpentadienyl, and butadienesulfonyls have been explored in detail.3 *To whom correspondence should be addressed. E-mail: mpaz@ cinvestav.mx. (1) Gamero-Melo, P.; Cervantes-Vasquez, M.; Sanchez-Castro, M. E.; Ramı´ rez-Monroy, A.; Paz-Sandoval, M. A. Organometallics 2004, 23, 3290. (2) Paz-Michel, B. A.; Cervantes-Vasquez, M.; Paz-Sandoval, M. A. Inorg. Chim. Acta 2008, 361, 3094. (3) Gamero-Melo, P.; Villanueva-Garcı´ a, M.; Robles, J.; Contreras, R.; Paz-Sandoval, M. A. J. Organomet. Chem. 2005, 690, 1379. pubs.acs.org/Organometallics

Published on Web 07/29/2010

Compounds based on the Cp*MCl fragment, such as the dimeric [Cp*MCl2]2 (M = Rh, Ir) and the tetrameric [Cp*RuCl]4, are particularly useful starting materials in organometallic chemistry. The metathesis reaction of [Cp*MCl2]2 (M = Rh, Ir) with lithium butadienesulfinate Li(SO2CHdCHCHdCH2) affords the dinuclear compounds [Cp*M(Cl)2(5-η-SO2CHd CHCHdCH2)(Li)(THF)]2 (M = Rh, Ir), whereas mononuclear [Cp*IrCl(1,2,5-η-SO 2 CHdCHCHdCH2 )]1 and [Cp*RhCl(5-η-SO 2 CHdCHCHdCH 2 )(5-η-S(O 2 -K þ)CHdCH-CHdCH2)]4 are obtained when potassium butadienesulfinate is used, showing the critical influence of the cation size on the final product. (4) Paz-Michel, B. A.; Gonzalez-Bravo, F. J.; Hernandez-Mu~ noz, L. S.; Paz-Sandoval, M. A. Organometallics, 2010, DOI: 10.1021/om901108y. r 2010 American Chemical Society

Article

Organometallics, Vol. 29, No. 17, 2010

3695

Scheme 1

Another kind of metathesis reaction with Cp*MCl2(PR3) [M = Rh, R = Me, Ph; M = Ir, R = Me, Ph] takes place in the presence of potassium butadienesulfinate to afford four rhodium S and W Cp*MCl(PR3)(5-η-butadienesulfonyl) (M = Rh, R = Me, Ph) isomers in good yields (76-96%). Meanwhile, the iridium isomers S and W for R = Me and exclusively the S-isomer for R = Ph are obtained, under harsher reaction conditions, in lower yields (6-62%).2 The syntheses of neutral Cp*Ru(II) and Cp*Ru(IV) pentadienyl5 and oxodienyl6 complexes have recently been published, as a result of the comparative exploration of the reactivity of useful precursors [Cp*RuCl2]2 and [Cp*RuCl]4. The reactivity of half-open ruthenocene η5-pentadienyl and η5-oxopentadienyl complexes toward exogenous ligand coordination, oxidative addition,7 and coupling reactions8 with unsaturated substrates is strongly influenced by the electronic and steric properties of both the metal and ancillary ligands. Thus, a comparative investigation of the new 5,5-dioxo-5thiapentadienide ligand’s reactivity provides an important assessment of the electronic factors that control the products of such reactions. Similarly to their pentadienyl analogues,9,10 these complexes are expected to exhibit a variety of bonding modes and rich reaction chemistry based on facile ligand rearrangements.11,12 In the case of the 5,5-dioxo-5-thiapentadienyl ligand, additional interactions through the sulfone group may be used as an assembling ligand and also to increase the nuclearity of the complexes formed. Herein we report our first results of a systematic exploration of the synthesis of heterodienyl metal complexes using [Cp*RuCl]4 (1) and the butadienesulfinate salts as synthons.

Results and Discussion A. Synthesis and Spectroscopy of Tetrameric RutheniumLithium Compounds 3-5. The tetrameric [Cp*Ru(1,2,5η-SO2CHdCR0 CHdCHR)LiCl]4 [R = R0 = H, (3); R = H, R0 =Me, (4); R=R0 =Me, (5)] complexes are isolated from reactions of the tetranuclear (Cp*RuCl)4 (1) with the (5) S anchez-Castro, M. E.; Paz-Sandoval, M. A. Organometallics 2008, 27, 6083. (6) S anchez-Castro, M. E.; Paz-Sandoval, M. A. Organometallics 2008, 27, 6071. (7) Navarro-Clemente, M. E.; Juarez-Saavedra, P.; CervantesV asquez, M.; Paz-Sandoval, M. A.; Arif, M. A.; Ernst, R. D. Organometallics 2002, 21, 592. (8) S anchez-Castro, M. E.; Ramı´ rez-Monroy, A.; Paz-Sandoval, M. A. Organometallics 2005, 24, 2875. (9) (a) Ernst, R. D. Chem. Rev. 1988, 88, 1255. (b) Ernst, R. D. Struct. Bonding (Berlin) 1984, 57, 1. (c) Ernst, R. D. Acc. Chem. Res. 1985, 18, 56. (d) Ernst, R. D. Comments Inorg. Chem. 1999, 21, 285. (10) Powell, P. Adv. Organomet. Chem. 1986, 125. (11) Bleeke, J. R. Organometallics 2005, 24, 5190. (12) Paz-Sandoval, M. A.; Rangel-Salas, I. I. Coord. Chem. Rev. 2006, 250, 1071.

corresponding lithium butadienesulfinate salts 2a-c. The reactions proceed under very mild conditions, giving high yields of 3-5, which can be isolated as yellow powders with melting points above 300 °C (Scheme 1). The color of the compounds from 3 to 5 became progressively darker and more soluble in nonpolar solvents, such as pentane and diethyl ether. Both 1H and 13C NMR spectroscopy (Tables 1 and 2) provide clear evidence of the butadienesulfonyl ligand in the 1,2,5η-bonding mode, which has been previously observed for a wide variety of thiapentadienyl,11,12,13a,14-17 sulfinylthiapentadienyl,12,13a and butadienesulfonyl iridium systems.1,2,11-13 As expected, the 13C NMR signals for the π-coordinated carbons C1 (δ 54.6, 53.5, and 71.8) and C2 (δ 77.1, 80.0, and 81.8) of 3, 4, and 5, respectively, are at lower frequency than the corresponding chemical shifts of the starting materials 2a-Li, 2b-Li, and 2c-Li at 123.1, 118.9, and 126.9 for C1 and 131.2, 132.9, and 132.1 for C2, respectively (Table 2). The 1 JC-H at C4 reflects a strong sp2 bond character according to the value of 172-178 Hz observed for compounds 3-5. The magnitude of the coupling constant must be influenced by the presence of the sulfone group at C4. A significant upfield shift is also reflected in the 1H NMR from coordination of the butadienesulfonyl ligand to the ruthenium atom (Table 1). The symmetric and asymmetric vibration modes of the SO2 fragment recorded by IR spectroscopy produce very strong and broad bands in the region of 1099-1093 and 991984 cm-1 and strong bands at 839-818 cm-1, characteristic of butadienesulfonyl ligands, where the delocalization of the negative charge over the oxygen-sulfur-oxygen atoms is present. (13) (a) Gamero-Melo, P. Ph.D. Dissertation, Cinvestav, 2004. (b) Melo-Trejo, P. Undergraduated Dissertation, ESIQIE/IPN, 2008. (c) CervantesVasquez, M.; Paz-Sandoval, M. A. Unpublished results. (14) (a) Bleeke, J. R.; Shokeen, M.; Wise, E. S.; Rath, N. P. Organometallics 2006, 25, 2486. (b) Bleeke, J. R.; Wise, E. S.; Shokeen, M.; Rath, N. P. Organometallics 2005, 24, 805. (c) Bleeke, J. R.; Hinkle, P. V.; Rath, N. P. Organometallics 2001, 20, 1939. (d) Bleeke, J. R.; Ortwerth, M. F.; Rohde, A. M. Organometallics 1995, 14, 2813. (e) Bleeke, J. R.; Ortwerth, M. F.; Chiang, M. Y. Organometallics 1993, 12, 985. (f) Bleeke, J. R.; Ortwerth, M. F.; Chiang, M. Y. Organometallics 1992, 11, 2740. (15) Angelici, R. J. Organometallics 2001, 20, 1259, and references therein. (16) (a) Bianchini, C.; Frediani, P.; Herrera, V.; Jimenez, M. V.; Meli, A.; Rincon, L.; Sanchez-Delgado, R. A.; Vizza, F. J. Am. Chem. Soc. 1995, 117, 4333. (b) Bianchini, C.; Casares, J. A.; Masi, D.; Meli, A.; Pohl, W.; Vizza, F. J. Organomet. Chem. 1997, 541, 143. (c) Bianchini, C.; Meli, A.; Peruzzini, M.; Vizza, F.; Fedriani, P.; Herrera, V.; Sanchez-Delgado, R. A. J. Am. Chem. Soc. 1993, 115, 2731. (d) Bianchini, C.; Jimenez, M. V.; Meli, A.; Vizza, F. Organometallics 1995, 14, 3196. (e) Bianchini, C.; Jimenez, M. V.; Meli, A.; Vizza, F. Organometallics 1995, 14, 4858. (f) Bianchini, C.; Jimenez, M. V.; Meli, A.; Moneti, S.; Vizza, F. J. Organomet. Chem. 1995, 504, 27. (g) Bianchini, C.; Jimenez, M. V.; Meli, A.; Moneti, S.; Vizza, F.; Herrera, V.; Sanchez-Delgado, R. A. Organometallics 1995, 14, 2342. (h) Bianchini, C.; Meli, A.; Peruzzini, M.; Vizza, F.; Moneti, S.; Herrera, V.; Sanchez-Delgado, R. A. J. Am. Chem. Soc. 1994, 116, 4370. (17) Chisholm, M., Ed. Modeling the Chemistry of Hydrotreating Processes. Polyhedron 1997, 16.

3696


Paz-Michel et al.

Table 1. 1H NMR Dataa for Butadienesulfinate Salts 2a-c-M (M = Li, K) and Ruthenium Compounds 3-8 and 12a-M compound 2a-Li

b,c,d

2a-Kb,c 2b-Lib,d b

2b-K

2c-Lib,c,d b,c

H1/H1b 5.38 (d) J = 17.5 5.43 (d) J = 16.7 5.45 (d) J = 17.0 5.49 (d) J = 17.2 6.04 (m)

2c-K

6.02 (m)

3e

3.25 (d) J = 10.4 3.28 (d) J = 10.3 3.48 (d) J = 9.9 2.75 (dd) J = 9.7, 2.7 2.53 (dd) J = 9.6, 2.0 3.20 (dd) J = 9.4, 2.5 3.73 (dq) J = 9.0, 6.1 2.52 (br) 5.15-5.24i

4

f

5g 6 6h 7 8 12a-Li

j

12a-K

12a-Kk 12a-Agk

12a-Agl

12a-(n-Bu)4Nm

2.56 (d) J = 10.7 5.21 (d) J = 17.4 2.33 (d) J = 10.6 5.24 (m) 2.48 (br) 5.28 (d) J = 9.5 2.32 (d) J = 10.3 5.37 (d) J = 13.5 2.23 (d) J = 8.4 5.19 (d) J = 10.2

b H10 (R)/H1 5.31 (d) J = 9.9 5.36 (d) J = 9.9 5.31 (d) J = 10.0 5.35 (d) J = 10.8 1.79 (d) J = 6.9 1.77 (d) J = 6.6 3.16 (d) J = 9.2 3.24 (d) J = 8.6 1.98 (d) J = 5.9 2.89 (dd) J = 8.6, 2.5 3.06 (dd) J = 8.5, 2.0 2.82 (s) J = 8.7, 2.5 1.38 (d) J = 6.1 2.62 (br) 5.15-5.24i 2.37 (d) J = 9.5 5.16 (d) J = 9.0 2.46 (d) J = 9.5 5.24 (m) 2.63 (d) J = 7.0 5.30 (d) J = 16.2 2.66 (d) J = 9.6 5.32 (d) J = 16.9 2.56 (d) J = 9.5 5.26 (d) J = 17.2

H2/H2b 6.96 (m) 7.02 (m) 7.10 (dd) J = 17.2, 10.8 7.14 (dd) J = 17.2, 10.8 6.83 (d) J = 15.3 6.82 (d) J = 15.4 3.50 (dt) J = 10.1, 9.5 3.44 (br) 4.07 (m) J = 9.2, 6.3 4.13 (ddd) J = 9.3, 8.8 4.64 (m) J = 2.0, 6.8 3.81 (d) J = 9.1 3.96 (d) J = 9.0 3.97 (t) J = 9.4 8.33 (br) 3.95 (t) J = 10.1 8.23 (dt) J = 10.6, 16.6 4.01 (t) J = 10.0 7.82 (m) 4.12 (t) J = 10.1 7.77 (m) 4.21 (t) J = 10.3 7.78 (m) 4.09 (t) J = 10.1 7.87 (m)

H3(R0 )/H3b

H4/H4b

Cp*

6.38 (dd) J = 11.0 6.44 (dd) J = 10.8, 10.6 1.86 (s)

5.89 (d) J = 11.0 5.94 (d) J = 10.6 5.83 (s)

1.90 (s)

5.87 (s)

1.86 (s)

5.72 (s)

1.85 (s)

5.71 (s)

6.13 (dd) J = 6.0 1.82 (s)

6.84 (d) J = 5.3 6.89 (s)

1.49 (s)

1.72 (s)

6.45 (s)

1.61 (s)

4.94 (t) J = 6.9 5.54 (t) J = 6.8 1.39 (s)

3.49 (d) J = 7.0 3.59i

1.52 (s) 1.86 (s)

3.38 (s)

1.42 (s)

1.49 (s)

3.20 (s)

1.45 (s)

6.09 (br) 5.83-5.94i

6.82 (br) 5.83-5.94i

1.63 (s)

6.18 (d) J = 5.6 5.78 (t) J = 11.1 6.08 (d) J = 4.5 5.85 (m) 6.24 (br)

7.55 (s, br) 6.03 (d) J = 11.1 6.83 (s, br) 5.95 (d) J = 9.5 6.56 (br)

1.55 (s)

5.96 (br)

6.00 (br)

1.67 (s)

6.22 (br)

6.25 (br)

5.97 (t) J = 11.0 6.09 (d) J = 4.5 5.87-5.92i

6.17 (br)

1.53 (s)

1.60 (s)

1.67 (s)

6.34 (br) 5.87-5.92i

1.68s)

a In C6D6. δ values are given in ppm and J in hertz. Assignments according to Figures 1 and 2. b D2O. c Reference 3. d 7Li δ = 5.34, 2a-Li; δ 7Li = 5.37, 2b-Li; δ 7Li = 5.42, 2c-Li. e 7Li δ = 5.32. f 7Li δ = 5.38. g 7Li δ = 5.48. h TDF. i Overlapped. j 7Li δ = 5.20. k In CDCl3. l In NCCD3. m In (CD3)2CO: (nBu)4N: 3.38 [m, 8H, CH2-(C3H7)]; 1.81-1.73 [m, 8H, (CH2)-CH2-(C2H5)]; 1.41 [sextet, J = 7.5 Hz, 8H, (C2H4)-CH2-Me]; 0.96 [t, J = 7.5 Hz, 12H, Me].

Compound 5 has been isolated in two pseudo-polymorphic crystal forms, as 5 in space group P421c and as 5 3 3THF in space group I4. In the structure of 5 in P421c, the tetramer resides on a crystallographic 4-fold inversion axis. The structure of 5 3 3THF in space group I4 has three solvent molecules of THF per tetramer, and the tetramers also occupy a crystallographic 4-fold-roto inversion axis. Thus, in both structures the tetramer symmetry is S4. Both structures exhibit disorder: in 5, the Cp* ligand is disordered over two positions in a 54:46 ratio. In 5 3 3THF there is 75.4(11)% of a THF molecule per ruthenium monomer, which results in the reported composition of 5 with three THF molecules. The ruthenium tetramers in both structures have similar geometries and metric parameters. Compound 5 and its distorted cubane-like kernel are shown in Figure 1. The data collection and selected bond distances and angles are described in Tables 3 and 4, respectively. The four Ru atoms are coordinated by nine atoms, five carbon atoms from the Cp* ligand, two carbons, and one

sulfur atom from the 5,5-dioxo-5-thiapentadienide anion, and a chloride. The Liþ cation present in the system is responsible for the tetramer formation. Each Liþ cation interacts with the Cl and O atoms from one Ru complex and with two oxygen atoms from two other Ru complexes. Thus, the coordination geometry about each Liþ cation is distorted tetrahedral, and according to the van der Walls radii,18 the distances between the lithium atoms imply no bonding. These kinds of interactions lead to the formation of a distorted cubane kernel similar to the one found in (Cp*RuCl)4 (1).19 The two oxygen atoms of the SO2 group participate in the tetramer formation; one oxygen atom interacts with the S and Li atoms, the other with the S and two Li cations. This (18) Batsanov, S. S. Inorg. Mater. 2001, 37, 871. (19) Fagan, P. J.; Mahoney, W. S.; Calabrese, J. C.; Williams, I. D. Organometallics 1990, 9, 1843.

Article


3697

Table 2. 13C NMR Dataa for Butadienesulfinate Salts 2a-c-M (M = Li, K) and Ruthenium Compounds 3-8 and 12a-M compound b,c,d

C1/C5/C1b

C2/C2b

C3/C6/C3b

2a-Li 2a-Kb,c,d 2b-Lib,d

123.1 123.1 118.9

131.2 131.2 132.9

2b-Kb,d

119.0

133.2

2c-Li 2c-Kb,c,d 3

126.9/19.7 126.9/19.6 54.6 (dd) J = 161.9, 155.7

132.1 132.1 77.1 (d) J = 155.7

4

53.5 (d) J = 159.9

80.0 (d) J = 155.7

5

71.8 (d) J = 153.8 21.6 (q) J = 126.8 52.6 (d) J = 169.9

81.8 (d) J = 150.7 86.6 (d) J = 163.0

98.9 (d) J = 166.0

47.2 (d) J = 172.2

7

52.4 (d) J = 151.4

86.3 (d) J = 162.2

46.7 (d) J = 176.0

8

66.0 (d) J = 164.0 19.7 (q) J = 126.1 51.3 121.2 50.7 122.0 51.5 121.4 50.9 121.8 50.2 120.8

89.9 (d) J = 154.0

110.4(s) 21.4 (q) J = 128.3 107.2 (s) 21.7 (q) J = 124.5

b,c,d

6

12a-Kd d,e

12a-K

12a-Agd,e 12a-Agd,f 12a-(n-Bu)4Nd,g

g

78.8 134.1 78.8 132.8 77.5 131.2 78.6 132.4 77.6 133.1

134.0 133.9 139.9 18.4 139.9 18.5 140.3/19.0 140.3/19.1 139.7 (d) J = 158.8

C4/C4b

151.7 (s) 19.8 (q) J = 128.7 153.5 (s) 20.5 (q) J = 127.6

134.2 126.8 134.5 127.5 134.1 129.5 134.1 129.0 133.5 128.2

Cp*

144.2 144.2 143.0 143.5 139.9 140.0 146.0 (d) J = 177.5 140.5 (d) J = 172.3 137.2 (d) J = 176.0

45.4 (d) J = 169.0 154.7 142.1 153.1 140.8 151.4 140.7 152.1 140.6 153.0 140.7

95.9 (s) 9.1 (q) J = 127.7 95.9 (s) 9.4 (q) J = 126.6 95.9 (s) 9.9 (q) J = 126.8 97.4 (s) 9.4 (q) J = 128.4 96.7 (s) 9.2 (q) J = 127.6 96.0 (s) 9.2 (q) J = 127.6 97.8 9.2 97.4 8.9 98.3 8.8 97.9 8.1 97.5 8.1

a In C6D6. δ values are given in ppm and J in hertz. Assignments according to Figures 1 and 2. b D2O. c Reference 3. d 13C{1H}. e In CDCl3. f In NCCD3. In (CD3)2CO: (n-Bu)4N: 58.4 (s, CH2-C3H7); 23.6 (s, CH2-CH2-C2H5); 19.5 (s, C2H4-CH2-Me); 13.1 (s, Me).

motif has been previosuly reported.20,21 As expected, the S-O distance to the former is slightly shorter than that to the latter, because the bond distances lengthen as the coordination number increases. The internal double bond of the sulfonyl ligand is not coordinated to the ruthenium center, which is clearly demonstrated by the typical sp2 C3-C4 bond length of 5 and 5 3 3THF at 1.334(16) and 1.320(14) A˚, respectively. In contrast, the terminal double bonds show respective C1-C2 bond lengths for 5 and 5 3 3THF of 1.406(16) and 1.400(14) A˚, due to their coordination to the ruthenium atom, as described above. The C1-C2-C3-C4 dihedral angles are 63.9(14)° and 67.7(13)°, which imply that the ligand can be described more accurately as a U conformer than an S one. (Crystal structure of 5 3 3THF is included in the Supporting Information.) B. Synthesis and Spectroscopy of Monomeric Ruthenium Compounds 6-8. If potassium butadienesulfinate is used in the reaction with (Cp*RuCl)4 (1) instead of the lithium salt, mononuclear allylsulfene ruthenium compounds [Cp*Ru(1-5-η-SO2CHdCR0 CHdCHR)] [R=R0 =H, (6); R=H, R0=Me, (7)] are isolated in 71% and 84% yields, respectively (Scheme 2). The analogous compound [Cp*RuCl(1-5-η-SO2CHd CMeCHdCHMe)] (8) was prepared directly by addition of (20) Henderson, K. W.; Kennedy, A. R.; MacDougall, D. J.; Shanks, D. Organometallics 2002, 21, 606. (21) Gais, H.-J.; van Gumpel, M.; Raabe, G.; M€ uller, J.; Braun, S.; Lindner, H. J.; Rohs, S.; Runsink, J. Eur. J. Org. Chem. 1999, 1627.

water to 5, in 63% yield (Scheme 3, vide infra). These complexes, 6-8, were isolated as pale brown powders with melting points of 187-188, 172-175, and 131-133 °C, respectively. They are similar to their corresponding tetramers in solubility (vide supra). Their melting points decrease as the number of methyl groups increases. The vibration modes of the SO2 group in the IR of the mononuclear compounds 6-8 showed narrow bands compared to tetrameric derivatives 3-5 and higher frequency values between 1193 and 1185 and 1059-1060 cm-1. The NMR spectra of the fully coordinated butadienesulfonyl ligand of compounds 6-8 are consistent with the formulation as an allyl-sulfene or allyl-thioaldehyde-dioxo ligand. All signals are shifted to lower frequency compared to the lithium or potassium butadienesulfinate salts 2a-c (Tables 1 and 2). An examination of the chemical shifts and coupling constants for compounds 6-8 suggests that they may be regarded as Ru(II) complexes, whose formal charge results from the presence of the Cp* anion and the η5-thiapentadienyl fragment coordinated to the ruthenium atom. At first sight, the chemical shift of C4 at ∼47 ppm (Table 2) and the corresponding JCH (∼172 Hz) appeared to us a sensitive probe of the presence of an η3-allylη2-sulfene ligand instead of an η5-fully delocalized Ru(II) typical complex, which would be expected to show a characteristic chemical shift for C4 at around 95-115 ppm, as in the case of its thiapentadienyl analogues such

3698


Paz-Michel et al.

Figure 1. Molecular structure of [Cp*Ru(1,2,5-η-SO2CHdCMeCHdCHMe)LiCl]4 (5) (hydrogen atoms have been excluded for clarity) and its corresponding distorted cubic array of the SO2 and Li atoms.

as Cp*Ru(SCHCHCHCH2)22a or [C6Me6Ru(SCHCHCHCH2)]PF6.22b However, after the X-ray diffraction study of compound 7 (Figure 2), a full delocalization of the dioxo(22) (a) Ramı´ rez-Monroy, A.; Paz-Sandoval, M. A. Unpublished results. [Cp*Ru(SCHdCHCHdCH2)]: 1H NMR (C6D6): δ 2.80 (d, 10.4, H1), 2.84 (d, 8.9, H10 ), 4.10 (m, H2), 5.04 (t, 5.7, H3), 5.87 (d, 5.2, H4), 1.57 (s). 13C NMR (C6D6): δ 49.1 (C1), 90.2 (C2), 97.7 (C3), 97.5 (C4), 92.4, 10.7 (Cp*). (b) Luo, S.; Rauchfuss, T. B.; Gan, Z. J. Am. Chem. Soc. 1993, 115, 4943. [C6Me6Ru(SCHdCHCHdCH2)]PF6: 1H NMR (CD2Cl2): δ 3.14 (ddd, 11.5, 1.5, 1.0, H1), 3.41 (dd, 9.0, 1.5, H10 ), 4.96 (dddd, 11.5, 9.0, 6.5, 1.2, 1.0, H2), 6.12 (t, 6.5, 5.5, 1.0, H3), 6.68 (dd, 5.5, 1.0, H4), 2.44 (s, C6Me6). 13C{1H} NMR (CD2Cl2): δ 60.33 (C1), 97.24 (C2), 99.62 (C3), 113.33 (C4), 107.75, 16.75 (C6Me6).

thiapentadienyl ligand is evident and the significantly lower frequency, when compare to that of the thiapentadienyl complexes, are attributed to the oxygen atoms, which tend to increase the nuclear magnetic shielding. Several ruthenium sulfene molecules have been reported in the literature: [Cp*Ru(η2-SO2CH2)(PMe3)2] and [CpRu(η2-SO2CHR)L2] (R = H, L = PMe3, 1/2 (S,S)-Ph2PCHMeCHMePPh2; R = H, Me, L = 1/2 Ph2PCH2PPh2, 1/2 Me2PC2H4PPh2),23-26 (23) Kuhnert, N.; Burzlaff, N.; Dombrowski, E.; Schenk, W. A. Z. Naturforsch. 2002, 57b, 259. (24) Schenk, W. A.; Urban, P.; Dombrowski, E. Chem. Ber. 1993, 126, 679.

Article


3699

Table 3. Crystal Data and Experimental Parameters for Compounds 5, 5 3 3THF, 6, and 7 formula fw cryst syst space group a (A˚) b (A˚) c (A˚) β (deg) V (A˚3) Z Dcalc (g/cm3) μ(Mo/KR)calc (mm-1) size (mm) F(000) 2θ range (deg) no. of reflns, collected no. of unique reflns no. of obsd reflns abs corr (Tmax, Tmin) R Rw wR2 (all data) gof

5

5 3 3THF

6

7

C16H24ClLiO2RuS 423.87 tetragonal P421c 14.9734(4) 14.9734(4) 16.7356(6) 90 3752.2(2) 8 1.501 0.71073 0.60 0.40 0.20 1728 4.86 to 54.90 20 080 4267(Rint = 0.1356) 2643 (F > 4σ(F)) 0.8114, 0.5606 0.0674 0.1269 0.1485 1.009

C64H156ClLiO2RuS 1133.41 tetragonal I4 19.220(3) 19.220(3) 13.008(3) 90 4805.3(14) 2 0.783 0.71073 0.37 0.3 0.22 1272 4.24 to 54.96 9591 5104(Rint = 0.0575) 3890 (F > 4σ(F)) 0.9400, 0.88459 0.0606 0.1508 0.1698 0.935

C14H20O2RuS 353.43 orthorhombic P212121 10.390(2) 11.241(2) 12.285(3) 90 1434.8(5) 4 1.636 0.71073 0.37 0.28 0.18 720 4.92 to 54.98 16 297 3253(Rint = 0.0452) 3021 (F > 4σ(F)) 0.8090, 0.6590 0.0553 0.1404 0.1439 1.047

C15H22O2RuS 367.46 monoclinic C2/c 19.9651(4) 11.1541(3) 15.7012(3) 97.6020 (10) 3465.81(13) 8 1.408 0.71073 0.51 0.31 0.15 1504 4.12 to 54.98 15 784 3895(Rint = 0.0232) 3594 (F > 4σ(F)) 0.8619, 0.5986 0.0279 0.0921 0.0938 1.097

Table 4. Selected Bond lengths and Bond Angles for compounds 5 and 5 3 3THF compound 5 bond length (A˚) C1-C2 C2-C3 C3-C4 C4-S1 S1-O1a S1-O2a O1a-Li1a Li1a-O2c Cl1-Li1d Cl1-Ru1 Ru1-Cl Ru1-C2 Ru1-S1 Li1a-O2b Li1a-Li1b Li1a-Li1c

1.406(16) 1.471(15) 1.334(16) 1.754(11) 1.482(6) 1.511(6) 1.955(16) 1.987(18) 2.372(17) 2.435(2) 2.172(9) 2.131(9) 2.273(2) 1.980(17) 3.11(3) 3.11(3)

compound 5 3 3THF bond length (A˚)

bond angle (deg) C1-C2-C3 C2-C3-C4 C3-C4-S1 C4-S1-O1a C4-S1-O2a Ru1-S1-O1a Ru1-S1-O2a C1-Ru1-C2 S1-Ru1-Cl1 Cl1-Ru1-C1 Cl1-Ru1-C2 O1a-S1-O2a S1-Ru1-C2 S1-Ru1-C1 Ru1-Cl1-Li1b C1C2C3C4

120.4(9) 119.3(10) 117.0(10) 103.9(5) 107.5(5) 117.2(3) 116.2(3) 38.1(4) 89.03(8) 84.8(4) 122.2(3) 108.0(3) 81.1(3) 86.7(3) 103.0(4) 63.90(1.4)

C1-C2 C2-C3 C3-C4 C4-S1 S1-O1a S1-O2a O1a-Li1a Li1a-O2c Cl1-Li1d Cl1-Ru1 Ru1-Cl Ru1-C2 Ru1-S1 Li1a-O2b Li1a-Li1b Li1a-Li1c

1.400(14) 1.516(13) 1.320(14) 1.762(8) 1.489(5) 1.501(5) 1.930(15) 1.964(14) 2.409(12) 2.445(2) 2.171(7) 2.161(8) 2.2651(19) 1.947(13) 3.49(2) 3.11(2)

bond angle (deg) C1a-C2a-C3a C2a-C3a-C4a C3a-C4a-S1a C4a-S1a-O1a C4a-S1a-O2a Ru1a-S1a-O1a Ru1a-S1a-O2a C1a-Ru1a-C2a S1-Ru1-Cl1 Cl1-Ru1-C1 Cl1-Ru1-C2 O1a-S1-O2a S1-Ru1-C2 S1-Ru1-C1 Ru1-Cl1-Li1b C1C2C3C4

121.4(8) 120.2(7) 115.9(7) 102.3(4) 106.7(4) 116.5(2) 116.7(2) 37.7(4) 88.39(7) 82.5(3) 118.9(3) 108.0(3) 80.7(2) 88.9(2) 103.2(3) 67.65(1.26)

Scheme 2

where 13C{1H} NMR values for the sulfene-carbon bond are also observed at lower frequencies. Consistent lowfrequency-shifted C4 and H4 chemical shifts have been detected for [η6-C6Me6Ru(η5-SO2CHCHCHCH2)]BF4,27a and a comparison of 13C NMR data (CDCl3) for C-S in cobalt complexes shows chemical shifts at 95.8 and (25) Schenk, W. A.; Bezler, J.; Burzlaff, N.; Hagel, M.; Steinmetz, B. Eur. J. Inorg. Chem. 2000, 287. (26) Schenk, W. A.; Urban, P. J. Organomet. Chem. 1991, 411, C27.

57.9 ppm for acyclic CpCo(η4-CH2CHCHS)27b and cyclic CpCo(η4-CHdCHCHdCHSO2),27c respectively. (27) (a) de la Cruz Cruz J. I.; Paz-Sandoval, M. A. Unpublished results. [η6-C6Me6Ru(η5-SO2CHdCHCHdCH2)]BF4: 1H NMR (CD3NO2): δ 3.13, dd, 3.3, 10.6 Hz, (H1); 4.03, dd, 3.4, 9.1 Hz, (H10 ); 5.56, m, 3.4, 7.2, 9.1, 10.7 Hz, (H2); 6.94, t, 7.2 Hz, (H3); 4.40, d, 7.4 Hz, (H4); 2.46, s, (C6Me6). 13C NMR (CD3NO2): δ 64.9, (C1); 93.4, (C2); 114.1, (C3); 46.2 (C4); 15.7, 104.0 (C6Me6). (b) Dittmer, D. C.; Takahashi, M. I.; Tsai, A. I.; Chang, P. L.; Blidner, B. B.; Stamos, I. K. J. Am. Chem. Soc. 1976, 98, 2795. (c) Albrecht, R.; Weiss, E. J. Organomet. Chem. 1991, 413, 355.

3700


Paz-Michel et al. Table 5. Selected Bond Lengths and Angles for Compound 7a bond length (A˚) C1-C2 1.418(4) C2-C3 1.434(4) C3-C4 1.416(3) C4-S1 1.751(3) S1-O1 1.4608(19) S1-O2 1.4710(19) Ru1-C1 2.191(2) Ru1-C2 2.165(3) Ru1-C3 2.244(2) Ru1-C4 2.238(2) Ru1-S1 2.2518(6) Ru1-Cp*cent 1.8429 (2) a

Figure 2. Molecular structure of Cp*Ru(1-5-η-SO2CHd CMeCHdCH2) (7) (hydrogen atoms have been excluded for clarity). Scheme 3

**

Reaction explored only for compound 6.

Crystals of 6 can be obtained by two different crystallization methods: slow evaporation of a concentrated toluene solution and indirect diffusion of pentane into a mixture of acetone/Et2O (1:4). However, in both cases the single-crystal structural determinations show distorted structures, which reveal only that the Ru(II) center in this monomeric complex is sandwiched between the Cp* and butadienesulfonyl ligand. The diene ligand has a U-shape, with the C11-C12-C13C14 torsion angle being 5(2)°. The bond distances from the metal to the acyclic ligand are imprecise because this sulfone ligand is disordered over two positions in a 58:42 ratio and was refined with restraints (crystal structure of 6 is included in the Supporting Information). Crystals of 7 are obtained by slow evaporation of THF. Crystal data and bond lengths and angles are in Tables 3 and 5, respectively. In contrast with the molecular structure of 6, the methyl-substituted compound 7 gives unquestionable evidence of the dioxo-η5-thiapentadienyl complex (Figure 2). Due to the presence of SO2 in the acyclic ligand, the structural parameters are considerably different from those of the pentadienyl and heteropentadienyl analogues. The bond lengths C1-C2 and C2-C3 of 7 [1.418(4), 1.434(4) A˚] are clearly longer and show more homogeneous delocalization (28) Trakarnpruk, W.; Arif, A. M.; Ernst, R. D. Organometallics, 1992, 11, 1686.

angle (deg) C1-C2-C3 C2-C3-C4 C3-C4-S1 C2-C3-C5 C1-C2-Ru1 C2-C3-Ru1 C3-C4-Ru1 O1-S1-O2 C6-C7-Ru1 C6-C7-C8 C6-C7-C11 C6-Ru1-C8

125.4(2) 125.0(2) 123.08(19) 117.2(2) 72.01(14) 68.07(14) 71.78(14) 113.17(11) 70.69(13) 107.9(2) 126.4(3) 63.16(9)

Dihedral angles formed by LSQ-planes 3.29(0.13)°.

in the enyl moiety than the corresponding ones for Cp*Ru(3-methyl-η5-pentadienyl) [1.374(3), 1.420(3) A˚],28 Cp*Ru(1,3-Me2-η5-oxopentadienyl) [C2-C3, 1.420(12) A˚],28 and Cp*Ru(3-methyl-η5-azapentadienyl) [1.38(1), 1.42(1) A˚].29 ˚ ] The Ru-C1 and Ru-C2 bond lengths [2.191(2), 2.165(3) A are also longer than those of the pentadienyl complex ˚ ],28 but similar to the heterodienyl [2.164(2), 2.126(2) A complexes, oxopentadienyl [2.178(7), 2.153(7) A˚]28 and azapentadienyl [2.199(9), 2.161(8) A˚],29 while Ru-C3 [2.244(2) A˚] and Ru-C4 [2.238(2) A˚] are significantly longer compare to those of pentadienyl [2.187(2), 2.126(2) A˚]28 and heterodienyl complexes [oxopentadienyl, 2.193(7), 2.142(9) A˚;28 azapentadienyl, 2.187(7), 2.194(7)29 A˚]. The C4-S1 bond length [1.751(3) A˚] is similar to rhodium isomers (PMe3)3Rh[1,2,5-η-SCHdC(Me)C(Me)dCH2] and (PMe3)3Rh[1,4,5-η-SdCHC(Me)dC(Me)CH2], where there is a C-S bond [1.741(3) A˚ ] and CdS bond [1.777(4) A˚], respectively,14a as well as iridium derivatives: [(COD)Ir(1,2-η-5-μ2-SCHdCHCHdCH2)]2 [1.757(10) A˚],13a [(COD)Ir(1,2-η-5-μ2-SOCHdCHCHdCH2)]2 [1.777(9) A˚],13a [(COD)Ir(1,2,5-SO2CHdCHCHdCH2)L] [L = PMe3, 1.747(10) A˚; PMe2Ph, 1.767(5) A˚; CO, 1.765(9) A˚],13b [Cp*IrCl(1,2,5-η-SO2CHdCHCHdCH2)] [1.774(8) A˚],1 and [Cp*Ir(Cl)2(5-η-SO2CHdCRCHdCHR)(Li)(THF)]2 [R=H, 1.770(8) A˚, R=Me, 1.768(6) A˚].1 It is interesting that this bonding mode has not been present in a wide number of iridium and rhodium complexes with thiapentadienyl and butadienesulfonyl ligands. Even when (COD)Ir(1,2,5-η-SO2CHdCHCHdCH2)13a,c and Ir(1,2,5-ηSCHdCHCHdCH2)(PMe3)314a,d,f are heated in THF or toluene at reflux, no evidence of the dioxo-η5-thiapentadienyl or η5-thiapentadienyl has been observed, respectively. The close analogue Cp*IrCl(1,2,5-η-SO2CHdCHCHdCH2) after addition of AgX (X = BF4, OTf) affords the 16 e- cationic complex [Cp*Ir(1,2,5-η-SO2CHdCHCHdCH2)]X instead of the 18 e- [Cp*Ir(1-5-η-SO2CHdCHCHdCH2)]X.13c C. Interconversion between Tetrameric 3-5 and Monomeric 6-8 Ruthenium Compounds. Interestingly, tetrameric 3-5 and monomeric 6-8 compounds easily interconvert into each other, as has been observed previously for tetrameric 1 and dimeric [Cp*Ru(OMe)]2 compounds.30 The interconversion reactions are shown in Scheme 3. On one hand, when 3-5 are dissolved in C6H6 and water is (29) Gutierrez, J. A.; Navarro-Clemente, M. E.; Paz-Sandoval, M. A.; Arif, A. M.; Ernst, R. D. Organometallics 1999, 18, 1068. (30) (a) Koelle, U.; Kossakowski, J. J. Chem. Soc., Chem. Commun. 1988, 549. (b) Koelle, U.; Kossakowski, J. J. Organomet. Chem. 1989, 362, 383. (c) K€olle, U.; Kang, B.-S. J. Organomet. Chem. 1990, 386, 267. (d) Loren, S. D.; Campion, B. K.; Heyn, R. H.; Don Tilley, T.; Bursten, B. E.; Luth, K. W. J. Am. Chem. Soc. 1989, 111, 4712.

Article

added to remove LiCl, complexes 6-8 can be isolated. The reaction of AgOTf with 3 in a 4:1 molar ratio, in THF at -110 °C, also afforded 6 in a 73% yield. On the other hand, an experiment performed in a sealed NMR tube with a C6D6 solution of 6 and 5 equiv of LiCl, and kept at 60 °C for 72 h, showed a quantitative transformation of 6 into compound 3, without evidence of any intermediates on the NMR time scale. According to these results, it is clear that the high polarity of water promotes the dissociation of LiCl, affording 6-8, while the addition of LiCl to 6 will yield the tetrameric structure by means of oxygen-lithium and rutheniumchlorine-lithium interactions. In order to establish factors that favor the stabilization of smaller or higher aggregation states attributed to each ligand coordination mode, subsequent NMR experiments were carried out, such as adding 5 equiv of KCl to a C6D6 solution of 6 in an air-sensitive NMR tube, under N2 atmosphere, and heating it to 60 °C. The results clearly differ from those observed in the presence of LiCl. There was no evidence of compound 3 or related species with similar hapticity. On the basis of these findings, the size of the alkaline metal is confirmed to be crucial in the isolation of the lithium derivative 3. In the case of the reaction with the larger potassium cation, the pathway suggests that completely different chemistry occurs and formation of organometallic species with the butadienesulfonyl ligand cannot be ruled out, but it has been unequivocally established that no tetrameric or other aggregated species with a coordination mode analogous to 3 exist (vide infra). The reaction of 1 with 2a-K (1:6) monitored at different times yields evidence of traces of the ruthenacyclopentadiene 9 as a side product, as well as the formation of two tentative intermediates proposed as 10 and 11, which will afford 6, as described in Figure 3 and Scheme 4. The reaction mixture at -110 °C was allowed to reach room temperature, and after 1 h the formation of 10 (B) and 11 (D) was observed (Figure 3). Thirty minutes later, compound 10 (B) remained present, while 11 (D) disappeared and compound 6 (C) appeared along with traces of dinuclear compound 9 (A). After 150 min, compound 10 (B) was fully transformed into 6 (C), whereas the concentration of compound 9 (A) remained constant. According to 1H and 13C NMR spectra we propose that 10 (B) and 11 (D) are intermediates, whereas 9 (A) is a minor product that can be formed from 6 (C) under higher energetic reaction conditions. The 1H and 13C{1H} NMR data for 9-11 are summarized in ref 31. It has been demonstrated that compound 1 could dissociate in the presence of THF, according to an NMR study of [Cp*RuCl]4 in THF-d8 as well as by dynamic light scattering (DLS) measurements (Figure 4, vide infra). According to the mechanism described in Scheme 4, compound 1131c is proposed as an analogous monomeric fragment of the tetranuclear compound 3, where potassium, instead of lithium, is balancing the negative charge. In the presence of a Cp*RuCl fragment, 11 could be transformed into 10, which (31) (a) Compound 9: 1H NMR (C6D6): δ 4.99, t, 2.2, 2.7 Hz, CH; 8.36, t, 2.2, 2.7 Hz, CH; 1.02, s, Cp*; 1.92, s, Cp*. 13C NMR (C6D6): δ 93.6, CH; 163.2, CH; 94.3, 9.4, Cp*, RuII; 103.9, 10.9, Cp*, RuIV. (b) Compound 10: 1H NMR (C6D6): δ n.o. H1, H10 ; 5.18, m, H2; 5.37, dd, 4.9, 5.2 Hz, H3; 3.09, d, 4.7 Hz, H4; 1.26, s, Cp*; 1.48, s, Cp*. 13C NMR (C6D6): δ 68.6, C1; 84.0, C2; 84.6, C3; n.o. C4; 88.2, 9.2, 92.8, 9.7 Cp*. (c) Compound 11: 1H NMR (C6D6): δ 3.04-3.15, br, H1, H10 ; 3.48, br, H2; 6.13, br, H3; 6.80, br, H4; 1.47, s, Cp*. 13C NMR (C6D6): δ 54.8, C1; 77.2, C2; 139.9, C3; 145.9, C4; 96.1, 9.3, Cp*.


3701

is tentatively assigned as a dinuclear derivative where a butadiene is coordinated to one of the Ru atoms. Finally, compound 6 can be obtained by losing KCl from 11 or losing Cp*RuCl and KCl from 10. The ruthenacyclopentadiene complex 9 is proposed to be formed by activation of C-H and C-SO2 bonds, either of compound 6 or 10. The former should be in the presence of Cp*RuCl. During isolation of 9, through a stoichiometric reaction of 6 and 1, a new intermediate has been detected. At the moment there is not certainty about the specific ruthenacyclopentadiene complexes that have been isolated, and more detailed studies are required, which include necessarily the corresponding crystalline structures.32 Several ruthenacyclopentadiene, such as [Cp*Cl2Ru(η2:η4-μ2-C4H4)RuCp*]33a and [Cp*(PMe3)Ru(η2:η4-μ2-C4H4)RuCp*],33b have been previously reported. D. Dynamic Laser-Light Scattering of Tetrameric Ruthenium Compounds 1 and 3 in THF. The possible dissociation of tetramers 1 and 3 in the presence of THF motivated us to gain insight into this phenomena via DLS measurements.34a A highly diluted sample of 1 in THF was investigated under different conditions: (a) freshly prepared at room temperature, (b) 30 min later at room temperature, (c) immediately after heating it to 30 °C, and (d) 1 h later after the sample cooled back to room temperature (Figure 4). After the first measurement it was clear that compound 1 generates a large number of aggregates whose nuclearity and size varied with time and temperature. The first two measurements, (a) and (b), showed the presence of particle size distributions of 24-190 nm (Figure 4a) and 14-190 nm (Figure 4b), respectively. The third and fourth measurements, (c) and (d), demonstrated the presence of particles of small diameters (0-7 nm, 24-164 nm, Figure 4c, and 1.7-10.0 nm, 78-220 nm, Figure 4d). In agreement with the NMR data, DLS shows a clear tendency for 1 to generate polydisperse mixtures in THF. Taking into consideration that the electronic characteristics of the mononuclear fragment of 3 would be similar to those of 6, and in order to establish its aggregation pattern (which does not mean its volume),34b DLS measurements of highly diluted solutions of 3 and 6 in THF were carried out. Samples were analyzed freshly prepared and 30 min later. In both cases, monodisperse mixtures with only one peak were observed. For 6 a size average distribution of 73 nm is observed (Figure 5a), whereas for 3 the average size distribution is 320 nm (Figure 5b). A consecutive measurement of 3 carried out upon addition of 10 μL of water shows its immediate dissociation and aggregation in particles with average size distributions similar to those of 6 (Figure 5c). (32) The synthesis of compound 9 was carried out with 6 (70.0 mg, 0.20 mmol) and 1 (53.8 mg, 0.05 mmol) under refluxing toluene (120 mL) for 70 h. The solution was cooled and filtered, and the solvent was removed under vacuum. The residue was treated as described for compounds 3-5 with the magnet technique, and then it was washed three times with diethyl ether (3 mL) and passed through a chromatographic column of SiO2 with THF. The dark red solid obtained shows 1H and 13C NMR described in ref 31a. IR (KBr, cm-1): 1667 (m, br), 1468 (vs, br), 1377 (vs), 1226 (m), 1172 (w), 1113 (vw), 1075 (w), 1022 (vs), 913 (vw), 840 (m), 732 (vw), 623 (vw), 549 (vw), 494 (vs), 441 (m). MS: 561, 525 (60). ESI þ TOF: m/z 561.0430; error ppm -0.4465; DBE 7.5. Mp: 298-301 °C dec. (33) (a) Campion, B. K.; Heyn, R. H.; Don Tilley, T. Organometallics 1990, 9, 1106. (b) Omori, H.; Suzuki, H.; Moro-Oka, Y. Organometallics 1989, 8, 1576. (34) (a) Low, P. M.; Yong, Y. L.; Yan, Y. K.; Hor, A. T. S.; Lam, S.; Chan, K. K.; Wu, C.; Au-Yeung, S. C. F.; Wen, Y.; Liu, L. Organometallics 1996, 15, 1369. (b) Method for Determination of Particle Size Distribution. Part 8. Photon Correlation Spectroscopy. International Organization for Standarization (ISO). Technical note, Malvern Instruments, 1996.

3702


Paz-Michel et al.

Figure 3. Monitoring reaction by 1H NMR of 1 and 2a-K. A = 9, B = 10, C = 6, D = 11.

In contrast with Figure 4, the spectra of 3 and 6 show the presence of only one well-defined peak, where the average size between them is 4:1. This result implies that compound 3 has aggregates 4 times bigger than those of 6, suggesting that the tetrameric structure remains significantly preserved in 3. The reactivity studies of 3 in the presence of H2O (Scheme 3, vide supra) along with the experiment depicted in Figure 5c support the fact that the fragmentation of 3 in THF solution is promoted only by the presence of water. The high stability of the tetranuclear structure 3 has been mainly attributed to the chelate effect. E. Synthesis, Spectroscopy, and Characterization of the Monomeric Ruthenium Ion-Pair Compounds 12a-M [M=K, Ag, n-Bu4N]. When 6 is treated in a molar 1:1 ratio with 2a-K in THF at room temperature or if 1 is treated with an excess of 2a-K, under similar conditions, the ion-pair compound [Cp*Ru(1,2,5-η-SO2CHdCHCHdCH2)(5-η-S(O2-Kþ)CHd CHCHdCH2)] (12a-K) is obtained in 70% or 45% yield, respectively (Scheme 5). The pale brown solid 12a-K has been fully characterized by high-resolution mass spectrometry, IR and NMR spectroscopy, and cyclic voltammetry. Selective and high-yield counterion exchange reactions occur for 12a-K in the presence of AgBF4 (71%) and n-Bu4NBF4 (66%) at room

temperature, to afford the corresponding compounds 12a-Ag and 12a-(n-Bu4N) (Scheme 5). Contrastingly, n-Bu4NPF6 does not transform completely to 12a-(n-Bu4N) due to the higher solubility of the KPF6 compared to KBF4 in THF solution.35 The 1H and 13C{1H} NMR spectroscopy of 12a-K provides clear evidence of two different butadienesulfonyl ligands coordinated in η2,1 and η1 fashion to the Cp*Ru complex (Tables 1 and 2). The ESI-TOF-MS analysis in the negative mode confirms an anionic discrete molecule with m/z 471.0232 amu. All new ion pairs 12a-M (M=K, Ag, n-Bu4N) are slightly air sensitive and soluble in most polar organic solvents and can be stored under N2 for a long period of time. The electrochemical oxidation of compound 12a-K discriminates that a localized ion pair, instead of an anionic organometallic compound, was isolated. Two experiments were carried out in order to demonstrate it. First, an equilibrium reaction was established in the presence of 12a-K and n-Bu4NPF6 as the electrolyte in THF. As a result (35) Linke, W. F.; Seidell, A. Solubilities of Inorganic and MetalOrganic Compounds, A Compilation of Solubilitiy Data from Periodical Literature, 4th ed.; American Chemical Society: Washington, D.C., 1965.

Article


3703

Figure 4. DLS measurements of compound 1 in THF. Scheme 4

Figure 5. DLS measurements of 6 (a) and 3 (b) in THF and 3 in THF and with traces of water (c).

The peaks are assigned to the oxidation processes as follows: the nonassociated sulfone group 12a- (signal Ia); the sulfone forming an ion pair with potasium 12a-K (signal IIIa), and the ruthenium center either in 12a- or 12a-K (signal IIa). This proposal is in agreement with the fact that ion-pair anions have higher oxidation potentials than the corresponding free anions.36 The low current intensity of Ia stems from the low concentration of the free 12a-, indicating that the equilibrium process described in eq 1 is shifted to the left. In order to induce a higher concentration of the free anionic species 12a-, n-Bu4NBF4 was used as the electrolyte. Because of the lower solubility of KBF4 in THF, the equilibrium of cation exchange depicted in eq 2 is shifted to the right, increasing the current intensity of Ia (Figure 6B).

R-SO2 - Kþ þ n-Bu4 Nþ BF4 - uR-SO2 þ ½n-Bu4 Nþ þ Kþ BF4 - V of this mixing process, KPF6 and the free anion RSO2(12a-) were formed. The negative charge of the sulfone fragment practically remained in the free anion, due to the large size of the cation [n-Bu4N]þ, which does not favor a strong interaction with 12a- (eq 1). In this ion exchange process, the precipitation of KPF6 is determining the equilibrium extent.

Once the system equilibrated according to eq 1, three signals were observed in the cyclic voltammogram (Figure 6A).

ð2Þ

Second, in order to confirm that signal Ia is due to the oxidation of a redox center such as the sulfinate group, a voltammetric experiment was carried out using the pure ligand 2a-K as a substructure of compound 12a-K (Figure 7). Because both 12a-K and 2a-K have a sulfinate group -SO2-, it can be directly assumed that 2a-K participates in (36) (a) Andrieux, C. P.; Gonzalez, F. J.; Saveant, J.-M. J. Electroanal. Chem. 2001, 498, 171. (b) Gonzalez Bravo F. J., unpublished results. In the case of tetrabutylammonium carboxylates in acetonitrile, it has been observed in our research group that the oxidation wave is enlarged and shifted toward more positive values when alkaline metal salts are added to the solution, which suggests that the negative charge on the carboxylic function is ion-pairing stabilized, and consequently this is less available for electron transfer. Such an ion-pairing phenomenon falls in line with the low solubility of the alkaline metal salts of carboxylic acids in polar solvents.

3704


Paz-Michel et al. Scheme 5

Figure 6. Cyclic voltammetry of a solution of 12a-K (2 mM) in THF on a glassy carbon electrode (Φ = 3 mm) at 0.1 V s-1. The supporting electrolytes were (A) n-Bu4NPF6 0.1 M and (B) nBu4NBF4 0.1 M.

cationic exchange equilibria similar to those involving compound 12a-K. Evidence of this is the high degree of overlap between waves A (Ep=0.55 V vs SCE) and B (Ep=0.49 V vs SCE) in Figure 7. This result confirms that signal Ia in Figure 6 corresponds to the oxidation of the anionic sulfone group. Consistent with the proposed cation exchange equilibrium for compounds 12a-K and 2a-K, the addition of KOTf to each of these solutions allows the formation of an ion pair between the potassium cation and negatively charged sulfone group, giving rise to the total suppression of the electroactivity of free species 12a- and 2a- in the potential range shown in Figure 7C and D. Other modifications of the ion-pairing equilibria included trapping the potassium cation with a crown ether, such as 18crown-6. The cyclic voltammetry of compound 12a-K in THF was studied in the presence of different amounts of crown-ether (Figure 8). An increase in the current intensity of signal Ia was observed along with the increase in the concentration of crown-ether, suggesting that the Kþ cation has been trapped by the ether, releasing higher concentrations of the free anion 12a- (Figure 8). Once again, addition of KOTf gives

Figure 7. Cyclic voltammetry in THF þ n-Bu4NBF4 0.1 M on a glassy carbon electrode (Φ = 3 mm) at 0.1 V s-1: (A) solution of 12a-K (2 mM) after addition of KOTf, (B) solution of 2a-K (2 mM) after addition of KOTf, (C) Ssolution of 12a-K (2 mM) before addition of KOTf, and (D) 2a-K (2 mM) after addition of KOTf .

Figure 8. Cyclic voltammetry of a solution of 12a-K (2 mM) in THF with n-Bu4NBF4 (0.1 M) on a glassy carbon electrode (Φ = 3 mm) at 0.1 V s-1, after addition of ether-18-crown-6 in concentrations of (A) 0, (B) 3.9, and (C) 37.2 mM.

evidence of the association of 12a- with Kþ, along with the regeneration of the electro-inactive compound 12a-K.

Article


3705

Scheme 6

Scheme 7

the walls. The solution was decanted, and the precipitate was dissolved in D2O and identified as 2a-K (see Supporting Information). Formation of 13a-K is promoted under reflux, but nevertheless, regeneration of 12a-K is always induced, along with precipitation of 2a-K.

Conclusion

The electrochemical experiments confirmed the presence of an ion-pair complex between the sulfinate moiety and potassium cation, instead of an anionic organometallic compound. G. Reactivity of Compounds 3, 6, and 12-K with Lithium and Potassium Butadienesulfinates. Spectroscopic Evidence of Tentative Formation of 13a-Li, 13a-K, and Related Aggregate Species. Compound 6 reacts with a 3-fold excess of 2a-Li under THF reflux for 2 h (Scheme 6), giving a mixture of [Cp*Ru(1,2,5-η-SO2CHdCHCHdCH2)(5-η-S(O2-Liþ)CHdCHCHdCH2)] (12a-Li) and [Cp*Ru(5-η-SO2CHd CHCHdCH2)(5-η-S(O2-Liþ)CHdCHCHdCH2)2] (13a-Li) that cannot be separated. Milder conditions do not promote the formation of any product. The 1H NMR did not give direct evidence of 13a-Li because the chemical shifts of the (5-η-SO2CHdCHCHd CH2) ligands have the same values as the analogous 5-ηligand in complex 12a-Li. However, the presence of 13a-Li is supported by the integration of the signals in the spectrum of the mixture of 12a-Li and 13a-Li, which shows a 1.0:0.3 ratio for (5-η-SO2CHdCHCHdCH2) and (1,2,5-η-SO2CHd CHCHdCH2), respectively. HRMS at a cone voltage of 215 V shows evidence of the monomeric 12a-Li, but also for more complex aggregate species, tentatively assigned as di- and trimeric species [Cp*Ru(1,2,5-η-SO2CHdCHCHdCH2)(5-ηS(O2-Liþ)CHdCHCHdCH2)]n (n=2, 3), as well as 13a-Li and mixed species, such as (12a-Li)(13a-Li). Compounds 3 and 12a-K also react in refluxing THF, with a large excess of 2a-K or 2a-Li, respectively. The HRMS also show that monomeric complexes, such as 12a-M and 13a-M (M = Li, K) are formed, and a clear tendency to form aggregate and mixed species is observed (see mass spectra of 3 þ 20 equiv of 2a-K and 12a-K þ 5 equiv of 2a-Li, which are included in the Supporting Information). Attempts to isolate 13a-K from the reaction between 12a-K and 5 equiv of 2a-K were unsuccessful due to the equilibrium between 13a-K and 12a-K (Scheme 7). The analysis of the filtered reaction by 1H NMR (acetoned6) showed 12a-K and 13a-K in a 1.0:0.3 ratio. After 7 h in an NMR tube, the sample produced a pale yellow powder on

Acyclic butadienesulfinate salts 2a-c-M [M=Li, K] are expected to have a promising synthetic potential in different fields of chemistry due to their facile synthesis and relevance of their intermolecular interactions. Particularly, in organometallic chemistry these salts have been shown to be excellent precursors in addition and metathesis reactions. The new transition metal ruthenium complexes exhibit the formation of new multinuclear aggregation states, according to the cations employed, going from typical electrostatic interactions with K to more covalent interactions with Li. The versatile chemistry of the butadienesulfinate salts 2a-c-M (M=Li, K) with 1 has been demonstrated through mass spectrometry (ESI-TOF-MS), IR, cyclic voltammetry, DLS, and 1H, 13C, and 7Li NMR studies. A variety of compounds have been formed, depending on the stoichiometry, type of cation, and reaction conditions, affording tetrameric, mononuclear, ion-pair complexes with different conformations and bonding modes. The chemistry of the butadienesulfinate salts and the butadienesulfonyl ligands in ruthenium complexes has given evidence of exchange of counterions, equilibrium reactions, interconversions, and C-SO2 and C-H bond activations. Interesting differences and analogies for these salts and ligands have also been found in the chemistry of (Cp*RhCl2)2 and discussed elsewhere.4 Our results clearly demonstrate how these butadienesulfinate salts could be utilized in the synthesis of new transition metal organometallic derivatives with novel properties, such as bonding mode, polarity, chirality, and peculiar reactivity. An impressive range of heteronuclear assemblies in the chemistry of these new unsaturatedsulfone molecules with intriguing properties is expected to be discovered.

Experimental Section General Procedures. Standard inert-atmosphere techniques were used for all syntheses and sample manipulations. The corresponding lithium and potassium butadienesulfinate salts 2a-c were weighed in a glovebox.37 Solvents were dried by (37) It is important to mention that the quality of the butadienesulfinate salts is quite dependent on the purity and yields of the reactions. The aging of these ligands could dramatically change the results, and it is already mentioned that manipulation in a drybox is highly recommended.

3706


standard methods (diethyl ether and THF with Na/benzophenone, toluene and benzene with metallic Na, pentane with CaH2, and acetone with K2CO3) and distilled under nitrogen prior to use. Compounds [Cp*RuCl]4,19,38 potassium butadienesulfinate (2a-K), and lithium 3,5-dimethylbutadienesulfinate (2c-Li) were prepared according to literature procedures.1,3 All other chemicals were used as purchased from Sigma-Aldrich, Fluka, Strem Chemicals, Merck, J. T. Baker, Isotec, and Cambridge Isotopes. Elemental analyses were performed at Cinvestav, using a Thermo-Finnigan Flash 112. The melting points were determined using a Gallenkamp melting point apparatus and are uncorrected. IR spectra were recorded on a Perkin-Elmer 6FPC-FT spectrophotometer using KBr with NaCl plates. 1H, 13 C, and 7Li NMR spectra were recorded on Jeol GSX-270, Eclipseþ400 MHz, or Bruker 300 MHz spectrometers in dry, deoxygenated, deuterated solvents. 1H and 13C NMR chemical shifts are reported relative to residual protium resonance in the solvent,39 and 7Li relative to LiCl. Mass Spectrometry. ESI mass spectra were recorded in positiveand negative-ion modes using an Agilent G1969A electrosprayionization time-of-flight spectrometer with an average of 11 scans. The analyte solutions of approximate concentration of 0.3 mM was delivered to the mass spectrometer source using a G1312A_1 bin pump. Assignment of major ions was aided by a comparison of the experimental and calculated isotope distribution patterns. Different cone voltages, flow rates, and mobile phase solvents are described in each case. a. Preparation of Samples 12a-M [M = K, Ag, n-Bu4N]. Samples were dissolved in MeCN, and their spectra were acquired using a cone voltage of 100 V and a flow rate of 0.4 mL/min using MeCN as mobile phase solvent. b. Preparation of the Different Aggregates of 12-Li and 13-Li. Reaction of 6 with 2a-Li (1:4); 3 with 2a-K (1:20), and 12a-K with 2a-Li (1:5) and LiCl (1:5) were carried out under reflux of THF for 2 h. An analyte of the filtered and evaporated mother liquors from each reaction was taken, and their spectra were acquired using a cone voltage of 215 V and a flow rate of 0.4 mL/ min using MeCN as mobile phase solvent. Dynamic Laser-Light Scattering Instrumentation and Measurements. For DLS measurements of compounds 1, 3, and 6, the samples were prepared in THF at highly diluted concentrations, and then they were filtered through a Millipore 0.5 μm LCR filter for dust removal and poured in a quartz cell. A commercial DLS spectrometer (Malvern Zetasizer Nano 90) equipped with a fast correlator card (minimum sample time is 12.5 ns) and temperature control from 2 to 90 °C was used for measurements. A He-Ne laser operating at 633 nm and 4.0 mW was used as the light source using a multiple narrow method. The primary beam was vertically polarized. Scattered intensity was taken at 90° to the incident beam. For the calculation of the hydrodynamic radius (Rh) in THF values of 0.4549 and 1.409 were used for the viscosity (η) and the refractive index (RI), respectively. A value of 1.4 was used as the refractive index of complexes 1, 3, and 6. Crystal Structure Determination. Crystals suitable for X-ray diffraction of compound 5 were obtained in two different tetragonal systems depending on the solvent used. From slow evaporation of a C6D6/Et2O (1:5) solution at -5 °C, a yellow polymorph (tetragonal space group P21/c) is obtained, whereas from a concentrated solution of THF at -15 °C reddish prismatic crystals of another polymorph were isolated (tetragonal space group I4). The first yellow pseudo-polymorph contains only complex 5. The composition of the reddish pseudopolymorph is 5 3 3THF. Both crystals of 5 were mounted in (38) (a) Fagan, P. J.; Ward, M. D.; Caspar, J. V.; Calabrese, J. C.; Krusic, P. J. J. Am. Chem. Soc. 1988, 110, 2981. (b) Fagan, P. J.; Ward, M. D.; Calabrese, J. C. J. Am. Chem. Soc. 1989, 111, 1698. (39) Gottlieb, H. E.; Kotlyar, V.; Nudelman, A. J. Org. Chem. 1997, 62, 7512.

Paz-Michel et al. a capillary. X-ray diffraction measurements were made at 173(2) K, on an Enraf Nonius-Kappa CCD diffractometer, using graphite-monochromated Mo KR radiation (λ = 0.71073 A˚). The data for the other two crystals were acquired in a similar fashion. The structures were solved by the direct method and the heavy-atom method, respectively, using SHELX-97 included in WinGX40 and refined by a full-matrix least-squares method based on F2. Absorption correction was performed with MultiScan.41 The refinement was performed as follows: All nonhydrogen atoms were refined with anisotropic thermal displacement coefficients unless specified otherwise. In compound 5 the Cp* ligand is disordered over two positions with the minor component contribution of 49.0(11)%. The crystal is a racemic twin with the minor component contribution of 23(10)%. In compound 5 3 3THF there is a partially (75.4(11)% of the time) occupied molecule of THF that was refined isotropically with an idealized geometry. The crystal is a racemic twin with the minor component contribution of 47.0(7)%. In structure 6 the diene ligand is disordered over two positions with the major component contribution of 57.8(5)%. The ligand was refined with restraints and constraints, and its C and O atoms were refined isotropically. This crystal is a racemic twin with a 49.0(11)% minor component contribution. Electrochemical Experiments. Tetrabutylammonium hexafluorophosphate 99% (n-Bu4NPF6) and tetrabutylammonium tetrafluoroborate 99% (n-Bu4NBF4) were used as the supporting electrolyte, and freshly distilled THF was used as solvent. All the solutions were purged with high-purity argon before each run and maintained over inert atmosphere during the experiment. The electrochemical apparatus consisted of a DEA-332 potentiostat (Radiometer Copenhagen) with positive feedback resistance compensation. A conventional three-electrode cell was used to carry out the voltammetric experiments. A glassy carbon disk of 3 mm diameter was used as a working electrode (Sigradur G from HTW, Germany). Prior to its use, it was carefully polished with 0.3 μm alumina powder (B€ uehler), rinsed with distilled water, and sonicated in ethanol. The counter electrode was a platinum mesh. The reference electrode was an aqueous saturated calomel electrode, SCE. A salt bridge, containing 0.2 M of the corresponding supporting electrolyte in THF, connected the cell with the reference electrode. All electrochemical experiments were performed at 25 °C. Synthesis of Compound Li[SO2CHdCHCHdCH2] (2a-Li). The synthesis of 2a-Li has been previously reported using LDA as a base in 67% yield.1,3 Herein, we describe an alternative synthetic procedure. To a solution of HN[Si(CH3)2]2 (0.4 mL, 1.92 mmol) in THF (25 mL), in a EtOH/N2 at -110 °C, was added dropwise a 1.6 M solution of n-BuLi (1.18 mL, 1.89 mmol). After stirring 5 min the reaction mixture gave a solution, which was allowed to warm at room temperature and stay 20 min at room temperature, giving a colorless solution. After the reaction mixture was cooled again to -110 °C, 2,5-dihydrothiophene-1,1-dioxide (2a) (225.0 mg, 1.90 mmol) in THF (5 mL) was added slowly to the anion. Afterward, the cold bath was removed and the solution was warmed at room temperature and stirred for 90 min, furnishing a white suspension. The solvent was evaporated, and the cream residue was washed five times with THF (10 mL) and dried under vacuum. The yield of the highly hygroscopic salt 2a-Li was 87% (205.0 mg, 1.65 mmol). ESI-TOF-MS: m/z 111.0027; error ppm 9.6164; DBE 2.5. Spectroscopic data were in agreement with an original sample. Synthesis of Compound Li[SO2CHdC(Me)CHdCH2] (2bLi). The reaction was carried out via a procedure similar to that described for 2a-Li, but with 2b (250.0 mg, 1.89 mmol). The yield of the highly hygroscopic salt 2b-Li, which did not melt, was 67% (175 mg, 1.27 mmol). ESI-TOF: m/z 131.0172; error ppm (40) Farugia, L. J. J. Appl. Crystallogr. 1999, 32, 837. (41) Blessing, C. F.; R., H. Acta Crystallogr. 1995, A51, 33.

Article -0.1903; DBE 2.5. IR (KBr): 2948 (m), 2920 (m), 1999 (m), 1966 (sh), 1819 (m), 1633 (m), 1581 (s), 1503 (w), 1441 (s), 1375 (s), 1316 (m), 1241 (m), 1175 (m), 1004 (vs/br), 900 (vs), 847 (vs), 804 (s), 782 (s), 697 (m), 622 (sh), 584 (m), 481 (sh), 451 (vs/br) cm-1. Synthesis of Compound K[SO2CHdC(Me)CHdCH2] (2b-K). Into a Schlenk flask equipped with a stir bar was placed t-BuOK (200.0 mg, 1.78 mmol) in THF (20 mL). In a similar procedure, sulfone 2b (250.0 mg, 1.89 mmol) was dissolved in THF (10 mL) and poured into the potassium tert-butoxide flask via cannula. The mixture was stirred at room temperature for 75 min. The solvent was removed until dryness, and the residue was washed five times with THF (5 mL) and dried under vacuum (2-3 h). The cream powder product 2b-K is highly hygroscopic and did not melt. The yield was 87% (280.0 mg, 1.64 mmol). ESI-TOF: m/z 131.0173; error ppm 0.5729; DBE 2.5. IR (KBr): 1692 (m), 1631 (sh), 1574 (m), 1443 (vs/br), 1418 (vs/br), 1378 (vs/br), 1170 (vw), 1020 (vs), 980 (vs), 902 (s), 833 (s), 806 (sh), 777 (m), 723 (m), 697 (m), 584 (m), 506 (m), 442 (m), 407 (m) cm-1. General Method of the Synthesis of [Cp*Ru(1,2,5-ηSO2CHdCR0 CHdCHR)LiCl]4 (R = R0 = H, 3; R = H, R0 = Me, 4; R=R0 =Me, 5). Into a Schlenk flask equipped with a stir bar were placed [Cp*RuCl]4 (150.0 mg, 0.138 mmol; 180.0 mg, 0.166 mmol; 140.0 mg, 0.129 mmol, respectively) and the corresponding lithium salt 2a-Li (76.0 mg, 0.613 mmol) or 2bLi (100.0 mg, 0.72 mmol) or 2c-Li (102.0 mg, 0.67 mmol), and the mixture was cooled to -110 °C. THF (25 mL) was added, and the mixture was stirred until it reached room temperature and then for an additional 2 h. The yellowish-brown solution was filtered and the solvent removed until dryness. The residue was dissolved in benzene (5 mL) and filtered, and the benzene removed under vacuum. The oily product was turned into a powder after the following procedure: the oily solid residue, in the presence of a magnetic stirrer, and 3 mL of pentane were cooled under liquid nitrogen until the residue was frozen. The bottom surface of the Schlenk was rubbed with an external strong magnet, until the frozen residue turned to a powder. Finally, the volatiles were removed in vacuo, and the yellow solid was rinsed with pentane (2 mL) and dried under vacuum. Compounds 3-5 do not melt until 300 °C. Compound 3 was obtained as a light yellow powder in 84% yield (179.0 mg, 0.113 mmol). Compound 4 was obtained as a mustard powder in 83% yield (226.0 mg, 0.138 mmol), and compound 5 was obtained as a dark yellow powder in 93% yield (204.0 mg, 0.120 mmol). Compound 3: IR (KBr): 1639 (m/br), 1614 (m/br), 1498 (w), 1458 (m), 1377 (m), 1300 (m), 1202 (m), 1099 (vs/br), 991 (vs/br), 878 (vw), 818 (s), 779 (m), 739 (m), 679 (w), 655 (m), 623 (vw), 562 (m), 525 (vw), 474 (m/br), 449 (m/br) cm-1. Anal. Calcd for C56H80Ru4Cl4O8S4Li4 (1583.36): C 42.48, H 5.10. Found: C 42.41, H 5.27. Compound 4: IR (KBr): 1638 (vs), 1498 (sh), 1457 (sh), 1439 (m), 1377 (m), 1317 (vw), 1293 (vw), 1255 (w), 1201 (w), 1093 (vs/br), 988 (vs/br), 910 (sh), 839 (s), 815 (sh), 771 (w), 679 (w), 604 (m), 586 (sh), 551 (m), 500 (m), cm-1. Anal. Calcd for C60H88Ru4Cl4O8S4Li4 (1638.64): C 43.98, H 5.42. Found: C 43.64, H 5.79. Compound 5: IR (KBr): 1636 (s/br), 1583 (sh), 1508 (w), 1438 (s), 1377 (s), 1304 (m), 1228 (m), 1113 (s), 1093 (vs/br), 984 (vs/br), 895 (m), 856 (m), 835 (s), 784 (m/br), 596 (w), 573 (vw), 545 (m), 501 (s), 417 (w), cm-1. Anal. Calcd for C64H96Ru4Cl4O8S4Li4 (1693.96): C 45.38, H 5.72. Found: C 45.10, H 5.87. General Method of the Synthesis of [Cp*Ru(1-5-η-SO2CHd CR0 CHdCHR] (R=R0=H, 6; R=H, R0=Me, 7). Into a Schlenk flask equipped with a stir bar were placed compound 1 (100 mg, 0.092 mmol; 110 mg, 0.101 mmol, respectively) and 2a-K (77.0 mg, 0.507 mmol) or 2b-K (75.0 mg, 0.441 mmol). THF (25 mL) was added, and the resulting brown suspension was stirred at room temperature for 3 h, giving an amber solution. The reaction mixture was filtered, the solvent was totally evaporated, and the remaining oily solid was dissolved in toluene (crude of 6) or benzene (crude of 7) (20 mL). After filtration, the solvent was


3707

evaporated and the foamy amber residue was treated as described for compounds 3-5 with the magnet technique, but instead adding pentane (5 mL) only once. The treatment was repeated three times, and the remaining solid was dried under vacuum for 3 h. Light brown powders were obtained for 6 and 7, which melt at 187-188 and 172-175 °C, respectively. Compound 6 was obtained in 71.0% yield (85.0 mg, 0.241 mmol) and compound 7 in 83.5% yield (124.0 mg, 0.338 mmol). Compound 6: IR (KBr): 1617 (w/br), 1477 (m/br), 1415 (sh), 1381 (m), 1301 (m), 1259 (vw), 1234 (m), 1189 (vs), 1116 (m), 1060 (vs/br), 926 (w), 782 (s/br), 719 (s/br), 667 (s/br), 548 (s), 462 (s), 408 (w), cm-1. EI: m/z 352(1), 290(100), 236(46), 64(27), 54(9), 48(13). Anal. Calcd for C14H20RuSO2 (353.45): C 47.57, H 5.72. Found: C 47.61, H 5.81. Compound 7: IR (KBr): 1627 (w/br), 1572 (w), 1477 (s), 1438 (m/sh), 1383 (s), 1316 (vw), 1284 (m), 1185 (vs), 1124 (m), 1059 (vs), 1033 (vs/sh), 835 (w), 788 (m), 690 (s), 619 (vw), 593 (w), 570 (w), 549 (s), 475 (s), 415 (m) cm-1. EI: m/z 368(2), 304(100), 287(64), 234(39), 64(42), 48(13). Anal. Calcd for C15H22RuSO2 (367.27): C 49.05, H 6.05. Found: C 49.23, H 6.14. Synthesis of Compound [Cp*Ru(1-5-η-SO2CHCMeCHCHMe)] (8). Into a Schlenk flask equipped with a stir bar, compound 5 (200.0 mg, 0.184 mmol) was completely dissolved in benzene (50 mL), and distilled water (20 mL) was added at room temperature, stirring strongly for 1 min. MgSO4 (20.0 g, 166 mmol) was added, and the mixture was stirred for 2 min. Two phases were formed: the organic phase was transferred into a flask with more MgSO4 (50.0 g, 414 mmol) and subsequently filtered into a Schlenk tube. The solvent was removed under vacuum, affording a pale brown powder in 63% yield (115 mg, 0.301 mmol). Mp: 131-133 °C. IR (KBr): 1639 (m/br), 1578 (w), 1474 (s), 1450 (s/br), 1381 (s), 1298 (vw), 1270 (vw), 1236 (w), 1193 (vs), 1133 (m), 1060 (vs/br), 1030 (vs), 976 (sh), 929 (vw), 876 (vw), 831 (w), 790 (m), 681 (w), 652 (vw), 619 (w), 585 (m), 560 (s), 531 (s), 463 (s), 408 (w) cm-1. EI: m/z 381(1), 318(70), 301(66), 236(14), 67(100), 64(53), 48(23). Anal. Calcd for C16H24RuSO2 (381.51): C 50.37, H 6.35. Found: C 50.62, H 7.00. Compounds 6 and 7 can also be obtained through this synthetic methodology starting from compounds 3 and 4 in 57% and 48% yields, respectively. Synthesis of Compound [Cp*Ru(1,2,5-η-SO2CHdCHCHd CH2)(5-η-S(O2-Kþ)CHdCHCHdCH2)] (12a-K). The reaction was carried out as described for 6 and 7, but with compound 6 (100.0 mg, 0.283 mmol) and 2a-K (52.0 mg, 0.342 mmol) in THF (15 mL) and stirring for 90 min at room temperature. The amber solution was filtered and the solvent evaporated under vacuum. The foamy residue was washed three times with pentane (2 mL). Compound 12a-K was dried, under vacuum, for 2 h and obtained as a brown powder in 70% yield (80.0 mg, 0.158 mmol). Mp: 136-140 °C (dec). IR (KBr): 1627 (m/br), 1570 (m), 1479 (m/br), 1413 (vw), 1378 (m), 1301 (s), 1262 (m), 1211 (w), 1136 (vs/sh), 1108 (vs), 1024 (vs), 912 (m), 808 (s), 748 (m), 716 (vw), 669 (s), 646 (s), 536 (s), 477 (m), 445 (m) cm-1. ESI þTOF: m/z 510.99530; error ppm -0.3495; DBE 5.5. ESI -TOF: m/z 471.0232; error ppm -0.0574; DBE 6.5. The synthesis of compound 12a-K can also be obtained from 1, instead of 6, with 20 equiv of 2a-K in 45% yield. Synthesis of Compound [Cp*Ru(1,2,5-η-SO2CHdCHCHd CH2)(5-η-S(O2-Agþ)CHdCHCHdCH2)] (12a-Ag). The solid mixture of 12a-K (100.0 mg, 0.196 mmol) and AgBF4 (38.0 mg, 0.195 mmol) was stirred under vacuum 5 min and cooled to -110 °C. THF (15 mL) was added, and the cooling bath was removed 5 min later, whereupon the resulting yellowishbrown suspension was stirred 40 min at room temperature. The reaction mixture was filtered, and the solvent was evaporated. The yellowish-green oily solid was washed three times with pentane (2 mL). A green fine powder was obtained in 70.5% yield (48.0 mg, 0.083 mmol). Mp: 173-179 °C (dec). ESI-TOF: m/z 471.0234; error ppm 0.3671; DBE 6.5. ESI þ TOF: m/z 106.9046; error ppm 0.5011; DBE 0.5. IR (KBr): 1624 (m/br), 1570 (m), 1479 (m/br), 1413 (vw), 1380 (m), 1301 (s), 1262 (m),

3708


1214 (vw), 1094 (vs/br), 1008 (vs/br), 808 (s), 744 (m), 670 (s), 646 (s/sh), 545 (s), 479 (m), 445 (m) cm-1. Synthesis of Compound [Cp*Ru(1,2,5-η-SO2CHdCHCHd CH2)(5-η-S(O2-n-Bu4Nþ)CHdCHCHdCH2)] (12a-n-Bu4N). The reaction was carried out as described for 12a-Ag, with compound 12a-K (100.0 mg, 0.196 mmol) and n-Bu4NBF4 (72.0 mg, 0.237 mmol). A yellowish-green powder was obtained in 66% yield (93.0 mg, 0.131 mmol), which melts at 130.4-132.3 °C (dec). ESI-TOF: m/z 471.0237; error ppm -1.3252; DBE 6.5. ESI þ TOF: m/z 242.2853; error ppm -0.0991; DBE -0.5. IR (KBr): 1702 (m), 1628 (m,br), 1572 (m), 1478 (s/br), 1418 (vw), 1383 (s), 1302 (s,br), 1250 (w), 1108 (vs,br), 1057 (vs/br), 1027 (vs/br), 909 (vw), 881 (vw), 810(s), 789 (s/sh), 742 (s), 671 (s), 646 (s/sh), 551 (m/sh), 533 (s/br), 481 (m/br), 445 (m/br) cm-1.

Acknowledgment. We thank IQI S. Buendı´ a Aceves and Dr. M. E. Navarro-Clemente from ESIQIE/IPN for use and assistance with the DLS equipment and M. A. Leyva, P. Juarez-Saavedra, and J. Solis-Huitr on for

Paz-Michel et al.

technical assistance. We also thank Drs. R. D. Ernst (University of Utah), R. J. Angelici (Iowa State University), B. Wrackmeyer (Bayreuth University), and E. Carmona (University of Sevilla) for suggestions and helpful discussions, and Conacyt for financial support (46556-Q) and a scholarship (B.P.M.). Supporting Information Available: Additional information on the 1H NMR of a mixture of 12-K and 13-K and mass spectra of 12a-M (M = Ag, n-Bu4N) are included. Further details of the structure determination of compounds 5, 5 3 3THF, 6 and 7, including atomic coordinates, bond lengths and angles, anisotropic displacement parameters, and torsion angles are available free of charge via the Internet at http://pubs.acs.org. CCDC 746538, CCDC 746539, CCDC 746540, and CCDC 776296 contain crystallographic data for compounds 5 3 3THF, 5, 6, and 7. This material can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam. ac.uk/data_request/cif.

Tetrameric, Allylsulfene, and Ion-Pair Ruthenium Compounds

Recommend Documents