HDS Model Systems. Coordination, Opening, and ... - ACS Publications

J. Am. Chem. SOC.1994,116, 4376438 I

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HDS Model Systems. Coordination, Opening, and Hydrogenation of Benzo[ b]thiophene at Iridium Claudio Bianchini,'Ja Andrea Meli,la Maurizio Peruzzini," Francesco Vizza,'. Simonetta Moneti," Verbica Herrera,lb and Roberto A. Shchez-Delgado'Jb Contribution from the Istituto per lo Studio della Stereochimica ed Energetica dei Composti di Coordinazione, CNR, 50132 Firenze, Italy, and Instituto Venezolano de Investigaciones Cientificas, IVIC, Caracas 1020 A, Venezuela Received January 11, 1994"

Abstract: The q4-benzene complexes [(triphOS)Ir(C6H6)]Y (Y = BPh4, l a ; PF6, lb) react with benzo[b]thiophene (BT) at room temperature to give the unprecedented [(triphos)Ir(q3-C,C,s-c&s)]Y (Y = BPh4, 2a; PF6, 2b) in which intact BT is coordinated to the metal center through the S atom and the C2=C3 bond. 2a and 2b are transformed upon mild thermolysis into the iridabenzothiabenzene complexes [ (triphos)Ir(q2-C,S-CgH6S)]Y (Y = BPh4,3a; PF6, 3b). An X-ray analysis has been carried out on 3a.1 .STHF.O.SEtOH. The coordination geometry around iridium may be described as a distorted trigonal-bipyramid, the metal c e t e r being surrounded by the three phosphorus atoms of triphos and by a carbon and a sulfur atom from a C-S-cleaved BT molecule. Crystal data: triclinic, space group Pi, a = 17.391(3) A, b = 16.957(4) A, c = 12.795(3) A, a = 77.51(2)", 6 = 80.98(2)", y = 75.50(2)", Z = 2, d-1, = 1.31 g ~ m - now ~ , = 7636, R = 0.072. Interaction of 2a with C O (1 atm, 20 "C) yields [(triphos)Ir(CO)2]BPh4 (4) plus free BT, whereas 3a requires more drastic conditions ( 5 atm, 70 "C) to eliminate BT and produce 4. 2a also reacts with H2 (1 atm, 20 "C) to produce [(triphos)Ir(H)2(q1-S-BT)]BPh4 (5), which can be independently prepared by treatment of [(triphos)Ir(H)2(THF)]BPh4 with BT; at 5 atm H2, free BT is obtained together with [(triphos)Ir(H)3], BPh3, and benzene, as a result of a heterolytic splitting of H2at the [(triphos)Ir(H)2]+ fragment assisted by the BPh4counteranion. The C-S-cleaved BT in 3a is readily hydrogenated (5 atm, 20 "C) to 2-ethylbenzenethiolate, producing [ (tripho~)Ir(H)~(o-S-(C~H4)C~Hs)l (8) plus BPh3 and benzene also via heterolytic splitting of H2 assisted by BPhd-; protonolysis of 8 with 2 equiv HC1 produces (triphos)IrC13 with concomitant liberation of 2-ethylbenzenethiol, a primary product of BT HDS. If the PF6- analogue 3b is used instead, the reaction with H2 under identical conditions yields the thiolate-bridged dimer [(triphos)IrH{p-o-S(C~H4)C~H~)~HIr(triphos)] (PF6)2 (9b). 3a also reactswith LiHBEt3 to give [(triphos)Ir(H)(qZ-C,~-c8H6s)] ( l l ) , which converts in THF solution at 66 "C into [(triphos)Ir(q3-S(C6H4)CH=CH2)] (12) by hydride migration to C2; neither 11 nor 12 react with Hz under mild conditions. Addition of HBFcOEt, to 12 yields [(triphos)Ir(q4-S(C6H4)C(H)Me)]BF4(13c), which does react with H2 even at 1 atm to give the thiolate-bridged dimer [(triphos)IrH(p-o-S(C~H~)C~H5~~HIr(triphos)](BF~)~ (9c). 13c also reacts with H- to give [(triphos)IrH(q2-S(C6H4)C(H)Me)] (14), which in turn reacts with H2and HBFcOEt2 to yield 8 and 9c, respectively.

Introduction Hydrodesulfurization (HDS) is the process through which sulfur is removed from petroleum and other fossil fuel feedstocks by reaction with hydrogen in order to produce environmentally friendlier fuels. Considering the current world petroleum production, this is probably the largest volume industrial application of transition-metal catalysis. Sulfur in fossil materials is contained in a variety of organic compounds, such as thiols, sulfides, disulfides, and the more refractory thiophenes, benzothiophenes, and dibenzothiophenes; residual sulfur in fuels is found predominantly as benzothiophenes and dibenzothiophenes, which makes these molecules particularly interesting for model studies2 A great deal of attention has been devoted to trying to define the mechanisms of the various steps involved in the HDS reaction 0

Abstract published in Advance ACS Abstracts, April 15, 1994.

(1) (a) ISSECC, CNR, Firenze. (b) IVIC, Caracas.

(2)(a) Mitchell, P. C. H. The Chemistry ofsome Hydrodesulphurisation Catalysts Containing Molybdenum; Climax Molybdenum Co. Ltd.: London, 1967. (b) Schuman, S.C.; Shalit, H. Catal. Reu. 1970,4,245.(c) Weisser, 0.; Landa, 0. Sulfide Catalysts. Their Properties and Applications; Pergamon: Oxford, 1973. (d) Gates, B. C.; Katzer, J. R.; Schuit, G. C. A. Chemistry of Catalytic Properties; McGraw-Hill: New York, 1979. (e) Satterfield, C. N. Heterogeneous Catalysis in Practice; McGraw-Hill: New York, 1980. (f) Geochemistry of Sulfur in Fossil Fuels; Orr, W. L., White, C. M., Eds. ACS Symposium Series 429; American Chemical Society: Washington, DC, 1990. (g) McCulloch, D. C. In Appliedlndustrial Catalysis; Leach, B. E., Ed.; Academic: New York, 1983;Vol. 1, p 69. (h) Lyapina, N. K.; Russ. Chem. Reu. (Engl. Transl.) 1982,51, 189. (i) Challenger, F. Aspects of the Organic Chemistry of Sulfur, Butterworths: London, 1959.

0002-786319411516-4370$04.50/0

of thiophene both on surfaces3 and on organometallic modelsa4 The coordination and reactivity of thiophene (T) on metal complexes has been explored in some detail, but much less is known about the coordination chemistry of benzo[b] thiophene (BT) .4 Concerning the bonding to metal centers, most of the wellcharacterized complexes known contain BT $-coordinated through the benzene ring,5 but the reactivity resulting from this type of coordination does not appear to parallel HDS-related reactions.6 ql-S BT coordination has been demonstrated in several (3) (a) Friend, C.M.; Roberts, J. T. Acc. Chem. Res. 1988,21,394. (b) Wiegand, B. C.; Friend, C. M. Chem. Reu. 1992,92,1.(c) Prins, R.;deBeer, V. H. J.; Somorjai, G. A. Catal. Rev.-Sci. Eng. 1989,31, 1. (4)(a) Angelici, R. J. Acc. Chem. Res. 1988,21, 387. (b) Angelici, R. J. Coord. Chem. Rev. 1990,105,61.(c) Rauchfuss, T.B. Prog. Inorg. Chem. 1991,39, 259. (d) Sanchez-Delgado, R. A. J. Mol. Carol., in press. ( 5 ) (a) Huckett, S. C.; Miller, L. L.; Jacobson, R. A.; Angelici, R. J. Organometallics 1988,7,686. (b) Chaudret, B.; Jalon, F.; Pbrez-Manrique, M.; Lahoz, F.;Plou, F. J.;SBnchez-Delgado, R. New.J. Chem. 1990,14331. (c) Fischer, E. 0.;Goodwin, H. A.; Kreiter, C. G.; Simmons, H. D., Jr.; Sonogashira, K.; Wild, S.B. J . Organomet. Chem. 1968,14,359.(d) Polam, J. R.; Porter, L. C. Organometallics 1993,12,3504. (6)(a) Huckett, S.C.; Angelici, R. J.; Ekman, M. E.; Schrader, G. L. J. Catal. 1988,113,36. (b) Chen, J.; Su,Y.; Jacobson, R. A.; Angelici, R. J. J. Organomet. Chem. 1992,428,415. (7)(a) Goodrich, J. D.; Nickias, P. N.; Selegue, J. P. Inorg. Chem. 1987, 26,3424. (b) Choi, M.-G.; Angelici, R. J. Organometallics 1992,!I, 3328. (c) Choi, M.-G.; Robertson, M. J.; Angelici, R. J. J. Am. Chem. SOC.1991, 113,4005. (d) Benson, J. W.; Angelici, R. J. Organometallics 1992,lI , 922. (e) Benson, J. W.; Angelici, R. J. Inorg. Chem. 1993,32,1871. (f) SanchezDelgado, R. A,; Herrera, V.; Bianchini, C.; Masi, D.; Mealli, C. Inorg. Chem. 1993,32,3766.(g) Clark, P. D.; Kirk, M. J.; Parvez, M. Can. J . Chem. 1993, 71, 199.

0 1994 American Chemical Society

HDS Model Systems cases,7 as well as an equilibrium between the 9' and q 2 - C - C bonding modes in Cp(C0)2Re(BT).7b.C Also, complexes containing 71-S and +C=C bonded BT have been suggested as possible intermediates in C-S bond breaking8 and C-C bond hydrogenationgJ0reactions. There are no authenticated examples of metal complexes containing BT $-bonded through t h e thiophenic ring, but such species have been proposed as possible intermediates in heterogeneous HDS reactions.68 Also, the complex [ (qS-BT)Rh(PPh3)2]+ has been suggested as an intermediate in the homogeneous catalytic hydrogenation of BT on the basis of the regioselectivity of the catalysis, together with theoretical calculations."Jbqc Besides the well-understood homogeneous catalytic hydrogenation of BT to l ,2-dihydrobenzo[b]thiophene(DHBT)9J0(which does not lead to desulfurized products), little is known about the reactivity of coordinated BT. C-S bond activation leading to ring-opened BT ligands has been reported in a very limited number of cases, vir. Cp*Rh(PMe)3(SCsH6)8 and (PMe3)3Ir(SC&& C1.11 Only one example of metal-assisted ring opening and hydrogenation of BT has been described so far. Rauchfuss reacted BTwith an iron cluster, Fe3(C0)'2,obtaining t h e benzothiaferrole Fe2(CsH&)(C0)6, which was subsequently hydrogenated to give primarily ethylbenzene together with some 2-ethylbenzenethiol, bis(2-ethylpheny1)sulfide and bis(2-ethylphenyl)di~ulfide.~~ Similarly, R U ~ ( C Oreacts ) ~ ~ with BT to yield the ring-opened Ru2(CsH6S)(C0)6, analogous to Rauchfuss' benzothiaferrole; thermolysis of this complex leads to sulfur extrusion and production Of RU2(CsH6)(C0)6.12b In this paper we report evidence for an unprecedented mode of BT coordination in [(triphos)Ir(q3-C,C,,S-C&&)]+ (2). Complex 2 yields the ring-opened derivative [(triphos)Ir(+C,SCsH6S)]+(3) upon mild thermolysis. T h e reactivity of 3 toward hydrogen, as well as hydride and proton sources, leads to the production of coordinated 2-ethylbenzenethiolato ligands and ultimately free 2-ethylbenzenethiol, which is one of the primary products of the heterogeneous HDS of BT. These observations provide detailed information at the molecular level, which hopefully will contribute to a better understanding of the various steps involved in the hydrodesulfurization of benzothiophenes. A preliminary communication of part of this work has already appeared." Experimental Section General Procedure. All reactions and manipulations were routinely performed under a nitrogen atmosphere by using standard Schlenk techniquesunless otherwisestated. Tetrahydrofuran (THF) was distilled from LiAlH4 and n-heptane from sodium. The solventswere stored over molecular sieves and purged with nitrogen prior to use. Commercial BT (Aldrich) was sublimed prior to use. LiHBEt3 (1.0 M solution in THF), HBFdsOEt2 (85% solution in OEtz), and BPhp were purchased from Aldrich. All other chemicals were commercial products and were used as received without further purification. Literature methods were used for the preparation of [(triphOS)Ir(C6H6)]Y(Y = BPh4, la; PF6, 1b)l4 and [(triphos)Ir(H)2(THF)]BPh4 (7).15 All metal complexes were ~~

(8) Jones, W. D.; Dong, L. J. Am. Chem. SOC. 1 6 1 , 113, 559. (9) Baralt, E.; Smith, S.J.; Hurwitz, I.; HorvBth, I. T.; Fish, R. H. J. Am. Chem. SOC. 1992, 114, 5187. (10) (a) Shchez-Delgado, R. A.; Gonzilez,E. Polyhedron 1989,8,1431. (b) Sinchez-Delgado, R. A. In Advances in Caralyst Design; Graziani, M., Rao,C. N.R.,Eds.; WorldScientificPublishingCo.: Singapore, 1991;p214. (c) Sinchez-Delgado,R. A.; Herrera, V.; Rindn, L.; Andriollo, A.; Martin, G. Organometallics 1994, 13, 553. (11) Selnau, H. E.; Merola, J. S. Organometallics 1993, 12, 1583. (12) (a) Ogilvy, A. E.; Draganjac, M.;Rauchfuss, T. B.; Wilson, S.R. Organometallics 1988, 7, 1171. (b) Arce, A. Personal communication. (13) Bianchini,C.; Meli, A.; Peruzzini, M.; Vizza, F.; Frediani, P.; Herrera, V.; Sinchez-Delgado, R. A. J. Am. Chem. SOC. 1993, 115, 7505. (14) (a) Bianchini,C.;Caulton,K. G.; Chardon, C.; Eisenstein,O.; Folting, K.; Johnson, T. J.; Meli, A.; Peruzzini, M.;Rauscher, D. J.; Streib, W. E.; 1991, 113, 5127. (b) Bianchini, C.; Caulton, Vizza, F. J . Am. Chem. SOC. K. G.; Chardon, C.; Doublet, M.-L.; Eisenstein, 0.;Jackson, S. A.; Johnson, T. J.; Meli, A.; Peruzzini, M.; Streib, W. E.; Vizza, F. Organometallics, accepted for publication. (15) Bianchini, C.; Caulton, K. G.; Johnson, T. J.; Meli, A.; Peruzzini, M.; Vizza, F. J . Am. Chem. Soc., accepted for publication.

J. Am. Chem. SOC.,Vol. 116, No. 10, 1994 4311 collected on sintered-glass frits and washed with appropriate solvents before being dried in a stream of nitrogen. Infrared spectra were recorded on a Perkin-Elmer 1600 Series FT-IR spectrophotometer using samples mulled in Nujol between KBr plates. Deuterated solvents for NMR measurements were dried over molecular sieves. 'H NMR spectra were obtained on either a Bruker ACP 200 (200.1 3 MHz) or a Bruker AMX 600 (600.14 MHz) spectrometer. lH NMR shifts were recorded relative to residual IH resonance in the deuterated solvent: CDzC12,8 5.32; THFds, 8 3.53 and 1.78. The I3C('H) NMR spectra were recorded on the Bruker ACP200instrument operatingat 50.32 MHz. The I3C('H)NMR shifts were given relative to the solvent resonance: CDzC12,6 54.4; THFd8,6 75.8 and 67.9; acetone-d6,8 205.1 and 30.2. 31P(lH)NMR spectra were recorded either on a Varian VXR 300 or a Bruker ACP 200 spectrometeroperating at 121.42and 8 1.01MHz, respectively. Chemical shifts are relative to external 85%H3PO4 with downfieldvalues reported as positive. Broad band and selective IH(3LP)NMR experiments were carried out on the Bruker ACP 200 instrument equipped with a 5-mm inverse probe and a BFX-5 amplifier device. I3C-DEPT, 2D-HETCOR, and 2D-COSY NMR experiments were conducted on the Bruker ACP 200 spectrometer. Conductivities were measured with an Orion Model 990101 conductance cell connected to a Model 101 conductivity meter. The conductivity data were obtained at sample concentrations of ca. M in nitroethane solutions at room temperature. GC analyses were performed on a Shimadzu GC-14 A gas chromatograph equipped with a flame ionizationdetector anda 30-m(0.25-mmi.d.,0.25-pm FT)SPB-1 Supelco fused silica capillary column. GC/MS analyses were performed on a Shimadzu QP 2000 apparatus equipped with a column identical to that used for GC analyses. Reactions under controlled pressure of hydrogen or carbon monoxide were performed with a Parr 4565 reactor equipped with a Parr 4842 temperature and pressure controller. Synthesisof [(Tripbos)Ir(~-C;C:sCdIcS)BP4 (2a). A solution of la (0.40 g, 0.33 mmol) and BT (1.77 g, 13.18 mmol) in THF (70 mL) was stirred in a thermostated water bath (25 "C)for 5 days. The solution gradually changed its color from yellow orange to red orange. Almost quantitative formation of benzene was detected by GC. After concentration under reduced pressure to ca. 20 mL, the remaining solution was diluted with ethanol (40 mL). On slow concentration under a steady stream of nitrogen, a red orange crystalline precipitate was obtained. This was collected by filtration and washed with ethanol and n-pentane. 'Hand3IP(lH)NMRspectrashowed almost completeconversion(>90%) of l a to 2a. Small amounts (+, 105 (62) MSH', 77 (45) C6Hst). (4) and BT. Reactlonof 8 withHBF4. Astoichiometricamount of neat HBF4.OEt2 Reaction of 30 with CO. A T H F (20 mL) solution of 39 (0.10 g, 0.08 (ca. 45 pL) was syringed into a yellow solution of 8 (0.20 g, 0.21 mmol) mmol) was pressurized with CO to 5 atm at 70 OC in a Parr reactor for in T H F (30 mL) at room temperature. After 30 min, ethanol (10 mL) 2 h. After being depressurized and vented under a nitrogen stream, the and n-heptane (20 mL) were added to the reaction mixture. On partial contents of the bomb were transferred into a Schlenk-type flask. The evaporation of the solvents under a brisk flow of nitrogen, yellow crystals volatiles were removed in vacuo at room temperature. Theyellow residue of [(triphos)IrH(p-o-S(C~H4)C2H5)2HIr(triphos)] (BF4)2 (9c) precipiwas characterized by IR and NMR spectroscopy as a 1:l mixture of tated in 80% yield. Anal. Calcd (found) for C ~ S H ~ S B ~ F ~C,I ~ ~ P ~ S ~ : [(tripho~)Ir(C0)2]BPh4~~ (4) and BT. 56.49 (56.38); H, 4.74 (4.74); Ir, 18.45 (18.35); S, 3.08 (2.89). IR: Reaction of 2a with Hydrogen. A. 1 atm. Hydrogen was bubbled v(1r-H) 2100 (s) cm-l. AM: 149 Stl cm2 mol-'. As the reaction was through a T H F (20 mL) solution of 2a (0.10 g, 0.08 mmol) at room monitored by NMR spectroscopy in THF-de, dihydrogen evolution was also detected (IH NMR: singlet at 4.7 ppm). temperature. After 3 h, the reaction mixture was concentrated to dryness in vacuo. Analysis of the residue by IR and NMR spectroscopy showed s y n t h e s i s o f [ ( T r i p h o s ) I r H ( ~ - ~ ~ C ~ ) ] (Toastirredsolution ll). cu. 15% conversion of 29 to [(triphos)Ir(H)2(&3-BT)]BPh4 (5) (see of 3a (0.30 g, 0.24 mmol) in THF (30 mL) at cu. 0 OC was added a 4-fold below). excess of LiHBEt3 (0.84 mL, 0.84 mmol). There was an immediate color B. 5 atm. A solution of 2a (0.10 g, 0.08 mmol) and toluene (20 pL, change from red orange to pale yellow. After ethanol (cu. 5 mL) was 0.19 mmol, GC internal standard) in T H F (20 mL) was pressurized with added to destroy the excess of LiHBEt3, the reaction mixture was allowed hydrogen to 5 atm at room temperature in a Parr reactor. After 3 h, the to reach room temperature. Addition of n-heptane (50 mL) and reactor was cooled to 0 "C. After being depressurized and vented under concentration gave sandy crystals of 11, which were collected by filtration a nitrogen stream, a sample of the solution was withdrawn and analyzed and washed with n-pentane; yield 80%. The reaction was also followed by GC/MS, which showed almost quantitative formation of BT and by 31P(lH)NMR spectroscopyin THF-ds. The reaction occurred already benzene. The rest of the solution was concentrated to dryness under at -70 OC; only the signals due to 3a and 11 were observed. Anal. Calcd vacuum, and the residue was found to contain [(triphos)IrH3]17 (6) and (found) for C49H6IrP3S: C, 61.81 (61.77); H, 4.87 (4.83); Ir, 20.19 Sina9:I ratio(1RandNMRspectroscopy)and triphenylboron(separated (20.00);S, 3.37 (3.25). IR: v(1r-H) 2082 (s); v(C=C) 1574 (m) cm-I. by sublimation at 70 OC, 0.5 Torr). The latter product was authenticated Compound 11 is rather unstable in solution at room temperature as it slowly converts to its isomer [(triphos)Ir(r13-S(CsH4)CH=CH2)] (12) (IH NMR) by comparison with an authentic specimen. On further (see below) (in THF at 20 OC, cu. 20%conversion occurs in 24 h). Solid exposure of the residue at 5 atm hydrogen pressure, all 5 converted to samples of 11 are stable when stored under nitrogen at low temperature, 6 and BT. whereas, at room temperature isomerization to 12 occurs also in the solid IndependentSynthesisof [(Triphos)Ir(H)2(q1-S-BT)lBPb (5). A solid state (cu. 30%conversion in 1 month). Compound 11 is stable at room sample of [(triphos)Ir(H)2(THF)]BPh4 (7) (0.20 g, 0.16 mmol) was temperature under 5 atm hydrogen pressure in T H F solution for 3 h. dissolved into a solution of BT (0.21 g, 1.6 mmol) in CH2CI2 (20 mL). After ca. 15 min, ethanol (10 mL) and n-heptane (20 mL) were added Thermal Isomerization of 11 to [(Triphos)Ir(d-S(CaH1)CH=CH3)1 to thereaction mixture. Partial evaporation of the solventsunder a steady (12). A THF (30 mL) solution of 11 (0.24 g, 0.25 mmol) was heated stream of nitrogen led to the precipitation of 5 as an off-white at reflux temperature for cu. 24 h. After concentration under reduced microcrystalline solid in 90% yield. Anal. Calcd (found) for C73H67pressure to cu. 10 mL, addition of n-heptane (30 mL) led to the BIrP3S: C, 68.91 (68.61); H, 5.31 (5.24); Ir, 15.11 (15.02); S, 2.52 precipitation of yellow crystals of 12 in 85% yield. Anal. Calcd (found) (2.41). AM: 52 &I cm2 mol-I. IR: v(1r-H) 2090 (s) cm-'. Complex for C49H46IrP3S: c, 61.81 (61.69); H, 4.87 (4.86);Ir, 20.19 (20.07);s, 5 is stable in the solid state and in deaerated common organic solvents 3.37 (3.22). As the reaction was monitored in THF-ds by ,IP(lH) NMR (THF, MeCN, acetone) at room temperature. spectroscopy at 66 OC, clean conversion of 11 to 12 was observed (1112 = 7 h). Compound 12is stableat room temperatureunder 5 atm hydrogen Reaction of 3a with Hydrogen. A solution of 3a (0.20 g, 0.16 mmol) pressure in THF solution. The compound is air-stable in both the solid in THF (20 mL) was pressurized with hydrogen to 5 atm at room state and solution. temperature in a Parr reactor for 3 h. After being depressurized and vented under a nitrogen stream, the contentsof the bomb were transferred Synthesis of [(Triphos)Ir(q4-S(C&)C(H)Me)] (Y = B P k 1 3 a ; BFh into a Schlenk-type flask. The volatiles were removed in vacuo. The 13c). Addition of a stoichiometric amount of HBF4.OEt2 (cu. 60 pL) pale yellow residue was crystallized from T H F and ethanol, giving to a yellow solution of 12 (0.27 g, 0.28 mmol) in T H F (30 mL) at cu. [(triphos)Ir(H)2(o-S(C6H4)C2Hs)] (8) as off-white crystals. They were 0 OC immediately gave a deep red solution. After 30 min, the reaction collected by filtration and washed with ethanol and n-pentane; yield 90%. mixture was allowed to warm to room temperature. On portionwise Anal. Calcd (found) forC49HsoIrP3S: C, 61.55 (61.43); H, 5.27 (5.23); addition of n-heptane (20 mL), red crystals of 13c precipitated in 80% Ir,20.10 (20.00);S, 3.35 (3.26). IR: v(Ir-H) 2048 (s) cm-'. Noreaction yield. Anal. Calcd (found) for C ~ ~ H ~ ~ B F ~C,I T56.59 P~S (56.43); : H, was observed at 1 atm hydrogen pressure. In a parallel reaction, 4.56 (4.43); Ir, 18.48 (18.24); S,3.08 (2.89). AM: 86 &I cm2mol-I. The triphenylboron was separated from the residue by either sublimation (70 reaction was also followed by 31P(1H)NMR spectroscopy in THF-ds. OC, 0.5 Torr) or extraction into n-pentane and authenticated ('H NMR) The reaction occurred already at -70 OC; only the signals due to 12 and 13c were observed. Metathetical reaction of 13c with NaBPh4 in CH2by comparison with an authentic specimen. Complex 8 is thermally stable in deaerated THF solution up to 150 OC. The complex is air-stable only C12/ethanol gave the tetraphenylborate salt 13s in almost quantitative in the solid state. yield. Anal. Calcd (found) for C73H67BIrP3S: C, 68.91 (68.00); H, 5.31 (5.14);Ir, 15.1 1 (14.89); S,2.52 (2.43). AM: 52 cm2mol-'. The Reaction of 3b with Hydrogen. Substitution of 3b for 3a and workup compounds are thermally stable in deaerated solvents such as THF, as above gave [(triphos)IrH(p+S(C6H4)C2H&HIr(triphos)] (PF& (9b) and acetone at room temperature. At higher temperature, slow as a yellow solid; yield 80%. Anal. Calcd (found) for C ~ S H ~ S F I ~ I ~ ~ P S SMeCN, Z: decomposition occurs. Also, the complexes are air-unstable in both the C, 53.50 (53.21); H, 4.49 (4.42); Ir, 17.47 (17.19); S,2.91 (2.78). IR: solid state and solution. v(Ir-H) 2100 (s) cm-I. AM: 154Q-l cm2mol-l. Complex9bis thermally stable in deaerated common organic solvents (THF, DMSO, MeCN, Reaction of 13s with Hydrogen. A. CHzCIz. A red solution of 13a acetone) at reflux temperature. The complex is air-stable in both the (0.20 g, 0.16 mmol) in CH2Cl2 (20 mL) was stirred under hydrogen solid state and solution. pressure (1-5 atm) at room temperature. After 3 h, the resulting yellow solution was concentrated to dryness under vacuum. The yellow residue Reaction of 8 with HCI. A sample of 8 (0.04 g, 0.04 mmol) was dissolved in 0.7 mL of CDzClz and placed in a 5-mm NMR tube under was characterized by IR and NMR spectroscopy as [(triphos)IrH(pnitrogen. The solution was frozen with liquid nitrogen, and a 2-fold o-S(C6H4)CzHs)zHIr(triphos)](BPh4)2 ( 9 4 . Anal. Calcd (found) for excess of gaseous HCI was syringed into the tube, which was then allowed C1&138BzIr2P6S2: c , 68.80 (68.58);H, 5.46 (5.51); Ir, 15.08 (14.98); S,2.52 (2.47). IR: v(Ir-H) 2100 (s) cm-'. AM: 99 P to reach room temperature. 31P(1H)and IH NMR spectra of this sample I cm2 mol-'. indicated the complete conversion of 8 to [(triphos)IrH(C1)2] (lO)I7 and B. THF. A red solution of 13a (0.20 g, 0.16 mmol) in THF (20 mL) was stirred under hydrogen pressure (1-5 atm) at room temperature. (16) (a) Barbaro, P.; Bianchini, C.; Meli, A.; Peruzzini, M.; Vacca, A.; After 3 h, a sample of the solution was withdrawn and analyzed by GC/ Vizza, F. Organometallics 1991,10,2227. (b) Siegl, W. 0.; Lapporte, S. J.; MS, which showed almost quantitative formation of benzene. The rest Collman, J. P. Inorg. Chem. 1971, 10, 2158. of the solution was concentrated to dryness under vacuum, and the residue (17) Janser, P.; Venanzi, L. M.; Bachechi, F. J . Orgunomel. Chem. 1985, was found to contain [(~~~~~os)I~(H)z(o-S(C~H~)C~H~))] (8) (IR and 296, 229.

J . Am. Chem. SOC.,Vol. 116, No. 10, 1994 4373

HDS Model Systems NMR spectroscopy) and triphenylboron, which was separated from the residue by either sublimation (70 OC, 0.5 Torr) or extraction inton-pentane and authenticated (IH NMR) by comparison with an authenticspecimen. Reaction of 13c with Hydrogen. A red solution of 13c (0.20 g, 0.19 mmol) in T H F (20 mL) was stirred under hydrogen pressure (1-5 atm) at room temperature. After 3 h, the resulting yellow solution was concentrated to dryness under vacuum. The yellow residue was characterized by IR and NMR spectroscopy as 9c. Synthesis of [(Triphos)IrH(q*-S(Cslq)C(H)Me)] (14). To a stirred THF (30 mL) solution of LiHBEt3 (0.68 mL, 0.68 mmol) at -70 OC was addedasolidsampleof13c (0.35g,0.34mmol). Theredsolidimmediately dissolved togivea pale yellow solution. After 15 min, thereaction mixture was allowed to reach room temperature, and then ethanol (10 mL) and n-heptane (30 mL) were added. On partial evaporation of the solvents under reduced pressure, compound 14 precipitated as sandy crystals, which were filtered off and washed with a cold 1:l mixture of ethanol and n-pentane; yield 60%. Anal. Calcd (found) for C49H48IrP& C, 61.68 (61.33); H, 5.07 (5.04); IR, 20.15 (20.03); S, 3.36 (3.14). IR: v(1r-H) 2132 (s) cm-l. When the reaction in THF-d8 was followed by 31P(1H)NMR spectroscopy at -70 "C, no intermediate species was detected along the conversion of 13c to 14. Reaction of 14 with Hydrogen. A solution of 14 (0.20 g, 0.21 mmol) in THF (20 mL) was pressurized with hydrogen to 5 atm at room temperature in a Parr reactor. After 3 h, the contents of the bomb were transferred into a Schlenk-type flask and concentrated to dryness under vacuum. The residue was characterized by IR and NMR spectroscopy as 8. No reaction was observed under 1 atm hydrogen pressure. Reactionof 14withHBF4. Astoichiometricamount ofneat HBF4.OEt2 (ca. 45 wL) was syringed into a yellow solution of 14 (0.20 g, 0.21 mmol) in T H F (30 mL) at room temperature. After 30 min, ethanol (10 mL) and n-heptane (20 mL) were added to the reaction mixture. On slow evaporation of the solvents, yellow crystals of 9c precipitated in 80% yield. X-ray Data Collection and Structure Determination of 3a.1.5THF. 0.5EtOH. A red-orange parallelepiped crystal was mounted on a glass fiber on a Philips PW 1100automaticdiffractometer. Unit cell dimensions were determined from least-squares refinement of the angular settings of 25 carefully centered reflections. As a general procedure, three standard reflections were collected every 2 h (no decay of intensities was observed in any case). Intensity data were corrected for Lorentz-polarization effects. Atomic scattering factors were those tabulated by Cromer and W a b e P with anomalous dispersion correction taken from ref 19. Absorption correction was applied by using the DIFABS program.20All the calculations were carried out on a Digital DEC 5000/200 computer by using the SHELX76 program.21 The structure was solved by heavyatom techniques. Refinement was done by full-matrix least-squares calculations initially with isotropic thermal parameters. Anisotropic thermal parameters were used for iridium and phosphorus atoms only. The phenyl rings were treated as rigid bodies of D6h symmetry ( c - c = 1.39 A) and calculated hydrogen atom positions (C-H = 1.08 A). T H F and ethanol solvent molecules were located at an advanced stage of refinement. All the atoms were treated as carbon atoms. Ethanol and one of the T H F solvent molecules were assigned a population factor of 0.5. Crystallographic and other relevant data collection are reported in Table 3.

Results T h e preparations and t h e principal reactions of t h e complexes described in this paper a r e illustrated in Schemes 1-6. Selected NMR spectral d a t a are collected in Table 1 (31P(lH)N M R ) and Table 2 (IH, I3C('HJN M R ) . W-DEFT, 13C-lH 2D-HETCOR, and IH-lH 2D-COSY spectra allowed t h e total and unequivocal assignment of all IH and 13Cresonances for all compounds as labeled on Table 2.

Coordination and Opening of Beazo[b]tbiophene at the [(triphos)Ir]+ Fragment. Stirring THF solutions of t h e v4-benzene complexes [(triphos)Ir(q4-C6H6)]Y (Y = BPh4, la; PF6, l b ] with an excess of BT at 25 O C slowly results in quantitative evolution of benzene and formation of the $-C,C,S-BT complexes [(triphos)(18) Cromer, D. T.; Waber, J. T. Acta Crystallogr. 1965, 18, 104. (19) International Tables of Crystallography; Kynoch: Birmingham, England, 1974; Vol. 4. (20) Walker, N.; Stuart, D. Acta Crystallogr. 1983, A39, 158. (211 Sheldrick. G. M. SHELX76 Program for Crvstal Structure Determinations; University of Cambridge: Cambridge, England, 1976. ~

Scheme 1

&7&-lY

THF, reflux

1a.b

%

\ 25 "C

/

THF, reflux

a; Y = BPhj b; Y = PF,

Table 1. 31PVH1NMR SDectral Data for the New Comulexes" coupling const, Hz patchem shift, ppmb plex tern PA) NPM) W Q ) J(PAPM) J(PAPQ) J(PMPQ) 2+ AM2 -l(br) -9(br) AMQC -0.7 -8.0 -9.2 11.0 6.2 17.0 3+ A3 -0S(br) AMzd -11.2 4.9 14.6 5' AM2 0.3 -16.4 16.6 8 AM2 -2.3 -25.3 14.4 92+ AM2 3.3(br) 8.8(br) AMf 3.6 9.0 9.2 11 AMQ -5.3 -32.7 -51.1 16.6 3.0 14.6 12 AMQ -11.2 -28.4 -35.4 21.8 7.5 34.2 13+ A3 -6S(br) A M g l(br) -ll(br) AMQC l(br) -8(br) -13(br) AMQd -3.4 -12.0 -23.4 26.8 8.6