Preparation and Reactivity of Stannyl Complexes of Ruthenium (II

Article pubs.acs.org/Organometallics

Preparation and Reactivity of Stannyl Complexes of Ruthenium(II) Stabilized by an Indenyl Ligand Gabriele Albertin,*,† Stefano Antoniutti,† Jesús Castro,‡ and Sebastiano Da Lio† †

Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia, Dorsoduro 2137, 30123 Venezia, Italy Departamento de Quı ́mica Inorgánica, Universidade de Vigo, Facultade de Quı ́mica, Edificio de Ciencias Experimentais, 36310 Vigo (Galicia), Spain

‡

S Supporting Information *

ABSTRACT: Trichlorostannyl complexes Ru(SnCl3 )(η 5 -C 9H 7 )(PPh3)L (1; L = P(OMe)3, P(OEt)3) were prepared by allowing chloro compounds RuCl(η5-C9H7)(PPh3)L to react with SnCl2·2H2O in ethanol. Treatment of compounds 1 with NaBH4 in ethanol yielded the tin trihydride derivatives Ru(SnH3)(η5-C9H7)(PPh3)L (2). The reaction of trichlorostannyl complexes 1 with MgBrMe in diethyl ether afforded the chlorodimethylstannyl derivatives Ru(SnClMe2)(η5C9H7)(PPh3)L (3), whereas reaction with Li+CCPh− in THF yielded the trialkynylstannyl compounds Ru[Sn(CCPh)3](η5-C9H7)(PPh3)L (4). Treatment of the trihydridostannyl complexes 2 with the alkyl propiolate HCCCOOR led to the trivinylstannyl derivatives Ru[Sn{C(COOR)CH2}3](η5-C9H7)(PPh3)L (5, 6; R = Me, Et). However, the reaction of [Ru]−SnH3 (2) with the propargylic alcohol HCCCPh2OH yielded the alkene H2C C(H)CPh2OH and the hydride RuH(η5-C9H7)(PPh3)L (7). Treatment of tin trihydride complexes 2 with H2O led to the trihydroxostannyl derivatives Ru[Sn(OH)3](η5-C9H7)(PPh3)L (8). Protonation of [Ru]−SnH3 (2) with triflic acid (HOTf) produced the very unstable dihydridostannyl compound Ru[SnH2(OTf)](η5-C9H7)(PPh3)L (9). Stabilization of SnH2 species was achieved by protonation with HOTf at −30 °C of the cyclopentadienyl compound Ru(SnH3)(η5-C5H5)(PPh3)[P(OMe)3], which yielded the complex Ru[SnH2(OTf)](η5-C5H5)(PPh3)[P(OMe)3] (10a). The complexes were characterized by spectroscopy (IR and 1H, 31P, 13C, and 119Sn NMR data) and by X-ray crystal structure determinations of Ru[Sn(CCPh)3](η5C9H7)(PPh3)[P(OEt)3] (4b) and Ru[Sn(OH)3](η5-C9H7)(PPh3)[P(OEt)3] (8b).

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INTRODUCTION

and thermally unstable tin dihydride complexes ([Ru]− SnH2(OTf)), are reported here.

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The chemistry of transition-metal stannyl complexes has long been under development,1−4 both because there is general interest in compounds containing trihalogen (SnX3), triorgano (SnR3), and recently2e,5 trihydride (SnH3) groups as ligands and because introduction of a stannyl group often changes the properties of complexes and may modify the activity of noblemetal catalysts.4 Our ongoing interest5,6 in the chemistry of stannyl complexes of the iron triad recently led to the synthesis and reactivity of numerous organostannyl ([M]−SnR3) and trihydridostannyl ([M]−SnH3) derivatives stabilized by the half-sandwich fragments6 M(η5-C5H5)(PPh3)L and M(η6-pcymene)(PPh3)L (L = phosphite), containing cyclopentadienyl and p-cymene as supporting ligands. We have now extended these studies to include the half-sandwich indenyl fragment7 M(η5-C9H7)(PPh3)L and found that this ligand can stabilize not only trihydrido- and triorganostannyl groups but also trihydroxystannyl (Sn(OH) 3 ) and dihydridostannyl (SnH2(OTf)) groups. Our results on the synthesis of the first trihydridostannyl species stabilized by an indenyl ligand and their reactions, leading to trihydroxostannyl ([Ru]−Sn(OH)3) © 2013 American Chemical Society

EXPERIMENTAL SECTION

General Comments. All synthetic work was carried out under an appropriate atmosphere (Ar, N2) with standard Schlenk techniques or in an inert-atmosphere drybox. Once isolated, the complexes were found to be relatively stable in air but, being thermically rather unstable, were stored under nitrogen at −25 °C. All solvents were dried over appropriate drying agents, degassed on a vacuum line, and distilled into vacuumtight storage flasks. RuCl3·3H2O was a Pressure Chemical Co. (USA) product, used as received. The phosphites P(OMe)3 and P(OEt)3 were Aldrich products, purified by distillation under nitrogen. Other reagents were purchased from commercial sources in the highest available purity and used as received. Infrared spectra were recorded on a Perkin-Elmer Spectrum-One FT-IR spectrophotometer. NMR spectra (1H, 13C, 31P, 119Sn) were obtained on an AVANCE 300 Bruker spectrometer at temperatures between −90 and +30 °C, unless otherwise noted. 1H and 13C spectra are referred to internal tetramethylsilane; 31P{1H} chemical shifts are reported with respect to 85% H3PO4 and 119Sn shifts with respect to Sn(CH3)4, and in both cases downfield shifts were considered positive. Received: April 2, 2013 Published: June 25, 2013 3651

dx.doi.org/10.1021/om400273y | Organometallics 2013, 32, 3651−3661

Organometallics

Article

All δ values are given in ppm and all J values in Hz. COSY, HMQC, and HMBC NMR experiments were performed with standard programs. The iNMR software package8 was used to treat NMR data. The conductivity of 10−3 mol dm−3 solutions of the complexes in CH3NO2 at 25 °C was measured on a Radiometer CDM 83 instrument. Elemental analyses were determined by the Microanalytical Laboratory of the Dipartimento di Scienze del Farmaco, University of Padova , Padova, Italy. Synthesis of Complexes. The indenyl complex RuCl(η5-C9H7)(PPh3)2 was prepared following the method previously reported.9 RuCl(η5-C9H7)(PPh3)L (L = P(OMe)3, P(OEt)3). An excess of the appropriate phosphite P(OR)3 (6.45 mmol) was added to a solution of RuCl(η5-C9H7)(PPh3)2 (1.00 g, 1.29 mmol) in thf (30 mL), and the reaction mixture was refluxed for 30 min. The solvent was removed under reduced pressure to give an oil, which was triturated with the appropriate alcohol, MeOH or EtOH (5 mL). Cooling the resulting solution to −25 °C yielded an orange solid, which slowly separated out (2−3 days) and was filtered and crystallized from CH2Cl2 and alcohol; yield ≥75%. L = P(OMe)3: 1H NMR (CD2Cl2, 25 °C) δ 7.65−7.25 (m, 15H, Ph), 6.91 (t m, 2H, H5+H6 Ind), 6.61 (d, 2H, H4+H7 Ind), 5.26 (m, 1H, H2 Ind), 3.46 (d, 9H, CH3), 3.42 (s br, 2H, H1+H3 Ind) ppm; 31 1 P{ H} NMR (CD2Cl2, 25 °C) δ AB spin syst, δA 152.7, δB 49.0, JAB = 75.3. Anal. Calcd for C30H31ClO3P2Ru (638.04): C, 56.47; H, 4.90; Cl, 5.56. Found: C, 56.66; H, 4.81; Cl, 5.70. L = P(OEt)3: 1H NMR (CD2Cl2, 25 °C) δ 7.50−7.25 (m, 15H, Ph), 6.85 (t m, 2H, H5+H6 Ind), 6.62 (d, 2H, H4+H7 Ind), 5.23 (m br, 1H, H2 Ind), 3.83 (m, 6H, CH2), 3.36 (s br, 2H, H1+H3 Ind), 1.10 (t, 9H, CH3); 31P{1H} NMR (CD2Cl2, 25 °C) δ AB, δA 147.5, δB 49.4, JAB = 76.5. Anal. Calcd for C33H37ClO3P2Ru (680.12): C, 58.28; H, 5.48; Cl, 5.21. Found: C, 58.43; H, 5.37; Cl, 5.39. Ru(SnCl3)(η5-C9H7)(PPh3)L (L = P(OMe)3 (1a), P(OEt)3 (1b)). In a 25 mL three-necked round-bottomed flask were placed solid samples of the appropriate chloro compound RuCl(η5-C9H7)(PPh3)L (1.0 mmol), an excess of SnCl2·2H2O (3.0 mmol, 0.68 g), and 20 mL of ethanol. The reaction mixture was refluxed for 2 h, and then the volume was reduced to about 5 mL by evaporation under reduced pressure. The yellow solid that separated out by warming the mixture to room temperature was filtered and crystallized from CH2Cl2 and alcohol; yield ≥85%. 1a: 1H NMR (CD2Cl2, 25 °C) δ 7.94−7.32 (m, 15H, Ph), 6.98 (t m, 2H, H5+H6 Ind), 5.92 (d, 2H, H4+H7 Ind), 5.68 (br, 1H, H1 or H3 Ind), 5.15 (t, 1H, H2 Ind), 4.53 (br, 1H, H1 or H3 Ind), 3.45 (d, 9H, CH3) ppm; 31P{1H} NMR (CD2Cl2, 25 °C) δ AB, δA 148.0, δB 51.0, JAB = 61.2, J31PA117Sn = 557.6, J31PB117Sn = 294.2; 13C{1H} NMR (CD2Cl2, 25 °C) δ 134−127 (m, Ph), 129.94 (s br, C5+C6 Ind), 122.17 (s br, C4+C7 Ind), 110.68 (s, C7a Ind), 105.70 (s, C3a Ind), 89.45 (d, C2 Ind), 70.19 (s, C1 Ind), 67.95 (d, C3 Ind), 57.2 (s, CH3); 119 Sn NMR (CD2Cl2, 25 °C) δ ABM, δM −44.4, JAM = 582.8, JBM = 308.0. Anal. Calcd for C30H31Cl3O3P2RuSn (827.65): C, 43.54; H, 3.78; Cl, 12,85. Found: C, 43.38; H, 3.90; Cl, 12.66%. 1b: 1H NMR (CD2Cl2, 25 °C) δ 7.94−7.30 (m, 15H, Ph), 6.92 (t, 2H, H5+H6 Ind), 5.82 (d, 2H, H4+H7 Ind), 5.70 (t br, 1H, H1 or H3 Ind), 5.12 (q, 1H, H2 Ind), 4.51 (br, 1H, H1 or H3 Ind), 3.84, 3.75 (m, 6H, CH2), 1.22 (t, 9H, CH3); 31P{1H} NMR (CD2Cl2, 25 °C) δ AB, δA 142.8, δB 50.4, JAB = 61.2, J31PA117Sn = 543.5, J31PB117Sn = 290.0; 13 C{1H} NMR (CD2Cl2, 25 °C) δ 135−125 (m, Ph), 130.1, 129.8 (s, C5+C6 Ind), 127.8, 122.1 (s, C4+C7 Ind), 111.1 (d, JCP = 4.8), 105.3 (dd, JCP = 7.3, JCP = 2.1) (C3a+C7a Ind), 70.3 (s, C2 Ind, J13C119Sn = 92, J13C117Sn = 88), 67.49 (d, C1+C3 Ind, JCP = 7.1), 63.35 (d, CH2), 16.20 (d, CH3); 119Sn NMR (CD2Cl2, 25 °C) δ ABM, δM −52.1, JAM = 570.1, JBM = 302.0. Anal. Calcd for C33H37Cl3O3P2RuSn (869.73): C, 45.57; H, 4.29; Cl, 12.23. Found: C, 45.76; H, 4.18; Cl, 12.07. Ru(SnH3)(η5-C9H7)(PPh3)L (L = P(OMe)3 (2a), P(OEt)3 (2b)). An excess of NaBH4 (16 mmol, 0.60 g) was added to a solution of Ru(SnCl3)(η5-C9H7)(PPh3)L (1; 0.80 mmol) in ethanol (10 mL), and the reaction mixture was refluxed for 30 min. The solvent was removed under reduced pressure to give an oil from which the complex was extracted with three 8 mL portions of toluene using a cellulose column

(5 cm) for the filtration. The extracts were evaporated to dryness under reduced pressure to give an oil, which was triturated with ethanol (2 mL). A yellow solid slowly separated out, which was filtered and dried under vacuum; yield ≥55%. 2a: IR (KBr) νSnH 1730 cm−1 (m br); 1H NMR (CD2Cl2, 25 °C) δ 7.55−6.81 (m, 17H, Ph and H5+H6 Ind), 6.73 (d, 2H, H4+H7 Ind), 5.12 (q, 1H, H2 Ind), 4.77 (br, 1H, H1 or H3 Ind), 4.58 (br, 1H, H1 or H3 Ind), ABX3 spin syst (X = 1H), δX 3.57, JAX = JBX = 1.0, J1H117Sn = 1247.5 (3H, SnH3), 3.14 (d, 9H, CH3); 31P{1H} NMR (CD2Cl2, 25 °C) δ AB, δA 160.1, δB 59.5, JAB = 57.1, J31PA117Sn = 352.5, J31PB117Sn = 245.7; 119Sn NMR (CD2Cl2, 25 °C) δ ABMX3, δM −312.5, JAM = 366.9, JBM = 257.7, JAX = JBX =1.0, JMX = 1303.5. Anal. Calcd for C30H34O3P2RuSn (724.32): C, 49.75; H, 4.73. Found: C, 49.62; H, 4.84. 2b: IR (KBr) νSnH 1734 cm−1 (m br); 1H NMR (CD2Cl2, 25 °C) δ 7.35−6.84 (m, 17H, Ph and H5+H6 Ind), 6.64 (d, 2H, H4+H7 Ind), 5.21 (m, 1H, H2 Ind), 4.77 (m, 1H, H1 or H3 Ind), 4.58 (m, 1H or H3, H1 Ind), 3.67, 3.55 (m, 6H, CH2), ABX3 (X = 1H), δX 3.58, JAX = 0.9, JBX = 0.8, J1H117Sn = 1238.9 (3H, SnH3), 1.00 (t, 9H, CH3); 31P{1H} NMR (CD2Cl2, 25 °C) δ AB, δA 153.6, δB 59.1, JAB = 56.0, J31PA117Sn = 352.7, J31PB117Sn = 253.1; 119Sn NMR (CD2Cl2, 25 °C) δ ABMX3, δM −311.7, JAM = 369.2, JBM = 263.9, JAX = JBX = 1.0, JMX = 1297.3. Anal. Calcd for C33H40O3P2RuSn (766.40): C, 51.72; H, 5.26. Found: C, 51.55; H, 5.17%. Ru(SnClMe 2 )(η 5-C9 H 7)(PPh 3)[P(OEt) 3] (3b). An excess of MgBrMe (0.9 mmol, 0.64 mL of a 1.4 mol dm−3 solution in thf) was added to a suspension of Ru(SnCl3)(η5-C9H7)(PPh3)[P(OEt)3] (1b; 0.115 mmol, 100 mg) in diethyl ether (10 mL) cooled to −196 °C. The reaction mixture was warmed to room temperature and stirred for 8 h. The solvent was removed under reduced pressure, leaving an oil from which the complex was extracted with three 10 mL portions of toluene using a cellulose column (3 cm) for the filtration. The extracts were evaporated to dryness to give an oil, which was triturated with ethanol (2 mL). A yellow solid slowly separated out, which was filtered and dried under vacuum: yield ≥45%; 1H NMR (C6D6, 25 °C) δ 7.73−6.95 (m, 15H, Ph), 6.83 (t br, 2H, H5+H6 Ind), 6.44 (d, 2H, H4+H7 Ind), 6.13 (t br, 1H, H2 Ind), 4.96 (s br, 1H, H1 or H3 Ind), 4.51 (s br, 1H, H1 or H3 Ind), 3.68 (m, 6H, CH2), 0.93 (t, 9H, CH3 phos), 0.61 (s, 6H, SnCH3, J1H119Sn = 35.0, J1H117Sn = 33.0); 31P{1H} NMR (C6D6, 25 °C) δ AB, δA 150.6, δB 56.0, JAB = 52.2, J31PA117Sn = 382.5, J31PB117Sn = 239.0; 13C{1H} NMR (C6D6, 25 °C) δ 140−123 (m, Ph), 109.7, 106.0 (s, C3a+C7a Ind), 93.6 (s, C2 Ind), 74.9, 68.0 (d, C1+C3 Ind), 61.3 (d, CH2), 16.1 (d, CH3 phos), 6.25, (d, SnCH3, JCP = 2.8, J13C119Sn = 156.6, J13C117Sn = 150.6); 119Sn NMR (C6D6, 25 °C) δ ABMX6, δM 272.8, JAM = 399.5, JBM = 249.0, JAX = JBX = 0.1, JMX = 36.0. Anal. Calcd for C35H43ClO3P2RuSn (828.90): C, 50.72; H, 5.23; Cl, 4.28. Found: C, 50.54; H, 5.12; Cl, 4.46%. Ru[Sn(CCPh)3](η5-C9H7)(PPh3)L (L = P(OMe)3 (4a), P(OEt)3 (4b)). An excess of lithium acetylide (Li+PhCC−; 1.43 mmol, 1.1 mL of a 1.3 mol dm−3 solution in thf) was added to a suspension of Ru(SnCl3)(η5-C9H7)(PPh3)L (1; 0.24 mmol) in diethyl ether (15 mL) cooled to −196 °C. The reaction mixture was warmed to room temperature and stirred for 3 h, and then the solvent was removed under reduced pressure. From the oil obtained, the complex was extracted with three 10 mL portions of toluene using a cellulose column (3 cm) for the filtration. The extracts were evaporated to dryness, leaving an oil, which was triturated with ethanol (2 mL). A yellow solid slowly separated out, which was filtered and crystallized from toluene and n-hexane; yield ≥75%. 4a: IR (KBr) νCC 2124 cm−1 (m); 1H NMR (CD2Cl2, 25 °C) δ 7.50−7.25 (m, 30H, Ph), 6.92 (t br, 2H, H5+H6 Ind), 6.43 (d, 2H, H4+H7 Ind), 5.35 (m, 1H, H2 Ind), 5.17, 4.81 (br, 2H, H1+H3 Ind), 3.48 (d, 9H, CH3); 31P{1H} NMR (CD2Cl2, 25 °C) δ AB, δA 153.7, δB 55.2, JAB = 59.6, J31PA117Sn = 492.2, J31PB117Sn = 290.9; 13C{1H} NMR (CD2Cl2, 25 °C) δ 143−125 (m, Ph), 128.7 (s, C5+C6 Ind), 122.8 (s, C4+C7 Ind), 108.2, 105.2 (d, C3a+C7a Ind), 106.8 (s, Cβ acetylide, J13C119Sn = 43.1, J13C117Sn = 41.8), 101.0 (d, Cα acetylide, J13C119Sn = 198.0, J13C117Sn = 190.6), 89.5 (s, C2 Ind), 70.8, 69.9 (s, C1+C3 Ind), 53.1 (d, 3652


Organometallics

Article

CH3); 119Sn NMR (CD2Cl2, 25 °C) δ ABM, δM −273.2, JAM = 514.9, JBM = 305.7. Anal. Calcd for C54H46O3P2RuSn (1024.67): C, 63.30; H, 4.52. Found: C, 63.44; H, 4.38. 4b: IR (KBr) νCC 2124 cm−1 (m); 1H NMR (CD3C6D5, 25 °C) δ 7.60−6.95 (m, 30H, Ph), 6.85 (m br, 2H, H5+H6 Ind), 6.19 (d, 2H, H4+H7 Ind), 5.58 (t br, 1H, H2 Ind), 5.05, 4.87 (s, 2H, H1+H3 Ind), 3.87, 3.72 (m, 6H, CH2), 1.08 (t, 9H, CH3); 31P{1H} NMR (CD3C6D5, 25 °C) δ AB, δA 148.4, δB 53.8, JAB = 58.3, J31PA117Sn = 487.0, J31PB117Sn = 302.5; 13C{1H} NMR (CD3C6D5, 25 °C) δ 137−127 (m, Ph + C4 to C7 Ind), 106.7 (s, Cβ acetylide, J13C119Sn = 53.0, J13C117Sn = 51.0), 101.4 (s, Cα acetylide, J13C119Sn = 254.0, J13C117Sn = 240.0), 90.9 (s, C2 Ind), 70.9, 69.8 (d, C1+C3 Ind), 61.1 (d, CH2), 16.1 (d, CH3); 119 Sn NMR (CD3C6D5, 25 °C) δ ABM, δM −274.3, JAM = 508.5, JBM = 316.8. Anal. Calcd for C57H52O3P2RuSn (1066.75): C, 64.18; H, 4.91. Found: C, 64.37; H, 4.78. Ru[Sn{C(COOR)CH2}3](η5-C9H7)(PPh3)L (R = Me, L = P(OMe)3 (5a), P(OEt)3 (5b); R = Et, L = P(OMe)3 (6a), P(OEt)3 (6b)). An excess of the alkyl propiolate HCCCOOR (1.6 mmol) was added to a solution of the appropriate complex Ru(SnH3)(η5C9H7)(PPh3)L (2; 0.12 mmol) in toluene (10 mL), and the reaction mixture was stirred at room temperature for 20 h. The solvent was removed under reduced pressure to give an oil, which was triturated with ethanol (2 mL). A yellow solid slowly separated out, which was filtered and crystallized from toluene and n-hexane; yield ≥70%. 5a: IR (KBr) νCO 1699 cm−1 (s); 1H NMR (CD2Cl2, 25 °C) δ 7.81−6.88 (m, 19H, Ph and H4 to H7 Ind), AB, δA 6.36, δB 5.48, JAB = 3.3, J1HA119Sn = 106.9, J1HB119Sn = 49.1, J1HA117Sn = 101.6, J1HB117Sn = 47.4 (6H, CH2 vinyl), 5.96 (t br, 1H, H2 Ind), 4.99, 4.09 (s br, 2H, H1+H3 Ind), 3.56 (s, 9H, CH3COO), 3.45 (d, 9H, CH3 phos); 31P{1H} NMR (CD2Cl2, 25 °C) δ AB, δA 153.8, δB 56.1, JAB = 55.9, J31PA117Sn = 392.7, J31PB117Sn = 241.6; 13C{1H} NMR (CD2Cl2, 25 °C) δ 173.15 (s, Cγ COOR, J13C119Sn = 32.0, J13C117Sn = 30.0), 152.97 (s, Cα vinyl, J13C119Sn = 188.0, J13C117Sn = 181.0), 134.99 (s, Cβ vinyl, J13C119Sn = 20.0, J13C117Sn = 19.0), 134−127 (m, Ph and C5+C6 Ind), 122.8 (s, C4+C7 Ind), 110.0, 105.5 (s, C3a+C7a Ind), 90.0 (br), 66.95 (d, JCP = 7.3) (C1+C3 Ind), 72.75 (d, C2 Ind, JCP = 15.0), 53.1 (d, CH3 phos), 51.1 (s, CH3COO); 119Sn NMR (CD2Cl2, 25 °C) δ ABM, δM −94.0, JAM = 409.4, JBM = 253.8. Anal. Calcd for C42H46O9P2RuSn (976.54): C, 51.66; H, 4.75. Found: C, 51.45; H, 4.88%. 5b: IR (KBr) νCO 1697 cm−1 (s); 1H NMR (C6D6, 25 °C) δ 7.16− 6.85 (m, 17H, Ph and H5+H6 Ind), AB, δA 6.79, δB 5.85, JAB = 3.4, J1HA119Sn = 105.9, J1HB119Sn = 49.0, J1HA117Sn = 101.4, J1HB117Sn = 47.2 (6H, CH2 vinyl), 6.61 (d, 2H, H4+H7 Ind), 6.33 (t br, 1H, H2 Ind), 5.17, 4.61 (s, 2H, H1+H3 Ind), 3.72, 3.62 (m, 6H, CH2 phos), 3.53 (s, 9H, CH3COO), 0.95 (t, 9H, CH3 phos); 31P{1H} NMR (C6D6, 25 °C) δ AB, δA 149.9, δB 53.9, JAB = 55.0, J31PA117Sn = 385.5, J31PB117Sn = 247.5; 119 Sn NMR (C6D6, 25 °C) δ ABM, δM −86.0, JAM = 402.5, JBM = 259.5. Anal. Calcd for C45H52O9P2RuSn (1018.62): C, 53.06; H, 5.15. Found: C, 56.23; H, 5.06. 6b: IR (KBr) νCO 1697 (s) cm−1; 1H NMR (CD3C6D5, 25 °C) δ 7.30−6.80 (m, 17H, Ph and H5+H6 Ind), AB, δA 6.70, δB 5.76, JAB = 3.2, J1HA119Sn = 105.8, J1HB119Sn = 49.9, J1HA117Sn = 101.8, J1HB117Sn = 47.9 (6H, CH2 vinyl), 6.55 (t, 2H, H4+H7 Ind), 6.24 (t br, 1H, H2 Ind), 5.16, 4.46 (s br, 2H, H1+H3 Ind), 4.10 (q, 6H, CH2 COOEt), 3.74, 3.68 (m, 6H, CH2 phos), 1.16 (t, 9H, CH3 COOEt), 1.01 (t, 9H, CH3 phos); 31P{1H} NMR (CD3C6D5, 25 °C) δ AB, δA 150.2, δB 53.4, JAB = 55.0, J31PA117Sn = 380.0, J31PB117Sn = 249.0; 119Sn NMR (CD3C6D5, 25 °C) δ ABM, δM −84.5, JAM = 397.0, JBM = 259.3. Anal. Calcd for C48H58O9P2RuSn (1060.70): C, 54.35; H, 5.51. Found: C, 54.17; H, 5.64. RuH(η5-C9H7)(PPh3)[P(OEt)3] (7b) and H2CC(H)CPh2(OH). In a 25 mL three-necked round-bottomed flask were placed 100 mg (0.13 mmol) of Ru(SnH3)(η5-C9H7)(PPh3)[P(OEt)3] (2b), an excess (0.7 mmol, 0.15 g) of the propargylic alcohol HCCC(OH)Ph2, and 5 mL of toluene. The reaction mixture was stirred for 24 h, the solvent was removed under reduced pressure, and the oil obtained was chromatographed on a 50 cm cellulose column, using petroleum ether

(40−60 °C) as eluent. The first fraction that eluted was colorless and gave, after evaporation of the solvent, the alkene H2CCC(OH)Ph2. The second fraction that eluted was orange and was evaporated to dryness, leaving an oil, which was triturated with ethanol (2 mL). An orange solid slowly separated out by cooling the resulting solution to −25 °C, which was filtered and dried under vacuum; yield ≥55%. 7b: 1H NMR (C6D6, 25 °C) δ 7.54−6.95 (m, 19H, Ph and H4 to H7 Ind), 5.74 (br, 1H, H2 Ind), 4.81, 4.64 (br, 2H, H1+H3 Ind), 3.97, 3.71 (m, 6H, CH2), 1.04 (t, 9H, CH3), −15.27 (dd, 1H, RuH, JPH = 14.0, JPH = 13.4); 31P{1H} NMR (C6D6, 25 °C) δ AB, δA 166.6, δB 67.3, JAB = 53.5. Anal. Calcd for C30H32O3P2Ru (603.59): C, 59.70; H, 5.34. Found: C, 59.54; H, 5.22. H2CC(H)CPh2(OH): 1H NMR (C6D6, 25 °C) δ ABC, δA 6.30, δB 5.26, δC 5.08, JAB = 17.0, JAC = 10.30, JBC = 1.50. Ru[Sn(OH)3](η5-C9H7)(PPh3)L (L = P(OMe)3 (8a), P(OEt)3 (8b)). An excess of H2O (10 μL, 0.55 mmol) was added to a solution of the appropriate complex Ru(SnH3)(η5-C9H7)(PPh3)L (2; 0.14 mmol) in toluene (15 mL), and the reaction mixture was stirred for 48 h. The solvent was removed under reduced pressure to give an oil, which was triturated with ethanol (2 mL). An orange solid slowly separated out, which was filtered and crystallized from toluene and n-hexane; yield ≥65%. 8a: 1H NMR (CD2Cl2, 25 °C) δ 7.93−7.05 (m, 17H, Ph+H5+H6 Ind), 6.44 (d, 2H, H4+H7 Ind), 5.97 (br, 1H, H2 Ind), 5.64, 5.31 (br, 2H, H1+H3 Ind), 3.68 (d, 9H, CH3); 31P{1H} NMR (CD2Cl2, 25 °C) δ AB, δA 152.9, δB 52.2, JAB = 52.2; 119Sn NMR (CD2Cl2, 25 °C) δ −112.0 (m br). Anal. Calcd for C30H34O6P2RuSn (772.31): C, 46.65; H, 4.44. Found: C, 46.82; H, 4.35. 8b: 1H NMR (CD2Cl2, 25 °C) δ 7.52−7.00 (m, 15H, Ph), 6.94 (t, 2H, H5+H6 Ind), 6.32 (d, 2H, H4+H7 Ind), 5.45 (br, 1H, H2 Ind), 5.21, 4.63 (br, 2H, H1+H3 Ind), 3.84, 3.70 (m, 6H, CH2), 1.18 (t, 9H, CH3); 1H NMR (CD2Cl2, −70 °C) δ 7.75−6.85 (m, 17H, Ph+H5+H6 Ind), 6.01 (br, 2H, H4+H7 Ind), 5.62 (br, 1H, H2 Ind), 5.13, 4.42 (br, 2H, H1+H3 Ind), 4.68 (br, 3H, OH), 3.75, 3.55 (br, 6H, CH2), 1.12 (t br, 9H, CH3); 31P{1H} NMR (CD2Cl2, 25 °C) δ AB, δA 149.6, δB 56.2, JAB = 56.0, J31PA117Sn = 568.0, J31PB117Sn = 322.5; 119Sn NMR (CD2Cl2, 25 °C) δ ABM, δM −74.0, JAM = 590.0, JBM = 341.5. Anal. Calcd for C33H40O6P2RuSn (814.40): C, 48.67; H, 4.95. Found: C, 48.46; H, 5.07. Protonation of Ru(SnH3)(η5-C9H7)(PPh3)[P(OEt)3] (2b) with HOTf: Synthesis of Ru[SnH2(OTf)](η5-C9H7)(PPh3)[P(OEt)3] (9b). A solution of Ru(SnH3)(η5-C9H7)(PPh3)[P(OEt)3] (2b; 40 mg, 0.052 mmol) in 1 mL of CD2Cl2 was placed in a 5 mm NMR tube closed with a septum cap and cooled to −40 °C. One equivalent of triflic acid (0.052 mmol, 4.6 μL) was added, the tube was placed into the probe of the NMR instrument precooled to −40 °C, and the spectra were recorded: 1H NMR (CD2Cl2, −40 °C) δ 6.08 (s br, 2H, SnH2); 31 1 P{ H} NMR (CD2Cl2, −40 °C) δ AB, δA 143.2, δB 46.7, JAB = 57.0. Ru(SnH3)(η5-C5H5)(PPh3)[P(OMe)3]. This complex was prepared following the method previously reported:6a 1H NMR (CD2Cl2, 25 °C) δ 7.31 (m, 15H, Ph), 4.57 (s, 5H, Cp), 3.21 (d, 9H, CH3), 2.83 (d, 3H, SnH3); 31P{1H} NMR (CD2Cl2, 25 °C) δ AB, δA 165.0, δB 60.3, JAB = 59.5. Ru[SnH2(OTf)](η5-C5H5)(PPh3)[P(OMe)3] (10a). This complex is thermally unstable and can only be prepared at low temperature (≤−30 °C). Method 1. One equivalent of triflic acid (HOTf; 13 μL, 0.148 mmol) was added to a solution of the complex Ru(SnH3)(η5C5H5)(PPh3)[P(OMe)3] (100 mg, 0.148 mmol) in toluene (5 mL) cooled to −196 °C. The reaction mixture was brought to −30 °C and stirred for 90 min at that temperature. A gummy yellow solid separated out which, after settling of the solvent, was recovered and kept at −30 °C. Method 2. A solution of Ru(SnH3)(η5-C5H5)(PPh3)[P(OMe)3] (0.047 mmol, 32 mg) in 1 mL of CD2Cl2 was placed in a 5 mm NMR tube closed with a septum cap and cooled to −30 °C. One equivalent of triflic acid (0.047 mmol, 4.2 μL) was added, the tube was placed in the probe of the NMR spectrometer precooled to −30 °C, and the spectra were recorded. 3653


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10a: IR (KBr) νSnH 1812 cm−1 (m br); 1H NMR (CD2Cl2, −30 °C) δ 8.97 (s br, 2H, SnH2), 7.38 (m, 15H, Ph), 4.82 (s, 5H, Cp), 3.33 (d, 9H, CH3); 31P{1H} NMR (CD2Cl2, −30 °C) δ AB, δA 161.3, δB 57.6, JAB = 54.1, J31PA117Sn = 466.8, J31PB117Sn = 286.4; 119Sn NMR (CD2Cl2, −30 °C) δ ABMX2, δM 266.6, JAM = 487.4, JBM = 300.6, JAX = JBX = 0.1, JMX = 1414.5. Crystal Structure Determination of 4b and 8b. Crystallographic data were collected on a Bruker Smart 1000 CCD diffractometer at CACTI (Universidade de Vigo) with graphitemonochromated Mo Kα radiation (λ = 0.71073 Å) and were corrected for Lorentz and polarization effects. SMART10 software was used for collecting data frames, indexing reflections, and determining lattice parameters, SAINT11 for integration of intensity of reflections and scaling, and SADABS12 for empirical absorption correction. The structure of 4b was solved by direct methods according to SIR2004,13 implemented in the WingX package14 and refined by full-matrix least squares on all F2 values with SHELXL9715 according to the Oscail suite.16 The crystallographic treatment of 8b was performed with the Oscail program.16 The structure was solved by direct methods and refined by full-matrix least squares based on F2.15 Two molecules were found in the asymmetric unit, with different arrangements of the indenyl ligand. In both cases, the Squeeze program17 was used to correct the reflection data for diffuse scattering due to disordered solvent. Non-hydrogen atoms were refined with isotropic thermal parameters. Hydrogen atoms were included in idealized positions and refined with isotropic displacement parameters. Details of crystal data and structural refinement are given in Table 1.

■

Table 1. Crystal Data and Structure Refinement Details 4b empirical formula formula wt temp, K wavelength, Å cryst syst space group unit cell dimens a, Å b, Å c, Å α, deg β, deg γ, deg V, Å3 Z calcd density, Mg/m3 abs coeff, mm−1 F(000) cryst size, mm θ range for data collection, deg index ranges

RESULTS AND DISCUSSION

no. of rflns collected no. of indep rflns

Preparation of Stannyl Complexes. Indenyl complexes RuCl(η5-C9H7)(PPh3)L were reacted with an excess of SnCl2·2H2O in ethanol to give the trichlorostannyl derivatives Ru(SnCl3)(η5-C9H7)(PPh3)L (1) in good yields (Scheme 1). The reaction involves the well-known insertion of SnCl2 into a Ru−Cl bond, affording the stannyl derivative 1. Treatment of [M]−SnCl3 complexes 1 with NaBH4 in ethanol yielded the trihydridostannyl derivatives Ru(SnH3)(η5-C9H7)(PPh3)L (2), which were isolated and characterized (Scheme 1). Substitution of the three chlorides in the SnCl3 group with H− was easy in the presence of NaBH4, affording stable trihydridostannyl derivatives 2 in good yields. The formation of 2 highlights the fact that the indenyl ligand can also stabilize tin trihydride complexes but, in contrast to the related cyclopentadienyl group,6a it requires the presence of both triphenylphosphine and phosphite in the fragment Ru(η5C9H7)(PPh3)L to give stable [M]−SnH3 derivatives. The use of the bis(triphenylphosphine) fragment Ru(η5-C9H7)(PPh3)2 yielded no stable SnCl3 or SnH3 derivatives. The new stannyl complexes 1 and 2 were separated as orange solids, stable in air and in solution of common organic solvents, where they behave as nonelectrolytes. Analytical and spectroscopic data (IR, NMR) support their formulation. In particular, the 1H NMR spectra of Ru(SnCl3)(η5-C9H7)(PPh3)L (1) showed the characteristic signals of both the indenyl group and the phosphine ligands, whereas the 31P spectra showed an AB quartet with 119Sn and 117Sn satellites. The 119Sn NMR spectra displayed a multiplet at −44.4 to −52.1 ppm, which could be simulated with an ABM model (M = 119Sn; A, B = 31P), matching the proposed formulation. The IR spectra of the trihydridostannyl complexes Ru(SnH3)(η5-C9H7)(PPh3)L (2) showed a medium-intensity, broad band at 1734−1730 cm−1, attributed to the νSnH of the SnH3 ligand. However, the presence of this group was confirmed by the 1H NMR spectra, which showed a multiplet at 3.58−3.57 ppm with the characteristic 119Sn and 117Sn

no. of rflns obsd (>2σ(I)) data completeness abs cor max and min transmission refinement method no. of data/restraints/ params goodness of fit on F2 final R indices (I > 2σ(I)) R indices (all data) largest diff peak and hole, e Å−3

Scheme 1.

a

8b

C57H52O3P2RuSn 1066.69 293(2) 0.71073 triclinic P1̅

C66H80O12P4Ru2Sn2 1628.70 293(2) 0.71073 monoclinic P2/n

10.790 14.526 19.564 71.58 82.00 79.27 2847.8 2 1.244 0.797 1084 0.42 × 0.13 × 0.08 1.49−25.09

20.9107(17) 14.9193(12) 25.726(2) 90 99.978(2) 90 7904.5(11) 4 1.369 1.130 3280 0.48 × 0.22 × 0.08 1.36−28.04

−12 ≤ h ≤ 12 −27 ≤ h ≤ 26 −17 ≤ k ≤ 17 −19 ≤ k ≤ 19 −23 ≤ l ≤ 23 −33 ≤ l ≤ 32 21896 73430 10029 (R(int) = 18986 (R(int) = 0.0334) 0.0605) 6422 10497 0.989 0.991 semiempirical from equivalents 0.7452 and 0.6930 0.7456 and 0.6169 full-matrix least squares on F2 10029/0/580 18986/0/787 0.978 R1 = 0.0401, wR2 = 0.0958 R1 = 0.0742, wR2 = 0.1069 0.790 and −0.391

1.015 R1 = 0.0470, wR2 = 0.1113 R1 = 0.0968, wR2 = 0.1257 2.650 and −1.996

a

L = P(OMe)3 (a), P(OEt)3 (b).

satellites, attributed to the resonance of SnH3. The protoncoupled 119Sn spectra further supported the presence of this ligand, showing a quartet of quartets at −312.5 (2a) and −311.5 (2b) ppm, due to coupling with the three hydrides and 3654


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with the two inequivalent phosphorus nuclei of the phosphines. As the 31P spectrum was an AB quartet, the 119Sn spectra could be simulated with an ABMX3 model (X = 1H), matching the proposed formulation. The easy substitution of the tin-bonded chloride by H− in [M]−SnCl3 complexes, yielding the trihydridostannyl derivatives 2, prompted us to test the reaction with other nucleophiles, in an attempt to prepare new organostannyl derivatives. The results showed that complexes Ru(SnCl3)(η5C9H7)(PPh3)L (1) react with reagents such as MgBrMe and Li+PhCC− to give dimethylstannyl and trialkynylstannyl complexes Ru(SnClMe2)(η5-C9H7)(PPh3)L (3) and Ru[Sn(CCPh)3](η5-C9H7)(PPh3)L (4), respectively, which were isolated in good yields and characterized (Scheme 2). Scheme 2.

a

Figure 1. ORTEP view of 4b. P1 represents a PPh3 ligand, and P2 represents a P(OEt)3 ligand. Selected bond distances (Å): Ru(1)− Sn(1), 2.5697(4); Ru(1)−Ct(centroid at Cp of indenyl), 1.9252(3); Ru(1)−P(1), 2.3204(11); Ru(1)−P(2), 2.2085(12); C(11)−C(12), 1.201(6); C(12)−C(13), 1.427(7); C(21)−C(22), 1.174(6). Selected bond angles (deg): Ct−Ru(1)−P(1), 126.09(3); Ct−Ru(1)−P(2), 125.64(4); P(2)−Ru(1)−P(1), 94.31(5); Ct−Ru(1)−Sn(1), 116.198(15); P(2)−Ru(1)−Sn(1), 91.43(4); P(1)−Ru(1)−Sn(1), 94.37(3). a

L = P(OMe)3 (a), P(OEt)3 (b).

the fold angle Ω of 5.8(5)° (vide infra; the fold angle Ω is defined as the angle between the plane of carbon atoms 1−3 and carbon atoms 1 and 3−5, where C(4) and C(5) are the hinge carbon atoms).7c,18 The absence of envelope deformation and the planarity of the pentagon were also confirmed by the value of the rms deviation of only 0.047 Å, confirming the η5 coordination mode of the ruthenium−carbon bond lengths, since the average between the two sets of distances (ΔM−C) differs by only 0.127 Å when Ru−C(1), Ru−C(2), and Ru− C(3) are compared with Ru−C(4) and Ru−C(5). Reported Ru−C and Ru−Ct distance values for Ru(η 5-indenyl) complexes19 are similar to those found in 4b. T h e st a n n y l l i g a n d is w o r t h y o f n o t e . T r i s (phenylacetylenide)stannyl complex 4b shows a Ru−Sn bond length of 2.5697(4) Å, which is comparable to that found in 8b (vide infra) or those in trichloro derivatives2j,k but shorter than those of trimethyl5c or triphenyl20 derivatives. To the best of our knowledge, there is only one example of a crystallographically characterized tris(phenylacetylenide)stannyl complex. It contains manganese, and the geometrical parameters of the stannyl ligand are similar to those found in 4b.2l,21 The average Sn−C bond length, 2.133(5) Å, is consistent with a single bond, where the sum of covalent radii of 2.11 Å22 and the short bond lengths (average 1.188(6) Å) of the α- and βcarbons of the acetylide fragment are as expected for a triple bond. These statements are made considering the values of the Sn−C−C and C−C−C bond angles of almost 180°; therefore, we can conclude that these carbon atoms have sp character. Regarding the disposition of the ligands around the metal for η5-indenyl, we find the stannyl ligand trans to the six-membered ring; therefore, this may be the ligand with higher trans influence,18 although steric requirements should be taken into consideration.

The reaction proceeded with substitution of tin-bonded chlorides with either methyl or acetylide, to give organostannyl derivatives 3 and 4. Note that the reaction with MgBrMe gave rise to the substitution of only two Cl− in the [Ru]−SnCl3 group, affording dimethyl derivatives Ru(SnClMe2)(η5-C9H7)(PPh3)L (3) as the final product. Organostannyl complexes 3 and 4 were isolated as yelloworange solids, stable in air and in solution of common organic solvents, where they behave as nonelectrolytes. Their formulation was supported by analytical and spectroscopic data (IR and NMR) and by an X-ray crystal structure determination of Ru[Sn(CCPh) 3 ](η 5 -C 9 H 7 )(PPh 3 )[P(OEt)3] (4b), an ORTEP drawing of which is shown in Figure 1. Trialkynylstannyl complexes of Ru and Os were previously prepared by us6a with either cyclopentadienyl (Cp) or tris(pyrazolyl)borate (Tp) as supporting ligands, but no suitable crystals for X-ray determination were obtained. In the present case, using the indenyl ligand allowed the structural characterization of one stannyl compound of this type. The complex consisted of a ruthenium atom in a halfsandwich piano-stool structure, coordinated by a η5-indenyl ligand and as the legs one tris(phenylacetylenide)stannyl ligand and two phosphine groups: one PPh3 and one P(OEt)3. The overall geometry of the complex is well-known to be octahedral and is marked by values near 90° for the angles P−Ru−P and Sn−Ru−P, between 91.43(4) and 94.37(3)°. The coordinative behavior of the indenyl ligand shows that the metal is centered in a η5 fashion, with scarce or no slippage, as demonstrated by the small difference between the Ru−Ct distance and that from the Ru atom to the best plane formed by the five carbon atoms (1.9252(3) vs 1.920(2) Å) or, mainly, by 3655


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Spectroscopic data (IR and NMR) of the tris(acetylide)stannyl complexes Ru[Sn(CCPh)3](η5-C9H7)(PPh3)L (4) indicated that a geometry like that found in the solid state was also present in solution. The IR spectra showed a mediumintensity band at 2124 cm−1 attributed to the νCC band of the Sn(CCPh)3 group. The presence of this ligand was confirmed by the 13C NMR spectra, which, in addition to the signals of indenyl and phosphine ligands, show two singlets at 101.0−101.4 and 106.8−106.7 ppm, with the characteristic 119 Sn and 117Sn satellites, attributed to the Cα and Cβ carbon resonances of the acetylide Sn(CCPh)3 groups. Attribution was based on the J13C119Sn values of 254−198 Hz for Cα and 53.0−43.1 Hz for Cβ. The 31P NMR spectra appeared as an AB multiplet, whereas those of 119Sn appeared as a doublet of doublets, which could be simulated with an ABM model, matching the proposed formulation for the complexes. In addition to the signals of indenyl and phosphine ligands, the 1H NMR spectra of the methylstannyl complex Ru(SnClMe2)(η5-C9H7)(PPh3)[P(OEt)3] (3b) showed a singlet at 0.61 ppm with the characteristic 119Sn and 117Sn satellites, attributed to the Sn-bonded methyl groups. The 13C spectra supported this attribution, showing a doublet at 6.25 ppm (J13C31P = 2.8, J13C119Sn = 156.6 Hz) which, in a HMQC experiment, was correlated with the proton singlet at 0.61 ppm, fitting the presence of the SnClMe2 ligand. However, further proof of the presence of the SnClMe2 group came from the proton-coupled 119Sn NMR spectra, which appeared as a quartet of multiplets (septets), due to coupling with the six protons of the two methyls and the two nonequivalent phosphorus nuclei of the phosphines. As the 31P spectrum was an AB2 quartet, that of 119Sn could be simulated with an ABMX6 model (M = 119Sn; X = 1H) and the good fit between the calculated and experimental spectra confirmed the proposed formulation for complex 3b (Figure 2).

Scheme 3.

a

a

R = Me, L = P(OMe)3 (5a), P(OEt)3 (5b); R = Et, L = P(OMe)3 (6a), P(OEt)3 (6b).

probably proceeds by sequential addition of HCCCOOR to Sn−H bonds but is too fast to allow isolation of the mono- and bis(vinyl) intermediates [Ru]−SnH2[C(COOR)CH] and [Ru]−SnH[C(COOR)CH2]2. Although only the tris(vinyl) complex is formed with an excess of alkyne, with an alkyne to [Ru]−SnH3 ratio lower than 3 the product was always a mixture of mono-, di-, and trivinyl complexes, which were not separated. Phenylacetylene was also reacted with trihydridostannyl complexes 2, but in this case no addition product was obtained. As HCCPh is unreactive, we treated the propargylic alcohol HCCCPh2OH with the tin trihydride complex Ru(SnH3)(η5-C9H7)(PPh3)L (2) and found a new reaction, yielding the alkene H2CC(H)CPh2OH and hydride RuH(η5-C9H7)(PPh3)L (7), which were separated in pure form and characterized (Scheme 4). The formation of the alkene and hydride in this reaction was rather surprising and prompted us to monitor the progress of the reaction by NMR in an attempt to detect intermediates. Unfortunately, apart from the alkene H2CC(H)CPh2OH, the hydride RuH(η5-C9H7)(PPh3)L, and traces of unidentified tin compounds, no other species were detected and no reasonable reaction path can therefore be proposed. The reaction of tin trihydride complexes with terminal alkynes was previously reported by us for Mn and Re carbonyl tin complexes5d and for Os p-cymene tin derivatives6b and was shown to yield trivinylstannyl derivatives with activated alkynes HCCCOOR. A similar reaction was also observed in our indenyl complexes Ru(SnH3)(η5-C9H7)(PPh3)L, and this result highlights a new example of the rare reaction5d,6b of the addition of terminal alkyne to a coordinated tin hydride species. In addition, a new reaction was shown by the propargyl alcohol HCCCPh2OH toward the SnH3 group bonded to the indenyl fragment Ru(η5-C9H7)(PPh3)L, yielding the corresponding alkene and hydride RuH(η5-C9H7)(PPh3)L (7). The new trivinylstannyl complexes Ru[Sn{C(COOR) CH2}3](η5-C9H7)(PPh3)L (5, 6) were isolated as orange solids, stable in air and in solution of common organic solvents, where they behave as nonelectrolytes. Analytical and spectroscopic data (IR and 1H, 13C, and 119Sn NMR) supported the proposed formulation. The IR spectra of 5 and 6 showed a strong band at 1699−1697 cm−1, attributed to the νCO band of the ester group C(COOR)CH2. The presence of the vinyl ligand was confirmed by the proton NMR spectra, which showed an AB quartet between 6.79 and 5.48 ppm, with the characteristic satellites of 119Sn and 117Sn, which were attributed to the HX and HY vinyl protons (Scheme 3). JHH values of 3.4− 3.2 Hz are characteristic of the geminal position of the two vinyl protons. A singlet at 3.56−3.53 ppm was also present in the spectra of 5 and was attributed to methyl substituents of

Figure 2. 119Sn NMR spectra of compound Ru(SnClMe2)(η5C9H7)(PPh3)[P(OEt)3] (3b) in C6D6 at 25 °C: (top) simulated spectrum; (bottom) experimental spectrum.

Reaction with Alkynes. Trihydridostannyl derivatives RuCl(SnH3)(η5-C9H7)(PPh3)L (2) were reacted with the alkyl propiolate HCCCOOR to give the trivinylstannyl complexes RuCl[Sn{C(COOR)CH2}3](η5-C9H7)(PPh3)L (5, 6), which were isolated as orange solids and characterized (Scheme 3). The reaction involved the addition of three Sn−H bonds to three alkynes, affording the tris(vinyl) derivatives 5 and 6. It 3656


Organometallics Scheme 4.

a

Article

a

L = P(OEt)3.

probably changes the properties of the tin trihydride ligand in these half-sandwich stannyl complexes, promoting the formation of the hydroxystannyl derivative. Conversely, the known oxophilic nature23,24 of tin compounds supports easy hydrolysis of the SnH3 group, yielding the Sn(OH)3 ligand. Metal complexes containing trihydroxostannyl as ligand are very rare,3k,26 and to the best of our knowledge, none have been reported for ruthenium. The monohydroxystannyl complex Ru[SnMe2(OH)]I(CO)(CN-p-tolyl)(PPh3)227 was obtained by substituting chloride with OH in the SnClMe2 group, but triple substitution has only been reported for the osmium derivative Os[Sn(OH)3](η2-S2CNMe2)(CO)(PPh3)2.3k Hydrolysis of our SnH3 group bonded to an indenyl fragment allows easy synthesis of the first trihydroxystannyl complexes of ruthenium. Complexes 8 were separated as yellow crystalline solids, stable in air and in solution of common organic solvents, where they behave as nonelectrolytes. Analytical and spectroscopic data (IR and NMR) supported the proposed formulation, which was further confirmed by an X-ray crystal structure determination of complex Ru[Sn(OH)3](η5-C9H7)(PPh3)[P(OEt)3] (8b), the ORTEP drawing of which is shown in Figure 3. The solution of the crystalline structure of compound 8b shows two molecules in the asymmetric unit, both consisting of a ruthenium atom in a half-sandwich piano-stool structure, coordinated by a η5-indenyl ligand and as the legs one trihydroxylstannyl ligand and two phosphine ligands: one PPh3 and one P(OEt)3 group. The overall geometry of these kinds of half-sandwich complexes is well-known to be octahedral and is marked by values near 90° for the angles P−Ru−P and Sn− Ru−P, between 89.91(4) and 95.62(3)° for one of the molecules and more distorted values for the other, 88.64(3) and 96.23(3)°. Both molecules differ in their disposition of the indenyl ligand (Figures 1 and 3). The coordinative behavior of the indenyl ligand shows that the metal is centered in a η5 fashion, with little or no slippage, as demonstrated by the fold angle Ω of 5.4(5)° for molecule 1 and 4.8(9)° for molecule 2 (the fold angle Ω defines the angle between the plane of carbon atoms 1−3 and carbon atoms 1 and 3−5, where C(4) and C(5) are the hinge carbon atoms).7c,18 The low value of this angle gives a planar pentagon (there is no envelope deformation), as noted by the rms deviations of the atoms with respect to the best plane, 0.022 and 0.021 Å, respectively. More information about the η5 coordination mode comes from the small difference between the Ru−Ct distance and that from the Ru atom to the best plane formed by the five carbon atoms (1.9255(4) vs 1.914(2) Å and 1.9169(4) vs 1.912(2) Å). Further confirmation comes from the ruthenium−carbon bond lengths: the average between the two sets of distances (ΔM−C) differs only between 0.09 and 0.16 Å when Ru−C(1), Ru−C(2), and Ru−C(3) are compared with Ru−C(4) and Ru−C(5). The Ru−C and Ru−

C(COOMe)CH2, whereas a quartet at 4.10 ppm and a triplet at 1.16 ppm of the ethyl group were found in the spectrum of 6b, fitting the presence of the vinyl group. Further support for the proposed formulation of 5 and 6 came from the 13 C NMR spectra of 5a, which showed three signals at 152.97, 134.99, and 173.15 ppm, each with the characteristic 119Sn and 117 Sn satellites, attributed to the Cα , Cβ and Cγ carbon resonances, respectively, of the Cα(CγOOMe)CβH2 group. This attribution was confirmed by HMQC and HMBC experiments and J13C119Sn values, which ranged between 188.0 Hz for Cα and 20−32 Hz for Cβ and Cγ. The 119Sn NMR spectra showed a doublet of doublets between −94.0 and −84.5 ppm, which could be simulated as an ABM system, matching the proposed formulation. The 1H NMR spectra of the hydride RuH(η5-C9H7)(PPh3)[P(OEt)3] (7b) show the characteristic signals of the indenyl ligand between 5.74 and 4.64 ppm and those of the PPh3 and P(OEt)3 phosphine ligands. In addition, a doublet of doublets was also found at −15.27 ppm, due to the hydride ligand coupled with two nonequivalent phosphorus nuclei of the phosphines. In the temperature range +20 to −80 °C, the 31 1 P{ H} NMR spectrum is an AB quartet, fitting the proposed formulation for the complex. Reactions with Water and Acids. The trihydridostannyl complexes Ru(SnH3)(η5-C9H7)(PPh3)L (2) reacted in solution with H2O to give the trihydroxystannyl complexes Ru[Sn(OH)3](η5-C9H7)(PPh3)L (8), which were isolated as solids and characterized (Scheme 5). Scheme 5.

a

a

L = P(OMe)3 (a), P(OEt)3 (b).

The reaction proceeded with hydrolysis of all three Sn−H bonds, yielding the hydroxystannyl derivative 8. Studies on the progress of the reaction by 1H NMR spectroscopy showed that addition of H2O to [Ru]−SnH3 species 2a caused the disappearance of the signal at 3.57 ppm of the SnH3 group and the appearance of a new signal near 4.6 ppm, which decreased on shaking and was attributed to free H2.25 The signals of trihydroxystannyl complex 8 also appeared in the spectra, suggesting that hydrolysis of tin trihydride proceeds to give [Ru]−Sn(OH)3 as the final product. The formation of trihydroxystannyl complexes Ru[Sn(OH)3](η5-C9H7)(PPh3)L (8) from the reaction of [Ru]−SnH3 species with H2O is somewhat surprising, since the related6a Ru(SnH3)(η5-C5H5)(PPh3)L is stable to hydrolysis and did not afford any [Ru]− Sn(OH)3 derivative. Substitution of the Cp ligand with indenyl 3657


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Figure 3. ORTEP view of 8b. P1 and P21 represent PPh3 ligands, and P2 and P22 represent P(OEt)3 ligands. Selected bond distances (Å): Ru(1)− Ct01, 1.9255(4); Ru(1)−P(1), 2.3138(12); Ru(1)−P(2), 2.2070(13); Ru(1)−Sn(1), 2.5639(5); Ru(2)−Ct02, 1.9169(4); Ru(2)−P(21), 2.3054(12); Ru(2)−P(22), 2.2380(12); Ru(2)−Sn(2), 2.5315(5). Selected bond angles (deg): Ct01−Ru(1)−P(1), 124.61(3); Ct01−Ru(1)−P(2), 124.26(4); P(1)−Ru(1)−P(2), 91.94(4); Ct01−Ru(1)−Sn(1), 121.463(19); P(1)−Ru(1)−Sn(1), 95.62(3); P(2)−Ru(1)−Sn(1), 89.91(4); Ct02− Ru(2)−P(21), 125.41(3); Ct02−Ru(2)−P(22), 126.92(3); P(21)−Ru(2)−P(22), 93.66(4); Ct02−Ru(2)−Sn(2), 116.787(19); P(22)−Ru(2)− Sn(2), 88.64(3); P(21)−Ru(2)−Sn(2), 96.23(3).

−74.0 ppm for 8b (at −112 ppm for 8a), fitting the proposed formulation for the complexes. The evolution of free H2 in the reaction with H2O of the complexes Ru(SnH3)(η5-C9H7)(PPh3)L (2) prompted us to study their protonation with Brønsted acids such as CF3SO3H (HOTf), in order to test whether evolution of H2 is followed by formation of a tin dihydride complex of the type [Ru]SnH2 or [Ru]−SnH2(OTf). The results showed that, at −40 °C in CD2Cl2, species 2 did react with 1 equiv of triflic acid, with the evolution of H2 and probable formation of the dihydridostannyl complex Ru[SnH2(OTf)](η5-C9H7)(PPh3)[P(OEt)3] (9b) (Scheme 6), which was very unstable even at low temperatures and was not fully characterized.

Ct distance values are comparable with those for other Ru(η5indenyl) complexes.19 Together with the spatial arrangement around the ruthenium atom, especially that of the indenyl ligand (vide supra), the stannyl ligand is the most interesting feature in this compound. To the best of our knowledge, the only crystallographically characterized compound containing a Sn(OH)3 as ligand is the trihydroxystannyl -capped cluster [Ni3(μ-dppm)3(μ3-Cl)(μ3Sn(OH)3]26 with Sn−O bond distances (2.039(7) Å) slightly longer than those found in 8b (between 1.976(5) and 2.012(3) Å). The Ru−Sn bond distances in 8b (2.5639(5) and 2.5315(5) Å) are slightly shorter (on average) than those found in formate complexes, such as in the dimeric [Ru(η5C 5 H 5 )[Sn{OC(H)O} 2 (μ-OH)]{P(OEt) 3 }(PPh 3 )] 2̧ (2.5655(3) Å).6a For half-sandwich η5-indenyl complexes, the arrangement of the ligands around the metal is sometimes a matter of discussion. It has been stated that the preferred conformation of the indenyl ligand relative to the ML3 fragment is such that the ligands with the greatest trans influence are trans to the sixmembered ring,18 although steric requirements should be recalled. There are two different molecules in the asymmetric unit of 8b, and one of them contains the stannyl ligand trans to the six-membered ring, but in the other we find the phosphite P(OEt)3 in this position. We conclude that both trans influences and steric requirements in these ligands are similar. At room temperature, the 1H NMR spectra of complexes Ru[Sn(OH)3](η5-C9H7)(PPh3)L (8) show the signals of the indenyl protons between 6.94 and 4.63 ppm, together with those of the phosphine ligands. No resonance attributable to the OH group was observed in the spectra. However, lowering of the sample temperature changed the profiles of the spectra and, at −70 °C, a new, slightly broader resonance at 4.68 ppm appeared for 8b and was attributed to the hydrogens of the stannyl ligand Sn(OH)3. The 31P NMR spectra appear as an AB quartet, with the satellites of 119Sn and 117Sn, whereas the 119Sn NMR spectra appear as an ABM multiplet (M = 119Sn) at

Scheme 6.

a

a

L = P(OEt)3.

Following the protonation of Ru(SnH3)(η5-C9H7)(PPh3)[P(OEt)3] (2b) with HOTf at low temperature (−40 °C) by NMR spectra, it was observed that the addition of a Brønsted acid caused the disappearance of the SnH3 signal at 3.58 ppm and the appearance of two new signals, one near 4.6 ppm, due to free H225 and another at 6.08 ppm, which may be attributed to the tin dihydride group SnH2(OTf) of the hypothesized cationic species 9b (Scheme 6). In order to support the formulation of 9b as a dihydridostannyl complex, the protoncoupled 119Sn NMR spectra at −40 °C of the protonated solution were recorded, but no significant results were obtained. Even at low temperatures, the complex decomposed during spectral acquisition, and no conclusive data on the formation of the tin dihydride complex could be detected. At this point, we thought that the instability of complex 9b might 3658


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model (M = 119Sn; X = 1H) with the parameters given in the Experimental Section, and the good fit between calculated and experimental spectra strongly supports the presence of the dihydridostannyl ligand. The IR spectrum of complex Ru[SnH2(OTf)](η5-C5H5)(PPh3)[P(OMe)3] (10a) also supports the presence of the SnH2(OTf) ligand, showing a medium-intensity, slightly broad band at 1812 cm−1, attributed to the νSnH band of the dihydridostannyl group. In the free state, tin(II) dihydride SnH2 is highly unstable and was only identified in product mixtures SnxHy via matrix isolation.28 Coordination to the metal fragment W(CO)5 allowed its stabilization in the complex IPr·SnH2·W(CO)5 (IPr = [(HCNAr)2C:]; Ar = 2,6-iPr2C6H3),29 which turned out to be the first and only stable transition-metal complex involving the heavy methylene congener SnH2 as a ligand. However, stabilization of SnH2 involved the strongly donating N-heterocyclic carbene IPr as a ligand, leading to tetracoordination of tin. In our case, the presence of the triflate ion as a donor group, giving SnH2(OTf), appears to be essential in stabilizing tin(II) dihydride species. Protonation of Ru(SnH3)(η5-C5H5)(PPh3)[P(OMe)3] with HBF4 does proceed, with H2 evolution, but it does not give stable dihydridostannyl species,30 probably owing to the very poor donating ability of the BF4− ion, which prevents formation of the SnH2(BF4) ligand. In the absence of a donor group, the SnH2 formed by protonation is probably unstable, according to theoretical studies,31 which predict the reduced propensity of SnH2 to form a π bond with a metal. Therefore, stabilization of a tin dihydride group as a ligand requires a donor group such as the triflates, in our case giving the SnH2(OTf) ligand. However, although the poor donating ability of the OTf− ion probably prevented stabilization of our dihydridostannyl complex 10a, thus excluding its X-ray crystal structure determination, IR and NMR data and low conductivity values32 provided strong evidence for the presence of a coordinated SnH2(OTf) group. For comparison, the stable29 IPr·SnH2·W(CO)5 showed the νSnH band at 1786 cm−1 and proton-coupled 119Sn NMR as a triplet at −309 ppm, both signals very similar to those observed in our dihydridostannyl species 10a.

be due to the indenyl group and that the related fragment with the cyclopentadienyl ligand Ru(η5-C5H5)(PPh3)L would be able to stabilize the tin dihydride [Ru]−SnH2(OTf) derivative. We therefore studied HOTf protonation of the trihydridostannyl complex6a containing the Cp ligand Ru(SnH3)(η5C5H5)(PPh3)[P(OMe)3] and observed that the reaction proceeded at −30 °C in toluene to give a yellow solid, which was characterized as the tin dihydride derivative Ru[SnH2(OTf)](η5-C5H5)(PPh3)[P(OMe)3] (10a) (Scheme 7). Scheme 7a

a

L = P(OMe)3.

Unfortunately, the resulting solid was thermally unstable and slowly decomposed at room temperature. However, it was stable at −30 °C, both as a solid and in solution of CH2Cl2, allowing full characterization. The reaction of Ru(SnH3)(η5C5H5)(PPh3)[P(OMe)3] with HOTf was also followed by NMR spectra at −30 °C in CD2Cl2 and showed that, in the proton spectra, the addition of a Brønsted acid caused the disappearance of the signal at 2.83 ppm of SnH3 and the appearance of two new signals, one near 4.6 ppm, due to free H2,25 and another at 8.97 ppm, with the characteristic satellites of the 119Sn and 117Sn nuclei, which was attributed to the dihydride group SnH 2 (OTf) of the compound Ru[SnH2(OTf)](η5-C5H5)(PPh3)[P(OMe)3] formed by protonation. However, strong support for the formation of the tin(II) hydride complex 10a came from proton-coupled 119Sn NMR spectra recorded at −30 °C, both on the solution of Ru(SnH 3 )(η 5 -C 5 H 5 )(PPh 3 )[P(OMe) 3 ] protonated with HOTf and on that of compound 10a in CD2Cl2 prepared at −30 °C. As the 31P NMR spectrum was an AB quartet with 119 Sn and 117Sn satellites, the 119Sn signals appeared as quartets of triplets (Figure 4), due to coupling with the two hydrides of SnH2(OTf) and the two nonequivalent P nuclei of the phosphines. The spectra were simulated with an ABMX2

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CONCLUSIONS

In this paper, we report that the indenyl ligand in the halfsandwich fragment Ru(η5-C9H7)(PPh3)L (L = phosphites) can stabilize both trihydridostannyl ([Ru]−SnH3) and organostannyl derivatives ([Ru]−SnClMe2 and [Ru]−Sn(CCPh)3). Among the properties shown by the [Ru]−SnH3 species is the reaction with terminal alkynes which, with alkyl propiolate, allows addition to the Sn−H bond to afford the trivinylstannyl derivatives Ru[Sn{C(COOR)CH2}3](η5-C9H7)(PPh3)L. With the propargyl alcohol HCCCPh2OH, the reaction proceeds to yield the alkene H2CC(H)CPh2OH and the hydride RuH(η5-C9H7)(PPh3)L. Also of interest is the reaction of the tin trihydride complex [Ru]−SnH3 with H2O, affording the unprecedented trihydroxystannyl complex of ruthenium Ru[Sn(OH)3](η5-C9H7)(PPh3)L. Protonation of [Ru]−SnH3 with triflic acid gives the very unstable tin dihydride derivative [Ru]−SnH2(OTf). Instead, stabilization of the heavy methylene analogue SnH2 was achieved with the cyclopentadienyl fragment Ru[SnH2(OTf)](η5-C5H5)(PPh3)L.

Figure 4. 119Sn NMR spectra of the compound Ru[SnH2(OTf)](η5C5H5)(PPh3)[P(OMe)3] (10a) in CD2Cl2 at −30 °C: (top) simulated spectrum; (bottom) experimental spectrum. 3659


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ASSOCIATED CONTENT

S Supporting Information *

CIF files giving crystallographic data for compounds 4b and 8b and tables giving selected bond distances and angles for these compounds. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*G.A.: fax, +390412348917; e-mail, [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The financial support of the MIUR (Rome)-PRIN 2009 is gratefully acknowledged. We thank Mrs. Daniela Baldan, from the Università Ca’ Foscari Venezia (Italy), for her technical assistance.

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REFERENCES

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(19) For recent examples of Ru(η5-indenyl) complexes see: (a) Manzini, S.; Urbina-Blanco, C. A.; Poater, A.; Slawin, A. M. Z.; Cavallo, L.; Nolan, S. P. Angew. Chem., Int. Ed. 2012, 51, 1042−1045. (b) Costin, S.; Widaman, A. K.; Rath, N. P.; Bauer, E. B. Eur. J. Inorg. Chem. 2011, 1269−1282. (c) Hoyle, M.-A. M.; Pantazis, D. A.; Burton, H. M.; McDonald, R.; Rosenberg, L. Organometallics 2011, 30, 6458− 6465. (20) Adams, R. D.; Kan, Y.; Trufan, E.; Zhang, Q. J. Cluster Sci. 2010, 21, 371−378. (21) Blokhin, A. I.; Pasynsky, A. A.; Torubaev, Yu. V.; Sheer, M. Russ. J. Coord. Chem. 2010, 36, 284−288. (22) Cordero, B.; Gómez, V.; Platero-Prats, A. E.; Revés, M.; Echeverría, J.; Cremades, E.; Barragán, F.; Á lvarez, S. Dalton Trans. 2008, 2832−2838. (23) (a) Rivière, P.; Rivière-Baudet, M.; Satgé, J., In Comprehensive Organometallic Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon Press: Oxford, U.K., 1982; Chapter 10. (b) Davies, A. G.; Smith, P. J. In Comprehensive Organometallic Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon Press: Oxford, U.K., 1982; Chapter 11. (24) (a) Shea, K. J.; Loy, D. A. Acc. Chem. Res. 2001, 34, 707−716. (b) Roesky, H. W.; Singh, S.; Jancik, V.; Chandrasekhar, V. Acc. Chem. Res. 2004, 37, 969−981. (25) Crabtree, R. H.; Lavin, M.; Bonneviot, L. J. Am. Chem. Soc. 1986, 108, 4032−4037. (26) Simón-Manso, E.; Kubiak, C. P. Angew. Chem., Int. Ed. 2005, 44, 1125−1128. (27) Clark, G. R.; Flower, K. R.; Roper, W. R.; Woodman, T. J.; Wright, L. J. Organometallics 1993, 12, 3810−3811. (28) Frison, G.; Sevin, A. J. Chem. Soc., Perkin Trans 2 2002, 1692− 1697. (29) Al-Rafia, S. M. I.; Malcolm, A. C.; Liew, S. K.; Ferguson, M. J.; Rivard, E. J. Am. Chem. Soc. 2011, 133, 777−779. (30) Protonation of Ru(SnH3)(η5-C5H5)(PPh3)[P(OMe)3] with HBF4·Et2O at −30 °C in CD2Cl2 showed evolution of H2 and the formation of unstable stannyl complexes, tentatively formulated as [Ru(SnH2)(η5-C5H5)(PPh3){P(OMe)3}]BF4. The proton-coupled 119 Sn NMR spectrum of the latter showed a broad signal near 248 ppm, the very poor resolution of which prevented any formulation of the stannyl ligand. (31) (a) Jacobsen, H.; Ziegler, T. Inorg. Chem. 1996, 35, 775−783. (b) Lein, M.; Szabó, A.; Kovács, A.; Frenking, G. Faraday Discuss. 2003, 124, 365−378. (32) Conductivity measurements of Ru[SnH2(OTf)](η5-C5H5) (PPh3[P(OMe)3] (10a) in CH2Cl2 at −30 °C gave ΛM values of 6.5−7.1 Ω−1 mol−1 cm2, which indicate some dissociation of a neutral complex, rather than behavior similar to that of a 1:1 electrolyte species. See: Geary, W. J. Coord. Chem. Rev. 1971, 7, 81−172.

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Preparation and Reactivity of Stannyl Complexes of Ruthenium (II

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