Preparation of Half-Sandwich Stannyl Complexes of Osmium (II)

ARTICLE pubs.acs.org/Organometallics

Preparation of Half-Sandwich Stannyl Complexes of Osmium(II) Gabriele Albertin,*,† Stefano Antoniutti,† and Jes
us Castro‡ † ‡

Dipartimento di Scienze Molecolari e Nanosistemi, Universita Ca' Foscari Venezia, Dorsoduro 2137, 30123 Venezia, Italy Departamento de Química Inorg
anica, Universidade de Vigo, Facultade de Química, Edificio de Ciencias Experimentais, 36310 Vigo (Galicia), Spain

bS Supporting Information ABSTRACT: Trichlorostannyl complexes OsCl(SnCl3)(η6-pcymene)P (1; P = P(OEt)3 (a), PPh(OEt)2 (b), PPh2OEt (c)) were prepared by allowing the dichloro compounds OsCl2(η6p-cymene)P to react with an excess of SnCl2, and treatment of complexes 1 with an excess of NaBH4 in ethanol yielded the trihydridostannyl complexes OsCl(SnH3)(η6-p-cymene)P (2). Reaction of trihydridostannyl complexes 2 with alkyl propiolates HCtCCOOR led to the trivinylstannyl derivatives OsCl[Sn{C(COOR)dCH2}3](η6-p-cymene)P (5, 6; R = Me, Et), which were characterized by spectroscopy (IR and 1H, 31P, 13C, and 119 Sn NMR spectra) and by an X-ray crystal structure determination of OsCl[Sn{C(COOMe)dCH2}3](η6-p-cymene)[PPh(OEt)2] (5b).

T

he preparation of transition-metal complexes containing stannyl ligands, [M]
SnX3 and [M]
SnR3, has received considerable attention over the last few decades,1
3 both from a fundamental point of view and because the introduction of a stannyl group often changes the properties of the complexes and may modify the activity of noble-metal catalysts.4 We are interested in the chemistry of stannyl complexes5 and have recently reported the synthesis and reactivity of the trihydridostannyl complexes [M]
SnH3 of ruthenium and osmium stabilized by the half-sandwich cyclopentadienyl fragments M(Cp)(PPh3)L (M = Ru, Os; L = phosphite).5e The interesting properties shown by the trihydridostannyl ligand SnH3 in these complexes prompted us to extend our study to arene complexes, to test whether other halfsandwich fragments can stabilize the tin trihydride group and how the reactivity of the stannyl group is influenced by the metal fragment. The results of these studies, which include the preparation and reactivity of the first stannyl complexes stabilized by arene ligands, are reported here.

’ EXPERIMENTAL SECTION Synthesis of Complexes. Compounds OsCl2(η6-p-cymene)P (P = P(OEt)3, PPh(OEt)2, PPh2OEt) were prepared following the method previously reported.6

OsCl(SnCl3)(η6-p-cymene)P (1; P = P(OEt)3 (a), PPh(OEt)2 (b), PPh2OEt (c)). Method 1. In a 25 mL three-necked round-

bottomed flask were placed solid samples of the appropriate complex OsCl2(η6-p-cymene)P (0.38 mmol), an excess of SnCl2 3 2H2O (1.14 mmol, 0.26 g), and 5 mL of ethanol. The reaction mixture was stirred at room temperature for 24 h, and the yellow solid that formed was filtered and crystallized from CH2Cl2 and ethanol; yield g85%. Method 2. In a 25 mL three-necked round-bottomed flask were placed solid samples of the appropriate complex OsCl2(η6-p-cymene)P r 2011 American Chemical Society

(0.38 mmol), an excess of anhydrous SnCl2 (0.76 mmol, 0.144 g), and 10 mL of 1,2-dichloroethane. The reaction mixture was refluxed for 1 h and cooled to room temperature. After filtration, the solvent was removed under reduced pressure and the oil obtained triturated with ethanol (3 mL). The yellow solid which separated out was filtered and crystallized from CH2Cl2 and ethanol; yield g80%. 1a: 1H NMR (CD2Cl2, 25 °C) δ 6.04, 5.88, 5.78, 5.73 (d, 4H, Ph pcym), 4.15 (m, 6H, CH2), 2.69 (m, 1H, CH p-cym), 2.19 (s, 3H, p-CH3 p-cym), 1.34 (t, 9H, CH3 phos), 1.23, 1.21 (d, 6H, CH3 iPr) ppm; 31 1 P{ H} NMR (CD2Cl2, 25 °C) δ 74.5, J31P117Sn = 643.9 Hz; 119Sn NMR (CD2Cl2) δ AM spin syst (A = 31P, M = 119Sn), at 25 °C, δM
500.0, JAM (J31P119Sn) = 667.0 Hz, at
30 °C, δM
499.8, JAM = 670.8 Hz. Anal. Calcd for C16H29Cl4O3OsPSn: C, 25.58; H, 3.89; Cl, 18.88. Found: C, 25.76; H, 3.75; Cl, 18.61. 1b: 1H NMR (CD2Cl2, 25 °C) δ 7.82
7.51 (m, 5H, Ph phos), 6.00, 5.80, 5.47, 5.18 (d, 4H, Ph p-cym), 4.15, 4.08 (m), 3.92 (qnt) (4H, CH2), 2.40 (m, 1H, CH p-cym), 2.09 (s, 3H, p-CH3 p-cym), 1.38, 1.36 (t, 6H, CH3 phos), 1.14, 1.03 (d, 6H, CH3 iPr); 31P{1H} NMR (CD2Cl2, 25 °C) δ 97.8, J31P117Sn = 540.0 Hz; 119Sn NMR (CD2Cl2, 25 °C) δ AM, δM
530.3, JAM = 565.0. Anal. Calcd for C20H29Cl4O2OsPSn: C, 30.67; H, 3.73; Cl, 18.11. Found: C, 30.44; H, 3.86; Cl, 18.30. 1c: 1H NMR (CD2Cl2, 25 °C) δ 7.85
7.48 (m, 10H, Ph phos), 6.04, 5.98, 5.23, 5.21 (d, 4H, Ph p-cym), 3.71 (qnt, 2H, CH2), 2.29 (m, 1H, CH p-cym), 2.07 (s, 3H, p-CH3 p-cym), 1.25 (t, 3H, CH3 phos), 1.02, 0.98 (d, 6H, CH3 iPr); 31P{1H} NMR (CD2Cl2) at 25 °C, δ 85.1, at
30 °C, 87.9, J31P117Sn = 521.5 Hz; 119Sn NMR (CD2Cl2,
30 °C) δ AM, δM
543.8, JAM = 543.5. Anal. Calcd for C24H29Cl4OOsPSn: C, 35.36; H, 3.59; Cl, 17.40. Found: C, 35.13; H, 3.65; Cl, 17.18.

OsCl(SnH3)(η6-p-cymene)P (2; P = PPh(OEt)2 (b), PPh2OEt (c)). In a 25 mL three-necked round-bottomed flask were placed solid Received: December 20, 2010 Published: March 17, 2011 1914

dx.doi.org/10.1021/om101184a | Organometallics 2011, 30, 1914–1919

Organometallics samples of the appropriate complex OsCl(SnCl3)(η6-p-cymene)P (1; 0.30 mmol) and an excess of NaBH4 (3.0 mmol, 0.113 g). The flask was cooled to
196 °C, and ethanol (10 mL) was added drop by drop. The resulting mixture was brought to 0 °C (ice bath) and stirred for 2
3 min. The solvent was removed under reduced pressure, leaving a solid, from which the trihydridostannyl complex was extracted at 0 °C with three 5 mL portions of toluene. The extracts were evaporated to dryness to give an oil which was triturated with n-hexane (5 mL). A yellow solid slowly separated out which was filtered and dried under vacuum; yield g55%. 2b: IR (KBr, cm
1) νSnH 1806, 1746 (m); 1H NMR (CD3C6D5, 25 °C) δ 7.76, 7.20
6.98 (m, 5H, Ph phos), 5.23, 5.05, 4.61, 4.40 (d, 4H, Ph p-cym), 3.96, 3.87, 3.81, 3.64 (m, 4H, CH2), AX3 (X = 1H), δX 3.72, JAX = 0.1 Hz, J1H117Sn = 1350 Hz (3H, SnH3), 2.35 (m, 1H, CH p-cym), 1.65 (s, 3H, p-CH3 p-cym), 1.13, 1.11 (t, 6H, CH3 phos), 0.95, 0.93 (d, 6H, CH3 iPr); 31P{1H} NMR (CD3C6D5, 25 °C) δ 102.1, J31P117Sn = 324.7 Hz; 119Sn NMR (CD2Cl2, 25 °C) δ AMX3, δM
465.0, JAM = 339.5 Hz, JAX = 0.1 Hz, JMX = 1412.5 Hz. Anal. Calcd for C20H32ClO2OsPSn: C, 35.33; H, 4.74; Cl, 5.21. Found: C, 35.52; H, 4.86; Cl, 5.04. 2c: IR (KBr, cm
1) νSnH 1756, 1730 (s); 1H NMR (CD2Cl2, 25 °C) δ 7.90, 7.64, 7.13, 6.98 (m, 10H, Ph phos), 5.35, 5.20, 4.32, 4.27 (d, 4H, Ph p-cym), 4.06, 3.67 (qnt, 2H, CH2), AX3, δX 3.81, JAX = 0.1 Hz, J1H117Sn = 1325.3 Hz (3H, SnH3), 2.20 (m, 1H, CH p-cym), 1.54 (s, 3H, p-CH3 p-cym), 1.03 (t, 3H, CH3 phos), 0.93, 077 (d, 6H, CH3 iPr); 31P{1H} NMR (CD2Cl2, 25 °C) δ 79.4, J31P117Sn = 306.7 Hz; 119Sn NMR (CD2Cl2, 25 °C) δ AMX3, δM
474.8, JAM = 320.4 Hz, JAX = 0.1 Hz, JMX = 1388.0 Hz. Anal. Calcd for C24H32ClOOsPSn: C, 40.49; H, 4.53; Cl, 4.98. Found: C, 40.31; H, 4,43; Cl, 4.75. OsCl(SnMe3)(η6-p-cymene)[PPh(OEt)2] (3b). An excess of MgBrMe Grignard reagent (0.92 mmol, 0.66 mL of a 1.4 mol dm
3 solution in toluene/tetrahydrofuran (thf) 3/1) was added to a solution of the complex OsCl(SnCl3)(η6-p-cymene)[PPh(OEt)2] (1b; 0.15 g, 0.192 mmol) in thf (10 mL) cooled to
196 °C. The reaction mixture was warmed to room temperature and stirred for 1 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 from the resulting solution, which was filtered and crystallized from toluene and ethanol; yield g60%. 1H NMR (CD2Cl2, 25 °C): δ 7.65
7.30 (m, 5H, Ph phos), 5.68, 5.64, 5.02, 4.76 (d, 4H, Ph p-cym), 4.06, 3.88, 3.70 (m, 4H, CH2), 2.40 (m, 1H, CH p-cym), 1.75 (s, 3H, p-CH3 p-cym), 1.30, 1.27 (t, 6H, CH3 phos), 1.15, 1.10 (d, 6H, CH3 iPr), 0.03 (s, 9H, SnCH3, J1H119Sn = 41.5 Hz, J1H117Sn = 39.8 Hz). 31P{1H} NMR (CD2Cl2, 25 °C): δ 105.6, J31P117Sn = 272.7 Hz. 13C{1H} NMR (CD2Cl2, 25 °C): δ 141
127 (m, Ph phos), 110.5 (d, C1 p-cym, JCP = 2.1), 87.9 (d, br, C4 p-cym), 84.95 (d, C3 p-cym, JCP = 5.5), 80.7 (d, br, C6 p-cym), 78.66 (d, C2 p-cym, JCP = 10.2), 77.56 (d, C5 p-cym, JCP = 2.3), 62.41, 62.06 (d, CH2 phos), 30.22 (s, CH p-cym), 23.28, 21.76 (s, CH3 iPr), 18.06 (s, p-CH3 p-cym), 16.4 (m, CH3 phos),
6.86 (s, SnCH3, J13C119Sn = 208.0, J13C117Sn = 199.0 Hz). 119Sn{1H} NMR (CD2Cl2, 25 °C): δ AM, δM
136.7, JAM = 286.5. Anal. Calcd for C23H38ClO2OsPSn: C, 38.27; H, 5.31; Cl, 4.91. Found: C, 38.42; H, 5.18; Cl, 4.75.

OsCl[Sn(CtCPh)3](η6-p-cymene)P (4; P = P(OEt)3 (a), PPh(OEt)2 (b)). An excess of lithium phenylacetylide (Liþ[PhCtC]
; 1.28

mmol, 0.85 mL of a 1.5 mol dm
3 solution in thf) was added to a solution of the appropriate complex OsCl(SnCl3)(η6-p-cymene)P (1; 0.25 mmol) in thf (10 mL) cooled to
196 °C. The reaction mixture was warmed to room temperature and stirred for 1 h. The solvent was removed under reduced pressure to give an oil which was triturated with ethanol (2 mL). A pale yellow solid slowly separated out, which was filtered and crystallized from toluene and ethanol; yield g65%. 4a: IR (KBr, cm
1) νCtC 2134 (m); 1H NMR (CD2Cl2, 25 °C) δ 7.49
7.28 (m, 15H, PhCt), 5.96, 5.82, 5.58, 5.51 (d, 4H, Ph p-cym), 4.16 (m, 6H, CH2), 2.72 (m, 1H, CH p-cym), 2.18 (s, 3H, p-CH3 pcym), 1.30 (t, 9H, CH3 phos), 1.24, 1.22 (d, 6H, CH3 iPr); 31P{1H} NMR (CD2Cl2, 25 °C) δ 80.2, J31P117Sn = 505.0 Hz; 13C{1H} NMR

ARTICLE

(CD2Cl2, 25 °C) δ 132
124 (m, PhCt), 106.98 (s, Cβ, J13C119Sn = 73.2 Hz, J13C117Sn = 70.0 Hz), 103.86 (d, C1 p-cym, JCP = 1.8 Hz), 98.84 (d, C4 p-cym, JCP = 2.7 Hz), 95.2 (s, CR, J13C119Sn = 334.0 Hz, J13C117Sn = 321.0 Hz), 83.55 (d, C3 p-cym, JCP = 8.5 Hz), 82.94 (d, C5 p-cym, JCP = 1.1 Hz), 82.10 (d, C2 p-cym, JCP = 3.1 Hz), 80.59 (d, C6 p-cym, JCP = 6.0 Hz), 63.4 (d, CH2 phos), 30.76 (s, CH p-cym), 23.01, 22.76 (s, CH3 i Pr), 18.08 (s, p-CH3 p-cym), 16.26 (d, CH3 phos); 119Sn NMR (CD2Cl2, 25 °C) δ AM, δM
485.7, JAM = 529.3 Hz. Anal. Calcd for C40H44ClO3OsPSn: C, 50.67; H, 4.68; Cl, 3.74. Found: C, 50.89; H, 4.58; Cl, 3.92. 4b: IR (KBr, cm
1) νCtC 2124 (m); 1H NMR (CD2Cl2, 25 °C) δ 7.89, 7.52
7.31 (m, 20H, Ph), 5.89, 5.80, 5.24, 4.97 (d, 4H, Ph p-cym), 4.23, 4.11, 3.89 (m, 4H, CH2), 2.46 (m, 1H, CH p-cym), 2.05 (s, 3H, pCH3 p-cym), 1.37, 1.34 (t, 6H, CH3 phos), 1.15, 1.13 (d, 6H, CH3 iPr); 31 1 P{ H} NMR (CD2Cl2, 25 °C) δ 100.3, J31P117Sn = 424.1 Hz; 13C{1H} NMR (CD2Cl2, 25 °C) δ 140
124 (m, PhCt), 107.81 (d, C1 p-cym, JCP = 2.2 Hz), 106.7 (s, Cβ, J13C119Sn = 70.4 Hz, J13C117Sn = 67.1 Hz), 93.15 (d, C4 p-cym, JCP = 1.2 Hz), 95.7 (s, CR, J13C119Sn = 344.0, J13C117Sn = 331.0 Hz), 85.35 (d, C3 p-cym, JCP = 4.3 Hz), 82.64 (d, C6 p-cym, JCP = 2.6 Hz), 82.30 (d, C5 p-cym, JCP = 4.7 Hz), 81.97 (d, C2 p-cym, JCP = 7.8 Hz), 64.32, 63.53 (d, CH2 phos), 30.05 (s, CH p-cym), 23.02, 22.00 (s, CH3 iPr), 17.83 (s, p-CH3 p-cym), 16.45, 16.03 (d, CH3 phos); 119Sn NMR (CD2Cl2, 25 °C) δ AM, δM
502.7, JAM = 444.2 Hz. Anal. Calcd for C44H44ClO2OsPSn: C, 53.92; H, 4.52; Cl, 3.62. Found: C, 54.05; H, 4.45; Cl, 3.77.

OsCl[Sn{C(COOR)dCH2}3](η6-p-cymene)[PPh(OEt)2] (5b, 6b; R = Me (5), Et (6)). To a solution of the complex OsCl(SnH3)-

(η6-p-cymene)[PPh(OEt)2] (2b; 0.20 g, 0.29 mmol) in toluene (10 mL) was added an excess of the appropriate alkyl propiolate HCtCCOOR (1.74 mmol), and the reaction mixture was stirred at room temperature for 24 h. The solvent was removed under reduced pressure to give an oil, which was triturated with n-hexane (6 mL). A yellow solid slowly separated out, which was filtered and crystallized from toluene and n-hexane; yield g65%. 5b: IR (KBr, cm
1) νCOO 1702 (s); 1H NMR (CD2Cl2, 25 °C) δ 7.71, 7.39 (m, 5H, Ph phos), XY (AB-type spin system, X, Y = 1H), δX 6.64, δY 6.06, JXY = 3.3 Hz, JX119Sn = 115.2 Hz, JY119Sn = 52.5 Hz, JX117Sn = 109.4 Hz, JY117Sn = 51.0 Hz (6H, dCH2), 5.47, 5.43, 5.22, 5.19 (d, 4H, Ph p-cym), 4.07, 3.97, 3.75, 3.66 (m, 4H, CH2 phos), 3.59 (s, 9H, OCH3), 2.35 (m, 1H, CH p-cym), 1.53 (s, 3H, p-CH3 p-cym), 1.26, 1.19 (t, 6H, CH3 phos), 1.11, 1.07 (d, 6H, CH3 iPr); 31P{1H} NMR (CD2Cl2, 25 °C) δ 100.1, J31P117Sn = 323.5 Hz; 13C{1H} NMR (CD2Cl2, 25 °C) δ 172.9 (s, Cγ, J13C119Sn = 35.0 Hz, J13C117Sn = 33.0 Hz), 150.7 (s, CR, J13C119Sn = 235.6 Hz, J13C117Sn = 226.9 Hz), 137.4 (s, Cβ, J13C119Sn = 23.1, J13C117Sn = 20.8 Hz), 130
128 (m, Ph phos), 116.5 (d, C4 p-cym, JCP = 4.5 Hz), 88.0 (br, C1 p-cym), 83.18 (d, C3 p-cym, JCP = 1.5 Hz), 81.89 (d, C5 pcym, JCP = 3.5 Hz), 79.60 (d, C6 p-cym, JCP = 11.8 Hz), 78.9 (d, br, C2 pcym), 63.5, 62.8 (d, CH2 phos), 51.3 (s, OCH3), 30.0 (s, CH p-cym), 22.3, 21.9 (s, CH3 iPr), 17.0 (s, p-CH3 p-cym), 16.3, 15.9 (d, CH3 phos); 119 Sn NMR (CD2Cl2, 25 °C) δ AM, δM
300.0, JAM = 336.8 Hz. Anal. Calcd for C32H44ClO8OsPSn: C, 41.24; H, 4.76; Cl, 3.80. Found: C, 41.11; H, 4.59; Cl, 3.97. 6b: IR (KBr, cm
1) νCOO 1696 (s); 1H NMR (CD2Cl2, 25 °C) δ 7.76, 7.40, 7.22 (m, 5H, Ph phos), XY, δX 6.69, δY 6.12, JXY = 3.5, JX119Sn = 115.3 Hz, JY119Sn = 52.9 Hz, JX117Sn = 110.9 Hz, JY117Sn = 50.0 Hz (6H, dCH2), 5.47, 5.42, 5.22, 5.20 (d, 4H, Ph p-cym), 4.07 (q, 6H, OCH2CH3), 3.77, 3.68 (m, 4H, CH2 phos), 2.37 (m, 1H, CH p-cym), 1.50 (s, 3H, p-CH3 p-cym), 1.30 (t, 9H, OCH2CH3), 1.24 (t, 6H, CH3 phos), 1.15, 1.09 (d, 6H, CH3 iPr); 31P{1H} NMR (CD2Cl2, 25 °C) δ 100.1, J31P117Sn = 319.5 Hz; 13C{1H} NMR (CD2Cl2, 25 °C) δ 172.5 (s, Cγ, J13C119Sn = 35.0 Hz, J13C117Sn = 33.0 Hz), 151.4 (s, CR, J13C119Sn = 244.3, J13C117Sn = 233.7 Hz), 137.5 (s, Cβ, J13C119Sn = 22.1, J13C117Sn = 20.8 Hz), 131
125 (m, Ph phos), 116.60 (d, C4 p-cym, JCP = 4.9 Hz), 116.51 (d, C1 p-cym, JCP = 5.3 Hz), 83.40 (d, C3 p-cym, JCP = 1.3 Hz), 81.6 (d, br, C5 p-cym), 79.46 (d, C6 p-cym, JCP = 12.2 Hz), 79.1 (d, br, C2 p-cym), 1915

dx.doi.org/10.1021/om101184a |Organometallics 2011, 30, 1914–1919

Organometallics Scheme 1a

a

ARTICLE

Scheme 3a

P = P(OEt)3 (a), PPh(OEt)2 (b), PPh2OEt (c).

Scheme 2a

a a

P = PPh(OEt)2 (b), PPh2OEt (c).

63.6, 62.8 (d, CH2 phos), 60.45 (s, OCH2CH3), 30.11 (s, CH p-cym), 22.52, 21.93 (s, CH3 iPr), 17.0 (s, p-CH3 p-cym), 16.4, 15.9 (d, CH3 phos), 14.4 (s, OCH2CH3); 119Sn NMR (CD2Cl2, 25 °C) δ AM, δM
302.2, JAM = 334.5 Hz. Anal. Calcd for C35H50ClO8OsPSn: C, 43.15; H, 5.17; Cl, 3.64. Found: C, 43.32; H, 5.04; Cl, 3.39.

Crystal Structure Determination of OsCl[Sn{C(COOMe)= CH2}3](η6-p-cymene)-[PPh(OEt)2] (5b). Crystallographic data were collected on a Bruker Smart 1000 CCD diffractometer at the CACTI (Universidade de Vigo) using graphite-monochromated Mo KR radiation (λ = 0.710 73 Å) and were corrected for Lorentz and polarization effects. The software SMART7 was used for collecting frames of data, indexing reflections, and determining lattice parameters, SAINT8 for integration of intensity of reflections and scaling, and SADABS9 for empirical absorption correction. The structure was solved and refined with the Oscail program10 by direct methods and refined by a full-matrix least-squares method based on F2.11 Non-hydrogen atoms were refined with anisotropic displacement 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 S1 in the Supporting Information.

’ RESULTS AND DISCUSSION The dichloro complexes OsCl2(η6-p-cymene)P react with an excess of SnCl2 to give the trichlorostannyl derivatives OsCl(SnCl3)(η6-p-cymene)P (1) in good yields (Scheme 1). The reaction proceeds with the apparent insertion of SnCl2 into the Os
Cl bond to give the trichlorostannyl complexes 1. However, only one of the two Os
Cl bonds undergoes insertion of the SnCl2 group, giving the monostannyl compounds 1, and even when a large excess of SnCl2 or long reaction times were applied, formation of the bis(stannyl) complex [Os]
(SnCl3)2 was not observed. The trichorostannyl complexes OsCl(SnCl3)(η6-p-cymene)P (1) react with NaBH4 in ethanol to give the trihydridostannyl derivatives OsCl(SnH3)(η6-p-cymene)P (2), which were isolated and characterized (Scheme 2). Crucial for successful synthesis was performing the reaction at 0 °C with short reaction times (2
3 min). Otherwise, large amounts of decomposition products were obtained, which prevented separation of pure samples of the complexes. It should be noted that the reaction proceeds with the substitution of only the tin-bonded and not the Os-bonded chlorides, giving trihydridostannyl derivatives 2. However, this result is due to the slow rate of substitution with H
of Os
Cl in comparison

P = P(OEt)3 (a), PPh(OEt)2 (b).

with the Sn
Cl group. For example, a slightly longer reaction time (10 min) gave a new reaction product unlike 2, the NMR spectra of which indicated that it contained an Os
H group. The presence of a doublet at
11.2 ppm in the 1H NMR spectrum of this reaction mixture does suggest that the reaction of OsCl(SnCl3)(η6-p-cymene)P with NaBH4 proceeds further, giving not only 2 but also probably either OsH(SnH3)(η6-p-cymene)P or OsH2(η6-p-cymene)P species, which unfortunately are unstable and cannot be isolated. Only under mild conditions, therefore, can the trihydridostannyl complexes 2 be separated in pure form. However, only complexes containing PPh(OEt)2 (2b) and PPh2OEt (2c) were obtained as solids: the related P(OEt)3 derivative 2a was an unstable oil and was not characterized. Trihydridostannyl complexes of Ru and Os have previously been obtained with tris(pyrazolyl)borate (Tp) and cyclopentadienyl (Cp) as supporting ligands.5e The use of OsCl(η6-pcymene)P fragments reveals that arene ligands such as η6-pcymene can also stabilize trihydridostannyl derivatives. The easy substitution of tin-bonded chloride ligands by H
in OsCl(SnCl3)(η6-p-cymene)P (1) precursors prompted us to extend our study to other nucleophilic reagents, to test whether new stannyl derivatives can be prepared. The results show that trichlorostannyl complexes 1 react with both the Grignard reagent MgBrMe, to give the trimethylstannyl derivatives OsCl(SnMe3)(η6-p-cymene)P (3), and the lithium acetylide Liþ[PhCtC]
, to give the trialkynylstannyl complexes OsCl[Sn (CtCPh)3](η6-p-cymene)P (4), in good yields (Scheme 3). All the stannyl complexes 1
4 were isolated as yellow solids, stable in air and in solutions of common organic solvents, where they behave as nonelectrolytes.12 Their formulation has been confirmed by analytical and spectroscopic (IR; 1H, 13C, 31P, 119 Sn NMR) data and by an X-ray crystal structure determination of the reaction product of the trihydridostannyl compound 2a with methyl propiolate, the complex OsCl[Sn{C(COOMe)dCH2}3](η6-p-cymene)[PPh(OEt)2] (5b) (see Figure 1). The 1H NMR spectra of the trichlorostannyl complexes OsCl(SnCl3)(η6-p-cymene)P (1) show the characteristic signals of p-cymene and phosphite ligands, whereas 31P spectra are singlets, with their characteristic 119Sn and 117Sn satellites. 119Sn NMR spectra show a doublet at
499.8 to
543.8 ppm due to coupling with the phosphorus nuclei, matching the proposed formulations. The IR spectra of the trihydridostannyl derivatives OsCl(SnH3)(η6-p-cymene)P (2) show two bands of strong intensity 1916

dx.doi.org/10.1021/om101184a |Organometallics 2011, 30, 1914–1919

Organometallics

ARTICLE

Scheme 4a

a

Figure 1. ORTEP view of OsCl[Sn{C(COOMe)dCH2}3](η6-pcymene)[PPh(OEt)2] (5b) drawn at the 30% probability level. The phenyl ring and the ethyl groups of the phosphane are omitted. Selected interatomic distances (Å): Os
Cl = 2.4758(16), Os
P(1) = 2.255(2), Os
Sn = 2.6609(6), Os
centroid = 1.7484(3).

between 1806 and 1730 cm
1, attributed to the νSnH band of the tin
hydride ligand. However, diagnostic for the presence of the stannyl group are both 1H and 119Sn NMR spectra. In addition to the signals of p-cymene and phosphite, the proton spectra show a signal at 3.72
3.81 ppm, with the 119Sn and 117Sn satellites attributed to the tin
hydride SnH3 group. The proton-coupled 119 Sn NMR spectra appear as a quartet of doublets at
465.0 to
474.8 ppm due to coupling with the three hydrides and the phosphorus nucleus of the phosphite (see Figure S1 in the Supporting Information). As the 31P NMR spectra are singlets at 102.1
79.4 ppm, the 119Sn spectra can be simulated with an AMX3 model (A = 31P, X = 1H) with the parameters reported in the Experimental Section. The good fit between calculated and experimental data strongly supports the presence of the trihydridostannyl group in the molecule. The 1H NMR spectrum of the trimethylstannyl complex OsCl(SnMe3)(η6-p-cymene)[PPh(OEt)2] (3b) shows a singlet at 0.03 ppm with the satellites of 119Sn and 117Sn nuclei attributed to the methyl protons of the SnMe3 group. In an HMQC experiment, this singlet was correlated with the singlet at
6.86 ppm in the 13 C NMR spectrum (see Figure S2 in the Supporting Information), thus confirming the proposed attribution. However, strong support for the presence of the stannyl group comes from the proton-coupled 119 Sn NMR spectrum, which appears as a complicated multiplet due to coupling with the nine hydrogen atoms of the methyl group and the phosphorus nucleus of the phosphite. Instead, the protondecoupled 119Sn{1H} NMR spectrum appears as a more simplified doublet at
136.7 ppm, matching the proposed formulation for the complex. The IR spectra of the trialkynylstannyl complexes OsCl[Sn(CtCPh)3](η6-p-cymene)[PPh(OEt)2] (4) show a mediumintensity band at 2134
2124 cm
1, attributed to the νCtC band of the acetylide group. However, diagnostic for the presence of the stannyl group are the 13C and 119Sn NMR spectra. In addition to the signals of the supporting ligands p-cymene and phosphite, the 13C spectra show singlets at 95.2 (4a) and 95.7 ppm (4b), with the characteristic 119Sn and 117Sn satellites attributed to the

R = Me (5), Et (6); P = PPh(OEt)2.

CR carbon resonance of the acetylide. Instead, the singlets at 106.98 (4a) and 106.7 ppm (4b), which in an HMQC experiment were correlated with the phenyl hydrogen resonance near 7 ppm, are due to the Cβ carbon atom of the acetylide. J13C119Sn values between 334.0 and 344.0 Hz in one case, and between 70.4 and 73.2 Hz in another, further support the attribution of CR and Cβ carbon resonances. 119Sn NMR spectra appear as doublets at
485.7 (4a) and
502.7 ppm (4b) due to coupling with the phosphorus nuclei of phosphites, matching the proposed formulation for trialkynylstannyl derivatives 4. Reactivity with Alkynes. Alkyl propiolates HCtCCOOR react with the trihydridostannyl complexes OsCl(SnH3)(η6-pcymene)P (2) to give the trivinylstannyl derivatives OsCl[Sn{C(COOR)dCH2}3](η6-p-cymene)P (5, 6), which were isolated as yellow solids and characterized (Scheme 4). Studies on the progress of the reaction by 1H NMR indicate that the sequential addition of Sn
H bonds to the alkyne gives first monovinyl [Os]
SnH2{C(COOR)dCH2}, then divinyl [Os]
SnH{C(COOR)dCH2}2, and last trivinylstannyl derivatives [Os]
Sn{C(COOR)dCH2}3 (5, 6). However, only trivinylstannyl complexes 5 and 6 could be isolated in pure form, in an excess of alkyne. Instead, with an alkyne to [Os]
SnH3 ratio of lower than 3, the product was always a mixture of mono-, di-, and trivinyl complexes, which were not separated. Phenylacetylene was also reacted with the trihydridostannyl precursors OsCl(SnH3)(η6-p-cymene)P (2), but in this case no addition product was obtained. It seems, therefore, that only activated alkynes such as alkyl propiolates can undergo addition of the Sn
H bond to afford trivinylstannyl derivatives. A similar result had previously been observed in Mn and Re tin complexes,5d the only known examples of reaction of the terminal alkyne with the coordinated tin hydride group. Although the addition of organotin hydrides RnSnH4
n (n = 1
3) to terminal acetylenes RCtCH is a well-known reaction,13 only one case of a tin hydride group coordinated in a metal complex has been reported.5d The reaction of pcymene trihydridostannyl complexes 2 also highlights the fact that the osmium metal fragments OsCl(η6-p-cymene)P may make the SnH3 ligand able to add itself to terminal alkynes, affording trivinylstannyl derivatives. It should be noted that the reaction of our complexes [Os]
SnH3 (2) not only proceeds with the addition of three Sn
H to three alkyne nuclei but also leads to the formation of only one of the two possible isomers, the [Os]
Sn{C(R)dCH2}3 molecule. Good analytical data were obtained for vinylstannyl complexes 5 and 6, which are yellow solids stable in air and in solution of common organic solvents, where they behave as nonelectrolytes.12 Their formulation is supported by analytical and spectroscopic (IR and 1H, 13C, 31P, 119Sn NMR) data and by an X-ray crystal structure determination of the complex 1917

dx.doi.org/10.1021/om101184a |Organometallics 2011, 30, 1914–1919

Organometallics OsCl[Sn{C(COOMe)dCH2 }3 ](η6 -p-cymene)[PPh(OEt)2] (5b), the ORTEP drawing of which is shown in Figure 1. The structure of the complex consists of an osmium atom η6-coordinated to a p-cymene molecule and to three donor atoms, leading to the formation of a “three-legged piano stool” structure. These ligands are a chloride ligand, a phosphonite PPh(OEt)2 ligand, and a tris(methyl-2-acrylate)stannyl group. In these kinds of halfsandwich complexes, the overall geometry of the complex is wellknown to be octahedral and is marked by near 90° values for the angles P(1)
Os
Cl (85.82(7)°), P(1)
Os
Sn (92.07(6)°), and Cl
Os
Sn (86.53(4)°). The average Os
C bond distance for the p-cymene ligand is 2.254(9) Å (Table S2 in the Supporting Information). These bond lengths are close to those of other related complexes14,15 and also show the different trans effects of the other ligands, as Os
C(1) and Os
C(2), trans to the phosphorus donor ligand, are the longer bonds. The atom labeled as C(1) also corresponds to the isopropyl-substituted carbon atom, and we found that it is usually the longer metal
C bond in p-cymene complexes.14 The distance Os
C(3) (trans to the chloride ligand) is slightly shorter than the other bonds. The aromatic benzene ring does not show any particular distortion, with an rms deviation from the best plane of 0.0312. The isopropyl substituent lies as far as possible from the bulky stannyl and phosphane ligands and is situated “over” the position occupied by the chloride ligand, with a Cl
Os
CT
C(1) torsion angle of 12.4(4)°. The distance from the osmium atom to the best plane formed by the benzene ring is 1.747(4) Å, virtually the same as that of the centroid (1.7484(3) Å). These values are similar to those reported for other p-cymene osmium complexes.15b,d The Os
P bond length is 2.255(2) Å, a value shorter than those found for several phosphane dichloro p-cymene osmium complexes.16 However, the Os
Cl bond length, 2.476(2) Å, is slightly longer than the values usually found in the literature.15a,b,d,e,h,16 The Os
Sn bond length is 2.6609(6) Å,17 slightly longer than that found for the formate complex OsH[Sn(OH){OC(H)dO}2]{PPh(OEt)2}4 (2.6249(5) Å)5h and the complex Os(SnH3)(Tp){P(OMe)3}(PPh3),5a (average 2.6416(5) Å) but slightly shorter than that found in OsH(CO)4(SnPh3)18 or in other triosmium compounds, with values between terminal tin ligands and the osmium atom in the range of 2.6789(2)
2.7382(2) Å.18,19 The environment of the tin atom is a distorted tetrahedron formed by the osmium moiety and three methyl-2-acrylate groups. The Sn
C bond lengths are 2.157(9), 2.191(10), and 2.205(10) Å. The first is slightly shorter, but these lengths are similar to those found in the rhenium complex previously described by our group with a tris(methyl-2-acrylate)stannyl ligand.5d The angles around the tin atom range from 97.5(3) to 121.5(2)°, with C
Sn
C angles of 100.97(4)° on average and Os
Sn
C angles of 117.1(3)° on average, as expected for a local C3v symmetry for this atom. These angle values are also similar to those found in the aforementioned rhenium complex. The IR spectra of vinylstannyl complexes OsCl[Sn{C(COOR)dCH2}3](η6-p-cymene)[PPh(OEt)2] (5b, 6b) show a strong band at 1702
1696 cm
1, attributed to the νCO band of the ester group of C(COOR)dCH2. The presence of the vinylstannyl ligand Sn
[C(COOR)dCH2]3 is confirmed by 1 H, 13C, and 119Sn NMR spectra. The proton spectra show an AB quartet between 6.69 and 6.06 ppm, with their characteristic satellites due to coupling with 119Sn and 117Sn and attributed to HX and HY vinyl protons (Scheme 4). The 2JHH value of 3.5
3.3 Hz is characteristic of the geminal position of the two vinyl protons. The spectra also show the signal of the substituent

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COOR groups, i.e. a singlet at 3.59 ppm for the methyl (5b), and one quartet at 4.07 ppm and one triplet at 1.30 ppm for the ethyl (6b), matching the presence of the vinyl group. In addition to the signals of the p-cymene and phosphite, the 13C NMR spectra also show three signals between 172.9 and 137.4 ppm, each with their characteristic 119Sn and 117Sn satellites, attributed to the Cγ, CR, and Cβ carbon resonances of the CR(CγOOR)dCβH2 group (see Figure S3 in the Supporting Information). This attribution was confirmed by HMQC and HMBC experiments and by the values of J13C119Sn, which range from 244.3 to 235.6 Hz for CR to 35.0 to 22.1 Hz for Cβ and Cγ. The 119Sn NMR signal appears as a doublet at
300.0 to
302.2 ppm due to coupling with the 31P nucleus of the phosphine. These data confirm the formulation proposed for the vinylstannyl complexes in a geometry similar to that observed in the solid state.

’ CONCLUSIONS This paper demonstrates that arene ligands in the appropriate fragments OsCl(η6-p-cymene)P are able to stabilize both trihydridostannyl complexes [M]
SnH3 and organostannyl derivatives [M]
SnMe3 and [M]
Sn(CtCPh)3. Among the properties shown by the [M]
SnH3 species, addition of terminal alkynes also occurs, yielding the trivinylstannyl derivatives OsCl[Sn{C(COOR)dCH2}3](η6-p-cymene)P. ’ ASSOCIATED CONTENT Supporting Information. A CIF file giving crystallographic data for compound 5b and text, tables, and figures giving experimental details, crystal data, and spectroscopic NMR data for selected compounds. This material is available free of charge via the Internet at http://pubs.acs.org.

bS

’ AUTHOR INFORMATION Corresponding Author

*Fax: þ39 041 234 8917. E-mail: [email protected].

’ ACKNOWLEDGMENT The financial support of the MIUR (Rome)-PRIN 2007 is gratefully acknowledged. We thank Mrs. Daniela Baldan, from the Universita Ca’ Foscari Venezia (Italy), for her technical assistance. ’ REFERENCES (1) (a) Mackay, K. M.; Nicholson, B. K. In Comprehensive Organometallic Chemistry, Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon Press: New York, 1982; Vol. 2, pp 1043
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