Synthesis of Unsupported Ln–Ga Bonds by Salt Metathesis and Ga

Article pubs.acs.org/Organometallics

Synthesis of Unsupported Ln−Ga Bonds by Salt Metathesis and Ga− Ga Bond Reduction Tanja Sanden,† Michael T. Gamer,† Anatoly A. Fagin,§ Valentina A. Chudakova,§ Sergey N. Konchenko,*,‡ Igor L. Fedushkin,*,§ and Peter W. Roesky*,† †

Institut für Anorganische Chemie and Helmholtz Research School: Energy-Related Catalysis, Karlsruher Institut für Technologie (KIT), Engesserstraße Geb. 30.45, 76128 Karlsruhe, Germany ‡ A.V. Nikolaev Institute of Inorganic Chemistry SB RAS, Prospekt Lavrentieva 3, 630090 Novosibirsk, Russia § G.A. Razuvaev Institute of Organometallic Chemistry of RAS, Tropinina Street 49, 603950 Nizhny Novgorod, Russia S Supporting Information *

ABSTRACT: Three gallyl lanthanide complexes [{(dipp-Bian)Ga}2Ln(thf)4] (Ln = Sm, Eu, Yb; dipp-Bian = 1,2-bis[(2,6diisopropylphenyl)imino]acenaphthene), in which the lanthanide atoms are coordinated by only two {(dipp-Bian)Ga}− ligands and THF, are reported. Two unsupported Ln−Ga bonds are found in each compound. The gallyl lanthanide complexes have been obtained by two synthetic pathways: (1) reductive insertion of the lanthanide metals into the Ga−Ga bond of [{(dippBian)Ga}]2 and (2) salt metathesis of [(dipp-Bian)GaK(thf)5] with LnI2. Moreover, the samarium compound [{(dippBian)Ga}2Sm(thf)4] was additionally obtained in a reductive pathway from SmI3 and [(dipp-Bian)GaK(thf)5]. The length of the Ln−Ga bond strongly depends on packing effects. The reaction of TmI2(thf)5 and [(dipp-Bian)GaK(thf)5] gave the Tm(III) complex [{(dipp-Bian)Ga−Ga(dipp-Bian)}(C4H8O)TmI(thf)5], in which one THF ring was opened and reduced twice, forming the formal double negative charged anion (O-CH2-CH2-CH2-CH2)2−. This thulium compound and its dysprosium analogue [{(dipp-Bian)Ga−Ga(dipp-Bian)}(C4H8O)DyI(thf)5] were also obtained in an alternative approach by reacting LnI2(thf)x (Ln = Tm, Dy) with [(dipp-Bian)Ga]2 in THF. All new compounds were structurally characterized by single-crystal X-ray diffraction. The ytterbium complex shows the shortest Yb(II)−Ga bond distances reported so far.

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two chromium centers,7−14 the unexpected discovery of the dimetallic sandwich compound [(η 5 -C 5 Me 5 )Zn−Zn(η 5 C5Me5)]15 and other Zn−Zn bonded species,16−19 group 1420−25 and 1526−29 metal-to-metal bonds4,30,31 such as K2Ar*GeGeAr, K2Ar*SnSnAr* (Ar* = C6H3-2,6-Trip2, Trip = C6H2-2,4,6-iPr),32 and [(2,6-Mes2H3C6)BiBi(C6H3-2,6Mes2)],33 and the recently reported Mg−Mg bond34 have

INTRODUCTION Since the pioneering work of F. A. Cotton in the mid-1960s on multiple metal-to-metal bonds, metal clusters have been well established in transition metal chemistry.1 In the past decade, increasing research efforts have been made in the area of new and unusual combinations of metal-to-metal bonds.2−4 In addition to the simple effort to find new combinations of metalto-metal bonds, the nature of their bonding and of their reactivity has been investigated. The preparation of metalloid main group metal clusters,3 gallium−gallium multiple bonds,5,6 stable chromium compounds with 5-fold bonding between the © 2012 American Chemical Society

Received: April 17, 2012 Published: May 25, 2012 4331

dx.doi.org/10.1021/om300309b | Organometallics 2012, 31, 4331−4339

Organometallics

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Scheme 1. Selected Compounds with Unsupported Lanthanide−Gallium Bonds: (Top) [(η5-C5Me5)2Eu−{Ga(η5-C5Me5)}2] and [(η5-C5Me5)2(thf)Yb−Ga(η5-C5Me5)]; (Bottom) [Ln(Ga{(ArNCH)2})2(tmeda)2] and [(dipp-Bian)Ga− La(C5Me4R)2(thf)]47,48,52

(Scheme 1), obtained by the reaction of [(η5-C5Me5)Ga] with the corresponding metallocenes of the lanthanides.48 The other approach is by salt metathesis of a lanthanide halide with an anionic gallium complex. As an example the divalent bis(gallyl)lanthanide complexes [Ln(Ga{(ArNCH)2})2(tmeda)2] (Ln = Sm, Eu, or Yb; Ar = 2,6-iPr2C6H3) (Scheme 1) and the trivalent (mono)gallyl complex [Tm(Ga{(ArNCH)2})2{(ArNCH)2}(tmeda)] have been prepared by the reaction of LnI 2 with [K(tmeda)][Ga{(ArNCH)2}].47 In a similar approach, one of us reported on the reaction of the anionic gallium compound [(dippBian)Ga −Na(Et 2 O ) 3 ] (dipp-Bian = 1,2-bis[(2,6diisopropylphenyl)imino]acenaphthene) with [(C5Me4Et)2LaCl2][K(thf)2] or [(C5Me5)2LaCl2][Na(Et2O)2], which resulted in the first complexes with gallium−lanthanum bonds, [(dipp-Bian)Ga−La(C5Me4Et)2(thf)] and [(dipp-Bian)Ga−La(C5Me5)2(thf)] (Scheme 1).67 Based on our previous work on metal-to-metal bonds,52,67 we report here on an oxidative approach for the formation of lanthanide−gallium bonds starting with lanthanide metals and related reactions.

opened new opportunities for further metal-to-metal bond research. Metal-to-metal bonds in rare earth element complexes have been seldom explored because the 4f-valence shell of the rare earth metal center is embedded in the interior of the ion and well shielded by the filled 5s and 5p orbitals.35 Last century’s examples of nonsupported metal-to-metal bonds are mainly limited to Ge−Ln and Sn−Ln compounds such as [(Ph3E)2Ln(thf)4] (Ln = Eu, Yb; E = Ge, Sn),36−38 [(SnPh3)(thf)2Yb(μPh)3Yb(thf)3],38 [(η5-C5H5)}2Ln-EPh3] (Ln = Er, Yb; E = Ge, Sn),39 [(Ph2Ge)4Yb(thf)4]·4THF,40 [Eu(GePh3)2(dme)3],41 [Yb(SnNep3)2(thf)2] (Nep = 2,2-dimethylpropyl),42 and [{(Me3Sn)3Sn}2Ln(thf)4] (Ln = Sm, Yb).43 For a long period of time, [(thf)(η5-C5H5)2Lu−Ru(CO)2(η5-C5H5)] has been the only known compound with a metal-to-metal bond between a d-metal and a lanthanide metal.44 In 2006 we reported [(η5-C5Me5)2Ln-Al(η5-C5Me5)] (Ln = Eu, Yb), which were the first compounds with group 13 to 4f-element bonds.45 The solid-state structures of these compounds contained individual Lewis acid−base adducts, and no unusually short intermolecular contacts were observed. Shortly after the discovery of Ln−Al bond complexes, P. Arnold, C. Jones,46,47 and we published Ga−Ln bond complexes.48 Very recently, also B−Ln bond complexes have been reported independently in two communications.49,50 Today a number of contributions in this area are known.51−55 In group 14 chemistry also low-valent tin−lanthanide bond complexes have been communicated.56,57 Besides the progress in main group chemistry, also fascinating compounds with metal-to-metal bonds between d-metals and rare earth elements were published by several groups.58−63 A general overview has been given in some recent reviews.64−66 Lanthanide−gallium bonds have so far been prepared by two synthetic pathways. One way is the formation of a Lewis-acid− base compound by attaching a gallium(I) compound onto a Lewis acidic lanthanide complex, e.g., [(η5-C5Me5)2Eu−{Ga(η5C 5 Me 5 )} 2 ] and [(η 5 -C 5 Me 5 ) 2 (thf)Yb−Ga(η 5 -C 5 Me 5 )]

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EXPERIMENTAL SECTION

All manipulations of air-sensitive materials were performed with the rigorous exclusion of oxygen and moisture in Schlenk-type glassware either on a dual-manifold Schlenk line, interfaced to a high-vacuum (10−3 Torr) line, or in an argon-filled MBraun glovebox. THF was distilled under nitrogen from potassium benzophenone ketyl prior to use. Hydrocarbon solvents (toluene and n-pentane) were dried using an MBraun solvent purification system (SPS-800). All solvents for vacuum line manipulations were stored in vacuo over LiAlH4 in resealable flasks. Deuterated solvents were obtained from Aldrich GmbH (99 atom % D) and were degassed, dried, and stored in vacuo over Na/K alloy in resealable flasks. NMR spectra were recorded on a Bruker Avance II 300 MHz and a Bruker Avance II 400 MHz FTNMR spectrometer. Chemical shifts are referenced to internal solvent resonances and are reported relative to tetramethylsilane. IR spectra 4332

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Table 1. Crystallographic Details of [{(dipp-Bian)Ga}2Sm(thf)4] (1), [{(dipp-Bian)Ga}2Sm(thf)4]·(thf)2(toluene) (1′), and [{(dipp-Bian)Ga}2Eu(thf)4] (2) chemical formula formula mass cryst syst a/Å b/Å c/Å β/deg unit cell volume/Å3 temperature/K space group Z radiation type μ/mm−1 reflns measd indep reflns Rint final R1 values (I > 2σ(I)) final wR(F2) values (all data) goodness of fit on F2

1

1′

2·(thf)2(toluene)

C88H112Ga2N4O4Sm 1579.61 monoclinic 13.7822(4) 14.3724(4) 20.1608(6) 90.656(2) 3993.3(2) 150(2) P21/n 2 Mo Kα 1.447 34 618 7239 0.0350 0.0196 0.0501 1.003

C103H136Ga2N4O6Sm 1815.95 monoclinic 12.7406(7) 15.4964(5) 24.3631(11) 99.393(4) 4745.6(4) 150(2) P21/n 2 Mo Kα 1.228 18 069 8536 0.0347 0.0333 0.0749 0.910

C103H136EuGaN4O6 1817.56 monoclinic 12.611(3) 15.433(3) 24.211(5) 99.49(3) 4647(2) 150 P21/n 2 Mo Kα 1.297 35 152 9858 0.0512 0.0359 0.0786 1.005

were obtained on a Bruker Tensor 34. Raman spectra were carried out with a Bruker MultiRAM. Elemental analyses were carried out with an Elementar Vario EL. [(dipp-Bian)Ga]2,67 [(dipp-Bian)GaK(thf)5],67 LnI268−70 (Ln = Sm, Eu, Yb), TmI2(thf)5,71 and DyI272 were prepared according to literature procedures. [{(dipp-Bian)Ga}2Sm(thf)4] (1). Route A. A 0.5 g (3.3 mmol) amount of Sm metal powder was activated with 1 drop of Hg. Then 0.5 g (0.4 mmol) of [(dipp-Bian)Ga]2 and 30 mL of THF were added. The reaction mixture was activated in an ultrasonic bath for 8 h at 60 °C, cooled to room temperature, filtered, and concentrated to 10 mL. Dark brown crystals (515 mg, 81%) were obtained by cooling at −15 °C overnight. Route B. THF (20 mL) was condensed at −78 °C onto a mixture of [(dipp-Bian)GaK(thf)5] (194 mg, 0.2 mmol) and SmI2(thf)2 (57 mg, 0.1 mmol), and the resulting reaction mixture was stirred overnight at room temperature. The solvent was evaporated under vacuum, and the residue was dissolved in toluene (7 mL). KI was filtered off. Slow evaporation of the solvent yielded 151 mg (96%) of [{(dippBian)Ga}2Sm(thf)4] as dark brown crystals. Route C. THF (20 mL) was condensed at −78 °C onto a mixture of [(dipp-Bian)GaK(thf)5] (291 mg, 0.3 mmol) and SmI3 (53 mg, 0.1 mmol), and the resulting reaction mixture was stirred overnight at room temperature. The solvent was evaporated under vacuum, and the residue was dissolved in toluene (7 mL). KI was filtered off. Slow evaporation of the solvent yielded 146 mg (92% based on Sm) of [{(dipp-Bian)Ga}2Sm(thf)4] as dark brown crystals. IR (ATR) [cm−1]: 3364 (vw), 3063 (vw), 2962 (vs), 2929 (s), 2868 (s), 2362 (vw), 2313 (vw), 2251 (vw), 2226 (vw), 2159 (w), 2102 (w), 2089 (vw), 2054 (vw), 2023 (vw), 1985 (vw), 1955 (vw), 1921 (vw), 1669 (w), 1643 (w), 1589 (w), 1575 (w), 1540 (vw), 1455 (s), 1382 (m), 1361 (w), 1328 (w), 1253 (w), 1193 (vw), 1116 (vw), 1059 (w), 924 (vw), 835 (vw), 816 (vw), 786 (w), 752 (m), 532 (m), 515 (m), 463 (m), 410 (m), 377 (m), 327 (m). Anal. Calcd for [(C72H80N4Ga2Sm)(thf)4] (found): C 66.91 (65.87); H 7.15 (7.18); N 3.55 (3.14). [{(dipp-Bian)Ga}2Eu(thf)4] (2). Route A. Eu metal powder (0.5 g, 3.3 mmol) was activated with 1 drop of Hg. Then 0.5 g (0.4 mmol) of [(dipp-Bian)Ga]2 and 30 mL of THF were added. The reaction mixture was stirred for 24 h, filtered, and concentrated to 10 mL. Dark brown crystals were obtained by cooling at −15 °C overnight. Yield: 540 mg, 84%. Route B. THF (20 mL) was condensed at −78 °C onto a mixture of [(dipp-Bian)GaK(thf)5] (194 mg, 0.2 mmol) and EuI2(thf)2 (55 mg, 0.1 mmol), and the resulting reaction mixture was stirred overnight at

room temperature. The solvent was evaporated under vacuum, and the residue was dissolved in toluene (7 mL). KI was filtered off. Slow evaporation of the solvent yielded 138 mg (87%) of [{(dippBian)Ga}2Eu(thf)4] as dark brown crystals. IR (ATR) [cm−1]: 3359 (vw), 3064 (vw), 2963 (vs), 2869 (m), 2398 (vw), 2281 (vw), 2248 (vw), 2098 (vw), 2071 (vw), 2034 (vw), 2008 (vw), 1977 (vw), 1930 (vw), 1669 (vw), 1590 (w), 1575 (w), 1455 (m), 1383 (w), 1361 (w), 1329 (w), 1254 (vw), 1193 (vw), 1105 (vw), 1059 (vw), 925 (vw), 835 (vw), 816 (vw), 786 (vw), 767 (vw), 752 (w), 705 (w), 623 (w), 577 (w), 533 (w), 463 (w), 381 (w), 327 (w). Raman [cm−1]: 74 (w), 256 (w), 414 (w), 521 (w), 549 (w), 588 (w), 620 (w), 804 (w), 877 (w), 892 (w), 930 (w), 1179 (w), 1353 (w), 1374 (m), 1417 (w), 1437 (s), 1472 (w), 1505 (vs), 1592 (w), 1606 (w). Anal. Calcd for [(C72H80N4Ga2Eu)(thf)4] (found): C 66.41 (66.84); H 7.14 (7.14); N 3.20 (3.54). [{(dipp-Bian)Ga)}2Yb(thf)4] (3). Route A. Yb metal powder (0.5 g, 2.9 mmol) was activated with 1 drop of Hg. Then 0.5 g (0.4 mmol) of [(dipp-Bian)Ga]2 and 30 mL of THF were added. The reaction mixture was stirred for 24 h, filtered, and concentrated to 10 mL. Dark brown crystals were obtained by cooling at −15 °C overnight. Yield: 500 mg, 76%. Route B. THF (20 mL) was condensed at −78 °C onto a mixture of [(dipp-Bian)GaK(thf)5] (194 mg, 0.2 mmol) and YbI2(thf)2 (57 mg, 0.1 mmol), and the resulting reaction mixture was stirred overnight at room temperature. The solvent was evaporated under vacuum, and the residue was dissolved in toluene (7 mL). KI was filtered off. Slow evaporation of the solvent yielded 127 mg (79%) of [{(dippBian)Ga}2Yb(thf)4] as dark brown crystals. 1 H NMR (300 MHz, d8-THF): δ 7.24−7.19 (m, 2H, arom. H), 7.15−7.05 (m, 10H, arom. H), 7.04−6.94 (m, 5H, arom. H), 6.69− 6.63 (m, 4H, arom. H), 6.58−6.53 (m, 4H, arom. H), 5.62 (d, J = 6.3 Hz, 4H, arom. H), 3.86 (dq, 6.9 Hz, 8H, CH(CH3)2), 2.33 (s, 3H, C6H5CH3), 1.24 (d, J = 6.9 Hz, 24H, CH(CH3)2), 1.08 (d, J = 6.9 Hz, 24H, CH(CH3)2) ppm. 13C{1H} NMR (300 MHz, d8-THF, 25 °C): δ 23.4 (CH(CH3)2), 25.2 (CH(CH3)2), 25.4 (C4H8O), 27.8 (CH(CH3)2), 67.2 (C4H8O), 114.6 (arom. CH), 120.5 (arom. CH), 121.8 (arom. CH), 122.4 (arom. CH), 122.6 (arom. CH), 123.2 (arom. CH), 126.2 (arom. CH), 130.8 (arom. C), 136.5 (arom. C), 144.9 (arom. C), 147.3 (arom. C) ppm. (In the NMR spectra some signals of a decomposition product were also observed.) IR (ATR) [cm−1]: 3352 (vw), 3061 (vw), 2959 (m), 2867 (w), 1921 (vw), 1667 (vw), 1641 (vw), 1589 (w), 1539 (vw), 1453 (m), 1437 (m), 1382 (w), 1361 (w), 1326 (w), 1253 (w), 1193 (w), 1146 (vw), 1106 (w), 1058 (m), 1043 (w), 961 (vw), 924 (m), 833 (w), 816 (m), 795 (m), 781 (s), 754 4333

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Table 2. Crystallographic Details of [{(dipp-Bian)Ga}2Yb(thf)4] (3), [{(dipp-Bian)Ga−Ga(dipp-Bian)}(C4H8O)TmI(thf)5] (4), and [{(dipp-Bian)Ga−Ga(dipp-Bian)}(C4H8O)DyI(thf)5] (5) chemical formula formula mass cryst syst a/Å b/Å c/Å β/deg unit cell volume/Å3 temperature/K space group Z radiation type μ/mm−1 reflns measd indep reflns Rint final R1 values (I > 2σ(I)) final wR(F2) values (all data) goodness of fit on F2

3

4·(thf)

5·3(thf)

C88H112Ga2N4O4Yb 1602.30 monoclinic 13.6617(5) 14.3216(4) 20.1983(9) 90.575(3) 3951.7(3) 150(2) P21/n 2 Mo Kα 1.902 24 572 7022 0.0889 0.0365 0.0731 0.881

C100H136Ga2IN4O7Tm 1941.40 monoclinic 46.0961(15) 20.8634(9) 25.2675(8) 122.319(2) 20535.8(13) 150(2) C2/c 8 Mo Kα 1.729 91 276 18 592 0.1066 0.0467 0.0746 1.006

C108H152DyGa2IN4O9 2079.18 monoclinic 45.875(7) 20.805(3) 25.246(4) 122.187(2) 20392(5) 100 C2/c 8 Mo Kα 1.610 85 256 19 935 0.2862 0.0786 0.2018 0.864

Scheme 2. Synthesis of Compounds 1−3

[{(dipp-Bian)Ga−Ga(dipp-Bian)}(C4H8O)DyI(thf)5] (5). Compound [(dipp-Bian)Ga]2 has been prepared in toluene using of 0.5 g (1.0 mmol) of dipp-Bian and an excess of gallium. After completion of the synthesis the toluene was removed under vacuum at ambient temperature. The residual crystalline solid of [(dipp-Bian)Ga]2 was dissolved in thf (40 mL). The formed deep-blue solution was added to DyI2 (0.416 g, 1.0 mmol). Upon shaking at room temperature within several minutes the solution turned green-brown. The mixture was filtered off and stored at ambient temperature overnight. Decantation of the mother liquor resulted in 950 mg (92%) of compound 5 as deep greenish crystals. Mp: 168−170 °C (dec). IR (ATR) [cm−1]: 3061 (w), 2958 (m), 2927 (w), 2866 (w), 1668 (m), 1641 (m), 1593 (m), 1508 (w), 1363 (m), 1343 (w), 1327 (w), 1274 (w), 1252 (m), 1177 (w), 1107 (m), 1066 (m), 1040 (m), 1003 (s), 924 (s), 850 (s), 834 (s), 805 (w), 787 (m), 750 (m), 667 (m), 642 (w), 618 (w), 575 (w). Titration of the dysprosium with EDTA in the presence of xylenol orange as indicator constantly gave no sharp color changeover. X-ray Crystallographic Studies of 1−6. A suitable crystal was covered in mineral oil (Aldrich) and mounted on a glass fiber. Crystals of 1−5 were transferred directly to either the −73 or −123 °C cold

(vs), 705 (w), 533 (vs). Anal. Calcd for [(C72H80N4Ga2Yb)(thf)4] (found): C 65.96 (65.16); H 7.05 (6.89); N 3.50 (3.53). [{(dipp-Bian)Ga−Ga(dipp-Bian)}(C4H8O)TmI(thf)5] (4). Route A. THF (20 mL) was condensed at −78 °C onto a mixture of bianGaK(thf)5 (194 mg, 0.2 mmol) and TmI2(thf)5 (78 mg, 0.1 mmol), and the resulting reaction mixture was stirred overnight at room temperature. The solvent was evaporated under vacuum, and the residue was dissolved in toluene (7 mL). KI was filtered off. Slow evaporation of the solvent yielded 161 mg (86%) of [{(dippBian)Ga−Ga(dipp-Bian)}(C4H8O)TmI(thf)5] as dark brown crystals. Route B. THF (20 mL) was condensed at −78 °C onto a mixture of [(dipp-Bian)Ga]2 (114 mg, 0.1 mmol) and TmI2(thf)5 (157 mg, 0.2 mmol), and the resulting reaction mixture was stirred for 16 h at 60 °C. TmI3 was filtered off. Slow evaporation of the solvent yielded 165 mg (88%) of [{(dipp-Bian)Ga−Ga(dipp-Bian)}(C4H8O)TmI(thf)5]. IR (ATR) [cm−1]: 3061 (w), 2958 (m), 2927 (w), 2866 (w), 1653 (w), 1637 (w), 1588 (w), 1571 (m), 1541 (w), 1456 (m), 1483 (m), 1382 (m), 1361 (m), 1327 (m), 1254 (m), 1193 (w), 1160 (w), 1145 (w), 1103 (w), 1058 (w), 1042 (m), 924 (m), 832 (m), 816 (m), 795 (m), 780 (m), 767 (s), 754 (vs), 684 (m), 668 (s), 532 (vs). Elemental analysis from ground single crystals constantly gave low carbon values. 4334

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Scheme 3. Synthesis of Compound 1

tion was obtained from the 1H and 13C{1H} NMR data to interpret the structure of compound 3. The 1H NMR spectrum shows the signals expected for the organic ligands, but the chemical shifts of the starting materials [(dipp-Bian)GaK(thf)5], [(dipp-Bian)Ga]2, and 3 are very similar. The protons observed by NMR seem to be too remote from the reactive metal center to be influenced by electron density changes. The isopropyl groups of the {(dipp-Bian)Ga}− unit show two overlaid quartets (appearing as a septet) (δ = 3.86 ppm) from the isopropyl CH group and two doublets from the nonequivalent isopropyl CH3 groups (δ = 1.24 and 1.08 ppm). Thus, two mirror planes can be drawn through the molecule in solution, which is consistent with the solid-state structure (vide inf ra). Although compounds 1−3 were crystallized from THF, we surprisingly observed the rapid formation of some signals in the NMR from a decomposition product by dissolving the compound in deuterated THF. Single crystals of two polymorphs of compound 1 were obtained. Both crystallize in the monoclinic space group P21/n with two molecules of 1 in the unit cell. The differences between the two polymorphs are the amount of solvent found in the unit cell. One polymorph crystallizes without solvent, whereas the other one has four additional molecules of THF and two additional molecules of toluene in the unit cell. To distinguish these polymorphs, we labeled the latter one as compound 1′ (= [{(dipp-Bian)Ga}2Sm(thf)4]·(thf)2(toluene)) (see also Figures 1, S1, and S2). Interestingly, single crystals

stream of a STOE IPDS 2 diffractometer. The data for 5 were collected on a Bruker SMART APEX diffractometer, using graphitemonochromated Mo Kα radiation (ω-scan technique, λ = 0.71073 Å). The structures were solved by the direct or Patterson method using SHELXS-9773 and were refined on F2 using SHELXL-97.73 SADABS was used to perform area-detector scaling and absorption corrections for compound 5. All non-hydrogen atoms were refined anisotropically. The final values of refinement parameters are given in Tables 1 and 2. The locations of the largest peaks in the final difference Fourier map calculation as well as the magnitude of the residual electron densities in each case were of no chemical significance. Positional parameters, hydrogen atom parameters, thermal parameters, and bond distances and angles have been deposited as Supporting Information.

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RESULTS AND DISCUSSION The reaction of [(dipp-Bian)Ga]2 with the amalgams of samarium, europium, and ytterbium gave the corresponding gallyl lanthanide complexes [{(dipp-Bian)Ga}2Ln(thf)4] (Ln = Sm (1), Eu (2), Yb (3)) in high yields (Scheme 2). Concomitant with the reaction the color of the solution changed from blue ([(dipp-Bian)Ga]2) to dark brown. The resulting complexes 1−3 each feature two unsupported Ln−Ga bonds. Besides the Ln−Ga bonds, the lanthanide atoms are coordinated only by four molecules of THF. In contrast, the related digallyl compounds of P. Arnold and C. Jones, [Ln{Ga[(ArNCH)2]}2(tmeda)2] (Ln = Sm, Eu, Yb; Ar = C6H3iPr2-2,6) (Scheme 1), could not be obtained from lanthanide metals in THF. The latter compounds were obtained by a salt metathesis approach from [K(tmeda)][Ga{(ArNCH)2}] with a half-equivalent of LnI2 in THF. The Ln− Ga bond could be stabilized only in the presence of tmeda.47 A related reductive insertion of a metal into the Ga−Ga bond described here is the reaction of [(dipp-Bian)Ga]2 with potassium leading to [(dipp-Bian)GaK(thf)5]. The attempt of reacting [(dipp-Bian)Ga]2 with other lanthanide metals under the same conditions as used for the preparation of compounds 1−3 did not succeed. Compounds 1−3 can also be obtained with the salt metathesis approach. The reaction of the potassium salt [(dipp-Bian)GaK(thf)5] with a half-equivalent of LnI2 (Ln = Sm, Eu, or Yb) in THF resulted in corresponding compounds 1−3 in high yields (Scheme 2). Furthermore, we have established a third approach for the samarium compound 1, as shown in Scheme 3. The reaction of the potassium salt [(dipp-Bian)GaK(thf)5] with SmI3 did not lead to an expected trigallyl compound. Instead the samarium ion was reduced from Sm(III) to Sm(II), and compound 1 was obtained in high yields (Scheme 3). Understandably, the reduction potential of [(dipp-Bian)GaK(thf)5] is large enough to reduce Sm(III). Complexes 1−3 were characterized by standard analytical/ spectroscopic techniques, and the solid-state structures were analyzed by single-crystal X-ray diffraction. NMR spectra were recorded from the diamagnetic compound 3 only. Although clearly resolved spectra were recorded, no sufficient informa-

Figure 1. Solid-state structure of 1 (shown is the polymorph without noncoordinated solvent). Compounds 2 and 3 are similar (see Supporting Information for ORTEP plots). Selected distances and angles are given in Table 3.

obtained for compound 2 were isostructural to compound 1′. Thus compound 2 contains four additional molecules of THF and two additional molecules of toluene in the unit cell. In contrast the isolated single crystals of compound 3 were isostrucural to the polymorph of compound 1 crystallized without any solvent. In principle it should be possible to isolate the other polymorphs of compounds 2 and 3 (Figures S2 and 4335

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look at the two polymorphs 1 and 1′ show that the Sm−Ga bond distances differ by about 0.1 Å. Clearly, the length of the Ln−Ga bond strongly depends on packing effects. The fact that other bond distances within the molecules are only slightly influenced by the packing indicates the weak nature of the Ln− Ga interaction. The Yb−Ga bond distance observed here is significantly shorter than the one in the gallium heterocycle ytterbium(II) complex [Yb{Ga[(ArNCH)2]}2(tmeda)2] (3.226 Å (mean)) 47 and in the divalent metallocene [(η 5 C5Me5)2(thf)Yb−Ga(η5-C5Me5)] (3.2872(4) Å).48 Thus, the Yb(II)−Ga bond distances in compound 3 are the shortest ones reported so far. The higher stability of compounds 1−3 compared to the previously published Ln(II)−Ga compounds might be a result of the shorter metal-to-metal bonds. But as already mentioned, packing effects have a significant influence on the stability of compounds. In addition to the two {(dipp-Bian)Ga}− ligands, the lanthanide atoms are coordinated by four molecules of THF as well. A nearly perfect coordination octahedron elongated along the Ga−Ln−Ga axis is formed by the six ligands around the lanthanide atoms. Thus, all bond angles are in the range of 90° and 180°. The N1−Ga−N2 bite angles of 84.61(5)° (1), 84.00(9)° (2), and 84.37(15)° (3) of the {(dipp-Bian)Ga}− ligands are in the expected range. Furthermore we were interested in studying the reaction of TmI2 with [(dipp-Bian)GaK(thf)5]. Running the reaction at low temperature (−78 °C) in THF did not result in the expected analogue of compounds 1−3. Instead a reduction of the solvent took place and the Tm(III) complex [{(dippBian)Ga−Ga(dipp-Bian)}(C4H8O)TmI(thf)5] (4) was formed (Scheme 4). The THF ring was opened and reduced twice, forming the formal double negative charged anion (O-CH2CH2-CH2-CH2)2−. At the same time, KI was formed and [(dipp-Bian)GaK(thf)5] was oxidized to give [(dipp-Bian)Ga]2. Compound 4 and its dysprosium analogue complex [{(dippBian)Ga−Ga(dipp-Bian)}(C4H8O)DyI(thf)5] (5) were also obtained in a more rational approach by reacting 2 equiv of LnI2(thf)x (Ln = Tm, Dy) with [(dipp-Bian)Ga]2 in THF (Scheme 4).

S3), but we are not interested in these crystallographic details. Data collection parameters and selected bond lengths and angles are given in Tables 1 and 3. Table 3. Selected Bond Lengths [Å] and Angles [deg] in the Complexes [{(dipp-Bian)Ga}2Sm(thf)4] (1), [{(dippBian)Ga}2Sm(thf)4]·(thf)2(toluene) (1′), [{(dippBian)Ga}2Eu(thf)4] (2), and [{(dipp-Bian)Ga}2Yb(thf)4] (3) Ln−Ga Ln−O1 Ln−O2 Ga−N1 Ga−N2 Ga−Ln−Ga Ga−Ln−O1 Ga−Ln−O1′ Ga−Ln−O2 Ga−Ln−O2′ O1−Ln−O2 O1−Ln−O2′ O1−Ln−O1′ O2−Ln−O2′ N1−Ga−N2

1

1′

2·(thf)2(toluene)

3

3.2358(2) 2.5444(12) 2.5105(15) 1.9362(14) 1.9567(13) 180.0 86.29(3) 93.71(3) 93.30(4) 86.70(4) 93.28(5) 86.72(5) 180.0 180.0 84.61(5)

3.3467(3) 2.525(2) 2.522(2) 1.968(2) 1.952(2) 180.0 93.89(5) 86.11(5) 90.25(6) 89.75(6) 91.53(8) 88.47(8) 180.0 180.0 83.89(9)

3.3239(6) 2.516(2) 2.505(2) 1.968(2) 1.958(2) 180.0 93.77(5) 86.23(5) 90.36(6) 89.64(6) 91.33(8) 88.67(8) 180.0 180.0 84.00(9)

3.1295(5) 2.428(3) 2.402(3) 1.933(4) . 1.965(3) 180.0 87.18(8) 92.82(8) 93.15(9) 86.85(9) 92.65(13) 87.35(13) 180.0 180.0 84.37(15)

Besides the polymorphism, all three compounds are similar to each other in the solid state. Each compound crystallizes with half a molecule in the asymmetric unit. A crystallographic inversion center is located in the lanthanide atom. Thus, the two {(dipp-Bian)Ga}− ligands are arranged in one plane. In contrast, two moieties in the corresponding structure of [{(dipp-Bian)Ga}2Ba(thf)5] are twisted with respect to each other.67 The two {(dipp-Bian)Ga}− ligands are arranged in a linear setup, forming a Ga−Ln−Ga angle of 180°. The Ln−Ga bond distances are 3.2358(2) Å (1), 3.3467(3) Å (1′), 3.3239(6) Å (2), and 3.1295(5) Å (3). At first glance, these values do not seem to follow the expected trend (Sm−Ga ≈ Eu−Ga > Yb−Ga) based on the effective ionic radii. A closer Scheme 4. Synthesis of Compound 4

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The solid-state structures of compounds 4 (Figure 2) and 5 (Figure S6) were established by single-crystal X-ray diffraction.

scaffold is strongly bent. The Ga−C73 bond distances are 1.985(5) Å (4) and 1.992(6) Å (5). The observed reactivity of [(dipp-Bian)Ga]2 is in line with a recently published reversible addition of different alkynes onto [(dipp-Bian)Ga]2.75,76 Similarly to compounds 4 and 5, related digallane complexes with bridging anionic σ- and π-donors were reported by W. Uhl ([{(Me 3 Si) 2 CH} 2 Ga−Ga{CH(SiMe 3 ) 2 }(σ-CCPh)][Li(thf)4]),77 G. Linti ([Li(thf)4][Ga2(SiPh3)5]),78 and C. Jones ([{(H)C(Ar)N]2Ga−Ga[N(Ar)C(H)}2{π-CpK(tmeda)2}]; Ar = 2,6-iPr2-C6H3).79 As a result of the anionic nature of the coordinating (O-CH2-CH2-CH2-CH2)2− ligand, the Ga−Ga bond distances of 2.5287(8) Å (4) and 2.5298(10) Å (5) are elongated compared to [(dipp-Bian)Ga]2 (2.3598(3) Å).80 In comparison to diethyl ether or THF, which does not coordinate to gallium in [(dipp-Bian)Ga]2, the anionic CH2 group of the (O-CH2-CH2-CH2-CH2)2− ligand is nucleophilic enough to give a Lewis acid−base adduct to Ga in [(dipp-Bian)Ga]2. Thus, the digallane acts as a nucleophile trap. Although ringopened THF compounds of the rare earth elements were reported earlier, e.g., [(η 5 -C 5 Me 5 )Cp*Sc(BH 4 ){μ-O(CH 2) 3 CH3 }]2 ,81 [(η 5 -C 5 Me5 ) 2 Ln{O(CH2 ) 4(C 5 Me5 )}thf] (Ln = La, Nd, Sm, Tm, Lu),82,83 [{Sc{μ-O(CH2)4(Dtp)}Cl2(thf)2}2] (Dtp = 2,5-di-tert-butyl-3,4-dimethylphospholide),84 [(η5-C5H5)2Lu-(μ-O(CH2)4P(C6H5)2)]2,85 and [(η5C5Me5)2Sm{O(CH2)4EPh2}(thf)] (E = P, As),86 compounds 4 and 5 have shown the first example of opening a THF ring to an (O-CH2-CH2-CH2-CH2)2− dianion in this area.

Figure 2. Solid-state structure of 4 (see Supporting Information for the structural parameters of compound 5 and ORTEP plots of 4 and 5). Selected distances [Å] and angles [deg]: Tm−O1 1.964(4), Tm− O2 2.379(4), Tm−O3 2.377(4), Tm−O4 2.362(4), Tm−O5 2.366(3), Tm−O6 2.389(4), Tm−I 3.0259(5), Ga1−Ga2 2.5287(8), Ga1−N1 1.914(4), Ga1−N2 1.923(4), Ga2−N3 1.924(4), Ga2−N4 1.930(4), Ga2−C73 1.985(5); O1−Tm−O2 86.23(14), O1−Tm−O3 89.99(15), O1−Tm−O4 91.53(15), O1−Tm−O5 87.68(14), O1− Tm−O6 94.74(15), O2−Tm−O3 72.40(13), O2−Tm−O4 145.18(13), O2−Tm−O5 142.06(13), O2−Tm−O6 72.05(13), O3−Tm−O4 72.86(13), O3−Tm−O5 145.04(13), O3−Tm−O6 143.71(13), O4−Tm−O5 72.34(13), O4−Tm−O6 142.67(12), O5−Tm−O6 71.20(12), O1−Tm−I 177.35(11), O2−Tm−I 91.81(10), O3−Tm−I 87.71(10), O4−Tm−I 89.05(9), O5−Tm−I 94.96(9), O6−Tm−I 86.35(9), N1−Ga1−N2 87.3(2), N3−Ga2−N4 86.5(2), N3−Ga2−C73 119.6(2), N4−Ga2−C73 118.1(2).

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SUMMARY In summary, we have synthesized three gallyl lanthanide complexes [{(dipp-Bian)Ga}2Ln(thf)4] (Ln = Sm, Eu, Yb), in which the lanthanide atoms are coordinated only by the two {(dipp-Bian)Ga}− ligands and THF. The gallyl lanthanide complexes have been obtained by two synthetic approaches. In the first approach the lanthanide metals were inserted into the Ga−Ga bond of [(dipp-Bian)Ga]2. In the second approach [(dipp-Bian)GaK(thf)5] was reacted with LnI2(thf)x. Moreover, the samarium compound [{(dipp-Bian)Ga}2Sm(thf)4] was obtained in a reductive pathway from SmI3 and [(dippBian)GaK(thf)5]. Attempts to obtain the related thulium complexes from thulium(II) diiodide and [(dipp-Bian)GaK(thf)5] gave the Tm(III) complex [{(dipp-Bian)Ga−Ga(dippBian)}(C4H8O)TmI(thf)5], in which one THF ring was opened and reduced twice, forming the formal double negative charged anion (O-CH2-CH2-CH2-CH2)2−. This thulium and the analogue dysprosium compound were also obtained in a more rational approach by reacting thulium(II) or dysprosium(II) diiodide with [(dipp-Bian)Ga]2 in THF.

Compound 4 crystallizes in the monoclinic space group C2/c, having one molecule of 4 and three molecules of THF in the asymmetric unit. From the noncoordinated solvent molecules, only one equivalent of THF could be refined, whereas the remaining THF molecules were heavily disordered. These solvent molecules were suppressed by using the SQUEEZE routine in PLATON.74 Compound 5 is isostructural to compound 4, but all THF molecules could be located. Selected bond lengths and angles of all compounds are given in the captions of Figures 2 and S6. The most remarkable feature in compounds 4 and 5 is the (O-CH2-CH2-CH2-CH2)2− dianion, which coordinates with the oxygen atom to the {LnI(thf)5} fragment, having Tm−O and Dy−O bonds with bond distances of 1.964(4) and 2.005(5) Å, respectively. These bond distances are significantly shorter than the Tm−O and Dy−O bond distances of the normal coordinated THF molecules (4: av 2.375(4) Å; 5: av 2.416 Å), which supports the anionic nature of (O-CH2-CH2-CH2-CH2)2−. The five THF molecules, the iodine atom, and the (O-CH2-CH2-CH2-CH2)2− dianion form a distorted pentagonal bipyramid around the rare earth ions in 4 and 5 with all five THF molecules in the plane. The sum of the five O−Ln−O bond angles between the THF molecules in the plane in both cases is close to an ideal value of 360° (4, 360.85°; 5, 361.22°). The negatively charged CH2− group of the (O-CH2-CH2-CH2-CH2)2− dianion binds to one of the two gallium atoms in [(dipp-Bian)Ga]2. As a result of this asymmetric coordination of the dianion, the [(dipp-Bian)Ga]2

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ASSOCIATED CONTENT

S Supporting Information *

X-ray crystallographic files in CIF format for the structure determinations of 1−5 are available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]; [email protected]; roesky@kit. edu. Notes

The authors declare no competing financial interest. 4337

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ACKNOWLEDGMENTS

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REFERENCES

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(29) Sasamori, T.; Mieda, E.; Nagahora, N.; Sato, K.; Shiomi, D.; Takui, T.; Hosoi, Y.; Furukawa, Y.; Takagi, N.; Nagase, S.; Tokitoh, N. J. Am. Chem. Soc. 2006, 128, 12582−12588. (30) Layfield, R. A. In Organometallic Chemistry; The Royal Society of Chemistry, 2008; Vol. 34, pp 155−165. (31) Sasamori, T.; Tokitoh, N. Dalton Trans. 2008, 1395−1408. (32) Pu, L.; Phillips, A. D.; Richards, A. F.; Stender, M.; Simons, R. S.; Olmstead, M. M.; Power, P. P. J. Am. Chem. Soc. 2003, 125, 11626−11636. (33) Twamley, B.; Sofield, C. D.; Olmstead, M. M.; Power, P. P. J. Am. Chem. Soc. 1999, 121, 3357−3367. (34) Green, S. P.; Jones, C.; Stasch, A. Science 2007, 318, 1754−1757. (35) Freeman, A. J.; Watson, R. E. Phys. Rev. 1962, 127, 2058−2075. (36) Bochkarev, L. N.; Makarov, V. M.; Hrzhanovskaya, Y. N.; Zakharov, L. N.; Fukin, G. K.; Yanovsky, A. I.; Struchkov, Y. T. J. Organomet. Chem. 1994, 467, C3−C5. (37) Bochkarev, M. N.; Khramenkov, V. V.; Rad’kov, Y. F.; Zakharov, L. N.; Struchkov, Y. T. J. Organomet. Chem. 1991, 408, 329−334. (38) Bochkarev, M. N.; Khramenkov, V. V.; Rad’kov, Y. F.; Zakharov, L. N.; Struchjkov, Y. T. J. Organomet. Chem. 1991, 421, 29−38. (39) Schumann, H.; Cygon, M. J. Organomet. Chem. 1978, 144, C43−C45. (40) Bochkarev, L. N.; Makarov, V. M.; Zakharov, L. N.; Fukin, G. K.; Yanovsky, A. I.; Struchkov, Y. T. J. Organomet. Chem. 1995, 490, C29−C31. (41) Fedorova, E. E.; Trifonov, A. A.; Bochkarev, M. N.; Girgsdies, F.; Schumann, H. Z. Anorg. Allg. Chem. 1999, 625, 1818−1822. (42) Cloke, F. G. N.; Dalby, C. I.; Hitchcock, P. B.; Karamallakis, H.; Lawless, G. A. J. Chem. Soc., Chem. Commun. 1991, 779−781. (43) Bochkarev, L. N.; Grachev, O. V.; Molosnova, N. E.; Zhiltsov, S. F.; Zakharov, L. N.; Fukin, G. K.; Yanovsky, A. I.; Struchkov, Y. T. J. Organomet. Chem. 1993, 443, C26−C28. (44) Beletskaya, I. P.; Voskoboynikov, A. Z.; Chuklanova, E. B.; Kirillova, N. I.; Shestakova, A. K.; Parshina, I. N.; Gusev, A. I.; Magomedov, G. K. I. J. Am. Chem. Soc. 1993, 115, 3156−3166. (45) Gamer, M. T.; Roesky, P. W.; Konchenko, S. N.; Nava, P.; Ahlrichs, R. Angew. Chem., Int. Ed. 2006, 45, 4447−4451. (46) Arnold, P. L.; Liddle, S. T.; McMaster, J.; Jones, C.; Mills, D. P. J. Am. Chem. Soc. 2007, 129, 5360−5361. (47) Jones, C.; Stasch, A.; Woodul, W. D. Chem. Commun. 2009, 113−115. (48) Wiecko, M.; Roesky, P. W. Organometallics 2007, 26, 4846− 4848. (49) Saleh, L. M. A.; Birjkumar, K. H.; Protchenko, A. V.; Schwarz, A. D.; Aldridge, S.; Jones, C.; Kaltsoyannis, N.; Mountford, P. J. Am. Chem. Soc. 2011, 133, 3836−3839. (50) Li, S.; Cheng, J.; Chen, Y.; Nishiura, M.; Hou, Z. Angew. Chem., Int. Ed. 2011, 50, 6360−6363. (51) Krinsky, J. L.; Minasian, S. G.; Arnold, J. Inorg. Chem. 2010, 50, 345−357. (52) Fedushkin, I. L.; Lukoyanov, A. N.; Tishkina, A. N.; Maslov, M. O.; Ketkov, S. Y.; Hummert, M. Organometallics 2011, 30, 3628−3636. (53) Minasian, S. G.; Krinsky, J. L.; Rinehart, J. D.; Copping, R.; Tyliszczak, T.; Janousch, M.; Shuh, D. K.; Arnold, J. J. Am. Chem. Soc. 2009, 131, 13767−13783. (54) Vlaisavljevich, B.; Miró, P.; Cramer, C. J.; Gagliardi, L.; Infante, I.; Liddle, S. T. Chem.Eur. J. 2011, 17, 8424−8433. (55) Liddle, S. T.; Mills, D. P.; Gardner, B. M.; McMaster, J.; Jones, C.; Woodul, W. D. Inorg. Chem. 2009, 48, 3520−3522. (56) Zeckert, K.; Zahn, S.; Kirchner, B. Chem. Commun. 2010, 46, 2638−2640. (57) Reichart, F.; Kischel, M.; Zeckert, K. Chem.Eur. J. 2009, 15, 10018−10020. (58) Arnold, P. L.; McMaster, J.; Liddle, S. T. Chem. Commun. 2009, 818−820. (59) Blake, M. P.; Kaltsoyannis, N.; Mountford, P. J. Am. Chem. Soc. 2011, 133, 15358−15361. (60) Butovskii, M. V.; Tok, O. L.; Bezugly, V.; Wagner, F. R.; Kempe, R. Angew. Chem., Int. Ed. 2011, 50, 7695−7698.

This work was supported by the Deutsche Forschungsgemeinschaft, the Helmholtz-Kolleg, “Energy-Related Catalysis”, the Russian Foundation of Basic Research (RFBR), and the BadenWürttemberg Stiftung GmbH. We thank Center for Crystallographic Study of the IOMC RAS for determination of the molecular structure of compound 5. We thank Prof. Dr. M. N. Bochkarev for a fruitful discussion. Dr. Tianshu Li is acknowledged for her support in the manuscript preparation.

(1) Cotton, F. A.; Curtis, N. F.; Harris, C. B.; Johnson, B. F. G.; Lippard, S. J.; Mague, J. T.; Robinson, W. R.; Wood, J. S. Science 1964, 145, 1305−1307. (2) Chisholm, M. H. Philos. Trans. R. Soc. London, Ser. A 2008, 366, 101−112. (3) Schnöckel, H. Dalton Trans. 2008, 4344−4362. (4) Wang, Y.; Robinson, G. H. Chem. Commun. 2009, 5201−5213. (5) Li, X.-W.; Pennington, W. T.; Robinson, G. H. J. Am. Chem. Soc. 1995, 117, 7578−7579. (6) Su, J.; Li, X.-W.; Crittendon, R. C.; Robinson, G. H. J. Am. Chem. Soc. 1997, 119, 5471−5472. (7) Noor, A.; Wagner, F. R.; Kempe, R. Angew. Chem., Int. Ed. 2008, 47, 7246−7249. (8) Noor, A.; Glatz, G.; Müller, R.; Kaupp, M.; Demeshko, S.; Kempe, R. Z. Anorg. Allg. Chem. 2009, 635, 1149−1152. (9) Noor, A.; Glatz, G.; Müller, R.; Kaupp, M.; Demeshko, S.; Kempe, R. Nat. Chem. 2009, 1, 322−325. (10) Hsu, C.-W.; Yu, J.-S. K.; Yen, C.-H.; Lee, G.-H.; Wang, Y.; Tsai, Y.-C. Angew. Chem., Int. Ed. 2008, 47, 9933−9936. (11) Nguyen, T.; Sutton, A. D.; Brynda, M.; Fettinger, J. C.; Long, G. J.; Power, P. P. Science 2005, 310, 844−847. (12) Frenking, G. Science 2005, 310, 796−797. (13) Wagner, F. R.; Noor, A.; Kempe, R. Nat. Chem. 2009, 1, 529− 536. (14) Wolf, R.; Ni, C.; Nguyen, T.; Brynda, M.; Long, G. J.; Sutton, A. D.; Fischer, R. C.; Fettinger, J. C.; Hellman, M.; Pu, L.; Power, P. P. Inorg. Chem. 2007, 46, 11277−11290. (15) Resa, I.; Carmona, E.; Gutierrez-Puebla, E.; Monge, A. Science 2004, 305, 1136−1138. (16) Schulz, S. Chem.Eur. J. 2010, 16, 6416−6428. (17) Grirrane, A.; Resa, I.; Rodríguez, A.; Carmona, E. Coord. Chem. Rev. 2008, 252, 1532−1539. (18) Carmona, E.; Galindo, A. Angew. Chem., Int. Ed. 2008, 47, 6526−6536. (19) Li, T.; Schulz, S.; Roesky, P. W. Chem. Soc. Rev. 2012, 3759− 3771. (20) Klinkhammer, K. W.; Fässler, T. F.; Grützmacher, H. Angew. Chem., Int. Ed. 1998, 37, 124−126. (21) Hino, S.; Olmstead, M.; Phillips, A. D.; Wright, R. J.; Power, P. P. Inorg. Chem. 2004, 43, 7346−7352. (22) Fukawa, T.; Lee, V. Y.; Nakamoto, M.; Sekiguchi, A. J. Am. Chem. Soc. 2004, 126, 11758−11759. (23) Stürmann, M.; Saak, W.; Klinkhammer, K. W.; Weidenbruch, M. Z. Anorg. Allg. Chem. 1999, 625, 1955−1956. (24) Olmstead, M. M.; Simons, R. S.; Power, P. P. J. Am. Chem. Soc. 1997, 119, 11705−11706. (25) Takagi, N.; Nagase, S. Organometallics 2007, 26, 469−471. (26) Evans, W. J.; Gonzales, S. L.; Ziller, J. W. J. Am. Chem. Soc. 1991, 113, 9880−9882. (27) von Hänisch, C.; Nikolova, D. Eur. J. Inorg. Chem. 2006, 2006, 4770−4773. (28) Sasamori, T.; Arai, Y.; Takeda, N.; Okazaki, R.; Furukawa, Y.; Kimura, M.; Nagase, S.; Tokitoh, N. Bull. Chem. Soc. Jpn. 2002, 75, 661−675. 4338

dx.doi.org/10.1021/om300309b | Organometallics 2012, 31, 4331−4339

Organometallics

Article

(61) Butovskii, M. V.; Tok, O. L.; Wagner, F. R.; Kempe, R. Angew. Chem., Int. Ed. 2008, 47, 6469−6472. (62) Döring, C.; Dietel, A.-M.; Butovskii, M. V.; Bezugly, V.; Wagner, F. R.; Kempe, R. Chem.Eur. J. 2010, 16, 10679−10683. (63) Butovskii, M. V.; Döring, C.; Bezugly, V.; Wagner, F. R.; Grin, Y.; Kempe, R. Nat. Chem. 2010, 2, 741−744. (64) Liddle, S. T.; Mills, D. P. Dalton Trans. 2009, 5592−5605. (65) Roesky, P. W. Dalton Trans. 2009, 1887−1893. (66) Jones, C.; Stasch, A. In The Group 13 Metals Aluminium, Gallium, Indium and Thallium: Chemical Patterns and Peculiarities; John Wiley & Sons, Ltd, 2011; pp 285−341. (67) Fedushkin, I. L.; Lukoyanov, A. N.; Tishkina, A. N.; Fukin, G. K.; Lyssenko, K. A.; Hummert, M. Chem.Eur. J. 2010, 16, 7563− 7571. (68) Watson, P. L.; Tulip, T. H.; Willams, I. In Synthetic Methods of Organometallic and Inorganic Chemistry, Vol. 6; Hermann, W. A., Brauer, G., Eds.; Thieme: Stuttgart, 1997; pp 26−28. (69) Namy, J. L.; Girard, P.; Kagan, H. B. Nouv. J. Chim. 1977, 1, 5. (70) Girard, P.; Namy, J. L.; Kagan, H. B. J. Am. Chem. Soc. 1980, 102, 2693−2698. (71) Bochkarev, M. N.; Fedushkin, I. L.; Fagin, A. A.; Petrovskaya, T. V.; Ziller, J. W.; Broomhall-Dillard, R. N. R.; Evans, W. J. Angew. Chem., Int. Ed. Engl. 1997, 36, 133−135. (72) Bochkarev, M. N.; Fagin, A. A. Chem.Eur. J. 1999, 5, 2990− 2992. (73) Sheldrick, G. M. Acta Crystallogr., Sect. A 2008, 64, 112−122. (74) Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7−13. (75) Fedushkin, I. L.; Nikipelov, A. S.; Lyssenko, K. A. J. Am. Chem. Soc. 2010, 132, 7874−7875. (76) Fedushkin, I. L.; Nikipelov, A. S.; Morozov, A. G.; Skatova, A. A.; Cherkasov, A. V.; Abakumov, G. A. Chem.Eur. J. 2012, 18, 255− 266. (77) Uhl, W.; Spies, T. Z. Anorg. Allg. Chem. 2000, 626, 1059−1064. (78) Linti, G.; Rodig, A.; Köstler, W. Z. Anorg. Allg. Chem. 2001, 627, 1465−1476. (79) Baker, R. J.; Jones, C.; Kloth, M.; Platts, J. A. Organometallics 2004, 23, 4811−4813. (80) Fedushkin, I. L.; Lukoyanov, A. N.; Ketkov, S. Y.; Hummert, M.; Schumann, H. Chem.Eur. J. 2007, 13, 7050−7056. (81) Bonnet, F.; Da Costa Violante, C.; Roussel, P.; Mortreux, A.; Visseaux, M. Chem. Commun. 2009, 3380−3382. (82) Evans, W. J.; Ulibarri, T. A.; Chamberlain, L. R.; Ziller, J. W.; Alvarez, D. Organometallics 1990, 9, 2124−2130. (83) Schumann, H.; Glanz, M.; Hemling, H.; Görlitz, F. H. J. Organomet. Chem. 1993, 462, 155−161. (84) Jaroschik, F.; Shima, T.; Li, X.; Mori, K.; Ricard, L.; Le Goff, X.F.; Nief, F.; Hou, Z. Organometallics 2007, 26, 5654−5660. (85) Schumann, H.; Palamidis, E.; Loebel, J. J. Organomet. Chem. 1990, 384, C49−C52. (86) Evans, W. J.; Leman, J. T.; Ziller, J. W.; Khan, S. I. Inorg. Chem. 1996, 35, 4283−4291.

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