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In), heptacyclic metallasiloxane cage compound
Inorganic Chemistry Communications 49 (2014) 37–40
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Inorganic Chemistry Communications journal homepage: www.elsevier.com/locate/inoche
Synthesis and structure of a heterotrimetallic (Li/Er/In), heptacyclic metallasiloxane cage compound☆ Volker Lorenz a, Cristian G. Hrib a, Peter G. Jones b, Frank T. Edelmann a,⁎ a b
Chemisches Institut der Otto-von-Guericke-Universität Magdeburg, 39106 Magdeburg, Germany Institut für Anorganische und Analytische Chemie der TU Braunschweig, Hagenring 30, 38106 Braunschweig, Germany
a r t i c l e
i n f o
Article history: Received 24 July 2014 Accepted 9 September 2014 Available online 10 September 2014 Keywords: Rare-earths Erbium Disiloxanediolates Indium X-ray structure
a b s t r a c t The unusual heterotrimetallic (Li/Er/In), heptacyclic metallasiloxane cage compound [{(Ph2SiO)2O}3{Li(THF)2} {InMe}]Er (2) has been prepared in 98% yield by reaction of the erbium bis(disiloxanediolate) derivative [{(Ph2SiO)2O}2{Li(THF)2}2]ErCl (1) with trimethylindium, InMe3. The product was structurally characterized by single-crystal X-ray diffraction. © 2014 Elsevier B.V. All rights reserved.
Well-defined molecular metal siloxides (=metallasiloxanes) comprising M–O–Si functionalities attract significant interest due to their diverse potential applications [1]. Not only are metal siloxides excellent molecular models for silica-supported heterogeneous metal catalysts [2], but they can also serve as precursors for new materials [3], nanoparticles [4], well-defined surface species [5], and homogeneous catalysts [6]. A particularly useful and versatile precursor for a large variety of metal siloxides is the simple and readily accessible 1,1,3,3tetraphenyl-disiloxane-1,3-diol, (HO)SiPh2OSiPh2(OH), which forms stable complexes with virtually all metallic elements across the Periodic Table ranging from lithium to uranium [1,7]. Among these, lanthanide disiloxanediolates form a well-investigated class of compounds [1]. Most prominent are heterometallic lanthanide bis(disiloxanediolates) of the type [{(Ph2SiO)2O}{Li(S)n}]2LnCl(S) (Ln = rare-earth metal; S = Et2O, THF, DME; n = 1, 2). In these complexes, two formally monoanionic [{(Ph2SiO)2O}{Li(S)n}]− units form a twelve-membered Si4O6Li2 inorganic ring system. While the smaller ions like Sc3+, Y3+, or Lu3+ fit into the center of the Si4O6Li2 ring (Scheme 1, A), the larger ions such as Er3+, Ho3+ (B), Pr3+ or Nd3+ (C) are more or less displaced from the center of the twelve-membered rings [1,7a]. Initial reactivity studies revealed that unusual heterometallic products could be isolated from reactions of these lanthanide bis(disiloxanediolates) with Group 13 metal trialkyls. Scheme 2 illustrates the outcome of reactions of type A complexes (Ln = Sc, Y) with AlMe3 and InMe3, resp. Treatment of the Sc complex with ☆ Dedicated to Professor Michael Veith on the occasion of his 70th birthday. ⁎ Corresponding author. E-mail address: [email protected] (F.T. Edelmann).
http://dx.doi.org/10.1016/j.inoche.2014.09.013 1387-7003/© 2014 Elsevier B.V. All rights reserved.
AlMe3 resulted in a Li–Al exchange reaction and formation of the heterotrimetallic (Li/Sc/Al) inorganic ring system [{(Ph2SiO)2O}2 {Li(THF)2}AlMe2]ScCl·THF. The related yttrium complex reacted with InMe3 under formation of a heterobimetallic (Y/In) disiloxanediolate complex in which two monomeric Me2InOMe ligands are stabilized through coordination to yttrium [7b]. Yet another, completely different product was obtained when a praseodymium complex of type C was treated with trimethylindium (Scheme 3). This reaction resulted in double insertion of InMe2 units into the 12-membered Si4O6Li2 inorganic ring system attached to praseodymium and formation of the novel ionic product [Li(THF)4][Pr {O(SiPh2OInMe2OSiPh2OSiPh2O)2}] [7c]. Thus far, all reactions of Ln-bis(disiloxanediolates) with Group 13 metal trialkyls had resulted in entirely different reaction products (Schemes 2 and 3). Complexes of the structural type B (Scheme 1) are formed with intermediate-sized Ln3 + ions such as Er3 + and Ho3 +. In the present study, we found that a reaction of the type B erbium bis(disiloxanediolate) complex [{(Ph2SiO)2O}2{Li(THF)2}2]ErCl (1) with trimethylindium yet again took an entirely different course (Scheme 4). The reaction of [{(Ph2SiO)2O}2{Li(THF)2}2]ErCl (1) with trimethylindium was carried out in toluene solution using a molar ratio of 1:3 [8]. The reaction mixture was first stirred at r.t. and then refluxed for 1 h. After removal of a small amount of insoluble material (presumably Li[InMe4]) by filtration, the product 2 crystallized directly from the concentrated filtrate in the form of colorless prisms. Meaningful NMR spectra of 2 could not be obtained due to the strongly paramagnetic nature of the Er3+ ion. After all, as is characteristic for the chemistry of metal disiloxanediolates, the usual combination of spectroscopic
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V. Lorenz et al. / Inorganic Chemistry Communications 49 (2014) 37–40
Scheme 1. Different structural types of lanthanide bis(disiloxanediolates).
methods and elemental analyses largely failed to provide sufficiently detailed information about the structure of the product. Fortunately, well-formed colorless single-crystals suitable for X-ray diffraction were obtained after several unsuccessful attempts when a saturated solution in a 1:1 mixture of THF and C6H6 was left to stand at r.t. for a few days [9]. The crystal structure determination revealed the unexpected formation of the unusual heterotrimetallic (Li/Er/In), heptacyclic metallasiloxane cage compound [{(Ph2SiO)2O}3{Li(THF)2}{InMe}]Er (2). Fig. 1 shows the molecular structure (a), the heptacyclic core (b), as well as selected bond lengths and angles. The compound crystallizes in the triclinic space group P-1 with one equivalent of THF and C6H6 in the unit cell. Certainly the most surprising result of the reaction shown in Scheme 4 is the complete rearrangement of the bis(disiloxanediolate) starting material [{(Ph2SiO)2O}2{Li(THF)2}2]ErCl (1) under formation of an erbium tris(disiloxanediolate) complex. As is shown in Fig. 1a, the central erbium atom is coordinated in a severely distorted octahedral fashion by six disiloxanediolate oxygen atoms. O–Er–O angles to the oxygens in trans-positions of the coordination octahedron are O3–Er–O4 154.47(10)°, O6–Er–O7 151.41(10)°, and O1–Er–O9 160.18(10)°, while those between oxygens in cispositions are in the fairly wide range of O–Er–O = 71.04(9)° (O1–Er– O4) to 108.48(10)° (O3–Er–O7). Two disiloxanediolate oxygens are bridged in the usual manner (cf. Scheme 1) by a Li(THF)+ 2 unit. The tetrahedral coordination geometry around lithium is also severely distorted. Here, the O–Li–O angles are in the wide range between 90.8(3)° (O6–Li–O9) and 125.4(10)° (O6–Li–O10). In contrast to all pre-
viously found examples [7], indium is incorporated in the product in the form of a formally dicationic monomethylindium unit, InMe2+. Togeth3+ ion, this compensates er with the Li(THF)+ 2 moiety and the Er the six negative charges of the three disiloxanediolate dianions. The monomethylindium unit bridges three disiloxanediolate oxygens to give a tricyclic Er(μ-O)3In cage resembling [1,1,1]-tricyclopentane. The resulting overall heterotrimetallic structure comprises a heptacyclic core consisting of three six-membered ErO3Si2 chelate rings, three four-membered ErO2In rings and one four-membered ErO2Li ring (Fig. 1b). With 2.110(3) Å (Er–O3) the shortest Er–O bond is formed with a disiloxanediolate oxygen bonded only to erbium. Slightly longer are the Er–O bonds within the ErO2Li ring (Er–O6 2.168(3) Å, Er–O9 2.176(3) Å), while the longest Er–O bonds are formed with the oxygens bridging erbium and indium (Er–O1 2.390(3) Å, Er–O4 2.391(2) Å, and Er–O7 2.359(3) Å). In the recently reported erbium disiloxanediolate cluster (c-C6H11)21Si21O36(SiMe3)Er2(THF)2Li4Cl2 the Er–O bonds were found to be in the range of 2.183(3)–2.235(3) Å [10]. Another rare example of a structurally verified complex comprising Er–O–Si bonds is the carborane species [Na2(THF)11][{η5:σ-Me2Si(C9H6)(C2B10H10)}{μη5:σ-(C9H6)SiMe2O}Er]2 [11]. With 2.051(2) Å the Er–O(Si) distance in this compound is comparably short, indicating the presence of metal dπ–oxygen pπ interactions. At this stage it is certainly premature to speculate about the reason for the different reaction modes of lanthanide bis(disiloxanediolates) with Group 13 metal trialkyls. As has been pointed out earlier [7], the lanthanide bis(disiloxanediolates) can be viewed as lanthanide complexes of metalla-crown ethers. It seems reasonable to assume that
Scheme 2. Reactions of type A Ln-bis(disiloxanediolates) with AlMe3 and InMe3, resp.
Scheme 3. Reaction of a type C Pr-bis(disiloxanediolate) complex with InMe3.
V. Lorenz et al. / Inorganic Chemistry Communications 49 (2014) 37–40
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Scheme 4. Synthesis of [{(Ph2SiO)2O}3{Li(THF)2}{InMe}]Er (2).
the degree of displacement of the central lanthanide ion from the Si4O6Li2 ring accounts for the observed difference modes of reactivity. Further studies in that direction are clearly warranted. In summarizing the results reported here, we succeeded in the preparation and structural characterization of a novel trimetallic (Li/Er/In), heptacyclic metallasiloxane cage compound, [{(Ph2SiO)2O}3{Li(THF)2} {InMe}]Er (2). The formation of this unusual product underlines the diversity of reactions between lanthanide bis(disiloxanediolates) and Group 13 metal trimethyl compounds. Acknowledgments This work was financially supported by the Otto-von-GuerickeUniversität Magdeburg. Appendix A. Supplementary material
(a)
Crystallographic data for the crystal structure reported in this paper can be obtained from the Cambridge Crystallographic Data Center, 12 Union Road, Cambridge CB21EZ, UK (fax: +44-1223-336-033; e-mail: [email protected] or http://www.ccdc.cam.ac.uk/) by referring to the CIF deposition code CCDC 972154 (2). Supplementary data to this article can be found online at http://dx.doi.org/10.1016/j.inoche. 2014.09.013. References
(b) Fig. 1. (a) Molecular structure of 2 in the crystal; (b) representation of the heptacyclic core of 2. Selected bond lengths [Å] and angles [°]: Er–O1 2.390(3), Er–O3 2.110(3), Er–O4 2.391(2), Er–O6 2.168(3), Er–O7 2.359(3), Er–O9 2.176(3), In–O1 2.096(3), In–O4 2.102(3), In–O7 2.118(3), In–C1 2.125(5), Li–O6 1.995(8), Li–O9 1.998(8), Li–O10 1.961(14), Li–O11 1.964(10). O3–Er–O4 154.47(10), O6–Er–O7 151.41(10), O1–Er–O9 160.18(10), O1–In–O4 82.85(11), O1–In–O7 82.28(11), O4–In–O7 83.10(10), O1–In–C1 133.2(2), O4–In–C1 128.38(19), O7–In–C1 129.2(3), O6–Li–O9 90.8(3), O6–Li–O10 125.4(10), O6–Li–O11 103.5(5), O9–Li–O10 118.2(8), O9–Li–O11 114.2(5), and O10–Li– O11 104.2(6).
[1] (a) Recent reviews on metal siloxides:M. Veith, Adv. Organomet. Chem. 53 (2006) 101–153; (b) M.M. Levitskii, B.G. Zavin, A.N. Bilyachenko, Russ. Chem. Rev. 76 (2007) 847–866; (c) T.J. Boyle, L.A.M. Ottley, Chem. Rev. 108 (2008) 1896; (d) M.M. Levitskii, V.V. Smirnov, B.G. Zavin, A.N. Bilyachenko, A.Y. Rabkina, Kinet. Catal. 50 (2009) 490–507; (e) V. Lorenz, A. Edelmann, S. Gießmann, C.G. Hrib, S. Blaurock, F.T. Edelmann, Z. Anorg. Allg. Chem. 636 (2010) 2172–2191; (f) C. Krempner, Eur. J. Inorg. Chem. (2011) 1689–1698. [2] (a) R. Murugavel, M. Walawalkar, G. Prabusankar, P. Davis, Organometallics 20 (2001) 2639–2642; (b) R. Fandos, A. Otero, A. Rodriguez, M.J. Ruiz, P. Terreros, Angew. Chem. Int. Ed. 40 (2001) 2884–2887; (c) K.L. Fujdala, R.L. Brutchey, T.D. Tilley, Top. Organomet. Chem. 16 (2005) 69–115; (d) J. Jarupatrakorn, M.P. Coles, T.D. Tilley, Chem. Mater. 17 (2005) 1818–1828. [3] (a) R. Murugavel, M.G. Walawalkar, M. Dan, H.W. Roesky, C.N.R. Rao, Acc. Chem. Res. 37 (2004) 763–774; (b) L.G. Hubert-Pfalzgraf, N. Touati, S.V. Pasko, J. Vaissermann, A. Abrutis, Polyhedron 24 (2005) 3066–3073; (b) A. Abrutis, L.G. Hubert-Pfalzgraf, S. Pasko, N. Touati, V. Kazlauskiene, Vacuum 81 (2006) 13–17; (b) S. Ehle, V. Brüser, V. Lorenz, C.G. Hrib, K. Saulich, S. Müller, A. Quade, F.T. Edelmann, Eur. J. Inorg. Chem. (2013) 1451–1457. [4] M. Veith, J. Freres, P. König, O. Schütt, V. Huch, J. Blin, Eur. J. Inorg. Chem. (2005) 3699–3710. [5] (a) J.-M. Basset, R. Psaro, D. Roberto, R. Ugo (Eds.), Modern Surface Organometallic Chemistry, Wiley-VCH, Weinheim, 2009;
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(b) O. Michel, S. König, K.W. Törnroos, C. Maichle-Mössmer, R. Anwander, Chem. Eur. J. 17 (2011) 11857–11867; (c) B. Marciniec, S. Rogalski, M.J. Potrzebowski, C. Pietraszuk, ChemCatChem 3 (2011) 904–910; (d) E. Le Roux, Y. Liang, K.W. Törnroos, F. Nief, R. Anwander, Organometallics 31 (2012) 6526–6537; (e) P.J. Cordeiro, P. Guillo, C.S. Spanjers, J.W. Chang, M.I. Lipschutz, M.E. Fasulo, R.M. Rioux, T.D. Tilley, ACS Catal. 3 (2013) 2269–2279; (f) P. Laurent, L. Veyre, C. Thieuleux, S. Donet, C. Copéret, Dalton Trans. 42 (2013) 238–248. [6] (a) I. Kownacki, B. Marciniec, K. Szubert, M. Kubicki, Organometallics 24 (2005) 6179–6183; (b) E. Mieczynska, A.M. Trzeciak, J.J. Ziolkowski, I. Kownacki, B.J. Marciniec, Mol. Catal. A Chem. 237 (2005) 246–253; (c) S.M. Bruno, B. Monteiro, M.S. Balula, C. Lourenco, A.A. Valente, M. Pillinger, P. Ribeiro-Claro, I.S. Goncalves, Molecules 11 (2006) 298–308; (d) I. Kownacki, B. Marciniec, A. Macina, S. Rubinsztajn, D. Lamb, Appl. Catal. A Gen. 317 (2007) 53–57. [7] (a) S. Gießmann, S. Blaurock, V. Lorenz, F.T. Edelmann, Inorg. Chem. 46 (2007) 10383–10389; (b) S. Gießmann, S. Blaurock, V. Lorenz, F.T. Edelmann, Inorg. Chem. 46 (2007) 10956–10958; (c) A. Edelmann, S. Blaurock, C. Hrib, F.T.J. Edelmann, Organomet. Chem. 695 (2010) 1026–1030; (d) V. Lorenz, A. Edelmann, S. Blaurock, C. Hrib, F.T. Edelmann, C. R. Chim. 13 (2010) 577–583. [8] Synthesis of [{(Ph2SiO)2O}3{Li(THF)2}2]ErCl (2): The reaction was carried out in a Schlenk flask under N2. A solution of 1.33 g (1.0 mmol) [{(Ph2SiO)2O}2{Li(THF)2}2] ErCl·2THF (1) [7d] in 50 ml toluene was treated with 0.48 g (3.0 mmol) InMe3.
[9]
[10] [11] [12]
The reaction mixture was stirred overnight, refluxed for 1 h and filtered through a P4 glass-frit to separate a white precipitate from the clear, almost colorless solution. After reducing the volume of the solution in vacuum to 15 ml the product crystallized in form of colorless prisms. These crystals were suitable of X-ray analysis. For analysis, the compound was thoroughly dried in vacuum at 50–70 °C for 4 h to remove residual solvents. Yield: 1.10 g (98%). Mp: 135–140 °C (dec). Anal. calcd for C81H79LiErInO11Si6 (Mr = 1686.04): C 57.70%; H 4.72%. Found: C 57.35%; H 4.46%. Mass spectrum (EI): m/z 792 (2%) [(Ph2SiO)4], 715 (10%) [(Ph2SiO)2OLiErInCH3], 637 (18%) [(Ph2SiO)2OLiErInCH3-Ph], 594 (100%) [(Ph2SiO)2OErCH3], 516 (80%) [(Ph2SiO)2OErCH3-Ph], 438 (45%) [(Ph2SiO)2OErCH3-2Ph]. IR (KBr): 3134w, 3068m, 3047m, 3000m, 2955m, 2932m, 2830w, 1960w, 1894w, 1826w, 1774w, 1635w, 1591m, 1485m, 1428s, 1306w, 1305w, 1240w, 1186w, 1121vs, 1036s, 1020s, 1009s, 953s, 899s, 742s, 710vs, 700vs, 683m, 668w, 528vs, 497m, and 411w cm−1. NMR resonances could not be assigned due to strong broadening and shifting of the signals as an effect of the paramagnetic Er3+ ion. The intensity data of 2 were registered on an Oxford Diffraction Nova A diffractometer using mirror-focussed CuKα radiation. Absorption corrections were applied using the multi-scan method. The structure was solved by direct methods (SHELXL-97) and refined by full matrix least-squares methods on F2 using SHELXL-97 [12]. Full crystal data and structure refinement parameters are summarized in Table S1, while bond lengths and angles are listed in Table S2 in the Supplementary information. V. Lorenz, S. Blaurock, C.G. Hrib, F.T. Edelmann, Eur. J. Inorg. Chem. (2010) 2605–2608. S. Wang, Q. Yang, T.C.W. Mak, Z. Xie, Organometallics 18 (1999) 4478–4487. (a) G.M. Sheldrick, SHELXL-97 Program for Crystal Structure Refinement, Universität Göttingen, Germany, 1997.; (b) G.M. Sheldrick, SHELXL-97 Program for Crystal Structure Solution, Universität Göttingen, Germany, 1997.
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Inorganic Chemistry Communications journal homepage: www.elsevier.com/locate/inoche
Synthesis and structure of a heterotrimetallic (Li/Er/In), heptacyclic metallasiloxane cage compound☆ Volker Lorenz a, Cristian G. Hrib a, Peter G. Jones b, Frank T. Edelmann a,⁎ a b
Chemisches Institut der Otto-von-Guericke-Universität Magdeburg, 39106 Magdeburg, Germany Institut für Anorganische und Analytische Chemie der TU Braunschweig, Hagenring 30, 38106 Braunschweig, Germany
a r t i c l e
i n f o
Article history: Received 24 July 2014 Accepted 9 September 2014 Available online 10 September 2014 Keywords: Rare-earths Erbium Disiloxanediolates Indium X-ray structure
a b s t r a c t The unusual heterotrimetallic (Li/Er/In), heptacyclic metallasiloxane cage compound [{(Ph2SiO)2O}3{Li(THF)2} {InMe}]Er (2) has been prepared in 98% yield by reaction of the erbium bis(disiloxanediolate) derivative [{(Ph2SiO)2O}2{Li(THF)2}2]ErCl (1) with trimethylindium, InMe3. The product was structurally characterized by single-crystal X-ray diffraction. © 2014 Elsevier B.V. All rights reserved.
Well-defined molecular metal siloxides (=metallasiloxanes) comprising M–O–Si functionalities attract significant interest due to their diverse potential applications [1]. Not only are metal siloxides excellent molecular models for silica-supported heterogeneous metal catalysts [2], but they can also serve as precursors for new materials [3], nanoparticles [4], well-defined surface species [5], and homogeneous catalysts [6]. A particularly useful and versatile precursor for a large variety of metal siloxides is the simple and readily accessible 1,1,3,3tetraphenyl-disiloxane-1,3-diol, (HO)SiPh2OSiPh2(OH), which forms stable complexes with virtually all metallic elements across the Periodic Table ranging from lithium to uranium [1,7]. Among these, lanthanide disiloxanediolates form a well-investigated class of compounds [1]. Most prominent are heterometallic lanthanide bis(disiloxanediolates) of the type [{(Ph2SiO)2O}{Li(S)n}]2LnCl(S) (Ln = rare-earth metal; S = Et2O, THF, DME; n = 1, 2). In these complexes, two formally monoanionic [{(Ph2SiO)2O}{Li(S)n}]− units form a twelve-membered Si4O6Li2 inorganic ring system. While the smaller ions like Sc3+, Y3+, or Lu3+ fit into the center of the Si4O6Li2 ring (Scheme 1, A), the larger ions such as Er3+, Ho3+ (B), Pr3+ or Nd3+ (C) are more or less displaced from the center of the twelve-membered rings [1,7a]. Initial reactivity studies revealed that unusual heterometallic products could be isolated from reactions of these lanthanide bis(disiloxanediolates) with Group 13 metal trialkyls. Scheme 2 illustrates the outcome of reactions of type A complexes (Ln = Sc, Y) with AlMe3 and InMe3, resp. Treatment of the Sc complex with ☆ Dedicated to Professor Michael Veith on the occasion of his 70th birthday. ⁎ Corresponding author. E-mail address: [email protected] (F.T. Edelmann).
http://dx.doi.org/10.1016/j.inoche.2014.09.013 1387-7003/© 2014 Elsevier B.V. All rights reserved.
AlMe3 resulted in a Li–Al exchange reaction and formation of the heterotrimetallic (Li/Sc/Al) inorganic ring system [{(Ph2SiO)2O}2 {Li(THF)2}AlMe2]ScCl·THF. The related yttrium complex reacted with InMe3 under formation of a heterobimetallic (Y/In) disiloxanediolate complex in which two monomeric Me2InOMe ligands are stabilized through coordination to yttrium [7b]. Yet another, completely different product was obtained when a praseodymium complex of type C was treated with trimethylindium (Scheme 3). This reaction resulted in double insertion of InMe2 units into the 12-membered Si4O6Li2 inorganic ring system attached to praseodymium and formation of the novel ionic product [Li(THF)4][Pr {O(SiPh2OInMe2OSiPh2OSiPh2O)2}] [7c]. Thus far, all reactions of Ln-bis(disiloxanediolates) with Group 13 metal trialkyls had resulted in entirely different reaction products (Schemes 2 and 3). Complexes of the structural type B (Scheme 1) are formed with intermediate-sized Ln3 + ions such as Er3 + and Ho3 +. In the present study, we found that a reaction of the type B erbium bis(disiloxanediolate) complex [{(Ph2SiO)2O}2{Li(THF)2}2]ErCl (1) with trimethylindium yet again took an entirely different course (Scheme 4). The reaction of [{(Ph2SiO)2O}2{Li(THF)2}2]ErCl (1) with trimethylindium was carried out in toluene solution using a molar ratio of 1:3 [8]. The reaction mixture was first stirred at r.t. and then refluxed for 1 h. After removal of a small amount of insoluble material (presumably Li[InMe4]) by filtration, the product 2 crystallized directly from the concentrated filtrate in the form of colorless prisms. Meaningful NMR spectra of 2 could not be obtained due to the strongly paramagnetic nature of the Er3+ ion. After all, as is characteristic for the chemistry of metal disiloxanediolates, the usual combination of spectroscopic
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V. Lorenz et al. / Inorganic Chemistry Communications 49 (2014) 37–40
Scheme 1. Different structural types of lanthanide bis(disiloxanediolates).
methods and elemental analyses largely failed to provide sufficiently detailed information about the structure of the product. Fortunately, well-formed colorless single-crystals suitable for X-ray diffraction were obtained after several unsuccessful attempts when a saturated solution in a 1:1 mixture of THF and C6H6 was left to stand at r.t. for a few days [9]. The crystal structure determination revealed the unexpected formation of the unusual heterotrimetallic (Li/Er/In), heptacyclic metallasiloxane cage compound [{(Ph2SiO)2O}3{Li(THF)2}{InMe}]Er (2). Fig. 1 shows the molecular structure (a), the heptacyclic core (b), as well as selected bond lengths and angles. The compound crystallizes in the triclinic space group P-1 with one equivalent of THF and C6H6 in the unit cell. Certainly the most surprising result of the reaction shown in Scheme 4 is the complete rearrangement of the bis(disiloxanediolate) starting material [{(Ph2SiO)2O}2{Li(THF)2}2]ErCl (1) under formation of an erbium tris(disiloxanediolate) complex. As is shown in Fig. 1a, the central erbium atom is coordinated in a severely distorted octahedral fashion by six disiloxanediolate oxygen atoms. O–Er–O angles to the oxygens in trans-positions of the coordination octahedron are O3–Er–O4 154.47(10)°, O6–Er–O7 151.41(10)°, and O1–Er–O9 160.18(10)°, while those between oxygens in cispositions are in the fairly wide range of O–Er–O = 71.04(9)° (O1–Er– O4) to 108.48(10)° (O3–Er–O7). Two disiloxanediolate oxygens are bridged in the usual manner (cf. Scheme 1) by a Li(THF)+ 2 unit. The tetrahedral coordination geometry around lithium is also severely distorted. Here, the O–Li–O angles are in the wide range between 90.8(3)° (O6–Li–O9) and 125.4(10)° (O6–Li–O10). In contrast to all pre-
viously found examples [7], indium is incorporated in the product in the form of a formally dicationic monomethylindium unit, InMe2+. Togeth3+ ion, this compensates er with the Li(THF)+ 2 moiety and the Er the six negative charges of the three disiloxanediolate dianions. The monomethylindium unit bridges three disiloxanediolate oxygens to give a tricyclic Er(μ-O)3In cage resembling [1,1,1]-tricyclopentane. The resulting overall heterotrimetallic structure comprises a heptacyclic core consisting of three six-membered ErO3Si2 chelate rings, three four-membered ErO2In rings and one four-membered ErO2Li ring (Fig. 1b). With 2.110(3) Å (Er–O3) the shortest Er–O bond is formed with a disiloxanediolate oxygen bonded only to erbium. Slightly longer are the Er–O bonds within the ErO2Li ring (Er–O6 2.168(3) Å, Er–O9 2.176(3) Å), while the longest Er–O bonds are formed with the oxygens bridging erbium and indium (Er–O1 2.390(3) Å, Er–O4 2.391(2) Å, and Er–O7 2.359(3) Å). In the recently reported erbium disiloxanediolate cluster (c-C6H11)21Si21O36(SiMe3)Er2(THF)2Li4Cl2 the Er–O bonds were found to be in the range of 2.183(3)–2.235(3) Å [10]. Another rare example of a structurally verified complex comprising Er–O–Si bonds is the carborane species [Na2(THF)11][{η5:σ-Me2Si(C9H6)(C2B10H10)}{μη5:σ-(C9H6)SiMe2O}Er]2 [11]. With 2.051(2) Å the Er–O(Si) distance in this compound is comparably short, indicating the presence of metal dπ–oxygen pπ interactions. At this stage it is certainly premature to speculate about the reason for the different reaction modes of lanthanide bis(disiloxanediolates) with Group 13 metal trialkyls. As has been pointed out earlier [7], the lanthanide bis(disiloxanediolates) can be viewed as lanthanide complexes of metalla-crown ethers. It seems reasonable to assume that
Scheme 2. Reactions of type A Ln-bis(disiloxanediolates) with AlMe3 and InMe3, resp.
Scheme 3. Reaction of a type C Pr-bis(disiloxanediolate) complex with InMe3.
V. Lorenz et al. / Inorganic Chemistry Communications 49 (2014) 37–40
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Scheme 4. Synthesis of [{(Ph2SiO)2O}3{Li(THF)2}{InMe}]Er (2).
the degree of displacement of the central lanthanide ion from the Si4O6Li2 ring accounts for the observed difference modes of reactivity. Further studies in that direction are clearly warranted. In summarizing the results reported here, we succeeded in the preparation and structural characterization of a novel trimetallic (Li/Er/In), heptacyclic metallasiloxane cage compound, [{(Ph2SiO)2O}3{Li(THF)2} {InMe}]Er (2). The formation of this unusual product underlines the diversity of reactions between lanthanide bis(disiloxanediolates) and Group 13 metal trimethyl compounds. Acknowledgments This work was financially supported by the Otto-von-GuerickeUniversität Magdeburg. Appendix A. Supplementary material
(a)
Crystallographic data for the crystal structure reported in this paper can be obtained from the Cambridge Crystallographic Data Center, 12 Union Road, Cambridge CB21EZ, UK (fax: +44-1223-336-033; e-mail: [email protected] or http://www.ccdc.cam.ac.uk/) by referring to the CIF deposition code CCDC 972154 (2). Supplementary data to this article can be found online at http://dx.doi.org/10.1016/j.inoche. 2014.09.013. References
(b) Fig. 1. (a) Molecular structure of 2 in the crystal; (b) representation of the heptacyclic core of 2. Selected bond lengths [Å] and angles [°]: Er–O1 2.390(3), Er–O3 2.110(3), Er–O4 2.391(2), Er–O6 2.168(3), Er–O7 2.359(3), Er–O9 2.176(3), In–O1 2.096(3), In–O4 2.102(3), In–O7 2.118(3), In–C1 2.125(5), Li–O6 1.995(8), Li–O9 1.998(8), Li–O10 1.961(14), Li–O11 1.964(10). O3–Er–O4 154.47(10), O6–Er–O7 151.41(10), O1–Er–O9 160.18(10), O1–In–O4 82.85(11), O1–In–O7 82.28(11), O4–In–O7 83.10(10), O1–In–C1 133.2(2), O4–In–C1 128.38(19), O7–In–C1 129.2(3), O6–Li–O9 90.8(3), O6–Li–O10 125.4(10), O6–Li–O11 103.5(5), O9–Li–O10 118.2(8), O9–Li–O11 114.2(5), and O10–Li– O11 104.2(6).
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[9]
[10] [11] [12]
The reaction mixture was stirred overnight, refluxed for 1 h and filtered through a P4 glass-frit to separate a white precipitate from the clear, almost colorless solution. After reducing the volume of the solution in vacuum to 15 ml the product crystallized in form of colorless prisms. These crystals were suitable of X-ray analysis. For analysis, the compound was thoroughly dried in vacuum at 50–70 °C for 4 h to remove residual solvents. Yield: 1.10 g (98%). Mp: 135–140 °C (dec). Anal. calcd for C81H79LiErInO11Si6 (Mr = 1686.04): C 57.70%; H 4.72%. Found: C 57.35%; H 4.46%. Mass spectrum (EI): m/z 792 (2%) [(Ph2SiO)4], 715 (10%) [(Ph2SiO)2OLiErInCH3], 637 (18%) [(Ph2SiO)2OLiErInCH3-Ph], 594 (100%) [(Ph2SiO)2OErCH3], 516 (80%) [(Ph2SiO)2OErCH3-Ph], 438 (45%) [(Ph2SiO)2OErCH3-2Ph]. IR (KBr): 3134w, 3068m, 3047m, 3000m, 2955m, 2932m, 2830w, 1960w, 1894w, 1826w, 1774w, 1635w, 1591m, 1485m, 1428s, 1306w, 1305w, 1240w, 1186w, 1121vs, 1036s, 1020s, 1009s, 953s, 899s, 742s, 710vs, 700vs, 683m, 668w, 528vs, 497m, and 411w cm−1. NMR resonances could not be assigned due to strong broadening and shifting of the signals as an effect of the paramagnetic Er3+ ion. The intensity data of 2 were registered on an Oxford Diffraction Nova A diffractometer using mirror-focussed CuKα radiation. Absorption corrections were applied using the multi-scan method. The structure was solved by direct methods (SHELXL-97) and refined by full matrix least-squares methods on F2 using SHELXL-97 [12]. Full crystal data and structure refinement parameters are summarized in Table S1, while bond lengths and angles are listed in Table S2 in the Supplementary information. V. Lorenz, S. Blaurock, C.G. Hrib, F.T. Edelmann, Eur. J. Inorg. Chem. (2010) 2605–2608. S. Wang, Q. Yang, T.C.W. Mak, Z. Xie, Organometallics 18 (1999) 4478–4487. (a) G.M. Sheldrick, SHELXL-97 Program for Crystal Structure Refinement, Universität Göttingen, Germany, 1997.; (b) G.M. Sheldrick, SHELXL-97 Program for Crystal Structure Solution, Universität Göttingen, Germany, 1997.