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Synthesis and crystal structure of the first “carbons apart” diamagnetic lutetiacarborane sandwich complex
Inorganic Chemistry Communications 5 (2002) 602–605 www.elsevier.com/locate/inoche
Synthesis and crystal structure of the first ‘‘carbons apart’’ diamagnetic lutetiacarborane sandwich complex Jianhui Wang a
a,b
, Shoujian Li a, Chong Zheng a, John A. Maguire b, Narayan S. Hosmane a,*
Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, IL 60115-2862, USA b Department of Chemistry, Southern Methodist University, Dallas, TX 75275-0314, USA Received 3 May 2002; accepted 25 May 2002
Abstract The reaction of closo-exo-5; 6-NaðTHFÞ2 -1-NaðTHFÞ2 -2; 4-ðSiMe3 Þ2 -2; 4-C2 B4 H4 (1) and anhydrous LuCl3 , in a molar ratio of 2:1, in dry benzene at 60 °C produced the first full-sandwiched lutetiacarborane complex, 2; 20 ; 4; 40 -ðSiMe3 Þ4 -3; 50 ; 60 -½ðl-HÞ3 NaðTHFÞ2 -1; 10 -commo-Luðg5 -2; 4-C2 B4 H4 Þ2 (2), as an off-white crystalline solid in 88% yield. Ó 2002 Elsevier Science B.V. All rights reserved. Keywords: Lutetiacarborane; Sandwich complex; Lutetium; Metallacarborane; Coordination; C2 B4 -carborane ligand
The chemistry of lanthanide complexes of the C2 B10 , C2 B9 , and C2 B4 carboranes of both the carbons ‘‘adjacent’’ and ‘‘apart’’ ligand systems began in the late 1980s with the first report on the sandwiched samaracarboranes of the formula ½3; 30 -ðTHFÞ2 -commo-3; 30 -Sm ðC2 B9 H11 Þ2 [1]. Subsequently, a number of half and full-sandwich icosahedral and supraicosahedral lanthanacarboranes have been reported [2]. The results in the ‘‘carbons adjacent’’ C2 B4 carborane systems have demonstrated that a number of unusual trinuclear Ln(III)-carboranes of the form, f½g5 -1-Ln-2; 3-ðSiMe3 Þ2 2; 3-C2 B4 H4 3 ½ðl2 -1-Li-2; 3-ðSiMe3 Þ2 -2;3-C2 B4 H4 Þ3 ðl3 OMeÞ-½l2 -Li ðTHFÞ3 ðl3 -OÞg or dihalolanthanide metal sandwiched complexes of the type, ½LiðTMEDAÞ2 ½1-Cl-1-ðl-ClÞ-2;20 ;3; 30 -ðSiMe3 Þ4 -5; 6-½ðl-HÞ2 LiðTM ED AÞ-4;40 ; 50 -½ðl-HÞ3 LiðTMEDAÞ-1; 10 -commo-Lnð2; 3-C2 B4 H4 Þ2 (Ln ¼ Ce, Nd, Sm, Gd, Tb, Dy, Ho, Er) can be synthesized. These results are of interest in that they show that, depending on the solvent used, quite different products can be obtained from very similar reactants [3]. On the other hand, the reaction of the ‘‘carbons apart’’ C2 B4 carborane ligands with the appropriate lanthanide *
Corresponding author. Tel.: +1-815-753-3556; fax: +1-815-7534802. E-mail address: [email protected] (N.S. Hosmane).
reagents resulted in an unprecedented dinuclear lanthanacarborane bent-sandwich complex, f1-½ðl-ClÞ2 Li ðTMEDAÞ-2; 20 ; 4; 40 -ðSiMe3 Þ4 -5; 50 ; 6; 60 -½ðl-HÞ4 LnðTM EDAÞðClÞðl-ClÞ LiðTMEDAÞ-1; 10 -commo-Lnðg5 -2; 4C2 B4 H4 Þ2 g (Ln ¼ Ho, Gd) [4]. These latter species are unusual in that the central (commo) Ln is g5 -bonded to each of the ‘‘carbons apart’’ C2 B3 faces, with the two B–HðterminalÞ groups of each opposing C2 B3 faces linking to an exo-polyhedral Ln(III)Cl(TMEDA) unit that is also bonded to an exo-polyhedral Li(TMEDA) group via two Ln–Cl–Li bridges [4]. Despite the demonstrated synthetic strategy for the desired iso-structural lanthanacarboranes, there have been no reports on the sandwiched lutetium complexes in either the C2 B9 and C2 B10 cages or the smaller C2 B4 carborane systems. The only report is on the synthesis of a half-sandwich chlorolutetiacarborane complex, ðg5 -C2 B9 H11 ÞLuðTHFÞ2 ðl-ClÞ2 NaðTHFÞ2 , who se unambiguous geometry has yet to be verified by Xray crystallography [5]. The inability to obtain the fullsandwich lutetiacarborane was rationalized on the basis that, regardless of the molar ratio of reactants, the fullsandwich lanthanacarboranes can be isolated only for the early lanthanide metals due to the so-called ‘‘ligand redistribution’’ reactions [5]. In order to test this hypothesis and as part of our ongoing research in this area, the ‘‘carbons apart’’ C2 B4 carborane ligand, closo-exo-5;
1387-7003/02/$ - see front matter Ó 2002 Elsevier Science B.V. All rights reserved. PII: S 1 3 8 7 - 7 0 0 3 ( 0 2 ) 0 0 4 9 1 - 4
J. Wang et al. / Inorganic Chemistry Communications 5 (2002) 602–605
603
Scheme 1. Synthesis of lutetiacarborane sandwich complex.
6-NaðTHFÞ2 -1-NaðTHFÞ2 -2; 4-ðSiMe3 Þ2 -2; 4-C2 B4 H4 (1) was reacted with anhydrous LuCl3 , in a molar ratio of 2:1, in dry benzene at 60 °C to produce, the novel lutetiacarborane complex, 2;20 ;4;40 -ðSiMe3 Þ4 -3;50 ;60 -½ðl-HÞ3 Na ðTHFÞ2 -1; 10 -commo-Luðg5 -2; 4-C2 B4 H4 Þ2 (2), as a diamagnetic off-white crystalline solid in 88% yield (see Scheme 1) [6]. To the best of our knowledge, this constitutes the first report on the fully-sandwiched lutetium complex in any of the carborane ligand systems. The results also show that the ligand redistribution phenomenon is not a general one that can be applied to all of the carborane ligand systems. The most important observation is the absence of any solvent coordination to the central metal atom in 2, unlike most of the lanthanacarboranes known to date [1–5]. This is presumably due to the use of dry benzene as a solvent and a higher reaction temperature (60 °C rather than the usual temperatures of 0–25 °C) that restrict the transfer of THF from the Na atom in the precursor to the central metal atom in the product. This observation could prove to be a significant advancement in the synthetic strategy in both lanthanacarborane chemistry and in the lanthanocene chemistry. The lutetiacarborane (2) is diamagnetic [7] and, therefore, satisfactory 1 H and 13 C-NMR spectra could be obtained [8]. Unfortunately, the 11 B NMR spectra, the potentially most useful tool in elucidating geometries of polyhedral boron cages, failed to provide any useful information due to the extreme broadness of the resonances. Nevertheless, the solution IR spectrum of 2 exhibits well-resolved terminal B–H stretches [9]. Such fine structures of B–H stretching bands have been previously observed for other closo- and commo-lanthanacarboranes and has been explained on the basis of unequal interactions of the boron-bound hydrogens with metal groups present in the complex [3]. In order to resolve any questions as to the geometry of 2 its solid-state structure, shown in Fig. 1 was determined by single-crystal X-ray analysis [10]. The structure shows a bent-sandwich geometry similar to those of the corre-
sponding cyclopentadienide complexes, ðC5 H5 Þ2 Lu ðCH2 SiMe3 ÞðTHFÞ, ðC5 H5 Þ2 Lu ð1-C6 H4 -4-MeÞðTHFÞ, ðC5 H5 Þ2 LuðBut ÞðTHFÞ [11]. The Cent(1)-Lu-Cent(2) angle of 138.3° in 2 is significantly larger than those observed in ðC5 H5 Þ2 LuðRÞðTHFÞ ½R ¼ CH2 SiMe3 ; 1-C6 H4 -4-Me; But complex (125.6°–130°) [11], the erbium complex of the mixed-carborane ligands (135.5°), fLiðTMEDAÞ2 g2 fcommo-1-½2; 3-ðSiMe3 Þ2 -2;3-C2 B4 H4 1-Er-½2; 4-ðSiMe3 Þ2 -2; 4-C2 B4 H4 g2 [3a], and the dimeric ‘‘carbons apart’’ yttracarborane sandwich complex ð131 1°Þ, fNaðTHFÞ3 g2 f½1-ðTHFÞ-1-ðl-HÞ2 -2; 20 ; 4; 40 -
Fig. 1. Perspective view of 2 with the thermal ellipsoids drawn at the ) and angles (°): Lu-ðC2 B3 50% probability level. Pertinent distances (A centroid 1, 2) 2.261, 2.230; Lu-C(11, 13, 21, 23) 2.644(7), 2.582(7), 2.586(6), 2.626(7); Lu-B(12, 14, 15, 22, 24, 25) 2.612 (7), 2.654 (7), 2.680(7), 2.618(7), 2.617(8), 2.590(9); (centroid 1)-Lu-(centroid 2) 138.3 (see supplementary publication No. CCDC 186147 for a detailed list of bond lengths and bond angles). The solvated THF molecules on the exo-polyhedral Naþ ion, and the exo-polyhedral SiMe3 groups are drawn with thin lines for clarity.
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J. Wang et al. / Inorganic Chemistry Communications 5 (2002) 602–605
ðSiMe3 Þ4 -1;10 -commo-Yð2; 4-C2 B4 H4 Þ2 2 g [12]. The central (commo) Lu is g5 -bonded to each of the ‘‘carbons apart’’ C2 B3 faces, while a unique B–HðterminalÞ group of a bonding face and the two adjacent B–HðterminalÞ groups of the opposing C2 B3 face are linked to an exo-polyhedral NaðTHFÞ2 unit. The two metal-C2 B3 (centroid) distances are indicative of tighter bonding of 2.261 and 2.230 A of the metal to the carborane ligands when compared ) in ðC5 H5 Þ LuðRÞðTHFÞ½R ¼ to those (2:35 1 A 2 CH2 SiMe3 , 1-C6 H4 -4-Me, But ] complex [11]. Since carborane ligands carry )2 charge, for charge compensation an additional ½NaðTHFÞ2 þ ion is present in the coordination sphere of 2. The absence of the coordinating solvent, THF, on the lanthanide metal indicates that it is possible to synthesize a number of other solvent-free lanthanacarboranes of both the small and large cage carborane systems and to explore their reaction chemistry. Such an investigation is currently underway in our laboratories.
[4]
[5] [6]
Supplementary material Crystallographic data for the structure reported in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication No. CCDC 186147. Copies of the data can be obtained free of charge from The Director, CCDC, 12 Union Road, Cambridge CB2 IEZ, England (Facsimile: ++44-1223-336033 or e-mail: [email protected]).
Acknowledgements [7]
This work was supported by grants from the National Science Foundation (CHE-9988045 and DMR9704048), the Robert A. Welch Foundation (N-1322 to JAM), the donors of the Petroleum Research Fund, administered by the American Chemical Society, and Northern Illinois University through Presidential Research Professorship.
References [1] M.J. Manning, C.B. Knobler, M.F. Hawthorne, J. Am. Chem. Soc. 110 (1988) 4458–4459. [2] (a) A.K. Saxena, N.S. Hosmane, Chem. Rev. 93 (1993) 1081–1124; (b) N.S. Hosmane, J.A. Maguire, J. Cluster Sci. 4 (1993) 297–349; (c) N.S. Hosmane, Y. Wang, A.R. Oki, H. Zhang, D. Zhu, E.M. McDonald, J.A. Maguire, Phosphorus, Sulfur, and Silicon 9394 (1994) 253–256; (d) Z. Xie, Coord. Chem. Rev. (2002) (in press). [3] (a) N.S. Hosmane, Y. Wang, H. Zhang, A.R. Oki, J.A. Maguire, E. Waldh€ or, W. Kaim, H. Binder, R.K. Kremer, Organometallics 14 (1995) 1101–1103;
[8]
[9]
[10]
(b) H. Zhang, A.R. Oki, Y. Wang, J.A. Maguire, N.S. Hosmane, Acta Crystallogr. Cryst. Struct. Commun. C51 (1995) 635– 638; (c) N.S. Hosmane, Y. Wang, A.R. Oki, H. Zhang, J.A. Maguire, Organometallics 15 (1996) 626–638; (d) N.S. Hosmane, Y. Wang, H. Zhang, J.A. Maguire, M. McInnis, T.G. Gray, J.D. Collins, R.K. Kremer, H. Binder, E. Waldh€ or, W. Kaim, Organometallics 15 (1996) 1006–1013; (e) H. Zhang, Y. Wang, J.A. Maguire, N.S. Hosmane, Acta Crystallogr. Cryst. Struct. Commun. 52 (1996) 640–643; (f) N.S. Hosmane, A.R. Oki, H. Zhang, Inorg. Chem. Commun. 1 (1998) 101–104; (g) C. Zheng, N.S. Hosmane, H. Zhang, D. Zhu, J.A. Maguire, Internet. J. Chem. 2 (1999) 10, http://www.ijc.com/articles/ 1999v2/10/; (h) N.S. Hosmane, Y. Wang, H. Zhang, Y. Zhu, J.A. Maguire, Inorg. Chem. Commun. 4 (2001) 547–550. (a) H. Zhang, Y. Wang, J.A. Maguire, N.S. Hosmane, Acta Crystallogr., Cryst. Struct. Commun. C52 (1996) 8–11; (b) N.S. Hosmane, S.-J. Li, C. Zheng, J.A. Maguire, Inorg. Chem. Commun. 4 (2001) 104–107; (c) N.S. Hosmane, Y. Wang, H. Zhang (unpublished results). K.-y. Chiu, Z. Zhang, T.C.W. Mak, Z. Xie, J. Organomet. Chem. 614/615 (2000) 107–112. Synthesis of 2: A 3.19 mmol (1.76 g) sample of closo-exo5; 6-NaðTHFÞ2 -1-NaðTHFÞ2 -2; 4-ðSiMe3 Þ2 -2; 4-C2 B4 H4 (1) (N.S. Hosmane, L. Jia, H. Zhang, J.W. Bausch, G.K.S. Prakash, R.E. Williams, T.P. Onak, Inorg. Chem. 30 (1991) 3793–3795) was reacted with 1.53 mmol of anhydrous LuCl3 (0.43 g) in dry benzene (20 ml) at 60 °C for 24 h, during which time the solution turned yellow turbid. The heterogeneous product mixture was then filtered in vacuo, and the solvent removed from the filtrate to collect a pale yellow solid that was extracted in benzene and filtered to collect a clear yellow solution. Removal of solvents from this clear solution gave a yellow solid that was later recrystallized from dry benzene to collect air-sensitive off-white crystals, identified as 2; 20 ; 4; 40 -ðSiMe3 Þ4 -3; 50 ; 60 -½ðl-HÞ3 Na ðTHFÞ2 -1; 10 -commo-Luðg5 -2; 4-C2 B4 H4 Þ2 (2), in 88% yield [1.14 g, 1.34 mmol; mp: > 250°C (dec); soluble in polar solvents and slightly soluble in n-hexane]. The X-ray quality crystals were grown from a solution mixture of n-hexane (10%) and benzene (90%) and subsequently used for X-ray analyses. The temperature-dependent magnetic susceptibility of 2 was determined using the Faraday balance (J.C. Dobson, J.H. Helms, P. Doppelt, B.P. Sullivan, W.E. Hatfield, Y.J. Meyer, Inorg. Chem. 28 (1989) 2200–2204). At the temperature range of 5–298 K the compound shows antimagnetic property that is consistent with the theoretical electronic arrangement of Luþ3 ion. The NMR spectral data of 2: 1 H NMR (C6 D6 , relative to external Me4 Si) d 3.71 [s(br), 12H, THF], 1.56 [s(br), 12H, THF], 0.74 [s, 18H, SiMe3 ], 0.68 [s, 18H, SiMe3 ]; 13 C NMR (C6 D6 , relative to external Me4 Si) d 128.6 [s(br), cage carbons (SiCB)], 70.6 [m, THF], 24.9 [m, THF], 2.19 [q(br), SiMe3 , 1 Jð13 C 1 HÞ ¼ 119 Hz], 1.84 [q(br), SiMe3 , 1 Jð13 C 1 HÞ ¼ 118:5 Hz]. IR spectral and analytical data: IR (cm1 , KBr pellet): 2536 (s, s), 2511 (s, s), 2468 (s, br), 2443 (br, sh), 2378 (s, s) [m (B-H)]; Anal. Calcd for [C24 H60 B8 O2 Si4 NaLu [THF]: C, 39.57; H, 8.07.Found: C, 39.92; H, 7.92. X-ray data for 2 (C24 H60 B8 Si4 LuNaO2 ; fw, 777.52; P 1): Data was collected at 173 (2) K on a Bruker SMART CCD PLATFORM , b ¼ 17:236 (4) A , c ¼ 17:828 diffractometer with a ¼ 13:933 (3) A , a ¼ 92:569ð4Þ°, b ¼ 98:332ð4Þ° c ¼ 91:026ð4Þ°; V ¼ 4230:8 (4)A 3 , Z ¼ 4, DðcalcdÞ ¼ 1:221 Mg=m3 . Of the 24810 reflections ð18Þ A collected ð2h ¼ 2:36–55:02°Þ, 17 997 reflections were independent and all were considered as observed ½I > 2rðIÞ. The data were corrected for Lorentz, polarization and absorption effects (Sheldrick, G.M. SADABS, Program for Empirical Absorption Correc-
J. Wang et al. / Inorganic Chemistry Communications 5 (2002) 602–605 tion of Area Detector Data, University G€ ottingen, Germany, 1996). The structure was solved by direct methods, and refined by full-matrix least-squares techniques using SH E L X T L (G.M. Sheldrick, SH E L X T L , Version 5.1, Bruker Analytical X-ray Systems, Madison, WI, 1997). All non-H atoms were refined anisotropically, while the positions of the methyl and methylene H’s were calculated. The final refinements converged at R1 ¼ 0:0639, wR2 ¼ 0:1413, and GOF ¼ 1:380 for observed reflections.
605
[11] (a) H. Schumann, W. Genthe, N. Bruncks, Angew. Chem. Intern. Ed. Engl. 20 (1981) 119–120; (b) H. Schumann, W. Genthe, N. Bruncks, J. Pickardt, Organometallics 1 (1982) 1194–1200; (c) W.J. Evans, A.L. Wayda, W.E. Hunter, J.L. Atwood, Chem. Commun. (1981) 292–293. [12] N.S. Hosmane, D. Zhu, H. Zhang, A.R. Oki, J.A. Maguire, Organometallics 17 (1998) 3196–3203.
Synthesis and crystal structure of the first ‘‘carbons apart’’ diamagnetic lutetiacarborane sandwich complex Jianhui Wang a
a,b
, Shoujian Li a, Chong Zheng a, John A. Maguire b, Narayan S. Hosmane a,*
Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, IL 60115-2862, USA b Department of Chemistry, Southern Methodist University, Dallas, TX 75275-0314, USA Received 3 May 2002; accepted 25 May 2002
Abstract The reaction of closo-exo-5; 6-NaðTHFÞ2 -1-NaðTHFÞ2 -2; 4-ðSiMe3 Þ2 -2; 4-C2 B4 H4 (1) and anhydrous LuCl3 , in a molar ratio of 2:1, in dry benzene at 60 °C produced the first full-sandwiched lutetiacarborane complex, 2; 20 ; 4; 40 -ðSiMe3 Þ4 -3; 50 ; 60 -½ðl-HÞ3 NaðTHFÞ2 -1; 10 -commo-Luðg5 -2; 4-C2 B4 H4 Þ2 (2), as an off-white crystalline solid in 88% yield. Ó 2002 Elsevier Science B.V. All rights reserved. Keywords: Lutetiacarborane; Sandwich complex; Lutetium; Metallacarborane; Coordination; C2 B4 -carborane ligand
The chemistry of lanthanide complexes of the C2 B10 , C2 B9 , and C2 B4 carboranes of both the carbons ‘‘adjacent’’ and ‘‘apart’’ ligand systems began in the late 1980s with the first report on the sandwiched samaracarboranes of the formula ½3; 30 -ðTHFÞ2 -commo-3; 30 -Sm ðC2 B9 H11 Þ2 [1]. Subsequently, a number of half and full-sandwich icosahedral and supraicosahedral lanthanacarboranes have been reported [2]. The results in the ‘‘carbons adjacent’’ C2 B4 carborane systems have demonstrated that a number of unusual trinuclear Ln(III)-carboranes of the form, f½g5 -1-Ln-2; 3-ðSiMe3 Þ2 2; 3-C2 B4 H4 3 ½ðl2 -1-Li-2; 3-ðSiMe3 Þ2 -2;3-C2 B4 H4 Þ3 ðl3 OMeÞ-½l2 -Li ðTHFÞ3 ðl3 -OÞg or dihalolanthanide metal sandwiched complexes of the type, ½LiðTMEDAÞ2 ½1-Cl-1-ðl-ClÞ-2;20 ;3; 30 -ðSiMe3 Þ4 -5; 6-½ðl-HÞ2 LiðTM ED AÞ-4;40 ; 50 -½ðl-HÞ3 LiðTMEDAÞ-1; 10 -commo-Lnð2; 3-C2 B4 H4 Þ2 (Ln ¼ Ce, Nd, Sm, Gd, Tb, Dy, Ho, Er) can be synthesized. These results are of interest in that they show that, depending on the solvent used, quite different products can be obtained from very similar reactants [3]. On the other hand, the reaction of the ‘‘carbons apart’’ C2 B4 carborane ligands with the appropriate lanthanide *
Corresponding author. Tel.: +1-815-753-3556; fax: +1-815-7534802. E-mail address: [email protected] (N.S. Hosmane).
reagents resulted in an unprecedented dinuclear lanthanacarborane bent-sandwich complex, f1-½ðl-ClÞ2 Li ðTMEDAÞ-2; 20 ; 4; 40 -ðSiMe3 Þ4 -5; 50 ; 6; 60 -½ðl-HÞ4 LnðTM EDAÞðClÞðl-ClÞ LiðTMEDAÞ-1; 10 -commo-Lnðg5 -2; 4C2 B4 H4 Þ2 g (Ln ¼ Ho, Gd) [4]. These latter species are unusual in that the central (commo) Ln is g5 -bonded to each of the ‘‘carbons apart’’ C2 B3 faces, with the two B–HðterminalÞ groups of each opposing C2 B3 faces linking to an exo-polyhedral Ln(III)Cl(TMEDA) unit that is also bonded to an exo-polyhedral Li(TMEDA) group via two Ln–Cl–Li bridges [4]. Despite the demonstrated synthetic strategy for the desired iso-structural lanthanacarboranes, there have been no reports on the sandwiched lutetium complexes in either the C2 B9 and C2 B10 cages or the smaller C2 B4 carborane systems. The only report is on the synthesis of a half-sandwich chlorolutetiacarborane complex, ðg5 -C2 B9 H11 ÞLuðTHFÞ2 ðl-ClÞ2 NaðTHFÞ2 , who se unambiguous geometry has yet to be verified by Xray crystallography [5]. The inability to obtain the fullsandwich lutetiacarborane was rationalized on the basis that, regardless of the molar ratio of reactants, the fullsandwich lanthanacarboranes can be isolated only for the early lanthanide metals due to the so-called ‘‘ligand redistribution’’ reactions [5]. In order to test this hypothesis and as part of our ongoing research in this area, the ‘‘carbons apart’’ C2 B4 carborane ligand, closo-exo-5;
1387-7003/02/$ - see front matter Ó 2002 Elsevier Science B.V. All rights reserved. PII: S 1 3 8 7 - 7 0 0 3 ( 0 2 ) 0 0 4 9 1 - 4
J. Wang et al. / Inorganic Chemistry Communications 5 (2002) 602–605
603
Scheme 1. Synthesis of lutetiacarborane sandwich complex.
6-NaðTHFÞ2 -1-NaðTHFÞ2 -2; 4-ðSiMe3 Þ2 -2; 4-C2 B4 H4 (1) was reacted with anhydrous LuCl3 , in a molar ratio of 2:1, in dry benzene at 60 °C to produce, the novel lutetiacarborane complex, 2;20 ;4;40 -ðSiMe3 Þ4 -3;50 ;60 -½ðl-HÞ3 Na ðTHFÞ2 -1; 10 -commo-Luðg5 -2; 4-C2 B4 H4 Þ2 (2), as a diamagnetic off-white crystalline solid in 88% yield (see Scheme 1) [6]. To the best of our knowledge, this constitutes the first report on the fully-sandwiched lutetium complex in any of the carborane ligand systems. The results also show that the ligand redistribution phenomenon is not a general one that can be applied to all of the carborane ligand systems. The most important observation is the absence of any solvent coordination to the central metal atom in 2, unlike most of the lanthanacarboranes known to date [1–5]. This is presumably due to the use of dry benzene as a solvent and a higher reaction temperature (60 °C rather than the usual temperatures of 0–25 °C) that restrict the transfer of THF from the Na atom in the precursor to the central metal atom in the product. This observation could prove to be a significant advancement in the synthetic strategy in both lanthanacarborane chemistry and in the lanthanocene chemistry. The lutetiacarborane (2) is diamagnetic [7] and, therefore, satisfactory 1 H and 13 C-NMR spectra could be obtained [8]. Unfortunately, the 11 B NMR spectra, the potentially most useful tool in elucidating geometries of polyhedral boron cages, failed to provide any useful information due to the extreme broadness of the resonances. Nevertheless, the solution IR spectrum of 2 exhibits well-resolved terminal B–H stretches [9]. Such fine structures of B–H stretching bands have been previously observed for other closo- and commo-lanthanacarboranes and has been explained on the basis of unequal interactions of the boron-bound hydrogens with metal groups present in the complex [3]. In order to resolve any questions as to the geometry of 2 its solid-state structure, shown in Fig. 1 was determined by single-crystal X-ray analysis [10]. The structure shows a bent-sandwich geometry similar to those of the corre-
sponding cyclopentadienide complexes, ðC5 H5 Þ2 Lu ðCH2 SiMe3 ÞðTHFÞ, ðC5 H5 Þ2 Lu ð1-C6 H4 -4-MeÞðTHFÞ, ðC5 H5 Þ2 LuðBut ÞðTHFÞ [11]. The Cent(1)-Lu-Cent(2) angle of 138.3° in 2 is significantly larger than those observed in ðC5 H5 Þ2 LuðRÞðTHFÞ ½R ¼ CH2 SiMe3 ; 1-C6 H4 -4-Me; But complex (125.6°–130°) [11], the erbium complex of the mixed-carborane ligands (135.5°), fLiðTMEDAÞ2 g2 fcommo-1-½2; 3-ðSiMe3 Þ2 -2;3-C2 B4 H4 1-Er-½2; 4-ðSiMe3 Þ2 -2; 4-C2 B4 H4 g2 [3a], and the dimeric ‘‘carbons apart’’ yttracarborane sandwich complex ð131 1°Þ, fNaðTHFÞ3 g2 f½1-ðTHFÞ-1-ðl-HÞ2 -2; 20 ; 4; 40 -
Fig. 1. Perspective view of 2 with the thermal ellipsoids drawn at the ) and angles (°): Lu-ðC2 B3 50% probability level. Pertinent distances (A centroid 1, 2) 2.261, 2.230; Lu-C(11, 13, 21, 23) 2.644(7), 2.582(7), 2.586(6), 2.626(7); Lu-B(12, 14, 15, 22, 24, 25) 2.612 (7), 2.654 (7), 2.680(7), 2.618(7), 2.617(8), 2.590(9); (centroid 1)-Lu-(centroid 2) 138.3 (see supplementary publication No. CCDC 186147 for a detailed list of bond lengths and bond angles). The solvated THF molecules on the exo-polyhedral Naþ ion, and the exo-polyhedral SiMe3 groups are drawn with thin lines for clarity.
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ðSiMe3 Þ4 -1;10 -commo-Yð2; 4-C2 B4 H4 Þ2 2 g [12]. The central (commo) Lu is g5 -bonded to each of the ‘‘carbons apart’’ C2 B3 faces, while a unique B–HðterminalÞ group of a bonding face and the two adjacent B–HðterminalÞ groups of the opposing C2 B3 face are linked to an exo-polyhedral NaðTHFÞ2 unit. The two metal-C2 B3 (centroid) distances are indicative of tighter bonding of 2.261 and 2.230 A of the metal to the carborane ligands when compared ) in ðC5 H5 Þ LuðRÞðTHFÞ½R ¼ to those (2:35 1 A 2 CH2 SiMe3 , 1-C6 H4 -4-Me, But ] complex [11]. Since carborane ligands carry )2 charge, for charge compensation an additional ½NaðTHFÞ2 þ ion is present in the coordination sphere of 2. The absence of the coordinating solvent, THF, on the lanthanide metal indicates that it is possible to synthesize a number of other solvent-free lanthanacarboranes of both the small and large cage carborane systems and to explore their reaction chemistry. Such an investigation is currently underway in our laboratories.
[4]
[5] [6]
Supplementary material Crystallographic data for the structure reported in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication No. CCDC 186147. Copies of the data can be obtained free of charge from The Director, CCDC, 12 Union Road, Cambridge CB2 IEZ, England (Facsimile: ++44-1223-336033 or e-mail: [email protected]).
Acknowledgements [7]
This work was supported by grants from the National Science Foundation (CHE-9988045 and DMR9704048), the Robert A. Welch Foundation (N-1322 to JAM), the donors of the Petroleum Research Fund, administered by the American Chemical Society, and Northern Illinois University through Presidential Research Professorship.
References [1] M.J. Manning, C.B. Knobler, M.F. Hawthorne, J. Am. Chem. Soc. 110 (1988) 4458–4459. [2] (a) A.K. Saxena, N.S. Hosmane, Chem. Rev. 93 (1993) 1081–1124; (b) N.S. Hosmane, J.A. Maguire, J. Cluster Sci. 4 (1993) 297–349; (c) N.S. Hosmane, Y. Wang, A.R. Oki, H. Zhang, D. Zhu, E.M. McDonald, J.A. Maguire, Phosphorus, Sulfur, and Silicon 9394 (1994) 253–256; (d) Z. Xie, Coord. Chem. Rev. (2002) (in press). [3] (a) N.S. Hosmane, Y. Wang, H. Zhang, A.R. Oki, J.A. Maguire, E. Waldh€ or, W. Kaim, H. Binder, R.K. Kremer, Organometallics 14 (1995) 1101–1103;
[8]
[9]
[10]
(b) H. Zhang, A.R. Oki, Y. Wang, J.A. Maguire, N.S. Hosmane, Acta Crystallogr. Cryst. Struct. Commun. C51 (1995) 635– 638; (c) N.S. Hosmane, Y. Wang, A.R. Oki, H. Zhang, J.A. Maguire, Organometallics 15 (1996) 626–638; (d) N.S. Hosmane, Y. Wang, H. Zhang, J.A. Maguire, M. McInnis, T.G. Gray, J.D. Collins, R.K. Kremer, H. Binder, E. Waldh€ or, W. Kaim, Organometallics 15 (1996) 1006–1013; (e) H. Zhang, Y. Wang, J.A. Maguire, N.S. Hosmane, Acta Crystallogr. Cryst. Struct. Commun. 52 (1996) 640–643; (f) N.S. Hosmane, A.R. Oki, H. Zhang, Inorg. Chem. Commun. 1 (1998) 101–104; (g) C. Zheng, N.S. Hosmane, H. Zhang, D. Zhu, J.A. Maguire, Internet. J. Chem. 2 (1999) 10, http://www.ijc.com/articles/ 1999v2/10/; (h) N.S. Hosmane, Y. Wang, H. Zhang, Y. Zhu, J.A. Maguire, Inorg. Chem. Commun. 4 (2001) 547–550. (a) H. Zhang, Y. Wang, J.A. Maguire, N.S. Hosmane, Acta Crystallogr., Cryst. Struct. Commun. C52 (1996) 8–11; (b) N.S. Hosmane, S.-J. Li, C. Zheng, J.A. Maguire, Inorg. Chem. Commun. 4 (2001) 104–107; (c) N.S. Hosmane, Y. Wang, H. Zhang (unpublished results). K.-y. Chiu, Z. Zhang, T.C.W. Mak, Z. Xie, J. Organomet. Chem. 614/615 (2000) 107–112. Synthesis of 2: A 3.19 mmol (1.76 g) sample of closo-exo5; 6-NaðTHFÞ2 -1-NaðTHFÞ2 -2; 4-ðSiMe3 Þ2 -2; 4-C2 B4 H4 (1) (N.S. Hosmane, L. Jia, H. Zhang, J.W. Bausch, G.K.S. Prakash, R.E. Williams, T.P. Onak, Inorg. Chem. 30 (1991) 3793–3795) was reacted with 1.53 mmol of anhydrous LuCl3 (0.43 g) in dry benzene (20 ml) at 60 °C for 24 h, during which time the solution turned yellow turbid. The heterogeneous product mixture was then filtered in vacuo, and the solvent removed from the filtrate to collect a pale yellow solid that was extracted in benzene and filtered to collect a clear yellow solution. Removal of solvents from this clear solution gave a yellow solid that was later recrystallized from dry benzene to collect air-sensitive off-white crystals, identified as 2; 20 ; 4; 40 -ðSiMe3 Þ4 -3; 50 ; 60 -½ðl-HÞ3 Na ðTHFÞ2 -1; 10 -commo-Luðg5 -2; 4-C2 B4 H4 Þ2 (2), in 88% yield [1.14 g, 1.34 mmol; mp: > 250°C (dec); soluble in polar solvents and slightly soluble in n-hexane]. The X-ray quality crystals were grown from a solution mixture of n-hexane (10%) and benzene (90%) and subsequently used for X-ray analyses. The temperature-dependent magnetic susceptibility of 2 was determined using the Faraday balance (J.C. Dobson, J.H. Helms, P. Doppelt, B.P. Sullivan, W.E. Hatfield, Y.J. Meyer, Inorg. Chem. 28 (1989) 2200–2204). At the temperature range of 5–298 K the compound shows antimagnetic property that is consistent with the theoretical electronic arrangement of Luþ3 ion. The NMR spectral data of 2: 1 H NMR (C6 D6 , relative to external Me4 Si) d 3.71 [s(br), 12H, THF], 1.56 [s(br), 12H, THF], 0.74 [s, 18H, SiMe3 ], 0.68 [s, 18H, SiMe3 ]; 13 C NMR (C6 D6 , relative to external Me4 Si) d 128.6 [s(br), cage carbons (SiCB)], 70.6 [m, THF], 24.9 [m, THF], 2.19 [q(br), SiMe3 , 1 Jð13 C 1 HÞ ¼ 119 Hz], 1.84 [q(br), SiMe3 , 1 Jð13 C 1 HÞ ¼ 118:5 Hz]. IR spectral and analytical data: IR (cm1 , KBr pellet): 2536 (s, s), 2511 (s, s), 2468 (s, br), 2443 (br, sh), 2378 (s, s) [m (B-H)]; Anal. Calcd for [C24 H60 B8 O2 Si4 NaLu [THF]: C, 39.57; H, 8.07.Found: C, 39.92; H, 7.92. X-ray data for 2 (C24 H60 B8 Si4 LuNaO2 ; fw, 777.52; P 1): Data was collected at 173 (2) K on a Bruker SMART CCD PLATFORM , b ¼ 17:236 (4) A , c ¼ 17:828 diffractometer with a ¼ 13:933 (3) A , a ¼ 92:569ð4Þ°, b ¼ 98:332ð4Þ° c ¼ 91:026ð4Þ°; V ¼ 4230:8 (4)A 3 , Z ¼ 4, DðcalcdÞ ¼ 1:221 Mg=m3 . Of the 24810 reflections ð18Þ A collected ð2h ¼ 2:36–55:02°Þ, 17 997 reflections were independent and all were considered as observed ½I > 2rðIÞ. The data were corrected for Lorentz, polarization and absorption effects (Sheldrick, G.M. SADABS, Program for Empirical Absorption Correc-
J. Wang et al. / Inorganic Chemistry Communications 5 (2002) 602–605 tion of Area Detector Data, University G€ ottingen, Germany, 1996). The structure was solved by direct methods, and refined by full-matrix least-squares techniques using SH E L X T L (G.M. Sheldrick, SH E L X T L , Version 5.1, Bruker Analytical X-ray Systems, Madison, WI, 1997). All non-H atoms were refined anisotropically, while the positions of the methyl and methylene H’s were calculated. The final refinements converged at R1 ¼ 0:0639, wR2 ¼ 0:1413, and GOF ¼ 1:380 for observed reflections.
605
[11] (a) H. Schumann, W. Genthe, N. Bruncks, Angew. Chem. Intern. Ed. Engl. 20 (1981) 119–120; (b) H. Schumann, W. Genthe, N. Bruncks, J. Pickardt, Organometallics 1 (1982) 1194–1200; (c) W.J. Evans, A.L. Wayda, W.E. Hunter, J.L. Atwood, Chem. Commun. (1981) 292–293. [12] N.S. Hosmane, D. Zhu, H. Zhang, A.R. Oki, J.A. Maguire, Organometallics 17 (1998) 3196–3203.