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Neutron diffraction studies on a system with a 4-coordinate hydrogen atom in an yttrium cluster
ARTICLE IN PRESS
Physica B 385–386 (2006) 231–233 www.elsevier.com/locate/physb
Neutron diffraction studies on a system with a 4-coordinate hydrogen atom in an yttrium cluster Muhammed Yousufuddina, Jens Baldamusb, Olivier Tardifb, Zhaomin Houb,, Sax A. Masonc, Garry J. McIntyrec, Robert Baua, a Department of Chemistry, University of Southern California, Los Angeles, CA 90089, USA RIKEN (Institute of Physical and Chemical Research), Hirosawa 2-1, Wako, Saitama 351-0198, Japan c Institut Laue Langevin, 6 rue Jules Horowitz, BP 156, 38042 Grenoble Cedex 9, France
b
Abstract A 4-coordinate H atom has been unambiguously located, by single-crystal neutron diffraction for the first time, in the center of the tetrahedral metal complex Y4H8(Cp00 )4(THF) [Cp00 ¼ C5Me4(SiMe3)]. The core of the molecule consists of a tetranuclear cluster with one interstitial, one face-bridging and six edge-bridging hydride ligands. The four individual Y–H distances to the unique interstitial hydride ligand are 2.184(16), 2.189(16), 2.221(13) and 2.168(12) A˚. Neutron data were collected on a 4-mm3 crystal at the Quasi–Laue diffractometer VIVALDI at ILL (Grenoble), and the present agreement factor is R ¼ 12.2% for 3566 reflections. r 2006 Elsevier B.V. All rights reserved. Keywords: Neutron diffraction; Metal cluster; Yttrium; 4-coordinate hydrogen
1. Introduction Neutron diffraction studies have shown that hydrogen atoms can occupy the interstitial sites of metal lattices. Accurate characterization of hydrogen atom positions is difficult by the X-ray diffraction technique, especially for H atoms situated in metal clusters. The tendency for H atoms to occupy vacant sites in metal clusters has led to unusually high coordination numbers (e.g. 3,5 and 6) of hydrogen in these compounds. Some years ago, the existence of 6coordinate hydrogen (m6-H) in the metal cluster anions [HCo6(CO)15] and [HRu6(CO)18] was established [1,2] using neutron diffraction (the former complex is shown in Fig. 1). More recently, we reported [3] the first neutron analysis of two examples of 5-coordinate H (m5-H) located in the [H2Rh13(CO)24]3 metal cluster anion shown in Fig. 2. But 4-coordinate hydrogen has remained elusive and to our knowledge, a neutron structure of 4-coordinate hydrogen (m4-H) in a covalent metal cluster complex has never been reported. Also corresponding author. Corresponding author. Tel.: +1 213 740 2692; fax: +1 213 740 0930.
E-mail address: [email protected] (R. Bau). 0921-4526/$ - see front matter r 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.physb.2006.05.052
Recently, the first X-ray structures showing evidence of m4-H atoms were reported by Hou and coworkers in the complexes [Cp00 LuH2]4(THF) [Cp00 ¼ C5Me4(SiMe3)] and [Cp00 YH2]4(THF) [4]. Their low-temperature X-ray analyses showed that the average H–M distance of the m4-H atom was 2.07(6) A˚ for the Lu complex. A neutron diffraction study of these compounds would provide more precise information concerning the H atom position and unambiguously confirm the notion of a 4-coordinate H atom. In this regard, we discuss herein the preliminary results showing the first example of a 4-coordinate H atom in an organometallic compound studied by neutron diffraction, in the metal cluster complex [Cp00 YH2]4(THF).
2. Crystallographic analysis A large yellow crystal with approximate dimensions 2.0 2.0 1.0 mm3 was sealed in a glass capillary and mounted on the VIVALDI instrument [5] at the Institut Laue-Langevin in Grenoble, France. Table 1 lists selected crystallographic data for the neutron analysis of [Cp00 YH2]4(THF).
ARTICLE IN PRESS 232
M. Yousufuddin et al. / Physica B 385–386 (2006) 231–233 Table 1 Neutron crystallographic data for complex [(C5Me4SiMe3)YH2]4(THF) Empirical formula Formula weight Crystal system Space group Volume Z Temperature Crystal size Wavelength range Min d-spacing observed No. of refl. collected No. of independent refl. No. of refl. with I42(1) No. of params refined GOFa Refinement method Final R [I42(1) data] a
C52 H100 O Si4 Y4 632.00 Triclinic P(1) 3196.9(10) A˚3 2 150(2) K 2.0 2.0 1.0 mm3 0.9-2.7 A˚ 0.72 A˚ 18291 4900 3566 1115 1.788 Full matrix, least-squares on F2 R1 ¼ 0.1216, wR2 ¼ 0.2661
Weight ¼ 1/[2(F2o)+(0.1000P)2], where P ¼ (Max(F2o,0)+2F2c )/3.
Fig. 1. ORTEP plot of the 6-coordinate hydrogen in [HCo6(CO)15] (ref. [1]).
Fig. 3. ORTEP plot of core of [Cp00 YH2]4(THF).
Fig. 2. Plot of one of the two 5-coordinate H atoms in [H2Rh13(CO)24]3 (ref. [3]).
Our neutron data analysis [6] has provided the first accurate neutron-diffraction measurement of a 4-coordinate H atom in a covalent molecular species. Fig. 3 shows a view of the core of [Cp00 YH2]4(THF). The 4-coordinate hydrogen atom occupies the interstitial site of the tetra-
hedral cluster. In addition to the 4-coordinate hydrogen atom, the H8Y4 core contains six edge-bridging hydrides and one face-bridging hydride giving each yttrium metal a valency of three (together with the negatively charged Cp00 ligands). The average interstitial Y–H distance is 2.191(14) A˚, and H1 is bonded to the four yttrium metals with the following dimensions: H1–Y1 ¼ 2.184(16) A˚, H1–Y2 ¼ 2.189(16) A˚, H1–Y3 ¼ 2.221(13) A˚ and H1–Y4 ¼ 2.168(12) A˚. The individual angles are close to the ideal tetrahedral angle of 109.51: Y1–H1–Y2 ¼ 114.3(5)1, Y1–H1–Y3 ¼ 113.9(5)1, Y1–H1–Y4 ¼ 115.6(5)1, Y2–H1–Y3 ¼ 102.1(5)1, Y2–H1– Y4 ¼ 106.5(5)1 and Y3–H1–Y4 ¼ 102.9(5)1. Closer inspection
ARTICLE IN PRESS M. Yousufuddin et al. / Physica B 385–386 (2006) 231–233 Table 2 Variation of Co–H distance with H coordination number Compound
H coord no.
Co–H dist(A˚)
Ref.
CoH(CO)4 Co2(m2-H)3(Z5-Cp*)2 Co3Fe(m3-H)(CO)9[P(OMe)3]3 [Co6(m6-H)(CO)15]
1 2 3 6
1.558(18) 1.641(6) 1.734(4) 1.823(13)
[7] [8] [9] [1]
of the core (Fig. 3) suggests a possible role for the face- and edge-bridging hydrides. The bridging hydrides appear to clamp onto the edges and surfaces of the tetrahedron which allows the hydride to safely occupy the interstitial site without causing the cluster to disintegrate. This particular bonding arrangement would probably not exist without the stabilizing presence of the other seven bridging hydrides. We had previously noted that there appears to be a relationship between the number of metal atoms surrounding a hydrogen atom and its corresponding M–H distance. In a series of cobalt compounds containing the following bonds: Co–H (terminal), Co2(m2-H), Co3(m3-H), Co6(m6-H), one can observe a gradual increase in Co–H distance (1.56, 1.64, 1.73, 1.82 A˚) along the above series [1,7–9]. This may reflect a decrease in Co–H bond order as the coordination number of hydrogen increases (Table 2). Curiously, one does not observe exactly the same trends in the present work. The title molecule allows us (uniquely) to compare three different types of linkages in the same compound: (m2-H), (m3-H) as well as (m4-H) metal–hydrogen bonds. The result is rather interesting: although there is the usual (expected) increase as one goes from V2(m2-H) [V ¼ 2.171 A˚] to V3(m3-H) [V ¼ 2.336 A˚], the V–H distance actually decreases in the next step, from V3(m3-H) [V ¼ 2.336 A˚] to V4(m4-H) [V ¼ 2.191 A˚]. The relative
233
shortness of the V4(m4-H) distance probably reflects the tightness of a tetrahedral cavity. In contrast, for an octahedral interstitial site, it is well-known that there is more than enough space to allow the H atom to ‘‘rattle around’’ inside the cavity, and in fact, there are several cases known in which a H atom in an octahedral site is offcentered [10,11]. References [1] (a) D.W. Hart, R.G. Teller, C.Y. Wei, R. Bau, G. Longoni, S. Campanella, P. Chini, T.F. Koetzle, Angew. Chem. Int. Ed. Engl. 18 (1979) 80; (b) D.W. Hart, R.G. Teller, C.Y. Wei, R. Bau, G. Longoni, S. Campanella, P. Chini, T.F. Koetzle, J. Am. Chem. Soc. 103 (1981) 1458. [2] P.F. Jackson, B.F.G. Johnson, J. Lewis, P.R. Raithby, M. McPartlin, W.J.H. Nelson, K.D. Rouse, J. Allibon, S.A. Mason, J. Chem. Soc. Chem. Commun. 3 (1980) 295. [3] R. Bau, M.H. Drabnis, L. Garlaschelli, W.T. Klooster, Z. Xie, T.F. Koetzle, S. Martinengo, Science 275 (1997) 1099. [4] (a) O. Tardif, M. Nishiura, Z. Hou, Organometallics 22 (2003) 1171; (b) D. Cui, O. Tardif, Z. Hou, J. Am. Chem. Soc. 126 (2004) 1312. [5] For a description of the VIVALDI instrument, see C. Wilkinson, J.A. Cowan, D.A.A. Myles, F. Cipriani, G.J. McIntyre, Neutron News 13 (2002) 37. [6] For a description of the treatment of data using theVIVALDI instrument, see E. Ding, B. Du, E.A. Meyers, S.G. Shore, M. Yousufuddin, R. Bau, G.J. McIntyre, Inorg. Chem. 44 (2005) 2459. [7] E.A. McNeill, F.R. Scholer, J. Am. Chem. Soc. 99 (1977) 6243. [8] F. Lutz, R. Bau, P. Wu, T.F. Koetzle, C. Krueger, J.J. Schneider, Inorg. Chem. 35 (1996) 2698. [9] R.G. Teller, R.D. Wilson, R.K. McMullan, T.F. Koetzle, R. Bau, J. Am. Chem. Soc. 100 (1978) 3071. [10] R.W. Broach, L.F. Dahl, G. Longoni, P. Chini, A.J. Schultz, J.M. Williams, Adv. Chem. Ser. 167 (1979) 93. [11] A.N. Fitch, S.A. Barrett, B.E.F. Fender, A. Simon, J. Chem. Soc. (Dalton) 3 (1984) 501.
Physica B 385–386 (2006) 231–233 www.elsevier.com/locate/physb
Neutron diffraction studies on a system with a 4-coordinate hydrogen atom in an yttrium cluster Muhammed Yousufuddina, Jens Baldamusb, Olivier Tardifb, Zhaomin Houb,, Sax A. Masonc, Garry J. McIntyrec, Robert Baua, a Department of Chemistry, University of Southern California, Los Angeles, CA 90089, USA RIKEN (Institute of Physical and Chemical Research), Hirosawa 2-1, Wako, Saitama 351-0198, Japan c Institut Laue Langevin, 6 rue Jules Horowitz, BP 156, 38042 Grenoble Cedex 9, France
b
Abstract A 4-coordinate H atom has been unambiguously located, by single-crystal neutron diffraction for the first time, in the center of the tetrahedral metal complex Y4H8(Cp00 )4(THF) [Cp00 ¼ C5Me4(SiMe3)]. The core of the molecule consists of a tetranuclear cluster with one interstitial, one face-bridging and six edge-bridging hydride ligands. The four individual Y–H distances to the unique interstitial hydride ligand are 2.184(16), 2.189(16), 2.221(13) and 2.168(12) A˚. Neutron data were collected on a 4-mm3 crystal at the Quasi–Laue diffractometer VIVALDI at ILL (Grenoble), and the present agreement factor is R ¼ 12.2% for 3566 reflections. r 2006 Elsevier B.V. All rights reserved. Keywords: Neutron diffraction; Metal cluster; Yttrium; 4-coordinate hydrogen
1. Introduction Neutron diffraction studies have shown that hydrogen atoms can occupy the interstitial sites of metal lattices. Accurate characterization of hydrogen atom positions is difficult by the X-ray diffraction technique, especially for H atoms situated in metal clusters. The tendency for H atoms to occupy vacant sites in metal clusters has led to unusually high coordination numbers (e.g. 3,5 and 6) of hydrogen in these compounds. Some years ago, the existence of 6coordinate hydrogen (m6-H) in the metal cluster anions [HCo6(CO)15] and [HRu6(CO)18] was established [1,2] using neutron diffraction (the former complex is shown in Fig. 1). More recently, we reported [3] the first neutron analysis of two examples of 5-coordinate H (m5-H) located in the [H2Rh13(CO)24]3 metal cluster anion shown in Fig. 2. But 4-coordinate hydrogen has remained elusive and to our knowledge, a neutron structure of 4-coordinate hydrogen (m4-H) in a covalent metal cluster complex has never been reported. Also corresponding author. Corresponding author. Tel.: +1 213 740 2692; fax: +1 213 740 0930.
E-mail address: [email protected] (R. Bau). 0921-4526/$ - see front matter r 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.physb.2006.05.052
Recently, the first X-ray structures showing evidence of m4-H atoms were reported by Hou and coworkers in the complexes [Cp00 LuH2]4(THF) [Cp00 ¼ C5Me4(SiMe3)] and [Cp00 YH2]4(THF) [4]. Their low-temperature X-ray analyses showed that the average H–M distance of the m4-H atom was 2.07(6) A˚ for the Lu complex. A neutron diffraction study of these compounds would provide more precise information concerning the H atom position and unambiguously confirm the notion of a 4-coordinate H atom. In this regard, we discuss herein the preliminary results showing the first example of a 4-coordinate H atom in an organometallic compound studied by neutron diffraction, in the metal cluster complex [Cp00 YH2]4(THF).
2. Crystallographic analysis A large yellow crystal with approximate dimensions 2.0 2.0 1.0 mm3 was sealed in a glass capillary and mounted on the VIVALDI instrument [5] at the Institut Laue-Langevin in Grenoble, France. Table 1 lists selected crystallographic data for the neutron analysis of [Cp00 YH2]4(THF).
ARTICLE IN PRESS 232
M. Yousufuddin et al. / Physica B 385–386 (2006) 231–233 Table 1 Neutron crystallographic data for complex [(C5Me4SiMe3)YH2]4(THF) Empirical formula Formula weight Crystal system Space group Volume Z Temperature Crystal size Wavelength range Min d-spacing observed No. of refl. collected No. of independent refl. No. of refl. with I42(1) No. of params refined GOFa Refinement method Final R [I42(1) data] a
C52 H100 O Si4 Y4 632.00 Triclinic P(1) 3196.9(10) A˚3 2 150(2) K 2.0 2.0 1.0 mm3 0.9-2.7 A˚ 0.72 A˚ 18291 4900 3566 1115 1.788 Full matrix, least-squares on F2 R1 ¼ 0.1216, wR2 ¼ 0.2661
Weight ¼ 1/[2(F2o)+(0.1000P)2], where P ¼ (Max(F2o,0)+2F2c )/3.
Fig. 1. ORTEP plot of the 6-coordinate hydrogen in [HCo6(CO)15] (ref. [1]).
Fig. 3. ORTEP plot of core of [Cp00 YH2]4(THF).
Fig. 2. Plot of one of the two 5-coordinate H atoms in [H2Rh13(CO)24]3 (ref. [3]).
Our neutron data analysis [6] has provided the first accurate neutron-diffraction measurement of a 4-coordinate H atom in a covalent molecular species. Fig. 3 shows a view of the core of [Cp00 YH2]4(THF). The 4-coordinate hydrogen atom occupies the interstitial site of the tetra-
hedral cluster. In addition to the 4-coordinate hydrogen atom, the H8Y4 core contains six edge-bridging hydrides and one face-bridging hydride giving each yttrium metal a valency of three (together with the negatively charged Cp00 ligands). The average interstitial Y–H distance is 2.191(14) A˚, and H1 is bonded to the four yttrium metals with the following dimensions: H1–Y1 ¼ 2.184(16) A˚, H1–Y2 ¼ 2.189(16) A˚, H1–Y3 ¼ 2.221(13) A˚ and H1–Y4 ¼ 2.168(12) A˚. The individual angles are close to the ideal tetrahedral angle of 109.51: Y1–H1–Y2 ¼ 114.3(5)1, Y1–H1–Y3 ¼ 113.9(5)1, Y1–H1–Y4 ¼ 115.6(5)1, Y2–H1–Y3 ¼ 102.1(5)1, Y2–H1– Y4 ¼ 106.5(5)1 and Y3–H1–Y4 ¼ 102.9(5)1. Closer inspection
ARTICLE IN PRESS M. Yousufuddin et al. / Physica B 385–386 (2006) 231–233 Table 2 Variation of Co–H distance with H coordination number Compound
H coord no.
Co–H dist(A˚)
Ref.
CoH(CO)4 Co2(m2-H)3(Z5-Cp*)2 Co3Fe(m3-H)(CO)9[P(OMe)3]3 [Co6(m6-H)(CO)15]
1 2 3 6
1.558(18) 1.641(6) 1.734(4) 1.823(13)
[7] [8] [9] [1]
of the core (Fig. 3) suggests a possible role for the face- and edge-bridging hydrides. The bridging hydrides appear to clamp onto the edges and surfaces of the tetrahedron which allows the hydride to safely occupy the interstitial site without causing the cluster to disintegrate. This particular bonding arrangement would probably not exist without the stabilizing presence of the other seven bridging hydrides. We had previously noted that there appears to be a relationship between the number of metal atoms surrounding a hydrogen atom and its corresponding M–H distance. In a series of cobalt compounds containing the following bonds: Co–H (terminal), Co2(m2-H), Co3(m3-H), Co6(m6-H), one can observe a gradual increase in Co–H distance (1.56, 1.64, 1.73, 1.82 A˚) along the above series [1,7–9]. This may reflect a decrease in Co–H bond order as the coordination number of hydrogen increases (Table 2). Curiously, one does not observe exactly the same trends in the present work. The title molecule allows us (uniquely) to compare three different types of linkages in the same compound: (m2-H), (m3-H) as well as (m4-H) metal–hydrogen bonds. The result is rather interesting: although there is the usual (expected) increase as one goes from V2(m2-H) [V ¼ 2.171 A˚] to V3(m3-H) [V ¼ 2.336 A˚], the V–H distance actually decreases in the next step, from V3(m3-H) [V ¼ 2.336 A˚] to V4(m4-H) [V ¼ 2.191 A˚]. The relative
233
shortness of the V4(m4-H) distance probably reflects the tightness of a tetrahedral cavity. In contrast, for an octahedral interstitial site, it is well-known that there is more than enough space to allow the H atom to ‘‘rattle around’’ inside the cavity, and in fact, there are several cases known in which a H atom in an octahedral site is offcentered [10,11]. References [1] (a) D.W. Hart, R.G. Teller, C.Y. Wei, R. Bau, G. Longoni, S. Campanella, P. Chini, T.F. Koetzle, Angew. Chem. Int. Ed. Engl. 18 (1979) 80; (b) D.W. Hart, R.G. Teller, C.Y. Wei, R. Bau, G. Longoni, S. Campanella, P. Chini, T.F. Koetzle, J. Am. Chem. Soc. 103 (1981) 1458. [2] P.F. Jackson, B.F.G. Johnson, J. Lewis, P.R. Raithby, M. McPartlin, W.J.H. Nelson, K.D. Rouse, J. Allibon, S.A. Mason, J. Chem. Soc. Chem. Commun. 3 (1980) 295. [3] R. Bau, M.H. Drabnis, L. Garlaschelli, W.T. Klooster, Z. Xie, T.F. Koetzle, S. Martinengo, Science 275 (1997) 1099. [4] (a) O. Tardif, M. Nishiura, Z. Hou, Organometallics 22 (2003) 1171; (b) D. Cui, O. Tardif, Z. Hou, J. Am. Chem. Soc. 126 (2004) 1312. [5] For a description of the VIVALDI instrument, see C. Wilkinson, J.A. Cowan, D.A.A. Myles, F. Cipriani, G.J. McIntyre, Neutron News 13 (2002) 37. [6] For a description of the treatment of data using theVIVALDI instrument, see E. Ding, B. Du, E.A. Meyers, S.G. Shore, M. Yousufuddin, R. Bau, G.J. McIntyre, Inorg. Chem. 44 (2005) 2459. [7] E.A. McNeill, F.R. Scholer, J. Am. Chem. Soc. 99 (1977) 6243. [8] F. Lutz, R. Bau, P. Wu, T.F. Koetzle, C. Krueger, J.J. Schneider, Inorg. Chem. 35 (1996) 2698. [9] R.G. Teller, R.D. Wilson, R.K. McMullan, T.F. Koetzle, R. Bau, J. Am. Chem. Soc. 100 (1978) 3071. [10] R.W. Broach, L.F. Dahl, G. Longoni, P. Chini, A.J. Schultz, J.M. Williams, Adv. Chem. Ser. 167 (1979) 93. [11] A.N. Fitch, S.A. Barrett, B.E.F. Fender, A. Simon, J. Chem. Soc. (Dalton) 3 (1984) 501.