A second monoclinic polymorph of {bis­[5-methyl-3-(trifluoro­meth­yl)pyrazol-1-yl]borato}{tris­[5-methyl-3-(trifluoro­meth­yl)pyrazol-1-yl]borato}cobalt(II): a structure containing a B—H⋯Co agostic inter­action

Robert T Stibrany; Joseph A Potenza

doi:10.1107/S1600536811021994

. 2011 Jun 11;67(Pt 7):m911–m912. doi: 10.1107/S1600536811021994

A second monoclinic polymorph of {bis[5-methyl-3-(trifluoromethyl)pyrazol-1-yl]borato}{tris[5-methyl-3-(trifluoromethyl)pyrazol-1-yl]borato}cobalt(II): a structure containing a B—H⋯Co agostic interaction

Robert T Stibrany ^a,^*, Joseph A Potenza ^a

PMCID: PMC3151874 PMID: 21836897

Abstract

The title compound, [Co(C₁₀H₁₀BF₆N₄)(C₁₅H₁₃BF₉N₆)], is a polymorph of the previously reported neutral cobalt(II) complex [Stibrany & Potenza (2010 ▶). Acta Cryst. E66, m506–m507], which contains one each of the monoanionic ligands, bis[5-methyl-3-(trifluoromethyl)pyrazol-1-yl]borate (Bp) and tris[5-methyl-3-(trifluoromethyl)pyrazol-1-yl]borate (Tp). A distorted octahedral coordination geometry of the Co^II atom results from ligation of an H atom, which is part of an agostic B—H⋯Co interaction [H⋯Co = 2.12 (3) Å], and by five imine N atoms, two from a Bp ligand and three from a Tp ligand. Weak intra- and intermolecular C—F⋯π interactions with F⋯centroid distances ranging from 3.025 (4) to 3.605 (4) Å are observed.

Related literature

For our study of nitrogen-containing heterocyles and their complexes with metal ions, see: Stibrany & Potenza (2006 ▶, 2009a ▶,b ▶); Stibrany et al. (1999 ▶, 2005 ▶, 2006 ▶). For a polymorph of the title compound, see: Stibrany & Potenza (2010 ▶). For oxidation studies of copper and cobalt complexes utilizing the title ligand, see: Gorun et al. (2000 ▶). For agostic interactions, see: Ruman et al. (2001 ▶, 2002 ▶); Siemer et al. (2001 ▶); Ghosh et al. (1998 ▶).

Experimental

Crystal data

[Co(C₁₀H₁₀BF₆N₄)(C₁₅H₁₃BF₉N₆)]
M _r = 829.08
Monoclinic,
a = 18.593 (2) Å
b = 12.1167 (13) Å
c = 30.720 (3) Å
β = 102.721 (2)°
V = 6751.1 (13) Å³
Z = 8
Mo Kα radiation
μ = 0.63 mm⁻¹
T = 298 K
0.28 × 0.24 × 0.12 mm

Data collection

Bruker SMART CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Blessing, 1995 ▶) T _min = 0.875, T _max = 1.00
32390 measured reflections
7431 independent reflections
5522 reflections with I > 2σ(I)
R _int = 0.032

Refinement

R[F ² > 2σ(F ²)] = 0.059
wR(F ²) = 0.167
S = 1.00
7431 reflections
495 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.69 e Å⁻³
Δρ_min = −0.32 e Å⁻³

Data collection: SMART WNT/2000 (Bruker, 2000 ▶); cell refinement: SAINT-Plus (Bruker, 2000 ▶); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEPIII (Burnett & Johnson, 1996 ▶) and ORTEP-32 (Farrugia, 1997 ▶); software used to prepare material for publication: SHELXTL (Sheldrick, 2008 ▶) and PLATON (Spek, 2009 ▶).

Supplementary Material

Crystal structure: contains datablock(s) I. DOI: 10.1107/S1600536811021994/rz2601sup1.cif

e-67-0m911-sup1.cif^{(31.9KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811021994/rz2601Isup2.hkl

e-67-0m911-Isup2.hkl^{(363.7KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Selected bond lengths (Å).

Co1—N7	2.100 (3)
Co1—H21B	2.12 (3)
Co1—N9	2.124 (3)
Co1—N3	2.124 (3)
Co1—N1	2.163 (3)
Co1—N5	2.172 (3)

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Table 2. Flourine interaction geometry (Å, °).

Cg1, Cg2, Cg3 and Cg4 are the centroids of the N3/N4/C9/C8/C7, N5/N6/C14/C13/C12, N7/N8/C19/C18/C17 and N9/N10/C24/C23/C22 rings, respectively.

C—F⋯Cg	C—F	F⋯Cg	C⋯Cg	C—F⋯Cg
C1—F1⋯Cg4	1.333 (5)	3.319 (4)	3.798 (5)	100.7 (3)
C1—F2⋯Cg2ⁱ	1.331 (4)	3.341 (3)	4.565 (4)	152.6 (2)
C1—F3⋯Cg4	1.316 (5)	3.273 (3)	3.798 (5)	103.3 (3)
C11—F9⋯Cg3	1.295 (5)	3.025 (4)	3.826 (4)	119.1 (3)
C16—F10⋯Cg1	1.298 (5)	3.252 (4)	4.279 (4)	135.8 (3)
C16—F10⋯Cg2	1.298 (5)	3.208 (3)	4.061 (4)	122.8 (2)
C16—F11⋯Cg4ⁱⁱ	1.324 (5)	3.605 (4)	4.467 (4)	123.0 (3)
C21—F13⋯Cg1	1.321 (5)	3.373 (3)	4.346 (5)	130.3 (3)

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Symmetry codes: (i) Inline graphic − x, − y, −z; (ii) − x, + y, − z.

Acknowledgments

Any acknowledgements?

supplementary crystallographic information

Comment

Our long-term interest in the synthesis and applications of nitrogen-containing heterocyles, such as expanded-ring imidazoles, and their complexes with metal ions (Stibrany & Potenza, 2009a) led us to prepare the title compound (I). With pyrazole, a variety of metal complexes has been prepared, predominantly with copper (Stibrany & Potenza, 2006), including the Cu(II) complex of an unusual (dimethylamino)methane bridged bis(pyrazole) ligand formed via a DMF aminalization (Stibrany et al., 1999) and a novel binuclear µ-oxalato(1-benzylpyrazole)₂(CF₃SO₃)₂copper(II) compound resulting from the fixation of carbon dioxide (Stibrany et al., 2005). A tris(pyrazolyl)arene ligand which forms geometrically constrained metal complexes has also been prepared (Stibrany et al., 2006), as has a sterically strained trigonal-bipyramidal Cu(II) complex containing a 1-benzylpyrazole ligand (Stibrany & Potenza, 2009b). Copper and cobalt complexes utlizing the title ligand were prepared for oxidation studies (Gorun et al., 2000).

Compound (I) (Fig. 1) contains a central Co(II) ion linked to a Tp and a Bp ligand. Ligation is effected by three imine N atoms of the Tp ligand, two imine N atoms of the Bp ligand, and an H atom which participates in a two-electron, three-center B—H···Co bond. The result is a distorted octahedral coordination geometry. Compound (I) is a polymorph of a previously reported structure of the same compound (II) (Stibrany & Potenza, 2010). The present polymorph was the result of a ligand displacement reaction in which a Tp ligand was added to a preformed Co(Bp)₂ complex to form (I).

A number of cobalt(II) complexes containing mixed bis (Bp)- and tris pyrazolylborates (Tp) and C—H···Co agostic interactions have been reported, with H···Co distances ranging from 2.03 Å (Ruman et al., 2002), 2.035 Å (Ruman et al., 2001) to 2.334 Å (Siemer et al., 2001). The H···Co distance in (I), 2.12 (3) Å, lies between these two extremes. Infrared spectral results also support the existence of an agostic 2-electron, 3-center bond in (I). B—H stretching vibrations for BH₂ groups in which one of the H atoms is involved in a 2-electron, 3-center bond with a metal ion typically lie in the range 2100–2500 cm^-1, with the lower value corresponding to the agostic interaction (Ghosh et al., 1998). In (I), IR bands at 2570 and 2492 cm^-1 are assigned as free B—H stretching vibrations, while the band at 2217 cm^-1 is assigned to the bound B—H group.

The coordination geometries of both polymorphs are similar: in both, the largest deviations from octahedral symmetry are found with the H—Co—N angles associated with the bound hydrogen atom. The polymorphs differ fundamentally in the behavior of the trifluoromethyl groups. In the first polymorph, the molecules formed layers linked by intermolecular C—H···F hydrogen bonds in such a way as to form chains along the a cell direction. In contrast, the current polymorph exhibits no such hydrogen bonds; rather PLATON (Spek, 2009) reveals six intramolecular and two intermolecular C—F···Cg interactions (Table 2).

Experimental

Both Tp and Bp ligands were prepared as previously reported (Gorun et al., 2000). To a flask containing 10 ml of acetonitrile, 60 mg of Co(Bp)₂ (0.088 mmol) was disssolved to give a red-purple solution. Then 44 mg of KTp (0.088 mmol) was added and the mixture was allowed to stir for 10 min. giving little color change. The mixture was filtered to remove any solids and yielded a clear red-purple solution, which was left to evaporate slowly. Upon evaporation, a major dichroic red-orange phase (compound (I)) was separated mechanically and characterized. IR (KBr pellet, cm^-1); 2570(Tp, B—H, w), 2492(Bp, B—H, w), 2217(Bp, B—H···Co, w), 1471(s), 1262(s), 1163(s), 1126(s), 1002(s), 800(m), 650(m).