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Methyltris(pyrazolyl)silanes: new tripodal nitrogen-donor ligands
Inorganic Chemistry Communications 2 (1999) 194–196
Methyltris(pyrazolyl)silanes: new tripodal nitrogen-donor ligands Eric E. Pullen a, Arnold L. Rheingold b,*, Daniel Rabinovich a,* a
Department of Chemistry, The University of North Carolina at Charlotte, 9201 University City Boulevard, Charlotte, NC 28223, USA b Department of Chemistry and Biochemistry, The University of Delaware, Newark, DE 19716, USA Received 12 January 1999
Abstract Two tridentate nitrogen-donor ligands, the methyltris(pyrazolyl)silanes MeSi(3,5-RR9pz)3 (RsR9sMe; RsBut, R9sH), have been synthesized and the X-ray structure of the latter has been determined. The first transition metal derivatives of these ligands, the cationic copper(I) complexes [LCu(NCMe)]q (where LsMeSi(3,5-Me2pz)3 or MeSi(3-Butpz)3), have been prepared and characterized analytically and spectroscopically. q 1999 Elsevier Science S.A. All rights reserved. Keywords: Pyrazoles; Silanes; Crystal structures; Copper(I) complexes
1. Introduction The tris(pyrazolyl)hydroborates [HB(3,5-RR9pz)3]y (Scheme 1, A) are among the most popular ligands in coordination chemistry since their introduction over 30 years ago [1–3]. The chemistry of their neutral, carbon-centered analogs, the tris(pyrazolyl)methanes (Scheme 1, B), is considerably less developed, and deals mainly with the HC(pz)3 and HC(3,5-Me2pz)3 ligands [4]. Only recently have bulkier tris(pyrazolyl)methane ligands bearing alkyl (Pri, But) or aryl (Ph) substituents in the 3-position been developed [5,6]. These sterically-demanding ligands are attractive in view of the success of the corresponding tris(pyrazolyl)hydroborates as ‘tetrahedral enforcers’ [7,8]. However, ligands such as HC(3-Rpz)3 (RsBut, Ph) are typically isolated only in low to moderate yields (25–55%) after a relatively cumbersome work-up that includes several purification steps [9,10]. Given the enhanced nucleophilicity of the Si–Cl bonds in chlorosilanes (e.g., MeSiCl3) relative to that of the C–Cl bonds in the chloroalkanes (e.g., HCCl3) commonly used to prepare HC(3,5-RR9pz)3, we set out to develop the syntheses of alkyltris(pyrazolyl)silanes (Scheme 1, C) as alternative neutral analogs of the tris(pyrazolyl)hydroborates. In addition, we are interested in assessing the effect on the ligand’s flexibility (i.e., cone angles) of the larger silicon atoms in R0Si(3,5-RR9pz)3 compared to the carbon centers in * Corresponding authors. D. Rabinovich: Tel.: q1-704-547 4442; Fax: q1-704-547 3151; E-mail: [email protected]. A.L. Rheingold: E-mail: [email protected].
Scheme 1. Tris(pyrazolyl) ligands.
tris(pyrazolyl)alkanes. To our surprise, the only literature references to the silanes RnSi(pz)4yn appear to be the unpublished work of Klanberg (see footnote 177 in Ref. [11]) and the X-ray structure of the dimethylpyrazolyl derivative MeSi(3,5-Me2pz)3 [12]. We present herein our syntheses of MeSi(3,5-Me2pz)3 and the bulkier tert-butylpyrazolyl derivative MeSi(3-Butpz)3, their complete characterization,
1387-7003/99/$ - see front matter q 1999 Elsevier Science S.A. All rights reserved. PII S 1 3 8 7 - 7 0 0 3 ( 9 9 ) 0 0 0 4 6 - 5
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and the preparation of the first transition metal complexes of these tridentate nitrogen-donor ligands.
2. Results and discussion 2.1. Ligand syntheses The methyltris(pyrazolyl)silanes MeSi(3,5-Me2pz)3 and MeSi(3-Butpz)3 were readily prepared by reacting methyltrichlorosilane with 3 equiv. of Li(3,5-Me2pz) or Li(3Butpz) 1, as illustrated in Eq. (1). pentane
MeSiCl3q3Li(3,5-RR9pz) ™ MeSi(3,5-RR9pz)3
(1)
y3LiCl
RsR9sMe; RsBut, R9sH The pure ligands, free from lithium chloride, were isolated as white solids in almost quantitative yield (ca. 95%) and fully characterized 2,3. They are stable in dry air for several months but are stored for convenience under nitrogen in a glovebox. They are soluble in common organic solvents, including aliphatic and aromatic hydrocarbons, dichloromethane, ethers, THF and acetonitrile, but they slowly decompose in the presence of solvents having acidic protons such as alcohols and water, a significant difference with the related tris(pyrazolyl)methanes. 2.2. Crystallography Single crystals of MeSi(3-Butpz)3 suitable for an X-ray diffraction study were obtained by slow evaporation of a benzene solution (Fig. 1) 4. The structure consists of discrete molecules of the compound with no unusually short intermolecular contacts. The silicon atom is roughly in a tetrahedral environment, with average C–Si–N and N–Si–N angles of 1138 and 1058, respectively. Overall, the structure is similar to but slightly more distorted than that of MeSi(3,5-Me2pz)3 [12], arguably a reflection of the increased bulk of the groups around silicon. The three substituted pyrazolyl groups in both 1 The lithium pyrazolates Li(3,5-Me2pz) and Li(3-Butpz) were obtained as pure white solids by deprotonation of 3,5-dimethylpyrazole (Aldrich) or 3-tert-butylpyrazole (prepared as in Ref. [7]) with LiBun (2.5 M solution in hexanes, Aldrich). 2 Selected data for MeSi(3,5-Me2pz)3: m.p.: 120–1238C; 1H NMR data (in C6D6): d 1.56 [s, 9 H, (CH3)2pz], 1.62 (s, 3 H, CH3Si), 2.16 [s, 9 H, (CH3)2pz], 5.66 (s, 3 H, CH); Anal. Calc. for C16H24N6Si: C, 58.5; H, 7.4; N, 25.6. Found: C, 58.5; H, 7.4; N, 26.1%. 3 Selected data for MeSi(3-Butpz)3: m.p.: 118–1218C; 1H NMR data (in C6D6): d 1.27 (s, 3 H, CH3Si), 1.34 [s, 27 H, C(CH3)3], 6.09 (d, 3JH–Hs2 Hz, 3 H, H-4 in 3-Butpz), 7.38 (d, 3JH–Hs2 Hz, 3 H, H–5 in 3-Butpz); Anal. Calc. for C22H36N6Si: C, 64.0; H, 8.8; N, 20.4. Found: C, 63.3; H, 8.8; N, 20.2%. 4 Crystal data for C22H36N6Si (at 193 K): monoclinic, space group P21/c ˚ , bs (No. 14), as17.9785(2), bs11.5008(2), cs12.0532(2) A ˚ 3, Zs4. The structure was refined by full90.133(2)8, Vs2492.20(7) A matrix least-squares on F2 to give final indices R1s0.0606 and R2ws0.1508.
Tuesday Apr 27 10:37 AM
˚ ): Fig. 1. Molecular structure of MeSi(3-Butpz)3. Selected bond lengths (A Si(1)–N(3) 1.741(2), Si(1)–N(1) 1.747(2), Si(1)–N(5) 1.747(2), Si(1)–C(1) 1.825(3). Selected bond angles (8): N(3)–Si(1)–N(1) 105.19(10), N(3)–Si(1)–N(5) 104.98(10), N(1)–Si(1)–N(5) 105.46(10), N(3)–Si(1)–C(1) 112.95(12), N(1)–Si(1)–C(1) 113.54(11), N(5)–Si(1)–C(1) 113.87(11).
silanes are canted and display a propeller-like arrangement about the silicon center. However, the molecules of MeSi(3Butpz)3 approach, but do not attain, the local C3 symmetry with respect to the Si–C(1) axis observed in MeSi(3,5Me2pz)3. The Si–C bond distances in MeSi(3-Butpz)3 and ˚ , respectively) MeSi(3,5-Me2pz)3 (1.825(3) and 1.84(1) A are comparable, and so are the average Si–N bond lengths ˚ ) in both species. All the other interatomic dis(ca. 1.75 A tances also appear to be normal [13]. 2.3. Copper(I) complexes We have started a survey of the coordination chemistry of the new tripodal methyltris(pyrazolyl)silane ligands. For example, the cationic tetrahedral copper(I) complexes [{h3MeSi(3,5-Me2pz)3}Cu(NCMe)]q and [{h3-MeSi(3Butpz)3}Cu(NCMe)]q (Scheme 2) were readily obtained by reacting THF or dichloromethane solutions of [Cu(NCMe)4]PF6 [14] with the corresponding ligands and
Scheme 2. [{h3-MeSi(3,5-RR9pz)3}Cu(NCMe)]PF6 complexes.
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isolated as the white air- and moisture-sensitive hexafluorophosphate salts in 65–75% yield 5,6. Solution 1H NMR spectra (in CD3CN or CDCl3) show slightly broadened peaks (relative to the free silanes) and equivalent substituted pyrazolyl rings in each complex, data which are consistent with the presence of facially-coordinated tridentate ligands in both derivatives. The lability of the acetonitrile ligands was verified by dissolving the compounds in CD3CN, whereupon one equivalent of CH3CN (d 1.96 ppm) was liberated immediately, as determined by 1H NMR spectroscopy. While closely resembling their carbon-centered analogs [6] and also other mononuclear complexes [LCu(NCMe)]X bearing tridentate nitrogen-donor ligands [15– 19], the new copper(I) compounds described herein are the first transition metal derivatives to be isolated for the methyltris(pyrazolyl)silane ligand system. It is also noteworthy that although MeSi(3,5-Me2pz)3 decomposes in the presence of Cu(II) and forms the cationic complex [Cu{h3-HC(3,5Me2pz)2(NMe2)}2]2q [20], the silane ligands appear to withstand a variety of Cu(I) environments.
3. Conclusions
Selected data for [{h3-MeSi(3,5-Me2pz)3}Cu(NCMe)]PF6: 1H NMR data (in CD3CN): d 1.45 (s, 3 H, CH3Si), 1.96 (s, 3 H, free CH3CN), 2.21 [s, 9 H, (CH3)2pz], 2.27 [s, 9 H, (CH3)2pz], 6.05 (s, 3 H, CH); Anal. Calc. for C18H27CuF6N7PSi: C, 37.4; H, 4.7; N, 17.0. Found: C, 36.4; H, 4.6; N, 16.5%. 6 Selected data for [{h3-MeSi(3-Butpz)3}Cu(NCMe)]PF6: 1H NMR data (in CDCl3): d 1.37 [s, 27 H, C(CH3)3], 1.48 (s, 3 H, CH3Si), 2.15 (s, 3 H, CH3CN), 6.01 (br s, 3 H, H-4 in 3-Butpz), 7.75 (br s, 3 H, H-5 in 3Butpz); Anal. Calc. for C24H39CuF6N7PSi: C, 43.5; H, 5.9; N, 14.8. Found: C, 42.4; H, 5.5; N, 15.4%.
Tuesday Apr 27 10:37 AM
Tables of crystal data collection, atomic coordinates, bond lengths, bond angles, anisotropic displacement parameters, and hydrogen atom coordinates, and ORTEP drawings for MeSi(3-Butpz)3 (8 pages) are available from the authors on request. Acknowledgements We thank the Camille and Henry Dreyfus Foundation and its Faculty Start-Up Grant Program for Undergraduate Institutions, Research Corporation for a Cottrell College Science Award, the donors of the Petroleum Research Fund, administered by the ACS, and The University of North Carolina at Charlotte for support of this research. References [1] [2] [3] [4]
[5] [6]
In summary, the methyltris(pyrazolyl)silanes MeSi(3,5Me2pz)3 and MeSi(3-Butpz)3 are not only viable alternatives to the tris(pyrazolyl)methane ligands, but they can be prepared more easily, without the need of any purification steps (e.g., chromatography), at a lower cost, and in excellent yields. While continuing to explore the coordination chemistry of these ligands, we are also currently pursuing the preparation of the related bis(pyrazolyl)dimethylsilanes Me2Si(3,5-RR9pz)2. 5
4. Supplementary material
[7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20]
S. Trofimenko, J. Am. Chem. Soc. 88 (1966) 1842. S. Trofimenko, Chem. Rev. 93 (1993) 943. N. Kitajima, W.B. Tolman, Prog. Inorg. Chem. 43 (1995) 419. A. Shaver, in: G. Wilkinson, R.D. Gillard, J.A. McCleverty (Eds.), Comprehensive Coordination Chemistry, vol. 2, Pergamon Press, Oxford, UK, 1987, pp. 245–259. C. Titze, J. Hermann, H. Vahrenkamp, Chem. Ber. 128 (1995) 1095. D.L. Reger, J.E. Collins, A.L. Rheingold, L.M. Liable-Sands, Organometallics 15 (1996) 2029. S. Trofimenko, J.C. Calabrese, J.S. Thompson, Inorg. Chem. 26 (1987) 1507. G. Parkin, Adv. Inorg. Chem. 42 (1995) 291. D.L. Reger, J.E. Collins, D.L. Jameson, R.K. Castellano, Inorg. Synth. 32 (1998) 63. D.L. Jameson, R.K. Castellano, Inorg. Synth. 32 (1998) 51. S. Trofimenko, Chem. Rev. 72 (1972) 497. S. Vepachedu, R.T. Stibrany, S. Knapp, J.A. Potenza, H.J. Schugar, Acta Crystallogr. C51 (1995) 423. F.H. Allen, O. Kennard, D.G. Watson, L. Brammer, A.G. Orpen, R. Taylor, J. Chem. Soc., Perkin Trans. II (1987) S1. G.J. Kubas, Inorg. Synth. 28 (1990) 68. R.T. Jonas, T.D.P. Stack, Inorg. Chem. 37 (1998) 6615. L.M. Berreau, J.A. Halfen, V.G. Young Jr., W.B. Tolman, Inorg. Chem. 37 (1998) 1091. A.J. Canty, L.M. Engelhardt, P.C. Healy, J.D. Kildea, N.J. Minchin, A.H. White, Aust. J. Chem. 40 (1987) 1881. W.E. Lynch, D.M. Kurtz Jr., S. Wang, R.A. Scott, J. Am. Chem. Soc. 116 (1994) 11030. M.J. Scott, R.H. Holm, J. Am. Chem. Soc. 116 (1994) 11357. R.T. Stibrany, S. Knapp, J.A. Potenza, H.J. Schugar, Inorg. Chem. 38 (1999) 132.
StyleTag -- Journal: INOCHE (Inorganic Chemistry Communications)
Article: 184
Methyltris(pyrazolyl)silanes: new tripodal nitrogen-donor ligands Eric E. Pullen a, Arnold L. Rheingold b,*, Daniel Rabinovich a,* a
Department of Chemistry, The University of North Carolina at Charlotte, 9201 University City Boulevard, Charlotte, NC 28223, USA b Department of Chemistry and Biochemistry, The University of Delaware, Newark, DE 19716, USA Received 12 January 1999
Abstract Two tridentate nitrogen-donor ligands, the methyltris(pyrazolyl)silanes MeSi(3,5-RR9pz)3 (RsR9sMe; RsBut, R9sH), have been synthesized and the X-ray structure of the latter has been determined. The first transition metal derivatives of these ligands, the cationic copper(I) complexes [LCu(NCMe)]q (where LsMeSi(3,5-Me2pz)3 or MeSi(3-Butpz)3), have been prepared and characterized analytically and spectroscopically. q 1999 Elsevier Science S.A. All rights reserved. Keywords: Pyrazoles; Silanes; Crystal structures; Copper(I) complexes
1. Introduction The tris(pyrazolyl)hydroborates [HB(3,5-RR9pz)3]y (Scheme 1, A) are among the most popular ligands in coordination chemistry since their introduction over 30 years ago [1–3]. The chemistry of their neutral, carbon-centered analogs, the tris(pyrazolyl)methanes (Scheme 1, B), is considerably less developed, and deals mainly with the HC(pz)3 and HC(3,5-Me2pz)3 ligands [4]. Only recently have bulkier tris(pyrazolyl)methane ligands bearing alkyl (Pri, But) or aryl (Ph) substituents in the 3-position been developed [5,6]. These sterically-demanding ligands are attractive in view of the success of the corresponding tris(pyrazolyl)hydroborates as ‘tetrahedral enforcers’ [7,8]. However, ligands such as HC(3-Rpz)3 (RsBut, Ph) are typically isolated only in low to moderate yields (25–55%) after a relatively cumbersome work-up that includes several purification steps [9,10]. Given the enhanced nucleophilicity of the Si–Cl bonds in chlorosilanes (e.g., MeSiCl3) relative to that of the C–Cl bonds in the chloroalkanes (e.g., HCCl3) commonly used to prepare HC(3,5-RR9pz)3, we set out to develop the syntheses of alkyltris(pyrazolyl)silanes (Scheme 1, C) as alternative neutral analogs of the tris(pyrazolyl)hydroborates. In addition, we are interested in assessing the effect on the ligand’s flexibility (i.e., cone angles) of the larger silicon atoms in R0Si(3,5-RR9pz)3 compared to the carbon centers in * Corresponding authors. D. Rabinovich: Tel.: q1-704-547 4442; Fax: q1-704-547 3151; E-mail: [email protected]. A.L. Rheingold: E-mail: [email protected].
Scheme 1. Tris(pyrazolyl) ligands.
tris(pyrazolyl)alkanes. To our surprise, the only literature references to the silanes RnSi(pz)4yn appear to be the unpublished work of Klanberg (see footnote 177 in Ref. [11]) and the X-ray structure of the dimethylpyrazolyl derivative MeSi(3,5-Me2pz)3 [12]. We present herein our syntheses of MeSi(3,5-Me2pz)3 and the bulkier tert-butylpyrazolyl derivative MeSi(3-Butpz)3, their complete characterization,
1387-7003/99/$ - see front matter q 1999 Elsevier Science S.A. All rights reserved. PII S 1 3 8 7 - 7 0 0 3 ( 9 9 ) 0 0 0 4 6 - 5
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Article: 184
E.E. Pullen et al. / Inorganic Chemistry Communications 2 (1999) 194–196
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and the preparation of the first transition metal complexes of these tridentate nitrogen-donor ligands.
2. Results and discussion 2.1. Ligand syntheses The methyltris(pyrazolyl)silanes MeSi(3,5-Me2pz)3 and MeSi(3-Butpz)3 were readily prepared by reacting methyltrichlorosilane with 3 equiv. of Li(3,5-Me2pz) or Li(3Butpz) 1, as illustrated in Eq. (1). pentane
MeSiCl3q3Li(3,5-RR9pz) ™ MeSi(3,5-RR9pz)3
(1)
y3LiCl
RsR9sMe; RsBut, R9sH The pure ligands, free from lithium chloride, were isolated as white solids in almost quantitative yield (ca. 95%) and fully characterized 2,3. They are stable in dry air for several months but are stored for convenience under nitrogen in a glovebox. They are soluble in common organic solvents, including aliphatic and aromatic hydrocarbons, dichloromethane, ethers, THF and acetonitrile, but they slowly decompose in the presence of solvents having acidic protons such as alcohols and water, a significant difference with the related tris(pyrazolyl)methanes. 2.2. Crystallography Single crystals of MeSi(3-Butpz)3 suitable for an X-ray diffraction study were obtained by slow evaporation of a benzene solution (Fig. 1) 4. The structure consists of discrete molecules of the compound with no unusually short intermolecular contacts. The silicon atom is roughly in a tetrahedral environment, with average C–Si–N and N–Si–N angles of 1138 and 1058, respectively. Overall, the structure is similar to but slightly more distorted than that of MeSi(3,5-Me2pz)3 [12], arguably a reflection of the increased bulk of the groups around silicon. The three substituted pyrazolyl groups in both 1 The lithium pyrazolates Li(3,5-Me2pz) and Li(3-Butpz) were obtained as pure white solids by deprotonation of 3,5-dimethylpyrazole (Aldrich) or 3-tert-butylpyrazole (prepared as in Ref. [7]) with LiBun (2.5 M solution in hexanes, Aldrich). 2 Selected data for MeSi(3,5-Me2pz)3: m.p.: 120–1238C; 1H NMR data (in C6D6): d 1.56 [s, 9 H, (CH3)2pz], 1.62 (s, 3 H, CH3Si), 2.16 [s, 9 H, (CH3)2pz], 5.66 (s, 3 H, CH); Anal. Calc. for C16H24N6Si: C, 58.5; H, 7.4; N, 25.6. Found: C, 58.5; H, 7.4; N, 26.1%. 3 Selected data for MeSi(3-Butpz)3: m.p.: 118–1218C; 1H NMR data (in C6D6): d 1.27 (s, 3 H, CH3Si), 1.34 [s, 27 H, C(CH3)3], 6.09 (d, 3JH–Hs2 Hz, 3 H, H-4 in 3-Butpz), 7.38 (d, 3JH–Hs2 Hz, 3 H, H–5 in 3-Butpz); Anal. Calc. for C22H36N6Si: C, 64.0; H, 8.8; N, 20.4. Found: C, 63.3; H, 8.8; N, 20.2%. 4 Crystal data for C22H36N6Si (at 193 K): monoclinic, space group P21/c ˚ , bs (No. 14), as17.9785(2), bs11.5008(2), cs12.0532(2) A ˚ 3, Zs4. The structure was refined by full90.133(2)8, Vs2492.20(7) A matrix least-squares on F2 to give final indices R1s0.0606 and R2ws0.1508.
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˚ ): Fig. 1. Molecular structure of MeSi(3-Butpz)3. Selected bond lengths (A Si(1)–N(3) 1.741(2), Si(1)–N(1) 1.747(2), Si(1)–N(5) 1.747(2), Si(1)–C(1) 1.825(3). Selected bond angles (8): N(3)–Si(1)–N(1) 105.19(10), N(3)–Si(1)–N(5) 104.98(10), N(1)–Si(1)–N(5) 105.46(10), N(3)–Si(1)–C(1) 112.95(12), N(1)–Si(1)–C(1) 113.54(11), N(5)–Si(1)–C(1) 113.87(11).
silanes are canted and display a propeller-like arrangement about the silicon center. However, the molecules of MeSi(3Butpz)3 approach, but do not attain, the local C3 symmetry with respect to the Si–C(1) axis observed in MeSi(3,5Me2pz)3. The Si–C bond distances in MeSi(3-Butpz)3 and ˚ , respectively) MeSi(3,5-Me2pz)3 (1.825(3) and 1.84(1) A are comparable, and so are the average Si–N bond lengths ˚ ) in both species. All the other interatomic dis(ca. 1.75 A tances also appear to be normal [13]. 2.3. Copper(I) complexes We have started a survey of the coordination chemistry of the new tripodal methyltris(pyrazolyl)silane ligands. For example, the cationic tetrahedral copper(I) complexes [{h3MeSi(3,5-Me2pz)3}Cu(NCMe)]q and [{h3-MeSi(3Butpz)3}Cu(NCMe)]q (Scheme 2) were readily obtained by reacting THF or dichloromethane solutions of [Cu(NCMe)4]PF6 [14] with the corresponding ligands and
Scheme 2. [{h3-MeSi(3,5-RR9pz)3}Cu(NCMe)]PF6 complexes.
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Article: 184
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isolated as the white air- and moisture-sensitive hexafluorophosphate salts in 65–75% yield 5,6. Solution 1H NMR spectra (in CD3CN or CDCl3) show slightly broadened peaks (relative to the free silanes) and equivalent substituted pyrazolyl rings in each complex, data which are consistent with the presence of facially-coordinated tridentate ligands in both derivatives. The lability of the acetonitrile ligands was verified by dissolving the compounds in CD3CN, whereupon one equivalent of CH3CN (d 1.96 ppm) was liberated immediately, as determined by 1H NMR spectroscopy. While closely resembling their carbon-centered analogs [6] and also other mononuclear complexes [LCu(NCMe)]X bearing tridentate nitrogen-donor ligands [15– 19], the new copper(I) compounds described herein are the first transition metal derivatives to be isolated for the methyltris(pyrazolyl)silane ligand system. It is also noteworthy that although MeSi(3,5-Me2pz)3 decomposes in the presence of Cu(II) and forms the cationic complex [Cu{h3-HC(3,5Me2pz)2(NMe2)}2]2q [20], the silane ligands appear to withstand a variety of Cu(I) environments.
3. Conclusions
Selected data for [{h3-MeSi(3,5-Me2pz)3}Cu(NCMe)]PF6: 1H NMR data (in CD3CN): d 1.45 (s, 3 H, CH3Si), 1.96 (s, 3 H, free CH3CN), 2.21 [s, 9 H, (CH3)2pz], 2.27 [s, 9 H, (CH3)2pz], 6.05 (s, 3 H, CH); Anal. Calc. for C18H27CuF6N7PSi: C, 37.4; H, 4.7; N, 17.0. Found: C, 36.4; H, 4.6; N, 16.5%. 6 Selected data for [{h3-MeSi(3-Butpz)3}Cu(NCMe)]PF6: 1H NMR data (in CDCl3): d 1.37 [s, 27 H, C(CH3)3], 1.48 (s, 3 H, CH3Si), 2.15 (s, 3 H, CH3CN), 6.01 (br s, 3 H, H-4 in 3-Butpz), 7.75 (br s, 3 H, H-5 in 3Butpz); Anal. Calc. for C24H39CuF6N7PSi: C, 43.5; H, 5.9; N, 14.8. Found: C, 42.4; H, 5.5; N, 15.4%.
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Tables of crystal data collection, atomic coordinates, bond lengths, bond angles, anisotropic displacement parameters, and hydrogen atom coordinates, and ORTEP drawings for MeSi(3-Butpz)3 (8 pages) are available from the authors on request. Acknowledgements We thank the Camille and Henry Dreyfus Foundation and its Faculty Start-Up Grant Program for Undergraduate Institutions, Research Corporation for a Cottrell College Science Award, the donors of the Petroleum Research Fund, administered by the ACS, and The University of North Carolina at Charlotte for support of this research. References [1] [2] [3] [4]
[5] [6]
In summary, the methyltris(pyrazolyl)silanes MeSi(3,5Me2pz)3 and MeSi(3-Butpz)3 are not only viable alternatives to the tris(pyrazolyl)methane ligands, but they can be prepared more easily, without the need of any purification steps (e.g., chromatography), at a lower cost, and in excellent yields. While continuing to explore the coordination chemistry of these ligands, we are also currently pursuing the preparation of the related bis(pyrazolyl)dimethylsilanes Me2Si(3,5-RR9pz)2. 5
4. Supplementary material
[7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20]
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StyleTag -- Journal: INOCHE (Inorganic Chemistry Communications)
Article: 184