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Complexes containing the [TeCl4X]− moiety (X = Cl or an aryl group)
Inorganica Chimica Acta 362 (2009) 3982–3986
Contents lists available at ScienceDirect
Inorganica Chimica Acta journal homepage: www.elsevier.com/locate/ica
Complexes containing the [TeCl4X] moiety (X = Cl or an aryl group) Peter B. Hitchcock, Michael F. Lappert *, Gang Li Department of Chemistry and Biochemistry, University of Sussex, Brighton BN1 9QJ, UK
a r t i c l e
i n f o
Article history: Received 27 February 2009 Accepted 12 May 2009 Available online 18 May 2009 Keywords: Aryltellurium chlorides Chlorides b-Dialdiminium complex Tellurium Zwitterionic complexes
a b s t r a c t Treatment of TeCl either K[{N(C6H3Pri2-2,6)C(H)}2CPh] [K(L)] (1) in thf/Et2O or [H2(L)]Cl (2) in Et2O 4 with þ furnished [Cl4TeCl HðLÞH OEt2]0.5(Et2O) (3), whilst 2TeClþ4 with a mixture of single equivalent portions of 2,6-Pri2C6H3NH2 and H(L) produced [Cl4TeðC6 H2 Pri 2 -3; 5- N H3 -4ÞðthfÞ2 0:5ðthfÞ] (4). The X-ray structures of each of crystalline 3 and 4 show that the Te atom is at the centre of an only slightly distorted square pyramid, with a Cl atom of 3 or a C of 4 in the axial position. The N1 and N2 atoms of the p-delocalised b-dialdiminium moiety of 3 have H-bond contacts, involving short N1–H OEt2 and N2–H Cl5 distances. The two longer of the four þTe–Cl bonds of 4 are close to the N atom of the neighbouring molecule; whilst two of the H atoms of each NH3 fragment are H-bonded to the O atoms of the two thf ligands, the third being close to two Cl atoms of an adjacent molecule, thus forming H-bonded chains of molecules. Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction
2. Results and discussion
The b-dialdiminato ligand, shown in its monoanionic p-delocalised form as L, has featured in lithium [1], sodium [2], potassium [3], aluminium [1], gallium [1], indium (InII, InIII) [1], germanium(IV) [3], tin (SnII, SnIV) [3], arsenic (As0, AsI, AsII, AsIII) [4] and copper [5] compounds, and in a p-substituted phenyl derivative as a phosphorus(III) complex [6]. Chemistry involving the ligand L may be compared with that implicating the ubiquitous L0 , or a related ligand having alternative N- and N’-substituents. The latter, unlike L, is sometimes prone to yield a metal complex in which either deprotonation of a C(Me) methyl groups, or a prototropic shift has occurred as in the formation from Li(L0 ) and PCl(Ph)X of HN(C6H3Pri2-2,6)C(Me)C{P(X)Ph}C(Me)NC6H3Pri2-2,6 (X = Ph [7a], Cl [7b]).
The principal objective was to extend b-dialdiminato ligand chemistry to tellurium. In the event, a b-dialdiminatotellurium compound has thus far eluded us.
Alkali metal b-diketiminates, such as Li(L0 ), have been much used as ligand transfer reagents; thus their reactions with a halide of a wide range of elements have been explored. Such studies have only recently been extended to include a halide of a group 16 element, with the report by Richards and co-workers on the synthesis (Scheme 1) and X-ray characterisation of the selenium and tellurium compounds A and B [8]. * Corresponding author. Tel.: +44 1273 678316; fax: +44 1273 876687. E-mail address: [email protected] (M.F. Lappert). 0020-1693/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2009.05.037
2.1. Synthesis of compounds 1–4 The reactions leading to 1–4 are summarised in Scheme 2. The starting organic material was the b-dialdimine H(L) [5a,b], which was used (i) as the precursor to K(L) (1) [3] or [H2(L)]Cl (2), and (ii) as a competing agent with 2,6-Pri2C6H3NH2 for TeCl4. As for (i), both 1 and 2 with an equal portion of TeCl4 yielded the crystalline b-dialdiminium pentachlorotellurate diethyl etherate (3) in modest (from 1) or excellent (from 2) yield. Regarding (ii), equivalent portions of H(L) and 2,6-Pri2C6H3NH2 with two equivalents of TeCl4 furnished in low yield (based on one equivalent of TeCl4) the crystalline compound 4. It is evident that in the isolation of 3 from K(L) and TeCl4 two additional equivalents of HCl are implicated. Whilst the adventitious incursion of moisture, leading to partial hydrolysis of TeCl4, cannot be excluded, it is possible that the HCl arose from a side-reaction involving TeCl4 and thf, with as coproduct
Cl2TeOCH=CHCH2CH2or Cl2TeOCH2CH=CHCH2. It is noteworthy that with another popular bulky diimine ligand, a,a0 -diiminopyridine, TeCl4 formed a neutral rather than zwitterionic product, with CH activation and elimination of HCl [9]. The experiment leading to 4 was designed to test the relative nucleophilicity of 2,6-Pri2C6H3NH2 and H(L) with respect to their reaction with TeCl4; it is for this reason that the latter was used in large excess. The isolation of crystalline 4, despite its low yield, is
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Li(L') + ECl4 THF E = Se H
H C
Me
i
2,6-Pr 2C6H3
E = Te
N
C
C
N+
CH Se
Me i
C6H3Pr 2-2,6 2,6-Pri2C6H3
Cl
H
H C C
N
+
NH
CH2 Te
Cl
Cl Cl
Cl
C6H3Pri2-2,6
C
Cl
B
A Scheme 1.
Ph
Ph KH
Ar
Cl Cl
Te
N
Cl
H
H
N
THF
Ar [H( L)] [5a,b]
Ar
HCl Me2 CO
N K
Ar
1
Cl
Cl Cl
Te Cl
O [H2 (L)]Cl
TeCl4 Et2O
8
2, yellow, 81%
4, pale yellow, 23%,X-rayv
OEt2
Cl H
O
N
1.TeCl4 2. −THF, + Et2O THF
TeCl4 Et2O/THF
Cl
NH 2 H
NH
Ph
N
H
N Ar + 3, [Cl4 TeCl ... H(L)H ... OEt2], yellow, 94% from 2 44% from 1
Ar
Scheme 2. (Ar ¼ C6 H3 Pri2 -2,6).
Fig. 1. The molecular structure of crystalline 3 with atom labelling scheme.
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consistent with the substituted aniline being the more reactive. The reaction pathway may however, have implicated H(L), having proceeded via [2,6-Pri2C6H3NH3][L] as an intermediate. Somewhat similar to 4 is the X-ray-characterised crystalline complex [NH2Et2][TeCl4(C6H4OPh-4)] [10], prepared from equimolar portions of TeCl3(C6H4OPh-4) and Me3SiNEt2; a suggested precursor was TeCl2(C6H4OPh-4)NEt2 which with 2HCl (the source of which was not obvious) gave the final product [11]. 2.2. The molecular structures of complexes crystalline 3 and 4 The molecular structure of the crystalline complex 3 is illustrated in Fig. 1, and selected geometrical parameters are listed in Table 1. The tellurium atom Te1 is in a distorted square pyramidal environment, the quasi-planar Te1Cl2Cl3Cl4Cl5 moiety has the atoms Cl2/Cl4 and Cl3/Cl5 mutually transoid with Cl1 apical; this moiety resembles the TeCl4C fragment of B [8a]. The remaining bond angles subtended at the Te1 atom of 3 range from 87.1° to 94.1°. The b-dialdiminium chain has hydrogen-bond contacts (N1–H O1s and N2–H Cl5) to the ether ligand and the TeeCl5 unit, as shown by the relatively short N1 O1s and N2 Cl5 distances (2.854 and 3.245 Å). The Te1 atom has somewhat close association with the C5, C6, and C7 atoms (Te C contacts are 3.569, 3.217 and 3.555 Å, respectively) of the phenyl ring attached to C2. The short central C–C distances of 1.387(6) and 1.394(6) Å in B [8a] are similar to the C1–C2 and C2–C3 bond lengths of 3 and
Table 1 Selected bond lengths (Å) and angles (°) for 3. Te1–Cl1 Te1–Cl2 Te1–Cl3 Te1–Cl4 Te1–Cl5 C1–C2 Cl2–Te1–Cl4 Cl3–Te1–Cl5 N1–C1–C2 N1–C10–C11 C1–C2–C3
2.3159(13) 2.5234(12) 2.5075(13) 2.4445(16) 2.4729(13) 1.390(5) 174.57(7) 176.46(5) 127.3(3) 118.3(3) 115.2(3)
N1–C1 N2–C3 N1–C10 N2–C22 C2–C4 C2–C3 C1–C2–C4 C2–C3–N2 C3–N2–C22 C3–N2 Cl5 C22–N2 Cl5
1.318(5) 1.314(5) 1.445(5) 1.444(5) 1.491(5) 1.388(5) 122.0(3) 126.2(3) 123.6(3) 111.5 99.6
indicate that there is p-delocalisation over these three carbon atoms; however, the C1–N1 and C3–N2 bonds of 3 are significantly shorter than the (H)N–C(Me) bond length of 1.344(5) Å of B [8a], consistent with the notion that such delocalisation in 3 extends to the two nitrogen atoms. The molecular structure of crystalline 4 is shown in Figs. 2 and 3; selected values for bond lengths and angles are in Table 2. The tellurium atom Te1 is in an only slightly distorted square pyramidal environment, atoms Cl1/Cl3 and Cl2/Cl4 are mutually transoid and C4 is in the apical position. The longer of the four Te1–Cl bonds (Te1–Cl1, Te1–Cl4) have close contacts to N10 –H1c0 (x, y+2, z½) of the neighbouring molecule involving Cl1 H1c0 and Cl4 H1c0 hydrogen bonds at 2.86 and 2.60 Å, respectively (Fig. 3). Of the three hydrogen atoms of the NH3 group, two (H1a and H1b) are hydrogen-bonded to the O2s and O5s atoms of thf groups (O H contacts are 1.89 and 1.87 Å, respectively) and the third is hydrogen-bonded to two Cl atoms of an adjacent molecule, thus forming hydrogen-bonded chains of molecules. There are two independent molecules in the unit cell and hence two chains, but data for only one are provided in Table 2 (the data for the other are closely similar); the dihedral angle between the almost coplanar Cl1Cl2Cl3Cl4Te1 and Cl5Cl6Cl7Cl8Te2 moieties is 43.7(5)°. The structure of the C4Te1Cl1Cl2Cl3Cl4 fragment is very similar to that i (C H OPh-4) [10] and in [Te Cl in [NH2Et2][TeCl 4 6 4 4{CH2C(NHC6H3Pr2þ i 2,6)C(H)C(Me)N(H)C6H3Pr2-2,6}](B) [8] (Table 3). Two other crystalline organotellurium(IV) chlorides related to 4 have been structurally characterised. The crystalline polymeric chain compound [{(l-Cl)TeCl3(C6H4OEt-4)}n] was obtained from TeCl4 and Li(C6H4OEt-4) [12]. The compound C was prepared from TeCl4 and N-acetyldi(allyl)amine [13].
CH2
+N Me
CH2
Cl
CH O
Fig. 2. The molecular structure of crystalline 4 with atom labelling scheme.
C
_ C H2
Te Cl
Cl Cl
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Fig. 3. Intermolecular contacts in crystalline 4 (thf molecules are omitted for clarity).
Table 2 Selected bond lengths (Å) and angles (°) for 4. Te1–Cl1 Te1–Cl2 Te1–Cl3 Te1–Cl4 Te1–C4 N1–C1 N1 Cl100 N1 Cl400 N1 O2s N1 O5s
2.560(2) 2.466(2) 2.475(3) 2.579(2) 2.127(7) 1.480(9) 3.433 3.424 2.730 2.727
C1–C2 C2–C3 C3–C4 C4–C5 C5–C6 C1–C6 N2 Cl600 N2 Cl500 N2 O1s N2 O3s
1.411(10) 1.402(10) 1.369(11) 1.402(10) 1.380(10) 1.385(10) 3.263 3.551 2.780 2.771
Cl1–Te1–Cl2 Cl1–Te1–Cl3 Cl1–Te1–Cl4 Cl2–Te1–Cl3 Cl2–Te1–Cl4 Cl3–Te1–Cl4 Cl1–Te1–C4
90.77(9) 177.75(10) 87.80(8) 89.89(9) 172.91(8) 87.80(8) 87.80(8)
Cl2–Te1–C4 Cl3–Te1–C4 Cl4–Te1–C4 Te1–C4–C3 Te1–C4–C5 C2–C1–N1 C6–C1–N1
87.2(2) 89.6(2) 85.8(2) 120.4(5) 119.2(5) 117.2(6) 119.7(6)
Symmetry transformation to generate equivalent atoms: 00 x, y, z + ½.
Table 3 Crystal data and structure refinement for 3 and 4. Compound
3
4
Formula M Crystal system Space group a (Å) b (Å) c (Å) a (°) b (°) c (°) U (Å) Z Absorption coefficient (mm1) Unique reflections, Rint Reflections with I > 2r(I) Final R indices [I > 2r(I)] R1, wR2 R indices (all data) R1, wR2
C33H43Cl5N2Te1.5(C4H10O) 883.72 triclinic P1 (No. 2) 9.9754(2) 14.3075(4) 16.3474(4) 107.454(1) 97.500(1) 93.530(1) 2194.14(9) 2 1.01 8531, 0.0044 6872 0.052, 0.111 0.069, 0.121
C12H19Cl4NTe2.5(C4H8O) 626.94 monoclinic Cc (No. 9) 37.3892(7) 9.7013(2) 16.8731(4) 90 95.407(1) 90 6093.0(2) 8 1.35 11426, 0.057 10195 0.053, 0.152 0.061, 0.159
3. Experimental 3.1. General details The preparations of H(L), K(L) (1), [Cl4TeCl H(L)H OEt2] 0.5(Et2O) (3) and [Cl4Te(C6H2Pri2-3,5-NH3-4)(thf)2]0.5(thf) (4) was carried out under an atmosphere of argon or in a vacuum, using Schlenk apparatus and vacuum line techniques. The thf and diethyl ether were reagent grade and were dried using sodium/benzophe-
none and freeze/thaw degassed prior to use. The C4D8O for NMR spectroscopy was stored over molecular sieves (A4). Elemental analysis of 3 was provided by the University of North London. Melting points were taken in sealed capillaries. The 1H and 13C{1H} NMR spectra were recorded in C4D8O at ambient temperature using a Bruker DPX 300 instrument and were referenced to residual solvent resonances. The compounds TeCl4 and 2,6-Pri2C6H3NH2 were commercial samples, which were rigorously dried before use; dried TeCl4 was stored as a standard solution (0.05 M) in diethyl ether. The
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compound H[{N(C6H3Pri2-2,6)C(H)}2CPh] [H(L)] was prepared as described in the literature [5a]. 3.2. Preparation of K[{N(C6H3Pri2-2,6)C(H)}2CPh] (1) A solution of H(L) (5.00 g, 10.7 mmol) was added to a suspension of KH (0.5 g, 12.5 mmol) in thf (ca. 100 ml) at ca. 25 °C. The mixture was heated under reflux for 8 h, then cooled and filtered to remove unreacted KH. The concentration of K(L) in the ethereal filtrate was established by titrating an aliquot portion with 0.1 M aqueous HCl. 3.3. Preparation of [H2{N(C6H3Pri2-2,6)C(H)}2CPh]Cl (2) Concentrated (36%) aqueous hydrochloric acid (0.20 g, 1.87 mmol) in acetone (10 ml) was added to the b-dialdimine H(L) (0.80 g, 1.72 mmol) in acetone (30 ml) at ca. 20 °C. The solution was set aside for 20 min, whereafter volatiles were removed in vacuo, first at 25 °C and then at 70 °C. The bright yellow residual solid 2 (0.70 g, 81%) was used without further purification.
þ
3.4. Preparation of [Cl4TeCl H(L)H OEt2] (3) from 2 A solution of tellurium(IV) chloride (0.29 g, 1.07 mmol) in diethyl ether (20 ml) was added to [H2(L)]Cl (2) (0.54 g, 1.07 mmol) in Et2O (30 ml) at ca. 20 °C. After ca. 20 min, the formation of a yellow precipitate was observed. The mixture was set aside with stirring for 12 h, and then filtered. The pale yellow filtrate was concentrated in vacuo to ca. 20 ml, and then stored at 25 °C. After 3 d, yellow needles of 3 (0.89 g, 94%), which readily lost Et2O upon drying (Anal. calc. for C33H43Cl5N2Te: C, 51.3; H, 5.61; N, 3.63. Found: C, 51.9; H, 5.28; N, 3.40%), mp. 165 °C (decomp.), were collected. 1H NMR (C4D8O): d 1.26 [d, 3J(1H–1H) 6.95, 24 H, CHMe2], 3.12 [septet, 3J(1H–1H) 6.95, 4 H, CHMe2], 7.24–7.42 (m, 6 H, C6H3Pri2), 7.62 (t, 1 H, p-H of Ph), 7.70 (d, 2 H, o-H of Ph), 7.78 (t, 2 H, m-H of Ph), 8.03 (d, 3J(1H–1H) 15.3, 2 H, NCH), 9.68 ppm (d, 3 1 J( H–1H) 15.3 Hz, 2 H, NH); 13C{1H} NMR (C4D8O): d 23.8 (CHMe2), 29.4 (CHMe2), 111.4 (CPh), 124.7 (m-CH of C6H3Pri2), 129.7 (ipso-C of Ph), 130.3 (o-CH of Ph), 130.7 (p-CH of Ph), 131.6 (m-CH of Ph), 131.8 (p-CH of C6H3Pri2), 135.7 (ipso-C of C6H3Pri2), 146.1 (o-C of C6H3Pri2), 166.3 ppm (NCH). 3.5. Preparation of 3 from K(L) (1) A solution of tellurium(IV) chloride (0.80 g, 2.97 mmol) in tetrahydrofuran (30 ml) was added to K(L) (1) (1.50 g, 2.97 mmol) in thf (20 ml) at ca. 0 °C. The colour of the mixture changed from pale yellow to red–brown, and was set aside with stirring for 24 h at ca. 20 °C, and then filtered. The red–orange filtrate was concentrated in vacuo to ca. 15 mL, and then stored at 20 °C. After 4 d, yellow crystals of 3 (0.55 g, 44%) were separated and shown to be identical to those obtained according to Section 3.4.
þ
3.6. Preparation of [Cl4Te(C6H2Pri2-3,5-NH3-4)(thf)2]0.5(thf) (4) A solution of tellurium(IV) chloride (1.43 g, 5.30 mmol) in diethyl ether (20 ml) was added to a solution of H(L) (1.24 g, 2.65 mmol) and 2,6-Pri2C6H3NH2 (0.50 ml, 2.65 mmol). The colour
of the mixture changed from pale yellow to orange, and was set aside with stirring for 48 h at ca. 20 °C, and then filtered. The yellow precipitate was dissolved in thf (15 ml) and stored at 25 °C. After 5 d, pale yellow crystals of 4 (0.34 g, 23% based on 2,6-Pri2C6H3NH2) were separated and identified as 4 (mp. 142–144 °C) by an X-ray diffraction study. 3.7. X-ray crystallographic studies of 3 and 4 Diffraction data were collected on a Nonius Kappa CCD diffractometer using monochromated Mo Ka radiation, k 0.71073 Å at 173(2) K. Crystals were coated in oil and then directly mounted on the diffractometer under a stream of cold nitrogen gas. The structures were refined on all F2 using SHELXL-97 [14]; absorption corrections for 3 and 4 were applied using MULTISCAN. Drawings used ORTEP-3 for Windows. Acknowledgements We thank Drs. M.P. Coles and A.V. Protchenko for helpful advice and the Royal Society for the award of a Sino-British Fellowship to G.L. Appendix A. Supplementary material CCDC 721734 and 721735 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: [email protected]. Supplementary data associated with this article can be found, in the online version, at doi:10.1016/ j.ica.2009.05.037.
References [1] Y. Cheng, D.J. Doyle, P.B. Hitchcock, M.F. Lappert, Dalton Trans. (2006) 4449. [2] Y. Cheng, P.B. Hitchcock, M.F. Lappert, M. Zhou, Chem. Commun. (2005) 752. [3] D.J. Doyle, P.B. Hitchcock, M.F. Lappert, G. Li, J. Organomet. Chem., in press, doi:10.1016/j.jorganchem.2009.03.044. [4] P.B. Hitchcock, M.F. Lappert, G. Li, A.V. Protchenko, Chem. Commun. (2009) 428. [5] (a) D.J.E. Spencer, N.W. Aboelella, A.M. Reynolds, P.L. Holland, W.B. Tolman, J. Am. Chem. Soc. 124 (2002) 2108; (b) D.J.E. Spencer, A.M. Reynolds, P.L. Holland, B.A. Jazdzewski, C. Duboc-Toia, L. Le Pape, S. Yokota, Y. Tachi, S. Itoh, W.B. Tolman, Inorg. Chem. 41 (2002) 6307; (c) X.-W. Li, J.-Q. Ding, W.-Q. Jin, Y.-X. Cheng, Inorg. Chim. Acta 362 (2009) 233. [6] P.B. Hitchcock, M.F. Lappert, G. Li, A.V. Protchenko, Chem. Commun. (2007) 846. [7] (a) P.J. Ragogna, N. Burford, M. D’eon, R. McDonald, Chem. Commun. (2003) 1052; (b) P.B. Hitchcock, M.F. Lappert, J.E. Nycz, Chem. Commun. (2003) 1142. [8] (a) A.F. Gushwa, J.G. Karlin, R.A. Fleischer, A.F. Richards, J. Organomet. Chem. 691 (2006) 5069; (b) A.F. Gushwa, A.F. Richards, Eur. J. Inorg. Chem. (2008) 728. [9] G. Reeske, A.H. Cowley, Chem. Commun. (2006) 4856. [10] R.K. Chadha, J.E. Drake, M.R. Khan, Can. J. Chem. 62 (1984) 32. [11] J.M. Miller, R.K. Chadha, J. Organomet. Chem. 216 (1981) 177. [12] P.H. Bird, V. Kumar, B.C. Pant, Inorg. Chem. 19 (1980) 2487. [13] J. Bergman, J. Sidén, K. Maartmann-Moe, Tetrahedron 40 (1984) 1607. [14] G.M. Sheldrick, SHELXL-97, Program for Refinement of Crystal Structures, University of Göttingen, Germany, 1997.
Contents lists available at ScienceDirect
Inorganica Chimica Acta journal homepage: www.elsevier.com/locate/ica
Complexes containing the [TeCl4X] moiety (X = Cl or an aryl group) Peter B. Hitchcock, Michael F. Lappert *, Gang Li Department of Chemistry and Biochemistry, University of Sussex, Brighton BN1 9QJ, UK
a r t i c l e
i n f o
Article history: Received 27 February 2009 Accepted 12 May 2009 Available online 18 May 2009 Keywords: Aryltellurium chlorides Chlorides b-Dialdiminium complex Tellurium Zwitterionic complexes
a b s t r a c t Treatment of TeCl either K[{N(C6H3Pri2-2,6)C(H)}2CPh] [K(L)] (1) in thf/Et2O or [H2(L)]Cl (2) in Et2O 4 with þ furnished [Cl4TeCl HðLÞH OEt2]0.5(Et2O) (3), whilst 2TeClþ4 with a mixture of single equivalent portions of 2,6-Pri2C6H3NH2 and H(L) produced [Cl4TeðC6 H2 Pri 2 -3; 5- N H3 -4ÞðthfÞ2 0:5ðthfÞ] (4). The X-ray structures of each of crystalline 3 and 4 show that the Te atom is at the centre of an only slightly distorted square pyramid, with a Cl atom of 3 or a C of 4 in the axial position. The N1 and N2 atoms of the p-delocalised b-dialdiminium moiety of 3 have H-bond contacts, involving short N1–H OEt2 and N2–H Cl5 distances. The two longer of the four þTe–Cl bonds of 4 are close to the N atom of the neighbouring molecule; whilst two of the H atoms of each NH3 fragment are H-bonded to the O atoms of the two thf ligands, the third being close to two Cl atoms of an adjacent molecule, thus forming H-bonded chains of molecules. Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction
2. Results and discussion
The b-dialdiminato ligand, shown in its monoanionic p-delocalised form as L, has featured in lithium [1], sodium [2], potassium [3], aluminium [1], gallium [1], indium (InII, InIII) [1], germanium(IV) [3], tin (SnII, SnIV) [3], arsenic (As0, AsI, AsII, AsIII) [4] and copper [5] compounds, and in a p-substituted phenyl derivative as a phosphorus(III) complex [6]. Chemistry involving the ligand L may be compared with that implicating the ubiquitous L0 , or a related ligand having alternative N- and N’-substituents. The latter, unlike L, is sometimes prone to yield a metal complex in which either deprotonation of a C(Me) methyl groups, or a prototropic shift has occurred as in the formation from Li(L0 ) and PCl(Ph)X of HN(C6H3Pri2-2,6)C(Me)C{P(X)Ph}C(Me)NC6H3Pri2-2,6 (X = Ph [7a], Cl [7b]).
The principal objective was to extend b-dialdiminato ligand chemistry to tellurium. In the event, a b-dialdiminatotellurium compound has thus far eluded us.
Alkali metal b-diketiminates, such as Li(L0 ), have been much used as ligand transfer reagents; thus their reactions with a halide of a wide range of elements have been explored. Such studies have only recently been extended to include a halide of a group 16 element, with the report by Richards and co-workers on the synthesis (Scheme 1) and X-ray characterisation of the selenium and tellurium compounds A and B [8]. * Corresponding author. Tel.: +44 1273 678316; fax: +44 1273 876687. E-mail address: [email protected] (M.F. Lappert). 0020-1693/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2009.05.037
2.1. Synthesis of compounds 1–4 The reactions leading to 1–4 are summarised in Scheme 2. The starting organic material was the b-dialdimine H(L) [5a,b], which was used (i) as the precursor to K(L) (1) [3] or [H2(L)]Cl (2), and (ii) as a competing agent with 2,6-Pri2C6H3NH2 for TeCl4. As for (i), both 1 and 2 with an equal portion of TeCl4 yielded the crystalline b-dialdiminium pentachlorotellurate diethyl etherate (3) in modest (from 1) or excellent (from 2) yield. Regarding (ii), equivalent portions of H(L) and 2,6-Pri2C6H3NH2 with two equivalents of TeCl4 furnished in low yield (based on one equivalent of TeCl4) the crystalline compound 4. It is evident that in the isolation of 3 from K(L) and TeCl4 two additional equivalents of HCl are implicated. Whilst the adventitious incursion of moisture, leading to partial hydrolysis of TeCl4, cannot be excluded, it is possible that the HCl arose from a side-reaction involving TeCl4 and thf, with as coproduct
Cl2TeOCH=CHCH2CH2or Cl2TeOCH2CH=CHCH2. It is noteworthy that with another popular bulky diimine ligand, a,a0 -diiminopyridine, TeCl4 formed a neutral rather than zwitterionic product, with CH activation and elimination of HCl [9]. The experiment leading to 4 was designed to test the relative nucleophilicity of 2,6-Pri2C6H3NH2 and H(L) with respect to their reaction with TeCl4; it is for this reason that the latter was used in large excess. The isolation of crystalline 4, despite its low yield, is
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Li(L') + ECl4 THF E = Se H
H C
Me
i
2,6-Pr 2C6H3
E = Te
N
C
C
N+
CH Se
Me i
C6H3Pr 2-2,6 2,6-Pri2C6H3
Cl
H
H C C
N
+
NH
CH2 Te
Cl
Cl Cl
Cl
C6H3Pri2-2,6
C
Cl
B
A Scheme 1.
Ph
Ph KH
Ar
Cl Cl
Te
N
Cl
H
H
N
THF
Ar [H( L)] [5a,b]
Ar
HCl Me2 CO
N K
Ar
1
Cl
Cl Cl
Te Cl
O [H2 (L)]Cl
TeCl4 Et2O
8
2, yellow, 81%
4, pale yellow, 23%,X-rayv
OEt2
Cl H
O
N
1.TeCl4 2. −THF, + Et2O THF
TeCl4 Et2O/THF
Cl
NH 2 H
NH
Ph
N
H
N Ar + 3, [Cl4 TeCl ... H(L)H ... OEt2], yellow, 94% from 2 44% from 1
Ar
Scheme 2. (Ar ¼ C6 H3 Pri2 -2,6).
Fig. 1. The molecular structure of crystalline 3 with atom labelling scheme.
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consistent with the substituted aniline being the more reactive. The reaction pathway may however, have implicated H(L), having proceeded via [2,6-Pri2C6H3NH3][L] as an intermediate. Somewhat similar to 4 is the X-ray-characterised crystalline complex [NH2Et2][TeCl4(C6H4OPh-4)] [10], prepared from equimolar portions of TeCl3(C6H4OPh-4) and Me3SiNEt2; a suggested precursor was TeCl2(C6H4OPh-4)NEt2 which with 2HCl (the source of which was not obvious) gave the final product [11]. 2.2. The molecular structures of complexes crystalline 3 and 4 The molecular structure of the crystalline complex 3 is illustrated in Fig. 1, and selected geometrical parameters are listed in Table 1. The tellurium atom Te1 is in a distorted square pyramidal environment, the quasi-planar Te1Cl2Cl3Cl4Cl5 moiety has the atoms Cl2/Cl4 and Cl3/Cl5 mutually transoid with Cl1 apical; this moiety resembles the TeCl4C fragment of B [8a]. The remaining bond angles subtended at the Te1 atom of 3 range from 87.1° to 94.1°. The b-dialdiminium chain has hydrogen-bond contacts (N1–H O1s and N2–H Cl5) to the ether ligand and the TeeCl5 unit, as shown by the relatively short N1 O1s and N2 Cl5 distances (2.854 and 3.245 Å). The Te1 atom has somewhat close association with the C5, C6, and C7 atoms (Te C contacts are 3.569, 3.217 and 3.555 Å, respectively) of the phenyl ring attached to C2. The short central C–C distances of 1.387(6) and 1.394(6) Å in B [8a] are similar to the C1–C2 and C2–C3 bond lengths of 3 and
Table 1 Selected bond lengths (Å) and angles (°) for 3. Te1–Cl1 Te1–Cl2 Te1–Cl3 Te1–Cl4 Te1–Cl5 C1–C2 Cl2–Te1–Cl4 Cl3–Te1–Cl5 N1–C1–C2 N1–C10–C11 C1–C2–C3
2.3159(13) 2.5234(12) 2.5075(13) 2.4445(16) 2.4729(13) 1.390(5) 174.57(7) 176.46(5) 127.3(3) 118.3(3) 115.2(3)
N1–C1 N2–C3 N1–C10 N2–C22 C2–C4 C2–C3 C1–C2–C4 C2–C3–N2 C3–N2–C22 C3–N2 Cl5 C22–N2 Cl5
1.318(5) 1.314(5) 1.445(5) 1.444(5) 1.491(5) 1.388(5) 122.0(3) 126.2(3) 123.6(3) 111.5 99.6
indicate that there is p-delocalisation over these three carbon atoms; however, the C1–N1 and C3–N2 bonds of 3 are significantly shorter than the (H)N–C(Me) bond length of 1.344(5) Å of B [8a], consistent with the notion that such delocalisation in 3 extends to the two nitrogen atoms. The molecular structure of crystalline 4 is shown in Figs. 2 and 3; selected values for bond lengths and angles are in Table 2. The tellurium atom Te1 is in an only slightly distorted square pyramidal environment, atoms Cl1/Cl3 and Cl2/Cl4 are mutually transoid and C4 is in the apical position. The longer of the four Te1–Cl bonds (Te1–Cl1, Te1–Cl4) have close contacts to N10 –H1c0 (x, y+2, z½) of the neighbouring molecule involving Cl1 H1c0 and Cl4 H1c0 hydrogen bonds at 2.86 and 2.60 Å, respectively (Fig. 3). Of the three hydrogen atoms of the NH3 group, two (H1a and H1b) are hydrogen-bonded to the O2s and O5s atoms of thf groups (O H contacts are 1.89 and 1.87 Å, respectively) and the third is hydrogen-bonded to two Cl atoms of an adjacent molecule, thus forming hydrogen-bonded chains of molecules. There are two independent molecules in the unit cell and hence two chains, but data for only one are provided in Table 2 (the data for the other are closely similar); the dihedral angle between the almost coplanar Cl1Cl2Cl3Cl4Te1 and Cl5Cl6Cl7Cl8Te2 moieties is 43.7(5)°. The structure of the C4Te1Cl1Cl2Cl3Cl4 fragment is very similar to that i (C H OPh-4) [10] and in [Te Cl in [NH2Et2][TeCl 4 6 4 4{CH2C(NHC6H3Pr2þ i 2,6)C(H)C(Me)N(H)C6H3Pr2-2,6}](B) [8] (Table 3). Two other crystalline organotellurium(IV) chlorides related to 4 have been structurally characterised. The crystalline polymeric chain compound [{(l-Cl)TeCl3(C6H4OEt-4)}n] was obtained from TeCl4 and Li(C6H4OEt-4) [12]. The compound C was prepared from TeCl4 and N-acetyldi(allyl)amine [13].
CH2
+N Me
CH2
Cl
CH O
Fig. 2. The molecular structure of crystalline 4 with atom labelling scheme.
C
_ C H2
Te Cl
Cl Cl
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Fig. 3. Intermolecular contacts in crystalline 4 (thf molecules are omitted for clarity).
Table 2 Selected bond lengths (Å) and angles (°) for 4. Te1–Cl1 Te1–Cl2 Te1–Cl3 Te1–Cl4 Te1–C4 N1–C1 N1 Cl100 N1 Cl400 N1 O2s N1 O5s
2.560(2) 2.466(2) 2.475(3) 2.579(2) 2.127(7) 1.480(9) 3.433 3.424 2.730 2.727
C1–C2 C2–C3 C3–C4 C4–C5 C5–C6 C1–C6 N2 Cl600 N2 Cl500 N2 O1s N2 O3s
1.411(10) 1.402(10) 1.369(11) 1.402(10) 1.380(10) 1.385(10) 3.263 3.551 2.780 2.771
Cl1–Te1–Cl2 Cl1–Te1–Cl3 Cl1–Te1–Cl4 Cl2–Te1–Cl3 Cl2–Te1–Cl4 Cl3–Te1–Cl4 Cl1–Te1–C4
90.77(9) 177.75(10) 87.80(8) 89.89(9) 172.91(8) 87.80(8) 87.80(8)
Cl2–Te1–C4 Cl3–Te1–C4 Cl4–Te1–C4 Te1–C4–C3 Te1–C4–C5 C2–C1–N1 C6–C1–N1
87.2(2) 89.6(2) 85.8(2) 120.4(5) 119.2(5) 117.2(6) 119.7(6)
Symmetry transformation to generate equivalent atoms: 00 x, y, z + ½.
Table 3 Crystal data and structure refinement for 3 and 4. Compound
3
4
Formula M Crystal system Space group a (Å) b (Å) c (Å) a (°) b (°) c (°) U (Å) Z Absorption coefficient (mm1) Unique reflections, Rint Reflections with I > 2r(I) Final R indices [I > 2r(I)] R1, wR2 R indices (all data) R1, wR2
C33H43Cl5N2Te1.5(C4H10O) 883.72 triclinic P1 (No. 2) 9.9754(2) 14.3075(4) 16.3474(4) 107.454(1) 97.500(1) 93.530(1) 2194.14(9) 2 1.01 8531, 0.0044 6872 0.052, 0.111 0.069, 0.121
C12H19Cl4NTe2.5(C4H8O) 626.94 monoclinic Cc (No. 9) 37.3892(7) 9.7013(2) 16.8731(4) 90 95.407(1) 90 6093.0(2) 8 1.35 11426, 0.057 10195 0.053, 0.152 0.061, 0.159
3. Experimental 3.1. General details The preparations of H(L), K(L) (1), [Cl4TeCl H(L)H OEt2] 0.5(Et2O) (3) and [Cl4Te(C6H2Pri2-3,5-NH3-4)(thf)2]0.5(thf) (4) was carried out under an atmosphere of argon or in a vacuum, using Schlenk apparatus and vacuum line techniques. The thf and diethyl ether were reagent grade and were dried using sodium/benzophe-
none and freeze/thaw degassed prior to use. The C4D8O for NMR spectroscopy was stored over molecular sieves (A4). Elemental analysis of 3 was provided by the University of North London. Melting points were taken in sealed capillaries. The 1H and 13C{1H} NMR spectra were recorded in C4D8O at ambient temperature using a Bruker DPX 300 instrument and were referenced to residual solvent resonances. The compounds TeCl4 and 2,6-Pri2C6H3NH2 were commercial samples, which were rigorously dried before use; dried TeCl4 was stored as a standard solution (0.05 M) in diethyl ether. The
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compound H[{N(C6H3Pri2-2,6)C(H)}2CPh] [H(L)] was prepared as described in the literature [5a]. 3.2. Preparation of K[{N(C6H3Pri2-2,6)C(H)}2CPh] (1) A solution of H(L) (5.00 g, 10.7 mmol) was added to a suspension of KH (0.5 g, 12.5 mmol) in thf (ca. 100 ml) at ca. 25 °C. The mixture was heated under reflux for 8 h, then cooled and filtered to remove unreacted KH. The concentration of K(L) in the ethereal filtrate was established by titrating an aliquot portion with 0.1 M aqueous HCl. 3.3. Preparation of [H2{N(C6H3Pri2-2,6)C(H)}2CPh]Cl (2) Concentrated (36%) aqueous hydrochloric acid (0.20 g, 1.87 mmol) in acetone (10 ml) was added to the b-dialdimine H(L) (0.80 g, 1.72 mmol) in acetone (30 ml) at ca. 20 °C. The solution was set aside for 20 min, whereafter volatiles were removed in vacuo, first at 25 °C and then at 70 °C. The bright yellow residual solid 2 (0.70 g, 81%) was used without further purification.
þ
3.4. Preparation of [Cl4TeCl H(L)H OEt2] (3) from 2 A solution of tellurium(IV) chloride (0.29 g, 1.07 mmol) in diethyl ether (20 ml) was added to [H2(L)]Cl (2) (0.54 g, 1.07 mmol) in Et2O (30 ml) at ca. 20 °C. After ca. 20 min, the formation of a yellow precipitate was observed. The mixture was set aside with stirring for 12 h, and then filtered. The pale yellow filtrate was concentrated in vacuo to ca. 20 ml, and then stored at 25 °C. After 3 d, yellow needles of 3 (0.89 g, 94%), which readily lost Et2O upon drying (Anal. calc. for C33H43Cl5N2Te: C, 51.3; H, 5.61; N, 3.63. Found: C, 51.9; H, 5.28; N, 3.40%), mp. 165 °C (decomp.), were collected. 1H NMR (C4D8O): d 1.26 [d, 3J(1H–1H) 6.95, 24 H, CHMe2], 3.12 [septet, 3J(1H–1H) 6.95, 4 H, CHMe2], 7.24–7.42 (m, 6 H, C6H3Pri2), 7.62 (t, 1 H, p-H of Ph), 7.70 (d, 2 H, o-H of Ph), 7.78 (t, 2 H, m-H of Ph), 8.03 (d, 3J(1H–1H) 15.3, 2 H, NCH), 9.68 ppm (d, 3 1 J( H–1H) 15.3 Hz, 2 H, NH); 13C{1H} NMR (C4D8O): d 23.8 (CHMe2), 29.4 (CHMe2), 111.4 (CPh), 124.7 (m-CH of C6H3Pri2), 129.7 (ipso-C of Ph), 130.3 (o-CH of Ph), 130.7 (p-CH of Ph), 131.6 (m-CH of Ph), 131.8 (p-CH of C6H3Pri2), 135.7 (ipso-C of C6H3Pri2), 146.1 (o-C of C6H3Pri2), 166.3 ppm (NCH). 3.5. Preparation of 3 from K(L) (1) A solution of tellurium(IV) chloride (0.80 g, 2.97 mmol) in tetrahydrofuran (30 ml) was added to K(L) (1) (1.50 g, 2.97 mmol) in thf (20 ml) at ca. 0 °C. The colour of the mixture changed from pale yellow to red–brown, and was set aside with stirring for 24 h at ca. 20 °C, and then filtered. The red–orange filtrate was concentrated in vacuo to ca. 15 mL, and then stored at 20 °C. After 4 d, yellow crystals of 3 (0.55 g, 44%) were separated and shown to be identical to those obtained according to Section 3.4.
þ
3.6. Preparation of [Cl4Te(C6H2Pri2-3,5-NH3-4)(thf)2]0.5(thf) (4) A solution of tellurium(IV) chloride (1.43 g, 5.30 mmol) in diethyl ether (20 ml) was added to a solution of H(L) (1.24 g, 2.65 mmol) and 2,6-Pri2C6H3NH2 (0.50 ml, 2.65 mmol). The colour
of the mixture changed from pale yellow to orange, and was set aside with stirring for 48 h at ca. 20 °C, and then filtered. The yellow precipitate was dissolved in thf (15 ml) and stored at 25 °C. After 5 d, pale yellow crystals of 4 (0.34 g, 23% based on 2,6-Pri2C6H3NH2) were separated and identified as 4 (mp. 142–144 °C) by an X-ray diffraction study. 3.7. X-ray crystallographic studies of 3 and 4 Diffraction data were collected on a Nonius Kappa CCD diffractometer using monochromated Mo Ka radiation, k 0.71073 Å at 173(2) K. Crystals were coated in oil and then directly mounted on the diffractometer under a stream of cold nitrogen gas. The structures were refined on all F2 using SHELXL-97 [14]; absorption corrections for 3 and 4 were applied using MULTISCAN. Drawings used ORTEP-3 for Windows. Acknowledgements We thank Drs. M.P. Coles and A.V. Protchenko for helpful advice and the Royal Society for the award of a Sino-British Fellowship to G.L. Appendix A. Supplementary material CCDC 721734 and 721735 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: [email protected]. Supplementary data associated with this article can be found, in the online version, at doi:10.1016/ j.ica.2009.05.037.
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