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First example of a CLICK reaction of a coordinated 4′-azido-2,2′:6′,2″-terpyridine ligand
Inorganic Chemistry Communications 13 (2010) 495–497
Contents lists available at ScienceDirect
Inorganic Chemistry Communications journal homepage: www.elsevier.com/locate/inoche
First example of a CLICK reaction of a coordinated 40 -azido-2,20 :60 ,200 -terpyridine ligand Edwin C. Constable *, Catherine E. Housecroft *, Jason R. Price, Luca Schweighauser, Jennifer A. Zampese Department of Chemistry, University of Basel, Spitalstrasse 51, CH 4056 Basel, Switzerland
a r t i c l e
i n f o
Article history: Received 4 January 2010 Accepted 21 January 2010 Available online 28 January 2010
a b s t r a c t The first example of a copper-catalysed [2 + 3] cycloaddition reaction of a coordinated 40 -azido-2,20 :60 ,200 terpyridine ligand is reported and the solid state structures of the precursor and product are described. Ó 2010 Elsevier B.V. All rights reserved.
Keywords: 2,20 :60 ,200 -Terpyridine Azide Iron Structure CLICK reaction
The copper-catalysed 1,3-dipolar cycloaddition (CLICK) reaction, in which an organic azide reacts with an alkyne, is becoming one of the methods of choice for conjugating biofunctionality with other structures [1–3]. The reactions usually proceed in high yield under mild conditions and, in contrast to the uncatalysed 1,3-dipolar cycloaddition [4], with high regiospecificity (Scheme 1). Although a vast number of these reactions have been described [1], relatively few examples of CLICK reactions involving preformed metal complexes of azido- or alkyne-functionalized ligands have been reported [5–21]. To the best of our knowledge, no CLICK reactions involving metal complexes of azido-oligopyridines in which the azide is directly attached to a pyridine ring have been described in the literature. In this communication we report the first example of such a reaction and the structural and spectroscopic characterization of the product. The azido-ligand 40 -azido-2,20 :60 ,200 -terpyridine 1 was prepared using the literature method in which 40 -hydrazino-2,20 :60 ,200 -terpyridine is treated with HNO2 [22,23]. The free ligand 1 (Scheme 2) has been demonstrated to undergo CLICK reactions with a variety of alkynes and the reactivity is not significantly different from that of other organic azides [24]. Complex [Fe(1)2][PF6]2 [22] was prepared as a deep purple crystalline solid by the reaction of FeCl24H2O with 1 in EtOH followed by precipitation with NH4PF6 [25]. Crystals of [Fe(1)2][PF6]2 suitable for X-ray diffraction [26] were obtained from EtOH and the structure of the cation is presented in Fig. 1. The {Fe(tpy)2} coordination unit exhibits typical * Corresponding authors. Tel.: +41 61 267 1001; fax: +41 61 267 1018. E-mail addresses: [email protected] (E.C. Constable), catherine. [email protected] (C.E. Housecroft). 1387-7003/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.inoche.2010.01.019
metrical parameters, and important bond lengths and angles are presented in the caption of Fig. 1. The angle between the least squares planes through each azido substituent and the pyridine ring to which it is attached is 9° and 22°, respectively. The directly ring-bonded azide nitrogen atom is approximately sp2-hybridized with C–N–N angles of 116–117°. This is similar to the free ligand 1 [22] and to the only other 4-azidopyridines which have been structurally characterized [27,28]. The crystal packing of the tpy complex shows the expected embraces [29] and the principal packing forces are p-stacking interactions between the outer rings of the tpy units. In the offset face-to-face interactions, the inter-ring distance is 3.4 Å and the alignment leads to a two-dimensional grid of cations. The reaction of [Fe(1)2][PF6]2 with phenylethyne in the presence of copper(I) iodide and ascorbic acid was investigated. Initial experiments in aqueous acetonitrile showed only very low conversion to a new purple complex, but better conversions were obtained in DMF. The reaction was dependent on the amount of copper(I) present and much higher yields were obtained with 30 mol% CuI than with 5 mol%, in both cases in the presence of ascorbic acid. The purple product of the reaction was purified by chromatography and precipitated as the hexafluoridophosphate salt to give a deep purple crystalline material. The IR spectrum of the product exhibited no azide stretching frequency (observed at 2110 cm1 in [Fe(1)2][PF6]2). The 1H NMR spectrum of a CD3CN solution of the complex exhibited a singlet at d 9.35 ppm assigned to the triazole proton of ligand 2 [30]. Final confirmation that the product of the reaction was the anticipated [Fe(2)2][PF6]2 cycloaddition product came from a single crystal X-Ray structural determination of [Fe(2)2][PF6]22DMF [31].
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E.C. Constable et al. / Inorganic Chemistry Communications 13 (2010) 495–497
H N N
D
Cu(I)
N
N N N
N Scheme 1. The copper-catalysed 1,3-dipolar cycloaddition reaction.
A
The structure of the [Fe(2)2]2+ cation in [Fe(2)2][PF6]22DMF is presented in Fig. 2. The structural determination confirms the formation of the [2 + 3] cycloaddition product and the generation of the 1,2,3-triazole ring. The DMF molecules and the hexafluoridophosphate counterions are disordered. All metrical parameters within the {Fe(tpy)2} moiety of [Fe(2)2][PF6]22DMF are typical, and closely resemble corresponding bond lengths and angles in [Fe(1)2][PF6]2. The 4-phenyl-1,2,3-triazole substituents are essentially coplanar with the tpy ligand to which they are bonded.
N
N
N
N
C N
B
B
N
N
N
N 1
A
N
N 2
Scheme 2. Structures of ligands 1 and 2 with labelling for NMR spectroscopic assignments.
In conclusion, we have shown that it is possible to use metal complexes of azido-functionalized oligopyridines in [2 + 3] cycloaddition (CLICK) reactions. We are currently extending these
Fig. 1. Structure of the [Fe(1)2]2+ cation in [Fe(1)2][PF6]2 (ellipsoids drawn at 40% probability level); hydrogen atoms have been omitted for clarity. Selected bond parameters: Fe1–N8 1.8770(17), Fe1–N2 1.8833(18), Fe1–N3 1.9700(18), Fe1–N1 1.9749(19), Fe1–N9 1.9767(18), Fe1–N7 1.9785(17), N4–N5 1.239(3), N5–N6 1.123(3), N10–N11 1.204(3), N11–N12 1.135(3) Å; N8–Fe1–N2 178.48(8), N2–Fe1–N3 81.13(7), N2–Fe1–N1 81.19(7), N8–Fe1–N9 81.30(7), N8–Fe1–N7 81.01(7)°.
Fig. 2. Structure of the [Fe(2)2]2+ cation in [Fe(2)2][PF6]22DMF (ellipsoids drawn at 40% probability level); hydrogen atoms other than the triazole proton have been omitted for clarity. Selected bond parameters: Fe1–N2 1.875(2), Fe1–N1 1.981(2), Fe1–N3 1.983(2)°, N2–Fe1–N1 81.13(9), N2–Fe1–N3 80.84(9), N1–Fe1–N3 161.97(9), C16–N4–N5 110.7(2), C16–N4–C8 130.1(2), N5–N4–C8 119.2(2)°.
E.C. Constable et al. / Inorganic Chemistry Communications 13 (2010) 495–497
observations to the functionalization of biomolecules with luminescent metal complexes. Acknowledgements We thank the Swiss National Science Foundation and the University of Basel for financial support. Appendix A. Supplementary material CCDC 760098 and 760099 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.inoche.2010.01.019. References [1] F. Amblard, J.H. Cho, R.F. Schinazi, Chem. Rev. 109 (2009) 4207. [2] H.C. Kolb, M.G. Finn, K.B. Sharpless, Angew. Chem., Int. Ed. 40 (2001) 2004. [3] V.V. Rostovtsev, L.G. Green, V.V. Fokin, K.B. Sharpless, Angew. Chem., Int. Ed. 41 (2002) 2596. [4] R. Huisgen, in: A. Padwa (Ed.), 1,3-Dipolar Cycloadditional Chemistry, Wiley, New York, 1984. [5] D.G. Cabrera, B.D. Koivisto, D.A. Leigh, Chem. Commun. (2007) 4218. [6] J.P. Collin, J. Frey, V. Heitz, J.P. Sauvage, C. Tock, L. Allouche, J. Am. Chem. Soc. 131 (2009) 5609. [7] J.P. Collin, J.P. Sauvage, Y. Trolez, K. Rissanen, New J. Chem. 33 (2009) 2148. [8] S. Durot, P. Mobian, J.P. Collin, J.-P. Sauvage, Tetrahedron 64 (2008) 8496. [9] C. Haensch, M. Chiper, C. Ulbricht, A. Winter, S. Hoeppener, U.S. Schubert, Langmuir 24 (2008) 12981. [10] M. Jauregui, W.S. Perry, C. Allain, L.R. Vidler, M.C. Willis, A.M. Kenwright, J.S. Snaith, G.J. Stasiuk, M.P. Lowe, S. Faulkner, Dalton Trans. (2009) 6283. [11] S. Knor, A. Modlinger, T. Poethko, M. Schottelius, H.J. Wester, H. Kessler, Chem. Eur. J. 13 (2007) 6082. [12] J.D. Megiatto, D.I. Schuster, J. Am. Chem. Soc. 130 (2008) 12872. [13] J.D. Megiatto, D.I. Schuster, Chem. Eur. J. 15 (2009) 5444. [14] P. Mobian, J.P. Collin, J.-P. Sauvage, Tetrahedron Lett. 47 (2006) 4907. [15] A.I. Prikhod’ko, F. Durola, J.-P. Sauvage, J. Am. Chem. Soc. 130 (2008) 448. [16] A.I. Prikhod’ko, J.-P. Sauvage, J. Am. Chem. Soc. 131 (2009) 6794. [17] J.P. Collman, N.K. Devaraj, C.E.D. Chidsey, Langmuir 20 (2004) 1051. [18] S.I. Fukuzawa, H. Oki, M. Hosaka, J. Sugasawa, S. Kikuchi, Org. Lett. 9 (2007) 5557.
497
[19] A.R. McDonald, H.P. Dijkstra, B.M.J.M. Suijkerbuijk, G.P.M. van Klink, G. van Koten, Organometallics 28 (2009) 4689. [20] I. Aprahamian, O.S. Miljanic, W.R. Dichtel, K. Isoda, T. Yasuda, T. Kato, J.F. Stoddart, Bull. Chem. Soc. Jpn. 80 (2007) 1856. [21] E.C. Constable, C.E. Housecroft, M. Neuburger, P. Rösel, Chem. Commun. (2010), in press. [22] R.A. Fallahpour, M. Neuburger, M. Zehnder, Synthesis (1999) 1051. [23] G. Lowe, A.S. Droz, J.J. Park, G.W. Weaver, Bioorg. Chem. 27 (1999) 477. [24] A. Winter, A. Wild, R. Hoogenboom, M.W.M. Fijten, M.D. Hager, R.A. Fallahpour, U.S. Schubert, Synthesis (2009) 1506. [25] FeCl24H2O (0.17 g, 0.88 mmol) was added to 1 (0.40 g, 1.46 mmol) in EtOH (60 mL) and the resulting purple solution filtered through celite after which excess NH4PF6 was added to the filtrate. The resulting precipitate was filtered over celite, washed with EtOH, H2O and Et2O. The solid was dissolved in MeCN and the solvent removed under reduced pressure to give [Fe(1)2][PF6]2 (0.36 g, 55.2%). 1H NMR (500 MHz, CD3CN): d/ppm 8.57 (s, 4H, HB3), 8.48 (d, 4H, J = 8.0 Hz, HA3), 7.88 (td, 4H, J = 8.0, 1.6 Hz, HA4), 7.13 (d, 4H, J = 6.7, HA6), 7.09 (m, 8H, HA5). ESI-MS: m/z 748.6 [MPF6]+ (calc. 749.1). [26] C30H20F12FeN12P2, M = 894.37, red block, orthorhombic, space group Pcca, a = 25.971(5), b = 12.964(3), c = 19.605(4) Å, U = 6601(2) Å3, Z = 8, Dc = l(Mo-Ka) = 0.669 mm1, T = 173(2) K. Total 127,025 1.800 Mg m3, reflections, 7938 unique, Rint = 0.0598. Refinement of 7453 reflections (516 parameters) with I > 2r (I) converged at final R1 = 0.0462 (R1 all data = 0.0492), wR2 = 0.1090 (wR2 all data = 0.1108), gof = 1.090. [27] A. Escuer, F.A. Mautner, M.A.S. Goher, M.A.M. Abu-Youssef, R. Vicente, Chem. Commun. (2005) 605. [28] S. Natarajan, K. Rajesh, V. Vijayakumar, J. Suresh, P.L.N. Lakshman, Acta Crystallogr., Sect. E 65 (2009) o671. [29] M.L. Scudder, H.A. Goodwin, I.G. Dance, New J. Chem. 23 (1999) 695. [30] Phenylethyne (0.097 g, 0.95 mmol) in DMF (8 mL), CuI (0.011 g, 0.055 mmol), sodium ascorbate (0.011 g, 0.060 mmol) and [Fe(1)2][PF6]2 (0.10 g, 0.112 mmol) were stirred at room temperature overnight, after which the solvent was removed under reduced pressure and water added. The resulting precipitate was collected by filtration over celite and washed with H2O and Et2O. The residue was dissolved in MeCN and treated with excess NH4PF6 to give [Fe(2)2][PF6]2 (0.032 g, 26.0%). 1H NMR (500 MHz, CD3CN) d/ppm 9.46 (s, 4H, HB3), 9.35 (s, 2H, HC), 8.66 (d, 4H, J = 7.9 Hz, HA3), 8.14 (d, 4H, J = 7.5 Hz, HC2), 7.97 (t, 4H, J = .8 Hz, HA4), 7.64 (t, 4H, J = 7.6 Hz, HC3), 7.54 (t, 2H, J = 7.3 Hz, HC4), 7.27 (d, 4H, J = 5.5 Hz, HA6), 7.15 (m, 4H, HA5). ESI-MS: m/z 953.5 [MPF6]+ (calc. 953.2). Found C 48.76, H 3.27, N 14.55; C46H32F12FeN12P2.2H2O requires 48.69, H 3.20, N 14.81%. [31] C52H46F12FeN14O2P2, M = 1244.82, black block, monoclinic, space group C2/c, a = 22.111(3), b = 15.1510(11), c = 18.255(2) Å, b = 120.361(8)°, U= 5276.8(11) Å3, Z = 4, Dc = 1.567 Mg m3, l(Mo-Ka) = 0.447 mm1, T = 173(2) K. Total 44,616 reflections, 5663 unique, Rint = 0.0646. Refinement of 5250 reflections (462 parameters) with I > 2r (I) converged at final R1 = 0.0548 (R1 all data = 0.0590), wR2 = 0.1334 (wR2 all data = 0.1363), gof = 1.091.
Contents lists available at ScienceDirect
Inorganic Chemistry Communications journal homepage: www.elsevier.com/locate/inoche
First example of a CLICK reaction of a coordinated 40 -azido-2,20 :60 ,200 -terpyridine ligand Edwin C. Constable *, Catherine E. Housecroft *, Jason R. Price, Luca Schweighauser, Jennifer A. Zampese Department of Chemistry, University of Basel, Spitalstrasse 51, CH 4056 Basel, Switzerland
a r t i c l e
i n f o
Article history: Received 4 January 2010 Accepted 21 January 2010 Available online 28 January 2010
a b s t r a c t The first example of a copper-catalysed [2 + 3] cycloaddition reaction of a coordinated 40 -azido-2,20 :60 ,200 terpyridine ligand is reported and the solid state structures of the precursor and product are described. Ó 2010 Elsevier B.V. All rights reserved.
Keywords: 2,20 :60 ,200 -Terpyridine Azide Iron Structure CLICK reaction
The copper-catalysed 1,3-dipolar cycloaddition (CLICK) reaction, in which an organic azide reacts with an alkyne, is becoming one of the methods of choice for conjugating biofunctionality with other structures [1–3]. The reactions usually proceed in high yield under mild conditions and, in contrast to the uncatalysed 1,3-dipolar cycloaddition [4], with high regiospecificity (Scheme 1). Although a vast number of these reactions have been described [1], relatively few examples of CLICK reactions involving preformed metal complexes of azido- or alkyne-functionalized ligands have been reported [5–21]. To the best of our knowledge, no CLICK reactions involving metal complexes of azido-oligopyridines in which the azide is directly attached to a pyridine ring have been described in the literature. In this communication we report the first example of such a reaction and the structural and spectroscopic characterization of the product. The azido-ligand 40 -azido-2,20 :60 ,200 -terpyridine 1 was prepared using the literature method in which 40 -hydrazino-2,20 :60 ,200 -terpyridine is treated with HNO2 [22,23]. The free ligand 1 (Scheme 2) has been demonstrated to undergo CLICK reactions with a variety of alkynes and the reactivity is not significantly different from that of other organic azides [24]. Complex [Fe(1)2][PF6]2 [22] was prepared as a deep purple crystalline solid by the reaction of FeCl24H2O with 1 in EtOH followed by precipitation with NH4PF6 [25]. Crystals of [Fe(1)2][PF6]2 suitable for X-ray diffraction [26] were obtained from EtOH and the structure of the cation is presented in Fig. 1. The {Fe(tpy)2} coordination unit exhibits typical * Corresponding authors. Tel.: +41 61 267 1001; fax: +41 61 267 1018. E-mail addresses: [email protected] (E.C. Constable), catherine. [email protected] (C.E. Housecroft). 1387-7003/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.inoche.2010.01.019
metrical parameters, and important bond lengths and angles are presented in the caption of Fig. 1. The angle between the least squares planes through each azido substituent and the pyridine ring to which it is attached is 9° and 22°, respectively. The directly ring-bonded azide nitrogen atom is approximately sp2-hybridized with C–N–N angles of 116–117°. This is similar to the free ligand 1 [22] and to the only other 4-azidopyridines which have been structurally characterized [27,28]. The crystal packing of the tpy complex shows the expected embraces [29] and the principal packing forces are p-stacking interactions between the outer rings of the tpy units. In the offset face-to-face interactions, the inter-ring distance is 3.4 Å and the alignment leads to a two-dimensional grid of cations. The reaction of [Fe(1)2][PF6]2 with phenylethyne in the presence of copper(I) iodide and ascorbic acid was investigated. Initial experiments in aqueous acetonitrile showed only very low conversion to a new purple complex, but better conversions were obtained in DMF. The reaction was dependent on the amount of copper(I) present and much higher yields were obtained with 30 mol% CuI than with 5 mol%, in both cases in the presence of ascorbic acid. The purple product of the reaction was purified by chromatography and precipitated as the hexafluoridophosphate salt to give a deep purple crystalline material. The IR spectrum of the product exhibited no azide stretching frequency (observed at 2110 cm1 in [Fe(1)2][PF6]2). The 1H NMR spectrum of a CD3CN solution of the complex exhibited a singlet at d 9.35 ppm assigned to the triazole proton of ligand 2 [30]. Final confirmation that the product of the reaction was the anticipated [Fe(2)2][PF6]2 cycloaddition product came from a single crystal X-Ray structural determination of [Fe(2)2][PF6]22DMF [31].
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H N N
D
Cu(I)
N
N N N
N Scheme 1. The copper-catalysed 1,3-dipolar cycloaddition reaction.
A
The structure of the [Fe(2)2]2+ cation in [Fe(2)2][PF6]22DMF is presented in Fig. 2. The structural determination confirms the formation of the [2 + 3] cycloaddition product and the generation of the 1,2,3-triazole ring. The DMF molecules and the hexafluoridophosphate counterions are disordered. All metrical parameters within the {Fe(tpy)2} moiety of [Fe(2)2][PF6]22DMF are typical, and closely resemble corresponding bond lengths and angles in [Fe(1)2][PF6]2. The 4-phenyl-1,2,3-triazole substituents are essentially coplanar with the tpy ligand to which they are bonded.
N
N
N
N
C N
B
B
N
N
N
N 1
A
N
N 2
Scheme 2. Structures of ligands 1 and 2 with labelling for NMR spectroscopic assignments.
In conclusion, we have shown that it is possible to use metal complexes of azido-functionalized oligopyridines in [2 + 3] cycloaddition (CLICK) reactions. We are currently extending these
Fig. 1. Structure of the [Fe(1)2]2+ cation in [Fe(1)2][PF6]2 (ellipsoids drawn at 40% probability level); hydrogen atoms have been omitted for clarity. Selected bond parameters: Fe1–N8 1.8770(17), Fe1–N2 1.8833(18), Fe1–N3 1.9700(18), Fe1–N1 1.9749(19), Fe1–N9 1.9767(18), Fe1–N7 1.9785(17), N4–N5 1.239(3), N5–N6 1.123(3), N10–N11 1.204(3), N11–N12 1.135(3) Å; N8–Fe1–N2 178.48(8), N2–Fe1–N3 81.13(7), N2–Fe1–N1 81.19(7), N8–Fe1–N9 81.30(7), N8–Fe1–N7 81.01(7)°.
Fig. 2. Structure of the [Fe(2)2]2+ cation in [Fe(2)2][PF6]22DMF (ellipsoids drawn at 40% probability level); hydrogen atoms other than the triazole proton have been omitted for clarity. Selected bond parameters: Fe1–N2 1.875(2), Fe1–N1 1.981(2), Fe1–N3 1.983(2)°, N2–Fe1–N1 81.13(9), N2–Fe1–N3 80.84(9), N1–Fe1–N3 161.97(9), C16–N4–N5 110.7(2), C16–N4–C8 130.1(2), N5–N4–C8 119.2(2)°.
E.C. Constable et al. / Inorganic Chemistry Communications 13 (2010) 495–497
observations to the functionalization of biomolecules with luminescent metal complexes. Acknowledgements We thank the Swiss National Science Foundation and the University of Basel for financial support. Appendix A. Supplementary material CCDC 760098 and 760099 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.inoche.2010.01.019. References [1] F. Amblard, J.H. Cho, R.F. Schinazi, Chem. Rev. 109 (2009) 4207. [2] H.C. Kolb, M.G. Finn, K.B. Sharpless, Angew. Chem., Int. Ed. 40 (2001) 2004. [3] V.V. Rostovtsev, L.G. Green, V.V. Fokin, K.B. Sharpless, Angew. Chem., Int. Ed. 41 (2002) 2596. [4] R. Huisgen, in: A. Padwa (Ed.), 1,3-Dipolar Cycloadditional Chemistry, Wiley, New York, 1984. [5] D.G. Cabrera, B.D. Koivisto, D.A. Leigh, Chem. Commun. (2007) 4218. [6] J.P. Collin, J. Frey, V. Heitz, J.P. Sauvage, C. Tock, L. Allouche, J. Am. Chem. Soc. 131 (2009) 5609. [7] J.P. Collin, J.P. Sauvage, Y. Trolez, K. Rissanen, New J. Chem. 33 (2009) 2148. [8] S. Durot, P. Mobian, J.P. Collin, J.-P. Sauvage, Tetrahedron 64 (2008) 8496. [9] C. Haensch, M. Chiper, C. Ulbricht, A. Winter, S. Hoeppener, U.S. Schubert, Langmuir 24 (2008) 12981. [10] M. Jauregui, W.S. Perry, C. Allain, L.R. Vidler, M.C. Willis, A.M. Kenwright, J.S. Snaith, G.J. Stasiuk, M.P. Lowe, S. Faulkner, Dalton Trans. (2009) 6283. [11] S. Knor, A. Modlinger, T. Poethko, M. Schottelius, H.J. Wester, H. Kessler, Chem. Eur. J. 13 (2007) 6082. [12] J.D. Megiatto, D.I. Schuster, J. Am. Chem. Soc. 130 (2008) 12872. [13] J.D. Megiatto, D.I. Schuster, Chem. Eur. J. 15 (2009) 5444. [14] P. Mobian, J.P. Collin, J.-P. Sauvage, Tetrahedron Lett. 47 (2006) 4907. [15] A.I. Prikhod’ko, F. Durola, J.-P. Sauvage, J. Am. Chem. Soc. 130 (2008) 448. [16] A.I. Prikhod’ko, J.-P. Sauvage, J. Am. Chem. Soc. 131 (2009) 6794. [17] J.P. Collman, N.K. Devaraj, C.E.D. Chidsey, Langmuir 20 (2004) 1051. [18] S.I. Fukuzawa, H. Oki, M. Hosaka, J. Sugasawa, S. Kikuchi, Org. Lett. 9 (2007) 5557.
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[19] A.R. McDonald, H.P. Dijkstra, B.M.J.M. Suijkerbuijk, G.P.M. van Klink, G. van Koten, Organometallics 28 (2009) 4689. [20] I. Aprahamian, O.S. Miljanic, W.R. Dichtel, K. Isoda, T. Yasuda, T. Kato, J.F. Stoddart, Bull. Chem. Soc. Jpn. 80 (2007) 1856. [21] E.C. Constable, C.E. Housecroft, M. Neuburger, P. Rösel, Chem. Commun. (2010), in press. [22] R.A. Fallahpour, M. Neuburger, M. Zehnder, Synthesis (1999) 1051. [23] G. Lowe, A.S. Droz, J.J. Park, G.W. Weaver, Bioorg. Chem. 27 (1999) 477. [24] A. Winter, A. Wild, R. Hoogenboom, M.W.M. Fijten, M.D. Hager, R.A. Fallahpour, U.S. Schubert, Synthesis (2009) 1506. [25] FeCl24H2O (0.17 g, 0.88 mmol) was added to 1 (0.40 g, 1.46 mmol) in EtOH (60 mL) and the resulting purple solution filtered through celite after which excess NH4PF6 was added to the filtrate. The resulting precipitate was filtered over celite, washed with EtOH, H2O and Et2O. The solid was dissolved in MeCN and the solvent removed under reduced pressure to give [Fe(1)2][PF6]2 (0.36 g, 55.2%). 1H NMR (500 MHz, CD3CN): d/ppm 8.57 (s, 4H, HB3), 8.48 (d, 4H, J = 8.0 Hz, HA3), 7.88 (td, 4H, J = 8.0, 1.6 Hz, HA4), 7.13 (d, 4H, J = 6.7, HA6), 7.09 (m, 8H, HA5). ESI-MS: m/z 748.6 [MPF6]+ (calc. 749.1). [26] C30H20F12FeN12P2, M = 894.37, red block, orthorhombic, space group Pcca, a = 25.971(5), b = 12.964(3), c = 19.605(4) Å, U = 6601(2) Å3, Z = 8, Dc = l(Mo-Ka) = 0.669 mm1, T = 173(2) K. Total 127,025 1.800 Mg m3, reflections, 7938 unique, Rint = 0.0598. Refinement of 7453 reflections (516 parameters) with I > 2r (I) converged at final R1 = 0.0462 (R1 all data = 0.0492), wR2 = 0.1090 (wR2 all data = 0.1108), gof = 1.090. [27] A. Escuer, F.A. Mautner, M.A.S. Goher, M.A.M. Abu-Youssef, R. Vicente, Chem. Commun. (2005) 605. [28] S. Natarajan, K. Rajesh, V. Vijayakumar, J. Suresh, P.L.N. Lakshman, Acta Crystallogr., Sect. E 65 (2009) o671. [29] M.L. Scudder, H.A. Goodwin, I.G. Dance, New J. Chem. 23 (1999) 695. [30] Phenylethyne (0.097 g, 0.95 mmol) in DMF (8 mL), CuI (0.011 g, 0.055 mmol), sodium ascorbate (0.011 g, 0.060 mmol) and [Fe(1)2][PF6]2 (0.10 g, 0.112 mmol) were stirred at room temperature overnight, after which the solvent was removed under reduced pressure and water added. The resulting precipitate was collected by filtration over celite and washed with H2O and Et2O. The residue was dissolved in MeCN and treated with excess NH4PF6 to give [Fe(2)2][PF6]2 (0.032 g, 26.0%). 1H NMR (500 MHz, CD3CN) d/ppm 9.46 (s, 4H, HB3), 9.35 (s, 2H, HC), 8.66 (d, 4H, J = 7.9 Hz, HA3), 8.14 (d, 4H, J = 7.5 Hz, HC2), 7.97 (t, 4H, J = .8 Hz, HA4), 7.64 (t, 4H, J = 7.6 Hz, HC3), 7.54 (t, 2H, J = 7.3 Hz, HC4), 7.27 (d, 4H, J = 5.5 Hz, HA6), 7.15 (m, 4H, HA5). ESI-MS: m/z 953.5 [MPF6]+ (calc. 953.2). Found C 48.76, H 3.27, N 14.55; C46H32F12FeN12P2.2H2O requires 48.69, H 3.20, N 14.81%. [31] C52H46F12FeN14O2P2, M = 1244.82, black block, monoclinic, space group C2/c, a = 22.111(3), b = 15.1510(11), c = 18.255(2) Å, b = 120.361(8)°, U= 5276.8(11) Å3, Z = 4, Dc = 1.567 Mg m3, l(Mo-Ka) = 0.447 mm1, T = 173(2) K. Total 44,616 reflections, 5663 unique, Rint = 0.0646. Refinement of 5250 reflections (462 parameters) with I > 2r (I) converged at final R1 = 0.0548 (R1 all data = 0.0590), wR2 = 0.1334 (wR2 all data = 0.1363), gof = 1.091.