The document attached has been archived with permission from the publisher.Spiro[3,3]heptane-2,6-dispiro-4,5-diazafluorene (4) has been synthesized in three steps from 1,10-phenanthroline. It crystallizes in the orthorhombic space group P212121 and has the two 4,5-diazafluorene metal binding domains mutually orthogonal.Peter J. Steel and Christopher J. Sumb

Steel, P.

Sumby, C.

Adelaide Research &amp; Scholarship

Issue in Honor of Prof. Rodney Rickards ARKIVOC 2004 (x) 7-12 ISSN 1424-6376 Page 7 ©ARKAT USA, Inc Synthesis and X-ray crystal structure of a bridging trispiran ligand  Peter J. Steel* and Christopher J. Sumby  Department of Chemistry, University of Canterbury, Private Bag 4800,  Christchurch, New Zealand E-mail: peter.steel@canterbury.ac.nz  Dedicated to Rod Rickards with admiration, affection and a Chupa Chup (received 19 Jan 04; accepted 18 Mar 04; published on the web 24 Mar 04)  Abstract Spiro[3,3]heptane-2,6-dispiro-4,5-diazafluorene (4) has been synthesized in three steps from 1,10-phenanthroline. It crystallizes in the orthorhombic space group P212121 and has the two  4,5-diazafluorene metal binding domains mutually orthogonal.  Keywords: Trispiran, diazafluorene, N-ligand, crystal structure    Introduction  Nitrogen-containing heterocyclic ligands are commonly used as bridges between metal centres and serve to facilitate communication between metals, such as energy or electron transfer or magnetic interactions.1,2 The magnitude of such interactions depends upon the distance between the metals, the extent of conjugation between the donor sites and the electronic properties of the heterocycles. In some cases surprisingly strong metal-metal interactions take place.3 Such ligands have found numerous applications in applied areas such as multi-electron catalysis, information storage, solar energy conversion, and artificial photosynthesis. Ligands that contain two 2,2’-bipyridine (bpy) subunits coordinate to metal atoms with the formation of stable five-membered chelate rings and have been extensively used in coordination chemistry.4 Recently we described the synthesis and complexes of assorted ligands that contain di-2-pyridylmethane units linked by saturated and unsaturated bridges.5-8  We now describe the synthesis and X-ray crystal structure of the novel trispiro ligand 4, which was designed to provide a ligand containing two mutually orthogonal bpy units separated by a rigid, saturated spacer group.     Issue in Honor of Prof. Rodney Rickards ARKIVOC 2004 (x) 7-12 ISSN 1424-6376 Page 8 ©ARKAT USA, Inc Results and Discussion  The synthetic procedure used to prepare 4 is shown in Scheme 1 and was based on the recently reported synthesis of the corresponding carbocyclic analogue.9 4,5-Diazafluorenone (1), prepared by oxidation of 1,10- phenanthroline,10 was subjected to Wolff-Kishner reduction according to a literature procedure.11 In our hands this resulted not only in the formation of the desired 4,5-diazafluorene (2) (36% yield) but also in the dimeric by-product 9,9’-bi-4,5-diazafluorene (3) (26% yield). This latter compound is itself a bridging ligand and useful precursor to the corresponding unsaturated 9,9’-bi-4,5-diazafluorenylidene.12 Conversion of 2 to its potassium salt and treatment with pentaerythrityl tetrabromide furnished the trispiran 4, albeit in somewhat disappointing yield (18%). This new compound was characterized by mass spectrometry and 1H and 13C NMR. However, subsequent attempts to prepare complexes of 4 failed to provide any stable metal complexes. We became concerned about the identity of this compound and therefore carried out a single crystal X-ray structure determination, in order to establish unambiguously the structure.  NNNNHHN NNNO+NNNN(1) (2)(3)(4)NH2NH2.H2OBr BrBrBrK  Scheme 1. Synthesis of the title ligand 4. Issue in Honor of Prof. Rodney Rickards ARKIVOC 2004 (x) 7-12 ISSN 1424-6376 Page 9 ©ARKAT USA, Inc Crystals of 4, suitable for X-ray crystallography, were obtained by recrystallisation from a mixture of dichloromethane and diethyl ether. The compound crystallizes in the chiral, orthorhombic space group P212121 with four molecules in the unit cell. The structure is confirmed as being the desired trispiran (Figure 1). Each spiro centre introduces an orthogonal orientation between the meanplanes of adjacent rings [90.8° at C(1), 90.6° at C(19) and 89.1° at C(39)] As a result the two 4,5-diazafluorene subunits are approximately orthogonal, but are still ideally placed to chelate to two metal atoms. Unlike the corresponding carbocyclic analogue,9 which has crystallographically imposed S4 symmetry, the cyclobutane rings are slightly puckered, which introduces a small curvature to the ligand in the solid state. The strain within the structure is apparent in the large deviations of the bond angles about C(1) from the tetrahedral value (Figure 1). A consideration of the packing reveals that molecules of 4 pack in a herringbone arrangement, with edge-to-face π-π interactions between adjacent molecules.    Figure 1. A perspective view of 4 shows the orthogonal arrangement of the two 4,5-diazafluorenyl ring systems. Selected bond lengths (Å) and angles (°): C(1)-C(2) 1.545(2), C(1)-C(5) 1.549(2), C(1)-C(4) 1.550(2), C(1)-C(3) 1.554(2), C(2)-C(19) 1.567(2), C(3)-C(19) 1.571(2), C(4)-C(39) 1.571(2), C(5)-C(39) 1.571(2), C(2)-C(1)-C(5) 121.26(14), C(2)-C(1)-C(4) 122.07(14), C(5)-C(1)-C(4) 88.66(11), C(2)-C(1)-C(3) 88.91(11), C(5)-C(1)-C(3) 119.39(14), C(4)-C(1)-C(3) 120.03(14), C(2)-C(19)-C(3) 87.53(11), C(5)-C(39)-C(4) 87.13(11).  Issue in Honor of Prof. Rodney Rickards ARKIVOC 2004 (x) 7-12 ISSN 1424-6376 Page 10 ©ARKAT USA, Inc Experimental Section  General Procedures. NMR spectra were recorded on a Varian 300 MHz NMR spectrometer. Melting points were performed on an Electrothermal melting point apparatus and are uncorrected.   Spiro[3,3]heptane-2,6-dispiro-4,5-diazafluorene (4). To a suspension of potassium metal (160 mg, 4.09 mmol) in THF (10 mL), under argon, was added compound 4,5-diazafluorene (2) (350 mg, 2.08 mmol), dissolved in THF (15 mL). This gave a purple solution that was stirred for one hour. Pentaerythrityl tetrabromide (205 mg, 0.53 mmol) was then added in THF (15 mL) and the solution refluxed overnight. After cooling, the solvent was removed in vacuo and water (20 mL) was added. The reaction mixture was extracted with dichloromethane (3 x 50 mL), the extracts dried over magnesium sulfate and the solvent removed in vacuo. The residue was dissolved in dichloromethane, run through a silica gel plug to give a purple solid, from which a significant amount of insoluble material was removed by subsequent elution through an alumina plug. Recrystallisation from dichloromethane-ether gave 4 as colourless crystals. Yield 38 mg (18%). M.p. 165-166°C. HRMS: calc. for C27H20N4 400.1688, found 400.1693. 1H NMR (CDCl3 + 3 drops CD3CN) δ 8.69 (d, 4H, H3’), 8.00 (d, 4H, H1’), 7.37 (dd, 4H, H2’), 3.11 (s, 8H, CH2). 13C NMR (CDCl3 + 3 drops CD3CN) δ 156.7, 149.2, 145.6, 130.4, 123.2, 44.57, 42.18, 31.00.  X-Ray crystallography. Data were collected with a Siemens SMART CCD area detector, using graphite monochromatized MoKα radiation (λ = 0.71073 Å). The intensities were corrected for Lorentz and polarization effects and for absorption.13 The structure was solved by direct methods using SHELXS14 and refined on F2, using all data, by full-matrix least-squares procedures using SHELXTL.15 All non-hydrogen atoms were refined with anisotropic displacement parameters. Hydrogen atoms were included in calculated positions, with isotropic displacement parameters 1.2 times the isotropic equivalent of their carrier carbons. Table 1 lists the final atomic coordinates. Complete crystallographic data, as a CIF file, have been deposited with the Cambridge Crystallographic Data Centre (CCDC No 228156). Copies can be obtained free of charge from: The Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, U.K. (e-mail: deposit@ccdc.cam.ac.uk). Crystal data for 4. C27H20N4, MW 400.47, orthorhombic, P212121, a = 10.232(4), b = 10.284(3), c = 19.020(7) Å, V = 2001.5(12) Å 3, Z = 4, T = -105°C, F(000) = 840, µ (MoKα) = 0.080 mm-1, Dcalcd = 1.329 g.cm-3, 2θmax 53° (CCD area detector, 99.7% completeness), wR(F2) =  0.0722 (all 4072 data), R = 0.0347 (2931 data with I > 2σI). Issue in Honor of Prof. Rodney Rickards ARKIVOC 2004 (x) 7-12 ISSN 1424-6376 Page 11 ©ARKAT USA, Inc Table 1. Atomic coordinates  ( x 104) and equivalent  isotropic displacement parameters (Å2x 103) for 1. U(eq) is defined as one third of  the trace of the orthogonalized Uij tensor   x y z U(eq) C(1) 5069(2) 6977(2) -1246(1) 36(1) C(2) 5351(2) 6056(2) -1870(1) 41(1) C(3) 4588(2) 8019(2) -1779(1) 41(1) C(4) 4183(2) 6569(2) -623(1) 39(1) C(5) 6148(2) 7336(2) -709(1) 38(1) C(11) 7383(2) 8085(2) -2637(1) 42(1) C(12) 8206(2) 8570(2) -3153(1) 49(1) C(13) 7793(2) 8602(2) -3845(1) 50(1) N(14) 6625(1) 8163(1) -4070(1) 42(1) N(15) 3872(1) 7014(1) -4255(1) 43(1) C(16) 2681(2) 6454(2) -4183(1) 48(1) C(17) 2131(2) 6125(2) -3550(1) 51(1) C(18) 2798(2) 6344(2) -2928(1) 47(1) C(19) 5035(2) 7154(2) -2416(1) 35(1) C(20) 6164(2) 7669(2) -2842(1) 33(1) C(21) 5845(2) 7709(2) -3563(1) 33(1) C(22) 4516(2) 7177(2) -3650(1) 34(1) C(23) 4041(2) 6863(2) -2978(1) 34(1) C(31) 4243(2) 9607(2) -75(1) 40(1) C(32) 3817(2) 10594(2) 361(1) 47(1) C(33) 3826(2) 10409(2) 1079(1) 47(1) N(34) 4270(2) 9344(1) 1405(1) 44(1) N(35) 5512(1) 6739(2) 1832(1) 44(1) C(36) 6058(2) 5560(2) 1864(1) 48(1) C(37) 6336(2) 4790(2) 1291(1) 50(1) C(38) 6045(2) 5232(2) 615(1) 43(1) C(39) 5147(2) 7224(2) -86(1) 32(1) C(40) 4676(2) 8481(2) 233(1) 33(1) C(41) 4704(2) 8413(2) 974(1) 36(1) C(42) 5275(2) 7159(2) 1176(1) 36(1) C(43) 5523(2) 6454(2) 556(1) 34(1) Issue in Honor of Prof. Rodney Rickards ARKIVOC 2004 (x) 7-12 ISSN 1424-6376 Page 12 ©ARKAT USA, Inc Acknowledgements  We thank the Royal Society of New Zealand Marsden Fund for generous financial support, and Bruce Clark for the mass spectrometry measurements.   References  1. Steel, P. J. Coord. Chem. Rev. 1990, 106, 227, and references therein. 2. Balzani, V.; Juris, A.; Venturi, M.; Campagna, S.; Serroni, S. Chem. Rev. 1996, 96, 759. 3. Richardson, C.; Steel, P. J.; D’Alessandro, D. M.; Junk, P. C.; Keene, F. R. J. Chem. Soc., Dalton Trans. 2002, 2775, and references therein. 4. Kaes, C.; Katz, A.; Hosseini, M. W. Chem. Rev. 2000, 100, 3553. 5. Steel, P. J.; Sumby, C. J. Chem. Commun. 2002, 5, 322. 6. Steel, P. J.; Sumby, C. J. Inorg. Chem. Commun. 2002, 5, 323. 7. D'Alessandro, D. M.; Keene, F. R.; Steel, P. J.; Sumby, C. J. Aust. J. Chem. 2003, 56, 657. 8. Steel, P. J.; Sumby, C. J. J. Chem. Soc., Dalton Trans. 2003, 4505. 9. Moll, O. P. Y.; Le Borgne, T.; Thuery, P.; Ephritikhine, M. Tetrahedron Lett. 2001, 42, 3855. 10. Eckhard, I. F.; Summers, L. A. Aust. J. Chem. 1973, 26, 2727. 11. Henderson, L. J.; Fronczek, F. R.; Cherry, W. R. J. Am. Chem. Soc. 1984, 106, 5876. 12. Riklin, M.; von Zelewsky, A. Helv. Chim. Acta 1996, 79, 2176. 13. Sheldrick, G. M.  SADABS, University of Göttingen, Germany, 1998. 14. Sheldrick, G. M. Acta Crystallogr. Sect. A 1990, 46, 467. 15. Sheldrick, G. M.  SHELXTL; Bruker Analytical X-ray Systems, 1997.  

Synthesis and X-ray crystal structure of a bridging trispiran ligand

Spiro[3,3]heptane-2,6-dispiro-4,5-diazafluorene (4) has been synthesized in three steps
from 1,10-phenanthroline. It crystallizes in the orthorhombic space group P2₁2₁2₁ and has
the two 4,5-diazafluorene metal binding domains mutually orthogonal

Steel, P.J.

Sumby, C.J.

UC Research Repository

Synthesis and X-ray crystal structure of a  bridging trispiran ligand  Peter J. Steel* and Christopher J. Sumby  Department of Chemistry, University of Canterbury, Private Bag 4800, Christchurch, New Zealand Email: peter.steel@canterbury.ac.nz  Dedicated to Rod Rickards with admiration, affection and a Chupa Chup   Abstract Spiro[3,3]heptane-2,6-dispiro-4,5-diazafluorene (4) has been synthesized in three steps from 1,10-phenanthroline. It crystallizes in the orthorhombic space group P212121 and has the two 4,5-diazafluorene metal binding domains mutually orthogonal.  Keywords: Trispiran, diazafluorene, N-ligand, crystal structure.    Introduction  Nitrogen-containing heterocyclic ligands are commonly used as bridges between metal centres and serve to facilitate communication between metals, such as energy or electron transfer or magnetic interactions.1,2 The magnitude of such interactions depends upon the distance between the metals, the extent of conjugation between the donor sites and the electronic properties of the heterocycles. In some cases surprisingly strong metal-metal interactions take place.3 Such ligands have found numerous applications in applied areas such as multi-electron catalysis, information storage, solar energy conversion, and artificial photosynthesis. Ligands that contain two 2,2’-bipyridine (bpy) subunits coordinate to metal atoms with the formation of stable five-membered chelate rings and have been extensively used in coordination chemistry.4 Recently we described the synthesis and complexes of assorted ligands that contain di-2-pyridylmethane units linked by saturated and unsaturated bridges.5-8  We now describe the synthesis and X-ray crystal structure of the novel trispiro ligand 4, which was designed to provide a ligand containing two mutually orthogonal bpy units separated by a rigid, saturated spacer group.    Results and Discussion  The synthetic procedure used to prepare 4 is shown in Scheme 1 and was based on the recently reported synthesis of the corresponding carbocyclic analogue.9 4,5-Diazafluorenone (1), prepared by oxidation of 1,10- phenanthroline,10 was subjected to Wolff-Kishner reduction according to a literature procedure.11 In our hands this resulted not only in the formation of the desired 4,5-diazafluorene (2) (36% yield) but also in the dimeric by-product 9,9’-bi-4,5-diazafluorene (3) (26% yield). This latter compound is itself a bridging ligand and useful precursor to the corresponding unsaturated 9,9’-bi-4,5-diazafluorenylidene.12 Conversion of 2 to its potassium salt and treatment with pentaerythrityl tetrabromide furnished the trispiran 4, albeit in somewhat disappointing yield (18%). This new compound was characterized by mass spectrometry and 1H and 13C NMR. However, subsequent attempts to prepare complexes of 4 failed to provide any stable metal complexes. We became concerned about the identity of this compound and therefore carried out a single crystal X-ray structure determination, in order to establish unambiguously the structure.   NNNNHHN NNNO+NNNN(1) (2)(3)(4)NH2NH2.H2OBr BrBrBrK  Scheme 1. Synthesis of the title ligand 4. Crystals of 4, suitable for X-ray crystallography, were obtained by recrystallisation from a mixture of dichloromethane and diethyl ether. The compound crystallizes in the chiral, orthorhombic space group P212121 with four molecules in the unit cell. The structure is confirmed as being the desired trispiran (Figure 1). Each spiro centre introduces an orthogonal orientation between the meanplanes of adjacent rings [90.8o at C(1), 90.6o at C(19) and 89.1o at C(39)] As a result the two 4,5-diazafluorene subunits are approximately orthogonal, but are still ideally placed to chelate to two metal atoms. Unlike the corresponding carbocyclic analogue,9 which has crystallographically imposed S4 symmetry, the cyclobutane rings are slightly puckered, which introduces a small curvature to the ligand in the solid state. The strain within the structure is apparent in the large deviations of the bond angles about C(1) from the tetrahedral value (Figure 1). A consideration of the packing reveals that molecules of 4 pack in a herringbone arrangement, with edge-to-face π-π interactions between adjacent molecules.   Figure 1. A perspective view of 4 shows the orthogonal arrangement of the two 4,5-diazafluorenyl ring systems. Selected bond lengths (Å) and angles (º): C(1)-C(2) 1.545(2), C(1)-C(5) 1.549(2), C(1)-C(4) 1.550(2), C(1)-C(3) 1.554(2), C(2)-C(19) 1.567(2), C(3)-C(19) 1.571(2), C(4)-C(39) 1.571(2), C(5)-C(39) 1.571(2), C(2)-C(1)-C(5) 121.26(14), C(2)-C(1)-C(4) 122.07(14), C(5)-C(1)-C(4) 88.66(11), C(2)-C(1)-C(3) 88.91(11), C(5)-C(1)-C(3) 119.39(14), C(4)-C(1)-C(3) 120.03(14), C(2)-C(19)-C(3) 87.53(11), C(5)-C(39)-C(4) 87.13(11).     Experimental Section  General Procedures. NMR spectra were recorded on a Varian 300 MHz NMR spectrometer. Melting points were performed on an Electrothermal melting point apparatus and are uncorrected. Elemental analyses were performed by the Campbell microanalytical laboratory at the University of Otago.  Spiro[3,3]heptane-2,6-dispiro-4,5-diazafluorene (4). To a suspension of potassium metal (160 mg, 4.09 mmol) in THF (10 mL), under argon, was added compound 4,5-diazafluorene (2) (350 mg, 2.08 mmol), dissolved in THF (15 mL). This gave a purple solution that was stirred for one hour. Pentaerythrityl tetrabromide (205 mg,  0.53 mmol) was then added in THF (15 mL) and the solution refluxed overnight. After cooling, the solvent was removed in vacuo and water (20 mL) was added. The reaction mixture was extracted with dichloromethane (3 x 50 mL), the extracts dried over magnesium sulfate and the solvent removed in vacuo. The residue was dissolved in dichloromethane, run through a silica gel plug to give a purple solid, from which a significant amount of insoluble material was removed by subsequent elution through an alumina plug. Recrystallisation from dichloromethane-ether gave 4 as colourless crystals. Yield 38 mg (18%). M.p. 165-166°C. HRMS: calc. for C27H20N4 400.1688, found 400.1693. 1H NMR (CDCl3 + 3 drops CD3CN) δ 8.69 (d, 4H, H3’), 8.00 (d, 4H, H1’), 7.37 (dd, 4H, H2’), 3.11 (s, 8H, CH2). 13C NMR (CDCl3 + 3 drops CD3CN) δ 156.7, 149.2, 145.6, 130.4, 123.2, 44.57, 42.18, 31.00.  X-Ray Crystallography. Data were collected with a Siemens SMART CCD area detector, using graphite monochromatized MoKα radiation (λ = 0.71073 Å). The intensities were corrected for Lorentz and polarization effects and for absorption.13 The structure was solved by direct methods using SHELXS14 and refined on F2, using all data, by full-matrix least-squares procedures using SHELXTL.15 All non-hydrogen atoms were refined with anisotropic displacement parameters. Hydrogen atoms were included in calculated positions, with isotropic displacement parameters 1.2 times the isotropic equivalent of their carrier carbons. Table 1 lists the final atomic coordinates. Complete crystallographic data, as a CIF file, have been deposited with the Cambridge Crystallographic Data Centre (CCDC No 228156). Copies can be obtained free of charge from: The Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, U.K. (e-mail: deposit@ccdc.cam.ac.uk). Crystal data for 4: C27H20N4, MW 400.47, orthorhombic, P212121, a = 10.232(4), b = 10.284(3), c = 19.020(7) Å, V = 2001.5(12) Å 3, Z = 4, T = -105oC, F(000) = 840, μ (MoKα) = 0.080 mm-1, Dcalcd = 1.329 g.cm-3, 2θmax 53o (CCD area detector, 99.7% completeness), wR(F2) =  0.0722 (all 4072 data), R = 0.0347 (2931 data with I > 2σI).  Table 1.  Atomic coordinates  ( x 104) and equivalent  isotropic displacement parameters (Å2x 103) for 1. U(eq) is defined as one third of  the trace of the orthogonalized Uij tensor. ______________________________________________________________   x y z U(eq) C(1) 5069(2) 6977(2) -1246(1) 36(1) C(2) 5351(2) 6056(2) -1870(1) 41(1) C(3) 4588(2) 8019(2) -1779(1) 41(1) C(4) 4183(2) 6569(2) -623(1) 39(1) C(5) 6148(2) 7336(2) -709(1) 38(1) C(11) 7383(2) 8085(2) -2637(1) 42(1) C(12) 8206(2) 8570(2) -3153(1) 49(1) C(13) 7793(2) 8602(2) -3845(1) 50(1) N(14) 6625(1) 8163(1) -4070(1) 42(1) N(15) 3872(1) 7014(1) -4255(1) 43(1) C(16) 2681(2) 6454(2) -4183(1) 48(1) C(17) 2131(2) 6125(2) -3550(1) 51(1) C(18) 2798(2) 6344(2) -2928(1) 47(1) C(19) 5035(2) 7154(2) -2416(1) 35(1) C(20) 6164(2) 7669(2) -2842(1) 33(1) C(21) 5845(2) 7709(2) -3563(1) 33(1) C(22) 4516(2) 7177(2) -3650(1) 34(1) C(23) 4041(2) 6863(2) -2978(1) 34(1) C(31) 4243(2) 9607(2) -75(1) 40(1) C(32) 3817(2) 10594(2) 361(1) 47(1) C(33) 3826(2) 10409(2) 1079(1) 47(1) N(34) 4270(2) 9344(1) 1405(1) 44(1) N(35) 5512(1) 6739(2) 1832(1) 44(1) C(36) 6058(2) 5560(2) 1864(1) 48(1) C(37) 6336(2) 4790(2) 1291(1) 50(1) C(38) 6045(2) 5232(2) 615(1) 43(1) C(39) 5147(2) 7224(2) -86(1) 32(1) C(40) 4676(2) 8481(2) 233(1) 33(1) C(41) 4704(2) 8413(2) 974(1) 36(1) C(42) 5275(2) 7159(2) 1176(1) 36(1) C(43) 5523(2) 6454(2) 556(1) 34(1)  Acknowledgements  We thank the Royal Society of New Zealand Marsden Fund for generous financial support, and Bruce Clark for the mass spectrometry measurements.   References  1. Steel, P. J. Coord. Chem. Rev. 1990, 106, 227, and references therein. 2. Balzani, V.; Juris, A.; Venturi, M.; Campagna, S.; Serroni, S. Chem. Rev. 1996, 96, 759. 3. Richardson, C.; Steel, P. J.; D’Alessandro, D. M.; Junk, P. C.; Keene, F. R. J. Chem. Soc., Dalton Trans. 2002, 2775, and references therein. 4. Kaes, C.; Katz, A.; Hosseini, M. W. Chem. Rev. 2000, 100, 3553. 5. Steel, P. J.; Sumby, C. J. Chem. Commun. 2002, 5, 322. 6. Steel, P. J.; Sumby, C. J. Inorg. Chem. Commun. 2002, 5, 323. 7. D'Alessandro, D. M.; Keene, F. R.; Steel, P. J.; Sumby, C. J. Aust. J. Chem. 2003, 56, 657. 8. Steel, P. J.; Sumby, C. J. Dalton Trans. 2003, 4505. 9. Moll, O. P. Y.; Le Borgne, T.; Thuery, P.; Ephritikhine, M. Tetrahedron Lett. 2001, 42, 3855. 10. Eckhard, I. F.; Summers, L. A. Aust. J. Chem. 1973, 26, 2727. 11. Henderson, L. J.; Fronczek, F. R.; Cherry, W. R. J. Am. Chem. Soc. 1984, 106, 5876. 12. Riklin, M.; von Zelewsky, A. Helv. Chim. Acta 1996, 79, 2176. 13. Sheldrick, G. M.  SADABS, University of Göttingen, Germany, 1998. 14. Sheldrick, G. M. Acta Crystallogr. Sect. A 1990, 46, 467. 15. Sheldrick, G. M.  SHELXTL; Bruker Analytical X-ray Systems, 1997.  Graphical Abstract  Synthesis and crystal structure of a bridging trispiran ligand  Peter J. Steel* and Christopher J. Sumby              NNNN

Synthesis and X-ray Crystal Structure of a Bridging Trispiran Ligand

Peter J. Steel

Christopher J. Sumby

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Synthesis and X-ray crystal structure of a bridging trispiran ligand

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Synthesis and X-ray crystal structure of a bridging trispiran ligand

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