ChemComm View Article Online
Published on 30 January 2014. Downloaded by University of Pittsburgh on 28/10/2014 01:57:19.
COMMUNICATION
Cite this: Chem. Commun., 2014, 50, 2922
View Journal | View Issue
Synthesis, structure and reactivity of group 4 corrole complexes† Rosa Padilla, Heather L. Buckley, Ashleigh L. Ward and John Arnold*
Received 2nd January 2014, Accepted 30th January 2014 DOI: 10.1039/c4cc00037d www.rsc.org/chemcomm
A series of early transition metal corrole complexes has been prepared via salt metathesis with the corresponding lithium corrole. Their characterization by single crystal X-ray diffraction, NMR, and absorption spectroscopy is described. Organometallic derivatives of the titanium complex were obtained via treatment of 2 with NaCp* or ClMgCH2SiMe3.
Metal complexes of tetrapyrrolic macrocycles have been intensively studied since the 1960’s1,2 to gain better insight into the mechanism of several enzymatic reactions, and to develop possible applications for a variety of fields, such as medicine, biology, energy conversion, and catalysis.3–10 While the ‘‘periodic table’’ of corrole metal complexes is not as rich as that of porphyrins, the diversity of metallocorrole complexes is constantly increasing.6 Recently, there has been renewed interest in the synthesis of early transition metal corrole complexes due to their scarcity in the literature in comparison with the analogous low-valent metalloporphyrin halide complexes.11,12 The chemistry of early metal corrole complexes has thus far been limited to oxo-derivatives featuring Ti, V,4 Cr,13–15 Mo,16,17 and W.18 These complexes reflect the oxophilic nature of the early transition metals. Synthesis of the corrole halide complexes of Fe and Mn has been achieved under acidic conditions. However, this methodology is unsuitable for early transition metal chemistry.19,20 Recently, the preparation of a lithium corrole metathesis reagent has allowed for the efficient synthesis of a range of new early transition metal, lanthanide, and actinide corrole complexes.21–23 Furthering this research, we have been interested in exploring titanium, zirconium and hafnium corrole chloride complexes due to the potential they have to exhibit rich organometallic chemistry similar to their porphyrin analogues. Department of Chemistry, University of California, Berkeley, California, 94720, USA. E-mail: [email protected]; Tel: +1 510 643 5181 † Electronic supplementary information (ESI) available: Experimental procedures, analytical data, NMR data, crystal data, CIF files for 2, 4, 5, and 6. CCDC 979184–979187. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4cc00037d
2922 | Chem. Commun., 2014, 50, 2922--2924
Treatment of [(Mes2(p-OMePh)corrole)Li3THF6]21 (1) with [TiCl4THF2] in toluene at 25 1C for 4 h provided the titanium(IV) corrole chloride complex [(Mes2( p-OMePh)corrole)TiCl] (2). After crystallization from a mixture of dichloromethane and hexanes, the product was isolated as dark brown crystals in 79% yield (Scheme 1). As with all the complexes described here, 2 is hydrolytically sensitive and must be handled with the exclusion of air and moisture. The complex was characterized
Scheme 1
Synthesis of Ti(IV), Zr(IV) and Hf(IV) complexes.
This journal is © The Royal Society of Chemistry 2014
View Article Online
Published on 30 January 2014. Downloaded by University of Pittsburgh on 28/10/2014 01:57:19.
Communication
by X-ray crystallography, ESI-MS, UV-visible spectroscopy, and 1 H NMR spectroscopy. To the best of our knowledge, this compound is the first metal halide corrole complex synthesized under mild conditions. The structure is in agreement with previously reported group 4 corroles, as well as the group 4 porphyrin dichlorides, which are all monomeric in the solidstate.11,21 The X-ray crystallographic data and collection parameters are summarized in Table S1 (ESI†). The crystal structure of 2 is shown in Fig. 1. The central titanium atom has a distorted square pyramidal geometry with a chloride bound in the apical position. The metal atom is displaced towards the chloride by 0.667 Å from the mean N4 plane of the corrole ligand, which is shorter than for other reported group 4 corrole complexes (Zr–N4 0.914 Å, Ti–N4 0.820 Å).21 The Ti–Cl distance (2.220(6) Å) is comparable to that of the azaoxa macrocycle Ti–Cl complex (2.293(7) Å).24 All the Ti–N bond lengths (1.985(2)–1.996(2) Å) are shorter than the corresponding values for [(Mes2( p-OMePh)corrole)TiCp*] (2.049(3) Å)21 and may be a result of the shape and geometry of the corrole moiety and also the relative orientation of the aryl substituents with respect to the corrole ring. The UVvisible spectrum of 2 displays a Q band (lmax = 550 nm) and a Soret band that is split into two peaks (lmax = 418, 405 nm). This is similar to the values reported for the titanium corrole [(Mes2( p-OMePh)corrole)TiCp*] (3) and is consistent with distortion of the macrocycle N4 plane.25,26 The 1H NMR data for this compound is in agreement with the structure found in the solid state. The spectrum displays four sets of signals corresponding to eight b-pyrrole protons ranging from 8.89–8.73 ppm. The resonances in the aromatic
Fig. 1 ORTEP view of (a) [(Mes2(p-OMePh)corrole)TiCl] (2) and (b) [(Mes2(p-OMePh)corrole)2Zr2(m-Cl)2(THF)2] (5) with ellipsoids at 50% probability. Hydrogen atoms omitted for clarity.
This journal is © The Royal Society of Chemistry 2014
ChemComm
region show the proton inequivalence resulting from the restricted rotation about all three C–Ar bonds at room temperature. The signals of the OCH3 and mesityl-CH3 protons appear as four singlets at 3.48, 2.48, 2.25 and 1.77 ppm. Complex 2 is a useful candidate to explore the synthetic accessibility and stability of group 4 alkyl corrole complexes, and the scope of this functionalization was assessed. Upon treatment of 2 with NaCp* in THF at room temperature, [(Mes2( p-OMePh)corrole)TiCp*] (3) was obtained and characterized by 1H NMR spectroscopy. The formulation of 3 is confirmed by the unambiguous characterization previously reported in our group.21 Additionally, reaction of 2 with ClMgCH2SiMe3 in THF at 25 1C results in a colour change from black to green and affords the compound [(Mes2( p-OMePh)corrole)TiCH2SiMe3] (4) after filtration and removal of the solvent. Crystallization from pentane at 40 1C gave green crystals suitable for X-ray diffraction. Fig. S12 (ESI†) shows the ORTEP representation of this molecule. The geometry around the Ti atom is square pyramidal with the alkyl group in the axial position. The Ti–N (1.978(2)–2.009(2) Å) distances are longer than for those in complex 2. The metal atom is displaced 0.656 Å out of the mean corrole plane towards the carbon atom of the alkyl group. This value is similar to complex 2 and the five-coordinate porphyrin [(OEP)ZrCH2SiMe3] analogue.27 Distinguishing features in the 1H NMR spectrum of 4 are the methyl and methylene signals for the alkyl group at 1.74 and 2.98 ppm that are shifted to high-field by corrole ring current effects. Building on our success in preparing titanium corrole chlorides, we set out to prepare the zirconium and hafnium analogues. The complex [(Mes2( p-OMePh)corrole)2Zr2(m-Cl)2(THF)2] (5) was synthesized by the metathesis reaction of [(Mes2( p-OMePh)corrole)Li36THF] with ZrCl4 in toluene at 40 1C (Scheme 1). The solution was then warmed to room temperature and stirred for 12 h. Evaporation of the solvent under vacuum, followed by washing with pentane and filtering, afforded 5 as a dark purple solid (41% yield). Likewise, reaction of HfCl4 with the corresponding lithium salt in DME resulted in the formation of the complex [(Mes2( p-OMePh)corrole)2Hf2(m-Cl)2] (6). Upon concentration of the solution until saturation, pink-purple needles were recrystallized in 45% yield. Both dimeric compounds have metal centers joined via bis(m-chloride) linkages, which is similar to the coordination mode found previously for the analogous actinide corroles.23 The Zr(IV) corrole 5 is shown in ORTEP view in Fig. 1. Each seven-coordinate metal atom is bound by a trianionic corrole unit, a THF ligand and two chlorides. The preference of Zr(IV) for a coordination number greater than six28–30 is realized in this dimer by additional binding of two chlorine atoms and THF. The metal to ligand distances, Zr–Cl (2.688(1) Å), and Zr–O (2.304(3) Å) are longer than the corresponding values for [Zr(TPP)C12(THF)] (Zr–Cl = 2.486(13) Å)28 and [(COT)ZrCI2(THF)] (Zr–O = 2.274(2) Å).28 The average Zr–N distance (2.164(3) Å) is shorter than for that found in the group 4 porphyrin oxo dimers.30,31 At the same time, the two metal ions reside well outside the N4 plane of the adjacent corrole
Chem. Commun., 2014, 50, 2922--2924 | 2923
View Article Online
ChemComm Table 1
1
NMR shifts for Zirconium (5) and Hafnium (6) dimersa
b-H C6H3HOMe
Published on 30 January 2014. Downloaded by University of Pittsburgh on 28/10/2014 01:57:19.
C6H2Me3 OCH3 C6H2Me2CH3 THF
Communication
5
6
8.07 (d, 2H), 8.02 (d, 2H), 7.90 (d, 4H), 7.77 (d, 2H), 7.67 (d, 2H), 7.63 (d, 2H), 7.54 (d, 2H) 7.56 (s, 1H), 7.48 (s, 1H), 7.44 (s, 1H), 7.10 (br, masked, 2H), 6.62 (s, 1H), 6.48 (s, 1H), 6.44 (s, 1H) 8.83 (s, 4H), 7.24 (s, 4H) 4.05 (s, 3H), 3.83 (s, 3H) 3.45 (s, 3H), 2.52 (s, 3H), 2.44 (s, 3H), 2.42 (s, 3H), 2.36 (s, 3H), 2.11–2.08 (br, masked, 6H), 2.04 (s, 6H), 0.75 (s, 3H), 1.13 (s, 3H), 1.15 (s, 3H) 0.86 (m, 8H), 1.33 (m, 8H)
8.59 (d, 4H), 8.46 (d, 4H), 8.34 (d, 4H), 8.20 (d, 4H) 7.18 (s, 8H) 7.16 (s, 8H) 3.29 (s, 6H) 3.12 (s, 6H), 2.47 (s, 6H), 2.46 (s, 6H), 2.02 (s, 12H), 1.98 (s, 6H)
a 1
H NMR (C6D5CD3, 25 1C, 400 MHz).
core (Zr–N4 = 1.355 Å).21 This structural description is in contrast with the Hf(IV) corrole dimer, which accommodates a high coordination number without an O-donating ligand in the molecule. The refinement of the crystal structure established that the Hf(IV) ion in the dimer is coordinated by four nitrogen of corrole ring and two chlorides, disordered over three positions (Hf–Cl = 2.296(4), 2.169(3), 2.121(3) Å). The Hf cation is displaced by 1.184 Å from the plane defined by the four N atoms of the corrole plane toward the chloride atoms. The four Hf–N distances are in the range 2.142(4)–2.157(4) Å. UV-vis spectra show a narrow splitting of Soret band (Zr-dimer: 411, 434 and Hf-dimer: 407, 411 nm). Additionally, both complexes show broad Q bands between 571 and 600 nm, in accord with the HOMO–LUMO transitions described by Gouterman four-orbital model for porphyrins and corroles.32 1 H NMR analysis of 5 at room temperature in toluene-d8 shows eight chemically inequivalent doublets for the b-protons (Table 1). Singlets were observed for p-methoxy and mesitylCH3 protons, implying an inequivalent environment of these groups and the slow rotation of the aryl rings on the NMR time scale. Examination of this data shows that the upper and lower corrole rings are in a staggered configuration. Two additional multiplets for the coordinated THF are seen at 0.86 and 1.33 ppm. For 6, six singlets were observed for the mesityl-CH3 protons, implying two inequivalent sets of mesityl groups consistent with C2 symmetry. The preparation of this series of group 4 halides provides the opportunity for exploration of new structures and reactivity in the chemistry of metal corrole complexes. Further studies are in progress and will be reported in due course. RP acknowledges the UC-MEXUS Fellowship. HLB acknowledges the International Fulbright Science and Technology Fellowship. We are grateful to Antonio DiPasquale (XRD), Zhongrui Zhou (MS), and Chris Canlas (NMR) for assistance with instrumentation.
Notes and references 1 2 3 4
A. W. Johnson and I. T. Kay, Proc. Chem. Soc., London, 1964, 89. A. W. Johnson and I. T. Kay, J. Chem. Soc., 1965, 1620. L. Cuesta and J. L. Sessler, Chem. Soc. Rev., 2009, 38, 2716–2729. S. Licoccia, R. Paolesse, E. Tassoni, F. Polizio and T. Boschi, J. Chem. Soc., Dalton Trans., 1995, 3617–3621.
2924 | Chem. Commun., 2014, 50, 2922--2924
5 W. Kwong, R. W. Sun, C. Lok, F. Siu, S. Wong, K. Low and C. Che, Chem. Sci., 2013, 4, 747–754. 6 L. Kupershmidt, Z. Okun, T. Amit, S. Mandel, I. Saltsman, A. Mahammed, O. Bar-Am, Z. Gross and M. B. H. Youdim, J. Neurochem., 2010, 113, 363–373. 7 I. Nigel-Etinger, A. Mahammed and Z. Gross, Catal. Sci. Technol., 2011, 1, 578–581. 8 L. Lvova, C. Di Nataleb, A. D’Amicob and R. Paolesse, J. Porphyrins Phthalocyanines, 2009, 13, 1169–1178. 9 G. S. Kottas, L. I. Clarke, D. Horinek and J. Michl, Chem. Rev., 2005, 105, 1281–1376. 10 I. Aviv-Harel and Z. Gross, Coord. Chem. Rev., 2011, 255, 717–736. 11 L. M. Berreau, J. A. Hays, V. G. Young and L. K. Woo, Inorg. Chem., 1994, 33, 105–108. 12 L. Simkhovich, N. Galili, I. Saltsman, I. Goldberg and Z. Gross, Inorg. Chem., 2000, 39, 2704–2705. 13 A. E. Meier-Callahan, H. B. Gray and Z. Gross, Inorg. Chem., 2000, 39, 3605–3607. 14 A. E. Meier-Callahan, A. J. Di Bilio, L. Simkhovich, A. Mahammed, I. Goldberg, H. B. Gray and Z. Gross, Inorg. Chem., 2001, 40, 6788–6793. 15 A. Mahammed, H. B. Gray, A. E. Meier-Callahan and Z. Gross, J. Am. Chem. Soc., 2003, 125, 1162–1163. 16 I. Luobeznova, M. Raizman, I. Goldberg and Z. Gross, Inorg. Chem., 2006, 45, 386–394. 17 R. S. Czernuszewicz, V. Mody, A. A. Zareba, M. B. Zaczek, M. Gałezowski, V. Sashuk, K. Grela and D. T. Gryko, Inorg. Chem., 2007, 46, 5616–5624. 18 I. Nigel-Etinger, I. Goldberg and Z. Gross, Inorg. Chem., 2012, 51, 1983–1985. 19 Z. Gross, JBIC, J. Biol. Inorg. Chem., 2001, 6, 733–738. 20 P. Singh, G. Dutta, I. Goldberg, A. Mahammed and Z. Gross, Inorg. Chem., 2013, 52, 9349–9355. 21 H. L. Buckley, W. A. Chomitz, B. Koszarna, M. Tasior, D. Gryko, P. J. Brothers and J. Arnold, Chem. Commun., 2012, 48, 10766–10768. 22 H. L. Buckley, M. R. Anstey, D. T. Gryko and J. Arnold, Chem. Commun., 2013, 49, 3104–3106. 23 A. L. Ward, H. L. Buckley and J. Arnold, J. Am. Chem. Soc., 2013, 135, 13965–13971. 24 R. M. Porter, A. A. Danopoulos and G. Reid, Inorg. Chem., 2006, 45, 6516–6522. 25 J. Vestfrid, M. Botoshansky, J. H. Palmer, A. C. Durrell, H. B. Gray and Z. Gross, J. Am. Chem. Soc., 2011, 133, 12899–12901. 26 J. Bendix, I. Dmochowski, H. Gray, A. Mahammed, L. Simkhovich and Z. Gross, Angew. Chem., Int. Ed., 2000, 39, 4048–4051. 27 H. Brand and J. Arnold, Angew. Chem., Int. Ed. Engl., 1994, 33, 95–97. 28 H. J. Kim, D. Whang, K. Kim and Y. Dot, Inorg. Chem., 1993, 32, 360–362. 29 D. J. Brauer and C. Kruger, Inorg. Chem., 1975, 14, 3053–3056. 30 J. L. Thorman, I. A. Guzei, V. G. Young and L. K. Woo, Inorg. Chem., 2000, 39, 2344–2351. 31 A. Falber, L. Todaro, I. Goldberg, M. V. Favilla and C. M. Drain, Inorg. Chem., 2008, 47, 454–467. 32 A. Ghosh, T. Wondimagegn and A. B. J. Parusel, J. Am. Chem. Soc., 2000, 122, 5100–5104.
This journal is © The Royal Society of Chemistry 2014
Published on 30 January 2014. Downloaded by University of Pittsburgh on 28/10/2014 01:57:19.
COMMUNICATION
Cite this: Chem. Commun., 2014, 50, 2922
View Journal | View Issue
Synthesis, structure and reactivity of group 4 corrole complexes† Rosa Padilla, Heather L. Buckley, Ashleigh L. Ward and John Arnold*
Received 2nd January 2014, Accepted 30th January 2014 DOI: 10.1039/c4cc00037d www.rsc.org/chemcomm
A series of early transition metal corrole complexes has been prepared via salt metathesis with the corresponding lithium corrole. Their characterization by single crystal X-ray diffraction, NMR, and absorption spectroscopy is described. Organometallic derivatives of the titanium complex were obtained via treatment of 2 with NaCp* or ClMgCH2SiMe3.
Metal complexes of tetrapyrrolic macrocycles have been intensively studied since the 1960’s1,2 to gain better insight into the mechanism of several enzymatic reactions, and to develop possible applications for a variety of fields, such as medicine, biology, energy conversion, and catalysis.3–10 While the ‘‘periodic table’’ of corrole metal complexes is not as rich as that of porphyrins, the diversity of metallocorrole complexes is constantly increasing.6 Recently, there has been renewed interest in the synthesis of early transition metal corrole complexes due to their scarcity in the literature in comparison with the analogous low-valent metalloporphyrin halide complexes.11,12 The chemistry of early metal corrole complexes has thus far been limited to oxo-derivatives featuring Ti, V,4 Cr,13–15 Mo,16,17 and W.18 These complexes reflect the oxophilic nature of the early transition metals. Synthesis of the corrole halide complexes of Fe and Mn has been achieved under acidic conditions. However, this methodology is unsuitable for early transition metal chemistry.19,20 Recently, the preparation of a lithium corrole metathesis reagent has allowed for the efficient synthesis of a range of new early transition metal, lanthanide, and actinide corrole complexes.21–23 Furthering this research, we have been interested in exploring titanium, zirconium and hafnium corrole chloride complexes due to the potential they have to exhibit rich organometallic chemistry similar to their porphyrin analogues. Department of Chemistry, University of California, Berkeley, California, 94720, USA. E-mail: [email protected]; Tel: +1 510 643 5181 † Electronic supplementary information (ESI) available: Experimental procedures, analytical data, NMR data, crystal data, CIF files for 2, 4, 5, and 6. CCDC 979184–979187. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4cc00037d
2922 | Chem. Commun., 2014, 50, 2922--2924
Treatment of [(Mes2(p-OMePh)corrole)Li3THF6]21 (1) with [TiCl4THF2] in toluene at 25 1C for 4 h provided the titanium(IV) corrole chloride complex [(Mes2( p-OMePh)corrole)TiCl] (2). After crystallization from a mixture of dichloromethane and hexanes, the product was isolated as dark brown crystals in 79% yield (Scheme 1). As with all the complexes described here, 2 is hydrolytically sensitive and must be handled with the exclusion of air and moisture. The complex was characterized
Scheme 1
Synthesis of Ti(IV), Zr(IV) and Hf(IV) complexes.
This journal is © The Royal Society of Chemistry 2014
View Article Online
Published on 30 January 2014. Downloaded by University of Pittsburgh on 28/10/2014 01:57:19.
Communication
by X-ray crystallography, ESI-MS, UV-visible spectroscopy, and 1 H NMR spectroscopy. To the best of our knowledge, this compound is the first metal halide corrole complex synthesized under mild conditions. The structure is in agreement with previously reported group 4 corroles, as well as the group 4 porphyrin dichlorides, which are all monomeric in the solidstate.11,21 The X-ray crystallographic data and collection parameters are summarized in Table S1 (ESI†). The crystal structure of 2 is shown in Fig. 1. The central titanium atom has a distorted square pyramidal geometry with a chloride bound in the apical position. The metal atom is displaced towards the chloride by 0.667 Å from the mean N4 plane of the corrole ligand, which is shorter than for other reported group 4 corrole complexes (Zr–N4 0.914 Å, Ti–N4 0.820 Å).21 The Ti–Cl distance (2.220(6) Å) is comparable to that of the azaoxa macrocycle Ti–Cl complex (2.293(7) Å).24 All the Ti–N bond lengths (1.985(2)–1.996(2) Å) are shorter than the corresponding values for [(Mes2( p-OMePh)corrole)TiCp*] (2.049(3) Å)21 and may be a result of the shape and geometry of the corrole moiety and also the relative orientation of the aryl substituents with respect to the corrole ring. The UVvisible spectrum of 2 displays a Q band (lmax = 550 nm) and a Soret band that is split into two peaks (lmax = 418, 405 nm). This is similar to the values reported for the titanium corrole [(Mes2( p-OMePh)corrole)TiCp*] (3) and is consistent with distortion of the macrocycle N4 plane.25,26 The 1H NMR data for this compound is in agreement with the structure found in the solid state. The spectrum displays four sets of signals corresponding to eight b-pyrrole protons ranging from 8.89–8.73 ppm. The resonances in the aromatic
Fig. 1 ORTEP view of (a) [(Mes2(p-OMePh)corrole)TiCl] (2) and (b) [(Mes2(p-OMePh)corrole)2Zr2(m-Cl)2(THF)2] (5) with ellipsoids at 50% probability. Hydrogen atoms omitted for clarity.
This journal is © The Royal Society of Chemistry 2014
ChemComm
region show the proton inequivalence resulting from the restricted rotation about all three C–Ar bonds at room temperature. The signals of the OCH3 and mesityl-CH3 protons appear as four singlets at 3.48, 2.48, 2.25 and 1.77 ppm. Complex 2 is a useful candidate to explore the synthetic accessibility and stability of group 4 alkyl corrole complexes, and the scope of this functionalization was assessed. Upon treatment of 2 with NaCp* in THF at room temperature, [(Mes2( p-OMePh)corrole)TiCp*] (3) was obtained and characterized by 1H NMR spectroscopy. The formulation of 3 is confirmed by the unambiguous characterization previously reported in our group.21 Additionally, reaction of 2 with ClMgCH2SiMe3 in THF at 25 1C results in a colour change from black to green and affords the compound [(Mes2( p-OMePh)corrole)TiCH2SiMe3] (4) after filtration and removal of the solvent. Crystallization from pentane at 40 1C gave green crystals suitable for X-ray diffraction. Fig. S12 (ESI†) shows the ORTEP representation of this molecule. The geometry around the Ti atom is square pyramidal with the alkyl group in the axial position. The Ti–N (1.978(2)–2.009(2) Å) distances are longer than for those in complex 2. The metal atom is displaced 0.656 Å out of the mean corrole plane towards the carbon atom of the alkyl group. This value is similar to complex 2 and the five-coordinate porphyrin [(OEP)ZrCH2SiMe3] analogue.27 Distinguishing features in the 1H NMR spectrum of 4 are the methyl and methylene signals for the alkyl group at 1.74 and 2.98 ppm that are shifted to high-field by corrole ring current effects. Building on our success in preparing titanium corrole chlorides, we set out to prepare the zirconium and hafnium analogues. The complex [(Mes2( p-OMePh)corrole)2Zr2(m-Cl)2(THF)2] (5) was synthesized by the metathesis reaction of [(Mes2( p-OMePh)corrole)Li36THF] with ZrCl4 in toluene at 40 1C (Scheme 1). The solution was then warmed to room temperature and stirred for 12 h. Evaporation of the solvent under vacuum, followed by washing with pentane and filtering, afforded 5 as a dark purple solid (41% yield). Likewise, reaction of HfCl4 with the corresponding lithium salt in DME resulted in the formation of the complex [(Mes2( p-OMePh)corrole)2Hf2(m-Cl)2] (6). Upon concentration of the solution until saturation, pink-purple needles were recrystallized in 45% yield. Both dimeric compounds have metal centers joined via bis(m-chloride) linkages, which is similar to the coordination mode found previously for the analogous actinide corroles.23 The Zr(IV) corrole 5 is shown in ORTEP view in Fig. 1. Each seven-coordinate metal atom is bound by a trianionic corrole unit, a THF ligand and two chlorides. The preference of Zr(IV) for a coordination number greater than six28–30 is realized in this dimer by additional binding of two chlorine atoms and THF. The metal to ligand distances, Zr–Cl (2.688(1) Å), and Zr–O (2.304(3) Å) are longer than the corresponding values for [Zr(TPP)C12(THF)] (Zr–Cl = 2.486(13) Å)28 and [(COT)ZrCI2(THF)] (Zr–O = 2.274(2) Å).28 The average Zr–N distance (2.164(3) Å) is shorter than for that found in the group 4 porphyrin oxo dimers.30,31 At the same time, the two metal ions reside well outside the N4 plane of the adjacent corrole
Chem. Commun., 2014, 50, 2922--2924 | 2923
View Article Online
ChemComm Table 1
1
NMR shifts for Zirconium (5) and Hafnium (6) dimersa
b-H C6H3HOMe
Published on 30 January 2014. Downloaded by University of Pittsburgh on 28/10/2014 01:57:19.
C6H2Me3 OCH3 C6H2Me2CH3 THF
Communication
5
6
8.07 (d, 2H), 8.02 (d, 2H), 7.90 (d, 4H), 7.77 (d, 2H), 7.67 (d, 2H), 7.63 (d, 2H), 7.54 (d, 2H) 7.56 (s, 1H), 7.48 (s, 1H), 7.44 (s, 1H), 7.10 (br, masked, 2H), 6.62 (s, 1H), 6.48 (s, 1H), 6.44 (s, 1H) 8.83 (s, 4H), 7.24 (s, 4H) 4.05 (s, 3H), 3.83 (s, 3H) 3.45 (s, 3H), 2.52 (s, 3H), 2.44 (s, 3H), 2.42 (s, 3H), 2.36 (s, 3H), 2.11–2.08 (br, masked, 6H), 2.04 (s, 6H), 0.75 (s, 3H), 1.13 (s, 3H), 1.15 (s, 3H) 0.86 (m, 8H), 1.33 (m, 8H)
8.59 (d, 4H), 8.46 (d, 4H), 8.34 (d, 4H), 8.20 (d, 4H) 7.18 (s, 8H) 7.16 (s, 8H) 3.29 (s, 6H) 3.12 (s, 6H), 2.47 (s, 6H), 2.46 (s, 6H), 2.02 (s, 12H), 1.98 (s, 6H)
a 1
H NMR (C6D5CD3, 25 1C, 400 MHz).
core (Zr–N4 = 1.355 Å).21 This structural description is in contrast with the Hf(IV) corrole dimer, which accommodates a high coordination number without an O-donating ligand in the molecule. The refinement of the crystal structure established that the Hf(IV) ion in the dimer is coordinated by four nitrogen of corrole ring and two chlorides, disordered over three positions (Hf–Cl = 2.296(4), 2.169(3), 2.121(3) Å). The Hf cation is displaced by 1.184 Å from the plane defined by the four N atoms of the corrole plane toward the chloride atoms. The four Hf–N distances are in the range 2.142(4)–2.157(4) Å. UV-vis spectra show a narrow splitting of Soret band (Zr-dimer: 411, 434 and Hf-dimer: 407, 411 nm). Additionally, both complexes show broad Q bands between 571 and 600 nm, in accord with the HOMO–LUMO transitions described by Gouterman four-orbital model for porphyrins and corroles.32 1 H NMR analysis of 5 at room temperature in toluene-d8 shows eight chemically inequivalent doublets for the b-protons (Table 1). Singlets were observed for p-methoxy and mesitylCH3 protons, implying an inequivalent environment of these groups and the slow rotation of the aryl rings on the NMR time scale. Examination of this data shows that the upper and lower corrole rings are in a staggered configuration. Two additional multiplets for the coordinated THF are seen at 0.86 and 1.33 ppm. For 6, six singlets were observed for the mesityl-CH3 protons, implying two inequivalent sets of mesityl groups consistent with C2 symmetry. The preparation of this series of group 4 halides provides the opportunity for exploration of new structures and reactivity in the chemistry of metal corrole complexes. Further studies are in progress and will be reported in due course. RP acknowledges the UC-MEXUS Fellowship. HLB acknowledges the International Fulbright Science and Technology Fellowship. We are grateful to Antonio DiPasquale (XRD), Zhongrui Zhou (MS), and Chris Canlas (NMR) for assistance with instrumentation.
Notes and references 1 2 3 4
A. W. Johnson and I. T. Kay, Proc. Chem. Soc., London, 1964, 89. A. W. Johnson and I. T. Kay, J. Chem. Soc., 1965, 1620. L. Cuesta and J. L. Sessler, Chem. Soc. Rev., 2009, 38, 2716–2729. S. Licoccia, R. Paolesse, E. Tassoni, F. Polizio and T. Boschi, J. Chem. Soc., Dalton Trans., 1995, 3617–3621.
2924 | Chem. Commun., 2014, 50, 2922--2924
5 W. Kwong, R. W. Sun, C. Lok, F. Siu, S. Wong, K. Low and C. Che, Chem. Sci., 2013, 4, 747–754. 6 L. Kupershmidt, Z. Okun, T. Amit, S. Mandel, I. Saltsman, A. Mahammed, O. Bar-Am, Z. Gross and M. B. H. Youdim, J. Neurochem., 2010, 113, 363–373. 7 I. Nigel-Etinger, A. Mahammed and Z. Gross, Catal. Sci. Technol., 2011, 1, 578–581. 8 L. Lvova, C. Di Nataleb, A. D’Amicob and R. Paolesse, J. Porphyrins Phthalocyanines, 2009, 13, 1169–1178. 9 G. S. Kottas, L. I. Clarke, D. Horinek and J. Michl, Chem. Rev., 2005, 105, 1281–1376. 10 I. Aviv-Harel and Z. Gross, Coord. Chem. Rev., 2011, 255, 717–736. 11 L. M. Berreau, J. A. Hays, V. G. Young and L. K. Woo, Inorg. Chem., 1994, 33, 105–108. 12 L. Simkhovich, N. Galili, I. Saltsman, I. Goldberg and Z. Gross, Inorg. Chem., 2000, 39, 2704–2705. 13 A. E. Meier-Callahan, H. B. Gray and Z. Gross, Inorg. Chem., 2000, 39, 3605–3607. 14 A. E. Meier-Callahan, A. J. Di Bilio, L. Simkhovich, A. Mahammed, I. Goldberg, H. B. Gray and Z. Gross, Inorg. Chem., 2001, 40, 6788–6793. 15 A. Mahammed, H. B. Gray, A. E. Meier-Callahan and Z. Gross, J. Am. Chem. Soc., 2003, 125, 1162–1163. 16 I. Luobeznova, M. Raizman, I. Goldberg and Z. Gross, Inorg. Chem., 2006, 45, 386–394. 17 R. S. Czernuszewicz, V. Mody, A. A. Zareba, M. B. Zaczek, M. Gałezowski, V. Sashuk, K. Grela and D. T. Gryko, Inorg. Chem., 2007, 46, 5616–5624. 18 I. Nigel-Etinger, I. Goldberg and Z. Gross, Inorg. Chem., 2012, 51, 1983–1985. 19 Z. Gross, JBIC, J. Biol. Inorg. Chem., 2001, 6, 733–738. 20 P. Singh, G. Dutta, I. Goldberg, A. Mahammed and Z. Gross, Inorg. Chem., 2013, 52, 9349–9355. 21 H. L. Buckley, W. A. Chomitz, B. Koszarna, M. Tasior, D. Gryko, P. J. Brothers and J. Arnold, Chem. Commun., 2012, 48, 10766–10768. 22 H. L. Buckley, M. R. Anstey, D. T. Gryko and J. Arnold, Chem. Commun., 2013, 49, 3104–3106. 23 A. L. Ward, H. L. Buckley and J. Arnold, J. Am. Chem. Soc., 2013, 135, 13965–13971. 24 R. M. Porter, A. A. Danopoulos and G. Reid, Inorg. Chem., 2006, 45, 6516–6522. 25 J. Vestfrid, M. Botoshansky, J. H. Palmer, A. C. Durrell, H. B. Gray and Z. Gross, J. Am. Chem. Soc., 2011, 133, 12899–12901. 26 J. Bendix, I. Dmochowski, H. Gray, A. Mahammed, L. Simkhovich and Z. Gross, Angew. Chem., Int. Ed., 2000, 39, 4048–4051. 27 H. Brand and J. Arnold, Angew. Chem., Int. Ed. Engl., 1994, 33, 95–97. 28 H. J. Kim, D. Whang, K. Kim and Y. Dot, Inorg. Chem., 1993, 32, 360–362. 29 D. J. Brauer and C. Kruger, Inorg. Chem., 1975, 14, 3053–3056. 30 J. L. Thorman, I. A. Guzei, V. G. Young and L. K. Woo, Inorg. Chem., 2000, 39, 2344–2351. 31 A. Falber, L. Todaro, I. Goldberg, M. V. Favilla and C. M. Drain, Inorg. Chem., 2008, 47, 454–467. 32 A. Ghosh, T. Wondimagegn and A. B. J. Parusel, J. Am. Chem. Soc., 2000, 122, 5100–5104.
This journal is © The Royal Society of Chemistry 2014
