Aryl-oxazoline chelates of first-row transition metals: Structures of {Κ-C,N-(o-C6H4)CMe2(COCH 2CMe2N)}FeCl(py) and [(Κ-C,N-(o-C6H 4)CMe2(COCH2CMe2N)}Cr(μ-Cl)] 2

Article abstract of DOI:10.1021/om100420z

Aryl-oxazoline synthons have been explored for the preparation of strong-field first-row transition metal chelate species. With 4,4-dimethyl-2-phenyloxazoline (HPhOx), no CH bond activations afforded complexation, and aside from Zn(Κ-C,N-4,4-Me₂-2-(o-C ₆H₄)oxazoline)₂ (Zn(PhOx)₂), aryl-coupling reactions were noted with 4,4-dimethyl-2-(2-lithiophenyl)oxazoline (LiPhOx) and MX₂; [Κ-N,N-{4,4-Me₂-(2-o-C ₆H₄)-2-oxazoline}₂]CoCl₂ (1-Co) was structurally characterized. Metalations with 4,4-dimethyl-2-benzyloxazoline (PhCH₂Ox) were prone to deprotonation, as exemplified by (Me ₂N)₃Ti(η-N-(4,4-dimethyl-(2-CHPh)oxazoline)) (2) and bis-N,N′-(4,4-dimethyl-(2-pyridylmethylyl)oxazoline)Fe (3). Oxidative addition of 4,4-dimethyl-2-(2-bromophenylpropan-2-yl)oxazoline (BrPhCMe ₂Ox) to Ni(COD)₂ provided [{Κ-C,N-(o-C ₆H₄)CMe₂(COCH₂CMe ₂N)}Ni]₂(μ-Br)₂ (4₂). With 4,4-dimethyl-2-(2-lithiophenylpropan-2-yl)oxazoline (LiPhCMe₂Ox), salt (FeBr₂) metathesis proved uncompetitive with oxazoline ring-opening, as exhibited by [{Κ-N,O-C₆H₄CMe ₂C=NCMe₂CH₂(μ-O)-}BrFe{Κ-N,O-C ₆H₄CMe₂C=NCMe₂CH₂(μ-O) -}FeBr]Li {Κ-N,O-C₆H₄CMe₂-C=NCMe ₂CH₂(μ-O)-}(DME) (5-Fe₂Li). Metatheses utilizing (PhCMe₂Ox)₂Zn, prepared from LiPhCMe ₂Ox and ZnCl₂, gave structurally characterized dichromium, i.e., [{Κ-C,N-(o-C₆H₄)CMe₂ (COCH ₂CMe₂N)}Cr]₂(μ-Cl)₂ (6 ₂), and iron, i.e., {Κ-C,N-{(o-C₆H ₄)CMe₂(COCH₂CMe₂N)}Fe(py)Cl (7) products. Bis-aryloxazoline metal complexes proved difficult to prepare, with {Κ-C,N-(o-C₆H₄)CMe₂(COCH ₂CMe₂N)}₂M (M = Ni, 9) the only clear example, although NMR evidence exists for M = Fe (8).

Full text of DOI:10.1021/om100420z

6642 Organometallics 2010, 29, 6642–6652
DOI: 10.1021/om100420z
Aryl-Oxazoline Chelates of First-Row Transition Metals: Structures
of {K-C,N-(o-C6H4)CMe2(COCH2CMe2N)}FeCl(py) and
‡
[(K-C,N-(o-C6H4)CMe2(COCH2CMe2N)}Cr(μ-Cl)]2
Emily C. Volpe, David R. Manke, Erika R. Bartholomew, Peter T. Wolczanski,* and
Emil B. Lobkovsky
Department of Chemistry & Chemical Biology, Baker Laboratory, Cornell University,
Ithaca, New York 14853, United States
Received May 4, 2010
Aryl-oxazoline synthons have been explored for the preparation of strong-field first-row transi-
tion metal chelate species. With 4,4-dimethyl-2-phenyloxazoline (HPhOx), no CH bond activations
afforded complexation, and aside from Zn(κ-C,N-4,4-Me2-2-(o-C6H4)oxazoline)2 (Zn(PhOx)2),
aryl-coupling reactions were noted with 4,4-dimethyl-2-(2-lithiophenyl)oxazoline (LiPhOx) and
MX2; [κ-N,N-{4,4-Me2-(2-o-C6H4)-2-oxazoline}2]CoCl2 (1-Co) was structurally characterized.
Metalations with 4,4-dimethyl-2-benzyloxazoline (PhCH2Ox) were prone to deprotonation, as
exemplified by (Me2N)3Ti(η-N-(4,4-dimethyl-(2-CHPh)oxazoline)) (2) and bis-N,N0-(4,4-dimethyl-
(2-pyridylmethylyl)oxazoline)Fe (3). Oxidative addition of 4,4-dimethyl-2-(2-bromophenylpropan-2-yl)-
oxazoline (BrPhCMe2Ox) to Ni(COD)2 provided [{κ-C,N-(o-C6H4)CMe2(COCH2CMe2N)}Ni]2-
(μ-Br)2 (42). With 4,4-dimethyl-2-(2-lithiophenylpropan-2-yl)oxazoline (LiPhCMe2Ox), salt (FeBr2)
metathesis proved uncompetitive with oxazoline ring-opening, as exhibited by [{κ-N,O-C6H4CMe2Cd
NCMe2CH2(μ-O)-}BrFe{κ-N,O-C6H4CMe2CdNCMe2CH2(μ-O)-}FeBr]Li {κ-N,O-C6H4CMe2-Cd
NCMe2CH2(μ-O)-}(DME) (5-Fe2Li). Metatheses utilizing (PhCMe2Ox)2Zn, prepared from
LiPhCMe2Ox and ZnCl2, gave structurally characterized dichromium, i.e., [{κ-C,N-(o-C6H4)CMe2
(COCH2CMe2N)}Cr]2(μ-Cl)2 (62), and iron, i.e., {κ-C,N-{(o-C6H4)CMe2(COCH2CMe2N)}Fe(py)Cl (7)
products. Bis-aryloxazoline metal complexes proved difficult to prepare, with {κ-C,N-(o-C6H4)-
CMe2(COCH2CMe2N)}2M (M=Ni, 9) the only clear example, although NMR evidence exists
for M=Fe (8).
Introduction
facilitates chemical reactivity by enabling lower energy path-
ways from reactant to product.1 In combination with some-
what lower bond energies,8 these factors explain the typically
greater rates of second-row transition metal complexes
relative to their third-row congeners and the widespread
use of Pd, Rh, etc., catalysts in bond-making and -breaking
processes requiring 2e- changes.9-11
Recent investigations in these laboratories have focused
on distinguishing electronic features that differentiate second-
row transition metal reactivity from that of the third row.1-7
The greater density of states (DOS) in second-row species
Following similar logic, first-row transition metals should
be even better suited for rapid chemical transformations
because their DOS is even greater, as spectroscopic investi-
gations have historically shown.12 Furthermore, the applica-
tion of first-row transition metals in stoichiometric and
‡ Dedicated to Dietmar Seyferth on the occasion of his retirement as Editor,
for his distinguished service, and for 35þ years of friendship to an old student.
*To whom correspondence should be addressed. E-mail: ptw2@
cornell.edu.
(1) Hirsekorn, K. F.; Hulley, E. B.; Wolczanski, P. T.; Cundari, T. R.
J. Am. Chem. Soc. 2008, 130, 1183–1196.
(2) Kuiper, D. S.; Douthwaite, R. E.; Mayol, A.-R.; Wolczanski,
P. T.; Lobkovsky, E. B.; Cundari, T. R.; Lam, O. P.; Meyer, K. Inorg.
Chem. 2008, 47, 7139–7153.
(8) Uddin, J.; Morales, C. M.; Maynard, J. H.; Landis, C. R.
Organometallics 2006, 25, 5566–5581.
(9) Hartwig, J. Organotransition Metal Chemistry: From Bonding to
(3) Kuiper, D. S.; Wolczanski, P. T.; Lobkovsky, E. B.; Cundari,
T. R. J. Am. Chem. Soc. 2008, 130, 12931–12943.
Catalysis; University Science Books: Sausilito, CA, 2009.
(10) Hegedus, L. S.; Soderberg, B. C. G. Transition Metals in the
Synthesis of Complex Organic Molecules; University Science Books:
Sausilito, CA, 2009.
€
(4) Kuiper, D. S.; Wolczanski, P. T.; Lobkovsky, E. B.; Cundari,
T. R. Inorg. Chem. 2008, 47, 10542–10553.
(5) Rosenfeld, D. C.; Kuiper, D. S.; Lobkovsky, E. B.; Wolczanski,
P. T. Polyhedron 2006, 25, 251–258.
(11) (a) Collman, J. P.; Hegedus, L. S.; Norton, J. R.; Finke, R. G.
Principles and Applications of Organotransition Metal Chemistry;
University Science Books: Mill Valley, CA., 1987. (b) Crabtree, R. H. The
Organometallic Chemistry of the Transition Metals, 4th ed.; John Wiley &
Sons: New York, 2005.
(12) Figgis, B. N.; Hitchman, M. A. Ligand Field Theory and Its
Applications; Wiley-VCH: New York, 2000.
(6) Rosenfeld, D. C.; Wolczanski, P. T.; Barakat, K. A.; Buda, C.;
Cundari, T. R.; Schroeder, F. C.; Lobkovsky, E. B. Inorg. Chem. 2007,
46, 9715–9735.
(7) Veige, A. S.; Slaughter, L. M.; Lobkovsky, E. B.; Wolczanski,
P. T.; Matsunaga, N.; Decker, S. A.; Cundari, T. R. Inorg. Chem. 2003,
42, 6204–6224.
r
pubs.acs.org/Organometallics
Published on Web 11/29/2010
2010 American Chemical Society

Article
Organometallics, Vol. 29, No. 24, 2010 6643
to support low-spin systems for a number of first-row transi-
tion metals.9-11 If this concept is to work within the frame-
work of classic coordination compounds, ancillary ligands
containing metal-carbon bonds must ultimately be pro-
tected from reacting, yet judiciously positioned to impart
their intrinsically greater fields. Herein are described initial
synthetic efforts directed at the metalation of oxazoline-
based ligands as sp2, aryl, C-based chelates.26-41 The struc-
tural diversity of oxazolines42 and the presence of complementary
heteroatom donors43-48 present an attractive target toward the
eventual preparation of multidentate ligands that can be sterically
or conformationally modified for ancillary applications.
Results
Figure 1. Angular overlap arguments show that both the inter-
action energy and orbital overlap favor C-based over N- and
O-based ligands in terms of field strength.
Oxazoline Ligands. Scheme 1 illustrates the set of ligands
examined to varying degrees in this study and shows their
syntheses, which are literature-derived or contain minor
modifications from published procedures. In all cases the
4,4-dimethyl-2-oxazolyl fragment was used because of the
convenient NMR handle presented by its methyl groups, and
its steric features. The cadmium acetate assisted condensa-
tion of 2,2-dimethyl-2-aminoethanol to benzonitrile49 proved
significantly superior to the uncatalyzed process, and the
product 4,4-dimethyl-2-phenyloxazoline (HPhOx, 80%) could
catalytic transformations has two major advantages: (1) they
are less expensive, assuming similar activity, and (2) depend-
ing on the metal, trace contamination (e.g., in drugs, food
containers, etc.) is usually less of a health issue when the com-
pounds are employed in the course of organic synthesis.13-16
Unfortunately, the field strengths of common coordination
complexes are weak enough that 1e- changes are more com-
mon, and these often prove detrimental to desired reactivity.17-19
In principle, carbon-based ligands can impart strong fields
to a first-row transition metal, as the illustration in Figure 1
reveals.20-24 Angular overlap arguments portray C-based
orbitals as having very good interaction energies due to their
relative proximity in energy to appropriate metal orbitals.12,25 In
comparison, N- and O-based ligands are less well matched
energetically due to their lower energy orbitals. Better orbital
overlap (SC > SN > SO) also contributes to the logic that
carbon-based ligands are strong field in nature. Ligands based
on main group elements of the second row (e.g., phosphines)
and below may match corresponding metal orbitals better in
energy, but this is compensated by overlaps that are signifi-
cantly attenuated due to the relative diffusivity of their
orbitals.
(26) (a) Nishiyama, H.; Ito, J. Chem. Commun. 2010, 46, 203–212.
(b) Nishiyama, H. Chem. Soc. Rev. 2007, 36, 1133–1141.
(27) Denmark, S. E.; Stavenger, R. A.; Faucher, A.-M.; Edwards,
J. P. J. Org. Chem. 1997, 62, 3375–3389.
(28) Stark, M. A.; Jones, G.; Richards, C. J. Organometallics 2000,
19, 1282–1291.
(29) Fossey, J. S.; Richards, C. J. J. Organomet. Chem. 2004, 689,
3056–3059.
(30) Fossey, J. S.; Richards, C. J. Organometallics 2004, 23, 367–373.
(31) Stol, M.; Snelders, D. J. M.; Godbole, M. D.; Havenith,
R. W. A.; Haddleton, D.; Clarkson, G.; Lutz, M.; Spek, A. L.; van
Klink, G. P. M.; van Koten, G. Organometallics 2007, 26, 3985–3994.
(32) Davies, D. L.; Al-Duaij, O.; Fawcett, J.; Giardiello, M.; Hilton,
S. T.; Russell, D. R. Dalton Trans. 2003, 4132–4138.
(33) Davies, D. L.; Al-Duaij, O.; Fawcett, J.; Singh, K. Organometallics
2010, 29, 0000.
(34) Wehman, E.; van Koten, G.; Jastrzebski, J. T. B. H.; Rotteveel,
M. A.; Stam, C. H. Organometallics 1988, 7, 1477–1485.
(35) Djukic, J.-P.; Michon, C.; Heiser, D.; Kyritsakas-Gruber, N.;
De Cian, A.; Doetz, K. H.; Pfeffer, M. Eur. J. Inorg. Chem. 2004, 10,
2107–2122.
The concept of using carbon-based ligands to impart
strong fields is as old as their applications in organometallic
chemistry, where ligands such as cyclopentadienyl are known
(36) Bonnardel, P. A.; Parish, R. V.; Pritchard, R. G. J. Chem. Soc.,
(13) Ritter, S. K. Chem. Eng. News 2008, 86, 53–57.
(14) de Meijere, A. Chem. Rev. 2000, 100, 2739–2740.
(15) (a) Sherry, B. D.; Furstner, A. Acc. Chem. Res. 2008, 11, 1500–
1511. (b) Furstner, A.; Martin, R. Chem. Lett. 2005, 34, 624–629.
(c) Furstner, A.; Leitner, A.; Mendez, M.; Krause, H. J. Am. Chem. Soc.
2002, 124, 13856–13863.
(16) Buchwald, S. L.; Bolm, C. Angew. Chem., Int. Ed. 2009, 48, 0000.
(17) (a) Klinker, E. J.; Shaik, S.; Hirao, H.; Que, L. Angew. Chem.,
Int. Ed. 2009, 48, 1291–1295. (b) Dhuri, S. N.; Seo, M. S.; Lee, Y. M.; Hirao,
H.; Wang, Y.; Nam, W.; Shaik, S. Angew. Chem., Int. Ed. 2008, 47, 3356–
3359.
Dalton Trans. 1996, 15, 3185–3193.
(37) Giri, R.; Chen, X.; Yu, J.-Q. Angew. Chem., Int. Ed. 2005, 44,
2112–2115.
(38) Chen, X.; Li, J.-J.; Hao, X.-S.; Goodhue, C. E.; Yu, J.-Q. J. Am.
Chem. Soc. 2006, 128, 78–79.
(39) Yuan, K.; Zhang, T. K.; Hou, X. L. J. Org. Chem. 2005, 70,
6085–6088.
(40) Neal, S. R.; You, J.; Ellern, A.; Sadow, A. D. Polyhedron 2010,
29, 544–552.
(41) Krumper, J. R.; Gerisch, M.; Suh, J. M.; Bergman, R. G.; Tilley,
T. D. J. Org. Chem. 2003, 68, 9705–9710.
(18) De Angelis, F.; Jin, N.; Car, R.; Groves, J. T. Inorg. Chem. 2006,
45, 4268–4276.
(42) Gant, T. G.; Meyers, A. I. Tetrahedron Lett. 1994, 50, 2297–
2360.
(43) Inagaki, T.; Phong, L. T.; Furuta, A.; Ito, J.; Nishiyama, H.
(19) For elucidation of catalysis involving 1e- changes, see: Poli, R.
Angew. Chem., Int. Ed. 2006, 45, 5058–5070.
(20) Volpe, E. C.; Wolczanski, P. T.; Lobkovsky, E. B. Organometallics
Chem.;Eur. J. 2010, 16, 3090–3096.
(44) Tondreau, A. M.; Darmon, J. M.; Wile, B. M.; Floyd, S. K.;
Lobkovsky, E.; Chirik, P. J. Organometallics 2009, 28, 3928–3940.
(45) Zhang, M.; Gao, R.; Hao, X.; Sun, W.-H. J. Organomet. Chem.
2008, 693, 3867–3877.
2010, 29, 364–377.
(21) Bower, B. K.; Tennent, H. G. J. Am. Chem. Soc. 1972, 94, 2512–
2513.
(22) Byrne, E. K.; Theopold, K. H. J. Am. Chem. Soc. 1989, 111,
3887–3896.
(23) Dimitrov, V.; Linden, A. Angew. Chem., Int. Ed. 2003, 42, 2631–
1633.
(46) Ferro, R.; Milione, S.; Bertolasi, V.; Capacchione, C.; Grassi, A.
Macromolecules 2007, 40, 8544–8546.
(47) Guillemot, G.; Neuburger, M.; Pfaltz, A. Chem.;Eur. J. 2007,
13, 8960–8970.
(24) Carnes, M.; Buccella, D.; Chen, J. Y. C.; Ramirez, A. P.; Turro,
N. J.; Nuckolls, C.; Steigerwald, M. Angew. Chem., Int. Ed. 2009, 48,
290–294.
(48) Godbole, M. D.; Puig, M. P.; Tanase, S.; Kooljman, H.; Spek,
A. L.; Bouwman, E. Inorg. Chim. Acta 2007, 360, 1954–1960.
(49) Kumar, S.; Kandasamy, K.; Singh, H. B.; Butcher, R. J. New
J. Chem. 2004, 28, 640–645.
(25) Richardson, D. E. J. Chem. Educ. 1993, 70, 372.

6644 Organometallics, Vol. 29, No. 24, 2010
Volpe et al.
Scheme 1
Scheme 2
be directly lithiated to afford LiPhOx (80%).50 The latter had
only modest stability at room temperature and was routinely
generated in situ when desired. Phenylacetic acid underwent
condensation with 2,2-dimethyl-2-aminoethanol without the
need for a catalyst to provide 4,4-dimethyl-2-benzyloxazoline
(PhCH2Ox).51 While 2-phenyl-2-methylpropionic acid could
be purchased, synthesis of the o-Br derivative required sequen-
tial methylation of 2-o-bromophenylethanoic acid.52 Conver-
sion to the acid chloride prior to condensation with 2,2-dimethyl-
2-aminoethanol was done after several condensation attempts
with 2-o-bromophenylethanoic acid failed. The acid chloride of
the o-Br and parent compound were used to prepare the amide,53
which was then cyclized with the aid of base to generate the
4,4-dimethyl-2-(2-phenylpropan-2-yl)oxazoline (HPhCMe2Ox)
ligand precursor or its o-Br analogue (BrPhCMe2Ox).54 The
latter could be lithiated at -78 °C to LiPhCMe2Ox, but this
species proved unstable upon warming (vide infra).
4,4-Dimethyl-2-phenyloxazoline. 1. Metalation Attempts.
Previous efforts in utilizing heterolytic CH bond activation to
generate an aryl-metal bond from 2-phenylpyridine were
modestly successful,55 but efforts to employ first-row transition
metal halides and triflates in a similar vein with 4,4-dimethyl-
2-phenyloxazoline (HPhOx) proved futile. Since direct lithiation to
afford LiPhOx was successful, this reagent was utilized in metath-
eses with various first-row transition metal halides. Furthermore,
LiPhOx was used to prepare two zinc reagents: the bis-phenyl-
oxazoline derivative Zn(κ-C,N-4,4-Me2-2-(o-C6H4)oxazoline)2
(50) Astley, S. T.; Stephenson, G. R. Synlett. 1992, 6, 507–509.
(51) Marshall, L. J.; Roydhouse, M. D.; Slawin, A. M. Z.; Walton,
J. C. J. Org. Chem. 2007, 72, 898–911.
(52) Beak, P.; Kerrick, S. T.; Gallagher, D. J. J. Am. Chem. Soc. 1993,
115, 10628–10636.
(53) Yuan, K.; Zhang, T. K.; Hou, X. L. J. Org. Chem. 2005, 70,
6085–6088.
(54) Evans, D. A.; Peterson, G. S.; Johnson, J. S.; Barnes, D. M.;
Campos, K. R.; Woerpel, K. A. J. Org. Chem. 1998, 63, 4541–4544.
(55) Volpe, E. C.; Chadeayne, A. R.; Wolczanski, P. T.; Lobkovsky,
E. B. J. Organomet. Chem. 2007, 692, 4774–4783.

Article
Organometallics, Vol. 29, No. 24, 2010 6645
(Zn(PhOx)2)50,56 and the oxazoline chloride species “ClZn-
(κ-C,N-4,4-Me2-2-(o-C6H4)oxazoline)” (ClZnPhOx), which,
in THF, could be construed as dimeric or a THF adduct, as
Scheme 2 illustrates.
First-row transition metal chlorides MCl2 (M = Mn, Fe, Co)
were chosen as an initial survey group to see whether the
lithium or zinc reagents could be effective metalation agents.
As Scheme 2 reveals, neither the lithium nor the zinc com-
pounds proved to be useful in the set of reactions conducted.
While paramagnetic products, some crystalline, were obtained,
the material was isolated in low yields (,50%), and the
coupled dimer of 4,4-dimethyl-(2-o-C6H4)-2-oxazoline was
identified in solution by 1H NMR spectral comparisons.57
A
blue-green crystal from the cobalt reaction was subjected to
single-crystal X-ray analysis, and, as suspected, the species
was identified as the N,N-adduct of {4,4-Me2-(2-o-C6H4)-
2-oxazoline}2,[κ-N,N-{4,4-Me2-(2-o-C6H4)-2-oxazoline}2]CoCl2
(1-Co). Apparently, metalation and reductive elimination, or
electron transfer and coupling, generated the organic dimer,
which was then scavenged by remaining CoCl2 in solution.
Although the conditions were varied, direct metalation with
these reagents (and other MX2) seemed remote, and the
approach was abandoned without further assay of the Mn
and Fe materials.
Figure 2. Molecular view of one of the two independent molecules
of [κ-N,N-{4,4-Me2-(2-o-C6H4)-2-oxazoline}2]CoCl2 (1-Co; mole-
˚
cule containing Co2 is not shown). Pertinent interatomic distances (A)
and angles (deg) and similar parameters in the Co2 molecule:
Co1N1,N2, 2.042(4), 2.045(4); Co2N3,N4, 2.037(4), 2.052(4);
Co1Cl1,Cl2, 2.2380(16), 2.2569(16); Co2Cl3,Cl4, 2.2189(15),
2.2486(16); N1C3,C1, 1.272(6), 1.495(6); N2C16,C18, 1.281(6),
1.505(6); N3C25,C23, 1.275(6), 1.490(6); N4C38,C40, 1.296(6),
1.503(6); N1Co1N2, 118.61(15); N3Co2N4, 118.12(16);
Cl1Co1Cl2, 115.05(6); Cl3Co2Cl4, 114.23(6); N1Co1Cl1,Cl2,
103.13(12), 109.98(11); N2Co1Cl1,Cl2, 108.25(12), 102.35(12);
N3Co2Cl3,Cl4, 106.07(12), 109.98(12); N4Co2Cl3,Cl4, 108.01(12),
100.72(12). Pertinent torsional angles (deg): N1C3C4C9, 60.3(7);
N3C25C26C31, 63.9(7); C4C9C10C15, 119.2(7); C26C31C32C37,
113.6(7); N2C16C15C10, 59.9(2); N4C38C37C32, 59.3(7).
2. Structure of [K-N,N-{4,4-Me2-(2-o-C6H4)-2-oxazoline}2]-
CoCl2 (1-Co). Figure 2 illustrates one of the two [κ-N,N-
(2-o-C6H4-4,4-Me2-2-oxazolyl)2]CoCl2 (1-Co) molecules in
the asymmetric unit, and Table 1 lists crystallographic and
refinement parameters. Despite the modest data quality, the
structure serves its purpose by revealing the oxidatively coupled
κ-N,N-(2-o-C6H4-4,4-Me2-2-oxazolyl)2 group bound to the
Co via the nitrogens of the oxazolines.58 Average CoN and
˚
CoCl bond lengths of 2.044(6) and 2.241(16) A, respectively,
are within reason for a pseudotetrahedral Co(II) center.
There are modest variations in the angles about the two
independent molecules. While the NCoN and ClCoCl angles
average 118.4(3)° and 114.6(6)°, respectively, the sets of
NCoCl angles reveal deviations: N1Co1Cl1,2 = 103.13(12)°,
109.98(11)°, N2Co1Cl1,2 = 108.25(12)°, 102.35(12)°,
N3Co2Cl3,4 = 106.07(12)°, 109.98(12)°, N4Co2Cl3,4 =
108.01(12)°, 100.72(12)°. The differences merely reflect the
ease of distortion in weak field, tetrahedral complexes and
are of little consequence. The molecular C2 symmetry of each
unit derives from the twist of the κ-N,N-(2-o-C6H4-4,4-Me2-
2-oxazolyl)2 group, which possesses oxazolyl-phenyl N-C-
C-C and phenyl-phenyl C-C-C-C dihedral angles of
roughly 60° and 116°, respectively.
o-Metalation of the phenyl group to give traditional anionic
equivalents of 4,4-dimethyl-2-(o-MC6H4CH2)oxazoline, where
M = Li, MgX, or ZnX/R, is prevented due to the acidity of these
protons. Transition metal bases may react in a similar vein.
In order to test these suspicions with a starting material
60
that would likely afford a diamagnetic product, Ti(NMe2)4
was treated with PhCH2Ox according to eq 1. Intact phenyl
resonances and a singlet corresponding to the lone vinylic H
at δ 5.81 accompanied methyl singlets in a 12:6:6 H ratio in
the 1H NMR spectrum of the product, consistent with
(Me2N)3Ti(η-N-(4,4-dimethyl-2-oxazoline)) (2). As a
4,4-Dimethyl-2-benzyloxazoline: Metalation Attempts. The
preceding efforts suggested that the bite angle of the potential
chelate κ-C,N-4,4-dimethyl-2-(o-phenyl)oxazoline (PhOx)
may be too small, thereby promoting reductive elimination.
Next, the 4,4-dimethyl-2-benzyloxazoline (PhCH2Ox) ligand
precursor was assayed for heterolytic CH bond activation with
various metal halides and species containing ligands of greater
basicity such as Fe{N(SiMe3)2}2(THF) and Fe{N(SiMe3)2}3.59
While color changes to orange and yellow solutions, respectively,
were evident, protolytic quenches of the material returned intact
PhOx, and the protons of the benzyl unit were suspect.
check on the spectral assignments, the known61 2-pyridyl
equivalent of PhCH2Ox, 2-pyCH2Ox, was treated with half
(56) Berman, A. M.; Johnson, J. S. J. Org. Chem. 2006, 71, 219–224.
(57) Nagano, T.; Hayashi, T. Org. Lett. 2005, 7, 491–493.
(58) For an interesting structural comparison, see: Kermagoret, A.;
Braunstein, P. Dalton Trans. 2008, 585–587.
(59) Olmstead, M. M.; Power, P. P.; Shoner, S. C. Inorg. Chem. 1991,
30, 2547–2551.
(60) Bradley, D. C.; Thomas, I. M. J. Chem. Soc. 1960, 3857–3861.
(61) Fryzuk, M. D.; Jafarpour, L.; Rettig, S. J. Tetrahedron: Asymmetry
1998, 9, 3191–3202.

6646 Organometallics, Vol. 29, No. 24, 2010
Volpe et al.
Table 1. Crystallographic Data for [K-N,N-(o-C6H4-4,4-Me2-2-oxazolyl)2]CoCl2 (1-Co), [{κ-N,O-C6H4CMe2CdNCMe2CH2(μ-O)-}
BrFe{κ-N,O-C6H4CMe2CdNCMe2CH2(μ-O)-}FeBr]Li{κ-N,O-C6H4CMe2CdNCMe2CH2(μ-O)-}(DME) (5-Fe2Li), [{κ-C,N-{(o-C6H4)-
CMe2(COCH2C-Me2N)}Cr]2(μ-Cl)2 (62), and {κ-C,N-{(o-C6H4)CMe2(COCH2CMe2N)}Fe(py)Cl (7)
b
1-Coa
5-Fe2Li
62
7c
formula
fw
space group
C22H24N2O2Cl2Co
478.29
P21/n
C50H72N3O7Br2Fe2Li
1105.59
P1
C28H36N2O2Cl2Cr2
607.49
P21/c
C22H26N2OClFe
425.75
P21/c
Z
a, A
b, A
˚
c, A
8
2
2
4
˚
˚
15.555(3)
10.169(2)
28.108(6)
90
90.88(3)
90
4445.8(15)
1.429
1.033
13.7059(10)
14.3972(10)
15.3609(11)
68.213(3)
84.999(4)
75.078(4)
2719.6(3)
1.350
2.051
173(2)
0.71073
R1 = 0.0639
wR2 = 0.1732
R1 = 0.1196
wR2 = 0.2031
1.037
6.9943(10)
26.459(4)
8.1697(11)
90
104.974(5)
90
1460.6(4)
1.381
0.954
203(2)
0.71073
R1 = 0.0534
wR2 = 0.1344
R1 = 0.0798
wR2 = 0.1499
1.052
15.8720(7)
9.0323(4)
15.5493(8)
90
109.904(3)
90
2096.00(17)
1.349
0.860
173(2)
0.71073
R1 = 0.0530
wR2 = 0.1408
R1 = 0.0774
wR2 = 0.1561
1.048
R, deg
β, deg
γ, deg
3
˚
V, A
F
calc, g cm-3
μ, mm-1
temp, K
173(2)
˚
λ (A)
0.71073
R1 = 0.0532
wR2 = 0.1027
R1 = 0.1215
wR2 = 0.1143
0.979
R indices [I > 2σ(I)]d,e
R indices (all data)d,e
GOFf
a Two molecules in the asymmetric unit. b One-half of the dimer in the asymmetric unit. c Asymmetric unit contains 1/2 of a C6H6 molecule. d R1 =
P
P
P
P
P
Fo| - |Fc
number of parameters.
/
|Fo|. e wR2 = [ w(|Fo| - |Fc|)2/ wFo
]
2 1/2. f GOF (all data) = [ w(|Fo| - |Fc|)2/(n - p)]1/2, n = number of independent reflections, p =
an equivalent of Fe{N(TMS)2}(THF)59 in the hope of mak-
ing a related bis-chelate according to eq 2. A cherry red solu-
tion occurred immediately in benzene-d6, and the 1H NMR
spectrum revealed free HN(TMS)2 and resonances of para-
magnetic material tentatively assigned to bis-N,N0-(4,4-dimethyl-
(2-pyridylmethylyl)oxazoline)Fe (3), including diastereotopic
methyl and methylene signals. Forays with Ti and Fe into
utilization of the oxazoline with the methylene backbone were
convincing enough with respect to CH2 deprotonation that
PhCH2Ox was abandoned as a prospective ligand.
4,4-Dimethyl-2-(2-phenylpropan-2-yl)oxazoline. 1. Oxidative
Addition Attempts with BrPhCMe2Ox. Heterolytic ArH bond
activation attempts with 4,4-dimethyl-2-(2-phenylpropan-2-yl)-
oxazoline (HPhCMe2Ox) and various metal halides and tri-
flates did not yield tractable products; often starting material
was recovered. Oxidative addition of 4,4-dimethyl-2-(2-(2-Br-
phenyl)propan-2-yl)oxazoline (BrPhCMe2Ox) to the proto-
typical metal reagent, Ni(COD)2,62 in toluene afforded [{κ-C,
N-(o-C6H4)CMe2(COCH2CMe2N)}Ni]2(μ-Br)2 (42) in 80%
yield as a dark pink solid (eq 3). The compound was
tentatively formulated as simple nitrogen adducts, “{(o-C6H4)-
CMe2(COCH2CMe2N)}2FeX2”, was isolated, subsequent
reductions failed to elicit tractable products.
2. Metathesis Attempts with LiPhCMe2Ox. While utiliza-
tion of BrPhCMe2Ox as a ligand precursor via oxidative addi-
tion is limited by choice of metal starting materials, especially if
carbonyl complexes, etc., are to be avoided because of potential
reactivity at the metal-carbon bond targeted, anion equiva-
lents are typically more versatile. As delineated above, 4,4-
dimethyl-2-(2-(2-Li-phenyl)propan-2-yl)oxazoline (LiPhCMe2Ox)
was prepared upon lithiation of the corresponding bromide for
use in metathesis reactions.
When LiPhCMe2Ox was generated in THF at -78 °C,
then warmed to 23 °C, the lithium reagent apparently rear-
ranged to a benzocyclobutanimine via internal attack at the
oxazoline CdN bond, followed by oxazoline C-O bond
opening to ultimately produce the alkoxide, C6H4[CMe2CdN]-
CMe2CH2OLi(THF)n. When cooled back to -78 °C and
treated with FeBr2, the alkoxide was trapped via metathesis
and the product that crystallized from DME was identified as
the mustard-yellow trinuclear complex [{κ-N,O-C6H4CMe2Cd
NCMe2CH2(μ-O)-}BrFe{κ-N,O-C6H4CMe2CdNCMe2CH2-
(μ-O)-}FeBr]Li{κ-N,O-C6H4CMe2-CdNCMe2CH2(μ-O)-}-
(DME) (5-Fe2Li), as shown in Scheme 3. When held at -78 °C
for 3 h, the lithiation reaction does produce LiPhCMe2Ox,
which was used in metathesis with ZnCl2 to afford the zinc
reagent (PhCMe2Ox)2Zn in 78% yield. Apparently reaction
with ZnCl2 occurs swiftly enough at -78 °C such that rearrange-
ment of the lithium reagent does not interfere with chloride
displacement. In order to avoid rearrangement complications,
(PhCMe2Ox)2Zn was exploited as a metathesis reagent.
3. Structure of 5-Fe2Li. Information about the data col-
lection and crystal refinement is given in Table 1, and a
molecular view of 5-Fe2Li is given in Figure 3 along with
pertinent core distances and angles. The structure serves to
confirm the intramolecular benzocyclobutanimine forma-
tion, as two such entities chelate the irons and a third chelates
the lithium. The pseudotetrahedral iron centers possess dis-
tances expected for Fe(II), and the cores are distorted primarily
sparingly soluble in toluene, THF, or CH2Cl2, but dissolved in
acetonitrile to give yellow-orange solutions. It is likely that the pur-
ported dimer, 42, is cleaved to give {κ-C,N-(o-C6H4)CMe2(CO-
CH2CMe2N)}NiBr(NCMe) (4-NCMe) and that the spectral
characterization in acetonitrile-d3 isofthisdiamagneticderivative.
Attempts to induce oxidative addition of BrPhCMe2Ox to
FeX2 (X = Cl, Br) through disproportionation of the iron
species;a method that was used with modest success in
these laboratories63;failed in this instance. While material
(62) Krysan, D. J.; Mackenzie, P. B. J. Org. Chem. 1990, 55, 4229–
4230.
(63) Frazier, B. A.; Wolczanski, P. T.; Lobkovsky, E. B. Inorg. Chem.
2009, 131, 11576–11585.

Article
Organometallics, Vol. 29, No. 24, 2010 6647
Scheme 3
number of equivalents of (PhCMe2Ox)2Zn resulted in the
transfer of only one aryl oxazoline to form the purple dimer
[{κ-C,N-(o-C6H4)CMe2(COCH2CMe2N)}Cr]2(μ-Cl)2 (62) in
40% yield upon crystallization from hot benzene. Solubility
in nonpolar solvents hampered 1H NMR spectral character-
ization of the dimer; hence its structure was determined by
X-ray crystallography. The dimer readily dissolved in THF,
but the observed paramagnetic spectral features are best
construed as those of the turquoise THF adduct {κ-C,N-
(o-C6H4)CMe2(COCH2CMe2N)}CrCl(THF) (6-THF). Square-
planar Cr(II) compounds are relatively common, and 62 and
6-THF are clear examples.65-69 Room-temperature Gouy
balance measurement of the susceptibility of 62 afforded a
μ
eff of 5.0 μB for the dimer. A μeff of 6.9 would be expected
for Cr(II) centers that were noninteracting, and a value of 8.9
would represent fully coupled Cr(II) cores; hence modest
antiferromagnetic coupling is probable.65-68 The THF ad-
duct 6-THF yielded a μeff of 4.9 in solution as measured by
Evans’ method, consistent with a normal high-spin S = 2
configuration. All attempts to transfer an additional oxazo-
line unit to 6-THF with (PhCMe2Ox)2Zn failed, with recov-
ery of starting material at low temperatures and evidence of
reduction at higher temperatures. Other anion equivalents,
e.g., LiPhCMe2Ox, whose rearrangement is a probable inter-
ference, have also failed to yield tractable products thus far.
Figure 3. Structure of 5-Fe2Li with solvent molecules removed.
Only those atoms of the bound DME that were not severely
˚
disordered are shown. Distances (A) and angles (deg) pertaining
to the metal cores: Fe1Br1, 2.4085(7); Fe2Br2, 2.4469(7); Fe1O1,
1.909(3); Fe1O2, 2.009(2); Fe2O2, 1.924(3); Fe2O3, 1.929(3);
Fe1N2, 2.125(3); Fe2N3, 2.122(3); Li1O1, 1.966(7); Li1O3,
1.915(7); Li1O4, 1.992(9); Li1N1, 2.112(7); O1Fe1O2, 111.89(11);
O1Fe1N2, 116.35(12); O2Fe1N2, 80.74(11); O1Fe1Br1, 118.13(8);
O2Fe1Br1, 110.08(8); N2Fe1Br1, 113.49(9); O2Fe2O3, 116.61(11);
O2Fe2N3, 124.91(12); O3Fe2N3, 82.40(12); O2Fe2Br2,
108.84(8); O3Fe2Br2, 117.20(9); N3Fe2Br2, 105.05(8); O1Li1O3,
109.0(3); O3Li1O4, 111.6(3); O1Li1O4, 115.3(4); O3LI1N1, 117.2(3);
O1Li1N1, 85.6(2); O4Li1N1, 115.7(3); Fe1O1Li1, 121.5(2);
Li1O3Fe2, 116.1(2); Fe1O2Fe2, 119.75(13).
70
The addition of 1 equiv of (PhCMe2Ox)2Zn to FeCl2(py)4
failed to transfer both oxazoline anion equivalents, but yielded,
upon crystallization from benzene, yellow {κ-C,N-{(o-C6H4)-
CMe2(COCH2CMe2N)}Fe(py)Cl (7, 50%), which was
1
structurally characterized by X-ray crystallography. H NMR
spectroscopic investigations of the product mixture revealed
a diamagnetic byproduct, presumably [ZnCl(ArOx)]2, and
the paramagnetic product. An Evans’ method measurement
of 7 provided a μeff of 4.7 μB, consistent with an S = 2 center
(65) Sydora, O. L.; Wolczanski, P. T.; Lobkovsky, E. B.; Buda, C.;
Cundari, T. R. Inorg. Chem. 2005, 44, 2606–2618.
(66) Sydora, O. L.; Kuiper, D. S.; Wolczanski, P. T.; Lobkovsky,
E. B.; Dinescu, A.; Cundari, T. R. Inorg. Chem. 2006, 45, 2008–2021.
(67) Edema, J. J. H.; Gambarotta, S.; van Bolhuis, F.; Smeets,
W. J. J.; Spek, A. L. Inorg. Chem. 1989, 28, 1407–1410.
(68) Edema, J. J. H.; Gambarotta, S.; van Bolhuis, F.; Spek, A. L.
J. Am. Chem. Soc. 1989, 111, 2142–2147.
via the chelate bite angles of the alkoxyimine ligand, which are
80.74° (11, Fe1) and 82.40° (12, Fe2).
4. Metathesis Attempts with (PhCMe2Ox)2Zn. Rearrange-
ment issues that surfaced during the employment of LiPhC-
Me2Ox were obviated through utilization of the zinc reagent
(PhCMe2Ox)2Zn, but a curious problem remained. Treat-
ment of chromous chloride as its THF adduct64 with any
(69) Terry, K. W.; Gantzel, P. K.; Tilley, T. D. Inorg. Chem. 1993, 32,
5402–5404.
(70) Golding, R. M.; Mok, K. F.; Duncan, J. F. Inorg. Chem. 1966, 5,
774–778.
(64) Kern, R. J. J. Inorg. Nucl. Chem. 1962, 24, 1105–1109.

6648 Organometallics, Vol. 29, No. 24, 2010
Volpe et al.
Scheme 4
with little orbital contribution. Attempts to put two oxazo-
lines on iron have met with some resistance. A new set of
paramagnetic resonances arises when 7 is treated with
LiPhCMe2Ox that was generated in situ, and the same set
71
is observed when FeBr2(THF)2 is exposed to 2 equiv of
LiPhCMe2Ox (in situ). The 1H NMR spectrum revealed four
broad 3H singlets consistent with two sets of diastereotopic
CMe2 units. A quench of the material (C6H6/H2O) derived
from 7 afforded HPhCMe2Ox, but no py; hence it is tentatively
formulated as {κ-C,N-(o-C6H4)CMe2(COCH2CMe2N)}2Fe (8)
based on 1H NMR shifts comparable to 7.
In one instance, 1 equiv of (PhCMe2Ox)2Zn has success-
fully been utilized to transfer both oxazolines. Treatment of
NiCl2(DME)72 with (PhCMe2Ox)2Zn generated pale orange,
diamagnetic {κ-C,N-(o-C6H4)CMe2(COCH2CMe2N)}2Ni (9)
in modest yield (25%) upon crystallization from an ether/
THF mixture. Its NMR spectra indicated that both CMe2
groups and the CH2 on the oxazoline have diastereotopic
substituents; hence the molecule is illustrated as having a
rippled structure55 that deviates from a simple square-planar
arrangement. Attempts to observe coalescence of the dia-
stereotopic protons were thwarted by decomposition at
80 °C, but since ready exchange was not seen, it is likely that a
simple turnstile exchange of the two oxazolines is not evident,
perhaps due to the steric interactions when an oxazoline CMe2
group swings past the phenyl of the other ligand. In addition,
a turnstile process would require the intermediacy of a pseudo-
square-planar intermediate of significantly higher energy.
5. Structure of [{K-C,N-(o-C6H4)CMe2(COCH2CMe2N)}-
Cr]2(μ-Cl)2 (62). The molecular structure of [{κ-C,N-(o-C6H4)-
CMe2(COCH2CMe2N)}Cr]2(μ-Cl)2 (62) is illustrated in Figure 4,
while pertinent details of the data collection are listed in
Figure 4. Molecular view of [{κ-C,N-(o-C6H4)CMe2(COCH2-
˚
CMe2N)}Cr]2(μ-Cl)2 (62). Distances (A) and angles (deg) of the
core: Cr1Cr1A, 3.5369(9); Cr1N1, 2.071(3); Cr1C10, 2.091(4);
Cr1Cl1, 2.4362(13); Cr1Cl1A, 2.3638(13); N1Cr1C10, 87.20(14);
N1CrCl, 93.82(10); N1Cr1Cl1A, 173.58(11); C10CrCl1, 171.55(12);
C10CrC1A, 94.82(11); Cl1CrCl1A, 85.08(4); Cr1Cl1Cr1A,
94.92(4).
distances listed in the caption of Figure 4 reveal no surprises
for a standard Cr(II) square-planar system.65-69 Note that
the sp3 center of the CMe2 unit spanning the Ph and oxazo-
line portions of the ligand gives the bidentate chelate a
“fold”, such that one CMe2 group is below the square plane
and the Ci-related CMe2 unit on the adjacent half of the
dimer is above it.
6. Structure of {K-C,N-(o-C6H4)CMe2(COCH2CMe2N)}-
Fe(py)Cl (7). Figure 5 illustrates the molecular skeleton of
{κ-C,N-(o-C6H4)CMe2(COCH2CMe2N)}Fe(py)Cl (7), and
the parameters affiliated with data collection and refinement
are given in Table 1. While the bond distances of the core
listed in the caption of Figure 5 are normal, the angles of the
core reveal a significant distortion from tetrahedral geom-
etry. The bite angle of the chelate is 95.73(13)°, significantly
larger than the 87.20(14)° angle it exhibits in the structure of
the chromium(II) dimer, 62, but still less than the 109.5°
expected for tetrahedral coordination. The Cl-Fe-C angle
˚
Table 1. The chromiums are at 3.5369(9) A from each other,
which is a distance that can accommodate antiferromagnetic
coupling interactions. The molecule possesses Ci symmetry,
which is also observed crystallographically, such that both
halves are equivalent. The remainder of the core is quite
regular, with all angles within 5° of 90°, and the bond
(71) Ittel, S. D.; English, A. D.; Tolman, C. A.; Jesson, J. P. Inorg.
Chim. Acta 1979, 33, 101–106.
(72) Ward, L. G. Inorg. Synth. 1971, 13, 154–164.

Article
Organometallics, Vol. 29, No. 24, 2010 6649
Figure 5. Molecular view of {κ-C,N-(o-C6H4)CMe2(COCH2-
˚
CMe2N)}Fe(py)Cl (7). Distances (A) and angles (deg) of the
core: Fe1C1, 1.984(4); Fe1N1, 2.053(3); Fe1N2, 2.090(3);
Fe1Cl1, 2.2797(8); N1Fe1Cl1, 107.74(8); N1Fe1N2, 105.43(11);
N1FeC1, 95.73(13); Cl1Fe1N2, 101.26(7); Cl1FeC1, 134.14(10);
N2FeC1, 109.82(13).
is splayed to 134.14(10)°, while the Cl-Fe-N1 and -N2
angles of 107.74(8)° and 101.26(7)° are slightly less than the
norm for a tetrahedron. The pyridine N2 is 105.43(11)° from
the N1 of the chelate and 109.82(13)° from the C1 of the
phenyl. So it appears that the CNNFe unit is roughly
pyramidal, albeit with angles less than the tetrahedral norm,
and the Cl is bent away from the phenyl and slightly toward
the pyridine. The latter distortion does not correspond to an
obvious steric interaction, but may alleviate some of the
antibonding character of the d orbital that is highest in
energy, which should be the one carrying the brunt of the
Fe-C σ* character.
Figure 6. Ligand field of {κ-C,N-(o-C6H4)CMe2(COCH2-
CMe2N)}2Ni (9) generated via DFT calculations.
Discussion
The work described above illustrates many of the methods
and accompanying pitfalls of utilizing the aryl-oxazoline
ligands in complexing first-row transition metals. Hetero-
lytic and other CH bond activations designed at complexa-
tion have thus far been unsuccessful, and potential five-
membered ring chelates suffered the fate of being oxidatively
coupled by MX2 starting materials, a common reaction. An
increase in the ring size of the chelate demanded that the
acidic CH2 unit coupling the aryl with the oxazoline be
exchanged for a CMe2 group, since complexation accompa-
nied by deprotonation was observed in test cases involving
titanium and iron.
7. Calculations on {K-C,N-(o-C6H4)CMe2(COCH2-
CMe2N)}2Ni (9). Since suitable crystals for an X-ray analysis
of {κ-C,N-(o-C6H4)CMe2(COCH2CMe2N)}2Ni (9) were not
obtained, a brief calculational study of the molecule was
undertaken. As Figure 6 reveals, the optimized geometry of 9
is the expected distorted square-planar C2 configuration:
˚
˚
d(NiCox) = 2.024 A, d(NiCAr) = 1.926 A, CoxNiCox = 103.7°,
CArNiCAr = 98.6°, bite angle CoxNiCAr = 94.1°. Despite the
significant distortion from pseudo-square-planar geometry,
the d orbital splitting diagram clearly reveals a “one over four”,
low-spin configuration that suggests the aryl-oxazoline is
imparting a strong field, in accord with the premise of the proj-
ect. While the ΔE = E(dx2-y2) - E(dxz) gap of >31 000 cm-1
is probably an overestimation derived from the usual DFT
problems in assessing the energies of virtual orbitals, the
number is consistent with the diamagnetic nature of the com-
plex and the strong field character of aryl ligands. The C2
arrangement ensures that the two dimethyl fragments and the
methylene group are diastereotopic, rendering four inequiva-
lent methyls and inequivalent methylene protons. Attempts
to locate the pseudo-square-planar intermediate that would
allow the diastereotopic groups to become equivalent were not
realized, but the square-planar species would not minimize;
hence it is a plausible transition state for the rearrangement. It is
also estimated to be >30 kcal/mol above the ground-state
structure, consistent with the NMR data.
The {κ-C,N-(o-C6H4)CMe2(COCH2CMe2N)} chelate was
successfully utilized in the synthesis of several compounds
containing Cr, Fe, and Ni. Aside from two diamagnetic
examples involving nickel, the remaining compounds were
not low spin. While this fact may seem discouraging in light
of the proposed utilization of carbon-based ligands as pro-
genitors of strong fields, the low coordination number com-
pounds realized in this study present difficulties in assessing
the project. For example, the d orbital splittings of {κ-C,
N-(o-C6H4)CMe2(COCH2CMe2N)}Fe(py)Cl (7) are intrin-
sically small because of pseudotetrahedral coordination and
the presence of only one Fe-Ar bond. The fold of the ligand
that is intrinsic to the sp3 nature of the CMe2 linkage between
phenyl and oxazoline units has consequences with regard to
the orientation of the Ar and N donation; hence the chelate
can vary its bite angle. This can be advantageous in adapting
the best configuration for a particular metal, but the CMe2
group may present a subtle steric problem for the addition
of other {κ-C,N-{(o-C6H4)CMe2(COCH2CMe2N)} units or

6650 Organometallics, Vol. 29, No. 24, 2010
Volpe et al.
other ligands. It was encouraging that the calculation of
{κ-C,N-(o-C6H4)CMe2(COCH2CMe2N)}2Ni (9) revealed
a ligand field splitting diagram consistent with that of a
square-planar species, despite the severe C2 distortion of the
complex. Clearly the presence of two M-Ar bonds has a
profound influence on the field about the metal, just as
proposed. Efforts to introduce related oxazoline-based che-
lates into octahedral settings are ongoing.
flushed with argon and charged with 15 mL of SOCl2. A 13
mmol amount of R,R-dimethylarylacetic acid (aryl = Ph, a;
2-BrPh, b) was added, and the solution heated to reflux for
3 h. The cooled mixture was then concentrated and triturated
with CH2Cl2 (2 ꢀ 5 mL). The oily product was dissolved in
15 mL of CH2Cl2. A solution of 2-amino-2-methyl-1-propanol
(1.39 g, 15.6 mmol) and NEt3 (2.72 mL, 19.5 mmol) in 20 mL
of CH2Cl2 was cooled to 0 °C. The acid chloride solution was
added dropwise under argon. The reaction was allowed to
warm slowly to 23 °C over 4 h and stirred for an addition 10 h.
The mixture was washed first with H2O (20 mL) then with
brine (20 mL), and the organics were dried over MgSO4,
filtered, and concentrated. The crude product was recrystal-
lized from 6:1 hexanes/ethyl acetate to yield a white, crystal-
line solid (90% after 3 crops).
Experimental Section
General Considerations. For metal complexes, manipulations
were performed using either glovebox or high-vacuum techniques.
Ligand syntheses were performed under argon using Schlenk
techniques. Hydrocarbon and ethereal solvents were dried over
and vacuum transferred from sodium benzophenone ketyl (with
3-4 mL of tetraglyme/L added to hydrocarbons). Methylene
chloride was distilled from and stored over CaH2. Benzene-d6
and toluene-d8 were sequentially dried over sodium and stored
over sodium. THF-d8 was dried over sodium benzophenone
A 10 mmol amount of the above amide, 4-(dimethylamino)-
pyridine (110 mg, 0.9 mmol), and NEt3 (3.1 mL, 22 mmol) were
dissolved in 30 mL of CH2Cl2. A solution of p-toluenesulfonyl
chloride in 20 mL of CH2Cl2 was added via syringe under argon.
After stirring at 23 °C for 2 days, the reaction mixture was
diluted with CH2Cl2 and extracted with saturated NH4Cl fol-
lowed by aqueous NaHCO3. The organic layer was dried over
MgSO4, treated with decolorizing carbon, filtered, and concen-
trated. The crude product was purified by flash chromatography
˚
keyl. Acetonitrile-d3 was dried over CaH2 and stored over 4 A
molecular sieves. The compounds 4,4-dimethyl-(2-benzyl)-
oxazoline (PhCH2Ox),51 Ti(NMe2)4,60 Fe{N(TMS)2}2(THF),59
Ni(COD)2,62 FeBr2(THF)2,71 CrCl2(THF),64 FeCl2(py)4,70 and
NiCl2(DME)72 were prepared according to literature proce-
dures. SOCl2 (Aldrich) was used immediately or distilled prior
1
(6:1 hexanes/ethyl acetate) to give a clear oil (65%). H NMR
(400 MHz, benzene-d6): δ 7.45 (d, J = 8, 1H), 7.18 (d, J = 8.0,
1H), 6.93 (t, J = 8, 1H), 6.66 (t, J = 8, 1H), 3.63 (s, 2H), 1.72
(s, 6H), 1.19 (s, 6H). 13C NMR (400 MHz, benzene-d6): δ 170.24,
144.75, 135.31, 128.59, 128.22, 127.81, 124.84, 79.82, 67.73,
42.86, 28.58, 27.94.
˚
to use; NEt3 (Aldrich) was dried and stored over 4 A molecular
sieves; ZnCl2 was dried according to a literature procedure;73 all
other reagents were purchased and used as received. All glass-
ware was oven-dried.
3. Zn(K-C,N-4,4-Me2-(o-C6H4)-2-oxazoline)2 (Zn(PhOx)2).
LiPhOx (1.99 g, 10.98 mmol) and ZnCl2 (0.75 g, 5.50 mmol)
were added to a 100 mL round-bottom flask to which 50 mL of
toluene was vacuum transferred at -78 °C. The mixture was
stirred at -78 °C for ∼4 h and allowed to warm to 23 °C over
10 h. After subsequent filtration and washing of the salt cake
with toluene, the solvent was removed. The product was triturated
(2 ꢀ 5 mL of pentane) and filtered in pentane, leaving a white
1Hand13C{1H} NMR spectra were obtained using Mercury-300,
Inova-400, and Inova-500 spectrometers, and chemical shifts are
reported relative to benzene-d6 (1H δ 7.16; 13C{1H} δ 128.39),
THF-d8 (1H δ 3.58; 13C{1H} δ 67.57), acetonitrile-d3 (1H δ 1.94;
13C{1H} δ 1.79), and toluene-d8 (1H δ 2.09; 13C{1H} δ 20.40).
Solution magnetic measurements were conducted via Evans’
method74 in benzene-d6 or toluene-d8. Solid-state magnetic
measurements were performed using a Johnson Matthey mag-
netic susceptibility balance calibrated with HgCo(SCN)4. Com-
bustion analyses were performed by Robertson Microlit
Laboratories, Madison, NJ, and by services at the University
of Erlangen-Nuremberg, Germany. Difficulties in obtaining
satisfactory and consistent values for the organometallic com-
pounds were noted; those reported were obtained for the purest
samples as determined from spectroscopic (principally NMR)
methods.
1
solid (1.82 g, 80%). H NMR (400 MHz, benzene-d6): δ 8.07
(d, J = 7.2, 1H), 8.03 (d, J = 8.0, 1H), 7.44 (t, J = 7.2, 1H), 7.22
(t, J = 7.6, 1H), 3.73 (s, 2H), 0.86 (s, 6H). 13C NMR (500 MHz,
benzene-d6): δ 173.64, 168.30, 139.61, 135.29, 131.70, 128.68,
125.87, 125.45, 82.43, 65.13, 28.52. Anal. Calcd for C22H24-
N2O2Zn: C, 63.95; H, 5.85; N, 6.77. Found: C, 63.60; H, 5.59;
N, 6.75.
4. [K-N,N-{4,4-Me2-(2-o-C6H4)-2-oxazoline}2]CoCl2 (1-Co).
A 500 mg portion of LiPhOx (2.74 mmol) and 178 mg of CoCl2
(1.37 mmol) were added to a 50 mL round-bottom flask to which
ether (25 mL) was vacuum transferred at -78 °C. The reaction
mixture was allowed to stir at -78 °C for 2 h, then warmed
slowly to 23 °C over 10 h. The mixture was filtered in ether,
stripped, triturated with hexanes (2 ꢀ 5 mL), and filtered to yield
a blue-green solid (395 mg, 60%). X-ray diffraction quality
Syntheses. 1. 4,4-Dimethyl-(2-pyridylmethyl)-2-oxazoline
(2-pyCH2Ox). To a solution of 2-pyridylacetonitrile75 (440 mg,
3.72 mmol) and 2-amino-2-methylpropanol (663 mg, 7.45 mmol)
in 10 mL of toluene was added 50 mg (0.186 mmol) of Cd(OAc)2
3
2H2O. The mixture was allowed to reflux under argon for 10 h.
After washing with H2O, the crude mixture was extracted with
CH2Cl2, dried over MgSO4, filtered, and concentrated to a light
brown oil. The crude oil was distilled under reduced pressure to
yield a yellow oil (70%). 1H NMR (400 MHz, benzene-d6): δ 8.43
(d, 1H, J = 4), 7.12 (d, 1H, J = 8), 7.02 (t, 1H, J = 8), 6.56 (t, 1H,
J = 6), 3.84 (s, 2H), 3.53 (s, 2H), 1.09 (s, 6H).
1
crystals were grown from THF/hexanes. H NMR (400 MHz,
benzene-d6): δ 7.61 (d, J = 8, 1H), 7.12 (m, 1H), 7.01 (t, J = 8,
1H), 6.81 (d, J = 8, 1H), 3.78 (s, 1H), 3.75 (s, 1H), 1.56 (s, 3H),
0.65 (s, 3H).
5. (NMe2)3Ti{η-N-(4,4-Me2-2-(CHPh)oxazolidine)} (2). A mix-
ture of Ti(NMe2)4 (500 mg, 2.23 mmol) and PhCH2Ox (423 mg,
2.23 mmol) in 20 mL of benzene was heated at 100 °C in a bomb
reaction vessel for 7 days. The solvent was removed to obtain a red-
orange oil. Addition of diethyl ether (20 mL) led to precipitation
of an orange solid, which was filtered and washed with ether (3 ꢀ
10 mL) to afford 240 mg (29%). 1H NMR (400 MHz, benzene-d6):
δ 7.32 (t, 2H, J = 7), 7.21 (d, 2H, J = 7), 7.05 (t, 1H, J = 7), 5.81
(s, 1H), 4.13(s, 2H),3.14(s, 12H), 2.55(s, 6H),1.30(s, 6H).13C{1H}
NMR (500 MHz, benzene-d6): δ 158.85, 141.84. 128.92, 128.53,
123.66, 102.14, 85.82, 66.47, 46.35, 42.44, 26.84.
2. 4,4-Dimethyl-2-(2-arylpropan-2-yl)-2-oxazoline (aryl = Ph,
HPhCMe2Ox; 2-BrPh, BrPhCMe2Ox). HPhCMe2Ox has
been synthesized previously.38 Herein both HPhCMe2Ox
and BrPhCMe2Ox were both synthesized via the following
modified procedure. A 50 mL three-neck round-bottom flask
fitted with a reflux condenser and external oil bubbler was
(73) Pray, A. R. Inorg. Synth. 1990, 28, 321–322.
(74) (a) Evans, D. F. J. Chem. Soc. 1959, 2003–2005. (b) Schubert,
E. M. J. Chem. Ed. 1992, 69, 62.
(75) Klapars, A.; Waldman, J. H.; Campos, K. R.; Jensen, M. S.;
McLaughlin, M.; Chung, J. Y. L.; Cvetovich, R. J.; Chen, C. Y. J. Org.
Chem. 2005, 70, 10186–10189.
6. Bis{N,N0-(4,4-dimethyl-(2-pyridylmethylyl)oxazoline)}Fe (3).
A benzene-d6 solutionofFe{N(TMS)2}2(THF) (20 mg, 0.045 mmol)

Article
Organometallics, Vol. 29, No. 24, 2010 6651
was added to 2-pyCH2Ox (17 mg, 0.089 mmol) in an NMR
tube. Upon addition, the solution turned cherry red. 1H NMR
(400 MHz, benzene-d6): δ 189.64 (s, 1H), 53.89 (s, 1H), 51.07
(s, 1H), 23.75 (s, 1H), 10.29 (s, 1H), -12.09 (s, 1H), -21.72
(s, 1H), -37.67 (s, 3H), -47.90 (s, 3H).
Zn(PhCMe2Ox)2 (250 g, 0.502 mmol) was distilled 15 mL of
THF at -78 °C. The suspension was stirred at -78 °C for 5 h,
allowed to warm to 23 °C, and stirred an additional 36 h. The
golden brown solution was filtered and washed (2 ꢀ 10 mL). The
filtrate was concentrated, cooled, and filtered cold to yield 100 mg
of yellow solid (52%). X-ray diffraction quality crystals were
grown by hot filtration and recrystallization from benzene.
b. BrPhCMe2Ox (250 mg, 0.844 mmol) in 5 mL of THF was added
7. [{K-C,N-(o-C6H4)CMe2(COCH2CMe2N)}Ni]2(μ-Br)2 (42).
A solution of BrPhCMe2Ox (108 mg, 0.365 mmol) in 5 mL
of toluene was added to Ni(COD)2 (100 mg, 0.365 mmol) at
-78 °C. Warming slowly to room temperature led to the forma-
tion of a pink precipitate. After stirring at 23 °C for ∼4 h, the
resulting dark pink solid was isolated by filtration and washing
several times with toluene (49 mg, 80%). The compound is only
sparingly soluble in toluene, THF, or dichloromethane, but
dissolves in acetonitrile to give an orange-yellow solution, which
is presumably {κ-C,N-(o-C6H4)CMe2(COCH2CMe2N)}NiBr-
(NCMe) (4-NCMe). 1H NMR (500 MHz, acetonitrile-d3): δ 7.17
(br s, 1H), 6.89 (d, J = 5.5, 1H), 6.83 (t, J = 7.2, 1H), 6.72 (t, J =
6.3, 1H), 4.01 (s, 2H), 2.43 (s, 6H), 1.38 (s, 6H). 13C NMR (500
MHz, acetonitrile-d3): δ 179.13, 149.04, 143.95, 138.62, 124.76,
124.45, 123.10, 82.60, 68.62, 44.59, 28.94, 27.70 (see Supporting
Information). Anal. Calcd for C28H36N2O2Ni: C, 47.38; H, 5.11;
N, 3.95. Found: C, 46.92; H, 4.92, N, 3.70.
n
to a solution of BuLi (0.58 mL, 1.6 M in hexanes) in 10 mL
of THF at -78 °C under argon. After 2 h at -78 °C, FeCl2(py)4
(374 mg, 0.844 mmol) was added via addition finger. The reaction
was kept at -78 °C for 5 h and then allowed to warm to 23 °C over
10 h. The yellow-brown reaction mixture was stripped, triturated
with benzene (2 ꢀ 5 mL), filtered, and washed several times (2 ꢀ
15 mL). Concentration of the solvent yielded a crystalline yellow
1
material, which was collected by filtration (190 mg, 58%). H
NMR (400 MHz, benzene-d6): δ 266.41 (1H), 246.08 (1H), 162.10
(2H), 137.15 (1H), 130.91 (1H), 80.85 (1H), 77.15 (1H), 42.38 (3H),
19.15 (2H), 15.36 (3H), -15.94 (2H), -32.35 (1H), -35.33 (3H).
Anal. Calcd for C19H23N2OClFe: C, 59.01; H, 6.00; N, 7.24.
Found: C, 59.01; H, 5.91; N, 5.73. μeff = 4.7 μB (Evans’ method
in C6D6).
13. {K-C,N-(o-C6H4)CMe2(COCH2CMe2N)}2Fe (8). a.BrPhC-
Me2Ox (46 mg, 0.155 mmol) in 2 mL of THF was added to a
solution of nBuLi (0.11 mL, 1.6 M in hexanes) in 5 mL of THF at
-78 °C. After 2 h at -78 °C, 7 (60 mg, 0.155 mmol) was added
via an addition finger. The reaction was allowed to warm to 23 °C
over 10 h. The light brown mixture was stripped of solvent,
triturated (2 ꢀ 5 mL) with Et2O, dissolved in 20 mL of Et2O, and
filtered through Celite. Yellow microcrystalline material was obtained
from a concentrated Et2O solution. b. BrPhCMe2Ox (170 mg,
8. [{K-N,O-C6H4-CMe2CdNCMe2CH2-(μ-O)}BrFe{K-N,O-
C6H4-CMe2CdNCMe2CH2(μ-O)}FeBr]Li{K-N,O-C6H4-CMe2Cd
NCMe2CH2-(μ-O)}(DME) (5-Fe2Li). nBuLi (0.21 mL, 1.6 M in
hexanes) was added to a solution of BrPhCMe2Ox (100 mg,
0.338 mmol) in 20 mL of THF at -78 °C under argon. This was
allowed to warm over 4 h and was stirred for an additional hour at
23 °C. The solution was cooled to -78 °C, and FeBr2(THF)2 (61mg,
0.169 mmol) added via addition finger. The reaction was kept at
-78 °C for 4 h and then allowed to warm slowly to 23 °C. The
reaction was filtered, stripped, triturated with pentane (2 ꢀ 5 mL),
and filtered to give 67 mg of mustard-yellow solid (43%). Red, X-ray
diffraction quality crystals were grown from a cold solution of DME.
9. (PhCMe2Ox)2Zn. nBuLi (0.42 mL, 1.6 M in hexanes) was
added to a solution of BrPhMe2Ox (200 mg, 0.676 mmol) in
40 mL of THF at -78 °C under argon. After 3 h at -78 °C,
ZnCl2 (46 g, 0.338 mmol) was added via addition finger. The
reaction was kept at -78 °C for at least 4 h and warmed to 23 °C
over 4 h. The reaction mixture was stripped, triturated with
benzene, and filtered, and the salt cake washed several times
(4ꢀ 30 mL). The mixture was stripped and triturated with pentane,
yielding 131 mg (78%) of white solid, which was collected by
filtration. 1H NMR (500 MHz, benzene-d6): δ 8.09 (dd, J = 6.5,
2.0, 1H), 7.49 (d, J = 7.0, 1H), 7.38-7.25 (m, 2H), 3.31 (s, 2H),
1.85 (s, 6H), 0.89 (s, 6H). 13C NMR (500 MHz, benzene-d6):
δ 177.88, 162.09, 151.94, 140.46, 125.79, 125.28, 123.59, 78.79,
68.34, 43.80, 31.00, 28.01. Anal. Calcd for C28H36N2O2Zn: C,
67.53; H, 7.29; N, 5.63. Found: C, 67.26; H, 7.50; N, 5.38.
10. [{K-C,N-(o-C6H4)CMe2(COCH2CMe2N)}Cr]2(μ-Cl)2 (62).
To a mixture of [CrCl2(THF)]2 (98 mg, 0.251 mmol) and Zn-
(PhCMe2Ox)2 (250 mg, 0.502 mmol) was distilled 15 mL of THF
at -78 °C. The suspension was stirred at -78 °C for 5 h and
warmed to 23 °C over 4 h. The resulting blue solution was filtered
through Celite and stripped. Trituration with benzene (2 ꢀ 5 mL)
resulted in formation of a purple solid (61 mg, 40%). X-ray
diffraction quality crystals were grown by hot filtration and
recrystallization from benzene. 1H NMR (400 MHz, benzene-
d6): δ17.17, 16.13, 14.00, 1.60, -2.86, -11.80, -77.80. Anal. Calcd
for C28H36N2O2Cl2Cr2: C, 55.36; H, 5.97; N, 4.61. Found: C,
55.73; H, 5.79; N, 4.06. μeff = 5.0 at 295 K (Gouy balance).
11. {K-C,N-(o-C6H4)CMe2(COCH2CMe2N)}CrCl(THF)
(6-THF). Purple 62 dissolves in THF to give a blue solution.
Evaporation of solvent gives a dark blue solid, presumably the
monomeric THF adduct. If dissolved in THF-d8, the NMR
n
0.556 mmol) in 2 mL of THF was added to a solution of BuLi
(0.38 mL, 1.6 M in hexanes) in 10 mL of THF at -78 °C. After 2 h at
-78 °C, FeBr2(THF)2 (100 mg, 0.278 mmol) was added via an
addition finger. The reaction was allowed to warm to 23 °C over
10 h. The mixture was stripped of all volatiles, triturated with Et2O
(2 ꢀ 5 mL), and filtered through Celite. Evaporation of the solvent
led to a tan solid with spectral features similar to the yellow material
above, but neither method affords pure material. 1HNMR(400MHz,
benzene-d6): δ 212.17 (1H), 139.71 (1H), 70.12 (1H), 19.70 (3H),
16.64 (1H), 13.29 (1H), -14.32 (3H), -29.03 (3H), -29.57 (1H),
-38.16 (3H).
14. {K-C,N-(o-C6H4)CMe2(COCH2CMe2N)}2Ni (9). To a mix-
ture of NiCl2(DME) (88 mg, 0.282 mmol) and Zn(PhCMe2Ox)2
(200 mg, 0.282 mmol) was distilled 25 mL of THF at -78 °C.
The yellow suspension was stirred at -78 °C for 5 h and slowly
warmed to room temperature. The resulting orange solution was
stripped, triturated with ether, and filtered to give a peach-colored
solid. The solid was recrystallized from an ether/THF mixture
1
to give a pale orange crystalline solid (34 mg, 25%). H NMR
(500 MHz, benzene-d6): δ 7.23 (δ, J = 7.2, 1H), 7.13 (d, J = 7.7,
1H), 6.98 (t, J = 7.3, 1H), 6.85 (t, J = 7.1, 1H), 3.66 (s, 3H), 3.36
(d, J= 8.1, 1H), 3.12 (d, J= 8.1, 1H), 1.81 (s, 3H), 0.94 (s, 3H), 0.69
(s, 3H). 13C NMR (500 MHz, benzene-d6): δ 177.82, 171.46, 148.36,
143.17, 124.28, 121.62, 121.20, 79.35, 68.97, 45.03, 35.51, 27.91,
25.47, 23.19 (see Supporting Information). Anal. Calcd for
C28H36N2O2Ni: C, 68.45; H, 7.39; N, 5.70. Found: C, 68.36; H,
7.30; N, 5.62.
Single-Crystal X-ray Diffraction Studies. Upon isolation, the
crystals were covered in polyisobutenes and placed under a 173
K N2 stream on the goniometer head of a Siemens P4 SMART
CCD area detector (graphite-monochromated Mo KR radia-
˚
tion, λ = 0.71073 A). The structures were solved by direct
methods (SHELXS). All non-hydrogen atoms were refined
anisotropically unless stated, and hydrogen atoms were treated
as idealized contributions (Riding model).
15. [K-N,N-{4,4-Me2-(2-o-C6H4)-2-oxazoline}2]CoCl2 (1-Co).
A blue-green prism (0.20 ꢀ 0.15 ꢀ 0.10 mm) was obtained from
THF. A total of 31 094 reflections were collected with 6389 being
symmetry independent (Rint = 0.1368), and 3233 were greater
1
spectrum shows a set of broad, paramagnetic peaks. H NMR
(400 MHz, THF-d8): δ 20.64, 17.86, 10.00, -2.00, -2.83, -16.55,
-79.06. μeff = 4.9 (Evans’ method in THF-d8).
12. {K-C,N-(o-C6H4)CMe2(COCH2CMe2N)}Fe(py)Cl (7).
a. To a mixture of FeCl2(py)4 (223 g, 0.502 mmol) and

6652 Organometallics, Vol. 29, No. 24, 2010
Volpe et al.
from equivalents was applied, and the refinement utilized w-1
than 2σ(I). A semiempirical absorption correction from equiva-
lents was applied, and the refinement utilized w-1 = σ2(Fo2) þ
=
σ2(Fo ) þ (0.0858p)2 þ 0.827p, where p = (Fo þ 2Fc2)/3.
Computational Details. The geometry of compound [bis-
oxazoline] was optimized and the electronic structure was
calculated using the Orca76 software package. The hybrid func-
tional B3LYP was used with the GTO basis sets published by the
Ahlrichs group.77-79 The triple-ζ basis set def2-TZVP(-f) was
used for nickel, and the remaining atoms were treated with the
double-ζ split-valence basis set def2-SV(P). The RIJCOSX
approximation80 was used to speed up calculations using an
auxiliary basis set that matched the orbital basis.
2
2
2
2
(0.0350p)2 þ 0.0p, where p = (Fo þ 2Fc )/3.
16. [{K-N,O-C6H4-CMe2CdNCMe2CH2-(μ-O)}BrFe{K-N,O-
C6H4-CMe2CdNCMe2CH2-(μ-O)}FeBr]Li{K-N,O-C6H4-
CMe2CdNCMe2CH2-(μ-O)}(DME) (5). A red block (0.10 ꢀ
0.10 ꢀ 0.03 mm) was obtained from DME. A total of 57 092 reflec-
tions were collected, with 13 571 being symmetry independent
(Rint = 0.0764), and 8050 were greater than 2σ(I). A semiempirical
absorption correction from equivalents was applied, and the
2
refinement utilized w-1 = σ2(Fo ) þ (0.1000p)2 þ 3.0822p, where
2
2
p = (Fo þ 2Fc )/3.
17. [{K-C,N-(4,4-Dimethyl-2-(2-phenylpropan-2-yl)oxazoline)}-
Cr]2(μ-Cl)2 (62). A purple block (0.30 ꢀ 0.15 ꢀ 0.05 mm) was
obtained from benzene. A total of 9496 reflections were col-
lected, with 2092 being symmetry independent (Rint = 0.0463), and
1516 were greater than 2σ(I). A semiempirical absorption correc-
tion from equivalents was applied, and the refinement utilized
Acknowledgment. We thank the National Science
Foundation (CHE-0718030) and Cornell University for
financial support, Prof. Karsten Meyer of the University
Erlangen-Nuremberg for experimental assistance, and
Elliott B. Hulley for the calculations.
w-1 = σ2(Fo ) þ (0.0727p)2 þ 2.5196p, where p = (Fo þ 2Fc2)/3.
18. {K-C,N-(4,4-Dimethyl-2-(2-phenylpropan-2-yl)oxazoline)}-
Fe(η-N-pyridyl)Cl (7). A yellow block (0.40 ꢀ 0.15 ꢀ 0.05 mm) was
obtained from benzene. A total of 20 134 reflections were collected,
with 3968 being symmetry independent (Rint = 0.0814), and 2930
were greater than 2σ(I). A semiempirical absorption correction
2
2
Supporting Information Available: CIF files of 1-Co, 5-Fe2Li,
62, and 7. This material is available free of charge via the Internet
at http://pubs.acs.org.
€
(77) Schafer, A.; Horn, H.; Ahlrichs, R. J. Chem. Phys. 1992, 97, 2571.
€
(78) Schafer, A.; Huber, C.; Ahlrichs, R. J. Chem. Phys. 1994, 100,
5829.
(76) Neese, F. Orca, an ab initio, DFT and Semiempirical Electronic
Structure Package, Version 2.7, Revision 0; Institut f€ur Physikalische und
(79) Weigend, F.; Ahlrichs, R. Phys. Chem. Chem. Phys. 2005, 7, 3297.
(80) Neese, F.; Wennmohs, F.; Hansen, A.; Becker, U. Chem. Phys.
2009, 356, 98.
€
Theoretische Chemie, Universitat Bonn: Bonn, Germany, August 2009.