Transition metal complexes supported by a neutral tetraamine ligand containing N, N-dimethylaniline units

Article abstract of DOI:10.1021/ic1008347

First-row transition metal-halide complexes of tris(2-dimethylaminophenyl) amine, L^Me, have been synthesized and characterized. X-ray crystallographic studies on [Co(L^Me)Br]BPh₄, [Ni(L ^Me)Cl]BPh₄, [Fe(L^Me)Cl]BPh₄, and [Cu(L^Me)Cl]BF₄ have been performed, and in all cases the ligand produces five-coordinate complexes with distorted trigonal bipyramidal coordination geometries. Where possible, comparisons have been made to the structures of related neutral tripodal ligands. Spectroscopic and magnetic studies of these complexes are also described. The Cu(I)-carbonyl complexes [Cu(L^Me)(CO)]PF₆ and [Cu(Me₆tren)(CO)]PF ₆ (Me₆tren = tris(N,N-dimethylaminoethyl)amine) have also been prepared. Infrared spectroscopic investigations of these carbonyl complexes confirm that L^Me is a less electron donating ligand than Me ₆tren and indicate that L^Me can impart a different coordination number in the solid-state.

Full text of DOI:10.1021/ic1008347

Inorg. Chem. 2010, 49, 7521–7529 7521
DOI: 10.1021/ic1008347
Transition Metal Complexes Supported by a Neutral Tetraamine Ligand Containing
N,N-dimethylaniline Units
Lei Chu, Kenneth I. Hardcastle, and Cora E. MacBeth*
Department of Chemistry, Emory University, Atlanta, Georgia 30322
Received April 27, 2010
First-row transition metal-halide complexes of tris(2-dimethylaminophenyl)amine, LMe, have been synthesized and
characterized. X-ray crystallographic studies on [Co(LMe)Br]BPh4, [Ni(LMe)Cl]BPh4, [Fe(LMe)Cl]BPh4, and [Cu(LMe)Cl]-
BF4 have been performed, and in all cases the ligand produces five-coordinate complexes with distorted trigonal
bipyramidal coordination geometries. Where possible, comparisons have been made to the structures of related
neutral tripodal ligands. Spectroscopic and magnetic studies of these complexes are also described. The Cu(I)-
carbonyl complexes [Cu(LMe)(CO)]PF6 and [Cu(Me6tren)(CO)]PF6 (Me6tren = tris(N,N-dimethylaminoethyl)amine)
have also been prepared. Infrared spectroscopic investigations of these carbonyl complexes confirm that LMe is a less
electron donating ligand than Me6tren and indicate that LMe can impart a different coordination number in the solid-state.
Introduction
extensively in biomimetic copper4-15 and iron16-23 chemistry
and as supporting scaffolds for copper-mediated atom-trans-
fer radical polymerization (ATRP).24-31 Some of the most
familiar ligands in this class include tris(2-aminoethyl)amine
(tren), tris(N,N-dimethylaminoethyl)amine (Me6tren), and
tris(2-pyridylmethyl)amine (TMPA), Chart 1.
Research in the area of multidentate ligand design is
motivated by the tenet that ancillary ligands play important
roles in regulating metal ion reactivity by influencing the
geometric, steric, and electronic features of the coordinated
metal ions.1 Within this field, neutral, tripodal, tetraamine
ligands have been widely studied.1-3 They have been utilized
(15) Karlin, K. D.; Hayes, J. C.; Juen, S.; Hutchinson, J. P.; Zubieta, J.
Inorg. Chem. 1982, 21(11), 4106–4108.
(16) Britovsek, G. J. P.; England, J.; White, A. J. P. Inorg. Chem. 2005,
44(22), 8125–8134.
(17) Lim, M. H.; Rohde, J.-U.; Stubna, A.; Bukowski, M. R.; Costas, M.;
Ho, R. Y. N.; Munck, E.; Nam, W.; Que, L. Jr. Proc. Natl. Acad. Sci. U. S.
A. 2003, 100(7), 3665–3670.
(18) Jensen, M. P.; Lange, S. J.; Mehn, M. P.; Que, E. L.; Que, L., Jr.
J. Am. Chem. Soc. 2003, 125(8), 2113–2128.
(19) Que, L., Jr.; Dong, Y. Acc. Chem. Res. 1996, 29(4), 190–196.
(20) Mandon, D.; Machkour, A.; Goetz, S.; Welter, R. Inorg. Chem. 2002,
41(21), 5364–5372.
(21) Diebold, A.; Hagen, K. S. Inorg. Chem. 1998, 37(2), 215–223.
(22) Chen, K.; Que, L., Jr. J. Am. Chem. Soc. 2001, 123(26), 6327–
6337.
(23) Costas, M.; Que, L., Jr. Angew. Chem., Int. Ed. 2002, 41(12), 2179–
2181.
(24) Cohen, N. A.; Tillman, E. S.; Thakur, S.; Smith, J. R.; Eckenhoff,
W. T.; Pintauer, T. Macromol. Chem. Phys. 2009, 210(3-4), 263–268.
(25) Baisch, U.; Poli, R. Polyhedron 2008, 27(9-10), 2175–2185.
(26) Pintauer, T.; Braunecker, W.; Collange, E.; Poli, R.; Matyjaszewski,
K. Macromolecules 2004, 37(8), 2679–2682.
*To whom correspondence should be addressed. E-mail: cora.macbeth@
emory.edu.
(1) Pettinari, C.; Marchetti, F.; Drozdov, A. Compr. Coord. Chem. II
2004, 1, 211–251.
(2) Blackman, A. G. Eur. J. Inorg. Chem. 2008, 17, 2633–2647.
(3) Blackman, A. G. Polyhedron 2005, 24(1), 1–39.
(4) Suzuki, M. Acc. Chem. Res. 2007, 40(7), 609–617.
(5) Komiyama, K.; Furutachi, H.; Nagatomo, S.; Hashimoto, A.; Hayashi,
H.; Fujinami, S.; Suzuki, M.; Kitagawa, T. Bull. Chem. Soc. Jpn. 2004, 77(1),
59–72.
(6) Hatcher, L. Q.; Karlin, K. D. Adv. Inorg. Chem. 2006, 58, 131–184.
(7) Dittler-Klingemann, A. M.; Hahn, F. E. Inorg. Chem. 1996, 35(7),
1996–1999.
(8) Karlin, K. D.; Kim, E. Chem. Lett. 2004, 33(10), 1226–1231.
(9) Becker, M.; Heinemann, F. W.; Schindler, S. Chem.;Eur. J. 1999,
5(11), 3124–3129.
(10) Wuertele, C.; Sander, O.; Lutz, V.; Waitz, T.; Tuczek, F.; Schindler,
S. J. Am. Chem. Soc. 2009, 131(22), 7544–7545.
(11) Lee, Y.; Park, G.-Y.; Lucas, H. R.; Vajda, P. L.; Kamaraj, K.; Vance,
M. A.; Milligan, A. E.; Woertink, J. S.; Siegler, M. A.; Narducci Sarjeant,
A. A.; Zakharov, L. N.; Rheingold, A. L.; Solomon, E. I.; Karlin, K. D.
Inorg. Chem. 2009, 48(23), 11297–11309.
(12) Fry, H. C.; Lucas, H. R.; Narducci Sarjeant, A. A.; Karlin, K. D.;
Meyer, G. J. Inorg. Chem. 2008, 47(1), 241–256.
(13) Wuertele, C.; Gaoutchenova, E.; Harms, K.; Holthausen, M. C.;
Sundermeyer, J.; Schindler, S. Angew. Chem., Int. Ed. 2006, 45(23), 3867–
3869.
(14) Hatcher, L. Q.; Karlin, K. D. J. Biol. Inorg. Chem. 2004, 9(6),
669–683.
(27) Matyjaszewski, K.; Xia, J. Chem. Rev. 2001, 101(9), 2921–2990.
(28) Wang, J.-S.; Matyjaszewski, K. J. Am. Chem. Soc. 1995, 117(20),
5614–5615.
(29) Pintauer, T.; Matyjaszewski, K. Chem. Soc. Rev. 2008, 37(6), 1087–
1097.
(30) Pintauer, T.; Matyjaszewski, K. Coord. Chem. Rev. 2005, 249
(11-12), 1155–1184.
(31) Eckenhoff, W. T.; Pintauer, T. Catal. Rev. - Sci. Eng. 2010, 52(1), 1–59.
r
2010 American Chemical Society
Published on Web 07/21/2010
pubs.acs.org/IC

7522 Inorganic Chemistry, Vol. 49, No. 16, 2010
Chu et al.
Chart 1
tetradentate ligand system that incorporates o-phenylenedia-
mine donors into the ligand backbone.39 We speculated that
the incorporation of the o-phenylenediamine unit into a tripo-
dal ligand would result in a more rigid, chelating tetraamine
framework that could display non-innocent behavior.40 Fur-
ther functionalization of tris(2-aminophenyl)amine to form
trianionic tris(amidate)amine39,41-43 and tris(amido)amine
ligands43-46 has since been described, but uncharged ligands
based on the N(o-PhNH2)3 unit that lack reactive protons
have remained unexplored. In an effort to create neutral,
tetradentate, tripodal ligand systems that produce metal
complexes with more rigid solution and solid-state topologies
and possess different electronic properties from their corre-
sponding alkyl amine and pyridyl counterparts, we sought
to synthesize and explore the coordination chemistry of
N(o-PhNMe2)3, LMe. We chose to target the hexamethyl deriva-
tive because methyl substituents are relatively small, and we
wanted to make a direct comparison with Me6tren. We
anticipated that any differences observed between LMe and
Me6tren could be attributed to the incorporation of the rigid
aryl backbone. Here, we describe the synthesis, coordination
chemistry, and spectral properties of later, first-row transi-
tion metal ions supported by LMe. The MII-halide complexes,
[MII(LMe)X]þ, of this ligand have been compared to similar
complexes supported by tetradentate ligands that incorpo-
rate alkyl units or pyridine rings into the five-membered,
chelating rings. The spectroscopic and magnetic properties
for the [MII(LMe)X]þ series of complexes have been measured
and used to provide information about the ligand field strength
of LMe. Finally, the Cu(I) carbonyl complexes of LMe and
Me6tren ([Cu(LMe)(CO)]þ and [Cu(Me6tren)(CO)]þ) have
been synthesized, characterized, and compared with other
Cu(I)-carbonyl complexes supported by tetraamine donor
ligands. These carbonyl complexes have been used to probe the
electron releasing nature of this class of ligands and to highlight
differences in their solid-state and solution-state topologies.
Recent research in the areas of dioxygen activation by
Cu(I)4-6,8,11,13,32-34 and hydrogen peroxide activation by
Fe(II)16,35-37 complexes has demonstrated that the electronic
and steric requirements of the tetraamine ligands play a
crucial role in regulating the reactivity of these complexes.
For example, Karlin and co-workers synthesized a series of
electronically varied ligands based on the TMPA scaffold by
introducing non-hydrogen substituents into the 4-pyridyl
position of the ligand, TMPAR.38 In weakly coordinating
solvents they found that the ligands with the greatest electron
donating ability (i.e., TMPAOMe and TMPANMe2) increased
the thermodynamic stability of the resulting [(TMPAR)-
CuII(O2-)]þ and [{(TMPAR)Cu}2(μ-1,2-O22-)]2þ complexes
and decreased the dissociation rates of these species. These
results were expected because dioxygen binding to Cu(I)
centers is a redox process that requires oxidation to Cu(II),
which would be favored by more electron-releasing ligand
scaffolds. In other work, Britovsek and co-workers investi-
gated the reactivity of hydrogen peroxide with a series of
Fe(II) bis(triflate) complexes supported by neutral, tetra-
amine ligands as alkane oxidation catalysts.16,37 They found
that the solution-state structures of the bis(triflate) complexes
and the mechanism of alkane oxidation was dependent on the
chelating ligands. These studies demonstrated that ligands
containing two or more pyridyl groups favored six-coordinate
species and prevented Fenton-type reaction chemistry.16 Sub-
sequent studies by these researchers using magnetic and spectro-
scopic studies confirmed that ligand rigidity and, therefore,
catalyst stability under oxidizing conditions is a key deter-
minant in the overall catalytic activity of these species.37
Our group recently reported the coordination chemistry
of Co(II) with tris(2-aminophenyl)amine, N(o-PhNH2)3, a
Results and Discussion
Syntheses. The neutral tetraamine ligand tris(2-dimethyl-
aminophenyl)amine, N(o-PhNMe2)3 (LMe), was synthe-
sized in good yield by reductive methylation47,48 of the pri-
mary amine precursor, N(o-PhNH2)3, (Scheme 1). The ligand
can be recrystallized from hot methanol to yield analytically
pure material. The LMe scaffold was used to synthesize five
first-row transition metal complexes, including four cationic
species with the general formula [M(LMe)X]þ (where M=
FeII, CoII, NiII, or CuII and X = Cl- or Br-). A general
(39) Jones, M. B.; MacBeth, C. E. Inorg. Chem. 2007, 46(20), 8117–8119.
(40) Warren, L. F. Inorg. Chem. 1977, 16(11), 2814–2819.
(41) Jones, M. B.; Newell, B. S.; Hoffert, W. A.; Hardcastle, K. I.; Shores,
M. P.; MacBeth, C. E. Dalton Trans. 2010, 39(2), 401–410.
(42) Jones, M. B.; Hardcastle, K. I.; MacBeth, C. E. Polyhedron 2010,
29(1), 116–119.
(43) Paraskevopoulou, P.; Ai, L.; Wang, Q.; Pinnapareddy, D.; Acharyya,
R.; Dinda, R.; Das, P.; Celenligil-Cetin, R.; Floros, G.; Sanakis, Y.; Choudhury,
A.; Rath, N. P.; Stavropoulos, P. Inorg. Chem. 2010, 49(1), 108–122.
(44) Celenligil-Cetin, R.; Paraskevopoulou, P.; Lalioti, N.; Sanakis, Y.;
Staples, R. J.; Rath, N. P.; Stavropoulos, P. Inorg. Chem. 2008, 47(23),
10998–11009.
(32) Schatz, M.; Becker, M.; Thaler, F.; Hampel, F.; Schindler, S.;
Jacobson, R. R.; Tyeklar, Z.; Murthy, N. N.; Ghosh, P.; Chen, Q.; Zubieta,
J.; Karlin, K. D. Inorg. Chem. 2001, 40(10), 2312–2322.
(33) Maiti, D.; Fry, H. C.; Woertink, J. S.; Vance, M. A.; Solomon, E. I.;
Karlin, K. D. J. Am. Chem. Soc. 2007, 129(2), 264–265.
(34) Lucas, H. R.; Li, L.; Narducci Sarjeant, A. A.; Vance, M. A.;
Solomon, E. I.; Karlin, K. D. J. Am. Chem. Soc. 2009, 131(9), 3230–3245.
(35) England, J.; Davies, C. R.; Banaru, M.; White, A. J. P.; Britovsek,
G. J. P. Adv. Synth. Catal. 2008, 350(6), 883–897.
(36) England, J.; Britovsek George, J. P.; Rabadia, N.; White Andrew,
J. P. Inorg. Chem. 2007, 46(9), 3752–3767.
(45) Celenligil-Cetin, R.; Paraskevopoulou, P.; Dinda, R.; Lalioti, N.;
Sanakis, Y.; Rawashdeh, A. M.; Staples, R. J.; Sinn, E.; Stavropoulos, P.
Eur. J. Inorg. Chem. 2008, 5, 673–677.
(37) England, J.; Gondhia, R.; Bigorra-Lopez, L.; Petersen, A. R.; White,
A. J. P.; Britovsek, G. J. P. Dalton Trans. 2009, 27, 5319–5334.
(38) Zhang, C. X.; Kaderli, S.; Costas, M.; Kim, E.-i.; Neuhold, Y.-M.;
Karlin, K. D.; Zuberbuehler, A. D. Inorg. Chem. 2003, 42(6), 1807–1824.
(46) Celenligil-Cetin, R.; Paraskevopoulou, P.; Dinda, R.; Staples, R. J.;
Sinn, E.; Rath, N. P.; Stavropoulos, P. Inorg. Chem. 2008, 47(3), 1165–1172.
(47) Borch, R. F.; Hassid, A. I. J. Org. Chem. 1972, 37(10), 1673–1674.
(48) Lane, C. F. Synthesis 1975, 3, 135–146.

Article
Inorganic Chemistry, Vol. 49, No. 16, 2010 7523
Scheme 1
Scheme 2
Figure 1. Thermal ellipsoid diagram of [HLMe]þ. All of the hydrogen
atoms except the acidic proton and the PF6 anion and have been
removed for clarity.
-
synthetic approach for the preparation of the FeII, CoII, and
NiII complexes is outlined in Scheme 2.
In a standard metalation procedure, the ligand and an
anhydrous metal dihalide salt were stirred together in
dichloromethane. In situ counteranion metathesis was
then performed by treating the reaction mixture with
1 equiv of sodium tetraphenylborate as a methanol solu-
tion. This procedure provides [Fe(LMe)Cl]BPh4, [Co-
(LMe)Br]BPh4, and [Ni(LMe)Cl]BPh4 in good yields
(60-90%). The copper analogue, [Cu(LMe)Cl]BF4, was
synthesized in a similar manner, except AgBF4 was used
in place of NaBPh4. In addition to metallating the ligand with
MII ions, we were also interested in exploring its coordi-
nation chemistry with Cu(I), given the utility of neutral
tetraamine ligands in Cu(I)-dioxygen chemistry. The Cu(I)
complex of LMe, [Cu(LMe)]þ, was synthesized by reacting
[Cu(CH3CN)4]PF6 directly with LMe in acetonitrile.
X-ray Crystallographic Studies. Attempts to isolate
X-ray quality crystals of LMe were unsuccessful. The mono-
protonated ligand salt, [HLMe]PF6, however, was readily
recrystallized from a mixture of tetrahydrofuran and diethyl
ether. The molecular structure of the cationic portion of this
species, [HLMe]þ, is shown in Figure 1. The acidic proton
(H1) was located in the difference map and refined isotropi-
cally. The molecular structure of the cation shows H1 resid-
ing on one of the N,N-dimethylaniline donors (N3). The
acidic proton is also interacting with two additional tertiary
amine donors (N1 and N2) through hydrogen bonding
Figure 2. Molecular structure of [Fe(LMe)Cl]BPh4 (A) and[Fe(Me6tren)Cl]-
BPh4 (B) drawn at 35% probability. Anions and hydrogen atoms have
been removed for clarity.
acetonitrile solution of the complex. The complex crystal-
lizes in the Pc space group. The molecular structure of
[Fe(LMe)Cl]þ, as determined by X-ray diffraction, is
shown in Figure 2A with selected bond lengths and angles
listed in Table 1. The equatorial plane about the iron is
composed of the three, N,N-dimethylaniline (ArNMe2)
donor groups. The axial positions are occupied by a
chloride ion and the apical tris(aryl)amine (Ar3N) donor
of the ligand backbone. The bond lengths and angles
found in [Fe(LMe)Cl]þ are similar to the bond lengths
and angles observed in [Fe(Me6tren)Cl]þ (Figure 2B), a
closely related iron complex derived from the tris(N,N-
dimethylaminoethyl)amine (Me6tren) scaffold. For exam-
interactions, as evidenced by the close N3 N2 and
N3 N1 through-space distances of 2.932(3) and
3 3 3
3 3 3
˚
2.797(3) A, respectively. The pyramidalization of the apical
nitrogen atom, N1, is approximately halfway between tri-
gonal planar and tetrahedral as the sum of the Cphenyl
-
P
0
N1-Cphenyl bond angles ( C-N1-C°) is 346.3°. This type
of pyramidalization is similar to what is observed in the
solid-state structure of tris(2-hydroxyphenyl)amine, N(o-
C6H4OH)3.49
The Fe(II) complex, [Fe(LMe)Cl]BPh4, was crystallized
as pale yellow needles by diffusing diethyl ether into an
˚
ple, the average Fe1-Nequatorial bond length of 2.182(4) A
(49) Kelly, B. V.; Tanski, J. M.; Anzovino, M. B.; Parkin, G. J. Chem.
Crystallogr. 2005, 35(12), 969–981.
displayed by [Fe(LMe)Cl]þ is slightly longer than the

7524 Inorganic Chemistry, Vol. 49, No. 16, 2010
Chu et al.
Table 1. Selected Bond Lengths (A) and Angles (deg) for [Fe(LMe)Cl]BPh4 and
[Fe(Me6tren)Cl]BPh4
The nickel complex, [Ni(LMe)Cl]BPh4, was crystallized
as green needles by the slow diffusion of diethyl ether into
a concentrated acetonitrile solution. The molecular struc-
ture of [Ni(LMe)Cl]þ is shown in Figure 3B, and pertinent
bond lengths and angles are listed in Table 2. The nickel
center in [Ni(LMe)Cl]þ sits in a distorted trigonal bipyr-
amidal coordination geometry (τ5 = 0.86). The average
˚
[Fe(LMe)Cl]þ
[Fe(Me6tren)Cl]þ
Fe1-Cl1
2.287(2)
2.241(4)
2.179(4)
2.177(4)
2.190(4)
177.15(11)
99.76(12)
104.43(10)
101.76(13)
78.60(15)
78.37(13)
77.31(15)
110.49(15)
115.23(14)
121.72(15)
2.3149(16)
2.234(4)
2.214(4)
2.185(4)
2.202(5)
Fe1-N1
Fe1-N2
Fe1-N3
˚
˚
Fe1-N4
Ni1-Nequatorial (2.110(3) A) and Ni1-Cl (2.267(1) A)
bond lengths displayed by [Ni(LMe)Cl]þ, are slightly
N1-Fe-Cl1
N2-Fe-Cl1
N3-Fe-Cl1
N4-Fe-Cl1
N1-Fe-N2
N1-Fe-N3
N1-Fe-N4
N2-Fe-N3
N3-Fe-N4
N2-Fe-N4
178.39(12)
99.10(12)
100.59(12)
99.58(13)
80.10(15)
81.02(15)
79.65(16)
116.58(16)
116.33(16)
118.67(16)
˚
shorter (ca. 0.02-0.03 A) than the corresponding bond
lengths displayed by the Ni(II) center in the correspond-
ing [Ni(Me6tren)Cl]þ complexes.52,53 The Ni(II) center in
[Ni(LMe)Cl]þ is distorted 0.29 A out of the equatorial
˚
plane toward the halide ligand.
The [Cu(LMe)Cl]BF4 was crystallized as light yellow-
green blocks from an acetonitrile/diethyl ether solution.
The copper(II) ion lies in a slightly distorted trigonal
bipyramidal coordination environment (τ5 = 0.97) and is
˚
average Fe1-Nequatorial bond length of 2.140(4) A ob-
served in the molecular structure of [Fe(Me6tren)Cl]þ.
˚
distorted 0.26 A out of the equatorial plane. The bond
˚
The axial Fe1-Cl bond length of 2.287(2) A observed in
lengths and angles are close to those observed in the
related [Cu(Me6tren)Cl]þ species (τ5 = 1.0).9,25 For ins-
tance, the average Cu1-Nequatorial bond length displayed
[Fe(LMe)Cl]þ is slightly shorter than the Fe1-Cl bond
þ
˚
length of 2.3149(16) A displayed by [Fe(Me6tren)Cl] ,
while the axial Fe1-N1 bond lengths displayed by both
complexes are very similar. The Fe(II) center in [Fe(LMe)Cl]þ
þ
by [Cu(LMe)Cl] is 2.144(3) A compared to 2.186(2) A for
˚
˚
[Cu(Me6tren)Cl]þ.
˚
is positioned 0.45 A above the equatorial plane while
The preceding X-ray diffraction studies demonstrate
that the LMe ligand can be used to stabilize five-coordi-
nate metal complexes with trigonal bipyramidal coordi-
nation geometries, and that these complexes have solid-
state molecular structures similar to those observed in
metal complexes supported by the closely related Me6tren
ligand. Like Me6tren, LMe appears to have enough steric
bulk to prevent the formation of octahedral metal
complexes.52 An important difference between the two
scaffolds, however, is that the LMe ligand scaffold gives
rise to FeII, NiII, and CuII complexes that display more
constrained Nequatorial-MII-N1 bond angles compared
to those observed in the corresponding [MII(Me6tren)X]þ
series of complexes. For each pair of complexes described
above, the average Nequatorial-MII-N1 bond angle in the
[M(LMe)X]þ complex was about 2° smaller than the
corresponding angle in the [MII(Me6tren)X]þ species.
We attribute the smaller Nequatorial-MII-N1 bond angles
(or bite angle) observed in the [M(LMe)X]þ series to the
slightly more constrained backbone afforded by the LMe
ligand framework
the Fe(II) center in [Fe(Me6tren)Cl]þ sits 0.37 A above
˚
the equatorial plane. The differences between the two
structures can be quantified by calculating the overall
five-coordinate structural parameter, τ5, displayed by the
complexes (where τ5=1.0 in an idealized trigonal bipyr-
amidal environment and τ5 =0.0 in an idealized square
pyramidal coordination geometry).50 The Fe(II) center in
[Fe(LMe)Cl]þ lies in a distorted trigonal bipyramidal
coordination geometry (τ5 = 0.92), whereas, the Fe(II)
center in [Fe(Me6tren)Cl]þ is held in an idealized trigonal
bipyramidal coordination geometry (τ5 = 1.0).
The structures of [Co(LMe)Br]BPh4, [Ni(LMe)Cl]BPh4,
and [Cu(LMe)Cl]BF4 were also determined by X-ray
diffraction studies. The results of these studies are shown
in Figure 3, and the metrical parameters for the three
complexes are listed in Table 2. For [Co(LMe)Br]BPh4,
Figure 1A, purple crystals were grown by slowly diffusing
ether into a concentrated acetonitrile solution of the
complex. The cobalt ion is situated in an idealized trigonal
bipyramidal coordination environment (τ5 = 1.0). The
bond lengths between the cobalt ion and the donor atoms
are very similar to the cobalt bond lengths displayed
by the structurally similar [Co(Me6tren)Br]Br complex
(τ5 = 1.0).25,51 For example, the Co1-Br and the average
Spectroscopic and Magnetic Properties of [MII(LMe)X]þ
Complexes. All complexes in this study were characterized
by infrared, UV-visible, and 1H NMR spectroscopies. The
infrared spectrum of the free ligand exhibits a medium
intensity C-N stretching band at 1314 cm-1 that shifts to
lower frequencies (1300-1255 cm-1) upon metal ion co-
ordination. The [Fe(LMe)Cl]BPh4 complex is colorless in
solution and gives rise to a paramagnetically broadened
1H NMR spectrum and a solution magnetic moment of
5.02 μB (CD3CN, 298 K) that is consistent with a high-spin,
S = 2 ground state. The [Co(LMe)Br]BPh4 species is violet
in solution and exhibits three absorption bands in its
UV-visible absorption spectrum and a magnetic moment
of 4.68 μB (CD3CN, 298 K). These data are consistent with
˚
Co1-Nequatorial bond lengths of 2.4167(4) A and
2.1306(19) A, respectively, in [Co(LMe)Br]þ are only
˚
slightly shorter than the corresponding bond lengths
˚
observed for [Co(Me6tren)Br]Br (2.4471(7) A and
˚
2.137(2) A, respectively). The axial Co1-N1 bond length
(2.2280(18) A) in [Co(LMe)Br]þ is somewhat elongated
˚
˚
(∼ 0.013 A) compared to the corresponding Co1-N1 bond
in [Co(Me6tren)Br]Br. The cobalt center in [Co(LMe)Br]þ
˚
is distorted 0.41 A above the equatorial plane formed by
the three equatorial amine nitrogen donors toward the
bromide ligand.
(50) Addison, A. W.; Rao, T. N.; Reedijk, J.; Van Rijn, J.; Verschoor,
G. C. J. Chem. Soc., Dalton Trans. 1984, 7, 1349–1356.
(51) Di Vaira, M.; Orioli, P. Inorg. Chem. 1967, 6(5), 955–957.
(52) Ciampolini, M.; Nardi, N. Inorg. Chem. 1966, 5(1), 41–44.
(53) Colpas, G. J.; Kumar, M.; Day, R. O.; Maroney, M. J. Inorg. Chem.
1990, 29(23), 4779–4788.

Article
Inorganic Chemistry, Vol. 49, No. 16, 2010 7525
Figure 3. Molecular structures of [Co(LMe)Br]BPh4 (A), [Ni(LMe)Cl]BPh4 (B), and [Cu(LMe)Cl]BF4 (C) drawn at 35% probability. Hydrogen atoms and
counteranions have been removed for clarity.
Table 2. Selected Bond Lengths (A) and Angles (deg) for [Co(LMe)Br]BPh4,
Table 3. Spectral Data for [Cu(Me6tren)Cl]þ, [Cu(TMPA)Cl]þ, and
˚
[Ni(LMe)Cl]BPh4, and [Cu(LMe)Cl]BF4
[Cu(LMe)Cl]þ in CH3CN
[Co(LMe)Br]þ
[Ni(LMe)Cl]þ
[Cu(LMe)Cl]þ
λ )
max/nm (ε/M-1 cm-1
M1-X1
2.4167(4)
2.2280(18)
2.1348(19)
2.1339(19)
2.123(2)
2.2667(13)
2.114(3)
2.135(3)
2.080(3)
2.114(3)
2.2121(8)
2.0512(18)
2.131(3)
2.140(3)
2.160(3)
[Cu(Me6tren)Cl]þ
[Cu(TMPA)Cl]þ
[Cu(LMe)Cl]þ
740 (187), 932 (440)a
632sh (90), 962 (210)b
782 (146), 1033 (306)c
M1-N1
M1-N2
M1-N3
a Ref 5. b Ref 15. c This work.
M1-N4
N1-M1-X1
N2-M1-X1
N3-M1-X1
N4-M1-X1
N1-M1-N2
N1-M1-N3
N1-M1-N4
N2-M1-N3
N3-M1-N4
N2-M1-N4
178.22(5)
100.07(5)
100.63(5)
102.54(5)
78.90(7)
78.67(7)
79.24(7)
117.97(8)
115.53(8)
115.71(7)
177.26(10)
97.56(10)
100.05(10)
96.62(10)
81.32(13)
82.69(13)
82.10(13)
115.33(14)
113.09(14)
125.81(14)
179.45(11)
96.88(7)
96.45(8)
97.45(8)
83.10(9)
83.10(10)
83.05(11)
121.48(10)
118.34(10)
115.89(10)
field ligand (Me6tren (932 nm) > TMPA (955 nm) > LMe
(1033 nm)).
To investigate the electron-donating nature of chelat-
ing ligands, it can be instructive to compare the carbon
~
monoxide stretching frequencies (vCO) for the corres-
ponding Cu(I)-carbonyl complexes.11,12,34,38,55 Karlin and
co-workers have also used the infrared spectra of Cu(I)-
carbonyl complexes to provide information about solution-
state coordination geometries and equilibria.12,34,56 For
example, all three pyridine donors are coordinated in the
solid-state molecular structure of [Cu(TMPA)CO]þ,12 and
an S=3/2 ground state. The green [Ni(LMe)Br]BPh4 com-
plex is high spin with a S=1 ground state, (μeff=3.47 μB,
(CD3CN, 298 K)). The magnetic and electronic absorption
data for [Fe(LMe)Cl]BPh4, [Co(LMe)Br]BPh4, and [Ni(LMe)-
Cl]BPh4 suggest that the trigonal bipyramidal geometry
observed in their solid-state structures is being maintained
in solution.
~
this five-coordinate complex gives rise to a single vCO
at 2077 cm-1 (nujol). In solution, however, the carbonyl
stretching frequency shifts to 2090 cm-1 in THF and
2092 cm-1 in CH3CN. The shift to higher frequency upon
dissolution is attributed to a change in coordination number
of the Cu(I) center. They have suggested that an equilibrium
exists between the five-coordinate species observed in the
solid-state and a four-coordinate species in which one of the
ligand arms is dissociated.11,12 The Cu(I) center in the four-
coordinate complex would be less electron-rich and would
weaken the carbon monoxide bond to a lesser extent result-
The electronic absorption spectrum of [Cu(LMe)Cl]BF4
exhibits two d-d absorption bands at 782 and 1033 nm with
molar extinction coefficients of 146 and 306 M-1 cm-1
,
respectively. This pattern of one low-energy absorbance
accompanied by a higher energy, lower intensity shoulder
indicates that a trigonal bipyramidal CuII coordination
geometry is being maintained in solution.15,32,54 Since
[Cu(LMe)Cl]þ, [Cu(Me6tren)Cl]þ,9,25 and the closely re-
lated [Cu(TMPA)Cl]þ15,32 all display nearly perfect tri-
gonal bipyramidal coordination environments (i.e., solid-
state τ5 values of 0.97, 1.0, and 1.0, respectively) and
solution-state electronic absorption spectra consistent with
this geometry being maintained in solution, it is possible to
compare the absorption maxima for these complexes to
determine the relative ligand field strengths for this series
of ligands.5 In Table 3, the d-d transitions for this series
of complexes are listed and suggest that Me6tren, which
gives rise to the most blue-shifted spectrum, is the strongest
~
ing in a larger vCO value.
To understand both the electron donating ability of
L
Me and its solution-state behavior, we set out to synthe-
size a Cu(I)-carbonyl complex of this ligand. The desired
complex, [Cu(LMe)(CO)]þ, was prepared by bubbling
excess carbon monoxide through an acetone solution of
[Cu(LMe)]PF6. X-ray quality crystals of [Cu(LMe)(CO)]þ
were obtained by layering a THF solution of the com-
plex with diethyl ether. The molecular structure of
[Cu(LMe)(CO)]PF6 is shown in Figure 4. The Cu(I) center
(55) Laitar, D. S.; Mathison, C. J. N.; Davis, W. M.; Sadighi, J. P. Inorg.
Chem. 2003, 42(23), 7354–7356.
(56) Kretzer, R. M.; Ghiladi, R. A.; Lebeau, E. L.; Liang, H.-C.; Karlin,
K. D. Inorg. Chem. 2003, 42(9), 3016–3025.
(54) Wei, N.; Murthy, N. N.; Karlin, K. D. Inorg. Chem. 1994, 33(26),
6093–6100.

7526 Inorganic Chemistry, Vol. 49, No. 16, 2010
Chu et al.
Figure 4. Molecular structure of [Cu(LMe)(CO)]PF6 drawn at 35%
probability. The anion (PF6-) and carbon hydrogen atoms have been
removed for clarity. Selected bond lengths (A) and angles (deg): Cu1-N1
Figure 5. Four-coordinate, κ3 isomer of [Cu(Me6tren)CO]þ.
˚
2.347(2), Cu1-N2 2.161(2), Cu1-N3 2.304(2), Cu1-N4 2.245(2),
Cu1-C25 1.838(3), C25-O1 1.124(4).
κ3-fashion (Figure 5). The κ3-coordination mode of Me6-
tren has been observed before in the solid-state molecular
structure of a square-planar palladium complex.61 In
Table 4. Infrared Stretching Frequencies for Cu(I)-Carbonyl Complexes
THF solutions, the vCO for [Cu(Me6tren)CO]þ shifts to
~
ν
CO (cm-1) nujol
ν
CO (cm-1) THF
lower frequencies suggesting the possible existence of an
equilibrium between the four- and five-coordinate species.
Low temperature 1H NMR experiments were attempted to
determine the identity of the five-coordinate species.
Specifically, we tried to determine if the five-coordinate
species contains the Me6tren ligand coordinated in a
κ4-coordination mode or if the fifth coordination site is
occupied by a coordinating solvent molecule. Unfortu-
nately, these experiements were not conclusive and com-
plicated by the limited solubility of [Cu(Me6tren)CO]þ in
[Cu(Me6tren)CO]PF6
[Cu(TMPA)CO]PF6
2098
2077
2088
2078
2090
2094
a
[Cu(LMe)CO]PF6
a Ref 12.
displays a distorted trigonal bipyramidal coordination
˚
with an average Cu-Nequatorial bond length of 2.24 A and
˚
a Cu-N1 bond length of 2.347(2) A. The relatively long
Cu(I);N bond lengths57 in this structure reflect the
relatively weak bonding interactions between the Cu(I)
center and the LMe ligand. For completeness, the Cu(I)-
carbonyl complex of the Me6tren ligand scaffold has also
been prepared and its infrared spectroscopy analyzed.
Unfortunately, this complex has yet to be isolated in a
crystalline form suitable for X-ray diffraction studies.
~
cold d8-THF. We do, however, note that the vCO of
[Cu(Me6tren)CO]þ in solution is sensitive to the nature
of the solvent (e.g., vCO=2078 cm-1 in THF and vCO
=
~
~
2085 cm-1 in CH3CN) suggesting that a coordinating
solvent molecule may be present in the five-coordinate
species. The carbonyl stretching frequencies for [Cu-
(TMPA)Cl]þ and [Cu(LMe)CO]þ are consistent with TMPA
being more electron donating than LMe. The overall elec-
The vCO values for [Cu(Me6tren)CO]þ, [Cu(TMPA)-
~
CO]þ, and [Cu(LMe)CO]þ are shown in Table 4. The
[Cu(TMPA)CO]þ and [Cu(LMe)CO]þ complexes show
similar trends. Both [Cu(TMPA)CO]þ and [Cu(LMe)-
tron donating ability of this series (Me6tren>TMPA>LMe
)
should be consistent with the pKa values of the con-
jugate acids of the ligand donor groups (i.e., [N,N-
dimethylethylaminium]þ (9.83 ( 0.28); [2-methylpyridi-
nium]þ (5.95 ( 0.28); and [N,N-dimethylbenyzlaminium]þ
(5.1 ( 0.28)).62
CO]þ exhibit their lowest vCO values (2077 cm-1 and
~
2088 cm-1) in nujol where both complexes are five-
coordinatþe.11,12,38 When [Cu(TMPA)CO]þ and [Cu-
(LMe)CO] are dissolved in THF their vCO values shift to
~
slightly higher frequencies (2090 cm-1 and 2094 cm-1
,
respectively) consistent with the presence of four-coordi-
nate species in solution.
Conclusions
A tetradentate, tetraamine ligand system, LMe, that incor-
porates N,N-dimethylaniline donor groups into a tripodal
framework has been synthesized by the reductive amination
of N(o-PhNH2)3. A series of MII-halide complexes, [MII-
(LMe)X]þ, have been synthesized, and their solution-state
and solid-state structures evaluated. The rigid aryl backbone
of LMe gives rise to five-coordinate, distorted trigonal bipyr-
amidal complexes that exhibitsmaller chelate bite angles than
those observed in five-coordinate MII-halide complexes sup-
ported by its alkyl congener, Me6tren. Electronic absorption
and infrared spectroscopy studies confirm that LMe is a weaker
field and less electron-donating ligand than both TMPA and
Me6tren. Comparative infrared spectroscopy studies on the
The vCO values for [Cu(Me6tren)CO]þ in a nujol mull
and in THF (Table 4) have also been recorded. The trends
~
observed for this complex are different. Specifically,
~
þ
[Cu(Me6tren)CO] exhibits its highest vCO value in nujol.
On the basis of the carbon monoxide stretching frequen-
cies reported for other four-coordinate Cu(I)-carbonyl
complexes supported by three uncharged nitrogen donor
ligands,12,58-60 we postulate that in the solid-state,
[Cu(Me6tren)CO]þ exists exclusively as a four-coordinate
complex with the Me6tren ligand coordinating in a
(57) Orpen, A. G.; Brammer, L.; Allen, F. H.; Kennard, O.; Watson,
D. G.; Taylor, R. J. Chem. Soc., Dalton Trans. 1989, 12, S1–S83.
(58) Kimura, E.; Koike, T.; Kodama, M.; Meyerstein, D. Inorg. Chem.
1989, 28(15), 2998–3001.
(59) Achternbosch, M.; Apfel, J.; Fuchs, R.; Kluefers, P.; Selle, A.
Z. Anorg. Allg. Chem. 1996, 622(8), 1365–1373.
(61) Ferguson, G.; Parvez, M. Acta Crystallogr., Sect. B: Struct. Crystal-
logr. Cryst. Chem. 1979, B35(9), 2207–2210.
(62) Scifinder, Web version; Chemical Abstracts Service: Columbus, Ohio,
2010. Calculated using Advanced Chemistry Development (ACD/Labs) Software
version V8.14 (1994-2010) RN: 121-69-7, 109-06-8, and 598-56-1.
(60) Kujime, M.; Kurahashi, T.; Tomura, M.; Fujii, H. Inorg. Chem.
2006, 46(2), 541–551.

Article
Inorganic Chemistry, Vol. 49, No. 16, 2010 7527
Cu(I)-carbonyl complexes [Cu(Me6tren)CO]þ and [Cu(LMe)-
CO]þ suggest these ligands can adopt different coordination
topologies about Cu(I). The weak-field electronic character-
istics and the less flexible nature of LMe ligand may help
create transition metal fragments that exhibit distinct reac-
tivity. Studies addressing the reactivity of the Cu(I) and
Fe(II) complexes supported by the LMe ligand are currently
underway in our laboratory.
2774, 1922, 1889, 1804, 1781, 1586, 1491, 1448, 1314, 1258,
954, 753.
Preparation of [HLMe]PF6. Off-white crystalline LMe (0.0749 g,
0.200 mmol) was dissolved in 10.0 mL of CH3CN at room
temperature. An aqueous solution of HPF6 (∼65 wt % in water,
0.0253 mL, 0.1860 mmol) was added dropwise to this solution. The
reaction was stirred for 1 h. All solvent was removed from the
reaction mixture using a rotary evaporator to yield a white powder.
The white powder was isolated on a medium porosity frit and
washed with Et2O (3 ꢀ 10 mL) (0.0937 g, 0.1800 mmol, 97%).
X-ray quality crystals were grown by diffusing Et2O into a THF
solution of the product. 1H NMR 7.94 (br), 7.72 (br), 7.60 (t), 7.02
(br), 3.48 (br, N-H), 2.54 (br, NH-CH3), 2.42(br, N-CH3). FTIR
Experimental Section
All reactions were performed using standard Schlenk tech-
niques or in an MBraun Labmaster 130 drybox under an
atmosphere of N2, unless otherwise stated. All reagents were
obtained from commercial vendors and were used without
further purification unless otherwise noted. Anhydrous sol-
vents were purchased from Sigma-Aldrich and further puri-
fied by sparging with Ar gas and passage over activated
alumina columns. Elemental analyses were performed by
Columbia Analytical Services, Tucson, AZ, or Atlantic
(KBr) vmax (cm-1): 3139; 2991, 2851, 2741, 2685, 2538, 2427 1490,
~
1448, 842.95; HR-MS(ESI): [HLMe þ
Found 375.25461.
]
m/z Calcd. 375.25478.
Preparation of [Fe(Me6tren)Cl]BPh4. To a slurry of FeCl2
(0.0715 g, 0.5641 mmol) in CH2Cl2 (10.0 mL) was added a
solution of Me6tren (0.1298 g, 0.5634 mmol) in 10.0 mL of
CH2Cl2. After stirring 30 min, NaBPh4 (0.1936 g, 0.5658 mmol)
was added dropwise as a MeOH solution (2 mL), and the
reaction stirred for an additional 3 h. During this time a large
amount of white precipitate had formed. The precipitate was
isolated on a medium porosity frit and washed with CH2Cl2 (2 ꢀ
2 mL). The filtrate and CH2Cl2 washings were combined and
concentrated to dryness to afford a white solid. Single crystals
suitable for X-ray diffraction studies can be obtained by slow
diffusion of Et2O into DMF solution of the complex. FTIR
1
Microlab, Inc., Norcross, GA. H and 13C NMR spectra
were recorded on a Varian Mercury 300 MHz spectrophoto-
meter at ambient temperature. Chemical shifts (δ) are
reportedinpartspermillion(ppm)andcouplingconstants(J)
are reported in hertz (Hz). NMR spectra were referenced
internally to residual solvent. IR spectra were recorded as
KBr pellets on a Varian Scimitar 800 Series FT-IR spectro-
photometer. Nujol and solution state IR spectra were re-
corded using the same spectrophotometer with KBr salt
plates. UV-visible absorption spectra were recorded on a
Cary 50 spectrophotometer using 1.0 cm quartz cuvettes.
Solution-state magnetic moments were measured using the
Evans’ method.63,64 Mass spectra were recorded in the Mass
Spectrometry Center at Emory University on a JEOL JMS-
SX102/SX102/A/E mass spectrometer. X-ray crystallogra-
phy studies were carried out in the X-ray Crystallography
Laboratory at Emory University on a Bruker Smart 1000
CCD diffractometer. The ligands tris(2-aminophenyl)amine,
N(o-PhNH2),39,46 and tris(2-dimethylaminoethyl)amine
(Me6tren)16 and [Cu(Me6tren)]PF610 were synthesized using
published literature procedures.
(KBr) vmax (cm-1): 1950, 1886, 1825, 1764; 1579; ν(NMe2) 1475,
~
1427, 736, 707. HRMS (ESI): [Fe(Me6tren)Cl]þ m/z Calcd.
321.15084. Found 321.15049 (100.00). Anal. Calcd (Found)
for [Fe(Me6tren)Cl]BPh4 CH3CN: C, 66.92 (66.91); H, 7.83
3
(7.96); N, 10.27 (9.87).
Preparation of [Fe(LMe)Cl]BPh4. To a suspension of FeCl2
(0.0390 g, 0.3077 mmol) in 10.0 mL of CH2Cl2 was added a
solution of LMe (0.1194 g, 0.3205 mmol) in 10.0 mL of CH2Cl2
dropwise. A solution of NaBPh4 (0.1084 g, 0.3168 mmol) in
MeOH (5 mL) was added dropwise to the reaction mixture, and
a precipitate formed immediately. The reaction mixture was
stirred for 4 h, and the white precipitate was removed by filtering
the reaction mixture through a medium porosity frit. The filtrate
was then layered with Et2O at room temperature. Colorless
needle-shaped crystals formed overnight. Colorless block crys-
tals, suitable for X-ray diffraction, were grown by diffusing
Et2O into a concentrated acetonitrile solution of the product.
UV-vis (CH3CN) λmax, nm (ε, M-1 cm-1): 297 (sh) 610 nm
(123). FTIR (KBr) ~vmax (cm-1): 3052, 2984, 2832, 2789, 1943,
1884, 1813, 1752; 1579, 1489, 1447, 1296, 1265, 1243, 734, 705.
1H NMR (CD3CN): 16.60 (br), 13.60 (br), 13.53 (br), 10.67 (br),
7.23(s), 6.97(t), 6.82(s). HRMS (ESI): [Fe(LMe)Cl]þ m/z Calcd.
465.15084. Found 465.15053. Anal. Calcd (Found) for [Fe-
(LMe)Cl]BPh4: C, 73.44 (73.31); H, 6.42 (6.63); N, 7.14 (7.05).
Tris(2-dimethylaminophenyl)amine, (LMe). An aqueous for-
maldehyde solution (37% by weight) (6.61 mL, 88.0 mmol) was
added to an acetonitrile (100 mL) solution of N(o-PhNH2)3
(0.7993 g, 2.75 mmol) and stirred. After 30 min, NaBH3CN
(1.6510 g, 26.3 mmol) was added to the solution as a solid.
Once all of the NaBH3CN was dissolved, concentrated HOAc
(0.6 mL) was added dropwise to adjust the pH to ∼7, and the
reaction mixture was stirred for 12 h. All volatiles were then
removed under reduced pressure to yield a sticky, off-white
solid. A KOH solution (2 M, 50 mL) was added to the crude
solid, and Et2O (3 ꢀ 20 mL) was used to extract the product. The
organic layers were combined and washed with KOH solution
(0.5 M, 50 mL). The organic layer was then extracted with an
aqueous HCl solution (1 M, 3 ꢀ 15 mL). The aqueous extracts
were combined and neutralized using solid KOH. The product
was then extracted using Et2O (3 ꢀ 20 mL). The Et2O washes
were combined and dried over K2CO3. The K2CO3 was removed
by filtration, and the filtrate concentrated to dryness using a
rotary evaporator to yield a light pink solid. The light pink solid
was recrystallized from hot methanol to yield the product as off-
white needles (77%, 0.7959 g). 1H NMR (CDCl3): 7.05 (dd, 3H,
J=1.8, J=7.5), 6.98 (td, 3H, J=1.8, J=6.9), 6.86 (td, 3H, J=1.8,
J=7.8), 6.78 (dd, 3H, J=1.8, J=7.8), 2.39 (s, 18H). HRMS
(ESI): þC24H30N4 m/z Calcd. 375.24705 Found 375.25461
μ
eff=5.03 μB (Evans Method, CD3CN, 298 K).
Preparation of [Co(LMe)Br]BPh4. To a stirred solution of LMe
(0.1862 g, 0.5 mmol) in 10.0 mL of CH2Cl2 was added CoBr2
(0.1088 g, 0.5 mmol). The reaction was stirred for 30 min, and
then NaBPh4 (0.1734 g, 0.5 mmol) was added dropwise as a
MeOH solution (2 mL). The reaction was refluxed under an
atmosphere of N2 for 3 h. The reaction mixture was cooled to
room temperature. All volatiles were removed under reduced
pressure to yield a purple precipitate. The precipitate was iso-
lated on a medium porosity frit, washed with MeOH (10 mL),
and dried under vacuum overnight (0.250 g, 60%,). Single
crystals for X-ray crystallographic studies were formed by the
slow diffusion of Et2O into a concentrated CH3CN solution of
the product. Bulk recrystallization can also be used to isolate
large quantities of analytical pure material by diffusion of Et2O
[Mþ1] . FTIR (KBr) vmax (cm-1): 3054, 2971, 291, 2820,
~
1
into THF solution of the product. H NMR (CD3CN): 19.45
(br), 14.95 (br), 14.50 (br), 8.80 (br), 7.24 (s), 6.98 (t), 6.80 (t).
(63) Evans, D. F. J. Chem. Soc. 1959, 2003–2005.
(64) Sur, S. K. J. Magn. Reson. 1989, 82, 169–173.

7528 Inorganic Chemistry, Vol. 49, No. 16, 2010
Chu et al.
Table 5. Crystal Data and Refinement Data
H[LMe
]
[Fe(LMe)Cl]BPh4 [Co(LMe)Br]BPh4 [Ni(LMe)Cl]BPh4
[Cu(LMe)Cl]BF4
[Cu(LMe)CO]PF6 [Fe(Me6tren)Cl]BPh4
empirical formula C24H31F6N4P C48H50BClFeN4 C50H53BBrCoN5 C50H53BClN5Ni C24H30BClCuF4N4 C25H30CuF6N4OP
C38H53BClFeN5
monoclinic
Pc
crystal system
space group
monoclinic
P2(1)/c
7.792(5)
20.721(12)
17.766(10)
90
monoclinic
Pc
monoclinic
P2(1)/n
12.5584(3)
18.1423(5)
19.2187(5)
90
monoclinic
P2(1)/n
12.5069(17)
18.029(2)
19.301(3)
90
orthorhombic
Pna2(1)
9.0188(5)
21.9007(14)
12.4198(7)
90
monoclinic
P2(1)/n
11.412(6)
14.348(7)
16.781(8)
90.00
˚
a, A
10.066(11)
11.957(13)
17.111(18)
90
12.487(5)
12.478(5)
23.570(10)
90
˚
b, A
˚
c, A
R, deg
β, deg
γ, deg
101.240(10)
90
99.318(18)
90
96.238(1)
90
96.055(2)
90
90
90
95.398(8)
90.00
90.510(7)
90
3
˚
V (A )
Z
crystal size, mm
2813(3)
4
2032(4)
2
4352.8(2)
4
4327.8(10)
4
2453.1(2)
4
2736(2)
4
3672(3)
4
0.51 ꢀ 0.05
ꢀ 0.04
0.15 ꢀ 0.04
ꢀ 0.04
0.43 ꢀ 0.30
ꢀ 0.20
0.15 ꢀ 0.06
ꢀ 0.05
0.52 ꢀ 0.30
ꢀ 0.28
0.18 ꢀ 0.13
ꢀ 0.04
0.20 ꢀ 0.15
ꢀ 0.10
T, K
ref. coll.
172(2)
50056
173(2)
34680
173(2)
34427
173(2)
60714
173(2)
28619
173(2)
57440
173(2)
63558
Indep. ref. (Rint
GOF on F2
)
7873[0.0870]
1.013
R1 = 0.0576
11425[0.1489]
1.002
R1 = 0.0592
8558[0.0611]
1.006
R1 = 0.0384
9157[0.2141]
1.019
R1 = 0.0670
8482[0.0525]
1.044
R1 = 0.0588
9522[0.0884]
1.036
R1 = 0.0551
20690[0.0623]
1.044
R1 = 0.0744
Final R indices
[I > 2σ(I)]
wR2 = 0.1153 wR2 = 0.0791
R indices (all data) R1 = 0.1211 R1 = 0.1963
wR2 = 0.1311 wR2 = 0.1110
wR2 = 0.0871
R1 = 0.0549
wR2 = 0.0950
wR2 = 0.1137
R1 = 0.1734
wR2 = 0.1443
wR2 = 0.1478
R1 = 0.0659
wR2 = 0.1552
wR2 = 0.1321
R1 = 0.1075
wR2 = 0.1566
wR2 = 0.2028
R1 = 0.0937
wR2 = 0.2151
FTIR (KBr) vmax (cm-1): 3056, 3044, 2984, 1492, 1449, 1258,
1204, 1146, 1095, 1004, 921, 773, 731, 706, 611. UV-vis
(CH3OH) λmax, nm (ε, M-1 cm-1): 510 (73), 534 (72) 620
(128). μeff = 4.68 μB (Evans Method, CD3CN, 298 K). Anal.
Calcd (found) for [Co(LMe)Br]BPh4: C, 69.24 (68.99); H, 6.05
(6.13); N, 6.73 (6.75).
Calcd. 475.14550. Found 472.14520 (100.00). μeff=1.83 μB
(Evans Method, CDCl3, 298 K).
~
Preparation of [Cu(LMe)]PF6. To an CH3CN solution (3.0 mL)
of [Cu(CH3CN)4]PF6 (0.0754 g, 0.2023 mmol) was added a
solution of LMe (0.0786 g, 0.2099 mmol) in CH3CN (3 mL). The
reaction was stirred at room temperature overnight. The solvent
was removed under reduced pressure to afford a white power. The
powder was washed with Et2O and dried on a sintered glass frit
(0.1058 g, 0.1815 mmol, 89.7%). The complex was recrystallized by
layering Et2O onto a concentrated CH3CN solution of the pro-
duct. Unfortunately, X-ray quality crystals of this complex could
Preparation of [Ni(LMe)Cl]BPh4. This complex was prepared
in a manner analogous to that of [Co(LMe)Br]BPh4, except
Ni(PPh3)2Cl2 was used in place of CoBr2. The product was
isolated as a green powder (90%, 0.3560 g). [Ni(LMe)Cl]BPh4
was recrystallized for X-ray diffraction studies by the diffusion
of Et2O into a concentrated acetonitrile solution of the product.
Bulk recrystallization of the crude material was achieved by
diffusing Et2O into a concentrated THF solution of the product
1
not be isolated. H NMR (CD3CN): 7.10 (3H), 7.00 (3H), 6.88
(3H), 6.70 (3H), 2.37 (18H). FTIR (KBr) vmax (cm-1): 3059, 2932,
~
2821, 2775, 1492, 1448, 1261, 1225, 1099, 1048, 841,771, 558. MS
(EM-ESI): [Cu(LMe)]þ m/z Calcd. 437.17665. Found 437.17560
(63Cu, 100), 439.17413 (65Cu, 44.33).
1
to yield pale yellow-green needles. H NMR (CD3CN): 23.54
(br), 16.48 (br), 14.80 (br), 7.22, 6.97 (t), 6.82 (t), 2.21 (br). FTIR
(KBr) vmax (cm-1): 3054, 3031, 2983, 2928 1492, 1426, 1426,
1259, 1198, 1144, 1094, 1032, 1005, 772, 733, 705, 613 585, 669.
Preparation of [Cu(LMe)(CO)]PF6. Solid [Cu(LMe)]PF6
(0.0512 g, 0.0878 mmol) was dissolved in dry acetone (10 mL)
and transferred to a Schlenk flask. The colorless solution was
then sparged with CO gas for 30 min. Over this time period, the
reaction mixture changed from colorless to light green. The
resulting solution was layered with Et2O and allowed to stand
overnight, whereupon green crystals of the product formed
(0.0266 g, 49.5%). Crystals suitable for X-ray crystallography
were grown by diffusing Et2O into a THF solution of the com-
plex. 1H NMR (CD3CN): 7.16 (3H), 7.00(3H), 6.85 (3H), 6.66
~
UV-vis (CH3OH) λmax, nm (ε, M-1 cm-1): 440 (112), 684 (30).
μ
eff = 3.47 μB (Evans Method, CD3CN, 298 K). Anal. Calcd
(found) for [Ni(LMe)Cl]BPh4 THF: C, 72.62 (72.54); H, 6.80
3
(6.78); N, 6.51 (6.61).
Preparation of [Cu(LMe)Cl]BF4. A green methanol solution
(8 mL) of CuCl2 (0.1338 g, 0.9952 mmol) was added to a stirring
methanol solution (15 mL) of LMe (0.3728 g, 0.9954 mmol)
resulting in the immediate formation of a dark red reaction
mixture. The reaction was stirred at room temperature for 10 min.
Colorless AgBF4 (0.1942 g, 0.9976 mmol) was then added
dropwise as a CH3OH solution (5 mL) to reaction mixture.
The reaction mixture turned brown at once with concomitant
formation of a white precipitate. The mixture was stirred over-
night and filtered through a pad of Celite to remove AgCl. The
filtrate was concentrated using a rotary evaporator to yield a
bright yellow solid. This solid was collected on a medium poro-
sity frit and washed with a 10:1 Et2O/CH3CN solution (10 mL)
to yield a yellow-green solid (0.49 g, 88%). Single crystals for
X-ray crystallography were grown by diffusing Et2O into satu-
(3H) 2.37 (18H). FTIR (KBr) vmax (cm-1): 3072, 2884, 2813, (CO)
~
2088, 1493, 1449, 1271, 1218, 1101, 1051, 1019, 840, 768, 558. FTIR
(THF) vmax (cm-1): (CO) 2094. FTIR (Nujol) vmax (cm-1):
(CO) 2088.
~
~
Preparation of [Cu(Me6tren)(CO)]PF6. Under an inert atmo-
sphere, a Schlenk flask was charged with Me6tren (0.10 g, 0.44
mmol), 10.0 mL of THF, and a stir bar and sealed with a septum.
In a separate Schlenk flask, [Cu(CH3CN)4]PF6 (0.16 g, 0.44
mmol) was dissolved in THF and fitted with a septum. Both
solutions were then saturated with CO (g) by bubbling each
solution with CO(g) for 30 min. The [Cu(CH3CN)4]PF6 solution
was transferred to the Me6tren solution via cannula. The reac-
tion mixture changed from colorless to pale green immediately.
The reaction mixture was layered with Et2O and allowed to
stand overnight, producing a pale green microcrystalline powder.
The solid was collected on a frit and washed with Et2O (0.150 g,
88%). The pale green solid is very reactive toward O2 and dif-
ficult to store as a solid or in solution for long periods of time.
1
rated CH3CN solution of crude product. H NMR (CD3CN):
~
18.20 (br), 13.55 (br), 12.00 (br), -4.4 (br). FTIR (KBr) vmax
(cm-1): 3054, 3031, 2931, 2852, 2820, 2775, 1492, 1472, 1288,
1062, 1007, 922, 732, 587, 480. UV-vis (CH3CN) λmax, nm
(ε, M-1cm-1): 430 (sh) (1052), 782 (146), 1033 (306). Anal.
Calcd (Found) for [Cu(LMe)Cl]BF4: C, 51.44 (51.73); H, 5.40
(5.44); N, 10.00 (10.18). HRMS (ESI): [Cu(LMe)Cl]þ m/z

Article
Inorganic Chemistry, Vol. 49, No. 16, 2010 7529
FTIR(THF) vmax (cm-1) (CO) 2078; FTIR (CH3CN) vmax (cm-1):
software. Frame integration and final cell refinements were done
using the SAINT66 software. All structures were solved using
Direct methods and difference Fourier techniques (SHELXTL,
V6.12).67 Hydrogen atoms were placed in their expected chemi-
cal positions using the HFIX command and were included in the
final cycles of least-squares with isotropic Uij’s related to the
atom’s ridden upon. All non-hydrogen atoms were refined
anisotropically except for the acetonitrile solvent molecules in
[Fe(Me6tren)Cl]BPh4, [Co(LMe)Br]BPh4, and [Ni(LMe)Cl]BPh4
and the disordered F atoms in [Cu(LMe)(CO)]PF6. Scattering
factors and anomalous dispersion corrections are taken from
the International Tables for X-ray Crystallography.68 Structure
solution, refinement, graphics, and generation of publication
materials were performed by using SHELXTL, V6.12 software.
Additional details of data collection and structure refinement
are given in Table 5. CCDC 766572-766578 contain the sup-
plementary crystallographic data for this manuscript. These
files can be obtained free of charge from the Cambridge Crystal-
lographic Data Centre via http://www.ccdc.cam.ac.uk/data_
request.cif.
~
~
(CO) 2085; FTIR (Nujol) vmax (cm-1) (CO) 2098.
~
Infrared Spectroscopies of Carbonyl Complexes. The solution-
state IR spectra for [Cu(LMe)(CO)]PF6 and [Cu(Me6tren)-
(CO)]PF6 were recorded by a modified literature procedure.12
In a 20.0 mL scintillation vial, solid complex (∼10-12 mg) was
dissolved in in 2.0 mL of solvent. The vial was fitted with a
septum, removed from the drybox and sparged with anhydrous
CO(g) for one minute. A gastight syringe was used to transfer the
solution to a solution IR cell (Internation Crystal Laboratories,
0.10 mm path length) fitted with two septa under a constant
stream of CO(g)
.
X-ray Diffraction Studies. Suitable crystals of [HLMe]PF6,
[Fe(Me6tren)Cl]BPh4, [Fe(LMe)Cl]BPh4, [Co(LMe)Br]BPh4,
[Ni(LMe)Cl]BPh4, [Cu(LMe)Cl]BF4, and [Cu(LMe)CO]PF6 were
coated with Paratone N oil, suspended in a small fiber loop, and
placed in a cooled nitrogen gas stream at 173 K on a Bruker D8
APEX II CCD sealed tube diffractometer with graphite mono-
˚
chromated MoKR (0.71073 A) radiation. Data were measured
using a series of combinations of j and ω scans with 10 s frame
exposures and 0.5° frame widths. Data collection, indexing, and
initial cell refinements were all carried out using APEX II65
Acknowledgment. We thank Dr. Rui Cao and Ms. Sheri
Lense for crystallographic assistance. The University Research Com-
mittee of Emory University is acknowledged for financial support.
(65) APEX II, 2005; Bruker AXS, Inc.: Madison, WI, 2005.
(66) SAINT, Version 6.45A; Bruker AXS, Inc.: Madison, WI, 2003.
(67) Sheldrick, G. M. Acta Crystallogr., Sect. A: Found. Crystallogr. 2008,
A64(1), 112–122.
(68) Wilson, A. J. C., Ed.; International Tables for X-ray Crystallography,
Vol. C.; Kynoch, Academic Publishers: Dordrecht, The Netherlands, 1992.
Supporting Information Available: Crystallographic data in
CIF format. This material is available free of charge via the
Internet at http://pubs.acs.org.