Synthesis and structural analysis of formamidinate-supported Mg complexes

Article abstract of DOI:10.1016/j.ica.2015.05.005

Abstract Reactions of 2-mesitylmagnesium bromide with N,N′-diarylformamidines afforded five Mg compounds [(DPhF)Mg(THF)₂]₂(μ-Br)₂ (1), [D(3,5-Xyl)F]₂Mg(THF)₂ (2), [D(2,6-Xyl)F]₂Mg(THF) (3),

Full text of DOI:10.1016/j.ica.2015.05.005

Inorganica Chimica Acta 434 (2015) 85–91
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Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Synthesis and structural analysis of formamidinate-supported Mg
complexes
Yi-Ju Tsai a, Michael B. Pastor a, Wenfeng Lo b, Qinliang Zhao a,
⇑
a Department of Chemistry, University of the Pacific, 3601 Pacific Avenue, Stockton, CA 95211, USA
b Department of Chemistry, Yeshiva University, 2495 Amsterdam Avenue, New York, NY 10033, USA
a r t i c l e i n f o
a b s t r a c t
Reactions of 2-mesitylmagnesium bromide with N,N0-diarylformamidines afforded five Mg compounds
[(DPhF)Mg(THF)2]2(
-Br)2 (1), [D(3,5-Xyl)F]2Mg(THF)2 (2), [D(2,6-Xyl)F]2Mg(THF) (3), [D(2-iPrPh)F]-
Article history:
Received 11 April 2015
Received in revised form 6 May 2015
Accepted 7 May 2015
l
MgBr(THF)3 (4), and [D(2-tBuPh)F]2Mg(THF) (5). Complexes 1, 2 and 4 displayed monomeric octahedral
metal centers supported by formamidinates, bromide counter anions, and coordinating THF solvent
molecules, while the metal cores in 3 and 5 were five-coordinated and in distorted square-pyramidal
geometries. Detailed structural analysis indicated that only dimagnesium or mononuclear complexes
were obtained through the use of formamidinate ligands. Ligands of increased steric demands resulted
in the formation of monomeric complexes. Solvent molecules and counter anions that can coordinate
to the metal cores further regulated the product conformation. Monoanionic formamidinates in the com-
plexes, mostly featuring two nearly identical N–C bonds on the N–C–N backbone upon complexation,
Available online 20 May 2015
Keywords:
Formamidinate
Synthesis
Magnesium complexes
Structural analysis
Conformation
exhibited a symmetric bidentate chelating (
g
2) coordination mode.
Ó 2015 Elsevier B.V. All rights reserved.
1. Introduction
change the steric properties of the ligands but also their electronic
properties, thus influencing the geometry and reactivities of the
resulting metal complexes [7]. Modified formamidinate-supported
metal complexes have established applications in catalyst develop-
ment [8], material of photoelectronic properties [9] and atomic
layer deposition [10].
There have been numerous amidinate-supported Mg complexes
displaying a variety of conformations in the literature; [11]
however, very few formamidinate-supported Mg complexes have
been structurally characterized [12]. Overall, there are only
four formamidinate-supported mononuclear Mg complexes
Mg[D(p-Tol)F]2(THF)2 (III in Fig. 1, D(p-Tol)F = N,N0-di(p-tolyl)-
formamidinate) [12a], Mg[D(p-Tol)F]2(DME) (IV, DME = 1,2-
dimethoxyethane) [12a], Mg[D(p-Tol)F]2(TMEDA) (V, TMEDA =
N,N,N0,N0-tetramethylethylene-1,2-diamine) [12a], Mg[D(o-Tol)F]2-
(THF)2 (VI, D(o-Tol)F = N,N0-di(o-tolyl)formamidinate) [12a], and
Formamidinates [HC(NR)2]ꢀ (R = alkyl, aryl, or silyl), a subclass
of amidinates ([R0C(NR)2]ꢀ, R0 = alkyl, aryl, amido or H) [1], have
attracted considerable interest from inorganic chemists due to
their convenient synthetic accessibility, vast tunability in terms
of electronic and steric properties, and broad versatility in
coordination modes [2]. Upon deprotonation of a formamidine,
the negative charge on the formamidinate can delocalize across
the N–C–N backbone, forming a four-electron-three-atom center
(I in Scheme 1). The two equivalent N binding sites can bind a
single metal atom [3] or two metal cores simultaneously as seen
in the classical ‘‘lantern-type’’ bimetallic complexes [4]. The
negative charge can also localize onto one N atom, resulting in
an asymmetric backbone with an amide and an imine group (II)
in which a portion or all of the three lone pairs of electrons can
bind metal atoms [5].
two binuclear complexes [(DPhF)Mg(THF)]2(
DPhF = N,N0-diphenylformamidinate) [12b], and {[D(2,6-iPr2Ph)F]-
Mg(THF)}2(
-Cl)2 (VIII, D(2,6-iPr2Ph)F = N,N0-bis(2,6-diisopropy-
l-THF)(l-Cl)2 (VII,
Another advantage of using formamidinates in coordination
chemistry is the great tunability presented through derivatization.
A large number of N,N0-diarylformamidine (DArFH) derivatives
containing various substituents on the aryl rings (e.g. alkyl, alkoxy,
halo and nitro groups) have been obtained and shown to support
metal complexes [6]. The substituent modifications do not only
l
lphenyl)formamidinate) [12c]. Comparison of synthesized Mg
complexes supported by amidinates [11,12] and other ligands
containing nitrogen coordinating sites [13] also revealed only
monomeric or dimeric complexes with various metal–ligand
ratios. Steric demands of the ligands played an important role in
controlling the product geometry, whereas participation of other
ions and molecules in coordination also has significant influence
⇑
Corresponding author.
E-mail address: qzhao@pacific.edu (Q. Zhao).
http://dx.doi.org/10.1016/j.ica.2015.05.005
0020-1693/Ó 2015 Elsevier B.V. All rights reserved.

86
Y.-J. Tsai et al. / Inorganica Chimica Acta 434 (2015) 85–91
R
R
R
N
N
N
R
R
- H+
I
N
H
N
N
H
N
N
H
N
N
H
N
R
Formamidine
R=alkyl, aryl, or silyl
N
D(3,5-Xyl)FH
D(2,6-Xyl)FH
DPhFH
II
Scheme 1. Lewis structures of formamidinates.
N
H
N
N
H
N
D(2-iPrPh)FH
D(2-tBuPh)FH
over the product conformations. Here, we set to explore whether
new conformations of magnesium complexes can be achieved by
synthesizing and structurally characterizing complexes using for-
mamidinate ligands of various steric demands, which were abbre-
viated as DPhFH, D(3,5-Xyl)FH, D(2,6-Xyl)FH, D(2-iPrPh)FH and
D(2-tBuPh)FH (Fig. 2).
Fig. 2. Formamidines and their abbreviated names.
Complex
4
was obtained from D(2-iPrPh)FH with 1 equiv.
MesMgBr by following Eq. (4). Crystals of compounds 1–4 were
obtained through evaporation diffusion at r.t. while complex 5
required a much lower temperature of ꢀ35 °C for successful crys-
tallization, which may be due to the greater solubility of 5 in hex-
anes promoted by the [D(2-tBuPh)F]ꢀ ligands.
2. Results and discussion
2.1. Syntheses
All formamidine ligands were obtained by heating triethy-
lorthoformate with 2-equiv. anilines without any solvent present,
following literature methods [2]. Syntheses of the Mg complexes
were accomplished by mixing the ligands with commercially avail-
able Grignard reagent 2-mesitylmagnesium bromide (MesMgBr) at
ꢀ35 °C. MesMgBr provided the Mg metal atoms and also acted as
the internal base to deprotonate the formamidine ligands.
Following Eq. (1), 2-equiv. DPhFH and 2-equiv. MesMgBr yielded
2 DPhFH þ 2 MesMgBr þ 4 THF
! ½ðDPhFÞMgðTHFÞ2ꢁ2ð
l
-BrÞ2ð1Þ þ 2 C9H12
ð1Þ
ð2Þ
2 Dð3; 5-XylÞFH þ 2 MesMgBr þ 2 THF
! ½Dð3; 5-XylÞFꢁ2MgðTHFÞ2ð2Þ þ MgBr2 þ 2 C9H12
2 LH þ 2 MesMgBr þ THF ! L2MgðTHFÞðL ¼ Dð2; 6-XylÞF in 3; L
bromide bridged bimetallic complex [(DPhF)Mg(THF)2]2(l-Br)2
¼ Dð2-tBuPhÞF in 5Þ þ MgBr2 þ 2 C9H12
ð3Þ
(1). As described in Eqs. (2) and (3), reactions of 2-equiv. ligands
of differing degrees of steric hindrance D(3,5-Xyl)FH, D(2,6-
Xyl)FH or D(2-tBuPh)FH and 2-equiv. MesMgBr in THF yielded bis-
formamidinate mononuclear complexes 2, 3 and 5, respectively,
where only the number of coordinating THF molecules varies.
Dð2-iPrPhÞFH þ MesMgBr þ 3 THF
! ½Dð2-iPrPhÞFꢁMgBrðTHFÞ3ð4Þ þ C9H12
ð4Þ
Fig. 1. Drawing of formamidinate-supported Mg complexes.

Y.-J. Tsai et al. / Inorganica Chimica Acta 434 (2015) 85–91
87
2.2. Structural analysis
Complex [(DPhF)Mg(THF)2]2(
l-Br)2 (1) crystallized in the tri-
ꢀ
clinic space group P1 with two molecules containing nearly identi-
cal bond matrices in each unit cell. As shown in Fig. 3, each
molecule was comprised of a dinuclear Mg2Br2 diamond core with
two bromide bridges in the center. The center of the Mg2Br2 dia-
mond core coincided with the inversion center of the molecule.
The two Mg–N coordinative bonds with lengths of 2.154(1) and
2.140(1) Å were very short, which forced the Mg atom close to
the C1 atom on the backbone (Mg1–C1: 2.526(2) Å, Table 1).
Each Mg atom, in a pseudo-octahedral ligand environment, was
supported by two monoanionic DPhF ligands in the equatorial
plane and a THF molecule on either side of the plane. The separa-
tion between the two Mg centers was 3.651(1) Å with no net bond-
Fig. 4. X-ray crystal structure of 2. Hydrogen atoms are omitted for clarity.
Ellipsoids are shown at the 50% probability level.
ing between the metal atoms. The geometry of complex
1
resembled the geometry of VIII in Fig. 1, in which only one THF
molecule was attached to each Mg center as a result of the high
steric demand from the ligands [12c]. The core structure of 1 was
also analogous to those possessed by the precursors that led to
the discovery of the first two unusual Mg–Mg single bonds [14].
The C–N bond lengths on the N–C–N backbone of the formamidi-
nate ligands were nearly identical, being 1.317(2) and 1.327(2) Å
for C1–N1 and C1–N2, respectively. The symmetric feature of the
N–C–N backbone demonstrated that the negative charge was delo-
Table 2
Selected bond lengths (Å) and angles (deg) in complexes 2 and 5.
2
5
Mg1–N1
Mg1–N2
Mg1–C1
Mg1–O1
C1–N1
C1–N2A
N1–C2
N1–C1–N2A
N1–Mg1–N2A
N1–Mg1–N2
N1–Mg1–N1A
N2–Mg1–N2A
N1–Mg1–O1
N1–Mg1–O1A
C1–N1–Mg1
2.1558(18)
2.1638(17)
2.532(2)
2.1154(15)
1.329(3)
1.323(3)
1.395(3)
117.04(19)
63.16(6)
116.84(6)
180.0
2.1442(6)
2.1487(7)
2.4642(8)
2.0318(9)
1.3236(9)
1.3267(9)
1.4204(9)
118.15(7)
63.96(2)
100.82(3)
144.52(4)
131.30(4)
107.74(2)
calized, leading to a conjugated
unit (I) with a symmet-
ric bidentate chelating
(
g2
)
coordination mode. Both
formamidinates were equivalent in solid state as well as in solu-
tion, as a single set of signals was observed in NMR.
When D(3,5-Xyl)FH was applied as the ligand, a bisformamidi-
nate mononuclear complex [D(3,5-Xyl)F]2Mg(THF)2 (2 in Fig. 4),
containing a nearly identical geometry to that of III and VI in
Fig. 1, was obtained. Complex 2 crystallized in the monoclinic space
group C2/c with one half of the Mg molecule in an asymmetric unit.
Mg1 resided on an inversion center that generated the other half of
180.0
89.72(6)
90.28(6)
89.97(13)
87.20(4)
the molecule. The coordinationgeometry about themagnesium cen-
ter resembled a slightly distorted octahedron with two THF mole-
cules in the axial positions. The Mg1 center and all four N atoms
from the two D(3,5-Xyl)F anions were in the same equatorial plane
and the linear O1–Mg1–O1A axis was completely perpendicular to
the equatorial plane. Both D(3,5-Xyl)F anions were equivalent by
symmetry in solid state as well as in solution as evidenced by a single
set of signals observed in NMR. The two Mg–N bond lengths of
2.156(2) and 2.164(2) Å (Table 2) were similar to each other. The
C–N bond lengths in the N–C–N backbone of the formamidinate
ligands were 1.329(3) and 1.323(3) for C1–N1 and C1–N2A, respec-
tively. Both formamidinate ligands in 2 exhibited the same biden-
tate chelating (g
2) coordination mode as those seen in 1.
The bisformamidinate mononuclear complex [D(2,6-Xyl)F]2Mg-
(THF) (3 in Fig. 5) contained a single magnesium center in a
distorted square pyramidal geometry. Unlike 1 and 2, only one
additional THF molecule was bound to the Mg center in 3 due to
the increased steric demand from the methyl groups on the ortho-
positions of the aryl rings. The geometry of 3 resembled those of
IV and V in which larger molecules DME and TMEDA (instead of
THF) provided the extra support. Based on the bond matrices in
Table 3, the complex contains a pseudo-C2 axis going through the
Mg1–O1 bond. The Mg–N bond lengths varied significantly, with
the short lengths of 2.083(5) and 2.082(5) Å and the longer lengths
of 2.167(4) and 2.151(4) Å. All four C–N bonds in the N–C–N back-
bones of the formamidinate ligands were similar in length, with an
Fig. 3. X-ray crystal structure of 1. Hydrogen atoms are omitted for clarity.
Ellipsoids are shown at the 50% probability level.
Table 1
Selected non-bonded separations, bond lengths (Å) and angles (deg) in complex 1.a
Mg1ꢂ ꢂ ꢂMg1A
Mg1–N1
Mg1–C1
Mg1–N2
Mg1–O1
Mg1–O2
Mg1–Br1
Mg1–Br1A
3.651(1)
2.154(1)
2.526(2)
2.140(1)
2.144(1)
2.114(1)
2.6355(7)
2.6547(6)
C1–N1
C1–N2
N1–C2
N1–C1–N2
N1–Mg1–N2
C1–N1–Mg1
Mg1–Br1–Mg1A
Br1–Mg1–Br1A
1.317(2)
1.327(2)
1.406(2)
116.4(1)
63.11(5)
90.05(9)
87.29(2)
92.71(2)
average distance of 1.310[7] Å, indicating a bidentate chelating (g2
coordination mode again for all formamidinates in 3.
)
A mono-formamidinate complex [D(2-iPrPh)F]MgBr(THF)3 (4 in
Fig. 6) was attained through the installation of a single iso-propyl
a
Bond matrices of one molecule in a unit cell were shown. Those in the other
molecule are nearly identical.

88
Y.-J. Tsai et al. / Inorganica Chimica Acta 434 (2015) 85–91
Table 4
Selected bond lengths (Å) and angles (deg) in complex 4.a
Mg1–N1
Mg1–N2
Mg1–C1
C1–N1
C1–N2
N1–C2
Mg1–O1
Mg1–O2
Mg1–O3
Mg1–Br1
2.163(13)
2.230(12)
2.582(15)
1.343(18)
1.301(18)
1.425(18)
2.130(11)
2.120(11)
2.103(11)
2.602(5)
N1–C1–N2
116.5(13)
61.5(4)
94.6(4)
94.0(4)
155.9(5)
107.3(4)
170.8(5)
87.9(3)
87.3(4)
96.7(3)
83.6(4)
92.5(3)
N1–Mg1–N2
N1–Mg1–O1
N1–Mg1–O2
N1–Mg1–O3
N1–Mg1–Br1
O1–Mg1–O2
O1–Mg1–Br1
O1–Mg1–O3
Br1–Mg1–O3
O2–Mg1–O3
Br1–Mg1–O2
a
Bond matrices of one molecule in an asymmetric unit were shown. Those in the
other molecule are nearly identical.
Fig. 5. X-ray crystal structure of 3. Hydrogen atoms are omitted for clarity.
Ellipsoids are shown at the 50% probability level.
Table 3
Selected bond lengths (Å) and angles (deg) in complex 3.
Mg1–N1
Mg1–N2
Mg1–C1
Mg1–N3
Mg1–N4
Mg1–C2
Mg1–O1
C1–N1
C1–N2
C2–N3
C2–N4
N1–C3
2.083(5)
2.167(4)
2.483(6)
2.151(4)
2.082(5)
2.482(6)
2.050(4)
1.311(6)
1.315(6)
1.293(6)
1.319(6)
1.427(6)
N1–C1–N2
N3–C2–N4
117.2(5)
117.1(5)
N1–Mg1–N2
N3–Mg1–N4
N1–Mg1–N3
N2–Mg1–N4
N1–Mg1–N4
N2–Mg1–N3
O1–Mg1–N1
O1–Mg1–N2
O1–Mg1–N3
O1–Mg1–N4
63.62(17)
63.50(18)
113.99(19)
113.13(19)
131.3(2)
173.64(19)
115.95(18)
92.57(17)
93.74(17)
112.76(17)
Fig. 7. X-ray crystal structure of 5. Hydrogen atoms are omitted for clarity.
Ellipsoids are shown at the 50% probability level.
Complex [D(2-tBuPh)F]2Mg(THF) (5 in Fig. 7) crystallized in the
monoclinic space group C2/c with one half of the Mg molecule in
an asymmetric unit. Atoms Mg1 and O1 from the THF molecule
resided on a twofold axis that generated the other half of the mole-
cule. Complex 5 also displayed a similar distorted square-pyrami-
dal environment as seen in 3. All four tert-butyl groups on the two
formamidinates were directing toward the same side, leaving
enough space for one single THF moiety. In comparison to 3, the
formamidinates in 5 bend further away from the Mg1-THF moiety
due to the amplified steric demands from the tert-butyl groups.
The two similar Mg–N bond lengths (2.1442(6) and 2.1487(7) Å,
respectively) forced the Mg center close to the C1 atom with a
short separation of 2.4642(8) Å (Table 2). Both formamidinates
were related by symmetry, thus equivalent in solid state. The C–
N bond lengths in the N–C–N backbone of the formamidinate
ligands (1.3236(9) and 1.3267(9) Å for sC1–N1 and C1–N2A,
respectively) indicated again a symmetric bidentate chelating
(g
2) coordination mode for formamidinates in 5.
Unlike Zn complexes of which clusters of various nuclearities
Fig. 6. X-ray crystal structure of 4. Hydrogen atoms are omitted for clarity.
have been demonstrated [15], only monomeric or dimeric Mg com-
plexes supported by amidinates [11,12] and other nitrogen-con-
taining ligands [13] were obtained. Steric properties of the
ligands played an important role in dictating the product confor-
mation and nuclearity. A halide-bridged dimagnesium complex
(1) was observed when the simplest N,N0-diarylformamidinate
was applied. Monomeric Mg complexes (2–5) were obtained when
steric demands of the ligands were augmented by placing substi-
tutes on the aryl rings. This phenomenon beared a resemblance
to that observed for amidinate-supported Mg complexes [11d].
Moreover, additional support for the Mg centers from the solvent
molecules and counter anions further regulated the product
conformation.
Ellipsoids are shown at the 50% probability level.
group on the ortho-position of each phenyl ring. 4, as a formamid-
inate-supported Mg complex, is unique in the sense that its geom-
etry is different from any of those in the literature (Fig. 1) and from
this study. The octahedral environment of the Mg center was com-
posed of one formamidinate ligand, three THF molecules, and one
bromide counter anion. Surprisingly, all three THF molecules were
in the equatorial plane while the bromide was in the axial position,
trans to one of the N atoms from the formamidinate. Selected bond
lengths and angles are provided in Table 4. X-ray diffraction data
for compound 4 was obtained at low quality, thus no detailed
description of the bond lengths was provided here.

Y.-J. Tsai et al. / Inorganica Chimica Acta 434 (2015) 85–91
89
Table 5
Crystallographic data of Mg complexes 1–5.
1a
2b
3a
4a
5c
Chemical formula
Formula weight
T (K)
Space group
C42H54Br2Mg2N4O4
C42H54MgN4O2
671.20
100(2)
C38H46MgN4O
599.10
100(2)
C31H47BrMgN2O3
599.93
C46H62MgN4O
711.30
150(2)
887.33
100(2)
100(2)
ꢀ
ꢀ
C2/c
P21/n
C2/c
P1
P1
Z
2
4
4
4
4
a (Å)
b (Å)
c (Å)
9.3408(15)
9.8531(18)
23.049(4)
88.356(8)
86.821(8)
74.731(7)
2043.1(6)
1.442
11.2168(5)
19.2274(8)
18.1729(9)
90
105.0960(10)
90
3784.1(3)
1.178
0.0980 (0.2320)
0.0745 (0.2021)
1.187
12.431(5)
14.968(5)
18.978(6)
90
108.43(2)
90
3350(2)
1.188
0.2224 (0.1944)
0.0835 (0.1532)
1.039
12.079(3)
16.195(4)
16.500(4)
71.773(14)
88.266(16)
89.095(16)
3064.4(13)
1.300
14.2235(5)
15.9237(6)
18.4845(7)
90
99.420(2)
90
4130.1(3)
1.144
0.0628 (0.1574)
0.0495 (0.1444)
1.079
a
(°)
b (°)
c
(°)
V (Å3)
Dc (g cmꢀ3
)
R1(wR2)d (all data)
0.0311 (0.0703)
0.0234 (0.0593)
1.104
0.1844 (0.4266)
0.1474 (0.4092)
1.104
R1(wR2)d [I > 2
r(I)]
Goodness-of-fit (GOF)
CCDC deposition No.
1058607
1058608
1058609
1058610
1058611
a
b
c
Mo Ka radiation.
Monochromatic radiation (k = 0.44280 Å).
Monochromatic radiation (k = 0.7749 Å).
P
P
P
P
d
2
R1
=
||Fo| ꢀ |Fc||/ |Fo|; wR2 = { [w(Fo ꢀ F2c)2]/ [w(Fo2)2]}1/2
.
was left stirring overnight at room temperature. Diffusion evapora-
tion crystallization with hexanes slowly diffusing into the product
solution of THF was set up at r.t. producing block-shaped clear
crystals suitable for X-ray diffraction studies. The resulting crystals
were collected by a frit, washed with hexanes (3 ꢃ 1.0 mL) and
then dried under vacuum. Crystal yield: 0.71 g, 41%. 1H NMR
(CDCl3, 600 MHz, d, ppm): 8.92 (s, 2H, N–CH–N), 7.26 (t, 8H, Ar–
H), 7.21 (d, 8H, Ar–H), 6.92 (t, 4H, Ar–H), 4.05 (br, 16H, O–CH2–
CH2 in THF), 1.86 (br, 16H, CH2–CH2–CH2 in THF). 13C NMR
(CDCl3, 150 MHz, d, ppm): 160.2, 149.1, 129.3, 121.0, 119.5,
69.94, 25.37. Anal. Calc. for C42H54Br2Mg2N4O4 (1): C, 56.85; H,
6.13; N, 6.31. Found: C, 56.68; H, 6.46; N, 6.29%.
3. Conclusions
From the reactions between formamidine derivatives and
MesMgBr, five new Mg compounds containing one halide-bridged
dimeric and four mononuclear Mg complexes were obtained and
structurally characterized. The Mg metal cores resided in either a
pseudo-octahedral or a distorted square pyramidal environment.
Structural analysis clearly demonstrated that the product geome-
try was strongly influenced by the size and position of the sub-
stituents on the ligands. Metallation of formamidinates with
increased steric demands produced only monomeric complexes.
Coordinating solvent molecules and counter anions were also
involved in governing the product geometries. The monoanionic
formamidinate ligands exhibited a symmetric bidentate chelating
4.3. Synthesis of [D(3, 5-Xyl)F]2Mg(THF)2 (2)
(g
2) coordination mode with the negative charge delocalized
across the N–C–N backbone.
0.502 g of a 1.0 M MesMgBr solution in THF (0.50 mmol), and
0.200 g D(3,5-Xyl)FH (0.79 mmol) were mixed in 10 mL of THF at
ꢀ35 °C, giving a light yellow solution upon stirring. The mixture
was stirred overnight at room temperature. Diffusion evaporation
crystallization was set up at r.t. using the THF solution with hex-
anes diffusing in, slowly producing block-shaped crystals suitable
for X-ray diffraction studies. The resulting crystals were collected
on a frit, washed with hexanes (3 ꢃ 1.0 mL) and then dried under
vacuum. Crystal yield: 0.054 g, 16% 1H NMR (CDCl3, 600 MHz, d,
ppm): 8.87 (s, 2H, N–CH–N), 6.78 (s, 8H, Ar–H), 6.58 (s, 4H, Ar–
H), 4.00 (s, 8H, O–CH2–CH2 in THF), 2.26 (s, 24H, C–CH3), 1.84 (s,
8H, CH2–CH2–CH2 in THF). 13C NMR (CDCl3, 150 MHz, d, ppm):
161.0, 148.5, 138.6, 123.1, 117.5, 69.7, 25.30, 21.54.
4. Experimental
4.1. General procedures
All manipulations were carried out using glove-box techniques
under a nitrogen atmosphere. Glassware was oven-dried at 150 °C
for a minimum of 10 h and cooled in an evacuated antechamber
prior to use in the glove box. Hexanes and THF were dried and
deoxygenated on
a Glass Contour System (SG Water USA,
Nashua, NH) and stored over 4 Å molecular sieves (Strem) prior
to use. Chloroform-d1 was purchased from Cambridge Isotope
Labs, degassed and stored over 4 Å molecular sieves in the glove
box prior to use. Non-halogenated solvents were typically tested
with a standard purple solution of sodium benzophenone ketyl of
THF in order to confirm effective oxygen and moisture removal. All
N,N0-diarylformamidine ligands were prepared, following a proce-
dure in the literature [2]. All other reagents were purchased from
commercial vendors and used without further purification unless
explicitly stated.
4.4. Synthesis of [D(2,6-Xyl)F]2Mg(THF) (3)
0.199 g of 1.0 M MesMgBr in THF (0.79 mmol) and 0.200 g
D(2,6-Xyl)FH (0.40 mmol) were mixed in 10 mL of THF at ꢀ35 °C,
giving a light yellow solution upon stirring. The mixture was stir-
red overnight at room temperature, and concentrated down to
1.0 mL under vacuum. The resulting light yellow milky solution
with white precipitate was washed with hexanes (3 ꢃ 1.0 mL)
and then dried under vacuum to give 3 as a white powder.
Isolated yield: 0.11 g, 92%. Diffusion evaporation crystallization
was set up at r.t. using THF solution with hexanes diffusing in,
slowly producing rectangular clear crystals suitable for X-ray
diffraction studies.1H NMR (CDCl3, 600 MHz, d, ppm): 7.71, 7.00,
4.2. Synthesis of [(DPhF)Mg(THF)2]2(l-Br)2 (1)
4.803 g of a 1.0 M MesMgBr solution in THF (4.78 mmol), and
0.750 g DPhFH (3.82 mmol) were mixed in 15 mL of THF at
ꢀ35 °C, giving a light yellow solution upon stirring. The mixture

90
Y.-J. Tsai et al. / Inorganica Chimica Acta 434 (2015) 85–91
6.85 (14H, Ar–H and N–CH–N), 3.83 (br, 4H, O–CH2–CH2 in THF),
2.33 (br, 24H, Ar–CH3) 1.79 (br, 4H, CH2–CH2–CH2 in THF). 13C
NMR (CDCl3, 150 MHz, d, ppm): 167.1, 133.0, 128.3, 125.3, 122.6,
69.83, 25.25, 19.94. Anal. Calc. for C38H46N4OMg: C, 76.18; H,
7.74; N, 9.35. Found: C, 76.23; H, 7.78; N, 9.27%.
to check and solve twining problems of the crystals. The position
of the heavy atoms was determined using direct methods in the
program SHELXTL [20]. Subsequent cycles of least-squares refine-
ment followed by difference Fourier syntheses revealed the posi-
tions of the remaining non-hydrogen atoms. Non-hydrogen
atoms, excluding three carbon atoms in compound 4 were refined
with anisotropic displacement parameters, and hydrogen atoms
were added in idealized positions. Selected bond lengths, non-
bonded separations, bond angles, and torsion angles are shown
in Tables 1–4. Crystallographic data is shown in Table 5. Figures
of X-ray crystal structures of complexes 1–5 (Figs. 3–7) were gen-
erated from Ortep-3 for Windows [21] and rendered using POV-
Ray v3.6 for Windows [22].
4.5. Synthesis of [D(2-iPrPh)F]MgBr(THF)3 (4)
2.258 g of 1.0 M MesMgBr solution in THF (2.25 mmol) and
0.500 g D(2-iPrPh)FH (1.78 mmol) were mixed in 10 mL of THF at
ꢀ35 °C, giving a light yellow solution upon stirring. The mixture
was stirred overnight at room temperature, and then concentrated
down to 1.0 mL under vacuum. The resulting light yellow milky
solution with white precipitate was washed with hexanes
(3 ꢃ 1.0 mL) and dried under vacuum to give 4 as a white powder.
Isolated yield: 0.72 g, 67%. Diffusion evaporation crystallization
was set up at r.t. using the THF solution with hexanes diffusing
in, slowly producing clear block-shaped crystals suitable for X-
ray diffraction studies. 1H NMR (CDCl3, 600 MHz, d, ppm): 8.15
(s, 1H, N–CH–N), 7.21–6.87 (m, 8H, Ar–H), 3.91 (br, 12H, O–CH2–
CH2 in THF), 3.64 (sep, 2H, Ar–CH–(CH3)2), 1.84 (br, 12H, CH2–
CH2–CH2 in THF), 1.19 (d, 12H, –CH–(CH3)2). 13C NMR (CDCl3,
150 MHz, d, ppm): 166.0, 147.7, 141.7, 126.2, 125.5, 122.4, 121.3,
69.44, 27.26, 25.42, 23.53. Anal. Calc. for C31H47BrMgN2O3 (4): C,
62.06; H, 7.90; N, 4.67. Found: C, 61.86; H, 8.18; N, 4.68%.
6. Other physical measurements
Elemental analyses were performed by Complete Analysis
Laboratories, Inc., Parsippany, New Jersey. 1H and 13C NMR spectra
were acquired on a JEOL ECA-600 NMR-spectrometer (600 MHz for
1H and 150 MHz for 13C NMR) with spinning at r.t. Samples were
sealed under
a nitrogen environment before being sent for
measurements.
Acknowledgments
We thank Dr. Vyacheslav V. Samoshin for the NMR measure-
ments, Dr. Yu-Sheng Chen for his help with the single crystal mea-
surement of compound 2, and Dr. Simon J. Teat for his help with
the single crystal measurement of compound 5. We gratefully
acknowledge the support from the Department of Chemistry at
University of the Pacific, Pacific Fund and SAAG Grant at
University of the Pacific, the NSF Major Research Instrumentation
Grant (CHE-0722654) for the funding of JEOL ECA-600 NMR spec-
trometer, and the general user proposals for beam time at the
Advanced Photon Source of Argonne National Laboratory and the
Advanced Light Source of Lawrence Berkeley National Lab.
ChemMatCARS Sector 15 is principally supported by the Divisions of
Chemistry (CHE) and Materials Research (DMR), National Science
Foundation, under grant number NSF/CHE-1346572. Use of the
Advanced Photon Source, an Office of Science User Facility oper-
ated for the U.S. Department of Energy (DOE) Office of Science by
Argonne National Laboratory, was supported by the U.S. DOE under
Contract No. DE-AC02-06CH11357. The Advanced Light Source is
supported by the Director, Office of Science, and Office of Basic
Energy Sciences of the U.S. Department of Energy under Contract
No. DE-AC02-05CH11231.
4.6. Synthesis of [D(2-tBuPh)F]2Mg(THF) (5)
0.821 g of 1.0 M MesMgBr in THF (0.84 mmol) and 0.40 g
D(2-tBuPh)FH (1.30 mmol) were mixed in 10 mL of THF at
ꢀ35 °C, giving a light yellow solution upon stirring. The mixture
was stirred overnight at room temperature. Diffusion evaporation
crystallization was set up using the THF solution with hexanes dif-
fusing in at room temperature for 24 h and then at ꢀ35 °C, slowly
producing clear block-shaped crystals suitable for X-ray diffraction
studies. The resulting crystals were collected on a frit, washed with
hexanes (3 ꢃ 1.0 mL) and then dried under vacuum. Crystal yield:
0.092 g, 20%. 1H NMR (CDCl3, 600 MHz, d, ppm): 8.07 (s, 2H, N–CH–
N), 7.28 (d, 4H, Ar–H), 7.06 (t, 4H, Ar–H), 7.00 (t, 4H, Ar–H), 6.63 (d,
4H, Ar–H), 3.91 (br, 4H, O–CH2–CH2 in THF), 1.84 (br, 4H, CH2–
CH2–CH2 in THF), 1.29 (s, 36H, –C–(CH3)3). 13C NMR (CDCl3,
150 MHz, d, ppm): 166.8, 148.0, 142.2, 126.5, 126.0, 125.6, 123.1,
70.2, 35.3, 25.2, 22.7.
5. X-ray structure determinations
Crystals were carefully sealed with Teflon- and Para-film in a
capped vial and stored in a N2 filled zip-lock bag before being
shipped out for analysis. Single crystals suitable for X-ray analysis
were coated with deoxygenated Paratone-N oil and mounted on
Kaptan loops. Crystallographic data for compounds 1, 3, and 4 were
collected at 100(2) K on a Siemens (Bruker) SMART CCD area detec-
Appendix A. Supplementary material
CCDC 1058607 (1), 1058608 (2), 1058609 (3), 1058610 (4) and
1058611 (5) contains the supplementary crystallographic data for
this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.
uk/data_request/cif. Supplementary data associated with this arti-
cle can be found, in the online version, at http://dx.doi.org/10.
1016/j.ica.2015.05.005.
tor instrument with Mo K
a radiation. Crystallographic data for
compound 2 were collected on Beamline ChemMatCARS Sector 15
at the Advanced Photon Source, Argonne National Lab using
monochromatic
radiation (k = 0.44280 Å) at
100(2) K.
Crystallographic Data for compound 5 was collected on Beamline
11.3.1 at the Advanced Light Source, Lawrence Berkeley National
Lab using monochromatic radiation (k = 0.7749 Å) at 150(2) K.
Raw data was integrated and corrected for Lorentz and polarization
effects using Bruker APEX2 v. 2009.1 [16]. Absorption corrections
were applied using SADABS [17]. Space group assignments were
determined by examination of systematic absences, E-statistics,
and successive refinement of the structures. The program PLATON
[18] was employed to confirm the absence of higher symmetry
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