D.A. Powell-Jia et al. / Inorganica Chimica Acta 363 (2010) 2728–2733
2729
moved under reduced pressure. The resulting green residue was
dissolved in THF and crystals were obtained via pentane diffusion
(13 mg, 59%). Found: C, 63.77; H, 7.58; N, 11.16%. NiIIpmbTHF
(C33H43N5O3Ni) requires C, 64.30; H, 7.03: N, 11.36%. FT-IR/cmÀ1
A
O
B
C
R
R
H
N
NH
N
X
N
But
N
N
O
M
Bz
m(NH) 3347; kmax (THF, nm (e
, MÀ1 cmÀ1)) 20 °C: 446
N
(Nujol):
(29); eff = 2.76; HRMS (ES+): exact mass calc. for C29H35N5NiO2
M
l
O
2
[M+H], 544.222. Found: 544.2215.
Fig. 1. The carboxyamido unit used to form an intramolecular H-bond (A), to form a
2.3. Physical methods
bidentate ligand (B), and the H2pmb ligand used in this study (C).
NMR spectra were obtained on either Bruker DRX-400 MHz or
Bruker Advance 500 MHz spectrometers. NMR solvents were used
as received. Electronic spectra were recorded with an Agilent 8453
spectrophotometer. FT-IR spectra were collected on a Varian 800
Scimitar Series FT-IR spectrophotometer and are reported in wave-
numbers. Mass spectra were recorded on a Waters LCT Premier
mass spectrometer operated in EI or APCI mode. Magnetic mo-
ments were determined using Evan’s method in DMSO [9]. Ele-
mental analyses were performed on a Perkin–Elmer 2400 Series
II CHNS analyzer.
literature procedure [8]. Elemental analyses for NiIIH2pmb and
NiIIH2pmb( 2-OAc)( 1-OAc) consistently gave low values for the
j j
percentages of carbon and nitrogen. We thus report high-resolution
mass spectral data for these complexes.
2.2. Preparation of complexes
2.2.1. {(Bis[N-(6-pivalamido-2-pyridylmethyl)]benzylamine)-
(dichloro)}nickelate(II)Á(NiIIH2pmbCl2)
A solution of H2pmb (50 mg, 0.103 mmol) in 3 mL of methanol
was treated with NiCl2Á6H2O (25 mg, 0.052 mmol). The solution
turned dark green and was stirred for 10 min. Orange crystals were
obtained through diffusion with diethyl ether into methanol
(46 mg, 72%). Found: C, 55.44; H, 6.22; N, 11.24%. NiIIH2-
pmbCl2Á1/2MeOH (C29.5H39N5O2.5NiCl2) requires C, 55.95; H, 6.21:
2.3.1. Crystallographic structural determination
Intensity data for the complexes were collected using a Bruker
SMART APEX II diffractometer using graphite-monochromated
Mo K
a radiation (k = 0.71073 Å). The SMART [10] program package
was used to determine the unit-cell parameters and for data collec-
tion (25 s/frame scan time) for a sphere of diffraction data. The raw
frame data was processed using SAINT [11] and SADABS [12] to yield
the reflection data files. Subsequent calculations were carried out
using the SHELXTL [13] program. The structure was solved by direct
methods and refined on F2 by full-matrix least-squares techniques.
The analytical scattering factors [14] for neutral atoms were used
throughout the analysis.
N, 11.06%. FT-IR/cmÀ1 (Nujol):
m(NH) = 3297; kmax (THF, nm
(
e
, MÀ1 cmÀ1)) 20 °C: 461 (124), À100 °C: 429 (89), kmax (acetone,
nm (
(MeCN, nm, (
kmax (DCM, nm (
(42), kmax (MeOH, nm, (
e
, MÀ1 cmÀ1)) 20 °C: 457 (101) and À90 °C: 417 (53), kmax
e
, MÀ1 cmÀ1)) 20 °C: 452 (88) and À40 °C: 446 (79),
e
, MÀ1 cmÀ1)) 20 °C: 452 (100) and À80 °C: 442
e
, MÀ1 cmÀ1)) 20 °C: 597 (11) and À90 °C:
555 (32); eff = 2.86.
l
2.3.1.1. NiIIH2pmbCl2. A green crystal of approximate dimensions
0.15 Â 0.21 Â 0.23 mm was used, giving diffraction symmetry of
2/m and systematic absences consistent with the monoclinic space
group P21/c. The structure was solved by direct methods and re-
fined on F2 by full-matrix least-squares techniques. Hydrogen
atoms associated with atoms C(20), C(21), and C(22) were included
using a riding model.
2.2.2. {(Bis[N-(6-pivalamido-2-pyridylmethyl)]benzylamine)-
(diacetato)}nickelate(II)Á(NiIIH2pmb(
j j
2-OAc)( 1-OAc))
A solution of NiIIH2pmbCl2 (58 mg, 0.081 mmol) in 3 mL of 1:1
MeCN:THF was treated with Me4NOAc (22 mg, 1.6 mmol). The or-
ange solution was stirred for 15 min, AgBF4 was added and allowed
to stir for an additional 10 min then filtered over Celite to remove
AgCl. The volatiles were removed and the resulting blue solid was
redissolved in THF. Blue crystals were obtained via pentane diffu-
sion into THF solution (45 mg, 84%). FT-IR/cmÀ1 (Nujol):
3406, 3315; kmax (THF, nm (
, MÀ1 cmÀ1)) 20 °C: 651 (16) and
À100 °C: 639 (39), kmax (MeCN, nm (
, MÀ1 cmÀ1)) 20 °C: 656
(20) and À40 °C: 645 (26), kmax (acetone, nm (
, MÀ1 cmÀ1))
eff = 2.84; HRMS (ES+): ex-
m(NH)
2.3.1.2. NiIIH2pmb(
j
2-OAc)(
j
1-OAc)ÁCH3CN. A blue crystal of approx-
e
imate dimensions 0.07 Â 0.26 Â 0.27 mm was employed, giving
diffraction symmetry of 2/m and the systematic absences consis-
tent with the monoclinic space groups P2/c and Pc. It was later
determined that space group Pc was correct. Hydrogen atoms were
either located from a difference-Fourier map and refined (x, y, z and
Uiso) or were included using a riding model. There were two
molecules of the formula-unit and two molecules of acetonitrile
solvent present. Attempts to solve the structure in space group
P2/c were unsuccessful. Analysis of the data using the PLATON [15]
program package suggested the space group assignment was
correct. The structure was refined using the TWIN instruction
[16], BASF = 0.372.
e
e
20 °C: 646 (19) and À80 °C: 645 (33);
l
act mass calc. for C31H40N5NiO4 [MÀOAc], 604.2433. Found:
604.2408.
2.2.3. {(Bis[N-(6-pivalamido-2-pyridylmethyl)][O-carboxyamido]-
benzylamine])(chloro)}nickelate(II) (NiIIHpmbCl)
Under argon, a solution of NiIIH2pmbCl2 (50 mg, 0.081 mmol) in
3 mL of THF was treated with KOBut (9.1 mg, 0.081 mmol) and was
allowed to stir for 20 min. Green crystals were obtained via pen-
tane diffusion into a THF solution (46 mg, 98%). FT-IR/cmÀ1 (Nu-
jol):
(35) and À100 °C: 639 (39). kmax (DCM, nm (
eff = 2.88; HRMS (APCI): exact
m(NH)3264, 3180; kmax (THF, nm (e
, MÀ1 cmÀ1)) 20 °C: 655
, MÀ1 cmÀ1)) 20 °C:
2.3.1.3. NiIIHpmbCl. A gold-green crystal of approximate dimen-
sions 0.15 Â 0.30 Â 0.35 mm gave diffraction symmetry of 2/m
and the systematic absences consistent with the monoclinic space
group P21/n that was later determined to be correct. Hydrogen
atoms were included using a riding model. There were two mole-
cules of the formula-unit present (Z = 8).
e
635 (25) and À90 °C: 635 (44);
l
mass calc. for C29H36N5NiO2Cl [M+H], 580.1989. Found: 580.1995.
2.2.4. {(Bis[N-(6-pivalamido-2-pyridylmethyl)-O-carboxyamido]-
benzylamine])}-nickelate(II) (NiIIpmb)
Under argon, a solution of NiIIH2pmbCl2 (25 mg, 0.041 mmol) in
3 mL of 1:1 THF:MeCN was treated with KOBut (9.1 mg,
0.081 mmol) and was allowed to stir for 20 min. Volatiles were re-
2.3.1.4. NiIIpmb(THF). The crystal of this complex isolated con-
tained one coordinated THF molecule. A colorless crystal of
approximate dimensions 0.13 Â 0.13 Â 0.22 mm was mounted on