Exceptional thermal stability and high volatility in mid to late first row transition metal complexes containing carbohydrazide ligands

Article abstract of DOI:10.1016/j.poly.2012.07.034

Treatment of metal(II) halides (metal = Cu, Ni, Co, Fe, Mn, Cr) with the potassium salts of carbohydrazides L¹-L⁶ afforded Cu(L¹)₂ (75%), Cu(L²)₂ (51%), Cu(L³)₂ (23%), Co(L¹)₂ (57%), Cr(L¹)₂ (62%), Ni(L¹)₂ (76%), Ni(L²)₂ (62%), Ni(L³)₂ (62%), Ni(L⁴)₂ (13%), Ni(L⁵)₂ (11%), Ni(L⁶)₂ (29%), [Fe(L¹)₂]₂ (28%), and [Mn(L¹)₂]₂ (12%) as crystalline solids, where L¹ = Me₂NNC(tBu)O^-, L² = Me₂NNC(iPr)O^-, L³ = Me₂NNC(Me) O^-, L⁴ = (CH₂)₅NNC(tBu)O ^-, L⁵ = (CH₂)₅NNC(iPr)O^-, and L⁶ = (CH₂)₅NNC(Me)O^-. These complexes were characterized by spectral and analytical techniques, and by X-ray crystal structure determinations for Cu(L¹)₂, Co(L ¹)₂, Cr(L¹)₂, Ni(L¹) ₂, and [Fe(L¹)₂]₂. Cu(L ¹)₂, Co(L¹)₂, Cr(L¹) ₂, and Ni(L¹)₂ exist as square planar, monomeric complexes, whereas [Fe(L¹)₂]₂ is a dimer. A combination of sublimation studies, thermal decomposition temperature determinations, and thermogravimetric/differential thermal analysis demonstrate that the Cu, Co, and Ni complexes Cu(L¹)₂, Cu(L ²)₂, Co(L¹)₂, Ni(L¹) ₂, and Ni(L²)₂ have the lowest sublimation temperatures and highest decomposition temperatures among the series. Additionally, these compounds have higher volatilities and thermal stabilities than commonly used ALD and CVD precursors. Hence, these new complexes have excellent properties for application as ALD precursors to Cu, Co, and Ni metal films.

Full text of DOI:10.1016/j.poly.2012.07.034

Polyhedron 52 (2013) 820–830
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Exceptional thermal stability and high volatility in mid to late first row
transition metal complexes containing carbohydrazide ligands
1
⇑
Mahesh C. Karunarathne , Thomas J. Knisley, Gabriel S. Tunstull, Mary Jane Heeg, Charles H. Winter
Department of Chemistry, Wayne State University, Detroit, MI 48202, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Available online 20 July 2012
Treatment of metal(II) halides (metal = Cu, Ni, Co, Fe, Mn, Cr) with the potassium salts of carbohydrazides
1
6
1
2
3
1
1
1
L –L afforded Cu(L )
2
(75%), Cu(L )
2
(51%), Cu(L )
2
(23%), Co(L )
2
(57%), Cr(L )
2
(62%), Ni(L )
2
(76%),
2
3
4
5
6
1
1
Ni(L )
2
(62%), Ni(L )
2
(62%), Ni(L )
2
(13%), Ni(L )
2
(11%), Ni(L )
2
(29%), [Fe(L )
2
]
2
(28%), and [Mn(L ) ]
2 2
ꢀ
Dedicated to Alfred Werner on the 100th
Anniversary of his Nobel Prize in Chemistry
in 1913.
1
ꢀ
6
2
ꢀ
3
(
12%) as crystalline solids, where L = Me
2
NN@C(tBu)O , L = Me
2
NN@C(iPr)O , L = Me
2
NN@C(Me)O ,
4
ꢀ
5
ꢀ
ꢀ
L = (CH
2
5
) NN@C(tBu)O , L = (CH
)
2 5
NN@C(iPr)O , and L = (CH
2
)
5
NN@C(Me)O . These complexes were
characterized by spectral and analytical techniques, and by X-ray crystal structure determinations for
1
1
1
1
1
1
1
1
1
Cu(L )
2
, Co(L )
2
, Cr(L )
2
, Ni(L )
2
, and [Fe(L )
2
]
2
. Cu(L )
2 2 2 2
, Co(L ) , Cr(L ) , and Ni(L ) exist as square planar,
Keywords:
Copper
Nickel
Cobalt
1
monomeric complexes, whereas [Fe(L )
2
]
2
is a dimer. A combination of sublimation studies, thermal
decomposition temperature determinations, and thermogravimetric/differential thermal analysis dem-
1
2
1
1
2
2 2 2 2 2
onstrate that the Cu, Co, and Ni complexes Cu(L ) , Cu(L ) , Co(L ) , Ni(L ) , and Ni(L ) have the lowest
Iron
Manganese
Chromium
Coordination compound
Atomic layer deposition
Film growth precursor
sublimation temperatures and highest decomposition temperatures among the series. Additionally, these
compounds have higher volatilities and thermal stabilities than commonly used ALD and CVD precursors.
Hence, these new complexes have excellent properties for application as ALD precursors to Cu, Co, and Ni
metal films.
Ó 2012 Elsevier Ltd. All rights reserved.
1
. Introduction
Thin films of first row transition metal elements have many
65 nm thick to reduce the electrical resistivity of the interconnect
structure [1,3]. Materials that are currently under consideration as
x
advanced barriers include TaN and WN (x = 0.5–1), as well as ter-
important current and future applications. Copper (Cu) is the con-
ductor of choice for interconnects in microelectronics devices, and
is currently applied in the etched trenches and vias through a two-
step process involving creation of a thin, conformal seed layer by
physical vapor deposition, followed by electrodeposition fill [1].
nary compositions of these materials containing carbon or Si [2].
However, 65 nm thick layers of these nitride-based barrier materi-
als may not serve as effective Cu diffusion barriers [1]. In response
to this concern, considerable effort has been directed toward iden-
tification of alternative barrier materials. Very thin films (65 nm)
of transition metals such as manganese (Mn) [4], Cr [5,6], Ru [5],
and others [6] have emerged as new Cu diffusion barrier materials.
It has been recently demonstrated that annealing of a 150 nm thick
2
However, Cu does not adhere well to SiO surfaces, and the crea-
tion of a continuous seed layer is difficult. In response to this chal-
lenge, other metal seed layers for Cu metallization have been
explored, including chromium (Cr), cobalt (Co), and ruthenium
90/10 Cu/Mn alloy film on SiO
tween 250 and 450 °C led to migration of the Mn atoms to the
SiO interface to form a segregated 2–8 nm MnSi layer between
the SiO and Cu layers [4]. Most significantly, this Mn-containing
2
substrates at temperatures be-
(
2
Ru) [1,2]. Cu readily diffuses into SiO layers and silicon (Si) sub-
strates during the high temperatures encountered in microelec-
tronics device fabrication. Therefore, a barrier between Cu and Si
is required. This barrier must stop the diffusion of Cu at deposition
temperatures long enough for manufacturing of the device, must
be unreactive toward Cu and Si, and should exhibit good adhesion
to Cu and Si. In addition, barriers in future devices should be
2
x y
O
2
layer served as a Cu diffusion barrier for up to 100 h at 450 °C
[4a] This work suggests that ultrathin Mn-based films can replace
current nitride-based barriers in future microelectronics devices.
There are other applications that require the growth of thin transi-
tion metal films. Magnetoresistive random access memory
(
MRAM) devices require thin, conformal layers of magnetic metals
⇑
Corresponding author. Tel.: +1 313 577 5224; fax: +1 313 577 8289.
E-mail address: chw@chem.wayne.edu (C.H. Winter).
Present address: Department of Chemistry, University of Sri Jayewardenepura,
such as nickel (Ni), Co, or iron (Fe) [7]. In a recent report, 2.9–
3.4 nm Cu nanocrystals grown by atomic layer deposition (ALD)
on silica showed high catalytic activity for the water gas shift
1
Nugegoda, Sri Lanka.
0
277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.07.034

M.C. Karunarathne et al. / Polyhedron 52 (2013) 820–830
821
2 2 2
reaction (CO + H O ? H + CO ) and performed better than plati-
num nanocrystals on silica supports [8]. Ni and nickel silicide (NiSi)
are important contact materials in microelectronics devices [9].
The smallest microelectronics device dimensions are scheduled
to reach 22 nm in 2012, and existing thin film deposition processes
will soon not be able to provide the required level of thickness con-
trol and conformality, especially in high aspect ratio features
1
6
Chart 1. Chemical structures of L –L .
[
3,10]. The ALD technique is well suited for nanoscale film growth,
since it produces inherently conformal films and affords angstrom-
level film thickness control due to its self-limited growth mecha-
nism [11]. In a typical ALD cycle, a metal precursor is carried in
the vapor phase by an inert carrier gas into the reaction chamber,
where it chemisorbs upon substrate surface reactive sites. Once all
available surface reactive sites have been consumed, the surface is
saturated, no further reactions can occur, and unreacted precursor
and reaction byproducts are removed from the reactor with an in-
ert gas purge. Next, a pulse of a second precursor vapor is passed
over the substrate, which reacts with surface-adsorbed metal pre-
cursor to produce the desired thin film material. To conclude the
deposition sequence, a second inert gas purge is then passed
through the reactor to remove reaction byproducts and excess pre-
cursor. Under optimized deposition conditions, the growth rate per
cycle remains constant, allowing the film thickness to be depen-
dent upon the number of deposition cycles. ALD precursors must
be thermally stable on the surface of the substrate at the deposi-
tion temperature, or else non-self-limited, chemical vapor deposi-
tion (CVD)-like growth occurs through precursor decomposition
[
28]. Problems with existing Cu ALD processes include high growth
temperatures, lack of self-limited growth in many systems due to
precursor thermal decomposition, low reactivity of the Cu precur-
sors toward the reducing co-reagents, incorporation of zinc in pro-
cesses using ZnEt
coverage in plasma processes. We have recently reported a 3-step
Cu ALD process that entails the use of Cu(OCHMeCH NMe , for-
mic acid, and hydrazine [29]. This process affords self-limited
growth between 100 and 170 °C with a high growth rate of
0
2
, and substrate damage and low conformal
2
2 2
)
.50 Å/cycle. However, self-limited growth is lost above 170 °C
due to thermal decomposition of Cu(OCHMeCH NMe . ALD pre-
2
2 2
)
cursors for Ni metal growth have contained amidinate, alkoxide,
or cyclopentadienyl ligands, and reducing co-reagents have in-
cluded ammonia plasma, hydrogen plasma, and molecular hydro-
gen [9,16]. Growth of Co metal films by ALD has used precursors
containing cyclopentadienyl, amidinate, and carbonyl ligands
[
30]. The associated reducing co-reagents were dimethylhydrazine,
ammonia plasma, hydrogen plasma, and nitrogen plasma. ALD
growth of Fe metal on aerogels was reported [31], but details were
not given. Mn and Cr metal films have not been grown by thermal
ALD, but a plasma ALD process for Cu/Mn alloy films was recently
reported using a Mn b-diketonate precursor [32]. Existing ALD pre-
cursors for Cu, Ni, and Co generally suffer from low thermal stabil-
ity, low reactivity toward reducing agents, or a combination of
both [9,16,30–32].
[
11]. In addition, the metal precursor should be highly reactive to-
ward a second precursor to afford the desired thin film material. Fi-
nally, ALD precursors should be as volatile as possible, since the
minimum deposition temperature is often a few degrees higher
than the precursor delivery temperature to avoid condensation in
the reactor lines.
Transition metal thin films need to be deposited by ALD to meet
future conformality and thickness uniformity requirements in
microelectronics devices and nanotechnology. In addition, the
metals should be deposited at the lowest possible temperatures
Herein, we report the synthesis, structure, and precursor prop-
erties of a series of Cu, Ni, Co, Fe, Mn, and Cr complexes that con-
1
6
tain carbohydrazide ligands chosen from L to L (Chart 1). The Cu,
Ni, and Co complexes are highly volatile, have very high solid state
decomposition temperatures, and thus have promising properties
for use as ALD precursors. Carbohydrazide ligands have previously
been widely used in Si [33] and Ge [34] compounds. However, the
coordination chemistry of these ligands with transition metals has
been limited to a few copper complexes [35], a nickel complex
(
ideally 6 100 °C) to afford the smallest surface roughnesses, pro-
mote facile nucleation, and give continuous films even at thick-
nesses of few nanometers [12]. Thermal ALD is greatly
a
preferred over plasma ALD, since the latter can lead to substrate
damage from the highly reactive growth species and conformal
coverage can be low due to surface radical recombination reactions
that remove the reducing coreagents [13]. In general, ALD precur-
sors for transition metal thin films should have thermal decompo-
sition temperatures of P200 °C and sublimation temperatures of
[
35a], and a platinum complex [36].
6
80 °C at low pressures to allow a wide temperature window for
2. Results and discussion
film deposition. Additionally, transition metal ALD precursors must
be highly reactive toward a reducing agent to afford high purity
metal films.
2.1. Synthetic aspects
1
6
ALD precursors processes for first row transition metal films are
The carbohydrazine ligand precursors L H–L H (Chart 1) were
prepared and characterized as described in Section 4 by treatment
of the carboxylic acid chloride with 1,1-dimethylhydrazine or 1-
aminopiperidine in the presence of triethylamine. Treatment of
best developed for Cu. Direct Cu ALD processes include CuL
at 100–150 °C (L = OCHMeCH NMe , b-ketiminate, b-diketiminate)
12,14], Cu(thd) /H at 190–260 °C (thd = 2,2,6,6-tetramethyl-3,5-
heptanedionate) [15], [Cu(sBuNCMeNsBu)] /H at 150–250 °C
16–18], Cu(hfac) /alcohol at 300 °C (hfac = 1,1,1,5,5,5-hexa-
fluoro-3,5-pentanedionate) [19], CuCl/H at 360–410 °C [20], and
2 2
/ZnEt
2
2
[
2
2
1
2
2
2
anhydrous copper(II) chloride with two equivalents of KL , KL ,
or KL (prepared in situ from L H–L H and potassium hydride) in
(1, 75%), Cu(L )
(3, 23%), respectively, as maroon crystals upon sublimation
of the crude products at 70–80 °C/0.05 Torr (Eq. (1)). Similar treat-
ment of cobalt(II) chloride or chromium(II) chloride with KL affor-
3
1
3
[
2
1
2
2
tetrahydrofuran afforded Cu(L )
2
2
(2, 51%), and
3
CuCl/Zn at 440–500 °C [21]. ALD Cu growth was claimed from a
Cu(I) b-diketiminate precursor and diethylsilane [22], but a later
study showed that this process proceeds by a pulsed chemical va-
por deposition (CVD) mechanism [23]. Indirect routes to Cu films
include reduction of ALD CuO by isopropanol [24], reduction of
Cu(L )
2
1
1
1
ded Co(L )
2
(4, 57%) and Cr(L )
2
(5, 62%) as red and orange
ꢁCH CN with
(6, 76%), Ni(L )
crystalline solids, respectively. Treatment of NiCl
2
3
1
6
1
2
ALD Cu
in conjunction with a ruthenium seed layer [26]. Plasma-based
ALD processes include Cu(acac) /hydrogen plasma (acac = 2,4-pen-
tanedionate) [27] and Cu(OCHMeCH NMe /hydrogen plasma
3
N with H
2
2
[25], and reduction of ALD Cu O by formic acid
two equivalents of KL –KL afforded Ni(L )
2
2
(7,
3
4
5
62%), Ni(L )
(8, 62%), Ni(L ) (9, 13%), Ni(L ) (10, 11%), and
2 2 2
(11, 29%) as orange crystals upon sublimation between 70
and 80 °C/0.05 Torr (Eq. (2)). Treatment of anhydrous iron(II)
6
2
Ni(L )
2
2
)
2 2

8
22
M.C. Karunarathne et al. / Polyhedron 52 (2013) 820–830
1
ment expected for a high-spin d4 Cr(II) center with four unpaired
electrons ( eff = 4.90 BM). Complexes 12 and 13 have solution
magnetic moments of 4.55 and 5.47 BM, respectively. These values
chloride or manganese(II) bromide with two equivalents of KL in
1
tetrahydrofuran afforded the dinuclear complexes [Fe(L )
2
]
2
(12,
(13, 12%), respectively (Eq. (3)). Similar treat-
ment of cobalt(II), chromium(II), iron(II), or manganese(II) halides
with the less sterically encumbered KL or KL did not generate iso-
lable products or gave very low yields.
l
1
2
8%) and [Mn(L )
2
]
2
are close to those expected for four and five unpaired electrons
2
3
(leff = 4.90, 5.92 BM), respectively, and may indicate the formation
of tetrahedral, monomeric structures for 12 and 13 in benzene. For
ð1Þ
ð2Þ
ð3Þ:
The structural assignments for 1–13 are based upon spectral
comparison, the solid state magnetic moments for 12 (7.99 BM)
and 13 (9.62 BM) were much higher than in solution.
and analytical data. In addition, X-ray crystal structure determina-
1
tions were carried out for 1, 4, 5, 6, and 12. The H NMR spectra of
1
–5, 12, and 13 show extremely broad resonances due to their
paramagnetic nature, while the corresponding spectra of 6–11 in
benzene-d exhibit sharp signals for the ligand substituents, which
can be attributed to spin-paired, diamagnetic d Ni(II) centers. The
solid state magnetic moment ( eff) values of 1–3 range between
.51 and 1.69 BM, which are close to the spin only magnetic mo-
2.2. Structural aspects
6
8
The crystal structures of 1, 4, 5, 6, and 12 were obtained to
establish the geometries about the metal centers and to assess
the bonding modes of the carbohydrazide ligands. Experimental
crystallographic data are summarized in Table 1 and selected bond
lengths and angles are presented in Tables 2 and 3. Perspective
views of 1, 4, 5, 6, and 12 are given in Figs. 1–5. A low precision
X-ray crystal structure determination of 13 demonstrated a dinu-
clear structure similar to that of 12. The spectral data of 2, 3, 7,
8, 9, 10, and 11 are similar to those of the structurally character-
ized complexes 1, 4, 5, and 6, which suggest similar, square planar
monomers for the former group of compounds.
l
1
9
ment expected for a d Cu(II) center with one unpaired electron
7
(
l
eff = 1.73 BM). Complex 4, which has a d electron configuration
and would be expected to have a magnetic moment value close to
.73 BM if low-spin or 3.87 BM if high-spin, exhibited magnetic
1
moment values of 2.17 BM both in the solid state and in benzene
solution. This value suggests a low spin configuration. Complex 5
has solid state and solution magnetic moments of 4.84 and 5.04
BM, respectively, which are close to the spin only magnetic mo-
Table 1
Crystal data and data collection parameters for 1, 4, 5, 6, and 12.
1
4
5
6
12
Formula
FW
Space group
C
14
H
30CuN
4
O
2
C
14
H
30CoN
4
O
2
C
14
H
30CrN
4
O
2
C
14
H
30
N
4
NiO
2
28 2 8 4
C H60Fe N O
684.54
P1ꢀ
349.96
P2 /n
345.35
P2 /n
338.42
P2 /n
345.13
P2 /n
1
1
1
1
a (Å)
b (Å)
c (Å)
5.6414(2)
8.8780(3)
17.9543(5)
5.65930(10)
8.8040(2)
18.0989(5)
5.6015(2)
9.0727(4)
17.5995(7)
5.6745(5)
8.7346(7)
18.2007(13)
11.3304(4)
12.6325(5)
13.4921(6)
81.6893
73.5693
89.3823
a
(°)
b (°)
(°)
94.233010
95.218010
91.6822
95.3795
c
3
V (Å )
896.78(5)
2
898.03(4)
2
894.03(6)
2
898.14(12)
2
1831.90(13)
2
Z
T (K)
k (Å)
100(2)
0.71073
1.296
1.227
2.47
100(2)
0.71073
1.277
0.965
2.60
100(2)
0.71073
1.257
0.649
2.95
100(2)
0.71073
1.276
1.090
5.89
100(2)
0.71073
1.241
0.833
9.76
q
l
calc (g cmꢀ3)
ꢀ
1
(mm
)
R(F) (%)
Rw(F) (%)
6.46
6.07
7.21
16.28
26.78
P||F
| ꢀ |F
|F
||/P |; Rw(F) = [P
w(F
ꢀ F
c
) / w(F
P
) ] for I > 2
r(I).
2
2
2
2 2 1/2
R(F) =
o
c
o
o
o

M.C. Karunarathne et al. / Polyhedron 52 (2013) 820–830
823
Table 2
Selected bond lengths (Å) and angles (°) for 1, 4, 5, and 6.
1
4
5
6
M–O
M–N
N–N
Core N–C
1.9023(7)
1.9924(8)
1.468(1)
1.298(1)
1.478(1)
1.8463(8)
1.938(1)
1.478(1)
1.291(2)
1.479(2)
1.480(2)
1.322(1)
1.9629(6)
1.840(1)
1.906(2)
1.479(3)
1.291(3)
1.476(4)
1.490(3)
1.315(3)
94.58(8)
85.42(8)
2.0910(7)
1.477(1)
1.297(1)
1.475(1)
1.480(1)
1.311(1)
N–CH
3
1
.478(1)
1.310(1)
96.75(3)
3.25(3)
C–O
N–M–O
95.49(4)
84.51(4)
99.99(3)
80.01(3)
8
Complexes 1, 4, 5, and 6 have four-coordinate monomeric struc-
tures with square planar geometry around the metal centers (Figs.
Fig. 1. Perspective view of 1 with thermal ellipsoids at the 50% probability level.
1
–4). All molecules have an inversion center located on the metal
atom. The carbohydrazide ligands are coordinated in a chelating
2
j
-fashion through the carbonyl oxygen atom and dimethylamino
nitrogen atom. The carbohydrazide ligand core C–N bond lengths
range between 1.291 and 1.298 Å, which are in between the dis-
tances expected for C–N single (1.46 Å) and C@N double bonds
(
1.21 Å) [37]. The oxygen and nitrogen donor atoms in the two li-
0
0
gands are mutually trans, with N–M–N and O–M–O angles of
80.00°. The intraligand N–M–O angles range between 80.01(3)°
1
and 85.42(8)°, and the related interligand angles lie between
Table 3
Selected bond lengths (Å) and angles (°) for 12.
Fe1–O1
Fe1–O2
Fe1–O3
Fe2–O2
Fe2–O3
Fe2–O4
Fe1–N1
Fe1–N5
Fe2–N3
Fe2–N7
N1–N2
N3–N4
N5–N6
N7–N8
N2–C1
N4–C8
1.954(4)
2.066(3)
2.111(3)
2.111(3)
2.061(3)
1.964(4)
2.197(4)
2.198(5)
2.235(5)
2.127(5)
1.482(6)
1.468(7)
1.462(6)
1.489(7)
1.305(7)
1.305(7)
1.301(7)
1.331(8)
1.300(6)
1.361(6)
1.340(6)
1.257(7)
Fig. 2. Perspective view of 4 with thermal ellipsoids at the 50% probability level.
N6–C15
N8–C22
C1–O1
C8–O2
C15–O3
C22–O4
Fig. 3. Perspective view of 5 with thermal ellipsoids at the 50% probability level.
O1–Fe1–O2
O1–Fe1–O3
O1–Fe1–N1
O1–Fe1–N5
O2–Fe1–O3
O2–Fe1–N1
O2–Fe1–N5
O3–Fe1–N1
O3–Fe1–N5
N1–Fe1–N5
O2–Fe2–O3
O2–Fe2–O4
O2–Fe2–N3
O2–Fe2–N7
O3–Fe2–O4
O3–Fe2–N3
O3–Fe2–N7
O4–Fe2–N3
O4–Fe2–N7
N3–Fe2–N7
Fe1–O2–Fe2
Fe1–O3–Fe2
108.0(2)
174.6(1)
77.9(2)
102.0(2)
77.4(1)
124.5(2)
127.4(2)
99.8(2)
73.6(2)
103.2(2)
77.4(1)
171.8(2)
125.2(2)
102.2(2)
108.5(2)
74.3(2)
125.3(2)
97.5(2)
79.2(2)
106.2(2)
102.5(1)
102.7(1)
Fig. 4. Perspective view of 6 with thermal ellipsoids at the 50% probability level.

8
24
M.C. Karunarathne et al. / Polyhedron 52 (2013) 820–830
Fig. 5. Perspective view of 12 with thermal ellipsoids at the 50% probability level.
Table 4
Sublimation temperature, melting point, solid state decomposition temperature,
percent recovery, and percent nonvolatile residue for 1–13.
Complex Sublimation
temperature
Melting
point (°C) decomposition
Solid state
%
%
recovery nonvolatile
residue
(°C/
temperature
0.05 Torr)
(°C)
1
2
3
4
5
6
7
8
9
0
1
2
3
70
75
80
75
137–139
118–121
184–187
137–140
143–146
140–142
125–128
164–166
203–205
115–117
230–232
155–157
92–94
255
247
225
245
150
323–325
317
320
282
248
273
160
96
>99
>99
98.1
97.7
–
>99
>99
>99
95.8
97.6
96.9
–
0.0
0.0
0.5
0.0
–
0.0
0.0
0.0
0.8
0.9
0.2
–
non-volatile
70
80
80
155
110
150
non-volatile
non-volatile
1
1
1
1
–
–
Fig. 6. TGA plots of complexes 1, 2, and 4.
9
4.58(8)° and 99.99(3)°. The two nitrogen atoms, two oxygen
atoms, and the metal ion are planar to <0.002 Å. The metal-nitro-
gen distances (1, 1.9924(8); 4, 1.938(1); 5, 2.0910(7); 6,
1
(
.906(2) Å) are uniformly longer than the metal–oxygen distances
1, 1.9023(7); 4, 1.8463(8); 5, 1.9629(6); 6, 1.840(1) Å), consistent
with neutral dimethylamino and anionic oxygen donor atoms,
respectively. A square planar Cu(II) complex, Cu(OC(O-2,4-Cl
NNMe [35a], with an inner coordination sphere similar to that
2 6 3
C H )
@
2 2
)
of 1, has Cu–O distances of 1.901(3) and 1.910(3) Å and Cu–N
distances of 1.985(3) and 2.001(3) Å. These values are very close
to those of 1. The square planar b-ketiminate complexes Co(OC
(
(
CH
Co–O 1.852(1), 1.854(1); Co–N 1.858(1), 1.862(1) Å) [38],
)) (Ni–O, 1.818(1); Ni–N,
.919(1) Å) [39], and Cr(OCMeCHCMeN(C (Cr–O 1.971(2),
.977(2); Cr–N 2.085(3), 2.091(3) Å) [40] have metal–oxygen
2 6 5 2 6 5 2 2 2 6 5 2 6 5
C H )CHC(CH C H )NCH CH NC(CH C H )CHC(CH C H )O)
Ni(OCMeCHCMeN(2,6-iPr
1
1
2
C
6
H
3
2
6 2
H11))
and metal–nitrogen bond lengths that are very similar to those
of 4–6.
Fig. 7. TGA plots of Ni complexes 6–11.
Compound 12 exists as a dinuclear complex in which each iron
atom is bonded to the nitrogen and oxygen donor atoms of one car-
2
bohydrazide ligand in a terminal
j
-fashion and to one nitrogen
C–N bond lengths range from 1.301(7) to 1.331(8) Å, which are
similar to slightly longer than those of 1, 4, 5, and 6. The geometry
around each iron center can be approximated as distorted trigonal
and two oxygen atoms of two bridging carbohydrazide ligands
with l-j :j -interactions (Fig. 5). The carbohydrazide ligand core
1
2

M.C. Karunarathne et al. / Polyhedron 52 (2013) 820–830
825
2
1:
2
bipyramidal with two oxygen atoms from one
j
and one
l-
j
j
Cu(OCHMeCH
2 2
NMe )
2
[29,42] is widely used as a Cu CVD and
ligand occupying the axial positions while two nitrogen atoms
ALD precursor. This complex sublimes at 90 °C/0.05 Torr [29], so
1–4 and 6–8 are slightly more volatile than this benchmark Cu
precursor. The low sublimation temperatures of 1–4 and 6–8
should allow low temperature ALD growth of Cu, Co, and Ni films
(probably < 100 °C), in concert with an appropriate co-reagent.
Complexes 1–4 and 6–11 also afford insights into how the various
substituents affect thermal decomposition temperatures. These
decomposition temperatures are a good estimate of the upper tem-
perature limit for self-limited ALD growth [29], and hence provide
valuable information. The thermal stability of the Cu precursors
decreases in the order 1 > 2 > 3, which follows decreasing ligand
steric bulk. The larger alkyl groups may decrease intermolecular
decomposition reactions, and thus increase thermal stability. The
decomposition points of 1–3 (255–225 °C) are considerably higher
2
1
2
from one
the other
index of trigonality,
j
and one
l
-
j
:
j
ligand and one oxygen atom from
ligand form the equatorial plane. The calculated
= 0.780, agrees well with this geometry
1
2
l-j :j
s
assignment [41]. Not surprisingly, the Fe–O bond lengths for the
terminal ligands (1.954(4), 1.964(4) Å) are shorter than those asso-
ciated with the bridging ligands (2.061(3), 2.066(3), 2.111(3),
2
.111(3) Å). Additionally, the iron–oxygen distances within the
Fe core are slightly asymmetric. The N–Fe–O bite angles associ-
2 2
O
ated with the bridging ligands (73.62(15)° and 74.28(16)°) are
smaller compared to the corresponding angles of the terminal li-
gands (77.88(16)° and 79.21(19)°). These values are also slightly
smaller than those observed in 1, 4, 5, and 6. As a result of the
strain of the molecule, the carbohydrazide ligand planes margin-
ally deviate from planarity, which can be defined by the N–N–C–
O torsion angles (terminal, 3.7(8)°, ꢀ2.8(9)°; bridging, 6.3(9)°,
2 2 2
than that of Cu(OCHMeCH NMe ) (185–188 °C) [29], which sug-
gests that self-limited Cu ALD with these precursors may occur
over a wider temperature range than is possible with Cu(OCH-
3
.2(7)°). All other bond lengths and angles are similar to those of
1, 4, 5, and 6.
2 2 2
MeCH NMe ) (100–170 °C) [29]. The TGA data suggest that the
isopropyl-substituted Cu complex 2 is slightly more volatile than
the tert-butyl-substituted Cu complex 1. The Co complex 4 has a
similar sublimation temperature and very similar TGA behavior
as the isostructural complex 1. Among the Ni complexes 6–11,
the dimethylamino-containing complexes 6–8 are significantly
more volatile than the piperidine-containing complexes 9–11.
Complexes 9–11 have similar volatilities irrespective of the ligand
core carbon-bound alkyl group size, but the isopropyl-substituted
complex 7 is more volatile than the tert-butyl- and methyl-substi-
tuted complexes 6 and 8. The volatility differences between 9–11
and 6–8 can be ascribed to the higher molecular weights of
9–11, but the evaporation rate trends of 6–8 are more subtle.
The asymmetric isopropyl groups in 2 and 7 may lead to less effi-
cient crystal packing, lower lattice energy, and higher volatility,
relative to 1, 3, 6 and 8. Overall, the Cu, Co, and Ni complexes 1,
2, 4, 6, and 7 have the highest volatilities and highest decomposi-
tion temperatures among 1–13. These complexes have excellent
properties for application as ALD precursors to Cu, Co, and Ni metal
films. Film deposition studies of these precursors will be published
separately. Finally, the carbohydrazide ligands do not have suffi-
cient steric bulk to afford monomeric Fe and Mn complexes. In-
stead, dinuclear complexes result that have poor volatilities and
low solid state decomposition temperatures.
2
.3. Evaluation of thermal stability and volatility
The preparative sublimation and decomposition temperature
data for 1–13 are summarized in Table 4. The Cu, Ni, and Co com-
plexes are volatile, and sublime at temperatures between 70 and
8
0 °C at 0.05 Torr. The Cr (5) and Fe (12) complexes undergo simul-
taneous decomposition during sublimation, whereas the Mn com-
plex 13 decomposes without sublimation. In preparative
sublimation experiments, 0.5–1.0 g samples of 1–4 and 6–11 sub-
limed within 4 h with no detectable residue and near-quantitative
recoveries. To determine decomposition ranges, a 2–3 mg sample
of each complex was sealed in melting point tubes under argon
at atmospheric pressure and was heated at the rate of 5 °C/min.
The samples sublimed out of the heated portion of the tube be-
tween 240 and 285 °C, and there was no residue or evidence of
any thermal decomposition when the tubes were inspected under
a microscope. Accurate thermal decomposition temperatures in
the condensed phase reported in Table 4 were measured by
restricting the samples to the hot region of the melting point appa-
ratus by using sealed melting point tubes that were no more than
8
mm long. The Ni complexes 6–11 are extremely thermally stable
and show no evidence for thermal decomposition at temperatures
below 248 °C. The analogous Cu and Co complexes 1 and 4 are sta-
ble up to 255 and 245 °C, respectively. Notably, 1, 2, 4, 6, 7, and 10
melt between 117 and 142 °C and exhibit a remarkably wide span
of temperatures (105–190 °C) after melting and prior to thermal
decomposition. Liquid precursors are desirable, since they avoid
the particles that can be generated with solid precursors [11].
Simultaneous thermogravimetric analyses (TGA) and differen-
tial thermal analyses (DTA) were performed on 1, 2, 4, and 6–11
to understand their volatilities and thermal stabilities. Complex 3
was too air sensitive to obtain these analyses, whereas 5 decom-
posed upon sublimation. Selected data are shown in Figs. 6 and
3
. Conclusions
We have prepared a series of Cu, Ni, Co, Fe, Mn, and Cr com-
1
plexes 1–13 containing carbohydrazide ligands selected from L
6
to L . These complexes adopt monomeric, square planar structures
for Cu, Ni, Co, and Cr, and dinuclear structures for Mn and Fe. A
combination of sublimation studies, thermal decomposition deter-
minations, and TGA/DTA demonstrate that the Cu, Co, and Ni com-
plexes 1, 2, 4, 6, and 7 have the highest volatilities and highest
decomposition temperatures among 1–13. Additionally, these
compounds have higher volatilities and thermal stabilities than
commonly used ALD and CVD precursors. Hence, the new com-
plexes have excellent properties for application as ALD precursors
to Cu, Co, and Ni metal films. The Cr complex 5, Fe complex 12, and
Mn complex 13 are nonvolatile.
7
. Complexes 1, 2, 4, and 6–11 have similar TGA traces with sin-
gle-step weight losses occurring between 150 and 250 °C. The final
percent residues upon reaching 450 °C were all 63.0%. These re-
sults further demonstrate the volatility and high thermal stabilities
of 1, 2, 4, and 6–11. Each DTA plot of 1, 2, 4, and 6–11 revealed two
endotherms associated with the melting and evaporation points.
Exothermic peaks associated with thermal decomposition were
not observed due to the complete evaporation at temperatures
lower than the decomposition points.
4. Experimental
The Cu, Co, and Ni complexes 1–4 and 6–11 allow insights into
how the ligand substituents affect volatility. The dimethylhydra-
zine-derived complexes 1–4 and 6–8 sublime with quantitative
recovery between 70 and 80 °C/0.05 Torr. The alkoxide complex
4.1. General considerations
All metal–organic reactions were performed under argon using
standard glove box and Schlenk line techniques. Tetrahydrofuran

8
26
M.C. Karunarathne et al. / Polyhedron 52 (2013) 820–830
and diethyl ether were freshly distilled from sodium benzophe-
none ketyl, toluene was distilled from sodium, and hexane was
suspension was then filtered through a sintered glass funnel to af-
ford a colorless solution. The volatile components were then re-
moved and the resultant pale yellow oil was distilled at 70 °C/
distilled from P
and 1-aminopiperidine were purchased from Acros Organics.
Anhydrous transition metal chlorides (CrCl , MnCl , FeCl , CoCl
NiCl , and CuCl ) were obtained from Strem Chemicals and were
2 5
O . All carboxylic acid chlorides, triethylamine,
3
0.05 Torr (lit. bp 98 °C/16 Torr [46]) to afford L H as a colorless li-
ꢀ
1
m
CO, s); 1H NMR
2
2
2
2
,
quid (4.34 g, 85%): IR (neat liquid, cm ) 1660 (
(C , 23 °C, d) major isomer, 8.61 (br s, 1H, NH), 2.18 (s, 6H,
N(CH ), 2.01 (s, 3H, CH ), minor isomer, 8.01 (br s, 1H, NH),
2.59 (s, 6H, N(CH ), 1.74 (s, 3H, CH
ppm) major isomer, 174.08 (s, C@O), 47.83 (s, N(CH
2
2
6 6
D
used as received. Potassium hydride (30 wt% dispersion in mineral
oil; washed with hexane before use) and 1,1-dimethylhydrazine
3
)
2
3
1
3
1
3
)
2
3 6 6
); C{ H} NMR (C D , 23 °C,
were purchased from Sigma–Aldrich. NiCl
according to a published procedure [43].
2
ꢁCH
3
CN was prepared
3
)
2
), 19.63 (s,
CH
CH
3
), minor isomer, 167.91 (s, C@O), 46.13 (s, N(CH
).
)
3 2
), 21.53 (s,
1
13
1
H and C{ H} NMR spectra were obtained at 300 and 75 MHz
in benzene-d . Infrared spectra were obtained as neat liquids, KBr
3
6
pellets, or Nujol mulls. Elemental analyses were performed by Mid-
west Microlab, Indianapolis, IN. Melting points were obtained on a
Thermo Scientific Mel-Temp 3.0 digital melting point apparatus
and are uncorrected. Magnetic susceptibility measurements in
benzene solution and in the solid state were determined using
the Evans method with a 500 MHz NMR spectrometer, and a John-
son–Matthey magnetic susceptibility balance, respectively. Ther-
4
4.5. Preparation of N-(1-piperidinyl)pivalamide (L H)
A 100 mL Schlenk flask was charged with 1-aminopiperidine
(2.156 mL, 19.97 mmol), triethylamine (2.782 mL, 19.97 mmol),
and diethyl ether (300 mL). Pivaloyl chloride (1.889 mL,
10.25 mmol) was slowly added to the stirred solution at 0 °C. The
resultant white solution was stirred at ambient temperature for
17 h. The solution was filtered through a coarse glass funnel to af-
ford a colorless solution. Volatile components were subsequently
removed and the resultant white powder was collected and sub-
mogravimetric analysis (TGA) was conducted on
a
TA
Instruments SDT 2960 TGA/DTA system between 50 and 450 °C,
using nitrogen as the flow gas with a heating rate of 10 °C/min.
Solution magnetic moments were measured in benzene solutions
using the Evans method [44].
4
limed at 111 °C/0.05 Torr to afford L H as colorless crystals
1
(
1.889 g, 51.3%): mp 141–143 °C; IR 1651 (
m
CO, s); H NMR (CDCl
3
,
0
0
1
4
.2. Preparation of N ,N -dimethylpivalohydrazine (L H)
23 °C, d) 6.30 (br s, 1H, NH), 2.71 (t, 4H, N(CH
3
)
2
), 1.67 (p, 4H, CH
); C{ H}(CDCl , 23 °C, ppm)
), 38.06 (s, C(CH ), 27.48 (s,
), 23.29 (s, CH ).
2
),
1
3
1
1
.37 (p, 2H, CH2,), 1.16 (s, 9H, (CH
175.27 (s, C@O), 56.70 (s, CH
C(CH ), 25.37 (s, CH
3
)
3
3
A 500-mL round bottomed flask was charged with 1,1-dimeth-
ylhydrazine (3.88 mL, 50 mmol), triethylamine (7.52 mL,
2
3 3
)
3
)
3
2
2
5
0
3 mmol), and diethyl ether (250 mL). To this stirred solution at
°C was slowly added pivaloyl chloride (6.28 mL, 50 mmol). The
5
resultant white suspension was stirred at ambient temperature
for 18 h. This suspension was then filtered through a sintered glass
funnel to afford a colorless solution. The volatile components were
4.6. Preparation of N-(1-piperidinyl)isobutyramide (L H)
4
In a fashion similar to the preparation of L H, treatment of a
diethyl ether (30 mL) solution of 1-aminopiperidine (2.155 mL,
19.97 mmol) and triethylamine (2.784 mL, 19.97 mmol) with iso-
butyryl chloride (2.092 mL, 19.97 mmol) afforded colorless crystals
of L H after workup (1.342 g, 39.5%): mp 127–129 °C; IR 1655 (
then removed and the resultant white solid was sublimed at 65 °C/
1
0
1
6
.05 Torr to afford L H as colorless crystals (6.95 g, 96%): mp 120–
ꢀ
1
1
22 °C; IR (KBr pellet, cm ) 1650 (
m
CO, s); H NMR (C
), 1.02 (s, 9H, C(CH
, 23 °C, ppm) 175.95 (s, C@O), 45.68 (s,
), 38.08 (s, C(CH ), 27.43 (s, C(CH ); ESI-HRMS: calcd
ONa ([M+Na] ) 167.1160, found 167.1152.
6
D
6
, 23 °C, d)
5
.84 (br s, 1H, NH), 2.61 (s, 6H, N(CH
3
)
2
3
)
3
);
m
CO
,
1
3
1
1
C{ H} NMR (C
N(CH
for C
6
D
6
s); H NMR (CDCl
(septet, 1H, CH(CH
(p, 2H, CH ), 1.70 (s, 6H CH(CH
NH), 3.0 (t, 4H, N(CH ), 1.38 (p, 4H, CH
(s, 6H, C(CH 2, minor isomer, 3.09 (septet, 1H, CH(CH
H, N(CH ), 1.38 (p, 4H, CH ), 1.36 (p, 2H, CH ) 1.86 (br s, 1H,
OH), 1.07 (s, 6H, CH(CH , 23 °C, ppm) major iso-
mer, 172.25 (s, C@O), 58.35 (s, N(CH ), 34.23 (s, CH ), 25.59 (s,
CH ), 25.26 (s, CH ), 19.03 (s, CH(CH ), minor isomer, 176.59 (s,
C@O) 56.96 (s, N(CH , 25.49 (s, CH ), 23.23 (s, CH ), minor isomer,
56.93 (s, N(CH ), 29.84 (s, CH(CH ), 22.98 (s, CH ),
18.80 (s, C(CH ).
3
, 23 °C, d) major isomer, 6.03 (br s, 1H, NH), 3.09
), 2.70 (t, 4H, N(CH ), 2.20 (p, 4H, CH ), 1.65
), minor isomer, 6.15 (br s, 1H,
), 1.36 (p, 2H, CH 1.09
), 2.70 (t,
3
)
2
3
)
3
3
)
3
3
)
2
2
)
2
2
+
7
H
16
N
2
2
3 2
)
2
)
2
2
2 ,
)
0
0
2
4.3. Preparation of N ,N -dimethylisobutyrohydrazine (L H)
3
)
3 2
)
4
2
)
2
2
2
1
13
1
In a fashion similar to the preparation of L H, treatment of a
3 2 3
) ); C{ H}(CDCl
diethyl ether (250 mL) solution of 1,1-dimethylhydrazine
3.88 mL, 50 mmol) and triethylamine (7.52 mL, 53 mmol) with
2
)
2
2
(
2
2
3 2
)
2
isobutyryl chloride (5.39 mL, 50 mmol) afforded L H as colorless
crystals upon crystallization from Et O and subsequent sublima-
tion at 60 °C/0.05 Torr (6.12 g, 94%): mp 94–96 °C (lit. mp [45]
2
)
2
2
2
2
2
)
3 2
), 25.59 (s, CH
2
2
3 2
)
ꢀ1
6 6
m D ,
CO, s); 1H NMR (C
8
9–90 °C); IR (KBr pellet, cm ) 1656 (
3 °C, d) major isomer, 8.22 (br s, 1H, NH), 3.19 (septet, 1H,
), 2.17 (s, 6H, N(CH ), 1.18 (d, 6H, CH(CH ), minor iso-
mer, 7.67 (br s, 1H, NH), 2.60 (s, 6H, N(CH ), 2.16 (septet, 1H,
); C{ H} NMR (C , 23 °C,
ppm) major isomer, 180.17 (s, C@O), 48.25 (s, N(CH ), 29.66 (s,
CH(CH ), 19.47 (s, CH(CH ), minor isomer, 174.95 (s, C@O),
6.01 (s, N(CH ), 33.73 (s, CH(CH
2
6
CH(CH
CH(CH
3
)
2
3
)
2
3
)
2
4.7. Preparation of N-(1-piperidinyl)acetamide (L H)
3 2
)
13
1
4
3
)
2
), 1.10 (d, 6H, CH(CH
3
)
2
6
D
6
In a fashion similar to the preparation of L H, treatment of a
diethyl ether (30 mL) solution of 1-aminopiperidine (1.375 mL,
12.74 mmol) and triethylamine (1.776 mL, 12.74 mmol), with acet-
yl chloride (0.9091 mL, 12.74 mmol) afforded colorless crystals of
L H after workup (0.227 g, 13%): mp 126–128 °C; IR 1672 (
3 2
)
3
)
2
3 2
)
4
3
)
2
3
)
2
), 19.73 (s, CH(CH
3
2
) ).
6
m
CO
,
0
0
3
1
4.4. Preparation of N ,N -dimethylacetohydrazine (L H)
s); H NMR (CDCl
3
, 23 °C, d) major isomer, 6.49 (br s, 1H, NH),
), 2.06 (s, 3H, CH ), 1.65 (p, 4H, CH , 1.38 (p,
), minor isomer, 6.27 (s, 1H, NH), 2.69 (t, 4H, N(CH ),
2
.69 (t, 4H N(CH
2
)
2
3
2
A 500-mL round bottom flask was charged with 1,1-dimethyl-
4H, CH
2
2 2
)
1
3
1
hydrazine (3.88 mL, 50 mmol), triethylamine (7.52 mL, 53 mmol),
and diethyl ether (250 mL). To this stirred solution at 0 °C was
slowly added acetyl chloride (3.63 mL, 50 mmol). The resultant
white suspension was stirred at ambient temperature for 18 h. This
1.88 (s, 3H, CH
23 °C, ppm) major isomer, 174.00 (s, C@O), 57.85 (s, N(CH
(s, CH ), 23.94 (s, CH ), minor isomer, 57.21 (s, N(CH , 25.17 (s,
CH ), 22.94 (s, CH ), 19.67 (s, CH ).
3
), 1.65 (p, 4H, CH
2
), 1.38 (p, 4H, CH
2
); C{ H}(CDCl
3
,
2 2
)
, 25.58
2
2
2 2
)
2
2
3

M.C. Karunarathne et al. / Polyhedron 52 (2013) 820–830
827
1
4
.8. Preparation of Cu(L )
2
(1)
suspension of anhydrous cobalt(II) chloride (1.000 g, 7.70 mmol) in
tetrahydrofuran (40 mL). The resultant black solution was stirred
for 5 h at ambient temperature. The volatile components were then
removed under reduced pressure and the resultant black paste was
dissolved in toluene (50 mL). The solution was filtered through a
1-cm pad of Celite on a coarse glass frit, and toluene was then re-
moved under reduced pressure. An analytically pure sample of 4
was obtained by sublimation at 75 °C/0.05 Torr to afford red crys-
A 100 mL Schlenk flask, equipped with a magnetic stir bar and a
1
rubber septum, was charged with L H (2.102 g, 14.58 mmol) and
tetrahydrofuran (50 mL). To this stirred solution at ambient tem-
perature was slowly added potassium hydride (0.614 g,
5.31 mmol) and the resultant colorless solution was stirred for
2 h. This solution was then slowly added over 30 min to a stirred
suspension of anhydrous copper(II) chloride (1.000 g, 7.29 mmol)
in tetrahydrofuran (40 mL). The resultant purple solution was stir-
red an additional 30 min at ambient temperature. The volatile
components were then removed under reduced pressure and the
resultant maroon solid was dissolved in toluene (50 mL). The solu-
tion was filtered through a 1-cm pad of Celite on a coarse glass frit,
and toluene was then removed under reduced pressure. An analyt-
ically pure sample of 1 was obtained as maroon crystals by subli-
mation at 70 °C/0.05 Torr (1.913 g, 75%): mp 137–139 °C; IR
1
1
ꢀ1
tals (1.516 g, 57%): mp 137–140 °C; IR (Nujol, cm ) 1577 (s), 1505
(m), 1416 (w), 1391 (s), 1366 (m), 1359 (m), 1331 (s), 1261 (w),
1223 (m), 1199 (s), 1181 (s), 1091 (m), 1029 (m), 1006 (m), 982
(s), 966 (w), 936 (w), 915 (w), 863 (w), 800 (m), 754 (w), 680
1
(s); H NMR (C
l
6
D
6
, 23 °C, d) 30.69 (s, very broad), ꢀ5.21 (s, broad);
eff = 2.17 BM in the solid state and benzene solution. Anal. Calc. for
C
14
4
H30CoN O
2
: C, 48.69; H, 8.76; N, 16.22. Found: C, 48.92; H, 8.71;
N, 16.36%.
ꢀ1
(
1
(
(
Nujol, cm ) 1559 (s), 1515 (m), 1391 (m), 1366 (m), 1358 (m),
338 (s), 1223 (m), 1206 (s), 1184 (m), 1092 (w), 1028 (w), 1008
m), 977 (m), 936 (w), 919 (w), 892 (w), 868 (w), 802 (w), 759
w), 637 (s); H NMR (C D , 23 °C, d) 0.81 (s, broad); leff = 1.51
6 6
and 1.69 BM in the solid state and in benzene solution, respec-
1
4
.12. Preparation of Cr(L )
2
(5)
A 200 mL Schlenk flask, equipped with a magnetic stir bar and a
1
reflux condenser, was charged with anhydrous chromium(II) chlo-
ride (1.000 g, 8.14 mmol) and tetrahydrofuran (40 mL). This sus-
tively. Anal. Calc. for C14 30CuN : C, 48.05; H, 8.64; N, 16.01.
Found: C, 48.05; H, 8.42; N, 16.09%.
H
4 2
O
1
pension was refluxed for 1 h. Upon cooling, a solution of KL
(
(
1
prepared from L H (2.347 g, 16.27 mmol) and potassium hydride
0.685 g, 17.09 mmol) in tetrahydrofuran (50 mL)) was cannulated
2
4
.9. Preparation of Cu(L )
2
(2)
slowly into the green suspension over a period of 30 min and the
resultant brown solution was stirred for 12 h at ambient tempera-
ture. The volatile components were then removed under reduced
pressure and the resultant brown solid was dissolved in hexane
In a fashion similar to the preparation of 1, treatment of anhy-
drous copper(II) chloride (1.000 g, 7.29 mmol) in tetrahydrofuran
40 mL) with KL (prepared from L H (1.898 g, 14.58 mmol) and
potassium hydride (0.614 g, 15.31 mmol) in tetrahydrofuran
50 mL)) for a 1 h at ambient temperature afforded 2 (1.197 g,
1%) as maroon crystals after sublimation at 75 °C/0.05 Torr: mp
18–121 °C; IR (Nujol, cm ) 1677 (m), 1650 (w), 1557 (s), 1420
m), 1384 (s), 1365 (s), 1354 (s), 1296 (m), 1277 (s), 1235 (m),
186 (m), 1164 (m), 1119 (m), 1100 (m), 1094 (m), 1011 (m),
85 (s), 959 (m), 928 (m), 890 (w), 837 (m), 783 (w), 742 (m),
2
2
(
(
60 mL). The solution was filtered through a 1-cm pad of Celite
on a coarse glass frit, and orange crystals of 5 formed from the
warm concentrated solution upon cooling to room temperature.
More crystals of the product were obtained from the concentrated
mother liquor at ꢀ25 °C (1.708 g, 62%): mp 143–146 °C; IR (Nujol,
(
5
1
ꢀ1
(
ꢀ1
cm ) 1562 (s), 1513 (s), 1418 (m), 1391 (s), 1365 (s), 1357 (s),
1
9
6
1
335 (s), 1261 (m), 1222 (s), 1202 (s), 1183 (s), 1090 (m), 1028
(
(
(
m), 1003 (m), 967 (s), 937 (w), 912 (w), 862 (m), 796 (m), 758
1
37 (s); H NMR (C
6
D
6
, 23 °C, d) 14.27 (s, very broad), 0.88 (s,
26Cu-
: C, 44.77; H, 8.14; N, 17.40. Found: C, 45.03; H, 8.02; N,
7.36%.
1
m), 640 (s); H NMR (C
s, broad); eff = 4.84 and 5.04 BM in solid state and benzene solu-
30CrN : C, 49.69; H, 8.94; N,
6.56. Found: C, 49.87; H, 8.91; N, 16.45%.
6 6
D , 23 °C, d) 106.51 (s, very broad), 3.64
broad);
N O
4 2
1
leff = 1.69 BM in the solid state. Anal. Calc. for C12H
l
tion, respectively. Anal. Calc. for C14
1
H
4 2
O
3
4
2
.10. Preparation of Cu(L ) (3)
1
4
.13. Preparation of Ni(L )
2
(6)
In a fashion similar to the preparation of 1, treatment of anhy-
drous copper(II) chloride (1.000 g, 7.29 mmol) in tetrahydrofuran
A 100 mL Schlenk flask, equipped with a magnetic stir bar and a
3
3
1
(
40 mL) with KL (prepared from L H (1.489 g, 14.58 mmol) and
potassium hydride (0.614 g, 15.31 mmol) in tetrahydrofuran
70 mL)) for 1 h at ambient temperature afforded 3 (0.446 g, 23%)
as maroon crystals after sublimation at 80 °C/0.05 Torr: mp 184–
rubber septum, was charged with L H (1.690 g, 11.72 mmol) and
tetrahydrofuran (50 mL). To this stirred solution at ambient tem-
perature was slowly added potassium hydride (0.494 g,
12.31 mmol) and the resultant colorless solution was stirred for
12 h. This solution was then slowly added to a stirred suspension
(
ꢀ
1
1
87 °C; IR (Nujol, cm ) 1680 (w), 1654 (m), 1574 (s), 1436 (s),
1
423 (s), 1418 (s), 1392 (s), 1329 (s), 1232 (m), 1189 (m), 1167
of NiCl
2
ꢁCH
3
CN (1.000 g, 5.86 mmol) in tetrahydrofuran (30 mL).
(
7
w), 1097 (w), 1031 (m), 1012 (m), 994 (s), 928 (m), 868 (w),
89 (w), 669 (s), 648 (s); 1H NMR (C
, 23 °C, d) 12.28 (s, very
broad); eff = 1.55 BM in the solid state. Anal. Calc. for C 18Cu-
: C, 36.15; H, 6.83; N, 21.08. Found: C, 36.33; H, 6.75; N,
1.07%.
The resultant yellow solution was stirred for 18 h at ambient tem-
perature. The volatile components were then removed under re-
duced pressure and the resultant yellow solid was dissolved in
toluene (50 mL). The solution was filtered through a 1-cm pad of
Celite on a coarse glass frit, and toluene was then removed under
reduced pressure. An analytically pure sample of 6 was obtained
by sublimation at 70 °C/0.05 Torr to afford orange crystals
6 6
D
l
8
H
4 2
N O
2
1
4.11. Preparation of Co(L )
2
(4)
ꢀ
1
(
1.537 g, 76%): mp 140–142 °C; IR (Nujol, cm ) 1573 (s), 1502
A 100 mL Schlenk flask, equipped with a magnetic stir bar and a
(m), 1415 (m), 1392 (s), 1366 (s), 1359 (m), 1340 (s), 1262 (w),
1223 (m), 1205 (s), 1189 (s), 1091 (w), 1029 (w), 1004 (m), 988
1
rubber septum, was charged with L H (2.221 g, 15.40 mmol) and
tetrahydrofuran (50 mL). To this stirred solution at ambient tem-
perature was slowly added potassium hydride (0.649 g,
6.17 mmol) and the resultant colorless solution was stirred for
2 h. This solution was then slowly added over 30 min to a stirred
(m), 936 (w), 917 (m), 893 (w), 866 (w), 802 (m), 752 (m), 683
1
(s); H NMR (C
6
D
6
, 23 °C, d) 2.44 (s, 6H, N(CH
); C{ H} NMR (C , 23 °C, ppm) 183.21 (s, C@O), 50.47
(s, N(CH ), 34.45 (s, C(CH ), 28.68 (s, C(CH ). Anal. Calc. for
3 2
) ), 1.23 (s, 9H,
1
3
1
1
1
C(CH
3
)
3
6 6
D
3
)
2
3
)
3
3 3
)

8
28
M.C. Karunarathne et al. / Polyhedron 52 (2013) 820–830
5
C
14
H
30
N
4
NiO
N, 16.34%.
2
: C, 48.72; H, 8.76; N, 16.23. Found: C, 48.90; H, 8.57;
KL5 (prepared from L H (1.188 g, 6.98 mmol) and potassium hy-
dride (0.285, 7.05 mmol) in tetrahydrofuran (30 mL)) for 17 h at
ambient temperature afforded 10 (0.304 g, 11%) as orange crystals
from sublimation at 110 °C/0.05 Torr: mp 115–117 °C; IR (Nujol,
2
4.14. Preparation of Ni(L )
2
(7)
ꢀ1
cm ) 1583 (s), 1349 (s), 1270 (s), 1205 (w), 1166 (m), 1178 (m),
1080 (s), 1046 (w), 1028 (w), 977 (m), 948 (m), 860 (m); 1
NMR (C , 23 °C, d) 3.50 (m, 4H, CH ), 3.07 (m, 4H, CH ), 2.57 (sep-
tet, 1H, CH(CH ), 2.24 (m, 2H, CH ), 1.20 (d, 6H, CH(CH );
, 23 °C, ppm) 180.70 (s, C@O), 58.36 (s, N(CH
30.31 (s, CH(CH ), 24.16 (s, CH ), 20.79 (s, CH ), 20.34 (s, CH
Anal. Calc. for C18 NiO
In a fashion similar to the preparation of 6, treatment of
NiCl CN (1.000 g, 5.86 mmol) in tetrahydrofuran (30 mL) with
KL (prepared from L H (1.526 g, 11.72 mmol) and potassium hy-
dride (0.494 g, 12.31 mmol) in tetrahydrofuran (50 mL)) for a
H
2
ꢁCH
3
6
D
6
2
2
2
2
)
3 2
2
3 2
)
1
3
1
C{ H}(C
6
D
6
2
)
2
),
).
1
8 h at ambient temperature afforded 7 (1.152 g, 62%) as orange
3
)
2
2
2
2
crystals upon sublimation at 80 °C/0.05 Torr: mp 125–128 °C; IR
H
34
N
4
2
: C, 54.43; H, 8.63; N, 14.11. Found:
ꢀ1
(
Nujol, cm ) 1578 (s), 1495 (m), 1416 (m), 1358 (s), 1348 (s),
C, 54.27; H, 8.71; N, 13.92%.
1
1
7
2
308 (m), 1291 (s), 1232 (m), 1195 (m), 1181 (m), 1165 (w),
6
103 (w), 1071 (s), 1005 (m), 993 (s), 919 (m), 897 (w), 821 (w),
4.18. Preparation of Ni(L )
2
(11)
1
49 (m), 725 (s); H NMR (C
6
D
6
, 23 °C, d) 2.48 (s, 6H, N(CH
3
)
2
),
); C{ H} NMR
, 23 °C, ppm) 181.30 (s, C@O), 50.52 (s, N(CH ), 30.04 (s,
CH(CH ), 20.58 (s, CH(CH ). Anal. Calc. for C12 NiO : C,
13
1
.44 (septet, 1H, CH(CH
3
)
2
), 1.12 (d, 6H, CH(CH
3
)
2
In a fashion similar to the preparation of 9, treatment of
NiCl CN (0.618 g, 3.62 mmol) in tetrahydrofuran (30 mL) with
KL (prepared from L H (1.029 g, 7.24 mmol) and potassium hy-
dride (0.295, 7.35 mmol) in tetrahydrofuran (25 mL)) for 17 h at
ambient temperature afforded 11 (0.723 g, 29%) as orange crystals
from sublimation at 150 °C/0.05 Torr: mp 230–232 °C; IR (Nujol,
(
C
6
D
6
3
)
2
2
ꢁCH
3
6
6
3
)
2
3
)
2
H
26
N
4
2
4
5.46; H, 8.27; N, 17.67. Found: C, 45.59; H, 8.23; N, 17.61%.
3
4.15. Preparation of Ni(L )
2
(8)
ꢀ1
cm ) 1591 (s), 1325 (s), 1302 (s), 1200 (s), 1159 (m), 1159 (m),
In a fashion similar to the preparation of 6, treatment of
NiCl CN (0.835 g, 4.895 mmol) in tetrahydrofuran (30 mL)
with KL (prepared from L H (1.000 g, 9.791 mmol) and potassium
hydride (0.401 g, 10.000 mmol) in tetrahydrofuran (50 mL)) for
1073 (w), 1046 (w), 1017 (w), 982 (m), 945 (m), 875 (m), 844
1
2
ꢁCH
3
(m), 770 (w), 711 (s), 662 (w), 636 (m); H NMR (C
6
D
6
, 23 °C, d)
), 1.83
, 23 °C, ppm) 174.47 (s, C@O),
), 20.25 (s, CH ), 16.67 (s, COCH ).
3
3
2 2 2 2
3.57 (d, 4H, N(CH ) ), 3.06 (m, 2H, CH ), 2.34 (m, 2H, CH
1
3
1
(s, 3H, CH
58.13 (s, N(CH
Anal. Calc. for C14
3
); C{ H} NMR (C
6 6
D
1
8 h at ambient temperature afforded 8 (0.792 g, 62%) as orange
2
)
2
), 24.03 (s, CH
H
2
2
3
crystals upon sublimation at 80 °C/0.05 Torr: mp 164–166 °C; IR
26
N
4
NiO
2
: C, 49.30; H, 7.68; N, 16.43. Found:
ꢀ1
(
Nujol, cm ) 1586 (s), 1337 (s), 1291 (s), 1232 (m), 1195 (m),
178 (m), 1104 (w), 1041 (w), 1032 (w), 995 (s), 919 (m), 891
w), 865 (w), 770 (m), 711 (s), 642 (s); 1H NMR (C
, 23 °C, d)
)); C{ H} NMR (C
3 °C, ppm) 175.00 (s, C@O), 50.51 (s, N(CH ), 20.58 (s, COCH
NiO : C, 36.82; H, 6.95; N, 21.47. Found: C,
7.17; H, 7.04; N, 21.19%.
C, 49.19; H, 7.78; N, 16.45%.
1
(
2
2
1
6
D
6
4.19. Preparation of [Fe(L )
2
]
2
(12)
1
3
1
.50 (s, 6H, N(CH
3
)
2
), 1.70 (s, 3H, CO(CH
3
6 6
D ,
3
)
2
3
).
A 100 mL Schlenk flask, equipped with a magnetic stir bar and a
1
Anal. Calc. for C
3
8
H
18
N
4
2
rubber septum, was charged with L H (1.051 g, 7.29 mmol) and
tetrahydrofuran (25 mL). To this stirred solution at ambient tem-
perature was slowly added potassium hydride (0.307 g,
7.66 mmol) and the resultant colorless solution was stirred for
4
4
.16. Preparation of Ni(L )
2
(9)
1
2 h. This solution was then slowly added over 30 min to a stirred
A 100 mL Schlenk flask, equipped with a magnetic stir bar and
suspension of anhydrous iron(II) chloride (0.464 g, 3.64 mmol) in
tetrahydrofuran (20 mL). The resultant pale blue solution was stir-
red for 3 h and the volatile components were then removed under
reduced pressure. The resultant pale blue paste was dissolved in
hexane (50 mL) and the pale green solution was filtered through
a 1-cm pad of Celite on a coarse glass frit. Hexane was then re-
moved under reduced pressure to afford 12 as a gray solid
(1.084 g, 87%). Pale green crystals of 12 suitable for single crystal
X-ray crystallographic analysis were obtained by slow crystalliza-
tion at ꢀ23 °C in hexane (0.349 g, 28%): mp 155–157 °C; IR (Nujol,
4
rubber septum, was charged with L H (1.000 g, 5.43 mmol) and
tetrahydrofuran (20 mL). To this stirred solution at ambient tem-
perature was slowly added potassium hydride (0.218 g,
.50 mmol) and the resultant colorless solution was stirred for
h. This was then slowly added to a stirred suspension of
5
2
2 3
NiCl ꢁCH CN (0.463 g, 2.715 mmol) in tetrahydrofuran (30 mL).
The resultant orange solution was stirred for 17 h at ambient tem-
perature. The volatile components were then removed under re-
duced pressure and the resultant orange solid was dissolved in
toluene (35 mL). The solution was filtered through a 1-cm pad of
Celite on a coarse glass frit, and the toluene was then removed un-
der reduced pressure. An analytically pure sample of 9 was ob-
tained by sublimation at 155 °C/0.05 Torr as orange crystals
ꢀ1
cm ); 1719 (w), 1632 (s), 1563 (s), 1554(s), 1523 (s), 1351 (s),
1340 (s), 1313 (m), 1262 (w), 1227 (w), 1210 (s), 1171 (s), 1090
(w), 1026 (w), 1009 (m), 963 (s), 860 (m), 608 (m);
and 4.55 BM in solid state and benzene solution, respectively. Anal.
Calc. for C28 : C, 49.13; H, 8.83; N, 16.37. Found: C,
51.75; H, 9.37; N, 16.63%.
leff = 7.99
ꢀ1
(
(
0.294 g, 13%): mp 203–205 °C; IR (Nujol, cm ) 1575 (s), 1357
2 8 4
H60Fe N O
s), 1339 (s), 1203 (s), 1166 (m), 1178 (m), 1072 (w), 1044 (w),
1
7
3
027 (w), 970 (m), 951 (m), 890 (w), 871 (w), 850 (w), 793 (m),
50 (w), 684 (s); 1H NMR (C
, 23 °C, d) 3.42 (d, 4H, N(CH ),
.05 (m, 4H, CH ), 2.21 (m, 4H, CH ), 1.30 (s, 9H, C(CH );
, 23 °C, ppm) 180.64 (s, C@O), 58.35 (s,
), 28.77 (s, C(CH ), 24.17 (s, CH ), 20.29 (s, CH ). Anal.
Calc. for C20 NiO : C, 56.49; H, 9.01; N, 13.18. Found: C,
6.81; H, 8.71; N, 13.13%.
1
6
D
6
2
)
)
3 3
2
2 2
4.20. Preparation of [Mn(L ) ] (13)
2
2
1
3
1
C{ H} NMR (C
N(CH
6
D
6
A 100 mL Schlenk flask, equipped with a magnetic stir bar and a
rubber septum, was charged with anhydrous manganese(II) bro-
mide (0.791 g, 3.64 mmol) and tetrahydrofuran (20 mL). To this
stirred suspension at ambient temperature was slowly added KL
prepared from L H (1.051 g, 7.29 mmol) and potassium hydride
(0.307 g, 7.66 mmol) in tetrahydrofuran (25 mL)). The resultant
suspension was stirred for 18 h and the volatile components were
then removed under reduced pressure. The resultant solid was dis-
solved in toluene (50 mL) and filtered through a 1-cm pad of Celite
2
)
2
3
)
3
2
2
H
38
N
4
2
1
5
1
(
5
4.17. Preparation of Ni(L )
2
(10)
In a fashion similar to the preparation of 9, treatment of
NiCl CN (0.596 g, 3.49 mmol) in tetrahydrofuran (25 mL) with
ꢁCH
2
3

M.C. Karunarathne et al. / Polyhedron 52 (2013) 820–830
[7] (a) S.H. Kang, JOM 60 (2008) 28;
829
on a coarse glass frit. Toluene was then removed under reduced
(
(
b) C.A.F. Vaz, J.A.C. Bland, G. Lauhoff, Rep. Prog. Phys. 71 (2008) 056501;
c) Y. Shiratsuchi, M. Yamamoto, S.D. Bader, Prog. Surf. Sci. 82 (2007) 121.
pressure to afford 13 as a pale brown solid (1.093 g, 88%). Colorless
crystals of 13 suitable for X-ray crystallographic analysis were ob-
tained from a concentrated solution in toluene at ꢀ25 °C (0.149 g,
[
8] C.-S. Chen, J.-H. Lin, T.-W. Lai, Chem. Commun. (2008) 4983.
[9] (a) H.-B.-R. Lee, S.-H. Band, W.-H. Kim, G.H. Gu, Y.K. Lee, T.-M. Chung, C.G. Kim,
C.G. Park, H. Kim, Jpn. J. Appl. Phys. 49 (2010) 05FA11;
ꢀ
1
1
2%): mp 92–94 °C; IR (Nujol, cm ) 1563 (s), 1550 (s), 1521 (m),
(
(
b) H.-B.-R. Lee, G.H. Gu, J.Y. Son, C.G. Park, H. Kim, Small 4 (2008) 2247;
c) C.-M. Yang, S.-W. Yun, J.-B. Ha, K.-I. Na, H.-I. Cho, H.-B. Lee, J.-H. Jeong, S.-H.
1
513 (m), 1391 (m), 1366 (s), 1353 (m), 1338 (s), 1316 (s), 1262
(
w), 1211 (s), 1192 (m), 1176 (s), 1092 (w), 1030 (w), 1010 (m),
Kong, S.-H. Hahm, J.-H. Lee, Jpn. J. Appl. Phys. 46 (2007) 1981;
(d) K.-W. Do, C.-M. Yang, I.-S. Kang, K.-M. Kim, K.-H. Back, H.-I. Cho, H.-B. Lee,
S.-H. Kong, S.-H. Hahm, D.-H. Kwon, J.-H. Lee, J.H. Lee, Jpn. J. Appl. Phys. 45
1
9
(
64 (m), 928 (w), 892 (w), 860 (w), 794 (w), 758 (w); H NMR
, 23 °C, d) 5.54 (s, broad); eff = 9.62 and 5.47 BM in solid state
and in benzene solution, respectively. Anal. Calc. for
6
C D
6
l
(
2006) 2975;
(e) J. Chae, H.-S. Park, S.-W. Kang, Electrochem. Solid State Lett. 5 (2002) C64.
10] (a) H. Kim, Surf. Coat. Technol. 200 (2006) 3104;
[
[
C
8
28
2
H60Mn N
8
O
4
: C, 49.26; H, 8.86; N, 16.41. Found: C, 50.61; H,
(
(
b) H. Kim, J. Vac. Sci. Technol., B 21 (2003) 2231;
c) S.M. Merchant, S.H. Kang, M. Sanganeria, B. van Schravendijk, T. Mountsier,
.78; N, 16.62%.
JOM – J. Miner. Met. Mater. Soc. 52 (2001) 43;
d) S.-Q. Wang, MRS Bull. 19 (1994) 30.
(
4
1
.21. X-ray crystallographic structure determinations of 1, 4, 5, 6, and
2
11] (a) M. Leskelä, M. Ritala, Angew. Chem., Int. Ed. 42 (2003) 5548;
(b) M. Leskelä, M. Ritala, Thin Solid Films 409 (2002) 138;
(
(
(
c) M. Ritala, M. Leskelä, Nanotechnology 10 (1999) 19;
d) L. Niinistö, Curr. Opin. Solid State Mater. Sci. 3 (1998) 147;
e) M. Ritala, Appl. Surf. Sci. 112 (1997) 223;
Diffraction data were measured on a Bruker X8 APEX-II kappa
geometry diffractometer with Mo radiation and a graphite mono-
chromator. Frames were collected at 100 K with the detector at
(f) T. Suntola, Thin Solid Films 216 (1992) 84;
g) M. Putkonen, L. Niinistö, Top. Organomet. Chem. 9 (2005) 125.
12] (a) V. Vidjayacoumar, D.J.H. Emslie, S.B. Clendenning, J.M. Blackwell, J.F.
Britten, A. Rheingold, Chem. Mater. 22 (2010) 4844;
(
[
4
0 mm and 0.3–0.5° between each frame. The frames were re-
corded for 3–5 s. APEX-II [47] and SHELX [48] software were used in
the collection and refinement of the models. All structures con-
tained discrete neutral complexes without ions or solvent.
(b) V. Vidjayacoumar, D.J.H. Emslie, J.M. Blackwell, S.B. Clendenning, J.F.
Britten, Chem. Mater. 22 (2010) 4854.
13] H.B. Profijt, S.E. Potts, M.C.M. van de Sanden, W.M.M. Kessels, J. Vac. Sci.
Technol., A 25 (2011) 050801.
14] B.H. Lee, J.K. Hwang, J.W. Nam, S.U. Lee, J.T. Kim, S.-M. Koo, A. Baunemann, R.A.
Fischer, M.M. Sung, Angew. Chem., Int. Ed. 48 (2009) 4536.
15] I.J. Hsu, B.E. McCandless, C. Weiland, B.G. Willis, J. Vac. Sci. Technol., A 27
[
[
[
Acknowledgments
(
2009) 660.
[
[
[
16] B.S. Lim, A. Rahtu, R.G. Gordon, Nat. Mater. 2 (2003) 748.
17] Z. Li, A. Rahtu, R.G. Gordon, J. Electrochem. Soc. 153 (2006) C787.
18] Z. Li, R.G. Gordon, D.B. Farmer, Y. Lin, J. Vlassak, Electrochem. Solid State Lett. 8
We are grateful to the U.S. National Science Foundation (Grant
No. CHE-0910475) and SAFC Hitech for support of this research.
(
2005) G182.
[
19] R. Solanki, B. Pathangey, Electrochem. Solid State Lett. 3 (2000) 479.
Appendix A. Supplementary data
[20] P. Mårtensson, J.-O. Carlsson, Chem. Vap. Deposition 3 (1997) 45.
[
[
21] M. Juppo, M. Ritala, M. Leskelä, J. Vac. Sci. Technol., A 15 (1997) 2330.
22] K.-H. Park, A.Z. Bradley, J.S. Thompson, W.J. Marshall, Inorg. Chem. 45 (2006)
CCDC 878262–878266 contain the supplementary crystallo-
graphic data for 1, 4, 5, 6, and 12. These data can be obtained free
of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or
from the Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
8480.
[23] J.S. Thompson, L. Zhang, J.P. Wyre, D.J. Brill, K.G. Lloyd, Thin Solid Films 517
(2009) 2845.
[
[
[
24] J. Huo, R. Solanki, J. Mater. Res. 17 (2002) 2394.
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