Tailoring Precursors for Deposition: Synthesis, Structure, and Thermal Studies of Cyclopentadienylcopper(I) Isocyanide Complexes

Article abstract of DOI:10.1021/acs.inorgchem.5b00448

We report here the synthesis and characterization of a family of copper(I) metal precursors based around cyclopentadienyl and isocyanide ligands. The molecular structures of several cyclopentadienylcopper(I) isocyanide complexes have been unambiguously determined by single-crystal X-ray diffraction analysis. Thermogravimetric analysis of the complexes highlighted the isopropyl isocyanide complex [(η⁵-C₅H₅)Cu(CNⁱPr)] (2a) and the tert-butyl isocyanide complex [(η⁵-C₅H₅)Cu(CN^tBu)] (2b) as possible copper metal chemical vapor deposition (CVD) precursors. Further modification of the precursors with variation of the substituents on the cyclopentadienyl ligand system (varying between H, Me, Et, and ⁱPr) has allowed the affect that these changes would have on features such as stability, volatility, and decomposition to be investigated. As part of this study, the vapor pressures of the complexes 2b, [(η⁵-MeC₅H₄)Cu(CN^tBu)] (3b), [(η⁵-EtC₅H₄)Cu(CN^tBu)] (4b), and [(η⁵-ⁱPrC₅H₄)Cu(CN^tBu)] (5b) over a 40-65 °C temperature range have been determined. Low-pressure chemical vapor deposition (LP-CVD) was employed using precursors 2a and 2b to synthesize thin films of metallic copper on silicon, gold, and platinum substrates under a H₂ atmosphere. Analysis of the thin films deposited onto both silicon and gold substrates at substrate temperatures of 180 and 300 °C by scanning electron microscopy and atomic force microscopy reveals temperature-dependent growth features: Films grown at 300 °C are continuous and pinhole-free, whereas films grown at 180 °C consist of highly crystalline nanoparticles. In contrast, deposition onto platinum substrates at 180 °C shows a high degree of surface coverage with the formation of high-density, continuous, and pinhole-free thin films. Powder X-ray diffraction and X-ray photoelectron spectroscopy (XPS) both show the films to be high-purity metallic copper.

Full text of DOI:10.1021/acs.inorgchem.5b00448

Article
pubs.acs.org/IC
Tailoring Precursors for Deposition: Synthesis, Structure, and
Thermal Studies of Cyclopentadienylcopper(I) Isocyanide Complexes
A. M. Willcocks,† T. Pugh,† S. D. Cosham,† J. Hamilton,† S. L. Sung,‡,§ T. Heil,∥ P. R. Chalker,‡
P. A. Williams,§ G. Kociok-Kohn,⊥ and A. L. Johnson*,†
̈
†Department of Chemistry, University of Bath, Bath BA2 7AY, United Kingdom
‡Centre for Materials and Structures, University of Liverpool, Liverpool L69 3GH, United Kingdom
§SAFC-Hitech, Power Road, Bromborough, Wirral CH62 3QF, United Kingdom
∥NanoInvestigation Centre at Liverpool, University of Liverpool, Liverpool L69 3GL, United Kingdom
⊥Chemical Crystallography Service, Department of Chemistry, University of Bath, Bath BA2 7AY, United Kingdom
S
* Supporting Information
ABSTRACT: We report here the synthesis and character-
ization of a family of copper(I) metal precursors based around
cyclopentadienyl and isocyanide ligands. The molecular
structures of several cyclopentadienylcopper(I) isocyanide
complexes have been unambiguously determined by single-
crystal X-ray diffraction analysis. Thermogravimetric analysis of
the complexes highlighted the isopropyl isocyanide complex
[(η5-C5H5)Cu(CNiPr)] (2a) and the tert-butyl isocyanide
complex [(η5-C5H5)Cu(CNtBu)] (2b) as possible copper
metal chemical vapor deposition (CVD) precursors. Further
modification of the precursors with variation of the
i
substituents on the cyclopentadienyl ligand system (varying between H, Me, Et, and Pr) has allowed the affect that these
changes would have on features such as stability, volatility, and decomposition to be investigated. As part of this study, the vapor
pressures of the complexes 2b, [(η5-MeC5H4)Cu(CNtBu)] (3b), [(η5-EtC5H4)Cu(CNtBu)] (4b), and [(η5-iPrC5H4)Cu-
(CNtBu)] (5b) over a 40−65 °C temperature range have been determined. Low-pressure chemical vapor deposition (LP-CVD)
was employed using precursors 2a and 2b to synthesize thin films of metallic copper on silicon, gold, and platinum substrates
under a H2 atmosphere. Analysis of the thin films deposited onto both silicon and gold substrates at substrate temperatures of
180 and 300 °C by scanning electron microscopy and atomic force microscopy reveals temperature-dependent growth features:
Films grown at 300 °C are continuous and pinhole-free, whereas films grown at 180 °C consist of highly crystalline nanoparticles.
In contrast, deposition onto platinum substrates at 180 °C shows a high degree of surface coverage with the formation of high-
density, continuous, and pinhole-free thin films. Powder X-ray diffraction and X-ray photoelectron spectroscopy (XPS) both
show the films to be high-purity metallic copper.
molecular nature of these processes. While advances in the
development of ALD precursors for copper metal deposition,
most notably the reduction of copper(II) species to copper(0)
metal in the presence of metal alkyls such as ZnEt2 and
AlMe3,3i,4 have been made over the past 6−7 years, the
significantly slower growth rate attributed to ALD processes
compared to CVD means that the design and development of
CVD precursors, specifically organometallic derivatives, are of
interest.
In principle, copper(0) compounds would be the most
desirable precursors; ligand dissociation would produce atom-
ized metal, and any such process should lead to the formation
of high-purity films, as is the case for the CVD of platinum
INTRODUCTION
■
The development of copper precursors for the production of
metallic thin films1 by both chemical vapor deposition (CVD)2
and atomic layer deposition (ALD)3 has been, and continues to
be, an area of significant interest to those in the micro-
electronics industry, mainly because of the numerous potential
applications in which these materials can be exploited.2d,e,3a,b As
the size downscaling of microelectronics continues, the use of
copper as an interconnect material in integrated circuitry has
increased.2c,e,3b The physical properties that make copper so
desirable for such applications include its very low resistivity
(significantly lower than aluminum and much lower than
tungsten) and electromigration resistance that is far superior to
that of aluminum (although inferior to that of tungsten).
The advantages of selective deposition and conformal
coverage of surfaces gained when using CVD and ALD over
other (physical) deposition techniques are derived from the
Received: February 24, 2015
© XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.5b00448
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Chart 1. Stable Copper(I) Cyclopentadienyl Complexes10−25
metal from Pt(PF3)4.5 To date, no such homoleptic copper(0)
complexes are known.
To date, only the phosphine adduct [CpCu(PEt3)] is
commercially available and has been studied as a CVD
precursor. The remaining N-heterocyclic carbene23 and
ylide25 adducts have not been investigated as potential
precursors thus far.
This leaves copper(I) and copper(II) compounds as
potential precursors for the CVD of copper metal. While
copper(II) species, and in particular the β-diketonate
derivatives of 1,1,1,5,5,5-hexafluoroacetylacetone,2b,d have
been used extensively for the CVD of copper, the inherent
instability of organometallic CuII d9 species means that, to date,
copper(II) organometallic species are unknown. As was already
noted, the inherent instability in copper(II) organometallics has
been utilized by groups working on the development of ALD
processes in which copper(II) organometallics are formed in
situ to form nascent copper metal,3i,4 but as CVD precursors,
their application has been limited.1
However, to mass produce copper thin films, laboratory
methods must be scalable for commercial production. While
the thermal behavior of [CpCu(PEt3)] and the MOCVD
process of copper deposition from it are well established,9b,c,26
[CpCu(PR3)] systems are not considered by industry to be
good copper sources for commercial CVD processing because
of a high degree of contamination of the copper thin
films.9n,o,q,15 Other precursors such as Cu(hfac)(VTMS)
(CupraSelect) and Cu(hfac)(alkyne) systems are equally
susceptible to contamination (specifically O and F), which
results in poor adhesion to layers such as Ta or TiN.2b,d,7
Consequently, new precursors that are preferably halogen-free
and contain as few heteroatoms as possible have been sought.
Foremost among these compounds is cyclopentadienylcopper
tert-butyl isocyanide, originally described by Saegusa et al. as a
catalyst in alkylidene-forming reactions in 1971.27 Since then, it
In contrast, the organometallic chemistry of copper(I)
species is considerably more extensive, with copper alkyl,
copper aryl, and copper alkynyl species all playing important
roles in catalytic bond-forming reactions,6 although the utility
of these species in deposition are limited by their tendency to
oligomerize, forming large aggregate species unsuitable for most
CVD processes. Of the organometallic copper(I) systems
known, it is the cyclopentadienyl derivatives [Cp−Cu−L] (L =
2e− donor ligand) that compete most effectively, in terms of
stability and volatility, with β-diketonate copper systems as
CVD precursors.7 The cyclopentadienyl ligand, which can
occupy three coordination sites around the metal center,
imparts a significant degree of thermal stability to complexes,
not present in copper alkyl ([R−Cu−L]), aryl ([Ar−Cu−L]),
or alkynyl ([R−CC−Cu−L]) derivatives.2d,7
has been used as a precursor for copper metal deposition;10,28
a
vinyl polymerization catalyst29 and a number of derivatives have
been reported.28a−c
As an extension of our continuing interest in the develop-
ment of precursors for copper thin-film formation,30 we
describe here the synthesis of a range of substituted
cyclopentadienylcopper alkyl and aryl isocyanide complexes
of the general form [(η5-C5H4R′)Cu(CNR′′)] (Scheme 1), in
an attempt to optimize the volatility and stability of these
prospective copper metal precursors, for application in the
CVD of copper thin films.
The cyclopentadienylcopper phosphine adduct [CpCu-
(PEt3)] was first described by Piper and Wilkinson around
1956,8 but it was not until the 1980s−1990s that this and
related complexes were developed as metal−organic CVD
(MOCVD) precursors.9 Subsequently, the number of copper
cyclopentadienyl complexes has increased, but despite their
utility, the number of systems known in the literature (Chart 1)
is still small relative to β-diketonate copper systems.2d,7
RESULTS AND DISCUSSION
■
Formation of the cyclopentadienylcopper(I) tert-butyl iso-
cyanide complex 2b was originally reported in 197127 from the
reaction of Cu2O with excess freshly distilled cyclopentadiene
(which also acts as a solvent) in the presence of tert-butyl
B
DOI: 10.1021/acs.inorgchem.5b00448
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
structures are well-known for copper(I) complexes, and it has
been shown for phosphine complexes of the general form
[CuX(PR3)] that their structure in the solid state depends not
only on the complex itself but also on the solvent used for
growing the crystal.32 While pure microcrystalline samples of
1a−1c could be isolated in moderate yields, crystals suitable for
single-crystal XRD analysis were not obtained.
Scheme 1. Synthetic Procedure for the Synthesis of
Copper(I) Chloride Isocyanide Adducts (1a−1f) and
Cyclopentadienylcopper(I) Isocyanide Adducts (2a−2f, 3a−
3c, 4b, and 5b)
In contrast, the reaction of aryl isocyanides d−f with
copper(I) chloride in THF (1:1), followed by hot filtration and
recrystallization, results in the formation of complexes that by
elemental analysis are consistent with the form [ClCu-
(CNAr)2].31c,f Amendment of the reaction stoichiometries
allowed isolation of the bis(isocyanide) adducts (1d−1f) in
high yield (73−88%) as colorless crystalline products. In all
cases, crystals suitable for single-crystal XRD analysis were
obtained. Figure 1 shows the molecular structure of complex
isocyanide to afford the desired complex, which can be
recrystallized to afford pure product. Despite this synthetically
unpretentious strategy, its utility is limited because the use of
methyl-, ethyl-, and other alkyl-substituted cyclopentadienyl
systems is typically expensive, which prohibits their use as a
solvent for the reaction. To this end, we have investigated the
salt metathesis synthesis of the cyclopentadienyl derivatives, by
stoichiometrically reacting sodium cyclopentadienide and the
methyl-, ethyl-, and isopropyl-substituted derivatives with a
range of alkyl and aryl isocyanide adducts of copper chloride.
Synthesis of Isocyanide Adducts of Copper(I) Chlor-
ide. Copper chloride adducts of both alkyl and aryl isocyanides
were initially synthesized from the stoichiometric reaction of
the RNC ligand and copper(I) chloride in tetrahydrofuran
(THF) in a 1:1 ratio, followed by filtration to remove unreacted
copper(I) chloride and recrystallization from THF. The
Figure 1. Molecular structure of the copper(I) chloride bis-
(xylylisocyanide) dimer 1e showing the labeling scheme used in the
text. Hydrogen atoms have been omitted for clarity, and thermal
ellipsoids are at the 30% probability level. Symmetry operation: 1 − x,
1 − y, −z.
1e, which crystallizes in the P1 space group with half of a
̅
molecule of the complex in the asymmetric unit cell.
Complexes 1d−1f are isotactic and isostructural in the solid
state and display the same gross structural features; for this
reason, only the molecular structure of 1e is described here.
In the solid state, complex 1e forms a halogen-bridged
complex, with two isocyanide ligands completing pseudote-
trahedral coordination of the copper atoms. The dimers 1d−1f
all have an imposed crystallographic Ci symmetry and contain
Cu···Cu units separated by distances between approximately
3.20 and 3.22 Å. The Cu−Cl bond distances in 1e show an
asymmetry of the binuclear unit [Cu(1)−Cl(1) = 2.4796(5) Å;
Cu(1)−Cl(1A) = 2.3641(5) Å], a feature that has been noted
previously within related complexes.31c,f The Cu−C bond
lengths [Cu(1)−C(11) = 1.896(2) Å; Cu(1)−C(21) =
1.903(2) Å] are similarly comparable to related systems in
the literature. The molecular structures of complexes 1d and 1f
are included in the Supporting Information and need no further
comment here.
1
resulting adducts were characterized by H and 13C NMR
spectroscopy, with 1H and 13C NMR spectra showing no
significant changes from the equivalent spectra of the free
ligands upon complexation, apart from the 13C chemical shifts
for the divalent CN carbon atoms; these are all reduced by
approximately 20 ppm, which can be attributed to loss of the
electron density associated with forming the metal−ligand
bond. These observations are consistent with those reported
previously in the literature.10,31 Because of the nature of these
adducts, the precise ratio of the isocyanide ligand to copper
chloride was impossible to ascertain from NMR analysis.
Therefore, elemental analysis was used to confirm the purity of
the samples, and where possible, single-crystal X-ray diffraction
(XRD) was used to unequivocally determine the molecular
structure of the adducts.
The direct reaction of copper chloride with the alkyl
isocyanides a−c (a, isopropyl isocyanide; b, tert-butyl
isocyanide; c, cyclohexyl isocyanide) results in the formation
of colorless crystalline materials in moderate-to-high yields
(56−89%), which were identified by elemental analysis as the
1:1 adducts (1a−1c)10,31a,b with what is assumed to be a
cubane-like molecular structure. Comparable cubane-like
Synthesis of Cyclopentadienylcopper(I) Isocyanide
Adducts. An attractive feature of the [(η5-Cp)Cu(CNR)]
complexes is that the sterics and electronics of the complexes
can be tuned by altering the substituents of either the Cp ring
or the R group of the isocyanide ligand to make a suitable
C
DOI: 10.1021/acs.inorgchem.5b00448
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 2. Diagram showing the molecular structures of complexes 2a−2d and 2f (50% probability ellipsoids). Symmetry transformations used to
3
1
generate equivalent atoms: in 2a, x, −y + /2, z; in 2f, −x + /2, y, z.
Table 1. Selected Bond Lengths and Angles for 2a−2d and 2f
2a
2b
2c
2d
2f
Cu(1)−C(11) (Å)
Cu(1)−Cpcent (Å)
ave Cu−Ccp (Å)
1.816(2)
1.833(5)
2.1846
1.815(2)
1.849(3)
2.198
1.810(2)
1.846(4)
2.196
1.798(3)
1.843(4)
2.194
1.805(3)
1.852(3)
2.209
ave C−Ccp (Å)
1.398
1.398
1.399
1.399
1.415
Cpcent−Cu(1)−C(11) (deg)
Cu(1)−C(11)−N(1) (deg)
C(11)−N(1)−C(12) (deg)
168.69(22)
174.40(18)
175.34(19)
173.06(22)
177.48(19)
177.22(19)
173.24(20)
176.11(19)
174.0(2)
176.15(19)
176.9(3)
176.4(3)
175.70(19)
178.9(3)
172.6(3)
precursor for copper CVD (or ALD). It has been previously
suggested that the size of the ligands (especially Cp ligands)
associated with particular precursors can play an important role
in determining its suitability.33
tion times (<2 h) between sodium cyclopentadienide and the
isocyanide adducts 1d−1f limits the formation of these
complexes, and selective crystallization from a hexane solution
at −28 °C allows complexes 2d−2f to be isolated pure and in
moderate yields.
Reaction of the copper(I) chloride isocyanide adducts with
either sodium cyclopentadienide (NaCp), sodium methylcy-
clopentadienide (NaCpMe), sodium ethylcyclopentadienide
(NaCpEt), or sodium isopropylcyclopentadienide (NaCpiPr)
in stoichiometric ratios results in formation of the η5-
cyclopentadienylcopper complexes 2a−2f, 3a−3c, 4b, and 5b,
respectively (Scheme 1), in quantitative yields. We have
reported elsewhere the intriguing reactivity of the aryl
isocyanide adducts 2d and 2f,31d along with the para-fluorinated
and nitrated derivatives [(η5-C5H5)CuCNC6H4F] and [(η5-
C5H5)CuCNC6H4NO2],34 with excess isocyanide ligand, to
form 6-aminofulvene-2-aldimine complexes.31b Reduced reac-
In an attempt to probe the effect of the R group of the
isocyanide ligand on the precursor’s suitability for copper CVD,
our initial studies focused on the synthesis of a family of
complexes in which this substituent was varied. Thus, the
complexes 2a [(η5-Cp)Cu(CNiPr)], 2b [(η5-Cp)Cu(CNtBu)],
2c [(η5-Cp)Cu(CNCy)], 2d [(η5-Cp)Cu(CNPh)], 2e [(η5-
Cp)Cu(CNXyl)], and 2f [(η5-Cp)Cu(CNMes)] were pre-
1
pared. In all cases, the H and 13C NMR spectra of these
systems (2a−2f) show a singlet resonance associated with the
1
Cp moiety: H NMR, δ 5.89−5.96 respectively (integrating to
five hydrogen atoms); 13C NMR, between δ 94.62 and 94.83.
D
DOI: 10.1021/acs.inorgchem.5b00448
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
1
The H and 13C NMR spectral resonances associated with the
Table 2. Expected % Residue, % Nonvolatile Residue, and
Onset of Volatilisation/Decomposition Temperature for
2a−2f
isocyanide groups show no significant change upon substitution
of Cl for Cp. Unfortunately, because of the fast relaxation time
of quaternary carbon atoms and 14N coupling, the CN
resonances are not observed in the 13C NMR spectra.
expected % for % nonvolatile residue (temp,
onset temp
a
precursor
Cu
°C)
(°C)
Crystalline materials suitable for single-crystal XRD experi-
ments were isolated for 2a−2d and 2f. In the solid state, 2a−2d
and 2f form discrete monomers with one-legged piano-stool
(pogo stick)-type geometries (Figure 2). In all cases, the central
copper atom of the complexes is bound to the C5H5 ligands in a
η5 fashion and the isocyanide ligand by the carbon atom in a κ1-
coordination mode. If we consider the C5H5 ligands as
occupying a single coordination site, the individual copper
geometries are almost linear, with Cpcentroid−Cu−C angles
between 168.69 and 176.15°. This variance in the angle is most
likely a consequence of packing forces rather than a reflection
of anything significant in the bonding description. The
remaining metrical data for complexes 2a−2d and 2f (Table
1) are in good agreement with other Cp and substituted CpCu
complexes, reflecting an apparent indifference to the nature of
the isocyanide.
2a
2b
2c
2d
2e
2f
32.1
30.0
26.7
27.4
24.5
23.2
36.0 (200)
34.8 (280)
45.4 (500)
55.9 (500)
42.2 (500)
36.8 (500)
100
121
119
98
b
b
b
82
125
a
b
The temperature at which 1% mass loss has occurred. % weight at
500 °C (stable residue not achieved).
produced (Chart 2) in which the isocyanide moiety was kept
the same (i.e., CNtBu) and the substituent group on the
cyclopentadienyl group was modified.
Chart 2
It is also worth noting that complexes 2a−2d and 2f are
scarce examples of structurally characterized CuCp systems
with the general form [(η5-C5H5)CuL] (L = 2e− donor ligand).
Thermogravimetric analyses (TGA) of complexes 2a−2f are
shown in Figure 3. Of the compounds analyzed, only 2a, 2b,
Complexes 3b, 4b, and 5b were synthesized using a
modification of the preparative method used for 2b. In these
cases, analytically pure samples were obtained from either
recrystallization from hexane (4b) or sublimation at reduced
pressure (3b and 5b).
1
The H NMR spectra for complexes 3−5b each contains an
unresolvable multiplet resonance between δ 5.70 and 5.73 for
the C5H4−R hydrogen protons, which correlate to resonances
between δ 91.69 and 92.17, 92.62 and 95.38, and 109.86 and
124.42, for the three equivalent carbon atoms in the η5-C5H4−
1
R rings in the 13C NMR spectra. Analysis of the H and 13C
NMR spectra for these complexes shows very little change in
t
the resonances associated with the BuNC ligand, compared to
both 1b and 2b. As with complexes 2a−2f, the CN resonances
are not observed in the 13C NMR spectra.
For 3b and 4b, crystals suitable for single-crystal XRD studies
were obtained, the molecular structures of which are shown in
Figure 4, with selected bond lengths and angles shown in Table
3.
While there is little obvious effect on the metrical data when
the molecular structures of 2b, 3b, and 4b are compared, there
is an obvious increase in the reactivity of the complexes as the
Cp substituent changes as HCp < MeCp < EtCp < iPrCp, with
the general sensitivity of these systems increasing throughout
the series, which correlates with the steric bulk of the Cp
ligands. What is most obvious from Figure 4 is the variation in
the Cpcent−Cu−C(11) angle, which again is thought to be a
consequence of packing forces.
TGA traces of complexes 2−5b are shown in Figure 5, the
most striking feature of which appears in the TGA trace of
complex 3b, showing a very clear, and distinct, two-step
decomposition pathway with an initial onset of mass loss of
33.8% (to 66.2%) between 107 and 114 °C, followed by a
further mass loss of 44.5% (down to 21.7%) between 130 and
218 °C (Table 4). With a residual mass of 21.7% at 218 °C
Figure 3. TGA traces of 2a−2f from 30 to 500 °C. Experiments were
run under N2 (50 mL/min) at a ramp rate of 20 °C/min.
and 2f were found to produce stable residues below 500 °C.
Compounds 2a and 2b were found to undergo mass loss to
yield stable residues of 36.0% and 34.8%, respectively, which are
slightly higher than the expected values for copper metal from
each respective complex (Table 2), indicating a significant
degree of incomplete decomposition or incorporation of carbon
into the residue. While 2a and 2b have single-step
decomposition pathways, 2c−2f display multistep decomposi-
tion pathways. For complexes 2c−2e, stable residues were not
achieved even at 600 °C. Of the complexes investigated,
complexes 2a and 2b show the greatest promise as potential
copper metal precursors, with 2b showing a higher degree of
thermal stability.
In an effort to ascertain the effect of derivatization of the
cyclopentadienyl moiety on features such as the stability,
volatility, and decomposition, a series of complexes were
E
DOI: 10.1021/acs.inorgchem.5b00448
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Table 4. Expected % Residue, % Nonvolatile Residue, and
Onset of Volatilization/Decomposition Temperature for 2−
5b
onset
temp
mp/
sublimation
point
expected %
for Cu
% nonvolatile
residue (temp, °C)
a
precursor
(°C)
2b
30.0
28.1
26.5
25.0
34.8 (280)
121
95 °C/40 °C,
0.1 Torr
3b
4b
5b
21.7 (218)
107
90
dec/70 °C, 0.1
Torr
b
33.6 (500)
dec/80 °C, 0.1
Torr
b
34.9 (500)
171
dec/80 °C, 0.1
Torr
Figure 4. Diagram showing the molecular structures of the methyl-
and ethylcyclopentadienylcopper (tert-butyl isocyanide) complexes 3b
and 4b (50% probability ellipsoids).
a
b
The temperature at which 1% mass loss has occurred. % weight at
500 °C (stable residue not achieved).
Table 3. Selected Bond Lengths and Angles for 2a−2d and 2f
For 4b and 5b, mass loss continued up to, and beyond, 500
°C, and in both cases, the % mass residue at 500 °C was greater
than that expected for the formation of copper metal.
As part of our study, vapor-pressure measurements were
carried out on 2−5b using a previously reported method and
apparatus.36 Details of these analyses are supplied in the SI. The
results of the vapor-pressure measurements of 2−5b are
depicted in Figure 6 and the numerical results shown in Table
3b
4b
Cu(1)−C(11) (Å)
Cu(1)−Cpcent (Å)
Cpcent−Cu(1)−C(11) (deg)
Cu(1)−C(11)−N(1) (deg)
1.810(2)
1.809(2)
1.845(5)
175.87(16)
178.1(2)
1.850(4)
169.86(17)
175.74(16)
Figure 6. Vapor-pressure measurements of 2−5b.
Figure 5. TGA traces of 2−5b from 40 to 500 °C. Experiments were
run under N2 (50 mL/min) at a ramp rate of 20 °C/min.
5. Each set of data was obtained at temperatures below the
melting points of the precursors. The vapor pressures of 2−5b
obey the general equation log P = A − B/T, where A and B are
free parameters, with the corresponding enthalpy of vapor-
ization or sublimation being deduced from parameter B (Table
5).37
As can be seen from the calculated vapor pressures of
complexes 2−5b at 60 °C, shown in Table 5, the order of
volatility is 3b > 4b ≫ 2b > 5b, which is attributed to the
difference in the Cp substituent such that the order of volatility
(which is lower than the expected residual mass for pure
copper), complex 2b appears to possess a small degree of
volatility.
Despite a clear two-step decomposition process for 3b,
assignment of each thermal event (CpMe vs CNtBu loss) has
not been possible because of the volatility of this complex,
making assignment of the thermal events problematic.
However, work by others has suggested that loss of the neutral
donor ligand (in this case, CNtBu) occurs initially to form
{CuCp} species.2d,35 Furthermore, such a chemisorption
mechanism is consistent with related studies by Coyle et al.,
who have shown that carbene-stabilized copper(I) silylamide
precursors work most efficiently at elevated temperatures
(>170 °C) in order to provide sufficient energy to break the
Cu−carbene bond, or in our case the Cu−isocyanide bond, to
form surface-chemisorbed copper(I) species, which then react
with a hydrogen coreagent.3m,n
i
can be viewed as MeCp > EtCp > HCp > PrCp; in fact, a
comparison of the vapor pressures of 3b and 4b at 60 °C with
commercially available copper precursors, specifically
cyclopentadienyl(triethylphosphine)copper(I) and CupraSelect
(200 and 150 mTorr, respectively) shows 3b and 4b to be more
volatile at these operating temperatures.35,38
Despite the significant effects of both the methyl and ethyl
substituents on the volatility of the cyclopentadienyl (tert-butyl
isocyanide) copper(I) systems 3b and 4b, the stability of
complex 4b was found to be low, and the compound was
observed to decompose upon standing at room temperature
F
DOI: 10.1021/acs.inorgchem.5b00448
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
a
Table 5. Vapor-Pressure Data for the Copper Metal Precursors 2−5b
precursor
A
B × 10−3
ΔHsub (kJ/mol)
temp range of measurement (°C)
calcd vapor pressure at 60 °C (mTorr)
2b
3b
4b
5b
15.9 0.5
13.5 0.2
21.2 0.6
17.3 0.4
4.77 0.16
3.67 0.06
6.29 0.19
5.36 0.12
39.7 1.4
30.5 0.5
52.3 1.6
44.6 1.0
35−70
30−65
35−65
40−75
33.76
290.99
203.93
15.48
a
Data are fitted to log P (mTorr) = A − 1000B/(T/K). Error margins are established by a linear regression method and given at the 95% confidence
interval.
over a period of weeks, producing a black microcrystalline
powder identified as copper metal. More significantly, attempts
to synthesize the corresponding methyl and ethylcyclopenta-
dienyl (isopropyl isocyanide) copper(I) complexes (3a and 4a)
and the methyl-cyclopentadienyl (cyclohexyl isocyanide)
copper(I) complex (3c) in the hope that these compounds
would be suitable and possibly liquid precursors were met with
mixed results; compound 4a could not be synthesized, and
multiple attempts to produce the complex under varied
conditions met with the formation of copper metal. Although
compounds 3a and 3c could be synthesized in adequate yields,
using the methodology outlined previously (Scheme 1), the
complexes were only stable for prolonged periods of time under
an argon atmosphere at −28 °C, features that inhibited full
characterization of the products by elemental analysis and
TGA. However, single crystals suitable for XRD analysis of
both 3a and 3c were obtained and the molecular structures
(which are included in the SI) determined, which show features
that match those of the complexes already described.
Table 6. General Physical Parameters for the LP-CVD of
Complex 2a and 2b
CVD parameters
2a
2b
2a
2b
substrate temp (°C)
operating pressure (Torr)
carrier gas
180
40
180
40
300
40
300
40
H2
0.3
0.3
60
H2
0.3
0.3
60
H2
0.3
0.3
60
H2
0.3
0.3
60
carrier flow rate (L/min)
bubbler flow rate (L/ min)
temp of the bubbler (°C)
temp of the gas lines (°C)
deposition duration (min)
75
75
75
75
60
60
60
60
(SEM) analysis of the films (Figure 7), which reveals the
presence of single crystals of copper metal between 400 nm and
1 μm in length, dispersed over the surface of the substrates.
The reduced stability of the methylcyclopentadienyl
derivatives 3a−3c and the ethyl system 4a is attributed, in
part, to the increased electron donor capacity of the substituted
cyclopentadienyl derivatives compared to C5H5.
Copper Deposition and Thin-Film Analysis. The results
of structural and thermal studies led us to focus initially on
production of the cyclopentadienyl and methylcyclopentadienyl
copper derivatives 2a, 2b, 3a, and 3b on multigram scales for
deposition studies. However, attempts to upscale the
production of systems 3a and 3b resulted in significantly
lower yielding reactions. Focus was therefore directed to the
production of complexes 2a and 2b, both of which are stable
under inert conditions for weeks to months and could be
successfully produced on a 5−10 g scale.
Copper was initially deposited onto silicon (400) wafers
using complexes 2a and 2b at low pressure (40 Torr) using a
cold-walled Electrogas CVD apparatus. However, because
copper has been shown to adhere poorly to silicon, gold on
silicon was also investigated as a suitable substrate. Copper
metal was deposited on both substrates at both 180 and 300
°C. In all of the deposition runs, the precursor was heated to 60
°C and the carrier gas lines were externally heated to 75 °C.
The pressure during deposition was maintained at 40 Torr,
using H2 as the carrier gas at a flow rate of 0.3 L/min. Typically,
H2 is used a reductant for copper precursors because it can
homolytically dissociate into hydrogen adatoms on clean
substrate surfaces.1,30a Table 6 shows the general physical
parameters used throughout the deposition experiments. In all
cases, films deposited using 2a or 2b under identical conditions
were indistinguishable; for this reason, the subsequent
discussion is limited to films deposited using 2b.
Figure 7. Micrographs of copper films deposited on gold/silicon (left)
and silicon (right) at a substrate temperature of 180 °C.
In stark contrast, those films deposited at 300 °C possessed a
metallic luster and appeared continuous on both silicon and
gold/silicon substrates. It should be noted that deposition runs
at temperatures below 180 °C failed to provide films with
sufficient coverage for analysis and have not been discussed
here; at intermediate temperatures between 180 and 300 °C,
low-pressue CVD (LP-CVD) copper films were discontinuous
and comparable to those grown at 180 °C. Only at 300 °C and
above were continuous pinhole-free films observed.
SEM analysis of films deposited onto gold/silicon at 300 °C
shows the films to be continuous and comprised of uniformly
granular-shaped particles (Figure 8) of approximately 200 mn
thickness. While films deposited onto silicon at 300 °C were
somewhat similar, larger particles of material on the film were
also present (Figure 8), likely to be a result of the thermal
mobility of copper, leading to particle agglomeration.30a
Films deposited at 180 °C for both precursors appeared
silvery-blue in color and discontinuous to the naked eye, a
feature that is confirmed by scanning electron microscopy
G
DOI: 10.1021/acs.inorgchem.5b00448
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 8. Micrographs of copper films deposited on gold/silicon (left)
and silicon (right) at a substrate temperature of 300 °C.
Figure 10. XPS profile of a film deposited at a substrate temperature
of 300 °C on silicon. Magnified regions for oxygen (left) and carbon
(right) are also shown.
Energy-dispersive X-ray (EDX) spectroscopy of all films
demonstrated the presence of copper as well as peaks
associated with the relevant substrates; an exemplar EDX plot
is shown in Figure 9.
Table 7. Elemental Analysis for Etched Copper Films
Deposited from 2b
atom %
substrate (temp,
°C)
copper oxygen carbon gold
silicon platinum
14.01
silicon (300)
60.39
3.08
1.81
0.33
21.51
14.43
1.15
gold/silicon (300) 74.33
9.42
platinum/silicon
(180)
54.66
43.86
remains (14.4−21.5%), which can arise from decomposition of
the cyclopentadienyl ligand,9b,o even in the presence of H2,40
when relatively high deposition temperatures are needed to
induce precursor decomposition.
However, if background elements (silicon and gold) are
removed from elemental analysis, we find that the films
produced are of moderately high purity (71 and 82 atom % of
copper, respectively) although still with a significant degree of
carbon inclusion. XPS data for films deposited onto silicon and
gold/silicon from complexes 2a and 2b at 180 °C are not
reported because of the inability to obtain reliable measure-
ments as a consequence of the significantly reduced surface
coverage and larger particle size.
In an attempt to reduce the carbon content within the
deposited films, platinum substrates [platinum-coated silicon
(400) wafers], which are considered to be oxide-free, show a
high affinity for copper, and are typically employed as both
strong adhesion and diffusion barrier materials in micro-
electronics,40 were investigated using 2a and 2b at deposition
temperatures of 180 °C. Platinum is also employed as a
hydrogenation catalyst, and as such, shows a high affinity to
hydrogen and the production of chemisorbed hydrogen, which
we believe is important in the reduction of copper(I) to copper
metal (Figure 11).
Figure 9. Typical EDX plot of copper films grown on a silicon (400)
wafer from 2a.
X-ray photoelectron spectrsocopy (XPS) analysis of the as-
deposited films revealed the presence of significant peaks
associated with C 1s (284 eV) and O 1s (532 eV) on the
surface. The Cu LMM auger ionization energy, which is a
clearer indicator of the copper oxidation state,39 indicates the
presence of Cu2O on the surface [570.72 eV (gold/silicon) and
570.77 eV (silicon)] of the deposited materials. However,
following an argon etch, the Cu LMM peak associated with
Cu2O disappears and is replaced with that associated with
metallic copper [567.8 eV (gold/silicon) and 567.7 eV
(silicon)], while peaks associated with carbon and oxygen are
reduced. Figure 10 shows a typical example of a copper XPS
spectrum. Table 7 shows the elemental profiles of the films
after a 4 min argon etch, as a function of the substrate and
deposition temperature. Analysis shows that films deposited
from 2a and 2b at 300 °C contain a small amount of oxygen
(1.8−3.1 atom %), but significant carbon contamination still
H
DOI: 10.1021/acs.inorgchem.5b00448
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 12. XRD pattern of continuous copper films deposited onto
silicon (300 °C), gold/silicon (300 °C), and platinum/silicon (300
°C) substrates.
Figure 11. (Top) Electron micrographs of the copper thin films
deposited onto a platinum/silicon wafer at 180 °C using complex 2a.
(Bottom) Micrograph showing the successive layers of silicon,
platinum, and copper metal.
over a wide temperature range (80−500 °C). In contrast, the
alkyl isocyanide derivatives 2a−2c showed significantly more
promise, with both the isopropyl (2a) and tert-butyl (2b)
derivatives displaying a single thermal decomposition event
with residual masses close to that expected for a copper-only
residue. As part of the study, the molecular structures of
complexes 2a−2d and 2f were unambiguously determined in
single-crystal XRD studies, and in all cases, the complexes
display linear pogo-stick-like geometries in the solid state.
A comparison of complexes 3−5b [(η5-R′C5H4)Cu-
Using identical protocols to those outlined in Table 6,
copper metal was successfully deposited at 180 °C onto
platinum/silicon using both 2a and 2b; to the naked eye, the
films displayed a significant metallic luster and appeared
pinhole-free. EDX (see the SI) clearly shows the presence of
copper with no evidence from EDX of an underlying platinum
substrate, suggesting a hole-free coverage.
Analysis of the films by SEM indeed shows the films
deposited onto platinum/silicon to be continuous and
approximately 200 nm thick, consisting of layers of micro-
crystals of copper of approximately 100 μm diameter that cover
the entirety of the platinum/silicon substrate.
Subsequent analysis of the films, using XPS (see ESI), shows
the presence of Cu2O on the surface of the deposited materials,
as indicated by the Cu LMM auger ionization (570.62 eV) and
a significant reduction in the carbon content of the film (Table
7). As before, etching of the sample indicates that oxygen
contamination is localized to the surface of the sample, as
indicated by the change in the Cu LMM ionization to that
associated with copper metal (567.76 eV).39 The removal of
underlying platinum from the analysis suggests that copper thin
films with ca. 97% purity are being formed.
It should also be noted that the growth of copper on
platinum substrates can result in partial incorporation of
platinum into the growing copper layer, forming a bilayer alloy
at the interface (Cu50Pt50).41 However, given an approximate
thickness of 200 nm, we see no evidence of this bilayer material
in the XPS data.
Powder XRD analysis (Figure 12) revealed the films to be
crystalline, showing a reflection at 2θ = 43.3° (highlighted red,
Figure 12), which corresponds to the copper (111) Miller
plane, and at 2θ = 50.5°, which corresponds to the copper
(200) Miller plane, both of which are associated with a face-
centered-cubic copper metal. All other reflections are associated
with the respective substrates.
Evaluation of the Precursor Properties and Thin
Films. The copper(I) cyclopentadienyl complexes containing
aryl-substituted isocyanide ligands, 2d−2f, proved to be less
than suitable as prospective CVD precursors, with TGA traces
showing high residual masses and incomplete decomposition
i
(CNtBu)], where R = Me (3b), Et (4b), Pr (5b), and the
parent unsubstituted complex shows that, despite their
isostructural nature, there are significant changes in the stability
and volatility of the complexes. TGA shows that for all of the
complexes thermal decomposition results in uncomplicated
mass loss processes, with residues close to those expected for
copper metal. Surprisingly, however, the methyl-substituted
derivative 3b shows the presence of a two-step decomposition
process. While our specific interest here is the growth of metal
thin films by CVD, complex 3b may also be useful in the ALD
growth of metal thin films by virtue of what appears to be a
thermally controlled stepwise decomposition process. The
prospective precursors 2−5b show the order of volatility to be
3b > 4b ≫ 2b > 5b, as calculated by vapor pressures.
Despite a favorable comparison of these properties against
the commercially available precursors cyclopentadienyl-
(triethylphosphine)copper(I) and CupraSelect, the lifetimes
of 3b and 4b were low, with the products decomposing to
copper metal upon standing at room temperature.
Subsequent CVD experiments therefore focused on the use
of complexes 2a and 2b. Thin films were deposited onto silicon
and gold substrates at 180 and 300 °C, under a reduced-
pressure H2 atmosphere. Films deposited onto silicon and gold
substrates at 180 °C were found to consist of a regular array of
copper metal nanoclusters (rods), the size of which appears to
be dependent on the deposition temperature and is likely to be
dependent on the deposition time also. In contrast, at high
temperatures films were found to be continuous and of
moderately high purity (71 and 82 atom % of copper,
respectively), as shown by XPS. Contrastingly, films deposited
onto platinum substrates at 180 °C were found to be
continuous, with ca. 97% purity and with significantly less
carbon and oxygen contamination. Significantly, complex 2b
represents a precursor capable of depositing continuous copper
metal films onto platinum substrates at low temperatures (<200
I
DOI: 10.1021/acs.inorgchem.5b00448
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
C28H44Cl4Cu4N4: C, 40.39; H, 5.32; N, 6.72. Found: C, 41.43; H,
5.12; N, 6.76.
Complexes 1d−1f were all synthesized in an analogous fashion. The
synthesis of [ClCu(CNPh)2]2 is given as an example.
°C). Studies into the utility of complexes 2a and 2b in plasma-
enhanced ALD of copper thin films are presently underway and
will be reported separately.
Synthesis of [ClCu(CNPh)2]2 (1d). Under an inert atmosphere of
argon gas, copper(I) chloride (0.990 g, 10.0 mmol) was placed in a dry
Schlenk tube, followed by THF (25 mL) to give a yellow slurry. To
this was added via syringe PhNC (2.06 g, 20.0 mmol). The reaction
mixture was left to stir for 30 min, followed by cannula filtration to
remove unreacted copper(I) chloride. The volatiles were removed in
vacuo, and the resulting off-white crude product was purified by
recrystallization from THF to afford 1d as colorless crystals (2.69 g,
EXPERIMENTAL SECTION
■
General Procedures. All reactions were carried out under an inert
atmosphere and in the absence of light using standard Schlenk
techniques. Solvents were dried over activated alumina columns using
an Innovative Technology solvent purification system and degassed
under an argon atmosphere. All other reagents were purchased from
commercial sources.
1
88%). H NMR (CDCl3, 300.22 MHz): δ 7.44 (br m, CH, 20H).
The aryl isocyanides PhNC, MesNC, and XylNC were prepared
13C{1H} NMR (CDCl3, 75.50 MHz): δ 126.13, 126.46, 129.51, 130.08
(C6H5), 145.50 (m, CN). Anal. Calcd for C28H20Cl2Cu2N4: C, 55.09;
H, 3.30; N, 9.18. Found: C, 54.82; H, 3.28; N, 9.17.
using a literature procedure.42 The alkyl isocyanides PrNC, BuNC,
and CyNC were bought from commercial sources and used without
further purification. The salts NaCp, NaMeCp, NaEtCp, and NaiPrCp
were all prepared according to a modified literature procedure.43
Elemental analyses were performed by Elemental Microanalysis
Ltd., Okehampton, Devon, U.K. 1H and 13C NMR spectra were
recorded on a Bruker Avance 300 MHz FT-NMR spectrometer as
saturated solutions in CDCl3; chemical shifts are quoted in units of
parts per million, relative to Me4Si (1H and 13C); coupling constants
are in hertz.
i
t
Synthesis of [ClCu(CNXyl)2]2 (1e). 1e was synthesized using 1.13 g
(11.4 mmol) of CuCl and 3.00 g of XylNC (22.8 mmol) to yield the
1
product as colorless crystals (3.02 g, 73%). H NMR (CDCl3, 300.22
MHz): δ 2.42 (s, o-CCH3, 24H), 7.08 (m, m-CH, 8H), 7.20 (m, p-CH,
4H). 13C{1H} NMR (CDCl3, 75.50 MHz): δ 18.62 (o-CCH3), 125.81,
127.75, 129.28, 135.23 (C6H3), 150.62 (br m, CN). Anal. Calcd for
C36H30Cl2Cu2N4: C, 59.83; H, 5.02; N, 7.75. Found: C, 59.73; H,
5.00; N, 7.67.
TGA of the complexes was performed at SAFC Hitech, Brom-
borough, U.K., using a Shimadzu TGA-51 thermogravimetric analyzer.
Data points were collected every second at a ramp rate of 20 °C/min
in a flowing (50 mL/min) N2 stream.
Synthesis of [ClCu(MesNC)2]2 (1f). 1f was synthesized using 2.47 g
(25.0 mmol) of CuCl and 7.26 mL of MesNC (50.0 mmol) to yield
1
the product as colorless crystals (7.20 g, 74%). H NMR (CDCl3,
300.22 MHz): δ 2.27 (s, p-CCH3, 12H), 2.37 (s, o-CCH3, 24H), 6.88
(s, m-CH, 8H). 13C{1H} NMR (CDCl3, 75.50 MHz): δ 18.68 (o-
CCH3), 21.24 (p-CCH3), 123.78, 128.63, 135.25, 139.84 (C6H2),
148.21 (m, CN). Anal. Calcd for C40H44Cl2Cu2N4: C, 49.18; H, 4.54;
N, 5.74. Found: C, 49.09; H, 4.54; N, 5.71.
XPS measurements were performed on a Kratos Axis Ultra-DLD
photoelectron spectrometer, utilizing monochromatic Al Kα radiation
(photon energy 1486.6 eV), at the University of Cardiff. Spectra were
calibrated to the C 2p peak. Samples were sputtered for a
predetermined set time over a 4-mm-wide area using 4 kV argon
ions using a minibeam I ion source. Spectra were collected at pass
energies of 80 and 160 eV for high-resolution and survey scans,
respectively, with the 100 μm apperature in place to focus on the
center of the etch pit.
Field-emission SEM analysis of the films was undertaken on a JEOL
JSM-6480LV scanning electron microscope with EDX capability.
Powder XRD of the films was performed on a Bruker D8 powder
diffractometer, using a copper-anode X-ray source (Kα wavelength =
1.5406 Å) at the University of Bath.
Synthesis of [CpCu(CNiPr)] (2a). 1a (2.02 g, 3.00 mmol) was added
to a dry Schlenk tube under an inert atmosphere of argon, followed by
THF (80 mL). The solution was then cooled (−78 °C), and sodium
cyclopentadienide (1.06 g, 12.0 mmol) in 40 mL of THF was added.
The mixture was left to stir for 16 h, and after this time, the volatiles
were removed under reduced pressure. Hexane (20 mL) was added to
the resultant residue, which was left to stir for 15 min, and the volatiles
were then removed under reduced pressure. The process was repeated
on two further occasions to remove any residual THF. Further hexane
(80 mL) was added, and the slurry was filtered through Celite to
remove any insoluble materials, followed by removal of the volatiles in
vacuo. The crude product was purified by recrystallization (hexane) to
afford 2a as pale-yellow crystals (1.24 g, 52%, mp 73 °C).1H NMR
(CDCl3, 300.22 MHz): δ 1.35 (dt, CH(CH3)2, 6H, J = 6.60 and 2.39
Hz), 3.81 (m, CH(CH3)2, 1H), 5.89 (s, C5H5, 5H). 13C{1H} NMR
(CDCl3, 75.50 MHz): δ 22.78 (CH(CH3)2), 47.84 (CH(CH3)2),
94.62 (C5H5), CN carbon not observed. Anal. Calcd for C9H12Cu1N1:
C, 54.67; H, 6.12; N, 7.08. Found: C, 54.60; H, 5.95; N, 7.13.
Synthesis of [CpCu(CNtBu)] (2b). 2b was synthesized in a fashion
analogous to that of 2a using 1b (14.57 g, 20 mmol) and sodium
cyclopentadienide (7.05 g, 80.0 mmol). The dried crude product was
further purified by sublimation (1 × 10−1 Torr, 40−50 °C) to afford
Synthesis of [ClCu(CNiPr)]4 (1a). Under an inert atmosphere of
argon gas, copper(I) chloride (4.95 g, 50.0 mmol) was placed in a dry
Schlenk tube, followed by THF (50 mL) to give a yellow slurry. To
this was added via syringe iPrNC (4.55 mL, 50.0 mmol). The reaction
mixture was left to stir for 30 min, followed by cannula filtration to
remove unreacted copper(I) chloride. The volatiles were removed in
vacuo, and the resulting off-yellow crude product was purified by
recrystallization from THF to afford 1a as pale-yellow crystals (7.46 g,
89%). 1H NMR (CDCl3, 300.22 MHz): δ 1.38 (d, CH(CH3)2, 6H, J =
6.64 Hz), 6.64 (sept, CH(CH3)2, 1H, J = 6.64 Hz). 13C{1H} NMR
(CDCl3, 75.50 MHz): δ 22.59 (CH(CH3)2), 47.33 (t, CH(CH3)2, J =
5.50 Hz), 136.60 (t, CN, J = 15.29 Hz) Anal. Calcd for
C16H28Cl4Cu4N4: C, 28.58; H, 4.20; N, 8.33. Found: C, 31.59; H,
4.70; N, 7.61.
1
2b as off-white crystals (15.25 g, 90%, mp 95 °C). H NMR (CDCl3,
Synthesis of [ClCu(CNtBu)]4 (1b). 1b was synthesized in a manner
analogous to that of 1a using 4.26 g (43.0 mmol) of CuCl and 4.84 mL
(43.0 mmol) of tBuNC to yield 1b as colorless crystals (5.58 g, 71%).
1H NMR (CDCl3, 300.22 MHz): δ 1.46 (s, C(CH3)3, 9H). 13C{1H}
NMR (CDCl3, 75.50 MHz): δ 30.05 (C(CH3)3), 56.50 (C(CH3)3),
134.62 (t, CN, J = 15.75 Hz). Anal. Calcd for C20H36Cl4Cu4N4: C,
32.97; H, 4.98; N, 7.69. Found: C, 33.40; H, 5.03; N, 7.73.
Synthesis of [ClCu(CNCy)]4 (1c). 1c was synthesized in a manner
analogous to that of 1a using 1.98 g (20.0 mmol) of CuCl and 2.49 mL
(20.0 mmol) of CyNC to yield 1c as colorless crystals (2.35 g, 56%).
1H NMR (CDCl3, 300.22 MHz): δ 1.42 (br m, CH2, 16H), 1.71 (br
m, CH2, 16H), 1.89 (br m, CH2, 8H), 3.72 (br m, CH, 4H). 13C{1H}
NMR (CDCl3, 75.50 MHz): δ 22.71, 24.70, 31.92 (CH2), 53.39 (t,
CH, J = 5.61 Hz), CN carbon not observed. Anal. Calcd for
300.22 MHz): δ 1.41 (s, C(CH3)3, 9H), 5.90 (s, C5H5, 5H). 13C{1H}
NMR (CDCl3, 75.50 MHz): δ 30.13 (C(CH3)3), 56.96 (C(CH3)3),
94.70 (C5H5), CN carbon not observed. Anal. Calcd for C11H17CuN:
C, 56.86; H, 6.69; N, 6.64. Found: C, 56.70; H, 6.68; N, 6.57.
Synthesis of [CpCu(CNCy)] (2c). 2c was synthesized in a fashion
analogous to that of 2a using 1c (1.67 g, 2.00 mmol) and sodium
cyclopentadienide (0.70 g, 8.00 mmol). The dark-brown crude
product was purified by recrystallization (hexane) to afford 2c as
1
white crystals (0.70 g, 37%, mp 118 °C). H NMR (CDCl3, 300.22
MHz): δ 1.36 (m, CH2, 4H), 1.65 (m, CH2, 4H), 1.84 (m, CH2, 2H),
3.63 (m, CH, 1H), 5.93 (s, C5H5, 5H). 13C{1H} NMR (CDCl3, 75.50
MHz): δ 22.75, 24.72, 31.10 (CH2), 53.72 (t, CH, J = 6.43 Hz), 94.64
(C5H5), CN carbon not observed. Anal. Calcd for C12H16Cu1N1: C,
60.61; H, 6.78; N, 5.89. Found: C, 60.78; H, 6.67; N, 5.97.
J
DOI: 10.1021/acs.inorgchem.5b00448
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Synthesis of [MeCpCu(CNiPr)] (3a). 3a was synthesized in a fashion
analogous to that of 2a using 1a (1.34 g, 2.00 mmol) and sodium
methyl cyclopentadienide (0.82 g, 8.00 mmol). The dark-brown crude
product was purified by recrystallization (hexane) to afford 3a as white
in a dark-yellow crude solid, which was purified by recrystallization
(hexane) to afford 3d as yellow crystals (0.990 g, 35%, mp 76 °C). 1H
NMR (CDCl3, 300.22 MHz): δ 5.95, (s, C5H5, 5H), 7.45−7.28 (m,
C6H5, 5H). 13C{1H} NMR (CDCl3, 75.50 MHz): δ 94.82 (C5H5),
121.74, 126.43, 129.61, 129.82 (C6H5), CN carbon not observed. Anal.
Calcd for C12H10Cu1N1: C, 62.19; H, 4.35; N, 6.04. Found: C, 67.76;
H, 5.56; N, 5.38.
1
crystals (1.14 g, 67%, mp 46 °C). H NMR (CDCl3, 300.22 MHz): δ
1.36 (doublets of triplets, CH(CH3)2, 6H, J = 6.56 and 2.3 Hz), 2.24
(s, C5H4CH3, 3H), 3.81 (septet of triplets, CH(CH3)2, 1H, J = 1.75
and 6.56 Hz), 5.70 (m, C5H4CH3, 5H). 13C{1H} NMR (CDCl3, 75.50
MHz): δ 14.44 (C5H4CH3), 22.76 (CH(CH3)2), 47.79 (CH(CH3)2),
92.15, 95.38, 109.90 (C5H4CH3), CN carbon not observed. The
complex was too unstable to characterize by elemental analysis.
Synthesis of [MeCpCu(CNtBu)] (3b). 3b was synthesized in a
fashion analogous to that of 2a using 7.29 g (10 mmol) of 1b and 4.12
g (40 mmol) of sodium methylcyclopentadienide. Sublimation (1 ×
10−1 Torr, 70 °C) of the crude product afforded 3b as off-yellow
Synthesis of [CpCu(XylNC)] (3e). 3e was synthesized in a fashion
analogous to that of 3d using 1e (1.00 g, 1.38 mmol) and sodium
cyclopentadienyl (0.243 g, 2.76 mmol). The crude solid that was
purified by recrystallization (hexane) to afford 3e as off-white crystals
1
(0.215 g, 30%, mp 132 °C). H NMR (CDCl3, 300.22 MHz): δ 2.35
(s, o-CCH3, 6H), 5.96 (s, C5H5, 5H), 7.08 (m, m-CH, 2H), 7.20 (m, p-
CH, 1H). 13C{1H} NMR (CDCl3, 75.50 MHz): δ 18.75 (CCH3),
94.83 (C5H5), 127.98, 129.36, 135.49 (C6H5), CN carbon not
observed. The complex was too unstable to characterize by elemental
analysis.
1
crystals (7.96 g, 88%). H NMR (CDCl3, 300.22 MHz): δ 1.42 (t,
C(CH3)3, 9H, J = 2.13 Hz), 2.24 (s, C5H4CH3, 3H), 5.70 (m,
C5H4CH3, 4H). 13C{1H} NMR (CDCl3, 75.50 MHz): δ 14.44
(C5H4CH3), 30.09 (C(CH3)3), 56.65 (C(CH3)3), 92.17, 95.38, 109.86
(C5H4CH3), CN carbon not observed. Anal. Calcd for C12H19CuN: C,
58.65; H, 7.14; N, 6.22. Found: C, 58.00; H, 7.14; N, 6.32.
Synthesis of [MeCpCu(CNCy)] (3c). 3c was synthesized in a fashion
analogous to that of 2a using 1c (0.83 g, 1 mmol) and sodium
methylcyclopentadienyl (0.35 g, 4 mmol). The crude dark-brown solid
was purified by recrystallization (hexane) to afford 3c as colorless
crystals (0.40 g, 40%, mp 111 °C). 1H NMR (CDCl3, 300.22 MHz): δ
1.38 (m, CH2, 4H), 1.68 (m, CH2, 4H), 1.87 (m, CH2, 2H), 2.24 (s,
C5H4CH3, 3H), 3.64 (m, CH, 1H), 5.71 (m, C5H4CH3, 5H). 13C{1H}
NMR (CDCl3, 75.50 MHz): δ 14.46 (C5H4CH3), 22.75, 24.70, 32.02
(CH2), 53.60 (m, CH, 1C), 92.14, 95.41, 109.95 (C5H5CH3), CN
carbon not observed. The complex was too unstable to characterize by
elemental analysis.
Synthesis of [CpCu(CNMes)] (3f). 3f was synthesized in a fashion
analogous to that of 3d using 1f (1.67 g, 2.15 mmol) and sodium
cyclopentadienyl (0.379 g, 4.30 mmol). The crude solid was purified
by recrystallization (hexane) to afford 3f as off-white crystals (0.72 g,
1
59%, mp 140 °C). H NMR (CDCl3, 300.22 MHz): δ 2.27 (s, p-
CCH3, 3H), 2.38 (s, o-CCH3, 6H), 5.96, (s, C5H5, 5H), 6.88 (s, m-CH,
2H). 13C{1H} NMR (CDCl3, 75.50 MHz): δ 18.59 (o-CCH3), 21.23
(p-CCH3), 94.81 (C5H5), 128.24, 135.13, 139.52 (C6H2, 6C), CN
carbon not observed. Anal. Calcd for C15H16Cu1N1: C, 65.79; H, 5.89;
N, 5.11. Found: C, 65.06; H, 5.89; N, 5.34.
Crystallography. Experimental details relating to the single-crystal
X-ray crystallographic studies are summarized in Table S1 in the SI.
For all structures, data were collected on a Nonius Kappa CCD
diffractometer at 150(2) K using Mo Kα radiation (λ = 0.71073 Å).
Structure solution and refinements were performed using SHELX8644
and SHELX9745 software, respectively. Corrections for absorption
were made in all cases. For all complexes, hydrogen atoms were
included at calculated positions. Data for complexes 1d−1f, 2a−2d. 2f,
3a−3c, and 4b have been deposited with the Cambridge Structural
Database as CCDC 1050605−1050616.
Synthesis of [EtCpCu(CNtBu)] (4b). 4b was synthesized in a fashion
analogous to that of 2a using 1b (1.25 g, 1.72 mmol) and sodium
ethycyclopentadienide (1.03 M in THF, 7.8 mL, 8.00 mmol). The
crude product that was purified by recrystallization (hexane) to afford
4b as colorless crystals (1.20 g, 73%). Sublimation (1 × 10−1 Torr, 70
°C) was also used to produce pure materials. 1H NMR (CDCl3,
300.22 MHz): δ 1.21 (t, C5H4CH2CH3, 3H, J3 = 7.56 Hz), 1.43 (s,
C(CH3)3, 9H), 2.54 (q, C5H4CH2CH3, 2H, J3 = 7.56 Hz), 5.72 (m,
C5H4CH2CH3, 4H). 13C{1H} NMR (CDCl3, 75.50 MHz): δ 17.87
(C5H4CH2CH3), 22.18 (C5H4CH2CH3), 30.29 (C(CH3)3), 56.92
(C(CH3)3), 92.02, 93.84, 118.58 (C5H4CH2CH3), CN carbon not
observed. Anal. Calcd for C13H21CuN: C, 60.23; H, 7.59; N, 5.86.
Found: C, 60.14; H, 7.34; N, 5.91.
ASSOCIATED CONTENT
* Supporting Information
■
S
Molecular structures of 1d and 1f, vapor pressure measure-
ments of 2b, 3b, 4b, and 5b, EDX plots, XPS profiles, and
crystallographic data for 1d−1f, 2a−2d, 3a−3c, and 4b. The
Supporting Information is available free of charge on the ACS
Publications website at DOI: 10.1021/acs.inorgchem.5b00448.
Synthesis of [(iPrCp)Cu(CNtBu)] (5b). 5b was synthesized in a
fashion analogous to that of 2a using 1b (0.51 g, 2.00 mmol) and
sodium isopropylcyclopentadienide (1.05 M in THF, 8.86 mL, 9.30
mmol). The crude product was purified by recrystallization (hexane)
followed by sublimation (1 × 10−1 Torr, 80 °C) to afford 5b as
AUTHOR INFORMATION
Corresponding Author
■
1
*E-mail: A.L.Johnson@bath.ac.uk. Tel: 44 (0)1225 384467.
Fax: 44 (0)1225 386231.
colorless crystals (1.42 g, 70%). H NMR (CDCl3, 300.22 MHz): δ
1.23 (m, C5H4CH(CH3)2, 6H), 1.42 (s, C(CH3)3, 9H), 2.85 (sept,
C5H4CH(CH3)2, 1H, J3 = 6.80 Hz), 5.73 (m, C5H4CH(CH3)2, 4H).
13C{1H} NMR (CDCl3, 75.50 MHz): δ 25.77, 27.69 (C5H4CH-
(CH3)2), 30.27 (C(CH3)3), 56.84 (C(CH3)3), 91.69, 92.62, 124.42
(C5H4CH(CH3)2), CN carbon not observed. Anal. Calcd for
C13H20CuN: C, 61.61; H, 7.94; N, 5.52. Found: C, 61.49; H, 7.72;
N, 5.57.
Synthesis of [CpCu(CNPh)] (3d). 1d (3.66 g, 6.00 mmol) and
sodium cyclopentadienyl (1.06 g, 12.0 mmol) were added to separate
dry Schlenk tubes under inert atmospheres of argon. THF (15 mL)
was added to each, and the sodium cyclopentadienyl solution was
transferred into the 1d solution via cannula. The mixture was then left
to stir for 16 h. The volatiles were removed under reduced pressure,
and dry hexane (20 mL) was added to the resultant residue. This was
left to stir for 15 min, and the volatiles were then removed under
reduced pressure. The process was repeated on two further occasions
to remove any residual THF. Further hexane (20 mL) was added, and
the slurry was filtered through Celite to remove any insoluble
materials, followed by the removal of volatiles in vacuo. This resulted
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We acknowledge financial support of the University of Bath and
EPSRC for the award of a CASE for New Academics (to
A.M.W.) and studentship (to T.P.). SAFC-Hitech is thanked
for both financial and technical support (to P.A.W. and S.L.S.).
REFERENCES
■
(1) Gordon, P. G.; Kurek, A.; Barry, S. T. ECS J. Solid State Sci.
Technol. 2015, 4, N3188−N3197.
(2) (a) Creighton, J. R.; Parmeter, J. E. Crit. Rev. Solid State Mater.
Sci. 1993, 18, 175−238. (b) Hampdensmith, M. J.; Kodas, T. T.
Polyhedron 1995, 14, 699−732. (c) Norman, J. A. T. J. Phys. IV 2001,
11, Pr3/497−Pr493/503. (d) Rickerby, J.; Steinke, J. H. G. Chem. Rev.
K
DOI: 10.1021/acs.inorgchem.5b00448
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
2002, 102, 1525−1549. (e) Luo, B.; Gladfelter, W. L. Chem. Vap.
Deposition 2009, 320−356. (f) Grodzicki, A.; Lakomska, I.; Piszczek,
P.; Szymanska, I.; Szlyk, E. Coord. Chem. Rev. 2005, 249, 2232−2258.
(3) (a) Lim, B. S.; Rahtu, A.; Gordon, R. G. Nat. Mater. 2003, 2,
749−754. (b) Mane, A. U.; Shivashankar, S. A. Mater. Sci. Semicond.
Process. 2004, 7, 343−347. (c) Li, Z.; Barry, S. T.; Gordon, R. G. Inorg.
Chem. 2005, 44, 1728−1735. (d) Park, K.-H.; Marshall, W. J. J. Am.
Chem. Soc. 2005, 127, 9330−9331. (e) Li, Z.; Gordon, R. G. Chem.
Vap. Deposition 2006, 12, 435−441. (f) Li, Z.; Rahtu, A.; Gordon, R.
G. J. Electrochem. Soc. 2006, 153, C787−C794. (g) Park, K.-H.;
Bradley, A. Z.; Thompson, J. S.; Marshall, W. J. Inorg. Chem. 2006, 45,
8480−8482. (h) Ma, Q.; Guo, H.-S.; Gordon, R. G.; Zaera, F. Chem.
Mater. 2010, 22, 352−359. (i) Vidjayacoumar, B.; Emslie, D. J. H.;
Clendenning, S. B.; Blackwell, J. M.; Britten, J. F.; Rheingold, A. Chem.
Mater. 2010, 22, 4844−4853. (j) Ma, Q.; Guo, H.; Gordon, R. G.;
Zaera, F. Chem. Mater. 2011, 23, 3325−3334. (k) Dey, G.; Elliott, S.
D. J. Phys. Chem. A 2012, 116, 8893−8901. (l) Huo, J.; Solanki, R.;
McAndrew, J. J. Mater. Res. 2002, 17, 2394−2398. (m) Hagen, D. J.;
Povey, I. M.; Rushworth, S.; Wrench, J. S.; Keeney, L.; Schmidt, M.;
Petkov, N.; Barry, S. T.; Coyle, J. P.; Pemble, M. E. J. Mater. Chem., C
2014, 2, 9205−9214. (n) Coyle, J. P.; Dey, G.; Sirianni, E. R.; Kemell,
M. L.; Yap, G. P. A.; Ritala, M.; Leskela, M.; Elliott, S. D.; Barry, S. T.
Chem. Mater. 2013, 25, 1132−1138.
(4) (a) Lee, B. H.; Hwang, J. K.; Nam, J. W.; Lee, S. U.; Kim, J. T.;
Koo, S. M.; Baunemann, A.; Fischer, R. A.; Sung, M. M. Angew. Chem.,
Int. Ed. 2009, 48, 4536−4539. (b) Emslie, D. J. H.; Chadha, P.; Price,
J. S. Coord. Chem. Rev. 2013, 257, 3282−3296. (c) Vidjayacoumar, B.;
Emslie, D. J. H.; Blackwell, J. M.; Clendenning, S. B.; Britten, J. F.
Chem. Mater. 2010, 22, 4854−4866.
(5) (a) Rand, M. J. J. Electrochem. Soc. 1973, 120, 686−693. (b) Xue,
Z. L.; Thridandam, H.; Kaesz, H. D.; Hicks, R. F. Chem. Mater. 1992,
4, 162−166. (c) Hierso, J. C.; Feurer, R.; Kalck, P. Coord. Chem. Rev.
1998, 178, 1811−1834. (d) Thurier, C.; Doppelt, P. Coord. Chem. Rev.
2008, 252, 155−169.
77. (q) Dupuy, C. G.; Beach, D. B.; Hurst, J. E., Jr.; Jasinski, J. M.
Chem. Mater. 1989, 1, 16−18. (r) Hara, K.; Shinozawa, T.; Yoshino, J.;
Kukimoto, H. J. Cryst. Growth 1988, 93, 771−775. (s) Hara, K.;
Kojima, T.; Kukimoto, H. Jpn. J. Appl. Phys., Part 2 1987, 26, L1107−
L1109.
(10) Kruck, T.; Terfloth, C. Chem. Ber. 1993, 126, 1101−1106.
(11) Johnson, A. L.; Willcocks, A. M.; Raithby, P. R.; Warren, M. R.;
Kingsley, A. J.; Odedra, R. Dalton Trans. 2009, 922−924.
(12) Werner, H.; Otto, H.; Ngokhac, T.; Burschka, C. J. Organomet.
Chem. 1984, 262, 123−136.
(13) (a) Cotton, F. A.; Marks, T. J. J. Am. Chem. Soc. 1970, 92, 5114.
(b) Tsuda, T.; Saegusa, T.; Hashimoto, T. J. Am. Chem. Soc. 1972, 94,
658−659.
(14) Ogorodnikova, N. A.; Kravtsov, D. N. Polyhedron 1985, 4, 311−
316.
(15) Kumar, R.; Fronczek, F. R.; Maverick, A. W.; Lai, W. G.; Griffin,
G. L. Chem. Mater. 1992, 4, 577−582.
(16) Tang, J. A.; Ellis, B. D.; Warren, T. H.; Hanna, J. V.; Macdonald,
C. L. B.; Schurko, R. W. J. Am. Chem. Soc. 2007, 129, 13049−13065.
(17) Hanusa, T. P.; Ulibarri, T. A.; Evans, W. J. Acta Crystallogr., Sect.
C: Cryst. Struct. Commun. 1985, 41, 1036−1038.
(18) Beach, D. B.; Kane, W. F.; Legoues, F. K.; Knors, C. J. Mater.
Res. Soc. Symp. Proc. 1990, 181, 73−77.
(19) Tacke, M.; Teuber, R. J. Mol. Struct. 1997, 408, 507−512.
(20) Macomber, D. W.; Rausch, M. D. J. Am. Chem. Soc. 1983, 105,
5325−5329.
(21) Lettko, L.; Rausch, M. D. Organometallics 2000, 19, 4060−4065.
(22) Macomber, D. W.; Hart, W. P.; Rausch, M. D.; Priester, R. D.;
Pittman, C. U. J. Am. Chem. Soc. 1982, 104, 884−886.
(23) Ren, H. P.; Zhao, X.; Xu, S. S.; Song, H. B.; Wang, B. Q. J.
Organomet. Chem. 2006, 691, 4109−4113.
(24) (a) Olbrich, F.; Schmidt, G.; Weiss, E.; Behrens, U. J.
Organomet. Chem. 1993, 456, 299−303. (b) Olbrich, F.; Behrens,
U.; Groger, G.; Weiss, E. J. Organomet. Chem. 1993, 448, C10−C12.
(25) Zybill, C.; Muller, G. Organometallics 1987, 6, 2489−2494.
(26) Turgambaeva, A. E.; Krisyuk, V. V.; Prud’homme, N.; Vahlas, C.
ECS Trans. 2009, 25, 1301−1308.
(6) (a) Dollimore, D. In Handbook of Copper Compounds and
Applications; Richardson, H. W., Ed.; CRC Press: Toronto, 1997; pp
231−264. (b) Lang, H.; Jakob, A.; Milde, B. Organometallics 2012, 31,
7661−7693.
(7) Kodas, T. T.; Hampden-Smith, M. J. The Chemistry of Metal
CVD; VCH: Cambridge, U.K., 1994.
(8) (a) Piper, T. S.; Wilkinson, G. J. Inorg. Nucl. Chem. 1956, 3, 104−
124. (b) Wilkinson, G.; Piper, T. S. J. Inorg. Nucl. Chem. 1956, 2, 32−
37.
(27) Saegusa, T.; Ito, Y.; Tomita, S. J. Am. Chem. Soc. 1971, 93,
5656−5661.
(28) (a) Grafe, A.; Heinen, R.; Klein, F.; Kruck, T.; Scherer, M.;
̈
Schober, M. Appl. Surf. Sci. 1995, 91, 187−191. (b) Blessmann, D.;
Grafe, A.; Heinen, R.; Jansen, F.; Kruck, T.; Terfloth, C. Mater. Sci.
̈
Eng., B 1993, 17, 104−107. (c) Blessmann, D.; Grafe, A.; Heinen, R.;
̈
(9) (a) Prud’hme, N.; Duguet, T.; Samelor, D.; Senocq, F.; Vahlas, C.
Appl. Surf. Sci. 2013, 283, 788−793. (b) Turgambaeva, A. E.;
Prud’homme, N.; Krisyuk, V. V.; Vahlas, C. Chem. Vap. Deposition
2012, 18, 209−214. (c) Senocq, F.; Turgambaeva, A.; Prud’homme,
N.; Patil, U.; Krisyuk, V. V.; Samelor, D.; Gleizes, A.; Vahlas, C. Surf.
Coat. Technol. 2007, 201, 9131−9134. (d) Shirakata, S.; Yudate, S.;
Terasako, T.; Isomura, S. Jpn. J. Appl. Phys., Part 2 1998, 37, L1033−
L1035. (e) Shirakata, S.; Tamura, K.; Isomura, S. Jpn. J. Appl. Phys.,
Part 2 1996, 35, L531−L534. (f) Shirakata, S.; Morita, K.; Isomura, S.
Jpn. J. Appl. Phys., Part 2 1994, 33, L739−L742. (g) Kondoh, E.;
Kawano, Y.; Takeyasu, N.; Ohta, T. J. Electrochem. Soc. 1994, 141,
3494−3499. (h) Chichibu, S.; Sudo, R.; Yoshida, N.; Harada, Y.;
Uchida, M.; Matsumoto, S.; Highuchi, H. Jpn. J. Appl. Phys., Part 2
1994, 33, L286−L289. (i) Honda, T.; Otoma, H.; Hara, K.; Yoshino,
J.; Kukimoto, H. Jpn. J. Appl. Phys., Part 2 1993, 32, L560−L562.
(j) Chichibu, S.; Yoshida, N.; Sudo, R.; Uchida, M.; Harada, Y.;
Matsumoto, S.; Higuchi, H. Proc. Electrochem. Soc. 1993, 93−25, 216−
224. (k) Kumar, R.; Fronczek, F. R.; Maverick, A. W.; Lai, W. G.;
Griffin, G. L. Chem. Mater. 1992, 4, 577−582. (l) Houlding, V. H.;
Maxwell, H., Jr.; Crochiere, S. M.; Farrington, D. L.; Rai, R. S.;
Tartaglia, J. M. Mater. Res. Soc. Symp. Proc. 1992, 260, 119−124.
(m) Chichibu, S.; Yoshida, N.; Higuchi, H.; Matsumoto, S. Jpn. J. Appl.
Phys., Part 2 1992, 31, L1778−L1780. (n) Gross, M. E. J. Electrochem.
Soc. 1991, 138, 2422−2426. (o) Beach, D. B.; LeGoues, F. K.; Hu, C.
K. Chem. Mater. 1990, 2, 216−219. (p) Beach, D. B.; Kane, W. F.;
Legoues, F. K.; Knors, C. J. Mater. Res. Soc. Symp. Proc. 1990, 181, 73−
Jansen, F.; Kruck, T.; Terfloth, C. Mater. Sci. Eng., B 1993, 33, 104−
107. (d) Artaud-Gillet, M. C.; Duchemin, S.; Odedra, R.; Orsal, G.;
Rega, N.; Rushworth, S.; Siebentritt, S. J. Cryst. Growth 2003, 248,
163−168. (e) Hermes, S.; Schroeder, F.; Amirjalayer, S.; Schmid, R.;
Fischer, R. A. J. Mater. Chem. 2006, 16, 2464−2472. (f) Mueller, M.;
Hermes, S.; Kaehler, K.; van den Berg, M. W. E.; Muhler, M.; Fischer,
R. A. Chem. Mater. 2008, 20, 4576−4587. (g) Mueller, M.; Lebedev,
O. I.; Fischer, R. A. J. Mater. Chem. 2008, 18, 5274−5281. (h) Xue, C.;
Papadimitriou, D.; Raptis, Y. S.; Esser, N.; Richter, W.; Siebentritt, S.;
Lux-Steiner, M. C. J. Appl. Phys. 2003, 94, 4341−4347.
(29) Saegusa, T.; Horiguchi, S.; Tsuda, T. Macromolecules 1975, 8,
112−114.
(30) (a) Willcocks, A. M.; Pugh, T.; Hamilton, J. A.; Johnson, A. L.;
Richards, S. P.; Kingsley, A. J. Dalton Trans. 2013, 42, 5554−5565.
(b) Willcocks, A. M.; Robinson, T. P.; Roche, C.; Pugh, T.; Richards,
S. P.; Kingsley, A. J.; Lowe, J. P.; Johnson, A. L. Inorg. Chem. 2012, 51,
246−257.
(31) (a) Bowmaker, G. A.; Hanna, J. V.; Hahn, F. E.; Lipton, A. S.;
Oldham, C. E.; Skelton, B. W.; Smith, M. E.; White, A. H. Dalton
Trans. 2008, 1710−1720. (b) Willcocks, A. M.; Gilbank, A.; Richards,
S. P.; Brayshaw, S. K.; Kingsley, A. J.; Odedra, R.; Johnson, A. L. Inorg.
Chem. 2011, 50, 937−948. (c) Benouazzane, M.; Coco, S.; Espinet, P.;
Barbera, J. Inorg. Chem. 2002, 41, 5754−5759. (d) Johnson, A. L.;
Willcocks, A. M.; Raithby, P. R.; Warren, M. R.; Kingsley, A. J.;
Odedra, R. Dalton Trans. 2009, 922−924. (e) Liu, M.; Reiser, O. Org.
L
DOI: 10.1021/acs.inorgchem.5b00448
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Lett. 2011, 13, 1102−1105. (f) Toth, A.; Floriani, C.; Chiesi-Villa, A.;
Guastini, C. J. Chem. Soc., Dalton Trans. 1988, 1599−1605.
(32) Peng, R.; Li, M.; Li, D. Coord. Chem. Rev. 2010, 254, 1−18.
(33) Putkonen, M.; Niinisto, L. Top. Organomet. Chem. 2005, 9,
̈
125−145.
(34) Willcocks, A. M.; Johnson, A. L.; Raithby, P. R.; Schiffers, S.;
Warren, J. E. Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 2011, 67,
M215−M217.
(35) Senocq, E.; Turgambaeva, A.; Prud’hmme, N.; Patil, U.; Krisyuk,
V. V.; Samelor, D.; Gleizes, A.; Vahlas, C. Surf. Coat. Technol. 2007,
201, 9131−9134.
(36) (a) Rushworth, S. A.; Smith, L. M.; Kingsley, A. J.; Odedra, R.;
Nickson, R.; Hughes, P. Microelectron. Reliab. 2005, 45, 1000−1002.
(b) Knisley, T. J.; Saly, M. J.; Heeg, M. J.; Roberts, J. L.; Winter, C. H.
Organometallics 2011, 30, 5010−5017. (c) Fulem, M.; Ruzick
a, K.;
̊
̌
̌
̌
Ruzick
a, V.; Hulicius, E.; Simece
̌
k, T.; Melichar, K.; Pangrac, J.;
́
̊
̌
̌
Rushworth, S. A.; Smith, L. M. J. Cryst. Growth 2003, 248, 99−107.
(37) van Mol, A. M. B.; Driessen, J. P. A. M.; Linden, J. L.; de Croon,
M. H. J. M.; Spee, C. I. M. A.; Schouten, J. C. Chem. Vap. Deposition
2001, 7, 101−104.
(38) See http://www.airproducts.com/~/media/downloads/c/
cupraselect-cutmvs/data-sheets/en-cutmvs-datasheet.pdf.
(39) Waechtler, T.; Ding, S. F.; Hofmann, L.; Mothes, R.; Xie, Q.;
Oswald, S.; Detavernier, C.; Schulz, S. E.; Qu, X. P.; Lang, H.; Gessner,
T. Microelectron. Eng. 2011, 88, 684−689.
(40) Martensson, P.; Carlsson, J. O. J. Electrochem. Soc. 1998, 145,
2926−2931.
(41) (a) Tsay, J. S.; Mangen, T.; Wandelt, K. Thin Solid Films 2001,
397, 152−156. (b) Holst, B.; Nohlen, M.; Wandelt, K.; Allison, W.
Surf. Sci. 1997, 377, 891−894.
(42) Tanabiki, M.; Tsuchiya, K.; Kumanomido, Y.; Matsubara, K.;
Motoyama, Y.; Nagashima, H. Organometallics 2004, 23, 3976−3981.
(43) Panda, T. K.; Gamer, M. T.; Roesky, P. W. Organometallics
2003, 22, 877−878.
(44) Sheldrick, G. M. SHELX-86, Computer Program for Crystal
Structure Determination; University of Gottingen: Gottingen, Germany,
̈
̈
1986.
(45) (a) Sheldrick, G. M. SHELX-97, Computer Program for Crystal
Structure Refinement; Univerity of Gottingen: Gottingen, Germany,
̈
̈
1997. (b) Sheldrick, G. M. Acta Crystallogr., Sect. A 2008, 64, 112−122.
M
DOI: 10.1021/acs.inorgchem.5b00448
Inorg. Chem. XXXX, XXX, XXX−XXX