Ligand influence on the formation of P/Se semiconductor materials from metal-organic complexes

Article abstract of DOI:10.1039/b802012d

The complexes [Ni{(SePⁱPr₂)₂N} ₂] (1), [Ni(Se₂PⁱPr₂)₂] (2), and [Co(Se₂PⁱPr₂)₂] (4) were synthesised and the X-ray single c

Full text of DOI:10.1039/b802012d

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www.rsc.org/dalton | Dalton Transactions
Ligand influence on the formation of P/Se semiconductor materials from
metal–organic complexes†‡
a
a
a
a
a
Arunkumar Panneerselvam, Chinh Q. Nguyen, John Waters, Mohammad A. Malik, Paul O’Brien,*
b
b
James Raftery and Madeleine Helliwell
Received 6th February 2008, Accepted 3rd April 2008
First published as an Advance Article on the web 23rd July 2008
DOI: 10.1039/b802012d
i
i
i
The complexes [Ni{(SeP Pr
2
)
2
N}
2
] (1), [Ni(Se
2
P Pr
2
)
2
] (2), and [Co(Se
2
P Pr ) ] (4) were synthesised and
2
2
the X-ray single crystal structures of (1) and (2) were determined. Thin films of nickel selenide, cobalt
selenide and cobalt phosphide have been deposited by the chemical vapour deposition method using
i
imidodiselenophosphinato-nickel(II) (1), -cobalt(II) [Co{(SeP Pr
2
)
2
N}
2
] (3), diselenophosphinato-
] (5), and -cobalt(III)
nickel(II) (2), -cobalt(II) (4) and diselenocarbamato-nickel(II) [Ni(Se
Co(Se CNEt ] (6) precursors.
2
CNEt
)
2 2
[
2
)
2 3
Introduction
2,4-pentanedionato) which can form neutral complexes of the type
22–27
[
M{(EPR
2
)
2
N}
2
].
Imidodichalcogenidophosphinato-, dichalcogenidophosphinato-
Recently we have synthesised a series of diselenophosphinato
and dichalcogenidocarbamato-metal complexes; [M{(EPR
2
) -
2
metal complexes as single-source precursors for the deposition
i
N}
2
], [M(E
2
PR
2
)
2
] and [M(E
2
CNR
2
)
2
], (R = Pr, Ph and E =
17,18
of metal selenide thin films.
The original method for the
S, Se) and (M = metal atom) have been used as single-
source precursors for the deposition of metal chalcogenide
thin films by chemical vapour deposition (CVD). Dichalco-
genidocarbamato complexes have been studied extensively for
the deposition of thin films by metal–organic (MO)CVD
preparation of dichalcogenidophosphinato complexes was based
28–30
on reactions between NaHE (E = S, Se) and R
2
P(E)Cl.
This
method worked for dithio and thioseleno derivatives but did not
give reproducible results for diseleno derivatives. We devised a
facile route for the preparation of diselenophosphinate ligands in
1–12
and aerosol-assisted (AA)-MOCVD,
whereas the use of
or diselenophosphinato-
complexes for the deposition of thin films is more
recent. It has been demonstrated that selenocarbamates such
−
the form of (R
HNEt )(R PSe
this method also produced the thioselenophosphinate ligands
2
PSe
2
) anions crystallised as alkylammonium salts
13–16
imidodichalcogenidophosphinato-
i
t
17,18
(
3
2
2
) (R = Pr, Bu, Ph).
With a small modification,
17,18
metal
+
−
i
[
(HNEt
3
) (R
2
PSSe) ] (R = Pr, Ph) with high yield and purity.
ꢀ
19
as [M(Se
2
CNRR )
2
]
(where M = Cd, Zn and R = hexyl,
−
The anions (R
and readily form complexes with several metals.
2
PE
2
) (E = S, Se) act as bidentate chelating ligands
ꢀ
R = methyl) are excellent precursors for the synthesis of Group
18
1
2 selenides but the synthesis of the diselenocarbamato ligand
The imidodichalcogenidophosphinato, dichalcogenidophos-
phinato and dichalcogenidocarbamato complexes have four or
six-membered ring structures. Several studies have shown that
the cleavage of the P–E bond in imidodichalcogenidophosphinato
involves the use of toxic and noxious carbon diselenide. The
imidodiselenophosphinato ligand, was prepared by the insertion
of elemental selenium into the P–N bond of R
20
2
PNHPR .
2
ꢀ
ꢀ
Imidodiphosphinic acid derivatives R
CH , C
; E = O, S) were first prepared by Schmidpeter et al.
The synthetic process was improved by Woollins and co-workers
2
P(E)NH(E)PR
2
(R, R =
complexes at an appropriate temperature leads to the deposition
21
H
5
15,16,31–34
3
6
of metal chalcogenide materials.
However our studies have
shown that in some cases, the products can be either the metal
chalcogenides or phosphides depending upon the nature of the
ꢀ
i
t
to make a wide range of derivatives with R, R = Et, Pr, Bu,
OEt, OPh and E = S, Se. A typical synthesis involves two steps, a
ligand.
simple condensation reaction of R
2
PCl with NH(SiMe
3
)
2
to give
i
Herein the synthesis and characterisation of [Ni{(SeP Pr
2
)
2
N}
2
]
R
2
PNHPR
2
followed by oxidation with O, S or Se. On deproto-
i
i
(
1), [Ni(Se
2
P Pr
2
)
2
] (2) and [Co(Se
2
P Pr ) ] (4) complexes and
2
2
−
nation of the amine, the molecule [R
a bidentate chelating ligand analogous to acetylacetonate (acac,
2
P(E)N(E)PR
2
] behaves as
X-ray single crystal structures of (1) and (2) are reported.
i
These complexes and [Co{(SeP Pr
2
)
2
N}
2
] (3), [Ni(Se
2
CNEt ) ]
2
2
(
5) and [Co(Se
2
CNEt ) ] (6) have been used as single-source
2
3
precursors to grow metal selenide or phosphide films by AA-
MOCVD. A comparative study on the deposition behaviour
of the imidodiselenophosphinato-, diselenophosphinato- and
diselenocarbamato-nickel and -cobalt complexes is presented.
a
The School of Chemistry and The School of Materials, The Uni-
versity of Manchester, Oxford Road, Manchester, UK M13 9PL.
E-mail: paul.obrien@manchester.ac.uk, azad.malik@manchester.ac.uk;
Fax: +44 (0)161 275 4598; Tel: +44 (0)161 275 4652
b
The School of Chemistry, The University of Manchester, Oxford Road,
Results and discussions
Manchester, UK M13 9PL
†
2
Based on the presentation given at Dalton Discussion No. 11, 23–25 June
008, University of California, Berkeley, USA.
CCDC reference numbers 675796, 675797 and 676882. For crystallo-
i
i
The complexes [Ni{(SeP Pr
2
)
2
N}
2
]
(1), [Ni(Se
2 2
)
2
P Pr
2
)
2
] (2),
i
35
i
[
Co{(SeP Pr
2
)
2
N}
2
]
(3) and [Co(Se
2
P Pr
] (4) were prepared by
‡
graphic data in CIF or other electronic format see DOI: 10.1039/b802012d
direct exchange reactions between the ligands and the metal salts
This journal is © The Royal Society of Chemistry 2008
Dalton Trans., 2008, 4499–4506 | 4499

in methanol (eqn (1) and (2)). All of these complexes are crystalline
solids and are soluble in common organic solvents. They are stable
at room temperature in air over several months.
i
i
2
[ Pr P(Se)NH(Se)P Pr ] + MCl ⋅6H O + 2NaOMe
2
2
2
2
MeOH
i
(1)
⎯
⎯⎯→[M{(SeP Pr ) N} ] + 2NaCl
2
2
2
for (1) and (3)
i
2
[( Pr PSe )(NHEt )] + MCl ⋅6H O
2
2
3
2
2
M=Ni(II),Co(II)
(
2)
MeOH
i
⎯
⎯⎯→[M(Se P Pr ) ] + 2(HNEt )Cl
2
2
2
3
for (2) and (4)
i
X-Ray single crystal diffraction study of [Ni{(SeP Pr
2
)
2
N}
2
] (1)
i
[
Ni{(SeP Pr
2
)
2
N}
2
] was crystallised from solution in THF by
evaporating at room temperature. The deep red solution gave two
types of crystals; dark red and green. This behaviour is consistent
with the well known Lifschitz salts.
36–38
Repeated crystallisations
of this complex from other solvents such as acetonitrile or
toluene produced similar results, despite the variations in solvent
◦
polarity. Crystallisation at lower temperature (∼ 4 C) leads to
a predominance of green crystals, whilst green crystals were the
sole product of crystallisation from a concentrated solution in
◦
THF, cooled to −18 C. It was speculated that crystallisation at
i
Fig. 1 X-Ray crystal structure of [Ni{(Se
2
P Pr
2
)
2
N}
2
], (a) tetrahedral and
higher temperatures might produce red crystals alone; however
repeated attempts to obtain crystals at temperatures significantly
above room temperature proved unsuccessful.
(
b) square planar. In the square planar structure, Ni is on a two-fold axis
and it is this two-fold axis acting on the ligand that generates the symmetry
related ligand to form the chemical unit.
Crystallographic analysis determined that the compound is
present in a tetrahedral form in the red crystals (Fig. 1(a)) and a
square planar form in the green crystals (Fig. 1(b)). X-Ray single
crystal diffraction studies on the compound in the square planar
form indicated the presence of a molecule of water with partial
occupancy in the crystal lattice and within a plausible hydrogen
or from the NiCl
summarised in Table 1 and crystallographic data are presented in
Table 2.
Several compounds, of the type [M{(EPR
Pd or Pt; E = S or Se; R = alkyl or Ph), have been reported
previously with similar structures. The literature provides
2
·6H
2
O. Selected bond distances and angles are
2
)
2
N}
2
] (M = Ni,
23,39–43
˚
bonding contact (2.70 A) of N1. The water molecule may have
come either from the undistilled solvent used for recrystallisation
examples of compounds which adopt either square planar or
◦
i
i
Table 1 Selected bond lengths ( A˚ ) and bond angles ( ) for [Ni{(SeP Pr
)
N}
] and [Ni(Se
P Pr
)
]
2
2
2
2
2
2
i
i
[
Ni{(SeP Pr
2
)
2
N}
2
]
2 2 2
[Ni(Se P Pr ) ]
Tetrahedral
Square planar
Square planar
Ni(1)–Se(1)
Ni(1)–Se(2)
Ni(1)–Se(3)
Ni(1)–Se(4)
N(1)–P(1)
N(1)–P(2)
N(2)–P(3)
N(2)–P(4)
P(1)–Se(1)
P(2)–Se(2)
P(3)–Se(3)
P(4)–Se(4)
2.400(1)
2.406(1)
2.405(1)
2.403(1)
1.593(4)
1.597(4)
1.595(4)
1.602(4)
2.190(1)
2.185(1)
2.183(1)
2.185(1)
2.356(1)
2.348(1)
2.348(1)
Se(1)–P(1)
2.170(6)
2.359(3)
2.173(6)
2.357(3)
2.357(3)
2.359(3)
Se(1)–Ni(1)
Se(2)–P(1)
Se(2)–Ni(1)
Ni(1)–Se(2A)
Ni(1)–Se(1A)
a
a
2.356(1)
1.605(3)
1.605(3)
1.605(3)
1.605(3)
2.202(1)
2.188(1)
a
2.202(1)
2.188(1)
P(1)–Se(1)–Ni(1)
P(1)–Se(2)–Ni(1)
84.82(1)
84.83(1)
180
90.26(9)a
89.74(9)a
89.74(9)
90.26(9)
180
a
Se(2)–Ni(1)–Se(2A)
Se(2)–Ni(1)–Se(1A)
Se(2A)–Ni(1)–Se(1A)
Se(2)–Ni(1)–Se(1)
Se(2A)–Ni(1)–Se(1)
Se(1A)–Ni(1)–Se(1)
Se(1A)–Ni(1)–Se(1)
Se(1)–Ni(1)–Se(2)
Se(1)–Ni(1)–Se(3)
Se(1)–Ni(1)–Se(4)
Se(2)–Ni(1)–Se(4)
N–P–Se
110.54(3)
107.48(3)
106.57(3)
108.30(3)
117.76(2)–118.62(2)
105.97(4)–107.39(4)
101.14(2)
78.88(2)
178.19(3)
78.88(2)
116.18(1)–116.50(1)
108.15(3)–113.47(3)
a
P–Se–Ni
99.99(2)
a
Symmetry generated.
4
500 | Dalton Trans., 2008, 4499–4506
This journal is © The Royal Society of Chemistry 2008

tetrahedral geometry in the solid state and compounds such
], show interconversion in solution between
tetrahedral and square planar forms. The variation in preferred
structure in these cases appears to be based solely on the steric
effects relating to the choice and arrangement of alkyl substituents,
nickel selenide. For precursor (3) the observed residue (5%) is
less than the calculated residue (16%) expected for CoSe or
CoP (10%). XRD analysis of the residue showed the presence
of CoSe and CoP with some unidentified impurities which
as [Ni{(SPMe
2
)
2
N}
2
2
42
2
2
2
may be the reason for the difference between the expected and
the observed values. The nickel selenophosphinato precursor
e.g. [Ni{(SPPh
to the mutual repulsion of the four bulky phenyl groups, whilst
Ni{(SPMe )(SPPh )N} ] is square planar with the bulky phenyl
groups arranged cis to one another. However, [Ni{(SeP Pr
2
)
2
N}
2
] is tetrahedral in the solid state probably due
◦
(2) showed weight loss between 235–298 C with the observed
[
2
2
2
residue (24%) matching fairly with the calculated residue of
42
i
2
)
2
N}
2
]
(22.5%) for NiSe. The cobalt selenophosphinato precursor (4)
◦
seems to be unique in its class in displaying both square planar and
tetrahedral configurations in the solid state. These observations
suggests that the steric effects of the isopropyl groups do not confer
significantly greater stability to either form, thus both are possible
and the assumed geometry is influenced by conditions such as
temperature. Both the tetrahedral and square planar forms display
similar patterns of bond lengths and angles to their literature
showed a single step decomposition between 180–312 C, with
the residue matching for CoSe
2
. The nickel (5) and cobalt (6)
selenocarbamato precursors showed weight loss between 189–
◦
◦
305 C and 271–396 C respectively. The observed residue for
both precursors corresponds to the expected residues for NiSe
and CoSe respectively. XRD analysis of the TGA residues of all
compounds other than (3) were as expected.
2
2
23,39–43
analogues.
i
Deposition of nickel selenide films from [Ni{(SeP Pr
2
)
2
N}
2
] (1) by
i
X- Ray crystal structure of [Ni(Se
2
P Pr
2
)
2
] (2)
AA-MOCVD
The diselenophosphinato-nickel complex has a square planar
coordination (Fig. 2). The Ni atoms are surrounded by a distorted
i
The as-obtained red crystals of the [Ni{(SeP Pr
2
)
2
N}
2
] complex
(
tetrahedral form) at room temperature was used for AA-MOCVD
◦
square of four Se atoms belonging to two bidentate chelating
studies. Deposition was carried out at temperatures 400–500 C
producing uniform black films. XRD studies show in each case,
monophasic hexagonal Ni0.85Se (JCPDS 18-0888) with preferred
orientation in the (101) direction. The highest peak intensity, and
thus the optimum crystallinity, was observed in the film deposited
i
ligands Pr
9
2
PSe . The bite angles at the Ni atoms are close to
2
◦
0 . There is a slight difference in the Ni–Se bond distances which
˚
vary from 2.357(3) to 2.359(3) A.
◦
at 450 C and the peak intensity was seen to diminish progressively
with either higher or lower temperatures. SEM studies revealed
that the films comprise mixtures of fibrous wires and rods. The
morphology of the films change from short, thin wires to thicker
and longer wires from lower temperatures (Fig. 3(a),(b)) to higher
temperatures (Fig. 3(c),(d)). EDX analysis shows the films contain
Ni :Se in a 1 : 1 ratio.
i
2 2 2
Fig. 2 X-Ray crystal structure of [Ni(Se P Pr ) ]. The square planar
structure is generated from the asymmetric unit by the centre of symmetry
upon which the Ni resides.
Differential scanning calorimetry
i
[
Ni{(SeP Pr
2
)
2
N}
2
] (1) was studied using differential scanning
◦
calorimetry (DSC) and showed an endotherm at 65–120 C,
below the melting point (190–192 C) of the complex with no
◦
accompanying mass loss. The energy associated with the process is
very small, it can be assumed to be related to a structural change.
Upon retrieval from the DSC apparatus, the sample was found
to be semi-plastic in nature and darker in colour, however this
state was unstable at room temperature and within minutes the
compound reverted to the dark red crystalline form.
Fig. 3 SEM images of nickel selenide films deposited on glass from
i
◦
◦
◦
◦
[
Ni{(SeP Pr
2
)
2
N}
2
] at (a) 425 C, (b) 450 C, (c) 475 C and (d) 500 C.
Thermogravimetric analysis
i
Deposition of nickel selenide films from [Ni(Se
AA-MOCVD
2
P Pr
2
)
2
] (2) by
Thermogravimetric analysis (TGA) of the nickel and cobalt
diselenoimidophosphinato precursors (1) and (3) revealed a single
◦
i
step decomposition with a weight loss between 261–371 C and
Deposition from [Ni(Se
2
P Pr
2
)
2
] gave thick black films at 350, 400
and 450 C. XRD (Fig. 4(a)) results revealed that all films were
composed of hexagonal Ni0.85Se (JCPDS 18-0888) with preferred
◦
◦
3
22–385 C respectively. The observed final residue (17%) for
(
1) is in fair agreement with the calculated residue (16%) for
This journal is © The Royal Society of Chemistry 2008
Dalton Trans., 2008, 4499–4506 | 4501

◦
Fig. 4 (a) XRD pattern of nickel selenide film deposited at 400 C.
*”—NiSe peak. SEM images of nickel selenide films deposited on glass
from [Ni(Se
“
2
Fig. 5 XRD patterns of (a) cobalt selenide (CoSe
and (b) cobalt phosphide (CoP
*”—Co Se Se “ꢁ”—cubic CoSe
“ꢀ”—Co
“ ”—CoSe, “●”—CoP peaks.
2
, orthorhombic)
) films deposited on glass at 525 C.
i
◦
◦
2
P Pr
2
)
2
] at (b) 400 C and (c) 350 C.
◦
2
“
9
8
,
3
4
,
2
, “#”—Co0.85Se and
growth along the (101) plane. Minor peaks for cubic NiSe
2
(JCPDS
2
◦
1
1-0552) were observed at 2h values of 30.23 and 36.94 . However,
SEM images revealed that the films were composed of flakes and
wedges at all growth temperatures (Fig. 6(a)–(d)). EDX analysis
of the wedge-like features showed that they were composed of
the morphologies analysed by SEM varied from a spherical
◦
◦
particles connected by wires at 400 C (Fig. 4(b)) to a mixture
of cubic crystallites and flakes at 350 C (Fig. 4(c)). EDX analysis
34–36% cobalt and 64–66% selenium with no major phosphorus
shows that the films were selenium rich (61%) with 36% nickel and
contamination. The flakes consist of 39–42% cobalt with 55–57%
selenium and 3–4% phosphorus.
3
% phosphorus.
Growth of cobalt selenide and cobalt phosphide films from
i
[
Co{(SeP Pr
2
)
2
N}
2
] (3) by AA-MOCVD
◦
Deposition of films was carried out at temperatures 375–525 C
◦
from (3) by AA-MOCVD. No deposition occured at 375 C and
◦
a very thin film was deposited at 400 C which could not be
characterised by XRD. Uniform black and partially adherent
◦
films were deposited at 425, 450, 475 and 525 C. XRD of the
◦
as-deposited films at 425 and 450 C showed cobalt selenide films.
◦
Surprisingly, the XRD of the as-grown films at 525 and 475 C
revealed the deposition of cobalt selenide and cobalt phosphide
films on separate glass substrates depending upon their position in
the AA-MOCVD reactor. Cobalt selenide films were deposited on
the substrates placed at the beginning of the deposition area of the
reactor, which is believed to be at lower temperature than chosen
for the film deposition. Cobalt phosphide films were deposited
on substrates placed at the centre of the deposition area where
the temperature is expected to be highest i.e., at the chosen
temperature for film deposition. XRD of the as-deposited cobalt
selenide films at all temperatures indicated that they are primarily
Fig. 6 SEM images of cobalt selenide films deposited on glass from
i
◦
◦
◦
[
Co{(SeP Pr
2
)
2
N}
2
] at (a) 525 C, (b) 475 C, (c) 450 and (d) 425 C.
Cobalt phosphide films were deposited on glass substrates
◦
placed at the hottest part of the reactor at 525 and 475 C. XRD
◦
patterns (Fig. 5(b)) of the films grown at 525 C corresponds
composed of orthorhombic CoSe
Co Se (JCPDS 15–0463), but the predominant growth is along
the (111) plane which is the 100% peak of CoSe (Fig. 5(a)).
Minor peaks corresponding to cubic Co Se (JCPDS 09-0233),
cubic CoSe (JCPDS 09-0234,“ꢀ”); hexagonal Co0.85Se (JCPDS
4-0333) and CoSe (JCPDS 15-0464, “ ”-unindexed) phases
were also observed.
2
(JCPDS 10-0408) and cubic
to monoclinic CoP
475 C showed orthorhombic CoP (JCPDS 29-0497) phase. The
morphology of the as-deposited cobalt phosphide films varied
2
(JCPDS 77-0263) whereas films deposited at
◦
3
4
2
◦
◦
◦
9
8
from irregular plates at 525 C to grassy features at 475
C
2
(Fig. 7(a),(b)). EDX of films deposited at both 525 and 475 C
are cobalt deficient and phosphorus rich with traces of selenium
44
2
◦
(∼ 4%). At 525 C, the films were composed of 29% cobalt and
4
502 | Dalton Trans., 2008, 4499–4506
This journal is © The Royal Society of Chemistry 2008

Fig. 9 SEM images of (a) nickel selenide films and (b) cobalt selenide
Fig. 7 SEM images of cobalt phosphide films deposited on glass from
films deposited on glass from [Ni(Se
2
CNEt
2
)
2
] and [Co(Se
2
CNEt
2
)
3
] at
i
◦
◦
[
Co{(SeP Pr
2
)
2
N}
2
] at (a) 525 C and (b) 475 C.
◦
4
50 C.
◦
7
1% phosphorus whereas at 475 C, the films contain 40% cobalt
composition suggested by EDX matched with the expected Co : Se
ratio of 1 : 2.
and 60% phosphorus.
i
Deposition from [Co(Se
2
P Pr
2
)
2
] (4) by AA-MOCVD
] (4) by AA-MOCVD gave thick
Deposition behaviour of imidoselenophosphinato-,
selenophosphinato- and selenocarbamato-metal complexes
i
Deposition from [Co(Se
2
P Pr
2 2
)
◦
black films at 450 C. No deposition was obtained at lower
Nickel selenide films deposited from imidoselenophosphinato,
selenophosphinato and selenocarbamato precursors showed in-
teresting features in their morphology, as studied by SEM
under similar deposition conditions (400 C). Fibrous mate-
rial was deposited from the imidoselenophosphinato precursor
temperatures. The films consist of a mixture of cubic Co
9
Se
8
(
JCPDS 09-0233) and orthorhombic CoP (JCPDS 29-0497)
phases as revealed by XRD analysis (Fig. 8(a)). The morphology
appears to be irregular grains of varying sizes (Fig. 8(b)). EDX
analysis shows that the film is composed of Co (24%), P (33%), Se
◦
(Fig. 10(a)) whereas spherical particles connected by wires were
(
43%).
deposited from selenophosphinato precursor (Fig. 10(b)) and
intertwined wires were deposited from the selenocarbamato
i
i
precursor (Fig. 10(c)). [Ni{(SeP Pr
2
)
2
N}
2
] and [Ni(Se
2
P Pr ) ]
2
2
deposited hexagonal Ni0.85Se films with preferred orientation along
the (101) direction whereas [Ni(Se
phase.
2
CNEt
2
)
2
] gave a cubic NiSe
2
Fig. 8 XRD pattern (a) and SEM image (b) of a mixture of cobalt selenide
i
and cobalt phosphide films deposited on glass from [Co(Se
2
P Pr
2
)
2
] at
◦
4
50 C. “*” CoP peaks.
Fig. 10 SEM images of nickel selenide films deposited from (a)
Deposition of nickel and cobalt selenide films from
selenocarbamato precursors by AA-MOCVD
i
i
[
Ni{(SeP Pr
2
)
2
N}
2
], (b) [Ni(Se
2
P Pr
2
)
2
] and (c) [Ni(Se
2
CNEt
2
)
2
] deposited
◦
at 400 C.
Preliminary AA-MOCVD studies from the selenocarbamato pre-
cursors deposited the corresponding metal selenide films. Nickel
◦
The morphology of the cobalt selenide films deposited at 450 C
from the imidoselenophosphinato precursor showed a mixture of
flakes and stacked rods (Fig. 11(a)). Irregular shaped particles
composed of a mixture of cobalt selenide and cobalt phosphide
were formed from the selenophosphinato precursor (Fig. 11(b)),
selenide films were deposited from [Ni(Se
2
CNEt ) ] (5) at 400 and
2
2
◦
450 C. SEM revealed the morphology (Fig. 9(a)) as irregular
◦
plates with size ranges from 1 to 2 lm for films deposited at 450 C,
◦
whereas at 400 C intertwined wires were observed (Fig. 10(c)).
EDX indicated nickel deficient films with a 1 : 2 ratio of nickel to
whereas the selenocarbamato precursor yielded bundled fibres of
i
selenium, the cubic NiSe
2
phase (JCPDS 11-0552) being confirmed
cobalt selenide (Fig. 11(c)). [Co{(SeP Pr
2
)
2
N}
2
] deposited cobalt
◦
◦
by XRD measurements. Cobalt selenide films were deposited from
selenide films at lower temperatures of 425 C and 450 C. Thin
films of cobalt phosphide and cobalt selenide were deposited at
◦
[
Co(Se
2
CNEt
2
)
3
] (6) at 450 C. XRD patterns of the films matched
◦
◦
with the cubic CoSe
2
(JCPDS 09-0234) and the morphology of
higher temperatures of 475 C and 525 C, depending upon the
position of the substrate in the reactor. XRD of the as-deposited
the film appears to be bundled fibres (Fig. 9(b). The elemental
This journal is © The Royal Society of Chemistry 2008
Dalton Trans., 2008, 4499–4506 | 4503

+
i
(
[
3.9 g, 93%). MS (EI/CI), m/z = [M ] 871, [Ni(SeP Pr
(SeP Pr N] 406; mp 190–192 C. Elemental analysis (Found:
C, 33.0; H, 6.2; N, 3.0; P, 13.8%, Calc. for C24 Se Ni: C,
3.1; H, 6.5; N, 3.2; P, 14.2%). The red powder on recrystallisation
2
)
2
N] 465,
i
◦
)
2 2
H
56
N
2
4
P
4
3
◦
at low temperature (4 C) predominantly produced 80% green
crystals with 20% red crystals.
i
[
Ni(Se
2
P Pr
2
)
2
] (2). In a typical experiment, a solution of
nickel(II) chloride hexahydrate (1.19 g, 5 mmol) in 5 ml MeOH
i
was added drop-wise to a solution of (HNEt
3
)( Pr
2
PSe ) (3.77 g,
2
1
1
0 mmol) in 100 ml of MeOH. The mixture was stirred for
h at room temperature under atmospheric pressure forming a
green precipitate, which was filtered off, washed with MeOH and
recrystallised in dichloromethane (35 ml) to obtain green crystals,
+
i
yield (2.58 g, 85%). MS (EI/CI), m/z = [M ] 608, [(Se
2
P Pr )] 275;
2
◦
mp 210–212 C. Elemental analysis (Found: C, 23.8; H, 4.5; P,
10.6; Ni, 9.4. Calc. for C H P Se Ni: C, 23.7; H, 4.6; P, 10.2; Ni,
9.6%); H NMR, d(300 MHz; CDCl ; Me Si) 1.43 (dd, 24H, J
Fig. 11 SEM images of cobalt selenide films deposited from
1
2
28
2
4
i
i
1
3
(
a) [Co{(SeP Pr
2
)
2
N}
2
], (b) [Co(Se
2
P Pr
2
)
2
] and (c) [Co(Se
2
CNEt
2
)
3
] de-
=
3
4
HH
◦
posited at 450 C.
3
3
6
.7 Hz, JPh = 19.9 Hz, 4 × CH(CH
3
)
2
), 2.07 (dsep, 4H, JHH
=
3
31
◦
6.7 Hz, JPh = 5.3 Hz, 4× CH(CH
3
)
2
). P NMR, d(162 MHz;
cobalt selenide films at 525–425 C showed the phase composition
as orthorhombic CoSe and cubic Co Se with the preferred ori-
entation along the (111) plane, whereas XRD of cobalt phosphide
1
CDCl
3
) 80.93 ( JPSe = 4.55 Hz).
2
3
4
i
[Co(Se P Pr ) ] (4). A similar procedure to (2) was carried out
2
2 2
◦
◦
films grown at 525 C and 475 C correspond to monoclinic CoP
2
using cobalt(II) chloride hexahydrate (1.19 g, 5 mmol) to obtain
a green powder. Recrystallisation from dichloromethane (40 ml)
i
and orthorhombic CoP. [Co(Se
and CoP films at 450 C irrespective of the position of the
substrate whereas [Co(Se
2
P Pr
2
)
2
] produced a mixture of
◦
+
Co
9
Se
8
gave green crystals. Yield (2.65 g, 87%). MS (EI/CI), m/z = [M ]
i
◦
2
CNEt
2
)
3
] deposited only CoSe
2
films at
609, [(Se P Pr )] 275; mp 121–123 C. Elemental analysis (Found:
2
2
◦
4
50 C.
C, 22.4; H, 4.4; P, 10.3; Co, 8.8. Calc. for C H P Se Co: C, 23.6;
1
2
28
2
4
H, 4.4; P, 10.2; Co, 9.7%).
Experimental
X-Ray crystallography
All reagents were purchased from Sigma-Aldrich chemical com-
pany and used as received. Solvents were distilled prior to use. H
NMR studies were carried out using a Bruker AC300 FTNMR
instrument. Mass spectra were recorded on a Micromass Trio
1
Single-crystal X-ray diffraction data for the compounds were
collected using graphite monochromated Mo-Ka radiation (k =
˚
0.71073 A) on a Bruker APEX diffractometer. The structure was
solved by direct methods and refined by full-matrix least squares
2
000 instrument. Infrared spectra were recorded on a Specac
2
47
−
1
on F . All non-H atoms were refined anisotropically. H atoms
were included in calculated positions, assigned isotropic thermal
parameters and allowed to ride on their parent carbon atoms. All
single reflectance ATR instrument (4000–400 cm , resolution
4
−
1
cm ). Elemental analysis was performed by the University
of Manchester micro-analytical laboratory. TGA measurements
were carried out by a Seiko SSC/S200 model under a heating
48
calculations were carried out using the SHELXTL package.
◦
−1
CCDC reference numbers: 676882 (1a), 675796 (1b) and
75797 (2).
rate of 10 C min under nitrogen. Melting point was recorded
on a Stuart melting point apparatus and uncorrected. DSC
measurements were performed on a Rheometric Scientific STA
6
Deposition of films by AA-MOCVD
1
500H instrument.
In a typical deposition, 0.20 g of the precursor was dissolved
in 20 ml toluene in a two-necked 100 ml round-bottom flask
with a gas inlet that allowed the carrier gas (argon) to pass
into the solution to aid the transport of the aerosol. This flask
was connected to the reactor tube by a piece of reinforced
tubing. The argon flow rate of 160 sccm was used for deposition
studies which was controlled by a Platon flow gauge. Seven glass
substrates (approx. 1 × 3 cm) were placed inside the reactor tube,
which is placed in a Carbolite furnace. The precursor solution
in a round-bottom flask was kept in a water bath above the
piezoelectric modulator of a PIFCO ultrasonic humidifier (Model
No. 1077). The aerosol droplets of the precursor thus generated
were transferred into the hot-wall zone of the reactor by carrier
gas. Both the solvent and the precursor were evaporated and
the precursor vapour reached the heated substrate surface where
thermally induced reactions and film deposition took place.
Synthesis
The ligands [ Pr
i
i
22
i
45
2
P(Se)NHP(Se) Pr
2
]
and [( Pr
2
PSe
2
) (HNEt )]
3
i
35
46a,b
and the complexes [Co{(SeP Pr
2
)
2
N}
2
], [Ni(Se
2
CNEt
2
)
2
]
and
46c
[
Co(Se
2
CNEt
2
)
3
]
were prepared according to the published
procedures.
i
[
Ni{(SeP Pr
2
)
2
N}
2
] (1). In a typical experiment, sodium
methoxide (0.53 g, 10 mmol) was added to a stirred solution of
SeP Pr ) NH (4.0 g, 10 mmol) in anhydrous methanol (100 cm ).
i
3
(
2
2
The resulting pink solution was stirred at room temperature for
0 min. Nickel(II) chloride hexahydrate (1.19 g, 5 mmol) was added
1
and the reaction stirred at room temperature for 2 h. The resulting
suspension was filtered and the recovered solid washed with
methanol (100 cm ) before drying under vacuum. The crude prod-
3
uct was recrystallised from THF (40 ml) to give a red powder, yield
4
504 | Dalton Trans., 2008, 4499–4506
This journal is © The Royal Society of Chemistry 2008

Table 2 Selected crystal data and refinement parameters for (1) and (2)
i
i
[
Ni{(SeP Pr
2
)
2
N}
2
]
[Ni(Se
2 2 2
P Pr ) ]
Square planar
Tetrahedral
Square planar
Empirical formula
Formula weight
Temperature/K
Crystal system
C
24
H
56.63NiN
2
O
0.31
P
4
Se
4
C
871.14
100(2)
Triclinic
P1
9.289(1)
12.913(2)
16.302(2)
79.058(2)
78.221(2)
69.895(2)
1782.3(4)
2
24
H
56NiN
2
P
4
Se
4
12 2 4
C H28NiP Se
608.83
100(2)
Monoclinic
P2(1)/n
9.287(1)
10.935(1)
10.136(1)
90
97.904(2)
90
1019.5(2)
2
1.983
8.236
876.82
100(2)
Monoclinic
C2/c
13.254(4)
21.292(4)
13.585(3)
90
112.961(5)
90
3530.2(1)
4
¯
Space group
a/A˚
b/A˚
c/A˚
◦
a/
b/
◦
◦
c /
V/A˚
Z
3
−
3
Density (calculated)/Mg m
Absorption coefficient/mm
F(000)
Crystal size/mm
h range for data collection/
1.650
4.874
1765
1.623
4.285
876
−
1
588
0.20 × 0.20 × 0.03
0.20 × 0.20 × 0.03
0.55 × 0.55 × 0.50
◦
1.91 to 28.35
1.29 to 27.10
2.75 to 26.37
Limiting indices
−13 ≤ h ≤ 17, −28 ≤ k ≤ 21,
−11 ≤ h ≤ 11, −16 ≤ k ≤ 15,
−20 ≤ l ≤ 20
−11 ≤ h ≤ 9, 13 ≤ k ≤ 13,
−10 ≤ l ≤ 12
−
17 ≤ l ≤ 16
Reflections collected
Unique reflections
Completeness to h (%)
Max. and min. transmission
Refinement method
Data/restraints/parameters
11098
14856
5643
4153 [R(int) = 0.0444]
7664 [R(int) = 0.0415]
2067 [R(int) = 0.0216]
◦
◦
◦
(h = 28.35 ) 94.1
(h = 27.10 ) 97.4
(h = 26.37 ) 99.4
0.8676 and 0.4424
Full-matrix least-squares on F
4153/0/170
0.8688 and 0.4453
Full-matrix least-squares on F
7664/0/332
0.1045 and 0.0929
Full-matrix least-squares on F
2067/0/92
2
2
2
2
Goodness-of-fit on F
0.983
1.074
1.074
Final R indices [I > 2r(I)]
R indices (all data)
Largest diff. peak and hole/e A˚
R1 = 0.0356, wR2 = 0.0680
R1 = 0.0577, wR2 = 0.0747
0.667 and −0.469
R1 = 0.0475, wR2 = 0.0995
R1 = 0.0637, wR2 = 0.1051
0.959 and −0.576
R1 = 0.0198, wR2 = 0.0470
R1 = 0.0224, wR2 = 0.0479
0.543 and −0.446
−
3
◦
Characterisation of thin films
X-Ray diffraction studies were performed on a Bruker AXS D8
475 C). The reason for this behaviour may be due to the large
˚
E · · · E “bite” (ca. 4 A) of the imidodiselenophosphinate ligand
49
inducing less strain on the metal–ligand ring. The Co–Se bond
diffractometer using Cu-K radiation. The samples were mounted
a
35
˚
length (2.435 A) in (3) is longer than Ni–Se bond length (2.400
A) in (1), so bond cleavage is more susceptible in (3) at higher
temperatures and hence it deposited cobalt selenide and cobalt
phosphide films.
◦
◦
flat and scanned between 10 and 70 in a step size of 0.05 with a
count rate of 9 s. Films were carbon coated using Edward’s E306A
coating system before carrying out SEM and EDX analyses. SEM
analysis was performed using a Philips XL 30FEG and EDX was
carried out using a DX4 instrument.
˚
Acknowledgements
Conclusions
A. P. is thankful to The University of Manchester for OSS funding.
C. Q. N. would like to acknowledge the Government of Vietnam
for financial support. The authors also thank EPSRC, UK for
grants to P. O’B. that have made some of this research possible.
i
The X-ray structure of [Ni{(SeP Pr
2
)
2
N}
2
] (1) revealed that the
compound is square planar in the green and tetrahedral in
i
the red crystals. This behaviour of [Ni{(SeP Pr
2
)
2
N}
2
] seems
to be unique in the class of imidodichalcogenidophosphinato
derivatives. Nickel selenide films were deposited from all three
classes of compounds [(1), (2) and (5)] but the morphology of the
films varied depending on the coordinating ligand. In the case
of cobalt, the selenocarbamato precursor (6) behaved similarly to
the corresponding nickel complex (5) and gave only cobalt selenide
films. But the selenophosphinato- and imidoselenophosphinato-
cobalt(II) precursors deposited different types of material when
compared to the nickel complexes. The selenophosphinato-cobalt
precursor (4) yielded a mixture of cobalt selenide and cobalt
phosphide films whereas the imidodiselenodiphosphinato-cobalt
precursor (3) produced two types of film, cobalt selenide and
cobalt phosphide at higher deposition temperatures (525 and
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506 | Dalton Trans., 2008, 4499–4506
This journal is © The Royal Society of Chemistry 2008