N-(Chalcogen)phosphorylated (chalcogen)ureas of zinc and cadmium(ii): SSPs for group 12-16 thin films

Article abstract of DOI:10.1039/c4nj00482e

The bis-chelates of zinc (7-11) and cadmium (12-17) with general formula [M{R₂P(X)NC(Y)NR′-η²-X,Y}₂] were obtained from ligands 1-6 (ⁱPr₂P(X)NHC(Y)NC₄H₈: 1: X = S, Y = S; 2: X = S, Y = O; 3: X = O, Y = S; 4: X = S, Y = Se, 5: X = Se, Y = S; Ph₂P(X)NC(Y)NC₅H₁₀: 6: X = S, Y = S). 4 and cadmium complex 15 are the first examples of this ligand system with carbon-bonded selenium as a donor atom. All the compounds were characterized by FTIR and multi-nuclear NMR spectroscopies, and microanalysis. The molecular structures of complexes 1, 7, 8, 11, and 15 were elucidated by single crystal X-ray diffraction. Thermal gravimetric analysis (TGA) and thermolysis experiments were carried out for the metal complexes. Selected pyrolysis residues were analyzed by scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and X-ray powder diffraction (XRPD). Remarkably, cadmium complex 13 gave a few crystals of CdS encrusted on the surface of CdO. Preliminary studies using the O,S-mixed cadmium complexes (13 and 14) as single source precursors (SSPs) were carried out for the deposition of thin films via AA-CVD. The results show that CdS films are obtained from both complexes, and in the case of 14 (the complex containing a PO fragment), persistent high carbon content was detected.

Full text of DOI:10.1039/c4nj00482e

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N-(Chalcogen)phosphorylated (chalcogen)ureas
of zinc and cadmium(II): SSPs for group 12–16 thin
films†
Cite this: New J. Chem., 2014,
38, 4702
Ivan D. Rojas-Montoya,a Alicia Santana-Silva,a Veronica Garcıa-Montalvo,*a
´
´
´
b
c
´
Miguel-Angel Munoz-Hernandez* and Margarita Rivera
˜
´
The bis-chelates of zinc (7–11) and cadmium (12–17) with general formula [M{R2P(X)NC(Y)NR0-Z2-X,Y}2]
were obtained from ligands 1–6 (iPr2P(X)NHC(Y)NC4H8: 1: X = S, Y = S; 2: X = S, Y = O; 3: X = O, Y = S;
4: X = S, Y = Se, 5: X = Se, Y = S; Ph2P(X)NC(Y)NC5H10: 6: X = S, Y = S). 4 and cadmium complex 15 are
the first examples of this ligand system with carbon-bonded selenium as a donor atom. All the com-
pounds were characterized by FTIR and multi-nuclear NMR spectroscopies, and microanalysis. The
molecular structures of complexes 1, 7, 8, 11, and 15 were elucidated by single crystal X-ray diffraction.
Thermal gravimetric analysis (TGA) and thermolysis experiments were carried out for the metal com-
plexes. Selected pyrolysis residues were analyzed by scanning electron microscopy-energy dispersive
spectroscopy (SEM-EDS) and X-ray powder diffraction (XRPD). Remarkably, cadmium complex 13 gave a
few crystals of CdS encrusted on the surface of CdO. Preliminary studies using the O,S-mixed cadmium
complexes (13 and 14) as single source precursors (SSPs) were carried out for the deposition of thin
films via AA-CVD. The results show that CdS films are obtained from both complexes, and in the case of
14 (the complex containing a PQO fragment), persistent high carbon content was detected.
Received (in Victoria, Australia)
28th March 2014,
Accepted 25th June 2014
DOI: 10.1039/c4nj00482e
www.rsc.org/njc
13 and 15 (III–V), 13 and 16 (III–VI), and 14 and 16 (IV–VI), which
are currently used in components of satellites, TV receivers, optical
Introduction
The rise of molecular nanotechnology has opened up many fiber communications devices, compact disk players, barcode
possibilities for using the basic strategies of coordination readers, full color advertising displays, and solar cells, among
chemistry to build up new materials and devices.1 Molecular others.5 SSPs comprise a large variety of ligands, such as seleno
precursors are becoming a major focus of interest for both the and thiocarbamates,6–10 thiophosphinates,11 silyl tellurates,12
synthesis and design of traditional and nanostructured materials. alkyl-xanthates,13,14 dithioacetylacetonates,15 thio and seleno-
Considerable efforts have been made to synthesize and use molec- carboxylates,16 thio and dithio-biuret17–22 and imidodichalcogen-
ular compounds as single source precursors (SSPs) to obtain metal phosphinates.23,24 The latter are very versatile ligands with general
chalcogenides as thin films or nanocrystals.2–4 Using SSPs, it is formula R2P(X)NHP(Y)R2 (X, Y = O, S, Se, Te), and have been widely
feasible to achieve semiconductors containing a wide variety of used to coordinate an extensive number of main group and
elements, including combinations from groups 12 and 16 (II–VI), transition metals.25,26
The variation in which one phosphorus atom is replaced
with a carbon atom, R2P(X)NHC(Y)R0 (LHX,Y with X = O, S, Se;
a
´
´
´
Instituto de Quımica, Universidad Nacional Autonoma de Mexico, Circuito Exterior,
Y = O, S; R = Oalkyl, Oaryl, aryl; and R0 = alkyl, aryl, arylNH,
alkylNH, alkyl2N)25,27,28 also contain a P–N fragment, and their
anions have the ability to form stable metal coordination
compounds.25,27–36 Some examples are the tetrahedral bis-
chelates of Co(II), Zn(II), and Cd(II),4,29,30,33 planar derivatives
´
´
Ciudad Universitaria, Mexico D.F. 04510, Mexico. E-mail: vgm@unam.mx;
Fax: +52-55-56-16-22-03
b
c
´
´
Centro de Investigaciones Quımicas, Universidad Autonoma del Estado de Morelos,
´
Av. Universidad 1001, Col. Chamilpa, Cuernavaca, Morelos C.P. 62209, Mexico
´
´
Instituto de Fısica, Dpto. Materia Condensada, Universidad Nacional Autonoma de
´
´
´
Mexico, Ciudad Universitaria, Mexico D.F. 04510, Mexico
† Electronic supplementary information (ESI) available: TGA/DSC analyses of all of Ni(II), Pd(II), and Pt(II),4,31,32 lanthanide tris-chelates that
possess optical properties,34 components of ion-selective elec-
complexes (Fig. S6). CCDC 986590–986594 for 1, 7, 8, 11 and 15. Details of the
trodes,35 and diorganotin(IV) complexes.36
X-ray structure analyses (Table S1). XRPD patterns of ZnO obtained from pyrolysis
of 8 (Fig. S2) and of the CdO and CdS mixture obtained from pyrolysis of 13
Herein we report the synthesis and characterization of ligands
(Fig. S3). GAXRD pattern of CdS film obtained from 13 (Fig. S4). SEM images of
with general formula R2P(X)NHC(Y)R0; R = iPr, R0 = pyrrolidine for
CdS thin film obtained from 14 (Fig. S5a and b). For ESI and crystallographic data
in CIF or other electronic format see DOI: 10.1039/c4nj00482e
1 (X, Y = S), 2 (X, Y = S, O), 3 (X, Y = O, S), 4 (X, Y = S, Se),
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5 (X, Y = Se, S) and R = Ph, R0 = piperidine for 6 (X, Y = S) and their Thermolinet 21100 furnace with a fixed temperature accord-
complexes, M(LX,Y)2; M = Zn(II), 7–11 and Cd(II), 12–17. 1, 7, 8, 11, ing to the TGA (400 1C for 13 and 500 1C for 14). The chamber
and 15 were analyzed by X-ray crystallography. 4 is the first contained 10 quartz substrates (1 cm2) on which the decom-
example of this type of ligand containing Y = Se, and 15 is the position reactions and film depositions took place in
first complex with this ligand. TGA and decomposition experi- B15 min. The argon flow rate was controlled by an INFRAt
ments in the solid state followed by FTIR were carried out for 7–17 rotameter. Grazing angle X-ray diffraction (GAXRD) analysis
in order to evaluate them as suitable SSPs for metal chalcogenide was performed on a Siemens D-500 diffractometer q–2q
thin films. Preliminary thin film depositions using 13 and 14 as with a grazing angle component and a scintillation counter
SSPs were performed by aerosol-assisted chemical vapor deposi- detector.
tion (AA-CVD).
General synthesis procedures
iPr2P(S)NHC(S)NC4H8 (1). Pyrrolidine (3.34 mL, 40 mmol)
was added to a stirred solution of iPr2P(S)NC(S) (8.28 g,
40 mmol) in MeCN (60 mL). After 4 hours, the solvent was
Experimental
Materials
removed under vacuum, dichloromethane was added, and then
All reactions were performed under an oxygen- and moisture-
the compound was precipitated with hexane. The obtained white
free argon atmosphere using standard Schlenk and glove-box
solid was filtered off and dried under vacuum. Yield: 9.43 g (90%).
M.p. 91–93 1C. 31P{1H} NMR (CDCl3, 298 K, 121.65 MHz): d =
techniques. Chemicals of commercial grade were purchased
from Aldrich and were used as supplied. Solvents were dried by
101.7 (s). 1H NMR (CDCl3, 300 MHz): d = 1.00–1.15 (m, 12H, CH3-iPr),
standard methods and freshly distilled prior to use. Ph2P(S)Cl,
1.83 (q, 2H, CH2-pyrrolidine), 1.98 (q, 2H, CH2-pyrrolidine), 3.33
iPr2P(X)Cl (X = O,37 S,38 Se39), Ph2P(S)NC(S)40 and iPr2P(X)NC(Y)
(t, 2H, NCH2-pyrrolidine), 3.45 (dsep, 2H, CH-iPr), 3.61 (t, 2H,
(Y = O,37 S,40 Se) were synthesized according to literature
NCH2-pyrrolidine), 5.28 (s, 1H, NH). 13C{1H} NMR (CDCl3, 298
methods for similar compounds. The K[R2P(X)NC(Y)NR0] salts
were prepared by treating the free ligands with potassium tert-
butoxide.
K, 75.56 MHz): d = 17.6 (CH3-iPr), 25.0 (CH2-pyrrolidine), 26.5
(CH2-pyrrolidine), 29.3 (CH-iPr), 48.5 (NCH2-pyrrolidine), 52.4
(NCH2-pyrrolidine), 176.2 (CQS). FTIR: n = 3364 n(NH), 2965,
2925, 2868 n(CH), 1501, 1280, 1013 n(CN/CQS), 879, 856 n(PN), 698,
674 n(PQS). EI (m/z): 278 corresponding to Pr2P(S)NHC(S)NC4H8.
Measurement of physical properties
i
NMR data (1H, 13C{1H} and 31P{1H}) were obtained using Jeol- Microanalysis calculated for C11H23N2S2P: N = 10.06, C = 47.45,
Eclipse 300 MHz and Varian-Inova 400 MHz instruments at H = 8.33%. Observed: N = 9.66, C = 47.19, H = 8.22%. Crystals
20 1C. Chemical shifts (ppm) are reported relative to SiMe4 for suitable for X-ray diffraction analysis were grown from hexane
1H and 13C NMR, and 85% H3PO4 for 31P NMR. The chemical solution.
composition was determined using an Elementar Vario EL III
The remaining ligands (2–6) were obtained according to this
instrument in the CHNS operation mode. The FTIR spectra procedure.
were recorded in the 4000–400 cmꢀ1 range on a Bruker Equinox
iPr2P(S)NHC(O)NC4H8 (2). Pyrrolidine (2.50 mL, 30 mmol)
55 Spectrometer using KBr pellets. The mass spectra were and iPr2P(S)NC(O) (5.73 g, 30 mmol). White solid. Yield: 6.68 g
recorded on a JEOL JMS-700 instrument. The TGA and differ- (85%). M.p. 99–101 1C. 31P{1H} NMR (CDCl3, 298 K, 121.65 MHz):
1
ential scanning calorimetry (DSC) analyses were obtained using d = 94.3 (s). H NMR (CDCl3, 300 MHz): d = 1.10–1.30 (m, 12H,
a TA INSTRUMENTS SDT Q600 V8.2 BUILD 100 instrument, CH3-iPr), 1.93 (q, 4H, CH2-pyrrolidine), 2.87 (dsep, 2H, CH-iPr),
using a nitrogen flux of 100 cm3 minꢀ1 and a temperature ramp 3.33 (t, 4H, NCH2-pyrrolidine), 4.72 (s, NH). 13C{1H} NMR
of 10 1C minꢀ1; in all cases the temperature interval was from (CDCl3, 298 K, 75.56 MHz): d = 16.8 (CH3-iPr), 25.7 (CH2-
ambient temperature to 600 1C. The pyrolysis experiments were pyrrolidine), 29.5 (CH-iPr), 46.2 (NCH2-pyrrolidine), 153.1 (CQO).
carried out in a Thermo Scientific Thermolyne Furnace Small FTIR: n = 3158 n(NH), 2963, 2928, 2874 n(CH), 1630 n(CQO), 1440
Benchtop Muffle. In a typical experiment, 100 mg of KBr was n(CN), 910, 901 n(PN), 694, 664 n(PQS). EI (m/z): 262 corre-
i
mixed with 1 mg of the corresponding complex to make a sponding to Pr2P(S)NHC(O)NC4H8. Microanalysis calculated
pellet. The pellet was placed in the muffle, and the temperature for C11H23N2SOP: N = 10.68, C = 50.38, H = 8.77%. Observed:
was increased to the desired temperature according to the N = 10.57, C = 50.06, H = 8.34%.
corresponding TGA; an FTIR spectrum was recorded during
iPr2P(O)NHC(S)NC4H8 (3). Pyrrolidine (1.58 mL, 19 mmol)
every step. XRPD analysis was performed on a Bruker D8 and iPr2P(O)NC(S) (3.64 g, 19 mmol). Yellow solid. Yield: 3.98 g
ADVANCE diffractometer. SEM images were recorded using a (80%). M.p. 105–106 1C. NMR: 31P{1H} NMR (CDCl3, 298 K,
Jeol JSM5600 LV coupled to a NORAN Energy Dispersive Spec- 121.65 MHz): d = 65.0 (s). H NMR (CDCl3, 298 K, 300 MHz):
1
trophotometer working at 20 keV. Preliminary AA-CVD thin film d = 1.08–1.24 (m, 12H, CH3-iPr), 1.88 (q, 2H, CH2-pyrrolidine),
deposits were obtained from 13 and 14; the spray was generated 2.01 (q, 2H, CH2-pyrrolidine), 3.10 (dsep, 2H, CH-iPr), 3.60
in a glass airbrush connected to a quartz reaction chamber (t, 2H, NCH2-pyrrolidine), 3.70 (t, 2H, NCH2-pyrrolidine), 7.11
using Ar as a carrier gas. In a typical deposition, B0.2 g of (s, NH). 13C{1H} NMR (CDCl3, 298 K, 75.56 MHz): d = 16.5
the SSP was dissolved in 40 mL of toluene, and the spray (CH3-iPr), 24.9 (CH2-pyrrolidine), 26.9 (CH-iPr), 27.9 (CH2-
was directed along the reaction chamber inside a cylindrical pyrrolidine), 49.1 (NCH2-pyrrolidine), 52.5 (NCH2-pyrrolidine),
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177.0 (CQS). FTIR: n = 3088 n(NH), 2964, 2869 n(CH), 1503, 673 filtrate was evaporated to dryness, yielding a white solid (0.26 g,
n(CN/CQS), 1182, 1148 n(PQO), 882, 852 n(PN). EI (m/z): 262 78%). M.p. 138–140 1C. 31P{1H} NMR (CDCl3, 298 K, 121.65
i
corresponding to Pr2P(O)NHC(S)NC4H8. Microanalysis calcu- MHz): d = 63.3 (s). 1H NMR (CDCl3, 298 K, 300 MHz): d = 1.09–
lated for C11H23N2OSP: N = 10.68, C = 50.38, H = 8.77%. 1.25 (m, 24H, CH3-iPr), 1.81 (m, 8H, CH2-pyrrolidine), 2.15–2.30
Observed: N = 10.63, C = 50.11, H = 8.35%.
(m, 4H, CH-iPr), 3.40 (t, 4H, NCH2-pyrrolidine), 3.65 (t, 4H,
iPr2P(S)NHC(Se)NC4H8 (4). Pyrrolidine (0.82 mL, 10 mmol) NCH2-pyrrolidine). 13C{1H} NMR (CDCl3, 298 K, 50.37 MHz):
i
and Pr2P(S)NHC(Se) (2.54 g, 10 mmol). White solid. Yield: d = 17.1 (CH3-iPr), 25.9 (CH-iPr), 32.1 (CH2-pyrrolidine), 32.2
2.44 g (75%). M.p. 109–110 1C. 31P{1H} NMR (CDCl3, 298 K, (CH2-pyrrolidine), 49.2 (NCH2-pyrrolidine), 49.9 (NCH2-pyrrolidine),
1
121.65 MHz): d = 104.4 (s). H NMR (CDCl3, 298 K, 300 MHz): 171.5 (CQS). FTIR: n = 2964, 2923, 2869 n(CH), 1498, 1248, 994
d = 1.09–1.25 (m, 12H, CH3-iPr), 1.93 (q, 2H, CH2-pyrrolidine), n(CN/CQS), 949, 917 n(PN), 579 n(PS). EI (m/z): 618 corre-
2.11 (q, 2H, CH2-pyrrolidine), 3.36 (t, 2H, NCH2-pyrrolidine), sponding to [Zn{iPr2P(S)NC(S)NC4H8-Z2-S,S}2]. Microanalysis
3.78 (m, 2H, NCH2-pyrrolidine), 3.80 (dsep, 2H, CH-iPr), 5.66 calculated for C22H44N4S4P2Zn: N = 9.04, C = 42.62, H =
(s, NH). 13C{1H} NMR (CDCl3, 298 K, 75.56 MHz): d = 16.4 7.10%. Observed: N = 8.83, C = 42.33, H = 6.67%. Crystals
(CH3-iPr), 22.0 (CH2-pyrrolidine), 25.4 (CH2-pyrrolidine), 28.4 suitable for X-ray diffraction analysis were grown from hexane
(CH-iPr), 47.5 (NCH2-pyrrolidine), 54.3 (NCH2-pyrrolidine), solution.
173.3 (s, CQSe). FTIR: n = 3342 n(NH), 2969, 2928, 2871
The complexes 8 to 10 were synthesized using similar
n(CH), 1504, 1249, 984 n(CN/CQSe), 879, 851 n(PN), 673 n(PS). procedures.
i
EI (m/z): 326 corresponding to Pr2P(S)NHC(Se)NC4H8. Micro-
[Zn{iPr2P(S)NC(O)NC4H8-g2-S,O}2] (8). 0.30 g (1.14 mmol) of
analysis calculated for (C11H23N2SSeP): N = 8.61, C = 40.61, 2 and 0.07 g (0.57 mmol) of ZnEt2. White solid. Yield: 0.21 g
H = 7.07%. Observed: N = 8.90, C = 40.35, H = 6.85%.
(65%). M.p. 91–92 1C. 31P{1H} NMR (CDCl3, 298 K, 121.65 MHz):
1
iPr2P(Se)NHC(S)NC4H8 (5). Pyrrolidine (3.36 mL, 41 mmol) d = 59.7 (s). H NMR (CDCl3, 298 K, 300 MHz): d = 1.09–1.25
i
and Pr2P(Se)NHC(S) (10.41 g, 41 mmol). White solid. Yield: (m, 24H, CH3-iPr), 1.73 (m, 8H, CH2-pyrrolidine), 1.96–2.07
12.02 g (90%). M.p. 86–88 1C. 31P{1H} NMR (CDCl3, 298 K, (m, 4H, CH-iPr), 3.27 (m, 8H, NCH2-pyrrolidine). 13C{1H}
1
121.65 MHz): d = 102.4 (s). H NMR (CDCl3, 298 K, 300 MHz): NMR (CDCl3, 298 K, 50.37 MHz): d = 16.3 (CH3-iPr), 25.8
d = 0.99–1.20 (m, 12H, CH3-iPr), 1.89 (q, 2H, CH2-pyrrolidine), (CH2-pyrrolidine), 29.8 (CH-iPr), 45.8 (NCH2-pyrrolidine),
2.02 (q, 2H, CH2-pyrrolidine), 3.33 (t, 2H, NCH2-pyrrolidine), 162.0 (CQO). FTIR: n = 2960, 2870 n(CH), 1470 n(CN), 930,
3.50 (t, 2H, NCH2-pyrrolidine), 3.60 (dsep, 2H, CH-iPr), 5.50 913 n(PN), 681, 662 n(PS). EI (m/z): 587 corresponding to
(s, NH). 13C{1H} NMR (CDCl3, 298 K, 75.56 MHz): d = 18.4 [Zn{iPr2P(S)NC(O)NC4H8-Z2-S,O}2]. Microanalysis calculated
(CH3-iPr), 24.4 (CH2-pyrrolidine), 26.4 (CH2-pyrrolidine), 29.0 for C22H44N4S2O2P2Zn: N = 9.53, C = 44.94, H = 7.4%. Observed:
(CH-iPr), 48.5 (NCH2-pyrrolidine), 52.4 (NCH2-pyrrolidine), N = 9.22, C = 44.50, H = 6.98%. Crystals suitable for X-ray
176.3 (CQS). FTIR: n = 3351 n(NH), 2966, 2929, 2870 n(CH), diffraction analysis were grown from hexane solution.
1497, 1276, 1016 n(CN/CQS), 880, 858 n(PN), 488 n(PQSe). EI
[Zn{iPr2P(O)NC(S)NC4H8-g2-O,S}2] (9). 0.30 g (1.14 mmol) of
(m/z): 326 corresponding to iPr2P(Se)NHC(S)NC4H8. Micro- 3 with 0.07 g (0.57 mmol) of ZnEt2. Yellow solid. Yield: 0.25 g
analysis calculated for C11H23N2SeSP: N = 8.61, C = 40.61, H = (75%). M.p. 198–199 1C. 31P{1H} NMR (CDCl3, 298 K, 121.65
7.07%. Observed: N = 8.66, C = 40.83, H = 6.95%.
MHz): d = 49.8 (s). 1H NMR (CDCl3, 298 K, 400 MHz): d = 1.05–
Ph2P(S)NHC(S)NC5H10 (6). Piperidine (3.0 mL, 30 mmol) 1.01 (m, 12H, CH3-iPr), 1.79 (m, 8H, CH2-pyrrolidine), 1.90
and Ph2P(S)NC(S) (7.53 g, 30 mmol). White solid. Yield: 8.64 g (m, 4H, CH-iPr), 3.35 (t, 4H, NCH2-pyrrolidine), 3.62 (t, 4H,
(80%). M.p. 120–122 1C. 31P{1H} NMR (CDCl3, 298 K, 121.65 NCH2-pyrrolidine). 13C{1H} NMR (CDCl3, 298 K, 100.74 MHz): d =
1
MHz): d = 53.1 (s). H NMR (CDCl3, 300 MHz): d = 1.56 (s (br), 15.9 (CH3-iPr), 25.4 (CH2-pyrrolidine), 26.3 (CH-iPr), 27.2 (CH2-
6H, CH2-piperidine), 3.76 (s (br), 4H, NCH2-piperidine), 6.11 pyrrolidine), 49.0 (NCH2-pyrrolidine), 49.5 (NCH2-pyrrolidine),
(s, 1H, NH), 7.36–7.41 (m, 6H, CH-phenyl), 7.87–7.95 (m, 4H, 169.6 (CQS). FTIR: n = 2967, 2869 n(CH), 1505, 1250, 987
CH-phenyl). 13C{1H} NMR (CDCl3, 298 K, 75.56 MHz): d = 24.0 n(CN/CQS), 1074 n(PO), 948, 917 n(PN). EI (m/z): 587 corre-
(CH2-piperidine), 25.7 (CH2-piperidine), 49.7 (NCH2-piperidine), sponding to [Zn{iPr2P(O)NC(S)NC4H8-Z2-O,S}2]. Microanalysis
128.3 (CH-phenyl), 131.4 (CH-phenyl), 131.7 (CH-phenyl), 181.6 calculated for C22H44N4O2S2P2Zn: N = 9.53, C = 44.94, H =
(CQS). FTIR: n = 3160 n(NH), 2952–2809 n(CH), 1434, 1311, 1047 7.40%. Observed: N = 9.34, C = 44.50, H = 7.29%.
n(CN/CQS), 918 n(PN), 658, 509 n(PQS). EI (m/z): 360 corre-
[Zn{iPr2P(Se)NC(S)NC4H8-g2-Se,S}2] (10). 5 (0.30 g, 0.92 mmol)
sponding to Ph2P(S)NHC(S)NC5H10. Microanalysis calculated for and ZnEt2 (0.06 g, 0.46 mmol). White solid. Yield: 0.29 g (89%).
C18H21PS2N2: N = 7.77, C = 60.00, H = 5.83%. Observed: N = 7.53, M.p. 109–110 1C. 31P{1H} NMR (CDCl3, 298 K, 121.65 MHz): d =
C = 59.93, H = 5.55.%.
58.7 (s). 1H NMR (CDCl3, 298 K, 300 MHz): d = 1.04–1.25 (m, 24H,
[Zn{iPr2P(S)NC(S)NC4H8-g2-S,S}2] (7). 0.3 g (1.07 mmol) of 1 CH3-iPr), 1.81 (m, 8H, CH2-pyrrolidine), 2.22–2.34 (m, 4H,
was added to a stirred solution of ZnEt2 (0.065 g, 0.53 mmol) in CH-iPr), 3.41 (t, 4H, NCH2-pyrrolidine), 3.66 (t, 4H, NCH2-
30 mL of toluene, causing vigorous gas evolution and the pyrrolidine). 13C{1H} NMR (CDCl3, 298 K, 75.56 MHz): d = 16.1
formation of a clear colorless solution, which was stirred for (CH3-iPr), 24.1 (CH-iPr), 30.0 (CH2-pyrrolidine), 30.8 (CH2-pyrrolidine),
4 h. Removal of the volatiles under reduced pressure produced 47.9 (NCH2-pyrrolidine), 48.7 (NCH2-pyrrolidine), 171.2 (CQS).
a cream solid, which was treated with hexane (10 mL) to give a FTIR: n = 2964, 2931, 2869 n(CH), 1496, 1248, 994 n(CN/CQS),
solid precipitate in the flask; the mixture was filtered and the 948, 915 n(PN), 416 n(PSe). EI (m/z): 714 corresponding to
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[Zn{iPr2P(Se)NC(S)NC4H8-Z2-Se,S}2]. Microanalysis calculated (CDCl3, 298 K, 81.1 MHz): d = 47.9 (s). 1H NMR (CDCl3,
for C22H44N4Se2S2P2Zn: N = 7.85, C = 37.03, H = 6.17%. 298 K, 400 MHz): d = 1.04–1.11 (m, 12H, CH3-iPr), 1.77–1.85
Observed: N = 7.42, C = 36.80, H = 5.89%.
(m, 8H, CH2-pyrrolidine), 1.87–1.95 (m, 4H, CH-iPr), 3.35 (t, 4H,
[Zn{Ph2P(S)NC(S)NC5H10-g2-S,S}2] (11). To an ethanolic NCH2-pyrrolidine), 3.65 (t, 4H, NCH2-pyrrolidine). 13C{1H} NMR
solution of the potassium salt of 6 (0.77 g, 1.93 mmol) was (CDCl3, 298 K, 100.74 MHz): d = 16.3 (CH3-iPr), 25.4 (CH-iPr),
added Zn(NO3)2 (0.20 g, 0.96 mmol); the mixture was stirred for 26.7 (CH2-pyrrolidine), 27.7 (CH2-pyrrolidine), 49.4 (NCH2-
4 h. After this time, the solvent was removed under reduced pyrrolidine), 49.9 (NCH2-pyrrolidine), 168.4 (CQS). FTIR: n =
pressure, and the solid was treated with hexane (15 mL). Some 2966, 2930, 2870 n(CH), 1511, 1249, 987 n(CN/CQS), 1078
of the solid was soluble in the hexane, and was separated from n(PO), 945, 915 n(PN). EI (m/z): 634 corresponding to
the mixture by cannula filtration and evaporated to dryness to [Cd{iPr2P(O)NC(S)NC4H8-Z2-O,S]}2. Microanalysis calculated
give a white solid. Yield: 0.61 g (82%). M.p. 191–193 1C. 31P{1H} for C22H44N4O2S2P2Cd: N = 8.82, C = 41.61, H = 6.93%.
NMR (121.65 MHz): d = 40.5 (s). 1H NMR (CDCl3, 298 K, Observed: N = 8.40, C = 41.58, H = 6.64%.
300 MHz): d = 1.57 (s (br), 12H, CH2-piperidine), 3.92 (s (br),
[Cd{iPr2P(S)NC(Se)NC4H8-g2-S,Se}2] (15). Potassium salt of 4
8H, NCH2-piperidine), 7.32 (m, 6H, CH-phenyl), 7.76 (m, 4H, (0.44 g, 1.22 mmol) and CdCl2 (0.12 g, 0.61 mmol). White solid.
CHAr). 13C{1H} NMR (CDCl3, 298 K, 75.56 MHz): d = 24.7 Yield: 0.31 g (66%). M.p. 150–151 1C. 31P{1H} NMR (CDCl3,
(CH2-piperidine), 26.17 (CH2-piperidine), 49.8 (NCH2-piperidine), 298 K, 81.1 MHz): d = 66.6 (s). 1H NMR (CDCl3, 298 K, 400 MHz):
128.2 (CH-phenyl), 130.8 (CH-phenyl), 131.3 (CH-phenyl), 174.8 d = 1.13–1.22 (m, 24H, CH3-iPr), 1.81–1.86 (m, 8H, CH2-
(CQS). FTIR: n = 2933.54, 2853.40 n(CH), 1492, 1298, 1005 pyrrolidine), 2.32–2.42 (m, 4H, CH-iPr), 3.41 (m, 4H, NCH2-
n(CN/CQS), 973 n(PN), 580, 522, 485, 399 n(PS). EI (m/z): 782 pyrrolidine) 3.70 (t, 4H, NCH2-pyrrolidine). 13C{1H} NMR
corresponding to [Zn{Ph2P(S)NC(S)NC5H10-Z2-S,S}2]. Micro- (CDCl3, 298 K, 100.74 MHz):
d =
17.2 (CH3-iPr), 25.4
analysis calculated for C36H40P2N4S4Zn: N = 7.14, C = 55.08, (CH2-pyrrolidine), 31.9 (CH-iPr), 49.5 (NCH2-pyrrolidine), 51.9
H = 5.10%. Observed: N = 6.96, C = 54.83, H = 5.05%. Crystals (NCH2-pyrrolidine), 163.1 (CQSe). FTIR: n = 2963, 2932, 2868
suitable for X-ray diffraction analysis were grown from dichloro- n(CH), 1501, 652 n(CN/CQSe), 938, 907, 869 n(PN), 690, 652
methane/hexane solution.
n(PS). EI (m/z): 762 corresponding to [Cd{iPr2P(S)NC(Se)NC4H8-
The remaining cadmium complexes 12–17 were obtained Z2-S,Se}2]. Microanalysis calculated for C22H44N4S2Se2P2Cd:
analogously from CdCl2.
N = 7.34, C = 34.63, H = 5.77%. Observed: N = 7.01, C = 34.22,
[Cd{iPr2P(S)NC(S)NC4H8-g2-S,S}2] (12). Potassium salt of 1 H = 5.68%. Crystals suitable for X-ray diffraction analysis were
(0.44 g, 1.4 mmol) and CdCl2 (0.13 g, 0.71 mmol). White solid. grown from dichloromethane/hexane solution.
Yield: 0.28 g (60%). M.p. 128–129 1C. 31P{1H} NMR (CDCl3,
[Cd{iPr2P(Se)NC(S)NC4H8-g2-Se,S}2] (16). Potassium salt of 5
298 K, 121.65 MHz): d = 62.9 (s). 1H NMR (CDCl3, 298 K, 300 MHz): (0.44 g, 1.22 mmol) and CdCl2 (0.12 g, 0.61 mmol). White solid.
d = 1.12–1.22 (m, 24H, CH3-iPr), 1.82 (m, 8H, CH2-pyrrolidine), Yield: 0.37 g (80%). M.p. 94–95 1C. 31P{1H} NMR (CDCl3, 298 K,
2.22–2.33 (m, 4H, CH-iPr), 3.40 (t, 4H, NCH2-pyrrolidine), 3.66 81.1 MHz): d = 61.3 (s). H NMR (CDCl3, 298 K, 400 MHz): d =
1
(t, 4H, NCH2-pyrrolidine). 13C{1H} NMR (CDCl3, 298 K, 75.56 MHz): 1.09–1.18 (m, 24H, CH3-iPr), 1.80 (m, 8H, CH2-pyrrolidine),
d = 16.0 (CH3-iPr), 25.0 (CH-iPr), 29.3 (CH2-pyrrolidine), 31.0 2.32–2.42 (m, 4H, CH-iPr), 3.43 (m, 4H, NCH2-pyrrolidine),
(CH2-pyrrolidine), 48.2 (NCH2-pyrrolidine), 49.1 (NCH2-pyrrolidine), 3.65 (m, 4H, NCH2-pyrrolidine). 13C{1H} NMR (CDCl3, 298 K,
170.1 (CQS). FTIR: n = 2964, 2932, 2869 n(CH), 1495, 1248, 992 100.74 MHz): d = 17.9 (CH3-iPr), 25.8 (CH2-pyrrolidine), 32.1
n(CN/CQS), 948, 915 n(PN), 681, 656 n(PS). EI (m/z): 667 corre- (CH-iPr), 49.3 (NCH2-pyrrolidine), 51.2 (NCH2-pyrrolidine),
sponding to [Cd{iPr2P(S)NC(S)NC4H8-Z2-S,S}2]. Microanalysis calcu- 177.7 (CQS). FTIR: n = 2961, 2931, 2867 n(CH), 1489, 1246,
lated for C22H44N4S4P2Cd: N = 8.40, C = 39.61, H = 6.60%. Observed: 994 n(CN/CQS), 950, 916 n(PN), 418 n(PSe). EI (m/z): 762
N = 8.29, C = 39.42, H = 6.47%.
corresponding to [Cd{iPr2P(Se)NC(S)NC4H8-Z2-Se,S}2]. Microa-
[Cd{iPr2P(S)NC(O)NC4H8-g2-S,O}2] (13). Potassium salt of 2 nalysis calculated for C22H44N4 Se2S2P2Cd: N = 7.34, C = 34.63,
(0.46 g, 1.52 mmol) and CdCl2 (0.14 g, 0.76 mmol). White solid. H = 5.77%. Observed: N = 7.09, C = 34.59, H = 5.37%.
Yield: 0.25 g (55%). M.p. 142–144 1C. 31P{1H} NMR (CDCl3,
[Cd{Ph2P(S)NC(S)NC5H10-g2-S,S}2] (17). CdCl2 (0.15 g, 0.45 mmol)
298 K, 81.1 MHz): d = 60.9 (s). 1H NMR (CDCl3, 298 K, 400 MHz): and the potassium salt of 6 (0.52 g, 0.868 mmol). White solid. Yield:
d = 1.12–1.19 (m, 24H, CH3-iPr), 1.73 (m, 8H, CH2-pyrrolidine), 0.832 g (87%). M.p. 224–226 1C. 31P{1H} NMR (CDCl3, 298 K,
2.06–2.11 (m, 4H, CH-iPr), 3.61 (m, 8H, NCH2-pyrrolidine). 121.65 MHz): d = 40.33 (s). H NMR (CDCl3, 298 K, 300 MHz):
1
13C{1H} NMR (CDCl3, 298 K, 50.37 MHz): d = 16.7 (CH3-iPr), d = 1.58 (s (br), 12H, CH2-piperidine), 3.94 (s (br), 8H, NCH2-
25.8 (CH2-pyrrolidine), 31.0 (CH-iPr), 45.6 (NCH2-pyrrolidine), piperidine), 7.41 (m, 6H, CH-phenyl), 7.87 (m, 4H, CH-phenyl).
163.7 (CQO). FTIR: n = 2959, 2932, 2868 n(CH), 1450 n(CN), 930, 13C{1H} NMR (CDCl3, 298 K, 75.56 MHz): d = 24.7 (CH2-
904 n(PN), 681, 648 n(PS). EI (m/z): 634 corresponding to piperidine), 26.3 (CH2-piperidine), 47.40 (NCH2-piperidine),
[Cd{iPr2P(S)NC(O)NC4H8-Z2-S,O}2]. Microanalysis calculated 128.26 (CH-phenyl), 130.84 (CH-phenyl), 131.19 (CH-phenyl),
for C22H44N4S2O2P2Cd: N = 8.82, C = 41.61, H = 6.93%. 174.7 (CQS). FTIR: n = 2921–2853 n(CH), 1495, 1278, 998
Observed: N = 8.53, C = 41.22, H = 6.83%.
n(CN/CQS), 969 n(PN), 669, 580, 520 n(PS). EI (m/z): 832
[Cd{iPr2P(O)NC(S)NC4H8-g2-O,S}]2 (14). 0.46 g (1.52 mmol) corresponding to [Cd{Ph2P(S)NC(S)NC5H10-Z2-S,S}2]. Micro-
of the potassium salt of 3 and CdCl2 (0.14 g, 0.76 mmol). Yellow analysis calculated for C36H40P2N4S4Cd: N = 6.73, C = 51.96,
solid. Yield: 0.33 g (70%). M.p. 178–179 1C. 31P{1H} NMR H = 4.81%. Observed: N = 6.55, C = 51.79, H = 4.70%.
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X-ray crystallographic study
Crystals of compounds 1, 7 and 8 suitable for X-ray diffraction
were obtained from saturated hexane solutions, while com-
pounds 11 and 15 were crystallized from dichloromethane/
hexane solutions, as described above. X-ray data were collected
with a Bruker APEX CCD diffractometer with Mo-Ka radiation.
The structures were refined using the software package SHELXTL
vers. 6.1.41 All of the non-hydrogen atoms were refined aniso-
tropically. The hydrogen atoms were fixed in calculated posi-
tions. Absorption correction was applied with one of the
following methods, specified in CCDC 986590–986594: multi-
scan (SADABS42), psi-scan (XPREP41), or by face indexing with
XPREP and SADABS for other CCD corrections. Further details
of the structure analyses are given in Table S1 of the ESI.† 7 and
Scheme 2 Synthesis of complexes 7–10.
solids and are soluble in a variety of solvents, such as hexane,
acetonitrile, ethanol, toluene, tetrahydrofuran and dichloromethane.
i
11 showed substitutional disorder. In the case of 7, one Pr
i
substituent and a Me group of the other Pr substituent on the
phosphorus atom were modelled in two orientations with
50 : 50% occupancy. In 11, a phenyl substituent on the phos-
phorus atom was modelled in two orientations with 58 : 42%
occupancy. In both cases, the components of the disorder were
refined anisotropically, applying appropriate restrains, and the
hydrogen atoms were fixed in calculated positions with the
same occupancies as the disordered non-hydrogen atoms.
Spectroscopic and structural analyses
The FTIR spectra of ligands 1–6 show the keto form,
R2P(X)NHC(Y)R (X, Y = O, S, Se), as the predominant tautomer
in the solid state, which is consistent with previous reports
relating to similar ligands.43 Accordingly, the spectra exhibit
absorptions at E3226 cmꢀ1, corresponding to n(NH), 1480 cmꢀ1
,
indicative of n(C–N), and 870 cmꢀ1, which is characteristic of
n(P–N). In the case of compounds containing N(H)–CQY (Y = S, Se),
the stretching vibration n(CQY) is strongly coupled to n(C–N), and
several absorptions that may be associated with both vibration
modes are observed.44,45 Hence 1, 3, 5 and 6 show three
Results and discussion
Ligands 1–5 were prepared by the reaction of the corresponding
isochalcogenocyanate (iPr2P(X)NC(Y): 1: X = S, Y = S; 2: X = S,
Y = O; 3: X = O, Y = S; 4: X = S, Y = Se, 5: X = Se, Y = S) with
pyrrolidine, while ligand 6 was obtained in the reaction of
Ph2P(S)NC(S) with piperidine (Scheme 1). All ligands are air-
stable solids except for 4 and 5, which turn red over one day
after exposure to air, although they can be stored under argon
almost indefinitely.
Zinc complexes 7–10 were obtained in the reaction of
diethylzinc (ZnEt2) with the corresponding ligand (1–3, 5) in
toluene at ambient temperature (Scheme 2). 11 and 12–17 were
prepared in ethanol at room temperature by reacting the
potassium derivatives of ligands 1–6 with Zn(NO3)2 and CdCl2,
respectively (Scheme 3). All complexes are air-stable crystalline
absorptions for n(CN/CQY), in the regions 1570–1395 cmꢀ1
,
1420–1260 cmꢀ1 and 1140–940 cmꢀ1, while 4 exhibits two
absorptions in the regions 1500–1400 and 700–600 cmꢀ1 The
absorptions related to the n(CQO) and n(PQX) are: 2, n(CQO)
1630 cmꢀ1; 3, n(PQO) 1148 cmꢀ1; 1, 2, 4, and 6, n(PQS)
B690 cmꢀ1; and 5, n(PQSe) 488 cmꢀ1
.
The FTIR spectra of 7–17 show the characteristic absorp-
tions expected upon chelation of the anionic ligand to the
metal center through the X and Y donors. After coordination,
the n(NH) absorption is absent, while the n(PQX) and n(CQY)
Scheme 1 Synthesis of ligands 1–6.
Scheme 3 Synthesis of complexes 11–17.
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vibrations are shifted to lower wavenumbers, which is indicative atoms and the SCN atoms is substantially more acute, 651 vs.
of M–(X,Y) coordination. In addition, both the n(P–N) and n(C–N) 171.51 in 1, which is most likely due to the additional stabili-
absorptions are shifted to higher wavenumbers, which is in zation of a weak pꢁ ꢁ ꢁp interaction of 5.470 Å between the two
agreement with an increase in bond order due to the redistribu- phenyl rings on phosphorus and the tetrahydroquinoline
tion of the electronic density around the XPNCY ring skeleton.
(Fig. 1). The P–S, C–S, N–P, and N–C bond lengths are consistently
In the multi-nuclear NMR study, all signals for ligands 1–6 shorter than the sum of covalent radii of the corresponding atoms
are consistent with the proposed keto tautomers. 1H NMR (Pcov = 1.07 Å, Scov = 1.05 Å, Csp2cov = 0.73 Å, Ncov = 0.71 Å),46 which
spectra show the resonance assigned to the NH moiety in the implies double bond character and therefore electron p delocaliza-
range d 4.72–7.11 ppm. 31P{1H} NMR spectra show a singlet tion along the entire SPNCSN fragment.
resonance that is shifted to low-field on going from O to S to Se,
The molecular structures of 7, 8, 11 and 15 are depicted in
consistent with decreased negative hyperconjugation on the Fig. 2. The coordination geometry about the metal centers is
phosphorus atom (3, d 65.0 ppm (X = O); 1, 2, and 4, d 94.1– tetrahedral, with mean bond angles of 110.51, 109.41, 109.51,
101.7 ppm (X = S); 5, d 102.4 ppm (X = Se); and 6, d 53.1 ppm and 109.51 for 7, 8, 11, and 15, respectively. The mean bite
(X = S, R = Ph)). In the 13C{1H} NMR spectra, the characteristic angles are more acute, as may be anticipated for the constric-
resonance of the CQY fragment is observed at d 153.1 ppm tions imposed by the ligand framework around the metal
for 2 (Y = O), d B178.0 ppm for 1, 3, 5, and 6 (Y = S), and centers (104.91 for 7, 105.81 for 8, 108.91 for 11, and 104.11
d 173.3 ppm for 4 (Y = Se).
for 15). The Zn–S bond lengths found in 7, 8 and 11 are in the
The NMR spectra of the Zn(II) and Cd(II) complexes show range 2.3039(9)–2.4289(12) Å, while the Zn–O bond lengths in 8
similar features to those of the ligands. It is noteworthy that the are 1.949(2) and 1.967(2) Å. They all are comparable to those in
NH resonance signal is absent, and that resonances are shifted [Zn{H2NC(S)NP(S)Ph2-Z2-S,S}2]29 and [Zn{C6H5C(S)NP(O)OiPr-
to high-field as result of chelate formation with concomitant Z2-S,O}2]4 (mean Zn–S, and Zn–O bond lengths: 2.2980 Å and
electronic density redistribution along the XPNCY fragment.
1.9599 Å, respectively). 15 exhibits mean Cd–S and Cd–Se bond
Single crystals of 1 suitable for X-ray diffraction analysis were lengths of 2.5474 and 2.6097 Å, respectively, which are compar-
obtained from CH2Cl2/hexane. Details of the crystal collection able to those found in complexes [Cd(N(SCNR2)2)2] (R = Me,
and refinement are given in Table S1 of the ESI.† The molecular Et)22 and [Cd(N(iPr2PSe)2)2]47 of 2.5065 and 2.6277 Å, respec-
structure is shown in Fig. 1, along with selected bond lengths tively. In general, the bond lengths described so far are margin-
and angles. 1 crystallizes in the monoclinic space group P2(1)/n, ally longer than the sum of the respective covalent radii
and no significant intermolecular contacts are observed. The (Zn–S, 2.30 Å; Zn–O, 1.91 Å; Cd–S, 2.49 Å; Cd–Se, 2.64 Å), in
molecular structure confirms that the predominant tautomer, accordance with single metal–chalcogen bonds.46 All com-
both in the solid state and solution, is the ketoamine form, as plexes can be described as spirocycles made of two fused six-
observed in the FTIR and NMR spectra and as reported for the membered rings with half-chair conformations, in which the
related R2P(X)NHC(Y)R4,27,29–33 ligands and R2P(X)NHP(Y)R2 phosphorus atoms are in the apex positions.
imidophosphinates.26 The sulfur atoms in 1 are oriented in an
Thermal behavior
anti fashion and are almost coplanar to the plane subtended by
the PNC moiety (deviation +0.27 Å S1, ꢀ0.24 Å S2). This Thermal analyses (TGA and DSC) in the range 25–600 1C were
configuration of the sulfur atoms may stem from a weak Sꢁ ꢁ ꢁH conducted to evaluate the thermal behavior of complexes 7–17,
intermolecular interaction (2.779 Å; Sꢁ ꢁ ꢁN 3.501 Å) between the and to ascertain the temperature of decomposition. The TGA/
sulfur atom bound to the electron-rich diisopropylphosphine DSC results are tabulated in Table 1. Similar thermal behavior
moiety and the hydrogen atom on the imide fragment.
was consistently observed for all complexes. Thermal stability is
The structure of the related ligand Ph2P(S)NHC(S)(C9H10N)40 observed up to 275 1C for the Zn complexes 7–11, and up to
also shows an anti disposition of the sulfur atoms, but in this 200 1C for the Cd complexes 12–17. At higher temperatures, all
case the dihedral angle of the main planes defined by the SPN complexes decompose cleanly, with just one pathway of decom-
position that ends at B400 1C for the Zn complexes and at
B375 1C for the Cd complexes. The final residue can be
associated with the corresponding metal chalcogenide; in the
case of mixed complexes (MLX,Y), it is related to the heavier
chalcogenide. In general, the DSC curves exhibit two principal
endothermic processes. The first is the melting temperature,
and the second is attributed to thermal decomposition of the
complexes, resulting in the metal sulfides or selenides. In order
to evaluate the decomposition of the proposed complexes,
thermolysis was carried out in three steps, using the TGA/
DSC results to fix the temperature in the muffle, and FTIR
spectroscopy in KBr pellets was carried out to monitor the
Fig. 1 Molecular structures of 1 (a) and Ph2P(S)NHC(S)(C9H10N)40 (b) at
the 50% probability level. Most hydrogen atoms have been omitted for
clarity. The structure of (b) has been redrawn from CIF 236537. Selected
bond lengths (Å) and angles (1) for 1: P1–S2 1.9421(7), P1–N1 1.6993(15),
progress of the pyrolysis. Samples were heated at B50 1C less
than the decomposition temperature; at this point the spectra
N1–H1 0.878(18), N1–C1 1.373(2), C1–S1 1.6753(18), C1–N2 1.332(2), P1–
N1–C1 130.38(12), S1–C1–N1 122.44(13), S2–P1–N1 106.31(6).
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Fig. 2 Molecular structures of 7, 8, 11 and 15 at the 30% probability level (hydrogen atoms have been omitted for clarity). Selected bond lengths (Å) and
angles (1) for 7: Zn1–S1 2.3143(13), Zn1–S2 2.4289(12), Zn1–S3 2.3841(12), Zn1–S4 2.3204(12), S1–P1 2.2195(16), S2–C7 1.918(4), C7–N1 1.246(5),
P1–N1 1.548(3), S1–Zn1–S2 99.78(4), S4–Zn1–S3 104.93(4), S1–Zn1–S3 124.09(4), S1–Zn1–S4 101.44(5), S2–Zn1–S3 106.27(5), S2–Zn1–S4 121.90(4),
Zn1–S2–C7 118.72(14), Zn1–S1–P1 104.17(6), S1–P1–N1 125.69(15), P1–N1–C7 123.6(3). 8: Zn1–O1 1.949(2), Zn1–S1 2.3039(9), Zn1–O2 1.967(2),
Zn1–S2 2.3200(8), O1–C1 1.287(3), S1–P1 2.0274(11), P1–N1 1.608(2), C1–N1 1.337(4), Zn1–O1–C1 128.22(19), Zn1–S1–P1 96.65(4), P1–N1–C1 126.6(2),
O1–Zn1–S1 105.81(6), O2–Zn1–S2 105.69(6), O1–Zn1–O2 108.49(9), O1–Zn1–S2 110.54(7), S1–Zn1–O2 108.51(6), S1–Zn1–S2 117.55(3). 11:
Zn1–S1 2.3174(8), Zn1–S2 2.3426(8), Zn1–S3 2.3135(8), Zn1–S4 2.3381(8), S1–C1 1.745(3), S2–P1 2.0038(10), C1–N1 1.315(3), P1–N1 1.600(2),
S1–Zn1–S2 108.00(3), S3–Zn1–S4 109.75(3), S1–Zn1–S3 115.40(3), S1–Zn1–S4 105.58(3), S2–Zn1–S3 104.12(3), S2–Zn1–S4 114.26(3), Zn1–S1–C1
109.46(10), Zn1–S2–P1 95.79(3), S2–P1–N1 118.35(9), P1–N1–C1 126.68(18). 15: Cd1–Se1 2.6329(8), Cd1–S1 2.5476(15), Cd1–Se2 2.5866(9),
Cd1–S2 2.5472(14), S1–P1 2.0195(18), Se1–C1 1.916(5), C1–N1 1.311(6), P1–N1 1.606(4), Se1–Cd1–S1 102.36(2), Se2–Cd1–S2 105.92(3), Se1–Cd1–S2
105.72(4), Se1–Cd1–Se2 117.25(3), S1–Cd1–S2 111.97(5), S1–Cd1–Se2 113.51(4), Se1–C1–N1 129.2(3), S1–P1–N1 118.27(16), P1–N1–C1 133.9(3).
Table 1 TGA and DSC results for each complex
Decomposition stage
T range of
decomposition (1C)
DSC peak: T at maximum
peak height (1C)
Melting
point (1C)
Obtained
residue (%)
1st stage
2nd stage
Compound
7
8
9
10
12
13
14
15
16
250
250
250
200
350
150
250
275
275
350
350
475
450
400
350
500
375
475
100
100
225
250
150
200
250
100
200
310
284
313
323
354
306
325
335
320
138–140
91–92
24.60
16.77
20.68
30.88
6.42
11.49
20.66
22.88
20.82
198–199
109–110
128–129
142–144
178–179
150–151
94–95
only exhibited the loss of hydration water. The next measurement absorptions due to the organic vibrations vanished, and the
was recorded at the temperature observed in the thermogram, intensities of the absorptions due to metal–chalcogen vibrations
which gave the maximum decomposition rate. Almost all began to rise; e.g. 8 showed a broad band at 450 cmꢀ1 and a weak
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one at 620 cmꢀ1 (Fig. S1, ESI†). Final experiments were performed
at 550 1C, where the FTIR spectra showed the complete absence of
absorptions attributed to organic vibrations, while those due to
metal–chalcogen vibrations were clearly visible, e.g. 8 n: 1149–
1039 cmꢀ1, 620 and 450 cmꢀ1 (Zn–O vibrations).48–50
SEM-EDS and XRPD analyses of the pyrolysis residues were
performed for complexes 8 and 13 (S,O-mixed Zn and Cd
complexes, respectively). For 8, the chemical composition is S
(0.57%), O (50.57%) and Zn (48.86%), giving 99% ZnO in the
hexagonal structure, according to the XRPD pattern (Fig. S2,
ESI†), which is consistent with the FTIR results. However, 13
gives a composite of CdO and CdS. Accordingly, the EDS
analysis shows S: 16.81%, O: 32.40%, and Cd: 50.79%, where
Fig. 4 SEM images of the as-deposited thin film obtained from 13 via
AA-CVD. (a) Clusters over a nanostructured surface. (b) Uniform nano-
particulate surface.
The EDS analysis shows that the as-deposited films of 13 are
58% of the sample is CdO. The SEM images shown in Fig. 3 composed of 45.45% S and 54.55% Cd, and is consistent with
provide additional evidence for this fact. In Fig. 3a, the irre- the results of the GAXRD experiment, in which only the diffrac-
gular material exhibits a few crystals of CdS encrusted on the tion pattern of hexagonal CdS was observed (Fig. S4, ESI†). SEM
surface of CdO, while Fig. 3b shows crystals of CdS. These two images (Fig. 4) of this deposit exhibit irregular clusters on a
components were also identified by XRPD analysis (Fig. S3, uniform nano-particulate surface, while the films obtained from
ESI,† cubic CdO and hexagonal CdS). The presence of oxides is 14 (Fig. S5, ESI†) show amorphous material on a quasi-regular
attributed to handling the sample in air. As far as we know, nano-particulate surface. Despite the topological imperfections
there is no other report on the production of a mixture such as observed, it is important that only CdS is obtained, in contrast to
the one described, in which two metallic chalcogenides are the mixture achieved in the thermolysis experiments without Ar
obtained from the same SSP. In a recent report, XPS experi- atmosphere. It also seems advantageous to use ligands with the
ments showed the presence of both the unoxidized and oxi- heavier donor atom (sulfur in this case) attached to the phos-
dized forms of iron sulfide in the as-deposited films obtained phorous atom, in order to prevent organic residues on films.
from Fe(SON(CNiPr2)2)3, a fact that can be ascribed to handling
the samples in air.19 [Ni{iPr2P(S)NP(Se)iPr2-Z2-S,S}2] leads to the
deposition of films of nickel phosphide or nickel selenide,
depending on the deposition temperature. In the same report,
Conclusions
a Ni0.85Se/Ni2P heterostructure was obtained by the deposition We have reported the syntheses and structures of Zn and Cd
of a layer of nickel phosphide at 475 1C, followed by deposition complexes 7–17. In all cases, single-crystal X-ray structures showed
of a nickel selenide film at 400 1C.51 It is also important to note bis-chelates with distorted tetrahedral geometries around the
that [Ni{iPr2P(Se)NP(Te)iPr2-Z2-Se,Te}2]52 leads to the deposi- metal centers. Six-membered metallacycles were obtained upon
tion of the heavier nickel chalcogenides, as was also observed complexation. TGA of the complexes showed a clean single-step
for [Ni{iPr2P(S)NP(Se)iPr2-Z2-S,S}2].51 A similar behavior was decomposition pathway in all cases, with residues that could be
observed for the zinc and cadmium sulfide films obtained related to the corresponding metal chalcogenides. FTIR spectra of
from SSPs with mixed S,O-biuret ligands.22
the thermolysis products at the point of maximum decomposition
In order to assess the behavior of our O,S-mixed complexes showed the absence of most of the absorptions due to the organic
as SSPs of thin films, we carried out preliminary studies on the moieties, while absorptions due to metal–chalcogen vibrations
deposition of thin films via AA-CVD with 13 and 14 at 400 1C were better resolved; this fact was also confirmed by the corre-
and 500 1C, respectively. The EDS analyses of both films exhibit sponding SEM-EDS and XRPD analyses. 13 and 14 were used as
essentially metal-enriched CdS; only the film obtained with the SSPs for preliminary depositions of cadmium sulfide thin films by
ligand containing a PQO group (14) shows a high carbon AA-CVD. The SEM-EDS and GAXRD of the films showed that the
residue (15.71% S, 16.06% Cd and 68.21% C).
deposits were essentially CdS. The preliminary deposition studies
presented herein evidence the suitability of the proposed com-
plexes as SSPs of nanocrystals or thin films of metal chalcogen-
ides. Further research will be focused on this topic.
Acknowledgements
We gratefully acknowledge support from UNAM-DGAPA (Project
Grant IN201311). I. D. Rojas-Montoya is thankful to CONACyT
for a PhD fellowship. We thank Antonio Morales Espino, Mario
Fig. 3 SEM images of the thermolysis residue of cadmium compound 13:
(a) irregular surface with CdS encrusted crystals. (b) CdS crystals encrusted
on the surface.
˜
Monroy Escamilla and Dr Carlos R. Magana Zavala for the XRPD
and SEM analyses.
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