Convenient synthesis of copper (I) thiolates and related compounds

Article abstract of DOI:10.1016/j.ica.2004.11.030

Copper (I) salts of various anions including thiolates, diethyl dithiocarbamate, diethyl dithiophosphate, trithiocyanurate, 1-cyano-3- methylisothiourea, 2-aminothiazole, and tetrakis(1-imidazolyl)borate are conveniently synthesized by reducing copper (II) sulfate in aqueous ammonia. The addition of phosphine ligands to several of the products is demonstrated, and the crystal structure of [Cu₂(MBT)₂(DPPE)₃] ? Et₂O (MBT = 2-mercaptobenzothiazolate, DPPE = 1,2-bis(diphenylphosphino)ethane) is reported.

Full text of DOI:10.1016/j.ica.2004.11.030

Inorganica Chimica Acta 358 (2005) 1331–1336
www.elsevier.com/locate/ica
Note
Convenient synthesis of copper (I) thiolates and related compounds
a
Lynda M. Nguyen , Megan E. Dellinger , Jeffrey T. Lee , Ronald A. Quinlan ,
a
a
a
b
Arnold L. Rheingold , Robert D. Pike
a,
*
a
Department of Chemistry, College of William and Mary, P.O. Box 8795, Williamsburg, VA 23187-8795, USA
b
Department of Chemistry, University of California, San Diego, La Jolla, CA 92093, USA
Received 1 November 2004; accepted 24 November 2004
Available online 30 December 2004
Abstract
Copper (I) salts of various anions including thiolates, diethyl dithiocarbamate, diethyl dithiophosphate, trithiocyanurate, 1-
cyano-3-methylisothiourea, 2-aminothiazole, and tetrakis(1-imidazolyl)borate are conveniently synthesized by reducing copper
(II) sulfate in aqueous ammonia. The addition of phosphine ligands to several of the products is demonstrated, and the crystal struc-
ture of [Cu2(MBT)2(DPPE)3]ÆEt2O (MBT = 2-mercaptobenzothiazolate, DPPE = 1,2-bis(diphenylphosphino)ethane) is reported.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: Copper (I); Thiolates; Phosphines; Dithiocarbamates; Dithiophosphates; Tetrakis(1-imidazolyl)borate
1. Introduction
oping a blue color indicative of copper (II). Dithioanion
salts of copper (I) are typically oligomeric, e.g. [Cu(S2C-
NEt2)]4 [7] and [Cu(S2P(OiPr)2)]n (n = 4, 6) [8].
Sulfur- and aromatic nitrogen-based anions form rel-
atively stable compounds with copper (I). This is due to
the favorable soft acid-soft base interaction. Recently,
Cu(I) thiolates and similar species have been attracting
considerable attention owing to their interesting photo-
chemical properties [1]. Copper (I) thiolates, which are
widely regarded as being polymeric, have been prepared
by direct addition of an excess of thiol to aqueous solu-
tions of copper (II) salts [2,3] or by electrochemical
reduction of Cu(II) in the presence of thiol [4]. Dithio-
carbamate salts of copper (I) have been prepared from
dithiuram disulfides or by conproportionation of the
copper (II) dithiocarbamate with copper metal [5].
Dithiophosphate salts of copper (I) can be made by
reacting dithiophosphates with copper (I) salts (such as
CuCl) dissolved in aqueous ammonia [6]. However,
the foregoing solutions are fairly unstable, readily devel-
A general strategy for the preparation of copper (I)
salts of sulfur and nitrogen anions was suggested by a
report of copper (I) acetylide synthesis from aqueous
solution [9]. The two-step procedure involves reduction
of copper (II) sulfate with hydroxylamine in the pres-
ence of ammonia to form the stable Cu(I) ammine com-
plex, and reaction with the acid or alkali form of the
desired anion, Eqs. (1) and (2) [10]. In this note, we dem-
onstrate the generality of this procedure for preparing a
variety of Cu(I) thiolates and related compounds,
including the diethyldithiocarbamate ðS2CNEt2ꢀÞ, diet-
hyldithiophosphate ðS2PðOEtÞ ꢀÞ, 1-cyano-3-meth-
2
ylisothioureate (CMITꢀ), tetrakis(1-imidazolyl)borate
ðBIm4ꢀÞ, 2-aminothiazolate, and trithiocyanurate
ðTTCꢀ; C3N3S ꢀÞ.
3
2CuSO4 þ 4NH3 þ 2NH2OH þ 2OHꢀ
*
Corresponding author. Tel.: +757 2212555; fax: +757 2212715.
E-mail address: rdpike@wm.edu (R.D. Pike).
! 2½CuðNH3Þ ꢁþ þ 2SO 2ꢀ þ N2 " þ4H2O:
ð1aÞ
2
4
0020-1693/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2004.11.030

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L.M. Nguyen et al. / Inorganica Chimica Acta 358 (2005) 1331–1336
4CuSO4 þ 8NH3 þ 2NH2OH þ 4OHꢀ
0.870 mmol) was suspended in the mixture. The tube
was sealed and heated to 100 ꢁC in an oil bath for 20
h. The cream colored product was collected via filtration
and washed with hot MeCN and ether. The solid was
vacuum dried (0.542 g, 0.327 mmol, 75.3%). X-ray qual-
ity crystals were grown by layering a solution of the
product in CHCl3 with ether in a 5-mm i.d. tube.
! 4½CuðNH3Þ ꢁþ þ 4SO 2ꢀ þ N2O " þ5H2O:
ð1bÞ
ð2Þ
2
4
½CuðNH3Þ ꢁþ þ OHꢀ þ HSR
2
! CuSR # þ2NH3 þ H2O:
2.5. Preparation of [Cu(BIm4)(PPh3)]
2. Experimental
Triphenylphosphine (0.325 g, 1.24 mmol) was dis-
solved in 80 mL CH3CN in a thick-walled reaction tube
and Cu(BIm4) (0.425 g, 1.24 mmol) was suspended in
the mixture. The tube was heated to 100 ꢁC in an oil
bath for 18 h. The suspension was filtered, yielding a
white solid which was washed with ether and vacuum
dried (0.632 g, 1.04 mmol, 51.7%). Other phosphine ad-
ducts of Cu(I) salts were prepared similarly.
2.1. General
All compounds were reagent grade and were used as
received. All copper-containing products were analyzed
for copper content by atomic absorption, as previously
described [11].
2.2. Preparation of CuSPh
2.6. X-ray crystallographic study
To an ice-cold mixture of 25 mL conc. aq. NH3 and
100 mL H2O was added CuSO4 Æ5H2O (6.26 g, 25.1
mmol) forming a royal blue-colored solution. Over a
period of 45 min., solid NH2OHÆHCl (3.89 g, 56.0
mmol) was added. Stirring overnight at 25 ꢁC under
N2 purge produced a colorless solution of [Cu(NH3)2]+.
Using a syringe, a solution of PhSH (2.84 g, 25.8 mmol)
in 125 mL EtOH was added. A pale yellow solid formed
immediately. The solid product was collected via filtra-
tion and was washed with H2O, EtOH, and ether in suc-
cession and vacuum-dried (3.89 g, 22.5 mmol, 89.6%).
Other Cu(I) thiolates and the 2-aminothiazolate were
prepared similarly.
Data collection was carried out at 173 K on a Bruker
Smart CCD diffractometer with graphite-monochro-
mated Mo Ka radiation (k = 0.71073 A), operating in
˚
the / and x scanning mode. The structure was solved
by direct methods and refined by full-matrix least-
squares on F2 [12]. All non-hydrogen atoms were refined
anisotropically. Hydrogen atoms were included in calcu-
lated positions and refined riding on the respective car-
bon bonded atoms. The asymmetric unit consists of
two crystallographically independent but chemically
similar molecules residing on inversion centers, and a
molecule of diethyl ether, one of the recrystallization
solvents. All software was part of the Bruker libraries
of programs (Bruker-AXS, Madison, WI).
2.3. Preparation of Cu(S2CNEt2)
A colorless solution of [Cu(NH3)2]+ was produced as
described above. Using a syringe, a solution of NaS2C-
NEt2 Æ3H2O (7.04 g, 31.3 mmol) in 80 mL H2O was
added. A yellow-brown solid formed immediately. The
product was collected via filtration and was washed with
H2O, EtOH, and ether in succession and vacuum-dried.
It was recrystallized by dissolving in CHCl3 and precip-
itating with ether. The golden product was filtered,
washed with additional ether, and vacuum dried (3.47
g, 16.4 mmol, 65.3%). Other Cu(I) compounds were
prepared similarly using aqueous solutions of
NH4S2P(OEt)2, Na(CMIT), Na(BIm4), and Na3(C3N3-
S3)Æ9H2O. These insoluble products were not
recrystallized.
3. Results and discussion
Reduction of CuSO4 in aqueous ammonia solution
by hydroxylamine proceeded smoothly when nitrogen
was continuously purged directly through the solution.
The complete reduction was signaled by the disappear-
ance of the blue Cu(II) color. The resulting solution
was sufficiently alkaline that acid substrates, such as thi-
ols, were spontaneously deprotonated, producing the
desired products, according to Eq. (2). The products
were readily isolated and yields were good to excellent
(Table 1). The results of elemental analysis confirmed
the expected identity of the products.
The new complexes prepared include the Cu(I) salts
of CMIT, BIm4 [13], 2-aminothiazolate, and TTC
(C3N3S3). Copper (II) compounds have been reported
for the TTC ligand [14]. However, the two TTC com-
pounds reported herein are the first incorporating
Cu(I). Thus reaction of three equivalents of Cu(I) with
2.4. Preparation of [Cu2(MBT)2(DPPE)3]
1,2-Bis(diphenylphosphino)ethane (DPPE) (0.520 g,
1.31 mmol) was dissolved in 80 mL MeCN in a thick-
walled reaction tube at 85 ꢁC, and Cu(MBT) (0.200 g,

L.M. Nguyen et al. / Inorganica Chimica Acta 358 (2005) 1331–1336
1333
Table 1
Copper compounds prepared
Compound
CuSPh
Color
Yield, %
89.6
Element
% (theory)
% (expt)
pale yellow
Cu
C
36.79
41.73
2.92
36.10
41.38
2.89
H
CuSCy
cream
cream
orange
74.9
64.2
71.2
Cu
C
35.55
40.31
6.20
35.70
39.46
6.15
H
CuS-n-C12H25
Cu(MBT)
Cu
C
23.99
54.40
9.51
23.80
54.33
9.58
H
Cu
C
27.65
36.59
1.75
27.70
36.75
1.76
H
N
6.10
6.16
[Cu2(MBT)2(DPPE)3]
Cu(S2CNEt2)
cream
75.3
65.3
Cu
C
7.68
66.77
4.87
8.37
65.99
4.77
H
N
1.69
1.86
golden
Cu
C
30.00
28.35
4.76
29.46
28.54
4.75
H
N
6.61
6.54
Cu(S2P(OEt)2)
white
white
64.3
74.2
Cu
C
25.54
19.31
4.05
25.39
19.19
4.02
H
Cu(CMIT)Æ1/2H2O
Cu
C
34.04
19.30
2.70
33.22
18.53
2.42
H
N
22.51
22.54
Cu(CMIT)(PPh3)
Cu(CMIT)(PPh3)2
Cu(CMIT)(DPPE)1/2
Cu(BIm4)
white
white
white
white
white
white
tan
100
Cu
C
13.87
57.33
4.35
14.23
55.29
4.27
H
N
9.55
9.92
86.9
86.9
94.4
84.2
57.9
57.0
Cu
C
8.82
66.70
4.88
9.14
65.45
4.85
H
N
5.98
6.11
Cu
C
16.86
50.99
4.28
16.13
49.99
4.28
H
N
11.14
9.97
Cu
C
18.55
42.07
3.53
17.95
41.86
3.56
H
N
32.70
32.55
Cu(BIm4)(PPh3)
Cu(BIm4)(DPPE)1/2
Cu(2-NH-thiazole)
Cu
C
10.50
59.57
4.50
10.28
57.78
4.38
H
N
18.52
18.49
Cu
C
11.73
55.42
4.46
11.51
53.87
4.28
H
N
20.68
21.01
Cu
C
39.06
22.15
38.66
22.11
(continued on next page)

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L.M. Nguyen et al. / Inorganica Chimica Acta 358 (2005) 1331–1336
Table 1 (continued)
Compound
Color
Yield, %
44.8
Element
% (theory)
% (expt)
H
N
1.86
17.22
1.84
17.03
Cu2H(C3N3S3)ÆH2O
Cu3(C3N3S3)Æ3/2H2O
brick red
Cu
C
39.67
11.25
0.94
40.16
11.57
1.08
H
N
13.12
13.54
red brown
91.7
Cu
C
48.65
9.19
0.77
49.63
9.58
0.73
H
N
10.72
12.14
Na3C3N3S3 produced Cu3(C3N3S3)Æ1.5H2O and the
reaction of two equivalents of Cu(I) with Na3C3N3S3
produced Cu2H(C3N3S3)ÆH2O. The use of one equiva-
lent of Cu(I) per TTC ligand yielded an impure product,
which did not correspond to a discrete stoichiometry.
Proposed structures for the insoluble complexes of
the CMIT, BIm4, and 2-aminothiazolate anions are
shown in Chart 1. The structures of the TTC complexes
are likely to be significantly more complicated and there-
fore speculation is probably not particularly useful.
A
non-polymeric Cu(I) thiolate complex was
produced by reacting the 2-mercaptobenzothiazolate
compound Cu(MBT) with 1,2-bis(diphenylphosphino)-
ethane (DPPE) in pressurized acetonitrile or toluene.
This reaction produced a 2:3 Cu(MBT):DPPE complex
which was structurally characterized as the Et2O solvate
by using X-ray crystallography (Fig. 1). Crystallo-
Fig. 1. Molecular structure of [Cu2(MBT)2(DPPE)3]ÆEt2O. Thermal
ellipsoids shown at 50%. One of two independent molecules shown; the
solvent molecule omitted. Hydrogen atoms omitted for clarity.
Table 2
Crystal and structure refinement data for [Cu2(MBT)2(DPPE)3]ÆEt2O
Cu
S
Cu
N
Formula
Formula weight
T (K)
C96H90Cu2N2OP6S4
1728.84
100
C
S
Me
H
N
N
N
C
Me
H
˚
Cu
N
N
k (A)
0.71073
colorless block
triclinic
Crystal habit
Crystal system
Space group
S
Cu
N
N
S
C
ꢀ
P1ð#2Þ
Me
H
N
N
N
˚
a (A)
16.6420(10)
17.2710(11)
18.3365(11)
112.1901(11)
90.0859(9)
118.3840(10)
2
C
Me
H
˚
N
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
Z
S
N
Cu
N
3
˚
NH
HN
V (A )
4186.0(4)
1.372
0.773
Dcalc (g cmꢀ3
)
N
B
N
Cu
Absorption coefficient, l (mmꢀ1
Scan technique
F(000)
)
S
N
N
/ and x
1800
S
N
N
N
Cu
N
Crystal size, mm
Residuals:a R1; wR2
Goodness-of-fit
0.25 · 0.20 · 0.10
0.068; 0.147
1.128
NH
HN
N
Cu
N
Cu
S
h Range for data collection (ꢁ)
1.23–25.00
P
P
a
R = R1 = iFo| ꢀ |Fci/ jFoj
for
observed
1=2
data
only.
P
P
2
2
2
2
2
Rw ¼ wR2 ¼ f ½wðF o ꢀ F c Þ ꢁ= ½wðF o Þ ꢁg for all data.
Chart 1.

L.M. Nguyen et al. / Inorganica Chimica Acta 358 (2005) 1331–1336
1335
Table 3
Selected bond lengths and angles for [Cu2(MBT)2(DPPE)3]ÆEt2Oa
Cu(1)–P(1)
Cu(1)–P(2)
Cu(1)–P(3)
C(2)–C(7)
Cu(1)–S(1)
C(3)–C(4)
S(1)–C(1)
S(2)–C(1)
N(1)–C(1)
S(2)–C(3)
N(1)–C(2)
C(2)–C(3)
C(4)–C(5)
C(5)–C(6)
C(6)–C(7)
a
2.3313(15), 2.3296(16)
2.2865(17), 2.2825(16)
2.2820(14), 2.2789(14)
1.352(9), 1.332(10)
2.3104(17), 2.3086(17)
1.348(8), 1.328(10)
1.717(6), 1.702(7)
1.750(6), 1.759(7)
1.297(8), 1.298(7)
1.693(6), 1.699(6)
1.414(8), 1.414(9)
1.439(9), 1.441(9)
1.392(10), 1.396(9)
1.362(10), 1.362(10)
1.352(9), 1.332(10)
P(1)–Cu(1)–P(2)
P(1)–Cu(1)–P(3)
P(2)–Cu(1)–P(3)
P(1)–Cu(1)–S(1)
P(2)–Cu(1)–S(1)
P(3)–Cu(1)–S(1)
Cu(1)–S(1)–C(1)
S(1)–C(1)–S(2)
N(1)–C(1)–S(1)
N(1)–C(1)–S(2)
C(1)–S(2)–C(3)
C(1)–N(1)–C(2)
N(1)–C(2)–C(3)
C(2)–C(3)–S(2)
89.47(6), 89.44(6)
107.86(6), 107.91(6)
115.65(6), 115.67(6)
109.46(6), 108.99(6)
118.59(6), 118.82(6)
112.63(6), 112.70(6)
106.9(2), 107.2(2)
117.9(4), 117.8(3)
127.4(5), 128.1(6)
114.6(5), 114.2(5)
92.2(3), 92.3(3)
110.3(6), 110.6(6)
115.3(6), 115.5(6)
107.5(4), 107.2(5)
Data pairs represent independent half molecules. Numbering corresponds to molecule shown in Fig. 1.
graphic and structural data are shown in Tables 2 and 3,
respectively. Structurally characterized copper (I) thio-
lates bearing solubilizing ligand (such as phosphines or
pyridines) are fairly rare [3,4]. X-ray analysis revealed
two independent half molecules and an ether solvent
molecule. The molecular structure of [Cu2(MBT)2(DP-
PE)3]ÆEt2O is composed of two copper centers bridged
by a DPPE ligand. A chelating DPPE ligand is coordi-
nated to each copper. A MBT ligand is coordinated to
each copper only through the thiolate sulfur atom. This
dimeric arrangement is directly analogous to that found
for [Cu2I2(DPPE)3] [15] which features terminal iodide
rather than terminal thiolate. Somewhat similar is
[Cu3I3(DPPE)3(2-pyridylthiolate)] [16]. In the latter
structure, both terminal and bridging iodides and both
chelating and bridging DPPE ligands are present.
free of charge at www.ccdc.cam.ac.uk/conts/retriev-
ing.html [or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax:
(internat.) +44-1223/336-033; email: deposit@ccdc.cam.
ac.uk].
Acknowledgements
This research was supported in part by the National
Science Foundation (Grant No. CHE-9983374), the Ca-
mille and Henry Dreyfus Foundation (Grant No. TH-
99-010), and also a Howard Hughes Medical Institute
grant through the Undergraduate Biological Sciences
Education Program to the College of William and
Mary.
The Cu(BIm4) and Cu(CMIT) salts were also found to
coordinate phosphine ligands. When a suspension of
Cu(BIm4) was heated in acetonitrile solution containing
PPh3 or DPPE, the products [Cu(BIm4)(PPh3)] and [Cu
(BIm4)(DPPE)1/2] were collected. The addition of a single
P(III) ligand per Cu(I) center suggests that the BIm4
anion coordination can be lowered from four- to three-
coordinate. Similarly, [Cu(CMIT)(PPh3)] and [Cu
(CMIT)(DPPE)1/2] have been obtained. Further studies
of these new metal-organic networks are on-going.
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