Copper-selenium interactions: Influence of alkane spacer and halide anion in the synthesis of unusual polynuclear copper(I) complexes with bis(diphenylselenophosphinyl)alkanes

Article abstract of DOI:10.1021/ic034010n

The reactions of copper(I) halides with bis(diphenylselenophosphinyl)alkanes, namely Ph₂P(Se)-(CH₂)_n-P(Se)Ph₂ {n = 1-4}, in acetonitrile are described. The ligand 1,3-bis(diphenylselenophosphinyl)propane {dppp-Se,Se} with copper(I) bromide and copper(I) iodide formed two unusual infinite coordination polymers, namely {Cu₂Br₂(μ₂- dppp-Se-Se)₂}_n, 1, and {Cu₃I₃(μ₂-dppp-Se,Se) ₂}_n, 2. Selenium bridged dinuclear complexes, [Cu₂Br₂((μ₃-dppm-Se,Se)₂], 3, and [Cu₂I₂(dppm-Se,Se)₂], 4, were formed using 1,1-bis(diphenylselenophosphinyl)methane {dppm-Se,Se}. Similarly, 1,2-bis(diphenylselenophosphinyl)ethane {dppe-Se,Se} and 1,4-bis(diphenylselenophosphinyl)butane {dppb-Se,Se} formed complexes, Cu₂Br₂(dppe-Se,Se)₂, 5, and Cu₂I₂(dppb-Se,Se), 6. These have been characterized with the help of analytical data, infrared spectroscopy, and, for compounds 1-3, X-ray crystallography. Compound 2, {Cu₃I₃((dppp-Se,Se)₂}_n, has two dppp-Se,Se molecules coordinating to two copper(I) atoms of the dinuclear Cu(μ-I)₂Cu core in unidentate fashion, with two pendant Ph₂P(Se)- moieties in trans orientation, and one of these groups is coordinated to another copper(I) copper(l) iodide moiety, thus forming the repeat unit (A), -CuI(μ-dppp-Se,Se)-Cu(μ-I)₂Cu(μ-dppp-Se,Se)-. This repeat unit (A) combined with another unit, and this process continued and finally formed the infinite polymer 2. In this polymer, the mononuclear CuISe₂ and dinuclear Cu₂(μ-I)₂Se₂ cores have distorted trigonal planar geometries around Cu centers. The Cu(2)?Cu(2)* separation of 2.643(1) A? is less than twice the van der Waals radius of Cu, 2.80 A?. The structure of polymer 1 is similar to that of 2, except that it has only mononuclear trigonal planar CuBrSe₂ units bridged by Se atoms of dppp-Se,Se ligand, and the repeat unit is -CuBr(μ₂-dppp-Se,Se)CuBr(μ₂-dppp-Se,Se)-. The formation of zigzag one-dimensional copper(I) coordination polymers (1 and 2), with trigonal planar copper(I) centers, provides the first examples of this type in tertiary phosphine chalcogenide chemistry. In contrast, the decrease in methylene chain length, from -(CH₂)₃- to -(CH₂)-, resulted in chelation by the dppm-Se,Se ligand, forming CuBr(dppm-Se,Se), which dimerized via Se donor atoms and formed [Cu₂Br₂(μ₃-dppm-Se,Se)₂], 3. It has a relatively less common central kernel, Cu(μ-Se)₂Cu, and each Cu atom is further bonded to one terminal Br and one Se atoms, and the geometry around each Cu center is distorted tetrahedral (bond angles, ca. 101-121°).

Full text of DOI:10.1021/ic034010n

Inorg. Chem. 2003, 42, 4731−4737
Copper−Selenium Interactions: Influence of Alkane Spacer and Halide
Anion in the Synthesis of Unusual Polynuclear Copper(I) Complexes
with Bis(diphenylselenophosphinyl)alkanes†
,‡
,§
Tarlok S. Lobana,* Rimple,‡ Alfonso Castineiras,* and Peter Turner|
Department of Chemistry, Guru Nanak DeV UniVersity, Amritsar-143 005, India, Departamento de
Quimica Inorganica, Facultad de Farmacia, UniVersidad de Santiago, 15782- Santiago, Spain,
and School of Chemistry, Crystal Structure Analysis Facility, The UniVersity of Sydney,
N.S.W. 2006, Australia
Received January 7, 2003
The reactions of copper(I) halides with bis(diphenylselenophosphinyl)alkanes, namely Ph2P(Se)−(CH ) −P(Se)Ph2
2 n
{n ) 1−4}, in acetonitrile are described. The ligand 1,3-bis(diphenylselenophosphinyl)propane {dppp-Se,Se} with
copper(I) bromide and copper(I) iodide formed two unusual infinite coordination polymers, namely {Cu2Br2(µ2-
dppp-Se−Se)2}n, 1, and {Cu3I3(µ2-dppp-Se,Se)2}n, 2. Selenium bridged dinuclear complexes, [Cu2Br2((µ3-dppm-
Se,Se)2], 3, and [Cu2I2(dppm-Se,Se)2], 4, were formed using 1,1-bis(diphenylselenophosphinyl)methane {dppm-
Se,Se}. Similarly, 1,2-bis(diphenylselenophosphinyl)ethane {dppe-Se,Se} and 1,4-bis(diphenylselenophosphinyl)butane
{dppb-Se,Se} formed complexes, Cu Br2(dppe-Se,Se)2, 5, and Cu I (dppb-Se,Se), 6. These have been characterized
2
2 2
with the help of analytical data, infrared spectroscopy, and, for compounds 1−3, X-ray crystallography. Compound
2, {Cu3I3((dppp-Se,Se)2}n, has two dppp-Se,Se molecules coordinating to two copper(I) atoms of the dinuclear
Cu(µ-I)2Cu core in unidentate fashion, with two pendant Ph2P(Se)− moieties in trans orientation, and one of these
groups is coordinated to another copper(I) iodide moiety, thus forming the repeat unit (A), −CuI(µ-dppp-Se,Se)-
Cu(µ-I)2Cu(µ-dppp-Se,Se)−. This repeat unit (A) combined with another unit, and this process continued and finally
formed the infinite polymer 2. In this polymer, the mononuclear CuISe2 and dinuclear Cu2(µ-I)2Se2 cores have
distorted trigonal planar geometries around Cu centers. The Cu(2)‚‚‚Cu(2)* separation of 2.643(1) Å is less than
twice the van der Waals radius of Cu, 2.80 Å. The structure of polymer 1 is similar to that of 2, except that it has
only mononuclear trigonal planar CuBrSe2 units bridged by Se atoms of dppp-Se,Se ligand, and the repeat unit is
−CuBr(µ2-dppp-Se,Se)CuBr(µ2-dppp-Se,Se)−. The formation of zigzag one-dimensional copper(I) coordination
polymers (1 and 2), with trigonal planar copper(I) centers, provides the first examples of this type in tertiary phosphine
chalcogenide chemistry. In contrast, the decrease in methylene chain length, from −(CH ) − to −(CH )−, resulted
2 3
2
in chelation by the dppm-Se,Se ligand, forming CuBr(dppm-Se,Se), which dimerized via Se donor atoms and
formed [Cu2Br2(µ3-dppm-Se,Se)2], 3. It has a relatively less common central kernel, Cu(µ-Se)2Cu, and each Cu
atom is further bonded to one terminal Br and one Se atoms, and the geometry around each Cu center is distorted
tetrahedral (bond angles, ca. 101−121°).
Introduction
with anionic or neutral ligands, and make close Cu‚‚‚Cu
contacts (less than twice the van der Waals radius of Cu,
2.80 Å).1 These properties of CuI have led to the formation
of oligomers, and polymers of diverse coordination net-
works.2 The study of inorganic-organic coordination net-
works in the past decade has helped in developing new
materials, which exhibit conducting, catalytic, and magnetic
Copper(I) is an important metal ion with soft Lewis acid
character and has a strong tendency to form covalent bonds,
* To whom all correspondence should be addressed. E-mail:
tarlokslobana@yahoo.co.in (T.S.L.); qiac01@uscmail.usc.es (A.C.).
† Dedicated to my grandfather (late) Sardar Bhola Singh and grandmother
(late) Sardarni Bishan Kaur of Village Gado Majra, P.O. Dhakansu Kalan,
Rajpura, Patiala Punjab, India.
‡ Guru Nanak Dev University.
(1) Inorganic Chemistry: Principles of Structure and ReactiVity, 4th ed.;
Huheey, J. E., Keiter, E. A., Keiter, R. L., Eds.; Harper Collins College
Publishers: New York, 1993.
§ Universidad de Santiago.
| The University of Sydney.
10.1021/ic034010n CCC: $25.00 © 2003 American Chemical Society
Published on Web 06/19/2003
Inorganic Chemistry, Vol. 42, No. 15, 2003 4731

Lobana et al.
exchange properties.3-10a Further, metal-selenium inter-
actions gain significance from the point of view of their
potential to provide precursors for MOCVD materials.10b,c
Tertiary phosphines are known to form tetranuclear and
hexanuclear complexes, as well as nanoclusters,11-13 while
tertiary phosphine sulfides only formed monomeric, dimeric,
or trimeric complexes.14,15 While tertiary phosphine selenides
have been known for a long time, the structural chemistry
of their complexes has not been widely reported.14,15 For
instance, triphenylphosphine selenide (Ph3PSe) formed Se-
bonded mononuclear (Au),16 and halogen-bridged dinuclear
(Cu, Hg), complexes.17-19 The 1,1-bis(diphenylselenophos-
phinyl)methane{dppm-Se,Se} formed the first examples of
structurally characterized mononuclear chelate complexes in
tertiary phosphine selenide chemistry (Zn, Hg).20,21 The
reaction of dppm-Se,Se with a copper(I) salt, namely, copper-
(I) bromide, has formed a selenium bridged dinuclear
complex 3 (structure V), exhibiting behavior different from
that of the mononuclear Zn, Hg complexes.20,21
Interestingly, the increase in chain length, from -(CH2)-
to -(CH2)2-, involving reaction of 1,2-bis(diphenylseleno-
phosphinyl)ethane (dppe-Se,Se), with copper(I) chloride,
resulted in a chloro- and seleno-bridged dinuclear complex,
7, [Cu2(µ-Cl)2(µ-dppe-Se,Se)2] (structure I).22 The change
of anion from chloro to iodo formed an unusual coordination
polymer, 8, [Cu4I4{Ph2P(Se)-CH2-CH2-PPh2(Se)}2]n (struc-
ture II, only repeat unit shown; each pendant Ph2P(Se)-
group combined with other four Cu4I4 units, and the process
continued, finally resulting in the formation of an infinite
three-dimensional polymer).23 Thus, in the case of copper-
(I) halides, the change of anion and alkane chain length has
formed different products (7 and 8). A further increase in
chain length from -(CH2)2- to -(CH2)3- has formed novel
zigzag one-dimensional copper(I) coordination polymers,
[{Cu2Br2(dppp-Se,Se)2]n, 1 (structure III), and [{Cu3I3(dppp-
Se,Se)2]n, 2 (structure IV). In this paper, crystal structures
of novel polymers 1 and 2 and selenium bridged dinuclear
complex, [Cu2Br2(dppm-Se,Se)2], 3 (structure V), are de-
scribed. In addition, the complexes 4-6, with stoichiometries
similar to 3, 7, and 8, respectively, are also discussed.
(2) (a) Hanton, L. R.; Richardson, C.; Robinson, W. T.; Turnbull, J. M.
Chem. Commun. 2000, 2465. (b) Zhang, Q.-F.; Leung, W.-H.; Xin,
X. Q.; Fun, H. K. Inorg Chem. 2000, 39, 417. (c) Ahlrichs, R.;
Besinger, J.; Eichhoefer, A.; Fenske, D.; Gbureck, A. Angew. Chem.,
Int. Ed. 2000, 39, 3929. (d) Zhang, J.; Xiong, R. G.; Zuo, J. L.; You,
X. Z. Chem. Commun. 2000, 1495. (e) Zhang, J.; Xiong, R. G.; Zuo,
J. L.; Che, C. M.; You, X. Z. J. Chem. Soc., Dalton Trans. 2000,
2898. (f) Aakeroy, C. B.; Beatty, A. M.; Lorimer, K. R. J. Chem.
Soc., Dalton Trans. 2000, 3869. (g) Graham, P. M.; Pike, R. D.; Sabat,
M.; Bailey, R. D.; Pennington, W. T. Inorg Chem. 2000, 39, 5121.
(3) Fortin, D.; Drouin, M.; Harvey, P. D. Inorg. Chem. 2000, 39, 2758
and references cited therein.
(4) Carlucci, L.; Ciani, G.; Moret, M.; Proserpio, D. M.; Rizzato, S. Angew.
Chem., Int. Ed. 2000, 39, 1506.
(5) Robson, R.; Abrahams, B. F.; Batten, S. R.; Gable, R. W.; Hoskins,
B. F.; Liu, J. Supramolecular Architecture; American Chemical
Society: Washington, DC, 1992; Chapter 19.
Experimental Section
(6) Munakata, M.; Wu, L. P.; Kuroda-Sowa, T. AdV. Inorg. Chem. 1999,
General Materials and Techniques. The oxidation of bis-
(diphenylphosphino)alkanes, {Ph2P-(CH2)n-PPh2, n ) 1, dppm;
n ) 2, dppe; n ) 3, dppp; and n ) 4, dppb}, using Se metal in
benzene, formed corresponding selenides, Ph2P(Se)-(CH2)n-P(Se)-
Ph2.14 Copper(I) bromide and copper(I) iodide were prepared by
the reduction of CuSO4‚5H2O using SO2 in the presence of NaBr
or NaI in water.24 Bis(diphenylphosphino)methane and -propane
were procured from Sigma-Aldrich Ltd., and bis(diphenylphos-
phino)ethane and -butane were prepared as reported.14,15 The C, H
elemental analyses were obtained with a Carlo-Erba 1108 mi-
croanalyzer. The melting points were determined with a Gallenkamp
electrically heated apparatus. IR spectra were recorded using KBr
pellets on a Pye Unicam SP 3-300 or FTIR-NICOLET 320 Fourier
46, 173.
(7) Janiak, C. Angew. Chem., Int. Ed. Engl. 1997, 36, 1431.
(8) Mitzi, D. B. Prog. Inorg. Chem. 1999, 48, 1.
(9) Clearfield. A. Prog. Inorg. Chem. 1998, 47, 371.
(10) (a) Kingsborough, R. P.; Swager, T. M. Prog. Inorg. Chem. 1999,
48, 123. (b) Cheng, Y.; Emge, T. J.; Brennan, J. G. Inorg. Chem.
1996, 35, 7339. (c) Cheng, Y.; Emge, T. J.; Brennan, J. G. Inorg.
Chem. 1996, 35, 342.
(11) Marsich, M.; Nardin, G.; Randaccio, L. J. Am. Chem. Soc. 1973, 95,
4053.
(12) Benzman, S. A.; Churchill, M. R.; Osborn, J. A.; Wormold, J. J. Am.
Chem. Soc. 1971, 93, 2063.
(13) Tran, D. T. T.; Taylor, N. J.; Corrigan, J. F. Angew. Chem., Int. Ed.
2000, 39, 935 and references therein.
(14) Lobana, T. S. Prog. Inorg. Chem. 1989, 37, 495.
(15) Lobana, T. S. In The Chemistry of Organophosphorus Compounds;
Hartley, F. R., Ed.; John Wiley and Sons: Chichester, U.K., 1992;
Vol. 2, Chapter 8.
-1
transform infrared spectrophotometers in the 4000-200 (400 cm
(16) Hussain, M. S. J. Crystallogr. Spectrosc. Res. 1986, 16, 91.
(17) Lobana, T. S. ; Verma, R.; Mahajan, R.; Tiekink, E. R. T. Z.
Kristallogr.sNew. Cryst. Struct. 1999, 214, 513.
(18) Lobana, T. S.; Singh, A.; Kaur, M.; Castineiras, A. Proc. Indian Acad.
Sci., Chem. Sci. 2001, 113, 89.
latter) range.
[Cu2Br2{dppp-Se,Se}2]n, 1. To a solution of copper(I) bromide
(0.030 g, 0.210 mmol) in dry acetonitrile (20 mL) was added a
(19) Glasser, L. S. D.; Ingram, L.; King, M. G.; McQuillan, G. P. J. Chem.
Soc. 1969, 2501.
(20) Lobana, T. S.; Hundal, R.; Turner, P. J. Coord. Chem. 2001, 53, 301.
(21) Lobana, T. S.; Hundal, R.; Singh, A.; Sehdev, A.; Turner, P.;
Castineiras, A. J. Coord. Chem. 2002, 55, 353.
(22) Lobana, T. S.; Mahajan, R.; Castineiras, A. Transition Met. Chem.
2001, 26, 440.
(23) Lobana, T. S.; Hundal, G. J. Chem Soc., Dalton Trans. 2002, 2203.
(24) Brauer, G. Handbook of PreparatiVe Inorganic Chemistry, 2nd ed.;
Academic Press: New York, 1965; Vol. 2.
4732 Inorganic Chemistry, Vol. 42, No. 15, 2003

Copper-Selenium Interactions
Table 1. Crystallographic Data for Compounds 1-3
solution of dppp-Se,Se (0.060 g, 0.105 mmol) in acetonitrile (30
mL), and the mixture was stirred for 6 h and filtered. The product
was obtained on slow evaporation of the solution at room
temperature (brown, 0.090 g, 60%; mp 168-170 °C). Anal. Calcd
for C54H52Cu2Br2P4Se4: C, 45.4; H, 3.64. Found: C, 45.1; H, 3.70.
Crystals were grown from acetonitrile at room temperature. Main
IR peaks (cm-1): ν(P-Se), 520 (m); ν(P-C) , 1101 (m).
params
1
2
3
empirical formula C54H52Cu2-
Br2P4Se4
C54H52Cu3-
I3P4Se4
C54H50Cu2-
Br2N2P4Se4
1453.58
293(2)
molecular mass
temp, K
cryst syst
space group
a, Å
1427.58
293(2)
1712.00
293(1)
triclinic
P1h (No.2)
9.759(1)
13.728(1)
22.118(2)
97.40(1)
93.68(1)
110.57(1)
2732.1(4)
2
monoclinic
C2/c (No. 15)
37.352(5)
9.638(1)
17.729(2)
90
111.98(1)
90
5918.3(13)
4
monoclinic
P21/n (No.14)
12.221(2)
15.965(2)
14.204(2)
90
94.52(1)
90
2762.7(7)
2
[Cu3I3{dppp-Se,Se}2]n, 2. To a solution of copper(I) iodide
(0.040 g, 0.210 mmol) in dry acetonitrile (15 mL) was added a
solution of dppp-Se,Se (0.060 g, 0.105 mmol) in acetonitrile (30
mL), and the mixture was stirred for 6 h and filtered. The product
was obtained on slow evaporation of the solution at room
temperature (white, 0.070 g, 65%; mp 144-146°C). Anal. Calcd
for C54H52Cu3I3P4Se4: C, 37.9; H, 3.04. Found: C, 38.1; H, 3.11.
Crystals were grown from acetonitrile at room temperature. Main
IR peaks (cm-1): ν(P-Se), 532 (m), 525 (m); ν(P-C), 1104 (m).
[Cu2Br2(dppm-Se,Se)2]‚2CH3CN, 3. To a solution of copper(I)
bromide (0.014 g, 0.098 mmol) in dry acetonitrile (10 mL) was
added a solution of dppm-Se,Se (0.053 g, 0.099 mmol) in
acetonitrile (20 mL), and the mixture was stirred for 6 h and filtered.
The product was obtained on slow evaporation of the solution at
room temperature (yellow, 0.047 g, 71%; mp 190-195 °C). Anal.
Calcd for C54H50Br2Cu2N2P4Se4: C, 44.6; H, 3.44. Found: C, 44.8;
H, 3.41. Crystals were grown from acetonitrile at room temperature.
Main IR peaks (cm-1): ν(P-Se), 500 (sb); ν(P-C), 1102 (s).
[Cu2I2(dppm-Se,Se)2], 4. To a solution of copper(I) iodide (0.018
g, 0.094 mmol) in dry acetonitrile (10 mL) was added a solution
of dppm-Se,Se (0.025, 0.046 mmol) in acetonitrile (20 mL), and
the mixture was stirred for 4 h and filtered. The product was
obtained on slow evaporation of the solution at room temperature
(white, 0.048 g, 70%; mp 136-138 °C). Anal. Calcd for C50H44I2-
Cu2P4Se4: C, 41.0; H, 3.01. Found: C, 40.5; H, 2.99. Main IR
peaks (cm-1): ν(P-Se), 500 (sb); ν(P-C), 1105 (s).
[Cu2Br2(dppe-Se,Se)2], 5. To a solution of copper(I) bromide
(0.014 g, 0.098 mmol) in dry acetonitrile (10 mL) was added a
solution of dppe-Se,Se (0.050, 0.092 mmol) in acetonitrile (20 mL),
and the mixture was stirred for 4 h and filtered. The product was
obtained on slow evaporation of the solution at room temperature
(yellow, 0.050 g, 74%; mp 98-100 °C). Anal. Calcd for C52H48-
Br2Cu2P4Se4: C, 44.62; H, 3.43. Found: C, 44.64; H, 3.25. Main
IR peaks (cm-1): ν(P-Se), 535 (m); ν(P-C), 1140 (s).
[Cu2I2(dppb-Se,Se)], 6. To a solution of copper(I) iodide (0.026
g, 0.136 mmol) in dry acetonitrile (10 mL) was added a solution
of dppb-Se,Se (0.076 g, 0.13 mmol) in acetonitrile (20 mL), and
the mixture was stirred for 4 h and filtered. The product was
obtained on slow evaporation of the solution at room temperature
(white, 0.046 g, 70%; mp 142-145 °C). Anal. Calcd for C28H28I2-
Cu2P2Se2: C, 34.8; H, 2.90. Found: C, 35.4; H, 2.91. Main IR
peaks (cm-1): ν(P-Se), 526 (s), 503 (s); ν(P-C), 1070 (s).
Ligand Main IR Peaks (cm-1). ν(P-Se), L: dppm-Se,Se, 512
(s); dppe-Se,Se, 548 (s); dppp-Se,Se, 531 (s); dppb-Se,Se, 537 (s).
X-ray Crystallography. A brown prismatic crystal of compound
1 (or white compound 2; yellow compound 3) was mounted on a
glass fiber and used for data collection. Crystal data were collected
at 293(2) K using a Bruker SMART CCD 1000 diffractometer.
Graphite monochromated Mo KR radiation (λ ) 0.71073 Å) was
used throughout. The data were processed with SAINT25 and
corrected for absorption using SADABS (transmission factors:
1.000-0.669, 1; 0.512-0.352, 2; 1.000-0.289, 3).26 The structure
was solved by direct methods using the program SHELXS-97,27
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
Z
D
calcd, Mg/m3)
1.735
5.058
10422, 0.0596
1.921
5.236
6033, 0.0336
1.747
5.005
µ(Mo KR)/mm-1
no. unique
4708, 0.0902
reflns, Rint
final R indices
[I > 2σ(I)]
final indices
(all data)
R1 ) 0.0544
R1 ) 0. 0295
R1 ) 0.0516
wR2 ) 0.0770 wR2 ) 0.0759 wR2 ) 0.0891
R1 ) 0.0969
wR2 ) 0.1676 wR2 ) 0.0866 wR2 ) 0.1365
R1 ) 0.0653
R1 ) 0.1174
and refined by full-matrix least-squares techniques against F2 using
SHELXL-97.28 Positional and anisotropic atomic displacement
parameters were refined for all non-hydrogen atoms. Hydrogen
atoms were placed geometrically, and positional parameters were
refined using a riding model. Isotropic atomic displacement
parameters for hydogen atoms were constrained to be 1.2 times
those of the respective C atoms. Criteria of a satisfactory complete
analysis were the ratios of rms shift to standard deviation less than
0.01 and no significant features in final difference maps. Atomic
scattering factors were taken from “International Tables for X-ray
Crystallography”,29 while molecular graphics were taken from
ZORTEP30a (compound 2)/PLATON/SCHAKAL30bc (compounds
1 and 3).30 A summary of crystal data, experimental details, and
refinement results is listed in Table 1.
Results and Discussion
Synthesis and IR Spectroscopy. Scheme 1 shows the
formation of complexes of copper(I) halides. Copper(I)
bromide and copper(I) iodide reacted with 1,3-bis(diphen-
ylselenophosphinyl)propane (dppp-Se,Se) in 2:2 (bromide)
and 3:2 (iodide) mole ratios and yielded complexes of
stoichiometry Cu2Br2(dppp-Se,Se)2, 1, and Cu3I3(dppp-
Se,Se)2, 2, even though their mixing ratios were 2:1 (metal
to ligand). The dppm-Se,Se, however, reacted in 1:1 mole
ratio {and a 2:1 Cu/L ratio also formed the same product}
forming Cu2X2(dppm-Se,Se)2 (X ) Br, 3, and X ) I, 4). It
may be noted that copper(I) iodide reacted with 1,2-bis-
(26) Sheldrick, G. M. SADABS. Program for Empirical Absorption
Correction of Area Detector Data; University of Go¨ttingen: Go¨ttingen,
Germany, 1997.
(27) Sheldrick, G. M. Acta Crystallgr. 1990, A46, 467.
(28) Sheldrick, G. M. SHELXL-97. Program for the Refinement of Crystal
Structures; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(29) International Tables for X-ray Crystallography; Kluwer Academic
Publishers: Dordrecht, The Netherlands, 1995; Vol. C.
(30) (a) Zsolnai, L. ZORTEP. A Program for the Presentation of Thermal
Ellipsoids; University of Heidelberg: Heidelberg, Germany, 1997. (b)
Spek, A. L. PLATON. A Multipurpose Crystallographic Tool; Utrecht
University: Utrecht, The Netherlands, 2002. (c) Keller, E. SCHAKAL-
97. A Computer Program for the Graphic Representation of Molecular
and Crystallographic Models; University of Freiburg: Freiburg,
Germany, 1997.
(25) SMART and SAINT. Area Detector Control and Integration Software;
Bruker Analytical X-ray Instruments Inc.: Madison, WI, 1997.
Inorganic Chemistry, Vol. 42, No. 15, 2003 4733

Lobana et al.
Scheme 1a
at 532 (m), 525 (m) cm-1. Compound 3 showed a broad
unresolved ν(P-Se) peak at 500 cm-1, and the same behavior
was shown by compound 4. Compound 5 showed only one
ν(P-Se) peak at 535 cm-1 with a shift of 13 cm-1. Finally,
compound 6 showed two peaks at 526 (s), 503 (s) cm-1.
The IR spectral trends of diagnostic ν(P-Se) peaks are
supported by the crystal structures of compounds 1-3 (vide
infra). X-ray crystallography has confirmed two types of PSe
groups for compounds 2 and 3 and only one type for
compound 1. The IR spectrum of 4 is similar to that of 3; of
5, it is similar to that of 7,22 and of 6, it is similar to that of
compound 8.23 Due to poor solubility of 1-6, solution phase
studies such as recording of NMR spectrum could not be
pursued.
Structures of Polymers 1 and 2. Figures 1 and 2 show
parts of polymers 1 and 2 along with numbering scheme.
The selected bond lengths and bond angles for all three
complexes (1-3) are listed in Table 2. The moiety Cu3I3-
(dppp-Se,Se)2 of polymer 2 has two dppp-Se,Se molecules
coordinating to two CuI centers of the dinuclear Cu(µ-I)2Cu
core, in unidentate fashion with two pendant Ph2P(Se)-
groups in trans orientations, and one of these two groups is
coordinated to another CuI center, thus forming the repeat
unit (A), -CuI(µ-dppp-Se,Se)Cu(µ-I)2Cu(µ-dppp-Se,Se)-
(structure IV). This repeat unit (A) with one Ph2P(Se)-
pendant group combined with another unit, and the process
continued and finally resulted in the formation of the infinite
polymer, 2. Interestingly, the increase in chain length from
-(CH2)2- to -(CH2)3- has formed a new zigzag polymer
2 instead of three-dimensional polymer of type 8.23 This
a The following synthetic conditions apply: (i) L ) dppm-Se,Se, X )
Br (3), I(4); (ii) L ) dppe-Se,Se, X ) Br(5), Cl (7); (iii) L ) dppb-Se,Se,
X ) I (6), L ) dppe-Se,Se, X ) I (8); (iv) L ) dppp-Se,Se, X ) Br (1);
(v) L ) dppp-Se,Se, X ) I (2).
(diphenylselenophosphinyl)ethane in a 2:1 ratio forming
infinite polymer 8, {Cu4I4(dppe-Se,Se)2}n,23 even though their
mixing ratio was 1:1. However, dppe-Se,Se reacted with
copper(I) chloride in a 1:1 ratio forming dimer 7,22 and also,
it reacted in the same ratio with copper(I) bromide (com-
pound 5) in conformity with their 1:1 mixing ratios. The
ligand 1,4-bis(diphenylselenophosphinyl)butane with cop-
per(I) iodide also reacted in 2:1 mole ratio, irrespective of
their mixing ratios, and this behavior is similar to that of
dppe-Se,Se (compound 8). Thus, the formation of dinuclear
or polynuclear complexes is being governed not by the
mixing ratios of the reactants, but rather by the type of the
anion, and the alkane chain length connecting -Ph2P(Se)-
groups. Recently, dppm-Se,Se was observed to form only
monomeric compounds, e.g., with Zn and Hg.20,21
The IR spectrum of dppp-Se,Se showed a strong peak due
to ν(P-Se) at 531 cm-1; in polymer 1, this peak shifted to
520 (m), and in 2, it splits into a closely lying pair of peaks
Figure 1. Part of the polymer [Cu2Br2{Ph2P(Se)-(CH2)3-P(Se)Ph2}2]n (1) along with numbering scheme.
4734 Inorganic Chemistry, Vol. 42, No. 15, 2003

Copper-Selenium Interactions
Table 2. Bond Lengths (Å) and Angles (deg) for Compounds 1-3
Compound 1
Cu(1)-Se(2)
Cu(1)-Se(1)
Cu(1)-Br(1)
Cu(1)‚‚‚Cu(2)
Cu(2)-Se(3)
Cu(2)-Br(2)
2. 361(1)
2. 429(1)
2. 380(2)
7.773(2)
2. 341(2)
2. 369(2)
Cu(2)-Se(4)*1a
Se(4)-Cu(2)*2
Se(1)-P(1)
2. 370(1)
2. 370(1)
2. 133(3)
2. 165(3)
2. 144(2)
2. 142(3)
Se(2)-P(2)
Se(3)-P(3)
Se(4)-P(4)
Se(2)-Cu(1)-Br(1)
Se(2)-Cu(1)-Se(1)
Br(1)-Cu(1)-Se(1)
Se(3)-Cu(2)-Br(2)
132.35(6) Br(2)-Cu(2)-Se(4)*1 105.52(6)
123.57(6) P(1)-Se(1)-Cu(1)
103.92(5) P(2)-Se(2)-Cu(1)
127.53(6) P(3)-Se(3)-Cu(2)
102.16(8)
100.76(8)
99.95(8)
Se(3)-Cu(2)-Se(4)*1 126.86(6) P(4)-Se(4)-Cu(2)*2
113.33(8)
Compound 2
Cu(1)-Se(1)
Cu(1)-Se(1)*3
Cu(1)-I(1)
Cu(2)-Se(2)
Cu(2)-I(2)*4
Cu(2)‚‚‚Cu(2)*4
2. 398(1)
2. 398(1)
2. 502(1)
2. 351(1)
2. 540(1)
2. 643(1)
Cu(2)-I(2)
Cu(2)*4-I(2)
I(2)‚‚‚I(2)*4
Se(2)-P(2)
Se(1)-P(1)
2. 615(1)
2. 540(1)
4. 426(1)
2.149(1)
2.147(1)
Se(1)-Cu(1)-Se(1)*3
Se(1)-Cu(1)-I(1)
Se(1)*3-Cu(1)-I(1)
Se(2)-Cu(2)-I(2)*4
P(2)-Se(2)-Cu(2)
96. 96(4) Se(2)-Cu(2)-I(2)
131. 52(2) I(2)-Cu(2)-I(2)*4
107.70(3)
118.33(3)
131. 52(2) Se(2)-Cu(2)-Cu(2)*4 165. 08(3)
133. 83(3) Cu(2)*4-I(2)-Cu(2)
106.16(4) P(1)-Se(1)-Cu(1)
61.67(3)
107. 04(4)
Figure 2. Part of the polymer [Cu3I3{Ph2P(Se)-(CH2)3-P(Se)Ph2}2]n (2)
Compound 3
along with numbering scheme.
Cu(1)-Br(1)
Cu(1)-Se(2)
Cu(1)-Se(1)*5
Cu(1)-Se(1)
Cu(1)‚‚‚Cu(1)*5
2. 397(2)
2. 416(2)
2. 507(2)
2.532(2)
3.182(3)
Se(1)‚‚‚Se(1)*5
Se(1)-P(1)
3.907(2)
2.150(3)
2.130(3)
2.507(2)
polymer 2 contains mononuclear (CuISe2) and dinuclear
{Cu2(µ-I)2Se2} cores. The geometry around each Cu center
is distorted trigonal planar {Se(1)-Cu(1)-Se(1), 96.96°,
Se(1)-Cu(1)-I(1), 131.52°, Se(1)-Cu(1)-I(1), 131.52°;
Se(2)-Cu(2)-I(2), 133.83°, Se(2)-Cu(2)-I(2), 107.70°, and
I(2)-Cu(2)-I(2), 118.33°} (Table 2). The plane defined by
Cu(1), Se(1), Se(1), and I(1) atoms formed an angle of 63.86°
with the plane defined by Cu(2), Se(2), I(2), and I(2) atoms.
The angles subtended at I(2) and I(2) atoms are acute
{Cu(2)-I(2)-Cu(2), 61.67°}.
Se(2)-P(2)
Se(1)-Cu(1)*5
Se(2)-Cu(1)-Br(1)
105.98(6) Br(1)-Cu(1)-Se(1)
120.35(7)
78.32(6)
100.00(8)
103.58(8)
103.78(8)
Se(2)-Cu(1)-Se(1)*5 111.64(6) Cu(1)*5-Se(1)-Cu(1)
Br(1)-Cu(1)-Se(1)*5 107.72(6) P(1)-Se(1)-Cu(1)*5
Se(2)-Cu(1)-Se(1)
109.46(6) P(1)-Se(1)-Cu(1)
Se(1)*5-Cu(1)-Se(1) 101.68(6) P(2)-Se(2)-Cu(1)
a Symmetry transformations used to generate equivalent atoms: *1 ) x
+ 1, y + 1, z; *2 ) x - 1, y - 1, z; *3 ) -x, y, -z + 1/2; *4 ) -x + 1/2,
-y + /2, -z + 1; *5 ) -x + 1, -y, -z + 1.
3
comparable with the literature values,17,18,23 and both of these
are shorter than the sum of the covalent radii of P and Se
atoms (2.27 Å).1 These distances indicate a weakening of
P-Se bonds upon complex formation, a fact not established
by IR spectroscopy.
The Cu(2)‚‚‚Cu(2) separation of 2.643(1) Å is less than
twice the van der Waals radius of Cu, 2.80 Å.1 This distance
is longer than that observed in polymer 8 [Cu‚‚‚Cu, 2.495
Å],23 comparable with that in the nanocluster Hg15Cu20S25-
(n-Pr3P)18 (Cu‚‚‚Cu, 2.54 Å)13 but shorter than that observed
in the dinuclear compound 7 (Cu‚‚‚Cu, 3.320 Å).18 In the
dinuclear Cu2(µ-I)2Se2 core, the Cu(2)-I(2) and Cu(2)-I(2)
distances {2.615(1) and 2.540(1) Å, respectively} reveal that
the central Cu(µ-I)2Cu core forms a parallelogram. The
terminal Cu(1)-I(1) bond distance of 2.502(1) Å observed
in the mononuclear CuISe2 core is shorter than the bridging
Cu-I distances. These Cu-I bonds have lengths less than
the sum of the radii of the Cu+and I- (2.97 Å).1
In polymer 1, dppp-Se,Se also acts as a bridging bidentate
ligand forming the repeat unit (B), -CuBr(µ-dppp-Se,Se)-
CuBr(µ-dppp-Se,Se)- (structure III), with one pendant
P(Se)Ph2 moiety. This repeat unit (B) combined with another
repeat unit via the Se donor atom of the pendant P(Se)Ph2
moiety, and this process continued and finally formed the
infinite polymer 1. There is only one type of mononuclear
CuBrSe2 core, and the geometry around each CuI center is
distorted trigonal planar {Se(2)-Cu(1)-Br(1), 132.35°, Se-
(2)-Cu(1)-Se(1), 123.57°, Br(1)-Cu(1)-Se(1) 103.92°}.
The planes defined by Se(1), Se(2), Br(1), Cu(1) and Se(3),
Se(4), Br(2), Cu(2) make an angle of 76.09°. In this polymer,
there is no close Cu‚‚‚Cu distance {Cu(1)‚‚‚Cu(2), 7.773(2)
Å} unlike that in 2 (vide supra). The Cu(1)-Br(1) bond
distance, 2.380(2) Å, which is much less than the sum of
the radii of Cu+ and Br- (2.73 Å),1 shows the formation of
a strong bond.
In polymer 2, the Cu-Se distances of the mononuclear
CuSe2I core are equal to {2.340(1) Å} but longer than the
Cu(2)-Se(2) distance (2.351(1) Å) of the dinuclear Cu(µ-
I)2Cu core. Thus, the binding of two iodine atoms to one
Cu atom shortens the Cu-Se bond distance and lengthens
Cu-I distances while the reverse is true when two Se atoms
bind to one Cu center. These Cu-Se bonds have lengths
less than the sum of the radii of Cu+ and Se2- ions (2.75
Å)1 but are comparable to similar Cu-Se bonds.17,18,23 As
expected, the P(1)-Se(1) bond distance is shorter {2.147-
(1) Å} than the P(2)-Se(2) bond distance {2.149(1) Å} but
As noted, polymer 1 has only one mononuclear repeating
core while polymer 2 has both mono- and dinuclear repeating
Inorganic Chemistry, Vol. 42, No. 15, 2003 4735

Lobana et al.
bridged dinuclear complex, [Cu2Cl2(µ3-dppm-S,S)2].31 How-
ever, in the unit cell two molecules of monomeric [CuCl(µ3-
dppm-S,S)] and one molecule of dimeric [Cu2Cl2(µ3-dppm-
S,S)2] were present unlike only dimeric units in the present
case. The large size of Br and Se might be responsible for
this apparent difference.
Each copper of dimer 3 is bonded to one Br, one terminal
Se, and two bridging Se donor atoms. The geometry around
each Cu center is distorted tetrahedral with bond angles in
the range ca. 101-120° {Se(1)-Cu-Se(1)* being shortest
and Br(1)-Cu(1)-Se(1) being the largest bond angles}. The
terminal Cu(1)-Se(2) bond distance of 2.416(2) Å is less
than the bridging Cu(1)-Se(1) and Cu(1)-Se(1)* distances
{2.532(2), 2.507(2) Å}. This shows that the Cu-Se bonds
are somewhat weak when Se is acting as a bridging atom.
The terminal Cu-Se bond length is similar to that observed
in 1 and 2, while the bridging Cu-Se bond length is similar
to that observed in 8 {2.550(2), 2.706(2) Å}.23 The Cu-Br
bond distance is 2.397(2) Å which shows the formation of
a strong bond similar to that observed in polymer 1. The
bridging Se leads to a long P(1)-Se(1) bond length {2.150-
(3) Å} versus the terminally bonded Se atom {2.130(3) Å}.
These P-Se distances are comparable with 1 and 2 and with
similar distances observed in the literature.17,18,23
In the central Cu2Se2 kernel, the Cu(1)‚‚‚Cu(1)* distance
is 3.182(3) Å which is more than twice the van der Waals
radius of Cu, 2.80 Å, indicating a lack of metal-metal
interaction.1 This Cu(1)‚‚‚Cu(1)* separation is more than that
observed in polymer 2 but less than that observed in the
chloro-bridged dimer 7 {Cu‚‚‚Cu, 3.20 Å}.22 The Se(1)‚‚‚
Se(1)* bond distance of 3.907(2) Å is more than twice the
van der Waals radius of Se, 3.80 Å, which rules out any
Se‚‚‚Se interaction. The Cu-Se-Cu* bond angle of 78.32-
(6)° and Se(1)-Cu-Se(1)* angle of 101.68° are similar to
those observed in analogous Cu(µ-S)2Cu bridges.36 The Cu-
(µ-Se)2Cu core is the first kernel reported in metal-tertiary
phosphine selenide chemistry,14,15,17-23 though Cu(µ-Se)Cu
with one Se bridging the two Cu atoms was reported
recently.23
Figure 3. Dinuclear [Cu2Br2{Ph2P(Se)-CH2-P(Se)Ph2}2]n (3) along with
numbering scheme.
cores. The behavior of mononuclear cores of both in respect
to bond distances is not the same. While the Cu-Se bond
distances of the CuSe2I core of 2 are equal, the same is not
true of the CuSe2Br core of 1 which shows different bond
distances {Cu(1)-Se(1), 2.429(1) Å, Cu(1)-Se(2), 2.360-
(1) Å}. Further analysis of Cu-Se and Cu-Br bond
distances reveals interesting information that the two adjacent
CuSe2Br cores of 1 have unequal bond lengths, and the
alternate units have equal bond lengths. The Cu-Se bond
distances of the adjacent Cu(2)Se2Br core {Cu(2)-Se(3),
2.341(2) Å, Cu(2)-Se(4)*, 2.370(1) Å} are shorter than
those of Cu(1)Se2Br core, as listed. In addition, the Cu-Br
bond distances are also different for the two adjacent cores
{Cu(1)-Br(1), 2.380(2) Å, Cu(2)-Br(2), 2.369(2) Å}. In
short, the Cu(1)Se2Br core has long bond distances while
the other core Cu(2)Se2Br has short distances. These Cu-
Se bond distances are comparable to those of polymer 2 and
other similar Cu-Se bonds.17,18,23
The P(1)-Se(1) bond distance of 2.133(3) Å is the shortest
among the four P-Se distances listed in Table 2 for polymer
1, and it is in line with the longest Cu(1)-Se(1) bond
distance. The trends in other P-Se distances are in near
conformity with the Cu-Se distances. The Cu-Se-P angles
at Se are not same in both the polymers. In 2, these angles
are nearly same {ca. 106-107°} while there is large variation
in Cu-Se-P angles in polymer 1 {ca. 99-113°} (Table 2).
The variations of bond angles and bond distances as
discussed might be the consequence of the electronic and
steric requirements of 1 which are different in the two cases.
Structure of Selenuim-Bridged Dinuclear Complex 3.
Figure 3 shows the structure of compound 3 along with a
numbering scheme. In this compound, the dppm-Se,Se acted
as a chelating ligand forming a monomeric species, CuBr-
(µ2-dppm-Se,Se), which dimerized via the Se atom of each
unit to yield [Cu2Br2(µ3-dppm-Se,Se)2]. Interestingly, the
sulfur analogue dppm-S,S also formed a similar sulfur-
A further comparison with tertiary phosphine sulfide
analogues may be appropriate. The ligand Ph2P(S)-CH2-
P(S)Ph2 (dppm-S,S) having one -CH2- group connecting
Ph2P(S)- groups essentially acts as a chelating ligand
forming six-membered rings,31 and in this respect, dppm-
Se,Se behaved in a similar way (3). In contrast, Ph2P(S)-
(CH2)2-P(S)Ph2 (dppe-S,S) acts both as a chelating (Hg,
Pd)32,33 ligand with seven-membered metallacyclic rings and
as a bridging ligand in the case of Cu34 and Te(IV).35 As
noted, dppm-Se,Se has formed monomeric chelate complexes
(e.g., Zn, Hg),20,21 and in 3, it dimerized as already discussed.
(31) Ainscough, E. W.; Bergen, H. A.; Brodie, A. M. J. Chem. Soc., Dalton
Trans. 1976, 1649.
(32) Lobana, T. S.; Sandhu, M. K.; Liddell, M. J.; Tiekink, E. R. T. J.
Chem. Soc., Dalton Trans. 1990, 691.
(33) Lobana, T. S.; Verma, R.; Singh, A.; Shikha, M.; Castineiras, A.
Polyhedron 2002, 21, 205.
(34) Brown, K. L. Acta Crystallogr. 1979, B35, 462.
(35) Novosad, J.; Tornroos, K. W.; Necas, M.; Slawin, A. M. Z.; Woollins,
J. D.; Husebye, S. Polyhedron 1999, 18, 2861.
(36) Lobana, T. S.; Castineiras, A. Polyhedron 2002, 21, 1603.
4736 Inorganic Chemistry, Vol. 42, No. 15, 2003

Copper-Selenium Interactions
Also, Ph2P(Se)-(CH2)2-P(Se)Ph2 (dppe-Se,Se) has formed
complexes with only the bridging mode of the ligand
(Cu).22,23 Polymers 1 and 2 formed with Ph2P(Se)-(CH2)3-
P(Se)Ph2 (dppp-Se,Se) are the only complexes structurally
characterized having an alkane spacer, -(CH2)3-. There is
no complex of Ph2P(S)-(CH2)3-P(S)Ph2 (dppp-S,S) with
any metal which is structurally characterized, and thus, no
comparison could be made.14,15
In summary, it is concluded here that both the chain length
connecting -P(Se)Ph2 groups and anion play an important
role in determining the type of the compound formation. The
formation of the zigzag one-dimensional copper(I) coordina-
tion polymers 1 and 2 with trigonal planar copper(I) centers
are the first examples in tertiary phosphine chalcogenide
chemistry.14,15,17-23 Also, 3 shows the first Se-bridging Cu-
(µ-Se)2Cu kernel ever reported in metal-phosphine chalco-
genide chemistry.14,15,17-23 The poor quality of crystals of
4-6 prevented their structure determination by X-ray
crystallography, and structures similar to those of 3, 7, and
8, respectively, are sugessted.
Acknowledgment. One of us (Rimple) thanks the uni-
versity for research facilities. Financial assistance from CSIR-
[01 (1444)/97/EMRsII] is gratefully acknowledged.
Supporting Information Available: X-ray crystal data in CIF
format {CCDC numbers 200946-200948}. This material is avail-
able free of charge via the Internet at http://pubs.acs.org.
IC034010N
Inorganic Chemistry, Vol. 42, No. 15, 2003 4737