Copper(I) complexes of bis(2-(diphenylphosphino)phenyl) ether: Synthesis, reactivity, and theoretical calculations

Article abstract of DOI:10.1021/ic7005474

The tricoordinated cationic Cu^I complex [Cu(κ²- P,P′-DPEphos)(κ¹-P-DPEphos)][BF₄] (1) (DPEphos = bis(2-(diphenylphosphino)phenyl) ether) containing a dangling phosphorus center was synthesized from the reaction

Full text of DOI:10.1021/ic7005474

Inorg. Chem. 2007, 46, 6535−6541
Copper(I) Complexes of Bis(2-(diphenylphosphino)phenyl) Ether:
Synthesis, Reactivity, and Theoretical Calculations
Ramalingam Venkateswaran,† Maravanji S. Balakrishna,*,† Shaikh M. Mobin,‡ and
Heikki M. Tuononen§
Phosphorus Laboratory, Department of Chemistry and National Single Crystal X-ray Diffraction
Facility, Indian Institute of Technology, Bombay, Mumbai 400 076, India, and Department of
Chemistry, UniVersity of JyVa¨skyla¨, P.O. Box 35, JyVa¨skyla¨ FI-40014, Finland
Received March 22, 2007
The tricoordinated cationic CuI complex [Cu( 2-P,P 1-P-DPEphos)][BF4] (1) (DPEphos
κ ′-DPEphos)(κ ) bis(2-
(diphenylphosphino)phenyl) ether) containing a dangling phosphorus center was synthesized from the reaction of
[Cu(CH3CN)4][BF4] with DPEphos in a 1:2 molar ratio in dichloromethane. When complex 1 is treated with MnO2,
elemental sulfur, or selenium, the uncoordinated phosphorus atom undergoes oxidation to form a P
in the formation of complexes of the type [Cu( -DPEphos)(
2-P,P 2-P,E-DPEphos-E)][BF4] (2, E
4, E Se) containing a Cu -DPEphos)(
E bond. The zigzag polymeric CuI complex [Cu( 2-P,P
(5) was prepared by the reaction of [Cu(CH3CN)4][BF4] with DPEphos and 4,4 -bipyridine in an equimolar ratio. The
d
E bond resulting
O; 3, E S;
-4,4 -bpy)]n[BF4]n
κ
′
κ
)
)
)
−
κ
′
µ
′
′
stereochemical influences of DPEphos on its coordination behavior are examined by density functional theory
calculations.
Introduction
partially functionalized or oxidized ligands are less extensive.
However, transition-metal complexes containing a variety
of dangling phosphorus ligands have been extensively
studied.7 Selective oxidation of one of the phosphorus centers
in a bis(phosphine) using H2O2, MnO2, S, and Se is very
difficult, since it always leads to the formation of a mixture
of products, which complicates the isolation of the desired
product. Often, Staudinger reactions of bis(phosphine)s with
organic azides afford partially oxidized monophosphineimine
derivatives in moderate yield.8-11 Furthermore, it is more
challenging to synthesize a mixed-ligand complex consisting
of a bis(phosphine) and its mono-oxide derivative. In the
past decade, there have been several reports on the DPEphos
ligand (DPEphos ) bis(2-(diphenylphosphino)phenyl) ether)
Mixed-ligand CuI complexes are of interest because of
their luminescent properties, which find applications in the
construction of sensors and organic light emitting diodes.1-4
In recent years, there have been several reports on mixed-
ligand complexes containing both bis(phosphines) and poly-
pyridyls.5,6 These complexes have been easily synthesized
by treating bis(phosphines) with appropriate metal precursors
followed by the addition of N-donor ligands. The mixed-
ligand systems consisting of both bis(phosphines) and
* To whom correspondence should be addressed. E-mail: krishna@
chem.iitb.ac.in. Fax: +91-22-5172-3480.
† Phosphorus Laboratory, Indian Institute of Technology.
‡ National Single Crystal X-ray Diffraction Facility, Indian Institute of
Technology.
(7) (a) Balakrishna, M. S.; Ramaswamy, K.; Abhyankar, R. M. J.
Organomet. Chem. 1998, 560, 131-136. (b) Balakrishna, M. S.; Klein,
R.; Uhlenbrock, S.; Pinkerton, A. A.; Cavell, R. G. Inorg. Chem. 1993,
32, 5676-5681. (c) Burrows, A. D.; Mahon, M. F.; Nolan, S. P.;
Varrone, M. Inorg. Chem. 2003, 42, 7227-7238. (d) Wong, E. H.;
Prasad, L.; Gabe, E. J.; Bradley, F. C. J. Organomet. Chem. 1982,
236, 321-331. (e) Bradley, F. C.; Wong, E. H.; Gabe, E. J.; Lee, F.
L.; Lepage, Y. Polyhedron 1987, 6, 1103-1110.
§ University of Jyva¨skyla¨.
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Hu, Z. Appl. Phys. Lett. 2006, 88, 213508.
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J.-F.; Zhou, Z.; Wegh, R. T.; Welter, R. AdV. Mater. 2006, 18, 1313-
1316.
(3) Zhang, Q.; Zhou, Q.; Cheng, Y.; Wang, L.; Ma, D.; Jing, X.; Wang,
F. AdV. Funct. Mater. 2006, 16, 1203-1208.
(4) Zhang, Q.; Zhou, Q.; Cheng, Y.; Wang, L.; Ma, D.; Jing, X.; Wang,
F. AdV. Mater. (Weinheim, Ger.) 2004, 16, 432-436.
(5) Kuang, S.-M.; Cuttell, D. G.; McMillin, D. R.; Fanwick, P. E.; Walton,
R. A. Inorg. Chem. 2002, 41, 3313-3322.
(6) Cuttell, D. G.; Kuang, S.-M.; Fanwick, P. E.; McMillin, D. R.; Walton,
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Chem. 2007, 1930-1938.
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10.1021/ic7005474 CCC: $37.00
Published on Web 07/07/2007
© 2007 American Chemical Society
Inorganic Chemistry, Vol. 46, No. 16, 2007 6535

Venkateswaran et al.
Scheme 1. Synthesis of [Cu(κ2-P,P-DPEphos)(κ1-P-DPEphos)][BF4]
(1) and [Cu(κ2-P,P-DPEphos)(µ-4,4′-bpy)]n[BF4]n (5). Reactions of 1
with MnO2, S, and Se
Figure 1. Molecular structure of complex 1. Hydrogen atoms have been
omitted for clarity.
because of its potential applications in various organic
transformation reactions.12-14 Recently, we reported the
synthesis of several ruthenium(II) complexes of DPEphos
and its iminophosphorane derivative.10,15 The DPEphos ligand
showed several interesting coordination modes with a RuII
center depending upon the bulkiness of other N, S, and P
donors. This investigation was aimed at exploring the
reactivity of 3d metals such as CuI toward DPEphos with
considerable stereochemical influences, which often produce
coordinatively unsaturated yet moderately stable 16-electron
complexes with wide catalytic applications. As a part of our
research interest,16 here we describe the reactions of [Cu-
(CH3CN)4][BF4] with DPEphos, which lead to the formation
of interesting tricoordinated CuI derivatives containing a free
PIII center that can be readily oxidized with chalcogens. The
stereochemical influences of DPEphos on its coordination
behavior are substantiated by density functional theory (DFT)
calculations.
Results and Discussion
Figure 2. Molecular structure of complex 2. Hydrogen atoms have been
omitted for clarity.
The treatment of [Cu(CH3CN)4][BF4] with DPEphos in
dichloromethane in a 1:2 molar ratio affords the mononuclear
complex [Cu(κ2-P,P′-DPEphos)(κ1-P-DPEphos)][BF4] (1) in
good yield. The mass spectrum of the complex 1 shows the
molecular ion peak at m/z 1139.21. The 31P{1H} NMR
spectrum of 1 shows a single resonance at -15.5 ppm
indicating all four phosphorus centers are equivalent. In
contrast to this observation, the solid-state structure of
complex 1 revealed that the CuI center is tricoordinated and
one of the phosphorus centers is left uncoordinated (Scheme
1). The 31P NMR spectrum suggests the presence of fluxional
behavior in the solution state, since the signal broadens at
-50 °C. The analogous reaction of [Cu(CH3CN)4][BF4] with
1,2-bis(diphenylphosphino)ethane (dppe) yielded [Cu(dppe)2]-
[BF4], in which CuI is tetracoordinated with tetrahedral
geometry.17 This difference in the reactivity may be due to
the large-bite diphenyl ether backbone and the overall
bulkiness of the DPEphos ligand, which probably prevents
the fourth PIII center from establishing a Cu-P bond.
Interestingly, the uncoordinated phosphorus center in
complex 1 on treatment with MnO2, S, or Se undergoes
oxidation to form the corresponding complexes 2-4, which
are identified from the mass spectra, where the molecular
ion peaks appear at m/z 1155.34, 1171.04, and 1219.25,
respectively. The 31P NMR spectrum of complex 2 shows
(12) Kranenburg, M.; van der Burgt, Y. E. M.; Kamer, P. C. J.; van
Leeuwen, P. W. N. M.; Goubitz, K.; Fraanje, J. Organometallics 1995,
14, 3081-3089.
(13) Kamer, P. C. J.; van Leeuwen, P. W. N. M.; Reek, J. N. H. Acc. Chem.
Res. 2001, 34, 895-904.
(14) van Leeuwen, P. W. N. M.; Kamer, P. C. J.; Reek, J. N. H.; Dierkes,
P. Chem. ReV. 2000, 100, 2741-2769.
(15) Venkateswaran, R.; Mague, J. T.; Balakrishna, M. S. Inorg. Chem.
2007, 46, 809-817.
(16) (a) Ganesamoorthy, C.; Balakrishna, M. S.; George, P. P.; Mague, J.
T. Inorg. Chem. 2007, 46, 848-858. (b) Punji, B.; Mague, J. T.;
Balakrishna, M. S. Inorg. Chem. 2006, 45, 9454-9464. (c) Punji, B.;
Mague, J. T.; Balakrishna, M. S. J. Organomet. Chem. 2006, 691,
4265-4272. (d) Chandrasekaran, P.; Mague, J. T.; Balakrishna, M.
S. Inorg. Chem. 2006, 45, 6678-6683. (e) Punji, B.; Mague, J. T.;
Balakrishna, M. S. Dalton Trans. 2006, 1322-1330.
(17) di Nicola, C.; Pettinari, C.; Ricciutelli, M.; Skelton, B. W.; Somers,
N.; White, A. H. Inorg. Chim. Acta 2005, 358, 4003-4008.
6536 Inorganic Chemistry, Vol. 46, No. 16, 2007

CuI Complexes of Bis(2-(diphenylphosphino)phenyl) Ether
The geometry around copper in complex 2 (Figure 2) is
pseudotetrahedral. The Cu1-P4, Cu1-P3, and Cu1-P2
bond distances are 2.2855(2), 2.2860(16), and 2.2953(15)
Å, respectively, which are slightly longer than those in
complex 1. The Cu-O bond distance is 2.356(5) Å, which
is slightly longer than those observed in complexes [Cu-
(dppeO)2][OTf] (2.117(6) Å) and [Cu(BozPHOS)2][OTf]
(2.127(19) and 2.122(19) Å) (BozPHOS ) 1,2-bis(2,5-
dimethylphospholano)benzene mono-oxide).19,20 In complex
4 (Figure 3), the CuI atom exists in distorted-tetrahedral
geometry. The Cu1-P1 (2.363(1) Å), Cu1-P2 (2.334(1) Å)
and Cu1-P3 (2.330(1) Å) bond distances are ca. 0.06-0.09
Å longer than those found in complex 1. The P2-Cu1-P3
and P3-Cu1-P1 bond angles of 112.80(3)° and 119.55(3)°
are similar to those of complex 2, whereas the P2-Cu1-P1
bond angle of 108.21(3)° is ca. 11.6° less than that in
complex 2. The Cu1-Se1 bond distance of 2.5877(6) Å is
comparable with the same distances (2.675(5) and 2.475(4)
Å) observed in [Cu(dppfSe)2][BF4] (dppf ) 1,1′-bis(diphe-
nylphosphino)ferrocene).21
Figure 3. Molecular structure of complex 4. Hydrogen atoms and
uncoordinated solvent molecules have been omitted for clarity.
The X-ray structural determination shows that complex 5
(Figure 4 and Table 2) exists as a zigzag polymer in which
the copper centers are present in a distorted-tetrahedral
environment. The structure shows a couple of nonidentical
copper centers, which are arranged in pairs alternate to each
other. The 4,4′-bipyridine acts as the bridging unit between
the two CuI centers to construct a polymeric chain in which
the alternate 4,4′-bipyridine rings are distorted with a dihedral
angle of 31.42° between the planes of two pyridyl rings,
whereas the adjacent units are coplanar. Generally, the
presence of extended conjugation between metal centers and
4,4′-bipyridine units indicates conducting properties.22,23 In
complex 5, the extended conjugation is absent due to the
twisting of aromatic groups in the 4,4′-bipyridine ligands,
which makes them non-coplanar. This may be due to the
packing strain in the solid state, which leads to the disorder
in the planarity of the 4,4′-bipyridine. The bond angles N2-
Cu1-N1, P2-Cu1-P1, N4-Cu2-N3, and P4-Cu2-P3 are
104.46(19)°, 113.28(6)°, 98.81(18)°, and 113.71(6)°, respec-
tively.
three sets of unresolved multiplets in the regions of 30.2,
-12.1, and -15.1 ppm, respectively, for P(dO), two P atoms
of the chelating ligand, and the copper-bound phosphorus
center of the mono-oxidized DPEphos. The 31P NMR spectra
of complexes 3 and 4 are similar to that of complex 2. The
structures of the complexes 2 and 4 are confirmed by X-ray
diffraction studies. Interestingly, the addition of an excess
of oxidizing agents did not cleave any of the Cu-P bonds.
The reaction of [Cu(CH3CN)4][BF4] with DPEphos and
4,4′-bipyridine in an equimolar ratio afforded a coordination
polymer [Cu(κ2-P,P′-DPEphos)(µ-4,4′-bpy)]n[BF4]n (5) as a
yellow crystalline solid in good yield. The 31P{1H} NMR
spectrum of complex 5 shows a single peak at -18.7 ppm,
which indicates that both phosphorus atoms are equivalent.
The presence of the 4,4′-bipyridine ligand in complex 5 is
confirmed by the aromatic proton resonances at 7.65 and
8.80 ppm as broad singlets with appropriate intensities in
the 1H NMR spectrum. The polymeric structure of complex
5 in the solid state is revealed by the X-ray structural results
discussed below and presented in Figure 4.
Theoretical Calculations. To ascertain that the overall
bulkiness of the DPEphos ligand is the single factor
determining the product of the reaction of [Cu(CH3CN)4]-
[BF4] with DPEphos, DFT calculations were performed for
the cationic systems in question. The geometry-optimized
structure for the three-coordinated [Cu(κ2-P,P′-DPEphos)-
(κ1-P-DPEphos)]+ (see Figure 5a) is in good agreement with
the X-ray crystal structure determined for 1: the calculated
values of some key parameters are Cu1-P1 ) 2.326 Å,
Cu1-P2 ) 2.338 Å, Cu1-P3 ) 2.318 Å, P1-Cu1-P2
) 113.8°, P2-Cu1-P3 ) 120.7°, P1-Cu1-P3 )
124.3°, and ∑ PCuP ) 358.8°. The average error in the
Molecular Structures. The complexes 1, 2, 4, and 5 are
recrystallized from the CH2Cl2/Et2O solvent mixture. All
these complexes are obtained as colorless crystalline solids
except the complex 5, which is yellow in color. The CuI
center in complex 1 (Figure 1) adopts a distorted trigonal-
planar geometry, which is evident from the sum of the three
P-Cu-P bond angles of 357.05° (Table 1). The uncoordi-
nated dangling phosphorus center is oriented toward the CuI
center at a distance of 3.958 Å, which is considerably longer
than the sum of the van der Waals radii of CuI and P (3.20
Å),18 thus indicating the absence of any bonding interactions.
The Cu1-P1, Cu1-P2, and Cu1-P3 bond distances are
2.2686(8), 2.2719(8), and 2.2782(9) Å, respectively, and are
comparable with those of [Cu(κ2-P,P′-DPEphos)(µ-NN)]-
[BF4] (2.2614(9) and 2.2712(7) Å) (NN ) 2,9-dimethyl-1,-
10-phenanthroline or 2,9-di-n-butyl-1,10-phenanthroline).5
(19) Saravanabharathi, D.; Nethaji, M.; Samuelson, A. G. Polyhedron 2002,
21, 2793-2800.
(20) Cote, A.; Charette, A. B. J. Org. Chem. 2005, 70, 10864-10867.
(21) Pilioni, G.; Longato, B.; Bandoli, G. lnorg. Chim. Acta 1998, 277,
163-170.
(22) Holliday, B. J.; Swager, T. M. Chem. Commun. 2005, 23-36.
(23) Heeger, A. J. Angew. Chem., Int. Ed. 2001, 40, 2591-2611.
(18) Bondi, A. J. Phys. Chem. 1964, 68, 441-451.
Inorganic Chemistry, Vol. 46, No. 16, 2007 6537

Venkateswaran et al.
Figure 4. Molecular structure of complex 5. Hydrogen atoms and uncoordinated solvent molecules have been omitted for clarity.
Table 1. Selected Bond Distances and Bond Angles for Complexes 1 and 2
complex 1
complex 2
bond distances (Å)
bond angles (deg)
P1-Cu1-P3
P1-Cu1-P2
P3-Cu1-P2
C54-O1-C55
C18-O2-C19
bond distances (Å)
bond angles (deg)
P4-Cu1-P3
P4-Cu1-P2
P3-Cu1-P2
P4-Cu1-O2
P3-Cu1-O2
P2-Cu1-O2
P1-O2-Cu1
Cu1-P1
2.2686(8)
2.2719(8)
2.2782(9)
1.366(4)
1.336(4)
3.958
121.85(3)
113.87(3)
121.33(3)
120.5(2)
117.9(2)
Cu1-P4
2.2855(15)
2.2860(16)
2.2953(15)
2.356(5)
112.52(6)
119.20(6)
119.85(6)
96.41(12)
89.39(13)
112.20(12)
161.6(3)
Cu1-P2
Cu1-P3
B1-F1
Cu1-P3
Cu1-P2
Cu1-O2
P1-O2
B1-F1
B1-F2
B1-F2
1.463(5)
Cu1‚‚‚P4
1.317(7)
1.318(6)
Table 2. Selected Bond Distances and Bond Angles for Complexes 4 and 5
complex 4
complex 5
bond distances (Å)
bond angles (deg)
P2-Cu1-P3
bond distances (Å)
bond angles (deg)
Cu1-P3
2.3303(10)
2.3344(9)
2.3634(9)
2.5877(6)
2.1513(9)
1.373(6)
112.80(3)
119.55(3)
108.21(3)
113.60(3)
106.35(3)
94.28(3)
Cu1-N2
Cu1-N1
Cu1-P2
Cu1-P1
Cu2-N4
Cu2-N3
Cu2-P4
Cu2-P3
B1-F1
2.072(5)
2.109(5)
2.2762(18)
2.2983(17)
2.078(4)
N2-Cu1-N1
N2-Cu1-P2
N1-Cu1-P2
N2-Cu1-P1
N1-Cu1-P1
P2-Cu1-P1
N4-Cu2-N3
N4-Cu2-P4
N3-Cu2-P4
N4-Cu2-P3
N3-Cu2-P3
P4-Cu2-P3
104.46(19)
112.62(15)
111.34(13)
107.23(14)
107.37(14)
113.28(6)
98.81(18)
112.13(14)
116.49(14)
103.67(14)
110.34(14)
113.71(6)
Cu1-P2
Cu1-P1
Cu1-Se1
P4-Se1
B1-F1
P3-Cu1-P1
P2-Cu1-P1
P3-Cu1-Se1
P2-Cu1-Se1
P1-Cu1-Se1
P4-Se1-Cu1
2.081(5)
B1-F2
1.387(6)
126.09(3)
2.2552(17)
2.2846(17)
1.400(12)
1.385(12)
B1-F2
predicted bond lengths is 0.035 Å with the single largest
deviations observed for the Cu-P interactions (ca. 0.06 Å
longer). The calculated bond angles are also fairly accurate
and generally show errors less than 2° for bonds involving
C, P, and Cu atoms. On the other hand, the calculated
torsional angles show larger deviations from the experimental
values. In particular, the torsional angles involving the
backbone atoms of the κ1-P-coordinated DPEphos ligand are
as much as 10° in error. This results in a significantly
elongated distance from the uncoordinated phosphorus atom
P4 to the CuI center in the calculated structure, 4.541 Å (cf.
3.958 Å found in the X-ray crystal structure of 1). The above
discrepancies result mainly from the flat potential energy
surface along the Cu1‚‚‚P4 bond at distances greater than
the sum of the van der Waals radii for these atoms.
The crystallographic data24 reported for the cation [Cu-
(PPh3)4]+ was used to build an analogous structure [Cu(κ2-
P,P′-DPEphos)2]+ in which the CuI center is four-coordinated
by two DPEphos ligands. The structure of this hypothetical
system was optimized with DFT and compared to the
structure determined for [Cu(κ2-P,P′-DPEphos)(κ1-P-DPEp-
hos)]+ (see Figure 5b). As expected, the coordination of the
CuI center to four phosphorus atoms instead of three increases
the Cu-P bond lengths significantly: the average bond
(24) Bowmaker, G. A.; Healy, P. C.; Engelhardt, L. M.; Kildea, J. D.;
Skelton, B. W.; White, A. H. Aust. J. Chem. 1990, 43, 1697-1705.
6538 Inorganic Chemistry, Vol. 46, No. 16, 2007

CuI Complexes of Bis(2-(diphenylphosphino)phenyl) Ether
Figure 5. Optimized structure of (a) [Cu(κ2-P,P′-DPEphos)(κ1-P-DPEphos)]+ and (b) [Cu(κ2-P,P′-DPEphos)2]+.
Table 3. Crystallographic Information for Complexes 1, 2, 4, and 5
1
2
4
5
formula
fw
cryst syst
space group
a (Å)
C72H56CuO2P4BF4
1227.41
orthorhombic
Pbcn
20.1286(16)
24.5174(17)
24.833(3)
90
90
90
12255(2)
8
1.331
C72H56CuO3P4BF4
1243.41
orthorhombic
Pbcn
20.187(5)
24.542(5)
24.756(4)
90
90
90
12265(4)
8
1.347
C73H58BCl2CuF4O2.5P4Se
1399.28
triclinic
C97H78B2Cl7.5Cu2F8N4O2P4
2022.09
triclinic
P1h
P1h
12.898(2)
13.6337(6)
19.150(2)
104.166(6)
94.444(12)
94.259(7)
3240.0(7)
2
13.803(2)
19.089(4)
20.051(5)
69.255(19)
77.065(16)
72.710(15)
4675.5(15)
2
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
F
calc (g cm-3
)
1.434
1.139
1428
1.436
0.805
2063
µ(Mo Ka) (mm-1
F(000)
)
0.520
5072
0.521
5136
cryst size (mm)
T (K)
0.22 × 0.26 × 0.33
0.21 × 0.31 × 0.33
0.35 × 0.30 × 0.28
0.17 × 0.21 × 0.33
150
293
150
150
2θ range (deg)
total no. reflns
3.0 - 25.0
10 745
3.1 - 25.0
10 546
3.0 - 25.0
11 256
3.0 - 25.0
16 433
no. of indep reflns
758 [Rint ) 0.041]
767 [Rint ) 0.141]
802 [Rint ) 0.034]
1141 [Rint ) 0.072]
GOF (F2)
1.089
0.776
1.104
1.030
a
R1
0.0489
0.1502
0.0580
0.1508
0.0388
0.1197
0.0736
0.2066
b
R2
2
2
2
2
2
2
a R1 ) ∑||Fo| - |Fc||/∑|Fo|. b R2 ) {[∑w(Fo - Fc )/∑w(Fo )2]}1/2, w ) 1/[σ2(Fo ) + (xP)2], where P ) (Fo + 2Fc )/3.
length for the four Cu-P bonds in [Cu(κ2-P,P′-DPEphos)2]+
is 2.454 Å. The coordination sphere around the central CuI
atom in [Cu(κ2-P,P′-DPEphos)2]+ is almost ideal tetrahedron
as evidenced by the P-Cu-P bond angle range of 104.5-
111.2°. The bond parameters in the two DPEphos ligands
are not significantly different between [Cu(κ2-P,P′-DPEp-
hos)2]+ and [Cu(κ2-P,P′-DPEphos)(κ1-P-DPEphos)]+ except
for the Cu-P-C and C-O-C bond angles, which are
opened up by 3-6° in the former species due to the increased
steric bulk of the two ligands.
To examine the differences and similarities in the bonding
of [Cu(κ2-P,P′-DPEphos)(κ1-P-DPEphos)]+ and [Cu(κ2-P,P′-
DPEphos)2]+ more closely, the energetics of the process in
which two DPEphos ligands chelate a CuI center either
unsymmetrically or symmetrically were determined. With
the use of the energy decomposition analysis method, the
steric and electronic contributions to the chelation energy
can be separated by the expression
in which ∆Eprep is the preparation energy required to alter
the geometry of two ground states of DPEphos ligands to
the geometry they acquire in the overall complex and ∆Eint
is the interaction energy between the prepared fragments and
the CuI center. The interaction energy ∆Eint can further be
decomposed into three physically meaningful terms
∆Eint ) ∆Velec + ∆EPauli + ∆Eorbital
in which ∆Velec is the classical electrostatic interaction
between the unperturbed charge distributions of the prepared
fragments, ∆EPauli is the exchange repulsion component
resulting from the destabilizing interactions between the
occupied orbitals on each fragment, and ∆Eorbital accounts
for the stabilizing interactions between the occupied and
empty fragment orbitals. The orbital interaction term can
additionally be partitioned into contributions from distinct
irreducible representations of the interacting system.
As seen from Table 4, the individual P-CuI interactions
are significantly weaker in [Cu(κ2-P,P′-DPEphos)2]+ than in
∆Echelation ) ∆Eprep + ∆Eint
Inorganic Chemistry, Vol. 46, No. 16, 2007 6539

Venkateswaran et al.
Table 4. Energy Decomposition Analysis of
rus center readily undergoes oxidation to form an 18-electron
complex with Cu-E (E ) O, S, or Se) bond. The large bite
angle of the diphenyl ether backbone and the overall
bulkiness of the ligand play a vital role for this interesting
feature of the complex 1. The complexes 2-4 are the first
examples of mixed-ligand CuI bis-chelating complexes
containing both bis(phosphine) and its monochalcogenide
(PQPdE) derivative. The Cu-O (2) and Cu-Se (4) bond
distances are ca. 0.2 Å longer than those found in analogous
compounds. The coordination polymer [Cu(κ2-P,P′-DPEp-
hos)(µ-4,4′-bpy)]n[BF4]n (5) exhibits a one-dimensional
zigzag polymeric structure. The distorted-tetrahedral CuI
centers are connected with 4,4′-bipyridine units, and the
aromatic rings of alternating units are tilted by an angle of
31.42°. The DFT calculations clearly indicate the stereo-
chemical influences of the ligand framework and the
phosphorus substituents on its coordination behavior. We are
currently investigating the catalytic utility of the tricoordi-
nated CuI complex in hydroamination and other related
organic transformation reactions.
[Cu(κ2-P,P′-DPEphos)(κ1-P-DPEphos)]+ and [Cu(κ2-P,P′-DPEphos)2]+ a
∆Echelation ∆Eprep ∆Eint ∆Velec ∆EPauli ∆Eorbital
[Cu(κ2-P,P-DPEphos)-
(κ1-P-DPEphos)]+
-740
-677
19 -759 -765
116 -793 -677
635
528
-600
-610
[Cu(κ2-P,P-DPEphos)2]+
a Energies are reported in kJ mol-1
.
[Cu(κ2-P,P′-DPEphos)(κ1-P-DPEphos)]+ (170 kJ mol-1 per
bond vs 250 kJ mol-1 per bond), but the total interaction
energy term ∆Eint is nevertheless more negative for the
complex [Cu(κ2-P,P′-DPEphos)2]+, which contains one more
P-CuI bond. Hence, if contributions from ∆Eprep are
neglected, the four-coordinate structure becomes the global
energy minimum by approximately 30 kJ mol-1. However,
the preparation energy ∆Eprep is almost 100 kJ mol-1 smaller
for the three-coordinate complex than for the four-coordinate
cation. This difference in ∆Eprep is more than enough to
compensate the less favorable bonding interactions in [Cu-
(κ2-P,P′-DPEphos)(κ1-P-DPEphos)]+, which alter the energy
of the three-coordinate structure with a dangling phosphorus
center 60 kJ mol-1 lower relative to the energy of the
symmetric four-coordinate system. Table 4 also shows the
contribution of ∆Velec, ∆EPauli, and ∆Eorbital in ∆Eint for both
complexes. We note that the ∆EPauli term, which is respon-
sible for the steric repulsion, is smaller for [Cu(κ2-P,P′-
DPEphos)2]+ due to its tetrahedral coordination and, hence,
elongated P-CuI distances and that the attractive electrostatic
interaction ∆Velec is more negative for [Cu(κ2-P,P′-DPEp-
hos)(κ1-P-DPEphos)]+ due to its significantly stronger P-CuI
interactions (see above). The orbital interaction terms are
predicted to be comparable between the two systems.
The above analysis clearly demonstrates that the coordina-
tion of a CuI center with four phosphorus atoms is, in
principle, the energetically most favorable situation, but the
entire energy gain will be lost in distorting the two DPEphos
ligands to a geometry that facilitates such coordination.
Hence, these results confirm that the observed difference in
the reactivity of dppe and DPEphos toward [Cu(CH3CN)4]-
[BF4] is in fact due to the overall bulkiness of the DPEphos
ligand, which allows P,P′-chelation to copper via only one
of the two ligands. This was conclusively confirmed by
running a full geometry optimization for a three-coordinate
structure analogous to [Cu(κ2-P,P′-DPEphos)(κ1-P-DPEp-
hos)]+ in which the four phenyl groups in the individual
DPEphos ligands were replaced with sterically much less
demanding methyl groups. Since the substitution of phenyl
to methyl lowers the preparation energy significantly, the
interaction energy term now dominates the total chelation
energy. Thus, the optimization leads to the immediate
coordination of the dangling phosphorus atom to the CuI
center, giving a four-coordinate structure with identical Cu-P
bonds at 2.345 Å (cf. calculated Cu-P bonds in [Cu(κ2-
P,P′-DPEphos)2]+ and [Cu(κ2-P,P′-DPEphos)(κ1-P-DPEp-
hos)]+ at 2.454 and 2.326 Å, respectively).
Experimental Section
General Methods. All manipulations were performed under an
atmosphere of dry nitrogen using standard Schlenk techniques. All
solvents were purified by conventional procedures and distilled
under nitrogen prior to use.25 DPEphos11 and [Cu(CH3CN)4][BF4]26
were prepared according to the published procedures. H2O2 (30%
solution in water) (Merck), MnO2 (SD-Fine), sulfur (Merck),
selenium (Lancaster), and 4,4′-bipyridine (Aldrich) were purchased
1
from commercial sources and used as received. The H and 31P-
{1H} NMR spectra were recorded using a Varian 400 Mercury Plus
spectrometer operating at the appropriate frequencies, using TMS
and 85% H3PO4 as the internal and external references, respectively.
Microanalyses were performed on a Carlo Erba Model 1112
elemental analyzer. Electrospray ionization (EI) mass spectrometry
experiments were carried out using a Waters Q-Tof micro-YA-
105 mass spectrometer. Melting points were recorded using capillary
tubes and are uncorrected.
Syntheses. [Cu(κ2-P,P′-DPEphos)(κ1-P-DPEphos)][BF4] (1). A
solution of [Cu(CH3CN)4][BF4] (0.100 g, 0.318 mmol) in CH2Cl2
(8 mL) was added dropwise to a stirring solution of DPEphos (0.342
g, 0.636 mmol) also in CH2Cl2 (15 mL) at room temperature. After
8 h, the reaction mixture was concentrated to a 5 mL volume, and
Et2O (5 mL) was added and allowed to stay at room temperature
for 1 day to obtain colorless crystals of 1. Yield: 93% (0.363 g,
0.295 mmol). Anal. Calcd for C72H56O2P4CuBF4: C, 70.45; H, 4.60.
Found: C, 70.48; H, 4.66. 1H NMR (400 MHz, CDCl3): δ 6.44-
7.28 (m, Ph, 56H). 31P{1H} NMR (162 MHz, CDCl3): δ -15.5
(s). MS (EI): m/z 1139.21 [M]+.
[Cu(κ2-P,P′-DPEphos)(κ2-P,O-DPEphos-O)][BF4] (2). A mix-
ture of 1 (0.060 g, 0.049 mmol) and MnO2 (50 mg) in CH2Cl2 (5
mL) was stirred for 2 h at room temperature and filtered to obtain
a colorless solution, which was concentrated to a 3 mL volume,
and Et2O (5 mL) was added to give colorless crystals of 2. Yield:
87% (0.053 g, 0.042 mmol). Anal. Calcd for C72H56O3P4CuBF4:
C, 69.55; H, 4.54. Found: C, 69.19; H, 4.38. 1H NMR (400 MHz,
CDCl3): δ 6.43-7.45 (m, Ph, 56H). 31P{1H} NMR (162 MHz,
Conclusion
(25) Armarego, W. L. F.; Perrin, D. D. Purification of Laboratory
Chemicals, 4th ed.; Butterworth-Heinemann Linacre House, Jordan
Hill: Oxford, U.K., 1996.
The 16-electron complex [Cu(κ2-P,P′-DPEphos)(κ1-P-
DPEphos)][BF4] (1) containing one uncoordinated phospho-
(26) Kubas, G. J. Inorg. Synth. 1979, 19, 90.
6540 Inorganic Chemistry, Vol. 46, No. 16, 2007

CuI Complexes of Bis(2-(diphenylphosphino)phenyl) Ether
CDCl3): δ 30.2 (q, PdO, 3JPP ) 6.6 Hz, 1P), -12.1 (s, br, Cu-P,
2P), -15.1 (s, br, Cu-P, 1P). MS (EI): m/z 1155.34 [M]+.
[Cu(κ2-P,P′-DPEphos)(κ2-P,S-DPEphos-S)][BF4] (3). A mix-
ture of 1 (0.060 g, 0.049 mmol) and elemental sulfur (0.0016 g,
0.049 mmol) in CH2Cl2 (5 mL) was stirred for 24 h at room
temperature and filtered. The filtrate was concentrated to 3 mL,
and Et2O (5 mL) was added to give colorless crystals of 3. Yield:
76% (0.047 g, 0.037 mmol). Anal. Calcd for C72H56O2SP4CuBF4:
internal basis set library. Geometry optimizations were performed
with Turbomole 5.9.31 The program ADF 2006.0132 was used to
calculate the individual components of ∆Eint in the energy
decomposition analysis (EDA). The analysis followed the Moro-
kuma-Ziegler partition scheme33 and utilized the PBEPBE func-
tional in combination with a STO-type all-electron basis sets of
TZP quality; scalar relativistic ZORA formalism was also applied
in all EDA calculations.
Crystal Structure Determination. Single crystals of 1, 2, 4,
and 5 suitable for X-ray diffraction were grown by the slow
diffusion of diethyl ether into dichloromethane solution and
mounted on a glass fiber with epoxy resin. Unit cell determination
and data were collected on an Oxford Diffraction XCALIBUR-S
CCD system using Mo KR radiation (λ ) 0.71073 Å). The
structures were solved and refined by full-matrix least-squares
techniques of F2 using SHELX-97 (SHELXL program package).34
The absorption corrections were done via a multiscan, and all data
were corrected for Lorentz and polarization effects. The non-
hydrogen atoms were refined with anisotropic thermal parameters.
All hydrogen atoms were geometrically fixed and allowed to refine
using a riding model.
1
C, 68.66; H, 4.48; S, 2.55. Found: C, 68.98; H, 4.62; S, 2.34. H
NMR (400 MHz, CDCl3): δ 5.48-7.60 (m, Ph, 56H). 31P{1H}
NMR (162 MHz, CDCl3): δ 35.5 (t, PdS, 3JPP ) 26 Hz, 1P), -6.3
(s, br, Cu-P, 1P), -9.1 (m, br, Cu-P, 1P), -14.1 (m, br, Cu-P,
1P). MS (EI): m/z 1171.04 [M]+.
[Cu(κ2-P,P′-DPEphos)(κ2-P,Se-DPEphos-Se)][BF4] (4). This
procedure is similar to that of 3, using selenium (0.004 g, 0.049
mmol). Yield: 82% (0.052 g, 0.040 mmol). Anal. Calcd for
C72H56O2SeP4CuBF4: C, 66.19; H, 4.32. Found: C, 66.51; H, 4.58.
1H NMR (400 MHz, CDCl3): δ 5.46-8.04 (m, Ph, 56H). 31P{1H}
NMR (162 MHz, CDCl3): δ 22.0 (m, br, PdSe, 1P), -7.8 (m, br,
Cu-P, 2P), -14.2 (s, br, Cu-P, 1P). MS (EI): m/z 1219.25 [M]+.
[Cu(κ2-P,P′-DPEphos)(µ-4,4′-bpy)]n[BF4]n (5). A mixture of
[Cu(CH3CN)4]BF4 (0.060 g, 0.191 mmol) and DPEphos (0.103 g,
0.191 mmol) in CH2Cl2 (10 mL) was stirred for 4 h at room
temperature. 4,4′-Bipyridine (0.030 g, 0.191 mmol) in CH2Cl2
solution was added to the reaction mixture dropwise and stirring
was continued for 4 h to get a clear yellow solution. The reaction
mixture was concentrated to 5 mL, and Et2O (5 mL) was added to
give yellow crystals of 3. Yield: 94% (0.152 g). Anal. Calcd for
C46H36OP2N2CuBF4: C, 65.38; H, 4.29; N, 3.31. Found: C, 65.21;
Acknowledgment. We are grateful to The Department
of Science and Technology (DST) for financial support of
this work through Grant SR/S1/IC-05/2003. We are thankful
to the Sophisticated Analytical Instrument Facility (SAIF)
IIT Bombay, Department of Chemistry IIT Bombay, and the
National Single Crystal X-ray Diffraction Facility IIT Bom-
bay, for the instrument facilities. R.V. is thankful to IIT
Bombay for JRF and SRF Fellowships.
1
H, 4.49; N, 3.21. H NMR (400 MHz, CDCl3): δ 6.71-7.54 (m,
Ph, 28H), 7.65 (s, bpy, 4H), 8.80 (s, br, bpy, 4H). 31P{1H} NMR
(162 MHz, CDCl3): δ -18.7 (s).
Supporting Information Available: X-ray crystallographic files
in CIF format for the structure determinations of 1, 2, 4, and 5.
This material is available free of charge via the Internet at
http://pubs.acs.org.
Computational Details. DFT calculations were performed
primarily for cations [Cu(κ2-P,P-DPEphos)2]+ and [Cu(κ2-P,P-
DPEphos)(κ1-P-DPEphos)]+. The molecular structures were fully
optimized by using a combination of the GGA PBEPBE exchange-
correlation functional (within the resolution of the identity
approximation)27-30 with the Ahlrichs’ triple-ú valence basis set
augmented by one set of polarization functions (def-TZVP). All
basis sets were used as they are referenced in the Turbomole 5.9
IC7005474
(31) Ahlrichs, R. et al. TURBOMOLE, Program Package for ab initio
Electronic Structure Calculations, version 5.9; Theoretical Chemistry
Group, University of Karlsruhe: Karlsruhe, Germany, 2006.
(32) ADF2006.01; SCM, Theoretical Chemistry, Vrije Universiteit: Am-
sterdam, The Netherlands. http://www.scm.com.
(27) Perdew, J. P.; Burke, K.; Ernzerhof, M. Phys. ReV. Lett. 1996, 77,
(33) (a) Ziegler, T.; Rauk, A. Theor. Chim. Acta 1977, 46, 1. (b) Ziegler,
T.; Rauk, A. Inorg. Chem. 1979, 18, 1558. (c) Ziegler, T.; Rauk, A.
Inorg. Chem. 1979, 18, 1755. (d) Bickelhaupt, F. M.; Baerends, E. J.
ReViews in Computational Chemistry; Lipkowitz, K. B., Boyd, D. B.,
Eds.; Wiley: New York, 2000; Vol. 15, pp 1-86.
3865-3868.
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(29) Perdew, J. P.; Ernzerhof, M.; Burke, K. J. Chem. Phys. 1996, 105,
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(30) Ernzerhof, M.; Scuseria, G. E. J. Chem. Phys. 1999, 110, 5029-5036.
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gen: Gottingen, Germany, 1997.
Inorganic Chemistry, Vol. 46, No. 16, 2007 6541