Group 11 complexes of the P,Te-centered ligand [TePiPr 2NPiPr2]": synthesis, structures, and insertion reactions of the copper(l) complex with chalcogens

Article abstract of DOI:10.1021/ic802428b

The lithium reagent [LiTePⁱPr₂NPⁱPr ₂] undergoes metathetical reactions with group 11 chlorides to give the complexes {M(TePⁱPr₂NPⁱPr ₂)}₃ (6: M = Cu; 7: M

Full text of DOI:10.1021/ic802428b

Inorg. Chem. 2009, 48, 3857-3865
Group 11 Complexes of the P,Te-Centered Ligand [TePiPr2NPiPr2]-:
Synthesis, Structures, and Insertion Reactions of the Copper(I) Complex
with Chalcogens
Jamie S. Ritch and Tristram Chivers*
Department of Chemistry, UniVersity of Calgary, 2500 UniVersity DriVe NW, Calgary,
Alberta T2N 1N4, Canada
Received December 22, 2008
The lithium reagent [LiTePiPr2NPiPr2] undergoes metathetical reactions with group 11 chlorides to give the complexes
{M(TePiPr2NPiPr2)}3 (6: M ) Cu; 7: M ) Ag) and (Ph3P)Au(TePiPr2NPiPr2) (8) as yellow crystalline solids. These
new complexes were characterized by single crystal X-ray diffraction and multinuclear NMR spectroscopy. The
tellurium atoms in the trimeric complexes 6 and 7 occupy bridging positions to give a Cu3Te3 ring in a twist-boat
conformation with short M · · · M contacts (M ) Cu, Ag). Variable temperature 31P NMR and ESI-MS spectra for 6
and 7 give evidence for the formation of several oligomers in tetrahydrofuran solution. The reactions of 6 with
dioxygen (or Me3NO), elemental sulfur, or red selenium generate the chalcogen-insertion products
{Cu(TePiPr2NPiPr2E)}3 (9: E ) O; 10: E ) S; 11: E ) Se), which were also structurally characterized by single
crystal X-ray diffraction and multinuclear NMR spectroscopy. The lighter chalcogens are two-coordinate while the
tellurium centers occupy bridging positions in the trimeric complexes 9-11 giving rise to Cu3Te3 rings in a chairlike
conformation.
Introduction
Tellurium-based ligands have been studied with increasing
interest in recent years, especially for the development of
metal complexes which are used as single source precursors
(SSPs) to solid state metal tellurides. These materials have
important applications in electronic devices such as photo-
voltaic cells or thermoelectric generators. Notably, the bulky
tellurolate ligand [(Me3Si)3SiTe]- has been used by Arnold
and co-workers to develop group 12 and 14 metal
complexes which produce metal telluride thin films or
powders upon thermolysis.1 The group of Bochmann has
prepared an N,Te-chelating class of ligand, tBu2P(Te)NHR
Homoleptic and heteroleptic metal complexes of this
ditellurido-imidodiphosphinato (PNP) ligand have been suc-
cessfully prepared by metathetical reactions of the sodium
salt (tmeda)Na[L1] with group 12, 13, and 15 metal halides.4
Some of these complexes have been used to deposit thin
films of phase-pure CdTe,5 Sb2Te3,6 and In2Te3,7 by the
method of aerosol-assisted chemical vapor deposition
(AACVD). Interestingly, the reaction of (tmeda)Na[L1] with
group 11 halides produces oligomeric complexes of the
formula {M[L1]}n (1: M ) Cu, n ) 3; 2: M ) Ag, n ) 6),
i
(R ) Pr, cyclohexyl), and shown that its group 12
complexes are suitable CVD precursors to group 12 metal
telluride thin films.2 Recent work in our group has focused
on using a Te,Te-chelating ligand, [(TePiPr2)2N]- (L1),
to develop metal complexes which are SSPs to these
important materials,3 as well as to investigate their often
unique structural chemistry.
(2) Bwembya, G. C.; Song, X.; Bochmann, M. Chem. Vap. Deposition
1995, 1, 78.
(3) Ritch, J. S.; Chivers, T.; Afzaal, M.; O’Brien, P. Chem. Soc. ReV.
2007, 36, 1622.
(4) Chivers, T.; Eisler, D. J.; Ritch, J. S. Dalton Trans. 2005, 2675.
(5) Garje, S. S.; Ritch, J. S.; Eisler, D. J.; Afzaal, M.; O’Brien, P.; Chivers,
T. J. Mater. Chem. 2006, 16, 966.
* To whom correspondence should be addressed. E-mail: chivers@
ucalgary.ca. Fax: (+1)403-289-9488. Phone: (+1)403-220-5741.
(1) Arnold, J.; Walker, J. M.; Yu, K. M.; Bonasia, P. J.; Seligson, A. L.;
Bourett, E. D. J. Cryst. Growth 1992, 124, 647.
(6) Garje, S. S.; Eisler, D. J.; Ritch, J. S.; Afzaal, M.; Chivers, T.; O’Brien,
P. J. Am. Chem. Soc. 2006, 128, 3120.
(7) Garje, S. S.; Copsey, M. C.; Afzaal, M.; O’Brien, P.; Chivers, T. J.
Mater. Chem. 2006, 16, 4542.
10.1021/ic802428b CCC: $40.75  2009 American Chemical Society
Inorganic Chemistry, Vol. 48, No. 8, 2009 3857
Published on Web 03/18/2009

Ritch and Chivers
Hg(TePPh2CPPh2)213andtheplatinum(II)complex(NCS)2Pt(o-
PhTe-C6H4-PPh2).14 The group 11 metals are also suitable
targets, in fact, many of the structurally characterized
examples of group 11 complexes containing tellurium are
large clusters featuring bridging Te2- or PhTe- ligands
and stabilizing neutral phosphine donors. For instance, in
1993 Fenske and Steck reported a family of compounds
with the general formula [CuxTey(PR3)z] (x + y ) 25-45,
z ) 8-12), which possess a large core of copper and
tellurium centers with copper-bound phosphine ligands on
the surface of the cluster.15 The nonanuclear silver(I)
tellurolate complex [Ag9(µ3-TePh)9(PEt2Ph)6] was pre-
pared by Fenske et al. in 1997.16 Since the copper(I) and
silver(I) complexes 1 and 2 are trimeric and hexameric
in the solid state, respectively, the structural influence of
replacing L1 with L2 merits investigation.
We now report the reaction of 5 with group 11 halides to
generate the homoleptic complexes {M(TePiPr2NPiPr2)}n (6:
M ) Cu; 7: M ) Ag) and the heteroleptic gold(I) complex
(Ph3P)Au(TePiPr2NPiPr2) (8), which were structurally char-
acterized in the solid state by single-crystal X-ray dif-
fraction and in solution by multinuclear NMR spectros-
copy. A variable-temperature 31P NMR study of 7 was
conducted to investigate its aggregation in solution.
Spectroscopic evidence for the formation of several
oligomers of 7 in THF is presented, a novel finding for
the mono- or dichalcogenido PNP class of ligand. The
reactions of 6 with elemental chalcogens (E ) O, S, Se)
provide rare examples of chalcogen-insertion reactions into
an M-P bond to generate the new heterodichalcogenido
PNP complexes {Cu(TePiPr2NPiPr2E)}3 (9: E ) O; 10: E
) S; 11: E ) Se). The solid-state structures and multi-
nuclear NMR solution spectra of complexes 9-11 are
discussed.
Scheme 1
via the linking of monomeric units through tellurium
bridges.8 In the case of the copper(I) complex 1, two of the
L1 ligands feature one tellurium center which is two-
coordinate and one which is three-coordinate (doubly bridg-
ing); the remaining ligand possesses two three-coordinate
chalcogens. The complex features two short Cu · · · Cu
distances (2.626(1) and 2.637(2) Å) as a result of this
bonding arrangement, which is distorted when compared to
the
related
selenium-based
complex
{Cu[(SePiPr2)2N]}3,9where all three ligands feature one
singly bridging and one doubly bridging chalcogen center
and there are no short Cu · · · Cu distances. The heteroleptic
monomeric complex (Ph3P)Au[L1] (3) is obtained by using
(Ph3P)AuCl(Scheme 1).8
Attempts to prepare the homoleptic gallium(III) complex
Ga[L1]3 by reaction of GaCl3 with (tmeda)Na[L1] resulted
in an interesting tellurium transfer reaction to give the
unprecedented complex {Ga(µ-Te)[TePiPr2NPiPr2]}2 (4), with
an accompanying redox process yielding the ditelluride
dimer (TePiPr2NPiPr2Te-)2.10,11 The presence of the new
P,Te bidentate ligand, [TePiPr2NPiPr2]- (L2), in complex 4
prompted attempts to prepare it in a rational manner. The
synthesis of the lithium derivative [LiTePiPr2NPiPr2] (5)
is readily achieved by deprotonation of the monotelluride
Experimental Section
12
TePiPr2NP(H)iPr2 with BuLi (eq 1). The complex 5 is
stable in tetrahydrofuran (THF) solution, but undergoes
decomposition by disproportionation when the solvent is
removed. The subsequent reactions of this in situ reagent
with group 12 chlorides generate the homoleptic complexes
M(TePiPr2NPiPr2)2 (M ) Zn, Cd, Hg) as crystalline solids
in good yields.12
n
Reagents and General Procedures. All solvents were dried and
distilled from Na/benzophenone and stored over 4 Å molecular
sieves prior to use. Deuterated solvents for NMR studies were
degassed using at least three freeze-pump-thaw cycles and stored
over 4 Å molecular sieves prior to use. Copper(I) chloride, silver(I)
chloride, trimethylamine N-oxide (anhydrous), and triphenylphos-
phinegold(I) chloride were purchased from Aldrich and used as
received. Elemental sulfur (Fisher Scientific) was sublimed prior
to use. The reagent (tht)AuCl (tht ) tetrahydrothiophene) was
synthesized from hydrogen tetrachloroaurate by the literature
method.17 Amorphous red selenium was freshly prepared by
reduction of selenium dioxide with sodium sulfite according to the
method of Bacon and Ingledew.18 THF solutions of the reagents
Since the two ligating atoms of L2, phosphorus and
tellurium, are both soft donors, this ligand is ideally suited
for coordination to the electron-rich late transition metals.
Several such metal complexes of P,Te-chelating ligands
have been reported, including the mercury(II) complex
(11) A related gold(III) complex, {Au(µ-Te)[TePiPr2NPiPr2]}2, was obtained
from the reaction of (tht)AuCl with (tmeda)Na[L1]: Eisler, D. J.;
Robertson, S. D.; Chivers, T. Can. J. Chem. 2009, 87, 39.
(12) Ritch, J. S.; Chivers, T. Dalton Trans. 2008, 957.
(13) Lusser, M.; Peringer, P. Inorg. Chim. Acta 1987, 127, 151.
(14) Gysling, H. J.; Luss, H. R. Organometallics 1984, 3, 596.
(15) Fenske, D.; Steck, J.-C. Angew. Chem., Int. Ed. Engl. 1993, 32, 238.
(16) Corrigan, J. F.; Fenske, D.; Power, W. P. Angew. Chem., Int. Ed. Engl.
1997, 36, 1176.
(8) Copsey, M. C.; Panneerselvam, A.; Afzaal, M.; Chivers, T.; O’Brien,
P. Dalton Trans. 2007, 1528.
(9) Afzaal, M.; Crouch, D. J.; O’Brien, P.; Raftery, J.; Skabara, P. J.;
White, A. J. P.; Williams, D. J. J. Mater. Chem. 2004, 14, 233.
(10) Copsey, M. C.; Chivers, T. Chem. Commun. 2005, 4938.
(17) Uson, R.; Laguna, A.; Laguna, M. Inorg. Synth. 1986, 26, 85.
(18) Bacon, M.; Ingledew, W. J. FEMS Microbiol. Lett. 1989, 58, 189.
3858 Inorganic Chemistry, Vol. 48, No. 8, 2009

Complexes of the P,Te-Centered Ligand [TePiPr2NPiPr2]-
(tmeda)Li(TePiPr2NPiPr2Se)19 and [LiTePiPr2NPiPr2]12 were pre-
pared according to the literature procedures. All manipulations were
performed under an inert atmosphere of argon using standard
glovebox and Schlenk techniques. Melting points (uncorrected) were
obtained from samples sealed in capillary tubes under argon.
54.3 (d of d, JP-P ) 230 Hz, JP-P ) 26, Au-PPh3). 125Te NMR
2
3
1
(CD2Cl2) δ: -532.6 (d, JTe-P ) 1195). Anal. Calcd for
C30H43NAuP3Te: C, 43.14; H, 5.19, N, 1.68. Found: C, 43.09; H,
5.28; N, 1.68. X-ray quality crystals of 8 were grown from a
concentrated solution of the complex in hot hexanes which was
stored at 5 °C.
1
Instrumentation. H, 31P, 77Se, and 125Te NMR spectra were
Attempted Synthesis of {Au(TePiPr2NPiPr2)}n. The attempted
preparation of this gold(I) complex employed a similar procedure
as for 8, with (tht)AuCl (214 mg, 0.67 mmol) as the source of
gold(I). The crude red oil product was extracted with toluene (25
mL) and filtered, pumped down to an oil, and extracted with
hexanes. The resulting deep red solution was stored at -35 °C
and yielded red crystals of the known compound {Au(µ-
Te)[TePiPr2NPiPr2]}2,11 which were identified by their unit cell
parameters.
recorded on either a Bruker DRX-400 or an AMX-300 NMR
spectrometer. Chemical shifts are reported in parts per million
(ppm), relative to the external standards Me4Si (1H), 85% H3PO4
(31P), Se2Ph2 (77Se), and Te2Ph2 125Te). Spin-spin coupling
(
constants are reported in hertz (Hz). Mass spectra of 6 and 7 were
recorded on a Bruker Esquire 3000 mass spectrometer using
electrospray ionization and an ion trap analyzer. Elemental analyses
were performed by the Analytical Services Laboratory, Department
of Chemistry, University of Calgary.
{Cu(TePiPr2NPiPr2)}3 (6). A solution of [LiTePiPr2NPiPr2] in
THF (30 mL, 1.33 mmol) at -78 °C was added dropwise over 10
min to a suspension of CuCl (131 mg, 1.32 mmol) in THF (20
mL) at room temperature, and the resulting yellow mixture was
stirred for 1 h. Removal of the volatiles under vacuum left an oily
yellow-orange solid, which was extracted with Et2O (25 mL) and
filtered through Celite over a 0.45 µm filter disk. The resulting
orange solution was concentrated to about 5 mL, and overnight
storage at -30 °C resulted in the formation of yellow rod-like
crystals of 6 (266 mg, 46%, mp 194-198 °C). 1H NMR (CD2Cl2)
δ: 2.32-2.09 (m, 2H, CH(CH3)2), 2.02-1.78 (m, 2H, CH(CH3)2),
1.46-0.99 (m, 24H, CH(CH3)2). 31P NMR (CD2Cl2) δ: 109.9 (d,
Synthesis of {Cu(TePiPr2NPiPr2O)}3 (9). A solution of 6 (137
mg, 0.10 mmol) in THF (25 mL) containing suspended Me3NO
(23 mg, 0.31 mmol) was stirred at room temperature for 2 d. The
volatiles were removed in vacuo, and the residual material was
extracted with hexanes, filtered through a 0.45 µm filter disk,
concentrated to about 15 mL, and stored at -35 °C for 3 d. Yellow
crystals of 9 were isolated from the mother liquor in two crops.
Drying the crystals under vacuum resulted in a visual loss of
crystallinity, suggesting the product contained a solvent of crystal-
lization that was removed upon exposure of the sample to low
pressure. Compound 9 was isolated as a yellow powder (72 mg,
51%, mp 159-160 °C). 1H NMR (CD2Cl2) δ: 2.21-2.03 (m, 2H,
CH(CH3)2), 1.96-1.78 (m, 2H, CH(CH3)2), 1.39-1.05 (m, 24H,
CH(CH3)2). 31P NMR (CD2Cl2) δ: 46.8 (d, 2JP-P ) 21, O-P), 11.8
2
1
2JP-P ) 101, Cu-P), 72.9 (d, JP-P ) 103, JTe-P ) 1085, Te-P).
1
125Te NMR (CD2Cl2) δ: -632.9 (d, JTe-P ) 1085). Anal. Calcd
2
1
(d, JP-P ) 21, JTe-P ) 1119, Te-P). 125Te NMR (CD2Cl2) δ:
for C36H84N3Cu3P6Te3: C, 32.80; H, 6.42, N, 3.19. Found: C, 32.90;
H, 6.72; N, 3.19. X-ray quality crystals of 6 were grown from a
concentrated Et2O solution at -30 °C.
1
-631.8 (d, JTe-P ) 1119). Anal. Calcd for C36H84Cu3N3O3P6Te:
C, 31.65; H, 6.20; N, 3.08. Found: C, 31.61; H, 6.38; N, 3.24.
Solvent-free X-ray quality crystals of 9 grew slowly from a solution
of 6 in Paratone oil which was exposed to the ambient atmosphere.
Synthesis of {Cu(TePiPr2NPiPr2S)}3 (10). A solution of 6 (0.44
mmol) in THF (50 mL) was prepared as described earlier, and after
1 h of stirring at room temperature it was cooled to -78 °C. This
solution was added to a suspension of sulfur (42 mg, 1.31 mmol)
in THF (15 mL) at -78 °C. The resulting dark yellow mixture
was stirred for 1 h at -78 °C and then warmed up to room
temperature, at which point the solution was red-brown in color.
Removal of the solvent in vacuo yielded an oily brown product,
which was extracted with hot hexanes (20 mL), filtered through a
0.45 mm pore size filter disk, concentrated to 15 mL, and stored at
-35 °C. After 5 days, pale yellow hexagonal prismatic crystals
were isolated from the mother liquor, which lost solvent upon
exposure of the sample to reduced pressure and heating to 100 °C.
Complex 10 was isolated as a yellow powder (165 mg, 26%, mp
154-155 °C). 1H NMR (CD2Cl2) δ: 2.09-1.95 (m, 4H, CH(CH3)2),
1.34-1.05 (m, 24H, CH(CH3)2). 31P NMR (CD2Cl2) δ: 65.3 (d,
2JP-P ) 30, S-P), 21.1 (d, 2JP-P ) 30, 1JTe-P ) 1173, Te-P). 125Te
{Ag(TePiPr2NPiPr2)}3 (7). The silver complex 7 was prepared
by using the same procedure as for 6, with AgCl (190 mg, 1.33
mmol) as the source of silver(I). Recrystallization from Et2O yielded
7 as a yellow crystalline solid (136 mg, 21%, mp 158-159 °C).
1H NMR (CD2Cl2) δ: 2.32-2.10 (m, 2H, CH(CH3)2), 1.94-1.80
(m, 2H, CH(CH3)2), 1.36-0.97 (m, 24H CH(CH3)2). 31P NMR
2
1
(CD2Cl2) δ: 112.4 (br dd, JP-P ) 90, JAg-P ) 444, Ag-P), 68.2
(d, JP-P ) 94, JTe-P ) 1077, Te-P). 125Te NMR (CD2Cl2) δ:
-856.9 (1JTe-P ) 1086). Anal. Calcd for C36H84N3Ag3P6Te3: C,
29.79; H, 5.83, N, 2.90. Found: C, 30.19; H, 5.74; N, 2.86. X-ray
quality crystals of 7 were grown from a concentrated Et2O solution
at -30 °C.
2
1
(Ph3P)Au(TePiPr2NPiPr2) (8). A solution of [LiTePiPr2NPiPr2]
in THF (30 mL, 0.66 mmol) at -78 °C was added dropwise over
10 min to a suspension of (Ph3P)AuCl (328 mg, 0.66 mmol) in
THF (20 mL) at -78 °C, and the resulting pale yellow mixture
was stirred for 30 min at -78 °C and 30 min at room temperature.
Removal of the volatiles under vacuum left a yellow oil, which
was extracted with toluene (25 mL) and filtered through Celite over
a 0.45 µm filter disk. Upon removal of the volatiles under vacuum
an orange oil remained, which began to crystallize. Dissolution of
the material into hot hexanes and cooling to 0 °C afforded yellow
crystalline 8 (292 mg, 53%, mp 123-124 °C). 1H NMR (CD2Cl2)
δ: 7.66-7.57 (m, 6H, P(C6H5)3), 7.48-7.37 (m, 9H, P(C6H5)3),
2.20-1.98 (m, 4H, CH(CH3)2), 1.33-0.99 (m, 24H, CH(CH3)2).
31P NMR (CD2Cl2, 298 K) δ: 137.3 (br m, Au-PiPr2), 74.7 (d, 2JP-P
1
NMR (CD2Cl2) δ: -628.7 (d, JTe-P ) 1170). Anal. Calcd for
C36H84Cu3N3P6S3Te3: C, 30.57; H, 5.99; N, 2.97. Found: C, 30.61;
H, 6.05; N, 3.01. X-ray quality crystals of 10·(C6H14)n grew from
a concentrated solution in hexanes at -35 °C.
Synthesis of {Cu(TePiPr2NPiPr2Se)}3 (11). Method A. The
complex 11 was prepared using the same procedure as for 10, by
reacting a solution of 6 (0.44 mmol) in THF at -78 °C with a
suspension of amorphous red selenium (105 mg, 1.33 mmol) in
THF (15 mL) at -78 °C. Yellow crystals of 11 were isolated from
the mother liquor in two crops (402 mg, 58%). The 31P NMR
spectrum indicated that the sample was about 84% pure, with
contamination by {Cu[(SePiPr2)2N]}3 and {Cu[(TePiPr2)2N]}3 in
1
) 62, JTe-P ) 1189, Te-P), 55.7 (br s, Au-PPh3); 31P NMR
2
2
(CD2Cl2, 193 K): 136.2 (d of d, JP-P ) 230 Hz, JP-P ) 56, Au-
PiPr2), 77.0 (d of d, 1JTe-P ) 1181, 2JP-P ) 56, 3JP-P ) 26, Te-P),
(19) Robertson, S. D.; Chivers, T. Dalton Trans. 2008, 1765.
Inorganic Chemistry, Vol. 48, No. 8, 2009 3859

Ritch and Chivers
Table 1. Crystallographic Data for 6-11a
CuL (6)
AgL (7)
AuL (8)
Cu(O,Te) (9)
Cu(S,Te) (10)
Cu(Se,Te) (11)
chemical formula C36H84Cu3N3P6Te3 C36H84Ag3N3P6Te3 C30H43AuNP3Te C36H84Cu3N3O3P6Te3 C36H84Cu3N3P6S3Te3 C36H84Cu3N3P6Se3Te3
formula weight
crystal system
space group
a, Å
b, Å
c, Å
1318.30
monoclinic
C2/c
40.314(8)
11.660(2)
24.565(5)
90
110.06(3)
90
10846(4)
8
1.615
2.951
0.0335
0.0407
0.1011
1.036
1451.29
monoclinic
C2/c
39.819(8)
11.851(2)
24.668(5)
90
109.74(3)
90
10957(4)
8
1.759
2.829
0.0394
0.0551
0.1769
1.066
835.13
monoclinic
P21
8.2699(5)
22.988(1)
9.3852(6)
90
114.38(3)
90
1625.1(4)
2
1366.30
triclinic
P1
1414.48
triclinic
P1
1555.18
triclinic
P1
j
j
j
14.4878(3)
15.2199(4)
15.4833(3)
108.465(1)
105.978(2)
108.983(2)
2776.5(1)
2
1.634
2.889
0.0379
0.0526
8.4700(17)
20.327(4)
21.099(4)
117.28(3)
96.25(3)
90.27(3)
3203.3(14)
2
1.467
2.597
0.0230
0.0289
8.4684(17)
20.421(4)
21.183(4)
117.27(3)
95.65(3)
91.29(3)
3230.8(14)
2
1.599
4.168
0.0356
0.0478
R, deg
ꢁ, deg
γ, deg
V, Å3
Z
Dcalcd, g cm-3
µ (MoKR), mm-1
Rint
1.707
5.573
0.0641
0.0401
0.0822
1.078
R1 [I > 2σ(I)]b
wR2 (all data)c
GOF on F2
0.1309
0.0905
1.097
0.1352
1.058
1.029
a λ (MoKR) ) 0.71073 Å, T ) -100 °C. b R1 ) ∑||Fo| - |Fc||/∑|Fo|. wR2 ) [∑w(Fo - Fc2)2/∑wFo ]1/2
.
c
2
4
Scheme 2
amounts of 10% and 6%, respectively. Further recrystallizations
1
did not improve the purity. H NMR (CD2Cl2) δ: 2.20-1.96 (m,
4H, CH(CH3)2), 1.30-1.05 (m, 24H, CH(CH3)2). 31P NMR
(CD2Cl2) δ: 58.5 (d, 2JP-P ) 31, 1JSe-P ) 555, Se-P, 11), 52.7 (s,
1
1JSe-P ) 530, {Cu[(SePiPr2)2N]}3), 28.7 (s, JTe-P ) 1270,
{Cu[(TePiPr2)2N]}3), 22.7 (d, 2JP-P ) 31, 1JTe-P ) 1195, Te-P, 11).
Synthesis of {Cu(TePiPr2NPiPr2Se)}3 (11). Method B. A
solution of (tmeda)Li(TePiPr2NPiPr2Se) (2.50 mmol) in THF (40
mL) at -78 °C was added to a suspension of CuCl (248 mg, 2.51
mmol) in THF (20 mL) at -78 °C, and then warmed to room
temperature, with stirring, for 30 min. The solvent was removed
from the resulting orange/gray solution under vacuum. Extraction
with hot hexanes (20 mL) and filtration through Celite over a 0.45
disorder of methyl groups on isopropyl substituents was observed
in the data sets for 6, 7, and 9. In these cases the affected carbon
atoms were modeled as isotropic mixtures over two positions, with
mild geometric restraints. The unit cells for compounds 10 and 11
contained heavily disordered hexane solvent molecules for which
no suitable model could be found. The electron density associated
with these fragments were removed from the reflection data using
the program SQUEEZE (PLATON),22 leaving voids of about 469
and 445 Å3 for 10 and 11, respectively.
µm filter disk yielded a clear yellow solution. Storage of this
solution at -35 °C for several days yielded yellow crystals which
contained co-crystallized solvent. Heating to 100 °C under vacuum
afforded a solvent-free yellow powder (400 mg, 31%, mp 157-158
°C). 1H NMR (CD2Cl2) δ: 2.20-1.96 (m, 4H, CH(CH3)2),
1.30-1.05 (m, 24H, CH(CH3)2). 31P NMR (CD2Cl2) δ: 58.5 (d,
1
2
1
2JP-P ) 31, JSe-P ) 555, Se-P), 22.7 (d, JP-P ) 31, JTe-P
)
1195, Te-P). 77Se NMR (CD2Cl2) δ: -292.7 (d, 1JSe-P ) 557 Hz).
125Te NMR (CD2Cl2) δ: -650.0 (d, JTe-P ) 1197). Anal. Calcd
1
for C36H84Cu3N3P6Se3Te3: C, 27.80; H, 5.44; N, 2.70. Found: C,
28.17; H, 5.22; N, 2.70. X-ray quality crystals of 11·(C6H14)n grew
from a concentrated solution in hexanes at -35 °C.
Results and Discussion
Synthesis of {M(TePiPr2NPiPr2)}3 (6: M ) Cu; 7: M
) Ag) and (Ph3P)Au(TePiPr2NPiPr2) (8). To investigate
the coordination chemistry of the lithiated monotellurido
ligand [LiTePiPr2NPiPr2] (5) toward the group 11 elements,
reactions were carried out with CuCl, AgCl, and (Ph3P)AuCl
(Scheme 2). Solutions of 5 in THF were prepared according
to the established protocol12 and then reacted with a THF
suspension of the corresponding metal chloride in a 1:1
stoichiometry. 31P NMR spectra of reaction aliquots indicated
that the metatheses proceeded rapidly (complete in less than
1 h) to give the desired ligand substitution products with
minimal unwanted side reactions. Extraction of the products
with diethyl ether or hexanes provided an easy method for
separation of the LiCl by-product. The copper(I) and silver(I)
complexes 6 and 7, respectively, were crystallized from cold
X-ray Crystallography. A suitable crystal of each complex was
selected, coated in Paratone oil, and mounted on a glass fiber. Data
were collected at 173 K on a Nonius KappaCCD diffractometer using
MoKR radiation (λ ) 0.71073 Å) with ω and ꢀ scans. The unit cell
parameters were calculated and refined from the full data set. Crystal
cell refinement and data reduction were carried out by using the Nonius
DENZO package. After reduction, the data were corrected for
absorption based on equivalent reflections using SCALEPACK (Non-
ius, 1998). The structures were solved by direct methods with
SHELXS-9720 and refinement was carried out on F2 against all
independent reflections by the full-matrix least-squares method by using
the SHELXL-97 program.21 Hydrogen atoms were calculated geo-
metrically and were riding on their respective atoms. All non-hydrogen
atoms were refined with anisotropic thermal parameters.
Crystallographic data are summarized in Table 1. No special
considerations were needed for the refinement of compound 8. Some
(21) Sheldrick, G. M. SHELXL-97, Program for refinement of crystal
structures; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(22) Van Sluis, P.; Spek, A. L. Acta Crystallogr., Sect. A. 1990, 46, 194.
(20) Sheldrick, G. M. SHELXS-97, Program for solution of crystal
structures; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
3860 Inorganic Chemistry, Vol. 48, No. 8, 2009

Complexes of the P,Te-Centered Ligand [TePiPr2NPiPr2]-
Et2O solutions to give analytically pure X-ray quality yellow
crystals in moderate yields (21-46%), and the heteroleptic
triphenylphosphinegold(I) complex 8 was likewise isolated
from a hexanes solution as yellow crystals (53% yield). So
far we have been unable to find a solvent system from which
reproducibly high crystalline yields for 6-8 are obtained,
despite the 31P NMR data indicating they are formed to the
exclusion of significant amounts of by-product during their
syntheses.
chalcogen PNP ligands is now complete. Attempts to prepare
(tmeda)Li(TePiPr2NPiPr2O), a potentially useful source of
this ligand, by reaction of Me3NO and TMEDA with
[LiTePiPr2NPiPr2] were unsuccessful.
To address the question of whether the reactivity of 6 is
general for other elemental chalcogens, we conducted a
reaction with elemental sulfur in THF. At room temperature
the mixture rapidly darkened in color, and a black precipitate
was formed, presumably elemental tellurium. After stirring
for 18 h, a reaction aliquot was analyzed by 31P NMR
spectroscopy, and resonances corresponding to three major
products were identified: one singlet and two sets of mutually
coupled doublets, all in comparable quantities. The singlet
at δ 59.2 was attributable to the disulfido PNP complex
{Cu[(SPiPr2)2N]}3, which has been previously reported.26
One of the other two products was presumed to be the desired
complex {Cu(TePiPr2NPiPr2S)}3 (10) [δ 65.3 (d, 2JP-P ) 30
Hz), 20.9 (d, 2JP-P ) 30 Hz)], and this was later confirmed
by its unambiguous synthesis (vide infra). The third com-
pound was tentatively assigned to be {Cu(SPiPr2NPiPr2)}3
[δ 83.1 (d, 2JP-P ) 22 Hz), 53.3 (d, 2JP-P ) 22 Hz)], as the
doublet at δ 53.3 is similar in chemical shift to the other
Cu-S-P resonances in the mixture, and the downfield
resonance at δ 83.1 is consistent with a Cu-P moiety.
Based on these data, it was concluded that both the
oxidation of the PIII center and the nucleophilic displacement
of Te by elemental sulfur occur significantly at room
temperature, giving the three products observed by 31P NMR.
When this reaction was performed under kinetic conditions
(slow addition at -78 °C), selective oxidation of the PIII
center occurred to give 10 almost exclusively, as judged by
31P NMR. The product can be recrystallized from hexanes
to give a pure material in 26% yield.
Attempts to insert selenium into the Cu-P bond of 6 using
elemental gray selenium were unsuccessful. Although the
reaction proceeds at room temperature, complicated mixtures
of products are formed; at low temperature no significant
reaction is observed. However, freshly prepared amorphous
red selenium reacts with 6 under similar conditions as with
elemental sulfur to give the selenium-insertion product,
{Cu(TePiPr2NPiPr2Se)}3 (11). This product was contaminated
by about 16% of the homodichalcogenido complexes
{(Cu[(EPiPr2)2N]}3 (E ) Se, Te), which were not removed
by further recrystallizations. A pure sample of 11 was
obtained in 31% yield by reaction of the heterodichalco-
genido lithium reagent (tmeda)Li(TePiPr2NPiPr2Se)19 with
CuCl.
Attempts to prepare a gold(I) complex of L2 with a more
labile supporting ligand were also made; the reaction of
(tht)AuCl (tht ) tetrahydrothiophene) with 5 at -78 °C
initially produced yellow solutions. However, upon workup
the color changed to deep red indicating a redox reaction
(AuI f AuIII) had occurred. Recrystallization of the red oil
from hexanes gave single crystals of the known complex
{(Au(µ-Te)[TePiPr2NPiPr2]}2,11 the formation of which
necessitates the decomposition of the initial product through
tellurium abstraction, and hence this sacrificial loss of ligand
led to the low yield observed (a few crystals).
The new complexes 6-8 all exhibited sharp melting
points, but a gradual darkening of the solids while heating
and the dark orange to red color of the resulting liquid phases
indicated thermal decomposition was likely occurring.
Crystalline samples of 6-8 are relatively stable to air and
moisture; samples left exposed to ambient conditions for days
showed no visible signs of decomposition.
Reactions of {Cu(TePiPr2NPiPr2)}3 (6) with Elemental
Chalcogens. During crystallographic studies it was noted
that yellow crystals of 6 slowly dissolved in Paratone oil,
and over a period of weeks colorless crystalline rods
formed from this solution. A single-crystal X-ray analysis
determined these new crystals were of the composition
{Cu(TePiPr2NPiPr2O)}3 (9). We suggest that this unex-
pected product is formed by the oxidation of 6 by
molecular O2, resulting in a formal oxygen atom insertion
into the Cu-P bond. This interesting observation led to
attempts to prepare this new compound by rational
synthesis. It was found that the room-temperature reaction
of 6 with an oxygen-atom transfer reagent, Me3NO, in
THF resulted in the desired transformation after several
days. The heterodichalcogenido complex 9 was obtained
as a pure product in 51% yield after recrystallization from
hexanes. Interestingly, crystals of the silver(I) monotel-
lurido complex 7 were also observed to form a new
crystalline product upon standing in Paratone oil. In this
case, however, the product formed was identified as the
known ditellurido complex {Ag[(TePiPr2)2N]}6,8 a result
of ligand disproportionation instead of O-atom insertion.
The synthesis of 9 represents the first example of a
complex containing a dichalcogenidoimidodiphosphinate
ligand [EPR2NPR2E′]- with E ) Te, E′ ) O. All other
possible mixed chalcogen ligands of this type have been
previously synthesized: for example, the protonated ligands
EPPh2NHPPh2E′ (E ) O, E′ ) S;23 E ) O, E′ ) Se;24 E )
S, E′ ) Se25) are all known, and the lithium derivatives
(tmeda)Li(TePiPr2NPiPr2E) (E ) S, Se) have been reported
recently.19 With the synthesis of 9 the series of mixed-
The formal insertion of elemental chalcogens into metal-
phosphorus bonds has been previously reported but does not
appear to be a well-studied transformation compared to, for
example, insertions of chalcogens into metal-carbon bonds.
The syntheses of 9-11 (Scheme 3) therefore represent
(23) Schmidpeter, A.; Groeger, H. Chem. Ber. 1967, 100, 3979.
(24) Slawin, A. M. Z.; Smith, M. B.; Woollins, J. D. J. Chem. Soc., Dalton
Trans. 1996, 3659.
(25) Bhattacharyya, P.; Slawin, A. M. Z.; Smith, M. B. J. Chem. Soc.,
Dalton Trans. 1998, 2467.
(26) Birdsall, D. J.; Slawin, A. M. Z.; Woollins, J. D. Inorg. Chem. 1999,
38, 4152.
Inorganic Chemistry, Vol. 48, No. 8, 2009 3861

Ritch and Chivers
Scheme 3
further cases of this relatively rare reaction. Selected ex-
amples include the tin(IV) compound Ph2P-SnEt3, which
was reported to react with dioxygen present in air to form
Ph2P(O)O-SnEt3,27 and the reaction of sulfur with the
copper(I) complex [(dmp)Cu(PPh3)2][BF4] (dmp ) 2,9-di-
methyl-1,10-phenanthroline) to yield the phosphine sul-
fide complex [(dmp)Cu(SPPh3)2][BF4].28 Stepwise selenium
insertion into the Pt-P bonds of [Pt((Ph2P)2CH2)2]Cl2
to give [Pt((Ph2P)2CH2)(SePPh2CH2PPh2)]Cl2 and then
[Pt(SePPh2CH2PPh2)2]Cl2 has also been reported.29 In a closer
analogy to the current work, the reaction of elemental sulfur or
tellurium with the lithium reagents [LiTePiPr2NPiPr2] (5) or
[LiSePiPr2NPiPr2], respectively, yielded the heterodichalco-
genido PNP complexes (tmeda)Li[TePiPr2NPiPr2E] (E ) S,
Se).19
Crystal Structures of 6-11. The solid-state structures
of 6 and 7 are isostructural and reveal a trimeric arrangement
with bridging tellurium centers. A representative thermal
ellipsoid plot of 6 is shown in Figure 1; selected bond lengths
and angles are displayed in Table 2. The trinuclear bonding
arrangement is a relatively common motif for group 11
dichalcogenido PNP complexes. For example, the related
species {Cu[(EPiPr2)2N]}3 (E ) S,26 Se,9 Te8) are all trimeric
and exhibit a core Cu3E3 ring. In 6 and 7, the M3Te3 rings
are highly distorted from a chairlike arrangement, instead
adopting a conformation best described as a twist-boat. Each
metal center is coordinated by a P,Te-chelating ligand, as
well as a tellurium atom from an adjacent ligand. The
resulting geometries about the metal centers are approxi-
mately trigonal planar (Σ>(M): M ) Cu, 349.3-359.4°; M )
Ag, 349.7-358.3°). The endocyclic angles for the central
ring are similar in each case: the Te-M-Te angles range
from 100.27(3)-131.58(4)° while the M-Te-M values fall
within the range 60.97(3)-67.88(3)°.
Figure 1. Representative thermal ellipsoid plot (30% probability) of 6 (M
) Cu) and 7 (M ) Ag). Only R-carbon atoms of isopropyl substituents are
shown, and hydrogen atoms are omitted for clarity.
Table 2. Selected Bond Lengths (Å) and Angles (deg) for
{M(TePiPr2NPiPr2)}3
6: M ) Cu
7: M ) Ag
M1-Te1
M1-Te3
M2-Te1
M2-Te2
M3-Te2
M3-Te3
M1-P1
M2-P3
M3-P5
P2-Te1
P4-Te2
P6-Te3
M1-M2
M2-M3
M3-M1
P1-N1
2.579(1)
2.570(1)
2.519(1)
2.647(1)
2.564(1)
2.566(1)
2.277(2)
2.243(2)
2.259(2)
2.484(2)
2.465(2)
2.483(2)
2.847(1)
2.645(1)
2.741(1)
1.635(5)
1.586(5)
1.643(5)
1.586(5)
1.639(5)
1.574(6)
2.804(1)
2.732(1)
2.682(1)
2.912(1)
2.722(1)
2.814(1)
2.431(3)
2.403(3)
2.433(3)
2.471(3)
2.460(3)
2.470(3)
3.019(2)
2.924(2)
3.036(1)
1.640(12)
1.577(11)
1.644(10)
1.584(11)
1.646(9)
1.583(9)
P2-N1
P3-N2
P4-N2
P5-N3
P6-N3
Te3-M1-Te1
M1-Te1-M2
Te1-M2-Te2
M2-Te2-M3
Te2-M3-Te3
M3-Te3-M1
P1-N1-P2
128.75(4)
67.88(3)
100.27(3)
60.97(3)
125.50(3)
64.53(3)
125.3(3)
124.7(3)
127.3(3)
131.58(4)
66.74(4)
102.82(4)
62.42(3)
125.66(4)
66.34(3)
128.7(6)
126.3(6)
129.2(6)
P3-N2-P4
P5-N3-P6
2.932(2) Å).16 The bond lengths for the M-P connectivities
are typical of neutral phosphine donor complexes (d(Cu-P)
) 2.243(2)-2.277(2) Å; d(Ag-P) ) 2.403(3)-2.433(3)
Å).31
Within the ligand framework the P-Te distances are
similar for 6 and 7 and range from 2.460(3) to 2.484(2) Å,
which are indicative of single-bond character. These values
are slightly longer than the analogous bond lengths observed
in the homoleptic group 12 complexes M(TePiPr2NPiPr2)2(M
TheM-Tedistancesin6and7(M)Cu:2.519(1)-2.647(1)
Å; M ) Ag: 2.682(1)-2.912(1) Å) are similar to those
observed in the complexes {M[(TePiPr2)2N]}n (1: M ) Cu,
n ) 3; 2: M ) Ag, n ) 6)8 and are also comparable to
oligomeric copper(I) and silver(I) tellurolate complexes such
as [Cu2(µ-TePh)2(PMe3)4] (d(Cu-Te) ) 2.6316(7)-2.6677(7)
Å),30 or [Ag9(µ3-TePh)9(PEt2Ph)6] (d(Ag-Te) ) 2.731(1)-
(27) Campbell, I. G. M.; Fowles, G. W. A.; Nixon, L. A. J. Chem. Soc.
1964, 1389.
(28) Reigle, R. K.; Casadonte, D. J.; Bott, S. G. J. Chem. Crystallogr. 1994,
24, 769.
(29) Peringer, P.; Schwald, J. J. Chem. Soc., Chem. Commun. 1986, 1625.
(30) DeGroot, M. W.; Cockburn, M. W.; Workentin, M. S.; Corrigan, J. F.
Inorg. Chem. 2001, 40, 4678.
(31) A search of the Cambridge structural database for R3P-M complexes
revealed mean bond distances of d(Cu-P) ) 2.254(1) Å and d(Ag-
P) ) 2.445(1) Å for 4646 and 2733 instances of each bond,
respectively.
3862 Inorganic Chemistry, Vol. 48, No. 8, 2009

Complexes of the P,Te-Centered Ligand [TePiPr2NPiPr2]-
Figure 3. Representative thermal ellipsoid plot (30% probability) of 9 (E
) O), 10 (E ) S), and 11 (E ) Se). Only R-carbon atoms of isopropyl
substituents are shown, and hydrogen atoms are omitted for clarity.
Figure 2. Thermal ellipsoid plot of 8 (30% probability). Hydrogen atoms
are omitted for clarity.
It is the longest reported Au-Te distance among gold(I)
complexes containing a tellurium-based ligand, and in fact
only one longer distance was found in the Cambridge
Structural Database: the gold telluraborane complex [Et4N][2-
Ph3P-closo-2,1-AuTeB10H10] exhibits Au-Te bond lengths
of 2.839(3) Å and 2.853(3) Å in two crystallographically
unique anions.34 The two Au-P bond lengths seen in 8 are
slightly different, with the triphenylphosphine ligand being
closer to the gold center by about 0.05 Å. Complex 8 is the
first example of a structurally characterized complex contain-
ing a AuP2Te core. Metrical parameters within the ligand
framework are similar to those seen in 6 and 7; normal P-Te
and P-N distances are observed.
Table 3. Selected Bond Lengths (Å) and Angles (deg) for
(Ph3P)Au(TePiPr2NPiPr2) (8)
Au1-Te1
Au1-P2
Au1-P3
P1-Te1
P1-N1
2.762(1)
2.343(3)
2.298(3)
2.439(3)
1.599(8)
1.637(9)
Te1-Au1-P3
Te1-Au1-P2
P2-Au1-P3
120.61(7)
93.89(7)
145.50(9)
P2-N1
) Zn, Cd, Hg), which were observed to be 2.430(2)-2.441(2)
Å,12 but are close to the observed distance of 2.453(1) Å in
the dimeric GaIII complex {Ga(µ-Te)[TePiPr2NPiPr2]}2 (4).10
Overall, the metrical parameters suggest a bonding situation
best described as a tellurolate/phosphine complex, rather than
a phosphine telluride/phosphide donor set. This suggestion
is supported by the P-N distances, which are indicative of
strong Te-PdN-P character in the ligand backbone, as
opposed to TedP-NdP.
A point of interest in these polynuclear copper(I) and
silver(I) complexes is the presence of relatively short M · · ·M
intramolecular distances, which are within the sums of the
van der Waals radii for Cu-Cu and Ag-Ag (2.8 Å and 3.44
Å, respectively). For 6 the distances range from 2.645(1) to
2.847(1) Å, and for 7 the values are between 2.924(2) and
3.036(1) Å. It is not unusual for short metal-metal distances
of this nature to be observed in complexes with bridging
ligands,32 and so it is not clear whether they represent true
metallophilic interactions or are imposed by the geometry
of ligands. The fact that the metal centers are all very nearly
trigonal planar (vide supra) may indicate that only weak
interactions, if any, are present.33
The new heterodichalcogenido PNP complexes 9-11 were
also characterized by single-crystal X-ray crystallography and
were found to have similar structures. A representative
thermal ellipsoid plot of 10 is shown in Figure 3; selected
metrical parameters are presented in Table 4.
As with 6, the copper(I) complexes 9-11 each exhibit a
trinuclear bonding arrangement with a central six-membered
Cu3Te3 ring. The lighter chalcogen occupies the third
coordination site at the metal centers, which all possess a
trigonal planar geometry (9: E ) O, Σ<Cu ) 359.7-359.9°;
10: E ) S, Σ<Cu ) 359.9-360.0°; 11: E ) Se, Σ<Cu )
359.7-359.9°). The central Cu3Te3 rings in 9-11 are
chairlike, indicating that the addition of an oxygen, sulfur,
or selenium atom to 6 (which has a distorted twist-boat
central ring) has a significant influence on the conformation
of this ring system. This is reflected by the change in the
average endocyclic Cu-Te-Cu angle upon going from 6
(ca. 64°) to 9-11 (ca. 89, 109, and 108°, respectively),
suggesting there is relief of ring strain in these chalcogenated
derivatives. The Cu-Te and P-Te distances are comparable
to those present in 6 (vide supra), and the Cu · · ·Cu distances
of >3.4 Å suggest no significant intramolecular attractions
exist between the metal centers in 9-11. The three outer
The crystal structure of 8 is shown in Figure 2, and
selected bond parameters are displayed in Table 3.
The complex 8 is monomeric in the solid state, showing
no close intermolecular contacts in the unit cell. The gold(I)
center is trigonal planar (Σ<(Au1) ) 360.0°) with a Au-Te
distance of 2.762(1) Å, which is significantly longer than
the corresponding distances observed in the ditellurido PNP
complex (Ph3P)Au[(TePiPr2)2N] (2.639(1) and 2.616(7) Å).8
(34) Ferguson, G.; Gallagher, J. F.; Kennedy, J. D.; Kelleher, A.-M.;
Spalding, T. R. Dalton Trans. 2006, 2133; The tellurium atoms in
this crystal structure are positionally disordered over several boron
sites, and the gold(I) center is pentavalent because of multicenter
bonding to the telluroborane; hence the quoted Au-Te bond distances
may not be representative of a normal two-electron dative bond.
(32) Pyykko¨, P. Chem. ReV. 1997, 88, 563.
(33) Chivers, T.; Parvez, M.; Schatte, G. Angew. Chem., Int. Ed. 1999, 38,
2217.
Inorganic Chemistry, Vol. 48, No. 8, 2009 3863

Ritch and Chivers
1JAg-P value of 444 Hz. The analogous resonance in complex
8 was very broad with no discernible coupling. The gold(I)
complex 8 exhibited an additional broad 31P resonance at δ
55.7 assigned to the PPh3 ligand. The broad nature of these
two resonances in the 31P NMR spectrum of 8 suggested
lability of the corresponding two metal-bound phosphorus
centers in solution at room temperature. A 31P NMR spectrum
of 8 obtained at 193 K exhibited three very sharp resonances,
illustrating that ligand exchange processes are slow with
respect to the NMR time scale at this temperature. Each
resonance displayed a doublet-of-doublets coupling pattern,
indicating that the individual 31P centers in 8 are spin-spin
Table 4. Selected Bond lengths (Å) and Angles (deg) for
{Cu(TePiPr2NPiPr2E)}3
9: E ) O
10: E ) S
11: E ) Se
Cu1-Te1
Cu1-Te2
Cu2-Te2
Cu2-Te3
Cu3-Te1
Cu3-Te3
Cu1-E1
Cu2-E2
Cu3-E3
P1-Te1
P3-Te2
P5-Te3
P2-E1
2.509(1)
2.490(1)
2.513(2)
2.487(1)
2.485(1)
2.506(1)
1.995(6)
2.012(6)
2.004(5)
2.470(2)
2.475(3)
2.477(3)
1.501(6)
1.510(6)
1.502(6)
2.519(1)
2.526(1)
2.516(1)
2.534(1)
2.531(1)
2.516(1)
2.244(2)
2.236(1)
2.241(1)
2.454(1)
2.447(1)
2.456(1)
2.021(2)
2.020(2)
2.026(2)
2.514(1)
2.519(1)
2.505(1)
2.532(1)
2.531(1)
2.514(1)
2.352(2)
2.369(1)
2.350(1)
2.450(2)
2.431(2)
2.452(2)
2.164(2)
2.162(2)
2.169(2)
2
coupled to the other two. The intraligand JP-P coupling
P4-E2
2
constant was determined to be 56 Hz, while a large JP-P
P6-E3
value of 230 Hz was observed for the Ph3P-Au-PiPr2 unit.
3
Te1-Cu1-Te2
Cu1-Te2-Cu2
Te2-Cu2-Te3
Cu2-Te3-Cu3
Te3-Cu3-Te1
Cu3-Te1-Cu1
126.49(5)
87.99(4)
125.92(6)
91.90(5)
125.38(5)
88.10(5)
112.89(4)
108.06(3)
115.11(3)
111.08(4)
111.36(3)
107.87(3)
113.36(4)
108.13(4)
116.27(4)
109.99(4)
112.68(4)
107.33(4)
A three-bond P-P coupling with a value of JP-P ) 26 Hz
across the Ph3P-Au-Te-PiPr2 fragment was also apparent.
The 125Te NMR spectra of 6-8 exhibited single resonances
1
split into doublets due to JTe-P coupling, with values
correlating well to those observed in the 31P NMR spectra.
The chemical shifts spanned a wide range (δ -632.9, -856.9
and -532.6, respectively), indicating a particular sensitivity
to the metal center bound to tellurium. A 77Se NMR spectrum
obtained for complex 11 exhibited a doublet at δ -292.7
Table 5. 31P and 125Te NMR Chemical Shifts (ppm) and Coupling
Constants (Hz) for Complexes 6-11 in CD2Cl2
2
1
compound δ(31P), P-M δ(31P), P-Te δ(31P), P-E JP-P JTe-P δ(125Te)
6
7
109.9
112.4
136.2
72.9
68.2
77.0
11.8
21.1
22.7
103 1085 -632.9
1
94
56
21
30
31
1077 -856.9
1181 -532.6
1119 -631.8
1173 -628.7
1195 -650.0
with a JSe-P value of 557 Hz, comparable to the value of
534 Hz for the related complex {Cu[(SePiPr2)2N]}3.9
The 31P NMR spectra of the heterodichalcogenido PNP
ligand complexes 9-11 exhibited a significant upfield shift
in both resonances when compared to those of the parent
copper(I) complex 6. The phosphorus centers bonded to the
lighter chalcogens resonated at δ 46.8, 65.3, and 58.5, while
for the tellurium-bound sites the chemical shifts were δ 11.8,
21.1, and 22.8 for 9-11, respectively. A diminution of the
2JP-P values was also noted (9: 21 Hz; 10: 30 Hz; 11: 31
Hz), suggesting a notable change in the electronic structure
in the P-N-P ligand backbone upon chalcogen insertion
into the Cu-P bond. Similar values for chemical shifts and
2JP-P coupling constants were found for the recently prepared
lithium derivatives (tmeda)Li[TePiPr2NPiPr2E] (E ) S, Se).19
8 (193K)
9
10
11
46.8
65.3
58.5
CuTePNPE rings are all oriented in the same direction, giving
the complexes a bowl-like motif. There are indications of
weak intermolecular Te · · · Te contacts in the case of 9
(d(Te· · · Te) ) 3.891-4.039 Å, sum of van der Waals radii
) 4.12 Å) between adjacent Cu3Te3 rings in the unit cell,
forming weakly bound dimers.
NMR Characterization of 6-11. The multinuclear (31P,
77Se, 125Te) NMR spectra of 6-11 in CD2Cl2 provided useful
insights into the structures of these compounds in solution
(Table 5). The monotellurido complexes 6-8 all showed two
distinct 31P environments attributable to the L2 ligand. Since
the crystal structures of 6 and 7 both possess six unique
phosphorus sites, this indicates the copper(I) and silver(I)
complexes of L2 are conformationally flexible in solution.
The metal-bound phosphorus centers exhibit resonances from
δ 109.9 to 137.3 and the tellurium-bound centers have values
in the narrow range of δ 68.2-74.7. Satellites arising from
coupling to 125Te were observed on the latter resonances,
1
The JTe-P values for 9-11 were found to be 1119, 1177,
and 1195 Hz, respectively. The 125Te NMR spectra exhibited
doublets with similar chemical shift values (δ -631.2,
-628.7, and -650.0 for 9-11, respectively) that closely
match that of 6 (-632.9), again suggesting a strong
dependence of the 125Te chemical shift on the identity of
the metal center.
1
with very similar JTe-P values of 1085 and 1077 Hz for 6
Variable Temperature NMR and ESI-MS Studies of
6 and 7. Certain features of the room temperature 31P NMR
spectrum of the silver(I) complex 7 suggested the occurrence
of exchange processes in solution. For example, the reso-
nance corresponding to the silver-bound site was quite broad
(fwhm ) ca. 600 Hz). Samples at higher dilutions yielded
no visible change in the spectra, indicating either an
intramolecular process or a rapid intermolecular exchange
that is not significantly affected by changes in concentration.
Previously, low-temperature 31P NMR spectra have been
obtained in studies of the homodichalcogenido PNP
complexes {M[(EPiPr2)2N]}3 in solution. The recently
and 7, respectively, and 1189 Hz for 8. The difference of
about 100 Hz in values may reflect the bridging (three-
coordinate) nature of the tellurium centers in 6 and 7. A
doublet pattern with magnitudes in the range 62-103 Hz
was observed in 6-8 for the tellurium-bound phosphorus
2
sites, arising from JP-P coupling to the metal-bound 31P
atoms. A corresponding broad doublet for the metal-bound
31P site was observed for 6; for the complex 7 the signal
was a broad doublet of doublets because of additional
spin-spin coupling to the two spin-active silver isotopes
(
107Ag: I ) 1/2, 52%; 109Ag: I ) 1/2, 48%) with an average
3864 Inorganic Chemistry, Vol. 48, No. 8, 2009

Complexes of the P,Te-Centered Ligand [TePiPr2NPiPr2]-
signals at m/z 378.25, 442.14, and 753.18 amu, the masses
and isotope distributions of which corresponded to [L2]+,
[{Cu(L2)} + H]+, and [{Cu(L2)}2 - Te + H]+, respectively.
No signal for the trimeric species was observed. These data
provide further evidence that an equilibrium between various
oligomeric species and the trimer may exist in THF solution.
Although no trimer was observed directly, it is possible that
larger oligomers are unstable under the conditions of the ESI
experiment (the monomer was observed as the protonated
parent ion, but the dimer was found to lose Te upon
ionization).
An ESI-MS spectrum of 7 in THF consisted of unidentified
ions associated with major fragmentation, indicating the
silver(I) complex appears to be much more labile under ESI
conditions. However, a repetition of this experiment in a 1:1
mixture of THF and acetonitrile yielded an improved
spectrum with the most intense signal at m/z 486.19 amu,
[{Ag(L2)} + H]+. Two less intense but clearly visible sig-
nals at m/z 840.88 and 968.86 amu were attributable to
[{Ag(L2)}2 - Te + H]+ and [{Ag(L2)}2 + H]+, respectively.
Based on the low temperature 31P NMR and ESI-MS data
for complexes 6 and 7, it is likely that there is a solution
equilibrium process in which the trimer is rapidly exchanging
with two or more other oligomers.
Figure 4. 31P NMR spectra of 7 in d8-THF at different temperatures.
reported ditellurido PNP complexes {M(TePiPr2)2N}n (M
) Cu, n ) 3; M ) Ag, n ) 6) exhibited singlet resonances
in their 31P NMR spectra, and no change was observed at
low temperature.8 Woollins and co-workers observed a
singlet in the 31P NMR spectrum of the disulfido copper(I)
complex {Cu(SPiPr2)2N]}3, and saw no additional signals
upon cooling.26 We recorded low-temperature 31P NMR
spectra of 7 to investigate its solution behavior in d8-THF
(Figure 4).
Upon cooling a sample to 233 K both resonances
broadened significantly, and new phosphorus environments
close to each signal emerged. At 193 K two sets of well-
resolved resonances were seen, as well as several very broad
signals. When the sample was cooled to 183 K, the latter
began to separate into individual resonances but remained
broad, indicating that even at this temperature chemical
exchange was still rapid on the NMR time scale. At least
four unique species could be detected in solution at this
temperature, with 1JAg-P coupling constants ranging from 403
to 513 Hz. No 125Te satellites could be resolved. The apparent
Conclusions
The first monochalcogenido PNP complexes of copper(I)
(6), silver(I) (7), and gold(I) (8) have been synthesized. X-ray
structural analysis reveals that 6 and 7 are trinuclear in the
solid state, while 8 is a monomer supported by a PPh3 ligand.
Variable-temperature NMR and ESI-MS studies of the
complexes 6 and 7 in THF provide evidence for the
simultaneous presence of several different oligomers in
solution, which may be related to the strain of the M3Te3
ring in these complexes. The copper(I) complex 6 reacts
readily with elemental oxygen, sulfur, or red selenium via
insertion into the Cu-P bond yielding the novel heterod-
ichalcogenido PNP complexes {Cu(TePiPr2NPiPr2E)}3 (9: E
) O; 10: E ) S; 11: E ) Se); complex 9 contains the first
example of the elusive O,Te dichalcogenido PNP ligand. The
new complexes 6-11 are potential sources of binary or
ternary chalcogenides of the coinage metals via AACVD
techniques. Such investigations will be the subject of future
studies.
doublet-of-triplets patterns observed for the silver-bound 31
P
resonances are likely due to the overlap of two doublet-of-
doublets patterns (2JP-P and 1JAg-P), where the difference in
1JAg-P between the two spin-active isotopes of silver (107Ag:
I ) 1/2, 51.82%; 109Ag: I ) 1/2, 48.18%) is similar to the
2
value of JP-P. When the sample was warmed to room
temperature, the original 31P NMR spectrum was reproduced.
These data indicate that several oligomers of the form
[Ag(TePiPr2NPiPr2)]n are rapidly interchanging in d8-THF
solution, possibly via dissociation of the parent trinuclear
complex into various [Ag(TePiPr2NPiPr2)]n oligomers in an
equilibrium. A repetition of this experiment using a d8-
toluene solution of 7 was performed. Similar results were
obtained in that four sets of resonances could be clearly seen;
however, no improvement in resolution was achieved.
Variable-temperature 31P NMR data for a d8-THF solution
of the copper(I) complex 6 were obtained using similar
conditions, and four unique oligomers were also observed
in solution at low temperature; however, no coupling
constants could be discerned as the signals were quite broad.
In an attempt to acquire more information concerning this
equilibrium, electrospray ionization mass spectrometry (ESI-
MS) was utilized to analyze THF solutions of 6 and 7. The
spectrum of the copper(I) complex 6 is dominated by three
Acknowledgment. The authors gratefully acknowledge
financial support from the Natural Sciences and Engineering
Research Council (Canada), Alberta Ingenuity (J.S.R.) and
the Izaak Walton Killam Memorial Foundation (J.S.R.), as
well as Wade White and Qiao Wu for the ESI-MS analysis
of 6 and 7.
Supporting Information Available: Crystallographic data in
CIF file format. This material is available free of charge via the
Internet at http://pubs.acs.org.
IC802428B
Inorganic Chemistry, Vol. 48, No. 8, 2009 3865