Homoleptic, heteroleptic and mixed-valent thallium and indium complexes of multidentate chalcogen-centred PCP-bridged ligands

Article abstract of DOI:10.1039/c1dt10646e

The metathetical reaction of [Li(TMEDA)][HC(PPh₂Se)₂] ([Li(TMEDA)]1) with TlOEt in a 1:1 molar ratio afforded a homoleptic Tl(i) complex as an adduct with LiOEt, Tl[HC(PPh₂Se)₂] ·LiOEt (7), which undergoes selenium-proton exchange upon mild heating (60 °C) to give the mixed-valent Tl(i)/Tl(iii) complex {[Tl][Tl{(Se) C(PPh₂Se)₂}₂]}_∞ (8). Treatment of TlOEt with [Li(TMEDA)]₂[(SPh₂P) ₂CE′E′C(PPh₂S)₂] (3b, E′ = S; 3c, E′ = Se) in a 2:1 molar ratio produced the binuclear Tl(i)/Tl(i) complexes Tl₂[(SPh₂P)₂CE′E′ C(PPh₂S)₂] (9b, E′ = S; 9c, E′ = Se), respectively. Selenium-proton exchange also occurred upon addition of [Li(TMEDA)]1 to InCl₃ to yield the heteroleptic complex (TMEDA)InCl[(Se)C(PPh₂Se)₂] (10a). Other examples of this class of In(iii) complex, (TMEDA)InCl[(E′)C(PPh₂E)₂] (10b, E = E′ = S; 10c, E = S, E′ = Se) were obtained via metathesis of InCl₃ with [Li(TMEDA)]₂[(E′)C(PPh ₂E)₂] (2b, E = E′ = S; 2c, E = S, E′ = Se, respectively). All new compounds have been characterized in solution by ¹H and ³¹P NMR spectroscopy and the solid-state structures have been determined for 8, 9c and 10a-c by single-crystal X-ray crystallography. Complex 8 is comprised of Tl⁺ ions that are weakly coordinated to octahedral [Tl{(Se)C(PPh₂Se)₂} ₂]^- anions to give a one-dimensional polymer. The complex 9c is comprised of two four-coordinate Tl⁺ ions that are each S,S′,S′′,Se bonded to the hexadentate [(SPh₂P) ₂CSeSeC(PPh₂S)₂]^2- ligand in which d(Se-Se) = 2.531(2) A. The six-coordinate In(iii) centres in the distorted octahedral complexes 10a-c are connected to a tridentate [(E′)C(PPh ₂E)₂]^2- dianion, a chloride ion and a neutral bidentate TMEDA ligand. The Royal Society of Chemistry 2011.

Full text of DOI:10.1039/c1dt10646e

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PAPER
Homoleptic, heteroleptic and mixed-valent thallium and indium complexes of
multidentate chalcogen-centred PCP-bridged ligands†
Maarit Risto,a Tristram Chivers*a and Jari Konua,b
Received 13th April 2011, Accepted 8th May 2011
DOI: 10.1039/c1dt10646e
The metathetical reaction of [Li(TMEDA)][HC(PPh2Se)2] ([Li(TMEDA)]1) with TlOEt in a 1 : 1 molar
ratio afforded a homoleptic Tl(I) complex as an adduct with LiOEt, Tl[HC(PPh2Se)2]·LiOEt (7), which
undergoes selenium–proton exchange upon mild heating (60 ◦C) to give the mixed-valent Tl(I)/Tl(III)
complex {[Tl][Tl{(Se)C(PPh2Se)2}2]}• (8). Treatment of TlOEt with [Li(TMEDA)]2[(SPh2P)2CE¢E¢C-
(PPh2S)2] (3b, E¢ = S; 3c, E¢ = Se) in a 2 : 1 molar ratio produced the binuclear Tl(I)/Tl(I) complexes
Tl2[(SPh2P)2CE¢E¢C(PPh2S)2] (9b, E¢ = S; 9c, E¢ = Se), respectively. Selenium–proton exchange also
occurred upon addition of [Li(TMEDA)]1 to InCl3 to yield the heteroleptic complex
(TMEDA)InCl[(Se)C(PPh2Se)2] (10a). Other examples of this class of In(III) complex,
(TMEDA)InCl[(E¢)C(PPh2E)2] (10b, E = E¢ = S; 10c, E = S, E¢ = Se) were obtained via metathesis of
InCl3 with [Li(TMEDA)]2[(E¢)C(PPh2E)2] (2b, E = E¢ = S; 2c, E = S, E¢ = Se, respectively). All new
compounds have been characterized in solution by 1H and 31P NMR spectroscopy and the solid-state
structures have been determined for 8, 9c and 10a–c by single-crystal X-ray crystallography. Complex 8
is comprised of Tl+ ions that are weakly coordinated to octahedral [Tl{(Se)C(PPh2Se)2}2]- anions to
give a one-dimensional polymer. The complex 9c is comprised of two four-coordinate Tl+ ions that are
each S,S¢,S¢¢,Se bonded to the hexadentate [(SPh2P)2CSeSeC(PPh2S)2]2- ligand in which d(Se–Se) =
˚
2.531(2) A. The six-coordinate In(III) centres in the distorted octahedral complexes 10a–c are connected
to a tridentate [(E¢)C(PPh2E)2]2- dianion, a chloride ion and a neutral bidentate TMEDA ligand.
Hg[HC(PPh2Se)2]2, also promotes proton–selenium exchange to
give a binuclear Hg(II)/Hg(II) complex of 2a.6
Introduction
Our recent development of a synthesis of the TMEDA-solvated
lithium derivative of the PCP-bridged monoanion [HC(PPh2Se)2]-
(1)1 has paved the way for a comparison of the coordination
behaviour of this selenium-centred ligand with that of the well-
studied PNP-bridged analogue.2,3 Metathetical reactions of 1 with
group 12 dihalides MCl2 proceed in the expected manner to give
homoleptic complexes M[HC(PPh2Se)2]2 (M = Zn, Hg) that exhibit
Se,Se¢ chelation,1 cf. M[N(PPh2Se)2]2.4,5 In distinct contrast to this
normal behaviour, however, the reactions of 1 with certain main
group dihalides MCl2 generate the triseleno PCP-bridged dianion
[(Se)C(PPh2Se)2]2- (2a) in homoleptic complexes with M(IV) (M =
Sn,Te) via a carbon-centred proton–selenium exchange combined
with redox disproportionation of the metal centre.6 Interestingly,
mild thermolysis of the mononuclear Hg(II) derivative of 1,
In order to circumvent the mechanistically obscure proton–
selenium exchange process7 for the production of the novel class of
trichalcogeno ligands of the type 2, we have prepared the dianions
2b and 2c as TMEDA-solvated Li+ derivatives, by the treatment
of Li2[C(PPh2S)2]8 with sulfur or selenium, respectively.9 The all-
selenium derivative cannot be obtained via this route because of the
unavailability of Li2[C(PPh2Se)2] owing to cleavage of P–Se bonds
by RLi reagents.1 One-electron oxidation of the dianions 2b and 2c
with I2 produces the dimeric dianions [(SPh2P)2CE¢E¢C(PPh2S)2]2-
(3b, E¢ = S; 3c, E¢ = Se) with elongated central chalcogen–chalcogen
bonds as S,S¢-chelated, TMEDA-solvated Li+ derivatives.9
The potential versatility of the multidentate chalcogen-centred
ligands 1–3 has been established through investigations of
their behaviour towards coinage metals.10,11 Intriguing binuclear
Cu(I)/Cu(I) complexes of the type 4 are formed by (a) treatment
of monoanion 1 with CuCl via the proton–selenium exchange
process (4a), (b) the redox reaction of monomeric dianion 2c with
CuCl2 (4c), or (c) metathesis of dimeric dianions 3b and 3c with
aDepartment of Chemistry, University of Calgary, Calgary, Alberta, Canada,
T2N 1N4. E-mail: chivers@ucalgary.ca; Fax: +1 403 289 9488; Tel: +1 403
220 5741
bCurrent address: Department of Chemistry, University of Jyva¨skyla¨, P.O.
Box 35, FI-40014, Jyva¨skyla¨, Finland
2
CuCl (4b and 4c).10,11 The h -Se2 motif observed in the complexes
4a and 4c is a novel bonding arrangement for RSe–SeR ligands.12
Coordination of the two copper centres to the central E–E bond
results in a (further) elongation of this bond compared to the
† Electronic supplementary information (ESI) available: variable temper-
1
ature 31P{ H} NMR spectra of 9b and 9c. CCDC reference numbers
821785–821789. For ESI and crystallographic data in CIF or other
electronic format see DOI: 10.1039/c1dt10646e
8238 | Dalton Trans., 2011, 40, 8238–8246
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©

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to yield the heteroleptic complex (TMEDA)InCl[(Se)C(PPh2Se)2]
(10a). Other examples of this class of In(III) complex,
(TMEDA)InCl[(E¢)C(PPh2E)2] (10b, E = E¢ = S; 10c, E = S, E¢ = Se)
can be obtained via metathesis of 2b or 2c with InCl3, respectively.
1
All new compounds have been characterized in solution by H
and 31P NMR spectroscopy and the solid-state structures of
8, 9c and 10a–c have been determined by single-crystal X-ray
crystallography.
Experimental
Reagents and general procedures
All reactions and the manipulations of products were
performed under an argon atmosphere by using standard
Schlenk techniques or an inert atmosphere glove box. The
compounds [H2C(PPh2)2] (Aldrich, 97%), TMEDA (Aldrich,
99%), MeLi (Aldrich, 1.6 M sol. in Et2O), InCl3 (Aldrich,
98%) and TlOEt (Aldrich, 98%) were used as received.
distance in the corresponding bis-E,E¢-chelated Li+ derivatives.
This bond-stretching is especially pronounced in the all-sulfur
system 4b for which DFT calculations indicate some diradicaloid
character.11,13 Silver (I) forms a binuclear Ag(I)/Ag(I) complex 5c
with the dimeric dianion 3c that is structurally similar to the
Cu(I) complex 4c.12 By contrast, the treatment of 3b or 3c with
Au(CO)Cl produces the mixed-valent Au(I)/Au(III) complexes 6b
and 6c, respectively, in which the central chalcogen–chalcogen
bond has been cleaved and the ligands are the tridentate dianions
[(E¢)C(PPh2S)2]2- (2b, E¢ = S; 2c, E¢ = Se).11
[Li(TMEDA)][HC(PPh2Se)2],1
[Li(TMEDA)]2[(E¢)C(PPh2S)2]
(E¢ = S, Se)9 and [Li(TMEDA)]2[(SPh2P)2CE¢E¢C(PPh2S)2] (E¢ = S,
Se)9 were prepared according to literature methods. The solvents
n-hexane, toluene, Et2O and THF were dried by distillation
over Na/benzophenone and CH2Cl2 over CaH2 under an argon
atmosphere prior to use. Elemental analyses were performed
by Analytical Services, Department of Chemistry, University of
Calgary.
Spectroscopic methods
The 1H, 7Li and 31P NMR spectra were obtained in CD2Cl2
or d8-THF on a Bruker DRX 400 spectrometer operating at
399.46, 155.53 and 161.71 MHz, respectively. The 1H spectra are
referenced to the solvent signal and the chemical shifts are reported
relative to (CH3)4Si. The 7Li and 31P NMR spectra are referenced
externally, and the chemical shifts are reported relative to a 1.0 M
solution of LiCl in D2O and to an 85% solution of H3PO4. The 13
C
and 77Se NMR spectra could not be obtained owing to the limited
solubility of the complexes in NMR solvents.
X-ray crystallography
Crystallographic data for 8, 9c·(CH2Cl2)7 and 10a–c are summa-
rized in Table 1. Crystals of all compounds were coated with
Paratone 8277 oil and mounted on a glass fibre. Diffraction
data were collected on a Nonius Kappa CCD diffractometer
In this context we were motivated to investigate the co-
ordination and redox chemistry of ligands of the type 1–3
towards heavy group 13 metals for which both +1 and +3
oxidation states are readily available. The reaction of 1 with
Tl(I) reagents was also of interest in view of our recent stud-
ies of the first Tl(I) complexes of dichalcogeno PNP-bridged
ligands [N(PPh2E)2]- (E = S, Se, Te), which form coordination
polymers.14 In this contribution we describe the reactions of
TlOEt with (a) the diseleno monoanion 1 and (b) the dimeric
dianions 3b and 3c. The former affords the mononuclear
Tl(I) complex, Tl[HC(PPh2Se)2]·LiOEt (7), as an intermediate,
which undergoes a selenium–proton exchange to give a mixed-
valent Tl(I)/Tl(III) complex {[Tl][Tl{(Se)C(PPh2Se)2}2]}• (8). The
latter reaction generates the binuclear Tl(I)/Tl(I) complexes
Tl2[(SPh2P)2CE¢E¢C(PPh2S)2] (9b, E¢ = S; 9c, E¢ = Se). Selenium–
proton exchange also occurs upon treatment of 1 with InCl3
˚
using monochromated Mo-Ka radiation (l = 0.71073 A) at
-100 ◦C. The data sets were corrected for Lorentz and polarization
effects, and an empirical absorption correction was applied to
the net intensities. The structures were solved by direct methods
using SHELXS-97 and refined using SHELXL-97.15,16 After full-
matrix least-squares refinement of the non-hydrogen atoms with
anisotropic thermal parameters, the hydrogen atoms were placed
˚
˚
in calculated positions (C–H = 0.95 A for –CH, 0.99 A for –
˚
CH2 and 0.98 A for –CH3 hydrogens). The isotropic thermal
parameters of the hydrogen atoms were fixed at 1.2 times that
of the corresponding carbon for –CH and –CH2 hydrogens, and
1.5 times for –CH3 hydrogens. In the final refinement the hydrogen
atoms were riding on their respective carbon atoms.
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Table 1 Crystallographic
data
for
{[Tl][Tl{(Se)C(PPh2Se)2}2]}•
(8),
Tl2[(SPh2P)2CSeSeC(PPh2S)2]·(CH2Cl2)7
(9c·(CH2Cl2)7)
and
(TMEDA)InCl[(Se)C(PPh2Se)2] (10a), (TMEDA)InCl[(S)C(PPh2S)2] (10b) and (TMEDA)InCl[(Se)C(PPh2S)2] (10c)a
8
9c·(CH2Cl2)7
10a
10b
10c
Emp. formula
Formula weight
Crystal system
Space group
C50H40P4Se6Tl2
1647.20
Monoclinic
C2/c
27.544(6)
12.641(3)
16.371(3)
90.00
118.85(3)
90.00
4992.2(17)
4
-100
2.192
10.985
0.26 ¥ 0.12 ¥ 0.04
3064
C107H94Cl14P8S8Se4Tl4
3513.68
Monoclinic
P21/c
15.101(3)
18.743(4)
22.487(5)
90.00
105.79(3)
90.00
6124(2)
2
-100
1.905
7.026
0.16 ¥ 0.10 ¥ 0.10
3364
C31H36ClInN2P4Se3
885.71
Monoclinic
P21/c
17.311(4)
16.969(3)
11.992(2)
90.00
107.99(3)
90.00
3350.4(12)
4
-100
1.756
C31H36ClInN2P4S3
745.01
Monoclinic
P21/c
17.380(4)
16.863(3)
11.805(2)
90.00
108.59(3)
90.00
3279.2(11)
4
-100
1.509
C31H36ClInN2P4S2Se
791.91
Monoclinic
P21/c
17.180(3)
16.748(3)
12.007(2)
90.00
108.28(3)
90.00
3280.4(11)
4
-100
1.603
˚
a/A
˚
b/A
˚
c/A
a (◦)
b (◦)
g (◦)
3
˚
V/A
Z
T/◦C
rc/g cm-3
m(Mo-Ka)/mm-1
Crystal size/mm
F(000)
4.164
0.36 ¥ 0.28 ¥ 0.20
1736
1.115
0.20 ¥ 0.18 ¥ 0.16
1520
2.161
0.16 ¥ 0.16 ¥ 0.12
1592
H range, deg.
Reflns collected
Unique reflns
Rint
Reflns [I > 2s(I)]
R1 [I > 2s(I)]b
wR2 (all data)c
GOF on F2
Completeness
2.04–25.03
8291
4374
0.0469
3688
0.0502
0.1672
1.130
0.995
2.62–25.03
20524
10721
0.0624
8053
0.0625
0.1280
1.096
0.991
2.15–25.03
11454
5888
0.0391
4984
0.0524
0.1160
1.116
0.996
2.71–25.02
5759
5759
0.0000
4625
0.0663
0.1344
1.132
0.995
2.73–25.03
9574
5751
0.0343
5137
0.0756
0.1667
1.341
0.991
1
a
2
4
2
l(Mo-Ka) = 0.71073 A. b R1 = RꢀFo|–|Fcꢀ/R|Fo|. c wR2 = [Rw(Fo -Fc2)2/RwFo ] .
˚
Two of the phenyl groups in compounds 10a–c were disordered.
The disorder was taken into account by refining the site occupation
factors of each disordered pair and constraining their sums to
unity. A chlorine atom in one of the solvating CH2Cl2 molecules
in 9c·(CH2Cl2)7 was disordered over two sites; this was included in
the refinement using partial site occupancy factors.
The powder was washed with toluene (20 mL) and dissolved
in 80 mL of warm (40 ◦C) THF. The solution was filtered
through a PTFE-disk and the solvent was evaporated under
vacuum. The product was washed with n-hexane (60 mL) to afford
{[Tl][Tl{(Se)C(PPh2Se)2}2]}• (8) as a dark purple powder (0.229 g,
74%). Elemental analysis calcd (%) for C50H40P4Se6Tl2: C, ◦36.46;
1
H, 2.45; found: C, 36.90; H, 2.55. H NMR (CD2Cl2, 23 C): d
◦
1
8.20–6.87 [m, 40H, C6H5]; 31P{ H} NMR (CD2Cl2, 23 C): d 52.4
[s, 1J(31P,77Se) = 533 Hz, 2J(31P,31P) = 45 Hz]. X-ray quality crystals
of 8 were obtained by layering n-hexane onto the CH2Cl2 solution
of 7 after 24 h at room temperature.
Synthesis of Tl[HC(PPh2Se)2]·LiOEt (7)
A solution of TlOEt (0.100 g, 0.40 mmol) in toluene (5 mL) was
added to a suspension of [Li(TMEDA)]1 (0.266 g, 0.40 mmol) in
toluene (30 mL) at -80 ◦C. The reaction mixture was stirred for 15
min at -80 ◦C and 2 h at 23 ◦C. The resulting powder was allowed to
settle and the solution was decanted via cannula. The product was
washed with toluene (40 mL)affording Tl[HC(PPh2Se)2]·LiOEt (7)
as a pale brown powder (0.241 g, 75%). Elemental analysis calcd
(%) for C27H26LiOP2Se2Tl: C, 40.65; H, 3.29; found: C, 40.40; H,
2.95. 1H NMR (d8-THF, 23 ◦C): d 7.88–7.09 [m, 20H, C6H5], 4.14
[qr, 2H, –CH2 of LiOEt], 2.59 [s, 1H, –CH of the PCP carbon],
Method B. A mixture of Tl[HC(PPh2Se)2]·LiOEt (7) (0.284 g,
0.36 mmol) and elemental selenium (0.015 g, 0.19 mmol) in toluene
(30 mL) was stirred at 60 ◦C for 3 days resulting in a dark grayish
solid and a purple solution. The powder was allowed to settle and
the solution was decanted via a cannula. The powder was washed
with toluene (20 mL) and dissolved in 80 mL of warm (40 ◦C) THF.
The solution was filtered through a PTFE-disk and the solvent was
evaporated under vacuum. The product was washed with hexane
(60 mL) to afford {[Tl][Tl{(Se)C(PPh2Se)2}2]}• (8) as a dark purple
powder (0.132 g, 90%), The identity of the product was confirmed
by both 31P NMR spectroscopy and X-ray crystallography (unit
cell measurement after recrystallization from CH2Cl2/n-hexane
mixture).
1.24 [t, 3H, –CH3 of LiOEt]; 7Li NMR (d8-THF, 23 ◦C): d 0.01;
◦
1
1
31P{ H} NMR (d8-THF, 23 C): d 22.7 [s, J(31P,77Se) = 584 Hz,
2J(31P,31P) = 26 Hz].
Synthesis of {[Tl][Tl{(Se)C(PPh2Se)2}2]}• (8)
Method A. A solution of TlOEt (0.188 g, 0.75 mmol) in toluene
(5 mL) was added to a mixture of [Li(TMEDA)]1 (0.500 g,
0.75 mmol) and elemental selenium (0.030 g, 0.38 mmol) in
toluene (30 mL) by using cannula. The reaction mixture was
stirred at 60 ◦C for 3 days. The resulting dark powder was
allowed to settle and the solution was decanted via cannula.
Synthesis of Tl2[(SPh2P)2CSSC(PPh2S)2] (9b)
A solution of TlOEt (0.080 g, 0.32 mmol) in toluene (5 mL) was
added to a suspension of [Li(TMEDA)]23b (0.193 g, 0.16 mmol)
in toluene (20 mL) at -80 ◦C. The reaction mixture was stirred for
8240 | Dalton Trans., 2011, 40, 8238–8246
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15 min at -80 ◦C and 2 h at 23 ◦C. The solvent was removed
by evaporation and the product was washed with Et2O (2 ¥
30 mL) affording Tl2[(SPh2P)2CSSC(PPh2S)2] (9b) as an orange-
red powder (0.174 g, 79%). Elemental analysis calcd (%) for
[m, 20H, C6H5], 2.81 [s, 6H, –CH3 of TMEDA], 2.74 [s (br), 2H,
–CH2 of TMEDA], 2.43 [s (br), 2H, –CH2 of TMEDA], 2.26 [s,
◦
1
6H, –CH3 of TMEDA]; 31P{ H} NMR (CD2Cl2, 23 C): d 48.0.
X-ray quality crystals were obtained by layering Et2O onto the
CH2Cl2 solution of 10b after 24 h at -20 ◦C.
1
C50H40P4S6Tl2: C, 43.97; H, 2.95; found: C, 44.01; H, 3.02. H
NMR (CD2Cl2, 23 ◦C): d 8.15–6.98 [m, 40H, C6H5]; 31P{ H}
1
NMR (CD2Cl2, 23 ◦C): d 48.2 [s (br), Dw1 ª 250 Hz]; 31P{ H}
1
Synthesis of (TMEDA)InCl[(Se)C(PPh2S)2] (10c)
2
NMR (CD2Cl2, -80 ◦C): d 63.9 [s (br)], 57.7 [s (br)], 49.7 [s (br)],
A solution of [Li(TMEDA)]22c (0.60 mmol, prepared in situ from
0.269 g of [H2C(PPh2S)2], 0.75 mL of MeLi, 0.139 g of TMEDA
and 0.047 g of selenium)9 in toluene (20 mL) was added to a
suspension of InCl3 (0.133 g, 0.60 mmol) in toluene (10 mL) at
-80 ◦C. The reaction mixture was stirred for 15 min at -80 ◦C and
46.6 [s (br)], 40.1 [s (br)].
Synthesis of Tl2[(SPh2P)2CSeSeC(PPh2S)2] (9c)
A solution of TlOEt (0.161 g, 0.65 mmol) in toluene (5 mL) was
added to a suspension of [Li(TMEDA)]23c (0.419 g, 0.32 mmol)
in toluene (20 mL) at -80 ◦C. The reaction mixture was stirred for
15 min at -80 ◦C and 2 h at 23 ◦C. The resulting dark red powder
was allowed to settle and the solution was decanted via cannula.
The product was washed with Et2O (30 mL) and n-hexane (30 mL)
affording Tl2[(SPh2P)2CSeSeC(PPh2S)2] (9c) as a dark red powder
(0.362 g, 77%). Elemental analysis calcd (%) for C50H40P4S4Se2Tl2:
h at 23 ◦C. The resulting powder was allowed to settle and the
1
2
1
solution was decanted via cannula. The product was washed with
n-hexane (20 mL) affording (TMEDA)InCl[(Se)C(PPh2S)2] (10c)
as a pale-yellow powder (0.380 g, 80%). Elemental analysis calcd
(%) for C31H36ClInN2P2S2Se: C, 47.02; H, 4.58; N, 3.54; found: C,
45.92; H, 4.61; N, 3.37. H NMR (CD2Cl2, 23 ◦C): d 8.20–6.83
1
[m, 20H, C6H5], 2.86 [s, 6H, –CH3 of TMEDA], 2.80 [s (br), 2H,
1
C, 41.14; H, 2.76; found: C, 41.68; H, 2.86. H NMR (CD2Cl2,
–CH2 of TMEDA], 2.45 [s (br), 2H, –CH2 of TMEDA], 2.34 [s,
23 ◦C): d 8.12–6.88 [m, 40H, C6H5]; 31P{ H} NMR (CD2Cl2,
◦
1
1
6H, –CH3 of TMEDA]; 31P{ H} NMR (CD2Cl2, 23 C): d 48.4.
X-ray quality crystals were obtained by layering Et2O onto the
CH2Cl2 solution of 10c after 24 h at 5 ◦C.
23 ◦C): d 47.3 [s (br) Dw1 ª 950 Hz]; 31P{ H} NMR (CD2Cl2,
1
2
-60 ◦C): d 50.4 [d, 2J(31P,31P) = 55 Hz], 49.2 [d, 2J(31P,31P) = 59 Hz],
ca. 41.2 [two overlapping doublets]. X-ray quality crystals were
obtained by layering n-hexane onto the CH2Cl2 solution of 9c
after 24 h at 5 ◦C.
Results and discussion
Synthesis and spectroscopic characterization of
Tl[HC(PPh2Se)2]·LiOEt (7) and {[Tl][Tl{(Se)C(PPh2Se)2}2]}•
(8): crystal structure of 8
Synthesis of (TMEDA)InCl[(Se)C(PPh2Se)2] (10a)
A mixture of [Li(TMEDA)]1 (0.337 g, 0.51 mmol) and InCl3
(0.056 g, 0.25 mmol) powders was cooled to -80 ◦C and cold
toluene (50 mL) was added via cannula. The reaction mixture
was stirred for 15 min at -80 ◦C and 4 h at 50 ◦C. The
resulting powder was allowed to settle and the solution was
decanted via cannula. The product was washed with toluene
(25 mL) affording (TMEDA)InCl[(Se)C(PPh2Se)2] (10a) as a pale-
yellow powder (0.157 g, 70%). Elemental analysis calcd (%) for
C31H36ClInN2P2Se3: C, 42.04; H, 4.10; N, 3.16; found: C, 41.98;
H, 4.19; N, 3.07. 1H NMR (CD2Cl2, 23 ◦C): d 8.24–6.81 [m, 20H,
C6H5], 2.87 [s, 6H, –CH3 of TMEDA], 2.79 [s (br), 2H, –CH2
of TMEDA], 2.45 [s (br), 2H, –CH2 of TMEDA], 2.32 [s, 6H,
The reaction between [Li(TMEDA)]1 and TlOEt in a 1 : 1 molar
◦
ratio in toluene at -80 C produced a very insoluble pale brown
1
powder upon warming up to room temperature. The 31P{ H}
NMR spectrum of this powder exhibited a single resonance at
d 22.7 with 77Se satellites [1J(31P,77Se) = 584 Hz, 2J(31P,31P) =
26 Hz]. These coupling constants are virtually equal with those
in [Li(TMEDA)]1,1 indicating negligible change in the geometry
1
of the ligand 1. The H NMR spectrum displayed a singlet for
the hydrogen in the PC(H)P unit and the typical signal patterns
7
for both phenyl and ethoxide groups. In addition, the Li NMR
spectrum showed the presence of Li+ cation with a singlet at
0.01 ppm. Collectively, the NMR data indicated the formation
of an LiOEt adduct of the homoleptic thallium(I) complex,
Tl[HC(PPh2Se)2]·LiOEt (7). An elemental (C, H) analysis of the
powder was also consistent with the formation of 7. However,
despite repeated attempts, crystals of sufficient quality for an
accurate single crystal X-ray structural determination could not
be obtained.17
–CH3 of TMEDA]; 31P{ H} NMR (CD2Cl2, 23 ◦C): d 50.2 [s,
1
2
1J(31P,77Se) = 512 Hz, J(31P,31P) = 29 Hz]. X-ray quality crystals
of 10a were obtained from the undisturbed reaction solution after
24 h at 23 ◦C.
Synthesis of (TMEDA)InCl[(S)C(PPh2S)2] (10b)
A solution of [Li(TMEDA)]22b (0.60 mmol, prepared in situ
from 0.269 g of [H2C(PPh2S)2], 0.75 mL of MeLi, 0.139 g of
TMEDA and 0.019 g of sulfur)9 in toluene (20 mL) was added
to a suspension of InCl3 (0.133 g, 0.60 mmol) in toluene (10 mL)
at -80 ◦C. The reaction mixture was stirred for 15 min at -80 ◦C
and 112 h at 23 ◦C. The resulting powder was allowed to settle and
the solution was decanted via cannula. The product was washed
with n-hexane (20 mL) affording (TMEDA)InCl[(S)C(PPh2S)2]
(10b) as a pale-yellow powder (0.315 g, 70%). Elemental analysis
calcd (%) for C31H36ClInN2P2S3: C, 49.97; H, 4.87; N 3.76; found:
C, 49.08; H, 4.87; N, 3.67. 1H NMR (CD2Cl2, 23 ◦C): d 8.20–6.82
After a prolonged reaction time or upon moderate heating
(60 ◦C), the singlet for 7 in the 31P{ H} NMR spectrum of
1
the reaction mixture was gradually replaced by two mutually
coupled doublets indicating the formation of the monoselenide
[H2C(PPh2)(PPh2Se)],18 while the colour of the solid turned from
pale brown to dark gray. The consumption of 7 was observed to
be faster and the yield of the dark solid higher when elemental
selenium was added to the reaction mixture (Method A in
Experimental section). The by-product in that case is the neutral
diselenide [H2C(PPh2Se)2]18 (Scheme 1).
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Scheme 1
After work-up, a dark purple powder was isolated for which
1
the 31P{ H} NMR spectrum displayed a singlet at d 52.4 with
77Se satellites [1J(31P,77Se) = 533 Hz, 2J(31P,31P) = 45 Hz]. The
1H NMR spectrum of this product showed only the presence
of phenyl groups and no signal for the PC(H)P hydrogen was
observed. Taken together, the NMR data suggested the formation
of the dianionic triseleno ligand [(Se)C(PPh2Se)2]2- (2a) via a Se–
H+ exchange process, cf. the production of the Sn(IV), Te(IV) and
Hg(II) complexes {Mn[(Se)C(PPh2Se)2]2} (n = 1, M = Sn, Te; n = 2,
M = Hg).6
Fig. 1 Molecular structure of {[Tl][Tl{(Se)C(PPh2Se)2}2]}• (8) with
atomic numbering scheme. Thermal ellipsoids have been drawn at 50%
probability level. Hydrogen atoms have been omitted for clarity. Symmetry
operation: (A) 2 - x, -y, 1 - z.
The same dark purple solid was also obtained in good yield by
heating a toluene solution of the isolated complex 7 at 60 ◦C for 3
days (Method B in Experimental Section), thus confirming that 7
is an intermediate in the formation of this new product.
An X-ray structural determination of one of the crystals
obtained by recrystallization of the dark purple powder from
a CH2Cl2–hexane mixture revealed a mixed-valent Tl(I)/Tl(III)
salt {[Tl][Tl{(Se)C(PPh2Se)2}2]}• (8), which is comprised of
centrosymmetric [Tl{(Se)C(PPh2Se)2}2]- anions ([Tl(2a)2]-) and
weakly associated thallous Tl+ counter cations arranged in a
one-dimensional polymer. The structure of 8 with the atomic
numbering scheme is shown in Fig. 1, and selected bond pa-
rameters are presented in Table 2. In the anion [Tl(2a)2]-, the
Tl(III) centre is coordinated to two tridentate, facially bound
triseleno ligands [(Se)C(PPh2Se)2]2- (2a), to give a slightly distorted
octahedral geometry with Tl(III)–Se distances of 2.674(2), 3.051(2)
Fig. 2 Polymeric strand of {[Tl][Tl{(Se)C(PPh2Se)2}2]}• (8). Thermal
ellipsoids have been drawn at 50% probability level. Phenyl groups have
been omitted for clarity. (Green: Tl; red: Se; purple: P; gray: C).
˚
˚
and 3.128(2) A (Fig. 1). The significantly shorter (by ca. 0.4 A)
˚
Tl–Se(C) bond (2.674(2) A) compared to the Tl–Se(P) contacts
˚
(3.051(2) and 3.128(2) A) is likely due to the localization of
20
˚
the negative charge in the dianion on the Se(C) atom. A less
pronounced disparity between Sn–Se(C) and Sn–Se(P) bond
(Ph4P)4[Tl4Se16] (d(Tl(III)–Se = 2.584(7)–2.8022(8) A), (2,2,2-
III
I
21
˚
crypt-K)3[Tl (Tl )4Se5] (d(Tl(III)–Se) = 2.543(4)–2.766(3) A).
˚
lengths of ca. 0.17 A is observed in the neutral tin(IV) complex,
While the Tl(III)–Se(C) distance in 8 is similar to those observed
in thallium selenides, the Tl(III)–Se(P) bonds are significantly
elongated when compared with Tl(III)–Se distances in binary
anions.
{Sn[(Se)C(PPh2Se)2]2} (Sn(2a)2).6 The [Tl(2a)2]- anions are weakly
associated with Tl(I) cations by relatively long Tl(I)–Se interactions
˚
(3.335(2)–3.481(2) A) to form continuous chains (Fig. 2). The
geometry at the Tl(I) ions is a distorted trigonal prism.
Structural data for compounds with Tl(I)–Se bonds are better
established than those of the Tl(III) analogues including some Tl(I)
complexes of selenium-containing ligands in addition to binary
thallium(I) selenide anions. Consequently, the Tl(I)–Se distances
in the octahedrally coordinated Tl(I) centre in 8 can be compared
There are scant data available in the literature describing
Tl(III)–Se bonds. Examples are restricted to compounds contain-
ing thallium(III) selenide or mixed thallium(I/III) selenide ions,
19
˚
e.g. (Et4N)3[Tl3Se3(Se4)3] (d(Tl(III)–Se) = 2.585(5)–2.686(6) A),
8242 | Dalton Trans., 2011, 40, 8238–8246
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˚
Table 2 Selected bond lengths (A) and bond angles (deg) in
{[Tl][Tl{(Se)C(PPh2Se)2}2]}• (8)
Tl1–Se1
Tl1–Se2
Tl1–Se3
Tl2–Se1
Tl2–Se2
Tl2–Se3
3.128(2)
3.051(2)
2.674(2)
3.335(2)
3.481(2)
3.460(2)
P1–Se1
P2–Se2
C1–P1
C1–P2
C1–Se3
2.169(3)
2.172(3)
1.766(10)
1.789(11)
1.899(11)
Se1–Tl1–Se2
Se1–Tl1–Se3
Se1–Tl1–Se2a
Se1–Tl1–Se3a
Se1–Tl1–Se1a
Se2–Tl1–Se3
Se2–Tl1–Se3a
83.41(3)
89.11(3)
96.59(3)
90.89(3)
180.0
81.28(3)
98.72(3)
Se2–Tl1–Se2a
Se3–Tl1–Se3a
Se1–P1–C1
Se2–P2–C1
P1–C1–Se3
P2–C1–Se3
P1–C1–P2
180.0(4)
180.0
115.1(4)
118.0(4)
110.9(5)
110.1(6)
118.5(6)
Symmetry operation:a 2 - x, -y, 1 - z.
with those seen in {Tl[(SePiPr2)2N]}• (d(Tl(I)–Se = 3.051(1)–
14
˚
3.647(2) A), as well as in [Tl{MeSe(CH2)nSeMe}]PF6 (n = 2,
22
˚
3) (d(Tl(I)–Se = 3.2769(8)–3.5058(8) A). The latter three com-
plexes form coordination polymers featuring highly coordinated
Scheme 2
thallium(I) centres. In comparison, the Tl(I)–Se distances for tri-
The identity of 9c was established in the solid state by single
crystal X-ray structural determination. As illustrated in Fig. 3,
the molecular structure of 9c displays a dinuclear, polycyclic
arrangement in which each Tl centre is S,S¢-chelated by one-
half of the dimeric ligand and S,Se-chelated by the other half.
Thus, in contrast to the TMEDA-solvated dilithio precursor
[Li(TMEDA)]23c (Scheme 2), the metal centres in 9c are drawn
towards the opposite half of the dianionic ligand through Tl ◊ ◊ ◊ E
(E = S, Se) contacts resulting in the polycyclic geometry and four-
coordinate Tl(I) atoms. By comparison with the formation of the
mixed-valent Au(I)/Au(III) complexes 6b and 6c from reactions
of [Li(TMEDA)]23b and [Li(TMEDA)]23c with Au(CO)Cl,11 the
dimeric (dichalcogenide) ligand remains intact in the reactions of
these precursors with TlOEt and no redox process is observed. The
complex 9c also differs structurally from the previously reported
and tetra-coordinated Tl(I) ions in [TlIII(TlI)4Se5]3- (d(Tl(I)–Se) =
2.814(4)–3.039(4) A) and [Tl2(Se2C C(CN)2)2]2- (d(Tl(I)–Se =
21
˚
23
˚
3.108(4)–3.162(4) A), respectively, are significantly shorter than
the related contacts in 8. This variation in Tl(I)–Se distances with
Tl(I) coordination number is expected and consistent with the
bond valence concept.24,25
The geometrical arrangement of the metal centre and ligands
in the [Tl(2a)2]- anion is similar to that observed in the neutral,
octahedral Sn(IV) complex Sn(2a)2.6 However, the P–C bond
-
˚
˚
lengths of 1.766(10) and 1.789(11) A in [Tl(2a)2] are ca. 0.03 A
˚
˚
longer, and the C–Se distance of 1.899(4) A is 0.03 A shorter than
the corresponding bonds in the tin(IV) complex. A similar disparity
is evident between the P–C and C–Se bond lengths in [Tl(2a)2]-
and those found in the tellurium and mercury complexes of the
dianion 2a, {Mn[SeC(PPh2Se)2]2} (n = 1, M = Te [Te(2a)2]; n = 2,
M = Hg [Hg2(2a)2]).6 The coordination environment of the PCP
carbon in the monoanion of 8 deviates significantly from planarity
ꢀ
ꢀ
(
∠C = 340◦), cf . ∠C = 341◦ and 342◦ in Sn(2a)2 and Te(2a)2,
respectively.6
The production of 8 via the intermediate 7 formally involves
the generation of the dianion [(Se)C(PPh2Se)2]2- (2a) from the
monoanionic [HC(PPh2Se)2]- ligand in 7 with concomitant redox
disproportionation of Tl(I) into Tl(III) and, presumably, thallium
metal, cf . the formation of the M(IV) complexes Sn(2a)2 and
Te(2a)2 from [HC(PPh2Se)2]- and MCl2 (M = Sn, Te).6 The mech-
anism of the Tl(I)→TI(III) oxidation is not currently understood,
however a related precedent involves the formation of tetrahedral
Tl(III) complexes via an internal redox process in thallium(I)-
polyselenide systems.19,26
Synthesis and spectroscopic characterization of
Tl2[(SPh2P)2CE¢E¢C(PPh2S)2] (9b, E¢ = S; 9c, E¢ = Se): crystal
structure of 9c
Fig. 3 Molecular structure of Tl2[(SPh2P)2CSeSeC(PPh2S)2]·(CH2Cl2)7
(9c·(CH2Cl2)7) with atomic numbering scheme. Thermal ellipsoids have
been drawn at 50% probability level. Hydrogen atoms and solvent
molecules have been omitted for clarity. The solid Tl–S bonds indicate
S,S¢-chelation of each terminus of the dimeric dianion 3, and the dashed
Tl-–E (E = S, Se) contacts are used for interactions to the opposite end of
the ligand.
The metathetical reaction of [Li(TMEDA)]23c with TlOEt in a 1 : 2
molar ratio at -80 ◦C proceeded cleanly to afford the dinuclear
Tl(I)/Tl(I) complex Tl2[(SPh2P)2CSeSeC(PPh2S)2] (9c) in good
yield (Scheme 2).
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˚
Table 3 Selected bond lengths (A) and bond angles (deg) in
and P1 ◊ ◊ ◊ Se2 contacts for phosphorus atom P1 are 5.723(4) and
3.958(4) A respectively, the corresponding interactions for P2
Tl2[(SPh2P)2CSeSeC(PPh2S)2]·(CH2Cl2)7 (9c·(CH2Cl2)7)
˚
˚
˚
are P2 ◊ ◊ ◊ Tl2 = 3.819(4) A and P2 ◊ ◊ ◊ Se2 = 4.726(4) A. Similar
disparity in P ◊ ◊ ◊ Tl and P ◊ ◊ ◊ Se interactions is evident between
Tl1–S1
Tl1–S2
Tl1–S4
Tl1–Se2
Tl2–S2
Tl2–S3
Tl2–S4
Tl2–Se1
Se1–Se2
Se1–C1
3.128(3)
2.999(3)
3.289(4)
3.203(2)
3.380(4)
3.070(3)
2.953(3)
3.221(2)
2.531(2)
1.882(10)
P1–C1
P2–C1
P3–C2
S4–P4
S1–P1
S2–P2
S3–P3
Se2–C2
P4–C2
1.757(11)
1.755(11)
1.741(11)
2.003(4)
1.993(4)
2.005(4)
1.991(4)
1.888(10)
1.765(11)
˚
P3 and P4 atoms [P3 ◊ ◊ ◊ Tl1 5.748(3) and P3 ◊ ◊ ◊ Se1 3.975(4) A;
˚
P4 ◊ ◊ ◊ Tl1 3.800(4) and P4 ◊ ◊ ◊ Se1 4.703(4) A]. In summary, the
low-temperature 31P NMR spectrum of 9c is consistent with the
solid-state structure.
The reaction of [Li(TMEDA)]23b with TlOEt in a 1 : 2 molar
ratio yielded a orange-red powder with elemental (C, H, N)
analysis that is consistent with the formation of the dinuclear com-
plex Tl2[(SPh2P)2CSSC(PPh2S)2] (9b) analogous to the selenium
S1–Tl1–S2
S1–Tl1–Se2
S2–Tl1–Se2
S3–Tl2–S4
S3–Tl2–Se1
S4–Tl2–Se1
S1–P1–C1
S2–P2–C1
90.77(8)
81.32(6)
97.93(6)
90.03(8)
83.27(6)
96.48(7)
116.5(4)
117.4(4)
S3–P3–C2
S4–P4–C2
P1–C1–Se1
P2–C1–Se1
P3–C2–Se2
P4–C1–Se2
P1–C1–P2
P3–C2–P4
115.5(4)
117.6(4)
116.3(6)
114.6(5)
117.9(6)
114.1(5)
123.8(6)
121.5(6)
1
congener 9c. The room temperature 31P{ H} NMR spectrum of
9b showed one broad resonance at d 48.3 (Dw1 ª 250 Hz) which,
2
although substantially narrower than the resonance observed for
9c (vide supra), is also indicative of fluxional behaviour. Variable
temperature NMR experiments, however, indicate a structural
disparity between 9b and 9c in solution. After cooling the solution
of 9b to -80 ◦C, only a partial resolution into five broad resonances
in the region of 63.9–40.1 ppm was observable (see Supplementary
Information†), cf. two pairs of mutually coupled doublets for
9c (vide supra). Unfortunately, despite numerous attempts, X-ray
quality crystals of 9b could not be obtained so the nature of the
structural differences in the solid state between 9b and 9c could
not be ascertained, although it is likely associated with the change
in the carbon-bound chalcogen from Se in 9c to S in 9b.
dinuclear coinage metal complexes 4a–c and 5c in which two
metal centres are E,E¢-chelated by one chalcogen atom in each
2
terminus of the dianionic ligand and h -bonded to the central
chalcogen–chalcogen linkage.10,11 However, the average P–C, P–
˚
S and C–Se bond lengths of ca. 1.75, 2.00, 1.88 A (Table 3),
respectively, in 9c as well as the bond angles involving these
atoms are comparable with the corresponding values in the
complexes 4c and 5c (and in 4b, where appropriate).11 These
parameters are also identical with those found in the bis-S,S¢-
chelated Li+ derivative [Li(TMEDA)]23c.9 The Tl–S distances
between the thallium centre and two sulfur atoms from the
one terminus of the dianionic ligand range from 2.953(3) to
Synthesis, spectroscopic characterization and crystal structures of
(TMEDA)InCl[(E¢)C(PPh2E)2] (10a, E = E¢ = Se; 10b, E = E¢ = S;
10c, E = S, E¢ = Se)
˚
The reaction of [Li(TMEDA)]1 with InCl3 in a 2 : 1 molar
ratio at 50 ◦C results in a selenium–proton exchange to give
the heteroleptic complex (TMEDA)InCl[(Se)C(PPh2Se)2] (10a)
as a pale yellow powder in 70% yield (Scheme 3). The related
sulfur-containing complexes (TMEDA)InCl[(S)C(PPh2S)2] (10b)
and (TMEDA)InCl[(Se)C(PPh2S)2] (10c) were obtained in 70
and 80% yields via metathetical reaction of [Li(TMEDA)]22b or
[Li(TMEDA)]22c with InCl3, respectively (Scheme 3). Previous ex-
amples of the formation of the triseleno dianion [(Se)C(PPh2Se)2]2-
3.128(3) A and are similar to those seen in the ladder polymer
{Tl[(SPiPr2)2N]}• (2.920(1) and 2.922(2) A) in which the Tl
˚
atoms are also four-coordinate.14 The Tl–S bond lengths between
thallium and one sulfur atom from the opposite terminus of the
dianionic ligand are longer (3.289(4) and 3.380(4) A) and approach
weak van der Waals interaction [
They are comparable to those seen in thioether complexes of
˚
ꢀ
ꢀ
= 2.47;
= 3.76].27,28
(cov)
(vdW)
29
˚
Tl(I) centres, e.g. [Tl([18]aneS6)][PF6] (3.164(5)–3.370(5) A) and
[Tl([24]aneS8)][PF6] (3.2851(3)–3.473(2) A).30 The Tl–Se distances
˚
˚
of 3.203(2) and 3.221(2) A in 9c also represent moderately
weak interactions, cf. the Tl(I)–Se interactions in 8 (Table 2).
˚
Consistently, the (C)Se–Se(C) bond length of 2.531(2) A in
˚
9c is only slightly elongated (by ca. 0.02 A) compared to the
corresponding distance in the bis-S,S¢-chelated dilithium reagent
[Li(TMEDA)]23c.9
1
The 31P{ H} NMR spectrum of 9c exhibited a broad singlet at d
47.3 ppm (Dw1 ª 950 Hz) at room temperature, indicating fluxion-
2
ality in solution. However, upon cooling to -60 ◦C, this resonance
was resolved into two doublets at d 50.4 [2J(31P,31P) = 55 Hz] and
49.2 [2J(31P,31P) = 59 Hz], and the mutually coupled pairs of these
doublets appear as an overlapping doublet at ca. 41.2 ppm without
clear resolution of the two distinct 2J(31P,31P) couplings (see
Supplementary Information†).31 Two of the phosphorus atoms
(P2 and P4) in the solid-state structure of 9c are constituents of
5-membered rings while the other two phosphorus centres (P1
and P3) are components of 6-membered rings, thereby resulting
in two discrete environments for these two pairs of phosphorus
atoms (Fig. 3 and Scheme 2). Consequently, while the P1 ◊ ◊ ◊ Tl2
Scheme 3
8244 | Dalton Trans., 2011, 40, 8238–8246
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˚
Table 4 Selected bond lengths (A) and bond angles (deg) in
(TMEDA)InCl[(Se)C(PPh2Se)2] (10a), (TMEDA)InCl[(S)C(PPh2S)2]
(10b) and (TMEDA)InCl[(Se)C(PPh2S)2] (10c)
10a (E = E¢ = Se)
10b (E = E¢ = S) 10c (E = S; E¢ = Se)
In1–E1
In1–E2
In1–E¢
In1–N1
In1–N2
In1–Cl1
E1–P1
E2–P2
C1–E¢
2.725(1)
2.745(9)
2.664(11)
2.441(6)
2.425(6)
2.506(2)
2.189(2)
2.190(2)
1.973(7)
1.741(7)
1.725(7)
2.619(2)
2.650(2)
2.540(2)
2.434(6)
2.390(7)
2.483(2)
2.034(3)
2.028(2)
1.803(7)
1.753(7)
1.739(6)
2.637(2)
2.626(3)
2.660(2)
2.392(9)
2.410(9)
2.491(2)
2.031(3)
2.028(4)
1.938(9)
1.735(9)
1.745(9)
C1–P1
C1–P2
C1–P1–E1 115.9(2)
C1–P2–E2 117.2(2)
114.9(2)
116.2(2)
107.3(4)
106.9(3)
117.2(3)
115.5(3)
106.0(4)
107.4(5)
P1–C1–E¢
107.0(3)
106.2(4)
P2–C1–E¢
P1–C1–P2 124.1(4)
122.0(4)
122.3(5)
Fig. 4 Molecular structure of (TMEDA)InCl[(Se)C(PPh2Se)2] (10a)
with atomic numbering scheme as representative of compounds
(TMEDA)InCl[(E¢)C(PPh2E)2] (10a, E = E¢ = Se; 10b, E = E¢ = S; 10c, E =
S, E¢ = Se). Thermal ellipsoids have been drawn at 50% probability level.
Hydrogen atoms have been omitted for clarity. Only the higher occupancy
portion of the disordered phenyl groups is shown.
from reactions of [Li(TMEDA)]1 and p-block metal halides (see
ref. 6 and the synthesis of 8 in this work) involve both Se–
H+ and redox disproportionation of the metal centre. In these
examples the reagents used involved group 13, 14 or 16 metal
centres in low oxidation states [Tl(I), Sn(II) or Te(II)]. By contrast,
the formation of 10a from [Li(TMEDA)]1 and the In(III) reagent
InCl3 is not accompanied by a redox process at the metal centre.32
Consistently, the Sn(IV) complex Sn(2a)2 is obtained in higher
yields from [Li(TMEDA)]1 by using SnCl4 rather than SnCl2
as the tin source.33 Interestingly, Leung and co-workers have
shown that the reaction of [Li(THF)(Et2O)][HC(PPh2S)2], the
dithio analogue of 1, with InCl3 in a 2 : 1 molar ratio produces
the S,C,S¢-bonded dimer [InCl{C(PPh2S)2}]2 via a process that
probably involves metathesis followed by dehydrochlorination by
the second equivalent of the lithium reagent.34
˚
E¢ = Se: 1.938(9) A) are also very similar to those seen in Pb(2b)
and Pb(2c).35 In addition, the PCP carbons in 10a–c all exhibit
ꢀ
a significant distortion from planarity ( ∠C is ca. 336◦) that is
found to be typical for the metal-coordinated tridentate dianions
2a–c.6,11,35
1
The 31P{ H} NMR spectra of 10a–c each displayed a single reso-
nance at d 50.2, 48.0 and 48.4 ppm, respectively. The 77Se satellites
2
were also observed for 10a [1J(31P,77Se) = 512 Hz, J(31P,31P) =
29 Hz]. The 1J(31P,77Se) and 2J(31P,31P) coupling constants are
somewhat smaller than the values observed for homoleptic tin
6
1
and thallium complexes, Sn(2a)2 and 8, respectively. In the H
NMR spectra of 10a–c two sets of singlets were observed for
the methyl and methylene protons of the TMEDA ligand, in
addition to the characteristic signal pattern for phenyl groups
of the chalcogenocarbonyl dianion. The NMR spectral features
thus indicate that the four N-methyl groups and four methylene
protons have two mutually different environments in solution.
One of the N-methyl groups in each terminus of the ligand and
one hydrogen atom in both CH2-groups are on the same side of
the indium coordination plane as the chlorine atom and the other
two N-methyl groups and methylene hydrogens of TMEDA are on
the same side of the coordination plane as the PCP carbon-bound
chalcogen of the [E¢C(PPh2E)2]2- ligand.
The crystal structures of 10a–c were determined by X-ray
crystallography. All three complexes crystallize in the space group
P21/c and form an isostructural series. A representative thermal
ellipsoid plot is shown in Fig. 4, and selected bond lengths and
angles are compared in Table 4. The solid-state structures of 10a–c
reveal discrete molecules in which the indium(III) centre is hexa-
coordinated by one tridentate [(E¢)C(PPh2E)2]2- ligand, one biden-
tate TMEDA molecule and one chloride ligand, giving a slightly
distorted octahedral geometry for the metal. A similar tridentate
bonding mode of the [(E¢)C(PPh2S)2]2- (E¢ = S, Se) dianions to a
metal centre prevails in the homoleptic complexes Sn(2a)2,6 Pb(2b)
-
and Pb(2c),35 as well as for the Tl[(Se)C(PPh2Se)2]2 anion in 8.
While the differences in In–N and In–Cl bond lengths between
10a–c are insignificant, the In–E and In–E¢ bond distances increase
as expected with the size of the chalcogens. The P–Se and P–C
bond lengths in 10a are similar to those seen in Sn(2a)2,6 but
slightly shorter that the values observed in 8, whereas the C–Se
Conclusions
The reaction of TlOEt with the anion [HC(PPh2Se)2]- pro-
duces a homoleptic thallium(I) complex as an adduct with
LiOEt which, upon mild heating, undergoes selenium–proton
exchange and redox disproportionation of the thallium centres
to give the mixed-valent complex {[Tl][Tl{(Se)C(PPh2Se)2}2]}•;
the latter exhibits an intriguing one-dimensional polymeric
structure. By contrast, treatment of TlOEt with the dimeric
˚
distance in 10a exhibits a slight increase of ca. 0.04–0.07 A
6
compared to those in Sn(2a)2 and 8. The P–S and P–C bond
˚
lengths in 10b and 10c are essentially equal at ca. 1.74 and 2.03 A,
respectively, and in agreement with the corresponding mean values
35
˚
of 1.74 and 2.04 A reported for both Pb(2b) and Pb(2c). The
C–E¢ distances in 10b and 10c (10b, E¢ = S: 1.8037(7) and 10c,
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anions [(SPh2P)2CE¢E¢C(PPh2S)2]2- (E¢ = S, Se) yields polycyclic,
binuclear Tl(I)/Tl(I) complexes in which the dimeric ligands
remain intact with little change in the central chalcogen–
chalcogen bond length for E = Se. Reaction of InCl3 with
[HC(PPh2Se)2]- generates the heteroleptic, mononuclear In(III)
complex (TMEDA)InCl[(Se)C(PPh2Se)2] via selenium–proton ex-
change with no detectable intermediate. An alternative route to
similar In(III) complexes is the metathesis of InCl3 with the triden-
tate dianions [(E¢)C(PPh2S)2]2- (E¢ = S, Se). These monofunctional
complexes (In–Cl linkage) offer scope for further investigations of
reaction chemistry at indium(III) centres harnessed by tridentate
chalcogen-centred ligands.
9 J. Konu, T. Chivers and H. M. Tuononen, Chem.–Eur. J., 2010, 16,
12977.
10 M. Risto, J. Konu and T. Chivers, Inorg. Chem., 2011, 50, 406.
11 J. Konu, T. Chivers and H. M. Tuononen, Chem. Eur. J., 2011, 17,
accepted for publication.
12 A search of the CCDC database revealed no structurally characterized
2
complexes with the h -E2 bonding mode for REER ligands when E =
Se, and only Nb and Ti complexes can be found for E = S: (a) P. J.
McKarns, M. J. Heeg and C. H. Winter, Inorg. Chem., 1998, 37, 4743;
(b) J. Okuda, S. Fokken, T. Kleinhenn and T. P. Spaniol, Eur. J. Inorg.
Chem., 2000, 1321.
13 Note that the dianionic ligands 3b and 3c are formally dimers of the
∑
corresponding monoanion radicals [(E¢)C(PPh2S)2]- (E¢ = S, Se).
14 J. S. Ritch and T. Chivers, Dalton Trans., 2010, 39, 1745.
15 G. M. Sheldrick, SHELXS-97, Program for solution of crystal struc-
tures, University of Go¨ttingen, Germany, 1997.
16 G. M. Sheldrick, SHELXL-97, Program for refinement of crystal
structures, University of Go¨ttingen, Germany, 1997.
17 An approximate solution of the X-ray data of twinned crystals revealed
the individual components of the adduct Tl[HC(PPh2Se)2]·LiOEt (7),
but the structure could not be refined satisfactorily. All subsequent
attempts to grow single crystals of 7 failed.
Acknowledgements
Financial support from the Natural Sciences and Engineering
Research Council (Canada) is gratefully acknowledged.
18 S. O. Grim and E. D. Walton, Inorg. Chem., 1980, 19, 1982.
19 S. S. Dhingra and M. G. Kanatzidis, Inorg. Chem., 1993, 32, 1350.
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22 N. J. Hill, W. Levason, M. E. Light and G. Reid, Chem. Commun., 2003,
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8246 | Dalton Trans., 2011, 40, 8238–8246
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The Royal Society of Chemistry 2011
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