Synthesis and redox behaviour of the chalcogenocarbonyl dianions [(E)C(PPh2S)2]2?: Formation and structures of chalcogenchalcogen bonded dimers and a novel selone

Article abstract of DOI:10.1002/chem.201001699

The lithium salts of the chalcogenocarbonyl dianions [(E)C(PPh ₂S)₂]^2? (E=S (4b), Se (4c)) were produced through the reactions between Li₂[C(PPh₂S)₂] and elemental chalcogens in the presenc

Full text of DOI:10.1002/chem.201001699

FULL PAPER
DOI: 10.1002/chem.201001699
Synthesis and Redox Behaviour of the Chalcogenocarbonyl Dianions
[(E)CACHTUNGTRENNUNG
(PPh2S)2]2ꢀ: Formation and Structures of Chalcogen–Chalcogen
Bonded Dimers and a Novel Selone**
Jari Konu,[a] Tristram Chivers,*[a] and Heikki M. Tuononen[b]
Abstract: The lithium salts of the chal-
cogenocarbonyl dianions [(E)C-
(PPh2S)2]2ꢀ (E=S (4b), Se (4c)) were
produced through the reactions be-
tween Li2[C(PPh2S)2] and elemental
N
(E=S),
[Li-
formation of 7b followed by protona-
tion to give {[Li(TMEDA)]-
[(SPh2P)2CSS(H)C(PPh2S)2]}—[Li-
(TMEDA)]8b. Attempts to identify the
transient radicals 5b and 5c by EPR
spectroscopy in conjunction with DFT
calculations of the electronic structures
of these paramagnetic species and their
dimers are also described. The crystal
ACHTUNGTRENNUNG
E
N
ACHTUNGTRENNUNG
ꢀC
(PPh2S)2] (E=S (5b), Se (5c))
ꢀ
G
chalcogens in the presence of tetrame-
thylethylenediamine (TMEDA). The
solid-state
structure
of
{[Li-
A
U
R
ACHTUNGTERN(NUNG PPh2S)2]}—
A
[{LiI
E
structures of [{Li
(TMEDA)}6c]·C7H8,
(TMEDA)]27b·(CH2Cl2)0.33
(THF)2]27b, [Li
(TMEDA)]8b·(CH2Cl2)2 and [Li([12]-
ACHTUNGTRNE(NNUG TMEDA)}24c], [{LiI-
clic with the Li+ cations bis-S,Se-che-
lated by the dianionic ligand. One-elec-
tron oxidation of the dianions 4b and
4c with iodine afforded the diamagnet-
ogous reaction with 4b resulted in the
G
[Li-
[Li-
E
U
,
N
ACHTUNGTRNE(NGNU TMEDA)]27c, [Li-
Keywords: chalcogens · electronic
structure · oxidation · radicals · tri-
dentate ligands
G
ACHTUNGTRENNUNG
ic
E
crown-4)2]8b were determined and sali-
ent structural features are discussed.
Introduction
rivative of 2 by Le Floch and co-workers opened the way
for wide-ranging investigations of this intriguing dithio PCP-
bridged ligand.[4,5] A variety of complexes with main group[6]
and with early[7] and late transition metals,[4,8] as well as lan-
thanides[9] and actinides,[10] were subsequently prepared by
metathesis of Li22 with metal halides and structurally char-
acterised. The recurring theme in these complexes is the
prevalence of strong interactions of the metal with the car-
bene centre of the ligand 2 (S,C,S-chelation).
In contrast to the extensively studied N-bridged, monoa-
nionic ligands [N
(PPh2E)2]ꢀ (1, E=S, Se), which predomi-
ACHTUNGTRENNUNG
nantly form E,E-chelated metal complexes without the par-
ticipation of the N atom,[1,2] the isoelectronic C-bridged dia-
nion [CACHTUNGTRENNUNG
(PPh2S)2]2ꢀ (2) exhibits strong metal–carbon interac-
tions in a variety of coordination complexes. The first exam-
ple, a binuclear PtII complex of 2, involved bis-C,S-chelation
and a quaternary carbon bridging the two metal centres.[3]
The recent development of a synthesis of the dilithium de-
Unusual carbon-centred reactivity is also observed in the
[a] Dr. J. Konu, Prof. T. Chivers
Department of Chemistry, University of Calgary
Calgary, AB T2N 1N4 (Canada)
Fax : (+1)403-289-9488
E-mail: chivers@ucalgary.ca
[b] Dr. H. M. Tuononen
redox behaviour of compounds 2. In contrast with the for-
mation of chalcogen–chalcogen bonds upon oxidation of N-
bridged ligands of type 1,[11] treatment of Li22 with the mild
oxidising agents C2Cl6 or I2 produces remarkably stable
monomeric or dimeric carbenoids, respectively.[12,13] The nu-
Department of Chemistry, University of Jyvꢀskylꢀ
P.O. Box 35, Jyvꢀskylꢀ, 40014 (Finland)
[**] E=S, Se
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201001699.
Chem. Eur. J. 2010, 16, 12977 – 12987
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
12977

cleophilic reactivity of 2 is also illustrated by the reaction
with CS2 to give the 1,1-ethylenedithiolate [S2C=C-
In this contribution we report the synthesis of dilithium
derivatives of the dianions 4b and 4c and the X-ray struc-
ture of [{LiACTHGUNETRNNU(G TMEDA)}24c] (TMEDA=tetramethylethylene-
diamine). Investigations of the oxidation of 4b and 4c with
iodine revealed the formation of 7b and 7c (Scheme 1),
A
The diseleno C-bridged monoanion [HC
isoelectronic with 1 (E=Se), was first prepared from the
neutral ligand [H2C(PPh2Se)2] and nBuLi and used as an in
A
ACHTUNGTRENNUNG
situ metathetical reagent for the preparation of homoleptic
MII (M=Fe, Co, Ni) complexes.[14] Competition between the
deprotonation process and cleavage of P=Se bonds by RLi
reagents makes this synthesis of 3 inefficient, and also pre-
empts the production of the Se analogue of the dianion 2.[15]
Consequently, we developed an alternative, high-yielding
ꢀ
synthesis of Li3 in which the P Se bonds are installed after
the deprotonation step and we showed that this reagent can
be used to prepare homoleptic ZnII and HgII complexes of
3.[16] Interestingly, the reactions of MCl2 (M=Sn, Te) with
Li3 in a 1:2 molar ratio produce homoleptic M(IV) com-
plexes of the triseleno dianion [(Se)CACTHNUTRGNEUNG
(PPh2Se)2]2ꢀ (4a)
through a redox process that formally involves selenium–
proton exchange.[17] A dinuclear HgII complex of 4a is
formed on mild heating of Hg(3)2.[17] Very recently, homo-
leptic PbII complexes of the related trichalcogeno dianions
4b and 4c were obtained by chalcogen insertion into the
II
Pb C bonds of dimeric, homoleptic Pb complexes of 2.[6a]
ꢀ
Scheme 1. Synthesis and oxidation of the chalcogenocarbonyl dianions
4b and 4c.
The first examples of metal complexes of ligands of type 4
exhibit notably different structural features, suggesting a
rich coordination chemistry.[6a,17,18] With this in mind, we
sought to develop an efficient synthesis of alkali metal de-
rivatives of these novel tridentate ligands that could be used
as metathetical reagents. Concomitantly, we considered that
investigations of the redox behaviour of these dianions
would represent a worthwhile endeavour in view of the pos-
sible generation of chalcogenocarbonyl radical anions of the
type 5 or the corresponding neutral chalcogenocarbonyls 6
upon oxidation. In this context it is pertinent to note that Le
Floch et al. have recently described the isolation of deep
purple alkali metal salts of the radical anion [Ph2C=C-
ꢀC
which are formally dimers of the corresponding anion radi-
cals 5b and 5c, respectively, upon one-electron oxidation.
The X-ray structures of [Li(L)]27b (L=TMEDA, (THF)2)
and [LiACTHNUTRGENUG(N TMEDA)]27c have been determined and the possi-
ble dissociation of these dimers into the paramagnetic spe-
cies 5b and 5c has been investigated by EPR spectroscopy.
Interestingly, the two-electron oxidation of 4c with I2 produ-
ces the unusual selone 6c[21] as a LiI adduct, whereas the at-
tempted two-electron oxidation of 4b with I2 generates the
protonated monoanion 8b; X-ray structures of [Li(L)]8b
(L=TMEDA, ([12]crown-4)2) were elucidated. The experi-
mental work is supported by DFT calculations that provide
insights into the molecular and electronic structures of the
radical anions 5b and 5c and of the corresponding dimers
7b and 7c, as well as confirmation of the molecular struc-
ture of the protonated species 8b.
ACHTUNGTRENNUNG(PPh2S)2] in which the electron-accepting phosphine sul-
fide substituents exert a stabilising influence on the alkene
ꢀC
radical.[19] Thioketyl radical anions [R2C=S] (e.g., R=tBu,
Me) have been characterised in solution by EPR spectrosco-
py, but salts of these anions have not been isolated.[20] The
effect of the PPh2S substituents on the stabilities of these
radical anions of type 5 was therefore of interest.
12978
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Chem. Eur. J. 2010, 16, 12977 – 12987

Synthesis and Redox Behaviour of Chalcogenocarbonyl Dianions
FULL PAPER
Results and Discussion
Synthesis and characterisation of {[Li
(PPh2S)2]} ([{Li(TMEDA)}24b] (E=S), [{Li
(E=Se)): Because the diseleno PCP-bridged dianion [C-
(PPh2Se)2]2ꢀ is not accessible (see above), the starting point
for the synthesis of tridentate ligands of the type 4 was the
known reagent Li2[C(PPh2S)2], which is prepared by treat-
ment of [H2C
(PPh2S)2] with two equivalents of MeLi.[4] Suc-
ACHTUNGTRENNUNG
A
R
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
ACHTUNGTRENNUNG
cessive addition of two equivalents of TMEDA at 238C and
then one equivalent of the elemental chalcogen either at
ꢀ808C (S) or at 08C (Se) produced dilithium salts of the tri-
chalcogeno dianions, [{LiACHTNUGTRENUNG(TMEDA)}24b] and [{Li-
ACHTUNGTRENNUNG(TMEDA)}24c] (Scheme 1), as analytically pure, orange-red
or red solids in excellent yields (86 and 91%, respectively).
Both compounds exhibit significant air and/or moisture sen-
sitivity even in the solid state, with exposure to ambient con-
ditions resulting in a rapid loss of the red colour.
1
The H and 13C{1H} NMR spectra of [{Li
C
and [{LiACHTUNGTRENNUNG
terns for TMEDA and phenyl groups (in the expected inten-
sity ratio); in the latter spectra signals attributable to the
PCP carbon were observed at d=141.1 and 141.2 ppm, re-
7
spectively. The Li and 31P{1H} NMR spectra exhibited sin-
glets at d=1.67 and 44.0 ppm, respectively, for [{Li-
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
Figure 1. Molecular structures of a) [{Li
AHCTUNGTRENNUNG
ACHTUNGTERN(NUNG TMEDA)}24c], and b) [{LiI-
shift of about 300 ppm in relation to that of the CSe reso-
nance observed for the homoleptic TeIV complex {Te[(Se)C-
level. Hydrogen atoms and solvate molecules (in [{LiI
have been omitted for clarity.
ACHTUNGTREN(NUNG TMEDA)}6c])
ACHTUNGTRENNUNG(PPh2Se)2]2} [TeACHTUNGTRENNUNG
(4a)2].[17,22] Taken together, the NMR spec-
troscopic data are consistent with the formation of the dia-
nions 4b and 4c, each incorporating two TMEDA-chelated
Li+ cations symmetrically coordinated to the dianion.
As depicted in Figure 1a, the solid-state structure of [{Li-
lengths of about 1.72 and 2.02 ꢂ, respectively, in [{Li-
AHCTUNGTREGNUN(N TMEDA)}24c] (Table 1) are about 0.02 ꢂ shorter, and the
ꢀ
G
C Se distance of 1.970(3) ꢂ is about 0.05 ꢂ longer, than the
corresponding bonds in the lead(II) complex Pb4c.[6a] A sim-
ꢀ
ꢀ
G
ilar disparity is evident between the P C and C Se bond
lengths in [{Li(TMEDA)}24c] and those of about 1.73–1.76
and 1.89–1.94 ꢂ, respectively, found in the group 12, 14 and
AHCTUNGTRENNUNG
ꢀ
ꢀ
ꢀ
nected by a common C Se bond. The P C and P S bond
Table 1. Selected interatomic distances [ꢂ] and angles [8] for [{Li
ACHUTGTNRENU(NG TMEDA)}24c] and [{LiIACTHUNGTRENNUNG
[{Li(TMEDA)}24c] [{LiI(TMEDA)}6c]
G
E
E
G
N
ACHTUNGTRENNUNG
C(1)–Se(1)
C(1)–P(1)
C(1)–P(2)
P(1)–S(1)
P(2)–S(2)
1.970(3) [1.963]
1.712(3) [1.732]
1.716(3) [1.736]
2.020(1) [2.051]
2.011(1) [2.038]
1.815(4) [1.821]
1.776(4) [1.788]
1.782(4) [1.789]
1.989(2) [2.015]
2.005(2) [2.022]
Li(1)–S(1)
Li(1)–S(2)
Li(1)–Se(1)
Li(2)–Se(1)
Se(1)–I(1)
2.416(6) [2.406]
2.390(5)[a] [2.373]
2.551(5) [2.517]
2.500(5) [2.500]
–
2.416(7) [2.399]
2.487(7) [2.399]
–
–
2.7218(7) [2.705]
P(1)-C(1)-P(2)
P(1)-C(1)-Se(1)
P(2)-C(1)-Se(1)
C(1)-P(1)-S(1)
C(1)-P(2)-S(2)
P(1)-S(1)-Li(1)
P(2)-S(2)-Li(2)
135.1(2) [133.3]
110.2(2) [110.3]
109.5(2) [112.2]
118.1(1) [117.9]
114.8(1) [114.4]
93.2(1) [93.2]
122.0(2) [121.6]
118.2(2) [117.2]
119.9(2) [121.2]
115.4(1) [115.6]
114.4(2) [115.6]
100.9(2) [104.9]
99.2(2) [102.0]
C(1)-Se(1)-I(1)
S(1)-Li(1)-S(2)
C(1)-Se(1)-Li(1)
C(1)-Se(1)-Li(2)
S(1)-Li(1)-Se(1)
S(2)-Li(2)-Se(1)
Li(1)-Se(1)-Li(2)
–
–
109.3(1) [109.4]
108.7(3) [108.7]
97.4(2) [97.8]
94.0(4) [96.2]
98.6(2) [99.9]
100.2(2) [99.9]
164.4(2) [159.4]
–
–
–
–
–
93.5(1) [96.0]
[a] Li(1)=Li(2).
Chem. Eur. J. 2010, 16, 12977 – 12987
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
12979

T. Chivers, J. Konu and H. M. Tuononen
16 complexes of the triseleno ligand 4a, {Mn[(Se)C-
(PPh2Se)2]2} (n=1, M=Sn [Sn(4a)2], Te [Te(4a)2]; n=2,
2A
A
R
ACHTUNGTRENNUNG
M=Hg [Hg CHTUNGTRENNUNG(4a)2]), the closest values belonging to the di-
meric HgII complex in which the carbon-bound selenium is
also three-coordinate.[17] The PCP carbon in [{Li-
ACHTUNGTRENNUNG
CHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
from planarity is more pronounced (S]Cꢁ3408).
One-electron oxidation of 4b and 4c: crystal structures and
NMR spectroscopic examination of {[Li
[(SPh2P)2CEEC(PPh2S)2]} (E=S [Li(TMEDA)]27b, Se [Li-
ACHTUNGTRENNUNG(TMEDA)]27c): Initial investigations of the oxidation of the
ACHTUNGTRNEN(UNG TMEDA)]2-
A
R
ACHTUNGTRENNUNG
dianions 4b and 4c were carried out with a view to the gen-
eration of the corresponding chalcogenocarbonyl radical
anions 5b and 5c and assessment of their stabilities. One-
electron oxidation was therefore attempted by the addition
of one-half equivalent of iodine to solutions of [{Li-
A
ACHTUNGRTEN(NUNG TMEDA)}24c], prepared in situ in
A
ACHTUNGTRENNUNG
yellow and orange powders, respectively, and identified after
recrystallisation by single-crystal X-ray structure determina-
tions.
The crystal structures of [Li
ACHTUNGTRNE(NNUG TMEDA)]27b and [Li-
ACHTUNGTRENNUNG(TMEDA)]27c (Figure 2) revealed the formation of diamag-
netic dianions, which are formally dimers of the radical
ꢀC
anions [(E)C
N
ꢀ
chalcogen–chalcogen (E E) bonds (E=S, Se) at a crystallo-
ꢀ
ꢀ
graphic symmetry centre. The central S S and Se Se bond
lengths of 2.222(2) and 2.508(1) ꢂ (Table 2) in [Li-
ACHTUNGTRENNUNG(TMEDA)]27b and [LiACHTUTGNREN(NGUN TMEDA)]27c, respectively, are sig-
nificantly longer than those of about 2.02–2.06 and 2.29–
Figure 2. Crystal structures of a) [Li
(TMEDA)]27c, with thermal ellipsoids drawn at the 50% probability
level. Hydrogen atoms and solvate molecules (in [Li(TMEDA)]27b) have
ACHTUNGTRNE(NUGN TMEDA)]27b, and b) [Li-
AHCTUNGTRENNUNG
Table 2. Selected interatomic distances [ꢂ] and angles [o] for [Li-
AHCTUNGTRENNUNG
A
ACHTUNGTRENNUNG(THF)2]27b and [LiACHTUNGTRENN(UGN TMEDA)]27c (calculated values
been omitted for clarity. Only the higher-occupancy portion of the disor-
dered sections is shown. Symmetry operation (A): 1ꢀx, ꢀy, ꢀz.
[Li
ACHTUNGTRENNUNG(TMEDA)]27b [LiACHTUNRTGEG(NNUN THF)2]27b [LiACTHNUGTRENUN(GN TMEDA)]27c
S(3)–(3A)
C(1)–S(3)
C(1)–P(1)
C(1)–P(2)
P(1)–S(1)
P(2)–S(2)
Li(1)–S(1)
Li(1)–S(2)
2.222(2)[a] [2.281] 2.213(2)[b]
2.508(1)[a,c] [2.524]
1.885(3)[a,c] [1.877]
1.746(3) [1.770]
1.751(3) [1.770]
2.003(1) [2.034]
1.994(1) [2.022]
2.455(6) [2.399]
2.440(6) [2.397]
1.736(3) [1.735]
1.761(3) [1.778]
1.753(3) [1.778]
2.002(1) [2.034]
1.999(2) [2.022]
2.390(6) [2.397]
2.404(6) [2.397]
1.760(3)
1.756(3)
1.753(3)
2.003(1)
1.991(1)
2.441(7)
2.467(7)
2.35 ꢂ observed in the diaryl dichalcogenides Ar2E2 (E=S,
Ar=C6H5, C6F5, 4-NO2C6H4, 2,4,6-iPr3C6H2; E=Se, Ar=
C6H5, C6F5, 4-NO2C6H4, 2,4,6-tBu3C6H2).[23] The S S distance
ꢀ
in [Li
N
2.177(13) ꢂ reported for an analogous P2C-S-S-CP2 unit in
the neutral dinuclear manganese(I) complex [(CO)4Mn-
(PPh2)2}Mn(CO)4)].[24] On the other hand, the
ACHUTNGREN{NUG (Ph2P)2CSSCAHCUTNGTRNENGUN
P(1)-C(1)-P(2)
P(1)-C(1)-S(3)
P(2)-C(1)-S(3)
C(1)-P(1)-S(1)
C(1)-P(2)-S(2)
P(1)-S(1)-Li(1)
P(2)-S(2)-Li(2)
S(1)-Li(1)-S(2)
119.1(2) [118.4]
119.0(2) [119.2]
118.0(2) [119.0]
118.1(1) [117.9]
115.8(1) [115.1]
99.6(2) [98.8]
119.1(2)
115.9(2)
117.0(2)
117.8(1)
114.7(1)
98.4(2)
121.7(2) [119.4]
118.1(2)[a,c] [118.8]
117.2(2)[a,c] [118.3]
117.6(1) [118.1]
115.0(1) [115.1]
95.6(2) [98.7]
106.3(2) [107.4]
110.3(2) [109.1]
106.3(1)[a,c] [106.9]
ꢀ
Se Se distance in [LiACHTUNTGRENUNG(TMEDA)]27c is about 0.19 ꢂ longer
than the corresponding distance in the dication [(CO)4Mn-
[25]
ꢀ
{(Ph2P)2C(H)SeSe(H)C
(PPh2)2}Mn(CO)4)]2+
.
The P C
ꢀ
and P S bond lengths in [Li
(TMEDA)]27b and [Li-
AHCTUNGTREG(NNUN TMEDA)]27c are essentially identical at about 1.75 and
106.2(2) [107.1]
108.1(2) [108.6]
104.4(2)
106.3(2)
ꢀ
2.00 ꢂ, respectively, although the mean Li S contacts in the
C(1)-S(3)-S(3A) 107.1(1)[a] [108.6] 105.9(1)[b]
ꢀ
latter compound are about 0.05 ꢂ longer. The Li S contacts
in [Li
(TMEDA)]27c are, however, equal to those in the
Symmetry operation (A): [a] 1ꢀx, ꢀy, ꢀz, [b] 2ꢀx, ꢀy, 2ꢀz. [c] S(3)=
Se(1), S(3A)=Se(1A).
THF-coordinated derivative of 7b, [Li
N
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Chem. Eur. J. 2010, 16, 12977 – 12987

Synthesis and Redox Behaviour of Chalcogenocarbonyl Dianions
FULL PAPER
Table 3. Selected interatomic distances [ꢂ] and angles [o] calculated for
[LiACTHNUGERTN(NUNG TMEDA)]5b and [LiACTHUNGTRENNUNG
from the THF crystallisation of [LiACTHNUTRGNEG(NU TMEDA)]27b, revealing
an unusual lability of the N,N’-chelated TMEDA ligand.
The THF- and TMEDA-coordinated lithium complexes of
A
[LiACTHUNGETRNNUG
(TMEDA)]5c[a]
ꢀ
the dianion 7b are isostructural (Figure 2a). The P C bond
C(1)–S(3)
C(1)–P(1)
C(1)–P(2)
P(1)–S(1)
P(2)–S(2)
Li(1)–S(1)
Li(1)–S(2)
1.700
1.793
1.787
2.024
2.018
2.400
2.400
1.841
1.781
1.786
2.025
2.019
2.402
2.402
lengths in the selenium derivative [Li
N
an elongation of about 0.04 ꢂ in relation to the precursor
4c, whereas the C Se bond in the former is significantly
shorter (by 0.09 ꢂ). The PCP carbon atoms in the anions 7b
and 7c exhibit only slight distortions from planarity
ꢀ
(S]C(1)ꢁ3568, 3528 and 3578 in [Li
ACHTUNGTRNE(NGNU TMEDA)]27b, [Li-
P(1)-C(1)-P(2)
P(1)-C(1)-S(3)
P(2)-C(1)-S(3)
C(1)-P(1)-S(1)
C(1)-P(2)-S(2)
P(1)-S(1)-Li(1)
P(2)-S(2)-Li(2)
S(1)-Li(1)-S(2)
121.4
121.5
117.0
117.0
116.0
101.0
104.1
109.9
121.4
116.6
121.5
116.7
115.7
100.9
104.2
109.6
G
ACHTUNGTRENNUNG
sequence of the centre of symmetry, the CSSC fragments in
7b and 7c are planar with trans C atoms (compare with
[(CO)4Mn
The 7Li and 31P{1H} NMR spectra of [Li
and [Li(TMEDA)]27c in CD2Cl2 showed singlets at d=1.20
(PPh2)2}Mn(CO)4)][24]).
ACHTUNGTRENNUNG{(Ph2P)2CSSCAHCUTNGTRENNGUN
AHCTUNGTRE(NGNUN TMEDA)]27b
ACHTUNGTRENNUNG
and 50.2 ppm and at d=1.24 and 50.5 ppm, respectively. In
addition, the characteristic patterns for phenyl and TMEDA
resonances were observed in the 1H NMR spectra. However,
[a] S(3)=Se(1).
the all-sulfur system [LiACTHNUTRGNE(NUG TMEDA)]27b exhibited broad sig-
7
nals (half-width of 325 Hz for the Li signal and 405 Hz for
the 31P signal) and after 30 min the singlet at d=50.2 ppm in
the 31P{1H} NMR spectrum was replaced by two singlets in
an approximately 1:1 ratio at d=48.8 and 51.8 ppm; these
were subsequently shown to arise from {[LiACTHUNGTRENNUNG
A
E
([LiACTHNGUTERN(UNG TMEDA)]8b;
below).[26] After 12 h in solution (THF, CH2Cl2 or CH3CN)
at 238C, both 7b and 7c had released their carbon-bound
chalcogens to give [H2CACHTNUTRGNE(NUG PPh2S)2] (9) as the final product
(1H NMR: d=3.84 ppm (t); 31P{1H} NMR at d=35.8 ppm
(s).[27]
Electronic structures of the dianions [(SPh2P)2CEEC-
A
R
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
Pertinent optimised structural parameters are given in
Table 2 and Table 3, respectively; there is an excellent
agreement between the theoretical and the experimental re-
sults. Notably, there is almost no change in the interatomic
distances and angles of the radicals 5b and 5c upon forma-
tion of the corresponding diamagnetic dimers 7b and 7c.
An inspection of the frontier orbitals of 5b and 5c and of
those of 7b and 7c reveals that the net chalcogen–chalcogen
bonding interaction in the dianions is solely due to the
(somewhat poor) overlap of the SOMOs of the monoanionic
radicals, which are themselves composed of an antibonding
combination of p-orbitals on the C=E bond (Figure 3). Con-
sequently, the calculated binding energies of 7b and 7c
(with respect to the monomers 5b and 5c in the geometry
they adopt in the dimers) are particularly small: 72 and
90 kJmolꢀ1, respectively, in accord with the elongated chalc-
ogen–chalcogen bonds observed in the solid-state structures.
The morphologies of the SOMOs of the monoanionic rad-
icals 5b and 5c (Figure 3a) parallel those of the structurally
Figure 3. Frontier molecular orbitals of [LiACTHNUTRGNEUNG
(TMEDA)]+ salts of a) 5b
(SOMO), and b) 7b (HOMO). Isosurfaces are drawn at contour values
ꢂ0.05.
ꢀC[20]
related radical anions [R2C=S]
(PPh2S)2] .
and [Ph2C=C-
ꢀC [19]
Although the p orbital at the carbon-bound
chalcogen atom makes significant contributions to the
SOMOs, the predicted hyperfine couplings (hfcs) to these
nuclei are small due to the vanishing s-wave contributions:
4.6 and 20.6 G for 5b and 5c, respectively (compared with
33
[20a]
ꢀC
a Sꢁ2 G for thioketyl anion radicals [R2C=S] ).
Conse-
quently, the largest hfcs in 5b (5c) of ꢀ19.4 (17.8) and
Chem. Eur. J. 2010, 16, 12977 – 12987
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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12981

T. Chivers, J. Konu and H. M. Tuononen
ꢀ19.8 (18.1) G are due to spin polarisation and involve the
two slightly inequivalent phosphorus centres. The interac-
tions of the unpaired electron with the two sulfur atoms and
with the protons at the four phenyl rings are considerably
smaller and do not give rise to any significant splitting of
the signal. The EPR spectra of 5b and 5c are hence expect-
ed each to be dominated by a broadened binomial triplet
with minor contributions from 33S and 77Se satellites.
falls in the range of 2.74–2.78 ꢂ reported for organoselenen-
yl iodides, which are stabilised by an intramolecular Se···N
ꢀ
interaction that, paradoxically, weakens the Se I bond
[36]
ꢀ
through electron donation into the Se I s* orbital. The
C–Se distance of 1.815(4) ꢂ falls within the 1.77–1.84 ꢂ
range reported for a wide variety of selenocarbonyl com-
pounds,[21,30] with selenoketones falling in the lower end of
that range.[37] It is comparable with the value of 1.817(7) ꢂ
found for N-methylbenzothiadiazole-2(3H)-selone.[38] We
note, however, that the C–Se distance in the selenium donor
Attempts to detect the radical anions 5b and 5c by moni-
toring CH2Cl2 solutions of the [LiACHTUNGTRNEUNG
(TMEDA)]+ salts of the
dimeric dianions 7b and 7c by EPR spectroscopy resulted
in each case in the observation of two radical species. How-
ever, the observed signal patterns could not be assigned to
5b and 5c with certainty.[28]
is elongated by 0.04–0.06 ꢂ in charge-transfer complexes
[35]
ꢀ
that contain strong Se I bonds. It thus seems reasonable
to infer that the C=Se distance in 6c, if it can be isolated,[31]
will be significantly shorter than the value of 1.815(4) ꢂ
found for the LiI adduct. The C–Se distance for the p-
bonded C=Se group in the copper complex of [(Se)C-
Two-electron oxidation of 4c: synthesis and crystal structure
of {[Li
(TMEDA)][I(Se)C
E
G
ACHTUNGTRENNUNG
The two-electron oxidation of the dianions 4b and 4c was
ACHTUNGTRENNUNG
investigated with a view to producing the neutral chalcoge-
N
ACHTUNGTRENNUNG
ꢀ
nocarbonyls EC
of the Se-containing derivative [{Li
G
R
ACHTUNGTRENNUNG
G
lengths along the series dianion 4c, monoanion 5c in the
dimer 7c and the neutral LiI adduct of 6c (about 1.71, 1.75
and 1.78 ꢂ, respectively) display a steady increase concomi-
tant with the shortening, and enhanced double bond charac-
ter, of the C–Se contact (1.970(3), 1.885(3) and 1.815(4) ꢂ,
respectively). A significantly less pronounced trend is noted
in the deviation from the planarity for the PCP carbon
atoms, with sums of the bond angles of about 355, 357 and
3608 in the dianion 4c, the dimeric dianion 7c and neutral
6c, respectively.
equivalent of iodine in toluene at ꢀ808C produced a dark
1
red powder. The H NMR spectrum of this red product in
CD2Cl2 displayed the characteristic signal patterns for both
phenyl and TMEDA groups with integrated intensities con-
sistent with the presence of one TMEDA ligand for each
[(Se)CACHTUNGTRENNUNG
(PPh2S)2] molecule. The 7Li NMR spectrum showed
the presence of a Li+ cation with a singlet at 1.64 ppm, and
the 31P{1H} NMR spectrum exhibited a single resonance at
54.2 ppm. The NMR spectroscopy data therefore indicated
the incorporation of (TMEDA)LiI in the red product.
The dark red powder was recrystallised from toluene/pen-
tane and shown by an X-ray structural determination to be
the TMEDA-solvated LiI adduct of the selone [(Se)C-
Two-electron oxidation of 4b: formation and crystal struc-
tures of {[Li(L)]
L=TMEDA, ([12]crown-4)2): The attempted two-electron
oxidation of the all-sulfur dianion in [{Li(TMEDA)}24b] by
ACHTUTGNRENUNG[(SPh2P)2CSS(H)CCAHTUNGTREN(NNGU PPh2S)2]} ([Li(L)]8b;
A
ACHTUNGTRENNUNG
S,S’-chelated by the neutral selone ligand and the iodide
anion is bonded to the carbon-bound selenium atom. Sele-
nocarbonyl compounds have attracted increasing attention
as a result of their applications in conducting materials and
biological systems.[21a,30] The stability of selenoketones R2C=
Se is enhanced if the substituents R (preferably both) con-
tain heteroatoms, especially R2N groups.[21a] The thiophos-
phoryl derivative 6c is a rare example of a selone in which a
phosphorus substituent is attached to the C=Se functionali-
ty.[18] We note, however, that the iodide ion in the adduct
addition of one equivalent of iodine to an Et2O solution at
ꢀ808C produced a pale yellow powder. In contrast with the
1
observations made with the Se analogue 4c, the H NMR
spectrum of this product in CD2Cl2 revealed the presence of
phenyl and TMEDA groups with integrated intensities con-
sistent with only one TMEDA group per two [(S)CACTHUNTRGNEUN(G PPh2S)2]
7
units. In addition, the Li NMR spectrum exhibited a singlet
at 1.32 ppm and the 31P{1H} NMR spectrum showed two sin-
glets in an approximately 1:1 ratio at d=48.8 and 51.8 ppm.
The chemical shifts of the latter resonances were notably
similar to those observed for the initial decomposition prod-
[{LiIACHTUNGTRENNUNG(TMEDA)}6c] appears to provide a necessary stabilis-
ing influence on this unusual selone.[31,32]
uct of [LiACTHNGUETRNNU(G TMEDA)]27b in various solvents (see above) and
The Se–I distance of 2.7218(7) ꢂ (Table 1) in [{LiI-
(TMEDA)}6c] represents a moderately strong interaction.
the product from the reaction between [LiACTHNGUETRNNU(G TMEDA)]27b
G
and [12]crown-4 (Scheme 1).[26] Collectively, these NMR
data suggest the formation of an unsymmetrical dimer that
ꢀ
This value is about 0.20 ꢂ longer than the covalent Se I
bond lengths in the selenenyl iodides ArSeI (Ar=2,4,6-
tBu3-C6H2, 2,4,6-Me3-C6H2;[33] for comparison, the sum of
the covalent radii of selenium and iodine is 2.50 ꢂ[34]), and it
is at the higher end of the distances (2.56–2.73 ꢂ) observed
by Devillanova et al. for charge-transfer complexes of se-
incorporates [LiACTHNUTRGNEUNG
(TMEDA)]+.
The identity of this yellow product was established by X-
ray structural determinations of two derivatives: {[Li(L)]-
A
E
([Li(L)]8b;
L=TMEDA,
([12]crown-4)2}. As depicted in Figure 4, the anionic compo-
nent of these monolithium salts is the monoanion
lones with I2 or IBr, which have been described as “strong”
[35]
Se I bonds. The Se–I distance in [{LiI
N
{[(SPh2P)2CSS(H)CACTHNGUTERNNUG
(PPh2S)2]}ꢀ (8b), a “protonated” deriva-
ꢀ
12982
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ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 12977 – 12987

Synthesis and Redox Behaviour of Chalcogenocarbonyl Dianions
FULL PAPER
anionic precursor 7b (by about 0.09 ꢂ, Table 4). The four-
coordinate C(2) atom in 8b, as would be expected, displays
ꢀ
ꢀ
an elongation in the P C and C S bond lengths of about
0.1 ꢂ relative to the three-coordinate C(1) atom in the
anionic half of the ligand, whereas the disparity in the P–S
ꢀC
distances between the anionic [(S)CACHTNUTRGNE(UNG PPh2S)2] and neutral
C
[H(S)C
The difference in P S bond lengths between the ion-sepa-
rated salt [Li([12]crown-4)2]8b and {Li(TMEDA)}8b is in-
ACHTUNTRGNEUNG(PPh2S)2] units is less pronounced (about 0.03 ꢂ).
ꢀ
AHCTUNGTRENNUNG
significant despite the Li–S contacts in the latter. However,
ꢀC
one of the P
(Ph2)S units of the [(S)C
N
former complex is situated over the C-S-S-C fragment, re-
sulting in a slight shortening of the S(3)–S(6) distance
(0.03 ꢂ) and an inequality of about 288 in the dihedral C(1)-
S(3)-S(6)-C(2) angle in relation to [LiACTHNUGRTENUNG(TMEDA)]8b. The
S(1)–H(2) distance of 2.964(4) ꢂ is slightly shorter than
those of 3.074(3) and 3.121(3) ꢂ reported for the corre-
sponding
A
contacts
in
the
dication
[(CO)4Mn-
indicating a
G
,
[24]
ꢀ
weak C H···S interaction in the solid state.
In summary, the dianionic all-sulfur system 7b exhibits a
pronounced tendency for proton abstraction, which pre-
empts the formation of the expected two-electron oxidation
product SCACTHNUTRGNE(UNG PPh2S)2. In this context we note that the
HOMO of 7b exhibits a significant contribution from the p
orbitals of the two backbone carbon atoms. In contrast, we
were unable to detect the formation of the analogous pro-
tonated species 8c as an intermediate of the decomposition
process for the selenium-containing system 7c despite the
Figure 4. Crystal structures of a) [LiACTHNUGTRNEUNG(TMEDA)]8b and b) the anion 8b in
the ion-separated salt [Li([12]crown-4)2]8b, with thermal ellipsoids drawn
at the 50% probability level. Hydrogen atoms of the phenyl and
observation that H2CACHTUNRGTNEUNG(PPh2S)2 is the final product from both
7b and 7c in solution (see above).
TMEDA groups, and solvate molecules in [Li
omitted for clarity.
ACHTUNGTREN(NUNG TMEDA)]8b, have been
Conclusions
tive of the dianion 7b.[39] The diamagnetic monoanion 8b is
ꢀC
We have developed a straightforward and efficient synthesis
formally made up of the radical anion 5b, [(S)C
G
of the trichalcogeno species [(E)C
their dilithium derivatives. One-electron oxidation of these
dianions produces the novel dichalcogenides
(PPh2S)2]2ꢀ (E=S, Se) as
ACHTUNGTRENNUNG
C
and a neutral radical [H(S)CACHTGNUTRENNUNG
ꢀ
an S S bond that is significantly shorter than that in the di-
Table 4. Selected interatomic distances [ꢂ] and angles [o] for [Li
ACTHNUTRGEN(UNG TMEDA)]8b and [Li([12]crown-4)2]8b (calculated values in square brackets).
[Li
N
[Li([12]crown-4)2]8b
[Li
G
[Li([12]crown-4)2]8b
C(1)–S(3)
C(1)–P(1)
C(1)–P(2)
P(1)–S(1)
P(2)–S(2)
S(3)–S(6)
1.709(4) [1.721]
1.769(4) [1.782]
1.752(4) [1.770]
1.986(2) [2.028]
1.998(2) [2.077]
2.140(1) [2.176]
1.732(4) [1.727]
1.768(4) [1.784]
1.758(4) [1.780]
1.980(2) [2.000]
1.977(2) [2.005]
2.112(2) [2.162]
C(2)–S(6)
C(2)–P(3)
C(2)–P(4)
P(3)–S(4)
P(4)–S(5)
Li(1)–S(1)
Li(1)–S(2)
1.831(4) [1.834]
1.869(4) [1.890]
1.867(4) [1.890]
1.949(2) [1.964]
1.950(2) [1.965]
2.410(7) [2.412]
2.412(7) [2.412]
1.827(4) [1.829]
1.859(4) [1.880]
1.873(4) [1.890]
1.947(2) [1.968]
1.952(1) [1.973]
–
–
P(1)-C(1)-P(2)
P(1)-C(1)-S(3)
P(2)-C(1)-S(3)
C(1)-P(1)-S(1)
C(1)-P(2)-S(2)
C(1)-S(3)-S(6)
P(1)-S(1)-Li(1)
P(2)-S(2)-Li(2)
121.8(2) [121.2]
115.1(2) [117.5]
122.9(2) [122.2]
115.5(1) [115.0]
117.5(1) [117.9]
111.9(1) [112.0]
104.8(2) [104.5]
98.2(2) [86.8]
125.5(2) [124.7]
111.8(2) [112.2]
117.3(2) [117.7]
116.3(1) [116.7]
118.6(1) [118.6]
112.0(1) [110.5]
–
P(3)-C(2)-P(4)
P(3)-C(2)-S(6)
P(4)-C(2)-S(6)
C(2)-P(3)-S(4)
C(2)-P(4)-S(5)
C(2)-S(6)-S(3)
S(1)-Li(1)-S(2)
C(1)-S(3)-S(6)-C(2)
113.6(2) [112.1]
109.4(2) [109.5]
110.0(2) [111.2]
113.6(1) [113.6]
113.7(1) [113.7]
104.9(1) [106.4]
110.0(3) [108.4]
117.9(2) [116.6]
112.5(2) [112.2]
109.2(2) [109.6]
112.2(2) [113.1]
112.3(1) [113.6]
114.5(1) [115.5]
109.4(1) [109.1]
–
–
90.0(2) [89.2]
Chem. Eur. J. 2010, 16, 12977 – 12987
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
12983

T. Chivers, J. Konu and H. M. Tuononen
[(SPh2P)2CEEC
(PPh2S)2]2ꢀ, which are formally dimers of
ꢀC.
the corresponding monoanion radicals [(E)CCAUTHGNTRNE(NGU PPh2S)2] The
ACHTUNGTRENNUNG
7c and 8b). The crystals of all compounds were coated with Paratone
8277 oil and mounted on glass fibres. Diffraction data were collected
with a Nonius KappaCCD diffractometer with use of monochromated
MoKa radiation (l=0.71073 ꢂ) at ꢀ1008C. The data sets were corrected
for Lorentz and polarisation effects, and empirical absorption correction
was applied to the net intensities. The structures were solved by direct
methods by use of SHELXS-97 and refined with SHELXL-97.[45,46] After
full-matrix least-squares refinement of the non-hydrogen atoms with ani-
sotropic thermal parameters, the hydrogen atoms were placed in calculat-
electronic structures of these radical anions and their dimers
have been elucidated, but attempts to characterise these
short-lived species by EPR spectroscopy were unsuccessful.
Two-electron oxidation of the dianion [(Se)C
produces the novel selone [(Se)C(PPh2S)2], which is stabi-
(PPh2S)2]2ꢀ
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
lised as the LiI adduct. In contrast, the attempted two-elec-
tron oxidation of the corresponding all-sulfur system produ-
ces a protonated species formally made up of the anion radi-
ꢀ
ꢀ
ꢀ
ꢀ
ed positions (C H=0.95 ꢂ for CH, 0.99 ꢂ for CH2 and 0.98 ꢂ for
CH3 hydrogen atoms). The isotropic thermal parameters of the hydrogen
ꢀ
atoms were fixed at 1.2 times that of the corresponding carbon for CH
ꢀC
C
ꢀ
ꢀ
and CH2 hydrogen atoms, and 1.5 times for CH3 hydrogen atoms. In
the structures of 8b the hydrogen atom bonded to the PCP carbon was
located from the Fourier density map and it was refined as isotropic. In
the final refinement the remaining hydrogen atoms were riding on their
respective carbon atoms.
cal [(S)C
U
ACHTUNGTRENNUNG
ꢀ
connected through an S S bond.
The tridentate [(E)C
N
[(SPh2P)2CEECACHTUNGTRENNUNG
(PPh2S)2]2ꢀ chalcogen-centred dianions (E=
S, Se) are potentially versatile ligands for the construction
of a wide variety of metal complexes. More specifically,
there is an intriguing possibility that metathesis of either of
these dianions with metal halides could, in certain cases,
lead to complexes of the elusive monoanion radicals [(E)C-
ꢀC
ACHTUNGTRENNUNG(PPh2S)2] , either through an internal redox process (one-
In the structures of [LiCAHTUNGNERTNN(GU TMEDA)]27b·AHCTNUTREGGNN(UN CH2Cl2)0.33 and [LiACTHNGUTREN(NUNG THF)2]27b the
carbon-bound sulfur atoms show positional disorder with site occupancy
factors of about 0.93:0.07 and 0.88:0.12, respectively, in the final refine-
ment. In addition, the structure of [LiACTHUNGTRENNUG(TMEDA)]27b·ACHUTNTGERN(NUGN CH2Cl2)0.33 is par-
tially solvated with an occupancy of 0.33 for the CH2Cl2 molecule that re-
sults in two orientations for the closest phenyl group in the ratio
0.67:0.33. One of the two solvate molecules in [LiACTHNUTRGNE(UNG TMEDA)]8b·
(CH2Cl2)2 is also disordered, with the refined occupancies of 0.59:0.41.
ꢀ
electron oxidation) or as a result of E E bond cleavage.
Such studies are in progress.
CCDC-780827, CCDC-780828, CCDC-780829, CCDC-780830, CCDC-
780831, CCDC-780832 and CCDC-780833 contain the supplementary
crystallographic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
Experimental Section
Synthesis of {[{LiACHTNUTRGENN(UG TMEDA)}24b]}: A solution of [H2CACHUTGNTREN(NUGN PPh2S)2] (0.538 g,
1.20 mmol) in toluene (10 mL) was cooled to ꢀ808C and MeLi (1.50 mL
General procedures: All reactions and the manipulations of products
were performed under argon with use of standard Schlenk techniques or
an inert atmosphere glovebox. The compounds [H2CACHTNUGTRENUNG(PPh2)2] (Aldrich,
97%), TMEDA (Aldrich, 99%), MeLi (Aldrich, 1.6m sol. in Et2O), I2
(Aldrich, 99.99+ %) and [12]crown-4 (Alfa Aesar, 98%) were used as
of a 1.6m solution in Et2O, 2.40 mmol) was added by syringe. The reac-
tion mixture was stirred for 15 min at ꢀ808C and for 2.5 h at 238C.[4]
A
solution of TMEDA (0.279 g, 1.20 mmol) in toluene (5 mL) was added at
238C to the cloudy solution of Li2[CACHTNUGRTNEG(UN PPh2S)2]. The reaction mixture was
stirred for 15 min, after which it was added at ꢀ808C to a suspension of
S8 (0.038 g, 1.20 mmol) in toluene (5 mL). The reaction mixture was
stirred for 15 min at ꢀ808C and for 2 h at 238C. The solvent was evapo-
rated under vacuum and the product was washed with n-hexane to afford
received. The dianion Li2[CACTHNUTRGNE(UNG PPh2S)2] (Li22) was prepared by a literature
method and was used in situ.[4] The solvents n-hexane, pentane, toluene,
Et2O and THF were dried by distillation over Na/benzophenone and
CH2Cl2 over CaH2 under argon prior to use. Elemental analyses were
performed by Analytical Services, Department of Chemistry, University
of Calgary.
[{LiACHTNUGRTNEUNG
(TMEDA)}24b] as an orange-red powder (0.748 g, 86%). 1H NMR
ꢀ
([D8]THF, 238C): d=6.88–7.97 (m, 20H; C6H5), 2.31 (s, 8H; CH2 of
TMEDA), 2.16 ppm (s, 24H; CH3 of TMEDA); 13C{1H} NMR: d=141.1
1
7
Spectroscopic methods: The H, Li, 13C{1H}, 31P{1H} and 77Se NMR spec-
tra were obtained in CD2Cl2 or in [D8]THF at 238C with a Bruker
DRX 400 spectrometer operating at 399.46, 155.24, 100.46, 161.71 and
ꢀ
1
(t, J (C,P)=43.7 Hz; PCP carbon), 134.3 (m, Ph), 132.1 (m, Ph), 129.5 (s,
ꢀ
Ph), 128.7 (s, Ph), 127.8 (m, Ph), 126.9 (m, Ph), 58.7 (s, TMEDA, CH2),
7
46.1 ppm (s, TMEDA, CH3); Li NMR: d=1.67 ppm; 31P{1H} NMR: d=
1
76.17 MHz, respectively. H and 13C{1H} spectra are referenced to the sol-
ꢀ
vent signal and the chemical shifts are reported relative to (CH3)4Si. 7Li,
31P{1H} and 77Se NMR spectra are referenced externally and the chemical
shifts are reported relative to a solution of LiCl in D2O (1.0m), to a solu-
tion of H3PO4 (85%) and to neat Me2Se, respectively.
44.0 ppm; elemental analysis calcd (%) for C37H52Li2N4P2S3: C 61.31, H
7.23, N 7.73; found: C 60.97, H 7.11, N 7.64.
Synthesis of {[{LiACHTNUTRGENN(UG TMEDA)}24c]}: A solution of [H2CACHUTGNTREN(NUGN PPh2S)2] (0.538 g,
1.20 mmol) in toluene (10 mL) was cooled to ꢀ808C and MeLi (1.50 mL
of 1.6m solution in Et2O, 2.40 mmol) was added by syringe. The reaction
mixture was stirred for 15 min at ꢀ808C and for 2.5 h at 238C.[4] A solu-
tion of TMEDA (0.279 g, 1.20 mmol) in toluene (5 mL) was added at
The X-band EPR spectra were recorded with a Bruker EMX 113 spec-
trometer fitted with a variable-temperature accessory.
Computational details: DFT calculations were performed for [{Li-
238C to the cloudy solution of Li2[CACHTNUGRTNEG(UN PPh2S)2]. The reaction mixture was
G
E
N
ACHTUNGTREN(NUNG TMEDA)}6c],
stirred for 15 min, after which it was added at 08C to a suspension of ele-
mental selenium (0.095 g, 1.20 mmol) in toluene (5 mL). The reaction
mixture was stirred for 15 min at 08C and for 2 h at 238C. The solvent
was evaporated under vacuum and the product was washed with n-
G
E
ACHTUNGTRENNUNG
tures were fully optimised by use of a combination of the PBE0 ex-
change-correlation functional[40] with the Ahlrichsꢃ triple-zeta valence
basis sets augmented by one set of polarisation functions (def-TZVP).[41]
Hyperfine couplings of radicals [LiACTHUNRTGENNUG(TMEDA)]5b and [LiACHTUNGTRENN(UGN TMEDA)]5c
hexane to afford [{LiACTHNUTRGNE(UNG TMEDA)}24c] as a red powder (0.843 g, 91%).
1H NMR ([D8]THF, 238C): d=6.88–7.80 (m, 20H; C6H5), 2.32 (s, 8H;
were calculated at the optimised geometries with the same basis set–den-
sity functional combination. All calculations were performed with the
Gaussian 03[42] and Turbomole 6.1[43] program packages. Visualisations for
Figure 3 were achieved with gOpenMol.[44]
CH2 of TMEDA), 2.16 ppm (s, 24H; CH3 of TMEDA); 13C{1H} NMR:
d=141.2 (t, J (C,P)=46.2 Hz; PCP carbon), 134.3 (m; Ph), 134.1 (s; Ph),
ꢀ
ꢀ
1
132.1 (m; Ph), 129.5 (s; Ph), 128.8 (s; Ph), 128.7 (s; Ph), 127.8 (m; Ph),
ꢀ
126.9 (m; Ph), 125.9 (m; Ph), 58.6 (s; TMEDA, CH2), 46.2 ppm (s;
X-ray crystallography: Crystallographic data for {[{Li
[{LiI(TMEDA)}6c]·C7H8, [Li(TMEDA)]27b·(CH2Cl2)0.33, [Li
[Li(TMEDA)]27c, [Li(TMEDA)]8b·(CH2Cl2)2 and [Li([12]crown-4)2]8b
are summarised in Table 5 (see Scheme 1 for the identities of 4c, 6c, 7b,
ACHTUNGTRENNUNG
TMEDA, CH3); 7Li NMR: d=2.05 ppm; 31P{1H} NMR: d=43.5 ppm;
ꢀ
G
G
E
ACHTUNGTRENNUNG
77Se NMR: d=ꢀ4.5 ppm; elemental analysis calcd (%) for
N
U
ACHTUNGTRENNUNG
C37H52Li2N4P2S2Se: C 57.58, H 6.79, N 7.26; found: C 57.36, H 6.45, N
12984
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Chem. Eur. J. 2010, 16, 12977 – 12987

Synthesis and Redox Behaviour of Chalcogenocarbonyl Dianions
FULL PAPER
7.19. X-ray quality crystals were obtained by layering n-
hexane onto the toluene solution of [{LiACTHUNGTRENNUNG
24 h at ꢀ208C.
Synthesis of [{LiIACHTUGNTERN(UNNG TMEDA)}6c]}: A
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
0.047 g of Se as described above) in toluene (20 mL) was
cooled to ꢀ808C and a solution of I2 (0.152 g, 0.60 mmol) in
toluene (20 mL) was added by cannula. The reaction mixture
was stirred for 15 min at ꢀ808C and for 2 h at 238C. The sol-
vent volume was reduced to about 10 mL and n-hexane
(40 mL) was added by cannula. The resulting white precipi-
tate (LiCl) was removed by filtration and the solution was
stored at ꢀ208C for 48 h to afford [{LiI
ACHTUNGTREN(NNUG TMEDA)}6c]·C7H8
as a dark red, crystalline powder (0.369 g, 71%). 1H NMR
(CD2Cl2, 238C): d=7.13–7.86 (m, 20H; C6H5 and 5H of
ꢀ
C7H8), 2.38 (s, 4H; CH2 of TMEDA), 2.29 (s; 3H of C7H8),
2.27 ppm (s, 12H; CH3 of TMEDA); 7Li NMR: d=
ꢀ
1.64 ppm; 31P{1H} NMR: d=54.2 ppm; elemental analysis
calcd (%) for C38H44ILiN2P2S2Se ([{LiIACTHUNRTGNEUNG(TMEDA)}6c] + 1
mole of toluene solvate (see NMR spectroscopic and crystal-
lographic data): C 52.6, H 5.11, N 3.23; found: C 52.17, H
5.17, N 3.33. 13C and 77Se NMR spectra were not obtained,
due to decomposition of the adduct in solution. X-ray quality
crystals were obtained by layering pentane onto the toluene
solution of [{LiI
Synthesis of [Li
(TMEDA)}24b] (1.20 mmol, prepared in situ from 0.538 g of
[H2C(PPh2S)2], 1.50 mL of MeLi, 0.279 g of TMEDA and
ACHTUNGTRENNUNG
A
A
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
0.038 g of S8 as described above) in toluene (20 mL) was
cooled to ꢀ808C and a solution of I2 (0.152 g, 0.60 mmol) in
toluene (10 mL) was added by cannula. The reaction mixture
was stirred for 15 min at ꢀ808C and for 2 h at 238C. The re-
sulting powder was allowed to settle and the solvent was
decanted by cannula. The precipitate was washed with tolu-
ene to afford [Li
ACHTUNGTNER(NUNG TMEDA)]27b as a yellow powder (0.430 g,
60%). 1H NMR (CD2Cl2, 238C): d=6.90–7.90 (brs, 40H;
ꢀ
ꢀ
C6H5), 2.25 (s, 8H; CH2 of TMEDA), 1.98 ppm (s, 24H;
CH3 of TMEDA); 7Li NMR: d=1.20 ppm; 31P{1H} NMR:
d=50.2 ppm; elemental analysis calcd (%) for
C62H72Li2N4P4S6: C 61.88, H 6.03, N 4.66; found: C 61.37, H
6.16, 4.64. At room temperature, solutions of [Li-
(TMEDA)]27b (THF, CH2Cl2, CH3CN) form [Li-
(TMEDA)]8b, followed by decomposition and formation of
[H2C
(PPh2S)2] (9) as shown by NMR spectroscopy.[27] X-ray
quality crystals were obtained by layering n-hexane on top
of the CH2Cl2 solution of [Li(TMEDA)]27b after 3 h at
238C. When n-hexane was layered onto the THF solution of
[Li(TMEDA)]27b, crystals of [Li(THF)2]27b were obtained
N
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
N
ACHTUNGTRENNUNG
after 12 h at 58C.
Synthesis of [Li
(TMEDA)]27c:
A
solution of [{Li-
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
was cooled to ꢀ808C and
a
0.60 mmol) in toluene (10 mL) was added by cannula. The
reaction mixture was stirred for 15 min at ꢀ808C and for 2 h
at 238C. The resulting powder was allowed to settle and the
solvent was decanted by cannula. The precipitate was
washed with toluene to afford [LiACTHNUTRGNEN(UG TMEDA)]27c as an
1
orange powder (0.578 g, 74%). H NMR (CD2Cl2, 238C): d=
ꢀ
7.13–7.63 (m, 40H; C6H5), 2.19 (s, 8H; CH2 of TMEDA),
1.88 ppm (s, 24H; CH3 of TMEDA); 7Li NMR: d=
ꢀ
1.24 ppm; 31P{1H} NMR: d=50.5 ppm; elemental analysis
calcd (%) for C62H72Li2N4P4S4Se2: C 57.40, H 5.59, N 4.32;
found: C 57.55, H 5.71, N 4.19. At room temperature, solu-
tions of [Li
ACHTUNGTRENNUNG
pose and eventually form [H2CAHCTUNGTRENNUNG
Chem. Eur. J. 2010, 16, 12977 – 12987
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
12985

T. Chivers, J. Konu and H. M. Tuononen
copy)[27] and elemental selenium. X-ray quality crystals were obtained by
C-L. Wa, K-W. Kan, T. C. W. Mak, Organometallics 2010, 29, 814–
layering Et2O on top of the CH2Cl2 solution of [Li
A
820; GeIV
: b) C. Foo, K-C. Lau, Y-F. Yang, C-W. So, Chem.
4 h at 238C.
Commun. 2009, 6816–6818.
[7] ZrIV: T. Cantat, L. Ricard, N. Mꢅzailles, P. Le Floch, Organometallics
2006, 25, 6030–6038.
Synthesis of [Li
(0.60 mmol, prepared in situ from 0.269 g of [H2CAHCTUNGTRENNUNG
(TMEDA)]8b:
A
solution of [{Li
ACHTUNGTRNEUN(NG TMEDA)}24b]
(PPh2S)2], 0.75 mL of
[8] RuII: T. Cantat, M. Demange, N. Mꢅzailles, L. Ricard, Y. Jean, P. Le
Floch, Organometallics 2005, 24, 4838–4841.
MeLi, 0.139 g of TMEDA and 0.019 g of S8 as described above) in Et2O
(20 mL) was cooled to ꢀ808C and a solution of I2 (0.152 g, 0.60 mmol) in
Et2O (20 mL) was added by cannula. The reaction mixture was stirred
for 15 min at ꢀ808C and for 2 h at 238C. The resulting pale yellow
powder was allowed to settle and the solvent was decanted by cannula.
The product was washed with pentane and Et2O and was identified as
[9] TmIII: a) T. Cantat, F. Jaroschik, L. Ricard, P. Le Floch, F. Nief, N.
Mꢅzailles, Organometallics 2006, 25, 1329–1332; SmIII: b) T. Cantat,
F. Jaroschik, F. Nief, L. Ricard, N. Mꢅzailles, P. Le Floch, Chem.
Commun. 2005, 5178–5180.
[10] UIV: a) J.-C. Tourneux, J.-C. Berthet, P. Thuꢅry, N. Mꢅzailles, P. Le
Floch, M. Ephritikhine, Dalton Trans. 2010, 39, 2494–2496; b) T.
Cantat, T. Arliguie, A. Noꢆl, P. Thuꢅry, M. Ephritikhine, P. Le Floch,
N. Mꢅzailles, J. Am. Chem. Soc. 2009, 131, 963–972.
[Li
(m, 40H; C6H5), 2.32 (s, 4H; CH2 of TMEDA), 1.93 ppm (s, 12H;
CH3 of TMEDA); 7Li NMR: d=1.32 ppm; 31P{1H} NMR: d=51.8 (s),
48.8 ppm (s). At room temperature, solutions of [Li(TMEDA)]8b (THF,
CH2Cl2, CH3CN) decompose and eventually form [H2C(PPh2S)2] (9) as
shown by NMR spectroscopy.[27] X-ray quality crystals of [Li-
(TMEDA)]8b were obtained by layering n-hexane onto the CH2Cl2 solu-
tion of the yellow powder after 3 d at ꢀ208C.
Synthesis of [Li([12]crown-4)2]8b: solution of [Li
ACHTUNGTRENNUNG
(TMEDA)]8b (0.210 g, 65%). 1H NMR (CD2Cl2, 238C): d=7.02–7.82
ꢀ
ꢀ
AHCTUNGTRENNUNG
[11] a) J. S. Ritch, T. Chivers, D. J. Eisler, H. M. Tuononen, Chem. Eur. J.
2007, 13, 4643–4653; b) T. Chivers, J. S. Ritch, S. D. Robertson, J.
Konu, H. M. Tuononen, Acc. Chem. Res. 2010, 43, 1053–1062 .
[12] T. Cantat, X. Jacques, L. Ricard, X. Le Goff, N. Mꢅzailles, P. Le
Floch, Angew. Chem. 2007, 119, 6051–6054; Angew. Chem. Int. Ed.
2007, 46, 5947–5950.
[13] J. Konu, T. Chivers, Chem. Commun. 2008, 4995–4997.
[14] A. Davison, D. L. Reger, Inorg. Chem. 1971, 10, 1967–1970.
[15] By contrast, the diseleno N-bridged monoanion 1 is readily prepared
AHCTUNGTRENNUNG
ACHTUNGTRENNUNG
A
ACHTUNGTRNEN(UNG TMEDA)]27b
(0.241 g, 0.20 mmol) in CH2Cl2 (20 mL) was cooled to 08C and a solution
of [12]crown-4 (0.070 g, 0.40 mmol) in CH2Cl2 (5 mL) was added by can-
nula. The reaction mixture was stirred for 10 min at 08C and for 1 h at
238C. The solvent was evaporated under vacuum and the product was
washed with Et2O and toluene to afford [Li([12]crown-4)2]8b as a bright
yellow powder (0.208 g, 79%). The use of 4 equivalents of [12]crown-4
(0.140 g, 0.80 mmol) also resulted in the formation of [Li([12]crown-
4)2]8b, based on the 1H NMR spectrum. 1H NMR (CD2Cl2, 238C): d=
by deprotonation of [HNACHTUNRGTNEUNG(PPh2Se)2] with KOtBu in ethanol without
ꢀ
significant cleavage of P Se bonds: P. Bhattacharyya, A. M. Z.
Slawin, D. J. Williams, J. D. Woollins, J. Chem. Soc. Dalton Trans.
1995, 2489–2495.
[16] J. Konu, H. M. Tuononen, T. Chivers, Inorg. Chem. 2009, 48, 11788–
11798.
ꢀ
6.95–8.22 (m, 40H; C6H5), 3.66 ppm (s, 32H; CH2 of [12]crown-4);
7Li NMR: d=ꢀ0.50 ppm; 31P{1H} NMR: d=51.0 (s), 47.3 ppm (s). At
[17] J. Konu, T. Chivers, Chem. Commun. 2010, 46, 1431–1433.
room temperature, solutions of {Li([12]crown-4)2}8b (THF, CH2Cl2,
[18] A trinuclear CuI/CuII complex in which the C=Se group of the neu-
CH3CN) decompose and eventually form [H2CACHTNUGRTNEUNG(PPh2S)2] (9) as shown by
NMR spectroscopy.[27] X-ray quality crystals of [Li([12]crown-4)2]8b were
obtained by layering n-hexane onto the CH2Cl2 solution of the yellow
powder after 5 h at 58C.
tral phosphoryl ligand [(Se)C
centre has been isolated in unspecified yield from the reaction of
[H2C(PPh2Se)2] with CuCl2·2H2O; D. Cauzzi, C. Graiff, M. Lanfran-
ACHTUNGTREN(NNUG PPh2O)2] is p-bonded to a metal
AHCTUNGTRENNUNG
chi, G. Predieri, A. Tiripicchio, J. Chem. Soc. Chem. Commun. 1995,
2443–2444.
[19] T. Cantat, F. Biaso, A. Momin, L. Ricard, M. Geoffroy, N. Mꢅzailles,
P. Le Floch, Chem. Commun. 2008, 874–876.
[20] a) C.-P. Klages, J. Voss, Angew. Chem. 1977, 89, 744–745; Angew.
Chem. Int. Ed. Engl. 1977, 16, 726–727; Angew. Chem. 1977, 89,
744–745; b) D. Helling, C.-P. Klages, J. Voss, J. Phys. Chem. 1980,
84, 3638–3646; c) A. G. Davies, A. G. Neville, J. Chem. Soc. Perkin
Trans. 2 1992, 171–173.
Acknowledgements
The authors gratefully acknowledge financial support from the Academy
of Finland (H.M.T) and the Natural Sciences and Engineering Research
Council (Canada). We thank Dr. T. L. Roemmele (University of Leth-
bridge) for carrying out the CV and SEEPR experiments.
[21] a) The term selenoketone is restricted to compounds of the type
R2C=Se in which R is a C-bonded substituent; if one or both of the
R groups involves a heteroatom bonded to the three-coordinate
carbon, these derivatives are referred to as selones or selenocarbon-
yl compounds. For a review, see T. Murai, S. Kato, Top. Curr. Chem.
2000, 208, 178–199; b) T. Murai, R. Hori, T. Maruyama, F. Shibahar,
Organometallics 2010, 29, 2400–2402.
[1] For reviews, see: a) I. Haiduc in Comprehensive Coordination
Chemistry II (Eds.: J. A. McCleverty, T. J. Meyer) Elsevier, Amster-
dam, 2003, pp. 323–347; b) C. Silvestru, J. E. Drake, Coord. Chem.
Rev. 2001, 223, 117–216; c) J. D. Woollins, J. Chem. Soc. Dalton
Trans. 1996, 2893–2901.
[2] Some exceptions that involve N-coordination have been reported,
primarily for lanthanides: a) C. G. Pernin, J. A. Ibers, Inorg. Chem.
2000, 39, 1222–1226; C. G. Pernin, J. A. Ibers, Inorg. Chem. 2000,
39, 1216–1221; C. G. Pernin, J. A. Ibers, Inorg. Chem. 1999, 38,
5478–5483; and also for Pd: b) M. Necas, M. R. S. J. Foreman, J.
Marek, J. D. Woollins, J. Novosad, New J. Chem. 2001, 25, 1256–
1263.
[3] J. Browning, K. R. Dixon, R. W. Hilts, Organometallics 1989, 8, 552–
554.
[4] a) T. Cantat, N. Mꢅzailles, L. Ricard, Y. Jean, P. Le Floch, Angew.
Chem. 2004, 116, 6542–6545; Angew. Chem. Int. Ed. 2004, 43, 6382–
6385; b) T. Cantat, L. Ricard, Y. Jean, P. Le Floch, N. Mꢅzailles, Or-
ganometallics 2006, 25, 4965–4976.
[22] A 77Se NMR chemical shift of 893 ppm was recently reported for
the monomeric PbII complex of 4c, {Pb[(Se)C
ACHTUNGTRENNUNG
900 ppm downfield from that of [{LiACTHUNGTRENNNUG
[23] a) J. D. Lee, M. W. R. Bryant, Acta Crystallogr. Sect. B 1969, 25,
2094–2101; b) M. Sacerdoti, G. Gilli, P. Domiano, Acta Crystallogr.
Sect. A 1975, 31, 327–329; c) C. M. Woodard, D. S. Brown, J. D. Lee,
A. G. Massey, J. Organomet. Chem. 1976, 121, 333–344; d) J. S.
Ricci, I. Bernal, J. Am. Chem. Soc. 1969, 91, 4078–4082; e) E. Del-
gado, E. Hernandez, N. Mansilla, F. Zamora, L. A. Martinez-Cruz,
Inorg. Chim. Acta 1999, 284, 14–19; f) R. Marsh, Acta Crystallogr.
1952, 5, 458–462; g) G. D. Morris, F. W. B. Einstein, Acta Crystal-
logr. Sect. C 1986, 42, 1433–1435; h) P. M. Dickson, M. A. D. McGo-
wan, B. Yearwood, M. J. Heeg, J. P. Oliver, J. Organomet. Chem.
1999, 588, 42–50.
[24] The dianion [(Ph2P)2CSSCACHTUNTRGNEUNG
(PPh2)2]2ꢀ in this complex is generated
[5] For a review, see: T. Cantat, A. Auffrant, P. Le Floch, Dalton Trans.
2008, 1957–1972.
from the reaction of a monuclear MnI complex of [(Ph2P)2CH]ꢀ
with elemental sulphur followed by treatment with Ph3: P. J. Ruiz,
M. Ceroni, O. V. Quinzani, V. Riera, M. Vivanco, S. Garcia-Granda,
[6] SnII and PbII complexes were prepared by amine elimination from
the neutral ligand [H2CACHTUNTRGENN(UG PPh2S)2] and M[NHCAUTNGTNERN(UGN SiMe3)2]2: a) W-P. Leung,
12986
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Chem. Eur. J. 2010, 16, 12977 – 12987

Synthesis and Redox Behaviour of Chalcogenocarbonyl Dianions
FULL PAPER
F. Van der Maelen, M. Lanfranchi, A. Tiripicchio, Chem. Eur. J.
2001, 7, 4422–4430.
[25] J. Ruiz, R. Arafflz, M. Ceroni, M. Vivanco, J. F. Van der Maelen, S.
García-Granda, Organometallics 2010, 29, 3058–3061.
[39] The signal for the carbon-bound hydrogen of the [H(S)CACHTUNGTRENNUNG(PPh2S)2]
unit was not detected in the 1H NMR spectrum of [Li(L)]8b [L=
TMEDA, ([12]crown-4)2] presumably owing to the overlapping reso-
nances of the phenyl groups, compare with the triplet observed at
[26] The reaction between [Li
G
d=6.99 ppm for the corresponding H atoms in the diprotonated di-
[24]
equivalents), performed in an effort to produce an ion-separated
salt of 7b, afforded a bright yellow powder which also showed two
singlets at d=47.3 and 51.0 ppm in the 31P{1H} NMR spectrum in
CD2Cl2. This product was subsequently identified as {[Li([12]crown-
cation [(CO)4Mn
G
G
.
How-
ever, the hydrogen atom in the PC(H)P unit was located from the
Fourier density map of the crystal structures and it was refined. We
also draw attention to the excellent agreement between the experi-
mental and calculated bond parameters of the anion 8b (Table 4).
[40] a) J. P. Perdew, K. Burke, M. Ernzerhof, Phys. Rev. Lett. 1996, 77,
3865–3868; b) J. P. Perdew, K. Burke, M. Ernzerhof, Phys. Rev. Lett.
1997, 78, 1396; c) J. P. Perdew, K. Burke, M. Ernzerhof, J. Chem.
Phys. 1996, 105, 9982–9985; d) C. Adamo, V. Barone, J. Chem.
Phys. 1999, 110, 6158–6170.
4)2]
ACHTUNGTRENNUNG[(SPh2P)2CSS(H)CACHUTNTGRNE(NUGN PPh2S)2]} {[Li([12]crown-4)2]8b} (see the Ex-
perimental Section).
[27] S. O. Grim, E. D. Walton, Inorg. Chem. 1980, 19, 1982–1987.
[28] We also attempted to detect the radical anions 5b and 5c by per-
forming the electrochemical oxidation of [{LiACTHNURTGNENG(U TMEDA)}24b]and
[{LiACHTUNGTRENNUNG(TMEDA)}24c] with the SEEPR method (Simultaneous Electro-
chemical and Electron Paramagnetic Resonance spectroscopy).[29]
The results of these experiments are summarised in the Supporting
Information.
[41] a) A. Schꢀfer, C. Huber, R. Ahlrichs, J. Chem. Phys. 1994, 100,
5829–5835.
[42] Gaussian 03, Revision C.02, M. J. Frisch, G. W. Trucks, H. B. Schle-
gel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, J. A. Montgom-
ery, Jr., T. Vreven, K. N. Kudin, J. C. Burant, J. M. Millam, S. S.
Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani,
N. Rega, G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K.
Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda,
O. Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P. Hratchian,
J. B. Cross, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann,
O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, P. Y.
Ayala, K. Morokuma, G. A. Voth, P. Salvador, J. J. Dannenberg,
V. G. Zakrzewski, S. Dapprich, A. D. Daniels, M. C. Strain, O.
Farkas, D. K. Malick, A. D. Rabuck, K. Raghavachari, J. B. Fores-
man, J. V. Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J. Cioslowski,
B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. L.
Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Na-
nayakkara, M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen,
M. W. Wong, C. Gonzalez, and J. A. Pople, Gaussian, Inc., Pitts-
burgh, PA, 2003.
[29] R. T. Boerꢅ, A. M. Bond, T. Chivers, S. W. Feldberg, T. L. Roem-
mele, Inorg. Chem. 2007, 46, 5596–5607.
[30] C. A. Bayse, E. R. Rafferty, Inorg. Chem. 2010, 49, 5365–5367.
[31] Subsequent attempts to prepare “LiI-free” 6c by the reaction be-
tween [LiI
equivalent of Me3SiOSO2CF3, or by performing the two-electron ox-
idation of [{Li(TMEDA)}24c] with 2 equivalents of [NO][SbF6] re-
ACHTUNGTRENNUNG(TMEDA)]6c and two equivalents of [12]crown-4 or one
N
sulted in decomposition.
[32] The stable compound [(Se)C
phenylcarbodiphosphorane, exhibits
about 1.99 ꢂ and significant retention of double bond character in
the PCP unit: H. Schmidbaur, C. E. Zybill, D. Neugebauer, Angew.
Chem. 1982, 94, 321–322; Angew. Chem. Int. Ed. Engl. 1982, 21,
310–311.
[33] a) W.-W. du Mont, S. Kubiniok, K. Peters, H.-G. von Schnering,
Angew. Chem. 1987, 99, 820–821; Angew. Chem. Int. Ed. Engl.
1987, 26, 780–781; b) J. Jeske, P. G. Jones, A. Martens-von Salzen,
W.-W. d Mont, Acta Crystallogr. Sect. E 2002, 58, o350-o352.
[34] L. Pauling, The Nature of the Chemical Bond, 3rd ed., Cornell Uni-
versity Press, Ithaca, 1960.
[43] TURBOMOLE 6.1, Program Package for ab initio Electronic Struc-
ture Caluclations, Theoretical Chemistry Group, University of Karls-
ruhe, Karlsruhe, 2009.
[35] F. Cristiani, F. Demartin, F. A. Devillanova, F. Isaia, V. Lippolis, G.
Verani, Inorg. Chem. 1994, 33, 6315–6324.
[36] a) A. Panda, G. Mugesh, H. B. Singh, R. J. Butcher, Organometallics
1999, 18, 1986–1992; b) G. Mugesh, A. Panda, H. B. Singh, R. J.
Butcher, Chem. Eur. J. 1999, 5, 1411–1421.
[44] a) L. J. Laaksonen, J. Mol. Graphics 1992, 10, 33–34; b) D. L. Berg-
man, L. J. Laaksonen, A. Laaksonen, J. Mol. Graphics Modell. 1997,
15, 301–306.
[45] SHELXS-97, Program for Crystal Structure Determination, G. M.
Sheldrick, University of Gçttingen, Gçttingen, 1997.
[37] a) K. Okuma, K. Kojima, I. Kaneko, Y. Tsujimoto, H. Ohta, Y. Yo-
komori, J. Chem. Soc. Perkin Trans. 1 1994, 2151–2159; b) P. R.
Brooks, J. A. Counter, R. Bishop, E. R. T. Tiekink, Acta Crystallogr.
Sect. C 1991, 47, 1939–1941.
[46] SHELXL-97, Program for Crystal Structure Refinement, G. M.
Sheldrick, University of Gçttingen, Gçttingen, 1997.
[38] S. Husebye, S. V. Lindeman, M. D. Rudd, Acta Crystallogr. Sect. C
1997, 53, 809–811.
Received: June 15, 2010
Published online: September 28, 2010
Chem. Eur. J. 2010, 16, 12977 – 12987
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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