A structural and theoretical study of the thiophosphinite and dithiophosphinate anions

Article abstract of DOI:10.1080/10426500801968169

Two novel lithium compounds containing either the phosphorus-chalcogenide anions [Ph2PS]- or [Cy2PS2]- were isolated as decomposition products in the attempted formation of phospha(V)guanidinate anions. Lithium diphenylthiophosphinite was structurally cha

Full text of DOI:10.1080/10426500801968169

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Phosphorus, Sulfur, and Silicon
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A Structural and Theoretical
Study of the Thiophosphinite
and Dithiophosphinate Anions
a
a
Natalie E. Mansfield , Martyn P. Coles & Peter B.
a
Hitchcock
a
Department of Chemistry , University of Sussex ,
Falmer, Brighton, UK
Published online: 10 Oct 2008.
To cite this article: Natalie E. Mansfield , Martyn P. Coles & Peter B. Hitchcock (2008)
A Structural and Theoretical Study of the Thiophosphinite and Dithiophosphinate
Anions, Phosphorus, Sulfur, and Silicon and the Related Elements, 183:11, 2685-2702
To link to this article: http://dx.doi.org/10.1080/10426500801968169
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Phosphorus, Sulfur, and Silicon, 183:2685–2702, 2008
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500801968169
A Structural and Theoretical Study of the
Thiophosphinite and Dithiophosphinate Anions
Natalie E. Mansfield, Martyn P. Coles,
and Peter B. Hitchcock
Department of Chemistry, University of Sussex, Falmer, Brighton, UK
Two novel lithium compounds containing either the phosphorus-chalcogenide
−
−
anions [Ph PS] or [Cy PS ] were isolated as decomposition products in
2
2
2
the attempted formation of phospha(V)guanidinate anions. Lithium diphenylth-
iophosphinite was structurally characterized as the dimeric TMEDA adduct
1
[
Li(Ph PS)(TMEDA)] (1), in which a rare example of the κ -S bonding mode
2 2
was observed for the anion. The dicyclohexyldithiophosphinate anion was incorpo-
rated into an aggregated structure with molecular formula [Li (Cy PS ) (OH)]
5
2
2 4
2
− −
2). DFT calculations were performed on the isolated [R PS] and [R PS ] an-
2 2 2
(
ions (R = Ph, Cy), indicating delocalization of electron density into the P-S bonds
for each model, in agreement with bond-lengths taken from crystallographic data.
Keywords Coordination compound; crystal structure; dithiophosphinate; DFT; lithium;
thiophosphinite
INTRODUCTION
We have been utilizing phospha(III) guanidines of general formula
ꢀ
ꢀ
ꢀ
i
1,2
R2PCNR NHR (R = Ph, Cy; R = Pr, Cy)
as a source of neutral
and anionic ligands in coordination chemistry for a number of years.
Incorporation of both nitrogen and phosphorus functionalities affords
many possible bonding modes at a metal center, and this diversity has
been noted in the solid state using X-ray diffraction experiments for a
3
−5
range of transition metal- and main-group compounds.
The original
purpose of this work was to explore the behavior of the corresponding
phospha(V)guanidinate anions in coordination chemistry, where addi-
tional bonding modes are potentially available through chalcogen·metal
Received 3 September 2007; accepted 31 January 2008.
The University of Sussex and the EPSRC are thanked for financial support.
Address correspondence to Dr. Martyn P. Coles, Department of Chemistry, University
of Sussex, Falmer, Brighton, BN1 9QJ, United Kingdom. E-mail: m.p.coles@sussex.ac.uk
2685

2
686
N. E. Mansfield et al.
interactions. However, the synthetic routes and conditions employed
did not lead to the desired compounds, and only decomposition products
−
containing the thiophosphinite or dithiophosphinate anions ([R2PS]
−
and [R2PS2] , respectively) were isolated. The molecular structures of
the resultant lithium species are, however, of interest in themselves as
they reveal a number of previously unobserved bonding patterns for
these widely studied anions. Density functional studies on the isolated
anions have been conducted to further our understanding of the bond-
ing within the products.
RESULTS AND DISCUSSION
Our first attempt at synthesizing the phospha(V)guanidinate anion in-
−
volved formation of the chalcogenidophosphinite anion, [R2PE] , via
deprotonation of the secondary phosphine chalcogenide. Given that the
conjugate acids of the thiophosphinites exist as the secondary phos-
phine sulfides unless highly electron withdrawing phosphorus sub-
6
stituents are present, we anticipated the presence of a P-centered
anion as a component of the reaction mixture that would react with
(
III)
a carbodiimide via P–C bond formation, analogous to the P
phos-
phaguanidines (Route I).1 However, important work in the area by
Davies et al. has shown that the negative charge in the analogous se-
lenophosphinite anion is essentially localized at selenium, illustrated
by an upfield shift in the 77Se NMR spectrum and the observation of
,2
7
Se-Li bonds in the molecular structure of [Li(Ph2PSe)(TMEDA)]2. See
Scheme 1.
In our approach, we formed the diphenylthiophosphinite anion,
−
n
[
Ph2PS] , by the addition of BuLi to a solution of Ph2P(S)H in THF.
i
i
The reaction mixture was added to a solution of PrN C N Pr, result-
ing in formation of a colorless solution. Despite trying numerous condi-
tions and solvent combinations, no pure solid product could be isolated
from this solution. Excess TMEDA was therefore added to the reaction
mixture to aid crystallization, affording colorless crystals (1) that were
analyzed by X-ray diffraction. No other clean product could be isolated
from this reaction.8
The molecular structure of 1 is shown in Figure 1; crystal struc-
ture and refinement data is collected in Table I and selected bond
lengths and angles in Table II. Compound 1 consists of the TMEDA
adduct of the lithium thiophosphinite anion, [Li(Ph2PS)(TMEDA)]2. In
the solid-state, 1 crystallizes as a dimer in which the sulfur atoms
−
of the [Ph2PS] anion bridge between two ‘Li(TMEDA)’ cations, giv-
◦
ing a highly puckered metallacycle, with a fold-angle of 141.8 be-
tween the two Li2S planes (Figure 1b). Within the metallacycle, the

Thiophosphinite and Dithiophosphinate Anions
2687
SCHEME 1 Potential routes to Li-salts of the phospha(V)guanidinate anion.
◦
internal angles are considerably more acute at sulfur [S(1) 76.86(16) ;
◦
◦
S(2) 77.53(16) ] than lithium [Li(1) 95.35(17); Li(2) 95.10(17) ], with an
˚
overall S· · ·S distance of 3.622 A. The sum of the angles at phospho-
◦
◦
◦
rus [ꢀangles: P(1) 306.51 ; P(2) 304.54 ] and sulfur [ꢀangles: S(1) 294.79 ;
◦
S(2) 301.42 ] indicate that that each atom is pyramidal. The lithium
◦
◦
atoms are in a distorted tetrahedral geometry [Li(1) 88.5(2) –123.7(2) ;
◦
◦
Li(2) 87.9(2) –126.9(2) ], with the most acute angle resulting from the
chelating TMEDA ligand.
The phosphorus-sulfur bond lengths in 1 [2.0661(11) A and
˚
.0710(11) A] are an intermediate value between P S single bonds
˚
2
[
˚
9
2.12 A] and the P S double bond within Ph2P S [average value of
˚
several crystal structures = 1.95 A], consistent with delocalization of
π-electron density into this bond. The sulfur-lithium distances [2.427(5)
˚
˚
A - 2.482(5) A] are unremarkable, being within the range noted in sim-
ilar dimeric lithium thiolates.
6
Despite being the subject of numerous studies, metallated thio-
phosphinites in which a sulfur-metal bond constitutes the only inter-
actions with the anion (i, Figure 2) are rare and structurally char-
acterized examples are limited to a single example involving the

2
688
N. E. Mansfield et al.
FIGURE 1 (a) ORTEP of [Li(Ph
molecules reduced to ‘ball and stick’ representation and hydrogens omitted for
clarity); (b) The core of 1, highlighting the folded Li metallacycle.
2 2
PS)(TMEDA)] (1) (ellipsoids at 30%, TMEDA
2
S
2
bis(cyclopentadienyl)titanium fragment,10 although the diphenylthio-
1
phosphinite anion has also been observed in a κ -S-mode to the boron
of a carborane cage.11 The ligand is much more commonly involved
in bonding to a metal through either the phosphorus atom (ii), as a
1
chelating κ -S, P-ligand using a combination of the phosphorus and
sulfur heteroatoms (iii), or as a bridge between two metal centers in
1
2
a κ -S:κ -P-mode (iv). It is also worth noting that, whilst the Li2S2
motif involving three-coordinate sulfur has been previously noted in a
1
2
13
14
range of alkyl, aryl and silyl thiolate compounds, the only struc-
turally characterized example in which a phosphorus-chalcogen moiety
1
5
is present involves the thiophosphonamide anion.
Isolation of the thiophosphinite anion from this reaction mixture in-
dicates that tautomerization between the P center in the starting
(V)
(
III)
reagent and the isolated P
salt has occurred (Scheme 2). Formation
of the four-membered metallacycle with bridging sulfur atoms and no
phosphorus·lithium contacts suggests that the negative charge in the
resultant anion is strongly associated with the chalcogen atom, as noted

Thiophosphinite and Dithiophosphinate Anions
2689
SCHEME 2 Proposed mechanistic pathway to compound 1.
above. Given that only a low yield of 1 was obtained, it is not possible to
definitively say that the anticipated reaction with the carbodiimide did
not occur; however, the accumulation of electron density at the chalco-
gen inferred from the crystal structure of 1 would disfavor formation
(III)
of the P–C bond, with the TMEDA therefore trapping the P
anion
FIGURE 2 Previously observed bonding modes for the thiophosphinite anion
i - iv) and the dithiophosphinate anion (v–vii).
(

2
690
N. E. Mansfield et al.
TABLE I Crystal Structure and Refinement Data for 1 and 2
1
2
Formula
Formula weight
Temperature (K)
C36H52Li2N4P2S2
680.72
173(2)
C96H178Li10O2P8S16
2194.50
173(2)
˚
Wavelength (A)
0.71073
0.71073
Crystal size (mm)
Crystal system
Space group
0.40 × 0.40 × 0.40
Monoclinic
P21/c (No.14)
13.7492(1)
17.3027(2)
17.1022(2)
100.87(1)
3995.57(7)
4
1.13
0.40 × 0.40 × 0.30
Monoclinic
P21/n (No.14)
16.0724(3)
17.0719(3)
22.0287(4)
99.309(1)
5964.77(19)
2
1.22
˚
a (A)
˚
b (A)
˚
c (A)
◦
β ( )
V (A )
˚
3
Z
Dc (Mg m 3)
−
Absorption coefficient (mm 1)
−
◦
0.24
3.74 to 24.76
31864
0.44
3.41 to 26.08
46751
θ range for data collection ( )
Reflections collected
Independent reflections
Reflections with I > 2σ(I)
Data/restraints/parameters
6704 [Rint = 0.174]
11581 [Rint = 0.049]
5834
9680
6704 / 0 / 415
1.061
11581 / 0 / 599
1.049
2
Goodness-of-fit on F
Final R indices [I > 2σ(I)]
R indices (all data)
Largest diff. peak / hole (e A
R1 = 0.069, wR1 = 0.188
R1 = 0.078, wR1 = 0.196
1.08 and −0.49
R1 = 0.043, wR1 = 0.101
R1 = 0.055, wR1 = 0.109
1.86 and −1.04
˚
−3
)
(
Scheme 2). An alternative route to phospha(V)guanidinate was there-
fore examined.
Reaction of isolated phospha(III)guanidines with nBuLi in THF
is a known route to the corresponding phosphaguanidinate anions,
ꢀ
−
[
R2PCNR 2] and has been used successfully in the generation of a
4
number of metal derivatives. Recent work from the Chivers’ group has
shown that reaction of a lithiated (imido)diphosphineimide with ele-
mental sulfur affords the corresponding NP(S)PN species, in which sim-
(
III)
(V)
ple oxidation of the P
center to P has occurred with no detrimen-
16
tal effect on the remainder of the ligand. We therefore considered the
possibility of reacting a solution of the phospha(III)guanidinate with
sulfur as a viable route to the target compounds (Scheme 1, Route III).
5
Reaction between Li(Cy2PC{NCy}2), and elemental sulfur in
toluene afforded a small number of colorless crystals upon work-up.
Analysis using NMR spectroscopic techniques was prevented by the
extremely low solubility of the product, precluding the acquisition of

Thiophosphinite and Dithiophosphinate Anions
2691
˚
◦
TABLE II Selected Bond Lengths (A) and Angles ( ) for
Li(Ph PS)(TMEDA)] (1)
[
2
2
P(1)-S(1)
S(1)-Li(1)
S(2)-Li(1)
2.0661 (11)
2.440 (5)
2.459 (5)
P(2)-S(2)
S(1)-Li(2)
S(2)-Li(2)
2.0710 (11)
2.482 (5)
2.427 (5)
Li(1)-N(1)
2.083 (6)
Li(1)-N(2)
2.116 (6)
Li(2)-N(3)
2.101 (6)
Li(2)-N(4)
2.103 (6)
C(1)-P(1)-C(7)
C(1)-P(1)-S(1)
C(7)-P(1)-S(1)
P(1)-S(1)-Li(1)
P(1)-S(1)-Li(2)
Li(1)-S(1)-Li(2)
99.19 (12)
103.88 (10)
103.44 (10)
108.16 (13)
109.32 (13)
76.86 (16)
C(19)-P(2)-C(25)
C(19)-P(2)-S(2)
C(25)-P(2)-S(2)
P(2)-S(2)-Li(1)
P(2)-S(2)-Li(2)
Li(1)-S(2)-Li(2)
98.69 (13)
103.54 (11)
102.31 (11)
115.85 (13)
108.04 (13)
77.53 (16)
any reliable data. The crystals were however suitable for analysis by
X-ray diffraction techniques, revealing a complex aggregated species of
formula [Li5(Cy2PS2)4(OH)]2 (2). The molecular structure of the asym-
metric unit of 2 is shown in Figure 3; crystal structure and refinement
data is collected in Table I and selected bond lengths and angles in
Table III.
Rather than generating the desired P(V)guanidinate anion, the
molecular structure of 2 indicates that degradation has occurred via
FIGURE 3 ORTEP of the asymmetric unit of 2 (ellipsoids at 30%, cyclohexyl
reduced reduced to stick representation and hydrogens except H1x omitted for
clarity).

2
692
N. E. Mansfield et al.
˚
◦
TABLE III Selected Bond Lengths (A) and Angles ( ) for
[
Li
5
(Cy
2
PS
2
)
4
(OH)]
2
(2)
P(1)-S(1)
P(2)-S(3)
P(3)-S(5)
P(4)-S(7)
S(1)-Li(1)
S(2)-Li(1)
S(3)-Li(1)
S(3)-Li(5)
S(5)-Li(4)
S(6)-Li(3)
S(7)-Li(3)
S(8)-Li(2)
Li(1)-O
2.0121(9)
P(1)-S(2)
P(2)-S(4)
P(3)-S(6)
P(4)-S(8)
S(1)· · ·Li(2)
S(2)· · ·Li(2)
S(3)-Li(4)
S(4)-Li(5)
S(5)-Li(5)
S(6)-Li(4)
S(7)-Li(5’)
S(8)-Li(3)
Li(2)-O
2.0069(10)
1.9986(8)
2.0202(9)
2.0069(9)
2.648(6)
2.791(5)
2.488(4)
2.425(4)
2.506(4)
2.512(4)
2.444(4)
2.511(5)
1.898(5)
1.921(5)
2.0377(8)
2.0295(8)
2.0155(8)
2.532(5)
2.476(5)
2.438(4)
2.501(4)
2.479(4)
2.454(5)
2.427(5)
2.468(5)
1.984(5)
1.956(5)
Li(3)-O
Li(4)-O
S(1)-P(1)-S(2)
S(5)-P(3)-S(6)
P(1)-S(1)-Li(1)
109.57(4)
S(3)-P(2)-S(4)
S(7)-P(4)-S(8)
P(1)-S(1)-Li(2)
P(1)-S(2)-Li(1)
Li(1)-S(2)-Li(2)
P(2)-S(3)-Li(4)
Li(1)-S(3)-Li(4)
Li(4)-S(3)-Li(5)
P(3)-S(5)-Li(4)
Li(4)-S(5)-Li(5)
P(3)-S(6)-Li(4)
P(4)-S(7)-Li(3)
Li(3)-S(7)-Li(5’)
P(4)-S(8)-Li(3)
111.95(4)
112.32(4)
81.26(11)
57.48(15)
76.52(13)
120.21(12)
79.83(10)
140.73(14)
82.47(10)
126.33(11)
106.34(12)
63.12(15)
114.65(10)
113.45(14)
64.04(16)
113.66(4)
79.98(12)
82.80(11)
56.12(15)
114.56(12)
67.52(14)
73.45(14)
81.77(10)
73.51(13)
81.13(10)
81.15(12)
123.21(15)
79.21(12)
Li(1)-S(1)-Li(2)
P(1)-S(2)-Li(2)
P(2)-S(3)-Li(1)
P(2)-S(3)-Li(5)
Li(1)-S(3)-Li(5)
P(2)-S(4)-Li(5)
P(3)-S(5)-Li(5)
P(3)-S(6)-Li(3)
Li(3)-S(6)-Li(4)
P(4)-S(7)-Li(5’)
P(4)-S(8)-Li(2)
Li(2)-S(8)-Li(3)
rupture of the P–Camidine bond, to afford the dicyclohexyldithiophosphi-
−
nate anion, [Cy2PS2] . The asymmetric unit is formed of four of these
anions aggregated with five lithium cations, with the charge balance
maintained by a hydroxyl group, assumed to originate from reaction
17
with adventitious water ; repeating the reaction with the rigorous ex-
clusion of moisture unfortunately did not afford tractable products. Two
of these neutral Li5(Cy2PS2)4(OH) units are joined by additional Li-S
ꢀ
˚
bonds [Li(5)-S(7 ) = 2.444(4) A], giving the overall formula for 2 as
[
Li5(Cy2PS2)4(OH)]2 (Figure 4), in which the two asymmetric units are
related by a crystallographic inversion center.
All five lithium atoms are four-coordinate and, unusually for
polylithio-structures, are located in an approximate plane [max devi-
˚
ation from the mean Li(1)-Li(5) plane = 0.22 A]. The Li· · ·Li contacts

Thiophosphinite and Dithiophosphinate Anions
2693
FIGURE 4 The inorganic core of 2 (excluding carbon and hydrogen atoms
except H1x), highlighting the dimeric arrangement of Li
linked by Li(5)-S(7 ) bonds, and the projection of the hydroxyl proton into the
cavity of the dimer.
5
(Cy
2
PS
2
)
4
(OH) units
ꢀ
˚
˚
are unexceptional [range 2.492(7) A – 2.983(6) A] being comparable
18
to those in related molecular (Li)n-clusters. The oxygen atom of the
˚
OH] group is located 0.579 A above the plane formed by Li(1)-Li(4)
Li-O distances: 1.898(5) A – 1.984(5) A], with the hydrogen atom point-
−
[
[
˚
˚
ing into the cavity between the two components of the dimer (Figure
). Such a µ4-capping arrangement for the hydroxyl anion has pre-
4
viously been noted, for example in the tetralithium derivative of tert-
butylcalix[4]arene,19 and has been considered as being related to a com-
20
ponent of the layered structure of LiOMe. It should be noted that the
2
1
22
deliberate encapsulation of LiOH into polylithio- and group 13 metal
clusters can be readily achieved, with a diverse range of structures pos-
sible depending largely on the nature of the supporting ligands.
The dicyclohexyldithiophosphinate anion has been crystallographi-
1
1
cally characterized as a chelating (κ -S:κ -S’) group to a range of metals
from throughout the periodic table (i.e., v, Figure 2), including main
2
3
10,24
group (Tl) transition metal (Ti, Cr, Cd, Hg)
lanthanide (Pr, Sm,
2
5
26
Dy, Lu) and actinide (U, Th) elements. In the case of cadmium, this
ligand was also found to bridge between metal centers (κ -S:κ -S) (vi)
and with thallium
with retention of a non-coordinating P S double bond. Many other ex-
amples of disubstituted dithiophosphinate anions are known27 and a
range of bonding modes have been observed. However, the molecular
structure of compound 2 displays several previously unobserved ligand-
metal interactions that are worthy of discussion.
1
2
ꢀ
(
III)
1
a monodentate (κ − S) mode was observed (vii),

2
694
N. E. Mansfield et al.
Within the core structure of 2, each of the four dithiophosphinate
anions interacts to a different extent with the lithium cations (Figure
). The first fragment centered on P(1) interacts with two formally four
5
1
1
ꢀ
coordinate lithium atoms in what we describe as a κ -S:κ -S:{pseudo-
2
2
ꢀ
˚
˚
κ -S:κ -S}-mode, containing characteristic Li(1)-S bonds [2.533(5) A
˚
˚
and 2.476(5) A] with notably longer Li(2)-S interactions [2.647(6) A
and 2.792(5) A]. All of these values are generally long compared with
the remaining lithium-sulfur bonds within 2, which fall in the range
˚ ˚
.425(4) A–2.512(4) A, and in comparison with experimentally deter-
2
˚
28
˚ 29
mined values for Li2S of 2.476 A and 2.494 A. This asymmetry in
the bonding of the dithiophosphinate to the two lithium atoms also
manifests itself in a pronounced difference in the angle between the
approximate ‘PS2’ and ‘LiS2’ planes; the P(1)-S(1)-S(2) : Li(1)-S(1)-S(2)
◦
dihedral angle is 155.7 , while the corresponding angle involving the
◦
Li(2)-S(1)-S(2) plane is 129.0 .
The geometry at phosphorus is distorted tetrahedral [angles in the
◦
◦
◦
˚
range 105.25(11) to 112.50(9) ] with a S-P-S angle of 109.57(4) . The
˚
phosphorus–sulfur bond lengths [2.0121(9) A and 2.0069(10) A] are
FIGURE 5 ORTEP representations of the four individual bonding modes of
the dicyclohexyldithiophosphinate anion in compound 2.

Thiophosphinite and Dithiophosphinate Anions
2695
˚
towards the short end of the range found within 2 [1.9986(8) A -
˚
2
[
.0377(8) A], close to the values found in the non-contacted ion pair,
TePh3][Ph2PS2].30 The values are consistent with delocalisation across
the S-P-S fragment, as noted above for 1.
1
1,2,3
ꢀ
The second fragment at P(2) displays a κ -S:κ
-S-bonding pattern
in which S(4) is unique within 2 as the only two-coordinate sulfur atom,
◦
subtended by an acute P(2)-S(4)-Li(5) angle of 82.47(10) . In contrast,
S(3) caps three lithium atoms with bonds lengths in the range 2.438(4)
˚
˚
A to 2.501(4) A, generating a four coordinate sulfur with angles in the
◦
◦
range 67.52(14) –140.73(14) . The phosphorus is distorted tetrahedral
with an S-P-S angle of 111.95(4) , larger than the corresponding angle
◦
at P(1) due to lateral interactions with Li(1) and Li(4). As expected,
˚
asymmetric P-S bond distances are noted [P(2)-S(3) 2.0377(8) A; P(2)-
S(4) 1.9986(8)] with the longer distance to the triply bridging chalcogen,
as expected.
The bonding pattern about Fragments 3 and 4 is similar in so much
as it may be described as κ1 -S:κ -S, with the anion interacting with
a total of three lithium atoms in each case. One of the lithium atoms
is chelated by the ligand, and the remaining two bond separately to
,2
1,3
ꢀ
−
each of the sulfur atoms from the [Cy2PS2] anion. The geometry does,
however, differ significantly with respect to the projection of the non-
chelating S-Li bonds, relative to the plane of the ‘PS2Li’ metallacycle.
In Fragment 3, lithium atoms 3 and 5 are transoid about the chelate
ring, whilst in Fragment 4 a cisoid arrangement is noted, with the
ꢀ
S(7)-Li(5 ) bond providing the link between the two Li5(Cy2PS2)4(OH)
units in 2. There does not appear to be a correlation between the Li-S
bonds lengths and the type of bonding to lithium, with both chelated
˚
˚
and non-chelated bonds spanning the range 2.427(5) A - 2.512(4) A. The
˚
˚
P-S distances [2.0069(9) A - 2.0295(8) A] are typical for this ligand and
◦
◦
the S-P-S angles [P(3) 112.32(4) ; P(4) 113.66(4) ] are larger than at
P(1) and P(2), reflecting the interaction of each sulfur with additional
lithium atoms.
COMPUTATIONAL STUDY
Density functional theory (DFT) calculations were performed on iso-
−
−
lated [R2PS] and [R2PS2] anions, where R = Ph and Cy for both
classes of ion. Clearly, in lithium complexes of the type described in
this paper, ionic contributions will dominate over any covalent lithium-
sulfur interactions and the overall directionality of the S-Li bonds
and ultimate connectivity that form in the solid-state will be largely
due to packing forces within the crystal. However, understanding the

2
696
N. E. Mansfield et al.
TABLE IV Calculated and Observed Bond Lengths and Angles for
−
[
R
2
PS] (A, R = Ph; B, R = Cy)
Observed
Calculated
a
R = Ph (A)
˚
˚
˚
P-S
P-C
2.066 A and 2.0710 A
1.848 A–1.858 A
2.066 A
˚
˚
˚
1.893 A
◦
◦
◦
ꢀangles P
304.54 and 306.51
309.23
b
R = Cy (B)
˚
˚
˚
2.086 A
P-S
P-C
2.107 A and 2.110 A
1.844 A–1.85 A
304.2 and 307.1
˚
˚
˚
˚
1.939 A and 1.928 A
◦
◦
◦
ꢀangles P
306.03
aValues taken from compound 1; and bvalues taken from Cp2Ti(Cy2PS)2, see
Reference 9.
distribution of π-electron density throughout the P S bond(s), and the
role that the phosphorus substituents have on the energies associated
with these orbitals is an important study and will hopefully lead to
a further understanding of the bonding within thiophosphinites and
dithiophosphinates.
Full optimization of the structures led to bond lengths and angles
that are generally in good agreement with the experimentally deter-
mined values (Tables IV and V). A significant difference is noted in
◦
◦
the S-P-S angles for the model dithiophosphinate complex D [121.26 ]
◦
compared with the values taken from compound 2 [109.57 to 113.66 ].
This is attributed to the presence of chelated a lithium atom to each of
TABLE V Calculated and Observed Bond Lengths and Angles for
−
[
R
2
PS
2
]
(C, R = Ph; D, R = Cy)
Observed
Calculated
a
R = Ph (C)
˚
˚
˚
˚
P S
P C
S P S
1.975 A and 2.004 A
1.833 A and 1.836 A
2.016 A
˚
˚
1.878 A
◦
◦
115.7
121.23
b
R = Cy (D)
˚
˚
◦
˚
˚
P S
P C
S P S
1.9986 A–2.0377 A
2.027 A
˚
◦
˚
1.831 A–1.843 A
109.57 –113.66
1.895 A
◦
121.26
a
Values taken from [Ph3Te][Ph2PS2], in which only weak secondary cation·anions
b
interactions are present, see Reference 29; and range of values taken from compound
2.

Thiophosphinite and Dithiophosphinate Anions
2697
FIGURE 6 Molecular orbital and energy level diagram for thiophosphinite
−
anions [R
2
PS] (A, R = Ph; B, R = Cy).
the anions within 2, which prevent the two P-S bonds from relaxing to
their most stable configuration.
Similar molecular orbital profiles are noted for both of the thiophos-
−
phinite anions [R2PS] (A, R = Ph; B, R = Cy), with a general increase
−1
(
∼10 kcal mol ) in the relative energies of the three highest occu-
pied MOs in the Cy-substituted derivative, B (Fig. 6). The calculated
(
[
NBO) charges on both sulfur [A, −0.862; B, −0.872] and phosphorus
A, +0.656; B, +0.674] are similar in each model, with a slight decrease
in the positive charge at phosphorus in A attributed to the more elec-
tron withdrawing phenyl substituents. The negative charge at sulfur is
consistent with the formation of the S-Li bonds, as noted in the X-ray
crystal structure of 1.
In A and B, the HOMO places electron density at both the phospho-
rus and sulfur atoms within a π*-symmetry orbital associated with the
phosphorus-sulfur bond. The main component of the HOMO-1 may be
considered as a p-type lone-pair orbital at sulfur orthogonal to the P-S
bond, although a notable distortion towards phosphorus results in elec-
tron density from this orbital contributing to the overall P-S bonding.
In contrast, the HOMO-2 clearly shows an element of π-bonding that
spans the P-S bond, consistent with a resultant bond order between
one and two, as inferred from the P-S bond length within the crystal
structure.
−
The dithiophosphinate anions [R2PS2] (C, R = Ph; D, R = Cy) in-
dicate an overall molecular orbital picture that is also largely indepen-
dent of the nature of the P-substituent with respect to the shapes of the
−
1
molecular orbitals, with a higher energy of ∼7 kcal mol for the HOMO
to HOMO-3 orbitals of dicyclohexyl compound, D (Fig. 7). A consider-
ably greater positive charge is calculated for the phosphorus atoms in
C and D compared with the corresponding thiophosphinite anions due

2
698
N. E. Mansfield et al.
FIGURE 7 Molecular orbital and energy level diagram for thiophosphinate
−
anions [R
2
PS
2
]
(C, R = Ph; D, R = Cy).
to the presence of two sulfur atoms; the charge is slightly enhanced in
C, again attributed to the phenyl groups.
In both models C and D highest energy occupied MOs are associated
with the S-P-S portion of the molecule. Both the HOMO and HOMO-1
are predominantly composed of p-type lone-pairs on each sulfur, with
a distortion of the lobes towards the phosphorus, as noted above for
the HOMO-1 in A and B. The major lobes of the HOMO-2 and HOMO-
3
orbitals in C and D are of π-symmetry and extend across the S-P-
S atoms, consistent with the observed delocalized bonding across this
portion of the molecule.
It is clearly evident from these model studies that considerable elec-
tron density is located at the sulfur atoms within both classes of anion,
and that several different filled orbitals are, in principle, available for
interaction with empty orbitals of the appropriate symmetry and en-
ergy at a metal center. It is likely this concentration of charge that has
led to these ions being such versatile ligands in coordination chemistry
to metals from across the periodic table.
EXPERIMENTAL
General Experimental Details
All manipulations were carried out under an inert atmosphere using
high vacuum Schlenk-line techniques or in a nitrogen-filled glove box
operating at <1 ppm oxygen. Solvents were dried and distilled from
an appropriate drying agent. The compounds Ph2PH (Aldrich), Cy2PH

Thiophosphinite and Dithiophosphinate Anions
n
2699
(
(
Strem), S (Aldrich), BuLi (2.5 M in hexanes, Acros) and TMEDA
Aldrich, distilled and stored under a nitrogen atmosphere) were pur-
chased from commercial sources and used as received, unless stated
ꢀ
ꢀ1,2
ꢀ
ꢀ2,31
otherwise. The compounds R2PCNR NHR , R2P(E)CNR NHR
and
i
5
Li(Cy2PCN Pr2) were made according to literature procedures. NMR
spectra were recorded using a Varian 400 MHz spectrometer at 400.1
H), 100.6 ( C H), 155.4 ( Li H) and 161.9 ( P H) MHz, from samples
at 30 C in [ H6]-benzene, unless otherwise stated; coupling constants
are quoted in Hz. Proton and carbon chemical shifts were referenced
internally to residual solvent resonances. Elemental analysis was per-
formed by Steve Boyer at the London Metropolitan University.
1
13
1
7
1
31
1
(
◦
2
[
Li(Ph PS)(TMEDA)] (1)
2
2
n
A solution of BuLi (2.25 mL of a 2.5 M solution in hexanes, 5.63
mmol) was added dropwise to a stirred solution of Ph2P(S)H (1.17 g,
◦
5
.37 mmol) in THF (∼30 mL) at −78 C. The resultant orange solution
was stirred at low temperature for 30 min and allowed to warm to room
temperature and stirred for a further 1 h. The solution was re-cooled
◦
i
i
to −78 C and a solution of PrN C N Pr (0.84 mL, 5.37 mmol) in THF
(
∼20 mL) was added resulting in decolorization of the solution. The
volatiles were removed under reduced pressure to afford a sticky white
solid. Attempted crystallization failed and so excess TMEDA (1.60 mL,
1
0.74 mmol) was added to a toluene solution and the mixture cooled to
◦
-
30 C, affording colorless crystals that were shown by X-ray diffraction
to correspond to [Li(Ph2PS)(TMEDA)]2 (1).
Compound 1 was independently synthesized according to the follow-
ing procedure. A slurry of excess elemental sulfur (0.13 g, 4.02 mmol,
1.5 equivalents) in toluene (15 mL) was added to a solution of Ph2PH
(
0.50 g, 2.68 mmol) in 25 mL toluene at room temperature. The ini-
tially cloudy solution was stirred for 1 h, after which time the solution
was clear and the formation of the P(V) sulfide, Ph2P(S)H was assumed
◦
n
to have gone to completion. The solution was cooled to 0 C and BuLi
1.10 mL of a 2.5 M solution in hexanes, 2.68 mmol) was added dropwise
(
via syringe, generating a white precipitate of the lithium salt. Excess
◦
TMEDA (0.60 mL, 4.02 mmol) was added at 0 C causing the precipi-
tate to dissolve. The resultant mixture was allowed to warm to room
temperature and stirred overnight, affording a slightly cloudy solution.
Filtration and removal of the volatiles afforded colorless crystals of the
1
desired product. Yield 0.67 g, 73%. H NMR: δ 8.54 (dd, JPH = 16, JHH =
8
, 4H, o-C6 H5), 7.12 (dt, JHH = 16, JPH = 4, 2H, p-C6 H5), 7.01 (m, 4H,
13 1
m-C6 H5), 1.89 (s, 12H, NMe2), 1.66 (s, 4H, CH2). C H NMR: δ 144.0
d, JCP = 79, i − C6H5), 134.3 (d, JCP = 17, C6H5), 131.0 (d, JCP = 11,
(

2
700
N. E. Mansfield et al.
3
1
1
C6H5), 129.5 (d, JCP = 3, C6H5), 56.2 (CH2), 45.6 (NMe). P H NMR:
1.4 (s). Li H NMR: δ 1.32 (s).
7
1
6
[
Li (Cy PS ) (OH)] (2)
5
2
2 4
2
◦
Precooled toluene (−78 C) was added to a solid mixture of
Li(Cy2PCNCy2) (0.10 g, 0.32 mmol) and elemental S (0.01 g, 0.32 mmol)
to afford a yellow /white suspension. The mixture was allowed to warm
to ambient temperature, and stirred for 16 h. Removal of volatiles
from the resultant cloudy, white solution afforded a crude white solid.
◦
Crystallization of 2 was achieved by slow cooling a hot (∼ 70 C) hep-
tane to ambient temperature, affording colorless crystals. Yield 36 mg
(
42% based on sulfur). Anal. calcd. for C96H178Li10O2P8S16 (2194.50):
C 52.54, H 8.18%. Found C 52.49, H 8.25%. IR (Nujol mull, KBr): 3680
−
1
cm υ(OH).
Crystallographic Details
Details of the crystal data, intensity collection, and refinement for com-
plexes 1 and 2 are listed in Table I. Crystals were covered in oil and suit-
able single crystals were selected under a microscope and mounted on a
Kappa CCD diffractometer. The structures were refined with SHELXL-
3
2
9
7. Additional features are described below:
[
Li (Cy PS ) (OH)] (2)
5
2
2 4
2
The H atom of the OH group was refined; other H atoms were in
riding mode. There is a residual peak of ca. 1.8 electrons close to S(2),
which is assumed to be spurious; the difference map is otherwise clean.
Crystallographic data for the structural analysis has been deposited
with the Cambridge Crystallographic Data Center, CCDC Nos. 635424
for compound 1 and 635425 for compound 2.
Theoretical Methods
The geometries and energies of the non-coordinated thiophosphinite
−
−
and dithiophosphinate anions, [R2PS] and [R2PS2] , were obtained
using density functional theory, specifically the Becke three parameter
33
34
exchange functional (B3) and the Lee correlation functional (LYP).
35
The 6-31G(d) basis set was chosen and all B3LYP calculations, in-
cluding NBO analysis36 were carried out with the Gaussian03 suite
of programs. The initial geometries of the phosphorus-sulfur cores were
taken from X-ray data [anion based on P(1) of compound 2 for mod-
els C and D], with the appropriate substitution of phenyl and cyclo-
hexyl substituents at phosphorus accomplished using GaussView. Each
37

Thiophosphinite and Dithiophosphinate Anions
2701
stationary point was confirmed to be a minimum having zero imaginary
vibrational frequencies.
REFERENCES
[
[
1] J. Grundy, M. P. Coles, and P. B. Hitchcock, Dalton Trans., 2573 (2003).
2] N. E. Mansfield, J. Grundy, M. P. Coles, and P. B. Hitchcock, J. Am. Chem. Soc., 128,
13879 (2006).
[
[
[
[
[
[
3] M. P. Coles and P. B. Hitchcock, Chem. Commun., 2794 (2002).
4] N. E. Mansfield, M. P. Coles, and P. B. Hitchcock, Dalton Trans., 2833 (2005).
5] N. E. Mansfield, M. P. Coles, and P. B. Hitchcock, Dalton Trans., 2052 (2006).
6] B. Walther, Coord. Chem. Rev., 60, 67 (1984).
7] R. P. Davies and M. G. Martinelli, Inorg. Chem., 41, 348 (2002).
8] [Li(Ph2PS)(TMEDA)]2 was subsequently made by an independent and more ratio-
nal route. See experimental section for details.
[
9] Average value calculated from six previously characterized compound containing
P
S single bonds.
[
[
10] L. Gelmini and D. W. Stephan, Organometallics, 6, 1515 (1987).
11] V. P. Balema, E. G. Rys, N. N. Godovikov, A. V. Polyakov, and Y. T. Struchkov, Russ.
Chem. Bull., 180 (1992).
[
12] (a) M. Aslam, R. A. Bartlett, E. Block, M. M. Olmstead, P. P. Power, and G. E. Sigel,
J. Chem. Soc., Chem. Commun., 1674 (1985); (b) K. Ruhlandt-Senge, U. Englich,
M. O. Senge, and S. Chadwick, Inorg. Chem., 35, 5820 (1996).
[
13] (a) J. J. Ellison and P. P. Power, Inorg. Chem., 33, 4231 (1994); (b) M. Niemeyer and
P. P. Power, Inorg. Chem., 35, 7264 (1996).
[
14] T. Komuro, T. Matsuo, H. Kawaguchi and K. Tatsumi, Dalton Trans., 1618 (2004);
E. Jesionka, A. Ciborska, J. Chojnacki, and W. Wojnowski, Acta Cryst. C, 61, m321
(
2005).
[
[
[
15] S. E. Denmark, K. A. Swiss, and S. R. Wilson, J. Am. Chem. Soc., 115, 3826 (1993).
16] M. C. Copsey and T. Chivers, Dalton Trans., 4114 (2006).
17] The presence of the hydroxyl group was confirmed in the bulk sample by elemental
analysis and a broad absorption centered at ∼ 3680 cm-1 in the IR spectrum.
18] (a) S. R. Boss, M. P. Coles, R. Haigh, P. B. Hitchcock, R. Snaith, and A. E. H.
Wheatley, Angew. Chem. Int. Ed., 42, 5593 (2003); (b) E. Iravani and B. Neumuller,
Organometallics, 24, 842 (2005); (c) D. R. Armstrong, W. Clegg, R. P. Davies, S. T.
Liddle, D. J. Linton, P. R. Raithby, R. Snaith, and A. E. H. Wheatley, Angew. Chem.
Int. Ed., 38, 3367 (1999); (d) S. R. Boss, J. M. Cole, R. Haigh, R. Snaith, A. E. H.
Wheatley, G. J. McIntyre, and P. R. Raithby, Organometallics, 23, 4527 (2004); (e)
M. P. Coles and P. B. Hitchcock, Chem. Commun., 3165 (2005); (f) S. R. Boss, M. P.
Coles, V. Eyre-Brook, F. Garc ´ı a, R. Haigh, P. B. Hitchcock, M. McPartlin, J. V. Morey,
H. Naka, P. R. Raithby, H. A. Sparkles, C. W. Tate, and A. E. H. Wheatley, Dalton
Trans., 5574 (2006).
[
[
19] M. G. Davidson, J. A. K. Howard, S. Lamb, and C. W. Lehmann, Chem. Commun.,
1607 (1997).
[
[
20] E. Weiss, Angew. Chem., Int. Ed. Engl., 32, 1501 (1993).
21] (a) T. Chivers, A. Downard, and M. Parvez, Inorg. Chem., 38, 4347 (1999); (b) C. Lam-
bert, F. Hampel, P. von Rag e´ Schleyer, M. G. Davidson, and R. Snaith, J. Organomet.
Chem., 487, 139 (1995).
[
22] J. Storre, C. Schnitter, H. W. Roesky, H.-G. Schmidt, M. Noltemeyer, R. Fleischer,
and D. Stalke, J. Am. Chem. Soc., 119, 7505 (1997).

2
702
N. E. Mansfield et al.
[
23] (a) J. S. Casas, E. E. Castellano, M. S. Garcia-Tasende, A. Sanchez, J. Sordo, E. M.
Vasquez-Lopez, and J. Zukerman-Schpector, Acta Cryst. C, 56, 182 (2000); (b) J. S.
Casas, E. E. Castellano, A. Castineiras, A. Sanchez, J. Sordo, E. M. Vasquez-Lopez,
and J. Zukerman-Schpector, J. Chem. Soc., Dalton Trans., 1403 (1995); (c) J. S. Casas,
M. S. Garcia-Tasende, A. Sanchez, J. Sordo, E. M. Vasquez-Lopez, E. E. Castellano,
and J. Zukerman-Schpector, Inorg. Chim. Acta, 239, 87 (1995).
[
[
24] T. Buranda and A. A. Pinkerton, Inorg. Chim. Acta, 170, 81 (1990).
25] (a) Y. Meseri, A. A. Pinkerton, and G. Chapuis, J. Chem. Soc., Dalton Trans., 725
(
1
1977); (b) A. A. Pinkerton and D. Schwarzenbach, J. Chem. Soc., Dalton Trans.,
300 (1980).
[
26] (a) A. E. Storey, F. Zonnevijlle, A. A. Pinkerton, and D. Schwarzenbach, Inorg. Chim.
Acta, 75, 103 (1983); (b) A. A. Pinkerton, A. E. Storey, and J.-M. Zellweger, J. Chem.
Soc., Dalton Trans., 1475 (1981).
[
[
[
27] F. Nief, Coord. Chem. Rev., 178, 13 (1998).
28] E. Zintl, A. Harder, and B. Dauth, Z. Elektrochem., 40, 588 (1934).
29] W. Buehrer, F. Altorfer, J. Mesot, H. Bill, P. Carron, and H. G. Smith, J. Phys.:
Condens. Matter, 3, 1055 (1991).
[
[
30] A. Silvestru, I. Haiduc, R. A. Toscano, and H. J. Breunig, Polyhedron, 14, 2047 (1995).
31] J. Grundy, M. P. Coles, A. G. Avent, and P. B. Hitchcock, Chem. Commun., 2410
(
2004).
32] G. M. Sheldrick, SHELXL-97, Program for the Refinement of Crystal Structures
G o¨ ttingen, 1997).
33] (a) A. D. Becke, Phys. Rev. A, 38, 3098 (1988); (b) A. D. Becke, J. Chem. Phys., 98,
372 (1993); (c) A. D. Becke, J. Chem. Phys., 98, 5648 (1993).
[
[
(
1
[
34] C. Lee, W. Yang, and R. G. Parr, Phys. Rev. B, 37, 785 (1988).
[
35] (a) G. A. Petersson and M. A. Al-Laham, J. Chem. Phys., 94, 6081 (1991); (b) G. A.
Petersson, A. Bennett, T. G. Tensfield, M. A. Al-Laham, and W. A. Shirley, J. Chem.
Phys., 89, 2193 (1988).
[
[
36] A. E. Reed, L. A. Curtiss, and F. Weinhold, Chem. Rev., 88, 899 (1988).
37] M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R.
Cheeseman, J. A. Montgomery 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. Foresman, 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, K. T., M. A. Al-Laham, C. Y. Peng, A. Nanayakkara, M. Challa-
combe, P. M. W. Gill, B. Johnson, W. Chen, M. W. Wong, C. Gonzalez, J. A. Pople
Gaussian 03; (Gaussian, Inc., Wallingford CT, 2004).