Synthesis of 2,6-bis(bis(2-(methylthio)phenyl)phosphino)-4-methylphenol, a novel polydentate ligand containing two tripodal [S,S,P,O] coordination pockets; crystal structure of the dimeric thallium(I) complex

Article abstract of DOI:10.1002/zaac.200600119

The reactions of bis(2-(methylthio)phenyl)chlorophosphine (5a) (2 equivalents) with the O-protected 2,6-dilithio-4-methylphenol followed by acidic workup led to the isolation of 2,6-bis(bis(2-(methylthio)phenyl)phosphino)-4- methylphenol (2). Analogous reactions do not proceed if the sterically bulkier bis(2-(tert-butylthio)phenyl)chlorophosphine (5b) is used instead of 5a. Compound 2 is a topological analog of binucleading ligands built on a 2,6-diaminophenol core, where two tripodal N- or O-ligating compartments are flanking the phenolate functionality. A distinguishing feature of 2 is the soft donor environment of the potentially [S,S,P]-ligating pockets flanking the phenolic OH group. Reaction of 2 with TlOEt lead to the formation of the dimeric thallium(I) phenoxide (3), which was characterized by a single crystal X-ray diffraction study. In addition to μ-phenoxide ligation, in the solid state each thallium atom also interacts with two phosphorus atoms from the opposing ligands. The interactions are not equivalent, with the two Tl ¹-P distances differing by ca. 0.3 A. No significant Tl...S interactions are present in the solid state. Room temperature ³¹P NMR measurements indicate the dynamic behavior of 3 in solution.

Full text of DOI:10.1002/zaac.200600119

DOI: 10.1002/zaac.200600119
Synthesis of 2,6-Bis(bis(2-(methylthio)phenyl)phosphino)-4-methylphenol,
a Novel Polydentate Ligand Containing Two Tripodal [S,S,P,O] Coordination
Pockets; Crystal Structure of the Dimeric Thallium(I) Complex
Aldona Beganskiene1), Natcharee Kongprakaiwoot, Rudy L. Luck, and Eugenijus Urnezius*
Houghton, MI / USA, Michigan Technological University, Department of Chemistry
Received May 9th, 2006.
Abstract. The reactions of bis(2-(methylthio)phenyl)chlorophos-
phine (5a) (2 equivalents) with the O-protected 2,6-dilithio-4-meth-
ylphenol followed by acidic workup led to the isolation of
2,6-bis(bis(2-(methylthio)phenyl)phosphino)-4-methylphenol (2).
Analogous reactions do not proceed if the sterically bulkier
bis(2-(tert-butylthio)phenyl)chlorophosphine (5b) is used instead of
5a. Compound 2 is a topological analog of binucleading ligands
built on a 2,6-diaminophenol core, where two tripodal N- or O-
ligating compartments are flanking the phenolate functionality. A
distinguishing feature of 2 is the “soft” donor environment of the
potentially [S,S,P]-ligating pockets flanking the phenolic OH group.
Reaction of 2 with TlOEt lead to the formation of the dimeric
thallium(I) phenoxide (3), which was characterized by a single cry-
stal X-ray diffraction study. In addition to µ-phenoxide ligation, in
the solid state each thallium atom also interacts with two phospho-
rus atoms from the opposing ligands. The interactions are not equ-
ivalent, with the two Tl ϪP distances differing by ca. 0.3 A. No
significant Tl···S interactions are present in the solid state. Room
temperature 31P NMR measurements indicate the dynamic beha-
vior of 3 in solution.
I
˚
Keywords: Thallium; P, S,
O ligand; Binucleating; Dimeric
thallium(I) complex; Crystal structure
Introduction
(Fig. 1) have been studied as a part of a broader interest in
biological dioxygen binding and activation processes [9, 10].
Structurally analogous ligands capable of forming bi-
metallic phenolates where the peripheral ligation to
“M-O-M” units is provided by “soft” ligating groups (eg,
phosphorus or sulfur) have not so far been reported. The
steric and electronic environments experienced by the tran-
sition metal atoms in such complexes should be substan-
tially different from those in 1. Consequently, different
chemical properties, such as small substrate binding and ac-
tivation, may be anticipated. Numerous ligands containing
both phosphorus and sulfur ligating groups have been ex-
tensively used in coordination chemistry, but well-defined
polydentate binucleating P,S ligands are not well developed
[11]. The syntheses of the potentially binucleating
P,S ligandϪ2,6-bis(bis(2-(methylthio)phenyl)phosphino)-4-
methylphenol (2, Fig. 1), and the dimeric thallium(I) com-
plex 3 are reported herein.
Bimetallic transition metal complexes where the metal cen-
ters are kept in close proximity by a bridging alkoxide or
phenoxide group have attracted considerable attention re-
cently as possible models for biological processes occurring
at bimetallic sites in certain metalloenzymes [1Ϫ3]. Since
the ligating environments experienced by the metal centers
in metalloenzymes are usually comprised of nitrogen or
oxygen-based functional groups, most of the targeted syn-
thetic bimetallic models are constructed around such
“hard“-donor ligands to better mimic the natural processes
occurring at the metal centers. Bicompartmental ligands
where the tripodal N- and/or O- ligating pockets are ap-
pended onto the parent 2,6-diaminophenol frame have been
successfully used for the syntheses of bimetallic complexes
1 (Fig. 1; M ϭ Cuϩ/2ϩ, Co2ϩ, and Fe2ϩ/3ϩ ions [4Ϫ8]).
Bimetallic copper complexes bearing the structural frame 1
* Prof. E. Urnezius
Results and Discussion
Department of Chemistry
Michigan Technological University
1400 Townsend Dr,
Houghton, MI 49931 / USA
e-mail: urnezius@mtu.edu
Recently we have developed synthetic methods allowing for
the syntheses of various 2,6-bis(phosphino)phenols [12].
Thus, symmetric 2,6-bis(phosphino)phenols can be ob-
tained via the reactions of chlorophosphines ClPR2 (R ϭ
Ph, iPr) with the organodilithium intermediate generated
from BuLi (2 equiv.) and THP-protected 2,6-dibromo-4-
methylphenol (THP ϭ tetrahydropyranyl). We were inter-
1) Visiting Fulbright Scholar. Permanent address: Dept. of General
and Inorganic Chemistry, Vilnius University, Naugarduko 24,
03255 Vilnius, Lithuania
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A. Beganskiene, N. Kongprakaiwoot, R. L. Luck, E. Urnezius
as a solid (31P NMR; δ 45.2) and its conversion to chloro-
phosphine 5a (31P NMR; δ 56.5) readily proceeds under
exposure to anhydrous HCl.
We have also explored another method for the synthesis
of amino- and chlorophosphines bearing the same topologi-
cal arrangement of P and S atoms. Direct ortho-lithiation
of some aryl-alkyl thioethers is well known [14], and we
have obtained compounds 4b and 5b (Eq. (2)) starting with
tert-butylphenylsulfide. Reactions proceed similarly to pro-
cedures depicted in Eq. 1, and 4b and 5b are isolated in
good (ϳ75 %) yields, suggesting that the significantly in-
creased steric bulk of the alkylthio substituents (methyl vs.
tBu) does not interfere with the syntheses. However, the
Figure 1. General structural motif for bimetallic complexes derived
from 2,6-diaminophenolates (1); our synthesized 2,6-Bis(bis(2-
(methylthio)phenyl)phosphino)-4-methylphenol (2), and its
thallium(I) complex (3).
1
data in the H and 31P NMR spectra of 4a and 4b clearly
indicate a more sterically congested environment around
the phosphorus atom in the latter. Different patterns for the
1
room temperature H NMR signals of the methylene pro-
ested in extending this methodology to the syntheses of
polydentate ligands, where the phosphorus atoms of the
2,6-bis(phosphino)phenol core serve as basal points for
well-defined, “soft” coordination pockets symmetrically
positioned around the phenolic OH group. To accomplish
this via the same synthetic procedure as used for
tons (-N(CH2CH3)2) for 4a (unresolved multiplet,
3.20 ppm) and 4b (very broad signal at 3.13 ppm) point to
a more hindered rotation around the P-N bond [15] in the
latter. The differences in the steric bulk of the alkylthio sub-
stituents are also most likely responsible for the substan-
tially different 31P NMR signals of 4a and 4b (45.2 ppm
and 52.8 ppm, respectively). On the other hand, chloropho-
sphines 5a and 5b display very close 31P NMR chemical
shift values (56.5 ppm and 56.9 ppm, respectively), as the
much smaller chlorine apparently is relatively easily accom-
modated by both bis(2-alkyl)phenylphosphine environ-
ments.
2,6-bis(phosphino)phenols,
suitable
chlorophosphines
ClPR2 are required: the electrophilic phosphorus(III) center
must have two donor groups positioned three bonds away.
The recently reported bis(2-(methylthio)phenyl)chloro-
phosphine 5a [13] fits such requirements, but the synthesis
reported requires rather complex solid-support chemistry
methods. We have developed a relatively simple synthetic
route for chlorophosphine 5a via conventional solution
chemistry methods utilizing readily available materials
(Eq. (1)). The intermediate aminophosphine 4a was isolated
As expected for chlorophosphines, 5a readily reacts with
the organodilithium intermediate generated from THP-
protected 2,6-dibromo-4-methylphenol, yielding the
2,6-bis(phosphino)phenol derivative 6 (Eq. (3)) in higher
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Synthesis of 2,6-Bis(bis(2-(methylthio)phenyl)phosphino)-4-methylphenol
1
than 50 % isolated yields. The room temperature H NMR
The addition of 1 equivalent of thallium ethoxide to a
THF solution of 2 immediately produces a slightly yellow
precipitate. Analysis of this solid by mass spectrometry sug-
gested a dimeric structure of the product (3, Eq. (5); m/z ϭ
1729.2). In general, thallium(I) phenolates or alkoxides are
well known to form higher nuclearity aggregates, and
dimeric thallium(I) compounds containing central [Tl2O2]
cores have been reported for bulky phenoxides [19, 20].
Complex 3 was found to have limited solubility in con-
ventional solvents (ether, THF, chloroform, toluene). How-
ever, it was sufficiently soluble in benzene to allow for
NMR investigations. Sharp signals were observed in the
spectrum of 6 (in C6D6) contains very broad, unresolved
signals for the aromatic protons and for the aliphatic pro-
tons attributed to the THP group. Such spectral features
are most likely caused by hindered rotation of the tetra-
hydropyranyloxy fragment around the phenolic C-O bond
due to the steric clashes with neighboring bis((2-methylthi-
o)phenyl)phosphine fragments. The thiomethyl groups are
also non-equivalent, as the ϪSCH3 protons resonate as two
sharp signals (1:1 ratio) at 1.98 and 1.96 ppm. The signals
in the aromatic region and peaks for the THP protons be-
come sharper with increasing temperature, but most of
them remain unresolved or broad in C6D6 solution at 65 °C.
The phosphorus atoms in 6 are equivalent in the 31P NMR
at room temperature, as a single, although somewhat broad
signal (s, Ϫ26.4 ppm) is observed. The δ value for the reson-
ance compares well with that reported for the structurally re-
lated (2-methoxyphenyl)bis(2-thiomethylphenyl)phosphine
(Ϫ30.0 ppm) [16].
Deprotection of the phenol functionality in 6 proceeds
smoothly with only catalytic amounts of Hϩ donors (p-
TsOH, or anhydrous HCl) required (Eq. (3)). Such depro-
tection procedures are typically used for the removal of me-
toxymethyl (MOM) and THP protecting groups in the
syntheses of o-phosphinophenols [17, 18]. Phenol 2 is ob-
tained as an air-sensitive (particularly in solution) crystal-
line substance, which is soluble in polar or aromatic organic
solvents (eg., THF, methanol, chloroform, benzene). The
31P NMR signal of 2 (Ϫ38.8 ppm) is shifted upfield in com-
parison to chemical shift value for 2,6-bis(diphenylphos-
phino)-4-methylphenol and 2,6-bis(diphenylphosphino)-4-
tert-butylphenol (both compounds have identical δ values,
Ϫ19.5 ppm) [12].
The reaction sequence depicted in Eq. (3) could not be
repeated with bis(2-(tert-butylthio)phenyl)chlorophosphine,
5b (Eq. (4)). The spectral signature of the starting material
5b was detected by 31P NMR as the only signal after several
hours in such reaction mixtures. Monitoring the reaction
mixture over an extended period of time (2 days, 25 °C)
showed the formation of a very low intensity peak centered
around Ϫ20 ppm. Our efforts to increase the yield or to
isolate this new material were not successful. Minimizing
the steric bulk of the O-protecting group of the 2,6-di-
bromo-4-methylphenol (methyl for THP, Eq. (4)) did not
yield significant improvements. Given into account the
steric hindrances already present in 6, the excessive steric
bulk imposed by the tert-butylthio groups in 5b seems to
be the most likely reason for the failure with this reaction
sequence (Eq. (4)).
1
room temperature H NMR spectrum of 3. Interestingly,
all thiomethyl groups are equivalent in solution, as judged
by a sharp singlet centered at 1.99 ppm. A broad signal cen-
tered at Ϫ2.8 ppm was observed in the 31P NMR spectum
of 3 Ϫ a change in the chemical shift value by ca. 35 ppm
from the signal of the parent phenol 2. Such 31P NMR
spectral features suggested possible Tl-P bonding interac-
tions in 3, but no discernible 205Tl,203Tl - 31P coupling could
be detected. Well-defined thallium-phosphorus coupling has
been previously reported for thallium(I) (phosphino)borate
complexes [21Ϫ23]. We decided to obtain crystals of 3 and
pursue its characterization via single crystal X-ray diffraction
methods to elucidate the nature of Tl-P interaction.
The compound crystallizes as a benzene solvate in the
¯
triclinic, P1 space group with one half of the dimer consti-
tuting the asymmetric unit. The structure suffers from dis-
order involving the thiomethyl groups, thus only the major
orientation of 3 is presented (Figure 2, a) and discussed. As
expected from the mass-spectrometric measurements, com-
pound 3 is a dimer, formed via intermolecular TlϪO inter-
actions between two phenolate moieties. Such dimeric
structures containing central [Tl2O2] cores have been
reported in structurally characterized TlI phenolates,
thallium(I) 2,4,6-tris(trifluoromethyl)phenoxide [24] and
{Tl[µ-O(C6H4)-(C6H4OH]}2 [19]. In both of these com-
pounds, bulky ligands protect the tetranuclear central core
limiting the coordination number at thallium to 2. On the
other hand, the thallium atoms in 3 have phosphorus and
sulfur donor groups in a nearby vicinity, thus higher metal
coordination numbers can be expected, especially since
some Tl-P interaction has been implied by the 31P NMR
data. Indeed, each metal atom (Tl···Tl distance is
˚
3.8466(9) A) in 3 is strongly coordinated to one of the phos-
phorus atoms from the ortho-phosphine functionalities
˚
(Figure 2, b). The Tl1 2-P2 bond distance (3.097(4) A) is
Ϫ
significantly longer than other known thallium(I)-phos-
phorus bonds, observed in zwitterionic phosphine-borates
˚
(2.878 Ϫ 3.0283(9) A [21Ϫ23], probably due to the geo-
metric preferences imposed by a rigid 5-membered ring
formed upon P,O-chelation to the thallium atom. A more
definitive P,O-chelation for o-phosphinophenolate ligands
is well established for transition metal complexes (nickel in
particular [25]). To the best of our knowledge, only one
thallium o-phosphinophenol complex has been briefly
mentioned [26]; similar P,O-complexes of other Group 13
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A. Beganskiene, N. Kongprakaiwoot, R. L. Luck, E. Urnezius
Figure 2 a) Thermal ellipsoid plot of 3 (hydrogen atoms and crystallization solvent (C6H6) omitted). b) Tl-P interactions (2-methylthio-
phenyl substituents omitted, with the exception of carbon atoms attached to phosphorus atoms). Selected bond distances and angles: T11-
˚
˚
˚
˚
O1 2.680(11) A, T11-2-O1 2.627(12) A, P1-T11 3.384(5) A, P2-T11-2 3.097(4) A; O1 T11-2 P2 61.7(2), T11-2 P2 C6 105.3(5), C1 O1 T11-
2 133.3(9). (Symmetry generated (-x, 1-y, z)).
˚
metals, gallium and indium, have been detailed recently
[27]. Interestingly, a closer inspection of the bond distances
and angles involving Tl and P environments in 3 suggests
the presence of another weaker thallium-phosphorus inter-
action between the Tl1 and P1 atoms. The bond distance
distances similar within experimental error (2.469(8) A
˚
and 2.461(10) A) [24]. Compound 3 is further disting-
uished by a much larger Tl-O-Tl angle (Tl1-O1-Tl1
2
92.9(4)°) whereas the corresponding values for TlI
2,4,6-tris(trifluoromethyl)phenoxide (70.8(4)°) and {Tl[µ-
O(C6H4)-(C6H4OH]}2 (76.7(4)°) are substantially smaller.
In fact, the [Tl2O2] core in 3 is almost rectangular, with an
O1-Tl-O1 2 angle also close to 90° (87.1(4)°).
˚
˚
(P1-Tl1 3.384(5) A) is significantly (ϳ0.3 A) longer than
that for Tl1 2-P2 bond, but this distance is within the sum
Ϫ
(ca. 3.49 A) of the rcov for TlI and the van der Waals radius
˚
of phosphorus. Further support for the presence of a bond-
ing interaction can be obtained from an analysis of the ge-
ometry around the P1 center. The bis(2-thiomethyl)phenyl-
phosphine moiety is rotated around the P1-C2 bond re-
sulting in a sterically congested (nearly eclipsed) orientation
of the C111-P1 and the C2-C3 bonds (the torsion angle
C111-P1-C2-C3 is only 9.6°). However, this twist around
the P1-C2 bond clearly positions the lone pair of electrons
on the phosphorus atom closer to the thallium atom, thus
maximizing the P1-Tl1 interaction. There are no Tl-S inter-
actions in 3, as the shortest thallium-sulfur distance
With this structural characterization of 3, a reinterpret-
ation of the NMR data for the compound becomes pos-
sible. The presence of only one signal in the 31P NMR spec-
trum of 3 suggests that a dynamic process is occurring in
solution, resulting in the formation of an average signal for
both phosphorus atoms. A dimer dissociation-association
process would be one possible explanation, but it is unlikely
given the observed stability of the [Tl2O2] core in the gas
phase. The rotation of the ligand around the O1-C1 bond
would be another possibility, but it is also unlikely given
the size of the ligand. This dynamic process could be the
rocking motion of the ligand resulting in simultaneous
shortening and lengthening of the Tl-P distances and wig-
gling of the [Tl2O2] core.
In summary, we have succeeded in designing and execut-
ing a synthetic strategy for the syntheses of 2,6-bis(bis(2-
(methylthio)phenyl)phosphino)-4-methylphenol. Bimetallic
transition metal complexes based on such ligand seem to be
a reasonable target, as tris(2-(methylthio)phenyl)phosphine
and other ligands bearing bis(2-(methylthio)phenyl)phos-
phino fragment have been shown to function as effective
chelating agents towards some transition metal centers
[28Ϫ31].
˚
(Tl1-S1) is 3.59(2) A.
The thallium-phosphorus interactions in 3 result in sub-
stantially different structural parameters for the central
[Tl2O2] core than those observed in other compounds with
the same structural motif. In particular, this four-center ring
in
3
is planar and asymmetric, with two different
˚
thalliumϪoxygen distances (Tl1-O1 2.627(12) A, and
Tl1 2-O1 2.680(11) A. The asymmetry in 3 is less pro-
nounced than that observed in {Tl[µ-O(C6H4)-(C6H4OH]}2,
where Tl-O distances of 2.52(1) A and 2.71(1) A were
observed [19]. A symmetric [Tl2O2] ring has been reported
for TlI 2,4,6-tris(trifluoromethyl)phenoxide, with Tl-O
˚
Ϫ
˚
˚
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Synthesis of 2,6-Bis(bis(2-(methylthio)phenyl)phosphino)-4-methylphenol
combined with hexanes washings after standing at Ϫ10 °C for two
days. Combined yield: 13.55 g (77 %) M.p. 104-105 °C.
Experimental Section
1H NMR (400 MHz, C6D6, 20 °C) δ 7.37 (m, 2H), 7.08 (4H, m, Ph), 6.99
(2H, m, Ph), 3.20 (4H, m, CH2CH3), 2.00 (6H, s, SCH3), 0.89 (6H, m,
CH2CH3). 31P NMR (162 MHz, C6D6, 20 °C) δ 45.2 (s). HRMS (FAB):
m/z ϭ 349.1091 (Mϩ); calcd for C18H24NPS2: 349.1088.
General Considerations
All the reactions were performed under air-free conditions by using
Schlenk techniques or in a dry box under a N2 atmosphere. Low
temperature (Ϫ80 °C) reactions were performed in Schlenk flasks
immersed in hexanes/N2(liq.) or ethanol/N2(liq.) slush, contained
in a Dewar flask. Solvents were purified before use by distillation
from Na-benzophenone ketyl (ether, THF, hexanes, heptane, ben-
zene) or CaH2 (toluene) under a N2 atmosphere. Et2NPCl2 [32],
tert-butylphenylsulfide [33], and THP-protected 2,6-dibromo-4-
methylphenol [12] were synthesized according to previously re-
ported procedures. Other reagents were obtained from commercial
suppliers and were used as received. 1H and 31P NMR measure-
ments were obtained on Varian INOVA 400 spectrometer. Spectra
are referenced to tetramethysilane (1H) and 85 % H3PO4 (31P) (ex-
ternal reference). Mass spectrometric measurements were per-
formed on a Shimadzu QP5050A mass-spectrometer, or at Mass
Spectrometric Facility of Michigan State University (East Lansing,
MI 48824-1319). Elemental analyses were performed at Galbraith
Laboratories, Inc (Knoxville, TN 37950-1610).
Bis-(2-(tert-butylthio)phenyl)-N,N-diethylaminophosphine (4b).
A
solution of n-butyllithium (36.2 mL, 58.0 mmol, 1.6 M in hexanes)
was added (dropwise) to a stirred cold (0 °C) solution of tert-butyl-
phenylsulfide (9.75 g 58.0 mmol) in hexanes (70 mL). N,N,NЈ,NЈ-
tetramethylenediamine (TMEDA, 11.1 mL, 68.0 mmol) was then
slowly (over 15 min) added to a cooled (0 °C) reaction mixture. It
was then stirred for 12 h while slowly warming up to room
temperature, yielding a pale-yellow suspension. A solution of N,N-
diethylaminodichlorophosphine (3.9 mL, 29.0 mmol) in hexanes
(10 mL) was then added dropwise to a cold (0 °C) stirred reaction
suspension. The reaction mixture was then stirred for 12 h and hy-
drolyzed with degassed water (20 mL). Ether (20 mL) was added,
the organic phase was separated, and dried over MgSO4. After the
removal of all volatiles in vacuo, 4b was obtained as a pale yellow
viscous oil. Yield: 9.3 g (74 %). Colorless crystals of 4b were
obtained upon prolonged (weeks) crystallization from hexanes
solution at Ϫ10 °C. M.p.: 79-81 °C.
1H NMR (400 MHz, C6D6, 20 °C) δ 7.60 (2H, m, Ph), 7.36 (2H, br, Ph),
7.04 (4H, m, Ph), 3.13 (4H, br, CH2CH3), 1.39 (18H, s, C(CH3)3), 0.88 (6H,
m, CH2CH3). 31P NMR (162 MHz, C6D6, 20 °C): δ 52.8 (s). HRMS (FAB):
m/z ϭ 434.2107 (MHϩ); calcd for C24H37NPS2: 434.2105.
Syntheses
2,6-bis(bis(2-(methylthio)phenyl)phosphino)-4-methylphenol (2). To a
stirred solution of 2,6-bis(bis(2-(methylthio)phenyl)phosphino)-4-
methyl-tetrahydro-2H-pyranyloxy-benzene) (4.0 g, 5.4 mmol) in
THF (160 mL), p-TsOH hydrate (0.16 g, 0.8 mmol) was added, and
the reaction mixture was stirred 12 h. The volatiles were removed
in vacuo, and the solid residue was recrystallized from THF/meth-
anol (10/30 mL) mixture. Yield: 1.6 g (46 %). M.p. 184-186 °C (de-
comp).
1H NMR (400 MHz, C6D6, 20 °C): δ 7.28 (4H, m, Ph), 7.02 (10H, m, Ph),
6.88 (4H, m, Ph), 1.94 (12H, s, SCH3), 1.74 (3H, s CH3). 31P NMR
(162 MHz, C6D6, 20 °C): δ Ϫ38.1 (s). HRMS (FAB): m/z ϭ 661.1048
(MHϩ); calcd for C35H35OP2S4: 661.1046.
Bis(2-(methylthio)phenyl)chlorophosphine (5a). To a stirred, cold
(0 °C) ether solution of bis(2-(methylthio)phenyl)-N,N-diethyl-
amino-phosphine (13.9 g, 40 mmol) was added a 2M HCl solution
in ether (40 mL, 80 mmol). After stirring for 12 h at room tempera-
ture, the reaction mixture was filtered, all volatiles were removed in
vacuo, and the resulting yellow solid was recrystallised from THF/
hexane mixture (30 mL/150 mL). Yield: 9.30 g (75 %). Melting
point: 88-90 °C. Spectroscopic characterizations (1H/31P NMR)
matched previously reported data [13].
Bis(2-(tert-butylthio)phenyl)chlorophosphine (5b). To a cold (0 °C)
stirred solution of bis-(2-tert-butylthio)phenyl-N,N-diethylamino-
phosphine (8.9 g, 19.0 mmol) in ether (80 mL) was added 4M HCl
solution in dioxane (40 mL, 39.0 mmol). After stirring 12 h at room
temperature, the reaction mixture was filtered, the solvents were
removed in vacuo, and the resulting yellow solid was recrystallised
from hexane (50 mL). Yield: 5.9 g (78 %). M. p.: 91-93 °C.
Thallium(I) 2,6-bis(bis(2-(methylthio)phenyl)phosphino)-4-phenoxide
(3). To a stirred cold (0 °C) solution of 2,6-bis(bis(2-(methyl-
thio)phenyl)phosphino)-4-methylphenol (1.134 g, 1.72 mmol) in
THF (40 mL) was added a solution of TlOEt (0.444 g, 1.78 mmol)
in THF (10 mL), resulting in immediate precipitation of a pale yel-
low solid. Filtration and drying in vacuo afforded 1.105 g of 3.
Yield: 72 %. M.p. 256-257 °C (decomp.). Combustion analysis was
performed on crystalline material obtained from heptane diffusion
into benzene solution of 3. Anal found C 51.63 %, H 4.15 %; calc
for C82H78O2P4S8Tl2 (3·2C6H6) C 52.26 %, H 4.17 %.
1H NMR (400 MHz, C6D6, 20 °C): δ 6.85-7.65 (8H, m, Ph), 1.25 (18H,
C(CH3)3). 31P NMR (162 MHz, C6D6, 20 °C): δ 56.9 (s). HRMS (FAB):
m/z ϭ 396.0905 (Mϩ); calcd for C20H26ClPS2: 396.0902.
2,6-bis(bis(2-(methylthio)phenyl)phosphino)-4-methyl-tetrahydro-
2H-pyranyloxy-benzene (6). To a stirred, cold (Ϫ80 °C) solution of
1H NMR (400 MHz, C6D6, 20 °C): δ 7.33 (4H, m, Ph), 7.01 (8H, m, Ph),
6.87 (6H, m, Ph), 1.99 (12H, s, SCH3), 1.92 (3H, s, CH3). 31P NMR
(162 MHz, C6D6, 20 °C) δ Ϫ2.8 (s, (br)). MS (FAB): m/z ϭ 1729.2 (MHϩ);
calcd for C70H67O2P4S8Tl2: 1729.1.
2,6-dibromo-4-methyl-tetrahydro-2H-pyranyloxybenzene
(2.1 g,
6.0 mmol) in THF (100 mL) was added a solution of 1.3 M sec-
butyllithium in hexanes (10 mL, 13.0 mmol) (using n-BuLi gives
similar results). The reaction mixture was allowed to stir at Ϫ80 °C
for 1 h, and a solution of bis(2-methylthiophenyl)chlorophosphine
(3.75 g, 12.5 mmol) in THF (10 mL) was added dropwise over
15 min. The reaction mixture was stirred at Ϫ80 °C for 15 min and
then allowed to slowly warm up to room temperature within 12 h.
After removal of the volatiles in vacuo, benzene (150 mL) was ad-
ded, and the reaction mixture was filtered. Volatiles were removed
in vacuo, the remaining oily solid was dissolved in THF (50 mL),
and the product was precipitated by adding hexane (50 mL). Yield:
2.3 g (54 %). M. p.: 158-160 °C.
Bis(2-(methylthio)phenyl)-N,N-diethylaminophosphine (4a). To
a
stirred cold (0 °C) solution of 2-iodothioanisole (25.0 g, 100 mmol)
in ether (370 mL) was added n-BuLi solution in hexanes (68.8 mL,
110 mmol). (Replacing 2-iodothioanisole with 2-bromothioanisole
gives similar yields). After stirring for 2 h at 0 °C, a solution
Cl2PNEt2 (7.2 mL, 50 mmol) in ether (10 mL) was slowly added
and the reaction mixture was stirred overnight at room tempera-
ture. The reaction mixture was filtered and the volume of the fil-
trate was reduced in vacuo to ca. 30 mL, resulting in the precipi-
tation of pale yellow solid 4a. The solid was isolated by filtration,
washed with hexanes (20 mL), and dried in vacuo, yielding 9.44 g
of 4a. Additional 4.11 g of pure 4a crystallized out from the filtrate
1H NMR (400 MHz, C6D6, 65 °C): δ 7.17 (4H, br m, Ph), 7.04 (6H, m, Ph),
6.92 (8H, m, Ph), 6.14 (1H, br, THP), 4.35 (1H, br, THP), 3.37 (1H, br,
Z. Anorg. Allg. Chem. 2006, 1879Ϫ1884
 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
1883

A. Beganskiene, N. Kongprakaiwoot, R. L. Luck, E. Urnezius
THP), 2.23 (1H, br m, THP), 2.07 (6H, s, SCH3), 2.06 (6H, s, SCH3), 1.93
(1H, br, THP), 1.74 (3H, s, CH3), 1.29 (4H, br m, THP). 31P NMR
(162 MHz, C6D6, 20 °C): δ Ϫ26.4 (s). HRMS (FAB): m/z ϭ 745.1624
(MHϩ); calcd for C40H43O2P2S4: 745.1621.
[4] T. N. Sorrell, A. S. Borovik, J. Chem. Soc. Chem. Commun.
1984, 1489.
[5] N. N. Murthy, M. Mahroof-Tahir, K. D. Karlin, J. Am. Chem.
Soc. 1993, 115, 10404.
[6] L. Cai, W. Xie, H. Mahmoud, Y. Han, D. J. Wink, S. Li, C. J.
O’Connor, Inorg. Chim. Acta 1997, 263, 231.
X-ray crystallography
[7] L. Li, A. A. N. Sarjeant, M. A. Vance, L. N. Zakharov, A. L.
Rheingold, E. I. Solomon, K. D. Karlin, J. Am. Chem. Soc.
2005, 127, 15360.
Single crystals suitable for X-ray diffraction experiment were ob-
tained by slow heptane diffusion into a benzene solution of 3. A
suitable crystal was selected, coated with epoxy resin and placed on
the head of a thin glass fiber, which was anchored in a goiniometer
mounting pin. The pin-mounted crystal was then inserted into the
goniometer head of the X-ray diffractometer and centered in the
beam path. Standard CAD4 centering, indexing, and data collec-
tion programs were utilized [34]. Twenty-five reflections between
10° and 15° in θ were located by a random search pattern, centered
and used in indexing. Final cell constants and orientation matrix
were obtained by collecting appropriate preliminary data, selecting
suitable reflections and refining by a least squares fit. During data
collection, three intensity standards and three orientation stand-
ards were measured at regular intervals to measure the rate of decay
of the crystal and to accommodate for crystal movement.
[8] L. Cai, Y. Han, H. Mahmoud, W. Xie, B. M. Segal, Inorg.
Chem. Commun. 1998, 1, 71.
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2004, 104, 1013.
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[12] A. Beganskiene, N. I. Nikishkin, R. L. Luck, E. Urnezius,
Heteroatom Chem. 2006, in press.
[13] P. J. Fagan, G. Li, Polymer-supported phosphorus ligands for
catalysis, E.I. du Pont de Nemours and Company, US patent
No WO 2000021663, 2000, p. 169.
[14] L. Horner, A. J. Lawson, G. Simons, Phosphorus Sulfur 1982,
12, 353.
Data were first reduced and corrected for absorption using psi-
scans [35] and then solved using the program SIR-02 [36] which
afforded a nearly complete solution for the non-H atoms. These
programs were utilized using the WinGX interface [37]. The models
were then refined using SHELXL97 [38] first with isotropic and
then anisotropic thermal parameters to convergence. The positions
and isotropic thermal parameters of the different H-atoms were
constrained according to the specifics arranged in the SHELXL97
program. It was apparent that two of the MeS groups were dis-
ordered. This was accounted for by including atoms at the various
sites and refining their occupancies constrained to unity. This re-
sulted in a 57(6) to 43(6) % occupancy ratio for S1-C1A and S11-
C11 respectively, and a 59(4) to 41(4) % occupancy ratio for S4-
C4A and S41-C41 respectively. A benzene molecule of solvation
was located and, as this was poorly defined, was defined con-
strained by an AFIX 66 parameter with the isotropic thermal par-
ameter of the 6 carbon atoms constrained to one variable which
was refined. H atoms, defined as stated above, were included for
the benzene molecule.
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J. Am. Chem. Soc. 1970, 92, 5206.
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J. Pursiainen, J. Organomet. Chem. 2000, 598, 235.
[17] F. Blume, S. Zemolka, T. Fey, R. Kranich, H.-G. Schmalz,
Adv. Synth. Catal. 2002, 344, 868.
[18] F. C. Krebs, P. S. Larsen, J. Larsen, C. S. Jacobsen, C.
Boutton, N. Thorup, J. Am. Chem. Soc. 1997, 119, 1208.
[19] A. A. El-Hadad, J. E. Kickham, S. J. Loeb, L. Taricani, D. G.
Tuck, Inorg. Chem. 1995, 34, 120.
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P. Lang, B. L. Scott, Inorg. Chem. 2001, 40, 2177.
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Peters, Chem. Commun. 2001, 2152.
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[24] H. W. Roesky, M. Scholz, M. Noltemeyer, F. T. Edelmann,
Inorg. Chem. 1989, 28, 3829.
[25] J. Heinicke, N. Peulecke, M. Köhler, M. He, W. Keim, J.
Organomet. Chem. 2005, 690, 2449.
˚
¯
Crystal data: C41H39O1P2S4Tl1, triclinic, P1, a ϭ 12.307(2) A, b ϭ
[26] T. B. Rauchfuss, Inorg. Chem. 1977, 16, 2966.
[27] K. Saatchi, B. O. Patrick, C. Orvig, Dalton. Trans. 2005, 2268.
[28] M. O. Workman, G. Dyer, D. W. Meek, Inorg. Chem. 1967,
6, 1543.
[29] L. P. Haugen, R. Eisenberg, Inorg. Chem. 1969, 8, 1072.
[30] M. F. M. Al-Dulaymmi, P. B. Hitchcock, R. L. Richards, Poly-
hedron 1989, 8, 1867.
˚
˚
13.377(5) A, c ϭ 14.815 (4) A, α ϭ 112.68(2)°, β ϭ 109.42(2)°,
γ ϭ 98.12(2)°, V ϭ 2018.1(10) A , Z ϭ 2, ρ ϭ 1.551 g cmϪ3, µ ϭ
3
˚
4.319 mmϪ1, 5254 reflections measured, 3987 unique. Final indices:
R1 ϭ 0.072, wR ϭ 0.225, (I>2sigma(I)); R indices (all data): R1 ϭ
0.104, wR ϭ 0.261. Goodness of fit 1.043. Full crystallographic
data has been deposited to the Cambridge Crystallographic Data
Centre (CCDC 299100); it can be requested via www.ccdc.cam.a-
c.uk/datarequest/cif.
[31] M. F. M. Al-Dulaymmi, P. B. Hitchcock, R. L. Richards, Poly-
hedron 1991, 10, 1549.
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[33] M. Micha-Screttas, C. G. Screttas, J. Org. Chem. 1977, 42,
1462.
Acknowledgments. Council for International Exchange of Scholars
is acknowledged for the Fulbright Visiting Scholar Grant (A.B.).
Acknowledgment is made to the Donors of the American Chemical
Society Petroleum Research fund, for partial support of this re-
search.
[34] CAD4 Express Software, Enraf-Nonius, Delft, The Nether-
lands, 1994.
[35] A. C. T. North, D. C. Phillips, F. S. Mathews, Acta Crystallogr.
1968, A24, 351.
[36] C. Giacovazzo, SIR2002 Program for Crystal Structure Solu-
tion, Inst. di Ric. per lo Sviluppo di Metodologie Cristallog-
rapfiche, CNR, Univ. of Bari, Italy, 2002.
[37] L. J. Farrugia, J. Appl. Crystallogr. 1999, 32, 837.
[38] G. M. Sheldrick, SHELXL97 Program for crystal structure re-
finement, University of Göttingen, Germany, 1997.
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1884
www.zaac.wiley-vch.de
 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2006, 1879Ϫ1884