Synthesis and first complexes of C4/5 P-bifunctional imidazole-2-thiones

Article abstract of DOI:10.1039/c3dt51557e

A synthetic route to C^4/5-bis(phosphinoyl)imidazole-2-thiones (7d,e) (d: R¹ = ⁿBu, R² = Me; e: R¹ = n-dodecyl, R² = Me) and C^4/5-bis(thio/selenophosphinoyl) imidazole-2-thiones (8b,c), (9a,b,e) and 10a (a: R¹ = R² = Me; b: R¹ = R² = Ph, c: R¹ = ⁱPr, R² = Me) is presented that employs initial C⁵ lithiation of mono-phosphinoyl/thiophosphinoyl substituted imidazole-2-thiones (3c-e)/(4a-c,e) followed by reaction with chlorodiphenylphosphane, leading to mixed phosphinoyl and phosphanyl substituted imidazole-2-thiones (5c-e) or mixed thiophosphinoyl and phosphanyl substituted imidazole-2-thiones (6a-c,e). Subsequent oxidation of mixed phosphinoyl and phosphanyl substituted imidazole-2-thione (5d,e) with H₂O₂-urea gives the bis(phosphinoyl) substituted imidazole-2-thiones (7d,e), and the oxidation of mixed thiophosphinoyl and phosphanyl substituted imidazole-2-thione (6a-c,e) using H₂O₂-urea, elemental sulfur or elemental selenium gives a set of mixed P(v)-chalcogenide substituted imidazole-2-thiones (8b,c), (9a,b,e) and 10a, respectively. P(v,v) substituted imidazole-2-thiones 7d and 9a reacted with tellurium tetrachloride, titanium tetrachloride or palladium dichloride to give complexes 11d, (12d and 12d′) and 14a, respectively, having a bidentate chelate (11d and 14a) or a monodentate bonding motif (12d,d′). The titanium complexes 12d,d′ slowly and selectively converted into the mono-ethoxy substituted product 13 possessing a seven membered chelate motif being unprecedented in the titanium chemistry of phosphine oxide donor ligands. The compounds were characterized by elemental analyses, spectroscopic and spectrometric methods and, in addition, X-ray diffraction studies in the case of 5c, 7d, 8b, 9a and 13.

Full text of DOI:10.1039/c3dt51557e

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Synthesis and first complexes of C4/5 P-bifunctional
imidazole-2-thiones†
Cite this: Dalton Trans., 2013, 42, 13126
Paresh Kumar Majhi,a Susanne Sauerbrey,a Alexander Leiendecker,a
Gregor Schnakenburg,a Anthony J. Arduengo III*b and Rainer Streubel*a
A synthetic route to C4/5-bis(phosphinoyl)imidazole-2-thiones (7d,e) (d: R1
= =
nBu, R2 = Me; e: R1
n-dodecyl, R2 = Me) and C4/5-bis(thio/selenophosphinoyl)imidazole-2-thiones (8b,c), (9a,b,e) and 10a (a:
R1 = R2 = Me; b: R1 = R2 = Ph, c: R1 = iPr, R2 = Me) is presented that employs initial C5 lithiation of mono-
phosphinoyl/thiophosphinoyl substituted imidazole-2-thiones (3c–e)/(4a–c,e) followed by reaction with
chlorodiphenylphosphane, leading to mixed phosphinoyl and phosphanyl substituted imidazole-
2-thiones (5c–e) or mixed thiophosphinoyl and phosphanyl substituted imidazole-2-thiones (6a–c,e).
Subsequent oxidation of mixed phosphinoyl and phosphanyl substituted imidazole-2-thione (5d,e) with
H2O2–urea gives the bis(phosphinoyl) substituted imidazole-2-thiones (7d,e), and the oxidation of mixed
thiophosphinoyl and phosphanyl substituted imidazole-2-thione (6a–c,e) using H2O2–urea, elemental
sulfur or elemental selenium gives a set of mixed P(V)-chalcogenide substituted imidazole-2-thiones (8b,
c), (9a,b,e) and 10a, respectively. P(V,V) substituted imidazole-2-thiones 7d and 9a reacted with tellurium
tetrachloride, titanium tetrachloride or palladium dichloride to give complexes 11d, (12d and 12d’) and
14a, respectively, having a bidentate chelate (11d and 14a) or a monodentate bonding motif (12d,d’).
The titanium complexes 12d,d’ slowly and selectively converted into the mono-ethoxy substituted
product 13 possessing a seven membered chelate motif being unprecedented in the titanium chemistry
of phosphine oxide donor ligands. The compounds were characterized by elemental analyses, spectro-
scopic and spectrometric methods and, in addition, X-ray diffraction studies in the case of 5c, 7d, 8b, 9a
and 13.
Received 12th June 2013,
Accepted 5th July 2013
DOI: 10.1039/c3dt51557e
www.rsc.org/dalton
with broken symmetry were investigated with respect to the
scalar couplings between the metal centre or C2 and the other
Introduction
Imidazole-2-thiones, which are cyclic analogs of thiourea, ring atoms.13 We envisioned that backbone substitution of
are of particular interest because of their wide range of imidazole-2-thiones and, ultimately, NHCs by electron with-
applications,1–3 e.g. as precursors to unusual thion-ylides,4 tri- drawing groups such as phosphinoyl groups not only will help
coordinate sulfuranes,5 desulfurizing agents for a thiirane,6 in to “tune” electronic properties and understand NMR features,
catalyzing cross-linking of polymers,7 complexating agents,8 but also to synthesize homo- and hetero-bimetallic complexes,
halogen free ionic liquids,9 stable N-heterocyclic carbenes hence enabling a new catalyst design.14 Therefore, backbone
(NHCs)10 as well as in the field of biologically11 active functionalization of imidazole-2-thiones is
compounds.
prospect, that includes ring-annellated15 and amino16 group
a promising
The electronic properties of NHCs can be influenced by substituted imidazole-2-thiones. On the other hand, organo-
electron withdrawing groups such as CN, Cl, NO2 positioned phosphorus compounds such as tertiary phosphine oxides,
in the backbone (C4 and C5);12 recently, 13C2 labelled NHCs sulfides, or selenides I, II (Fig. 1) bearing O, S, or Se donor
atoms have been the subject of numerous investigations
because of their coordination chemistry, extractive metallurgy,
catalytic properties, and structural chemistry.17 Among them,
aInstitut für Anorganische Chemie, Rheinische Friedrich-Wilhelms-Universität Bonn,
the carbon bridged bisphosphanes II, III have been extensively
used in coordination chemistry because of their chelation to
metals, and their metal complexes have been employed in
catalysis.18 The combination of good σ-donor properties,
and minimal steric demands in combination with the rigidity
offered by ortho-phenylene-type backbones that increases
Gerhard-Domagk-Str. 1, 53121 Bonn, Germany. E-mail: r.streubel@uni-bonn.de;
Fax: +49-228-73-9616
bDepartment of Chemistry, The University of Alabama, Tuscaloosa, AL 35487, USA.
E-mail: aj@ajarduengo.net
†Electronic supplementary information (ESI) available. CCDC 888238–888241
and 934725. For ESI and crystallographic data in CIF or other electronic format
see DOI: 10.1039/c3dt51557e
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Fig. 1 Various types of organophosphorus ligands I–VI.
resistance of the ligand against dissociation from the metal the steric demand of one n-butyl group (at one nitrogen
makes chelates of the structural type III especially interesting. centre) is not sufficient to selectively direct the lithiation
Recently, phosphane substituted imidazoles IV have been syn- and the following phosphanylation and, hence, the C4 and C5
thesized and their reactivity and spectroscopic properties (positional) isomers were obtained. Following this protocol,20
studied.19 However, flexible access to a library of imidazole-2- 2a–e were synthesized and used for P-oxidation to obtain the
thione substituted phosphanes has not achieved considerable C-phosphinoyl derivatives 3 and the C-thiophosphinoyl deriva-
attention, until reports on 4-phosphanylated 1,2-dialkyl imida- tives 4 as starting materials (Scheme 1). In the case of 3d,e and
zole-2-thiones V, their oxidation and complexation reactions 4e mixtures of both C4/5 positional isomers (denoted hereafter
appeared.20 From this perspective it is particularly useful to as 3d′,e′ and 4e′) (ratio 2.3 : 1 (3d : 3d′), 2 : 1 (3e : 3e′), 2 : 1
synthesize compounds of type VI having P(III) and/or P(V) (4e : 4e′)) were used as such for further transformations
centres and imidazole-2-thiones as rigid spacers, thus being without any purification or separation. Deprotonation of 3c–e
able to start studying their coordination properties. Addition- and 4a–c,e was achieved in THF using nBuLi (−78 °C). Sub-
ally, synthesis of homo- and hetero-bimetallic complexes using sequent addition of 1 equivalent of chlorodiphenylphosphane
imidazole-2-thiones as precursors to imidazole-2-ylidenes21 afforded imidazole-2-thiones 5c–e and 6a–c,e having mixed-
and novel P-functional ionic liquids9 may prove realistic. valence P(V/III) substituents (Scheme 2); completion of the reac-
Herein, the first synthesis of backbone-bifunctional imidazole- tions was monitored by 31P NMR spectroscopy. In the case of
2-thiones (type VI) having pairs of P(V/III) and P(V/V) phos- 4c–e (X = O) the reaction did not proceed selectively to 5c–e
phorus substituents is presented. Furthermore, a preliminary and yielded a mixture of products that could not be identified;
study on the coordination abilities of P(V/V) systems using nevertheless, small amounts of 5c were obtained through crys-
tellurium tetrachloride, titanium tetrachloride and palladium tallization, sufficient to perform an X-ray diffraction analysis.
dichloride suggests that this ligand design may prove generally
useful for both transition metals and main-group elements.
In contrast to the P-oxide derivatives, selective reactions
were observed for P-sulfides to yield 6a–c,e (X = S); the reaction
of 4e yielded two C4/5 positional isomers of 6e,e′ in a 1.7 : 1
ratio. After removal of lithium chloride, the crude products
were purified by crystallization from toluene, followed by
washing with n-pentane, thus giving 6a–c as colourless
Results and discussion
Recently, a facile protocol to access C-phosphinoyl substituted solids. In contrast, 5c precipitated from a methylene chloride
imidazole-2-thiones has been reported.20 It was observed that solution of the crude product mixture on standing at ambient
Scheme 1 Synthesis of phosphinoyl and thiophosphinoyl substituted imidazole-2-thiones.
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Scheme 3 Synthesis of C,C’-bis(phosphinoyl) imidazole-2-thiones.
Scheme 2 Synthesis of mixed-valence P(V/III) imidazole-2-thiones.
of the plane of the imidazole-2-thione ring. The folding angle
of the P(1)–C(2)–C(3) plane and the imidazole best plane is
4.29(19)° while that for the P(2)–C(3)–C(2) and imidazole
planes is 5.19(18)°. Hence, the torsion angle between the
P(1)–C(2)–C(3) and P(2)–C(3)–C(2) planes is 9.5(2)°. The P(1)–
O(1) bond vector is directed away from P(2) with a tilt angle of
5.73(11)° with respect to the imidazole ring plane.
Various oxidation reactions displayed in Schemes 3 and 4
are possible for these bis(phosphorus) adducts. Reaction of a
mixture of 5d,d′ (ratio 1.6 : 1) and 5e,e′ (ratio 1.7 : 1) with
H2O2–urea led to the P(V,V) substituted imidazole-2-thiones
7d,e. Since 5d and 5d′ and/or 5e and 5e′ are two positional
isomers, upon oxidation both of the isomers gave single pro-
ducts 7d,e and no further isomerization is observed for 7d,e.
These products were purified by column chromatography
using silica as the stationary phase and diethyl ether–petrol
ether as the eluent. The 31P{H} NMR spectra of 7d,e each
showed two distinguishable signals at 22.2 and 24.4 ppm (7d)
and 22.3 and 24.4 ppm (7e), which can be assigned to the two
magnetically (and chemically) inequivalent phosphinoyl
groups. Upon oxidation, both phosphorus nuclei appeared
Fig. 2 Molecular structure of compound 5c; hydrogen atoms have been
omitted for clarity (50% probability level). Selected bond distances (Å) and
angles (°): C(1)–N(1) 1.371(2), C(1)–N(2) 1.3372(2), C(2)–C(3) 1.3737(1),
C(1)–S(1) 1.6844(16), P(1)–O(1) 1.4832(12), P(1)–C(2) 1.8279(16), P(1)–C(8)
1.7958(16), P(1)–C(14) 1.8045(16); C(2)–P(1)–C(8) 105.75(7), C(2)–P(1)–C(14)
104.89(7), C(3)–P(2)–C(26) 104.25(7), C(8)–P(1)–O(1) 112.17(7), C(14)–P(1)–O(1)
111.61(7).
3
as singlets indicating that the JP,P coupling between the
phosphorus nuclei was significantly diminished, so that no
coupling was observed. Compound 7e showed a remarkably
low melting point (128 °C) compared to the other C,C′-bis-
(phosphanyl/phosphinoyl) substituted imidazole-2-thione
temperature. The constitution of compounds 5c and 6a–c,e
1
was established by H, 13C, and 31P NMR spectroscopy. Based
on previous observations on mono-substituted imidazole-
2-thiones,20 the assignments of resonances in the 31P{1H}
NMR spectra of 5c–e were straightforward: doublets at about
20 to 22 ppm are typical for P(V) environments (P(O)Ph2) and
those at −35 to −33 ppm for P(III) (PPh2); the resonances dis-
3
played JP,P couplings of 7–11 Hz. Similarly, 6a–c,e showed
doublets at about 29 to 31 ppm ((S)PPh2) and −33 to −28 ppm
(PPh2) with 3JP,P couplings of 11–19 Hz.
For compound 5c a single-crystal X-ray diffraction study was
performed using a crystal obtained from a super-saturated
methylene chloride solution at ambient temperature. Com-
pound 5c crystallizes in a monoclinic lattice with space group
P21/n; the molecular structure is shown in Fig. 2 and selected
structural parameters are given in the figure caption of the
corresponding compound; for crystallographic data see
Table S1 (ESI† section).
The determined bond lengths and angles of 5c are within
the typical ranges observed for diphenylphosphanyl and
diphenylphosphinoyl substituted imidazoles21 and imidazole-
2-thiones.20 The atoms P(1) and P(2) are staggered slightly out
Scheme 4 Synthesis of mixed P(V/V) substituted imidazole-2-thiones.
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Fig. 3 Molecular structure of compound 7d; hydrogen atoms have been
omitted for clarity (50% probability level). Selected bond distances (Å) and
angles (°): C(1)–N(1) 1.367(3), C(1)–N(2) 1.371(3), C(2)–C(3) 1.367(3), C(1)–S(1)
1.6777(1), P(1)–O(1) 1.4857(1), P(1)–C(2) 1.832(2), P(1)–C(9) 1.8007(2),
P(1)–C(15) 1.8046(2); N(1)–C(1)–N(2) 105.42(19), C(3)–C(2)–N(1) 106.8(2),
C(3)–C(2)–P(1) 31.95(18), N(1)–C(2)–P(1) 120.85(17), C(9)–P(1)–C(2) 108.38(11),
C(2)–C(3)–P(2) 127.71(18).
Fig. 4 Molecular structure of compound 8b; hydrogen atoms have been
omitted for clarity (50% probability level). Selected bond distances (Å) and
angles (°): C(1)–N(1) 1.376(3), C(1)–N(2) 1.369(3), C(2)–C(3) 1.375(3), C(4)–N(1)
1.453(3), C(1)–S(1) 1.665(2), P(1)–S(2) 1.9169(10), P(2)–O(1) 1.604(2), P(1)–C(16)
1.808(2); C(2)–P(1)–C(16) 107.22(11), C(2)–P(1)–C(22) 104.55(11), C(2)–P(1)–S(2)
113.22(10), C(3)–P(2)–C(28) 108.94(11), C(3)–P(2)–O(1) 114.32(10), C(22)–P(1)–
S(2) 112.89(9).
derivatives described in this paper and, hence, could serve as a
precursor to P-bifunctional ionic liquids.
Reactions of compounds 6a–c,e with H2O2–urea, elemental
sulfur or selenium allowed synthesis of a set of mixed P(V/V)-
chalcogenide substituted imidazole-2-thiones. The reaction of
6b,c with H2O2–urea gave C4-thiophosphinoyl, C5-phosphinoyl
imidazole-2-thiones 8b,c. The reaction of 6a,b,e(e′) with
elemental sulfur or selenium led quantitatively and selectively
to 9a,b,e and 10a, respectively. As previously mentioned, the
reaction of 6e,e′ with elemental sulfur provided the single
product 9e. Compounds 8b,c were recrystallized from hot
toluene and obtained as white solids. Compounds 9a,b,e and
10a were crystallized directly from the reaction mixtures.
Analytical data on these new compounds are presented in the
Experimental section. As mentioned previously, upon oxi-
dation both P(V) phosphorus nuclei appeared as singlets in the
31P{H} NMR spectra and no 3JP,P couplings were observed.
Single-crystal X-ray diffraction analysis was performed for
7d, 8b and 9a. Selected bond parameters are given in the
figure caption of the corresponding compounds, and for crys-
tallographic data see Tables S1 and S2 (ESI† section). The
molecular structures of 7d, 8b and 9a are shown in Fig. 3–5,
respectively, and provide unambiguous constitutional proof.
Irrespective of the substitution pattern in the backbone of
the imidazole-2-thione moiety, it was observed that the CvS
bond length of 5c, 7d, 8b and 9a remained constant. It is note-
worthy that atoms P(1) and P(2) for 7d are found slightly out of
the plane of the imidazole-2-thione ring: the folding angle of
the P(1)–C(2)–C(3) plane and the C(1)–N(2)–C(2)–C(3)–N(1)
plane is 8.0(3)° and that of the P(2)–C(3)–C(2) plane and the
C(1)–N(2)–C(2)–C(3)–N(1) plane is 0.7(3)°. The torsion angle
between the P(1)–C(2)–C(3) plane and the P(2)–C(3)–C(2) plane
is 8.6(3)°. Furthermore, two different dihedral angles were
found for the O–P–C units and the imidazole-2-thione ring
Fig. 5 Molecular structure of compound 9a; hydrogen atoms have been
omitted for clarity (50% probability level). Selected bond distances (Å) and
angles (°): C(1)–N 1.3648(15), C(1)–N#1 1.3649(15), C(2)–C(2)#1 1.377(3), C(3)–
N 1.4679(16), C(1)–S(1) 1.6768(19), P–S(2) 1.9501(5), P–C(2) 1.8223(13), P–C(4)
1.8259(14); C(2)–P–C(4) 101.64(6), C(10)–P–C(2) 108.49(6), N–C(2)–P 118.77(9),
C(10)–P–S(2) 116.34(5), C(2)–P–S(2) 114.04(5), C(5)–C(4)–P 118.28(10),
C(9)–C(4)–P 121.90(10).
plane: 23.54(15)° for the O(1)–P(1)–C(2) plane and 28.69(16)°
for the O(2)–P(2)–C(3) plane, respectively.
As observed above for 7d, atoms P(1) and P(2) in compound
8b are slightly out of the imidazole ring plane: the folding
angle of the P(1)–C(2)–C(3) plane and the C(1)–N(2)–C(2)–C(3)–
N(1) plane is 1.8(3)° and that of the P(2)–C(3)–C(2) plane and
the C(1)–N(2)–C(2)–C(3)–N(1) plane is 6.5(3)°. The torsion
angle between the P(1)–C(2)–C(3) plane and the P(2)–C(3)–C(2)
plane is 8.0(4)°. Two different dihedral angles were found
for the E–P–C units and the imidazole-2-thione ring plane:
79.49(13)° for the S(2)–P(1)–C(2) plane and 83.14(14)° for the
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O–P(2)–C(3) plane, respectively. The PO and the PS units are
located on opposite sides of the imidazole-2-thione plane.
Also in the structure of compound 9a, both P atoms are
slightly out of the plane of the imidazole-2-thione ring having
two PS units on opposite sides of the imidazole-2-thione plane
and are connected by a C2 axis.
Coordination chemistry studies
A methylene chloride solution of 7d was treated with tellurium
tetrachloride at ambient temperature to obtain 11d; similarly,
reaction of 7d with titanium tetrachloride afforded 12d and
12d′ (Scheme 5). The products were obtained as red (11d) and
yellow (12d, 12d′) solids after removal of the solvent in vacuo
and repeated washing with n-pentane followed by drying of the
residue. The coordination of 7d to the tellurium and titanium
Fig. 6 Molecular structure of complex 13; hydrogen atoms have been omitted
for clarity (50% probability level). Selected bond distances (Å) and angles (°):
C(2)–N(1) 1.363(3), C(2)–N(2) 1.368(3), C(1)–C(3) 1.374(3), C(2)–S 1.672(2), Ti–
O(1) 2.0662(16), Ti–O(3) 1.7474(16), Ti–Cl(3) 2.3930(7), P(1)–O(1) 1.5052(16);
C(3)–P(2)–O(2) 113.12(10), C(1)–P(1)–O(1) 109.70(8), O(2)–Ti–O(1) 80.82(6),
centres was confirmed by NMR spectroscopy, e.g. the 31P{1H} O(3)–Ti–O(2) 172.01(7).
NMR spectrum of 11d showed two signals having slightly
different chemical shifts compared to the starting material
(24.6 and 23.3 ppm (11d) vs. 24.4 and 22.2 ppm (7d)), whereas molecules and 13, they were omitted for clarity in Fig. 6. The
two sets of two signals downfield of the later resonances were structure of 13 shows a distorted octahedral geometry of the
observed for the titanium complexes (29.8, 27.1 ppm and 29.2, Ti(IV) centre having a chelating bis(phosphinoyl) substituted
imidazole-2-thione ligand. Although coordination of phos-
phine oxides to a titanium centre is known,23 in general, for-
27.6 ppm, ratio 1.3 : 1) which were attributed to the two mono-
coordinated phosphinoyl titanium adducts 12d and 12d′.
Single-crystal X-ray diffraction analysis was performed using mation of a seven-membered metallacyclic ring consisting of a
bisphosphine oxide ligand has not yet been reported in the
a crystal obtained from a saturated methylene chloride–diethyl
ether (1 : 1) solution of 12d and 12d′ at low temperature Cambridge Crystallographic Data Base. It should be noted that
(−20 °C, 4 weeks). The result showed the molecular structure synthesis of a related seven-membered metallacyclic ring of
TiCl4 with diester ligands of the type cis RO(O)C–CvC–C(O)OR
of complex 13 (Fig. 6), revealing a new 7-membered chelate
motif and that one of the chloride ligands was replaced by an and their use in Ziegler–Natta catalysis has been reported by
ethoxy group.
Iiskola and coworkers.24 The titanium coordination environ-
ment has a distorted octahedral geometry as revealed by the
Albeit the pathway of product formation is unclear, cleavage
of diethyl ether upon coordination to titanium tetrachloride bond angles at the Ti centre: all trans angles are equal to 172°,
with elimination of ethyl chloride and ethoxy substitution of a whereas most of the cis angles deviate much from 90°, e.g.
chloride has been reported by Mutin and coworkers.22 For crys-
O(2)–Ti–Cl 85.3(1)°. The titanium–oxygen bond lengths are sig-
tallographic data of 13 see Table S2 (see ESI† section); selected nificantly different (Ti–O(3) 1.74(0), Ti–O(2) 2.04(0) and Ti–
structural parameters are given in the figure caption. The unit O(1) 2.06(0) [Å]), thus revealing the covalent and coordinative
bonding nature. Only slight bond elongation was observed
cell of 13 contains three methylene chloride molecules. Since
there is no strong interaction between these (solvent) for both PvO bonds upon coordination to the titanium centre
Scheme 5 Synthesis of the first P(V/V) imidazole-2-thione Te(IV) (11d) and Ti(IV) (12d, 12d’) complexes.
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studies on catalytic reactions using new titanium complexes
are underway.
Experimental section
General considerations
Scheme 6 Synthesis of the first Pd(II) complex of a P(V/V) imidazole-2-thione.
The lithiation/phosphanylation reactions were performed
under an argon atmosphere, using common Schlenk tech-
niques and dry solvents. Tetrahydrofuran, diethyl ether,
pentane, and toluene were dried over sodium wire/benzophe-
none, methylene chloride over calcium hydride and further
purified by subsequent distillation. Chlorodiphenylphosphane
was distilled prior to use and stored under an argon atmos-
phere; other chemicals were used as received. All NMR spectra
were recorded on a Bruker AX-300 spectrometer (300.1 MHz
for 1H, 75.5 MHz for 13C, 121.5 MHz for 31P). The 1H and
13C spectra were referenced to the residual proton resonances
and the 13C signals of the deuterated solvents and 31P to 85%
H3PO4 as the external standard, respectively. Melting points
were determined in one-side melted off capillaries using a
Büchi Type S or a Carl Roth Type MPM-2 apparatus; they are
uncorrected. Elemental analyses were carried out on a Vario
EL gas chromatograph. Mass spectrometric data were collected
on a Kratos MS 50 spectrometer using EI, 70 eV. The infrared
spectra were recorded on a Nicolet 380 FT-IR spectrometer
using KBr pellets or via total reflection (diamond ATR). The
UV/Vis spectra were recorded in solution on a Shimadzu
UV-1950 PC spectrometer. The X-ray diffraction analyses were
performed on a Nonius Kappa CCD or a Bruker X8-KappaApex
TT type diffractometer at 123(2) or 100(2) K, respectively. The
structures were solved by direct methods refined by the full-
matrix least-squares technique in anisotropic approximation
for non-hydrogen atoms using the SHELXS97 and SHELXL9725
program packages. Hydrogen atoms were located from Fourier
synthesis and refined isotropically. Crystallographic data for
the structures reported in this paper have been deposited with
the Cambridge Crystallographic Data Centre as supplementary
publication no. CCDC-888238 (5c), CCDC-888239 (7d), 888240
(8b), CCDC-888241 (9a), CCDC-934725 (13).
(P(1)–O(1) 1.50(0) and P(2)–O(2) 1.49(0) Å vs. P(1)–O(1) 1.48(1)
and P(2)–O(2) 1.47(1) Å in 7d).
Finally, the reactivity of 9a towards a cationic metal(II)
centre was investigated, using palladium(II) as a case in point.
When a solution of 9a was treated with palladium dichloride
(Scheme 6) at ambient temperature no reaction occurred after
several days. Then the suspension was heated to 65 °C for a
longer period of time (16 h) through which an orange solution
was formed. Complex 14a was obtained as an orange solid
after removal of the solvent in vacuo and repeated washing
with n-pentane and drying of the residue. The 31P{1H} NMR
spectrum of complex 14a showed a similar chemical shift com-
pared to the starting material (29.6 ppm (14a) vs. 29.8 ppm
(9a)); low solubility of 14a prevented the acquisition of good
quality 13C NMR data. Taking the previous results into con-
sideration, the chelating κS,κS-coordination of the ligand 9a to
the palladium centre can be deduced from the appearance of a
singlet in the 31P{1H} NMR spectrum. The presence of two
chloride ligands in 14a was confirmed via pos. ESI-MS experi-
ments which showed the m/z value 760.90 for the cation
Na[C29H26Cl2N2P2PdS3]+ (Na-14a) and the m/z value 702.94 of a
cationic fragment (after loss of chloride from the molecule
ion) that possessed one chloride ligand [C29H26ClN2P2PdS3]+.
Conclusions
A facile and effective protocol was presented that enables
synthesis of C4/5 disubstituted imidazole-2-thiones bearing
diphenylphosphinoyl and diphenylphosphanyl groups or
diphenylthiophosphinoyl and diphenylphosphanyl groups. It
was observed that the directional abilities of P-sulfides are
superior to P-oxides in the C-lithiation step. Subsequent oxi-
Typical lithiation and phosphanylation procedure for the
synthesis of 5c–e and 6a–c,e
dation of the diphosphanyl group using H2O2–urea, elemental In a Schlenk flask, the P(V)-substituted imidazole-2-thiones
sulfur or selenium selectively led to homo/hetero-chalcogenide 3c–e or 4a–c,e (10 mmol each) were dissolved in 50 mL of THF
P(V/V)-substituted imidazole-2-thiones. First investigations on and cooled to −78 °C. 6.9 mL n-butyllithium (1.6 M in
the ligand properties of bisphosphine oxide and sulphide n-hexane, 11 mmol) was added and the reaction mixture was
derivatives towards cationic metal(IV) and metal(II) centres slowly warmed to −40 °C and stirred for 2 h at this temp-
revealed a preferred chelating mode in the case of the system erature. The reaction mixture was cooled again to −78 °C and
tellurium tetrachloride/bisphosphine oxide and palladium 1.98 mL (11 mmol) of chlorodiphenylphosphane (Ph2PCl) was
dichloride/bisphosphine sulphide, whereas titanium tetra- added and the reaction mixture stirred overnight while
chloride/bisphosphine oxide preferred a κO-mono coordi- warming to ambient temperature. The solution was then con-
nation. Upon chloride substitution the resulting ethoxy centrated in vacuo (8 × 10−3 mbar), the dry residue taken up in
trichlorotitanium complex preferred the chelating bonding methylene chloride (50 mL) and filtered over a G3 frit
mode of the bisphosphine oxide ligand; the latter also rep- equipped with a layer of Celite® to remove lithium chloride.
resent the first example of such a titanium complex. Currently, The filtrate was collected and the solvent was removed in vacuo
This journal is © The Royal Society of Chemistry 2013
Dalton Trans., 2013, 42, 13126–13136 | 13131

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(8 × 10−3 mbar). The crude product was purified via crystalliz-
1,3-Diphenyl-4-diphenylthiophosphinoyl-5-diphenylphosphanyl-
ation from hot toluene (20 mL) followed by washing with imidazole-2-thione (6b). Yield: 5.21 g (8.0 mmol, 80%), colour-
n-pentane (2 × 15 mL). In doing so colourless to light yellowish less solid, m.p. 260 °C. 1H NMR (300 MHz, CDCl3): δ = 6.66
crystals of 5c and 6a–c were obtained. 5d,e were not selectively (dd, JH,H = 8.3 Hz, JH,H = 1.3 Hz, 2H, C6H5–H), 6.92 (t, JH,H
obtained and, therefore, were used for further transformations 7.5 Hz, 2H, C6H5–H), 7.00 (td, JP,H = 7.7 Hz, JH,H = 7.1 Hz, JH,H
=
=
without separation or purification. In the case of 6e, two posi- 1.3 Hz, 4H, C6H5–H), 7.10–7.36 (m, 18H, C6H5–H), 7.93 (ddd,
tional (C4 (6e)- and C5 (6e′) substituted) isomers were obtained JP,H = 14.3 Hz, JH,H = 7.2 Hz, JH,H = 1.3 Hz, 4H, C6H5–H). 13C
in a 1.7 : 1 ratio (6e : 6e′).
{1H} NMR (75.0 MHz, CDCl3): δ = 128.2 (d, JP,C = 6.1 Hz, C6H5),
1-Isopropyl-3-methyl-4-diphenylphosphinoyl-5-diphenylphos- 128.4 (d, JP,C = 18.4 Hz, C6H5), 128.4 (s, C6H5), 128.6 (s, C6H5),
phanyl-imidazole-2-thione (5c). Colourless crystals, 1H NMR 128.6 (s, C6H5), 129.0 (s, C6H5), 129.3 (s, C6H5), 130.1 (s, C6H5),
3
1
2
(300 MHz, CDCl3): δ = 1.23 (d, JH,H = 7.1 Hz, 6H, C3H7–CH3), 131.5 (d, JP,C = 2.9 Hz, C6H5), 132.9 (dd, JP,C = 53.2 Hz, JP,C
3.57 (s, 3H, N3–CH3), 4.31 (hept, 3JH,H = 7.1 Hz, 1H, C3H7–CH), 17.2 Hz, C5), 131.9 (d, JP,C = 2.5 Hz, C6H5), 132.1 (d, JP,C
7.21 (dd, JP,H = 8.2 Hz, JH,H = 7.1 Hz, 4H, C6H5–H), 7.27–7.39 19.7 Hz, C6H5), 132.1 (d, JP,C = 2.4 Hz, C6H5), 132.2 (d, JP,C
=
=
=
=
1
(m, 12H, C6H5–H), 7.96 (dd, JP,H = 14.0 Hz, JH,H = 8.1 Hz, 4H, 2.6 Hz, C6H5), 132.6 (d, JP,C = 2.1 Hz, C6H5), 135.3 (dd, JP,C
C6H5–H). 31P {1H} NMR (121.5 MHz, CDCl3): δ = −33.2 (d, 87.3 Hz, JP,C = 33.4 Hz, C4), 136.0 (d, JP,C = 56.8 Hz, PIII-ipso-
2
1
3JP,P = 10.2 Hz, Ph2P-Imz), 21.4 (d, JP,P = 10.2 Hz, Ph2PvO). C6H5), 137.0 (d, JP,C = 78.8 Hz, PV-ipso-C6H5), 173.6 (dd, JP,C
=
=
=
3
1
Adduct 5c precipitated in small amounts only after keeping 5.0 Hz, CvS). 31P NMR (121.5 MHz, CDCl3): δ = −28.4 (m, 3JP,H
3
3
3
the crude mixture in dichloromethane over two weeks at room 7.7 Hz, JP,P = 18.6 Hz), 30.3 (m, JP,H = 14.3 Hz, JP,P
temperature; the crystals thus obtained were used for the X-ray 18.6 Hz). IR (KBr, cm−1): ˜ν = 3052 (w, ν(C–H)), 1596 (m,
diffraction study.
1-n-Butyl-3-methyl-4(5)-diphenylphosphinoyl-5(4)-diphenyl- (Et2O): λmax: 209 nm. EA: calc. for C39H30N2P2S2: C, 71.76, H,
phosphanyl-imidazole-2-thione NMR 4.63, N, 4.29, S, 9.82; found: C, 71.96, H, 4.89, N, 4.16, S, 9.88.
(5d(d′)). 31P {1H}
ν(CvC)), 1437 (vs) 1156 (m, ν(CvS)), 634 (s, ν(PvS)). UV/Vis
(121.5 MHz, THF): δ = −35.3 (d, 3JP,P = 7.8 Hz) and 20.2 (d, 3JP,P
=
1-Isopropyl-3-methyl-4-diphenylthiophosphinoyl-5-diphenyl-
7.8 Hz) (5d), −31.9 (d, 3JP,P = 6.8 Hz) and 19.8 (d, 3JP,P = 6.8 Hz) phosphanyl-imidazole-2-thione (6c). Yield: 4.0 g (7.20 mmol
(5d′) (5d : 5d′ 1.6 : 1 ratio) and unidentified products (37%); 72%), colourless solid, m.p. 232 °C. 1H NMR (300 MHz,
3
oily product.
CDCl3): δ = 1.13 (d, JH,H = 7.1 Hz, 6H, C3H7–CH3), 3.50 (s, 3H,
1-n-Dodecyl-3-methyl-4(5)-diphenylphosphinoyl-5(4)-diphenyl- N3–CH3), 4.11 (hept, JH,H = 7.1 Hz, 1H, C3H7–CH), 7.25 (dd,
phosphanyl-imidazole-2-thione NMR JP,H = 8.2 Hz, JH,H = 7.1 Hz, 4H, C6H5–H), 7.29–7.41 (m, 12H,
(5e(e′)). 31P {1H}
3
(121.5 MHz, THF): δ = −35.3 (d, 3JP,P = 7.9 Hz) and 20.0 (d, 3JP,P
=
C6H5–H), 7.93 (dd, JP,H = 14.0 Hz, JH,H = 8.1 Hz, 4H, C6H5–H).
7.9 Hz) (5e), −31.9 (d, 3JP,P = 6.7 Hz) and 19.6 (d, 3JP,P = 6.7 Hz) 13C{1H} NMR (75.0 MHz, CDCl3): δ = 17.6 (s, C3H7–CH3), 35.4
(5e′) (5e : 5e′ 1.7 : 1 ratio) and unidentified products (45%); oily (s, N3–CH3), 52.7 (s, C3H7–CH), 128.7 (d, JP,C = 13.2 Hz, C6H5),
1
2
product.
1,3-Dimethyl-4-diphenylthiophosphinoyl-5-diphenylphosphanyl- 19.1 Hz, C6H5), 131.3 (d, JP,C = 19.1 Hz, C6H5), 131.8 (d, JP,C
128.7 (dd, JP,C = 117.3 Hz, JP,C = 49.4 Hz, C4), 129.0 (d, JP,C
=
=
imidazole-2-thione (6a). Yield: 4.10 g (7.80 mmol, 78%), 2.5 Hz, C6H5), 131.8 (d, JP,C = 11.0 Hz, C6H5), 132.2 (s, C6H5),
1
1
2
1
colourless solid, m.p. 245 °C. H NMR (300 MHz, CDCl3): δ = 132.9 (dd, JP,C = 52.2 Hz, JP,C = 20.3 Hz, C5), 133.9 (d, JP,C
=
2.93 (s, 3H, N3–CH3), 3.56 (s, 3H, N1–CH3), 7.01–7.42 (m, 16H, 63.7 Hz, PIII-ipso-C6H5), 134.4 (d, JP,C = 102.6 Hz, PV-ipso-
C6H5–H), 7.48–7.83 (m, C6H5–H). 13C{1H} NMR (75.0 MHz, C6H5), 167.5 (d, JP,C = 5.1 Hz, CvS). 31P NMR (121.5 MHz,
1
CDCl3): δ = 36.0 (s br, N1–CH3), 36.3 (s, N3–CH3), 128.7 (d, 1JP,C
=
CDCl3): δ = −34.3 (m, JP,H = 8.2 Hz, JP,P = 16.5 Hz), 30.2 (m,
3
3
60.8 Hz, PIII-ipso-C6H5), 128.9 (d, JP,C = 16.9 Hz, C6H5), 3JP,H = 14.0 Hz, 3JP,P = 16.5 Hz). MS (EI, 70 eV): m/z (%) 556 (75)
129.0 (d, JP,C = 13.6 Hz, C6H5), 130.3 (dd, 1JP,C = 50.9 Hz, 2JP,C
=
=
[M]+, 524 (30) [M − S]+, 479 (100) [M − S − C3H7]+, 437 (100)
[M − 2S − C3H7 − CH3]+, 183 (50) [P(C6H5)2]+. HR-MS:
15.6 Hz, C5), 131.0 (d, JP,C = 18.8 Hz, C6H5), 131.6 (d, JP,C
1
87.6 Hz, PV-ipso-C6H5), 132.0 (d, JP,C = 3.1 Hz, C6H5), 132.2 (d, 556.1326, calc.: 556.1326. IR (KBr, cm−1): ˜ν = 3049 (w, ν(C–H)),
JP,C = 3.1 Hz, C6H5), 132.9 (d, JP,C = 14.9 Hz, C6H5), 133.5 (dd, 1584 (m, ν(CvC)), 1436 (vs), 1385 (m) 1176 (s, ν(CvS)), 644
1JP,C = 102.2 Hz, JP,C = 38.5 Hz, C4), 169.8 (dd, JP,C = 4.9 Hz, (s, ν(PvS)). UV/Vis (Et2O): λmax: 270 nm. EA: calc. for
2
CvS). 31P NMR (121.5 MHz, CDCl3): δ = −32.9 (m, JP,H
=
=
C31H30N2P2S2: C, 66.89, H, 5.43, N, 5.03, S, 11.52; found: C,
66.41, H, 5.43, N, 4.91, S, 11.68.
1-n-Dodecyl-3-methyl-4(5)-diphenylthiophosphinoyl-5(4)-diphenyl-
3
3
3
3
6.4 Hz, JP,P = 10.5 Hz), 29.9 (m, JP,H = 14.3 Hz, JP,P
10.5 Hz). MS (EI, 70 eV): m/z (%) 528 (68) [M]+, 496 (52)
[M − S]+, 451 (100) [M − C6H5]+, 419 (30) [M − C6H5 − S]+, phosphanyl-imidazole-2-thione (6e(e′)). Yield of the 6e : 6e′
405 (8) [M − C6H5 − S − CH3]+, 344 (8) [M − P(C6H5)2]+, 329 (5) mixture (both isomers): 6.41 g (9.3 mmol, 93%), yellow dense
[M − P(C6H5)2 − CH3]+, 312 (5) [M − P(C6H5)2 − S]+, 183 (21) liquid, 31P {1H} NMR (121.5 MHz, THF): δ = −32.3 (d, JP,P
=
=
3
[P(C6H5)2]+. HR-MS (C29H26N2P2S2): found: 528.1018, 11.0 Hz) and 30.3 (d, JP,P = 11.0 Hz) (6e), {−31.9 (d, JP,P
3
3
calc.: 528.1013. IR (KBr, cm−1): ˜ν = 3052 (w, ν(C–H)), 1582 10.8 Hz) and 29.0 (d, 3JP,P = 10.8 Hz) (6e′)} (6e : 6e′ 1.7 : 1 ratio).
(w, ν(CvC)), 1431 (s), 1372 (vs) 1163 (s, ν(CvS)), 644 (s,
Procedure for the generation of C-phosphinoyl derivatives
ν(PvS)). UV/Vis (Et2O): λmax: 271 nm. EA: calc. C, 65.89, H,
4.96, N, 5.30, S, 12.13; found: C, 64.79, H, 5.02, N, 5.12, S, To 1 mmol of the phosphane derivatives 6b,c, dissolved
11.82.
in 15 mL of chloroform, 0.094 g (1 mmol) of the
13132 | Dalton Trans., 2013, 42, 13126–13136
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hydrogenperoxide–urea adduct was added into
a
round 115.1 Hz, ipso-C6H5), 131.7 (d, JP,C = 10.5 Hz, C6H5), 132.3 (d,
bottom flask and the reaction mixture was stirred until 31P JP,C = 10.5 Hz, C6H5), 132.6 (d, JP,C = 3.1 Hz, C6H5), 169.6 (dd,
NMR showed complete conversion of the starting material JP,C = 5.5 Hz, CvS). 31P NMR (121.5 MHz, CDCl3): δ = 22.3
3
3
(ca. 3 h). The reaction mixture was then filtered over a funnel (quint br, JP,H = 12.9 Hz), 24.4 (quint br, JP,H = 13.2 Hz). MS
equipped with filter paper to remove the urea, and the filtrate (EI, 70 eV): m/z (%) 682 (55) [M]+, 649 (47) [M − S]+, 498 (11)
was collected and concentrated in vacuo (8 × 10−3 mbar). The [M − CH3 − C12H25]+, 482 (46) [M − S − C12H24]+, 465 (21)
crude product was purified via crystallization from hot toluene [M − O − Ph2PO]+, 449 (100) [M − S − Ph2PO]+, 281 (11)
and the obtained crystalline material was washed with [M − S − Ph2PO − C12H24]+, 201 (61) [Ph2PO]+, 77 (12) [Ph]+. IR
n-pentane (2 × 5 mL) and dried in vacuo (8 × 10−3 mbar).
(KBr, cm−1): ˜ν = 3061 and 2010 (w, ν(C–H)), 1512 (m, ν(CvC)),
7d,e were synthesized by taking the crude reaction mixtures 1438 (s), 1375 (s), 1339 (s), 1265 (s), 1182 (vs, ν(CvS)). UV/Vis
(ratios 1.6 : 1 (5d : 5d′) and 1.7 : 1 (5e : 5e′)) obtained from 5d,e (CH2Cl2): λmax: 269 nm. EA: calc. for C40H48N2O2P2S: C, 70.36,
(coming from 3e) and subsequent reaction with 0.94 g H, 7.09, N, 4.10, S, 4.69; found: C, 70.06, H, 6.35, N, 4.13, S,
(10 mmol) of the H2O2–urea adduct. The products were iso- 4.76.
lated after purification by column chromatography at room
1,3-Diphenyl-4-diphenylthiophosphinoyl-5-diphenylphosphi-
temperature using silica as the stationary phase and diethyl noyl-imidazole-2-thione (8b). Yield: 0.55 g (0.83 mmol, 83%),
1
ether as the eluent.
colourless solid, m.p. 307 °C. H NMR (300 MHz, CDCl3): δ =
3
1-n-Butyl-3-methyl-4,5-bis(diphenylphosphinoyl)imidazole-2- 7.06–7.36 (m, 26 H, C6H5–H), 7.64–7.74 (dd, JH,H = 14.3 Hz,
thione (7d). Yield: 2.28 g (4.0 mmol, 40%) (the given yield is 4JH,H = 7.1 Hz, 4H, C6H5–H). 13C{1H} NMR (75.0 MHz, CDCl3):
with reference to the starting material 3d used), colourless δ = 124.3 (s, C6H5), 127.1 (d, JP,C = 1.4 Hz, C6H5), 127.4 (d, JP,C
=
1
solid, m.p. 198 °C. 1H NMR (300 MHz, CDCl3): δ = 0.71 (t, 3JH,H
=
13.3 Hz, C6H5), 127.4 (d, JP,C = 90.5 Hz, P(O)-ipso-C6H5), 127.5
7.3 Hz, 3H, C4H9–CH3), 1.03–1.16 (m, 2H, C4H9–CH2), (d, JP,C = 13.2 Hz, C6H5), 127.6 (d, JP,C = 4.2 Hz, C6H5), 129.1 (d,
1.31–1.45 (m, 2H, C4H9–CH2), 3.34 (s, 3H, N3–CH3), 4.44 (t, 1JP,C = 66.5 Hz, P(S)-ipso-C6H5), 129.5 (d, JP,C = 4.4 Hz, C6H5),
1
2
3JH,H = 8.2 Hz, 2H, C4H9–CH2), 7.22–7.50 (m, 16H, C6H5–H), 129.9 (dd, JP,C = 109.5 Hz, JP,C = 13.7 Hz, C5), 130.1 (d, JP,C
=
=
=
7.61–7.72 (m, 4H, C6H5–H). 13C{1H} NMR (75.0 MHz, CDCl3): δ 11.7 Hz, C6H5), 130.2 (d, JP,C = 3.0 Hz, C6H5), 130.4 (d, JP,C
= 13.5 (C4H9–CH3), 19.8 (C4H9–CH2), 30.2 (C4H9–CH2), 36.7 11.6 Hz, C6H5), 131.4 (d, JP,C = 34.0 Hz, C6H5), 131.6 (dd, 1JP,C
(N3–CH3), 49.0 (C4H9–CH2), 128.0 (d, JP,C = 13.4 Hz, C6H5), 91.3 Hz, JP,C = 15.7 Hz, C4), 135.1 (d, JP,C = 43.0 Hz, C6H5),
2
128.6 (d, JP,C = 13.2 Hz, C6H5), 130.4 (dd, JP,C = 112.8 Hz, JP,C 136.8 (s, C6H5), 171.8 (dd, JP,C = 3.8 Hz, CvS). 31P{1H} NMR
1
2
= 15.7 Hz, C4/C5), 131.2 (d, JP,C = 113.7 Hz, ipso-C6H5), 131.6 (121.5 MHz, CDCl3): δ = 14.1 (s, PvO), 30.8 (s, PvS). MS (EI,
1
(d, JP,C = 112.6 Hz, ipso-C6H5), 131.6 (d, JP,C = 10.9 Hz, C6H5), 70 eV): m/z (%) 668 (18) [M]+, 636 (15) [M − S]+, 559 (100)
1
131.7 (dd, 1JP,C = 110.8 Hz, JP,C = 15.4 Hz, C5/C4), 132.3 (d, JP,C [M − S − Ph]+, 452 (8) [M − Ph2PS]+, 434 (12) [M − S −
2
= 11.1 Hz, C6H5), 132.4 (d, JP,C = 2.4 Hz, C6H5), 132.6 (d, 1JP,C
=
Ph2PO]+, 217 (10) [Ph2PS]+, 201 (19) [Ph2PO]+. HR-MS: found:
2.9 Hz, C6H5), 167.5 (dd, JP,C = 5.5 Hz, CvS). 31P NMR 668.1260, calc.: 668.1260. EA: calc. for C39H30N2OP2S2: C,
3
(121.5 MHz, CDCl3): δ = 22.2 (quint br, JP,H = 13.0 Hz), 24.4 70.04, H, 4.52, N, 4.19, S, 9.59, found: C, 68.92, H, 4.67, N,
(quint br, JP,H = 13.1 Hz). MS (EI, 70 eV): m/z (%) 570 (83) 4.32, S, 9.36.
3
[M]+, 537 (38) [M − S]+, 514 (10) [M − C4H8]+, 493 (21)
1-Isopropyl-3-methyl-4-diphenylthiophosphinoyl-5-diphenyl-
[M − C6H5]+, 437 (100) [M − C4H8 − C6H5]+, 201 (47) [Ph2PO]+, phosphinoyl-imidazole-2-thione (8c). Yield: 0.43
g
(0.
77 (12) [Ph]+. IR (KBr, cm−1): ˜ν = 2961 and 2910 (w, ν(C–H)), 75 mmol, 75%), colourless solid, m.p. 215 °C. 1H NMR
3
1589 (m, ν(CvC)), 1437 (s), 1395 (s), 1337 (s), 1270 (s), 1187 (300 MHz, DMSO(d6)): δ = 1.26 (d, JH,H = 6.7 Hz, 6H, C3H7–
(vs, ν(CvS)). UV/Vis (CH2Cl2): λmax: 268 nm. EA: calc. for CH3), 3.23(s, 3H, N3–CH3), 4.14 (sept, 1H, C3H7–CH), 7.67–7.23
C32H32N2O2P2S: C, 67.36, H, 5.65, N, 4.91, S, 5.62; found: C, (m, 16 H, C6H5–H), 8.03 (dd, 4H, C6H5–H). 13C{1H} NMR
67.35, H, 5.40, N, 4.93, S, 5.96.
1-n-Dodecyl-3-methyl-4,5-bis(diphenylphosphinoyl)imidazole-2- CH3), 54.1 (s, C3H7–CH), 128.2 (d, JP,C = 11.0 Hz, C6H5), 128.9
(75.0 MHz, DMSO(d6)): δ = 17.2 (s, C3H7–CH3), 30.6 (s, N3–
1
2
thione (7e). Yield: 2.04 g (3.0 mmol, 30%) (the given yield is (d, JP,C = 10.6 Hz), 130.0 (dd, JP,C = 112.6 Hz, JP,C = 11.0 Hz,
with reference to the starting material 3e), colourless solid, C5), 130.5(d, JP,C = 11.5 Hz, C6H5), 131.2 (d, JP,C = 3.1 Hz,
3
m.p. 128 °C. 1H NMR (300 MHz, CDCl3): δ = 0.80 (t, JH,H
=
C6H5), 131.4 (d, JP,C = 11.7 Hz, C6H5), 131.4 (d, JP,C = 56.8 Hz,
6.9 Hz, 3H, C12H25–CH3), 0.97–1.38 (m, 20H, C12H25–CH2), P(S)-ipso-C6H5), 133.2 (d, JP,C = 2.8 Hz, C6H5), 133.4 (d, JP,C
=
=
3
1
2
3.30 (s, 3H, N3–CH3), 4.38 (t, JH,H = 8.3 Hz, 2H, C12H25–CH2), 91.0 Hz, P(O)-ipso-C6H5), 133.7 (dd, JP,C = 112.6 Hz, JP,C
7.17–7.46 (m, 16H, C6H5–H), 7.56–7.65 (m, 4H, C6H5–H). 11.0 Hz, C4), 166.7 (dd, JP,C = 4.7 Hz, CvS). 31P{1H} NMR
13C{1H} NMR (75.0 MHz, CDCl3): δ = 14.1 (C12H25–CH3), 22.7 (121.5 MHz, DMSO(d6)): δ = 21.1 (s, PvO), 31.9 (s, PvS). MS
(C12H25–CH2), 26.6 (C12H25–CH2), 28.2 (C12H25–CH2), 29.0 (EI, 70 eV): m/z (%) 572 (12) [M]+, 540 (12) [M − S]+, 526 (12)
(C12H25–CH2), 29.3 (C12H25–CH2), 29.4 (C12H25–CH2), 29.5 [M − S − CH3]+, 463 (28) [M − S − Ph]+, 417 (100) [M − 2Ph]+, 201
(C12H25–CH2), 29.6 (C12H25–CH2), 31.9 (C12H25–CH2), 36.7 (N3– (70) [Ph2PO]+. IR (KBr, cm−1): ˜ν = 3055, 2986 (w, ν(C–H)), 1438
CH3), 49.3 (C12H25–CH2), 128.0 (d, JP,C = 13.3 Hz, C6H5), 128.6 (m, ν(CvC)), 1374 (vs), 1426 (s), 1278 (s), 1162 (s, ν(CvS)).
1
2
(d, JP,C = 13.3 Hz, C6H5), 130.2 (dd, JP,C = 103.8 Hz, JP,C
=
UV/Vis (CH2Cl2): λmax: 254 nm. HR-MS: found: 572.1275, calc.:
15.9 Hz, C4/C5), 131.1 (d, JP,C = 113.7 Hz, ipso-C6H5), 131.6 572.1275. EA: calc. for C31H30N2OP2S2: C, 65.02, H, 5.28, N,
1
(dd, JP,C = 100.7 Hz, JP,C = 15.4 Hz, C5/C4), 131.7 (d, JP,C
=
4.89, S, 11.20; found: C, 64.28, H, 5.49, N, 5.01, S, 11.22.
1
2
1
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Procedure for the generation of C-thio- and C-selenophos-
phinoyl derivatives
128.5 (dd, 1JP,C = 98.8 Hz, 2JP,C = 28.9 Hz, C4/C5), 129.1 (d, JP,C
13.4 Hz, C6H5), 129.1 (d, JP,C = 13.4 Hz, C6H5), 130.3 (d, JP,C
=
=
=
1
10.4 Hz, C6H5), 130.5 (d, JP,C = 10.4 Hz, C6H5), 131.3 (d, JP,C
To a solution of phosphane derivatives 6a,b,e (1 mmol) in 1.8 Hz, C6H5), 170.0 (dd, JP,C = 5.0 Hz, CvS). 31P NMR
15 mL of toluene, 0.032 g (1 mmol) of elemental sulfur or (121.5 MHz, CDCl3): δ = 29.1 (quint br, JP,H = 14.5 Hz),
3
0.078 g (1 mmol) of selenium was added into a 50 mL Schlenk 30.2 (quint br, 3JP,H = 14.5 Hz). MS (EI, 70 eV): m/z (%) 714 (20)
tube and heated for 3 h at 110 °C. The reaction mixture was [M]+, 682 (10) [M − S]+, 650 (12) [M − 2S]+, 605 (70) [M − S −
cooled down to ambient temperature, whereby the product CH3]+, 497 (10) [M − Ph2P(S)]+, 217 (68) [Ph2PS]+, 185 (48)
precipitated in the form of colourless crystals. The obtained [Ph2P]+, 77 (12) [Ph]+. IR (KBr, cm−1): ˜ν = 3054 and 2922
crystals were washed with n-pentane (2 × 5 mL) and dried (w, ν(C–H)), 1594 (m, ν(CvC)), 1460 (s), 1436 (s), 1390 (s), 1158
in vacuo (8 × 10−3 mbar).
(vs, ν(CvS)). UV/Vis (CH2Cl2): λmax: 271 nm. EA: calc.
1,3-Dimethyl-4,5-bis(diphenylthiophosphinoyl)imidazole-2- for C40H48N2P2S3: C, 67.20, H, 6.77, N, 3.92, S, 13.45; found:
thione (9a). Yield: 0.50 g (0.9 mmol, 90%) colourless solid, C, 66.54, H, 6.05, N, 3.68, S, 12.88.
1
m.p. 318 °C (dec.). H NMR (300 MHz, CDCl3): δ = 3.35(s, 6H,
1,3-Dimethyl-4-diphenylthiophosphinoyl-5-diphenylseleno-
(10a). Yield: 0.52
(0.86 mmol, 86%), colourless solid, m.p. more than 327 °C
CH3), 7.71–7.11 (m, 20H, C6H5–H). 13C{1H} NMR (75.0 MHz, phosphinoyl-imidazole-2-thione
g
1
2
CDCl3): δ = 34.9 (s, CH3), 127.2 (dd, JP,C = 71.3 Hz, JP,C
=
14.7 Hz, C4&C5), 127.7 (d, 1JP,C = 66.7 Hz, ipso-Ph), 128.2 (d, JP,C (limit of the apparatus). H NMR (300 MHz,CDCl3): δ = 2.28 (s
1
= 13.5 Hz, C6H5), 129.5 (d, JP,C = 10.9 Hz, C6H5), 130.4 (d, JP,C
=
br, 3H, N1–CH3), 4.72 (d, 3JP,H = 4.7 Hz, N3–CH3), 7.05–7.65 (m,
3.2 Hz, C6H5), 164.3 (s br, CvS). 31P NMR (121.5 MHz, CDCl3): 20H, C6H5–H). 13C{1H} NMR (75.0 MHz, CDCl3): δ = 36.3 (s,
δ = 29.8 (bq, JP,H = 14.0 Hz). MS (EI, 70 eV): m/z (%) 560 (12) N1–CH3), 36.4 (s, N3–CH3), 128.1 (d, JP,C = 1.4 Hz, C6H5), 128.3
3
[M].+, 529 (20) [M − 2CH3]+, 528 (60) [M − S]+, 497 (19) [M − (d, JP,C = 2.5 Hz, C6H5), 129.5 (d, JP,C = 20.0 Hz, C6H5), 130.5 (d,
2 CH3 − S]+, 496 (56) [M − 2S]+, 452 (27) [M − 2CH3 − Ph]+, 451 JP,C = 9.0 Hz, C6H5), 164.0 (s br, CvS) (other missing signals
(100) [M − S − Ph]+, 420 (10) [M − 2CH3 − S − Ph]+, 419 (40) could not be resolved due to the low signal to noise ratio
[M − 2S − Ph]+, 310 (10) [M − Ph2P(S) − S]+, 217 (25) [Ph2PS]+, caused by poor solubility). 31P NMR (121.5 MHz, CDCl3): δ =
1
3
185 (19) [Ph2P]+. IR (KBr, cm−1): ˜ν = 3054, 2982 (w, ν(C–H)), 22.3 (qq, 3JP,H = 15.3 Hz, JSe,P = 776 Hz, PvSe), 30.0 (qq, JP,H
=
1435 (m, ν(CvC)), 1373 (vs), 1356 (s), 1158 (s, ν(CvS)). UV/Vis 15.2 Hz, PvS). MS (EI, 70 eV): m/z = 608 (34) [M]+, 576 (21)
(CH2Cl2): λmax: 265 nm. EA: calc. for C29H26N2P2S3: C, 62.12, [M − S]+, 544 (37) [M − 2S]+ 217 (35) [Ph2PS]+. HR-MS
H, 4.67, N, 5.06, S, 17.16; found: C, 60.50, H, 4.77, N, 4.55, S, (C29H26N2P2S2Se): found: 608.018, calc.: 608.017.
15.40.
General procedure for the synthesis of 11d and (12d and 12d′)
1,3-Diphenyl-4,5-bis(diphenylthiophosphinoyl)imidazole-2-
thione (9b). Yield: 0.56 g (0.82, 82%), colourless solid, m.p. To 0.20 g (0.35 mmol) of derivative 7d, dissolved in 10 mL of
315 °C. 1H NMR (300 MHz, CD2Cl2): δ = 7.22–6.91 (m, 22H, methylene chloride, 0.09 g (0.35 mmol) of tellurium tetrachlor-
C6H5–H), 7.57–7.46 (dd, 8H, C6H5–H). 13C{1H} NMR ide for 11d or 0.34 mL (0.35 mmol) of titanium tetrachloride
(75.0 MHz, CD2Cl2): δ = 127.5 (s, C6H5), 128.5 (s, C6H5), 128.7 (1 M solution in methylene chloride) for (12d and 12d′) was
1
2
(d, JP,C = 13.8 Hz, C6H5), 129.9 (dd, JP,C = 93.2 Hz, JP,C = 13.5 added and stirred at ambient temperature until the starting
1
Hz, C4&C5), 130.2 (d, JP,C = 85.4 Hz, PV-ipso-C6H5), 131.1 (d, material was consumed (31P NMR control). The solvent was
JP,C = 5.1 Hz, C6H5), 131.2 (s, C6H5), 136.0 (s, N-ipso-C6H5), then removed in vacuo (8 × 10−3 mbar) and the yellowish-red
163.3 (s br, CvS). 31P NMR (121.5 MHz, CD2Cl2): δ = 30.4 (bq, colored solid was washed with n-pentane (2 × 5 mL) and dried
3JP,H = 13.7 Hz). MS (EI, 70 eV): m/z (%) 684 (20) [M]+, 652 (29) in vacuo (8 × 10−3 mbar).
[M − S]+, 620 (15) [M − 2S]+, 575 (100) [M − S − Ph]+, 468 (40)
[Tetrachloro{[1-n-butyl-3-methyl-4,5-bis(diphenylphosphinoyl)-
[M − Ph2PS]+, 435 (12) [M − S − Ph2PS]+, 217 (25) [Ph2PS]+. IR imidazol-2-thione]-κOP,κOP}tellurium(IV)] (11d). Yield: 0.27 g
(KBr, cm−1): ˜ν = 3138 and 3052 (w, ν(C–H)), 1590 (m, ν(CvC)), (0.32 mmol, 93%), red solid, m.p. 216 °C (dec.). 1H NMR
3
1492 (s, ν(P–CvC)), 1438 (s), 1413 (s), 1168 (vs, ν(CvS)). (300 MHz, CDCl3): δ = 0.61 (t, JH,H = 7.2 Hz, 3H, C4H9–CH3),
UV/Vis (CH2Cl2): λmax: 270 nm. HR-MS (C39H30N2P2S3): found: 0.82–0.92 (m, 2H, C4H9–CH2), 1.14–1.23 (m, 2H, C4H9–CH2),
684.1046, calc.: 684.1040.
3.62 (s, 3H, N3–CH3), 4.40 (s br, 2H, C4H9–CH2), 7.25–7.45 (m,
1-n-Dodecyl-3-methyl-4,5-bis(diphenylthiophosphinoyl)imid- 12H, C6H5–H), 7.54–7.66 (m, 8H, C6H5–H). 13C{1H} NMR
azole-2-thione (9e). Yield: 0.60 g (0.84 mmol, 84%), colourless (75.0 MHz, CDCl3): δ = 12.3 (C4H9–CH3), 18.8 (C4H9–CH2), 30.4
solid, m.p. 191 °C. 1H NMR (300 MHz, CDCl3): δ = 0.81 (t, 3JH,H
=
(C4H9–CH2), 38.6 (N3–CH3), 50.5 (C4H9–CH2), 127.9 (d, JP,C
=
=
6.8 Hz, 3H, C12H25–CH3), 1.19 (m, 18H, C12H25–CH2), 1.70 13.7 Hz, C6H5), 128.0 (d, JP,C = 14.1 Hz, C6H5), 130.8 (d, JP,C
(m, 2H, C12H25–CH2), 3.35 (s, 3H, N3–CH3), 3.85 (t, JH,H
=
11.3 Hz, C6H5), 131.2 (d, JP,C = 11.4 Hz, C6H5), 132.5 (s br);
8.3 Hz, 2H, C12H25–CH2), 7.11–7.29 (m, 12H, C6H5–H), some signals were not observed. 31P NMR (121.5 MHz, CDCl3):
7.46–7.60 (m, 8H, C6H5–H). 13C{1H} NMR (75.0 MHz, CDCl3): δ
24.6 (quint br), 23.3 (quint br). Pos-ESI-MS:
3
δ
=
+
= 14.1 (C12H25–CH3), 22.7 (C12H25–CH2), 26.6 (C12H25–CH2), (C32H32N2O2P2S)TeCl3 calcd (found) 804.97 (804.98). IR (ATR,
27.2 (C12H25–CH2), 29.0 (C12H25–CH2), 29.4 (C12H25–CH2), 29.6 cm−1): ˜ν = 2960 (s), 1588 (s), 1436 (vs), 1394 (br), 1311 (br),
(C12H25–CH2), 29.7 (C12H25–CH2), 31.9 (C12H25–CH2), 36.9 (N3– 1260 (w), 1119 (s), 1025 (w), 818 (b), 728 (s), 686 (vs). UV/Vis
1
CH3), 49.6 (C12H25–CH2), 127.8 (d, JP,C = 99.4 Hz, ipso-C6H5), (CH2Cl2): λmax: 230 nm.
13134 | Dalton Trans., 2013, 42, 13126–13136
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[Tetrachloro{[1-n-butyl-3-methyl-4,5-bis(diphenylphosphinoyl)-
imidazol-2-thione]-κOP,κOP}titanium(IV)] (12d and 12d′). Yield
Acknowledgements
of both isomers: 0.25 g (0.32 mmol, 94%), yellow solid, 1H RS gratefully acknowledges the University of Bonn, the SFB 813
NMR of the major isomer (300 MHz, CDCl3): δ = 0.52 (t, 3JH,H
=
“Chemistry at Spin Centers”, the COST action cm0802 “PhoSciNet”
7.3 Hz, 3H, C4H9–CH3), 1.24–1.32 (m, 2H, C4H9–CH2), 3.06 (s, and the DAAD PPP USA program; AJA the National Science
3H, N3–CH3), 3.68 (m, 2H, C4H9–CH2), 4.82 (s br, 2H, C4H9– Foundation (CHE-0413521 and CHE-0115760) for providing the
CH2), 7.27–7.37 (m, 12H, C6H5–H), 7.44–7.54 (m, 8H, C6H5–H). funding for this study. AJA gratefully acknowledges the Saxon
13C{1H} NMR of the major isomer (75.0 MHz, CDCl3): δ = 13.2 Endowment of the University of Alabama. G.S. thanks Prof. A. C.
(C4H9–CH3), 19.5 (C4H9–CH2), 29.7 (C4H9–CH2), 37.4 (N3–CH3), Filippou for support.
1
49.0 (C4H9–CH2), 126.3 (d, JP,C = 120.6 Hz, ipso-C6H5), 126.9
1
(d, JP,C = 119.4 Hz, ipso-C6H5), 129.2 (d, JP,C = 14.0 Hz, C6H5),
129.4 (d, JP,C = 14.6 Hz, C6H5), 132.7 (s br), 134.3 (s br); some
References
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29.8 (quint br), 27.1 (quint br) and 29.2 (quint br) & 27.6
(quint br) in a 1.3 : 1 ratio. Pos-ESI-MS: (C32H32N2O2P2S)
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1310 (s), 1202 (w), 1168 (s), 1117 (s), 1091 (s), 1061 (vs), 996 (s),
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3
CDCl3):
C29H26ClN2P2PdS3
C29H26Cl2N2NaP2PdS3 calcd (found) 760.9039 (760.9039). IR
δ
=
29.6 (br q, JP,H
=
13.9 Hz). Pos-ESI-MS:
+
calcd (found) 702.9454 (702.9454),
+
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13136 | Dalton Trans., 2013, 42, 13126–13136
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