Rearrangement and redistribution reaction of Ph2PCH2TMS with PhAsCl2 or AsCl3

Article abstract of DOI:10.1080/10426507.2019.1631310

The attempted synthesis of bis(diphenylphosphinomethyl) phenylarsane and tris(diphenylphosphinomethyl) arsane through condensation of chloro arsanes and diphenyl (trimethylsilylmethyl) phosphane yielded a number of side products originating from migratory and redox-reactions in addition to the targeted ligands. An unexpected, 1,3,4-phosphadiarssolan-1-ium salt was obtained and crystallographically characterized as an A-shaped chlorido adduct.

Full text of DOI:10.1080/10426507.2019.1631310

Phosphorus, Sulfur, and Silicon and the Related Elements
ISSN: 1042-6507 (Print) 1563-5325 (Online) Journal homepage: https://www.tandfonline.com/loi/gpss20
Rearrangement and redistribution reaction of
Ph2PCH2TMS with PhAsCl2 or AsCl3
Arvind Kumar Gupta, Joshua P. Green & Andreas Orthaber
To cite this article: Arvind Kumar Gupta, Joshua P. Green & Andreas Orthaber (2019):
Rearrangement and redistribution reaction of Ph2PCH2TMS with PhAsCl2 or AsCl3, Phosphorus,
Sulfur, and Silicon and the Related Elements, DOI: 10.1080/10426507.2019.1631310
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PHOSPHORUS, SULFUR, AND SILICON AND THE RELATED ELEMENTS
https://doi.org/10.1080/10426507.2019.1631310
Rearrangement and redistribution reaction of Ph2PCH2TMS with PhAsCl2
or AsCl3
Arvind Kumar Gupta, Joshua P. Green, and Andreas Orthaber
€
Department of Chemistry – Ångstrom Laboratories, Synthetic Molecular Chemistry, Uppsala University, Uppsala, Sweden
ABSTRACT
ARTICLE HISTORY
Received 17 May 2019
Accepted 9 June 2019
The attempted synthesis of bis(diphenylphosphinomethyl) phenylarsane and tris(diphenylphosphi-
nomethyl) arsane through condensation of chloro arsanes and diphenyl (trimethylsilylmethyl)
phosphane yielded a number of side products originating from migratory and redox-reactions in
addition to the targeted ligands. An unexpected, 1,3,4-phosphadiarssolan-1-ium salt was obtained
and crystallographically characterized as an A-shaped chlorido adduct.
KEYWORDS
Phosphonium; arsane;
condensation reac-
tion; ligands
GRAPHICAL ABSTRACT
Introduction
Results and discussion
methylene bridged
Oligophosphanes, in particular the tridentate bis-(diphenyl- The
hexaphosphane
ligand
phosphinomethyl) phenyl phosphane (dppp, 1), have been bisf[(diphenylphosphinomethyl)phenylphosphinomethyl]-
extensively studied and used to prepare diverse multinuclear phenylphosphinog methane (8) has previously been pre-
coordination compounds of copper,[1] silver,[2] gold,[3] and pared in almost quantitative yields by the facile condensa-
platinum,[4] as well as mixed metallic systems.[5] Recently, tion of a silyl-substituted methylene phosphane (6) with the
variations of this motif that alter the phosphane substitu- chlorophosphane 7.[17] This observed reactivity inspired us
ents[6] or expand the coordination environment[7,8] have led to attempt the preparation of the tridentate ligand with
to interesting opto-electronic materials (Figure 1).
mixed pnictogen donors, i.e. dpap (2), through the reaction
of neat Ph2PCH2TMS (9) with PhAsCl2 (10). Elimination of
two equivalents of TMS-Cl was expected to lead to the
desired ligand 2 (Scheme 1). Surprisingly, this product was
only formed in small amounts, while a multitude of phos-
phorus-containing side products were observed by 31P NMR
Elemental substitution of phosphorus with arsenic in the
dppm ligand, as seen in bis(diphenylphosphinomethyl) phe-
nylarsane (2, dppa) or bis(diphenylarsinomethyl) phenyl-
phosphane (3, dpap), gave rise to numerous coordination
compounds in which all three or only the two outermost
donor sites are involved in the complexation of multi-metal- spectroscopy of the crude reaction mixture (Figure 2).
lic centers.[9,10] Recently, interesting solid state transforma- Resonances grouped around –22 ppm indicate that a number
tions of a dinuclear gold complex have been associated with of different phosphanes were formed, while the downfield
dramatic optical changes for the bis(diphenylarsino)ethane shifted signals at around þ30 ppm would suggest that seren-
ligand 4.[11] Our and others efforts to further explore the dipitous oxidation or quaternization of the phosphorus cen-
coordination chemistry of arsine and arsole based ligands ters occurred. Chromatographic work-up of this complex
has led to materials with interesting optical, electronic and mixture led to the identification of some phosphanes that
catalytic properties.[12–16]
were formed during this reaction: the symmetric
€
Department of Chemistry – Ångstrom Laboratories, Synthetic Molecular Chemistry, Uppsala
CONTACT Andreas Orthaber
Andreas.orthaber@kemi.uu.se
University, Uppsala, Sweden.
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/gpss.
ß 2019 The Author(s). Published by Taylor & Francis Group, LLC.
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distribution, and reproduction in any medium, provided the original work is properly cited.

2
A. K. GUPTA ET AL.
Scheme 1. Attempted synthesis of the tridentate P-As-P ligand 2, and the identified side products 11–13 and oxidized derivatives (14, 15) thereof, which were
obtained after the purification process. Conditions: i) neat, 90–100 ꢁC.
Scheme 2. Attempted synthesis of the triphosphane ligand 16 and observed side products in particular the phosphonium salt 17. (i) room temperature, DCM. (ii)
neat, 90–100 ꢁC.
bisdiphenylphosphino methane (11, dppm), the mixed
diphenylarsino diphenylphosphino methane (12, dpma), and
diphenylmethylphosphane (13, dpmp) were identified based
on crystallographic analysis and/or NMR data. These identi-
fied products clearly indicate that multiple reactions such as
protodesilylation as well as phenyl- and methyl-migrations
occur under these conditions. Additional oxidized deriva-
tives have been identified from this complex mixture.
We were also able to chromatographically isolate and 2,
and colorless crystals of the desired product were then
obtained by slow hexane diffusion into a DCM solution of
2. The structure solves in the orthorhombic space group
Pca2(1) [a ¼ 10.663(3); b ¼ 10.096(3); c ¼ 24.660(6), R1¼
5.1%]. The ligand exhibits a rather twisted arrangement, in
contrast to many of the previously reported coordination
compounds.[1,3,4] This arrangement leads to a relatively
short intramolecular P1ꢀꢀꢀP2 distance of 4.001(4) Å, whereas
the phosphorus-arsenic separation is in the expected range
(ca. 3 Å) (Figure 3).
Figure 1. Common polyphosphane and –arsane ligand systems and an
example of a dinuclear arsane gold complex. Synthesis of a methylene bridged
polyphosphane (8) by a condensation reaction and silyl chloride elimination.
singlet at 31.7 ppm. The compound associated with the res-
onance at 21.5 ppm was assigned to the formation of
diphenyl phosphane oxide based on literature data.[19] After
18 h, the 31P-NMR spectrum revealed the major phos-
phorus-containing products had resonances at ca. –7, þ22,
30.5, and 33.5 ppm in an approximate ratio of 6.1:1:2.5.
Initial purification by passing the crude reaction mixture
through an alumina plug led to the disappearance of the
–7 ppm resonance and the appearance of two new peaks at
–21.0 and –25.9 ppm, as well as a major peak at þ31.2 ppm.
The two phosphanes 11 (-25.7 ppm) and 12 (-21.0 ppm)
were again identified as side products in this complex reac-
tion mixture. A similarly complex reaction mixture was
obtained when the reaction was carried out without solvent
We have also reacted AsCl3 with three equivalents of 9 in
an attempt to synthesize the triphosphane ligand 16
(Scheme 2). Similarly, the allegedly simple reaction afforded
a multitude of reaction products, with the exact mixture
depending on whether the reaction was carried out neatly or
in a solvent (e.g., DCM). When performed in DCM, the
reaction initially gave rise to two very broad signals in its
31P-NMR spectra centered around –15 and –7 ppm, as well
1
as a sharp signal at þ21.5 (doublet, JPH ¼ 477 Hz) and a at elevated temperatures. A major product associated with

PHOSPHORUS, SULFUR, AND SILICON AND THE RELATED ELEMENTS
3
1
Figure 2. Crude 31Pf Hg-NMR of reaction (I).
Figure 4. ORTEP18 representation of the solid state structure of 17. Ellipsoids
are drawn at 50% probability levels. Selected bond lengths [Å] and angles [ꢁ]:
As1-C13 1.974(8), As1-Cl2 2.242(3), As1-As2 2.4763(15), As2-C14 1.973(9), As2-
Cl1 2.258(2), C13-P1 1.796(9), C14-P1 1.789(9), As1-Cl3 2.876(3), As2-
Cl3 2.783(3).
Figure 3. ORTEP18 representation of the solid state structure of 2. Ellipsoids are
drawn at 50% probability levels. Selected bond lengths [Å] and angles [ꢁ]: As1-
C8 1.982(9), P1-C8 1.833(8), P2-C7 1.841(9), P1ꢀꢀꢀP2 4.001(4), As1ꢀꢀꢀP2 3.118(3),
P1ꢀꢀꢀAs1 3.100(3). C7-As1-C8 95.5(3), P2-C7-As1 109.6(4), P1-C8-As1 108.6(4).
one of the downfield shifted phosphorus resonances could
be isolated by simple extraction of the crude product with
acetonitrile. Slow crystallization by evaporation from a satu-
rated solution afforded colorless crystals of the unexpected
phosphonium salt 17 (Figure 4). Similarly, the correspond-
ing dichloromethane solvate (17ꢀCH2Cl2) was obtained by
diffusion of DCM into an acetonitrile solution of 17.
Formation of this product is associated with a redox reac-
tion at the arsenic center and methyl migrations, but prob-
ably involves other migratory steps as well. The 31P-NMR
spectrum shows a single resonance at 36.6 ppm, while the
1H-NMR shows a broad singlet for the methylene protons
at 1.57 ppm.
The structural analysis of 17 [orthorhombic space group
Pna21; a ¼ 12.2004(7), b ¼ 18.0162(9), c ¼ 7.8796(4) Å)
shows the formation of an As-As bond (2.4763(15) Å)
together with a phosphonium center. The resulting 1,3,4-
phosphodiarsolan-1-ium heterocycle provides an interesting
Figure 5. Different packing motifs seen in the solid-state structures of 10ꢀDCM
motif with two As-Cl units (2.242(3) and 2.258(2) Å) and (a) and 10 (b).

4
A. K. GUPTA ET AL.
[2] Che, C.-M.; Yip, H.-K.; Li, D.; Peng, S.-M.; Lee, G.-H.; Wang,
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Silver(I) Complexes: Spectroscopy, Luminescent Properties and
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the third chloride atom bridging between the two arsenic
centers (As-Cl3 2.783(3) and 2.876(3) Å) giving a unique A-
shaped arrangement. The Cl3 chloride has long distances to
the nearest phosphonium centers (intramolecular: 3.272(3)
and intermolecular: 4.238(3) Å); however, it also displays a
weak C-HꢀꢀꢀCl interaction with one of the phenyl substitu-
ents (Cl3-H2 3.086 Å). The sums of the angles around both
arsenic centers (excluding the As-Cl3 contacts) are 293.0
and 290.8ꢁ, resulting in a rather peculiar bonding situation.
Moreover, the As-As single bond distance (2.4763(15) Å) is
relatively long compared to previously reported diarsanes
(2.40-2.45 Å[20]) but significantly shorter than in the steric-
ally encumbered dimer of the latent and stable arsinyl rad-
ical (TMS2CH)2Asꢀ (2.587 Å).[21] A related five membered
heterocycle - a dihalo-diarsa-cyclopentane derivative - has
previously been reported as a halogenation product of As3-
nortricyclane.[22] Similar to our observations, a complex
equilibrium of products was observed under these experi-
mental conditions.
ꢀ
[3] Bardajı, M.; Laguna, A.; Orera, V. M.; Villacampa, M. D.
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[5] Tanase, T.; Begum, R. A.; Toda, H.; Yamamoto, Y. Linearly
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ꢂ
The [ndr (nþ1)pr] emissions of linear silver(I) and gold(I)
The structure solution of the DCM solvate gives very simi-
lar metrics to the phosphonium salt, however the packing
motifs differ significantly. While the DCM solvate leads to a
shifted face-to-face arrangement of the A-motif (Figure 5a)
the solvent free structure shows the A-motifs in a side-on
packing motif (Figure 5b).
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Conclusions
The simple TMS-Cl elimination in the reaction of chloro-
phosphanes with silyl-substituted methylene phosphanes
contrasts the complex behavior for chloro arsanes (Ph-AsCl2
and AsCl3). The mixed pnictogen ligand bis(diphenylphos-
phinomethyl) phenylarsane was crystallographically charac-
terized. The observed reactivities indicate that migratory and
redox reactions are responsible for the complexity of this
allegedly simple condensation reaction ultimately giving the
unexpected 1,3,4-phosphadiarsolan-1-ium salt, with an A
shaped As2Cl3 motif.
[11] England, K. R.; Lim, S. H.; Luong, L. M. C.; Olmstead, M. M.;
Balch, A. L. Vapoluminescent Behavior and the Single-Crystal-
to-Single-Crystal Transformations of Chloroform Solvates of
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[12] Gupta, A. K.; Akkarasamiyo, S.; Orthaber, A. Rich
Coordination Chemistry of p-Acceptor Dibenzoarsole Ligands.
Inorg. Chem. 2017, 56, 4504–4511. DOI: 10.1021/acs.inorgchem.
7b00100.
[13] Green, J. P.; Gupta, A. K.; Orthaber, A. Effect of Arsenic
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Properties of Dithieno[3,2-b:20,30-d]Arsoles. Eur. J. Inorg. Chem.
2019, DOI: 10.1002/ejic.201801169.
[14] Pfeifer, G.; Papke, M.; Frost, D.; Sklorz, J. A. W.; Habicht, M.;
Mu€ller, C. Clicking the Arsenic–Carbon Triple Bond: An Entry
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[15] Ishidoshiro, M.; Matsumura, Y.; Imoto, H.; Irie, Y.; Kato, T.;
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Arsole via an Unusual Exo-Endo Stereochemically Controlled
Experimental
Experiments are carried out under inert conditions unless
stated otherwise. NMR data are recorded on a JEOL EXC
operating at a proton frequency of 400 MHz. X-ray crystal-
lography: All the measurements were performed using
graphite-monochromatized MoKa radiation at 150 K using a
Bruker D8 APEX-II equipped with a CCD camera. The
structure was solved by direct methods (SHELXS) and
refined by full-matrix least-squares techniques against
23
F2 (SHELXL).[ ]
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