Efficient one-pot synthesis of diphenyl(pyrazin-2-yl)phosphine and its AgI, AuI and PtII complexes

Article abstract of DOI:10.1016/j.mencom.2020.05.014

A convenient one-pot synthesis of diphenyl(pyrazin-2-yl)phosphine has been developed based on reaction of Ph₃P with metallic lithium followed by treatment of the Ph₂PLi formed with 2-chloropyrazine. The Ag^I, Au^I and Pt^II chloride complexes derived from this phosphine have been synthesized and structurally characterized.

Full text of DOI:10.1016/j.mencom.2020.05.014

Mendeleev
Communications
Mendeleev Commun., 2020, 30, 305–307
Efficient one-pot synthesis of diphenyl(pyrazin-2-yl)phosphine
and its Agi, Aui and Ptii complexes
Maxim I. Rogovoy,a Maria P. Davydova,a Irina Yu. Bagryanskayab and Alexander V. Artem’ev*a
a A. V. Nikolaev Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences,
630090 Novosibirsk, Russian Federation. E-mail: chemisufarm@yandex.ru
b N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Russian Academy
of Sciences, 630090 Novosibirsk, Russian Federation
DOI: 10.1016/j.mencom.2020.05.014
A convenient one-pot synthesis of diphenyl(pyrazin-2-yl)-
phosphine has been developed based on reaction of Ph3P
with metallic lithium followed by treatment of the Ph2PLi
formed with 2-chloropyrazine. The Agi, Aui and Ptii chloride
complexes derived from this phosphine have been synthesized
and structurally characterized.
ꢀAgꢁClꢁLꢁꢂ
ꢀAuLClꢂ
N
N
N
PPhꢃꢄLi
ꢅꢆꢇ
N
PPh2
Cl
ꢀPtL2Cl2ꢂ
ꢀ
Keywords: diphenyl(pyrazin-2-yl)phosphine, lithiation, pyrazine, triphenylphosphine, silver(i) complexes, gold(i) complexes,
platinum(ii) complexes.
In the last two decades, pyridylphosphines have attracted interest
as ligands for diverse molecular complexes and coordination
polymers, which demonstrate excellent catalytic performance,1–8
luminescent properties,9–11 biological activity12 and magnetic
features.13 The specific disposition of the hard nitrogen and soft
phosphorus atoms in pyridylphosphines provides an opportunity
for design of poly- and heterometallic complexes including those
with metallophilic interactions.14,15 Thus, about seven hundred
mono- and polymetallic assemblies were prepared using
commercially available diphenyl(pyridin-2-yl)phosphine.16
By contrast, the corresponding diazine analogues bearing
pyrimidin-2-yl or pyrazin-2-yl substituents are much less
investigated. As an example, diphenyl(pyrimidin-2-yl)phosphine
was employed for the synthesis of Agi and Aui complexes,
Aui–Agi clusters as well as several dinuclear clusters.17–20
For diphenyl(pyrazin-2-yl)phosphine, only few [Cu2I2] type
complexes have been described.21,22 Concerning the synthesis of
these phosphines, it was described for diphenyl(pyrimidin-2-yl)-
phosphine only,18,20,23,24 while the preparation procedure and
spectral characteristics for diphenyl(pyrazin-2-yl)phosphine are
still lacking. Among the close analogues of the latter,
(3-methylpyrazin-2-yl)diphenylphosphine has been synthesized
via metalation of diphenylphosphine with BuLi followed by
reaction with 2-chloro-3-methylpyrazine.25
obtained after recrystallization from MeOH/CH2Cl2 being 20%.
The protocol elaborated has proved to be also relevant for
the synthesis of diphenyl(pyrimidin-2-yl)phosphine 2 from
2-chloropyrimidine in 36% non-optimized yield.
Phosphine 1 was isolated as colorless powder which slowly
oxidized in air to the corresponding phosphine oxide. Therefore,
although this phosphine can be handled in air, it should be
stored in inert atmosphere. The 1H, 13C{1H} and 31P{1H} NMR
as well as FT-IR spectra of compound 1 confirm its structure
and demonstrate the expected signal patterns. The structure of
phosphine 1 has also been established by X-ray diffraction
technique26,27 featuring trigonal pyramidal geometry of
phosphorus atom (Figure 1) with C–P–C angles ranging from
99.60(6) to 105.06(6)°.‡
Having in hands the title phosphine, we have surveyed its
coordination ability toward Agi, Aui and Ptii centers aiming to
N
N
N
Cl
i, ii
Ph3P
[Ph2PLi]
iii
N
PPh2
1 (20%)
Scheme 1 Reagents and conditions: i, Li, THF, 25 °C, 5 h; ii, Me3SiCl,
Herein, we report one-pot organometallics-free synthesis of
diphenyl(pyrazin-2-yl)phosphine 1 from air-stable and readily
available precursors. As our experiments have revealed, this
phosphinecanreadilybeaccessedviareactionof2-chloropyrazine
with lithium diphenylphosphide (Ph2PLi) in situ generated by
treatment of Ph3P with metallic lithium in THF (room
temperature, 5 h) followed by quenching of by-produced PhLi
with Me3SiCl (Scheme 1).† The non-optimized yield of 1
25 °C, 10 min; iii, 2-chloropyrazine, –20 to 25 °C, 3 h.
added on stirring, the resulting mixture was kept for 10 min and then
cooled down to –20 °C. Suspension of 2-chloropyrazine (5.7 g, 0.05 mol)
in THF (15 ml) was added dropwise, the resulting mixture was warmed
to room temperature and stirred for 3 h. Water (50 ml) was added and the
quenched mixture was extracted with CH2Cl2 (3×30 ml). The combined
organic extract was washed with H2O, dried with MgSO4 and evaporated
in vacuo. The crude residue was recrystallized from
MeOH–CH2Cl2 (5:1, v/v) affording colorless crystals of product 1.
Yield: 3.0 g (20%).
†
Synthesis of diphenyl(pyrazin-2-yl)phosphine 1. To a solution of
‡
Crysta–l data for 1. C16H13N2P, 0.50×0.20×0.10 mm, triclinic, space
triphenylphosphine (13.0 g, 0.05 mol) in absolute THF (50 ml), pieces of
lithium metal (1.2 g, 0.176 mol) were added, and the mixture was stirred
at room temperature for 5 h. Hereupon, Me3SiCl (5.4 g, 0.05 mol) was
group P1, a = 5.8848(3), b = 10.3298(5) and c = 11.9224(6) Å,
a = 69.607(2)°, b = 87.818(2)° and g = 83.598(2)°, V = 675.09(6) Å3,
© 2020 Mendeleev Communications. Published by ELSEVIER B.V.
on behalf of the N. D. Zelinsky Institute of Organic Chemistry of the
Russian Academy of Sciences.
– 305 –

Mendeleev Commun., 2020, 30, 305–307
Au
Cl
P
P
N
C
ꢀ
N
C
ꢀ
Figure 1 Molecular structure of diphenyl(pyrazin-2-yl)phosphine 1.
Figure 3 Molecular structure of complex [Au(1)Cl].
design new potential pre-catalysts and luminescent materials.§
The interaction of 1 with AgCl in a 1:1 molar ratio has been
found to afford tetranuclear [Ag4Cl4(1)4] complex (54% yield),
whose structure is represented by Ag4Cl4 cube supported by the
ligands in P-monodentate manner (Figure 2).‡ The closest
Ag···Ag contacts of 3.607 Å rule out the appearance of
argentophilic interactions within Ag4Cl4 module. Reaction of 1
with AuCl taken as Au(tht)Cl (tht = tetrahydrothiophene) results
in linear [Au(1)Cl] complex (81% yield)§ with the pyrazine ring
being non-coordinated (Figure 3).‡ The packing of [Au(1)Cl]
features no intramolecular aurophilic contacts, typically found in
crystals of such complexes. Again, the P-coordination of this
phosphine has been observed in cis-[Pt(1)2Cl2] complex
(Figure 4),‡ synthesized as CH2Cl2 solvate in 89% yield reacting
with Pt(COD)2Cl2 (COD = cycloocta-1,5-diene).§ Considering
the presence of one or several pyrazine rings in complexes
Pt
Cl
P
N
C
Figure 4 Molecular structure of complex cis-[Pt(1)2Cl2]·CH2Cl2, H atoms
and CH2Cl2 molecule are omitted for clarity.
presented, the latter seem to be promising metalloligands for
coordination-driven assembly of diverse metal-organic polymers.
The phase purity of the above complexes has been verified
by FT-IR, NMR and elemental analysis data.§ The FT-IR
spectra are in agreement with the X-ray results demonstrating
vibrations of the coordinated phosphine
1 backbone.
According to TGA and DTG analyses, the complexes have
high thermal stability and start to decompose at least above
200 °C. Complex cis-[Pt(1)2Cl2]·CH2Cl2 completely loses its
solvate molecule at ~150 °C. Complexes [Au(1)Cl] and
cis-[Pt(1)2Cl2] were soluble in organic solvents and thus were
investigated by NMR spectroscopy, which confirmed a
retention of their molecular structures upon dissolution.
1H NMR resonances of the complexes are shifted downfield
relative to those of free phosphine 1. The 31P{1H} NMR
spectra of [Au(1)Cl] and cis-[Pt(1)2Cl2] contain sharp singlets
at 26.97 and 6.79 ppm (cf. dP = –8.13 ppm for phosphine 1).
The 31P{1H} NMR peak of the PtII complex is flanked by a set
Ag
Cl
P
C
N
Figure 2 Molecular structure of complex [Ag4Cl4(1)4], H atoms are
omitted for clarity.
1
of 195Pt–31P satellites, with the specific JPt–P coupling
constant being 1835 Hz.
Z = 2, dcalc = 1.300 g cm–3, μ = 0.19 mm–1, data/restraints/parameters
3642/172/0, S = 1.03. Final R indices [I > 2s(I)]: R1 = 0.0431,
wR2 = 0.1002. R indices (all data): R1 = 0.0554, wR2 = 0.1087.
In summary, an efficient one-pot synthesis of
diphenyl(pyrazin-2-yl)phosphine has been elaborated starting
from available triphenylphosphine, 2-choropyrazine and
lithium metal. The coordination behavior of this polydentate
ligand has been examined in reactions with Agi, Aui and Ptii
chlorides, revealing the P-monodentate ligation pattern in the
complexes synthesized, namely [Ag4Cl4(1)4], [Au(1)Cl] and
cis-[Pt(1)2Cl2]. These findings contribute to the coordination
chemistry of P,N-ligands and to the synthesis of organo-
phosphorus compounds.
Crystal
data
for
[Ag4Cl4(1)4].
– C64H52Ag4Cl4N8P4,
0.20×0.20×0.10 mm, triclinic, space group P1, a = 11.5541(5),
b = 11.9705(5) and c = 24.1849(9) Å, a = 102.932(2)°, b = 99.327(2)°
and g = 91.431(2)°, V = 3210.5(2) Å3, Z = 2, dcalc = 1.686 g cm–3,
μ = 1.52 mm–1, data/restraints/parameters 14766/757/27, S = 1.021. Final
R indices [I > 2s(I)]: R1 = 0.0444, wR2 = 0.0984. R indices (all data):
R1 = 0.0838, wR2 = 0.1141.
Crystal data for [Au(1)Cl]. C16H13AuClN2P, 0.40×0.20×0.20 mm,
orthorhombic, space group Pna21, a = 12.939(2), b = 11.537(2) and
c = 10.849(2) Å, V = 1619.6(5) Å3, Z = 4, dcalc = 2.037 g cm–3,
μ = 9.34 mm–1, data/restraints/parameters 2816/155/23, S = 1.04. Final R
indices [I > 2s(I)]: R1 = 0.0475, wR2 = 0.0985. R indices (all data):
R1 = 0.0782, wR2 = 0.1121.
This work was supported by the Russian Science Foundation
(project no. 18-73-10086). We are grateful to the Multi-Access
Chemical Service Center, Siberian Branch of the Russian
Academy of Sciences, for the single crystal XRD analysis.
Crystal data for cis-[Pt(1)2Cl2]·CH2Cl2. C33H28Cl4N4P2Pt,
0.50×0.30×0.10 mm, monoclinic, space group P21/n, a = 10.6817(6),
b = 21.6533(11) and c = 14.4428(7) Å, b = 91.266(2)°, V = 3339.7(3) Å3,
Z = 4, dcalc = 1.749 g cm–3, μ = 4.65 mm–1, data/restraints/parameters
9232/397/0, S = 1.03. Final R indices [I > 2s(I)]: R1 = 0.0413,
wR2 = 0.0829. R indices (all data): R1 = 0.0787, wR2 = 0.0961.
CCDC 1966849–1966852 contain the supplementary crystallographic
data for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via http://www.ccdc.cam.ac.uk.
Online Supplementary Materials
Supplementary data associated with this article can be found
in the online version at doi: 10.1016/j.mencom.2020.05.014.
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