1H-1,2,4-diazaphospholes: Synthesis, structural characterization, and DFT calculation

Article abstract of DOI:10.1016/j.molstruc.2013.10.063

A few 1H-1,2,4-diazaphospholes H[3,5-R₂dp] (R = methyl (5a), p-tolyl (5b), 1-naphthyl (5c), 2-furanyl (5d), 2-thienyl (5e), and isopropyl (5f)) were prepared and structurally characterized by a substantial experimental modification of the synth

Full text of DOI:10.1016/j.molstruc.2013.10.063

Accepted Manuscript
1
H-1,2,4-Diazaphospholes: Synthesis, Structural Chracterization, and DFT Cal-
culation
Jun-Wen Wang, Ling-Yan Ding, Bing-Qiang Wang, Yao-Yun He, Yue Guo,
Xue-Feng Jia, Wenjun Zheng
PII:
S0022-2860(13)00922-8
DOI:
http://dx.doi.org/10.1016/j.molstruc.2013.10.063
MOLSTR 20120
Reference:
To appear in:
Journal of Molecular Structure
Received Date:
Revised Date:
Accepted Date:
15 May 2013
3 October 2013
25 October 2013
Please cite this article as: J-W. Wang, L-Y. Ding, B-Q. Wang, Y-Y. He, Y. Guo, X-F. Jia, W. Zheng, 1H-1,2,4-
Diazaphospholes: Synthesis, Structural Chracterization, and DFT Calculation, Journal of Molecular Structure
(
2013), doi: http://dx.doi.org/10.1016/j.molstruc.2013.10.063
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1
H-1,2,4-Diazaphospholes: Synthesis, Structural
Chracterization, and DFT Calculation
a,b
a,b
b
a,b
a,b
Jun-Wen Wang, Ling-Yan Ding, Bing-Qiang Wang, Yao-Yun He, Yue Guo, Xue-Feng
a,b
,a,b,c
Jia, and Wenjun Zheng
a
Institute of Organic Chemistry, Shanxi Normal University, Gongyuan Street 1, Linfen, Shanxi
Province 041004, Peoples Republic of China
b
School of Chemical and Materials Science, Shanxi Normal University, Gongyuan Street 1,
Linfen, Shanxi Province 041004, Peoples Republic of China
c
Key Laboratory of Magnetic Molecules and Magnetic Information Material, Ministry of
Education, Peoples Republic of China
E-mail: wjzheng@sxnu.edu.cn
KEYWORDS: DFT calculation, 1H-1,2,4-diazaphosphole, Hydrogen bonding, Synthesis, X-ray
diffraction analysis
1

Abstract: A few 1H-1,2,4-diazaphospholes H[3,5-R dp] (R = methyl (5a), p-tolyl (5b),
2
1
-naphthyl (5c), 2-furanyl (5d), 2-thienyl (5e), and isopropyl (5f)) were prepared and structurally
characterized by a substantial experimental modification of the synthetic protocol. The molecules
of all compounds are linked into oligomers via the bridges of NHN hydrogen bonds in solid
state. The tetrameric feature of 5a, and 5df represents a new motif of hydrogen-bonded
1
H-1,2,4-diazaphospholes in solid state. The DFT calculation at the B3LYP/6-311++G** level
suggested the possible proton disorder with intermolecular solid state proton transfer (ISSPT)
between 1H-1,2,4-diazaphosphole rings.
2

1
. Introduction
Heterocycles containing a low-coordinated phosphorus center have found widespread
1
2
3
applications ranging from ligand in metal complexes, devices in material science to
4
7
fundamental importance in theoretical and experimental research. 1H-1,2,4-Diazaphosphole
H[3,5-R dp], exhibiting electrochemical and coordinating properties endowed by the
2
2
3
low-coordinated P(  ) atom, represents a class of unique aromatic five-membered heterocyclic
8
,6
9
system, and may be viewed as a hybrid molecule of the corresponding phosphole and
1
0
5
pyrazole (P-doping pyrazole), or as a 1H-1,2,4-trizole (pyrazole) analogue in which 4-nitrogen
2
3
7
atom (4-CH group) is replaced by a phosphorus atom (  ) (Chart 1). The recent theoretical
analysis has suggested that the 1H-1,2,4-diazaphosphole unit is a highly potential efficient
electronic transfer bridge which can greatly enhance the second-order polarizability (β) values of
11
organic molecules for obtaining good second-order nonlinear optical (NLO) properties.
Especially, as attested to by a few of the reports on the emerging application to complexes and
1
2
catalysis as a 6-aromatic monoanionic ligand, the 1H-1,2,4-diazaphosphole can be even
1
3
reduced to a persistent dianionic radical form, of which the electronic structure disobeys 4n + 2
1
3
2
3
14
Hückel rule. This unusual result, upon the low-coordinated phosphorus (  ) atom, has
1
3
attracted interest in an extensive family of persistent 1,2,4-diazaphosphole dianion radicals that
1
5
16
are potential in polymerization catalysis, electron-reservoir complexes, magnetic molecular
1
7
17
18,19
materials, conducting materials, and biochemistry.
Moreover, being an isoelectronic
species of the 1H-1,2,4-triazole, pyrazole, and phosphole, the 1H-1,2,4-diazaphosphole with the
1
4
unique electronic structure is expected to be a motif in a number of small organic molecules,
or to be an excellent candidate for the investigation of intermolecular solid state proton transfer
2
0,21
22
(
ISSPT),
and may possess a wide range of agricultural, pharmaceutical and catalytic
4
a,9,23
activities.
However, in contrast to 1H-1,2,4-triazole, pyrazole, and phosphole, the
1
H-1,2,4-diazaphosphole chemistry is still at its early stage to date, and attempts to synthesize an
extensive family of 1H-1,2,4-diazaphospholes have been unsuccessful since several H[3,5-R dp]
2
8
,24
(R = H, Ph, tBu) were reported in 1984.
This has prompted us to prepare a few particularly
designed 1H-1,2,4-diazaphospholes incorporating varied substituents at 3,5-positions with steric
3

and electronic effects, which are expected to be highly potential building blocks for further
2
5,1114,2022
synthetic chemistry.
Herein, we report the synthesis of
a
few
1
1
H-1,2,4-diazaphopholes H[3,5-R dp] with a variant protocol (R = methyl (5a), p-tolyl (5b),
2
-naphthyl (5c), 2-furanyl (5d), 2-thienyl (5e), isopropyl (5f)). The X-ray diffraction analysis
revealed that molecular structures of 5a-f present intermolecular interactions with ISSPT or with
NHN hydrogen bonding.
Chart 1.
2
．Experimental
2
.1. General methods
All manipulations were carried out in an argon atmosphere under anaerobic conditions using
standard Schlenk, vacuum line and glove box techniques. Solvents were distilled over
1
31
1
13
1
appropriate drying agents under argon prior to use. H, P{ H }, and C{ H} NMR spectra were
1
31
1
recorded on a Bruker AVANCE600 spectrometer ( H NMR(600 MHz), P{ H } NMR(243
1
3
1
MHz ), and C{ H} NMR(150 MHz)) and chemical shifts reported in ppm.
2
.2. General procedure for the preparation of compound 3
To a solution of the corresponding N,N-dimethylamide (2, 187.0 mmol) in anhydrous ether
(500 mL), oxalyl chloride (412.0 mmol) was slowly added under the stirring by a syringe at room
temperature. After gas evolution ceased the suspension was stirred for further 6 hours and then
filtered. The white solid was washed with anhydrous ether (20 mL  3) and dried in vacuum to
afford 3 as pure solid.
1
2
.2.1. α-Chloro-N,N-dimethyl-p-tolylmethanaminium chloride (3b): M.p. = 8083°C; H NMR
4

(
CDCl , ppm) δ = 7.84, (d, 2 H, Ph), 7.33 (d, 2 H, Ph), 3.99 (s, 3 H, NCH ), 4.01 (s, 3 H, NCH ),
3
3
3
1
3
1
2
1
.40 (s, 3 H, CH Ph); C{ H} NMR (CDCl , ppm) δ = 173.38 (ClC), 146.45, 129.99, 129.77,
3 3
29.01, 127.75 (5s, CPh), 49.93 (s, NC), 49.06 (s, NC), 21.85 (s, CCH ). Anal. Calcd. For
3
C H NCl : C 55.06, H 6.01, N 6.42; Found: C 55.28, H 6.09, N 6.35.
10
13
2
1
2
.2.2. α-Chloro-N,N-dimethyl-(1-naphthyl)methanaminium chloride (3c): M.p. = 8587°C; H
NMR (CDCl , ppm) δ = 8.47, 8.09, 7.94, 7.68, 7.587.62 (m, 7 H, 1-naphthyl ring), 4.43 (s, 3 H,
3
1
3
1
NCH ), 3.92 (s, 3 H, NCH ); C{ H} NMR (150 MHz, CDCl , ppm) δ = 173.34 (s, CCl),
3
3
3
1
1
5
34.10, 133.20, 129.40, 129.20, 128.20, 127.98, 125.30, 124.80, 123.50 (9s, C atoms on
-naphthyl ring), 49.77 (s, NC), 49.21 (s, NC). Anal. Calcd. For C H NCl : C 61.43, H 5.16, N
1
3
13
2
.51; Found: C 61.32, H 5.10, N 5.60.
1
2
.2.3. α-Chloro-N,N-dimethyl-thiophylmethanaminium chloride (3e): M.p. = 120121°C; H
NMR (CDCl , ppm) δ = 8.43 (d, 1 H, CHCS), 8.19 (d, 1 H, CHS ), 7.31 (t, 1 H, CHCS), 4.26 (s,
3
1
3
1
3
H, NCH ), 4.09(s, 3 H, NCH ); C{ H} NMR (CDCl , ppm) δ = 162.60, 162.59 (d, CCl), (s,
3 3 3
CCl), 142.43, 141.97, 131.50, 130.13 (4s, C on 2-thienyl ring), 49.90 (s, NCH ). Anal. Calcd. For
3
C H NCl S: C 40.01, H 4.32, N 6.67; Found: C 40.13, H 4.22, N 6.72.
7
9
2
2
.3. General procedure for the preparation of compound 4
To solution of (100.0 mmol) in anhydrous acetonitrile (250 mL),
tris(trimethylsilyl)phosphine P(SiMe ) (3.644mmol/mL, 60.0 mmol) was slowly added by a
a
3
3
3
syringe within 1 hour. The volatile components were removed under reduced pressure (0.01
mmHg). The resulting residue was washed with anhydrous ether (10 mL  3) to give 4 as colored
solid.
2
.3.1. α-[[(Dimethylamino)ethylidene]phosphino]-N,N-dimethyl-methylmethanaminium chloride
1
(
4a): M.p. = 126128°C; H NMR (CDCl , ppm) δ = 3.53 (s, 6 H, NCH ), 3.52 (s, 6 H, NCH ),
3
3
3
5

3
1
1
13
1
2
1
.77 (s, 6 H, CCH ); P{ H} NMR (CDCl , ppm) δ = 81.93(s); C{ H} NMR (CDCl , ppm) δ =
3 3 3
71.50, 170.40 (2s, NCP), 43.69 (s, NCH ), 38.02 (s, NCH ), 21.50 (s, CH ). Anal. Calcd. For
3
3
3
C H ClN P: C 46.05, H 8.69, N 13.42; Found: C 45.95, H 8.75, N 13.01.
8
18
2
2
.3.2. α-[[(Dimethylamino)-p-tolyl-methylene]phosphino]-N,N-dimethyl-p-tolyl-methanaminium
1
chloride (4b): M.p. = 140143°C; H NMR (CDCl , ppm) δ = 6.25, 5.95 (m, 8 H, Ph ring), 3.26
3
3
1
1
(
s, 6 H, NCH ), 2.65 (s, 6 H, NCH ), 1.70 (s, 6 H, p-tolylCH ); P{ H} NMR (CDCl , ppm) δ
3
3
3
3
1
3
1
=
114.30(s); C{ H} NMR (CDCl , ppm) δ = 204.11, 203.65 (2s, NCP), 140.19, 134.78, 128.19,
3
1
27.58 (4s, C on p-tolyl rings), 46.22 (s, NCH ), 46.03 (d, NCH ), 45.57 (s, NCH ), 20.90 (s,
3 3 3
p-tolylCH ). Anal. Calcd. For C H ClN P: C 66.57, H 7.26, N 7.76; Found: C 66.49, H 7.34,
3
20 26
2
N 7.59.
2
.3.3.
α-[[(Dimethylamino)-1-naphthyl-methylene]phosphino]-N,N-dimethyl-1-naphthyl-
1
methanaminium chloride (4c): M.p. = 184187°C; H NMR (CDCl , ppm) δ = 7.327.26, 7.05,
3
3
1
1
6
.90, 6.49 (m, 14 H, 1-naphthyl), 3.93 (s, 6 H, NCH ), 2.82 (s, 6 H, NCH ); P{ H} NMR
3 3
1
3
1
(
CDCl , ppm) δ = 117.45(s); C{ H} NMR (CDCl , ppm) δ = 203.16, 202.67 (2s, NCP), 133.53,
3
3
1
33.49, 131.69, 129.61, 128.86, 128.87, 128.01, 127.61, 127.41, 126.50, 124.85, 124.57 (12s, C
on 1-naphthyl rings), 46.34, 46.12 (d, NCH ), 46.07 (s, NCH ). Anal. Calcd. For C H ClN P: C
3
3
26 26
2
7
2.13, H 6.05, N 6.47; Found: C 72.35, H 6.13, N 6.38.
2
.3.4. α-[[(Dimethylamino)-furanyl-methylene]phosphino]-N,N-dimethyl-furyl-methanaminium
1
chloride (4d): M.p. = 155157°C; H NMR (CDCl , ppm) δ = 7.14, 6.39, 6.04 (m, 6 H, 2-furyl),
3
3
1
1
13
1
3
.48 (s, 6 H, NCH ), 3.13 (s, 6 H, NCH ); P{ H} NMR (CDCl , ppm) δ = 95.28(s); C{ H}
3 3 3
NMR (CDCl , ppm) δ = 188.11, 187.65 (2s, NCP), 147.59, 121.26, 112.46 (3s, C on 2-furanyl
3
rings), 46.65, 46.81 (d, NCH ), 46.23 (s, NCH ). Anal. Calcd. For C H ClN O P: C 53.77, H
3
3
14 18
2
2
5
.80, N 8.96; Found: C 53.89, H 5.71, N 8.84.
6

2
.3.5.
α-[[(Dimethylamino)-thienyl-methylene]phosphino]-N,N-dimethyl-thiophyl-
1
methanaminium chloride (4e): M.p. = 172174°C; H NMR (CDCl , ppm) δ = 7.51, 6.85, 6.71
3
3
1
1
(
m, 6 H, 2-thienyl), 3.80 (s, 6 H, NCH ), 3.44 (s, 6 H, NCH ); P{ H} NMR (CDCl , ppm) δ =
3 3 3
1
3
1
1
1
31.3(s); C{ H} NMR (CDCl , ppm) δ = 194.60, 194.15 (2s, NCP), 139.18, 133.61, 131.36,
3
28.84 (4s, C on 2-thienyl), 47.36 (s, NCH ), 46.21 (s, NCH ). Anal. Calcd. For C H ClN S P:
3
3
14 18
2 2
C 48.76, H 5.26, N 8.12; Found: C 48.83, H 5.32, N 8.07.
2
.3.6.
α-[[(Dimethylamino)-iso-propyl-methylene]phosphino]-N,N-dimethyl-iso-propyl-
1
methanaminium chloride (4f): M.p. = 101103°C; H NMR (CDCl , ppm) δ = 3.37 (br, 12 H,
3
3
1
1
NCH ), 2.49, 3.07 (m, 2 H, CH), 1.19 (d, 12 H, CCH ); P{ H} NMR (CDCl , ppm) δ = 31.8(s);
3
3
3
1
3
1
1
1
C{ H} NMR (CDCl , ppm) δ = 221.23 (d, J
= 6.0 Hz), 210.56 (d, J
= 6.0 Hz, NCP),
3
PC
PC
3
7.22 (s, NCH ), 37.09 (s, NCH ), 22.04 (s, CCH ), 21.51 (s, CH ). Anal. Calcd. For
3 3 3 3
C H ClN P: C 54.43, H 9.90, N 10.58; Found: C 54.50, H 9.81, N 10.65.
12
26
2
2
.4. General procedure for the preparation of compound 5
To a solution of 4 (10.0 mmol) in 100 mL chloroform, anhydrous hydrazine (20.0 mmol) was
added slowly. The reaction mixture was stirred for 24 h at room temperature, and then heated to
reflux for 48 h (only for 4a). After the volatile components were removed under reduced pressure,
water (50 mL) was added to the resulting residue. The mixture was extracted with ether (3 × 20
mL). The combined organic layers were dried with MgSO , filtered, and the solvent was removed
4
under reduced pressure. The resulting solid was purified by the recrystallization from the mixed
solvents of ethyl acetate and petroleum ether (1:1) or by sublimation in high vacuum (0.01
mmHg) to afford 5a at 80°C (5c at 140°C, 5d at 210°C, 5e at 185°C, and 5f at 45°C) as pure
white solid.
1
2
.4.1. 1H-3,5-dimethyl-1,2,4-diazaphosphole (5a): M.p. = 99101°C. H NMR (CD Cl, 23°C): δ
3
3
31
1
=
11.21 (br., 1 H, NH), 2.55 (d, 6 H , J = 9.0 Hz, CH ) ppm. P{ H} NMR (CD Cl, 23°C):
PH
3
3
7

13
1
δ = 81.95 (sept. J = 9.0 Hz). C{ H} NMR (CD Cl, 23 °C): δ = 15.97 (very br., δ = 0.4 ppm,
3
1/2
7b
CH ), 175 (br., PCN) ppm. Anal. Calcd. For C H N P: C 42.11, H 6.18, N 24.55; Found: C
3
4
7
2
4
1.95, H 6.08, N 24.46.
1
2
.4.2. 1H-3,5-di(p-tolyl)-1,2,4-diazaphosphole (5b): M.p. = 257258ºC. H NMR (CD Cl,
3
3
3
2
3 °C): δ = 11.5 (br., NH), 7.73 (d, J
= 7.2 Hz, 4 H, ArH), 7.27 (d, J
= 7.2 Hz, 4 H,
PH
PH
3
1
1
13
1
ArH), 2.42 (s, 6 H, CH ); P{ H} NMR(CDCl , 23 °C): δ = 72.51 (s); C{ H} NMR (CDCl
3
3
3,
7
c
2
3°C): δ = 178.20 (s, PCN), 139.22, 129.72, 126.09, 126.03 (4s, C for phenyl rings), 21.34 (s,
CH ). Anal. Calcd. For C H N P: C 72.17, H 5.68, N 10.52; Found: C 71.98, H 5.60, N 10.42.
3
16 15
2
1
2
.4.3. 1H-3,5-di(1-naphthyl)-1,2,4-diazaphosphole (5c): M.p. = 167169°C. H NMR (CD Cl,
3
3
2
3°C): δ = 9.5 (very br., 1 H, NH), 8.44 (d, J
= 7.8 Hz, 2 H), 7.927.94 (m, overlapped, 4
PH
3
31
1
H), 7.76 (d, J = 7.0 Hz, 2 H), 7.547.57 (m, overlapped, 6 H). P{ H} NMR (CD Cl, 23°C):
PH
3
13
1
1
δ = 94.33 (s) ppm. C{ H} NMR (CD Cl, 23 °C): δ = 175.99 (d, J = 73.5 Hz, PCN), 131.37
3
PC
2
3
3
(
d, J = 16.5 Hz, ipsoC), 127.82 (d, J = 24 Hz, PCC), 125.55 (d, J = 17.4 Hz, PCC),
PC
PC
PC
4
1
31.15 (d, J
= 6.0 Hz, PCCC), 125.32, 126.26, 126.91, 128.48, 129.49, 133.97 (6s, C for
PC
naphthyl rings) ppm. Anal. Calcd. For C H N P: C 78.10, H 4.47, N 8.28; Found: C 78.40, H
2
2
15
2
4
.48, N 8.24.
1
2
.4.4. 1H-3,5-difuranyl-1,2,4-diazaphosphole (5d): M.p. = 235237°C. H NMR (CD Cl, 23°C):
3
4
3
δ = 11.91 (br., 1 H, NH), 7.43 (d, J
= 18 Hz, 2 H), 6.79 (d, J
= 36.0 Hz, 2 H), 6.453,
PH
PH
4
31
1
13
1
6
.447 (dd, J = 18.0 Hz, 2 H) ppm. P{ H} NMR (CD Cl, 23°C): δ = 69.85 (s) ppm. C{ H}
PH
3
3
NMR (CD Cl, 23 °C): δ = 142.62 (d, J
= 12.0 Hz, PCCC), 148.52 (br., ipsoC), 166.0 (br.,
3
PC
PCN), 142.61, 111.95, 108.17 (3s, C for furanyl rings) ppm. Anal. Calcd. For C H N O P: C
1
0
7
2
2
5
5.06, H 3.23, N 12.84; Found: C 54.86, H 3.20, N 12.75.
1
2
.4.5. 1H-3,5-dithienyl-1,2,4-diazaphosphole (5e): M.p. = 206207°C. H NMR (CD Cl, 23°C):
3
8

3
4
δ = 11.0 (br., 1 H, NH), 7.43 (d, J
= 36 Hz, 2 H), 7.33 (d, J
= 48 Hz, 2 H), 7.07 (dd,
PH
PH
3
1
1
13
1
overlapped, 2 H) ppm. P{ H} NMR (CD Cl, 23°C): δ = 74.96 (s) ppm. C{ H} NMR (CD Cl,
3
3
1
2
3
2
4
3°C): δ = 170.5 (d, J = 51.0 Hz, PCN), 126.33 (d, J = 12.0 Hz, PCC), 125.76 (d, J
=
PC
PC
PC
.5 Hz, PCCC), 127.99 (s, C for thienyl rings), 126.35 (br., CS) ppm. Anal. Calcd. For
C H N PS : C 47.99, H 2.82, N 11.19; Found: C 47.76, H 2.83, N 11.14.
10
7
2
2
1
2
.4.6. 1H-3,5-diisopropyl-1,2,4-diazaphosphole (5f): M.p. = 6265 °C. H NMR (CD Cl, 23°C):
3
3
31
1
δ = 11.4 (br., 1 H, NH), 1.38 (d, 6 H , J = 6.6 Hz, CH ), 3.22 (sept. 2 H, CH), P{ H} NMR
PH
3
1
3
1
3
(
CD Cl, 23°C): δ = 66.85 (s). C{ H} NMR (CD Cl, 23 °C): δ = 24.43, 24.39 (d, J = 6.0 Hz,
3 3 PC
2
1
CH ), 30.85, 30.75 (d, J = 15.0 Hz, CH), 186.8, 186.5 (d, J = 45.0 Hz, PCN) ppm. Anal.
3
PC
PC
Calcd. For C H N P: C 56.46, H 8.88 N 16.46; Found: C 56.53, H 8.30, N 16.61.
8
15
2
2
.5 Computational details
To understand the nature of proton disorder and the intermolecular hydrogen bonds about 5bc,
we have performed a series calculations on two static hydrogen-bonding models 5bm (5cm)
2
5
using Gaussian 03 program package. We first compared the results with B3LYP and MP2
methods on a simplified 1H-1,2,4-diazaphosphole dimer for the geometrical optimization,
respectively. Both of the methods give, however, almost identical values, indicating that B3LYP
2
6
method is reliable to obtain the geometries of 5bm and 5cm. Therefore, the monomer and
2
6
dimer of 5bm and 5cm are optimized at the B3LYP/6-311++G** level. All harmonic
frequencies are real for the stable structures.
2
.6 X-ray crystallography
The single-crystal X-ray diffraction data of 5 were collected using a Bruker SMART CCD
diffractometer operating at 50 kV and 20 mA using Mo-Kα radiation (λ = 0.71073 Å). An
empirical absorption correction was applied using the SADABS program. The structures were
solved by direct methods, and all non-hydrogen atoms were subjected to anisotropic refinement
9

2
27
by full-matrix least squares on F using the SHELXTL package. The H atoms were included in
calculated positions with isotropic thermal parameters related to those of the supporting carbon
atoms but were not included in the refinement. All non-hydrogen atoms were found from the
difference Fourier syntheses. All calculations were performed using the Bruker Smart program.
CCDC 938848(5a), 938849(5b), 938850(5c), 938851(5d), 938852(5e), and 938853(5f)
contain the supplementary crystallographic data for compound 5, respectively. These data can be
obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44
1
223 336 033; or email: data_request@ccdc.cam.ac.uk.
3
. Results and discussion
3
.1 Synthesis
As shown in Scheme 1, N,N-dimethylimidoyl chloride 3 was prepared by the acylation of
RCOCl (1) with Me NH, followed treatment with oxalyl chloride, or simply by the reaction of
2
2
8,29
the commerical available N,N-dimethylamide RCONMe (2)
and oxalyl chloride in
2
anhydrous ether. Compound 3 presents colors in green (3a), white (3b, 3f), yellow-white (3c),
30
and milky (3d, 3e), respectively. The treatment of 3af with P(SiMe3)3 in anhydrous
acetonitrile afforded the corresponding 1,3-bis(dimethylamino)-2-phosphoaallyl chlorides 4a
31
1
(
black), 4bf (yellow to reddish-brown) in good yields. The chemical shifts of 4af in P{ H}
NMR spectra extend over a remarkably large range (Table 1).
Scheme 1. Synthesis of compounds 35, and the possible dynamic situation of 5 in solid state.
1
0

Table 1. Preparation of compounds 3, 4, and 5 with varied substituted groups
3
1
Entry reactant reagent
R
product
p-tolyl 3b
P NMR, δ (ppm)
Yield (%)
75
1
2
3
4
5
6
7
8
9
1
2b
2c
2e
3a
3b
3c
3d
3e
3f
Me NH

2
Me NH
1-naphthyl 3c
2-thienyl 3e
methyl 4a

79
2
Me NH

89
2
P(SiMe3)3
P(SiMe3)3
P(SiMe3)3
P(SiMe3)3
P(SiMe3)3
P(SiMe3)3
H NNH
89.6(s)
105.6(s)
117.9(s)
95.3(s)
131.0(s)
93
p-tolyl 4b
88
1-naphthyl 4c
2-furanyl 4d
2-thienyl 4e
isopropyl 4f
methyl 5a
78
73
78
31.8(s)
83
3
0
4a
4b
4c
4d
4e
4f
81.95(sept.), J = 9.0Hz
72.5(s)
16
2
2
2
2
2
2
2
11
H NNH
2
p-tolyl 5b
79
1
1
1
1
2
3
4
5
H NNH
1-naphthyl 5c
2-furanyl 5d
2-thienyl 5e
isopropyl 5f
94.3(s)
85
2
H NNH
2
69.9(s)
80
H NNH
2
75.0(s)
82
H NNH
2
66.9(s)
61
The titled compounds 5af were prepared by the reaction of dry hydrazine at ambient
temperature with 4bf and at reflux with 4a (Scheme 1), respectively. The small amount of
moisture in the system, such as using hydrazine hydrate, will lead to the significant yield
decrease of 5, likely due to hydrolysis of reactant 4. Compound 5 can be isolated by the
11

sublimation (except for 5b) in high vacuum using a Büchi Glass Oven (B585) or by the
recrystallization from the mixed solvents of ethyl acetate and petroleum ether (1:1), exhibiting
sharp, reversible melting points at 99C (5a), 257C (5b), 167C (5c), 235C (5d), 206C (5e),
and 63C (5f). The compound 5 is very soluble in CH Cl and CH Cl and well soluble in THF
3
2
2
and ether, but not soluble in n-hexane. All compounds were obtained in fair or good yields
except for 5a (Table 1). We tried to improve the low yield of 5a by optimizing the reaction
condition or by using varied amines such as diphenylamine or di-c-hexylamine as a starting
material, but not successful.
3
.2 NMR Spectra
1
31
1
13
1
H, P{ H}, and C{ H} NMR spectra and element analysis data are consistent with the
2
6
13
1
formulas of 3be, 4, and 5. Compounds (4a-f) are asymmetric cations, therefore, in C{ H}
1
NMR spectra, two doublets are expected for two equivalent carbon atoms ( J ) with different
P-C
1
13
1
JP-C values. As expected, two doublets were observed for 4f in C{ H} NMR spectrum but only
two singlets were found for 4a-4e, probably due to the consequence of a dynamic process in
1
solution. In the H NMR spectra, compound 5 exhibits broad resonances at δ = 9.511.9 ppm
(
CDCl ) for NH absorptions (one doublet at δ = 2.56 ppm (CDCl ) assigned to CH groups for
3
3
3
5
a), indicating the dynamic process of NHN hydrogen bonds (PCH coupling) in the
3
1
3
1
solution. In the C{ H} NMR spectrum of 5a, an unusual broad signal at δ = 15.97 ppm (δ
=
/2
1
0
.4 ppm) was observed, attributable to the CH groups in the solution on account of the dynamic
3
process of tautomeric 5a (probably due to overlapped PC coupling signals) being relatively
13
1
31
1
slow on the C{ H} NMR time scale. The P{ H} NMR septet resonance at δ = 81.95 ppm
3
(
JPH = 9.0 Hz) for 5a seems due to the results of the spin coupling with the six methyl protons
1
8
(
versus the triplet resonance at δ = 82.8 ppm ( J
= 44.1 Hz) for PCH in H[dp]) while the
PH
3
1
1
exclusively observed sharp P{ H} NMR single resonances suggest the formation of 5b5f
Table 1). However, attempt to elucidate the dynamic situation of NHN hydrogen bonding
was not successful in the solutions at varied temperatures and only the broader resonances were
(
1
2

observed for NH absorptions. At this point, we have noted that the dynamic process for NHN
1
5
15
hydrogen bonds of N labeled pyrazoles was elucidated by N NMR spectroscopy under varied
2
1
1
temperatures. Notably, the expected doublets resulting from PC coupling ( JPC) were not
7
b,26
observed for 5a and 5b, probably due to the broad resonances.
3
.3 Structure conformatios in solid state
The crystal structures of 5a, and 5df featured cyclic tetramers that present a pseudo 42m (D )
2
h
internal symmetry, of which only a 2-fold axis remains as a crystallographic element while 5bc
2
6,27
formed cyclic dimers with a pseudo 2-fold axis (Table 2).
All structures present exclusively
the NHN hydrogen bond bridges in solid state, by which the molecules are linked into
oligomers. The intermolecular hydrogen bonds of 5 in the solid state are evidenced by the special
2
6
molecular orientation in the packing diagram. No any PH tautomeric structure was observed,
3
1
consistent with the recently theoretical calculation results. The small difference between two
nitrogen internal angles for 5 (except for 5f) is likely attributable to the disordered NH protons
(Table 3).
Table 2. Crystal and Data Collection Parameters of Compounds 5a-f
Compounds
formula
fw
5a
5b
5c
5d
5e
5f
C H N P
4
C H N P
32 30
C H N P
22 15
C H N O P
10
C H N PS
10
C H N P
8
7
2
4
2
2
7
2
2
7
2
2
15
2
114.09
532.54
338.33
218.15
250.27
170.19
Cryst. size (mm)
Cryst. Syst.
Space group
a (Å)
0.10 × 0.03 × 0.03
Triclinic
P-1
0.27 × 0.25 × 0.18
Triclinic
P-1
0.49 × 0.36 × 0.10 0.08 × 0.03 × 0.02 0.45 × 0.28 × 0.11
0.30 × 0.20 × 0.20
Monoclinic
P2(1)/c
Monoclinic
P2(1)/c
8.670(2)
8.036(2)
24.936(7)
90
Monoclinic
C2/c
Monoclinic
C2/c
8.6220(5)
9.8843(6)
15.4697(10)
80.166(4)
89.008(4)
75.641(4)
1257.98(13)
8
9.6653(16)
9.6809(16)
16.449(3)
74.227(3)
75.002(3)
75.181(3)
1402.0(4)
2
12.7274(2)
19.2423(3)
16.9663(3)
90
26.914(5)
9.9285(19)
20.764(4)
90
19.7027(18)
10.7761(10)
27.0431(18)
90
b (Å)
c (Å)
α(deg)
β(deg)
97.589(3)
90
93.2190(10)
90
126.155(2)
90
132.144(4)
90
γ(deg)
3
V (Å )
1722.2(8)
4
4148.57(12)
16
4480.0(15)
16
4257.3(6)
16
Z
-
3
Dc (g cm )
1.205
1.257
1.305
1.397
1.484
1.062
-
1
Absorption coefficient (mm ) 0.318
0.183
0.165
0.244
0.583
0.207
1
3

F (000)
480
560
704
1792
2048
1472
T (K)
296
298
298
296
298
238
range (deg)
reflns measured
unique reflns
θmax (deg)
1.34 – 25.00
17353
1.31 – 27.00
7460
2.37 – 25.50
8612
2.12 – 25.00
13345
3546
1.87 – 25.50
11531
4149
1.39 - 24.15
18218
4423
5883
3197
6806
25.00
27.00
25.50
0.0230
25.00
25.50
25.00
Rint
0.0435
0.0257
0.0283
0.0360
0.0691
Max and min Transmn
0.9905 and 0.9689
0.9678 and 0.9522
0.9837 and 0.9234 0.9951 and 0.9807 0.9386 and 0.7794
0.9598 and 0.9405
a
R1, wR2 [I > 2σ(I)]
0.0979, 0.2695
0.0859, 0.2478
0.0453, 0.1110
0.0652, 0.1820
0.0658, 0.1594
0.0618, 0.1243
b
R1, wR2 (all data)
0.1272, 0.2875
1.070
0.1239, 0.2892
1.098
0.0550, 0.1174
0.0957, 0.2122
1.036
0.1022, 0.1836
1.025
0.1848, 0.1729
0.954
GOF
1.031
0.342
–0.185
.
-
3
)
0.965
0.706
0.254
0.422
0.203
-
3
)
–0.345
–0.431
-0.262
-0.343
-0.195
a
b
2
2 2
2 2 0.5
R1 = Σ|Fo| –|Fc|/Σ|Fo|. wR2 = [Σw(Fo – Fc ) /Σw(Fo ) ]
As far as the molecular structure of 5a is concerned (Fig. 1), the influence of phosphorus atom
is manifested in the tetrameric conformation of 5a compared to that of cyclic trimeric
2
1
3
,5-dimethyl-pyrazole. At this point, the distorted tetrameric geometry of 5a may be less
2
1
favorable to the concerted proton migration as trimeric 3,5-dimethyl-pyrazole. The bond
lengths and angles of 5a (Table 3) are slightly longer and less acute than those found in H[dp]
(P(1)C(3) 1.710(3) Å, N(1)C(2) 1.305(3) Å, N(1)N(2) 1.323(3) Å, C(3)P(1)C(2),
2
0a
8
5.1(1)°).
Figure 1. Crystal structure of 5a. Bond distances [Å] and angles [deg.] are located in Table 3.
1
4

As illustrated in Figures 23, the average planes formed by p-tolyl (naphthyl) groups and the
heterocycle ring are not coplanar (twisted) in 5b (5c). The dihedral angles are likely caused by an
intramolecular interaction of adjacent groups due to a repulsive interaction between the CH of
2
0b
p-tolyl (or naphthyl) groups and the NH. The conformation of 5b is similar to that found in
2
0b
previously reported 1H-3,5-diphenyl-1,2,4-diazaphosphole. However, it is surprising that 5c
presents only one molecular conformation with much more twisted one (the average naphthyl
dihedral is 46.1(1)°), obviously rising from the steric effects of the bulky naphthyl groups. The
remarkable feature of the structures 5b-c is that the difference of the internal angles between at
N(1) and N(2) are much larger, for example in 5b (115.5(4)° vs. 111.1(4)°), than that found in 5a
(115.1(5)° vs. 112.2(6)°), probably suggesting that the tautomers are less stable (Table 3). The
bond lengths and angles of 5b and 5c (Table 3) are comparable with those found in H[3,5-Ph dp]
2
(P(1)C(1) 1.7404(18) Å, N(1)C(1) 1.329(2) Å, N(1)N(2) 1.341(2) Å, C(3)P(1)C(2),
2
0b
8
7.16(9)°).
Figure 2. Crystals structure of 5b. Bond distances [Å] and angles [deg.] are located in Table 3.
1
5

Figure 3. Crystal structure of 5c. Bond distances [Å] and angles [deg.] are located in Table 3.
Table 3. Selected Bond Distances [Å] and Angles [deg.] for 5
Compound N1N2
N1C2
P1C2
C3P1C2 C2N1N2 C3N2N1
5
5
5
5
5
5
a
b
c
d
e
f
1.352(7)
1.358(5)
1.346(2)
1.333(4)
1.349(4)
1.347(5)
1.319(8) 1.748(8)
1.351(5) 1.751(5)
1.327(2) 1.741(2)
1.331(4) 1.730(4)
1.323(4) 1.742(4)
1.337(5) 1.721(5)
87.2(3)
112.2(6)
111.1(4)
111.7(6)
111.6(3)
113.4(3)
109.9(5)
115.1(5)
115.5(4)
115.5(2)
114.6(3)
113.3(3)
116.0(5)
87.2(2)
87.21(8)
86.11(18)
86.63(17)
87.0(3)
1
6

Figure 4. Crystal structure of 5d. Bond distances [Å] and angles [deg.] are located in Table 3.
The crystal structures of 5d and 5e can be seen in Figures 4 and 5, respectively. The
crystallographic symmetry imposed a 2-fold axis through the molecules. The tetramers are held
together by four symmetry related hydrogen bonds. Due to the different orientation of two
furanyl (thienyl) groups to the heterocycle, there are two independent molecular conformations
for 5d (A and B ) and 5e (A ) and (B ), respectively. Two oxygen (sulfur) atoms at furanyl
5
d
5d
5e
5e
(thienyl) rings are at the orientation to the nigrogen atoms of the heterocycle (A) while one of
two oxygen (sulfur) atoms is at opposite position of nitrogen atoms (B). The tetrameric structural
conformation of 5d (5e) thus consists from two independent A and B, respectively. In sharply
contrast to the conformation of 5b, the furanyl and thienyl rings attached to the heterocycle are
almost coplanar (only slightly twisted) and the average dihedral angle of furanyl (thienyl) groups
and heterocycle ring is only 3.3(2)° (5d) (8.115(171)° for 5e), respectively, probably due to the
2
0b
absence of a repulsive interaction between the O(S) and the NH. The bond lengths and angles
of 5d and 5e (Table 3) are comparable with those found in H[3,5-tBu dp] (P(1)C(1) 1.737(5) Å,
2
2
0a
N(1)C(1) 1.330(5) Å, N(1)N(2) 1.360(5) Å, C(3)P(1)C(2), 87.3(2)°).
1
7

Figure 5. Crystal structure of 5e. Bond distances [Å] and angles [deg.] are located in Table 3.
Figure 6. Crystal structure of 5f. Bond distances [Å] and angles [deg.] are located in Table 3.
As shown in Figure 6, the molecular structure of 5f presents in a tetrameric conformation,
quite similar to that found in 5a. Unfortunately, we cannot compare the structure of 5f with that
of corresponding 1H-3,5-diisopropylpyrazole because the structure of the latter is still unknown
3
3
owing to its syrupy appearance. Only the structure of 1H-3,5-diisopropyl-4-nitropyrazole,
3
3
solved by X-ray powder diffraction analysis, was reported in a dimeric conformation. The
influence of the phosphorus atom is thus demonstrated again in the difference in the
3
3
conformation compared to that of dimeric 1H-3,5-diisopropyl-4-nitropyrazole. Notably, the
difference of the internal nitrogen angles is up to 7° (Table 3), significantly larger than those
found in 5a-e. This may suggest that compound 5f present much less intermolecular solid state
proton transfer (ISSPT) and the NH proton is thus much localized, probably owing to the bulky
isopropyl groups.
2
0b
Although the 5bc structures are somewhat similar to those of H[3,5-Ph dp] (two dimers),
2
2
0a
32
H[3,5-tBu dp] (dimer), and 3,5-di-tert-butylpyrazole (dimer), the present tetrameric feature
2
2
0a
of 5a, and 5df are in sharply contrast to the trimeric helix H[dp]
and trimeric
1
8

2
1a
3
,5-dimethylpyrazole, represents a new motif of hydrogen-bonded 1H-1,2,4-diazaphospholes
to date.
3
.4 Analysis of hydrogen bonding
On the basis of the difference between two nitrogen internal angles, the positions of NH
protons seemed neither localized nor freely refined. Nevertheless, the data are sufficient for a
general structural characterization and have presented some useful information for the
preliminary discussion of hydrogen bridging phenomena and proton disorder (Table 4).
Table 4. Geometrical parameters of 5bm and 5cm obtained at the B3LYP/6-311++G** level and
the corresponding experimental values of 5b and 5c (bond lengths (Å) and angles (°))
5
bm (R = p-tolyl)
5b
5cm (R = 1-naphthyl)
5c
monomercalcd dimercalcd
dimerexp
115.5(4)
111.1(4)
2.898
monomercalcd dimercalcd
dimerexp
115.5(2)
111.7(6)
2.823
CN(2)N(1)
CN(1)N(2)
N(1A)N(2B)
6-311++G**
6-311++G**
6-311++G**
118.9
109.4

118.1
110.0
2.940
119.1
109.4

118.3
110.1
2.925
Considering the proton is static, the optimized dimeric 5bm(5cm) structure is close to that of
monomeric 5bm(5cm), represented by a small difference (no more than 1°) at the corresponding
internal nitrogen angles, suggesting the hydrogen bonds are with the negligible effect on the
conformation. Showing a difference 9.5°, two internal nitrogen angles in monomeric 5bm are
2
3
1
18.9° and 109.4°, close to the ideal values of sp - and sp -hybridized nitrogen atoms,
respectively. Similarily, this difference is 8.1°(118.1°110.0°) in dimeric 5bm, only deviating
1
.4° from that of monomeric 5bm.
The experimental results shown, however, that the difference of two internal nitrogen angles is
only 4.4° for 5b, much smaller than the calculation value (9.5° and 8.1°) for monomeric and
dimeric 5bm. The significant differences between computational results of hydrogen-bonding
model 5bm and the experimental values are presumably ascribed to a certain degree of ISSPT in
crystal 5b, which results in an equalization of two internal nitrogen angles. In addition,
1
9

calculation results presented that the linear distance N(1A)···N(1B) between two diazaphosphole
rings is 2.940 Å, longer than the experimental value (2.898 Å). This change might be regarded as
the additional consequence of ISSPT. The calculation results for 5cm afforded the similar
conclusion to those of 5bm, presumably indicating that 5c are in an amount of dynamic proton
disorder with ISSPT as well.
Upon the experimental and calculating results, it can be concluded that a small difference of
two internal nitrogen angles origins to some extent from the hydrogen transfer (5a5e) while a
large difference of two internal nitrogen angles indicates the hydrogen bonding in solid state (5f).
The hydrogen bonding lengths, angles and the position of hydrogen atoms varied
2
6
significantly. For example, the nitrogen-hydrogen bond length d(D-H), hydrogen bond length
d(HA) and the hydrogen bond angle <(DHA) are 0.86 Å, 2.10 Å, and 150.1 for 5a whereas
these values are 1.00 Å, 1.93 Å, and 162 for 5f, respectively. The differences are probably due
to the effect of the substutuents at 3,5-position. It is notable that the bond lengths of NN
(1.333(4)1.352(7) Å), NC (1.319(8)1.351(5) Å), PC (1.721(5)1.751(5) Å) and the CPC
angle (86.11(18)87.21(8)) in 5 are comparable with those found in previously known
2
0
1
H-1,2,4-diazaphospholes, indicating the stability of the heterocycle.
We also calculated the NICS-values of the heterocyclic ring of 5bm. The difference between
the NICS(0)-values of monomeric and dimeric 5bm (-13.8 for monomeric 5bm and -12.2 for
dimeric 5bm) are rather small, so the hydrogen bonds have little effect on the aromaticity of the
heterocyclic system
4
. Conclusion
In summary, we have prepared and structurally characterized
a
few of
1
H-1,2,4-diazaphospholes, some of which present in a new motif with hydrogen bonds in solid
state. Both the experimental and theoretical results suggested that 5ae might be good candidates
for intermolecular solid state proton transfer (ISSPT). The successful preparation and isolation of
5
are a new addition to 1H-1,2,4-diazaphosphole chemistry, which are highly potential as
2
0

1
3,14
2,12,13
versatile building blocks in organic radical chemistry,
organometallic syntheses,
3
5,11
22
chemical materials,
drug design as well as intermolecular solid state proton transfer
2
021,31
study.
Acknowledgements
We gratefully acknowledge financial support from the Program for the Top Young and
Middle-aged Innovative Talents of Higher Learning Institutions of Shanxi (TYMIT 2011), the
Doctoral Foundation of Chinese Education Ministry (Grant No. 20111404110001), National
Natural Science Foundation of China (NSFC; Grant No. 21272143), and Program for Changjiang
Scholar and Innovative Research Team in University (IRT1156), State R&D Program of China
(No. 2012BAE06B08), and the State Key Laboratory of Advanced Technology for
Comprehensive Utilization of Platinum Metals.
Appendix A. Supplementary data
The X-ray crystallographic and spectroscopic data, the crystallographic plots of 5, and the
details of the density functional calculation for 5bm and 5cm are contained in the Supporting
Information. Supplementary data associated with this article can be found in the online version,
at http://dx.doi.org/xxx/xxx.
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6 (2010) 5976.
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2
2
0759; (b) The ovservation of the broad PC coupling ransonance ( JPC) for 5a is
likely the consequence of recording the spectrum around the coalescence temperature;
1
(
c) The expected doublet ( J
 53 Hz) was not observed for 5b, only a singlet was
PC
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2
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A few of asymmetrical 1H-3,5-disubstituted-diazaphospholes were prepared by [2+3]
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tBuCP (ClP=C(SiMe )Ph) with diazomethane RCH=N , but these routes are
3
2
exclusively involved in the cumbersome preparation of low-yield starting material
2
3

phosphaalkynes and phophaalkenes, see: (a) W. Rösch, M. Regitz, Angew. Chem. Int.
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[
[
26]
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See the Supporting Information.
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[
28]
While 2a and 2f are commercial available, compounds 2be were prepared referred to
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2
4

[
29]
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5
62 (2001) 11.
2
5

Highlight
►
Six previously inaccessible 1H-1,2,4-diazaphospholes were prepared and
structurally characterized.
All compounds are exclusively via the bridges of NHN hydrogen bonds in
solid state, by which the molecules are linked into oligomers.
The tetrameric feature of the compounds represents a new motif of
hydrogen-bonded 1H-1,2,4-diazaphospholes.
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