Isolation of Phosphinoimino-2-imidazoline

Article abstract of DOI:10.1002/zaac.201600184

The phosphinoimino-2-imidazoline 4 was synthesized by a salt elimination reaction between LiNIPr [NIPr = 1,3-bis(2,6-(diisopropylphenyl)imidazolin-2-ylidenamino)] and 2-chloro-1,3,2-diazaphospholene. DFT study revealed that the HOMO of 4 involves the lone pair orbitals on the P atom and the N atom at the exocyclic P–N bond. Compound 4 displays selectivity in coordinating to acids. Thus, the N atom at the exocyclic P–N bond coordinates to a hard acid (HCl) which eventually led to the cleavage of the P–N bond, while the central P atom forms a dative bond with a soft Lewis acid, BH₃.

Full text of DOI:10.1002/zaac.201600184

Journal of Inorganic and General Chemistry
www.zaac.wiley-vch.de
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
DOI: 10.1002/zaac.201600184
Isolation of Phosphinoimino-2-imidazoline
Che Chang Chong,[a] Rakesh Ganguly,[b] Yongxin Li,[b] and Rei Kinjo*[a]
Keywords: N-heterocyclic phosphanes; Coordination chemistry; Carbenes; Lewis bases; Lithium
Abstract. The phosphinoimino-2-imidazoline 4 was synthesized by a bond. Compound 4 displays selectivity in coordinating to acids. Thus,
salt elimination reaction between LiNIPr [NIPr = 1,3-bis(2,6-(diiso-
propylphenyl)imidazolin-2-ylidenamino)] and 2-chloro-1,3,2-diaza-
the N atom at the exocyclic P–N bond coordinates to a hard acid (HCl)
which eventually led to the cleavage of the P–N bond, while the central
phospholene. DFT study revealed that the HOMO of 4 involves the P atom forms a dative bond with a soft Lewis acid, BH3.
lone pair orbitals on the P atom and the N atom at the exocyclic P–N
which may undergo dimerization to form IV. However, inter-
Introduction
mediate V was not detected by any spectroscopy, presumably,
Chemistry of singlet nitrenes, monovalent and neutral nitro-
due to the rapid dimerization. In recent years, it has been dem-
gen compounds featuring two lone pairs and an unoccupied p-
onstrated that N-heterocyclic carbenes (NHCs) effectively sta-
orbital at the central N atom, has been of significant impor-
bilize highly reactive main group species thermodynamically
and kinetically.[9,10] We envisaged that the incorporation of
NHCs into phosphinonitrene V would stabilize the molecule,
allowing for the isolation. Thus, the carbene Ǟ NPR2 donation
would occur from the σ lone pair of carbene into the empty
orbital at the terminal N atom, and concomitantly one of elec-
tron lone pairs of the N atom could be delocalized over the
formally unoccupied p-orbital on the carbene carbon. Herein,
we report the synthesis, X-ray diffraction analysis, and compu-
tational studies of phosphinoimino-2-imidazoline (Figure 1).
We also describe its reactivity towards acids.
tance because transient nitrenes are widely involved in plethora
reactions ranging from C–H activation to ring expansion pro-
cesses.[1] Over the past decades, nitrenes have eluded isolation
due to their kinetic and thermodynamic instability, and they
could exist in stable form only at the metal coordination
sphere.[2] For metal-free derivatives, Dervan and co-workers
reported the aminonitrenes, N-(2,2,5,5-tetramethylpyrrolidyl)-
nitrene (Ia) and N-(2,2,6,6-tetramethylpiperidyl)nitrene (Ib),
which are stable enough to be characterized spectroscopically
at –78 °C in solution, but thermally unstable and could not
be isolated.[3] Recently, by using two imidazolidin-2-iminato
ligands, Bertrand and co-workers successfully prepared the
first room temperature stable phosphinonitrene II, in which the
P–N bond displays multiple bond character owing to the do-
nation of the P lone pair to the terminal central N atom.[4]
Despite the recent advancement in nitrene chemistry,[5] the
synthesis of nitrene derivatives still remains highly challeng-
ing.
In 2008, Gudat and co-workers reported that the thermolysis
of 2-azido-1,3,2-diazaphospholenes III afforded spirocyclic
cyclodiphosphaznes IV.[6,7] The formation of IV implied that
the reaction involved the phosphinonitrene monomer V,[8]
* Prof. Dr. R. Kinjo
E-Mail: rkinjo@ntu.edu.sg
[a] Division of Chemistry and Biological Chemistry
School of Physical and Mathematical Sciences
Nanyang Technological University
21 Nanyang Link
Figure 1. Transient (Ia–b) and isolable (II) nitrenes, and formation of
cyclodiphosphazenes IV from III.
Singapore 637371, Singapore
[b] NTU-CBC Crystallography Facility
Nanyang Technological University
21 Nanyang Link
Results and Discussion
Singapore 637371, Singapore
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/zaac.201600184 or from the au-
thor.
At first, we attempted a trapping reaction. In the presence
of excess amounts of carbene 1, thermolysis of compound III
Z. Anorg. Allg. Chem. 0000, ᭿,(᭿), 0–0
1
© 0000 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Journal of Inorganic and General Chemistry
www.zaac.wiley-vch.de
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
was examined in C6D6 solution at 65 °C (Scheme 1a). After
the reaction, only a complex mixture was obtained. Next, we
tested construction of the target molecule. Treatment of 2 with
nBuLi yielded the corresponding N-lithiated species LiNIPr
[NIPr = 1,3-bis(2,6-(diisopropylphenyl)imidazolin-2-ylidena-
mino)] in situ,[11] which was subsequently reacted with 3 in
THF to afford phosphinoimino-2-imidazoline 4 in 58% yield
(Scheme 1b). The 31P NMR spectrum of 4 in C6D6 shows a
resonance at δ = 90.0 ppm, which is slightly shifted upfield
compared to that in 3 (δ =157.3 ppm).
Figure 2. Crystal structure of 4 with thermal ellipsoids set at 30%
probability level. All hydrogen atoms are omitted for clarity. Selected
bond lengths /Å and angles /°: P1–N1 1.712(2), P1–N2 1.724(2), P1–
N3 1.694(2), N3–C11 1.283(3), C11–N4 1.388(3), C11–N5 1.394(3),
P1–N3–C11 127.30(17), N2–P1–N1 91.48(10), N4–C11–N5
103.86(19).
Scheme 1. Synthesis of 4.
A single crystal was obtained from a benzene solution of 4
and subjected to X-ray diffraction analysis (Figure 2). The cen-
tral phosphorus atom displays a distorted trigonal pyramidal
arrangement. The exocyclic P1–N3 bond length [1.694(2) Å]
is slightly shorter than the endocyclic P–N bonds [P1–N1
1.712(2) Å, P1–N2 1.724(2) Å]. The N3–C11 bond length
[1.283(3) Å] is within the range of a typical C(sp2)=N bond[12]
and comparable to that in 2 (1.2888 Å). To understand its elec-
tronic property, DFT calculations were performed for 4 at the
B3LYP/6-31G(d) level of theory. The crystal structure of 4 is
well reproduced by its optimized structure. The HOMO of 4
(Figure 3) is a mixture of lone pair orbitals on the P atom and
the adjacent N3 atom. The hybridization of the orbitals involv-
ing the lone pair of electrons on the P1 and N3 atoms are sp0.68
and sp3.19, respectively. Wiberg bond index (WBI) values of
the P1–N3 (0.81) and the C1–N3 (1.61) confirm the single
bond and double bond nature, respectively, indicating that 4b
Figure 3. The HOMO of 4 (hydrogen atoms are omitted for clarity).
and 4c are weaker resonance contributors than the canonical acids. Reaction between 4 and a stoichiometric amount of HCl
form 4a. resulted in the cleavage of the exocyclic P–N bond to generate
Compound 4 is thermally stable; when heated in toluene NHP–Cl 3 concomitant with the formation of 2, which was
at 110 °C overnight no sign of decomposition was observed. confirmed by 1H and 31P NMR spectroscopy (Scheme 2).
Meanwhile, it rapidly undergoes hydrolysis upon exposure to Thus, the P atom in 4 formally acts as an electrophilic center
water. We turned our interest to the reactivity of 4 towards to accept a chloride in this reaction.
Z. Anorg. Allg. Chem. 0000, 0–0
2
© 0000 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Journal of Inorganic and General Chemistry
www.zaac.wiley-vch.de
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
N3–C11 bond length of 1.299(2) Å is slightly longer than that
[1.283(3) Å] in 4. The P1–N3–C11 angle of 130.64(13)° is
larger than that [127.30(17)°] in 4. A DFT study on 5 reveals
that WBI value for the P1–N3 bond (0.88) is larger than that
(0.81) in 4 whilst WBI for the N3–C11 bond (1.47) is smaller
that (1.61) in 4.
Scheme 2. Reaction of 3 with HCl and BH3·THF.
One of the reaction mechanisms involves the initial proton-
ation of the central N atom in 4 to generate the ionic intermedi-
ate A, followed by the formation of the P–Cl bond along with
the cleavage of the exocyclic P–N bond (Scheme 3). Note that
A can be deemed as a cationic phosphoranimine AЈ supported
by a carbene ligand.[13] Alternative pathway could involve the
initial protonation at the P atom to give the phosphonium ion
B followed by a nucleophilic attack of the chloride anion to
furnish C. Subsequent proton shift from the P atom to the
imino-N atom may afford 3. As a preliminary mechanistic
study, we performed the reaction of 4 with triflic acid
(1 equiv.), which displayed a broad singlet at δ = 196.6 ppm
as the major product in the crude 31P{1H} NMR spectrum (see
the Supporting Information). Since the 31P signal does not
show a P–H coupling, the major product would putatively
correspond to the intermediate A rather than B (Scheme 3).
Figure 4. (a) Crystal structure of one of the two main molecules in the
asymmetric unit 5 with thermal ellipsoid set at 30% probability level.
Hydrogen atoms except for those on the B atom and benzene mol-
ecules are omitted for clarity. Selected bond lengths /Å and angles
/°: P1–N1 1.6824(16), P1–N2 1.7084(16), P1–N3 1.6241(16), P1–B1
1.915(2), N3–C11 1.299(2), C11–N4 1.381(2), C11–N5 1.377(2), P1–
N3–C11 130.64(13), N1–P1–N2 94.34(8), N4–C11–N5 104.74(15).
Conclusions
By incorporation of an imidazoline unit, we have synthe-
sized and fully characterized phosphinoimino-2-imidazoline
(4). The reactivity of 4 with Brønstead and Lewis acids re-
vealed that 4 has two donor sites and the reaction site. Thus,
the addition of hard acid H+ to 4 resulted in the formation of
a bond with the imino-N atom, while the soft acid, BH3,
formed a dative bond with the softer P atom in 4. The former
led to the cleavage of the P–N bond concomitant with the for-
mation of the P–Cl bonds to furnish 3 and 2, whereas the latter
afforded a stable Lewis acid base adduct 5.
Scheme 3. Proposed mechanism for the formation of 3 from 4.
Isolation and full characterization of such species are sub-
jects of our ongoing study. We reasoned that a soft Lewis acid
would interact strongly with the softer central P atom instead
of the central N atom in 4 based on HSAB rule.[14] To bear
out this hypothesis, BH3 was added to a toluene solution of 4
at ambient temperature (Scheme 2). After work-up, an upfield
shift from 4 (δ = 90.0 ppm) was observed for the product 5
(δ = 80.3 ppm) in the 31P NMR spectrum. Recrystallization
from a saturated benzene solution afforded crystals suitable for
X-ray diffraction analysis, which unanimously confirmed the
formation of Lewis adduct 5 (Figure 4). The phosphorus atom
adopts a distorted tetrahedral arrangement including a dative
P–B bond, and the P1–N3 bond length [1.6241(16) Å] is
Experimental Section
Materials and Method: All reactions were performed in an atmo-
sphere of argon by using standard Schlenk or dry box techniques; sol-
1
vents were dried with Na metal, K metal or CaH2. H, 13C{1H}, 31P
slightly shorter than that in 4 [1.694(2) Å]. Meanwhile, the and 11B NMR spectra were obtained with either Bruker AV 400 or
Z. Anorg. Allg. Chem. 0000, 0–0
3
© 0000 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Journal of Inorganic and General Chemistry
www.zaac.wiley-vch.de
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
AVIII 400 MHz BBFO1 spectrometers at 298 K unless otherwise anisotropic refinement. The hydrogen atoms were generated geometri-
stated. Coupling constants J are given in Hz. Electrospray ionization cally and allowed to ride in their respective parent atoms; they were
(ESI) mass spectra were obtained at the Mass Spectrometry Laboratory assigned appropriate isotropic thermal parameters and included in the
at the Division of Chemistry and Biological Chemistry, Nanyang Tech- structure-factor calculations. The results associated with crystallo-
nological University. Melting points were measured with OptiMelt graphic data collection and structure refinements are summarized in
Stanford Reseach System. Compounds 2[10] and 3[8] were prepared Table 1. The crystal structures of 4 and 5 were drawn using ORTEP-
according to the literature procedures.
3 program.[17]
Synthesis of 4: nBuLi (1.6 m in hexane, 3.2 mL, 5.12 mmol) was
added at –78 °C to a THF solution (30 mL) of 2 (2.02 g, 5.00 mmol).
The reaction mixture was warmed to room temperature and stirred for
2 h. 3 was dissolved in THF, added dropwise to the reaction mixture
at room temperature and stirred for overnight. Subsequently, THF was
removed under vacuo and toluene was added to the residue. After fil-
tration of LiCl, the solvent was removed in vacuo to yield an oily
residue. Washing with pentane (10 mL) and filtration gives an off-
white compound 4 (58% yield). Mp: 208 °C. 1H NMR (400 MHz,
Table 1. Summary of data collection and sStructure refinement for 4
and 5.
4
5
Formula
Fw
C37H58N5P
603.85
C43H67BN5P
695.79
Crystal systen
Space group
Size /mm3
T /K
orthorhombic
Pbca
0.160ϫ0.200ϫ0.280
103(2)
triclinic
P1
0.160ϫ0.220ϫ0.260
103(2)
¯
3
3
C6D6): δ = 7.24 (t, J = 7.6 Hz, 2 H, ArH), 7.14 (d, J = 7.6 Hz, 4 H,
a /Å
b /Å
c /Å
α /°
19.349(2)
19.313(2)
19.622(2)
90
90
90
7332.5(14)
8
1.094
9.9932(5)
12.8508(6)
32.4198(16)
91.6290(18)
95.1147(17)
91.5658(17)
4143.3(3)
4
1.115
0.101
100259
0.9740/ 0.9840
18865
3
ArH), 5.88 (s, 2 H, NCH), 3.28 [sept, J = 6.8 Hz, 4 H, CH(CH3)2],
3
3.19 (m, 2 H, NCH2), 2.91 (m, 2 H, NCH2), 1.47 [d, J = 6.8 Hz, 12
3
4
H, CH(CH3)2], 1.20 [d, J = 6.8 Hz, 12 H, CH(CH3)2], 0.96 [d, JP–H
= 0.8 Hz, 18 H, C(CH3)3]. 13C NMR (100 MHz, C6D6): δ = 148.0
(ArC-N), 143.3 (d, JP,C = 15.0 Hz, C=N), 135.7 (ArC–C), 129.4
(ArC–H), 123.8 (ArC–H), 115.3 (NCH), 52.7 [d, JP,C = 10.0 Hz, q-
β /°
2
γ /°
V /A3
2
Z
C(CH3)3], 44.5 (d, 2JP,C = 8.0 Hz, CH2), 29.7 (d, 3JP,C = 12.0 Hz, CH3),
29.1 (CH), 24.9 (CH3), 22.9 (CH3). 31P NMR (160 MHz, C6D6): δ =
90.0 ppm. HRMS (ESI): m/z calcd. for C37H59N5P: 604.4508 [[M +
H]]+; found: 604.4508.
dcalcd. /g·cm–3
μ /mm–1
Refl collected
Tmin/ Tmax
Nmeasd
0.106
109723
0.9710 / 0.9830
6603
Synthesis of 5: Compound 4 (0.25 g, 0.41 mmol) and BH3·THF (1.0 m
in THF, 0.50 mL, 0.50 mmol) were dissolved in toluene (20 mL) and
stirred for 1 h. The solvent was removed in vacuo and recrystallized
from benzene to give a colorless crystal of 5 (53% yield). Mp.
139 °C(decomposed). 1H NMR (400 MHz, C6D6): δ = 7.23 (t, 3J =
[Rint
]
0.1581
0.0480
0.1044
1.020
0.0905
0.0547
0.1173
1.024
R [I Ͼ 2σ(I)]
Rw[I Ͼ 2σ(I)]
GOF
Largest diff peak
0.212/–0.262
0.337/–0.414
/ hole /e·Å–3
3
7.8 Hz, 2 H, p-CH), 7.14 (d, J = 7.8 Hz, 4 H, m-CH), 6.06 (s, 2 H,
NCH), 3.31 [sept, 3J = 6.8 Hz, 4 H, CH(CH3)2], 3.00 (m, 2 H, NCH2),
2.89 (m, 2 H, NCH2), 1.47 [d, 3J = 6.8 Hz, 12 H, CH(CH3)2], 1.11 [d,
3J = 6.8 Hz, 12 H, CH(CH3)2], 1.02 [s, 18 H, C(CH3)3]. 13C NMR
(100 MHz, C6D6): δ = 147.7 (ArC-N), 143.5 (d, 2JP,C = 10.0 Hz, C=N),
135.0 (ArC–C), 129.7 (ArC–H), 124.4 (ArC–H), 116.6 (NCH), 54.3
[d, JP,C = 4.0 Hz, q-C(CH3)3], 45.2 (CH2), 30.1 (d, JP,C = 3.0 Hz,
CH3), 28.8 (CH), 25.7 (CH3), 22.9 (CH3) 31P NMR (160 MHz, C6D6):
80.0 (br). 11B NMR (128 MHz, C6D6): –31.0 (br). HRMS (ESI): m/z
calcd. for C37H62N5PB: 618.4836 [[M + H]]+; found: 618.4807.
Crystallographic data (excluding structure factors) for the structures in
this paper have been deposited with the Cambridge Crystallographic
Data Centre, CCDC, 12 Union Road, Cambridge CB21EZ, UK. Copies
of the data can be obtained free of charge on quoting the depository
numbers CCDC-1481348 and CCDC-1481349 (Fax: +44-1223-336-
033; E-Mail: deposit@ccdc.cam.ac.uk, http://www.ccdc.cam.ac.uk).
2
3
Supporting Information (see footnote on the first page of this article):
Reaction of 3 with HCl: Compound 4 (25 mg, 0.041 mmol) and one
equivalent of HCl (1.0 m solution in Et2O) were added to CDCl3
(0.5 mL) in a J-Young NMR tube at room temperature. The reaction
was monitored by NMR spectroscopy, which confirmed a clean forma-
tion of 3 and 2.
NMR spectra of the title compounds, details on the DFT calculations.
Acknowledgements
We are grateful to the Nanyang Technological University (NTU) and
Ministry of Education, Singapore (MOE2013-T2–1-005) for financial
support.
Theoretical Studies: Gaussian 09 was used for all density functional
theory (DFT) calculations.[15] Geometries optimizations and fre-
quencies calculations for 3 were performed at B3LYP/6-31G(d) level
of theory, whereas Natural Bond Orbital (NBO) analysis was per-
formed at B3LYP/6-31G(d,p) level of theory. The coordinates (XYZ)
for compound 4 and 5 are given in the Supporting Information.
References
[1] a) C. Wentrup, Acc. Chem. Res. 2011, 44, 393; b) M. S. Platz, in:
Reactive Intermediate Chemistry, (Eds.: R. A. Moss, M. S. Platz,
M. Jones Jr), Wiley-Interscience, Hoboken, 2004, pp. 501–559.
[2] a) C. T. Saouma, J. C. Peters, Coord. Chem. Rev. 2011, 255, 920;
b) T. W. Hayton, Dalton Trans. 2010, 39, 1145; c) J. F. Berry,
Comments Inorg. Chem. 2009, 30, 28; d) R. A. Eikey, M. M. Abu-
Omar, Coord. Chem. Rev. 2003, 243, 83; e) B. A. MacKay, M. D.
Fryzuk, Chem. Rev. 2004, 104, 385.
Crystal Structure Determination: X-ray data collection and struc-
tural refinement. Intensity data for compounds 4 and 5 were collected
with a Bruker APEX II diffractometer. The crystals of 4 and 5 were
measured at 103(2) K. The structure was solved by direct phase deter-
mination (SHELXS-2014) and refined for all data by full-matrix least-
squares methods on F2.[16] All non-hydrogen atoms were subjected to
Z. Anorg. Allg. Chem. 0000, 0–0
4
© 0000 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Journal of Inorganic and General Chemistry
www.zaac.wiley-vch.de
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
[3] a) W. D. Hinsberg, P. B. Dervan, J. Am. Chem. Soc. 1978, 100,
Angew. Chem. Int. Ed. 2010, 49, 5930; g) D. Franz, E. Irran, S.
1608; b) P. G. Schultz, P. B. Dervan, J. Am. Chem. Soc. 1980,
102, 878; c) W. D. Hinsberg, P. G. Schultz, P. B. Dervan, J. Am.
Chem. Soc. 1982, 104, 766; d) P. B. Dervan, M. E. Squillacote,
P. M. Lahti, A. P. Sylwester, J. D. Roberts, J. Am. Chem. Soc.
1981, 103, 1120.
Inoue, Dalton Trans. 2014, 43, 4451; h) D. Franz, E. Irran, S.
Inoue, Angew. Chem. Int. Ed. 2014, 53, 14264; i) D. Franz, T.
Szilvási, E. Irran, S. Inoue, Nat. Commun. 2015, 6, 10037; j) T.
Ochiai, D. Franz, X.-N. Wu, S. Inoue, Dalton Trans. 2015, 44,
10952; k) T. Ochiai, D. Franz, E. Irran, S. Inoue, Chem. Eur.
J. 2015, 21, 6704; l) M. W. Lui, C. Merten, M. J. Ferguson, R.
McDonald, Y. Xu, E. Rivard, Inorg. Chem. 2015, 54, 2040.
[11] a) S. Beer, K. Brandhorst, C. G. Hrib, X. Wu, B. Haberlag, J.
Grunenberg, P. G. Jones, M. Tamm, Organometallics 2009, 28,
1534; b) M. Tamm, D. Petrovic, S. Randoll, S. Beer, T. Bannen-
berg, P. G. Jones, J. Grunenberg, Org. Biomol. Chem. 2007, 5,
523; c) N. Kuhn, M. Göhner, M. Grathwohl, J. Wiethoff, G.
Frenking, Y. Chen, Z. Anorg. Allg. Chem. 2003, 629, 793.
[4] F. Dielmann, O. Back, M. Henry-Ellinger, P. Jerabek, G. Frenk-
ing, G. Bertrand, Science 2012, 337, 1526.
[5] a) F. Dielmann, D. M. Andrada, G. Frenking, G. Bertrand, J. Am.
Chem. Soc. 2014, 136, 3800; b) F. Dielmann, G. Bertrand, Chem.
Eur. J. 2015, 21, 191.
[6] S. Burck, D. Gudat, M. Nieger, C. A. Schalley, T. Weilandt, Dal-
ton Trans. 2008, 3478.
[7] For reviews on N-heterocyclic phospholene, see: a) D. Gudat,
Dalton Trans. 2016, 45, 5896; b) D. Gudat, Acc. Chem. Res. 2010, [12] C(sp2) = N bonds: F. H. Allen, O. Kennard, D. G. Watson, L.
43, 1307; c) S. Burck, D. Gudat, M. Nieger, W.-W. D. Mont, J.
Am. Chem. Soc. 2006, 128, 3946; d) D. Gudat, A. Haghverdi, M.
Nieger, Angew. Chem. Int. Ed. 2000, 39, 3084.
Brammer, A. G. Orpen, R. Taylor, J. Chem. Soc. Perkin Trans. 1I
1987, S1–S19.
[13] F. Dielmann, C. E. Moore, A. L. Rheingold, G. Bertrand, J. Am.
Chem. Soc. 2013, 135, 14071.
[8] a) G. Sicard, A. Baceiredo, G. Bertrand, J.-P. Majoral, Angew.
Chem. Int. Ed. Engl. 1984, 23, 459; b) A. Baceiredo, G. Bertrand,
J. P. Majoral, G. Sicard, J. Jaud, J. Galy, J. Am. Chem. Soc. 1984,
106, 6088; c) G. Bertrand, J. P. Majoral, A. Baceiredo, Acc. Chem.
Res. 1986, 19, 17; d) J. Tirreé, D. Gudat, M. Nieger, E. Niecke,
Angew. Chem. Int. Ed. 2001, 40, 3025; e) R. J. Wehmschulte,
M. A. Khan, S. I. Hossain, Inorg. Chem. 2001, 40, 2756; f) X.
Zeng, H. Beckers, H. Willner, Angew. Chem. Int. Ed. 2009, 48,
4828.
[9] a) L. J. Murphy, K. N. Robertson, J. D. Masuda, J. A. C. Clyb-
urne, in: N-heterocyclic Carbenes: Effective Tools for Organome-
tallic Synthesis (Ed.: S. P. Nolan), Wiley-VCH, Weinheim, 2014,
pp 427–497; b) E. Rivard, Struct. Bonding (Berlin) 2014, 156,
203; c) Y. Wang, G. H. Robinson, Inorg. Chem. 2014, 53, 11815;
d) D. Martin, M. Soleilhavoup, G. Bertrand, Chem. Sci. 2011, 2,
389; e) C. D. Martin, M. Soleilhavoup, G. Bertrand, Chem. Sci.
2013, 4, 3020.
[14] R. G. Pearson, J. Am. Chem. Soc. 1963, 85, 3533.
[15] Gaussian 09, Revision E.01, M. J. Frisch, G. W. Trucks, H. B.
Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, G. Scal-
mani, V. Barone, B. Mennucci, G. A. Petersson, H. Nakatsuji, M.
Caricato, X. Li, H. P. Hratchian, A. F. Izmaylov, J. Bloino, G.
Zheng, J. L. Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fu-
kuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao,
H. Nakai, T. Vreven, J. A. Montgomery Jr., J. E. Peralta, F. Ogli-
aro, M. Bearpark, J. J. Heyd, E. Brothers, K. N. Kudin, V. N. Sta-
roverov, R. Kobayashi, J. Normand, K. Raghavachari, A. Rendell,
J. C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi, N. Rega, J. M.
Millam, M. Klene, J. E. Knox, J. B. Cross, V. Bakken, C. Adamo,
J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Aus-
tin, R. Cammi, C. Pomelli, J. W. Ochterski, R. L. Martin, K. Mo-
rokuma, V. G. Zakrzewski, G. A. Voth, P. Salvador, J. J. Dannen-
berg, S. Dapprich, A. D. Daniels, Ö. Farkas, J. B. Foresman, J. V.
Ortiz, J. Cioslowski, D. J. Fox, Gaussian Inc., Wallingford, CT,
USA, 2009.
[10] For selected examples of main group compounds stabilized by
imidazolin-2-iminato ligands, see: a) T. Ochiai, D. Franz, S. In-
oue, Chem. Soc. Rev. 2016, published online, DOI: 10.1039/ [16] SHELEXL-2014: a) G. M. Sheldrick, Acta Crystallogr., Sect. C
C6CS00163G; b) A. D. K. Todd, W. L. McClennan, J. D. Masuda,
RSC Adv. 2016, 6, 69270; c) T. Ochiai, T. Szilvási, D. Franz, E.
Irran, S. Inoue, Angew. Chem. Int. Ed. 2016, 55, 11619; d) T.
Ochiai, D. Franz, X.-N. Wu, E. Irran, S. Inoue, Angew. Chem. Int.
Ed. 2016, 55, 6983; e) S. Inoue, K. Leszczyn´ska, Angew. Chem.
Int. Ed. 2012, 51, 8589; f) R. Kinjo, B. Donnadieu, G. Bertrand,
2015, 71, 3; SHELEXL-97: b) G. M. Sheldrick, Acta Crystallogr.,
Sect. A 2008, 64, 112.
[17] L. J. Farrugia, J. Appl. Crystallogr. 2012, 45, 849.
Received: May 23, 2016
Published Online: ᭿
Z. Anorg. Allg. Chem. 0000, 0–0
5
© 0000 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Journal of Inorganic and General Chemistry
www.zaac.wiley-vch.de
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
C. C. Chong, R. Ganguly, Y. Li, R. Kinjo* ...................... 1–6
Isolation of Phosphinoimino-2-imidazoline
Z. Anorg. Allg. Chem. 0000, 0–0
6
© 0000 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim