Iminophosphoranyl Dichlorophosphines R3PNPCl2
The coordination of the σ4λ5 phosphorus atoms (P1) is in phoranyl dichlorophosphines 2a–c were determined by single-
all structures (2a–c) slightly distorted tetrahedral [106.5(1)– crystal X-ray diffraction. The effect of the strong electron do-
115.1(1)°]. The σ3λ3 phosphorus atoms (P2) are coordinated nating iminophosphoranyl group is demonstrated by the elong-
pyramidal. The Cl–P–Cl and the N–P–Cl bond angles are in ation of the P–Cl bonds. The molecular structures have con-
all three structures in the same range (Table 2). The P–N–P firmed that the orientation of the PCl2 unit towards the phos-
angles in 2a and 2b are almost equal [141.4(1)° and 139.1(1)°], phonium phosphorus atom is different compared to that in the
however the P–N–P angle of 2c is about 10° higher related phosphoniumylidyl dichlorophosphines.
2
[151.1(1)°]. This is consistent with the different JPP coupling
constants of 2a, 2b, and 2c. The P–N bond lengths
[1.588(2) Å / 1.592(2) Å (2a), 1.591(2) Å / 1.585(2) Å (2b)
Experimental Section
and 1.597(2) Å / 1.558(2) Å (2c)] are in the range between a
double and a single bond (1.52 and 1.76 Å).[17] The P–C and
the C–C bond lengths are in the expected range.
General: All manipulations were carried out in dry argon using stan-
dard Schlenk techniques. Solvents were dried according to standard
procedures and were freshly distilled before use. Phosphorus trichlo-
ride was purchased from Fluka, Trimethylsilyl azide from ABCR. The
silylcompounds R3PNSiMe3 1 (R = Ph, pTol, Cy) were prepared ac-
cording to the literature procedures,[13] the dichlorophosphines 2
acoording to the published procedure for 2a.[10]
The P–Cl bond lengths of the iminophosphoranyl di-
chlorophosphines are with 2.144(1) Å / 2.136(1) Å (2a),
2.150(1) Å / 2.155(1) Å (2b) and 2.171(1) Å / 2.176(1) Å (2c)
almost equal. Compared to aminodichlorophosphines R2NPCl2
the P–Cl bond lengths are elongated [2.092(1) Å / 2.091(1) Å
in Me2NPCl2 and Cy2NPCl2, respectively].[18,19] This elong-
ation is caused by the strong electron donating properties of the
R3PN substituent, precisely by the negative hyperconjugation.
Electron density from one lone pair of the nitrogen atom is
donated into the σ* orbital of the P–Cl bond and therefore this
bond is destabilized and elongated.[20] Similar properties were
observed for certain diaminochlorophosphines[21,22] where the
P–Cl bond lengths are, due to the negative hyperconjugation,
also elongated. In comparison with the phosphoniumylidyl
dichlorophosphines (Ph3PC(R)PCl2), the situation is different.
In these phosphines there is also a strong electron donating
group attached to the phosphorus atom and therefore the P–Cl
bonds are also elongated but the bond lengths are not equal.
In Ph3PC(Me)PCl2 for example one P–Cl bond is about 0.09 Å
longer as the other one [2.099(1) Å / 2.188(1) Å].[7]
Also the orientation of the PCl2 unit in the solid state is
different in the phosphoniumylidyl dichlorophosphines. In 2a
the position of the chlorine atom Cl1 is almost in the plane
built by P1–N1–P2 [torsion angle P1–N1–P2–Cl1: –12.3(2)°]
whereas the other chlorine atom Cl2 is almost perpendicular
to this plane [torsion angle P1–N1–P2–Cl2: 88.6(2)°]. In the
phosphoniumylidyl dichlorophosphines the P–C–P plane di-
vides the Cl–P–Cl angle more or less in halves.[7] In 2c the
orientation of the PCl2 unit is comparable to 2a. The chlorine
atom Cl1 is nearly in a plane built by P1–N1–P2 [torsion angle
P1–N1–P2–Cl1: 16.6(2)°] and Cl2 is almost perpendicular to
this plane [torsion angle P1–N1–P2–Cl2: –83.8(2)°]. However
in 2b the orientation is a bit different. There the PCl2 unit is a
bit twisted. The torsion angles in 2b have values of 33.2(2)°
(P1–N1–P2–Cl1) and –67.2(2)° (P1–N1–P2–Cl2). This indi-
cates a certain structural flexibility of the R3PN substituent.
NMR Spectroscopy: 1H, 13C and 31P{1H} NMR spectra were re-
corded with JOEL Eclipse 270 and Joel EX 400 instruments operating
at 270 and 400 MHz (1H), at 68 and 100 MHz (13C), and at 109 and
162 MHz (31P), respectively. The chemical shifts (δ) are quoted in
units of ppm, relative to external standards Me4Si (1H and 13C) and
85% H3PO4 (31P). Multiplicities are abbreviated as follows: s, singlet;
d, doublet and m, multiplet. Coupling constants (J) are given in Hertz
(Hz). All spectra were measured, if not mentioned otherwise, at 25 °C.
Elemental Analysis: Elemental analyses (C, H, N) were performed by
the Microanalytical Laboratory of the Department of Chemistry, LMU
Munich, with a Heraeus Elementar Vario El instrument.
Mass Spectrometry: Mass spectrometric data were obtained with a
JOEL Mstation JMS 700 spectrometer using the direct DEI mode.
X-ray Crystal Structure Determination: The low-temperature X-ray
diffraction of 2a, 2b, and 2c was performed with an Oxford XCalibur3
diffractometer equipped with a Spellman generator (voltage 50 kV,
current 40 mA) and a KappaCCD detector, operating with Mo-Kα radi-
ation (λ = 0.7107 Å). Data collection at 100 K/173 K was performed
using the CrysAlis CCD software,[23] the data reductions were carried
out using the CrysAlis RED software.[24] The solution and refinement
of the structure was performed with the programs SHELXS[25] and
SHELXL-97[26] implemented in the WinGX software package[27] and
finally checked with the PLATON software.[28] The absorption correc-
tion was performed with the SCALE3 ABSPACK multi-scan
method.[29] In the crystal structure, the hydrogen atoms were included
in the refinements in calculated positions. Selected data and parameters
of the X-ray analysis are given in Table 3.
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-965837 (2a), CCDC-965839 (2b), and CCDC-965838
(2c) (Fax: +44-1223-336-033; E-Mail: deposit@ccdc.cam.ac.uk,
http://www.ccdc.cam.ac.uk).
Conclusions
Synthesis of Ph3PNPCl2 (2a): To
a solution of PCl3 (4.1 g,
One new iminophosphoranyl dichlorophosphine (2b) was
synthesized by the reaction of pTol3PNSiMe3 and PCl3. The
compound 2c could be isolated in pure form for the first time
30.0 mmol) in THF (30 mL), a solution of 1a (10.5 g, 30.0 mmol) in
THF (30 mL) was added dropwise at 0 °C. The mixture was stirred at
room temperature overnight to complete the reaction. After removal
of the solvent in vacuo, the colorless residue was crystallized from
1
and fully characterized by NMR spectroscopy (31P, 13C, H).
Furthermore the first molecular structures of the iminophos- acetonitrile as colorless crystals. The compound was filtered off and
Z. Anorg. Allg. Chem. 2014, 962–967
© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim