Synthesis and properties of di-isopropylamino derivatives of diphosphanes and triphosphanes: The x-ray structure of (ipr2n) 2p-p(sime3)2

Article abstract of DOI:10.1080/10426500902718273

(ⁱPr₂N)₂PCl (3) reacts with P(SiMe ₃)2Li yielding crystalline (ⁱPr₂N) ₂P-P(SiMe₃)₂ (1). Compound 1 crystallizes in the orthorhombic space group Pbca. The lithiation of 1 with BuLi yields ( ⁱPr₂N)₂P-P(SiMe₃)Li (2). Compound 2 reacts with 3 with the formation of (ⁱPr₂N) ₂P-P(SiMe₃)-P(NⁱPr₂)₂ (4) in high yield. Attempts to lithiate 4 with BuLi in THF solution in order to obtain (iPr₂N) ₂P-PLi-P(NⁱPr₂) ₂were unsuccessful, probably due to strong electron donation of the ⁱPr₂N groups into the P-P-P skeleton in 4.

Full text of DOI:10.1080/10426500902718273

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Synthesis and Properties
of Di-isopropylamino
Derivatives of Diphosphanes
and Triphosphanes: The
X-Ray Structure of ( i
Pr2N)2P–P(SiMe3)2
Wioleta Domańska-Babul a , Katarzyna Baranowska a
& Jerzy Pikies a
a Chemical Faculty, Department of Inorganic
Chemistry , Gdańsk University of Technology ,
Gdańsk, Poland
Published online: 26 Mar 2009.
To cite this article: Wioleta Domańska-Babul , Katarzyna Baranowska & Jerzy Pikies
(2009) Synthesis and Properties of Di-isopropylamino Derivatives of Diphosphanes and
Triphosphanes: The X-Ray Structure of ( i Pr2N)2P–P(SiMe3)2 , Phosphorus, Sulfur, and
Silicon and the Related Elements, 184:4, 936-941, DOI: 10.1080/10426500902718273
To link to this article: http://dx.doi.org/10.1080/10426500902718273
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Phosphorus, Sulfur, and Silicon, 184:936–941, 2009
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500902718273
Synthesis and Properties of Di-isopropylamino
Derivatives of Diphosphanes and Triphosphanes:
The X-Ray Structure of (iPr2N)2P–P(SiMe3)2
´
Wioleta Domanska-Babul, Katarzyna Baranowska,
and Jerzy Pikies
Chemical Faculty, Department of Inorganic Chemistry, Gdan´sk
University of Technology, Gdan´sk, Poland
(iPr N) PCl (3) reacts with P(SiMe ) Li yielding crystalline (iPr N) P–P(SiMe )
3 2
2
2
3 2
2
2
(1). Compound 1 crystallizes in the orthorhombic space group Pbca. The lithiation
of 1 with BuLi yields (iPr N) P–P(SiMe )Li (2). Compound 2 reacts with 3 with the
2
2
3
formation of (iPr N) P–P(SiMe )–P(NiPr ) (4) in high yield. Attempts to lithiate
2
2
3
2 2
4 with BuLi in THF solution in order to obtain (iPr N) P–PLi–P(NiPr ) were
2
2
2 2
unsuccessful, probably due to strong electron donation of the iPr N groups into the
2
P-P-P skeleton in 4.
Keywords Diphosphanes; lithiation; triphosphanes; X-ray structures
INTRODUCTION
In the course of our studies on the phosphanylphosphinidenes R2P–P
as ligands in transitions metal complexes,1,2 we successfully exploited
lithiated diphosphanes R2P–P(SiMe3)Li as precursors of R2P–P lig-
t
ands. From the reaction of Bu2P–P(SiMe3)Li with Cp2ZrCl2, we ob-
tained the complex [µ-(1,2:2-η-tBu2P=P){Zr(Cl)Cp2}2] containing both
t
a side-on and a terminally bonded Bu2P–P ligand with two zirco-
nium metal centers. In the presence of PPhMe2, this reaction yields
t
[(η1− Bu2P–P)Zr(PPhMe2)Cp2]—a complex with terminally bonded
tBu2P–P.3 Moreover we have found that tBu2P–PLi–PtBu2 reacts with
t
[(Et3P)2MCl2] (M = Ni, Pd) to form [(1,2-η− Bu2P=P–PtBu2)M(PEt3)Cl]
Received 14 December 2007; accepted 30 January 2008.
Dedicated to Professor Marian Mikolꢀajczyk from the CBMiM PAN in Lꢀ o´dz´, Poland,
on the occasion of his 70th birthday.
W. D.-B. and J. P. thank the Polish State Committee of Scientific Research (project
No. 1 T09A 148 30) for financial support.
Address correspondence to Prof. Dr. Jerzy Pikies, Chemical Faculty, Department of
Inorganic Chemistry, Gdan´sk University of Technology, G. Narutowicza St. 11/12, Pl-80-
952 Gdan´sk, Poland. E-mail: pikies@chem.pg.gda.pl
936

Diphosphanes and Triphosphanes
937
(M = Ni, Pd).4 We intended to expand our studies on other lithium
t
derivatives of triphosphanes R2P–PLi–PR2 (R
ꢀ
i
tempt to synthesize di-isopropylamino derivative (R = Pr2N) failed,
and we obtained only (iPr2N)2P–P(SiMe3)–P(NiPr2)2 (4). Syntheses and
properties of these compounds are reported herein.
RESULTS AND DISCUSSION
Synthesis
(iPr2N)2P–P(SiMe3)–P(NiPr2)2 (4) was prepared according to the se-
quence described by Equations (1) and (2).
(iPr2N)2P − P(SiMe3)Li (2) + Me3SiBu
(1)
(iPr2N)2P − P(SiMe3)Li (2) + (iPr2N)2PCl (3) → (iPr2N)2P
−P(SiMe3) − P(NiPr2)2 (4) + LiCl
(2)
´
The syntheses of 1 and 2 were conducted according to Domanska-Babul
et al.,5 the synthesis of 3 similarly to King and Sundaram,6 and the syn-
thesis of 4 similarly to Bender et al.7 We obtained a much higher yield
of 4 than previously reported, probably because we used the isolated
(iPr2N)2P–P(SiMe3)Li (2), and the synthesis was conducted at temper-
atures not higher than 20◦C. Moreover, we have found that, even at
room temperature, (iPr2N)2P–P(SiMe3)Li undergoes a slow decompo-
sition leading to the formation of phosphetanes and polyphosphorus
compounds.5
We studied the reactivity of 4 towards BuLi in THF solution in or-
der to obtain the related lithium compound (iPr2N)2P–P(Li)–P(NiPr2)2.
The expected product was not detected. The 31P-NMR spectrum of
the reaction solution revealed only the resonances of 4. Such an un-
usual lack of reactivity of this P–SiMe3 bond can not be caused by
the sterical hindrance of the adjacent P(NiPr2)2 groups in 4. In the
crowded molecule tBu2P–P(SiMe3)–PtBu2, the lithiation of the P–
SiMe3 bond is an easy process.8 The lithiation product does not form
from the reaction of 4 with BuLi, probably because of electronic fac-
tors. Tertiary phosphanes containing two NR2 ligands are very strong
σ-donors,9 and these nitrogen substituents must have strong electron-
donor properties towards the P-skeleton. Thus, the electron-donor
properties of four NiPr2 groups increase the anionic character of the
SiMe3 group and prevent the nucleophilic substitution at the silicon
atom.

938
W. Doman´ska-Babul et al.
X-Ray Crystallographic Studies of 1
Single crystal X-ray diffraction data were recorded on a KUMA KM4
diffractometer with graphite-monochromated MoKα radiation using
the Sapphire 2 CCD detector (Oxford Diffraction Ltd.). The appara-
tus was equipped with an open flow thermostat (Oxford Cryosystems),
which enabled experiments at 120 K. Data was collected in four series
of 152 frames using ω scan with scan width of 0.75 deg. The structures
were solved with direct methods and refined with the SHELX97 pro-
gram package10] with the full matrix least-squares refinement based on
F2. Because of low X-ray absorption by the crystals, no absorption cor-
rections were applied. All non-hydrogen atoms were refined anisotrop-
ically. Hydrogen atoms were refined in geometrically idealized position
with isotropic temperature factors 1.2 times the equivalent isotropic
temperature factors Ueq of their attached atoms (1.5 for CH3 groups).
Crystal Data, Measurement Conditions, and Refinement
Parameters for (iPr2N)2P–P(SiMe3)2 (1)
C18H46N2P2Si2, yellow plate, 0.5 × 0.2 × 0.2 mm, orthorhombic, space
group Pbca, a = 15.687(3) Å, b = 17.353(3) Å, c = 19.033(4) Å, α = ß
= γ = 90.00◦, V = 5181.1(17) Å3, ρcalc. = 1.048 g.cm−3. Data collection:
2θmax = 51◦, Mo Kα 0.71073 Å, ω -2θ scan mode; T = 120.0(2) K, 32463
measured and 4811 independent reflections, 4504 reflections with I
> 2σ(I), Lorentzian polarization10), absorption corrections: none (µ =
0.269 mm−1). Structure solution and refinement: SHELX 9711, no. of
parameters 231, refinement against |F2| R = 0.0890, wR = 0.1482 for I
> 2σ(I), R = 0.0972, wR = 0.1519 for all data, residual electron density:
peak 0.344, hole –0.304 eA−3
.
Compound 1 crystallized orthorhombic in a space group Pbca. An
ORTEP view of 1 is shown in Figure 1.
The molecular structure of 1 in the crystal is similar to that of
(iPr2N)2P–P(SiMe2t Bu)2.12 The P1-P2 distance of 224.03(13) pm is in
the range of a P-P single bond, and the P-Si distance 225.97(14) pm
(mean) is typical for a P–Si single bond. The coordination around the
phosphorus atoms P1 and P2 is tetrahedral, with the sum of angles
around these phosphorus atoms being 332.00(6) deg and 321.39(12)
deg, respectively. The arrangement around N1 and N2 is almost planar;
the sum of angles around N1 is 359.5(2)deg and around N2 is 356.7(2)
deg. In the apparently similar compound (iPr2N)2P–P (SiMe3)Li, the P-
P distance (218.9 pm) and the P-Si distance (220.2 pm) are shorter, and
the arrangement around the anionic phosphorus atom is much more
planar (sum of angles = 348.29 deg).5

Diphosphanes and Triphosphanes
939
FIGURE 1 An ORTEP view of the molecular structure of 1 in the crystal; hy-
drogen atoms not shown, ellipsoids are drawn at 30 % probability level. Selected
bond lengths [pm] and angles [◦]: P1-P2 224.03(13); N1-P2 169.6(3); N2-P2
170.3(3); P1-Si3 225.22(14); P1-Si4 226.78(14); Si3-P1-Si4 105.54(5); P2-P1-Si3
98.94(5); P2-P1-Si4 127.52(6); N1-P2-N2 109.22(15); N1-P2-P1 109.80(11); N2-
P2-P1 102.37(11); C2-N1-C5 115.0(3); C2-N1-P2 127.9(2); C5-N1-P2 116.6(2);
C11-N2-C8 116.3(3); C11-N2-P2 123.5(2); C8-N2-P2 116.9(2).
We studied the molecular structure of 4 at a low temperature by
single crystal X-ray diffraction. The results were however very similar
to those reported previously.7
Crystallographic data for the structures of compounds 1 and 4
have been deposited with the Cambridge Crystallographic Data Cen-
tre, CCDC-670414 (1) and CCDC-670415 (4). Copies of the data can
be obtained free of charge on application to The Director, CCDC,
12 Union Road, Cambridge CB2 1EZ, UK (Fax: int. code (1223)336
033; e-mail for inquiry: fileserv@ccdc.cam.ac.uk; e-mail for deposition:
deposit@ccdc.cam.ac.uk).
EXPERIMENTAL
All manipulations were performed in flame-dried Schlenk type
glassware on a vacuum line. THF and toluene were dried over
Na/benzophenone and distilled under nitrogen. Petroleum ether was
dried over Na/benzophenone/diglyme and distilled under nitrogen. 31
P
NMR spectra were recorded with a Varian 500 spectrometer (external
standard 85% H3PO4) at ambient temperature.

940
W. Doman´ska-Babul et al.
Synthesis of (iPr2N)2P–P(SiMe3)2 (1)
P(SiMe3)2Li (17.83 g, 0.049 mol) was dissolved in THF (120 mL) and
then slowly dropped to a cooled (–35◦C) solution of (iPr2N)2PCl (13.04
g, 0.049 mol) in THF (100 mL). The reaction mixture was stirred for
3 h at –35◦C, then allowed to warm to room temperature and stirred
for another 12 h. The obtained solution was evaporated to dryness
under vacuum (1 mTorr). The resulting yellow residue was dissolved
in petroleum ether, filtrated, and then concentrated. After one day at
ambient temperature, pale-yellow crystals of (iPr2N)2P–P(SiMe3)2 were
1
deposited. Yield: 14.4 g, 72%. 31P{ H} NMR (C6D6): δ = 80.9 (P(NiPr2)2),
–156.1 (P(SiMe3)2), 1JPP = 470.3Hz.5
Synthesis of (iPr2N)2PCl (3)
A solution of PCl3 (80.2 g, 0.58 mol) in petroleum ether (100 mL) was
i
slowly added to a cooled (10◦C) solution of Pr2NH (232 g, 2.3 mol)
in petroleum ether (1000 mL). The reaction mixture was heated to
reflux and stirred for 20 h. The reaction mixture was filtrated, and the
solvent was evaporated under reduced pressure. The resulting yellow
oil residue was dissolved in hexane (300 mL), and after one day at
ambient temperature, colorless crystals of (iPr2N)2PCl were obtained.
1
Yield: 89.2 g, 58%. 31P{ H} NMR (C6D6): δ = 135.0.6
Synthesis of (iPr2N)2P–P(SiMe3)–P(NiPr2)2 (4)
A solution of (iPr2N)2P–P(SiMe3)Li·2.6THF (1.38 g, 2.6 mmol) in
toluene (20 mL) was added dropwise to a cooled (–40◦C) solution of
(iPr2N)2PCl (0.41 g, 1.5 mmol) in toluene (20 mL). The obtained mix-
ture was stirred for 3 h at –40◦C, then warmed up to room temper-
ature, and the solvent was evaporated under vacuum (1 mTorr). The
residue was dissolved in pentane (50 mL), filtrated, and concentrated.
After one day at –30◦C, pale yellow crystals of (iPr2N)2P–P(SiMe3)–
P(NiPr2)2 were deposited. Yield: 0.6 g; 70%. 31P1H NMR (C6D6): δ =
94.9 (P(NiPr2)2), –75.9 (P(SiMe3), 1JPP = 415.4 Hz.7
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