Synthesis and characterization of 1,3-bis[2,4,6-tri(tert-butyl)phenyl]-2,4- bis[tri(tert-butyl)silyl]-1,3-diinda-2,4-diphosphetane, a dimeric phosphanylidene indane with three-coordinate indium and phosphorus atoms

Article abstract of DOI:10.1016/j.inoche.2005.06.006

The metathesis reaction of potassium tri(tert-butyl)silylphosphanide with bis[2,4,6-tri(tert-butyl)phenyl]indium bromide gives (2,4,6-tBu ₃C₆H₂)₂In-P(H)SitBu₃ (1a), the subsequent elimination of tri(tert-butyl)benzene yields [(2,4,6-tBu₃C₆H₂)In-PSitBu₃] ₂ (2a) which can be regarded as a dimeric phosphanylidene indane. The X-ray structure confirms the dimeric nature of this 1,3-diinda-2,4- diphosphetane with three-coordinate indium and phosphorus atoms and short In-P bond lengths of 250 pm. The analogous reaction with the gallium derivative and the smaller potassium triisopropylsilylphosphanide leads to the formation of monomeric (2,4,6-tBu₃C₆H₂)₂Ga-P(H) SiiPr₃ (1b) with three-coordinate gallium and phosphorus atoms.

Full text of DOI:10.1016/j.inoche.2005.06.006

Inorganic Chemistry Communications 8 (2005) 809–812
www.elsevier.com/locate/inoche
Synthesis and characterization of
1,3-bis[2,4,6-tri(tert-butyl)phenyl]-2,4-bis[tri(tert-butyl)silyl]-1,3-
diinda-2,4-diphosphetane, a dimeric phosphanylidene indane
with three-coordinate indium and phosphorus atoms
a
Thomas Rotter , Alexander N. Kneifel , Peter Mayer , Matthias Westerhausen
b
b
a,
*
a
Friedrich-Schiller-Universita¨t Jena, Institute of Inorganic and Analytical Chemistry, August-Bebel-Str. 2, D-07743 Jena, Germany
Ludwig-Maximilians-University Munich, Department of Chemistry and Biochemistry, Butenandtstr. 9, D-81377 Munich, Germany
b
Received 27 April 2005; accepted 2 June 2005
Available online 19 July 2005
Abstract
The metathesis reaction of potassium tri(tert-butyl)silylphosphanide with bis[2,4,6-tri(tert-butyl)phenyl]indium bromide gives
(2,4,6-tBu3C6H2)2In–P(H)SitBu3 (1a), the subsequent elimination of tri(tert-butyl)benzene yields [(2,4,6-tBu3C6H2)In–PSitBu3]2
(2a) which can be regarded as a dimeric phosphanylidene indane. The X-ray structure confirms the dimeric nature of this 1,3-
diinda-2,4-diphosphetane with three-coordinate indium and phosphorus atoms and short In–P bond lengths of 250 pm. The
analogous reaction with the gallium derivative and the smaller potassium triisopropylsilylphosphanide leads to the formation of
monomeric (2,4,6-tBu3C6H2)2Ga–P(H)SiiPr3 (1b) with three-coordinate gallium and phosphorus atoms.
Ó 2005 Elsevier B.V. All rights reserved.
Keywords: Phosphanylgallanes; Phosphanylindanes; Phosphetanes; Gallium; Indium; Silylphosphanes
1. Introduction
a pyramidal environment. The monomeric digallylphos-
phane MesP{Ga(Trip)2}2 Æ Et2O [6] (Trip = 2,4,6-
iPr3C6H2) contains a planar three-coordinate phosphorus
center. In [tBu3SiP(H)-Ga(l-PSitBu3)]2 a Ga–P–Ga het-
eroallylic system with one planarily coordinated P atom
(Ga–P 225.8 pm) is realized, the other bridging phos-
phorus atom (Ga–P 233.6 pm) is in a pyramidal envi-
ronment [7]. Only very few dimeric phosphanylindanes
with In2P2 cycles such as [(allyl)2InPtBu2]2 [8], [Et2InP
(SiMe3)2]2 [1], and [Ph2InP(SiMe3)2]2 [9] with four-
coordinate indium and phosphorus atoms have been
synthesized. As of yet no dimeric phosphanylidenein-
dane with three-coordinate indium atoms is known.
Also a monomeric phosphanylideneindane of the type
Phosphanylgallanes and phosphanylindanes of the
type R2E–PR02 oligomerize and form cyclic compounds
whereas oligomeric phosphanylideneindanes RE = PR0
give cubane or hexagonal prismatic structures [1,2],
depending on the bulkiness of the substituents R and
R0. The expectation that small phosphanylgallanes and
indanes are valuable precursors for the synthesis of
GaP and InP induced an intense research with respect
to these semiconductors [3]. Monomeric phosphanyl-
gallanes such as (tBu)2GaP(tBu)SiPh3 [4] or (2,4,6-
Me3C6H2)2GaP(tBu)2 [5] contain phosphorus atoms in
0
RIn = PR remains unknown. This fact can be under-
stood as a consequence of the high standard enthalpies
for the oligomerization process according to equation
*
Corresponding author. Tel.: +49 3641 9 48110.
E-mail address: m.we@uni-jena.de (M. Westerhausen).
1387-7003/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2005.06.006

810
T. Rotter et al. / Inorganic Chemistry Communications 8 (2005) 809–812
HIn = PH ! 1/2[HInPH]2 with
a
value of ꢀ150
Elimination of tri(tert-butyl)benzene and formation of
the 1,3-digalla- and 1,3-diinda-2,4-diphosphetanes leads
to a low-field shift of the 31P resonance of approximately
60 ppm.
kJ molꢀ1 [10].
(2,4,6-tBu3C6H2)2InBr reacts at low temperatures
with KP(H)SitBu3 in heptane. The metathesis step yields
(2,4,6-tBu3C6H2)2In–P(H)SitBu3 (1a) and the subse-
quent intramolecular metalation step eliminates 1,3,5-
tri(tert-butyl)benzene and (2,4,6-tBu3C6H2)In = PSitBu3
is formed which dimerizes immediately to the 1,3-diinda-
2,4-diphosphetane [(2,4,6-tBu3C6H2)InPSitBu3]2 (2a). In
order to verify the intermediate we changed the group
13 metal and varied the bulkiness of the trialkylsilyl
group. The metathesis reaction of (2,4,6-tBu3C6H2)2-
GaCl with KP(H)SiiPr3 yielded a mixture of monomeric
(2,4,6-tBu3C6H2)2Ga–P(H)SiiPr3 (1b) (see Fig. 1) and
traces of dimeric [(2,4,6-tBu3C6H2)GaPSiiPr3]2 (2b)
(Eq. (1)) which results from an elimination of 2,4,6-
tBu3C6H3. In 1b [11] the dihedral angle between the gal-
lium-bound 2,4,6-tBu3C6H2 ligand and the H atom at
the phosphorus (H–P–Ga–C1) lies at 20°. This fact sug-
gests an intramolecular synelimination of 1,3,5-
tBu3C6H3 to give the corresponding phosphanylidene
gallane and indane (A), respectively, which dimerizes
immediately. Also the bulkier tri(tert-butyl)silyl ligand
leads to the formation of monomeric (2,4,6-tBu3C6H2)2
GaP(H)SitBu3 (1c) and dimeric [(2,4,6-tBu3C6H2)GaP-
SitBu3]2 (2c). The NMR data are summarized in Table 1.
tBu
tBu
+ KP(H)SiR3
- KX
H
tBu
tBu
(2,4,6-tBu3C6H2)2E-X
E
P
SiR3
tBu
tBu
1a: E = In, R = tBu
1b: E= Ga, R=iPr
1c: E = Ga, R= tBu
tBu
- 1,3,5-tBu3C6H3
tBu
tBu
SiR3
E
P
R3Si
P
P
SiR3
E
x2
E
tBu
tBu
tBu
tBu
tBu
tBu
2a: E = In, R = tBu
2b: E = Ga,R= iPr
2b: E= Ga, R= tBu
A
ð1Þ
The molecular structure of 2a is represented in Fig. 2.
Very small In–P bond lengths of 250 pm are found with-
in the In2P2 cycle with three-coordinate In and P atoms.
The angle sum at In1 is 360°. Due to sterical reasons the
2,4,6-tri(tert-butyl)phenyl ligands show a perpendicular
arrangement to the In2P2 ring. The phosphorus atom
P1 shows a trigonal pyramidal environment with an an-
gle sum of 342°. Relevant structural parameters are
compared with those of related compounds (Table 2).
The Ga–P and In–P bond lengths depend on the coordi-
nation number and the charge of the group 13 and 15
elements. In order to overcome the large dimerization
energy of phosphanylidene indanes and gallanes steri-
cally more demanding ligands have to be chosen at the
group 13 element and phosphorus atom.
C1
P1
H1
Ga1
Si
C19
2. Experimental
Fig. 1. Molecular structure of 1b. The ellipsoids represent a proba-
bility of 25%. The H atoms are neglected for clarity reasons. Selected
bond lengths (pm): Ga1–P1 235.3(3), P1–Si1 221.9(5), Ga1–C1 198(1),
Ga1–C19 203(1); angles (°): C1A–Ga1–C19 128.6(5), C1A–Ga1–P1
113.6(3), C19–Ga1–P1 113.6(4), Ga1–P1–Si1 120.8(2).
2.1. General remarks
All reactions were performed in an argon atmo-
sphere. The solvents were thoroughly dried and distilled

T. Rotter et al. / Inorganic Chemistry Communications 8 (2005) 809–812
811
Table 1
Selected NMR data for 1 and 2 (C6D6)
1a
1b
1c
2a
2b
2c
d(31P)
ꢀ238.9
ꢀ214.81
ꢀ227.6
ꢀ187.0
ꢀ147.0
ꢀ165.9
1J(P,H)/Hz
196
200
205
–
–
–
prior to use. KP(H)SitBu3 [15] was prepared according
to the literature procedure.
(p-tBu), 1.09 (SitBu). 13C NMR (C6D6): d 156.3,
150.4, 123.5, 119.7, 35.1, 33.7, 32.6, 31.4, 30.7, 30.6.
29Si{1H} NMR (C6D6): 28.7. 31P NMR (C6D6): d
ꢀ187.0. IR [cmꢀ1]: m 2963 s, 2905 w, 2862 w, 1596 w,
1478 w, 1391 w, 1363 w, 1262 vs, 1095 vs, 1021 vs, 898
w, 804 vs. MS–EI+ [m/z]: 1181 (M+), 1124 (M+ ꢀ tBu).
Synthesis of 2a. (2,4,6-tBu3C6H2)2InBr (0.27 g,
1.0 mmol) was dissolved in 20 mL of heptane and added
to a suspension of freshly prepared potassium tri(tert-
butyl)silylphosphanide (0.27 g, 1.0 mmol) in 15 mL of
heptane at ꢀ78 °C. The reaction mixture was slowly
warmed to room temperature whereby a colorless solid
precipitated. This solid material was removed and the
volume of the solution reduced to a few milliliters. At
30 °C colorless crystals of [(2,4,6-tBu3C6H2)InPSitBu3]2
2.2. X-ray structure determination of 2a
Data was collected on a STOE IPDS diffractometer
˚
with graphite Mo Ka radiation (k = 0.71073 A). Crys-
1
(0.37 mmol, 37%) precipitated. M.p. 248 °C. H NMR
tallographic details are summarized in Table 3. The
structure was solved and refined with the programs
SIR97 [16], SHELXL-93 and SHELXL-97 [17].
Neutral scattering factors were taken from Cromer
and Mann [18] and for the hydrogen atoms from
Stewart et al. [19].
(C6D6): d 7.62 (aromatic H), 1.80 (o-tBu), 1.39
Si2
P2
Table 3
Crystallographic data of 2a as well as details of the structure solution
and refinement proceduresa
C1
C19
In1
In2
P1
Compound
2a
Formula
FW (g molꢀ1
T (K)
In2C60H112P2Si2
1181.29
200
Si1
)
ꢀ
Space group
˚
P1
a (A)
˚
13.9067(4)
15.6528(4)
17.3559(5)
68.386(1)
84.244(1)
67.035(2)
3229.8(2)
2
b (A)
˚
c (A)
Fig. 2. Molecular structure of 2a. The ellipsoids represent a proba-
bility of 25%. The H atoms are neglected for clarity reasons and
carbon atoms drawn with arbitrary radii. Selected bond lengths (pm):
In1–P1 251.5(2), In1–P2 250.3(2), In2–P1 249.3(2), In2–P2 250.9(2),
P1–Si1 225.5(3), P2–Si2 226.9(3), In1–C1 219.7(6), In2–C19 219.5(6);
angles (°): P1–In1–P2 92.2(6), P1–In1–C1 131.5(2), P2–In1–C1
136.0(2), P1–In2-P2 92.6(6), P2–In2–C19 134.0(2), P1–In2–C19
132.77(17), In2–P2–Si2 129.4(9), In1–P2–In2 86.5(6), In1–P2–Si2
126.0(9), In1–P1–Si1 125.4(9), In2–P1–Si1 130.0(9).
a (°)
b (°)
c (°)
V (nm3)
Z
dcalcd (g cm3)
1.215
0.833
l (mmꢀ1
F(0 0 0)
)
1256
6.2 < 2h < 50.0
35,468
Scan range (°)
Measured data
Unique data (Rint
)
11,210 (0.096)
None
595
Table 2
Absorption correction
Parameters
Restraints
Comparison of selected structural parameters of selected phosphanylgallanes
and phosphanylindanes (E = Ga, In; average values of bond lengths (pm) and
angles (°))
0
0.1205
wR2 (all data, on F2)
a
a
R1 (all data)
E–P
P–Si
E–C
EPE
PEP
Lit.
0.1144
7165
Ph3GaP(SiMe3)3
[Me2GaP(SiMe3)2]2
1b
254.0 228.2 200
244.8 225.4 198.3
235.3 221.9 201
229.5 225.9 201
–
–
[12]
[13]
Data with I > 2r(I)
R1[I > 2r(I)]
91.8
88.2
0.0621
1.02
Goof sb on F2
Residual density (e nmꢀ3
a
–
–
–
–
–
–
–
–
(tBu)2GaP(tBu)SiPh3
[4]
)
1.61/ꢀ0.79
(2,4,6-Me3C6H2)2GaP(tBu)2 232.1
–
–
198.3
[5]
P
P
Definition of the R values: R1 ¼ ð kF oj ꢀ jF ckÞ= jF oj; wR2 ¼
MesP{Ga(Trip)2}2 Æ Et2O
(Me3CCH2)3InP(SiMe3)3
[Ph2InP(SiMe3)2]2
2a
225.7
198.2 136.2
[6]
P
P
2
2
1=2
2
½wðF 2o ꢀ F c2Þ ꢁ= ½wðF 2oÞ ꢁg
with wꢀ1 ¼ r2ðF 2oÞ þ ð0.0385PÞ ,
288.0 227.1 221
261.2 226.2
–
[14]
f
where P ¼ ðF 2o þ 2F c2Þ=3.
92.97 87.03 [9]
86.59 92.41
P
2
1=2
b
s ¼ f ½wðF 2o ꢀ F c2Þ ꢁ=ðNo ꢀ NpÞg
.
250.5 226.2 219.6

812
T. Rotter et al. / Inorganic Chemistry Communications 8 (2005) 809–812
[4] M.A. Petrie, K. Ruhlandt-Senge, P.P. Power, Inorg. Chem. 31
(1992) 4038–4039.
Supporting information available
[5] G. Linti, R. Frey, W. Ko¨stler, H. Schwenk, Chem. Ber. Recueil
130 (1997) 663–668.
Crystallographic data (excluding structure factors)
has been deposited with the Cambridge Crystallographic
Data Centre as Supplementary Publication No. CCDC-
269322 for 2a. Copies of the data can be obtained free of
charge on application to CCDC, 12 Union Road, Cam-
bridge CB2 1EZ, UK (e-mail: deposit@ccdc.cam.ac.uk).
[6] M.A. Petrie, P.P. Power, Inorg. Chem. 8 (1993) 1309–1312.
[7] S. Weinrich, H. Piotrowski, M. Vogt, A. Schulz, M. Westerhau-
sen, Inorg. Chem. 43 (2004) 3756.
[8] R.D. Culp, A.H. Cowley, A. Decken, R.A. Jones, Inorg. Chem.
36 (1997) 5165–5172.
[9] R.L. Wells, A.T. McPhail, L.J. Jones, M.F. Self, Polyhedron 2
(1993) 141–147.
[10] A.Y. Timoshkin, H.F. Schaefer, Inorg. Chem. 43 (2004) 3080–
3089.
[11] M. Westerhausen, T. Rotter, unpublished results (structural
Acknowledgments
ꢀ
˚
parameters of 1b: triclinic, space group P1; a = 20.027(4) A,
This work was supported financially by the German
Research Foundation (Deutsche Forschungsgemeins-
chaft DFG, Bonn/Germany). Furthermore, Th. Rotter
wishes to express his gratitude to the Fonds der Chem-
ischen Industrie (FCI) for a Ph.D. Scholarship. We also
˚
˚
b = 11.023(3) A, c = 21.902(5) A, a = 90.205(3)°; b = 94.706(4)°;
c = 89.885(5)°; V = 4818(2) A , Z = 2).
[12] R.L. Wells, S.R. Aubuchon, M.F. Self, Organometallics 11 (1992)
3
˚
3370–3375.
[13] D. Wiedmann, H.-D. Hausen, J. Weidlein, Z. Anorg. Allg. Chem.
621 (1995) 1351–1357.
acknowledge the support of Prof. P. Klufers.
¨
[14] M.F. Self, A.T. McPhail, L.J. Jones III, R.L. Wells, Polyhedron 4
(1994) 625–634.
[15] M. Westerhausen, S. Weinrich, H. Piotrowski, Z. Naturforsch. B
56 (2001) 576–580.
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