σ-metathesis reaction and E-H activation (E = P, As) of diphosphanyl- and diarsanylsilanes in the presence of the metal complex fragments [(dppe)M] (M = Ni, Pd, Pt; dppe = 1,2-(Ph2P)2C2H4)

Article abstract of DOI:10.1016/S0022-328X(01)01348-1

The synthesis of the first 1-metalla-2,4-diphospha-3-silacyclobutanes [(dppe)M(PH)₂Sit-Bu(Is)] 1a (M = Ni, Is = 2,4,6-triisopropylphenyl, dppe = 1,2-bis(diphenylphosphino)ethane), 1c (M = Pd), 1d (M = Pt) and the analogous 1-nickela-2,4-diarsa-3-silacyclobutane [(dppe)Ni(AsH)₂Sit-Bu(Is)] (1b) is reported, which was achieved by salt metathesis reaction of t-Bu(Is)Si(EHLi)₂ (2a, E = P; 2b, E = As) with the respective metal chlorides [(dppe)MCl₂] in toluene at - 70 °C. They were characterized by means of multinuclear NMR spectroscopy, mass spectrometry and combustion analysis. Their variable temperature ¹H- and ³¹P-NMR spectra are in accordance with fast ring inversion processes and inversion of configuration at the E atoms (E = P, As), suggesting the presence of different diastereomeric forms in solution. The structures of the main diastereomeric form of 1a (triclinic, P1?) and of the isotypic derivatives 1c and 1d (monoclinic, P2₁/c), respectively, were determined by X-ray diffraction analyses. The latter revealed all cis oriented E-H and t-Bu-Si bonds and puckered ME₂Si rings. Upon heating of 1a and 1b in toluene, the first 1-metalla-2,4-diphospha-3-silabicyclo[1.1.0]butane 3a and its arsenic analogue 3b was formed through intramolecular dehydrogenation reaction and were isolated in the form of orange crystals in 60 and 85% yield, respectively. The latter exist in the two diastereomeric forms (t-Bu)endo-3a, (t-Bu)exo-3a (molar ratio 4:1) and (t-Bu)endo-3b, (t-Bu)exo-3b, respectively. Their structures were established by X-ray diffraction analysis which revealed normal P-P (2.231(1) A?) and As-As single bond distances (2.451(1) A?), suggesting that the Ni atom offsets most of the ring strain effects caused by the Si ring atom. In contrast to 1a and 1b, heating of 1c (M = Pd) in toluene at 80 °C affords, under evolution of H₂, merely the first dipalladiphosphasilabicyclo[1.1.1]pentane (4a) which was isolated in the form of black crystals in 65% yield. The analogous nickel compound 4b is accessible by the salt metathesis reaction of 1,3-dilithiated [(dppe)Ni(PLi)₂Sit-Bu(Is)] with [(dppe)NiCl₂] and was isolated in the form of red crystals in 79% yield. Both complexes 4a and 4b were structurally characterized by X-ray diffraction. Surprisingly, the Pt complex 1d remains unchanged even after prolonged heating in boiling toluene.

Full text of DOI:10.1016/S0022-328X(01)01348-1

Journal of Organometallic Chemistry 643–644 (2002) 468–478
www.elsevier.com/locate/jorganchem
s-Metathesis reaction and EꢀH activation (E=P, As) of
diphosphanyl- and diarsanylsilanes in the presence of the metal
complex fragments [(dppe)M] (M=Ni, Pd, Pt;
dppe=1,2-(Ph2P)2C2H4)
Matthias Driess a,*, Felix Franke, Hans Pritzkow b
a Lehrstuhl fu¨r Anorganische Chemie I: Moleku¨l- und Koordinationschemie, Fakulta¨t fu¨r Chemie der Ruhr-Uni6ersita¨t, Uni6ersita¨tsstrasse 150,
D-44801 Bochum, Germany
b Anorganisch-chemisches Institut der Uni6ersita¨t, Im Neuenheimer Feld 270, D-69120 Heidelberg, Germany
Received 27 August 2001; accepted 3 October 2001
Dedicated to Professor F. Mathey on the occasion of his 65th birthday
Abstract
The synthesis of the first 1-metalla-2,4-diphospha-3-silacyclobutanes [(dppe)M(PH)2Sit-Bu(Is)] 1a (M=Ni, Is=2,4,6-triiso-
propylphenyl, dppe=1,2-bis(diphenylphosphino)ethane), 1c (M=Pd), 1d (M=Pt) and the analogous 1-nickela-2,4-diarsa-3-sila-
cyclobutane [(dppe)Ni(AsH)2Sit-Bu(Is)] (1b) is reported, which was achieved by salt metathesis reaction of t-Bu(Is)Si(EHLi)2 (2a,
E=P; 2b, E=As) with the respective metal chlorides [(dppe)MCl2] in toluene at −70 °C. They were characterized by means of
multinuclear NMR spectroscopy, mass spectrometry and combustion analysis. Their variable temperature 1H- and 31P-NMR
spectra are in accordance with fast ring inversion processes and inversion of configuration at the E atoms (E=P, As), suggesting
(
the presence of different diastereomeric forms in solution. The structures of the main diastereomeric form of 1a (triclinic, P1) and
of the isotypic derivatives 1c and 1d (monoclinic, P21/c), respectively, were determined by X-ray diffraction analyses. The latter
revealed all cis oriented EꢀH and t-BuꢀSi bonds and puckered ME2Si rings. Upon heating of 1a and 1b in toluene, the first
1-metalla-2,4-diphospha-3-silabicyclo[1.1.0]butane 3a and its arsenic analogue 3b was formed through intramolecular dehydro-
genation reaction and were isolated in the form of orange crystals in 60 and 85% yield, respectively. The latter exist in the two
diastereomeric forms (t-Bu)endo-3a, (t-Bu)exo-3a (molar ratio 4:1) and (t-Bu)endo-3b, (t-Bu)exo-3b, respectively. Their structures
,
were established by X-ray diffraction analysis which revealed normal PꢀP (2.231(1) A) and AsꢀAs single bond distances (2.451(1)
,
A), suggesting that the Ni atom offsets most of the ring strain effects caused by the Si ring atom. In contrast to 1a and 1b, heating
of 1c (M=Pd) in toluene at 80 °C affords, under evolution of H2, merely the first dipalladiphosphasilabicyclo[1.1.1]pentane (4a)
which was isolated in the form of black crystals in 65% yield. The analogous nickel compound 4b is accessible by the salt
metathesis reaction of 1,3-dilithiated [(dppe)Ni(PLi)2Sit-Bu(Is)] with [(dppe)NiCl2] and was isolated in the form of red crystals in
79% yield. Both complexes 4a and 4b were structurally characterized by X-ray diffraction. Surprisingly, the Pt complex 1d remains
unchanged even after prolonged heating in boiling toluene. © 2002 Elsevier Science B.V. All rights reserved.
Keywords: s-Metathesis reaction; Bond activation; Phosphides; Arsanides; Metal complex fragments
1. Introduction
that of carbon [1]. In line with this, the larger ring
strain of three- and four-membered silaheterocycles is
caused by the reluctance of silicon to undergo s,p
hybridization [2]. This leads, in butterfly-like tetrasilabi-
cyclo[1.1.0]butanes, to unusual electronic features in
which the SiꢀSi bridgehead bond possesses diradical
character [3]. Not only that, as revealed by theoretical
calculations, one of the most interesting features of
The influence of silicon as a framework atom on the
ring strain in small cycles is considerably stronger than
* Corresponding author.
E-mail address: matthias.driess@ac1.ruhr-uni-bochum.de (M.
Driess).
0022-328X/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)01348-1

M. Driess et al. / Journal of Organometallic Chemistry 643–644 (2002) 468–478
469
2. Experimental
heterosilabicyclo[1.1.0]butanes is the existence of bond-
stretch isomers, which differ primarily in the distance
between the bridgehead atoms. Hence fragile bridge-
head bonds are also observed in 1,3-diphospha-2,4-disi-
labicyclo[1.1.0]butanes and their arsenic analogues I
which have EꢀE bridgehead distances about 6% longer
2.1. General procedures
All manipulations with reagents, syntheses and spec-
troscopic measurements were carried out under anaero-
bic conditions in a Ar atmosphere. Solvents were
purified by conventional methods and stored under an
Ar atmosphere. The starting materials tert-butyl-
isityldiphosphanylsilane (2a) and its arsenic analogue
2b were prepared according to the literature [6,7]. The
[(dppe)MCl2] salts (M=Ni, Pd, Pt) were obtained by
standard methods, using the respective KMCl3 salts
and dppe.
,
than those in unstrained cyclic diphosphanes (2.22 A)
,
and diarsanes (2.35 A), respectively [4]. However, sub-
stitution of the two peripheral diorganosilandiyl frag-
ments R2Si: in I by isovalent electronic transition metal
complex fragments results in a drastic change of the
character of the EꢀE bridgehead bond. In fact, the EꢀE
distances in isostructural M2E2 complexes II (M=tran-
,
sition metal; E=P, As) are ca. 0.1–0.15 A shorter than
expected for normal EꢀE single bonds due to favorable
s-donor and p-acceptor MꢀE interactions, according to
the Dewar–Chatt–Duncanson model (Scheme 1) [5].
The opposite electronic influence of the transition
metal center in II compared to that of the Si atoms in
I prompted us to prepare the first mixed SiE2M hetero-
cycles A and B, respectively. In line with this, we
expected that the EꢀE bridgehead bond in the new type
of hybridic compounds A is probably less fragile than
2.2. Physical measurements
1H-NMR (300 MHz), 31P-NMR (81 MHz) spectra
were recorded in a Bruker WH300 spectrometer at
room temperature (r.t.) unless otherwise stated. Chemi-
cal shifts (l) are given relative to external standards
(1H: SiMe4; 31P: 85% aq. H3PO4). Mass spectra were
recorded in a Finnigan MAT8230 spectrometer and all
isolated compounds gave C,H combustion analyses
consistent with their formulas.
in
the
respective
2,4-diphospha-1,3-disilabicy-
clo[1.1.0]butanes I. Interestingly, the latter liberate
silanediyl fragments through heating which undergo
insertion reaction into the EꢀE bridgehead bond of I
[6]. This raised the question whether A could serve as
an analogous transfer reagent of carbene-like silanediyl
and/or metal complex fragments [X] ([X]=SiR2, [M])
across the EꢀE bond in A, affording asterane-like com-
plexes of the type C (Scheme 2).
2.3. Synthesis of the 3-tert-butyl-3-isityl-1-[1,2-
bis(diphenylphosphino)ethane]-1-metalla-2,4-
diphospha-3-silacyclobutanes (1a, 1c, 1d) and of
3-tert-butyl-3-isityl-1-[bis(diphenyl-phosphino)ethane]-
1-metalla-2,4-diarsa-3-silacyclobutane (1b)
2.3.1. General synthetic procedure
A solution of 1.1 mmol of 2a and 2b, respectively, in
20 ml THF was treated with 1 ml of a 2.5 M solution
of BuLi in hexane at 0 °C. The solution was allowed to
warm up to r.t. and the solvent was removed in vacuo.
The orange solid residue was taken up in 10 ml toluene
and added to a suspension of 1.1 mmol of the respec-
tive [(dppe)MCl2] complex (M=Ni, Pd, Pt) in 10 ml
toluene at −78 °C. The mixture was warmed up to r.t.
and stirred for 10 h. Subsequently, LiCl was filtered off
and the orange–red solution was concentrated to ca. 10
ml and left for crystallization at r.t. Fractional crystal-
lization affords the desired products in only moderate
yields. The main products are the respective dehydro-
genated compounds, that is, the heterobicy-
clo[1.1.0]butanes 3a, 3b or heterobicyclo[1.1.1]pentanes
4a, 4b (see below).
Scheme 1. Heterobicyclo[1.1.0]butane types I und II.
1a. Yield: 0.32 g (0.40 mmol, 36%), orange plates,
1
m.p. 141–142 °C (dec.). H-NMR (C6D6): l=1.35 (d,
3JHH=7 Hz, 6H, p-CH(CH3)2); 1.42 (s, 9H, C(CH3)3),
1.46 (d,3JHH=6.4 Hz, 6H, o-CH(CH3)2), 1.66
2
(d,3JHH=7 Hz, 6H, o-CH(CH3)2), 1.98 (d, br, JHH
=
16 Hz, 4H, PCH2), 2.24 (s, CH3 of solvate toluene),
3
2.91 (sept, JHH=6.6 Hz, 1H, p-CH(CH3)2), 4.28 (sept,
Scheme 2. Compound types A, B and C.

470
M. Driess et al. / Journal of Organometallic Chemistry 643–644 (2002) 468–478
3JHH=6.6 Hz, 2H, o-CH (CH3)2), 7.25 (m, arom. H),
2.4. Synthesis of 3-tert-butyl-3-isityl-1-[1,2-bis-
(diphenylphosphino)ethane]-1-nickela-2,4-diphospha-3-
silabicyclo[1.1.0]butane (3a) and 3-tert-butyl-3-isityl-
1-[1,2-bis(diphenylphosphino)ethane]-1-nickela-2,4-
diarsa-3-silabicyclo[1.1.0]butane (3b)
7.29 (m, arom. H), 7.78 (m, arom. H). 31P-NMR
2
(C6D6): l= −190 (br, PH), 51.3 (t, J=1/2ꢀ JPP,cis
+
2JPP,transꢀ=22.0 Hz, dppe). EIMS; m/z (%): 806 ([M−
2H]+, 17), 749 ([M−2H−C(CH3)3]+, 10), 457
([Ni(dppe)]+, 10), 398 ([dppe]+, 82), 353 ([M−dppe−
C(CH3)3]+, 100). C45H58NiP4Si (809.6): Calc.: C, 66.76;
H, 7.22. Anal. Found: C, 66.53; H, 7.20%.
3a. A solution of 0.43 g (1.10 mmol) of 2a in 20 ml
THF was treated with 1 ml of a 2.5 M solution of BuLi
in hexane at 0 °C. The pale yellow solution was al-
lowed to warm up to r.t. and the solvent was removed
in vacuo. The yellow residue was taken up in 10 ml
toluene and added to a suspension of 1.10 mmol of
[(dppe)NiCl2] in 10 ml toluene at 0 °C. The reaction
mixture was warmed up to r.t. and stirred for 10 h.
Subsequently, LiCl was filtered off and the deep brown
solution was concentrated to ca. 10 ml and left for
crystallization at r.t., resulting in a mixture of the
(t-Bu)endo-3a and (t-Bu)exo-3a isomers. Yield: 0.48 g
(0.60 mmol, 60%), orange solid; m.p. 181–184 °C
(dec.). Single crystals of (t-Bu)endo-3a suitable for X-
ray diffraction analysis result from concentrated ben-
zene solutions at r.t. Alternatively, heating of solutions
of 1a for 12 h in boiling toluene affords also a mixture
of endo, exo-3a in the ratio of ca. 4:1. 1H-NMR (C6D6):
l=0.75 (s, C(CH3)3, (t-Bu)endo-3a), 1.12 (s, C(CH3)3,
(t-Bu)exo-3a), 0.86, 1.34, 1.45, 1.51, 1.60, 1.83
(d,3JHH=7 Hz, each set 3H, o-CH(CH3)2), 2.91 (sept,
3JHH=6.6 Hz, 1H, p-CH(CH3)2), 4.60 (sept, 3JHH=6.6
1b. Yield: 0.46 g (0.45 mmol, 40.9%), orange plates,
1
m.p. 154–155 °C (dec.). H-NMR (C6D6): l=1.36 (d,
3JHH=7 Hz, 6H, p-CH(CH3)2); 1.40 (s, 9H, C(CH3)3),
1.44 (d,3JHH=6.4 Hz, 6H, o-CH(CH3)2), 1.69
2
(d,3JHH=7 Hz, 6H, o-CH(CH3)2), 2.02 (d, br, JHH
=
16 Hz, 4H, PCH2), 2.23 (s, CH3 of solvate toluene),
3
3.04 (sept, JHH=6.6 Hz, 1H, p-CH(CH3)2), 4.41 (sept,
3JHH=6.6 Hz, 2H, o-CH (CH3)2), 7.26 (m, arom. H),
7.31 (m, arom. H), 7.75 (m, arom. H). EIMS; m/z (%):
1019 ([M−2H]+, 11), 962 ([M−2H−C(CH3)3]+, 9),
457 ([Ni(dppe)]+, 10), 398 ([dppe]+, 78), 575 ([M−
dppe−C(CH3)3]+, 100). C45H58As2NiP2Si (1022.6):
Calc.: C, 52.85; H, 5.72. Anal. Found: C, 52.67; H,
5.69%.
1c. Yield: 0.26 g (0.30 mmol, 27%), yellow rhombic
crystals, m.p. 170–175 °C (dec.). 1H-NMR (C6D6):
l=1.22 (d, 3JHH=7 Hz, 6H, p-CH(CH3)2), 1.41 (s,
9H, C(CH3)3), 1.39 (s, 9H, C(CH3)3), 1.61 (br, 12H,
o-CH(CH3)2), 1.9–2.1 (br, 4H, PCH2), 2.77 (sept,
3JHH=6.6 Hz, 1H, p-CH(CH3)2), 4.4 (br, 2H, o-
CH(CH3)2), 7.00 (m, arom. H), 7.56 (br, aromat. H),
7.77 (br, aromat. H). 31P-NMR (C6D6): l= −272 (br,
PH); −225 (br, PH), −216 (br, PH), 35–40 (br, m,
PCH2). EIMS; m/z (%): 854 ([M−2H]+, 48), 797
([M−2H−C(CH3)3]+, 58), 734 ([M−2H−C6H5−
CH(CH3)2]+, 33), 504 ([Pd(dppe)]+, 10), 398 ([dppe]+,
60); 183 ([Ph2Pꢀ2H]+, 100). C45H58P4PdSi (857.3):
Calc.: C, 63.05; H, 6.82; Anal. Found: C, 62.78; H,
6.77%.
3
Hz, 1H, o-CH(CH3)2), 4.77 (sept, JHH=6.6 Hz, 1H,
o-CH(CH3)2); 6.96–7.35 (m, arom. H), 7.80 (m, arom.
H), 7.97 (m, arom. H). 31P-NMR (C6D6): l= −82.9
2
(pseudo-t, J=1/2ꢀ JPP,cis+2JPP,transꢀ=30.8 Hz, PSi, (t-
2
Bu)endo-3a), −73.8 (pseudo-t, J=1/2ꢀ JPP,cis
+
2JPP,transꢀ=32.4 Hz, PSi, (t-Bu)exo-3a); 51.5 (pseudo-t,
J=1/2ꢀ JPP,cis+2JPP,transꢀ=32.4 Hz, PPh, (t-Bu)endo-
2
3a), 58.1 (pseudo-t, J=1/2ꢀ JPP,cis+2JPP,transꢀ=30.8 Hz,
2
PPh, (t-Bu)exo-3a). EIMS; m/z (%): 806 ([M]+, 17),
749 ([M−2H−C(CH3)3]+, 10), 457 ([Ni(dppe)]+, 10),
398 ([dppe]+, 82), 353 ([M−dppe−C(CH3)3]+, 100).
C45H56NiP4Si (807.6): Calc.: C, 66.92; H, 6.98. Anal.
Found: C, 66.69; H, 6.90%.
1d. Yield: 0.52 g (0.55 mmol, 50%); yellow rhombic
1
plates, m.p. 233–235 °C (dec.). H-NMR (C6D6): l=
3
1.21 (d, JHH=7 Hz, 6H, p-CH(CH3)2), 1.39 (d,3JHH
=
6.6 Hz, 6H, o-CH(CH3)2), 1.40 (s, 9H, C(CH3)3), 1.61
3b. An exo, endo-isomer mixture of 3b was synthe-
sized and isolated similar to the procedure for 3a,
starting off from 1.12 g (1.10 mmol) 2b and 1.10 mmol
of [(dppe)NiCl2]. Crystallization at r.t. affords a mix-
ture of the expected endo, exo-isomers, (t-Bu)endo-3b
and (t-Bu)exo-3b, in the ratio of 8:1 (1H-NMR). Yield:
0.88 g (0.86 mmol, 78%), orange solid; m.p. 171–
174 °C (dec.). Single crystals of (t-Bu)endo-3b, suitable
for X-ray diffraction analysis, result from concentrated
(d,3JHH=6.6 Hz, 6H, o-CH(CH3)2), 1.95 ( br, 4H,
3
PCH2), 2.90 (sept, JHH=7 Hz, 1H, p-CH(CH3)2), 4.33
(br., 2H, o-CH(CH3)2), 6.97 (m, 10H arom. H), 7.06
3
4
(td, 8H, JHH=6 Hz, JHH=1.8 Hz, arom. H), 7.78
(m, arom. H), 7.14 (s, 2H, arom. H of Is), 7.60 (pseudo
2
3
t, JPH=11 Hz, JHH=6 Hz, arom. H), 7.82 (pseudo t,
2JPH=11 Hz, 3JHH=6 Hz, arom. H of PPh). 31P-NMR
(C6D6): l= −211 (br, PH), 44.2 (tm, JPtP=1120 Hz,
PPh), 43.2 (tm, JPtP=1120 Hz, PPh). EIMS; m/z (%):
1
1
1
benzene solutions at r.t. H-NMR (C6D6): l=0.70 (s,
943 ([M−2H]+, 44), 887 ([M−2H−C(CH3)3]+, 100),
825 ([M−2H−C6H5−CH(CH3)2]+, 33), 593 ([Pt(-
dppe)]+, 25), 398 ([dppe]+, 82). C45H58P4PtSi (946.0):
Calc.: C, 57.13; H, 6.18. Anal. Found: C, 56.84; H,
6.15%.
C(CH3)3, (t-Bu)endo-3b), 1.19 (s, C(CH3)3, (t-Bu)exo-
3b), 0.84, 1.38, 1.54, 1.59, 1.63, 1.87 (d,3JHH=7 Hz,
3
each set 3H, o-CH(CH3)2), 2.97 (sept, JHH=6.6 Hz,
1H, p-CH(CH3)2), 4.58 (sept, 3JHH=6.6 Hz, 1H, o-
CH(CH3)2), 4.83 (sept, 3JHH=6.6 Hz, 1H, o-

M. Driess et al. / Journal of Organometallic Chemistry 643–644 (2002) 468–478
471
CH(CH3)2); 6.97–7.35 (m, arom. H), 7.91 (m, arom.
H), 7.95 (m, arom. H). EIMS; m/z (%): 895 ([M]+, 14),
836([M−2H−C(CH3)3]+, 12), 457 ([Ni(dppe)]+, 8),
440 ([M−dppe−C(CH3)3]+, 100), 398 ([dppe]+, 91).
C45H56As2NiP2Si (895.5): Calc.: C, 60.35; H, 6.30. Anal.
Found: C, 60.05; H, 6.24%.
9H, C(CH3)3), 1.38 (d,3JHH=7 Hz, 6H, o-CH(CH3)2),
1.61 (d,3JHH=7 Hz, 6H, o-CH(CH3)2), 2.20 (s, CH3 of
solvate toluene), 2.86 (m, br, 1H, p-CH(CH3)2), 4.41 (t,
3JHH=7 Hz, 2H, o-CH(CH3)2), 6.8–7.3 (m, arom. H),
7.4–8.1 (m, arom. H), 8.02 (m, arom. H). 31P-NMR
(C6D6): l= −60.5 (s, PSi), 19.4 (m, PPh), 23.7 (m,
PPh). EIMS; m/z (%): 1049 ([M−C2H4−PPh2]+, 12);
992 ([M−C2H4−PPh2−t-Bu]+, 25), 806 ([M−
Ni·dppe]+, 33), 749 ([M−Ni(dppe)−t-Bu]+, 46), 686
([M−Ni(dppe)−Ph−i-Pr]+, 21), 398 ([dppe]+, 91),
183 [PPh2ꢀ2H]+, 100). C71H80P6Ni2Si (1264.7): Calc.:
C, 67.43; H, 6.37. Anal. Found: C, 67.12; H, 6.35%.
2.5. Synthesis of 3-tert-butyl-3-isityl-2,4-diphospha-1,
5-bis[1,2-bis(diphenylphosphino)ethane]-1,5-dipallada-
3-silabicyclo[1.1.1]pentane (4a) and 3-tert-butyl-3-
isityl-2,4-diphospha-1,5-bis[1,2-bis(diphenylphosphino)-
ethane]-1,5-dinickela-3-silabicyclo[1.1.1]pentane (4b)
4a. A solution of 0.43 g (1.10 mmol) of 2a in 20 ml
THF was treated with 1 ml of a 2.5 molar solution of
BuLi in hexane at 0 °C. The pale yellow solution was
allowed to warm up to r.t. and the solvent was removed
in vacuo. The yellow residue was taken up in 10 ml
toluene and added to a suspension of 1.10 mmol of
[(dppe)PdCl2] in 10 ml toluene at 0 °C. The reaction
mixture was warmed up to r.t. and stirred for 10 h.
Subsequently, LiCl was filtered off and the dark red
solution was concentrated to ca. 10 ml. Crystallization
at r.t. affords black rhombic plates of the toluene
solvate but only in 25% yield. Alternatively, 4a is
accessible through thermolysis of 1c: A solution of 1.10
mmol 1c in 30 ml toluene is heated for 12 h at 80 °C,
giving a deep red solution. After concentration of the
latter to ca. 10 ml, the product crystallizes at r.t. in the
form of a toluene solvate. Yield: 0.47 g (0.35 mmol,
2.6. X-ray crystallographic studies of 1a, 1c, 1d, 3a,
3b, 4a and 4b
Crystal data are compiled in Table 1. Intensity data
were collected for 1a, 1c, 1d, 3a, 3b, 4a in a Siemens
Stoe AED2 diffractometer (Mo–Ka radiation, u=
,
0.71073 A, ꢀ-scan, T= −70 °C) and for 4b in a
,
Syntex R3 (Mo–Ka radiation, u=0.71073 A, ꢀ-scan,
T=22 °C). A semiempirical absorption correction was
applied („-scans). The structures were solved by direct
methods and refined by full matrix least squares based
on F2 with all measured reflections. Non-hydrogen
atoms were refined anisotropically. Hydrogen atoms
were included in calculated positions (except the hydro-
gens at the P-atoms in 1a and 1d, which were located
and refined). In 1c one of the P-atoms is disordered
over two positions. Some of the structures are isotypic:
1c and 1d, but not 1a; 3a and 3b; 4a and 4b. All
compounds except 1c and 1d crystallize with solvent
molecules, 1a with toluene, 3a, 3b, 4a and 4b with
benzene.
1
65%); m.p. 191–195 °C (dec.). H-NMR (C6D6): l=
1.21 (d,3JHH=7 Hz, 6H, p-CH(CH3)2), 1.28 (s, 9H,
C(CH3)3), 1.30 (d,3JHH=7 Hz, 6H, o-CH(CH3)2), 1.50
(d,3JHH=7 Hz, 6H, o-CH(CH3)2), 2.22 (s, CH3 of
solvate toluene), 2.80 (m, br, 1H, p-CH(CH3)2), 4.30 (t,
3JHH=7 Hz, 2H, o-CH(CH3)2), 6.6–7.2 (m, arom. H),
7.3–8.1 (m, arom. H), 7. 97 (m, arom. H). 31P-NMR
(C6D6): l= −80.0 (s, PSi), 19.7 (m, PPh), 22.7 (m,
PPh). EIMS; m/z (%): 1145 ([M−C2H4−PPh2]+, 19);
1088 ([M−C2H4−PPh2−t-Bu]+, 39), 855 ([M−
Pd·dppe]+, 41), 797 ([M−Pd(dppe)−t-Bu]+, 43), 735
([M−Pd(dppe)−Ph−i-Pr]+, 32), 398 ([dppe]+, 85),
183 [PPh2ꢀ2H]+, 100). C71H80P6Pd2Si (1360.2): Calc.:
C, 62.69; H, 5.93. Anal. Found: C, 62.45; H, 5.88%.
4b. A solution of 1.10 mmol 1a in 20 ml THF was
treated with 1 ml of a 2.5 M solution of BuLi in hexane
at 0 °C. The clear red solution was allowed to warm up
to r.t. and slowly added to a suspension of 1.10 mmol
of [(dppe)NiCl2] in 10 ml toluene at 0 °C. Subse-
quently, the reaction mixture was warmed up to r.t. and
stirred for 10 h. LiCl was removed upon filtration and
the dark red solution was concentrated to ca. 10 ml
from which the product crystallizes as toluene solvate
at r.t. in the form of dark red plates. Yield: 1.10 g (0.87
mmol, 79%); m.p. 187–190 °C (dec.). 1H-NMR (C6D6):
l=1.26 (d, 3JHH=7 Hz, 6H, p-CH(CH3)2), 1.33 (s,
3. Results and discussion
3.1. Synthesis of the metallasilacyclobutanes 1a–1d
The sterically congested diphosphanyl- and di-
arsanylsilanes 2a and 2b [6,7] were employed as starting
materials for the synthesis of the M(EH)2Si-heterocy-
clobutanes 1a–d and transformed in a two-step process.
Thus, partial lithiation of the EH2 moieties in 2a,b with
two molar equivalents BuLi and subsequent salt
metathesis reaction with the [M(dppe)]Cl2 complexes
(M=Ni, Pd, Pt; dppe=1,2-(Ph2P)2C2H4) at −70 °C
affords the M(EH)2Si-heterocyclobutanes 1a–d in mod-
erate yield (Scheme 3). The latter were isolated in the
form of orange (1a,b) and yellow crystals (1c–1d).
Their composition was confirmed by correct combus-
tion analyses (C, H) and mass spectrometry.
1
The variable temperature H- and 31P-NMR spectra
of the complexes in C7D8 suggest SiME2-ring inversion

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M. Driess et al. / Journal of Organometallic Chemistry 643–644 (2002) 468–478
473
Since the d8-metal centers M(2+) in 1 (M=Ni, Pd,
Pt) are, as expected, planar tetracoordinate, which was
confirmed by X-ray diffraction analysis (see below), the
P atoms in 1a, 1c and 1d could represent an AA%XX% (1,
1**) or an ABXY spin system (1*) (A, B=PH-31P
nuclei, X, Y=dppe-31P nuclei). However, our efforts to
distinguish the different configurations by means of
low-temperature NOESY 31P-NMR experiments, in-
2
spection of the J(P, P)-constants and analysis through
31P-NMR simulations were unsuccessful. Tentative as-
signment of different species in solution was possible in
the case of the 31P-NMR spectrum of 1d at −40 °C,
which shows three good resolved multiplets with 195Pt
satellites for the P-ring nuclei (P1, P2: l= −209.2,
−217.1 and −257.7) (Fig. 1) and three signals for the
corresponding dppe-P nuclei (P3, P4: l=48.5, 48.9,
51.1).
Scheme 3. Synthesis of 1a–d, starting from 2a and 2b.
Simulations of the multiplet signals for the PH phos-
phorus centers P1 and P2 (without 195Pt satellites)
2
revealed a relatively large difference between the J(P,
P) constants of the signals at l= −209.2, (2J(P1,
P2)=37.6 Hz), −257.7 (2J(P1, P2)=30.4 Hz) and
that at −217.1. (2J(P1, P2)=54.4 Hz). Since large
magnitudes of 2J(P, P) constants are diagnostic for
trans orientation of the respective lone pairs at phos-
phorus [10], the less intense multiplet at l= −217.1
Scheme 4. Dynamic processes of 1 in solution.
2
with a relatively large J(P1, P2) constant can be as-
signed to the diastereomeric form 1d* with l (P1)=l
(P2). The corresponding almost identical 2J(P1, P3) and
2J(P1, P4) constants of 61.5 Hz and J(P, H)=166.8
1
and, at the same time, inversion of configuration at the
E atoms (E=P, As). Such dynamic processes were also
obtained for related 1,3,2,4-Si2(EH)2 heterocyclobu-
tanes (E=P, As) [8]. The latter exhibit, as expected,
high ring flexibility and strongly reduced P/As-inversion
barriers in the range of 10–15 kcal mol−1 in compari-
son to the values of PH3 (35 kcal mol−1) and AsH3 (38
kcal mol−1), respectively [9]. The 31P-NMR spectra of
1a and 1c,d consists of two different phosphorus reso-
nance regions which were assigned to the respective P
atoms of the dppe ligand and the higher shielded PH
31P nuclei. While each of the spectra of 1a and 1d show
only a broad set of signals for the two chemically
inequivalent sorts of P atoms at room temperature, 1c
exhibits already three broad, superimposed sets of sig-
nals for the P atoms of the dppe ligand at l=35–40
and, correspondingly, three broad sets of resonances at
l= −216, −225 and −272 for the PH phosphorus
atoms. Which configurations are expected in solution?
Basically, one expects the presence of the three
diastereomeric forms 1, 1* and 1**, whereby 1* is also
enantiomeric, as shown in Scheme 4. The isomers can
be converted to one another by ring inversion (1/1**),
P inversion (1/1*) and coupled processes (1*/1**),
respectively.
Hz for 1d* are inconspicuous. However, the cis-
diastereomer 1d, having the bulky aryl group at silicon
in equatorial position, is probably preferred over 1d**
for steric reasons. Thus, the higher populated multiplet
at l= −209.2 is assigned to the diastereomer 1d. The
preference for the latter configuration was confirmed by
X-ray diffraction analysis of 1a–d.
3.2. Solid state structures of 1a, 1c and 1d
Only one of the possible diastereomeric forms with
all cis oriented EꢀH and t-BuꢀSi bonds, identical with
1 in Scheme 4, could be crystallized. This is in accor-
dance with 31P-NMR studies of 1d, which revealed the
same configuration prevailing presently in solution at
−40 °C. The crystal structures of the M(EH)2Si hete-
rocyclobutanes 1a, 1c and 1d (E=P; M=Ni, Pd, Pt)
were determined and results (see Tables 1 and 2) for 1a
(
(triclinic, P1) and the isotypic homologues 1c,d (mono-
clinic, P21/c) are depicted in Figs. 2–4.
The four-membered M(EH)2Si rings are puckered
and the bulky aryl group at silicon prefers the exo
position. The puckering angles between the Si1E1E2
and E1E2M planes in 1a (53.05(6)°) versus 1c (averaged

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M. Driess et al. / Journal of Organometallic Chemistry 643–644 (2002) 468–478
Fig. 1. P1, P2-part of the 31P-NMR spectrum of 1d in C7D8 at −40 °C.
3.3. Synthesis of the NiP2Si- and NiAs2Si-hetero-
bicyclo[1.1.0]butanes (3a,b) and the M2P2Si-hetero-
bicyclo[1.1.1]pentanes (4a,b; M=Ni, Pd)
36.3°) and 1d (36.34(5)°) are significantly different due
to the different radii of Ni(2+) versus Pd(+2) and
Pt(+2), respectively, but they are larger than the val-
ues for related 1,3,2,4-Si2(EH)2 heterocyclobutanes
(E=P, As) [8]. Since the P1 ring atom in 1c is disor-
dered, but could be refined in two split positions P1A
and P1B (Fig. 3), the resulting geometric parameter for
the four-membered SiP2Pd ring are less accurate and
deserve no discussion. The H atoms at the pyramidal
coordinated P/As atoms are cis oriented and the Si
atom is distorted tetrahedrally surrounded. While the
SiꢀP, P1ꢀM1 and P2ꢀM1 distances are inconspicuous,
The one-pot reaction of 2a with BuLi and
[M(dppe)Cl2] leads at 0 °C instead of −70 °C not
only to the Ni(PH)2Si heterocyclobutan (1a) but also to
Table 2
,
Selected bond lengths (A) and bond angles (°) for 1a, 1c and 1d
1a [M=Ni] 1c [M=Pd]
1d [M=Pt]
Bond lengths
M1ꢀP1
M1ꢀP2
M1ꢀP3
M1ꢀP4
Si1ꢀP1
,
the intramolecular P1ꢀP2 distance of 2.91 A in 1a is
2.264(2)
2.240(2)
2.158(1)
2.182(2)
2.236(2)
2.235(2)
2.324(8)/2.450(9) a 2.383(2)
,
remarkably short. The latter is ca. 0.4 A shorter than
2.367(1)
2.323(1)
2.314(1)
2.371(2)
2.286(2)
2.279(2)
those values observed in 2,4,1,3-Si2(PH)2 heterocy-
,
clobutanes (ca. 3.30 A) [8], although the SiꢀP and
2.243(7)/2.274(a) a 2.259(2)
NiꢀP1/NiꢀP2 distances are practically equal. This im-
plies that the NiꢀP bond is probably less polar than the
SiꢀP bond, which diminishes the repulsive PꢀP
interaction.
Si1ꢀP2
2.248(1)
2.252(2)
Bond angles
Si1ꢀP1ꢀM1
Si1ꢀP2ꢀM1
P1ꢀSi1ꢀP2
P1ꢀM1ꢀP2
P3ꢀM1ꢀP4
Si1ꢀP1ꢀP2/
M1ꢀP1ꢀP2
85.42(6)
86.02(6)
80.82(7)
80.11(6)
88.78(6)
53.05(6)
90.9(3)/87.0(3) a
89.66(4)
89.46(7)
89.92(7)
87.10(8)
81.66(6)
85.28(5)
36.34(5)
84.2(4)/90.7(2) a
79.9(3)/83.8(2) a
84.93(3)
The M1ꢀP3 and M1ꢀP4 distances of the dppe-P
atoms are shorter than the respective values of the PH
phosphorus atoms. The difference is probably due to a
higher donor ability of the dppe-P atoms and stronger
polarized MꢀP bonds, despite the fact that P3 and P4
atoms are four-coordinate in contrast to P1 and P2.
43.44(4)/29.21(2)
a The P1 atom has two split positions (P1A/P1B).

M. Driess et al. / Journal of Organometallic Chemistry 643–644 (2002) 468–478
475
the dehydrogenated stereoisomers (t-Bu)endo-3a and
(t-Bu)exo-3a with PꢀP bridgehead bonds. The reaction
progress and presence of different product isomers can
be easily monitored by means of 31P-NMR spec-
troscopy. While 1a reveals only one broad signal at
l= −190 for the ring P atoms, the products t-
Bu(endo)-3a and t-Bu(exo)-3a show each a sharp
pseudo triplet signal, corresponding to the respective
AA%XX% spin system (A=ring-P atom, X=dppe-P
atom) at l= −82.9 ((t-Bu)endo-3a) and −73.8 ((t-
Bu)exo-3a) in the ratio of ca. 5:7:2. Dehydrogenation of
residual 1a to 3a can be achieved upon heating of the
reaction mixture for 8 h in boiling toluene, but only if
H2 is completely removed in the system (Scheme 5).
According to 31P-NMR spectroscopy, a mixture of
the isomers (t-Bu)endo-3a and (t-Bu)exo-3a results in
the ratio of ca. 4:1 which remains unchanged even after
heating at higher temperature (130 °C). This proves
that ring inversion and configurational isomerization
are disfavored. In contrast, P2Si2-bicyclo[1.1.1]butanes
A with different sterically congested exo, endo sub-
stituents at silicon can rearrange to the thermodynamic
product via rotation of a silandiyl moiety in the transi-
tion state [4]. The resulting ratio of isomers of 3a also
reflects the fact that the t-Bu-endo isomer 1a is mainly
present in solution from which the preferred formation
of (t-Bu)endo-3a can be easily interpreted. The mecha-
nism of the dehydrogenation of 1a is hitherto unknown.
It has been shown that the conversion of 1a in toluene
into the mixture of isomers of 3a is concentration-inde-
pendent (zero order), according to kinetic studies by
means of 1H- and 31P-NMR spectroscopy. This sug-
gests that the dehydrogenation occurs in a stepwise
intramolecular process, as outlined in Scheme 6: pre-
sumably, the reactive intermediate K is formed via
reductive elimination of [M] and concomitant PꢀP bond
formation. Subsequently, K undergoes intramolecular
PꢀH activation through insertion of [M] into a PꢀH
bond and the SiE2M-butterfly skeleton 3 is finally
formed upon H2 elimination.
Fig. 2. Solid state structure of 1a. H atoms were omitted for clarity.
Fig. 3. Solid state structure of 1c. H atoms were omitted for clarity.
Fig. 4. Solid state structure of 1d. H atoms were omitted for clarity.
Similar mechanisms were already discussed for the
formation of diphosphorus (P2) and diphosphene com-
plexes (RP=PR), starting off from metathesis reac-
tions of silyphosphanes with [(dppe)MCl2] complexes
(M=Ni, Pd, Pt) [11]. While the conversion of the
Si(AsH)2Ni cycles 1b into the SiAs2Ni-butterfly skele-
ton in 3b through AsꢀH activation occurs similarly
under relatively mild reaction conditions, the congener
Si(PH)2M cycles 1c (M=Pd) and 1d (M=Pt) behave
differently. Remarkably, prolonged heating of 1c in
toluene at 80 °C affords the corresponding dipallasi-
ladiphosphabicyclo[1.1.1]pentane derivative 4a as solely
detectable product (31P-NMR) which was isolated in
the form of black crystals in 65% yield. This result
implies a higher tendency for the hypothetical SiP2Pd-
butterfly skeleton in 3c to undergo intermolecular
[(dppe)Pd] transfer in comparison to the SiP2Ni-frame
Scheme 5. Synthesis of 3a,b and 4a,b, starting from 1a–c.

476
M. Driess et al. / Journal of Organometallic Chemistry 643–644 (2002) 468–478
work in 3a. The thermolysis of 1c to 4a can be fully
suppressed through addition of ‘free’ dppe ligand to the
solutions. Accordingly, the dehydrogenation of 1a to 3a
and of 1b to 3b, respectively, can also be suppressed
upon addition of dppe. This suggests that the rate
determining step for the dehydrogenation is strongly
influenced by the mobility of the 14 valence electron
complex fragments [M]. In contrast to the reactivity of
1a–1c, the Si(PH)2Pt skeleton in 1d remains unchanged
even if heated in boiling toluene for several days. This
implies that the [(dppe)Pt] fragment is surprisingly the
least mobile organometallic moiety [M] within the series
of compounds, probably because of the higher phos-
phanido PtꢀP bond polarity [12]. An alternative access
to dimetallasiladiphosphabicyclo[1.1.1]pentanes is fur-
ther demonstrated by the two step synthesis of dark red
crystalline 4b in 79% yield, starting off from 1a via
lithiation at phosphorus and salt metathesis reaction
with [Ni(dppe)Cl2]. The 31P-NMR spectra of 4a and 4b
show multiplet pattern of higher order of a AA%BB%XX%
spin system (A,B=dppe-P nuclei, X=phosphido-P nu-
clei). The spectra prove, as expected, the presence of
two planar tetracoordinated M(+2) centers in the
M2P2Si skeletons in 4a and 4b, which was confirmed by
X-ray diffraction analysis (see below). The two chemi-
cally inequivalent sorts of dppe-P atoms in 4a and 4b
each show two pairs of multiplets at l=22.7, 19.7 and
23.7, 19.4, respectively, and represent the AA%BB% part
of the six spin systems. However, the phosphido-P
atoms reveal a broad unresolved signal at l= −80.0
(4a) and −60.5 (4b), respectively, and represent the
XX% part of the spin system. Since the latter broad
unresolved resonance signals remain even at −30 °C,
the spectra simulations revealed useless results.
Scheme 6. Proposed mechanism for the intramolecular dehydrogena-
tion of 1 to 3 and rearrangement of 3 to 4.
Table 3
,
Selected bond lengths (A) and bond angles (°) for 3a and 3b
3a (E=P)
3b (E=As)
Bond lengths
Ni1ꢀE1
Ni1ꢀE2
Ni1ꢀP3
Ni1ꢀP4
E1ꢀE2
2.261(1)
2.234(1)
2.164(1)
2.161(1)
2.223(1)
2.224(1)
2.215(1)
2.346(1)
2.353(1)
2.151(1)
2.146(1)
2.451(1)
2.327(1)
2.333(1)
3.4. Molecular structures of (t-Bu)endo-3a and
(t-Bu)endo-3b
Si1ꢀE1
Si1ꢀE2
Bond angles
Si1ꢀE1ꢀNi1
Si1ꢀE2ꢀNi1
E1ꢀSi1ꢀE2
E1ꢀNi1ꢀE2
P3ꢀNi1ꢀP4
Si1ꢀE1ꢀE2
Si1ꢀE2ꢀE1
Ni1ꢀE1ꢀE2
Ni1ꢀE2ꢀE1
Si1ꢀE1ꢀE2/M1ꢀE1ꢀE2
Single crystals, suitable for X-ray diffraction analysis,
could merely be isolated from the respective (t-
Bu)endo-isomers of 3a and 3b in benzene solutions. The
isotypical compounds crystallize as benzene-solvates in
86.77(4)
87.65(5)
60.12(5)
59.30(4)
90.80(4)
59.74(4)
60.15(4)
59.75(4)
60.95(4)
74.84(4)
85.71(4)
85.43(5)
63.46(4)
62.87(4)
91.01(5)
58.39(4)
58.14(4)
58.69(3)
58.44(4)
74.20(4)
(
the triclinic space group P1. Selected geometric data of
the compounds are summarized in Table 3. As ex-
pected, the SiE2Ni skeletons are with 74.8 (3a: E=P,
see Fig. 5) and 74.2° (3b: E=As, see Fig. 6), respec-
tively, stronger puckered than the respective precursors
1a and 1b. Compound (t-Bu)endo-3b represents the
first 2,4-diarsametallabicyclo[1.1.0]butane which could
be structurally characterized by an X-ray diffraction
analysis.
The NiꢀP distances of the bridgehead P atoms in
,
endo-3a are with 2.261(1) und 2.234(1) A almost identi-
cal and resemble the values observed in analogous
butterfly-like Ni2P2 complexes [5,11]. However, they are
,
up to 0.1 A longer than the NiꢀP distances with the
dppe-P atoms. The NiꢀAs distances in (t-Bu)endo-3b
,
(2.346(1), 2.353(1) A) are only marginally different but,
as expected, significantly longer than the values in the
dinuclear nickel(+1) arsanido complex [(Me3P)NiAst-
Fig. 5. Solid state structure of 3a. H atoms were omitted for clarity.

M. Driess et al. / Journal of Organometallic Chemistry 643–644 (2002) 468–478
477
E1ꢀSi1ꢀE2 and E1ꢀNiꢀE2 angles are inconspicuous
and little different from those values of related systems
[4,5].
3.5. Molecular structures of 4a,b
The isotypical compounds 4a,b crystallize in the
(
space group P1 and have an asterane-like SiP2M2 skele-
ton at which neither the PꢀP distances of 3.00 (4a, see
,
Fig. 7) and 2.84 A (4b, see Fig. 8), respectively, nor the
,
MꢀM distances (3.02 (4a) and 2.89 A (4b)) suggest any
Fig. 6. Solid state structure of 3b. H atoms were omitted for clarity.
favorable PꢀP- and MꢀM-s interactions, respectively.
The SiM2P2 skeletons are isostructural with that of the
currently reported Si2P2Pt skeleton in a platinadiphos-
phadisilabicyclo[1.1.1]pentane which has a PꢀP distance
3
,
of 3.063(7) A [14]. The pyramidally l -coordinated
phosphorus atoms and the almost equidistant M1ꢀP1,
M1ꢀP2, M2ꢀP1 and M2ꢀP2 distances in 4a and 4b
reflect the expected electronic features for metal phos-
phido complexes of that type. Selected distances and
angles for 4a,b are summarized in Table 4.
As expected, the metal(+2) centers are tetragonal-
planar coordinate and the respective MꢀP distances for
the dppe-P atoms are significantly shorter. The SiꢀP
distances in 4a and 4b show only marginally differences
but lead to relatively acute endocyclic PꢀSiꢀP angles of
83.87(6) (4a) and 79.15(8)° (4b), respectively. Similarly,
the endocyclic P1ꢀM1ꢀP2 and P1ꢀM2ꢀP2 angles in 4a
and 4b are also almost identical. However, the latter are
in 4a ca. 6° but in 4b only ca. 0.9° smaller than the
respective P1ꢀSi1ꢀP2 angle. Apparently, this reflects
geometric restrictions and minimizes ring strain. The
Fig. 7. Solid state structure of 4a. H atoms were omitted for clarity.
Table 4
,
Selected bond lengths (A) and bond angles (°) for 4a and 4b
Fig. 8. Solid state structure of 4b. H atoms were omitted for clarity.
4a (M=Pd)
4b (M=Ni)
Bond lengths
M1ꢀP1
M1ꢀP2
M2ꢀP1
M2ꢀP2
M1ꢀP3
M1ꢀP4
M2ꢀP5
M2ꢀP6
Si1ꢀP1
,
Bu2]2 (NiꢀAs 2.27 and 2.26 A) [13], while the NiꢀP
2.394(1)
2.387(1)
2.385(1)
2.379(1)
2.329(1)
2.309(1)
2.330(1)
2.328(1)
2.244(2)
2.247(1)
3.026(1)
2.259(2)
2.259(2)
2.248(2)
2.255(2)
2.216(2)
2.185(2)
2.202(2)
2.200(2)
2.234(2)
2.229(2)
2.890(1)
,
distances (2.151(1), 2.146(1) A) are practically identical
with the respective values in (t-Bu)endo-3a. The EꢀE
distances in (t-Bu)endo-3a (E=P, 2.23(1) A) and (t-
Bu)endo-3b (E=As, 2.451(1) A) are practically identi-
,
,
cal with the values of unstrained EꢀE bonds in
,
respective diphosphanes (PꢀP: 2.22 A) and diarsanes
,
(AsꢀAs: 2.35–2.44 A). This is remarkable since the EꢀE
Si1ꢀP2
M1ꢀM2
distances in Si2E2-butterfly skeletons ca. 6% longer,
while analogous Ni2E2-butterfly derivatives have ca. 5%
shorter EꢀE bridgehead distances [5,13]. Apparently,
the nickel atom in the hybridic butterfly-like SiE2Ni
skeletons reduces charge repulsion between the nega-
Bond angles
Si1ꢀP1ꢀM1
Si1ꢀP1ꢀM2
M1ꢀP1ꢀM2
P1ꢀSi1ꢀP2
P1ꢀM1ꢀP2
P1ꢀM2ꢀP2
P3ꢀM1ꢀP4
83.87(6)
86.97(6)
78.59(4)
83.44(6)
77.38(5)
77.72(5)
84.63(2)
85.29(7)
87.35(7)
79.74(6)
79.15(8)
78.01(6)
78.31(6)
86.60(7)
tively polarized bridgehead E atoms (Sid+ꢀEd−ꢀNid+
through its p-acceptor character. This proves that the
Ni atom offsets most of the ring strain effects caused by
the Si ring atom. The SiꢀE distances and the endocyclic
)

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M. Driess et al. / Journal of Organometallic Chemistry 643–644 (2002) 468–478
(b) R. Jones, D.J. Williams, Y. Kabe, S. Masamune, Angew.
Chem. Int. Ed. Engl. 25 (1986) 173;
(c) T. Kawase, S.A. Batcheller, S. Masamune, Chem. Lett.
(1987) 227;
MꢀP distances are inconspicuous and practically identi-
cal with the values in 1a, 1c and 3a, respectively (see
Tables 2 and 3).
(d) M. Kira, T. Iwamoto, C. Kabuto, J. Am. Chem. Soc. 118
(1996) 10303;
(e) T. Iwamoto, M. Kira, Chem. Lett. (1998) 277.
[4] (a) M. Driess, A.D. Fanta, D.R. Powell, R. West, Angew. Chem.
Int. Ed. Engl. 28 (1989) 1038;
4. Supporting material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC nos. 164584–164590 for com-
pounds 1a, 1c, 1d, 3a, 3b, 4a and 4b, respectively.
Copies of this information may be obtained free of
charge from The Director, CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (Fax: +44-1223-336033;
e-mail: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).
(b) M. Driess, H. Pritzkow, M. Reisgys, Chem. Ber. 124 (1991)
1923;
(c) A.D. Fanta, R.P. Tan, N.M. Comerlato, M. Driess, D.R.
Powell, R. West, Inorg. Chim. Acta 198–200 (1992) 733;
(d) M. Driess, R. Janoschek, H. Pritzkow, Angew. Chem. Int.
Ed. Engl. 31 (1992) 460;
(e) M. Driess, H. Pritzkow, S. Rell, R. Janoschek, Inorg. Chem.
36 (1997) 5212.
[5] (a) H. Scha¨fer, D. Binder, D. Fenske, Angew. Chem. Int. Ed.
Engl. 24 (1985) 522;
(b) H. Scha¨fer, D. Binder, Z. Anorg. Allg. Chem. 546 (1987) 55;
(c) Reviews: O.J. Scherer, Acc. Chem. Res. 32 (1999) 751;
(d) K.H. Whitemire, Adv. Organomet. Chem. 42 (1998) 1.
[6] M. Driess, H. Pritzkow, M. Reisgys, Chem. Ber. 124 (1991)
1931.
Acknowledgements
We are grateful to the Deutsche Forschungsgemein-
schaft, the Fonds der Chemischen Industrie and the
Ministerium fu¨r Schule, Wissenschaft und Forschung
des Landes Nordrhein-Westfalen for financial support.
[7] M. Driess, H. Pritzkow, Chem. Ber. 127 (1994) 477.
[8] (a) M. Baudler, H. Jongebloed, Z. Anorg. Allg. Chem. 458
(1979) 9;
(b) M. Baudler, T. Pontzen, Z. Anorg. Allg. Chem. 491 (1982)
27;
(c) G. Fritz, Adv. Inorg. Chem. 31 (1987) 171;
(d) G. Fritz, R. Biastoch, Z. Anorg. Allg. Chem. 535 (1986) 63
(see also [6]).
References
[9] (a) S. Nagase, General and Theoretical Aspects, in: S. Patai
(Ed.), The Chemistry of Organic Arsenic, Antimony and Bis-
muth Compounds, Wiley, New York, 1994, p. 1 (and cited
references therein);
[1] (a) R.S. Grev, H.F. SchaeferIII III, J. Am. Chem. Soc. 109
(1987) 6569;
(b) P.v.R. Schleyer, in: H.G. Viehl, R. Janoschek, R. Merenyi
(Eds.), Substituent Effects in Radical Chemistry, Reidel, Dor-
drecht, 1986, p. 69;
(c) Review: Y. Apeloig, Theoretical Aspects of Organosilicon
Compounds, in: S. Patai, Z. Rappoport (Eds.), The Chemistry of
Silicon Compounds, Part 1, Wiley, New York, 1989, p. 89ff;
(d) D.B. Kitchen, J.E. Jackson, L.C. Allen, J. Am. Chem. Soc.
112 (1990) 3408;
(b) Review: D.G. Gilheany, Chem. Rev. 94 (1994) 1339;
(c) M. Driess, K. Merz, C. Monse´, Z. Anorg. Allg. Chem. 626
(2000) 2264.
[10] J. Hahn, Higher Order Spectra of Polyphosphorus Compounds,
in: J.G. Verkade, L.D. Quin (Eds.), Phosphorus-31 NMR Spec-
troscopy in Stereochemical Analysis, VCH, Weinheim, 1987, p.
348.
[11] H. Scha¨fer, D. Binder, Z. Anorg. Allg. Chem. 560 (1988) 65 (and
references cited therein; see also [5]).
[12] D.K. Wicht, S.N. Paisner, B.M. Lew, D.S. Glueck, G.P.A. Yap,
M. Liable-Sands, A.L. Rheingold, C.M. Haar, S.P. Nolan,
Organometallics 17 (1998) 652.
[13] R.A. Jones, B.R. Wittlesy, Inorg. Chem. 25 (1986) 852.
[14] A.D. Fanta, M. Driess, D.R. Powell, R. West, J. Am. Chem.
Soc. 113 (1991) 7806.
(e) S. Nagase, Polyhedron 10 (1991) 1299.
[2] (a) J.A. Boatz, M.S. Gordon, J. Phys. Chem. 92 (1988) 3037;
(b) W. Kutzelnigg, Angew. Chem. 96 (1984) 262; Angew. Chem.
Int. Ed. Engl. 23 (1984) 272;
(c) R. Janoschek, Chem. Unserer Zeit 21 (1988) 128;
(d) W.W. Schoeller, T. Dabisch, Inorg. Chem. 26 (1987) 1081.
[3] (a) S. Masamune, Y. Kabe, S. Collins, D.J. Williams, R. Jones,
J. Am. Chem. Soc. 107 (1985) 5552;