Reactions of methyl(phenyl)silylene with CO and PH3-the formation of acid-base complexes

Article abstract of DOI:10.1016/S0022-328X(01)01363-8

The thermal reaction of methyl(phenyl)silylene 1a with CO and PH₃, respectively, was investigated using matrix isolation spectroscopy in combination with DFT calculations. The silylene 1a was produced by UV irradiation (λ>400 nm followed by λ>3

Full text of DOI:10.1016/S0022-328X(01)01363-8

Journal of Organometallic Chemistry 641 (2002) 156–164
www.elsevier.com/locate/jorganchem
Reactions of methyl(phenyl)silylene with CO and PH3—
the formation of acid–base complexes
Holger Bornemann, Wolfram Sander *
Lehrstuhl fu¨r Organische Chemie II der Ruhr-Uni6ersita¨t, D-44780 Bochum, Germany
Received 17 July 2001
This work is dedicated to Professor Rolf Gleiter on the occasion of his 65th birthday
Abstract
The thermal reaction of methyl(phenyl)silylene 1a with CO and PH3, respectively, was investigated using matrix isolation
spectroscopy in combination with DFT calculations. The silylene 1a was produced by UV irradiation (u\400 nm followed by
u\350 nm) of (phenyl)silyldiazomethane 2 in high yields. The thermal reaction of 2 with CO in CO-doped argon matrices
produces the acid–base adduct 3 which was identified by IR and UV spectroscopy. The analogous reaction with PH3 produced
the acid–base adduct 4. Complex 4 is photolabile and on irradiation with UV light (u\350 nm) rearranges to methylphenyl(phos-
phino)silane 5, the product of the insertion of the silicon atom into a PH bond. © 2002 Published by Elsevier Science B.V.
Keywords: Silylene; Silaketene; Carbon monoxide; Phosphane; Matrix isolation; IR spectroscopy; DFT calculation
vacant p-orbital at the silicon atom [1–3]. Thus, silyle-
nes undergo reactions both with Lewis-acids and -
1. Introduction
bases. The formation of complexes with Lewis-bases
has been used to stabilize silylenes and tame its reactiv-
ity [3–6]. Recently we reported on the synthesis of
nes is linked to the presence of both a lone pair and a
Silylenes 1 are highly reactive intermediates of key
importance in many reactions. The reactivity of silyle-
methyl(phenyl)silylene 1a in solid argon at 10 K in high
yields by irradiation of the diazo compound 2 (Scheme
1) [7]. We were also able to investigate the thermal
reaction of 1a with molecular oxygen in O2-doped
argon matrices at temperatures between 35 and 40 K.
At these temperatures, the mobility of small trapped
molecules is high enough to allow bimolecular reac-
tions, as long as the activation barriers are essentially
zero [8].
The reaction of dimethylsilylene 1b with CO in low-
temperature matrices was described by Arrington. In
the IR spectrum an intense absorption at 1962 cm−1
was assigned to the adduct of 1b with CO. A compari-
son of the IR spectrum with semiempirical and RHF
ab-initio calculations did not allow to determine the
structure—linear ketene versus a bent complex. In a
3-methylpentane glass a UV absorption with a maxi-
mum at 342 nm was assigned to the reaction product.
Similar UV maxima in solid 3-methylpentane were also
described by Pearsall and West [9]. The structure of the
Scheme 1.
* Corresponding author. Tel.: +49-234-3224593; fax: +49-234-
3214353.
E-mail address: wolfram.sander@ruhr-uni-bochum.de (W. Sander).
0022-328X/02/$ - see front matter © 2002 Published by Elsevier Science B.V.
PII: S0022-328X(01)01363-8

H. Bornemann, W. Sander / Journal of Organometallic Chemistry 641 (2002) 156–164
157
Table 1
IR spectroscopic data for methyl(phenyl)silylene–CO adduct 3
Argon, 10 K
DFT (B3LYP/6-311++G(2d,p))
Assignment c
a
b
a
b
w (cm−1
)
I
wi/w
No.
w (cm−1
)
I
wi/w
3074.9
3061.3
3018.3
3001.2
2909.4
1992.1
1988.7
1984.8
1484.6
1431.6
1411.9
1
1.000
1.000
1.000
1.000
1.000
0.978
0.978
0.978
1.000
1.000
1.000
48
47
43
42
41
40
3185
3174
3107
3093
3027
2058
2
1.000
1.000
1.000
1.000
1.000
0.977
CꢀH str
CꢀH str
CH3 asym. str
CH3 asym. str
CH3 sym. str
CO str
2
1
1
2
3
1
1
1
100
100
3
13
12
37
36
35
34
31
28
20
19
18
17
16
12
1518
1470
1464
1463
1285
1102
808
799
752
713
699
1
1
1
1
1
2
3
1
4
4
1
1
1.000
1.000
1.000
1.000
1.000
1.000
1.000
0.999
1.000
1.000
1.000
0.993
Skel. ring, in pl. CꢀH
HCH bend
HCH bend
HCH bend, ring str
CH3 sym. bend
In pl. CꢀH bend
CH3 rock
CH2 twist
CꢀH wag
CꢀH wag
Ring breathing
SiꢀCO str, CH3 def
1241.1
1086.2
783.9
4
3
10
1.000
1.000
1.000
737.3
699.4
691.6
8
27
6
1.000
1.000
0.999
468
a Relative intensity based on the strongest peak.
b Ratio of the frequencies of the 13CO versus 12CO isotopomers.
c The assignment of experimental and calculated IR absorption is based on peak position and peak intensities and for the weak absorptions only
tentative.
2. Results and discussion
SiH2–CO adduct was investigated by Hamilton and
Schaefer using ab-initio theory [10]. These authors pre-
dicted a weakly bound non-planar structure whereas
the linear ketene structure was calculated to be a transi-
tion state. More recently Maier et al. was able to
generate the adduct of the parent silylene SiH2 with CO
in an argon matrix [11]. By comparison of the experi-
mental with DFT calculated IR spectra these authors
could show that the adduct has a bent and not a linear
ketene type structure. Beccera and Walsh were able to
demonstrate that SiH2 reacts with CO in the gas phase
essentially without an activation barrier [12].
The stabilization of silylenes 1 by the formation of an
adduct with amines has been demonstrated in a number
of examples [13]. However, reactions of 1 with phos-
phanes have not been reported. Due to the weaker PꢀH
bond, compared to the NꢀH bond, insertion reactions
could provide alternative reaction channels in these
cases.
2.1. Reaction of 1a with CO
Photolysis (u\400 nm followed by u\350 nm) of
(phenyl)silyldiazomethane 2 in an 0.5% CO-doped ar-
gon matrix at 10 K resulted in high yields of
methyl(phenyl)silylene 1a. Annealing of the matrix for
several min at 35 K results in the formation of ca. 50%
of a new product 3. Most characteristic in the IR
spectrum of 3 is a very strong and broad absorption at
1988 cm−1 (Table 1, Fig. 1). If 13CO is used in the
experiment this absorption is red-shifted by 45 cm−1
,
while the other IR bands of 3 exhibit only very small or
no shifts. This allows to assign the 1988 cm−1 absorp-
tion to the CO stretching vibration of the adduct of 1a
and CO, 3 (Scheme 2).
The carbonylation reaction of 1a to give 3 was also
followed by UV spectroscopy. Irradiation of 2 results in
the characteristic 260 and 482 nm absorptions of
Here we describe thermal reactions of silylene 1a with
CO and PH3 under the conditions of matrix isolation.
This technique allows to cleanly prepare and character-
ize the silylenes. In a second step, the thermal reaction
with CO and PH3, respectively, is induced by annealing
the matrix at a temperature where diffusion of small
molecules becomes rapid.
silylene 1a and an additional broad band with umax
=
348 nm (Fig. 2). The latter absorption strongly grows
during the thermal reaction and is consequently as-
signed to adduct 3. Simultaneously, the bands of 1a
decrease in intensity. The formation of 3 is reversible,
and photolysis (u\375 nm) of the CO adduct 3 results
in the partial recovery of 1a.

158
H. Bornemann, W. Sander / Journal of Organometallic Chemistry 641 (2002) 156–164
The structures and relative energies of the products
of the carbonylation were calculated using DFT meth-
ods (B3LYP/6-311+ +G(2d,p) including zero point
energy ZPE) (Scheme 3). The reaction of
methyl(phenyl)silylene 1a with CO to give 3 is calcu-
lated to be exothermic by 11.5 kcal mol−1. Its planar
isomer, the methyl(phenyl)silaketene, proved to be no
minimum on the potential energy surface. Instead, a
transition state TS is found, in agreement with calcula-
tions published by Hamilton and Schaefer [10] and
Maier et al. [11]. TS is 10.5 kcal mol−1 higher in energy
than adduct 3 and connects the two rotational con-
formers of 3.
2.2. Reaction of 1a with PH3
Fig. 2. UV–vis spectra showing the photochemistry of
(phenyl)silyldiazomethane (2) and the bimolecular reaction of
methyl(phenyl)silylene 1a and CO: (a) spectrum of 2, matrix-isolated
in argon at 12 K containing 0.5% CO; (b) same spectrum after 400
nm irradiation. The major constituent is now a mixture of 1-phenylsi-
lene and (phenyl)silyldiazirine; (c) same spectrum after 350 nm irradi-
ation. The major constituent is now silylene 1a; (d) same spectra after
annealing for 2, 5 and 10 min. The major constituent is now adduct
3; (e) same spectrum after 375 nm irradiation. The major constituent
is now a mixture of 1a and 3.
Irradiation (u\400 nm followed by u\350 nm) of
diazo precursor 2 in an 0.25% PH3-doped argon matrix
at 10
K
resulted also in high yields of
Scheme 3.
methyl(phenyl)silylene 1a. Annealing of this matrix for
a few minutes at 35 K leads to the disappearance of ca.
30% of 1a and the formation of a new compound 4
exhibiting strong IR absorptions at 2301 and 984 cm−1
(Table 2, Fig. 3). These bands are due to PꢀH stretch-
ing and deformation vibrations, respectively, but can-
not be assigned to PH3 (monomer or aggregates). The
comparison of the experimental IR spectrum with cal-
culations at the B3LYP/6-311+ +G(2d,p) level of the-
ory allows the assignment of the newly formed
compound to methyl(phenyl)silylene-PH3 adduct 4
(Scheme 4).
Fig. 1. Center: difference IR spectrum showing the thermally induced
reaction of methyl(phenyl)silylene 1a and CO. Bands pointing down-
wards are disappearing during the process of annealing and assigned
to 1a, bands pointing upwards are appearing and mainly assigned to
the methyl(phenyl)silylene–CO adduct 3. Bottom: IR spectrum of 1a,
calculated at the B3LYP/6-311+ +G(2d,p) level of theory. Top: IR
spectrum of 3, calculated at the B3LYP/6-311+ +G(2d,p) level of
theory.
The bimolecular reaction between 1a and PH3 was
again followed by UV spectroscopy. On annealing the
matrix the characteristic silylene absorptions disappear,
whereas the adduct 4 does not show any strong UV
absorptions.
Methyl(phenyl)silylene-PH3 adduct 4 is photochemi-
cally unstable. On UV irradiation (u\350 nm) all
bands of 4 completely disappear and a set of absorp-
tions assigned to a new compound 5 is growing in. The
most intense absorption of 5 is found at 2135 cm−1
,
Scheme 2.
typical of a SiꢀH stretching vibration. A characteristic

H. Bornemann, W. Sander / Journal of Organometallic Chemistry 641 (2002) 156–164
159
absorption splitted into two components at 2327 and
2323 cm−1 indicates the presence of PꢀH bonds (Table
3, Fig. 4). The most reasonable photochemical reaction
of 4 is the insertion of the silicon center into a PH bond
(Scheme 5). This assumption could be verified by com-
parison of the experimental IR spectrum with IR data
of methyl(phenyl)phosphinosilane 5, calculated at the
(B3LYP/6-311+ +G(2d,p)) level of theory.
For the reaction of the parent silylene SiH2 with PH3
some thermodynamic data were calculated by
Raghavachari et al. at the MP4SDTQ/6-31(d,p)//6-
31G(d) level of theory [14]. According to these calcula-
tions the SiH2–PH3 complex is stabilized by 17.5 kcal
mol−1 and the corresponding insertion product by 53.1
kcal mol−1. The activation barrier for the rearrange-
ment was determined to 19.7 kcal mol−1. In addition a
second transition state with a large barrier of 37.0 kcal
mol−1 was located.
The relative stabilities and structures of the products
of the reaction of 1a with PH3 were calculated using
B3LYP/6-311+ +G(2d,p) +ZPE theory (Scheme 6).
To compare these results with the data published by
Raghavachari et al [14]. we also calculated the SiH3+
PH3 reaction at the same level of theory. The formation
of the SiH2–PH3 adduct is exothermic by 19.3 kcal
mol−1 in good agreement with the published data. The
phosphinosilane is stabilized by 52.4 kcal mol−1, and
the activation barrier for this rearrangement is calcu-
lated to 16.7 kcal mol−1, again in agreement with the
MP4 data.
The formation of the methyl(phenyl)silylene–PH3
adduct 4 is predicted to be only slightly exothermic by
7.0 kcal mol−1, while the PH insertion product 5 is 41.0
kcal mol−1 more stable than 4. For the Cs-symmetrical
PH3 adduct of 1a a transition state is calculated which
connects both rotamers of 4 and is 28.2 kcal mol−1
Table 2
IR spectroscopic data for methyl(phenyl)silyleneꢀPH3 adduct 4
Argon, 10 K
DFT (B3LYP/6-311++G(2d,p))
Assignment b
a
w (cm−1
)
I
No.
w (cm−1
)
I a
3081.6
3065.2
4
10
54
53
52
51
50
49
48
47
46
45
44
41
40
39
38
37
36
35
34
32
31
30
29
27
26
21
20
19
18
17
15
14
13
12
3181
3169
3161
3151
3132
3080
3068
3006
2477
2452
2322
1516
1469
1463
1461
1357
1292
1274
1211
1121
1108
1095
1094
1017
1015
791
14
17
2
1
3
CꢀH str
CꢀH str
CꢀH str
CꢀH str
3052.7
3017.1
2995.3
2954.9
5
5
4
CꢀH str
8
5
CH3 asym. str
CH3 asym. str
CH3 sym. str
PꢀH str
PꢀH str
PꢀH str
Skel. ring, in pl. CꢀH
HCH bend
HCH bend
HCH bend, in pl. CꢀH bend
In pl. CꢀH bend
In pl. CꢀH bend, ring str
CH3 sym. bend
In pl. CꢀH bend
HPH bend
12
10
5
16
100
1
3
4
4
2
3
5
1
6
13
10
1
21
48
13
5
14
17
3
13
15
8
2399.0
2300.7
1478.4
1424.1
1417.4
1409.5
1325.3
1255.5
1230.2
5
100
4
1
2
4
3
2
2
1135.5
1096.1
1084.0
4
17
15
HPH bend
In pl. CꢀH bend, SiꢀC str
In pl. CꢀH bend
PH3 sym. bend, ring breathing
PH3 sym. bend
CH2 twist
CH3 rock
CꢀH wag
984.3
977.6
773.0
746.2
735.3
699.6
675.5
630.2
504.3
58
14
15
4
21
18
3
764
750
713
689
615
509
443
431
CꢀH wag
8
22
SiꢀCH3 str
PH3 def, CꢀH wag
PH3 rock, CH3 def
PH3 rock, CꢀH wag
1
a Relative intensity based on the strongest peak.
b The assignment of experimental and calculated IR absorption is based on peak positions and peak intensities and for the weak absorptions
only tentative.

160
H. Bornemann, W. Sander / Journal of Organometallic Chemistry 641 (2002) 156–164
,
bonds. With 1.144 A the CꢀO distance is slightly elon-
gated compared to uncomplexed CO. The SiꢀCꢀO
bond angle is calculated to 161.8°. Compared to 1a the
change of the structural parameters of the silylene
moiety of 3 is negligibly small [7].
As expected, the transition state structure of
methyl(phenyl)silaketene (TS) shows Cs symmetry. The
,
SiꢀC distance is with 1.743 A considerably shorter than
,
in 3, but ca. 0.040 A longer than calculations predict
for SiꢀC bonds of different silenes [15,16]. Thus, with
,
1.167 A the CꢀO bond is elongated compared to 3 and
shows a double bond character. The SiꢀC(Ph) bond
,
length is calculated to 1.845 A clearly indicating p-delo-
calization of the silaketene moiety and the phenyl
substituent.
Fig. 3. Center: difference IR spectrum showing the thermally induced
reaction of methyl(phenyl)silylene 1a and PH3. Bands pointing down-
wards are disappearing during the process of annealing and assigned
to 1a, bands pointing upwards are appearing and mainly assigned to
the methyl(phenyl)silylene–PH3 adduct 4. Bottom: IR spectrum of
1a, calculated at the B3LYP/6-311+ +G(2d,p) level of theory. Top:
IR spectrum of 4, calculated at the B3LYP/6-311+ +G(2d,p) level
of theory.
The geometry of methyl(phenyl)silylene-PH3 adduct
4 was also optimized by the same DFT method (Fig. 6).
The
calculation
predicts
a
dihedral
angle
(C(Me)ꢀSiꢀC(Ph)ꢀP) of 96.8° which is significantly
smaller than in the adduct 3 and fits better to the
idealized model of Lewis acid–base complexes. The
,
SiꢀP distance is calculated to 2.404 A which is in
excellent agreement with the value predicted by
Raghavachari et al. [14] for the parent system at the
MP4SDTQ/6-31G(d,p)//6-31(d) level of theory (also
,
2.404 A), but is definitely elongated regarding the nor-
,
mal range of SiꢀP single bond (d(SiꢀP) of 5: 2.290 A).
,
In spite of that, with 1.934 A, respectively, the SiꢀC
bonds due to both substituents are slightly longer than
calculated for 3.
Scheme 4.
The C(Me)ꢀSiꢀC(Ph)ꢀP dihedral angle of the transi-
higher in energy. The barrier for the [1,2]-H migration
from phosphorous to silicon is also 28.2 kcal mol−1
,
tion state structure connecting adduct
4
and
methyl(phenyl)phosphinosilane 5 is calculated to 126.0°
and thus is already as large as predicted for 5. The SiꢀP
and thus high enough to prevent the direct formation of
5 under matrix isolation conditions. The activation
barrier of the thermal reaction of 1a with PH3 leading
to 4 is essentially zero or extremely small (less than 1–2
kcal mol−1), otherwise this reaction would not be rapid
at temperatures as low as 35 K.
,
distance is with 2.257 A even smaller than in silane 5.
3. Experimental
Thus, compared to SiH2 the formation of acid–base
complexes of 1a with CO or PH3 results in a smaller
stabilization. This is rationalized by the stabilizing in-
teraction between the vacant p-orbital at the silicon
atom and the p system of the phenyl substituent, result-
ing in a lower affinity to external electron donors.
3.1. Calculations
The density functional theory calculations were car-
ried out using the GAUSSIAN 98 suite of programs [17]
on a Silicon Graphics Origin 2000 R10000 or a Power
Challenge R12000 workstation. Geometry optimiza-
tions and frequency calculations of the singlet species
were performed at the B3LYP [18] level of theory with
6-31G(d,p) and 6-311+ +G(2d,p) basis sets.
2.3. Calculated structures of silylene adducts 3 and 4
The fully geometry optimized structure of adduct 3 is
very similar to the parent SiH2–CO adduct calculated
by Maier et al. [11]. At the B3LYP/6-311+ +G(2d,p)
level of theory the dihedral angle of the silylene moiety
and CO is calculated to 103.7°, clearly indicating the
bonding interactions between the HOMO of CO and
the LUMO the silylene (Fig. 5). The SiꢀC bond length
3.2. Materials and general methods
1H- and 13C-NMR spectra were taken at 200.1 and
50.3 MHz, respectively (Bruker AM 400), in CDCl3 as
solvent. Mass spectra (EI, 70 eV) were taken on a
Varian MAT CH7 instruments. All reactions involving
moisture-sensitive silicon reactants were performed un-
,
of 1.887 A is within the normal range of SiꢀC single

H. Bornemann, W. Sander / Journal of Organometallic Chemistry 641 (2002) 156–164
161
der an atmosphere of dry argon. Precursor 2 for matrix
experiments was purified by preparative scale GLC
using a Siemens RGC 202 gas chromatograph.
triflate was quantitatively. 1H-NMR (CDCl3, 200
MHz): l 7.32–7.67 (m, 5H, Ph), 5.25 (s, 2H, SiH2).
13C-NMR (CDCl3, 50 MHz): l 135.79, 133.32, 129.21,
1
128.74, 126.52, 121.90, J(C,F) 314 Hz.
3.3. Phenylsilyl trifluoromethanesulfonate
3.4. (Phenyl)silyldiazomethane (2)
The triflate was prepared in analogy to a procedure
by Bassindale and Stout [19] for the synthesis of
dimethylsilyl triflate. Trifluoromethanesulfonic acid (36
mmol, 3.2 ml) was added dropwise to neat diphenylsi-
lane (36 mmol, 6.6 g) at room temperature. After
complete addition, benzene (formed as coproduct) was
slowly removed under vacuum. The yield of phenylsilyl
Compound 2 was synthesized in analogy to a proce-
dure by Martin [20] for the synthesis of (trimethylsi-
lyl)diazomethane.
Freshly
prepared
phenylsilyl
trifluoromethanesulfonate (36 mmol, 9.3 g) was added
dropwise to equimolar quantities of diazomethane (36
mmol, 1.5 g in 100 ml of diethyl ether) and ethyldiiso-
Table 3
IR spectroscopic data for methyl(phenyl)phosphinosilane 5
Argon, 10 K
DFT (B3LYP/6-311++G(2d,p))
Assignment b
a
a
w (cm−1
)
I
No.
w (cm−1
)
I
3093.4
3076.6
5
54
53
52
51
50
49
48
47
46
45
44
41
40
39
38
37
36
35
34
32
31
30
24
3185
3174
3165
3153
3150
3102
3096
3026
2371
2363
2201
1523
1465
1464
1460
1362
1298
1294
1214
1127
1099
1096
902
10
15
1
2
3
4
4
3
27
24
55
1
5
1
4
2
6
5
CꢀH str
CꢀH str
CꢀH str
CꢀH str
8
5
9
3060.8
3029.1
CꢀH str
CH3 asym. str
CH3 asym. str
CH3 sym. str
PH2 asym. str
PH2 sym. str
2977.6
2326.7
2322.8
2134.8
1498.5
1436.3
11
22
25
100
5
SiꢀH str
Skel. ring, in pl. CꢀH
In pl. CꢀH, HCH bend
HCH bend
3
1433.4
1334.2
1252.2
4
3
26
HCH bend
Skel. ring, in pl. CꢀH
In pl. CꢀH, ring str
CH3 sym. bend
In pl. CꢀH bend
In pl. CꢀH bend, SiꢀC str
HPH bend, in pl. CꢀH
HPH bend, in pl. CꢀH
SiꢀH def, CH3 rock
1
19
6
3
48
1116.1
1060.0
43
13
877.5
874.1
836.2
832.3
825.1
756.2
743.5
726.8
702.3
66
37
76
55
21
5
15
22
18
22
852
100
SiꢀH def, CH3 def, PH2 twist
21
20
19
18
17
16
15
13
12
788
760
747
714
709
681
658
597
475
1
8
25
27
1
7
2
18
7
SiꢀH def, CH3 rock, PH2 def
PH2 def, CꢀH wag
SiꢀH def, CꢀH wag
672.5
4
PH2 twist, SiꢀH def
SiꢀCH3 str, PH2 def
SiꢀH def, CH3 def, PH2 def
SiꢀPH2 str, CꢀH wag
588.3
468.7
463.3
14
8
7
11
436
9
a Relative intensity based on the strongest peak.
b The assignment of experimental and calculated IR absorption is based on peak positions and peak intensities and for the weak absorptions
only tentative.

162
H. Bornemann, W. Sander / Journal of Organometallic Chemistry 641 (2002) 156–164
Scheme 5.
Scheme 6.
Fig. 4. Center: difference IR spectrum showing the photochemistry
(375 nm irradiation) of methyl(phenyl)silylene–PH3 adduct 4. Bands
pointing downwards are disappearing during the irradiation and
assigned to 4, bands pointing upwards are appearing and mainly
assigned to methyl(phenyl)phosphinosilane (5). Bottom: IR spectrum
of 4, calculated at the B3LYP/6-311+ +G(2d,p) level of theory.
Top: IR spectrum of 5, calculated at the B3LYP/6-311+ +G(2d,p)
level of theory.
distillate was finally purified by preparative GLC (OV
101, 0.5 m, 60 °C, detector/injector 80 °C). H-NMR
1
(CDCl3, 200 MHz): l 7.60–7.65 (m, 2H, Ph), 7.40–7.42
(m, 3H, Ph), 4.77 (d, 2H, SiH2), 2.87 (t, 1H, CHN2).
13C-NMR (CDCl3, 50 MHz): l 135.11, 130.40, 128.26,
15.47. EIMS (m/e (%)): 148 (26) [M+], 120 (18) [M+−
N2], 119 (38) [M+−(N2+H)], 105 (100), 93 (28), 91
(19). IR (argon, 10 K): 3063.1 (1), 2195.3 (2), 2180.0
(2), 2154.6 (3), 2134.0 (7), 2093.0 (14), 2088.2 (100),
2082.9 (51), 1433.0 (5), 1274.0 (2), 1265.8 (8), 1158.0
(2), 1119.3 (11), 951.5 (2), 940.4 (9), 862.2 (100), 860.3
(5), 856.8 (87), 853.7 (9), 851.1 (11), 847.7 (1), 779.1 (3),
746.4 (2), 709.8 (6), 699.0 (2), 587.0 (4), 507.0 (1), 495.6
(3), 451.9 (1) cm−1 (relative intensity). UV (argon, 12
K): umax=220, 228 nm.
propylamine (40 mmol, 5.2 g) at −65 °C. After com-
plete addition the mixture was slowly warmed to 0 °C
and the white precipitate was removed by rapid filtra-
tion through a frit. The yellow solution was concen-
trated in a first step at −50 °C in vacuo in order to
remove excess diazomethane. In a second step, 2 (0.8 g,
15%) was obtained after distillation of the residue un-
der reduced pressure (ꢀ30 °C/0.2 mbar). The yellow
Fig. 5. Geometries and some structural data of methyl(phenyl)silylene 1a, its CO adduct 3 and its isomeric silaketene calculated at the
B3LYP/6-311+ +G(2d,p) level of theory.

H. Bornemann, W. Sander / Journal of Organometallic Chemistry 641 (2002) 156–164
163
Fig. 6. Geometries and some structural data of adduct 4 and several of its isomers calculated at the B3LYP/6-311+ +G(2d,p) level of theory.
3.5. Matrix spectroscopy
844.3 (5), 840.5(3), 838.9 (9), 701.0 (28), 590.2 (3), 582.1
(10), 470.4 (9) cm−1 (relative intensity).
Matrix isolation experiments were performed by
standard techniques with an APD CSW-202 Displex
closed cycle helium cryostat. Matrices were produced
by deposition of argon (Messer Griesheim, 99.9999%)
or mixtures of argon and CO (Messer Griesheim,
99.997%), 13CO (Deutero GmbH, 99.0%) or PH3
(Messer Griesheim, 99.9%), respectively, on top of a
CsI (IR) or sapphire (UV–vis) window at a rate of ca.
0.15 mmol min−1 at 30 K. Infrared spectra were
recorded by using an Equinox 55 FTIR spectrometer
with a standard resolution of 0.5 cm−1 in the range
400–4000 cm−1. UV–vis spectra were recorded on a
Hewlett–Packard 8452A diode array spectro-
photometer with a resolution of 2 nm. Irradiations were
carried out using Osram HBO 500 W/2 mercury
high-pressure arc lamps in Oriel housings equipped
with quartz optics. IR irradiation from the lamps was
absorbed by a 10 cm path of water. For wavelength
selection dichronic mirrors (‘cold mirrors’) in
combination with Schott cutoff filters (50% trans-
mission at the wavelength specified) were used.
3.7. 1-Phenylsilene (8)
Irradiation of matrix-isolated (phenyl)silyldiazo-
methane (2) with u\400 nm produced 1-phenylsilene
(8). IR (argon, 10 K): 2192.3 (13), 1433.4 (56), 1317.9
(3), 1282.5 (3), 1191.3 (3), 1122.4 (100), 964.5 (28),
960.9 (19), 917.7 (7), 851.7 (38), 737.6 (42), 656.7 (10),
646.2 (6), 450.7 (9) cm−1 (relative intensity).
3.8. Methyl(phenyl)silylene (1a)
Irradiation of matrix-isolated (phenyl)silyldiazo-
methane (2) with u\400 nm followed by u\350 nm
produced methyl(phenyl)silylene 1a. IR (argon, 10 K):
3085.7 (2), 3075.1 (15), 3055.3 (4), 3023.6 (6), 2964.9
(6), 1585.5 (33), 1496.2 (3), 1429.5 (48), 1378.4 (1),
1332.0 (5), 1260.5 (4), 1217.7 (16), 1187.8 (10), 1159.3
(2), 1091.7 (100), 953.6 (19), 777.7 (13), 735.2 (66),
695.5 (61), 686.8 (11), 666.1 (7), 657.9 (3), 649.7 (3),
575.4 (5) cm−1 (relative intensity). UV (argon, 12 K):
umax=260, 482 nm.
3.6. (Phenyl)silyldiazirine (6)
Irradiation of matrix-isolated (phenyl)silyldiazo-
methane 2 with u\400 nm produced (phenyl)silyl-
diazirine (6). IR (argon, 10 K): 2174.8 (13), 2171.7 (7),
2162.0 (5), 2151.7 (31), 2149.9 (6), 2147.1 (7), 1638.7
(4), 1433.4 (18), 1294.9 (5), 1191.3 (1), 1121.4 (20),
948.7 (4), 936.8 (35), 858.6 (100), 855.7 (3), 848.1 (4),
Acknowledgements
Financial support by the Deutsche Forschungsge-
meinschaft and the Fonds der Chemischen Industrie is
gratefully acknowledged.

164
H. Bornemann, W. Sander / Journal of Organometallic Chemistry 641 (2002) 156–164
[12] R. Becerra, R. Walsh, J. Am. Chem. Soc. 122 (2000)
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