The reactivity of phosphagermaallene Mes*P=C=Ge(t -Bu)tip toward aldehydes and ketones: An experimental and theoretical study

Article abstract of DOI:10.1021/om100233y

Phosphagermaallene Mes*P=C=Ge(t-Bu)Tip 1 (Tip = 2,4,6- triisopropylphenyl, Mes* = 2,4,6-tri-tert-butylphenyl) has been obtained by an improved synthesis in relation to the previously reported preparation starting from t-BuGeCl₃. Very short Ge=C (1.761(2) A) and P=C (1.625(2) A) double bond lengths, trigonal planar geometry around the Ge atom, and GeCP bond angle of 166.57° are indicative of an heteroallenic structure for 1. Its reactions with crotonaldehyde and cinnamaldehyde lead to 1-oxa-2-germacyclobutanes by a [2 + 2] cycloaddition between the Ge=C and C=O double bonds; with methyl vinyl ketone, both a [2 + 4] cycloaddition between the Ge=C and the O=C-C=C moieties and an ene-reaction are observed leading to a 1-oxa-2-germacyclohex-5-ene and a germyl(butadienyl)ether, respectively. With acetophenone, an ene-reaction occurs to afford exclusively a germyl(vinyl)ether. DFT calculations have been performed to explain the regiochemistry observed.

Full text of DOI:10.1021/om100233y

2566 Organometallics 2010, 29, 2566–2578
DOI: 10.1021/om100233y
The Reactivity of Phosphagermaallene Mes*PdCdGe(t-Bu)Tip toward
Aldehydes and Ketones: an Experimental and Theoretical Study
§
,†
†
ꢀ §
ꢀ
F. Ouhsaine,†,‡ E. Andre, J. M. Sotiropoulos, J. Escudie,* H. Ranaivonjatovo, H. Gornitzka,
N. Saffon,^ K. Miqueu,§ and M. Lazraq‡
†
ꢀ
Universite de Toulouse, UPS, LHFA, 118 route de Narbonne, F-31062 Toulouse, France CNRS, LHFA,
UMR 5069, F-31062 Toulouse cedex 09, France, Laboratoire d’Ingenierie Moleculaire et Organometallique
‡
ꢀ
ꢀ
ꢀ
(LIMOM), BP 1796, Faculteꢀdes Sciences Dhar El Mehraz, UniversiteꢀSidi Mohamed Abdellah, Feꢁs-Atlas,
ꢁ
§
Fes, Morocco, Institut Pluridisciplinaire de Recherche sur l’Environnement et les Materiaux, UMR-CNRS
ꢀ
ꢀ
ꢀ
ꢀ
5254, Universite de Pau et des Pays de l’Adour, Helioparc 2 Avenue du President Angot, 64053 Pau cedex 09,
France, Laboratoire de Chimie de Coordination du CNRS, 205 route de Narbonne, 31077 Toulouse cedex 04,
France, and ^Structure Feꢀdeꢀrative Toulousaine en Chimie Moleꢀculaire, FR 2599, Universiteꢀ Paul Sabatier,
118 route de Narbonne, 31062 Toulouse cedex 09, France
Received March 26, 2010
Phosphagermaallene Mes*PdCdGe(t-Bu)Tip 1 (Tip = 2,4,6-triisopropylphenyl, Mes* = 2,4,6-
tri-tert-butylphenyl) has been obtained by an improved synthesis in relation to the previously
˚
˚
reported preparation starting from t-BuGeCl3. Very short GedC (1.761(2) A) and PdC (1.625(2) A)
double bond lengths, trigonal planar geometry around the Ge atom, and GeCP bond angle of 166.57ꢀ
are indicative of an heteroallenic structure for 1. Its reactions with crotonaldehyde and cinnamaldehyde
lead to 1-oxa-2-germacyclobutanes by a [2 þ 2] cycloaddition between the GedC and CdO double
bonds; with methyl vinyl ketone, both a [2 þ 4] cycloaddition between the GedC and the OdC-CdC
moieties and an ene-reaction are observed leading to a 1-oxa-2-germacyclohex-5-ene and a germyl-
(butadienyl)ether, respectively. With acetophenone, an ene-reaction occurs to afford exclusively a
germyl(vinyl)ether. DFT calculations have been performed to explain the regiochemistry observed.
Introduction
heteroallenes E14dCdE0,3 compounds with an additional
CdE0 double bond to the E14dC double bond; until now,
only compounds of the type >E14dCdC< (E14 = Si,4-6
=
Ge, E15 = P;10 E14 = Sn, E15 = N11) have been obtained,
and their chemical behavior is still poorly documented [SiCN
Heteroalkenes >E14dC< (E14 = Si,1 Ge,1f,2 Sn1f,2b-d),
compounds in which one doubly bonded carbon atom has
been replaced by a heavier element of group 14, have
attracted much attention the last decades due to their great
reactivity and their marked difference with the correspond-
ing alkenes; their chemical behavior begins to be well-known.
Meanwhile, the next challenge has been the synthesis of
Ge4,7) and >E14dCdE15- (E14 = Si, E15 = N,8 P;9 E14
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*To whom correspondence should be addressed. Phone: (33) 5 61 55
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Silicon Compounds; Rappoport, Z., Apeloig, Y., Ed.; Wiley: New York,
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r
pubs.acs.org/Organometallics
Published on Web 05/19/2010
2010 American Chemical Society

Article
Organometallics, Vol. 29, No. 11, 2010 2567
Scheme 1
Scheme 2
derivatives are better considered as silylene-isocyanide
complexes than azasilaallenes >SidCdN-; due to the easy
cleavage of the silicon-carbon bond, they generally behave
like silylenes and isocyanides; the same phenomenon has
been reported for SnCN compounds]. We have prepared the
first stable compound with two heavier group 14 and 15
elements, the phosphagermaallene Mes*PdCdGe(t-Bu)Tip
(Tip =2,4,6-triisopropylphenyl, Mes*=2,4,6-tri-tert-butyl-
phenyl),10b and studied its chemical behavior toward chalco-
gens12 and saturated aldehydes (benzaldehyde) and ketones
(benzophenone, fluorenone).10b With such carbonyl deriva-
tives, only [2 þ 2] cycloadditions between the GedC and
CdO double bonds leading to oxagermetanes have been ob-
served (Scheme 1).
phosphagermapropene 3 and of phosphagermaallene 1 are
presented in Figures 1 and 2.
In 3, torsion angles C21-P1-C1-Ge1 (-164.94(9)ꢀ) and
C21-P1-C1-Cl1 (2.478(14)ꢀ) prove the formation of the E-
isomer, as previously postulated.10b The three Ge-C bond
lengths lie within the standard values,15 as well as the PdC one.
˚
The GedC double bond length in 1 (1.761(2) A) is the
shortest one reported until now; such a bond length is
1.783(2) A in the germaallene Tbt(Mes)GedCdCR27c (CR2=
˚
fluorenylidene, Tbt=2,4,6-[(Me3Si)2CH]3C6H2) and generally
between 1.77 and 1.86 A in germenes >GedC<.16,17 A rather
˚
important shortening (10.2%) is observed in relation to the
˚
corresponding Ge1-C1 single bond (1.961(2) A) in 3. The
PdC bond length (1.625(2) A) is in very good agreement with
˚
We have been interested in continuing our investigation on
the chemical behavior of phosphagermaallene Mes*PdCd
Ge(t-Bu)Tip 1 by studying its reactivity with other types of
carbonyl derivatives.
those reported in phosphaallene Mes*PdCdCPh2 (1.625(4)18a
and 1.63 A18b) and in diphosphaallene Mes*PdCdPMes*
˚
19
(1.630(8) and 1.635(8) A ). The sum of angles on the germa-
˚
nium atom (359.77ꢀ) shows a planar environment around this
atom. The angle γ between the mean plane C1-Ge1-C2-
C6 and the plane C1-P1-C21 (84.0ꢀ) is close to the ideal 90ꢀ
expected in a pure allenic structure and in good agreement
with the corresponding angle reported for other hetero-
allenes (for example 79.3ꢀ in arsaallene Mes*AsdCdCR2,
which has also doubly bonded group 14 and 15 elements).20
The P1-C1-Ge1 bond angle (166.57(14)ꢀ) is also in the
range of EdCdE0 bond angles reported for other hetero-
allenes which generally vary from 159 to 175ꢀ: 159.2ꢀ in Tbt-
(Mes)GedCdCR2,7c 168.0ꢀ in Mes*PdCdCPh2,18a 172.6(5)ꢀ
in Mes*PdCdPMes*,19 and 175.6(6)ꢀ in Mes*AsdCd
AsMes*.21
We present in this paper the reactivity of 1 toward
R-ethylenic aldehydes and ketones and toward a saturated
ketone, which has protons in R of the CO group, such as
acetophenone. DFT calculations were used to explain the
regiochemistry observed. In the first part, we describe an
improved synthesis of phosphagermaallene 1, its X-ray
structure, the first one for a heteroallene with two heavier
doubly bonded group 14 and 15 elements, and its electronic
configuration.
Results and Discussion
a. Synthesis and X-ray Structure Determination of Phos-
phagermaallene Mes*PdCdGe(t-Bu)Tip 1. tert-Butyl-2,4,6-
triisopropylphenyl(dimethoxy)germane 2 involved in the
preparation of phosphagermaallene 1 was previously ob-
tained from TipGeCl3, a derivative rather long to prepare in
a pure state.10b The yield in dimethoxygermane Tip(t-Bu)Ge-
(OMe)2 2 and its preparation time were improved starting
from t-BuGeCl3,13 followed by methoxylation to t-BuGe-
(OMe)314 and addition of TipLi. Phosphagermaallene 1 was
then prepared as previously described in a quantitative yield
according to 31P NMR analysis by dechlorofluorination of
the fluorophosphagermapropene 3 by t-BuLi at low tem-
perature (Scheme 2).10b
All these data (short GedC and PdC bond lengths,
planarity around the Ge atom, wide PdCdGe bond angle not
far to 180ꢀ, and angle between planes C-Ge-C and C-P-C
(84ꢀ) close to 90ꢀ) prove that 1 has an heteroallenic structure.
(15) (a) Baines, K. M.; Stibbs, W. G. Coord. Chem. Rev. 1995, 145,
157. (b) Holloway, C. E.; Melnik, M. Main Group Met. Chem. 2002, 25,
185.
ꢀ
ꢀ
(16) Lazraq, M.; Escudie, J.; Couret, C.; Satge, J.; Dammel, R.
Angew. Chem., Int. Ed. Engl. 1988, 27, 828.
(17) (a) Meyer, H.; Baum, G.; Massa, W.; Berndt, A. Angew. Chem.,
Int. Ed. Engl. 1987, 26, 798. (b) Tokitoh, N.; Kishikawa, K.; Okazaki, R.
J. Chem. Soc., Chem. Commun. 1995, 1425. (c) Leung, W.-P.; Kan, K.-W.;
So, C.-W.; Mak, T. C. W. Organometallics 2007, 26, 3802. (d) Meiners, F.;
Saak, W.; Weidenbruch, M. Organometallics 2000, 19, 2835. (e) Pampuch,
B.; Saak, W.; Weidenbruch, M. J. Organomet. Chem. 2006, 691, 3540. (f)
Lee, V. Ya.; Ichinohe, M.; Sekiguchi, A. J. Am. Chem. Soc. 2002, 124, 9962.
(18) (a) Yoshifuji, M.; Toyota, K.; Inamoto, N.; Hirotsu, K.;
Higuchi, T.; Nagase, S. Phosphorus Sulfur 1985, 25, 237. (b) Appel, R.;
Good single crystals of the extremely air and mois-
ture sensitive phosphagermaallene 1 were obtained by cool-
ing a saturated solution in Et2O in a sealed tube; single cry-
stals of 3 were obtained from pentane. Crystal structures of
€
Folling, P.; Josten, B.; Siray, M.; Winkhaus, V.; Knoch, F. Angew. Chem.,
Int. Ed. Engl. 1984, 23, 619.
(19) Karsch, H. H.; Reisacher, H.-U.; Muller, G. Angew. Chem., Int.
ꢀ
€
(12) Ouhsaine, F.; Ranaivonjatovo, H.; Escudie, J.; Saffon, N.;
Lazraq, M. Organometallics 2009, 28, 1973.
(13) Puff, H.; Franken, S; Schuh, W.; Schwab, W. J. Organomet.
Chem. 1983, 254, 33.
Ed. Engl. 1984, 23, 618.
(20) Bouslikhane, M.; Gornitzka, H.; Ranaivonjatovo, H.; Escudie,
ꢀ
J. Organometallics 2002, 21, 1531.
(21) Bouslikhane, M.; Gornitzka, H.; Escudie, J.; Ranaivonjatovo,
ꢀ
ꢀ
€
ꢀ
(14) Ranaivonjatovo, H.; Escudie, J.; Couret, C.; Satge, J.; Drager,
M. New J. Chem. 1989, 13, 389.
H.; Ramdane, H. J. Am. Chem. Soc. 2000, 122, 12880.

2568 Organometallics, Vol. 29, No. 11, 2010
Ouhsaine et al.
The frontier molecular orbitals (FMO) of 1 are centered on
the allene fragment and contain almost no participation from
Ge and P substituents. The LUMO corresponds to the π*PC
orbital, while the HOMO can be described as an antibonding
combination of the πGeC orbital and the phosphorus lone
pair np. These FMO are surrounded by the π*GeC orbital in
LUMOþ1, two π orbitals centered on the Mes* group in
HOMO-1(π1Mes*) andHOMO-2 (π2Mes*), andthe πPC orbital
in HOMO-3. It is noteworthy that the πGeC orbital is more
accessible than the πPC one by about 1.25 eV. Thus, it appears
that the reactivity involving the allene π system should occur
preferentially on the GedC double bond.
Figure 1. Structure of 3. Thermal ellipsoids are drawn at the
50% probability level. All hydrogen atoms are omitted for
˚
clarity. Selected bond lengths (A), bond angles (deg) and torsion
The investigation of the geometrical parameters and the
main molecular orbitals of the real molecule 1 gave mean-
ingful information on the allene reactivity. However, in the
case of mechanistic studies (particularly when looking for
transition state structures), working with the complete sys-
tem seems unreasonable in regard to computation time. The
model compound 1H has been chosen, where sterically
hindered substituents of Mes*PdCdGe(t-Bu)Tip have been
replaced by hydrogen atoms. This approximation is moti-
vated by the fact that the orbitals of the different substituents
do not contribute significally to the FMO of 1. The main
geometrical parameters of 1 and 1H are compared in Table 1.
It appears that the results obtained for the experimental
molecule and its model are in good agreement, showing that
the replacement of sterically hindering substituents in 1 has a
negligible effect on the phosphagermaallene geometry. The
main MOs of 1H are depicted in Figure 3 and compared to
those of 1. MOs in the 1H model are not modified to any
great extent. One can note that the HOMO-3 in 1 corres-
ponds to the HOMO-1 in 1H due to the absence of the two
nonbonding π orbitals (HOMO-1 and HOMO-2) centered
on the Mes* group. The comparison of the MOs energetic
positions in 1 and 1H reveals a global orbital energy shift for
the model. This shift can be explained by the σ-donor effect
of alkyl and aryl groups in 1 that destabilizes the allene
orbital and makes them more accessible than in 1H. Despite
this difference in energy, the shape and the order of the main
MOs of the experimental molecule and of the model are
almost identical. This means that 1 and 1H will share the
same chemical behavior.
angles (deg): Ge1-F1 1.768(1), Ge1-C1 1.961(2), Ge1-C6
1.968(2), Ge1-C2 1.976(2), Cl1-C1 1.742(2), P1-C1 1.673(2),
P1-C21 1.839(2), F1-Ge1-C1 96.23(6), F1-Ge1-C6 106.26(6),
C1-Ge1-C6 114.09(7), F1-Ge1-C2 103.63(6), C1-Ge1-C2
116.53(6), C6-Ge1-C2 116.57(7), C1-P1-C21 102.96(8), P1-
C1-Cl1 125.71(10), P1-C1-Ge1 119.22(9), Cl1-C1-Ge1
114.00(8), Cl1-C1-Ge1-F1 -81.69(9), C21-P1-C1-Ge1
-164.94(9), C21-P1-C1-Cl1 2.478(14).
Figure 2. Structure of 1. Thermal ellipsoids are drawn at the
50% probability level. All hydrogen atoms and rotation dis-
order of tert-butyl group are omitted for clarity. Selected bond
˚
lengths (A) and bond angles (deg): Ge1-C1 1.761(2), Ge1-C6
c. Theoretical Approach of the Reaction of HPdCdGeH2
1H with Methyl Vinyl Ketone and Crotonaldehyde. As a
first approach, the reactivity of phosphagermaallene with
R-ethylenic aldehydes and ketones can be considered by
means of the molecular orbital theory. To that purpose,
the main orbitals of 1H and those of methyl vinyl ketone and
crotonaldehyde are presented in Figure 4. These R-ethylenic
carbonyls are the most simple as well as the most commonly
used in synthesis. As the nature of the main MOs of these
two carbonyls is identical, only those of methyl vinyl ketone
have been reported. The energy levels of crotonaldehyde
orbitals are given in parentheses. The comparison between
HOMO1H-LUMOcarbonyl and HOMO-1carbonyl-LUMOþ
11H gaps is, in both cases, in favor of a nucleophilic attack of
the phosphagermaallene on the R-ethylenic carbonyl
(respectively 4.52 eV versus 5.83 eV for methyl vinyl ketone
and 4.41 eV versus 5.55 eV for the crotonaldehyde). The
HOMO of 1H, centered on πGeC, would interact with the
LUMO of the R-ethylenic carbonyl. This latter corresponds
to the bonding combination of the π*CC and π*CO orbitals.
From the theoretical point of view, interaction between
GedC and CdO moieties have been reported in the
1.951(2), Ge1-C2 1.986(8), P1-C1 1.625(2), P1-C21 1.869(2),
C1-Ge1-C6 114.43(9), C1-Ge1-C2 125.51(15), C6-Ge1-C2
119.81(15), C1-P1-C21 103.15(11), P1-C1-Ge1 166.57(14),
angle between the mean plane C1-Ge1-C2-C6 and the plane
C1-P1-C21 84.0.
b. Electronic Structure of Mes*PdCdGe(t-Bu)Tip 1 and
HPdCdGeH2 1H. To go further into the description of the
electronic structure of 1 and to study its possible chemical
behavior with R-ethylenic aldehydes and ketones (experi-
mentally used), DFT calculations were carried out at the
B3LYP/6-31G(d,p) level. The main geometrical parameters
calculated for Mes*PdCdGe(t-Bu)Tip and the parent com-
pound HPdCdGeH2 1H are reported in Table 1 and com-
pared to the experimental ones.
One can notice a good agreement between calculated and
˚
experimental values, with variations of only ∼0.01 A on
bond lengths and of ∼1.4% on Ge-C-P bond angle. In
particular, the planarity around the Ge atom and the or-
ientation of the Mes* group (R1) are well described. The
main molecular orbitals (MO) of 1 and 1H have been drawn
in Figure 3.

Article
Organometallics, Vol. 29, No. 11, 2010 2569
˚
Table 1. Comparison of Selected Bond Lengths (A) and Bond Angles (deg) Calculated for 1 and 1H with Experimental Results
Figure 3. Plot (cutoff: 0.05), nature (main contribution), and energetic positions (εi: Kohn-Sham energies) of the main molecular
orbitals (MOs) for compounds 1 and 1H.
literature.22 In particular, Mosey and co-workers have in-
vestigated the [2 þ 2] cycloaddition between formaldehyde
and germene H2CdGeH2 and found a concerted mechanism
cycloaddition can be also envisaged. The choice between
these two mechanisms should depend on the contribution of
each atom CR, Cβ, and O in the lowest unoccupied molecular
orbital of the methyl vinyl ketone or crotonaldehyde. In
particular, if the carbonyl carbon CR contribution (orbital
coefficient) is more important than the one of Cβ, then a
[2 þ 2] cycloaddition should be observed, involving a GedC
attack on the CRdO. This reaction is symmetrically per-
mitted through a supra-antara approach. On the contrary, if
the Cβ contribution for the LUMO orbital is more important
than that of CR, a [2 þ 4] cycloaddition should occur through
a supra-supra attack of GedC on CdCβ. For the methyl
vinyl ketone and crotonaldehyde, we have found that the CR
and Cβ contributions are similar in the LUMO, making
with a barrier around 17 kcal mol-1 (DFT and CASSCF
3
studies). In the present work, we investigated mechanistic
studies involving the phosphagermaallene HPdCdGeH2
and R-ethylenic aldehydes and ketones. The presence of
an unsaturation in the carbonyl compounds OdC(R)-
C(H)dC(H)R0 enriches the reactivity of this system. Indeed,
aside from a [2 þ 2] cycloaddition between the germanium
carbon double bond and the carbonyl group, a [2 þ 4]
(22) Mosey, N. J.; Baines, K. M.; Woo, T. K. J. Am. Chem. Soc. 2002,
124, 13306.

2570 Organometallics, Vol. 29, No. 11, 2010
Ouhsaine et al.
Figure 4. Plot (cutoff: 0.05), nature (main contribution), and energetic positions (εi: Kohn-Sham energies) of the principal molecular
orbitals (MO) for compounds 1H and methyl vinyl ketone. The energetic positions of crotonaldehyde orbitals are given in parentheses.
Scheme 3
possible both mechanisms. Consequently, it seemed inter-
esting to experimentally explore the competition between
these two cycloaddition reactions.
d. Reaction of 1 with Crotonaldehyde, Cinnamaldehyde,
Methyl Vinyl Ketone, and Acetophenone. By addition of one
molar equivalent of E-cinnamaldehyde to a cooled solution
of 1 in Et2O, a unique new compound was observed in 31P
NMR (4 = 254.3 ppm, d, 3JPH = 15.8 Hz), which was iso-
lated in 80% yield. With E-crotonaldehyde, two compounds
3
5 (δ31P=257.9 ppm, JPH=15.2 Hz) and 50 (δ31P=257.0
ppm, 3JPH=14.3 Hz) were formed in the ratio 85/15; only the
major product 5 could be purified by fractional crystal-
lization in 69% yield. The low-field 31P chemical shifts for
4 and 5 proved that the PdC double bond was still present
and that only the GedC unsaturation has been involved
in the reaction. Four-membered ring structures formed by a
[2 þ 2] cycloaddition between the GedC and CdO double
bonds were evidenced by the examination of the OCH
moiety in 13C NMR (4: δ = 88.91 ppm, JCP = 21.8 Hz, 5:
δ = 89.85 ppm, JCP = 21.4 Hz) and in 1H NMR (4: δ = 4.89
ppm, dd, 3JHH = 4.6 Hz, 3JHP = 15.8 Hz; 5: δ = 4.97 ppm,
dd, 3JHH = 7.6 Hz, 3JHP = 15.2 Hz) (Scheme 3). In the six-
membered rings which would be formed by [2 þ 4] cyclo-
additions between the GedC and the OdC-CdC units, the
corresponding signals should be at much lower field. Thus,
only the [2 þ 2] cycloaddition between the GedC double
bond and the CdO moiety occurred to lead to oxagerme-
tanes with exocyclic PdC double bonds (Scheme 3), contrary
to the case of germene Mes2GedCR2,23 where a [2 þ 4]
cycloaddition is observed with R-ethylenic aldehydes. The
structures of 4 (Figure 5) and 5 (Figure 6) were unambigu-
ously proved by an X-ray structure determination. The CdC
double bond presents as expected the E-configuration
as in the starting aldehyde. For the PdC double bond, an
E-configuration (Mes* trans in relation to the germanium
atom) was also determined and the Tip group, bulkier than
ꢀ
ꢀ
(23) Lazraq, M.; Escudie, J.; Couret, C.; Satge, J.; Soufiaoui, M.
Organometallics 1992, 11, 555.

Article
Organometallics, Vol. 29, No. 11, 2010 2571
Figure 7. Structure of 6. Thermal ellipsoids are drawn at the
50% probability level. All hydrogen atoms are omitted for
˚
clarity. Selected bond lengths (A) and bond angles (deg):
Figure 5. Structure of 4. Thermal ellipsoids are drawn at the
50% probability level. All hydrogen atoms and disorder of an
isopropyl group are omitted for clarity. Selected bond lengths
Ge1-O1 1.822(2), Ge1-C1 1.959(3), C1-C2 1.519(4), C2-C3
1.508(4), C3-C4 1.316(4), O1-C4 1.375(3), C4-C5 1.503(4),
Ge1-C6 1.976(3), Ge1-C10 1.986(3), P1-C1 1.664(3), P1-C25
1.867(3), O1-Ge1-C1 95.62(10), C1-P1-C25 106.45(13),
C4-O1-Ge1 121.84(18), C2-C1-P1 128.4(2), C2-C1-Ge1
110.48(19), P1-C1-Ge1 119.37(14), C3-C2-C1 114.2(2), C4-
C3-C2 127.6(3), C3-C4-O1 125.7(3).
˚
(A) and bond angles (deg): Ge1-O1 1.825(9), Ge1-C1
1.952(13), O1-C2 1.429(15), C1-C2 1.559(19), Ge1-C11
1.975(14), Ge1-C15 1.983(14), P2-C1 1.637(15), P2-C30
1.865(12), C2-C3 1.514(17), C3-C4 1.315(17), C4-C5 1.476(17),
O1-Ge1-C1 76.1(5), C2-O1-Ge1 95.0(7), C1-P2-C30
105.8(7), C2-C1-P2140.0(9),C2-C1-Ge1 86.1(8), P2-C1-Ge1
133.9(7), O1-C2-C3 115.7(10), O1-C2-C1 102.5(9), C3-C2-
C1 114.6(12).
˚
Ge-O bonds (1.825 to 1.831 A) are slightly elongated in
15
˚
relation to the standard one 1.75-1.83 A.
The four-membered ring in oxagermetane 4 is nearly planar
(O1-Ge1-C1-C2 = 3.93ꢀ, Ge1-C1-C2-O1 = -4.94ꢀ,
C1-C2-O1-Ge1=5.31ꢀ and C2-O1-Ge1-C1=-4.28ꢀ);
similar, however slightly larger torsion angles (7.24 to 9.71ꢀ),
are found in oxagermetane 5. Higher folding angles from 8 to
23ꢀ are generally reported in other oxagermetanes.24
By contrast to crotonaldehyde and cinnamaldehyde, a
completely different reaction occurred with methyl vinyl
ketone, leading to the six-membered ring compound 6 and
to the germyl(butadienyl)ether 7 (ratio 40/60) (Scheme 3).
The cyclic compound 6 was obtained in a pure state in 38%
yield by fractional crystallization of the reaction mixture
(pentane); unfortunately, the germylether 7 could not be
isolated completely pure but was contaminated with about
10% of 6 (20% yield in 7). The six-membered ring structure
of 6 was proved in the 31P NMR spectrum without decou-
pling of proton by a doublet of doublet (JPH = 14.0 and
21.3 Hz) due to the coupling of phosphorus with the
two unequivalent protons of the CH2 moiety. In a four-
membered ring 1-oxa-2-germetane (analogous to 4 and 5), these
two protons should not couple with the phosphorus atom.
Moreover, in the 1H NMR spectrum, these two protons show
signals at relatively high field (2.27 and 2.48 ppm) versus around
4 ppm expected for vinylic protons. The structure of 6 was
unambiguously proved by an X-ray study (Figure 7), which
displays, like those of 4 and 5, an E-configuration for the
Mes*PdC moiety.
Figure 6. Structure of 5. Thermal ellipsoids are drawn at the
50% probability level. All hydrogen atoms are omitted for
˚
clarity. Selected bond lengths (A) and bond angles (deg):
Ge1-O1 1.831(1), Ge1-C1 1.965(2), O1-C2 1.451(2), C1-C2
1.539(2), Ge1-C28 1.953(2), Ge1-C24 1.984(2), C1-P1 1.661(2),
P1-C6 1.860(2), C2-C3 1.490(2), C3-C4 1.310(2), C4-C5
1.499(2), O1-Ge1-C1 75.09(5), Ge1-C1-C2 87.14(9), C1-
C2-O1 101.49(11), C2-O1-Ge195.13(8),C2-C1-P1 138.95(11),
P1-C1-Ge1 133.09(8), C1-P1-C6 104.49(7), C3-C2-C1
117.46(12).
t-Bu, is on the same side as the H atom of the OCH moiety).
3
The structure of 7 was also evidenced from the 1H and 13
C
As the 31P chemical shifts and the JPH coupling constants
NMR spectra by the presence of the HH0CdCH-CdCHH0
moiety. In the 31P NMR spectrum without proton decou-
pling, a doublet was observed at 336.0 ppm (JPH = 23.4 Hz),
indicative of the presence of a proton on the sp2 carbon atom
doubly bonded to the phosphorus atom.
are about the same in 5 and 50, we suppose that both
compounds present an E-configuration of the PdC double
bond. We tentatively assign 50 to the isomer of 5 with Tip and
the CHdCHMe moiety on the same side, such a feature
being disfavored in the case of cinnamaldehyde due to the
bulkier CHdCHPh.
As both [2 þ 4] cycloaddition and ene-reaction (or reaction
with the enolic form, see further) occurred in the case of an
Despite the high steric hindrance in derivatives 4 and 5,
˚
the normal range15 as well as P-C and PdC distances. The
the intracyclic Ge-C bond lengths (1.954 to 1.966 A) are in
ꢀ
(24) Lazraq, M.; Couret, C.; Escudie, J.; Satge, J.; Drager, M.
Organometallics 1991, 10, 1771.
ꢀ
€

2572 Organometallics, Vol. 29, No. 11, 2010
Ouhsaine et al.
Scheme 4
energy is 10 kcal mol-1, and the final product lies 50 kcal mol-1
3
3
below the reactants. In agreement with the Hammond postulate,
the corresponding transition state structure is close to those
of the reactants. The O1-H7 bond length is close to that of the
˚
˚
enol form (1.06 A versus 0.97 A), while the C5-H7 distance is
˚
˚
still long (1.76 A). The Ge6-O1 distance (2.08 A) is relatively
long compared to what is observed in 7H (1.82 A).
˚
R-ethylenic ketone, which possesses a CH3 bonded to the CO
group, it was interesting to compare with another ketone,
which has also a CH3 bonded to the CO function; we have
chosen acetophenone, which presents only the possibility of
a [2 þ 2] cycloaddition and not both [2 þ 2] and [2 þ 4] ones
like methyl vinyl ketone.
For the keto form, the pathway is also a one step reaction
involving the Tk transition state. Compound 7H is obtained
via a concerted, also asynchronous, attack of oxygen of the
carbonyl group on the germanium atom with a proton
transfer occurring, this time, from the methyl group to the
allenic carbon. The transition state lies 11 kcal mol-1 over
3
In this case, only the ene-reaction was observed, leading to
the sole germyl(ethenyl)ether 8, which was isolated in 85%
yield (Scheme 4). The structure of 8 was proved by the
the reactants energy, while the product lies 32 kcal mol-1
3
˚
below. The C5-H7 distance (1.78 A) is comparable with
that found for Te with a Ge6-O1 distance (1.98 A) shorter
˚
1
presence of vinylic protons at 3.73 and 3.42 ppm in the H
NMR spectrum and by a doublet at low field (331.6 ppm,
JPH = 23.9 Hz) in the 31P NMR spectrum.
than in Te. Whereas this latter is almost formed, coherent
with the fact that in Tk the germanium environment
is slightly tetrahedral (ΣGe = 354ꢀ), the C5-H7 bond is
It was not possible in germylethers 7 and 8 to assign the
configuration around the PdC double bond from the size of
the 2JPH and 1JPC coupling constants. In the closely related
phosphagermapropene Mes*PdC(H)GeMe3,25 with the
˚
not formed. The C6-H7 bond (1.19 A) is longer than in
˚
the ketone (1.09 A) with an increasing bond length (about
10%) comparable to the one of the hydroxyl in the enol
form.
2
same Mes*PdC(H)Ge skeleton, JPdCH couplings of 23.5
and 26.4 Hz and JPdC couplings of 56.0 and 67.4 Hz have
In the two different pathways, the final product shows an
important thermodynamic stabilization compared with re-
agents, characteristic of nonreversible processes. The energy
barriers of these two reactions have almost the same magni-
1
2
been reported for Z- and E-isomers, respectively. The JPH
coupling constants found in 7 (23.4 Hz) and in 8 (23.9 Hz)
should be infavorof a Z-configuration, but the 1JPC couplings
(87.6 Hz in 7 and 76.0 Hz in 8) are in favor of the E-isomer.
Thus, when there is not the possibility of a [2 þ 4] cyclo-
addition, the ene-reaction is the sole reaction to occur. A
similar behavior was observed between germene Mes2-
GedCR2 and acetone, leading exclusively to the transient
germyl(vinyl)ether Mes2Ge(CHR2)-OC(Me)dCH2.24 How-
ever, in this case, this derivative underwent the Lutsenko
rearrangement to give the more stable germylketone Mes2-
Ge(CHR2)-CH2COMe.24 Derivative 8, probably due to a
greater steric hindrance on the germanium atom, did not
undergo such a rearrangement and was perfectly stable.
e. Theoretical Aspects of the Reactions. Methyl Vinyl
Ketone. To look further into the reactivity of 1H, we compared
the energy profiles of the different possible reactions leading to
the experimentally characterized products. In the case of methyl
vinyl ketone reaction, four different mechanisms can be con-
sidered as the most likely to occur (Figure 8): [2 þ 2] and [2 þ 4]
cycloadditions affording 9H and 6H, respectively, and ene-
reaction with the keto form or reaction with the enol form of
methyl vinyl ketone to give 7H.
Experimentally, a mixture of compounds 6 and 7 is ob-
served, which highlights the competition between at least two
different mechanisms. While the presence of oxagermine 6
indicates that one of them is a [2 þ 4] cycloaddition, the
germyl(butadienyl)ether 7 can be formed in two different
manners depending on the tautomeric form adopted by the
methyl vinyl ketone. To determine the most favored pathway
and thus the reactive form of the keto-enol equilibrium, the
energetic profiles of the ene-reaction and of the reaction with
the enol form are compared in Figure 9.
tude (11 and 10 kcal mol-1 for the keto and enol forms,
3
respectively). This means that the two reactions have the
same kinetic, or in other words that the two tautomers have
the same reactivity. Therefore, the path favored depends
only on the keto-enol equilibrium which is, as expected,
shifted to the keto form (18 kcal mol-1 more stable than enol
3
in the gas phase). This equilibrium is known to be sensitive to
solvent.26 In particular, the enol form can be stabilized by
hydrogen bonding, but as the reaction occurs in aprotic
solvent, the system should not be affected strongly by this
effect and the situation should be close to the calculated one
in gas phase. The keto tautomer is then the favored isomer,
and thus the reaction with the enol form can be neglected in
regard to the ene-reaction.
The energetic profiles of [2 þ 2] and [2 þ 4] cycloadditions
have also been calculated. They are depicted in Figure 10 as
well as the previously described ene-reaction.
The [2 þ 2] cycloaddition mechanism is a one step reaction
leading to the formation of compound 9H through T[2þ2]
.
The allene attack on the carbonyl function occurs via an
intermediate approach between supra-supra and supra-
antara facial (C2-O1-Ge6-C5 dihedral ≈39ꢀ). The struc-
ture of the TS is peculiar. The P8dC5 bond length remains in
the range of a double bond, the Ge6-C5 bond length
˚
increases (þ0.12 A) compared with 1H and the GeCP bond
angle decreases drastically (-40ꢀ). The C2-C5 bond has not
˚
˚
been formed (3.02 A). The Ge-O1 distance (1.96 A) and the
almost planar environment of the germanium atom (ΣGe =
357ꢀ) indicate that only a weak interaction between the
oxygen atom and the germanium one exists. This geometrical
modification can be highlighted considering the shape of the
MOs. The HOMO corresponds to a lone pair localized on the
C5 atom in antibonding interaction with the phospho-
rus lone pair, whereas the LUMOþ1 is a π*PdC orbital
From the enol form, compound 7H is obtained through
the Te transition state via a concerted asynchronous attack of
the oxygen atom of the hydroxyl group on the germanium
with a proton transfer to the allenic carbon. The activation
(26) Rappoport, Z., Ed., The Chemistry of Enols; Wiley: Chichester,
UK, 1990.
(25) Goede, S. J.; Bickelhaupt, F. Chem. Ber. 1991, 124, 2677.

Article
Organometallics, Vol. 29, No. 11, 2010 2573
Figure 8. Summary of the different mechanisms considered for reaction of 1H with methyl vinyl ketone. Like for phosphagermaallene,
the names of these products have been labeled with “H” to figure replacement of sterically hindering substituents by hydrogen atoms.
(a) Ene-reaction or reaction with enolic form.
Figure 9. Energy profiles (ΔG in kcal mol-1) of the reaction between 1H and the keto or enol form of methyl vinyl ketone.
3
(See Supporting Information for the plot of the MOs). As a
consequence, this TS can be viewed as a carbenoid form.
by about 30ꢀ in relation to a standard supra-supra facial
approach. The geometrical parameters of the allene moiety are
not modified to any great extent compared to those calculated
The [2 þ 4] cycloaddition leads to the formation of
27
˚
compound 6H through T[2þ4]
.
In this mechanism, the
for 1H (GeCP bond angle: þ1ꢀ, GedC: þ0.016 A, PdC:
˚
allene approach is clearly supra-supra facial (C4-O1-
Ge6-C5 dihedral angle ≈ -5ꢀ). However, the attack deviates
-0.002 A). The Ge-O1 and C4-C5 bonds have not yet been
formed (2.22 and 3.15 A, respectively) but the mechanism
˚
remains asynchronous.
Like the ene-reaction, both of the cycloadditions are
exergonic, 6H being the thermodynamic product of these
(27) A first step, consisting in a 180ꢀ rotation of the terminal CH2
group around the C2-C3 axis, has been omitted for the sake of clarity.

2574 Organometallics, Vol. 29, No. 11, 2010
Ouhsaine et al.
Figure 10. Energy profiles (ΔG in kcal mol-1) of [2 þ 2] and [2 þ 4] cycloadditions as well as ene-reaction for methyl vinyl ketone.
3
˚
Selected bond lengths (A) and bond angles (deg).
reactions. Indeed, 6H is 24 kcal mol-1 more stable than 9H,
ketone. When going from the ketone to the aldehyde, the
activation energy of the [2 þ 2] cycloaddition is decreased by
3
and 18 kcal mol-1 more stable than 7H. The comparison of
the activation energies for the two cycloaddition reactions is
3
5 kcal mol-1, while the one of [2 þ 4] cycloaddition is
3
also in favor of the [2 þ 4] cycloaddition (8 kcal mol-1 versus
increased by 7 kcal mol-1. The competition between the
3
3
18 kcal mol-1 for the [2 þ 2] one). Thus, it seems clear that
two mechanisms seems to be influenced by the carbonyl deri-
vatives. Nevertheless, taking into account the small differ-
ence between the two activation barriers, it was difficult for
us to conclude unambiguously. The steric hindrance of the
phosphagermaallene could also affect the small difference in
energy of the calculated activation barriers. For this reason,
the [2 þ 2] and [2 þ 4] cycloaddition barriers have also been
calculated with the real molecule 1. In this case, the approach
of the carbonyl is hindered by the phosphagermaallene
3
the [2 þ 4] cycloaddition is preferred to the [2 þ 2] one. When
the [2 þ 4] cycloaddition is compared to the ene-reaction, one
can note that both reactions present a barrier lower than that
found for the [2 þ 2] cycloaddition. The difference in energy
between the two activation barriers (3 kcal mol-1) is too
3
small to differentiate the kinetics of the two mechanisms.
This leads to the conclusion that the reactions occur simul-
taneously to form the two products. Computational con-
siderations are in agreement with experimental results: a
mixture of compound 6 and 7 is observed while compound 9
is not formed.
substituents, as shown by the activation barriers (18 kcal
3
mol-1 for [2 þ 2] and 22 kcal mol-1 for [2 þ 4] cyclo-
3
addition), which are slightly higher than with 1H. But, more
important, the difference in energy between the two mechan-
isms, although still small, is slightly more marked. This
confirms the trend observed with the model compound and
tends to show that the [2 þ 2] species observed experimen-
tally with crotonaldehyde is the kinetically controlled pro-
duct of the reaction while the [2 þ 4] cycloadduct obtained
with the ketone is the both kinetically and thermodynami-
cally controlled derivative.
Crotonaldehyde. In the case of the reaction with croton-
aldehyde, the [2 þ 2] and [2 þ 4] cycloadditions are also the
reactions in competition. By contrast with methyl vinyl
ketone, the [2 þ 2] cyclo-product is the unique species
obtained experimentally. The [2 þ 2] and [2 þ 4] cycload-
dition pathways are presented in Figure 11. The geome-
trical parameters of the two transition states exhibit
characteristics similar to those calculated for methyl vinyl
ketone. The difference in energy between 5H and 10H is
In conclusion, phosphagermaallene 1, which presents
a typical heteroallenic structure, is very reactive toward
R-ethylenic aldehydes and ketones and acetophenone. In
all cases, only the GedC double bond has been involved in
the reactions. When ene-reactions and [2 þ 2] cycloadditions
are possible, the ene-reaction occurs exclusively (case of
acetophenone). By contrast, when an ene-reaction is in
competition with a [2 þ 4] cycloaddition (case of methyl
vinyl ketone), both reactions occur. DFT calculations show
that the reaction with the enol form can be neglected in
relation to the ene-reaction and allow to understand the
regiochemistry of the reactions.
significant (15 kcal mol-1) and in favor of the [2 þ 4]
3
cycloadduct, which is the most thermodynamically stable
compound. However it is noteworthy that, for both path-
ways, the important stabilization of the products com-
pared to the reactants prevents the reversibility of the
processes.
The comparison of the two activation barriers is here
slightly in favor of the [2 þ 2] cycloaddition (13 kcal mol-1
3
versus 15 kcal mol-1 for [2 þ 4] cycloaddition). The differ-
3
ence in energy is too small to be significant, but it stresses out
a difference in behavior compared to the case of methyl vinyl

Article
Organometallics, Vol. 29, No. 11, 2010 2575
Figure 11. Reaction of 1H with crotonaldehyde. Energy profiles (ΔG in kcal mol-1) of [2 þ 2] and [2 þ 4] cycloadditions. Selected
3
˚
bond lengths (A) and bond angles (deg).
Experimental Section
1.54 mmol) in Et2O (20 mL) cooled to -78 ꢀC. The reaction mixture
became immediately red. By gradually warming to room tempera-
ture, a red-orange solution was obtained. A 31P NMR analysis (δ
249.9 ppm) showed the quantitative formation of phosphagermaal-
lene 1. In all cases, addition of aldehydes and ketones was performed
on such crude solutions of phosphagermaallene 1 containing LiF
without further purification.
All experiments were carried out in flame-dried glassware
under an argon atmosphere using high-vacuum-line techniques.
Solvents were freshly dried using an SPS-5MB system. NMR
spectra were recorded (with CDCl3 as solvent) on a Bruker
Avance 300 spectrometer at the following frequencies: 1H,
300.13 MHz (reference TMS); 13C, 75.47 MHz (reference TMS);
31P, (121.51 MHz) (reference H3PO4). Melting points were
determined on a Wild Leitz-Biomed apparatus. Mass spectra
were obtained on a Hewlett-Packard 5989A spectrometer by EI
at 70 eV and on a Nermag R10-10 spectrometer by CI. Ele-
mental analyses were performed by the “Service de Micro-
analyse de l0Ecole de Chimie de Toulouse”.
tert-Butyl(trimethoxy)germane. t-BuGe(OMe)3 was obtained
as previously described14 from t-BuGeCl313 and identified by its
bp (117-119 ꢀC/10-2 mm Hg) and 1H NMR spectrum.
13C NMR δ (ppm): 28.16 (CMe3), 31.10 (CMe3), 54.48 (OMe).
MS (EI, 70 eV, m/z, %): 224 (M, 3), 192 (M - MeOH, 10), 168
(M - t-Bu þ 1, 15), 137 (M - t-Bu - OMe þ 1, 60), 105 (M -
t-Bu - 2OMe, 60), 57 (t-Bu, 100).
tert-Butyl-2,4,6-triisopropylphenyl(dimethoxy)germane. A so-
lution of n-BuLi 1.6 M in hexane (19 mL, 30 mmol) was added to
a solution of TipBr (8.5 g, 30 mmol) in 60 mL of THF cooled
to -80 ꢀC. After 2 h stirring, TipLi was slowly canulated to a
solution of t-BuGe(OMe)3 (6.7 g, 30 mmol) cooled to -80 ꢀC.
The reaction mixture was warmed to room temperature, sol-
vents were eliminated in vacuo, and 30 mL of pentane were
added. Pure Tip(t-Bu)Ge(OMe)2 was obtained from pentane as
white crystals (9.61 g, 75%) and identified by NMR and mp to
Tip(t-Bu)Ge(OMe)2 previously obtained by the reaction be-
tween t-BuLi and TipGe(OMe)3.14
3-tert-Butyl-3-(2,4,6-triisopropylphenyl)-1-(2,4,6-tri-tert-butylphe-
nyl)phosphagermaallene 1. Phosphagermaallene 1 was synthesized
as previously described10b by addition of a solution of tert-butyl-
lithium 1.6 M in pentane (1.1 mL) to a solution of fluoro-
phosphagermapropene Mes*PdC(Cl)-Ge(t-Bu)(F)Tip 3 (1.04 g,
Reaction of Cinnamaldehyde with Phosphagermaallene 1.
Cinnamaldehyde (180 mg, 1.36 mmol) was added via syringe
to a solution of 1 (1.34 mmol) cooled to -50 ꢀC; an orange
coloration was observed. After stirring overnight, LiF was
eliminated by filtration; 4 crystallized from Et2O by cooling at
-20 ꢀC; white crystals of 4 were washed with pentane: 805 mg
(80%), mp 180 ꢀC.
1H NMR δ (ppm): 1.16 and 1.22 (2s, 2 ꢀ 9 H, t-BuGe and p-t-
Bu of Mes*), 1.19-1.31 (m, 18H, CHMeMe0 of Tip), 1.42 and
1.47 (2s, 2 ꢀ 9H, o-t-Bu of Mes*), 2.80-3.00 (m, 3H, CHMe-
3
3
Me0of Tip), 4.89 (dd, JHP = 15.8 Hz, JHH = 4.6 Hz, 1H,
3
3
O-CH), 5.36 (dd, JHH = 4.6 Hz, JHH = 16.0 Hz, 1H,
CH-CH-O), 6.28 (d, 3JHH = 16.0 Hz, 1H, Ph-CH), 6.99 and
7.00 (2s, 2 ꢀ 1H, arom H of Tip), 7.08-7.22 (m, 5H, H of Ph),
7.27 and 7.31 (2s, 2 ꢀ 1H, arom H of Mes*).
13C NMR δ (ppm): 23.58, 23.84, 23.97, 25.38, 27.09, 27.40 (d,
J
PC = 5.5 Hz), 34.20 and 34.92 (CH and CH3 of Tip), 27.83 and
31.33 (GeCMe3 and p-CMe3), 32.96 (d, JPC = 6.0 Hz) and 33.72
(d, JPC = 8.3 Hz) (o-CMe3), 37.79 and 37.98 (CMe3), 88.91 (d,
J
CP = 21.8 Hz, OCH), 120.81, 121.13, 122.03, and 122.60 (arom
CH of Mes* and Tip), 126.61, 127.32, and 128.04 (arom CH of
Ph and PhCH), 129.73 (d, JCP = 7.8 Hz, dCHCHO), 131.37
(d, JCP = 5.3 Hz, ipso-C of Tip), 137.70 (ipso-C of Ph), 138.63
(d, JCP = 69.1 Hz, ipso-C of Mes*), 149.56, 150.51, 152.51,
153.03, 153.38, and 154.80 (arom C of Mes*, Ph and Tip), 196.73
(d, JCP = 73.0 Hz, CdP).
31P NMR δ (ppm): 254.3 (d, 3JPH = 15.8 Hz).
MS (EI, 70 eV, m/z, %): 754 (Mþ, 20), 738 (Mþ - O, 7), 698
(Mþ - t-Bu þ 1, 25), 641 (Mþ - 2t-Bu þ 1, 80), 565 (Mþ - t-BuGe
- t-Bu - 1, 30), 509 (Mþ - t-BuGe - 2 t-Bu, 70), 493 (Mþ - Mes*

2576 Organometallics, Vol. 29, No. 11, 2010
Ouhsaine et al.
Table 2. Crystal Data for Compounds 1 and 3
1
3
empirical formula
formula wt
temp (K)
C
621.43
38H61GeP
C38H61ClFGeP
675.88
173(2)
0.40 ꢀ 0.30 ꢀ 0.05
173(2)
0.40 ꢀ 0.40 ꢀ 0.40
crystal size (mm3)
cryst syst
space group
monoclinic
C2/c
monoclinic
C2/c
˚
a (A)
43.1008(7)
10.2532(2)
17.4178(3)
90
98.543(1)
90
7611.9(2)
8
0.869
53069
9396 [R(int) = 0.0530]
semiempirical
0.9579 and 0.7226
9396/132/413
1.026
R1 = 0.0413, wR2 = 0.0926
R1 = 0.0693, wR2 = 0.1032
0.484 and -0.298
32.739(3)
10.024(1)
25.812(2)
90
113.402(2)
90
7774.2(12)
8
0.926
26637
˚
b (A)
˚
c (A)
R (deg)
β (deg)
γ (deg)
3
˚
V (A )
Z
abs coeff (mm-1
)
no. of rflns collected
no. of independent rflns
abs cor
11804 [R(int) = 0.0361]
semiemppirical
1.0000 and 0.7084
11804/0/397
max/min transmission
no. of data/restraints/params
goodness of fit on F2
final R indices (I > 2s(I))
R indices (all data)
1.025
R1 = 0.0376, wR2 = 0.0883
R1 = 0.0622, wR2 = 0.0972
0.551 and -0.366
largest diff peak, hole (e A-3
)
- O,35),465(Mþ - Mes*PdC- 1, 15), 421 (Mþ - Mes*P - t-Bu,
15), 403 (Mþ - Tip(t-Bu)GeO - 1, 40), 275 (Mes*P - 1, 60), 57
(t-Bu, 100).
Anal. Calcd for C47H69GeOP (754.43) C, 74.91; H, 9.23%.
Found: C, 75.28; H, 9.36%.
solution of phosphagermaallene (1.42 mmol) cooled to -50
ꢀC. After warming to room temperature, a 31P NMR spectrum
showed the formation of two derivatives at 277.0 and 336.1 ppm
(ratio 40/60). The solvents were eliminated under reduced
pressure and replaced by 30 mL of pentane. LiF was eliminated
by filtration. By recrystallization from pentane, the oxagermine
6 was the first to crystallize and could be obtained completely
pure (375 mg, 38%, mp 125 ꢀC). By contrast, the germylether 7
could only be obtained in 90% purity with the presence of about
10% of 6.
Reaction of Crotonaldehyde with Phosphagermaallene 1. Cro-
tonaldehyde (102 mg, 1.46 mmol) was added via syringe to
a solution of phosphagermaallene 1 (1.46 mmol) cooled to
-50 ꢀC. An orange coloration appeared immediately. A 31P
NMR spectrum showed the formation of 2 products at 257.9
ppm (3JPH = 15.2 Hz) (85%) and 257.0 ppm (3JPH = 14.3 Hz)
(15%). After elimination of LiF by filtration, the filtrate was
crystallized from Et2O; only the major isomer 5 was isolated
as white crystals (695 mg, 69%, mp 182 ꢀC).
Oxagermine 6. 1H NMR δ (ppm): 1.14-1.20 (m, CH3 of Tip),
1.26 and 1.27 (2s, 2 ꢀ 9H, t-BuGe and p-t-Bu of Mes*), 1.39 and
1.47 (2s, 2 ꢀ 9H, o-t-Bu of Mes*), 1.57 (s, 3H, Me); 2.27 (ddd,
2
3
JHH = 17.6 Hz, JHP = 14 Hz, 3JHH = 6.4 Hz, 1H, CHH0),
0
0
1H NMR δ (ppm): 1.11 (d, 3JHH = 6.6 Hz, 6H, o-CHMeMe0
of Tip), 1.19 (d, 3JHH = 6.9 Hz, 6H, o-CHMeMe0 of Tip), 1.28
(d, 3JHH = 6.2 Hz, 6H, p-CHMeMe0 of Tip), 1.13 and 1.24 (2s,
2 ꢀ 9H, t-BuGe and p-t-Bu of Mes*), 1.35 and 1.48 (2s, 2 ꢀ 9H,
0
0
2.48 (ddd, 2JHH = 17.6 Hz, 3JHP = 21.3 Hz, 3JHH = 2.0 Hz,
1H, CHH0), 2.80 (sept, 3JHH = 6.9 Hz, 1H, p-CHMeMe0 of Tip),
3.4 (broad s, Δν1/2 = 24.5 Hz, 1H, o-CHMeMe0 of Tip), 3.68
3
3
(dd, JHH = 6.4 Hz, JHH = 2.0 Hz, 1H, CHH0-CH), 3.78
(broad s, Δν1/2 = 25.9 Hz, 1H, o-CHMeMe0 of Tip), 6.98 (2s,
2 ꢀ 1H, arom H of Tip), 7.30 (2s, 2 ꢀ 1H, arom H of Mes*).
13C NMR δ (ppm): 22.03, 22.77 (d, JCP = 3.5 Hz), 23.50
(broad s), 25.09 (broad s), 25.76 (broad s), 26.70 (broad s), 27.45
(d, JPC = 5.6 Hz), 30.31, 30.83 (broad s), 32.36, 32.45, and 32.91
(CH and CH3 of Tip, GeCMe3, CMe3 of Mes* and Me), 29.31,
33.54 (d, 2JPC = 16.1 Hz), 33.85, 37.00, and 37.10 (d, JPC = 1.0 Hz)
(CH2 and CMe3), 93.43 (d, JPC = 6.4 Hz, dCH), 120.05, 120.23
(broad s), 120.61, and 121.55 (broad s) (arom CHofTipandMes*),
128.20 (d, JPC = 8.9 Hz, ipso-C of Tip), 135.32 (d, JPC = 76.5 Hz,
ipso-C of Mes*), 148.40, 148.54, 151.26, 153.26, 153.41 (d, JPC =2.9
Hz), 153.55, 156.01 (arom C of Tip and of Mes*, dCMe), 181.77 (d,
0
0
3
o-t-Bu of Mes*), 1.39 (d, JHH = 6.5 Hz, 3H, MeCHd), 2.79
(sept, 3JHH = 6.8 Hz, 3H, CHMeMe0 of Tip), 4.51 (dq, 3JHH
=
=
6.7 Hz, 3JHH = 14.9 Hz, 1H, CHdCHMe), 4.85 (ddd, 4JHP
1.5 Hz, 3JHH = 7.6 Hz, 3JHH = 14.9 Hz, 1H, CHdCHMe), 4.97
3
3
(dd, JHH = 7.6 Hz, JHP = 15.2 Hz, 1H, CHO), 6.93 (s, 2H,
arom H of Tip), 7.15 and 7.23 (2s, 2 ꢀ 2H, arom H of Mes*).
13C NMR δ (ppm): 18.00 (MeCH), 23.43, 23.90 (d, JPC = 8.4
Hz), 25.47, 26.97, 27.42 (d, JPC = 5.9 Hz), 34.17, 34.80, and
37.50 (d, JPC = 5.8 Hz) (CH and CH3 of Tip), 27.86 and 31.44
(GeCMe3 and p-CMe3), 32.87 (d, JPC = 6.2 Hz, o-CMe3) and
33.77 (d, JPC = 8.3 Hz, o-CMe3), 34.87, 37.83, 37.93 (CMe3),
89.85 (d, JPC = 21.4 Hz, OCH), 120.7, 121.06, 121.29, and
122.29 (arom CH of Tip and Mes*), 123.93 (dCHMe), 131.40
JCP = 74.3 Hz, CdP).
31P NMR δ (ppm): 273.13 (dd, 3JPH = 14 Hz, 3JPH = 21.3 Hz).
MS (EI, 70 eV, m/z, %): 692 (Mþ, 10), 635 (Mþ - t-Bu, 100),
579 (Mþ - 2 t-Bu þ1, 10), 565 (Mþ - 2 t-Bu - CH3 þ 2, 5),
360 (Tip(t-Bu)GeO-C þ 2, 70), 277 (Mes*P þ 1, 90), 57 (t-Bu,
100).
3
(d, JCP = 5.3 Hz, ipso-C of Tip), 131.93 (d, JPC = 7.9 Hz,
CHdCHMe), 137.62 (d, 1JPC=70.0 Hz, ipso-C of Mes*), 148.99,
150.43, 152.34 (d, JPC=2.8 Hz), 152.46, 153.31 and 154.82 (arom C
of Tip and Mes*), 197.24 (d, JPC = 73.0 Hz, CdP).
31P NMR δ (ppm): 257.9 (d, 3JPH = 15.2 Hz).
MS (EI, 70 eV, m/z, %): 692 (Mþ, 30), 635 (Mþ - t-Bu, 30),
Anal. Calcd for C42H67GeOP (691.55) C, 72.95; H, 9.77%.
Found: C, 72.81; H, 9.56%.
579 (Mþ - 2t-Bu þ 1, 100), 447 (Mþ - Mes*, 50), 341 (Mþ
-
Germylether 7. 1H NMR δ (ppm): 0.62-1.70 (m, CHMeMe0
of Tip and t-Bu), 2.69-2.86 (m, 3H, CHMeMe0 of Tip), 3.70 (s,
1H, OCdCHH0), 3.92 (s, 1H, OCdCHH0), 5.01 (d, 3JHH = 10.2
TipGeO - t-Bu - 1, 50), 289 (TipGeC, 50), 277 (TipGe, 90), 275
(Mes*P - 1, 90), 231 (TipGe - iPr - 3, 40), 57 (t-Bu, 100).
Anal. Calcd for C42H67GeOP (691.55) C, 72.95; H, 9.77%.
Found: C, 73.11; H, 9.66%.
3
Hz, 1H, CHdCHH0; H cis in relation to H), 5.67 (d, JHH
=
0
16.9 Hz, 1H, CHdCHH0; H0 trans in relation to H), 6.09 (ddd,
Reaction of Methyl Vinyl Ketone with Phosphagermaallene 1.
Methyl vinyl ketone (100 mg, 1.42 mmol) was added to a
JHH = 1 Hz, 3JHH = 10.2 Hz, 3JHH = 16.9 Hz, CHdCHH ),
4
0
0

Article
Organometallics, Vol. 29, No. 11, 2010 2577
Table 3. Crystal Data for Compounds 4, 5, and 6
4
5
6
empirical formula
formula wt
temp (K)
C47H69GeOP
753.58
173(2)
0.60 ꢀ 0.40 ꢀ 0.40
monoclinic
C2/c
37.647(14)
9.876(4)
29.559(17)
90
127.753(4)
90
8689(7)
8
0.774
18893
4473
C42H67GeOP
691.52
173(2)
0.60 ꢀ 0.40 ꢀ 0.40
monoclinic
P21/n
10.239(1)
15.474(1)
25.510(2)
90
92.992(1)
90
4036.4(4)
4
0.827
49041
9198
C42H67GeOP
691.52
173(2)
crystal size (mm3)
cryst syst
space group
0.20 ꢀ 0.20 ꢀ 0.10
triclinic
P1
˚
a (A)
10.0287(4)
14.7045(5)
14.8994(6)
102.737(2)
106.859(2)
98.330(2)
1999.02(13)
2
˚
b (A)
˚
c (A)
R (deg)
β (deg)
γ (deg)
3
˚
V (A )
Z
abs coeff (mm-1
)
0.835
15929
8110
no. of rflns collected
no. of ind rflns
[R(int) = 0.1194]
none
[R(int) = 0.0307]
none
[R(int) = 0.0552]
semiempirical
0.9211 and 0.8508
8110/0/425
0.987
R1 = 0.0463,
wR2 = 0.0879
R1 = 0.0835,
wR2 = 0.1006
0.501
abs cor
max/min transmission
no. of data/restraints/params
goodness of fit on F2
final R indices
(I > 2s(I))
R indices (all data)
4473/85/495
1.235
9198/0/425
1.028
R1 = 0.1250,
wR2 = 0.2576
R1 = 0.1528,
wR2 = 0.2690
0.549
R1 = 0.0297,
wR2 = 0.0740
R1 = 0.0419,
wR2 = 0.0813
0.52
largest diff peak,
hole (e A-3
)
and -0.988
and -0.220
and -0.566
2
7.78 (d, JHP = 23.4 Hz, 1H, CHdP), 6.91 (s, 2H, arom H of
Tip), 7.27 (s, 2H, arom H of Mes*).
MS (EI, 70 eV, m/z, %): 742 (Mþ, 0.5), 685 (Mþ - t-Bu, 1),
623 (Mþ - PhCOMe þ 1,1), 565 (Mþ - PhCOMe - t-Bu, 20),
465 (Mþ - Mes*P - 1, 90), 57 (t-Bu, 100).
13C NMR δ (ppm): 22.74, 24.57, 25.15, 27.42 (d, JCP = 5.1
Hz), 30.28, 30.60, 32.55, 32.88, 33.00, 33.05, 33.15 (CH and CH3
of Tip and CMe3), 28.70 and 37.08 (CMe3), 94.44 (OCdCH2),
112.41 (CHdCH2), 120.63, 120.68, and 121.16 (arom CH of Tip
and Mes*), 128.95 (d, JPC = 7.0 Hz, ipso-C of Tip), 135.50
(CH2dCH), 142.96 (d, JPC = 73.1 Hz, ipso-C of Mes*), 148.21,
148.79, 149.58 (d, JCP = 4.3 Hz), 151.80, 154.18, and 155.98
(arom C of Tip and of Mes*, CO), 169.71 (d, JPC =87.6 Hz,
PdCH).
Anal. Calcd for C46H69GeOP (741.61) C, 74.50; H, 9.38%.
Found: C, 74.71; H, 9.46%.
X-ray Structure Determinations for 1, 3, 4, 5, and 6. All data
were collected at low temperatures using an oil-coated shock-
cooled crystal on a Bruker-AXS APEX II diffractometer with
˚
Mo KR radiation (λ = 0.71073 A). The structures were solved by
direct methods28 and all non-hydrogen atoms were refined aniso-
tropically using the least-squares method on F2 (Tables 2 and 3).29
In the case of compound 4, we obtained only weak diffracting
crystals resulting in high R values; only the data with the
31P NMR δ (ppm): 336 (d, 2JHP = 23.4 Hz).
MS (EI, 70 eV, m/z, %): 692 (Mþ, 20), 635 (Mþ - t-Bu, 70),
579 (Mþ - t-Bu þ 1, 25), 447 (Mþ - Mes*, 90), 415 (Mþ
-
˚
resolution between 1 and 4 A were taking into account for the
refinement (Table 3).
Mes*P - 1, 25), 57 (t-Bu, 100).
Computational Details. Calculations were performed with the
Gaussian 03 suite of programs,30 using the density functional
method.31 The hybrid exchange functional B3LYP32 set was
used. B3LYP is a three parameter functional developed by
Becke that combines the Becke gradient-corrected exchange
Reaction of Acetophenone with Phosphagermaallene. Aceto-
phenone (169 mg, 1.41 mmol) was added to a solution of phos-
phagermaallene (1 equiv) cooled to -50 ꢀC. The solution became
red immediately. After stirring overnight at room temperature, the
solvents were removed in vacuo and replaced by 30 mL of pentane.
LiF was filtrated off; cooling the pentanic solution to -20 ꢀC
afforded 889 mg (85%, mp 205 ꢀC) of white crystals of 8.
(28) SHELXS-97, Sheldrick, G. M. Acta Crystallogr., Sect. A:
Found. Crystallogr. 1990, 46, 467.
(29) Sheldrick, G. M. SHELXL-97, Program for Crystal Structure
1H NMR δ (ppm): 0.93 (d, 3JHH = 6.4 Hz, 6H, o-CHMeMe0
of Tip), 1.09 (d, 3JHH = 6.4 Hz, 6H, o-CHMeMe0 of Tip), 1.14
(d, 3JHH = 6.9 Hz, 6H, p-CHMeMe0 of Tip), 1.21 (s, 9H, p-t-Bu
or t-BuGe), 1.27-1.33 (m, 27H, t-BuGe or p-t-Bu and o-t-Bu of
Mes*), 2.73 (sept, 3JHH = 6.9 Hz, 1H, p-CHMeMe0 of Tip), 3.07
(broad s, Δν1/2 = 29.5 Hz, 2H, o-CHMeMe0 of Tip), 3.73 (s, 1H,
CdCHH0), 4.42 (s, 1H, CdCHH0), 6.91 (s, 2H, arom H of Tip),
7.16-7.23 (m, 5H, arom H of Ph), 7.63 (m, 2H, arom H of
Mes*), 7.84 (d, 2JHP = 23.9 Hz, 1H, PdCH).
€
Refinement; University of Gottingen, 1997.
(30) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
Robb, M. A.; Cheeseman, J. R.; Montgomery, J. A.; Vreven, T., Jr.;
Kudin, K. N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.;
Barone, V.; Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson,
G. A.; Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, R.; Fukuda, J.;
Hasegawa, M.; Ishida, T.; Nakajima, Y.; Honda, O.; Kitao, H.; Nakai,
M. X.; Klene, X.; Li, K.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.;
Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.;
Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.;
Morokuma, K.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Zakrzewski,
V. G.; Dapprich, S.; Daniels, A. D.; Strain, M. C.; Farkas, D. K.; Malick,
A. D.; Rabuck, K.; Raghavachari, J. B.; Foresman, J. V.; Ortiz, Q.; Cui,
A. G.; Baboul, S.; Clifford, O.; Cioslowski, J.; Stefanov, B. B.; Liu, G.;
Liashenko, A.; Piskorz, P.; Komaromi, I.; Martin, R. L.; Fox, D. J.; Keith,
T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.; Challacombe, M.;
Gill, P. M. W.; Johnson, B.; Chen, W.; Wong, M. W.; Gonzalez, C.; Pople,
J. A. Gaussian 03, Revision D-02; Gaussian, Inc.: Pittsburgh, PA, 2003.
(31) Parr, R. G.; Yang, W. Functional Theory of Atoms and Molecules;
Breslow, R., Goodenough, J. B., Eds.; Oxford University Press: NewYork, 1989.
13C NMR δ (ppm): 23.88, 25.76, 26.30, 28.63 (d, JPC = 4.7
Hz), 31.40, 33.76, and 34.09 (d, JPC = 9.9 Hz) (CMe3, CH and
CH3 of Tip), 29.64 and 34.87 (GeCMe3 and p-CMe3 of Mes*),
38.19 (o-CMe3 of Mes*), 90.51 (CdCH2), 121.82 and 122.36
(arom CH of Mes* and Tip), 125.68, 127.85, and 127.84 (arom
CH of Ph), 129.95 (d, JPC = 0.9 Hz, ipso-C of Tip), 139.9 (ipso-C
of Ph), 143.88 (d, JPC = 73.2 Hz, ipso-C of Mes*), 149.36,
149.99, 152.93, 155.28, and 157.91 (arom C of Mes* and Tip and
CO), 170.86 (d, JPC = 76.0 Hz, CdP).
31P NMR δ (ppm): 331.65 (d, 2JPH = 23.9 Hz).

2578 Organometallics, Vol. 29, No. 11, 2010
Ouhsaine et al.
functional and the Lee-Yang-Parr and Vosko-Wilk-Nusair
correlation functional with part of the exact HF exchange
energy. All Gaussian calculations were done in combination
with the 6-31G(d,p) basis set for all atoms. Geometry optimiza-
tions were carried out without any symmetry restrictions; the
nature of the extrema (minimum and transition states) was
verified with analytical frequency calculations. To ensure that
the transition states are connected to the right minima, IRC
calculations were conducted using the Schlegel-Gonzalez
algorithm.33 All Gibbs free energies have been zero-point energy
(ZPE) and temperature corrected using unscaled density func-
tional frequencies.
Acknowledgment. We are grateful to the Agence Na-
tionale pour la Recherche (contract ANR-08-BLAN-
0105-01) and PhoSciNet (CM0802) for financial support.
The theoretical work was granted access to the HPC
resources of Idris under allocation 2010 (i2010080045)
made by GENCI (Grand Equipement National de Calcul
Intensif).
(32) (a) Becke, A. D. Phys. Rev. A 1988, 38, 3098. (b) Becke, A. D.
J. Chem. Phys. 1993, 98, 5648. (c) Lee, C.; Yang, W.; Parr, R. G. Phys. Rev.
B 1988, 37, 785.
(33) (a) Gonzalez, C.; Schlegel, H. B. J. Chem. Phys. 1989, 90, 2154.
(b) Gonzalez, C.; Schlegel, H. B. J. Phys. Chem. 1990, 94, 5523.
Supporting Information Available: CIF files for 1, 3, 4, 5, and
6. Theoretical calculation details. This material is available free
of charge via the Internet at http://pubs.acs.org.