The reactivity of phosphagermaallene tip(t-Bu)Ge=C=PMes* with doubly and triply bonded nitrogen compounds

Article abstract of DOI:10.1021/ic1014913

Phosphagermaallene Tip(t-Bu)Ge=C=PMes* (1; Mes* = 2,4,6-tri-tert-butylphenyl, Tip = 2,4,6-triisopropylphenyl) gives, with N-benzylidenemethylamine and pivalonitrile, [2+2] cycloadditions between the Ge=C double bond and the C=N and C≡N unsaturations, leading to the formation of the corresponding four-membered heterocycles 2 and 9. With N-tert-butyl-α-phenylnitrone and benzonitrile oxide, [2+3] cycloadditions occur to form the five-membered ring derivatives 6 and 7. By treatment of 1 with derivatives which possess weak acidic hydrogens in α of the C=N or C≡N multiple bond, two types of reactions were observed: an ene reaction with methyl(benzylideneamino)acetate and a 1,2 addition with acetonitrile to afford azadienyl(germyl)ether (4) and 3-germa-1-phosphapropene (8), respectively. In the case of benzonitrile, phosphagermaallene 1 behaves as a 1,3-dipole, to give, via a cyclic phosphagermacarbene intermediate, the tricyclic derivative 10.

Full text of DOI:10.1021/ic1014913

Inorg. Chem. 2010, 49, 10497–10505 10497
DOI: 10.1021/ic1014913
The Reactivity of Phosphagermaallene Tip(t-Bu)GedCdPMes* with Doubly and
Triply Bonded Nitrogen Compounds
Dumitru Ghereg,†,‡ Heinz Gornitzka,*,§,|| Jean Escudie,*,†,‡ and Sonia Ladeira^
ꢀ
†
‡
ꢀ
Universite de Toulouse, UPS, LHFA, 118 Route de Narbonne, F-31062 Toulouse, France, CNRS, LHFA, UMR
5069, F-31062 Toulouse cedex 09, France, §CNRS, LCC (Laboratoire de Chimie de Coordination), 205 route de
Narbonne, F-31077 Toulouse cedex 4, France, Universite de Toulouse, UPS, INP, LCC, F-31077 Toulouse, France,
||
ꢀ
^
ꢀ ꢀ
ꢀ
ꢀ
and Structure Federative Toulousaine en Chimie Moleculaire, FR 2599, Universite Paul Sabatier, 118 Route de
Narbonne, 31062 Toulouse cedex 09, France
Received July 26, 2010
Phosphagermaallene Tip(t-Bu)GedCdPMes* (1; Mes* = 2,4,6-tri-tert-butylphenyl, Tip = 2,4,6-triisopropylphenyl) gives, with
N-benzylidenemethylamine and pivalonitrile, [2þ2] cycloadditions between the GedC double bond and the CdN and CtN
unsaturations, leading to the formation of the corresponding four-membered heterocycles 2 and 9. With N-tert-butyl-
R-phenylnitrone and benzonitrile oxide, [2þ3] cycloadditions occur to form the five-membered ring derivatives 6 and 7. By
treatment of 1 with derivatives which possess weak acidic hydrogens in R of the CdN or CtN multiple bond, two types of
reactions were observed: an ene reaction with methyl(benzylideneamino)acetate and a 1,2 addition with acetonitrile to afford
azadienyl(germyl)ether (4) and 3-germa-1-phosphapropene (8), respectively. In the case of benzonitrile, phosphagermaal-
lene 1 behaves as a 1,3-dipole, to give, via a cyclic phosphagermacarbene intermediate, the tricyclic derivative 10.
Introduction
>SidCdC<1-3 or >GedCdC<,1,4 can be successfully
synthesized as stable derivatives by the use of bulky substitu-
ents, which kinetically stabilize the reactive double bonds.
With two different heavy elements of groups 14 and 15,
only one transient phosphasilaallene, Ph(Tip)SidCdPMes*5
(Mes* = 2,4,6-tri-tert-butylphenyl, Tip =2,4,6-triisopropyl-
phenyl), and two phosphagermaallenes, the transient Mes2Ged
CdPMes*6 and the stable and isolable Tip(t-Bu)GedCd
PMes*,7 have been reported. These compounds are particu-
larly interesting since they present several possibilities of
reactions: by the PdC double bond or by the lone pair at
phosphorus like ;PdCdX derivatives and by the extremely
reactive SidCorGedC double bond like sila- and germaallenes
>SidCdC< and >GedCdC<. A behavior of silylene >Si:
or germylene >Ge: can also be envisaged if the EdC double
bond (E = Si, Ge) would cleave as in SiCN8 and SnCN9
Alkenes and allenes are among the most important com-
pounds in organic chemistry: they are the precursors of many
derivatives and organic functions by the addition of various
reagents on the CdC double bond. Their heavier analogues
EdE0 and EdCdE0 (E, E0 = Si, Ge, Sn, N, P, As) have only
been postulated as transient intermediates for a long time.
However, heavier heteroallenes, such as phosphaallenes
;PdCdX1 (X = C, N, P, As, O, S) and some metallaallenes
*To whom correspondence should be addressed. E-mail: escudie@
chimie.ups-tlse.fr (J.E.), gornitzka@lcc-toulouse.fr (H.G.).
(1) For reviews on heteroallenes, see: (a) Escudie, J.; Ranaivonjatovo, H.;
Rigon, L. Chem. Rev. 2000, 100, 3639–3696. (b) Eichler, B.; West, R. Adv.
Organomet. Chem. 2001, 46, 1–46. (c) Escudie, J.; Ranaivonjatovo, H. Organome-
ꢀ
ꢀ
tallics 2007, 26, 1542–1559. (d) Appel, R. In Multiple Bonds and Low Coordination
in Phosphorus Chemistry; Regitz, M., Scherer, O. J., Eds.; Thieme: Stuttgart,
Germany, 1990; pp 157-219. (e) Yoshifuji, M. Dalton Trans. 1998, 3343–3349.
(2) (a) Miracle, G.; Ball, J. L.; Powell, D. R.; West, R. J. Am. Chem. Soc.
1993, 115, 11598–11599. (b) Trommer, M.; Miracle, G. E.; Eichler, B. E.; Powell,
D. R.; West, R. Organometallics 1997, 16, 5737–5747. (c) Eichler, B. E.; Miracle,
G. E.; Powell, D. R.; West, R. Main Group Met. Chem. 1999, 22, 147–162. (d)
Ichinohe, M.; Tanaka, T.;Sekiguchi, A. Chem. Lett. 2001, 30, 1074–1075. (e)Spirk,
S.; Belaj, F.; Albering, J. H.; Pietschnig, R. Organometallics 2010, 29, 2981–2986.
(3) For transient >SidCdC<, see: (a) Kunai, A.; Matsuo, Y.; Ohshita,
J.; Ishikawa, M.; Aso, Y.; Otsubo, T.; Ogura, F. Organometallics 1995, 14,
1204–1212 and references therein. (b) Kerst, C.; Ruffolo, R.; Leigh, W. J.
Organometallics 1997, 16, 5804–5810. (c) Kerst, C.; Rogers, C. W.; Ruffolo,
R.; Leigh, W. J. J. Am. Chem. Soc. 1997, 119, 466–471.
ꢀ
(5) Rigon, L.; Ranaivonjatovo, H.; Escudie, J.; Dubourg, A.; Declercq,
J.-P. Chem.;Eur. J. 1999, 5, 774–781.
ꢀ
(6) Ramdane, H.; Ranaivonjatovo, H.; Escudie, J.; Mathieu, S.; Knouzi,
N. Organometallics 1996, 15, 3070–3075.
ꢀ
(7) (a) El Harouch, Y.; Gornitzka, H.; Ranaivonjatovo, H.; Escudie, J.
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J. Organomet. Chem. 2002, 643-644, 202–208. (b) Ouhsaine, F.; Andre, E.;
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Sotiropoulos, J.-M.; Escudie, J.; Ranaivonjatovo, H.; Gornitzka, H.; Saffon, N.;
Miqueu, K.; Lazraq, M. Organometallics 2010, 29, 2566–2578.
(8) (a) Takeda, N.; Suzuki, H.; Tokitoh, N.; Okazaki, R.; Nagase, S.
J. Am. Chem. Soc. 1997, 119, 1456–1457. (b) Takeda, N.; Kajiwara, T.; Suzuki,
H.; Okazaki, R.; Tokitoh, N. Chem.;Eur. J. 2003, 9, 3530–3543. (c) Abe, T.;
Iwamoto, T.; Kabuto, C.; Kira, M. J. Am. Chem. Soc. 2006, 128, 4228–4229.
(4) (a) Eichler, B. E.; Powell, D. R.; West, R. Organometallics 1998, 17, 2147–
2148. Eichler, B. E.; Powell, D. R.; West, R. Organometallics 1999, 18, 540–545.
(b) Kishikawa, K.; Tokitoh, N.; Okazaki, R. Organometallics 1997, 16, 5127–5129.
(c) Tokitoh, N.; Kishikawa, K.; Okazaki, R. Chem. Lett. 1998, 27, 811–812.
€
(9) Grutzmacher, H.; Freitag, S.; Herbst-Irmer, R.; Sheldrick, G. M.
Angew. Chem., Int. Ed. Engl. 1992, 31, 437–438.
r
2010 American Chemical Society
Published on Web 10/13/2010
pubs.acs.org/IC

10498 Inorganic Chemistry, Vol. 49, No. 22, 2010
Ghereg et al.
Chart 1
Scheme 1
Figure 1. Structure of 4. Thermal ellipsoids are drawn at the 50%
probability level. All hydrogen atoms are omitted; t-Bu and i-Pr groups
˚
are simplified for clarity. Selected bond lengths (A) and bond angles
(deg): Ge1-C20 1.961(2), Ge1-C1 1.995(2), Ge1-C16 1.983(2), C20-P1
1.671(2), P1-C21 1.856(2), Ge1-O1 1.833(2), O1-C40 1.320(2),
C40-C41 1.348(3), C41-N1 1.389(2), N1-C42 1.286(2), Ge1-C20-P1
148.9(1), C20-P1-C21 111.9(1), Ge1-O1-C40 135.1(2), C40-C41-N1
120.5(2), C41-N1-C42 118.5(2), N1-C42-C43 122.7(2).
in the formed four-membered heterocycle, derivative 2 is
perfectly stable, probably owing to the steric protection
caused by the bulky substituents on the germanium and
phosphorus atoms.
derivatives. Despite their high potential in organometallic
synthesis, the reactivity of >E14dCdE15; derivatives has
been poorly studied until now: in the case of >SidCdP;,
only the reaction with MeOH5 and, in that of >GedCdP-,
only the reactions with MeOH,6 MeLi,6 water,6 aldehydes,7
and ketones,7 and chalcogens10 have been reported. All of these
reactions occur exclusively via the E14dC double bond. By
contrast, dimerization observed with transient species involves
both E14dC and PdC double bonds.5,6
We present here the reactivity of phosphagermaallene
Tip(t-Bu)GedCdPMes* (1) toward doubly and triply
bonded nitrogen compounds such as imines (I), nitriles (II),
a nitrone (III), and a nitrile oxide (IV) (Chart 1).
By contrast, when the methyl group on the nitrogen
atom is replaced by the CH2COOMe group, a totally
different reaction is observed: the addition of methyl-
(benzylideneamino)acetate (3) to phosphagermaallene
(1) leads only to the formation of the azadienyl(germyl)-
ether (4) by an ene reaction (Scheme 1). The structure of 4
was evidenced by a doublet at low field in the 31P NMR
spectrum (δ = 324.3 ppm, 2JPH = 21.6 Hz) characteristic
for a Ge;CHdP moiety; the carbon atom doubly bonded
to the phosphorus was observed at 162.71 ppm with a 1JPC
coupling constant of 69.6 Hz. The formation of the Z
isomer for the PdCH unsaturation was only proved by an
X-ray structural analysis (Figure 1) since the values of the
2JPH and 1JPC coupling constants in the CHdPMes* unit
are not significantly different for Z and E isomers in
compounds of the type GeC(H)dP;.11 This study addi-
tionally revealed the stereochemistry of the 2-azadiene
structure PhCHdN;CHdC< with a Z configuration
for the CdC double bond and E for the CdN one.
In 2 and 4, the methyls of each i-Pr of the Tip group are
diastereotopic. For compound 4, two doublets and two
singlets are observed in 1H and 13C NMR spectra,
respectively, for the o-i-Pr groups. By contrast, in the
cyclic compound 2, four doublets and four singlets are
found due to a nonequivalence of the o-i-Pr groups caused
by the hindered rotation of the Tip group around the
Ge-C(ipso) bond, consecutive to the greater steric hin-
drance. In 2 and 4, the o-t-Bu groups of Mes* resonate as
two signals (2s in 1H NMR and 2d in 13C NMR) due also
to the hindered rotation of the Mes* group.
Results and Discussion
Imines. We have studied the reactivity of 1 with two
imines which present different substitution patterns on
the nitrogen atom: PhCHdNMe, for which a [2þ2] cyclo-
addition between the CdN and GedC or PdC double
bonds is expected, and PhCHdN;CH2;COOMe.
From the latter, various reactions could occur: [2þ2]
cycloadditions involving the CdN or the CdO double
bonds and an ene reaction with the CH2 unit.
In fact, phosphagermaallene 1 reacts with the N-benzyli-
denemethylamine by an exclusive [2þ2] cycloaddition be-
tween the GedC and CdN double bonds, leading to the
formation of the corresponding four-membered ring 1-aza-
2-germacyclobutane (2; Scheme 1). The PdC double bond is
not involved in the reaction, as shown by the low-field che-
=
3
mical shift in the 31P NMR spectrum (258.4 ppm, JHP
13.6 Hz). The 1H and 13C NMR data for the CHPh moiety
=
(δ1H = 5.05 ppm, 3JPH=13.6 Hz; δ13C=80.89 ppm, 2JCP
19.3 Hz) confirm the regiochemistry of this reaction, with the
nitrogen atom bonded to the germanium atom, in agreement
with the polarity GeδþdCδ-. Despite the high ring strain
The results obtained from these two imines demonstrate
that the ene reaction is preferred to the cycloaddition when
2
(11) For example, in Me3GeC(H)dPMes*, the JPH coupling constants
are 23.5 (Z) and 26.4 (E) and the 1JPdC coupling constants are 56.0 (Z) and
67.4 (E). Goede, S. J.; Bickelhaupt, F. Chem. Ber. 1991, 124, 2677–2684.
ꢀ
(10) Ouhsaine, F.; Ranaivonjatovo, H.; Escudie, J.; Saffon, N.; Lazraq,
M. Organometallics 2009, 28, 1973–1975.

Article
Inorganic Chemistry, Vol. 49, No. 22, 2010 10499
Scheme 2
Scheme 3
Figure 2. Structure of 6. Thermal ellipsoids are drawn at the 50%
probability level. All hydrogen atoms and a non-coordinating Et2O
molecules are omitted; t-Bu and i-Pr groups are simplified for clarity.
an electron withdrawing group (e.g., methoxycarbonyl) is
present in the R position of the CdN unsaturation.
˚
Selected bond lengths (A) and bond angles (deg): Ge1-C31 1.992(2),
Whereas a similar [2þ2] cycloaddition was observed
between germene Mes2GedCR2 and N-benzylideneethyl-
amine12 (by the GedC and CdN double bonds), a com-
pletely different reaction occurred with the iminoester 313
(Scheme 2). In this case, the five-membered heterocycle 5was
formed by a [2þ3] cycloaddition between the germene and
the 1,3-dipole azomethine ylide 30 formed from 3 by a
prototropic shift probably assisted by the germene.14
Ge1-C1 2.008(2), Ge1-C16 2.034(2), C31-C24 1.567(3), C24-N1
1.481(3), N1-O1 1.473(2), O1-Ge1 1.821(2), C31-P1 1.679(2),
P1-C32 1.852(2), Ge1-C31-C24 103.9(2), C31-C24-N1 108.1(2),
C24-N1-O1 103.9(2), N1-O1-Ge1 106.4(1), O1-Ge1-C31 87.8(1),
C31-P1-C32 115.9(1), P1-C31-Ge1 144.6(2).
Scheme 4
1,3-Dipoles. A nearly quantitative [2þ3] cycloaddition,
involving the GedC double bond, occurs between 1 and the
1,3-dipolar derivative N-tert-butyl-R-phenylnitrone, leading
to the formation of the five-membered ring 1-oxa-2-aza-5-
germacyclopentane (6; Scheme 3). The 31P NMR study of
the crude reaction mixture (δ31P = 337.0 ppm) shows the
˚
Ge1-C1 = 2.008(2) A, and particularly Ge1-C16 =
3
˚
2.034(2) A) in relation to the standard ones (1.94-
1.98 A).
presence of only one isomer. The JPH coupling constant
PdC (1.679(2) A) double bond15c and P-C
15a,b
˚
˚
(22.6 Hz) corroborates the expected regiochemistry of the
reaction with the CH(Ph) moiety of the nitrone bonded to the
central carbon atom of the GeCP unit. This CH presents
˚
(1.852(2) A) single bond lengths are in the normal range.
To determine whether a [2þ3] addition process is also
realizable with other 1,3-dipoles, such as nitrile oxides, the
phosphagermaallene (1) was allowed to react with PhCt
NfO, generated in situ from N-hydroxy-benzimoyl chloride.
A similar cycloadduct, the 1-oxa-2-aza-5-germacyclopent-2-
ene (7), was formed in 72% yield (Scheme 3) and was
characterized by low-field shifts in 31P NMR (296.7 ppm)
and 13C NMR spectra (175.63 ppm, 2JCP =25.5HzforCdN
and 182.71 ppm, 1JCP = 69.8 Hz for CdP). Mass spectro-
metry displays the molecular peak and a fragment corre-
sponding to Tip(t-Bu)GeO, consistent with the proposed
regiochemistry. However, cycloadduct 7 is a thermally stable
compound, and no cycloreversion by a [5]f[2þ3] process,
leading to transient germanone Tip(t-Bu)GeO, has been
observed, even by refluxing in toluene.
1
expected chemical shifts in H and 13C NMR spectra with
large PH and PC coupling constants (δ1H = 5.16 ppm, d,
2
3JPH = 22.6 Hz, δ13C = 78.04 ppm, d, JCP = 50.5 Hz).
These spectral findings were confirmed by an X-ray study
(Figure 2), which demonstrated the formation of the Z
isomer at the level of the PdC double bond and additionally
showed that the phenyl group is placed in front of the tert-
butyl group less bulky than the Tip group. In the formed five-
membered ring, four atoms, O1, Ge1, C31, and C24, are
about in the same plane, the nitrogen atom being out by
˚
0.72 A. Like in compounds 4, 8, and 10 (see further), the
˚
Ge-C bonds are slightly elongated in 6(Ge1-C31=1.992(2) A,
ꢀ
ꢀ
(12) Lazraq, M.; Escudie, J.; Couret, C.; Satge, J.; Soufiaoui, M. Orga-
nometallics 1991, 10, 1140–1143.
It is worth noting that a related behavior was reported
by Tokitoh in the case of various doubly bonded and
aromatic heavier group 14 derivatives E14dY (E14 = Si,
ꢀ
(13) Ech-Cherif El Kettani, S.; Escudie, J.; Couret, C.; Ranaivonjatovo,
H.; Lazraq, M.; Soufiaoui, M.; Gornitzka, H.; Cretiu Nemes, G. Chem.
Commun. 2003, 1662–1663.
(14) The high reactivity of germenes towards acidic hydrogens is well
established. For reviews on germenes, see: (a) Baines, K. M.; Stibbs, W. G.
ꢀ
Adv. Organomet. Chem. 1996, 39, 275–324. (b) Escudie, J.; Couret, C.;
(15) (a) Baines, K. M.; Stibbs, W. G. Coord. Chem. Rev. 1995, 145, 157–
200. (b) Holloway, C. E.; Melnik, M. Main Group Met. Chem. 2002, 25, 185–
266. (c) Fischer, R. C.; Power, P. P. Chem. Rev. 2010, 110, 3877–3923.
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Ranaivonjatovo, H. Coord. Chem. Rev. 1998, 178-180, 565–592. (c) Escudie,
J.; Ranaivonjatovo, H. Adv. Organomet. Chem. 1999, 44, 113–174.

10500 Inorganic Chemistry, Vol. 49, No. 22, 2010
Ghereg et al.
Scheme 5
by the 31P NMR spectrum, which displays a signal at 322.5
ppm with a 2JPH coupling constant of 23.7 Hz characteristic
of the HCdPMes* unit. Unexpectedly, the diastereotopic
protons of the CH2CtN fragment resonate as only one
singlet in 1H NMR, corresponding to two hydrogen atoms.
The X-ray study of 8 proves the formation of the E isomer
(Figure 3).
With pivalonitrile, only a [2þ2] cycloaddition was
observed between the GedC double bond and the nitrile
function, leading to the formation of 1-aza-2-germacyclo-
but-1-ene (9) with an exocyclic PdC double bond
(Scheme 5). Probably owing to a good steric protection
caused by bulky Tip and t-Bu groups, the Ge-N bond,
generally easily hydrolyzable, is relatively insensitive in 9,
which can be handled in the air for a short period of time.
Cycloadduct 9 was characterized by a very low-field shift in
13C NMR for the sp2 carbon atom bonded to nitrogen (δ =
196.08 ppm, 2JPC = 28.4 Hz), which proves the regiochem-
istry of the reaction. A similar very low-field shift (198.41
ppm) was reported for the closely related four-membered
ring derivative obtained in the reaction of Mes2GedCR2
with pivalonitrile.23 The endocyclic sp2 carbon atom doubly
bonded to the phosphorus resonates at 181.81 ppm with a
large 1JCP coupling constant (103.5 Hz). Signals in the range
of 162.71-194.45 ppm are observed for carbon atoms in the
Ge;CdP unit of 2, 4, 6, 7, 8, and 9. The resonances at lower
fields (194.45 (2), 192.51 (6), 182.71 (7), and 181.81 (9) ppm)
correspond to those for cyclic compounds, whereas those at
higher fields (162.71 (4) and 175.75 (8) ppm) are due to those
for acyclic ones. In 1H NMR, acyclic derivative 8 presents
similar data to those of acyclic germylether 4 (two doublets
for o-i-Pr due to the free rotation of the Tip group); four-
membered ring compound 9 has similar characteristics to
those of 2 (four doublets for o-i-Pr of the Tip group and two
singlets for o-t-Bu of the Mes* group due to their hindered
rotation). In the less sterically encumbered acyclic derivative
8, a unique singlet is even observed for the o-t-Bu of the Mes*
group, showing its free rotation on the NMR time scale. The
chemical shifts of phosphorus (δ 31P), of the central carbon
atom bonded to phosphorus and to germanium (δ 13CGeCP),
and of the carbon atom bonded to the nitrogen atom
Figure 3. Structure of 8. Thermal ellipsoids are drawn at the 50%
probability level. All hydrogen atoms and a disorder of a t-Bu group
are omitted; t-Bu and i-Pr groups are simplified for clarity. Selected bond
˚
lengths (A) and bond angles (deg): Ge1-C1 1.985(2), Ge1-C18 1.991(2),
Ge1-C16 2.004(2), C16-C17 1.439(2), C17-N1 1.148(2), Ge1-C22
1.955(2), C22-P1 1.661(2), P1-C23 1.856(2), Ge1-C22-P1 126.85(7),
C22-P1-C23 101.15(7).
Y=C<,16 S;17 E14=Ge, Y=C<,18 CdC<, 19 S;20 E14=Sn,
Y = C<,21 S22) with the structurally close mesitonitrile
oxide MesCtNfO, giving the corresponding five-mem-
bered sila-, germa-, and stanna-heterocycles (Scheme 4),
respectively.
Nitriles. We have examined the behavior of phospha-
germaallene 1 with three different nitriles such as aceto-
nitrile, which has mobile hydrogens in the R of the triple
bond, and two nitriles without such hydrogen atoms and
bearing an alkyl or an aryl group.
With acetonitrile, a 1,2 addition of a C-H bond onto the
GedC double bond occurs, leading only to the formation of
the 3-germa-1-phosphapropene (8; Scheme 5), as indicated
(16) Tokitoh, N.; Shinohara, A.; Matsumoto, T.; Sasamori, T.; Takeda,
N.; Furukawa, Y. Organometallics 2007, 26, 4048–4053.
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1994, 116, 11578–11579.
(18) (a) Nakata,N.;Takeda, N.;Tokitoh, N.J. Am. Chem. Soc. 2002,124,6914–
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(20) Tokitoh, N.; Matsumoto, T.; Manmaru, K.; Okazaki, R. J. Am.
Chem. Soc. 1993, 115, 8855–8856.
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5065.

Article
Inorganic Chemistry, Vol. 49, No. 22, 2010 10501
Table 1. NMR data for the obtained and related compounds
Scheme 6
into a C-H bond are well-known.24 Transient carbene 11
would be formed by a [3þ2] cycloaddition between the
GedCdP moiety of the phosphagermaallene, behaving
as a 1,3-dipole, and the CtN triple bond. We must note
that such behavior of 1,3-dipole has never been observed
for other heteroallenes of the type E14dCdC, E14dCdE15,
or E15dCdE15.
Figure 4. Structure of 10. Thermal ellipsoids are drawn at the 50%
probability level. All hydrogen atoms and disorders of a t-Bu and an i-Pr
group are omitted; t-Bu and i-Pr groups are simplified for clarity. Selected
Despite the presence of three chiral centers, only one
diastereoisomer was formed. The X-ray study shows that
the two six-membered rings (the ring with phosphorus
and the ring substituted by two t-Bu groups) are nearly in
˚
bond lengths (A) and bond angles (deg): Ge1-C1 1.996(3), Ge1-C5
1.975(3), Ge1-C27 1.997(3), Ge1-N1 1.899(2), N1-C20 1.276(3),
C20-P1 1.899(3), P1-C27 1.827(3), C27-C28 1.524(4), C28-C29
1.539(4), C29-C32 1.549(4), C32-C37 1.415(4), C37-P1 1.841(3),
Ge1-C27-P1 99.4(2), C27-P1-C20 92.2(2), P1-C20-N1 118.7(2),
C20-N1-Ge1 112.3(2), N1-Ge1-C27 93.1(1), C27-P1-C37 105.7(2).
˚
the same plane. The P1-C20 bond length (1.899(3) A) is
˚
longer than the two other P-C bonds (P1-C27 =1.827(3) A
˚
and P1-C37=1.841(3) A). The five-membered ring presents
13
(δ
some 1-oxa-2-germacyclobutanes and for the synthesized
C
), together with relevant coupling constants for
an envelope geometry with the P1, C20, N1, and Ge1 atoms in
the same plane.
CN
Monitoring the reaction by 31P NMR between-80 ꢀC and
room temperature did not allow detection of the transient
carbene 11, which probably rearranges immediately after its
formationtothefinalproduct10. We attempted to chemically
characterize 11 by trapping reactions; however, as its lifetime
seems to be very short, the trapping agent must be added to
the phosphagermaallene solution before the addition of
benzonitrile. The problem is the high reactivity of the GedC
double bond, which complicates the choice of the trapping
agent. Triphenylphosphine, an efficient reagent for silyl-
(phosphino)carbenes24,25 and inert toward phosphagermaal-
lene 1, failed to trap the intermediate carbene 11, perhaps
because of the weak stability in solution of the latter as well as
of the steric overcrowding around the carbene center.
products, are listed in Table 1.
While a [2þ2] cycloaddition could be expected in the
reaction of phosphagermaallene with benzonitrile, like in
the case of pivalonitrile, a completely different and un-
expected reaction occurred. The 31P NMR spectrum of the
crude reaction mixture showed a unique signal at 5.4 ppm,
a relatively high-field shift, characteristic for three-
coordinated phosphorus atoms, thus indicating that the
PdC double bond has been involved in the reaction. The
stability toward oxygen and moisture of the isolated
product suggests that the GedC double bond has also
reacted. The structure of the adduct 10 (Scheme 5) was
determined by an X-ray study (Figure 4). The formation
of this tricyclic derivative can reasonably be explained by
the intermediate formation of the cyclic phosphagerma-
carbene (11; a PGeHC carbene, analogous to the well-
known NHCs), followed by insertion of the carbenic
carbon atom into the C-H bond of an ortho tert-butyl
group of the Mes* group. Such insertions of a carbene
(24) Reviews: (a) Doyle, M. P.; Duffy, R.; Ratnikov, M.; Zhou, L. Chem.
Rev. 2010, 110, 704–724. (b) Ritleng, V.; Sirlin, C.; Pfeffer, M. Chem. Rev. 2002,
102, 1731–1770. (c) Kakiuchi, F.; Murai, S. Acc. Chem. Res. 2002, 35, 826–834.
(d) Jia, C.; Kitamura, T.; Fujiwara, Y. Acc. Chem. Res. 2001, 34, 633–639.

10502 Inorganic Chemistry, Vol. 49, No. 22, 2010
Ghereg et al.
Scheme 7
Table 2. Crystal Data for Compounds 4 and 6
Table 3. Crystal Data for Compounds 8 and 10
4
6
8
10
empirical formula
C
48H72GeNO2P
C49H76GeNOP,
(C4H10O)0.5
835.77
193(2) K
triclinic
P1
empirical formula
fw
temp
C
662.50
193(2) K
monoclinic
P21/c
21.710(16)
9.831(8)
19.999(15)
90
40 H64GeNP
C45H66GeNP
724.57
193(2) K
triclinic
P1
10.5721(2)
12.6065(3)
17.4404(4)
81.459(1)
86.387(1)
68.519(2)
2138.87(9) A3
2
fw
temp
798.65
193(2) K
triclinic
P1
9.2525(1)
11.0188(2)
23.1235(3)
98.915(1)
95.089(1)
93.842(1)
cryst syst
space group
cryst syst
space group
˚
a (A)
˚
˚
b (A)
a (A)
10.9509(2)
12.2987(2)
19.9337(3)
97.910(1)
99.636(1)
105.745(1)
˚
b (A)
˚
c (A)
˚
c (A)
R (deg)
β (deg)
γ (deg)
vol
Z
abs coeff
reflns collected
independent reflns
R (deg)
β (deg)
γ (deg)
vol
Z
abs coeff
reflns collected
independent reflns
113.189(9)
90
3924(5) A3
4
3
3
˚
˚
2311.99(6) A
2
2499.67(7) A
2
0.847 mm-1
101 060
19 550
0.782 mm-1
44 342
7822
[R(int) = 0.0664]
multiscan
0.819/0.939
7822/9/446
1.015
R1 = 0.0436,
wR2 = 0.0972
R1 = 0.0662,
wR2 = 0.1082
0.627 and
-0.443 e A-3
0.733 mm-1
37910
11955
0.676 mm-1
55247
9151
[R(int) = 0.0516]
multiscan
0.659/0.812
19 550/9/408
1.011
R1 = 0.0409,
wR2 = 0.0967
R1 = 0.0775,
wR2 = 0.1132
0.676 and
-0.926 e A-3
[R(int) = 0.0358]
Multiscan
0.820/0.865
11 955/5/495
1.023
R1 = 0.0380
wR2 = 0.0899
R1 = 0.0519
wR2 = 0.0960
0.688 and
[R(int) = 0.0389]
Multiscan
0.806/0.874
9151/31/547
1.033
abs correction
min/max transm
data/restraints/params
goodness-of-fit on F2
final R indices [I > 2σ(I )]
abs correction
min/max transm
data/restraints/params
goodness-of-fit on F2
final R indices [I > 2σ(I )]
R1 = 0.0343
wR2 = 0.0829
R1 = 0.0454
wR2 = 0.0901
0.621 and
R indices (all data)
R indices (all data)
largest diff. peak and hole
largest diff. peak and hole
-3
-3
˚
˚
-0.277 e A
-0.422 e A
furnish [2þ2]-cycloaddition products. We summarized these
differences in Scheme 7.
The reaction of benzonitrile with phosphagermaallene 1is
completely different than that occurring with the germene
Mes2GedCR2, for which a [2þ4] cycloaddition was ob-
served between the CtN triple bond and the GedC;CdC
dienic system (involving the fluorenylidene group), followed
by rearomatization via a 1,3-H shift (Scheme 6).23
By contrast, the transient silene Me2SidCH228 generated
by the pyrolysis of the corresponding silacyclobutane under-
goes an insertion reaction into a C-H bond of acetonitrile,
similar to that observed with germene Mes2GedCR223 and
phosphagermaallene Tip(t-Bu)GedCdPMes*.
With regard to other heavier heteroalkenes, a [2þ2þ2]
In conclusion, phosphagermaallene 1 displays very rich
and varied reactivity since it gives selectively, depending
on the reagents, cycloaddition, insertion, or ene reactions via
the GedC double bond or behaves as a 1,3-dipole involving
both GedC and CdP double bonds. In most of the cases,
only the GedC double bond of 1 is involved, and the ene
reaction or 1,2 addition of C-H is preferred to [2þ2]
cycloaddition when both reactions are possible. The reactiv-
ity of the cumulative GedC double bond of 1 and that of the
isolated GedC double bond of germene Mes2GedCR2 are
somewhat different, particularly toward benzonitrile and
26
cycloadduct of PhCtN with the silene Me2SidC(SiMe3)2
has been reported so far, while the SidE15 (E15 = P, As)
double bond in phospha- and arsa-silenes Tip2SidE15Si-
(i-Pr)3 reacts with the CtN triple bond of benzonitrile27 to
(25) The carbene Me3Si-C-PR2 (R = cyclohexyl) rather similarly substituted
as 11 (phosphino and silyl groups on the carbon atom instead of phosphino and
germyl groups) has been successfully trapped by Ph3P and other phosphines.
Goumri-Magnet, S.; Polishchuk, O.; Gornitzka, H.; Marsden, C.; Baceiredo, A.;
Bertrand, G. Angew. Chem., Int. Ed. 1999, 38, 3727-3729.
(26) Wiberg, N.; Preiner, G.; Schieda, O. Chem. Ber. 1981, 114, 3518–
3532.
(27) Driess, M.; Pritzkow, H.; Rell, S.; Winkler, U. Organometallics 1996,
15, 1845–1855.
(28) Bush, R. D.; Golino, C. M.; Roark, D. N.; Sommer, L. H.
J. Organomet. Chem. 1973, 59, C17–C20.

Article
Inorganic Chemistry, Vol. 49, No. 22, 2010 10503
methyl(benzylideneamino)acetate. Compared with other
unsaturated compounds of group 14 elements, phospha-
germaallene Tip(t-Bu)GedCdPMes* has been shown an
unprecedented example of cycloaddition in the reaction with
benzonitrile, while similar behavior was observed in the case
of acetonitrile. The 1,3-dipole behavior of 1, a new mode of
reaction for a heteroallene, allows the formation of a cyclic
phosphagermacarbene intermediate, a novel type of cyclic
carbene (PGeHC). Further investigations on the chemical
reactivity of phosphagermaallene 1towards a large variety of
unsaturated reagents are now in progress.
3JCP=4.5 Hz, ipso-C of Tip); 138.53 (d, 1JCP=73.5 Hz, ipso-C of
Mes*); 141.21 (d, 3JCP =6.2Hz,ipso-C of Ph); 148.74 (p-C of Mes*);
149.21 ( p-C of Tip); 152.63 and 152.72 (d, 2JCP = 3.9 Hz) (o-C of
Mes*); 152.90 and 153.59 (o-C of Tip); 194.45 (d, 1JCP = 75.2 Hz,
CdP). 31P NMR (121.51 MHz): δ 258.4 (d, 3JHP = 13.6 Hz). MS
(m/z, %): 742 (M þ H, 1), 685 (M - t-Bu þ H, 15), 566 (M -
PhCHdNMe - t-Bu + H, 5), 510 (M - PhCHdNMe - 2t-Bu þ
2H, 5), 377 (Mes*PdCdCHPh - H, 8), 275 (Mes*P - H, 25), 233
(TipGe - i-Pr - H, 20), 118 (PhCHdNMe-H, 15), 57 (t-Bu, 100).
Anal. Calcd for C46H70GeNP (740.63): C, 74.60; H, 9.53%. Found:
C, 74.72; H, 9.44%.
Synthesis of 4. A solution of methyl(benzylidene)aminoacetate
(0.177 g, 1 mmol) in diethyl ether (5 mL) was added dropwise to a
solution of phosphagermaallene 1(1 mmol) in diethyl ether (10 mL)
at -78 ꢀC. The mixture was allowed to warm to room temperature,
was stirred for 12 h, and then was filtered. The solvents were
removed and replaced with pentane (10 mL), to give a yellow
precipitate (0.58 g, 73%, mp 172 ꢀC). 1H NMR (300.13 MHz): δ
Experimental Section
All experiments were carried out in flame-dried glassware
under a nitrogen and argon atmosphere using high-vacuum-line
techniques. Solvents were dried and freshly distilled 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; 13C, 75.47 MHz (reference TMS);
31P, 121.51 MHz (reference H3PO4). Melting points were de-
termined 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. Elemental
analyses were performed by the Service de Microanalyse de
l’Ecole de Chimie de Toulouse. NMR spetra have been eluci-
dated using COSY, HMBC, and HSQC techniques.
3
0.74 (s, 9H, GeCMe3), 1.14 and 1.21 (2d, JHH = 6.6 Hz, 2 ꢀ
3
6H, o-CHMeMe0), 1.27 and 1.29 (2d, JHH = 6.6 Hz, 2 ꢀ 3H,
p-CHMeMe0), 1.37 (s, 9H, p-CMe3 of Mes*), 1.49 and 1.57 (2s, 2 ꢀ
9H, o-CMe3 ofMes*), 2.91(sept,3JHH=6.6 Hz, 1H, p-CHMeMe0),
3.15 (broad signal, 2H, o-CHMeMe0), 3.62 (s, 3H, OMe), 5.80 (s,
1H, CHdC), 7.08-7.17 (m, 5H, Ph), 7.10 (s, 2H, m-CH of Tip),
7.34 and 7.37 (2s, 2 ꢀ 1H, m-CH of Mes*), 7.87 (s, 1H, CHdN),
7.89 (d, 2JPH = 21.6 Hz, CHdP). 13C NMR (75.47 MHz): δ 23.76
and 24.03 (p-CHMeMe0); 25.59 and 25.83 (o-CHMeMe0); 27.80
(GeCMe3); 29.35 (GeCMe3); 31.40 (p-CMe3 of Mes*); 34.01
X-Ray Structure Determinations for 4, 6, 8, and 10. All data
were collected at low temperatures using an oil-coated shock-
cooled crystal on a Bruker-AXS APEX II diffractometer with
4
4
( p-CHMeMe0); 34.23 (d, JCP = 8.8 Hz) and 34.71 (d, JCP
=
7.5 Hz; o-CMe3 of Mes*); 34.87 (p-CMe3 of Mes*); 38.45 and 38.86
(o-CMe3 of Mes*); 54.24 (OMe); 99.76 (CHdC); 121.39 and 122.55
(m-CH of Mes*); 122.40 (m-CH of Tip); 126.97, 127.59, and 128.28
(o-, m-, and p-CH of Ph); 133.06 (ipso-C of Tip); 138.50 (ipso-C of
Ph); 141.93 (d, 1JCP = 74.8 Hz, ipso-C of Mes*); 146.63 (CHdN);
149.41 (p-C of Tip); 149.79 (p-C of Mes*); 153.73 and 154.69 (o-C
˚
Mo KR radiation (λ = 0.71073 A). The structures were solved by
direct methods,29 and all non-hydrogen atoms were refined
anisotropically using the least-squares method on F2.30 For
crystal data, see Tables 2 and 3.
Synthesis of 1. Phosphagermaallene 1 was synthesized as
previously described7 via the addition of a solution of 1.7 M tert-
butyllithium in pentane (0.6 mL) to a solution of fluorophospha-
germapropene Tip(t-Bu)Ge(F);C(Cl)dPMes* (0.676 g, 1 mmol)
in diethylether (10 mL) cooled to -78 ꢀC. A 31P NMR analysis
(δ 249.9 ppm) showed the nearly quantitative formation of phos-
phagermaallene 1. Solutions of 1 containing LiF were used directly
without further purification.
of Mes*); 154.70 (o-C of Tip); 160.15 (CHdC); 162.71 (d, 1JCP
=
69.6 Hz, CHdP). 31P NMR (121.51 MHz): δ 324.3 (brs). MS (m/z,
%): 799 (M, 1), 742 (M - t-Bu, 5), 623 (M - PhCHdN;CHd
COOMe, 40), 597 (M - Tip þ H, 25), 565 (M - PhCHdN;CHd
COOMe - t-Bu - H, 15), 509 (M - PhCHdN;CHdCOOMe -
2t-Bu, 35), 333 (Ge(t-Bu)Tip - H, 10), 275 (Mes*P - H, 20), 233
(TipGe - i-Pr - H, 15), 57 (t-Bu, 100). IR (KBr, cm-1): 1630 (Cd
N). Anal. Calcd for C48H72GeNO2P (798.66): C, 72.19; H, 9.09%.
Found: C, 72.23; H, 9.26%.
Synthesis of 2. To a solution of phosphagermaallene 1 (1 mmol)
in diethyl ether (10 mL) was added N-benzylidenemethylamine
(0.119 g, 1 mmol) at -78 ꢀC, and the mixture was stirred at room
temperature for 3 h. After filtration, volatiles were removed under a
vacuum, and the residue was dissolved in pentane. The saturated
solution was stored at -20 ꢀC to give a yellow crystalline product
(0.59 g, 80%, mp 156 ꢀC). 1H NMR (300.13 MHz): δ 1.16 and 1.53
Synthesis of 6. To a solution of phosphagermaallene 1 (1 mmol)
in diethyl ether (10 mL) was added at -78 ꢀC N-tert-butyl-R-
phenylnitrone (0.177 g, 1 mmol) dissolved in 10 mL of THF. The
color of the solution changed from brown to yellow. The mixture
was allowed to warm to room temperature and stirred for 2 h. After
this time, the solvent was removed under reduced pressure, and the
residue was dissolved in 30 mL of pentane. Lithium salts were
filtered off, and the solvents partially removed under vacuum con-
ditions to generate a saturated solution. Storage of the solution at
-20 ꢀC afforded colorless crystals of 6 (0.61 g, 76%, mp 166 ꢀC). 1H
NMR (300.13 MHz): δ 0.62 and 1.17 (2d, 3JHH = 6.6 Hz, 2 ꢀ 6H,
o-CHMeMe0), 1.08 and 1.34 (2s, 2 ꢀ 9H o-CMe3 of Mes*), 1.14
(s, 9H, NCMe3), 1.21 (d, 3JHH = 6.6 Hz, 6H, p-CHMe2), 1.27 (s,
9H, p-CMe3 ofMes*), 1.31(s, 9H, GeCMe3), 2.82 (sept, 3JHH =6.6
Hz, 1H, p-CHMe2), 3.29 (brs, 2H, o-CHMeMe0), 5.16 (d,
3JPH = 22.6 Hz, 1H, PhCH), 6.89 (s, 2H, m-CH of Tip), 7.20-
7.22 (m, 2H, p-CH of Ph and one m-CH of Mes*), 7.29-7.33 (m,
3H, m-CH of Ph and one m-CH of Mes*), 7.58 (d, 3JHH = 6.9 Hz,
2H, o-CH of Ph). 13C NMR (75.47 MHz): δ 23.84 (p-CHMe2),
25.52 and 25.94 (o-CHMeMe0), 27.32 (NCMe3), 30.57 (GeCMe3),
(2s, 2ꢀ 9H, o-CMe3 of Mes*); 1.25, 1.27, 1.36, and 1.41 (4d, 3JHH
=
6.6 Hz, 4 ꢀ 3H, o-CHMeMe0); 1.32 (s, 9H, GeCMe3); 1.35 (d,
3JHH=6.6 Hz, 6H, p-CHMeMe0); 1.44 (s, 9H, p-CMe3 of Mes*);
2.45 (s, 3H, NMe); 2.85 and 3.34 (2sept, 3JHH = 6.6 Hz, 2 ꢀ 1H,
o-CHMeMe0); 2.97 (sept, 3JHH = 6.6 Hz, 1H, p-CHMeMe0); 5.05
(d,3JPH=13.6 Hz, 1H, PhCH);6.61-6.64 (m, 2H, Ph); 6.96 and 7.42
(2s, 2 ꢀ 1H, m-CH of Mes*); 7.01-7.08 (m, 3H, Ph); 7.11 and 7.14
(2s, 2 ꢀ 1H, m-CH of Tip). 13C NMR (75.47 MHz): δ 23.75, 24.64,
25.99, and 26.53 (o-CHMeMe0); 23.83 and 23.96 ( p-CHMeMe0);
29.73 (GeCMe3); 31.56 (p-CMe3 of Mes*); 32.40 (d, 3JCP=3.2 Hz,
4
4
GeCMe3); 32.83 (d, JCP =8.7 Hz) and 33.08 (d, JCP =6.0 Hz)
(o-CMe3 of Mes*); 33.98 (NMe); 34.03 (p-CHMeMe0); 34.80
( p-CMe3 of Mes*); 36.02 and 36.17 (o-CHMeMe0); 37.44 and
38.10 (o-CMe3 of Mes*); 80.89 (d, 2JCP=19.3 Hz, PhCH); 120.91,
121.54, 121.56, and 121.96 (m-CH of Tip and Mes*); 136.32 (d,
4
31.17 (p-CMe3 of Mes*), 33.05 (d, JCP = 7.2 Hz) and 33.30 (d,
4JCP = 6.0 Hz; o-CMe3 of Mes*), 33.86 (p-CHMe2), 34.16 (o-
CHMeMe0), 34.84 (p-CMe3 of Mes*), 36.44 (GeCMe3), 38.36 and
38.44 (o-CMe3 of Mes*), 60.53 (NCMe3), 78.04 (d, 2JCP = 50.5 Hz,
PhCH), 122.00 (m-CH of Tip), 122.33 and 122.89 (m-CH of Mes*),
(29) SHELXS-97: Sheldrick, G. M. Acta Crystallogr. 1990, A46,
467-473.
€
€
(30) Sheldrick, G. M. SHELXL-97; University of Gottingen: Gottingen,
Germany, 1997.

10504 Inorganic Chemistry, Vol. 49, No. 22, 2010
Ghereg et al.
1
126.45 (p-CH of Ph), 127.64 (m-CH of Ph), 130.22 (d, 4JCP =4.1Hz,
ipso-C of Tip), 144.32 (d, JCP = 69.9 Hz, ipso-C of Mes*),
149.59 (p-C of Mes*), 149.93 (p-C of Tip), 152.67 (o-C of Mes*),
1
o-CH of Ph), 131.75 (ipso-C of Tip), 131.75 (d, JCP = 75.5 Hz,
154.92 (o-C of Tip), 175.75 (d, JCP = 74.1 Hz, CH=P). 31P
1
ipso-C of Mes*), 147.13 (d, 3JCP = 13.0 Hz, ipso-C of Ph), 149.58
(p-C of Tip), 149.80 (p-C of Mes*), 152.14 (d, 2JCP = 4.5 Hz) and
152.45 (d, 2JCP = 6.6 Hz; o-C of Mes*), 154.88 (o-C of Tip), 192.51
NMR (121.51 MHz): δ 322.5 (d, 2JPH = 23.7 Hz). MS (m/z, %):
663 (M, 5), 621 (M - CH2CN - 2H, 5), 607 (M - t-Bu þ H, 30),
566 (M - t-Bu - CH2CN, 5), 509 (M - 2t-Bu - CH2CN, 15), 418
(M - Mes*, 5), 377 (M - Mes* - CH2CN - H, 5), 346 (M -
Mes*P - CH2CN - H, 5), 275 (Mes*P - H, 15), 233 (GeTip - i-Pr
- H, 15), 57 (t-Bu, 100). IR (KBr, cm-1):2232(CtN). Anal. Calcd
for C40H64GeNP (662.51): C, 72.52; H, 9.74%. Found: C, 72.72; H,
9.70%.
1
(d, JCP = 59.6 Hz, CdP). 31P NMR (121.51 MHz): δ 337.0 (d,
3JPH = 22.6 Hz). MS (m/z, %): 799 (M, 5), 728 (M - N(t-Bu), 5),
670 (M - t-Bu - N(t-Bu) - H, 5), 598 (M - Tip þ2H, 5), 555
(M - Mes* þ H, 1), 333 (Ge(t-Bu)Tip - H, 10), 275 (Mes*P - H,
25), 233 (TipGe - i-Pr - H, 15), 57 (t-Bu, 100). Anal. Calcd for
C49H76GeNOP (798.71): C, 73.69; H, 9.59%. Found: C, 73.81; H,
9.62%.
Synthesis of 9. A mixture of phosphagermaallene 1 (1 mmol)
in 10 mL of diethyl ether and pivalonitrile (0.083 g, 1 mmol) was
heated overnight at 70 ꢀC in a sealed tube. After the filtration to
remove LiF and evaporation of solvents under reduced pres-
sure, crystallization from pentane at -20 ꢀC afforded 0.55 g
(78%) of 9 (mp 183 ꢀC). 1H NMR (300.13 MHz): δ 0.68 (s, 9H,
Synthesis of 7. A solution of N-hydroxy-benzimoyl chloride
(0.155 g, 1 mmol) in 20 mL of diethyl ether was added dropwise
to a solution of phosphagermaallene 1 (1 mmol) in 10 mL of
diethyl ether and 7 mL of triethylamine (about 50-fold molar
excess) over a period of 1 h, while maintaining the temperature
between -80 and -70 ꢀC. The reaction mixture was allowed to
warm to room temperature, and stirring was continued at room
temperature for 6 h. The solvent was removed under vacuum
conditions and the residue extracted with pentane (40 mL). The
filtrate was concentrated under vacuum conditions until 7 was
precipitated of as a yellow powder (0.53 g, 72% mp 118 ꢀC). 1H
NMR (300.13 MHz): δ 0.69 and 1.24 (2d, 3JHH = 6.6 Hz, 2 ꢀ
6H, o-CHMeMe0), 1.15 and 1.41 (2s, 2 ꢀ 9H o-CMe3 of Mes*),
1.28 and 1.30 (2d, 3JHH = 6.6 Hz, 2 ꢀ 3H, p-CHMeMe0), 1.32 (s,
3
NCCMe3); 1.00, 1.12, 1.24, and 1.45 (4d, JHH = 6.6 Hz, 4 ꢀ
3H, o-CHMeMe0); 1.31 (s, 9H, GeCMe3); 1.33 and 1.34 (2d,
3JHH = 6.6 Hz, 2 ꢀ 3H, p-CHMeMe0); 1.36 (s, 9H, p-CMe3 of
Mes*); 1.61 and 1.66 (2s, 2 ꢀ 9H, o-CMe3 of Mes*); 2.97 (sept,
3JHH = 6.6 Hz, 1H, p-CHMeMe0); 3.19 and 3.59 (2sept, 3JHH
=
6.6 Hz, 2 ꢀ 1H, o-CHMeMe0); 6.95 and 7.10 (2s, 2 ꢀ 1H, m-CH
of Tip); 7.35 and 7.41 (2s, 2 ꢀ 1H, m-CH of Mes*). 13C NMR
(75.47 MHz): δ 23.91 and 23.94 (p-CHMeMe0); 24.08, 25.17,
25.78, and 25.86 (o-CHMeMe0); 28.45 (NCCMe3); 28.93
(GeCMe3); 31.37 (p-CMe3 of Mes*); 33.64 (d, 4JCP = 6.7 Hz)
9H, p-CMe3 of Mes*), 1.35 (s, 9H, GeCMe3), 2.82 (sept, 3JHH
=
4
6.6 Hz, 1H, p-CHMeMe0), 3.31 (brs, 2H, o-CHMeMe0),
7.10-7.19 (m, 5H, Ph), 7.11 (s, 2H, m-CH of Tip), 7.35 and
7.39 (2s, 2 ꢀ 1H, m-CH of Mes*). 13C NMR (75.47 MHz): δ
23.80 and 23.81 (p-CHMeMe0); 25.55 and 25.97 (o-CHMeMe0);
30.60 (GeCMe3); 31.15 (p-CMe3 of Mes*); 33.02 (d, 4JCP = 7.0
and 33.85 (d, JCP = 6.1 Hz; o-CMe3 of Mes*); 33.99, 34.15,
and 34.29 (o- and p-CHMeMe0); 34.96 (p-CMe3 of Mes*); 37.93
and 38.27 (o-CMe3 of Mes*); 121.12 and 121.55 (m-CH of Tip);
121.97 and 122.14 (m-CH of Mes*); 131.90 (d, 3JCP = 3.2 Hz,
1
ipso-C of Tip); 142.02 (d, JCP = 86.5 Hz, ipso-C of Mes*);
149.97 and 150.16 (p-C of Mes* and Tip); 153.50, 153.78,
4
Hz) and 33.25 (d, JCP = 6.2 Hz; o-CMe3 of Mes*); 33.88 (p-
1
CHMeMe0); 34.11 (o-CHMeMe0); 34.80 (p-CMe3 of Mes*);
36.35 (GeCMe3); 38.41 and 38.48 (o-CMe3 of Mes*); 121.50
and 122.65 (m-CH de Mes*); 122.68 (m-CH de Tip); 127.57,
128.56, and 128.23 (o-, m- and p-CH of Ph); 134.56 (ipso-C
154.62, and 155.06 (o-C of Mes* and Tip); 181.81 (d, JCP
=
103.5 Hz, CdP); 196.08 (d, 2JCP = 28.4 Hz, CdN). 31P NMR
(121.51 MHz): δ 219.6. MS (m/z, %): 705 (M, 2), 648 (M -
t-Bu, 25), 622 (M - t-BuCN, 5), 510 (M - 2t-Bu - t-BuCN þ
2H, 15), 275 (Mes*P - H, 20), 84 (t-BuCN þ H, 5), 57 (t-Bu,
100). IR (KBr, cm-1): 1597 (CdN). Anal. Calcd for C43H70-
GeNP (704.59): C, 73.30; H, 10.01%. Found: C, 73.39; H,
9.95%.
1
of Tip); 135.47 (d, JCP = 73.9 Hz, ipso-C of Mes*); 138.89
(ipso-C of Ph); 149.43 (p-C of Tip); 149.88 (p-C of Mes*);
153.56 and 154.65 (o-C of Mes*); 154.89 (o-C of Tip); 175.63 (d,
2JCP = 25.5 Hz, CdN); 182.71 (d, 1JCP = 69.8 Hz, CdP). 31
P
NMR (121.51 MHz): δ 296.7. MS (m/z, %): 742 (M þ H, 1),
685 (M - t-Bu þ H, 5), 629 (M - 2t-Bu þ 2H, 5), 510 (M -
PhCNO - 2t-Bu þ 2H, 5), 350 (Tip(t-Bu)GeO, 5), 289 (Mes*
PC þ H, 12), 277 (TipGe, 45), 231 (Mes* - Me þ H, 30), 57 (t-
Synthesis of 10. To a solution of 1 (1 mmol) in diethyl ether
(10 mL) was added benzonitrile (0.103 g, 1 mmol) at -78 ꢀC. The
mixture was stirred at room temperature for 3 h. The solvents
were removed under reduced pressure, and the remaining
brownish powder was extracted with 50 mL of pentane. Con-
centration of the solution to 10 mL, followed by the slow
evaporation of the solvent, provided 0.45 g (62%) of 10 (mp
188 ꢀC). 1H NMR (300.13 MHz): δ 1.17, 1.18, 1.29, and 1.56 (4d,
3JHH = 6.6 Hz, 4 ꢀ 3H, o-CHMeMe0); 1.32 (d, 3JHH = 6.6 Hz,
6H, p-CHMeMe0); 1.35 and 1.71 (2s, 2 ꢀ 9H, CMe3); 1.40 (s,
3H, CMeMe0); 1.42 (s, 12H, GeCMe3 and CMeMe0); 1.84 (m,
1H, CHH0); 2.20 (m, 1H, CHH0); 2.47 and 3.12 (2sept, 3JHH = 6.6
Bu, 100). IR (KBr, cm-1): 1596 (CdN). Anal. Calcd for C45
-
H66GeNOP (740.58): C, 72.98; H, 8.98%. Found: C, 72.80; H,
8.79%.
Synthesis of 8. One equivalent of acetonitrile (0.041 g, 1
mmol) was added to a solution of 1 (1 mmol) in 10 mL of diethyl
ether, cooled to -78 ꢀC. The reaction mixture gradually turned
from brown to light yellow after overnight stirring at room
temperature. LiF was then filtered off, and the solvents were
removed under vacuum conditions. Recrystallization of the
crude material from pentane at -20 ꢀC afforded white crystals
of 8 (0.52 g, 78%, mp 178 ꢀC). 1H NMR (300.13 MHz): δ 1.00
Hz, 2 ꢀ 1H, o-CHMeMe0); 2.61 (m, 1H, CHP); 2.94 (sept, 3JHH
=
6.6 Hz, 1H, p-CHMeMe0); 6.74 (d, 3JHH = 7.5 Hz, 2H, o-CH of
Ph); 7.00 (t, 3JHH = 7.5 Hz, 1H, p-CH of Ph); 7.08 and 7.11 (2s, 2 ꢀ
1H, m-CH of Tip); 7.25 (t, 3JHH = 7.5 Hz, 2H, m-CH of Ph); 7.43
3
and 1.20 (2d, JHH = 6.9 Hz, 2 ꢀ 6H, o-CHMeMe0), 1.22 (d,
3JHH = 6.9 Hz, 6H, p-CHMe2), 1.30 (s, 9H, p-CMe3 of Mes*),
1.36 (s, 9H, GeCMe3), 1.51 (s, 18H, o-CMe3 of Mes*), 2.25 (s,
(brs, 2 ꢀ 1H, arom CH). 13C NMR (75.47 MHz): δ 23.23 (d, 1JCP
=
21.5 Hz, CHP); 23.63 and 23.88 (p-CHMeMe0); 25.31, 25.55, 26.15,
and 27.73 (o-CHMeMe0); 29.15 (d, 3JCP = 1.0 Hz, GeCMe3); 30.12
(d, 4JCP = 5.6 Hz, GeCMe3); 31.21 and 33.17 (d, 4JCP = 12.1 Hz;
CMe3); 33.43 and 33.66 (CMeMe0); 33.92 (p-CHMeMe0); 34.72 and
3
2H, CH2CN), 2.77 (sept, JHH = 6.9 Hz, 2H, o-CHMeMe0),
2.83 (sept, 3JHH = 6.9 Hz, 1H, p-CHMe2), 6.97 (s, 2H, m-CH of
Tip), 7.33 (s, 2H, m-CH of Mes*), 7.88 (d, JPH = 23.7 Hz,
2
3
3
CH=P). 13C NMR (75.47 MHz): δ 7.60 (d, JCP = 11.5 Hz,
37.63 (o-CHMeMe0); 34.97 and 38.10 (d, JCP = 1.6 Hz; CMe3);
CH2CN), 23.71 (p-CHMe2), 25.16 and 25.70 (o-CHMeMe0),
28.80 (d, 4JCP = 4.8 Hz, GeCMe3), 28.90 (GeCMe3), 31.27 (p-
CMe3 of Mes*), 33.89 (p-CHMe2), 34.01 (d, 4JCP = 7.5 Hz, o-
CMe3 of Mes*), 34.80 (p-CMe3 of Mes*), 35.16 (o-CHMeMe0),
37.97 (o-CMe3 of Mes*), 120.66 (CtN), 121.56 (m-CH of
37.25 (d, 3JCP =1.4Hz,CMeMe0);37.60(CHH0); 119.58 (d, 3JCP
=
2.0 Hz, o-CH of Ph); 121.12 and 123.03 (m-CH of Tip); 121.85 (d,
3JCP = 8.2 Hz) and 122.60 (arom CH); 123.02 (d, 1JCP = 28.8 Hz,
P-Carom); 123.22 (p-CH of Ph); 128.39 (m-CH of Ph); 129.86 (d,
3JCP = 4.3 Hz, ipso-C of Tip); 149.17 and 150.95 (CCMe3); 150.18
(p-C of Tip); 153.25 (d, 2JCP = 6.5 Hz, ipso-C of Ph); 153.25 and
3
Mes*), 122.44 (m-CH of Tip), 129.99 (d, JCP = 6.5 Hz,

Article
Inorganic Chemistry, Vol. 49, No. 22, 2010 10505
154.96 (o-C of Tip); 155.28 (d, 2JCP = 23.4 Hz, CCMeMe0); 176.38
Acknowledgment. We are grateful to the Agence Nationale
pour la Recherche (contract ANR-08-BLAN-0105-01) and
PhoSciNet (CM0802) for financial support.
1
(d, JCP = 25.5 Hz, CdN). 31P NMR (121.51 MHz): δ 5.4. MS
(m/z, %): 725 (M, 2), 623 (M - PhCN þ H, 10), 566 (M - t-Bu -
PhCN þ H, 10), 333 (Tip(t-Bu)Ge - H, 8), 277 (TipGe, 100),
57 (t-Bu, 80). IR (KBr, cm-1): 1604 (CdN). Anal. Calcd for C45-
H66GeNP (724.58): C, 74.59; H, 9.18%. Found: C, 74.47; H,
9.28%.
Supporting Information Available: CIF files for 4, 6, 8, and 10.
This material is available free of charge via the Internet at http://
pubs.acs.org.