Mes2Ge=C=PAr: The first germaphosphaallene

Article abstract of DOI:10.1021/om9600248

The first germaphosphaallene, 3, has been obtained by debromofluorination of the (fluorogermyl)bromophosphaalkene 7 and characterized by ³¹P NMR (240 ppm) and ¹³C NMR (280.9 ppm for the allenic carbon) at low temperature. Methanol and methyllithium react exclusively with the Ge=C double bond to afford the corresponding adducts 9 and 10. In the absence of a trapping reagent, 3 gives two types of dimer, 13a (involving two Ge=C bonds) and 14a (involving one Ge=C and one P=C bond).

Full text of DOI:10.1021/om9600248

3070
Organometallics 1996, 15, 3070-3075
Mes2GedCdP Ar : Th e F ir st Ger m a p h osp h a a llen e
Hassan Ramdane, Henri Ranaivonjatovo, and J ean Escudie´*
He´te´rochimie Fondamentale et Applique´e, UPRES associe´e au CNRS No. 5069, Universite´
Paul Sabatier, 118 route de Narbonne, 31062 Toulouse Cedex, France
Simon Mathieu
Laboratoire de Physique Quantique, IRSAMC-CNRS, Universite´ Paul Sabatier, 118 route de
Narbonne, 31062 Toulouse Cedex, France
Noureddine Knouzi
Laboratoire de Chimie Bioorganique, Faculte´ des Sciences El-J adida, BP 20,
El-J adida, Morocco
Received J anuary 17, 1996X
The first germaphosphaallene, 3, has been obtained by debromofluorination of the
(fluorogermyl)bromophosphaalkene 7 and characterized by 31P NMR (240 ppm) and 13C NMR
(280.9 ppm for the allenic carbon) at low temperature. Methanol and methyllithium react
exclusively with the GedC double bond to afford the corresponding adducts 9 and 10. In
the absence of a trapping reagent, 3 gives two types of dimer, 13a (involving two GedC
bonds) and 14a (involving one GedC and one PdC bond).
In tr od u ction
two heavy elements of group 14 and 15, Ge,Ge-dimesityl-
P-(2,4,6-tri-tert-butylphenyl)germaphosphaallene (3)
(Chart 2).
Many stable doubly-bonded compounds of the group
14 and 15 elements such as “heteroalkenes” >MdC<
(M: Si,1 Ge,2 Sn3) or -PdC<4 have been synthesized
and studied, but very little is known about heavy
analogs of cumulenes in which one or two atoms of the
first row have been replaced by elements such as Si,
Ge, and Sn and P, As, and Sb, respectively. Thus, only
two “heavy allenes” of the type >MdCdX with a group
14 element, the silaallene 1 obtained by West5 and the
stannaketenimine 2 prepared by Gru¨tzmacher,6 have
been structurally characterized to date (Chart 1).
With a group 15 element, only some phosphaallenes
of the type -PdCdX4d,7 (X: C, O, N, P, S) have been
prepared.
Resu lts a n d Discu ssion
We have chosen the mesityl and “supermesityl”
groups as substituents since they are widely used to
provide steric stabilization of low-coordinate derivatives
of germanium2 and phosphorus.4 As the simultaneous
creation of >GedC< and -PdC< double bonds seems
unlikely, we thought that the best strategy to synthesize
3 was first form the -PdC< double bond since it is
generally much less reactive than the >GedC< double
bond and thus, hopefully, would be inert during the rest
of the synthesis.
a . Syn th esis a n d Ch a r a cter iza tion of 3. We have
prepared the precursor 7 according to the process used
by Bickelhaupt for the synthesis of ArPdC(Br)MMe3
(M: Si, Ge, Sn):8 addition of n-butyllithium at low
temperature to the dibromophosphaalkene 48a and then
quenching the resulting lithio compound 5 with dimesi-
tyldifluorogermane (6) (eq 1).
We report here the synthesis and some aspects of the
reactivity of the first metastable allene that contains
X Abstract published in Advance ACS Abstracts, J une 1, 1996.
(1) For reviews see: (a) Raabe, G.; Michl, J . Chem. Rev. 1985, 85,
419. (b) Raabe, G.; Michl, J . In the Chemistry of Organosilicon
Compounds; Patai, S., Rappoport, G., Eds.; Wiley: New York, 1989;
Chapter 17, p 1015. (c) Brook, A. G.; Baines, K. M. Adv. Organomet.
Chem. 1986, 25, 1.
(2) For reviews see: (a) Barrau, J .; Escudie´, J .; Satge´, J . Chem. Rev.
1990, 90, 283. (b) Escudie´, J .; Couret, C.; Ranaivonjatovo, H.; Satge´,
J . Coord. Chem. Rev. 1994, 130, 427.
(3) (a) Meyer, H.; Baum, G.; Massa, W.; Berger, S.; Berndt, A.
Angew. Chem., Int. Ed. Engl. 1987, 26, 547. (b) Anselme, G.; Rana-
ivonjatovo, H.; Escudie´, J .; Couret, C.; Satge´, J . Organometallics 1992,
11, 2748. (c) Scha¨fer, A.; Weidenbruch, M.; Saak, W.; Pohl, S. J . Chem.
Soc., Chem. Commun. 1995, 1157. (d) Kuhn, N.; Kratz, T.; Blaeser,
D.; Bo¨se, R. Chem. Ber. 1995, 128, 245.
(4) For reviews see: (a) Lochschmidt, S.; Schmidpeter, A. Phospho-
rus Sulfur 1986, 29, 73. (b) Appel, R.; Knoll, F. Adv. Inorg. Chem. 1989,
33, 259. (c) Markovski, L. N.; Romanenko, V. D. Tetrahedron 1989,
45, 6019. (d) Appel, R. In Multiple bonds and low coordination in
phosphorus chemistry; Regitz, M., Scherer, O. J ., Eds.; Georg Thieme
Verlag: Stuttgart, New York, 1990; p 157.
(5) Miracle, G. E.; Ball, J . L.; Powell, D. R.; West, R. J . Am. Chem.
Soc. 1993, 115, 11598.
(6) Gru¨tzmacher, H.; Freitag, S.; Herbst-Irmer, R.; Sheldrick, G. S.
Angew. Chem., Int. Ed. Engl. 1992, 31, 437.
As reaction b of eq 1 is slow, the best yield in 7 was
obtained when the reaction mixture was stirred for 1 h
at -80 °C, after addition of the difluorogermane 6 to 5
(7) (a) Gouygou, M.; Koenig, M.; Escudie´, J .; Couret, C. Heteroatom.
Chem. 1991, 2, 221. (b) Yoshifuji, M.; Niitsu, T.; Shiomi, D.; Inamoto,
N. Tetrahedron Lett. 1989, 30, 5433.
(8) (a) Goede, S. J .; Bickelhaupt, F. Chem. Ber. 1991, 124, 2677. (b)
Van der Sluis, M.; Wit, J . B. M.; Bickelhaupt, F. Organometallics 1996,
15, 174.
S0276-7333(96)00024-6 CCC: $12.00 © 1996 American Chemical Society
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Mes2GedCdPAr
Organometallics, Vol. 15, No. 13, 1996 3071
Ch a r t 1a
d
a
Ad ) adamantyl.
Ch a r t 2
addition of MeLi or MeOLi on the PdC bond is not
observed. The formation of 3 by reacting 11 with MeLi
or LDA does not occur.
b. Dim er iza tion of 3. In the absence of trapping
reagent, the germaphosphaallene 3 gives two types of
dimers: the “classical” head-to-tail dimer 13a (dimer-
ization between two GedC double bonds) and the
unexpected dimer 14a due to the cycloaddition between
a GedC and a PdC double bond. 14a is the major
compound : 12/88 13a /14a .
13a and 14a have completely different solubilities;
14a is very soluble in Et2O and other organic solvents
(pentane, THF), whereas 13a is poorly soluble and
consequently was easily separated from the reaction
mixture in the form of a yellow powder.
14a was characterized in 31P NMR spectroscopy,
showing an AX spectrum with the expected low field
shift for the dicoordinate phosphorus atom (+269.5 ppm)
and a signal at +61.3 ppm for the tricoordinate phos-
phorus atom with a large 2J PCP coupling constant (225.4
Hz) (Scheme 2).
at -120 °C. At this temperature the carbenoid 5 is
stable. 7 can also be obtained in one pot by adding two
equiv of n-butyllithium to a mixture of 4 and 6 in Et2O
since at -120 °C n-butyllithium does not react with the
germanium-fluorine bond of 6.
The debromofluorination of 7 to give germaphos-
phaallene 3 was effected with n-butyllithium at low
temperature (a similar method to create a >GedC<
double bond was used by Wiberg for the formation of
transient germenes9). The reaction, followed by 31P
NMR between -85 °C and room temperature, showed
the immediate formation of the lithio compound 8, as
shown by a doublet at 397.4 ppm (3J PF ) 16.9 Hz).
Elimination of LiF occurred at -60 °C to give the
expected germaphosphaallene 3 (eq 2).
From the large phosphorus-phosphorus coupling
constant (225.4 Hz), it seems that the unsymmetrical
isomer obtained is 14a since the literature data show
2
that J PP is generally around 15-30 Hz in cis structures
such as 14b, whereas it is larger than 100 Hz in trans
structures such as 14a 12 (Chart 3).
14a could not be obtained as a crystalline compound
but only as a reddish, viscous oil which was air sensitive
due to the presence of the GedC double bond. Addition
of methyllithium to the GedC unsaturation followed by
methanolysis afforded derivative 15, which was char-
acterized. The AX system observed in the 31P NMR
According to the 31P NMR spectrum, 3 was formed in
about 65-70% yield and was stable below -50 °C. Its
structure was proved by low field shifts in 31P NMR (δ
240.0 ppm, characteristic of a P(II) derivative) and in
13C NMR (δ 280.9 ppm, d, 1J CP ) 54.3 Hz for the allenic
carbon). Similar chemical shifts were observed for the
allenic carbon of diphosphaallene ArPdCdPAr (276.2
spectrum with a signal at low field (352.6 ppm, 2J PCP
)
112.9 Hz), characteristic of a dicoordinate phosphorus,
proved that methyllithium reacted only with the GedC
double bond. In 1H NMR spectrum the tert-butyl and
mesityl groups appeared as very broad signals. The
extremely large steric congestion hinders the free rota-
tion of these groups at room temperature. Broad signals
were also observed for the tert-butyl groups in 13C NMR
spectrum.
1
ppm, J CP ) 58 Hz10) and arsaphosphaallene ArPdCd
AsAr (299.5 ppm, 1J CP ) 75.1 Hz11). The structure of 3
was also proved by its chemical reactivity. Addition of
methanol or methyllithium followed by methanolysis at
-40 °C afforded the new phosphaalkenes 9 and 10,
respectively. A regiospecific reaction was observed with
exclusive addition to the GedC double bond according
to the Geδ+dCδ- polarity (Scheme 1).
9 and 10 have been identified by their physicochem-
ical data as well as by their independent synthesis from
phosphaalkene 12:8a successive addition of n-butyl-
lithium and of 6 at low temperature afforded 11; further
reaction with MeOLi or methyllithium gave 9 and 10,
respectively, in nearly quantitative yield (Scheme 1);
The “classical” head-to-tail dimer 13 isolated im-
mediately after dimerization was the trans isomer 13a
1
as proved by the H NMR spectrum which displays two
equivalent Ar and four equivalent mesityl groups. After
7 days at room temperature in solution, a mixture of
13a /13b was observed in 42/58 ratio. The same ratio
was obtained from 13a after only 2 h of irradiation (254
nm). The thermodynamic equilibrium between 13a and
(9) Wiberg, N.; Kim, C. K. Chem. Ber. 1986, 119, 2966 and 2980.
(10) Appel, R.; Fo¨lling, P.; J osten, P.; Siray, M.; Winkhaus, V.;
Knoch, F. Angew. Chem. Int. Ed. Engl. 1984, 23, 619.
(11) Ramdane, H.; Ranaivonjatovo, H.; Escudie´, J .; Satge´, J .; Knouzi,
N. To be submitted for publication.
(12) (a) Yoshifuji, M.; Sasaki, S.; Inamoto, N. Tetrahedron Lett. 1989,
30, 839. (b) Karsch, H. H.; Reisacher, H. U. Phosphorus Sulfur 1988,
35, 203; 1988, 36, 69. (c) Yoshifuji, M.; Niitsu, T.; Toyota, K.; Inamoto,
N. Tetrahedron Lett. 1988, 29, 333. (d) Appel, R.; Behnke, C. Z. Anorg.
Allg. Chem. 1987, 555, 23.
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3072 Organometallics, Vol. 15, No. 13, 1996
Ramdane et al.
Sch em e 1
Sch em e 2
Sch em e 3
Ch a r t 3
aromatic H of the Mes groups cis to the lone pairs are
not really affected at low temperature.
The isomerization of 13a to 13b, which is the major
isomer when the thermodynamic equilibrium is estab-
lished, seems surprising since the trans isomer 13a
should be a priori less hindered and, for this reason,
more abondant. However, we may suppose that a
folding of the four-membered ring along the Ge-Ge axis
combined with a torsion around the PdC double bond
could relieve the steric strain in 13b.
In contrast to the unsymmetrical isomer 14a , 13a ,b
with only PdC double bonds are unreactive toward air
and moisture and even toward methyllithium.
The two types of dimerization of 3, although unex-
pected, have some precedent in the very similar behav-
ior observed for ketene13 with formation of both sym-
metrical and unsymmetrical dimers due to the cyclo-
addition between two CdC bonds or between one CdC
and one CdO bond (Scheme 3).
However, the energy differences between lactone and
dione formation transition structures are small and for
example, with alkyl or aryl substituents on carbon
instead of hydrogen, the dione product is generally the
most important.14 In phosphacumulenes, -PdCdX
(X: O15 or S16), different dimers are obtained depending
on X. Thus phosphaketene undergoes a dimerization
13b was unambiguously proved by a 2 h irradiation of
pure 13b leading again to the mixture 13a /13b in 42/
58 ratio.
The cis structure of 13b was obvious from the 1H
NMR spectrum which exhibits very different mesityl
groups: the ortho methyl groups on the mesityl cis to
the aromatic rings are about 1 ppm high field shifted
in relation to those on the mesityl trans to the aromatic
rings (1.55 and 2.51 ppm); a large splitting was also
observed for the aromatic protons of the mesityls (6.35
and 6.75 ppm). This large difference of chemical shift
is of course due to their location cis or trans to the lone
pairs or to the aromatic rings. Another argument for
1
this attribution was given by the low-temperature H
NMR spectrum of 13b: in the mesityl groups, the
signals at high field for the o-Me (1.55 ppm) and the
aromatic hydrogens (6.35 ppm) widen when the tem-
perature decreases; at -45 °C, the signal of the o-Me
even disappears completely. The widening of these
signals is of course due to the slow rotation of the
mesityl groups caused by the steric hindrance; thus,
these signals can be attributed to the Mes groups cis to
the Ar groups. On the contrary, the signals at 2.51 and
6.75 ppm corresponding respectively to the o-Me and
(13) Tenud, L.; Weilemann, M.; Dallwigk, E. Helv. Chim. Acta 1977,
100, 975.
(14) Salzner, U.; Bachrach, S. M. J . Am. Chem. Soc. 1994, 116, 6850.
(15) Appel, R.; Paulen, W. Tetrahedron Lett. 1983, 24, 2639.
(16) Appel, R.; Fo¨lling, P.; Krieger, L.; Siray, M.; Knoch, F. Angew.
Chem., Int. Ed. Engl. 1984, 23, 970.
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Mes2GedCdPAr
Organometallics, Vol. 15, No. 13, 1996 3073
Ch a r t 4
Ch a r t 5
The adducts 24 and 25 are found to be disfavored with
respect to the adducts 22 and 23 by about 25 kcal/mol.
22 and 23 are in turn disfavored with respect to 20 and
21 by about 18 kcal/mol. The head-to-head products 21,
23, and 25 are significantly more stable than the head-
to-tail dimers 20, 22, and 24. The corresponding energy
differences are calculated at 1, 6, and 5 kcal/mol for the
three cases, respectively. Without ignoring the signifi-
cant butadiene-type conjugation occurring in the head-
to-head dimers, all these relative energies can be
accounted for using mean bond energies.
In agreement with these theoretical results, dimers
like 24 and 25 are not actually observed; only dimers
like 20 and 22 are obtained. However, the arrangement
20, predicted to be the most favorable, is only the minor
product observed.
Although the calculations favor the head-to-head
dimers 21 and 23 (probably due to the butadiene-type
conjugation they undergo), it is not surprising that only
the head-to-tail dimers 20 and 22 were experimentally
observed, given our very bulky substituents.
between two PdC bonds (eq 3), and phosphathioketene
between one PdS and one CdS bond (eq 4).
The main difference between the theoretical conclu-
sions on the model compounds and the experimental
results on the substituted compounds bearing mesityl
and tri-tert-butylphenyl groups is the ordering 22 < 20
whereas 14a is preponderant over 13. On the other
hand, the calculations show very little difference in
energy between the cis and the trans PH arrangements
for 20, which is in agreement with the cis-trans
thermodynamic equilibrium observed for 13.
Perhaps the most interesting result of this potential
surface exploration is the apparently unexpected ther-
modynamic stability of the bicyclic derivatives 26 and
27, which were calculated to lie 15 kcal/mol below 20
and 21. The existence of such bicyclo frames is made
possible here, owing to the large difference between the
P-P, Ge-P, and Ge-Ge bond lengths (2.2-2.5 Å) and
the CdC distance (1.34 Å). This dissymmetry allows a
butterfly type arrangement, which relieves the cyclic
strain that could at first be expected (Chart 5).
However calculations on the dimerization of phos-
phaketene 16 have shown that the relative activation
energies for the dimerization pathways involving two
PdC bonds or one PdC and one CdO bond are sensitive
to computational level and, thus, are close.14
Preliminary calculations17-20 have been performed on
model dimers 20-25 resulting from the couplings of the
two molecules of germaphosphaallene H2GedCdPH
(Chart 4).
Exp er im en ta l Section
Gen er a l Exp er im en ta l Con sid er a tion s. All ex-
periments were carried out in flame-dried glassware
under an atmosphere of argon. Et2O and THF were
distilled from sodium/benzophenone prior to use. NMR
spectra were recorded on the following spectrometers:
1H, Bruker AC 80 (80.13 MHz) and Bruker AC 200
(200.13 MHz); 13C, Bruker AC 200 (50.32 MHz) (refer-
ence: TMS); 19F, Bruker AC 80 (75.39 MHz) (refer-
ence: CF3COOH); 31P, Bruker AC 80 (32.44 MHz) and
Bruker AC 200 (80.01 MHz) (reference: H3PO4 85%).
The NMR solvent was always CDCl3. Melting points
have been determined on a Leitz 350 apparatus. Mass
spectra have been collected on a Hewlett-Packard 5989
A spectrometer by EI at 70 eV and on a Nermag R 10010
spectrometer by CI with CH4 and referenced to 74Ge and
(17) Restricted Hartree-Fock calculations have been performed with
the GAUSSIAN 92 package.18 For carbon, phosphorus, and germanium
atoms, effective core potentials were used.19 For all atoms, the valence
atomic basis sets consist of four Gaussian functions contracted to a
double-ú level and augmented by a polarization function. The geom-
etries are optimized by using a gradient technique. For the sake of
reproductibility, the total valence energy for 21 is calculated at
-34.374 365 au.
(18) Gaussian 92, Revision E.3: Frisch, M. J .; Trucks, G. W.; Head-
Gordon, M.; Gill, P. M. W.; Wong, M. W.; Foresman, J . B.; J ohnson, B.
G.; Schlegel, H. B.; Robb, M. A.; Replogle, E. S.; Gomperts, R.; Andres,
J . L.; Raghavachari, K.; Binkley, J . S.; Gonzalez, C.; Martin, R. L.;
Fox, D. J .; Defrees, D. J .; Baker, J .; Stewart, J . J . P.; Pople, J . A.
Gaussian, Inc., Pittsburgh, PA, 1992.
(19) Durand, Ph.; Barthelat, J .-C. Theor. Chim. Acta 1975, 38, 283.
(20) A theoretical study of the potential energy surface at a higher
level of theory is in progress. The full set of results including
methodological details, all geometrical parameters, and correlation
corrections will be published separately.
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3074 Organometallics, Vol. 15, No. 13, 1996
Ramdane et al.
79Br. Elemental analyses were performed by the “Ser-
vice de Microanalyse de l’Ecole de Chimie de Toulouse”.
1H NMR: δ 1.35 (s, 9H, p-t-Bu), 1.47 (s, 18H, o-t-Bu),
5
2.26 (s, 6H, p-Me), 2.38 (d, J HF ) 1.6 Hz, 12H, o-Me),
4
6.81 (s, 4H, H aromatic Mes), 7.39 (d, J HP ) 1.2 Hz,
4 and 12 have been prepared according to the proce-
dure of Bickelhaupt8 respectively from ArPCl2, CHBr3,
and BuLi or ArPCl2, CHI3, and BuLi at low temperature
(-90 °C).
2H, H aromatic Ar), 8.13 (dd, 3J HF ) 2.9 Hz, 2J HP ) 24.7
3
Hz, 1H, PdCH). 31P NMR: δ 334.7 (dd, J PF ) 32.0
Hz, 2J PH ) 24.8 Hz). 19F{1H} NMR: δ -99.6 (d, 3J FP
)
32.0 Hz). 13C NMR: δ 21.20 (s, p-Me), 23.26 (s, o-Me),
31.42(s, p-(CH3)3C), 33.96 (d, 4J CP ) 7.9 Hz, o-(CH3)3C),
35.00 (s, p-C(CH3)3), 38.25 (s, o-C(CH3)3), 122.05 (s, m-C
Ar), 129.05 (s, m-C Mes) 139.68 (s, p-C Mes), 142.83 (s,
o-C Mes), 149.82 (s, p-C Ar), 152.78 (s, o-C Ar), 169.87
(dd, 1J CP ) 69.5 Hz, 2J CF ) 9.4 Hz, PdC). MS EI (m/z):
619 (M - 1, 31); 605 (M - Me, 1); 563 (M - t-Bu, 83);
543 (M - t-Bu - F - 1, 10); 331 (Mes2GeF, 37); 311
(Mes2Ge - 1, 16); 275 (ArP - 1, 94); 57 (t-Bu, 100). Anal.
Calcd for C37H52FGeP: C, 71.75; H, 8.46. Found: C,
71.41; H, 8.33.
Syn th esis of 7. A solution of 1.6 M n-BuLi in hexane
(5.1 mL, 8.2 mmol) was slowly added (during 30 min)
to a solution of 4 (3.68 g, 8.2 mmol) in 75 mL of Et2O
cooled at -90 °C. The reaction mixture was stirred for
1 h at -90 °C and then cooled at -120 °C; a suspension
of Mes2GeF2 (2.86 g, 8.2 mmol) in 25 mL of Et2O was
added. After 1 h of stirring at -80 °C, the mixture was
allowed to warm very slowly (overnight) to room tem-
perature. The solvents were eliminated in vacuo, and
the residue was dissolved in 50 mL of pentane; LiF was
filtered out. Recrystallization from pentane at -20 °C
afforded 2.10 g (35%) of white crystals of 7 (mp 163-
165 °C).
Syn th esis of 9. a . F r om 3. To a solution of 0.36 g
(0.52 mmol) of 7 in Et2O (2 mL) cooled at -90 °C was
added 1 equiv of 1.6 M n-BuLi in hexane (0.33 mL); the
solution turned orange. The reaction mixture was
stirred for 15 min at -40 °C and then cooled at -80 °C,
and a 2-fold excess of methanol was added; the reaction
mixture turned from red to yellow. After removal of
solvents, addition of pentane, and filtration, 9 was
characterized by NMR. 9 was not obtained completely
pure in this reaction, because trace amounts of 7 and
11 (hydrolysis of 8) could not be removed. The yield of
9, calculated from NMR, was 80%.
1H NMR: δ 1.34 (s, 9H, p-t-Bu), 1.46 (d, J HP ) 0.4
5
5
Hz, 18H, o-t-Bu), 2.27 (s, 6H, p-Me), 2.43 (d, J HF ) 2.0
Hz, 12H, o-Me), 6.84 (s, 4H, H aromatic Mes), 7.42 (d,
4J PH ) 1.5 Hz, 2H, H aromatic Ar). 31P NMR: δ 321.3
3
3
(d, J PF ) 29.8 Hz). 19F NMR: δ -97.6 (d, J FP ) 29.8
Hz). 13C NMR: δ 21.18 (s, p-Me), 23.35 (d, J CF ) 3.4
4
Hz, o-Me), 31.36 (s, p-(CH3)3C), 33.16 (d, 4J CP ) 7.1 Hz,
o-(CH3)3C), 35.06 (s, p-(CH3)3C), 37.99 (s, o-(CH3)3C),
122.39 (s, m-C Ar), 129.21 (s, m-C Mes), 133.09 (dd, 3J CP
2
1
) 5.2 Hz, J CF ) 11.1 Hz, C ipso Mes), 138.30 (d, J CP
) 66.6 Hz, C ipso Ar), 140.05 (s, p-C Mes), 143.15 (s,
o-C Mes), 150.92 (s, p-C Ar), 153.09 (d, J CP ) 2.2 Hz,
o-C Ar), 157.71 (dd, J CF ) 10.4 Hz, J CP ) 86.6 Hz,
PdCGe). MS EI (m/z): 697 (M - 1, 1); 683 (M - Me,
1); 641 (M - t-Bu, 1); 619 (M - Br, 2); 603 (M - Br -
Me - 1, 1); 565 (M - Me - Mes + 1, 3); 331 (Mes2GeF,
4); 311 (Mes2Ge - 1, 3); 275 (ArP - 1, 8); 272 (MesGeBr,
1); 57 (t-Bu, 100). Anal. Calcd for C37H51BrFGeP: C,
63.64; H, 7.36. Found: C, 63.42; H, 7.20.
b. F r om 11. A solution of 1.6 M n-BuLi in hexane
(0.53 mL, 0.85 mmol) was slowly added to 10 mL of
MeOH. The resulting solution of MeOLi was added to
a solution of 11 (0.53 g, 0.85 mmol) in Et2O (20 mL)
cooled at -78 °C. After warming of the solution to room
temperature and removal of Et2O, 30 mL of pentane was
added. LiF was filtered out. Recrystallization of crude
9 from pentane at -30 °C afforded 0.45 g (85%) of white
crystals (mp: 143-145 °C).
2
2
1
5
1H NMR: δ 1.33 (s, 9H, p-t-Bu), 1.43 (d, J HP ) 0.4
Ch a r a cter iza tion of 3. The reaction was carried out
in a 10 mm diameter NMR tube in order to perform
NMR studies at low temperature. To a solution of 0.25
g (0.36 mmol) of 7 in a mixture of THF-d8 (1 mL) and
toluene-d8 (0.5 mL) cooled at -90 °C was added 1 equiv
of 1.6 M n-BuLi in toluene-d8 (0.7 mL) (hexane, solvent
of n-BuLi, was removed in vacuo and replaced by
toluene-d8); the solution turned orange. A 31P NMR
spectrum showed the formation of the lithio compound
8. When the reaction mixture was warmed between
-70 and -40 °C, the germaphosphaallene 3 was formed
and evidenced by 31P NMR (δ: 239.7 ppm). After
cooling of the sample at -80 °C to avoid dimerization
of 3, a 13C NMR spectrum showed the signal of the
Hz, 18H, o-t-Bu), 2.24 (s, 6H, p-Me), 2.32 (s, 12H, o-Me),
3.37 (s, 3H, OMe), 6.78 (s, 4H, H aromatic Mes), 7.36
4
2
(d, J HP ) 1.1 Hz, 2H, H aromatic Ar), 8.25 (d, J HP
)
25.5 Hz, 1H, PdCH). 31P NMR (C6D6): δ 325.7 (d, 2J PH
) 25.5 Hz). 13C NMR: δ 21.13 (s, p-Me), 23.45 (s, o-Me),
31.42 (s, p-(CH3)3C), 33.84 (d, 4J CP ) 7.8 Hz, o-(CH3)3C),
34.97 (s, p-C(CH3)3), 38.22 (s, o-C(CH3)3), 52.25 (s, OMe),
121.92 (s, m-C Ar), 128.83 (s, m-C Mes), 138.81 (s, p-C
Mes), 143.14 (s, o-C Mes), 149.39 (s, p-C Ar), 152.74 (s,
1
o-C Ar), 172.23 (d, J CP ) 71.3 Hz, PdC). MS EI (m/z):
632 (M, 8); 575 (M - t-Bu, 5); 545 (M - t-Bu - OMe +
1, 6); 343 (Mes2GeOMe, 69); 275 (ArP - 1, 57); 193
(MesGe, 16); 179 (MesGe - Me + 1, 25); 57 (t-Bu, 100).
Anal. Calcd for C38H55OGeP: C, 72.28; H, 8.78.
Found: C, 72.39; H, 8.70.
1
allenic carbon at δ 280.93 ppm (d, J CP ) 54.3 Hz).
Syn th esis of 11. A 8.5 mL portion of a solution of
1.6 M n-BuLi in hexane (13.7 mmol) was added drop-
wise to a solution of 12 (5.70 g, 13.7 mmol) in Et2O (50
mL) cooled at -80 °C. After 10 min and then cooling
at -120 °C, a suspension of Mes2GeF2 (4.50 g, 13.7
mmol) in Et2O (30 mL) was slowly added under vigorous
stirring. The reaction mixture (orange-yellow) was very
slowly warmed to room temperature in 2 h. The
solvents were eliminated in vacuo and replaced by 50
mL of pentane. LiI was filtered off. Crude 11 was
recrystallized from pentane to afford 2.90 g (35%) of
yellow crystals (mp 148-150 °C).
Syn th esis of 10. a . F r om 3. The procedure was
exactly the same as previously described for 9. Addition
of MeLi (2 equiv) at -80 °C to 3 caused a change from
red to orange yellow. After warming of the solution to
room temperature, a slight excess of methanol was
added. After the usual workup, 10, with some amounts
of 7 and 11, was obtained. The NMR yield was 75%.
Pure 10 could be obtained from 11.
b. F r om 11. To a solution of 11 (0.53 g, 0.85 mmol)
in Et2O (10 mL) cooled at -78 °C was added dropwise
1 equiv of 1.6 M MeLi in hexane. After being warmed
+
+

Mes2GedCdPAr
Organometallics, Vol. 15, No. 13, 1996 3075
to room temperature, the reaction mixture was heated
for 1 h at reflux. After the usual workup (elimination
of Et2O, addition of pentane, filtration), recrystallization
from pentane gave 0.42 g (80%) of white crystals of 10
(mp 74-76 °C).
excess of 1.6 M MeLi in Et2O (2.5 mL, 4.06 mmol). The
reaction mixture was heated at reflux for 30 min and
turned purple. Methanol (4.06 mmol) in pentane (10
mL) and then an excess of methyl iodide were succes-
sively added. After elimination of Et2O in vacuo, 30 mL
of pentane was added. Lithium salts were filtered out.
15 was isolated in the form of a purple powder: 2.00 g
(80%, mp 148-150 °C).
4
1H NMR: δ 1.03 (d, J HP ) 0.9 Hz, 3H, GeMe), 1.33
(s, 9H, p-t-Bu), 1.40 (d, 5J HP ) 0.5 Hz, 18H, o-t-Bu) 2.24
(s, 18H, o- and p-Me), 6.74 (s, 4H, H aromatic Mes), 7.35
4
2
(d, J HP ) 1.1 Hz, 2H, H aromatic Ar), 8.37 (d, J HP
)
2
31P NMR: AX system, δA 352.6 (d, J PP ) 112.9 Hz,
26.3 Hz, 1H, PdCH). 31P NMR (C6D6): δ 310.8 (d, 2J PH
) 26.3 Hz). 13C NMR: δ 5.59 (d, 3J CP ) 12.0 Hz, MeGe),
21.06 (s, p-Me), 24.24 (s, o-Me), 31.44 (s, p-(CH3)3C),
33.79 (d, 4J CP ) 7.7 Hz, o-(CH3)3C), 34.96 (s, p-C(CH3)3),
38.26 (s, o-C(CH3)3), 121.87 (s, m-C Ar), 128.80 (s, m-C
Mes), 137.22 (d, J CP ) 6.7 Hz, C ipso Mes), 137.76 (s,
p-C Mes), 142.41 (s, o-C Mes), 149.14 (s, p-C Ar), 152.67
(s, o-C Ar), 177.59 (d, J CP ) 71.9 Hz, PdC). MS (m/z):
2
PdC), δX 31.9 (d, J PP ) 112.9 Hz, P-C). 1H NMR: δ
1.14 (d, 4J HP ) 0.7 Hz, 3H, CH3Ge); 1.26-1.45 (m, 27H,
t-Bu); 1.88-2.37 (m, 18H, o- and p-Me); 6.42-7.41 (m,
6H, H aromatic Mes and H aromatic Ar). 13C NMR: δ
13.53 (s, CH3Ge); 21.07 (s, p-CH3); 23.76, 24.32, 24.48,
24.78, 24.95 (o- + p-CH3); 31.67 (s, p-(CH3)3C); 33.76,
33.99, 34.11 (broad s, o-(CH3)3C); 29.89, 35.14 (s,
3
1
3
p-(CH3)3C); 38.56 (d, o-(CH3)3C, J CP ) 4.5 Hz); 121.93,
616 (M, 3); 559 (M - t-Bu, 26); 543 (M - t-Bu - Me -
1, 1); 439 (M - t-Bu - Mes - 1, 15); 327 (Mes2GeMe,
16); 276 (ArP, 15); 275 (ArP - 1, 69); 207 (MesGeMe -
1, 20); 193 (MesGe, 23); 57 (t-Bu, 100). Anal. Calcd for
C38H55GeP: C, 74.16; H, 9.01. Found: C, 74.06; H, 9.01.
Syn th esis of Dim er s 14a a n d 13a . A solution of
1.6 M n-BuLi in hexane (2.2 mL, 3.5 mmol) was slowly
added to a solution of 7 (2.42 g, 3.5 mmol) in Et2O (20
mL) cooled at -80 °C; the reaction mixture turned
orange yellow and was stirred for 15 min. During the
warming to room temperature, the mixture gradually
turned red and then dark red. 13a , almost insoluble
in Et2O, could be isolated by filtration and was recrys-
tallized from CHCl3. Et2O was eliminated from the
solution containing 14a . A 50 mL portion of pentane
was added, and LiF was filtered off. 31P NMR spectrum
of the solution showed the formation of 14a . 14a , with
a reactive GedC double bond, could not be obtained in
122.49 (m-C Ar) 128.37, 128.80, 128.92, 128.99, 129.30
(m-C Mes); 136.45, 136.88, 137.06, 137.22 (p-C Mes);
142.16, 142.45, 142.86, 142.91 (o-C Mes); 149.52, 150.06
(p-C Ar); 153.83, 154.32 (o-C Ar). MS EI (m/z): 1042
(M - 3t-Bu - 1, 1); 1025 (M - C6H2t-Bu2 - 1, 2); 983
[M - Ar′ + 1 (Ar′ ) Ar - Me), 3]; 953 (M - Ar - Me -
H, 1); 888 (M - Mes2GeMe + 1, 1); 851 (M - Mes - Ar
+ 1, 1); 600 (Mes2GedCdPAr, 3); 430 (Mes2GedCdPAr
- 3t-Bu + 1, 3); 327 (Mes2GeMe, 15); 57 (t-Bu, 100).
Anal. Calcd for C75H106Ge2P2: C, 74.15; H, 8.80.
Found: C, 73.88; H, 8.51.
Isola tion of 13a ,b. After some days at room tem-
perature, a solution of 13a in Et2O or CHCl3 gave a
mixture of 13a ,b.
13a is very slightly soluble in pentane whereas 13b
is fairly soluble. Thus, addition of pentane to a mixture
of 13a /13b solubilizes 13b: filtration affords solid 13a ,
whereas 13b is obtained after removal of solvent from
the filtrate.
13b: 1H NMR δ 1.05 (s, 18H, o-t-Bu); 1.26 (s, 9H, p-t-
Bu); 1.55 (s, 6H, o-Me cis to Ar rings); 2.10 (s, 3H, p-Me
cis to Ar rings); 2.24 (s, 3H, p-Me cis to lone pairs); 2.51
(s, 6H, o-Me cis to lone pairs); 6.35 (s, 2H, H aromatic
Mes cis to Ar rings); 6.75 (s, 2H, H aromatic Mes cis to
lone pairs); 7.02 (s, 2H, H aromatic Ar).
pure form.
2
14a : 31P NMR (C6D6) AX system, δA 269.5 (d, J PP
)
2
225.4 Hz, PdC), δX 61.3 (d, J PP ) 225.4 Hz, P-C).
13a : 0.20 g, Rdt ) 10%, mp 290 °C, dec. 1H NMR: δ
1.04 (s, 18H, o-t-Bu), 1.30 (s, 9H, p-t-Bu), 2.08 (s, 12H,
o-Me), 2.15 (s, 6H, p-Me), 6.51(s, 4H, H aromatic Mes),
7.04 (broad signal, 2H, H aromatic Ar). 31P NMR
(C6D6): δ 381.0. 13C NMR: δ 20.85 (s, p-Me), 25.36 (s,
o-Me), 31.47 (s, p-(CH3)3C), 33.85 (s, o-(CH3)3C), 34.74
(s, p-C(CH3)3), 38.42 (s, o-C(CH3)3), 122.08 (s, m-C Mes),
128.34 (s, m-C Ar), 137.17 (s, p-C Mes), 142.34 (s, o-C
Mes), 148.51 (s, p-C Ar), 152.89 (s, o-C Ar). MS CI (CH4)
(m/z): 1199 (M + 1); 1183 (M - Me, 15); 1080 (M -
Mes + 1, 43); 1023 (M - Mes - t-Bu + 1, 22); 953 (M -
Ar, 100). Anal. Calcd for C74H102Ge2P2: C, 74.14; H,
8.58. Found: C, 74.01; H, 8.38.
13b: 31P NMR δ 374.7 ppm.
Ack n ow led gm en t. The authors thank G. Trinquier
(Laboratoire de Physique Quantique, IRSAMC-CNRS,
Toulouse, France) and S. Iwata (Institute for Molecular
Science, Okazaki, J apan) for helpful discussions. The
Institute for Molecular Science is also acknowledged for
providing computing facilities.
Syn th esis of 15. To a dark red solution of 14a (2.03
mmol) prepared as previously described was added an
OM9600248
+
+