Preparation, structural characterization, and reactivities of (digermanyl)lithium. Its application to the synthesis of bis(1,1-dipheny 1-2,2,2-trimethyldigermanyl)platinum(II)

Article abstract of DOI:10.1246/cl.2007.414

(Pentamethyldigermanyl)lithium (Me3GeGeMe2Li, 1a) and (1,1-diphenyl-2,2,2- trimethyldigermanyl)lithium (MeaGeGe-Ph₂Li, 1b) were prepared and characterized by spectroscopic methods. The structure of (digermanyl)lithium 1b was established by X-ray diffraction. The reaction of 1b with cis-PtCl ₂-(PMe₂Ph)₂ gave the expected substitution product, transPt(Me₃GePh₂Ge)₂(PMe ₂Ph)₂. Copyright

Full text of DOI:10.1246/cl.2007.414

414
Chemistry Letters Vol.36, No.3 (2007)
Preparation, Structural Characterization, and Reactivities of (Digermanyl)lithium.
Its Application to the Synthesis of Bis(1,1-diphenyl-2,2,2-trimethyldigermanyl)platinum(II)
Kunio Mochida,ꢀ Satoshi Ogawa, Noriaki Naito, Abd El-Al Gaber,# Yoko Usui, and Masato Nanjo
Department of Chemistry, Faculty of Science, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo 171-8588
(Received December 18, 2006; CL-061481; E-mail: kunio.mochida@gakushuin.ac.jp)
(Pentamethyldigermanyl)lithium (Me3GeGeMe2Li, 1a) and
(1,1-diphenyl-2,2,2-trimethyldigermanyl)lithium (Me3GeGe-
Ph2Li, 1b) were prepared and characterized by spectroscopic
methods. The structure of (digermanyl)lithium 1b was establish-
ed by X-ray diffraction. The reaction of 1b with cis-PtCl2-
(PMe2Ph)2 gave the expected substitution product, trans-
Pt(Me3GePh2Ge)2(PMe2Ph)2.
Group 14 element-centered alkali metals show a number of
interesting and useful reactions not only in group 14 element
chemistry but also in organic synthesis.1,2 Their nucleophilicity
makes them valuable reagents for introducing group 14 element
groups into molecules. Group 14 element-centered anions also
play important roles as one electron-transfer and reducing
reagents. Kraus and Foster pioneered the preparation of
triphenylgermyl alkali metal in liquid ammonia solvents,3
and later trialkylgermyl alkali metals in hexamethylphosphoric
triamide (HMPA)2e were introduced. Despite the large number
of these reports on monogermyl alkali metals,2 digermanyl alkali
metals had never been isolated and characterized. The cleavage
of germanium–germanium bonds is readily effected by alkali
metals. We report herein the first preparation of (pentamethyldi-
germanyl)lithium, Me3GeGeMe2Li (1a) and (1,1-diphenyl-
2,2,2-trimethyldigermanyl)lithium, Me3GeGe-Ph2Li (1b), and
structural characterization of 1b by X-ray diffraction analysis.
We also describe the preparation of bis(1,1-diphenyl-2,2,2-tri-
methyldigermanyl)platinum(II) by the treatment of 1b with
cis-dichloroplatinum(II).
Figure 1. Molecular structure of 1b.
one trimethylgermyl (Me3Ge) group and two phenyl groups are
arranged so as to give the eclipsed conformation relative to the
three THF molecules in 1b. The bond angles around the anionic
germanium atom are contracted (the sum of the angles is 315ꢂ).
The NMR spectrum shows that 1b has three THF molecules
7
coordinated to the lithium atom. The Li NMR chemical shift
observed at ꢀ 0.36 is reasonable for the completely THF solvated
monomer 1b.
Hydrolysis of 1 with D2O gave the corresponding deuterio-
digermanes quantitatively. On reaction of 1 with trimethyl-
chlorosilane (Me3SiCl), substitution reactions occurred to give
the corresponding Me3Si-substituted digermanes (1a 59%, 1b
83%). The reaction of 1b with alkyl, phenyl, and benzyl halides
gave the corresponding substitution products. These results are
summarized in Table 1.
As shown in Table 1, (digermanyl)lithium 1b is a useful
nucleophilic reagent for formation of the Ge–Ge–C bond under
mild conditions.
The treatment of pentamethyldigermane (Me3GeGeMe2H)
and 1,1-diphenyl-2,2,2-trimethyldigermane (Me3GeGePh2H)
in THF with one molar amount of tert-butyllithium in hexane
at low temperature produced Me3GeGeMe2Li (1a) and
Me3GeGePh2Li (1b), respectively, in quantitative yields (eq 1).
(Digermanyl)lithium, 1a and 1b, were characterized by NMR
analysis4 and chemical trapping experiments.
Continuously, we have undertaken hitherto unknown Ge–
Ge–Pt bond formation by the treatment of Pt–Cl bond with 1b.
Complex cis-PtCl2(PMe2Ph)2 reacted with two molar amounts
t-BuLi/THF
Me3GeGeR2H
Me3GeGeR2Li
(1)
Table 1. Reactions of Me3GeGePh2Li (1b) with electrophilesa
R = Me (1a), −40 °C, 10 min; R = Ph (1b), −10 °C, 1 h
The (digermanyl)lithium 1b could be recrystallized from
pentane at ꢁ15 ꢂC as air-sensitive colorless needles. Like other
organolithium compounds, 1b was highly inflammable in the
air. The (digermanyl)lithium 1a was very unstable and its isola-
tion failed. The molecular structure of 1b was unequivocally
confirmed by X-ray diffraction.5 The lithium atom is coordinated
Reagent
Product
Yield/%b
D2O
Me3GeGePh2D
Me3GeGePh2SiMe3
(Me3Ge)2GePh2
Me3GeGePh2Me
Me3GeGePh2Et
Me3GeGePh2CH2Ph
Me3GeGePh3
100
83
63
100
100
100
19
Me3SiCl
Me3GeCl
MeI
EtBr
PhCH2Cl
PhBr
˚
by three THF molecules and Ge–Li distance of 2.683(8) A. The
Ge–Li distance of 1b is somewhat longer than that of monoger-
myllithium, R3GeLi (2.57–2.67 A).6–9 The Ge–Ge bond distance
˚
of 2.4601(6) A is longer than those of (Me2Ge)6 (2.375 A)10 and
aReactions were carried out at r.t. for 30 min in hexane. bGC
yields.
˚
˚
is the same as those of (Ph2Ge)6 (2.46 A).11 As shown in Figure 1,
˚
Copyright Ó 2007 The Chemical Society of Japan

Chemistry Letters Vol.36, No.3 (2007)
415
Wilkinson, F. G. A. Stone, E. W. Abel, Pergamon Press,
1982, Vol. 2, Chap. 9, pp. 99–104. d) D. A. Armitage, in Com-
prehensive Organometallic Chemistry, ed. by G. Wilkinson,
F. G. A. Stone, E. W. Abel, Pergamon Press, 1995, Vol. 2,
Chap. 1, p. 22. e) T. B. Lambert, W. J. Schulz, Jr., in The Chem-
istry of Organic Silicon Compounds, ed. by S. Patai, Z. Rapport,
Wily, Chichester, U.K., 1989, pp. 1007–1010. f) M. Fujita, T.
Hiyama, J. Synth. Org. Chem. Jpn. 1984, 30, 67.
2
a) M. Lesbre, P. Mazerolles, J. Satge, in The Organic Com-
pounds of Germanium, Interscience Publishers, New York,
1971, pp. 646–688. b) P. Riviere, M. R.-Baudet, J. Satge, Com-
prehensive Organometallic Chemistry, ed. by G. Wilikinson,
F. G. A. Stone, E. W. Abel, Pergamon Press, 1982, Vol. 2,
Chap. 10, pp. 468–473. c) P. Riviere, M. R.-Baudet, J.
Satge, Comprehensive Organometallic Chemistry, ed. by G.
Wilikinson, F. G. A. Stone, E. W. Abel, Pergamon Press,
1995, Vol. 2, Chap. 5, pp. 174–176. d) N. S. Vyazankin,
G. A. Razuvaev, E. N. GladyshEv, S. P. Korneva, J. Organo-
met. Chem. 1967, 7, 353. e) E. J. Bulten, J. G. Noltes, Tetra-
hedron Lett. 1966, 4389; J. Organomet. Chem. 1971, 29, 397.
f) K. Mochida, J. Synth. Org. Chem. Jpn. 1991, 49, 288.
C. A. Kraus, L. S. Foster, J. Am. Chem. Soc. 1927, 49, 457.
1aꢃ3thf: 1H NMR (ꢀ, C6D6) 0.54 (s, 9H), 0.68 (s, 6H), 1.23 (m,
12H), 3.39 (m, 12H); 7Li NMR (ꢀ, C6D6) 0.54. 1bꢃ3thf:
1H NMR (ꢀ, C6D6) 0.58 (s, 9H), 1.25 (m, 12H), 3.38 (m,
12H), 7.12–8.00 (m, 10H); 13C NMR (ꢀ, C6D6) 1.1, 25.4
(THF), 68.4 (THF), 124.4, 127.2, 137.0, 137.6; 7Li NMR (ꢀ,
C6D6) 0.36.
Figure 2. Molecular structure of 2.
of 1b in benzene at room temperature for 1 h to give trans-
Pt(GePh2GeMe3)2(PMe2Ph)2 (2) as pale yellow crystals.
3
4
r.t., 1 h
benzene
cis-PtCl2(PMe2Ph)2 + 2Me3GeGePh2Li
1b
trans-Pt(Me3GeGePh2)2(PMe2Ph)2 (2)
2
Complex 2 in C6D6 was stable and did not isomerize to the
cis isomer at room temperature for a few days. The structure
of 2 was established by spectroscopic methods12 coupled with
X-ray analysis.13
Complex 2 has distorted square-planar trans geometry with
the dihedral angles between the planes composed of P(1)–Pt(1)–
Ge(1) and P(2)–Pt(1)–Ge(3) being 29.4ꢂ. The deformation from
planarity is considered to be caused by a steric repulsion between
the bulky ligands. The sum of four angles about platinum was
367ꢂ (Figure 2).
.
5
Crystallographic data for 1b 3thf: C27H43O3Ge2Li, Mr ¼
567:73, monoclinic, P21=n, a ¼ 10:7550ð6Þ, b ¼ 15:0150ð18Þ,
ꢂ
3
˚
˚
c ¼ 17:7410ð17Þ A, ꢁ ¼ 95:931ð6Þ , V ¼ 2849:6ð5Þ A , Z ¼
4, Dcalcd ¼ 1:323 g cmꢁ3, Fð000Þ ¼ 1184, ꢂ ¼ 2:133 mmꢁ1
,
R ¼ 0:0612 (I > 2ꢃðIÞ), wR2 ¼ 0:1576 (all data), GOF =
1.277.
S. Freitag, R. H. Irmer, L. L.ameyer, D. Stalke, Organo-
metallics 1996, 15, 2839.
6
7
8
9
J. H. Hong, Y. Pan, P. Boudjouk, Angew. Chem., Int. Ed. 1996,
35, 186.
A. Kawachi, Y. Tanaka, K. Tamao, Eur. J. Inorg. Chem. 1999,
461.
M. Nanjo, M. Maehara, Y. Ushida, Y. Awamura, K. Mochida,
Tetrahedron Lett. 2005, 46, 8945.
˚
The Pt–Ge distances of 2 (2.4882(8) and 2.5269(8) A) are
14
˚
similar to those of Pt(R3Ge)2(tert-phosphine)2 (2.44–2.52 A).
˚
The Ge–Ge distances of 2 (2.4698(11) and 2.4748(13) A) are
11
˚
somewhat longer than those of (Ph2Ge)6 (2.46 A).
The 1H NMR of complex trans-2 displayed two methyl
signals of the platinum-bound GePh2GeMe3 at 0.31 (s) ppm
and PMe2Ph ligands at 1.38 ppm (virtual triplet). The 31P NMR
10 W. Jensen, R. Jacobson, J. Benson, Cryst. Struct. Commun.
1975, 4, 299.
11 Von M. Drager, L. Ross, D. Simon, Z. Anorg. Allg. Chem. 1980,
¨
466, 145.
showed a singlet with satellites at ꢁ11:4 ppm (1JPt{P
¼
12 2: 1H NMR (ꢀ, C6D6) 0.31 (s, 9H), 1.38 (vt with two satellites,
JPt{P ¼ 32:8 Hz, JP{H ¼ 3:1 Hz, 10H), 7.26–7.62 (m, 20H);
13C NMR (ꢀ, C6D6) 1.8, 18.8, 125.7, 126.7, 127.7, 129.4,
131.0, 135.8, 137.5, 149.5; 31P NMR (ꢀ, C6D6) ꢁ11:4 (s, with
two satellites, JPt{P ¼ 2788 Hz).
2788 Hz).
Further applications of the (digermanyl)lithium species in
organogermanium synthesis will be reported soon.
This work was supported by Grant-in-Aid for Scientific
Research on Priority Areas (No. 16033256, Reaction Control
of Dynamic Complexes) from Ministry of Education, Culture,
Sports, Science and Technology, Japan.
13 Crystallographic data for 2: C46H60Ge4P2Pt, Mr ¼ 1160:33,
ꢀ
P1,
23:617ð6Þ A,
triclinic,
a ¼ 10:411ð3Þ,
b ¼ 10:7140ð14Þ,
ꢁ ¼ 96:092ð11Þ,
c ¼
˚
ꢄ ¼ 94:738ð13Þ,
ꢅ ¼
115:097ð13Þꢂ, V ¼ 2348:2ð9Þ A , Z ¼ 2, Dcalcd ¼ 1:641
3
˚
g cmꢁ3
,
Fð000Þ ¼ 1144, ꢂ ¼ 5:596 mmꢁ1
,
R ¼ 0:0768
References and Notes
#
(I > 2ꢃðIÞ), wR2 ¼ 0:2170 (all data), GOF = 1.345.
14 a) K. Mochida, T. Wada, K. Suzuki, W. Hatanaka, Y.
Nishiyama, M. Nanjo, A. Sekine, Y. Ohashi, M. Sakamoto,
A. Yamamoto, Bull. Chem. Soc. Jpn. 2001, 74, 123. b) K.
Mochida, T. Wada, W. Hatanaka, Y. Nishiyama, M. Suzuki,
M. Nanjo, Main Group Metal Chem. 2001, 24, 647. c) Y. Usui,
T. Fukushima, M. Nanjo, K. Mochida, K. Akasaka, T. Kudo,
S. Komiya, Chem. Lett. 2006, 35, 810.
Gakushuin invited researcher (1999) from Assiut University,
Egypt.
1
a) D. D. Davis, C. E. Gray, Organomet. Chem. Rev., Sect. A
1970, 6, 283. b) I. Fleming, in Comprehensive Organic
Chemistry, ed. by D. Barton, W. D. Ollis, Pergamon Press,
Oxford, U.K., 1979, Vol. 3, pp. 664–669. c) D. A. Armitage,
in Comprehensive Organometallic Chemistry, ed. by G.
Published on the web (Advance View) February 10, 2007; doi:10.1246/cl.2007.414