Formation and ring expansion of germaplatinacycles via dehydrogenative Ge-Ge and Ge-Pt bond-forming reactions

Article abstract of DOI:10.1021/om900505k

The bis(germyl)platinum complex [Pt(GeHPh₂)₂(dmpe)] (1) (dmpe= l,2-bis(dimethylphosphino)ethane) reacts with a small excess Of H₂GePh₂ at 90 °C to produce four-membered germaplatinacycle [Pt(GePh₂GePh₂GePh₂)(dmpe)] (2). Further reaction of 2 with excess H₂GePh₂ at 90 °C forms tetragermaplatinacyclopentane [Pt(GePh₂GePh ₂GePh₂GePh₂)(dmpe)] (3), while 3 is obtained also by the direct reaction of excess H₂GePh₂ with 1 for a prolonged period. Complexes 1-3 were characterized by X-ray crystallography and NMR spectroscopy. Germaplatinacycles 2 and 3 react with H₃GePh to cause cleavage of the Pt-Ge bonds and formation of the oligogermanes H(GePh ₂)₃H and H(GePh2)₄H respectively.

Full text of DOI:10.1021/om900505k

6014 Organometallics 2009, 28, 6014–6019
DOI: 10.1021/om900505k
Formation and Ring Expansion of Germaplatinacycles via
Dehydrogenative Ge-Ge and Ge-Pt Bond-Forming Reactions
Makoto Tanabe, Masaya Hanzawa, Naoko Ishikawa, and Kohtaro Osakada*
Chemical Resources Laboratory, Tokyo Institute of Technology, 4259-R1-3 Nagatsuta, Midori-ku,
Yokohama 226-8503, Japan
Received June 15, 2009
The bis(germyl)platinum complex [Pt(GeHPh2)2(dmpe)] (1) (dmpe=1,2-bis(dimethylphosphino)-
ethane) reacts with a small excess of H2GePh2 at 90 °C to produce four-membered germaplatinacycle
[Pt(GePh2GePh2GePh2)(dmpe)] (2). Further reaction of 2 with excess H2GePh2 at 90 °C forms
tetragermaplatinacyclopentane [Pt(GePh2GePh2GePh2GePh2)(dmpe)] (3), while 3 is obtained also by
the direct reaction of excess H2GePh2 with 1 for a prolonged period. Complexes 1-3 were characterized
by X-ray crystallography and NMR spectroscopy. Germaplatinacycles 2 and 3 react with H3GePh to
cause cleavage of the Pt-Ge bonds and formation of the oligogermanes H(GePh2)3H and H(GePh2)4H,
respectively.
Introduction
Cp2MCl2 (Chart 1A).6 A similar tetragermacyclopentane invol-
ving ytterbium center, [Yb(GePh2GePh2GePh2GePh2)-
a
Metallacycles composed of metal-containing four-, five-,
and six-membered rings are classified as important organo-
metallic compounds because of their roles as key inter-
mediates in the metal-catalyzed metathesis1 and oligomer-
izations2 of alkenes. The metallacycloalkanes containing
group 10 transition metals have long been investigated for
their preparation and chemical properties since the 1970s.3-5
In spite of abundant metallacycloalkanes of the late transi-
tion metals, there has been a limited number of reports of
Si- and Ge-containing metallacycles. Marschner et al.
synthesized zirconocena- and hafnocenacyclopentasilanes
(THF)4], was prepared as one of the products from the reaction
of metallic Yb with Ph2GeCl2.7 Mochida and co-workers
synthesized four- and five-membered silagermaplatina-
cycles [Pt(GePh2(SiMe2)nGePh2)(PPh3)2] (n = 1, 2) via the
cyclization of the hydrido(germyl)platinum complex
[PtH(GePh2(SiMe2)nGeHPh2)(PPh3)2].8 Recently, Braddock-
Wilking reported that the thermal reactions of [PtMe2(dppe)]
(dppe = 1,2-bis(diphenylphosphino)ethane) with sila- and
germafluorene H2ER2 (ER2 = SiC12H8 or GeC12H8) in
1:4 ratio afforded the two five-membered platinacycles
[M(Si(SiMe3)2SiMe2SiMe2Si(SiMe3)2)(C5H5)2] (M=Zr, Hf)
from the metathesis reaction of an oligosilyl dianion with
[Pt(ER2ER2ER2ER2)(dppe)] (Chart 1B). They proposed
PtdER2 intermediates formed via 1,2-H migration of silyl
or germyl (Pt-ER2H) platinum complexes to account
for smooth formation of the metallacycles.9 We reported
*To whom correspondence should be addressed. E-mail: kosakada@
res.titech.ac.jp.
(1) (a) Chappell, S, D.; Cole-Hamilton, D. J. Polyhedron 1982, 1, 739–
777. (b) Jennings, P. W.; Johnson, L. L. Chem. Rev. 1994, 94, 2241–2290. (c)
Eisch, J. J.; Aradi, A. A.; Lucarelli, M. A.; Qian, Y. Tetrahedron 1998, 54,
preparation of
a five-membered tetragermapalladacycle
ꢀ
1169–1184. (d) Campora, J.; Palma, P.; Carmona, E. Coord. Chem. Rev.
[Pd(GePh2GePh2GePh2GePh2)(dmpe)] (dmpe=1,2-bis(dime-
thylphosphino)ethane) (Chart 1C), from the thermal reaction
of [Pd(GeHPh2)2(dmpe)] in the presence of excess H2GePh2.10
The reaction involves several Ge-Ge bond-forming reactions,
but 1H and 31P{1H} NMR measurements of the reaction
mixture did not provide information of the reaction mecha-
nism and their intermediates. In this paper, we present the
1999, 193-195, 207–281. (e) Blom, B.; Clayton, H.; Kilkenny, M.; Moss,
J. R. Adv. Organomet. Chem. 2006, 54, 149–205.
(2) (a) Dixon, J. T.; Green, M. J.; Hess, F. M.; Morgan, D. H.
J. Organomet. Chem. 2004, 689, 3641–3668. (b) Wass, D. F. Dalton Trans.
2007, 816–819.
(3) (a) Grubbs, R. H.; Miyashita, A.; Liu, M.-I. M.; Burk, P. L. J. Am.
Chem. Soc. 1977, 99, 3863–3864. (b) Grubbs, R. H.; Miyashita, A. J. Am.
Chem. Soc. 1978, 100, 1300–1302. (c) Grubbs, R. H.; Miyashita, A.; Liu, M.;
Burk, P. J. Am. Chem. Soc. 1978, 100, 2418–2425.
(4) (a) Diversi, P.; Ingrosso, G.; Lucherini, A. J. Chem. Soc., Chem.
Commun. 1978, 735–736. (b) Diversi, P.; Ingrosso, G.; Lucherini, A.;
Murtas, S. J. Chem. Soc., Dalton Trans. 1980, 1633–1637. (c) Ozawa, F.;
Yamamoto, A.; Ikariya, T.; Grubbs, R. H. Organometallics 1982, 1, 1481–
1485.
(5) (a) McDermott, J. X.; White, J. F.; Whitesides, G. M. J. Am.
Chem. Soc. 1973, 95, 4451–4452. (b) McDermott, J. X.; White, J. F.;
Whitesides, G. M. J. Am. Chem. Soc. 1976, 98, 6521–6528. (c) Casey,
C. P.; Scheck, D. M.; Shusterman, A. J. J. Am. Chem. Soc. 1979, 101, 4233–
4236. (d) Miyashita, A.; Takahashi, M.; Takaya, H. J. Am. Chem. Soc. 1981,
103, 6257–6259.
(6) Kayser, C.; Kickelbick, G.; Marschner, C. Angew. Chem., Int. Ed.
2002, 41, 989–992.
(7) Bochkarev, L. N.; Makarov, V. M.; Zakharov, L. N.; Fukin, G. K.;
Yanovsky, A. I.; Struchkov, Y. T. J. Organomet. Chem. 1995, 490, C29–C31.
(8) Usui, Y.; Hosotani, S.; Ogawa, A.; Nanjo, M.; Mochida, K.
Organometallics 2005, 24, 4337–4339.
(9) Braddock-Wilking, J.; Bandrowsky, T.; Praingam, N.; Rath,
N. P. Organometallics 2009, 28, 4098–4105.
(10) Tanabe, M.; Ishikawa, N.; Hanzawa, M.; Osakada, K. Organo-
metallics 2008, 27, 5152–5158.
r
pubs.acs.org/Organometallics
Published on Web 09/25/2009
2009 American Chemical Society

Article
Organometallics, Vol. 28, No. 20, 2009 6015
Chart 1
Scheme 1
preparation, structures, and chemical reactions of the four- and
five-membered germaplatinacycles.
Results and Discussion
A bis(germyl)platinum complex with diphenylgermyl
groups, [Pt(GeHPh2)2(dmpe)] (1), was obtained in 86% yield
from the reaction of [PtMe2(dmpe)] with H2GePh2 at 60 °C in
tetragon of 2 is equal to 359.49(4)°, indicating high planarity of
the four-membered ring. This contrasts with most metallacy-
clobutanes, which contain a puckered four-membered ring.
Molecule 3 contains a five-membered PtGe4 ring with an
envelope conformation. Chart 2 summarizes bond parameters
toluene. Similar reaction of H2SiPh2, giving
a bis-
(silyl)platinum complex [Pt(SiHPh2)2(dmpe)], was reported
to proceed at higher reaction temperature (90 °C).11 Treatment
of 1 with H2GePh2 in 1:1.2 molar ratio at 90 °C produced
trigermaplatinacyclobutane [Pt(GePh2GePh2GePh2)(dmpe)]
(2) in 87% yield (Scheme 1). Complexes with monodentate
phosphine and triorganogermyl ligands, cis-[Pt(GePh2R)2-
(PMe2Ph)2] (R = Ph, Me), undergo thermal isomerization
to give an equilibrium mixture of the cis and trans complexes
and do not cause any Ge-Ge bond-forming reactions.12
Further reaction of excess H2GePh2 with the isolated complex
2 at 90 °C for 48 h afforded the five-membered tetragerma-
of complexes 1-3, [Pt(GeR2GeR2GeR2GeR2)(dppe)] (GeR2=
GeC12H8),9 and [Pd(GePh2GePh2GePh2GePh2)(dmpe)].10
˚
The two Pt-Ge bonds of 3 (2.4643(4), 2.4769(4) A) are
slightly longer than those of bis(germyl)platinum complex 1
˚
(2.4411(6), 2.4527(4) A), trigermaplatinacycle 2 (2.451(1),
˚
2.4542(9) A), and[Pt(GeR2GeR2GeR2GeR2)(dppe)] (GeR2 =
9
˚
GeC12H8) (2.4426(7), 2.4384(7) A). The Ge-Ge distances of 2
platinacycle [Pt(GePh2GePh2GePh2GePh2)(dmpe)] (3) in
29% yield (Scheme 1). The 1H NMR spectrum of the reaction
mixture in C6D6 shows two Ge-H hydrogen signals at
δ 5.57 and 5.68, which are assigned to H(GePh2)2H13 and
H(GePh2)3H14 formed by the reactions. Heating of 1 in the
presence of excess H2GePh2 at the same temperature produces
3 directly in 61% yield.
˚
˚
(2.456(1), 2.578(1) A) and 3 (2.4174(5)-2.4646(5) A) are
similar to cyclic Ge compounds such as cyclopentagermane
16
˚
(2.438(3)-2.473(2) A) and cyclohexagermane (2.456(2)-
2.466(2) A). Although the Ge-Pt-Ge and Ge-Ge-Ge
17
˚
bond angles of 2 (83.14(3)°, 80.53(3)°) are significantly smaller
than the two Pt-Ge-Ge bond angles (96.32(3)°, 99.50(3)°),
two coordinating Ge atoms are at too remote positions to have
Figure 1 shows the molecular structure of 1 determined by
X-ray crystallography. The Pt-Ge bonds of 1 (2.4527(4),
˚
a Ge Ge interaction (3.255(1) A). The four-membered Pt
3 3 3
complex with a disiloxy ligand, [Pt(SiMe2-O-SiMe2)(dppe)],18
wasreportedtoexhibitaSi Si contact with a shorter distance
˚
2.4411(6) A) are within the range of the Pt-Ge bonds of cis-
bis(germyl)platinum complexes with phosphine ligands
3 3 3
(2.4271(15)-2.4985(13) A)12,15 and are longer than the Pd-Ge
t
t
19
˚
˚
˚
(2.549(2) A) than the Si-Si bond of Bu 3Si-SiBu 3 (2.697 A).
1
bonds of the Pd analogue [Pd(GeHPh2)2(dmpe)] (2.4259(2),
10
The H NMR spectrum of 1 shows a Ge-H hydrogen
signal at δ 5.82 with reasonable coupling constants (3JP-H
=
˚
˚
2.4266(3) A). The Pt-P bonds of 1 (2.293(1), 2.295(2) A) are
slightly shorter than the Pd-P bonds of the analogous Pd
complex (2.3066(6), 2.3147(7) A). Figure 2 shows crystallo-
2
14.4 Hz, JPt-H = 101 Hz). The 31P{1H} NMR spectra of
1-3 contain a single signal flanked with 195Pt satellites (1:
JPt-P = 1895 Hz, 2: JPt-P = 1819 Hz, 3: JPt-P = 1851 Hz).
[Pt(SiHPh2)2(dmpe)] exhibits a small coupling constant (δ
37.0, JPt-P = 1456 Hz)11 due to the larger trans influence of
the Si than the Ge ligands. Integration of the 1H NMR peaks
gives a ratio of the ortho hydrogens of the μ-GePh2 ligands of
2 and 3 that is consistent with the respective four- and five-
membered metallacyclic structures. The 13C{1H} NMR
spectrum of 2 exhibits two signals assigned to the ipso carbon
of the GePh2 groups. The signal at δ 147.2 with a large
coupling constant (63 Hz) is attributed to the GePh2 groups
˚
graphic results of square-planar complexes 2 and 3 with four-
and five-membered rings composed of Ge and Pt atoms,
respectively. The sum of the four bond angles within the PtGe3
(11) (a) Tanabe, M.; Osakada, K. J. Am. Chem. Soc. 2002, 124, 4550–
4551. (b) Tanabe, M.; Osakada, K. Chem.;Eur. J. 2004, 10, 416–424.
(12) (a) Mochida, K.; Wada, T.; Suzuki, K.; Hatanaka, W.; Nishiyama,
Y.; Nanjo, M.; Sekine, A.; Ohashi, Y.; Sakamoto, M.; Yamamoto, A. Bull.
Chem. Soc. Jpn. 2001, 74, 123–137. (b) Mochida, K.; Fukushima, T.; Suzuki,
M.; Hatanaka, W.; Takayama, M.; Usui, Y.; Nanjo, M.; Akasaka, K.; Kudo, T.;
Komiya, S. J. Organomet. Chem. 2007, 692, 395–401.
ꢀ
(13) Feher, F.; Plichta, P. Inorg. Chem. 1971, 10, 609–610.
ꢀ
ꢀ
€
(16) (a) Ross, L.; Drager, M. Z. Naturforsch. 1983, 38b, 665–673. (b)
(14) (a) Castel, A.; Riviere, P.; Satge, J.; Ko, Y. H. J. Organomet.
ꢀ
ꢀ
€
Ross, L.; Drager, M. Z. Anorg. Allg. Chem. 1984, 519, 225–232.
Chem. 1988, 342, C1–C4. (b) Castel, A.; Riviere, P.; Satge, J.; Ko, H. Y.
Organometallics 1990, 9, 205–210.
€
(17) (a) Drager, M.; Ross, L.; Simon, D. Z. Anorg. Allg. Chem. 1980,
€
(15) (a) Yamashita, H.; Kobayashi, T.; Tanaka, M.; Samuels, J. A.;
Streib, W. E. Organometallics 1992, 11, 2330–2333. (b) Mochida, K.;
Karube, H.; Nanjo, M.; Nakadaira, Y. Organometallics 2005, 24, 4734–
4741. (c) Usui, Y.; Hosotani, S.; Ogawa, A.; Nanjo, M.; Mochida, K.
Organometallics 2005, 24, 4337–4339.
466, 145–156. (b) Drager, M.; Ross, L. Z. Anorg. Allg. Chem. 1981, 476,
95–104.
(18) Pham, E. K.; West, R. Organometallics 1990, 9, 1517–1523.
(19) Wiberg, N.; Schuster, H.; Simon, A.; Peters, K. Angew. Chem.,
Int. Ed. Engl. 1986, 25, 79–80.

6016 Organometallics, Vol. 28, No. 20, 2009
Tanabe et al.
Chart 2
Figure 1. ORTEP drawing of 1 with thermal ellipsoids shown at
˚
the 50% probability level. Selected bond distances (A) and angles
(deg): Pt-Ge1 2.4527(4), Pt-Ge2 2.4411(6), Pt-P1 2.293(1),
Pt-P2 2.295(2), Ge1-H1 1.57(4), Ge2-H2 1.87(3), Ge1-Pt-
Ge2 90.63(2), Ge1-Pt-P2 93.40(3), Ge2-Pt-P1 90.97(4),
P1-Pt-P2 85.06(4).
Figure 3 shows the 31P{1H} NMR spectrum during the
ring expansion reaction from 2 to 3 in the presence of
H2GePh2 in C6D6 at 100 °C. The signal of 2(δ36.2) is decreased
upon heating the reaction mixture, and a new signal due to
complex 3 is observed at δ 33.6. After 11 days, the signal of 2
becomes negligible, while complex 3 was formed as the major
product of the reaction (Figure 3c). Small signals with an AB
pattern (JP-P=8.9 Hz) at δ 34.5 (JPt-P=1946 Hz) and δ 35.8
(JPt-P=1815 Hz) may be assigned to unsymmetrical Pt inter-
mediates having different Ge ligands, although 1Hand13CNMR
data for the species were not obtained due to small intensity and/
or overlapping of the peaks. We reported the conversion of a
dinuclear Pd complex with bridging germylene and digermene
ligands, [{Pd(dmpe)}2(μ-Ge2Ph4)(μ-GePh2)], into palladager-
macycle [Pd(GePh2GePh2GePh2GePh2)(dmpe)], in which the
31P{1H} NMR spectrum of the mixture shows analogous minor
signals due to an intermediate with two different Ge ligands.10
Scheme 2 shows the plausible pathway for ring expansion
from four- to five-membered germaplatinacycles. Addition
of H2GePh2 to the solution leads to cleavage of a Pt-Ge
bond of 2 to form a trigermyl(germyl)platinum intermediate
A. This intermediate may correspond to the minor 31P NMR
signals at δ 34.5 and 35.8 in Figures 3b and c. R-Hydrogen
migration of GePh2H groups accompanied with partial
dissociation of dmpe ligands forms a platinum-germylene
structure B. Subsequent migration of the trigermyl unit to
the Ge center in the PtdGe bond affords a tetragermyl-
(hydrido)platinum intermediate C. Tetragermaplatinacyclo-
pentane 3 is obtained by the intramolecular cyclization of C,
together with elimination of H2. A similar pathway was
proposed to account for formation of analogous Pt9 and
Pd10 complexes. Braddock-Wilking et al. reported that Pt(0)
complex [Pt(η2-C2H4)(PPh3)2] caused dehydrogenative
Ge-Ge bond formation of H2GeC12H8 to give a diplatinum
complex with bridging digermene ligands, [{PtH(PPh3)2}2-
(μ-GeC12H8GeC12H8)].20 Banaszak Holl,21 Mochida,22 and
Ishii23 reported conversion of the bis(germyl)platinum to
(digermyl)platinum complexes via facile rearrangement of
Figure 2. ORTEP drawings of (a) 2 and (b) 3 with thermal
ellipsoids shown at the 50% probability level. Selected bond
distances (A) and angles (deg) for 2: Pt-Ge1 2.451(1), Pt-Ge3
˚
2.4542(9), Pt-P1 2.282(2), Pt-P2 2.278(3), Ge1-Ge2 2.578(1),
Ge2-Ge3 2.456(1), Ge1-Pt-Ge3 83.14(3), Pt-Ge1-Ge2
96.32(3), Ge1-Ge2-Ge3 80.53(3), Pt-Ge3-Ge2 99.50(4). Se-
˚
lected bond distances (A) and angles (deg) for 3: Pt-Ge1
2.4643(4), Pt-Ge4 2.4769(4), Pt-P1 2.285(1), Pt-P2 2.285(1),
Ge1-Ge2 2.4251(5), Ge2-Ge3 2.4174(5), Ge3-Ge4 2.4646(5),
Ge1-Pt-Ge4 89.76(1), Pt-Ge1-Ge2 108.91(2), Ge1-Ge2-
Ge3 101.25(2), Ge2-Ge3-Ge4 99.79(2), Pt1-Ge4-Ge3
116.34(2).
(20) (a) Braddock-Wilking, J.; Corey, J. Y.; White, C.; Xu, H.; Rath,
N. P. Organometallics 2005, 24, 4113–4115. (b) White, C. P.; Braddock-
Wilking, J.; Corey, J. Y.; Xu, H.; Redekop, E.; Sedinkin, S.; Rath, N. P.
Organometallics 2007, 26, 1996–2004.
bonded with the Pt atom, while the signal at δ 147.5 with a
small 2JPt-C value (40 Hz) is due to the central GePh2 group.
Two ipso carbon signals of 3 at δ 148.4 (2JPt-C = 39 Hz) and
141.9 (2JPt-C = 14 Hz) are assigned on the basis of compar-
ison of the peak positions to those of 2.
(21) Bender, J. E.IV; Litz, K. E.; Giarikos, D.; Wells, N. J.;
Banaszak Holl, M. M.; Kampf, J. W. Chem.;Eur. J. 1997, 3, 1793–1796.
(22) Arii, H.; Nanjo, M.; Mochida, K. Organometallics 2008, 27, 4147–
4151.
(23) Nakata, N.; Fukazawa, S.; Ishii, A. Organometallics 2009, 28,
534–538.

Article
Organometallics, Vol. 28, No. 20, 2009 6017
Figure 3. 31P{1H} NMR spectra during the conversion of 2 into 3 in the presence of H2GePh2 (a) at 0 h, (b) after 4 days at 100 °C, and
(c) after 11 days at 100 °C. The two doublets (δ 34.5 and 35.8) labeled with an asterisk may be assigned as an intermediate complex with
two different Ge ligands.
Scheme 2
Scheme 3
(L = (PPh3)2, PPh2(CH2)2PPh2) was promoted by various
nucleophilic or electrophilic reagents, and the complexes
released organogermyl compounds upon the reactions.24
Addition of excess H3GePh to the solution of 2 or 3 produces
tri- and tetragermanes H(GePh2)3H and H(GePh2)4H in
76% and 66% yields, respectively (eq 1). Elimination of
trigermane from the ring-strained complex 2 easily occurs at
room temperature, while the Pt-Ge bond cleavage of the
five-membered complex 3 requires heating for 36 h at 90 °C and
affords the tetragermane. The isolated oligogermanes were
characterized on the basis of the 1H and 13C{1H} NMR
spectroscopic data and their comparison with authentic data.14
The Pt-containing product was not isolated nor characterized
due to facile conversion into mixtures of the insoluble di- or
multinuclear complexes with bridging Ge ligands.
the primary or secondary germyl ligands, as shown in
Scheme 3. The Ge-Ge bond formation promoted at the Pt
center was considered to proceed through PtdGe intermedi-
ates, which underwent insertion of GeAr2 units into the Pt-Ge
bond, or to undergo reductive elimination of digermane and
subsequent reoxidative addition of the Ge-H bonds.
The Pt-Ge bond cleavage of the four- and five-membered
digermaplatinum complexes [Pt(GeMe2(CH2)2GeMe2)L2]
ꢀ
(24) (a) Barrau, J.; Rima, G.; Cassano, V.; Satge, J. Inorg. Chim. Acta
ꢀ
The above reaction suggests exchange of the chelating Ge
ligands with primary germyl groups derived from PhGeH3.
Scheme 4 shows the plausible pathway for preparation of
1992, 198-200, 461–467. (b) Barrau, J.; Rima, G.; Cassano, V.; Satge, J.
Organometallics 1995, 14, 5700–5703. (c) Barrau, J.; Rima, G.; Cassano, V.
Main Group Met. Chem. 1996, 19, 283–299.

6018 Organometallics, Vol. 28, No. 20, 2009
Table 1. Crystallographic Data and Details of Refinement of 1, 2, and 3
Tanabe et al.
1
2
3
formula
fw
C
846.99
30H38Ge2P2Pt 1/2toluene
3
C42H46Ge3P2Pt
1025.63
0.35 ꢁ 0.36 ꢁ 0.53
monoclinic
yellow
P21/n (No. 14)
17.783(7)
15.928(8)
15.164(5)
102.04(3)
4201(3)
4
1.622
2008
5.344
11 456
9618
0.051
5059
C61H64Ge4P2Pt
1344.57
0.25 ꢁ 0.41 ꢁ 0.52
orthorhombic
colorless
P212121 (No. 19)
11.927(2)
20.208(4)
cryst size/mm
cryst syst
cryst color
space group
0.08 ꢁ 0.15 ꢁ 0.17
monoclinic
colorless
P21/c (No. 14)
17.672(4)
11.870(2)
17.501(3)
118.373(3)
3230(1)
4
1.740
1676
6.2724
22 578
7072
0.032
6404
˚
a/A
˚
b/A
˚
c/A
23.619(4)
β/deg
3
˚
V/A
5693(2)
4
1.569
2664
4.6184
47 180
12 988
0.034
12248
Z
Dcalcd/g cm-3
F(000)
μ/mm-1
no. of reflns measd
no. of unique reflns
Rint
no. of obsd reflns
(I > 2.00σ(I))
no. of variables
R1, Rw (I > 2σ(I))
R1, wR2 (all data)
GOF on F2
361
434
614
0.0351, 0.0938
0.0386, 0.0963
1.044
0.0443, 0.1097
0.1378, 0.1416
1.009
0.0273, 0.0479
0.0293, 0.0487
1.001
Scheme 4
Experimental Section
General Procedures. All manipulations of the complexes
were carried out using standard Schlenk techniques under an
argon or nitrogen atmosphere. Hexane and toluene were
purified by using a solvent purification system (Glass Con-
tour). The 1H, 13C{1H}, and 31P{1H} NMR spectra were
recorded on Varian Mercury 300 and JEOL EX-400 spectro-
meters. Chemical shifts in 1H and 13C{1H} NMR spectra were
referenced to the residual peaks of the solvents used. The peak
positions of the 31P{1H} NMR spectra were referenced to
external 85% H3PO4 (δ 0) in C6D6. IR absorption spectra
were recorded on a Shimadzu FT/IR-8100 spectrometer. Ele-
mental analysis was carried out using a LECO CHNS-932 or
Yanaco MT-5 CHN autorecorder. H2GePh2 was obtained
from reduction of Cl2GePh2 (Sigma-Aldrich) by LiAlH4.
[PtMe2(dmpe)]25 was prepared according to the reported pro-
cedure.
Preparation of [Pt(GeHPh2)2(dmpe)] (1). To a toluene solu-
tion (6 mL) of [PtMe2(dmpe)] (296 mg, 0.79 mmol) was added
excess H2GePh2 (542 mg, 2.37 mmol) in one portion. The
solution was stirred for 6 h at 60 °C. Removal of the solvent
under reduced pressure gave a solid, which was washed three
times with hexane/toluene (3:1) and dried in vacuo to give 1 as a
white solid (545 mg, 86%). Recrystallization of 1 from hexane/
toluene (3:1) at room temperature (rt) gave colorless crystals
suitable for X-ray crystallography. Anal. Calcd for
oligogermanes from germaplatinacycles. Addition of PhGe-
H3 causes metathesis reaction between the Pt-Ge bonds of
the Pt complexes and H-Ge bonds of the additive to form a
trigermyl(germyl)platinum complex (A0), similar to structure
A in Scheme 2. Primary organogermanes show high reactiv-
ity toward exchange reaction of the germyl ligands to release
oligogermanes.
Conclusion
We presented the preparation and structure of four- or
five-membered germaplatinacycles from a bis(germyl)-
platinum complex depending on the amount of added
H2GePh2. Compared to analogous reactions of related Pt9
and Pd10 complexes, the four-membered Pt complex 2 was
newly isolated and formed the five-membered complex 3
upon reaction with H2GePh2. The results established the
route involving ring-expansion of the four-membered
Ge-containing metallacycle to the five-membered one,
although it is not clear whether the reaction route is domi-
nant in the direct reaction of 1 with H2GePh2, yielding 3 or
not. These isolated germacycles also react with excess
PhGeH3 to lead to the Pt-Ge bond cleavage of the cyclic
oligogermyl ligands rather than the rearrangement for
Ge-Ge bond formation. All these results demonstrate a
new route to prepare linear oligogermane dihydrides directly
from diarylgermanes.
C33H45Ge2P2Pt (1/2C6H14): C, 46.96; H, 5.37. Found: C,
3
46.96; H, 4.97. 1H NMR (300 MHz, C6D6, rt): δ 7.82 (dd, 8H,
C6H5 ortho, JH-H=7.5, 1.8 Hz), 7.23-7.16 (m, 12H, C6H5 meta
and para, JH-H=6.9 Hz), 5.82 (m, 2H, GeH, 3JP-H=14.4 Hz,
2JPt-H=101 Hz), 0.85 (d, 12H, PCH3, 2JP-H=9.3 Hz, JPt-H
=
24.6 Hz), 0.63 (m, 4H, CH2, JP-H = 17.1 Hz). 13C{1H} NMR
3
(75 MHz, C6D6, rt): δ 146.6 (t, C6H5 ipso, JP-C = 5.5 Hz,
3
2JPt-C = 44 Hz), 137.0 (t, C6H5 ortho, JPt-C=16 Hz), 127.6
(C6H5 para), 127.0 (C6H5 meta), 29.9 (m, PCH2), 13.0 (m, PCH3,
2JP-C = 29 Hz). 31P{1H} NMR (121 MHz, C6D6, rt): δ 35.6
(JPt-P=1895 Hz). IR (KBr): 1869, 1935 (νGe-H) cm-1
.
Preparation of [Pt(GePh2GePh2GePh2)(dmpe)] (2). To a to-
luene solution (3 mL) of 1 (330 mg, 0.41 mmol) was added
H2GePh2 (113 mg, 0.49 mmol). The reaction mixture was stirred
(25) Smith, D. C. Jr.; Haar, C. M.; Stevens, E. D.; Nolan, S. P.;
Marshall, W. J.; Moloy, K. G. Organometallics 2000, 19, 1427–1433.

Article
Organometallics, Vol. 28, No. 20, 2009 6019
for 1.5 h at 90 °C. Removal of the solvent under reduced
pressure and washing the resulting pale yellow solid with hexane
(3 ꢁ 3 mL) yielded 2 (366 mg, 87%). Recrystallization from
hexane/toluene (3:1) at rt gave yellow crystals of 2 suitable for
X-ray crystallography. Anal. Calcd for C42H46Ge3P2Pt: C, 49.18;
H, 4.52. Found: C, 48.39; H, 4.31. 1H NMR (300 MHz, C6D6,
rt): δ 7.79 (dd, 8H, C6H5 ortho, JH-H=7.4, 1.6 Hz), 7.70 (m, 4H,
C6H5 ortho), 7.13-7.04 (m, 18H, C6H5 meta and para), 0.85 (d,
ortho), 7.44 (m, 8H, C6H5 ortho), 7.03 (m, 18H, C6H5 meta and
para), 5.68 (s, 2H, GeH). 13C{1H} NMR (75 MHz, THF-d8, rt):
δ 137.9 (C6H5 ipso), 136.6 (C6H5 ipso), 136.6 (C6H5 ortho), 136.3
(C6H5 ortho), 129.5 (C6H5 meta or para), 129.4 (C6H5 para),
129.1 (C6H5 meta or para), 129.0 (C6H5 meta). IR (KBr): 2012
(νGe-H) cm-1
.
Reaction of 3 with PhGeH3. To a stirred suspension of
complex 3 (81.4 mg, 0.065 mmol) in 3 mL of toluene was added
a 6-fold amount of PhGeH3 (59.6 mg, 0.39 mmol). The reaction
mixture was allowed to stir for 36 h at 60 °C, then filtered to
remove unreacted compounds and evaporated to give a pale
yellow solid. The resulting material was washed twice with
20 mL of hexane, dissolved in 5 mL of ether, then passed
through a Florisil column. The solvent was removed from the
eluted solutions in vacuo to give the tetragermane H(GePh2)4H14
as a white solid (39 mg, 66%). 1H NMR (300 MHz, C6D6, rt): δ
7.50 (d, 8H, C6H5 ortho, JH-H = 6.3 Hz), 7.38 (d, 8H, C6H5
ortho, JH-H = 6.0 Hz), 6.99 (m, 24H, C6H5 meta and para), 5.62
(s, 2H, GeH). 13C{1H} NMR (75 MHz, THF-d8, rt): δ 138.1
(C6H5 ipso), 137.0 (C6H5 ipso), 136.9 (C6H5 ortho), 136.4 (C6H5
ortho), 129.3 (C6H5 para), 129.2 (C6H5 para), 128.9 (C6H5 meta),
2
12H, PCH3, JP-H = 9.3 Hz, JPt-H = 25.5 Hz), 0.62 (m, 4H,
PCH2, 2JP-H = 16.7 Hz). 13C{1H} NMR (75 MHz, THF-d8, rt):
3
2
δ 147.5 (t, C6H5 ipso, JP-C =5.2 Hz, JPt-C =40 Hz), 147.2
(t, C6H5 ipso, 3JP-C=5 Hz, 2JPt-C=63 Hz), 137.8 (C6H5 ortho,
2JPt-C=18 Hz), 136.5 (C6H5 ortho), 127.9, 127.6, 127.3, 127.1
(C6H5 meta and/or para), 30.6 (m, PCH2), 14.7 (m, PCH3,
2
3JP-C = 28 Hz, JPt-C = 44 Hz). 31P{1H} NMR (121 MHz,
C6D6, rt): δ 36.2 (JPt-P=1819 Hz).
Preparation of [Pt(GePh2GePh2GePh2GePh2)(dmpe)] (3). A
mixture of 2 (101 mg, 0.098 mmol) and excess H2GePh2 (112 mg,
0.49 mmol) in toluene solution (3 mL) was heated for 48 h at
90 °C. The solvent was evaporated to dryness, and the resulting
white solid was recrystallized from toluene/hexane (1:4) to yield
3 as colorless crystals (35 mg, 29%). The 1H NMR spectrum of
the reaction mixture in C6D6 before purification showed two
Ge-H hydrogen signals at δ 5.57 and 5.68, which were assigned
to H(GePh2)2H13 and H(GePh2)3H14 (literature: δ 5.58 and
5.65). Anal. Calcd for C54H56Ge4P2Pt: C, 51.78; H, 4.51. Found:
C, 50.96; H, 4.57. 1H NMR (300 MHz, C6D6, rt): δ 7.72 (dd, 8H,
C6H5 ortho, JH-H = 6.6, 2.7 Hz), 7.50 (dd, 8H, C6H5 ortho,
128.9 (C6H5 meta). IR (KBr): 1998 (νGe-H) cm-1
.
X-ray Crystallography. Crystals of 1, 2, and 3 suitable for
an X-ray diffraction study were mounted on Micro-
Mounts (MiTeGen). The crystallographic data of 1 and 3 were
collected on a Rigaku Saturn CCD area detector equipped with
˚
monochromated Mo KR radiation (λ = 0.71073 A) at 150 K.
The data of 2 were collected on a Rigaku AFC-7R automated
four-cycle diffractometer at rt. Calculations were carried
out using the program package Crystal Structure, version 3.8,
for Windows. The positional and thermal parameters of non-
hydrogen atoms were refined anisotropically on F2 by the full-
matrix least-squares method using SHELXL-97.26 Hydrogen
atoms, except for the GeH hydrogens of 1, were placed at
calculated positions and refined with a riding mode on their
corresponding carbon atoms. Crystallographic data and details
of refinement of 1, 2, and 3 are summarized in Table 1.
J
H-H=7.7, 1.7 Hz), 7.07-6.92 (m, 24H, C6H5 meta and para),
2
0.79 (m, 12H, PCH3, JP-H =9.6 Hz, JPt-H =21.7 Hz), 0.61
(m, 4H, CH2, 2JP-H=17 Hz). 13C{1H} NMR (75 MHz, THF-d8,
rt): δ 148.4 (t, C6H5 ipso, 3JP-C = 5.5 Hz, 2JPt-C = 39 Hz), 141.9
(t, C6H5 ipso, 3JPt-C=14.4 Hz), 138.5 (C6H5 ortho, 2JPt-C=17.3
Hz), 137.6 (C6H5 ortho), 127.7 (C6H5 meta), 127.5 (C6H5 meta),
127.2 (C6H5 para), 127.1 (C6H5 para), 30.8 (m, PCH2), 13.9 (d,
2
2
PCH3, JP-C = 29 Hz, JPt-C = 39 Hz). 31P{1H} NMR (121
MHz, C6D6, rt): δ 33.6 (JPt-P=1851 Hz).
Direct Preparation of 3 from 1. Direct preparation of 3 from
complex 1 is as follows: Complex 1 (88 mg, 0.11 mmol),
H2GePh2 (251 mg, 1.10 mmol), and toluene (3 mL) were added
to a 25 mL Schlenk and stirred for 28 h at 90 °C. The solvent was
removed under reduced pressure to produce the residual solid,
which was recrystallized from toluene/hexane (1:4) to remove
oligogermanes as byproduct. The product 3 was obtained as
colorless crystals (84 mg, 61%).
Acknowledgment. This work was financially supported
by Grants-in-Aid for Scientific Research for Young
Chemists (No. 21750057), for Scientific Research (No.
1925008), and for Scientific Research on Priority Areas
(No. 19027018), from the Ministry of Education, Culture,
Sport, Science, and Technology, Japan. We are grateful
to Dr. Norio Nakata (Saitama University) for helpful
discussions.
Reaction of 2 with PhGeH3. When a 4-fold amount of PhGeH3
(108 mg, 0.71 mmol) was added to a 5 mL toluene solution of 2
(182 mg, 0.18 mmol), the reaction mixture turned from yellow
to colorless and was stirred for 2 h at rt. The reaction mixture
was filtered, and the solvent removed under reduced pressure.
The resulting solid material was reprecipitated with hexane
repeatedly to give H(GePh2)3H14 as a white solid (92.4 mg,
Supporting Information Available: Crystallographic data for
1, 2, and 3 as a CIF file. This material is available free of charge
via the Internet at http://pubs.acs.org.
(26) Sheldrick, G. M. SHELXL-97: Program for Crystal Structure
Refinement; University of Gottingen: Germany, 1997.
1
76%). H NMR (300 MHz, C6D6, rt): δ 7.60 (m, 4H, C6H5