Preparation and structural characterization of 1,4-digerma-2-buten-1,4- diylplatinum(II) complexes and their reactions with alkynes, carbon monoxide, and isocyanides

Article abstract of DOI:10.1021/om058021v

1,4-Digerma-2-buten-1,4-diylplatinum(II) complexes were prepared by treatment of a (η-ethylene)(triphenylphosphine)platinum(0) complex with (Z)-α,β-bis(dialkylgermyl)styrenes, and their structures were determined by spectroscopic analysis coupled with X-ray diffraction methods. Thermolysis of 1,4-digerma-2-buten-1,4-diylplatinum(II) complexes afforded linear and cyclic trigermanes and a dinuclear platinum complex. The 1,4-digerma-2-buten-1,4-diylplatinum(II) complexes reacted with alkynes to give the corresponding insertion products, cyclic germy(germylvinyl)platinum(II) species, whose structures have been determined by spectroscopic analysis. The cyclic germy(germylvinyl)platinum(II) complexes were found to easily liberate 1,4-digermacyclohexa-2,5-dienes and a platinum(O) complex. The reactions of 1,4-digerma-2-buten-1,4-diylplatinum(II) complexes with carbon monoxide and isocyanides afforded the corresponding platinum complexes containing one carbon monoxide and one isocyanide ligand, respectively.

Full text of DOI:10.1021/om058021v

4734
Organometallics 2005, 24, 4734-4741
Preparation and Structural Characterization of
1,4-Digerma-2-buten-1,4-diylplatinum(II) Complexes and
Their Reactions with Alkynes, Carbon Monoxide, and
Isocyanides
Kunio Mochida,*,† Hironori Karube,† Masato Nanjo,† and Yasuhiro Nakadaira†,‡
Department of Chemistry, Faculty of Science, Gakushuin University, 1-5-1 Mejiro,
Toshima-ku, Tokyo 171-8588, Japan, and Department of Chemistry, The University of
Electro-Communications, Chofu, Tokyo 182-8588, Japan
Received April 13, 2005
1,4-Digerma-2-buten-1,4-diylplatinum(II) complexes were prepared by treatment of a
(η-ethylene)(triphenylphosphine)platinum(0) complex with (Z)-R,â-bis(dialkylgermyl)styrenes,
and their structures were determined by spectroscopic analysis coupled with X-ray diffraction
methods. Thermolysis of 1,4-digerma-2-buten-1,4-diylplatinum(II) complexes afforded linear
and cyclic trigermanes and a dinuclear platinum complex. The 1,4-digerma-2-buten-1,4-
diylplatinum(II) complexes reacted with alkynes to give the corresponding insertion products,
cyclic germyl(germylvinyl)platinum(II) species, whose structures have been determined by
spectroscopic analysis. The cyclic germyl(germylvinyl)platinum(II) complexes were found
to easily liberate 1,4-digermacyclohexa-2,5-dienes and a platinum(0) complex. The reactions
of 1,4-digerma-2-buten-1,4-diylplatinum(II) complexes with carbon monoxide and isocyanides
afforded the corresponding platinum complexes containing one carbon monoxide and one
isocyanide ligand, respectively.
The transition metal-catalyzed addition of group 14
(germyl)platinum(II) complexes.4 We have previously
reported on the preparation, structural characterization,
and interesting reactivity of bis(phenyl-substituted ger-
myl)platinum(II) complexes.4e We describe in this paper
the preparation, structural characterization, and reac-
tions of new cyclic bis(germyl)platinum(II) complexes.
element catenate compounds to unsaturated organic
substrates is a useful and fundamental process in group
14 element and organometallic chemistry.1 The addition
of group 14 element catenates to C-C triple and double
bonds, i.e., bis-silylation,2 has attracted considerable
current interest as applied to the synthesis of functional
molecules and in applications to selective organic syn-
thesis and advanced materials. In such reactions, bis-
(silyl)palladium(II) and bis(silyl)platinum(II) complexes
have been proposed as key intermediates, and their
structures and reactivities have been amply investi-
gated.3 In contrast to the extensive study of complexes
containing Pd- and Pt-Si bonds, there have been few
reports regarding bis(germyl)palladium(II) and bis-
(3) (a) Chatt, J.; Eaborn, C.; Kapoor, P. N. J. Chem. Soc. (A) 1970,
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Organomet. Chem. 1977, 131, 377. (d) Kobayashi, T.; Hayashi, T.;
Yamashita, H.; Tanaka, M. Chem. Lett. 1988, 1411. (e) Kobayashi, T.;
Hayashi, T.; Yamashita, H.; Tanaka, M. Chem. Lett. 1989, 467. (f)
Yamashita, H.; Kobayashi, T.; Hayashi, T.; Tanaka, M. Chem. Lett.
1990, 1447. (g) Tanaka, M.; Uchimaru, Y.; Lautenschlager, H.-J.
Organometallics 1991, 10, 16. (h) Grundy, S. L.; Holmes-Smith, R. D.;
Stobart, S. R.; Williams, M. A. Inorg. Chem. 1991, 30, 3333. (i)
Yamashita, H.; Tanaka, M.; Goto, M. Organometallics 1992, 11, 3227.
(j) Heyn, R. H.; Tilley, T. D. J. Am. Chem. Soc. 1992, 114, 1917. (k)
Michalczyk, M. J.; Recatto, C. A.; Calabrese, J. C.; Fink, M. J. J. Am.
Chem. Soc. 1992, 114, 7955. (l) Sasaki, S.; Ieki, M. J. Am. Chem. Soc.
1993, 115, 2373. (m) Hikida, T.; Onitsuka, K.; Sonogashira, K.;
Hayashi, T.; Ozawa, F. Chem. Lett. 1995, 985. (n) Ozawa, F.; Hikida,
T. Organometallics 1996, 15, 4501. (o) Ozawa, F.; Hikida, T.; Hasebe,
K.; Mori, T. Organometallics 1998, 17, 1018. (p) Ozawa, F.; Kamite, J.
Organometallics 1998, 17, 5630. (q) Gehrhus, B.; Hitchcock, P. B.;
Lappert, M. F.; Maciejewski, H. Organometallics 1998, 17, 55599. (r)
Kang, Y.; Kang, S. O.; Ko, J. Organometallics 1999, 18, 1818. (s)
Ozawa, F. J. Organomet. Chem. 2000, 611, 332. (t) Kalt, D.; Schubert,
U. Inorg. Chim. Acta 2000, 301, 211. (u) Tanabe, M.; Osakada, K. J.
Am. Chem. Soc. 2002, 124, 4550. (v) Kim, Y.-J.; Choi, E.-H.; Lee, S.
W. Organometallics 2003, 22, 3316.
* To whom correspondence should be addressed. E-mail:
kunio.mochida@gakushuin.ac.jp. Fax: +81-3-5992-1029.
† Gakushuin University.
‡ The University of Electro-Communications.
(1) (a) Miller, R. D.; Michle, J. Chem. Rev. 1989, 89, 1359. (b)
Beletskaya. I.; Moberg, C. Chem. Rev. 1999, 99, 3435. (c) Suginome,
M.; Ito, Y. Chem. Rev. 2000, 100, 3221.
(2) (a) West, R. In Comprehensive Orgnometallic Chemistry; Wilkin-
son, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon: New York, 1982;
Vol. 2, p 376. (b) West, R. In Comprehensive Orgnometallic Chemistry;
Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon: New York,
1995; Vol. 2, p 77. (c) Ojima, I. In The Chemistry of Organic Silicon
Compounds; Patai, S., Rappoport, Z., Eds., John Wiley & Sons: New
York, 1989. (d) Tilley, T. D. In The Silicon-Heteroatom Bond; Patai,
S., Rappoport, E., Eds.; John Wiley & Sons: Chichester, 1991; Chapter
9. (e) Murai, S.; Chatani, N. J. Synth. Org. Chem. Jpn. 1993, 51, 421,
and references therein. (f) Yamashita, H.; Tanaka, M. Bull. Chem. Soc.
Jpn. 1995, 68, 403, and references therein. (g) Suginome, M.; Oike,
H.; Park, S.-S.; Ito, Y. Bull. Chem. Soc. Jpn. 1996, 69, 1996, and
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685, 218. (i) Yoshida, H.; Ikadai, J.; Shudo, M.; Ohshita, J.; Kunai, A.
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Org. Lett. 2004, 6, 3341.
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1995, 14, 5700. (b) Barrau, J.; Rima, G.; Cassano, V. Main Group Met.
Chem. 1996, 19, 283. (c) Komoriya, H.; Kako, M.; Nakadaira, Y.;
Mochida, K. Organometallics 1996, 15, 2014. (d) H. Komoriya, H.;
Kako, M.; Nakadaira, Y.; Mochida, K. J. Organomet. Chem. 2000, 611,
420. (e) Mochida, K.; Wada, T.; Hatanaka, W.; Nanjo, M.; Sikine, A.;
Ohashi, Y.; Sakamoto, M.; Yamamoto, A. Bull. Chem. Soc. Jpn. 2001,
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2003, 76, 1023.
10.1021/om058021v CCC: $30.25 © 2005 American Chemical Society
Publication on Web 08/26/2005

1,4-Digerma-2-buten-1,4-diylplatinum(II) Complexes
Organometallics, Vol. 24, No. 20, 2005 4735
Results and Discussion
Preparation and Structural Characterization
of 1,4-Digerma-2-buten-1,4-diylplatinum(II) Com-
plexes. We have previously reported that a strained
germacycle having a Ge-Ge bond, 1,2-digermacyclobut-
3-ene, reacts smoothly with alkynes in the presence of
an appropriate catalyst to give the corresponding inser-
tion products, 1,4-digermacyclohexa-2,5-dienes, in mod-
erate to good yield.5 1,4-Digerma-2-buten-1,4-diylplat-
inum(II) complexes have been proposed as key inter-
mediates in platinum-catalyzed insertion reactions of
alkynes into the Ge-Ge bond of 1,2-digermacyclobut-
3-enes. Our interest in the structure and properties of
the Ge-Pt bond prompted us to prepare a readily
accessible strained 1,4-digerma-2-buten-1,4-diylplati-
num(II) complex as a model compound for such inter-
mediates.
The 1,4-digerma-2-buten-1,4-diylplatinum(II) (1) was
prepared by the treatment of (η-ethylene)bis(triphen-
ylphosphine)platinum(0) with 1. 5 equiv of (Z)-R,â-bis-
(dialkylgermyl)styrenes in toluene at room temperature
for 10 min, which afforded 1,1,4,4-tetraalkyl-2-phenyl-
1,4-digerma-2-buten-1,4-diylplatinum(II) (1a: alkyl )
methyl, 69% yield; 1b: alkyl ) ethyl, 84% yield) as
white crystals.6
Figure 1. ORTEP view of 1b. Thermal ellipsoids are
drawn at 30% probability levels, and hydrogen atoms are
omitted for clarity.
Table 1. Selected Bond Lengths (Å) and
Bond Angles (deg) of
1,4-Digerma-2-buten-1,4-diylplatinum(II) (1b)
Pt(1)-Ge(1) 2.4569(8)
Pt(1)-P(1) 2.3375(17)
Ge(1)-C(1) 2.003(7)
Pt(1)-Ge(2) 2.4850(7)
Pt(1)-P(2) 2.3458(18)
Ge(1)-C(1) 2.003(7)
Ge(1)-Pt(2)-P(1) 92.23(5)
Ge(2)-Pt(1)-P(2) 90.95(5)
C(1)-C(2) 1.324(10)
P(1)-Pt(1)-P(2) 95.87(6)
Ge(1)-Pt(1)-Ge(2) 81.40(3)
(germyl)platinum(II) complexes and similar to those of
the cis-isomer.4c
Thermolysis. The thermolysis of platinum(II) com-
plex 1a was examined in a sealed NMR tube. In toluene
it was thermally stable at 120 °C for 5 days. However,
heating 1a in toluene at 175 °C for 15 h led to complete
decomposition with formation of trigermanes (14%) and
1,2,3-trigermcyclopent-4-ene (13%) as the major prod-
ucts. Trace amounts of dinuclear platinum(II) complex
Platinum(II) complex 1 is sensitive to air and mois-
ture at room temperature. The structure of 1 was
determined by spectroscopic methods coupled with X-ray
crystallography. Fortunately, complex 1b could be iso-
lated as white crystals by recrystallization from a 1:1
mixture of hexane and toluene at room temperature for
3-5 days.
The structure of platinum complex 1b was finally
confirmed by X-ray diffraction analysis, as shown in
Figure 1. The crystal data and refinement data are
summarized in the Experimental Section. Selected bond
lengths and angles are tabulated in Table 1.
Complex 1b has a distorted square-planar geometry,
with the dihedral angle between the planes composed
of Ge(1)-Pt(1)-Ge(2) and P(1)-Pt(1)-P(2) being 9.7°.
The deformation from planarity is considered to be
caused by a steric repulsion between the bulky ligands.
The two germyl groups are bound to the platinum
center, with the bite angle, Ge(1)-Pt(1)-Ge(2), being
81.40°. In contrast, the P(1)-Pt(1)-P(2) bite angle is
95.87°. The bond lengths of Pt-Ge (2.4569(8) and
2.4850(7) Å) are shorter than those of trans-bis(germyl)-
platinum(II) complexes and similar to those of the cis-
isomer. In contrast, the Pt-P bond length (2.3375(17)
and 2.3458(18) Å) is longer than those of trans-bis-
and unidentified products containing germanium also
were detected. Fragments of linear and cyclic triger-
mane structures were carefully identified by NMR and
GC-MS data by comparison with related germanium
compounds.7-9 The structure of the dinuclear platinum-
(II) complex was established by spectroscopic and X-ray
diffraction methods.10
(7) Rivie´re, P.; Satge´, J.; Dousse, G.; R-Baudet, M.; Couret, C. J.
Organomet. Chem. 1974, 72, 339.
(5) Mochida, K.; Karube, H.; Nanjo, M.; Nakadaira, Y. J. Organomet.
Chem. 2005, 690, 2967.
(6) Complexes containing a Pt-Ge bond have been prepared by the
reaction of (η-ethylene)bis(triphenylphosphine)platinum(0) with hy-
drogermanes: Barrau, J.; Rima, G.; Cassano, V.; Satge. J. Inorg. Chim.
Acta 1992, 461, 198.
(8) Mochida, K.; Yoneda, I,; Wakasa, M. J. Organomet. Chem. 1990,
399, 53.
(9) Billeb, G,; Neumann, W. P.; Steinhoff, G. Tetrahedron Lett. 1988,
5245.
(10) Taylor, N. J.; Chieh, P. C.; Carty, A. J. J. Chem. Soc., Chem.
Commun. 1975, 448.

4736 Organometallics, Vol. 24, No. 20, 2005
Mochida et al.
The presence of trigermanes and 1,2,3-trigermacy-
clopent-4-ene may have been due to the generation of a
dimethylgermylene unit from 1a.12 The germylene then
inserted into the activated Ge-Ge bond of 1,2-digerma-
cyclobut-3-ene, produced by reductive elimination from
1a with the regeneration of platinum species to afford
1,2,3-trigermacyclopent-4-ene. It is well known that the
dimerization of germylenes gives the corresponding
digermenes, followed by the addition of the germylene
to the Ge-Ge double bond to afford trigermanes.4c,9,11,12
The position of the methyl and phenyl groups on the
germanium atoms of the trigermanes is unclear. Methyl
groups on the germanium atom may be exchanged with
phenyl groups of phosphine ligands above 120 °C.
Reactions of Platinum(II) Complex 1 with Al-
kynes. As reported, platinum-catalyzed insertion reac-
tions of acetylenes into the Ge-Ge bond of the strained
1,2-digermacyclobut-3-enes in toluene smoothly pro-
duced the corresponding 1,4-digermacyclohexa-2,5-
dienes in moderate to good yield.4c,5 1,4-Digerma-2-
buten-1,4-diylplatinum(II) compounds 1 have been
proposed as model compounds of intermediates in such
reactions. To examine the reactivity of 1, which is
assumed to be involved in the platinum-catalyzed inser-
tion of alkynes into the Ge-Ge bond of germacycles, we
treated 1 with 5.0 molar equiv of phenylacetylene at
room temperature for 10 min. The reaction gave a
mixture of 3,5-diphenyl-1,4-digermacyclohexa-2,5-diene
and 2,5-diphenyl-1,4-digermacyclohexa-2,5-diene (1:1)
(1a) and (3:4) (1b), respectively, in moderate to good
yield. (η-Phenylacetylene)bis(triphenylphosphine)plat-
inum(0) also was formed. All compounds were identified
by NMR spectroscopy and by GC-MS data.3n,m,p,4e,13
alkyne insertion reactions of 1a based on NMR spec-
troscopy. Thus, the reaction of complex 1a with 0.92
equiv of methyl propiolate at room temperature for 10
min in C6D6 was followed by NMR spectroscopy.
The 31P NMR spectrum showed two signals at 29.0
ppm (JPt-P ) 2198 Hz, JP-P ) 17 Hz) and 29.9 ppm
(Jt-P ) 2219 Hz, JP-P ) 17 Hz) in diminished intensity
assigned to 1a and two new sets (2a and 2b in
approximately 3:1 ratio), two signals: 24.1 ppm (d with
two satellites, JPt-P ) 2200 Hz, JP-P ) 15 Hz) and 25.3
ppm (d with two satellites, JPt-P ) 1822 Hz, JP-P ) 15
Hz), and 22.5 ppm (d, JP-P ) 15 Hz) and 25.5 ppm (d,
JP-P ) 15 Hz). The Pt satellites in 2b could not be
observed in the 31P NMR spectrum due to its low
1
intensity. The H NMR spectrum of 2a showed three
singlets at -0.71 ppm (JPt-H ) 14 Hz) due to the methyl
group of the platinum-bound dimethylgermyl group (Pt-
GeMe2), at 1.03 ppm due to another dimethylgermyl
group (GeMe2), at 3.41 ppm due to the methyl ester
group (CO2Me), and multiplet signals in the range 6.80-
7.80 ppm due to the phenyl groups and the olefinic
proton. The 1H NMR spectrum of 2b showed three
methyl signals at -0.44 ppm (JPt-H ) 11 Hz) due to Pt-
GeMe2, at 1.15 ppm due to GeMe2, at 3.43 ppm due to
CO2Me, and multiplets in the range 6.75-7.70 ppm due
to the phenyl groups and olefinic protons. The 13C NMR
spectrum of 2a/2b could not be observed due to their
short lifetimes.
Stirring the C6D6 solution of 2a/b at room tempera-
ture for 10 h resulted in the decomposition of 2a/b
(100%) with formation of a 3:1 mixture of the corre-
sponding insertion products (3a,b) together with (η-
methylpropiolate)bis(triphenylphosphine)platinum(0). 1,4-
Digermacyclohexa-2,5-dienes (3a,b) were characterized
by NMR and GC-MS spectra.
The reactions of 1b with other terminal and internal
alkynes such as 1-hexyne, methyl propiolate, and l-phen-
yl-1-propyne also gave the corresponding 1,4-digerma-
cyclohexa-2,5-dienes in moderate to good yield. Internal
alkynes such as diphenylacetylene, bis(trimethylsilyl)-
acetylene, and dimethyl acetylenedicarboxylate proved
to be unreactive toward 1b under various conditions.
The results of 1b with alkynes are summarized in the
Experimental Section.
The cyclic germyl(vinylgermyl) type platinum(II) com-
plex (2) is a possible intermediate in the reactions of 1
with alkynes in the process of liberating alkyne-inser-
tion products.3n,4e To detect the cyclic germyl(vinylger-
myl) type platinum(II) complex, we treated 1 with
alkynes under various conditions. Among the alkynes
examined, methyl propiolate is the most suitable for
These results indicate that cyclic germyl(vinylger-
myl)platinum(II) complex 2 is an intermediate in the
reactions of 1 with alkynes in the process of liberating
alkyne-inserted products.14
(13) Koie, Y.; Shinoda, S.; Saito, Y. J. Chem. Soc., Dalton Trans.
1981, 1082.
(14) Ozawa, F.; Mori, T. Organometallics 2003, 22, 3593, and
references therein.
(11) Billeb, G.; Brauer, H.; Neumann, W. P.; Weisbeck, M. Orga-
nometallics 1992, 11, 2069.
(12) Neumann, W. P. Chem. Rev. 1991, 91, 311.

1,4-Digerma-2-buten-1,4-diylplatinum(II) Complexes
Organometallics, Vol. 24, No. 20, 2005 4737
Reactions of Platinum(II) Complex 1a with Car-
bon Monoxide. Although many interesting reactions
of bis(germyl)platinum(II) complexes toward unsatur-
ated organic compounds via the Pt-Ge bond cleavage
have been reported, there has been no study of the
insertion of small molecules such as carbon monoxide
into the Pt-Ge bond in these complexes. A large excess
of carbon monoxide was bubbled into a C6D6 solution of
1a at room temperature for 3 h. The product was
identified to be the 1,4-digerma-2-butene-1,4-diyl plati-
num complex containing both phosphine and CO ligands
(4). Evaporation of benzene followed by rapid chroma-
tography on silica gel, elution with benzene, gave 4 as
colorless crystals in 71% isolated yield. Platinum(II)
complex 4 was formed by replacement of only one
phosphine ligand of 1a with CO despite the fact that
CO was bubbled into the solution for a long time.
Complex 4 was stable at room temperature in air. Bis-
(triphenylphosphine)platinum carbonate ([Pt(PPh3)2-
CO3]) was formed as a minor byproduct. The identify of
all products was determined by IR and NMR spectros-
copy. The structure of [Pt(PPh3)2CO3] was established
by X-ray diffraction. The IR spectrum of 4 displayed a
strong absorption band at 2038 cm-1 due to the ν(CdO)
ligand. An NMR examination of 4 in C6D6 at 23 °C
showed the presence of I and II, isomers of the plati-
num(II) complex in an approximately 1:1 ratio. The 1H
NMR spectrum of 4 displays two sets of methyl signals
on germanium at 0.23, 1.00 ppm and 0.29, 1.09 ppm.
The singlets at 0.23 and 0.29 ppm are flanked with Pt
satellites (JPt-H ) 15.7 and 18.7 Hz, respectively),
whereas the doublets coupled with a phosphine ligand
at 1.00 and 1.09 ppm are flanked with Pt satellites
(JP-H ) 2.3 Hz and JPt-H ) 20.1 Hz, JP-H ) 2.2 Hz and
JPt-H ) 20.5 Hz, respectively). The 31P NMR of 4 in C6D6
shows two singlet signals at 25.6 and 26.4 ppm with Pt
satellites (JPt-P ) 2022 and 2044 Hz, respectively). The
JPt-P values in 4 are smaller than those of trans-bis-
(silyl or germyl)(tert-phosphine)platinum(II) complexes
(JPt-P ) ca. 2600 Hz) and are consistent with those of
cis-bis(silyl or germyl)(tert-phosphine)platinum(II) com-
plexes and bis(germyl)platinum complexes with chelat-
ing diphosphines.4e
Ozawa and co-workers have reported the insertion of
CO into the Pt-C bond of alkyl(silyl)platinum(II)
complexes.3n As far as we know, there have been no
reports of CO insertion into the Pt-group 14 element
bonds.
Reactions of Platinum(II) Complex 1a with Or-
ganic Isocyanides. The reactivity of platinum(II)
complex 1a with organic isocyanides (CNR), which are
isoelectronic with CO, was examined. Reactions of 1a
with 1 molar equiv of CNR (R ) tert-Bu and cyclohexyl)
in toluene at room temperature for 1 h gave new 1,4-
digerma-2-butene-1,4-diylplatinum(II) complexes (5) con-
taining both phosphine and isocynanide ligands. Evapo-
ration of toluene and unreacted isocyanide followed by
preparative TLC on silica gel gave platinum(II) com-
plexes 5 as colorless crystals in 49-80% isolated yield,
which are very stable at room temperature in air.
Complex 5 was formed regardless of the amount of
isocyanide used. The structures of 5 were determined
by IR and NMR analysis coupled with X-ray diffraction
analysis.
The NMR spectrum of 5a in CD2Cl2 at 23 °C showed
the presence of isomers I and II in an approximately
3:1 ratio. On the other hand NMR examination of 5b
showed a single isomer I.
Very recently, reactions of bis(silyl)platinum(II) com-
plexes with organic isocyanides have been reported by
Kim and co-workers3v to give the corresponding bis-
(silyl)platinum(II) complexes containing both phosphine
and isocyanide ligands. NMR spectra of new bis(silyl)-
platinum(II) complexes containing both phosphine and
isocyanide ligands broaden at room temperature due to
cis-trans isomerism.
The molecular structures of 5a-I and 5b have been
determined by X-ray diffraction, as shown in Figures 2
and 3. Platinum(II) complexes containing both phos-
phine and isocyanide ligands, 5a-I and 5b, could be
isolated as colorless crystals by recrystallization from
benzene at room temperature for a few days. The crystal
data and refinement data are summarized in the
Experimental Section. Selected bond lengths and angles
are tabulated in Table 2.
Both 5a-I and 5b have distorted square-planar cis
geometries, with the dihedral angles between the planes
composed of Ge(1)-Pt(1)-Ge(2) and P(1)-Pt(1)-C(13)
being 9.11° and 14.02°, respectively. The deformation
from planarity is considered to be caused by a steric
repulsion between the bulky ligands. The two germyl
groups are bound to the platinum center, with the bite
angle, Ge(1)-Pt(1)-Ge(2), being 81.77° for 5a and
83.09° for 5b. In contrast, the bite angles, P(1)-Pt(1)-
C(13), for 5a and 5b are 99.9° and 93.6°, respectively.
The bond lengths of Pt-Ge (2.4515(8) and 2.4430(11)
Å for 5a and 2.424(10) and 2.4265(14) Å for 5b) are
similar to those of cis-bis(germyl)platinums(II) and are
The preparation of [Pt(PPh3)2CO3] by the reaction of
[Pt(PPh3)4] with oxygen under a carbon dioxide atmo-
sphere and its structural characterization by X-ray
analysis have been reported by Dell’Amico and co-
workers15 and other groups.16,17
(15) Abram, U.; Dell’Amico, B. D.; Calderazzo, F.; Marchetti, L.;
Stra¨hle, J. J. Chem. Soc., Dalton Trans. 1999, 4093.
(16) Andrews, M. A.; Gould, G. L.; Klooster, W. T.; Koenig, K. S.;
Voss, E. J. Inorg. Chem. 1996, 35, 5478.
(17) Hayward, J. P.; Blake, D. M.; Wilkinson, G.; Nyman, C. J. J.
Am. Chem. Soc. 1970, 92, 5873.

4738 Organometallics, Vol. 24, No. 20, 2005
Mochida et al.
Figure 3. ORTEP view of 5b: (a) top view, (b) side view.
Thermal ellipsoids are drawn at 30% probability levels, and
hydrogen atoms are omitted for clarity.
Figure 2. ORTEP view of 5a-I: (a) top view, (b) side view.
Thermal ellipsoids are drawn at 30% probability levels, and
hydrogen atoms are omitted for clarity.
Table 2. Selected Bond Lengths (Å) and
Bond Angles (deg) of
1,4-Digerma-2-buten-1,4-diylplatinum(II)
Containing Both Phosphine and Isocyanide
Ligands, 5a-I and 5b
shorter than those of trans-bis(germyl)platinums(II).
The bond lengths of P(1)-Pt(1) (2.2981(19) Å for 5a and
2.354(3) Å for 5b) are similar to those of cis- and trans-
bis(germyl)platinum(tert-phosphine)plantinum(II) com-
plexes.4e The Pt-C bond lengths (1.984(12) Å for 5a and
2.02(2) Å for 5b) are similar to those in bis(silyl)-
platinum(II) containing isocyanide and slightly longer
than those found in other platinum-isocyanide com-
plexes.3v These results are due to the high trans influ-
ence of the germyl ligand.
5a-I
Pt(1)-Ge(1) 2.4515(8)
Pt(1)-P(1) 2.2981(19)
Ge(1)-C(1) 1.982(8)
Pt(1)-Ge(2) 2.4430(11)
Pt(1)-C(13) 1.984(12)
Ge(2)-C(2) 1.995(5)
Ge(1)-Pt(1)-C(13) 83.9(3)
Ge(2)-Pt(1)-P(1) 95.15(5)
C(1)-C(2) 1.342(13)
P(1)-Pt(1)-C(13) 99.9(3)
Ge(1)-Pt(1)-Ge(2) 81.77(3)
5b
Pt(1)-Ge(1) 2.4241(10)
Pt(1)-P(1) 2.35483)
Pt(1)-Ge(2) 2.4265(14)
Pt(1)-C(13) 2.02(2)
Ge(1)-C(1) 1.972(11)
C(1)-C(2) 1.381(16)
Ge(2)-C(2) 1.915(11)
Experimental Section
Ge(1)-Pt(1)-C(13) 89.9(3)
Ge(2)-Pt(1)-P(1) 94.74(7)
P(1)-Pt(1)-C(13) 93.6(3)
Ge(1)-Pt(1)-Ge(2) 83.09(4)
General Methods. All manipulations of air-sensitive com-
pounds were performed under N2 or argon using standard
1
Schlenk line techniques. H, 13C, and 31P NMR spectra were
Materials. Solvents were dried by refluxing over sodium
benzophenone ketyl under a nitrogen atmosphere and were
distilled just before use. Alkynes and organic isocyanides were
commercially available. 1,4-Digermacyclohexa-2,5-dienes,5 (Z)-
R,â-(dimethylgermyl)styrene,5 (η-ethylene)bis(triphenylphos-
phine)platinum,18 and (η-phenylacetylene)bis(triphenylphos-
phine)platinum13 were prepared according to reported proce-
dures.
recorded on a Varian Unity Inova-400 MHz. GC-MS spectra
were measured with a JEOL JMS-DX 303 mass spectrometer.
The UV and UV-vis spectra were recorded on a Shimadzu
UV 2200 spectrometer. IR spectra were recorded on a Shi-
madzu FT IR 4200 spectrometer. Gas chromatographic analy-
ses were performed with a Shimadzu GC-8A equipped with 1
m 20% SE30. X-ray crystallographic data and diffraction
intensities were collected on a MacScience DIP2030 diffrac-
tometer utilizing graphite-monochromated Mo KR (λ ) 0.71073
Å) radiation. The structures were solved by direct methods
using the program system SIR-92 and refined with all data
on F2 by means of SHELXL-97. A refinement was performed
by a Silicon Graphics O2 with maXus.
Preparation of (Z)-r,â-(Diethylgermyl)styrene. A di-
ethyl ether solution (40 mL) of bis(chlorodiethylgermyl)styrene
(3.76 g, 10.3 mmol) and LiAlH4 (0.39 g, 10.3 mmol) was stirred
(18) Blake, D. M.; Roundhill, D. M. Inorg. Synth. 1978, 18, 120.

1,4-Digerma-2-buten-1,4-diylplatinum(II) Complexes
Organometallics, Vol. 24, No. 20, 2005 4739
Table 3. Crystallographic Data for 1b, 5a-I, and 5b
1b
5a-I
5b
formula
C
52H56Ge2P2Pt
C35H42Ge2NPPt
847.94
0.20 × 0.20 × 0.20
monoclinic
Pn
C
37H44Ge2NPPt
molecular wt
cryst size (mm)
cryst syst
space group
unit cell dimens
a (Å)
1083.18
873.97
0.35 × 0.30 × 0.25
0.10 × 0.06 × 0.06
monoclinic
Pn
triclinic
P1h
12.5340(16)
12.9030(17)
17.1630(13)
106.463(7)
94.423(7)
115.172(5)
1234.8(5)
2
9.5910(4)
11.0280(5)
16.7050(5)
9.3510(6)
11.2320(7)
17.0280(7)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
1707.72(12)
2
1735.34(17)
2
Z
radiation Mo KR (Å)
temperature (K)
0.71070
120
0.71070
120
1.649
4037
1.050
0.0372
0.1070
0.71070
120
1.673
4109
1.243
0.0472
0.1309
Dcalc (g cm-3
)
1.534
no. of unique reflns
goodness-of-fit
R1 (I > 2σ(I))
wR2
6158
0.952
0.0398
0.1109
at 40 °C for 3 h. After hydrolysis with water, pure (Z)-R,â-bis-
(diethylgermyl)styrene was obtained by silica gel chromatog-
raphy on a short column packed with silica gel, eluting with
hexane (1.6 g, 4.4 mmol, 43% yield): 1H NMR (δ, C6D6) 0.86-
1.18 (m, 20H), 4.45-4.59 (m, 1H), 4.67 (quint., J ) 3.5 Hz),
6.81 (d, J ) 6.2 Hz, 1H), 7.04-7.23 (m, 5H); 13C NMR (δ,
CDCl3) 5.9, 6.8, 10.2, 10.5, 126.1, 126.2, 128.0, 142.7, 147.9,
160.5; GC-MS m/z (relative intensity) 366 (M+, 8), 337 (100),
236 (33). Anal. Calcd for C16H28Ge2: C, 52.57; H, 7.72. Found:
C, 52.78; H, 7.95.
Preparation of Bis(triphenylphosphine)-2-phenyl-
2-butene-1,1,4,4-tetramethyl-1,4-digerma-1,4-diylplati-
num (1a). A solution of bis(dimethylgermyl)styrene (161 mg,
521 µmol) and (η-ethylene)bis(triphenylphosphine)platinum
(208 mg, 278 ηmol) in degassed toluene (4 mL) was placed in
a 25 mL Schlenk tube. After the mixture had been stirred at
room temperature for 10 min, the toluene was removed under
reduced pressure. Washing the residue with hexane gave pure
bis(triphenylphosphine)-2-phenyl-2-butene-1,1,4,4-tetramethyl-
1,4-digerma-1,4-diylplatinum (1a) (241 mg, 235 µmol, 84.4%
yield). 1a: 1H NMR (δ, C6D6) 0.41 (s with two satellites,
JPt-H ) 15 Hz, 6H), 0.47 (s with two satellites, JPt-H ) 15 Hz,
6H), 6.77-7.64 (m, 35H, phenyl, 1H, CHd); 31P NMR (δ, C6D6)
29.0 (d with two satellites, JPt-P ) 2198 Hz, JP-P )17 Hz),
29.9 (d with two satellites, JPt-P ) 2219 Hz, JP-P ) 17 Hz);
13C NMR (δ, CD2Cl2) 4.1, 5.8, 124.8, 126.7, 127.5, 127.7, 127.8,
128.4, 129.5, 134.1, 134.2, 134.4, 135.2, 135.7, 146.5, 152.1.
Anal. Calcd for C48H48Ge2P2Pt: C, 56.13; H, 4.71. Found: C,
56.22; H, 4.92.
Preparation of Bis(triphenylphosphine)-2-phenyl-2-
butene-1,1,4,4-tetraethyl-1,4-digerma-1,4-diylplatinum
(1b). The same procedure was used in the reaction of bis-
(diethylgermyl)styrene (169 mg, 462 µmol) with (η-ethylene)-
bis(triphenylphosphine)platinum (201 mg, 269 ηmol) in toluene
(4 mL). Pure bis(triphenylphosphine)-2-phenyl-2-butene-1,1,4,4-
tetraethyl-1,4-digerma-1,4-diylplatinum (1b) was isolated (200
mg, 185 µmol, 69% yield). 1b: 1H NMR (δ, C6D6) 0.45-1.42
(m, 20H), 6.75-7.67 (m, 36H); 13C NMR (δ, CD2Cl2) 11.6, 11.8,
12.6, 12.8, 124.4, 126.5, 127.2, 127.4, 127.4, 129.2, 129.4, 131.7,
134.1, 134.1, 135.5, 147.9, 150.5, 165.1; 31P NMR (δ, C6D6) 28.8
(d with two satellites, JPt-P ) 2144 Hz, JP-P ) 20 Hz), 25.8 (d
with satellites, JPt-P ) 2091 Hz, JP-P ) 20 Hz). Anal. Calcd
for C52H56Ge2P2Pt: C, 56.72; H, 5.13. Found: C, 56.98; H, 5.33.
Thermolysis of Bis(triphenylphosphine)-2-phenyl-
2-butene-1,1,4,4-tetramethyl-1,4-digerma-1,4-diylplati-
num (1a). A mixture of 1a (86 mg, 84 µmol) in o-xylene (1.1
mL) was heated under argon in a sealed NMR tube at 175 °C
for 15 h. Evaporation of o-xylene followed by preparative TLC
on silica gel eluted with benzene gave two kinds of linear
trigermanes, Me8-nPhnGe3 (n ) 2, 3) (14%) and 1,2-3-triger-
mcyclopentene (13%), and a dinuclear platinum(II) complex,
[Pt2(PPh3)2(PPh2)2] (trace). The germanium compounds were
carefully characterized by 1H, 13C, 31P NMR, and GC-MS data,
which were compared with those of related germanium
compounds. The identity of the dinuclear platinum(II) complex,
[Pt2(PPh3)2(µ-PPh2)2], was determined by NMR and X-ray
diffraction methods. 1,1,2,2,3,3-Hexamethyl-4-phenyl-1,2,3-
germacyclopenta-4-ene:9,10 1H NMR (δ, CDCl3) 0.35 (s, 12H),
0.39 (s, 6H), 6.75-7.45 (m, 6H); 13C NMR (δ, CDCl3) -1.01,
-0.07, 0.27, 126.52, 127.74, 128.53, 140.88, 149.72, 161.74; GC-
MS m/z (relative intensity) 410 (M+, 59), 395 (80), 308 (45),
293, 206 (50), 175 (50), 119 (100). Linear trigermanes,
Me8-nPhnGe3 (n ) 2, 3):7,8 1H NMR (δ, CDCl3) 0.04 (s), 0.31
(s), 0.32 (s), 6.75-7.50 (m); 13C NMR (δ, CDCl3) -1.1, -0.47,
0.25, 1.04, 126.52, 127.74, 128.53, 140.88; GC-MS m/z (relative
intensity) for n ) 2, 462 (M+, 5), 447 (M+ - Me, 30), 345
(M+ - GeMe3, 20), 283 (M+ - GeMe2Ph, 10), 243 (GeMePh2
,
+
100), 181 (GeMe2Ph+, 50); GC-MS m/z (relative intensity) for
n ) 3, 462 (M+, 462), 447 (M+ - Me, 25), 283 (M+ - GeMe2-
Ph, 25), 243 (Ph2MeGe+, 15), 181 (PhMe2Ge+, 100).
Reactions of Bis(triphenylphosphine)-2-phenyl-2-bu-
tene-1,1,4,4-tetramethyl-1,4-digerma-1,4-diylplatinum (1a)
with Phenylacetylene. To an NMR tube containing 1,4-
digermabut-2-ene-1,4-diylplatinum (20 mg, 19 µmol) were
added phenylacetylene (34 mg, 194 µmol) and C6D6 (0.7 mL)
under argon. The solution was degassed under vacuum and
stirred at room temperature for 10 min. GC and GC-MS
analyses of the reaction mixture showed that 1a was com-
pletely consumed to give the corresponding 1,4-digermacyclo-
hexa-2,5-dienes.4c The crude solution was chromatographed on
silica gel TLC to give a 1:1 mixture of 1,1,4,4-teramethyl-2,5-
diphenyl-1,4-digermacyclohexa-2,5-diene and 1,1,4,4-tetra-
methyl-2,6-diphenyl-1,4-digermacyclohexa-2,5-diene (8 mg, 15
µmol, 95% yield): 1H NMR (δ, C6D6) 0.40 (s, 6H), 0.43 (s, 6H),
6.82 (s, 1H), 6.90 (s, 1H), 7.20-7.37 (m, 10H), 7.20-7.37 (m,
10H); 13C NMR (δ, CDCl3) -1.20, -0.26, 0.09, 126.02, 126.24,
126.43, 126.45, 128.18, 128.31, 143.34, 144.05, 145.52, 146.43,
159.95, 161.70; MS m/z (relative intensity) 410 (M+, 22), 395
(21), 308 (17), 293 (30), 206 (19), 191 (27), 173 (41), 119 (100),
89 (100).
Reactions of Bis(triphenylphosphine)-2-phenyl-2-bu-
tene-1,1,4,4-tetraethyl-1,4-digerma-1,4-diylplatinum (1b)
with Alkynes. The platinum-catalyzed insertion reactions of
alkynes into the Ge-Ge bond of 1b are summarized in Table
4.
As a representative example, the reaction of 1b with
phenylacetylene is described. To an NMR tube containing 1,4-
digermabut-2-ene-1,4-diylplatinum (20 mg, 19 µmol) were

4740 Organometallics, Vol. 24, No. 20, 2005
Table 4. Reactions of 1,2-Digerma-2-buten-1,4-diylplatinum(II) (1b) with Alkynes
Mochida et al.
1,2-digerma-2-buten-
1,4-diylplatinum
product ratio
(2-isomer:3-isomer)
run
alkyne
conditions
yield/%
1
2
3
4
1b
1b
1b
1b
Bu-CtC-H
rt, 98 h
87
95
84
89
1:1
3:4
1:1
1:1
Ph-CtC-H
rt, 10 min
rt, 12 h
MeO2C-CtC-H
Ph-CtC-Me
rt, 160 h
added phenylacetylene (34 mg, 194 µmol) and C6D6 (0.7 mL)
under an argon atmosphere. The solution was degassed under
vacuum and stirred at room temperature for 10 min. GC and
GC-MS analyses of the reaction mixture showed that 1b was
completely consumed to give corresponding 1,4-digermacyclo-
hexa-2,5-dienes. The crude solution was chromatographed on
silica gel TLC to give a 3:4 mixture of 1,1,4,4-teraethyl-2,5-
diphenyl-1,4-digermacyclohexa-2,5-diene and 1,1,4,4-tetraethyl-
2,6-diphenyl-1,4-digermacyclohexa-2,5-diene (8 mg, 16 µmol,
95% total isolated yield):5 1H NMR (δ, C6D6) 0.89-1.17 (m,
40H, EtGe), 6.90 (s, 2H, CHd), 6.97 (s, 2H, CHd), 7.07-7.35
(m, 20H, phenyl); 13C NMR (δ, CDCl3) 7.23, 7.40, 7.97, 9.14,
9.39, 9.45, 11.23, 12.42, 125.90, 125.91, 126.06, 126.07, 126.15,
126,23, 126.44, 127.56, 128.10, 128.11, 128.21, 128.22, 128.28,
128.64, 129.99, 130.23, 133.19, 140.00, 142.63, 142.70, 146.39,
147.30, 159.07, 160.11; MS m/z (relative intensity) 466 (M+,
7), 437 (100), 408 (18), 161 (18), 132 (16). 1-Heynes (16.0 mg,
194 µmol) and 1b (20 mg, 19 µmol): 1,1,4,4-Tetraethyl-2-butyl-
5-phenyl-1,4-digermacyclohexa-2,5-diene and 1,1,4,4-tetraethyl-
3-butyl-5-phenyl-1,4-digermacyclohexa-2,5-diene (8 mg, 17
µmol, 87% isolated yield): 1H NMR (δ, C6D6) 0.84-1.24 (m,
40H, EtGe), 1.24-1.53 (m, 18H, C-Bu), 6.57 (s, 1H, CHd),
6.62 (s, 1H, CHd), 6.91 (s, 1H, CHd), 6.93 (s, 1H, CHd), 7.02-
7.36 (m, 10H, phenyl); 13C NMR (δ, CDCl3) 7.10, 7.41, 8.11,
8.42, 9.65, 10.66, 12.66, 14.46, 22.87, 30.06, 30.84, 31.08, 31.46,
38.16, 40.53, 41.47, 125.89, 125.96, 126.08, 126.22, 128.03,
128.09, 128.25, 128.62, 129.97, 133.07, 136.45, 137.18, 137.42,
142.60, 143.04, 147.36; MS m/z (relative intensity) 417 (100),
386 (13), 335 (23), 316 (10), 161 (11). 1-Phenyl-1-propyne (24
mg, 200 µmol) and 1b (20 mg, 19 µmol): 1,1,4,4-Tetraethyl-
2-methyl-3,5-diphenyl-1,4-digermacyclohexa-2,5-diene and
1,1,4,4-tetraethyl-3-methyl-2,5-diphenyl-1,4-digermacyclohexa-
2,5-diene (8 mg, 18 µmol, 89% isolated yield): 1H NMR (δ,
C6D6) 0.83-1.38 (m, 40H, EtGe), 1.53 (s, 3H, C-Me), 6.93 (s,
dilylplatinum (1a) and methyl propiolate decayed, making
possible immediate observation of a buildup of new NMR
signals of the products of the methyl propiolate insertion into
the Ge-Ge bond of 1a (2a,b). NMR signals of the methyl
propionate insertion products 2a,b gradually disappeared, and
other signals assigned to 1,4-digermacyclohexa-2,5-dienes
(3a,b) appeared, which were observed as final products. (η-
Methyl propiolate)bis(triphenylphosphine)platinum was also
detected by NMR analysis.13 Cyclic germyl(vinylgermyl)-
platinum 2a: 1H NMR (δ, C6D6) -0.17 (s, JPt-H ) 14 Hz, 6H,
PtGeCH3), 1.03 (s, 6H, GeCH3), 3.41 (s, 3H, CO2Me), 6.77-
7.64 (m, 37H, phenyl, 1H, CHd); 31P NMR (δ, C6D6) 24.1 (d
with two satellites, JP-P ) 15 Hz, JPt-P ) 2200 Hz), 25.3 (d
with two satellites, JP-P ) 15 Hz, JPt-P ) 1822 Hz). 2b: 1H
NMR (δ, C6D6) -0.44 (s, JPt-H ) 11 Hz, 6H, PtGeCH3), 1.15
(s, 6H, GeCH3), 3.43 (s, 3H, CO2Me), 6.77-7.64 (m, 37H,
phenyl, 1H, CHd); 31P NMR (δ, C6D6) 22.5 (d with two
satellites, JP-P ) 15 Hz), 25.8 (d with two satellites, JP-P ) 15
Hz).
Reactions of Bis(triphenylphosphine)-2-phenyl-2-bu-
tene-1,1,4,4-tetramethyl-1,4-digerma-1,4-diylplatinum (1a)
with Methyl Propiolate. In an NMR tube with a septum
seal were placed 1,4-digermabut-2-ene-1,4-diylplatinum (20
mg, 19 µmol), methyl propiolate (17 µL, 194 µmol), and C6D6
(0.7 mL) at ambient temperature. The solution was degassed
and sealed under vacuum. The progress of the reaction was
examined by means of NMR spectroscopy. The reaction
mixture was separated by preparative silica gel TLC eluting
with a 5:2 mixture of hexane/benzene. A 3:1 mixture of 1,1,4,4-
tetramethyl-2-carboxylate-5-phenyl-1,4-digermacyclohexa-2,5-
diene and 1,1,4,4-tetramethyl-3-carboxylate-5-phenyl-1,4-
digermacyclohexa-2,5-diene was obtained in 87% yield (8 mg,
17 µmol): 1H NMR (δ, C6D6) 0.34 (s, 6H), 0.41 (s, 6H), 0.50 (s,
6H), 0.59 (s, 6H), 3.73 (s, 3H), 3.74 (s, 3H), 6.65 (s, 1H), 6.76
(s, 1H) <7.95 (s, 1H), 7.97 (s, 1H), 7.13-7.46 (m, 10H); 13C
NMR (δ, CDCl3) -1.39, -0.5, 0, 2.48, 51.84, 52.11, 125.96,
126.08, 126.20, 126.49, 126.70, 128.15, 128.27, 128.70, 141.41,
143.98, 146.25, 150.57, 158.68, 160.12, 160.43, 161.62, 239.64,
139.64; MS m/z (relative intensity) 392 (M+, 49), 377 (10), 346
(27), 316 (14), 259 (100), 244 (23), 133 (18), 118 (46), 103 (36).
Anal. Calcd for C16H22O2Ge2: C, 49.08; H, 5.66. Found: C,
49.25; H, 5.43.
1H, CHd), 6.95 (s, 1H, CHd), 7.01-7.35 (m, 10H, phenyl); 13
C
NMR (δ, CDCl3) 6.18, 6.35, 6.42, 6.49, 9.10, 9.34, 9.36, 9.50,
19.87, 20.03, 125.16, 125.21, 125.95, 126.26, 126.31, 127.10,
127.20, 127.25, 128.01, 128.03, 128.12, 128.15, 128.24, 128.29,
128.31, 130.00, 133.20, 142.99, 143.12, 143.45, 143.72, 146.88,
148.05, 159.65; MS m/z (relative intensity) 480 (M+, 8), 451
(100), 436 (18), 407 (18), 350 (19), 335 (43), 306 (8), 205 (16),
160 (32). Methyl propiolate (17 mg, 200 µmol) and 1b (20 mg,
19 µmol): 1,1,4,4-Tetraethyl-2-methylcarboxylate-5-phenyl-
1,4-digermacyclohexa-2,5-diene and 1,1,4,4-tetraethyl-2-meth-
ylcarboxylate-6-phenyl-1,4-digermacyclohexa-2,5-diene (7 mg,
16 µmol, 84% isolated yield): 1H NMR (δ, C6D6) 0.79-1.39 (m,
40H, EtGe), 3.41 (s, 3H, CO2Me), 3.42 (s, 3H, CO2Me), 6.76 (s,
1H, CHd), 6.91 (s, 1H, CHd), 8.34 (s, 1H, CHd), 8.36 (s, 1H,
CHd), 6.94-7.35 (m, 10H, phenyl); 13C NMR (δ, CDCl3) 6.97,
7.38, 7.60, 7.79, 8.07, 9.27, 9.33, 9.39, 51.79, 52.01, 125.85,
125.99, 126.39, 126.59, 128.15, 128.27, 129.99, 140.88, 143.22,
147.14, 149.14, 158.87, 159.81, 160.33, 160.68, 67.42, 243.14,
143.15; MS m/z (relative intensity) 448 (M+, 9), 419 (54), 390
(100), 361 (23), 332 (21), 317 (11), 259 (9), 230 (7).
NMR Study of Reactions of Bis(triphenylphosphine)-
2-phenyl-2-butene-1,1,4,4-tetramethyl-1,4-digerma-1,4-
diylplatinum (1a) with Methyl Propionate. In an NMR
tube with a septum seal were placed 1,4-digermabut-2-ene-
1,4-diylplatinum (20 mg, 19 µmol), methyl propiolate (1.6 µL,
18 µmol), and C6D6 (0.7 mL). The solution was degassed and
sealed under vacuum. The progress of the reaction was
monitored at room temperature for 10 min by means of NMR
spectroscopy. The NMR signals assigned to 1,4-digerma-1,4-
Reactions of 1,4-Digermabut-2-ene-1,4-diylplatinum-
(II) (1a) with Carbon Monoxide. A solution of 1a (20 mg,
19.5 µmol) in C6D6 (2.2 mL) was stirred under carbon monoxide
(1 atm) at room temperature for 22 h. The solution was
concentrated to dryness under reduced pressure to give the
crude product, which was dissolved in benzene. The reaction
mixture was eluted by separative silica gel TLC with benzene.
White crystals were obtained in 71% yield (11 mg, 14 µmol):
1H NMR (δ, C6D6, 23 °C) 0.23 (s with two satelliteds, JPt-H
)
15.7 Hz, 6H), 0.29 (s with two satellites, JPt-H ) 18.7 Hz, 6H),
1.02 (d with two satellites, JP-H ) 2.3 Hz, JPt-H ) 20.1 Hz,
6H), 1.09 (d with two satellites, JP-H ) 2.2 Hz, JPt-H ) 20.1
Hz, 6H), 6.80-7.63 (m, 42H); 31P NMR (δ, C6D6, 23 °C) 25.6 (s
with two satellites, JPt-P ) 2022 Hz), 26.4 (s with two satellites,
JPt-P ) 2044 Hz); 13C NMR (δ, CD2Cl2, 23 °C) 3.39, 4.20, 5.04,
5.95, 125.52, 125.81, 126.72, 126.75, 127.74, 128.06, 128.40,
128.63, 128.63, 128.77, 128.77, 129.07, 130.76, 130.79, 133.59,
133.67, 133.77, 133.93, 134.04, 134.18, 222.04, 239.89; IR
(cm-1) 2038.6(CO). Anal. Calcd for C31H33Ge2OPPt: C, 46,96;
H, 4.20. Found: C, 72.25; H, 4.45.

1,4-Digerma-2-buten-1,4-diylplatinum(II) Complexes
Organometallics, Vol. 24, No. 20, 2005 4741
Reactions of 1,4-Digermabut-2-ene-1,4-diylplatinum-
(II) (1a) with tert-Butyl Isocyanide. To a Schlenk flask
containing 1a (30 mg, 29 µmol) were added toluene (2 mL)
and tert-butyl isocyanide (30 µL, 268 µmol), in that order. After
it had been stirred for 1 h at room temperature, the reaction
mixture was completely evaporated under vacuum, and the
resulting residue became solid when benzene was added. The
solids were filtered and washed with hexane. Recrystallization
from benzene gave white crystals of (tert-butylisocyanide)-
(triphenylphosphine)-2-phenyl-1,1,4,4-tetramethyl-1,4-diger-
mabuta-2-ene-1,4-dilylplatinum (20 mg, 23 µmol, 80% yield):
1H NMR (δ, CD2Cl6, 23 °C) -0.32 (s with two satellites,
JPt-H ) 14.6 Hz, 6H), -0.30 (s with two satellites, JPt-H ) 14.6
it had been stirred for 1 h at room temperature, the reaction
mixture was completely evaporated under vacuum. The result-
ing residue became solid on addition of benzene. The solids
were filtered and washed with hexane. Recrystallization from
benzene gave white crystals of (tert-cyclohexylisocyanide)-
(triphenylphosphine)-2-phenyl-1,1,4,4-tetramethyl-1,4-diger-
mabuta-2-ene-1,4-dilylplatinum (42 mg, 48 µmol, 49% yield):
1H NMR (δ, CD2Cl6, 23 °C) -0.29 (br, 6H), 0.44 (br, 6H), 1.05-
1.73 (m, 10h), 3.38 (br, 1H), 6.67-7.65 (m, 21H); 31P NMR (δ,
CD2Cl2, -50 °C) 25.0 (br, s with two satellites, JPt-P ) 2022
Hz); 13C NMR (δ, CD2Cl2, 23 °C) 3.16 (br), 5.81 (br), 23.27,
25.11, 32.24, 25.11, 32.24, 54.56, 125.14, 126.78, 126.82,
128.24, 128.37, 130.03, 133.98, 134.15, 134.97, 135.48, 153.88
(br). Anal. Calcd for C37H44Ge2PNPt: C, 50.85; H, 5,07.
Found: C, 50.55; H, 4.82.
Hz, 6H), 0.41 (d with two satellites, JP-H ) 2.2 Hz, JPt-H
)
19.4 Hz, 6H), 0.46 (d with two satellites, JP-H ) 2.2 Hz,
JPt-H ) 19.0 Hz, 6H), 1.15 (s, 9H), 1.16 (s, 9H), 6.74-7.62 (m,
42H); 31P NMR (δ, CD2Cl2, 23 °C) 25.0 (s with two satellites,
JPt-P ) 2035 Hz), 25.8 (s with two satellites, JPt-P ) 2040 Hz);
13C NMR (δ, CD2Cl2, 23 °C) 3.03, 3.87, 4.77, 5.65, 29.8, 29.9,
29.9, 30.01, 125.24, 126.73, 126.78, 126.82, 127.53, 127.86,
128.22, 128.34, 128.51, 128.67, 130.01, 131.93, 131.96, 132.09,
133.87, 133.98, 134.00, 134.14, 134.16, 134.24, 153.88, 153.97;
IR (cm-1) 2158.2 ν (CN). Anal. Calcd for C35H42Ge2PNPt: C,
47.63; H, 4.99. Found: C, 47.85; H, 4.70.
Acknowledgment. We thank Miss Mariko Kanai
for preliminary experiments of this study. This work
was supported by a Grant-in-Aid for Priority Area
Research on “Dynamic Complex” from the Ministry of
Education, Culture, Science, Sports, and Technology,
Japan.
Reactions of 1,4-Digermabut-2-ene-1,4-diylplatinum-
(II) (1a) with Cyclohexyl Isocyanide. To a Schlenk flask
containing 1a (100 mg, 97 µmol) were added toluene (3 mL)
and tert-butyl isocyanide (36 µL, 292 µmol), in that order. After
Supporting Information Available: This material is
available free of charge via the Internet at http://pubs.acs.org.
OM058021V