Reaction of isocyanides with [(PPh3)2Pt(η3-CH2CCPh)] + and the formation of the indenyl complex trans-[(PPh3)2Pt(η 1-1H-inden-2-yl)(CNC(CH3)3)]+

Article abstract of DOI:10.1021/om980806w

The reaction of [(PPh₃)₂Pt(η³-CH₂CCPh)]X (X = CF₃SO₃^-, BF₄^-, PF₆^-) with CNR (R = C(CH₃)₃, CH₂Ph) yields a mixture of the η¹-propargyl and -allenyl complexes trans-[(PPh₃)₂-Pt(η¹-CH ₂C≡CPh)(CNR)]⁺ and trans-[(PPh₃)₂Pt(η¹-CPh=C=CH ₂)(CNR)]⁺, respectively, in about a 6/1 proportion. Isolation of the pure propargyl complex was possible in several cases (R = C(CH₃)₃, X = CF₃SO₃^-; R = CH₂Ph, X = BF₄^-, PF₆^-). In solution the cationic complex trans-[(PPh₃)₂Pt(η¹-CH ₂C=CPh)(CNC(CH₃)₃)]⁺ rearranges to an indenyl complex which was isolated as the triflate salt trans-[(PPh₃)₂Pt(η ¹-1H-inden-2-yl)(CNC(CH₃)₃)]CF ₃SO₃ (4). In contrast trans-[(PPh₃)₂Pt(η¹-CH ₂C≡CPh)(CNCH₂Ph)]⁺ does not undergo this rearrangement under similar conditions. The structure of 4·2THF has been determined by X-ray diffraction techniques.

Full text of DOI:10.1021/om980806w

Organometallics 1999, 18, 787-792
787
Rea ction of Isocya n id es w ith [(P P h 3)2P t(η3-CH2CCP h )]+
a n d th e F or m a tion of th e In d en yl Com p lex
tr a n s-[(P P h 3)2P t(η1-1H-in d en -2-yl)(CNC(CH3)3)]+
Martin N. Ackermann,* Ravi K. Ajmera, and Helen E. Barnes
Department of Chemistry, Oberlin College, Oberlin, Ohio 44074
J udith C. Gallucci and Andrew Wojcicki*
Department of Chemistry, The Ohio State University, Columbus, Ohio 43210
Received September 25, 1998
The reaction of [(PPh3)2Pt(η3-CH2CCPh)]X (X ) CF3SO3-, BF4-, PF6-) with CNR (R )
C(CH3)3, CH2Ph) yields a mixture of the η1-propargyl and -allenyl complexes trans-[(PPh3)2-
Pt(η1-CH2CtCPh)(CNR)]+ and trans-[(PPh3)2Pt(η1-CPhdCdCH2)(CNR)]+, respectively, in
about a 6/1 proportion. Isolation of the pure propargyl complex was possible in several cases
(R ) C(CH3)3, X ) CF3SO3-; R ) CH2Ph, X ) BF4-, PF6-). In solution the cationic complex
trans-[(PPh3)2Pt(η1-CH2CtCPh)(CNC(CH3)3)]+ rearranges to an indenyl complex which was
isolated as the triflate salt trans-[(PPh3)2Pt(η1-1H-inden-2-yl)(CNC(CH3)3)]CF3SO3 (4). In
contrast trans-[(PPh3)2Pt(η1-CH2CtCPh)(CNCH2Ph)]+ does not undergo this rearrangement
under similar conditions. The structure of 4‚2THF has been determined by X-ray diffraction
techniques.
In tr od u ction
Following the observation that CO reacts with [(PPh3)2-
Pt(η3-CH2CCPh)]+ to afford a mixture of the η1-propar-
gyl and η1-allenyl products,4 we endeavored to extend
this investigation to organic isocyanides. Transition-
metal chemistry of organic isocyanides often parallels
that of CO; however, significant differences also have
been noted.5
Cationic transition-metal η3-propargyl/allenyl com-
plexes of platinum, [(PPh3)2Pt(η3-CH2CCR)]+, add nu-
cleophiles (NuH) either to the central carbon atom of
the η3-bonded ligand1-3(eq 1) or to the metal center.4
In this paper we report on reactions of [(PPh3)2Pt(η3-
CH2CCPh)]+ with the isocyanides CNC(CH3)3 and
CNCH2Ph. In the course of these investigations we
observed that one of the products of the aforementioned
reactions, trans-[(PPh3)2Pt(η1-CH2CtCPh)(CNC(CH3)3)]+,
undergoes an unprecedented rearrangement to trans-
[(PPh3)2Pt(η1-1H-inden-2-yl)(CNC(CH3)3)]+, which was
characterized by X-ray diffraction analysis as the
In the latter reactions, η1-propargyls (e.g., with Br-), η1-
allenyls (e.g., with P(CH3)3), or both (with CO) have been
obtained (eq 2). Owing to their cationic nature, these
-
CF3SO3 salt. We also report studies on this unusual
rearrangement.
Exp er im en ta l Section
η1-hydrocarbyl complexes present themselves as poten-
tially valuable substrates for studies of ligand reactions
of η1-propargyl and η1-allenyl with a variety of nucleo-
philes.
Gen er a l P r oced u r es a n d Mea su r em en ts. All reactions
and manipulations of air- and moisture-sensitive compounds
were carried out under an atmosphere of argon or nitrogen
using standard procedures.6 Elemental analyses were per-
formed by Atlantic Microlabs, Inc, Norcross, GA. Infrared
spectra were recorded on a Perkin-Elmer Model 1760 or Model
337 spectrophotometer. 1H, 2H, 13C, and 31P NMR spectra were
recorded on a Bruker AM-250 or AC200 spectrometer. Signals
for the CtN carbon atom of the cynanide and isocyanide
ligands were not observed. 2D XHCORR spectra were obtained
on a Bruker AM-500 spectrometer.
* To whom correspondence should be addressed. M.N.A.: e-mail,
martin.ackermann@oberlin.edu; fax, 440-775-6682. A.W.: email,
wojcicki.1@osu.edu; fax, 614-292-1685.
(1) Review: Wojcicki, A. New J . Chem. 1994, 18, 61.
(2) Baize, M. W.; Blosser, P. W.; Plantevin, V.; Schimpff, D. G.;
Gallucci, J . C.; Wojcicki, A. Organometallics 1996, 15, 164 and
references therein.
(3) (a) Huang, T.-M.; Chen, J .-T.; Lee, G.-H.; Wang, Y. J . Am. Chem.
Soc. 1993, 115, 1170. (b) Huang, T.-M.; Hsu, R.-H.; Yang, C.-S.; Chen,
J .-T.; Lee, G.-H.; Wang, Y. Organometallics 1994, 13, 3657. (c) Cheng,
Y.-C.; Chen, Y.-K.; Huang, T.-M.; Yu, C.-I.; Lee, G.-H.; Wang, Y.; Chen,
J .-T. Organometallics 1998, 17, 2953 and references therein.
(4) Blosser, P. W.; Schimpff, D. G.; Gallucci, J . C.; Wojcicki, A.
Organometallics 1993, 12, 1993.
(5) Selected reviews: (a) Yamamoto, Y. Coord. Chem. Rev. 1980,
32, 193. (b) Singleton, E.; Oosthuizen, H. E. Adv. Organomet. Chem.
1983, 22, 209.
(6) Shriver, D. F.; Drezdzon, M. A. The Manipulation of Air-Sensitive
Compounds, 2nd ed.; Wiley: New York, 1986.
10.1021/om980806w CCC: $18.00 © 1999 American Chemical Society
Publication on Web 01/28/1999

788 Organometallics, Vol. 18, No. 4, 1999
Ackermann et al.
Ma ter ia ls. All solvents were purified by distillation under
nitrogen or argon from suitable drying agents. Dichloro-
methane was distilled from P4O10, benzene and THF were
distilled from sodium benzophenone ketyl, and hexanes were
distilled from calcium hydride. Reagents were obtained from
various commercial sources and were used as received unless
otherwise indicated. Literature procedures were followed to
synthesize C6H5CtCCH2Br,7 [(PPh3)2Pt(η3-CH2CCPh)]CF3SO3
(1),2 and C6D5I.8
and reprecipitated by addition of 15 mL of ether. This solid
was collected by filtration and washed with 5 mL of a 2/5
CH2Cl2/ether mixture. It then was dissolved in CH2Cl2, the
solution was filtered, the volume was reduced, and hexanes
were added to cause precipitation. The white solid was filtered
off, washed with hexanes, and dried under vacuum. The yield
of trans-[(PPh3)2Pt(CNC(CH3)3)2](CF3SO3)2 varied; the maxi-
mum was 35 mg (0.0296 mmol, 5.8%) starting from 506 mg
(0.514 mmol) of 1. 31P{1H} NMR (CD2Cl2): δ 9.80 (s, J PtP
)
The deuterated compounds C6D5CtCCH2OH,9,10 C6D5Ct
CCH2Br,7 trans-BrPt(PPh3)2(η1-CH2CtCC6D5),2 and [(PPh3)2-
Pt(η3-CH2CCC6D5)]CF3SO32 were synthesized by the methods
referenced for synthesis of the undeuterated counterparts and
2001 Hz). 1H NMR (CD2Cl2): δ 7.9-7.4 (br, Ph), 0.68 (s, CH3).
IR (Nujol): ν(CtN) 2239 cm-1. Anal. Calcd for C48H48F6N2O6P2-
PtS2: C, 48.69; H, 4.09. Found: C, 48.64; H, 4.14.
Reaction of [(P P h 3)2P t(η3-CH2CCP h )]CF3SO3 with CNC-
(CH3)3 a t 55 °C. A sample of 104 mg (0.103 mmol) of 1 was
dissolved in 5 mL of CH2ClCH2Cl. The solution was cooled to
-10 °C, and 0.36 mL of a 0.96 M solution of CNC(CH3)3 (3.4
equiv) in benzene was added dropwise. The yellow-brown
solution lightened to a paler yellow color. The solution was
heated in an oil bath at 55-60 °C for 5 h. The solution was
cooled to room temperature, and 60 mL of hexanes were added
slowly to yield a yellow precipitate. The liquid was removed,
and the solid was washed several times with hexanes and then
was dried under vacuum. The yield of trans-[(PPh3)2Pt(CN)-
(CNC(CH3)3)]CF3SO3 (5) was 78 mg (0.080 mmol, 77%).
1
were characterized by NMR spectroscopy. In each case the H
NMR spectrum was identical with that for the undeuterated
compound except for the absence of the phenyl protons of the
CCPh group.
The salts [(PPh3)2Pt(η3-CH2CCPh)]PF6 and [(PPh3)2Pt(η3-
CH2CCPh)]BF4 were obtained by substituting AgPF6 or AgBF4,
respectively, for AgCF3SO3 in the synthesis of 1.2 Proton and
31P NMR spectra in CD2Cl2 for the platinum complex were
identical with that of 1.
R ea ct ion of [(P P h 3)2P t (η3-CH 2CCP h )]CF 3SO3 w it h
CNC(CH3)3 a t -30 °C. A solution of 506 mg (0.514 mmol) of
1 in 7 mL of CH2Cl2 was cooled to -30 °C, and then 0.57 mL
of a 1.0 M solution of CNC(CH3)3 (1.1 equiv) in benzene was
added dropwise. The yellow-brown solution lightened to a paler
yellow color. After several minutes hexanes were added slowly
to the cold solution until precipitation was complete (ca. 60
mL). The liquid was removed, and the precipitate was washed
twice with 5 mL portions of hexanes. The solid was dissolved
in 7 mL of CH2Cl2 at room temperature, and ether was added
dropwise. After 16 mL had been added, the solution was stirred
while a white solid slowly precipitated. (In some cases a small
amount of a granular white precipitate appeared after the first
few milliliters of ether were added but before the main white
solid began to form. This granular solid was filtered off before
addition of ether to the solution was continued. See below for
characterization of this solid.) Further ether was added to the
solution in 3-4 mL increments, followed by stirring, until a
total of 35 mL had been added. The white solid of trans-
[(PPh3)2Pt(η1-CH2CtCPh)(CNC(CH3)3)]CF3SO3 (2) was col-
lected by filtration, washed several times with ether, and dried
under vacuum at 45-50 °C; the yield was 300 mg (0.281 mmol,
1
31P{1H} NMR (CD2Cl2): δ 12.5 (s, J PtP ) 2168 Hz). H NMR
(CD2Cl2): δ 7.6 (br, Ph), 0.69 (s, CH3). 13C{1H} NMR
(CD2Cl2): δ 134.4 (t, J PC ) 6.4 Hz, ortho Ph), 132.7 (s, para
Ph), 129.4 (t, J PC ) 5.8 Hz, meta Ph), 127.7 (t, J PC ) J PtC
)
31.4 Hz, ipso Ph), 60.9 (s, C(CH3)3), 28.2 (s, CH3). IR (Nujol)
ν(CtNC(CH3)3) 2208 cm-1, ν(CtN) 2151 cm-1. Anal. Calcd for
C43H39F3N2O3P2PtS: C, 52.82; H, 4.02. Found: C, 52.21; H,
4.35.
Rea r r a n gem en t of tr a n s-[(P P h 3)2P t(η1-CH2CtCP h )-
(CNC(CH3)3)]CF 3SO3 (2) to tr a n s-[(P P h 3)2P t(η1-1H-in d en -
2-yl)(CNC(CH3)3)]CF 3SO3 (4). A sample of 203 mg (0.191
mmol) of 2 was dissolved in 10 mL of CH2Cl2 and heated to
reflux. The reaction was monitored by 31P NMR until conver-
sion was complete (ca. 5 h). (Samples taken for NMR analysis
were returned to the reaction mixture.) The solvent volume
was reduced to 3 mL, and 20 mL of hexanes was added to
produce a precipitate. The liquid was discarded, and the
remaining solid was washed twice with 3 mL of hexanes. The
solid was dissolved in 3 mL of CH2Cl2, and 20 mL of ether
was added slowly to provide a small amount of a precipitate
which was shown by 31P NMR to be a mixture of many
components. The precipitate was removed and discarded, and
the liquid was pumped to dryness to provide trans-[(PPh3)2-
Pt(η1-1H-inden-2-yl)(CNC(CH3)3)]CF3SO3 (4) as an off-white
solid. The yield of 4 was 154 mg (0.144 mmol, 76%). 31P{1H}
1
55%). 31P{1H} NMR (CD2Cl2): δ 19.1 (s, J PtP ) 2821 Hz). H
NMR (CD2Cl2): δ 7.9-6.8 (m, Ph), 1.50 (t, J PH ) 9.1 Hz, J PtH
) 81 Hz, CH2), 0.59 (s, CH3). 13C{1H} NMR (CD2Cl2): δ 135-
128 (m, Ph), 94.0 (s, J PtC ) 74 Hz, CPh), 83.0 (s, J PtC ) 26 Hz,
CtPh), 58.9 (s, C(CH3)3), 28.4 (s, CH3), 1.5 (s, J PtC ) 474 Hz,
CH2). IR (Nujol): ν(CtN) 2213 cm-1. Anal. Calcd for C51H46F3-
NO3P2PtS: C, 57.41; H, 4.35. Found: C, 57.18; H, 4.44.
The filtrate from which 2 was separated was pumped dry
to give 138 mg of a yellow-gold solid which, by NMR, was
shown to be a mixture of 2 and the η1-allenyl complex trans-
[(PPh3)2Pt(η1-CPhdCdCH2)(CNC(CH3)3)]CF3SO3 (3). Attempts
to isolate pure 3 were unsuccessful. Spectroscopic data for 3
were obtained from the mixture. 31P{1H} NMR (CD2Cl2): δ
16.3 (s, J PtP ) 2716 Hz). 1H NMR (CD2Cl2): δ 7.9-6.8 (m, Ph),
3.42 (t, J PH ) 4.2 Hz, J PtH ) 38 Hz, CH2), 0.65 (s, CH3). 13C{1H}
NMR (CD2Cl2): δ 203.8 (t, J PC ) 4 Hz, CdCdCH2), 134-126
1
NMR (CD2Cl2): δ 14.9 (s, J PtP ) 2730 Hz). H NMR (CD2Cl2):
δ 7.8-6.7 (m, Ph, C6H4), 5.97 (t, J PtH ) 31 Hz, J PH ) 1.5 Hz,
CH), 1.84 (s, J PtH ) 11 Hz, CH2), 0.67 (s, CH3). 13C{1H} NMR
(CD2Cl2): δ 154.8 (t, J PC ) 11.7 Hz, J PtC ) 732 Hz, PtCdC),
147.6 (s, J PtC ) 61.2 Hz, PtCdCHC), 147.3 (s, J PtC ) 19.7 Hz,
PtCCH2C), 135.0 (t, J PC ) 4.7 Hz, CdCH), 134.1 (t, J PC ) 6.3
Hz, ortho Ph), 131.8 (s, para Ph), 128.9 (t, J PC ) 5.6 Hz, meta
Ph), 128.5 (t, J PC ) J PtC ) 29.4 Hz, ipso Ph), 124.7, 122.1, 121.1,
117.8 (C6H4), 58.9 (s, C(CH3)3), 45.2 (s, J PtC ) 42.0 Hz, CH2),
28.4 (s, CH3). IR (Nujol): ν(CtN) 2208 cm-1. Anal. Calcd for
C
51H46F3NO3P2PtS: C, 57.41; H, 4.35. Found: C, 57.24; H,
4.42.
In vest iga t ion s of F a ct or s Th a t Migh t Ca u se R e-
(m, Ph), 100.5 (t, J PC ) 8.6 Hz, PhCdCdCH2), 69.6 (s, J PtC
46 Hz, PhCdCdCH2), 59.4 (s, C(CH3)3), 28.7 (s, CH3). IR
(Nujol): ν(CtN) 2208 cm-1, ν(CdCdC) 1911 cm-1
)
.
a r r a n gem en t. Investigations of the effects of various sub-
stances or factors on the rearrangement of 2 to 4 were carried
out by monitoring the 31P NMR spectra of samples in sealed
NMR tubes over time. Usually a sample to be tested was
dissolved in the solvent, and the solution was divided between
two NMR tubes. One was sealed as the control sample, while
the test substance was added to the other sample. The NMR
tubes were left at room temperature. If no reaction was
occurring or if the reaction was proceeding very slowly, the
The initial granular solid that sometimes appeared in the
above procedure was purified by dissolution in 6 mL of CH2Cl2
(7) Padwa, A.; Meske, M.; Ni, Z. Tetrahedron 1995, 51, 89.
(8) J oh, T.; Doyama, K.; Fujiwara, K.; Maeshima, K.; Takahashi, S.
Organometallics 1991, 10, 508.
(9) Alami, M.; Ferri, F.; Linstrumelle, G. Tetrahedron Lett. 1993,
34, 6403.
(10) Sonogashira, K.; Tohda, Y.; Hagihara, N. Tetrahedron Lett.
1975, 4467.

Reactions of [(PPh3)2Pt(η3-CH2CCPh)]+ with Isocyanides
Organometallics, Vol. 18, No. 4, 1999 789
Ta ble 1. Cr ysta l Da ta a n d Exp er im en ta l Deta ils
for tr a n s-[(P P h 3)2P t(η1-1H-in d en -2-yl)-
(CNC(CH3)3)]CF 3SO3‚2THF (4‚2THF )
sealed NMR tubes were heated in a 55 °C oil bath for periods
of 15-60 min.
Syn th esis of [(P P h 3)2P t(η1-CH2CtCC6D5)(CNC(CH3)3)]-
CF 3SO3 a n d Its Rea r r a n gem en t to th e In d en yl Com p lex.
A sample of 0.219 g (0.223 mmol) of [(PPh3)2Pt(η3-CH2CCC6D5)]-
CF3SO3 was taken through the same sequence of steps as those
described above for the reaction of 1 with CNC(CH3)3. Products
and their purity were determined by 1H and 31P{1H} NMR
spectroscopy. The spectra of the η1-propargyl complex [(PPh3)2-
Pt(η1-CH2CtCC6D5)(CNC(CH3)3)]CF3SO3 were identical to
those of the undeuterated complex (2) except for the absence
of the phenyl protons of the η1-CH2CtCPh group in the 1H
spectrum in the 6.7-7.0 ppm range.
formula
fw
C59H62F3NO5P2PtS
1211.24
cryst syst
space group
a, Å
orthorhombic
Pnma
21.029(2)
b, Å
16.287(3)
c, Å
15.851(2)
5428.9
4
1.48
V, Å3
Z
D
calcd, g cm-3
cryst size, mm
0.12 × 0.12 × 0.23
A sample of [(PPh3)2Pt(η1-CH2CtCC6D5)(CNC(CH3)3)]CF3-
SO3 rearranged to the indenyl complex in CD2Cl2 over 2 days
µ(Mo KR), cm-1
scan type
27.31
ω
1.10
4-50
0.728-0.764
208
1
at room temperature. The H and 31P{1H} NMR spectra of the
scan range, deg (in ω)
2θ limits, deg
product were identical with those of the undeuterated com-
transmissn factors
temp, K
1
pound (4) except for the absence of signals in the H spectrum
in the 6.7-7.0 ppm range from the C6H4 protons on the indenyl
group.
scan speed, deg min-1 (in ω)
data collected
3, with up to 3 rescans
+h, +k, +l
Syn th esis of tr a n s-[(P P h 3)2P t(η1-CH2CtCP h )(CNCH2-
P h )]P F 6. The procedure was similar to that for the synthesis
of 2 and employed amounts of solvents proportional to the scale
of the reaction. Thus, a solution of 282 mg (0.288 mmol) of
[(PPh3)2Pt(η3-CH2CCPh)]PF6 in 4 mL of CH2Cl2 was cooled to
-30 °C, followed by dropwise addition of 0.58 mL of a 0.5 M
solution of CNCH2Ph in benzene. The solid isolated after
addition of excess hexanes was dissolved in 4 mL of CH2Cl2.
Slow addition of 8 mL of ether gave a white precipitate, which
was mainly the desired η1-propargyl complex. This solid was
dissolved in 1.5 mL of CH2Cl2 and reprecipitated with 8 mL
of ether. The solid was isolated, washed with ether, and
pumped dry. The yield of trans-[(PPh3)2Pt(η1-CH2CtCPh)-
(CNCH2Ph)]PF6 was 100 mg (0.091 mmol, 31%). 31P{1H} NMR
(CDCl3): δ 18.6 (s, J PtP ) 2792 Hz, PPh3), -145.2 (septet, J PF
) 713 Hz, PF6-). 1H NMR (CDCl3): δ 7.7-6.3 (m, Ph), 3.88 (s,
J PtH ) 11 Hz, CNCH2Ph), 1.55 (t, J PH ) 18 Hz, J PtH ) 81 Hz,
CH2CtCPh). 13C{1H} NMR (CDCl3): δ 135-124 (m, Ph), 94.6
(s, J PtC ) 71 Hz, CPh), 82.5 (s, J PtC ) 27 Hz, CtCPh), 47.4 (s,
CH2Ph), 0.4 (s, J PtC ) 477 Hz, CH2CtC). IR (Nujol): ν(CtN)
2255 cm-1. Anal. Calcd for C53H44F6NP3Pt: C, 58.03; H, 4.04.
Found: C, 57.85; H, 3.98.
no. of unique data
no. of unique data used in refinement
final no. of variables
R(F)b
5335
2591a
329
0.050
0.047
1.38
Rw(F)c
error in obsn of unit wt, e
With Fo > 3σ(Fo2). R(F) ) ∑||Fo| - |Fc||/∑|Fo|. c Rw(F) )
a
2
b
2
1/2
[∑w(|Fo| - |Fc|)2/∑wFo
]
with w ) 1/σ2(Fo).
Pt complex and the triflate ion each contain a mirror plane.
The indenyl ligand lies in the mirror plane and appears to be
ordered. The Pt, C(10), N, C(11), and C(12) atoms also lie in
the mirror plane. There are two solvent molecules of THF in
the asymmetric unit, and each is bisected by a mirror plane.
In each THF molecule, only the oxygen atom lies in the mirror
plane. Both THF molecules contain large thermal parameters
and were refined only isotropically. The hydrogen atoms are
included in the model at calculated positions with C-H ) 0.98
Å and fixed. The final refinement cycle was based on the 2591
intensities with I > 3σ(I) and 329 variables and resulted in
final agreement factors of R ) 0.050 and Rw ) 0.047. The final
difference electron density map contains maximum and mini-
mum peak heights of 1.19 and -1.04 e/Å3.13 The largest peaks
are in the vicinity of the THF molecules. Neutral atom
scattering factors were used15 and include terms for anomalous
dispersion.16 A summary of the crystal data and the details of
the intensity data collection and refinement are provided in
Table 1.
Cr ysta llogr a p h ic An a lysis of tr a n s-[(P P h 3)2P t(η1-1H-
in den -2-yl)(CNC(CH3)3)]CF3SO3‚2THF (4‚2THF). Clear and
colorless crystals of 4‚2THF were grown by slow evaporation
of a solution of CH2Cl2/THF. All data collection was done at
208 K with a Molecular Structure Corp. low-temperature
system. Examination of the diffraction pattern on a Rigaku
AFC5S diffractometer indicated an orthorhombic crystal sys-
tem. On the basis of the systematic absences, the space group
possibilities are restricted to Pnma and Pn21a. Unit cell
constants were obtained by a least-squares fit of the setting
angles for 25 reflections in the 2θ range 21-29° with Mo KR
radiation (λ(KR1) ) 0.709 30 Å). Six standard reflections were
measured during data collection and indicated that the crystal
was stable. Data reduction was done with the teXsan pack-
age.11 Intensity statistics strongly indicated that the space
group was centrosymmetric.
The structure was solved with the Patterson method in
SHELXS-8612 in Pnma. Expansion of the model was done with
DIRDIF.13 Full-matrix least-squares refinements based on F
were performed in teXsan;11 the function minimized was
∑w(|Fo| - |Fc|)2 with w ) 1/σ2(Fo). An analytical absorption
correction was applied to the data.14 With Z ) 4 in Pnma,
crystallographic symmetry is imposed on the structure. The
Resu lts a n d Discu ssion
The complex [(PPh3)2Pt(η3-CH2CCPh)]CF3SO3 (1) re-
acts with tert-butyl isocyanide in CH2Cl2 at or below
room temperature to give as the principal products the
η1-propargyl complex 2 and the η1-allenyl complex 3 in
about a 6-8/1 ratio (eq 3). Thus, nucleophilic addition
by isocyanide occurs at the platinum center in the
manner of the isoelectronic CO but differs in the product
ratio, which was about 1/1 with CO.4 The identification
of the products as the η1-propargyl and -allenyl com-
1
pounds follows from the H and 13C NMR data. In the
1H NMR the diagnostic resonances of the η1-propargyl
(15) Scattering factors for the non-hydrogen atoms are from: Cromer,
D. T.; Waber, J . T. International Tables for X-ray Crystallography;
Kynoch Press: Birmingham, England, 1974; Vol. IV, Table 2.2A. The
scattering factor for the hydrogen atom is from: Stewart, R. F.;
Davidson, E. R.; Simpson, W. T. J . Chem. Phys. 1965, 42, 3175.
(16) Creagh, D. C.; McAuley, W. J . In International Tables for
Crystallography; Wilson, A. J . C., Ed.; Kluwer Academic: Boston, 1992;
Vol. C, Table 4.2.6.8.
(11) teXsan: Crystal Structure Analysis Package, Version 1.7-2;
Molecular Structure Corp., The Woodlands, TX 77381, 1995.
(12) SHELXS86: Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467.
(13) DIRDIF: Parthasarathi, V.; Beurskens, P. T.; Slot, H. J . B. Acta
Crystallogr. 1983, A39, 860.
(14) De Meulenaer, J .; Tompa, H. Acta Crystallogr. 1965, 19, 1014.

790 Organometallics, Vol. 18, No. 4, 1999
Ackermann et al.
four CH carbon atoms of the six-membered ring. Iden-
tification of the remaining indenyl carbon resonances
was facilitated by a 2D XHCORR spectrum. This
spectrum was particularly important for locating the
carbon of the CH group of the five-membered indenyl
ring, which has a weak intensity and is at the low-field
edge of the phenyl carbon atoms of the PPh3 groups.
The large coupling to platinum (J PtC ) 732 Hz) for the
resonance at 154.8 ppm identifies the carbon bonded to
platinum.
and -allenyl CH2 protons are at 1.50 ppm (J PH ) 9.1
Hz, J PtH ) 81 Hz) and 3.4 ppm (J PH ) 4.2 Hz, J PtH ) 38
Hz), respectively. The relative abundance of the two
compounds is more easily obtained in the 31P{1H} NMR,
where the propargyl complex resonates at 19.1 ppm
(J PtP ) 2821 Hz) and the allenyl complex resonates at
16.3 ppm (J PtP ) 2716 Hz). The propargyl product 2 can
be isolated in pure form as a white solid by selective
precipitation, by addition of diethyl ether to a CH2Cl2
solution of the mixture; careful attention to the propor-
tion of the two solvents is essential for success. This
separation is also very sensitive to the anion involved.
The structure of the cationic platinum complex in 4
is shown in Figure 1, and selected bond lengths and
bond angles are presented in Table 2. The coordination
geometry around the Pt atom is square planar, and the
indenyl ligand lies in a mirror plane in the complex. The
C-C bond lengths in the five-membered ring show that
the double bond is localized between C(1) and C(2).
Relatively few complexes of indene in which a transition
metal is σ-bonded to the 2-carbon are known,18-22 and
even fewer, shown below, have only the simple metal-
indene bonding found in 4:18,19
-
-
Thus, reactions of the analogous BF4 and PF6 salts
of 1 with CNC(CH3)3 result in the same product mixture
of η1-propargyl and -allenyl complexes, but all attempts
to obtain the pure propargyl product by selective
precipitation were unsuccessful. However, the identity
1
of 3 as an η1-allenyl complex is confirmed by the H and
13C NMR data, which are nearly identical with those of
the analogous CO complex [(PPh3)2Pt(CO)(η1-CPhdCd
CH2)]+,4 and by the IR band at 1911 cm-1 due to the
CdCdC group.17
The rearrangement of 2 to 4 was unexpected, and the
factors that control it are not yet understood. From a
variety of studies, the only firm conclusion that can be
drawn is that the rearrangement does not occur if any
of the allenyl complex 3 is present. Thus, a sample of 2
that contains 3 shows no rearrangement even when
heated at 55 °C for several days in dichloromethane in
a sealed NMR tube; furthermore, addition of a mixture
of 2 and 3 to a sample of 2 that is undergoing re-
arrangement causes the rearrangement to cease. The
rearrangement appears to be solvent-independent, hav-
ing been observed in dichloromethane, chloroform, THF,
and 1,2-dichloroethane. Since silver ion is a possible
trace contaminant from the synthesis of 1, a few grains
of AgO3SCF3 were added to a solution of 2 in CH2Cl2.
This does enhance the rate of the rearrangement, but
not dramatically. Addition of p-toluenesulfonic acid to
test the possibility of acid catalysis did increase the rate
of loss of 2, but there were a multitude of products that
prevented the clear identification of any 4 among them.
Addition of THF saturated with KOH had no effect.
In solution pure 2 undergoes rearrangement to the
η1-indenyl complex 4. This reaction goes to completion
over times varying from a few hours to several days at
room temperature. During the conversion, NMR peaks
due to another species, presumably an intermediate,
grow and then disappear. In the 31P{1H} NMR (CD2Cl2)
a singlet appears at 15.7 ppm (J PtP ) 2791 Hz). The
proton NMR has a new peak at 0.64 ppm, assigned to
the tert-butyl group, and a singlet at 3.69 ppm that
shows coupling to platinum (J PtH ) 20 Hz). No attempt
was made to isolate this species due to its low abun-
dance in the mixture.
Identification of 4 as a 1H-inden-2-yl complex was
initially proposed on the basis of NMR data and
subsequently confirmed by a crystal structure. Several
features of the NMR spectra were particularly impor-
tant in reaching a structural assignment. In the proton
spectrum the CH vinyl proton appears at 5.97 ppm with
coupling to both platinum and phosphorus (J PtH ) 31
Hz, J PH ) 1.5 Hz). The CH2 protons resonate at 1.84
ppm and show coupling only to platinum (J PtH ) 11 Hz).
In the 13C NMR spectrum the aromatic region differs
substantially from that of the propargyl complex 2,
showing four resonances of equal intensity at 124.7,
122.1, 121.1, and 117.8 ppm which are assigned to the
Clearly any mechanistic proposals for the rearrange-
ment are speculative at this time, but catalysis by an
electrophile such as in Scheme 1 is a possibility, where
H+ or Ag+ are two possible candidates for E. This
scheme is similar to that for the [3 + 2] cycloaddition
(18) Alt, H. G.; Han, J . S.; Rogers, R. D. J . Organomet. Chem. 1993,
454, 165.
(19) Licht, E. H.; Alt, H. G.; Milius, W.; Abu-Orabi, S. J . Organomet.
Chem. 1998, 560, 69.
(20) Chen, H.; J ohnson, B. F. G.; Lewis, J .; Raithby, P. R. J . Chem.
Soc., Chem. Commun. 1990, 373.
(21) Chen, H.; Fajardo, M.; J ohnson, B. F. G.; Lewis, J .; Raithby, P.
R. J . Organomet. Chem. 1990, 389, C16.
(17) Wouters, J . M. A.; Klein, R. A.; Elsevier: C. J .; Ha¨ming, L.;
Stam, C. H. Organometallics 1994, 13, 4586.
(22) Matsuzaka, H.; Hirayama, Y.; Nishio, M.; Mizobe, Y.; Hidai,
M. Organometallics 1993, 12, 36.

Reactions of [(PPh3)2Pt(η3-CH2CCPh)]+ with Isocyanides
Organometallics, Vol. 18, No. 4, 1999 791
Sch em e 1
is obscured because of the PPh3 groups in our system.
Also, the coupling between the CH and CH2 protons
(about 4 Hz in the Ru complexes), if present, cannot be
resolved in the 3.69 ppm signal because of broadening
due to unresolved coupling with phosphorus and the
coupling to platinum. The failure of 2 to undergo
rearrangement if the allenyl complex 3 is present would
be explained if 3 reacts more rapidly with E than does
2 and thereby ties up the catalyst.
Rearrangement of 2 to 4 requires the loss of an ortho
proton from the phenyl ring on the propargyl group and
addition of a proton to the five-membered ring, presum-
ably at what becomes the CH position. Since no deute-
rium is incorporated into the indenyl group when the
rearrangement occurs in CD2Cl2 or CDCl3, these sol-
vents cannot play a role in the rearrangement. Two
other potential sources of this proton are the proton that
is in the ortho position on the phenyl ring and any
residual water in the solvent or on the glassware. Taken
together, two different experiments confirm that water
is the source of the proton.
F igu r e 1. ORTEP drawing of the cationic complex in 4‚
2THF. The non-hydrogen atoms are represented by 50%
probability thermal ellipsoids. The hydrogen atoms are
drawn as circles with an artificial radius.
Ta ble 2. Selected Bon d Dista n ces (Å) a n d Bon d
An gles (d eg) for 4‚2THF
Pt-P
2.328(2)
1.999(17)
1.50(2)
1.49(2)
1.41(2)
1.37(2)
1.41(3)
1.48(2)
1.50(2)
Pt-C(1)
2.037(15)
1.11(2)
1.34(2)
1.46(2)
1.38(2)
1.36(3)
1.39(2)
1.53(3)
Pt-C(10)
N-C(11)
C(1)-C(9)
C(3)-C(4)
C(4)-C(5)
C(6)-C(7)
C(8)-C(9)
C(11)-C(13)
N-C(10)
C(1)-C(2)
C(2)-C(3)
C(3)-C(8)
C(5)-C(6)
C(7)-C(8)
C(11)-C(12)
That water can be the source of the proton was
demonstrated by running the rearrangement reaction
in CD2Cl2 in an NMR tube that was passified with D2O
prior to use and to which a drop of D2O was added at
the start of the reaction. The relative area of the CH
signal of the five-membered ring of the resultant indenyl
product was reduced to 46% of the expected value, while
the area of the CH2 group was unaffected. The presence
of the CD group in some complexes of 4 was confirmed
P-Pt-P′a
177.1(2)
91.28(7)
179(2)
126(1)
111(2)
107(2)
119(2)
121(2)
119(2)
132(2)
177(2)
106(1)
P-Pt-C(1)
88.80(7)
174.7(7)
125(1)
108(1)
132(2)
121(2)
120(2)
119(2)
109(2)
104(1)
104(2)
P-Pt-C(10)
C(1)-Pt-C(10)
Pt-C(1)-C(2)
C(2)-C(1)-C(9)
C(2)-C(3)-C(4)
C(4)-C(3)-C(8)
C(4)-C(5)-C(6)
C(6)-C(7)-C(8)
C(3)-C(8)-C(9)
C(1)-C(9)-C(8)
N-C(11)-C(12)
C(10)-N-C(11)
Pt-C(1)-C(9)
C(1)-C(2)-C(3)
C(2)-C(3)-C(8)
C(3)-C(4)-C(5)
C(5)-C(6)-C(7)
C(3)-C(8)-C(7)
C(7)-C(8)-C(9)
Pt-C(10)-N
2
by H NMR.
To test the ortho phenyl proton as a possible source
of the CH proton in the indenyl complex, [(PPh3)2Pt(η1-
CH2CCC6D5)(CNC(CH3)3)]CF3SO3 was synthesized, in
which all of the phenyl protons on the propargyl group
have been replaced with deuterium atoms. The indenyl
complex resulting from the rearrangement of this
compound showed no incorporation of deuterium at
either the CH or CH2 positions of the five-membered
ring on the basis of relative areas of these two signals
and by 2H NMR. Hence, the proton that is lost from the
carbon of the propargyl phenyl group does not get
incorporated into the five-membered ring. Accordingly,
if the rearrangement occurs as in Scheme 1, there must
be proton exchange prior to formation of the CH bond
of the five-membered indenyl ring. The mix of CH- and
CD-containing indenyl product in the D2O experiment
must be due to incomplete removal of H2O in the
system.
N-C(11)-C(13)
a
1
P′ is related to P by the crystallographic mirror plane x, /2 -
y, z.
reaction of η1-propargyl complexes.23 The involvement
of a metal allene species would be consistent with the
transient proton NMR resonance at 3.69 ppm (J PtH
)
20 Hz) observed for a possible intermediate in the
rearrangement. This shift is close to that of 3.7 and 4.0
ppm found for two isomers of CpRu(CO)2(η2-CH2dCd
CHPh)+.24 If E is H+ in our scheme, a signal for the CH
proton also should be present. This resonance appears
at 7.3 and 7.9 ppm in the Ru complexes, a region that
When the initial reaction mixture of 1 and tert-butyl
isocyanide is heated at 55 °C in the presence of a
substantial excess of tert-butyl isocyanide, trans-[(PPh3)2-
Pt(CN)(CNC(CH3)3)]CF3SO3 (5) is obtained in high
(23) Wojcicki, A. In Fundamental Research in Organometallic
Chemistry; Tsutsui, M., Ishii, Y., Yaozeng, H., Eds.; Van Nostrand
Reinhold: New York, 1982; pp 569-597.
(24) Shuchart, C. E.; Willis, R. R.; Wojcicki, A. J . Organomet. Chem.
1992, 424, 185.

792 Organometallics, Vol. 18, No. 4, 1999
Ackermann et al.
yield. Neither 2 nor 3 remains as a product and must
have reacted further to give 5. This requires loss of the
propargyl or allenyl group and may involve formation
of trans-[(PPh3)2Pt(CNC(CH3)3)2](CF3SO3)2 as an inter-
mediate product. The latter is observed to form in small
amounts even at -30 °C when only a small excess of
isocyanide is present (see Experimental Section). De-
alkylation of one of the coordinated isocyanides of trans-
[(PPh3)2Pt(CNC(CH3)3)2](CF3SO3)2 would lead to 5. Iso-
cyanides coordinated to both Pt(II)25-27 and Pt(IV)28 are
well-known to undergo dealkylation.
exceeded the propargyl complex in abundance. However,
the intensity of the combined signals became weaker
with time even as the allenyl-to-propargyl ratio contin-
ued to grow. The solution also became discolored, and
other NMR signals began to appear. The equilibrium
interconversion of η1-propargyl and -allenyl platinum
complexes has been studied for neutral complexes of the
type trans-Pt(CH2CtCPh)(X)(PPh3)2 and is proposed to
occur via an η3-propargyl/allenyl intermediate.29 The
rate of interconversion depends on the identity of X. It
seems likely that this mechanism also could be operative
in our cationic isocyanide complexes and could account
for the appearance of the allenyl complex. However, the
slowness of the appearance of the allenyl complex and
the accompanying decompositon suggest that equilib-
rium was not attained. The reason for the failure of the
η1-propargyl complexes containing CNCH2Ph to undergo
rearrangement to an indenyl complex is not clear but
may be due to the lower basicity of the CNCH2Ph group,
which makes the propargyl group less susceptible to
electrophilic attack (see Scheme 1).23
In the interest of pursuing the generality of the above
results, reaction 3 was carried out using CNCH2Ph in
place of CNC(CH3)3. The reaction also was carried out
-
-
using the analogous BF4 and PF6 salts of 1. In all
cases H and 31P NMR spectra confirmed the production
1
of the comparable η1-propargyl and -allenyl complexes
in about the same proportion as in the reactions using
CNC(CH3)3. However, separation of the pure propargyl
-
-
complex could be achieved only in the BF4 and PF6
cases. This demonstrates the sensitivity of this separa-
tion to the nature of the coordinated isocyanide as well
as to the counterion. Neither the BF4- nor the PF6- salt
of the propargyl complex was observed to rearrange to
an indenyl product in dichloromethane solution. On long
storage in solution at room temperature, no changes
occurred in the 31P NMR spectrum. Heating a solution
as in the case of 2 resulted in a gradual reduction over
several days in the intensity of the propargyl complex
peak in the 31P NMR spectrum and the growth of the
peak due to the allenyl complex, which eventually
Ack n ow led gm en t. M.N.A. is grateful to Oberlin
College for a sabbatical leave, under which this work
was initiated at The Ohio State University. H.E.B.
thanks the Dow Chemical Foundation for summer
support through a grant to Oberlin College. This work
was supported in part by The Ohio State University.
Su p p or tin g In for m a tion Ava ila ble: Tables of bond
lengths and bond angles, atomic positional parameters, and
anisotropic displacement parameters for 4‚2THF. This ma-
terial is available free of charge via the Internet at
http://pubs.acs.org.
(25) Treichel, P. M.; Hess, R. W. J . Chem. Soc., Chem. Commun.
1970, 1626.
(26) Treichel, P. M.; Hess, R. W. J . Am. Chem. Soc. 1970, 92, 4731.
(27) Treichel, P. M.; Knebel, W. J .; Hess, R. W. J . Am. Chem. Soc.
1971, 93, 5424.
(28) Crociani, B.; Nicolini, M.; Richards, R. L. Inorg. Chim. Acta
1975, 12, 35.
OM980806W
(29) Ogoshi, S.; Fukunishi, Y.; Tsutsumi, K.; Kurosawa, H. Inorg.
Chim. Acta 1997, 265, 9.