Stability and reactivity of the cis-PtIIR(alkyne) fragment (R = alkyl): An unprecedented rearrangement to form the PtII(η3-allyl) moiety

Article abstract of DOI:10.1039/a607345j

The complexes [PtR(η²-E-MeO₂CCH=CHCO₂Me)(phen)] ⁺BF₄^- (R = Me 1a or Et 1b; phen = 1,10-phenanthroline) reacted with alkynes yielding the corresponding products [PtR(η²-alkyne)(ph

Full text of DOI:10.1039/a607345j

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Stability and reactivity of the cis-PtIIR(alkyne) fragment (R = alkyl):
an unprecedented rearrangement to form the PtII(ç3-allyl) moiety
Maria E. Cucciolito,a Vincenzo De Felice,b Ida Orabona a and Francesco Ruffo*,†,a
a
Dipartimento di Chimica, Università degli Studi di Napoli ‘Federico II’, via Mezzocannone 4,
I-80134 Napoli, Italy
b Facoltà di Agraria, Università del Molise, via Tiberio 21/A, I-86100, Campobasso, Italy
The complexes [PtR(η2-E-MeO CCH᎐CHCO Me)(phen)]ϩBF Ϫ (R = Me 1a or Et 1b; phen = 1,10-
᎐
2
2
4
phenanthroline) reacted with alkynes yielding the corresponding products [PtR(η2-alkyne)(phen)]ϩBF4Ϫ 2. These
᎐
can be isolated in the case of disubstituted electron-rich alkynes, while the electron-poor MeO CC᎐CCO Me
᎐
2
2
inserted into the Pt᎐R bond leading to the corresponding σ-vinyl derivative. Type 2 complexes containing alk-1-
ynes undergo an unprecedented rearrangement to form stable [Pt(η3-allyl)(phen)]ϩBF4Ϫ products. Mechanistic
aspects of the reaction are discussed.
1
Alkyne complexes of platinum() have been known since 1945.1
A substantial upgrowth in the knowledge of their chemistry
was prompted in the early 1970s by Clark and co-workers,2
who found that the stability and reactivity of square-planar
complexes trans-[PtMeL2(η2-alkyne)]ϩ (L = phosphine) was
markedly affected by the solvent and by the nature of the
unsaturated ligand. Only with disubstituted electron-rich
alkynes it was possible to isolate the complexes,2h,i while in all
other cases further rearrangements occurred, i.e. (i) nucleo-
philic attack of the solvent,2g,i (ii) insertion reactions2a,b,i or (iii)
acetylide formation.2c,i
Little attention has been devoted to the chemistry of square-
planar platinum() complexes3 having an alkyl group and an
alkyne in mutual cis position, although this arrangement
deserves particular attention due to its proposed occurrence in
many reactive intermediates.4 As a part of our research dealing
with alkene and alkyne palladium() and platinum() deriv-
atives,5 we aimed to investigate the synthetic feasibility of cat-
ionic complexes of general formula [PtR(N,NЈ-chelate)(η2-
alkyne)]ϩ. In this paper we report the results, in comparison
with what previously found for trans-[PtMeL2(η2-alkyne)]ϩ
complexes.2 Also discussed is an unprecedented and remarkable
rearrangement of the above N,NЈ-chelate species containing
alk-1-ynes which leads to π-allyl products [Pt(η3-allyl)(N,NЈ-
chelate)]ϩ.
relevant NMR spectral features are: (i) H NMR PtMe reson-
ances fall in the range (δ 0.9–1.3) generally observed for square-
planar complexes of type [PtMe(L)(N,NЈ-chelate)];7 (ii) the two
halves of phen are not equivalent, the H2 and H9 protons of
phen coupling to 195Pt to different extents [2J(Pt᎐H) = ca. 50
and <15 Hz, respectively] with the smallest value attributed to
the proton which is close to the N atom trans to Me; (iii) the
alkyne signals also split due to coupling with 195Pt which indi-
cates that the exchange of the unsaturated ligand between dif-
ferent metal centres is slow on the NMR time-scale, in contrast
with analogous olefin complexes which undergo fast exchange
phenomena.5d
On the whole, the chemical behaviour of type 2 complexes
which contain alkynes bearing electron-donor substituents
resembles that of the analogous derivatives trans-[PtMeL2(η2-
alkyne)]ϩ described by Chisholm and Clark.2h,i In fact, no inser-
tion of the unsaturated ligand into the platinum–alkyl bond
occurs even after standing for several hours in nitromethane
solution. We recall that examples of migratory insertion of ali-
phatic alkynes into the Pt᎐Me bond are known.8 However, they
concern cycloalkynes (e.g. cyclohexyne), and the main driving
force of the reaction is probably the release of constraints
which exist in the strained ligands.
Type 1 precursors have been also treated with terminal
᎐
electron-rich alkynes (RC᎐CH). After the attainment of a
᎐
transient type 2 species [see below and path (ii)], stable η3-allyl
derivatives 3 rapidly form [path (iii)]. The NMR spectrum of
the reacting mixture recorded within a few minutes from the
addition of the alkyne to a solution of 1a or 1b discloses the
Results and Discussion
The chemistry developed in this work is depicted in Scheme 1.
The starting compounds were the recently described 5d square-
quantitative formation of the final product. Thus, reaction of 1a
with PhC᎐CH, PhCH C᎐CH or Bu C᎐CH affords respectively
planar complex [PtMe(η2-E-MeO CCH᎐CHCO Me)(phen)]ϩ-
n
᎐
᎐
᎐
᎐
2
2
᎐
᎐
᎐
2
Ϫ
[Pt(η3-CH2CHCHPh)(phen)]ϩ 3a, [Pt(η3-CH2CHCHCH2Ph)-
(phen)]ϩ 3b and [Pt(η3-CH2CHCHBun)(phen)]ϩ 3c. Analog-
ously, 1b and phenylacetylene lead to [Pt{η3-CH(Me)CHCH-
Ph}(phen)]ϩ 3d. These new complexes belong to a known class
of allyl derivatives.9 Only 3a exists in pure syn form, while in the
other cases a mixture of the syn (70–80) and anti (20–30%) com-
plexes is observed. The NMR spectral features as well as the
factors which stabilize the syn or the anti form have been dis-
cussed thoroughly elsewhere.9
BF4 1a (phen = 1,10-phenanthroline) and its related ethyl
derivative 1b. They can be prepared in situ by adding a solution
of the appropriate trialkyloxonium salt to the three-co-ordinate
complex [Pt(η2-E-MeO CCH᎐CHCO Me)(phen)]6 [path (i)].
᎐
2
2
As generally found for an electron-poor olefin, dimethyl fuma-
rate is weakly bound to the four-co-ordinate metal centre.
Hence, it can be rapidly replaced by other ligands, e.g. alkynes.
Reaction (ii) is very fast and the fate of the resulting type 2
product depends on the nature of the alkyne. Electron-rich di-
substituted alkynes afford stable complexes, in analogy with the
related trans-[PtMeL2(η2-alkyne)]ϩ derivatives.2h,i The products
can be isolated in high yield by adding diethyl ether to the
reaction mixture and have been characterized through ele-
mental analyses and NMR spectroscopy (Table 1). The most
Aiming to gain information about the mechanism of the
π-allyl formation, we have monitored the additions of Ph-
CH C᎐CH and PhC᎐CH to complex 1a through NMR spec-
troscopy at 253 K. Under these conditions type 2 complexes (2f
and 2g, respectively) can clearly be detected in the early stage of
the reaction. The reaction of 1a and 1b with deuteriophenyl-
᎐
᎐
᎐
᎐
2
† E-Mail: ruffo@chemna.dichi.unina.it
J. Chem. Soc., Dalton Trans., 1997, Pages 1351–1354
1351

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CO2Me
N
Pt
N
R2
N
CO2Me
Pt+
N
(i )
3
(iii )
R
CO2Me
N
R
N
Pt+
(ii )
Pt+
N
CR1
N
CR2
MeO2C
1a R = Me
1b R = Et
+ L
(iv )
2
L
N
Pt+
R
N
MeO2C
CO2Me
4
1
2
1
2
n
1
2
᎐
Scheme 1 (i) R3OBF4 (R = Me or Et); (ii) R C᎐CR ; (iii) R = H, R = Ph, CH2Ph, Bu ; (iv) R , R = CO2Me
᎐
Table 1 Selected NMR and analytical data for type 2 complexes
1H a [13C b] NMR (δ)
Analysis (%)c
f
f,g
᎐
Complex
H2 of phen d,e C᎐C
Pt᎐CHx
Other signalse,h
C
H
N
᎐
2
᎐
2a [PtMe(η -MeC᎐CMe)(phen)]BF4
9.36 (51, d)
9.51 (53, d)
9.37 (52, d)
9.32 (52, d)
[72.6 (162, 2 C)]
1.03 (76, 3 H)
[Ϫ10.9 (1 C)]
2.35 (49, 6 H)
[8.3 (2 C)]
38.6
(38.45)
49.1
(49.5)
44.3
(44.55)
39.75
(39.65)
3.2
(3.25)
3.35
(3.25)
3.3
(3.25)
3.45
5.45
(5.25)
4.35
(4.25)
4.75
(4.7)
4.95
᎐
2
᎐
2b [PtMe(η -PhC᎐CPh)(phen)]BF4
[82.4 (208, 2 C)]
1.23 (76, 3 H)
[Ϫ8.8 (674, 1 C)]
1.13 (77, 3 H)
[Ϫ9.8 (694, 1 C)]
1.73 (q, 83, 2 H)
[4.0 (684, 1 C)]
᎐
2
᎐
2c [PtMe(η -PhC᎐CMe)(phen)]BF4
[82.1 (1 C)]
[74.1 (1 C)]
[71.2 (216, 2 C)]
2.69 (45, 3 H)
[9.4 (1 C)]
᎐
2
᎐
2d [PtEt(η -MeC᎐CMe)(phen)]BF4
2.38 (51, 6 H)
1.03 (36, t, 3 H)
[16.5 (32, 1 C)]
[7.9 (32, 2 C)]
0.94 (33, t, 3 H)
[16.9 (33, 1 C)]
3.75 (br, 2 H)
᎐
(3.5)
(5.15)
2
᎐
2e [PtEt(η -PhC᎐CPh)(phen)]BF4
9.5 (br)
[83.2 (226, 2 C)]
1.94 (q, 81, 2 H)
[6.9 (653, 1 C)]
0.89 (73, 3 H)
1.04 (74, 3 H)
50.2
(50.25)
3.3
(3.45)
4.35
(4.2)
᎐
2
i
᎐
2f [PtMe(η -PhCH2C᎐CH)(phen)]BF4 9.18 (d)
᎐
2
i
᎐
2g [PtMe(η -PhC᎐CH)(phen)]BF4
9.28 (50, d)
᎐
a At 270 or 200 MHz and 298 K; in CD3NO2, CHD2NO2 (δ 4.33) as internal standard. b At 67.9 or 50.3 MHz and 298 K; in CD3NO2, 13CHD2NO2 (δ
62.8) as internal standard. c Calculated values in parentheses. d Refers to the proton close to the N atom trans to the alkyne. The other phen protons
f
resonate in the ranges 9.1–8.8 (H4, H7, H9), 8.3–8.0 (H3, H5, H6, H8). e 3J(Pt᎐H) Hz in parentheses (when measurable). 1J(Pt᎐C) Hz in parentheses
(when measurable). g 2J(Pt᎐H) Hz in parentheses. h 2J(Pt᎐C) Hz in parentheses. i Recorded at 253 K, see text.
᎐
acetylene (PhC᎐CD) proceeds in both cases with quantitative
resulting σ-vinyl derivative. However, as far as we know, the
insertion of terminal alkynes into platinum()–alkyl bonds has
never been reported, although η2-alk-1-yneplatinum() com-
plexes are very reactive.‡
We wish to underline that rearrangement (iii) is novel and is
of interest also because it affords a new route to π-allyl
derivatives.
᎐
deuteriation at C3 and subsequent formation of [Pt(η3-CH2-
CHCDPh)(phen)]ϩ and [Pt{η3-CH(Me)CHCDPh}(phen)]ϩ,
respectively. Furthermore, the addition of phenylacetylene to
[PtI(CD3)(phen)] in the presence of AgBF4 yields [Pt(η3-CD2-
CDCHPh)(phen)]ϩ. The position of deuteriation was clearly
deduced by comparing the 1H NMR spectra of the non-
deuteriated products with those of the corresponding labelled
compounds.
Complex 1a has been also treated with an alkyne containing
᎐
electron-withdrawing substituents, i.e. MeO CC᎐CCO Me. The
᎐
2
2
With this in mind we propose the mechanism depicted in
Scheme 2. It is suggested that a type 2 derivative is formed,
which undergoes a hydride shift. A similar migration has been
first NMR spectrum of the reaction mixture discloses that the
ϩ
᎐
proposed by Chisholm and Clark 2i and affords a Pt᎐Cϩ᎐C(H)R
‡ When PhC᎐CH was treated with trans-[PtL2LЈ(Me)] precursors,
᎐
᎐
acetylide formation 2c,i or nucleophilic attack 2g,i of the solvent to the co-
ordinated unsaturated ligand were observed. Although alk-1-ynes were
known to give stable complexes in co-ordinatively saturated environ-
ments,5b,10 only very recently a stable square-planar platinum() com-
plex has been described.11
fragment. A further rearrangement prompted by the cis geom-
etry of 5 would account for the formation of the final type 3
product. Other mechanisms may be formulated, e.g. insertion
of the alkyne into the Pt᎐Me bond and rearrangement of the
1352
J. Chem. Soc., Dalton Trans., 1997, Pages 1351–1354

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᎐
of MeO CC᎐CCO Me into the Pt᎐Me bond occurs, and 4b is
᎐
2
2
Me
CH
N
formed.
Pt+
N
Conclusion
CR
This work has extended the scant knowledge3 of alkylplat-
inum() complexes containing a cis η2-bonded alkyne, through
the study of novel species of general formula [PtR(η2-
alkyne)(phen)]ϩ 2. While in some cases the results have pointed
out a behaviour analogous to that of trans-[PtMeL2(η2-
alkyne)]ϩ complexes,2 the attainament of the cis geometry has
allowed us to observe a remarkable and unprecedented reac-
tion. More precisely, type 2 complexes containing terminal
alkynes have been observed at 253 K. As the temperature rises
they undergo a fast intramolecular rearrangement which affords
π-allyl derivatives. According to the proposed mechanism
(Scheme 2) this reaction appears to be prompted by the cis
geometry of the alkyne and of the alkyl group.
2
CH2
N
Pt
N
H
C
+
C(H)R
5
On the other hand, type 2 species are stable in the presence of
disubstituted electron-rich alkynes, which are not sufficiently
electrophilic to undergo a migratory insertion reaction. Con-
C2
C1
N
Pt+
2
ϩ
N
᎐
versely, [PtMe(η -MeO CC᎐CCO Me)(phen)] 2h, which con-
᎐
2
2
tains an electron-poor alkyne, can be detected only at 253 K,
while at room temperature the unsaturated ligand rapidly
inserts into the Pt᎐Me bond. This is in agreement with previous
studies concerning the insertion of electron-poor alkynes into
Pt᎐Me bonds.2j,3a,5b In these cases, however, η2 species similar to
2h were only invoked as intermediates, but could never be
detected.
R
C3
3
Scheme 2
reaction is poorly chemoselective. However, among unidentified
products and free dimethyl fumarate, a complex showing
asymmetric phen and a signal at δ 2.38 coupled to 195Pt
[4J(Pt᎐H) = 14 Hz] is formed in yields higher than 60%. Its
NMR features are compatible with a square-planar product
Experimental
Proton and 13C NMR spectra were recorded on a 270 MHz
NMR (Bruker model AC-270) or a 200 MHz spectrometer
(Varian model Gemini). The following abbreviations are used in
description of NMR multiplicities: app, apparent; d, doublet;
dd, double doublet; no attribute, singlet; m, multiplet; t, triplet.
[Pt{C(CO Me)᎐C(Me)CO Me}L(phen)]ϩ (L = e.g. H2O) 4a
᎐
2
2
possibly formed by cis insertion 2a,5b of the alkyne into the
Pt᎐Me bond of the elusive intermediate [PtMe(η2-Me2-
ϩ
᎐
OCC᎐CCO Me)(phen)] 2h [path (iv), Scheme 1]. The cis
arrangement of the methoxycarbonyl groups in 4a does not
allow the formation of the five-membered cyclometallated ring
The complex [Pt(η2-E-MeO CCH᎐CHCO Me)(phen)]6 and
᎐
2
᎐
2
2
13
Et3OBF4 were prepared according to literature methods.
Alkynes and Me3OBF4 are commercially available and were
used without further purification. Nitromethane§ was stored
over A4 molecular sieves. Dichloromethane was distilled from
CaCl2 immediately before use.
Pt᎐C(CO Me)᎐C(Me)C(O)OMe, similar to those previously
᎐
2
reported.6 Therefore, the empty co-ordination site resulting
from the insertion reaction must be occupied by some weak L
(e.g. H2O) donor present in solution. If MeCN is added to the
reaction mixture 4a transforms into the corresponding species
Preparations
[Pt{C(CO Me)᎐C(Me)CO Me}(MeCN)(phen)]ϩ 4b, which has
᎐
2
2
2
1
2
1
2
been identified by comparison with related products.5b No
᎐
[PtMe(ç -R C᎐CR )(phen)]BF (R = R = Me 2a or Ph 2b;
᎐
4
R1 = Me, R2 = Ph 2c). A solution of Me3OBF4 (0.030 g, 0.20
attempts have been made to isolate it in the solid state.
When the addition of Me OCC᎐CCO Me to complex 1a is
mmol) in nitromethane (1 cm3) was added to solid [Pt(η2-E-
᎐
᎐
2
2
MeO CCH᎐CHCO Me)(phen)] (0.10 g, 0.20 mmol). The
᎐
2
2
performed at 253 K the spectrum shows a fluxional product,
which is accompanied by free dimethyl fumarate. A broad sig-
nal centred at δ 0.9 is attributed to Me on Pt. Thus, it appears
that at this stage the insertion has not yet occurred, and that the
appropriate alkyne (0.20 mmol) was added to the resulting red
solution of complex 1a. Careful addition of diethyl ether (5
cm3) afforded the product as a beige glassy solid, which was
washed with diethyl ether and dried under vacuum (yield 70–
80%).
2
ϩ
᎐
product [PtMe(η -MeO CC᎐CCO Me)(phen)] 2h is detectable
᎐
2
2
by NMR spectroscopy. Its fluxionality is likely due to a fast
alkyne exchange which may occur through association of
another ligand, possibly H2O. The ability of 2h to add a fifth
ligand has been also observed by adding acetonitrile to the cold
reaction mixture. In this case the PtMe resonance sharpens and
195Pt satellites become detectable [2J(Pt᎐H) = 74 Hz]. Moreover,
the signal shifts to δ 0.60. This high-field value is very close to
that recently measured 5b (δ 0.71) for the trigonal-bipyramidal
2
1
2
[PtEt(ç -R C᎐CR )(phen)]BF (R1 = R2 = Me 2d or Ph
᎐
᎐
4
2e). A solution of Et3OBF4 (0.038 g, 0.20 mmol) in dichloro-
methane (1 cm3) was added to solid [Pt(η2-E-MeO CCH᎐
᎐
2
CHCO2Me)(phen)] (0.10 g, 0.20 mmol). The addition of the
appropriate alkyne (0.20 mmol) to the resulting red solution of
complex 1b started the precipitation of the product. Diethyl
ether (5 cm3) was slowly added to complete the precipitation of
a beige solid, which was washed with diethyl ether and dried
under vacuum (yield 70–80%).
2
ϩ
᎐
[PtMe(η -MeO CC᎐CCO Me)(MeCN)(dmphen)]
᎐
2 2
complex
(dmphen = 2,9-dimethyl-1,10-phenanthroline), the stability of
which is due to the presence of a crowded bidentate ligand.12
Therefore, we may assume that acetonitrile participates in the
dynamic process, which possibly occurs through the formation
of the substitution-labile five-co-ordinate adduct [PtMe(η2-
§ HPLC-grade nitromethane is required, since a less pure solvent was
found to contain traces of acetonitrile or propionitrile, which prevent
the attainment of complex 1a and afford only the corresponding
[PtMe(RCN)(phen)]ϩ complexes.
ϩ
᎐
MeO CC᎐CCO Me)(MeCN)(phen)] . Finally, when the reac-
tion mixture is allowed to stand at room temperature, insertion
᎐
2
2
J. Chem. Soc., Dalton Trans., 1997, Pages 1351–1354
1353

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[Pt(ç3-CH2CHCHR)(phen)]BF4 (R = Ph 3a, CH2Ph 3B or
Bun 3c). A solution of Me3OBF4 (0.030 g, 0.20 mmol) in nitro-
methane (1 cm3) was added to solid [Pt(η2-E-MeO CCH᎐
H2
R3s
R3a
R1s
᎐
2
CHCO2Me)(phen)] (0.10 g, 0.20 mmol). The appropriate
R1a
R1 = H or Me
R3 = H or Ph, CH2Ph, Bu
᎐
alkyne RC᎐CH (0.20 mmol) was added to the resulting red solu-
᎐
tion of complex 1a and the product obtained in quantitative
yield by removing the solvent under vacuum and by washing the
beige glassy solid with diethyl ether. Selected 1H NMR data (see
Scheme 3) (200 MHz, solvent CD3NO2, standard CHD2NO2,
Scheme 3
δ
4.33): 3a
δ
5.73 [1 H, d, app t, 2J(PtH2) 80,
Monitoring of the reactions through low-temperature 1H NMR
spectroscopy
3
3J(H2H3a) = 3J(H2H1a) 11.5, J(H2H1s) 7, H2], 4.45 (2 H, m, H1s
and H3a) and 3.42 [1 H, d, J(PtH2) 80, H1a]; 3b (syn) 5.15 [1
2
H, d app t, J(H2H3a) = 3J(H2H1a) 11, J(H2H1s) 7, H2], 4.4 (1
3
3
A typical procedure was as follows: a solution of Me3OBF4
(0.006 g, 0.04 mmol) in deuterionitromethane (0.6 cm3) was
H, m, H1s), 3.55 (2 H, m, PhCH2), 3.25 (1 H, dd, H1a) and 2.77
added to solid [Pt(η2-E-MeO CCH᎐CHCO Me)(phen)] (0.020
(1 H, m, H3a); 3b (anti), 5.35 [1 H, d app t, J(H2H1a) 13,
3
᎐
2
2
3J(H2H3s) = 3J(H2H1s) 7, H2] and 3.87 (2 H, m, PhCH2); 3c (syn);
5.01 [1 H, d app t, 2J(PtH2) 81, 3J(H2H3a) = 3J(H2H1a) 11,
g, 0.04 mmol). The red solution containing complex 1a was
transferred to an NMR tube, which was cooled at 253 K. The
appropriate alkyne (0.04 mmol) was added with a microsyringe
and the spectra were recorded at regular intervals of time.
3J(H2H1s) 6.5, H2], 4.15 [1 H, dd, J(H1aH1s) 2, H1s], 3.55 (1 H,
2
m, H3a), 3.01 [1 H, dd, 2J(PtH1a) 72, H1a] and 1.01 (3 H, t, Me);
3c (anti), 5.30 [1 H, d app t, 3J(H2H1a) 13, 3J(H2H3s) = 3J(H2H1s)
7, H2], 4.25 [1 H, dd, 2J(H1aH1s) 2.5 Hz, H1s], 3.18 (1 H, dd, H1a)
and 0.85 (3 H, t, Me) (Found: C, 43.8; H, 3.0; N, 4.8.
C21H17BF4N2Pt 3a requires C, 43.55; H, 2.95; N, 4.85. Found:
C, 44.45; H, 3.1; N, 4.8. C22H19BF4N2Pt 3b requires C, 44.55;
H, 3.25; N, 4.7. Found: C, 40.8; H, 3.7; N, 5.05. C19H21BF4-
N2Pt 3c requires C, 40.8; H, 3.8; N, 5.0%).
Acknowledgements
We thank the Consiglio Nazionale delle Ricerche and the Min-
istero dell’Università e della Ricerca Scientifica e Tecnologica
for financial support, the Centro Interdipartimentale di Meto-
dologie Chimico-Fisiche, Università di Napoli ‘Federico II’,
for NMR facilities, and Professor A. Panunzi for helpful
discussion.
[Pt{ç3-CH(Me)CHCHPh}(phen)]BF4 3d.
A solution of
Et3OBF4 (0.038 g, 0.20 mmol) in dichloromethane (1 cm3) was
added to solid [Pt(η2-E-MeO CCH᎐CHCO Me)(phen)] (0.10 g,
᎐
References
2
2
0.20 mmol). Phenylacetylene (0.020 g, 0.20 mmol) was added to
the resulting solution of complex 1b. Diethyl ether (5 cm3) was
slowly added to afford the product as a beige solid, which was
washed with diethyl ether and dried under vacuum (0.090 g,
1 H. Hel’man, A. D. Bukhovetz and E. Meilakh, C. R. (Dokl.) Acad.
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2 (a) H. C. Clark and R. J. Puddephatt, Inorg. Chem., 1970, 9, 2670;
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M. H. Chisholm and H. C. Clark, Chem. Commun., 1970, 763; (d)
H. C. Clark and J. D. Ruddick, Inorg. Chem., 1970, 9, 1226; (e) H. C.
Clark and R. J. Puddephatt, Inorg. Chem., 1971, 10, 18; ( f ) M. H.
Chisholm, H. C. Clark and D. H. Hunter, Chem. Commun., 1971,
809; (g) M. H. Chisholm and H. C. Clark, Inorg. Chem., 1971, 10,
1711; (h) M. H. Chisholm and H. C. Clark, Inorg. Chem., 1971, 10,
2557; (i) M. H. Chisholm and H. C. Clark, J. Am. Chem. Soc., 1972,
94, 1532; (j) M. H. Chisholm, H. C. Clark and L. E. Manzer,
Inorg. Chem., 1972, 11, 1269; (k) M. H. Chisholm and H. C. Clark,
Inorg. Chem., 1973, 12, 991; (l) T. G. Appleton, M. H. Chisholm,
H. C. Clark and K. Yasufuku, J. Am. Chem. Soc., 1974, 96, 6600.
3 (a) H. C. Clark, C. R. Jablonsky and K. Von Werner, J. Organomet.
Chem., 1974, 82, C51; (b) R. Usòn, J. Forniés, M. Tomàs,
B. Menjòn, C. Fortuño, A. J. Welch and D. E. Smith, J. Chem. Soc.,
Dalton Trans., 1993, 275.
1
76%). Selected H NMR data: syn, syn, δ 5.48 [1 H, app t,
2J(PtH2) 80, 3J(H2H3a) = 3J(H2H1a) 11, H2], 4.40 [1 H, d,
3
2J(PtH3a) 75, H3a], 3.92 [1 H, m, J(H1aHM e) 6, H1a] and 1.86
3
[3 H, d, J(PtH) 12, Me1s]; syn-Ph,, anti-Me, 5.78 [1 H, dd,
3J(H2H3a) 10, 3J(H2H1s) 6, H2], 4.73 (1 H, d, H3a) and 1.52 [3 H,
3
d, J(PtH) 12 Hz, Me1a] (Found: C, 44.35; H, 3.1; N, 4.65.
C22H19BF4N2Pt requires C, 44.55; H, 3.25; N, 4.7%).
᎐
Monitoring of the addition of MeO CC᎐CCO Me and MeCN to
᎐
2
2
complex 1a with formation of 4a and 4b
A solution of Me3OBF4 (0.006 g, 0.04 mmol) in deuterio-
nitromethane (0.6 cm3) was added to solid [Pt(η2-E-
MeO CCH᎐CHCO Me)(phen)] (0.020 g, 0.04 mmol). The red
᎐
2
2
4 J. P. Collmann, L. S. Hegedus, J. R. Norton and R. G. Finke,
Principles and Applications of Organotransition Metal Chemistry,
University Science Books, Mill Valley, CA, 1987.
solution containing complex 1a was transferred to an NMR
᎐
tube and MeO CC᎐CCO Me (0.006 g, 0.04 mmol) added with
᎐
2
2
a microsyringe. The spectrum disclosed the presence of 4a in
5 (a) V. De Felice, M. E. Cucciolito, A. De Renzi, F. Ruffo and D.
Tesauro, J. Organomet. Chem., 1995, 493, 1; (b) V. De Felice, A. De
Renzi, F. Giordano and D. Tesauro, J. Chem. Soc., Dalton Trans.,
1993, 1927; (c) M. E. Cucciolito, A. De Renzi, F. Giordano and F.
Ruffo, Organometallics, 1995, 14, 5410; (d) I. Orabona, A. Panunzi
and F. Ruffo, J. Organomet. Chem., 1996, 525, 295; (e) A. De Renzi,
I. Orabona and F. Ruffo, Inorg. Chim. Acta, in the press.
6 V. De Felice, A. De Renzi, F. Ruffo and D. Tesauro, Inorg. Chim.
Acta, 1994, 219, 169.
higher than 60% yield. Addition of MeCN (0.002 g, 0.05 mmol)
1
converted 4a into 4b. Selected H NMR data: 4a, δ 9.30 (1 H,
d), 9.25 (1 H, d), 8.90 (2 H, app d), 8.2 (4 H, m) and 2.38 [3 H,
4J(PtH) 14, C(Me)CO2Me]; 4b, 9.35 (1 H, d), 9.20 (1 H, d), 8.95
(2 H, app t), 8.22 (2 H, d), 8.20 (1 H, dd), 8.06 (1 H, dd), 2.83 [3
H, 4J(PtH) 16, MeCN] and 2.32 [3 H, 3J(PtH) 14 Hz,
C(Me)CO2Me].
7 M. E. Cucciolito, V. De Felice, A. Panunzi and A. Vitagliano,
Organometallics, 1989, 8, 1180.
8 T. G. Appleton, M. A. Bennett, A. Singh and T. Yoshida, J. Organo-
met. Chem., 1978, 154, 369.
9 M. Sjögren, S. Hansson, P. O. Norrby, B. Åkermark, M. E. Cuc-
ciolito and A. Vitagliano, Organometallics, 1992, 11, 3954 and refs.
therein.
10 H. C. Clark and L. E. Manzer, Inorg. Chem., 1974, 13, 1291.
11 D. Steinborn, M. Tschoerner, A. von Zweidorf, J. Sieler and
H. Bögel, Inorg. Chim. Acta, 1995, 234, 47.
᎐
Addition of PhC᎐CH to [PtI(CD )(phen)] in the presence of
᎐
3
AgBF4: formation of [Pt(ç3-CD2CDCHPh)(phen)]ϩ
To a solution of [Pt(η2-E-MeO CCH᎐CHCO Me)(phen)] (0.10
᎐
2
2
g, 0.20 mmol) in chloroform (3 cm3) was added an excess of
CD3I (200 µl). The solution was dried under vacuum and the
residue washed with diethyl ether affording [PtI(CD3)(phen)] in
quantitative yield. A solution of AgBF4 (0.010 g, 0.05 mmol)
᎐
and PhC᎐CH (0.005 g, 0.05 mmol) in deuterionitromethane (1
᎐
12 V. G. Albano, G. Natile and A. Panunzi, Coord. Chem. Rev., 1994,
133, 67.
13 H. Meerwein, Org. Synth., 1973, Coll. Vol. V, 1080.
cm3) was added to solid [PtI(CD3)(phen)] (0.026 g, 0.05 mmol).
After 1 h of stirring the suspension was filtered. The filtrate was
transferred to an NMR tube and the spectrum revealed the
quantitative formation of [Pt(η3-CD2CDCHPh)(phen)]ϩ.
Received 28th October 1996; Paper 6/07345J
1354
J. Chem. Soc., Dalton Trans., 1997, Pages 1351–1354