Cyclooctadienemethylplatinum complexes: Synthesis, reactivity, molecular structure and spectroscopic properties of the organometallic hydroxoplatinum(II) complex [(COD)PtMe(OH)]

Article abstract of DOI:10.1016/S0022-328X(99)00500-8

Organometallic complexes of the type [(COD)PtMeL] (COD = 1,5-cyclooctadiene, L = Cl, I, OH, Me, -CH₂C(O)CH₃, -C≡C-Ph, pyridine, N-methyl-pyrazinium) and the dinuclear complex [{(COD)PtMe}₂(μ-C≡C-C≡C)] were prepared and characterised by ¹H-NMR spectroscopy. The crystal structures for the complexes with L = Cl, OH and Me are reported. The complex [(COD)PtMe(OH)] is a unique example of a platinum complex containing an olefin and a hydroxy ligand on the same metal centre. It reacts with C-H acidic substrates to form Pt-C bonds. Representative reactions with acetone, phenylacetylene and 1,3-butadiyne and the corresponding products are reported.

Full text of DOI:10.1016/S0022-328X(99)00500-8

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Journal of Organometallic Chemistry 592 (1999) 128–135
Cyclooctadienemethylplatinum complexes: synthesis, reactivity,
molecular structure and spectroscopic properties of the
organometallic hydroxoplatinum(II) complex [(COD)PtMe(OH)]
Axel Klein *, Karl-Wilhelm Klinkhammer, Thomas Scheiring
Institut fu¨r Anorganische Chemie, Uni6ersita¨t Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany
Received 16 June 1999; received in revised form 26 July 1999; accepted 8 August 1999
Abstract
Organometallic complexes of the type [(COD)PtMeL] (COD=1,5-cyclooctadiene, L=Cl, I, OH, Me, ꢀCH2C(O)CH3,
ꢀCꢁCꢀPh, pyridine, N-methylꢀpyrazinium) and the dinuclear complex [{(COD)PtMe}2(m-CꢁCꢀCꢁC)] were prepared and charac-
1
terised by H-NMR spectroscopy. The crystal structures for the complexes with L=Cl, OH and Me are reported. The complex
[(COD)PtMe(OH)] is a unique example of a platinum complex containing an olefin and a hydroxy ligand on the same metal
centre. It reacts with CꢀH acidic substrates to form PtꢀC bonds. Representative reactions with acetone, phenylacetylene and
1,3-butadiyne and the corresponding products are reported. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Crystal structure; Cyclooctadiene platinum complexes; Hydroxoplatinum(II)
ries) and also the strong p-acceptor ligand N-
methylꢀpyrazinium. The introduction of the hydroxy
group to form [(COD)PtMe(OH)] was also investi-
gated. This species is of special interest since hydroxo-
alkyl- or hydroxoarylplatinum complexes of the type
[(R3P)2PtR(OH)] (R=alkyl or aryl) are known to de-
protonate CꢀH acidic substrates to form PtꢀC bonds
[8,9] or to undergo insertion reactions with CO, SO2
and COS [10]. Organometallic hydroxoplatinum com-
plexes are also of relevance in catalysis, e.g. in the
transformation of olefins during the Wacker process
[11]. In this paper we report the synthesis and charac-
terisation of several compounds [(COD)PtMeL] as well
as the X-ray structures of some members of this series.
1. Introduction
Organoplatinum(II) complexes [(COD)PtRL] (R=
alkyl or aryl) with COD (1,5-cyclooctadiene) as an
easily exchangeable ligand have been known for
decades and are used as precursors for mono- and
polynuclear organometallic platinum(II) compounds
[1–3]. They are also of interest for the generation of
organoplatinum reaction centres on catalyst surfaces
for heterogeneous catalysis [4] or as potential precur-
sors for chemical vapour deposition (CVD) of platinum
[5] and also as anti-tumour agents [6]. In view of the
recent developments on the use of Group 10
organometallics in catalysis [7], it is of interest to
investigate the chemical and spectroscopic properties of
some basic molecules. Therefore a series of compounds
of the type [(COD)PtMeL] was prepared and examined,
with L representing a broad range of ligands including
weak s-donors (and p-donors) such as chlorine and
iodine, coordinating solvents like acetone, THF or
pyridine (with increasing donor capabilities in this se-
2. Experimental
2.1. Instrumentation
1H-NMR spectra were recorded on a Bruker AC 250
spectrometer. IR vibrational spectra were taken on a
Perkin–Elmer FT-IR spectrometer Paragon 1000
PC.
* Corresponding author. Tel.: +49-711-685-4235; fax: +49-711-
685-4165.
E-mail address: klein@iac.uni-stuttgart.de (A. Klein)
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00500-8

A. Klein et al. / Journal of Organometallic Chemistry 592 (1999) 128–135
129
2.2. Materials and procedures
solution to dryness. The oily brown residue was dis-
solved in 5 ml of acetone and filtered. After addition of
heptane (15 ml) an off-white oily solid was precipitated
The platinum complexes [(COD)PtCl2], [(COD)PtI2],
[(COD)PtMe2] and [(COD)PtMeCl] were prepared ac-
cording to the procedures by Clark and Manzer [1a].
[(COD)PtMeI] was obtained from [(COD)PtMeCl] us-
ing NaI. Other reagents were commercially available
and used without further purification. All preparations
and physical measurements were carried out in dried
solvents under an argon atmosphere, using Schlenk
techniques. All reactions involving silver salts were
performed under light protection.
1
and characterised by H-NMR spectroscopy; satisfac-
tory elemental analyses could not be obtained. 1H-
NMR (CD3NO2) l: 5.65 (s, 2H, 2J(PtꢀaCHꢂ)=30.8
Hz), 4.95 (s, 2H, 2J(PtꢀbCHꢂ)=90.4 Hz), 2.44–2.83
(m, 8H), 2.40 (s, 6H, acetone), 0.88 (s, 3H,
2J(PtꢀCH3)=64.33).
2.3.2. [(COD)PtMe(OH)] (4)
To a suspension of 100 mg of [(COD)PtMeCl] (0.283
mmol) in 30 ml of THF 72 mg of AgPF6 (0.285 mmol)
were added. After stirring at ambient temperature for
40 min the AgCl was filtered off and the resulting
colourless solution was treated with 20 mg KOH (0.356
mmol) in 2 ml of deaerated water. After stirring for 10
min the reaction mixture was evaporated to dryness.
The residue was dissolved in 10 ml of CH2Cl2 and
filtered. Upon evaporation of the solvent a pale brown
solid was isolated. Yield: 61 mg (0.18 mmol, 64%).
Anal. Calc. for C9H16OPt: C, 32.24; H, 4.81. Found: C,
32.08; H, 4.79%. 1H-NMR (CDCl3) l: 5.45 (s, 2H,
2.3. Preparation of complexes
2.3.1. [(COD)PtMe(acetone)](PF6) (1), [(COD)
PtMe(py)](PF6) (2) and [(COD)PtMe(Meꢀpz)]-
(PF6)2 (3)
A solution of 100 mg of [(COD)PtMeCl] (0.283
mmol) in 30 ml of acetone was mixed with 72 mg of
AgPF6 (0.285 mmol). AgCl immediately precipitated
yielding an opaque solution. Stirring was continued for
30 min at ambient temperature and AgCl was filtered
2
2J(PtꢀaCHꢂ)=33.1 Hz), 4.11 (s, 2H, J(PtꢀbCHꢂ)=65
off yielding
a
colourless solution. [(COD)PtMe-
Hz), 2.08–2.59 (m, 8H), 0.63 (s, 3H, 2J(PtꢀCH3)=
76.1), a signal for PtꢀOH was not detected [12]. IR
(CDCl3) cm−1: 3690 (m, w(PtꢀOH)), 3056, 3001, 2969,
2924, 2874, 2839, 2997 (s, w(H2ꢀC), w(HꢀCꢂ)).
(py)](PF6) (2) was prepared by adding 25 mg of
pyridine (0.30 mmol) to this solution. The mixture was
stirred for 2 h. Evaporation of the solvents gave a fine
colourless powder. Recrystallisation from acetone gave
colourless microcrystals. Yield: 96 mg (0.18 mmol,
63%). Anal. Calc. for C14H20F6NPPt: C, 31.00; H, 3.72;
2.3.3. [(COD)PtMe(CH2C(O)CH3)] (5)
Freshly prepared [(COD)PtMe(OH)] (95 mg, 0.283
mmol) obtained as above was dissolved in 10 ml of
acetone. Upon filtration and evaporation of the solvent
an off-white solid resulted. Yield: 90 mg (0.24 mmol,
85%). Anal. Calc. for C12H20OPt: C, 38.40; H, 5.37.
1
N, 2.58. Found: C, 31.09; H, 3.81; N, 2.63%. H-NMR
(acetone-d6) l: 8.91 (d, 2H, 3J(H2ꢀH3)=5.77 Hz,
H2,6ꢀpy), 8.17 (tt, 1H, 3J(H4ꢀH3)=7.97 Hz,
4J(H4ꢀH2)=1.37 Hz, H4ꢀpy), 7.80 (m, 2H, H3,5ꢀpy),
5.48 (s, 2H, 2J(PtꢀaCHꢂ)=34.1 Hz), 5.30 (s, 2H,
2J(PtꢀbCHꢂ)=72.1 Hz), 1.80–2.58 (m, 8H), 0.84 (s,
1
Found: C, 38.13; H, 5.35%. H-NMR (CDCl3) l: 5.11
(s, 2H, 2J(PtꢀaCHꢂ)=37.9 Hz), 4.77 (s, 2H,
2
3H, J(PtꢀCH3)=70.8).
2
2J(PtꢀbCHꢂ)=51 Hz), 2.80 (s, 2H, J(PtꢀCH2)=122.8
4
Hz), 2.17–2.42 (m, 8H), 2.02 (s, 3H, J(PtꢀCCCH3)=
2.3.1.1. [(COD)PtMe(Meꢀpz)](PF6)2 (3). A 70 mg
(0.293 mmol) sample of N-methylꢀpyrazinium hexa-
fluorophosphate (Meꢀpz)(PF6) was added to the filtered
solution obtained as above. A faint yellow colour ap-
peared. After stirring for 3 h the solvents were distilled
off. The yellowish grey residue was dissolved in acetone
and filtered. Slow evaporation of the solvent gave pale
yellow microcrystals. Yield: 105 mg (0.15 mmol, 53%).
Anal. Calc. for C14H22F12N2P2Pt: C, 23.91; H, 3.15; N,
2
15.8 Hz), 0.86 (s, 3H, J(PtꢀCH3)=77.1). IR (CDCl3)
cm−1: 2972, 2926, 2889, 2839, 2804 (s, w(H2ꢀC),
w(HꢀCꢂ)), 1626 (s, w(CꢂO)).
2.3.4. [(COD)PtMe(CꢁCPh)] (6)
A 20 mg (0.06 mmol) sample of [(COD)PtMe(OH)]
was dissolved in 20 ml of THF and mixed with 20 mg
of phenylacetylene (0.2 mmol). The mixture was stirred
for 1 h. Small amounts of a black solid were removed
by filtration and the clear solution evaporated to dry-
ness. The resulting brown solid was washed with hep-
tane and dried in vacuo. Yield: 18 mg (0.043 mmol,
71%). Anal. Calc. for C17H20Pt: C, 48.68; H, 4.81.
1
3.98. Found: C, 24.43; H, 3.15; N, 4.11%. H-NMR
(acetone-d6) l: 9.73 (s, 2H, H2,6ꢀMeꢀpz), 9.35 (d, 2H,
H3,5ꢀMeꢀpz), 5.60 (s, 2H, 2J(PtꢀaCHꢂ)=33.6 Hz),
5.09 (s, 2H, 2J(PtꢀbCHꢂ)=88.5 Hz), 4.78 (s, 3H,
H3Cꢀpz,) 2.37–2.80 (m, 8H), 0.79 (s, 3H,
2J(PtꢀCH3)=66.13).
1
Found: C, 48.03; H, 4.73%. H-NMR (CDCl3) l: 7.37
(d, 2H, 3J(HꢀH), o-Ph), 7.11–7.23 (m, 3H, m-Ph,
2
p-Ph), 5.51 (s, 2H, J(PtꢀaCHꢂ)=33 Hz), 4.92 (s, 2H,
2J(PtꢀbCHꢂ)=51.3 Hz), 2.28–2.53 (m, 8H), 1.03 (s,
2.3.1.2. [(COD)PtMe(acetone)](PF6) (1). The solvento
complex 1 was prepared by evaporating the filtered
2
3H, J(PtꢀCH3)=76.64).

130
A. Klein et al. / Journal of Organometallic Chemistry 592 (1999) 128–135
3. Results and discussion
2.3.5. [{(COD)PtMe}2(v-CꢁCꢀCꢁC)] (7)
A 40 mg (0.12 mmol) sample of [(COD)PtMe(OH)]
was dissolved in 50 ml of THF and mixed with ca. 0.2
ml of 1,3-butadiyne. The mixture immediately turned
yellow, then reddish–brown after 5 min and was
stirred for 1 h. The volume was reduced to 10 ml
which lead to precipitation of a black–brown material.
Filtration, extraction of the residue with two 5 ml
portions of THF and evaporation of the combined
filtrates to dryness gave a slightly brownish microcrys-
talline material. This was recrystallised twice from
CH2Cl2 and dried in vacuo yielding off-white micro-
crystals. Yield: 26 mg (0.038 mmol, 32%). Anal. Calc.
for C22H30Pt2: C, 38.59; H, 4.42. Found: C, 38.14;
H, 4.25%. 1H-NMR (CDCl3) l: 5.44 (s, 2H,
3.1. Synthesis and general properties
The cationic organoplatinum compounds [(COD)-
PtMeL]+ were prepared in high yields by reacting
[(COD)PtMeCl] with silver hexafluorophosphate and
addition of the desired nucleophile L to the intermedi-
ate solvento complex [(COD)PtMe(solvent)]+ (1) (see
Scheme 1, solvent=THF or acetone). Their identity
1
was checked by elemental analysis and H-NMR spec-
troscopy, the assignments being supported by coupling
to platinum (195Pt isotope with I=0.5 in 33.8% natu-
ral abundance, other isotopes I=0).
The organometallic hydroxoplatinum complex
[(COD)PtMe(OH)] (4) was prepared by adding KOH
2
2J(PtꢀaCHꢂ)=36.3 Hz), 4.79 (s, 2H, J(PtꢀbCHꢂ) 50.7
1
to the solvento complex. H-NMR spectra did not give
Hz), 2.15–2.60 (m, 8H), 0.92 (s, 3H, 2J(PtꢀCH3)=
77.6).
a signal for the OH proton. IR spectroscopy (in
CDCl3 solution) however showed a band at 3690
cm−1 for the OꢀH vibration. While the compounds
with pyridine or N-methylꢀpyrazinium are prepared in
acetone solution the preparation of [(COD)PtMe(OH)]
has to be performed in THF. If acetone is employed as
solvent deprotonation occurs leading to the acetonyl
complex [(COD)PtMe(CH2C(O)CH3)] (5) exclusively.
In order to confirm that the basic species is indeed the
hydroxoplatinum complex 4 and not excess KOH, a
sample of pure [(COD)PtMe(OH)] was dissolved in
2.3.6. [(bpy)PtMe(CH2C(O)CH3)] (8)
A total of 20 mg [(COD)PtMe(CH2C(O)CH3)] (5)
(0.053 mmol) and 20 mg of 2,2%-bipyridine (0.128
mmol) were dissolved in 50 ml of toluene and stirred
at 40°C for 2 days. The orange solution was evapo-
rated to give a red solid that was washed with heptane
and dried in vacuo. Yield: 21 mg (0.05 mmol, 93%).
Anal. Calc. for C14H16N2O1Pt: C, 39.72; H, 3.81; N,
1
1
acetone-d6 (99%). The H-NMR spectrum disclosed the
6.62. Found: C, 39.54; H, 3.91; N, 6.59%. H-NMR
(CDCl3) l: 9.87 (d, 1H, 3J(PtꢀH6%)=16.5 Hz,
3J(H6%ꢀH5%)=5.5 Hz), 9.15 (d, 1H, 3J(PtꢀH6)=28.8
Hz, 3J(H6ꢀH5)=6.6 Hz), 8.09 (ddd, 3J(H4%ꢀH5%)=
7.42 Hz, 3J(H4%ꢀH3%)=8.25 Hz, 4J(H4%ꢀH6%)=1.65
Hz), 8.04 (ddd, 1H, 3J(H4ꢀH5)=7.43 Hz,
formation of ca. 96% of [(COD)PtMe(CD2C(O)CD3)],
[(COD)PtMe(CDHC(O)CD3)] (triplet signal 2J(Hꢀ
D)=2.29 Hz) and [(COD)PtMe(CD2C(O)CD2H)]
2
(quintet signal J(HꢀD)=2.30 Hz), respectively (1.5%
each). This demonstrates that the hydroxoplatinum
moiety is able to deprotonate acetone (pKa=20) and
to form a PtꢀC bond even in the presence of water.
4
3J(H4ꢀH3)=7.97 Hz, J(H4ꢀH6)=1.65 Hz), 7.99 (d,
4J(H3%ꢀH5%)=1.37 Hz), 7.96 (d, 4J(H3ꢀH5)=1.38
2
Hz), 3.16 (s, 2H, J(PtꢀCH2)=124.8 Hz), 2.16 (s, 3H,
2
4J(PtꢀCCCH3)=23.37 Hz), 1.24 (s, 3H, J(PtꢀCH3)=
80.28).
2.4. General procedures for crystal structure analyses
For all three compounds data collection was per-
formed at T=173(2) K on a Siemens P4 diffractome-
,
ter with Mo–Ka radiation (u=0.71073 A) using an
empirical absorption correction („-scan; min./max.
transmission factors: [(COD)PtMe(OH)] 0.22/0.43;
[(COD)PtMe2] 0.53/0.64; [(COD)PtMeCl] 0.33/0.41).
The structures were solved by the Patterson method
using the SHELXTL-PLUS package [13] and refinement
was carried out with SHELXL-93 employing full-matrix
least-squares methods on F2 [14] with Fo2 = −3|(Fo2).
All non-hydrogen atoms were treated anisotropically,
hydrogen atoms were included by using appropriate
riding models, and H(01) of the hydroxy group on
[(COD)PtMe(OH)] was found from the Fourier map.
Scheme 1. Synthetic procedures for novel complexes [(COD)PtMeL].

A. Klein et al. / Journal of Organometallic Chemistry 592 (1999) 128–135
131
Scheme 2. Reaction of [(COD)PtMe(OH)] (4) with 1,3-butadiyne. Formation of the dinuclear (7) and mononuclear complex.
This reaction was then applied to other CꢀH acidic
compounds such as phenylacetylene (HCꢁCPh, pKa=
18.5) and 1,3-butadiyne (pKa=20.5, Scheme 2). The
first reaction yielded the PtꢀC bonded acetylide com-
plex [(COD)PtMe(CꢁCꢀPh)] (6). From the second reac-
catalyst and amine bases to abstract HCl (Hagihara or
Stille coupling) [17] or deprotonation/metathesis se-
quences using organolithium compounds [18]. Com-
parable procedures starting from RhꢀOH [19] or
RuꢀOH [20] precursors were recently reported to lead
to novel acetylide complexes. It is worth noting that
during the preparation of [(COD)PtMe2] according to
the procedure described by Clark and Manzer [1a], we
observed that the first crop of crystalline material,
obtained from the ether solution, contains two minor
tion
the
dinuclear
complex
[{(COD)PtMe}2-
(m-CꢁCꢀCꢁC)] (7) was obtained. In the crude material
prior to recrystallisation we observed a second species
1
with the following H-NMR (CDCl3) l: 5.43 (s, 2H,
2
2J(PtꢀaCHꢂ)=35 Hz), 4.93 (s, 2H, J(PtꢀbCHꢂ)=51.0
5
1
Hz), 2.20–2.53 (m, 8H), 1.97 (s 1H, J(PtꢀC4H)=11
products as inferred from H-NMR studies. One side
2
Hz), 0.95 (s, 3H, J(PtꢀCH3)=76.18). The species ap-
product is the monoalkylated [(COD)PtMeI]; the other
is [(COD)PtMe(OH)]. The latter is most likely gener-
ated during the aqueous work-up from [(COD)PtMe2]
with the formation of methane and [(COD)PtMe(OH)].
Pure [(COD)PtMeI] did not react under comparable
conditions with added KOH, thus supporting this
assumption.
peared in 1:3 ratio to the dinuclear complex (8) and we
assign this species to the monomolecular complex
[(COD)PtMe(CꢁCꢀCꢁCꢀH)]. After recrystallisation
from CH2Cl2, only traces of this compound were left in
the resulting solids but equivalent amounts of the
chloro complex [CODPtMeCl] were detected instead.
We therefore assume that the mononuclear complex is
much more labile in chlorinated solvents than the dinu-
clear complex 7.
1
3.2. H-NMR spectroscopy
The same type of reaction was described for phos-
phine-stabilised organometallic hydroxoplatinum com-
1H-NMR spectra of [(COD)PtMeL] in solution ex-
hibit broad singlets for the olefinic COD protons with
platinum satellites due to coupling to 195Pt. For unsym-
metrically substituted complexes (L"Me) two sets of
signals appear. 195Pt coupling constants to the high-field
signal (HbCꢂ) vary from 51 to 90 Hz, whereas the 195Pt
coupling of the low field signal (HaCꢂ) varies only
slightly from 31 to 38 Hz (Tables 1 and 2). The latter
signal can thus be attributed to the olefinic protons
trans to the methyl substituent in accord with the
assignment by Clark and Manzer [1a]. The variation of
the 195Pt coupling constants on the low-field position
reflects the influence of various trans located donors L.
plexes of the type [(R%P)2PtR(OH)] (R=alkyl or aryl).
3
It was shown that the hydroxy group is sufficiently
basic to deprotonate a variety of weak acids HX such
as p-MeC6H4OH, CH3C(O)CH3, CH3NO2, PhCCH,
CH3C(O)NH2, PhNHCH3 [9]. The [CODPtMe(OH)]
complex may prove to be advantageous over its phos-
phine analogues since the COD ligand is easily replaced
by other ligands L. As a first example we reacted the
acetonyl complex 5 with 2,2%-bipyridine (bpy) to obtain
the novel complex [(bpy)PtMe(CH2C(O)CH3)] (8)
(Scheme 3).
At present we are investigating this reaction as a
general methodology of forming PtꢀC bonds with HꢀC
acidic substrates. Acetylide and diacetylide complexes
of platinum have been of great interest during the past
decade as candidates for non-linear optical or liquid-
crystalline materials [15]. They may also be used to
construct platinum-containing dendrimers and poly-
mers with acetylides as rigid spacers [16]. The method-
ology described herein may prove to be a good
alternative to the now well-established methods using
platinumꢀchloro substrates, copper(I) halogenides as
Scheme 3. Reaction of complex 5 to the bipyridine complex 8 with
numbering for the bpy ligand.

132
A. Klein et al. / Journal of Organometallic Chemistry 592 (1999) 128–135
Table 1
Selected 1H-NMR data of neutral organoplatinum complexes in CDCl3 *
Compound
2J(PtꢀCH3)
2J(PtꢀaCH)
2J(PtꢀbCH)
l H3CꢀPt
l HaC
l HbC
[CODPtCl2]
[(COD)PtMeCl]
[(COD)PtMeI]
[(COD)PtMe(OH)] (4)
[(COD)PtMe(CꢁCꢀCꢁCꢀH)]
[(COD)PtMe(CꢁCꢀPh)] (6)
[(COD)PtMe(CH2C(O)CH3)] (5)
[{(COD)PtMe}2(m-CꢁCꢀCꢁC)] (7)
[(COD)PtMe2]
–
68.50
32.47
37.86
33.14
35.33
32.96
37.95
36.26
40.80
68.50
76.38
74.87
65.05
52.78
51.27
51.02
50.91
40.80
–
5.58
5.51
5.52
5.45
5.43
5.51
5.11
5.44
4.78
5.58
4.48
4.63
4.11
4.93
4.92
4.77
4.80
4.78
71.32
72.18
76.07
76.18
76.64
77.13
77.56
82.33
0.89
1.10
0.63
0.95
1.03
0.86
0.92
0.72
* Coupling constants in Hz, chemical shifts l in ppm versus TMS as standard. a,b For an assignment of the olefinic protons see text.
Table 2
Selected 1H-NMR data of cationic and neutral organoplatinum complexes in acetone-d6 *
Compound
2J(PtꢀCH3)
2J(PtꢀaCH)
2J(PtꢀbCH)
l H3CꢀPt
l HaC
l HbC
[(COD)PtMe(acetone)](PF6) (1) c
[(COD)PtMe(Meꢀpz)](PF6)2 (3)
[(COD)PtMe(py)](PF6) (2)
64.33
66.13
70.82
30.80
33.55
34.10
90.45
88.52
72.07
0.88
0.79
0.84
5.65
5.60
5.48
4.95
5.09
5.30
[(COD)PtMeI]
[(COD)PtMeCl]
[(COD)PtMe(OH)] (4)
[(COD)PtMe(CD2C(O)CD3)] (5)
[(COD)PtMe2]
73.13
72.90
68.74
78.35
83.33
38.14
32.52
31.90
37.67
41.47
74.66
74.33
73.68
51.02
41.47
0.99
0.76
0.75
0.80
0.61
5.44
5.39
5.55
5.09
4.74
4.71
4.51
4.39
4.79
4.74
* Coupling constants in Hz, chemical shifts l in ppm versus TMS as standard. a,b For an assignment of the olefinic protons see text.
c Measured in CD3NO2.
The 2J(PtꢀbCHꢂ) coupling constants as listed in Table 1
increase along the series CH3Bm-CꢁCꢀCꢁCBCH2-
C(O)CH3 B CꢁCꢀPh B CꢁCꢀCꢁCꢀH B OH B I B Cl
with decreasing donor strength of the ligand L. This
phenomenon can be attributed to the trans influence
90.5 (+118%, Table 2). This is in perfect agreement
with the cis influence of the ligand L derived from the
classical explanation using the hybridisation concept
[21].
It is worth focusing on the positioning of the 195Pt
coupling constants for the hydroxy complex 4 and the
pyridine complex 2. Although pyridine (pKa=5.25) is a
much weaker base than OH−, the 2J(PtꢀbCHꢂ) is
smaller for [CODPtMe(py)]+ than for [CODPt-
Me(OH)]. Also for the 2J(PtꢀCH3) the sequence is
py\OH. This means that OH reveals only weak trans-
and cis-influence in [CODPtMe(OH)] very much closer
to I or Cl than to the strong alkyl ligands. There is
good agreement with NMR spectroscopic results on a
series of compounds of the type [(dppe)PtMe(X)].
Alkoxide and hydroxide ligands reveal here also only
moderate to weak trans influence and the binding prop-
erties are best described as covalent linkages in the
organic solutions studied [8e,11a].
1
and was also reported for coupling constants (195Pt, H,
13C, 15N or 31P) in other square planar complexes
[8e,10e,21]. The 2J(PtꢀbCHꢂ) coupling constants for
cationic complexes are listed in Table 2. They also
increase along the series pyBMeꢀpzBacetone with
decreasing donor strength of the ligand L. The
2J(PtꢀaCHꢂ) coupling constants increase slightly with
increasing donating power of the ligand L but show no
systematic correlation. The chemical shifts of the
olefinic protons do also not correlate in a systematic
way.
The methylene protons of the COD ligand are lo-
cated at around 2 ppm as broad multiplets. The reso-
nance for the methyl substituent is found at ca. 1 ppm
as a singlet with platinum satellites. The 2J(PtꢀCH3)
coupling constants decrease with decreasing basicity of
the ligand L. The effect of the variation of L has a
different sign and is much less pronounced than for the
2J(PtꢀbCHꢂ) coupling constants. Going from L=Me
We did not succeed in locating the OH proton in
[(COD)PtMe(OH)] in solvents like CDCl3, acetone-d6
or benzene-d6 [12]. Protons of the ligand L maintain
their typical signal patterns but are generally shifted
downfield upon coordination to the (COD)PtMe frag-
ment as pyridine or N-methylꢀpyrazinium or free forms
for acetone or phenylacetylene, respectively.
2
to L=acetone the J(PtꢀCH3) coupling constants de-
crease from 41.5 to 30.8 (−23%), whereas the
2J(PtꢀbCHꢂ) coupling constants increase from 41.5 to

A. Klein et al. / Journal of Organometallic Chemistry 592 (1999) 128–135
133
Table 3
Crystallographic data and structure refinement a
Compound
[(COD)PtMe(OH)] (4)
[(COD)PtMe2]
[(COD)PtMeCl]
Empirical formula (Fw)
Space group
C9H16OPt (335.31)
P21/c
C10H18Pt (333.33)
P21/c
C9H15ClPt (353.75)
C2/c
Crystal system
Monoclinic
Monoclinic
Monoclinic
,
a (A)
8.1872(17)
18.264(5)
7.3588(18)
115.940(17)
989.5(4)
2.2511
8.1705(11)
18.222(2)
7.3452(8)
115.890(9)
983.8(2)
2.2511
14.998(3)
6.9660(10)
19.114(4)
102.03(3)
1953.1(6)
2.406
,
b (A)
,
c (A)
i (°)
3
,
V (A )
Dcalc (g cm−3
)
Z
4
4
8
Absorption coefficient v (mm−1
F(000)
)
14.127
624
14.201
624
14.578
1312
q Range (°)
2.23–30.00
2.24–30.00
2.18–29.91
Limiting indices
−115h54, −255k525,
−95l510
−115h510, −255k53,
−15l510
−205h520, −95k56,
−265l526
No. of reflections collected
No. of independent reflections
Rint
5741
2893
0.0396
3660
2869
0.0396
6464
2814
0.0846
Data/restraints/parameters
Goodness-of-fit on F2 b
Final R indices [I\2|(I)] c
R indices (all data)
2892/0/103
1.090
R1=0.0330, wR2=0.0697
R1=0.0492, wR2=0.0753
1.671 and −1.651 d
2868/0/99
1.047
R1=0.0430, wR2=0.1124
R1=0.0525, wR2=0.1194
4.597 and −3.327 d
2812/0/98
1.085
R1=0.0489, wR2=0.1257
R1=0.0543, wR2=0.1356
3.002 and −3.517 d
Largest difference peak and hole
−3
,
(e A
)
a
,
Measurement conditions: temperature 173(2) K, wavelength u=0.71073 A.
b GOF={Sw(ꢀFoꢀ −ꢀFcꢀ ) /(n−m)}0.5; n=no. of reflections; m=no. of parameters.
2
2 2
c R=(SꢀꢀFoꢀ−ꢀFcꢀꢀ)/SꢀFoꢀ, wR={S[w(ꢀFoꢀ −ꢀFcꢀ ) ]/S[w(F4o)]}0.5
.
2
2 2
d
,
Located 0.7–1.8 A beneath the Pt atom.
environment. The mean deviation from a best plane
including platinum, the methyl carbon, Cl, O or C of
the ligand L and the intermediate positions between the
3.3. Crystal structure determination of [(COD)PtMe-
(OH)], [(COD)PtMeCl] and [(COD)PtMe2]
,
,
olefinic carbons is 0.0051 A for L=Cl, 0.0225 A for
Colourless crystals (in each case cubes approx. 0.3×
0.2×0.2 mm in size) were obtained from a saturated
solution of [(COD)PtMe(OH)] or [(COD)PtMe2] in di-
ethyl ether at −30°C or upon slow evaporation of a
solution of [(COD)PtMeCl] in CHCl3. They were sub-
jected to X-ray diffraction and the structures were
solved according to procedures given in Section 2.
Results are provided in Tables 3–5. The purity of the
,
L=Me and 0.0260 A for L=OH.
The distances from platinum to the binding atom in
the ligands L increase in the series MeBOHBCl with
a rather long PtꢀO distance in [(COD)PtMe(OH)] of
Table 4
,
Bond lengths (A) of [(COD)PtMe(OH)], [(COD)PtMe2] and
[(COD)PtMeCl]
1
crystalline material was checked by H-NMR and was
generally 099%. Plots of the structures are provided in
Figs. 1 and 2.
[(COD)PtMe(OH)] [(COD)PtMe2] [(COD)PtMeCl]
Pt(1)ꢀC(1)
Pt(1)ꢀL
2.126(7)
2.134(6)
2.164(8)
The complexes [(COD)PtMe2] and [(COD)PtMe-
(OH)] both crystallise in the space group P21/c,
whereas [(COD)PtMeCl] crystallises in C2/c. This
might be due to the different crystallisation procedure.
The cell constants of the former two are very similar.
Replacement of CH3 with OH in the refinement proce-
dures gave in all cases significantly higher residuals,
therefore the assignment is unambiguous. There are no
relevant intermolecular interactions other than van der
Waals interactions and most importantly, there are no
hydrogen bridges present in [(COD)PtMe(OH)]. In all
three complexes the platinum atom has a square planar
2.194(5) (O)
2.100(6) (C)
2.216(7)
2.330(2) (Cl)
2.151(6)
Pt(1)ꢀC(14) 2.216(6)
Pt(1)ꢀC(18) 2.229(6)
Pt(1)ꢀC(13) 2.247(7)
Pt(1)ꢀC(17) 2.240(6)
C(12)ꢀC(13) 1.523(11)
C(12)ꢀC(19) 1.541(12)
C(13)ꢀC(14) 1.368(10)
C(14)ꢀC(15) 1.506(10)
C(15)ꢀC(16) 1.536(11)
C(16)ꢀC(17) 1.516(10)
C(17)ꢀC(18) 1.389(10)
C(18)ꢀC(19) 1.513(10)
2.226(8)
2.233(7)
2.253(8)
2.278(8)
2.186(8)
2.286(8)
1.504(10)
1.541(11)
1.388(12)
1.508(12)
1.531(13)
1.531(12)
1.374(11)
1.499(11)
1.513(15)
1.509(13)
1.401(11)
1.502(10)
1.516(12)
1.501(11)
1.376(11)
1.502(13)

134
A. Klein et al. / Journal of Organometallic Chemistry 592 (1999) 128–135
Table 5
Selected bond angles (°) of [(COD)PtMe(OH)], [(COD)PtMe2] and
[(COD)PtMeCl]
[(CODPtMe(OH)] [(COD)PtMe2] [(COD)PtMeCl]
C(1)ꢀPt(1)ꢀL(1)
83.7(2)
85.1(3)
96.0(3)
92.8(3)
163.3(3)
160.3(3)
95.4(3)
92.6(3)
163.9(3)
160.4(3)
80.8(3)
81.3(3)
88.1(3)
95.7(3)
86.1
85.6(3)
95.8(4)
92.2(3)
161.5(2)
160.8(2)
95.8(2)
91.8(2)
162.9(3)
162.0(3)
81.1(3)
80.8(3)
88.2(3)
95.9(3)
86.1
C(1)ꢀPt(1)ꢀC(13) 95.9(3)
C(1)ꢀPt(1)ꢀC(14) 93.0(3)
L(1)ꢀPt(1)ꢀC(13) 164.3(2)
L(1)ꢀPt(1)ꢀC(14) 159.9(2)
L(1)ꢀPt(1)ꢀC(17) 97.0(2)
L(1)ꢀPt(1)ꢀC(18) 94.1(2)
C(1)ꢀPt(1)ꢀC(17) 163.6(3)
C(1)ꢀPt(1)ꢀC(18) 160.2(3)
C(13)ꢀPt(1)ꢀC(18) 81.0(3)
C(14)ꢀPt(1)ꢀC(17) 80.7(3)
C(13)ꢀPt(1)ꢀC(17) 87.9(2)
C(14)ꢀPt(1)ꢀC(18) 95.5(3)
Fig. 2. View of [(COD)PtMe2].
Bite angle a
85.9
this and more detailed investigations of properties of
the PtꢀOH bond like exchange kinetics are necessary.
The platinum methyl distance increases across the series
MeBOHꢀCl taking for the two different methylꢀPt
a Bite angle for the COD ligand taken from averaged position for
C13ꢀC14 and C17ꢀC18, respectively.
,
distances an averaged value of 2.117 A. This correlates
with a decrease in donating power of the ligand L and
2
an increase in the J(PtꢀCH3) coupling constants in the
1H-NMR spectra. The distances between Pt and the
olefinic carbons in trans position to the methyl sub-
stituent (HaCꢂ) decrease in the same series whereas the
distances to the cis-oriented olefinic carbons (HbCꢂ)
increase. For the COD ligand no significant alternation
in the bond lengths is detected. For the complex
[(COD)PtMe2] two different PtꢀC distances and conse-
quently unequal distances from platinum to the two
sets of olefinic carbons are observed. Therefore the
molecule does not retain its C2 symmetry in the crystal.
This is in full agreement with a recent work reporting
solid state 13C-NMR data for [(COD)PtMe2] [24]. Four
different resonances were observed for the olefinic car-
bons which clearly indicates the asymmetry of this
molecule in the solid state.
Fig. 1. View of [(COD)PtMe(OH)].
,
2.194(4) A. Comparable compounds like [(dppe)Pt-
The bond angles of the three complexes do not
change significantly upon variation of the ligand L and
the bite angles of the COD chelate ligand, being taken
from the averaged positions of C13ꢀC14 and C17ꢀC18,
respectively, are also very similar (Table 5).
Me(OH)] [11a] or [(tBu2bpy)PtMe(O(H)ꢀ{B(C6F5)3}]
[22] show significantly shorter distances of 2.025(8) or
,
2.062(2) A, respectively and also shorter PtꢀC1 dis-
,
tances of 2.087(10) or 2.037(3) A, respectively. Unfortu-
nately, comparison with the latter compound is not
straightforward, since the triarylborane acceptor on the
oxygen atom will surely influence the PtꢀO distance. A
database survey gave mean values for Pt(II)ꢀOH dis-
4. Summary
,
,
tances of 2.006 A and average values of 2.107 A for
Pt(II)ꢀCH3 distances [23]. Isomorphous replacement of
OH by Cl can be excluded since the purity of the
With [(COD)PtMe(OH)] the first example of an
organotransition metal complex is presented that con-
tains a hydroxy and an olefin function bound to the
same metal centre. This addresses the still unresolved
question of how the attack of OH towards olefin com-
plex species proceeds in transition metal-catalysed oxi-
dations of olefins (e.g. in the Wacker process). The
complex [(COD)PtMe(OH)] reacts with CꢀH acidic
1
crystals (checked by H-NMR) was at least 99%. Gen-
erally it can be stated that all the PtꢀL and PtꢀCH3
distances are rather long in the present complexes,
which can be explained with a high donor strength of
the COD ligand, but the PtꢀOH is exceptionally long.
At present we cannot find a reasonable explanation for

A. Klein et al. / Journal of Organometallic Chemistry 592 (1999) 128–135
135
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compounds to form new PtꢀC bonds. This method
could be applied to the synthesis of novel platinum
acetylide complexes as was shown for some examples,
providing an alternative to established pathways.
The structural and spectroscopic characterisation of a
series of organoplatinum complexes of the type
[(COD)PtMeL] reveals interesting aspects of the elec-
tronic structure and reactivity of these compounds.
1H-NMR spectroscopy reveals that the 195Pt coupling
constants to the protons of the methyl substituent and
the olefinic groups vary with the donor strength (basic-
ity) of the ligand L as anticipated from the trans and cis
influence. The OH− ligand in [(COD)PtMe(OH)] re-
veals only weak influence in this respect. The bond
distances and bond angles taken from X-ray crystallo-
graphic studies of three of the complexes show the same
trends. The crystal structure determination of
[(COD)PtMe(OH)] reveals for the first time the molecu-
lar structure of a square planar organometallic hydroxo-
methylplatinum(II) complex with an exceptionally long
PtꢀO distance.
[12] For complexes of the type [(R% P)2PtMe(OH)] there are two
3
reports that the OꢀH resonance was found e.g. l=1.55 (dd
5. Supplementary material
2J(PtꢀH)=44.4 Hz, R% P=PPh3) [9b] or not found as for R3% P=
3
Cy3P [9c] or (R3% P)2=dppe or dppp [9c,d,e]. The same is true for
the observation of the w(OꢀH) vibration (compare Ref. [9c] with
Refs. [9e,10].
Ten Tables and four Figures describing further X-ray
structural details for [(COD)PtMe(OH)], [(COD)PtMe2]
and [(COD)PtMeCl] are available from the author
upon request.
[13] G.M. Sheldrick, SHELXTL-PLUS, An Integrated System for Solv-
ing, Refining and Displaying Crystal Structures from Diffraction
Data, Siemens Analytical X-Ray Instruments Inc., Madison, WI,
1989.
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Acknowledgements
Rainer F. Winter, Stuttgart, is acknowledged for
providing the sample of 1,3-butadiyne. Professor Dr W.
Kaim is thanked for financial support.
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