Mechanistic investigation of the thermal decomposition of Biphen(OPi-Pr)PtEt2: An entrance into C-C single bond activation?

Journal of Organometallic Chemistry 690 (2005) 5215–5236

www.elsevier.com/locate/jorganchem

Mechanistic investigation of the thermal decomposition of

Biphen(OPi-Pr)PtEt₂: An entrance into C–C single bond activation?

*

Klaus Ruhland , Eberhardt Herdtweck

TU Mu¨nchen, Department Chemie, Lehrstuhl fu¨r Anorganische Chemie, Lichtenbergstr. 4, D-85748 Garching, Germany

Received 29 January 2005; received in revised form 7 April 2005; accepted 7 April 2005

Available online 15 June 2005

Abstract

Biphen(OPi-Pr) and (COD)PtCl₂give Biphen(OPi-Pr)PtCl₂which upon treating with ethyl Grignard forms Biphen(OP-

i-Pr)PtEt₂. The thermal decomposition of Biphen(OPi-Pr)PtEt₂was investigated in the temperature range of 353–383 K. The clean

and quantitative formation of the Pt(Ethene) adduct was observed. X-ray structures of a molecule in the solid state of all three reac-

tion products and two further related complexes with phenyl ﬁngers instead of i-Pr have been determined. For the complexes with

i-Pr ﬁngers a decisive deviation from a square plane is observed in contrast to the complexes with phenyl ﬁngers. The P–Pt–P angle

increases from about 95ꢀ in Biphen(OPi-Pr)PtCl₂to about 120ꢀ in Biphen(OPi-Pr)Pt(Ethene), forcing the bridging C–C single bond

˚

of the biphenyl fragment as near as 4.17 A to the Pt center. No through-space coupling between the bridging C atoms and the Pt

center could be observed in ¹³C NMR spectroscopy. No bond lengthening of the bridging C–C single bond in the biphenyl fragment

was observed in Biphen(OPi-Pr)Pt(Ethene) in comparison to the precursor complexes. The thermal decomposition of Biphen(OP-

i-Pr)PtEt₂can be described by a ﬁrst-order kinetic and the activation parameters were determined (temperature range: 353–383 K;

DH^ꢀ= 173.8 16.2 kJ/mol and DS^ꢀ= 104.7 44.1 J/(mol K)). The reaction kinetics were also measured for perdeuterated ethyl

groups yielding in a kinetic isotopic eﬀect of 1.56 0.14 which was almost temperature-independent. Selective deuteration at a

and b position of the ethyl group, respectively, showed that b-H elimination takes place fast in comparison to the complete ther-

molysis. In the temperature range of 333–353 K only a scrambling of the deuterium atoms was found without further decomposition

(temperature range: 333–353 K; D_scramH^ꢀ= 76.1 15.2 kJ/mol, D_scramS^ꢀ= ꢀ80.7 45.5 J/(mol K) for Biphen(OPi-Pr)PtEt₂-d⁶).

The ethene is not lost during the scrambling process. The scrambling process is connected with a primary KIE decisively larger than

1.56. Biphen(OPi-Pr)Pt(Ethene) exchanges the coordinated ethene with ethene in solution as proven by labeling experiments. Both a

dissociative and an associative mechanism could be shown to take place as ethene exchange reaction by means of VT¹H NMR spec-

troscopy via line shape analysis (temperature range: 333–373 K; D_assH^ꢀ= 26.9 29.6 kJ/mol, D_assS^ꢀ= ꢀ148.0 87.5 J/(mol K), D_diss

H^ꢀ= 86.0 6.5 kJ/mol, D_dissS^ꢀ= 5.4 17.8 J/(mol K)). The Pt(0) complex formed during the dissociative loss of ethene activates

several substrates among them: O₂, H₂, H₂SiPh₂via Si–H activation, MeI presumably via forming a cationic methyl adduct and

ethane via C–H activation but it was proven that the bridging C–C single bond of the biphenyl fragment is not even temporarily

1

broken. The materials were characterized by means of H NMR, ¹³C NMR, ³¹P NMR, ¹⁹⁵Pt NMR, EA, MS, IR, X-ray analysis

and polarimetric measurement where necessary.

Keywords: Pt complexes; Reaction mechanism; C–C activation; Kinetic isotope eﬀect

1. Introduction

Despite of the growing interest in it [1], the controlled

activation and cleavage of C–C single bonds by transi-

tion metal complexes is still one of the most challenging

*

Corresponding author. Tel.: +49 89 289 13096; fax: +49 89 289

13473.

E-mail address: klaus.ruhland@ch.tum.de (K. Ruhland).

doi:10.1016/j.jorganchem.2005.04.048

5216

K. Ruhland, E. Herdtweck / Journal of Organometallic Chemistry 690 (2005) 5215–5236

and yet least well understood reactions in chemistry. The

challenging character originates from the usually low

thermodynamic stability of metal carbon bonds and

the kinetic inertness (orbital reorientation during the

cleavage) and steric protection (substituents on the car-

bon atoms) of C–C single bonds. In many of these re-

spects especially the bridging C–C single bond in

biphenyl fragments provides promising perspectives:

metal–C(sp²) bonds (formed in the process of activation)

are thermodynamically more stable than M–C(sp³)

bonds [2]. The two sp²-carbons are sterically easier

available than sp³-carbons and the orbital reorientation

energy is expected to be lower because of the participa-

tion of the phenyl p-orbitals which are ideally directed

toward the metal center. Moreover, decomposition reac-

tions, as for instance b-H elimination, after a potential

activation are not likely to occur in biphenyl fragments.

Remembering the great success of C–C coupling reac-

tions yielding in biphenyls catalyzed in general by group

10 metals and also remembering the principle of micro-

scopic reversibility the cleavage of the bridging C–C

single bond in a biphenyl fragment must for sure be

kinetically allowed. Taking all this into account, it must

come as a surprise that reports into this area are rare

and disappointing. The intermolecular reaction was only

performed successfully using the highly strained biphen-

ylene (Scheme 1) [3].

Suzuki

Kumada

Negishi

Stille

PR₃

M

R₃P

M

M: Ni, Pd, Pt

PR₃

M

R₃P

M

M: Ni, Pd, Pt

PR₃

Scheme 1.

successful examples of this strategy is that of Milstein

and co-workers [4e–h] using a pincer ligand. But even

with these additional aspects no bridging C–C single

bond in a non-strained biphenyl fragment could yet be

cleaved to our knowledge. Our idea to enhance the

chance for a C–C single bond activation was to not only

statically bring the C–C single bond near to the metal by

chelating assistance but by additionally inducing an im-

pulse of motion along the potential reaction coordinate

for the activation through the experimental settings

(Scheme 2). We decided to use the thermolysis of Pt

diethyl complexes for this purpose.

No reports about a successful activation of the bridg-

ing C–C single bond in non-strained biphenyl fragments

went into our attention, yet. The most prominent and

promising strategy to enable the activation of non-

strained C–C single bonds is to do it intramolecularely

by chelating assistance [4], forcing and ﬁxing the C–C

single bond under focus statically near to the metal cen-

ter and generating in general a favorable ﬁve-membered

ring in case of a cleavage of that bond. One of the most

The strategy may be visualized by a ‘‘shouting an ar-

row’’ picture. The arrow in this picture is either the

diethyl fragment in (1) or the coordinated ethene in (4)

in Scheme 2. The chord of the bow is the chelating

(1)

P

Pt

O

β-H elimination

(A)

P

H

(2)

Pt

Red. elimination

(B)

(5)

(4)

P

(C)

P

(D)

Pt

P

(3)

Scheme 2.

K. Ruhland, E. Herdtweck / Journal of Organometallic Chemistry 690 (2005) 5215–5236

5217

ligand. Thus, by removing the diethyl fragment (via b-H

elimination and reductive elimination) or the ethene (via

dissociation) – i.e., by shouting the arrow- the starting

Pt-complex suddenly ﬁnds itself in a situation of a

Pt(0) center with coordination number two striving for

a linear overall coordination geometry. This ‘‘relaxation

of the bow’’ induces the impulse of motion along the po-

tential reaction coordinate and oﬀers an additional driv-

ing force for a C–C single bond cleavage or activation.

As linker between the biphenyl fragment and the coordi-

nating phosphorus ‘‘hands’’ we chose an oxo-group be-

cause C–O as well as the O–P represent the shortest

bond lengths we could think of as bridging unit and,

thus, would force the C–C-single bond under focus as

close as possible to the metal center.

with triethylamine as base and at room temperature.

For the ligands [1], [2] and [4] with less electrophilic dial-

kyl ‘‘ﬁngers’’ the synthesis is done in the more polar ace-

tonitrile and at 60 ꢀC to obtain good yields. Ligands [2]

and [3] are both white solids and fairly stable to air ([3]

being more stable than [2]). Longer storage should be

done under inert gas atmosphere, though. Ligand [1] is

a colorless oil that forms macro-crystals at room tem-

perature over weeks and must be rigorously stored un-

der inert gas to prevent oxidation of the phosphorus.

The signals in ³¹P NMR for ligands [1], [2] and [4] show

up at about 146 ppm; for ligand [3] the signal is found at

113 ppm. The cis-[ligand]PtCl₂complexes were received

by ligand exchange reaction between (COD)PtCl₂and

the ligand in CH₂Cl₂at room temperature in good yields

(Scheme 4). It was checked by mass spectroscopy that

oligomerization or polymerization via intermolecular

reaction is not a concern in this reaction even if it is

worked at high concentration.

2. Results and discussion

2.1. Ligand synthesis and complexation

All complexes show C₂symmetry in NMR spectros-

copy, though, as will be shown below in the solid state

most of the complexes are found to be C₁symmetric.

The two phosphorus atoms are equivalent and the

The ligands that contain the biphenyl fragment were

synthesized according to Scheme 3.

For ligand [3] with phenyl ‘‘ﬁngers’’ on the phospho-

rus hand the synthesis is best performed in diethylether

1

coupling constant J_PPtto ¹⁹⁵Pt is about 4150 Hz prov-

ing the cis conﬁguration at the metal center [5]. After

Ph

P

Ph

OH

O

P

Et₂O

[3]

+ 2

NEt₃, RT

Cl

Ph

Alk

Alk=i-Pr, Cy

P

Alk

OH

Alk=i-Pr [1]

Alk=Cy [2]

O

P

Acetonitrile

NEt₃, 60 ˚C

+ 2

Alk=i-Pr [4]

Cl

P

Alk

Scheme 3.

R: Ph, i-Pr, Cy

R

P

R

P

R

P

R

P

R

Cl

O

EtMgCl

Et O

O

T>80 C

CH Cl

O

2

+

Pt

O

Cl

2

P

R

P

R

P

R

Scheme 4.

5218

K. Ruhland, E. Herdtweck / Journal of Organometallic Chemistry 690 (2005) 5215–5236

treatment of cis-[ligand]PtCl₂with two equivalents of

EtMgBr in diethylether the cis-[ligand]PtEt₂complex is

received for all ligands in acceptable yields (Scheme 4).

ellipsoids are drawn at the 30% probability level. Hydro-

gen atoms are omitted for clarity.

Table 1 and Scheme 6 show that a decisive structural

change takes place during the course of the synthesis

with [1] according to Scheme 4. The P–Pt–P angle in-

creases from about 95ꢀ in [1]PtCl₂to 110ꢀ in [1]PtEt₂

up to 120ꢀ in [1]Pt(Ethene). The distortion of the pseu-

do-square plane becomes larger forcing the bridging

C–C single bond of the biphenyl fragment nearer to

the Pt center, as was planned in the basic strategy. The

three X-ray structures of [1]PtCl₂, [1]PtEt₂and

[1]Pt(Ethene) can – concerning the biphenyl fragment

– be regarded as spot shots of the trajectory along the

C–C activation pathway. Table 1 and Scheme 6 also

show that for [3]PtCl₂and [3]PtEt₂the distortion away

from the pseudo-square planar geometry is much less

pronounced. It will be shown later in this paper that

there is also a great diﬀerence in the behavior of the

two complexes ([1]PtEt₂and [3]PtEt₂) concerning the

thermal decomposition.

DFT calculations in ^GAUSSIAN-03 [7] for [1]Pt(Ethene)

using diﬀerent functionals (B3LYP, B3PW91) and dif-

ferent basis sets (LANL2DZ, 6-311g(d,p) for C H O P

and Stuttgart ECP60MDF [8] for Pt) did not reproduce

the large P–Pt–P angle found by X-ray analysis for

[1]Pt(Ethene) (Table 2). For [1]PtEt₂, the P–Pt–P is also

calculated decisively too small, while in the case of

[3]PtEt₂the structure calculation is satisfactory even

on the B3LYP/LANL2DZ level. We conclude from this

that the structure of [3]PtEt₂is dominated by electronic

2.2. Structural and spectroscopic comparison of the

complexes employed

If [1]PtEt₂is heated to temperatures higher than 356

K in toluene-d⁸a clean decomposition reaction yielding

into [1]Pt(Ethene) starts (Schemes 4 and 5). This behav-

1

ior is known for related complexes [6]. Via H NMR

spectroscopy, the evolution of ethane can be detected

as a singulet at 0.76 ppm. Also, traces of free ethene

show up after some time as a singulet at 5.25 ppm.

The ³¹P NMR shows the disappearance of a peak at

1

160 ppm with a coupling constant J_PPt= 1971 Hz

belonging to the starting material in favor of a new peak

at 186 ppm with a coupling constant ¹J_PPt= 4060 Hz for

[1]Pt(Ethene) (Scheme 5).

The reaction yields quantitatively into the product

peak at 186 ppm. In some cases the reaction solution

turns darker with the reaction time, but neither ¹H

NMR nor ³¹P NMR spectroscopy give hints for signiﬁ-

cant amounts of any decomposition products. [1]Pt(Eth-

ene) can be isolated by removing the toluene in vacuo

and crystallized from hexane. An X-ray structure of a

molecule in the solid state could be received which is

shown in Scheme 6 in comparison with X-ray structures

of [1]PtCl₂, [3]PtCl₂, [3]PtEt₂and [1]PtEt₂shown as OR-

TEP style plot of the compound in the solid. Thermal

Scheme 5.

K. Ruhland, E. Herdtweck / Journal of Organometallic Chemistry 690 (2005) 5215–5236

5219

Scheme 6.

Table 1

Comparison of the most indicative structural parameters determined by X-ray analysis

[3]PtCl₂

[3]PtEt₂

[1]PtCl₂

[1]PtEt₂

2.2671(8)

[1]Pt(Ethene)

˚

Pt–P1 (A)

2.2305(6)

2.2200(8)

2.3532(6)

2.3490(8)

1.482(4)

4.824(3)

4.247(3)

2.2492(7)

2.2653(7)

2.128(3)

2.114(3)

1.491(4)

4.875(3)

4.304(3)

2.2321(12)

2.2291(11)

2.3671(12)

2.3534(12)

1.483(7)

2.2470(4)

2.1194(19)

1.488(2)

˚

Pt–P2 (A)

2.2702(9)

2.126(4)

2.135(3)

1.493(5)

4.670(3)

4.676(3)

˚

Pt–X1 (A)

˚

Pt–X2 (A)

˚

C_a–C_b(bridging) (A)

˚

Ptꢁ ꢁ ꢁC_a(bridging) (A)

4.391(4)

4.896(4)

4.170(2)

˚

Ptꢁ ꢁ ꢁC_b(bridging) (A)

P–Pt–P (ꢀ)

X–Pt–X (ꢀ)

91.92(3)

89.05(3)

91.81(3)

84.40(11)

95.52(4)

89.12(4)

109.08(3)

81.45(13)

120.27(2)

39.25(8)

Crystallographic data are given in Table 6 at the end of the paper.

Table 2

Calculated structure parameters of [1]Pt(Ethene) and the X-ray data for comparison

X-ray

2.247

B3LYP/LANL2DZ

B3LYP/6-311g(d,p)^a

B3PW91/6-311g(d,p)^a

˚

Pt–P (A)

2.404

2.134

1.458

2.315

2.140

1.435

2.287

2.120

1.437

˚

Pt–C (A)

2.119

1.424

˚

C@C (Ethene) (A)

P–Pt–P (ꢀ)

C–Pt–C (ꢀ)

a

120.3

39.3

99.7

39.9

103.2

39.2

103.3

39.6

For Pt the Stuttgart, ECP60MDF basis set was used [8].

5220

K. Ruhland, E. Herdtweck / Journal of Organometallic Chemistry 690 (2005) 5215–5236

factors while that of [1]PtEt₂and [1]Pt(Ethene) is dom-

inated by sterics. The structure of the [ligand]PtCl₂com-

plex seems to be dominated by electronic eﬀects in both

cases [1]PtCl₂and [3]PtCl₂. We propose that this is be-

cause in the latter case the decline in the trans inﬂuence

along the P–Pt–X axis is most pronounced and, thus,

leads to the strongest electronic stabilization if the

square planar geometry is realized through synergistic

electronic push/pull eﬀect.

stant is a function mainly of the ligand trans to the P

atom, the bond length P–Pt and – in chelating ligands

with two P donors – of the bond angle P–Pt–P [5]. In

1

our case the J_PPtis dominated almost completely by

the trans-ligand which itself, of course, inﬂuences the

P–Pt bond length. Switching from [1]PtCl₂with

1

¹J_PPt= 4147.2 Hz to [1]PtEt₂the J_PPtdrops to 1971.4

Hz as a consequence of the much stronger trans inﬂu-

ence of an alkyl group in comparison to Cl. In [1]Pt(Eth-

1

ene), however, J_PPtis found to be 4060.7 Hz which is

X-ray structures of a molecule in the solid have been

reported for (PPh₃)₂Pt(Ethene) [9a] and (PCy₃)₂Pt(Eth-

ene) [9b]. While the C@C bond length of coordinated

not in accordance with the assumption of two alkyl li-

gands trans to the P atoms and, thus, in contradiction

to a metallacyclopropane description.

The chemical shift in ¹⁹⁵Pt NMR spectroscopy,

unfortunately, does not allow to distinguish between

Pt(II) and Pt(0) unequivocally [5d]. A key question for

the success of the proposed strategy is: Does the Pt cen-

ter know about the existence of the bridging C atoms in

˚

ethene (1.424 A in [1]Pt(Ethene) was found to be longer

˚

in both complexes (1.434 and 1.440 A) the P–Pt–P angle

was reported to be decisively smaller (111.6ꢀ and 116.3ꢀ).

Considering the X-ray analysis data, one would think

[1]Pt(Ethene) is best described as a Pt(II) center within a

metallacyclopropane because of the pseudo-square pla-

nar structure found. The spectroscopic data tell a diﬀer-

ent story, though. In ¹³C NMR spectroscopy, the

coordinated ethene shows up at about 16 ppm as broad

pseudo-triplet. No coupling to ³¹P can be resolved in con-

trast to the Pt–CH₂carbon atom in [1]PtEt₂which shows

the expected doublet of doublets of a pseudo-triplet in

¹³C NMR spectroscopy (Fig. 1). The carbon atoms in

[1]Pt(Ethene) behave (concerning coupling and chemical

shift in ¹³C NMR spectroscopy) similar to the PtCH₂–

CH₃indicating that on the time scale of ¹³C NMR spec-

troscopy the coordinated ethene is freely rotating and,

thus, [1]Pt(Ethene) is better described as a Pt(0) complex

with coordinated ethene. The rotational behavior of eth-

ene, coordinated to Pt(0) has been studied before [10].

˚

the biphenyl fragment about 4.17 A away and can we

prove that? One criterion would be a bond lengthening

of the bridging C–C single bond in the biphenyl frag-

ment, but as Table 1 shows, this is unequivocally not ob-

served. Another possibility is to watch out for a

through-space coupling between the ¹⁹⁵Pt center and

the ¹³C nuclei of the bridging carbon atoms in the biphe-

nyl fragment potentially visible in ¹³C NMR spectros-

4

copy (a J_CPtthrough-bond coupling is too small to be

detected). That through-space coupling between Pt and

C atoms does play a role, can be seen in Fig. 1. We as-

sume that the large J_CPtcoupling of the three methyl

groups on the far left in Fig. 1 which in [1]PtCl₂is not

present (they show up as singulets each), are at least

partly due to a through-space coupling, clearly visible

in [1]PtEt₂and [1]Pt(Ethene). These methyl groups are

1

Also, the J_PPtis not in accordance with the assump-

tion of a Pt(II)–metallacyclopropane. This coupling con-

Fig. 1. Aliphatic area of the ¹³C NMR spectrum of [1]PtEt₂in toluene-d⁸.

K. Ruhland, E. Herdtweck / Journal of Organometallic Chemistry 690 (2005) 5215–5236

5221

˚

1/T [1/K]

about 3.5 A away from the Pt center. However, it was

carefully checked for [1]Pt(Ethene) and [4]Pt(Ethene)

that unequivocally no through-space coupling between

the ¹⁹⁵Pt center and the bridging C atoms of the biphe-

nyl fragment is detectable (the location of the signals for

the bridging carbon atom in the ¹³C NMR spectrum was

conﬁrmed through measurement without broad band

decoupling. The bridging carbons show up as singulets

under those conditions with a chemical shift that

unequivocally allows to distinguish them from the sec-

ond quarternary carbon atom in the molecule bound

to oxygen.) Thus, in the starting complex [1]Pt(Ethene)

(the ‘‘drawn bow’’) there is, unfortunately, no evidence

that the two reaction partners (the Pt center and the

bridging C–C single bond in the biphenyl fragment)

know of each other.

0,00265

-14

0.0027

0.00275

0.0028

-14.5

-15

R²= 0,9858

-15.5

-16

-16.5

-17

R²= 0,9771

-17.5

-18

Fig. 3. Eyring plot for the thermal decomposition of [1]PtEt₂(h) and

[1]PtEt₂-d¹⁰(}) in toluene-d⁸using the data of Table 3.

comparison to the non-deuterated compound. The IR

spectrum shows a shift of several peaks in the area of

2970 cm^ꢀ1into the region of 2200–2052 cm^ꢀ1for

[1]PtEt₂-d¹⁰and two peaks at 2310 and 2133 cm^ꢀ1for

[1]Pt(Ethene-d⁴). The result of the Eyring plot for the

perdeuterated starting material is seen in Fig. 3. Table

3 shows the quantitative data of the plot in Fig. 3.

As can be seen from Fig. 3, a signiﬁcant but small ki-

netic isotopic eﬀect (KIE) H/D of 1.56 0.14 can be

established that is almost temperature independent. A

value of 1.4 0.1 was reported for the thermolysis of

t-(PPh₃)₂Pd(CH₂CD₃)₂[11c]. Unfortunately, such small

kinetic isotopic eﬀects cannot unequivocally be inter-

preted without further investigation. A primary kinetic

2.3. Mechanistic investigation of the thermal

decomposition

The thermal decomposition of [1]PtEt₂was success-

fully described by ﬁrst-order kinetics in [1]PtEt₂shown

in Fig. 2 for two concentrations at 363 K.

The kinetics were investigated for several tempera-

tures in the range of 353–378 K to determine the activa-

tion parameters. An evaluation of the data via Eyring

plot yields in a good correlation to a straight line (Fig.

3).

From this plot the activation parameters for the ther-

mal decomposition of [1]PtEt₂were determined to be

DH^ꢀ= 173.8 16.2 kJ/mol and DS^ꢀ= 104.7 44.1 J/

(mol K) (errors are given with a conﬁdence radius of

95.4% according to Studentꢁs distribution). To get more

insight into the mechanism of this reaction the thermal

decomposition was also performed for [1]PtEt₂-d¹⁰with

perdeuterated ethyl groups. This compound was re-

ceived analogously to the non-deuterated complex using

commercial CD₃CD₂Br as starting material. The peaks

for the ethyl group and the coordinated ethene disap-

Table 3

Rate constants for the thermal decomposition of [1]PtEt₂and [1]Pt-

Et₂-d¹⁰

T (K) k_H/decompof [1]PtEt₂k_D/decompof [1]PtEt₂-d¹⁰k_H/k_D

((1/s) · 10⁴)

377

375

1.955 0.008

1.750 0.008

1.245 0.01

–

1.57 0.01

–

374.5 1.545 0.003

373 0.952 0.005

370.8 0.822 0.013

368 0.497 0.008

365.7 0.400 0.005

–

0.550 0.033

0.458 0.015

0.350 0.008

0.228 0.008

0.200 0.033

0.100 0.017

1.73 0.11

1.79 0.07

1.42 0.04

1.75 0.07

1.27 0.22

1.40 0.26

1

pear in H NMR spectroscopy. In ³¹P NMR spectros-

363

358

0.253 0.013

0.140 0.012

copy,

a slight shift (0.2 ppm) is observed in

time [min]

0

100

200

300

400

500

0

-0.2

-0.4

-0.6

-0.8

-1

c = 57.2 mg/mL

c = 120 mg/mL

i-Pr

P

i-Pr

Pt

P

i-Pr

Pt

T=363 K

O

CH

3

O

3

P

i-Pr

-1.2

i-Pr

Fig. 2. Evaluation of the thermal decomposition of [1]PtEt₂at 363 K described by ﬁrst-order kinetics at two diﬀerent concentrations of [1]PtEt₂in

toluene-d⁸.

5222

K. Ruhland, E. Herdtweck / Journal of Organometallic Chemistry 690 (2005) 5215–5236

isotopic eﬀect with small transition angle [12a] or a sec-

ondary isotopic eﬀect (especially since the KIE is found

to be almost temperature-independent [12b]) can in prin-

ciple be responsible for the behavior determined. To be

able to distinguish between these two cases we examined

the partially deuterated complexes [1]Pt(CD₂CH₃)₂-

([1]PtEt₂-d⁴) and [1]Pt(CH₂CD₃)₂([1]PtEt₂-d⁶). Both

complexes showed KIE H/D of 1.4–1.5 (measurements

at 363 K and 373 K). The reason for this contradictive

ﬁnding is a scrambling of the deuterium atoms via b-H

elimination (sub-equilibrium (A) in Scheme 2) which is

fast in comparison to the complete thermal decomposi-

tion. This can unequivocally be monitored by ³¹P NMR

spectroscopy (Scheme 7).

In the temperature range of 323–348 K the scrambling

process can be examined as the only reaction taking

place. Thermal decomposition cannot be observed in this

temperature range before completion of the scrambling.

If the scrambling process in [1]PtEt₂-d⁶is examined un-

der an atmosphere of unlabeled ethene no inﬂuence onto

the kinetics is found and the ﬁnal peak pattern in ³¹P

NMR spectroscopy is unchanged to the reaction under

argon atmosphere. This proves that the b-H elimina-

tion/re-insertion occurs exclusively intramolecularely.

The ethene does not leave the coordination sphere during

the process. This kind of scrambling behavior has been

reported before in a (PPh₃)₂Pt(Butyl)₂complex [11a,b].

For t-(PR₃)₂PdEt₂it was reported that no scrambling

takes place during the course of thermal decomposition

[11c]. If [1]PtEt₂-d⁶or [1]PtEt₂-d⁴is heated to 363 K un-

der an atmosphere of unlabeled ethene after less than 30

min the ﬁnal peak pattern (Scheme 7) is reached in the

starting material and remains constant during the further

course of the thermal decomposition while for the prod-

uct [1]Pt(Ethene) only one peak for unlabeled coordi-

nated ethene is found in contrast to 3 peaks (one large

and two small ones) that are found under argon atmo-

sphere. Thus, exchange of ethene in solution with

[1]Pt(Ethene) does take place. This will be explained in

detail below. Scheme 8 summarizes the knowledge about

sub-equilibrium (A) of Scheme 2. In both cases ([1]PtEt₂-

d⁶or [1]PtEt₂-d⁴) six isomers are possible via scrambling.

Five of them are clearly resolved in the peak pattern

shown in Scheme 7.

The scrambling is a three-step process including b-H

elimination, rotation of the coodinated ethene and re-

insertion. All these processes are, as proven before, intra-

molecular, and the overall scrambling can be described

successfully by a ﬁrst-order kinetic in [1]PtEt₂(with

k_scramꢂ k_b-Hsince the mono-ethyl complex with coordi-

nated ethene cannot be detected). The evaluation was

done by subtracting the peak pattern at time t from the

ﬁnal distribution pattern and integration of the residing

Peak for the starting material (Scheme 7). Quantitative

data for [1]PtEt₂-d⁶is listed in Table 4. An Eyring plot

is shown in Fig. 4 yielding in DH^ꢀ= 76.1 15.2 kJ/mol

and DS^ꢀ= ꢀ80.7 45.5 J/(mol K) for the overall scram-

bling process. Later in this paper will be proven that with

the scrambling process must be connected a primary KIE

much larger than 1.56. This is in accordance with our

qualitative observation that [1]PtEt₂-d⁴scrambles faster

than does [1]PtEt₂-d⁶.

These parameters are in accordance with the assump-

tion that the b-H elimination is the rate-determining step

final state

d⁶

time

final state

d⁴

i-Pr

P

O

Pt

O

P

i-Pr

166.0

165.0

164.0

163.0

162.0

161.0

160.0

159.0

158.0

157.0

156.0

155.0

154.0

153.0

(ppm)

Scheme 7.

K. Ruhland, E. Herdtweck / Journal of Organometallic Chemistry 690 (2005) 5215–5236

5223

α

(1)

α

(2)

H(D)

β

P

β

P

k_β-H

(not observed)

Pt

H(D)

Pt

k_insert

P

k_redEl

k_scram

k_rotk_rot

thermal decomposition

k_redEl

β

(1)

β

(2)

H(D)

α

P

α

P

k_β-H

(not observed)

Pt

H(D)

Pt

k_insert

k_redEl<k_scram≈k_β-H<<k_insert, k_rot

Scheme 8.

in the scrambling process (negative DS^ꢀbecause the free

rotation of the ethyl group is decreased).

Table 4

Rate constants for the deuterium scrambling in [1]PtEt₂-d⁶

A mechanism stated for the complete thermal decom-

position must explain the almost temperature-indepen-

dent KIE H/D of 1.56 and the positive activation

T (K)

K_scramin [1]PtEt-d⁶((1/s) · 10⁵)

338.5

331.5

327

7.92 0.54

4.38 0.42

2.33 0.78

1.85 0.51

entropy. Scheme

possibilities.

9

shows the most convincing

323

In pathway (a), the KIE is caused through a primary

KIE with small transition angle which is expected for an

intramolecular reductive elimination. The positive acti-

vation entropy is explained because ethane is on its

way to leave the molecule. The fact that the product 4

exchanges coordinated ethene with free ethene in solu-

tion is not a contradiction to pathway (a) as will be

shown below. In pathway (b), the KIE is explained

through a secondary KIE caused through the loss of eth-

ene (change sp³-like to sp²of the etheneꢁs carbons) as

rate determining step. A secondary KIE would be in

accordance with the almost temperature-independent

KIE which is rarely found for primary KIEꢁs [12b]. This

step is dissociative and would be in accordance with a

1/T [1/K]

0.003

0.0029

-12.8

0.00295

0.00305

0.0031

0.00315

-13

-13.2

-13.4

-13.6

-13.8

-14

-14.2

-14.4

-14.6

R²= 0.9758

Fig. 4. Eyring plot for the deuterium scrambling in [1]PtEt₂-d⁶using

the data of Table 4.

(1)

(2)

P

loss of

ethene

P

H

P

k_β-H

H

Pt

k_insert

P

rate-determining

(a)

(b)

reductive elimination

(4)

P

Pt

P

(3)

Scheme 9.

5224

K. Ruhland, E. Herdtweck / Journal of Organometallic Chemistry 690 (2005) 5215–5236

positive activation entropy, too. The reductive elimina-

tion in pathway (b) can be excluded as rate determining

step since in that case incorporation of ethene from the

solution should have been found. Also if the thermal

decomposition is carried out in pyridine-d⁵instead of

toluene-d⁸the kinetic behavior does not change signiﬁ-

cantly. If the rate-determining step was the reductive

elimination in pathway (b) generating a coordinatively

unsaturated compound in the transition state with the

ground state being coordinatively saturated, one would

have expected an acceleration of the reaction when

switching to a coordinating solvent. Performing the

thermal decomposition under 133 bar of ethene did

not inﬂuence the kinetics. From this experiment it can

be concluded that an ethene coordination/de-coordina-

tion equilibrium is not important for the rate determin-

ing step. To inﬂuence a potential transition state

including the loss of ethene (along pathway (b) in

Scheme 9), the pressure of ethene must be at least 350

bar to see a reliable eﬀect. This was, unfortunately,

out of the range we could examine. Taking all together,

our results support pathway (b) in Scheme 9 (especially

the weak temperature dependence of the KIE is easier to

understand then), but we cannot unequivocally distin-

guish between pathway (a) and (b). Taking into account

the principle of microscopic reversibility pathway (a)

seems not very likely, since it would mean that ethane

attacks directly [1]Pt(Ethene) to build [1]PtEt₂. If

[1]Pt(Ethene-d⁴) is heated to 363 K under an atmosphere

of unlabeled ethane over hours the incorporation of

(partially) unlabeled coordinated ethene is found. Thus,

sub-equilibrium (B) of Scheme 2 is reversible (Fig. 5).

Fig. 5 shows that the incorporation ofH atoms with the

time follows the order d⁴h⁰! d³h¹d²h²! d¹h³! d⁰h⁴.

From this behavior, we must conclude that the scrambling

process must be connected with a large primary KIE,

much larger than 1.56. In that case the complete equilib-

rium shown in Scheme 10 is shifted time after time to

the more and more H-atom-containing compounds with-

out forming [1]Pt)Ethene-d⁰in the ﬁrst place.

At this point it must be stated that while [2]PtEt₂and

[1]PtEt₂cannot be distinguished on the base of kinetic

measurements of the thermolysis, [3]PtEt₂shows a deci-

sively diﬀerent behavior when heated in toluene to tem-

peratures of about 350 K. If a sample of [3]PtEt₂in

toluene-d⁸is heated to temperatures of 358 K the only

change that is observed in ¹H NMR spectroscopy is that

the phenyl ﬁngers begin to rotate in the time scale of the

NMR measurement. The signals of the phenyl protons

and the signals for the CH₂-group of the ethyl ligands

broaden (T_coal= 378 K). The signal for the CH₃-group

of the ethyl ligands does not change. For an induction

period of 1 h nothing else is observed. Then an addi-

tional pseudo-triplet at about 145 ppm (¹J_PPt= 4132

7 h

0 h

4 h

5 h

8 h

d⁴

d⁰

i-Pr

P

i-Pr

CH

Pt

CD

i-Pr

2

i-Pr

P

i-Pr

CD

Pt

CD

i-Pr

P

i-Pr

CH

Pt

CH

i-Pr

P

i-Pr

CDH

Pt

P

i-Pr

CH

Pt

CHD

i-Pr

O

CH

2

3

T=363 K

2

i-Pr

+

time

O

3

CD

2

i-Pr

P

i-Pr

P

i-Pr

CHD

i-Pr

Pt

CHD

i-Pr

200 199 198 197 196 195 194 193 192 191 190 189 188 187 186 185 184 183 182 181 180 179 178 177 176 175 174 173

(ppm)

Fig. 5. ³¹P NMR of [1]Pt(Ethene-d⁴) that is heated to 363 K under an atmosphere of unlabeled ethane in toluene-d⁸.

K. Ruhland, E. Herdtweck / Journal of Organometallic Chemistry 690 (2005) 5215–5236

5225

short-living in

(I_H)

comparison to I_D

because of fast

insertion

CH₂

H

Pt

CD₂H

C

D₂

fast

back reaction

(I_H)

CD₂

short-living in

comparison to I_D

because of fast

insertion

CH₃CH₃

CH₂

H

CD₂

Pt

H

Pt

CD₂H

DH₂

C

D₂C

C

D₂

(I_H)

slower back reaction

because of

fast

back reaction

primary KIE

longer-living in

comparison to I_H

because of slower

insertion

CDH

CD₂

D

CDH

Pt

CH₃CH₃

Pt

DH₂

D₂C

C

D₂

(I_D)

slower back reaction

because of

primary KIE

longer-living in

comparison to I_H

because of slower

insertion

CH₂

CD₂

D

CH₂

Pt

CH₃CH₃

etc.

Pt

D₂C

(I_D)

Scheme 10.

Hz) appears in the ³¹P NMR spectrum and the peaks of

the ethyl ligands disappear slowly in the ¹H NMR spec-

trum. Peaks of free ethane and ethene show up. How-

ever, the reaction does not go cleanly to completion

and it must be concluded that the new product (most

likely [3]Pt(Ethene)) is not stable. This behavior is not

yet well understood.

As was mentioned the product of the thermal decom-

position, [1]Pt(Ethene), exchanges the coordinated eth-

ene with ethene in solution. This exchange does not

only occur during the course of the thermal decomposi-

tion. If [1]Pt(Ethene-d⁴) dissolved in toluene is left under

an atmosphere of unlabeled ethene, exchange of the

coordinated ethene-d⁴by unlabeled ethene is observed

at room temperature after 30 min. We were interested

whether this exchange is a dissociative or an associative

process since this is essential for our basic strategy out-

lined in Scheme 2. If the process is dissociative, com-

pound 3 in Scheme 2 must at least be temporarily

available and, thus the entrance to sub-equilibrium (D)

in Scheme 2 is open. As can be seen from Fig. 6 which

shows an excerpt of the ¹H NMR spectrum of [1]Pt(Eth-

ene) in the range of 1.5–5.5 ppm at diﬀerent tempera-

tures, this investigation could be done by ¹H-VT

NMR measurement through line shape analysis.

line width at half height of the peak of free ethene which

was found to be 2.75 Hz. The measurement was done at

diﬀerent concentrations of ethene. The concentration of

it was received via integration of the peak for free ethene

and that of coordinated ethene (Fig. 6). The latter con-

centration was known through the experimental settings.

The evaluation was performed analogously to a similar

exchange problem (exchange of the center metal in crown

ethers) which is published [13]. The line shape of the peak

of free ethene was ﬁtted using the equations in [13b,c].

The parameters to be ﬁtted were the intensity of the peak

and the averaged life time s over both positions (free and

coordinated ethene) as described in [13b,c]. Table 5

shows the s values received from the curve ﬁt at diﬀerent

concentrations of ethene and diﬀerent temperatures. Fig.

7 shows an example of the curve ﬁt.

Using Eq. (1) [13a], both the associative and the dis-

sociative kinetic parameters for the exchange of ethene

in [1]Pt(Ethene) could be extracted (Table 5)

1=ðs½etheneꢃ Þ ¼ k_diss=½etheneꢃ þ k_ass

.

ð1Þ

total

free

Fig. 8 shows the plots according to Eq. (1) and Fig. 9

shows the Eyring plot using the data of Table 5. It

should be pointed out that the large uncertainty for

the k_assvalues is an intrinsic problem of a curve ﬁt in

which the experimental data show up as inverse param-

eters (1/(s [ethene]_total), 1/[ethene]_free).

Fig. 6 shows that with increasing temperature both the

peak for free ethene at 5.25 ppm and that for coordinated

ethene at 1.8 ppm begin to broaden more and more. Free

ethene alone, dissolved in toluene-d⁸, did not show any

broadening when performing the same measurement.

This control experiment also served to receive the natural

From Fig. 9 the activation parameters D_dissH^ꢀ=

86.0 6.5 kJ/mol and D_dissS^ꢀ= 5.4 17.8 J/(mol K) as

well as

D D

_assH^ꢀ= 26.9 29.6 kJ/mol and _assS^ꢀ=

ꢀ148.0 87.5 J/(mol K) are received. These values are

5226

K. Ruhland, E. Herdtweck / Journal of Organometallic Chemistry 690 (2005) 5215–5236

Fig. 6. ¹H NMR spectrum of [1]Pt(Ethene) with added free ethene at diﬀerent temperatures.

in accordance with the expectation that the dissociative

barrier should be enthalpically dominated with a posi-

tive activation entropy while in the associative pathway

the barrier is entropically dominated with a low activa-

tion enthalpy. It is to be mentioned that D_scramH^ꢀin

[1]PtEt₂is lower than D_dissH^ꢀis in [1]Pt(Ethene). This

can be taken as an additional explanation why the

scrambling in [1]PtEt₂occurs strictly intramolecularely,

though the electronic situation in both cases is, of

course, not completely comparable. We had expected

²J_PHtrans= 31.8 Hz), but it is not stable enough to be iso-

lated. If [1]Pt(Ethene) is stirred at room temperature with

excess of H₂SiPh₂, [1]Pt(H)(SiHPh₂) is formed quantita-

tively (d_Pa= 181.5 ppm, d_Pb= 190.9 ppm ¹J_PaPt= 1961.6

1

Hz, J_PbPt= 2867.0 Hz, ²J_PaPb= 22.7 Hz (P_atrans to H,

P_btrans to SiHPh₂), d_H= ꢀ2.78 ppm, ¹J_PtH= 844.3 Hz,

2

²J_PHcis= 161.8 Hz, J_PHtrans= 31.9 Hz). If [1]Pt(Ethene)

is treated with 1 eq of MeI the slow appearance of a new

broad pseudo-triplet in ³¹P NMR spectroscopy is ob-

served at 153.5 ppm (¹J_PPt= 3101.7 Hz) in the range of

minutes, which is accompanied with a broad pseudo-

triplet in the ¹H NMR spectrum at ꢀ12.5 ppm

(ⁿJ_PtH= 1308.9 Hz) and a peak at 5.25 ppm for free eth-

ene. This reaction does not go to completion. We ascribe

these peaks to the structure shown in Scheme 11 resulting

D

_dissS^ꢀto be somewhat larger. The value determined

speaks in favor of an early transition state. The data

found are an indirect evidence that compound 3 in

Scheme 2 exists temporarily. The data are unequivocally

good enough to state that both pathways (associative

and dissociative) take place; the dissociation of ethene

from (PPh₃)₂Pt(Ethene) and (PCy₃)₂Pt(Ethene) in solu-

tion has been reported [14].

To further support the existence of 3 in Scheme 2, we

tried [1]Pt(Ethene) in several test reactions with sub-

strates that usually react with L₂Pt(0) compounds

(Scheme 11).

from

a methyl transfer onto the Pt forming a

{[1]PtMe⁺I^ꢀ} ion pair. This would be in accordance with

the assumption that the oxidative addition of MeI should

be a non-concerted two-step process. Since the back-side

attack of the I^ꢀanion in the second step is blocked

through the biphenyl backbone of [1], the oxidative addi-

tion is trapped after the ﬁrst step (methyl transfer). A sim-

ilar structure has been proposed by Stille for a Pd(II)

complex [16]. Since the J_PtHcoupling constant of 1309.8

Hz is too large for a ²J coupling, we propose that an inter-

action of the methylꢁs H atoms with the Pt center must be

present (¹J_PtHcoupling constants of the magnitude found

are not uncommon) with a free rotation axis along the

Pt–C connection which leads to no visible J_PHcoupling.

[1]Pt(Ethene), when heated on air at 353 K for 4 h

yields quantitatively into [1]PtO₂complex (d_P= 124.1

1

ppm, J_PPt= 4145.6 Hz, d_Pt= ꢀ4219.2 ppm, IR: 1634.4

cm^ꢀ1(s)). If [1]Pt(Ethene) is stirred at room temperature

under an atmosphere of H₂, [1]PtH₂can be detected

1

(d_P= 183.8 ppm (br), J_PPt= 1091.7 Hz, d_H= ꢀ3.43

1

ppm (br), J_PtH= 1029.5 Hz, J_PHcis= 121.3 Hz,

2

K. Ruhland, E. Herdtweck / Journal of Organometallic Chemistry 690 (2005) 5215–5236

5227

Table 5

Quantitative data for the evaluation of the ethene exchange behavior of [1]Pt(Ethene)

T (K)

Total ethene (mol/L)

Free ethene (mol/L)

Exchange time s (s)

k_diss(1/s)

k_ass(L/(mol s))

333

0.0488

0.064

0.07

0.00279

0.0038

0.011

0.12 0.02

0.07 0.02

0.3 0.2

0.448 0.019

8.3 5.9

0.0732

0.093

0.105

0.0122

0.032

0.044

343

353

363

373

0.0488

0.064

0.07

0.00279

0.0038

0.011

0.045 0.01

0.05 0.01

0.10 0.05

0.11 0.07

0.12 0.02

0.5 0.15

1.221 0.061

2.180 0.111

6.637 0.084

12.433 0.490

10.0 19.1

11.7 45.4

20.3 25.2

30.8 147.0

0.0732

0.093

0.105

0.178

0.0122

0.032

0.044

0.117

0.40 0.15

0.0488

0.064

0.07

0.00279

0.0038

0.011

0.025 0.015

0.03 0.015

0.065 0.02

0.08 0.01

0.07 0.02

0.25 0.02

0.15 0.07

0.0732

0.093

0.105

0.178

0.0122

0.032

0.044

0.117

0.0488

0.064

0.07

0.00279

0.0038

0.011

0.0085 0.002

0.009 0.002

0.025 0.005

0.034 0.008

0.072 0.02

0.080 0.009

0.0732

0.093

0.105

0.178

0.0122

0.032

0.044

0.117

0.0488

0.064

0.07

0.00279

0.0038

0.011

0.0045 0.002

0.005 0.002

0.012 0.003

0.015 0.005

0.017 0.003

0.024 0.002

0.045 0.009

0.0732

0.093

0.105

0.178

0.0122

0.032

0.044

0.117

Performing the thermolysis of [1]Pt(Ethene) the C–C

activated compound 5 in Scheme 2 could never be iso-

lated or detected. Unfortunately, we did not succeed in

synthesizing compound 5 of Scheme 2 by treating

(COD)PtCl₂with two equivalents of the ortho-metal-

lated phosphinite 2-M–Ph(OP(i-Pr)₂), M = Li, MgI

(Scheme 12) to prove that this compound is thermody-

namically stable in the temperature range employed

and to examine the back-reaction (reductive elimina-

tion) of sub-equilibrium (D) of Scheme 2.

The ortho-metallated phosphinite seems to rearrange

to the phenolate shifting the phosphine into the ortho-po-

sition both for the Grignard and the lithium compound

according to the ³¹P NMR signal for the hydrolyzed

product received when quenching the ortho-metallation

attempt (starting material (o-I-phenyl)–O–PR₂) with

water at low temperatures (singulet in the negative d-area).

Since we were not able to detect 3 or 5 of Scheme 2 we

calculated the molecules and their thermodynamic

0

5.2

5.4

5.3

ppm

Fig. 7. Curve ﬁt of the ¹H NMR spectrum with [ethene]_total= 0.105

mol/L, [ethene]_free= 0.044 mol/L and T = 373 K. s was received to be

0.024 s.

Concerning sub-equilibrium (C) in Scheme 2 it can,

thus, be stated that the equilibrium is far on the left

but partially and temporarily (3) is formed via dissocia-

tion of ethene, thus, opening up the pathway to sub-

equilibrium (D) in Scheme 2.

5228

K. Ruhland, E. Herdtweck / Journal of Organometallic Chemistry 690 (2005) 5215–5236

5000

4500

4000

3500

3000

2500

2000

1500

1000

500

P

k_ass

R²= 0,9918

Pt

P

Pt

k_diss

P

R²= 0,9983

R²= 0,9785

Increasing T

R²= 0,9868

R²= 0,9875

0

50

100

150

200

1/[ethene]_free

250

300

350

400

Fig. 8. Plots according to Eq. (1) with the data of Table 5.

R

4

R

O

P

R= Ph, i-Pr

R

R²= 0,9246

O

3

2

1

P

Cl

R

M

Pt

+

2

Pt

R

P

Cl

R

O

M=MgI, Li

R²= 0,9916

0

0.0026

-1

0.0027

0.0028

0.0029

0.003

0.0031

0.0032

M

O

R

P

-2

1/T [1/K]

R

Fig. 9. Eyring plot for the dissociative (h) and the associative (})

pathway in the ethene exchange of [1]Pt(Ethene).

Scheme 12.

stability on the B3LYP/LANL2DZ level. Compound 3

was found as local minimum with a P–Pt–P of 150.8ꢀ

and a distance of the Pt center to the bridging C atoms

uct) in comparison to 3. However, the calculations on

the B3LYP/LANL2DZ level also predict 3 in Scheme

2 and free ethene to be more stable than 4 in Scheme

2 which is unequivocally wrong. This conﬁrms our expe-

rience (not only remembering the low predictive power

of the structure of [1]Pt(Ethene), demonstrated above)

˚

in the biphenyl fragment of 3.48 A. According to these

calculations the C–C activated product should be ther-

modynamically favored (both the cis and the trans prod-

P

O

P

H

Pt

P

H

Pt

C

I

H

O

Pt

O₂

H₂

MeI

P

O

P

Pt

P

H₂SiPh₂

Ethane

P

H

Pt

P

H

P

SiHPh₂

Pt

P

Scheme 11.

K. Ruhland, E. Herdtweck / Journal of Organometallic Chemistry 690 (2005) 5215–5236

5229

O

P

(5’)

Pt

P

O

loss of

stereoselectivity

!

H

O

P

O

H

P

Pt

P

Pt

P

CH₃

O

P

CH₃

O

(1’)

(4’)

(3’)

Scheme 13.

that the LANL2DZ basis set is critical to describe tran-

sition metals of the third row satisfactory both concern-

ing the structure and the thermochemistry [15].

To still check whether the sub-equilibrium (D) in

Scheme 2 exists but is invisible because compound 5 is

too unstable to be observed, an indirect way for the

detection was tried based on the potential loss of chiral-

ity of the axially chiral ligand backbone, if 5 is formed as

intermediate (Scheme 13).

We did not try to synthesize ligand [1] enantioselec-

tively but used ligand [4] instead for which the biphenol

is available enantiomerically pure. [4]PtCl₂and [4]PtEt₂

could both be synthesized and show large [a]^Navalues

of ꢀ211.9ꢀ and ꢀ230.3ꢀ, respectively. The thermolysis

of [4]PtEt₂yielded cleanly into [4]Pt(Ethene). The kinetic

is similar to that of [1]PtEt₂but was not examined in

detail. If the reaction is carried out at 363 K under an

atmosphere of ethene to prevent a possible loss of stere-

oselectivity the product [4]Pt(Ethene) shows an [a]^Naof

ꢀ248.9ꢀ (the measurement was done in toluene saturated

with ethene). If [4]Pt(Ethene) is heated in toluene-d⁸for

72 h (this was the longest time period we could heat a

sample without signiﬁcant amount of oxidation product,

detected as a peak at 60 ppm in ³¹P NMR spectroscopy,

appeared) at 378 K, no signiﬁcant decrease in [a]^Nawas

observed. Unfortunately, we must, thus, conclude that

under the conditions employed not even temporarily

the bridging C–C single bond is activated.

slower than 12 s^ꢀ1at 378 K (this is the dissociative ex-

change rate of the coordinated ethene). From this we

conclude that the approach of the bridging C–C single

bond to the metal center is not the most important part

of the activation energy for the cleavage of that bond. A

future strategy is to employ coordinated oleﬁns which

are more weakly bound (propene, i-butene) to oﬀer the

bridging C–C single bond more time to be activated.

Electron-withdrawing groups on the biphenyl fragment

should also increase the chance for an activation [3e].

By switching from Pt(0) to Pt(II) using [1]PtMe⁺as

starting material the inﬂuence of the center metalꢁs oxi-

dation state is to be examined. As long as we are able to

organize money for it, we will not stop trying to contrib-

ute our part to solve the problem of cleaving non-

strained and non-activated C–C single bonds. Taking

the positive side of our results we have proven that

(4⁰) retains its stereochemical information even at ele-

vated temperature. According to the high [a]^Navalues

the stereochemical information is distinctive. Remem-

bering the activation reactions summarized in Scheme

11, we see a high potential in using the easily available

and fairly stable (4⁰) in catalytic stereoselective reactions

such as hydrogenation or hydrosilylation, which we are

planning to examine in the nearest future.

4. Experimental

Manipulations and experiments were performed under

an argon atmosphere using standard Schlenk techniques

and/or in an argon-ﬁlled glove-box if not mentioned

otherwise. Diethylether was distilled from benzophe-

none/sodium and stored under an argon atmosphere over

molecular sieves. Dichloromethane, CDCl₃, pentane and

3. Conclusion

We must state that our initial target to activate the

non-strained C–C bridge of the biphenyl fragment was

not reached or at least that this reaction is decisively

5230

K. Ruhland, E. Herdtweck / Journal of Organometallic Chemistry 690 (2005) 5215–5236

acetonitrile were degased with dinitrogen for 30 min, dis-

tilled and stored under argon over molecular sieves.

K₂PtCl₄and S-(ꢀ)-1,1⁰-Bi-2-naphthol were purchased

from Strem Chemicals and used without further manipu-

lation. Ethene 2.7 and dihydrogen 5.0 were received from

Messer Grießheim and used as delivered. Ethane was

generated by ethanolysis of ethyl Grignard. 1Z,5Z-cyclo-

octadiene (COD), chlorodiphenylphosphane, chlo-

rodiisopropylphosphane, chlorodicyclohexylphosphane,

2,2⁰-dihydroxbiphenyl, ethyl-Grignard (2 M in dietheyle-

ther), H₂SiPh₂, CD₃CD₂Br, CD₃COCl, LiAlD₄and

CH₃COBr were purchased from Aldrich and used with-

out further puriﬁcation. (COD)PtCl₂was synthesized

according to the literature [17].

The NMR measurement was performed on a Bruker

AMX400. ¹H NMR (7.24 ppm, 400 MHz) and ¹³C

NMR (77.0 ppm, 100 MHz) spectra were referred to

the CDCl₃/CHCl₃resonances, ³¹P NMR (161 MHz) to

85% H₃PO₄as external standard, ¹⁹⁵Pt NMR (ꢀ3329

ppm, 85.6 MHz) to (COD)PtCl₂as external standard.

FTIR measurement was done on a JASCO FI7IR-

460plus machine using KBr pellets. [a]^Ddata were deter-

mined on a Perkin–Elmer 241MC polarimeter.

4.1.2. Ph(OPCy) [2]

White solid (yield 97%). ¹H NMR (CDCl₃, ppm):

1.05–1.95 (44H, m, Cy), 6.92 (2H, t, CH-arom.), 7.25

(2H, t, CH-arom.), 7.37 (2H, d, CH-arom.), 7.55 (2H,

d, CH-arom.). ¹³C{¹H} NMR (CDCl₃, ppm): 26.08 (d,

J_CP= 12.4 Hz), 26.89 (s), 27.21 (s), 37.76 (d,

¹J_CP= 16.8 Hz), 117.52 (d, J_CP= 19.0 Hz), 120.66 (s),

3

2

128.16 (s), 129.75 (s), 131.39 (s), 156.99 (d, J_CP= 8.77

Hz, P–O–C). ³¹P{¹H} NMR (CDCl₃, ppm):147.0 (s).

EA Calc. for C₃₆H₅₂O₂P₂: C, 74.7; H, 9.1; P, 10.7.

Found: C, 73.82; H, 9.19; P, 10.10%.

4.1.3. Biphen(OPPh) [3]

White solid (yield 95%). ¹H NMR (CDCl₃, ppm):

7.02–7.26 (m). ¹³C{¹H} NMR (CDCl₃, ppm): 118.2 (d,

³J_CP= 16.5 Hz), 122.31 (s), 128.15 (d, J_CP= 17.9 Hz),

3

128.70 (s), 129.15 (s). 130.08 (d, J_CP= 22.6 Hz),

1

131.44 (s), 141.37 (d, J_CP= 17.9 Hz), 155.12 (d,

²J_CP= 9.9 Hz, P–O–C). ³¹P{¹H} NMR (CDCl₃, ppm):

112.8 (s). EA Calc. for C₃₆H₂₈O₂P₂: C, 78.0; H, 5.1; P,

11.2. Found: C, 78.8; H, 5.14; P, 10.64%.

4.1.4. S-Naph(OPi-Pr) [4]

Viscose white oil (yield 92%). ¹H NMR (CDCl₃,

3

ppm): 0.44 (3H, d J_HH= 9.5 Hz, CHCH₃), 0.46 (3H,

4.1. General synthesis of the ligands

3

d

³J_HH= 9.5 Hz, CHCH₃), 0.54 (3H, d J_HH= 7.25

3

Route 1. 6 mmol of 2,2⁰-dihydroxybiphenyl were

dissolved in 50 mL of diethylether. 23 mmol of triethyl-

amine were added. Then 12.5 mmol of chlorodiphenyl-

phosphine were added dropwise. Immediately, a white

precipitation formed. It was stirred over night. The next

day the white solid was removed by ﬁltration and

washed with 50 mL of diethylether. From the combined

ether extracts the solvent was removed. A white solid

resulted.

Route 2. 6 mmol of 2,2⁰-dihydroxybiphenyl were

dissolved in 40 mL of acetonitrile. 23 mmol of triethyl-

amine were added. Then 12.5 mmol of chlorodialkyl-

phosphine were added dropwise. It was then heated to

60 ꢀC over night. During that time a white precipitate

formed. The next day 40 mL of pentan were added

and it was stirred for 1 h. Then the pentane phase was

separated via cannula into a new ﬂask from which the

pentane was removed in vacuo to yield the ligand.

Hz, CHCH₃), 0.58 (3H, d J_HH= 7.28 Hz, CHCH₃),

0.86 (12H, m, CHCH₃), 1.30 (2H, br hept, CHCH₃),

3

1.64 (2H, hept J_HH= 7.21 Hz, CHCH₃), 7.16 (4H, m,

Ar-H), 7.33 (2H, mm Ar-H), 7.72 (2H, br

3

d

³J_HH= 10.6 Hz, Ar-H), 7.95 (2H, d J_HH= 9.3 Hz,

Ar-H), 8.01 (2H, d J_HH= 9.6 Hz, Ar-H). ¹³C{¹H}

3

2

NMR (CDCl₃, ppm): 15.72 (d, J_CP= 7.4 Hz), 17.10

2

(d, J_CP= 6.2 Hz), 17.33 (d, J_CP= 14.8 Hz), 17.40 (d,

1

¹J_CP= 21.0 Hz), 27.86 (d, J_CP= 18.5 Hz), 27.69 (d,

1

¹J_CP= 16.0 Hz), 118.19 (d, J_CP= 20.9 Hz), 120.84 (s),

123.50 (s), 125.94 (s), 126.01 (s), 127.79 (s), 128.77 (s),

3

2

129.32 (s), 134.21 (s), 153.97 (d, J_CP= 8.6 Hz, P–O–

C). ³¹P{¹H} NMR (CDCl₃, ppm): 145.6 (s). EA Calc.

for C₃₂H₄₀O₂P₂: C, 74.11; H, 7.77; P, 11.94. Found: C,

Na

25 ^ꢄC;toluene

74.30; H, 7.99; P, 11.94%. ½aꢃ

¼ ꢀ64.7^ꢄ.

4.2. General synthesis of the PtCl₂complexes

To a suspension of 0.3 mmol of (COD)PtCl₂in 10

mL of CH₂Cl₂was added a solution of 0.3 mmol of

the ligand in 10 mL of CH₂Cl₂. The mixture was allowed

to stir overnight. A clear solution resulted. The next day

the solvent was removed in vacuo. A white solid re-

mained which was washed with 10 mL of pentane and

dried in vacuo.

4.1.1. Biphen(OPi-Pr) [1]

Colorless oil (yield 85%). H NMR (CDCl₃, ppm):

1

0.79–0.85 (24H, m, CH–CH₃), 1.61 (m, 4H, CH–CH₃),

6.87 (t, 2H, CH–arom.). ¹³C{¹H} NMR (CDCl₃,

2

ppm): 16.81 (d, J_CP= 8.75 Hz, CHCH₃), 17.51 (d,

1

²J_CP= 19.52 Hz, CHCH₃), 27.99 (d, J_CP= 17.31 Hz,

3

CHCH₃), 117.27 (d, J_CP= 19.5 Hz) 120.58 (s), 128.17

4

(s), 129.51 (d, J_CP= 1.2 Hz), 131.55 (s), 156.75 (d,

4.2.1. [1]PtCl₂

White solid (yield 89%). ¹H NMR (CDCl₃, ppm):

²J_CP= 8.0 Hz, P–O–C). ³¹P{¹H} NMR (CDCl₃, ppm):

147.67. EA Calc. for C₁₈H₃₆O₂P₂: C, 68.9; H, 8.7; P,

14.8. Found: C, 68.08; H, 8.62; P, 14.11%.

2

0.86 (3H, d, J_HH= 7.1 Hz, CH–CH₃), 0.90 (3H, d,

2

²J_HH= 7.1 Hz, CH–CH₃), 1.08 (3H, d, J_HH= 7.2 Hz,

K. Ruhland, E. Herdtweck / Journal of Organometallic Chemistry 690 (2005) 5215–5236

5231

CH–CH₃), 1.12 (3H, d, ²J_HH= 7.4 Hz, CH–CH₃), 1.45–

1.54 (12H, m, CH–CH₃), 2.46 (2H, m, CH–CH₃), 3.34

(s), 978.7 (s), 928.6 (m), 902.5 (m), 775.2 (m), 755.9

(w), 689.4 (s), 593.9 (w), 526.5 (s), 496.6 (m). EA Calc.

for C₃₆H₂₈Cl₂O₂P₂Pt: C, 52.7; H, 3.4; P, 7.5; Cl, 8.6.

Found: C, 52.29; H, 3.62; P, 7.11; Cl, 9.34%. MS

(FAB, m/z): 748.3 (M ꢀ Cl, correct isotope pattern).

2

(2H, m, CH–CH₃), 7.17 (2H, d, J_HH= 8.0 Hz, CH-

2

arom.), 7.29 (2H, t, J_HH= 7.4 Hz, CH-arom.), 7.37–

7.42 (4H, m, CH-arom.). ¹³C{¹H} NMR (CDCl₃,

ppm): 18.05 (s, CHCH₃), 18.15 (s, CHCH₃), 18.86 (s,

1

CHCH₃), 19.94 (s, CHCH₃), 32,76 (d, J_CP= 35.5 Hz,

4.2.4. [4]PtCl₂

White solid (yield 76%). ¹H NMR (CDCl₃, ppm):

1

CHCH₃), 34.05 (d, J_CP= 35.7 Hz, CHCH₃), 120.78

3

0.39 (3H, d J_HH= 6.8 Hz, CHCH₃), 0.43 (3H, d

(s), 125.37 (s), 129.69 (s), 130.15 (s), 132.36 (s), 150.90

2

(d, J_CP= 13.2 Hz, P–O–C). ¹⁹⁵Pt{¹H} NMR (CDCl₃,

³J_HH= 7.0 Hz, CHCH₃), 0.72 (3H, d J_HH= 6.9 Hz,

3

1

3

CHCH₃), 0.76 (3H, d J_HH= 6.8 Hz, CHCH₃), 1.38

ppm): ꢀ4122.8 (t, J_PPt= 4147.2 Hz). ³¹P{¹H} NMR

1

(CDCl₃, ppm): 123.4 (s), 123.4 (d, J_PPt= 4147.2 Hz).

(3H,

d

³J_HH= 6.9 Hz, CHCH₃), 1.41 (3H,

d

FT-IR (cm^ꢀ1): 3064 (w), 2967 (s), 2930 (s), 2871 (s),

1596 (w), 1568 (w), 1498 (s), 1476 (s), 1431 (s), 1384

(w), 1365 (w), 1242 (s), 1208 (s), 1127 (w), 1101 (s),

1047 (m), 1031 (m), 932 (s), 899 (s), 769 (s), 756 (s),

725 (w), 664 (m), 638 (m), 620 (m), 599 (m), 535 (m),

519 (m). EA Calc. for C₂₄H₃₆Cl₂O₂P₂Pt: C, 42.1; H,

5.3; P, 9.1; Cl, 10.36. Found: C, 41.73; H, 5.44; P,

9.35; Cl, 10.02%. MS (FAB, m/z): 648.3 (M ꢀ Cl, cor-

rect isotope pattern).

³J_HH= 6.2 Hz, CHCH₃), 1.65 (3H, d J_HH= 6.9 Hz,

3

CHCH₃), 1.69 (3H, d J_HH= 7.0 Hz, CHCH₃), 2.18

(2H, br hept, CHCH₃), 3.27 (2H, br hept, CHCH₃),

3

7.13 (2H, d J_HH= 8.7 Hz, Ar-H), 7.29 (2H, t

³J_HH= 8.2 Hz, Ar-H), 7.45 (2H, t J_HH= 8.0 Hz, Ar-

3

H), 7.50 (2H, d J_HH= 8.5 Hz, Ar-H), 7.91 (2H, d

³J_HH= 8.5 Hz, Ar-H), 7.99 (2H, d J_HH= 8.7 Hz, Ar-

3

H). ¹³C{¹H} NMR (CDCl₃, ppm): 16.85 (s, CHCH₃),

18.30 (s, CHCH₃), 18.47 (s, CHCH₃), 20.85 (s, CHCH₃),

33.39 (d, ¹J_CP= 16.1 Hz, CHCH₃), 33.80 (d, ¹J_CP= 20.1

Hz, CHCH₃), 119.83 (s), 123.36 (s), 125.63 (s), 125.66

(s), 127.39 (s), 128.16 (s), 130.59 (s), 130.83 (s), 133.36

4.2.2. [2]PtCl₂

White solid (yield 67%). ¹H NMR (CDCl₃, ppm):

2

0.64–3.06 (44H, m, Cy), 7.11 (2H, d, J_HH= 8.0 Hz,

2

(s), 148.92 (d, J_CP= 12.1 Hz, C–O–P). ¹⁹⁵Pt{¹H}

2

CH-arom.), 7.28 (2H, t, J_HH= 7.44 Hz, CH-arom.),

1

NMR (CDCl₃, ppm): ꢀ4228.8 (t, J_PPt= 4022.9 Hz).

7.38–7.43 (4H, m CH-arom.). ¹³C{¹H} NMR (CDCl₃,

³¹P{¹H} NMR (CDCl₃, ppm): 127.5 (s), 127.5 (d,

¹J_PPt= 4022.9 Hz). FT-IR (cm^ꢀ1): 3053.0 (w), 2963

(w), 2926 (w), 2870 (w), 1587 (w), 1504 (w), 1567 (s),

1360 (w), 1228 (s), 1077 (m), 1028 (m), 991 (s), 880

(w), 826 (s), 748 (m), 693 (m). EA Calc. for

C₃₂H₄₀Cl₂O₂P₂Pt: C, 48.99; H, 5.14; P, 7.89; Cl, 9.04.

2

ppm): 25.82 (s), 26.18 (s), 26.68 (d, J_CP= 13.2 Hz),

2

27.31 (s), 27.97 (s), 29.34 (d, J_CP= 15.1 Hz), 43.38 (d,

1

¹J_CP= 34 Hz), 44.84 (d, J_CP= 34.1 Hz), 120.54 (d,

3

³J_CP= 2.8 Hz), 125.06 (s), 129.78 (d, J_CP= 3.3 Hz),

2

130.10 (s), 131.23 (s), 151.26 (d, J_CP= 14 Hz, P–O–

1

C). ¹⁹⁵Pt{¹H}(CDCl₃, ppm): ꢀ4119.4 (t, J_PPt= 4141.3

Found: C, 48.27; H, 5.07; P, 7.44; Cl, 9.90%.

¼ ꢀ211.9^ꢄ. MS (FAB, m/z): 784.1 (M ꢀ Cl,

Na

25 ^ꢄC;toluene

Hz). ³¹P{¹H} NMR (CDCl₃, ppm): 118.7 (br s), 118.7

½aꢃ

1

(br d, J_PPt= 4141.3 Hz). FT-IR (cm^ꢀ1): 3064 (w),

correct isotope pattern).

2926 (s), 2851 (s), 1496 (m), 1476 (m), 1432 (m), 1249

(m), 1205 (m), 1101 (m), 1047 (w), 1004 (w), 942 (m),

894 (m), 851 (w), 768 (m), 731 (w), 589 (w). EA Calc.

for C₁₈H₃₆Cl₂O₂P₂Pt: C, 51.2; H, 6.2; P, 7.3; Cl, 8.4.

Found: C, 51.07; H, 6.10; P, 6.96; Cl, 8.40%.

4.3. General synthesis of the PtEt₂complexes

0.15 mmol of [ligand]PtCl₂were suspended in 5 mL

of diethylether. The suspension was cooled to ꢀ30 ꢀC.

Then 0.45 mmol of ethylmagnesiumbromide in diethyle-

ther were added dropwise via syringe. The reaction mix-

ture was stirred for 1 h. Then 0.5 mL of 1,4-dioxane

were added and the white precipitate was removed by ﬁl-

tration through aluminium oxide and washed with 10

mL of diethylether. From the combined ether extracts

the solvent was removed in vacuo. An oﬀ-white solid

resulted.

4.2.3. [3]PtCl₂

White solid (yield 75%). ¹H NMR (CDCl₃, ppm):

2

6.78 (2H, d, J_HH= 7.36 Hz, CH-arom.), 7.08–7.51

(28H, m CH-arom.). ¹³C{¹H} NMR (CDCl₃, ppm):

122.24 (s), 125.80 (s), 127.88 (pseudo-t, J_CPt= 12.6

Hz), 127.92 (pseudo-t, J_CPt= 12.6 Hz), 129.71 (s), 130.

13 (s), 131. 42 (s), 131. 76 (s), 132.12 (s), 132.01 (m, over-

lapping with the peak at 132.12), 132.38 (d of pseudo-t,

J_CP= 14.6 Hz, J_CPt= 14.4 Hz), 132.11 (s), 133.43 (s),

4.3.1. [1]PtEt₂

White solid (yield 62%). ¹H NMR (toluene-d⁸, ppm):

2

134.16 (s), 150. 73 (d, J_CP= 8.85 Hz P–O–C). ¹⁹⁵Pt

1

2

0.61 (3H, d, J_HH= 7.3 Hz, CH–CH₃), 0.65 (3H, d,

NMR (CDCl₃, ppm): ꢀ4150.7 (t, J_PPt= 4230.4 Hz).

³¹P{¹H} NMR (CDCl₃, ppm): 88.39 (s), 88.39 (d,

¹J_PPt= 4230.4 Hz). FT-IR (cm^ꢀ1): 3047.8 (w), 2955.2

(w), 2864.2 (w), 1645.9 (w), 1516.7 (m), 1463.7 (s),

1433.8 (m), 1269.9 (w), n1245.8 (w), 1206.3 (m), 1099.2

²J_HH= 7.2 Hz, CH–CH₃), 0.88 (3H, d, J_HH= 7.2 Hz,

2

CH–CH₃), 0.91 (3H, d, J_HH= 7.3 Hz, CH–CH₃),

0.86–1.34 (10H, m, Ethyl), 1.34–1.39 (12H, m, CH–

CH₃), 2.06 (2H, m, CH–CH₃), 2.66 (2H, m, CH–CH₃),

5232

K. Ruhland, E. Herdtweck / Journal of Organometallic Chemistry 690 (2005) 5215–5236

2

7.03 (2H, d, J_HH= 8.1 Hz, CH-arom.), 9.1 (2H, t,

²J_HH= 7.5 Hz, CH-arom.), 7.23–7.26 (4H, m, CH-

arom.). ¹³C{¹H} NMR (toluene-d⁸, ppm): 13.50 (dd,

nyl-H), 7.02 (8H, pseudo-t, phenyl-H), 7.36 (6H, pseu-

do-t, phenyl-H), 7.46 (6H, pseudo-t, phenyl-H).

¹³C{¹H} NMR (CDCl₃, ppm): 15.47 (pseudo-t with t,

²J_CPcis= 10.1 Hz, J_CPtrans= 106.6 Hz, J_CPt= 418.3

³J_CP= 1.7 Hz, J_CPt= 14.4 Hz, PtCH₂–CH₃), 16.47

2

1

2

3

2

Hz, Pt–CH₂), 16.93 (t, J_CP= 3.0 Hz, J_CPt= 22.0 Hz,

PtCH₂–CH₃), 17.60 (pseudo–t, J_CPt= 65.4 Hz,

PCHCH₃), 18.41 (pseudo–t, J_CPt= 99.6 Hz, PCHCH₃),

18.48 (pseudo–t, J_CPt=50.3 Hz, PCHCH₃), 19.84 (pseudo

–t, J_CPt= 80.5 Hz, J_CPt= 17.3 Hz, PCHCH₃), 31.29 (d

(dd, ²J_CPcis= 10.9 Hz, ²J_CPtrans= 120.7 Hz, ¹J_CPt= 643.9

Hz, Pt–CH₂), 122.2 (s), 124.2 (s), 127.50 (pseudo-t,

J_CPt= 10.3 Hz, ortho-C of PPh), 127.66 (pseudo-t,

J_CPt= 8.7 Hz, ortho-C of PPh), 128.48 (s), 130.05 (s),

130.91 (pseudo-t, J_CPt= 11.2 Hz, ortho-C of PPh),

131.30 (s), 131.419 (s), 132.33 (pseudo-t, J_CPt= 15.6,

1

with pseudo-t, J_CP= 18.49 Hz, J_CPt= 17.3 Hz, PC

1

HCH₃), 31.88 (d with pseudo-t, J_CP= 24.66 Hz,

1

ortho-C of PPh), 137.11 (d with pseudo-t, J_CP= 45.3

J_CPt= 17.2 Hz, PCHCH₃), 121.38 (s), 124.59 (s), 131.47

(s), 132.52 (s), 153.80 (pseudo-t, J_CPt= 8.85 Hz).

¹⁹⁵Pt{¹H} NMR (toluene-d⁸, ppm): ꢀ4494.2 (t,

¹J_PPt= 1971.4 Hz). ³¹P{¹H} NMR (toluene-d⁸, ppm):

Hz, J_CPt= 43.0 Hz, P-C), 138.21 (d with pseudo-t,

¹J_CP= 39.7 Hz, J_CPt= 44.1 Hz, P-C), 152.64 (pseudo-t,

J_CPt= 8.6 Hz, P–O–C). ¹⁹⁵Pt{¹H} NMR (toluene-d⁸,

1

ppm): ꢀ4460.0 (t, J_PPt= 1937.1 Hz). ³¹P{¹H} NMR

1

159.40 (s), 159.40 (d, J_PPt= 1971.4 Hz). FT-IR (cm^ꢀ1):

(toluene-d⁸, ppm): 123.8 (s), 123.8 (d, J_PPt= 1937.1

3066 (w), 2924 (s), 2853 (s), 1466 (m), 1378 (w), 1261

(m), 1207 (m), 1103 (m), 1019 (m), 903 (w), 802 (w),

759 (w), 677 (w), 464 (w). EA Calc. for C₂₈H₄₆O₂P₂Pt:

C, 50.1; H, 6.9; P, 9.2. Found: C, 50.58; H, 6.98; P,

8.78%. MS (FAB, m/z): 614.3 (100%, M ꢀ ethane).

Hz). EA Calc. for C₄₀H₃₈O₂P₂Pt: C, 59.48; H, 4.74; P,

7.67. Found: C, 59.32; H, 4.65; P, 7.97%.

4.3.4. [4]PtEt₂

White solid (yield 64%). ¹H NMR (toluene-d⁸, ppm):

3

0.17 (3H, d, J_HH= 7.4 Hz, CHCH₃), 0.21 (3H, d,

3

4.3.2. [2]PtEt₂

³J_HH= 7.4 Hz, CHCH₃), 0.56 (3H, d, J_HH= 7.4 Hz,

White solid (yield 49%). ¹H NMR (CDCl₃, ppm): 0.5–

2.44 (54H, m, Cy and Ethyl), 6.97 (2H, d, ²J_HH= 7.5 Hz,

CH-arom.), 7.10 (2H, t, ²J_HH= 7.3 Hz, CH-arom.), 7.24

(4H, m, CH-arom.). ¹³C{¹H} NMR (CDCl₃, ppm): 12.53

CHCH₃), 0.59 (3H, d, J_HH= 7.2 Hz, CHCH₃), 1.04

3

(3H, d, J_HH= 7.4 Hz, CHCH₃), 1.31 (3H, d,

3

³J_HH= 7.4 Hz, CHCH₃), 1.37 (3H, d, J_HH= 7.4 Hz,

3

CHCH₃), 1.37 (3H, d, J_HH= 7.4 Hz, CHCH₃), 1.41

2

3

(3H, d, J_HH= 7.4 Hz, CHCH₃), 1.31–1.41 (10H, m,

(dd with pseudo-t, J_PCcis= 107.6 Hz, J_PCtrans= 10.2

1

Hz, J_CPt= 635.0 Hz, Pt–CH₂), 16.04 (t with pseudo-t,

3

Pt-CH₂H₃), 1.67 (2H, hept, J_HH= 7.4 Hz, CHCH₃),

2

3

2.40 (2H, hept, J_HH= 7.4 Hz, CHCH₃), 6.94 (2H, d

³J_CP= 2.6 Hz, J_CPt= 22.4 Hz, Pt–CH₂ꢀCH₃), 17.61

3

(pseudo-t, J_CPt= 11.3 Hz, PCHCH₃), 18.40 (pseudo-t,

J_CPt= 15.1 Hz, PCHCH₃), 18.48 (pseudo-t, J_CPt= 7.5

Hz, PCHCH₃), 19.82 (pseudo-t, J_CPt= 14.6 Hz,

³J_HH= 9.8 Hz, Ar-H), 7.13 (2H, t J_HH= 7.4 Hz, Ar-

3

H), 7.21 (2H, d J_HH= 9.8 Hz, Ar-H), 7.36 (2H, d

3

³J_HH= 7.3 Hz, Ar-H), 7.62 (4H, d J_HH= 7.4 Hz, Ar-

1

PCHCH₃), 31.28 (d with pseudo-t, J_CP= 17.1 Hz,

H). ¹³C{¹H} NMR (CDCl₃, ppm): 13.76 (dd with

pseudo-t, ¹J_CPt= 576.0 Hz, ²J_CPcis= 103.6 Hz,

²J_CPtrans= 10.1 Hz, Pt–CH₂), 16.08 (t with pseudo-t,

J_CPt= 17.0 Hz, P–CH–CH₃), 31.94 (d with pseudo-t,

¹J_CP= 24.1 Hz, J_CPt= 16.1 Hz, P–CH–CH₃), 120.93

(s), 123.14 (s), 128.77 (s), 131.08 (s), 131.85 (s), 153.22

(pseudo-t, 10.1 Hz, C–O–P). ¹⁹⁵Pt{¹H} NMR (toluene-

2

³J_CP= 3.0 Hz, J_CPt= 19.7 Hz, Pt–CH₂CH₃), 16.60

(pseudo-t, J_CPt= 15.8 Hz, PCH–CH₃), 16.60 (pseudo-t,

J_CPt= 9.8 Hz, PCH–CH₃), 18.22 (pseudo-t, J_CPt= 15.8

Hz, PCH–CH₃), 18.70 (pseudo-t, J_CPt= 10.9 Hz PCH–

CH₃), 20.52 (pseudo-t, JCPt=10.4 Hz PCH–CH₃),

1

d⁸, ppm): ꢀ4464.7 (t, J_PPt= 1945.7 Hz). ³¹P{¹H}

1

NMR (CDCl₃, ppm): 150.4 (s), 150.4 (d, J_PPt= 1945.7

Hz). FT-IR (cm^ꢀ1): 3064 (w), 2927 (s), 2848 (s), 1497

(m), 1473 (m), 1444 (m), 1253 (m), 1216 (m), 1101 (m),

910 (m), 850 (w), 815 (w), 757 (m), 664 (w), 497 (w).

EA Calc. for C₄₀H₆₂O₂P₂Pt: C, 57.75; H, 7.51; P, 7.45.

Found: C, 57.79; H, 7.61; P, 7.87%.

1

31.38 (d with pseudo-t, J_CP= 23.1 Hz, J_CPt= 46.3 Hz,

1

PCHCH₃), 31.78 (d with pseudo-t, J_CP= 28.2 Hz,

J_CPt= 56.3 Hz, PCHCH₃), 122.00 (s), 122.93 (s),

124.70 (s), 125.52 (s), 126.45 (s), 127.67 (s), 129.20 (s),

130.65 (s), 133.92 (s), 151.45 (pseudo-t, J_CPt= 6.0 Hz,

C–O–P). ¹⁹⁵Pt{¹H} NMR (toluene-d⁸, ppm): ꢀ4636.1

4.3.3. [3]PtEt₂

White solid (yield 56%). ¹H NMR (toluene-d⁸, ppm):

1

(t, J_PPt= 1968.8 Hz). ³¹P{¹H} NMR (toluene-d⁸,

3

1.21 (6H, pseudo-t with d of t, J_HH= 8.6 Hz,

1

ppm): 162.1 (s), 162.1 (d, J_PPt= 1968.8 Hz).

4

³J_PtH= 57.6 Hz, J_PH= 8.6 Hz, CH₂–CH₃), 1.64 (4H,

C₃₆H₅₀O₂P₂Pt: C, 56.02; H, 6.53; P, 8.03. Found: C,

¼ ꢀ230.3^ꢄ.

Na

25 ^ꢄC;toluene

3

dd of q with pseudo-t, J_HH= 8.6 Hz, J_PtH= 105.4

2

55.97; H, 6.60; P, 8.52%. ½aꢃ

3

Hz, J_PHcis= 67.2 Hz, J_PHtrans= 2.8 Hz, CH₂ꢀCH₃),

6.54 (2H, dd, J_HH= 7.6 Hz, J_HH= 1.8 Hz, backbone

phenyl-H), 6.62 (2H, t, J_HH= 7.6 Hz backbone phenyl-

H), 6.80 (2H, t, J_HH= 7.3 Hz, backbone phenyl-H),

6.84 (2H, dd, J_HH= 7.3, J_HH= 1.8 Hz, backbone phe-

4.4. General procedure for the thermal decomposition

Between 15 and 80 mg of [ligand]PtEt₂were dissolved

in 0.5 mL of toluene-d⁸and put into a J. Young NMR

K. Ruhland, E. Herdtweck / Journal of Organometallic Chemistry 690 (2005) 5215–5236

5233

1

pseudo-t, J_CP= 26.3 Hz, J_CPt= 19.9 Hz, CHCH₃),

2

tube. The NMR tube was heated in an oil bath for de-

ﬁned time periods. The temperature was regulated by

a contact thermometer and double-checked by a digital

thermometer in the oil bath. The temperature was con-

stant up to 1 ꢀC. After a deﬁned time period the sam-

ple was taken out of the oil bath and cooled down in an

ice bath. Then the sample was measured by means of ¹H

and ³¹P NMR spectroscopy and put back into the oil

bath.

1

2

32.75 (d of pseudo-t, J_CP= 55.6 Hz, J_CPt= 12.4 Hz,

CHCH₃), 121.52 (s), 121.97 (s), 124.98 (s), 125.20 (s),

125.36 (s), 129.99 (s), 133.06 (s), 152 (br s). ¹⁹⁵Pt{¹H}

1

NMR (toluene-d⁸, ppm): ꢀ5188.4 (t, J_PPt= 3999.7

Hz). ³¹P{¹H} NMR (toluene-d⁸, ppm): 186.3 (s), 186.3

Na

25 ^ꢄC;toluene

1

(d, J_PPt= 4000.7 Hz). ½aꢃ

¼ ꢀ248.9^ꢄ.

4.5. VT measurement with [1]Pt(Ethene)

4.4.1. [1]Pt(Ethene)

Oﬀ-white solid (yield quantitative). H NMR (tolu-

An NMR tube containing 0.5 mL of toluene-d⁸and

20 mg of [1]Pt(Ethene) was placed into a Schlenk tube

under ethene atmosphere. Then the ethene atmosphere

was replaced by argon. Diﬀerent concentrations of eth-

ene were achieved by carefully evacuating the Schlenk

tube and reﬁlling with argon until the desired concentra-

tion of ethene determined by ¹H NMR spectroscopy was

reached. The temperature control unit of the NMR ma-

chine was calibrated with a sample of 1,2 ethanediol

[18]. The measurement was done in 10 K steps. The tem-

perature was allowed to reach a constant level for 15

min at each step. The measurement was done both

increasing the temperature from 333 to 373 K and by

decreasing the temperature from 373 K to room temper-

ature. The average value received from the ‘‘up’’ and

‘‘down’’ measurement was taken for the kinetic

evaluation.

1

ene-d⁸, ppm): 0.74 (12H, m, CH–CH₃), 1.055 (3H, d,

2

²J_HH= 7.2 Hz, CH–CH₃), 1.09 (3H, d, J_HH= 7.3 Hz,

2

CH–CH₃), 1.20 (3H, d, J_HH= 6.9 Hz, CH–CH₃), 1.29

2

(3H, d, J_HH= 6.5 Hz, CH–CH₃), 1.34 (2H, hept,

2

²J_HH= 7.1 Hz, CH–CH₃), 1.88 (4H, m, J_HPt= 90 Hz,

2

CH₂), 2.22 (, 2H, hept, J_HH= 6.3 Hz, CH–CH₃), 6.82

2

(2H, t, J_HH= 7.4 Hz, CH-arom.), 6.9–7.23 (6H, m,

CH-arom.). ¹³C{¹H} NMR (toluene-d⁸, ppm): 16.75

1

(pseudo-t, J_CPt= 17.6 Hz, ethene-C), 16.91 (pseudo-t,

J_CPt= 7.3 Hz, CHCH₃), 17.41 (pseudo-t, J_CPt= 5.8

Hz, CHCH₃), 17.80 (pseudo-t, J_CPt= 20.5 Hz, CHCH₃),

(one CH₃group overlayed by solvent peak), 27.23 (d of

1

pseudo-t, J_CP= 25.6 Hz, J_CPt= 27.0 Hz, CHCH₃),

1

33.15 (d of pseudo-t, J_CP= 52.7 Hz, J_CPt= 29.3 Hz,

CHCH₃), 122.29 (s), 122.78 (s), 131.29 (pseudo-t,

J_CPt= 22.4 Hz, ortho-CH), 132.95 (s, bridging C–C),

153.97 (br pseudo-t). ¹⁹⁵Pt{¹H} NMR (toluene-d⁸,

4.6. Single-crystal X-ray structure determination of

compounds [1]PtCl₂, [1]PtEt₂, [1]Pt(Ethene),

[3]PtCl₂Æ CH₂Cl₂and [3]PtEt₂Æ 0.5C₄H₁₀O

1

ppm): ꢀ5105.4 (t, J_PPt= 4060.73 Hz). ³¹P{¹H} NMR

1

(toluene-d⁸, ppm): 186.7 (s), 186.7 (d, J_PPt= 4060.7

Hz). FT-IR (cm^ꢀ1): 3064 (w), 2959 (s), 2926(s), 2878

(s), 1575 (w), 1455 (m), 1384 (m), 1261 (s), 1209 (s),

1101 (s), 1022 (s), 881 (s), 802 (s), 765 (s), 664 (m), 505

(w). EA Calc. for C₂₆H₄₀O₂P₂Pt: C, 48.7; H, 6.28; P,

9.65. Found: C, 48.10; H, 6.31; P, 9.10%.

Crystal data and details of the structure determina-

tion are presented in Table 6. Suitable single crystals

for the X-ray diﬀraction study were grown from diethyl

ether (for [ligand]Pt(Alk)_n) or pentane/dichloromethane

(for [ligand]PtCl₂). A clear colorless plate (yellow prism,

pale yellow fragment, colorless fragment, pale yellow

fragment) was stored under perﬂuorinated ether, trans-

ferred in a Lindemann capillary, ﬁxed, and sealed. Pre-

liminary examination and data collection were carried

out on an area detecting system (NONIUS, MACH3,

j-CCD) at the window of a rotating anode (NONIUS,

FR951) and graphite monochromated Mo Ka radiation

4.4.2. [4]Pt(Ethene)

3

¹H NMR (toluene-d⁸, ppm): 0.24 (3H, d, J_HH= 7.3

3

Hz, CHCH₃), 0.28 (3H, d, J_HH= 7.3 Hz, CHCH₃),

3

0.47 (3H, d, J_HH= 7.4 Hz, CHCH₃), 0.51 (3H, d,

³J_HH= 7.3 Hz, CHCH₃), 0.92 (2H, hept, J_HH= 7.3

3

Hz, CHCH₃), 1.04 (3H, d, J_HH= 7.4 Hz, CHCH₃),

3

1.07 (3H, d, J_HH= 7.3 Hz, CHCH₃), 1.27 (3H, d,

³J_HH= 7.4 Hz, CHCH₃), 1.31 (3H, d, J_HH= 7.4 Hz,

(k = 0.71073 A). The unit cell parameters were obtained

3

˚

2

CHCH₃), 1.92 (2H, br s with d, J_PtH= 53.9 Hz, eth-

by full-matrix least-squares reﬁnement of 4860 (5522,

2463, 6481, 7385) reﬂections. Data collection were per-

formed at 123 (173, 173, 173, 173) K (OXFORD

CRYOSYSTEMS) within a h-range of 1.79ꢀ < h <

25.34ꢀ (2.22ꢀ < h < 25.35ꢀ, 2.15ꢀ < h < 25.33ꢀ, 2.11ꢀ <

h < 25.35ꢀ, 1.92ꢀ < h < 25.36ꢀ). Measured with 4 (10, 9,

9, 9) data sets in rotation scan modus with Du/

Dx = 1.0ꢀ (Du/Dx = 2.0ꢀ, Du/Dx = 2.0ꢀ, Dx = 1.0ꢀ,

Du/Dx = 1.0ꢀ). A total number of 18640 (68991,

30027, 63970, 122675) intensities were integrated.

Raw data were corrected for Lorentz, polarization,

2

ene-H), 1.97 (2H, br s with d, J_PtH= 53.9 Hz, ethene-

3

H), 2.29 (2H, hept, J_HH= 7.4 Hz, CHCH₃), 6.98 (2H,

3

d, J_HH= 14.7 Hz, Naph-H), 7.02 (2H, d, J_HH= 7.3

3

Hz, Naph-H), 7.15 (2H, t, J_HH= 9.8 Hz, Naph-H),

3

7.33 (2H, d J_HH= 9.8 Hz, Naph-H), 7.40 (2H, d

³J_HH= 9.8 Hz, Naph-H), 7.61 (2H, d J_HH= 9.8 Hz,

3

Naph-H). ¹³C{¹H} NMR (toluene-d⁸, ppm): 14.96

1

(pseudo-t, J_CPt= 19.0 Hz, ethene-C), 16.14 (pseudo-t,

J_CPt= 7.3 Hz, CHCH₃), 16.71 (pseudo-t, J_CPt= 3.6

Hz, CHCH₃), 18.00 (br pseudo-t, CHCH₃), 26.41 (d of

5234

K. Ruhland, E. Herdtweck / Journal of Organometallic Chemistry 690 (2005) 5215–5236

Table 6

Crystallographic data for [1]PtCl₂, [1]PtEt₂, [1]Pt(Ethene), [3]PtCl₂Æ CH₂Cl₂and [3]PtEt₂Æ 0.5C₄H₁₀

O

Complex

[1]PtCl₂

[1]PtEt₂

[1]Pt(Ethene)

[3]PtCl₂Æ CH₂Cl₂[3]PtEt₂Æ 0.5C₄H₁₀O

Formula

Formula weight

Color/habit

C₂₄H₃₆Cl₂O₂P₂Pt C₂₈H₄₆O₂P₂Pt

684.45

Colorless/plate

C₂₆H₄₀O₂P₂Pt

641.60

Pale yellow/fragment Colorless/fragment Pale yellow/fragment

C₃₇H₃₀Cl₄O₂P₂Pt C₈₄H₈₆O₅P₄Pt₂

671.67

Yellow/prism

905.43

1689.57

Crystal dimensions (mm³)

Crystal system

Space group

0.05 · 0.15 · 0.15 0.08 · 0.10 · 0.23 0.23 · 0.25 · 0.43 0.13 · 0.25 · 0.56 0.12 · 0.34 0.42

Monoclinic

P2₁/c (No. 14)

9.9986(2)

14.6637(3)

18.5545(4)

101.9791(13)

2661.15(10)

4

Monoclinic

C2/c (No. 15)

33.1954(3)

9.5783(1)

18.5887(2)

106.4384(5)

5668.79(10)

8

Monoclinic

C2/c (No. 15)

12.0343(1)

15.3551(2)

13.9530(1)

91.8165(5)

2577.05(4)

4

Monoclinic

P2₁/n (No. 14)

8.9801(1)

24.5095(1)

15.7767(1)

96.3945(3)

3450.81(5)

4

Orthorhombic

Pbca (No. 61)

9.9727(1)

21.1883(1)

34.3638(2)

90

˚

a (A)

˚

b (A)

˚

c (A)

b (ꢀ)

3

˚

V (A )

7261.23(9)

4

173

Z

T (K)

D_calc(g cm^ꢀ3

123

1.708

173

1.574

173

1.654

173

1.743

)

1.546

3.990

3384

l (mm^ꢀ1

F(000)

)

5.613

1352

5.085

2704

5.589

1280

4.502

1776

h Range (ꢀ)

Index ranges (h,k,l)

1.79–25.34

12, 17, 22

18640

2.22–25.35

39, 11, 22

68991

2.15–25.33

14, 18, 16

30027

2.11–25.35

10, 29, 19

63970

1.92–25.36

12, 25, 41

122675

Number of reﬂections collected

Number of independent reﬂections/R_int

Number of observed reﬂections (I > 2(I))

Number of data/restraints/parameters

R1/wR2 (I > 2(I))^a

R1/wR2 (all data)^a

Goodness-of-ﬁt on F^2a

Largest diﬀerence in peak and hole (e A

4865/0.050

4393

5189/0.057

4103

2368/0.035

2351

6298/0.050

5920

6634/0.050

6121

4865/0/288

0.0311/0.0717

0.0364/0.0739

1.106

5189/0/482

0.0216/0.0354

0.0346/0.0381

1.038

2368/0/222

0.0104/0.0264

0.0105/0.0265

1.143

6298/0/415

0.0182/0.0432

0.0206/0.0441

1.082

6634/0/455

0.0201/0.0504

0.0233/0.0517

1.052

ꢀ3

˚

)

+1.72 and ꢀ1.14 +0.84 and ꢀ0.62 +0.41 and ꢀ0.46

+0.68 and ꢀ0.51

+0.89 and ꢀ0.73

P

R₁= (i_Fo| ꢀ |F_ci)/ |F_o|; wR₂¼ f ½wðF ²_oꢀ F _c²Þ ꢃ= ½wðF _o²Þ ꢃg¹⁼²; GOF ¼ f ½wðF _o²ꢀ F ²_cÞ ꢃ=ðn ꢀ pÞg

.

2

1=2

a

and, arising from the scaling procedure, for latent decay

4.6.3. [1]Pt(Ethene)

and absorption eﬀects. After merging [R_int= 0.050

(0.057, 0.035, 0.050, 0.050)] a sum of 4865 (5189, 2368,

6298, 6634) (all data) and 4393 (4103, 2351, 5920,

6121) [I > r(I)], respectively, remained and all data were

used. The structures were solved by a combination of

direct methods and diﬀerence Fourier syntheses. All

non-hydrogen atoms were reﬁned with anisotropic dis-

placement parameters. Full-matrix least-squares reﬁne-

ments with 288 (482, 222, 415, 455) parameters were

Small extinction eﬀects were corrected with the

SHELXL-97 procedure [e = 0.00028(4)]. The molecule is

located on a crystallographic twofold axis.

4.6.4. [3]PtEt₂Æ 0.5C₄H₁₀O

The solvent molecule diethyl ether is disordered over

two positions.

P

2

carried out by minimizing

wðF ²_oꢀ F ²_cÞ with the

5. Supplementary material

SHELXL-97 weighting scheme and stopped at shift/err

<0.001 (0.002, 0.001, 0.002, 0.002). The ﬁnal residual

electron density maps showed no remarkable features.

Neutral atom scattering factors for all atoms and anom-

alous dispersion corrections for the non-hydrogen atoms

were taken from International Tables for Crystallo-

graphy. All calculations were performed on an Intel

Pentium II PC, with the STRUX-V system, including

the programs ^PLATON, SIR-92, and SHELXL-97 [19].

Crystallographic data (excluding structure factors)

for the structures reported in this paper have been

deposited with the Cambridge Crystallographic Data

Centre as supplementary publication Nos. CCDC-

273528 ([1]PtCl₂), CCDC-273531 ([1]PtEt₂), CCDC-

273530 ([1]Pt(Ethene)), CCDC-273532 ([3]PtCl₂Æ

CH₂Cl₂), and CCDC-273529 ([3]PtEt₂Æ 0.5C₄H₁₀O).

Copies of the data can be obtained free of charge on

application to CCDC, 12 Union Road, Cambridge

CB2 1EZ, UK (fax: +44 1223 336 033; e-mail:

deposit@ccdc.cam.ac.uk).

4.6.1. [1]PtEt₂, [1]Pt(Ethene)

All hydrogen atoms were found and reﬁned with indi-

vidual isotropic displacement parameters.

4.6.2. [1]PtCl₂, [3]PtCl₂Æ CH₂Cl₂,

[3]PtEt₂Æ 0.5C₄H₁₀O

All hydrogen atoms were placed in ideal positions

Acknowledgements

K.R. thanks the Fonds der chemischen Industrie

for a Liebig grant. K.R. thanks Prof. Dr. mult.

(riding model).

K. Ruhland, E. Herdtweck / Journal of Organometallic Chemistry 690 (2005) 5215–5236

5235

[6] G.R. Nuzzo, T.J. McCarthy, G.M. Whitesides, Inorg. Chem. 20

(4) (1981) 1312–1314.

W.A. Herrmann for ﬁnancial support. E.H. thanks R.

Jaeger, S. Beer and S. Randoll for there help during

the course of the X-ray measurements.

[7] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A.

Robb, J.R. Cheeseman, J.A. Montgomery Jr., T. Vreven, K.N.

Kudin, J.C. Burant, J.M. Millam, S.S. Iyengar, J. Tomasi, V.

Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G.A.

Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R.

Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O.

Kitao, H. Nakai, M. Klene, X. Li, J.E. Knox, H.P. Hratchian,

J.B. Cross, C. Adamo, J. Jaramillo, R. Gomperts, R.E. Strat-

mann, O. Yazyev, A.J. Austin, R. Cammi, C. Pomelli, J.W.

Ochterski, P.Y. Ayala, K. Morokuma, G.A. Voth, P. Salvador,

J.J. Dannenberg, V.G. Zakrzewski, S. Dapprich, A.D. Daniels,

M.C. Strain, O. Farkas, D.K. Malick, A.D. Rabuck, K. Ragh-

avachari, J.B. Foresman, J.V. Ortiz, Q. Cui, A.G. Baboul, S.

Cliﬀord, J. Cioslowski, B.B. Stefanov, G. Liu, A. Liashenko, P.

Piskorz, I. Komaromi, R.L. Martin, D.J. Fox, T. Keith, M.A.

Al-Laham, C.Y. Peng, A. Nanayakkara, M. Challacombe,

P.M.W. Gill, B. Johnson, W. Chen, M.W. Wong, C. Gonzalez,

J.A. Pople, ^GAUSSIAN-03, Revision B.01, Gaussian, Inc., Pitts-

burgh, PA, 2003.

References

[1] (a) A.E. Shilov, G.B. Shulꢁpin, Chem. Rev. 97 (1997) 2879–2932;

(b) R.H. Crabtree, Chem. Rev. 85 (1985) 245–269;

(c) J. Halpern, Inorg. Chim. Acta 100 (1985) 41–48;

(d) G.W. Parshall, Acc. Chem. Res. 8 (1975) 113–117;

(e) A.E. Shilov, G.B. Shulꢁpin (Eds.), Activation and Catalytic

Reactions of Saturated Hydrogencarbons in the Presence of Metal

Complexes, Kluwer Academic Publishers, Dortrecht, 2000;

(f) J.A. Davies, P.L. Watson, J.F. Liebman, A. Greenberg (Eds.),

Selective hydrocarbon activation, VCH, New York/Weinheim,

1990;

(g) P.W.N.M. van Leeuwen, K. Morokuma, J.H. van Lenthe

(Eds.), Theoretical aspects of homogeneous catalysis, Kluwer

Academic Publishers, Dotrecht, 1995;

[8] The Basis set was obtained from the Extensible Computational

Chemistry Environment Basis Set Database, Version 02/25/04, as

developed and distributed by the Molecular Science Computing

Facility, Environmental and Molecular Sciences Laboratory

which is part of the Paciﬁc Northwest Laboratory, P.O. Box

999, Richland, WA 99352, USA, and funded by the US

Department of Energy. The Paciﬁc Northwest Laboratory is a

multi-program laboratory operated by Battelle Memorial Institute

for the US Department of Energy under Contract DE-AC06-

76RLO 1830. Contact David Feller or Karen Schuchardt for

further information.

(h) A.D. Ryabov, Chem. Rev. 90 (1990) 403–424;

(i) W.D. Jones, F.J. Feher, Acc. Chem. Res. 22 (1989) 91–100;

(j) B.A. Arndtsen, R.G. Bergman, T.A. Mobley, T.H. Peterson,

Acc. Chem. Res. 28 (1995) 154–162;

(k) B. Rybtchinski, D. Milstein, Angew. Chem. Int. Ed. 38 (1999)

870–883;

(l) Chul-Ho Jun, Chem. Soc. Rev. 33 (2004) 610–618.

[2] J.A. Martinho, J.L. Beauchamp, Chem. Rev. 90 (1990) 629–688.

[3] (a) B.L. Edelbach, R.J. Lachicotte, W.D. Jones, J. Am. Chem.

Soc. 120 (1998) 2843–2853;

[9] (a) P.-T. Cheng, S.C. Nyburg, Can. J. Chem. 50 (6) (1972) 912–

916;

(b) G. Ujaque, F. Maseras, O. Eisenstein, L. Liable-Sands, A.L.

Rheingold, W. Yao, R.H. Crabtree, New J. Chem. (1998) 1493–

1498;

(b) H.C. Clark, G. Ferguson, Mark J. Hampden-Simith, B.

Kaitner, H. Ruegger, Polyhedron 7 (1988) 1349–1353.

[10] N.C. Harrison, M. Murray, J.L. Spencer, F.G.A. Stone, J. Chem.

Soc., Dalton Trans. (1978) 1337–1342.

(c) Z. Lu, C.H. Jun, S.R. de Gala, M.P. Sigalas, O. Eisenstein,

R.H. Crabtree, Organometallics 14 (1995) 1168–1175;

(d) C.N. Iverson, W.D. Jones, Organometallics 20 (2001) 5745–

5750;

[11] (a) G.M. Whitesides, J.F. Gaasch, E.R. Stedronsky, J. Am.

Chem. Soc. 94 (1972) 5258–5270;

(e) X. Zhang, G.B. Carpenter, D.A. Sweigart, Organometallics 18

(1999) 4887–4888.

(b) J. Chatt, R.S. Coﬀey, A. Gough, D.T. Thompson, J. Chem.

Soc. (A) (1968) 190–194;

[4] (a) J.W. Suggs, C.-H. Jun, J. Am. Chem. Soc. 106 (1984) 3054;

(b) J.W. Suggs, C.-H. Jun, J. Am. Chem. Soc. 108 (1986) 4679;

(c) J.W. Suggs, C.-H. Jun, J. Chem. Soc., Chem. Commun. (1985)

92;

(c) F. Ozawa, T. Ito, A. Yamamoto, J. Am. Chem. Soc. 102

(1980) 6457–6463.

[12] (a) H. Kwart, J. Slutsky, S.F. Sarner, J. Am. Chem. Soc. 95

(1973) 5242–5244;

(d) N. Chatani, Y. Ie, F. Kakiuchi, S. Murai, J. Am. Chem. Soc.

121 (1999) 8645;

(b) P. Krumbiegel, Isotopieeﬀekte, Akademie-Verlag GmbH,

Berlin, 1970.

(e) S.-Y. Liou, M.E. van der Boom, D. Milstein, Chem. Commun.

(1998) 687;

[13] (a) M. Shampsique, E. Karkhaneei, A. Afkhami, Polyhedron 17

(1998) 3809–3814;

(f) B. Rybtchinski, S. Oevers, M. Montag, A. Vigalok, H.

Rozenberg, J.M.L. Martin, D. Milstein, J. Am. Chem. Soc. 123

(2001) 9064–9077;

(b) H. Gunther, NMR spectroscopy, Wiley, Chichester, 1995, p.

339;

(c) J.M. Ceraso, P.B. Smith, J.S. Landers, J.L. Dye, J. Phys.

Chem. 81 (8) (1977) 760–765.

(g) A. Sundermann, O. Uzan, D. Milstein, J.M.L. Martin, J. Am.

Chem. Soc. 122 (2000) 7095–7104;

[14] (a) J.P. Birk, J. Halpern, A.L. Pickard, Inorg. Chem. (1968)

2672–2673;

(h) B. Rybtchinski, D. Milstein, J. Am. Chem. Soc. 121 (1999)

4528–4529;

(b) H.C. Clark, G. Ferguson, Mark J. Hampden-Simith, B.

Kaitner, H. Ruegger, Polyhedron 7 (1988) 1349–1353.

[15] K. Ruhland, E. Herdtweck, Adv. Synth. Catal. 347 (2005) 398–404.

[16] A. Gillie, J.K. Stille, J. Am. Chem. Soc. 102 (1980) 4933–4941.

[17] J. Chatt, L.M. Vallarino, L.M. Venanzi, J. Chem. Soc. (1957)

2496–2505.

(i) C.-H. Jun, C.W. Moon, D.-Y. Lee, Chem. Eur. J. 8 (2002) 2423;

(j) C.-H. Jun, H. Lee, J. Am. Chem. Soc. 121 (1999) 880;

(k) C.-H. Jun, D.-Y. Lee, H. Lee, J.-B. Hong, Angew. Chem. Int.

Ed. 39 (2000) 3070;

(l) C.-H. Jun, H. Lee, S.-G. Lim, J. Am. Chem. Soc. 123 (2001) 751.

[5] (a) C.A. Tolman, Chem. Rev. 77 (1977) 313;

(b) R. Mason, D.W. Merck, Angew. Chem. 90 (1978) 195;

(c) P.S. Pregosin, Transition metal nuclear magnetic resonance,

Elsevier, Amsterdam, 1991;

[18] (a) A.L. van Geet, Anal. Chem. 42 (1970) 679–680;

(b) H. Friebolin, G. Schilling, L. Pohl, Org. Magn. Reson. 12

(1979) 569–573;

(c) C. Piccinni-Leopardii, O. Fabre, J. Reisse, Org. Magn. Reson.

8 (1976) 233–236;

(d) C. Brevard, P. Granger, Handbook of High Resolution

Multinuclear NMR, Wiley, Chichester, 1981.

5236

K. Ruhland, E. Herdtweck / Journal of Organometallic Chemistry 690 (2005) 5215–5236

(d) F.H. Ko¨hler, X. Xie, Magn. Reson. Chem. 35 (1997) 487–492.

[19] (a) Data Collection Software for Nonius j-CCD devices, Delft,

The Netherlands, 2001.;

(d) A.J.C. Wilson (Ed.), International Tables for Crystallography,

vol. C, Kluwer Academic Publishers, Dordrecht, 1992, Tables

6.1.1.4, 4.2.6.8, and 4.2.4.2;

(b) Z. Otwinowski, W. Minor, Methods Enzymol. 276 (1997) 307ﬀ;

(c) A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi,

M.C. Burla, G. Polidori, M. Camalli, ^SIR-92, J. Appl. Crystallogr.

27 (1994) 435–436;

(e) A.L. Spek, ^PLATON: A multipurpose crystallographic tool,

Utrecht University, Utrecht, The Netherlands, 2001;

(f) G.M. Sheldrick, ^SHELXL-97, Universita¨t Go¨ttingen, Go¨ttingen,

Germany, 1998.

Article Doi

Mechanistic investigation of the thermal decomposition of Biphen(OPi-Pr)PtEt2: An entrance into C-C single bond activation?

DOI: 10.1016/j.jorganchem.2005.04.048

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