The methoxycarbonylation of vinyl acetate catalyzed by palladium complexes of [1,2-phenylenebis(methylene)]bis[di(tert-butyl)phosphine]

Article abstract of DOI:10.1002/hlca.200690174

Palladium complexes of [1,2-phenylenebis(methylene)]bis[di(tert-butyl) phosphine] (1) catalyze the methoxycarbonylation of vinyl acetate (=ethenyl acetate) in the presence of methanesulfonic acid (Scheme 1). High selectivities to ester products can be obtained if free phosphine ligand is in excess over the amount of added acid (Table 1). Selectivities to methyl 2-acetoxypropanoate, a precursor to lactate esters, can be as high as 3.6:1 at low temperature and pressure (Table 2). Replacing ^tBu by ⁱPr groups leads to less-active catalysts and lower selectivities to the branched product. Replacing the phenylene moiety by a naphthalenediyl moiety also gives lower activity, but with similar selectivity to the phenylene-based analogues. Linear hydrocarbon-chain linkers as the backbone instead of the phenylenebis(methylene) linker leads to poor catalysis, except for a propane-1,3-diyl linker, which gives good rates but poor branched selectivity (Table 5). The effect of different reaction conditions on the catalysis is discussed. The syntheses of the new xylene-based diphosphines 2-5 with one to four ⁱPr groups replacing the ^tBu groups at the P-atoms of 1 and of the ligands 6 and 7 based on 1,2- and 2,3-dimethylnaphthalene are also described (Schemes 2 and 3).

Full text of DOI:10.1002/hlca.200690174

Helvetica Chimica Acta – Vol. 89 (2006)
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The Methoxycarbonylation of Vinyl Acetate Catalyzed by Palladium
Complexes of [1,2-Phenylenebis(methylene)]bis[di(tert-butyl)phosphine]
by Adam J. Rucklidgea), George E. Morrisb), Alexandra M. Z. Slawina), and David J. Cole-Hamilton*a)
a) EaStCHEM, School of Chemistry, University of St. Andrews, St. Andrews, Fife, KY16 9ST, UK
(phone: +44-1334-463805; fax: +44-1334-464808; e-mail: djc@st-and.ac.uk)
b) BP Chemicals, Ltd., Salt End, Hull, HU12 8DS, UK
In celebration of the work of Giambattista Consiglio, a fine, imaginative scientist
Palladium complexes of [1,2-phenylenebis(methylene)]bis[di(tert-butyl)phosphine] (1) catalyze the
methoxycarbonylation of vinyl acetate (=ethenyl acetate) in the presence of methanesulfonic acid
(Scheme 1). High selectivities to ester products can be obtained if free phosphine ligand is in excess
over the amount of added acid (Table 1). Selectivities to methyl 2-acetoxypropanoate, a precursor to lac-
tate esters, can be as high as 3.6 :1 at low temperature and pressure (Table 2). Replacing tBu by iPr groups
leads to less-active catalysts and lower selectivities to the branched product. Replacing the phenylene
moiety by a naphthalenediyl moiety also gives lower activity, but with similar selectivity to the phenyl-
ene-based analogues. Linear hydrocarbon-chain linkers as the backbone instead of the phenylenebis-
(methylene) linker leads to poor catalysis, except for a propane-1,3-diyl linker, which gives good rates
but poor branched selectivity (Table 5). The effect of different reaction conditions on the catalysis is dis-
cussed. The syntheses of the new xylene-based diphosphines 2–5 with one to four iPr groups replacing the
tBu groups at the P-atoms of 1 and of the ligands 6 and 7 based on 1,2- and 2,3-dimethylnaphthalene are
also described (Schemes 2 and 3).
Introduction. – In the drive to make chemical processes and products more sustain-
able, lactate esters have been identified as possible alternative solvents because of their
low vapor pressure, good solubilizing properties, and biodegradability. Their (S) forms
are attractive monomers for the production of biodegradable polymers with properties
similar to those of polyethene or polystyrene. Optically pure lactate esters are currently
produced from the fermentation of glucose obtained from starch [1], but an alternative
route would be the alkoxycarbonylation of vinyl acetate (=ethenyl acetate) to form
alkyl esters, which, upon removal of the acetyl group would give the desired hydroxy-
propanoic acid (lactate for the branched product) esters (Scheme 1). An asymmetric
version of this reaction could also be envisaged. Although vinyl acetate is derived
from ethene and acetic acid, it is a cheap and very readily available feedstock.
Drent [2] has reported the methoxycarbonylation of vinyl acetate using palladium
acetate and (propane-1,3-diyl)bis[di(tert-butyl)phosphine] as the catalyst system. In
MeOH/diglyme (=1,2-dimethoxyethane) at 758 and 40 bar CO, the methyl ester was
formed with a branched/linear (b/l) ratio of 2 :1 at a rate of 200 mol (g Pd h)ꢀ1.
Kudo et al. [3] showed that methoxycarbonylation of vinyl acetate can be catalyzed
by PdCl2/PPh3 in the presence of 2,6-lutidine (=2,6-dimethylpyridine) at 1208 and
200 bar. A considerable quantity of methyl acetate was formed due to the methanolysis
© 2006 Verlag Helvetica Chimica Acta AG, Zürich

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Helvetica Chimica Acta – Vol. 89 (2006)
Scheme 1. The Alkoxycarbonylation of Vinyl Acetate as a Step in the Production of Alkyl Lactates
of vinyl acetate. A preliminary account [4] and a patent [5] containing some of the
results reported in this paper appeared alongside a paper from Tanaka and co-workers
[6] in which palladium complexes of [1,2-phenylenebis(methylene)]bis[di(tert-butyl)-
phosphine] (=bis{(di(tert-butyl)phosphino]methyl}benzene=dtbpmb; 1) and a solid
acid catalyst were used to promote the methoxycarbonylation of vinyl acetate at 60
bar and 608 with a b/l ratio of 2.7, but with some loss of vinyl acetate to methanolysis.
Diphosphine 1 has been shown to be an excellent ligand for the Pd-catalyzed
methoxycarbonylation of ethene [7], a process which is currently being commercial-
ized. The system Pd/1 is also highly active for the methoxycarbonylation of long-
chain alkenes [8] giving very high linear selectivities, of unsaturated esters and acids
giving very high selectivities to a,w-diesters [9], of styrene giving high branched selec-
tivity [6], or of aromatic chlorides to benzoic acid esters [10]. We now report details of
the methoxycarbonylation of vinyl acetate catalyzed by palladium complexes of 1
under mild conditions in the presence of methanesulfonic acid.
Results and Discussion. – Synthesis of Diphoshines. A series of diphosphines based
on a xylene backbone (see 2–5), a naphthalene backbone (see 6 and 7), or a chain back-
bone (8–10) were synthesized for use in the Pd-catalyzed methoxycarbonylation of
vinyl acetate (see Schemes 2 and 3). Ligands 2 and 6 were synthesized by reacting
1,2-C6H4(CH2K)2 (for 2) or the analogue derived from 2,3-dimethylnaphthalene (for
6) with the appropriate lithium chlorophosphine as previously reported for 1 [11].
The other symmetrically substituted diphosphines, 3 and 7, were prepared by the reac-
tion of Li[R1R2PBH3] with 1,2-C6H4(CH2Br)2 (for 3) or the analogue derived from 1,2-
dimethylnaphthalene (for 7) (see Scheme 2). The two diastereoisomers of ligand 3,
rac-3 and meso-3, were separated by fractional recrystallization of the borane adduct
prior to removal of the borane by refluxing the adduct in Et2NH to give the free ligand.
G
The rac-isomer of the borane adduct, rac-3·2 BH3, was characterized crystallographi-
cally, Fig. 1.
The unsymmetrical diphosphines were synthesized by using a method adapted from
Leone and Consiglio [12]. They prepared dicyclohexyl{{2-[(diphenylphosphino)me-
thyl]phenyl}methyl}phosphine
(=1-[(dicyclohexylphosphino)methyl]-2-[(diphenyl-
phosphino)methyl]benzene) by the reaction of lithium dicyclohexylphosphide with
1,5-dihydro-2,4,3-benzodioxathiepin 3,3-dioxide followed by lithium diphenylphos-
phide. The synthesis of the more-basic di(tert-butyl)phosphine analogues by this
method leads to a problem. Once the first phosphine group is added to the backbone

Helvetica Chimica Acta – Vol. 89 (2006)
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Scheme 2. Synthesis of Symmetrically Substituted Ligands Used for the Methoxycarbonylation of
Vinyl Acetate.
i) KOtBu/BuLi. ii) R1R2PCl. iii) N-Bromosuccinimide (NBS)/(PhC(O)O)2. iv) Li[R1R2PBH3]. v) Et2
NH.
G
of the ligand, the strongly nucleophilic P-atom can undergo a nucleophilic attack at the
second CH
2OSOꢀ3 group and form the stable cyclic phosphonium sulfate. This attack
AHCTREUNG
can be stopped by using the borane-protected phosphide, as the lone electron pair at
the introduced atom is in the PꢀB dative bond and hence the nucleophilicity of the
P-atom is reduced (Scheme 3). The second phosphine group can then be introduced,
and the borane groups can be removed by refluxing in Et2
gave di(tert-butyl){{2-[(diisopropylphosphino)methyl]phenyl}methyl}phosphine (4)
and di(tert-butyl){{2-{[(tert-butyl)isopropylphosphino]methyl}phenyl}methyl}phos-
A
phine (5) in 73 and 74% yield, respectively.
Stabilityof Vinyl Acetate. Initial studies on the catalytic methoxycarbonylation of
vinyl acetate (see below) showed significant formation of methyl acetate and 1,1-dime-
thoxyethane from the methanolysis of vinyl acetate. To restrict the methanolysis, stabil-
ity tests were carried out. Vinyl acetate was stirred with MeOH in toluene together with
combinations of promoters such as 1 and methanesulfonic acid (MeSO3
A
Vinyl acetate is stable in the presence of 1, but if MeSO3H is present, the majority of
AHCTREUNG
the vinyl acetate is converted to methyl acetate even at room temperature, confirming
that the transesterification of vinyl acetate is catalyzed by acid. However, if both the
acid MeSO3H and the phosphine 1 are present together, there is minimal degradation
N
of the vinyl acetate. As expected, the higher the reaction temperature, the greater the
extent of degradation of vinyl acetate, although the side reaction is still inhibited if both
acid and base are added together (i.e., the phosphonium salt is present rather than the
free acid). Tanaka and co-workers have shown that polymeric acids can also reduce the
side reactions whilst allowing activity from the same catalytic system [6]. An under-
standing of the effect of acid on vinyl acetate degradation means that it is possible to

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Helvetica Chimica Acta – Vol. 89 (2006)
Fig. 1. Molecular stucture and numbering scheme for rac-3·2 BH3. The (R,R) enantiomer is shown,
but the crystals contain equal numbers of the (R,R) and (S,S) isomers. P(1)ꢀC(1) 1.8482(13), P(1)ꢀ
C(13) 1.8488(14), P(1)ꢀC(9) 1.8717(14), P(1)ꢀB(1) 1.9270(17), P(8)ꢀB(8) 1.8424(14), P(8)ꢀC(20)
1.8510(15), P(8)ꢀC(16) 1.8629(15), and P(8)ꢀB(8) 1.9200(16) Å; C(13)ꢀP(1)ꢀC(1) 105.05(6), C(13)ꢀ
P(1)ꢀC(9) 109.98(6), C(1)ꢀP(1)ꢀC(9) 102.66(6), C(13)ꢀP(1)ꢀB(1) 111.61(7), C(1)ꢀP(1)ꢀB(1)
114.26(7), C(9)ꢀP(1)ꢀB(1) 112.67(8), C(8)ꢀP(8)ꢀC(20) 104.64(7), C(8)ꢀP(8)ꢀC(16) 104.42(7),
C(20)ꢀP(8)ꢀC(16) 112.91(7), C(8)ꢀP(8)ꢀB(8) 113.08(6), C(20)ꢀP(8)ꢀB(8) 109.11(8), and C(16)ꢀ
P(8)ꢀB(8) 112.42(7) Å.
Scheme 3. Synthesis of Unsymmetrical Diphosphines
i) SOCl2, CH2Cl2, 08, 2 h. ii) NaIO4, RuO4, 1,2-C2H4Cl2/MeCN/H2O 1:1:1.5. iii) Li[tBu2PBH3], THF,
warmed from ꢀ788. iv) Li[R1R2 PBH3], THF, warmed from ꢀ788. v) Et2
A

Helvetica Chimica Acta – Vol. 89 (2006)
1787
tailor the reaction conditions so that no free acid is present in the system and hence that
no degradation occurs. Catalytic results show that the phosphonium salt derived from 1
and MeSO3
reaction. As a result of these studies, the majority of catalytic reactions were carried
out with an excess of phosphine ligand over MeSO3H.
H is sufficiently acidic to protonate the P-center and initiate the catalytic
AHCTREUNG
a
Table 1. Stabilityof Vinyl Acetate in the Presence of MeOH
)
MeSO3
A
1 [mmol]
258
808
VAM [%]
AcOMe [%]
VAM [%]
AcOMe [%]
0
1
0
1
0
0
1
1
100
50
100
100
0
50
0
100
0
100
100
0
100
0
0
0
a) Reaction conditions: vinyl acetate (VAM) (2 ml), MeOH (2 ml), toluene (9 ml), reaction time 3 h.
Methoxycarbonylation Catalysis in the Presence of Diphosphine Ligand 1. For
ethene, one of the best methoxycarbonylation catalyst systems known is the [Pd(1)] cat-
alyst employed by Lucite [7]. Vinyl acetate methoxycarbonylation was initially
attempted with similar ratios of Pd/1/MeSO3
used in ethene carbonylation: [Pd2(dba)3] (10 mg, 0.01 mmol, 10ꢀ3 M; dba=1,5-diphe-
nylpenta-1,4-dien-3-one), 1 (8.7 mg, 0.02 mmol), MeSO3H (27 ml, 0.4 mmol), MeOH
H, but at a higher concentration than
AHCTREUNG
(18 ml), and vinyl acetate (2 ml), 808, 10 bar. After 3 h, the reaction was stopped,
and the conversion of vinyl acetate was found to be 100% with a selectivity to the esters
of 9% and a b/l ratio of 15.6 :1. The remaining products were AcOMe and 1,1-dime-
thoxyethane, which arise because of the high acid concentration (excess MeSO3H) in
C
the system, which catalyzes the methanolysis of vinyl acetate. Omission of 1 led to
100% conversion of the vinyl acetate but with full selectivity to the degradation prod-
ucts.
To overcome the degradation problem, the ratio of 1 to Pd was varied to find the
optimum ratio (Fig. 2). During this, the ratio of ligand to acid was kept constant at
1:1 thus ensuring that no free acid was present. The result for the reaction where the
1/Pd ratio is 5 :1 shows a drop in the b/l ratio. It is believed that the b/l ratio at a 1/
Pd ratio of 2.5 :1 is artificially inflated because of the low conversion. We have
shown in other studies that the b/l ratio drops as the conversion increases. The b/l
ratio decreases with temperature (Fig. 3) and increases as the pressure of CO is reduced
(Fig. 4). A possible explanation is that CO displaces the coordinated C=O in a five-
membered chelate, thus removing any extra stability of the alkyl intermediate in the
branched-chain pathway and rendering the linear and branched pathways of similar
activation energy (Scheme 4). Five-membered chelates of this kind are observed during
the methoxycarbonylation or copolymerization of ethene with CO [13][14].
The maximum b/l ratio of 3.6 :1 was obtained with the Pd/1 system when the CO
pressure was 3 bar and the reaction was carried out at room temperature (Table 2, com-
pound 1)

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Helvetica Chimica Acta – Vol. 89 (2006)
Fig. 2. Effect of 1/Pd ratio on the products from the methoxycarbonylation of vinyl acetate.
[Pd2(dba)3] (0.05 mmol), vinyl acetate (2 ml), MeOH (11 ml), MeSO3H (same mol amount as mol of
A
ligand), 808, CO (30 bar), 3 h.
Fig. 3. Effect of reactor temperature on the methoxycarbonylation of vinyl acetate. [Pd2(dba)3] (0.05
mmol), 1 (0.5 mmol), vinyl acetate (2 ml), MeOH (11 ml), MeSO3H (0.5 mmol), CO (30 bar), 3 h.
AHCTREUNG

Helvetica Chimica Acta – Vol. 89 (2006)
1789
Fig. 4. Effect of CO pressure on the b/l ratio of the methoxycarbonylation of vinyl acetate. [Pd2(dba)3]
(0.05 mmol), 1 (0.5 mmol), vinyl acetate (2 ml), MeOH (11 ml), MeSO3H (0.5 mmol), 808, 3 h.
AHCTREUNG
Scheme 4. Disruption of Chelate Binding of the Alkyl Intermediates in Methoxycarbonylation of Vinyl
Acetate
Table 2. Methoxycarbonylation of Vinyl Acetate with Different Diphosphine Ligandsa)
Ligand
Conversion [%]
Selectivity to esters [%]
b/l
1
2
3
35
0
7
8
7
47
13
15
18
100
n.a.b)
100
100
100
28
85
100
100
3.6
n.a.b)
0.8
rac-3
meso-3
4
5
6
7
0.8.
0.8
1.4
2.0
3.6
3.6
a) [Pd2(dba)3] (0.05 mmol), ligand (0.5 mmol), MeSO3
mmol), CO (3 bar), 258, 3 h. b) n.a.=not applicable.
A

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Helvetica Chimica Acta – Vol. 89 (2006)
Methoxycarbonylation Catalysis in the Presence of Related Ligands. In an attempt to
improve the b/l ratio of the products of the methoxycarbonylation of vinyl acetate over
the Pd/1/MeSO3H system, derivatives of 1 were tested in the catalysis (Table 2). Retain-
A
ing the xylene backbone of the ligand but altering the electronic effect slightly by using
a naphthalene-1,2-diyl instead of a 1,2-phenylene moiety does not alter the b/l ratio but
reduces the reaction rate (compounds 6 and 7, Table 2). We reasoned that better
branched selectivity might be obtained if the steric congestion around the Pd-center
were slightly reduced. However, it appears to be crucial that the substituents at the
t
t
i
P-atoms are Bu groups (Table 2). When one Bu group is replaced by Pr (compound
5), the conversion and branched selectivity are reduced. As further substitution is car-
ried out, the conversion and selectivity drop further. Once all four tBu groups have been
replaced by iPr groups, the ligand is no longer capable of producing an active catalyst.
As ligand 3 has three different substituents at both of the P-atoms, the ligand has
four diastereoisomers. Both the meso and rac forms were tested in the catalysis, and
they gave exactly the same result as the racemic mixture.
In the presence of ligand 7 and the optimum ratio 7/Pd of 5 :1, the MeSO
tration was varied. As can be seen in Fig. 5, the yield of methyl acetoxypropanoates
increases up to a MeSO3H/Pd ratio of 10 :1 (MeSO3H/7 2). Assuming that all the cata-
lyst is present as [Pd(7)HX]+ (X=CO, vinyl acetate, or MeOH), the ratio of free
MeSO3H/free 7 is 9 :4 at this point so that excess free acid is present in the system
3H concen-
A
ACHTREUNG
AHCTREUNG
(Table 3). After this, the yield of esters drops dramatically as a result of competitive
methanolysis of the vinyl acetate catalyzed by the excess acid. The b/l ratio is almost
insensitive to [MeSO3H] (see Fig. 6).
N
Fig. 5. Effect of acid concentration on the rate and ester selectivityof the methoxcyarbonlyation of
vinyl acetate. [Pd2(dba)3] (0.5 mmol), 7 (0.5 mmol), vinyl acetate (22 mmol), MeOH (11 ml), CO (3
bar), 258, 3 h.
Steric and Electronic Effects of Ligands. Changing from tBu to iPr not only reduces
the steric bulk at the metal center, but is also expected to reduce the electron-donating
power of the ligand. The electron-donating effects of the ligands L were studied by syn-
thesizing [Mo(CO)
A
~
diene)Mo(CO)4] with the relevant ligands. The value of the nCO was used to evaluate

Helvetica Chimica Acta – Vol. 89 (2006)
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Fig. 6. Effect of acid concentration on the branched selectivity of the methoxycarbonylation of vinyl
acetate. [Pd2(dba)3] (0.5 mmol), 7 (0.5 mmol), vinyl acetate (22 mmol), MeOH (11 ml), 3 bar, 258, 3 h.
Table 3. Quantities of Different Species Present in the Reaction Solution and Different Quantities of Acid
Addeda)
Acid added
[mmol]
[Pd(phosphine)] complex Quaternized P-atoms
Free P-atoms
[mmol]
Free acid
[mmol]
[mmol]
[mmol]
0.5
0.7
1.0
2.0
0.1
0.1
0.1
0.1
0.5
0.7
0.8
0.8
0.3
0.1
0
0
0
0.1
1.1
0
a) Pd (0.1 mmol), 7 (0.5 mmol).
Table 4. Comparison of the Highest Frequency nCO (in cmꢀ1) Band for [Mo(CO)4
Bidentate Phosphine Ligands La)
A
~
L
Ph2
PCH2
U
A
2
3
Et2
A
CH2
T
6
7
1
~
nCO
2021 [17]
2019
2013
2012 [18]
2007
2007
2006
a) Spectra recorded in CH2Cl2 solution.
~
the ligand-donor properties. The lower the frequency of nCO, the greater is the electron-
t
donating power of the ligand. As can be seen from Table 4, the ligands with four Bu
groups at the P-atom, i.e., 1, 6, and 7, are the most electron-donating. They also give
the highest rates and selectivities to the branched product in the methoxycarbonylation
N
of vinyl acetate. However, they are the most sterically crowded of the ligands, so it is
difficult to disentangle steric from electronic effects in this case. The catalytic mecha-
nism has clearly been shown to proceed via a hydride mechanism, at least for the
methoxycarbonylation of ethene or linear alkenes such as oct-1-ene [8][15][16]. A
greater electron density on the metal center would be expected to lead to more of
the Pd-centers being present in the catalytically active form ([PdH(1)X]+, X=CO,
MeOH, or vinyl acetate) and hence a higher rate. In addition, the rate-determining
step in the carbonylation of ethene or oct-1-ene is known to be late in the cycle – prob-
ably methanolysis and this step is accelerated by the presence of bulky ligands, although
the exact mechanism of the methanolysis reaction is still the subject of some debate. It,
therefore, seems that bulky highly electron donating ligands should give the highest
reaction rates, and this is indeed observed.

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Helvetica Chimica Acta – Vol. 89 (2006)
We originally anticipated that the regioselectivity might be controlled by the steric
influences exerted by the ligand, with the bulkiest ligands giving the lowest branched
selectivity. However, this is clearly not the case because ligands with all tBu substituents
give the highest branched selectivities.
Methoxycarbonylation of Vinyl Acetate in the Presence of Other Electron-Rich
Diphosphine Ligands. It seems that highly electron-donating phosphine ligands are
required for the successful Pd-catalyzed methoxycarbonylation of vinyl acetate. Ligand
1 has a semi-rigid backbone as the central two C-atoms are contained in an aromatic
ring. The effect of replacing the backbone by straight alkyl chains was studied by
using the ligands (ethane-1,2-diyl)bis[di(tert-butyl)phosphine] (8), (propane-1,3-diyl)-
bis[di(tert-butyl)phosphine] (9), and (butane-1,4-diyl)bis[di(tert-butyl)phosphine]
(10). The results obtained are shown in Table 5. Ligand 8 produced no ester product,
and there was 100% degradation of the vinyl acetate. Ligand 10 with a C4 backbone
produced only trace amounts of the ester product. However, a considerable amount
of vinyl acetate was degraded to AcOMe. This is surprising as there were enough P-
atoms present to bind all of the acid in the solution, and this should have prevented
vinyl acetate degradation. Ligand 9, on the other hand, gave high conversion of the
vinyl acetate with 100% selectivity to the esters. Unfortunately the b/l ratio was only
0.79 :1. Under the same reaction conditions, with 1 as the ligand, the b/l ratio was
1.2 :1. Drent [2] has reported that when 9/[Pd(OAc)2] was used in the methoxycarbony-
lation of vinyl acetate, a b/l ratio of 2 :1 was obtained. Drent used a reaction temperature
of 758 and a CO pressure of 40 bar, as opposed to 808 and 30 bar used in this study.
Table 5. Methoxycarbonylation of Vinyl Acetate Catalyzed by Palladium Complexes of tBu2P(CH2)nPtBu2
8–10 (n=2–4)a)
Ligand
Conversion [%]
Selectivity to esters [%]
b/l
8
9
10
100
97
70
0
100
2
n.a.b)
0.79 :1
0.87:1
a) [Pd2(dba)3] (0.05 mmol)], vinyl acetate (VAM) (2 ml), ligand (0.5 mmol), MeSO3
H (0.5 mmol), MeOH
A
(11 ml), 808, 3 h. b) n.a.=not applicable.
Mechanistic Considerations. From the mechanistic studies that have been carried
out on Pd-complexes of 1 for the methoxycarbonylation of alkenes, it has been
shown that the catalytic cycle follows the hydride mechanism [16][19][20]. As palla-
dium hydrides are renowned for their instability, it can be reasoned that the success
of systems containing 1 is due to the high degree of electron donation, which stabilizes
[PdH(1)X]+ (X=CO or vinyl acetate). If this were the only criterion necessary for a
successful ligand, it should be possible to carry out the catalysis with other electron-
rich ligands. However, as described above, not all electron-rich diphosphines are suc-
cessful. Ligand 8, with a C2H4 backbone, showed no activity towards the methoxycar-
bonylation of vinyl acetate, whereas 9, with a C3H6 backbone, showed good activity,
and 10, with a C4H8 backbone, showed low activity. This is the same order of reactivity
as is observed for ethene, and there is some dispute whether this can be attributed to the
different bite angles of the ligands giving different steric constraints [21] at the active

Helvetica Chimica Acta – Vol. 89 (2006)
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site where the carbonylation takes place, or whether ligands such as 1 and 9 have just
the right balance between chelate strength and the ability to become unidentate in the
acyl intermediate [13], thus reducing the electron density sufficiently to encourage
nucleophilic attack of MeOH.
As indicated above, it appears that the selectivity to branched product is under elec-
tronic control, with the most-electron-donating ligands giving the highest branched
selectivity. For ethene [16] and oct-1-ene [20] methoxycarbonylation, the rate-deter-
mining step is late in the catalytic cycle (probably methanolysis of the Pd–acyl
bond). If this were the case for vinyl acetate also, the selectivity should arise from an
increased relative rate of methanolysis for the branched acyl complex relative to the
linear when using the more-electron-donating ligands. However, the exact mechanism
of methanolysis in these systems is the subject of some debate [13][21], so it is very dif-
ficult to offer any real mechanistic insight into why the most-elctron-donating ligands
give the highest selectivity.
Conclusions. – Pd/1 Complexes are the most-active catalysts yet discovered for the
methoxycarbonylation of vinyl acetate. They also produce the highest selectivity to the
branched product, which is a precursor to lactate esters. Attempts to increase the selec-
tivity by reducing the steric bulk of the ligand (replacing tBu by iPr) were unsuccessful
leading to lower rates and lower branched selectivities. Replacing the 1,2-phenylene
moiety in the backbone by a naphthalene-1,2-diyl gave catalysts with similar selectivi-
ties but lower activity.
We thank BP Chemicals, Ltd. for a studentship (A. J. R.).
Experimental Part
General. All manipulations of air-sensitive materials were carried out in oven-dried glassware by
using standard Schlenk line and catheter-tubing techniques under dry, deoxygenated Ar. Ar was dried
through a glass column packed with chromium(II)/silica gel. Solid and liquid chemicals were purchased
from Aldrich, Acros, Avacodo, and Strem and used as received. All gases were purchased from BOC.
Petroleum ether (40–608), Et2O, and THF were distilled over sodium diphenylketyl. CH2Cl2 was distilled
G
over CaH2, and toluene was distilled over Na. Vinyl acetate was distilled over CaCl2 and was stored at 08
in a flask wrapped in tinfoil to exclude light. 1H-, 13C-, and 31P-NMR Spectra: Varian-300, Bruker-300, or
Varian-500 NMR spectrometers. The ligands 1 [11], 9 [22], and 10, 1,5-dihydro-2,4,3-benzodioxathiepin
3,3-dioxide [23], and [Mo(CO)
[1,2-Phenylenebis(methylene)]bis[diisopropylphosphine] (2). Xylene-a,a’-diyl dipotassium (={m-[1,
2-phenylenebis(methylene)]}dipotassium) [25] (2.86 g, 15.7 mmol) was dissolved in Et2O (100 ml) and
U
AHCTREUNG
cooled to ꢀ208. Chlorodiisopropylphosphine (=bis(1-methylethyl)phosphinous chloride; 5 g, 32.7
mmol) was added slowly and the soln. allowed to warm to r.t. after which it was stirred overnight. The
soln. was removed by filtration and the potassium chloride salt was washed with Et
N
N
evaporated from the combined fractions, and the resulting oil was purified by distillation: 355 mg
1
3
1
(6%) of 2. H-NMR (300 MHz, CDCl3): 1.06 (dd, J(P,H)=12, J(H,H)=7, 12 H, MeCHP); 1.08 (dd,
3J(P,H)=12, J(H,H)=7, 12 H, MeCHP); 1.57–1.82 (m, 3 H, MeCHP); 3.05 (s, 2 ArCH2
P); 7.00–7.08
A
1
(m, 2 arom. H); 7.12–7.20 (m, 2 arom. H). 13C-NMR (75 MHz, CDCl3): 19.4 (d, 2J(P,C)=12,
MeCHP); 19.7 (d, 2J(P,C)=13, MeCHP); 23.3 (d, 1J(P,C)=15, MeCHP); 27.9 (d, 1J(P,C)=8,
ArCH2P); 28.6 (d, J(P,C)=8, ArCH2P); 126.0, 131.1, 131.2 (3s, Ar); 137.8 (s, ArCH2P). 31P-NMR (121
1
MHz, CDCl3, H3PO4): 5.2 (s, ArCH2
PiPr2). HR-ES-MS (pos.): 339.2365 (C20
G
A
Anal. calc. for C20H36P2 (338.45): C 71.0, H 10.7; found: C 70.7, H 11.0.

1794
Helvetica Chimica Acta – Vol. 89 (2006)
(tert-Butyl)isopropylphosphine–Borane (1/1). tert-Butyldichlorophosphine (=(1,1-dimethylethyl)-
phosphonous dichloride; 9.72 g, 61.1 mmol) was dissolved in Et2O (50 ml) and cooled to 08. To this, 2M
AHCTREUNG
isopropylmagnesium chloride in hexane (30.5 ml, 61 mmol) was slowly added, and the soln. was allowed
to warm to r.t. In the 31P{1H}-NMR spectrum of the soln., only a signal at d(P) 139.9 was present, which is
t
consistent with the literature value for BuCliPrP [26]. The soln. was filtered, the residue washed with
Et2O (2×20 ml), and the solvent was evaporated from the combined org. layers leaving a yellow oil.
G
This oil was slowly added to a DMF (20 ml) soln. of NaBH4 (3.02 g, 80 mmol) cooled to 08. Upon com-
plete addition, the soln. was allowed to warm to r.t. and stirred for 16 h. H2O (20 ml) was added carefully,
and the resultant solution was extracted with Et2O (3×30 ml). The combined org. phase was washed suc-
E
cessively with H2O (2×20 ml) and brine (2×20 ml) and dried (MgSO4), and the solvent was evaporated:
title product (7.22 g, 81%). Clear oil. 1H-NMR (300 MHz, CDCl3): 0.18 (br. q, 1J(B,H)=50, PH(BH3));
1.09 (dd, 3J(P,H)=13, 3J(H,H)=7, 3 H, MeCHP); 1.15 (dd, 3J(P,H)=13, 3J(H,H)=7, 3 H, MeCHP); 1.22
(d, 3J(P,H)=14, 18 H, MeCP); 2.29 (dd, 3J(H,H)=7, 2J(P,H)=2, 1 H, MeCHP); 3.92 (dq, 1J(P,H)=352,
2J(B,H)=7, PH(BH3)). 13C-NMR (75 MHz, CDCl3): 17.2 (s, MeCHP); 20.9 (s, MeCHP); 25.5 (d, J=26,
MeCP); 26.3 (s, MeCP). 31P-NMR (121 MHz, CDCl3, H3PO4): 37.7 (q, 1J(P,B)=50). Anal. calc. for
C7H20BP (146.02): C 57.6, H 13.8; found: C 57.4, H 13.9.
Diastereoisomer Mixture of [1,2-Phenylenebis(methylene)]bis[(tert-butyl)isopropylphosphine]–Bor-
ane (1/2). (tert-Butyl)isopropylphosphine–borane (1/1) (3.78 g, 25.9 mmol) was dissolved in THF (30
ml) and cooled to 08. To this soln., 2.5M BuLi in hexane (10.3 ml, 25.9 mmol) was added slowly, and
the soln. was allowed to warm to r.t., before stirring for 30 min. The soln. was cooled to 08, and a THF
(20 ml) soln. of a,a-o-dichloroxylene (=1,2-bis(chloromethyl)benzene; 2.23 g, 12.8 mmol) was added
dropwise with the soln. temp. not being allowed to rise above 58. Upon complete addition, the soln.
was allowed to warm to r.t. and stirred for 16 h. H2O (30 ml) was added to the soln., the aq. layer was
extracted with Et2O (2×30 ml), the combined org. phase washed with H2O (30 ml) and 10% brine
N
(2×30 ml) and dried (MgSO4), the solvent evaporated, and the obtained white solid recrystallized
1
from hexane: 4.36 g (93%) diastereoisomer mixture. Colorless crystals. M.p. 153–1548. H-NMR (500
1
3
3
MHz, CD2Cl2): 0.29 (q, J(P,B)=85, 2 PBH3); 1.07 (dd, J(P,H)=14, J(H,H)=7, 3 H, MeCHP); 1.07
3
3
3
3
(dd, J(P,H)=13, J(H,H)=7, 3 H, MeCHP); 1.25 (d, J(P,H)=13, 9 H, MeCP); 1.26 (dd, J(P,H)=14,
3J(H,H)=7, 3 H, MeCHP); 1.28 (d, J(P,H)=13, 9 H, MeCP); 1.28 (dd, J(P,H)=13, J(H,H)=7, 3 H,
3
3
3
MeCHP); 1.99 (dd, 2J(P,H)=7, 3J(H,H)=7, 2 H, MeCHP); 2.02 (dd, 2J(P,H)=7, 3J(H,H)=7, 2 H,
2
2
2
2
MeCHP); 3.14 (dd, J(H,H)=15, J(P,H)=15, 1 H, ArCH2P); 3.29 (dd, J(H,H)=15, J(P,H)=10, 1 H,
A
2
2
2
2
ArCH2
ArCH2
P); 7.12–7.20 (m, 3 arom. H); 7.28–7.30 (m, 1 arom. H). 31P-NMR (202 MHz, CD2Cl2, H3PO4):
39.2 (q, 1J=50, rac-ArCH2PtBu2); 40.7 (q, 1J=50, meso-ArCH2PtBu2). 13C-NMR (75 MHz, CDCl3):
P); 3.38 (dd, J(H,H)=15, J(P,H)=13, 1 H, ArCH2
P); 3.64 (dd, J(H,H)=15, J(P,H)=7, 1 H,
AHCTREUNG
A
ACHTREUNG
19.3 (d, J=40, MeCHP); 19.5 (d, J=54, MeCHP); 23.9 (d, J=28, MeCHP); 24.2 (d, J=28, MeCHP);
25.2 (d, J=26, MeCP); 25.4 (d, J=25, MeCP); 27.7 (d, J=6, MeCP); 27.8 (s, MeCP); 31.5 (d, J=28,
ArCH
ArCH
C
U
B2
NaPþ2 ;
N
i
i
G
U
H46
calc. 417.3159). Anal. calc. for C22H46B2P2 (394.17): C 67.0, H 11.8; found: C 66.9, H 11.9.
rac-[1,2-Phenylenebis(methylene)]bis[(tert-butyl)isopropylphosphine]–Borane (1/2). A racemic mix-
ture containing all four diastereoisomers of [1,2-phenylenebis(methylene)]bis[(tert-butyl)isopropylphos-
phine]–borane (1/2) was dissolved in hot MeOH and was left to cool. The colorless crystals produced
were collected by filteration and recrystallized three more times from MeOH until the product was dia-
stereoisomerically pure. The configuration of the structure was determined by single-crystal X-ray dif-
1
1
fraction (see below). M.p. 1678. H-NMR (300 MHz, CD2Cl2): 0.29 (q, J(P,B)=85, 2 PBH3); 1.07 (dd,
3J(P,H)=13, 3J(H,H)=7, 6 H, MeCHP); 1.28 (d, 3J(P,H)=13, 18 H, MeCP); 1.28 (dd, 3J(P,H)=13,
3J(H,H)=7, 6 H, MeCHP); 1.99 (dd, 2J(P,H)=7, 3J(H,H)=7, 2 H, MeCHP); 3.14 (dd, 2J(H,H)=15,
2
2
2J(P,H)=15, 2 H, ArCH2
ACHTREUNG
AHCTREUNG
1
N
G
A
N
ACHTREUNG

Helvetica Chimica Acta – Vol. 89 (2006)
1795
meso-[1,2-Phenylenebis(methylene)]bis[(tert-butyl)isopropylphosphine]–Borane (1/2). The solvent
of the soln. left from the first recrystallization of rac-[1,2-phenylenebis(methylene)]bis[(tert-butyl)isopro-
pylphosphine]–borane (1/2) (see above) was evaporated and the solid was recrystallized from hot MeOH.
The colorless crystals produced were collected by filtration and recrystallized three times from MeOH
1
until the product became diastereoisomerically pure. M.p. 1408. H-NMR (500 MHz, CD2Cl2): 0.29 (q,
1J(P,B)=85, 2 PBH3); 1.07 (dd, 3J(P,H)=13, 3J(H,H)=7, 6 H, MeCHP); 1.25 (d, 3J(P,H)=13, 18 H,
MeCP); 1.26 (dd, 3J(P,H)=14, 3J(H,H)=7, 6 H, MeCHP); 2.02 (dd, 2J(P,H)=7, 3J(H,H)=7, 2 H,
2
2
2
2
MeCHP); 3.29 (dd, J(H,H)=15, J(P,H)=10, 2 H, ArCH2P); 3.38 (dd, J(H,H)=15, J(P,H)=13, 2 H,
ArCH2P); 7.29 (m, 4 arom. H). 13C-NMR (75 MHz, CDCl3): 19.5 (d, J=54, MeCHP); 24.2 (d, J=28,
MeCHP); 25.4 (d, J=25, MeCP); 27.7 (d, J=6, MeCP); 31.5 (d, J=28, ArCH
(2s, arom. CH); 134.5 (m, ArCH
2PtBu2iPr2). 31P-NMR (202 MHz, CD2Cl2, H3PO4): 40.7 (q, 1J=50,
meso-ArCH H46B2
2PtBu2). HR-ES-MS (pos.): 417.3161 ([M+Na]+, C22 NaP2þ ; calc. 417.3159). Anal.
calc. for C22H46B2P2 (394.17): C 67.0, H 11.8; found: C 67.3, H 11.7.
2PtBuiPr); 127.4, 132.5
AHCTREUNG
A
G
A
ACHTREUNG
Racemic [1,2-Phenylenebis(methylene)]bis[(tert-butyl)isopropylphosphine] (3). Racemic [1,2-phe-
nylenebis(methylene)]bis[(tert-butyl)isopropylphosphine]–borane (1/2) (450 mg, 1.1 mmol) was dis-
solved in degassed Et2NH (20 ml) and heated under reflux for 16 h. The soln. was cooled, and the solvent
G
was evaporated. The white paste was dissolved in toluene (10 ml), and the soln. was passed through a
short column of SiO2 under an inert atmosphere. The column was washed with toluene (20 ml), and
the solvent was subsequently evaporated from the combined washings: 3 (346 mg (86%). Clear oil.
3
3
3
1H-NMR (300 MHz, CDCl3): 1.06 (dd, J(P,H)=14, J(H,H)=7, 3 H, MeCHP); 1.07 (dd, J(P,H)=13,
3J(H,H)=7, 3 H, MeCHP); 1.10 (dd, J(P,H)=14, J(H,H)=7, 3 H, MeCHP); 1.10 (d, J(P,H)=14, 9
3
3
3
3
3
3
3
H, MeCP); 1.11 (dd, J(P,H)=14, J(H,H)=7, 3 H, MeCHP); 1.12. (dd, J(P,H)=13, J(H,H)=7, 3 H,
MeCHP); 1.72 (dd, 2J(P,H)=7, 3J(H,H)=7, 2 H, MeCHP); 1.73 (dd, 2J(P,H)=7, 3J(H,H)=7, 2 H,
2
2
2
2
MeCHP); 2.90 (dd, J(H,H)=15, J(P,H)=15, 1 H, ArCH2P); 2.95 (dd, J(H,H)=15, J(P,H)=10, 1 H,
A
2
2
2
2
ArCH2P); 2.99 (dd, J(H,H)=15, J(P,H)=13, 1 H, ArCH2P); 2.35 (dd, J(H,H)=15, J(P,H)=7, 1 H,
ArCH2P); 7.52–7.60 (m, 4 arom. H). 13C-NMR (75 MHz, CDCl3): 19.3 (d, J=16, MeCHP); 19.7 (d,
J=18, MeCHP); 23.4 (d, J=12, MeCHP); 23.5 (d, J=12, MeCHP); 26.3 (d, J=25, MeCP); 26.4 (d,
J=25, MeCP); 29.9 (d, J=14, MeCP); 30.0 (d, J=14, MeCP); 30.3 (d, J=15, ArCH
J=15, ArCH
2PtBuiPr); 126.1, 126.4, 128.3, 128.7 (4s, arom. CH); 137.5 (m, ArCH2PtBu2iPr2); 137.7 (m,
PtBu2); 12.5 (s, meso-ArCH2-
NaPþ2 ; calc. 417.3178). Anal. calc. for C22H40P2
2PtBuiPr); 30.5 (d,
A
ACHTREUNG
i
ArCH
PtBu2). HR-ES-MS (pos.): 417.3159 ([M+Na]+, C22
(366.50): C 72.1, H 11.1; found: C 72.3, H 11.3.
A
ACHTREUNG
A
G
A
ACHTREUNG
rac-[1,2-Phenylenebis(methylene)]bis[(tert-butyl)isopropylphosphine] (rac-3). As described for 3,
with rac-[1,2-phenylenebis(methylene)]bis[(tert-butyl)isopropylphosphine]–borane (1/2) (322 mg, 0.8
mmol), and Et
2NH (20 ml): rac-3 (215 mg, 72%). Clear oil. 1H-NMR (300 MHz, CDCl3): 1.06 (dd,
E
3J(P,H)=14, 3J(H,H)=7, 3 H, MeCHP); 1.11 (dd, 3J(P,H)=14, 3J(H,H)=7, 3 H, MeCHP); 1.12 (dd,
3J(P,H)=13, 3J(H,H)=7, 3 H, MeCHP); 1.73 (dd, 2J(P,H)=7, 3J(H,H)=7, 2 H, MeCHP); 2.90 (dd,
2
2
2
2J(H,H)=15, J(P,H)=15, 1 H, ArCH2P); 2.35 (dd, J(H,H)=15, J(P,H)=7, 1 H, ArCH2P); 7.52–7.60
(m, 4 arom. H). 13C-NMR (75 MHz, CDCl3): 19.3 (d, J=16, MeCHP); 19.7 (d, J=18, MeCHP); 23.4
(d, J=12, MeCHP); 23.5 (d, J=12, MeCHP); 26.3 (d, J=25, MeCP); 26.4 (d, J=25, MeCP); 29.9 (d,
J=14, MeCP); 30.0 (d, J=14, MeCP); 30.3 (d, J=15, ArCH
126.1, 128.7 (2s, arom. CH); 137.7 (m, ArCH
rac-ArCH2
A
N
i
ACHTREUNG
A
N
ACHTREUNG
meso-[1,2-Phenylenebis(methylene)]bis[(tert-butyl)isopropylphosphine] (meso-3). As described for
3, with meso-[1,2-phenylenebis(methylene)]bis[(tert-butyl)isopropylphosphine]–borane (1/2) (450 mg,
1.2 mmol) and Et
2NH (20 ml): meso-3 (334 mg, 83%). Clear oil. 1H-NMR (300, CDCl3): 1.07 (dd,
U
3J(P,H)=13, 3J(H,H)=7, 3 H, MeCHP); 1.10 (dd, 3J(P,H)=14, 3J(H,H)=7, 3 H, MeCHP); 1.10 (d,
3J(P,H)=14, 9 H, MeCP); 1.72 (dd, 2J(P,H)=7, 3J(H,H)=7, 2 H, MeCHP); 2.95 (dd, 2J(H,H)=15,
2
2
2J(P,H)=10, 1 H, ArCH2
G
G
H). 13C-NMR (75 MHz, CDCl3): 19.3 (d, J=16, MeCHP); 19.7 (d, J=18, MeCHP); 23.4 (d, J=12,
MeCHP); 23.5 (d, J=12, MeCHP); 26.3 (d, J=25, MeCP); 26.4 (d, J=25, MeCP); 29.9 (d, J=14,
MeCP); 30.0 (d, J=14, MeCP); 30.3 (d, J=15, ArCH
N
N

1796
Helvetica Chimica Acta – Vol. 89 (2006)
128.7 (2s, arom. CH); 137.5 (m, ArCH2
AHCTREUNG
A
N
ACHTREUNG
Di(tert-butyl)phosphine–Borane (1/1). NaBH2 (1.30 g, 34 mmol) was dissolved in dry and degassed
DMF (30 ml). The soln. was cooled to 08 and di(tert-butyl)chlorophosphine (=bis(1,1-dimethylethyl)-
phosphinous chloride; 6.00 g, 33.2 mmol) was added dropwise. Upon complete addition, the soln. was
allowed to warm to r.t. and stirred for 16 h. H2O (30 ml) was slowly added to the soln. followed by Et2
A
(30 ml). The aq. layer was extracted with Et2O (2×20 ml), the combined org. phase washed with H2O (30
AHCTREUNG
ml) and brine (2×30 ml) and dried (MgSO4), the solvent evaporated, and the obtained white solid recrys-
1
tallized from hexane: title compound (4.88 g, 92%). Colorless crystals. M.p. 418. H-NMR (300 MHz,
3
1
2
CDCl3): 1.34 (d, J(P,H) J=13, 18 H, MeCP); 4.12 (dq, J(P,H)=351, J(H,B)=7). 13C-NMR (75 MHz,
CDCl3): 29.3 (d, 2J(P,C)=2, Me3
H3PO4): 49.0 (q, 1J(P,B)=49, ArCH2P(BH3)(tBu)2). HR-ES-MS (pos.): 183.1456 ([M+Na]+, C22
ACHTREUNG
AHCTREUNG
NaPþ2 ; calc. 183.1450). Anal. calc. for C8H22BP (160.05): C 60.0, H 13.9; found: C 60.1, H 13.9.
Di(tert-butyl){{2-[(diisopropylphosphino)methyl]phenyl}methyl}phosphine–Borane (1/2). Di(tert-
butyl)phosphine–borane (1/1) (574 mg, 3.6 mmol) was dissolved in THF (20 ml) and cooled to 08. To
this, 2.5M BuLi in hexane (1.45 ml, 3.6 mmol) was slowly added, and the soln. was allowed to warm to
r.t. This soln. was slowly added to a THF (30 ml) soln. of 1,5-dihydro-2,4,3-benzodioxathiepin 3,3-dioxide
(581 mg, 3.6 mmol) cooled to ꢀ788. After complete addition, the soln. was warmed to r.t. and stirred for
30 min. A 31P{1H}-NMR spectrum of the soln. showed one peak at d(P) 50.3 indicating full deprotonation
of the phosphine. The soln. was recooled to ꢀ788, and a THF (20 ml) soln. of LiPiPr2
C
After this time, H2O (20 ml) was carefully added, and the soln. was extracted with Et2O (3×20 ml).
G
The combined org. phase was washed successively with H2O (20 ml) and brine (2×20 ml) and dried
(MgSO4), the solvent evaporated, and the crude solid recrystallized from hexane: title product (1.12 g,
79%). Colorless crystals. M.p. 114–1158. 1H-NMR (300 MHz, CDCl3): ꢀ0.45 to +0.92 (br. m, 2
PBH3); 0.93 (dd, 3J(P,H)=14, 3J(H,H)=7, 6 H, MeCHP); 1.02 (dd, 3J(P,H)=14, 3J(H,H)=7, 6 H,
MeCHP); 1.09 (d, 3J(P,H)=12, 18 H, MeCP); 1.82 (dsept., 2J(P,H)=10, 3J(H,H)=7, 2 H, MeCHP);
3.13 (d, 2J(P,H)=12, 2 H, ArCH2P); 3.25 (d, 2J(P,H)=12, 2 H, ArCH2P); 7.10–7.22 (m, 3 arom. H);
7.55–7.62 (m, 1 arom. H). 13C-NMR (75 MHz, CDCl3): 17.8 (d, J=8, MeCHP); 22.0 (d, J=32,
MeCHP); 24.4 (d, J=24, MeCP); 26.7 (d, J=26, ArCH
A
ArCH
A
(121 MHz, CD2Cl2, H3PO4): 35.2 (m, ArCH2P(BH3)iPr2); 50.0 (m, ArCH2P(BH3)tBu2). ES-MS (pos.):
417.27 (100, [M+Na]+, based on 11B). Anal. calc. for C22H46B2P2 (294.17): C 67.0, H 11.8; found: C
66.8, H 11.6.
Di(tert-butyl){{2-[(diisopropylphosphino)methyl]phenyl}methyl}phosphine (4). Di(tert-butyl){{2-
[(diisopropylphosphino)methyl]phenyl}methyl}phosphine–borane (1/2) (0.96 g, 2.4 mmol) was dissolved
in Et
N
N
leaving a white paste which was dissolved in toluene (10 ml) and passed through a plug of SiO2. Toluene
(10 ml) was used to wash the column, and the solvent was evaporated from the combined org. fractions
leaving a crude white solid. Recrystallizing from MeOH gave 4. (0.82 g, 93%). White powder. M.p.
43–448. 1H-NMR (300, CDCl3): 0.93 (dd, 3J(P,H)=14, 3J(H,H)=7, 6 H, MeCHP); 1.02 (dd,
3
3
2
3J(P,H)=14, J(H,H)=7, 6 H, MeCHP); 1.09 (d, J(P,H)=12, 18 H, MeCP); 1.82 (dsept., J(P,H)=10,
3J(H,H)=7, 2 H, MeCHP); 3.13 (d, J(P,H)=12, 2 H, ArCH2P); 3.25 (d, J(P,H)=12, 2 H, ArCH2
7.10–7.22 (m, 3 arom. H); 7.55–7.62 (m, 1 arom. H). 13C-NMR (75 MHz, CDCl3): 17.6 (d, J=8,
MeCHP); 22.2 (d, J=32, MeCHP); 24.4 (d, J=24, ArCH
2PiPr2); 26.8 (d, J=26, MeCP); 30.1 (d,
J=24, MeCP); 33.5 (d, J=24, ArCH2
PtBu2); 127.0, 127.1, 131.6, 132.9 (4s, arom. CH); 131.1 (s,
ArCH2); 135.0 (s, ArCH2). 31P-NMR (121 MHz, CD2Cl2, H3PO4): 5.3 (s, ArCH2PiPr2); 28.5 (s, ArCH2-
PtBu2). HR-ES-MS (pos.): 367.2691 (C22 P2þ ; calc. 367.2684). Anal. calc. for C22H40P2 (366.50): C
H41
72.1, H 11.0; found: C 72.3, H 11.3.
P);
2
2
AHCTREUNG
AHCTREUNG
AHCTREUNG
A
N
ACHTREUNG
Di(tert-butyl){{2-{[(tert-butyl)isopropylphosphino]methyl}phenyl}methyl}phosphine–Borane (1/2).
Di(tert-butyl)phosphine–borane (511 mg, 3.2 mmol) was dissolved in THF (20 ml) and cooled to 08. To

Helvetica Chimica Acta – Vol. 89 (2006)
1797
this, 2.5M BuLi in hexane (1.3 ml, 3.2 mmol) was slowly added and the soln. allowed to warm to r.t. This
soln. was slowly added to a THF (30 ml) soln. of 1,5-dihydro-2,4,3-benzodioxathiepin 3,3-dioxide (516
mg, 3.2 mmol) cooled to ꢀ788. After complete addition, the soln. was warmed to r.t. and stirred for 30
min. A 31P{1H}-NMR spectrum of the soln. showed one peak at d 50.3 indicating full deprotonation of
the phosphine. The soln. was recooled to ꢀ788, and a THF (20 ml) soln. of LiPtBuiPr(BH3) (prepared
from (tert-butyl)isopropylphosphine–borane (1/1) (467 mg, 3.2 mmol) in THF cooled to 08 and 2.5M
BuLi in hexane (1.3 ml, 3.2 mmol)) was added slowly. After the addition, the soln. was allowed to
warm to r.t. and stirred for 3 h. After this time, H2O (20 ml) was carefully added, and the soln. was
extracted with Et2O (3×20 ml). The combined org. phase was washed successively with H2O (20 ml)
G
and brine (2×20 ml) and dried (MgSO4), the solvent evaporated, and the crude solid recrystallized
1
from hexane: title product (1.20 g, 87%). Colorless crystals. M.p. 1518. H-NMR (300, CDCl3): ꢀ0.11
3
3
3
3
to +1.02 (m, 2 PBH3); 1.12 (dd, J(P,H)=14, J(H,H)=7, 3 H, MeCHP); 1.28 (dd, J(P,H)=14, J(H,
H)=7, 3 H, MeCHP); 1.25 (d, 3J(P,H)=12, 9 H, MeCP); 1.29 (d, 3J(P,H)=12, 9 H, MeCP); 1.30 (d,
3J(P,H)=12, 9 H, MeCP); 2.03 (dsept., 2J(P,H)=11, 3J(H,H)=7, 1 H, MeCHP); 3.18–3.68 (m, 4 H,
ArCH2
J=11, MeCHP); 23.7 (d, J=28, MeCHP); 24.8 (d, J=24, ArCH2
(d, J=7, MeCP); 33.3 (d, J=7, ArCH
2PtBu2); 127.0, 131.7, 132.9 (3s, arom. CH); 133.6 (ArCH2P);
135.0 (ArCH
2P). 31P-NMR (121 MHz, CD2Cl2, H3PO4): 41.8 (q, 1J(P,B)=72, PtBuiPr(BH3)); 50.1 (q,
1J(P,B)=74, PtBu2(BH3)). ES-MS (pos.): 431.30 (100; based on 11B). Anal. calc. for C23H48B2P2
P); 7.10–7.21 (m, 3 arom. H); 7.53–7.63 (m, 1 arom. H). 13C-NMR (75 MHz, CDCl3): 19.2 (d,
PiPrtBu); 25.5 (d, J=26, MeCP); 29.0
AHCTREUNG
AHCTREUNG
AHCTREUNG
(408.20): C 67.7, H 11.9; found: C 67.7, H 12.1.
Di(tert-butyl){{2-{[(tert-butyl)isopropylphosphino]methyl}phenyl}methyl}phosphine (5). As descri-
bed for 4, with di(tert-butyl){{2-{[(tert-butyl)isopropylphosphino]methyl}phenyl}methyl}phosphine–bor-
1
ane (0.85 g, 2.1 mmol) and Et
2NH (10 ml): 5 (0.67 g, 85%). M.p. 68–698. H-NMR (300, CDCl3): 1.02
3
3
3
3
(dd, J(P,H)=10, J(H,H)=7, 6 H, MeCHP); 1.05 (d, J(P,H)=11, 9 H, MeCP); 1.06 (d, J(P,H)=11, 9
H, MeCP); 1.07 (d, 3J(P,H)=11, 9 H, MeCP); 2.92–3.00 (m, 4 H, ArCH2P); 6.96–7.01 (m, 2 arom. H);
7.20–7.24 (m, 1 arom. H); 7.50–7.54 (m, 1 arom. H). 13C-NMR (75 MHz, CDCl3): 20.9 (d, J=9,
MeCHP); 22.7 (d, J=18, MeCH); 24.1 (d, J=20, MeCP); 26.4 (d, J=24, MeCP); 27.1 (d, J=24, ArCH2-
A
N
131.0 (d, J=10), 131.3 (d, J=14), 131.4 (d, J=17, arom. CH); 138.2 (d, J=7, ArCH2P); 139.1 (d, J=11,
ArCH2P). 31P-NMR (121 MHz, CD2Cl2, H3PO4): 16.7 (s, ArCH2PtBuiPr); 28.6 (s, ArCH2PtBu2). HR-ES-
MS (pos.): 381.2845 (C23H43
Pþ2 ; calc. 381.2840). Anal calc. for C23H42P2 (380.53): C 72.6, H 11.1; found: C
72.3, H 11.3.
A
ACHTREUNG
A
ACHTREUNG
1,2-Bis(chloromethyl)naphthalene. A mixture of 1-(chloromethyl)-2-methylnaphthalene (5.16 g, 27.1
mmol) in 1,2-dichloroethane (30 ml) and dibenzoyl peroxide (150 mg) was stirred until all solids were dis-
solved. Then, N-chlorosuccinimide (3.73 g, 28 mmol) was added. The soln. was heated under reflux and
stirred for 40 h. The soln. was cooled and the solid removed by filtration and washed with cold 1,2-
dichloroethane (10 ml). The soln. was washed with H2O (3×30 ml), the org. layer dried (MgSO4), the sol-
vent evaporated, and the crude yellow solid dissolved in hot benzene/hexane 1:1, and filtered hot to
remove any remaining succinimide compounds. The soln. was cooled and the title compound recrystal-
lized: 4.61 g (76%). White solid. M.p. 1318. 1H-NMR (300 MHz, (D6)acetone): 4.95 (s, ArCH2
Cl); 5.26 (s,
G
2 H, ArCH2Cl); 7.51 (m, 2 arom. H); 7.57 (m, 2 arom. H); 7.86 (m, 2 arom. H). 13C-NMR (75 MHz,
(D6)acetone): 40.2 (s, ArCH2Cl); 45.2 (s, ArCH2Cl); 125.9, 128.5, 129.1, 129.6, 130.5, 131.8, 133.4,
134.0, 135.7, 136.5 (10s, arom. C). EI-MS: 226.0 (M+ (37Cl)), 224.0 (M+ (35Cl)). Anal. calc. for
C12H10Cl2 (225.11): C 64.0, H 4.5; found: C 64.5, H 3.7.
[Naphthalene-2,3-diylbis(methylene)]bis[(di(tert-butyl)phosphine] (6). To an Et2O (10 ml) soln. of
U
2,3-dimethylnaphthalene (2.56 g, 16.4 mmol) and KOtBu (4.03 g, 36 mmol) cooled to ꢀ788, 2.5M BuLi
in hexane (14.4 ml, 36 mmol) was added slowly. The soln. was allowed to warm to r.t. and then heated
under reflux for 2 h. The soln. was cooled to 08 and di(tert-butyl)chlorophosphine (6.84 ml, 6.50 g, 36
mmol) was added over 20 min. The soln. was warmed to r.t. and stirred for 16 h, during which time a
salt formed. After filtration, H2O (10 ml) was slowly added. Then, the aq. layer was extracted with Et2O
E
(2×20 ml), the combined org. phase washed successively with H2O (20 ml) and brine (2×20 ml) and
dried (MgSO4), the solvent evaporated, and the obtained white solid recrystallized from hot MeOH: 6
(4.92 g, 68%). M.p. 1488. 1H-NMR (300, CDCl3): 1.16 (d, 3J(P,H)=11, 36 H, MeCHP); 3.22 (d,

1798
Helvetica Chimica Acta – Vol. 89 (2006)
2J(P,H)=4, 4 H, ArCH2P); 7.30–7.40 (m, 2 arom. H); 7.70–7.77 (m, 2 arom. H); 8.02–8.08 (m, arom. H).
1
2
1
13C-NMR (75 MHz, CDCl3): 27.3 (d, J(P,C)=24, MeCP); 32.5 (d, J(P,C)=13, MeCP); 33.3 (d, J(P,
C)=23, ArCH2P); 125.4, 127.3, 129.4, 132.2 (4s, arom. C); 138.4 (dd, 2J(P,C)=10, 3J(P,C)=2,
ArCH2P). 31P-NMR (121 MHz, CDCl3, H3PO4): 26.3 (s, ArCH2PtBu2). HR-ES-MS (pos.): 445.3138 (C28-
A
H
ACHTREUNG
AHCTREUNG
AHCTREUNG
thalene (1.20 g, 5.3 mmol) was added dropwise, not allowing the temp. to rise above 58. Upon complete
addition, the soln. was allowed to warm to r.t. and stirred for 16 h. H2O (30 ml) was added, the aq. layer
extracted with Et2O (2×30 ml), the combined org. layer washed with H2O (30 ml) and brine (2×30 ml)
A
and dried (MgSO4), and the solvent evaporated: off-white oil. To this, hexane was added and the title
compound crystallized: 1.08 g (43%). Pure white solid. M.p. 173–1748. 1H-NMR (300 MHz, CDCl3):
ꢀ0.02 to +2.11 (br., 42 H, BH3 and MeC); 3.18–4.40 (br., 4 H); 7.45 (t, J=7.0, 1 arom. H); 7.53 (t,
J=7.0, 1 arom. H); 7.68 (d, J=8.5, 1 arom. H); 7.80 (d, J=8.5, 1 arom. H); 7.92 (d, J=8.5, 1 arom.
H); 8.15 (d, J=8.5, 1 arom. H). 13C-NMR (75 MHz, CDCl3): 22.4 (d, 1J(P,C)=22, Me3CP); 26.7 (d,
1J(P,C)=23, Me3CP); 29.0 (d, 2J(P,C)=14, Me3CP); 33.6 (d, 1J(P,C)=25, ArCH2P); 34.6 (d,
A
1J(P,C)=25, ArCH2P); 125.0, 125.7, 126.2, 127.0, 128.7, 129.3, 130.8, 133.2, 133.4 (9s, arom. CH); 134.3
(s). 31P-NMR (121 MHz, CDCl3, H3PO4): 53.1 (br. t, 1J(P,B)=94, ArCH2
U
G
thylene)]bis[di(tert-butyl)phosphine]–borane (1/2) (1.08 g, 2.3 mmol) was dissolved in degassed Et2NH
U
(20 ml) and heated under reflux. The soln. was cooled and the solvent evaporated. The white solid
was dissolved in toluene (10 ml), and the soln. was passed through a short column of SiO2 under an
inert atmosphere. The column was washed with toluene (30 ml), the solvent subsequently evaporated,
and the obtained off-white solid recrystallized from MeOH: 7 (854 mg, 84%). M.p. 1458. 1H-NMR
(300 MHz, CDCl3): 1.14 (d, 3J(P,H)=11, 18 H, MeCP); 1.15 (d, 3J(P,H)=10, 18 H, MeCP); 3.25 (d,
2J(P,H)=3, 2 H, ArCH2P); 3.52 (br. s, 2 H, ArCH2P); 7.32–7.42 (m, 1 arom. H); 7.45–7.53 (m, 1
arom. H); 7.58 (d, 3J(H,H)=8, 1 arom. H); 7.68–7.76 (m, 2 arom. H); 8.40 (d, 3J(H,H)=8, 1 arom.
H). 13C-NMR (75 MHz, CDCl3): 27.7 (d, J=23, MeCP); 29.8 (d, J=13, MeCP); 29.9 (d, J=13,
MeCP); 32.1 (d, J=22, ArCH
129.3, 129.6, 131.2 (8s, arom. CH); 132.5 (d, J=11, ArCH2P); 133.1 (d, J=5, ArCH2P). 31P-NMR (121
MHz, CDCl3, H3PO4): 34.4 (s, ArCH2PtBu2); 35.4 (s, ArCH2PtBu2). HR-ES-MS (pos.): 444.3149 (C28
H47-
Pþ2 ; calc. 445.3153). Anal. calc. for C28H46P2 (444.61): C 75.6, H 10.4; found: C 75.4, H 10.6.
Tetracarbonyl{[1,2-phenylenebis(methylene)]bis[di(tert-butyl)phosphine-kP]}molybdenum
([Mo(CO)4(1)]). [Mo(CO)4(norborna-2,5-diene)] (150 mg, 0.5 mmol) was dissolved in CH2Cl2 (10 ml),
A
G
AHCTREUNG
ACHTREUNG
A
ACHTREUNG
and 1 (200 mg, 0.5 mmol) was added. The soln. was heated under reflux for 2 h and then cooled.
MeOH (10 ml) was added, and the CH2Cl2 was evaporated precipitating a yellow solid. The soln. was fil-
tered, and the solid was washed with MeOH: [Mo(CO)4(1)] (173 mg, 57%). M.p. 1908 (dec.). IR (CH2Cl2;
E
selected data): 2006 (MoꢀCO), 1894 (MoꢀCO), 1878 (MoꢀCO), 1859 (MoꢀCO). 1H-NMR (300 MHz,
CDCl3): 1.40 (d, 3J(P,H)=11, 36 H, MeCP); 3.42 (d, 2J(P,H)=5, 4 H, ArCH2PtBu2); 7.10–7.12 (m, 2 arom.
A
H); 7.32–7.35 (m, 2 arom. H). 13C-NMR (75 MHz, CDCl3): 30.1 (s, MeCP); 31.6 (d, J=14, MeCP); 37.2
2
(d, J=4, ArCH
A
213.3 (t, 2J(P,C)=8, PꢀMoꢀCO); 215.8 (t, 2J(P,C)=8, PꢀMoꢀCO); 215.3 (d, 2J(P,C)=8, PꢀMoꢀ
CO). 31P-NMR (121 MHz, CDCl3): 57.9. Anal. calc. for C28H44MoO4P2 (602.53): C 55.8, H 7.4; found:
C 56.0, H 7.4.
Tetracarbonyl{[1,2-phenylenebis(methylene)]bis[diisopropylphosphine-kP]}molybdenum
([Mo(CO)
G
(1)], with [Mo(CO)4
ACHTREUNG
mmol), CH2Cl2 (10 ml), and 2 (101 mg, 0.3 mmol): [Mo(CO)4
ACHTREUNG
(CH2Cl2; selected data): 2019 (MoꢀCO); 1924 (MoꢀCO); 1908 (MoꢀCO); 1869 (MoꢀCO). 1H-NMR
(300, CDCl3): 1.24 (dd, 3J(P,H)=14, 3J(H,H)=7, 12 H, MeCHP); 1.28 (dd, 3J(P,H)=14, 3J(H,H)=7,
12 H, MeCHP); 2.12 (sept., 3J(H,H)=7, 4 H, MeCHP); 3.03 (d, 2J(P,H)=7, 4 H, ArCH2PiPr2);
E

Helvetica Chimica Acta – Vol. 89 (2006)
1799
7.01–7.04 (m, 2 arom.H ); 7.12–7.15 (m, 2 arom. H). 13C-NMR (75 MHz, CDCl3) 19.0 (s, MeCHP); 19.9
(s, MeCHP); 27.6 (d, 1J(P,C)=9, MeCHP); 31.4 (s, ArCH2
P); 126.9 (s, Ar); 131.7 (s, arom. CH); 135.9 (s,
A
ArCH2P); 207.4 (d, 2J(P,C)=8, PꢀMoꢀCO); 213.1 (t, 2J(P,C)=8, PꢀMoꢀCO); 215.2 (t,
2J(P,C)=8, PꢀMoꢀCO); 215.0 (d, 2J(P,C)=8, PꢀMoꢀCO). 31P-NMR (121 MHz, CD2Cl2, H3PO4):
35.5 (s, ArCH2(iPr)2
Mo). Anal. calc. for C24H36MoO4P2 (546.43): C 52.75, H 6.6; found: C 52.5, H 6.7.
A
Tetracarbonyl{[1,2-phenylenebis(methylene)]bis[(tert-butyl)isopropylphosphine-kP]}molybdenum
([Mo(CO)4(3)]). As described for [Mo(CO)4(1)], with [Mo(CO)4(norborna-2,5-diene)] (100 mg, 0.3
mmol), CH2Cl2 (10 ml), and 3 (110 mg, 0.3 mmol): [Mo(CO)4(3)] (109 mg, 63%). M.p. 1898 (dec.). IR
A
N
ACHTREUNG
AHCTREUNG
1
(CH2Cl2; selected data): 2013 (MoꢀCO), 1909 (MoꢀCO), 1893 (MoꢀCO), 1864 (MoꢀCO). H-NMR
3
3
3
3
(300, CDCl3): 1.25 (dd, J(P,H)=14, J(H,H)=7, 6 H, MeCHP); 1.27 (dd, J(P,H)=14, J(H,H)=7, 6
H, MeCHP); 1.40 (d, 3J(P,H)=11, 18 H, MeCP); 2.10 (sept., 3J(H,H)=7, 2 H, MeCHP); 3.38 (d,
2J(P,H)=7, 4 H, ArCH2PtBuiPr); 7.04–7.07 (m, 2 arom H); 7.12–7.14 (m, 2 arom. H). 13C-NMR (75
A
1
MHz, CDCl3): 19.1 (s, MeCHP); 19.9 (s, MeCHP); 25.3 (s, MeCP); 27.4 (d, J(P,C)=9, MeCHP); 30.2
(s, MeCP); 31.4 (s, ArCH2P); 126.5 (s, Ar); 131.7 (s, arom CH); 136.1 (s, ArCH2P); 207.3 (d,
2J(P,C)=8, PꢀMoꢀCO); 213.1 (t, 2J(P,C)=8, PꢀMoꢀCO); 215.3 (t, 2J(P,C)=8, PꢀMoꢀCO); 214.9
(d, J(P,C)=8, PꢀMoꢀCO). 31P-NMR (121 MHz, CD2Cl2, H3PO4): 42.1 (s, ArCH2P(tBuiPr)Mo). Anal.
2
calc. for C26H46MoO4P2 (580.53): 53.8, H 8.0; found: C 53.7, H 8.1.
Tetracarbonyl{[naphthalene-2,3-diylbis(methylene)]bis[(di(tert-butyl)phosphine-kP]}molybdenum
([Mo(CO)
mmol), CH2Cl2 (10 ml), and 6 (182 mg, 0.3 mmol): [Mo(CO)4
(CH2Cl2; selected data): 2007 (MoꢀCO), 1900 (MoꢀCO), 1881 (MoꢀCO), 1861 (MoꢀCO). H-NMR
A
G
A
AHCTREUNG
1
(300, CDCl3): 1.38 (d, 3J(P,H)=11, 36 H, MeCP); 3.40 (d, 2J(P,H)=4, 4 H, ArCH2PtBu2); 7.29–7.38
G
(m, 2 arom. H); 7.58–7.64 (m, 2 arom. H); 7.71 (s, 2 arom. H). 13C-NMR (75 MHz, CDCl3): 30.4 (s);
2
31.7 (d, J=14); 38.2 (s); 126.6, 127.2, 132.1, 132.2 (4s, arom CH); 135.5 (s, Ar); 207.4 (d, J(P,C)=8,
PꢀMoꢀCO); 213.4 (t, 2J(P,C)=8, PꢀMoꢀCO); 215.2 (t, 2J(P,C)=8, PꢀMoꢀCO); 215.3 (d, 2J(P,
C)=8, PꢀMoꢀCO). 31P-NMR (121 MHz, CD2Cl2, H3PO4): 60.9 (s, ArCH2P(tBu)2
C
(pos.): 649.1880 ([MꢀCO+Na]+, C31
A
(653.60): C 58.9, H 7.1; found: C 58.6, H 7.3.
Tetracarbonyl{[naphthalene-1,2-diylbis(methylene)]bis[di(tert-butyl)phosphine-kP]}molybdenum
([Mo(CO)
mmol), CH2Cl2 (10 ml), and 7 (182 mg, 0.3 mmol): [Mo(CO)4
(CH2Cl2; selected data): 2007 (MoꢀCO), 1896 (MoꢀCO), 1880 (MoꢀCO), 1860 (MoꢀCO). H-NMR
(300, CDCl3): 1.48–1.62 (m, 36 H, MeCP); 3.56 (d, 2J(P,H)=12, 2 H, ArCH2PtBu2); 3.91 (d,
2J(P,H)=8, 2 H, ArCH2PtBu2); 7.38–7.62 (m, 4 arom. H); 7.78 (d, 3J(H,H)=6, 1 arom. H); 8.21 (d,
3J(H,H)=6, 1 arom. H). 13C-NMR (75 MHz, CDCl3): 25.2 (s, MeCP); 31.6 (d, J=14, MeCP); 38.1 (d,
A
G
A
AHCTREUNG
1
AHCTREUNG
AHCTREUNG
J=6, ArCH2
N
N
132.2, 133.3, 133.7, 135.4 (5s, Ar); 207.3 (d, 2J(P,C)=8, PꢀMoꢀCO); 213.4 (t, 2J(P,C)=8, PꢀMoꢀ
CO); 215.4 (t, 2J(P,C)=8, PꢀMoꢀCO); 215.8 (d, 2J(P,C)=8, PꢀMoꢀCO). 31P-NMR (121 MHz,
5
5
CD2Cl2, H3PO4): 58.0 (d, J(P,P)=24, ArCH2P(tBu)2
A
G
ES-MS (pos.): 649.1880 ([MꢀCO+Na+], C31
H4698MoNaO3P2; calc. 649.1874). Anal. calc. for
C32H46MoO4P2 (652.60): C 58.9, H 7.1; found: C 58.6, H 7.3.
Example of Ligand Testing in Methoxycarbonylation of Vinyl Acetate. [Pd2(dba)3] (23 mg, 0.05 mmol
Pd) and 1 (197 mg, 0.5 mmol) were weighed into a Schlenk flask under N2, to which MeOH (11 ml) was
added. After all of the solid had dissolved, MeSO3H (48 mg, 0.5 mmol) was added, followed by vinyl ace-
G
tate (1.8 g, 21 mmol). This soln. was added to a Fischer-Porter bottle that had been evacuated and back
filled with N2 three times. CO was added to a pressure of 3 bar, and the soln. was kept at 258 with an oil
bath. After 3 h, the soln. was cooled and the CO slowly vented. A portion of the soln. was hydrolzed with
NaHCO3 and then analyzed by GC.
X-RayCrsytallographyfor
rac-[1,2-Phenylenebis(methylene)]bis[(tert-butyl)isopropylphosphine]-
Borane (1/2). C22H46B2P2, M 394.15; colorless prism grown from MeOH, crystal size 0.2×0.08×0.08
mm, monoclinic, P2(1)/c, a=12.630(2), b=18.239(2), c=11.595(2) Å, b=110.869(4)8; V=2495.6(7)
Å3, Z=4, Dcalc =1.049 mg mꢀ3; MoKa radiation (confocal optic, l 0.71073 Å), m=0.179 mmꢀ1
,
T=93(2) K. The 15220 data (4467 (R(int)=0.0224), 2.06<q<25.34) were collected on a Rigaku-

1800
Helvetica Chimica Acta – Vol. 89 (2006)
MM007/MercuryCCD diffractometer and were corrected for absorption. The structure was solved by
direct methods and refined by full-matrix least-squares on F2 values of all data [27] to give
wR={S[w(F2oF2c )2]/S[w(F2o)2]}1/2 =0.0905, conventional R=0.0352 for F values of reflections with
F2o >2s( F2o) [4170 observed reflections], S=0.993 for 242 parameters. Residual electron density
extremes were 0.357 and ꢀ0.253 eÅꢀ3. CCDC-294580 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/
cif. from the Cambridge Crystallograhic Data Centre.
REFERENCES
[1] G. Taylor, Chem. Ind. 2002, 6, 12.
[2] E. Drent, E. Kragtwijk, to Shell Oil Company, EP0495548, 1992.
[3] K. Kudo, Y. Oida, K. Mitsuhashi, S. Mori, K. Komatsu, N. Sugita, Bull. Chem. Soc. Jpn. 1996, 69,
1337.
[4] A. J. Rucklidge, G. E. Morris, D. J. Cole-Hamilton, Chem. Commun. 2005, 1176.
[5] A. J. Rucklidge, G. R. Eastham, D. J. Cole-Hamilton, WO2004050599, 2004.
[6] H. Ooka, T. Inoue, S. Itsuno, M. Tanaka, Chem. Commun. 2005, 1173.
[7] W. Clegg, G. R. Eastham, M. R. J. Elsegood, R. P. Tooze, X. L. Wang, K. Whiston, Chem. Commun.
1999, 1877.
[8] C. Jimenez-Rodriguez, D. F. Foster, G. R. Eastham, D. J. Cole-Hamilton, Chem. Commun. 2004,
1720.
[9] C. Jimenez-Rodriguez, G. R. Eastham, D. J. Cole-Hamilton, Inorg. Chem. Commun. 2005, 8, 878.
[10] C. Jimenez-Rodriguez, G. R. Eastham, D. J. Cole-Hamilton, Dalton Trans. 2005, 1826.
[11] G. R. Eastham, P. D. Newman, R. P. Tooze, R. A. Campbell, P. G. Edwards, J. M. Thorpe, to ICI plc,
WO9947528, 1999.
[12] A. Leone, G. Consiglio, Helv. Chim. Acta. 2005, 88, 210.
[13] R. A. M. Robertson, D. J. Cole-Hamilton, in ‘Catalytic Synthesis of Alkene–Carbon Monoxide
Copolymers and Cooligomers’, Ed. A. Sen, Kluwer, Dordrecht, 2003, p. 37.
[14] R. A. M. Robertson, D. J. Cole-Hamilton, Coord. Chem. Rev. 2002, 225, 67.
[15] G. R. Eastham, B. T. Heaton, J. A. Iggo, R. P. Tooze, R. Whyman, S. Zacchini, Chem. Commun.
2000, 609.
[16] G. R. Eastham, R. P. Tooze, M. Kilner, D. F. Foster, D. J. Cole-Hamilton, J. Chem. Soc., Dalton
Trans. 2002, 1613.
[17] M. R. I. Zubiri, M. L. Clarke, D. F. Foster, D. J. Cole-Hamilton, A. M. Z. Slawin, J. D. Woollins, J.
Chem. Soc., Dalton Trans. 2001, 969.
[18] J. Chatt, H. R. Watson, J. Chem. Soc. 1961, 4890.
[19] R. P. Tooze, K. Whiston, A. P. Malyan, M. J. Taylor, N. W. Wilson, J. Chem. Soc., Dalton Trans. 2000,
3441.
[20] C. Jimenez, D. F. Foster, G. R. Eastham, D. J. Cole-Hamilton, Chem. Commun. 2004, 1720.
[21] P. van Leeuwen, M. A. Zuideveld, B. H. G. Swennenhuis, Z. Freixa, P. C. J. Kamer, K. Goubitz, J.
Fraanje, M. Lutz, A. L. Spek, J. Am. Chem. Soc. 2003, 125, 5523.
[22] N. Carr, B. J. Dunne, L. Mole, A. G. Orpen, J. L. Spencer, J. Chem. Soc., Dalton Trans. 1991, 863.
[23] M. K. O’Brien, A. W. Sledeski, L. K. Truesdale, Tetrahedron Lett. 1997, 38, 509.
[24] M. Y. Darensbourg, M. Pala, S. A. Houliston, P. Kidwell, D. Spencer, S. S. Chojnacki, J. H. Reiben-
spies, Inorg. Chem. 1992, 31, 1487.
[25] P. D. Newman, R. A. Campbell, R. P. Tooze, G. R. Eastham, J. M. Thorpe, P. G. Edwards,
WO9947528, 1999.
[26] W.-W. du Mont, M. Karnap, J. Mahnke, R. Martens, C. Druckenbrodt, J. Jeske, P. G. Jones, Chem.
Ber./Recl. 1997, 1619.
[27] G. M. Sheldrick, SHELXTL Version 6.10, Bruker AXS, Madison WI, 2001.
Received January17, 2006