Hemilability and regioselectivity in palladium and platinum complexes of dppm(E) [E = O, S, Se] ligands

Article abstract of DOI:10.1016/j.jorganchem.2010.08.015

Hemilability and nonrigidity in a series of mixed P^PE donor ligands where E = O, S, or Se have been studied in palladium and platinum complexes of the type [M{κ²-(dimethylamino)ethylnaphthyl-C,N)}(P^PE)][SbF ₆] where P^PE = Ph₂PCH₂P(E)Ph₂.The role of the donor in hemilability, regioselectivity and the binding preferences of particular donors trans to the metallated carbon atom were also investigated. NMR parameters including couplings to ¹⁹⁵Pt and ⁷⁷Se were investigated for cis and trans isomers. The magnitude of ²J ¹³C-⁷⁷Se couplings can readily distinguish the cis and trans isomers. A large through-space ¹³C-⁷⁷Se ³J coupling was observed in one of the amino methyl groups of the dppm(Se) complexes.

Full text of DOI:10.1016/j.jorganchem.2010.08.015

Journal of Organometallic Chemistry 695 (2010) 2644e2650
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Hemilability and regioselectivity in palladium and platinum complexes
of dppm(E) [E ¼ O, S, Se] ligands
*
J.W. Faller , Tracey Friss, Jonathan Parr
Yale University, P.O. Box 208107, New Haven, CT 06520-8107, United States
a r t i c l e i n f o
a b s t r a c t
Article history:
Hemilability and nonrigidity in a series of mixed P^P]E donor ligands where E ¼ O, S, or Se have been
studied in palladium and platinum complexes of the type [M{k
2-(dimethylamino)ethylnaphthyl-C,N)}
Received 28 July 2010
Received in revised form
10 August 2010
Accepted 12 August 2010
Available online 20 August 2010
(P^P]E)][SbF6] where P^P]E ¼ Ph2PCH2P(E)Ph2.The role of the donor in hemilability, regioselectivity
and the binding preferences of particular donors trans to the metallated carbon atom were also inves-
tigated. NMR parameters including couplings to 195Pt and 77Se were investigated for cis and trans
isomers. The magnitude of 2 13Ce77Se couplings can readily distinguish the cis and trans isomers. A large
J
through-space 13Ce77Se 3J coupling was observed in one of the amino methyl groups of the dppm(Se)
Keywords:
Hemilabile
T-shaped intermediates
Selenium-77 NMR
dppm(O)
complexes.
Ó 2010 Elsevier B.V. All rights reserved.
dppm(S)
dppm(Se)
1. Introduction
Another area of significant activity is in the potential application
in CeC bond forming reactions, particularly in the catalysis of
Hemilabile ligands have played a key role in a number of
important reactions catalyzed by transition-metal complexes [1e4].
As an example, a ligand combining two different donors, forexample
a hard and a soft donor atom combination such as P^O can exist in
SuzukieMiyaura cross-coupling of haloarenes with arylboronic
acids (Eq. (2)) where there has been intense activity recently in an
effort to identify systems that can use less reactive haloarenes [6,7].
k2
$
k1 equilibria as shown in Eq. (1), in which the relative
concentrations of O-bound and P-bound complexes depend upon
the relative labilities of the MeP and MeO bonds. The opening of the
chelate can occur bya dissociative process or be initiated byattack at
the metal by solvent or other ligands. The differential donor prop-
erties in heterobidentate ligands have been useful in controlling
catalytic activity, even in cases where hemilability is not involved.
One of the early notable successes associated with complexes of
P^O-ligands was their application in the Shell higher olefin process
which utilizes a nickel-catalyzed oligomerization of ethylene [5].
Bulky monohapto phosphine ligands canpromote the generation
of unsaturated palladium(0) and palladium(II) intermediates and
enhance their catalytic activity in coupling reactions [8]. Generally,
14-electron intermediates are implicated in many of these reactions,
but isolations of such complexes are very rare. The first example of
an isolated monomeric (aryl)palladium(II) monophosphine
complex was only reported recently by Hartwig [9,10]. Since these
intermediates are rareand usuallyunstable, the potential to stabilize
them temporarily with hemilabile ligands is an attractive alterna-
tive. During a catalytic cycle, dissociation of the more labile donor
can create an open site on the metal for substrate binding, while re-
coordination of that donor can temporarily stabilize a potentially
coordinatively unsaturated metal center that may be generated in
another step in the catalytic process. Some of the early bulky ligands
which were successful contained an alkoxy group that may have
* Corresponding author. Fax: þ1 203 432 6144.
E-mail address: jack.faller@yale.edu (J.W. Faller).
0022-328X/$ e see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.08.015

J.W. Faller et al. / Journal of Organometallic Chemistry 695 (2010) 2644e2650
2645
acted as a weak or transient donor [11,12]. More recent studies of
N
N
ligand structure by Buchwald generalized the effectiveness of bulky
ligands such as dicyclohexyl(20,60-dimethoxybiphenyl)phosphine
and the importance of coordinative unsaturation in the mechanism
[13]. Increasingly, evidence suggests that hemilability may play
a role with these bulky ligands, but that the bonding involves P^C
chelates rather than P^O chelates. We have found that even Cy2P
systems containing a potential chelate with a Me2N donor linked
through a biphenyl backbone actually involve chelation of a P and
two of the carbons in the biphenyl [14]. There have also been several
recent publications suggesting the use of hemilabile ligands for
Suzuki couplings [15,16].
Despite recent reviews on the subject [3,4], there is relatively
little information on the kinetics in hemilabile systems or the ease
of dissociation of one donor of a hemilabile ligand in a given
system. Usually, an assertion is made that the system contains
a hemilabile ligand, but this has seldom translated into any
measurements of the importance of hemilability in a reaction. Even
the degree of dissociation of the more labile donor or the rate of its
dissociation may be open to wildly different opinions. For example,
the monosulfide of BINAP, BINAP(S), was claimed to be a readily-
E
P
P
P
M
M
E
P
M = Pd, cis-1
M = Pt, cis-2
M = Pd, trans-1
M = Pt, trans-2
Fig. 1. The isomers of (k
2-dman-C,N)Pd(dppmE) complexes.
the coupling of 77Se with 31P generally would be reduced on binding
to the metal with respect to the free phosphine selenide[24] and this
change in coupling provides spectroscopic evidence of coordination
of the selenium. The 1JSe,P coupling in a is 732.3 Hz which is reduced
to 571.5 Hz in 1a Only the trans isomer appears to be present as
suggested by long range coupling of phosphorus to the carbon and
hydrogen nuclei in the methyl groups on the nitrogen as 3JP,C ¼ 2.5,
w0.8 Hz and 4JP,H ¼ 3.4,1.6 Hz. Evidence for the trans arrangement is
also indicated by the absence of a large phosphorus coupling to any
of the lowfield carbon nuclei. In the diphos complex analogousto1a,
the ipso carbon resonates at d
157.7 and shows 2JP,C of 114.0 and 2.1 Hz
for the trans and cis couplings to the phosphorus. The E in a P]E
generally does not allow substantial correlations of spin through it
such that very small couplings through the chalcogen to the ipso
carbon would be expected. An appreciation of the attenuation of
3J couplings to be expected through Se bonds can be found from the
prepared chiral monodentate phosphine in
a paper entitled
“Diphosphine mono-sulfides: readily available chiral mono-
phosphines” [17]. The assumption was made that the P]S would
be such a poor donor that the
k
2-P,S form would be unstable relative
to the
k
1-P form. In some cases that may be the true; we, however,
3
example of N(Ph2P]Se)2Pd(PMe2Ph)Cl which showed JP,P of 16.1
have found that the half-life for the interconversion of isomers in
a BINAP(S) ruthenium complex [18], which requires a change from
and 12.1 Hz [25].
The 77Se 2J coupling is also attenuated rapidly since a negligible
coupling is observed to the methylene carbon in the ligand in 1a.
The largest 77See13C coupling observed is the 2J coupling through
k
2-P,S to the
formation of the
significant amount of the
k
1-P form, was 22 days, implying that the rate of
k
1-P form was extremely slow and that no
k
1-P form would be observable.
palladium to the carbon at d 153.3 of 30.7 Hz. Hence, it is clear that
We have now investigated complexes of several potentially
hemilabile ligands in an effort to assess the importance of the rela-
the observed isomer is that with the P]Se trans to C. This is further
evidenced by consideration of analogous platinum complexes (vide
infra). Thus, even though one might argue that the selenium of the
phosphine selenide is the softer donor relative to phosphorus, it
occupies the position previously ascribed to the harder donor. One
might also note that an example of a complex with an S-donor trans
to C was also found for a polycyclic P^P]S variant of 1. [19] Thus, as
observed in earlier arguments regarding hard-soft effects, some-
times the opposite donor is preferred and the selectivity is anti-
symbiotic. This suggests that some revision of the “rule of thumb for
isomeric preferences” is in order.
tive hardness of the donors and the relative ease of forming the k
1-P
form. In this context we have chosen a series of P^P]E (E ¼ O, S, Se)
chelates bound to a (C,N)-cyclometallated (dimethylamino)ethyl-
napthylene, [(k k
2-dman-C,N)Pd(P^P]E)]SbF6 1 or [( 2-dman-C,N)Pt
(P^P]E)]SbF6 2. This cyclometallated ligand scaffold provides a rigid
unsymmetrical framework that avoids complications from confor-
mational equilibria within its five-membered ring, as well as
providing donors of significantly different trans influence.
2. Results and discussion
2.1. (k
2-dman-C,N)Pd(dppmE)
2.2. (k
2-dman-C,N)Pt(dppmE)
It has been suggested, based on the results of a number of X-ray
structure determinations of the preferred geometric isomer, that
The assignment of the isomeric structures in the platinum
complexes is much more straightforward. The 31Pe195Pt coupling is
strongly influenced by the ligands trans to the phosphorus [26],
such that typically in complexes of this L-C,N type with bisphos-
with a heterobidentate chelate bound to (k
2-dman-C,N)Pd, “the
softest of the two donors invariably takes up the position trans to
the Me2N group” [19e21]. Thus with a P,O donor set, the O would
occupy the site trans to the carbon, as in trans-1. This was, in fact,
observed for the relevant case of the binding of the P^O donor
BINAP(O) [22]. It was of interest to determine if the cis isomer
would be observed with softer P]E donors. In any case, the relative
hemilability of the donors trans to the carbon would be relevant in
consideration of mechanisms of the SuzukieMiyaura reactions in
the presence of heterobidentate ligands.
1
phine chelates the JP,Pt trans to carbon is approximately half the
magnitude of that trans to nitrogen [27]. Upon addition of ligands a,
b, or c to [(k
2-dman-C,N)PtCl]2 both cis and trans isomers are
formed initially in approximately equal amounts and, depending
upon conditions, the mixture slowly converts to a single isomer in
solution (Fig. 2). Complex 2a interconverts with a half-life of
The determination of regiochemistry will be discussed relative to
the complex 1 containing ligand a, shown in Fig. 1. Rather than
a bridged dimer, one would anticipate a chelated structure for
complexes of a as shown for 1a (E]Se) and found in the crystal
structure of (dppmSe)Pd(SeCN)(CN) [23]. The downfield shift of the
P(III) resonance upon coordination of 64.12 ppm is also indicative of
chelation to form a five-membered ring [23]. Expectations are that
PPh2
S
Ph2P
PPh2
O
PPh2
Se
Ph2P
Ph2P
b
c
a
Fig. 2. Heterobidentate ligands investigated.

2646
J.W. Faller et al. / Journal of Organometallic Chemistry 695 (2010) 2644e2650
Table 2
Deviation (Å) from the Pt1eN1eC26 plane.
2a(E]Se)
2c(E]O)
E
P1
P2
0.0523 (10)
0.0679 (19)
0.1773 (22)
ꢁ0.0954 (37)
0.0775 (14)
0.0376 (15)
P1
C1
C26
C2
Pt1
carbons in the phenyl in a transoid position if this were a major
factor and this is not observed. In cis-2a the most downfield reso-
P2
nance in the 13C spectrum, [
d
150.38 (dd, JC,P ¼ 111.9, 10.2 Hz)] has
N1
a long relaxation time and also shows a large coupling to 31P as
expected for a carbon trans to P.
Se1
The crystal structures of 2a and 2c are similar and some selected
bond lengths and angles are given in Table 1. The preference for
selenium to bind with angles [MeEeP] closer to 90ꢀ and that of
oxygen to accommodate a wide range of angles are evident in the
relative [PteEeP] angles of 101.14(9) and 120.1(3)ꢀ respectively. In
comparing a with c, the PteP1eC1 bond angle opens significantly in
ordertoaccommodatetheanglepreference, aswellasthelongerP]E
bond lengthwithselenium. A more puckeredchelatering isproduced
with the selenium ligand as indicated in the deviation of P2 out of the
plane containing the platinum, nitrogen and carbon (Table 2).
Fig. 3. An ORTEP view of the cation of 2a showing 50% thermal ellipsoids.
approximately 70 h. Initially, two P(III) resonance patterns are
1
observed for 2a with 4015 Hz and 2014 Hz JP,Pt couplings and
eventually only the resonances of the isomer with the
1JP,Pt ¼ 4015 Hz persist. This isomer was purified by recrystallization
and identified as the trans isomer by an X-ray crystallographic
determination (see Fig. 3). An interesting feature of the 31P NMR of
the disfavored cis isomer is that the 31P signal of the P(V) which is
trans to N also shows a fairly large coupling to 195Pt of 136 Hz,
whereas this coupling is only w10 Hz when it is trans to C. One
might anticipate that the 13C spectra would be indicative of the
binding modes, but the platinum satellites are broad, such that
sensitivity is an issue in locating them. With the ligand enriched in
77Se, 77See13C couplings can be readily observed. The 77See13C
couplings are somewhat smaller than might be expected and
attenuate rapidly. A 2JSe,C of only 5.0 Hz is resolved in the methylene
carbon of trans-2a, and only one of the aromatic carbons shows
3. Relative hemilability
None of these palladium and platinum complexes showed any
indication of hemilability via a dynamic NMR spectrum in the
absence of additional ligands. In order to test the relative bond
strengths, the palladium complexes were treated with 3,5-lutidine
or triphenylphosphine to determine if added ligand could compete
with the P]E donor for an open site.
a moderately large coupling [
d
142.7, JSe,C ¼ 28.0 Hz JP,C ¼ 5.1,
2.5 Hz], presumably the naphthyl carbon directly bound to plat-
inum. Notably, one of the N-methyl groups in trans-2a shows
a relatively large 77See13C coupling (22.8 Hz). As this would
correspond to a 3J coupling, it would be expected to have attenu-
ated significantly; hence, it may be enhanced by a through-space
mechanism (the closest Se.. CeN distance is 3.212(9) Å). A “4J”
77See1H coupling of 7.3 Hz coupling to the N-methyl is also
observed in trans-2a. Comparable values are also observed in trans-
1a for 77See13C coupling (21.9 Hz) and 77See1H coupling (7.3 Hz).
We attribute these unusually large coupling values primarily to
through-space coupling, but alternatively, one might invoke a weak
bonding interaction between the methyl hydrogen atoms and the
selenium [note that the hydrogen atom positions shown in Fig. 3 are in
calculated positions]. Some contribution to this 3J 77See13C coupling
could arise from the orientation of the methyl in a cisoid arrange-
ment and the involvement of a Karplus-type mechanism; however,
an even larger coupling would be expected for one of the ipso
On addition of lutidine, only the ligand with an oxygen donor
showed a significant conversion to monodentate coordination.
Palladium complex 1c comprising a dppm(O) ligand showed
a mixture of
k
2-P,O and
k
1-P forms in the presence of added
N
P
E
P
Pt
N
P
C
Pt
P
E
C
N
C
Pt
P
E
P
Table 1
Selected bond lengths (Å) and angles (deg) for 2a and 2c.
N
C
2a (E]Se)
2c (E]O)
E
P
P
Pt
PteP1
PteE
PteN1
PteC26
P2eE
PteEeP2
PteP1eC1
EePteP1
P1eC1eP2
2.223 (2)
2.500 (1)
2.133 (6)
2.048 (7)
2.152 (2)
101.41 (6)
111.3 (3)
91.95 (5)
111.2 (4)
2.216 (1)
2.157 (4)
2.111 (4)
1.977 (5)
1.522 (4)
119.8 (2)
102.7 (2)
87.1 (1)
N
C
Pt
P
E
P
107.4 (3)
Scheme 1. Isomerization of a T-shaped intermediate.

J.W. Faller et al. / Journal of Organometallic Chemistry 695 (2010) 2644e2650
2647
Table 3
Comparison of 31P NMR parameters.
Ph2PCH2P(Se)Ph2 (JP,P) (JP,Se) {JPt,P
}
Ph2PCH2P(S)Ph2 (JP,P) {JPt,P
ꢁ28.44; 39.96 (77.2)
}
Ph2PCH2P(O)Ph2 (JP,P) {JPt,P
}
Free ligand
ꢁ27.48 [3J ¼ 14.1];
30.75 (85.3) [1J ¼ 732.0]
36.44[5.7]; 30.47 (34.0) [571.5]
e
ꢁ28.62; 27.76 (50.1)
Pd k2
Pd k1
Pt k2
34.22; 47.20 (30.3)
e
27.93; 52.80 (17.8)
24.34; 31.11 (br)
cis 28.36 [4.1]{2013.5}; 36.10 (68.0)[521]{136.4}
cis 24.93 {1965.2}; 56.55 (63.1){135}
cis 22.09 {1900.5}; 73.22 (33.2){w120 br}
trans 11.23 {4064.7};
60.25 (10.8) ]{w10 br}
trans 17.02 [5.4]{4014.8};
30.42 (25.9)[549]{10}
e
trans 14.84 {4000.2};
49.02 (23.0){11}
e
Pt k1
7.42 {4072.0}; 25.22 (br)
3,5-lutidine. The 31P NMR showed two pairs of doublets at low
temperature and broadening at room temperature attributable to
via a TeYeT rearrangement as shown in Scheme 1. The relatively
slow cis to trans isomerizations of the sulfide and selenium
complexes in the platinum complexes [t1/2 (2a) w 70 h; t1/2
(2b) w 140; t1/2 (2c) w 20 h] further suggest that the hemilability in
these complexes is limited, but with 2c the fastest. The TeYeT
interconversion would be expected to have a lower barrier [29e32],
especially since the P(III) is trans to the labilizing carbon. These slow
rates of isomerization presumably reflect the greater difficulty of
breaking the PdeS and PdeSe bonds.
more rapid interconversion of
Eq. (3). The extent to which the
k k
2-P,O and 1-P complexes as shown in
k
1-P complex was formed depended
upon the relative amount of lutidine added, the displacement of the
P]O donor by the lutidine being essentially quantitative. Similar
behavior was found for 1c and 2c, where the P]O was again selec-
tively displaced by the lutidine. In the case of trans-2c, two different
sets of P(III) resonances were observed in the 31P NMR spectrum at
room temperature after addition of lutidine with two different, but
large, values for 195Pte31P coupling (k2 4145 Hz;
k
1 4072 Hz) sup-
1-P rather than 1-O. In both complexes
4. NMR assignments
porting the assignment as k k
the large 1J(195Pt,31P) indicates that the P(III) is trans to the Me2N. The
upfield shiftof the P(III) resonancealsosuggests thelossofthechelate
Since 31P resonances for phosphines generally shift downfield
considerably upon coordination, these resonances are generally in
the same region of the spectrum as those for the P(V) resonance of
the P]E. It is generally difficult to conclusively assign these reso-
nances in bisphosphine monoxide and monosulfide palladium
complexes. For the monoselenides, the 77Se satellites reliably
indicate the P(V) resonance. Fortunately, the 195Pt satellites
conclusively identify the P(III) resonances in the platinum
complexes. The 31P data for the complexes studied are summarized
in Table 3.The coordination shifts for the P(III) in cis-2a and trans-2a
are 55.84 ppm and 44.50 ppm, respectively. The shifts are large
ring in forming the k
1-complex [28]. The spectra broaden above room
temperature indicative of interconversion of the
complexes.
k k
2-P,O and 1-P
None of the complexes comprising bisphosphine monosulfide
or -monoselenide ligands showed any indication of displacement of
either donor by NMR in the presence of added lutidine. This would
seem to indicate that the P]S and P]Se donors form less labile
interactions with the palladium and platinum centers than the P]
O, an observation consistent with HSAB ideas. It also true, however,
that the chelate rings formed exhibit different bond angles and ring
geometries which may also contribute significantly to the differ-
ences in lability.
Table 5
When triphenylphosphine was added to solutions of the
complexes 1aec or 2aec, neither coordination of the added
Crystallographic data.
2a
2c
phosphine nor the formation of
tion of triphenylphosphine selenide to a solution of the palladium
precursor [(
2-dman-C,N)PdCl]2 gives rise to a rapid exchange of
k
1-P species was observed. Addi-
Color, shape
Empirical formula
Pale yellow, block
C40H40Cl2F6NP2PtSbSe
Colorless, block
C79H78Cl2F12N2O2
P4Pt2Sb2Se2
k
the two halves of the dimer that is evidenced by the conversion of
the two signals due to the unique methyl protons seen in the 1H
NMR of the precursor to a single doublet. This indicates a reversible
bridge-cleaving and complexation of the phosphine selenide. This
reversible coordination shows that a monodentate phosphine
Formula weight
Radiation/Å
1177.41
2143.96
Mo-Ka (monochr.)
0.71075
223
Orthorhombic
P212121 (No. 19)
Mo-K
a
(monochr.)
0.71075
223
Orthorhombic
P212121 (No. 19)
T/K
Crystal system
Space group
Unit cell dimensions
a/Å
selenide is not a strong ligand for the [(k
2-dman-C,N)PdCl] frag-
12.7033 (5)
17.3755 (7)
19.8277 (8)
4376.5 (3)
4
12.8402 (4)
18.4915 (5)
18.3289 (5)
4351.9 (2)
2
ment in the absence of a second donor to give a chelate, an
observation suggesting that, in designing hemilabile ligands, it is
critical to consider the ligand as a whole rather than taking the
different donors in isolation.
b/Å
c/Å
V/Å3
Z
Dcalc/g cmꢁ3
1.787
48.778
1.636
40.080
A simple mechanism for the cisetrans isomerization would
m
/cmꢁ1 (Mo-K
a)
involve the formation of the k
1 intermediate and its interconversion
Crystal size/mm
Refl: total, unique,
Frpairs
0.20 ꢂ 0.10 ꢂ 0.10
0.19 ꢂ 0.15 ꢂ 0.15
45234, 9880, 4430
45701, 9904, 4428
Rint
No. Obs
Parameters
Ra1), wRb2), GOF
Ra1), wRb2), GOF
inverted
0.0722
9880
487
0.0473, 0.1018, 1.046
0.0732, 0.1782, 1.773
0.0484
9904
523
0.0362, 0.0737, 1.071
0.0691, 0.1675, 2.365
Table 4
Selenium-77 NMR parameters.
d
1J(31Pe77Se)
3J(31Pe77Se)
1J(195Pte77Se)
Free dppmSe
Pd (1a)
Pt (2a) trans
Pt (2a) cis
ꢁ292.5
ꢁ116.0
ꢁ107.0
ꢁ51.0
732
572
549
521
13.1
No
No
Flack parameter
0.036 (7)
ꢁ1.12 < 2.25
0.004 (5)
ꢁ0.42 < 0.93
(I); b) wR2 ¼ [S[w(F2o ꢁ F2c)2]/S[w(F2o)2]]1/2
Resid. density/e Åꢁ3
363
265
No
a) R1 ¼ SkFoj ꢁ jFck/SjFoj, for all I > 2
s
.

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J.W. Faller et al. / Journal of Organometallic Chemistry 695 (2010) 2644e2650
owing to the inclusion in a chelate ring [28] and the difference
presumably largely reflects the difference in trans influence of the N
and C. On the other hand, the coordination shifts for the P(V)
associated with Se binding in cis-2a and trans-2a are 5.35 ppm and
ꢁ0.33 ppm, respectively. The P(V) coordination shifts observed in
2b and 2c, however, are substantial (34.54 ppm for trans-2c). A
markedly larger coordination shift was observed for P(III) in trans-
1a, consistent with typical behavior seen for second versus third
row transition metals; however only a minor shift was observed for
6.2. NMR data and analyses
2-dman-C,N)Pd(dppmSe)]SbF6 (1a)
6.2.1. [(
k
1H NMR (500 MHz, CD2Cl2)
d: 7.93 (ddd, J ¼ 12.4, 7.3, 1.0 Hz, 2H,
arom.), 7.71e7.13 (m, 22H, arom.), 6.93 (d, J ¼ 8.6 Hz, 1H, arom.),
6.54 (dd, J ¼ 8.6, 7.1 Hz, 1H, arom.), 4.60 (ddd, JH,H ¼ 14.5, JH,P ¼ 11.4,
9.3 Hz, JH,Se ¼ 2.4 Hz, 1H, CH2), 4.52 (dq, J ¼ 6.3, 6.1 Hz, 1H, CHCH3),
4.12 (ddd, JH,H ¼ 14.5, JH,P ¼ 14.5, 9.8 Hz, 1H, CH2), 3.19 (d,
JH,H ¼ 3.5 Hz, JH,Se ¼ 7.3 Hz 3H, NCH3), 3.01 (d, J ¼ 1.6 Hz, 3H, NCH3),
P(V). In the case of 1a and 2a the changes in
d
of the P(V) resonances
2.02 (d, J ¼ 6.3 Hz, 3H, CCH3). 31P NMR (202 MHz, CD2Cl2)
d 36.44 (d,
are distinctly smaller than observed in b and c analogs, perhaps due
to the difference in the geometries of the selenium-containing rings
with respect to those containing oxygen or sulfur. The large vari-
ability of the shifts upon coordination suggests that assignments to
P(III) and P(V) in palladium complexes of ligands similar to b and c
should be made with caution.
JP,P ¼ 34.0 Hz, JP,Se ¼ 5.7 Hz), 30.47 (d, JP,P ¼ 34.0 Hz, JP,Se ¼ 571.5 Hz).
13C NMR (125 MHz, CD2Cl2)
d [selected resonances] 153.19 (dd,
JC,P ¼ 2.6, 2.6 Hz, JC,Se ¼ 30.7 Hz, NapthC-Pd), 149.50 (d, JC,P ¼ 2.3 Hz,
1C, Napth), 135.92 (d, JC,P ¼ 2.3 Hz, 1C, arom.), 134.68 (d,
JC,P ¼ 14.0 Hz, JC,Se ¼ 3.6 Hz, Napth), 134.20e123.66, (arom.),130.13
(s, JC,Se ¼ 3.6 Hz, Napth), 126.13 (d, JC,P ¼ 5.6 Hz, JC,Se ¼ 2.5 Hz, Napth),
74.54 (d, JC,P ¼ 2.6 Hz CHCH3), 53.00 (d, JC,P ¼ 3.0 Hz NCH3), 52.01
(dd, JC,P ¼ 2.0, 2.0 Hz, JC,Se ¼ 21.9 Hz NCH3), 45.27 (dd, JC,P ¼ 45.4,
24.4 Hz, JC,Se ¼ 5.8 Hz CH2), 24.57 (s, CCH3). 77Se NMR (95 MHz,
2
The JP,P coupling generally decreases upon binding of the free
ligand in a chelate. This coupling is also much larger (w3 times as
much) in the cis complexes than in the trans complexes. The 77Se
data (Table 4) show downfield coordination shifts upon binding in
a chelate. The coordination shifts are larger for the palladium
complex than for the platinum complexes, which is in opposition to
the trend observed for P(III) binding.
CD2Cl2) ꢁ116.0 (d, JSe,P
¼
572 Hz). Anal. Calcd for
C39H38F6NP2PdSbSe: C, 46.66; H, 3.82; N, 1.40%. Found: C, 46.85; H,
3.91; N, 1.40%.
6.2.2. [(
k
2-dman-C,N) Pt(dppmSe)]SbF6 (2a)
: 7.93 (dd, J ¼ 12.6, 8.0 Hz, 2H,
5. Conclusion
1H NMR (500 MHz, CD2Cl2)
d
arom.), 7870e7.30 (m, 22H, arom.), 6.94 (d, J ¼ 8.6 Hz, 1H, arom.),
6.73 (dd, J ¼ 8.6, 3.5 Hz, JH,Se ¼ 2.1 Hz, JH,Pt ¼ 50.1 Hz br, 1H, arom.),
4.80 (dq, J ¼ 6.2, 6.1 Hz, JH,Pt ¼ w50 Hz br, 1H, CHCH3), 4.27 (ddd,
JH,H ¼ 10.8, JH,P ¼ 6.1, 4.8 Hz, JH,Se w 0.5 Hz, 1H, CH2), 3.89 (ddd,
JH,H ¼ 10.8, JH,P ¼ 8.0, 4.0 Hz, JH,Se ¼ 7.3 Hz, 1H, CH2), 3.06 (d,
J ¼ 1.8 Hz, 3H, NCH3), 2.92 (d, J ¼ 1.6 Hz, 3H, NCH3), 1.92 (d,
Within the series of palladium and platinum complexes of
bisphosphine monochalcogens studied, it seems that only the
bisphosphine monoxides show any propensity for hemilabile
behavior in the presence of strong nucleophiles. This is probably
largely a result of the preference of the soft metals used for the
softer donors sulfur and selenium, with which they form stronger
interactions. The extent to which differences in the conformation of
the metallo-bisphosphine monochalcogen rings also influence this
behavior is not clear but from the crystallographic studies it can be
seen that these differences are significant.
J ¼ 6.3 Hz, 3H, CCH3). 31P NMR (202 MHz, CD2Cl2)
d trans 30.42 (d,
JP,P ¼ 25.9 Hz, JP,Se ¼ 549.0 Hz JP,Pt w 10 Hz P(V)), 17.02 (d,
JP,P ¼ 25.9 Hz, JP,Se ¼ 5.4 Hz, JP,Pt ¼ 4014.8 Hz P(III)); cis 36.10 (d,
JP,P ¼ 68.0 Hz, JP,Se ¼ 521.0 Hz JP,Pt ¼ 136.4 Hz P(V),), 28.36 (d,
JP,P ¼ 68.0 Hz, JP,Se ¼ 4.1 Hz, JP,Pt
¼
2013.5 Hz P(III)). 13C NMR
trans [selected resonances] 148.17 (s, 1C,
(125 MHz, CD2Cl2)
d
6. Experimental
Napth), 142.67 (dd, JC,P ¼ 2.5, 5.1 Hz, JC,Se ¼ 28.1 Hz, 1C, Napth),
135.75, (d, JC,P ¼ 3.0 Hz, arom.), 134.88, (d, JC,P ¼ 8.4 Hz, JC,Se ¼ 5.3 Hz
Napth), 134.25e122.55, (arom.), 75.71 (d, JC,P ¼ 3.0 Hz, JC,Pt w 42 Hz,
CHCH3), 54.12 (d JC,P ¼ 3.1 Hz NCH3), 52.68 (br s, JC,Se ¼ 22.8 Hz
NCH3), 44.13 (dd, JC,P ¼ 46.0, 32.7 Hz, JC,Se ¼ 5.0 Hz, CH2), 23.32 (s,
All synthetic manipulations were performed under a nitrogen
atmosphere using standard Schlenk techniques. The previously
known P,P ¼ E ligands a, b, and c, were prepared according to the
published methods [33] and characterization data were in accord
with those previously reported [Pd(dimethylaminoethylnaphthyl-
C,N)Cl]2 (3) and [Pt(dimethylaminoethylnaphthyl-C,N)Cl]2 (4) were
prepared according to literature precedent [27,34]. NMR spectra
were recorded on Bruker 400 or 500 MHz instruments and the
chemical shifts reported in ppm relative to TMS, phosphoric acid or
dimethyl selenide via reference to solvent resonances and corre-
CCH3).
d
cis [selected resonances] 150.38 (dd, JC,P ¼ 111.9, 10.2 Hz
NapthC-Pt), 149.82 (s, Napth), 135.50e122.55 (arom.), 79.16 (d,
JC,P ¼ 10.4 Hz CHCH3), 55.56 (s, NCH3), 52.82 (d JC,P ¼ 4.6 Hz NCH3),
39.29 (dd, JC,P ¼ 46.8, 22.4 Hz, JC,Se ¼ 5.5 Hz, CH2), 23.63 (s, CCH3).
77Se NMR (95 MHz)
cis ꢁ51.0 (d, JP,Se ¼ 521 Hz, JSe,Pt ¼ 265 Hz). Anal. Calcd for
C39H38F6NP2PtSbSe$C4H10O: C, 44.27; H, 4.15; N, 1.20%. Found: C,
44.40; H, 3.78; N, 1.42%.
d
trans ꢁ107.0 (d, JP,Se ¼ 549 Hz, JSe,Pt ¼ 363 Hz);
lation with
X
values [35,36]. The 1H and 13C shifts were referenced
to TMS via reference to the solvent. Selenium-77 couplings were
also evaluated with a sample enriched in 77Se for accuracy. The 77Se
couplings could be readily observed in natural abundance in the 31P
spectra, but required enrichment to be located in the 13C spectra.
6.2.3. [(
1H NMR (500 MHz, CD2Cl2)
k
2-dman-C,N)Pd(dppmS)]SbF6 (1b)
d
: 7.25 (ddd, J ¼ 12.5, 8.5, 1.3 Hz, 2H,
arom.), 7.81e7.30 (m, 22H, arom.), 6.95 (d, J ¼ 8.7 Hz, 1H, arom.),
6.57 (dd, J ¼ 8.6, 7.0 Hz, 1H, arom.), 4.55 (dq, J ¼ 6.2, 6.1 Hz, 1H,
CHCH3), 4.20 (ddd, JH,H ¼ 13.2, JH,P ¼ 8.8, 8.5 Hz, 1H, CH2), 4.03 (ddd,
JH,H ¼ 13.2, JH,P ¼ 8.9, 8.5 Hz, 1H, CH2), 3.21 (d, J ¼ 3.7 Hz, 3H, NCH3),
3.03 (d, J ¼ 1.6 Hz, 3H, NCH3), 2.00 (d, J ¼ 6.3 Hz, 3H, CCH3). 31P NMR
6.1. General procedure for preparation of [(
SbF6
k k
2-dman-C,N)M( 2-L)]
The [(
k
2-dman-C,N)M]2 dimer, 3 or 4, (0.0300 mmol), the ligand
(202 MHz, CD2Cl2)
Anal. Calcd for C39H38F6NP2PdSbS 0.5C4H10O: C, 50.04; H, 4.50; N,
d
47.20 (d, JP,P ¼ 30.3 Hz), 34.22 (d, JPP ¼ 30.3 Hz).
(0.0600 mmol) and an excess of sodium hexafluoroantimonate
(0.0473 g, 0.183 mmol) were combined in a flask prior to the
addition of 7 mL of methylene chloride. After stirring for 18 h, the
solution was filtered through Celite to remove insoluble material
and the solvent was removed under vacuum. The complexes were
recrystallized from methylene chloride/diethyl ether.
1.39%. Found: C, 50.32; H, 4.48; N, 1.52%.
6.2.4. [(
1H NMR (400 MHz, CD2Cl2)
arom.), 7.77e7.30 (m, 22H, arom.), 6.94 (d, J ¼ 8.5 Hz, 1H, arom.),
k
2-dman-C,N)Pt(dppmS)]SbF6 (2b)
: 7.93 (ddd, J ¼ 12.6, 7.2, 1.3 Hz, 2H,
d

J.W. Faller et al. / Journal of Organometallic Chemistry 695 (2010) 2644e2650
2649
6.72 (dd, J ¼ 8.5, 3.0 Hz, JH,Pt ¼ 54.3 Hz, 1H, arom.), 4.79 (dq, J ¼ 6.4,
6.0 Hz, JH,Pt ¼ 53.5 Hz, 1H, CHCH3), 4.27 (ddd, JH,H ¼ 10.8, JH,P ¼ 8.4,
6.2 Hz, JH,Pt ¼ 64.9 Hz, 1H, CH2), 3.88 (ddd, JH,H ¼ 10.8, JH,P ¼ 10.4,
5.3 Hz, JH,Pt nr,1H, CH2), 3.54 (d, J ¼ 3.5 Hz, JH,Pt ¼ 19.8 Hz, 3H, NCH3),
3.06 (d, J ¼ 1.6 Hz, JH,Pt ¼ 29.8 Hz, 3H, NCH3), 1.91 (d, J ¼ 6.3 Hz, 3H,
was used. Calculations were performed using the Crystal Structure
crystallographic software package [38] except for refinement,
which was performed using SHELXL-97 [39]. Both 2a and 2c crys-
tallized in the orthorhombic space group P212121. The cell for 2a
also included four molecules of methylene chloride. The cell for 2c
included two molecules of methylene chloride and showed
a disorder of two orientations of the hexafluoroantimonate.
CCH3). 31P NMR (162 MHz, CD2Cl2)
d
trans 49.02 (d, JP,P ¼ 23.0 Hz,
J
P,Pt w 11 Hz P(V)), 14.78 (d, JP,P ¼ 23.0 Hz, JP,Pt ¼ 4000.2 Hz P(III)); cis
56.55 (d, JP,P ¼ 63.1 Hz, JP,Pt ¼ 135 Hz P(V),), 24.93 (d, JP,P ¼ 63.1 Hz,
JP,Pt ¼ 1965.2 Hz P(III)); Anal. Calcd for C39H38F6NP2PtSbS H2O: C,
44.10; H, 3.79; N, 1.30%. Found: C, 43.92; H, 3.87; N, 1.29%.
Acknowledgements
We thank the donors of the Petroleum Research Fund admin-
istered by the American Chemical Society for support of our work
(PRF#43212).
6.2.5. [(
1H NMR (500 MHz, CD2Cl2)
k
2-dman-C,N)Pd(dppmO)]SbF6 (1c)
d
: 7.84 (ddd, J ¼ 12.7, 8.1, 1.1 Hz, 2H,
arom.), 7.71e7.13 (m, 22H, arom.), 7.03 (d, J ¼ 8.5 Hz, 1H, arom.),
6.52 (dd, J ¼ 8.5, 6.3 Hz, 1H, arom.), 4.56 (dq, J ¼ 6.3, 6.1 Hz, 1H,
CHCH3), 3.68 (ddd, JH,H ¼ 11.0, JH,P ¼ 6.8, 5 Hz, 1H, CH2), 3.64 (ddd,
JH,H ¼ 11.0, JH,P ¼ 8.0, 6.50 Hz,1H, CH2), 3.09 (d, J ¼ 3.6 Hz, 3H, NCH3),
3.05 (d, J ¼ 1.6 Hz, 3H, NCH3), 1.98 (d, J ¼ 6.4 Hz, 3H, CCH3). 31P NMR
Appendix A. Supplementary data
Crystallographic data for the structural analysis has been
deposited with the Cambridge Crystallographic Data Centre, CCDC
No. 784352 and 784353 for compounds 2a and 2c. Copies of this
information may be obtained free of charge from: The Director,
CCDC, 12 Union Road, Cambridge, CB2 1EZ UK; Fax. (int code) þ44
(1223)336 033; or Email: deposit@ccdc.cam.ac.uk or www:http://
www.ccdc.cam.ac.uk.
(202 MHz, CD2Cl2)
d
52.80 (d, JP,P ¼ 17.8 Hz, 1P,), 27.93 (d,
JPP ¼ 17.8 Hz). Anal. Calcd for C39H38F6NP2PdSbO: C, 49.79; H, 4.07;
N, 1.49%. Found: C, 49.42; H, 4.12; N, 1.45%.
6.2.6. [(
k
2-dman-C,N)Pt(dppmO)]SbF6 (2c)
: trans 7.91 (ddd, J ¼ 12.6, 7.2, 1.1 Hz,
1H NMR (400 MHz, CD2Cl2)
d
2H, arom.), 7.80e7.31 (m, 22H, arom.), 6.98 (d, J ¼ 8.6 Hz,1H, arom.),
6.63 (dd, J ¼ 8.5, 2.9 Hz, JH,Pt ¼ 66.3 Hz, 1H, arom.), 4.86 (dq, J ¼ 6.3,
6.0 Hz, JH,Pt ¼ 61.7 Hz, 1H, CHCH3), 3.65 (ddd, JH,H ¼ 10.7, JH,P ¼ 6.3,
3.8 Hz, 1H, CH2), 3.53 (ddd, JH,H ¼ 10.7, JH,P ¼ 8.1, 4.5 Hz, 1H, CH2),
3.35 (d, J ¼ 3.1 Hz, 3H, NCH3), 3.08 (d, J ¼ 1.6 Hz, JH,Pt ¼ 26.6 Hz, 3H,
NCH3), 1.91 (d, J ¼ 6.3 Hz, 3H, CCH3). 31P NMR (162 MHz, CD2Cl2)
References
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6.2.7. 31P NMR spectra of free ligands
6.2.7.1. dppmSe (a). 31P NMR (202 MHz, CD2Cl2)
d 30.75 (d,
JP,P ¼ 85.6 Hz), ꢁ27.52 (d, JP,P ¼ 85.6 Hz, JP,Se ¼ 732.0 Hz). 77Se NMR
(95 MHz, CD2Cl2) ꢁ292.5 (dd, 1JSe,P ¼ 732 Hz, 3JSe,P ¼ 13 Hz).
6.2.7.2. dppmS (b). 31P NMR (162 MHz, CD2Cl2)
JP,P ¼ 77.2 Hz), ꢁ28.44 (d, JP,P ¼ 77.2 Hz).
d
39.96 (d,
27.76 (d,
6.2.7.3. dppmO (c). 31P NMR (162 MHz, CD2Cl2)
JP,P ¼ 50.1 Hz), ꢁ28.62 (d, JP,P ¼ 50.1 Hz).
d
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6.2.8. Treatment of 1c and 2c with 3,5-lutidine
31
6.2.8.1. [1c þ 0.5 eq lutidine]. P NMR (ꢁ70 ꢀC) 31P NMR (202 MHz,
CD2Cl2)
JP,Pt ¼ 4145 Hz,
d
52.11 (d, JP,P ¼ 18.0 Hz,
k
2-P(V)), 26.83 (d, JP,P ¼ 18.0 Hz,
k
2-P(III)); 1-P(V)), 24.34 (s, br, 1-P(III)).
d 31.11 (s, br, k k
6.2.8.2. [2c þ 0.5 eq lutidine]. 31P NMR 31P NMR (202 MHz, CD2Cl2)
d
62.24 (d, JP,P ¼ 10.6 Hz,
k
2-P(V)), 11.19 (d, JP,P ¼ 10.6 Hz,
JP,Pt ¼ 4145.0 Hz,
k
2-P(III));
d
25.22 (d, JP,P ¼ nr, JP,Pt w 54 Hz
k
1-P(V)),
7.42 (d, JP,P ¼ nr, JP,Pt ¼ 4072 Hz,
k
1-P(III)).
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All of the measurements were made on a Rigaku CCD SCXmini
diffractometer using monochromated Mo-K radiation. Data are
summarized in Table 5. The structure was solved by direct methods
[37] and expanded using Fourier techniques. The non-hydrogen
atoms were refined anisotropically. Hydrogen atoms were refined
using the riding model. Full-matrix least squares refinement on F2
a
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J.W. Faller et al. / Journal of Organometallic Chemistry 695 (2010) 2644e2650
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