P-C and C-C bond formation by Michael addition in platinum-catalyzed hydrophosphination and in the stoichiometric reactions of platinum phosphido complexes with activated alkenes

Article abstract of DOI:10.1021/om060631n

We recently proposed a new mechanism for platinum-catalyzed hydrophosphination of activated alkenes, in which nucleophilic attack of a phosphido ligand in the intermediate hydride complex Pt(diphos)(PR ₂)-(H) (1) on the alkene H₂C=CH(X) (X = CN or CO ₂R) gave the zwitterion Pt(diphos)(H)(PR₂CH ₂CHX) (2), containing a cationic Pt center and a phosphine ligand with a pendent stabilized carbanion. Subsequent C-H bond formation involving the Pt-H and the carbanion would yield the product R₂PCH ₂CH₂X (3) and regenerate the catalyst, while attack of the carbanion on another alkene would yield byproducts derived from more than one alkene, such as R₂P(CH₂CH(X))_nCH ₂CH₂X (7). Several tests of this mechanism and related pathways for product and byproduct formation were investigated. Attempts to trap the proposed carbanion with another electrophile led to the development of a Pt-catalyzed three-component coupling of secondary phosphines, tert-butyl acrylate, and benzaldehyde, yielding the functionalized phosphines R ₂PCH₂CH(CO₂t-Bu)(CHPh(OH)) (R₂P = Ph₂P (10a); R₂P = Me(Is)P (10b, Is = 2,4,6-(i-Pr) ₃C₆H₂)). Reactions of the complexes Pt(diphos)(R′)(PR₂) (diphos = (R,R)-Me-Duphos, R′ = Me, PR₂ = PPh₂ (11), PPh(i-Bu) (12); R′ = Ph, PR ₂ = PMeIs (13); diphos = dppe, R' = Me, PR₂ = PPh ₂ (14), PPh(i-Bu) (15)), models for 1, with tert-butyl acrylate or acrylonitrile gave mixtures of products including Pt-(diphos)(R′)(CH(X) CH₂PR₂) (A, X = CO₂t-Bu or CN), Pt(diphos)(R′)(CH(X)CH₂CH(X)CH₂PR₂) (B), R₂PCH₂CH₂X (3), R₂P(CH ₂CH(X))_n(CH₂CH₂X) (7), and, in some cases, the dinuclear phosphido-bridged cations [(Pt(diphos)(Me)) ₂(μ-PR₂)]⁺ (17). When tert-butanol or water was added to these reactions, more of the phosphines 3 and 7, and less of the intermediates A and B, were formed. Decomposition of A and B gave unidentified platinum dialkyls (C), tentatively formulated as Pt(diphos)(R′)(CH(X) R″). The complex Pt(dppe)(Me)(CH(Me)CO₂t-Bu) (21), a model for A, B, and C, was generated either from Pt(dppe)(Cl)-(CH(Me)CO₂t-Bu) (20) and ZnMe₂ or from Pt(dppe)(Me)(Cl) (19) and ZnBr(CH(Me)CO ₂t-Bu)·THF; complexes 20 and 21 did not react with tert-butyl acrylate. These observations are consistent with the proposed nucleophilic mechanism for P-C and C-C bond formation.

Full text of DOI:10.1021/om060631n

Organometallics 2006, 25, 5757-5767
5757
P-C and C-C Bond Formation by Michael Addition in
Platinum-Catalyzed Hydrophosphination and in the Stoichiometric
Reactions of Platinum Phosphido Complexes with Activated Alkenes
Corina Scriban,† David S. Glueck,*,† Lev N. Zakharov,‡ W. Scott Kassel,‡
Antonio G. DiPasquale,‡ James A. Golen,‡ and Arnold L. Rheingold‡
Department of Chemistry, 6128 Burke Laboratory, Dartmouth College, HanoVer, New Hampshire, 03755,
and Department of Chemistry, UniVersity of California, San Diego, 9500 Gilman DriVe, La Jolla,
California 92093
ReceiVed July 13, 2006
We recently proposed a new mechanism for platinum-catalyzed hydrophosphination of activated alkenes,
in which nucleophilic attack of a phosphido ligand in the intermediate hydride complex Pt(diphos)(PR2)-
(H) (1) on the alkene H2CdCH(X) (X ) CN or CO2R) gave the zwitterion Pt(diphos)(H)(PR2CH2CHX)
(2), containing a cationic Pt center and a phosphine ligand with a pendent stabilized carbanion. Subsequent
C-H bond formation involving the Pt-H and the carbanion would yield the product R2PCH2CH2X (3)
and regenerate the catalyst, while attack of the carbanion on another alkene would yield byproducts
derived from more than one alkene, such as R2P(CH2CH(X))nCH2CH2X (7). Several tests of this mechanism
and related pathways for product and byproduct formation were investigated. Attempts to trap the proposed
carbanion with another electrophile led to the development of a Pt-catalyzed three-component coupling
of secondary phosphines, tert-butyl acrylate, and benzaldehyde, yielding the functionalized phosphines
R2PCH2CH(CO2t-Bu)(CHPh(OH)) (R2P ) Ph2P (10a); R2P ) Me(Is)P (10b, Is ) 2,4,6-(i-Pr)3C6H2)).
Reactions of the complexes Pt(diphos)(R′)(PR2) (diphos ) (R,R)-Me-Duphos, R′ ) Me, PR2 ) PPh2
(11), PPh(i-Bu) (12); R′ ) Ph, PR2 ) PMeIs (13); diphos ) dppe, R′ ) Me, PR2 ) PPh2 (14), PPh(i-Bu)
(15)), models for 1, with tert-butyl acrylate or acrylonitrile gave mixtures of products including Pt-
(diphos)(R′)(CH(X)CH2PR2) (A, X ) CO2t-Bu or CN), Pt(diphos)(R′)(CH(X)CH2CH(X)CH2PR2) (B),
R2PCH2CH2X (3), R2P(CH2CH(X))n(CH2CH2X) (7), and, in some cases, the dinuclear phosphido-bridged
cations [(Pt(diphos)(Me))2(µ-PR2)]+ (17). When tert-butanol or water was added to these reactions, more
of the phosphines 3 and 7, and less of the intermediates A and B, were formed. Decomposition of A and
B gave unidentified platinum dialkyls (C), tentatively formulated as Pt(diphos)(R′)(CH(X)R′′). The complex
Pt(dppe)(Me)(CH(Me)CO2t-Bu) (21), a model for A, B, and C, was generated either from Pt(dppe)(Cl)-
(CH(Me)CO2t-Bu) (20) and ZnMe2 or from Pt(dppe)(Me)(Cl) (19) and ZnBr(CH(Me)CO2t-Bu)‚THF;
complexes 20 and 21 did not react with tert-butyl acrylate. These observations are consistent with the
proposed nucleophilic mechanism for P-C and C-C bond formation.
merization, might also occur (2 f 6, Scheme 2). C-H bond
formation via 6 or its neutral isomer 8 would then yield
phosphines derived from more than one alkene (7), which are
commonly observed as byproducts in such reactions.3 Alterna-
tively, 7 could be formed by single or repeated alkene insertion
into the Pt-C bond of 4, followed by reductive elimination from
8.4
We hypothesized that protonation of zwitterion 2 with a weak
acid HY would yield cationic phosphine complex 9. Pt-H
deprotonation by the conjugate base Y- would yield 3 and
regenerate 1 (Scheme 3). If intermediate 2 reacted more quickly
with acid than with the alkene, then adding HY might suppress
Introduction
Recently, we proposed a new mechanism for Pt-catalyzed
hydrophosphination of activated alkenes (Scheme 1).1 P-H
oxidative addition to yield hydride 1 followed by attack of the
nucleophilic phosphido group at the alkene would give zwit-
terion 2, which might form phosphine 3 via two complementary
pathways. Carbanion attack at the cationic platinum hydride
would yield 3, complexed to Pt(0). Subsequent displacement
of 3 by a secondary phosphine, followed by oxidative addition,
would regenerate 1. Alternatively, carbanion attack at platinum,
along with Pt-P dissociation, could generate alkyl hydride 4,
perhaps via five-coordinate 5. The intermediates 4, which might
also form from 1 by coordination/migratory insertion, have been
observed in stoichiometric reactions; they decomposed, presum-
ably by C-H reductive elimination, to yield 3.2
(2) (a) Wicht, D. K.; Kourkine, I. V.; Lew, B. M.; Nthenge, J. M.; Glueck,
D. S. J. Am. Chem. Soc. 1997, 119, 5039-5040. (b) Wicht, D. K.; Kourkine,
I. V.; Kovacik, I.; Glueck, D. S.; Concolino, T. E.; Yap, G. P. A.; Incarvito,
C. D.; Rheingold, A. L. Organometallics 1999, 18, 5381-5394. (c) Kovacik,
I.; Wicht, D. K.; Grewal, N. S.; Glueck, D. S.; Incarvito, C. D.; Guzei, I.
A.; Rheingold, A. L. Organometallics 2000, 19, 950-953.
(3) Wicht, D. K.; Glueck, D. S. Hydrophosphination and Related
Reactions. In Catalytic Heterofunctionalization. From Hydroamination to
Hydrozirconation; Togni, A., Grutzmacher, H., Eds.; Wiley-VCH: Wein-
heim, 2001; pp 143-170.
Carbanion attack on additional alkene, as in anionic poly-
* Corresponding author. E-mail: Glueck@dartmouth.edu.
† Dartmouth College.
‡ University of California, San Diego.
(1) Scriban, C.; Kovacik, I.; Glueck, D. S. Organometallics 2005, 24,
4871-4874.
(4) Costa, E.; Pringle, P. G.; Smith, M. B.; Worboys, K. J. Chem. Soc.,
Dalton Trans. 1997, 4277-4282.
10.1021/om060631n CCC: $33.50 © 2006 American Chemical Society
Publication on Web 10/24/2006

5758 Organometallics, Vol. 25, No. 24, 2006
Scriban et al.
Scheme 1. Possible Mechanisms for Product Formation in
Pt-Catalyzed Hydrophosphination of Activated Alkenes
([Pt] ) Pt(diphos), X ) CN or CO2R)
Chart 1. Three Probes of the Mechanisms in Schemes 1-3a
a (a) Trapping zwitterion 2 with a new external electrophile E; (b)
hydride-free models of 2; (c) models of 4 without Pt-H and pendent
PR2 groups ([Pt] ) Pt(diphos), X ) CN or CO2R).
Scheme 4. Proposed Mechanism of Reaction of Zwitterion
2 with Benzaldehyde, by Analogy with the
Phosphine-Catalyzed Morita-Baylis-Hillman Reaction
([Pt] ) Pt(diphos), X ) CN or CO2R)
Scheme 2. Possible Mechanisms for Byproduct Formation
in Pt-Catalyzed Hydrophosphination of Activated Alkenes
([Pt] ) Pt(diphos), X ) CN or CO2R)
Scheme 3. A Protic Additive HY Suppressed Formation of
Byproducts in Pt-Catalyzed Hydrophosphination of
Activated Alkenes ([Pt] ) Pt(diphos), X ) CN or CO2R)
Results and Discussion
(a) Trapping Zwitterion 2 with a New External Electro-
phile. The proposed mechanism for nucleophilic catalysis of
the Morita-Baylis-Hillman (MBH) reaction6 (Scheme 4)
suggested trapping 2 with benzaldehyde.
In a MBH mechanism, Michael addition of the phosphine
catalyst to an alkene yields a zwitterion, which is trapped by
the aldehyde. Proton transfer and loss of the phosphine then
gives the product.7 Similarly, reaction of zwitterion 2 with an
aldehyde (“MBH plus”), followed by proton transfer, would
yield phosphine 10. Because this reaction would compete with
“normal” hydrophosphination, the product ratio 3/10 would
reflect the selectivity of zwitterion 2 for reaction with the internal
(Pt-H) and external (PhCHO) electrophiles.8
byproduct formation, and indeed this was observed with the
weak acids tert-butanol and water.1
Indeed, Pt((R,R)-Me-Duphos)(trans-stilbene) was a catalyst
precursor for the three-component reaction of secondary phos-
phines (PHPh2 or PHMe(Is), Is ) 2,4,6-(i-Pr)3C6H2) with tert-
butyl acrylate and benzaldehyde to yield ∼1:1 mixtures of
We devised three additional probes of the intermediacy of
proposed zwitterion 2 (Chart 1): (a) trapping 2 with a new
external electrophile, instead of t-BuOH or water; (b) replacing
the acidic Pt-H in 2 with an alkyl group to promote carbanion
attack on an alkene, yielding analogues of 6;5 (c) preparing
analogues of Pt-alkyl 4 to test the proposed insertion of an
alkene into the Pt-C bond (intermediate 4 f 8, Scheme 2).
These probes provided additional evidence for the nucleophilic
attack/zwitterion mechanism of Schemes 1-3.
(6) Basavaiah, D.; Rao, A. J.; Satyanarayana, T. Chem. ReV. 2003, 103,
811-891.
(7) Methot, J. L.; Roush, W. R. AdV. Synth. Catal. 2004, 346, 1035-
1050.
(8) Formation of 10 and 3 could also be explained without invoking
zwitterion 2. Alkyl hydride intermediate 4 could undergo either reductive
elimination, yielding hydrophosphination product 3, or insertion of ben-
zaldehyde into the Pt-C bond to yield an alkoxy hydride, which would
afford 10 by O-H reductive elimination. Although we cannot distinguish
these mechanisms, the proposed insertion of an aldehyde into a Pt-C bond
does not appear to be known; see: Krug, C.; Hartwig, J. F. Organometallics
2004, 23, 4594-4607, and references therein.
(5) C-C reductive elimination from 4-R′ is expected to be slower than
C-H reductive elimination from 4. See: Collman, J. P.; Hegedus, L. S.;
Norton, J. R.; Finke, R. G. Principles and Applications of Organotransition
Metal Chemistry; University Science Books: Mill Valley, CA, 1987.
McCarthy, T. J.; Nuzzo, R. G.; Whitesides, G. M. J. Am. Chem. Soc. 1981,
103, 3396-3403.

Platinum-Catalyzed Hydrophosphination
Organometallics, Vol. 25, No. 24, 2006 5759
Scheme 5. Pt-Catalyzed Three-Component “MBH Plus”
Coupling (Pt catalyst precursor )
Pt((R,R)-Me-Duphos)(trans-stilbene), PR2 ) PPh2 (a) or
PMeIs (c))10
phosphines 10 and 3 (Scheme 5). As expected, the ratio 10/3
increased when excess benzaldehyde was used.9
Figure 1. ORTEP diagram of Ph2PCH2CH(CO2t-Bu)(CHPh(OH))
(10a).
Although neat PHPh2 and PhCHO reacted quickly11 and Pt-
catalyzed addition of PH3 to formaldehyde is known,12 we found
that secondary phosphines reacted very slowly with benzalde-
hyde in toluene even in the presence of a Pt(Me-Duphos)
catalyst, and the reaction of PHPh2 and PhCHO appeared to be
reversible under these conditions. Subsequent addition of tert-
butyl acrylate to these reaction mixtures yielded 10 and 3. The
PPh2 derivative 10a was separated from 3a, obtained as a
mixture highly enriched in one diastereomer, and characterized
by X-ray crystallography (see Figure 1, Table 1, and the
Supporting Information). Although the Pt catalyst is chiral,
neither of the diastereomers of 10a were enantiomerically
enriched (see the Experimental Section for details).
could not be identified; its tentative formulation in Scheme 6
is discussed in more detail below. The organic products included
phosphines 3 and 7 (n g 1)15 and alkene 16,16 whose formation
from tert-butyl acrylate is catalyzed by nucleophilic phos-
phines.16,17 With excess alkene, 3 was converted to 7.1 In some
cases, the dinuclear cations 17, known to form on decomposition
of 14 and 15, were also observed.13c
Intermediates A were identified by their 31P NMR spectra
(Table 2 and Supporting Information), which were similar to
those of the previously reported analogues.2,14
Table 3 summarizes 31P NMR spectral data for intermediates
B, whose PR2 chemical shifts were similar to those of the
(b) Hydride-Free Models of Zwitterion 2. Several com-
plexes Pt(diphos)(R′)(PR2) are known;13 we also prepared Pt-
((R,R)-Me-Duphos)(Me)(PPh2) (11). Its structure (Figure 2,
Table 1, and the Supporting Information) was similar to that of
the PPh(i-Bu) analogue 12.13c
The reactions of Pt hydrocarbyl phosphido complexes 11-
15 with tert-butyl acrylate or acrylonitrile are summarized in
Scheme 6 and Table S1 (Supporting Information). Complicated
product mixtures, which depended on the Pt precursor and the
reaction conditions, were formed (see the Experimental Section
and the Supporting Information for details).
5
structurally related phosphines 7; as expected, JPt-P was not
observed. The JPt-P(diphos) values were similar to those of
intermediates A and the related Pt dialkyl 21 (see below).
The lifetime of intermediates A depended on the substituents
of the Pt complex and the alkene (Table S1 and Supporting
Information). For example, treatment of Pt(dppe)(Me)(PMes2)
(18, Mes ) 2,4,6-Me3C6H2) with acrylonitrile cleanly gave the
“insertion” product A-18′ (Scheme 7),2a,b but the PPh2 analogue
14 formed A-14′, B-14′, and phosphine 3a′. With excess
acrylonitrile, A-14′ was converted to B-14′.
The complexes Pt(diphos)(Me)(PR2) and Pt((R,R)-Me-Du-
phos)(H)(PPhIs) reacted with acrylonitrile to give olefin “inser-
tion” products A.2,14 Similar products were formed from 11-
15, but A was not stable under the reaction conditions (in some
cases, it decomposed even at low temperature). Mixtures of
diastereomers of the “double-insertion” products B also formed,
and A was often converted to B, especially in the presence of
excess alkene. Both A and B decomposed to yield C, which
In most cases, decomposition of A in the presence of alkene
gave the longer-lived B. Over time, and especially in the
presence of excess alkene, both A and B were converted to
complexes C. The nature of these products did not depend on
the original phosphido group; both Pt(dppe)(Me)(PPh2) (14) and
Pt(dppe)(Me)(PPh(i-Bu)) (15), for example, gave the same
product C on reaction with tert-butyl acrylate. These compounds
could not be isolated, but the JPt-P values (Table 4) suggested
that they retain the Pt(diphos)(R′) fragment and that the
unidentified fourth ligand has a large trans influence, similar
to that of the functionalized alkyl group in intermediates A and
B.18 A possible structure for C (Scheme 6) is discussed in more
detail below.
(9) For a related fluoride-catalyzed coupling of silylphosphines, see: (a)
Hayashi, M.; Matsuura, Y.; Watanabe, Y. Tetrahedron Lett. 2005, 46, 5135-
5138. (b) Hayashi, M.; Matsuura, Y.; Watanabe, Y. Tetrahedron Lett. 2004,
45, 9167-9169.
(10) Several phosphines R2PCH2CH2X (3) were prepared, differing in
X and PR2. Numbering scheme: for X ) CO2t-Bu, PPh2 ) a, PPh(i-Bu)
) b, PMeIs ) c. Numbering for X ) CN is similar but with an additional
′. For example, Ph2PCH2CH2CO2t-Bu is 3a, MeIsPCH2CH2CO2t-Bu is 3c,
and Ph2PCH2CH2CN is 3a′. A similar scheme applies to compounds 10a
and 10c.
(11) Muller, G.; Sainz, D. J. Organomet. Chem. 1995, 495, 103-111.
(12) (a) Harrison, K. N.; Hoye, P. A. T.; Orpen, A. G.; Pringle, P. G.;
Smith, M. B. J. Chem. Soc., Chem. Commun. 1989, 1096-1097. (b) Hoye,
P. A. T.; Pringle, P. G.; Smith, M. B.; Worboys, K. J. Chem. Soc., Dalton
Trans. 1993, 269-274.
(c) Model Compounds without Pt-H and Pendent PR2
Groups. We prepared the complexes Pt(dppe)(R)(CHMe(CO2t-
Bu)) (R ) Cl (20) or Me (21), Scheme 8) to test the importance
of the pendent PR2 group in their reactions with alkenes.
Carbene insertion into the Pt-Me bond of 19 gave 20, as
(15) Several phosphines R2P(CH2CH(X))nCH2CH2X (7) were prepared,
differing in n, X, and PR2. Numbering scheme: for X ) CO2t-Bu, PPh2 )
a, PPh(i-Bu) ) b, PMeIs ) c; n ) 1 or 2. Numbering for X ) CN is
similar but with an additional ′. For example, Ph2P(CH2CH(CO2t-Bu)CH2-
CH2CO2t-Bu) is 7a1, MeIsP(CH2CH(CO2t-Bu))2CH2CH2CO2t-Bu is 7c2,
and Ph2P(CH2CH(CN))2CH2CH2CN is 7a1′.
(16) (a) Amri, H.; Rambaud, M.; Villieras, J. Tetrahedron Lett. 1989,
30, 7381-7382. (b) Amri, H. Personal communication.
(17) McClure, J. D. J. Org. Chem. 1970, 35, 3045-3048.
(18) Appleton, T. G.; Clark, H. C.; Manzer, L. E. Coord. Chem. ReV.
1973, 10, 335-422.
(13) (a) For Pt(dppe)(Me)(PR2) (PR2 ) PPh2 (14) or PPh(i-Bu) (15)),
see: Wicht, D. K.; Paisner, S. N.; Lew, B. M.; Glueck, D. S.; Yap, G. P.
A.; Liable-Sands, L. M.; Rheingold, A. L.; Haar, C. M.; Nolan, S. P.
Organometallics 1998, 17, 652-660. (b) For Pt((R,R)-Me-Duphos)(Ph)-
(PMeIs) (13), see: Scriban, C.; Glueck, D. S. J. Am. Chem. Soc. 2006,
128, 2788-2789. (c) For Pt((R,R)-Me-Duphos)(Me)(PPh(i-Bu)) (12), see:
Scriban, C.; Wicht, D. K.; Glueck, D. S.; Zakharov, L. N.; Golen, J. A.;
Rheingold, A. L. Organometallics 2006, 25, 3370-3378.
(14) Wicht, D. K.; Kovacik, I.; Glueck, D. S.; Liable-Sands, L. M.;
Incarvito, C. D.; Rheingold, A. L. Organometallics 1999, 18, 5141-5151.

5760 Organometallics, Vol. 25, No. 24, 2006
Scriban et al.
Table 1. Crystallographic Data for Ph2PCH2CH(CO2t-Bu)(CH(Ph)(OH)) (10a), Pt((R,R)-Me-Duphos)(Me)(PPh2) (11),
Pt(dppe)(Cl)(CH(Me)(CO2t-Bu))‚CH2Cl2 (20‚CH2Cl2), and Pt(dppe)(Me)(CH(Me)(CO2t-Bu))‚THF (21‚THF)
10a
C26H29O3P
420.46
P2(1)
11
20‚CH2Cl2
21‚THF
formula
fw
space group
a, Å
b, Å
c, Å
C31H41P3Pt
C34H39Cl3O2P2Pt
843.03
C38H48O3P2Pt
809.79
701.64
P2(1)
9.7369(14)
Pna2(1)
P2(1)/n
10.7290(11)
9.6080(10)
11.2870(11)
90
92.169(2)
90
17.3082(10)
10.2818(6)
19.0494(11)
90
90
90
10.2780(4)
19.017(3)
15.778(2)
90
91.064(3)
90
17.6054(7)
20.0000(8)
90
99.7550(10)
90
R, deg
â, deg
γ, deg
V, Å3
1162.7(2)
2921.0(7)
3390.0(3)
3566.6(2)
Z
2
4
4
4
D(calc), g/cm3
µ(Mo KR), mm-1
temp, K
R(F), %a
Rw(F2), %a
1.201
0.142
1.595
4.986
1.652
4.500
1.508
4.058
100(2)
213(2)
213(2)
100(2)
4.14
10.03
2.87
6.40
4.22
10.37
2.79
6.50
2
2
2
2
2
a Quantity minimized ) Rw(F2) ) ∑[w(Fo - Fc )2]/∑[(wFo )2]1/2; R ) ∑∆/∑(Fo), ∆ ) |(Fo - Fc)|, w ) 1/[σ2(Fo ) + (aP)2 + bP], P ) [2Fc
+
2
Max(Fo ,0)]/3. A Bruker CCD diffractometer was used in all cases.
impurities.20 Nevertheless, 21 was characterized by multinuclear
NMR spectroscopy. Its 31P NMR spectrum was similar to that
of intermediates A and B, consistent with their proposed
structures, and also to that of the unidentified Pt complex C
(Table 5).
Complexes 20 and 21 were crystallographically characterized
(see Figures 3 and 4, Table 1, and the Supporting Information).
The structures were similar to that of Pt((S,S)-Diop)(Cl)(CH-
(Me)CO2Et)) (20-Diop-Et),19 with the expected significant bite
angle differences between Diop (∼100°) and dppe (∼86°).21
No reaction occurred after addition of excess t-Bu acrylate
to 20-Diop-Et,19 20, or impure 21, even after several days at
room temperature.22 In contrast, the unstable intermediate A-14,
which, unlike model 21, contains a pendent PPh2 group, was
observed only at low temperature on treatment of 14 with t-Bu
acrylate.
Mechanism of P-C and C-C Bond Formation in the
Reaction of Pt-Phosphido Complexes with Activated Alk-
enes. The reactions of Scheme 6 resulted in P-C and C-C
bond formation, yielding intermediates A and B and phosphines
3 and 7. How do these compounds form and interconvert?
Scheme 9 shows the proposed mechanism. After formation of
zwitterion 2-R′, carbanion attack at the Pt center would yield
A, while attack on another alkene would give B, via 6-R′.
Reversibility of these steps would explain the observed conver-
sion of A to B.
Figure 2. ORTEP diagram of Pt((R,R)-Me-Duphos)(Me)(PPh2)
(11), showing one of the two molecules in the unit cell.
a
Scheme 6
Formation of phosphines 3 and 7 would require an acid,
perhaps adventitious water, to protonate the carbanion in
zwitterions 2-R′ and 6-R′.23 Deliberately adding a weak acid
should promote this reaction, in preference to formation of A
and B (Scheme 9). As predicted, when 14 or 15 was treated
with 5 equiv of tert-butyl acrylate in 1:1 toluene/t-BuOH,
a Reactions of Pt(diphos)(R′)(PR2) complexes with tert-butyl acrylate
and acrylonitrile. [Pt] ) Pt((R,R)-Me-Duphos), R′ ) Me, PR2 ) PPh2
(11), PPh(i-Bu) (12); R′ ) Ph, PR2 ) PMeIs (13); [Pt] ) Pt(dppe), R′
) Me, PR2 ) PPh2 (14), PPh(i-Bu) (15), X ) CN or CO2t-Bu. Complex
C could not be identified; a tentative formulation is shown (see the
text for discussion). For 17, [Pt] ) Pt(dppe), R ) Ph (17a) or i-Bu
(17b); [Pt] ) Pt((R,R)-Me-Duphos), R ) i-Bu.
(20) Hama, T.; Liu, X.; Culkin, D. A.; Hartwig, J. F. J. Am. Chem. Soc.
2003, 125, 11176-11177. For Pt(dppe)Me2 and Pt(dppe)(Me)(Cl), see:
Appleton, T. G.; Bennett, M. A.; Tomkins, I. B. J. Chem. Soc., Dalton
Trans. 1976, 439-446.
(21) Dierkes, P.; van Leeuwen, P. W. N. M. J. Chem. Soc., Dalton Trans.
1999, 1519-1529.
(22) Complex 21 was prepared by the Me2Zn route (Experimental
Section) and isolated in ca. 90% purity; the major impurities were precursor
20 and Pt(dppe)Me2. Neither 21 nor these impurities reacted with tert-butyl
acrylate in C6D6 at room temperature.
(23) Although solvents were dried by standard methods and reactions
were carried out under nitrogen in dry glassware, acrylonitrile and tert-
butyl acrylate were not dried or distilled. Some of the dependence of the
results in Table S1 (Supporting Information) on the scale and stoichiometry
might be due to differing amounts of adventitious water.
previously described for related complexes.19 Treatment of 20
with dimethylzinc generated dialkyl 21. This reaction seemed
to be an equilibrium, but addition of excess ZnMe2 led to
formation of Pt(dppe)Me2, which was difficult to separate from
the desired product. Complex 21 could also be generated cleanly
by reaction of 19 with the Reformatsky reagent ZnBr(CHMeCO2t-
Bu)‚THF, but attempts to isolate the pure compound were
unsuccessful; Pt(dppe)Me2 and Pt(dppe)(Me)(Cl) were the major
(19) Bergamini, P.; Costa, E.; Cramer, P.; Hogg, J.; Orpen, A. G.; Pringle,
P. G. Organometallics 1994, 13, 1058-1060.

Platinum-Catalyzed Hydrophosphination
Organometallics, Vol. 25, No. 24, 2006 5761
Table 2. Selected 31P NMR Data for the “Insertion” Intermediates Pt(diphos)(R′)(CH(X)CH2PR2) (A)
number, Diphos
R′
X
PR2
PPh2
PPh(i-Bu)
PMeIs
PPh2
δ P3 (JPt-P, JPP)
A-11, (R,R)-Me-Duphosa
A-12, (R,R)-Me-Duphosb,c
A-13, (R,R)-Me-Duphosb,e
A-14, dppef
Me
Me
Ph
Me
Me
CO2t-Bu
CO2t-Bu
CO2t-Bu
CO2t-Bu
CN
-10.5 (296, 34), -11.6 (265, 34)
-21.4 (196, 21), -23.6 (158, d)
-40.2 (280, 32), -43.0 (d, 29), -42.1 (d, 40)
-16.8 (159, d)
A-14′, dppee
PPh2
-15.2 (153, 11)
b
c
d
e
f
a In toluene-d8, -75 °C. Not all of the expected diastereomers were observed. In toluene-d8, -50 °C. Not resolved. In toluene-d8, 21 °C. In toluene-
d8, -40 °C.
Table 3. 31P NMR Data for “Double-Insertion” Products Observed in the Reaction of tert-Butyl Acrylate and Acrylonitrile with
Pt(diphos)(Me)(PR2) (B)
number, Diphos
B-14′, dppe
X
PR2
δ P1 (JPt-P
)
δ P2 (JPt-P
)
δ P3
a
CN
PPh2
PPh2
46.6 (2295)
47.6 (2307)
49.3 (2173)
46.3 (2167)
49.5 (2191)
46.6 (2179)
49.3 (2165)
46.4 (e)
66.1 (2142)
65.8 (2133)
66.4 (2145)
65.5 (2127)
66.5 (2139)
65.5 (2122)
66.2 (2146)
65.9 (2138)
66.4 (2136)
48.9 (1772)
48.7 (1769)
46.4 (1770)
48.9 (1781)
46.0 (1762)
49.0 (1877)
46.2 (1760)
48.5 (e)
68.1 (1756)
67.2 (1773)
68.9 (1764)
65.7 (1764)
68.9 (1765)
65.6 (1769)
68.0 (1752)
66.1 (1756)
67.3 (1769)
-19.4
-19.6
-18.4
-17.8
-32.3
-31.7
-31.3
-31.0
-18.1
-19.7
-19.0
-18.7
-31.0
-31.3
-31.5
-32.2
-32.3
-32.4
-32.8
-33.3
a,b
B-14, dppe
B-15, dppe
CO2t-Bu
CO2t-Bu
PPh(i-Bu)a,c,d
f,c
B-11, (R,R)-Me-Duphos
B-12, (R,R)-Me-Duphos
CO2t-Bu
CO2t-Bu
PPh2
PPh(i-Bu)f,g
a In toluene-d8. J12 values for the two diastereomers were 6 and 5 Hz, respectively. The assignment of the P3 peaks to the four diastereomers was based
b
c
d
e
f
g
on integration of the P1-P3 peaks. J12 values for all four diastereomers were 5 Hz. Not observed. In C6D6. The assignment of the P3 peaks to the various
diastereomers and observation of all the expected Duphos signals were not possible due to the complexity of the Duphos region.
Table 4. 31P NMR Data for Compounds C, Formed in the
a
Scheme 7
Reaction of Pt(diphos)(R′)(PR2) with CH2dCH(X)a
diphos
R′
X
δ (P1) (JPt-P
)
δ (P2) (JPt-P
)
J12
dppe
dppe
Me CN
Me CO2t-Bu 47.1 (2289)
45.5b
48.5b
48.3 (1778)
66.1 (1758)
62.4 (1677)
3
3
3
3
(R,R)-Me-Duphos Me CO2t-Bu 66.6 (2249)
(R,R)-Me-Duphos Ph CO2t-Bu 59.6 (2200)
b
a Solvent ) toluene-d8, J in Hz. JPt-P was not detected.
acrylonitrile promoted the formation of phosphines 3 and 7 (see
Scheme 11 for results with the acrylate and the Supporting
Information for more details). With both alkenes, the “dry”
reactions gave small amounts of phosphines 3 and 7; most of
the PPh2 moiety was in intermediates B-14 and B-14′. With
added water, phosphines 3a and 7a1 (for acrylate) or 3a′ (for
acrylonitrile) formed more quickly; they were the major PPh2-
containing compounds in the mixture.
We next sought to explain the conversion of 3 into 7 in the
presence of alkene, as well as the formation of the Pt product
C. If protonation of 2-R′ to give 3 were reVersible, then
subsequent formation and protonation of 6-R′ would complete
the conversion of 3 to 7. This reaction would require 1 equiv
a [Pt] ) Pt(dppe).
intermediates A and B were not observed. Instead, phosphines
3 and 7 (for 14) or 7 (for 15) and the dinuclear cations [(Pt-
(dppe)(Me))2(µ-PPhR)]+ (R ) Ph (17a), R ) i-Bu, (17b))
formed (Scheme 10),13c perhaps by trapping the [Pt(dppe)(Me)]+
fragment with the phosphido starting material.
Similarly, adding 1 equiv of water to the reactions of Pt-
(dppe)(Me)(PPh2) (14) with 10 equiv of tert-butyl acrylate or

5762 Organometallics, Vol. 25, No. 24, 2006
Scriban et al.
Scheme 8. Synthesis of r-Functionalized Pt Alkyl
Complexes ([Pt] ) Pt(dppe))
Table 5. Selected 31P NMR Data for the Intermediates
Pt(dppe)(Me)(CH(CO2t-Bu)CH2PPh2) (A-14),
Pt(dppe)(Me)(CH(CO2t-Bu)CH2CH(CO2t-Bu)CH2PPh2)
(B-14), the Model Compound
Pt(dppe)(Me)(CHMe(CO2t-Bu)) (21), and Product C (for
which a tentative structure is shown)a
Figure 4. ORTEP diagram of Pt(dppe)(Me)(CH(Me)CO2t-Bu)‚
THF (21‚THF); the solvent molecule is not shown.
Scheme 9. Proposed Mechanism of P-C and C-C Bond
Formation in the Reaction of Pt-Phosphido Complexes with
Activated Alkenes ([Pt] ) Pt(diphos), X ) CN or CO2t-Bu,
HY ) weak acid)
complex
δ (P1) (JPt-P
)
δ (P2) (JPt-P
)
JPP (dppe)
A-14b
B-14c
44.4 (2211)
49.3 (2173)
46.3 (2167)
47.3 (2094)
47.1 (2289)
47.6 (1849)
46.4 (1770)
48.9 (1781)
48.9 (1794)
48.3 (1778)
4
6
5
5
3
21d
Cc
a Labeling: P1 is trans to the functionalized alkyl, P2 is trans to Me, P3
b
is the pendent PPh2 group. In toluene-d8, -20 °C. Additional couplings
to the PPh2 group (P3) were also observed in the dppe signals (J13 ) 13,
c
d
J23 ) 10), but the PPh2 peak was broad. In toluene-d8. In C6D6.
Scheme 10. t-BuOH-Promoted Phosphine Formation in the
Reactions of 14 and 15 with tert-Butyl Acrylate ([Pt] )
Pt(dppe), R ) Ph (14) or i-Bu (15), X ) CO2t-Bu)
Scheme 11. Water-Promoted Phosphine Formation in the
Reaction of Pt(dppe)(Me)(PPh2) (14) with tert-Butyl Acrylate
([Pt] ) Pt(dppe), X ) CO2t-Bu)
Figure 3. ORTEP diagram of Pt(dppe)(Cl)(CH(Me)CO2t-Bu)‚CH2-
Cl2 (20‚CH2Cl2), with the solvent molecule omitted.
of the acid HY and might reversibly produce the Pt complex
Pt(diphos)(R′)(Y) (Scheme 9). If HY was water, then Pt(diphos)-
(R′)(OH) should act as a base toward phosphine 3, yielding
intermediate 2-R′ and, from it, complexes A and B.24
To test this hypothesis, we treated the known hydroxide Pt-
(dppe)(Me)(OH) (22)24 with the phosphine PPh2CH2CH2CN
(3a′) (Scheme 12). The initial major product was A-14′. Small
amounts of the phosphido complex Pt(dppe)(Me)(PPh2) (14)
and the dinuclear cation 17a, known to arise from decomposition
of 14,13c were also observed. The minor products B-14′ and
7a1′ might arise from acrylonitrile formed in the precedented
A-14′f 14 conversion.2 More 14 was formed from A-14′ over

Platinum-Catalyzed Hydrophosphination
Organometallics, Vol. 25, No. 24, 2006 5763
Scheme 12. Reaction of a Platinum Hydroxide Complex
However, several questions remain unanswered. Although Pt
hydroxides appear to be competent intermediates, they were not
observed during the stoichiometric reactions, and the eventual
Pt products, C, have not been identified. The 31P NMR data
are consistent with formulation of these complexes as Pt-
(diphos)(R′)(CH(X)CH2OH) (24), which might be formed by
“insertion” of alkene into the Pt-O bond of a hydroxide
species.27 However, platinum hydroxides 22 and 23 did not react
with acrylonitrile or tert-butyl acrylate, and the reaction of Pt-
(dppe)(Me)(OH) (22) with HOCH2CH2CN did not give C. We
also considered the possibility that the acid HY in Scheme 9
might be the alkene itself, but no 1H NMR vinyl signals expected
for the resulting Pt complexes were observed in the mixtures.
with a Cyanoethylphosphine ([Pt] ) Pt(dppe))a
Conclusions
a Although acrylonitrile was not observed directly, its formation in
the proposed A-14′/14 equilibrium is consistent with the products 14,
7a1′, and B-14′.
We conclude that formation of a zwitterion by nucleophilic
attack of a Pt-PR2 group on an activated alkene is involved in
P-C and C-C bond formation in Pt-catalyzed hydrophosphi-
nation. This hypothesis is consistent with the reactivity of the
model compounds Pt(diphos)(R′)(PR2) summarized in Scheme
9. The mechanism also has predictive value, exemplified in the
effect of protic additives in Pt-catalyzed hydrophosphination
(Scheme 3)1 and related stoichiometric reactions (Schemes 10
and 11) and in the new Pt-catalyzed three-component coupling
(“MBH plus” reaction, Schemes 4 and 5).
Scheme 13. Reaction of a Platinum Hydroxide Complex
with a Cyanoethylphosphine Derived from 2 equiv of
Acrylonitrile ([Pt] ) Pt(dppe))
Related mechanisms may be important in the chemistry of
other metal-heteroatom bonds. For example, formation of a
zwitterion via nucleophilic attack of the amido group in Cu-
(IPr)(NHPh) on acrylonitrile was recently proposed,28 and such
pathways may also be relevant in the reactions of activated
alkenes with Pt-anilide and -phenoxide complexes.29
time, consistent with a shift in the equilibrium between them
driven by consumption of acrylonitrile. Similar observations with
Pt((R,R)-Me-Duphos)(Ph)(OH) (23)25 are described in the
Experimental Section.
Experimental Section
Unless otherwise noted, all reactions and manipulations were
performed in dry glassware under a nitrogen atmosphere at 20 °C
in a dry box or using standard Schlenk techniques. Petroleum ether
(bp 38-53 °C), ether, THF, toluene, and CH2Cl2 were dried using
columns of activated alumina.30 NMR spectra were recorded using
Varian 300 or 500 MHz spectrometers. 1H and 13C NMR chemical
shifts are reported versus Me4Si and were determined by reference
to the residual 1H and 13C solvent peaks. 31P NMR chemical shifts
are reported versus H3PO4 (85%) used as an external reference.
Coupling constants are reported in Hz, as absolute values. Unless
indicated, peaks in NMR spectra are singlets. Elemental analyses
were provided by Schwarzkopf Microanalytical Laboratory or
Quantitative Technologies Inc. Reagents were from commercial
suppliers, except for the following compounds, which were made
by the literature procedures: Pt((R,R)-Me-Duphos)(trans-stilbene),31
PHMe(Is),32 (S)-[Pd(NMe2CH(Me)C6H4)Cl]2,33 Pt(dppe)(Me)(P-
These experiments showed that Pt-mediated conversion of
phosphine 3 into 7 via the reversible proton-transfer chemistry
of Scheme 9 is plausible. The reverse process occurred on
treatment of 22 with 7a1′ (Scheme 13). The major initial product
was phosphido complex 14, along with a little cation 17a, and
the phosphine 3a′, whose concentration increased over time.
Thus, the mechanism proposed in Scheme 9 is consistent with
a number of experimental observations, including the formation
and interconversion of intermediates A and B and phosphines
3 and 7. It is also consistent with the substituent effects observed.
Intermediate A was less reactive for Me-Duphos complexes than
for dppe, perhaps because five-coordinate intermediates (such
as 5 in Scheme 1) required for the A f zwitterion 2-R′
conversion are less readily accessible for the more sterically
demanding diphosphine.26 This idea is also consistent with the
comparison between isolable Pt(dppe)(Me)(CH(CN)CH2PMes2)
(A-18′) and the more reactive PPh2 analogue A-14′ (Scheme
7). Moreover, the lack of reactivity of A-18′ and the model
complexes Pt(dppe)(X)(CH(Me)CO2t-Bu) (X ) Cl or Me, 20
and 21) with acrylonitrile and tert-butyl acrylate, respectively,
suggests that byproduct formation does not occur by classical
migratory insertion of an alkene into the Pt-C bond of
intermediates like A.
(27) (a) Bennett, M. A.; Jin, H.; Li, S.; Rendina, L. M.; Willis, A. C. J.
Am. Chem. Soc. 1995, 117, 8335-8340. (b) Bryndza, H. E.; Calabrese, J.
C.; Wreford, S. S. Organometallics 1984, 3, 1603-1604.
(28) Munro-Leighton, C.; Blue, E. D.; Gunnoe, T. B. J. Am. Chem. Soc.
2006, 128, 1446-1447.
(29) (a) Cowan, R. L.; Trogler, W. C. Organometallics 1987, 6, 2451-
2453. (b) Cowan, R. L.; Trogler, W. C. J. Am. Chem. Soc. 1989, 111, 4750-
4761.
(30) Pangborn, A. B.; Giardello, M. A.; Grubbs, R. H.; Rosen, R. K.;
Timmers, F. J. Organometallics 1996, 15, 1518-1520.
(31) Wicht, D. K.; Zhuravel, M. A.; Gregush, R. V.; Glueck, D. S.; Guzei,
I. A.; Liable-Sands, L. M.; Rheingold, A. L. Organometallics 1998, 17,
1412-1419.
(32) Brauer, D. J.; Bitterer, F.; Dorrenbach, F.; Hessler, G.; Stelzer, O.;
Kruger, C.; Lutz, F. Z. Naturforsch. B 1996, 51, 1183-1196.
(33) Otsuka, S.; Nakamura, A.; Kano, T.; Tani, K. J. Am. Chem. Soc.
1971, 93, 4301-4303.
(24) The basic nature of Pt-hydroxides has been studied in detail. For
example, Pt(dppe)(Me)(OH) reacted with acetonitrile to give Pt(dppe)(Me)-
(CH2CN) (Appleton, T. G.; Bennett, M. A. Inorg. Chem. 1978, 17, 738-
747).
(25) Scriban, C.; Glueck, D. S.; Golen, J. A.; Rheingold, A. L.,
manuscript in preparation.
(26) See Table S1 (Supporting Information) for details.

5764 Organometallics, Vol. 25, No. 24, 2006
Scriban et al.
PhR) (R ) Ph or i-Bu),13a,c Pt(dppe)(Me)(OH),34 Pt((R,R)-Me-
Duphos)(Ph)(PMeIs),13b Pt((R,R)-Me-Duphos)(Ph)(OH),25 Pt(dppe)-
(Me)(Cl),35 Pt((S,S)-Diop)(Me)(CH(Me)CO2Et),19 Pt((R,R)-Me-
Duphos)(Me)(Cl),13c and MeCH(ZnBr)(CO2t-Bu)‚THF.20
Reaction of Benzaldehyde and PHPh2 in the Absence of a
Catalyst. A solution of PHPh2 (45 mg, 0.24 mmol) in toluene-d8
(0.3 mL) was transferred to an NMR tube, which was fitted with
a septum. Benzaldehyde (25.5 mg, 24.4 µL, 0.24 mmol) was added
via microliter syringe, and the reaction mixture was monitored by
31P NMR spectroscopy. After 10 min, unreacted PHPh2 and a small
new peak at δ 5.6 (ratio 16:1) were observed in the mixture. This
peak could be assigned to Ph2PCH(Ph)(OH) (lit. 31P NMR (CH2-
Cl2): δ 4.2).11 Adding 5 mol % Pt((R,R)-Me-Duphos)(trans-
stilbene) did not promote further formation of this phosphine.
Catalytic Reaction of tert-Butyl Acrylate with 5 equiv of
Benzaldehyde and PHPh2. Synthesis of Three-Component
Coupling Product 10a. To Pt((R,R)-Me-Duphos)(trans-stilbene)
(8.2 mg, 0.012 mmol, 5 mol %) in toluene (0.2 mL) was added
PHPh2 (45 mg, 0.24 mmol) in toluene (0.3 mL). The mixture was
transferred to an NMR tube, which was fitted with a septum.
Benzaldehyde (127 mg, 122 µL, 4.8 mmol) was added via microliter
syringe, and the reaction mixture was monitored by 31P NMR
spectroscopy. After 20 min, unreacted PHPh2 and Ph2PCH(Ph)-
(OH), in an approximate ratio 2:1, were observed. tert-Butyl acrylate
(35 µL, 0.24 mmol) was added via microliter syringe. After 10
min, PPh2CH2CH2CO2t-Bu (3a, δ -14.2) and the two diastereomers
of the hydroxyphosphine product 10a (δ -18.1, -18.7, in an
approximate ratio 3:1) were observed; all the PHPh2 had been
consumed. The ratio 3a:10a was 1:3.0, and the ratio between the
two diastereomers of 10a was 2.9:1.
The catalyst was removed from the reaction mixture on a silica
column (5 cm height, 0.6 cm diameter), using a 9:1 petroleum ether/
THF mixture as eluent. The catalyst did not elute. After removing
the solvent under vacuum, 100 mg of a mixture of a white solid
and a colorless oil was obtained. Proton and sodium adducts of the
oxidized phosphine 10a were observed by mass spectroscopy.1
HRMS: m/z calcd for C26H30O4P+ (MOH+) 437.1882, found
437.1869. HRMS: m/z calcd for C26H29O4NaP+ (MONa+) 459.1701,
found 459.1689.
The mixture was washed with petroleum ether (3 portions of
0.5 mL) to give white crystals suitable for X-ray crystallography.
The washings were collected, and the solvent was removed under
vacuum, yielding a colorless oil. 31P{1H} NMR (C6D6) of the white
crystals (10a): δ -18.9 (a), -19.3 (b) (ratio a:b ) 8.5:1). 31P-
{1H} NMR (C6D6) of the washings (a mixture of 10a and 3a): δ
-14.7 (3a), -18.9 (a), -19.3 (b). Ratio 3a:10a ) 1.7:1, ratio a:b
) 1:2.4. The white solid was washed further with petroleum ether
(3 portions of 0.5 mL), and 60 mg (60% yield) of white crystals of
10a was obtained (ratio a:b ) 12.6:1).
134.1 (d, J ) 20, Ar, a), 134.0 (d, J ) 20, Ar, b), 133.0 (d, J )
18, b), 132.8 (d, J ) 18, a), 129.4 (Ar), 129.2 (d, J ) 7, Ar),
129.0 (d, J ) 6, Ar), 128.68 (Ar), 128.67 (Ar), 128.0 (Ar), 127.3
(Ar, a), 127.1 (Ar, b), 81.5 (CO2CMe3), 76.6 (d, J ) 11, CH, b),
75.6 (d, J ) 10, CH, a), 51.6 (d, J ) 11, CH, a), 51.2 (d, J ) 17,
CH, b), 29.7 (d, J ) 15, CH2, b), 28.4 (CMe3, b), 28.3 (CMe3, a),
27.1 (d, J ) 14, CH2, a).
Reaction of PHMe(Is) and Benzaldehyde in the Absence of
Catalyst. A solution of PHMe(Is) (50 mg, 0.2 mmol) in toluene
(0.5 mL) was transferred into an NMR tube, which was fitted with
a septum. Benzaldehyde (21 mg, 20 µL, 0.2 mmol) was added via
microliter syringe, and the mixture was monitored over time, by
31P NMR spectroscopy. No reaction was observed after 3 days.
Catalytic Reaction of tert-Butyl Acrylate with Benzaldehyde
and PHMe(Is). Synthesis of Three-Component Product 10c. To
Pt((R,R)-Me-Duphos)(trans-stilbene) (8.2 mg, 0.012 mmol, 5 mol
%) in toluene-d8 (0.2 mL) was added PHMe(Is) (60 mg, 0.24 mmol)
in toluene-d8 (0.3 mL). Benzaldehyde (25.5 mg, 24.4 µL, 0.24
mmol) was added via microliter syringe. The reaction mixture was
transferred to an NMR tube and monitored by 31P NMR spectro-
scopy. The only species observed in the mixture after 1 week were
Pt((R,R)-Me-Duphos)(H)(PMeIs) and unreacted PHMe(Is). tert-
Butyl acrylate (35 µL, 0.24 mmol) was added via microliter syringe.
After 3 h PMe(Is)(CH2CH2CO2t-Bu) (3c, δ -47.2), along with four
other diastereomeric phosphines 10c (δ -50.9, -51.4, -52.0,
-52.9), was observed in the reaction mixture (the 3c/10c ratio was
1:1.1). The Pt species observed during and after catalysis was Pt-
((R,R)-Me-Duphos)(t-Bu acrylate).1 The ratio between the phos-
phines was essentially the same after 1 day. The catalyst was
removed from the reaction mixture on a silica column (10 cm
height, 1 cm diameter), using a 9:1 petroleum ether/THF mixture
as eluent. The catalyst did not elute. A colorless oil was obtained.
HRMS: m/z calcd for 10c, C30H46O3P+ (MH+) 485.3185, found
485.3184. 31P{1H} NMR (toluene-d8): δ -50.9, -51.4, -52.0,
-52.9 (ratio 3.4:5.4:3.2:1). Pt((R,R)-Me-Duphos)(H)(PMeIs). 31P-
{1H} NMR (toluene-d8, 21 °C): δ 77.7 (dd, J ) 129, 9, JPt-P
)
1657), 70.4 (JPt-P ) 1910), -55.3 (d, J ) 129, 9, JPt-P ) 970).
Catalytic Reaction of tert-Butyl Acrylate with 5 equiv of
Benzaldehyde and PHMe(Is). To Pt((R,R)-Me-Duphos)(trans-
stilbene) (8.2 mg, 0.012 mmol, 5 mol %) in toluene (0.2 mL) was
added PHMe(Is) (60 mg, 0.24 mmol) in toluene (0.3 mL). The
mixture was transferred to an NMR tube, which was fitted with a
septum. Benzaldehyde (127 mg, 122 µL, 4.8 mmol), followed by
tert-butyl acrylate (35 µL, 0.24 mmol), was added via microliter
syringe, under N2. After 10 min, PMeIs(CH2CH2CO2t-Bu) (3c, δ
-46.5) and the four diastereomers of the hydroxyphosphine product
10c (δ -50.2, -50.8, -51.3, -52.3, in an approximate ratio 4:4:
4:1) were observed, along with unreacted PHMe(Is). The ap-
proximate ratio 3c/10c was 1:3.0. The only Pt species observed
during catalysis was Pt((R,R)-Me-Duphos)(tert-butyl acrylate).1 The
reaction was complete after 24 h.
A sample of this mixture of 10a was added to a slight excess of
(S)-[Pd(NMe2CH(Me)C6H4)Cl]2 (31P NMR (C6D6): δ 38.4, 37.6,
33.5, 31.5; ratio 14.8:12.8:1:1). The ratio between the two major
species was ∼1:1, the ratio between the two minor ones was also
∼1:1, and the ratio between the major and the minor peaks was
13.8:1, similar to the ratio a:b ) 12.6:1, within the experimental
error, so no ee was observed.
The catalyst was removed from the reaction mixture on a silica
column (5 cm height, 0.6 cm diameter), using a 9:1 petroleum ether/
THF mixture as eluent. Some catalyst also eluted. A pale yellow
oil (114 mg) was obtained. This mixture contained 10c (mostly)
plus 3c and PhCHO, which were identified by multinuclear NMR
spectroscopy. Phosphines 10c were not obtained in pure form, but
they were identified spectroscopically.
31P{1H} NMR (C6D6): δ -47.1 (3c), -51.0 (a), -51.6 (b),
-52.1 (c), -53.0 (d). The ratio 3c:10c ) 1:3.3. The ratio a:b:c:d
) 3.2:3.2:3.5:1. In an attempt to measure the enantiomeric excess
of the diastereomers of 10c, the mixture was added to (S)-[Pd-
(NMe2CH(Me)C6H4)Cl]2 (31P NMR (C6D6): δ 12.0, 9.8, 9.5, 9.3,
8.2, 7.2, 7.1, 3.3). Separately, a sample of independently synthesized
3c was also added to the Pd reporter complex (31P NMR (C6D6):
δ 12.0, 9.8 corresponding to the two diastereomeric Pd complexes).
The signals at δ 9.5/9.3 and 7.2/7.1 due to Pd complexes of 10c
The following NMR data for 10a are reported as a mixture of
1
two diastereomers a:b ) 12.6:1, unless otherwise indicated. H
NMR (C6D6): δ 7.39-7.32 (m, 4H, Ar), 7.18-7.14 (m, 2H, Ar),
7.10-6.96 (m, 9H, Ar), 4.89 (dd, J ) 6, 3, 1H, a), 4.85 (t, J ) 7,
1H, b), 3.03 (d, J ) 7, 1H, b), 2.91-2.87 (m, 1H, b), 2.81-2.74
(m, 1H, a), 2.68-2.53 (m, 3H), 2.34-2.29 (m, 1H, b), 1.33 (9H,
Me, b), 1.30 (9H, Me, a). 13C{1H} NMR (C6D6): δ 174.3 (CO2t-
Bu), 142.3 (quat), 140.5 (d, J ) 13, quat), 138.3 (d, J ) 15, quat),
(34) Bryndza, H. E.; Fong, L. K.; Paciello, R. A.; Tam, W.; Bercaw, J.
E. J. Am. Chem. Soc. 1987, 109, 1444-1456.
(35) Clark, H. C.; Jablonski, C. R. Inorg. Chem. 1975, 14, 1518-1526.

Platinum-Catalyzed Hydrophosphination
Organometallics, Vol. 25, No. 24, 2006 5765
were in ∼1:1 ratio, but these spectra did not provide enough
information to assess the ee of 10c.
The following NMR data are reported for a mixture of four
(A-14, Table 2) was observed immediately after addition of the
acrylate at -50 °C, but disappeared on warming above 0 °C. The
phosphines PPh2CH2CH2CO2t-Bu (3a)10 and PPh2(CH2CH(CH2-
CH2CO2t-Bu)(CO2t-Bu)) (7a1)15 were observed immediately after
addition of the acrylate at -50 °C in an approximate ratio 3a:7a1
) 4:3. The ratio varied little on warming the reaction mixture to
room temperature (over ∼4 h), but the mixture was mostly 7a1
after 1 day. One diastereomer of B-14 (δ -20.0, -50 °C) could
also be observed immediately after the addition of the acrylate.
Once the temperature reached -20 °C, the second diastereomer of
B-14 was also observed (Table 3). The ratio between the two
diastereomers was almost unchanged over 1 day (∼1:1.5). The
amount of starting compound 14 decreased over time, but it was
still observed, after 1 day, as was an unidentified peak at -11.7
ppm. Note that unreacted tert-butyl acrylate was always observed
diastereomers of 10c, a:b:c:d ) 3.2:3.2:3.5:1, unless otherwise
1
indicated. Selected H NMR (C6D6) signals: δ 4.98 (t, J ) 6, d),
4.90 (dd, J ) 6, 3), 4.86 (t, J ) 6), 4.79 (dd, J ) 6, 3). 13C{1H}
NMR (C6D6): δ 174.62 (CO2t-Bu), 174.59 (CO2t-Bu), 174.12 (m,
CO2t-Bu), 156.2-156.0 (m, quat), 150.9-150.8 (m, quat), 143.6
(quat, Ph, d), 143.2 (quat, Ph, c), 142.8 (quat, Ph), 142.6 (quat,
Ph), 131.7-131.4 (m, quat), 130.0 (Ph), 129.5 (Ph, d), 129.3 (Ph),
129.2 (Ph, c), 128.8-128.6 (m, Ph), 128.1-127.9 (m, Ph), 127.5
(Ph), 127.4 (Ph), 127.3 (Ph), 127.2 (Ph), 122.8-122.6 (m, Is), 81.31
(OCMe3, d), 81.30 (OCMe3, c), 81.1 (OCMe3), 81.0 (OCMe3), 76.9
(d, J ) 14, CH, c), 76.4 (d, J ) 12, CH), 76.1 (d, J ) 12, CH, d),
75.9 (d, J ) 11, CH), 54.3 (d, J ) 28, CH-OH), 53.7 (d, J ) 27,
CH-OH, c), 53.6 (d, J ) 24, CH-OH), 53.1 (d, J ) 25, CH-OH,
d), 35.15-34.99 (m, CH, i-Pr), 32.1-31.8 (m, CH, i-Pr), 30.6 (d,
J ) 16, CH2), 30.2 (d, J ) 16, CH2, d), 28.7 (d, J ) 15, CH2),
28.4 (C(CH3)3), 28.34 (C(CH3)3, d), 28.31 (C(CH3)3), 28.2 (C(CH3)3),
28.1 (d, J ) 16, CH2), 25.7-25.1 (m, Me, Is), 24.5-24.3 (m, Me,
Is), 14.7 (d, J ) 33), 13.3 (d, J ) 17, 2 P-Me), 12.4 (d, J ) 18,
P-Me, d), 12.1 (d, J ) 18, P-Me).
1
in the H NMR spectrum.
Excess tert-butyl acrylate (0.5 equiv) was added, and the reaction
mixture was monitored over time, at room temperature. The Pt-
PPh2 31P NMR signal disappeared after 1 day, but it could be
observed again in the mixture after 4 days. Phosphines 3a and 7a1
were still observed; the latter became the major PPh2 species after
4 days, while the amount of B-14 decreased. The Pt complex C
(Table 4) was the major Pt(dppe) component in the mixture after
1 h and remained the major component over time. Peaks due to
Pt((R,R)-Me-Duphos)(Me)(PPh2) (11). PHPh2 (18.7 mg, 0.1
mmol) was added with a microsyringe to a stirring solution of Pt-
((R,R)-Me-Duphos)(Me)(Cl) (55.2 mg, 0.1 mmol) in THF (10 mL).
NaOSiMe3 (11.3 mg, 0.1 mmol) in THF (5 mL) was added to the
reaction mixture, which immediately turned yellow. The slurry was
filtered through Celite, and the filtrate was concentrated under
vacuum. Petroleum ether was added to the yellow residue, yielding
a yellow precipitate, which was washed with petroleum ether.
Drying the precipitate under vacuum yielded 65 mg (93%) of yellow
powder.
1
alkene 16 were also observed in the H NMR spectrum after 4
days.
More acrylate (0.5 equiv) was added. Once again, 14 disappeared,
to reappear after 2 weeks, while B-14 remained unchanged. The
major components of the mixture were C and phosphine 7a1. After
8 days new peaks in the PPh2 region, which showed no Pt-P
coupling, could be observed. Their intensity increased slightly over
time, and presumably they belong to tertiary phosphines that contain
more tert-butyl acrylate molecules (δ -18.7, -19.9, -22.2; 7an,
n > 1). Also, after 2 weeks, the tert-butyl acrylate almost
disappeared, but a large amount of its dimer (16) was observed by
1H NMR spectroscopy.
Anal. Calcd for C31H41P3Pt: C, 53.06; H, 5.89. Found: C, 52.65;
H, 6.19. 31P{1H} NMR (C6D6): δ 66.9 (dd, J ) 142, 9, JPt-P
)
1929), 63.1 (dd, J ) 18, 9, JPt-P ) 1749), -28.9 (dd, J ) 142, 18,
1
JPt-P ) 1077). H NMR (C6D6): δ 8.00 (broad, 4H, Ar), 7.36-
Reaction of Pt(dppe)(Me)(PPh2) (14) with 10 equiv of tert-
Butyl Acrylate with or without 1 equiv of H2O (entry 3, Table
S1). A suspension of Pt(dppe)(Me)(PPh2) (14, 79 mg, 0.1 mmol)
in toluene (0.5 mL) was transferred into an NMR tube fitted with
a septum. H2O (2 mg, 2 µL, 0.1 mmol) was added with a microliter
syringe, followed by tert-butyl acrylate (128 mg, 144 µL, 1 mmol).
The mixture was monitored by 31P NMR spectroscopy. After 15
min, no unreacted Pt(dppe)(Me)(PPh2) was observed. The main
components of the mixture were phosphines 7a1 and 3a and an
7.18 (m, 6H, Ar), 7.07-6.99 (m, 4H, Ar), 3.26-3.19 (m, 1H, CH),
2.73-2.54 (m, 1H, CH), 2.53-2.46 (m, 1H, CH), 2.40-2.25 (m,
2H, CH2), 2.05-1.95 (m, 1H, CH), 1.88-1.76 (m, 2H, CH2), 1.75-
1.65 (m, 2H, CH2), 1.59 (dd, J ) 18, 7, 3H, CH3), 1.53-1.27 (m,
2H, CH2), 1.20 (dd, J ) 18, 7, 3H, CH3), 1.06 (ddd, J ) 14, 14, 4,
JPt-H ) 66, 3H, Pt-CH3), 0.63 (dd, J ) 15, 8, 3H, CH3), 0.61 (dd,
J ) 15, 8, 3H, CH3). 13C{1H} NMR (C6D6): δ 147.6-146.7 (m,
quat), 145.6 (dd, J ) 36, 34, quat), 138.8-137.8 (m, quat), 136.1
(broad, Ar), 133.6 (dd, J ) 57, 14), 130.8 (d, J ) 40), 127.7 (d, J
) 5, Ar), 125.7 (broad, Ar), 42.2 (d, J ) 27), 41.4 (d, J ) 26),
37.8 (broad), 37.6, 37.3-37.1 (m), 35.7 (d, J ) 24), 34.9-34.5
(m), 17.9 (m, Me), 17.3 (d, J ) 10, Me), 14.6 (Me), 14.1 (Me),
3.5 (dd, J ) 89, 6, Pt-Me).
Reaction of Pt Hydrocarbyl Phosphido Complexes 11-15
with Activated Alkenes (Table S1, Supporting Information).
These experiments were all performed in NMR tubes, by a general
procedure, and the results are summarized in Table S1 and Scheme
6 and discussed in the text. Since many experiments differed only
in scale or stoichiometry, only representative ones are included here;
see the Supporting Information for details.
Reaction of t-Bu acrylate with Pt(dppe)(Me)(PPh2) (14) at
Low Temperature (entry 1, Table S1). A solution of Pt(dppe)-
(Me)(PPh2) (14, 40 mg, 0.05 mmol) in toluene-d8 (0.5 mL) was
transferred into an NMR tube, which was fitted with a septum.
The NMR tube was cooled to -50 °C, and tert-butyl acrylate (7
µL, 6.4 mg, 0.05 mmol) was added with a microliter syringe. The
tube was immediately inserted in the NMR spectrometer, which
was previously cooled to -50 °C, and the reaction was monitored
by 31P and 1H NMR spectroscopy, from -75 °C to room
temperature.
unidentified Pt compound (δ 39.7 (JPt-P ) 1844), 37.1 (JPt-P
)
3454)). Compound B-14 (1:1 mixture of diastereomers) and a small
amount of C were also observed. After 3 days the major PPh2-
containing species was phosphine 7a1, along with small amounts
of 3a. More C was observed, while the amount of B-14 decreased.
The unidentified Pt compound was still observed, along with another
unidentified Pt species (δ 32.0). Some other small peaks (maybe
analogues of Pt-dialkyls B-14 containing more acrylates) were also
observed: δ 48.1, 48.0, 47.7, 45.6, -18.5, -19.7. After 6 days,
the amount of the δ 31.8 species (JPt-P ) 3736, likely Pt(dppe)2)36
increased. After several weeks, a small amount of crystals had
formed in the NMR tube; they were identified crystallographically
as cation 17a (Supporting Information).
In a companion experiment on the same scale, but without
deliberately added water, after 20 min, the starting phosphido
complex was consumed, and the major Pt complex present was
B-14, plus a little C, and small amounts of the phosphines 3a and
7a1, as in a related smaller-scale experiment (entry 2, Table S1).
Synthesis of PPh2(CH2CH(CN)(CH2CH2CN) (7a1′) by Pt-
(36) (a) Clark, H. C.; Kapoor, P. N.; McMahon, I. J. J. Organomet. Chem.
1984, 265, 107-115. (b) Chaloner, P. A.; Broadwood-Strong, G. T. L. J.
Chem. Soc., Dalton Trans. 1996, 1039-1043.
The Pt-dialkyl product Pt(dppe)(Me)(CH(CO2t-Bu)CH2PPh2)

5766 Organometallics, Vol. 25, No. 24, 2006
Scriban et al.
Catalyzed Reaction of H2CdC(CN)(CH2CH2CN) (2-methylene-
glutaronitrile) with PHPh2.15 To Pt((R,R)-Me-Duphos)(trans-
stilbene) (8.2 mg, 0.012 mmol, 5 mol %) in toluene (0.2 mL) was
added PHPh2 (44.7 mg, 0.24 mmol) in toluene (0.3 mL). The
mixture was transferred into an NMR tube, which was fitted with
a septum. 2-Methyleneglutaronitrile (25.5 mg, 26.1 µL, 0.24 mmol)
was added via a microliter syringe. The reaction went to completion
in ∼1 day, according to 31P NMR spectroscopy. The catalyst was
removed on a silica column (5 cm height, 0.6 cm diameter), using
a 7:3 petroleum ether/THF mixture as eluent. The catalyst did not
elute. A total of 70 mg (99% yield) of a colorless oil was obtained.
CH2CH2CN (7a1′). A solution of PPh2CH2CH(CN)CH2CH2CN (17
mg, 0.06 mmol) in toluene (0.2 mL) was added to a suspension of
Pt(dppe)(Me)(OH) (36 mg, 0.06 mmol) in toluene (0.3 mL). The
mixture was transferred into an NMR tube and monitored by 31P
NMR spectroscopy. After 30 min, no unreacted Pt(dppe)(Me)(OH)
was observed, but 7a1′ was a major component of the mixture,
along with Pt(dppe)(Me)(PPh2) (14). A little of the cation [(Pt-
(dppe)(Me))2(µ-PPh2)]+ (17a) and a very small amount of PPh2-
CH2CH2CN (3a′) were also observed. Over time, a symmetrical Pt
complex (δ 31.9, JPt-P ) 3735, likely Pt(dppe)2)36 formed, and the
amount of PPh2CH2CH2CN (3a′) also increased. After two weeks,
the solvent was removed under vacuum. Toluene-d8 (0.5 mL) was
added to the mixture, which was transferred to an NMR tube.
According to 31P{1H} NMR spectroscopy, the mixture consisted
of Pt(dppe)(Me)(PPh2), Pt(dppe)2, PPh2CH2CH2CN, and unreacted
PPh2CH2CH(CN)CH2CH2CN. 1H NMR spectroscopy did not show
the presence of any vinyl species.
Adducts of the oxidized phosphine with both a proton and a
sodium ion were observed by mass spectroscopy.1 HRMS: m/z
calcd for C18H18N2OP+ (MOH+) 309.1157, found 309.1147.
HRMS: m/z calcd for C18H17N2NaOP+ (MONa+) 331.0976, found
1
331.0983. 31P{1H} NMR (C6D6): δ -20.4. H NMR (C6D6): δ
7.30-7.20 (m, 4H, Ph), 7.10-7.03 (m, 6H, Ph), 2.12-2.03 (m,
1H, CH), 1.90 (dd, J ) 14, 8, 1H), 1.68 (dd, J ) 17, 7, 1H), 1.56-
1.48 (m, 1H), 1.43-1.32 (m, 1H), 1.22-1.14 (m, 1H), 1.13-1.05
(m, 1H). 13C{1H} NMR (C6D6): δ 137.6 (d, J ) 13, quat), 137.5
(d, J ) 13, quat), 133.6 (d, J ) 20, Ph), 133.3 (d, J ) 19, Ph),
129.9 (Ph), 129.8 (Ph), 129.41 (d, J ) 7, Ph), 129.36 (d, J ) 6,
Ph), 120.2 (d, J ) 6, CN), 118.2 (CN), 31.5 (d, J ) 17, CH2), 29.3
(d, J ) 10, CH2), 28.8 (d, J ) 21, CH), 14.8 (CH2). Addition of a
slight excess of (S)-[Pd(NMe2CH(Me)C6H4)Cl]2 showed that the
phosphine was formed in 16% ee (31P{1H} NMR (C6D6): δ 35.3,
33.9, ratio 1:1.4, 16% ee).
Pt(dppe)(Cl)(CH(Me)CO2t-Bu) (20). To a stirring solution of
Pt(dppe)(Me)(Cl) (19, 451 mg, 0.7 mmol) in CH2Cl2 (20 mL) was
added N2CHCO2t-Bu (215 µL, 1.6 mmol) via a microliter syringe.
The mixture was stirred for 16 h. The colorless solution was
concentrated under vacuum, and petroleum ether was added to the
residue, yielding a white precipitate. The white product was washed
with petroleum ether (3 × 10 mL) and dried under vacuum, yielding
450 mg (85%) of white powder. Recrystallization from CH2Cl2 and
petroleum ether gave crystals of a CH2Cl2 solvate suitable for X-ray
crystallography.
Reaction of Pt(dppe)(Me)(OH) (22) with PPh2CH2CH2CN
(3a′). A solution of PPh2CH2CH2CN (7 mg, 0.03 mmol) in toluene
(0.2 mL) was added to a suspension of Pt(dppe)(Me)(OH) (22, 19
mg, 0.03 mmol) in toluene (0.3 mL). The mixture was transferred
into an NMR tube and monitored by 31P NMR spectroscopy. After
1.5 h, no unreacted Pt(dppe)(Me)(OH) was observed, but PPh2-
CH2CH2CN was a major component of the mixture, along with
Pt(dppe)(Me)(CH(CN)CH2PPh2) (A-14′). Small amounts of Pt-
(dppe)(Me)(PPh2) (14) and the cation [(Pt(dppe)(Me))2(µ-PPh2)]+
(17a) and very small amounts of the two diastereomers of Pt(dppe)-
(Me)((CH(CN)CH2)2PPh2) (B-14′) and PPh2CH2CH(CN)CH2CH2-
(CN) (7a1) were also observed. Over time, yellow crystals (perhaps
Pt(dppe)(Me)(PPh2), which is not very soluble in toluene) were
observed on the walls of the NMR tube. An unidentified, sym-
metrical Pt species (δ 31.9, JPt-P ) 3735), probably Pt(dppe)2, was
observed,36 and the amount of 14 increased, at the expense of A-14′.
After 2 weeks, the solution was separated from the crystals and
the solvent was removed under vacuum. Toluene-d8 (0.5 mL) was
added to the mixture, which was transferred to an NMR tube.
According to 31P{1H} NMR spectroscopy, the mixture consisted
of Pt(dppe)(Me)(PPh2), Pt(dppe)2, and unreacted PPh2CH2CH2CN.
Reaction of Pt((R,R)-Me-Duphos)(Ph)(OH) (23) with PPh2-
CH2CH2CN (3a′). A solution of PPh2CH2CH2CN (9 mg, 0.04
mmol) in toluene (0.2 mL) was added to a solution of Pt((R,R)-
Me-Duphos)(Ph)(OH) (23, 21 mg, 0.04 mmol) in toluene (0.3 mL).
The mixture was transferred into an NMR tube and monitored by
31P NMR spectroscopy. After 1 h (∼50% conversion), Pt((R,R)-
Me-Duphos)(Ph)(CH(CN)CH2PPh2) (A, 2 diastereomers, ∼1:1) and
a small amount of Pt((R,R)-Me-Duphos)(Ph)(PPh2) were observed.
Reaction proceeded slowly over 2 weeks, when a small amount of
Pt((R,R)-Me-Duphos)(Ph)(OH) was still observed.
Anal. Calcd for C33H37ClO2P2Pt‚CH2Cl2: C, 48.44; H, 4.66.
Found: C, 48.84; H, 5.04. The presence of CH2Cl2 was detected
by 1H NMR (CD2Cl2). 31P{1H} NMR (CD2Cl2): δ 43.1 (d, J ) 3,
1
JPt-P ) 4196), 42.8 (d, J ) 3, JPt-P ) 1898). H NMR (CD2Cl2):
δ 8.16-8.12 (m, 2H), 7.92-7.87 (m, 2H), 7.86-7.82 (m, 2H),
7.62-7.58 (m, 1H), 7.54-7.40 (m, 13H), 2.62-2.29 (m, 4H),
1.79-1.71 (m, 1H), 1.50 (9H), 0.62 (t, J ) 8, JPt-H ) 34, 3H).
13C{1H} NMR (CD2Cl2): δ 179.0 (d, J ) 4, CdO), 135.4 (d, J )
12, Ar), 134.0 (d, J ) 11, Ar), 133.6 (d, J ) 11, Ar), 132.7 (d, J
) 11, Ar), 132.3 (d, J ) 2, Ar), 131.8 (d, J ) 47, quat), 131.5 (d,
J ) 3, Ar), 131.3 (d, J ) 2, Ar), 131.2 (d, J ) 3, Ar), 130.5 (d, J
) 44, quat), 129.18 (Ar), 129.17 (Ar), 129.10 (Ar), 129.08 (Ar),
129.06 (Ar), 128.97 (Ar), 128.86 (Ar), 128.78 (Ar), 128.7 (d, J )
57, quat), 127.0 (d, J ) 60, quat), 77.4 (CMe3), 31.9 (dd, J ) 43,
17), 29.1 (CMe3), 28.9 (dd, J ) 87, 4), 26.1 (dd, J ) 35, 8), 15.1
(d, J ) 5, CH3).
Generation of Pt(dppe)(Me)(CH(Me)CO2t-Bu) (21). Method
I. A solution of MeCH(ZnBr)(CO2t-Bu)‚THF (195.5 mg, 0.56
mmol) in THF (10 mL) was added to a stirring slurry of Pt(dppe)-
(Me)(Cl) (19, 214.6 mg, 0.33 mmol) in THF (10 mL). The reaction
mixture immediately turned clear. 31P NMR spectroscopy showed
that the only Pt species present in the mixture was 21. The solution
was concentrated under vacuum, and the residue was dissolved in
toluene. The slurry was filtered through Celite, and the filtrate was
concentrated under vacuum. Petroleum ether was added to the white
residue, yielding a white precipitate. Drying the precipitate under
vacuum yielded 220 mg of white powder. Analyzing the product
by 31P NMR (C6D6 or THF-d8) showed the presence of 21, Pt-
(dppe)Me2 (major impurity), and unreacted Pt(dppe)(Me)(Cl).
Method II. To a stirring slurry of Pt(dppe)(Cl)(CH(Me)CO2t-
Bu) (20, 100 mg, 0.13 mmol) in toluene (20 mL) was added ZnMe2
(71.6 µL of a 2 M solution in toluene, 0.14 mmol) via a microliter
syringe, and a white precipitate formed immediately. The slurry
was filtered through Celite, and the filtrate was concentrated under
vacuum. Petroleum ether was added to the white residue, yielding
a white precipitate. Drying the precipitate under vacuum yielded
50 mg of white powder. Analyzing the product by 31P NMR (THF-
d8) showed the presence of 21 along with Pt(dppe)Me2 and
unreacted 20 as impurities. Crystals suitable for X-ray crystal-
lography were obtained when the THF-d8 solution was kept at -25
Pt((R,R)-Me-Duphos)(Ph)(CH(CN)CH2PPh2). 31P{1H} NMR
(toluene): diastereomer a: δ 65.2 (d, J ) 3, JPt-P ) 1676), 61.7
(dd, J ) 19, 3, JPt-P ) 2171), -12.9 (d, J ) 19, JPt-P ) 194);
diastereomer b: δ 62.3 (JPt-P ) 1669), 59.4 (dd, J ) 7, 3, JPt-P
2173), -14.8 (d, J ) 7, JPt-P ) 115).
)
Pt((R,R)-Me-Duphos)(Ph)(PPh2). 31P{1H} NMR (toluene): δ
61.9 (dd, J ) 128, 11, JPt-P ) 1886), 59.2 (dd, J ) 16, 11, JPt-P
) 1602), -35.4 (dd, J ) 128, 16, JPt-P ) 1027).
Reaction of Pt(dppe)(Me)(OH) (22) with PPh2CH2CH(CN)-

Platinum-Catalyzed Hydrophosphination
Organometallics, Vol. 25, No. 24, 2006 5767
°C for 7 days. 31P{1H} NMR (THF-d8): δ 48.7 (d, J ) 5, JPt-P
)
76.3 (CMe3), 30.4-29.8 (m, CH2), 29.8 (C(CH3)3), 24.0 (dd, J )
83, 4, JPt-C ) 547, Pt-CH), 17.1 (d, J ) 6, JPt-C ) 30, CH3), 3.6
(dd, J ) 92, 7, Pt-Me).
1802), 47.6 (d, J ) 5, JPt-P ) 2118). 31P{1H} NMR (C6D6): δ
1
48.9 (d, J ) 5, JPt-P ) 1794), 47.3 (d, J ) 5, JPt-P ) 2094). H
NMR (C6D6): δ 8.08-8.01 (m, 2H, Ar), 7.68-7.56 (m, 4H, Ar),
7.37-7.29 (m, 2H, Ar), 7.26-7.20 (m, 2H, Ar), 7.19-7.13 (m,
2H, Ar), 7.06-6.95 (m, 8H, Ar), 3.84-3.75 (m, JPt-H ) 118, 1H,
Pt-CH), 2.09-1.74 (m, 4H), 1.66 (9H, t-Bu), 1.48 (t, J ) 7, JPt-H
) 58, 3H, Me), 1.31 (t, J ) 7, JPt-H ) 68, 3H, Me). 13C{1H} NMR
Acknowledgment. We thank the National Science Founda-
tion for support, and Cytec Canada for gifts of phosphines.
(C6D6): δ 180.4 (m, JPt-C ) 45, CdO), 135.7 (d, J ) 12, JPt-C
)
Supporting Information Available: Details of the X-ray
crystallographic studies, including CIF documents, and additional
experimental and characterization data. This material is available
free of charge via the Internet at http://pubs.acs.org.
18, Ar), 134.1 (d, J ) 11, Ar), 133.9 (d, J ) 12, Ar), 132.7 (d, J
) 11, Ar), 131.3 (d, J ) 2, Ar), 130.9 (d, J ) 2, Ar), 130.8 (d, J
) 2, Ar), 130.3 (d, J ) 2, Ar), 129.2 (d, J ) 10, Ar), 129.1 (d, J
) 10, Ar), 128.91 (d, J ) 10, Ar), 128.86 (d, J ) 10, Ar); the
remaining four expected Ar peaks could not be assigned confidently;
OM060631N