Chiral Terminal Platinum (II) Phosphido Complexes: Synthesis, Phosphorus Inversion, and Acrylonitrile Insertion

Article abstract of DOI:10.1021/om9903700

The chiral Pt(II) phosphido complex Pt(dppe)(Me)[P(Mes)(Men)] (dppe = Ph₂PCH₂CH₂-PPh₂, Mes = 2,4,6-Me₃C₆H₂, Men = (-)menthyl, 1) was prepared by proton transfer from racemic mesityl(-)menthylphosphine to the methoxide ligand of Pt(dppe)(Me)(OMe). Treatment of Pt(dcpe)[CH(Me)(CN)](Br) with alkali metal phosphides gives Pt(dcpe)[CH(Me)-(CN)](PRR′) (dcpe = Cy₂PCH₂CH₂PCy₂, Cy = cyclo-C₆H₁₁, R = H, R′ = Mes* - 2,4,6-(t-Bu)₃C₆H₂, 13; R = Me, R′ = Ph, 14). The related series of complexes Pt(diphos*)(Me)-(PRR′) (diphos* = S,S-Chiraphos, R = Ph, R′ = Is = 2,4,6-(i-Pr)₃C₆H₂), 5; R = Me, R′ = Mes*, 6; diphos* = R-Tol-Binap, R = Me, R′ = Mes*, 7) containing chiral diphosphine ligands has been prepared by deprotonation of the cations [Pt(diphos*)(Me)(PHRR′)][BF₄] 2, 3, and 4, respectively. The cations, synthesized from Pt(diphos*)(Me)(Cl), AgBF₄, and the appropriate secondary phosphine, were isolated as a mixture of diastereomers (2 and 3) or a single isomer (4). Phosphido complexes 1 and 5-7 show only one set of ³¹P NMR resonances in solution even at low temperature, consistent either with the existence of a single diastereomer or with rapid inversion at phosphorus. However, low-temperature spectra of 13 and 14 reveal the existence of the expected two diastereomers, which interconvert by phosphorus inversion and rotation about the Pt-P bond with barriers of approximately 11.5 and 15.5 kcal/mol, respectively. Treatment of 6 and 7 with HBF₄ protonates the phosphido ligand and generates diastereomeric mixtures of the cations 3 and 4, respectively. Acrylonitrile inserts into the Pt-P bond of 1 to give the dialkyl complex Pt(dppe)(Me)[CH(CN)CH₂P(Mes)(Men)] (9) as a mixture of four diastereomers; similar product mixtures (10-12) are obtained with 5-7. Complexes 4·3CH₂Cl₂, 5, and the secondary phosphine PH(Me)(MeS*) (8) were structurally characterized by X-ray crystallography.

Full text of DOI:10.1021/om9903700

Organometallics 1999, 18, 5141-5151
5141
Ch ir a l Ter m in a l P la tin u m (II) P h osp h id o Com p lexes:
Syn th esis, P h osp h or u s In ver sion , a n d Acr ylon itr ile
In ser tion
Denyce K. Wicht, Ivan Kovacik, and David S. Glueck*
Department of Chemistry, Dartmouth College, 6128 Burke Laboratory,
Hanover, New Hampshire 03755
Louise M. Liable-Sands, Christopher D. Incarvito, and Arnold L. Rheingold
Department of Chemistry, University of Delaware, Newark, Delaware 19716
Received May 18, 1999
The chiral Pt(II) phosphido complex Pt(dppe)(Me)[P(Mes)(Men)] (dppe ) Ph2PCH2CH2-
PPh2, Mes ) 2,4,6-Me3C6H2, Men ) (-)menthyl, 1) was prepared by proton transfer from
racemic mesityl(-)menthylphosphine to the methoxide ligand of Pt(dppe)(Me)(OMe). Treat-
ment of Pt(dcpe)[CH(Me)(CN)](Br) with alkali metal phosphides gives Pt(dcpe)[CH(Me)-
(CN)](PRR′) (dcpe ) Cy2PCH2CH2PCy2, Cy ) cyclo-C6H11, R ) H, R′ ) Mes* ) 2,4,6-
(t-Bu)3C6H2, 13; R ) Me, R′ ) Ph, 14). The related series of complexes Pt(diphos*)(Me)-
(PRR′) (diphos* ) S,S-Chiraphos, R ) Ph, R′ ) Is ) 2,4,6-(i-Pr)3C6H2), 5; R ) Me, R′ )
Mes*, 6; diphos* ) R-Tol-Binap, R ) Me, R′ ) Mes*, 7) containing chiral diphosphine ligands
has been prepared by deprotonation of the cations [Pt(diphos*)(Me)(PHRR′)][BF4] 2, 3, and
4, respectively. The cations, synthesized from Pt(diphos*)(Me)(Cl), AgBF4, and the appropriate
secondary phosphine, were isolated as a mixture of diastereomers (2 and 3) or a single isomer
(4). Phosphido complexes 1 and 5-7 show only one set of 31P NMR resonances in solution
even at low temperature, consistent either with the existence of a single diastereomer or
with rapid inversion at phosphorus. However, low-temperature spectra of 13 and 14 reveal
the existence of the expected two diastereomers, which interconvert by phosphorus inversion
and rotation about the Pt-P bond with barriers of approximately 11.5 and 15.5 kcal/mol,
respectively. Treatment of 6 and 7 with HBF4 protonates the phosphido ligand and generates
diastereomeric mixtures of the cations 3 and 4, respectively. Acrylonitrile inserts into the
Pt-P bond of 1 to give the dialkyl complex Pt(dppe)(Me)[CH(CN)CH2P(Mes)(Men)] (9) as a
mixture of four diastereomers; similar product mixtures (10-12) are obtained with 5-7.
Complexes 4‚3CH2Cl2, 5, and the secondary phosphine PH(Me)(Mes*) (8) were structurally
characterized by X-ray crystallography.
Sch em e 1
In tr od u ction
Recently, we have provided evidence that P-C bond
formation in Pt-catalyzed hydrophosphination of acry-
lonitrile occurs by insertion of the olefin into a Pt-
phosphido bond (Scheme 1).1 The model compounds
M(dppe)(Me)(PHMes*) (M ) Pd, Pt; Mes* ) 2,4,6-
(t-Bu)3C6H2) undergo selective insertion to afford
M(dppe)(Me)[CH(CN)CH2PHMes*] as a mixture of di-
astereomers in about a 2:1 ratio. This observation
suggests that a chiral Pt(diphos*) fragment (diphos* )
chiral diphosphine) might catalyze asymmetric hydro-
phosphination of secondary phosphines PHRR′ to give
enantio-enriched tertiary phosphines PRR′(CH2CH2CN)
(Scheme 2). In this case, oxidative addition of racemic
PHRR′ would give a phosphido hydride intermediate
Pt(diphos*)(PRR′)(H) as a mixture of diastereomers.
Since barriers to pyramidal inversion in transition metal
phosphido complexes are low,2 these isomers should
interconvert readily by inversion at phosphorus.3 If one
is energetically favored, then two of the four possible
alkyl hydride diastereomers would be formed preferen-
tially on acrylonitrile insertion, and reductive elimina-
tion would yield preferentially one enantiomer of the
configurationally stable4 tertiary phosphine PRR′(CH2-
CH2CN) via thermodynamic resolution.5 Alternatively,
the phosphido hydride diastereomers might interconvert
(1) (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.; Yap, G.
P. A.; Incarvito, C. D.; Rheingold, A. L. Organometallics, accepted for
publication.
10.1021/om9903700 CCC: $18.00 © 1999 American Chemical Society
Publication on Web 11/22/1999

5142 Organometallics, Vol. 18, No. 24, 1999
Wicht et al.
Sch em e 2
Sch em e 3
data for this and other compounds) contains sharp dppe
resonances and a broad phosphido signal. At -75 °C,
the phosphido peak is sharp, while the dppe signals
undergo small changes in chemical shift and coupling
constants. A similar spectrum is observed at 80 °C,
although the phosphido resonance is still rather broad.
While these observations are consistent with the pro-
posed structure for 1, they are ambiguous about the
possible inversion process. We assume that the unusual
broadness of signals due to the cis dppe and phosphido
P nuclei is due to a dynamic process involving rotation
about the Pt-P(Mes)(Men) bond, which affects the
environment of the neighboring cis dppe group. This
interpretation is supported by similar observations in
related complexes (see 5 below and the preceding
article.)8
more quickly than they react with acrylonitrile; if one
reacts faster than the other, then enantio-enriched
product could be formed via dynamic kinetic resolution.6
To investigate these possibilities, we report here
studies of phosphorus inversion in model chiral Pt(II)
phosphido complexes and of the diastereoselectivity of
acrylonitrile insertion in these compounds.
Resu lts a n d Discu ssion
We studied three types of Pt(diphos)(R)(PR′R′′) com-
plexes: one has a chiral phosphido substituent, another
contains a chiral diphos ligand, and a third includes a
chiral Pt-bound alkyl group. If phosphorus inversion is
slow on the NMR time scale, the NMR spectra should
exhibit signals due to both expected diastereomers, as
long as one diastereomer is not much higher in energy
than the other. For example, the iron-phosphido com-
plex (R,R)-Fe(Cp){1,2-C6H4(PMePh)2}(PHPh)2c exists at
-65 °C as a 4.5:1 mixture of diastereomers, as shown
by the observation of two different Cp resonances in the
1H NMR spectrum. As the temperature is raised, these
At 21 °C in toluene-d8, the 1H NMR spectrum of 1
shows only one set of signals for the Mes (δ 3.01, 6H;
2.11 (3H)) and Pt-Me (δ 0.88, m, J Pt-H ) 72 Hz, 3H)
groups, as well as for the menthyl isopropyl and methyl
groups. As the sample is cooled, the o-Me mesityl
resonance broadens and finally decoalesces into two
peaks (-75 °C) at δ 3.56 (3H) and 3.19 (3H), consistent
with restricted rotation about the P-C(Mes) bond at
this temperature. The other signals broaden but do not
undergo other significant changes on cooling. From
these data, we cannot tell if one diastereomer of complex
1 is so energetically favored that the other is not
observed or if the two possible isomers are rapidly
interconverting on the NMR time scale.
To prepare related phosphido complexes with chiral
chelating diphosphine ligands, the cations [Pt(diphos*)-
(Me)(PHRR′)][BF4] (diphos* ) S,S-Chiraphos; R ) Ph,
R′ ) Is ) 2,4,6-(i-Pr)3C6H2), 2; R ) Me, R′ ) Mes*, 3;
diphos* ) R-Tol-Binap, R ) Me, R′ ) Mes*, 4, Scheme
4) were synthesized from Pt(diphos*)(Me)(Cl), a slight
excess of the corresponding phosphine, and AgBF4.
Pt(S,S-Chiraphos)(Me)(Cl) was previously prepared by
the addition of the diphosphine ligand to Pt(COD)(Me)-
(Cl);9 the new compound Pt(R-Tol-Binap)(Me)(Cl) was
made in the same way (see the Experimental Section).
Since secondary phosphines racemize quickly, 1 equiv
of a phosphine should give a thermodynamic mixture
of diastereomers [Pt(diphos*)(Me)(PHRR′)]+. For ex-
ample, Wild3b has reported that [Pt{1,2-C6H4(PMePh)2}-
{PH(Me)(Ph)}Cl]+ exists as a 2:1 mixture of isomers,
one of which was isolated by fractional recrystallization.
Similar results were observed for the cations 2 and 3,
which were obtained as mixtures of diastereomers (1:1
for 2, 3:1 for 3). Although 4 is initially formed as a 10:1
mixture of isomers, according to 31P NMR monitoring,
stirring the reaction mixture at room temperature for
1
signals coalesce; from the H NMR data, the barrier to
pyramidal inversion at phosphorus was reported to be
60 kJ mol-1
.
The complex Pt(dppe)(Me)[P(Mes)(Men)] (Mes ) 2,4,6-
Me3C6H2, Men ) (-)-menthyl, 1) was prepared from
racemic mesitylmenthylphosphine3a and Pt(dppe)(Me)-
(OMe) (Scheme 3), as reported for a variety of other
secondary phosphines.7 The room-temperature 31P{1H}
NMR spectrum of 1 (toluene-d8; see Table 1 for 31P NMR
(2) For examples, see: (a) Buhro, W. E.; Gladysz, J . A. Inorg. Chem.
1985, 24, 3505-3507. (b) Simpson, R. D.; Bergman, R. G. Organo-
metallics 1992, 11, 3980-3993. (c) Crisp, G. T.; Salem, G.; Wild, S. B.;
Stephan, F. S. Organometallics 1989, 8, 2360-2367. (d) Malisch, W.;
Maisch, R.; Meyer, A.; Greissinger, D.; Gross, E.; Colquhoun, E. J .;
McFarlane, W. Phosphorus Sulfur 1983, 18, 299-302. (e) Baker, R.
T.; Whitney, J . G.; Wreford, S. S. Organometallics 1983, 2, 1049-1051.
(f) Bonnet, G.; Kubicki, M. M.; Moise, C.; Lazzaroni, R.; Salvadori, P.;
Vitulli, G. Organometallics 1992, 11, 964-967. (g) Fryzuk, M. D.; J oshi,
K.; Chadha, R. K.; Rettig, S. J . J . Am. Chem. Soc. 1991, 113, 8724-
8736. (h) Malisch, W.; Gunzelmann, N.; Thirase, K.; Neumayer, M. J .
Organomet. Chem. 1998, 571, 215-222. For a review, see: (i) Rogers,
J . R.; Wagner, T. P. S.; Marynick, D. S. Inorg. Chem. 1994, 33, 3104-
3110.
(3) Diastereoselectivity in the oxidative addition is also possible.
Since secondary phosphines readily racemize in solution by acid- or
base-catalyzed processes, dynamic resolution might also occur in this
step. See: (a) Bader, A.; Pabel, M.; Wild, S. B. J . Chem. Soc., Chem.
Commun. 1994, 1405-1406. (b) Bader, A.; Nullmeyers, T.; Pabel, M.;
Salem; G.; Willis, A. C.; Wild, S. B. Inorg. Chem. 1995, 34, 384-389.
(4) (a) Baechler, R. D.; Mislow, K. J . Am. Chem. Soc. 1970, 92, 3090.
(b) Mislow, K. Trans. N. Y. Acad. Sci. 1973, 35, 227-242.
(5) (a) Beak, P.; Basu, A.; Gallagher, D. J .; Park, Y. S.; Thayumana-
van, S. Acc. Chem. Res. 1996, 29, 552-560. (b) Vedejs, E.; Donde, Y.
J . Am. Chem. Soc. 1997, 119, 9293-9294. (c) Wolfe, B.; Livinghouse,
T. J . Am. Chem. Soc. 1998, 120, 5116-5117.
(7) 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.
(8) Wicht, D. K.; Glueck, D. S.; Liable-Sands, L. M.; Rheingold, A.
L. Organometallics 1999, 18, 5130.
(9) Payne, N. C.; Stephan, D. W. J . Organomet. Chem. 1981, 221,
203-221.
(6) (a) Ward, R. S. Tetrahedron: Asymmetry 1995, 6, 1475-1490.
(b) Noyori, R.; Tokunaga, M.; Kitamura, M. Bull. Chem. Soc. J pn. 1995,
68, 36-56. (c) Caddick, S.; J enkins, K. Chem. Soc. Rev. 1996, 25, 447-
456.

Chiral Terminal Pt(II) Phosphido Complexes
Organometallics, Vol. 18, No. 24, 1999 5143
Ta ble 1. 31P NMR Da ta for [P t(d ip h os)(R)(X)]n + (1-7, 13, 14)a -c
diphos, R (No.)
dppe, Me (1)
X
δ(P1) (J Pt-P
)
δ(P2) (J Pt-P
)
δ(P3) (J Pt-P
)
J 12
J 13
J 23
P(Mes)(Men)
48.2 (1782)
44.3
(br, 1920)
49.2
(1920)
42.3
(1917)
47.3
(1749)
47.0
(1628)
47.6
(1661)
45.8
(1737)
16.6
-16.5
(v br)
-9.4
166
-75 °C
50.7
(1830)
47.3
(1759)
51.3
(2814)
51.2
(2813)
49.5
(2773)
52.7
(2805)
22.5
(1770)
22.0
183
159
375
385
384
395
(1115)
-21.7
(br, 1100)
-22.1
(2593)
-30.4
(2532)
-36.1
(2684)
-46.2
(2591)
80 °C
Chiraphos, Me (2a )d
(2b)
PH(Ph)(Is)
17
17
17
16
17
23
23
12
11
18
7
18
18
14
19
Chiraphos, Me (3a )d
(3b)
PH(Me)(Mes*)
Tol-Binap, Me
Tol-Binap, Me (4a )
(4b)e
Cl
(4395)
14.9
(1832)
16.7
PH(Me)(Mes*)
-32.0
(2736)
-41.4
(2646)
-21.0
(1126)
-13.1
(1176)
5.9
(1050)
-81.5
(br)
-80.9
(717)
-77.7
(720)
-92.0
(643)
-71
(v br)
-74.7
(754)
-65.7
(814)
-77.5
(746)
-66.5
(824)
410
416
188
171
128
112
112
119
114
100
98
20
21
(2986)
23.3
Chiraphos, Me (5)
Chiraphos, Me (6)
Tol-Binap, Me (7)
dcpe, CH(Me)(CN) (13)
50 °C
P(Ph)(Is)
48.8
(1981)
47.9
(1816)
20.0
(1883)
60.0
(2004)
59.8
(1993)
61.2
(2043)
60.9
(2033)
60.0
48.2
(1904)
51.0
(1932)
22.5
(2037)
54.2
(2031)
54.4
(2030)
54.0
(2035)
52.6
(2028)
55.6
(2098)
55.4
(2094)
55.7
(2082)
55.3
(2097)
55.7
P(Me)(Mes*)
P(Me)(Mes*)
PHMes*
4
3
6
13a (-60 °C)d
13b (-60 °C)
dcpe, CH(Me)(CN) (14)
(90 °C)
P(Me)(Ph)
8
8
8
8
8
(1810)
14a (22 °C)d
59.7f
(1835)
59.7f
(1835)
59.6
(1849)
59.6
(1852)
14b (22 °C)
14a (-20 °C)
14b (-20 °C)
105
100
106
(2093)
a
Temperature ) 22 °C except where noted. Chemical shifts in ppm, external ref 85% H3PO4, coupling constants in Hz. P1 and P2 are
the diphos P nuclei; P3 is trans to P1. n ) 0 for 1, 5-7, and 13 and 14; n ) 1 for 2-4. c Solvents: toluene-d8 for 1, 5, 14; CD2Cl2 for 3,
b
d
4a , and Pt(Tol-Binap)(Me)(Cl); CDCl3 for 2, 4b; C6D6 for 6, 7; THF-d8 for 13. Isomer ratios: 1:1 for 2, 3:1 for 3, 7:3 for 13, 65:35 for 14.
Labels: major isomer a, minor isomer b. e The Pt satellites on the Tol-Binap signals were not resolved. f P1 resonance is an average
signal for the two isomers.
Sch em e 4
cations 2-4 provide information about the symmetry
and dynamics of these compounds. The chiral centers
in 2 cause the o-isopropyl methyl groups of the isityl
group to be diastereotopic; as expected, they give rise
1
to two different H and 13C signals for both 2a and 2b
1
in the NMR spectra. In the H NMR spectrum, these
protons appear as four doublets at δ 0.97, δ 0.96, δ 0.82,
and δ 0.80 (the two upfield signals overlap to give an
apparent triplet), all with coupling to the methine
proton of approximately 6 Hz. In the 13C NMR spectrum,
four singlets between δ 24.4 and δ 24.0 are assigned to
the isopropyl methyl carbons. Overlapping resonances
due to the ortho and para Mes* t-Bu groups of 3a and
3b appear in the 1H NMR spectrum at δ 1.39 and δ 1.25,
respectively. The ortho signal is broad, presumably due
to hindered rotation around the P-C bond of the bulky
Mes* group. Similar broadening is observed in the 13C
NMR peaks due to these tert-butyl groups. The 1H NMR
spectrum of 4 shows three t-Bu signals, two due to o-
a few hours causes conversion to a single diastereomer,
which can be isolated in pure form. The coordinated
secondary phosphines in cations 2-4 show character-
istic J Pt-P (2532-2736 Hz), J PP (375-410 Hz), and J PH
(347-384 Hz) coupling constants, as well as weak PH
IR stretches at 2400 cm-1 (see Table 1 and the Experi-
mental Section).10
(10) Appleton, T. G.; Bennett, M. A. Inorg. Chem. 1978, 17, 738-
747.
1H and 13C NMR spectra of the bulky aryl groups in

5144 Organometallics, Vol. 18, No. 24, 1999
Wicht et al.
given in Table 2, and further details are in the Experi-
mental Section and the Supporting Information.
Two equally occupied positions for the hydrogen atom
were located in 8, and the average P-H distance is
1.417(6) Å, similar to previously reported P-H distances
11
in secondary phosphines, 1.36(7) Å in PHMes2 and
1.30(1) Å in PH(Ph)(Is).12 The C(Mes*)-P-C(Me) angle
is 99.71(11)°, while the average H-P-C(Me) and H-P-
C(Mes*) angles are 104.85(4)° and 107.65(4)°, respec-
tively.
The hydrogen atom on the coordinated phosphine in
Pt complex 4 could not be located, but the P-C bond
distances do not change significantly on complexation:
compare 1.840(2) Å [P-C(Mes*)] and 1.829(3) [P-C(Me)]
in 8 to the P-C bond distances of 1.843(7) Å [P-C(Mes*)]
and 1.848(8) Å [P-C(Me)] in 4. The C(Mes*)-P-C(Me)
angle opens slightly upon complexation (104.5(3)° from
99.71(11)°), as might be expected on going from three-
to four-coordinate phosphorus. The geometry at the Pt
center in 4 is close to the expected square plane, the
angles between adjacent ligands ranging from
92.48(6)° (Tol-Binap bite angle) to 87.7(2)° [P(coordi-
nated phosphine)-Pt-C(Me)]. The Pt-P(phosphine)
bond distance is 2.353(2) Å, which is the same as the
Pt-P(Tol-Binap) bond distance of 2.352(2) Å for the P
trans to Me. The Pt-P(Tol-Binap) bond length for the
P trans to the secondary phosphine is slightly shorter
at 2.308(2) Å, consistent with the trans influence
F igu r e 1. ORTEP diagram of [Pt(R-Tol-Binap)(Me)(PH-
(Me)Mes*][BF4] (4)‚3 CH2Cl2. Thermal ellipsoids at 30%
probability. Counterion, solvent molecules, and hydrogen
atoms are omitted for clarity. Selected bond lengths (Å) and
angles (deg): Pt-C(1) ) 2.130(7), Pt-P(1) ) 2.353(2),
Pt-P(2) ) 2.352(2), Pt-P(3) ) 2.308(2), P(1)-C(2) )
1.848(8), P(1)-C(11) ) 1.843(7), C(1)-Pt-P(1) ) 87.7(2),
P(1)-Pt-P(2) ) 92.09(6), P(2)-Pt-P(3) ) 92.48(6), P(3)-
Pt-C(1) ) 89.0(2), C(1)-Pt-P(2) ) 169.1(2), P(1)-Pt-P(3)
) 172.28(7).
expected from the Pt-P coupling constants (1J Pt-P
)
2986 Hz (trans to P) and 1832 Hz (trans to Me)).
Treatment of 2-4 with the appropriate base (LiN-
(SiMe3)2 for 2 and 3, KOt-Bu for 4) generates the
phosphido complexes Pt(diphos*)(Me)(PRR′) (diphos* )
S,S-Chiraphos; R ) Ph, R′ ) Is, 5; R ) Me, R′ ) Mes*,
6; diphos* ) R-Tol-Binap, R ) Me, R′ ) Mes*, 7)
(Scheme 4). The S,S-Chiraphos complexes 5 and 6 are
bright orange, and 7 is dark purple. They were charac-
1
terized spectroscopically by H, 31P, and 13C NMR and
IR and by elemental analysis and X-ray crystallography
(see below) for 5, but 6 and 7 decompose in the solid
state and could not be obtained analytically pure.
In contrast to the cationic precursors, for which
diastereomeric mixtures could be observed, the NMR
spectra of neutral complexes 5-7 show only one set of
signals, which are characteristic of the expected neutral
phosphido complexes (Table 1) and similar to those of
the previously described compounds Pt(dppe)(Me)-
(PRR′).7
F igu r e 2. ORTEP diagram of PH(Me)(Mes*) (8). Thermal
ellipsoids at 30% probability. The two equally occupied
positions for the P-H hydrogen are shown; other hydrogen
atoms are omitted for clarity. Selected bond lengths (Å) and
angles (deg): P(1)-C(7) ) 1.829(3), P(1)-C(1) ) 1.840(2),
P-H (av) ) 1.417(6), C(1)-P(1)-C(7) ) 99.71(11), H-P-
C(1) (av) ) 107.65(4), H-P-C(7) (av) ) 104.85(4).
As in cationic precursor 2, the o-isopropyl methyl
groups in 5 are diastereotopic, and in the 1H NMR
spectrum, two doublets (2J HH ) 7 Hz) at δ 1.24 and δ
1.16 are assigned to these sets of protons. In the 13C
NMR spectrum, four resonances for the carbons of the
o-CHMe2 groups are observed; the methine carbon
signals appear at δ 33.9 and δ 33.7 and the methyl
carbons at δ 26.0 and δ 24.3. Similar results were
observed for the related complex Pt(dppe)(COC3F7)-
(PPhIs).8 For 6 and 7, as in the cationic precursors,
restricted rotation about the P-C(Mes*) bond is ob-
t-Bu groups at δ 1.76 and δ 1.49 and one due to a p-
t-Bu group at δ 1.26, indicative of restricted rotation
around the P-C(Mes*) bond. Accordingly, four reso-
nances for the two types of carbons on the o-t-Bu groups
are observed in the 13C NMR spectrum at 40.5 (CMe3),
39.9 (CMe3), 35.1 (CMe3), and 33.7 (CMe3).
Recrystallization of 4 from CH2Cl2/ether produced
crystals of a dichloromethane solvate suitable for X-ray
crystallography. For comparison, crystals of the second-
ary phosphine PH(Me)(Mes*) (8) were obtained from
methanol; the ORTEP diagrams for 4‚3CH2Cl2 and 8
are shown in Figures 1 and 2, respectively, with selected
bond lengths and angles. The crystallographic data are
(11) Bartlett, R. A.; Olmstead, M. M.; Power, P. P.; Sigel, G. A. Inorg.
Chem. 1987, 26, 1941-1946.
(12) Brauer, D. J .; Bitterer, F.; Do¨rrenbach, F.; Hebler, G.; Stelzer,
O.; Kru¨ger, C.; Lutz, F. Z. Naturforsch. 1996, 51b, 1183-1196.

Chiral Terminal Pt(II) Phosphido Complexes
Organometallics, Vol. 18, No. 24, 1999 5145
Ta ble 2. Cr ysta llogr a p h ic Da ta for [P t(R-Tol-Bin a p )(Me)(P H(Me)Mes*)][BF 4] (4)‚3CH2Cl2,
P t(S,S-Ch ir a p h os)(Me)(P P h Is) (5), a n d P H(Me)(Mes*) (8)
4‚3CH2Cl2
5
8
formula
fw
space group
a, Å
b, Å
c, Å
C
71H82BCl6F4P3Pt
C50H59P3Pt
947.97
P21212
21.0134(5)
22.2821(4)
9.5472(2)
C19H33
292.42
P21/n
9.958(7)
11.630(2)
16.155(4)
92.91(4)
1868(1)
4
P
1522.88
P212121
17.0739(1)
19.0657(1)
21.6890(3)
â, deg
V, Å3
7060.33(11)
4
4470.22(16)
4
Z
cryst color, habit
D(calc), g/cm3
µ(Mo KR), cm-1
temp, K
diffractometer
radiation
R(F), %a
R(wF2), %a
colorless block
1.433
23.33
218(2)
Siemens P4/CCD
yellow block
1.409
32.79
colorless block
1.039
1.39
244(2)
Siemens P4
198(2)
Siemens P4/CCD
Mo KR (λ ) 0.71073 Å)
2.85
5.01
11.52
4.80
10.78
7.45
Quantity minimized ) R(wF2) ) ∑[w(Fo - Fc2)2]/∑[(wFo2)2]1/2; R ) ∑∆/∑(Fo), ∆ ) |(Fo - Fc)|.
a
2
served by 1H NMR; the o-t-Bu methyl signals are
observed at δ 1.98 and 1.97 for 6 and δ 2.28 and δ 2.17
for 7.
Several interpretations of these results are possible.
If the phosphido ligands were planar, only one isomer
would be expected. However, related complexes (and 5,
see below) contain pyramidal phosphido groups in the
solid state, and 31P NMR data are consistent with the
same structure in solution.7 Assuming pyramidal ge-
ometry, the phosphido complexes could exist as single
diastereomers, or rapid inversion at phosphorus could
give time-averaged NMR signals of the expected iso-
mers. A third explanation is that there is an excess of
one isomer, and the minor isomer is present in such low
concentration that it cannot be detected by NMR
spectroscopy. Finally, coincidental overlap of the NMR
signals of the two isomers seems unlikely, given the
good separations observed for the cationic precursors.
Acquisition of the 31P NMR spectra at low temperature
was inconclusive; the signals of 6 and 7 remain un-
changed at a temperature as low as -90 °C. Complex 5
behaved similarly to 1 in that the peaks due to the
phosphido ligand and the dppe phosphorus trans to the
methyl become broad and disappear into the baseline
of the 31P NMR spectrum at -60 °C, again presumably
due to hindered rotation about the Pt-P(Ph)(Is) bond.
Since solution data gave ambiguous results on inver-
sion rate, we studied the solid-state structure of phos-
phido complex 5. Recrystallization from toluene/petro-
leum ether at -25 °C gave crystals suitable for X-ray
diffraction (for details, see Table 2, the Experimental
Section, and the Supporting Information). The ORTEP
diagram (Figure 3) shows that the particular crystal
selected has the S configuration at the pyramidal
phosphido ligand. While consistent with the NMR
observations of a single set of resonances, this structure
is not necessarily representative of the bulk material
and does not rule out rapid inversion in solution.
The structure of 5 (for selected bond lengths and
angles see the figure caption) is very similar to that of
the two previously reported Pt(II) phosphido methyl
complexes Pt(dppe)(Me)(PMes2) and Pt(dppe)(Me)-
(PHMes*).7 The geometry at the metal center is slightly
distorted square planar. The largest angle between
ligands is 101.78(5)° [P(Chiraphos)-Pt-P(phosphido)]
F igu r e 3. ORTEP diagram of Pt(S,S-Chiraphos)(Me)-
(PPhIs) (5). Thermal ellipsoids at 30% probability; hydro-
gen atoms are omitted for clarity. Selected bond lengths
(Å) and angles (deg): Pt-C(50) ) 2.139(6), Pt-P(3) )
2.3622(15), Pt-P(2) ) 2.2972(12), Pt-P(1) ) 2.2845(14),
C(50)-Pt-P(3) ) 84.07(18), P(3)-Pt-P(2) ) 101.78(5),
P(2)-Pt-P(1) ) 85.51(5), P(1)-Pt-C(50) ) 89.34(18),
C(50)-Pt-P(2) ) 173.71(17), P(3)-Pt-P(1) ) 164.83(5).
and is presumably due to steric interactions between
the Chiraphos phenyl groups and the P(Ph)(Is) ligand.
Accordingly, the P(phosphido)-Pt-C(Me) angle
(84.07(18) Å) is less than the idealized 90°. The Chira-
phos bite angle is 85.51(5)°, and the P(Chiraphos)-
Pt-C(Me) angle is 89.34(18)°. The geometry at phos-
phorus in the P(Ph)(Is) ligand is pyramidal; the sum of
the angles at P is 333.3° (compare 328.5° for tetrahedral
and 360° for planar geometries). The Pt-P(phosphido)
bond length of 2.3622(15) Å is similar to those for the
Pt-PMes2 (2.351(2) Å) and Pt-PHMes* (2.378(5) Å)
complexes. The Pt-P(Chiraphos) bond trans to Me is
slightly longer than the Pt-P(Chiraphos) bond trans to
P(Ph)(Is), 2.2972(12) and 2.2845(14) Å, respectively.
This is consistent with a slightly greater trans influence
for methyl than for the phosphido ligand and is also
reflected in the Pt-P coupling constants from the 31P
NMR spectrum (1904 and 1981 Hz, respectively).
If the NMR resonances observed for 5-7 reflect a
single diastereomer in solution, one would expect pro-
tonation of the phosphido ligand with HBF4 to regener-

5146 Organometallics, Vol. 18, No. 24, 1999
Wicht et al.
Sch em e 5
ate a single cationic diastereomer. However, treatment
of the Chiraphos complex 6 with HBF4 regenerates
cationic 3 as a mixture of diastereomers in a 2:1 ratio
(Scheme 4). Although Tol-Binap cation 4 was originally
obtained as a single diastereomer, protonation of 7 with
HBF4 gave a 3:1 mixture of diastereomers of 4. The
stability of the minor isomer under these conditions
allowed assignment of some characteristic NMR reso-
nances for it (see Table 1 and the Experimental Section).
These protonation experiments give product isomer
ratios that are different from the (presumably thermo-
dynamic) ones observed in the original syntheses of the
cations. These observations are not consistent with the
presence of single diastereomers of the phosphido
complexes 6 and 7, since these should be protonated
selectively to give single cationic diastereomers. It is
possible that the resulting cations could isomerize by
inversion of free secondary phosphines formed by re-
versible dissociation, the inversion being catalyzed by
traces of acid or base. However, this process does not
account for the observed isomer ratios or for the
observation that the mixture of isomers of Tol-Binap
complex 4 prepared by protonation is stable to isomer-
ization in CDCl3 or CD2Cl2 solution for weeks. However,
this mixture isomerizes completely to the major dia-
stereomer in CD2Cl2 under conditions similar to those
of the original synthesis. Thus, addition of a drop of CD3-
CN to a CD2Cl2 solution of the mixture causes isomer-
ization over the course of 1 day; a similar experiment
in which a small amount of PH(Me)(Mes*) and a drop
of CD3CN are added gives much faster conversion (30
min). These results are consistent with an associative
mechanism for the isomerization.
values characteristic of trans Me (1804-1843 Hz) and
cyanoalkyl groups (2160-2200 Hz). The P(Mes)(Men)
signals show the expected coupling to a dppe P (26-29
Hz) and to Pt (221-247 Hz). The CN IR stretch at 2183
cm-1 (KBr), at lower energy than usual cyanide absorp-
tions, is typical of CN groups â to the metal center, as
previously described for related cyanoalkyl complexes.14
These spectroscopic results are similar to those observed
in the isolated insertion products Pt(dppe)(Me)[CH-
(CN)CH2PMes2]
and
Pt(dppe)(Me)[CH(CN)CH2-
PHMes*].1
Similar diastereoselective insertions were observed in
NMR tube experiments with the other chiral phosphido
complexes (Table 3). When a solution of 5 in C6D6 is
treated with an excess (approximately 20 equiv) of
acrylonitrile at room temperature, the bright orange
color fades to yellow over a period of 15 min. Signals
due to the P(Ph)(Is) group in diastereomers 10a -d
appear as doublets between δ -19 and -23, similar to
the chemical shift of P(Ph)(Is)(CH2CH2CN) at δ -26
(CDCl3).15 Complexes 6 and 7 also undergo insertion of
acrylonitrile, but the reactions are much slower, taking
up to a day to reach completion.
The protonation results are explained most simply if
6 and 7 exist as mixtures of diastereomers, for which
we observe only one set of NMR signals due to rapid
inversion at phosphorus. Protonation would then give
noninterconverting cations, for which separate NMR
resonances are seen. Alternatively, isomerization via
inversion could occur slowly on the NMR time scale, but
faster than reaction with HBF4; in this case, a minor,
unobserved diastereomer could react more quickly than
the major one with the acid to give the observed
products.13 Since protonation is fast, this scenario is
unlikely.
The reaction of chiral phosphido complexes 1 and 5-7
with acrylonitrile provides another indirect probe of
inversion at phosphorus. If these complexes exist as
single diastereomers in solution, then acrylonitrile
insertion should afford only two of the possible four
diastereomeric products, since the configuration at the
phosphido P will not change. Alternatively, if the
phosphido ligand is inverting rapidly, four diastereo-
meric products are expected.
The observation of four product diastereomers in
these reactions is not consistent with the existence of
the neutral chiral phosphido complexes as single dia-
stereomers in solution. Instead, it suggests that inver-
sion at the phosphido ligand is occurring rapidly.
However, it is possible that 1 and 5-7 exist as diaster-
eomeric mixtures greatly enriched in one isomer and
that the minor isomer, although unobserved by NMR,
reacts more quickly than the major one with acryloni-
trile to yield the four observed insertion products. This
would require isomer interconversion to be slow on the
NMR time scale but faster than the reaction with
acrylonitrile; as in the related protonations, this seems
unlikely since insertion is fast, at least in two of the
four cases investigated.
These studies provide indirect evidence that inversion
at the phosphido P atom is fast on the NMR time scale
in solution in complexes containing either a chiral
phosphorus substituent or a chiral chelating diphos-
phine. We obtained direct evidence for rapid inversion
in a related class of terminal phosphido complexes
containing a chiral Pt-bound alkyl group.
Complex 1 reacts quickly with acrylonitrile to give the
insertion product Pt(dppe)(Me)[CH(CN)CH2P(Mes)-
(Men)] (9), which causes the yellow-orange color of 1 to
bleach rapidly, giving an analytically pure off-white
solid after workup (Scheme 5). The insertion is diaste-
reoselective, yielding a 2.2:2:1.1:1 mixture of four dia-
stereomers, according to 31P NMR, which provides the
simplest spectroscopic method for differentiating these
We have previously described the synthesis of Pt(II)
complexes that contain the CH(Me)(CN) group by
(14) (a) Reger, D. L.; Garza, D. G. Organometallics 1993, 12, 554-
558. (b) Reger, D. L.; Garza, D. G.; Lebioda, L. Organometallics 1992,
11, 4285-4292. (c) Reger, D. L.; McElligott, P. J . J . Organomet. Chem.
1981, 216, C12-C14. (d) Reger, D. L. Inorg. Chem. 1975, 14, 660-
664. (e) Ros, R.; Renaud, J .; Roulet, R. Helv. Chim. Acta 1975, 58, 133-
139.
(15) P(Ph)(Is)(CH2CH2CN) is prepared by the base-catalyzed addi-
tion of acrylonitrile to PH(Ph)(Is). Complete experimental details and
characterizing data will be published elsewhere.
1
compounds (Table 3). The dppe resonances show J Pt-P
(13) Halpern, J . Science 1982, 217, 401-407.

Chiral Terminal Pt(II) Phosphido Complexes
Organometallics, Vol. 18, No. 24, 1999 5147
Ta ble 3. 31P NMR Da ta for P t(d ip h os)(Me)[CH(CN)CH2P RR′] Com p lexesa -c
diphos (no.)
dppe (9a )d
9b
9c
PRR′
δ(P1) (J Pt-P
)
δ(P2) (J Pt-P
)
δ(P3) (J Pt-P
)
J 13
isomer ratio
P(Mes)(Men)
45.3 (2176)
46.0 (2200)
46.5 (2200)
45.9 (2160)
47.8 (1837)
48.6 (1819)
48.4 (1804)
47.4 (1843)
-17.0 (221)
-18.8 (228)
-15.0 (227)
-10.0 (247)
-26.8 (299)
-20.7 (296)
-22.4 (264)
-23.4 (235)
-19.2 (312)
-29.1 (297)
-33.5 (253)
-36.2 (f)
26
26
26
29
35
36
27
26
35
34
29
26
42
24
41
26
2.2
2
1.1
1
3
3
1
2
3
12
2
9d
Chiraphos (10a -d )e
P(Ph)(Is)
58.6-55.9, 51.2-49.9, 48.1-47.1,
43.3-42.6, 39.1-38.0
Chiraphos (11a -d )e
Tol-Binap (12a -d )e
P(Me)(Mes*)
P(Me)(Mes*)
56.2-53.8, 48.8-47.9, 45.8-45.0,
41.1-40.6, 36.5-36.2
1
1
3
1
34.0-29.6, 24.5-23.7, 22.5-21.2,
20.3-20.0, 17.0-16.1,10.8-10.2
-27.3 (f)
-28.3 (260)
-32.5 (f)
-35.1 (262)
2
a
b
Temperature ) 22 °C. Chemical shifts in ppm, external ref 85% H3PO4, coupling constants in Hz. P1 and P2 are the diphos P nuclei;
the [CH(CN)(CH2PRR′)] group, which contains P3, is trans to P1. c Solvents: toluene-d8 for 9, C6D6 for 10, THF for 11, 12. For 9a -d ,
d
J 12 ) 3 Hz. e For 10-12, the diphos P signals are multiplets for which assignments and identification of Pt-P couplings were not possible.
f The low concentrations of 11d , 12a , and 12c made it impossible to resolve the Pt-P couplings.
Ta ble 4. Va r ia ble-Tem p er a tu r e NMR Da ta for
Ch ir a l P t[CH(Me)(CN)] P h osp h id o Com p lexesa
Sch em e 6
complex
resonanceb
∆ν (Hz)c
Tc (K)
∆Gcq (kcal/mol)
13
PHMes*
2894
268
59
165
2214
71
273
258
243
243
363
328
298
11.2
11.7
11.8
11.3
15.3
16.0
15.6
cis dcpe P
trans dcpe P
PHMes*
PMePh
cis dcpe P
trans dcpe P
14
oxidative addition of CH(Me)(CN)(Br) to Pt(0) and the
conversion of Pt(dcpe)[CH(Me)(CN)](Br) (dcpe ) Cy2-
PCH2CH2PCy2, Cy ) cyclo-C6H11) to Pt(dcpe)[CH(Me)-
(CN)](PHMes*) (13) by treatment with LiPHMes*
(Scheme 6).1b Similarly, reaction of NaP(Me)(Ph) with
Pt(dcpe)[CH(Me)(CN)](Br) gives Pt(dcpe)[CH(Me)(CN)]-
11
a
Solvent: THF-d8 for 13, toluene-d8 for 14. Estimated errors
are different for each resonance; “typical” errors are 5 Hz in ∆ν;
10 °C in Tc, and 0.5 kcal/mol in ∆Gcq. Cis and trans are defined
b
with respect to the phosphido ligand. Appropriate nucleus in
italics. c ∆ν values from slow-exchange spectra at -60 °C (31P, 13),
-40 °C (1H, 13), and -20 °C (14).
(PMePh) (14, Scheme 6). The IR spectrum of 14 (νCN
)
2185 cm-1) is similar to that of 13.
toluene-d8 in a 65:35 ratio (Table 1). Peaks due to the
dcpe phosphorus cis to the phosphido ligand are resolved
for the two isomers and show coupling constants similar
to those for 13. An average signal is observed for the
other dcpe P. On heating, the two sets of 31P NMR peaks
(phosphido and cis dcpe) resolved at room temperature
coalesce, while at low temperature the trans dcpe
resonance is resolved as two closely spaced signals.
These data are consistent with fluxional processes
involving a combination of phosphorus inversion and
rotation about the Pt-P bond, which operate on the
NMR time scale for 13 and 14 and thus interconvert
the two diastereomers of these complexes. By measuring
Since the CH(Me)(CN) ligand is racemic, it is highly
unlikely that only one diastereomer of these complexes
can be present in solution. This is in contrast to
phosphido complexes 1 and 5-7, which contain homo-
chiral centers, and suggests that NMR observation of
the two expected diastereomers should be possible.
At room temperature in THF-d8 solution, the 31P{1H}
NMR spectrum of 13 shows only one set of peaks,
including a broad phosphido resonance at δ -81.5 (Table
1). At -60 °C, this signal decoalesces into two separate
peaks at δ -77.7 (d, 2J PP ) 119, 1J Pt-P ) 720 Hz, major)
2
1
and -92.0 (d, J PP ) 114, J Pt-P ) 643 Hz, minor) in a
7:3 ratio. At this temperature the dcpe resonances are
also observed for both species. At 50 °C in THF-d8, an
average spectrum including a sharper phosphido reso-
nance is observed. Variable-temperature spectra in
toluene-d8 (Experimental Section) are similar to those
in THF-d8.
1
the coalescence temperatures of the 31P and/or H NMR
signals, approximate values for the barriers to these
processes were obtained by standard methods.16 Some
details of the NMR studies and the ∆G‡ values obtained
(ca. 11.5 kcal/mol for 13 and 15.5 kcal/mol for 14) are
shown in Table 4.
1
Similarly, the room-temperature H NMR spectrum
In the literature on metal phosphido complexes, it has
been assumed that the fluxional process associated with
such barriers is a combination of phosphorus inversion
and rotation about the M-P bond. The interconversion
of diastereomers might, however, occur by different
pathways, two of which are illustrated in Scheme 7. In
one, an intermediate with five-coordinate platinum and
bridging phosphido groups fragments by Pt-P cleavage
(THF-d8) shows one set of peaks, including a PH signal
2
3
2
at δ 5.18 (br dd, 1H, J PH ) 209, J PH ) 8, J Pt-H ) 56
Hz). Rotation about the P-C(Mes*) bond is slow on the
NMR time scale, giving rise to two different o-t-Bu
signals at 1.67 and 1.66 ppm. At -40 °C, signals due to
the two different isomers are observed, including PH
1
resonances at δ 5.27 (br d, 1H, J PH ) 210 Hz, major)
1
and 4.94 (br d, 1H, J PH ) 205 Hz, minor).
For complex 14, the two expected diastereomers can
(16) Friebolin, H. Basic One- and Two-Dimensional NMR Spectros-
copy, 2nd ed.; VCH: Weinheim, 1993.
be observed by 31P NMR at room temperature in

5148 Organometallics, Vol. 18, No. 24, 1999
Wicht et al.
nitrogen atmosphere at 20 °C in a drybox or using standard
Schlenk techniques. Petroleum ether (bp 38-53 °C), ether,
THF, and toluene were dried and distilled before use from Na/
benzophenone. CH2Cl2 and acetonitrile were distilled from
CaH2.
Sch em e 7
Unless otherwise noted, all NMR spectra were recorded on
a Varian 300 MHz spectrometer. 1H and 13C NMR chemical
shifts are reported relative to Me4Si and were determined by
reference to the residual 1H or 13C solvent peaks. 31P NMR
chemical shifts are reported relative to H3PO4 (85%) used as
an external reference. Unless otherwise noted, peaks in NMR
spectra are singlets. Coupling constants are reported in hertz
(Hz). Infrared spectra were recorded on a Perkin-Elmer 1600
series FTIR machine and are reported in cm-1 for KBr pellets.
Elemental analyses were provided by Schwarzkopf Microana-
lytical Laboratory. Unless otherwise noted, reagents were from
commercial suppliers. The following compounds were made by
the literature procedures: Pt(dppe)(Me)(OMe),17 PH(Mes)-
(Men),3a Pt(COD)(Me)(Cl),18 Pt(S,S-Chiraphos)(Me)(Cl),9 PH-
(Ph)(Is),12 PH(Me)(Mes*),19 PH(Me)(Ph).20
P t (d p p e)(Me)[P (Mes)(Men )] (1). Racemic mesityl(-)-
(menthyl)phosphine (140 mg, 0.48 mmol) and Pt(dppe)(Me)-
(OMe) (286 mg, 0.45 mmol) were combined in ca. 4 mL of THF
to give an orange solution with a little yellow solid remaining.
The solution was filtered through Celite, layered with petro-
leum ether, and cooled to -20 °C to give, after 1 day, large
yellow crystals. The crystals were collected and washed with
three 2 mL portions of petroleum ether to give 89 mg of orange
solid. The initial petroleum ether washes were yellow, and this
complex has some solubility in this solvent, so solvent was
evaporated from the combined mother liquor and washes and
the residue was recrystallized from ca. 1-2 mL of THF by
layering with petroleum ether as above to give, after washing,
104 mg of light orange-yellow crystals, which formed an orange
powder on drying (total yield ) 193 mg, 49%). A sample for
analysis was recrystallized a second time from THF/petroleum
ether to give yellow-orange crystals. The reaction was quan-
titative according to 31P NMR, so additional material can be
recovered from the filtrate. 1H NMR (toluene-d8, 21 °C): δ
7.81-7.66 (m, 6H, Ar), 7.45-7.41 (m, 2H, Ar), 7.12-6.98 (m,
12H, Ar), 6.79 (2H, Ar), 3.78-3.65 (m, 1H, CHMe2), 3.01 (6H,
o-Me), 2.11 (3H, p-Me), 2.28-0.70 (m, 13H, unresolved dppe
+ menthyl resonances), 1.19 (d, J ) 7.2, 3H, CHMe2), 0.88 (m,
2J Pt-H ) 72, 3H, Pt-Me), 0.76 (d, J ) 6.6, 3H, CHMe2), 0.63
(3H, menthyl CHMe). IR: 2917, 1484, 1436, 1186, 1102, 999,
881, 823, 746, 692, 647, 532, 484. Anal. Calcd for C46H57P3Pt:
C, 61.52; H, 6.41. Found: C, 61.25; H, 6.36.
to exchange phosphido ligands between metal centers,
resulting in inversion at phosphorus (Scheme 7a). In the
other, reversible ionization of the Pt-P bond to give an
ion pair could interconvert the isomers (Scheme 7b). To
test these possibilities, we recorded variable-tempera-
ture NMR spectra of 13 at concentrations differing by
a factor of 3 and in solvents of differing polarity (THF
and toluene). As no changes in the temperature depen-
dence of the spectra were seen, it is likely that the
possibilities of Scheme 7 are not important in this
system and that the measured barriers are indeed those
for the P inversion and rotation process.
Con clu sion s
We prepared platinum(II) phosphido complexes Pt-
(diphos)(Me)(PRR′) containing a fixed chiral center
either at a phosphido substituent or at the diphosphine
ligand, as well as two Pt(dcpe)[CH(Me)(CN)](PRR′)
complexes with a chiral Pt alkyl group. For the first two
classes of compounds, there is indirect evidence for rapid
phosphorus (PRR′) inversion on the NMR time scale.
The cationic precursors [Pt(diphos*)(Me)(PHRR′)]+ exist
as a mixture of diastereomers, but NMR spectra of the
neutral phosphido complexes show only a single set of
resonances even at low temperature, and Pt(Chiraphos)-
(Me)[P(Ph)(Is)] crystallized as a single diastereomer.
These observations are consistent with the presence of
only one diastereomer in solution, but could also be
explained by rapid inversion at the phosphido phospho-
rus or by the presence of a diastereomeric mixture
greatly enriched in one isomer. However, the reactivity
of these complexes (protonation and acrylonitrile inser-
tion) is not consistent with the single-diastereomer
model and is instead most easily explained by rapid
phosphorus inversion. For the CH(Me)(CN) complexes,
low-barrier phosphorus inversion processes could be
observed directly by variable-temperature NMR spec-
troscopy, and we have made similar observations in
closely related Pt(II) fluoroacyl phosphido complexes.8
We have also shown that chiral Pt(II) phosphido
complexes undergo diastereoselective acrylonitrile in-
sertion. The origin of the stereoselection and the ap-
plication of these results to the catalytic asymmetric
preparation of tertiary phosphines from racemic second-
ary phosphines is currently under investigation. In
particular, the relative rates of phosphorus inversion
and acrylonitrile insertion shown in Scheme 2 will
determine if such catalytic reactions are enantioselec-
tive.
[P t(S,S-Ch ir aph os)(Me)(P H(P h )Is)][BF4] (2). To a stirred
solution of Pt(S,S-Chiraphos)(Me)(Cl) (205 mg, 0.305 mmol)
and PH(Ph)Is (105 mg, 0.336 mmol) in CH2Cl2 (7 mL) was
added AgBF4 (59 mg, 0.31 mmol) dissolved in CH3CN (3 mL).
Immediate formation of AgCl was observed, and the reaction
mixture was stirred vigorously at room temperature for 30
min. The reaction mixture was filtered and the solvent
removed under vacuum. The white residue was washed with
three 2 mL portions of ether, dried, and dissolved in a
minimum amount of CH2Cl2. The CH2Cl2 solution was filtered,
and ether was added. Cooling of this solution to -25 °C gave
288 mg (91%) of a 1:1 mixture of diastereomers in two crops.
A sample for analysis was recrystallized two times from CH2-
Cl2/ether. The NMR spectra are reported as a mixture of
1
diastereomers (a and b) unless otherwise indicated. H NMR
(CDCl3): δ 7.82-7.56 (m, 15H, Ar), 7.42-7.21 (m, 6H, Ar),
7.12-6.92 (m, 6H, Ar), 7.02 (dd, 1J PH ) 384, 3J PH ) 6, 1H, PH-
(17) Bryndza, H. E.; Calabrese, J . C.; Wreford, S. S. Organometallics
1984, 3, 1603-1604.
(18) Clark, H. C.; Manzer, L. E. J . Organomet. Chem. 1973, 59, 411-
Exp er im en ta l Section
428.
(19) See ref 12 and ref 5b therein.
Gen er a l P r oced u r es. Unless otherwise noted, all reactions
and manipulations were performed in dry glassware under a
(20) Roberts, N. K.; Wild, S. B. J . Am. Chem. Soc. 1979, 101, 6254-
6260.

Chiral Terminal Pt(II) Phosphido Complexes
Organometallics, Vol. 18, No. 24, 1999 5149
1
3
(Ph)Is, diastereomer b), 6.45 (dd, J PH ) 375, J PH ) 10, 1H,
PH(Ph)Is, diastereomer a), 3.10-2.99 (m, 2H, o-CHMe2), 2.92-
(Ar), 127.0 (Ar), 126.7 (Ar), 126.4 (Ar), 126.3 (Ar), 126.2 (Ar),
126.0 (Ar), 125.0 (Ar), 123.7 (Ar), 123.2 (Ar), 122.1 (Ar), 121.3
(Ar), 21.5 (p-tol Me), 21.4 (p-tol Me), 21.2 (p-tol Me), 21.1 (p-
2.83 (m, 1H, p-CHMe2), 2.51-2.23 (m, 2H, CHMe), 1.25-1.21
3
2
(m, 6H, p-CHMe2), 1.18-1.01 (m, 6H, CHMe), 0.97 (d, J HH
)
tol Me), 11.2 (dd, J PC ) 97, 6, Pt-Me, Pt satellites were not
6, 3H, o-CHMe2), 0.96 (d, 3J HH ) 6, 3H, o-CHMe2), 0.82 (d, 3J HH
resolved). Anal. Calcd for C49H43ClP2Pt‚2/3Et2O: C, 63.73; H,
3
) 6, 3H, o-CHMe2), 0.80 (d, J HH ) 6, 3H, o-CHMe2), 0.39-
5.14. Found: C, 63.40; H, 5.17. The presence of ether in the
0.32 (m, J Pt-H ) 60, 3H, Pt-Me). 13C{1H} NMR (CDCl3): δ
analytical sample was confirmed by H NMR.
2
1
153.0-152.7 (m, quat. Ar), 136.0-135.5 (m, Ar), 134.2-134.1
(m, Ar), 132.9 (broad, Ar), 132.4-132.0 (m, Ar), 131.2-130.8
(m, Ar), 129.6-128.9 (m, Ar), 128.6-128.4 (m, Ar), 127.0-
[P t (R -Tol-Bin a p )(Me)(P H (Me)Mes*)][BF 4] (4). To a
stirred solution of Pt(R-Tol-Binap)(Me)(Cl) (302 mg, 0.33
mmol) in CH2Cl2 (5 mL) was added AgBF4 (64 mg, 0.33 mmol)
dissolved in CH3CN (5 mL). Immediate formation of AgCl
occurred, as indicated by a white precipitate. PH(Me)Mes* (105
mg, 0.36 mol) dissolved in CH2Cl2 (2 mL) was added to the
reaction mixture, which was stirred vigorously for 2 h. The
pale yellow solution was filtered, and the solvent was removed
in vacuo. The resulting solid was washed with three 2 mL
portions of petroleum ether. Recrystallization from CH2Cl2/
ether at -25 °C yielded 329 mg (80%) of a pale yellow
crystalline solid shown to be a single diastereomer by NMR.
1H NMR (CD2Cl2): 7.71-7.29 (m, 18H, Ar), 7.09-7.01 (m, 6H,
123.3 (m, quat. Ar), 122.8-122.5 (m, Ar), 38.5-36.0 (m,
3
CHMe), 34.1 (p-CHMe2, b), 34.0 (p-CHMe2, a), 33.2 (d, J PC
)
3
10, o-CHMe2, a), 33.0 (d, J PC ) 10, o-CHMe2, b), 24.4
(o-CHMe2, a), 24.2 (o-CHMe2, a), 24.1 (o-CHMe2, b), 24.0 (o-
CHMe2, b), 23.6 (p-CHMe2, a), 23.5 (p-CHMe2, b), 14.0-13.2
2
(m, CHMe), 2.2 (dm, J PC ) 70, Pt-Me, b, Pt satellites were
not resolved), 0.2 (dm, 2J PC ) 65, Pt-Me, a, Pt satellites were
not resolved). IR: 3055, 2955, 2877, 2400 (w, PH), 1533, 1477,
1438, 1400, 1366, 1311, 1277, 1233, 1211, 1183, 1055 (BF4),
916, 883, 750, 688, 550, 527. Anal. Calcd for C50H60BF4P3Pt:
C, 57.97; H, 5.85. Found: C, 57.52; H, 5.83.
1
Ar), 6.50-6.39 (m, 6H, Ar), 6.17 (dm, J PH ) 381, 1H, PH),
2.51 (3H, p-tol Me), 2.42 (3H, p-tol Me), 2.01 (6H, p-tol Me),
1.76 (9H, o-CMe3), 1.49 (9H, o-CMe3), 1.26 (9H, p-CMe3), 1.04-
[P t (S,S-Ch ir a p h os)(Me)(P H(Me)Mes*)][BF 4] (3). To a
stirred slurry of Pt(S,S-Chiraphos)(Me)(Cl) (320 mg, 0.476
mmol) in CH2Cl2 (10 mL) was added a solution of AgBF4 (93
mg, 0.48 mmol) dissolved in CH3CN (2 mL). Immediate
reaction occurred as indicated by the formation of AgCl. PH-
(Me)(Mes*) (153 mg, 0.524 mmol) dissolved in CH2Cl2 (2 mL)
was added to the reaction mixture, which was stirred vigor-
ously for 30 min. The pale yellow solution was filtered, and
the solvent was removed under vacuum. The white solid was
washed with ether (three 5 mL portions) and dried. Recrys-
tallization from CH2Cl2/ether at -25 °C yielded 387 mg (80%)
of a mixture of diastereomers in a ratio of approximately 3:1.
The NMR spectra are reported as a mixture of diastereomers
(a and b) unless otherwise indicated. 1H NMR (CD2Cl2): δ
3
2
0.98 (m, J Pt-H ) 24, 3H, PMe), 0.13-0.06 (m, J Pt-H ) 59,
3H, Pt-Me). 13C{1H} NMR (CD2Cl2): δ 154.6 (Ar), 154.5 (Ar),
153.6 (Ar), 152.6-152.5 (m, Ar), 143.0 (Ar), 142.2 (Ar), 141.9
(Ar), 141.7 (Ar), 135.5-135.2 (m Ar), 134.9-134.6 (m, Ar),
134.3 (Ar), 134.1 (Ar), 133.6 (Ar), 130.3 (Ar), 130.2 (Ar), 129.1-
128.9 (m, Ar), 128.4-127.8 (m, Ar), 126.9 (Ar), 126.8 (Ar), 123.5
(Ar), 121.5 (Ar), 120.8 (Ar), 40.5 (o-CMe3), 39.9 (o-CMe3), 35.2
(p-CMe3), 35.1 (o-CMe3), 33.7 (o-CMe3), 30.9 (p-CMe3), 21.5 (p-
tol Me), 21.4 (p-tol Me), 21.3 (p-tol Me), 21.2 (p-tol Me), 14.3
1
2
(d, J PC ) 36, PMe), 9.5 (d, J PC ) 68, Pt-Me, Pt satellites
were not resolved). IR: 2955, 2866, 2400 (w, PH), 1555, 1494,
1450, 1400, 1361, 1305, 1222, 1188, 1055 (BF4), 916, 872, 805,
744, 694, 672, 650, 600, 511, 433. Anal. Calcd for C68H76BF4P3-
Pt: C, 64.40; H, 6.05. Found: C, 64.04; H, 6.17.
1
8.02-7.45 (broad m, 22H, Ar), 6.80 (dm, J PH ) 383, 1H, PH,
1
diastereomer b), 6.03 (dm, J PH ) 374, 1H, PH, diastereomer
a), 2.29-2.16 (m, 2H, CHMe), 1.39 (broad, 21H, o-CMe3 and
PMe), 1.25 (broad, 9H, p-CMe3), 1.13-1.07 (broad m, 6H,
P t(S,S-Ch ir a p h os)(Me)[P (P h )Is] (5). To a stirred slurry
of [Pt(S,S-Chiraphos)(Me)(PH(Ph)Is)][BF4] (396 mg, 0.382
mmol) in THF (5 mL) was added LiN(SiMe3)2 (121 mg, 0.722
mmol) dissolved in THF (5 mL). The reaction mixture im-
mediately became homogeneous and bright orange and was
stirred at room temperature for 1 h. The solvent was removed
under vacuum, and the orange solid was washed twice with
petroleum ether (5 mL) and dried. The solid was extracted with
toluene (20 mL) and filtered. The filtrate was concentrated
under vacuum (to approximately 5 mL). Petroleum ether was
added to the toluene solution, and cooling of this solution to
-25 °C gave 284 mg (78%) of orange solid in two crops. 1H
NMR (toluene-d8): δ 7.92-7.79 (m, 4H, Ar), 7.54-7.48 (m, 2H,
Ar), 7.15-6.98 (m, 18H, Ar), 6.69-6.58 (m, 3H, Ar), 4.70-4.55
2
2
CHMe), 0.44 (m, J Pt-H ) 60, Pt-Me, a), 0.04 (m, J Pt-H ) 60,
Pt-Me, b). 13C{1H} NMR (CD2Cl2): δ 155.8-155.6 (m, quat.
Ar), 155.5-154.7 (broad m, quat. Ar), 152.7 (quat. Ar), 152.5
(quat. Ar), 136.9-136.4 (m, Ar), 133.8 (Ar), 133.4-133.2 (m,
Ar), 133.2 (Ar), 132.7-131.5 (m, Ar), 130.1-129.2 (m, Ar),
128.3-123.2 (m, quat. Ar), 118.6 (quat. Ar), 118.0 (quat. Ar),
39.9-39.3 (m, CHMe), 39.2 (o-CMe3), 38.8-38.4 (broad, o-
CMe3), 37.9-36.5 (m, CHMe), 35.1 (p-CMe3), 34.2 (o-CMe3),
34.2-33.8 (broad, o-CMe3), 30.9 (p-CMe3), 14.8 (dm, 1J PC ) 36,
2
1
P-Me), 14.1-13.4 (m, CHMe), 7.2 (dm, J PC ) 72, J Pt-C
)
1
528, Pt-Me, a), 3.2 (dm, J PC ) 71, Pt-Me, b, Pt satellites
were not resolved). IR: 2955, 2877, 2400 (w, PH), 1538, 1477,
1433, 1361, 1183, 1061 (BF4), 916, 883, 750, 694, 550, 527.
Anal. Calcd for C48H64BF4P3Pt: C, 56.74; H, 6.36. Found: C,
56.26; H, 6.00.
3
(m, 2H, o-CHMe2), 2.98 (septet, J HH ) 7, 1H, p-CHMe2), 1.94
2
(broad, 2H, CHMe), 1.25 (d, J HH ) 7, 6H, p-CHMe2), 1.24 (d,
3J HH ) 7, 6H, o-CHMe2), 1.16 (d, 3J HH ) 7, 6H, o-CHMe2), 0.69-
2
0.63 (m, 3H, CHMe), 0.67-0.63 (m, 3H, J Pt-H ) 67, Pt-Me),
P t(R-Tol-Bin a p )(Me)(Cl). In the air, to a stirred solution
of Pt(COD)(Me)(Cl) (350 mg, 0.98 mmol) dissolved in CH2Cl2
(5 mL) was added R-Tol-Binap (671 mg, 0.98 mmol) dissolved
in CH2Cl2 (2 mL). The pale yellow solution was stirred at room
temperature for 10 min. The solvent was removed in vacuo,
and the resulting solid was washed with three 2 mL portions
of ether. The solid was recrystallized from CH2Cl2/ether at -25
°C to yield 703 mg (77%) of pale yellow Pt(R-Tol-Binap)(Me)-
(Cl). 1H NMR (CD2Cl2): δ 7.73-7.28 (broad m, 20H, Ar), 7.06-
7.03 (m, 2H, Ar), 6.70-6.62 (m, 2H, Ar), 6.48-6.42 (m, 4H,
Ar), 2.45 (6H, p-tol Me), 1.99 (3H, p-tol Me), 1.98 (3H, p-tol
0.58-0.52 (m, 3H, CHMe). 13C{1H} NMR (toluene-d8):
δ
155.2-155.1 (m, quat. Ar), 147.6 (quat. Ar), 137.1-136.6 (m,
Ar), 133.7-133.5 (m, Ar), 132.4-132.3 (m, Ar), 132.1-132.0
(m, Ar), 131.2 (Ar), 130.8 (Ar), 130.0 (Ar), 129.4 (Ar), 128.7-
127.8 (m, Ar), 126.5-126.4 (m, Ar), 125.4-124.7 (m, quat. Ar),
123.2 (Ar), 121.2-121.1 (m, Ar), 39.3-38.5 (m, CHMe), 36.6-
35.8 (m, CHMe), 34.7 (p-CHMe2), 33.9 (o-CHMe2), 33.7 (o-
CHMe2), 26.0 (o-CHMe2), 25.2 (p-CHMe2), 24.3 (o-CHMe2),
2
14.3-14.0 (m, CHMe), 3.1 (d, J PC ) 73, Pt-Me, Pt satellites
were not resolved). IR: 3055, 2955, 2866, 1477, 1433, 1377,
1311, 1277, 1183, 1100, 1055, 933, 877, 744, 694, 527. Anal.
Calcd for C50H59P3Pt: C, 63.34; H, 6.29. Found: C, 62.51; H,
6.28.
3
2
Me), 0.44 (dd, J PH ) 8, 4, J Pt-H ) 55, 3H, Pt-Me). 13C{1H}
NMR (CD2Cl2): δ 141.1 (Ar), 140.6 (Ar), 140.4 (Ar), 139.9 (Ar),
139.4-139.3 (m, Ar), 137.6-137.4 (m, Ar), 136.1-135.9 (m,
Ar), 135.2-134.8 (m, Ar), 134.0 (Ar), 133.7 (Ar), 133.6 (Ar),
133.2 (Ar), 133.1 (m, Ar), 132.5 (Ar), 132.0 (Ar), 131.2 (Ar),
130.4 (Ar), 128.8-127.8 (m, Ar), 127.6 (Ar), 127.4 (Ar), 127.2
P t(S,S-Ch ir a p h os)(Me)[P (Me)(Mes*)] (6). To a solution
of [Pt(S,S-Chiraphos)(Me)(PH(Me)Mes*)][BF4] (165 mg, 0.163
mmol) in THF (5 mL) was added a solution of LiN(SiMe3)2 (33

5150 Organometallics, Vol. 18, No. 24, 1999
Wicht et al.
1
mg, 0.20 mmol) in THF (1 mL). The solution immediately
turned bright orange. The solvent was removed under vacuum,
and the orange residue was extracted with toluene (15 mL)
and filtered. The toluene was removed under vacuum and the
bright orange-yellow solid was dissolved in warm petroleum
ether, filtered, and concentrated to approximately 5 mL.
Cooling of this solution to -25 °C overnight gave 104 mg (69%)
of an orange-yellow solid. The compound was stable in solution,
but decomposition to an unidentified white solid occurred in
the solid state. 1H NMR (C6D6): δ 8.23-8.18 (m, 2H, Ar), 7.99-
7.83 (m, 4H, Ar), 7.68-7.65 (m, 2H, Ar), 7.39-7.33 (m, 2H,
Ar), 7.25-6.97 (m, 12H, Ar), 1.98 (9H, o-CMe3), 1.97 (9H,
and H NMR showed a mixture of diastereomers of 4 in a ratio
of approximately 3:1. Some characteristic resonances of the
minor diastereomer could be assigned. 1H NMR (CDCl3): δ
0.39 (m, J Pt-H ) 59, Pt-Me); see Table 1 for 31P NMR data.
1
The ratio of diastereomers does not change over a period of 2
weeks in CDCl3 or CD2Cl2. However, a sample of the 3:1
mixture of diastereomers in CD2Cl2 and one drop of CD3CN
isomerizes to the major diastereomer in 1 day at room
temperature. Alternatively, to a solution of the 3:1 diastere-
omeric mixture (39 mg, 0.031 mmol) in CD2Cl2 was added PH-
(Me)(Mes*) (3 mg, 0.01 mmol) and one drop of CD3CN. After
30 min the H and 31P NMR spectra showed complete isomer-
ization to the major diastereomer.
1
3
o-CMe3), 1.89-1.81 (m, 2H, CHMe), 1.81-1.76 (m, 3H, J Pt-H
) 47, PMe), 1.32 (9H, p-CMe3), 0.72-0.59 (m, 6H (CHMe) +
3H (2J Pt-H ) 69, Pt-Me)). 13C{1H} NMR (C6D6): δ 158.5-158.4
(m, quat. Ar), 157.8-157.1 (m, quat. Ar), 147.5 (quat. Ar),
142.5-141.9 (m, quat. Ar), 137.6-137.3 (m, Ar), 134.0-133.8
(m, Ar), 132.8-132.6 (m, Ar), 131.8-131.5 (m, Ar), 131.4-
131.2 (m, quat. Ar), 130.8 (quat. Ar), 130.2-130.0 (m, Ar),
129.6 (Ar), 129.2 (Ar), 129.1 (Ar), 123.8-123.6 (m, quat. Ar),
123.0-122.8 (m, Ar), 42.6-41.8 (m, CHMe), 40.7-40.6 (m, 2
o-CMe3 and p-CMe3), 38.2-37.6 (m, CHMe), 35.3-35.1 (m, 2
P t(d p p e)(Me)[CH(CN)CH2P (Mes)(Men )] (9). An excess
of acrylonitrile (ca. 0.1 mL) was added via syringe to an NMR
tube containing 70 mg of 1 (0.078 mmol) in ca. 1 mL of toluene-
d8. The yellow-orange color of 1 bleached quickly, giving a
colorless solution within minutes. The 31P{1H} NMR spectrum
showed quantitative conversion to 9 as a mixture of four
diastereomers a -d . The solvent was removed under vacuum,
and the light yellow residue was stirred with petroleum ether
(4 × 3 mL) to give a white powder, sparingly soluble in
petroleum ether. The solvent was decanted and the powder
dried in vacuo to give 50 mg (67%) of the analytically pure
product, which can be further recrystallized from THF/
petroleum ether.
1
3
o-CMe3), 32.0 (p-CMe3), 19.9 (dd, J PC ) 31, J PC ) 6, P-Me),
2
1
15.3-14.8 (m, CHMe), 2.0 (ddd, J PC ) 81, 8, 3, J Pt-C ) 596,
Pt-Me).
P t(R-Tol-Bin a p )(Me)(P (Me)Mes*) (7). To a white slurry
of [Pt(R-Tol-Binap)(Me)(PH(Me)Mes*)][BF4] (411 mg, 0.324
mmol) in THF (15 mL) was added potassium tert-butoxide (55
mg, 0.49 mmol) dissolved in THF (5 mL). The reaction mixture
immediately became dark brownish-red, and the solvent was
removed in vacuo. The dark purple solid was dissolved in
toluene and filtered. The toluene was removed in vacuo and
the residue washed with a minimum amount of cold petroleum
ether to give 310 mg (81%) of product. A sample which was
pure by 1H NMR could be recrystallized from petroleum ether
at -25 °C. However in the solid state the product decomposed
to an unidentified gray solid. 1H NMR (C6D6): δ 8.29-7.67
(m, 8H, Ar), 7.31-7.11 (m, 12H, Ar), 6.98-6.88 (m, 3H, Ar),
6.63-6.54 (m, 5H, Ar), 6.11-6.09 (m, 2H, Ar), 2.28 (9H,
o-CMe3), 2.17 (9H, o-CMe3), 2.15 (3H, p-tol Me), 2.02 (3H, p-tol
Me), 1.79 (3H, p-tol Me), 1.69 (3H, p-tol Me), 1.51-1.46 (m,
3J Pt-H ) 49, 3H, PMe), 1.33 (9H, p-CMe3), 0.64-0.56 (m, 2J Pt-H
) 67, 3H, Pt-Me). 13C{1H} NMR (C6D6): δ 157.9-157.5 (m,
quat. Ar), 155.0 (quat. Ar), 147.4 (quat. Ar), 142.1 (quat. Ar),
141.4-141.3 (m, quat. Ar), 140.7 (quat. Ar), 140.3 (quat. Ar),
139.8-139.6 (m, quat. Ar), 139.4-139.2 (m, quat. Ar), 138.2-
138.0 (m, quat. Ar), 136.7-135.6 (m, Ar), 134.9-134.8 (m, Ar),
134.3-133.8 (m, quat. Ar), 129.6 (Ar), 128.9-128.1 (m, Ar),
126.6-125.6 (m, Ar), 125.0-124.9 (m, Ar), 124.5-124.4 (m,
Due to the complexity of the 1H NMR spectrum, complete
assignment and integration of the resonances was not possible.
1H NMR (C6D6): δ 7.81-7.41 (m, 7H, Ar), 7.23-6.96 (m, 13H,
Ar), 6.76-6.70 (m, 2H, Mes), 3.34-3.29 (m), 2.68 and 2.62 (6H,
o-Me), 2.14, 2.09, and 2.06 (3H, p-Me), 2.80-1.40 (m), 1.33-
1.13 (m), 1.05-1.03 (m), 0.98-0.86 (m), 0.70-0.66 (m), 0.43-
0.41(m), 0.38-0.35 (m). IR (KBr): 2949, 2923, 2183, 1435,
1103, 746, 693, 532. Anal. Calcd for C49H60NP3Pt: C, 61.87;
H, 6.37; N, 1.47. Found: C, 61.79; H, 6.81; N, 1.39.
Tr ea tm en t of P t(S,S-Ch ir a p h os)(Me)[P (P h )Is] (5), P t-
(S,S-Ch ir a p h os)(Me)[P (Me)Mes*] (6), a n d P t(R-Tol-Bi-
n a p )(Me)[P (Me)Mes*] (7) w ith Acr ylon itr ile. (1) To an
NMR tube containing Pt(S,S-Chiraphos)(Me)[P(Ph)Is] (20 mg,
0.022 mmol) in C6D6 was added acrylonitrile (30 µL, 0.46
mmol) via microliter syringe. The bright orange color faded to
pale yellow immediately. (2) To an NMR tube containing Pt-
(S,S-Chiraphos)(Me)[P(Me)Mes*] (50 mg, 0.054 mmol) in THF
was added acrylonitrile (5 µL, 0.076 mmol) via microliter
syringe. After 30 min, the bright orange color of the solution
faded to pale yellow. (3) To an NMR tube containing Pt(R-
Tol-Binap)(Me)[P(Me)Mes*] (20 mg, 0.017 mmol) in THF was
added acrylonitrile (20 µL, 0.30 mmol) via microliter syringe.
After 24 h the color faded to pale yellow. For 31P NMR data,
see Table 3.
Cr ysta llogr a p h ic Str u ctu r a l Deter m in a tion . Crystal
data collection and refinement parameters are given in Table
2. Suitable crystals for single-crystal X-ray diffraction were
selected and mounted either in a nitrogen-flushed, thin-walled
capillary, and flame sealed, or on the tip of a fine glass fiber
with epoxy cement. The data for 4 and 5 were collected on a
Siemens P4 diffractometer equipped with a SMART/CCD
detector.
The systematic absences in the diffraction data are uniquely
consistent with the reported space groups. The structures were
solved by direct methods, completed by subsequent difference
Fourier syntheses, and refined by full-matrix least-squares
procedures. An empirical absorption correction was applied to
the data of 4 and 5, based on a Fourier series in the polar
angles of the incident and diffracted beam paths, and was used
to model an absorption surface for the difference between the
observed and calculated structure factors.21 No absorption
corrections for 8 were required because there was less than
10% variation in the integrated ψ-scan intensities. Axial
Ar), 124.0-123.9 (m, Ar), 121.6-121.5 (m, Ar), 41.0 (d, 3J PC
)
7, o-CMe3), 40.8 (o-CMe3), 36.2 (broad, o-CMe3), 35.2 (p-CMe3),
34.8 (d, 4J PC ) 17, o-CMe3), 31.9 (p-CMe3), 21.8 (p-tol Me), 21.7
1
(p-tol Me), 21.5 (p-tol Me), 21.4 (p-tol Me), 18.5 (dm, J PC
)
2
39, PMe), 8.9 (ddd, J PC ) 80, 8, 2, Pt-Me, Pt satellites were
not resolved). Anal. Calcd for C68H75P3Pt: C, 69.18; H, 6.42.
Found: C, 71.48; H, 6.73.
Tr ea tm en t of P t(S,S-Ch ir a p h os)(Me)[P (Me)Mes*] (6)
w ith HBF 4. To an orange solution of Pt(S,S-Chiraphos)(Me)-
[P(Me)Mes*] (33 mg, 0.036 mmol) in diethyl ether (2 mL) was
added HBF4‚Me2O (6 µL, 0.04 mmol) via microliter syringe.
The orange color quickly faded, and a white precipitate formed.
The solvent was pipetted off, and the white solid was dried to
give 33 mg (92%) of 3 as a 2:1 mixture of diastereomers,
confirmed by 31P and 1H NMR.
Tr eatm en t of P t(R-Tol-Bin ap)(Me)[P (Me)Mes*] (7) with
HBF 4. To a purple solution of Pt(R-Tol-Binap)(Me)[P(Me)Mes*]
(48 mg, 0.041 mmol) in diethyl ether (2 mL) was added HBF4‚
Me2O (7 µL, 0.05 mmol) via microliter syringe. The purple color
quickly faded, and an off-white precipitate formed. The solvent
was removed under vacuum, and the residue was washed with
diethyl ether (2 mL) and dried to give 42 mg (81%) of 4. 31P
(21) Walker, N.; Stuart, D. Acta Crystallogr. 1983, A39, 158-166.

Chiral Terminal Pt(II) Phosphido Complexes
Organometallics, Vol. 18, No. 24, 1999 5151
1
photographs of 5 confirm that no doubling along the c-axis was
missed and there is no 21 screw axis along c. Three molecules
of dichloromethane were located in the asymmetric unit of 4,
the C-Cl distances were fixed to an average C-Cl distance,
and the atoms were refined isotropically. Two equally occupied
positions for the hydrogen atom on phosphorus in 8 were
located from the difference map and allowed to refine. The
hydrogen atom on the phosphorus atom of 4 could not be
located from the difference map and was ignored. All other
non-hydrogen atoms were refined with anisotropic displace-
ment parameters. All other hydrogen atoms were treated as
idealized contributions.
Bu). H NMR (toluene-d8, -40 °C): 7.65 (br, 1H, Ar, a + b),
2
7.52 (br, 1H, Ar, a + b), 5.62 (br d, 1H, J PH ) 210, PH, a),
5.31 (br d, 1H, 2J PH ) 206, PH, b), 2.85 (br m, 1H of a + 1H of
b, CH), 2.50-1.00 (br m, 48H of a + 48H of b of dcpe + 3H of
a + 3H of b of CH(Me)CN), 2.03, 1.92, 1.85 (all br, 18H of a +
18H of b, o-t-Bu), 1.42 (9H of a + 9H of b, p-t-Bu).
P t(d cp e)[CH(Me)(CN)][P (Me)P h ] (14). A white suspen-
sion of 150 mg (0.2 mmol) of Pt(dcpe)[CH(Me)(CN)](Br) in 10
mL of THF was treated with 10 mL of a yellow THF solution
of freshly prepared NaP(Me)Ph (0.4 mmol), formed by reaction
of 73.2 mg (0.4 mmol) of NaN(SiMe3)2 and 49.5 mg (0.4 mmol)
of PH(Me)(Ph). The suspension became yellow, and it was
stirred at room temperature for 2 h. The solvent was then
removed in vacuo, and the yellow-orange solid residue was
extracted with ca. 20 mL of toluene. The toluene extract was
filtered through Celite, the toluene was removed in vacuo, and
addition of an excess of petroleum ether to the viscous residue
precipitated a yellow solid. This was separated, washed three
times with ca. 5 mL of petroleum ether, and dried in vacuo.
The solid was then dissolved in ca. 5 mL of toluene, and the
resulting solution was passed down a column of Silica gel 60
(ca. 5 mm in height, as well as in diameter). Removal of toluene
in vacuo from the eluent gave a yellow microcrystalline solid,
which was washed with ca. 2 × 5 mL of petroleum ether and
finally dried in vacuo (yield: 80 mg, 50%). NMR showed this
material was a mixture of two diastereomers, a and b.
1H NMR (22 °C, C6D6): δ 7.78, 7.60, 7.22 and 7.02 (all m,
5H of a + 5H of b, Ar), 2.85-0.80 (br m, 52 H (dcpe + CH(Me)-
CN) of a + 55 H (dcpe + CH(Me)CN + PPh(Me) of b), 1.80
All software and sources of the scattering factors are
contained in the SHELXTL (5.03 and 5.10) program libraries
(G. Sheldrick, Siemens XRD, Madison, WI).
P t(d cp e)[CH(Me)(CN)](P HMes*) (13). The synthesis and
some characterizing data for this complex were reported
previously.1b Additional variable-temperature NMR data (ac-
quired on a 500 MHz instrument) are as follows.
1H NMR (THF-d8, 22 °C): δ 7.35 (1H, Ar), 7.25 (1H, Ar),
2
3
2
5.18 (br dd, 1H, J PH ) 209, J PH ) 8, J Pt-H ) 56, PH), 2.67
(br m, 1H, CH), 2.50-1.00 (br m, 48H, dcpe), 1.67 (9H,
o-t-Bu), 1.66 (9H, o-t-Bu), 1.31 (9H, p-t-Bu), 0.80 (virtual t, 3H,
3J HH ) 7, 4J PH ) 7, 3J Pt-H ) 50, Me). 1H NMR (THF-d8, 50 °C):
2
3
δ 7.35 (1H, Ar), 7.25 (1H, Ar), 5.18 (ddd, 1H, J PH ) 209, J PH
3
2
) 8, J PH ) 2, J Pt-H ) 56, PH), 2.67 (br m, 1H, CH), 2.50-
1.00 (br m, 48H, dcpe), 1.67 (9H, o-t-Bu), 1.66 (9H, o-t-Bu),
1.31 (9H, p-t-Bu), 0.80 (virtual t, 3H, 3J HH ) 7, 4J PH ) 7, 3J Pt-H
) 50, Me). H NMR (THF-d8, -40 °C): δ 7.34 (1H, Ar, major
isomer a), 7.33 (1H, Ar, minor isomer b), 7.24 (1H, Ar, a), 7.23
1
2
4
3
(3H, apparent t, J PH ) 6, J PH ) 6, J Pt-H ) 49, PPh(Me) of
a). 1H NMR (22 °C, THF-d8): δ 7.28, 7.06, 6.88 (all m, 5H of a
+ 5H of b, Ar), 2.80-0.80 (br m, 55 H (dcpe + CH(Me)CN +
PPh(Me) of a + 55 H (dcpe + CH(Me)CN + PPh(Me) of b). IR:
2916, 2850, 2185, 1577, 1478, 1446, 1329, 1289, 1273, 1195,
1120, 1040, 1024, 1008, 917, 891, 867, 853, 821, 803, 738, 698,
666, 650, 535, 517, 490. Anal. Calcd for C36H60NP3Pt: C, 54.40;
H, 7.61; N 1.76. Found: C, 54.50; H, 7.85; N, 1.88.
2
(1H, Ar, b), 5.27 (br d, 1H, J PH ) 210, PH, a), 4.94 (br d, 1H,
2J PH ) 205, PH, b), 2.62 (br m, 1H of a + 1H of b, CH), 2.50-
1.00 (br m, 48H of a + 48H of b, dcpe), 1.73, 1.68, 1.62 (all s,
18H of a + 18H of b, o-t-Bu), 1.31 (9H of a + 9H of b, p-t-Bu),
3
4
3
0.89 (apparent t, 3H of a + 3H of b, J HH ) 7, J PH ) 7, J Pt-H
) 50, Me).
31P{1H} NMR (toluene-d8, 22 °C): δ 60.1 (d, J PP ) 103,
2
1J Pt-P ) 1977), 54.4 (1J Pt-P ) 2023), -80.5 (br). 31P{1H} NMR
2
1
(toluene-d8, 90 °C): δ 59.8 (dd, J PP ) 107, 6, J Pt-P ) 1951),
54.9 (br, 1J Pt-P ) 2015), -79.3 (br d, 2J PP ) 108, 1J Pt-P ) 686).
31P{1H} NMR (toluene-d8, -60 °C, major isomer a, ca. 70%):
δ 61.1 (d, 2J PP ) 116, 1J Pt-P ) 2041), 53.9 (1J Pt-P ) 2016), -76.3
Ack n ow led gm en t. We thank the NSF Career Pro-
gram, the Petroleum Research Fund, administered by
the American Chemical Society, the Exxon Education
Foundation, DuPont, and Union Carbide (Innovation
Recognition Program) for partial support, and Prof. R.
P. Hughes for helpful discussions. The University of
Delaware thanks the NSF (CHE-9628768) for their
support of the purchase of the CCD-based diffractome-
ter.
(d, J PP ) 116, J Pt-P ) 718). 31P{1H} NMR (toluene-d8, -60
2
1
2
1
°C, minor isomer b, ca. 30%): δ 60.5 (d, J PP ) 109, J Pt-P not
resolved), 52.4 (1J Pt-P ) 2019), -90.7 (d, J PP ) 109, J Pt-P
)
2
1
1
643). H NMR (toluene-d8, 22 °C): δ 7.62 (1H, Ar), 7.50 (1H,
2
3
2
Ar), 5.46 (br dd, 1H, J PH ) 208, J PH ) 8, J Pt-H ) 56, PH),
2.85 (br m, 1H, CH), 2.50-1.00 (br m, 48H of dcpe + 3H of
CH(Me)CN), 1.94 (9H, o-t-Bu), 1.87 (9H, o-t-Bu), 1.42 (9H, p-t-
Bu). 1H NMR (toluene-d8, 90 °C): δ 7.59 (1H, Ar), 7.47 (1H,
Ar), 5.44 (br dd, 1H, J PH ) 208, J PH ) 8, J Pt-H ) 56, PH),
2.85 (br m, 1H, CH), 2.50-1.00 (br m, 48H of dcpe + 3H of
CH(Me)CN), 1.91 (9H, o-t-Bu), 1.85 (9H, o-t-Bu), 1.42 (9H, p-t-
Su p p or tin g In for m a tion Ava ila ble: Details of the crys-
tal structure determinations. This material is available free
of charge via the Internet at http://pubs.acs.org.
2
3
2
OM9903700