Cyclometalation of dimesitylphosphine in cationic palladium(II) and platinum(II) complexes: P-H vs C-H activation

Article abstract of DOI:10.1021/om000164o

The cationic complexes [M(dppe)(R)(PHMes₂)][OTf] (M = Pd, R = Me (1), Ph (2); M = Pt, R = Me (3), Et (4); dppe = Ph₂PCH₂CH₂PPh₂, Mes = 2,4,6-Me₃C₆H₂, OTf = OSO₂CF₃) were prepared by the reaction of the corresponding M(dppe)(R)(X) (X = Cl, I) with AgOTf and PHMes₂. When they were allowed to stand in THF or CH₂Cl₂ solution, the Pd complexes underwent cyclometalation, forming [Pd(dppe)(CH₂C₆H₂(Me)₂PHMes)][OTf] (5). Thermolysis of Pt complexes 3 and 4 gave [Pt(dppe)(CH₂C₆H₂(Me)₂PHMes)][OTf] (6), along with ethylene in the latter case. Reaction of Pt(dppe)(Et)(Cl) with AgOTf generated [Pt(dppe)(H)]₂²⁺, which on treatment with PHMes₂ also yielded 6. Treatment of 1, 2 and 3, 4 with triflic acid gave 5 and 6, respectively. The cyclometalation of 1 is acid-catalyzed; the intermediacy of [Pd(dppe)(PHMes₂)]²⁺ in these reactions was supported by formation of 5 from sources of the [Pd(dppe)]²⁺ fragment and dimesitylphosphine.

Full text of DOI:10.1021/om000164o

2882
Organometallics 2000, 19, 2882-2890
Cyclom eta la tion of Dim esitylp h osp h in e in Ca tion ic
P a lla d iu m (II) a n d P la tin u m (II) Com p lexes: P -H vs C-H
Activa tion
Michael A. Zhuravel, Navrose S. Grewal, and David S. Glueck*
6128 Burke Laboratory, Department of Chemistry, Dartmouth College,
Hanover, New Hampshire 03755
Kin-Chung Lam and Arnold L. Rheingold
Department of Chemistry, University of Delaware, Newark, Delaware 19716
Received February 22, 2000
The cationic complexes [M(dppe)(R)(PHMes2)][OTf] (M ) Pd, R ) Me (1), Ph (2); M ) Pt,
R ) Me (3), Et (4); dppe ) Ph2PCH2CH2PPh2, Mes ) 2,4,6-Me3C6H2, OTf ) OSO2CF3) were
prepared by the reaction of the corresponding M(dppe)(R)(X) (X ) Cl, I) with AgOTf and
PHMes2. When they were allowed to stand in THF or CH2Cl2 solution, the Pd complexes
underwent cyclometalation, forming [Pd(dppe)(CH2C6H2(Me)2PHMes)][OTf] (5). Thermolysis
of Pt complexes 3 and 4 gave [Pt(dppe)(CH2C6H2(Me)2PHMes)][OTf] (6), along with ethylene
in the latter case. Reaction of Pt(dppe)(Et)(Cl) with AgOTf generated [Pt(dppe)(H)]22+, which
on treatment with PHMes2 also yielded 6. Treatment of 1, 2 and 3, 4 with triflic acid gave
5 and 6, respectively. The cyclometalation of 1 is acid-catalyzed; the intermediacy of [Pd-
(dppe)(PHMes2)]2+ in these reactions was supported by formation of 5 from sources of the
[Pd(dppe)]2+ fragment and dimesitylphosphine.
Ch a r t 1. Th r ee P oten tia lly Rea ctive Sites in
Dim esitylp h osp h in e a n d Meta l Com p lexes F or m ed
fr om It by Activa tion of P -H, P -C, a n d C-H
Bon d s, Resp ectively
In tr od u ction
The chemistry of secondary phosphines (PHR2) is
usually dominated by the reactive P-H bond. Oxidative
addition of this bond or deprotonation of coordinated
secondary phosphines often leads to phosphido com-
plexes.1 Recently, for example, we showed that treat-
ment of Pt(dppe)(trans-stilbene) with dimesitylphos-
phine (PHMes2; Mes ) 2,4,6-Me3C6H2) led to initial
formation of Pt(dppe)(PMes2)(H) (dppe ) Ph2PCH2CH2-
PPh2; reaction at site A in Chart 1). However, this was
followed by an unusual P-C oxidative addition (site B)
to give the thermodynamic product Pt(dppe)(Mes)-
(PHMes).2 Another potentially reactive site (C) in di-
mesitylphosphine is the ortho-substituted methyl group,
as observed recently in rhenium carbonyl chemistry.3
Trimesitylphosphine (PMes3) readily undergoes analo-
gous cyclometalation reactions4 at Pd(II) and Pt(II),5 and
the Pd complex [Pd(CH2C6H2(Me)2PMes2)(µ-OAc)]2 and
related compounds are excellent catalyst precursors for
the Heck reaction.6 Here we report cyclometalation of
dimesitylphosphine at Pd(II) and Pt(II) centers, in which
the methyl C-H bond is activated selectively in the
presence of the P-H bond. Evidence for an acid-
catalyzed cyclometalation pathway involving cationic,
coordinatively unsaturated intermediates is also pre-
sented.
* To whom correspondence should be addressed. E-mail:
David.Glueck@Dartmouth.Edu.
(1) For examples, see: (a) Chatt, J .; Davidson, J . M. J . Chem. Soc.
1964, 2433-2445. (b) Hayter, R. G. J . Am. Chem. Soc. 1962, 84, 3046-
3053. (c) Bader, A.; Nullmeyers, T.; Pabel, M.; Salem, G.; Willis, A. C.;
Wild, S. B. Inorg. Chem. 1995, 34, 384-389. (d) Leoni, P. Organome-
tallics 1993, 12, 2432-2434. (e) Levason, W. In The Chemistry of
Organophosphorus Compounds; Hartley, F. R., Ed.; Wiley: Chichester,
England, 1990; Vol. 1; pp 567-641.
(2) Kourkine, I. V.; Sargent, M. D.; Glueck, D. S. Organometallics
1998, 17, 125-127.
(3) Florke, U.; Haupt, H.-J . Z. Kristallogr. New Cryst. Struct. 1998,
213, 269-270.
(5) (a) Dias, S. A.; Alyea, E. C. Transition Met. Chem. 1979, 4, 205-
206. (b) Alyea, E. C.; Ferguson, G.; Malito, J .; Ruhl, B. L. Organome-
tallics 1989, 8, 1188-1191. (c) Alyea, E. C.; Malito, J . J . Organomet.
Chem. 1988, 340, 119-126. (d) We found (see the Supporting Informa-
tion) that reaction of PHMes2 with Pd(OAc)2 did not give analogous
cyclometalated complexes.
(4) (a) 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; pp 297-300. (b)
Ryabov, A. D. Chem. Rev. 1990, 90, 403-424.
(6) (a) Herrmann, W. A.; Brossmer, C.; Reisinger, C.-P.; Riermeier,
T. H.; Ofele, K.; Beller, M. Chem. Eur. J . 1997, 3, 1357-1364. (b)
Herrmann, W. A.; Bohm, V. P. W.; Reisinger, C.-P. J . Organomet.
Chem. 1999, 576, 23-41.
10.1021/om000164o CCC: $19.00 © 2000 American Chemical Society
Publication on Web 06/22/2000

Cyclometalation of Dimesitylphosphine
Organometallics, Vol. 19, No. 15, 2000 2883
Ta ble 1. Selected NMR a n d IR Da ta for Com p lexes 1-6 a n d 9-10a ,b
compd (M, R)
δ(P1) (J Pt-P
)
δ(P2) (J Pt-P
)
δ(P3) (J Pt-P
)
J 12
J 13
J 23
δ(PH)
J PH
ν(PH)
1 (Pd, Me)c
2 (Pd, Ph)
3 (Pt, Me)
4 (Pt, Et)
9 (Pd, Cl)
10 (Pd, NCMe)d
5 (Pd)
59.5
50.6
54.9 (2846)
53.6 (3011)
62.8
67.3
54.7
50.1 (2767)
42.7
44.6
49.6 (1692)
47.4 (1506)
65.5
67.0
43.8
44.2 (1788)
-47.2
-49.9
-42.8 (2553)
-43.6 (2713)
-43.3
-43.9
-14.8
-17.7 (2632)
33
24
4
4
4
b
29
7
367
361
379
375
418
337
339
352
26
b
6.52
6.38
7.01
7.09
6.14
5.92
6.53
b
357, 12
358, 19
378
2318
2329
b
17
17
23
20
30
15
382
b
369, 13
386, 10
364, 12
362e
2402
2397
2381
2390
6 (Pt)
a
Solvents: CD2Cl2 for 1, 2, 5, 6, and 10; acetone-d6 for 3, 4, and 9. 31P NMR chemical shift reference: external 85% H3PO4. Coupling
constants are in Hz. IR data are in cm-1 for KBr pellets. Not observed. c For the 13CH3-labeled 1a , J P -C ) 80 Hz. Dication. e From the
b
d
2
31P NMR spectrum.
Sch em e 1
Sch em e 2
with 13CH3I gave Pd(dppe)(13CH3)(I) in good yield.9 This
labeled precursor was converted to [Pd(dppe)(13CH3)-
(PHMes2)][OTf] (1a ), which decomposed in CD2Cl2 in a
sealed NMR tube after 2 days to give 13CH4, observed
as a doublet at δ 0.26 (1J CH ) 126) in the 1H NMR
spectrum and a quintet at δ -4.39 (1J CH ) 126) in the
13C NMR spectrum.10 No 13C incorporation in the
decomposition product was observed. Phenyl complex
2 decomposed in CD2Cl2 to give benzene (δ 7.35),
confirmed by adding a small amount of benzene to the
solution.
Resu lts a n d Discu ssion
The complexes [Pd(dppe)(Me)(PHMes2)][OTf] (1; OTf
) OSO2CF3), [Pd(dppe)(Ph)(PHMes2)][X] (2), and [Pt-
(dppe)(Me)(PHMes2)][OTf] (3) were prepared by the
reaction of Pd(dppe)(R)(X′) (R ) Ph, X′ ) I; R ) Me, X′
) Cl, I; X ) BF4, OTf) and Pt(dppe)(Me)(Cl) with AgOTf
or AgBF4 and subsequent addition of PHMes2 (Scheme
1). The synthesis of [Pt(dppe)(Et)(PHMes2)][OTf] (4)
requires that PHMes2 be added before AgOTf (see
below). The complexes were isolated in good yields as
yellow crystalline solids and characterized by spectro-
scopy and by elemental analysis. The 31P NMR data for
Cationic complex 5 was obtained as a yellow solid by
recrystallization from THF/petroleum ether and char-
acterized by NMR and IR spectroscopy and FAB mass
spectroscopy as well as by X-ray crystallography. The
dppe 31P{1H} NMR signals (Table 1, CD2Cl2) of 5 do not
change much as compared to 1 and 2; the phosphine
peak, however, shifts downfield to δ -14.8 (2J PP ) 339,
30 Hz), which is consistent with the formation of a
1
1-4 as well as selected H NMR and IR data character-
izing the PH groups are summarized in Table 1.
On standing in THF or CH2Cl2 solution over a period
of 2-5 days, complexes 1 and 2 started to decompose;
heating or prolonged standing at room temperature led
to complete reaction. The decomposition rates varied
widely, depending on the sample (see below), and
depended on the solvent; qualitatively, reaction occurred
faster in THF or CH2Cl2 than in acetone and did not
occur at all in acetonitrile.7 Spiking confirmed that the
same Pd-containing product formed from 1 and 2,
suggesting the loss of the phenyl and methyl ligands
and formation of the cyclometalated complex [Pd(dppe)-
(CH2C6H2(Me)2PHMes)][OTf] (5) (Scheme 2).
chelating ligand.11 The P-H coupling constant (1J PH
)
371 Hz) indicates that the proton is not removed from
the phosphorus. The FAB mass spectrum shows the
parent ion peak at m/z 773.1. The diastereotopic Pd-
CH2 protons give rise to an AB quartet at δ 3.51-3.43
1
(2J HH ) 15 Hz) in the H{31P} NMR spectrum (CD2Cl2),
consistent with data for other cyclometalated com-
The loss of methane and benzene from 1 and 2 was
observed directly. The reaction of Pd(dba)(dppe)8 (formed
in situ by the addition of 1 equiv of dppe to Pd(dba)2)
(9) See the Supporting Information for synthetic details. For a
similar preparation of Pd(bipy)(Me)(I), see: Byers, P. K.; Canty, A. J .
Organometallics 1990, 9, 210-220.
(10) (a) Alei, M. J .; Wageman, W. E. J . Chem. Phys. 1978, 68, 783-
784. (b) Horvath, I. T.; Cook, R. A.; Millar, J . M.; Kiss, G. Organome-
tallics 1993, 12, 8-10.
(7) See the Supporting Information for details. See also ref 18.
(8) Herrmann, W. A.; Thiel, W. R.; Brossner, C.; Ofele, K.; Prier-
meier, T.; Scherer, W. J . Organomet. Chem. 1993, 461, 51-60.
(11) Garrou, P. E. Inorg. Chem. 1975, 14, 1435-1439.

2884 Organometallics, Vol. 19, No. 15, 2000
Zhuravel et al.
Sch em e 3
pounds.12 In the 13C{1H} NMR spectrum (CD2Cl2) the
cyclometalated CH2 group gives rise to a doublet at δ
40.6 (2J PC ) 82 Hz).
Thermolysis of the Pt cations 3 and 4 led to the
formation of the analogous cyclometalated Pt complex
[Pt(dppe)(CH2C6H2(Me)2PHMes)][OTf] (6) (Schemes 2
1
and 3). Ethylene was also observed by H NMR in a
sealed NMR tube experiment with 4, which suggests
that heating of 4 leads to â-elimination and formation
of [Pt(dppe)(H)(PHMes2)]+, which decomposes with the
loss of H2 (see below). Spectral data for 6 (Table 1) are
similar to those for the Pd analogue 5, including an AB
pattern of 1H{31P} NMR signals for the Pt-CH2 protons
2
at δ 3.56 (2J HH ) 17, J Pt-H ) 67 Hz, CDCl3) and 3.42
(2J Pt-H ) 54 Hz).
Cyclometalated complex 6 could also be prepared at
room temperature by adding AgOTf to Pt(dppe)(Et)(Cl)
before addition of PHMes2. However, when the reaction
was conducted at -78 or -40 °C ethyl phosphine com-
plex 4 was formed (Scheme 3). To better understand this
behavior, we added AgOTf to a solution of Pt(dppe)(Et)-
(Cl) in CH2Cl2; this gave the dinuclear dication [Pt
F igu r e 1. ORTEP diagram of 2 with thermal ellipsoids
at 30% probability. Tetrafluoroborate anion and hydrogen
atoms, except the hydrogen atom of the phosphine, are
omitted for clarity.
(J Pt-P ) 1853 Hz), 36.0 (J Pt-P ) 4646 Hz)).14 At -20
2+
(dppe)(H)]2 (7; Scheme 3) as the major product. The
°C, the chloro complex had all reacted and signals were
31P{1H} NMR (CH2Cl2) spectrum of this reaction mix-
ture showed a major signal at δ 38.9 (J Pt-P ) 4167 Hz),
2+
observed due to [Pt(dppe)(H)]2 (7) and to ethylene (δ
5.39). From -20 to 21 °C, signals due to 7 and ethylene
increased in intensity, although Pt(dppe)(Et)(OTf) re-
mained the major constituent of the reaction mixture.
These observations are consistent with the synthetic
results; ethyl complex 4 is presumably formed from
Pt(dppe)(Et)(OTf) at low temperature before it decom-
poses by â-elimination.
The cyclometalated complex 5 and precursors 2 and
4 were also characterized by X-ray crystallography. The
structure of 4 was suitable only for establishing the
atom connectivity and is reported in the Supporting
Information. The crystal structures of 2 as the tet-
rafluoroborate salt and 5 as the triflate salt with cocrys-
tallized toluene are shown in Figures 1 and 2. Data
collection and structure refinement are summarized in
Table 2, selected bond lengths and angles appear in
Table 3, and additional details are given in the Experi-
mental Section and the Supporting Information.
1
and the H NMR (CD2Cl2) spectrum included a hydride
1
resonance at δ -4.39 (2J PH ) 10, 64, J Pt-H ) 592 Hz).
Several related dications have been prepared with
bulkier, more electron-rich diphosphines.13 This reaction
was not clean (for example, another hydride signal was
observed at δ -4.11), and complex 7 decomposed in
solution. Treatment of the reaction mixture with PHMes2
gave 6 as the major product (Scheme 3).
Treatment of Pt(dppe)(Et)(Cl) with AgOTf at -78 °C
in CD2Cl2, followed by warming of the solution, was
monitored by NMR (Scheme 3). From -40 to -30 °C,
most of the Pt(dppe)(Et)(Cl) was converted to what is
presumably Pt(dppe)(Et)(OTf) (31P{1H} NMR δ 52.7
(J Pt-P ) 1644 Hz), 46.7 (J Pt-P ) 4886 Hz); compare
Pt(dppe)(Me)(OTf), 31P{1H} NMR (acetone-d6) δ 56.0
(12) (a) Fornies, J .; Martin, A.; Navarro, R.; Sicilia, V.; Villarroya,
P. Organometallics 1996, 15, 1826-1833. (b) Louie, J .; Hartwig, J . F.
Angew. Chem., Int. Ed. Engl. 1996, 35, 2359-2361.
(13) Mole, L.; Spencer, J . L.; Litster, S. A.; Redhouse, A. D.; Carr,
N.; Orpen, A. G. J . Chem. Soc., Dalton Trans. 1996, 2315-2321.
(14) Hill, G. S.; Yap, G. P. A.; Puddephatt, R. J . Organometallics
1999, 18, 1408-1418.

Cyclometalation of Dimesitylphosphine
Organometallics, Vol. 19, No. 15, 2000 2885
Ta ble 3. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for [P d (d p p e)(P h )(P HMes2)][BF 4] (2) a n d
[P d (d p p e)(CH2C6H2(Me)2P HMes)][OTf] (5)
2
5
Pd-P(1)
Pd-P(2)
Pd-P(3)
Pd-C
2.3013(15)
2.3559(15)
2.3446(16)
2.055(6)
2.381(3)
2.415(3)
2.380(3)
2.137(13)
P(1)-Pd-P(2)
P(3)-Pd-C
P(3)-Pd-P(2)
C-Pd-P(1)
85.12(5)
91.97(17)
94.82(6)
88.21(17)
84.54(9)
82.7(3)
102.74(10)
90.0(3)
Sch em e 4a
F igu r e 2. ORTEP diagram of 5‚0.5C7H8 with thermal
ellipsoids at 50% probability. Triflate anion, solvent mol-
ecule, and hydrogen atoms, except the hydrogen atom of
the phosphine, are omitted for clarity.
Ta ble 2. Cr ysta llogr a p h ic Da ta for
[(P d (d p p e)(P h )(P HMes2)][BF 4] (2) a n d
[P d (d p p e)(CH2C6H2(Me)2P HMes)][CF 3SO3] (5)‚0.5
Tolu en e.
2
5‚0.5(toluene)
formula
fw
space group
a, Å
b, Å
c, Å
C
50H52F4P3BPd
C48.5H50F3O3P3PdS
969.26
P1h
939.04
P1h
a
[Pd] ) Pd(dppe).
12.1139(2)
13.0924(2)
13.9935(2)
88.5821(4)
82.5610(3)
83.9039(6)
2188.09(5)
2
11.4171(2)
14.0653(2)
16.5162(2)
86.0325(8)
82.0153(3)
72.8459(8)
2508.58(5)
2
the C-Pd-PHMes2 angle decreases from 91.97(17)° in
2 to 82.7(3)° in the five-membered ring of 5. Perhaps to
relieve strain in this ring, the Pd-P and Pd-C bond
lengths in it are slightly longer than in precursor 2. The
Pd-P(dppe) bond lengths in 5 are also somewhat longer
than in 2; perhaps this occurs to minimize steric
interactions with the relatively inflexible cyclometalated
ring and its substituents. Other structural features, like
the square-planar geometry and dppe bite angle, remain
essentially unchanged.16
Mech a n ism of Cyclom eta la tion . The erratic rates
observed for cyclometalation suggested an acid-cata-
lyzed mechanism (Scheme 4), analogous to a similar
pathway proposed by Thorn in a related Pt(II) system.17
Protonation of 1 or 2 by adventitious acid, followed by
reductive elimination of CH4 or C6H6, could give [Pd-
(dppe)(PHMes2)]2+ (8). Benzylic C-H activation followed
by loss of a proton would then give 5. According to this
mechanism, added acid should speed up cyclometala-
tion, added acid scavenger should slow it down, and the
proposed intermediate, [Pd(dppe)(PHMes2)]2+, if pre-
pared independently, should form cyclometalated 5.
These predictions were tested, as described below, and
the results are consistent with the proposed mecha-
nism.18
R, deg
â, deg
γ, deg
V, Å3
Z
cryst color, habit
D(calcd), g cm-3
µ(Mo KR), cm-1
temp, K
diffractometer
radiation
R(F), %a
R(wF2), %a
yellow plate
1.425
5.86
colorless plate
1.283
5.55
203(3)
173(2)
Siemens P4/CCD
Mo KR (λ ) 0.710 73 Å)
5.67
16.54
7.56
25.85
Quantity minimized: R(wF2) ) ∑[w(Fo - Fc2)2]/∑[(wFo2)2]1/2
R ) ∑∆/∑(Fo), ∆ ) |(Fo - Fc)|.
;
a
2
Bulky ligands and the associated steric interactions
are known to promote cyclometalation.4 The shortest
calculated Pd-C and Pd-H distances for dimesitylphos-
phine in 2, 3.447(7) and 2.845(7) Å, respectively, do not
suggest any unusual interaction between the mesityl
Me groups and the metal center. However, it was noted
previously that due to the repulsive nature of axial CH-
Pd interactions such positions are normally avoided;
therefore, the presence of hydrogen in an axial position
(Mes Me group above the square plane) may serve as
an indication of steric strain.15
(16) The average dppe-Pd bite angle is 85.03°; see: Dierkes, P.;
van Leeuwen, P. W. N. M. J . Chem. Soc., Dalton Trans. 1999, 1519-
1529.
(17) Thorn, D. L. Organometallics 1998, 17, 348-352.
(18) The variation of cyclometalation rate with sample made it
difficult to reliably establish the effect of added reagents, solvent, or
conditions on the rate. To minimize these difficulties, when investigat-
ing one such variable, we used samples of 1 from the same synthetic
batch, solvents from the same storage container, and groups of NMR
tubes that had been cleaned and dried side by side.
Several significant structural changes occur on con-
version of 2 to cyclometalated 5 (Table 3). As expected,
(15) (a) Rheingold, A. L.; Fultz, W. C. Organometallics 1984, 3,
1414-1417. (b) As noted by a reviewer, more recent work has suggested
that such M-H-C interactions have an attractive component. For a
recent discussion, see: Hambley, T. W. Inorg. Chem. 1998, 37, 3767-
3774.

2886 Organometallics, Vol. 19, No. 15, 2000
Zhuravel et al.
Sch em e 5
Reaction of 9 with AgOTf in THF gave PHMes2 and
the known Pd(dppe)(OTf)2 (11).19 A similar reaction in
acetone gave 11, PHMes2, and a small amount of 5; on
standing, triflate complex 11 was slowly converted to
5. Treatment of independently prepared 11 with PHMes2
in THF or acetone gave 5 on heating or standing at room
temperature. In acetone, [Pd(dppe)(PHMes2)(OTf)][OTf]
(12) was cleanly formed initially; the same complex is
also apparently formed in THF, although the 31P NMR
spectra are not as well resolved as in acetone.20 Reaction
of 11 with PHMes2 in acetonitrile, however, gives 10.
These results are consistent with the intermediacy of
the fragments [Pd(dppe)(PHMes2)(L)]2+ and [Pd(dppe)-
(PHMes2)(X)]+ in cyclometalation and the requirement
for a vacant coordination site in [Pd(dppe)(PHMes2)]2+
via dissociation of L (solvent) or X (counterion).
Sch em e 6
Reactions with more weakly coordinating anions are
consistent with this idea (Scheme 7). Treatment of Pd-
(dppe)Cl2 with 1.2 equiv of AgBF4 and 1 equiv of
PHMes2 in THF gave a 1:4 ratio of cyclometalated 5 and
chloro complex 9 after 2 days. Addition of another 0.8
1. Ad d ed Acid . In NMR tubes, three separate
acetone solutions of 1 were treated with 1 equiv (1), 0.5
equiv (2), and 0.05 equiv (3) of triflic acid and then
heated to 50 °C (Scheme 5). The reaction of the Pd-C
bond with the strong acid is slow, according to 31P NMR
monitoring. After 5 h, no reaction was seen in sample 3
and in a control sample (4) containing no HOTf, while
samples 1 and 2 showed 10% and 8% conversion to 5,
respectively. After 23 h of heating 70% conversion was
observed for sample 1, 50% for sample 2, 13% for sample
3, and only a trace of 5 was seen for sample 4. After 72
h of heating samples 1 and 2 had reacted completely, a
trace of 1 remained in sample 3, and 44% conversion
was observed for sample 4.
2. Ad d ed Ba se. Proton Sponge (1,8-bis(dimethylami-
no)naphthalene) was chosen as a base, since it reacts
very slowly with the coordinated dimesitylphosphine in
1. Two samples of 1 in THF were prepared, 0.2 equiv of
Proton Sponge was added to one of them, and the
samples were heated to 50 °C (Scheme 5). After 2 days
of heating, considerable cyclometalation (ca. 50%) oc-
curred in the control sample, while no 5 formed in the
sample containing Proton Sponge; instead, minor de-
composition occurred. After 4 days of heating the base-
free sample showed complete conversion to 5 and only
a trace (less than 5%) of 5 was observed in the sample
containing Proton Sponge.
3. Th e P r op osed In t er m ed ia t e [P d (d p p e)(P -
HMes2)]2+ (8). To generate 8, we planned to abstract
chloride from [Pd(dppe)(PHMes2)(Cl)][OTf] (9), with
Ag+. Complex 9 was prepared either by treatment of 1
with aqueous HCl or by reaction of Pd(dppe)Cl2 with
AgOTf and PHMes2 in THF (Scheme 6; see Table 1 for
selected NMR and IR data). As desired, silver(I) salts
removed chloride from 9; the results depended on
counterion and solvent (Scheme 7). Treatment of 9 with
AgOTf in acetonitrile gave mostly [Pd(dppe)(PHMes2)-
(NCMe)][OTf] (10), which was also the major product
formed on reaction of 1 equiv of HOTf with 1 in
acetonitrile or from Pd(dppe)Cl2, AgOTf, and PHMes2
in acetonitrile. Although this acetonitrile complex (Table
1) could not be obtained pure, it did not undergo
cyclometalation to give 5.
gave complete conversion to 5. Similar
equiv of AgBF4
reactions involving Pd(dppe)Cl2, 2 equiv of AgBF4, and
1 equiv of PHMes2 in THF or acetone also afforded 5,
but the formation of 1 equiv of acid complicated isolation
of the product. Attempts to run the reaction in the
presence of base (for example, K2CO3), were not suc-
cessful.
These experiments are consistent with the proposed
acid-catalyzed mechanism, but do not rule out other
possible pathways. For example, direct benzylic oxida-
tive addition, followed by loss of RH, would give 5 (path
A, Scheme 8).21 Alternatively (path B), P-H oxidative
addition and reductive elimination could form [Pd-
(dppe)(PMes2)]+. Benzylic oxidative addition and P-H
reductive elimination would then yield 5.
We attempted to test the latter mechanism by moni-
toring decomposition of [Pd(dppe)(13CH3)(PDMes2)][OTf]
(1b) by NMR. Assuming no complications from isotope
effects, cyclometalation of 1b via P-H activation (path
B) should give 13CH3D, whereas C-H activation (path
A) or an acid-catalyzed pathway (Scheme 4) should give
13CH4. Complex 1b was prepared by H-D exchange
between 1a and D2O. Unfortunately, when 1b was
heated, H-D scrambling was faster than cyclometala-
tion and caused partial conversion to 1a before cyclo-
metalation occurred. NMR monitoring showed that the
methane formed was mostly 13CH4 with ca. 5% CH3D.
In contrast, decomposition of 1b formed by addition of
DOTf to 1a gave mostly 13CH3D with a small amount
of 13CH4. Details of these experiments can be found in
the Supporting Information, but the lability of the
P-H(D) bond and its likely exchange with adventitious
or deliberately added proton sources made them incon-
clusive; we cannot tell if the P-H(D) proton in 1 is
incorporated in the methane formed.
(19) Fallis, S.; Anderson, G. K.; Rath, N. P. Organometallics 1991,
10, 3180-3184.
(20) Complex 12 is described as a triflate complex for convenience,
although it is possible that solvent and/or water displaces triflate from
Pd in 12, as in acetonitrile complex 10.
(21) van der Boom, M. E.; Liou, S.-Y.; Shimon, L. J . W.; Ben-David,
Y.; Milstein, D. Organometallics 1996, 15, 2562-2568.

Cyclometalation of Dimesitylphosphine
Organometallics, Vol. 19, No. 15, 2000 2887
Sch em e 7
Sch em e 8
Con clu sion s
or using standard Schlenk techniques. Petroleum ether
(bp 38-53 °C), ether, THF, and toluene were dried and
distilled before use by employing Na/benzophenone.
CH2Cl2 was distilled from CaH2. Acetone and acetoni-
trile were degassed by purging with N2 and stored over
molecular sieves.
The cationic Pd(II) and Pt(II) complexes [M(dppe)(R)-
(PHMes2)]+ (1-4) decompose by cyclometalation of a
mesityl methyl group, while the usually reactive PH
group remains intact in the final product. Mechanistic
studies of cyclometalation of the Pd(II) complexes are
consistent with an acid-catalyzed pathway via the coor-
Unless otherwise noted, all NMR spectra were re-
corded by using a Varian 300 MHz spectrometer. 1H or
13C NMR chemical shifts are reported vs Me4Si and
dinatively unsaturated fragment [Pd(dppe)(PHMes2)]2+
However, we have not been able to rule out other
possible mechanisms or to establish the source or nature
of the proposed acid catalyst.22
.
1
were determined by reference to the residual H or 13C
solvent peaks. 31P NMR chemical shifts are reported vs
H3PO4 (85%) used as an external reference. Coupling
constants are reported in Hz. Unless otherwise noted,
absolute values are reported for all experimental cou-
pling constants. Unless otherwise noted, peaks in NMR
spectra are singlets. Infrared spectra were recorded on
KBr pellets using a Perkin-Elmer 1600 series FTIR
machine and are reported in cm-1. Elemental analyses
were provided by Schwarzkopf Microanalytical Labora-
tory. Low-resolution FAB mass spectroscopy was per-
formed by S. L. Mullen on a VG ZAB-SE instrument at
the University of Illinois.
Exp er im en ta l Section
Gen er a l Deta ils. Unless otherwise noted, all reac-
tions and manipulations were performed in dry glass-
ware under a nitrogen atmosphere at 20 °C in a drybox
(22) A reviewer suggested that adventitious water might be the
impurity responsible for catalyzing cyclometalation. There is precedent
for this idea (see: Cave, G. W. V.; Fanizzi, F. P.; Deeth, R. J .; Errington,
W.; Rourke, J . P. Organometallics 2000, 19, 1355-1364), and we
cannot rule it out.

2888 Organometallics, Vol. 19, No. 15, 2000
Zhuravel et al.
Unless otherwise noted, reagents were obtained from
commercial suppliers. The following compounds were
made by the literature procedures: Pd(dppe)(Ph)I,23 Pd-
(dba)2,24 Pd(dppe)(Me)(Cl),25 PHMes2,26 Pt(dppe)(Et)-
(Cl),27 Pt(dppe)(Me)(Cl),28 Pd(dppe)Cl2,29 and Pd(dppe)-
(OTf)2.19
[P d (d p p e)(Me)(P HMes2)][OTf] (1). Pd(dppe)(Me)-
(Cl) (118 mg, 0.21 mmol) was suspended in a mixture
of 2 mL of THF and 0.5 mL of MeCN. AgOTf (55 mg,
0.21 mmol) and PHMes2 (57 mg, 0.21 mmol) were
introduced simultaneously with constant stirring to
produce a dark gray precipitate. The reaction was
protected from light. After 60 min of stirring the solution
was filtered and its volume was reduced to 2 mL.
Petroleum ether was added, and the solution was cooled
to -25 °C. The product was obtained as 160 mg (80%
yield) of yellow solid, which decomposed partially on
Calcd for C50H52BF4P3Pd: C, 63.95; H, 5.58. Found: C,
63.83; H, 5.78.
1H NMR (CD2Cl2): δ 7.58-7.34 (m, 16H, Ar), 7.31-
4
7.21 (m, 4H, Ar), 6.66 (d, 4H, J PH ) 3), 6.62-6.42 (m,
1
3
5H, Ar), 6.38 (dd, 1H, J PH ) 358, J PH ) 14), 2.52 (m,
4H, dppe CH2), 2.17 (6H, Mes), 2.05 (br, 12H, Mes). 13C-
{1H} NMR (CD2Cl2): δ 154.0 (m, J PC ) 100, quat), 142.2
(d, J PC ) 8), 141.5 (quat), 136.7 (m), 133.7 (d, J PC ) 11),
132.8 (d, J PC ) 12), 132.2 (m), 130.3 (d, J PC ) 8), 129.7
(d, J PC ) 10), 129.5 (d, J PC ) 10), 129.2, 128.8 (d, J PC
)
12), 127.9, 127.8 (d, J PC ) 7), 123.6, 121.1 (m, J PC ) 45,
quat), 27.7 (dd, J PC ) 26, 18, dppe CH2), 26.6 (dd, J PC
) 26, 18, dppe CH2), 23.2 (m, Mes), 21.0 (Mes). IR: 3052,
2966, 2918, 2329 (PH), 1602, 1563, 1469, 1435, 1103,
1053 (BF4), 729, 693.
[P t(d p p e)(Me)(P HMes2)][OTf] (3). To a slurry of
Pt(dppe)(Me)(Cl) (201 mg, 0.312 mmol) in THF (10 mL)
prepared in the air were added CH3CN (0.5 mL), a
solution of AgOTf (80 mg, 0.312 mmol) in THF (1 mL),
and a solution of PHMes2 in THF (2 mL), and the
resulting purple mixture was stirred for 12 h. The
reaction mixture was filtered through Celite to give a
clear solution, and solvent was removed under vacuum.
The solid residue was dissolved in toluene, and addition
of diethyl ether and cooling to -25 °C gave the final
product in three crops as 246 mg (77% yield) of white
solid. Anal. Calcd for C46H50F3O3P3PtS: C, 53.75; H,
4.90. Found: C, 53.52; H, 5.09.
1H NMR (acetone-d6): δ 7.88-7.78 (m, 4H, Ar), 7.74-
7.58 (m, 10H, Ar), 7.54-7.38 (m, 6H, Ar), 7.01 (dm, 1J PH
) 378, 1H, PH), 6.90 (4H, Ar), 3.04-2.60 (m, 4H, CH2),
2.31 (12H, o-Me), 2.28 (6H, p-Me), 0.52-0.43 (m, 2J Pt-H
) 60, 3H, Me). 13C{1H} NMR (acetone-d6): δ 143.3-
142.8 (m, quat Ar), 142.2 (d, J PC ) 2, quat Ar), 134.4-
133.8 (m, Ar), 133.8-133.3 (m, Ar), 133.0 (d, J PC ) 3,
Ar), 132.5 (d, J PC ) 2, Ar), 131.2 (d, J PC ) 8, Ar), 130.3
(d, J PC ) 11, Ar), 129.8 (d, J PC ) 10, Ar), 129.1 (quat
Ar), 128.4 (quat Ar), 29.1-28.1 (m, dppe CH2), 23.5 (d,
J PC ) 9, o-Me), 21.0 (p-Me), -1.4 (dm, J PC ) 73, Me, Pt
satellites were not resolved). IR: 3056, 2933, 1600, 1433,
1267, 1222, 1150, 1104, 1030, 877, 853, 821, 751, 695,
636, 532, 487, 433.
attempted recrystallization. Anal. Calcd for C46H50
-
SO3F3P3Pd: C, 58.82; H, 5.37. Found: C, 57.26; H, 5.36.
We were unable to obtain satisfactory analyses despite
numerous attempts, presumably because of this decom-
position.
1H NMR (CD2Cl2): δ 7.66-7.28 (m, 20H, Ar), 6.77 (d,
1
3
4J PH ) 3, 4H, Ar), 6.52 (dd, J PH ) 357, J PH ) 12, 1H,
PH), 2.60-2.44 (m, 4H, dppe CH2), 2.23 (6H, Mes), 2.17
(12H, Mes), 0.35 (ddd, J PH ) 5, 6, 8, 3H, Me). 13C{1H}
3
NMR (CD2Cl2): δ 142.4 (d, J PC ) 7), 142.0 (d, J PC ) 8),
141.5 (d, J PC ) 2), 133.7-133.4 (m), 133.3 (d, J PC ) 12),
133.1 (d, J PC ) 11), 132.6 (d, J PC ) 12), 132.1 (dd, J PC
) 45, 3), 130.8-130.6 (m), 130.6 (d, J PC ) 8), 129.9,
129.8 (d, J PC ) 11), 129.6, 129.4 (d, J PC ) 10), 128.2 (d,
2
J PC ) 47), 28.3-27.1 (m, dppe CH2), 23.3 (d, J PC ) 9,
Mes), 21.0 (Mes), 5.3 (d, 2J PC ) 77, Me). IR: 3054, 2966,
2919, 2318 (PH), 1604, 1437, 1264, 1157, 1104, 1031,
853, 749.
[P d (d p p e)(13CH3)(P HMes2)][OTf] (1a ) was pre-
pared similarly from Pd(dppe)(13CH3)(I). Selected spec-
tral data: 1H NMR (CD2Cl2) δ 0.35 (m, Me, 1J CH ) 134);
2
13C{1H} NMR (CD2Cl2) δ 5.3 (dm, J PC ) 80, Me).
[P d (d p p e)(P h )(P HMes2)][BF 4] (2). Pd(dppe)(Ph)-
(I) (46 mg, 0.07 mmol) was dissolved in THF. AgBF4
(13 mg, 0.07 mmol) was added as a MeCN solution to
produce a gray precipitate. The reaction mixture was
protected from light and stirred for 15 min. It was then
filtered, and PHMes2 (18 mg, 0.07 mmol) was added
with stirring to the pale yellow solution. After 60 min
of stirring the solution was filtered and the volume of
the solution was reduced to 3 mL. Petroleum ether was
added, and cooling to -25 °C gave the product as 29
mg (52% yield) of yellow crystals. Additional recrystal-
lization gave yellowish crystals of X-ray quality. Anal.
[P t(d p p e)(Et)(P HMes2)][OTf] (4). To a slurry of Pt-
(dppe)(Et)(Cl) (196 mg, 0.30 mmol) in THF (2 mL) was
added a solution of PHMes2 (85 mg, 0.31 mmol) in THF
(1 mL) followed by a solution of AgOTf (81 mg, 0.31
mmol) in 1 mL of THF. The resulting purple slurry was
stirred for 2 h and then filtered through Celite to give
a yellow solution. The solvent was removed under
vacuum, the tan solid residue was dissolved in THF,
and addition of diethyl ether and cooling to -30 °C gave
the product in three crops as 210 mg of white, air-stable
solid (68% yield). Anal. Calcd for C47H52F3O3P3PtS: C,
54.18; H, 5.03. Found: C, 53.88; H, 5.03.
(23) Mann, G.; Baranano, D.; Hartwig, J . F.; Rheingold, A. L.; Guzei,
I. A. J . Am. Chem. Soc. 1998, 120, 9205-9219.
(24) Maitlis, P. M.; Rettig, M. F. Inorg. Synth. 1990, 28, 111.
(25) Dekker, G. P. C. M.; Buijs, A.; Elsevier, C. J .; Vrieze, K.; van
Leeuwen, P. W. N. M.; Smeets, W. J . J .; Spek, A. L.; Wang, Y. F.; Stam,
C. H. Organometallics 1992, 11, 1937-1948.
1H NMR (acetone-d6): δ 7.84-7.34 (m, 20H, Ar), 7.09
1
(dm, J PH ) 382, 1H, PH), 6.85 (4H, Ar), 2.86-2.60 (m,
(26) Bartlett, R. A.; Olmstead, M. M.; Power, P. P.; Sigel, G. A. Inorg.
Chem. 1987, 26, 1941-1946.
4H, dppe CH2), 2.30 (br, 12H, o-Me), 2.23 (6H, p-Me),
1.52-1.18 (m, 2H, ethyl CH2), 0.37-0.11 (m, 3H, ethyl
CH3). 13C{1H} NMR (acetone-d6): δ 143.3-143.0 (m,
quat Ar), 142.3 (d, J PC ) 2, quat Ar), 134.7-134.1 (m,
Ar), 134.1-133.4 (m, Ar), 133.1 (d, J PC ) 2, Ar), 132.7-
132.4 (m, Ar), 131.3 (d, J PC ) 8, Ar), 130.6 (quat Ar),
130.3 (d, J PC ) 11, Ar), 129.9 (d, J PC ) 10, Ar), 128.7
(quat Ar), 127.9 (quat Ar), 29.1-28.0 (m, dppe CH2),
(27) (a) Appleton, T. G.; Bennett, M. A. Inorg. Chem. 1978, 17, 738-
747. (b) Bryndza, H. E.; Calabrese, J . C.; Marsi, M.; Roe, D. C.; Tam,
W.; Bercaw, J . E. J . Am. Chem. Soc. 1986, 108, 4805-4813. (c) Slack,
D. A.; Baird, M. C. Inorg. Chim. Acta 1977, 24, 277-280.
(28) (a) Clark, H. C.; J ablonski, C. R. Inorg. Chem. 1975, 14, 1518-
1526. (b) Appleton, T. G.; Bennett, M. A.; Tomkins, I. B. J . Chem. Soc.,
Dalton Trans. 1976, 46, 439-446.
(29) Steffen, W. L.; Palenik, G. J . Inorg. Chem. 1976, 15, 2432-
2439.

Cyclometalation of Dimesitylphosphine
Organometallics, Vol. 19, No. 15, 2000 2889
23.8-23.4 (m, o-Me), 21.0 (p-Me), 15.1 (d, J PC ) 3, ethyl
CH3), ethyl CH2 was not resolved. IR: 3054, 2915, 1603,
1437, 1271, 1222, 1191, 1148, 1103, 1030, 877, 853, 821,
750, 695, 636, 531, 486, 432.
Calcd for C45H47P3O3F3SClPd: C, 56.36; H, 4.94.
Found: C, 56.22; H, 5.30.
1H NMR (CD2Cl2): δ 8.04-7.76 (m, 8H, Ph), 7.70-
7.42 (m, 12H, Ph), 6.83 (d, 4H, 4J PH ) 4, Mes), 6.14 (dd,
3J PH ) 13, 1J PH ) 369, 1H, PH), 3.48-3.26 (m, 2H, CH2),
2.85-2.62 (m, 2H, CH2), 2.26 (broad, 12H, Me), 2.23
(broad, 6H, Me). 13C{1H} NMR (CD2Cl2): δ 142.5 (d, J PC
) 8), 142.2 (d, J PC ) 3), 133.8 (d, J PC ) 3), 133.5 (dd,
[P d (d p p e)(P H(Mes)(CH2C6H2Me2))][OTf] (5). [Pd-
(dppe)(Me)(PHMes2)][OTf] (42 mg, 0.04 mmol) was
dissolved in 1 mL of acetone, HOTf (395 µL, 1 vol %
solution in acetone, 0.04 mmol) was added via microliter
syringe, and the solution was heated for 3 days at 60
°C. The solution was filtered, diethyl ether was added,
and cooling to -25 °C gave the product as 35 mg (85%
yield) of orange solid. Slow evaporation of THF from a
solution in toluene/THF (5:1) gave crystals of X-ray
quality. Anal. Calcd for C45H46SO3F3P3Pd: C, 58.54; H,
5.02. Found: C, 57.60; H, 5.25.
J PC ) 2, 11), 133.2 (broad d, J PC ) 11), 132.9 (d, J PC
)
3), 130.8 (d, J PC ) 8), 129.9 (d, J PC ) 12), 129.8 (d, J PC
) 12), 127.6 (dm, J PC ) 50), 125.3 (dm, J PC ) 56), 24.3-
23.9 (m), 23.7 (d, J PC ) 88), 21.1. IR: 3055, 3023, 2960,
2918, 2402 (P-H), 2294, 1603, 1558, 1437, 1259 (OTf),
1223, 1152, 1103, 1030, 853, 750.
[P d (d p p e)(P HMes2)(NCMe)][X] (X ) OTf, BF 4)
(10). Meth od 1. To a solution of 9 (46 mg, 0.05 mmol)
in 1 mL of MeCN was added AgOTf (12 mg, 0.05 mmol),
and the resulting slurry was filtered to give an orange
solution.
Meth od 2. To a slurry of Pd(dppe)Cl2 (41 mg, 0.07
mmol) in 2 mL of MeCN was added AgOTf (37 mg, 0.14
mmol) and PHMes2 (19 mg, 0.07 mmol), and the result-
ing slurry was stirred for 5 min. The reaction mixture
was filtered to give an orange solution.
1H NMR (CD2Cl2): δ 7.70-7.32 (m, 17H, Ar), 7.36-
1
7.29 (m, 2H, Ar), 7.13-6.62 (m, 5H), 6.53 (dd, J PH
)
364, 3J PH ) 12, 1H, P-H), 3.54 (m, 2J HH ) 15, 1H, CH2),
3.49 (m, J HH ) 15, 1H, CH2), 2.64-2.30 (m, 4H, dppe
2
CH2), 2.27 (3H, Me), 2.25 (3H, Me), 1.94 (broad, 6H, Me),
1.92 (3H, Me). 13C{1H} NMR (CD2Cl2): δ 157.3 (m, J PC
) 41, Ar), 143.7, 142.7, 142.1, 141.7, 133.9-133.3 (m,
Ar), 132.8-132.5 (m, Ar), 131.8 (d, J PC ) 13, Ar), 131.2
(m, Ar), 130.8-129.3 (m, Ar), 128.9-127.6 (m, Ar),
122.6, 122.0-121.6 (m), 120.0, 40.6 (d, 2J PC ) 83), 28.9-
28.5 (m, dppe CH2), 23.7-23.3 (m, Me), 22.8-22.4 (m,
Me), 21.2-21.0 (m, Me), 21.1-20.0 (m, Me). IR: 3054,
3023, 2963, 2916, 2865, 2381 (PH), 1603, 1563, 1436,
1266 (OTf), 1223, 1151, 1104, 852, 809, 749, 694, 637.
FAB-MS (3-NBA): 773.1 (M+), 695.1, 587.1, 545.1,
476.0, 427.0.
Meth od 3. To a slurry of Pd(dppe)Cl2 (68 mg, 0.12
mmol) in 3 mL of THF was added AgBF4 (23 mg, 0.12
mmol) in acetonitrile (1 mL) and PHMes2 (32 mg, 0.12
mmol). No visible reaction occurred. The 31P NMR
spectrum of the reaction mixture showed PHMes2 and
a small amount of the product 10. An additional 1.2
equiv of AgBF4 was added to the reaction mixture, the
solid dissolved, and the solution turned orange. The
mixture was filtered, diethyl ether was added, and
cooling to -25 °C gave a pale yellow solid which was
washed with diethyl ether and dried under vacuum. The
31P NMR spectrum of the solid showed the product as
well as a small amount of “Pd(dppe)(BF4)2” (31P{1H}
NMR δ 77) and an unidentified impurity.
[P t (d p p e)(P H (Mes)(CH 2C6H 2Me2))][OTf] (6). In
the air, a 25 mL ampule was charged with a solution of
[Pt(dppe)(Me)(PHMes2)][OTf] (410 mg, 0.40 mmol) in
Cl2HCCHCl2 (6 mL). The ampule was evacuated, and
the solution was heated at 95-100 °C for 4 days. Solvent
was then removed under reduced pressure to give the
crude product as a white solid, which was redissolved
in THF/toluene (1:1) and crystallized by the addition of
diethyl ether and petroleum ether and cooling to -25
°C to give the product as 212 mg (53% yield) of white
solid. Anal. Calcd for C45H46SO3F3P3Pt: C, 53.41; H,
4.58. Found: C, 52.89; H, 4.93.
1H NMR (CD2Cl2): δ 7.84-7.62 (m, 15H), 7.58-7.40
4
1
(m, 5H), 6.84 (d, 4H, J PH ) 4), 5.92 (dd, 1H, J PH
)
386, 3J PH ) 10), 3.38-3.16 (m, 2H, CH2), 2.75-2.50 (m,
2H, CH2), 2.24 (6H, Me), 2.17 (12H, Me), 1.83 (broad,
3H, MeCN). 13C{1H} NMR (CD2Cl2): δ 143.3 (d, J PC
)
3), 142.2 (dd, J PC ) 2, 9), 134.6 (m), 134.0 (d, J PC ) 3),
133.6-132.9 (m), 131.4 (d, J PC ) 9), 131.9-130.6 (m),
130.3 (d, J PC ) 12), 128.6, 125.7 (dm, J PC ) 50), 124.6,
123.9-123.1 (m), 117.6 (dm, J PC ) 51, CN), 32.4 (dd,
1H NMR (CD2Cl2): δ 8.2-6.5 (m, 25H, Ar and PH),
3.8-3.2 (m, 2H, Pt-CH2), 2.8-2.2 (m, 4H, dppe CH2),
2.27 (3H, Me), 2.25 (3H, Me), 1.98 (br, 3H, Me), 1.91
(3H, Me), 1.89 (br, 3H, Me). 13C{1H} NMR (CD2Cl2): δ
157.9-157.6 (m), 144.1, 142.9-142.0 (m), 139.9, 134.2-
134.0 (m), 133.8-133.3 (m), 133.0-132.6 (m), 131.9-
131.7 (m), 131.2 (m), 130.9-130.4 (m), 130.1-129.1 (m),
128.1-127.1 (m), 126.0-125.2 (m), 122.6, 121.4, 120.9,
3
J PC ) 13, 37, CH2), 23.3 (d, J PC ) 9, Me), 22.7 (dd, J PC
) 8, 34, CH2), 21.1 (Me), 2.6 (m, Me). IR: 3058, 2965,
2923, 2319, 2291, 1603, 1558, 1438, 1410, 1380, 1269,
1158, 1104, 1030, 998, 931, 853, 817, 752, 723.
Cr ystallogr aph ic Str u ctu r al Deter m in ation . Crys-
tal data and data collection and refinement parameters
are given in Table 2. No evidence of symmetry higher
than triclinic was observed in the diffraction data of 2
and 5. The centrosymmetric space group option P1h was
chosen for both structures, which yielded chemically
reasonable and computationally stable results of refine-
ment. The palladium atom in structure 2 was located
by Patterson synthesis, and the structure of 5 was
solved by direct methods. Both structures were com-
pleted by subsequent difference Fourier syntheses and
refined by full-matrix least-squares procedures. Empiri-
cal SADABS absorption correction was applied to the
2
1
120.1, 35.5 (d, J PC ) 76, J Pt-C ) 507), 30.5 (dd, J PC
)
16, 34), 29.5 (dd, J PC ) 15, 38), 22.7 (broad), 22.0 (broad),
21.1 (m), 20.2 (m). IR: 3054, 3023, 2964, 2917, 2859,
2390, 1600, 1564, 1436, 1263, 1150, 1104, 1030, 852,
820, 751, 695.
[P d (d p p e)(Cl)(P HMes2)][OTf] (9). To a slurry of
Pd(dppe)Cl2 (89 mg, 0.16 mmol) in 2 mL of THF/MeCN
(10:1) was added AgOTf (40 mg, 0.16 mmol) and
PHMes2 (42 mg, 0.16 mmol), and the reaction mixture
was stirred for 5 min. The solution was filtered, petro-
leum ether was added, and cooling to -30 °C gave the
product as 136 mg (92% yield) of orange solid. Anal.

2890 Organometallics, Vol. 19, No. 15, 2000
Zhuravel et al.
data set of 5. The asymmetric unit of 2 contains one
palladium cation and a tetrafluoroborate anion, and the
asymmetric unit of 5 contains one palladium cation, a
triflate anion, and half of a molecule of toluene which
is disordered over an inversion center. All non-hydrogen
atoms, except C(50) of the disordered toluene molecule
in 5, were refined with anisotropic displacement pa-
rameters. The hydrogen atom on phosphorus in both
structures was located from a difference map, and the
thermal parameters were refined. The hydrogen atoms
of the toluene molecule in 5 were ignored, and the
remaining hydrogen atoms were treated as idealized
contributions. The relatively high R factor of the struc-
ture of 5 may be attributed to the high thermal activity
associated with the triflate counterion and the disor-
dered toluene molecule. All software and sources of the
scattering factors are contained in the SHELXTL (5.10)
program library.30
Ack n ow led gm en t. We thank the NSF Career Pro-
gram, DuPont, and Union Carbide (Innovation Recogni-
tion Award) for support, Dartmouth College for Presi-
dential and Zabriskie Fellowships for N.S.G., and the
Department of Education for a GAANN fellowship for
M.A.Z. The University of Delaware acknowledges the
NSF (Grant CHE-9628768) for their support of the
purchase of the CCD-based diffractometer.
Su p p or tin g In for m a tion Ava ila ble: Details of the crys-
tal structure determinations and additional experimental
information. This material is available free of charge via the
Internet at http://pubs.acs.org.
OM000164O
(30) Sheldrick, G. Siemens XRD, Madison, WI.