Notes
Organometallics, Vol. 19, No. 6, 2000 1203
+
not submitted for elemental analysis because they are a
straightforward extension of the previously reported complexes
5 and 6.
when Pt(PPh3)2(C2H4) reacts with (arene)Mn(CO)3
complexes.9 It is only when there is a good alternative
binding site for the platinum that an analogue of 10 is
not formed. For complexes 5-7 this alternative site is
the olefinic double bond, and the platinum prefers to
bind there rather than at a carbonyl carbon. With 8,
however, the two methyl groups sufficiently inhibit
binding of the platinum to the olefinic site that 10 is
the only product formed.
[{Styr en e‚P t(P P h 3)2}Mn (CO)3]BF4 (9) an d Related Com -
p lexes. Pt(PPh3)2(C2H4) (142 mg, 0.19 mmol) was added to a
suspension of [(styrene)Mn(CO)3]BF4 (5, 57 mg, 0.17 mmol)
in CH2Cl2 (20 mL) at room temperature under nitrogen. An
immediate color change from yellow to orange-red occurred,
and an IR spectrum indicated that the conversion to 9 was
complete within a few minutes. The solution was stirred for 1
h and then concentrated. Upon addition of diethyl ether, [9]-
BF4 precipitated as a yellow powder. Yield: 85% (154 mg). IR
(CH2Cl2): νCO 2062 (s), 2003 (s, br) cm-1. 1H NMR (CD2Cl2): δ
7.6-6.9 (m, 30H), 6.36 (m, 1H), 5.57 (m, 2H), 5.12 (d, J ) 7
Hz, 1H), 4.27 (m, 1H), 3.33 (d, J ) 9 Hz, 1H), 2.58 (m, 1H),
2.03 (m, 1H). 31P NMR (CD2Cl2): δ 28.17 (dd, J P-P ) 23 Hz,
J P-Pt ) 3510 Hz), 27.17 (dd, J P-P ) 23 Hz, J P-Pt ) 4250 Hz).
Anal. Calcd for
C47H38O3P2MnPtBF4: C, 53.78; H, 3.65.
Found: C, 53.60; H, 3.44.
In conclusion, it has been demonstrated that η6-
coordination of Mn(CO)3+ to the arene ring in styrenes
greatly facilitates η2-binding of the olefinic double bond
to Pt(PPh3)2. These results may be of relevance to the
hydroprocessing of unsaturated heterocycles such as
benzothiophenes and benzofurans, for which it is thought
that η2-bonding may precede hydrogenation and/or
insertion reactions.
Coordination of Pt(PPh3)2 to complexes 6 and 7 was ac-
complished by the same procedure. For [{R-methylstyrene‚Pt-
(PPh3)2}Mn(CO)3]BF4: yield 92%. IR (CH2Cl2): νCO 2056 (s),
1993 (s, br) cm-1. 1H NMR (CD2Cl2): δ 7.5-6.9 (m, 30H), 6.25
(t, J ) 6 Hz, 1H), 5.56 (t, J ) 6 Hz, 1H), 5.47 (t, J ) 6 Hz,
1H), 4.91 (d, J ) 7 Hz, 1H), 4.25 (d, J ) 6 Hz, 1H), 2.52 (m,
1H), 2.02 (m, 1H), 1.75 (Me). 31P NMR (CD2Cl2): δ 28.29 (dd,
J P-P ) 19 Hz, J P-Pt ) 3650 Hz), 25.45 (dd, J P-P ) 19 Hz, J P-Pt
) 4110 Hz). For [{cis-R-methylstyrene‚Pt(PPh3)2}Mn(CO)3]-
BF4: yield 84%. IR (CH2Cl2): νCO 2061 (s), 1999 (s, br) cm-1
.
Exp er im en ta l Section
1H NMR (CD2Cl2): δ 7.5-7.0 (m, 30H), 6.40 (m, 1H), 6.25 (m,
1H), 5.61 (d, J ) 5 Hz, 1H), 5.49 (m, 1H), 5.41 (m, 1H), 4.46
(m, 1H), 1.89 (d, J ) 6 Hz, 1H), 1.17 (Me). 31P NMR (CD2Cl2):
Ma t er ia ls. All synthetic procedures were done under
nitrogen. Styrenes were purchased from commercial sources
and used without further purification. Solvents were HPLC
grade and were opened only under nitrogen. Pt(PPh3)2(C2H4)
was prepared by a literature method.10 1H and 31P NMR
spectra were recorded on a Bruker 400 MHz instrument; 31P
chemical shifts are relative to 85% phosphoric acid external
reference.
Styr en e Com p lexes [5-8]BF 4. The styrene and R-meth-
ylstyrene complexes 5 and 6 have been previously reported
and characterized.11 We synthesized 5-8 by two general
methods, the first of which is a slightly modified version of
that reported by Chung et al.11
Meth od 1. Mn(CO)5Br (1.0 g) and AgBF4 (1.1 equiv) were
dissolved in CH2Cl2 (40 mL) and refluxed for 30 min with the
exclusion of light. The desired styrene (3 equiv) in CH2Cl2 (10
mL) was then added and the reaction mixture refluxed
overnight. After cooling to room temperature, the solution was
filtered through Celite and concentrated to ca. 10 mL. Diethyl
ether was then added to precipitate [5-8]BF4 as a yellow
powder in yields in the range 70-85%.
δ 29.28 (dd, J P-P ) 28 Hz, J P-Pt ) 3950 Hz), 28.69 (dd, J P-P
27 Hz, J P-Pt ) 3770 Hz). Anal. Calcd for C48H40O3P2-
MnPtBF4: C, 54.20; H, 3.79. Found: C, 54.17; H, 3.42.
)
Coordination of Pt(PPh3)2 to free styrene was followed by
31P NMR. Upon addition of a 10-fold excess of styrene to Pt-
(PPh3)2(C2H4) (30 mg) in CD2Cl2 (3 mL, 5 mm NMR tube, N2),
the 31P resonance shifted from δ 36.14 (d, J P-Pt ) 3720 Hz) to
new resonances at δ 34.30 (dd, J P-P ) 55 Hz, J P-Pt ) 3790
Hz), 32.22 (dd, J P-P ) 55 Hz, J P-Pt ) 3730 Hz), which are
assigned to Pt(PPh3)2(styrene). With 1 equiv of styrene, the
reaction proceeded about 50% to completion within several
minutes, with no change occurring for 1 h thereafter. Similar
experiments with R-methylstyrene and cis-â-methylstyrene
showed no reaction over a period of several hours.
Ad d ition of P t(P P h 3)2(C2H4) to [8]BF 4 To Gen er a te 10.
To [8]BF4 (40 mg) in CH2Cl2 (10 mL) was added Pt(PPh3)2-
(C2H4) (1.1 equiv) at room temperature. An immediate color
change from yellow to red occurred, and IR analysis indicated
complete and clean conversion to [10]BF4. All attempts to
isolate [10]BF4 led to its reversion to starting cation, [8]BF4.
In situ characterization of [10]BF4: IR (CH2Cl2): νCO 1983 (s),
Meth od 2. [(Acenaphthene)Mn(CO)3]BF4 (0.20 g), prepared
by method 1 as previously reported,12 was combined with the
desired styrene (4 equiv in 15 mL of CH2Cl2) in a pressure
tube and heated to 70 °C for 3 h. After cooling to room
temperature, the solution was concentrated and the product
precipitated with diethyl ether. The yields ranged from 75 to
94%.
1783 (s) cm-1 31P NMR (CD2Cl2): δ 33.64 (d, J P-Pt ) 4000 Hz),
.
28.69 (dd, J P-P ) 27 Hz, J P-Pt ) 3770 Hz).
Cr ysta l Str u ctu r e of [{Styr en e‚P t(P P h 3)2}Mn (CO)3]-
BF 4 (9). A single crystal of [9]BF4, grown by vapor diffusion
of diethyl ether into a CH2Cl2 solution at room temperature,
was mounted on a glass fiber. X-ray data collection was carried
out using a Siemens P4 diffractometer equipped with a CCD
area detector and controlled by SMART version 5 software.
Data reduction was carried out by SAINT version 5 software
and by SADABS and included profile analysis and an empirical
absorption correction. The structure was determined by direct
methods and refined on F2 using the SHELXTL PC version 5
package. Only half of the expected 38 hydrogen atoms ap-
peared in a difference map because the scattering was domi-
nated by the heavier atoms. Each hydrogen was introduced
in an ideal position, riding on the atom to which it is bonded;
each was refined with an isotropic temperature factor 20%
For [7]BF4: IR (CH2Cl2): νCO 2081 (s), 2023 (s, br) cm-1. 1H
NMR (CD2Cl2): δ 6.75 (t, J ) 6 Hz, 2H), 6.41 (m 4H), 6.20 (d,
J ) 11 Hz, 1H), 2.07 (d, J ) 7 Hz, Me). For [8]BF4: IR (CH2-
1
Cl2): νCO 2079 (s), 2022 (s, br) cm-1. H NMR (CD3COCD3): δ
6.99 (t, J ) 6 Hz, 2H), 6.71 (d, J ) 6 Hz, 2H0, 6.61 (t, J ) 6
Hz, 1H), 6.26 (s, 1H), 1.99 (s, 2Me). Complexes 7 and 8 were
(9) Watson, E. J ., Li, H., Sweigart, D. A. Unpublished results.
(10) Nagel, U. Chem. Ber. 1982, 115, 1998.
(11) Son, S. U.; Lee, S. S.; Chung, Y. K. J . Am. Chem. Soc. 1997,
119, 7715.
(12) Sun, S.; Yeung, L. K.; Sweigart, D. A.; Lee, T.-Y.; Lee, S. S.;
Chung, Y. K.; Switzer, S. R.; Pike, R. D. Organometallics 1995, 14,
2613.