Platinum-molybdenum complexes of cyclic tropynes, cumulenes, and alkynes

Article abstract of DOI:10.1021/om950732d

The bis(triphenylphosphine)platinum complexes of tropyne (1), cyclohepta-3,5-dien-1-yne (12), and cyclohepta-1,5-dien-3-yne (13) react rapidly with (η⁶-p-xylene)Mo(CO)₃ in a mixture of CD₂Cl₂ and THF-d₈ to give the bimetallic complexes 4-6. Reduction of 4 with LiAl(O-t-Bu)₃H or KBEt₃H gives a mixture of 5-7 (essentially quantitative) in a ratio of 5:10:85 and 8:21:71, respectively. The major isomer contains a 1,2,3,5-cycloheptatetraene ring, a ring system that has previously been inaccessible either free or complexed to a transition metal. Hydride abstraction from 5, 6, or 7 regenerates 4. X-ray crystal structures for 5 and 7 are reported. The absolute configuration of complex 7 in the crystal was determined.

Full text of DOI:10.1021/om950732d

596
Organometallics 1996, 15, 596-603
P la tin u m -Molybd en u m Com p lexes of Cyclic Tr op yn es,
Cu m u len es, a n d Alk yn es
J erzy Klosin, Khalil A. Abboud, and W. M. J ones*
Department of Chemistry, University of Florida, Gainesville, Florida 32611
Received September 14, 1995X
The bis(triphenylphosphine)platinum complexes of tropyne (1), cyclohepta-3,5-dien-1-yne
(12), and cyclohepta-1,5-dien-3-yne (13) react rapidly with (η6-p-xylene)Mo(CO)3 in a mixture
of CD2Cl2 and THF-d8 to give the bimetallic complexes 4-6. Reduction of 4 with LiAl(O-
t-Bu)3H or KBEt3H gives a mixture of 5-7 (essentially quantitative) in a ratio of 5:10:85
and 8:21:71, respectively. The major isomer contains a 1,2,3,5-cycloheptatetraene ring, a
ring system that has previously been inaccessible either free or complexed to a transition
metal. Hydride abstraction from 5, 6, or 7 regenerates 4. X-ray crystal structures for 5
and 7 are reported. The absolute configuration of complex 7 in the crystal was determined.
In tr od u ction
attach the Mo(CO)3 fragment to the tropyne ring in 1.
Indeed, reaction of the tropyne complex 1 with 1 equiv
of (η6-p-xylene)Mo(CO)3 at room temperature in a
mixture of CD2Cl2 and THF-d8 led to an essentially
instantaneous color change from red to brown-red.
Comparison of the NMR spectra of this solution with
the tropyne complex synthesized more conveniently by
hydride abstraction from a mixture of 5 and 6 (vide
infra) confirmed the essentially quantitative yield of 4
(Scheme 1). Unfortunately, we were unable to grow
crystals of this red-brown solid that were suitable for
X-ray diffraction. However, the bimetallic complex was
completely characterized by multinuclear NMR spec-
In contrast to benzyne1 and its transition metal
complexes,2 which have been studied extensively, to date
published information about tropyne, benzyne’s next
higher homologue, has been limited to platinum3 (1)
and zirconium4 (2) complexes of the parent and one
1
troscopy, IR, and HRMS. In the H NMR, in addition
platinum complex of a dibenzannelated analog (3).5 As
a continuation of our work on the chemistry of 1, and
its cycloheptadienyne precursors 12 and 13, we have
now prepared their Mo(CO)3 bimetallic complexes (4-
6) and have made the surprising discovery that reduc-
tion of the tropyne complex gives a good yield of a new
C7H6 ring system.
to PPh3 signals three different resonances are displayed
in the range δ 5.55-6.1 ppm with the one at δ 5.55 ppm
showing coupling to the 195Pt nucleus. The multiplicity
of these three signals is the same as that of 1 but each
is shifted ca. 3 ppm upfield from 1. Both the 19F{1H}
and the 31P{1H} NMR show singlets whereas the 195Pt-
{1H} NMR exhibits a triplet centered at δ -4087.6 ppm.
The chemical shift of the 195Pt nucleus is 308 ppm
upfield from the corresponding resonance for complex
1. The IR spectrum displays two very strong bands
(2036, 1976 cm-1) in the metal carbonyl region. These
stretching frequencies are ca. 40 cm-1 lower than those
of the Mo(CO)3 complex of the tropylium cation which
is consistent with a somewhat more electron-rich tro-
pyne ring in the former [from electron donation from
bis(triphenylphosphine)platinum]. The carbonyl region
in the 13C NMR shows only one peak, even at -100 °C,
indicating a very low barrier for rotation of the molyb-
denum tricarbonyl around the molybdenum-seven-
membered-ring axis.
Hyd r id e Red u ction of (P P h 3)2P t{η2[(η7-C7H5)Mo-
(CO)3]} (4). Reduction of 4 with either KBEt3H or LiAl-
(O-t-Bu)3H was noticeably cleaner (as shown by the 31P
NMR) than the corresponding reactions with 1 or 2,
giving a mixture in which 7 is the major product (5:6:7
) 5:10:85 for LiAl(Ot-Bu)3H and 8:21:71 for KBEt3H)
(Scheme 2). Selective formation of 7 from hydride
addition to the tropyne carbon indicated by arrow b was
not only unexpected but was of particular interest
because the resulting 1,2,3,5-cycloheptatetraene ring in
Resu lts a n d Discu ssion
P r ep a r a tion of 4 by Tr op yn e-Ar en e Exch a n ge.
It has been found6 that reaction of [Mo(η7-C7H7)(η6-
C6H6)]+ with nucleophilic ligands leads to displacement
of benzene leaving the tropylium ligand intact. This
suggests that the tropylium ion may be bonded to
molybdenum more strongly than arenes. Since tropyne
can be regarded as a substituted tropylium ion and since
the aromatic ring can be readily displaced7 in (η6-arene)-
Mo(CO)3 by more basic arenes, it occurred to us that it
might be possible to use an arene exchange reaction to
X Abstract published in Advance ACS Abstracts, December 1, 1995.
(1) Hoffmann, R. Q. Dehydrobenzene and Cycloalkynes; Verlag
Chemie: Weinheim, Germany, 1967.
(2) Bennett, M. A.; Schwemlein, H. P. Angew. Chem., Int. Ed. Engl.
1989, 28, 1320.
(3) Lu, Z.; Abboud, K. A.; J ones, W. M. J . Am. Chem. Soc. 1992,
114, 10991.
(4) Lu, Z.; J ones, W. M. Organometallics 1994, 13, 1539.
(5) Klosin, J .; Abboud, K. A.; J ones, W. M. Organometallics 1995,
14, 2892.
(6) Ashworth, E. F.; Green, J . C.; Green, M. L. H.; Knight, J .; Pardy,
R. B. A. J . Chem. Soc., Dalton Trans. 1977, 1693.
(7) Muetterties, E. L.; Bleeke, J . R.; Sievert, A. L. J . Organomet.
Chem. 1979, 178, 197.
0276-7333/96/2315-0596$12.00/0 © 1996 American Chemical Society

Pt-Mo Complexes
Organometallics, Vol. 15, No. 2, 1996 597
Sch em e 1
F igu r e 1. Structure and labeling scheme for 7 with 40%
probability of thermal ellipsoids. Triphenylphosphine
phenyl rings are omitted for clarity.
Sch em e 3
Sch em e 2
7 has not been previously reported; to date the only
recorded butatriene confined to a seven-membered ring
is 9,8 which was prepared by desilabromination of 8 with
KF followed by isomerization.
H1. The remaining signals in the spectrum were
assigned on the basis of a 2D COSY experiment. The
195Pt{1H} and 31P{1H} NMR appeared as doublets of
1
doublets centered at δ -4420.2 (dd, J Pt-P′ ) 3124 Hz,
1J Pt-P′′ ) 3282.5 Hz) and a pair of doublets at δ 23.81,
2
23.55 (d, J P′-P′′ ) 9.2 Hz), respectively, which is
consistent with the C1 symmetry for 7. The 13C{1H}
NMR exhibited a broad singlet in the carbonyl region
which decoalesced at -35 °C to three resonances of
equal intensity. This observation indicates that the
molecule is fluxional and that the origin of this process
is a rapid spinning of the Mo(CO)3 fragment around the
metal-seven-membered-ring axis. The IR spectrum
showed three very strong peaks in the carbonyl region
Attempts to prepare a platinum complex of 1,2,3,5-
cycloheptatetraene (11) by â-elimination had yielded
only 12,9 13,9 and 1410 (Scheme 3).
The cumulene complex crystallized from the reaction
1
mixture to give red crystals in 42% yield. Its H NMR
with stretching frequencies (1947, 1870.8, 1847 cm-1
lower than 15 (1970, 1908, 1856 cm-1 11
and interest-
)
showed six different resonances with two showing
coupling to the 195Pt nucleus. One of these signals (at
δ 3.85) showed coupling to one of the methylene protons
and was therefore assigned to H4. Consequently the
other signal coupled to 195Pt at δ 5.84 was assigned to
)
ingly even lower (ca. 10 cm-1) then 5 (see below). The
structure of 7 was further confirmed by hydride ab-
straction to regenerate 4 and by an X-ray diffraction
study. The two minor reduction products 5 and 6 which
were formed as a result of hydride addition to the
tropyne carbons indicated by arrows a (5) and c (6)
(8) Zoch, H.-G.; Szeimies, G.; Romer, R.; Schmitt, R. Angew. Chem.,
Int. Ed. Engl. 1981, 20, 877.
(9) Lu, Z.; Abboud, K. A.; J ones, W. M. Organometallics 1993, 12,
1471.
(10) Winchester, W. R.; Gawron, M.; Palenik, G. J .; J ones, W. M.
Organometallics 1985, 4, 1894.
(11) The IR spectrum of (C7H8)Mo(CO)3 was measured in our
laboratory under the same condition as those of other complexes.

598 Organometallics, Vol. 15, No. 2, 1996
Klosin et al.
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for Com p lex 7
Sch em e 4
Pt-P1
2.287(5)
2.084(13)
1.80(2)
1.84(2)
1.75(2)
2.36(2)
2.33(2)
2.45(2)
1.98(2)
2.05(3)
1.33(2)
1.42(3)
1.58(4)
Pt-P2
2.293(6)
2.01(2)
1.84(2)
1.81(2)
1.82(2)
2.38(2)
2.40(3)
2.50(2)
2.03(3)
1.30(3)
1.39(3)
1.28(4)
1.52(3)
Pt-C1
Pt-C2
P1-C51
P1-C71
P2-C31
Mo-C1
Mo-C3
Mo-C5
Mo-C8
Mo-C10
C1-C7
C3-C4
C5-C6
P1-C61
P2-C21
P2-C41
Mo-C2
Mo-C4
Mo-C7
Mo-C9
C1-C2
C2-C3
C4-C5
C6-C7
P1-Pt-P2
P2-Pt-C1
C1-Pt-C2
C2-C1-C7
C3-C2-Pt
C4-C3-C2
C6-C5-C4
C1-C7-C6
Mo-C9-O2
106.7(2)
111.0(7)
37.0(9)
139.(2)
152.(2)
125.(2)
128.(2)
110.(2)
178.(2)
P1-Pt-C1
P2-Pt-C2
C2-Pt-P1
C2-C1-Pt
C3-C2-C1
C5-C4-C3
C7-C6-C5
Mo-C8-O1
Mo-C10-O3
141.3(8)
148.0(5)
105.0(5)
68.4(9)
130.(2)
125.(3)
115.(2)
176.(2)
179.(2)
the least-squares plane is 0.08(3) Å for C3) whereas C6
is 0.68(3) Å above this plane. The dihedral angle
between the planes defined by C7-C6-C5 and C7-C1-
C2-C3-C4-C5 is equal to 127(2) °C. This value is in
the normal range for molybdenum cycloheptatriene
complexes.12 A bond length analysis could not be made
due to low data quality. Unfortunately all attempts to
get better data sets were unsuccessful.
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for Com p lex 5
Pt-P1
Pt-C1
2.275(2)
2.033(10)
1.818(9)
1.826(8)
1.824(90
2.453(10)
2.379(10)
2.35(2)
1.950(14)
2.008(11)
1.524(15)
1.39(2)
Pt-P2
Pt-C2
2.297(2)
2.025(10)
1.836(8)
1.829(9)
1.847(9)
2.364(9)
2.359(13)
2.466(14)
1.945(12)
1.292(14)
1.422(14)
1.40(2)
P r ep a r a tion of 5 a n d 6 by Ar en e Exch a n ge.
Complexes 12 and 13 can be viewed as substituted
cycloheptatrienes, and since cycloheptatriene is known
to bind to the Mo(CO)3 fragment more strongly than
arenes (by ca. 7 kcal/mol),13 it should be possible to use
an arene exchange reaction to attach the Mo(CO)3
moiety to the seven-membered ring in 12 and 13
(Scheme 4). Indeed, addition of THF-d8 to a mixture of
equivalent amounts of 12, 13 (6:1), and (η6-p-xylene)-
Mo(CO)3 in an NMR tube led to a rapid color change
P1-C51
P1-C71
P2-C31
Mo-C1
Mo-C3
Mo-C5
Mo-C8
Mo-C10
C1-C7
C3-C4
C5-C6
P1-C61
P2-C21
P2-C41
Mo-C2
Mo-C4
Mo-C6
Mo-C9
C1-C2
C2-C3
C4-C5
C6-C7
1.36(3)
1.50(2)
P1-Pt-P2
P2-Pt-C1
C1-Pt-C2
C2-C1-C7
C3-C2-Pt
C4-C3-C2
C6-C5-C4
C1-C7-C6
Mo-C9-C2
102.42(8)
114.4(3)
37.1(4)
133.9(11)
152.0(8)
121.6(11)
134.(2)
P1-Pt-C1
P2-Pt-C2
C2-Pt-P1
C2-C1-Pt
C3-C2-C1
C5-C4-C3
C7-C6-C5
Mo-C8-O1
Mo-C10-C3
143.2(3)
151.2(3)
106.2(3)
71.1(6)
134.2(10)
127.1(14)
129.7(14)
177.1(10)
176.9(8)
1
from yellow to deep red. After 15 min, analysis by H
and 31P NMR showed total disappearance of starting
materials and formation of 5 and 6 (65% isolated yield
from benzene/hexane) in a 6:1 ratio which was the same
as that of 12 to 13. In addition to the PPh3 signals, the
1H NMR of 5 (the major isomer) exhbited six different
proton resonances two of which (at δ 5.4 and 2.4 ppm)
showed coupling to the 195Pt nucleus. The peak at δ
5.4 ppm is assigned to the vinyl proton H1 while the
peak at δ 2.4 ppm is assigned to the methylene proton
Hd. The minor isomer 6 shows four peaks with only
one (at δ 4.5 ppm) coupled to the 195Pt nucleus. The
peak at δ 4.5 is therefore assigned to H1′. The remain-
ing signals in the spectrum of 5 and 6 are assigned
based on a 2D COSY experiment. The proton reso-
nances of both 5 and 6 are shifted upfield relative to 12
and 13. The 195Pt{1H} NMR of the mixture of 5 and 6
shows a doublet of doublets centered at δ -4480.4
(1J Pt-P′ ) 3326.4 Hz, 1J Pt-P′′ ) 3418 Hz) and a triplet at
δ -4449 (1J Pt-P ) 3323 Hz) as expected for complexes
with C1 (5) and Cs (6) symmetry, respectively.
107.8(10)
175.7(11)
(Scheme 2) were identified by comparison with authen-
tic samples synthesized as described below.
Cr ysta l Str u ctu r e of (P P h 3)2P t[η2(η6-C7H6)Mo-
(CO)3] (7). Suitable crystals for X-ray diffraction
analysis were obtained from a mixture of benzene and
hexane at -16 °C. A thermal ellipsoid drawing of 7 is
presented in Figure 1, while crystal data are included
in Table 3. Selected bond distances and angles and final
fractional atomic coordinates are provided in Tables 1
and 4, respectively. Complex 7 crystallized in mono-
clinic, noncentrosymmetric space group P21 with one
molecule of benzene located in the general position.
Complex 7 is chiral, and since it crystallized in a
noncentrosymmetric space group, only one enantiomer
can be present in the crystal. By refining both enan-
tiomers with the same data set and comparing the
refinement results, we were able to determine the
absolute configuration of the complex in the crystal (for
more information see the Experimental Section). The
geometry around the Pt atom is square planar. The
platinum atom is bonded to two phosphorus and two
carbon atoms. Six carbon atoms belonging to the seven-
membered ring are coplanar (maximum deviation from
(12) (a) Dunitz, J . D.; Pauling, P. Helv. Chim. Acta 1960, 43, 2188.
(b) Chen, J .; Yin, J .; Lei, G.; Xu, W.; Shao, M.; Zhang, Z.; Tang, Y. J .
Organomet. Chem. 1987, 329, 69. (c) Adams, H.; Bailey, N. A.; Willett,
D. G.; Winter, M. J . J . Organomet. Chem. 1987, 333, 61. (d) Wieser,
M.; Sunkel, K.; Robl, C.; Beck, W. Chem. Ber. 1992, 125, 1369. (e)
Breimair, J .; Weidmann, T.; Wagner, B.; Beck, W. Chem. Ber. 1991,
124, 2431.
(13) Nolan, S. P.; de la Vega, R. L.; Hoff, C. D. Organometallics 1986,
5, 2529.

Pt-Mo Complexes
Organometallics, Vol. 15, No. 2, 1996 599
F igu r e 2. 195Pt{1H} and 31P{1H} spectra of a mixture of complexes 5 and 6.
Ta ble 3. Cr ysta llogr a p h ic Da ta
5
7
A. Crystal Data (298 K)
a, Å
b, Å
c, Å
11.909(2)
29.260(3)
12.033(2)
90.06(1)
4193(1)
1.630
9.500(2)
20.346(4)
13.710(4)
110.20(2)
2487(1)
â, deg
V, Å3
d
calc, g cm-3 (298 K)
1.426
empirical formula
fw
C
46H36O3P2MoPt‚1/2C6H6
C46H36O3P2MoPt‚C6H6
423.11
1028.77
cryst system
space group
F(000), electrons
cryst size, mm3
monoclinic
P21/n
2028
0.32 × 0.23 × 0.1
monoclinic
P21
1056
0.21 × 0.15 × 0.11
B. Data Collection (298 K)
Mo KR (0.710 73)
ω-scan
radiation (λ, Å)
mode
scan range
background
scan rate, deg min-1
2θ range, deg
range of hkl
symmetrically over 1.2° about KR1,2 max
offset 1.0 and -1.0 in ω from KR1,2 max
3-6
3-50
3-6
3-55
-1 e h e 12
-4 e k e 26
-17 e l e 17
8412
7152
3.16
0.514, 0.723
0 e h e 14
0 e k e 34
-14 e l e 14
7933
7377
3.75
tot. reflcns measd
unique reflcns
abs coeff µ(Mo KR), mm-1
min, max transm
0.404, 0.722
C. Structure Refinement
S, goodness-of-fit
reflcns used
1.2
1.45
4229, I > 2.5σ(I)
527
5.49, 5.67
2.34
4330, I > 3σ(I)
505
3.81, 4.03
1.7
no. of variables
R, wR,a
%
R
int, %
max shift/esd
0.002
-1.2
1.1
0.031
-1
2.2
min peak in diff Fourier map, e Å-3
max peak in diff Fourier map, e Å-3
a
Relevant expressions are as follows, where Fo and Fc represent, respectively, the observed and calculated structure-factor amplitudes.
Function minimized was w(|Fo| - |Fc|)2, where w ) (σ(F))-2. R ) ∑(||Fo| - |Fc||/∑|Fo|, wR ) [∑w(|Fo| - |Fc|)2/∑|Fo| ]1/2, and S ) [∑w(|Fo|
2
- |Fc|)2/(m - n)]1/2
.
The 31P{1H} NMR of 5 and 6 is also consistent with
ature 13C{1H} NMR spectrum of 5 and 6 does not exhibit
the proposed structures (Figure 2). The room-temper-
any signals in the carbonyl region. The spectrum

600 Organometallics, Vol. 15, No. 2, 1996
Klosin et al.
Ta ble 4. F r a ction a l Coor d in a tes a n d Equ iva len t
Isotr op ica Th er m a l P a r a m eter s (Å2) for th e Non -H
Atom s of Com p lex 7 w ith Solven t Coor d in a tes Not
In clu d ed
Sch em e 5
atom
x
y
z
U
Pt
Mo
P1
P2
O1
O2
O3
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
C21
C22
C23
C24
C25
C26
C31
C32
C33
C34
C35
C36
C41
C42
C43
C44
C45
C46
C51
C52
C53
C54
C55
C56
C61
C62
C63
C64
C65
C66
C71
C72
C73
C74
C75
C76
0.94281(7)
0.9845(2)
0.7398(6)
1.0082(6)
0.813(2)
0.705(2)
1.139(2)
1.103(2)
0.993(2)
0.947(3)
1.030(3)
1.158(3)
1.276(3)
1.221(2)
0.877(2)
0.802(2)
1.086(3)
1.191(2)
1.307(3)
1.447(4)
1.466(3)
1.356(3)
1.220(2)
0.894(3)
0.955(4)
0.848(4)
0.704(3)
0.646(3)
0.741(3)
1.019(2)
0.972(3)
0.963(3)
1.018(3)
1.076(3)
1.073(2)
0.801(3)
0.929(3)
0.990(4)
0.904(4)
0.775(3)
0.720(3)
0.621(2)
0.673(2)
0.590(3)
0.455(3)
0.403(2)
0.486(2)
0.602(2)
0.518(3)
0.417(4)
0.386(3)
0.466(2)
0.576(2)
0.0
0.98550(4)
1.25039(12)
0.8739(4)
0.8899(4)
1.1063(12)
1.3211(14)
1.4207(11)
1.1338(11)
1.1208(12)
1.194(2)
1.302(2)
1.347(2)
1.296(2)
1.2105(13)
1.156(2)
1.295(2)
1.363(2)
0.959(2)
0.919(2)
0.970(2)
1.063(2)
1.104(2)
1.056(2)
0.856(2)
0.858(2)
0.821(3)
0.794(2)
0.797(2)
0.823(2)
0.769(2)
0.675(2)
0.580(2)
0.586(2)
0.672(2)
0.769(2)
0.837(2)
0.899(2)
0.868(2)
0.780(2)
0.713(2)
0.745(2)
0.7501(13)
0.6657(12)
0.582(2)
0.573(2)
0.655(2)
0.7444(14)
0.9354(14)
0.914(2)
0.965(3)
1.023(2)
1.044(2)
0.9999(12)
0.0384(2)
0.0516(7)
0.046(2)
0.045(2)
0.075(7)
0.112(10)
0.095(9)
0.048(7)
0.043(8)
0.056(10)
0.065(11)
0.088(14)
0.097(12)
0.066(10)
0.047(10)
0.069(10)
0.076(14)
0.057(9)
0.066(11)
0.09(2)
0.078(12)
0.102(14)
0.069(10)
0.049(11)
0.09(2)
0.14(3)
0.090(14)
0.10(2)
0.066(12)
0.048(9)
0.074(11)
0.11(2)
0.11(2)
0.11(2)
0.055(10)
0.045(10)
0.077(14)
0.083(14)
0.077(14)
0.089(13)
0.059(10)
0.055(9)
0.067(10)
0.087(13)
0.086(12)
0.082(11)
0.078(11)
0.053(9)
0.085(13)
0.09(2)
-0.02742(12)
0.0540(3)
-0.0791(3)
-0.1403(8)
-0.0293(10)
-0.1319(8)
0.008(2)
seven-membered ring in 5 is more electron rich than
cycloheptatriene itself.14
0.0487(9)
0.0814(11)
0.0856(13)
0.0582(15)
0.0361(14)
-0.0154(12)
-0.0986(12)
-0.0277(12)
-0.0956(14)
-0.1139(10)
-0.1169(12)
-0.144(2)
To test this suggestion, a mixture of 12 and 13 (6:1;
total 1 equiv) was added to 2 equiv of 15 in CD2Cl2 in
an NMR tube at room temperature and formation of 5
1
and 6 was monitored by H and 31P NMR (Scheme 5).
Within experimental detection, both platinum com-
plexes showed complete conversion to the corresponding
Mo(CO)3 complexes, although at different rates. Reac-
tion of 5 was complete within 12 h whereas the minor
isomer required 4 days. The reason for this reactivity
difference is not clear. In a control experiment (Scheme
5) 1 equiv of 5, 6 was mixed with 3 equiv of cyclohep-
tatriene and monitored as above. As expected, no
reaction was observed even after 1 week at room
temperature.
-0.1720(13)
-0.1727(14)
-0.1435(12)
-0.1488(11)
-0.211(2)
-0.265(2)
-0.2584(14)
-0.2000(14)
-0.1456(13)
-0.0473(10)
-0.0812(14)
-0.059(2)
The fact that the Mo(CO)3 moiety transfers from 15
to 12, 13 and that the equilibrium lies, within detection,
exclusively toward the more sterically hindered reagents
is clear evidence of the greater basicity of the cyclohep-
tadienyne ring in the bis(triphenylphosphine)platinum
complexes when compared with cycloheptatriene. Com-
plexes 5, 6 reacted rapidly with triphenylcarbenium
tetrafluoroborate in CD2Cl2 at room temperature to give
4 in high yield (90%, confirmed by 31P{1H} and 1H
NMR). In fact hydride abstraction from 5 and 6 is the
superior way to prepare 4. The structure of the major
cycloheptadienyne complex (5) was confirmed by X-ray.
Cr ysta l Str u ctu r e of (P P h 3)2P t[η2(η6-C7H6)Mo-
(CO)3] (5). A deep red crystal suitable for X-ray
diffraction study was obtained from a mixture of hexane
and benzene at 4 °C. A thermal ellipsoid drawing of 5
is depicted in Figure 3, while crystal data are listed in
Table 3. Selected bond distances and angles and final
fractional atomic coordinates are provided in Tables 2
and 5, respectively. Complex 5 crystallized in mono-
clinic, centrosymmetric space group P21/n. The geom-
etry around the Pt atom is square planar with the Pt
atom coordinated to two P atoms and two carbon atoms
belonging to the seven-membered ring. The C1-C2
distance is 1.292(14) Å and is comparable to other
platinum cycloalkyne complexes.15 Six carbons (C1-
C6) of the seven-membered ring are almost coplanar
(maximum deviation from the least-squares plane is
0.02(1) Å for C4) whereas the C7 is 0.44(1) Å above this
plane. The dihedral angle between planes defined by
C1-C2-C3-C4-C5-C6 and C1-C7-C6 is 150(1)°.
This angle is significantly larger than the corresponding
angle (128 and 138°)12 in any other reported molybde-
num cycloheptatriene complexes. It is thought that the
reason for this difference lies in the hybridization at C1
0.004(3)
0.0449(15)
0.0162(9)
0.1310(11)
0.1606(13)
0.2200(12)
0.2498(15)
0.2253(13)
0.1643(11)
0.0180(10)
0.012(2)
-0.0189(14)
-0.0505(14)
-0.0440(12)
-0.009(2)
0.0756(10)
0.1319(14)
0.145(2)
0.098(2)
0.0421(13)
0.0303(12)
0.090(14)
0.072(11)
0.063(9)
obtained at -20 °C, however, reveals three carbonyl
signals of equal intensity that are assigned to the major
isomer 5. This observation is explained as in the case
of 7 as due to rapid rotation of the molybdenum
tricarbonyl moiety around the axis perpendicular to the
seven-membered ring.
The IR spectrum of the mixture of 5 and 6 shows a
medium-size absorption at 1610 cm-1 which is assigned
to the triple bond coordinated to the metal center in 5.
The same absorption in 129 is at 1710 cm-1, which
indicates that coordination of molybdenum to 12 causes
a decrease in the bond order of the triple bond. The IR
spectrum also shows three very strong bands (1956.7,
1886.8, 1845.7 cm-1) in the metal carbonyl region.
Interestingly, these carbonyl stretches have lower fre-
quencies (ca. 15 cm-1) than those of tricarbonylmolyb-
denum cycloheptatriene (15), which suggests that the
(14) Cotton, F. A.; Wilkinson, G. Advanced Inorganic Chemistry;
J ohn Wiley & Sons: New York, 1988; p 60.
(15) Robertson, G. B.; Whimp, P. O. J . Am. Chem. Soc. 1975, 97,
1051.

Pt-Mo Complexes
Organometallics, Vol. 15, No. 2, 1996 601
Ta ble 5. F r a ction a l Coor d in a tes a n d Equ iva len t
Isotr op ica Th er m a l P a r a m eter s (Å2) for th e Non -H
Atom s of Com p lex 5 w ith Solven t Coor d in a tes Not
In clu d ed
atom
x
y
z
U
Pt
Mo
P1
P2
O1
O2
O3
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
C21
C22
C23
C24
C25
C26
C31
C32
C33
C34
C35
C36
C41
C42
C43
C44
C45
C46
C51
C52
C53
C54
C55
C56
C61
C62
C63
C64
C65
C66
C71
C72
C73
C74
C75
C76
0.02666(3)
-0.12729(9)
-0.0100(2)
0.2192(2)
0.103410(10)
0.08044(3)
0.17023(7)
0.09954(8)
0.0571(3)
0.0938(3)
0.1858(3)
0.0497(3)
0.0797(3)
0.0862(4)
0.0560(6)
0.0178(5)
-0.0018(5)
0.0008(4)
0.0669(4)
0.0876(4)
0.1482(4)
0.1293(3)
0.1441(3)
0.1640(4)
0.1700(4)
0.1572(4)
0.1368(3)
0.0421(3)
0.0338(4)
0.40757(3) 0.04087(10)
0.15654(7) 0.0709(4)
0.4972(2)
0.4152(2)
0.0463(8)
-0.0809(7)
0.1378(6)
0.3291(8)
0.3530(7)
0.3210(8)
0.0395(7)
0.0447(7)
0.122(5)
0.127(5)
0.084(3)
0.063(4)
0.055(4)
0.082(5)
0.1030(9)
-0.2232(9)
-0.0907(7)
-0.0474(9)
-0.1233(8)
-0.2372(9)
-0.2912(11)
-0.244(2)
-0.141(2)
-0.0510(12)
0.0162(12)
-0.1907(11)
-0.1023(9)
0.2862(7)
0.3963(8)
0.4433(9)
0.3820(10)
0.2739(10)
0.2253(8)
0.2770(8)
0.3877(9)
0.4269(11) -0.0104(4)
0.3606(12) -0.0464(4)
0.2513(13) -0.0388(4)
0.2092(9)
0.2925(7)
0.3205(8)
0.3662(9)
0.3835(9)
0.3564(8)
0.3105(7)
-0.0010(7)
0.0563(7)
0.0685(9)
0.0194(9)
-0.0409(8)
-0.0510(7)
-0.1565(6)
-0.1887(7)
-0.3010(9)
-0.3819(8)
-0.3516(8)
-0.2394(7)
0.0671(7)
0.0891(7)
0.1422(8)
0.1752(9)
0.1592(8)
0.1050(7)
0.2490(10) 0.112(7)
0.1962(13) 0.127(9)
0.1986(12) 0.123(9)
0.2861(11) 0.114(7)
0.0858(10) 0.088(6)
0.0085(10) 0.091(5)
F igu r e 3. Structure and labeling scheme for 5 with 40%
probability of thermal ellipsoids. Triphenylphosphine
phenyl rings are omitted for clarity.
0.1474(7)
0.2993(7)
0.2999(8)
0.060(4)
0.048(3)
0.061(4)
and C2, which is intermediate between sp and sp2.
Because of the sp character of C1 and C2 the bond
angles about these atoms tend to be larger than 120°
which results in flattening of the seven-membered ring.
Attem p ts To Relea se 11 fr om 7. As mentioned
above, methods that were successful for the preparation
of 12 and 13 failed to yield 11. As a possible source of
11, Mo(CO)3 removal from 7 was therefore explored.
From the outset it was recognized that this goal
provided a special challenge since any reagent used to
effect Mo(CO)3 displacement must either be inert to
platinum or give a nonproductive reaction. 1,10-
Phenanthroline appeared to qualify in the first category
because it does not displace PPh3 from platinum but is
known to react with 15 displacing cycloheptatriene.16
Indeed, as a test case, addition of 1,10-phenanthroline
to a mixture of 5 and 6 gave a good recovery of 12 and
13. As expected, this reaction is much slower for 5 and
6 at room temperature (t1/2 for 5 ) ca. 2 days, t1/2 for 6
) ca. 6 days) than the corresponding reaction with 15,
which, under the same conditions, is complete within
minutes. Unfortunately, 7 showed no detectable reac-
tion with phenanthroline, even after several days at
room temperature. Similarly, treatment of a mixture
of 5 and 6 with 3.5 equiv of PPh3 led to displacement of
Mo(CO)3 (presumably concomitant with nonproductive
PPh3 exchange) but, again, much slower than displace-
ment from 15; t1/2 for 5 at room temperature ) ca. 3
days and t1/2 for 6 at room temperature ) ca. 2 weeks
while reaction with 15 was complete within minutes.
However, as with the phenanthroline, 7 showed no
detectable reaction with PPh3, even after 1 week at room
temperature. These reactivity differences qualitatively
correlate with the CO absorptions in the infrared, which,
in turn, presumably reflect differences in triene basici-
ties. Steric resistance from the (Ph3P)2Pt moiety might
also retard Mo(CO)3 displacement from 5-7 relative to
15.
0.2084(10) 0.078(5)
0.1131(9)
0.1113(9)
0.2036(8)
0.4029(7)
0.079(5)
0.086(5)
0.059(4)
0.052(3)
0.3812(10) 0.082(5)
0.3685(11) 0.099(6)
0.3798(10) 0.100(6)
0.4071(12) 0.112(6)
0.0049(3)
0.1221(3)
0.0930(3)
0.1102(5)
0.1558(5)
0.1849(4)
0.1685(3)
0.1685(3)
0.1335(3)
0.1312(4)
0.1632(4)
0.1986(4)
0.2012(3)
0.1883(3)
0.2221(3)
0.2329(4)
0.2107(4)
0.1769(3)
0.1662(3)
0.2212(3)
0.2253(3)
0.2635(4)
0.2973(4)
0.2926(3)
0.2553(3)
0.4179(9)
0.5389(7)
0.6246(8)
0.7215(9)
0.074(4)
0.048(3)
0.063(4)
0.086(5)
0.7343(10) 0.086(5)
0.6486(9)
0.5505(8)
0.6479(7)
0.6990(7)
0.8112(8)
0.8755(9)
0.8313(8)
0.7159(8)
0.4789(7)
0.4039(8)
0.3902(9)
0.4528(9)
0.5246(9)
0.5384(8)
0.4540(8)
0.3405(8)
0.2976(9)
0.070(4)
0.058(4)
0.043(3)
0.053(3)
0.067(4)
0.078(5)
0.061(4)
0.054(3)
0.040(3)
0.060(4)
0.080(5)
0.073(4)
0.065(4)
0.057(4)
0.045(3)
0.057(4)
0.077(5)
0.3692(11) 0.080(5)
0.4809(11) 0.077(5)
0.5228(8)
0.059(4)
techniques. Solvents were distilled under nitrogen prior to
use, toluene, THF, and Et2O from sodium benzophenone ketyl,
hexane from sodium benzophenone ketyl/tetraglyme mixture,
and methylene chloride from CaH2. NMR spectra were
measured on a Varian XL-300 (FT 300 MHz, 1H; 75 MHz, 13C;
282 MHz, 19F; 121 MHz, 31P; 64 MHz, 195Pt). 1H NMR and
13C{1H} NMR spectra are referenced to the residual solvent
peaks and are reported in ppm relative to tetramethylsilane.
19F NMR spectra are referenced to external CFCl3. 31P{1H}
NMR spectra are referenced to external 85% H3PO4 in D2O.
195Pt{1H} NMR spectra are referenced to an external saturated
solution of Na2PtCl4 in D2O. All J values are given in Hz.
Infrared spectra were measured on a Perkin-Elmer 1600 FTIR
spectrometer. Mass spectra (positive FAB) were obtained on
the Finnigan Mat 95Q. Elemental analyses were performed
in the microanalysis laboratory in the Chemistry Department
at the University of Florida. Melting points were measured
in open capillaries and are not corrected. Triphenylcarbenium
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All experiments involving or-
ganometallic compounds were carried out under an atmo-
sphere of purified N2 using Schlenk, vacuum line, and drybox
(16) Behrens, H.; Lindner, E.; Lehnert, G. J . Organomet. Chem.
1970, 22, 439.

602 Organometallics, Vol. 15, No. 2, 1996
Klosin et al.
tetrafluoroborate, 1,10-phenanthroline, and 1 M THF solutions
of KBEt3H and LiAl(OtBu)3H were purchased from Aldrich
Chemical Co. All compounds were used as received. The
following compounds were prepared as described in the
literature, without any modification: (η6-p-xylene)Mo(CO)3,17
(PPh3)2Pt(η2-C7H6) (12, 13).9
990.0765; found, m/e 990.0645. 1H NMR (CD2Cl2): δ 7.25-
3
7.45 (m, 30H, PPh3), 6.10 (m, 1H, H2), 5.65 (t, 1H, J H1-H2
)
3
3
10.8 Hz, H3), 5.55 (t, 1H, J ) 5.8 Hz, J H1-Pt ) 36.7 Hz, H1).
13C{1H} NMR (CD2Cl2, -40 °C): δ 212.02 (s, CO), 133.56 (d,
J C-P ) 12.6 Hz, PPh3), 132.10 (d, 1J C-P ) 51.3 Hz, PPh3-ipso),
130.86 (s, PPh3-para), 128.48 (d, J C-P ) 10.5 Hz, PPh3), 111.28
(dd, 2J C-Pcis ) 4.3 Hz, 2J C-Ptrans ) 93.6 Hz, C4), 100.75 (d, J C-P
P r ep a r a tion of (P P h 3)2P t[η2(η6-C7H6)Mo(CO)3] (5, 6). A
Schlenk tube was charged with 0.56 g (0.692 mmol) of 12 and
13 and 0.198 g (0.692 mmol) of (η6-p-xylene)Mo(CO)3. To this
mixture was added 25 mL of THF at room temperature. The
Schlenk tube was wrapped with aluminum foil, and the
mixture was stirred for 20 min at room temperature. The
solvent was evaporated in vacuum, and the residue was
dissolved in 20 mL of benzene. To this solution was added 35
mL of hexane, and the solution was filtered through a cannula
into another Schlenk tube. The Schlenk tube was placed in
the freezer (-16 °C) for 1 day. The supernatant was decanted
leaving 0.44 g of red crystals (61.7% yield, 6:1 for 5:6), mp 147-
149 °C (dec). IR (KBr): 3052 w, 2802 w, 1956.7 s (CO), 1886.8
s (CO), 1845.7 s (CO), 1610.7 m (coordinated CC), 1479.7 m,
1302 w, 1183.5 w, 1159.6 w, 1095.5 m, 1027.9 w, 744 m, 695
s, 523 s cm-1. HRMS (FAB): calcd for (M + 1)+, m/e 992.0921;
found, 992.0959. Anal. Calcd for C46H36O3P2MoPt; 0.5C6H6:
C, 57.21; H, 3.82. Found: C, 57.22; H, 3.76. Data for complex
5 are as follows. 1H NMR (CD2Cl2): δ 7.1-7.5 (m, 30H, PPh3),
6.10 (td, 1H, 3J H2-H3 ) 7.1 Hz, 3J H2-H1 ) 3.1 Hz, H2), 5.55 (dd,
) 10.7 Hz, J C-Pt ) 50.4, C2), 97.96 (s, C3), 87.08 (t, J C-P
)
7.9, C1). 31P{1H} NMR (CD2Cl2): δ 20.25 (s). 19F NMR (CD2-
Cl2): δ -152.78 (s). 195Pt{1H} NMR (CD2Cl2): δ -4087.6 (t,
1J Pt-P ) 3267 Hz).
P r ep a r a tion of (P P h 3)2P t[η2(η6-C7H6)Mo(CO)3] (7).
A
250 mg (0.224 mmol) amount of 4 was dissolved in 7 mL of
THF, and the Schlenk tube was cooled to -78 °C. To this
solution was added slowly 250 mL of a 1 M solution of LiAl-
(OtBu)3H dissolved in 2 mL of THF. During addition the color
changed noticeably from red-brown to deep red. The mixture
was stirred at low temperature for 20 min and then was
warmed to room temperature. The solvent was removed in
vacuum and the residue dissolved in 10 mL of benzene followed
by addition of 15 mL of hexane. The solution was filtered and
placed in the freezer (-16 °C). After a few days red crystals
were collected (120 mg, 42% yield), mp 133-136 °C (dec). IR
(KBr): 3052 w, 2828 w, 1947 s (CO), 1870.8 s (CO), 1847 s
(CO), 1560 m, 1478.5 m, 1434 w, 1385 m, 1095.8 m, 745.6 m,
694.4 s, 678 s cm-1
.
HRMS (FAB): calcd for (M + 1)+, m/e
4
3
3
1H, J H1-P ) 6.2 Hz, J H1-H2 ) 3.7 Hz, J H1-Pt ) 40.2, H1),
992.0921; found, m/e 992.1014. Anal. Calcd for C46H36O3P2-
MoPt‚C6H6: C, 58.49; H, 3.96. Found: C, 58.53; H, 4.05. 1H
NMR (CD2Cl2): δ 7.1-7.45 (m, 30H, PPh3), 5.84 (td, 1H, J )
3
4.47 (t, J H3-H2,4 ) 8 Hz, H3), 4.13 (p, 1H, J H-H ) 4 Hz, H4),
3.51 (dtd, 1H, 2J Hd-Hu ) 15.7 Hz, 3J Hd-H ) 5.4 Hz, J Hd-H ) 1.8
3
2
3
Hz, J Hd-Pt ) 59.4 Hz, Hd), 3.21 (dd, 1H, J Hu-Hd ) 15.7 Hz,
1.2 Hz, J ) 5 Hz, J H1-Pt ) 44.4, H1), 4.90 (m, H2), 3.85 (td,
3
J Hu-H ) 1.4 Hz, Hu). 13C{1H} NMR (CD2Cl2, -30 °C):
δ
1H, J ) 1.5 Hz, J ) 6.3 Hz, J H4-Pt ) 50.4, H4), 3.17 (m, H3),
2
229.69, 221.37, 218.74, 135.6 (qd, J ) 22.5 Hz, J ) 1.8 Hz,
PPh3-ipso), 134.25 (m, PPh3), 129.95 (s, PPh3-para), 128.26 (m,
PPh3), 103.03, 100.47 (dd, 2J C-Pcis ) 7 Hz, 2J C-Ptrans ) 83.5 Hz),
3.08 (m, Hd), 2.49 (d, 1H, J Ha-Hd ) 12.3 Hz, Hu). 13C{1H}
NMR (CD2Cl2): δ 224.8 [-50 °C, 231.83, 222.52, 218.31],
135.12 (d, 1J C-P ) 4.6 Hz, PPh3-ipso), 134.42 (m, PPh3), 130.31
(dd, J C-P ) 2.3 Hz, J C-P ) 5.3 Hz, PPh3-para), 128.47 (m,
PPh3), 112.15 (dd, 2J C-Pcis ) 7.5 Hz, 2J C-Ptrans ) 90.5 Hz), 107.13
(d, J C-P ) 10.6 Hz, J C-Pt ) 68.3), 102.10 (dd, 2J C-Pcis ) 7.5 Hz,
2J C-Ptrans ) 83 Hz), 86.93 (t, J C-P ) 8.3 Hz), 62.81, 48.5 (t, J C-P
) 9.1 Hz), 29.99 (d, J C-P ) 8.3, J C-Pt ) 44.5 Hz). 31P{1H} NMR
2
98.19 (d, J C-P ) 10.3 Hz, J C-Pt ) 54.7), 97.2 (dd, J C-Pcis ) 4.7
Hz, 2J C-Ptrans ) 83.6 Hz), 82.41 (t, J C-P ) 8.5), 75.63 (d, J C-P
)
7.5, J C-Pt ) 48.3), 29.12 (t, J C-P ) 8). 31P NMR (CD2Cl2): δ
2
2
22.15 (d, J P′-P′′ ) 13.8 Hz), 23.73 (d, J P′-P′′ ) 13.8 Hz). 195Pt
1
1
NMR (CD2Cl2): δ -4480.4 (dd, J Pt-P′ ) 3326.4 Hz, J Pt-P′′
)
2
2
3418 Hz). Data for complex 6 are as follows. 1H NMR (CD2-
(CD2Cl2): δ 23.81 (d, J P′-P′′ ) 9.2 Hz), 23.55 (d, J P′-P′′ ) 9.2
Cl2): δ 7.1-7.5 (m, 30H, PPh3), 4.99 (br d, 2H, J H1′-H2′ ) 7.2
Hz). 195Pt{1H} NMR (CD2Cl2): δ -4420.2 (dd, J Pt-P′ ) 3124
Hz, J Pt-P′′ ) 3282.5 Hz).
3
1
3
1
Hz, J H1′-Pt ) 30 Hz, H1′), 3.37 (m, 2H, H2′), 2.92 (dt, 1H,
2J Hd-Hu ) 13.2 Hz, J Hd-H1′ ) 8.6 Hz, Hd), 2.36 (br d, 1H, 2J Hu-Hd
Rea ction of 7 w ith Tr ip h en ylca r bon iu m Tetr a flu o-
r obor a te. A 20 mg (0.02 mmol) amount of 7 and 7 mg (0.021
mmol) of triphenylcarbenium tetrafluoroborate were dissolved
in 0.5 mL of CD2Cl2. After 15 min NMR measurements (1H
and 31P{1H}) showed clean formation of 4 (spectroscopic data
were identical to those of the compound obtained from hydride
abstraction from 5 and 6).
Rea ction of 12, 13 w ith (η6-C7H8)Mo(CO)3 (15). A 50
mg (0.062 mmol) of amount 12, 13 and 17 mg (0.062 mmol) of
15 were placed in an NMR tube equipped with a PTFE valve
and dissolved in 0.5 mL of CD2Cl2. The reaction was moni-
tored by 1H and 31P{1H} NMR. The major isomer (12) reacted
within 12 h whereas the minor one (13) required 4 days. On
the basis of 31P NMR, the final reaction mixture consisted of
predominantely 5, 6 with a small amount of other unidentified
phosphorus-containing products.
Rea ction of 5, 6 w ith 1,10-P h en a n th r olin e. A 50 mg
(0.05 mmol) amount of 5, 6 and 19 mg (0.11 mmol) of 1,10-
phenanthroline were dissolved in 0.5 mL of CD2Cl2. The major
isomer (5) reacts faster (t1/2 ) 2 days) than the minor one (6)
(t1/2 ) 6 days) to give a mixture of 12 and 13. On the basis of
31P NMR, the final reaction mixture consisted of almost
exclusively 12, 13 contaminated with a small amount of other
unidentified phosphorus-containing products.
Rea ction of 5, 6 w ith Tr ip h en ylp h osp h in e. A 50 mg
(0.05 mmol) amount of 5, 6 and 45 mg (0.18 mmol) of
triphenylphosphine were dissolved in 0.5 mL of CD2Cl2. The
major isomer (5) reacts faster (t1/2 ) 3 days) than the minor
one (6) (t1/2 ) 2 weeks) to give a mixture of 12 and 13. On the
basis of 31P NMR, the final reaction mixture consisted of
) 13.2 Hz, Hu). 13C NMR (CD2Cl2): δ 97.53, 56.19 (t, J C-P
)
8.1), 28.93. 31P{1H} NMR (CD2Cl2): δ 22.91 (s). 195Pt{1H}
1
NMR (CD2Cl2): δ -4449 (t, J Pt-P ) 3323 Hz).
P r ep a r a t ion of (P P h 3)2P t [η2(η7-C7H 5)Mo(CO)3] (4).
Meth od I. A 27 mg (0.03 mmol) amount of 1 was dissolved
in 0.3 mL of THF-d8 and 0.3 mL of CD2Cl2. To this solution
was added 12 mg (0.042 mmol) of (η6-p-xylene)Mo(CO)3. The
color started to change at once from red to brown red; 20 min
1
after the addition the H and 31P{1H} NMR showed virtually
quantitative formation of 4.
Meth od II. A 230 mg (0.223 mmol) amount of 5 and 6 was
dissolved in 10 mL of CH2Cl2 in a Schlenk tube wrapped in
aluminum foil. To this solution 82 mg (0.248 mmol) of
triphenylcarbenium tetrafluoroborate dissolved in 3 mL of CD2-
Cl2 was added dropwise at room temperature. After 1 h of
stirring 20 mL of hexane was added and the solution was
filtered. To the filtrate more hexane (30 mL) was added, and
the Schlenk tube was placed in the freezer (-16 °C). After 1
day the supernatant was decanted leaving a red oil which
solidified after applying a vacuum (200 mg, 80% yield). This
solid was at least 95% pure as shown by NMR (see Supporting
1
Information for H, 31P, and 195Pt spectra), mp 97-99 °C (dec).
Unfortunately, 4 could not be obtained either as an analytically
pure material nor could a single crystal suitable for X-ray
diffraction be grown. IR (KBr): 3025 w, 2036.2 s (CO), 1976.2
br, s (CO), 1550 w, 1481.3 m, 1436.4 s, 1097 s, 1083 br s, 1058
br s, 746 m, 695 s cm-1
.
HRMS (FAB): calcd for M+, m/e
(17) Strohmeier, W. Chem. Ber. 1961, 94, 3337.

Pt-Mo Complexes
Organometallics, Vol. 15, No. 2, 1996 603
primarily 12, 13 contaminated with a small amount of other
unidentified phosphorus-containing products.
reflections with F > 5σ(F) gave R and wR values of 5.49 and
5.67%, respectively. Since the space group P21 is chiral, the
absolute configuration of the structure was determined by
refining the other enantiomer with the same data. This
refinement yielded R and wR values of 6.27 and 7.10%,
respectively. Using the Hamilton19 test, the structure of the
enantiomer was rejected at a confidence level of 99.95%.
Additionally, the chirality/polarity20 factor η (a factor multiply-
ing f ′′) was refined to 0.40(3). The η value should normally
refine to 1 with a small esd for the correct enantiomer or -1
for the wrong enantiomer. Perhaps η did not refine to a value
of 1 for 7 because of the small number of Friedel relative
reflections that were collected. The linear absorption coef-
ficient was calculated from values from ref 21. Scattering
factors for non-hydrogen atoms were taken from Cromer and
Mann22 with anomalous-dispersion corrections from Cromer
and Liberman,23 while those of hydrogen atoms were from
Stewart, Davidson, and Simpson.24
Cr ysta llogr a p h ic An a lysis for 5 a n d 7. Data for both
complexes were collected at room temperature on a Siemens
R3m/V diffractometer equipped with a graphite monochroma-
tor utilizing Mo KR radiation (λ ) 0.710 73 Å). In each case,
32 reflections with 20.0° e 2θ e 22.0° were used to refine the
respective cell parameters. Totals of 7933 and 8412 reflec-
tions, for 5 and 7, respectively, were collected using the ω-scan
method. Four reflections were measured every 96 reflections
to monitor instrument and crystal stability (maximum cor-
rection on I was 1 and 4%, for 5 and 7, respectively).
Absorption corrections were applied on the basis of the
measured crystal faces using SHELXTL plus,18 the absorption
coefficient, µ, was 3.75 and 3.16 mm-1, for 5 and 7, respectively
(minimum and maximum transmission factors are 0.404 and
0.722 for 5 and 0.514 and 0.723 for 7, respectively).
Both structures were solved by the heavy-atom method in
SHELXTL plus17 from which the locations of the heavy atoms
were obtained. The rest of the non-hydrogen atoms were
obtained from subsequent difference Fourier maps. The
structures were refined in SHELXTL plus using full-matrix
least squares. The non-H atoms of the complexes were treated
anisotropically, whereas the benzene molecules C atoms of 7
were refined with isotropic thermal parameters; the C atoms
of the benzene molecule in 5 were refined with anisotropic
thermal parameters. The positions of the hydrogen atoms
were calculated in ideal positions, and their isotropic thermal
parameters were fixed. The asymmetric unit of 5 contains the
complex and one half of a benzene molecule of crystallization,
while the asymmetric unit of 7 contains one complex and two
partial benzene molecules of crystallization. The site-occupa-
tion factors of these benzene molecules were dependently
refined. One refined to 0.55(1), and consequently the other
partial benzene has an occupation factor of 0.45(1). In the final
cycle of refinement of 5, 4330 reflections with F > 6σ(F) gave
R and wR values of 3.81 and 4.03%, respectively. For 7, 4229
Ack n ow led gm en t. Support of this research by the
National Science Foundation and the Chevron Research
and Technology Co. is gratefully acknowledged.
Su p p or tin g In for m a tion Ava ila ble: 1H, 31P, and 195Pt
NMR spectra of 4 and thermal ellipsoid drawings showing full
numbering schemes and tables of atomic positional and
thermal parameters, anisotropic thermal parameters for non-
hydrogen atoms, and comprehensive bond lengths and angles
(25 pages). Ordering information is given on any current
masthead page.
OM950732D
(19) Hamilton, C. H. Acta Crystallogr. 1965, 18, 502.
(20) Rogers, D. Acta Crystallogr. 1981, A37, 734.
(21) International Tables for X-ray Crystallography; Kynoch Press:
Birmingham, England, 1974; Vol. IV, p 55 (present distributor: D.
Reidel, Dordrecht, The Netherlands).
(22) Cromer, D. T.; Mann, J . B. Acta Crystallogr. 1968, A24, 321.
(23) Cromer, D. T.; Liberman, D. J . Chem. Phys. 1970, 53, 1891.
(24) Stewart, R. F.; Davidson, E. R.; Simpson, W. T. J . Chem. Phys.
1965, 42, 3175.
(18) Sheldrick, G. M. SHELXTL plus, version 4.21/V, Siemens XRD,
Madison, WI, 1990.