Reactions of molybdenum and tungsten phosphenium complexes with sulfur and selenium

Article abstract of DOI:10.1021/om9605490

The reactions of the phosphane [(Me₃Si)₂N](Ph)PCl with NaCpMo(CO)₃ and NaCpW(CO)₃ give the respective metallophosphenium complexes Cp(CO)₂M{P(Ph)[N(SiMe₃)₂]} (M = Mo (4a), W (4b)). The subsequent reactions of 4a,b with S and Se produce unexpectedly different products: Cp(CO)₂(S)M{P(Ph)[N(SiMe₃)₂]} (M = Mo (7a)); Cp(CO)₂MSP(Ph)[N(SiMe₃)₂] (M = W (7b)); Cp(CO)₂MseP(Ph)[N(SiMe₃)₂] (M = Mo (8a), W (8b)). The compounds have been fully characterized by elemental analyses and spectroscopic data, and the molecular structures of 4a, 7a,b, and 8a have been determined by single-crystal X-ray diffraction techniques. The molecular structure of 7a displays a long, terminal Mo-S bond, while 7b and 8a contain M-E-P three-membered rings.

Full text of DOI:10.1021/om9605490

Organometallics 1997, 16, 449-455
449
Rea ction s of Molybd en u m a n d Tu n gsten P h osp h en iu m
Com p lexes w ith Su lfu r a n d Selen iu m
Hans-Ulrich Reisacher, William F. McNamara, Eileen N. Duesler, and
Robert T. Paine*
Department of Chemistry, University of New Mexico, Albuquerque, New Mexico 87131
Received J uly 8, 1996X
The reactions of the phosphane [(Me3Si)2N](Ph)PCl with NaCpMo(CO)3 and NaCpW(CO)3
give the respective metallophosphenium complexes Cp(CO)2M{P(Ph)[N(SiMe3)2]} (M ) Mo
(4a ), W (4b)). The subsequent reactions of 4a ,b with S and Se produce unexpectedly different
products: Cp(CO)2(S)M{P(Ph)[N(SiMe3)2]} (M ) Mo (7a )); Cp(CO)2MSP(Ph)[N(SiMe3)2] (M
) W (7b)); Cp(CO)2MSeP(Ph)[N(SiMe3)2] (M ) Mo (8a ), W (8b)). The compounds have been
fully characterized by elemental analyses and spectroscopic data, and the molecular
structures of 4a , 7a ,b, and 8a have been determined by single-crystal X-ray diffraction
techniques. The molecular structure of 7a displays a long, terminal Mo-S bond, while 7b
and 8a contain M-E-P three-membered rings.
Sch em e 1
In tr od u ction
The reactions of monochlorophosphanes, (X)(Y)PCl,
with NaCpM(CO)3 (M ) Cr, Mo, W) produce, via salt
elimination, the neutral metallophosphane complexes
CpM(CO)3[P(X)(Y)] (1) (Scheme 1).1-4 The phosphorus
atom in 1 is pyramidal, and the M-P bond is formally
pure σ in character. Due to the Lewis basicity of the
phosphane center and the lability of the CO ligands,
examples of 1 tend to decarbonylate, forming neutral
metallophosphenium complexes 2.1-4 Despite this fact,
As and Sb analogs of 1 have been identified in matrix
X Abstract published in Advance ACS Abstracts, J anuary 1, 1997.
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389, 325. (e) Leise, M.; Zsolnai, L.; Lang, H. Polyhedron 1993, 12, 1257.
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Dubois, D. A.; Duesler, E. N.; Paine, R. T. Organometallics 1983, 2,
1903. (e) Hutchins, L. D.; Duesler, E. N.; Paine, R. T. Organometallics
1984, 3, 399. (f) McNamara, W. F.; Duesler, E. N.; Paine, R. T.; Ortiz,
J . V.; Ko¨lle, P.; No¨th, H. Organometallics 1986, 5, 380. (g) Paine, R.
T.; McNamara, W. F.; J anik, J . F.; Duesler, E. N. Phosphorus Sulfur
1987, 30, 241. (h) Reisacher, H.-U.; Duesler, E. N.; Paine, R. T. Chem.
Ber. 1996, 129, 279. (i) Hutchins, L. D. Ph.D. Thesis, University of
New Mexico, 1983.
isolation infrared spectroscopic studies,5 and the mo-
lecular structures of CpM(CO)3[PdC(SiMe3)2]2f (M )
Mo, W) and CpMo(CO)3{P(Cl)[(tBu3C6H2O)]}3e have
been determined by single-crystal X-ray diffraction
techniques. Structural determinations for examples of
2 are more abundant, and these compounds feature a
trigonal planar phosphorus atom environment and a
short, formal MdP multiple bond.1-4
The chemistry of 1 and 2 has been of interest in
several groups.1-4 Much of the reactivity of 1 derives
from the nucleophilicity of the uncommitted phosphorus
lone pair, and additions of H3B‚THF, Ni(CO)4, and CH3I
to CpW(CO)2(Me3P)(PPh2), for example, result in forma-
tion of adducts CpW(CO)2(Me3P)[P(A)(Ph)2] (A ) H3B,
(CO)3Ni, and CH3+).2d Oxidations with S8 and Br2 also
occur at the electron-rich PPh2 center.
The nucleophilic reactivity of the planar phosphorus
atom of 2 should be diminished since the phosphorus
lone pair present in 1 is now involved in MdP multiple
(5) Mahmoud, K. A.; Rest, A. J .; Luksza, M.; J o¨rg, K.; Malisch, W.
Organometallics 1984, 3, 501.
S0276-7333(96)00549-3 CCC: $14.00 © 1997 American Chemical Society

450 Organometallics, Vol. 16, No. 3, 1997
Reisacher et al.
Sch em e 2
bonding. Experimentally, Malisch reports that CpM-
(CO)2[POCMe2CMe2O] (M ) Cr, Mo, W)2d and CpMo-
[P(NMe2)2])2a react with S8 to give thio-bridged species
3a (E ) S). Similarly, reaction of CH2N2 with the
former compound produces a [2+1] cycloaddition species
3b (E ) CH2), and addition of Fe2(CO)9 results in 3c (E
) Fe(CO)4). Another example of 2, CpW(CO)2[P(tBu)2],
reacts with S8, Se, CH2N2, (MeP)5, Me2P, Fe2(CO)9, and
Ru3(CO)10, each forming [2+1] cycloaddition products
3.2c In addition, Lang3b,f describes reactions on bifunc-
tional σ3,λ4-phosphanediyl phosphenium complexes, CpM-
(CO)2[P(R)CtCR], CpM(CO)2[P(R)C(H)dC(H)R], and
CpM(CO)2[P(R)CH2CtCH], which undergo [2+1] cy-
cloadditions with CH2N2, Fe(CO)5, PhN3, and (2,4,6-
Me3C6H2)N3. Finally, by using different synthetic strat-
egies, Nakazawa6 outlines reactions of a cationic
metallophosphenium species CpFe(CO)(R)[PN(Me)CH2-
CH2N(Me)], which readily undergoes migratory inser-
tion and base addition to produce, for example, {CpFe-
(CO)(PPh3)[PN(Me)CH2CH2N(Me)(R)]}BF4.
These observations clearly show that the reactivity
of 1 and 2 differ, but the phosphorus atom seems to
retain some nucleophilic activity. In fact, we have
observed that H3B‚THF adds across the MdP double
bond in CpMo(CO)2{P(Ph)[N(Me3Si)2]} (4a ) giving 5.4f
or by running the reaction at 23 °C or at THF reflux.
With reflux, 90-100% of the expected CO is released
in about 6 h. No effort was made to isolate or charac-
terize the intermediate species 9.
Compounds 4a ,b each show a parent ion envelope
(m/e 433-423, 4a , and m/e 576-571, 4b) in electron
impact mass spectra as well as an intense fragment ion
envelope [M - 2CO+]. The infrared spectra of the
compounds show two strong bands in the terminal
carbonyl stretching region: 4a , 1948 and 1876 cm-1; 4b,
1941 and 1869 cm-1. These data are consistent with
the presence of two terminal CO groups, and they
compare favorably with values of 1954 and 1876 cm-1
reported previously for Cp(CO)2MoP(NMe2)2.4c The 31P-
{1H} NMR spectra each show a single, low-field reso-
nance typical of metallophosphenium complexes: 4a , δ
316; 4b, δ 267.4 The resonance for 4b also shows
satellites due to tungsten-phosphorus coupling, and the
In addition, we find that 4a reacts with Fe2(CO)9 to give
6,4h which does not feature a simple three-membered
ring core as in 3 but instead displays a bridging CO
interaction between the Mo and Fe centers. In the
present report, the oxidation reactions of 4a and CpW-
(CO)2{P(Ph)[N(SiMe3)2]} (4b) with S8 and Se are de-
scribed along with spectroscopic and single-crystal X-ray
diffraction studies.
1
large value, J PW ) 702 Hz, is consistent with the
anticipated strong MdP σ/π overlap involving a planar,
formally sp2-hybridized phosphenium ion center. The
1
Resu lts a n d Discu ssion
13C{1H} and H NMR spectra show resonances that are
unambiguously assigned to the N(SiMe3)2, Cp, and
phenyl groups.
The 1:1 combinations of [(Me3Si)2N](Ph)PCl with
NaCpMo(CO)3 and NaCpW(CO)3 in THF solution pro-
duce metallophosphenium complexes Cp(CO)2Mo{P(Ph)-
[N(SiMe3)2]} (4a ) and Cp(CO)2W{P(Ph)[N(SiMe3)2]} (4b)
in high yields as crystalline purple solids that are
moisture and air sensitive. This chemistry is illustrated
in Scheme 2. It is likely that the respective metallo-
phosphane complexes Cp(CO)3M{P(Ph)[N(SiMe3)2]}(Mo
(9a ); W (9b)) form at low temperature as indicated by
the rapid color change in the reaction solution without
noticeable formation of CO. Upon standing of the
solution at -78 °C, CO is slowly released and ap-
proximately 30% of the expected CO is recovered after
6 h by using a Toepler pump. The overall rate of CO
loss is enhanced by continuous removal of the CO and/
The molecular structure of 4a was determined by
single crystal X-ray diffraction analysis,7 and a view of
the molecule is shown in Figure 1. Selected bond
distances and angles are summarized in Table 2. The
molecule has C1 symmetry with the molybdenum atom
having a three-legged piano stool pseudo-octahedral
geometry. The average Mo-CO and MoCtO distances,
1.949(3) and 1.151(5) Å, are identical to the values
displayed by CpMo(CO)2[POCH2CH2NCMe3]4e (10),
(7) The molecular structure of 4b was also determined; however,
disorder in the phenyl ring precluded full anisotropic refinement. The
crystallographic data include: monoclinic, space group Cc (No. 9), a )
12.475(1) Å, b ) 11.319(3) Å, c ) 16.777(5) Å, R ) γ ) 90°, â ) 102.92-
(2)°, V ) 2309.0(12) Å3, Z ) 2, Dcalcd ) 1.39 g cm-3. The molecular
structure was essentially identical to that observed for 4a with W-P
) 2.252(6) Å and P-N ) 1.68(2) Å.
(6) Nakazawa, H.; Yamaguchi, Y.; Mizuta, T.; Ichimura, S.; Miyoshi,
K. Organometallics 1995, 14, 4635.

Molybdenum and Tungsten Phosphenium Complexes
Organometallics, Vol. 16, No. 3, 1997 451
warming of the solution to 0 °C and then room temper-
ature, the purple color of 4 is discharged and replaced
by a yellow-orange color. Analysis of the raw reaction
mixtures by infrared and 31P NMR spectroscopy shows
a complete disappearance of 4 from the reaction mixture
and the appearance of two new νCO frequencies and a
single 31P NMR resonance. The products 7a ,b are
isolated in high yield and recrystallized as orange
crystalline solids. The chemistry is summarized in eq
1.
F igu r e 1. Molecular geometry and atom-labeling scheme
for Cp(CO)2Mo{P(Ph)[N(SiMe3)2]} (4a ) with H atoms omit-
ted. Thermal ellipsoids are represented at the 25% prob-
ability level.
CpMo(CO)2[PN(Me)CH2CH2NMe]4a (11), and CpMo-
The mass spectra for compounds 7a ,b display a
parent ion envelope as well as fragment ion envelopes
corresponding to [M - CO+] and [M - 2CO+]. In each
case, the [M - 2CO+] envelope is considerably more
intense than the [M - CO+] envelope. The infrared
spectra for the compounds show two bands in the CO
stretch region: 7a , 1960 and 1886 cm-1, and 7b, 1952
and 1873 cm-1 (cyclohexane solution). These are shifted
only slightly up-frequency from the respective starting
materials 4a ,b. Each compound shows a single 31P
NMR resonance centered at δ 73 and 33.9, respectively.
The latter resonance shows satellite doublet splitting
1J PW ) 268.6 Hz. This is significantly reduced from the
value in 4b and suggests that the phosphorus atom is
(CO)2[PN(bz)CH2CH2N(bz)]4c (12). The C(1)-Mo-C(2)
bond angle, 81.7(1)°, on the other hand, is somewhat
smaller than the angles observed in 10 (86.1(2)°), 11
(85.3(3)°), and 12 (85.2(3)°), which contain cyclic phos-
phenium ion fragments. The Mo, P, N, and C(16) atoms
form a plane8 that is approximately perpendicular to
the Mo(CO)2 plane (interplanar angle 98.6°), and the
sums of angles about the P and N atoms are 359.2 and
359.3°, respectively. The P, N, Si(1), and Si(2) atoms
also comprise a plane,8 and it makes an angle of 91.2°
with the MoPNC(16) plane. The Mo-P distance of
2.248(1) Å is short compared with the typical range of
PfMo dative bond lengths (2.42-2.53 Å)9 found in
metal phosphane complexes,9 and this bond shortening
has been previously offered1-4 in support of ModP
multiple bonding. It is interesting, however, that the
bond shortening in 4a is not as large as found in 10
(2.207(1) Å), 11 (2.213(1) Å), and 12 (2.212(2) Å), which
suggests that the P(Ph)[N(SiMe3)2]+ fragment may be
a weaker π-acid. This is consistent with the changes
in substituent groups on the fragment relative to
P(NR2)2+ and P(OR)(NR2)+ species. The P-N distance
of 1.698(2) Å is also significantly longer than the P-N
bond lengths in 10 (1.660(3) Å), 11 (1.645(5) Å), and 12
(1.655 Å (avg)). This is consistent with the presence of
competitive π overlap between the N and Si atoms that
would be expected to reduce the N-P π bond interac-
tion. The P-N distance in 4a is, in fact, closer to the
value found in the phosphane (H3Si)2NPF2,10 1.680(4)
Å. The Si-N distance in 4a , 1.764 Å (avg), is compa-
rable with the Si-N distance in (H3Si)2NPF2, 1.755(4)
Å.
1
in a pyramidal environment. The 13C and H NMR data
show resonances that are assigned to the Me3Si, Cp, and
Ph groups, and they are shifted only slightly from those
in the starting materials. It is interesting to note that
both compounds display two 13C{1H} resonances for the
(CH3)3Si groups indicating that they are in inequivalent
1
environments. The H NMR spectrum for 7a displays
two singlets of equal intensity for the N(SiMe3)2, and
their resonance positions are nearly 1 ppm downfield
of the singlet observed for 7b. These are the only
spectroscopic data that suggest that 7a ,b may have
different structures.
The molecular structure of 7a was determined by
X-ray diffraction techniques, and a view of the molecule
is shown in Figure 2. Selected bond distances and
angles are presented in Table 2. Somewhat surpris-
ingly, 7a does not display either of the expected struc-
tures, 7′ or 7′′, shown here. Instead, the compound has
Subsequent combinations of 4a ,b with an equimolar
amount of sulfur in methylcyclohexane or benzene
solution at -78 °C produce no reactions; however, upon
(8) The least-squares plane involving the MoPN and C(16) atoms
calculated for 4a is described by 10.6589x - 0.9025y + 5.2963z )
0.6029. The deviations from the plane are as follows: Mo, 0.023 Å; P,
-0.071 Å; N, 0.024 Å, C(16), 0.023 Å. The plane involving PN Si(1)
and Si(2) is described by 3.8812x + 9.6735y - 8.0053z ) 7.3523. The
deviations from the plane are as follows: P, -0.0214 Å; N, 0.0649 Å;
Si(1), -0.0218 Å, and Si(2), -0.0217 Å.
a four-legged piano stool structure in which the Mo atom
is seven coordinate and bonded to an η5-C5H5 ring, two
terminal CO groups, the phosphorus atom of the phos-
phenium ion ligand, and a terminal sulfur atom. The
molecule has C1 symmetry, and the CO groups are cis
(9) Corbridge, D. E. C. The Structural Chemistry of Phosphorus;
Elsevier: Amsterdam, 1974.
(10) Laurenson, G. S.; Rankin, D. W. H. J . Chem. Soc., Dalton Trans.
1981, 425.

452 Organometallics, Vol. 16, No. 3, 1997
Reisacher et al.
Ta ble 1. Cr ysta llogr a p h ic Da ta for Cp (CO)2Mo{P (P h )[N(SiMe3)2} (4a ), Cp (CO)2Mo(S){P (P h )[N(SiMe3)2]}
(7a ), Cp (CO)2WSP (P h )[N(SiMe3)2] (7b), a n d Cp (CO)2MoSeP (P h )[N(SiMe3)2] (8a )
4a
7a
7b
8a
mol formula
fw
C19H28NO2Si2PMo
485.5
C19H28NO2Si2PSMo
517.6
C19H28NO2Si2PSW
605.5
C19H28NO2Si2PSeMo
564.52
cryst syst
space group
a, Å
b, Å
c, Å
monoclinic
Cc
12.527(2)
11.328(2)
16.789(2)
90
102.95(1)
90
2321.9(6)
4
7.32
1.39
triclinic
P1h (No. 2)
9.673(2)
11.328(2)
11.579(2)
87.29(2)
77.82(1)
82.74(2)
1230.0(4)
2
monoclinic
P21/n
11.396(1)
17.245(3)
12.309(2)
90
91.49(1)
90
2418.2(5)
4
tetragonal
P41 (No. 76)
10.228(1)
10.228(1)
23.191(3)
90
90
90
2426.0(6)
4
23.2
1.55
R, Å
â, Å
γ, Å
V, Å3
Z
µ, cm-1
7.74
1.397
53.1
1.66
D
calcd, g cm-3
F(000)
1000
532
1192
1136
cryst dimens, mm
reciprocal space
scan type
2θmax, deg
Tmin/max
no. of reflcns measd
unique reflcns
obsd reflcns
params refined
Ra/Rw
0.25 × 0.41 × 0.46
(h,k,hl and ( h,kh,l
θ-2θ
0.23 × 0.23 × 0.08
(h,(k,(l
ω
0.14 × 0.25 × 0.39
(h,+k,+l
θ-2θ
0.23 × 0.41 × 0.69
(h,k,l
ω
55
60
50
55
0.498/0.521
7632
6732
5924, F > 5σ(F)
233
0.802/0.877
7593
4344
3237, F > 4σ(F)
274
0.392/1.00
12,288
5544
4573, F > 3σ(F)
244
0.235/0.259
13,129
5582
5262, F > 3σ(F)
108
0.0267/0.0273
0.0457/0.0359
0.0644/0.0508
0.0753/0.084
a
2
R ) ∑(||Fo| - |Fc||)/∑|Fo|; Rw ) [∑w(|Fo| - |Fc|)2/∑w|Fo| ]1/2
.
Ta ble 2. Str u ctu r a l P a r a m eter s for Cp (CO)2Mo{P (P h )[N(SiMe3)2} (4a ), Cp (CO)2Mo(S){P (P h )[N(SiMe3)2]}
(7a ), Cp (CO)2WSP (P h )[N(SiMe3)2] (7b), a n d Cp (CO)2MoSeP (P h )[N(SiMe3)2] (8a )
(a) Bond Lengths (Å)
4a
7a
7b
8a
M-P
Mo-P
2.248(1)
1.948(3)
1.951(3)
1.150(5)
1.153(4)
1.819(2)
1.698(2)
1.763(2)
1.766(2)
Mo-P
2.519(1)
1.948(5)
1.952(6)
1.145(6)
1.145(7)
1.835(4)
1.695(4)
1.774(3)
1.774(3)
W-P
2.411(2)
1.939(9)
1.950(9)
1.155(11)
1.162(11)
1.820(6)
1.680(6)
1.784(6)
1.781(6)
2.023(2)
Mo-P
2.411(1)
1.957(4)
1.959(4)
1.148(6)
1.150(6)
1.826(4)
1.682(3)
1.779(3)
1.783(4)
M-CO
Mo-C(1)
Mo-C(2)
C(1)-O(1)
C(2)-O(2)
P-C(16)
P-N
Mo-C(1)
Mo-C(2)
C(1)-O(1)
C(2)-O(2)
P-C(16)
P-N
W-C(1)
W-C(2)
C(1)-O(1)
C(2)-O(2)
P-C(8)
P-N
Mo-C(1)
Mo-C(2)
C(1)-O(1)
C(2)-O(2)
P-C(3)
P-N
CtO
P-C
P-N
Si-N
Si(1)-N
Si(2)-N
Si(1)-N
Si(2)-N
Si(1)-N
Si(2)-N
P-S
Si(1)-N
Si(2)-N
P-S
P-Se
M-S
M-Se
P-Se
2.168(1)
2.671(1)
Mo-S
2.509(1)
W-S
2.538(2)
Mo-Se
(b) Bond Angles (deg)
4a
7a
7b
8a
C(1)-Mo-C(2)
Mo-P-C(16)
Mo-P-N
81.7(1)
128.7(1)
127.3(1)
103.2(1)
C(1)-Mo-C(2)
75.1(2)
118.4(2)
123.5(1)
105.6(2)
74.1(2)
C(1)-W-C(2)
77.0(4)
122.9(2)
126.9(2)
106.1(3)
109.7(2)
69.2(1)
C(1)-Mo-C(2)
Mo-P-C(3)
Mo-P-N
77.3(2)
122.9(1)
125.9(1)
106.1(2)
107.7(1)
71.1(1)
Mo-P-C(16)
Mo-P-N
W-P-C(8)
W-P-N
N-P-C(8)
S-P-C(8)
W-P-S
N-P-C(16)
N-P-C(16)
S-Mo-P
N-P-C(3)
Se-P-C(3)
Mo-P-Se
Mo-Se-P
W-S-P
S-W-P
71.1(6)
48.2(1)
58.7(1)
50.2(1)
Se-Mo-P
to each other. There is no evidence for a trans isomer
in the solid state or in solution as determined by the
31P NMR spectra at 23 °C.
2.348 Å. The C-C bond distances within the ring also
vary (1.419(8)-1.370(10) Å, avg 1.394 Å); however, the
size of the esd’s make detailed comparisons of these
distances undependable. Similar distortions in other
CpMo(S) fragments have been noted,11 and it has been
suggested that these result from electronic perturba-
tions within the fragment.12 The phosphorus atom now
The M-CO and CtO bond lengths in 7a are identical
within experimental error to those found in 4a . The
C(1)-Mo-C(2) bond angle, 75.1(2)°, is slightly com-
pressed from that in 4a . The Mo-C bond distances
involving the Cp ring are more asymmetric than in 4a ,
Mo-C(21) (2.390(5) Å), Mo-C(22) (2.311(5) Å), Mo-
C(23) (2.271(6) Å), Mo-C(24) (2.290(5) Å), and Mo-
C(25) (2.385(6) Å), and the average value 2.329 Å is
slightly shorter than the average M-C distance in 4a ,
(11) Rakowski-DuBois, M.; DuBois, D. L.; Van Derveer, M. C.;
Haltiwanger, R. C. Inorg. Chem. 1981, 20, 3064.
(12) Mingos, D. M. P.; Minshall, P. C.; Hursthouse, M. B.; Wil-
loughby, S. D.; Malid, K. M. A. J . Organomet. Chem. 1979, 181, 169.
Mingos, D. M. P. Trans. Am. Crystallogr. Assoc. 1980, 16, 17.

Molybdenum and Tungsten Phosphenium Complexes
Organometallics, Vol. 16, No. 3, 1997 453
F igu r e 3. Molecular geometry and atom-labeling scheme
F igu r e 2. Molecular geometry and atom-labeling scheme
for Cp(CO)2(S)Mo{P(Ph)[N(SiMe3)2]} (7a ) with H atoms
omitted. Thermal ellipsoids are represented at the 25%
probability level.
for Cp(CO)2WSP(Ph)[N(SiMe3)2] (7b) with H atoms omit-
ted. Thermal ellipsoids are represented at the 25% prob-
ability level.
the Mo-S distance in 7a . The W-CO, CtO, P-N, and
P-C(phenyl) bond distances and the C(1)-W-C(2)
angle are comparable with the corresponding param-
eters in 7a . Although 7b can be classed as a four-legged
piano stool, the geometry about the W atom is much
more asymmetric than in 7a as indicated by the follow-
ing angles: P-W-S (48.2(1)°), S-W-C(2) (122.3(3)°),
C(2)-W-C(1) (77.0(4)°), and C(1)-W-P (103.0(3)°).
This asymmetry is imposed by the formation of the
displays a pyramidal geometry with a sum of bond
angles of 347.5°, and the Mo-P distance of 2.519(1) Å
is substantially longer than in 4a , which places it at
the upper end of the range of Mo-P single bond
distances. In fact, it is comparable to the value in the
related compound cis-CpMo(CO)2(Br)(PPh3), 2.538(2)
Å.13 The terminal Mo-S distance, 2.509(1) Å, is rela-
tively long and certainly outside the typical range found
for terminal ModS bonds (1.937-2.129 Å).14 It is also
longer than the Mo-S single bond distances in several
M-S-M bridged conditions: [(MeC5H4)MoS2]2 (2.300(2)
Å),11 MoS92- (2.359(1) Å),15 [(CS4)2MoS]2- (2.35(3) Å).16
This might suggest that 7a has the sulfur-bridging
structure depicted by 7′; however, the P‚‚‚S separation
is 3.032 Å, which is well beyond the sum of covalent
radii, 2.47 Å. Further, despite the bulky nature of the
(Me3Si)2N and Ph groups on the phosphorus atom, the
arrangement of the four piano stool legs around the Mo
atom is relatively symmetrical, as indicated by the
following bond angles: P-Mo-S (74.1( )°), S-Mo-C(2)
(79.3(2)°), C(2)-Mo-C(1) (76.1(2)°), and C(1)-Mo-P
(79.0(2)°). Thus the Mo-S bond vector cannot be
considered as displaced toward the P atom.
three-membered W-S-P ring.
The reactions of 4a ,b with equimolar amounts of
selenium were examined in C6H6 solution at room
temperature. In both cases, the purple color of the
starting material solution is rapidly converted to a dark
red color upon addition of the Se, and the products Cp-
(CO)2MoSeP(Ph)[N(SiMe3)2] (8a ) and Cp(CO)2WSeP-
(Ph)[N(SiMe3)2] (8b) are isolated in high yield as red
crystalline solids. The chemistry is summarized in eq
2.
The P-N distance in 7a , 1.695(4) Å, is unchanged
from that in 4a , and the P-C(16) distance, 1.835(4) Å,
is only slightly elongated compared to the starting
material. The N atom is still trigonal planar in 7a , and
the average N-Si bond length, 1.774 Å, is slightly
longer than the average distance in 4a , 1.764 Å.
In contrast, the molecular structure determination for
7b reveals the structure type 7′ suggested by Malisch.2
A view of the molecule is shown in Figure 3, and selected
bond lengths and angles are given in Table 2. The W,
S, and P atoms form a three-membered ring in which
the W-P distance 2.411(2) Å is intermediate between
the values found for 4a , 4b,7 and 7a . Further, the P-S
distance 2.023(2) Å is within the expected single bond
range9 as opposed to the nonbonding condition found
in 7a , while the W-S distance 2.538(2) Å is longer than
The mass spectra of both 8a ,b display a parent ion
envelope as well as fragment ion envelopes correspond-
ing to [M - CO+] and [M - 2CO+], and as with 7a ,b,
the {M - 2CO+] ion envelope is considerably more
intense. Both compounds display two infrared bands
in the CO stretch region: 8a , 1959 and 1886 cm-1, and
8b, 1951 and 1875 cm-1 (cyclohexane solution). These
data are identical to those found for 7a ,7b. The
compounds show a single resonance in the 31P NMR
spectra, each split into doublets by P-Se coupling: 8a ,
(13) Sim, G. A.; Sime, J . G.; Woodhouse, D. I.; Knox, G. R. Acta
Crystallogr. 1979, 35b, 2403.
(14) Huneke, J . T.; Enemark, J . H. Inorg. Chem. 1978, 17, 3698.
(15) Simhon, E. D.; Baenziger, N. C.; Kanatzidis, M.; Draganjac, M.;
Coucouvanis, D. J . Am. Chem. Soc. 1981, 103, 1218.
(16) Coucouvanis, D.; Draganjac, M. J . Am. Chem. Soc. 1982, 104,
6820.
1
1
δ 85.9, J PSe ) 497.8 Hz; 8b, δ 43.92, J PSe ) 469.2 Hz.

454 Organometallics, Vol. 16, No. 3, 1997
Reisacher et al.
a vacant out-of-plane π* symmetry MO distributed over
the P atom and two N atoms of P(X)(Y)+. In 4a ,b, since
neither the Ph group nor the N(SiMe3)2 group will be
as efficient at out-of-plane p orbital overlap compared
to NR2, the π back-donation from the metal will occur
into an orbital more localized on the P atom. It is
reasonable to assume that the HOMO in 4a ,b will be
the π symmetry MfP MO, whose electron density will
be largely localized on the P atom, or it will be the
remaining occupied d orbital (dyz) that is nonbonding
with respect to the M-P(X)(Y) unit. These orbitals are
probably very similar in energy, and the precise orbital
composition of the HOMO will depend upon the elec-
tronic character of the substituents on the P atom and
the specific metal atom and its substituents.
The electrons in the HOMO orbital of 4a ,b will be the
focus of approaching electrophiles such as Lewis acids
and oxidants. In the case of BH3 attack on 4a which
produced 5,4f it was suggested that the π-symmetry
MofP HOMO donates electron density into the empty
p orbital on the BH3 fragment, forming a B-P σ bond.
In addition, this is supplemented by interaction of the
LUMO of 4 (the antibonding component of the MofP π
bond) with electron density from one of the degenerate
HOMO orbitals (B-H bonds) on the BH3 fragment. This
results in the B-H-Mo bridge bond that is largely
polarized toward the metal. A similar picture may be
utilized to rationalize the structure of 6 containing the
CO group bridging the Cp(CO)2Mo fragment and the Fe-
(CO)3 fragment.
F igu r e 4. Molecular geometry and atom-labeling scheme
for Cp(CO)2MoSeP(Ph)[N(SiMe3)2] (8a ) with H atoms omit-
ted. Thermal ellipsoids are represented at the 25% prob-
ability level.
1
The latter also shows 184W satellite coupling J PW
)
290.2 Hz. It is interesting that, like 7b, the 31P chemical
1
shift for 8b appears upfield of that for 8a . The H and
13C NMR data are also consistent with the proposed
formulation of the compound, and the 13C{1H} spectra
reveal inequivalent SiMe3 group environments.
The molecular structure of 8a was determined and
found clearly to have the structure type 7′. A view of
the molecule is shown in Figure 4, and bond lengths
and angles are summarized in Table 2. The structure
By extension, we suggest here that a related view may
be employed to understand the bonding in 7b, 8a , and
8b. If the HOMO electron density were fully localized
on the phosphorus atom (e.g., in a P atom lone pair),
oxidation by S or Se would be expected to produce a
terminal thio- or selenophosphoryl species 7′′. Alter-
natively, a more ionic structure +P-E- might develop
in an intermediate species. The resulting electron-rich
chalcogen could then donate into the MdP π* LUMO
is virtually identical to that of 7b except that the MoSeP
three-membered ring is larger, as expected for substitu-
tion of S by Se: P-Se (2.168(1) Å) and Mo-Se (2.671(1)
Å).
Su m m a r y
The results of this study demonstrate that the met-
allophosphenium complexes 4a ,b react with sulfur and
selenium to produce, in each case, a single product in
high yield. In three of the four combinations, metal-
phosphorus-chalcogen three-membered ring structures
of the general type illustrated by 7′ are formed. These
are related to structures proposed earlier by Malisch
and co-workers for related metallophosphenium
species.2a,d However, combination of S8 with 4a pro-
duces an unusual and unexpected species 7a that
contains a terminal Mo-S single bond. Although the
mechanism for these formal oxidation reactions is
unknown and detailed MO analyses for 7 and 8 have
not yet been attempted, some speculation on how the
molecules form in two classes (7a vs 7b, 8a and 8b) may
be worthwhile based upon previous MO analyses for Cp-
(CO)2M[P(NR2)2]4b,i and 5.4f,17 These calculations reveal
that the metal-phosphorus bond in examples of 2 with
X ) Y ) NR2 can be considered to involve P atom lone
pair donation from the planar phosphenium ion frag-
orbital, resulting in formation of the M-E-P three-
membered ring. This analysis, in fact, can be extended
to rationalize the attack of carbenoid fragments ob-
served by Malisch and our group on Cp(CO)2MP(X)(Y)
species.
The unique result embodied by the structure of 7a
(long, terminal Mo-S bond) remains unrationalized by
this picture. We can only suggest that small differences
in relative orbital energies and characters for 4a + S8
(reactants) and the product 7a must provide stabiliza-
tion for this unexpected structure. It will be interesting
to see if other reactions of 4a ,b and other examples of
2 produce related structural variations. These experi-
mental results also may encourage higher level compu-
tational efforts on these interesting molecules.
Exp er im en ta l Section
ment P(X)(Y)+ into an empty LUMO (dz ) on the
2
Gen er a l P r oced u r es. Standard inert-atmosphere tech-
niques were used for the manipulation of all reagents and
products. Infrared spectra were recorded on a Nicolet Model
6000 FT-IR spectrometer from NaCl solution cells or KBr
pellets. Mass spectra were recorded from a Finnegan GC/MS
system by using the solids inlet probe. NMR spectra were
recorded from Varian FT-80A, GE NT-360, and J EOL GSX-
400 NMR spectrometers. Spectral standards were Me4Si (1H
CpMo(CO)2- fragment. This σ bond component is
supplemented by π back-donation from an occupied
-
metal d orbital (dxz) on the CpMo(CO)2 fragment into
(17) The MO calculations related to 5 were performed on a simplified
model containing a PH2 fragment instead of the P(Ph)[N(SiMe3)2]
fragment.

Molybdenum and Tungsten Phosphenium Complexes
Organometallics, Vol. 16, No. 3, 1997 455
and 13C), H3PO4 (31P), and Se (77Se). NaCpMo(CO)3,18 NaCpW-
(CO)3,19 and [(Me3Si)2N]P(Ph)Cl20 were prepared as described
in the literature. All solvents were rigorously dried with
appropriate drying agents, distilled, and stored over fresh
drying agent.
7.53 (Ph complex multiplet). 7a : orange solid; mp 147-150
°C. Anal. Calcd for MoSPSi2O2NC19H28: C, 44.09; H, 5.45;
N, 2.71. Found: C, 44.74; H, 5.63; N, 2.84. Mass spectrum
(30 eV): m/e 519 (M+, 98Mo), 491 (M - CO+), 463 (M - 2CO+).
Infrared spectrum (cyclohexane, cm-1): 1960 (vs), 1886 (vs).
31P{1H} NMR (CH2Cl2): δ 73. 13C{1H} NMR (CD2Cl2): δ 4.57
(3J CSiNP ) 3.9 Hz, CH3), 4.94 (CH3) 93.74 (Cp), 128-131
(multiplet, Ph). 1H NMR (CD2Cl2): δ 1.45 (CH3), 1.36 (CH3),
5.51 (Cp), 7.37-7.45 (Ph). 7b: orange solid; mp 212-214 °C.
Anal. Calcd for WSPSi2O2NC19H28: C, 37.69; H, 4.66; N, 2.31.
Found: C, 36.66; H, 4.73; N, 2.32. Mass spectrum (30 eV):
m/e 606 (M+, 186W), 550 (M - 2CO). Infrared spectrum
(cyclohexane, cm-1): 1952 (vs), 1873 (vs). 31P{1H} NMR
(C6D6): δ 33.9 (1J PW ) 268.6 Hz). 13C{1H} (C6D6): δ 4.43 (CH3),
P r ep a r a tion of Cp (CO)2M{P (P h )[N(SiMe3)2]} (M ) Mo
(4a ), W (4b)). Typically, [(Me3Si)2N]P(Ph)Cl (1.71g, 2.3 mmol)
was injected dropwise over 10 min with a syringe through a
septum port into a 100 mL Schlenk vessel held at -78 °C
containing NaCpM(CO)3 (2.3 mmol) dissolved in THF (50 mL)
under dry nitrogen. During this time, the solution color
changed from pale yellow to dark purple. The mixture was
then warmed slowly to 23 °C and refluxed overnight under a
nitrogen atmosphere. The solvent was vacuum evaporated
from the resulting mixture, and the dark purple residue was
extracted with benzene and filtered to remove solids (NaCl).
The filtrate was evaporated to dryness leaving a purple
microcrystalline solid. Yield: 90%. Multigram quantities of
both reagents were obtained in an identical fashion by scaling
up the starting quantities of reagents. The course of both
reactions was also studied on a smaller scale for the purpose
of measuring evolved CO with a Toepler pump. In each case,
90-100% of the expected 1 equiv of CO was recovered.
4.82 (CH3), 91.8 (Cp), 128-139 (Ph). 1H (C6D6): δ 0.54 (J PH
)
0.7 Hz, CH3), 5.34 (Cp), 7.6-7.4 (Ph). 8a : orange solid; mp
136-138 °C. Anal. Calcd for MoSePSi2O2NC19H28: C, 40.43;
H, 5.00; N, 2.48. Found: C, 40.57; H, 5.27; N, 2.53. Mass
spectrum (30 eV): m/e 567 (M+, 98Mo, 80Se), 539 (M - CO+),
511 (M - 2CO+), 431 (M - Se+). Infrared spectrum (cyclo-
hexane, cm-1): 1959 (vs), 1886 (vs). 31P{1H} NMR (C6D6): δ
85.9 (J PSe ) 497.8 Hz). 13C{1H} (C6D6): δ 4.77 (J PC ) 2.7 Hz,
1
CH3), 92.9 (Cp), 128.9-142. (Ph) H NMR (C6D6): δ 0.5 (J PH
) 2.2 Hz; CH3), 5.24 (Cp), 7.8 (Ph). 8b: orange solid; mp 136-
138 °C. Anal. Calcd for WSePSi2O2NC19H28: C, 34.98; H, 4.33;
N, 2.15. Found: C, 34.88; H, 4.48; N, 2.15. Mass spectrum
(30 eV): 653 (M+, 184W, 80Se), 597 (M - 2CO+). Infrared
spectrum (cyclohexane, cm-1): 1951 (vs), 1875 (vs). 31P{1H}
NMR (C6D6): δ 43.9 (J PW ) 290.2 Hz, J PSe ) 469.2 Hz). 13C-
{1H} (C6D6): δ 4.56 (CH3), 4.98 (J PC ) 3.0 Hz, CH3), 91.29 (Cp),
128-140 (Ph). 1H (C6D6): δ 0.27 (J PH ) 2.5 Hz, CH3), 5.06
(Cp), 7.4 (Ph).
Cr ysta l Str u ctu r e Deter m in a tion s. Single crystals of 4a ,
7a ,b, and 8a were obtained by cooling saturated solutions of
the compounds to -20 °C and allowing these to stand for 1-14
days at -10 °C. Crystals were sealed in glass capillary tubes
under dry nitrogen. Data were collected on a Siemens P3/F
four circle diffractometer using Mo KR (λ ) 0.710 69 Å) at 20
°C radiation, a scintillation counter, highly oriented graphite
crystal monochromator, and pulse height analyzer. An em-
pirical absorption correction based upon ψ scans was applied
to each data set. Redundant and equivalent data were
averaged and converted to unscaled |Fo| values following
corrections for Lorentz and polarization effects. The calcula-
tions were performed on a Siemens P3 structure solution
system using SHELXTL programs. Neutral atom scattering
factors were employed. The structures were solved by stan-
dard heavy atom methods. Non-hydrogen atoms were refined
Oxid a tion Ch em istr y. P r ep a r a tion of Cp (CO)2(S)M-
{P (P h )[N(SiMe3)2]} (M ) Mo, 7a ), Cp (CO)2MSP (P h )-
[N(SiMe3)2] (M ) W, 7b), a n d Cp (CO)2MSeP (P h )N(SiMe3)2
(M ) Mo (8a ), W (8b)). In a typical reaction, 4a (0.32 g,
0.67mmol) was dissolved in methylcyclohexane or benzene (50
mL) and cooled to -78 °C. To this stirred solution was added
slowly a solution of sulfur (0.21 g, 0.67mmol) in methylcyclo-
hexane or benzene (∼15 mL). Following addition, the mixture
was warmed to 23 °C and stirred overnight. As the mixture
approached room temperature, the dark purple solution turned
yellow-orange. The resulting solution was filtered to remove
a very small amount of suspended solid. The filtrate was
evaporated to dryness leaving a microcrystalline solid, 7a ,
which was recrystallized from either benzene or THF. Com-
pounds 7b, 8a , and 8b were prepared in an identical fashion.
In each case, the product was a crystalline solid recovered in
95% or better yield following one recrystallization.
Ch a r a cter iza tion Da ta . 4a : purple solid; mp 155-157 °C.
Anal. Calcd for MoSi2PO2NC19H28: C, 47.00; H, 5.81; N, 2.88.
Found: C, 47.78; H, 5.99; N, 2.90. Mass spectrum (30 eV):
m/e 487 (M+, 98Mo), 431 (M - 2CO+, 98Mo). Infrared spectrum
(cyclohexane, cm-1): 1948 (vs), 1876 (vs), 1256 (m), 1100 (w),
1081 (w), 1014 (m), 903 (m), 874 (m), 859 (m), 844 (m), 789
(w), 758 (w), 740 (w). 31P{1H} NMR (C6D6): δ 316. 13C{1H}
NMR (CD2Cl2): δ 3.30 (3J CSiNP ) 2.7 Hz, CH3), 93.13 (2J CMoP
) 1.7 Hz, Cp), 128-131 (complex multiplet, Ph). 1H NMR
(CD2Cl2): δ 0.32 (CH3), 5.6 (Cp), 7.5 (Ph). 4b: purple solid;
mp 165-168 °C. Anal. Calcd for WSi2PO2NC19H28: C, 39.79;
H, 4.92; N, 2.44. Found: C, 39.65; H, 5.02; N, 2.57. Mass
spectrum (30 eV): m/e 575 (M+, 186W), 517 (M - 2CO, 186W).
Infrared spectrum (cyclohexane, cm-1): 1941 (vs), 1869 (vs),
1255 (m), 1017 (w), 904 (m), 875 (m), 859 (m), 847 (m), 797
(w). 31P{1H} NMR (C6D6): δ 267, 1J WP ) 702 Hz. 13C{1H} NMR
(CD2Cl2): δ 3.28 (3J CSiNP ) 2.2 Hz, CH3), 91.9 (Cp), 127-132
(complex multiplet, Ph). 1H (CD2Cl2): δ 0.37 (CH3), 5.73 (Cp),
anisotropically and hydrogen atoms isotropically with Uiso
1.2Ueq for the parent atom. A summary of crystallographic
)
data are presented in Table 1.
Ack n ow led gm en t is made to the National Science
Foundation Grant CHE-8503550 for support of this
research. We also wish to thank our colleague, Profes-
sor J . V. Ortiz, for stimulating discussion over the
bonding in these compounds.
Su p p or tin g In for m a tion Ava ila ble: Tables of data col-
lection and structure solution details, fractional atomic coor-
dinates and U values, anisotropic displacement factors, full
bond distances and angles, and H coordinates for 4a , 7a ,b,
and 8a (41 pages). Ordering information is given on any
current masthead page.
(18) King, R. B.; Iqbal, M. Z.; King, A. D. J . Organomet. Chem. 1979,
171, 53.
(19) Fischer, E. O. Inorg. Synth. 1963, 7, 136.
(20) McNamara, W. F.; Reisacher, H.-U.; Duesler, E. N.; Paine, R.
T. Organometallics 1988, 7, 1313.
OM9605490