Formation and reactivity of a transient cationic alkyl phosphinidene complex

Article abstract of DOI:10.1021/om101025c

Reaction of the chloroisopropylphosphido complex [Cp*Mo(CO) ₃{P(Cl)i-Pr}] (1) with AlCl₃ generates the transient cationic alkylphosphinidene complex [Cp*Mo(CO)₃ {P(i-Pr)}][AlCl₄] (2). If it is generated in the presence of diphenylacetylene, 2 undergoes a (1 + 2) cycloaddition to form the phosphirene complex [Cp*Mo(CO)₃{P(i-Pr)C(Ph)C- (Ph)}][AlCl₄] (3). Reaction of 2 with PPh₃ forms the phosphine- coordinated phosphinidene complex [Cp*Mo(CO)₃{P(PPh₃)(i-Pr)}] [AlCl₄] (4). Compound 2 reacts with Ph₂SiH₂ to insert the phosphinidene phosphorus atom into the Si-H bond, forming the secondary silylphosphine complex [Cp*Mo(CO)₃ {P(H)(SiHPh ₂)(i-Pr)}][AlCl₄] (5). Similarly, 2 reacts with ferrocene to activate a C-H bond, resulting in the formation of [Cp*Mo(CO) ₃{P(H)(i-Pr)(C₅H₄FeC₅H ₅)}][AlCl₄] (6).

Full text of DOI:10.1021/om101025c

ARTICLE
pubs.acs.org/Organometallics
Formation and Reactivity of a Transient Cationic Alkyl
Phosphinidene Complex
Rakesh A. Rajagopalan and Brian T. Sterenberg*
Department of Chemistry and Biochemistry, University of Regina, 3737 Wascana Parkway, Regina, Saskatchewan,
Canada S4S 0A2
S Supporting Information
b
ABSTRACT: Reaction of the chloroisopropylphosphido com-
plex [Cp*Mo(CO)3{P(Cl)i-Pr}] (1) with AlCl3 generates the
transient cationic alkylphosphinidene complex [Cp*Mo(CO)3
{P(i-Pr)}][AlCl4] (2). If it is generated in the presence of
diphenylacetylene, 2 undergoes a (1 þ 2) cycloaddition to form
the phosphirene complex [Cp*Mo(CO)3{P(i-Pr)C(Ph)C-
(Ph)}][AlCl4] (3). Reaction of 2 with PPh3 forms the phos-
phine-coordinated phosphinidene complex [Cp*Mo(CO)3{P(PPh3)(i-Pr)}][AlCl4] (4). Compound 2 reacts with Ph2SiH2 to insert
the phosphinidene phosphorus atom into the SiꢀH bond, forming the secondary silylphosphine complex [Cp*Mo(CO)3
{P(H)(SiHPh2)(i-Pr)}][AlCl4] (5). Similarly, 2 reacts with ferrocene to activate a CꢀH bond, resulting in the formation of
[Cp*Mo(CO)3{P(H)(i-Pr)(C5H4FeC5H5)}][AlCl4] (6).
’ INTRODUCTION
Although the electrophilicity on the phosphinidene phosphorus
is reduced by the π donation from N, these phosphinidenes still
react as electrophiles.6,7,11,19 Since that initial paper, analogous
complexes of Fe, Os, Co, and Re have also been reported.6,7,20
We were interested in extending this methodology to the
formation of cationic terminal phosphinidene complexes with
alkyl or aryl substituents, with the expectation that replacement
of the π-donor amino substituent with an alkyl substituent would
increase the electrophilicity of the resulting phosphinidene
complex. Unfortunately, this methodology is much less versatile
in the formation of alkylphosphinidene compelxes, as many
candidate metal anions simply reduce dichloroalkylphosphines,
rather than substituting chloride to form the targeted chloropho-
sphido complexes.21 Although an alkylchlorophosphido complex
of iron has been described, attempts to form a phosphinidene via
chloride abstraction were not successful.22 Senturk and Carty
showed that the phosphido complex [Cp*Mo(CO)3{P(Cl)-
(i-Pr)}] (1) can be formed by this methodology.23 Here we report
the formation and reactivity of the cationic alkylphosphinidene
complex [Cp*Mo(CO)3(P-i-Pr)][AlCl4] (2), derived from 1 via
chloride abstraction. We will also compare the reactivity of 2 with
that of the aminophosphinidene analogue [Cp*Mo(CO)3(PN-i-
Pr2)][AlCl4] and show that the alkylphosphinidene is more
electrophilic, as expected.
Terminal phosphinidene complexes can be considered phos-
phorus analogues of carbene complexes. Like carbenes, their
reactivity ranges between nucleophilic and electrophilic ex-
tremes. Lappert and co-workers reported the first stable nucleo-
philic phosphinidenes in 1987,1 and the reactivity of nucleophilic
phosphinidene complexes has been well studied.2 The first
electrophilic phosphinidenes were transient species, generated
in situ by the thermal decomposition of 7-phosphanorborna-
diene complexes, and their reactivity has been well studied by
trapping reactions with different substrates.3 Several alternate
routes to transient electophilic phosphinidene complexes have
since been described.4ꢀ6 Characteristic reactions of electrophilic
phosphinidenes include (1 þ 2) cycloaddition, nucleophilic
attack at phosphorus, and bond insertions. The (1 þ 2)
cycloaddition reactions of electrophilic phosphinidenes are ex-
emplified by addition of alkenes and alkynes to phosphinidene
complexes to form phosphirane and phosphirene rings.5,7ꢀ9
Nucleophilic attack at terminal phosphinidene is illustrated by
their reactions with phosphines, which result in PꢀP bond
formation.10,11 Depending on the nature of the phosphinidene,
phosphine coordination to the phosphinidene P atom can be
weak and reversible11 or strong.6,10 Insertion reactions of elec-
trophilic phosphinidenes into OꢀH and NꢀH bonds,9 strained
CꢀN and CꢀO bonds,12 carbonꢀtransition-metal bonds,13 and
carbonꢀhalogen bonds14 have been described. A few isolated
examples of phosphinidene insertion into CꢀH bonds have also
been observed.15ꢀ17
’ RESULTS AND COMPOUND CHARACTERIZATION
The phosphido precursor [Cp*Mo(CO)3{P(Cl)(i-Pr)}] (1)
can be formed via reaction of Cp*Mo(CO)3ꢀ with i-PrPCl2, as
shown in Scheme 2. An alternate route to 1 developed in our
Stable electrophilic terminal phosphinidene complexes of Mo,
W, and Ru were first reported in 2001.18 They were formed via
chloride abstraction from chloroaminophosphido complexes
(Scheme 1) and are stabilized by π donation from N to P.
Received: October 29, 2010
Published: May 09, 2011
r
2011 American Chemical Society
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Scheme 1
Figure 1. ORTEP diagram of [Cp*Mo(CO)3{P(i-Pr)C(Ph)C(Ph)}]-
[AlCl4] (3). Hydrogen atoms and the counterion have been omitted.
Selected distances (Å) and angles (deg): MoꢀP = 2.5090(5), PꢀC4 =
1.779(2), PꢀC5 = 1.784(2), C4ꢀC5 = 1.329(3); PꢀC5ꢀC4 = 67.9(1),
PꢀC4ꢀC5 = 68.3(1), C4ꢀPꢀC5 = 43.78(9).
Scheme 2
solution shows a complex mixture of products and no character-
istic low-field signal for a phosphinidene complex. This is not
surprising, given the absence of heteroatom stabilization. At-
tempts to observe a phosphinidene complex at low temperature
were not successful. At temperatures below 0 °C, the chloride
abstraction reaction from 1 was effectively suppressed. Above
this temperature, decomposition of the phosphinidene is rapid,
and only the decomposition products were observed.
In order to demonstrate that a phosphinidene complex is
being generated, the chloride abstraction reaction was carried out
in the presence of diphenylacetylene (Scheme 3). The reaction
occurs readily at room temperature and results in the formation
of the expected phosphirene complex [Cp*Mo(CO)3{P(i-Pr)-
C(Ph)C(Ph)}][AlCl4] (3) as the only observed product. The
31P NMR spectrum of 3 shows a singlet at δ ꢀ106.9, in the high-
field region expected for a phosphirene complex.25
The structure of 3 was confirmed by X-ray crystallography
(Figure 1). The cationic metal complex shows a four-legged
piano-stool geometry, with three legs occupied by carbonyl
ligands and the fourth by the phosphirene P atom. The isopropyl
group is oriented away from the Cp* ring, and the methyl groups
of the i-Pr group are oriented away from the metal. The MoꢀP
bond length of 2.509 Å is typical for an MoꢀP single bond, and
the structural parameters of the phosphinidene ring are as
expected.25 Reaction with alkynes to form phosphirenes is
considered a characteristic reaction of terminal electrophilic
phosphinidene complexes, and the observed product is strong
supporting evidence for a transient phosphinidene.26
Scheme 3
The electrophilicity of the isopropylphosphinidine 2 toward the
moderately nucleophilic phosphine PPh3 was examined. Genera-
tion of 2 in the presence of PPh3 led to the phosphine-coordinated
phosphinidene complex [Cp*Mo(CO)3{P(PPh3)(i-Pr)}][AlCl4]
(4) (Scheme 4). This reactivity contrasts with that of the
analogous aminophosphinidene complex, which does not react
with triphenylphosphine, although it reacts with more basic
phosphines.11 The 31P NMR spectrum of 4 shows doublets at δ
36.3 and ꢀ19 with a common coupling constant of 459 Hz. This
large coupling constantindicates a directPꢀP bond and falls in the
middle of the range of PꢀP couplings observed in other phos-
phine-coordinated phosphinidene complexes (361ꢀ607 Hz).10,11
Compound 4 has been structurally characterized, and the
ORTEP diagram is shown in Figure 2. The geometry at the metal
laboratory avoids the use of the costly reagent i-PrPCl2 by
forming 1 via reaction of the known dichlorophosphido complex
[Cp*Mo(CO)3PCl2]24 with Zn(i-Pr)2. This is the method we
now routinely use to synthesize 1.
The chloride group on the chloroisopropylphosphido ligand
of complex 1 can be readily abstracted using the Lewis acid AlCl3.
Chloride abstraction, however, does not generate a stable
phosphinidene complex. The 31P NMR spectrum of the reaction
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ARTICLE
Scheme 4
Scheme 5
Figure 2. ORTEP diagram of [Cp*Mo(CO)3{P(PPh3)-i-Pr}][AlCl4]
(4). Hydrogen atoms and the counterion have been omitted. Selected
distances (Å) and angles (deg): Mo1ꢀP1 = 2.5826(5), P1ꢀP2 =
2.1630(6), P1ꢀC4 = 1.890(2); Mo1ꢀP1ꢀP2 = 116.35(2), Mo1ꢀ
P1ꢀC4 = 115.04(6), C4ꢀP1ꢀP2 = 103.47(6).
center is again a four-legged piano stool with carbonyl ligands on
the three legs and the phosphine-coordinated phosphinidene
ligandontheother leg. The geometryatP1is pyramidal, indicating
the presence of a stereoactive lone pair. The lone pair is directed
toward the Cp* ring, allowing the isopropyl group and the
triphenylphosphine moiety to point away from the Cp* ring.
The geometry at P2 is tetrahedral, and the P1ꢀP2 bond distance is
2.163 Å. This distance is closer to a PꢀP single bond (typically
2.21 Å)27 than a PdP double bond (1.985ꢀ2.050 Å in
diphosphenes).28 However, it is significantly shorter than the
PꢀP bond lengths observed in the analogous phosphine-coordi-
nated aminophosphinidenes (2.215ꢀ2.266 Å)6,11 but is compar-
able in length to the PꢀP bond (2.156 Å) in [W(CO)4
{P(PEt3)C(O)OEt)], formed by trapping the transient phosphi-
nidene [W(CO)4{PC(O)OEt)] with triethylphosphine.10
Figure 3. ORTEP diagram of [Cp*Mo(CO)3{P(H)(SiHPh2)(i-Pr)}]
(5). Hydrogen atoms, other than SiꢀH and PꢀH, and the counterion
have been omitted. Selected distances (Å) and angles (deg): Mo1ꢀP1 =
2.533(1), P1ꢀSi1 = 2.296(2); Mo1ꢀP1ꢀC4 = 118.7(2), Mo1ꢀ
P1ꢀSi1 = 117.70(7), Si1ꢀP1ꢀC4 = 105.9(2).
formation of a PꢀH bond. The resonance is further split by small
couplings of 4 Hz to SiH. The SiꢀH resonance appears at δ 5.5 as
a doublet of doublet of doublets, with a 29 Hz coupling to P, 4 Hz
coupling to PꢀH, and a 2 Hz coupling to the isopropyl CH.
Coupling of the SiꢀH with PH and P and 29Si satellites in the 31
spectrum confirm the formation of a PꢀSi bond.
P
The reactivity of the transient phosphinidene 2 toward bond
activation reactions was investigated by generating it in the
presence of diphenylsilane. The reaction results in insertion of
the phosphinidene P atom into the SiꢀH bond, forming the silyl
isopropyl secondary phosphine complex [Cp*Mo(CO)3{P(H)
(SiHPh2)(i-Pr)}] (5) (Scheme 5). Analogous reactivity has been
The ORTEP diagram for the X-ray crystal structure of 5 is
shown in Figure 3. The metal geometry is again a four-legged
piano stool with three carbonyl ligands and one isopropyl silyl
secondary phosphine. The MoꢀP bond length is 2.534 Å, which
is close to the MoꢀP distance observed in the acetylene (3) and
phosphine (4) trapped complexes. The PꢀSi bond length is
2.296 Å, which is typical for a PꢀSi single bond.31 Both P and Si
are tetrahedral, and the substituents are staggered, with the two
hydrogen substituents in relative gauche positions (dihedral
angle 79.6°). The groups on P are oriented such that the large
SiHPh2 group is directed away from Cp*.
described for stable aminophosphinindene complexes.29 The 31
P
NMR of 5 shows a singlet at δ ꢀ64.5 with 29Si satellites and a
1JPSi value of 26 Hz. The presence of the electron-donating
isopropyl group and the relatively electropositive silyl and PH
1
groups shifts the P resonance to high field.30 The H NMR
spectrum shows a doublet of doublets at δ 4.35 that corresponds
to the PꢀH. The large JPH coupling of 326 Hz confirms the
The transient phosphinidene 2 was also found to be suffi-
ciently electrophilic to activate CꢀH bonds. Generation of 2 in
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Figure 4. Calculated and experimental isotope patterns for the molec-
ular ion peak of 6.
the presence of 1 equiv of ferrocene resulted in insertion of
the phosphinidene phosphorus into the CꢀH bond of the
ferrocene to form the ferrocenylisopropylphosphine complex
[Cp*Mo(CO)3{P(H)(i-Pr)(C5H4FeCp)}][AlCl4] (6) (Scheme5).
Although 6 could not structurally characterized, as the crystals
did not diffract, spectroscopic evidence strongly supports the
proposed structure. The 31P NMR spectrum shows a sharp
Figure 5
results from the lack of a π-donor substituent, although the
smaller steric size of the isopropyl group on P may also influence
the reactivity. The greater electrophilicity of the alkylphosphini-
dene is also evident in the structure of the adduct, which has a
significantly shorter and stronger PꢀP bond than any of the
structurally characterized phosphine-coordinated aminopho-
sphinidene complexes.6,11
XꢀH bond activation reactions are characteristic reactions of
terminal electrophilic phosphinidene complexes. These reactions
occur either by initial coordination to P followed by proton
transfer or by a concerted mechanism. Here, we have shown that
the SiꢀH bond can be activated by the transient alkylpho-
sphinidene complex, resulting in insertion of the phosphinidene
P atom into the SiꢀH bond. The same reactivity has previously
been demonstrated with aminophosphinidenes and was ex-
pected for the alkylphosphinidene.
In contrast to the case for aminophosphinidenes, the alkylpho-
sphinidene is also capable of activating the CꢀH bond of
ferrocene. The greater reactivity toward CꢀH bonds reflects
the alkylphosphinidene’s greater electrophilicity. However, this
cationic phosphinidene is still not sufficiently electrophilic to
activate CꢀH bonds other than those of ferrocene. For example,
it is unreactive toward activated aromatic CꢀH bonds. The
reactivity of the cationic alkylphosphinidene complex 2 toward
ferrocene suggests that its electrophilicity is similar to that of the
well-studied transient phosphinindene complexes [W(CO)4
(PR)], which behave similarly toward ferrocene and also fail to
activate other CꢀH bonds.16 Thus, the donor ability of the Cp*
ligand in 2, which is expected to decrease electrophilicity at P, is
offset by the positive charge on the complex, which increases
electrophilicity.
Direct CꢀH activation by electrophilic phosphinidene com-
plexes has potential as a synthetic tool for PꢀC bond formation.
Intramolecular CꢀH activation has been described.15 However,
examples of direct intermolecular CꢀH activation are limited to
activation of the CꢀH bonds in ferrocene. In order to develop
CꢀH activation by terminal electrophilic phosphinidene com-
plexes into a useful synthetic tool, the electrophilicity of the
phosphinidene must be further increased to extend the range of
potential substrates. This might be achieved by replacing the
1
singlet at δ 17. The H NMR spectrum shows a doublet at
δ 5.73 that corresponds to the PꢀH. The large coupling of
378 Hz indicates the direct PꢀH bond. The five H atoms of the
free Cp moiety of ferrocene give a sharp singlet at δ 4.3, while
the phosphine-bound cyclopentadienyl ring shows broad sin-
glets at δ 4.56 (1H), 4.54 (2H), and 4.26 (1H). The 13C NMR
spectrum shows five chemically inequivalent Cp carbons for the
phosphine-bound Cp ring, all of which show phosphorus
coupling with J values ranging from 8 to 46 Hz, clearly dem-
onstrating the addition of the phosphinidene to the Cp ring.
Further evidence for the proposed structure comes from the
electrospay mass spectrum, which shows an isotope pattern
centered at m/z 575 that corresponds to the predicted masses
for the cation of the product (Figure 4).
’ DISCUSSION
The bonding in electrophilic phosphinidene complexes is best
conceptualized by considering them to be derived from the
singlet state of free phosphinidene, which contains two lone pairs
and an empty pz orbital. One lone pair forms a σ-donor
interaction to the transition metal, while the second lone pair
remains stereoactive, leading to the bent geometry at phos-
phorus. The electrophilicity at P results from the empty pz
orbital. In aminophosphinidene complexes, this empty pz orbital
is stabilized by π donation from the heteroatom substituent and
from filled metal d orbitals (Figure 5). The heteroatom stabiliza-
tion of terminal electrophilic phosphinidene complexes is analo-
gous to the heteroatom stabilization of Fischer carbenes and
accounts for the fact that the only known stable terminal
electrophilic phosphinidene complexes are aminophosphini-
denes. In contrast, the empty p orbital in electrophilic alkylphos-
phinidene complexes is only stabilized by metal-to-phosphorus
back-donation. Since the Cp*Mo(CO)3 fragment is cationic and
relatively electron poor, the alkylphosphinidene complex de-
scribed here is expected to be strongly electrophilic because there
is little electronic stabilization of the empty pz orbital.
þ
Cp*Mo(CO)3 fragment with a more electron-poor metal
In the phosphine trapping experiments, the transient alkyl-
phosphinidene is significantly more reactive than its aminopho-
sphinidene analogue. Unlike the aminophosphinidene, the
alkylphosphinidene reacts with triphenylphosphine. The greater
reactivity of 2 can be attributed to the greater electrophilicity that
fragment such as Re(CO)5þ. Synthetic routes to such complexes
are being developed in our group.
In summary, we have shown that a transient cationic alkyl
phosphinidene complex can be generated by chloride abstraction
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1
from a chloroalkylphosphido complex. This is the first cationic
alkylphosphinidene complex to be described. As expected, it
reacts as an electrophilic phosphinidene, and we have demon-
strated examples of three characteristic reactions of electrophilic
phosphinidenes: (1 þ 2) cycloaddition, coordination by nucleo-
philes, and bond insertion reactions. The ability of the alkylphos-
phinidene to activate the CꢀH bond in ferrocene clearly
demonstrates that alkylphosphinidenes are more electrophilic
than the corresponding aminophosphinidenes.
phosphirene ring C), 109.4 (s, C5(CH3)5), 39.8 (d, JPC = 8 Hz,
PCH(CH3)2), 20.3 (d, 2JPC = 2 Hz, PCH(CH3)2), 10.9 (s, C5(CH3)5).
MS (electrospray, CH2Cl2 solution): m/z 569 (Mþ). Anal. Calcd for
C30H32O3PAlCl4Mo: C, 48.94; H, 4.38. Found: C, 48.59; H, 4.42.
Synthesis of [Cp*Mo(CO)3{P(PPh3)i-Pr}][AlCl4] (4).
[Cp*Mo(CO)3{P(i-Pr)Cl] (1; 20 mg, 0.047 mmol) and PPh3 (19 mg,
0.071 mmol) were dissolved in CH2Cl2 (0.5 mL). The resulting solution
was added to AlCl3 (9 mg, 0.071 mmol), resulting in an immediate color
change from yellow to dark red. The solvent was removed in vacuo, and
the residue was extracted into CH2Cl2 (0.5 mL) and crystallized as dark
red crystals by slow diffusion of hexane into the CH2Cl2 solution. Yield:
30 mg, 77%. IR (CH2Cl2 solution, cmꢀ1, ν(CO)): 2036, 1970 sh,
’ EXPERIMENTAL SECTION
1946 cmꢀ1
.
31P{1H} NMR: δ 36.4 (d, 1JPP = 459.3 Hz, MoPP), ꢀ19.9
General Comments. All procedures were carried out under a
nitrogen atmosphere using standard Schlenk techniques or in an inert-
atmosphere glovebox. THF was distilled from Na/benzophenone.
Dichloromethane and hexane were purified using solvent purification
columns containing alumina (dichloromethane) or alumina and copper
catalyst (hexane). Deuterated chloroform was distilled from P2O5. The
NMR spectra were recorded in CDCl3 using a Varian Mercury 300
spectrometer operating at 300.179 MHz (1H) and 121.515 MHz
(31P{1H}). Infrared spectra were recorded in solution in hexane or
CH2Cl2. Mass spectra were recorded using a Finnigan-Matt TSQ-700
mass spectrometer equipped with electrospray ionization and a Harvard
syringe pump.
Synthesis of [Cp*Mo(CO)3{P(Cl)i-Pr}] (1). This compound was
prepared using a modification of the method developed by Senturk
et al.23 To pentamethylcyclopentadiene (0.52 g, 3.8 mmol, 0.60 mL) in
50 mL of THF was added n-butyllithium (1.5 mL of 2.5 M solution in
hexane, 3.8 mmol). Molybdenum hexacarbonyl (1.00 g, 3.78 mmol)
was then added, and the resulting suspension was heated under reflux
for 12 h, resulting in a orange solution of Li[Cp*Mo(CO)3]. This
solution was added in small portions to a solution of dichloroisopro-
pylphosphine (0.93 mL, 7.5 mmol) in 50 mL of THF at ꢀ80 °C. The
reaction mixture was stirred for 30 min at ꢀ80 °C and then warmed to
0 °C. The solvent was removed under vacuum at 0 °C. The red-orange
residue obtained was extracted into pentane (25 mL). The pentane was
removed under vacuum at 0 °C, and the orange oil obtained was
dissolved in a minimum amount of hexane. The hexane solution was
then cooled to ꢀ35 °C for 24 h, resulting in the formation of large
orange crystals. At room temperature, these crystals revert to an oil;
thus, they were stored at ꢀ35 °C. Yield: 0.89 mg, 56%. IR (hexane
solution, cmꢀ1, ν(CO)): 2007, 1945, 1916. 31P NMR: δ 268.7. 1H NMR:
1
1
(d, JPP = 459.3 Hz, MoPP). H NMR: δ 7.85ꢀ7.60 (multiplets, Ph),
2.17 (m, CH(CH3)2), 1.93 (s, 15H, Cp*), 1.083 (dd, 3H, 3JHP = 15.4 Hz.
3JHH = 7.2 Hz, CH3), 1.081 (dd, 3H, 3JHP = 15.6 Hz, 3JHH = 7.0 Hz, CH3).
13C NMR: δ 228.3 (d, 2JCP = 26 Hz, MoCO), 226.6 (s, MoCO), 225.4
(s, MoCO), 134.1 (dd, JPC = 9 Hz, JPC = 3 Hz, Ph), 133.9 (s, Ph), 130.0
(d, JPC = 12 Hz, Ph), 123.7 (dd, 1JPC = 67 Hz, 2JPC = 8 Hz, ipso-Ph), 109.4
1
2
(s, C5(CH3)5), 28.6 (dd, JCP = 28 Hz, JCP = 2 Hz, PCH(CH3)2),
25.1 (d, 2JPC = 8 Hz, PCH(CH3)2), 25.0 (d, 2JPC = 8 Hz, PCH(CH3)2),
10.8 (d, JPC = 6 Hz, C5(CH3)5). Anal. Calcd for C34H32O3P2AlCl4Mo:
C, 49.78; H, 4.55. Found: C, 49.51; H, 4.75.
Synthesis of [Cp*Mo(CO)3{P(H)(SiHPh2)(i-Pr)}][AlCl4] (5).
[Cp*Mo(CO)3{P(i-Pr)Cl] (1; 20 mg, 0.047 mmol) was dissolved in
CH2Cl2 (0.5 mL), and SiH2Ph2 (17 μL, 0.094 mmol) was added. The
resulting solution was mixed well and added to AlCl3 (9 mg, 0.071
mmol), resulting a color change from yellow to dark red. The solvent
was removed in vacuo, and the residue was extracted into CH2Cl2
(0.5 mL) and crystallized as pale yellow crystals by slow diffusion
of hexane into the CH2Cl2 solution. Yield: 29 mg, 82%. IR (CH2Cl2
solution, cmꢀ1): ν(CO) 2051, 1988, 1966, ν(SiH) 2171. 31P{1H}
NMR: δ ꢀ64.5. 1H NMR: 7.80ꢀ7.44 (m, Ph), δ 5.54 (dd, 1H,
2JPH = 28 Hz, 3JHH = 4 Hz, SiꢀH), 4.35 (dd, 1JPH = 327 Hz, 3JHH = 4 Hz,
PH), 2.48 (m, CH(CH3)2), 2.04 (s, 15H, Cp*), 1.29 (dd, 3H, 3JPH =9.9Hz,
3JHH = 7.4 Hz, CH3), 1.22 (dd, JPH = 13.0 Hz, JHH = 7.2 Hz, CH3).
13C NMR: δ 231.5 (s, MoCO), 228.4 (d, 2JCP = 26 Hz, MoCO), 227.3 (d,
2JCP = 24 Hz, MoCO), 136.3 (d, JCP = 2 Hz, Ph), 136.1 (d, JCP = 2 Hz,
Ph), 135.8 (s, Ph), 134.7 (s, Ph), 132.43 (s, Ph), 132.39 (s, Ph), 131.4
(s, Ph), 130.1 (s, Ph), 129.5 (s, Ph), 129.4 (s, Ph), 128.5 (s, Ph), 128.3
3
3
1
(s, Ph), 108.6 (s, C5(CH3)5), 26.4 (d, JCP = 18 Hz, PCH(CH3)2),
25.5 (d, 2JCP = 6 Hz, PCH(CH3)2), 20.3 (d, 2JCP = 2 Hz, PCH(CH3)2),
11.0 (s, C5(CH3)5). Note: the silyl phosphine complex is extremely
sensitive to SiꢀP bond cleavage. As a result, satisfactory elemental analysis
for 5 could not beobtained, asbulksamples alwayscontaindecomposition
products (see ref 29 for a discussion of the SiꢀP cleavage mechanism in
related silylphosphines).
2
3
δ 2.31 (d sept, 1H, JHP = 27.9 Hz, JHH = 7 Hz, CH(CH3)2), 1.96
3
3
(s, 15H, C5(CH3)5), 1.37 (dd, 3H, JHP = 23.4 Hz, JHH = 7.2 Hz,
CH(CH3)2), 1.36 (d, 3H, JHH = 6.9 Hz, CH(CH3)2). 13C NMR:
3
δ 236.8 (d, 2JCP = 9 Hz, MoCO), 229.1 (s, MoCO), 225.0 (s, MoCO),
1
106.6 (s, C5(CH3)5), 36.4 (d, JCP = 47 Hz, PCH(CH3)2), 22.7
2
2
(d, JCP = 18 Hz, PCH(CH3)2), 21.3 (d, JCP = 3 Hz, PCH(CH3)2),
10.6 (d, JPC = 6 Hz, C5(CH3)5). Anal. Calcd for C16H22O3PClMo:
C, 45.25; H, 5.22. Found: C, 45.06; H, 5.34.
Synthesis of [Cp*Mo(CO)3{P(H)(i-Pr)(C10H9Fe)}][AlCl4] (6).
[Cp*Mo(CO)3{P(i-Pr)Cl] (1; 20 mg, 0.047 mmol) and ferrocene (8.8
mg, 0.047 mmol) were dissolved in CH2Cl2 (0.5 mL). The resulting
solution was added to AlCl3 (9.5 mg, 0.071 mmol), resulting in an
immediate color change from yellow to dark red. The solvent was
removed in vacuo, and the residue was extracted into CH2Cl2 (0.5 mL)
and crystallized as orange crystals by slow diffusion of diethyl ether into
the CH2Cl2 solution. Yield: 30 mg, 85%. IR (cast, cmꢀ1, ν(CO)): 2035,
Synthesis of [Cp*Mo(CO)3{P(i-Pr)C(Ph)C(Ph)}][AlCl4] (3).
[Cp*Mo(CO)3{P(i-Pr)Cl] (1; 20 mg, 0.047 mmol) and diphenylace-
tylene (17 mg, 0.017 mmol) were dissolved in CH2Cl2 (0.5 mL). The
resulting solution was added to AlCl3 (12.6 mg, 0.094 mmol), resulting
in a color change from pale yellow to dark red. The solvent was removed
in vacuo, and the residue was extracted into CH2Cl2 (0.5 mL) and
crystallized as orange crystals by slow diffusion of diethyl ether into the
CH2Cl2 solution. Yield: 21 mg, 63%. IR (cast, cmꢀ1, ν(CO)): 2035,
1970, 1944. 31P{1H} NMR: δ ꢀ106.9. 1H NMR: δ 7.9ꢀ7.3 (multiplets,
Ph), 2.28 (septet, 1H, 2JHH = 7.2 Hz, CH(CH3)2), 1.66 (s, 15H, Cp*),
0.93 (dd, 6H, 2JHP = 21.0 Hz, 3JHH = 7.2 Hz, CH(CH3)2). 13C NMR: δ
229.3 (d, 2JCP = 3 Hz, MoCO), 229.2 (d, 2JCP = 36 Hz, MoCO), 132.5 (s,
Ph), 131.7 (s, Ph), 130.7 (d, 3JPC = 6 Hz, o-Ph), 130.3 (s, Ph), 128.6 (d,
3JPC = 5 Hz, o-Ph), 126.5 (d, 2JPC = 6 Hz, ipso-Ph), 125.7 (d, 1JPC = 14 Hz,
1965 sh, 1948. 31P{1H} NMR: δ 17.2 (s). H NMR: δ 5.73 (d, 1H,
1
1JPH = 378 Hz, PꢀH), 4.58 (s, 1H, Cp), 4.55 (s, 2H, Cp), 4.31 (s, 5H,
Cp), 4.27 (s, 1H, Cp), 3.17 (septet, 1H, CH(CH3)2, 3JHH = 9 Hz), 1.87
(s, 15H, Cp*), 1.37 (dd, 3H, 3JPH = 12 Hz, 3JHH = 9 Hz, CH3), 1.30 (dd,
3JPH = 12 Hz, 3JHH = 9 Hz, CH3). 13C NMR: δ 231.1 (s, MoCO), 229.1
(d, 2JCP = 27 Hz, MoCO), 228.3 (s, MoCO), 108.6 (s, C5(CH3)5), 74.1
(d, JCP = 8.8 Hz, C5H4P), 73.1 (d, 1JCP = 46 Hz, C5H4P), 73.0 (d, JCP
=
8.3 Hz, C5H4P), 71.7 (d, JCP = 14.8 Hz, C5H4P), 71.3 (d, JCP = 8.3 Hz,
C5H4P), 70.6 (s, FeC5H5), 33.3 (d, 1JCP = 31 Hz, PCH(CH3)2), 20.8 (d,
2937
dx.doi.org/10.1021/om101025c |Organometallics 2011, 30, 2933–2938

Organometallics
ARTICLE
(12) Marinetti, A.; Mathey, F. Organometallics 1987, 6, 2189.
(13) Devaumas, R.; Marinetti, A.; Mathey, F.; Ricard, L. J. Chem. Soc.,
Chem. Commun. 1988, 1325.
2JCP = 26 Hz, PCH(CH3)2), 16.1 (d, 2JPC = 14 Hz, PCH(CH3)2), 10.9
(s, C5(CH3)5). MS (electrospray, CH2Cl2 solution): m/z 569ꢀ582
(Mþ isotope pattern, see Figure 5). Anal. Calcd for C26H32O3AlCl4-
FePMo: C, 41.97; H, 4.33. Found: C, 41.48; H, 4.36.
(14) Khan, A. A.; Wismach, C.; Jones, P. G.; Streubel, R. Chem.
€
Commun. 2003, 2892. Ozbolat, A.; Khan, A. A.; von Frantzius, G.;
Nieger, M.; Streubel, R. Angew. Chem., Int. Ed. 2007, 46, 2104. Tran Huy,
N. H.; Mathey, F. J. Org. Chem. 2000, 65, 652.
’ ASSOCIATED CONTENT
(15) Champion, D. H.; Cowley, A. H. Polyhedron 1985, 4, 1791.
(16) Svara, J.; Mathey, F. Organometallics 1986, 5, 1159.
(17) Tran Huy, N. H.; Compain, C.; Ricard, L.; Mathey, F.
J. Organomet. Chem. 2002, 650, 57.
S
SupportingInformation. CIF files giving crystallographic
b
data for 3ꢀ5. This material is available free of charge via the
Internet at http://pubs.acs.org.
(18) Sterenberg, B. T.; Udachin, K. A.; Carty, A. J. Organometallics
2001, 20, 2657.
’ AUTHOR INFORMATION
(19) Graham, T. W.; Udachin, K. A.; Carty, A. J. Chem. Commun.
2005, 5890.
(20) Sterenberg, B. T.; Udachin, K. A.; Carty, A. J. Organometallics
Corresponding Author
*E-mail: brian.sterenberg@uregina.ca.
2003, 22, 3927.
(21) Nakazawa, H.; Buhro, W. E.; Bertrand, G.; Gladysz, J. A. Inorg.
Chem. 1984, 23, 3431.
’ ACKNOWLEDGMENT
(22) Malish, W.; Angerer, W.; Cowley, A. H.; Norman, N. C. J. Chem.
Soc., Chem. Commun. 1985, 1811.
(23) Senturk, O. S.; Carty, A. J. Unpublished results.
(24) Maisch, R.; Barth, M.; Malisch, W. J. Organomet. Chem. 1984,
260, C35.
We thank Bob McDonald and Mike Ferguson (University of
Alberta) for X-ray data collection and the NSERC (Discovery
Grant to B.T.S.) and the University of Regina for funding.
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