Synthesis and structural characterization of the first thermally stable, neutral, and electrophilic phosphinidene complexes of vanadium

Article abstract of DOI:10.1021/om100915v

The first thermally stable, neutral, electrophilic phosphinidene complexes of vanadium, [CpV(CO)₃{η¹-P(NR₂)}] (R = ⁱPr (3a), Cy (3b)), have been prepared by the reaction of [Na] ₂[CpV(CO)₃]

Full text of DOI:10.1021/om100915v

ARTICLE
pubs.acs.org/Organometallics
Synthesis and Structural Characterization of the First Thermally Stable,
Neutral, and Electrophilic Phosphinidene Complexes of Vanadium
Todd W. Graham,* Konstantin A. Udachin, Marek Z. Zgierski, and Arthur J. Carty
Steacie Institute for Molecular Sciences, National Research Council of Canada, 100 Sussex Drive, Ottawa, ON, K1A 0R6 Canada, and
The Ottawa-Carleton Chemistry Institute, University of Ottawa, Ottawa, ON, K1N 6N5 Canada
S Supporting Information
b
ABSTRACT: The first thermally stable, neutral, electrophilic
phosphinidene complexes of vanadium, [CpV(CO)3{η1-P-
(NR2)}] (R = iPr (3a), Cy (3b)), have been prepared by the
reaction of [Na]2[CpV(CO)3] with Cl2PNR2. The molecules
3a and 3b have been characterized by microanalysis, IR, and 1H
and 31P{1H} NMR spectroscopy, and for 3a also by single-crystal
X-ray diffraction. The structure of 3a exhibits a piano stool
geometry closely related to that of CpV(CO)4 with an η1-phosphinidene ligand replacing CO in one of the basal coordination sites of
the vanadium atom (V(1)-P(1) = 2.300(2) Å). The reactivity of 3a toward a variety of unsaturated substrates: PhCt
CPh, di-tBu-imidazol-2-ydene, PhN3, and Ph2CdNdN has been examined to probe the electrophilic (or nucleophilic) character of the
low-coordinate P(I) site. In all cases reactions occur exclusively at the phosphinidene phosphorus atom, without CO displacement, affording
examples of P-coordinated phosphirene [CpV(CO)3{P(NiPr2)CPhdCPh}] (7), abnormal NCN carbene adduct [CpV(CO)3{P(NiPr2)-
4-cyclo-C3H2-1,3-(NtBu)2)}] (8), diazaphosphaimine [CpV(CO)3{P(NiPr2)dN-NdCPh2}] (12), and P-coordinated phosphaimine
[CpV(CO)3{P(NiPr2)dNPh}] (14) complexes. The η1-phosphaimine complexes 12 and 14 lose carbon monoxide to yield derivatives
[CpV(CO)2{P(NiPr2)N-NdCPh2}] (9) and [CpV(CO)2{P(NiPr2)dNPh}] (15), which contain η2-(P,N)-coordinated phosphai-
mine ligands. An η3-(P,N,N)-bound phosphaimine ligand is present in an isomer of 9, namely, [CpV(CO)2{P(NiPr2)N-NdCPh2}], 13.
Complexes 3a, 7, 8, 9, 14, and 15 have been characterized by X-ray crystallography.
’ INTRODUCTION
Our own interest in terminal phosphinidene complexes was
stimulated by a longstanding interest in chemical transformations
at bridging, μ-PR ligands in clusters32,33 and by the discovery in
2001 of a synthetic route to isolable, cationic, terminal phosphi-
nidene complexes of molybdenum and tungsten, [Cp*M(CO)3-
{PNiPr2}]AlCl4 (M = Mo, W), involving halide abstraction from
[Cp*M(CO)3{P(Cl)NiPr2}].34 At the time these were the first
fully characterized, electrophilic, terminal phosphinidene complexes,
although NMR spectroscopic evidence had been reported35 for a
related iron cation, [Cp*Fe(CO)2{PNiPr2}]þ, and the phosphaor-
ganic chemistry of transient electrophilic phosphinidenes such as
[(CO)5WdPR] and [(CO)4FedPR)], generated in situ, had been
elegantly explored by Mathey36 and co-workers and Lammertsma
et al.37 The Lammertsma group has recently reported the direct
observation of the phosphinidene complex [W(CO)5(η1-PAr)]
(Ar = aryl) by electrospray ionization tandem mass spectrometry
(ESI-MS/MS), and the chemistry displayed by this reactive species
matches that observed in solution.38
Although stable, terminal phosphinidene (phosphanediyl)
complexes have been known for less than two decades,1 the chemistry
of this fascinating class of molecules has undergone rapid develop-
ment in recent years for several substantive reasons: (i) Phosphini-
dene (R-P) ligands are the heavier congeners of imides (R-N) and
are also isolobal with carbenes (R2C).2,3 Transition metal-phosphi-
nidene complexes are therefore analogous to better known metal-
carbenes and imides. In fact, both nucleophilic phosphinidene com-
plexes,4-20 with an MdP double bond formally derived from the
combination of triplet RP with a triplet ground state metal fragment,
and electrophilic complexes21-26 containing essentially M-P single
bonds resulting from singlet RP-singlet metallic moieties are now well
known. The chemistry of these two classes of molecules is now being
intensively explored.4,21,22,27-29 (ii) The presence and nature of
metal-main group element multiple bonding (MdP, MtP) in
these complexes is of theoretical and reactivity interest.30 (iii) In
terminal M-PR molecules, the phosphorus atom is in a low oxida-
tion state (þ1) and coordination number (2), providing an oppor-
tunity to explore fundamentally different chemistry at a P(I) center.31
Low-coordinate nonmetals, deficient in electrons, should exhibit high
reactivity. (iv) Like metal-carbene complexes, phosphinidene ana-
logues have considerable potential in phosphaorganic synthesis and
catalytic chemistry.4
Over the past few years we have isolated a series of cationic,
terminal complexes including the remaining member [Cp*Cr(CO)3-
{PNiPr2}]þ of the Cr, Mo, W triad, the iron group compounds
[Cp*Fe(CO)2{PNiPr2}]þ (M = Fe, Ru, Os), the rhenium cation
Received: September 22, 2010
Published: February 16, 2011
r
2011 American Chemical Society
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Scheme 1
Figure 2. ORTEP diagram of compound 3a. Selected bond lengths (Å)
and angles (deg): V(1)-P(1) 2.3200(2); P(1)-N(1) 1.6520(6); V(1)-
P(1)-N(1) 120.65(2); P(1)-N(1)-C(4) 117.54(4); P(1)-N(1)-
C(7) 127.79(4).
In the present work, we set out to synthesize neutral, terminal
phosphinidene complexes in an effort to further explore the
limits of stability, the molecular and electronic structures, and
the reactivity of these compounds. We describe herein the first
neutral and electrophilic, terminal phosphinidene complexes
of vanadium, [CpV(CO)3{P(NR2)}] (R = iPr, Cy), their reac-
tions with a variety of unsaturated ligands, and the nature of
the products.
Figure 1. 31P NMR spectrum of compound 3a.
[Re(CO)5{PNiPr2}]þ, and the cobalt complex [Co(CO)3(PPh3)-
{PNiPr2}]þ.21,23-25,34 These molecules, all of which have been struc-
turally characterized, display several important features. They are ther-
mally stable, despite in some notable cases, such as the Re and Co
compounds, the lack of sterically encumbered substituents on the
metal or phosphorus ligand. The thermal stability of [Re(CO)5-
{P(NiPr2)}}þ compared to the reported instability of the isoelec-
tronic [W(CO)5(PR)] is particularly notable. Clearly it would seem
that electronic factors, including the presence of donor substituents
on the nonmetal, are responsible for the enhanced stability of the Re
cation. Close examination of metal-phosphorus bond lengths in this
set of compounds confirms that the M-P bond has mostly single-
bond character with a modest shortening due to Mdπ-Ppπ back-
donation. The latter is strengthened when a CO group is displaced by
a stronger donor phosphine, thus supporting the bonding model.27
Chemically these phosphinidene complexes are clearly electrophilic,
forming adducts via P-P bond formation at the phosphinidene
phosphorus atom with phosphines and diphosphines,8,27,28 affording
P-bound phosphirenes with alkynes,23 generating P-coordinated
phosphaalkenes and phosphaimines with diazoalkanes and organic
azides,22 and undergoing four-electron, two-step oxidation at the P(I)
center with sulfur.39 Such reactions parallel the properties of transient
electrophilic phosphinidenes [(CO)5WdPR] as demonstrated by
Mathey.36
’ RESULTS AND DISCUSSION
The dark brown complexes [CpV(CO)3{η1-P(NR2)}] (R =
iPr (3a), Cy (3b)) were formed in quantitative yield via the
reaction of [Na]2[CpV(CO)3] with Cl2PNR2 (Scheme 1). The
high solubility of the compounds resulted in isolation of the
compounds in 80% and 62% yield, respectively.
The 31P NMR spectrum (Figure 1) of 3a shows a broad flat-
1
topped resonance centered at δ 1100, whereas the H NMR
spectrum shows only the expected Cp and iPr resonances. The
unusual shape of the 31P resonance is likely due to coupling to
51V (I = 7/2) and to N. The iPr methyl resonances appear as two
sharp doublets (δ 1.30 and 1.00), suggesting restricted rotation
about the P-N bond on the NMR time scale.
The formulation of 3a was confirmed crystallographically, and
the structure (Figure 2) features a typical piano-stool geometry,
with the PNiPr2 and three CO ligands occupying the base and a
Cp ligand in the apical position. The V(1)-P(1) separation
(2.3200(2) Å) is only slightly shorter than a typical V-P single
bond length (ca. 2.44 Å) and is longer than the VdP separation
(2.1602(6) Å) in the nucleophilic phosphinidene complex
Theoretical (DFT) studies of terminal phosphinidene com-
plexes have shown that the character (nucleophilic, electrophilic)
of the phosphinidene fragment can be influenced by the metal
fragment, particularly the donor or acceptor properties of the
ligands and the substituents on the phosphorus atom. Strong
donors (e.g., Cp*) favor nucleophilicity and π-acid ligands favor
electrophilicity at the metal, while π-donor substituents on
phosphorus favor electrophilic behavior.
[(Nacnac)V(CH2 Bu)(dPMes*)] (Mes* = 2,4,6-tBu3-C6H2).11
t
The V(1)-P(1) separation in 3a agrees remarkably well with the
calculated bond distance for CpV(CO)3dPH (2.307 Å).30 The
NiPr2 fragment is planar and, in conjunction with the short
P(1)-N(1) separation (1.6520(6) Å), indicates a substantial π-
interaction between P and N. Complexes 3a/3b are the first ther-
mally stable, neutral, electrophilic phosphinidenes to be reported
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Figure 4. ORTEP diagram of compound 8. Selected bond lengths (Å)
and angles (deg): V(1)-P(1) 2.5782(8); P(1)-N(1) 1.717(2); P(1)-
C(15) 1.888(3); N(2)-C(15) 1.420(3); N(2)-C(17) 1.337(3); N(3)-
C(16) 1.372(3); N(3)-C(17) 1.331(3); C(15)-C(16) 1.365(4);
V(1)-P(1)-N(1) 110.47(8); V(1)-P(1)-C(15) 111.18(8); N(1)-
P(1)-C(15) 101.7(1).
dition20 reactions, affording phosphametallacyclobutene complexes.3
We found that the addition of diphenylacetylene to 3a (Scheme 2)
results in the quantitative formation of the crystallographically
characterized (Figure 3) phosphirene complex [CpV(CO)3{η1-
P(NiPr2)C(Ph)dC(Ph)}] (7), which displays a broad 31P NMR
resonance centered at δ -19.
Binding of the alkyne to the phosphinidene phosphorus
results in a significant lengthening of the V(1)-P(1) separation
to 2.455(2) Å (cf. 2.3200(2) Å in 3a); the other bond distances
and angles are unremarkable.
Figure 3. ORTEP diagram of compound 7. Selected bond lengths (Å)
and angles (deg):V(1)-P(1) 2.455(2); P(1)-N(1) 1.684(4); P(1)-
C(10) 1.791(5); P(1)-C(11) 1.778(5); V(1)-P(1)-N(1)117.5(2);
V(1)-P(1)-C(10) 127.7(2); V(1)-P(1)-C(11) 124.2(2); N(1)-
P(1)-C(10) 111.4(2); N(1)-P(1)-C(11) 111.1(2); P(1)-N(1)-
C(18) 126.9(3); P(1)-N(1)-C(21) 117.0(3); C(10)-P(1)-C(11)
43.9(2).
Scheme 2
The electrophilicity of 3a has also been demonstrated by the
reaction with the singlet carbene di-tBu-imidazol-2-ydene, which
results in the quantitative formation of the donor-acceptor
adduct [CpV(CO)3{η1-P(NiPr2)(4-cyclo-C3H2(NtBu)2)}] (8)
(Scheme 2), which displays a broad 31P NMR resonance at δ 72.
The 1H NMR spectrum of 8 shows resonances due to the iPr and
tBu groups, in addition to two downfield signals at δ 7.60 and
7.79. The nonequivalence of the latter two signals suggests that
the carbene fragment is bound to the PNiPr2 fragment via C4 rather
than the normal C2 position. The formulation was confirmed via
X-ray crystallography (Figure 4), and the structure features an NCN-
stabilized phosphinidene complex where the “ylidene” moiety of the
NCN carbene precursor has migrated from C2 to C4; the binding of
the carbene to the phosphinidene phosphorus results in substan-
tial lengthening of both the V(1)-P(1) and P(1)-N(1) bonds
(2.5782(8) and 1.717(2) Å, respectively), and the long P(1)-C(15)
bond (1.888(3) Å) indicates that the latter interaction is primarily
donor-acceptor in nature. A related tungsten phosphinidene com-
plex containing a donor bis(amino)cyclopropylidene moiety has
been recently reported by the Bertrand group.41 We have recently
reported that the reactions of bimetallic μ-phosphinidene com-
plexes [Mn2(CO)8{μ-P(NiPr2)}] and [Co2(CO)4(μ-dppm){μ-P-
(NiPr2)}] afford similar abnormal NCN carbene adducts and that
the migration of the ylidene moiety appears to be induced by steric
interactions between bulky di-R-imidazolylidene R groups and either
the metal-bound ligands or the NiPr2 group bound to phosphorus.42
We were also interested in the interaction of 3a with other
types of reagents that are typically used to introduce carbene
fragments into molecules. For example, the addition of Ph2CdNdN
to 3a (Scheme 3) results in the formation of the new complex
and are also the first electrophilic phosphinidene complexes of
vanadium.
The isoelectronic electrophilic cation [Cp*Mo(CO)3{η1-P-
(NiPr2)}]AlCl4 (4) reacts readily with nucleophiles such as PEt3,
initially forming the phosphine-stabilized phosphinidene adduct
[Cp*Mo(CO)3{η1-P(NiPr2)(PEt3)}]AlCl4 (5), which then
loses a CO ligand and forms the new phosphinidene complex
[Cp*Mo(CO)2(PEt3){η1-P(NiPr2)}]AlCl4 (6), where PEt3 mi-
gration from the coordinated PNR2 fragment to the metal has
occurred.27 The addition of PEt3 to [CpV(CO)3{η1-P(NiPr2)}]
(3a), however, causes no change, and this led us to speculate
whether 3 would display electrophilic or nucleophilic reactivity.
The reaction of phosphinidene complexes toward alkynes is one of
the transformations used to determine whether the phosphinidene
complexes exhibit nucleophilic or electrophilic characteristics: coordi-
nated electrophilic PR fragments undergo 2þ1 cycloaddition reac-
tions with alkynes to form three-membered-ring-containing phosphi-
renes,40 whereas their nucleophilic analogues undergo 2þ2 cycload-
[CpV(CO)2{η2-P(NiPr2NNdCPh2)] (9), which displays two 31
P
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Scheme 3
Scheme 4
Figure 5. ORTEP diagram of compound 9. Selected bond lengths (Å)
and angles (deg): V(1)-P(1) 2.5247(4); V(1)-N(3) 1.900(1); P(1)-
N(1) 1.677(1); P(1)-N(3) 1.686(1); N(2)-N(3) 1.388(2); N(2)-
C(26) 1.294(2); V(1)-P(1)-N(1) 112.02(4); V(1)-P(1)-N(3)
48.79(4); V(1)-N(3)-P(1) 89.32(5); V(1)-N(3)-N(2) 141.73(9);
N(1)-P(1)-N(3) 107.02(6); P(1)-N(3)-N(2) 122.50(9); N(3)-
N(2)-C(26) 118.3(1).
NMR resonances at δ 93 and -10 in a ratio of approximately 1:2.5.
Single crystals of the new complex were readily obtained, and when
dissolved in C6D6 the 31P NMR spectrum showed the above reso-
nances in the same ratio.
The complex crystallizes as a single isomer, and the X-ray
structure (Figure 5) indicates that the diphenyldiazomethane
fragment is bound to the phosphinidene group; carbonyl loss has
also occurred with the vacant coordination site taken up by one
of the P-bound nitrogens. The V(1)-P(1) and V(1)-N(3)
separations (2.5247(4) and 1.900(1) Å, respectively) are long
single bonds, whereas P(1)-N(1) and P(1)-N(3) are short
single bonds (1.677(1) and 1.686(1) Å, respectively). These results
contrast observations obtained with related cationic iron and group VI
metal containing phosphinidenes, which, upon reaction with diphe-
nyldiazomethane, form the complexes [CpFe(CO)2{η1-P(NiPr2)d
N-NdCPh2}]AlCl4 (10) and [CpM(CO)3{η3-P(NiPr2)NNd
CPh2}]AlCl4 (M = Cr, Mo, W) (11), which contain η1- and
η3-phosphadiazaallene ligands, respectively.22 We propose that the
reaction sequence to form complex 9 proceeds through the unstable
complex 12 (Scheme 3), which then undergoes CO loss to form the
product. 31P NMR spectra recorded early in the reaction show the
presence of a compound with a broad resonance appearing at δ 324,
which likely corresponds to complex 12, based on the similarity of the
chemical shift to related vanadium complexes (vide supra). Complex
Figure 6. ORTEP diagram of compound 14. Selected bond lengths (Å)
and angles (deg): V(1)-P(1) 2.362(1); P(1)-N(1) 1.646(3); P(1)-
N(2) 1.547(3); V(1)-P(1)-N(1) 122.7(1); V(1)-P(1)-N(2)
132.0(1); N(1)-P(1)-N(2) 105.2(2).
11 displays a downfield 31P NMR chemical shift (M = W, δ 125; M =
Mo, δ 152; M = Cr, δ 195), and, on the basis of the two resonances
appearing in the 31PNMRspectrumofcomplex9, we suggest that the
diphenyldiazaphosphallene ligandundergoes interconversionbetween
the η2 (δ(31P) -10) and η3 (δ(31P) 95) binding modes (compound
13) rapidly on the NMR time scale.
Organic azides are commonly used to introduce nitrene
fragments (RN) into molecules, and on the basis of the results
described above it was of interest to examine the reactivity of
complex 3 with PhN3. The low-temperature addition of PhN3 to
3a results in N2 loss and oxidation of the P(I) ligand with the
formation of the new phosphaimine complex [CpV(CO)3{η1-
P(NiPr2)dNPh}] (14) (Scheme 4). Complex 14 displays a
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characterized complex, [CpV(CO)3{η2-P(NiPr2)N-NdCPh2}]
(9); in solution 9 interconverts with η3-ligand-containing species
[CpV(CO)2{η3-P(NiPr2)N-NdCPh2}] (13). The addition of
PhN3 to 3a results initially in the formation of an unstable
phosphaaimine complex, which readily transforms to a new species
that contains a four-electron-donor phosphaimine ligand, [CpV-
(CO)2{η2-P(NiPr2)NPh}] (15). The results described above in-
dicate the remarkable utility of electrophilic phosphinidene com-
plexes for the synthesis of new types of phosphorus-containing
ligands.
’ EXPERIMENTAL SECTION
General Comments. All procedures were carried out using
standard Schlenk techniques or in an Innovative Technologies glovebox
under a nitrogen atmosphere. THF and ether were distilled from Na/
benzophenone. Dichloromethane and pentane were purified using solvent
purification columns containing alumina (dichloromethane) or alumina and
copper catalyst (pentane). C6D6 was vacuum distilled from Na/benzophe-
none. NMR spectra were recorded at 400 MHz (1H) or 161.975 (31P{1H}).
Cl2PNR2 (R=iPr, Cy)44 and [Na]2[CpV(CO)3]45 were prepared according
to the literature procedures. CpV(CO)4 and di-tBu-imidazol-2-ylidene were
obtained from Strem Chemicals and used as received. All other reagents were
obtained from Aldrich and were used as received.
Figure 7. ORTEP diagram for compound 15: Selected bond lengths
(Å) and angles (deg): V(1)-P(1) 2.528(2); V(1)-N(1) 1.929(4);
P(1)-N(1) 1.689(5); P(1)-N(2) 1.673(5); V(1)-P(1)-N(1)
49.7(2); V(1)-P(1)-N(2) 112.9(2); V(1)-N(1)-P(1) 88.4(2);
N(1)-P(1)-N(2) 107.3(2).
broad 31P NMR resonance centered at δ 333, and the 1H NMR
spectrum of 14 shows only the expected Cp, iPr, and Ph signals.
The compound has been characterized crystallographically,
and the structure (Figure 6) features a piano stool geometry with
a P-coordinated η1-iPr2NPdNPh ligand, which displays a short
V(1)-P(1) interaction (2.362(2) Å) and a planar iPr2NPdNPh
ligand (P(1)-N(1) 1.646(3) Å, P(1)-N(2) 1.547(3) Å); the
short V-P separation may indicate some back-donation into the
vacant p-orbital on phosphorus in the complex (cf. V(1)-P(1)
2.3200(2) Å in [CpV(CO)3{η1-P(NiPr2)}] (3a)). The PdN bond
length is similar to the analogous separation (1.545(2) Å) in the free
phosphaimine (Me3Si)2NPdNSiMe3.43 Complex 14 contains a rare
example of a coordinated η1-phosphaimine ligand.
a. [CpV(CO)3{η1-P(NR2)}] (R = iPr (3a); R = Cy (3b)). These com-
pounds were prepared in an analogous fashion, and only the synthesis of
compound 3a is described. A 1.212 g (5.314 mmol) sample of CpV-
(CO)4 was added to Na/Hg (1.060 g Na, 46.11 mmol) in 25 mL of
THF, and the mixture was stirred overnight, forming a yellow suspension
of [Na]2[CpV(CO)3]. The suspension was decanted and then cooled to -
45 °C. Cl2PNiPr2 (1.201 g, 5.944 mmol) was added, resulting in the
formation of a brown solution, which was stirred at room temperature for
30 min, and then the solvent was removed in vacuo. The residue was
extracted with 7 ꢀ 10 mL of pentane; the extracts were filtered through
Celite, combined, and then concentrated to ca. 10 mL. Cooling the mixture
to -45 °C overnight and removing the solvent with a pipet allowed for the
isolation of 75% (1.321 g) of compound 3a as a brown crystalline solid.
Further concentration of the mother liquor and cooling to -45 °C overnight
routinely afforded an 80% (1.409 g) combined yield of the product. 3a: 1H
NMR (δ, C6D6, 25 °C): 5.25 (sept., 3JHH = 6.6 Hz, 1H, CH(CH3)2); 5.04
Orange tricarbonyl complex 14 is unstable and readily loses a
CO ligand to form the new green complex [CpV(CO)2{η2-
P(NiPr2)NPh}] (15). The 31P NMR spectrum of 15 shows a sharp
resonance at δ-11, and the 1H NMR spectrum shows signals due to
3
(s, 5H, C5H5); 3.89 (m, 1H, CH(CH3)2); 1.30 (d, JHH = 6.6 Hz, 6H,
CH(CH3)2); 1.00 (d, 3JHH = 6.6 Hz, 6H, CH(CH3)2). 31P NMR (δ, C6D6,
25 °C): 1100 (broad, flat-topped signal). IR (νCO, cm-1, ether): 1953 (s);
1896 (m); 1868 (s). Anal. Calcd for C14H19NO3PV: C, 50.8; H, 5.8; N, 4.2.
Found: C, 50.6; H, 6.2; N, 4.2. 3b: Yield: 62%. 1H NMR (δ, C6D6, 25 °C):
5.08 (s, 5H, C5H5); 4.91 (m, 1H, Cy); 3.73 (m, 1H, Cy); 2.21 (m, 2H, Cy);
i
the Cp, Pr, and Ph groups. A single crystal of complex 15 was
obtained, and the X-ray structure (Figure 7) shows that carbonyl loss
has occurred and that the vacant coordination site has been taken up
by the NPh fragment. The geometry around phosphorus is signifi-
cantly pyramidalized and closely resembles that found in donor-
acceptor adducts such as [Re(CO)5{P(NiPr2)(PPh3)}]AlCl4 (2)8
or in compound 8. The V(1)-P(1) separation (2.528(2) Å) is a
long single bond, and N(1) is planar. The V(1)-N(1) separation
(1.929(4) Å) is a single bond, whereas the P(1)-N(1) and P(1)-
N(2) distances (1.689(5) and 1.673(5) Å, respectively) are slightly
shortened single bonds.
1.78-1.40 (m, 18H, Cy). 31PNMR(δ, C6D6, 25°C): 1111. IR (νCO, cm-1
,
ether): 1952 (s); 1893 (m); 1867 (s). Anal. Calcd for C20H27NO3PV: C,
58.4; H, 6.6; N, 3.4. Found: C, 58.5; H, 6.6; N, 3.5.
b. [CpV(CO)3{η1-P(NiPr2)C(Ph)dC(Ph)} (7). A 40 mg (0.224 mmol)
sample of diphenylacetylene was added at -45 °C to 74 mg (0.223 mmol)
of [CpV(CO)3{η1-P(NiPr2)}] in 1 mL of pentane. The mixture was stirred
at room temperature for 2 h, during which time a crystalline red solid
precipitated. The solvent was decanted, and the solid was then washed with 2
mL of cold (-45 °C) pentane and dried in vacuo. Yield: 70% (83 mg). 1H
NMR (δ, C6D6, 25 °C): 7.90 (m, 4H, C6H5); 7.20-7.15 (m, 4H, C6H5);
7.06 (m, 2H, C6H5); 4.43 (s, 5H, C5H5); 3.38 (sept., 3JHH = 6.8 Hz, 2H,
’ CONCLUSIONS
We have described the synthesis and structural characterization of
the first thermally stable, neutral, electrophilic phosphinidene com-
i
plexes [CpV(CO)3{η1-P(NR2)}] (R = Pr (3a); Cy (3b)); the
3
CH(CH3)2); 1.00 (d, JHH = 6.8 Hz, 12H, CH(CH3)2). 31P NMR (δ,
C6D6, 25 °C): -19 (br). IR (νCO, cm-1, ether): 1956 (s); 1870 (s,
shoulder); 1862 (s). Anal. Calcd for C28H29NO3PV: C, 66.0; H, 5.7; N, 2.8.
Found: C, 65.8; H, 5.3; N, 3.0.
complexes are also the first electrophilic phosphinidene complexes of
vanadium. The electrophilic nature of the complexes is clearly
indicated by the reaction of 3a with diphenylacetylene and di-tBu-
imidazol-2-ylidene, which form phosphirene and abnormal carbene-
stabilized phosphinidene complexes, respectively. The reaction of
complex 3a with diphenyldiazomethane provides a novel, structurally
c. [CpV(CO)3{η1-P(NiPr2)(4-cyclo-C3H2-1,3-(NtBu)2)}] (8). A 27 mg
(0.149 mmol) sampleof1,3-bis(tBu)imidazol-2-ylidene was added to 50 mg
(0.150 mmol) of compound 1a in 1 mL of THF at -45 °C. The solution
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Table 1. Crystallographic Data for Compounds 3a, 7-9, 14, and 15
3a
7
8
9
14
15
formula
fw
C
14H19NO3PV
C28H29NO3PV
509.43
C25H39N3O3PV
511.50
C26H30N3O2PV
498.46
C20H24N2O3PV
422.32
C19H24N2O2PV
394.31
331.21
T, K
125(2)
373(2)
373(2)
273(2)
100(2)
100(2)
cryst syst
space group
unit cell dimens
a, Å
monoclinic
P2(1)/c
monoclinic
P2(1)/c
monoclinic
P2(1)/n
monoclinic
Cc
orthorhombic
Pcba
monoclinic
P2(1)/n
13.0972(6)
8.7514(4)
13.8930(7)
96.581(3)
1581.9(1)
4
14.622(2)
7.9968(8)
21.098(2)
92.693(7)
2464.2(5)
4
18.301(1)
8.5447(6)
18.745(1)
116.968(3)
2612.6(3)
4
12.2647(5)
22.7564(9)
9.8417(4)
117.801(2)
2429.8(2)
4
12.202(2)
10.882(2)
29.912(6)
12.935(5)
10.411(4)
15.338(6)
94.670(7)
2058.8(14)
4
b, Å
c, Å
β, deg
V, A3
3971.8(13)
8
Z
D(calcd), Mg/m3
μ, mm-1
reflns collected
independ reflns
1.391
1.373
1.300
1.363
1.413
1.272
0.733
0.498
0.471
0.502
0.603
0.573
117 992
11 450 [R(int)
= 0.0386]
0.0293
31 355
48 683
52 373
27 273
7858
2912 [R(int)
= 0.2227]
0.0550
4570 [R(int)
= 0.1010]
0.0490
11 063 [R(int)
= 0.0387]
0.0319
3055 [R(int)
= 0.0337]
0.0492
0.1080
1808 [R(int)
= 0.0654]
0.0594
R1 [Fo2 g 2σ(Fo2)]
wR2 (all data)
0.0868
0.1432
0.1523
0.1037
0.1493
was stirred for 1 h, and then pentane was added until incipient precipitation;
cooling to -45 °C overnight resulted in the formation of a red crystalline
solid. The solvent was decanted, and the solid was then dried in vacuo. Yield:
65% (50 mg). 1H NMR (δ, CD2Cl2, 25 °C): 7.79 (s, 1H, dCH); 7.60 (s,
concentrated until precipitation (ca. 3 mL). After cooling overnight to
-45 °C the orange solid was washed with 2 ꢀ 5 mL of cold pentane and
then dried in vacuo. Yield: 30% (93 mg). 1H NMR (δ, C6D6, 25 °C):
7.08 (m, 2H, C6H5); 6.81 (m, 1H, C6H5); 6.61 (m, 2H, C6H5); 4.48 (s,
5H, C5H5);3.53 (m, 2H, CH(CH3)2);1.27 (d, 3JHH = 5.4 Hz, CH(CH3)2).
31P NMR (δ, C6D6, 25 °C): 323 (broad, flat-topped signal). This com-
pound is not stable, and we were unable to obtain microanalysis.
3
1H, dCH); 4.92 (s, 5H, C5H5); 3.68 (sept., JHH = 6.2 Hz, 2H, CH-
(CH3)2); 1.87 (s, 9H, C(CH3)3); 1.61 (s, 9H, C(CH3)3); 1.23 (br s, 6H,
CH(CH3)2);0.97(brs, 6H, CH(CH3)2).31PNMR(δ, CD2Cl2, 25°C): 72
(br). IR (νCO, cm-1, CH2Cl2): 1962 (w); 1891 (s); 1795 (s). Anal. Calcd
for C25H39N3O3PV: C, 58.7; H, 7.7; N, 8.2. Found: C, 58.4; H, 7.4; N, 8.1.
d. [CpV(CO)n{ηm-P(NiPr2)(NNdCPh2)} (n = 2, m = 2 (9); n = 3, m =
1 (12); n = 2, m = 3 (13)). A 44 mg (0.227 mmol) sample of
Ph2CdNdN was added at -45 °C to 75 mg (0.226 mmol) of
[CpV(CO)3{η1-P(NiPr2)}] in 1 mL of THF. After 10 min a sample
of the reaction mixture was taken and the 31P and 1H NMR spectra were
recorded, showing the presence of a small amount of compound 12, in
addition to complexes 9 and 13. The mixture was stirred for 1 h, and then
the solvent was removed in vacuo. The green solid was dissolved in a
minimum volume of pentane and then cooled to -45 °C overnight,
e. [CpV(CO)2{η2-P(NiPr2)NPh}] (15). The pentane solutions from
the above reaction were combined and stirred overnight at room tempera-
ture. The mixture was then concentrated to ca. 1 mL and cooled to -45 °C
overnight, resulting in the formation of a green crystalline solid. Yield: 50%
(154 mg, based on remaining amount of vanadium from the above reaction).
1HNMR(δ, C6D6,25°C): 7.21-7.10 (m, 4H, C6H5);6.90(m,1H,C6H5);
5.32 (s, 5H, C5H5); 2.65 (m, 2H, CH(CH3)2); 1.06 (br s, 6H, CH(CH3)2);
0.98 (br s, 6H, CH(CH3)2). 31P NMR (δ, C6D6, 25 °C): -11. IR (νCO
,
cm-1, ether): 1968 (s); 1857 (s). Anal. Calcd for C19H24N2O2PV: C, 58.9;
H, 6.1; N, 7.1. Found: C, 58.8; H, 6.0; N, 7.2.
1
resulting in the formation of a green crystalline solid. 9: H NMR (δ,
’ ASSOCIATED CONTENT
C6D6, 25 °C): 6.81-7.60 (m, 10H, C6H5); 5.15 (s, 5H, C5H5); 2.88
(sept., 3JHH = 6.7 Hz), 2H, CH(CH3)2); 1.22 (m, 12H, CH(CH3)2). 31
P
S
Supporting Information. X-ray crystallographic data in
b
NMR (δ, C6D6, 25 °C): -11. IR (νCO, cm-1, ether) for mixture of 9
and 13: 1957 (s); 1927 (m); 1870 (s); 1859 (s). 12: 1H NMR (δ, C6D6,
25 °C): 6.75-7.50 (m, 10H, C6H5); 5.09 (s, 5H, C5H5); 3.25 (m, 2H,
CH(CH3)2); 1.12 (m, 12H, CH(CH3)2). 31P NMR (δ, C6D6, 25 °C):
384 (br). This compound is unstable, and it was not possible to obtain an
IR spectrum or microanalytical data. 13: Yield 75% (84 mg). 1H NMR
(δ, C6D6, 25 °C): 6.81-7.65 (m, 10H, C6H5); 5.12 (s, 5H, C5H5); 3.34
(m, 2H, CH(CH3)2); 1.09 (m, 12H, CH(CH3)2). 31P NMR (δ, C6D6,
25 °C): 94. Anal. Calcd for C26H29N3O2PV: C, 62.7; H, 5.9; N, 8.4.
Found: C, 62.5; H, 6.1; N, 8.0.
CIF format for compounds 3a, 7-9, 14, and 15. This material is
available free of charge via the Internet at http://pubs.acs.org.
’ AUTHOR INFORMATION
Corresponding Author
*Phone: 001 519 995 4183. E-mail: tgraham.ja@gmail.com.
’ ACKNOWLEDGMENT
This work was supported by the National Research Council of
Canada and the Natural Sciences and Engineering Research
Council of Canada (to A.J.C.).
e. [CpV(CO)3{η1-P(NiPr2)dNPh}] (14). A solution of 88 mg (0.739
mmol) of PhN3 in 3 mL of THF was added dropwise to 244 mg (0.736
mmol) of [CpV(CO)3{η1-P(NiPr2)}] in 10 mL of THF at -80 °C. The
mixture was warmed to room temperature and stirred for 45 min,
resulting in the formation of a yellow-green solution. The solvent was
removed in vacuo, and the residue extracted with pentane (4 ꢀ 5 mL);
the extracts were filtered through Celite, and the solvent was
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