A general synthesis of phosphaalkenes at zirconium with liberation of phosphaformamides

Article abstract of DOI:10.1039/c2dt32322b

A general, atom-economical method for the synthesis of phosphaalkenes is reported via the net coupling of primary alkyl or aryl phosphines with aryl or alkyl isocyanides at zirconium. The phosphorus-containing ligand can be liberated as the phosphaformamide from zirconium by reaction with an organic electrophile. The Royal Society of Chemistry 2013.

Full text of DOI:10.1039/c2dt32322b

Dalton
Transactions
View Article Online
View Journal | View Issue
PAPER
A general synthesis of phosphaalkenes at zirconium
with liberation of phosphaformamides†
Cite this: Dalton Trans., 2013, 42, 1159
Andrew J. Roering,‡a L. Taylor Elrod,§a Justin K. Pagano,a Sarah L. Guillot,a
Stephanie M. Chan,a Joseph M. Tanskib and Rory Waterman*a
Received 2nd October 2012,
Accepted 18th October 2012
A general, atom-economical method for the synthesis of phosphaalkenes is reported via the net coupling
of primary alkyl or aryl phosphines with aryl or alkyl isocyanides at zirconium. The phosphorus-containing
ligand can be liberated as the phosphaformamide from zirconium by reaction with an organic
electrophile.
DOI: 10.1039/c2dt32322b
www.rsc.org/dalton
significant loss in purification steps. Thus, continued develop-
ment and application of phosphaalkene chemistry depends
Introduction
After decades of interest, molecules containing PvC bonds, upon new and efficient synthetic methods. This report outlines
phosphaalkenes, have retained continual prominence within a broad method for the synthesis of phosphaalkenes at zirco-
the chemical and materials science communities.1 The PvC nium via insertion into Zr–P bonds followed by rearrangement,
moiety displays heightened reaction chemistry, parallel to that a reaction initially reported as a synthetic peculiarity.9 As part
of alkenes,2 which engenders phosphaalkenes unique impor- of this now general transformation, these phosphorus-contain-
tance as pivotal components in electronically intriguing ing ligands can be liberated from zirconium as phosphaform-
materials,3 key molecular precursors in the preparation of amides by reaction with an organic electrophile.
organophosphines,4 and the structural basis for new classes of
transition-metal ligands.3c,5
Unlike alkenes, which are fundamental products of the
Results and discussion
petrochemical industry, phosphaalkenes must be prepared
Phosphaalkene synthesis
synthetically. Effective methods for the preparation of these
A family of zirconium–phosphaalkene complexes were syn-
thesized by reaction of zirconium phosphide complexes, pre-
pared from primary phopshines,10 with a series of isocyanides
(eqn (1)).
molecules are well known, and these can be roughly divided
into condensation, typified by the phospha-Peterson reaction,
and elimination routes.4b,d,6 It must be noted that reactions of
metal phosphinidene complexes are an interesting organo-
metallic addition to that suite.7 While these methods are
effective, they are costly in terms of chemical waste and the
compatibility of some functionalities with synthetic con-
ditions. For example, the phospha-Peterson reaction was
limited to aryl phosphines until only recently.8 Moreover, the
high purity demanded by current applications leads to
ð1Þ
aDepartment of Chemistry, University of Vermont, Cook Physical Sciences Building,
Burlington, VT 05405, USA. E-mail: rory.waterman@uvm.edu;
Fax: +1 802 656-8705; Tel: +1 802 656-0278
This set of reactions was intended to establish the general-
ity of the reaction in that both phenyl and cyclohexyl (i.e., aryl
and alkyl) phosphido complexes as well as aryl and alkyl
isocyanides are able to undergo facile PvC bond formation at
bDepartment of Chemistry, Vassar College, Poughkeepsie, NY 12604, USA
†Electronic supplementary information (ESI) available: Variable temperature
NMR data for 7 (pdf) as well as crystallographic data. CCDC 900053 (6), 900054 zirconium (Table 1). Additionally, the use of 2-chlorotolyl-
(8), 900055 (7), 900056 (12), and 900057 (15). For ESI and crystallographic data
isocyanide begins to establish functional group tolerance in this
chemistry. Reactions proceeded cleanly and gave products in
high isolated yields. For example, treatment of (1) with aryl iso-
in CIF or other electronic format see DOI: 10.1039/c2dt32322b
‡Current address: Department of Chemistry and Biochemistry, University of San
Diego, San Diego, CA 92110, USA.
cyanides (eqn (1), R′ = phenyl, 2,6-ClMeC6H3) resulted in the
formation of phosphaalkene products (N3N)Zr[N(Ph)C(H) =
§Current address: Department of Chemistry, Brown University, Providence, RI
02906, USA.
This journal is © The Royal Society of Chemistry 2013
Dalton Trans., 2013, 42, 1159–1167 | 1159

View Article Online
Paper
Dalton Transactions
and 189.9, respectively, which are also shifted upfield as com-
pared to the respective aryl derivatives.
Table 1 Reaction conditions to form phosphaalkene complexes illustrated in
eqn (1)
The 1H NMR spectrum of 7 displayed broad peaks in the
1H NMR spectrum at ambient temperature suggesting a
dynamic process occurring on the NMR timescale. To investi-
gate this, a variable-temperature NMR study was undertaken.
Cooling toluene-d8 solution of 7 to less than 278 K resulted in
the appearance of a new resonance near the phosphaalkene
proton. This behavior is implicit of an E/Z isomerization of
the phosphaalkene (eqn (2)). The coupling constants for each
resonance, 12 Hz and 5 Hz, respectively, allow an assignment
of the δ 10.04 resonance as the E isomer with the resonance at
δ 9.62 as the Z isomer based on the magnitude of coupling
constants for other phosphaalkene compounds.4b The
existence of both isomers at low temperature demonstrates a
relatively low activation barrier, which was calculated to be
Entry
R/cmpd
R′
Temp [°C]
Yield [%]
1
2
3
4
Ph (1)
Ph (1)
Ph (1)
Ph (1)
Ph (1)
Cy (2)
Ph (1)
Ph
25
25
100
90
80
100
25
92
80
86
84
89
50
78
Ara
Mes
tBu
5
Cy
6
Ara
7b
CH2Ph
a Ar = 2,6-ClMeC6H3. b Reported in ref. 9.
Table 2 Selected 1H, 13C, and 31P{1H} NMR data (δ) with coupling constants
(Hz) in benzene-d6 of phosphaalkenes moieties
Cmpd.
1H(JPH
)
13C(JPC
)
31P
9.50(6) kcal mol−1 11
.
(N3N)ZrN(Ph)C(H)vPPh (3)
(N3N)ZrN(Ar)C(H)vPPh (4)a
(N3N)ZrN(Mes)C(H)vPPh (5)
(N3N)ZrN(tBu)C(H)PPh (6)b
(N3N)ZrN(Cy)C(H)vPPh (7)
(N3N)ZrN(Ar)C(H)vPCy (8)a
(N3N)ZrN(CH2Ph)C(H)vPPh (9)d
10.09(6)
10.29(13)
10.38(12)
10.10(9)
9.90(9)
190.0(45)
194.4c
195.1(53)
187.1(29)
189.9(54)
189.9(54)
193.1(56)
108.1
100.4
95.2
0.484c
87.9
120.0
91.9
ð2Þ
10.16(14)
10.29c
a Ar = 2,6-ClMeC6H3. b NMR spectra collected in toluene-d8. c Broad
resonance. d Reported in ref. 9.
These reactions are also successful for alkyl-substituted
phosphines. Reaction of 2 with (2,6-ClMeC6H3)NuC at 100 °C
resulted in the formation of phosphaalkene product (N3N)Zr-
[N(Ar)C(H)vPCy] (8) in moderate yield (Table 1, entry 6).
NMR spectroscopic data (1H, 13C, and 31P) of 8 were similar to
P(Ph)] (3) and (N3N)Zr[N(2,6-ClMeC6H3)C(H) = P(Ph)] (4) in
good to excellent yields of 92 and 80% respectively (Table 1,
entries 1 and 2). Both reactions occurred at ambient temp-
erature, similar to the previously reported example (Table 1,
entry 7). Compounds 3 and 4 have pseudo-C3v-symmetry with
1
the aryl products (Table 2). Monitoring the reaction by H and
31P NMR spectroscopy in benzene-d6 solution showed high
conversion (>90%) to 8. The lower than typical isolated yield
may be a consequence of product lipophilicity.
1
respect to the ligand backbone as well as diagnostic H NMR
spectroscopic features of the PvC(H) moiety with resonances
as doublets at δ 10.09 and 10.29 with JPH = 6 and 13 Hz,
respectively (Table 2).
Structural characterization
Solid-state structures, determined by X-ray crystallography, aid
in confirming the identification and further understanding of
these complexes. Cooling concentrated ethereal solutions of
7 or 8 at −30 °C for extended periods resulted in X-ray quality
crystals. The molecular structures of compounds 7 and 8,
shown in Fig. 1 and 2, respectively, are highlighted by short
P–C bonds confirming the spectroscopic indications of P–C
π-bonding. Also observed for both structures are relatively long
Zr–N bonds for the phosphaalkene ligand as compared to
those of amido (N3N)ZrNRR′ derivatives, suggestive of limited
ligand-to-metal π-donation.10 These nitrogen atoms are planar
and likely involved in a delocalized π-system with the phospha-
alkene as has been seen for other amine-substituted
phosphaalkenes.12
The solid-state structure of 6 provides insight into its par-
ticular 31P NMR chemical shift (Table 2). Unlike the related
phosphaalkene compounds that have been characterized,
complex 6, which features both a long P–C bond and a short
C–N bond, contains a phosphaformamidinate moiety rather
than a phosphaalkene (Fig. 3). Additional support comes from
Reaction of mesityl isocyanide with 1 at ambient temp-
erature was ineffective, whereas conducting the reaction at
100 °C resulted in good yields of the phosphaalkene product
(Table 1, entry 3). Similar to other zirconium phosphaalkenes
compounds, the phosphaalkene hydrogen atom was observed
1
downfield at δ 10.38 as a doublet with JPH = 12 Hz by H NMR
spectroscopy (Table 2, entry 3). The need for increased heat to
afford the phosphaalkene product is rationalized by the steric
bulk of the mesityl group of the isocyanide.
The use of alkyl isocyanides have also been shown to
provide PvC bonds in moderate to good yields (Table 1,
entries 4, 5, 7). Unlike simple aryl derivatives, reaction of alkyl
isocyanides with 1 required heating to afford phosphaalkene
1
products. The H NMR spectra of (N3N)Zr[(tBu)NCvP(Ph)] (6)
and (N3N)Zr[(Cy)NCvP(Ph)] (7) yielded resonances at δ 10.10
and 9.90, respectively, as doublets with JPH = 9 Hz for both
complexes. These chemical shifts are notably upfield relative
to those for the aryl derivatives. The 13C NMR spectra of 6 and
7 provide phosphaalkene carbon atom resonances at δ 187.1
1160 | Dalton Trans., 2013, 42, 1159–1167
This journal is © The Royal Society of Chemistry 2013

View Article Online
Dalton Transactions
Paper
Fig. 1 Molecular structure of 7 with thermal ellipsoids drawn at the 50% level.
Hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and angles
(°): Zr–N(1) = 2.1740(7), Zr–N(2) = 2.0959(8), Zr–N(3) = 2.4725(8), Zr–N(4) =
2.0649(8), Zr–N(5) = 2.0990(9), N(1)–C(7) = 1.3497(11), C(7)–P(1) = 1.7234(9),
C(7)–P(1)–C(1) = 100.96(4), P(1)–C(7)–N(1) = 128.96(6).
Fig. 3 Molecular structure of 6 with thermal ellipsoids drawn at the 50% level.
One of two independent molecules in the unit cell are shown. Hydrogen atoms
are omitted for clarity. Selected bond lengths (Å) and angles (°): Zr–N(11) =
2.1156(13), Zr–N(12) = 2.1320(12), Zr–N(13) = 2.0997(12), Zr–N(14) = 2.4498(12),
Zr–N(15) = 2.3745(12), Zr–P(1) = 2.8014(4), C(116)–P(1) = 1.8222(2), N(15)–
C(116)
= 1.304(2), N(15)–C(116)–P(1) = 115.22(11), C(116)–P(1)–C(121) =
105.81(7).
Table 3 Selected 1H and 31P NMR data (δ) from 1,1-insertion products
Cmpd.
1H PHPh (JPH
)
31P
(N3N)Zr[C(PHPh)vNMes] (10)
(N3N)Zr[C(PHPh)vNtBu]
(N3N)Zr[C(PHPh)vNCy]
5.91 (266 Hz)
6.16 (258 Hz)
6.33 (261 Hz)
−27.7
−48.7
−49.9
triamidoamine zirconium fragment, η2 bonding is observed.14
Furthermore, the structure of 6 also displays η2 bonding (vide
supra). Therefore, these compounds are unique in that they are
the only metal compounds with a phosphaalkene-containing
ligand to not have an interaction of the PvC moiety with the
metal.
Fig. 2 Molecular structure of 8 with thermal ellipsoids drawn at the 50% level.
Hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and angles
(°): Zr–N(1) = 2.2067(1), Zr–N(2) = 2.085(1), Zr–N(3) = 2.070(1), Zr–N(4) = 2.536(1),
Zr–N(5) = 2.200(1), C(23)–P(1) = 1.708(2), C(23)–N(5) = 1.372(2), P–C(23)–N(5) =
128.80(11), C(23)–P–C(24) = 99.17(7).
The mechanism of phosphaalkene formation is hypoth-
esized to occur through a rearrangement of a phosphine-
substituted iminato complex, the 1,1-insertion product of
(N3N)ZrPHR with R′NuC. Support for this mechanism was
garnered via stoichiometric reactions of phosphido complexes
with isocyanide reagents. Reaction of 1 with MesNuC resulted
in the isolation of (N3N)Zr[η2-C(PHPh)vN(Mes)] (10) as yellow
microcrystals in 67% yield (eqn (3)). The 1H NMR spectrum
of 10 shows pseudo-C3v-symmetry with respect to the ligand
backbone. Key observations in establishing the identity of
10 spectroscopically are a phosphine proton resonance in
the bond angles around phosphorus, where the sum of the
angles indicates that phosphorus is pyramidal (∑∠ ∼ 309°). A
direct comparison of the solid state structure of 6 can be made
with a phosphaguanidate complex (N3N)Zr[N,N:η2-(iPrN)2C-
(PPh2)].13 Complex 6, (N3N)Zr[N,P:η2-N(tBu)vC(H)PPh], is the
tautomer of the sought phosphaalkene complex (N3N)Zr-
[N(tBu)C(H)vPPh]. At present, it is unclear why this tautomeri-
zation is facile while the cyclohexyl derivative 7 is isolated as
the phosphaalkene complex. This apparent tautomerization
merits further investigation.
1
the H NMR spectrum at δ 5.91 as a doublet with JPH = 266 Hz
and an imine resonance at δ 266.9 as a doublet with JPC
=
101 Hz in the 13C NMR spectrum (Table 3). All data for 10
are consistent with that for related insertion products.9,15
Compound 10 is not stable for extended periods. Efforts
to grow X-ray quality crystals would frequently result in the
isolation of 5. Heating solutions of 10 gave 5 in quantitative
yield.
The structures of the phosphaalkene complexes are
unusual in that neither the phosphorus lone pair nor the
double bond of the PvC moiety are associated with the zirco-
nium center. For phosphaguanidate complexes of the
This journal is © The Royal Society of Chemistry 2013
Dalton Trans., 2013, 42, 1159–1167 | 1161

View Article Online
Paper
Dalton Transactions
ð3Þ
Though reaction with many isocyanide reagents resulted in
the formation of phosphaalkene products (vide supra), the use
of mesityl isocyanide afforded the only isolable 1,1-insertion
product. For example, in the reaction of 1 with tert-butyl or
cyclohexyl isocyanide resulted intermediate complexes consist-
ent with 1,1-insertion products were identified as observed by
1H and 31P NMR spectroscopy in benzene-d6 solution
(Table 3). Unfortunately, efforts to isolate these products prior
to rearrangement failed and only products 6 and 7 were iso-
lated, respectively.
Fig. 4 Molecular structure of 12 with thermal ellipsoids drawn at the 50%
level. Hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and
angles (°): Zr–N(1) = 2.093(1), Zr–N(2) = 2.121(1), Zr–N(3) = 2.127(1), Zr–N(4) =
2.475(1) Zr, N(5) = 2.232(1), Zr–C(18) = 2.293(2), P(2)–C(18) = 1.817(2), C(18)–P(2)–
C(25) = 100.74(7), C(18)–P(2)–C(31) = 109.71(7), C(25)–P(2)–C(31) = 102.22(7).
That (N3N)Zr[η2-C(PHPh)vNtBu] was observed in solution
en route to formation of phosphaformamidinate 6 suggests
that these 1,1-insertion products are a common intermediate.
Thus, 6 may represent a deviation from the rearrangement
reaction that would produce a phosphaalkene rather than 6,
the apparent product of tautomerization of a phosphaalkene
complex. That 6 might be a local minimum was tested:
Solutions of 6 in benzene-d6 were heated to 100 °C for
extended periods, but no alternative products were formed and
6 remained unreacted. The energetics of these tautomers are
of further interest.
reported by Hey-Hawkins.15 No mention is made of further
reactivity of the η2-iminoacyl product in that report, but the
results herein suggest that the secondary phosphide substitu-
ent, P(SiMe3)2, would be reticent to the rearrangement that is
facile for primary phosphines (vide infra).
Additional support for a 1,1-insertion product as an inter-
mediate came from a secondary phosphide complex (N3N)-
ZrPPh2 (11). Reaction of 11 with one equiv. of benzylisocyanide
Reaction with electrophiles
resulted in formation of (N3N)Zr[η2-C(PPh2)vNCH2Ph] (12) as These zirconium-bound phosphaalkene complexes react with
analytically pure orange crystals in 81% yield. The key spectro- electrophiles to release the phosphorus-containing fragment
scopic observations in the assignment of the compound and generate (N3N)ZrX byproducts (eqn (4)). Reaction of 5
include a 31P NMR resonance at δ 2.94 and νCN = 1694 cm−1 in with one equiv. of methyliodide afforded (N3N)ZrI and Mes-
the infrared.
(Me)NvC(H)PPh (13). The phosphaformamidine 13 was puri-
Single crystals of 12 were grown from ethereal solution, and fied by flash silica chromatography. These products can also
the molecular structure is presented in Fig. 4. The compound be separated by fractional crystallization from non-polar
features an η2-iminoacyl ligand with Zr–N(5) = 2.232(1) Å, solvents such as pentane, but several crystallization steps are
which is intermediate in distance between those for the amido required. The 1H NMR spectrum of 13 reveals an imine proton
and amine nitrogen donor atoms of the triamidoamine ligand at δ 8.19 as a doublet with JPH = 44 Hz, an upfield shift
in these complexes. This bond length is consistent with from that of 3, and the 31P NMR spectrum of 13 shows a
a metal–nitrogen σ-bond and, as expected, no π-donation. singlet at δ 22.3. Key to the assignment of the phosphaform-
There is nothing exceptional about the diphenylphosphide amidine, JPC = 14.1 Hz was measured for the imine carbon in
substituent with P–C(18) = 2.293(2) Å.
the 13C{1H} NMR spectrum. In a similar reaction, the addition
Heating solutions of 12 in benzene-d6 for extended periods of methyl triflate to 3 results in the formation of compound 13
1
at temperatures as high as 100 °C resulted in no change as well as a product presumed to be (N3N)ZrOTf. The H and
prior to decomposition to a complex mixture of unidentifiable 31P NMR spectra of the organophosphorus product from these
products. That little clean chemistry happened without exceed- separate reactions are identical.
ing the stability of the compound suggests that the migration
Other organic electrophiles are also successful in liberating
of a phenyl substituent is not favorable. At this point, it is a phosphaformamide products. For example, reaction of 5
unclear if the resultant phosphaalkene complex is unstable with benzylbromide in benzene solution resulted in the for-
with a relatively bulky substituent at carbon or if the barrier is mation of (N3N)ZrBr and MesNvCP(CH2Ph)Ph (14). Com-
significantly higher for phenyl migration.
pound 14 was isolated by passing the crude reaction mixture
It is important to note that the 1,1-insertion of an iso- through silica, though isolated yields of 14 were low (<10%).
1
cyanide into a zirconium–phosphorus bond was originally The H NMR spectra of 14 shows an imine proton at δ 8.20 as
1162 | Dalton Trans., 2013, 42, 1159–1167
This journal is © The Royal Society of Chemistry 2013

View Article Online
Dalton Transactions
Paper
a doublet with JPH = 44 Hz. The NMR spectra and coupling Such a reaction pathway is more satisfying because the phospha-
constants of 14 are similar to that of complex 13. alkene phosphorus is considerably less sterically encumbered
Definitive assignment of the phosphaformamide product than is nitrogen.
resulted from the reaction of a more crystalline electrophile.
A catalytic variant of this reaction, where the organopho-
Treatment of 5 with tritylchloride in diethylether at ambient sphorus fragment is lost by cyclometalation of a trimethylsilyl
temperature resulted in the formation of the phosphaform- substituent, may select for the phosphaamidine (PvC)
amide, MesNvCP(Ph)(CPh3) (15), and (N3N)ZrCl. Compound product over the phosphaformamide. Unfortunately, efforts to
15 was passed the crude reaction mixture through a short path make this reaction catalytic have been unsuccessful. Multiple
of silica and crystallized to analytical purity from Et2O in 81% equivalents of starting phosphine and isocyanide are con-
yield. The imine proton of 15 can be found at δ 8.48 as a sumed, but complex mixtures of products, some apparently
doublet with JPH = 36 Hz in the 1H NMR spectrum.
arising from reaction of PvC bonds with starting materials,
are observed. The implication is that conditions to promote
product liberation are in competition with undesired reactions
of starting materials. Though ligand-to-metal π-donation
appears to be attenuated in these phosphaalkene complexes
(vide supra), the Zr–N bond is still likely to be strong,10 which
is known to pose a challenge for promoting product liberation
over alternative reaction pathways.17
ð4Þ
Concluding remarks
Compound 15 was subject to an X-ray crystallography study.
Crystals of 15 were obtained by cooling a concentrated ethereal
solution at −30 °C for extended periods. The solid state struc-
ture of 15 is highlighted by the short CvN bond length of
1.264(2) Å, which is well within range of typical CvN bonds
(Fig. 5). The X-ray study also reveals a pyramidal, sp3 hybri-
dized geometry, around phosphorus (Σ ∠307°).
Two reasonable pathways may explain why reactions of
electrophiles with the zirconium phosphaalkene complexes
produce phosphaformamides rather than phosphamidines.
One possibility is that phosphaamidine products are formed
initially, then these products tautomerize to the phosphaform-
amide. This seems unlikely because there are known phos-
phamidines (R2NC(H)vPR′),16 and these are stable molecules.
The second possibility is that the electrophile reacts with phos-
phorus before nitrogen to give the phosphaformamide directly.
In summary, insertion reactions of isocyanides into terminal
zirconium primary phosphido complexes is a mild and general
route to phosphaalkene products. This process appears to
occur via a 1,1-insertion of the isocyanide into the Zr–P bond
followed by a rearrangement. Liberation of the phosphaform-
amide products from the metal can be accomplished by reac-
tion with organic electrophiles, which were confirmed by
structural characterization of the trityl derivative, 15.
This insertion and rearrangement represents a new, general
alternative in phosphaalkene syntheses and provides phospha-
alkene products in perhaps the most atom economical
route to be seen. There have been no observations to suggest
this reaction should be unique to zirconium or isocyanides,
but primary phosphines appear to be key in the rearrangement
process. Thus, alternative metals and reagents are currently
under exploration.
Experimental section
General considerations
All manipulations were performed under
a
nitrogen
atmosphere with dry, oxygen-free solvents using an M. Braun
glove box or standard Schlenk techniques. Benzene-d6 was
purchased from Cambridge Isotope Laboratory then degassed
and dried over NaK alloy. Celite-454 was heated to a temp-
erature greater than 180 °C under dynamic vacuum for at least
8 h. Elemental analyses were performed on an Elementar
microcube. NMR spectra were recorded with either a Bruker
AXR or Varian 500 MHz spectrometer in benzene-d6 or
toluene-d8 and are reported with reference to residual solvent
resonances (δ 7.16 and δ 128.0 for benzene-d6 or 2.09 for
toluene-d8) or external 85% H3PO4 (0.00). Infrared spectra were
collected on a Perkin Elmer System 2000 FT-IR spectrometer or
Fig. 5 Molecular structure of 15 with thermal ellipsoids drawn at the 50%
level. Hydrogen atoms omitted for clarity. Selected bond lengths (Å) and angles
(°): C(1)–P = 1.930(2), C(20)–P = 1.825(2), C(26)–P = 1.832(2), C(26)–N = 1.264(2),
C(1)–P–C(20) = 103.48(7), C(20)–P–C(26) = 103.60(7), P–C(26)–N = 120.43(13).
This journal is © The Royal Society of Chemistry 2013
Dalton Trans., 2013, 42, 1159–1167 | 1163

View Article Online
Paper
Dalton Transactions
Bruker Alpha FT-IR with an ATR plate at a resolution of
(N3N)Zr[N(Mes)C(H)vPPh] (5). A PTFE-valved Schlenk tube
1 cm−1. GCMS spectra were collected on a Varian Saturn 2100T was charged with 1 (100 mg, 0.178 mmol), mesityl isocyanide
gas chromatograph-mass spectrometer. Starting materials (26 mg, 0.178 mmol), and 4 mL benzene solvent. The yellow
(N3N)ZrPHPh (1), (N3N)ZrPHCy (2), and (N3N)ZrPPh2 (11) were solution was placed in a 100 °C oil bath and stirred for 12 h.
prepared by a reported syntheses.10 Phenylisocyanide was pre- The flask was then brought into the glove-box, and the
pared from a literature route.18 Mesitylisocyanide was prepared benzene was lyophilized under reduced pressure. The crude
as a light brown solid by an analogous procedure from 2,4,6- mixture was purified by washing the solid with hexanes
trimethylaniline. The light brown solid was sublimed at 40 °C leaving colorless microcrystals (108 mg, 0.153 mmol, 86%).
under vacuum to afford mesitylisocyanide as a colorless crys- 1H (500.1 MHz): δ 10.38 (d, JPH = 12 Hz, CH, 1 H) 7.88 (t, C6H5,
talline solid. All other reagents and solvents were obtained 2 H), 7.23 (m, C6H5, 2 H), 7.08 (m, C6H5, 1 H), 6.91 (s, C9H11,
from commercial sources and dried by conventional means.
2 H), 3.20 (t, CH2, 6 H), 2.61 (s, CH3, C9H11, 6 H), 2.27 (t, CH2,
6 H), 2.18 (s, CH3, C9H11, 3 H), 0.045 (br s, CH3, 27 H). 13C{1H}
(125.8 MHz): δ 195.1 (d, JPC = 53 Hz, CvP), 146.3 (s, C6H5),
145.9 (s, C6H5), 145.6 (d, JPC = 7 Hz, C6H5), 135.3 (s, Ar), 133.5
Phosphaalkene syntheses
(N3N)Zr[N(Ph)C(H)vPPh] (3). A 50 mL round bottom flask (s, Ar), 133.3 (s, Ar), 133.2 (s, Ar), 130.6 (s, Ar), 126.3 (s, Ar), 3
was charged with 1 (100 mg, 0.178 mmol) and ca. 5 mL resonances missing and assumed to be under the benzene-d6
benzene solvent. To the flask was added a 2 mL benzene solvent peak, 65.3 (s, CH2), 46.4 (s, CH2), 20.9 (s, C9H11), 20.8
solution of PhNuC (18 mg, 0.178 mmol). An instant color (C9H11), 1.1 (s, CH3). 31P{1H} (202.4 MHz): δ 95.2 (s). IR (KBr,
change from yellow to pale yellow was observed, and the Nujol): 2944 w, 2888 w, 2848 w, 1365 m, 1245 s, 1031 s, 926 s,
solution was stirred at ambient temperature for 2 h. The flask 828 s, 781 s, 731 s, 675 m, 545 m. Anal Calcd for
was then placed in the freezer, and the benzene was lyophi- C31H56N5PSi3Zr: C, 52.79; H, 8.00; N, 9.93. Found: C, 52.56; H,
lized under reduced pressure yielding brown microcrystals 8.19; N, 10.09.
of the title compound (109 mg, 0.163 mmol, 92%).
(N3N)ZrN(C4H9)vC(H)PPh (6). A PTFE-valved Schlenk tube
1H (500.1 MHz): δ 10.09 (d, JPH = 6 Hz, CH, 1 H) 7.84 (t, C6H5, 2 was charged with 1 (100 mg, 0.178 mmol), tert-butyl isocyanide
H), 7.39 (d, C6H5, 2 H), 7.24 (t, C6H5, 2 H), 7.17 (t, C6H5, 2 H), (14.9 mg, 0.178 mmol), and ca. 3 mL benzene solvent. The
7.06 (t, C6H5, 1 H), 6.95 (t, C6H5, 1 H), 3.28 (t, CH2, 6 H), 2.37 solution was heated to 90 °C for 2.5 h. The tube was then
(t, CH2, 6 H), 0.12 (s, CH3, 27 H). 13C{1H} (125.8 MHz): δ 190.0 brought into the glovebox, and the benzene was lyophilized
(d, JPvC = 45 Hz, PvC), 150.6 (d, JPC = 6 Hz, C6H6), 133.1 (d, under reduced pressure to yield yellow microcrystals of the
JPC = 14.5 Hz, C6H6), 129.1 (s, C6H6), 2 resonances missing and titled compound (96 mg, 0.149 mmol, 84%). All NMR
assumed to be under the benzene-d6 solvent peak, 127.1 (s, spectroscopy of this compound was performed in toluene-d8
C6H6), 124.5 (s, C6H6), 123.8 (s, C6H6), 63.6 (s, CH2), 47.7 (s, and at 273 K. 1H (500.1 MHz): δ 10.10 (d, JPH = 8.5 Hz, CH,
CH2), 1.65 (s, CH3). 31P{1H} (202.4 MHz): δ 108.1 (s). IR (KBr, 1 H), 7.87 (t, C6H5, 2 H), 7.34 (d, C6H5 2 H), 7.17 (t, C6H5, 1 H),
Nujol): 2405 w, 2098 w, 1937 w, 1585 s, 1377 s, 1344 m, 1242 s, 3.36 (bs, CH2, 6 H), 2.48 (bs, CH2, 6 H), 1.43 (s, CH3, 9 H), 0.44
1151 s, 1047s, 1021 s, 928 s, 893 m. Anal Calcd for (s, CH3, 27 H). 13C{1H} (125.8 MHz): δ 187.1 (d, JPC = 29 Hz,
C28H50N5PSi3Zr: C, 50.71; H, 7.60; N, 10.56. Found: C, 50.41; C–P), 132.0 (s, C6H5), 125.9 (s, C6H5), 1 resonance missing and
H, 7.29; N, 10.43.
assumed to be under the toluene-d8 solvent peak, 61.6 (bs,
(N3N)Zr[N(2-Cl-6-MeC6H3)C(H)vPPh] (4). A 50 mL round CH2), 59.4 (s, CH3), 48.0 (s, C), 30.8 (bs, CH2), 2.16 (bs, CH3).
bottom flask was charged with 1 (50 mg, 0.089 mmol) and 31P{1H} (202.4 MHz): δ 0.484 (s, C–P). IR (KBr, Nujol): 1463 s,
ca. 5 mL benzene solvent. To the flask, a 2 mL benzene solution 1363 s, 1240 s, 1142 w, 1037 m, 945 w, 827 w, 733 w, 721
of 2-chloro-6-methylphenylisocyanide (13 mg, 0.089 mmol) s. Anal Calcd for C26H54N5PSi3Zr: C, 48.55; H, 8.46; N, 10.89.
was added. The color of the solution changes from yellow Found: C, 48.67; H, 8.59; N, 10.72.
to light red after ∼1 min. The solution was allowed to stir
(N3N)Zr[N(Cy)C(H)vPPh] (7). A PTFE-valved Schlenk tube
for 8 h at ambient temperature at which time the benzene was was charged with 1 (100 mg, 0.178 mmol), CyNuC (19.5 mg,
lyophilized under reduced pressure yielding colorless micro- 0.178 mmol) and ca. 4 mL benzene solvent. The resulting pale-
crystals of the title compound (51 mg, 0.071 mmol, 80%). yellow solution was heated in an oil bath at 80 °C for 3 h. The
1H (500.1 MHz): δ 10.29 (d, JPH = 13 Hz, CH, 1 H), 7.87 (t, Ar, 2 tube was then brought into the glove box and the benzene was
H), 7.26 (d, Ar, 1 H), 7.19 (t, Ar, 2 H), 7.07 (t, Ar, 1 H), 6.95 (d, lyophilized under reduced pressure to afford compound 7 as
Ar, 1 H), 6.78 (t, Ar, 1 H), 3.20 (t, CH2, 6 H), 2.61 (s, CH3, 3 H), colorless microcrystals (106 mg, 0.158 mmol, 89%). 1H
2.28 (t, CH2, 6 H), 0.11 (s, CH3, 27 H). 13C{1H} (125.8 MHz): (500.1 MHz, toluene-d8): 9.90 (d, JPH = 8.6 Hz, 1 H, CH), 7.80 (t,
δ 194.4 (br s, CvP), 146.6 (d, JPC = 7 Hz, Ar), 144.8 (d,), 136.1 C6H5, 2 H), 7.19 (t, C6H5, 2 H), 7.05 (m, C6H5, 1 H), 3.67 (m,
(s, Ar), 133.0 (s, Ar), 132.9 (s, Ar), 131.3 (s, Ar), 130.0 (s, Ar), C6H10, 1 H), 3.21 (t, CH2, 6 H), 2.37 (t, CH2, 6 H), 1.80 (m,
128.6 (s, Ar), 126.4 (s, Ar), 126.2 (s, Ar). 31P{1H} (202.4 MHz): δ C6H10, 2 H), 1.62 (m, C6H10, 3 H), 1.37 (m, C6H10, 3 H), 1.23
100.4 (s). IR (KBr, Nujol): 1581 w, 1462 s, 1260 s, 1160 s, 1040 (m, C6H10, 2 H), 0.17 (s, CH3, 27 H). 31P{1H} (202.4 MHz):
s, 925 s, 836 s, 786 s, 736 m, 679 w. Anal Calcd for δ 87.9 (s). IR (KBr, Nujol): 2360 m, 1461 s, 1377 s, 1245 s, 1043
C29H51ClN5PSi3Zr: C, 48.94; H, 7.22; N, 9.84. Found: C, 48.88; s, 936 s, 836 s, 783 s. Anal Calcd for C29H51ClN5PSi3Zr: C,
H, 7.53; N, 9.99.
50.25; H, 8.43; N, 10.46. Found: C, 50.39; H, 8.62; N, 10.36.
1164 | Dalton Trans., 2013, 42, 1159–1167
This journal is © The Royal Society of Chemistry 2013

View Article Online
Dalton Transactions
Paper
(N3N)Zr[N(2-Cl-6-MeC6H3)C(H)vPCy] (8). A PTFE-valved 2 H), 3.47 (t, CH2, 6 H), 2.64 (t, CH2, 6H), 0.188 (s, CH3, 27 H).
Schlenk tube was charged with 2 (100 mg, 0.176 mmol), 13C{1H} (125.8 MHz): δ 144.9 (d, CvN, JPC = 38.6 Hz), 128.9 (s,
2-chloro-6-methylphenylisocyanide (26.7 mg, 0.176 mmol), C6H5), 128.8 (s, C6H5), 128.7 (s, C6H5), 128.6 (s, C6H5), 136.5
and ca. 5 mL benzene solvent. The resulting pale yellow (d, C6H5, JPC = 10.8 Hz), 135.9 (d, C6H5, JPC = 10.8 Hz), 129.5 (s,
solution was heated at 100 °C for 18 h. The tube was then C6H5), 61.3 (s, CH2), 47.8 (s, CH2), 1.9 (s, CH3). 31P{1H}
brought into the glovebox and the benzene was lyophilized (202.4 MHz): δ 2.96 (s). IR (KBr, Nujol): 1694 s (νCN,), 1584 w,
under reduced pressure. The crude mixture was taken up in 1461 s, 1378 m, 1245 m, 1054 s, 940 s, 910 w, 832 s, 792 m,
minimal Et2O and filtered through Celite. The solution was 698 m, 574 w cm−1. Anal Calcd for C35H56N5PSi3Zr: C, 55.80;
concentrated under reduced pressure until incipient crystalli- H, 7.49; N, 9.30. Found: C, 55.61; H, 7.34; N, 9.01.
zation. The solution was allowed to warm to room temperature
Liberation of phosphaformamides
to redissolve the solid, and the solution was cooled to −30 °C
yielding yellow microcrystals of 8 (63 mg, 0.0878 mmol, 50%).
(Mes)(Me)NC(H)vPPh (13). Method 1. A 50 mL round
1H (500.1 MHz): δ 10.16 (d, JPH = 14 Hz, CH, 1 H), 7.23 (d, Ar, 1 bottom flask was charged with 5 (75 mg, 0.106 mmol), Methyl-
H), 6.92 (d, Ar, 1 H), 6.75 (t, Ar, 1 H), 3.23 (t, CH2, 6 H), 2.57 (s, iodide (15.1 mg, 0.106 mmol) and 3 mL Et2O solvent. The reac-
CH3, 3 H), 2.32 (t, CH2, 6 H), 2.11 (m, C6H11, 2 H), 1.80 (m, tion was stirred at ambient temperature for 2 h where the
C6H11, 2 H), 1.57 (m, C6H11, 3 H), 1.42 (m, C6H11, 2 H), 1.22 solvent was evaporated under reduced pressure. The residual
(m, C6H11, 2 H), 0.121 (s, CH3, 27 H). 13C{1H} (125.8 MHz): solid was dissolved in hexanes and filtered through a plug of
δ 189.9 (d, JPC = 54 Hz, CvP), 130.1 (s, Ar), 2 resonances silica (∼0.075 mg) and dried to afford the title compound as
1
missing and assumed to be under the benzene-d6 solvent an oil (19 mg, 0.072 mmol, 68%). H (500.1 MHz): δ 8.19 (d,
peak, 126.3 (s, Ar), 65.2 (s, CH2), 46.2 (s, CH2), 35.4 (d, JPC = 12 JPH = 45 Hz, CH, 1 H), 7.47 (t, C6H5, 2 H), 7.08 (m, C6H5, 2 H),
Hz), 27.8 (s, C6H11), 26.4 (s, C6H11), 20.9 (s, C6H11), 1.30 (s, 6.74 (s, C6H2, 2 H), 2.15 (s, C6H2, 3 H), 2.04 (s, C6H2, 6 H), 1.56
CH3). 31P{1H} (202.4 MHz): δ 120.0 (s). IR (KBr, Nujol): 2362 m, (d, JPH = 3 Hz, CH3). 13C NMR (125.8 MHz) δ 176.5 (d, JPC
=
1462 s, 1376 s, 1260 w, 1158 w, 1041 w, 926 m, 836 m, 722 14.1 Hz, CvP), 136.1 (s, Ar), 136.0 (s, Ar), 133.8 (d, JPC = 19.1
s. Anal Calcd for C29H57ClN5PSi3Zr: C, 48.53; H, 8.01; N, 9.76. Hz, C6H5) 129.4 (s, Ar), 129.3 (s, Ar), 129.2 (s, Ar), 1 aromatic
Found: C, 48.72; H, 8.32; N, 10.05.
resonance assumed under solvent peak, 126.7 (s, Ar), 21.1 (s,
CH3), 18.7 (s, CH3), 9.2 (s, N–CH3). 31P{1H} (202.4 MHz): δ
−22.3.
1,1-Insertion reactions
(N3N)Zr[C(PHPh)vN(Mes)] (10). A scintillation vial was
Method 2. A 50 mL round bottom flask was charged with 5
charged with 1 (50 mg, 0.0893 mmol) and ca. 2 mL Et2O (98.5 mg, 0.140 mmol), methyl triflate (22.1 mg, 0.140 mmol),
solvent and the solution was cooled to −30 °C. A cold, 2 mL and 3 mL benzene solvent. The reaction was stirred at ambient
Et2O solution of MesNuC (13 mg, 0.0893 mmol) was added temperature for 4 h, then the benzene was lyophilized. The
dropwise to the solution of (N3N)ZrPHPh. The resulting color- residue was dissolved in hexanes, and the solution was filtered
less solution was allowed to stir for 10 min as the solution through a plug of silica. The solution was then concentrated
warmed to ambient temperature where upon Et2O was evapor- under reduced pressure and cooled to −30 °C for several days.
ated under reduced pressure. The resulting solid was extracted 13 (mg, 0.078 mmol, 57%) was obtained as an off-white solid.
into minimal Et2O and filtered through Celite and cooled to Spectroscopic data for this compound is identical to that from
−30 °C where the product was collected as yellow microcrystals Method 1. MS (CI (benzene)): 270 [M + H]+.
1
(43 mg, 0.0598 mmol, 67% yield). H (500.1 MHz): δ 6.84 (m,
(Mes)NvC(H)P(CH2Ph)(Ph) (14). A PTFE-valved Schlenk
Mes, 2 H), 5.91 (d, JPH = 266 Hz, PH, 1 H), 3.26 (t, CH2, 6 H), tube was charged with 5 (75 mg, 0.106 mmol), PhCH2Br
2.48 (t, CH2, 6 H), 2.07 (s, CH3, 6 H), 0.167 (s, CH3, 27 H). 13C (18 mg, 0.106 mmol), and 5 mL benzene solvent. The mixture
{1H} (125.8 MHz): δ 266.4 (d, JPC = 101 Hz, NvC), 149.8 (d, JPC was heated to 80 °C for 2 h. The solution was then flashed
= 15 Hz, C6H6), 135.1 (d, Ar), 134.6 (s, Ar), 134.4 (s, Ar), 131.3 through a plug of silica and the benzene was then lyophilized
(s, Ar), 3 resonances assumed to be under the solvent peak, to afford the title product as a pale yellow oil (29 mg,
1
64.6 (s, CH2), 46.7 (s, CH2), 20.8 (s, C9H11), 20.1 (s, C9H11), 2.2 0.083 mmol, 78%). H (500.1 MHz): δ 8.21 (d, JPH = 44 Hz, CH,
(s, CH3). 31P{1H} (202.4 MHz): δ −27.7 (s).
1 H), 7.47 (m, C6H5, 7 H), 7.11–7.01 (m, C6H5, 3 H), 6.77 (s,
(N3N)Zr[C(PPh2)vNCH2Ph] (12). A 3 mL Et2O solution of 11 C6H2, 2 H), 3.78 (d, JPH = 14 Hz, CH2, 1 H), 3.33 (dd JPH = 14
(50 mg, 0.079 mmol) was cooled to −30 °C, and to that solu- Hz, JHH = 4 Hz, CH2, 1 H), 2.16 (s, CH3, 3 H), 2.10 (s, CH3, 6 H).
tion was added a cold 1 mL Et2O solution of benzyl iso- 13C{1H} (125.8 MHz): δ 175.0 (d, JPC = 16.0 Hz, CvN), 135.3 (d,
cyanide (9.2 mg, 0.079 mmol). After 1 h, resulting light orange JPC = 19.8 Hz, C6H5), 133.3 (s, C6H2), 130.2 (s, C6H2), 130.1 (s,
solution was dried under reduced pressure. The residue was C6H2), 129.5 (s, C6H5), 128.9 (s, C6H5), 2 aromatic resonances
dissolved in Et2O, and the solution was filtered then concen- assumed to be under solvent peak, 126.7 (d, JPC = 32.8 Hz,
trated under reduced pressure and cooled to −30 °C for several CH2), 23.3 (s, CH3), 21.2 (s, CH3). 31P{1H} (202.4 MHz): δ
days. Light orange crystals were collected in several crops −6.67. MS (CI(benzene)): 346 [M + H]+.
and dried under reduced pressure (48 mg, 0.064 mmol, 81%).
(Mes)NvC(H)P(Ph)(CPh3) (15). A 50 mL round bottom flask
1H (500 MHz): δ 8.00 (t, C6H5, 4 H), 7.44 (d, C6H5, 2 H, J = was charged with 5 (100 mg 0.141 mmol) and tritylchloride
7.4 Hz), 7.23 (m, C6H5, 6 H), 7.20 (m, C6H5, 3 H), 5.11 (s, CH2, (39 mg, 0.141 mmol) and 5 mL of diethylether. The reaction is
This journal is © The Royal Society of Chemistry 2013
Dalton Trans., 2013, 42, 1159–1167 | 1165

View Article Online
Paper
Dalton Transactions
Table 4 Crystal data and structure refinement parameters for compounds 6, 7, 8, 12 and 15
6
7
8
12
15
Formula
M
C
26H54N5PSi3Zr
C28H56N5PSi3Zr
669.24
C29H57ClN5PSi3Zr
717.71
C35H56N5PSi3Zr
753.31
C35H32NP
497.59
643.20
Crystal system
Color
a/Å
b/Å
c/Å
α/°
β/°
Monoclinic
Colorless
20.806(1)
19.687(1)
18.640(1)
90
115.838(1)
90
6871.7(6)
P21/c
Monoclinic
Yellow
10.1609(10)
20.3994(19)
16.9631(16)
90
91.791(2)
90
3514.3(6)
P21/n
Triclinic
Monoclinic
Yellow
11.2901(9)
19.5468(16)
18.9804(16)
90
105.424(1)
90
4037.8(6)
P21/n
Monoclinic
Colorless
9.3521(9)
9.9508(9)
29.528(3)
90
94.906(1)
90
2737.9(4)
P21/c
Colorless
10.6702(4)
11.2128(4)
16.7109(6)
83.704(1)
72.392(1)
78.761(1)
1866.4(1)
γ/°
V/Å3
ˉ
P1
2
Space group
Z
8
4
4
4
θ range/°
μ/mm−1
N
1.60 to 30.57
0.494
110 878
21 007
1.56 to 32.20
0.483
65 436
1.85 to 30.51
0.531
30 223
2.17 to 27.45
0.430
46 730
2.16 to 30.57
0.124
42 804
Nind
12 205
11 282
9248
8388
Rint
0.0410
0.0289
0.0651
0.463; −0.313
1.011
0.0474
0.0626
0.1380
5.358; −1.010
1.083
0.0286
0.0297
0.1294
0.710; −0.323
1.029
0.0474
0.0362
0.0724
0.359; −0.397
1.017
0.0703
0.0543
0.1380
5.358; −1.010
1.083
R1a (I > 2σ(I))
wR2b (I > 2σ(I))
Δρmax; Δρmin/e Å3
GoF on R1
a R1 = ||Fo| – |Fc|| / Σ|Fo|. b wR2 = {Σ[w(Fo2 – Fc2)2] / Σ[w(Fo2)2]}1/2
.
allowed to stir at ambient temperature for 8 h, then the
solution is filtered through a plug of silica followed by 4 mL of
Acknowledgements
diethylether. The solution was then concentrated to ∼2 mL This work was supported by the U. S. National Science Foun-
and cooled to −30 °C to give crystals of 13 in three crops dation (NSF, CHE-0747612) and the Research Corporation for
(61 mg, 120 mmol, 81%). 1H (500.1 MHz): δ 8.47 (d, JPH
=
Science Advancement (Cottrell Scholar Award to R. W.).
36 Hz, CH, 1 H), 7.55 (m, C6H5, 2 H), 7.34 (m, C6H5, 6 H), Summer support was provided by through a Noyce Summer
7.12–6.89 (m, C6H5, 12 H), 6.69 (s, C6H2, 2 H), 2.10 (s, CH3, Internship at the University of Vermont (NSF DUE-0934714)
3 H), 2.01 (s, CH3, 6 H). 13C{1H} (125.8 MHz) δ 173.3 (d, JPC
=
to S. L. G. and by the American Chemical Society (ACS)
12.7 Hz, CvN), 151.7 (s, Ar), 145.6 (s, Ar), 145.5 (s, Ar), 133.6 Project SEED and the Green Mountain ACS Local Section for
(d, JPC = 56.1 Hz, C6H5), 130.8 (d, JPC = 10.6 Hz, C(C6H5)), 129.6 S. M. C. X-ray crystallographic facilities were provided by the
(s, Ar), 3 aromatic resonances assumed to be under solvent NSF (CHE-0521237 to J. M. T and CHE-1039436 to R. W.).
peak, 127.8 (s, Ar), 127.0 (s, Ar), 126.7 (s, Ar), 23.3 (s, CH3), The authors thank Dr Charles Campana of Bruker AXS for
21.1 (s, CH3). 31P{1H} (202.4 MHz): δ 20.6. Anal. Calcd for the collection of X-ray data for and assistance in the solution
C35H32NP: C, 84.48; H, 6.48; N, 2.81. Found: C, 84.77; H, 6.72; of 8.
N, 2.81.
Notes and references
X-ray crystallography
1 F. Mathey, Angew. Chem., Int. Ed., 2003, 42, 1578–1604.
X-Ray diffraction data were collected on a Bruker APEX 2 CCD
platform diffractometers (MoΚα, λ = 0.71073 Å) at 125 K. A
suitable crystal of compounds were mounted in a nylon loop
with Paratone-N cryoprotectant oil. The structures were solved
using direct methods and standard difference map techniques
and were refined by full-matrix least squares procedures on F2
with SHELXTL (version 6.14).19 All non-hydrogen atoms were
refined anisotropically. Hydrogen atoms on carbon were
included in calculated positions and were refined using a
riding model. The solution of structure 7 exhibited disorder
and a trimethylsilyl substituent was modeled. Despite some
unusual parameters, a second independent data set collected
on a different sample yielded the same molecular structure.
Crystal data and refinement details are presented in Table 4.
2 K. B. Dillon, F. Mathey and J. F. Nixon, Phosphorus: The
Carbon Copy: From Organophosphorus to Phospha-Organic
Chemistry, Wiley, Chichester, 1998.
3 (a) T. Baumgartner and R. Réau, Chem. Rev., 2006, 106,
4681–4727; (b) P. W. Siu and D. P. Gates, Conjugated Polym.
Synth., 2010, 215–227; (c) J. I. Bates, J. Dugal-Tessier and
D. P. Gates, Dalton Trans., 2010, 39, 3151–3159;
(d) D. P. Gates, in New Aspects in Phosphorus Chemistry V,
ed. J.-P. Majoral, Springer, Berlin/Heidelberg, 2005,
vol. 250, pp. 107–126; (e) R. C. Smith, X. Chen and
J. D. Protasiewicz, Inorg. Chem., 2003, 42, 5468–5470;
(f) R. C. Smith and J. D. Protasiewicz, J. Am. Chem. Soc.,
2004, 126, 2268–2269; (g) R. C. Smith and
J. D. Protasiewicz, Eur. J. Inorg. Chem., 2004, 998–1006;
1166 | Dalton Trans., 2013, 42, 1159–1167
This journal is © The Royal Society of Chemistry 2013

View Article Online
Dalton Transactions
Paper
(h) M. P. Washington, V. B. Gudimetla, F. L. Laughlin, 10 A. J. Roering, A. F. Maddox, L. T. Elrod, S. M. Chan,
N. Deligonul, S. He, J. L. Payton, M. C. Simpson and
J. D. Protasiewicz, J. Am. Chem. Soc., 2010, 132, 4566–4567;
(i) X.-L. Geng, Q. Hu, B. Schäfer and S. Ott, Org. Lett., 2010,
12, 692–695.
M. B. Ghebreab, K. L. Donovan, J. J. Davidson,
R. P. Hughes, T. Shalumova, S. N. MacMillan,
J. M. Tanski and R. Waterman, Organometallics, 2009,
28, 573–581.
4 (a) L. Weber, Eur. J. Inorg. Chem., 2000, 2425–2441; 11 (a) H. S. Gutowsky and C. H. Holm, J. Chem. Phys., 1956,
(b) R. Appel, in Multiple Bonds and Low Coordination in
Phosphorus Chemistry, ed. M. Regitz and O. J. Scherer,
25, 1228–1234; (b) M. Raban, D. Kost and E. H. Carlson,
J. Chem. Soc,. Chem. Commun., 1971, 656–657.
Georg Thieme Verlag, Stuttgart, 1990; (c) A. C. Gaumont 12 K. Paasch, M. Nieger and E. Niecke, Angew. Chem., Int. Ed.,
and J. M. Denis, Chem. Rev., 1994, 94, 1413–1439; 1995, 34, 2369–2370.
(d) L. N. Markovski and V. D. Romanenko, Tetrahedron, 13 A. J. Roering, S. E. Leshinski, S. M. Chan, T. Shalumova,
1989, 45, 6019–6090; (e) F. Mathey, Acc. Chem. Res., 1992,
25, 90–96.
S. N. MacMillan, J. M. Tanski and R. Waterman, Organo-
metallics, 2010, 29, 2557–2565.
5 (a) P. Le Floch, Coord. Chem. Rev., 2006, 250, 627–681; 14 A. J. Roering, S. E. Leshinski, S. M. Chan, S. N. MacMillan,
(b) L. Weber, Coord. Chem. Rev., 2005, 249, 741–763;
(c) L. Weber, Angew. Chem., Int. Ed., 2002, 41, 563–572;
J. M. Tanski and R. Waterman, Organometallics, 2010, 29,
2557–2565.
(d) L. Weber, Angew. Chem., Int. Ed., 1996, 35, 271–288; 15 F. Lindenberg, J. Sieler and E. Hey-Hawkins, Polyhedron,
(e) J. F. Nixon, Chem. Rev., 1988, 88, 1327–1362; 1996, 15, 1459–1464.
(f) O. J. Scherer, Angew. Chem., Int. Ed., 1985, 24, 924–943; 16 (a) M. Song, B. Donnadieu, M. Soleilhavoup and
(g) M. Yoshifuji, Pure Appl. Chem., 2005, 77, 2011–2020;
(h) F. Ozawa and M. Yoshifuji, Dalton Trans., 2006, 4987–
4995.
6 R. Appel and F. Knoll, Adv. Inorg. Chem., 1989, 33, 259–361.
7 (a) D. W. Stephan, Angew. Chem., Int. Ed., 2000, 39, 315–
329; (b) H. Aktas, C. J. Slootweg and K. Lammertsma,
G. Bertrand, Chem.–Asian J., 2007, 2, 904–908; (b) K. Issleib,
H. Schmidt and E. Leißring, Synth. React. Inorg. Met.-Org.
Chem., 1988, 18, 215–223; (c) G. Becker, W. Uhl and
H.-J. Wessely, Z. Anorg. Allg. Chem., 1981, 479, 41–56;
(d) K. Issleib, H. Schmidt and H. Meyer, J. Organomet.
Chem., 1978, 160, 47–57.
Angew. Chem., Int. Ed., 2010, 49, 2–14; (c) R. Waterman, 17 A. F. Maddox, K. A. Erickson, J. M. Tanski and
Dalton Trans., 2009, 18–26. R. Waterman, Chem. Commun., 2011, 47, 11769–11771.
8 J. I. Bates, B. O. Patrick and D. P. Gates, New J. Chem., 2010, 18 B. Kim, J. M. Beebe, Y. Jun, X. Y. Zhu and C. D. Frisbie,
34, 1660–1666. J. Am. Chem. Soc., 2006, 128, 4970–4971.
9 S. N. MacMillan, J. M. Tanski and R. Waterman, Chem. 19 G. M. Sheldrick, Acta Crystallogr., Sect. A: Found. Crystal-
Commun., 2007, 4172–4174.
logr., 2008, A64, 112–122.
This journal is © The Royal Society of Chemistry 2013
Dalton Trans., 2013, 42, 1159–1167 | 1167