Reactivity studies of a T-shaped yttrium carbene: C-F and C-O bond activation and C=C bond formation promoted by [Y(BIPM)(I)(THF)2] (BIPM = C(PPh2NSiMe3)2)

Article abstract of DOI:10.1021/om301016j

The yttrium carbene complex [Y(BIPM)(I)(THF)₂] (1; BIPM = C(PPh₂NSiMe₃)₂) was reacted with a range of unsaturated substrates. The reaction of 1 with the phosphaalkyne PCBu ^t afforded the [2 + 2] cycloaddition product [Y{C(PPh ₂NSiMe₃)₂(PCBu^t)- κ⁴C,C′,N,N′}(I)] (2). Similarly, the reactions of 1 with the heteroallenes N,N′-dicyclohexylcarbodiimide and tert-butyl isocyanate gave the [2 + 2] cycloaddition products [Y{C(PPh ₂NSiMe₃)₂[C(NCy)₂]- κ⁴C,N,N′,N″}(I)(THF)] (3) and [Y{C(PPh ₂NSiMe₃)₂[C(O)(NBu^t)]- κ⁴C,N,N′,O}(I)(THF)₂] (4), respectively. In contrast, the reaction of 1 with tert-butyl isothiocyanate afforded the ketenimine Bu^tN=C=C(PPh₂NSiMe₃)₂ (5), with the concomitant formal elimination of YSI(THF) _n . The sterically demanding arylamine 2,6- diisopropylphenylamine reacted with 1 via a 1,2-addition across the Y=C bond to yield the anilide-methanide complex [Y(BIPMH)(NHDipp)(I)(THF)] (6; Dipp = C ₆H₃Prⁱ₂-2,6). The reaction of 1 with the benzopyrone coumarin affords the ring-opened dinuclear aryloxide-enolate complex [Y₂{C(PPh₂NSiMe₃)₂[C(O) (CHCHC₆H₄O-2)]-κ²-N,O:μ,κ- O′}₂(I)(μ-I)(THF)] (7), which is postulated to form by sequential Y-O, C-C, and C=C bond formation and cleavage of the C-O ester linkage and the C=O and Y=C double bonds. Benzoyl fluoride reacts with 1 to afford ¹/₂ equiv of the bis-enolate complex [Y{C(PPh ₂NSiMe₃)₂[C(O)(Ph)]-κ²N,O} ₂(I)] (8) with formal elimination of YF₂I(THF) _n by ligand scrambling. Complexes 2-8 have been characterized by X-ray crystallography, multielement NMR spectroscopy, FTIR spectroscopy, and CHN microanalyses.

Full text of DOI:10.1021/om301016j

Article
pubs.acs.org/Organometallics
Reactivity Studies of a T‑Shaped Yttrium Carbene: C−F and
C−O Bond Activation and CC Bond Formation Promoted
by [Y(BIPM)(I)(THF)2] (BIPM = C(PPh2NSiMe3)2)
David P. Mills, William Lewis, Alexander J. Blake, and Stephen T. Liddle*
School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, U.K.
S
* Supporting Information
ABSTRACT: The yttrium carbene complex [Y(BIPM)(I)(THF)2] (1; BIPM =
C(PPh2NSiMe3)2) was reacted with a range of unsaturated substrates. The
reaction of 1 with the phosphaalkyne PCBut afforded the [2 + 2] cycloaddition
product [Y{C(PPh2NSiMe3)2(PCBut)-κ4C,C′,N,N′}(I)] (2). Similarly, the
reactions of 1 with the heteroallenes N,N′-dicyclohexylcarbodiimide and
tert-butyl isocyanate gave the [2 + 2] cycloaddition products [Y{C-
(PPh2NSiMe3)2[C(NCy)2]-κ4C,N,N′,N″}(I)(THF)] (3) and [Y{C-
(PPh2NSiMe3)2[C(O)(NBut)]-κ4C,N,N′,O}(I)(THF)2] (4), respectively. In
contrast, the reaction of 1 with tert-butyl isothiocyanate afforded the
ketenimine ButNCC(PPh2NSiMe3)2 (5), with the concomitant formal
elimination of “YSI(THF)n”. The sterically demanding arylamine 2,6-
diisopropylphenylamine reacted with 1 via a 1,2-addition across the YC
bond to yield the anilide−methanide complex [Y(BIPMH)(NHDipp)(I)-
(THF)] (6; Dipp = C6H3Pri2-2,6). The reaction of 1 with the benzopyrone
coumarin affords the ring-opened dinuclear aryloxide−enolate complex [Y2{C(PPh2NSiMe3)2[C(O)(CHCHC6H4O-2)]-κ2-
N,O:μ,κ-O′}2(I)(μ-I)(THF)] (7), which is postulated to form by sequential Y−O, C−C, and CC bond formation and
cleavage of the C−O ester linkage and the CO and YC double bonds. Benzoyl fluoride reacts with 1 to afford 1/2 equiv of
the bis-enolate complex [Y{C(PPh2NSiMe3)2[C(O)(Ph)]-κ2N,O}2(I)] (8) with formal elimination of “YF2I(THF)n” by ligand
scrambling. Complexes 2−8 have been characterized by X-ray crystallography, multielement NMR spectroscopy, FTIR
spectroscopy, and CHN microanalyses.
substituents in stabilizing molecular mononuclear lanthanide and
actinide carbenes is illustrated by the formation of polymetallic
clusters with bridging methylidene fragments in their absence.6
Cavell was the first to report a bis(phosphorus-stabilized)
lanthanide carbene complex in 2000, namely [Sm(BIPM)-
(NCy2)(THF)], by the double deprotonation of the parent
methane with the homoleptic complex samarium(III) tris-
(dicyclohexylamide).7 This synthetic route required forcing
conditions, and perhaps as a consequence no reactivity studies
have been reported for [Sm(BIPM)(NCy2)(THF)] to date.
More recently, Le Floch and co-workers prepared a neodymium-
(III) carbene with a related ligand framework, [Nd{C-
(PPh2NPri)2}{HC(PPh2NPri)2}], by unusually facile deprotona-
tion of the methanide precursor [Nd{HC(PPh2NPri)2}2(I)] with
potassium bis(trimethylsilyl)amide, but no reactivity studies have
been reported.8
INTRODUCTION
■
The field of f-block carbene chemistry is poorly developed in
comparison to transition-metal carbene chemistry, which has
been investigated extensively as a consequence of the synthetic
utility of these systems.1 Most of the previously reported
f-block carbene chemistry in the literature is that of dative,
Lewis basic N-heterocyclic carbenes,2 but there are consid-
erably fewer examples of f-block carbene complexes that are not
derived from stable free carbenes.3 This can be attributed to the
energetic mismatch of the relevant frontier orbitals of the formal
LnC or AnC double bond, which makes the preparation of
such complexes synthetically challenging. However, the highly
polarized bonding in these systems promises interesting
reactivities.4 It is noteworthy that the modest amount of
covalency in the MC double bond of early-metal carbene
complexes has led to them being more commonly referred to as
geminal methanediides, which may be a more appropriate
description of the bonding in these systems.5
́
Le Floch, Nief, and Mezailles employed salt metathesis
methodologies to prepare the lanthanide bis(diphenylthio-
The most successful strategy that has been employed to
overcome the inherent instability of LnC or AnC linkages
is the use of bulky phosphorus(V) substituents, such as in
bis(diphenylthiophosphinoyl)carbenes, {C(PPh2S)2}2−, and
bis(diphenyliminophosphorano)carbenes, {C(PPh2NR)2}2−,
(e.g., BIPM, R = SiMe3).3 The importance of the phosphorus
phosphinoyl)carbene complexes [Ln{C(PPh2S)2}(μ-I)(THF)2]2
Special Issue: Recent Advances in Organo-f-Element Chemistry
Received: October 29, 2012
Published: February 12, 2013
© 2013 American Chemical Society
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(Ln = Sm, Tm)9 and [Li(THF)4]][Ln{C(PPh2S)2}2] (Ln = Sm,
Tm)10 from samarium(III) or thulium(III) triiodide. The neutral
lanthanide carbenes were found to react rapidly with
benzophenone to afford the expected alkene Wittig product,
Ph2CC(PPh2S)2, whereas the anionic carbenes were found to
react more sluggishly, with the “open” metallo-oxetane
intermediates [Ln{C(PPh2S)2(Ph2CO)}2{Li(THF)}] (Ln =
greater covalency than 1 and its congeners, and they typically
react with ketones and aldehydes to liberate the anticipated
alkene Wittig products.19
We reported a preliminary reactivity study of [Y(BIPM)-
(CH2Ph)(THF)] in 2009.14 The reaction of [Y(BIPM)-
(CH2Ph)(THF)] with diphenyldiazene afforded [Y(BIPM)-
{N(Ph)N(Ph)(CH2Ph-κ2N,N′)}] by a 1,2-migratory insertion
of azobenzene into the Y−Calkyl bond, and no reactivity was
observed at the YCcarbene bond even when another 1 equiv of
diphenyldiazene was added. The reaction of [Y(BIPM)-
(CH2Ph)(THF)] with benzophenone similarly furnished
[Y(BIPM){OC(CH2Ph)Ph2}(THF)] by a 1,2-migratory insertion
into the Y−Calkyl bond, and the addition of a further 1 equiv of
benzophenone afforded the bridging methanediide dimer
[Y(μ-BIPM){OC(CH2Ph)Ph2}]2 on heating the reaction mixture,
with no alkene Wittig products observed. It is noteworthy that
the generated bridging methanediide product does not incorpo-
rate an extra 1 equiv of benzophenone, but its formation is directly
proportional to the quantity of benzophenone added.
́
Sm, Tm) isolated from the reaction mixture. Mezailles and
Ephritikhine have reported the mononuclear lithium-free
uranium(IV) bis(diphenylthiophosphinoyl)carbene complexes,
namely [U{C(PPh2S)2}2(py)2], [U{C(PPh2S)2}(Cp)2] (Cp =
C5H5) and [U{C(PPh2S)2}(BH4)2(THF)2], which were formed
form salt metathesis reactions employing the borohydride
precursor [U(BH4)4].11 The salt metathesis methodology was
́
extended by Berthet, Cantat, Mezailles, and Ephritikhine to
prepare the first uranyl(VI) carbene, [UO2{C(PPh2S)2}(py)2],
from [UO2(OTf)2].12 Initial reactivity studies of these uranium-
(IV) and uranyl(VI) bis(diphenylthiophosphinoyl)carbene com-
plexes with ketones and aldehydes have led exclusively to the
isolation of the expected alkene Wittig products.11,12
The reactivity of 1 was first reported in 2009, when it was
generated in situ by the deprotonation of [Y(BIPMH)-
(I)2(THF)] with benzylpotassium and reacted with the
gallium(I) heterocycle [K(tmeda)][Ga{N(Dipp)ArCH}2]
(Dipp = C6H3Pri2-2,6, tmeda = N,N,N′,N′-tetramethylethyle-
nediamine)20 to yield [Y(BIPM){Ga[N(Dipp)CH]2}(THF)2].
This complex exhibits the first structurally characterized Ga−Y
bond16 and is notable, as there few f-element metal−metal
bonds in the literature.21 A preliminary reactivity study of 1 was
reported in tandem with an initial reactivity study of
[Y(BIPM)(CH2SiMe3)(THF)],22 the latter of which was
shown to react sequentially with 3 equiv of benzophenone to
afford first [Y(BIPM){OC(CH2SiMe3)Ph2}(THF)] by a 1,2-
migratory insertion into the Y−Calkyl bond and then the yttrium
methanide alkoxide [Y(BIPMH){OC(CH2SiMe3)Ph2}O-
{(CPh2)(OCPh)C6H4}], which is coordinated by a substituted
isobenzofuran. In this reaction, regioselective activation of an
ortho phenyl proton of benzophenone by the YC bond
occurs to generate the methanide, and the generated carbanion
reacts at the ketyl carbon of a second molecule of
benzophenone to form a C−C bond, which then undergoes
an intramolecular rearrangement to form a C−O bond. In
contrast, 1 was shown to react with 2 equiv of benzophenone to
give the oxymethylbenzophenone-coordinated yttrium metha-
nide complex [Y(BIPMH){OCPh(C6H4)-2-C(O)Ph2}(I)]
(Scheme 1), which was converted to the substituted iso-
benzofuran complex by a salt metathesis reaction with [KOC-
(CH2SiMe3)Ph2]. The wider applicability of 1 in effecting the
activation of ketones was explored, with the reaction of 1 with
2 equiv of PhCOBut generating the diastereomeric substituted
isobenzofuran complex [Y(BIPMH)O{(CPhBut)(OCBut)-
C6H4}(I)] directly, with no oxymethylbenzophenone-coordinated
intermediate isolated. 1 reacts with the enolizable ketone
PhCOMe to furnish a substituted cyclohexene dypnopinacol,
which is formed by C−H activation at the α-methyl group
of the ketone and then undergoes cyclotetramerization and
dehydration, which again is in contrast to the reactivity of
transition-metal carbene complexes with enolizable ketones.23
The nonclassical reactivity of 1 and [Y(BIPM)(CH2SiMe3)-
(THF)] with ketones prompted us to further investigate the
reactivity of lanthanide carbenes with unsaturated substrates.
Herein, we report the reactivity of 1 with heteroallenes, amines,
cyclic esters, acyl halides and tert-butylphosphaalkyne.
In 2008 we reported the yttrium alkyl carbene complex
[Y(BIPM)(CH2SiMe3)(THF)], which is prepared by the
facile double deprotonation of the methane precursor H2C-
(PPh2NSiMe3)2 (BIPMH2) by [Y(CH2SiMe3)3(THF)2].13 The
mild synthesis of [Y(BIPM)(CH2SiMe3)(THF)] is in contrast
to the forcing conditions required to prepare [Sm(BIPM)-
(NCy2)(THF)]7 and provides a rare opportunity to investigate
the reactivity of the YC double bond. The isolation of
[Y(BIPM)(CH2SiMe3)(THF)] allowed for the first time a
comparison of Ln−Calkyl and LnCcarbene bonds, and DFT
analysis of the bonding suggests a predominantly electrostatic
YC bond, with the HOMO and HOMO-2 principally
describing the lone pairs at the methanediide center and the
HOMO-1 primarily representing the Y−Calkyl bond.13 Follow-
ing the synthesis of [Y(BIPM)(CH2SiMe3)(THF)], we
reported the synthesis of the related lanthanide carbenes
[Ln(BIPM)(CH2Ph)(THF)] (Ln = Y;14 Ln = Dy, Er15) and
[Ln(BIPM)(I)(THF)2] (Ln = Y (1);16,17 Ln = Er17), which
were also synthesized by double-deprotonation strategies
from yttrium alkyl precursors. The solid-state structure of 1
revealed that the BIPM ligand adopts a flat, T-shaped geometry
at the methanediide center, which is in contrast to the typical
pseudo-boat conformation adopted by the yttrium alkyl carbene
systems, thus warranting further investigation.17 However, DFT
analysis of [Y(BIPM)(CH2Ph)(THF)] and 1 revealed frontier
orbital manifolds similar to those of [Y(BIPM)(CH2SiMe3)-
(THF)], which differ principally in their frontier orbital
ordering.14,17 Therefore, although the ligand framework of 1
has maximized its potential for increased covalency by being in
an ideal geometry for orbital overlap, it does not display
appreciable differences in its bonding to [Y(BIPM)(CH2SiMe3)-
(THF)] and [Y(BIPM)(CH2Ph)(THF)].
The double deprotonation of BIPMH2 by lanthanide benzyls
was extended to larger lanthanides, but it was found that in
these cases the coordination sphere was large enough to allow a
single deprotonation of a second molecule of BIPMH2 to afford
[Ln(BIPM)(BIPMH)] (Ln = La, Ce, Pr, Nd, Sm, Gd).15 It was
later found that salt elimination reactions are more appropriate
to access BIPM complexes for the larger lanthanides, such as
in [La{C(PPh2NMes)2}(I)(THF)3] (Mes = C6H2Me3-2,4,6).18
These synthetic methodologies were also employed by us
to prepare uranium(IV), -(V) and -(VI) carbene derivatives
of bis(diphenyliminophosphorano)methanediides, which display
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2 is postulated to form by the initial side-on coordination of
the phosphaalkyne, which is preferred to end-on coordination
for these species due to the π character of their HOMO.25 This
would then be followed by nucleophilic attack of a lone pair of
the methanediide of 1 to form a C−P bond, with the triple
bond of the alkyne converting to an alkene to allow the forma-
tion of a new polarized Y−C bond. [2 + 2] cycloaddition
reactions of phosphaalkynes are relatively rare,25 and head-to-tail
cycloadditions at metal centers are scarce.26 Germane to this
point, the Schrock alkylidenes [M(CHBut)(NDipp)(OR)2]
(M = Mo, R = CMe(CF3)2, CMe2(CF3); M = W, R =
CMe(CF3)2) react with ButCP to afford the carbenes
[M{CHButP(OR)C(But)-κ2C,C′}(NDipp)(OR)] (M = Mo,
R = CMe(CF3)2, CMe2(CF3); M = W, R = CMe(CF3)2) as
major products, which form via a [2 + 2] cycloaddition reaction
followed by a 1,3-migration of an alkoxide from the metal center
to phosphorus.26a,b Other notable examples of head-to-tail
[2 + 2] cycloaddition reactions of ButCP include the reaction
between ButCP and [Ti(Cp*)2(CCH2)] (Cp* = C5Me5) to
form [Ti(Cp*)2{C(P)(CCH2)(But)-κ2C,P}], where a head-to-
tail isomer was detected by NMR spectroscopy,26c and the
reaction between ButCP, ButNH2 and [Ti(Cp)(Cl)3], where a
head-to-tail intermediate forms during the formation of
[Ti(Cp)(Cl){P(NBut)(CHBut)(NHBut)-κ2C,N].26d
Scheme 1. Previously Reported Reactions of 1 with Aryl
Ketones
RESULTS AND DISCUSSION
■
Treatment of 1 with ButCP24 afforded the 1-phospha-3-
metallacyclobutene product [Y{C(PPh2NSiMe3)2(PCBut)-
κ4C,C′,N,N′}(I)] (2), following a [2 + 2] cycloaddition
reaction, in 14% crystalline yield (Scheme 2). The low yield
is a reflection of the high solubility of 2; indeed, derivatives of 1
are generally very soluble, often resulting in low crystalline
yields, whereas inspection of the crude reaction mixtures by
NMR spectroscopy suggests that in all the reactions reported
here the isolated compounds represent the major products.
The 31P{1H} NMR spectrum of 2 in d8-THF exhibits a broad
resonance at δ −72.23 ppm and a doublet at δ 1.62 ppm (2JPP
=
13.0 Hz). The broad signal at high field is assigned as the
phosphalkene-P(III) center and is comparable to that observed
for [Mo{CHButP[OCMe(CF3)2]C(But)-κ2C,C′}(NDipp)-
{OCMe(CF3)2}] (δ −105.7 ppm [C6D6]).26a No 2JPP coupling
Scheme 2. Synthesis of 2−8
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constant could be extracted from this resonance, due to the
broad nature of the signal; however, this coupling was resolved
in the second resonance, which corresponds to the imino-P(V)
centers. No methanide or phosphaalkene resonances could be
observed in the 13C{1H} NMR spectrum of 2, which we
attribute to extensive JPC and JYC couplings reducing the
intensity of these signals to baseline values. The quaternary
carbon of the tert-butyl group is observed as a doublet at δ
28.81 ppm (2JPC = 6.0 Hz), which is similar to those observed
for [Mo{CHButP[OCMe(CF3)2]C(But)-κ2C,C′}(NDipp)-
statistically indistinguishable but compare favorably with the
corresponding distances observed for [Mo{CHButP[OCMe-
(CF3)2]C(But)-κ2C,C′}(NDipp){OCMe(CF3)}] (P−C(av) =
1.822(9) Å)26a and [Ti(Cp*)2{C(P)(CCH2)(But)-κ2C,P}]
(PC = 1.701(5) Å).26c
In common with the reaction of 1 with ButCP, treatment of 1
with the heteroallenes N,N′-dicyclohexylcarbodiimide and tert-
butyl isocyanate gave the [2 + 2] cycloaddition products
[Y{C(PPh2NSiMe3)2[C(NCy)2]-κ4C,N,N′,N″}(I)(THF)] (3)
and [Y{C(PPh2NSiMe3)2[C(O)(NBut)]-κ4C,N,N′,O}(I)-
(THF)2] (4), respectively, each in 54% crystalline yield
(Scheme 2). The formation of 3 is analogous to the preparation
of [Zr{C(PPh2NSiMe3)2[C(NCy)2]-κ4C,N,N′,N″}(Cl)2] and
[Hf{C(PPh2NSiMe3)2[C(NAr)2]-κ4C,N,N′,N″}(Cl)2] (Ar =
p-tolyl).27 In contrast, the formation of 4 differs from the
synthesis of [M{C(PPh2NSiMe3)2[C(O)(NAd)]-κ4C,N,N′,N″}-
(Cl)2] (M = Zr, Hf, Ad = adamantyl, C10H15),27 wherein the
heteroallene forms M−N bonds upon cycloaddition, rather than
the Y−O bond formed in 4. We suggest this differing [2 + 2]
cycloaddition behavior reflects the increased preference for
O-donor ligands in early metals. The 31P{1H} NMR spectra of 3
and 4 exhibit doublet resonances with identical coupling
2
{OCMe(CF3)2}] (δ 33.3 and 33.4 ppm, JPC = 18 and 15 Hz
[C6D6]).26a
The molecular structure of 2 is illustrated in Figure 1,
and selected bond lengths and angles are given in Table 1.
2
2
constants (3, δ 16.57 ppm, JYP = 3.2 Hz; 4, δ 20.39, JYP
=
3.2 Hz); these are downfield of the resonance for 1, which also
exhibits a greater JYP value (1, δ 3.48 ppm, JYP = 13.0 Hz),17
but are comparable to that of [Zr{C(PPh2NSiMe3)2[C(NCy)2]-
κ4C,N,N′,N″}(Cl)2] (δ 21.0 ppm).27 The methanide carbons of
3 and 4 resonate as the expected triplet of doublets in their
respective 13C{1H} NMR spectra (3, δ 20.71 ppm, JPC = 102.7
Hz, JYC = 2.3 Hz; 4, δ 31.39 ppm, JPC = 111.9 Hz, JYC = 2.3 Hz),
with chemical shifts and coupling constants that are typical
for yttrium bis(iminophosphorano)methanide complexes16,22,29
and [Zr{C(PPh2NSiMe3)2[C(NCy)2]-κ4C,N,N′,N″}(Cl)2] (δ
15.5 ppm, JPC = 96.0 Hz).27 The former heteroallene quaternary
carbons of 3 and 4 also exhibit coupling with the two 31P nuclei
(3, δ 153.15 ppm, dd, 2JPC = 6.1 Hz, 3.8 Hz; 4, δ 156.26 ppm, t,
2JPC = 2.8 Hz) that is comparable in magnitude to that observed
for [Zr{C(PPh2NSiMe3)2[C(NCy)2]-κ4C,N,N′,N″}(Cl)2] (δ
2
2
Figure 1. Molecular structure of 2 with selective atom labeling.
Displacement ellipsoids are set at 40% probability, and hydrogen
atoms are omitted for clarity. Symmetry operation to generate the
148.7 ppm, bt, JPC = 4 Hz).27
2
The solid-state structures of 3 and 4 were determined by
X-ray crystallography (Figures 2 and 3; selected bond lengths
and angles are compiled in Table 1). In common with 2 and
[Zr{C(PPh2NSiMe3)2[C(NCy)2]-κ4C,N,N′,N″}(Cl)2],27 the
four-coordinate, dianionic ligands of 3 and 4 exhibit a
propeller-shaped geometry with N(1), N(2), and N(3) (3)
or N(1), N(2), and O(1) (4) at the vertices of an approximate
triangle. The coordination sphere of the yttrium centers are
completed by an iodide and one (3) or two (4) THF ligands,
which presumably reflects the varying steric demands of the
organic ligand frameworks in 3 and 4. Both complexes exhibit
bond lengths and angles that are typical for early-metal
bis(iminophosphorano)methanides and Y−Cmethanide distances
(3, Y(1)−C(1) 2.644(8) Å; 4, 2.676(3) Å) that are comparable
to those in other closely related yttrium methanides.16,22,29 The
C(32)−N(3) (1.393(10) Å) and C(32)−N(4) (1.276(10) Å)
distances of 3 and the corresponding C(32)−O(1) (1.338(3) Å)
and C(32)−N(3) (1.274(3) Å) distances of 4 indicate localized
single and double bonds, respectively, as was reported for
[Zr{C(PPh2NSiMe3)2[C(NCy)2]-κ4C,N,N′,N″}(Cl)2] (C−N =
1.384(5) and 1.285(5) Å).27 As expected, the Y(1)−N(3) amide
distance of 3 (2.267(7) Å) and the Y(1)−O(1) alkoxide distance
of 4 (2.2133(19) Å) are shorter than the other Y−N and Y−O
bond lengths in these complexes and are statistically invariant to,
3
complete structure: x, − y + /2, z.
The tetradentate ligand framework in 2 is dianionic and
propeller-shaped and exhibits three essentially planar fused
four-membered metallocycles: two PNCY and one PC2Y. The
crystal structure of 2 exhibits exact Cs symmetry, whereby a
mirror plane intersects C(1), Y(1), I(1), P(2), and C(17), with
two PNCY rings oriented 50.1(6)° to the mirror plane. The
iodide ligand is trans to the methanide center (C(1)−Y(1)−
I(1) = 176.0(6)°) and resides in a pocket approximately
equidistant between the CMe3 and SiMe3 groups. The distances
and angles within the six-membered CP2N2Y assembly are
unremarkable, as is the Y(1)−C(1) distance (2.556(16) Å),
which is statistically indistinguishable from that observed for
[Y(BIPMH)(I)2(THF)] (Y−C 2.599(2) Å).16 The N(1)−
Y(1)−N(1A) bite angle (116.7(6)°) is comparable to the
corresponding angle in [Zr{C(PPh2NSiMe3)2[C(NCy)2]-
κ4C,N,N′,N″}(Cl)2] (N−Zr−N = 120.0(1)°).27 The Y(1)−
C(17) distance of 2 (2.36(3) Å) is notably short, residing
toward the lower end of the range of reported Y−C distances
(2.124−3.135 Å), and is comparable to previously reported
YC bonds (2.356−2.422 Å).28 The P(2)−C(1) (1.82(2) Å)
and P(2)−C(17) (1.71(2) Å) bond distances of 2 are
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Table 1. Selected Bond Lengths (Å) and Angles (deg) for 2−8
2
6·C4H8O
Y(1)−C(1)
Y(1)−N(1)
C(1)−P(1)
C(17)−P(2)
N(1)−Y(1)−N(1A)
P(2)−C(17)−Y(1)
C(17)−P(2)−C(1)
P(1)−C(1)−P(2)
2.556(16)
2.305(11)
1.761(11)
1.71(2)
Y(1)−C(17)
Y(1)−I(1)
C(1)−P(2)
2.36(3)
Y(1)−C(1)
Y(1)−N(1)
Y(1)−N(3)
C(1)−P(1)
2.619(6)
2.414(5)
2.232(5)
1.756(6)
1.605(5)
Y(1)−I(1)
Y(1)−N(2)
Y(1)−O(1)
C(1)−P(2)
2.9865(6)
2.417(5)
2.386(4)
1.755(6)
1.607(5)
99.0(2)
2.937(2)
1.82(2)
P(1)−N(1)
1.633(10)
96.9(5)
116.7(6)
96.8(11)
105.9(11)
116.4(7)
P(1)−N(1)−Y(1)
N(1)−P(1)−C(1)
P(1)−C(1)−P(1A)
C(1)−Y(1)−I(1)
P(1)−N(1)
P(2)−N(2)
108.8(7)
125.7(14)
176.0(6)
N(1)−Y(1)−N(2)
P(2)−N(2)−Y(1)
N(2)−P(2)−C(1)
Y(1)−N(3)−C(36)
93.18(17)
98.5(2)
P(1)−N(1)−Y(1)
N(1)−P(1)−C(1)
P(1)−C(1)−P(2)
106.1(3)
123.0(3)
107.6(3)
159.0(4)
3
7·3.25C7H8
Y(1)−C(1)
Y(1)−N(1)
Y(1)−N(3)
C(1)−P(1)
P(1)−N(1)
C(1)−C(32)
C(32)−N(4)
N(1)−Y(1)−N(2)
N(2)−Y(1)−N(3)
P(2)−N(2)−Y(1)
N(2)−P(2)−C(1)
P(1)−C(1)−C(32)
C(1)−C(32)−N(3)
C(32)−C(1)−Y(1)
P(2)−C(1)−Y(1)
2.644(8)
2.375(6)
2.267(6)
1.742(7)
1.600(7)
1.550(10)
1.276(10)
96.8(2)
Y(1)−I(1)
3.0284(9)
2.351(6)
2.407(5)
1.758(7)
1.601(7)
1.393(10)
Y(1)−N(2)
Y(1)−O(1)
C(1)−P(2)
P(2)−N(2)
C(32)−N(3)
Y(1)−I(2)
Y(1)−O(1)
Y(1)−O(3)
Y(1)···C(31)
C(1)−P(2)
3.1990(6)
2.158(4)
2.333(4)
3.075(8)
1.792(6)
1.622(5)
1.311(7)
1.340(8)
3.1915(6)
2.294(4)
2.308(4)
1.801(6)
1.546(5)
1.386(8)
1.469(8)
101.74(13)
67.339(14)
113.8(2)
119.9(5)
120.0(2)
Y(1)−N(2)
Y(1)−O(2)
Y(1)−O(5)
C(1)−P(1)
P(1)−N(1)
C(1)−C(32)
C(32)−C(33)
Y(2)−I(1)
Y(2)−N(4)
Y(2)−O(4)
Y(2)···C(74)
C(45)−P(4)
P(4)−N(4)
C(76)−O(4)
C(77)−C(78)
Y(1)−O(5)−Y(2)
Y(1)−N(2)−P(2)
P(2)−C(1)−C(32)
C(32)−O(1)−Y(1)
N(4)−P(4)−C(45)
2.330(5)
2.273(3)
2.236(4)
1.795(6)
1.540(5)
1.400(8)
1.476(8)
2.9572(6)
2.391(4)
2.146(4)
3.308(8)
1.789(6)
1.615(5)
1.309(7)
1.328(9)
102.43(15)
121.1(2)
111.8(4)
123.4(3)
113.4(3)
P(2)−N(2)
N(1)−Y(1)−N(3)
P(1)−N(1)−Y(1)
N(1)−P(1)−C(1)
P(1)−C(1)−P(2)
P(2)−C(1)−C(32)
C(32)−N(3)−Y(1)
P(1)−C(1)−Y(1)
95.9(2)
98.3(3)
110.2(4)
122.9(4)
122.6(5)
107.0(5)
85.4(3)
C(32)−O(1)
C(33)−C(34)
Y(2)−I(2)
Y(2)−O(2)
Y(2)−O(5)
109.1(2)
97.9(3)
108.0(4)
112.6(5)
108.6(6)
86.7(4)
C(45)−P(3)
P(3)−N(3)
84.1(3)
C(45)−C(76)
C(76)−C(77)
Y(1)−O(2)−Y(2)
Y(1)−I(2)−Y(2)
N(2)−P(2)−C(1)
C(1)−C(32)−O(1)
Y(2)−N(4)−P(4)
4
Y(1)−C(1)
Y(1)−N(1)
Y(1)−O(1)
Y(1)−O(3)
C(1)−P(2)
P(2)−N(2)
C(32)−N(3)
N(1)−Y(1)−N(2)
N(2)−Y(1)−O(1)
P(2)−N(2)−Y(1)
N(2)−P(2)−C(1)
P(1)−C(1)−C(32)
C(1)−C(32)−O(1) 111.9(2)
C(32)−C(1)−Y(1)
P(2)−C(1)−Y(1)
2.676(3)
Y(1)−I(1)
Y(1)−N(2)
Y(1)−O(2)
C(1)−P(1)
P(1)−N(1)
C(1)−C(32)
C(32)−O(1)
N(1)−Y(1)−O(1)
P(1)−N(1)−Y(1)
N(1)−P(1)−C(1)
P(1)−C(1)−P(2)
P(2)−C(1)−C(32)
3.0539(4)
2.359(2)
2.417(2)
2.2133(19)
2.5170(19)
1.744(3)
2.4427(19)
1.733(3)
1.610(2)
P(4)−C(45)−C(76) 112.9(4)
C(45)−C(76)−O(4) 119.1(5)
1.610(2)
1.524(3)
C(76)−O(4)−Y(2)
127.2(4)
1.274(3)
1.338(3)
8·1.5C7H8
99.76(8)
101.06(7)
98.10(10)
109.70(12)
126.35(15)
114.60(18)
100.10(7)
98.98(10)
109.82(12)
116.49(19)
Y(1)−I(1)
Y(1)−O(2)
Y(1)−N(3)
Y(1)···C(65)
C(1)−P(2)
3.0406(5)
2.145(3)
2.412(4)
3.548(7)
1.804(5)
1.539(4)
1.310(5)
1.795(4)
1.548(4)
1.311(5)
121.2(2)
113.8(3)
113.86(19)
Y(1)−O(1)
Y(1)−N(1)
Y(1)···C(28)
C(1)−P(1)
P(1)−N(1)
C(1)−C(32)
C(39)−P(3)
P(3)−N(3)
C(39)−C(70)
2.125(3)
2.384(4)
3.038(8)
1.810(4)
1.607(4)
1.374(7)
1.819(4)
1.607(4)
1.378(6)
C(32)−O(1)−Y(1) 107.85(15)
P(1)−C(1)−Y(1)
83.09(14)
86.07(10)
P(2)−N(2)
84.71(10)
C(32)−O(1)
C(39)−P(4)
P(4)−N(4)
C(70)−O(2)
Y(1)−N(1)−P(1)
P(1)−C(1)−C(32)
Y(1)−N(3)−P(3)
5·0.5C7H8
C(32)−N(3)
C(1)−C(32)
C(1)−P(1)
P(1)−N(1)
N(1)−P(1)−C(1)
P(1)−C(1)−P(2)
P(2)−C(1)−C(32)
1.322(4)
1.809(3)
1.207(3)
1.809(3)
1.532(2)
113.45(12)
118.23(19)
172.9(3)
C(1)−P(2)
P(2)−N(2)
N(2)−P(2)−C(1)
P(1)−C(1)−C(32)
C(1)−C(32)−N(3)
N(1)−P(1)−C(1)
C(1)−C(32)−O(1)
N(3)−P(3)−C(39)
C(39)−C(70)−O(2)
112.0(2)
122.7(4)
115.04(19)
121.7(4)
1.535(2)
115.32(12)
122.09(14)
118.8(2)
P(3)−C(39)−C(70) 111.7(3)
or longer than, the terminal amide and alkoxide distances, re-
spectively, found in the complexes [Y(BIPMH)(NPh)2]
(2.264(2) Å mean)29a and [Y(BIPM){OC(CH2SiMe3)Ph2}-
(THF)] (2.037(10) Å).22
With 3 prepared, we investigated the analogous reaction of 1
with tert-butyl isothiocyanate. However, instead of forming the
anticipated [2 + 2] cycloaddition product, the Wittig product
compound ButNCC(PPh2NSiMe3)2 (5) was isolated in
22% crystalline yield, presumably with concomitant formal
elimination of “YSI(THF)n” (Scheme 2). This reactivity is
unusual, given that the yttrium center of 1 is extremely oxophilic
and does not effect a similar reaction with tert-butyl isocyanate.
It is noteworthy that a [2 + 2] cycloaddition reaction has been
implicated in the reaction of a titanium alkylidene with tert-butyl
isocyanate,30 and to the best of our knowledge there is only one
example in the literature of a desulfurization of isocyanates
mediated by a metal-bound carbene.31 The novel ketenimine 5
gives a characteristic strong absorption at 2048 cm−1 in the FTIR
spectrum, resulting from stretching modes of the CCN
moiety, which compares well to those for the P(III)
diphosphinoketenimine ButNCC(PPh2)2 (ν(CCN)
2030 and 2002 cm−1 (in CH2Cl2)).32 In the 13C{1H} NMR
spectrum of 5 the former methanediide carbon was observed at
δ 55.86 ppm (t, JPC = 100.3 Hz) and the central carbon of the
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Figure 4. Molecular structure of 5·0.5C7H8 with selective atom
labeling. Displacement ellipsoids are set at 40% probability, and
hydrogen atoms and lattice solvent are omitted for clarity.
Figure 2. Molecular structure of 3 with selective atom labeling.
Displacement ellipsoids are set at 40% probability, and hydrogen
atoms are omitted for clarity.
mutually cis and trans to the CC bond. The C(1)−C(32)
(1.322(4) Å) and C(32)−N(3) (1.207(3) Å) distances and
almost linear C(1)−C(32)−N(3) angle of 5 (172.9(3)°) are
comparable to the corresponding distances and angles observed
for [Cu{C(PPh2O)2(CNBut)-κ2-O,O}2(BF4)][BF4] (CC =
1.346(4) Å, CN = 1.175(4) Å, CNC = 173.8(4)°).32 All
other bond lengths and angles in 5 are unremarkable.33
The reaction of 1 with 2,6-diisopropylphenylamine proceeds
via a 1,2-addition across the YC bond to yield the anilide−
methanide complex [Y(BIPMH)(NHDipp)(I)(THF)] (6) in
59% crystalline yield after workup (Scheme 2). This reactivity
was also observed for the complex [Hf(BIPM)(Cl)2], which
was shown to react with p-tolylamine to give [Hf(BIPMH)-
(NHC6H4Me-4)(Cl)2].27 The 31P{1H} NMR spectrum of 6
(d8-THF) exhibited a doublet resonance at δ 19.17 ppm (2JYP
=
6.5 Hz), which is comparable to those in 3, 4, and other closely
related complexes.16,22,29 The signal arising from the NH
1
group was observed in the H NMR spectrum of 6 (d8-THF)
at δ 4.59 ppm, which is upfield of that reported for
[Hf(BIPMH)(NHC6H4Me-4)(Cl)2] (δ 6.46 ppm (C6D6))27
but is comparable to the value reported for the related yttrium
pyridyl-1-azaallyl−anilide [Y{(C6H3Pri2-2,6)NC(Me)CH-
(C5H3N-1,SiMe2CH2-2)-κ3C,N,N′}(NHDipp)(THF)] (δ 4.75
ppm (C6D6)).34 Similarly, the resonance of the methanide
proton of 6 (δ 1.26 ppm) is upfield of that observed for
[Hf(BIPMH)(NHC6H4Me-4)(Cl)2] (δ 2.36 ppm (C6D6))27
but is comparable to those for other yttrium bis(imino-
phosphorano)methanide complexes.16,22,29 The expected triplet
of doublets corresponding to the methanide carbon atom was
observed in the 13C{1H} NMR spectrum of 6 (δ 17.91 ppm,
JPC = 87.5 Hz, JYC = 4.5 Hz) but cannot be compared to the
13C{1H} NMR spectrum of [Hf(BIPMH)(NHC6H4Me-4)-
(Cl)2], as this has not been reported.27 However, the resonance
Figure 3. Molecular structure of 4 with selective atom labeling.
Displacement ellipsoids are set at 40% probability, and hydrogen
atoms and lattice solvent are omitted for clarity.
ketenimine at δ 162.63 ppm (t, 2JPC = 5.9 Hz). A single resonance
is observed in the 31P{1H} NMR spectrum at δ −2.58 ppm in
C6D6 (cf. δ −10.5 ppm in CD2Cl2 observed for ButNC
C(PPh2)2).32
The molecular structure of 5·0.5C7H8 was determined by
X-ray crystallography and is illustrated in Figure 4; selected
bond lengths and angles can be found in Table 1. 5 exhibits a
geometry similar to those of the analogous Wittig products
Ph(H)CC(PPh2NSiMe3)219b and R(H)CC(PPh2NSiMe3)2
(R = 9-anthracene),19d with the two NSiMe3 substituents
2
for the anilide ipso carbon at δ 151.99 ppm (d, JYC = 3.0 Hz)
compares well to the corresponding value reported for
[Y{(C6H3Pri2-2,6)NC(Me)CH(C5H3N-1,SiMe2CH2-2)-
κ3C,N,N′}(NHDipp)(THF)] (δ 151.8 ppm (C6D6)).34
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The molecular structure of 6·C4H8O was determined and
is illustrated in Figure 5, with selected bond lengths and angles
“methanide−alkoxide” intermediate. This then rearranges by
breaking the Y−C and ester linkages to generate the CC
double bond and the “aryloxide−enolate” product. An absorption
is observed in the FTIR spectrum of 7 (ν 1627 cm−1) which is
assigned as the CC functional group. The 31P{1H} NMR
spectrum of 7 exhibits two doublet resonances (δ 4.91 and 28.32
2
ppm, JPP = 37.3 Hz), indicative of inequivalent iminophosphor-
ano arms of the ligand scaffold as a result of one being coordinated
and the other being pendant. The 1H and 13C{1H} NMR spectra
of 7 are complex as a result of the highly asymmetric coordination
environment (see below) apparently persisting in THF solution,
which is additionally evidenced by the low solubility of 7 in
d6-benzene. However, the spectra are readily assigned and
noteworthy resonances are observed in the 13C{1H} NMR
spectrum of 7 for the low-field O-bound enolate carbon (δ 184.75
2
ppm, dd, JPC = 13.6 and 3.5 Hz) and the former methanediide
carbon (δ 98.60 ppm, dd, JPC = 119.7 and 91.6 Hz), which couple
to the two inequivalent 31P nuclei. The aryloxide ipso carbon
resonates as a doublet at δ 162.31 ppm (2JYC = 6.0 Hz), which is
similar to the corresponding value reported for [Y(ODipp)3-
(THF)2] (δ 157.92 ppm, JYC = 5.0 Hz).37
2
The molecular structure of 7·3.25C7H8 is illustrated in
Figure 6, and selected bond lengths and angles are given in
Figure 5. Molecular structure of 6·C4H8O with selective atom labeling.
Displacement ellipsoids are set at 40% probability, and hydrogen
atoms (except amide and methanide hydrogens) and lattice solvent are
omitted for clarity.
given in Table 1. The bis(iminophosphorano)methanide
framework adopts an open-book conformation,3b,c with a
Y−C distance (2.619(6) Å) that is characteristic of complexes
of this class.16,22,27 The Y(1)−N(3) distance (2.232(5) Å) and
nonlinear Y(1)−N(3)−C(36) angle (159.0(4)°) of 6 are similar
to the corresponding values observed for [Y{(C6H3Pri2-2,6)NC-
(Me)CH(C5H3N-1,SiMe2CH2-2)-κ3-C,N,N′}(NHDipp)(THF)]
(Y−N = 2.197(5) Å; Y−N−C = 154.9(4)°).34 The coordination
sphere about the six-coordinate yttrium center is completed by
an iodide and a THF molecule.
The reaction of 1 with the benzopyrone coumarin affords, via
ring opening of the α,β-unsaturated cyclic lactone, the ring-opened
dinuclear aryloxide−enolate complex [Y2{C(PPh2NSiMe3)2-
[C(O)(CHCHC6H4O-2)]-κ2-N,O:μ,κ-O′}2(I)(μ-I)(THF)] (7)
(Scheme 2) in 15% crystalline yield. In contrast, previously
reported reactions of chromium35 and titanium36 carbenes with
coumarin have yielded exclusively the corresponding metallo-
Wittig product by reaction at the ketone functionality. 7 is
proposed to form by sequential Y−O, C−C, and CC bond
formation and cleavage of the C−O ester linkage and the CO
and YC double bonds (Scheme 3). Following coordination of
coumarin to yttrium through the ketone lone pair, nucleophilic
attack of the ketyl carbon by the carbene occurs, which leads to a
Figure 6. Molecular structure of 7·3.25C7H8 with selective atom
labeling. Displacement ellipsoids are set at 40% probability, and
hydrogen atoms and lattice solvent are omitted for clarity.
Table 1. 7 is dinuclear, and both yttrium centers exhibit
distorted-pentagonal-bipyramidal geometries, although they
have different ligand environments. The formation of formal
C(1)C(32) (1.400(8) Å) and C(45)C(76) (1.386(8) Å)
double bonds (idealized bond lengths from sum of covalent
radii: C−C, 1.50 Å; CC, 1.34 Å)38 results in only one
bis(iminophosphorano) arm of each aryloxide−enolate ligand
Scheme 3. Proposed Mechanism of Formation of 7
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coordinating to Y(1) and Y(2), respectively, with the other
N-substituents isolated from the metal coordination environ-
ment. The C(32)−O(1) (1.311(7) Å) and C(76)−O(4)
(1.309(7) Å) distances are also indicative of some delocaliza-
tion (idealized bond lengths from sum of covalent radii: C−O,
1.38 Å; CO, 1.24 Å).38 The enolate Y(1)−O(1) (2.158(4) Å)
and Y(2)−O(4) (2.146(4) Å) bonds, which are best compared
spectrum as a consequence of the two iminophosphorano arms
2
being inequivalent (δ −0.18 and 29.27 ppm, JPP = 35.6 Hz).
Notable resonances observed in the 13C{1H} NMR spectrum of
8 include the two carbons of the CC double bond, which
exhibit the expected multiplicities and couplings to 31P (δ 93.36
2
ppm, dd, JPC = 112.7 and 89.6 Hz; δ 185.80 ppm, d, JPC
=
2.8 Hz), although the carbon bound to oxygen only couples to
one 31P center and this coupling constant is smaller than that
observed for 7.
Single crystals of 8·1.5C7H8 were grown, and the structure
was determined by X-ray crystallography, which is depicted in
Figure 7 with selected bond lengths and angles compiled in
with those found for [Y{N(SiMe3)C6H3Pri -2,6}2-
2
(OCHCH2){ClLi(THF)3}] (2.103(7) Å),39 [{Y(Cp*2)}2-
(μ-OCHCHCC)] (2.213(6) Å),40 and [Y(Cp)2(η2-OC-
(CPh2-4)(Ph2-7,7)(O-6){3.2.0})] (2.106(2) Å),41 give rise to
six-membered Y−N−P−C−C−O metallacycles that exhibit
pseudo-chair conformations. The aryloxide groups bridge the
two yttrium centers (Y−O range 2.236(4)−2.308(4) Å,
2.278(4) Å mean) and exhibit a mean Y−O distance that is
statistically indistinguishable from the mean bridging aryloxide
Y−O distance observed for [Y(OC6H3Me2-2,6)2(μ-OC6H3Me2-
2,6)(THF)]2 (2.276(6) Å mean).42 The coordination spheres of
Y(1) and Y(2) are supplemented by a THF and a bridging
iodide ligand or one bridging and one terminal iodide, re-
spectively. Completing the coordination sphere at each yttrium,
the close approach of two methyl groups of the N(SiMe3) sub-
stituents leads to two Y···H contacts per yttrium center (range
2.730−3.262 Å), and short Y(1)···C(31) (3.075(8) Å) and
Y(2)···C(74) (3.308(8) Å) distances are observed. Comparable
agostic-type interactions have previously been reported for
group 1 BIPMH complexes.43
Benzoyl fluoride reacts with 1 to afford the bis-enolate
complex [Y{C(PPh2NSiMe3)2[C(O)(Ph)]-κ2N,O}2(I)] (8)
(Scheme 2) in 13% crystalline yield. This is accompanied by
the formation of a white powder that exhibits very low
solubility in THF which is consistent with the formal formation
of “YF2I(THF)n”. The isolation of 8 is noteworthy, as to the
best of our knowledge this is the first report of the reactivity of
benzoyl fluoride with an early-metal carbene complex. Since the
precoordination of ketones to yttrium prior to further reaction
has been demonstrated previously,22 it is postulated that the
formation of 8 proceeds initially by coordination of benzoyl
fluoride to yttrium through the lone pair of the ketone,
followed by nucleophilic attack of the ketyl carbon by the
carbene to form a C−C bond and an alkoxide (Scheme 4). This
Figure 7. Molecular structure of 8·1.5C7H8 with selective atom
labeling. Displacement ellipsoids are set at 40% probability, and
hydrogen atoms and lattice solvent are omitted for clarity.
Table 1. The yttrium center of 8 exhibits an approximately
pentagonal-bipyramidal geometry, with N(1) and N(3)
occupying the axial sites and O(1), O(2), C(28), C(65), and
I(1) taking up the equatorial positions. Four agostic-type C−
H···Y interactions (Y···H range 2.763−3.540 Å; Y(1)···C(28) =
3.038(8) Å, Y(1)···C(65) = 3.548(7) Å) from two of the
methyl groups of the N-silyl substitutuents are apparent, and
these are similar to those observed in 7 (see above). Also in
common with 7, the ligand scaffolds of 8 have only one
coordinated iminophosphorano arm each and upon coordina-
tion form six-membered pseudo-chair metallacycles and exhibit
similar Y−O (2.135(5) Å mean), C−O (1.311(3) Å mean) and
CC (1.376(7) Å mean) distances. All other metrical
parameters in the structure of 8 are unremarkable.
Scheme 4. Proposed Mechanism of Formation of 8
SUMMARY AND CONCLUSIONS
■
A reactivity study of the planar T-shaped carbene [Y(BIPM)-
(I)(THF)2] (1) with unsaturated substrates is reported. 1 has
been shown to react with a phosphaalkyne in a head-to-tail
fashion to afford [Y{C(PPh2NSiMe3)2(PCBut)-κ4C,C′,N,N′}-
(I)] (2) by a [2 + 2] cycloaddition reaction. A similar reactivity
profile was observed for the reactions between 1 and hetero-
allenes, which furnished [Y{C(PPh2NSiMe3)2[C(NCy)2]-
κ4C,N,N′,N″}(I)(THF)] (3) and [Y{C(PPh2NSiMe3)2[C(O)-
(NBut)]-κ4C,N,N′,O}(I)(THF)2] (4). The reaction of 1 with
the heteroallene tert-butyl isothiocyanate does not fit this
pattern and instead yields the ketenimine ButNC
C(PPh2NSiMe3)2 (5), with the concomitant formal elimination
of “YSI(THF)n” by a pseudo-Wittig reaction. An arylamine has
been shown to undergo a 1,2-addition reaction across the YC
bond of 1, such as in the synthesis of the anilide−methanide
alkoxide then rearranges by cleavage of the Y−Cmethanide linkage
and the C−F bond with concomitant formation of a CC
double bond and a Y−F bond to give the intermediate complex
“[Y{C(PPh2NSiMe3)2[C(O)(Ph)]-κ2N,O}(F)(I)(THF)x]”.
Then, rapid rearrangement to 8 and the thermodynamically
favored product “YF2I(THF)n” by ligand scrambling occurs. As
with 7, 8 exhibits two doublet resonances in the 31P{1H} NMR
1246
dx.doi.org/10.1021/om301016j | Organometallics 2013, 32, 1239−1250

Organometallics
Article
1
H, 6.62; N, 5.28. H NMR (d6-benzene, 298 K): δ 0.26 (s, 18H,
Si(CH3)3), 0.46 (m, 2H, CH-2ax NCy), 1.00 (m, 2H, CHax NCy), 1.17
(m, 2H, CHax NCy), 1.40 (m, 4H, OCH2CH2), 1.51 (m, 2H, CHax
NCy), 1.67 (m, 4H, CH NCy), 1.79 (d, 2H, CHeq NCy), 2.01 (m, 4H,
complex [Y(BIPMH)(NHDipp)(I)(THF)] (6). Unusually, the
reaction between 1 and coumarin afforded the ring-opened
dinuclear aryloxide−enolate complex [Y2{C(PPh2NSiMe3)2-
[C(O)(CHCHC6H4O-2)]-κ2N,O:μ,κ-O′}2(I)(μ-I)(THF)] (7)
instead of the Wittig product that is formed in the reactions of
early-transition-metal carbenes with coumarin.35,36 The non-
classical reactivity of yttrium carbenes with carbonyl-functionalized
organic substrates has been observed previously22 and highlights
how the chemistry of lanthanide carbenes contrasts and
complements the chemistry of more established transition-metal
carbenes. Finally, benzoyl fluoride has been shown to react with 1
to afford the bis-enolate complex [Y{C(PPh2NSiMe3)2[C(O)-
(Ph)]-κ2N,O}2(I)] (8) and “YF2I(THF)n” in a novel trans-
formation of benzoyl fluoride mediated by a metal carbene. We
are currently investigating the further synthetic utility of lanthanide
carbenes with unsaturated organic substrates and will report on
these findings in due course.
CHeq NCy), 2.83 (m, 2H, CH-2eq NCy), 3.56 (m, 1H, CH-1ax NCy),
3.81 (m, 4H, OCH2CH2), 4.29 (m 1H, CH-1ax NCy), 6.76 (t, JHH
7.4 Hz, 4H, m-Ph-CH), 6.88 (t, JHH = 7.4 Hz, 2H, p-Ph−CH), 7.00
(m, JHH = 7.4 Hz, 6H, m- and p-Ph-CH), 7.50 (dd, JPH = 11.6 Hz,
3JHH = 7.2 Hz, 4H, o-Ph-CH), 7.95 (dd, 3JPH = 12.2 Hz, 3JHH = 6.4 Hz,
4H, o-Ph-CH). 13C{1H} NMR (d6-benzene, 298 K): δ 5.94
(Si(CH3)3), 20.71 (dt, JPC = 102.7 Hz, JYC = 2.3 Hz, CP2), 25.21
(OCH2CH2), 25.79 (C-4 NCy), 26.67 (C-3 NCy), 27.04 (C-3 NCy),
34.47 (C-2 NCy), 34.72 (C-2 NCy), 55.86 (C-1 NCy), 57.89 (C-1
3
=
3
3
3
2
NCy), 68.70 (OCH2CH2), 127.25 (vt, JPC = 6.1 Hz, o-Ph-CH),
130.37 (p-Ph-CH), 130.66 (p-Ph-CH), 132.65 (vt, JPC = 5.0 Hz,
m-Ph-CH), 132.93 (vt, JPC = 5.0 Hz, m-Ph-CH), 136.78 (dd, JPC
3
3
=
3
2
118.8 Hz, JPC = 11.5 Hz, ipso-Ph-C), 153.15 (dd, JPC = 6.1 Hz,
3.8 Hz, CN2). 31P{1H} NMR (d6-benzene, 298 K): δ 16.57 (d, JYP
=
2
3.2 Hz, CP2). 29Si{1H} NMR (d6-benzene, 298 K): δ −3.90 (SiMe3).
FTIR ν/cm−1 (Nujol): 1534 (m), 1245 (m), 1231 (m), 1109 (m),
1069 (m), 1049 (m), 1018 (m), 988 (m), 839 (s, br), 766 (m), 743
(m), 695 (m), 655 (w), 602 (m), 578 (w), 535 (w), 521 (m).
Preparation of [Y{C(PPh2NSiMe3)2[C(O)(NBut)]-κ4C,N,N′,O}(I)-
(THF)2] (4). A solution of ButNCO (0.20 g, 2.00 mmol) in toluene
(10 mL) was added dropwise to a precooled (−78 °C) suspension of
[Y(BIPM)(I)(THF)2] (1.83 g, 2.00 mmol) in toluene (10 mL). The
white slurry was slowly warmed to room temperature with stirring
over 24 h. The mixture was filtered, reduced in volume, and stored at
−25 °C overnight to afford 4 as colorless crystals. A second crop was
obtained. Yield: 1.10 g, 54%. Anal. Calcd for C44H63IN3O3P2Si2Y: C,
EXPERIMENTAL SECTION
■
General Considerations. All manipulations were carried out using
standard Schlenk techniques, or an MBraun UniLab glovebox, under
an atmosphere of dry nitrogen. Solvents were dried by passage through
activated alumina towers and degassed before use. All solvents were
stored over potassium mirrors (with the exception of THF, which was
stored over activated 4 Å molecular sieves). Deuterated solvents were
distilled from potassium, degassed by three freeze−pump−thaw cycles,
and stored under nitrogen. 117 and ButCP24 were prepared according
to published procedures. All other chemicals were purchased, and all
solid reagents were dried under vacuum for 3 h and all liquid reagents
were dried over 4 Å molecular sieves and distilled before use. 1H, 13C,
29Si, and 31P NMR spectra were recorded on a Bruker 400 spectro-
meter operating at 400.2, 100.6, 79.5, and 162.0 MHz, respectively;
chemical shifts are quoted in ppm and are relative to TMS (1H, 13C,
and 29Si) and external 85% H3PO4 (31P). FTIR spectra were recorded
on a Bruker Tensor 27 spectrometer. Elemental microanalyses were
carried out by Mr. Stephen Boyer at the Microanalysis Service, London
Metropolitan University, U.K. or by Dr. Tong Liu at the University of
Nottingham.
1
52.01; H, 6.25; N, 4.14. Found: C, 51.95; H, 6.18; N, 4.17. H NMR
(d6-benzene, 298 K): δ 0.49 (s, 18H, Si(CH3)3), 1.15 (s, 9H,
C(CH3)3), 1.39 (m, 8H, OCH2CH2), 4.04 (m, 8H, OCH2CH2), 6.65
3
3
(vt, JHH = 7.2 Hz, 4H, m-Ph-CH), 6.74 (t, JHH = 7.2 Hz, 2H,
3
p-Ph-CH), 7.14 (m, JHH = 7.4 Hz, 6H, m- and p-Ph-CH), 7.85 (dd,
3JPH = 12.8 Hz, 3JHH = 6.8 Hz, 4H, o-Ph-CH), 8.29 (dd, 3JPH = 12.8 Hz,
JHH = 6.8 Hz, 4H, o-Ph-CH). 13C{1H} NMR (d6-benzene, 298 K): δ
4.17 (Si(CH3)3), 25.10 (OCH2CH2), 30.07 (C(CH3)3), 31.39 (dt,
JPC = 111.9 Hz, JYC = 2.3 Hz, CP2), 52.48 (C(CH3)3), 71.09
2
2
(OCH2CH2), 127.03 (vt, JPC = 6.1 Hz, o-Ph-CH), 127.34 (vt, JPC
=
6.1 Hz, o-Ph-CH), 130.24 (p-Ph-CH), 130.70 (p-Ph-CH), 133.00 (vt,
Preparation of [Y{C(PPh2NSiMe3)2(PCBut)-κ4C,C′,N,N′}(I)] (2).
A solution of ButCP (0.26 g, 1.00 mmol) in toluene (10 mL) was
added dropwise to a precooled (−78 °C) suspension of [Y(BIPM)-
(I)(THF)2] (0.92 g, 1.00 mmol) in toluene (10 mL). The yellow
slurry was slowly warmed to room temperature with stirring over 24 h.
The mixture was filtered, reduced in volume to 2 mL, and stored at
5 °C overnight to afford 2 as colorless crystals. Yield: 0.12 g, 14%.
Anal. Calcd for C36H47IN2P3Si2Y: C, 49.54; H, 5.43; N, 3.21. Found:
C, 49.44; H, 5.46; N, 3.25. 1H NMR (d8-THF, 298 K): δ 0.06 (s, 18H,
Si(CH3)3), 0.23 (s, 9H, C(CH3)3), 7.14 (vt, 3JHH = 7.2 Hz, 8H, m-Ph-
CH), 7.24 (m, 3JHH = 7.2 Hz, 4H, p-Ph-CH), 7.42 (m, 8H, o-Ph-CH).
13C{1H} NMR (d8-THF, 298 K): δ 2.09 (Si(CH3)3), 2.67 (C(CH3)3),
3JPC = 5.3 Hz, m-Ph-CH), 133.07 (dd, JPC = 118.9 Hz, 3JPC = 22.2 Hz,
3
ipso-Ph-C), 134.19 (vt, JPC = 5.3 Hz, m-Ph-CH), 134.70 (dd, JPC
=
120.4 Hz, 3JPC = 14.6 Hz, ipso-Ph-C), 156.26 (t, 2JPC = 2.8 Hz, NCO).
31P{1H} NMR (d6-benzene, 298 K): δ 20.39 (d, JYP = 3.2 Hz, CP2).
2
29Si{1H} NMR (d6-benzene, 298 K): δ −3.99 (SiMe3). FTIR ν/cm−1
(Nujol): 1601 (m), 1553 (w), 1348 (w), 1244 (m), 1218 (w), 1166
(w), 1109 (s), 1067 (s), 1038 (s), 836 (s), 772 (m), 741 (m), 693
(m), 661 (m), 607 (m), 543 (w), 519 (m), 508 (m).
Preparation of ButNCC(PPh2NSiMe3)2 (5). A solution of
ButNCS (0.25 g, 2.20 mmol) in toluene (10 mL) was added dropwise
to a precooled (−78 °C) suspension of [Y(BIPM)(I)(THF)2] (1.83 g,
2.00 mmol) in toluene (10 mL). The white slurry was slowly warmed
to room temperature with stirring over 24 h. The mixture was filtered,
reduced in volume to 2 mL, and stored at 5 °C overnight to afford 5
as colorless crystals. Yield: 0.28 g, 22%. The bulk material was
determined to be contaminated with YI3 byproduct. Anal. Calcd for
C36H47N3P2Si2·YI3: C, 38.97; H, 4.27; N, 3.79. Found: C, 38.98; H,
4.69; N, 3.17. 1H NMR (d6-benzene, 298 K): δ 0.26 (s, 18H,
Si(CH3)3), 0.79 (s, 9H, C(CH3)3), 7.04 (m, 12H, p- and m-Ph-CH),
7.93 (m, 8H, o-Ph-CH). 13C{1H} NMR (d6-benzene, 298 K): δ 4.14
(Si(CH3)3), 29.74 (C(CH3)3), 55.86 (t, JPC = 100.3 Hz, CP2), 59.77
2
3
28.81 (d, JPC = 6.0 Hz, C(CH3)3), 125.08 (vt, JPC = 6.2 Hz, m-Ph-
CH), 125.55 (d, 2JPC = 24.5 Hz, o-Ph-CH), 126.16 (d, 2JPC = 25.3 Hz,
3
o-Ph-CH), 126.94 (p-Ph-CH), 129.03 (vt, JPC = 6.2 Hz, m-Ph-CH),
139.95 (vt, JPC = 48.3 Hz, ipso-Ph-C), CP3 and PCBut not observed.
31P{1H} NMR (d8-THF, 298 K): δ −72.23 (br, PCBut), 1.62 (d, 2JPP
=
13.0 Hz, CP2). 29Si{1H} NMR (d8-THF, 298 K): δ −2.74 (SiMe3).
FTIR ν/cm−1 (Nujol): 1588 (w, br), 1436 (s), 1158 (m), 1113 (s),
1073 (s), 1060 (s), 1039 (s), 935 (m), 840 (s), 769 (m), 752 (m), 739
(m), 712 (m), 693 (m) 655 (m), 622 (m), 607 (m), 553 (m), 510 (m).
Preparation of [Y{C(PPh2NSiMe3)2[C(NCy)2]-κ4C,N,N′,N″}(I)-
(THF)] (3). Toluene (20 mL) was added to a precooled (−78 °C)
mixture of [Y(BIPM)(I)(THF)2] (1.83 g, 2.00 mmol) and C(NCy)2
(0.41 g, 2.00 mmol). The white slurry was slowly warmed to room
temperature with stirring over 24 h. The mixture was filtered, reduced
in volume, and stored at −25 °C overnight to afford 3 as colorless
crystals. A second crop was obtained. Yield: 1.14 g, 54%. Anal. Calcd
for C48H68IN4OP2Si2Y: C, 54.84; H, 6.53; N, 5.33. Found: C, 54.74;
2
(C(CH3)3), 127.67 (vt, JPC = 6.6 Hz, o-Ph-CH), 130.43 (p-Ph-CH),
3
132.13 (vt, JPC = 5.9 Hz, m-Ph-CH), 136.96 (dd, JPC = 107.6 Hz,
3JPC = 1.5 Hz, ipso-Ph-C), 162.63 (t, JPC = 5.9 Hz, ButNCCP2).
2
31P{1H} NMR (d6-benzene, 298 K): δ −2.58 (CP2). 29Si{1H} NMR
(d6-benzene, 298 K): δ −0.69 (SiMe3). FTIR ν/cm−1 (Nujol): 2048
(s, CCN stretch), 1589 (m, br), 1403 (s), 826 (m), 728 (m),
693 (m).
1247
dx.doi.org/10.1021/om301016j | Organometallics 2013, 32, 1239−1250

Organometallics
Article
Table 2. Crystallographic Data for 2−5
2
3
4
5·0.5C7H8
formula
C36H47IN2P3Si2Y
872.66
C48H68IN4OP2Si2Y
1050.99
C44H63IN3O3P2Si2Y
1015.90
C36H47N3P2Si2·0.5C7H8
685.95
fw
cryst size, mm
0.04 × 0.06 × 0.09
orthorhombic
Pnma
0.03 × 0.06 × 0.06
triclinic
0.15 × 0.25 × 0.25
monoclinic
0.02 × 0.12 × 0.18
triclinic
cryst syst
space group
P1
̅
P21/n
P1
̅
a, Å
20.021(3)
11.8218(3)
13.8371(4)
16.3160(4)
92.766(2)
99.723(2)
107.467(2)
2495.39(11)
2
11.8331(13)
17.3545(18)
23.769(2)
14.986(3)
15.291(3)
17.647(4)
90.56(3)
102.89(3)
100.20(3)
3874.6(13)
4
b, Å
19.555(2)
c, Å
10.4855(8)
α, deg
β, deg
102.276(2)
γ, deg
V, Å3
4105.1(9)
4
4769.5(8)
4
Z
ρcalcd, g cm−3
μ, mm−1
1.412
1.399
1.415
1.176
9.763
1.938
2.027
1.838
no. of rflns measd
no. of unique rflns, Rint
no. of rflns with F2 > 2σ(F2)
transmn coeff range
9593
8771
30165
30371
3812, 0.1353
2024
8771, 0.083
6659
10935, 0.0374
8122
13743, 0.0433
10686
0.591−0.760
0.0961, 0.1916
0.1780, 0.2595
1.067
0.89−0.94
0.0741, 0.1405
0.1103, 0.1569
1.181
0.6312−0.7508
0.0357, 0.0752
0.0600, 0.0834
1.006
0.89−0.99
0.0499, 0.1282
0.0662, 0.1374
1.057
a
R, Rw (F2 > 2σ(F2))
a
R, Rw (all data)
a
S
no. of params
219
533
505
793
max, min diff map, e Å−3
1.925, −2.05
0.786, −0.722
1.061, −0.469
0.459, −0.509
a
Conventional R = ∑||Fo| − |Fc||/∑|Fo|; Rw = [∑w(Fo − Fc2)2/∑w(Fo )2]1/2; S = [∑w(Fo − Fc2)2/((no. data) − (no. params))]1/2 for all data.
2
2
2
3
Preparation of [Y(BIPMH)(NHDipp)(I)(THF)] (6). NH2Dipp
3.67 (m, 4H, OCH2CH2), 4.92 (dd, JHH = 13.2 and 1.6 Hz, 2H,
OCCHCHAr), 5.18 (d, 3JHH = 13.2 Hz, 2H, OCCHCHAr), 6.60
(ddd, 3JHH = 7.2 Hz, 4JHH = 1.2 Hz, 2H, Ar-CH), 6.65 (dd, 3JHH = 7.6
Hz, 4JHH = 2.0 Hz, 2H, Ar-CH), 6.69 (br m, 2H, Ar-CH), 6.88 (br m,
(0.42 mL, 2.20 mmol) was added dropwise via syringe to a precooled
(−78 °C) suspension of [Y(BIPM)(I)(THF)2] (1.83 g, 2.00 mmol) in
toluene (10 mL). The white slurry was slowly warmed to room
temperature with stirring over 24 h. Volatiles were removed in vacuo,
and the resulting white solid was recrystallized from THF (12 mL) to
afford 6 as colorless crystals. A second crop was obtained. Yield: 1.29 g,
59%. Anal. Calcd for C51H73IN3O2P2Si2Y: C, 55.98; H, 6.73; N, 3.84.
Found: C, 55.76; H, 6.57; N, 3.65. 1H NMR (d8-THF, 298 K): δ 0.29
(s, 18H, Si(CH3)3), 0.98 (d, JHH = 5.2 Hz, 12H, CH(CH3)2), 1.26 (br,
3
3
4H, Ph-CH), 7.06 (t, JHH = 7.6 Hz, 4H, Ph-CH), 7.07 (t, JHH = 7.6
3
Hz, 4H, Ph-CH), 7.14−7.36 (m, 8H, Ar-CH), 7.41 (t, JHH = 7.2 Hz,
2H, Ar-CH), 7.50 (br m, 2H, Ar-CH), 7.64 (dd, 3JHH = 5.8 Hz, 4JHH
=
3.0 Hz, 4H, Ph-CH), 8.06 (br m, 2H, Ph-CH), 7.64 (ddd, JPH = 14.0
Hz, JHH = 7.2 Hz, JHH = 2.8 Hz, 4H, o-Ph-CH). 13C{1H} NMR
(d8-THF, 298 K): δ 3.39 (Si(CH3)3), 3.42 (Si(CH3)3), 4.57
(Si(CH3)3), 4.61 (Si(CH3)3), 25.43 (OCH2CH2), 67.35 (OCH2CH2),
98.60 (dd, JPC = 119.7 and 91.6 Hz, P2CCO), 116.08 (OCCHCH),
120.84 (OCCHCH), 125.71 (Ar-CH), 126.17 (br, Ar-CH), 126.20
(Ar-CCHCH), 127.06 (Ar-CH), 127.19 (Ar-CH), 127.30 (Ar-CH),
127.41 (Ar-CH), 127.53 (Ar-CH), 127.66 (d, 2JPC = 6.0 Hz, o-Ph-CH),
127.79 (Ar-CH), 129.22 (Ar-CH), 129.48 (d, 3JPC = 2.0 Hz, m-Ph-CH),
3
4
2
1H, HCP2), 1.82 (m, 4H, OCH2CH2), 1.92 (t, JPH = 2.6 Hz, 1H,
HCP2), 3.18 (m, 2H, CH(CH3)2), 3.67 (m, 4H, OCH2CH2), 4.59 (s,
3
1H, NHDipp), 6.35 (t, JHH = 6.8 Hz, 1H, p-Dipp-CH), 6.75 (d,
3JHH = 6.8 Hz, 2H, m-Dipp-CH), 7.02 (br, 4H, Ph-CH), 7.23 (br, 4H,
3
Ph-CH), 7.31 (t, JHH = 8.0 Hz, 4H, Ph-CH), 7.44 (br, 4H, Ph-CH),
3
3
7.50 (d, JHH = 6.0 Hz, 4H, Ph-CH), 8.08 (t, JHH = 8.0 Hz, 4H,
o-Ph-CH). 13C{1H} NMR (d8-THF, 298 K): δ 4.72 (Si(CH3)3), 17.91
(dt, JPC = 87.5 Hz, JYC = 4.5 Hz, HCP2), 23.35 (CH(CH3)2), 25.41
(OCH2CH2), 28.37 (CH(CH3)2), 67.27 (OCH2CH2), 114.22
130.01 (vt, JPC = 3.0 Hz, m-Ph-CH), 130.62 (d, 3JPC = 3.0 Hz, m-Ph-
3
CH), 131.33 (vt, 3JPC = 5.0 Hz, o-Ph-CH), 131.89 (br, Ar-CH), 132.12
3
(ipso-Ar-C), 132.31 (Ar-CH), 132.38 (d, JPC = 3.0 Hz, m-Ph-CH),
3
132.49 (Ar-CH), 133.06 (ipso-Ph-C), 133.54 (ipso-Ph-C), 134.08 (d,
(p-Dipp-CH), 121.59 (m-Dipp-CH), 127.53 (d, JPC = 14.1 Hz,
2JPC = 10.0 Hz, o-Ph-CH), 134.31 (d, 2JPC = 12.1 Hz, o-Ph-CH), 134.57
3
m-Ph-CH), 128.15 (d, JPC = 12.1 Hz, m-Ph-CH), 130.13 (p-Ph-CH),
2
(ipso-Ph-C), 135.41 (ipso-Ph-C), 136.48 (ipso-Ph-C), 139.76 (d, JPC
=
131.16 (p-Ph-CH), 131.62 (d, JPC = 11.1 Hz, o-Ph-CH), 132.83
6.0 Hz, ipso-Ph-C), 140.67 (d, JPC = 6.0 Hz, ipso-Ph-C), 162.31 (d,
(ipso-Ph-C), 133.68 (ipso-Ph-C), 134.10 (o-Dipp-C), 133.50 (d, JPC
=
2JYC = 6.0 Hz, Ar-CO), 184.75 (dd, 2JPC = 13.6 and 3.5 Hz, P2CCO).
10.1 Hz, ipso-Ph-C), 136.47 (d, JPC = 9.1 Hz, ipso-Ph-C), 151.99 (d,
2
31P{1H} NMR (d8-THF, 298 K): δ 4.91 (d, JPP = 37.3 Hz, CPNY),
2JYC = 3.0 Hz, ipso-Dipp-C). 31P{1H} NMR (d8-THF, 298 K): δ 19.17
2
28.32 (d, JPP = 37.3 Hz, CPN). 29Si{1H} NMR (d8-THF, 298 K):
2
(d, JYP = 6.5 Hz, HCP2). 29Si{1H} NMR (d8-THF, 298 K): δ −1.83
δ −15.68, −15.40, −1.65 (SiMe3). FTIR ν/cm−1 (Nujol): 1627 (m,
CC stretch), 1588 (m), 1565 (m), 1295 (s), 1223 (m), 1106 (s),
1046 (s), 828 (s), 744 (s), 693 (m), 548 (m), 518 (m).
(SiMe3). FTIR ν/cm−1 (Nujol): 1587 (w, br), 1404 (m), 929 (w),
831 (m), 693 (m).
Preparation of [Y2{C(PPh2NSiMe3)2[C(O)(CHCHC6H4O-2)]-
κ2N,O:μ,κO′}2(I)(μ-I)(THF)] (7). Toluene (20 mL) was added to a
precooled (−78 °C) mixture of [Y(BIPM)(I)(THF)2] (1.83 g, 2.00
mmol) and coumarin (0.29 g, 2.00 mmol). The yellow slurry was
slowly warmed to room temperature with stirring over 24 h. The
mixture was filtered, reduced in volume to 2 mL, and stored at 5 °C
overnight to afford 7 as colorless crystals. Yield: 0.33 g, 15%. Anal.
Calcd for C84H96I2N4O5P4Si4Y2: C, 52.83; H, 5.07; N, 2.94. Found: C,
52.71; H, 4.98; N, 2.91. 1H NMR (d8-THF, 298 K): δ −0.31 (s, 18H,
Si(CH3)3), 0.09 (s, 18H, Si(CH3)3), 1.81 (m, 4H, OCH2CH2),
Preparation of [Y{C(PPh2NSiMe3)2[C(O)(Ph)]-κ2N,O}2(I)] (8). A
solution of PhCOF (0.27 g, 2.20 mmol) in toluene (10 mL) was added
dropwise to a precooled (−78 °C) suspension of [Y(BIPM)(I)-
(THF)2] (1.83 g, 2.00 mmol) in toluene (10 mL). The yellow slurry
was slowly warmed to room temperature with stirring over 24 h. The
mixture was filtered away from the resulting white powder, reduced in
volume to 10 mL, and stored at 5 °C overnight to afford 8 as colorless
crystals. Yield: 0.22 g, 13%. Anal. Calcd for C76H86IN4O2P4Si4Y: C,
1
59.29; H, 5.63; N, 3.64. Found: C, 59.12; H, 5.76; N, 3.55. H NMR
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Organometallics
Article
Table 3. Crystallographic Data for 6−8
6·C4H8O
7·3.25C7H8
8·1.5C7H8
formula
C47H65IN3OP2Si2Y·C4H8O
1094.05
C84H96I2N4O5P4Si4Y2·3.25C7H8
2208.94
C76H86IN4O2P4Si4Y·1.5C7H8
1677.74
fw
cryst size, mm
0.05 × 0.13 × 0.39
monoclinic
0.05 × 0.10 × 0.15
triclinic
0.02 × 0.04 × 0.17
triclinic
cryst syst
space group
P21/c
P1
̅
P1
̅
a, Å
12.2756(2)
14.0687(6)
16.9323(7)
22.4949(9)
96.996(3)
90.722(4)
93.541(4)
5307.5(4)
2
12.4201(3)
16.6524(4)
22.1146(3)
83.0555(16)
82.7864(15)
69.759(2)
4242.65(15)
2
b, Å
45.6639(7)
c, Å
9.47291(14)
α, deg
β, deg
99.2161(15)
γ, deg
V, Å3
5241.50(14)
4
Z
ρcalcd, g cm−3
μ, mm−1
1.386
1.382
1.313
7.514
7.434
5.447
no. of rflns measd
no. of unique rflns, Rint
no. of rflns with F2 > 2σ(F2)
transmn coeff range
21575
37164
30022
9428, 0.045
8440
18755, 0.042
16371
15187, 0.048
12513
0.279−0.717
0.0483, 0.134
0.0582, 0.137
1.23
0.68−0.85
0.0579, 0.165
0.0651, 0.176
1.19
0.93−0.99
0.0479, 0.113
0.0623, 0.120
1.10
a
R, Rw (F2 > 2σ(F2))
a
R, Rw (all data)
a
S
no. of params
569
1123
905
max, min diff map, e Å−3
1.21, − 0.93
1.57, −2.64
0.69, −0.92
a
Conventional R = ∑||Fo| − |Fc||/∑|Fo|; Rw = [∑w(Fo − Fc2)2/∑w(Fo )2]1/2; S = [∑w(Fo − Fc2)2/((no. data) − (no. params))]1/2 for all data.
2
2
2
(d6-benzene, 298 K): δ 0.01 (s, 18H, Si(CH3)3), 0.11 (s, 18H,
Si(CH3)3), 6.84 (t, 3JHH = 7.2 Hz, 8H, Ph-CH), 6.89 (d, 3JHH = 7.2 Hz,
8H, Ph-CH), 6.91−7.13 (br m, 12H, Ph-CH), 7.22 (br m, 2H,
Ph-CH), 7.31 (d, 3JHH = 6.8 Hz, 4H, Ph-CH), 7.35−7.70 (br m, 10H,
Ph-CH), 7.89 (br m, 2H, Ph-CH), 8.08 (br m, 2H, Ph-CH), 8.27
(br m, 2H, Ph-CH). 13C{1H} NMR (d6-benzene, 298 K): δ 1.18
(Si(CH3)3), 4.09 (d, JYC = 3.0 Hz, Si(CH3)3), 4.35 (d, JYC = 4.0 Hz,
Si(CH3)3), 93.36 (dd, JPC = 112.7 Hz, 89.6 Hz, CP2), 127.14 (Ph-CH),
127.70 (Ph-CH), 127.94 (Ph-CH), 128.33 (Ph-CH), 128.76 (Ph-CH),
129.09 (Ph-CH), 129.32 (br, Ph-CH), 129.55 (Ph-CH), 130.42 (Ph-
with anisotropic displacement parameters for all non-hydrogen atoms
and with constrained riding hydrogen geometries; Uiso(H) was set at
1.2 (1.5 for methyl groups) times Ueq of the parent atom. The largest
features in final difference syntheses were close to heavy atoms and
were of no chemical significance. Highly disordered solvent molecules
of crystallization in 5·0.5C7H8, 7·3.25C7H8, and 8·1.5C7H8 could not be
modeled and were treated with the Platon SQUEEZE procedure.44
Programs used were Bruker AXS SMART45 and CrysAlisPro46
(control), Bruker AXS SAINT45 and CrysAlisPro46 (integration), and
SHELXTL47 and OLEX248 (structure solution and refinement and
molecular graphics).
3
CH), 130.64 (Ph-CH), 131.52 (t, JPC = 5.0 Hz, m-Ph-CH), 131.94
(br, Ph-CH), 132.42 (Ph-CH), 132.57 (Ph-CH), 132.68 (Ph-CH),
134.35 (br, ipso-Ph-C P), 138.99 (d, JPC = 101.6 Hz, ipso-Ph-C P),
ASSOCIATED CONTENT
* Supporting Information
CIF files giving crystallographic data for 2−8. This material is
available free of charge via the Internet at http://pubs.acs.org.
■
2
140.72 (ipso-Ph-C), 140.81 (ipso-Ph-C), 185.80 (d, JPC = 2.8 Hz,
S
2
PhCO). 31P{1H} NMR (d6-benzene, 298 K): δ −0.18 (d, JPP = 35.6
2
Hz, CPN), 29.27 (d, JPP = 35.6 Hz, CPNY). 29Si{1H} NMR
(d6-benzene, 298 K): δ −15.82, −15.51, −3.32 (SiMe3). FTIR ν/cm−1
(Nujol): 1590 (w, br), 1403 (m), 1155 (w), 1105 (m), 742 (m), 691 (m),
539 (w).
AUTHOR INFORMATION
Corresponding Author
*E-mail: stephen.liddle@nottingham.ac.uk.
Notes
■
X-ray Crystallography. Crystal data for compounds 2−8 are
given in Tables 2 and 3, and further details of the structure
determinations are given in the Supporting Information. Bond lengths
and angles are given in Table 1. Crystals were examined variously on a
Bruker APEX CCD area detector diffractometer using graphite-
monochromated Mo Kα radiation (λ = 0.71073 Å) or on an Oxford
Diffraction SuperNova Atlas CCD diffractometer using mirror-
monochromated Cu Kα radiation (λ = 1.5418 Å). Intensities were
integrated from data recorded on 0.3° (APEX) or 1° (SuperNova)
frames by ω rotation. Data for 3 were collected by the National Service
on a Bruker-Nonius APEX II diffractometer using confocal mirror-
monochromated Mo Kα radiation (λ = 0.71073 Å) with intensities
integrated from data recorded on φ and ω scans. Cell parameters were
refined from the observed positions of all strong reflections in each data
set. Semiempirical absorption correction based on symmetry-equivalent
and repeat reflections (APEX) or Gaussian grid face-indexed absorption
correction with a beam profile correction (Supernova) were applied.
The structures were solved variously by direct and heavy atom methods
and were refined by full-matrix least squares on all unique F2 values,
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We thank the Royal Society for a University Research Fellowship
(S.T.L.), and the EPSRC, European Research Council, and the
University of Nottingham for generously supporting this work.
We also thank the EPSRC UK National X-ray Crystallography
Service at the University of Southampton49 for the collection of
the crystallographic data for 3.
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