Synthetic, structural, NMR, and computational study of a geminally bis(peri-substituted) tridentate phosphine and its chalcogenides and transition-metal complexes

Article abstract of DOI:10.1021/ic3024875

Coupling of two acenaphthene backbones through a phosphorus atom in a geminal fashion gives the first geminally bis(peri-substituted) tridentate phosphine 1. The rigid nature of the aromatic backbone and overall crowding of the molecule result in a rather inflexible ligand, with the three phosphorus atoms forming a relatively compact triangular cluster. Phosphine 1 displays restricted dynamics on an NMR time scale, which leads to the anisochronicity of all three phosphorus nuclei at low temperatures. Strained bis- and tris(sulfides) 2 and 3 and the bis(selenide) 4 have been isolated from the reaction of 1 with sulfur and selenium, respectively. These chalcogeno derivatives display pronounced in-plane and out-of-plane distortions of the aromatic backbones, indicating the limits of their angular distortions. In addition, we report metal complexes with tetrahedral [(1)Cu(MeCN)][BF ₄] (5), square planar [(1)PtCl][Cl] (6), trigonal bipyramidal [(1)FeCl₂] (7), and octahedral fac-[(1)Mo(CO)₃] (8) geometries. In all of these complexes the tris(phosphine) backbone is distorted, however to a significantly smaller extent than that in the mentioned chalcogenides 2-4. Complexes 5 and 8 show fluxionality in ³¹P and ¹H NMR. All new compounds 1-8 were fully characterized, and their crystal structures are reported. Conclusions from dynamic NMR observations were augmented by DFT calculations.

Full text of DOI:10.1021/ic3024875

Article
pubs.acs.org/IC
Synthetic, Structural, NMR, and Computational Study of a Geminally
Bis(peri-substituted) Tridentate Phosphine and Its Chalcogenides
and Transition-Metal Complexes
Matthew J. Ray, Rebecca A. M. Randall, Kasun S. Athukorala Arachchige, Alexandra M. Z. Slawin,
̈
Michael Buhl, Tomas Lebl, and Petr Kilian*
School of Chemistry, EaStChem, University of St Andrews, Fife KY16 9ST, United Kingdom
*
S Supporting Information
ABSTRACT: Coupling of two acenaphthene backbones
through a phosphorus atom in a geminal fashion gives the
first geminally bis(peri-substituted) tridentate phosphine 1.
The rigid nature of the aromatic backbone and overall
crowding of the molecule result in a rather inflexible ligand,
with the three phosphorus atoms forming a relatively compact
triangular cluster. Phosphine 1 displays restricted dynamics on
an NMR time scale, which leads to the anisochronicity of all
three phosphorus nuclei at low temperatures. Strained bis- and
tris(sulfides) 2 and 3 and the bis(selenide) 4 have been
isolated from the reaction of 1 with sulfur and selenium,
respectively. These chalcogeno derivatives display pronounced
in-plane and out-of-plane distortions of the aromatic back-
bones, indicating the limits of their angular distortions. In addition, we report metal complexes with tetrahedral
[
[
(1)Cu(MeCN)][BF ] (5), square planar [(1)PtCl][Cl] (6), trigonal bipyramidal [(1)FeCl ] (7), and octahedral fac-
4
2
(1)Mo(CO) ] (8) geometries. In all of these complexes the tris(phosphine) backbone is distorted, however to a significantly
3
31
1
smaller extent than that in the mentioned chalcogenides 2−4. Complexes 5 and 8 show fluxionality in P and H NMR. All new
compounds 1−8 were fully characterized, and their crystal structures are reported. Conclusions from dynamic NMR observations
were augmented by DFT calculations.
INTRODUCTION
to synthesize a hexakis(phosphine) ligand that forms binuclear
complexes in which it behaves as a tridentate ligand to two
metal centers simultaneously (L). Ortho-substituted phenyl
■
Chelating ligands have been used extensively in coordination
chemistry due to the enhanced control of steric and electronic
properties, stereochemistry, and coordination number that they
give compared to monodentate ligands. The combination of the
coordination properties of phosphines and benefits of chelation
make tridentate phosphines excellent ligands. Compared with
bidentate phosphines, relatively few tridentate phosphines have
been reported in the literature, which is surprising considering
the advantages bidentate phosphines have over monodentate
species in many important homogeneous catalytic processes. Of
the tridentate phosphines reported to date, the triphos ligands
8
groups are popular structural motifs in tridentate phosphines as
their rigidity helps to preorganize the donor atoms into a
configuration that favors chelation of a metal. This has been
9
10
11
9
demonstrated in ligands M, N, O, and P. A similar motif
based on an indole heterocycle) was utilized in the
(
12
construction of ligand Q. 1,3,5-Tris(phosphino)-substituted
cyclohexanes have also been shown to act as tridentate
13
14
phosphine ligands when in the chair conformation (R, S,
1
5
T ).
1
Peri-substituted naphthalenes represent another rigid frame-
A and B are by far the most studied; there are over 300 papers
work potentially useful for the construction of tridentate
published on various aspects of reactivity of A and over 370 on
B. B has provided the basic structure for a number of variations,
differing in both the phosphine substituents (C, D, E, F ) and
the bridging chain length (G, H, I ) (see Scheme 1). A C-
chiral derivative of these ligands (J) has also been reported
from a modified synthetic method starting from an
1
6,17
ligands.
Schmutzler and others have reported a large series
2
3
4
of bis(phosphino)naphthalene ligands, conveniently synthe-
sized by the reaction of 1,8-dilithionaphthalene with 2 molar
2
5
17−21
equiv of a chlorophosphine (Scheme 2).
The coordination chemistry of these ligands, and in particular
that of 1,8-bis(diphenylphosphino)naphthalene (dppn, R = R′
6
enantiomerically pure alkyl bromide. A similar strategy was
employed in the synthesis of another C-chiral ligand, Pigiphos
7
(
K), based on a ferrocenylphosphine backbone. Functionaliza-
Received: November 14, 2012
Published: March 27, 2013
tion of both cyclopentadienide rings of ferrocene has been used
©
2013 American Chemical Society
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Inorganic Chemistry
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a
Scheme 1. Selected Tridentate Phosphine Ligands in the Literature
a
Cy = cyclohexyl.
Scheme 2. Synthesis of 1,8-Bis(phosphino)naphthalenes
removal of volatiles in vacuo and subsequent washing with
acetonitrile, 1 was obtained as a yellow solid in 68% yield in
good purity. An optimization of the reaction conditions showed
that the yield of 1 was maximized by slow addition of iPrPCl2
and maintaining a low temperature for an extended period after
the addition. 1 is air stable as a solid or in solution in organic
solvents.
31
1
The P{ H} NMR spectrum of 1 in toluene-d (202.4 MHz,
8
2
98 K) shows two broad resonances between +2 and −18 ppm,
which implies restricted dynamics of the molecule in solution
Figure 1, spectrum a). The expected AB pattern (δ = −1.8
(
2
A
ppm, δ = −8.1 ppm; J = 140 Hz) was revealed when the
sample was heated to 353 K (Figure 1, spectrum b). The
observed magnitude of J coupling in 1 is somehow smaller,
B
AB
=
Ph), has been explored extensively. Dppn forms a wide range
of complexes with middle and late transition metals with
coordination numbers ranging from 3 to 6 and has proven to be
an excellent small bite angle ligand due to the unique steric
constraints imposed by peri-substitution. However, no tridentate
ligands based on a geminally bis(peri-substituted) naphthalene
framework have been reported in the literature so far. We
report here the synthesis and reactivity of such a tridentate
phosphine, 1, which is the first example of what may potentially
develop into a new family of ligands with tight geometrical
restraints.
4
PP
however, comparable with that observed by MAS solid-state
3
1
1
21
P{ H} NMR for dppn (199 Hz). Two ABC patterns in a
31
1
5
1
(
8:42 ratio become apparent in the P{ H} NMR spectrum of
at 223 K, suggesting that two rotamers are present in solution
3
1
Figure 1, spectrum c). This is supported by the P EXSY
spectrum, which showed exchange between the two ABC spin
systems. The coupling pattern for the two ABC spin systems
was simulated (Figure 1, spectrum d). The resulting values are
as follows (B denotes the inner phosphorus atom): δB1 = −1.52
ppm, δA1 = −4.53 ppm, δC1 = −15.59 ppm, δB2 = −10.88 ppm,
RESULTS AND DISCUSSION
Ligand 1, Sulfides 2 and 3, and Selenide 4. Recently we
■
δA2 = −11.87 ppm, δ = −17.14 ppm, J
= 93.9, J
=
C2
A1−B1
B1−C1
1
42.3, J
= 0, J
= 139.7, J
= 137.6, JA2−C2 = 7.3
p u b l i s h e d t h e p r e p a r a t i o n2 o f 5 - b r o m o - 6 -
A1−C1
A2−B2
B2−C2
2
(
diisopropylphosphino)acenaphthene. We now use this
Hz).
compound as the principal starting material in the synthesis
of the new tridentate ligand 1 (Scheme 3). First, a lithium−
halogen exchange reaction with nBuLi in diethyl ether at −78
Detailed line shape analysis, which would yield thermody-
namic parameters of hindered rotation processes in a solution
of 1, was not possible due to the complexity of the spin system.
However, we were able to observe two coalescence conditions,
both for the interchange between the A1B1C1 and A2B2C2
spin systems observed in the slow motion regime. Thus, the
C1−C2 pair of resonances coalesce at 259.5 K, which
°
C afforded 5-lithio-6-(diisopropylphosphino)acenaphthene.
This was without isolation reacted with 1/2 equiv of iPrPCl2
at the same temperature. The salt byproducts were removed by
filtration through a sinter with a filtration aid (Celite). After
4
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Scheme 3. Synthesis of Compounds 1−8
Figure 1. Variable-temperature 31P NMR spectra of 1 in toluene-d at 202.4 MHz: (a) broad resonances at 298 K, (b) AB pattern at 353 K, (c) two
8
2
31
ABC patterns in a ratio of 58:42 at 223 K due to two rotamers, (d) simulated P coupling pattern with assignments.
−
1
corresponds to a barrier of 11.7 kcal mol , while the A1−A2
Calculations at the B3LYP level indicate that restricted
rotation around the P1−C13 bond (see Figure 2 for the
numbering of atoms) may correspond to slow interchange
between the A1B1C1 and A2B2C2 spin systems observed in
pair of resonances coalesce at 269.4 K with a barrier of 11.4 kcal
mol (see Table S1 and Figure S1 in the Supporting
Information).
−
1
4
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Table 1. Selected Bond Lengths (Å) and Angles (deg) for
1
·MeCN, 2, 3·(CH ) CO, and 4
3 2
1
·MeCN
2
3·(CH ) CO
4
3
2
C1−P1
C22−P1
C9−P2
C30−P3
1.856(6)
1.851(5)
1.836(5)
1.850(5)
3.17
1.856(6)
1.856(7)
1.846(6)
1.843(7)
3.61
1.830(8)
1.852(8)
1.834(11)
1.849(9)
3.91
1.848(5)
1.854(5)
1.850(5)
1.857(5)
3.81
P1···P2
P1···P3
3.15
3.89
4.07
3.69
P2···P3
4.42
6.15
6.19
6.06
P1−S1
1.966(3)
1.957(3)
1.972(4)
106.9(4)
124.0(6)
131.4(8)
126.2(6)
+21.6(8)
P2−S/Se2
P3−S/Se3
C1−P1−C22
P1−C1−C10
C1−C10−C9
C10−C9−P2
splay angle
1.970(3)
1.945(3)
104.0(3)
122.2(5)
132.2(5)
129.5(5)
+23.9(5)
2.1251(12)
2.1249(14)
103.67(19)
121.0(3)
100.94(19)
125.5(4)
128.7(4)
120.9(4)
+15.1(4)
Figure 2. Crystal structure of 1 with ellipsoids drawn at 50%
probability. The cocrystallized molecule of MeCN and hydrogen
atoms are omitted and iPr groups are shown in stick form for clarity.
131.9(4)
126.6(4)
+19.5(4)
31P NMR at low temperature. Two local minima corresponding
to the two possible conformers were localized on the potential
(
ring bearing
a
P2)
−1
P1−C22−C31
123.6(3)
128.5(4)
127.2(5)
132.1(6)
124.8(6)
131.2(7)
122.5(3)
131.5(4)
surface, differing by 0.4 kcal mol (B3LYP level, −0.6 kcal
−1
C22−C31−
mol at the B3LYP-D3 level), with a transition barrier of ca. 12
−1
23
C30
kcal mol . The positions of the inner iPr group with respect
to the outer phosphorus atoms (P2 and P3) are rather different
in the two optimized structures of rotamers, which corresponds
C31−C30−P3
splay angle
123.6(4)
+12.6(4)
131.5(6)
+30.8(6)
127.4(7)
+23.4(7)
129.7(3)
+23.7(4)
(
ring bearing
well with the observed anisochronicity of P2 and P3 (in 31
NMR) in the two low-temperature ABC spin systems.
P
a
P3)
a
See Figure 3.
In addition to the exchange of the two ABC spin systems
observed at low temperature, an additional process takes place
which exchanges resonances A and C. This eventually results in
an AB pattern, which is observed at 353 K (at 202.4 MHz; see
2
Figure 1, spectrum b). We have not succeeded in obtaining the
thermodynamic parameters of this process as the faster
exchange of the two ABC spin systems “masks” this slower
process. We can speculate that the slower exchange process
Figure 3. Definition of a splay angle.
involves rotation around the inner P−C
bonds (P1−C1
Acenap
1
9
and P1−C22).
Nap(PiPr ) ). The bond angles around the phosphorus atoms
2
2
Interestingly, the related peri-substituted bis(phosphines)
Nap(PiPr ) and Nap(PCy ) (Nap = naphthalene-1,8-diyl)
in 1 are only slightly more acute vs the ideal tetrahedral angle,
with C22−P1−C13 being the most acute at 98.1(3)°.
2
2
2 2
3
1
1
19
exhibit a sharp singlet in their P{ H} NMR spectra. This
Reactivity toward chalcogens provides information on the
extent of the steric crowding in 1,8-bis(phosphino)-
suggests that the rotation around the P−C bonds is relatively
Nap
2
4−26
unhindered in these compounds, which contrasts sharply with
the situation in the geminally bis(peri-substituted) ligand 1.
The crystal structure of 1 (as an acetonitrile monosolvate) is
shown in Figure 2, with structural data given in Tables 1 and 4.
The molecule of 1 crystallizes in a conformation which brings
the three phosphorus atoms into proximity to form a relatively
naphthalenes.
To establish how the extra crowding
concomitant with geminal bis(peri-substitution) affects the
sterics of the phosphorus centers in 1, we performed a series of
reactions with elemental sulfur and selenium.
1 was treated with 3.2 equiv of sulfur in refluxing toluene.
This was followed by evaporation of volatiles. The resulting
orange oil had a complex 31P{ H} spectrum, indicating that a
mixture of products forms. Extraction of the orange oil with
hexane and subsequent crystallization from diethyl ether/
acetone gave two distinct types of crystals, which were shown
to be the bis(sulfide) 2 and tris(sulfide) 3. The crystals were
large enough and formed in sufficiently high quantities to allow
for mechanical separation and full characterization by single-
1
compact triangular P cluster. The P···P distances across the
3
peri-positions are very similar, 3.17 Å (P1···P2) and 3.15 Å
(
P1···P3). These are only slightly longer than the respective
P···P values observed in Nap(PiPr ) (2.944(1) and 2.927(1) Å
2
2
19
for the two molecules in the unit cell). The angle between the
two acenaphthene mean planes in 1 is 62.0°, which results in
the relatively short distance between the two outer phosphorus
atoms (P2···P3) of 4.42 Å. Both acenaphthene rings show a
similar extent of out-of-plane twist, with the inner P1 atom
being 0.23 Å out of the P2-bearing ring mean plane and 0.14 Å
out of the P3-bearing ring mean plane. Atoms P2 and P3 are
displaced 0.47 and 0.28 Å out of their respective acenaphthene
rings. The in-plane distortion of the peri-regions in 1 is also
comparable to that observed in related 1,8-bis(phosphino)-
naphthalenes, the splay angles (Figure 3) in 1 being +15.1° and
1
31
1
31
crystal X-ray diffraction, H, P{ H}, and P NMR, MS, and
elemental analysis. Both 2 and 3 have poor solubility in organic
solvents, which prevented acquisition of their C{ H} NMR
13
1
31
1
spectra. All signals in the P{ H} NMR spectra of 2 and 3 are
broadened at 25 °C; the half-width of the peaks is 70−220 Hz
for 2 and 15−25 Hz for 3 (both at 121.5 MHz). Thus, 2
displayed three broad singlets at δ = 13.3, 73.6, and 84.8 ppm,
P
while 3 exhibited broad singlets at δ = 65.7, 68.3, and 84.2
ppm. No fine structure of the peaks (potentially stemming from
P
+
12.6° (9.8° and 10.2° in the two molecules in the unit cell of
4
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Inorganic Chemistry
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3
1
through-space coupling between the P nuclei) was observable,
presumably due to the broadening. While in the spectrum of 2
it is possible to assign the peak at δ = 13.3 ppm to the inner
P
phosphorus atom due to its distinct chemical shift, the
similarity in the chemical shifts of P atoms in 3 does not
allow similar assignment there with any certainty. The signals in
1
the H NMR spectra of both 2 and 3 were also broadened,
3
1
1
which hindered their complete assignment. The P{ H} NMR
spectrum of the crude mixture after reaction showed 2 and 3
were the major components; other phosphorus-containing
products were present in smaller amounts. Interestingly, the
3
1
1
same distribution of products was observed by P{ H} NMR
when NEt was added to the reaction mixture or when larger
3
excesses of S8 and/or longer reaction times were used,
indicating that the same equilibrium ratio of bis(sulfide) 2
and tris(sulfide) 3 becomes established in all cases. Both 2 and
3
are air stable in the solid state or when dissolved in organic
solvents; however, both compounds decompose in chlorinated
solvents slowly as indicated by slow darkening of their solutions
over several days.
The crystal structures of 2 and 3 (as acetone monosolvates)
are shown in Figures 5−7, with structural data given in Tables 1
and 4. The molecule of 2 is significantly more strained than that
of 1 due to the increase of steric bulk on thionation of the two
outer phosphorus atoms. While the overall geometry of the
molecule remains similar to that of 1 (the angle between mean
planes of the acenaphthene rings being almost the same, 61.7°),
profound changes are seen in all other metric parameters of 2.
The P···P distances are all increased to 3.61 Å (P1···P2), 3.89 Å
Figure 5. Crystal structure of 2 with ellipsoids drawn at 50%
probability. Hydrogen atoms are omitted and iPr groups are shown in
stick form for clarity.
(
P1···P3), and 6.15 Å (P2···P3). The out-of-plane distortions
are also increased; P1 is 0.80 and 0.49 Å out of the plane of the
two acenaphthene rings, while P3 and P2 are 0.83 and 0.42 Å
displaced from their respective acenaphthene mean planes. In
the same vein, splay angles (Figure 3) are more obtuse in 2
[
+23.9(5)° and +30.8(6)°] than those in 1.
Differing conformations of the iPr P(S) groups with respect
2
to the inner P atom (P1) are observed in the structure of 2.
While sulfur atom S3 points approximately toward the peri-gap
(
the C31−C30−P3−S3 dihedral angle is 22.9(6)°), the other
sulfur atom S2 points away from its peri-gap (the C10−C9−
P2−S2 dihedral angle is 154.8(5)°). This results in an
approximately linear arrangement of the P1, P2, and S2
atoms, the angle P1···P2S2 being 174.5°. We also observed
slight shortening of the P1···P2 distance vs P1···P3 (3.61 vs
Figure 6. Crystal structure of 3 with ellipsoids drawn at 50%
probability. The cocrystallized molecule of acetone and hydrogen
atoms are omitted and iPr groups are shown in stick form for clarity.
3
.89 Å) and slight elongation of the P2−S2 bond distance vs
P3−S3 [1.970(3) vs 1.945(3) Å], all this being indicative of a
weak donor−acceptor interaction from the lone pair on P1 into
the σ* P2S2 antibonding orbital (Figure 4). To assess this
potential onset of 3c−4e bonding, we computed Wiberg bond
indices (WBIs) at the B3LYP/6-31+G* level of density
0.03 is computed between the (inner) P1 and (outer) P2 atoms
28
in 2 (optimized distance 3.70 Å, experimental 3.61 Å). Even
more negligible WBIs (below 0.01) were computed between
the P1 and P3 atoms in 2 and also between all P atoms in the
tris(sulfide) 3.
27
functional theory. However, a barely noticeable WBI of
As expected, 3 continues the trend of increasing crowding
with further thionation. While the angle between the two
acenaphthene mean planes is reduced to 52.7°, the P···P
distances are elongated to 3.91 Å (P1···P2), 4.07 Å (P1···P3),
and 6.19 Å (P2···P3). Notably, the P1···P3 distance is the
longest P···P peri-distance reported, the previous record being
held by the bis(selenide) Nap[P(OiPr ) Se] with a P···P
2
2
2
29
distance of 3.92 Å. The out-of-plane distortions (see Figure
7) are also more pronounced, with the (inner) P1 atom being
displaced 1.04 and 1.14 Å from the two acenaphthene mean
Figure 4. Orbitals involved in weak P1···P2S2 3c−4e bonding in 2.
Note that the P1···P2S2 angle is 174.5°.
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Se) groups with respect to their respective peri-gaps. Thus, both
selenium atoms in the structure of 4 are pointing away from the
peri-gap [C10−C9−P2-Se2, 148.1(3)°; C31−C30−P3−Se3,
1
51.1(3)°], while in the structure of 2 one of the sulfur atoms
points away and one toward the peri-gap [C10−C9−P2−S2,
54.8(5)°; C31−C30−P3-S3, 22.9(6)°]. Optimized gas-phase
1
structures of these conformers (B3LYP level) differ in energy
only a little; the conformation with both chalcogen atoms in the
structure pointing away from the peri-gap was found to be more
stable in both cases, by 0.9 and 2.4 kcal mol− for bis(sulfide) 2
and bis(selenide) 4, respectively. In the X-ray structure of 4
both P1···P2−Se2 and P1···P3−Se3 motifs adopt almost linear
arrangements. Such a geometry allows for 3c−4e bonding, with
the electron density from the P1 phosphine center being
donated to the antibonding σ* orbital of the PSe bonds;
however, calculations reveal negligible (<0.01) WBIs for these
particular interactions.
1
Figure 7. Selected part of a molecule of 3 (in the crystal) illustrating
the extent of out-of-plane distortions in the peri-region and at the
acenaphthene ring. The dihedral angle P1−C22···C30−P3 is 60.1°.
Ellipsoids are drawn at 50% probability.
31
1
The P{ H} spectrum of 4 consists of broad singlets (half-
width 105−200 Hz at 121.5 MHz) at δ = 14.6 ppm (inner P
P
planes, while the P2 and P3 atoms are displaced 1.15 and 1.20
Å from their respective acenaphthene mean planes. The
twisting of the actual acenaphthene rings is also very distinct,
with atoms C22 and C30 being placed 0.22 and 0.20 Å above
and below the mean acenaphthene plane. Interestingly, splay
angles [+21.6(8)° and +23.4(7)°; see Figure 3] show that in-
plane distortions in 3 are significant, however slightly smaller
than in bis(sulfide) 2.
atom) and 78.8 and 86.0 ppm (outer P atoms). Signals in the
1
H NMR spectrum were also broadened. As with 2, poor
solubility of 4 in organic solvents prevented characterization by
13
1
77
1
C{ H} and Se{ H} NMR. 4 was further characterized by
MS and microanalyses.
Coordination Chemistry of 1. The molecular structure of
indicates that the three phosphorus atoms are in an
1
arrangement suitable for cooperative coordination to a single
transition-metal center, forming a well-defined coordination
pocket. We have indeed isolated complexes of tetrahedral,
square planar, trigonal bipyramidal, and octahedral geometries,
with 1 acting as a tridentate ligand in each case. These are
discussed below.
The reaction of tris(phosphine) 1 with 3.2 equiv of gray
3
1
1
selenium was performed in boiling toluene. The P{ H} NMR
of the mixture after the reaction was complex; however,
recrystallization of the crude product from hexane afforded
analytically pure bis(selenide) 4 as yellow needle-shaped
crystals in 21.5% yield. The X-ray crystal structure of 4 is
shown in Figure 8, with structural data given in Tables 1 and 4.
The reaction of 1 with [Cu(MeCN) ][BF ] in thf led to the
4 4
formation of the complex [(1)Cu(MeCN)][BF ] (5). It was
4
obtained in the form of an air/moisture-sensitive pale yellow
powder and was purified by recrystallization from thf. The
31
1
P{ H} NMR spectrum of 5 exhibits two broad signals at δ =
P
−
18.7 ppm (br t, inner P) and 6.1 ppm (br s, 2 × outer P).
Broadening of the signals (the half-width of both signals is ca.
1
70−180 Hz at 162.0 MHz) precludes detailed analysis;
2
however, an approximate value of J = 50−60 Hz was read
PP
from the spectrum. An interesting feature is that on
coordination of 1 to copper(I) (i.e., formation of 5) the
chemical shift of the inner P atom moves toward lower
frequency (to δ = −18.7 ppm) compared with that in the free
P
ligand (δP = −1.4 ppm), which is the opposite direction
normally observed on metal coordination. Coordination of
triphos (A) (δP = −27.3 ppm) to copper to form [Cu-
30
(
triphos)(MeCN)][PF ] (δ = −20.6 ppm) is an example
6
P
where the opposite trend is observed.
The crystal structure of 5 is shown in Figure 9, with
structural data given in Tables 2, 3 and 5. Despite our repeated
efforts using a variety of solvents and crystallization techniques,
we have only been able to grow relatively small crystals of 5,
which are thin platelets. Hence, our structural data are rather
poor; however, they are adequate to demonstrate connectivity
Figure 8. Crystal structure of 4 with ellipsoids drawn at 50%
probability. Hydrogen atoms are omitted and iPr groups are shown in
stick form for clarity.
The overall geometry of 4 is rather similar to that of bis(sulfide)
and support the assignment of the structure. The molecule
−
2
. The angle between the acenaphthene mean planes is 56.1°,
crystallizes as a separated cation with a BF
4
counteranion,
and the peri-distances are 3.81 Å (P1···P2), 3.69 Å (P1···P3),
and 6.06 Å (P2···P3).
together with 1/2 of a solvated molecule of thf. The copper
center is tetrahedrally coordinated, with the three phosphine
groups of 1 adopting a tripodal geometry and a N-coordinated
acetonitrile completing the coordination. The “across peri-gap”
The most contrasting feature of the structure of 4 with regard
to 2 is the conformation of the two (outer) iPr P(E) (E = S,
2
4
351
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Inorganic Chemistry
Article
Table 3. Selected Nonbonded Distances (Å), Angles (deg),
and Displacements (Å) Associated with the Tris(phosphine)
1
Ligands within Complexes 5· / thf, 6·CH Cl , 7·thf, and fac-
2
2
2
a
8
·MeCN
fac-
8·MeCN 1·MeCN
1
5
· / thf 6·CH Cl2
7·thf
3.36
2
2
P1···P2
P1···P3
P2···P3
3.43
3.43
4.01
66.9
3.36
3.22
4.64
46.9
3.31
3.32
4.03
87.2
3.17
3.15
4.42
62.0
3.41
5.15
46.8
b
interplanar angle
c
Splay Angles
21.2(4)
ring bearing P2
ring bearing P3
16.0(8)
18.3(8)
11.0(4)
22.1(4)
19.6(5)
21.4(5)
15.1(4)
12.6(4)
6.3(5)
d
Out-of-Plane Displacements
P1 (from plane
bearing P2)
0.65
0.36
0.69
0.33
0.23
P2
0.77
0.66
0.22
0.64
1.05
0.37
0.25
0.16
0.47
0.14
Figure 9. Crystal structure of the cation of 5 with ellipsoids drawn at
P1 (from plane
bearing P3)
−
50% probability. The BF4 counterion, cocrystallized molecule of thf
(
hemisolvate), and hydrogen atoms are omitted and iPr groups are
P3
0.68
1.04
0.29
0.32
0.28
shown in stick form for clarity.
a
Relevant data for free ligand (1·MeCN) are included for ease of
b
comparison. Angle between the two acenaphthene mean planes
Table 2. Selected Bond Lengths (Å) and Angles (deg) for
c
d
within the molecule. For definition see Figure 3. Displacements of
phosphorus atoms from the acenaphthene mean planes.
1
5
· / thf, 6·CH Cl , 7·thf, and fac-8·MeCN
2
2
2
1
5
· / thf
2
3
0
P1−Cu1
P3−Cu1
P1−Cu1−P2
P2−Cu1−P3
P2−Cu1−N1
2.231(3)
2.254(3)
100.24(9)
P2−Cu1
N1−Cu1
P1−Cu1−P3
P1−Cu1−N1
P3−Cu1−N1
2.241(3)
2.057(8)
99.90(9)
114.3(3)
102.5(3)
2
.2742(17) Å], while the slight elongation of the Cu−N
bond in 5 (2.057(8) Å) vs that in the mentioned triphos
complex (1.939(5) Å) indicates bonding of MeCN may be
slightly more labile in 5. Coordination of 1 to copper(I) results
in overall leveling of the P···P distances within the ligand. Thus,
the peri-P···P distances (P1···P3 and P1···P2) are both slightly
elongated at 3.43 Å, while the P2···P3 separation decreases to
126.33(10)
113.2(2)
6
2.2146(14)
2.3097(15)
95.78(5)
·CH Cl
2
2
P1−Pt1
P2−Pt1
P1−Pt1−P2
P1−Pt1−P3
P2−Pt1−P3
P3−Pt1
Cl1−Pt1
Cl1−Pt1−P1
Cl1−Pt1−P2
Cl1−Pt1−P3
2.3364(15)
2.3550(17)
170.98(5)
86.21(5)
4
.01 Å.
The reaction of 1 with PtCl (cod) (cod =1,5-cyclooctadiene)
in CH Cl gave another ionic complex, [(1)PtCl][Cl] (6),
2
90.07(5)
2
2
173.43(5)
88.48(6)
which was isolated as a colorless air-stable solid in quantitative
7
·thf
31
1
195
1
yield. The P{ H} and Pt{ H} NMR spectra of 6 display a
P1−Fe1
P2−Fe1
P3−Fe1
P1−Fe1−P2
P1−Fe1−Cl1
Cl1−Fe1−Cl2
P2−Fe1−Cl1
P2−Fe1−Cl2
2.4240(12)
2.6539(13)
2.5453(13)
82.79(4)
Fe1−Cl1
Fe1−Cl2
2.2737(14)
2.3130(17)
complex splitting pattern, which was simulated as an ABCX (A,
B, and C = P; X = Pt) spin system. The P{ H} NMR
spectrum consists of three sets of multiplets (δ = 27.5 ppm, δB
−6.3 ppm, and δ = 12.7 ppm (Figure 10)), while a complex
multiplet is observed in the Pt{ H} NMR spectrum (δ =
4656.2 ppm (Figure 11)). The trans- J coupling (JAC
26.4 Hz) has a significantly larger magnitude than the cis- J
coupling (JAB = JBC = 22.0 Hz), and the magnitude of the J
coupling from the inner phosphorus atom ( J = 3048 Hz) is
significantly higher than those from the outer atoms ( J
230 Hz, J = 2270 Hz). Hence, the complexity of this
spectrum is largely down to the unexpected anisochronicity of
the outer phosphorus atoms (A and C), resulting in observable
trans- J coupling and a complex splitting pattern.
The crystal structure of 6 is shown in Figures 12 and 13, with
structural data given in Tables 2, 3, and 5. Compound 6
crystallizes as an ion-separated complex cation with a chloride
counterion and a cocrystallized molecule of CH Cl . The
platinum atom adopts a square planar geometry with slight
distortion toward tetrahedral. Thus, the angles around the
central atom are P1−Pt1−Cl1 = 170.98(5)° and P2−Pt1−P3 =
173.45(5)°; atoms P1 and Cl1 lie 0.12 Å above and atoms P2
and P3 lie 0.12 Å below the mean plane through the P1, P2, P3,
and Cl1 atoms. Of the bond angles about the Pt center, P1−
Pt1−P2 is the most obtuse (95.78(5)°) and Cl1−Pt1−P2 is the
most acute at 86.21(5)°. The P−Pt bond lengths are similar to
31
195
31
1
A
P1−Fe1−P3
P1−Fe1−Cl2
P2−Fe1−P3
P3−Fe1−Cl1
P3−Fe1−Cl2
86.64(4)
130.82(5)
163.44(4)
100.03(5)
87.99(5)
=
C
108.05(5)
121.02(5)
95.36(5)
195 1
X
2
−
3
=
PP
2
PP
89.31(5)
1
PPt
fac-8·MeCN
2.4855(15)
1
BX
P1−Mo1
P3−Mo1
C41−Mo1
P1−Mo1−P2
P2−Mo1−P3
P1−Mo1−C41
P2−Mo1−C40
P2−Mo1−C42
P3−Mo1−C41
P2−Mo1
C40−Mo1
C42−Mo1
P1−Mo1−P3
P1−Mo1−C40
P1−Mo1−C42
P2−Mo1−C41
P3−Mo1−C40
P3−Mo1−C42
C40−Mo1−C42
2.5289(17)
1.960(6)
1.972(6)
82.16(5)
176.50(14)
91.08(15)
91.84(16)
94.83(15)
82.73(14)
90.3(2)
1
=
AX
2.5633(16)
1.956(5)
1
2
CX
82.50(5)
104.49(5)
100.23(15)
96.57(15)
169.50(13)
163.66(16)
83.2(2)
2
PP
2
2
C40−Mo1−C41
C41−Mo1−C42
81.1(2)
angles on copper are the most acute [P1−Cu1−P3, 99.90(9)°;
P1−Cu1−P2, 100.24(9)°], while the angle P2−Cu1−P3 is the
most obtuse at 126.33(10)°. The P−Cu bond lengths in 5
[
2.231(3)−2.254(3) Å] are similar to those in the related
complex [Cu(triphos)(MeCN)][PF ] [2.2540(18)−
6
4
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Inorganic Chemistry
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Table 4. Crystallographic Data for 1·MeCN, 2, 3·(CH ) CO, and 4
3
2
1
·MeCN
2
3·C H O
4
3
6
chemical formula
C H NP
C H P S
C H OP S
C H P Se
2
4
1
54
3
39 51
3
2
42 57
3
3
39 51
3
fw
653.81
676.87
767.01
cryst dimens/mm
cryst syst
space group
a/Å
0.10 × 0.10 × 0.05
monoclinic
0.15 × 0.15 × 0.03
triclinic
0.12 × 0.12 × 0.03
monoclinic
0.18 × 0.06 × 0.02
monoclinic
P2 /n
1
P1
̅
P2 /c
1
P2 /n
1
11.898(4)
16.866(6)
18.703(7)
11.332(4)
12.573(3)
13.868(3)
67.97(2)
79.63(3)
80.50(2)
1791.4(8)
2
16.969(5)
13.057(3)
20.051(6)
12.3969(13)
21.308(3)
13.836(2)
b/Å
c/Å
α/deg
β/deg
99.789(8)
111.872(6)
92.761(3)
γ/deg
V/ Å3
3698(2)
4
4123(2)
4
3650.5(7)
4
Z
−
3
D
1.174
1.255
1.236
1.402
calcd/g cm
−
1
μ/cm
1.897
3.096
3.275
21.842
27661 (6396)
0.0677
0.0451
0.1469
no. of reflns measd (unique)
23183 (6678)
0.0894
0.0753
15015 (7132)
0.0895
30878 (7258)
0.1358
0.1317
0.3340
Rint
a
R1
0.0997
b
wR2
0.2538
0.3152
a
b
2
o
2
c
2
2
o
2
1/2
2
2
o
2
2
o
2
c
I > 2σ(I). R1 = ∑||F | − |F ||/∑|F |. wR2 = {∑[w(F − F ) ]/∑w(F ) } . w = 1/[σ (F ) + [(ap) + bp]], where p = [(F ) + 2F ]/3.
o
c
o
Table 5. Crystallographic Data for 5, 6·CH Cl , 7·thf, and fac-8·MeCN
2
2
1
5
· / thf
6·CH Cl2
7·thf
fac-8·MeCN
2
2
chemical formula
C H BCuF NO0.5P3
C H Cl P Pt
C H Cl FeO P
C H MoNO P
44 54 3 3
4
3
58
4
40 53
4
3
43 59
2
3
fw
840.21
963.68
811.61
833.78
cryst dimens/mm
cryst syst
space group
a/Å
0.10 × 0.10 × 0.01
monoclinic
C2/c
0.10 × 0.10 × 0.10
triclinic
0.12 × 0.12 × 0.12
triclinic
0.10 × 0.03 × 0.03
triclinic
P1
̅
P1
̅
P1
̅
30.00(2)
11.288(2)
12.521(2)
16.974(3)
65.323(7)
72.968(9)
75.140(9)
2059.3(6)
2
10.4430(6)
11.4725(7)
19.353(2)
93.871(7)
101.123(7)
112.837(8)
2070.6(3)
2
10.962(4)
11.985(4)
15.257(5)
96.390(6)
90.902(5)
100.702(5)
1956.1(11)
2
b/Å
12.361(6)
22.309(11)
c/Å
α/deg
β/deg
92.409(7)
γ/deg
V/ Å3
8264(7)
8
Z
−
3
D
1.350
1.554
1.302
1.415
calcd/g cm
−
1
μ/cm
6.959
37.964
6.407
4.990
no. of reflns measd (unique)
39144 (7579)
0.2001
0.1825
0.4874
19947 (7441)
0.0736
20111 (7516)
0.0452
19925 (7135)
0.0627
Rint
a
R1
0.0432
0.0614
0.0655
b
wR2
0.1099
0.1611
0.1470
a
b
2
o
2
c
2
2
o
2
1/2
2
2
o
2
2
o
2
c
I > 2σ(I). R1 = ∑||F | − |F ||/∑|F |. wR2 = {∑[w(F − F ) ]/∑w(F ) } . w = 1/[σ (F ) + [(ap) + bp]], where p = [(F ) + 2F ]/3.
o
c
o
3
1
those reported in the triphos B analogue [Pt(triphos)Cl]Cl,
(P2). On the other hand, a significant in-plane strain is present,
with a splay angle (Figure 3) of +21.2(4)°. In contrast, the
acenaphthene ring bearing the P3 atom shows extensive out-of-
plane distortion, with atoms P1 and P3 being displaced by 0.64
and 1.04 Å from their acenaphthene planes. The splay angle for
this ring (+6.3(5)°) shows little in-plane distortion is present.
Interestingly, the very different types of distortions result in
comparable across peri-gap distances of P2···P1 = 3.36 Å and
P1···P3 = 3.22 Å. The P2···P3 distance is 4.64 Å, and the angle
between the two acenaphthene rings is 46.9°. Hence, differing
distortions within peri-regions of the two acenaphthene units
result in variance of the P2−Pt1 and P3−Pt1 bond lengths.
These differences are likely to be preserved in the solution,
giving a possible explanation for observed anisochronicity of
with the inner phosphorus atom in 6 displaying a shorter bond
to Pt than the outer atoms [P1−Pt1, 2.2146(14) Å; P2−Pt1,
2
.3097(15) Å; P3−Pt1, 2.3364(15) Å], which is in keeping
1
with their respective J coupling constants. Notably, due to
PPt
the more flexible and less crowded ligand, the triphos B
complex [Pt(triphos)Cl]Cl does not exhibit a significant
difference in P−Pt bond length for the outer phosphorus
atoms and the two outer phosphorus atoms are isochronous in
3
1
P NMR.
The geometries of the two acenaphthene rings in 6 are rather
different. The acenaphthene ring bearing the P2 atom is almost
coplanar with the central PtP Cl moiety. The out-of-plane
distortions of this ring are very moderate; the displacements
from the mean acenaphthene plane are 0.36 Å (P1) and 0.22 Å
3
31
1
195
1
atoms P2 and P3 in the P{ H} and Pt{ H} NMR spectra of
4
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Inorganic Chemistry
Article
3
1
1
Figure 10. Experimental (bottom) and simulated (top and middle) P{ H} NMR spectra of 6 (CDCl , 162.0 MHz). The middle spectrum
3
simulates signals of an isotopomer with NMR-active 1 Pt nuclei (satellite spectrum), and the top spectrum is from isotopomers with NMR-inactive
95
Pt nuclei.
Figure 11. 195Pt{ H} NMR spectra of 6 (CD Cl , 58.1 MHz): experimental (bottom) and simulated (top).
1
2
2
Figure 12. Crystal structure of the cation of 6 with ellipsoids drawn at
0% probability. The chloride counterion, cocrystallized molecule of
CH Cl , and hydrogen atoms are omitted for clarity.
Figure 13. Alternative view of the cation of 6 illustrating differing
distortions of the two acenaphthene units. Ellipsoids are drawn at 50%
probability. The chloride counterion, cocrystallized molecule of
CH Cl , and hydrogen atoms are omitted and iPr groups are shown
5
2
2
2
2
in stick form for clarity.
6. The side-on view of the crystal structure of 6 (Figure 13)
clearly shows the very different environments of the two outer
phosphorus atoms.
The crystal structure of 7 is shown in Figure 14, with
structural data given in Tables 2, 3, and 5; the complex
cocrystallizes with a molecule of thf. The central iron(II) atom
adopts a distorted trigonal bipyramidal (tbp) geometry, with
atom P1 and the two chloride ligands occupying the equatorial
part of the molecule. The corresponding (equatorial) angles are
Reaction of 1 with FeCl ·4H O in thf gave a bright red
2
2
solution from which [(1)FeCl ] (7) was isolated as an air-stable
2
32
red solid. 7 does not show any signals in the NMR spectra,
but was fully characterized by X-ray diffraction, IR, and MS, and
its purity was established by elemental analysis.
4
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Inorganic Chemistry
Article
spectrum of the same sample at 185 K (bottom spectrum in
Figure 15) displayed four broad multiplets at δ = 27.6−29.1,
P
3
0.9−31.5, 32.5−33.2, and 33.3−34.4 ppm in an approximate
31
integral ratio of 2:1:1:2. The P EXSY spectrum at 185 K
showed that all four of these multiplets are exchanging, which is
consistent with two different isomers of 8 being present in the
solution. Given that even at 185 K the spectrum was very
broad, we have been unable to deduce further structural or
thermodynamic information from it.
Notably, a facile room temperature transformation between
fac- and mer-isomers was observed previously in tricarbonyl-
33
molybdenum complexes in solution. Since such an exchange
would be consistent with our NMR observations, we have
performed a computational investigation in this respect. Our
computations indicated that fac- and mer-isomers of 8 are
relatively close in energy. A representative mer-isomer was
located (B3LYP/6-31+G* level) and turned out to be ca. 4 kcal
Figure 14. Crystal structure of 7 with ellipsoids drawn at 50%
probability. The cocrystallized molecule of thf and hydrogen atoms are
omitted and iPr groups are shown in stick form for clarity.
−1
mol less stable that the fac-isomer (see Table S3 in the
Supporting Information). Indeed, the more stable fac-isomer of
8
was found in the solid state by X-ray diffraction; see below. It
P1−Fe1−Cl1 = 108.05(5)°, P1−Fe1−Cl2 = 130.82(5)°, and
Cl1−Fe1−Cl2 = 121.02(5)°. Atoms P2 and P3 adopt axial
positions, with the P2−Fe1−P3 angle being 163.44(4)°. All
three Fe−P bond lengths differ slightly from each other; the
equatorial P1−Fe1 is the shortest at 2.4240(12) Å, and the two
axial bonds are elongated to 2.6539(13) (P2−Fe1) and
should be noted though that the mer-arrangement was found in
all known related Mo complexes with chelating tris-
34
(
phosphines).
We have also investigated the energetics of the displacement
of one of the outer phosphine donor atoms of the chelating
ligand with a molecule of acetonitrile. This was believed to be
plausible due to the strain in the coordinated tridentate ligand
observed in the solid-state structure of 8 (see below) and the
fact that acetonitrile (from cocrystallization) may have been
available. However, this process was found to be endothermic
by at least 15 kcal mol− and further disfavored by entropy (see
Table S3 in the Supporting Information) and can therefore be
safely excluded.
Crystallization from MeCN yielded complex fac-8 as brown
crystals (17.5% yield). The crystalline material was used for
further characterization by IR and Raman spectroscopy, and the
purity was verified by microanalysis. Some of the crystals were
of sufficient quality for X-ray diffraction work. The structure of
fac-8 is shown in Figure 16, with structural data given in Tables
2, 3, and 5. The complex cocrystallizes with a molecule of
MeCN. The geometry around the Mo atom is distorted
octahedral, with facial coordination of the tris(phosphine)
2.5453(13) Å (P3−Fe1).
The P···P distances across the peri-gap [P1···P2, 3.36 Å;
P1···P3, 3.41 Å] are (like in 5 and 6) only slightly elongated
with respect to the free ligand 1; the P2···P3 distance in 7 is
5
.15 Å. The overall structural changes adopted by the ligand to
1
form square planar and trigonal bipyramidal complexes 6 and 7,
respectively, are very similar.
Complex 7 represents the first structurally characterized tbp
iron complex with three phosphorus and two halide ligands.
Structural data of a number of octahedral complexes with four
phosphorus and two halide ligands have been reported; these
generally contain a pair of bidentate phosphine ligands.
The molybdenum complex [(1)Mo(CO) ] (8) was obtained
3
from the reaction of 1 with [Mo(CO) (MeCN) ] in CH Cl .
3
3
2
2
3
1
1
The major peaks in the P{ H} NMR spectrum of 8 are a
triplet at δ = 32.0 ppm and a doublet at δ = 35.0 ppm, J
1 Hz (top spectrum in Figure 15). The P{ H} NMR
2
≈
P
P
PP
3
1
1
3
Figure 15. 31P{ H} NMR spectra of 8 (CD Cl , 202.4 MHz) at 298 K (top) and 185 K (bottom).
1
2
2
4
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Inorganic Chemistry
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and 13C{ H} NMR, including measurement of H{ P}, H−H DQF
COSY, H−P HMQC, H−C HSQC, and H−C HMBC experiments.
NMR measurements were performed at 25 °C unless otherwise
1
1
31
3
1
indicated; 85% H PO was used as an external standard in P, TMS as
an internal standard in H and C NMR. The NMR numbering
3
4
1
13
scheme for compounds 1−8 is shown in Scheme 4. NMR spectra
Scheme 4. NMR Numbering Scheme for 1−8
(
3
spin systems) were simulated using the DAISY module in TopSpin
.1 or using MestreNova. Correct isotopic patterns were found in
38 39
Figure 16. Crystal structure of fac-8. The cocrystallized molecule of
MeCN and hydrogen atoms are omitted and iPr groups are shown in
stick form for clarity.
the MS spectra for all assigned peaks.
Tridentate Phosphine 1. nBuLi (2.3 mL of 2.5 M solution in
hexanes, 5.73 mmol) was added dropwise to the solution of 5-bromo-
6
-(diisopropylphosphino)acenaphthene (2.0 g, 5.73 mmol) in diethyl
ligand. The tris(phosphine) ligand distortions in fac-8 are
essentially limited to those in-plane, resulting in large positive
splay angles of +19.6(5)° and +21.4(5)°. The peri-distances are
slightly increased in fac-8 [P1···P2, 3.31; P1···P3, 3.32 Å]
compared with the free ligand 1, while the P2···P3 separation in
fac-8 decreases significantly to 4.03 Å.
ether (80 mL) at −78 °C. The mixture was stirred at −78 °C for 2 h,
and then iPrPCl (0.42 g, 0.37 mL, 2.87 mmol) in diethyl ether (20
2
mL) was added dropwise over 1 h at −78 °C. The resulting yellow
suspension was stirred at −78 °C for 2 h before being warmed to room
temperature and stirred for 16 h. The suspension was filtered through
a sinter (porosity 3) using a filtration aid (Celite). The solids on the
sinter were washed with diethyl ether (40 mL). The volatiles were
removed from the filtrate in vacuo to give an orange oil which was
stirred with MeCN (20 mL) for 10 min to give a yellow solid
suspended in a dark orange solution, the solution containing mainly
unreacted starting material. The solid was isolated by filtration and
dried in vacuo to give 1 as a yellow powder (1.2 g, 68.0% yield); this
material was of sufficient purity for further syntheses. Analytically pure
material was obtained by recrystallization from diethyl ether. Large
yellow oblong crystals suitable for X-ray diffraction work were grown
from MeCN at 2 °C. Anal. Calcd for C H P : C, 76.45; H, 8.39.
CONCLUSION
■
Despite the rigid nature of the geminal bis(acenaphthene)
backbone, the tris(phosphine) ligand 1 accommodates a
surprisingly wide range of bonding geometries in both
chalcogenides and transition-metal complexes. This is possible
via large angular distortions of the peri-regions and the
independent nature of in-plane and out-of-plane distortions.
Overall, formation of chalcogenides 2−4 results in much
more “open” structures than formation of the transition-metal
complexes 5−8. Thus, while the P···P across peri-gap spacings
in the chalcogenides range from 3.61 to 4.07 Å, in the
transition-metal complexes a range of 3.31−3.43 Å is observed.
On the same note, the P2···P3 distances range from 6.06 to
39
51 3
1
Found: C, 76.33; H, 8.27. H NMR (400.1 MHz, CDCl ): δ = 0.57−
3
1.58 (complex br m, 10 × iPr CH , 30H), 1.79−2.32 (br m, 5 × iPr
3
CH, 5H), 3.23−3.37 (m, 2 × CH , 4H), 6.91−7.56 (complex br m, 8
2
1
×
Ar CH, 8H) ppm. Higher temperature H NMR spectra in toluene-
d8 displayed additional complexity. P{ H} NMR (202.4 MHz,
31
1
toluene-d , 298 K): two broad resonances between δ = +2 and −18
8
ppm. 31P{ H} NMR (202.4 MHz, toluene-d , 353 K): AB system, δ
1
8
2
A
6
.19 Å in the chalcogenides 2−4, while they are between 4.01
31
1
=
−1.8 ppm, δ = −8.1 ppm; J = 140 Hz. P{ H} NMR (202.4
MHz, toluene-d , 223 K): two ABC patterns in a ratio of 58:42 (B
B
AB
and 5.15 Å in the series 5−8.
8
The structure of iron complex 7 and even more so the
structure of platinum complex 6 are remarkable in the differing
nature of distortions within their two acenaphthene units, one
of them showing significant in-plane distortions and much
diminished out-of-plane distortions and the other one showing
the opposite alterations. The rigidity of the ligand results in all
three M−P bonds in each complex 5−8 being at least slightly
unequal in the crystal, this is in contrast to complexes of the
much more flexible triphos family of ligands.
denotes the inner phosphorus atom), δB1 = −1.52 ppm, δA1 = −4.53
ppm, δC1 = −15.59 ppm, δB2 = −10.88 ppm, δ = −11.87 ppm, δ
=
A2
C2
−17.14 ppm; J
= 93.9, J
= 142.3, J
= 0, J
= 139.7,
A1−B1
B1−C1
A1−C1
A2−B2
B2−C2 = 137.6, JA2−C2 = 7.3 Hz. 13C{ H} NMR (67.9 MHz, C
1
D
6
): δ =
J
6
1
6.9−24.9 (complex br m, iPr CH ), 25.0−26.8 (br m, iPr CH), 30.3
3
(
s, CH ), 30.7 (s, CH ), 31.3−32.1 (br m, iPr CH), 119.3 (s, C3 or
2
2
C7), 119.5 (s, C3 or C7), 134.8−136.6 (br s, C2 or C8), 135.2 (s, C2
or C8), 147.2 (s, C4 or C6), 148.8 (s, C4 or C6) ppm. Raman (glass
−1
capillary, cm ): ν 3066 (m, νAr−H), 2945 (br m), 2921 (br, s), 2903
(
(
br, m), 2867 (s, νC−H), 1608 (s), 1565 (s), 1444 (s), 1415 (s), 1315
br, s), 881 (m), 820 (m), 713 (m), 655 (m), 585 (m), 571 (m), 555
EXPERIMENTAL SECTION
−1
■
(m). IR (KBr disk, cm ): ν 2944 (s), 2863 (s, νC−H), 1605 (s), 1458
(s), 1380 (m), 1360 (m), 1318 (m), 1256 (m), 1151 (m), 1097 (m),
1032 (s), 878 (m), 839 (s), 819 (s), 651 (m). MS (CI+): m/z 613.3
General Procedures. Experiments were carried out under an
atmosphere of dry nitrogen using standard Schlenk techniques or
under an argon atmosphere using a dry glovebox unless indicated
otherwise. Solvents were dried on an MBraun solvent purification
system and stored over molecular sieves prior to use. 5,6-
+
+
(M + H ), 569.3 (M − C H ), 343.19 (C H P ), 287.16
(C H OP), 271.17 (C H P), 135.1. Mp: 181−185 °C.
3
7
21 29 2
18
24
18 24
Reaction of 1 with S to give Sulfides 2 and 3. Powdered sulfur
8
3
5
Dibromoacenaphthene,
5-bromo-6-(diisopropylphosphino)-
(33 mg, 0.13 mmol) and 1 (0.20 g, 0.33 mmol) in toluene (20 mL)
were heated under reflux for 3 h to give an orange solution. Solvent
was removed in vacuo to give an orange oil, which was extracted with
hexane (20 mL), and the solvent was removed in vacuo. The resulting
oil was redissolved in diethyl ether/acetone, and the solution was left
2
2
36
37
acenaphthene, PtCl (cod), and [Mo(CO) (MeCN) ] were
2
3
3
prepared according to literature procedures. iPrPCl was purchased
2
from Sigma-Aldrich and used without further purification. Where
possible, new compounds were fully characterized by 31P, P{ H}, H,
31
1
1
4
356
dx.doi.org/10.1021/ic3024875 | Inorg. Chem. 2013, 52, 4346−4359

Inorganic Chemistry
Article
to crystallize by slow evaporation in air. This gave crystals of two
distinct types, large cubelike orange crystals and small yellow flakes. X-
ray crystallography showed the orange crystals to be the bis(sulfide) 2
and the yellow crystals to be the tris(sulfide) 3. Manual separation of
these crystals allowed the isolation of 2 (52 mg, 22.6%) and 3 (41 mg,
[(1)PtCl][Cl] 6. A solution of 1 (0.12 g, 0.20 mmol) in CH Cl (8
2
2
mL) was added to a suspension of PtCl (cod) (73 mg, 0.20 mmol) in
2
CH Cl (2 mL) to give a yellow solution, which was stirred for 16 h at
2
2
room temperature. Evaporation of volatiles in vacuo yielded 6 as a
white powder (0.18 g, quantitative yield). Recrystallization from
CH Cl /hexane yielded analytically pure material as well as colorless
1
7.8%) for full characterization.
2
2
Data for Bis(sulfide) 2. Anal. Calcd for C H P S : C, 69.20; H,
needle crystals suitable for X-ray crystallography. Anal. Calcd for
39
51 3 2
.59. Found: C, 69.13; H, 7.60. 31P{ H} NMR (121.5 MHz, CDCl ):
1
1
7
C H Cl P Pt: C, 53.31; H, 5.85. Found: C, 53.24; H, 5.79. H NMR
3
39 51
2 3
3
1
δ = 13.3 (br s, PiPr), 73.6 (br s, PiPr ), 85.0 (br s, PiPr ) ppm.
P
(400.1 MHz, CDCl ): δ = 0.10−0.28 (m, 6H, iPr CH ), 0.58−0.81
2
2
3
3
NMR (121.5 MHz, CDCl ): δ = 13.2 (br s, PiPr), 73.6 (br s, PiPr ),
(m, 6H, iPr CH ), 0.96−1.06 (m, 3H, iPr CH ), 1.10−1.19 (m, 3H,
3
2
3
3
1
8
+
4
4.8 (br s, PiPr ) ppm. H NMR (300.1 MHz, CDCl ): δ = −0.30 to
iPr CH ), 1.40−1.54 (m, 9H, iPr CH ), 1.58−1.67 (m, 3H, iPr CH ),
2
3
3
3
3
1.95 (complex br m, 10 × iPr CH , 30H), 2.41−5.05 (complex br m,
3
2.97−3.10 (br s, 1H, iPr CH), 3.30−3.40 (m, 3H, iPr CH), 3.41−3.58
× CH and 5 × iPr CH, 13H), 6.85−7.90 (complex br m, 8 × Ar
2
(br m, 8H, CH ), 3.88−4.04 (br s, 1H, iPr CH), 7.33−7.43 (m, 2H, Ar
2
+
CH, 8H) ppm. MS (ES+): m/z 699.3 (M + Na ), 375.2.
CH), 7.44−7.54 (m, 2H, Ar CH), 7.61 (d, 2H, J = 7.3 Hz, Ar CH),
Data for Tris(sulfide) 3. Anal. Calcd for C H P S : C, 66.07; H,
31
1
39
51
3
3
7.87−7.95 (m, 1H, Ar CH), 8.11−8.20 (m, 1H, ArCH) ppm. P{ H}
7
=
.25. Found: C, 65.95; H, 7.33. 31P{ H} NMR (121.5 MHz, C D ): δ
1
31
6
6
NMR (162.0 MHz, CDCl ): ABC spin system (A, B, and C = P),
3
65.7 (br s), 68.3 (br s), 84.2 (br s) ppm. 31P NMR (121.5 MHz,
195
with Pt satellites forming an ABCX spin system subspectrum (A, B,
1
C D ): δ = 65.7 (br s), 68.3 (br s), 84.2 (br s) ppm. H NMR (300.1
31
195
2
2
6
6
and C = P; X = Pt), δP = 27.5 ppm ( J = 22.0 Hz, J = 326.4
A AB AC
MHz, CDCl ): δ = −0.32 to +1.97 (complex br m, 10 × iPr CH ,
1
2
1
3
3
Hz, J = 2230.0 Hz, outer P), δP = −6.3 ppm ( J = 22.0 Hz, J
1
AX
B
BC
BX
3
0H), 2.34 (br s, iPr CH, 1H), 2.51−2.85 (complex br m, 4 × CH
2
= 3048.0 Hz, inner P), δP = 12.7 ppm ( J = 2270.0 Hz, outer P).
C CX
and 1 × iPr CH, 9H), 3.52−3.80 (br s, iPr CH, 1H), 5.04−5.40 (br s,
iPr CH, 2H), 6.50−7.76 (complex br m, 8 × Ar CH, 8H) ppm.
Reaction of 1 with Se to give Bis(selenide) 4. Powdered gray
selenium (82.2 mg, 1.06 mmol) and 1 (0.20 g, 0.33 mmol) in toluene
195
1
Pt{ H} NMR (58.1 MHz, CD Cl ): δ = −4656.2 ppm (m, X part
2
2
Pt
31
195
31
1
of an ABCX spin system; A, B, and C = P; X = Pt; see P{ H}
13
1
NMR). C{ H} NMR (75.5 MHz, CDCl ): δ = 15.6−16.0 (m, PiPr
3
CH ), 16.9−17.4 (m, PiPr CH ), 18.3−19.2 (m, PiPr CH ), 19.5−
3
3
2
3
(
20 mL) were heated under reflux for 3 h to give a dark green
1
1
2
3
3
1
0.6 (m, PiPr CH ), 24.7 (d, J = 26.7 Hz, iPr CH), 26.9 (d, J
=
2
3
CP
CP
suspension. Solvent was removed in vacuo to give a green-gray oil,
which was extracted with hexane (20 mL). The resulting yellow
solution was concentrated and left to stand at room temperature,
which led to deposition of large clusters of yellow needle-shaped
crystals of 4. These were isolated by filtration and dried in vacuo (54
1
0.4 Hz, iPr CH), 28.1 (d, J = 31.4 Hz, iPr CH), 30.4 (s, CH2),
CP
0.6 (s, CH ), 31.0 (s, CH ), 31.2 (s, CH ), 34.5−35.3 (m, iPr CH),
2
2
2
18.7−119.2 (m, C3 or C7), 119.9−120.7 (m, C3 or C7), 135.0 (s, C2
or C8), 135.4 (s, C2 or C8), 137.1 (s, C2 or C8), 138.6 (s, C2 or C8),
52.4 (s, C4 or C6), 153.2 (s, C4 or C6), 154.1 (s, C4 or C6), 155.6
1
mg, 21.5% yield). Anal. Calcd for C H P Se : C, 60.78; H, 6.67.
3
9
51
3
2
−1
Found: C, 60.88; H, 6.76. 3 P{ H} NMR (121.5 MHz, CDCl ): δ =
1
1
1
(s, C4 or C6) ppm. IR (KBr disk, cm ): ν 2961 (s), 2926 (s), 2869 (s,
νC−H), 1595 (m), 1460 (m), 1261 (s), 1095 (s), 1037 (s), 804 (s).
3
31
4.6 (br s, PiPr), 78.8 (br s, PiPr ), 86.0 (br s, PiPr ) ppm. P NMR
2
2
+
MS (ES+): m/z 842.6 (cation ). Mp: 158−163 °C.
(
121.5 MHz, CDCl ): δ = 14.4 (br s, PiPr), 78.2 (br s, PiPr ), 86.2 (br
3
2
1
[(1)FeCl ] 7. A solution of 1 (0.2 g, 0.33 mmol) in thf (8 mL) was
2
s, PiPr ) ppm. H NMR (300.1 MHz, CDCl ): δ = −1.05 to +1.46
(
2
3
added to a suspension of FeCl ·4H O (64 mg, 0.33 mmol) in thf (1
2
2
complex br m, 10 × iPr CH , 30H), 1.48−1.92 (complex br m, 4 5 ×
3
mL) at room temperature, giving a dark red solution almost
instantaneously. After the solution was stirred for 3.5 h, the volatiles
were removed in vacuo to give 7 as a red powder (0.22 g, 92.0% yield).
Red oblong crystals suitable for X-ray crystallography work were
grown from thf and diethyl ether at room temperature. Anal. Calcd for
C H Cl FeP : C, 63.34; H, 6.95. Found: C, 63.31; H, 7.03. IR (KBr
iPr CH, 5H), 3.31−3.49 (br m, 2 × CH , 8H), 7.19−7.42 (br m, 8 ×
2
Ar CH, 8H) ppm. MS (ES+): m/z 811.1 (M+O+Na), 795.1 (M +
Na), 747.3, 729.1 (M − C H ), 576.2, 569.3 (M-2Se−C H ), 423.1,
3
7
3
7
3
81.1, 343.2.
[
(1)Cu(MeCN)][BF ] 5. A solution of 1 (0.25 g, 0.41 mmol) in thf
4
(
10 mL) was added to a solution of [Cu(MeCN) ][BF ] (0.13 g, 0.41
39 51
2
3
4
4
−
1
disk, cm ): ν 2959 (s), 2927 (s), 2869 (m, νC−H), 1597 (m), 1461
m), 1260 (s), 1098 (br s), 1028 (br s), 845 (m), 804 (s). MS
MALDI-TOF+): m/z 751.2, 738.2 (M+), 719.2, 703.2 (M − Cl ),
mmol) in thf (5 mL) at room temperature, giving a yellow suspension.
After the solution was stirred for 16 h, the volatiles were removed in
vacuo to give 5 as a pale yellow powder (0.33 g, quantitative yield).
Analytically pure material was obtained by recrystallization from thf.
Colorless rod-shaped crystals suitable for X-ray crystallography were
grown from thf at 2 °C. Anal. Calcd for C H BCuF NP : C, 61.24;
(
(
6
6
1
−
+
+
+
67.3 (1 + 2O + Na ), 645.3 (1 + 2O + H ), 629.3 (1 + O + H ),
01.3 (1 − iPr + 2O), 585.3 (1 − iPr + O), 375.2, 359.2, 343.2. Mp:
81−185 °C.
4
1
54
4
3
1
[(1)Mo(CO) ] 8. Mo(CO) (86 mg, 0.33 mmol) was refluxed in
H, 6.77; N, 1.74. Found: C, 61.13; H, 6.66; N, 1.86. H NMR (400.1
MHz, CD CN): δ = 0.56 (dd, 6H, J = 16.7 Hz, J = 6.9 Hz, iPr
CH ), 0.83 (dd, 6H, J = 12.0 Hz, J = 6.8 Hz, iPr CH ), 0.94 (dd,
3
6
3
3
MeCN (20 mL) for 6 h to give a yellow solution of [Mo-
3
HP
HH
37
3
3
(
CO) (MeCN) ]. The volatiles were removed in vacuo, and
3 3
3
HP
HH
3
3
3
CH Cl (2 mL) was added, followed by a solution of 1 (0.20 g,
6
H, J = 16.0 Hz, J = 6.8 Hz, iPr CH ), 1.10−1.17 (m, 12H, iPr
2
2
HP
HH
3
0
.33 mmol) in CH Cl (6 mL). The initially orange suspension turned
CH ), 2.21−2.33 (m, 1H, inner iPr CH), 2.35−2.47 (m, 2H, outer iPr
2 2
3
CH), 2.56−2.70 (m, 2H, outer iPr CH), 3.29−3.40 (m, 8H, CH ),
dark brown and was stirred for 16 h and then filtered. The volatiles
were removed from the filtrate in vacuo to give crude 8 as a cream
solid. Recrystallization from MeCN gave fac-8 in the form of cube-
shaped brown crystals (48 mg, 17.5% yield). Anal. Calcd for
2
3
3
7
(
.33 (d, 2H, J = 7.3 Hz, H3), 7.43 (d, 2H, J = 7.2 Hz, H7), 7.52
HH HH
3
3
3
3
t, 2H, J = J = 7.5 Hz, H2), 7.81 (t, 2H, J = J = 7.1 Hz,
HP HH HP HH
3
1
1
H8) ppm. P{ H} NMR (162.0 MHz, CD CN): δ = −18.7 (br t,
3
2
31
iPrP), 6.1 (br s, 2 × iPr P) ppm, J = 50−60 Hz. P NMR (162.0
C
44
H
54MoNO
Found: C, 62.75; H, 6.53; N, 1.60. H NMR (499.9 MHz, CD
= 0.51−1.63 (complex br m, 10 × iPr CH , 30H), 1.68−1.87 (br m, 2
× iPr CH, 2H), 2.66−2.94 (br m, 2 × iPr CH, 3H), 3.32−3.47
(complex br m, 4 × CH , 8H), 7.17−7.87 (complex br m, 8 × Ar CH,
8H) ppm. P{ H} NMR (202.4 MHz, CD Cl , 298 K): δ = 32.0 (br
t), 35.0 (br d) ppm, JPP ≈ 31 Hz. P{ H} NMR (202.4 MHz,
CD Cl
3 3
P (MeCN solvate): C, 63.38; H, 6.53; N, 1.68.
2
PP
1
MHz, CD CN): δ = −18.7 (br m, iPrP), 6.1 (br m, 2 × iPr P) ppm.
Cl ): δ
2 2
3
2
1
3
1
C{ H} NMR (75.5 MHz, CD CN): δ = 17.5 (s, iPr CH ), 18.2 (s,
3
3
3
2
iPr CH ), 19.8 (m, iPr CH ), 20.1 (d, J = 11.5 Hz, iPr CH ), 20.5
3
3
CP
3
(
m, iPr CH ), 24.8−25.3 (m, outer iPr CH), 30.4 (s, CH ), 30.6 (s,
2
3
2
3
31
1
CH ), 33.1−33.4 (m, central iPr CH), 120.0 (s, C7), 120.2 (d, J
=
2
2
2
CP
1
4
31
1
4
1
.1 Hz, C3), 120.4−120.8 (m, C10), 123.6 (d, J = 14.0 Hz, C9),
36.0 (s, C8), 136.6 (s, C2), 140.0−140.5 (m, C1), 141.4−141.6 (m,
CP
, 185 K): δ = 27.6−29.1 (br m), 30.9−31.5 (br m), 32.5−33.2
−1
2
2
C5), 151.6 (s, C4 or C6), 152.4 (s, C4 or C6) ppm. Raman (glass
(br m), 33.3−34.4 (br m) ppm. Raman (glass capillary, cm ): ν 3071
−1
capillary, cm ): ν 3074 (m), 2930 (s), 2732 (m), 1984 (m), 1857 (br,
(m), 2925 (s, νC−H), 1811 (br, νC−O), 1610 (m), 1563 (m), 1443
−1
m), 1732 (br, m), 1609 (m), 1562 (m), 1504 (br, m), 1444 (m), 1414
(m), 1415 (m), 1314 (s), 584 (m). IR (KBr disk, cm ): ν 2905 (s,
br), 2874 (m, νC−H) 1937 (s, νC−O), 1842 (s, νC−O), 1632 (m),
1453 (br, m), 1316 (m), 1037 (m), 853 (m), 832 (m), 632 (m).
(
(
m), 1313 (s), 1124 (br, s), 817 (m), 586 (m). MS (ES+): m/z 675
cation − MeCN). Mp: 158−161 °C.
+
4
357
dx.doi.org/10.1021/ic3024875 | Inorg. Chem. 2013, 52, 4346−4359

Inorganic Chemistry
Article
X-ray Experimental Details. Tables 4 and 5 list details of the data
collection and refinement. Data for compound 1 were collected at
(5) Goikhman, R.; Aizenberg, M.; Ben-David, Y.; Shimon, L. J. W.;
Milstein, D. Organometallics 2002, 21, 5060−5065.
−
180(1) °C by using a Rigaku MM007 high-brilliance RA generator
(6) Jia, G.; Man Lee, H.; Williams, I. D. Organometallics 1996, 15,
4235−4239.
and Mercury charge-coupled device (CCD) system using ω and φ
scans. Data for 2 and 3 were collected at −148(1) °C on the St
Andrews robotic diffractometer, a Rigaku ACTOR-SM with a Saturn
(7) Barbaro, P.; Togni, A. Organometallics 1995, 14, 3570−3573.
(8) Smaliy, R. V.; Beauperin, M.; Mielle, A.; Richard, P.; Cattey, H.;
Kostyuk, A. N.; Hierso, J. Eur. J. Inorg. Chem. 2012, 1347−1352.
724 CCD area detector using ω steps accumulating area detector
images spanning at least a hemisphere of reciprocal space. Data for
compounds 4−8 were collected at −180(1) °C by using a Rigaku
MM007 high-brilliance RA generator with a Saturn 70 CCD area
detector using ω scans. All instruments use Mo Kα radiation (λ =
(9) Hartley, J. G.; Venanzi, L. M.; Goodall, D. C. J. Chem. Soc. 1963,
3
930−3936.
10) Whited, T. W.; Rivard, E.; Peters, P. C. Chem. Commun. 2006,
613−1615.
11) Mankad, N. P.; Rivard, E.; Harkins, S. B.; Peters, J. C. J. Am.
Chem. Soc. 2005, 127, 16032−16033.
12) Bauer, R. C.; Gloaguen, Y.; Lutz, M.; Reek, J. N. H.; de Bruin,
B.; van der Vlugt, J. I. Dalton Trans. 2011, 40, 8822−8829.
13) Mayer, H. A.; Otto, H.; Kuehbauch, H.; Fawzi, R. J. Organomet.
Chem. 1994, 472, 347−354.
14) Mayer, H. A.; Stoessel, P.; Fawzi, R.; Steimann, M. J. Organomet.
Chem. 1995, 492, C1−C3.
15) Mayer, H. A.; Stoessel, P.; Fawzi, R.; Steimann, M. Chem. Ber.
995, 128, 719−723.
16) Kilian, P.; Knight, F. R.; Woollins, J. D. Chem.Eur. J. 2011, 17,
302−2328.
17) Kilian, P.; Knight, F. R.; Woollins, J. D. Coord. Chem. Rev. 2011,
(
1
(
0
.71075 Å). Intensities were corrected for Lorentz polarization and for
absorption. The structures were solved by direct methods. Refine-
ments were done by full-matrix least-squares based on F using
2
(
40
SHELXTL. The structures of 3 and 5 while satisfactory for proof of
connectivity are of low quality. In both cases repeated attempts yielded
very poor crystals, often highly twinned and with high degrees of
solvation. The results presented here were from the best samples
measured after several attempts. In both cases thin platelets were used
for the final determinations.
(
(
(
1
(
2
CCDC 910652−910659 contain the supplementary crystallographic
data for this paper. These data can be obtained free of charge via www.
ccdc.cam.ac.uk/data_request/cif, by e-mail to data_request@ccdc.cam.
ac.uk, or by contacting The Cambridge Crystallographic Data Centre,
(
1
2 Union Rd., Cambridge CB2 1EZ, U.K. Fax: +44 1223 336033.
Computational Details. Geometries were fully optimized at the
1
(
(
387−1413.
18) Costa, T.; Schimdbaur., H. Chem. Ber. 1982, 115, 1374−1378.
BP86 or B3LYP level of density functional theory (DFT), employing
the 962(d) basis on Se, the Stuttgart−Dresden relativistic
pseudopotential on Mo (denoted SDD), and the 6-31G* or 6-
19) Karacar, A.; Thonnessen, H.; Jones, P. G.; Bartsch, R.;
Schmutzler, R. Heteroat. Chem. 1997, 53, 539−550.
(20) Karacar, A.; Freytag, M.; Thonnessen, H.; Jones, P. G.; Bartsch,
3
9
1+G* basis elsewhere. Energies are reported at the B3LYP/SDD/
62(d)/6-31+G* level. For more details and references, see the
R.; Schmutzler, R. J. Organomet. Chem. 2002, 643, 68−80.
(21) Jackson, R. D.; James, S.; Orpen, A. G.; Pringle, P. G. J.
Organomet. Chem. 1993, 458, C3−C4.
Supporting Information.
(22) Wawrzyniak, P.; Fuller, A. L.; Slawin, A. M. Z.; Kilian, P. Inorg.
ASSOCIATED CONTENT
■
Chem. 2009, 48, 2500−2506.
*
S
Supporting Information
(23) For details see Table S2 in the Supporting Information.
3
1
1
CIF files for 1−8, coalescence P{ H} NMR spectra and
relevant thermodynamic data for ligand 1, and additional
computational results and details, including thermodynamic
data, plots, and coordinates of optimized structures of
conformers of ligand 1 and isomers of complex 8. This
material is available free of charge via the Internet at http://
pubs.acs.org.
(24) Karacar, A.; Freytag, M.; Thonnessen, H.; Omelanczuk, J.;
Jones, P. G.; Bartsch, R.; Schmutzler, R. Heteroat. Chem. 2001, 2, 102−
113.
(
25) Omelanczuk, J.; Karacar, A.; Freytag, M.; Jones, P. G.; Bartsch,
R.; Mikolajczyk, M.; Schmutzler, R. Inorg. Chim. Acta 2003, 350, 583−
91. Karacar, A.; Freytag, M.; Thonnessen, H.; Omelanczuk, J.; Jones,
P. G.; Bartsch, R.; Schmutzler, R. Z. Anorg. Allg. Chem. 2000, 626,
361−2372.
26) Kilian, P.; Slawin, A. M. Z.; Woollins, J. D. Dalton Trans. 2003,
5
2
(
AUTHOR INFORMATION
■
3876−3885.
Corresponding Author
E-mail: pk7@st-andrews.ac.uk. Fax: +44 1334 463808. Phone:
44 1334 467304.
(27) WBIs are a measure of the covalent character of a bond. They
are used routinely to assess bonding interactions between formally
nonbonded atoms. See: Wiberg, K. B. Tetrahedron 1968, 24, 1083−
*
+
1
(
096.
28) According to the second-order perturbation analysis in a natural
Notes
The authors declare no competing financial interest.
bond orbital (NBO) analysis (Reed, A. E.; Curtiss, L. A.; Weinhold, F.
Chem. Rev. 1988, 88, 899−926) this donor−acceptor interaction is
very weak, amounting to just 1 kcal/mol.
ACKNOWLEDGMENTS
■
(
29) Somisara, D. M. U. K.; Bu
Slawin, A. M. Z.; Woollins, J. D.; Kilian, P. Chem.Eur. J. 2011, 17,
666−2677.
30) Cain, M. F.; Hughes, R. P.; Glueck, D. S.; Golen, J. A.; Moore,
C. E.; Rheingold, A. L. Inorg. Chem. 2010, 49, 7650−7662.
31) Sevillano, P.; Habtemariam, A.; Parsons, S.; Castineiras.; Garcia,
M. E.; Sadler, P. J. J. Chem. Soc., Dalton Trans. 1999, 2861−2870.
32) For a discussion of spin states of tbp complexes see Sacconi, L.;
Di Vaira, M. Inorg. Chem. 1978, 17, 810−815.
33) Cano, M.; Campo, J. A.; Perez-Garcia, V.; Guttierrez-Puebla, E.;
Alvarez-Ibarra, C. J. Organomet. Chem. 1990, 382, 397−406.
(34) All Mo complexes with RP(CH CH CH PR ligands, i.e.,
̈
hl, M.; Lebl, T.; Richardson, N. V.;
We thank Mrs. C. E. R. Horsburgh at the University of St
Andrews and the National Mass Spectrometry Service Centre
at the University of Swansea for measurement of mass spectra.
We thank the EPSRC, School of Chemistry, EaStChem, and
COST action CM0802 PhoSciNet for financial support.
2
(
(
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