Geminally Substituted Tris(acenaphthyl) and Bis(acenaphthyl) Arsines, Stibines, and Bismuthine: A Structural and Nuclear Magnetic Resonance Investigation

Article abstract of DOI:10.1021/acs.inorgchem.6b01079

Tris(acenaphthyl)- and bis(acenaphthyl)-substituted pnictogens (iPr₂P-Ace)₃E (2-4) (E = As, Sb, or Bi; Ace = acenaphthene-5,6-diyl) and (iPr₂P-Ace)₂EPh (5 and 6) (E = As or Sb) were synthesized and fully characterized by multinuclear nuclear magnetic resonance (NMR), high-resolution mass spectrometry, elemental analysis, and single-crystal X-ray diffraction. The molecules adopt propeller-like geometries with the restricted rotational freedom of the sterically encumbered iPr₂P-Ace groups resulting in distinct NMR features. In the tris(acenaphthyl) species (2-4), the phosphorus atoms are isochronous in the ³¹P{¹H} NMR spectra, and the rotation of the three acenaphthyl moieties around the E-C_ipso bond is locked. On the other hand, the bis(acenaphthyl) species show a fluxional behavior, resulting in an AX to A₂ spin system transition in the ³¹P{¹H} variable-temperature NMR spectra. This allowed elucidation of remarkable through-space couplings (^8TSJ_PP) of 11.5 Hz (for 5) and 25.8 Hz (for 6) at low temperatures. In addition, detailed line shape analysis of the thermodynamic parameters of the restricted rotation of the "propeller blades" in 5 was performed in the intermediate temperature region and also at coalescence. The lone pairs on the pnictogen atoms in 2-6 are oriented such that they form a bowl-shaped area that is somehow buried within the molecule.

Full text of DOI:10.1021/acs.inorgchem.6b01079

Article
pubs.acs.org/IC
Geminally Substituted Tris(acenaphthyl) and Bis(acenaphthyl)
Arsines, Stibines, and Bismuthine: A Structural and Nuclear Magnetic
Resonance Investigation
Brian A. Chalmers, Christina B. E. Meigh, Phillip S. Nejman, Michael Buhl, Tomas Lebl, J. Derek Woollins,
́
̌
́
̈
Alexandra M. Z. Slawin, and Petr Kilian*
EaStChem School of Chemistry, University of St Andrews, St Andrews, Fife KY16 9ST, U.K.
S
* Supporting Information
ABSTRACT: Tris(acenaphthyl)- and bis(acenaphthyl)-sub-
stituted pnictogens (iPr2P-Ace)3E (2−4) (E = As, Sb, or Bi;
Ace = acenaphthene-5,6-diyl) and (iPr2P-Ace)2EPh (5 and 6)
(E = As or Sb) were synthesized and fully characterized by
multinuclear nuclear magnetic resonance (NMR), high-
resolution mass spectrometry, elemental analysis, and single-
crystal X-ray diffraction. The molecules adopt propeller-like
geometries with the restricted rotational freedom of the
sterically encumbered iPr2P-Ace groups resulting in distinct
NMR features. In the tris(acenaphthyl) species (2−4), the
phosphorus atoms are isochronous in the 31P{1H} NMR
spectra, and the rotation of the three acenaphthyl moieties
around the E−Cipso bond is locked. On the other hand, the bis(acenaphthyl) species show a fluxional behavior, resulting in an AX
to A2 spin system transition in the 31P{1H} variable-temperature NMR spectra. This allowed elucidation of remarkable through-
space couplings (8TSJPP) of 11.5 Hz (for 5) and 25.8 Hz (for 6) at low temperatures. In addition, detailed line shape analysis of
the thermodynamic parameters of the restricted rotation of the “propeller blades” in 5 was performed in the intermediate
temperature region and also at coalescence. The lone pairs on the pnictogen atoms in 2−6 are oriented such that they form a
bowl-shaped area that is somehow buried within the molecule.
complex G, which was obtained from the reaction of
tetrakis(diphenylphosphino)-p-xylene with Fe2(CO)9.7
INTRODUCTION
■
Tridentate phosphines have been described extensively in the
literature, with the majority of the reports focusing on their use
in catalysis.1 As for other phosphines, the versatility of
tridentate phosphines as ligands stems from the ability to
manipulate the steric and electronic properties by varying the
groups attached to the phosphorus donor atoms. In addition,
flexibility of the linkages joining the donor atoms in
multidentate ligands is also tunable. The rather flexible ligand,
triphos (A) (Figure 1), is one of the most extensively studied
tridentate phosphines as mentioned in a recent review by Ilia.2,3
Ligand B represents a less flexible tris(phosphine), with ortho-
substituted phenyl linkages favoring metal chelation.4 On the
other hand, tetradentate phosphines such as C,5 D,6 and E4
have been much less explored, often because of the challenging
multistep synthesis involved. Coordination chemistry of these
ligands is somehow complicated by the variety of coordination
modes these ligands display, which makes their chemistry
somehow less predictable. An example of this coordinative
variety includes the bimetallic iron(II) complex F in which one
tetrakis(phosphine) ligand D is coordinating in a bidentate
mode, and the other in a tridentate mode to one metal atom
and monodentate to the other.6 More rigid tetradentate
phosphines also form bimetallic bidentate systems such as
We have recently reported a synthetic and coordination
study of the first geminally bis(peri-substituted) tridentate
phosphine (H).8 It was synthesized by the reaction of 1 with
1/2 equiv of iPrPCl2, giving the tris(phosphine) in a respectable
yield (68%). Tris(phosphine) H displayed complex variable-
temperature (VT) nuclear magnetic resonance (NMR)
behavior. At room temperature, a broad singlet was observed
in the 31P{1H} NMR spectrum, which resolved to an AB2
system at an elevated temperature (353 K). When the sample
was cooled to 223 K, two ABC spin systems were observed,
because two rotamers of the compound are present in solution.
The complexity of the dynamic processes prevented the
extraction of detailed thermodynamic parameters by 31P{1H}
VT NMR spectroscopy. Tris(phosphine) H was shown to act
as a tridentate ligand forming square planar, tetrahedral,
trigonal bipyramidal, and octahedral complexes with various
metals (Pt, Cu, Fe, and Mo).
Tris(phosphine) H is somewhat similar to 1,8,9-trisubsti-
tuted anthracenes, in which the central atom (in position 9)
Received: May 1, 2016
© XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.6b01079
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 1. Selected literature examples of tri- and tetradentate phosphines (A−E), metal complexes (F and G), and 1,8,9-substituted anthracenes (I−
K) discussed herein.
Scheme 1. Preparation of Compounds 2−6
also experiences two proximate peri-interactions. We have
previously synthesized a short series of tris(phosphino)-
anthracenes with a particular interest in their peri-region
bonding and through-space interactions.9 Compound I shows
nally bis(peri-substituted) pnictogens. These provide rather
similar connectivity with respect to the central atom, which
experiences two proximate peri-interactions. In contrast to the
1,8,9-trisubstituted anthracene manifold, the bis(peri-substi-
tuted) pnictogen platform provides additional angular flexibility
as these molecules are not rigidly planar. Rather importantly,
geminally bis(peri-substituted) species are synthetically much
more viable. In this work, we report the synthesis and
characterization of a bis(peri-substituted) arsine and stibine,
which represent heavier homologues of ligand H. In addition,
tris(peri-substituted) arsine, stibine, and bismuthine are
reported; these represent the first examples of a new class of
rigid tetradentate (P3E) tris(peri-substituted) pnictine ligands.
no formal P−P bonding interaction, though it does show a
4TS
remarkable
J
PP
of 104 Hz in an A2M spin system. The Lewis
base-stabilized meta-phosphonate (J) was synthesized from the
reaction of I with methanol and selenium, and the double
Lewis-base stabilized phosphenium (K) was somehow
unexpectedly synthesized by the reaction of I with P2I4 in
1,2-dichloroethane. While of high interest for their interesting
bonding, several aspects make pnictogen 1,8,9-trisubstituted
anthracenes rather challenging species with which to work.
First, six synthetic steps are required in the preparation of I,
starting from commercially available 1,8-dichloroanthraqui-
none.9,10 The yields at each step range between 51 and 93%,
which means multigram quantities of I are not easily accessible.
Another issue with 1,8,9-trisubstituted anthracenes species is
that the central ring becomes dearomatized rather easily as
shown by Hayes.11 In a search for replacement of synthetically
challenging 1,8,9-anthracenes, our attention turned to gemi-
RESULTS AND DISCUSSION
■
Syntheses. 5-Bromo-6-(diisopropylphosphino)-
acenaphthene (1) was used as the principal precursor in all
syntheses described in this study.12 The low-temperature
lithium−halogen exchange reaction with n-butyllithium yielded
5-lithio-6-(diisopropylphosphino)acenaphthene (1′), which
was, without isolation, subjected to C−E coupling with either
B
DOI: 10.1021/acs.inorgchem.6b01079
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 2. Crystal structures of 2−4. Solvating molecules (toluene for 3 and CH2Cl2 for 4) and hydrogen atoms have been omitted, with isopropyl
groups simplified for the sake of clarity. Ellipsoids are plotted at the 40% probability level.
a
Table 1. Selected Bond Lengths, Displacements (angstroms), and Angles (degrees) for Compounds 2−6
2
3·C7H8
4·2CH2Cl2
5·CH2Cl2
6·2.5C7H8
Distances
CAce−P
C−E1
P···P
P9···E1
P29···E1
P49···E1
1.846(3), −1.853(3)
2.002(2), −2.021(3)
4.838(1), −5.251(1)
3.2051(9)
1.832(6), −1.839(5)
2.212(6), −2.224(5)
4.947(2), −5.484(2)
3.305(1)
1.80(2), −1.85(1)
2.31(1), −2.34(1)
5.066(6), −5.484(5)
3.240(3) [3.279(4)]
3.250(4) [3.218(3)]
3.250(3) [3.242(4)]
1.837(7), −1.839(7)
1.965(6), −2.003(7)
4.970(3)
1.837(2), −1.845(2)
2.183(2), −2.214(2)
5.2409(9)
3.120(2)
3.1684(7)
3.1938(8)
3.197(1)
3.188(2)
3.2513(7)
3.162(1)
3.172(2)
-
-
Angles
C−E1−C
P···E1···P
splay angles
96.4(1), −98.7(1)
98.91(2), −110.30(2)
16.5
93.6(2), −97.3(2)
99.59(4), −114.98(4)
10.1
91.7(5), −96.0(5)
103.3(1), −115.1(1)
15.9 [16.0]
97.2(3), −100.0(3)
103.97(5)
93.80(6), −96.04(6)
109.44(2)
b
15.5
15.2
15.9 [15.7]
15.2
17.1
14.1
16.5
15.7
14.8
16.0 [16.0]
P−C···C−E1
15.5(1)
1.3(1)
8.3(1)
34.7(3)
0.0(3)
0.1(3)
2.8(7) [2.5(7)]
6.3(7) [1.5(7)]
7.4(7) [8.6(8)]
0.5(4)
9.3(4)
8.2(1)
13.3(1)
Out-of-Plane Displacements
P
E
0.139−0.391
0.197−0.273
0.194−0.599
0.197−0.881
0.025−0.338
0.027−0.442
0.102−0.211
0.194−0.314
0.041−0.216
0.379−0.431
a
b
Values in brackets are for the second molecule in the asymmetric unit. The splay angle equals the sum of the bay region angles − 360°.
1/3 molar equiv of ECl3 (E = As, Sb, or Bi) or /2 equiv of
PhECl2 (E = As or Sb) (Scheme 1). After aqueous workup
under oxygen free conditions, novel compounds 2−6 were
isolated as air sensitive white to yellow powders in moderate to
high yields (32−80%). Compounds 2−6 are all hydrolytically
stable and were fully characterized by multinuclear NMR
spectroscopy (1H, 13C, and 31P), single-crystal X-ray diffraction,
mass spectrometry, and infrared and Raman spectroscopy, with
the homogeneity confirmed by microanalysis.
1
Dichlorophenylarsine was prepared by the SO2 reduction of
phenylarsonic acid in the presence of HCl.13 Dichlorophenyl-
stibine was prepared by the redistribution reaction of SbCl3 and
SbPh3.14,15 Multiple attempts to synthesize PhBiCl2 via a
related route resulted in the desired species being significantly
contaminated by Ph3Bi, Ph2BiCl, and BiCl3, with purification by
recrystallization from various solvents proving to be ineffective.
The subsequent reaction of this impure material with 1′
resulted in complex, inseparable mixtures.
C
DOI: 10.1021/acs.inorgchem.6b01079
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 3. Crystal structures of 5 and 6. Solvating molecules (CH2Cl2 for 5 and toluene for 6) and hydrogen atoms have been omitted, with isopropyl
and phenyl groups simplified for the sake of clarity. Ellipsoids are plotted at the 40% probability level.
While bis(peri-substituted) tridentate phosphine H has been
Because of the large size and almost spherical shape of
molecules 2−4, the crystals have large voids that accommodate
solvent easily. In all cases (except for one incidence of 2),
minor (unmodelled) disorder of the solvent was observed in
the crystal structures.
Bis(acenaphthyl) Species 5 and 6. The crystal structures of
5 and 6 (Figure 3 and Table 1) show slight alleviation of the
steric congestion around the central pnictogen atom (for 5, E =
As; for 6, E = Sb) as one of the large iPr2P-Ace units has been
replaced with a phenyl ring.
1
prepared by the reaction of 1′ with /2 molar equiv of iPrPCl2
cleanly with a good yield (68%),8 the low-temperature reaction
1
of 1′ with /3 molar equiv of PCl3 gave a complex mixture of
products (as judged by 31P{1H} NMR). Therefore, the tris(peri-
substituted) phosphorus-centered congener of the series of 2−
4 was deemed inaccessible by this route and was not pursued
further.
Structural Investigations. Tris(acenaphthyl) Species 2−
4. Crystal structures of compounds 2−4 are shown in Figure 2,
with selected data listed in Table 1. In each case, the central
pnictogen atom (As in 2, Sb in 3, and Bi in 4) adopts a trigonal
pyramidal geometry, with a slight increase in the acuteness of
the Cipso−E−Cipso angles following the As, Sb, Bi sequence (see
Table 1). No strong dative interactions are formed between the
Lewis basic iPr2P groups and the central pnictogen atom as
indicated by P···E distances, which range between 3.1 and 3.3
Å. The observed positive splay angles (10.1−16.5°) further
support this notion. Despite three bulky peri groups being
attached to the pnictogen centers in 2−4, there are no major
distortions of acenaphthene rings, with only moderate to
medium in-plane and out-of-plane displacement of the peri
atoms observed (Table 1). More significant deviations are
observed only in one of the acenaphthene rings of 3, which
shows P and Sb out-of-plane displacements of 0.60 and 0.88 Å,
with a corresponding P19−C9···C1−Sb1 dihedral angle of
34.7(3)°. This is a significant increase versus those of the other
two acenaphthene moieties in this molecule; however, this
anomaly is readily explained through a local trade-off for
decreased in-plane distortion in this particular peri motif that
can be observed as a slightly diminished splay angle of 10.1°.
For comparison, displacements in related singly acenaphthyl-
substituted iPr2P-Ace-SbPh2 are 0.111 and 0.039 Å, with a splay
angle of 15.7(4)°.15
As seen for the tris(acenaphthyl) species 2−4, no strong
dative interactions are present between the central pnictogen
atoms and the iPr2P groups, with P···E distances in the range of
3.12−3.25 Å. The arsenic and antimony atoms attain a trigonal
pyramidal geometry. When sub-van der Waals contacts are
taken into account, the As and Sb atoms display distorted
tetragonal pyramidal geometry formed by three carbon atoms
and two proximal iPr2P groups, with the lone pair on the E
atoms protruding through the base of the pyramid to complete
the pseudo-octahedral coordination. There are no major
distortions in either 5 or 6, with the largest out-of-plane
displacement being ∼0.4 Å. The splay angles range between
14.1° and 17.1°; also, the P−C···C−E dihedral angles compare
well to the related parameters in compounds 2−4. As described
above, a collinear arrangement of all Cipso−E···P motifs
observed in crystal structures of 5 and 6 is consistent with
the onset of an n(P)→σ*(E−C) 3c−4e interaction. As in the
crystal structures of 2−4, in both 5 and 6, solvent was
incorporated into the crystal structure because of the large
voids formed on packing.
NMR Spectroscopy. Tris(acenaphthyl) Species 2−4.
Compounds 2−4 show sharp singlets at δP −13.0 (2), −19.1
(3), and −21.3 (4), indicating a slight increase in shielding of
the phosphorus atoms on the descending group.15 Because of
the crowded, propeller-like geometry of 2−4, the 1H and
13C{1H} NMR spectra display multiple anisochronous signals
for chemically equivalent groups. Using 2 as an example, four
CH3 and two CH environments are observed as complex
multiplets in the 1H and 13C{1H} NMR spectra (Figure 5). The
signals of methyl carbon atoms (δC 21.3−18.9) are second-
order multiplets, corresponding to AA′A″X spin systems (A =
31P, and X = 13C). Despite considerable effort, which included
acquisition of the spectra at high field (16.4 T, 700 MHz
instrument) and many iterative attempts, we have not been able
Because of the specifics of the peri substitution, all P···E
distances are significantly sub-van der Waals [77−80% using
van der Waals radii (RvdW) values of 1.95 Å (P), 2.05 Å (As),
2.20 Å (Sb), and 2.30 Å (Bi)].16 If these short contacts were
taken into account, the central pnictogen atom could also be
viewed as attaining distorted octahedral geometry with its lone
pair protruding through one of the octahedron faces. A
collinear arrangement of all Cipso−E···P motifs observed in the
crystal structures of 2−4 is consistent with the onset of an n(P)
→ σ*(E−C) 3c−4e interaction (see Figure 9).
D
DOI: 10.1021/acs.inorgchem.6b01079
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
8TS
to simulate the spin systems to extract J couplings. This is
because methyl carbons not only couple with 31P atoms
separated by two bonds (2JCP) but also have also non-negligible
couplings with more distant phosphorus atoms. These two
couplings, with a formal separation of 10 bonds (10TSJCP), have
different magnitudes, which results in a complex second-order
signal. The shape of the signals is very sensitive to subtle
changes in the coupling constants, which made the iterative
fitting impossible. While we cannot determine the exact
J
is remarkable because there is no direct overlap of the
PP
lone pairs on phosphorus atoms. The transfer of magnetization
is highly likely to involve two through-space interactions
because of the overlap of the two phosphorus lone pairs with
the diffuse arsenic lone pair [n(P)···n(As) ···n(P) interaction
(Figure 4)].
Detailed line shape analysis of the 31P{1H} VT NMR spectra
(see Figure S18 of the Supporting Information for the Eyring
plot) yielded thermodynamic parameters of ΔH⧧ = 57.1 kJ
mol−1 and ΔS⧧ = −17.5 J mol−1 K−1 for the interchange
process in 5. For completeness, the coalescence method gave a
rotational barrier ΔG⧧ of 62.3 kJ mol−1 at 340 K for 5. These
data complement those obtained for the related tris-
(phosphine) H, mentioned above. Because of the complexity
of the dynamic processes in tris(phosphine) H, in which two
ABC spin systems were present in the slow motion regime, the
interchange process (equivalent to that described for 5) was
masked, hence precluding determination of the exchange
barrier through either line shape analysis or the coalescence
method.
magnitude of these long-range couplings, we can confirm
10TS
both these
J
CP
couplings are very likely non-negligible (i.e.,
>2 Hz) and different in each of the four diastereotopic methyl
groups in 2−4. The through-bond component (through 10
bonds, 10J) is likely to be very small, if not zero.17 Hence, it is
highly likely that the couplings involve two through-space
components (through two peri gaps); i.e., the magnetization is
transferred due to the overlap of lone pairs on each of the two
phosphorus atoms with the lone pair on the central arsenic
atom (Figure 4).
Compound 6 shows features similar to those of its arsenic
homologue 5. The 31P{1H} NMR spectrum of 6 at 298 K
(109.4 MHz) shows an extremely broad resonance (Figure 7).
A variable-temperature NMR study revealed a sharp singlet (δP
−17.5) at 363 K (fast motion regime) and two sharp doublets
(δP −21.2 and −24.2) at 223 K (slow motion regime). The
increased magnitude of 8TSJPP between 5 and 6 (11.5 Hz vs 25.8
Hz, both at 223 K) can be attributed to the larger antimony
atom acting as a more efficient mediator of magnetic spin
information between the two phosphorus atoms (see Figure 4).
The coalescence temperature of 6 was 303 K (at 109.4 MHz),
which corresponds to a rotational barrier ΔG⧧ of 62.0 kJ mol−1.
This is remarkably similar to the energy barrier associated with
interchange in 5, obtained from the detailed line shape analysis
(ΔG⧧ = 62.4 kJ mol−1 at 303 K).
Figure 4. Graphical representation of the magnetization transfer
pathway in long-range couplings. Bonds (formally) involved in the
transfer are colored blue, and lone pairs involved in the transfer
(through space) are colored red. The left panel shows one of the
10TS
J
couplings between a CH3 carbon atom and a distant P atom in
CP
8TS
molecules 2−4. The right panel shows
two P atoms in molecules 5 and 6.
J
coupling between the
PP
Computational Investigations. To complement these
findings, we performed calculations at the B3LYP-D3/6-31G*
level of density functional theory (DFT). Taking the arsenic
compounds 2 and 5 as representatives, we optimized their
structures starting from the single-crystal X-ray coordinates and
subjected their wave functions were to natural bond orbital
(NBO) analysis.18 The distances between the formally
nonbonded As and P atoms are reasonably well reproduced
at that level, e.g., for the mean As···P distance in 2 (DFT, 3.151
Å; X-ray, 3.189 Å).19 The localized lone pairs on phosphorus
and arsenic atoms are visualized in Figure 8; these are
somewhat “buried” within the molecules, in particular for
tris(acenaphthyl) derivative 2, indicating they may not be
readily available for coordination chemistry.
In a similar vein, isopropyl CH environments (δC 26.8−25.8
in 2) display complex multiplets, corresponding to AA′A″X
spin systems (Figure 5).
Low-temperature (222 K) 31P{1H} NMR spectra of 2−4 did
not display any observable line broadening or other notable
changes, indicating no additional interlocking takes place at this
temperature.
Bis(acenaphthyl) Species 5 and 6. The 31P{1H} NMR
spectrum of 5 in d8-toluene (121.5 MHz, 298 K) shows two
broad resonances at δP −11.5 and −14.4 (Figure 6). This is
consistent with the molecule experiencing restricted rotational
dynamics in solution, presumably around the As−CAcenap bonds
[As1−C1 and As1−C21 (see Figure 3)]. In line with this, all
Arguably, there is repulsion between the lone pairs on As and
P atoms. There are, however, weak attractions between these
atoms counteracting this repulsion. In a second-order
perturbation analysis, these are identified as n(P) → σ*(As−
1
signals in the H NMR spectrum of 5 (298 K, 300.1 MHz)
were broadened, while very broad signals were observed in the
13C{1H} NMR spectrum at the same temperature (75.5 MHz)
(see the Supporting Information).
C
ipso) dative interactions worth approximately 10−11 kcal/mol
each (for one of them, the relevant pair of NBOs is depicted in
Figure 9). These interactions are likely to support the collinear
arrangement of Cipso−E···P motifs observed throughout the
crystal structures of 2−5. These dative interactions give rise to
notable Wiberg bond indices (WBIs) between the arsenic and
phosphorus atoms, on the order of 0.10−0.11.20 Slightly lower
but still notable WBIs (approximately 0.07−0.09) and donor−
acceptor energies (approximately 7−9 kcal/mol) are obtained
at the same DFT level when the X-ray structures are employed
To gain insight into the dynamic behavior of 5, a variable-
temperature NMR study was performed in the range of 223−
373 K (Figure 6). When the sample of 5 was warmed to 373 K,
a singlet was observed in the 31P{1H} NMR spectrum at δP
−10.5, indicating that the two phosphorus environments
interchange rapidly at this temperature. When the sample was
cooled to 223 K, the 31P{1H} NMR spectrum revealed two
sharp doublets at δP −13.2 and −16.9 (8TSJPP = 11.5 Hz),
consistent with a simple AX spin system. The magnitude of
E
DOI: 10.1021/acs.inorgchem.6b01079
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 5. NMR spectra of 2, the alkyl region of the 1H NMR spectrum (recorded at 700.1 MHz) (top) and the alkyl region of the 13C{1H} NMR
spectrum (recorded at 176.1 MHz) (bottom).
Figure 6. Variable-temperature 31P{1H} NMR spectra of 5 in d8-
toluene at 121.5 MHz.
Figure 7. Variable-temperature 31P{1H} NMR spectra of 6 in d8-
toluene at 109.4 MHz. Minor peaks are from an unrelated impurity.
without minimization. Similar characteristics have been found
between other heavier chalcogen and pnictogen atoms in peri-
naphthalene positions, where such notable dative interactions
and WBIs have been taken as evidence of the onset of
multicenter bonding.15,21,22
CONCLUSION
Detailed structural and NMR spectroscopic study of bis-
(phosphinoacenaphthyl) and tris(phosphinoacenaphthyl) pnic-
■
F
DOI: 10.1021/acs.inorgchem.6b01079
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 8. Plot of the lone pair NBOs in compounds 2 (left) and 5 (right). Hydrogen atoms have been omitted for the sake of clarity; isodensity
values are 0.08 au. Molecules are viewed from “above” looking down the As lone pair; for other views, see the Supporting Information.
take place. This is because the direct overlap of the two
phosphorus atoms is ineffective, the P···P distances ranging
from 4.838(1) to 5.484(5) Å (see Table 1 and the plot of the
lone pair NBOs in Figure 8). The lone pairs on the pnictogen
atoms form a bowl-like environment, which, however, is
somehow buried within the molecule. Coordination chemistry
of these potential tetradentate (2−4) and tridentate (5 and 6)
ligands will be studied next.
EXPERIMENTAL SECTION
■
General Considerations. All reactions and manipulations were
performed under an atmosphere of nitrogen using standard Schlenk
techniques or under an argon atmosphere in a Saffron glovebox. Dry
solvents were either collected from an MBraun Solvent Purification
System or dried and stored according to common procedures.23
Compound 1 was prepared according to the published procedure.12
Antimony trichloride was purchased from Sigma-Aldrich and purified
by vacuum sublimation before use. Dichlorophenylarsine (PhAsCl2)13
and dichlorophenylstibine (PhSbCl2)14,15 were prepared according to
the published procedures; further details are in the Supporting
Information. Other chemicals were purchased from Acros Organics,
Sigma-Aldrich, or Alfa Aesar and used as received. Caution!
Organoarsenic halides and arsenic halides are powerful vessicants, which
cause severe irritation and blistering if allowed to come in contact with skin.
Suitable precautions, including the use of neoprene or rubber gloves
when handling these, should be taken. Further experimental details are
provided in the Supporting Information.
Figure 9. Plot of one pair of NBOs involved in dative interactions in 2:
red, lone pair donor on P; gray/turquoise, antibonding σ*(As−C)
acceptor orbital. H atoms have been omitted for the sake of clarity;
isodensity values are 0.08 au.
Synthetic Methods. (iPr2P-Ace)3As (2). To a cooled (−78 °C)
stirred solution of 1 (3.75 g, 10.7 mmol) in diethyl ether (100 mL)
was added dropwise over 1 h n-butyllithium (4.30 mL, 2.5 M in
hexanes, 10.7 mmol). The resulting solution was left to stir for a
further 1 h at −78 °C. To this was added dropwise over 2 h a solution
of arsenic trichloride (300 μL, 65 mg, 3.6 mmol) in diethyl ether (10
mL). The solution was left to warm to ambient temperature overnight.
The volatiles were removed in vacuo and replaced with toluene (100
mL). The solution was washed with degassed water (45 mL) and the
organic layer dried over magnesium sulfate. After filtration, the
volatiles were again removed in vacuo to give a yellow powder (7.58 g,
80%) (mp >250 °C). Crystals suitable for X-ray diffraction work were
tines confirmed the sterically crowded nature of these
molecules, with sub-van der Waals P···E contacts across the
peri region. However, relatively high yields and moderate
acenaphthene ring distortions indicate that the blade-like
arrangement of the substituents in these propeller-shaped
molecules is rather accommodating. The relative simplicity of
the 31P{1H} NMR spectra of 5 and 6 at low temperatures
allowed determination of the long-range 8TSJPP couplings. Their
magnitudes (11.5 and 25.8 Hz) are remarkable. The transfer of
magnetization is likely to involve two through-space
interactions in which the central pnictogen’s lone pair acts as
a “relay”; i.e., n(P)···n(E)···n(P) interactions (E = As or Sb)
1
grown from chloroform at room temperature. H NMR (Figure 10)
(700.1 MHz, CDCl3): δH 7.62 (3H, dd, 3JHH = 7.1 Hz, 7tsJHP = 1.7 Hz,
H-8), 7.57 (3H, d, 3JHH = 7.1 Hz, H-2), 7.29 (3H, m, H-7), 6.86 (3H,
3
d, JHH = 7.1 Hz, H-3), 3.43−3.24 (12H, m, H-11,12), 2.15 (3H, h,
G
DOI: 10.1021/acs.inorgchem.6b01079
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
white precipitate that was collected via filtration. The solid was washed
with diethyl ether (2 × 10 mL) and then degassed water (10 mL) and
dried in vacuo for 4 h. The product was obtained as a white powder
(300 mg, 0.29 mmol, 32%) (mp 202−203 °C dec). X-ray quality
crystals of 4 were grown from a saturated solution in dichloromethane
1
3
at 0 °C. H NMR (500.1 MHz, CDCl3): δH 8.60 (3H, dd, JHH = 6.9
7ts
3
Hz,
J
= 2.4 Hz, H-8), 7.60 (3H, dd, JHH = 7.2 Hz, 3JHP = 2.8 Hz,
HP
H-2), 7.27 (3H, d, 3JHH = 7.1 Hz, H-3), 6.85 (3H, d, 3JHH = 6.8 Hz, H-
3
7), 3.38−3.19 (12H, m, H11/12), 2.10 (3H, h, JHH = 6.9 Hz, H-16),
3
3
1.89 (3H, h, JHH = 6.8 Hz, H-13), 1.22 (9H, dd, ∼q, JHP = 13.4 Hz,
3JHH = 7.0 Hz, H-17), 1.12 (9H, dd, ∼q, 3JHP = 10.1 Hz, 3JHH = 6.9 Hz,
3
3
H-18), 0.63 (9H, dd, ∼q, JHP = 14.4 Hz, JHH = 6.8 Hz, H-14), 0.17
(9H, dd, ∼q, JHP = 12.6 Hz, JHH = 6.9 Hz, H-15). 13C NMR (125.8
MHz, CDCl3): δC 176.6 (s, qC-9), 148.8 (s, qC-4), 146.6 (s, C-8),
145.3−144.9 (m, qC-10), 144.0 (s, qC-6), 141.5−141.3 (m, qC-5),
132.7 (s, C-2), 132.6−132.4 (m, qC-1), 123.5 (s, C-7), 117.9 (s, C-3),
130.2 (s, C-11/12), 130.1 (s, C-11/12), 27.0−26.7 (m, C-16), 25.5−
25.3 (m, C-13), 21.5−21.2 (m, C-18), 20.3−20.1 (m, C-17), 19.9−
19.5 (m, C14,15). 31P{1H} NMR (202.5 MHz, CDCl3): δP −21.3 (s).
Infrared data (KBr disc, cm−1): ν = 3022w (νAr−H), 2948s (νC−H),
1631br, 1460s, 1322s, 1245s. Raman data (glass capillary, cm−1): ν =
3048m (νAr−H), 1570m, 999s, 211s. Elemental Anal. Calculated for
C54H66P3Bi: C, 63.77; H, 6.46. Found: C, 63.64; H, 6.46. HRMS
(APCI+): m/z (%) calcd for C54H67P3Bi 1017.4244, found 1017.4254
[M + H+].
3
3
Figure 10. NMR numbering scheme for compounds 2−6.
3JHH = 6.8 Hz, H-16), 1.72−1.65 (3H, m, H-13), 1.19−1.13 (18H, m,
3
3
H-17,18), 0.47 (9H, dd, JHP = 13.4 Hz, JHH = 6.7 Hz, H-15), −0.04
(9H, dd, 3JHP = 12.1 Hz, 3JHH = 7.0 Hz, H-14). 13C{1H} NMR (176.1
MHz, CDCl3): δC 147.9 (s, qC-6), 145.7 (s, qC-4), 143.1−142.5 (m,
2
1JCP ≈ 49 Hz, qC-1), 141.0−140.7 (m, ∼dt, JCP ≈ 29 Hz, qC-10),
140.5 (s, C-2), 140.2−140.1 (m, qC-5), 133.8 (s, C-8), 132.4−132.0
(m, qC-9), 119.6 (s, C-3), 118.2 (s, C-7), 30.1 (s, C-11/12), 29.6 (s,
C-11/12), 26.8−26.4 (m, C-16), 26.1−25.8 (m, C-13), 21.1−20.9 (m,
C-18), 20.3−20.1 (m, C-17), 19.8−19.6 (m, C-14), 19.2−18.9 (m, C-
15). 31P{1H} NMR (202.5 MHz, CDCl3): δP −13.0 (s). Infrared data
(KBr disc, cm−1): ν = 3021w (νAr−H), 2921vs (νC−H), 1871m, 1607s,
1319s, 842vs. Raman data (glass capillary, cm−1): ν = 3061m (νAr−H),
2929s (νC−H), 1607s, 1561s, 1466s, 1412s, 1322vs, 580s. Elemental
Anal. Calcd for C54H66P3As: C, 73.46; H, 7.53. Found: C, 73.28; H,
7.45. HRMS (APCI+): m/z (%) calcd for C54H67P3As 883.3666,
found 883.3647 (100) [M + H+]; calcd for C36H44P2As 613.2134,
found 613.2109 (45) [M − iPr2P-Ace]; calcd for C18H23PAs 345.0753,
found 345.0738 (5) [M − 2 × iPr2P-Ace + H].
(iPr2P-Ace)2AsPh (5). To a cooled (−78 °C), rapidly stirring
solution of 1 (3.00 g, 8.6 mmol) in diethyl ether (75 mL) was added
over a period of 1 h n-butyllithium (3.5 mL, 2.5 M solution in hexanes,
8.6 mmol), and the mixture was left to stir for 2 h at the same
temperature. A solution of dichlorophenylarsine (0.96 g, 0.58 mL, 4.6
mmol) in diethyl ether (10 mL) was added dropwise over 1 h and the
resulting solution left to warm to ambient temperature overnight.
Additional diethyl ether (110 mL) was added, along with degassed
water (25 mL), and the solution was stirred vigorously for 10 min. The
organic layer was separated and dried over magnesium sulfate. The
volatiles were removed in vacuo to give a yellow powder that was dried
in vacuo for 3 h (1.91 g, 64%) (mp 160 °C). X-ray quality crystals of 5
were grown from dichloromethane at −35 °C. 1H NMR (300.1 MHz,
d8-toluene, 298 K): δH 7.76 (br s), 7.56 (br s), 7.59 (br s), 6.93 (br s),
6.75 (br s), 2.97 (br s, H-11,12), 2.47 (br s), 2.16 (br s), 1.98 (br s),
1.85 (br s), 1.51 (3H, br s, 1 × CH3), 1.46 (3H, br s, 1 × CH3), 1.29
(3H, br s, 1 × CH3), 1.09 (3H, br s, 1 × CH3), 1.03 (3H, br s, 1 ×
CH3), 0.57 (3H, br s, 1 × CH3), 0.33 (3H, br s, 1 × CH3), 0.15 (3H,
(iPr2P-Ace)3Sb (3). Compound 3 was prepared using the same
procedure that was used for compound 2 except using 1 (3.00 g, 8.6
mmol) in diethyl ether (100 mL), n-butyllithium (3.4 mL, 2.5 M in
hexanes, 8.6 mmol), antimony trichloride (650 mg, 2.9 mmol) in
diethyl ether (8 mL), toluene (50 mL), and degassed water (25 mL),
giving a yellow powder (2.46 g, 32%) (mp >250 °C). Crystals suitable
1
for X-ray diffraction work were grown from toluene at −35 °C. H
NMR (500.1 MHz, CDCl3): δH 7.85 (3H, d, 3JHH = 6.6 Hz, H-2), 7.61
1
3
3
br s, 1 × CH3). H NMR (300.1 MHz, d8-toluene, 223 K): δH 8.19
(3H, d, JHH = 6.2 Hz, H-8), 7.29 (3H, d, JHH = 7.3 Hz, H-7), 6.84
(3H, d, 3JHH = 6.9 Hz, H-3), 3.40−3.25 (12H, m, H-11,12), 2.14 (3H,
h, 3JHH = 6.8 Hz, H-16), 1.88 (3H, dh, 2JHP = 13.5 Hz, 3JHH = 6.8 Hz,
H-13), 1.21 (9H, m, H-18), 1.16 (9H, m, H-17), 0.56 (9H, m, H-14),
0.11 (9H, m, H-15). 13C{1H} NMR (125.8 MHz, CDCl3): δC 148.3
3
3
3
(1H, d, JHH = 7.2 Hz, H-8), 7.90 (1H, dd, JHH = 7.2 Hz, JHP = 2.2
Hz, H-2), 7.66 (1H, d, 3JHH = 7.1 Hz, H-8′), 7.61 (1H, dd, 3JHH = 7.2
3
3
3
Hz, JHP = 3.1 Hz, H-2′), 7.54 (1H, dd, JHH = 7.3 Hz, JHP = 3.0 Hz,
H-21), 7.51 (1H, d, 3JHH = 7.5 Hz, H-20), 7.40 (1H, pseudo dd, 3JHH
=
1
7.5 Hz, H-22), 7.22−7.15 (2H, m, H-20′,21′), 7.05−6.99 (2H, m, H-
(s, qC-6), 145.7 (d, JCP = 57.6 Hz, qC-1), 145.2 (s, qC-4), 143.2 (s,
3′,7′), 6.96 (1H, d, 3JHH = 7.2 Hz, H-3), 6.79 (1H, d, 3JHH = 7.2 Hz, H-
C-2), 143.0−142.8 (m, qC-10), 140.0−139.8 (m, qC-5), 133.2 (s, C-
8), 131.8−131.5 (m, qC-9), 120.2 (s, C-3), 118.2 (s, C-7), 30.2 (s, C-
11/12), 29.9 (s, C-11/12), 27.1−26.8 (m, C-16), 25.6−25.4 (m, C-
13), 21.0−20.8 (m, C-18), 20.0−19.9 (m, C-17), 19.8−19.7 (m, C-
15), 19.6−19.5 (m, C-14). 31P NMR (202.5 MHz, CDCl3): δP −19.1
(s). Infrared data (KBr disc, cm−1): ν = 3024w (νAr−H), 2922vs, 2864vs
(νC−H), 1604s, 1587s, 1461s, 1320s. Raman data (glass capillary,
cm−1): ν = 3059m (νAr−H), 2926vs (νC−H), 2870s (νC−H), 1321vs,
579s. Elemental Anal. Calcd for C54H66P3Sb: C, 69.76; H, 7.15. Found:
C, 69.63; H, 7.27. HRMS (APCI+): m/z (%) calcd for C54H67P3Sb
929.3488, found 929.3496 (12) [M + H+]; calcd for C36H44P2Sb
659.1951, found 659.1956 (100) [M − iPr2P-Ace].
(iPr2P-Ace)3Bi (4). To a cooled (−78 °C) rapidly stirring stirred
solution of 1 (1.00 g, 2.86 mmol) in diethyl ether (25 mL) was added
dropwise over 30 min n-butyllithium (1.2 mL, 2.5 M in hexanes, 2.95
mmol). The resulting yellow suspension was stirred for 3 h at this
temperature. A cooled (−78 °C) suspension of BiCl3 (296 mg, 0.94
mmol) in diethyl ether (30 mL) was prepared and stirred rapidly. The
first suspension was added via cannula to the BiCl3 with the mixture
being stirred for 1.5 h at this temperature. The reaction mixture was
allowed to warm to ambient temperature overnight, resulting in a
3
7), 3.08−2.85 (8H, m, H-11,11′,12,12′), 2.51 (1H, h, JHH = 7.0 Hz,
H-13), 1.95 (1H, h, 3JHH = 6.8 Hz, H-13′), 2.16 (1H, br s, H-16), 1.84
(1H, h, 3JHH = 6.7 Hz, H-16′), 1.56 (3H, dd, 3JHP = 12.6 Hz, 3JHH = 7.2
Hz, 1 × CH3), 1.50 (3H, dd, 3JHP = 11.5 Hz, 3JHH = 6.9 Hz, 1 × CH3),
1.13−1.04 (6H, m, 2 × CH3), 0.61 (3H, dd, 3JHP = 15.7 Hz, 3JHH = 6.6
Hz, 1 × CH3), 0.35 (3H, dd, 3JHP = 13.2 Hz, 3JHH = 6.8 Hz, 1 × CH3),
3
3
0.22 (3H, JHP = 13.5 Hz, JHH = 6.7 Hz, 1 × CH3). 13C{1H} NMR
(75.5 MHz, d8-toluene, 298 K): no signals were observed due to
extreme broadening. 13C{1H} NMR (75.5 MHz, d8-toluene, 223 K):
low solubility prevented acquisition of the spectrum. 31P{1H} NMR
(162.0 MHz, d8-toluene, 293 K): δP −11.6 (s), −14.4 (s). 31P{1H}
NMR (162.0 MHz, d8-toluene, 223 K): δP −13.2 (d, 8tsJPP = 11.5 Hz),
8ts
−16.9 (d,
J
= 11.5 Hz). 31P{1H} NMR (162.0 MHz, d8-toluene,
PP
373 K): δP −10.5 (s). Infrared data (KBr disc, cm−1): ν = 3064w
(νAr−H), 2947vs (νC−H), 1872m, 1460s, 1319s, 840s, 736s. Raman data
(glass capillary, cm−1): ν = 3066m (νAr−H), 2948s (νC−H), 1607s,
1564s, 1445s, 1322vs, 582s. Elemental Anal. Calcd (%) for
C42H49P2As·1/2CH2Cl2: C, 69.62; H, 6.87. Found: C, 69.61; H, 6.62.
HRMS (APCI+): m/z (%) calcd for C42H50P2As 691.2598, found
691.2604 (10) [M + H+]; calcd for C36H44P2As 613.2129, found
H
DOI: 10.1021/acs.inorgchem.6b01079
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
613.2127 (55) [M − Ph]; calcd for C18H22PAs 421.1066, found
421.1060 (100) [M − iPr2P-Ace].
ACKNOWLEDGMENTS
■
This work was financially supported by the EPSRC and COST
actions CM0802 PhoSciNet and SM1302 SIPs. The authors
thank the University of St Andrews NMR Service and the
EPSRC UK National Mass Spectrometry Facility at Swansea
University (NMSF).
(iPr2P-Ace)2SbPh (6). Compound 6 was prepared using the same
procedure as per compound 5 using 1 (1.00 g, 2.90 mmol) in diethyl
ether (30 mL), n-butyllithium (1.1 mL, 2.5 M in hexanes, 2.90 mmol),
dichlorophenylstibine (390 mg, 1.45 mmol) in diethyl ether (20 mL),
additional diethyl ether (25 mL), and degassed water (10 mL), giving
a yellow powder (1.63 g, 77%) (mp 165−167 °C). Crystals suitable for
X-ray diffraction work were grown from toluene under ambient
conditions. 1H NMR (500.1 MHz, d8-toluene, 298 K): δH 8.02 (1H, d,
REFERENCES
■
(1) Broda, H.; Hinrichsen, S.; Tuczek, F. Coord. Chem. Rev. 2013,
257, 587.
(2) Pascariu, A.; Iliescu, S.; Popa, A.; Ilia, G. J. Organomet. Chem.
2009, 694, 3982.
(3) Hewertson, W.; Watson, H. R. J. Chem. Soc. 1962, 1490.
(4) Hartley, J. G.; Venanzi, L. M.; Goodall, D. C. J. Chem. Soc. 1963,
3930.
(5) Kyba, E. P.; Hudson, C. W.; McPhaul, M. J.; John, A. M. J. Am.
Chem. Soc. 1977, 99, 8053.
(6) Jana, B.; Hovey, M.; Ellern, A.; Pestovsky, O.; Sadow, A. D.;
Bakac, A. Dalton Trans. 2012, 41, 12781.
(7) Barney, A. A.; Fanwick, P. E.; Kubiak, C. P. Organometallics 1997,
16, 1793.
(8) Ray, M. J.; Randall, R. A. M.; Athukorala Arachchige, K. S.;
3
3
3JHH = 7.0 Hz), 7.86−7.78 (m), 7.56 (dd, JHH = 7.1 Hz, JHP = 3.5
Hz), 7.20−7.06 (m), 6.75 (br s), 7.02 (br s), 6.99 (br s), 6.83 (br s),
2.99 (br s, H-11,12), 2.13−2.06 (m), 2.16 (br s), 2.08−1.88 (m),
1.59−0.08 (12H, v. br s, 8 × CH3). 1H NMR (400.1 MHz, d8-toluene,
223 K): δH 8.16 (br s), 7.56 (br s), 7.47 (br s), 7.28−6.87 (br m),
3.06−2.77 (br s, H-11,12), 2.24−2.07 (br s, H-13), 2.00−1.82 (br s,
H-13), 1.47 (3H, dd, 3JHP = 14.7 Hz, 3JHH = 7.1 Hz, 1 × CH3), 1.37−
0.99 (6H, m, 2 × CH3), 0.73 (3H, dd, 3JHP = 15.6 Hz, 3JHH = 6.9 Hz, 1
× CH3), 0.53 (3H, dd, 3JHP3 = 14.0 Hz, 3JHH = 6.9 Hz, 1 × CH3), 0.20
3
(3H, dd, JHP = 14.1 Hz, JHH = 7.1 Hz, 1 × CH3). 13C{1H} NMR
(75.5 MHz, d8-toluene, 298 K): no signals were observed due to
extreme broadening. 13C{1H} NMR (75.5 MHz, d8-toluene, 223 K):
low solubility prevented acquisition of the spectrum. 31P{1H} NMR
(162.0 MHz, d8-toluene, 298 K): δP −17.2 to −22.2 (v. br s). 31P{1H}
NMR (109.4 MHz, d8-toluene, 363 K): δP −17.5 (s). 31P{1H} NMR
́
Slawin, A. M. Z.; Buhl, M.; Lebl, T.; Kilian, P. Inorg. Chem. 2013, 52,
̈
4346.
(109.4 MHz, d8-toluene, 223 K): δP −21.2 (d, 8tsJPP = 25.8 Hz), −24.2
(9) Kilian, P.; Slawin, A. M. Z. Dalton Trans. 2007, 3289.
(10) Yamashita, M.; Watanabe, K.; Yamamoto, Y.; Akiba, K. Chem.
Lett. 2001, 1104.
(11) Ritch, J. S.; Julienne, D.; Rybchinski, S. R.; Brockman, K. S.;
Johnson, K. R. D.; Hayes, P. G. Dalton Trans. 2014, 43, 267.
(12) Wawrzyniak, P.; Fuller, A. L.; Slawin, A. M. Z.; Kilian, P. Inorg.
Chem. 2009, 48, 2500.
8ts
(d,
J
= 25.8 Hz). Infrared data (KBr disc, cm−1): ν = 3057m
PP
(νAr−H), 2922vs (νC−H), 2824vs (νC−H), 1601s, 1461s, 1247s, 844s.
Raman data (glass capillary, cm−1): ν = 3049m (νAr−H), 2928m
(νC−H), 2858m (νC−H), 1603m, 1328vs. Elemental Anal. Calcd (%) for
C42H49P2Sb: C, 68.40; H, 6.70. Found: C, 68.35; H, 6.76. HRMS
(APCI+): m/z (%) calcd for C42H50P2Sb 737.2420, found 737.2415
(65) [M + H+]; calcd for C36H44P2Sb 659.1956, found 659.1945 (100)
[M − Ph].
(13) Adams, E.; Jeter, D.; Cordes, A. W.; Kolis, J. W. Inorg. Chem.
1990, 29, 1500.
X-ray Diffraction. The crystallographic details relating to this work
can be found in the Supporting Information. CCDC 1476664−
1476668 contain the crystallographic data for this paper. These data
can be obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif. Multiple data
collections of all samples (2−6) were conducted, with crystals grown
from a variety of solvents. The best quality data sets were used for
refinements. In all but one case (2), solvent was incorporated into the
crystals. Because of the close-to-spherical shape of molecules 2−6, the
incorporation of disordered solvent into the crystals could not be
prevented. Although some of the crystal data sets appear to be of lower
quality upon first inspection, they are sufficient to demonstrate the
connectivity for the purposes of this work.
(14) Herrmann, W. A.; Karsch, H. H. Synthetic Methods of
Organometallic and Inorganic Chemistry Volume 3: Phosphorus, Arsenic,
Antimony and Bismuth; Thieme: New York, 1996; Vol. 3.
(15) Chalmers, B. A.; Buhl, M.; Athukorala Arachchige, K. S.; Slawin,
̈
A. M. Z.; Kilian, P. Chem. - Eur. J. 2015, 21, 7520.
(16) Batsanov, S. S. Inorg. Mater. 2001, 37, 871.
(17) Hierso, J.-C. Chem. Rev. 2014, 114, 4838.
(18) Reed, A. E.; Curtiss, L. A.; Weinhold, F. Chem. Rev. 1988, 88,
899.
(19) Note that empirical dispersion corrections are instrumental for
reaching this good agreement; at the standard B3LYP/6-31G* level,
the P−As bond distances are significantly overestimated (e.g., mean
value of 3.306 A in 2).
(20) Wiberg, K. B. Tetrahedron 1968, 24, 1083.
(21) Nordheider, A.; Hupf, E.; Chalmers, B. A.; Knight, F. R.; Buhl,
M.; Mebs, S.; Chęcinska, L.; Lork, E.; Camacho, P. S.; Ashbrook, S. E.;
́
Athukorala Arachchige, K. S.; Cordes, D. B.; Slawin, A. M. Z.;
Beckmann, J.; Woollins, J. D. Inorg. Chem. 2015, 54, 2435.
(22) Knight, F. R.; Diamond, L. M.; Athukorala Arachchige, K. S.;
Sanz Camacho, P.; Randall, R. A. M.; Ashbrook, S. E.; Buhl, M.;
Slawin, A. M. Z.; Woollins, J. D. Chem. - Eur. J. 2015, 21, 3613.
(23) Armarego, W. L. F.; Chai, C. L. L. Purification of Laboratory
Chemicals, 6th ed.; Elsevier: Burlington, MA, 2009.
ASSOCIATED CONTENT
̈
■
S
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.6b01079.
̈
Further synthetic details, NMR spectra of compounds
2−6, 31P{1H} VT NMR spectra of 5 and 6 (including the
Eyring plot for 5), further X-ray diffraction details,
additional computational details, and coordinates of the
DFT-optimized structures (PDF)
Crystallographic data (CIF)
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: pk7@st-andrews.ac.uk.
Notes
The authors declare no competing financial interest.
I
DOI: 10.1021/acs.inorgchem.6b01079
Inorg. Chem. XXXX, XXX, XXX−XXX