Sterically encumbered tin and phosphorus peri-substituted acenaphthenes

Article abstract of DOI:10.1021/ic5014768

A group of sterically encumbered peri-substituted acenaphthenes have been prepared, containing tin moieties at the 5,6-positions in 1-3 ([Acenap(SnR ₃)₂], Acenap = acenaphthene-5,6-diyl; R₃ = Ph₃ (1), Me₃ (2); [(Acenap)₂(SnMe ₂)₂] (3)) and phosphorus functional groups at the proximal peri-positions in 4 and 5 ([Acenap(PR₂)(PⁱPr ₂)] R₂ = Ph₂ (4), Ph(ⁱPr) (5)). Bis(stannane) structures 1-3 are dominated by repulsive interactions between the bulky tin groups, leading to peri-distances approaching the sum of van der Waals radii. Conversely, the quasi-linear C_Ph-P...P three-body fragments found in bis(phosphine) 4 suggest the presence of a lp(P)-σ*(P-C) donor-acceptor 3c-4e type interaction, supported by a notably short intramolecular P...P distance and notably large J _PP through-space coupling (180 Hz). Severely strained bis(sulfides) 4-S and 5-S, experiencing pronounced in-plane and out-of-plane displacements of the exocyclic peri-bonds, have also been isolated following treatment of 4 and 5 with sulfur. The resulting nonbonded intramolecular P...P distances, ～4.05 A and ～12% longer than twice the van der Waals radii of P (3.60 A), are among the largest ever reported peri-separations, independent of the heteroatoms involved, and comparable to the distance found in 1 containing the larger Sn atoms (4.07 A). In addition we report two metal complexes with square planar [(4)PtCl₂] (4-Pt) and octahedral cis-[(4)Mo(CO)₄] (4-Mo) geometries. In both complexes the bis(phosphine) backbone is distorted, but notably less so than in bis(sulfide) 4-S. All compounds were fully characterized, and except for bis(phosphine) 5, crystal structures were determined.

Full text of DOI:10.1021/ic5014768

Article
pubs.acs.org/IC
Sterically Encumbered Tin and Phosphorus peri-Substituted
Acenaphthenes
Brian A. Chalmers, Kasun S. Athukorala Arachchige, Joanna K. D. Prentis, Fergus R. Knight, Petr Kilian,*
Alexandra M. Z. Slawin, and J. Derek Woollins*
EaStCHEM, School of Chemistry, University of St. Andrews, St. Andrews, Fife, KY16 9ST United Kingdom
*
S Supporting Information
ABSTRACT: A group of sterically encumbered peri-sub-
stituted acenaphthenes have been prepared, containing tin
moieties at the 5,6-positions in 1−3 ([Acenap(SnR ) ],
3
2
Acenap = acenaphthene-5,6-diyl; R = Ph (1), Me (2);
3
3
3
[
(Acenap) (SnMe ) ] (3)) and phosphorus functional groups
2 2 2
at the proximal peri-positions in 4 and 5 ([Acenap(PR )-
(
2
i
i
P Pr )] R = Ph (4), Ph( Pr) (5)). Bis(stannane) structures
2 2 2
1
−3 are dominated by repulsive interactions between the
bulky tin groups, leading to peri-distances approaching the sum
of van der Waals radii. Conversely, the quasi-linear C -P···P
Ph
three-body fragments found in bis(phosphine) 4 suggest the
presence of a lp(P)−σ*(P−C) donor−acceptor 3c-4e type
interaction, supported by a notably short intramolecular P···P distance and notably large J through-space coupling (180 Hz).
PP
Severely strained bis(sulfides) 4-S and 5-S, experiencing pronounced in-plane and out-of-plane displacements of the exocyclic
peri-bonds, have also been isolated following treatment of 4 and 5 with sulfur. The resulting nonbonded intramolecular P···P
distances, ∼4.05 Å and ∼12% longer than twice the van der Waals radii of P (3.60 Å), are among the largest ever reported peri-
separations, independent of the heteroatoms involved, and comparable to the distance found in 1 containing the larger Sn atoms
(
4.07 Å). In addition we report two metal complexes with square planar [(4)PtCl ] (4-Pt) and octahedral cis-[(4)Mo(CO) ] (4-
2
4
Mo) geometries. In both complexes the bis(phosphine) backbone is distorted, but notably less so than in bis(sulfide) 4-S. All
compounds were fully characterized, and except for bis(phosphine) 5, crystal structures were determined.
2
,8,9,11
INTRODUCTION
prepared (for example E−H).
In these compounds, P···P
■
separations are remarkably 6−13% longer than the sum of van
der Waals radii and can be explained by the increased crowding
of the bay-region by the introduction of bulky chalcogen atoms
in A−C and the severe Coulombic repulsion experienced by7
the closely aligned positively charged phosphorus centers in D.
The series of 1,8-bis(trimethylelement)naphthalenes F−H
represents a set of equally strained molecules, and in spite of
The capability for naphthalene and related polycyclic aromatic
hydrocarbons to accommodate atoms or groups larger than
hydrogen at the proximal peri-positions, at distances well within
the sum of their van der Waals radii, stems from their ability to
minimize steric strain, and thus achieve a relaxed geometry, by
either distorting the usually rigid carbon framework or by
4
−6
1
,2
forming a direct bond between the peri-substituents.
having larger heteroatoms at the proximal peri-positions [r
vdW
Naturally, when larger atoms are constrained in this cramped
environment they suffer greater steric hindrance as a result of
increased repulsive nonbonding interactions between over-
lapping orbitals, leading to greater deformation of the organic
12
(
Sn) 2.17 Å, (Ge) 2.11 Å; (Si) 2.10 Å; cf. (P) 1.80 Å] these
molecules display marginally shorter nonbonded distances than
9
A−D. With all three compounds adopting the same
1
−3
conformation in the solid, bis(stannane) derivative F
incorporating the larger congener unsurprisingly exhibits the
largest peri-separation [3.864 Å], with shorter but comparable
backbone and subsequently longer peri-distances.
The
number, size, and nature of the functional groups bound to
the peri-atoms, and the type of organic backbone employed,
however, can also determine the degree of strain present in
these systems, and impose large separations between the closely
aligned peri-atoms. This is aptly demonstrated by comparing
the compounds of Figure 1, the only peri-substituted systems
reported up until now with separations larger than 3.8 Å.
Interestingly, the largest separation is found between
phosphorus atoms in tris(sulfide) A [4.072(3) Å],
distances observed for the lighter elements of the group [G
9
3
.809 Å; H 3.803 Å]. In each case, the separation represents a
distance ∼10% shorter than the sum of van der Waals radii. In
contrast, the corresponding C···C separation in 1,3,6,8-tetra-
tert-butylnaphthalene I is 14% longer than twice the van der
4
−11
12
Waals radius of C (3.4 Å) and at 3.861 Å is comparable to the
4
,11
with
5
−7,11
similar values observed for bis(phosphorus) B−D,
compounds with much larger peri-heteroatoms having been
despite
Received: June 20, 2014
Published: July 31, 2014
©
2014 American Chemical Society
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Inorganic Chemistry
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Figure 1. Severely strained peri-substituted systems incorporating nonbonded distances greater than 3.8 Å. −10
4
9
,10
Sn···Sn distance observed in bis(stannane) F.
This is
donation from the chalcogen moiety notably shortening the
attributed to the differing alignment of the two peri-substituted
tert-butyl groups rather than the presence of additional groups
intramolecular B···E distance and subsequently reducing the
19
electron deficiency of the boron center. The effects of steric
repulsion are similarly reduced by employing a second rigid
organic backbone, which imposes additional geometric
constraints on the molecule and adds extra stabilization by
incorporating the peri-atoms into a central heterocyclic ring
10
in the 3 and 6 positions.
The extent of repulsion operating in the bay-region between
peri-functionalities is thus dictated by a number of structural
factors, all of which combine to determine the degree of
molecular distortion required to relieve the buildup of steric
strain and achieve a minimum energy geometry. Under
certain geometric conditions, however, attractive noncovalent
intramolecular interactions, involving lone-pair orbitals, are
known to counterbalance the repulsion between heavier
congeners in sterically crowded systems and thus play an
20−22
system.
This is illustrated by the notable reduction in peri-
1
,2
distance by 0.3−0.4 Å for cyclic 1,8-naphthalenediyl com-
2
1,22
pounds N and O (Figure 2)
compared to the
corresponding distances in strained 1,8-bis(trimethylelement)-
9
naphthalenes F−H (Figure 1). Furthermore, the aforemen-
tioned proximity of the peri-atoms in peri-substituted systems
2
,13−16
allows compounds with a stabilizing bridging geometry to be
important role in controlling their fine structures.
For
2
3,24
17
formed (for example P, Q; Figure 2)
and specifically
example, in bis(telluride) J and tin−phosphorus derivative
1
8
bidentate coordination to a metal center to create a chelate ring
K, the delocalization of a lone-pair to an antibonding σ*(E−
C) orbital, forms a donor−acceptor three-center four-electron
2
5,26
(
for example R).
In the present study, we explore the relationship between
(
3c-4e) type interaction, leading to peri-distances significantly
attraction and repulsion occurring within sub-van der Waals
distances in a number of sterically restricted peri-substituted
systems. Herein we report the synthesis and structural study of
severely strained acenaphthenes 1−3 incorporating bulky tin−
tin moieties in the proximal positions ([Acenap(SnR ) ]
shorter than the sum of van der Waals radii (J 3.3674(19) Å,
1
2,17,18
∑
rvdW 4.12 Å; K 2.815(3) Å, ∑r
3.97 Å; Figure 2).
vdW
Similar lp(E) → p(B) donor−acceptor interactions are
observed in boron−chalcogen systems of type L and to a
lesser extent in their cationic derivatives M, with electron
3
2
Acenap = acenaphthene-5,6-diyl; R = Ph (1), Me (2);
3
3
3
27
[
(Acenap) (SnMe ) ] (3)) and compare the degree of
2 2 2
repulsion in these systems to heteroleptic bis(phosphines) 4
i
i
and 5 ([Acenap(PR )(P Pr )] R = Ph (4), Ph( Pr) (5)), their
2
2
2
2
respective strained bis(sulfide) derivatives 4-S and 5-S
i
i
(
(
[Acenap(P(S)R )(P(S) Pr )] R = Ph (4-S), Ph( Pr)
5-S)) and metal complexes [(4)PtCl ] (4-Pt) and cis-
2
2
2
2
2
[
(4)Mo(CO) ] (4-Mo) (Figure 3).
4
RESULTS AND DISCUSSION
■
(
Bis(acenaphth-5,6-yl)trialkyltin derivatives 1−3: Bis-
stannanes) [Acenap(SnR ) ] 1−3 were prepared following a
3
2
procedure similar to that used previously in the preparation of
1
7
comparable bis(chalcogen) systems. For their synthesis, the
N,N,N′,N′-tetramethyl-1,2-ethanediamine (TMEDA) complex
of 5,6-dilithioacenaphthene was treated with 2 equiv of the
respective triorganotin chloride [Ph SnCl, Me SnCl,
3
3
Me SnCl ] to afford [Acenap(SnPh ) ] (1), [Acenap(SnMe ) ]
Figure 2. Stabilization of large heteroatoms and groups in peri-
2
2
3 2
3 2
substituted systems via weak attractive interactions, additional rigid
(2), and [(Acenap) (SnMe ) ] (3) in moderate to good yield
2 2 2
17−19,21−26
backbone, bridging geometries, and metal complexation.
[48 (1), 65 (2), 60% (3); Scheme 1]. All three compounds
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observed for both derivatives (1 31 Hz; 2 37 Hz) suggest only a
limited through-space component contributes to the overall
4
JSnSn coupling in these systems. This is in line with the notably
large Sn···Sn peri-separations observed in the solid in each case
(
vide infra), and comparable to previously reported
4
119
117
J( Sn, Sn) values for Me Sn(CH ) SnMe (34.4 Hz) and
cyclic 1,1,5,5-tetramethyl-1,5-distannacyclooctane (30.3 Hz).
3
2 3
3
28
As expected, the δ119Sn for the cyclic derivative 3 (−60.3 ppm)
lies between the values for 1 and 2, shifted upfield from the
trimethyltin derivative following the replacement of two methyl
groups with the less electron-donating bridging acenaphthene
fragment. The greater restriction imposed on the geometry of
the peri-region in 3 by the presence of two rigid acenaphthene
backbones results in a notably shorter peri-separation than
observed in 1 and 2 (vide infra), with transannular Sn···Sn
1
19
117
interaction leading to a minor increase in J( Sn, Sn)
coupling (65 Hz) due to the presence of a small through-
space coupling component.
Single crystals suitable for X-ray work were obtained for 1 by
diffusion of hexane into a saturated solution of the compound
in dichloromethane and for 2 and 3 by recrystallization from
THF and chloroform solutions of the respective compounds at
−
30 °C. All three compounds crystallize with one molecule in
the asymmetric unit. Selected interatomic bond lengths and
angles are listed in Table 2. Further crystallographic
information is listed in the Supporting Information (SI).
Table 2. Selected interatomic distances [Å] and angles [°]
for Acenap[SnR ] compounds 1−3
Figure 3. Sterically crowded bis(stannanes) 1−3, bis(phosphines) 4
and 5, strained bis(sulfides) 4-S and 5-S, metal complexes 4-Pt and 4-
Mo and bromine−phosphorus precursors 6 and 7.
3
2
16
compd
1
2
3
SnR3
SnPh3
SnMe3
SnMe2
Scheme 1. Preparation of 5,6-Bis(trialkyltin)acenaphthenes
peri-Region-Distances
a
1−3 via 5,6-Dilithioacenaphthene−TMEDA Complex
Sn(1)···Sn(2)
4.0659(9)
0.274
3.9693(6)
0.371
3.6574(6)
0.683
a
∑
rvdW - Sn···Sn
a
%
∑rvdW
94
91
84
Sn(1)−C(1)
Sn(2)−C(9)
2.165(3)
2.164(4)
2.163(3)
2.160(4)
2.164(5)
2.161(6)
peri-Region Bond Angles
Sn(1)−C(1)−C(10)
C(1)−C(10)−C(9)
Sn(2)−C(9)−C(10)
128.8(2)
129.5(3)
128.5(2)
386.8(4)
26.8
127.6(2)
129.5(3)
127.5(3)
384.6(5)
24.6
123.6(4)
127.1(5)
123.1(3)
373.8(7)
13.8
∑
of bay angles
a
b
Conditions: (i) Ph SnCl (1); Me SnCl (2); Me SnCl (2 equiv) (3);
splay angle
3
3
2
2
Et O, −10 °C, 1 h.
C(4)−C(5)−C(6)
Out-of-Plane Displacement
Sn(1)
111.1(3)
111.2(3)
111.4(5)
2
−1.045(1)
0.725(1)
1.023(1)
0.962(1)
were characterized by multinuclear magnetic resonance spec-
troscopy and mass spectrometry, and the homogeneity of the
new compounds was confirmed by microanalysis. 119Sn NMR
spectroscopic data for the series is displayed in Table 1.
Sn(2)
−0.735(1)
−0.845(1)
Central Naphthalene Ring Torsion Angles
C:(6)−(5)−(10)−(1)
C:(4)−(5)−(10)−(9)
−174.3(3)
−175.7(3)
173.3(4)
175.6(4)
−175.2(5)
The 1 Sn{ H} NMR spectra for bis(stannanes) 1−3 display
19
1
−176.5(5)
a
b
1
19
117
van der Waals radii used for calculations: rvdW(Sn) 2.17 Å; Splay
angle: ∑ of the three bay-region angles −360.
single peaks with satellites attributed to Sn− Sn coupling.
The NMR signal for triphenyltin derivative 1 (−120.8 ppm) is
shifted notably upfield compared to the trimethyltin analogue 2
1
19
117
(−24.3 ppm), and the relatively small J( Sn, Sn) values
Table 1. 31P and 119Sn NMR Spectroscopy Dataa
1
2
3
4
5
4-S
5-S
4-Pt
4-Mo
119Sn
−120.8
31
−24.3
37
−60.3
65
31
P{ H}
JPP
1
−11.3, −12.8
180
−9.7, −13.4
160
82.0, 48.6
0
79.6, 56.8
0
13.4, −2.3
26
43.1, 34.5
34
JSnSn
a
All spectra were run in CDCl ; δ (ppm), J (Hz).
3
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Figure 4. Thermal ellipsoid plots (40% probability) of bis(stannanes) 1 and 2 (H atoms omitted for clarity).
1
2
The double substitution of extremely bulky tin moieties at
the peri-positions in 1 and 2 unsurprisingly causes substantial
repulsion and a buildup of steric pressure between the two
closely located tin centers as a result of occupied orbital
overlap. In order to accommodate such large atoms or groups,
severe deformation of the acenaphthene carbon framework is
required, with in-plane and out-of-plane distortions and
buckling of the aromatic ring system (angular strain) necessary
to help partially alleviate steric strain. In both compounds,
considerable distortion of the exocyclic CAcenap−Sn bonds
within the bay-region is evident from exceptionally large
positive splay angles, with the divergence of the peri-bonds
greater for the bulkier triphenyltin derivative [1 26.8°]
compared to the smaller trimethyltin analogue [2 24.6°]
Waals radii of Sn [4.34 Å] and statistically of equal magnitude
to the largest peri-separation previously reported for a geminally
bis(peri-substituted) tridentate phosphine tris(sulfide) (Figure
4
1 A; 4.072(3) Å). It is interesting to note that the Sn···Sn
distance in 2 is only marginally longer than the peri-separation
reported for the naphthalene analogue [3.864 Å].
Strained bis(stannanes) 1 and 2 adopt conformations similar
to those of corresponding 1,8-bis(trimethylelement)-
naphthalenes G (Ge) and F (Sn) (Figure 1), with the R Sn
groups aligning in each case such that a pair of Sn−C bonds,
one from each Sn center (Sn1−C3 and Sn2−C37 in 1; Sn1−
C14 and Sn2−C17 in 2; Figure 6), aligns roughly perpendicular
9
9
3
(
Figure 4).
Further deformation of the bay geometry is achieved in both
cases by substantial displacement of the two peri-tin atoms to
opposite sides of their respective mean acenaphthene planes by
∼1 Å (Figure 5). In addition to the distortions within the bay-
Figure 6. Thermal ellipsoid plots (40% probability) of bis(stannanes)
1
and 2 showing the (R ) Sn group conformations (phenyl rings in 1
3 3
are shown in wireframe, and H atoms are omitted in both cases for
clarity).
to the mean acenaphthene plane (Figure 6). The severe out-of-
plane displacement experienced by the two Sn atoms in both 1
and 2 results in the two perpendicular alkyl groups being in
close proximity, in contrast to the distal arrangement of the
9
,10
groups in the carbon analogue of 2.
Along with
corresponding R Sn group conformations, 1 and 2 also exhibit
Figure 5. Thermal ellipsoid plots (40% probability) showing the
degree of out-of-plane distortion in bis(stannanes) 1 and 2 (phenyl
rings in 1 are shown in wireframe, and H atoms are omitted in both
cases for clarity).
3
comparable geometries around each tin center, which are best
described as distorted tetrahedral; C−Sn−C angles lie in the
range 99.64(14)−120.86(15)° and for each tin center average
to ∼109° (Table 3).
region, both acenaphthene skeletons are notably twisted,
resulting in central C−C−C−C torsion angles deviating from
planarity by up to 7°. Consequently, exceptionally long
nonbonded intramolecular Sn···Sn peri-distances are observed
in both compounds, with a marginal lengthening of the peri-gap
for the bulkier triphenyltin moiety 1 [4.0659(9) Å] compared
to the trimethyltin analogue 2 [3.9693(6) Å]. The distance of
the former is only 6% shorter than twice the sum of van der
In contrast to bis(stannane) “monomers” 1 and 2, formed
from the reaction of the 5,6-dilithioacenaphthene−TMEDA
complex with organotin monochlorides (Ph SnCl, Me SnCl),
3
3
treatment of the intermediate with organotin dichloride
Me SnCl affords a “dimeric” compound 3 in which two
2
2
dimethyltin groups are linked by two acenaphthene-5,6-diyl
ligands to form an 8-membered dimetallacycle (Figure 7). As a
consequence of the C symmetry (crystallizing in the triclinic P1
̅
i
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Table 3. Bond Angles [deg] Categorizing the Geometry around Sn in 1−3
1
2
3
1
C(1)−Sn(1)−C(13)
C(1)−Sn(1)−C(19)
C(1)−Sn(1)−C(25)
107.87(12)
106.69(13)
119.43(15)
107.31(14)
99.64(14)
C(1)−Sn(1)−C(13)
C(1)−Sn(1)−C(14)
C(1)−Sn(1)−C(15)
104.87(16)
120.04(17)
107.74(15)
103.4(2)
C(1)−Sn(1)−C(9 )
131.21(19)
C(1)−Sn(1)−C(13)
C(1)−Sn(1)−C(14)
C(9 )−Sn(1)−C(13)
C(9 )−Sn(1)−C(14)
C(13)−Sn(1)−C(14)
102.8(2)
103.28(17)
104.03(19)
102.3(2)
1
C(13)−Sn(1)−C(19)
C(13)−Sn(1)−C(25)
C(19)−Sn(1)−C(25)
C(9)−Sn(2)−C(31)
C(9)−Sn(2)−C(37)
C(9)−Sn(2)−C(43)
C(31)−Sn(2)−C(37)
C(31)−Sn(2)−C(43)
C(37)−Sn(2)−C(43)
C(13)−Sn(1)−C(14)
C(13)−Sn(1)−C(15)
C(14)−Sn(1)−C(15)
C(9)−Sn(2)−C(16)
C(9)−Sn(2)−C(17)
C(9)−Sn(2)−C(18)
C(16)−Sn(2)−C(17)
C(16)−Sn(2)−C(18)
C(17)−Sn(2)−C(18)
1
106.9(2)
114.93(13)
108.84(13)
120.86(15)
104.31(13)
115.51(14)
104.97(15)
99.98(13)
112.77(17)
108.10(16)
115.61(17)
104.84(16)
116.35(18)
105.0(2)
113.4(2)
105.75(19)
1
resonance in the H NMR spectrum of 3, however, suggests a
ring-inversion process takes place in solution, as predicted for
21
the naphthalene analogue. Similar to 1 and 2, the single tin
environment in 3 exhibits distorted tetrahedral geometry,
although with more obtuse C−Sn−C angles in the range
1
02.3(2)−131.21(19)°, which average to 110°.
The geometrical constraints present in the structure of 3
imposed by the two rigid acenaphthene backbones fix the
dimethyltin moieties in close proximity. The reduced freedom
of the now cyclic CAcenap−Sn peri−bonds results in a marked
decrease in in-plane distortion compared with trimethyltin
derivative 2, with the splay angle notably compressed from
2
4.6° (2) to 13.8° (3) as the tin centers are held more closely
together. Further reduction in the distortion of the
acenaphthene geometry upon cyclization in 3 is evident from
reduced C−C−C−C central torsion angles (∼5°) which
indicate an increase in the planarity of the carbon skeleton.
Nevertheless, the degree of out-of-plane displacement in 3 is
consistent with that of its monomeric analogue, with the two
tin atoms displaced to opposite sides of each acenaphthene
mean plane by up to 1 Å (Figure 7). The significant reduction
in in-plane distortion upon cyclization of 3 indicates that the
peri-atoms are fixed more closely together than in the
corresponding monomer, and indeed the nonbonded trans-
annular Sn···Sn peri-separation across the distannacycle
[3.6374(6) Å] is notably shorter than the equivalent distance
in 2 [3.9693(6) Å], although slightly longer than in the
Figure 7. Thermal ellipsoid plots (40% probability) of cyclic
bis(stannane) 3 (H atoms are omitted for clarity).
space group) only one crystallographically independent
acenaphthene fragment exists within the asymmetric unit, and
similarly only a single crystallographically unique tin environ-
ment is present.
In the crystal, 3 adopts a conformation similar to that of its
21
naphthalene analogue, aligning the two acenaphthene carbon
skeletons on the same plane and displacing the bridging
dimethyltin groups to opposite sides of the molecule. As a
result, the central 8-membered distannacycle is forced to adopt
21
naphthalene analogue [3.56 Å].
Bis(phosphines) 4 and 5 and Their Bis(sulfides) 4-S
i
i
and 5-S: Heteroleptic bis(phosphines) [Acenap(PR )(P Pr )]
2
2
a chairlike arrangement with two methyl groups (C13/C13 )
i
4 and 5 were prepared through stepwise halogen−lithium
occupying equatorial positions and two (C14/C14 ) located
exchange reactions of previously reported 5-(bromo)-6-
axially (Figure 8). The presence of a single methyl group
i
(
(
diisopropylphosphino)acenaphthene [Acenap(Br)(P Pr )]
2
16
6) and novel 5-(bromo)-6-(isopropylphenylphosphino)-
acenaphthene [Acenap(Br)(PPh Pr)] (7), respectively. 7 was
i
synthesized following standard literature procedure in moderate
29
yield (40%), starting from 5,6-dibromoacenaphthene and
i
ClP(Ph) Pr; the synthesis of the latter is omitted from this
manuscript but is included in the SI for completeness. Crystals
of 6 and 7 suitable for X-ray crystallography were grown from
ethanol; the structures of 6 and 7 are shown in Figure 9, and
selected bond lengths and angles are given in Table S4 (in the
SI).
For the synthesis of 4 and 5, the two bromine precursors 6
and 7 were independently treated with a single equivalent of n-
butyllithium in diethyl ether under an oxygen and moisture-free
nitrogen atmosphere, at −78 °C. Without isolation, addition of
Figure 8. Thermal ellipsoid plot (40% probability) showing the chair
conformation of the 8-membered distannacycle in 3 (H atoms are
omitted for clarity).
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3
1
1
The P{ H} NMR spectra of bis(phosphines) 4 (δ = −11.3
A
ppm, δ = −12.8 ppm, J = 180 Hz) and 5 (δ = −9.7 ppm, δ
B
AB
A
B
=
−13.4 ppm, J = 160 Hz) reveal expected pseudoquartets
AB
associated with typical AB spin systems, both of which correlate
well with simulated coupling patterns (Figures S1 and S5, in the
SI). The relatively large JPP coupling present in both systems (4
1
80 Hz, 5 160 Hz) is indicative of a considerable through-space
interaction through the phosphorus lone-pairs, which is notably
absent in bis(sulfides) 4-S and 5-S following oxidation of the
III
V
phosphorus centers from P to P (Figures S2 and S6, in the
31
1
SI). In the P NMR ( H coupled) spectra of both compounds
additional splitting from the hydrogens of the isopropyl groups
i
is observed, with the signal for P (P Pr ) now appearing as a
A
2
Figure 9. Thermal ellipsoid plots (40% probability) of [Acenap(Br)-
i
i
doublet of doublets of septets in both 4 (δ = −11.3 ppm, J =
PP
2 3
P
(
P Pr )] (6) (left) and [Acenap(Br)(PPh Pr)] (7) (right) (H atoms
2
1
80 Hz, J = 24.5 Hz, J = 11.8 Hz) and 5 (δ = −9.7 ppm,
are omitted for clarity).
PH
PH
P
2 3
JPP = 160 Hz, J = 25.4 Hz, J = 12.8 Hz) and the
PH
PH
i
i
resonance for P (PPh Pr) in 5 displaying as a broad doublet.
B
the respective chlorophosphine [ClPPh , ClP Pr ] at the same
2
2
Yellow crystals of 4 suitable for X-ray crystallography were
obtained from a saturated solution of the compound in
acetonitrile at −30 °C, while recrystallization by diffusion of
hexane into saturated solutions of the respective compound in
dichloromethane afforded colorless blocks of 4-S and 5-S. All
three compounds crystallize with one molecule in the
asymmetric unit. Selected interatomic bond lengths and angles
are listed in Table 4. Further crystallographic information can
be found in the SI. Growing crystals of 5 was attempted using
various techniques but was unsuccessful.
reaction temperature subsequently afforded [Acenap(PPh )-
2
i
i
i
(
P Pr )] (4) and [Acenap(PPh Pr)(P Pr )] (5) in good yields
2
2
[
87 (4), 78% (5), Scheme 2]. Further treatment of phosphines
and 5 with 2 equiv of elemental sulfur in refluxing toluene
4
over 3 h afforded the corresponding bis(sulfides) 4-S and 5-S in
good yield [77% (4-S), 85% (5-S), Scheme 2].
Scheme 2. Preparation of Heteroleptic Bis(phosphines)
i
[
Acenap(PR )(P Pr )] 4 and 5 and Their Corresponding
2
2
a
Bis(sulfides) 4-S and 5-S
Within the molecular structure of bis(phosphine) 4, the two
P−C bonds adopt perpendicular (type A) and coplanar (type
Ph
B) alignments with respect to the mean acenaphthene
1
3,17
plane,
with the latter affording a quasi-linear C −P···P
Ph
three-body fragment that has the potential to promote the
delocalization of the phosphorus lone-pair of the P( Pr ) group
i
2
to an antibonding σ*(P−C ) orbital on the opposite side of
a
Ph
Conditions: (i) nBuLi (1 equiv), Et O, −78 °C, 1 h; (ii) ClPPh (4)/
17,18
2
2
i
the peri-gap.
Conveniently, the two isopropyl groups
ClP Pr (5) (1 equiv), Et O, −78 °C, 1 h; then RT (iii) S (2 equiv),
toluene, reflux, 3 h.
2
2
occupy positions on opposite sides of the acenaphthene plane
1
3,30
with an axial-twist configuration (type AC)
that orientates
Table 4. Selected Interatomic Distances [Å] and Angles [deg] for 4, 4-S, 4-Pt, 4-Mo, and 5-S
cmpd
4
4-S
4-Pt
4-Mo
5-S
peri-Region Bond Distances
P(1)···P(2)
3.100(2)
0.500
4.051(2)
−0.451
113
3.213(6)
0.387
3.289(1)
0.311
4.041(1)
−0.441
112
a
∑
rvdW - P···P
a
%
∑rvdW
86
89
91
P(1)−C(1)
P(2)−C(9)
1.851(5)
1.862(4)
1.850(6)
1.849(5)
1.818(14)
1.780(14)
1.836(4)
1.843(4)
1.853(4)
1.828(3)
peri-Region Bond Angles
P(1)−C(1)−C(10)
C(1)−C(10)−C(9)
P(2)−C(9)−C(10)
121.8(3)
128.8(4)
123.7(4)
374.3(8)
14.3
127.4(4)
132.6(5)
127.2(4)
387.2(8)
27.2
124.8(10)
128.5(12)
121.1(10)
374.4(19)
14.4
122.7(3)
130.0(4)
126.0(3)
378.7(6)
17.7
126.3(3)
131.7(3)
126.2(2)
384.2(5)
24.2
∑
of bay angles
b
splay angle
C(4)−C(5)−C(6)
110.8(4)
110.9(5)
110.3(13)
110.1(4)
110.6(3)
Out-of-Plane Displacement
P(1)
P(2)
0.233(1)
0.989(1)
0.453(1)
0.337(2)
1.179(1)
−0.053(1)
−1.206(1)
−0.689(1)
−0.359(2)
−1.218(1)
Central Naphthalene Ring Torsion Angles
C:(6)−(5)−(10)−(1)
C:(4)−(5)−(10)−(9)
178.3(4)
−177.2(4)
−163.3(5)
−167.4(5)
177.7(11)
169.5(11)
175.2(4)
176.5(4)
−164.6(3)
−164.7(3)
a
b
van der Waals radii used for calculations: rvdW(P) 1.80 Å. Splay angle: ∑ of the three bay-region angles −360°.
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Figure 10. Thermal ellipsoid plots (40% probability) of bis(phosphine) 4 showing the conformation of the PR groups and CH···π interaction
2
(
middle) and the degree of out-of-plane distortion (right) (all but one H atoms are omitted for clarity).
Figure 11. Thermal ellipsoid plots (40% probability) of strained bis(sulfides) 4-S and 5-S (H atoms are omitted for clarity).
i
the lone-pair of the P( Pr ) group pointing directly at the
As anticipated, the crystal structures of 4-S and 5-S (Figure
2
opposing phosphorus atom across the bay (Figure 10).
11) are considerably more strained than that of 4, due to the
excessive overcrowding of the bay-region caused by the
increased bulk of the phosphorus moieties upon thionation.
Repulsive forces dominating these systems induce dramatic
buckling of the carbon framework and extreme displacement of
the exocyclic peri-bonds. Maximum C−C−C−C central
acenaphthene torsion angles of ∼17° (cf. 3° for 4) illustrate
the degree to which the rigid organic scaffolds have been
twisted from their naturally planar environment, with the out-
of-plane distortions resulting in displacement of the two
phosphorus atoms in each case by ∼1.2 Å (Figure 12). In the
same vein, splay angles in the bay-region are substantially more
obtuse in 4-S [27.2°] and 5-S [24.2°] than in 4 [14.3°] due to
In conjunction with the notably large J through-space
PP
3
1
1
coupling (180 Hz) observed in the P{ H} NMR spectrum of
4, the notably short intramolecular P···P distance (3.100(2) Å;
14% shorter than twice the van der Waals radius of P) and the
close to linear C −P···P angle of 175.65(1)° provide further
Ph
support for a weakly attractive three-center four-electron (3c-
4e) type interaction operating between the peri-atoms in this
system. Along with the additional stabilization provided by an
intramolecular CH···π interaction between adjacent isopropyl
and phenyl groups [H15B···Cg(25−30) 3.137(1) Å; Figure 10,
Table S5, in the SI], these weakly attractive intramolecular
forces help to counterbalance the steric repulsion of the two
phosphorus atoms and thus reduce the degree of molecular
distortion within the acenaphthene framework. Consequently,
the organic backbone shows only a minor deviation from
planarity with maximum central C−C−C−C torsion angles ca.
the exocyclic P−C
bonds tilting further apart to minimize
Acenap
the steric collisions.
Additional distortion of the carbon skeleton involves
widening of the C1−C10−C9 bay-angle (mean 132° cf. ideal
31
1
1
27°), elongation of the bonds around C10 (average lengths
.45 Å cf. ideal 1.42 Å) and stretching of the central C5−C10
2° and a standard deviation from the mean plane of only 0.02
Å. In addition, P(2) essentially lies on the mean plane with
P(1) experiencing only a minor out-of-plane distortion,
displaced by only 0.2 Å (Figure 10). The most significant
deformation of the acenaphthene geometry occurs within the
plane of the molecule where the exocyclic P−CAcenap bonds
diverge with a splay angle of 14.3°.
bond from 1.39 Å to an average of 1.41 Å, although it is worth
noting that despite the extensive deformations occurring at the
top of the molecule closest to the repulsive interactions, the
presence of the ethylene bridge ensures the bonds around C5
retain their ideal length (average 1.42 Å) and the C4−C5−C6
angle remains at 111°.
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Platinum(II) (4-Pt) and Molybdenum(0) (4-Mo) Com-
plexes of Bis(phosphine) 4: Treatment of bis(phosphine) 4
with PtCl (cod) (cod =1,5-cyclooctadiene) in CH Cl at room
2
2
2
temperature, followed by removal of the volatiles by
evaporation, afforded the monomeric, mononuclear [{Acenap-
i
(
PPh )(P Pr )}{PtCl }] complex 4-Pt as a white solid in
2
2
2
excellent yield (87%; Scheme 3). The corresponding reaction
Scheme 3. Coordination Chemistry of Bis(phosphine) 4:
i
Preparation of [{Acenap(PPh )(P Pr )}{PtCl }] (4-Pt) and
2
2
2
i
a
[
{Acenap(PPh )(P Pr )}{MoCO }] (4-Mo)
2 2 4
Figure 12. Thermal ellipsoid plots (40% probability) of strained
bis(sulfides) 4-S and 5-S illustrating the extent of out-of-plane
distortion and buckling of the acenaphthene framework (H atoms are
i
omitted and Ph and Pr groups are shown in wireframe for clarity).
The overall degree of molecular distortion occurring in 4-S
and 5-S is best quantified by considering the magnitude of the
nonbonded intramolecular P···P distances, which at 4.051(2) Å
a
Conditions: (i) [PtCl (cod)], CH Cl , RT, 12 h; (ii) [(nbd)Mo-
2
2
2
(CO) ], CH Cl , RT, 12 h.
4 2 2
(
4-S) and 4.041(1) Å (5-S) are considerably longer (∼13%)
12
than the sum of van der Waals radii of two P atoms (3.60 Å).
of 4 with [(nbd)Mo(CO) ] (nbd = norbornadiene) under the
same reaction conditions afforded [{Acenap(PPh )(P Pr )}-
{
4
i
These distances are comparable to the distance found in 1
containing the much larger Sn atoms [4.0659(9) Å], and are
among the largest ever reported peri-separations, independent
2
2
Mo(CO) }] 4-Mo as a brown solid in good yield (60%;
4
Scheme 3).
11
of the heteroatoms involved.
31
1
The P{ H} NMR spectrum of 4-Pt exhibits two doublets at
Similar to strained bis(stannanes) 1 and 2, the SPR2
i
2
δ 13.4 ppm (P Pr ) and −2.3 ppm (PPh ) ( J = 26.1 Hz),
P
2
2
PP
groups in 4-S and 5-S are located such that a pair of P−Z
31
195
each accompanied by a set of satellites attributed to P− Pt
bonds (PS on P(2); P−C on P(1)) align roughly
1
i
iPr
coupling ( J = 3352 Hz (P Pr ) and 3407 Hz (PPh ); Figure
PPt 2 2
perpendicular to the mean acenaphthene plane (Figure 13).
195
1
S3, in the SI). The single resonance in the Pt{ H} NMR
spectrum appears as an anticipated doublet of doublets,
1
centered at δPt −4504.1 ppm, with J coupling constants
PPt
31
1
correlating to the values found in the P{ H} NMR spectrum
1
(
Figure S4, in the SI). While the 31P ( H coupled) NMR
spectrum of 4-Pt displays additional splitting from the coupling
to the isopropyl hydrogens, the overlap of peaks prevents the
JPH coupling from being determined. The coupling can be
1
observed, however, in the H NMR spectrum, which reveals
two doublets of septets for the two magnetically inequivalent
2
3
PCH hydrogen environments ( J = 18.6 Hz, J = 7.0 Hz;
HP
HH
2
3
JHP = 16.5 Hz, J = 5.5 Hz) and a pair of doublet of doublets
for the inequivalent methyl groups ( J = 17.9 Hz, J = 7.0
Hz; J = 16.2 Hz, J = 7.0 Hz). Correspondingly, the
P{ H} NMR spectrum of 4-Mo revealed two doublets at δ
P
HH
Figure 13. Thermal ellipsoid plots (40% probability) of strained
3
3
HP
HH
bis(sulfides) 4-S and 5-S showing the conformation of the SPR
2
3
3
i
groups (majority of H atoms are omitted and Ph and Pr groups are
HP HH
31
1
shown in wireframe for clarity).
i
2
4
3.1 ppm (P Pr ) and 34.5 ppm (PPh ) ( J = 33.5 Hz).
2 2 PP
1
Similar to 4-Pt the H NMR spectrum enabled J coupling to
PH
the isopropyl hydrogens to be determined; however, due to the
overlap of resonances this was only possible for the
magnetically inequivalent methyl groups represented by a pair
The extent of the out-of-plane distortion, concomitant with the
buckling of the carbon framework in both compounds, results
in the sulfur atoms on each P(2) aligning close to the isopropyl
groups on the adjacent phosphorus atoms, allowing for C−H···
S type weak hydrogen bonds to exist across the peri-gap in each
case [H13···S(2) 4-S 2.691(1) Å, 5-S 2.864(1) Å; H16···S(2)
3
3
3
of doublet of doublets ( J = 14.9 Hz, J = 6.9 Hz; J =
HP
HH
HP
3
1
5.8 Hz, J = 7.0 Hz).
HH
Colorless crystalline blocks of 4-Pt and yellow platelet
crystals of 4-Mo suitable for X-ray crystallography were grown
from diffusion of hexane into a saturated solution of the
respective products in dichloromethane. The crystal structures
of 4-Pt and 4-Mo are shown in Figure 14, and selected
interatomic bond lengths and angles are listed in Table 4.
Further crystallographic information can be found in the SI.
The structures of related monomeric platinum(II) 4-Pt and
molybdenum(0) 4-Mo complexes both involve bidentate P/P
coordination of the unsymmetrical bis(phosphine) ligand 4 to
form six-membered chelate rings involving the central metal
4
-S 2.678(1) Å, 5-S 2.676(1) Å; Figure 13, Table S5, in the SI].
Additional C−H···S close contacts are observed between S(2)
and the isopropyl and phenyl rings on P(2) [4-S H20···S(2)
2.720(1) Å; 5-S H21C···S(2) 2.868(1) Å, H27···S(2) 2.922(1)
Å; Figure 13, Table S5, in the SI]. The proximal arrangement of
the phosphorus moieties also places a phenyl ring on P(2) in
close contact with the axial isopropyl group on P(1) such that
an additional CH···π interaction acts to further stabilize this
conformation [4-S H14···Cg(25−30) 3.008(1) Å; 5-S H15···
Cg(22−27) 2.688(1) Å; Figure 13, Table S5, in the SI].
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Figure 14. Thermal ellipsoid plots (40% probability) of platinum(II) 4-Pt and molybdenum(0) 4-Mo complexes of bis(phosphine) 4 (H atoms are
omitted for clarity).
Figure 15. Thermal ellipsoid plots (40% probability) of 4-Pt and 4-Mo reduced to their central six-membered MP C rings for clarity to show the
2
3
contrasting distorted boat and twisted envelope conformations, respectively.
Table 5. Bond Lengths [Å] and Angles [deg] Categorizing the Geometry around Pt and Mo in 4-Pt and 4-Mo
4
-Pt
4-Mo
platinum region distances
molybdenum region distances
P(1)−Pt(1)
2.236(4)
2.203(4)
2.349(4)
2.345(4)
P(1)−Mo(1)
P(2)−Mo(1)
Mo(1)−C(31)
2.5204(11)
Mo(1)−C(32)
Mo(1)−C(33)
Mo(1)−C(34)
1.998(5)
1.998(5)
1.969(5)
P(2)−Pt(1)
Pt(1)−Cl(1)
Pt(1)−Cl(2)
2.4825(10)
2.040(5)
platinum region angles
molybdenum region angles
P(1)−Pt(1)−P(2)
Cl(1)−Pt(1)−Cl(2)
Cl(1)−Pt(1)−P(2)
Cl(2)−Pt(1)−P(1)
Cl(1)−Pt(1)−P(1)
Cl(2)−Pt(1)−P(2)
92.73(13)
86.78(14)
90.25(13)
91.16(14)
170.55(13)
173.25(13)
P(1)−Mo(1)−P(2)
P(1)−Mo(1)−C(31)
P(1)−Mo(1)−C(32)
P(1)−Mo(1)−C(33)
P(1)−Mo(1)−C(34)
P(2)−Mo(1)−C(31)
P(2)−Mo(1)−C(32)
P(2)−Mo(1)−C(33)
82.19(4)
P(2)−Mo(1)−C(34)
C(31)−Mo(1)−C(32)
C(31)−Mo(1)−C(33)
C(31)−Mo(1)−C(34)
C(32)−Mo(1)−C(33)
C(32)−Mo(1)−C(34)
C(33)−Mo(1)−C(34)
89.79(14)
87.70(18)
171.21(18)
85.44(19)
83.67(18)
87.57(18)
92.48(19)
94.94(13)
100.46(13)
88.32(13)
171.97(13)
96.20(12)
175.11(13)
92.34(13)
i
atom. As required by the geometry of the ligand the two
phosphine groups adopt a cis-orientation around the four-
coordinate platinum in 4-Pt and the six-coordinate molybde-
num center in 4-Mo, which occupy typical square-planar and
octahedral coordination environments, respectively.
bond distance (2.236(4) Å; P Pr ) is marginally longer than the
2
Pt(1)−P(2) distance (2.203(4) Å; PPh ). This is consistent
with an increase in the electronegativity of the phosphine
moiety and concomitant increase in the s character of the Pt−P
bond, which is mirrored in the P NMR with an expected
increase in J coupling resulting from a shorter bond (Pt−
P Pr 3352 Hz; Pt−PPh 3407 Hz). The extent of out-of-plane
distortion experienced by the two P−CAcenap peri-bonds, which
is concomitant with a considerable twist of the acenaphthene
scaffold, results in the mean Pt(1)−Cl(1)−Cl(2)−P(1)−P(2)
2
31
1
In 4-Pt the geometry around the metal center is somewhat
distorted, with the phosphorus atoms displaced to opposite
sides of the Cl(1)−Pt(1)−Cl(2) plane by up to 0.4 Å, although
within the plane angles around Pt lie between 86.78(14)−
PPt
i
2
2
92.73(13)° and average to 90.2°. As expected, the Pt(1)−P(1)
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plane lying at 29° to that of the acenaphthene backbone. In
addition, with the phosphorus atoms displaced by up to 0.7 Å
from the mean plane and maximum C−C−C−C central
torsion angles approaching 11°, the PtP C ring is severely
buckled and adopts a conformation best described as a
distorted boat (Figure 15). The resulting transannular P···P
peri-distance [3.213(6) Å] is marginally longer than the
equivalent distance observed in the free ligand 4 [3.100(2)
Å] but considerably shorter than that in bis(sulfide) 4-S
interaction is predicted to occur in 5 which exhibits a similar JPP
of 160 Hz. Conversely, the corresponding bis(sulfide)
derivatives 4-S and 5-S prepared by treating the parent
bis(phosphines) with elemental sulfur by refluxing in toluene,
are highly strained due to the increased crowding of the peri-
region upon thionation. In each case, extreme in-plane
distortion (splay angles up to 27°) is accompanied by severe
buckling of the carbon framework (maximum C−C−C−C
torsion angles ∼17°), with the phosphorus atoms displaced
from the mean acenaphthene plane by up to 1.2 Å.
Subsequently, nonbonded intramolecular P···P distances [4-S
4.051(2) Å; 5-S 4.041(1) Å] are considerably longer (∼13%)
than the sum of van der Waals radii and are comparable to the
2
3
[
4.051(2) Å].
The octahedral environment around the molybdenum center
in 4-Mo is marginally distorted, with angles in the range
2.19(4)−100.46(13)° (average 90.1°). In contrast to 4-Pt, the
MoP C six-membered chelate ring adopts a twisted envelope-
8
11
2
3
largest ever reported peri-separations.
type conformation hinged about the P···P vector, with Mo
Treatment of bis(phosphine) 4 with PtCl (cod) (cod =1,5-
2
positioned 1.230(1) Å above the mean P C plane and with the
cyclooctadiene) and [(nbd)Mo(CO) ] (nbd = norbornadiene)
2
3
4
P(1)−Mo(1)−P(2) plane inclined by 135° (Figure 15 and
Table 5). While the out-of-plane ligand distortions are notably
reduced in 4-Mo compared to those of the platinum complex,
in CH Cl2 at room temperature afforded monomeric,
2
mononuclear complexes [(4)PtCl ] (4-Pt) and cis-[(4)Mo-
2
(CO) ] (4-Mo), with distorted square planar and octahedral
4
greater in-plane displacement of the P−C
peri-bonds
metal geometries, respectively. Both complexes involve
bidentate P/P coordination of the unsymmetrical, cis-orientated
bis(phosphine) ligand 4, which forms a six-membered chelate
ring involving the central metal atom. In each case the
bis(phosphine) backbone is distorted but notably less so than
in bis(sulfide) 4-S, with comparable P···P distances of 3.213(6)
Å and 3.289(1) Å.
Acenap
occurs in order to accommodate the octahedral metal
environment, with an increased splay angle of 17.7° and a
marginally longer P···P separation [3.289(1) Å] observed
compared to those of 4-Pt [14.4°; 3.213(6) Å].
CONCLUSION
■
Bis(stannanes) 1−3, incorporating bulky tin moieties in the
proximal peri-positions on the acenaphthene backbone, have
been prepared following standard halogen−lithium exchange
reactions giving the N,N,N′,N′-tetramethyl-1,2-ethanediamine
EXPERIMENTAL SECTION
■
All experiments were carried out under an oxygen- and moisture-free
nitrogen atmosphere using standard Schlenk techniques and glassware.
Reagents were obtained from commercial sources and used as
received. Dry solvents were collected from an MBraun solvent system.
Elemental analyses were performed at the London Metropolitan
(
TMEDA) complex of 5,6-dilithioacenaphthene and reaction
with the respective organotin chloride [Ph SnCl, Me SnCl,
3
3
Me SnCl ]. These strained systems are dominated by repulsive
2
2
1
13
119
forces which result in substantial buckling of the acenaphthene
framework and major displacement of the exocyclic peri-bonds,
leading to intramolecular Sn···Sn distances approaching the
sum of van der Waals radii. The distance in triphenyltin
derivative 1 [4.0659(9) Å] is only 6% shorter than the sum of
University. H, C and Sn NMR spectra for 1−3 were recorded on
a Jeol GSX 270 MHz NMR spectrometer with δ(H), δ(C), and δ(Sn)
referenced to external tetramethylsilane and tetramethylstannane,
1
13
31
195
respectively. H, C, P, and Pt NMR spectra for 4, 4-S, 5-S, 4-Pt,
-Mo were recorded on a Bruker AVANCE III 500 MHz NMR
4
12
spectrometer with δ(H), δ(C), δ(P), and δ(Pt) referenced to external
van der Waals radii of Sn [4.34 Å] and statistically of equal
1
tetramethylsilane, phosphoric acid, and Na (PtCl ), respectively. H,
2
6
magnitude to the largest peri-separation previously reported
13
31
C and P NMR spectra for 5 were recorded on a Bruker Avance 500
4
[
4.072(3) Å]. The addition of the second acenaphthene
MHz NMR spectrometer with the same external references above.
fragment in distannacycle 3 acts to partially overcome the
repulsion between the two tin atoms, reducing the Sn···Sn
distance from 3.9693(6) Å in 2 to 3.6374(6) Å. The relatively
large peri-distances observed in 1−3, coupled with the small
13
1
Assignments of C and H NMR spectra were made with the help of
H−H COSY, HSQC and HMBC experiments. All measurements were
performed at 25 °C. All δ values reported for NMR spectroscopy are
in parts per million (ppm). Coupling constants (J) are given in Hertz
119
117
119
(
Hz). All JSnSn values listed in the experimental represent
J( Sn, Sn) values obtained in the
Sn NMR spectra,
119
117
experimentally obtained J( Sn, Sn) SSCCs. Mass spectrometry
was performed by the University of St. Andrews Mass Spectrometry
Service. Electrospray mass spectrometry (ES-MS) was carried out on a
Micromass LCT orthogonal accelerator time-of-flight mass spectrom-
eter. 5,6-Dibromoacenaphthene [AcenapBr2] and 5-(bromo)-6-
(
suggest only a limited through-space contribution to the overall
coupling in these systems (1 31 Hz; 2 37 Hz; 3 65 Hz).
i
Heteroleptic bis(phosphines) [Acenap(PR )(P Pr )] 4 and 5
2
2
have been prepared through stepwise halogen−lithium
exchange reactions of bromine−phosphorus precursors
28
i
16
diisopropylphosphino)acenaphthene [Acenap(Br)(P Pr )] (6)
2
i
16
i
[
Acenap(Br)(P Pr )] (6) and [Acenap(Br)(PPh Pr)] (7). In
2
were prepared from standard reported procedures.
[Acenap(SnPh ) ] (1). A solution of 5,6-dibromoacenaphthene
the crystal, 4 adopts a conformation incorporating a quasi-linear
3
2
C −P···P three-body fragment with the correct geometry to
(1.09 g, 3.49 mmol) in diethyl ether (100 mL) was cooled to −10 to 0
Ph
°
C on an ice−ethanol bath, and to this was added a solution of
promote the delocalization of the phosphorus lone-pair of the
i
TMEDA (1.5 mL, 9.44 mmol). The mixture was allowed to stir for 15
min before a solution of n-butyllithium (2.5 M) in hexane (3.1 mL,
P( Pr ) group to the adjacent antibonding σ*(P−C ) orbital.
2
Ph
The notably short intramolecular P···P distance (3.100(2) Å;
4% shorter than twice the van der Waals radius of P) and the
7
.69 mmol) was added dropwise over a period of 15 min. During these
operations, the temperature of the mixture was maintained at −10 to 0
C. The mixture was stirred at this temperature for a further 1 h,
1
close to linear C −P···P angle of 175.65(1)° suggest a weakly
Ph
°
attractive three-center four-electron (3c-4e) type of interaction
before a solution of triphenyltin chloride (2.69 g, 6.98 mmol) in
diethyl ether (100 mL) was added dropwise. The mixture was allowed
to warm to room temperature and then stirred overnight before being
washed with 0.1 M sodium hydroxide (2 × 60 mL). The organic layer
operates between the peri-atoms in this system, which is
supported by notably large J through-space coupling (180
PP
3
1
1
Hz) observed in the P{ H} NMR spectrum. A similar
8
804
dx.doi.org/10.1021/ic5014768 | Inorg. Chem. 2014, 53, 8795−8808

Inorganic Chemistry
Article
was dried over magnesium sulfate and concentrated under reduced
pressure to afford a cream-colored solid. The crude product was
refluxed with hexane for 30 min, affording a white solid precipitate
which was collected by filtration. An analytically pure sample was
obtained from recrystallization by diffusion of hexane into a saturated
solution of the compound in tetrahydrofuran (1.43 g, 48%); mp 180−
Hz, 3JHP = 4.3 Hz, Acenap 4-H), 7.25 (1H, d, 3JHH = 7.3 Hz, Acenap 3-
2
H), 3.53−3.41 (4H, m, Acenap 2 × CH ), 2.30 (2H, m (∼t sept), J
2
HP
3
6
= 14.0 Hz, J = 6.9 Hz, J = 2.2 Hz, PCH 13-H), 1.26 (6H, dd,
HH
HP
3
3
3
JHP = 13.0 Hz, J = 6.9 Hz, 2 × CH 14-H), 0.87 (6H, dd, J =
HH
3
HP
3
13
1
11.4 Hz, J = 6.9 Hz, 2 × CH , 14-H); C{ H} NMR (CDCl ,
HH
3
3
1
Me Si, 126 MHz) δ 148.4(q), 148.3 (q), 141.2 (dd, J = 27.3 Hz,
JCP = 4.2 Hz, 15-qC), 140.0 (dd, J = 6.0 Hz, J = 1.8 Hz, Acenap
1a-qC), 139.6 (dd, J = 26.3 Hz, J = 20.0 Hz, Acenap 5a-qC),
CP CP
38.0 (s, Acenap 4-C), 135.0 (s, Acenap 7-C), 134.6 (dd, J = 17.8
4
C
CP
1
3
5
3
3
1
82 °C. H NMR (CDCl , Me Si, 270 MHz) δ 7.80 (2H, d, J
=
3
4
H
HH
CP CP
3
3
6
.9 Hz, J
= 63/59, Acenap 4,7-H), 7.32 (2H, d, J = 6.9 Hz,
2
2
HSn
HH
Acenap 3,8-H), 7.27−7.14 (6H, m, SnPh-p), 7.14−6.96 (24H, m,
2
1
CP
1
3
1
SnPh-o,m), 3.49 (4H, s, Acenap 2 × CH ); C{ H} NMR (CDCl ,
6
1
3
2
3
Hz, J = 3.1 Hz, PPh-o), 131.8 (dd, J = 26.4 Hz, J = 6.0 Hz,
CP CP CP
2
Me Si, 76 MHz) δ 149.4 (q), 142.8 (s, J = 33 Hz, Acenap 4,7-C),
1
3
4
C
CSn
Acenap 5-qC), 131.2 (dd, J = 27.0 Hz, J = 8.9 Hz, Acenap 6-
CP CP
2
41.8 (q), 137.3 (s, J = 36 Hz, SnPh-o), 134.2 (q), 129.3 (q), 128.8
CSn CSn
59 Hz, Acenap 3,8-C), 30.1 (s, Acenap 2xCH ); Sn{ H} NMR
3
CSn
qC), 128.3 (d, J = 6.1 Hz, PPh-m), 127.8 (s, PPh-p), 119.6 (s,
CP
3
2
Acenap 3-C), 119.5 (s, Acenap 8-C), 30.3 (s, Acenap CH ), 30.0 (s,
2
1
19
1
=
1
5
2
Acenap CH ), 26.5 (dd, J = 17.2 Hz, J = 6.2 Hz, PCH 13-C),
20.2 (dd, J = 18.0 Hz, J = 3.3 Hz, 2 × CH 14-C), 20.0 (dd, J
CP
= 11.7 Hz, J = 2.6 Hz, 2 × CH 14-C); P NMR (CDCl , H PO ,
2 CP CP
+
(
CDCl , Me Sn, 101 MHz) δ −120.8 (s, J
= 31 Hz); MS (ES ):
2
6
2
3
4
Sn
SnSn
CP
CP
3
m/z (%) 351.02 (70) [SnPh ], 383.05 (100) [SnPh OMe], 503.08
6
31
3
3
CP
3
3
3
4
+
(
30) [M − SnPh ], 875.09 (21) [M + Na]; Anal. Calcd for
4
2
3
203 MHz) AB spin system: δ −11.3 (dd of sept, J = 180.0 Hz, J
P
PP
PH
C H Sn : C, 67.65; H, 4.49. Found: C, 68.07; H, 4.91.
3
4
4
8
38
2
= 24.5 Hz, J = 11.8 Hz, P ), −12.8 (d, J = 180.0 Hz, P );
PH
A
PP
B
[
Acenap(SnMe ) ] (2). Experimental details were the same as for
31 1
3
2
P{ H} NMR (CDCl , H PO , 203 MHz) AB spin system: δ −11.3
3
3
4
P
compound 1 but with [Acenap(Br) ] (1.03 g, 3.31 mmol), TMEDA
4
4
2
(
d, J = 180.0 Hz, P ), −12.8 (d, J = 180.0 Hz, P ); HRMS (ES
PP
A
PP
B
(
1.4 mL, 8.93 mmol), 2.5 M solution of n-butyllithium in hexane (2.9
+
): m/z: Calcd for (M + H) C H P : 455.2057, found: 455.2048;
30 33 2
mL, 7.28 mmol) and Me SnCl (1.7 mL, 1.32 g, 6.62 mmol). The crude
3
Anal. Calcd for C H P : C, 79.28; H, 7.10. Found: C, 79.18; H, 7.04.
3
0
32 2
product was washed with ethanol, and the title compound was
collected by filtration as a white solid. An analytically pure sample was
i
[
Acenap(SPPh )(SP Pr )] (4-S). Elemental sulfur (0.14 g,
2
2
i
4
.40 mmol) and [Acenap(PPh )(P Pr )] (4) (1.00 g, 2.20 mmol) in
2 2
obtained from recrystallization in THF at −30 °C (1.04 g, 65%); mp
dry toluene (50 mL) were heated under reflux for 3 h. After cooling to
room temperature, the volatiles were removed in vacuo to give the title
compound as a pale-yellow powder (0.88 g, 77%); mp 203−205 °C.
Crystals suitable for X-ray diffraction were grown from vapor diffusion
of hexane into a saturated solution of the compound in dichloro-
1
1
J
32−134 °C. H NMR (CDCl , Me Si, 270 MHz) δ 7.67 (2H, d,
3
4
H
3
3
3
= 6.6 Hz, J = 58/56 Hz, Acenap 4,7-H), 7.24 (2H, d, J
=
HH
HSn
HH
6
.6 Hz, Acenap 3,8-H), 3.34 (4H, s, Acenap 2 × CH ), 0.34 (18H, s,
2
3
13
1
JHSn = 53/51 Hz, 6 × SnCH ); C{ H} NMR (CDCl , Me Si, 76
MHz) δC 148.1 (q), 143.7 (q), 139.8 (q), 139.3 (s, J
Acenap 4,7-C), 138.6 (q), 119.0 (s, J = 53 Hz, Acenap 3,8-C), 29.9
3
3
4
3
= 32 Hz,
1
3
CSn
methane. H NMR (CDCl , Me Si, 500 MHz) δ 8.90 (1H, dd, J
=
4
3
4
H
HP
3
3
CSn
16.9 Hz, J = 7.3 Hz, Acenap 7-H), 7.52 (1H, dd, J = 19.6 Hz,
2
HH
HP
(
s, Acenap 2 × CH ), 18.5 (q), −4.5 (s, J
= 347/331 Hz, 6 ×
3
3
2
CSn
JHH = 7.3 Hz, Acenap 4-H), 7.50 (1H, d, J = 7.3 Hz, Acenap 8-H),
119
1
HH
SnCH ); Sn{ H} NMR (CDCl , Me Sn, 101 MHz) δ −24.3 (s,
JSnSn = 37 Hz); MS (ES ): m/z (%) 134.93 (100) [SnMe], 164.97
3
4
3
3
4
Sn
7
.46−7.39 (4H, m, PPh-o), 7.39−7.34 (2H, dt, J = 7.2 Hz, J
=
+
HH
HH
3
1
.5 Hz, PPh-p), 7.31−7.27 (4H, m, PPh-m), 7.15 (1H, d, J = 7.3
HH
(
3
4
28) [SnMe ], 197.00 (24) [SnMe OMe], 303.02 (5) [C H SnMe ],
3
3
3
12
8
3
Hz, 3-H), 4.03−3.94 (2H, m ∼sept, J = 6.6 Hz, PCH H-13), 3.51−
+
HH
49.02 (7) [M − SnMe + OMe]; Anal. Calcd for C H Sn : C,
3
3
3
18 26
2
3
6
.42 (4H, m, Acenap 2 × CH ), 1.29 (6H, dd, J = 17.6 Hz, J
=
2
HP
HH
5.06; H, 5.46. Found: C, 45.18; H, 5.45.
3
3
.5 Hz, 2xCH 14-H), 0.19 (6H, dd, J = 18.5 Hz, J = 6.9 Hz, 2 ×
CH 14-H); C{ H} NMR (CDCl , Me Si, 126 MHz) δ 153.1 (q),
51.5 (q), 144.9 (d, J = 10.5 Hz, Acenap 7-C), 142.4 (d, J = 13.7
Hz, Acenap 4-C), 139.1 (dd, J = 10.6 Hz, J = 8.7 Hz, Acenap 1a-
qC), 135.1 (d, J = 85.7 Hz, 15-qC), 133.7 (dd, ∼t, J = 8.7, J
.7 Hz, Acenap 5a-qC), 131.8 (d, J = 10.0 Hz, PPh-o), 131.1 (d,
JCP = 2.9 Hz, PPh-p), 128.5 (d, J = 12.4 Hz, PPh-m), 126.2 (d, J
= 59.9 Hz, Acenap 6-qC), 123.2 (d, J = 84.4 Hz, Acenap 5-qC),
3
HP
HH
[
Acenap (SnMe ) ] (3). Experimental details were the same as for
13
1
2
2 2
3
3
4
C
compound 1 but with [Acenap(Br) ] (1.12 g, 3.60 mmol), TMEDA
2
2
2
1
CP CP
(
1.6 mL, 9.74 mmol), 2.5 M solution of n-butyllithium in hexane (3.2
3
3
CP
CP
mL, 7.93 mmol) and Me SnCl (1.58 g, 7.19 mmol). The crude
2
2
1
2
2
=
CP
CP
CP
product was washed with ethanol, and the title compound was
collected by filtration as a white solid. An analytically pure sample was
2
8
CP
4
3
1
CP
CP
obtained by recrystallization from chloroform (0.28 g, 60%); mp 215−
1
1
CP
2
17 °C (decomp); H NMR (CDCl , Me Si, 270 MHz) δ 7.75 (4H,
3
4
H
3
3
3
3
3
120.3 (d, J = 12.4 Hz, Acenap 8-C), 118.5 (d, J = 14.9 Hz,
CP CP
d, J = 6.9 Hz, J = 59 Hz, 2 × Acenap 4,7-H), 7.30 (4H, d, J
HH
HSn
HH
4
Acenap 3-C), 30.4 (s, Acenap CH ), 30.0 (s, Acenap CH ), 29.6 (d,
2
2
=
×
(
(
6.9 Hz, J = 83 Hz, 2 × Acenap 3,8-H), 3.37 (8H, s, 2 × Acenap 2
HSn
2 13 1
1
2
JCP = 48.0 Hz, PCH 13-C), 17.8 (d, J = 2.1 Hz, 2 × CH 14-C),
CP
31
3
CH ), 0.61 (12H, s, J
= 52 Hz, 4 × SnCH ); C{ H} NMR
HSn 3
2
2
1
7.0 (d, J = 2.1 Hz, 2 ×H 14-C); P NMR (CDCl , H PO , 203
CP 3 3 3 4
31 1
CDCl , Me Si, 76 MHz) δ 148.3 (q), 142.7 (q), 139.7 (q), 139.6
q), 138.4 (s, J = 38 Hz, Acenap 4,7-C), 119.4 (s, J = 57 Hz,
3
4
C
3
4
MHz) δ 82.0 (br s, P ), 48.8−48.3 (m, P ); P{ H} NMR (CDCl ,
P
A
B
3
CSn
CSn
2
H PO , 203 MHz) δ 82.0 (s, P ), 48.6 (s, P ); MS (ES+): m/z (%)
Acenap 3,8-C), 30.0 (s, Acenap 4xCH ), −3.1 (s, J = 366 Hz, 4 ×
3 4 P A B
2
CSn
119
1
541.13 (100) [M + Na], 487.19 (20) [M − S + H]; Anal. Calcd for
SnCH ); Sn{ H} NMR (CDCl , Me Sn, 101 MHz) δ −60.3 (s,
3
3
4
Sn
+
+
C H P S : C, 69.47; H, 6.22. Found: C, 69.31; H, 6.18.
JSnSn = 65 Hz); MS (ES ): m/z (%) 602.96 (90) [M ], 624.98 (100)
30 32 2 2
i
[Acenap(PPh )(P Pr )]PtCl (4-Pt). To a suspension of dichloro-
[
5
M + Na]; Anal. Calcd for C H Sn : C, 55.87; H, 4.69. Found: C,
2 2 2
28
28
2
(1,5-cyclooctadiene)platinum(II) (0.33 g, 0.88 mmol) in dichloro-
5.95; H, 4.89.
i
methane (6 mL) was added dropwise a solution of 4 (0.40 g, 0.88
mmol) in dichloromethane (20 mL). The solution was left to stir at
room temperature overnight. The volatiles were removed in vacuo to
[
Acenap(PPh )(P Pr )] (4). To a cooled (−78 °C), rapidly stirring
2
2
i
solution of [Acenap(Br)(P Pr )] (4.00 g, 11.5 mmol) in THF (60 mL)
2
was added dropwise (over 1 h) a solution of n-butyllithium (2.5 M) in
hexane (4.6 mL, 11.5 mmol). The solution was left to stir at this
temperature for a further 2 h. To this, a solution of chlorodiphenyl-
phosphine (2.52 g, 2.0 mL, 11.5 mmol) in THF (8 mL) was added
dropwise over a 1 h period. The solution was left to warm to room
temperature overnight. The volatiles were removed in vacuo and
replaced with diethyl ether (100 mL) and washed with degassed water
1
give a white powder (0.55 g, 87%); mp >250 °C. H NMR (CDCl ,
3
3
3
Me Si, 500 MHz) δH 7.99 (1H, dd, J = 9.8 Hz, J = 7.5 Hz,
4
HP
HH
3
Acenap 7-H), 7.57 (1H, d, J = 7.5 Hz, Acenap 8-H), 7.51−7.47
HH
(
2H, m, PPh-o), 7.46−7.43 (2H, m, PPh-o), 7.43−7.38 (6H, m, PPh-
3 4
m,p), 7.35 (1H, dd, JHH = 7.4 Hz, JHH = 1.2 Hz, Acenap 3-H), 7.20
3
3
(1H, dd, JHP = 13.3 Hz, JHH = 7.4 Hz, Acenap 4-H), 3.58−3.51 (4H,
2
(
20 mL). The yellow organic layer was separated and dried over
m, Acenap 2 × CH ), 3.49−3.37 (2H, m, ∼2d sept, JHP = 18.6 Hz,
2
3 2 3
magnesium sulfate. Volatiles were again removed in vacuo to give a
yellow solid that was dried in vacuo for 2 h (4.50 g, 87%). H NMR
(
JHH = 7.0 Hz, 1 × PCH 13-H, and JHP = 16.5 Hz, JHH = 5.5 Hz, 1 ×
1
3
3
PCH 13-H), 1.26 (6H, dd, J = 17.9, J = 7.0 Hz, 2 × CH 14-H),
HP HH 3
3 3 13 1
3
3
CDCl , Me Si, 500 MHz) δ 7.83 (1H, dd, J = 7.2 Hz, J = 2.7
0.92 (6H, dd, J = 16.2 Hz, J = 7.0 Hz, 2 × CH 14-H); C{ H}
HP HH 3
3
4
H
HH
HP
Hz, Acenap 7-H), 7.50−7.43 (4H, m, PPh-o), 7.45−7.42 (1H, m,
NMR (CDCl , Me Si, 126 MHz) δ 153.4 (q), 153.0 (q), 139.8 (dd
(∼t), J = 8.5 Hz, J = 8.5 Hz, Acenap 1a-qC), 139.1 (d, J = 5.8
3 4 C
3
3
3
2
Acenap 8-H), 7.42−7.36 (6H, m, PPh-m,p), 7.34 (1H, dd, J = 7.3
HH
CP
CP
CP
8
805
dx.doi.org/10.1021/ic5014768 | Inorg. Chem. 2014, 53, 8795−8808

Inorganic Chemistry
Article
Hz, Acenap 4-C), 137.1 (dd, J = 12.3 Hz, 2JCP = 8.7 Hz, Acenap 5a-
2
= 12.0 Hz, J = 7.1 Hz, CH 21-H), 1.24 (3H, dd, J = 14.6 Hz,
HH 3 HP
3
3
CP
2
2
3
3
3
qC), 134.4 (d, J = 2.8 Hz, Acenap 7-C), 134.0 (d, J = 10.7 Hz,
PPh-o), 131.1 (d, J = 2.4 Hz, PPh-o), 129.8 (d, J = 69.2 Hz, 15-
qC), 128.6 (s, PPh-p), 128.2 (d, J = 11.9 Hz, PPh-m), 119.8 (d, J
10.7 Hz, Acenap 8-C), 119.3 (d, J = 8.9 Hz, Acenap 3-C), 112.8
dd, J = 74.9 Hz, J = 8.4 Hz, Acenap 5-qC), 110.6 (dd, J
0.3 J = 9.8 Hz, Acenap 6-qC), 30.4 (s, Acenap CH ), 30.3 (s,
Acenap CH ), 27.9 (d, J = 36.2 Hz, PCH 13-C), 19.1 (s, 2 × CH
4-C), 17.7 (s, 2 × CH 14-C); P NMR (CDCl , H PO , 203 MHz)
JHH = 6.8 Hz, CH 17-H), 1.23 (3H, dd, J = 14.4 Hz, J = 7.1
Hz, CH 18-H), 1.18 (3H, dd, J = 13.5 Hz, J = 6.8 Hz, CH 15-
3 HP HH 3
H), 0.58 (3H, dd, J = 13.3 Hz, J = 7.0 Hz, CH 14-H); C{ H}
NMR (CDCl , Me Si, 126 MHz) δ 148.1 (q), 148.0 (q), 141.4 (dd,
3 4 C
JCP = 13.1 Hz, J = 6.7 Hz, 22-qC), 140.2 (d, J = 21.2 Hz,
Acenap 5a-qC), 140.0 (dd, J = 14.3 Hz, J = 7.4 Hz, Acenap 1a-
CP CP
qC), 135.1 (s, Acenap 7-C), 134.5 (s, Acenap 4-C), 134.2 (dd, J
CP
CP
3 HP HH
2
1
3
3
CP
CP
3
3
3
3
13
1
CP
CP
HP HH 3
3
=
(
5
CP
1
3
1
1
5
2
=
CP
CP
CP
CP CP
3
3
3
CP
2
1
2
2
CP
3
=
CP
3
1
1
6
1
3
3
3
3
4
15.3 Hz, J = 2.9 Hz, PPh-o), 131.8 (dd, J = 29.1 Hz, J = 6.4
CP CP CP
1
1
δ 13.4 (m, J = 3351 Hz, P ), −2.3 (m, J = 3405 Hz, P );
P{ H} NMR (CDCl , H PO , 203 MHz) δ 13.4 (d, J = 3351 Hz,
1
3
P
PPt
A
PPt
B
Hz, Acenap 5-qC), 131.4 (dd, J = 28.1 Hz, J = 5.1 Hz, Acenap 6-
CP CP
qC), 127.6 (d, J = 6.7 Hz, PPh-m), 127.3 (s, PPh-p), 119.3 (s,
Acenap 8-C), 119.2 (s, Acenap 3-C), 30.1 (s, Acenap CH ), 30.0 (s,
2
3
2
1
1
1
1
3
3
3
4
P
PPt
CP
1
2
J
PP
95
= 26.1 Hz, P ), −2.3 (d, J = 3405 Hz, J = 26.1 Hz, P );
A
PPt
PP
B
1
1
1
Pt{ H} NMR (CD Cl , Na(PtCl ), 107.0 MHz) δ −4504.1 (dd,
Acenap CH ), 27.7 (dd ∼t, J = 18.3 Hz, PCH 16-C), 26.9 (dd, J
2
2
6
Pt
2
CP
CP
1JPPt = 3407.3 Hz, 3351.9 Hz); MS (ES ): m/z (%) 719.32 (100) [M
−
5
1
5
= 17.1 Hz, J = 5.8 Hz, PCH 19-C), 25.7 (dd, J = 20.8 Hz, J
=
CP
CP
CP
2
6
−
H]; Anal. Calcd for C H P Cl Pt: C, 50.01; H, 4.48. Found: C,
14.6 Hz, PCH 13-C), 20.8 (dd, JCP = 6.4 Hz, JCP = 2.6 Hz, CH
3
21-
17-C), 20.2 (d,
14-C), 20.0 (d, JCP = 14.8 Hz, CH 15-C), 19.6
(dd, J = 13.1 Hz, J = 2.7 Hz, CH 20-C); P NMR (CDCl ,
30
32
2
2
2
4
9.92; H, 4.57.
[
C), 20.7 (s, CH 18-C), 20.6 (d, JCP = 18.5 Hz, CH
3
3
i
2
2
Acenap(PPh )(P Pr )]Mo(CO) (4-Mo). To a suspension of
Mo(CO) (nbd) (0.35 g, 1.1 mmol) in dichloromethane (20 mL)
was added dropwise a solution of 4 (0.50 g, 1.1 mmol) in
dichloromethane (15 mL). The solution was left to stir at room
temperature overnight. The volatiles were removed in vacuo to give a
pale-brown powder. Analytically pure material was obtained by
J
CP = 16.1 Hz, CH
3
3
2
2
4
2
6
31
4
CP
CP
3
3
4
H PO , 203 MHz) AB spin system: δ −9.7 (dd of sept, J = 160.3
3
4
P
PP
2
3
4
Hz, J = 25.4 Hz, J = 12.8 Hz, P ), −13.4 (br d, J = 160.3 Hz,
PH
PH
A
PP
PB); 31P{ H} NMR (CDCl , H PO , 203 MHz) AB spin system: δ
1
3
3
4
P
4
4
−9.7 (d, J = 160.3 Hz, P ), −13.4 (d, J = 160.3 Hz, P ); MS
PP
A
PP
B
+
recrystallization from dichloromethane/hexane at room temperature
(ES ): m/z (%): 443.30 (100) [M + Na]; Anal. Calcd for C H P : C,
27 34 2
1
(
7
0.45 g, 60%); mp 236 °C. H NMR (CDCl , Me Si, 500 MHz) δ
77.10; H, 8.15. Found: C, 76.92; H, 8.14.
3
4
H
3
3
i
.77 (1H, dd, ∼t, J = 7.8 Hz, J = 7.8 Hz, Acenap 7-H), 7.43−
.35 (11H, m, Acenap 8-H, PPh-o,m,p), 7.29 (1H, dd, J = 11.0 Hz,
JHH = 7.3 Hz, Acenap 4-H), 7.21 (1H, d, J = 7.3 Hz, Acenap 3-H),
[Acenap(SPPh )(SP Pr )] (5-S). Elemental sulfur (0.14 g,
HP
HH
2
2
3
7
4.40 mmol) and 5 (0.93 g, 2.20 mmol) in dry toluene (50 mL) were
heated under reflux for 3 h. After cooling to room temperature, the
volatiles were removed in vacuo to give the product as a pale-yellow
powder. Crystals suitable for X-ray diffraction were grown from vapor
HP
3
3
HH
3
J
.50−3.42 (4H, m, Acenap 2 × CH ), 2.25−2.17 (2H, m, ∼d sept,
2
3
3 3
= 7.1 Hz, PCH 13-H), 0.98 (6H, dd, J = 14.9 Hz, J = 6.9
HH
HP HH
3
3
Hz, 2 × CH 14-H), 0.92 (6H, dd, J = 15.8 Hz, J = 7.0 Hz, 2 ×
CH 14-H); C{ H} NMR (CDCl , Me Si, 126 MHz) δ 218.2 (dd,
diffusion of hexane into a saturated solution of the compound in
dichloromethane (0.90 g, 85%); mp 133 °C. H NMR (CDCl
500 MHz) δ 8.68 (1H, dd, JHP = 16.5 Hz, JHH = 7.3 Hz, Acenap 7-
3
HP
HH
13
1
1
, Me
Si,
3
3
4
C
3
4
2
2
2
3
3
JCP = 23.3 Hz, J = 8.9 Hz, CO 19-qC), 215.0 (dd, J = 23.4 Hz,
H
CP
CP
2
CP
3
3
2J = 9.9 Hz, CO 21-qC), 211.4 (dd, ∼t, J = 9.0 Hz, J = 9.0 Hz,
2
HP
HH
H), 8.20 (1H, dd, J = 15.8 Hz, J = 7.3 Hz, Acenap 4-H), 7.60−
CP
CP
2
3
7.53 (2H, m, PPh-o), 7.47−7.42 (3H, m, Acenap 3,8-H, PPh-p), 7.40−
CO 20-qC), 151.7 (q), 150.3 (q), 141.0 (dd, ∼t, J = 7.8 Hz, J
=
CP
CP
1
7.35 (2H, m, PPh-m), 3.95−3.83 (1H, br s, PCH 16-H), 3.50−3.39
7
.7 Hz, Acenap 1a-qC), 139.5 (s, Acenap 4-C), 138.8 (dd, J = 33.7
CP
5
2
2
(1H, m, PCH 13-H), 3.45 (4H, s, Acenap 2 × CH ), 2.72−2.63 (1H,
3 3
Hz, J = 2.9 Hz, 15-qC), 138.0 (dd, J = 18.1 Hz, J = 13.0 Hz,
Acenap 5a-qC), 132.7 (s, PPh-o), 132.6 (s, Acenap 7-C), 128.1 (s,
PPh-p), 128.0 (s, PPh-m), 125.1 (dd, J = 22.5 Hz, J = 3.0 Hz,
2
CP
CP
CP
m, PCH 19-H), 1.19 (3H, dd, J = 17.6 Hz, J = 6.6 Hz, CH 17-
HP
HH
3
3
3
1
3
H), 1.07 (3H, dd, J = 17.2 Hz, J = 6.7 Hz, CH 15-H), 0.84
HP HH 3
CP
CP
3
3
3
1
3
(
3H, dd, J = 18.7 Hz, J = 6.8 Hz, CH 20-H), 0.59 (3H, dd, J
Acenap 6-qC), 123.8 (dd, J = 29.8 Hz, J = 2.1 Hz, Acenap 5-
HP HH 3 HP
CP
CP
3
3
3
3
=
18.0 Hz, J = 6.8 Hz, CH 21-H), 0.43 (3H, dd J = 18.0 Hz,
HH 3 HP
qC), 119.2 (d, J = 6.3 Hz, Acenap 3-C), 118.8 (d, J = 5.3 Hz,
Acenap 8-C), 31.0 (s, Acenap CH ), 30.0 (s, Acenap CH ), 28.7 (dd,
JCP = 16.2 Hz, J = 3.3 Hz, PCH 13-C), 18.6 (d, J = 5.1 Hz, 2 ×
CH 14-C), 17.7 (d, J = 4.7 Hz, 2 × CH 14-C); P NMR (CDCl ,
H PO , 203 MHz) δ 43.7−42.6 (m, P ), 34.7−34.0 (m, P ); P{ H}
NMR (CDCl , H PO , 203 MHz) δ 43.1 (d, J = 33.5 Hz, P ), 34.5
d, J = 33.5 Hz, P ). Anal. Calcd for C H P MoO : C, 61.64; H,
.87. Found: C, 60.66; H, 6.49.
CP
CP
3
3
3
JHH = 6.8 Hz, CH 18-H), 0.30 (3H, dd, J = 18.6 Hz, J = 6.9
3
HP
HH
2
2
1
5
2
13
1
Hz, CH
(
14-H); C{ H} NMR (CDCl
, Me
Si, 126 MHz) δ
152.6
CP
CP
3
3
4
C
2
2
31
q), 150.9 (q), 143.6 (br s, Acenap 7-C), 139.6 (dd ∼t, J = 9.4 Hz,
CP
3
CP
3
3
2
31
1
Acenap 1a-qC), 137.6 (d, J = 9.4 Hz, Acenap 4-C), 133.6 (dd ∼t,
CP
3
4
P
A
B
2
2
2
JCP = 6.6 Hz, Acenap 5a-qC), 132.4 (d, JCP = 9.0 Hz, PPh-o), 131.3
3
3
4
P
PP
A
2
4
1
(
(d, JCP = 2.4 Hz, PPh-p), 129.6 (d, JCP = 74.8 Hz, 22-qC), 128.1 (d,
JCP = 11.6 Hz, PPh-m), 126.8 (d, JCP = 63.7 Hz, Acenap 6-qC), 121.5
PP
B
34 32
2
4
3
1
4
i
i
1
3
[
Acenap(PPh Pr)(P Pr )] (5). To a cooled (−78 °C), rapidly
(d, J = 79.7 Hz, Acenap 5-qC), 120.3 (d, J = 12.7 Hz, Acenap 3-
2
CP CP
i
3
1
stirring solution of [Acenap(Br)(P PrPh)] 7 (4.00 g, 11.5 mmol) in
THF (60 mL) was added dropwise a solution of n-butyllithium (2.5
M) in hexane (4.6 mL, 11.5 mmol) over 1 h. The solution was left to
stir at −20 °C for a further hour before being recooled to −78 °C. To
this a solution of chlorodiisopropylphosphine (1.75 g, 1.83 mL, 11.5
mmol) in THF (8 mL) was added dropwise over a 1 h period. The
solution was left to warm to room temperature overnight. The volatiles
were removed in vacuo and replaced with diethyl ether (100 mL) and
washed with degassed water (20 mL). The yellow organic layer was
separated and dried over magnesium sulfate. Volatiles were again
removed in vacuo to give a yellow oil that was dried in vacuo for 2 h.
Solid material was obtained by storing the oil at −35 °C (3.77 g, 78%).
C), 118.4 (d, J = 13.6 Hz, Acenap 8-C), 36.4 (d, J = 58.0 Hz,
CP CP
PCH 19-C), 30.3 (s, Acenap CH ), 30.0 (s, Acenap CH ), 29.5 (d, J
= 47.3 Hz, PCH 13-C), 29.2 (d, J = 45.7 Hz, PCH 16-C), 18.0 (s,
CH 17-C), 17.6 (s, CH 15-C), 17.5 (s, CH 18-C), 17.2 (s, CH 14-
C), 17.0 (s, CH 21-C), 16.2 (s, CH 20-C); P NMR (CDCl ,
H PO , 203 MHz) δ 79.6 (br s, P ), 56.8 (br s, P ); P{ H} NMR
1
2
2
CP
1
CP
3
3
3
3
3
1
3
3
3
3
1
1
3
4
P
A
B
+
(CDCl , H PO , 203 MHz) δ 79.6 (br s, P ), 56.8 (s, P ); MS (ES ):
3
3
4
P
A
B
m/z (%): 507.15 (100) [M + Na]; Anal. Calcd for C H P S : C,
66.90; H, 7.08. Found: C, 67.04; H, 7.10.
2
7
34 2 2
i
[Acenap(Br)(P PrPh)] (7). To a cooled (−78 °C) rapidly stirring
solution of 5,6-dibromoacenaphthene (5.0 g, 16.03 mmol) in
tetrahydrofuran (60 mL) was added dropwise a solution of n-
butyllithium (2.5 M) in hexane (6.4 mL, 16.03 mmol) over 1 h, and
the mixture was left to stir for a further 2 h at the same temperature. A
solution of chloroisopropylphenylphosphine (2.7 mL, 3.0 g, 16.03
mmol) in tetrahydrofuran (8 mL) was then added over 1.5 h. The
solution was allowed to warm up to room temperature overnight. The
volatiles were removed in vacuo, and the solvent was replaced with
diethyl ether (70 mL) and washed with degassed water (25 mL). The
organic layer was removed and dried over magnesium sulfate and then
was filtered; the solvent was removed in vacuo to reveal a yellow solid.
1
3
H NMR (CDCl , Me Si, 500 MHz) δ 7.93 (1H, dd, J = 7.2 Hz,
3
4
H
HH
3J = 3.3 Hz, Acenap 7-H), 7.15 (1H, dd, J = 7.1 Hz, J = 2.9
3
3
HP
HH
HP
3
Hz, Acenap 4-H), 7.71−7.67 (2H, m, PPh-o), 7.42 (1H, d, J = 7.2
HH
3
Hz, Acenap 8-H), 7.37 (1H, d, J = 7.1 Hz, Acenap 3-H), 7.35−7.31
HH
(
2H, m, PPh-m), 7.30−7.27 (1H, m, PPh-p), 4.96 (4H, s, Acenap 2 ×
3 2 6
CH ), 2.67−2.59 (1H, m ∼ddh, J = 7.0 Hz, J = 4.1 Hz, J
=
HP
2
HH
HP
2
.8 Hz, PCH 16-H), 2.44−2.35 (1H, m, PCH 19-H), 2.26−2.18 (1H,
2 3 6
m ∼ddh, J = 13.9 Hz, J = 7.0 Hz, J = 2.8 Hz, PCH 13-H),
HP
HH
HP
3
3
3
1
.38 (3H, dd, J = 11.7 Hz, J = 7.1 Hz, CH 20-H), 1.29 (dd, J
HP HH 3 HP
8
806
dx.doi.org/10.1021/ic5014768 | Inorg. Chem. 2014, 53, 8795−8808

Inorganic Chemistry
Article
Notes
1
3
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
Elemental analyses were performed by Stephen Boyer at the
London Metropolitan University. Mass spectrometry measure-
ments were performed by Caroline Horsburgh at the University
of St Andrews Mass Spectrometry Service. The work in this
project was supported by the Engineering and Physical Sciences
Research Council (EPSRC), EaStCHEM and the University of
St Andrews.
C), 120.1 (s, Acenap 8-C), 115.7 (q), 30.2 (s, Acenap CH ), 29.8 (s,
2
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1
2
■
Acenap CH ), 27.0 (d, J = 14.2 Hz, PCH), 20.4 (d, J = 19.8 Hz,
2
CP
CP
2
31
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* Supporting Information
S
Additional experimental details (including 31P and 195Pt NMR
spectra), crystallographic data and figures. This material is
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AUTHOR INFORMATION
Corresponding Authors
J.D.W.: Fax: (+44) 1334-463384. E-mail: jdw3@st-and.ac.uk.
P.K.: E-mail: pk7@st-and.ac.uk.
■
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dx.doi.org/10.1021/ic5014768 | Inorg. Chem. 2014, 53, 8795−8808

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