P-N/P-P bond metathesis for the synthesis of complex polyphosphanes

Article abstract of DOI:10.1021/ja305406x

A unique hexaphosphane featuring a 2,2′-bi(1,2,3- triphosphacyclopentane) moiety (19) and an ethylene-bridged bis- isotetraphosphane (27^c,m) were both selectively prepared in efficient one-pot syntheses from easily accessible tris(3,5-dimethyl-

Full text of DOI:10.1021/ja305406x

Article
pubs.acs.org/JACS
P−N/P−P Bond Metathesis for the Synthesis of Complex
Polyphosphanes
Kai-Oliver Feldmann†,‡ and Jan J. Weigand*,†
†Institut fur Anorganische und Analytische Chemie and ‡Graduate School of Chemistry, Westfalische Wilhelms-Universitat Munster,
̈
̈
̈
̈
Corrensstrasse 30, 48149 Munster, Germany
̈
S
* Supporting Information
ABSTRACT: A unique hexaphosphane featuring a 2,2′-
bi(1,2,3-triphosphacyclopentane) moiety (19) and an ethyl-
ene-bridged bis-isotetraphosphane (27c,m) were both selec-
tively prepared in efficient one-pot syntheses from easily
accessible tris(3,5-dimethyl-1-pyrazolyl)phosphane (14) and
1,2-bis(phenylphosphanyl)ethane (18c,m). The formation of
27c,m is an example of a highly efficient P−P bond formation
via protolysis. In contrast, the formation of 19 comprises
P−N/P−P bond metathesis steps. This constitutes a novel
synthetic approach toward the preparation of complex
polyphosphanes. Detailed spectroscopic investigations form the basis for a mechanistic understanding of this unprecedented
methodology. Furthermore, the preparation of a unique dinuclear iron−carbonyl complex which features hexaphosphane 19 as a
bridging ligand illustrates the potential use of complex polyphosphanes such as 19 as ligands in transition metal chemistry.
Scheme 1. Selected Synthetic Methods A−E for the
Generation of P−P Bonds in Polyphosphanes
INTRODUCTION
■
Polyphosphanes display a fascinating structural variety which
illustrates the propensity of phosphorus to form P−P bonds in
a multitude of acyclic, cyclic, and cagelike motifs.1−4 Several
synthetic methods for the preparation of polyphosphanes from
P1-sources were developed4,5 and certainly form the basis for
the structural diversity within this class of compounds. Scheme
1 summarizes the most important synthetic methods for the
generation of P−P bonds. Salt metathesis reactions of a metal
phosphide with a halophosphane are most commonly
employed (Scheme 1, method A).4 The required phosphides
are usually accessed via in situ reduction of a halophosphane
with a group 1 or 2 metal (method A1)4 or the reaction of silyl-
substituted phosphanes with lithium alkyls (method A2).5a
Silyl- or stannyl-substituted phosphanes may be alternatively
reacted with chlorophosphanes.5b The driving force for this P−
P coupling reaction is the formation of the strong Si−Cl (490
3 kJ mol−1) or Sn−Cl (425 17 kJ mol−1) bonds, respectively
(Scheme 1, method B).6 In the presence of a base, coupling of a
halophosphane and a primary or secondary phosphane can be
effected (method C). This procedure is typically used for the
preparation of cyclophosphanes with thermodynamically
favored ring sizes.7 Similarly, reactions of secondary phos-
phanes and amino-substituted phosphanes8 yield P−P bonded
compounds with concomitant formation of a secondary amine
(method D). These reactions commonly require elevated
temperatures. Some transition metal-1,9 and main group-
mediated approaches10 are described as well. For example,
P−P bond formation can be achieved via catalytic dehydrogen-
ative coupling of primary and secondary phosphanes using, for
example, Ru-based catalysts (method E).11
Despite these many different methods for P−P bond
formation, the preparation of complex polyphosphanes is
commonly either a nonselective low yielding process requiring
laborious workup procedures or a tedious multistep procedure.
Received: June 10, 2012
© XXXX American Chemical Society
A
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Harsh conditions, such as elevated temperatures, highly basic
media, and use of demanding and very toxic reagents are often
necessary. For example, the preparation of hexaphosphane 2a
(Scheme 2; a: R = iPr, b: R = tBu) requires as many as six steps,
Scheme 4. Generalized Reaction Equations of Bond
Metathesis Reactions of Type C−C/C−C, P−P/P−P, and
P−N/P−P
Scheme 2. Exemplary Preparation of Lithium Triphosphide
Li[1a] and Synthesis of Hexaphosphanes 2a,b (a: R = iPr, b:
R = tBu)
Related reactions of diphosphanes were reported with
compounds comprising P−H,16,19 P−Cl,16 or P−N bonds.
To the best of our knowledge, only one example is known for
the latter. If diphosphane 3 is reacted with Me2PNMe2 (8)
quantitative conversion to mixed diphosphane 9 and
(F3C)2PNMe2 (10) is observed (Scheme 5, eq I).16 A related
starting from P(SiMe3)3 as the P1 unit.12 The last step involves
reductive coupling of 2 equiv of triphosphide Li[1a] with 1,2-
dibromoethane, yielding a complex product mixture. Hexa-
phosphane 2a cannot be isolated and readily decomposes in the
reaction mixture above −30 °C. Nevertheless, it is structurally
characterized.12 The same holds true for the tBu-substituted
derivative 2b,13 even though a more efficient synthesis for
Li[1b] is available.13a Decomposition pathways of polypos-
phanes are often discussed to proceed via disproportionation
reactions accompanied by P−P bond rupture and intermo-
lecular scrambling processes.14,15 Very few cases of selective
scrambling reactions involving di- and polyphosphanes were
reported. Trifluoromethyl- (3)16 or tBu-substituted (4)17
diphosphanes, for example, react with tetramethyldiphosphane
(5) to quantitatively form the nonsymmetrically substituted
diphosphanes 6 and 7 (Scheme 3).
Scheme 5. Formation of Diphosphanes 9 and 13 via P−N/
a
P−P Exchange
a
(a) C6D6, RT, quantitative in solution; (b) neat, 132 °C, 2 h.
reaction was reported for triphosphane 11 which reacts with
F3CP(NMe2)2 (12) to form diphosphane 13 (Scheme 5, eq II).
This reaction, however, requires elevated temperatures (132
°C) and leads to a mixture of products.17
Scheme 3. Two Examples of P−P/P−P Metathesis Reactions
in which Symmetrically Substituted Diphosphanes 3−5
Scramble in Solution Quantitatively to the
Additional protocols for the generation of P−P bonds are
vital to further develop polyphosphane chemistry. During our
investigations of the reactivity of highly charged phosphorus
cations with nucleophiles,20 we found that the P−N bonds in
pyrazolyl-substituted PIII compounds are particularly labile and
can be easily cleaved.21 Accordingly, tri- and isotetraphosphane
15 and 16 can be prepared via the reaction of tris(3,5-dimethyl-
1-pyrazolyl)phosphane (14, pyr = 3,5-dimethyl-1-pyrazolyl)22
with secondary phosphane Cy2PH in excellent yields (Scheme
6).23 This approach toward P−P bond formation is related to
the reaction of primary or secondary phosphanes with
alkylaminophosphanes (Scheme 1, method D).8 The use of
pyrazolylphosphanes, however, is advantageous, as the reactions
proceed at ambient temperature and the yields are excellent. In
extension, we now report on the formation of polyphosphanes
via unprecedented P−N/P−P bond metathesis (Scheme 4,
bottom). This constitutes a novel synthetic approach and,
therefore, opens a new avenue in polyphosphane chemistry.
a
Nonsymmetrically Substituted Diphosphanes 6 and 7
a
(a) C6D6, RT, reaction time not indicated; (b) CH2Cl2, RT, 14 days.
From a more general perspective, this reaction allows for the
crosswise exchange of bonding partners of the starting materials
A−B and C−D to form the products A−D and C−B. This is a
typical feature of a bond metathesis as, for example, found in
olefin metathesis (denoted here as C−C/C−C bond meta-
thesis; Scheme 4, top). In these reactions, the total number of
bonds remains constant.18 Accordingly, scrambling reactions of
di- and polyphosphanes can be considered as P−P/P−P bond
metatheses (Scheme 4, middle).
RESULTS AND DISCUSSION
■
By analogy with the reaction of Cy2PH with 14 we assumed
that the related reaction of a bis-secondary phosphane, such as
bis(phenylphosphanyl)ethane24 with 14 would result in the
formation of two P−P bonds, yielding a symmetrically
B
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Scheme 6. Preparation of Triphosphane 15 and
a
Isotetraphosphane 16 from 14 and Cy2PH
a
(a) n = 2, −2 3,5-dimethylpyrazole (17), CH3CN, RT, 15 h, 91%; (b)
n = 3, −3 17, CH3CN, RT, 7 d, 95%; pyr =3,5-dimethyl-1-pyrazolyl.
substituted triphosphane (Scheme 7, R = Ph). This type of
bond formation is a comproportionative coupling and is
denoted here as type I.
Figure 1. 31P{1H} NMR spectrum of 19 (CD2Cl2, 300 K; insets show
experimental (upward) and fitted spectra (downward)); AA′XX′X″X‴
1
spin system: δ(PA) = −41.8 ppm, δ(PX) = 13.2 ppm; J(PAPA′) =
1
1
1
1
Scheme 7. Generalized P−P Bond Formation via Reactions
of a Bis-secondary Phosphane and 14 (3,5-dimethylpyrazole
= 17)
−137.0 Hz, J(PAPX) = J(PAPX′) = J(PA′PX″) = J(PA′PX‴) = −258.5
Hz, 2J(PAPX″2) = 2J(PAPX‴) = 2J(PA′PX) = 2J(PA′PX′) = 142.5 Hz,
2J(PXPX′) = J(PX″PX‴) = 1.9 Hz, J(PXPX‴) = J(PX′PX″) = 31.7 Hz,
3
3
3
3J(PXPX″) = J(PX′PX‴) = 49.5 Hz.
The reaction of 1,2-bis(phenylphosphanyl)ethane 18c,m
(∼1:1 mixture of the chiral (rac-18c) and achiral (meso-18m)
diastereomers; c = chiral, m = meso) and 14 in a 1:1 ratio in
CH3CN yielded a colorless precipitate which was isolated by
filtration, washed several times with CH3CN and dried in
vacuo. The 31P{1H} NMR spectrum of the dissolved precipitate
(CD2Cl2, 300 K) is depicted in Figure 1 and confirms the
formation of a single, highly symmetrical product which was
subsequently identified as hexaphosphane 19. Single crystals
suitable for X-ray single crystal structure determination were
obtained by slow diffusion of n-hexane into a solution of 19 in
CH2Cl2. The molecular structure of 19 is depicted in Figure 2.
An inversion symmetrical arrangement of two 1,2,3-triphos-
phacyclopentane rings fused via the central phosphorus atoms
in an antiperiplanar fashion is observed. The P−P bond lengths
are comparable to those of the respective bonds in related
hexaphosphanes 2a,b12,13c (e.g., P2−P2i: 2.2337(7) Å vs
2.1873(9) Å in 2a and 2.200(2) Å in 2b). In contrast to 2a,b
the P1−P2−P3 angle in 19 (97.81(2)°) is defined by the five-
membered ring geometry and is therefore significantly more
acute than in the related acyclic derivatives (2a: 113.11(2)°;12
2b: 107.10(4)°13c). The P2i−P2−P1 (93.21(2)°) and P2i−P2−
P3 (95.56(2)°) angles in 19 are more acute than the
corresponding angles in the related hexaphosphanes (2a:
117.98(7) and 116.10(7)°;12 2b: 107.95(4) and
112.09(4)°13c). This is attributed to the antiperiplanar
conformation with respect to the P2−P2i bond. In contrast,
hexaphosphanes 2a12 and 2b13c display a gauche conformation
resulting in increased steric repulsion and thus in larger bond
angles. Similar to other structurally characterized 1,2,3-
triphosphacyclopentane derivatives, a twist (4T5)25,26 con-
Figure 2. Molecular structure of 19 (hydrogen atoms are omitted for
clarity and thermal ellipsoids are displayed at 50% probability);
selected bond lengths [Å] and angles [deg]: P1−P2 2.2075(5), P2−P3
2.2270(5), P2−P2i 2.2337(7); P1−P2−P3 97.81(2), P1−P2−P2i
93.21(2), P3−P2−P2i 95.56(2); i = −x+2, −y+1, −z.
formation is observed for the 1,2,3-triphosphacyclopentane
rings (Figure 3A,B).27 The substituents on this fragment adopt
an all-trans arrangement (Figure 3, A). This is in agreement
with prior reports of 1,2,3-triphosphacyclopentane derivatives
which indicate that a cis−trans arrangement (Figure 3, B and
D) is thermodynamically less favorable and only observed for
substituents of very small steric demand.28
C
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reasonably soluble in benzene, poorly soluble in CH2Cl2
(∼10 mg/mL), and insoluble in CH3CN. To illustrate the
stability of compound 19 and its potential use as a multidentate
ligand toward transition metal moieties, complex 21 was
prepared via the reaction of 2 equiv of Fe2(CO)9 with
hexaphosphane 19 in THF (Scheme 8). The reaction
Scheme 8. Preparation of Complex 21 from the Reaction of
a
19 and Fe2(CO)9
Figure 3. All-trans and cis−trans conformers of 1,2,3-substituted 1,2,3-
triphosphacyclopentanes. The twist conformer (4T5, A and B) is
defined by the coplanarity of three atoms and the midpoint of the
opposite bond; C4 is located above, C5 below the plane. The envelope
conformer (2E, C and D) is defined by four coplanar atoms with one
phosphorus atom (P2) above the plane.
a
(a) −2 Fe(CO)5, THF, RT, 72 h, 28% (top); examples for
polyphosphane−Fe(CO)4 complexes (22 and 23, bottom).23
The observation of an AA′XX′X″X‴ spin system in the
31P{1H} NMR spectrum of 19 is in contrast to the molecular
structure in the solid state. A twist conformer as observed in the
solid state would render the P1 and P3 atoms chemically
unequal which would be inconsistent with the observed spin
system. Therefore, it is proposed that the conformation in
solution is best understood as a time-averaged envelope
conformation of an all-trans-1,2,3-triphosphacyclopentane
moiety (Figure 3, C). This is in line with previously reported
spectroscopic analyses of 1,2,3-triphosphacyclopentane deriva-
tives28 and related interconversion processes of the conformers
of organic five-membered rings.29,30 Indication for the presence
of a cis−trans isomer of 19 (Figure 3, D) is not observed. The
chemical shift of the resonance corresponding to PA (δ(PA) =
−41.8 ppm) is in the expected range for the central P atom of
isotetraphosphanes (e.g., (Ph2PM)3PA δ(PA) = −57.2 ppm;
THF).31 The resonance corresponding to PX in 19 (δ(PX) =
13.2 ppm) compares well with those reported for P atoms
incorporated in a saturated five-membered ring (e.g., PB in all-
trans-1,2,3-triphenyl-1,2,3-triphosphacyclopentane (20), AB2
spin system, δ(PA) = −14.7 ppm, δ(PB) = 17.2 ppm,
1J(PAPB) = 273 Hz).32 The 1J(PAPX) coupling constant
(−258.5 Hz) derived from the fit33 of the experimental
31P{1H} NMR spectrum is also comparable to the correspond-
ing coupling in 20 (1J(PAPB) = 273 Hz). It is noteworthy that
the NMR spectroscopic parameters of 19 are remarkably
distinct from those reported for 2a,b.12,13a Importantly, the
proceeded smoothly at ambient temperature in the dark, and
compound 21 was found to be the major product in solution
after a reaction time of 72 h according to 31P NMR
spectroscopic investigations. Significant decomposition of the
hexaphosphane framework was not observed. All volatiles were
removed from the reaction mixture in vacuo, and the residue
was dissolved in toluene. Slow evaporation of toluene at −18
°C yielded 21 as orange crystals in 28% yield (not optimized).
The molecular structure of 21 (Figure 4) shows hexaphosphane
19 coordinated to two [Fe(CO)4] moieties. The coordinating
phosphorus atoms in 21 (P1, P1i) occupy an axial position of
the pseudotrigonal bipyramidal coordination spheres around
the iron atoms. This mode of coordination is reminiscent of
that in the previously reported iron complexes 22 and 23
(Scheme 8, bottom).23
The coordination of the P6-core to the iron−carbonyl
moieties in 21 does not show a significant influence on the P−P
bond lengths. However, the P6 framework in 21 adopts a
gauche arrangement which is in contrast to the antiperiplanar
arrangement observed in the molecular structure of 19. This
change in the conformation of the P6-core is attributed to steric
effects, because an antiperiplanar arrangement would result in
strong steric repulsion of the [Fe(CO)4] moieties. As a result of
the gauche conformation, the P2−P3 and P2i−P3i bonds are
almost eclipsed (dihedral angle 19.93(3)°) which results in a
widening of the P3−P2−P2′ angle in 21 (105.46(1)°) in
comparison to the respective angle in 19 (95.56(2)°). The
31P{1H} NMR spectrum of 21 (CD2Cl2, 300 K, Figure 5)
displays an AA′MM′XX′ spin system. The chemical shifts of the
PA (−47.4 ppm) and PM (15.3 ppm) atoms are similar to those
of the respective resonances of 19 (δ(PA) = −41.8 ppm, δ(PX)
= 13.8 ppm). In contrast, the resonance of the P atoms
coordinated to the iron atoms is shifted to significantly lower
field (δ(Px) = 93.0 ppm). A similar downfield shift upon
coordination to [Fe(CO)4] moieties was also observed for the
related complexes 22 and 23.23 The absolute value of the
1J(PAPA′) coupling constant (1J(PAPA′) = −317.5 Hz) is
significantly larger than the absolute value of the respective
1
absolute value of the J(PAPA′) coupling constant in 19 (137.0
Hz) is distinctly smaller than the corresponding coupling
constants observed for 2a,b (a: 1J(PAPA′) = 669 Hz; b:
1J(PAPA′) = 467.5 Hz). This small coupling constant is in
agreement with the substantially smaller sum of the bond
angles (Σ)34 on the PA atoms of 19 (Σ = 286.6°) compared to
the corresponding parameter of compounds 2a,b (2a: Σ =
347.2°; 2b: Σ = 327.1°) and, furthermore, indicates a
predominantly antiperiplanar arrangement of the lone pairs of
electrons on PA and PA′ in 19 in solution.35
Analytically pure 19 appears to be indefinitely stable in the
solid state (under Ar or N2) at ambient temperature and has a
defined melting range (197−199 °C). Compound 19 is
D
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Furthermore, the introduction of the [Fe(CO)4] moiety
1
causes a significant increase in the absolute value of the J(PP)
coupling constant via the P−P bonds adjacent to P−P bonds
1
which involve the coordinated P atom (defined as J(PP)remote
,
Table 1). This effect is also observed for complexes 22 and
1
1
Table 1. J(PP)remote and J(PP)close Coupling Constants of
Complexes 21−23 and the Corresponding Free Ligands 15,
16, and 19
Figure 4. Molecular structure of 21 (hydrogen atoms are omitted for
clarity and thermal ellipsoids are displayed at 50% probability);
selected bond lengths [Å] and angles [deg]: P1−P2 2.2179(5), P1−
Fe1 2.2399(4), P2−P2i 2.2270(7), P2−P3 2.2297(5); P2−P1−Fe1
119.63(2), P1−P2−P2i 97.71(2), P1−P2−P3 95.74(2), P2i−P2−P3
105.46(1), C16−Fe1−C17 114.07(8), C16−Fe1−C18 117.54(8),
C17−Fe1−C18 128.28(8), C16−Fe1−C15 92.69(7), C17−Fe1−
C15 91.34(7), C18−Fe1−C15 89.49(8), C16−Fe1−P1 89.88(5),
C17−Fe1−P1 88.74(5), C18−Fe1−P1 88.23(5), C15−Fe1−P1
177.15(6); i = −x, y, −z+1/2.
23.23 The respective values of the iron complexes (gray rows)
along with the corresponding coupling constants of the free
ligands (white rows) are listed in Table 1. In contrast, the
1
absolute values of the J(PP) coupling constants involving the
coordinated P atom (1J(PP)close) are not uniformly larger than
the absolute values of the corresponding coupling constants in
the free ligands (Table 1).
Overall, compound 19 represents the first isolable and fully
characterized hexaphosphane featuring this bonding motif and
the corresponding iron−carbonyl complex 21 is unprece-
dented. Neverthless, the formation of hexaphosphane 19 raises
several questions because we initially assumed that the reaction
of 14 and 18c,m would proceed according to the previously
introduced reaction pathway type I (Scheme 7, R = Ph).
Consequently, the formation of all-trans-triphosphane 24 and
pyrH (17) was anticipated (Scheme 9). This is apparently not
the case, rendering further investigations necessary to gain a
detailed understanding of the reaction.
Figure 5. 31P{1H} NMR spectrum of 21 (CD2Cl2, 300 K; insets show
experimental (upward) and fitted spectra (downward)); AA′MM′XX′
spin system: δ(PA) = −47.4 ppm, δ(PM) = 15.3 ppm, δ(PX) = 93.0
The 31P{1H} NMR spectrum of the supernatant solution of
the reaction of 18c,m and 14 in a 1:1 ratio is depicted in Figure
6. Resonances corresponding to a series of different compounds
1
1
1
ppm; J(PAPA′) = −317.5 Hz, J(PAPM) = −314.0 Hz, J(PAPX) =
−276.7 Hz, 2J(PAPM′) = 2J(PA′PM) = −2.0 Hz, 2J(PAPX′) = 2J(PA′PX) =
2
2
3
103.1 Hz, J(PMPX) = J(PM′PX′) = 1.1 Hz, J(PMPM′) = 163.8 Hz,
3J(PMPX′) = J(PM′PX) = 5.3 Hz, J(PXPX′) = 51.0 Hz.
3
3
Scheme 9. Anticipated Formation of Compound 24 from the
a
Reaction of 18c,m and 14 in a Ratio of 1:1
coupling constant in 19 (1J(PAPA′) = −137.0 Hz). This is
attributed to a predominantly gauche conformation with
respect to the PA−PA′ bond in 21. The comparably large
3J(PMPM′) coupling constant indicates a short distance between
the lone pairs of electrons on the PM atoms.4b Thus, the
eclipsed arrangement of the P2−P3 and P2i−P3i bonds
observed in the solid state apparently also constitutes the
major contribution to the conformation of 21 in solution.
a
The reaction with 18m is preferred (see text).
E
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27c,m were obtained as a colorless precipitate in decent yield
(54%, Scheme 10). It is important to note that only meso-18m
Scheme 10. Formation of Diasteriomeric Polyphosphanes
rac-27c (only the (R,R) enantiomer is shown) and meso-
a
(R,S)-27m from the Reaction of 18c,m and 14 in a 6:4 Ratio
a
(a) −12 17, CH3CN, over night, RT, 54%; an approximate 1:1
mixture of 18c and 18m was employed.
Figure 6. 31P{1H} NMR spectrum of the supernatant of the reaction
of 14 and 18c,m in a 1:1 ratio (CH2Cl2, C6D6 capillary, 300 K).
can react with 14 according to reaction path type I (Scheme 7)
to form the favored and exclusively observed (vide infra) all-
trans-1,2,3-triphosphacyclopentane moieties in 27c,m. Thus, the
formation of a mixture of diastereomers 27c,m results from the
incorporation of either the chiral rac-1,2-bis(phosphanyl)ethane
moiety in rac-27c or the meso-R,S-moiety in meso-27m as the
central bis(phosphanyl)ethane fragment. As the major amount
of employed meso-18m is consumed in the formation of the five-
membered ring moieties, the probability of incorporation of the
rac-bis(phosphanyl)ethane moiety, i.e., the formation of rac-27c
is higher than the formation of meso-27m.
are observed. Residual phosphane 14 (δ = 72.4 ppm)22 and
hexaphosphane 19 are identified next to small amounts of
triphosphane 24. We were able to isolate a very small amount
(8.0 mg) of the oxygen- and moisture-sensitive triphosphane 24
from the reaction mixture by column chromatography which
allowed for spectroscopic characterization. The 31P{1H} NMR
spectrum is depicted in Figure 7. Resonances of a characteristic
Accordingly, the 31P{1H} NMR spectrum of the isolated
mixture of diastereomers 27c,m dissolved in C6D6 reveals two
sets of signals corresponding to rac-27c and meso-27m. The
intensity of the resonances corresponding to rac-27c is
significantly higher than that of the resonances corresponding
to meso-27m if the NMR sample is measured immediately after
preparation (Figure 8, bottom, resonances corresponding to
rac-27c are shown in blue, those of meso-27m are shown in red
for the high field resonance). Within 14 h, isomerization occurs
Figure 7. 31P{1H} NMR spectrum of 24 (CD2Cl2, 300 K; insets show
experimental (upward) and fitted spectra (downward)); A2M spin
1
system (δ(PA) = 21.2 ppm, δ(PM) = 63.5 ppm, J(PAPM) = −277.5
Hz).
A2M spin system (δ(PA) = 21.2 ppm, δ(PM) = 63.5 ppm,
1J(PAPM) = −277.5 Hz, CD2Cl2, 300 K) are observed and
indicate the all-trans arrangement of the aryl substituents. The
chemical shift of PA is comparable to that of the corresponding
nuclei in 19 (PX) and to those of corresponding resonances in
related 1,2,3-triphosphacyclopentane derivatives.32 The reso-
nance corresponding to PM in 24 is shifted to significantly lower
field due to the electron-withdrawing effect of the pyrazolyl
substituent.23 The J(PAPM) coupling constant (−277.5 Hz) is
1
similar to that of 19. By analogy with the discussion of the
conformation of 19 in solution, a time-averaged 2E con-
formation can also be assumed for all-trans-24 (Figure 3, C).
Furthermore, the 31P{1H} NMR spectrum of the supernatant
solution displays resonances corresponding to rac- and meso-
bis(phenylphosphanyl)ethane derivatives 25c,m, and minor
amounts of polyphosphanes 26I,II and 27c,m are observed
(vide infra).
Figure 8. 31P{1H} NMR spectra of the mixture of diastereomers 27c
(marked in blue for the high-field resonance, PA) and 27m (marked in
red for the high-field resonance, PA) in C6D6; recording of the spectra
commenced 15 (bottom), 270 (middle) and 660 (top) minutes after
dissolution (512 scans each, PD = 2 s, 300 K).
It was found that the mixture of diastereomers of
octaphosphane 27c,m can be selectively prepared from 18c,m
and 14 in CH3CN if a ratio of 6:4 is employed. Compounds
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in benzene solution to give an approximate 1:1 mixture of the
diastereomers 27c,m (Figure 8). ΔI (green) indicates the
approximate difference in the intensities of the resonances
corresponding to the two distinct diastereomers). Significant
decomposition of 27c,m in solution is observed after several days
only. The observed isomerization is much faster in CH2Cl2
solution, giving the equilibrated mixture of diastereomers in less
than 30 min. From such a sample, the 31P{1H} NMR
parameters of 27c,m were derived by iterative fitting33 of the
experimental 31P{1H} NMR spectrum (Table 2). The
Table 2. 31P{1H} NMR Spectroscopic Parameters of the
Diastereomers rac-27c and meso-27m Obtained from Iterative
Fitting
rac-27c
meso-27m
δ [ppm]
A
M
X
Y
−41.5
−26.4
2.6
−41.0
−26.9
2.6
3.4
3.2
ad
,
1
J [Hz]
1J(PAPM) = J(PA′PM′
)
−178
−269
−254
108
−128
−266
−255
114
1J(PAPX) = J(PA′PX′)
1J(PAPY) = J(PA′PY′)
2J(PMPX) = J(PM′PX′)
2J(PMPY) = J(PM′PY′)
1
1
2
2
Figure 9. 31P{1H} NMR spectrum of 27c,m (CD2Cl2, 300 K; insets
show experimental (upward) and fitted spectra of the mixture of
diastereomers (black downward) and deconvoluted spectra of rac-27c
(blue, downward) and meso-27m (red, downward); very small amounts
of 19 indicate slow decomposition in solution.
135
135
2J(PXPY) = J(PX′PY′)
6
5
2
3J(PMPM′
4J(PAPM′) = J(PA′PM)
5J(PAPA′)
5J(PMPX′) = J(PM′PX)
)
−26
−28
b
b
4
1
1
c
c
0
0
c
c
5
1
1
c
c
5J(PMPY′) = J(PM′PY)
2
2
5
triphosphacyclopentane derivatives (compare, for example,
a
1,2,3-triphenyl-1,2,3-triphosphacyclopentane 1J(PAPB) = 273
Decimal places of the coupling constants are not reported because of
Hz).32 Coupling constants of similar size as the J(PMPM′)
3
insufficient accuracy of the fit caused by the high complexity of the
experimental 31P{1H} NMR spectrum and broad line widths at half
coupling constant in 27c,m are observed for other 1,2-
b
height of the observed resonances. Approximate value as the line
bis(phosphanyl)ethane derivatives (e.g., 1-dimethylphosphino-
c
width at half height is larger than the observed coupling constant. Set
2-diisopropylethane: J(PP) = 25.2 Hz, C6H6).37 The observed
3
d
value which was not iterated. 6J and 7J coupling constants were set to
2J(PMPX) and 2J(PMPY2) coupling constants are remarkably large
zero.
2
(2J(PMPX) = 108 Hz, J(PM′PX′) = 135 Hz (rac-27c); J(PMPX)
2
2
= 114 Hz, J(PM′PX′) = 135 Hz (meso-27m)). J(PP) coupling
constants in related isotetraphosphane moieties are generally
smaller than 20 Hz (e.g., (Me(Me3Si)P)2PP(SiMe3)2: 2J(PP) =
5.1 Hz).38 By analogy with the discussion of the large
3J(PMPM′) coupling constant in 21 (vide supra), this is
attributed to short distances between the lone pairs on PM
and PX/Y in 27c,m. This is in line with the proposed
antiperiplanar arrangement with respect to the PA−PM bond
which is exemplarily illustrated by the Newman projections
along the PA−PM bonds of (S,S)-27c depicted in Figure 10.4
Similarly, large 2J(PP) coupling constants due to close distances
between the lone pairs of electrons on the involved P atoms
were reported for polyphosphanes 29 (2J(PP) = 283.2 Hz)39
experimental and fitted spectra of the mixture of diastereomers
as well as the deconvoluted spectra of rac-27c and meso-27m are
presented in Figure 9. Both diastereomers are fitted as
AA′MM′XX′YY′ spin systems. An approximate ratio of 48:52
(rac-27c:meso-27m) was deduced from the iterative fit of the
concentration. The resonances corresponding to the PA and PM
nuclei in both diastereomers (δ(PA) = −41.5 ppm, δ(PM) =
−26.4 ppm (rac-27c); δ(PA) = −41.0 ppm, δ(PM) = −26.9 ppm
(meso-27m)) are in the expected range for the corresponding P
atoms of isotetraphosphane fragments (vide supra). Similar to
hexaphosphane 19, the resonances corresponding to PX and PY
are observed at lowest field (δ(PX) = 2.6 ppm, δ(PY) = 3.2 ppm
(rac-27c); δ(PX) = 2.6 ppm, δ(PY) = 3.4 ppm (meso-27m)) in
the typical region for P atoms incorporated in 1,2,3-
triphosphacyclopentane rings.28,32 The observation of three
chemically unequal P atoms within each five-membered ring
moiety indicates hindered rotation around the PA−PM bond. By
analogy with the above discussion of 19, a twist or a cis−trans
conformation of the five-membered rings in solution can be
excluded. The definite assignment of PX and PY is not possible.
The magnitudes of the 1J(PAPX) and 1J(PAPY) coupling
1
constants (1J(PAPX) = −269 Hz, J(PAPY) = −254 Hz (rac-
1
1
27c); J(PAPX) = −266 Hz, J(PAPY) = −255 Hz (meso-27m))
Figure 10. Examples of polyphosphanes featuring comparably large
2J(PP) coupling constants and proposed conformation of (S,S)-27c.
are comparable to those of the aforementioned 1,2,3-
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and 28 (2J(PP) = 118.1 Hz40) as depicted in Figure 10. 2J(PP)
coupling constants within all-trans-1,2,3-triphosphacyclopen-
tane fragments are rarely reported but seem to be much smaller
or not observable36 (e.g., 1,2,3-triethyl-1,2,3-triphospha-4-
Scheme 11. Formation of Hexaphosphane 19 via Three
a
Equilibrium Reactions I−III Starting from 27c,m and 14
28
2
methylcyclopentane J(PP) = 2.2 Hz).
During our investigation, we succeeded in crystallizing meso-
27m from a very dilute CH3CN solution of the diasteriomeric
mixture of 27c,m (see Experimental Section for details). The
obtained molecular structure is shown in Figure 11. The
Figure 11. Molecular structure of meso-27m (hydrogen atoms are
omitted for clarity, and thermal ellipsoids are displayed at 50%
probability); selected bond lengths [Å] and angles [deg]: P1−P2
2.224(1), P2−P3 2.194(1), P2−P4 2.218(1); P3−P2−P4 95.08(5),
P3−P2−P1 97.97(5), P4−P2−P1 95.92(5); i = −x, −y, −z.
inversion symmetrical molecular structure of meso-27m
confirms the all-trans conformation of the triphosphacyclo-
pentane moieties which was already deduced from spectro-
scopic observations in solution. The observed bond lengths and
angles in this fragment are in agreement with the corresponding
parameters in previously published, related triphosphacyclo-
pentane derivatives.41 Furthermore, an antiperiplanar con-
formation with respect to the P2−P4 bond is observed in the
solid state which is similar to that proposed as the dominant
conformation in solution.
a
(a) CH2Cl2, RT, 15 h.
(approximately 38%), and 24 (<1% according to 31P NMR
spectroscopy). Further purification via recrystallization from
common solvents, sublimation, or column chromatography
under argon was not successful. However, multinuclear NMR
spectroscopic investigations of the filtrate allowed for the
identification of all resonances expected for 26I,II and 25c,m in
While octaphosphanes 27c,m are formed from the reaction of
18c,m and 14 in a 1:0.66 ratio hexaphosphane 19 is obtained
from reaction mixtures containing a 1:0.8 ratio of 18c,m:14.
Therefore, it was of interest, if the diasteriomeric mixture of
27c,m would react with 14 to yield hexaphosphane 19. It was
found that the formation of 19 proceeds via three equilibrium
reactions I−III (Scheme 11) involving the intermediates 24
and 26I,II. In the first step, 14 and 27c,m form triphosphacy-
clopentane 24 which subsequently reacts with a further
equivalent of 27c,m in the second equilibrium reaction to
form 19 and 26I,II. The latter reacts with 24 to form a second
equivalent of 19 and 25c,m. All of these reactions represent P−
N/P−P bond metathesis reactions according to Scheme 4.
These conclusions are based on NMR spectroscopic inves-
tigations of mixtures of 27c,m and 14 in various ratios and are
discussed in detail in the following paragraphs.
the H, 13C{1H}, and 31P{1H} NMR spectra.
1
Next to the resonances of 24 and 25c,m four complex
resonances are observed (Figure 12A). Of these, the resonance
at lowest field can be clearly assigned to PX of 19. Close
inspection of the remaining complex resonances revealed that
these are composed of several overlapping signals. The group of
signals at high field is composed of the resonances of five
chemically unequal P nuclei. Figure 12 (enlargement B) shows
the high field group of resonances (black) overlaid with the
experimental spectra of 19 (red) and 27c,m (green). By
comparison, the resonances of 19 and 27c,m can thus be
assigned. Additionally, peaks corresponding to diastereomeric
pentaphosphanes 26I,II are observed in this group of over-
lapping resonances. Similar analyses of the two remaining
complex groups of resonances (Figure 12, C, D) reveal that
each is composed of resonances corresponding to 27c,m (green)
and 26I,II. A fourth resonance corresponding to 26I,II is found
to overlap with the resonances of 25c,m. Each of the resonances
of 26I,II displays a first-order dddd splitting which only in the
case of the resonance at lowest field is not entirely resolved due
Figure 12A shows the 31P{1H} NMR spectrum of the
reaction mixture of 27c,m and 14 in a 5:2 ratio in CH2Cl2
solution after a reaction time of 15 h. Resonances
corresponding to 19 (vide supra) and 25c,m are observed.
The latter was spectroscopically characterized. Removal of all
volatiles from the reaction mixture in vacuo, stirring of the
residue in CH3CN, and storage at −35 °C gave a colorless
suspension which was filtered. The obtained filtrate contained a
mixture of diastereomers 25c,m (approximately 61%), 26I,II
H
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Table 3. 31P{1H} NMR Spectroscopic Parameters Derived
from the Experimental Spectrum and used for the
Simulation of the Spectra of 26I,II
diastereomer 1
diastereomer 2
δ [ppm]
A
−40.5
−27.4
2.2
−39.7
−28.1
1.9
M
X
Y
3.4
3.3
Z
39.8
−179
−269
−255
107
131
5
40.5
−179
−269
−255
106
134
3
J [Hz]
1J(PAPM)
1J(PAPX)
1J(PAPY)
2J(PMPX)
2J(PMPY)
2J(PXPY)
3J(PMPz)
4J(PAPZ)
5J(PXPZ)
5J(PYPZ)
−36
3
−42
4
3
4
3
3
3
(3J(PMPM′) = −26 Hz (rac-27c), J(PMPM′) = −28 Hz (meso-
27m)). Consequently, pentaphosphanes 26I,II are proposed to
display the configuration depicted in Figure 13 (top). Given the
Figure 12. 31P{1H} NMR spectrum of the reaction mixture of 18c,m
and 14 in a 5:2 ratio in CH2Cl2 solution after a reaction time of 15 h
(A, CH2Cl2, C6D6 capillary, 300 K); inset and enlargements B−D
show the experimental spectrum (upward, black) overlaid with the
experimental spectra of pure 19 (upward, red, CD2Cl2, 300 K) and
27c,m (upward, green, CD2Cl2, 300 K) where applicable and the
simulated spectra of the diastereomers of 26I,II (brown and blue,
downward).
Figure 13. Configuration of pentaphosphanes 26I,II (top) and
observed pair of diastereomers (I, II) comprising a pair of enantiomers
each.
to increased line widths. Thus, the coupling constants were
directly read from the experimental spectrum and used to
simulate the 31P{1H} NMR spectra of 26I,II. The obtained
simulated spectra of the two diastereomers are depicted in
brown and blue in Figure 12 (A (inset), B−D, downward). The
splitting pattern is exemplarily depicted for one diastereomer.
The derived 31P{1H} NMR spectroscopic parameters of 26I,II
which were used for the simulation are listed in Table 3.
The chemical shifts of the resonances corresponding to the
PA, PM, PX and PY nuclei of 26I,II and the observed coupling
constants are very similar to the corresponding parameters of
27c,m. Therefore, it is very likely that pentaphosphanes 26I,II are
all-trans configuration of the five-membered ring (vide supra),
two diastereomers (I, II) each comprising a pair of enantiomers
are possible (Figure 13) and are observed in the 31P{1H} NMR
spectrum. The unambiguous assignment of the resonances to
the corresponding diastereomers is not possible.
The above reaction was carried out in a 5:2 ratio of 27c,m:14.
Employing a 1:1 ratio instead, the 31P{1H} NMR spectrum
presented in Figure 14 (green) is obtained from the reaction
mixture after a reaction time of 15 h. The 31P{1H} NMR
spectrum of the 5:2 reaction is also depicted in Figure 14 (red)
for comparison. While minor amounts of starting material 14
are still present in the 1:1 reaction mixture, the increased
amount of 14 apparently leads to the increased formation of 19
as indicated by the comparably higher intensities of the
resonances of 19. In contrast, significantly less intense
structurally related to the isotetraphosphane moiety in 27c,m
.
Atoms PZ display chemical shifts which are very similar to those
of 25c,m. Thus, atoms PZ can be assumed to bear a phenyl and a
pyrazolyl substituent. The observed, prominent doublet
splittings of these two resonances (3J(PMPZ) = −35.8 Hz
3
(diastereomer 1), J(PMPZ) = −42.0 Hz (diastereomer 2)) are
comparable to the 3J(PMPM′) coupling constants in 27c,m
I
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Scheme 13. P−N/P−P Metathesis as a Powerful Strategy in
the Synthesis of Complex Polyphosphanes
type II constitutes a reductive coupling of P atoms originating
from 14 and is thus distinctly different from P−P bond
formation of type I (Scheme 7). This constitutes a novel
synthetic approach toward P−P bond formation starting from
easily accessible pyrazolylphosphanes.
Figure 14. 31P{1H} NMR spectra of the reaction mixtures of 27c,m and
14 in a 1:1 (green) and 5:2 (red) ratio in CH2Cl2 solution after
reaction times of 15 h (C6D6 capillary, 300 K); * impurities.
resonances are observed for 27c,m and 26I,II in the spectrum of
the 1:1 reaction compared to that of the reaction employing a
5:2 ratio. Overall, it is therefore concluded that the formation of
19 from 27c,m and 14 proceeds via the intermediates 26I,II and
24 as already depicted in Scheme 11. The addition of excess 14
shifts the equilibrium in favor of the formation of 19. This
detailed understanding of the reaction of 27c,m with 14 allows
for the formulation of a reaction equation for the formation of
19 from 14 and 18c,m (Scheme 12).
EXPERIMENTAL SECTION
■
All manipulations were performed in a Glovebox MB Unilab or using
Schlenk techniques under an atmosphere of purified argon (Westfalen
AG). Dry, oxygen-free solvents (CH2Cl2, CH3CN (distilled from
CaH2, respectively), Et2O, C6H6 (distilled from Na/benzophenone
respectively), n-hexane (distilled from Na)) were employed.
Deuterated benzene (C6D6) was purchased from Sigma-Aldrich and
distilled from Na. Anhydrous deuterated acetonitrile (CD3CN) and
dichloromethane (CD2Cl2) were purchased from Sigma-Aldrich. All
distilled and deuterated solvents were stored either over molecular
sieves (4 Å; CH2Cl2, CH3CN, C6D6, CD2Cl2, CD3CN) or potassium
mirror (n-hexane, Et2O, C6H6). Fe2(CO)9 was purchased from Sigma-
Aldrich. Tris(3,5-dimethyl-1-pyrazolyl)phosphane22 and 1,2-bis-
(phenylphosphanyl)ethane24 were prepared according to literature
procedures. All glassware was oven-dried at 160 °C prior to use. NMR
spectra were measured on a Bruker AVANCE III (1H (400.03 MHz),
13C (100.59 MHz), 31P (161.94 MHz)), at 300 K. All carbon-13 NMR
spectra were exclusively recorded with broad band proton decoupling.
Reported numbers of atoms in the 13C spectra were indirectly deduced
from the cross-peaks in 2D correlation experiments (HMBC, HSQC).
Chemical shifts were referenced to δTMS = 0.00 ppm (1H, 13C) and
δH PO (85%) = 0.00 ppm (31P, externally). Chemical shifts (δ) are
Scheme 12. Reaction Equation for the Formation of 19 from
a
18c,m and 14
a
(a) −10 17, CH3CN, RT, 20 h, 58%; an approximate 1:1 mixture of
3
4
18c and 18m was employed (according to 31P NMR spectroscopy), but
reported in ppm. Coupling constants (J) are reported in hertz.
Absolute values are reported, except for coupling constants derived by
means of line shape iteration (vide infra). Assignments of individual
resonances were performed using 2D techniques (HMBC, HSQC,
HH−COSY, PP-COSY) where necessary. For compounds which give
rise to a higher order spin-system in the 31P{1H} NMR spectrum, the
resolution-enhanced 31P{1H} spectrum was transferred to the software
gNMR, version 5.0.33 The full line shape iteration procedure of gNMR
was applied to obtain the best match of the fitted to the experimental
isomerization of the chiral P atoms occurs (vide supra).
Hexaphosphane 19 is formed in a unique combination of P−
P bond formation via protolysis (type I, Scheme 7) and P−N/
P−P bond metathesis reactions involving intermediates 24,
26I,II, and 27c,m from a 5:4 mixture of 18c,m:14. Employing a
slight excess of 14 increases the isolated yield of 19 (58%) as a
consequence of the shifting of the involved equilibrium
reactions as described above.
42
1
spectrum. J(31P31P) coupling constants were set to negative values,
and all other signs of the coupling constants were obtained
accordingly. The designation of the spin system was performed by
convention. The furthest downfield resonance is denoted by the latest
letter in the alphabet, and the furthest upfield by the earliest letter.
Melting points were recorded on an electrothermal melting point
apparatus (Barnstead Electrothermal IA9100) in sealed capillaries
under argon atmosphere and are uncorrected. Infrared (IR) and
Raman spectra were recorded at ambient temperature using a Bruker
Vertex 70 instrument equipped with a RAM II module (Nd:YAG laser,
1064 nm). The Raman intensities are reported in percent relative to
the most intense peak and are given in parentheses. An ATR unit
(diamond) was used for recording IR spectra. The intensities are
reported relative to the most intense peak and are given in parentheses
using the following abbreviations: vw = very weak, w = weak, m =
medium, s = strong, vs = very strong, sh = shoulder. Elemental
analyses were performed on a Vario EL III CHNS elemental analyzer
CONCLUSION
■
In summary, an efficient one-pot synthesis of hexaphosphane
19 featuring a 2,2′-bi(1,2,3-triphosphacyclopentane) moiety
was found. This compound represents the first isolable and fully
characterized hexaphosphane comprising this type of branched
polyphosphane motif. The stability of hexaphosphane 19 was
demonstrated by the preparation of the unprecedented,
dinuclear iron−carbonyl complex 21 which features hexaphos-
phane 19 as a bridging ligand. Detailed NMR spectroscopic
investigations yielded an in-depth understanding of the
mechanism of the formation of 19. Unique ethylene-bridged
bis-isotetraphosphanes 27c,m were identified as intermediates,
isolated and fully characterized.
at the IAAC, University of Munster, Germany.
̈
Most importantly, this study demonstrates the applicability
of P−N/P−P bond metathesis in the preparation of complex
polyphosphanes (type II, Scheme 13). P−P bond formation of
X-ray Data Collection and Reduction. Suitable single crystals of
19 and 21 were obtained by slow diffusion of n-hexane into a solution
of 19 in CH2Cl2 or by slow evaporation of a solution of 21 in toluene
J
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at −30 °C. Single crystals of 27m were obtained from the NMR sample
of the supernatant of the 5:2 reaction mixture of 27c,m and 14 in
CD3CN at room temperature. The crystals were coated with Paratone-
N oil, mounted using a glass fiber-pin, and frozen in the cold nitrogen
stream of the goniometer. X-ray diffraction data of compounds 19 and
21 were collected at 153(2) K on a Bruker AXS APEX CCD
diffractometer equipped with a rotation anode K using graphite-
monochromated Mo Kα radiation (λ = 0.71073 Å) and of 27m on
Bruker Quazar CCD diffractometer equipped with a microfocus sealed
tube using montel mirror-monochromated Mo Kα radiation (λ =
0.71073 Å). Diffraction data were collected over the full sphere, and
the frames were integrated using the Bruker SMART43 software
package employing the narrow frame algorithm. Data were corrected
for absorption effects using the SADABS routine (empirical multiscan
method). For further crystal and data collection details, see Table 4.
Structure Solution and Refinement. Atomic scattering factors
for non-hydrogen elements were taken from the literature tabulations.
Structure solutions were found by using direct methods as
implemented in the SHELXS-97 package44 and were refined with
SHELXL-9745 against F2, initially using isotropic and later anisotropic
thermal parameters for all non-hydrogen atoms. Positions of hydrogen
atoms were calculated and allowed to ride on the carbon atom to
which they are bonded, assuming C−H bond length of 0.95 Å. H-atom
temperature factors were set at 1.20 times the isotropic temperature
factor of the C atom to which they are bonded. The H-atom
contributions were calculated but not refined. Neither magnitude nor
positions of the remaining peaks in the final difference Fourier map are
of any chemical significance.
Preparation of 1,1′,3,3′-Tetraphenyl-2,2′-bi(1,2,3-triphos-
pholane) (19). A solution of 1,2-bis(phenylphosphino)ethane
(18c,m) (0.739 g, 3.00 mmol, 1.00 equiv, 1:1 mixture of the chiral
(18c) and meso (18m) isomers) in CH3CN (8 mL) was slowly added
to a solution of tris(3,5-dimethyl-1-pyrazolyl)phosphane (0.739 g, 3.00
mmol, 1.00 equiv) in CH3CN (12 mL). The initially colorless solution
turned into a pale yellow suspension shortly after addition was
completed. The mixture was stirred at ambient temperature for 24 h.
The obtained colorless precipitate was filtered off and washed with
CH3CN (4 × 5 mL), and all volatiles were removed in vacuo. Single
crystals suitable for X-ray single crystal structure determination were
obtained via slow diffusion of n-hexane into a solution of 19 in CH2Cl2
at ambient temperature. The filtrate was further processed for the
isolation of 24 (vide infra). Yield: 0.381 g (58%); mp: 197−199 °C;
Raman (100 mW, [cm−1]): 3085(7), 3047(71), 2943(12), 2923(26),
2897(60), 1583(81), 1569(8), 1431(6), 1409(11), 1156(15),
1096(26), 1027(48), 997(100), 687(6), 636(16), 618(12), 495(27),
469(23), 427(39), 402(8), 325(6), 299(8), 263(11), 240(18),
201(25), 169(39), 120(8), 104(35); IR (ATR, [cm−1]): 3647(vw),
2942(vw), 2889(w), 1581(w), 1567(vw), 1474(w), 1428(w),
1402(w), 1325(vw), 1301(vw), 1256(vw), 1224(vw), 1175(vw),
1151(w), 1112(vw), 1064(w), 1024(w), 996(w), 967(vw), 870(w),
782(w), 740(vs), 694(s), 644(w), 634(w), 498(m), 482(w), 452(w);
1H NMR (CD2Cl2, 300 K, [ppm]): δ = 7.40 (8H, m, C4-H), 7.23
(12H, m, C5-H, C6-H), 2.82 (8H, m, C1-H, C2-H); 13C{1H} NMR
(CD2Cl2, 300 K, [ppm]): δ = 138.4 (4C, C3), 132.4 (8C, C4), 128.8
(8C, C5), 128.3 (4C, C6), 32.9 (4C, C1, C2); 31P{1H} NMR
(CD2Cl2, 300 K, [ppm]): AA′XX′X″X‴ spin system: δ(PA) = −41.8
(2P), δ(PX) = 13.2 (4P); 1J(PAPA′) = −137.0 Hz, 1J(PAPX) = 1J(PAPX′)
Table 4. Crystallographic Data and Details of the Structure
Refinements of Compounds 19, 21, and 27m
19
21
27m
formula
Mr [g mol−1
C28H28P6
550.32
C36H28Fe2O8P6
886.10
C42H42P8
794.52
]
color, habit
colorless
plate
yellow plate
colorless
plate
crystal system
space group
a [Å]
triclinic
monoclinic
C2/c
monoclinic
P21/c
P1
̅
7.8833(9)
9.520(1)
9.840(1)
96.954(2)
102.101(1)
106.323(1)
680.1(1)
1
14.8647(5)
13.8772(5)
19.5756(7)
90
13.140(2)
15.312(2)
10.269(1)
90
b [Å]
c [Å]
α [deg]
β [deg]
γ [deg]
V [Å3]
110.079(1)
90
94.958(4)
90
3792.6(2)
4
2058.4(4)
2
Z
T [K]
153(1)
153(1)
153(1)
crystal size [mm]
0.12 × 0.05
× 0.04
1.344
0.07 × 0.07 ×
0.14 × 0.08
× 0.03
1.282
0.01
ρc [g cm−3
F(000)
]
1.552
286
1800
828
λMo Kα [Å]
0.71073
2.16, 27.88
0.71073
2.07, 27.87
0.71073
1.56, 27.87
1
1
2
2
= J(PA′PX″) = J(PA′PX‴) = −258.5 Hz, J(PA2PX″) = J(PAPX‴) =
θmin [deg],
θmax [deg]
2J(PA′PX) = J(PA′PX′) = 142.5 Hz, J(PXPX′) = J(PX″PX‴) = 1.9 Hz,
2
2
3J(PXPX‴) = J(PX′PX″) = 31.7 Hz, J(PXPX″) = J(PX′PX‴) = 49.5 Hz;
3
3
3
index range
10 ≥ h ≥
−10
19 ≥ h ≥ −19
18 ≥ k ≥ −18
15 ≥ h ≥
−17
elemental analysis: calcd for C28H28P6: C: 61.1, H: 5.1, found: C: 59.6,
H: 4.9; MS-ESI-EM: 551.0692 (MH+), calcd for C28H29P6: 551.0873.
Preparation of 1,1′-(1,1′,3,3′-Tetraphenyl-2,2′-bi(1,2,3-
triphospholane))bis(iron(0)tetracarbonyl) (21). THF (80 mL)
12 ≥ k ≥
20 ≥ k ≥
−11
−13
12 ≥ l ≥ −12
0.412
25 ≥ l ≥ −25
1.069
12 ≥ l ≥ −23
0.368
μ [mm−1
]
absorption
correction
SADABS
SADABS
SADABS
reflections collected
reflections unique
Rint
6398
3192
0.0155
2907
19042
4532
14406
4864
0.0237
3936
0.0496
3097
reflections obsd
[F > 3σ(F)]
residual density
0.400
−0.194
0.359
−0.188
0.441
−0.277
[e Å−3
]
parameters
GOOF
154
235
226
1.054
0.0278
0.0750
883610
1.025
0.0243
0.0608
883611
1.019
5.65
R1 [I > 2σ(I)]
wR2 (all data)
CCDC
13.98
883612
was added to a mixture of 19 (0.37 g, 0.66 mmol, 1 equiv) and
Fe2(CO)9 (0.485 g, 1.33 mmol, 2 equiv) in the dark. The mixture was
K
dx.doi.org/10.1021/ja305406x | J. Am. Chem. Soc. XXXX, XXX, XXX−XXX

Journal of the American Chemical Society
Article
stirred for 72 h. Slow dissolution of the orange crystals of Fe2(CO)9
was observed. All volatiles were removed from the mixture in vacuo,
and the resulting solid was dissolved in toluene (80 mL). Slow removal
of toluene in vacuo and storage at −18 °C yielded 21 as pale orange
crystals. Yield: 0.161 g (28%); mp: decomp at T > 120 °C; Raman (10
mW, [cm−1]): 3059(49), 2942(10), 2916(52), 2055(28), 1986(74),
1937(87), 1922(10), 1595(47), 1516(9), 1189(6), 1158(9), 1102(15),
1028(31), 1003(100), 666(9), 641(7), 618(14), 480(11), 466(21),
439(72), 406(9), 330(22), 217(7); IR (ATR, [cm−1]): 3058(vw),
2905(vw), 2046(s), 1978(w), 1913(vs, br, sh), 1582(vw), 1481(vw),
1433(w), 1415(vw), 1400(vw), 1302(vw), 1230(vw), 1186(vw),
1118(vw), 1089(w), 999(w), 876(w), 784(w), 742(m), 691(m),
1
666(w), 608(vs), 514(m); H NMR (THF-d8 , 300 K, [ppm]): δ =
7.61 (4H, m, C4-H), 7.25 (6H, m, C5-H, C6-H), 7.14 (4H, m, C8-H),
7.08−6.98 (6H, m, C9-H, C10-H), 3.61 (2H, m, ν1/2 = 26.4 Hz, C2-
H), 3.16 (2H, m, ν1/2 = 42.2 Hz, C1-H), 2.98 (2H, pseudo quint, C2-
H), 2.63 (2H, m, ν1/2 = 27.6 Hz, C1-H); 1H{31P} NMR (THF-d8 , 300
K, [ppm]): δ = 7.61 (4H, m, C4-H), 7.25 (6H, m, C5-H, C6-H), 7.14
(4H, m, C8-H), 7.08−6.98 (6H, m, C9-H, C10-H) 3.61 (2H, ddd,
3 gauche
3 anti
2JC2‑H,C2‑H = 15.0 Hz, J
= 5.5 Hz, J
= 5.2 Hz,
= 5.5 Hz,
C2‑H,C1‑H
C2‑H,C1‑H
2
3 gauche
C2-H), 3.16 (2H, ddd, JC1‑H,C1‑H = 13.7 Hz, J
C2‑H,C1‑H
2
3Janti
= 6.3 Hz, C1-H), 2.98 (2H, ddd, JC2‑H,C2‑H = 15.0 Hz,
C2‑H,C1‑H
3JgaucheC2‑H,C1‑H = 9.3 Hz, 3JantiC2‑H,C1‑H = 6.3 Hz, C2-H), 2.63 (2H, ddd,
3 gauche
3 anti
2JC1‑H,C1‑H = 13.7 Hz, J
= 9.3 Hz, J
= 5.2 Hz,
C2‑H,C1‑H
C2‑H,C1‑H
C1-H); 13C{1H} NMR (THF-d8, 300 K, [ppm]): δ = 214.5 (8C,
pseudo tt, CO), 137.8 (2C, m, C3), 137.1 (2C, m, C7), 132.1 (4C,
pseudo sept, C8), 130.9 (6C, m, C4, C6), 129.6 (4C, m, C5), 128.9
(4C, pseudo t, C9), 128.8 (2C, s, C10), 40.1 (2C, pseudo t, C2), 31.6
(2C, pseudo t, C1); 31P{1H} NMR (THF-d8, 300 K, [ppm]):
AA′MM′XX′ spin system: δ(PA) = −47.4 (2P), δ(PM) = 15.3 (2P),
δ(PX) = 93.0 (2P); J(PAPA′) = −317.5 Hz, J(PAPM) = J(PA′PM′) =
−314.0 Hz, 1J(PAPX) = 1J(PA′PX′) = −276.7 Hz, 2J(PAPM′) = 2J(PA′PM)
= −2.0 Hz, 2J(PAPX′) = 2J(PA′PX) = 103.1 Hz, 2J(PMPX) = 2J(PM′PX′) =
1.1 Hz, 3J(PMPM′) = 163.8 Hz, 3J(PMPX′) = 3J(PM′PX) = 5.3 Hz,
3J(PXPX′) = 51.0 Hz; elemental analysis: calcd for C36H28Fe2O8P6: C:
mmol, 1.5 equiv, 1:1 mixture of the chiral (18c) and meso (18m)
isomers) in CH3CN (2 mL) was slowly added to a solution of tris(3,5-
dimethyl-1-pyrazolyl)phosphane (0.16 g, 0.50 mmol, 1.0 equiv) in
CH3CN (3 mL). A colorless oil formed during the addition which
gradually turned into a colorless solid. The mixture was stirred
overnight. The resulting colorless suspension was filtered. The
obtained solid was stirred in CH3CN (5 × 8 mL) for 20 min, filtered
off, respectively, and dried in vacuo. Obtained 27c,m is a mixture of the
diastereomers 27m and 27c in a ratio of approximately 48(27c):52-
(27m). [Remark: The phenyl substituents on a single triphosphacy-
clopentane moiety are chemically inequivalent. As the resonances in
1
1
1
48.8, H: 3.2, found: C: 49.4, H: 3.2.
Isolation and Spectroscopic Characterization of 1-(1,3-
Diphenyl-1,2,3-triphospholan-2-yl)-3,5-dimethylpyrazole (24).
1
the H and 13C spectra corresponding to these substituents are not
separated, both substituents are marked uniformly as A.] Yield: 0.108 g
(54%); mp: 161−163 °C; Raman (50 mW, [cm−1]): 3048(81),
2922(11), 2899(38), 1584(50), 1408(11), 1247(6), 1156(13),
1093(14), 1027(27), 1000(100), 738(17), 690(9), 640(9), 617(8),
510(12), 464(11), 426(18), 238(10), 202(12), 138(14); IR (ATR,
[cm−1]): 3046(vw), 2896(vw), 1583(vw), 1478(w), 1431(m),
1406(w), 1303(vw), 1224(vw), 1183(vw), 1155(w), 1080(vw),
1064(w), 1025(w), 999(w), 870(w), 787(m), 739(s), 722(w),
692(vs), 666(w), 647(m), 508(w), 499(s), 482(m), 465(w),
453(w); 1H NMR (CD2Cl2 , 300 K, [ppm]): δ = 7.70 (8H, m,
Cortho(B)-H), 7.37 (4H, m, Cpara(B)-H), 7.36 (8H, m, Cmeta(B)-H),
7.29 (8H, m, Cortho(A)-H), 7.21−7.11 (32H, Cmeta(A)-H, Cortho(A)-H,
Cpara(A)-H), 2.63−2.17 (24H, m, CH2); 13C{1H} NMR (CD2Cl2, 300
K, [ppm]): δ = 138.1 (8C, m, Cipso(A)), 136.2 (4C, m, Cipso(B)),
134.5 (8C, m, Cortho(B)), 132.5 (8C, pseudo-ddd, Cortho(A)), 132.2
(8C, pseudo-ddd, Cortho(A)), 129.9 (2C, pseudo-t, Cpara(B)), 129.8
(2C, pseudo-t, Cpara(B)), 128.8−128.5 (24C, m, Cmeta(A,B)),
128.3(4C, pseudo-t, Cpara(A)), 128.1 (4C, pseudo-t, Cpara(A)), 32.7
(4C, pseudo-dd, CH2(C)), 32.2 (4C, pseudo-d, CH2(C)), 25.1 (4C,
s(broad), ν1/2 = 44 Hz, CH2(D)); 31P{1H} NMR (CD2Cl2, 300 K,
[ppm]): rac-27c: AA′MM′XX′YY′ spin system: δ(PA) = −41.5 (2P),
δ(PM) = −26.4 (2P), δ(PX) = 2.6 (2P), δ(PY) = 3.4 (2P); 1J(PAPM) =
From the filtrate prepared according to the synthetic procedure for 19,
triphosphane 24 was isolated by column chromatography under argon
employing Al2O3 (dried at 380 °C for 72 h) as the stationary phase in
a column of 2.5 cm in diameter which was filled to a height of 15 cm.
Et2O was used as the eluent and 20 fractions of 5 mL were collected.
24 was isolated from fractions 11−13 (yield: 8 mg) and was
characterized by means of 1H and 31P{1H} NMR spectroscopy. It
decomposed in solution during the measurement of the 13C{1H}
NMR spectrum which prevented the assignment of the resonances. 1H
NMR (CD2Cl2 , 300 K, [ppm]): δ = 7.26−7.18 (10 H, m, Ph), 5.85
4
(1H, d, J(HP) = 2.6 Hz, C2-H), 3.20 (2H, m, C6-H), 2.85 (2H, m,
C6-H), 2.45 (3H, s, C5-H), 2.19 (3H, s, C4-H); 31P{1H} NMR
(CD2Cl2, 300 K, [ppm]): A2M spin system: δ(PA) = 21.2 (2P), δ(PM)
1
1
1
1
1J(PA′PM′) = −178 Hz, J(PAPX) = J(PA′PX′) = −269 Hz, J(PAPY) =
= 63.5 (1P); J(PAPM) = −277.5 Hz.
1J(PA′PY′) = −254 Hz, J(PMPX) = J(PM′PX′) = 108 Hz, J(PMPY) =
Preparation of a Mixture of Diastereomers 1-((1R)-((1R,3S)-
1,3-Diphenyl-1,2,3-triphospholan-2-yl)(phenyl)phosphino)-2-
((1S)-((1R,3S)-1,3-diphenyl-1,2,3-triphospholan-2-yl)(phenyl)-
phosphino)ethane (27m) and rac-1,2-Bis(((1R,3S)-1,3-diphenyl-
1,2,3-triphospholan-2-yl)(phenyl)phosphanyl)ethane (27c). A
solution of 1,2-bis(phenylphosphino)ethane (18c,m) (0.19 g, 0.75
2
2
2
2J(PM′PY′) = 135 Hz, J(PXPY) = J(PX′PY′) = 6 Hz, J(PMPM′) = −26
2
2
3
4
4
5
5
Hz, J(PAPM′) = J(PA′PM) = 1 Hz, J(PAPA′) = 0 Hz, J(PMPX′) =
5J(PM′PX) = 1 Hz, J(PMPY′) = J(PM′PY) = 2 Hz, J and J coupling
5
5
6
7
constants were not observed; meso-27m: AA′MM′XX′YY′ spin system:
L
dx.doi.org/10.1021/ja305406x | J. Am. Chem. Soc. XXXX, XXX, XXX−XXX

Journal of the American Chemical Society
Article
δ(PA) = −41.0 (2P), δ(PM) = −26.9 (2P), δ(PX) = 2.6 (2P), δ(PY) =
(m, C1 (25c,m), C1 (26I,II)), 149.4−148.9 (m, C3 (25c,m), C1 (26I,II)),
139.2−139.0 (m, C6 (25c,m), C6, C12, C16 (26I,II)), 134.9 (m, C13
(26I,II)), 132.7 (m, C17 (26I,II)), 132.4−132.0 (m, C7 (26c,m), C7
(26I,II)), 130.9−130.6 (m, C9 (25c,m), C9, C15 (26I,II)), 129.5 (m, C8
(25c,m), C8, C14, C18 (26I,II)), 129.0 (s, C19 (26I or 26II)), 128.9 (s,
C19 (26I or 26II)), 107.7 (m, C2 (25c,m), C2 (26I,II)), 32.7 (m, C20 or
C21 (26I,II)), 32.4 (m, C20 or C21 (26I,II)), 25.6−25.5 (m, C10
(25c,m), C10, C11 (26I,II)), 14.1 (s, C4 (25c,m), C4 (26I,II)), 12.7−
12.5 (m, C5 (25c,m), C5 (26I,II)); 31P{1H} NMR (CD3CN, 300 K,
[ppm]): δ = 40.3 (s, 26c/m), 39.9 (m, Z-parts of the AMXYZ spin
systems of 26I,II), 39.9 (s, 25c/m), 37.6 (m, unassigned), 4.6−1.3 (m,
X- and Y-parts of the AMXYZ spin systems of 26I,II), −26.0−(−29.9)
(m, M-parts of the AMXYZ spin systems of 26I,II), −37.3−(−42.2)
(m, A-parts of the AMXYZ spin systems of 26I,II).
1
1
1
1
3.2 (2P); J(PAPM) = J(PA′PM′) = −173 Hz, J(PAPX) = J(PA′PX′) =
1
1
2
2
−266 Hz, J(PAPY) = J(PA′PY′) = −255 Hz, J(PMPX) = J(PM′PX′) =
2
2
2
2
114 Hz, J(PMPY) = J(PM′PY′) = 135 Hz, J(PXPY) = J(PX′PY′) = 5
Hz, 3J(PMPM′) = −28 Hz, 4J(PAPM′) = 4J(PA′PM) = 1 Hz, 5J(PAPA′) = 0
5
5
5
5
6
Hz, J(PMPX′) = J(PM′PX) = 1 Hz, J(PMPY′) = J(PM′PY) = 2 Hz, J
and 7J coupling constants were not observed; elemental analysis: calcd
for C42H42P8: C: 63.5, H: 5.2, found: C: 63.4, H: 5.3; MS-ESI-EM:
795.1271 (MH+), calcd for C42H43P8: 795.7266; 519.0849 (M, −1,3-
diphenyl-1,2,3-triphospholide), calcd for C28H28P5: 519.0879.
Reactions of 27c,m with 14. 1. Reaction in a 5:2 Ratio.
Spectroscopic Characterization of 25c,m and 26I,II. A solution of
14 (10.1 mg, 0.032 mmol, 2 equiv) in CH2Cl2 (0.5 mL) was added to
a solution of 27c,m (63.6 mg, 0.080 mmol, 5 equiv) in CH2Cl2 (0.5
1
mL). The resulting pale yellow solution was stirred for 15 h. H, 31P,
2. Reaction in a 1:1 Ratio. A solution of 14 (6.4 mg, 0.02 mmol, 1
equiv) in CH2Cl2 (0.5 mL) was added to a solution of 27c,m (15.9 mg,
0.02 mmol, 1 equiv) in CH2Cl2 (0.5 mL). The resulting pale yellow
solution was stirred for 15 h. 1H, 31P, and 31P{1H} NMR spectra were
recorded (C6D6 capillary, 300 K). The following resonances were
observed in the 31P{1H} NMR spectrum which is depicted in Figure
14. 31P{1H} NMR (CH2Cl2, C6D6 capillary, 300 K, [ppm]): δ = 72.0
(s, 14), 63.6 (m, M-part of the A2M spin system of 24), 40.8 (s,
25c/m), 40.6 (dddd, Z-part of the AMXYZ spin system of 26,
diastereomer 2), 39.9 (dddd, Z-part of the AMXYZ spin system of 26,
diastereomer 1), 39.6 (s, 25c/m), 21.3 (m, A-part of the A2M spin
system of 24), 13.3 (m, X-part of the AA′XX′X″X‴ spin system of 19),
4.9−0.8 (m, X- and Y-parts of the AA′MM′XX′YY′ spin systems of
27c,m and X- and Y-parts of the AMXYZ spin systems of 26I,II), −1.6
(m, unassigned), −4.6 (m, unassigned), −25.7−(−29.4) (m, M-parts
of the AA′MM′XX′YY′ spin systems of 27c,m and the AMXYZ spin
systems of 26I,II), −37.4−(−45.0) (m, A-parts of the AA′XX′X″X‴
spin system of 19, the AA′MM′XX′YY′ spin systems of 27c,m and the
AMXYZ spin systems of 26I,II).
and 31P{1H} NMR spectra of the mixture were measured (C6D6
capillary, 300 K). The resonances observed in the 31P{1H} NMR
spectrum, which is depicted in Figures 12 and 14, are listed below. The
spin systems of 26I,II were analyzed in detail (Figure 12), and the
derived parameters are also listed below. All volatiles were removed in
vacuo from the remaining reaction mixture resulting in the formation
of a semicrystalline, colorless residue which was suspended in CH3CN
(1 mL) and filtered. The filtrate was stored at −35 °C for 15 h,
resulting in the formation of small amounts of a colorless precipitate
which were filtered off. All volatiles were removed from the filtrate in
vacuo, yielding a colorless solid which was found to contain
approximately 1:1 mixtures of the diastereomers of 25c,m as the
major component (approximately 64%) and the diastereomers of 26I,II
(approximately 33%) as well as minor amounts of unidentified
byproduct. Further purification of 25c,m via crystallization, sublimation,
or column chromatography was not successful. However, multinuclear
NMR experiments (CD3CN, 300 K) of the enriched sample of 25c,m
allowed for the assignment of the resonances corresponding to 25c,m
1
and 26I,II in the H, 13C{1H}, and 31P{1H} NMR spectra which are
given below. Resonances observed in the 31P{1H} NMR spectrum of
the reaction mixture: 31P{1H} NMR (CH2Cl2, C6D6 capillary, 300 K,
[ppm]): δ = 63.6 (m, M-part of the A2M spin system of 24), 40.7 (s,
25c/m), 40.6 (dddd, Z-part of the AMXYZ spin system of 26,
diastereomer 2), 39.9 (dddd, Z-part of the AMXYZ spin system of 26,
diastereomer 1), 39.6 (s, 25c/m), 21.3 (m, A-part of the A2M spin
system of 24), 13.3 (m, X-part of the AA′XX′X″X‴ spin system of 19),
4.9−0.8 (m, X- and Y-parts of the AA′MM′XX′YY′ spin systems of
27c,m and X- and Y-parts of the AMXYZ spin systems of 26,
diastereomers 1 and 2), −4.6 (m, unassigned), −25.7−(−29.4) (m, M-
parts of the AA′MM′XX′YY′ spin systems of 27c,m and the AMXYZ
spin systems of 26, diastereomers 1 and 2), −37.4−(−45.0) (m, A-
parts of the AA′XX′X″X‴ spin system of 19, the AA′MM′XX′YY′ spin
systems of 27c,m and the AMXYZ spin systems of 26, diastereomers 1
and 2).31P{1H} NMR Parameters of 26I,II in the Reaction Mixture
Diastereomer 1: 31P{1H} NMR (CH2Cl2, C6D6 capillary, 300 K);
AMXYZ spin system: δ(PA) = −40.5 ppm (1P), δ(PM) = −27.4 ppm
(1P), δ(PX) = 2.2 ppm (1P), δ(PY) = 3.4 ppm (1P), δ(PZ) = 39.8 ppm
(1P); 1J(PAPM) = −179.0 Hz, 1J(PAPX) = −269.0 Hz, 1J(PAPY) =
ASSOCIATED CONTENT
* Supporting Information
Crystallographic information files. This material is available free
■
S
of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
jweigand@uni-muenster.de
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We appreciate having been financially supported by the Fonds
der Chemischen Industrie (fellowship to K.-O.F.), the DFG
(WE 4621/2-1), the European COST network PhosSciNet
(CM0802), and the ERC (SynPhos 307616). J.J.W. thanks
Prof. F. Ekkehardt Hahn (WWU Muenster) for his support,
and Prof. Robert Wolf (University of Regensburg) for helpful
discussions.
2
2
2
−255.0 Hz, J(PMPX) = 107.0 Hz, J(PMPY) = 131.0 Hz, J(PXPY) =
3
4
5
4.5 Hz, J(PMPZ) = −35.8 Hz, J(PAPZ) = 3.0 Hz, J(PXPZ) = 3.4 Hz,
5J(PYPZ) = 3.0 Hz. Diastereomer 2: 31P{1H} NMR (CH2Cl2, C6D6
capillary, 300 K); AMXYZ spin system: δ(PA) = −39.7 ppm (1P),
δ(PM) = −28.1 ppm (1P), δ(PX) = 1.9 ppm (1P), δ(PY) = 3.3 ppm
1
1
REFERENCES
(1P), δ(PZ) = 40.5 ppm (1P); J(PAPM) = −179.0 Hz, J(PAPX) =
■
1
2
2
−269.0 Hz, J(PAPY) = −255.0 Hz, J(PMPX) = 106.0 Hz, J(PMPY) =
(1) Gomez-Ruiz, S.; Hey-Hawkins, E. Coord. Chem. Rev. 2011, 255,
1360.
(2) (a) Scheer, M.; Balazs, G.; Seitz, A. Chem. Rev. 2010, 110, 4236.
(b) Giffin, N. A.; Masuda, J. D. Coord. Chem. Rev. 2011, 255, 1342.
2
3
4
134.0 Hz, J(PXPY) = 3.0 Hz, J(PMPZ) = −42.0 Hz, J(PAPZ) = 3.5
Hz, 5J(PXPZ) = 3.0 Hz, 5J(PYPZ) = 3.0 Hz.Resonances Observed in the
31P{1H} NMR Spectrum of the Enriched Sample of 25c,m
1H NMR (CD3CN, 300 K, [ppm]): δ = 7.71−7.60 (m, C13-H
(26I,II)), 7.50−7.07 (m, Caryl-H (25c,m), Caryl-H (26I,II)), 5.89 (s, C2-
H, (25c,m), C2-H (26I,II)), 2.67−2.47 (m, C10-H, (25c,m), C10-H,
C11-H (26I,II)), 2.62−2.27 (m, C20-H, C21-H, (26I,II), 2.40−2.33 (m,
C5-H, (25c,m), C5-H (26I,II)), 2.20−2.01 (m, C10-H, (25c,m), C10-H,
C11-H (26I,II)), 2.18−2.10 (25c,m), 2.15−2.12 (m, C4-H, (25c,m), C4-
H (26I,II)); 13C{1H} NMR (CD3CN, 300 K, [ppm]): δ = 153.5−153.4
(3) (a) Honle, W.; von Schnering, H. G. Z. Kristallogr. 1980, 153,
̈
339. von Schnering, H. G.; Honle, W. Phosphides: Solid State
̈
Chemistry. In Encyclopedia of Inorganic Chemistry; King, R. B., Ed.;
Wiley: Chichester, U.K., 1994; p 3106. (c) Pottgen, R.; Honle, W.; von
̈
̈
Schnering, H. G. Phosphides: Solid State Chemistry. In Encyclopedia of
Inorganic Chemistry, 2nd ed.; King, R. B., Ed.; Wiley: Chichester, U.K.,
2005; Vol. VIII, p 4255, and reference therein.
M
dx.doi.org/10.1021/ja305406x | J. Am. Chem. Soc. XXXX, XXX, XXX−XXX

Journal of the American Chemical Society
Article
(4) (a) Baudler, M. Angew. Chem., Int. Ed. Engl. 1982, 21, 492.
(b) Baudler, M. Angew. Chem., Int. Ed. 1987, 26, 419. (c) Baudler, M.;
Glinka, K. Chem. Rev. 1993, 93, 1623. (d) Baudler, M.; Glinka, K.
Chem. Rev. 1994, 94, 1273.
(33) Budzelaar, P. H. M. gNMR for Windows (5.0.6.0). NMR
Simulation Program, IvorySoft 2006).
(34) (a) Gil, V. M. S.; von Philipsborn, W. Magn. Reson. Chem. 1989,
27, 409. (b) McFarlane, H. C. E.; McFarlane, W. J. Chem. Soc., Chem.
Commun. 1975, 582.
(5) (a) Fritz, G. Comments Inorg. Chem. 1982, 6, 329. (b) Fritz, G.
(35) Del Bene, J. E.; Elguero, J. J. Phys. Chem. A 2006, 110, 12543.
(36) Hitchcock, P. B.; Lappert, M. F.; Leung, W.-P.; Yin, P. J. Chem.
Soc., Dalton Trans. 1995, 3925.
(37) Brown, L. D.; Datta, S.; Kouba, J. K.; Smith, L. K.; Wreford, S. S.
Inorg. Chem. 1978, 17, 729.
Adv. Inorg. Chem. 1987, 171.
(6) Luo, Y. R. Comprehensive Handbook of Chemical Bond Energies;
CRC Press: Boca Raton, 2007.
(7) (a) Haiduc, I. The Chemistry of Inorganic Ring Systems; Wiley-
Interscience: London, 1970. (b) Kosolapoff, G. M.; Maier, L. Organic
Phosphorus Compounds; Wiley-Interscience: New York, 1972.
(8) (a) Maier, L. Helv. Chim. Acta 1966, 49, 1119. (b) Niecke, E.;
(38) Fritz, G.; Jarmer, M.; Matern, E. Z. Anorg. Allg. Chem. 1990, 586,
47.
(39) Baudler, M.; Makowka, B. Z. Anorg. Allg. Chem. 1985, 528, 7.
(40) Baudler, M.; Aktalay, Y.; Tebbe, K.-F.; Heinlein, T. Angew.
Chem., Int. Ed. Engl. 1981, 11, 967.
(41) (a) von Schneering, H. G.; May, W. Z. Naturforsch. B 1978, 33,
698. (b) Kazul’kin, D. N.; Ryabov, A. N.; Izmer, V. V.; Churakov, A.
V.; Beletskaya, I. P.; Burns, C. J.; Voskoboynikov, A. Z. Organometallics
2005, 24, 3024.
(42) (a) McFarlane, H. C. E.; McFarlane, W.; Nash, J. Dalton Trans.
1980, 240. (b) Aime, S.; Harris, R. K.; McVicker, E. M.; Fild, M.
Dalton Trans. 1976, 2144. (c) Forgeron, M. A. M.; Gee, M.;
Wasylishen, R. E. J. Phys. Chem. 2004, 108, 4895. (d) Del Bene, J. E.;
Elguero, J.; Alkorta, I. J. Phys. Chem. 2004, 108, 3662.
(43) SMART; Bruker AXS, 2000 program package.
(44) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467.
Ruger, R.; Krebs, B. Angew. Chem., Int. Ed. Engl. 1982, 21, 544.
̈
(c) Burg, A. B. J. Am. Chem. Soc. 1961, 83, 2226. (d) Jurkschat, K.;
Mugge, C.; Tzschach, A.; Uhlig, W.; Zschunke, A. Tetrahedron Lett.
1982, 23, 1345. (e) Mazieres, M. R.; Rauzy, K.; Bellan, J.; Sanchez, M.;
Pfister-Guillouzo, G.; Senio, A. Phosphorus, Sulfur, Silicon 1993, 76, 45.
(9) (a) Etkin, N.; Fermin, M. C.; Stephan, D. W. J. Am. Chem. Soc.
1997, 119, 2954. (b) Greenberg, S.; Stephan, D. W. Chem. Soc. Rev.
́
2008, 37, 1482. (c) Gomez-Ruiz, S.; Frank, R.; Gallego, B.; Zahn, S.;
Kirchner, B.; Hey-Hawkins, E. Eur. J. Inorg. Chem. 2011, 739.
(10) (a) Less, R. J.; Melen, R. L.; Naseri, V.; Wright, D. S. Chem.
Commun. 2009, 4929. (b) Beswick, M. A.; Choi, N.; Harmer, C. N.;
Hopkins, A. D.; McPartlin, M.; Wright, D. S. Science 1998, 281, 1500.
(11) (a) Waterman, R. Cur. Org. Chem. 2008, 12, 1322. (b) Bohm, V.
̈
P. W.; Brookhart, M. Angew. Chem., Int. Ed. 2001, 40, 4694.
(12) Kovacs, I.; Krautscheid, H.; Matern, E.; Fritz, G. Z. Anorg. Allg.
Chem. 1994, 1369.
(45) Sheldrick, G. M. SHELXL-97; Universitat Gottingen, 1997.
̈
̈
(13) (a) Fritz, G.; Mayer, B.; Matern, E. Z. Anorg. Allg. Chem. 1992,
607, 19. (b) Kovacs, I.; Fritz, G. Z. Anorg. Allg. Chem. 1994, 620, 1.
(c) Fritz, G.; Goesmann, H.; Mayer, B. Z. Anorg. Allg. Chem. 1992,
607, 26. (d) Fritz, G.; Vaahs, T. Z. Anorg. Allg. Chem. 1987, 552, 18.
(14) Baudler, M.; Reuschenbach, G.; Hahn, J. Z. Anorg. Allg. Chem.
1981, 482, 27.
(15) Fritz, G.; Vaahs, T. Z. Anorg. Allg. Chem. 1987, 553, 85.
(16) Avens, L. R.; Cribbs, L. V.; Mills, J. L. Inorg. Chem. 1989, 28,
211.
(17) Cowley, A. H.; Dierdorf, D. S. J. Am. Chem. Soc. 1969, 91, 6609.
(18) Carey, F. A.; Sundberg, J. Advanced Organic Chemistry, Part B:
Reactions and Synthesis, 5th ed.; Springer: New York, 2008.
(19) Avens, L. R.; Cribbs, L. V.; Mills, J. L. Inorg. Chem. 1989, 28,
205.
(20) (a) Weigand, J. J.; Feldmann, K.-O.; Echterhoff, A. K. C.; Ehlers,
A. W.; Lammertsma, K. Angew. Chem., Int. Ed. 2010, 49, 6178.
(b) Feldmann, K.-O.; Schulz, S.; Klotter, F.; Weigand, J. J.
ChemSusChem 2011, 4, 1805.
(21) (a) Feldmann, K.-O.; Weigand, J. J. Angew. Chem., Int. Ed. 2012,
51, 6566. (b) Feldmann, K.-O.; Weigand, J. J. Angew. Chem., Int. Ed.
2012, 51, 7545.
(22) Fischer, S; Peterson, L. K.; Nixon, J. F. Can. J. Chem. 1974, 52,
3981.
(23) Feldmann, K.-O.; Frohlich, R.; Weigand, J. J. Chem. Commun.
̈
2012, 48, 4296.
(24) Issleib, K.; Weichmann, H. Chem. Ber. 1968, 101, 2197.
(25) Dyker, C. A.; Riegel, S. D.; Burford, N.; Lumsden, M. D.;
Decken, A. J. Am. Chem. Soc. 2007, 129, 7464.
(26) Pople and Cremer ring puckering analysis: (a) Cremer, D.;
Pople, J. A. J. Am. Chem. Soc. 1975, 97, 1354. (b) Spek, A. L. J. Appl.
Crystallogr. 2003, 36, 7.
(27) von Schnering, H. G.; May, W. Z. Naturforsch. B 1978, 33, 698.
(28) Baudler, M.; Tolls, E.; Clef, E.; Koch, V; Kloth, B. Z. Anorg. Allg.
Chem. 1979, 456, 5.
(29) Strauss, H. L. Annu. Rev. Phys. Chem. 1983, 34, 301.
(30) Albrand, J. P.; Robert, J. B. Chem. Commun. 1974, 644.
(31) Scheer, M.; Gremler, S.; Herrmann, E.; Grunhagen, U.; Dargatz,
̈
M.; Kleinpeter, E. Z. Anorg. Allg. Chem. 1991, 600, 203.
(32) Baudler, M.; Vesper, J.; Sandmann, H. Z. Naturforsch. B 1972,
27, 1007.
N
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