Oxidation products of calcium and strontium bis(diphenylphosphanide)

Article abstract of DOI:10.1021/ic300975s

The tetrahydrofuran adducts [(thf)₄M(PPh₂) ₂] (M = Ca, Sr) are air sensitive and can easily be oxidized by chalcogens. Metalation of diphenylphosphane oxide, diphenylphosphinic acid, and diphenyldithiophosphinic acid as well as salt metathetical approaches of the potassium salts with MI₂ allow the synthesis of [(thf) ₄Ca(OPPh₂)₂] (1), [(dmso)₂Ca(O ₂PPh₂)₂] (2), [(thf)₃Ca(O ₂PPh₂)I]₂ (3), [(thf)₃Ca(S ₂PPh₂)₂] (4), [(thf)₂Ca(Se ₂PPh₂)₂] (5), [(thf)₃Sr(S ₂PPh₂)₂] (6), [(thf)₃Sr(Se ₂PPh₂)₂] (7), and [(thf)₂Ca(O ₂PPh₂)(S₂PPh₂)]₂ (8), respectively. The diphenylphosphinite anion in 1 contains a phosphorus atom in a trigonal pyramidal environment and binds terminally via the oxygen atom to calcium. The diphenylphosphinate anions act as bridging ligands leading to polymeric structures of calcium bis(diphenylphosphinates). Therefore strong Lewis bases such as dimethylsulfoxide (dmso) are required to recrystallize this complex yielding chain-like 2. The chain structure can also be cut into smaller units by ligands which avoid bridging positions such as iodide and diphenyldithiophosphinate (3 and 8, respectively). In general, diphenyldithio- and -diselenophosphinate anions act as terminal ligands and allow the isolation of mononuclear complexes 4 to 7. In these molecules the alkaline earth metals show coordination numbers of six (5) and seven (4, 6, and 7).

Full text of DOI:10.1021/ic300975s

Article
pubs.acs.org/IC
Oxidation Products of Calcium and Strontium
Bis(diphenylphosphanide)
Tareq M. A. Al-Shboul, Gritt Volland, Helmar Gorls, Sven Krieck, and Matthias Westerhausen*
̈
Institute of Inorganic and Analytical Chemistry, Friedrich Schiller University of Jena, Humboldtstrasse 8, D-07743 Jena, Germany
S
* Supporting Information
ABSTRACT: The tetrahydrofuran adducts [(thf)4M(PPh2)2]
(M = Ca, Sr) are air sensitive and can easily be oxidized by
chalcogens. Metalation of diphenylphosphane oxide, diphenyl-
phosphinic acid, and diphenyldithiophosphinic acid as well as
salt metathetical approaches of the potassium salts with MI2
allow the synthesis of [(thf)4Ca(OPPh2)2] (1), [(dmso)2Ca-
(O2PPh2)2] (2), [(thf)3Ca(O2PPh2)I]2 (3), [(thf)3Ca-
(S2PPh2)2] (4), [(thf)2Ca(Se2PPh2)2] (5), [(thf)3Sr-
(S2PPh2)2] (6), [(thf)3Sr(Se2PPh2)2] (7), and [(thf)2Ca-
( O 2 P P h 2 ) ( S 2 P P h 2 ) ] 2 ( 8 ) , r e s p e c t i v e l y . T h e
diphenylphosphinite anion in 1 contains a phosphorus atom
in a trigonal pyramidal environment and binds terminally via the oxygen atom to calcium. The diphenylphosphinate anions act as
bridging ligands leading to polymeric structures of calcium bis(diphenylphosphinates). Therefore strong Lewis bases such as
dimethylsulfoxide (dmso) are required to recrystallize this complex yielding chain-like 2. The chain structure can also be cut into
smaller units by ligands which avoid bridging positions such as iodide and diphenyldithiophosphinate (3 and 8, respectively). In
general, diphenyldithio- and -diselenophosphinate anions act as terminal ligands and allow the isolation of mononuclear
complexes 4 to 7. In these molecules the alkaline earth metals show coordination numbers of six (5) and seven (4, 6, and 7).
diphenylphosphanides were prepared via calciation of
Ph2PH4,5 and metathetically from [(thf)4Ca(Ph)I] and KPPh2
yielding [(thf)4Ca(Ph)PPh2].6 Calcium-catalyzed intermolecu-
lar hydrophosphanylation of carbodiimides,7,8 alkenes,5 and
alkynes5,9,10 led to the formation of tertiary phosphanes. The
high reactivity of calcium phosphanides was employed to
intramolecularly cleave an aryl alkyl ether yielding derivatives of
calcium 2-(alkylphosphanido)phenolate.11,12
The diphenylphosphinites of the alkaline earth metals
represent a poorly investigated substance class. Metalation of
diphenylphosphane oxide with phenylmagnesium bromide
yielded Ph2PO-MgBr with a chemical shift of δ(31P) = 90.0.13
Whereas attempts to prepare homoleptic calcium bis-
(diphenylphosphinites) failed, Hill and co-workers14 obtained
heteroleptic dimeric diketiminatocalcium diphenylphosphinite
with bridging phosphinite anions binding via the oxygen atom.
The isolation of another heteroleptic complex [(thf)4Ca(PPh2)-
(OPPh2)] with a terminal O-bound phosphinite anion
succeeded after inadvertent aerial oxidation of [(thf)4Ca-
(PPh2)2].3
INTRODUCTION
■
Phosphorus-containing anions can be derived from the neutral
acids. Contrary to homologous nitrogen-based oxoacids,
phosphorus often favors tetra-coordination and, hence,
(distorted) tetrahedral environments. Step-wise oxidation of
phosphane PH3 leads to phosphinous acid (H2P−OH) or
phosphane oxide (H3PO), phosphonous acid [HP(OH)2] or
phosphinic acid [H2P(O)OH], and finally to phosphorous acid
[P(OH)3] or phosphonic acid [HP(O)(OH)2]. The tautomeric
couples differ by the coordination number of the phosphorus
center. Substitution of H atoms by phenyl groups hinders this
migration, and the phenyl groups remain bound at phosphorus,
leading to the oxidation products diphenylphosphinous acid
(Ph2POH) or diphenylphosphane oxide (Ph2HPO) and also to
higher oxidized diphenylphosphinic acid [Ph2P(O)OH].
Deprotonation yields diphenylphosphinite (Ph2PO−) and
−
diphenylphosphinate (Ph2PO2 ) anions.
The bis(diphenylphosphanides) (the deprotonation product
of diphenylphosphane Ph2PH) of the heavy alkaline earth
metals M represent a well investigated substance class which
has attracted interest for many years for several reasons. The
tetrahydrofuran (thf) adducts [(thf)4M(PPh2)2] (M = Ca, Sr)
are soluble in common organic donor solvents (Lewis bases),
are easily prepared,1,2 and are effective catalysts in hydro-
phosphanylation reactions. For the calcium complex, cis and
trans isomers were observed in the solid state with the option
to stabilize cis-isomeric calcium bis(diphenylphosphanide) with
tetradentate hexamethyltriethylenetetraamine.3 Heteroleptic
Contrary to the shadowy existence of the alkaline earth metal
phosphinites, the higher oxidized diphenylphosphinates have
attracted much more interest. Beryllium phosphinates form
coordination polymers which were studied approximately half a
century ago;15−18 thereafter the interest in these compounds
Received: May 11, 2012
Published: June 22, 2012
© 2012 American Chemical Society
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diminished most probably because of the toxicity of beryllium
dusts. The phosphinates of the heavier alkaline earth metals
were studied by IR spectroscopy to investigate the symmetry of
the O−P−O moiety.19 Calcium methylphenylphosphinates
were soluble in water and methanol and precipitated as
dihydrates; the anhydrous complexes could be isolated at 100
°C in vacuo.20 Singly and doubly deprotonated P,P′-
diphenylmethylenediphosphinic acid H2C[P(Ph)(O)OH]2
forms polymeric structures with magnesium and calcium ions.21
The oxidation of diphenylphosphanide with the homologous
chalcogens leads to thio- and selenophosphinites and
-phosphinates. Especially the phosphinates have been reported
extensively mainly as ligands in transition metal chemistry
because they show diverse coordination patterns as mono-
dentate (monometallic monoconnective), iso- and anisobiden-
tate (monometallic biconnective, symmetric or asymmetric
binding mode), or bridging (bimetallic biconnective and
triconnective) ligands.22−25 Special interest is given to these
anions because their complexes offer applications in catalysis,
MOCVD processes, separation procedures, and as lubricants.
Bildstein and Sladky investigated the oxidation of LiPPh2
with chalcogens in THF and found a linear correlation between
the chemical 31P NMR shift and the Pauling electronegativity of
the chalcogen for Ph2PE-Li (diphenylchalcogenophosphinites)
and Ph2PE2Li (diphenyldichalcogenophosphinates).26 Reduc-
tion of diphenylphosphinic and -thiophosphinic chloride with
sodium or magnesium as well as metalation of diphenylphos-
phane oxide and sulfide also yielded the corresponding
diphenylchalcogenophosphinites.27 These Ph2PE− anions
show a diverse coordination behavior as terminal or bridging
ligands via the chalcogen atom or as bridging ligands via the
phosphorus and chalcogen bases. The last mentioned binding
mode was found in [(tmeda)LiSePPh2]2.28 Addition of borane
BH3 to the diphenylchalcogenophosphinites led to blocking of
the Lewis basic behavior at the phosphorus atom, and thus
protected phosphinites acted as terminal ligands at potassium.29
Also sterically protected d0 metals only allowed that the
diphenylthiophosphinites acted as terminal ligands in [Cp2Ti-
(SPPh2−)2].30 The diphenyldichalcogenophosphinate anions
Ph2PE2 generally act as bidentate ligands which can be
bound terminally at one metal center28,30 or occupy bridging
positions.31 In hydrate complexes the water molecules are able
to replace the soft chalcogeno bases in the inner coordination
sphere of the s-block metals as shown for [(H2O)5(thf)-
Na2(Se2PPh2)2].32
Calciation of diphenylphosphinic acid with [(thf)2Ca{N-
(SiMe3)2}2] yielded insoluble, colorless, and air-stable calcium
bis(diphenylphosphinate) according to eq 2. Addition of
dimethylsulfoxide (DMSO) allowed growing single crystals of
[(dmso)2Ca(O2PPh2)2] (2) suitable for X-ray diffraction
studies, but the insolubility still hampered recording of NMR
data. Oxidation of [(thf)4Ca(PPh2)2] with N2O or air also
allowed the preparation of Ca(O2PPh2)2. To isolate more
soluble diphenylphosphinate complexes of calcium, a meta-
thetical approach was chosen. The reaction of K(O2PPh2) with
calcium diiodide in tetrahydrofuran initially yielded [(thf)3Ca-
(O2PPh2)I]2 (3) and insoluble KI allowing NMR spectroscopic
characterization, and a chemical shift of δ(31P) = 17.1 was
recorded. However, this calcium phosphinate complex showed
a Schlenk-type equilibrium with the homoleptic congeners,
Ca(O2PPh2)2 and CaI2 being favored (eq 3). The insolubility of
Ca(O2PPh2)2 in common organic solvents eased isolation of a
pure complex but also pulled the equilibrium toward these
homoleptic derivatives. This solubility behavior and a melting
point above 300 °C hint toward a polymeric structure of
calcium diphenylphosphinate.
The diphenyldichalcogenophosphinates were prepared by
oxidation of [(thf)4Ca(PPh2)2] with selenium (eq 4) or by
The lack of information on heavier alkaline earth metal
complexes initiated investigations regarding synthesis and
coordination behavior of diphenylphosphinites and -phosphi-
nates toward calcium and strontium.
oxidation of {KPPh2} with the corresponding chalcogen and
subsequent metathesis reaction with MI2 (M = Ca, Sr)
according to eq 5 yielding [(thf)3Ca(S2PPh2)2] (4), [(thf)2Ca-
RESULTS AND DISCUSSION
■
Synthesis. Inadvertent oxidation of [(thf)4Ca(PPh2)2] with
air led to the formation of heteroleptic [(thf)4Ca(PPh2)-
(OPPh2)].3 However, aerial oxidation does not provide an
effective access to these phosphinites because they were also air
sensitive. The acidity of diphenylphosphane oxide is rather low
but metalation with [(thf)2Ca{N(SiMe3)2}2] yielded calcium
bis(diphenylphosphinite) 1 as tetrakis(thf) adduct [(thf)4Ca-
(OPPh2)2] according to eq 1. This complex was isolated as an
air-sensitive colorless crystalline solid. The δ(31P) value of 1
[δ(31P) = 83.0] is in accordance with the chemical shifts of
LiOPPh2 [δ(31P) = 93.8,27 88.933] and of ClMgOPPh2 [δ(31P)
= 90.027,34].
(Se2PPh2)2] (5), [(thf)3Sr(S2PPh2)2] (6), and [(thf)3Sr-
(Se2PPh2)2] (7), respectively. Analogously to the synthesis of
[(dmso)2Ca(O2PPh2)2] 2, metalation of diphenyldithiophos-
phinic acid with [Ca{N(SiMe3)2}2] yielded [(thf)3Ca-
(S2PPh2)2] (4), according to eq 6. The isolation of
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NMR Characterization. Selected NMR parameters are
summarized in Table 1 clarifying dependencies between
a
Table 1. Selected NMR Data of 1 and 3 to 7
M(Te2PPh2)2 (M = Ca, Sr) from the reaction of the
diphenylphosphanides of calcium and strontium with tellurium
did not succeed. In dependency of the chalcogen atom,
strikingly different solubility behavior was observed. Whereas
the diphenylphosphinates are insoluble in common organic
solvents, the dithio- and diselenophosphinates exhibited
significant solubility in donor solvents such as tetrahydrofuran.
The 31P NMR shifts of these compounds are nearly
independent from the alkaline earth metal and show δ(31P)
values of 61 and 22 for Ph2PS2 and Ph2PSe2 , respectively.
The independency of the shift from the metal clearly speaks for
highly ionic complexes with electrostatic forces dominating the
bonding situation.
For the preparation of mixed diphenylphosphinates two
pathways are feasible. On the one hand, a mixture of
Ca(O2PPh2)2 and [(thf)3Ca(S2PPh2)2] (4) allowed the
isolation of crystalline [(thf)2Ca(O2PPh2)(S2PPh2)]2 (8);
however, the insolubility of Ca(O2PPh2)2 leads to an
unfavorable shift of the equilibrium (eq 7). Nevertheless, a
b
c
compound
M
E
δ(31P) δ(i-13C)
1J(PC)
33.8
1J(PSe)
[(thf)4Ca(PPh2)2]
Ca
Ca
Ca
Ca
Ca
Sr
−13.1
83.0
153.2
157.0
139.8
143.9
142
1
3
4
5
6
7
O
O
S
35.5
17.1
136.9
78.0
61.5
d
Se 21.8
61.5
Se 22.4
(broad)
79.2
574.1
633.6
S
144.2
142.0
Sr
61.4
−
−
a
M, alkaline earth metal; E, chalcogen. Complex 2 was insoluble and
therefore, no reliable NMR data were obtained. For comparison
reasons, selected parameters of [(thf)4Ca(PPh2)2] are included.1. M,
b
c
d
alkaline earth metal. E, chalcogen. Resonance is very broad and
doublet pattern is not resolved.
oxidation state of P, chalcogen and NMR values. The chemical
shift of the phosphorus atom of the diphenylphosphanide anion
in [(thf)4Ca(PPh2)2] was observed at rather high field.1,2
Oxidation to diphenylphosphanide leads to a significant low
field shift as one could expect for deshielded atoms and in
agreement with the lithium derivatives. For LiEPPh2 sub-
stitution of oxygen by its heavier homologues leads to high field
shifted 31P resonances [δ(31P) = 88.9 (E = O), 20.7 (S), 6.5
(Se), and −35.7 (Te)].26 In both complexes, [(thf)4Ca(PPh2)2]
as well as 1, the tricoordinate P atoms are in distorted trigonal
pyramidal environments. Further oxidation and enhancement
of the coordination number (formation of distorted tetrahedral
coordination spheres at P) leads to slightly high field shifted
δ(31P) values compared to the phosphinite derivative 1.
Surprisingly, the 31P NMR resonance of oxygen-containing
diphenylphosphinate deviates significantly from those of
homologous thio- and selenophosphinates. This finding could
be a consequence of different structural characteristics such as
the widened O−P−O bond angle and the significantly different
few single crystals of 8 were obtained enabling a crystal
structure determination. On the other hand, another procedure
involved the oxidation of [(thf)4Ca(PPh2)2] with an equimolar
mixture of sulfur and selenium.
The 31P NMR spectrum clearly showed the formation of
Ph2PS2− (δ = 61.6), Ph2PSSe− (δ = 44.1), and Ph2PSe2− anions
(δ = 22.8) with the mixed chalcogen species being the minor
component. Crystals from this reaction mixture were
investigated by desorption electron impact (DEI) mass
spectrometry (Figure 1). The mass distribution of the mother
peaks clearly verifies that all possible isomers are formed; the
signal intensity decreases with increasing mass and, hence,
selenium content. In addition, the isotopic pattern agrees with
the expected isotope distribution.
−
coordination pattern; whereas Ph2PO2 acts as a bridging
ligand the heavier homologous anions Ph2PS2 and Ph2PSe2
−
−
anions coordinate terminally as chelate bases. The chemical
shifts of the ipso-carbon atoms are rather similar for the
oxidized phosphinite and phosphinate anions but a low field
shifted resonance was detected for [(thf)4Ca(PPh2)2].1 In
accordance with a larger P−C bond length for [(thf)4Ca-
1
(PPh2)2] a smaller J(PC) coupling constant was observed.
To evaluate the coordination behavior of these phosphorus-
based anions, the crystal structures were determined.
Molecular Structures. Molecular structure and numbering
scheme of [(thf)4Ca(OPPh2)2] (1) are shown in Figure 2. The
calcium atom Ca1 lies on a crystallographic inversion center
and is embedded in a distorted octahedral environment with
trans arranged anionic phosphinite ligands. The phosphinite
anion contains a trigonal pyramidal phosphorus atom (av. angle
sum at P1 306.34°) with a C1−P1−C7 bond angle of 98.30(6)
°. The O1−P1−C1/7 angles are slightly larger (104.41(6)° and
103.63(6)°) because of repulsion between the P−O and P−C
bonds. These angles suggest mainly p(P)-orbital character of
the bonds and a lone pair of mainly s-character. This finding
explains the low basicity of the phosphorus atom and the
reduced tendency to act as a Lewis base. Nevertheless, borane
adducts of phosphinites with P−B bonds were studied by
Wagner and co-workers.29 The P1−O1 distance of 155.7(1)
Figure 1. DEI mass spectrum of a mixture obtained via oxidation of
[(thf)4Ca(PPh2)2] with sulfur and selenium. Masses for [Ca-
(S2PPh2)2] (538), [Ca(S2PPh2)(SSePPh2)]2 (586), indistinguishable
[Ca(S2PPh2)(Se2PPh2)]2 and [Ca(SSePPh2)2]2 (634), [Ca(SSePPh2)-
(Se2PPh2)]2 (682), and [Ca(Se2PPh2)2]2 (730 m/e) are detected with
decreasing intensity for increasing amount of selenium. The isotopic
pattern supports the assignment to the corresponding formula.
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Figure 2. Molecular structure and numbering scheme of [(thf)4Ca-
(OPPh2)2] (1). Symmetry related atoms (−x+1, −y−1, −z+1) are
marked with the letter “A”. The ellipsoids represent a probability of
40%. H atoms are neglected for clarity reasons. Selected bond lengths
(pm): Ca1−O1 220.65(9), Ca1−O2 239.20(9), Ca1−O3 238.53(10),
O1−P1 155.73(10), P1−C1 185.3(1), P1−C7 185.6(1); angles
(deg.): O1−Ca1−O1A 180, O1−Ca1−O2 91.18(3), O1−Ca1−O3
87.71(4), O2−Ca1−O3 93.35(3), O1−P1−C1 104.41(6), O1−P1−
C7 103.63(6), C1−P1−C7 98.30(6).
pm represents a characteristic single bond as do the P1−C1 and
P1−C7 values (av. 185.5 pm). The rather small Ca1−O
distances are a consequence of small intramolecular steric
strain. The Ca1−O1 distance to the phosphinite anion is
significantly smaller than the values of the Ca1−Othf bonds
because of enhanced electrostatic attraction.
For the higher oxidized phosphorus-based anions, the root
compound diphenylphosphinic acid [Ph2P(O)OH] may serve
as a reference.35 The P−O [152.6(6) pm] and PO [148.6(6)
pm] bond lengths differ only slightly because this acid shows
intermolecular asymmetric O−H···O hydrogen bridges leading
to O−H distances of 117 and 130 pm. The P−C bond lengths
exhibit an average value of 178.6 pm. The P−O as well as P−C
bonds are shorter than observed in the phosphinite anion
because the higher oxidation state reduces the radius of the
phosphorus atom and strengthens the electrostatic attraction to
negatively polarized substituents.
Figure 3. Cut-out of the strand of polymeric [(dmso)2Ca(O2PPh2)2]∞
(2) (top). The asymmetric unit contains two half molecules A and B.
In the cut-out the atoms are shown with arbitrary radii and the
hydrogen atoms are neglected for clarity reasons. At the bottom, the
distorted octahedral coordination sphere of calcium Ca1B (molecule
B) and the numbering scheme is displayed. Selected bond lengths for
molecule A [molecule B] (pm): Ca1A−O1A 231.1(2) [235.8(2)],
Ca1A−O2A 229.9(2) [228.7(2)], Ca1A−O3A 236.0(2) [235.8(2)],
S1A−O3A 153.6(3) [149.7(3)], P1A−O1A 149.6(2) [149.9(2)],
P1A−O2A 149.2(2) [149.9(2)], P1A−C1A 181.7(3) [181.7(3)],
P1A−C7A 181.6(3) [181.6(3)]; angles (deg.): O1A−P1A−O2A
119.8(1) [119.9(1)], O1A−P1A−C1A 107.5(1) [109.4(1)], O1A−
P1A−C7A 108.6(1) [108.6(1)], O2A−P1A−C1A 109.1(2)
[108.2(1)], O2A−P1A−C7A 107.6(1) [107.8(1)], C1A−P1A−C7A
103.0(2) [101.4(1)].
Molecular structure and numbering scheme of polymeric
[(dmso)2Ca(O2PPh2)2] (2) is displayed in Figure 3. Again, the
calcium ions have distorted octahedral coordination spheres
with the dmso ligands in a trans arrangement. The
diphenylphosphinate anions occupy a bridging position leading
to eight-membered (CaOPO)2 rings. These structural units are
aligned to a one-dimensional chain-like coordination polymer.
The phosphinate anions exhibit equal P−O bond lengths
with an average value of 149.6 pm. These parameters verify a
charge delocalization within the OPO fragment leading to a
strengthening of the PO bonds. The P−C distances with an
average value of 181.7 pm are elongated by 3 pm compared to
the diphenylphosphinic acid. Charge delocalization reduces the
electrostatic attraction between the phosphinate anion and the
metal cation leading to an average Ca−O distance of 231.4 pm
which is only slightly smaller than the value of the Ca−Odmso
bond (av. 235.9 pm).
Figure 4. Structural motif of [(thf)3Ca(O2PPh2)I]2 (3) showing the
connectivity of the dimer and the formation of an eight-membered
(Ca−O−P−O)2 ring with bridging phosphinate anions. The atoms are
drawn with arbitrary radii.
The structural motif of [(thf)3Ca(O2PPh2)I]2 (3) is
represented in Figure 4. The quality of the structure is rather
poor because of poor crystal quality. Recrystallization efforts led
to formation of homoleptic insoluble Ca(O2PPh2)2 and CaI2
hampering the collection of high quality single crystals. The
central structural motif is again the eight-membered (CaOPO)2
ring with the alkaline earth metal atoms in distorted octahedral
environments. The iodide anion is trans positioned to one of
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the diphenylphosphinate oxygen atoms. Vacant coordination
sites are filled with thf ligands in a meridional fashion. A
detailed discussion of bond parameters is not recommended
but the structure of the diphenylphosphinate anion is very
similar to that described for 2.
Molecular structures and numbering schemes of the calcium
derivatives [(thf)3Ca(S2PPh2)2] (4) and [(thf)2Ca(Se2PPh2)2]
(5) are displayed in Figures 5 and 6, respectively. Surprisingly,
intramolecular repulsion of the ligands in 4 lengthens the Ca−
Othf bonds. The coordination sphere of the heptacoordinate
calcium atom of 4 is a pentagonal bipyramid with the sulfur
atoms in the pentagonal plane and two thf ligands in axial
positions. Because of different coordination numbers, the
calcium−sulfur and calcium−selenium bonds differ only by a
rather small value of 6 pm or 2.0%. In complex 5 with a hexa-
coordinate calcium center in a distorted octahedral coordina-
tion sphere the thf ligands show a cis arrangement. This fact
leads to the formation of enantiomeric Λ- and Δ-isomers,
which crystallize in a non-centrosymmetric space group,
however, the Flack parameter of 0.786(7) suggests twinning
and crystallization of both isomers.
The strontium derivatives [(thf)3Sr(S2PPh2)2] (6) and
[(thf)3Sr(Se2PPh2)2] (7) both contain hepta-coordinate
alkaline earth metal centers, and the Sr−S and Sr−Se bonds
differ by 15 pm or 4.7%. The structure of one molecule of 6 is
represented in Figure 7. Contrary to the diphenylphosphinate
Figure 5. Molecular structure and numbering scheme of [(thf)3Ca-
(S2PPh2)2] (4). The ellipsoids represent a probability of 40%, H atoms
are neglected for clarity reasons. Selected bond lengths (pm): Ca1−
O1 240.7(2), Ca1−O2 243.5(2), Ca1−O3 237.3(2), Ca1−S1
291.18(10), Ca1−S2 292.17(9), Ca1−S3 294.34(10), Ca1−S4
291.03(10), P1−S1 199.6(1), P1−S2 198.8(1), P2−S3 199.4(1),
P2−S4 199.3(1), P1−C1 181.6(3), P1−C7 182.2(3), P2−C13
182.8(3), P2−C19 181.4(3); angles (deg.): S1−Ca1−S2 69.80(2),
S1−Ca1−S3 149.17(3), S1−Ca1−S4 140.98(3), S2−Ca1−S3
140.87(3), S2−Ca1−S4 71.47(2), S3−Ca1−S4 69.83(2), O1−Ca1−
O2 84.48(10), O1−Ca1−O3 172.15(9), O2−Ca1−O3 87.70(10),
O2−Ca1−S1 74.62(7), O2−Ca1−S3 74.59(7).
Figure 7. Molecular structure and numbering scheme of [(thf)3Sr-
(Se2PPh2)2] (7). Only molecule A of three crystallographically
independent molecules A, B, and C is displayed. The ellipsoids
represent a probability of 40%, H atoms are neglected for clarity
reasons. Selected bond lengths of molecule A [molecule B] {molecule
C}: Sr1A−O1A 258.1(4) [255.3(4)] {256.6(4)}, Sr1A−O2A 254.3(4)
[253.2(4)] {253.5(4)}, Sr1A−O3A 251.6(4) [257.2(4)] {251.6(4)},
Sr1A−Se1A 318.12(9) [319.34(9)] {319.61(9)}, Sr1A−Se2A
315.95(8) [317.83(8)] {316.83(8)}, Sr1A−Se3A 316.17(9)
[325.63(9)] {322.01(9)}, Sr1A−Se4A 318.04(7) [313.81(7)]
{316.26(8)}.
anions which coordinate as bridging ligands to two calcium
atoms, the diphenyldithio- and -diselenophosphinate anions
always bind as bidentate chelate ligands to one alkaline earth
metal atom.
Figure 6. Molecular structure and numbering scheme of [(thf)2Ca-
(Se2PPh2)2] (5). The asymmetric unit contains two molecules A and
B, only molecule A is shown. The ellipsoids represent a probability of
40%, H atoms are not drawn. Selected bond lengths of molecule A
[molecule B] (pm): Ca1A−O1A 235.3(4) [232.8(4)], Ca1A−O2A
234.3(4) [233.8(4)], Ca1A−Se1A 298.0(2) [298.8(1)], Ca1A−Se2A
297.6(2) [295.8(2)], Ca1A−Se3A 295.8(2) [298.1(1)], Ca1A−Se4A
299.9(2) [300.1(2)], P1A−Se1A 216.2(2) [215.9(2)], P1A−Se2A
215.3(2) [215.7(2)], P2A−Se3A 215.5(2) [215.5(2)], P2A−Se4A
215.8(2) [216.2(2)], P1A−C1A 182.8(7) [182.7(6)], P1A−C7A
182.0(6) [182.4(5)], P2A−C13A 182.3(7) [181.7(6)], P2A−C19A
181.7(6) [182.4(6)].
To verify this coordination behavior mixed [(thf)2Ca-
(O2PPh2)(S2PPh2)]2 (8) was isolated. Molecular structure
and numbering scheme of centrosymmetric 8 is displayed in
Figure 8. All structural features discussed above are realized in
this dimeric molecule. The diphenylphosphinate anions act as
bridging ligands leading to a dinuclear complex. The
homologous diphenyldithiophosphinate anions appear as
terminal chelate ligands. Nevertheless, the environment of the
hexa-coordinate calcium atom resembles the coordination
sphere of [(dmso)2Ca(O2PPh2)2] (2) with the thf ligands in
a trans arrangement. The anionic ligands show similar
parameters as in the complexes discussed above.
the thf content of 5 is lower than that of 4; this fact leads to
significantly smaller Ca−Othf distances for 5 whereas the
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tetrahedrally coordinated phosphorus atoms suggesting sp3
hybridization. This higher s-orbital contribution and the higher
oxidation state of P lead to a significant shortening of the P−C
and P−O bonds. Because of the rather small P−O distances
electrostatic repulsion between the oxygen atoms enhances the
O−P−O angle. Larger P−E bond lengths reduce this
intraligand repulsion and smaller E−P−E angles are observed.
An increasing oxidation of the phosphorus atom leads to a
high field shift of the 31P NMR resonances. As already studied
by Bildstein and Sladky26 for the lithium salts LiEPPh2
substitution of oxygen by its heavier homologues also leads
to a high field shift [δ(31P) = 88.9 (E = O), 20.7 (S), 6.5 (Se),
and −35.7 (Te)]. A comparable observation is true for the
−
−
phosphinates [δ(31P) = 17.1 (Ph2PO2 ), 62 (Ph2PS2 ), 44
(Ph2PSSe−), 23 (Ph2PSe2 )]; however, the oxygen-based
−
Figure 8. Molecular structure and numbering scheme of [(thf)2Ca-
(O2PPh2)(S2PPh2)]2 (8). The ellipsoids represent a probability of
40%, H atoms are not shown for clarity reasons. Symmetry related
atoms (−x+1, −y, −z) are marked with the letter “A”. Selected bond
lengths (pm): Ca1−O1 223.6(3), Ca1−O2A 221.2(3), Ca1−O3
237.4(3), Ca1−O4 236.4(3), Ca1−S1 284.4(1), Ca1−S2 290.9(1),
P1−S1 200.5(1), P1−S2 199.4(1), P1−C1 182.8(4), P1−C7
182.1(4), P2−O1 148.8(3), P2−O2 149.7(3), P2−C13 181.4(4),
P2−C19 180.4(4); environment of Ca1 (deg.): O1−Ca1−O2A
107.0(1), O1−Ca1−O3 85.6(1), O1−Ca1−O4 91.8(1), O1−Ca1−
S1 89.24(8), O1−Ca1−S2 159.72(9), O3−Ca1−O2A 89.4(1), O3−
Ca1−O4 174.7(1), O3−Ca1−S1 93.45(8), O3−Ca1−S287.35(7),
O4−Ca1−O2A 86.8(1), O4−Ca1−S1 91.20(8), O4−Ca1−S2
96.58(8), S1−Ca1−O2A 163.65(8), S1−Ca1−S2 72.22(3), S2−
Ca1−O2A 91.86(8).
phosphinate represents an exception because of a different
bonding situation. The oxygen-based phosphinates always act
as bridging ligands whereas the homologous thio- and
selenophosphinates occupy terminal positions. For LiS2PPh2
and ClMgS2PPh2 very similar chemical 31P NMR shifts of
δ(31P) = 59.8 and 59.0, respectively, were observed verifying
the small influence of the cations on the anions and
emphasizing the ionic nature of all these phosphinite and
phosphinate complexes.
EXPERIMENTAL SECTION
■
General Remarks. All manipulations were carried out under an
argon atmosphere using standard Schlenk techniques. The solvents
were dried according to common procedures and distilled in an argon
atmosphere, deuterated solvents were dried over sodium, degassed,
SUMMARY AND CONCLUSION
■
1
and saturated with argon. The yields given are not optimized. H and
The oxidation of [(thf)4Ca(PPh2)2] leads to [(thf)4Ca-
(OPPh2)2] (1) which was prepared via calciation of
diphenylphosphane oxide. The phosphinates are insoluble in
common organic solvents but in the presence of dmso
polymeric [(dmso)2Ca(O2PPh2)2]∞ (2) was isolated. Homol-
ogous derivatives are accessible either via deprotonation of
diphenyldithiophosphinic acid or metathetically via reaction of
the potassium salts K(E2PPh2) (E = O, S, Se) with [(thf)4CaI2]
or [(thf)5SrI2]. All complexes with the exception of calcium
bis(diphenylphosphinate) are soluble in THF. This anion acts
as a bridging ligand leading to polymeric chain-like structures
whereas diphenylphosphinite, diphenyldithio-, and -diseleno-
phosphinate anions appear as terminally bound chelate ligands
at calcium and strontium. This coordination behavior is
maintained in heteroleptic complexes [(thf)3Ca(O2PPh2)I]2
(3) and [(thf)2Ca(O2PPh2)(S2PPh2)]2 (8).
13C{1H} NMR spectra were recorded on Bruker AC 200 MHz, AC
400, or AC 600 spectrometers. Chemical shifts are reported in parts
per million and referenced to SiMe4 using the residual signal of the
deuterated solvent as internal standard. Starting [(thf)4Ca(PPh2)2],1,2
[Ca{N(SiMe3)2}2], and [(thf)2Ca{N(SiMe3)2}2]39−41 were prepared
according to literature procedures.
Synthesis of [(thf)4Ca(OPPh2)2] (1). Diphenylphosphane oxide
(0.37 g, 1.83 mmol) was added at −78 °C to a stirred solution of
[Ca{N(SiMe3)2}2] (0.46 g, 0.91 mmol) in 10 mL of THF. The
solution was slowly warmed to room temperature (r.t.) and stirred
overnight. Then the volume of the reaction mixture was reduced in
vacuo to half of the original volume. Storage at −20 °C yielded 0.465 g
of colorless crystals of 1 (0.64 mmol, 69%).
Physical data: Elemental analysis (C40H52CaO6P2, 730.86): calc.: C
1
65.73, H 7.17; found: C 65.70, H 7.14. H NMR (400 MHz, 298 K,
3
[D8]THF): δ = 1.77 (thf), 3.63 (thf), 6.98 (2H, t, JH,H = 8.4 Hz, p-
CH), 7.09 (4H, t, 3JH,H = 6.5 Hz, m-CH), 7.54 (4H, t, 3JH,H = 6.9 Hz,
o-CH). 13C{1H} NMR (101 MHz, 298 K, [D8]THF): δ = 126.3 (p-
C), 127.5 (m-C, 3JC,P = 3.8 Hz), 129.4 (o-C, 2JC,P = 20.5 Hz), 157.0 (i-
C, 1JC,P = 35.5 Hz). 31P{1H} NMR (162 MHz, 298 K, [D8]THF): δ =
83.0 (s).
All these alkaline earth metal complexes exhibit mainly ionic
bonding situations with small influence of the metal on the
structure of the anions. Because of the ionic nature of the
−
Ph2PE2 complexes (E = O, S, Se) charge delocalization is
Synthesis of [(dmso)2Ca(O2PPh2)2] (2). Diphenylphosphinic acid
(0.26 g, 1.19 mmol) was added to a stirred solution of [Ca{N-
(SiMe3)2}2] (0.21 g, 0.59 mmol) in 8 mL of a 1:1 mixture of THF and
methanol. The solution was stirred overnight at r.t. A white precipitate
formed and was collected by filtration. The solid was suspended in 2
mL of DMSO and stored at r.t. for 3 weeks. This procedure led to
formation of a colorless crystals of 2 (0.26 mmol, 71%).
Physical data: M.p above 300 °C. Elemental analysis
(C28H32CaO6P2S2, 630.68): calc.: C 53.32, H 5.11, S 10.17; found:
C 53.14, H 5.04, S 10.15. IR: 1628 w, 1437 w, 1412 w, 1261 vs, 1177
m, 1097 s, 1023 s, 999 w, 954 w, 865 m, 802 vs, 755 w, 723 m, 699 m,
563 m, 540 w.
observed within the E-P-E moieties and both chalcogen atoms
bind to the same metal atom as chelate ligands (E = S, Se) or in
a bridging manner to two metal atoms (E = O). This behavior
is characteristic for these ligands as it is also found in complexes
of indium(III)31,36,37 and antimony(III),36 but the radius of
gallium(III) is too small and a coordination number of four is
realized by one bidentate ligand and two monodentate
phosphinate anions.36 Contrary to these metal complexes,
characteristic single and double bonds were found in covalently
bound molecules such as [Ph2P(Se)]2Se.38
The diphenylphosphinite anion shows small bond angles at P
suggesting a large p(P) orbital contribution in the P−O and P−
C bonds. The diphenylphosphinate anions represent distorted
Synthesis of [(thf)3Ca(O2PPh2)I]2 (3). Method A. A suspension of
diphenylphosphinic acid (0.58 g, 2.66 mmol) in 15 mL of THF was
added to a suspension of KH (0.11 g, 2.66 mmol) in 5 mL of THF and
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Table 2. Selected Structural Parameters (Average Values) for the Alkaline Earth Metal Complexes [(thf)4Ca(OPPh2)2] (1),
[(dmso)2Ca(O2PPh2)2] (2), [(thf)3Ca(O2PPh2)I]2 (3), [(thf)3Ca(S2PPh2)2] (4), [(thf)2Ca(Se2PPh2)2] (5), [(thf)3Sr(S2PPh2)2]
a
(6), [(thf)3Sr(Se2PPh2)2] (7), and [(thf)2Ca(O2PPh2)(S2PPh2)]2 (8)
comp.
M
C.N.(M)
E
ligand
M−E
M−Othf
P−E
P−C
E−P−E′
C−P−C′
1
2
Ca
Ca
6
6
O
O
220.7
230.5
232.3
224.9
291.7
292.7
297.8
297.8
297.3
299.1
302.8
303.9
303.0
302.9
317.0
317.1
318.6
319.7
318.2
319.1
222.4
287.6
238.9
155.7
149.4
149.9
149.3
199.2
199.4
215.8
215.7
215.8
215.9
199.1
199.6
199.5
199.7
215.5
215.1
214.8
215.6
214.9
215.8
149.3
200.0
185.5
181.7
181.7
181.7
181.9
182.1
182.4
182.0
182.6
182.1
183.1
182.5
182.6
181.0
182.4
181.6
182.1
182.7
182.4
182.5
180.9
182.5
98.3
b
A1
B1
236.0
119.8
119.9
117.9
113.8
114.4
114.1
114.1
114.0
114.3
115.3
116.0
115.9
115.0
114.6
114.4
114.2
114.5
114.2
113.8
117.9
116.0
103.0
101.4
106.2
101.2
104.4
103.6
103.2
104.9
103.5
101.6
105.3
104.4
100.7
104.4
104.5
104.5
104.4
103.3
103.2
105.8
104.6
b
235.8
c
3
Ca
Ca
6
7
O
S
253.9
240.5
4
A1
A2
A1
A2
B1
B2
A1
A2
B1
B2
A1
A2
B1
B2
C1
C2
A1
A2
5
Ca
6
7
7
Se
234.8
233.3
252.7
255.0
254.7
255.2
253.9
236.9
6
7
Sr
S
Sr
Se
8
Ca
6
O
S
a
The molecules are distinguished by the letters A, B, and C, and the ligands within one molecule are numbered; thus ligand B2 addresses the second
b
ligand of molecule B (M alkaline earth metal, E chalcogen atom, C.N. coordination number of the alkaline earth metal center). Ca−Odmso
.
c
Structural motif due to poor crystal quality; the constitution is verified but a detailed structure discussion is impossible.
stirred for 1 h. CaI2 (0.78 g, 2.65 mmol) was added to this solution,
and the reaction mixture was stirred overnight. Insoluble KI was
removed by filtration. The volume of the filtrate was reduced under
vacuum to one-third of the original volume, and the resulting solution
was stored at −25 °C for 1 d yielding 0.95 g of colorless crystals
(30%).
Method B. Diphenylphosphinic acid (0.78 g, 3.62 mmol) was added
to potassium carbonate K2CO3 (0.25 g, 1.81 mmol) in 10 mL of water
and heated for 15 min. Then the water was removed by distillation.
The residue was dried in vacuo to give 0.90 g of potassium salt (98%)
which was dissolved in 10 mL of THF. After addition of calcium iodide
(1.05 g, 3.57 mmol) and stirring overnight at r.t. KI was removed by
filtration, and the volume of the filtrate was reduced to one-third of its
original volume. This concentrated solution was stored in a freezer.
After 1 d colorless crystals precipitated and were collected on a cooled
frit and dried under reduced pressure (1.5 g, 36%).
The solution was stirred overnight. Then the volume was reduced to 7
mL. After addition of a few milliliters of pentane and storage of this
solution at −25 °C, 0.57 g of colorless crystals formed within 2 weeks
(79%).
Physical Data. Mp 254−257 °C (dec.). Elemental analysis
(C36H44CaO3P2S4, 755.02): calc.: C 57.27, H 5.87, S 16.99; found:
C 57.04, H 5.84, S 17.25. IR: 1585 w, 1569 w, 1460 vs, 1377 vs, 1305 s,
1173 m, 1156 m, 1096 s, 1068 w, 1026 s, 999 w, 917 w, 873 m, 744 s,
703 s, 666 m, 653 s, 613 s, 566 vs, 491 m, 483 m. 1H NMR ([D8]THF,
200.13 MHz): δ 7.28 (m, Ph, m- and p-CH), 8.06 (m, Ph, o-CH), 1.74
and 3.62 (THF). 13C NMR (50.32 MHz, [D8]THF): δ = 143.9 d (Ci,
1JPC = 78.0 Hz); δ = 131.1 d (Co, 2JPC = 11.5 Hz); δ = 129.8 s (Cp), δ
= 127.9 d (Cm, 3JPC = 12.5 Hz), δ = 67.1, 25.2 (THF). 31P{1H} NMR
([D8]THF, 81.013 MHz): δ 61.5. MS (EI, m/z (%)): 538 (15%)
[Ca(S2PPh2)2]+, 289 (100%) [CaS2PPh2]+, 249 (10%) [Ph2PS2]+, 217
(4%) [Ph2PS]+, 183 (5%) [Ph2P − 2H]+.
Synthesis of [(thf)2Ca(Se2PPh2)2] (5). [(thf)4Ca(PPh2)2] (0.17 g,
0.24 mmol) in 10 mL of THF was added dropwise to a suspension of
0.15 g of Se (1.89 mmol) in 8 mL of THF at −78 °C. The mixture was
stirred for 6 h at the same temperature and then warmed to r.t. giving a
clear yellow solution. Excess of selenium was removed by filtration.
The volume of the solution was reduced to 5 mL, then 4 mL of
toluene were added to the filtrate. At −25 °C colorless crystals of 5
precipitated within 3 days (0.17 g, 81%).
Physical Data. Elemental analysis C44H68Ca2I2O10P2, 1200.96):
1
Calc.: C 48.00, H 5.71; found: C 47.88, H 5.63. H NMR (400 MHz,
298 K, [D8]THF): δ 1.73 (thf), 3.60 (thf), 7.15 (4H, dt, m-CH), 7.33
(2H, p-CH), 7.66 (4H, o-CH), 13C NMR (150.9 MHz, 298 K,
3
[D8]THF): δ 26.3 (thf), 68.2 (thf), 128.1 (m-C, JC,P = 12.5 Hz),
130.4 (p-C), 131.9 (o-C, 2JC,P = 9.4 Hz), 139.8 (i-C, 1JC,P = 136.9 Hz).
31P{1H} NMR (161.9 MHz, 298 K, [D8]THF): δ = +17.1 (s).
Synthesis of [(thf)3Ca(S2PPh2)2] (4). Method A. A THF solution
of KPPh2 (0.5 M, 6.6 mL, 3.3 mmol) was added to a suspension of S8
(0.21 g, 6.6 mmol) in 10 mL of THF and stirred for 6 h at −35 °C.
Thereafter the solution was warmed to r.t. and stirred for additional 12
h. Complete conversion to K(S2PPh2) was controlled by 31P NMR
spectroscopy. CaI2 (0.48 g, 1.65 mmol) was added to this solution at
−78 °C and then the reaction was warmed to r.t. and stirred for 2 h.
Precipitated KI was removed by filtration. The volume of the filtrate
was reduced to half of the original volume at −25 °C. Cooling of this
solution gave colorless crystals of 1 (0.98 g, 80%).
Physical Data. Mp 198−202 °C (dec.). Elemental analysis
(C32H36CaO2P2Se4, 755.02): calc.: C 44.15, H 4.17; found: C 42.68,
H 4.44. IR: 1607 w, 1571 w, 1458 vs, 1377 vs, 1305 m, 1261 m, 1180
w, 1154 w, 1089 s, 1067 w, 1026 s, 918 m, 873 m, 800 m, 743 s, 689 s,
1
618 m, 543 vs, 518 vs, 472 s. H NMR ([D8]THF, 200.13 MHz): δ
7.25 (m, Ph, m- and p-CH), 8.06 (m, Ph, o-CH), 1.74 and 3.62
(THF). 13C NMR (100.65 MHz, [D8]THF): δ = 142 (Ci, very broad);
2
δ = 131.8 d (Co, JPC = 11.6 Hz); δ = 130.0 s (Cp), δ = 127.9 d (Cm
3JPC = 12.5 Hz); δ = 67.1, 25.2 (THF). 31P{1H} NMR ([D8]THF,
Method B. Ca{N(SiMe3)2}2 (0.342 g, 0.96 mmol) was dissolved in
18 mL of THF at −78 °C, and 0.48 g (1.92 mmol) of
diphenyldithiophosphinic acid in 10 mL of THF was added dropwise.
1
81.013 MHz): δ 21.8 (s + d satellites, JPSe = 574.1 Hz). 77Se NMR
([D8]THF, 76.334 MHz): δ −17.7 (d). MS (EI, m/z (%)): 726 (4%)
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Table 3. Crystal Data and Refinement Details for the X-ray Structure Determinations of the Compounds 1−8
1
2
3
4
formula
C40H52CaO6P2
730.84
C28H32CaO6P2S2
630.68
C40H52Ca2I2O8P2
1056.72
−140(2)
monoclinic
P21/n
C36H42CaO3P2S4
752.96
fw (g mol−1
)
T/°C
−140(2)
monoclinic
P21/c
−90(2)
triclinic
−90(2)
monoclinic
P21/c
crystal system
space group
a/ Å
P1
̅
9.7050(2)
8.5891(1)
23.5100(6)
90
5.7704(2)
15.4651(8)
16.8331(6)
89.439(3)
88.309(3)
83.633(2)
1492.23(11)
2
11.2639(5)
19.4276(9)
12.5674(5)
90
20.0027(6)
12.9986(5)
15.7385(5)
90
b/ Å
c/ Å
α/ deg
β/ deg
γ/ deg
V/ Å3
92.052(1)
90
101.267(2)
90
108.126(2)
90
1958.47(7)
2
2697.1(2)
2
3889.0(2)
4
Z
ρ (g cm−3
)
1.239
1.404
1.301
1.286
μ (cm−1
)
2.86
4.97
14.54
4.91
measured data
12668
11416
17978
25959
data with I > 2σ(I)
unique data/Rint
wR2 (all data, on F2)
4052
4328
4081
5751
4472/0.0246
0.0883
6791/0.0541
0.1333
6136/0.0475
0.3986
8806/0.0582
0.1381
a
a
R1 (I > 2σ(I))
0.0329
0.0535
0.1176
0.0522
b
s
1.112
0.894
1.532
1.018
res. dens./e Å−3
CCDC No.
0.298/−0.293
880401
5
0.391/−0.450
880402
6
1.314/−1.294
motif
0.690/−0.385
880403
8
7
formula
fw (g mol−1
C32H36CaO2P2Se4
870.47
C36H44O3P2S4Sr
802.51
C36H44O3P2Se4Sr
C32H36CaO4P2S2, C4H8O
722.85
)
990.11
T/°C
−90(2)
monoclinic
P21
−90(2)
monoclinic
P21
−90(2)
monoclinic
P21/n
−90(2)
monoclinic
crystal system
space group
a/ Å
P21/n
8.8990(18)
26.290(5)
15.472(3)
90
15.7762(4)
13.1205(5)
20.0254(6)
90
17.2391(3)
32.1960(4)
21.9626(4)
90
12.7135(3)
17.4860(4)
19.4052(5)
90
b/ Å
c/ Å
α/ deg
β/ deg
γ/ deg
V/ Å3
103.45(3)
90
108.406(2)
90
102.443(1)
90
100.702(1)
90
3520.5(12)
4
3933.0(2)
4
11903.6(3)
12
4238.90(18)
4
Z
ρ (g cm−3
)
1.642
1.355
1.657
1.133
μ (cm−1
)
44.32
16.97
51.41
3.57
measured data
18541
28263
71584
28446
data with I > 2σ(I)
unique data/Rint
wR2 (all data, on F2)
10258
10285
13934
6729
12241/0.0403
0.0817
16922/0.0622
0.1136
26636/0.1144
0.1059
9650/0.0465
0.2440
a
a
R1 (I > 2σ(I))
0.0389
0.0586
0.0580
0.0733
b
s
1.038
0.948
0.924
1.057
res. dens./e Å−3
Flack-parameter
CCDC No.
0.398/−0.518
0.786(7)
880404
0.425/−0.344
0.028(6)
1.331/−0.862
1.225/−0.407
880405
880406
880407
a
2
2
2
Definition of the R indices: R1 = ∑||Fo| − |Fc||/∑|Fo|; wR2 = {∑[w(Fo − Fc2)2]/∑[w(Fo )2]}1/2 with w−1 = σ2(Fo ) + (aP)2 + bP; P = [2Fc2
+
b
Max(Fo ]/3. s = {∑[w(Fo − Fc2)2]/(No − Np)}1/2
.
2
2
[Ca(Se2PPh2)2]+, 383 (20%) [CaSe2PPh2]+, 343 (8%) [Ph2PSe2]+,
264 (32%) [Ph2PSe]+, 183 (85%) [Ph2P]+.
toluene were added. At −25 °C 0.39 g of colorless crystals of 6 formed
and were collected after 24 h (78%).
Synthesis of [(thf)3Sr(S2PPh2)2] (6). A 0.5 M solution of KPPh2
(2.76 mL, 1.38 mmol) in THF was added to a suspension of S8 (0.09
g, 2.76 mmol) in 10 mL of THF and stirred for 6 h under an argon
atmosphere at −35 °C. Then the solution was stirred overnight at r.t.
[(thf)5SrI2] (0.483 g, 0.688 mmol) was added to this solution at −35
°C. Thereafter the reaction mixture was warmed to r.t. and stirred for
2 h. The precipitate (KI) was removed by filtration. The volume of the
filtrate was reduced to half of the original volume and then 3 mL of
Physical Data. Mp 107−110 °C (dec.). Elemental analysis
(C36H44SrO3P2S4, 802.56): calc.: C 53.88, H 5.53, S 15.98; found: C
53.04, H 5.48, S 15.87. IR: 1634 w, 1457 vs, 1377 vs, 1305 s, 1173 m,
1156 m, 1096 s, 1068 w, 1026 s, 998 w, 917 w, 874 m, 745 s, 721 w,
702 s, 662 m, 650 s, 612 s, 562 vs, 491 m, 482 m. 1H NMR ([D8]THF,
200.13 MHz): δ 7.25 (m, Ph, m- and p-CH), 8.02 (m, Ph, o-CH), 1.74
and 3.62 (THF). 13C NMR (50.32 MHz, [D8]THF): δ = 144.2 d (Ci,
1JPC = 79.2 Hz); δ = 131.1 d (Co, 2JPC = 11.5 Hz); δ = 129.8 s (Cp), δ
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= 127.9 d (Cm, 3JPC = 12.6 Hz); δ = 67.1, 25.2 (THF). 31P{1H} NMR
([D8]THF, 81.013 MHz): δ 61.5. MS (EI, m/z (%)): 586 (36%)
[Sr(S2PPh2)2]+, 554 (48%) [Sr(S2PPh2)(SPPh2)]+, 337 (60%)
[SrS2PPh2]+, 249 (4%) [Ph2PS2]+, 217 (64%) [Ph2PS]+, 183 (100%)
[Ph2P − 2H]+.
Synthesis of [(thf)3Sr(Se2PPh2)2] (7). A 0.5 M solution of KPPh2
(2.41 mL, 1.21 mmol) in THF was added to a suspension of Se (0.19
g, 2.42 mmol) in 10 mL of THF and stirred for 6 h under an argon
atmosphere at −35 °C and then at r.t. overnight. [(thf)5SrI2] (0.423 g,
0.603 mmol) was added to this solution at −35 °C, and then the
reaction mixture was warmed to r.t. and stirred for additional 2 h. The
solution was filtered to remove precipitated KI. The volume of the
filtrate was reduced to half of the original volume. Addition of 3 mL of
hexane and storage at −25 °C afforded 0.49 g of colorless crystals of 7
within 3 days (82%).
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Physical Data. Mp 118−121 °C (dec.). Elemental analysis
(C36H44SrO3P2Se4, 990.14): calc.: C 43.67, H 4.48; found: C 42.40,
H 4.12. IR: 1608 w, 1571 w, 1456 vs, 1378 vs, 1341 w, 1304 s, 1177 m,
1156 w, 1091 s, 1067 w, 1030 s, 998 w, 918 m, 876 m, 746 s, 689 s,
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NMR (50.32 MHz, [D8]THF): δ = 142.0 d (Ci, JPC = 61.4 Hz); δ =
3
131.8 d (Co, 2JPC = 11.9 Hz); δ = 129.9 s (Cp), δ = 127.8 d (Cm JPC
=
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1
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X-ray Structure Determination. The intensity data for the
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The structures were solved by direct methods (SHELXS44) and
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2
refined by full-matrix least-squares techniques against Fo (SHELXL-
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ASSOCIATED CONTENT
* Supporting Information
■
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Crystallographic data in CIF format. This material is available
free of charge via the Internet at http://pubs.acs.org.
Crystallographic data (excluding structure factors) has been
deposited with the Cambridge Crystallographic Data Centre as
supplementary publication CCDC-880401 for 1, CCDC-
880402 for 2, CCDC-880403 for 4, CCDC-880404 for 5,
CCDC-880405 for 6, CCDC-880406 for 7, and CCDC-880407
for 8. Copies of the data can be obtained free of charge on
application to CCDC, 12 Union Road, Cambridge CB2 1EZ,
UK [E- mail: deposit@ccdc.cam.ac.uk].
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AUTHOR INFORMATION
Corresponding Author
*Fax: +49 3641 948102. E-mail: m.we@uni-jena.de.
■
(33) Issleib, K.; Walther, B.; Fluck, E. Z. Chem 1968, 8, 67.
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Notes
(35) Fenske, D.; Mattes, R.; Lons, J.; Tebbe, K.-F. Chem. Ber. 1973,
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The authors declare no competing financial interest.
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R. Polyhedron 1995, 14, 3087−3094.
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