N-(2,6-Dimethylphenyl)diphenylphosphinamine chalcogenides (S, Se) and a zirconium complex possessing phosphanylamide in the coordination sphere

Article abstract of DOI:10.1039/c2nj40646b

We report the syntheses of N-(2,6-dimethylphenyl)-P,P- diphenylphosphinothioic amide Ph₂P(S)NH-(2,6-Me₂C ₆H₃)] (2) and N-(2,6-dimethylphenyl)-P,P- diphenylphosphinoselenoic amide Ph₂P(Se)NH-(2,6-Me₂C ₆H₃)] (3) by the reaction of N-(2,6-dimethylphenyl)-P,P- diphenylphosphinamine [Ph₂PNH-(2,6-Me₂C₆H ₃)] (1) with elemental sulphur and selenium respectively. When the phosphinamine compound 1 was treated with n-BuLi and subsequently with zirconocenedichloride in an equimolar ratio, the corresponding zirconium complex [{η⁵-Cp₂ZrCl(η²-N(2,6-Me ₂C₆H₃)PPh₂}] (5) was obtained in good yield. The solid state structures of all the compounds were established by single crystal X-ray diffraction analysis. In zirconium complex 5, a highly strained three membered metallacycle was observed. In addition, the solid state structure of [Ph₂P(O)NH(2,6-Me₂C₆H ₃)] (4) was also determined. In the solid state structure, compound 4 shows extensive intermolecular hydrogen bonding through oxygen atoms, whereas a lesser extent of intermolecular hydrogen bonding was noted in compound 2, due to the presence of the less electronegative sulphur atom. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.

Full text of DOI:10.1039/c2nj40646b

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PAPER
N-(2,6-Dimethylphenyl)diphenylphosphinamine chalcogenides (S, Se) and
a zirconium complex possessing phosphanylamide in the coordination
spherew
Kishor Naktode, Ravi K. Kottalanka and Tarun K. Panda*
Received (in Victoria, Australia) 25th July 2012, Accepted 13th August 2012
DOI: 10.1039/c2nj40646b
We report the syntheses of N-(2,6-dimethylphenyl)-P,P-diphenylphosphinothioic amide
Ph2P(S)NH-(2,6-Me2C6H3)] (2) and N-(2,6-dimethylphenyl)-P,P-diphenylphosphinoselenoic
amide Ph2P(Se)NH-(2,6-Me2C6H3)] (3) by the reaction of N-(2,6-dimethylphenyl)-P,P-
diphenylphosphinamine [Ph2PNH-(2,6-Me2C6H3)] (1) with elemental sulphur and selenium
respectively. When the phosphinamine compound 1 was treated with n-BuLi and subsequently
with zirconocenedichloride in an equimolar ratio, the corresponding zirconium complex
[{Z5-Cp2ZrCl(Z2-N(2,6-Me2C6H3)PPh2}] (5) was obtained in good yield. The solid state structures
of all the compounds were established by single crystal X-ray diffraction analysis. In zirconium
complex 5, a highly strained three membered metallacycle was observed. In addition, the solid
state structure of [Ph2P(O)NH(2,6-Me2C6H3)] (4) was also determined. In the solid state structure,
compound 4 shows extensive intermolecular hydrogen bonding through oxygen atoms, whereas a
lesser extent of intermolecular hydrogen bonding was noted in compound 2, due to the presence
of the less electronegative sulphur atom.
exhibit unusual co-ordination modes but also can be used for a
Introduction
number of catalytic transformations such as polymerization
reactions.21 Very recently, Fryzuk and co-workers have
Use of various P–N ligands is one of the alternatives to using
cyclopentadienyl ligands, and in using this approach, amide
reported a series of three member metallacycle of lanthanide
ligands are successfully used today for the design of new
phosphinoamido complexes [{3,5-Me2C6H3NP(CHMe2)2}3-
M(THF)] (M = Sc, Y) by using alkane elimination route.22
transition-metal compounds having well defined reaction
centres.1,2 Recently, there has been significant research effort
Herein we describe the syntheses of N-(2,6-dimethylphenyl)-
in employing inorganic amines and imines. P–N ligand sys-
tems, such as monophosphanylamides (R2PNR0),3–6 diphos-
P,P-diphenylphosphinothioic amide [Ph2P(S)NH-(2,6-Me2-
C6H3)] (2), N-(2,6-dimethylphenyl)-P,P-diphenylphosphino-
phanylamides [(Ph2P)2N],4,7,8 phosphoraneiminato (R3PN),9
selenoic amide Ph2P(Se)NH-(2,6-Me2C6H3)] (3) and the
zirconium complex [{Z5-Cp2ZrCl(Z2-PPh2N(2,6-Me2C6H3)}]
(5). Full characterization and structural studies of all the
phosphinimino-methanides [(RNPR02)2CH],10–14 phosphinimino-
methandiides [(RNPR02)2C],15–18 and diiminophosphinates
[R2P(NR0)]19 are well known today as ligands and have
compounds have been made. In addition, the solid structure
proved their potency in transition and rare earth metal
of [Ph2P(O)NH(2,6-Me2C6H3)] (3) is also reported.
chemistry. Roesky and co-workers introduced one chiral
Compound 2 was prepared in good yield by the reaction
phosphinamine [HN(CHMePh)(PPh2)] into the early transition-
metal chemistry as well as in lanthanide chemistry.20 It was
involving N-(2,6-dimethylphenyl)-diphenylphosphinamine [Ph2P-
NH(2,6-Me2C6H3)] (1) with elemental sulphur in a 1 : 1 molar
shown that some of the early transition-metal complexes
ratio at ambient temperature in toluene (Scheme 1). The title
having P–N ligands in the coordination sphere, may not only
compound has been characterized by standard analytical/
spectroscopic techniques and the solid-state structure was
established by single crystal X-ray diffraction.
Department of Chemistry, Indian Institute of Technology Hyderabad,
Ordnance Factory Estate, Yeddumailaram 502205, Andhra Pradesh,
India. E-mail: tpanda@iith.ac.in; Fax: +91(40) 2301 6032;
Tel: +91(40) 2301 6036
In the FT-IR spectrum of the compound 2, a strong
absorption at 643 cmꢀ1 is observed, which can be assigned
as characteristic PQS bond stretching. The absorbances for
P–N (923 cmꢀ1), P–Ph (1434 cmꢀ1) and N–H (3267 cmꢀ1
)
w Crystallographic details for compounds 2–5 are available. CCDC
reference numbers 878241–878242 and 893244–893245. For crystallo-
graphic data in CIF or other electronic format see DOI: 10.1039/
c2nj40646b
bond stretchings are positioned well in the expected ranges.
For compound 2, the 1H NMR spectrum shows a sharp singlet
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of compound 2 (Fig. 1, left), a relatively weak interaction
between the N–H proton of one molecule and the sulfur atom
in the adjacent molecule is observed (N1ꢁ ꢁ ꢁS1 3.461 and
H21aꢁ ꢁ ꢁS1 2.660 A).25
The selenium compound 3 was prepared in good yield in a
similar fashion to compound 2, involving reaction with 1 and
elemental selenium in a 1 : 1.5 molar ratio at ambient tempera-
ture in toluene (Scheme 1). The characterization of 3 was made
by standard analytical/spectroscopic techniques and the solid-
state structure was established by single crystal X-ray diffrac-
tion (Fig. 1, right). For compound 3, a strong absorption at
909 cmꢀ1 is observed, and can be attributed to characteristic
Scheme 1 Syntheses of chalcogenides of [Ph2PNH(2,6-Me2C6H3)].
for six methyl groups at the 2,6-position of the phenyl groups
of the aniline moiety at 2.00 ppm. The amine N–H proton
shows a broad signal at d = 4.24 ppm which is slightly high
frequency shifted compared to that of diphenylphosphinamine
1 (d = 3.70 ppm).23 The signals of the phenyl protons are in
1
PQSe bond stretching.23 In the H NMR spectrum, a sharp
1
the expected range in the H NMR spectrum. In the 31P{1H}
singlet for six methyl groups at the 2,6-position of the phenyl
groups of the aniline moiety at 1.99 ppm, and for the amine
N–H proton, a broad signal at d = 4.20 ppm is observed,
which is comparable to that of compound 1 (2.04 and
3.70 ppm) and 2 (2.00 and 4.24 ppm) respectively.23 In the
31P{1H} NMR spectra, one signal is observed at 53.6 ppm,
which is slightly lower frequency shifted compared to that of
compound 2 (56.3 ppm). Compound 3 crystallizes in the
tetragonal space group P43, having four molecules in the unit
cell. Structural parameters for compound 3 are given Table 1.
The P–Se distance of 2.1019(8) A is in agreement with the
reported value and can be considered as a P–Se double bond.26
P1–N1 1.656(3) A, C1–N1 1.441(4) A are also similar to that
of compound 2. Like compound 2, the phosphorus geometry is
tetrahedral and the bond angles around the phosphorus atom
are also similar. However, no hydrogen bonding was observed
in the selenium compound.
NMR spectra one signal is observed at 56.3 ppm, representing
that one phosphorus atom is present in the molecule. The
significantly high frequency shift of the phosphorus signal
compared to compound 1 (d 35.8 ppm) can be explained due
to the presence of moderately electronegative sulphur atoms
over the phosphorus atom (Fig. 1).
Compound 2 crystallizes in the tetragonal space group P41,
having four molecules in the unit cell. Structural parameters
for compound 2 are given Table 1. The bond distances of
P1–N1 [1.662(2) A] and P1–C9 [1.811(2) A], P1–C15 [1.821(2) A]
are in the range of that in phosphorus compounds known in
the literature.23 The P–S distance 1.952(8) A is elongated
compared to the P–S bond as a double bond, and is compar-
able with the literature [1.4921(7) A].23 The C1–N1 bond
distance of 1.437(3) A and P1–N1–C1 angle of 124.76(18)1
are unperturbed by sulfur on the phosphorus, and nicely
matches with the sp3 hybrid geometry of the middle amine
nitrogen atom which bears a amine proton in it. The phos-
phorus atoms is also sp3 hybridized and adopts a tetrahedral
geometry around it, and the bond angles of S1–P1–N1
111.84(8)1, S1–P1–C15 115.03(10)1, N1–P1–C9 105.80(11)1
and C15–P1–C9 102.35(10)1 are comparable to the ideal angle
(1091) for tetrahedral arrangements. In the solid state structure
Compound 4, [Ph2P(O)NH(2,6-Me2C6H3)] was synthesized
in a straight forward reaction compared to the literature
procedure, and the spectroscopic data was in accordance with
the reported values (Scheme 1).27 The solid-state structure of
compound 4 was established by single crystal X-ray diffraction
analysis (Fig. 2).
Compound 4 crystallizes in the orthorhombic space group
P212121, having two molecules in the asymmetric unit and
eight molecules present in the unit cell. Structural parameters
for compound 4 are given Table 1. The bond distances of
P1–N1 (P2–N2) [1.6455(19) and 1.6478(19) A] are slightly
shorter than those of compound 2 and 3 [1.662(2) and
1.656(3) A], and P1–C9 (P2–C29) [1.809(3) and 1.809(3) A],
P1–C15 (P2–C35)[1.796(2) and 1.804(2) A] are also slightly
shorter, but in the range of those in phosphorus compounds
known in the literature.28 The P–O distances, 1.4901(16) and
1.4914(16) A, are in good agreement for considering the P–O
bond as double bond and is comparable with the literature
[1.4736(19) A in 2,6-iPr2C6H3NHP(O)Ph2].28 The C1–N1
(C21–N2) bond distances [1.446(3) and 1.441(3) A] and
P1–N1–C1 (P2–N2–C21) angles [124.30(14) and 119.04(15)1],
are unperturbed by oxidation of phosphorus, and nicely
matches with the sp3 hybrid geometry of the middle amine
nitrogen atom, which bears an amine proton. The phosphorus
atom is also sp3 hybridized and adopts a tetrahedral geometry,
and the bond angles of O1–P1–N1 (O2–P2–N2) [113.46(10) and
111.98(9)1], O1–P1–C15 (O2–P2–C35) [112.47(10) and 113.26(10)1],
N1–P1–C9 (N2–P2–C29) [109.17(10) and 109.93(10)1], and
C15–P1–C9 (C35–P2–C29) [105.65(11) and 104.62(11)1] are
Fig. 1 Molecular structure of 2 (left) and 3 (right) with thermal
ellipsoids drawn at the 30% level. Selected bond lengths (A) and bond
angles (1)
— compound 2: P1–S1 1.9516(8), P1–N1 1.662(2),
C1–N1 1.437(3), P1–C15 1.821(2), P1–C9 1.811(2), P1–N1–C1
124.76(18), N1–P1–S1 111.84(8), N1–P1–C15 108.02(12), N1–P1–C9
105.80(11), C15–P1–C9 102.35(10), C9–P1–S1 114.03(9), C15–P1–S1
115.03(10); compound 3: P1–Se1 2.1019(8), P1–N1 1.656(3),
C1–N1 1.441(4), P1–C15 1.822(3), P1–C9 1.811(3), P1–N1–C1
125.2(2), N1–P1–Se1 111.27(10), N1–P1–C15 108.29(15), N1–P1–C9
105.78(15), C15–P1–C9 102.28(13).C9–P1–Se1 114.02(11), C15–P1–Se1
114.47(12).
c
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Table 1 Crystal data and structure refinement for 2–5
2
3
4
5
CCDC No.
Empirical
formula
878241
C20H20NPS
893245
C20H20NPSe
878242
C20H20NOP
893244
C176H180Cl4N4P4Zr4
Formula
weight
337.40
384.30
321.34
2981.80
Temperature 150(2) K
Wavelength 1.54184 A
150(2) K
1.54184 A
Tetragonal, P43
150(2) K
0.71069 A
Orthorhombic, P212121
150(2) K
1.54184 A
Orthorhombic, Pnma
Crystal sys-
tem, space
group
Tetragonal, P41
Unit cell
dimensions
a = 11.8572(2) A, b =
a = 11.8869(2) A, b =
a = 9.068(5) A, b = 19.055(5) a = 14.2392(12) A, b =
11.8572(2) A, c = 12.3816(3) A, 11.8869(2) A, c = 12.6006(3) A, A, c = 20.228(5) A, a = 901, 14.6310(18) A, c = 180321(17)
a = 901, b = 901, g = 901
a = 901, b = 901, g = 901
b = 901, g = 901
A, a = 901, b = 901, g = 901
Volume
1740.77(6) A3
1780.44(6) A3
3495(2) A3
3756.7(7) A3
Z, Calculated 4, 1.287 Mg mꢀ3
density
4, 1.424 Mg mꢀ3
8, 1.221 Mg mꢀ3
1, 1.318 Mg mꢀ3
Absorption
coefficient
F(000)
2.489 mmꢀ1
3.676 mmꢀ1
0.161 mmꢀ1
3.682 mmꢀ1
712
784
3.72 to 70.801
1360
1.47 to 25.81
1552
3.89 to 70.85
Theta range 3.73 to 70.801
for data
collection
Limiting
indices-
Reflections
collected/
unique
ꢀ14 r h r 14, ꢀ14 r k r 4, ꢀ14 r h r 11, ꢀ14 r k r 7, ꢀ6 r h r 10, ꢀ23 r k r 17, ꢀ17 r h r 16, ꢀ17 r k r 9,
ꢀ13 r l r 15
ꢀ11 r l r 15
ꢀ24 r l r 23
ꢀ21 r l r 18
3803/2402 [R(int) = 0.0290]
3497/2336 [R(int) = 0.0169]
8782/5909 [R(int) = 0.0249] 10002/3695 [R(int) = 0.0491]
Completeness 98.3%
96.7%
97.9%
98.1%
to y = 71.25
Absorption
correction
Max. and
min.
Empirical
0.74 and 0.58
Empirical
0.599 and 0.470
Empirical
0.988 and 0.95
Empirical
0.60 and 0.42
transmission
Refinement
method
Full-matrix least-squares on F2 Full-matrix least-squares on F2 Full-matrix least-squares on F2 Full-matrix least-squares on F2
Data/
2402/1/210
2336/1/210
5909/0/419
1.036
3695/260/320
1.047
restraints/
parameters
Goodness-of- 1.070
1.059
fit on F2
Final R
indices
R1 = 0.0321, wR2
R1 = 0.0292, wR2 = 0.0783
R1 = 0.0385, wR2 = 0.0123 R1 = 0.0509, wR2 = 0.1186
[I 4 2s(I)]
R indices
(all data)
Absolute
structure
parameter
R1 = 0.0336, wR2 = 0.0827
R1 = 0.0296, wR2 = 0.0786
ꢀ0.04(2)
R1 = 0.0402, wR2 = 0.1043 R1 = 0.0674, wR2 = 0.1304
ꢀ1.73(8)
0.01(2)
Largest diff. 0.155 and ꢀ0.376 eAꢀ3
0.579 and ꢀ0.316 eAꢀ3
0.274 and ꢀ0.293 eAꢀ3
0.505 and ꢀ1.291 eAꢀ3
peak and hole
comparable to the ideal angle (1091) for tetrahedral arrange-
ments. The solid state structure of compound 4 reveals that
the N–H proton of one molecule of compound 4 is inter-
molecularly hydrogen bonded (Oꢁ ꢁ ꢁH–N) to the more electro-
negative oxygen atom present in the adjacent molecule of 4
(N2ꢁ ꢁ ꢁO1 2.814 and H2ꢁ ꢁ ꢁO1 2.059 A). The interaction
between the methyl protons (H8Cꢁ ꢁ ꢁO1 2.566 A) and adjacent
phenyl protons (H36ꢁ ꢁ ꢁO1 2.823 A) with the oxygen atom of
the second molecule are also noticed, and they are within the
range of hydrogen bonding distances.29 However, in the
1H NMR spectra, all the methyls protons give only one singlet,
indicating the dynamic behaviour of the molecule, where
the short interactions might be due to close packing in the
solid state.
The zirconium complex [{Z5-Cp2ZrCl(Z2-PPh2N(2,6-Me2C6H3)}]
(5) was obtained as the major product by a two step reaction of
phosphinamine (1), n-BuLi and subsequently with zirconocene
dichloride in THF, followed by crystallization from toluene/
n-pentane (Scheme 2). The new complex has been charac-
terized by standard analytical/spectroscopic technique and the
solid state structure of the complex 5 was determined by single
crystal X-ray diffraction analysis (Fig. 3).
Compound 5 crystallizes in the orthorhombic space group
Pnma, having one molecule of 5 in the unit cell along with one
disordered toluene. Structural parameters for compound 5
are given Table 1. The [Ph2PN(2,6-Me2C6H3)}ꢀ ligand is
co-ordinated to the center metal zirconium atom in a chelating
(Z2) fashion. The structure reveals a pseudo-five-fold co-ordination
c
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atoms are perfectly coplanar. The cyclopentadienyl rings are
asymmetrically attached to the metal ion having Zr–C dis-
tances of 2.522(4) to 2.568(4) A. The Zr–Ct distance is 2.240 A,
where Ct represents the centroid of the cyclopentadienyl ring.
A three membered metallacycle N1–P1–Zr1 is formed by
nitrogen, phosphorus, and zirconium atoms, having the bond
distances of Zr1–N1 2.201(4) and Zr1–P1 2.634(2) A. In the
literature, a similar geometry is observed for compounds
[Z5-Cp2Zr(Cl)[{Z2-N(SiMe3)P(H)N(SiMe3)2}], which can be
prepared by reaction of Me3SiNQP–N(SiMe3)2 with [Z5-
Cp2Zr(Cl)H]30 and in [Z5-Cp2Zr(Cl){Z2-N(PPh2)2].31
The 1H NMR spectra shows a sharp doublet for the protons
of the Cp unit, which is shifted to a lower frequency (d 6.06)
when compared with the starting material [Z5-Cp2ZrCl2]
(d 6.50).32 The doublet is a result of coupling to the phosphorus
atom, with a coupling constant of 1.6 Hz, which is much smaller
than the reported value (17.5 Hz) in [Z5-C5H5)2Zr(Cl)N-
(CHMePh)(PPh2)].20 The [Ph2PN(2,6-Me2C6H3)]ꢀ ligand shows
a characteristic signal of a singlet for the methyl groups at the
2,6-position, and the expected signals for phenyl photons. Also,
characteristic is the 31P NMR spectrum. At room temperature,
compound 5 shows one signal in the 31P{1H} NMR spectrum
(d 49.2 ppm), which is slightly shifted relative to 1 (d 35.8).
Fig. 2 Molecular structure of 4 with thermal ellipsoid drawn at the
30% level. Selected bond lengths (A) and bond angles (1) — molecule 1
(bottom): P1–O1 1.4901(16), P1–N1 1.6455(19), C1–N1 1.446(3),
P1–C15 1.796(2), P1–C9 1.809(3), P1–N1–C1 124.30(14), N1–P1–O1
113.46(10), N1–P1–C15 105.85(10), N1–P1–C9 109.17(10), C15–P1–C9
105.65(11), O1–P1–C15 112.47(10), O1–P1–C9 109.87(10); molecule 2
(top): P2–O2 1.4914(16), P2–N2 1.6478(19), C21–N2 1.441(3),
P2–C29 1.809(3), P2–C35 1.804(2), P2–N2–C21 119.04(15), N2–P2–O2
111.98(9), N2–P2–C29 109.93(10), N2–P2–C35 105.89(10), O2–P2–C35
113.26(10), O2–P2–C29 110.80(11).
Conclusions
In conclusion we have synthesized two chalcogenides
N-(2,6-dimethylphenyl)-P,P-diphenylphosphinothioic amide
and N-(2,6-dimethylphenyl)-P,P-diphenylphosphinoselenoic
amide and observed that the analogous oxygen compound
[Ph2P(O)NH(2,6-Me2C6H3)] shows extensive intermolecular
hydrogen bonding in the solid state compared to the sulphur
analogue. We have also introduced the N-(2,6-dimethylphenyl)-
P,P-diphenylphosphinamine ligand into zirconium chemistry
by synthesizing [{Z5-Cp2ZrCl(Z2-PPh2N(2,6-Me2C6H3)}]. Further
reactions of these phosphinamine derivatives as ligands in
transition and rare earth metal chemistry are currently in
progress in our laboratory.
Scheme 2 Synthesis of zirconium complex [{Z5-Cp2ZrCl(h2-PPh2N-
(2,6-Me2C6H3)}](5).
Experimental section
General
All manipulations of air-sensitive materials were performed
with the rigorous exclusion of oxygen and moisture in flame-
dried Schlenk-type glassware, either on a dual manifold
Schlenk line interfaced to a high vacuum (10ꢀ4 torr) line, or
in an argon-filled M. Braun glove box. THF was pre-dried
over Na wire and distilled under nitrogen from sodium
and benzophenone ketyl prior to use. Hydrocarbon solvents
(toluene and n-pentane) were distilled under nitrogen from
LiAlH4 and stored in the glove box. 1H NMR (400 MHz) and
31P{1H} NMR (161.9 MHz) spectra were recorded on a
BRUKER AVANCE III-400 spectrometer. BRUKER
ALPHA FT-IR was used for FT-IR measurement.
HRMS was measured by an Agilent Technology Q-TOF
Fig. 3 Molecular structure of 5 with thermal ellipsoid drawn at the
30% level omitting hydrogen atoms for clarity. Selected bond lengths (A)
and bond angles (1): Zr1–N1 2.201(4), Zr1–P1 2.634(2), Zr1–Cl2 2.5273(14),
Zr1–C5 2.522(4), Zr1–C2 2.528(4), Zr1–C6 2.529(4), Zr1–C1 2.544(4),
Zr1–C3 2.568(4), P1–N1 1.640(4), P1–C4 1.823(4), N1–C10 1.442(6),
Zr–Ct 2.240, N1–Zr–Cl2 81.64(11), N1–Zr1–P1 38.33, N1–P1–Zr1
85.26(18), N1–Zr1–Ct1 115.6, P1–Zr1–Ct1 104.3 (Ct = centroid).
sphere of the ligands around the zirconium atom if the ring
centroids of the cyclopentadienyl rings are considered as
co-ordination positions. A three membered metallacycle
N1–Zr1–P1 is formed. The P and N atoms are co-ordinated
to the (Z5-C5H5)2ZrCl fragment, and the N, P, Zr and Cl
instrument. Elemental analyses were performed on
a
BRUKER EURO EA at the Indian Institute of Technology
Hyderabad. N-(2,6-Dimethylphenyl)-diphenylphosphinamine
c
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[Ph2P-NH(2,6-Me2C6H3)] (1) was prepared according to the
literature procedure.24
31P-{1H} NMR (161.9 MHz, C6D6):
d
C176H180Cl4N4P4Zr4(2981.82), Calcd C 70.89 H 6.08 N 1.88;
=
49.2 ppm.
Found C 70.12 H 5.74 N 1.58.
Syntheses
X-ray crystallographic studies of 2, 3, 4 and 5
[Ph2P(S)NH-(2,6-Me2C6H3)] (2). Compound 1 (0.50 g,
1.63 mmol) and elemental sulfur (0.05 g, 1.63 mmol) were
placed in a 50 mL Schlenk tube and 20 mL toluene was added
to it. The reaction mixture was heated to 60 1C for 6 h. After
removal of the solvent in vacuo, a white solid of compound 2
was formed. Yield: 480 mg, (87%). The compound was re-
crystallized from toluene at room temperature.
Single crystals of compounds 2–4 were grown from a solution
of toluene or THF (for 4) and compound 5 was grown from
toluene/pentane under an inert atmosphere at a temperature
of ꢀ35 1C. In each case, a crystal of suitable dimensions was
mounted on a CryoLoop (Hampton Research Corp.) with a
layer of light mineral oil and placed in a nitrogen stream at
150(2) K. All measurements were made on a Oxford Supernova
X-calibur Eos CCD detector with graphite-monochromatic
CuKa (1.54184 A) (for 2, 3, and 5) and MoKa (0.71069 A)
(for 4) radiation. Crystal data and structure refinement para-
meters are summarized in the Table 1. The structures were
solved by direct methods (SIR92)33 and refined on F2 by full-
matrix least-squares methods; using SHELXL-97.34 Non-
hydrogen atoms were anisotropically refined. H-atoms were
included in the refinement on calculated positions riding
on their carrier atoms. The function minimized was
1H NMR (400.1 MHz, CDCl3): d = 7.91 (d, 2H, JH–H
=
7.5 Hz, Ph), 7.88 (d, 2H, JH–H = 7.5 Hz, Ph), 7.45–7.30
(m, 6H, Ph), 6.90–6.88 (m, 3H, Ph), 4. 24 (br, 1H, NH), 2.00
(s, 3H, CH3) ppm. 31P-{1H} NMR (161.9 MHz, CDCl3): d =
56.31 ppm. IR, (selected peaks): u = 923 (P–N), 1434 (P–Ph),
3267 (N–H), 643 (PQS) cmꢀ1. Elemental analysis: C20H20NPS
(337.11) Calcd C 71.19 H 5.95 N 4.15; Found C 70.89 H
5.79 N 4.02.
[Ph2P(Se)NH-(2,6-Me2C6H3)] (3). Similar to the synthesis
1
of compound 2. Yield: 0.54 g (91%). H NMR (400.1 MHz,
P
2 2
[
w(Fo2-Fc ) ] (w = 1/[s2(Fo2) + (aP)2 + bP]), where P =
CDCl3): d = 7.92–7.87 (m, 4H, Ph), 7.43–7.37 (m, 6H, Ph),
6.90–6.88 (br. s, 3H, Ph), 4.20 (br, 1H, –NH), 1.99 (s, 3H,
–CH3), ppm. 31P-{1H} NMR (161.9 MHz, CDCl3): d =
53.6 ppm. IR, (selected peaks): u = 909 (P–N), 1358 (P–Ph),
3224 (N–H), 568 (PQS) cmꢀ1. C20H20NPSe (384.31), Calcd C
62.50 H 5.25 N 3.64; Found C 61.99 H 4.95 N 3.43.
(Max(Fo2,0) + 2Fc )/3 with s2(Fo2) from counting statistics.
2
P
P
The function R1 and wR2 were ( ||Fo| ꢀ |Fc||)/ |Fo| and
P
P
2
[
w(Fo
ꢀ
Fc ) / (wFo4)]1/2
2 2
,
respectively. The solvent
toluene molecules were disordered about special positions. In
order to model these it was necessary to apply rigid hexagon
constraints to the rings and additional restraints were used to
ensure appropriate bond lengths and angles for the methyl
groups. The thermal parameters did not refine to appropriate
values and so thermal similarity and vibration restraints were
also applied. The ORTEP-3 program was used to draw the
molecule. Crystallographic data (excluding structure factors)
for the structures reported in this paper [CCDC 878241 (2),
878242 (4), 893245 (3), and 893244 (5)] is available.w
[Ph2P(O)NH(2,6-Me2C6H3)] (4). Compound 4 was syn-
thesized in a modified method compared to the literature
procedure.27 Aqueous hydrogen peroxide (30% w/w, 0.15 mL,
1.46 mmol) was added drop wise to a suspension of compound 1
(0.45 g, 1.46 mmol) in THF (20 mL) and the mixture was kept
under stirring conditions for 30 min at room temperature. The
volume was concentrated in vacuo to ca. 1–2 mL and addition
of n-hexane (20 mL) gave a white solid which was collected by
filtration [Yield: 0.56 g, (86%). m.p. 145 1C]. Compound 4 was
crystallized from THF solution.
Acknowledgements
1H NMR (400.1 MHz, C6D6): d = 8.0–7.80 (m, 4H, Ph),
7.10–6.70 (m, 6H, Ph), 7.90 (br. s, 3H), 3.77 (br, 1H,
Ph2P-NH), 2.05 (s, 3H, –CH3), ppm. 31P-{1H} NMR
(161.9 MHz, CDCl3): d = 67.83 ppm. IR, (selected peaks):
This work was supported by the Department of Science and
Technology India (DST) under the SERC Fast Track Scheme
(SR/FT/CS-74/2010) and start-up grant from IIT Hyderabad.
K. N. and R. K. thanks UGC, India for their PhD fellowship.
Generous support from K. Mashima, Osaka University, Japan
is gratefully acknowledged. We are thankful to W. Fraser for
helpful discussions regarding solid state structures.
u = 929 (P–N), 1446 (P–Ph), 3162 (N–H), 1195 (PQO) cmꢀ1
.
C20H20NOP (321.35), Calcd C 74.75 H 6.27 N 4.36; Found C
74.05 H 5.87 N 4.09.
[{g5-Cp2ZrCl(g2-PPh2N(2,6-Me2C6H3)}](5). To a stirring
solution of zirconocenedichloride (94 mg, 0.32 mmol) in
THF (10 mL), lithium salt (N-diphenylphosphino)-2,6-
dimethyl aniline in THF [prepared from n-BuLi (0.32 mL of
1.6 M solution) and 1 (102 mg, 0.32 mmol)] was added
dropwise at room temperature and stirred for 24 h. The
reaction mixture evaporated to dryness and was extracted
using toluene. The filtrate was evaporated in vacuo to produce
a white residue which was crystallized in toluene/pentane.
Yield: 155 mg (65%).
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