Synthesis of (β-phenylethynyl)-gem- diphenyltrifluorocyclotriphosphazene and its reaction with RCpCo(PPh 3)2 [R = MeOC(O)]

Article abstract of DOI:10.1016/j.ica.2011.01.064

Reaction of gem-diphenyltetrafluorocyclotriphosphazene with in situ generated lithiated phenylacetylene resulted in the formation of the first example of a gem-diphenyltrifluorophosphazene based alkyne (β- phenylethynyl)-gem-diphenyltrifluorocyclotriphosphazene (NPPh ₂)(NPF₂)[NP(F)CCPh] 1. Reaction of this alkyne with η⁵-(MeOC(O)C₅H₄)Co(PPh₃) ₂ resulted in the formation of a CpCo stabilized cyclobutadiene complex [η⁵-carbomethoxycyclopentadienyl][η⁴-1,3- bis(gem-diphenyltrifluorocyclotriphosphazenyl)-2,4-diphenylcyclobutadiene] cobalt 2, having two gem-diphenyltrifluorophosphazene moieties trans to each other on the cyclobutadiene ring. The reaction also yielded two structural isomers of the PPh₃ stabilized cobaltacyclopentadiene compounds 3 and 4 having gem diphenyl trifluorophosphazene moieties present in the 2,4 and 2,5 positions of the metallacycle. The reaction in addition yielded a novel spirocyclic phosphazacyclopentadiene compound bound to a CpCo unit in the η⁴-mode 5. All the compounds were characterized by ¹H, ¹³C, ³¹P and ¹⁹F NMR spectroscopy and compounds 2, 3 and 5 were also structurally characterized by X-ray crystallography.

Full text of DOI:10.1016/j.ica.2011.01.064

Inorganica Chimica Acta 372 (2011) 175–182
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Synthesis of (b-phenylethynyl)-gem-diphenyltrifluorocyclotriphosphazene and
its reaction with RCpCo(PPh3)2 [R = MeOC(O)]
⇑
Muthiah Senthil Kumar, Dheeraj Kumar, Anil J. Elias
Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Available online 31 January 2011
Reaction of gem-diphenyltetrafluorocyclotriphosphazene with in situ generated lithiated phenylacetylene
resulted in the formation of the first example of a gem-diphenyltrifluorophosphazene based alkyne (b-
phenylethynyl)-gem-diphenyltrifluorocyclotriphosphazene (NPPh2)(NPF2)[NP(F)C„CPh] 1. Reaction of
Dedicated to Prof. S.S. Krishnamurthy,
Department of Inorganic and Physical
Chemistry, Indian Institute of Sciences,
Bangalore, India.
this alkyne with
ene complex [g g
g
5-(MeOC(O)C5H4)Co(PPh3)2 resulted in the formation of a CpCo stabilized cyclobutadi-
5-carbomethoxycyclopentadienyl][ 4-1,3-bis(gem-diphenyltrifluorocyclotriphosphaze-
nyl)-2,4-diphenylcyclobutadiene]cobalt 2, having two gem-diphenyltrifluorophosphazene moieties
trans to each other on the cyclobutadiene ring. The reaction also yielded two structural isomers of the
PPh3 stabilized cobaltacyclopentadiene compounds 3 and 4 having gem diphenyl trifluorophosphazene
moieties present in the 2,4 and 2,5 positions of the metallacycle. The reaction in addition yielded a novel
Keywords:
Diphenyltetrafluorophosphazene
Cobalt cyclopentadienyl
Cyclobutadiene
Cobaltacylopentadiene
Phosphazenylalkynes
Phosphazacyclopentadiene
spirocyclic phosphazacyclopentadiene compound bound to a CpCo unit in the
g
4-mode 5. All the com-
pounds were characterized by 1H, 13C, 31P and 19F NMR spectroscopy and compounds 2, 3 and 5 were also
structurally characterized by X-ray crystallography.
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
fluorine atoms on the fluorophosphazene trimer by phenyl groups
can be expected to have both steric as well as electronic effects on
Among perhalogenated trimeric cyclophosphazenes, hexachloro
and hexafluoro substituted heterocycles are the most well known
and these are widely used as precursors for realizing new phospha-
zene based molecules. Organophosphazenes, derived from these
cyclophosphazenes by nucleophilic substitution reactions have
been used for both fundamental studies and useful applications
[1]. Among such organophosphazene derivatives, monoaryl and
geminal diaryl substituted trimeric chloro and fluorophosphazenes
form an interesting class of compounds, which, unlike N3P3Cl6 and
N3P3F6, are easy to handle due to their increased air and moisture
stability and lesser volatility. Some of the aryl derivatives have
been reported as potential precursors for realizing high molecular
weight phosphazene polymers, chiral phosphazene compounds
and multi-site coordination ligands, and have also been used as
scaffolds for generating multi-ferrocenyl assemblies [2–6]. Gem-
diphenyltetrafluorophosphazene has especially been the subject
of both experimental and theoretical studies. A recent study by
Allen and coworkers has elaborated the origin of bond variations
in gem-diphenylphosphazene molecules [7]. A scan of the literature
indicates that unlike the reactions of the aryl and gem-diaryl
chlorophosphazenes [4,8], the reactions of aryl substituted fluoro-
phosphazenes have been little explored. The replacement of
its substitution reactions.
Allen and coworkers have shown that the pentafluorophos-
phazenyl substituted acetylene, F5P3N3C„CPh can be an interest-
ing reagent for the synthesis of novel fluorophosphazene derived
clusters by their reactions with metal carbonyls such as Co2(CO)8
and Fe2(CO)9 [9]. Our studies on the reactions of (b-phenyleth-
ynyl)pentafluorocyclotriphosphazene
(PhC„CP3N3F5)
with
RCpCo(PPh3)2 and RCpCoCOD have resulted in the unprecedented
formation of novel fluorophosphazene based cobaltometallocyclic
compounds and RCpCo stabilized 1,3-cyclohexadiene complexes
[10,11]. It has also been observed from our previous studies that
the reactivity of the fluorophosphazene based alkyne, PhC„C-
P3N3F5, with various cobalt complexes considerably differs from
other alkynes [11]. In this paper we report the synthesis of the
new cyclophosphazene based alkyne, (b-phenylethynyl)-gem-
diphenyltrifluorocyclotriphosphazene and describe its reactions
with RCpCo(PPh3)2 [R = MeOC(O)].
2. Experimental section
2.1. Materials and physical measurements
⇑
All manipulations of the complexes were carried out using
standard Schlenk techniques under nitrogen atmosphere.
Corresponding author. Tel.: +91 11 26591504; fax: +91 11 26581102.
E-mail address: eliasanil@gmail.com (A.J. Elias).
0020-1693/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2011.01.064

176
M.S. Kumar et al. / Inorganica Chimica Acta 372 (2011) 175–182
Tetrahydrofuran, xylene and toluene were freshly distilled from so-
dium benzophenone ketyl under nitrogen atmosphere and used.
Sodium salt of carbomethoxycyclopentadiene [12] and tris(tri-
phenylphosphine)cobalt chloride [13] were prepared according to
literature procedures. Dimethylcarbonate and triphenylphosphine
(Aldrich) were used as such. 1H and 13C {1H} spectra were recorded
on a Bruker Spectrospin DPX-300 NMR spectrometer at 300 and
75.47 MHz, respectively. 31P{1H} and 19F{1H} NMR spectra were
recorded on a Bruker Spectrospin DPX-400 NMR spectrometer at
121 and 376 MHz, respectively. IR spectra in the range
4000–250 cmÀ1 were recorded on a Nicolet Protége 460 FT-IR
spectrometer as KBr pellets. Elemental analyses were carried out
on a Carlo Erba CHNSO 1108 elemental analyzer. Mass spectra
were recorded in the FAB mode using a JEOL SX 102/DA-6000 mass
spectrometer.
as the first and second fractions. The third fraction which came
out while using 3% ethylacetate/hexane solvent mixture as eluent
was identified as the cobaltacyclopentadienyl metallacycle (com-
pound 4). Yield: 0.39 g (19%). Mp: 191 °C. IR (m
, cmÀ1): 1723s
(C@O), 1436w, 1223vs (P@N), 1151w, 936w, 896s (P–F), 815s (P–
F), 729w and 694(P–F). NMR (CDCl3): 1H, d 3.47 (s, 3H, –COOCH3),
5.24 (s, 1H, –CpH), 5.57 (s, 1H, –CpH), 5.60 (s, 1H, –CpH), 5.70 (s,
1H, CpH), 6.02–7.84 (m, 45H, –PhH); 13C{1H}, d 51.96 (–CH3),
84.71, 86.92 (C4 ring C), 85.66, 96.30, 97.27 (–CpC), 125.33,
125.86, 126.03, 127.53, 127.67, 127.85, 128.08, 128.26, 130.66,
134.77, 134.91 (PhC), 169.27 (C@O); 31P{1H},
d 3.36 (tm,
1
1JP–F = 900 Hz, –PF2), 20.16 (d, JP–P = 41 Hz, –PPh2), 35.84 [dm,
1JP–F = 960 Hz, –PF(C)], 54.33 (s, –PPh3); 19F{1H},
d
À70.13
1
1
(dm, JP–F = 885 Hz, –PF2), À61.45 (dm, JP–F = 902 Hz, –PF2),
1
1
À32.79 [d, JP–F = 965 Hz, –PF(C)], À30.40 [d, JP–F = 972 Hz, –
PF(C)]. MS (ES) [m/z (species)]: 1339 [M]+, 1361 [M+Na]+; Anal.
Calc. for C65H52CoF6N6O2P7: C, 58.31; H, 3.91; N, 6.28. Found: C,
58.28; H, 3.88; N, 6.25%.
Suitable crystals of compounds 2, 3 and 5 were obtained by
slow evaporation of their saturated solutions in ethyl acetate/
hexane solvent mixtures. X-ray diffraction studies of crystals
mounted on a capillary were carried out on a BRUKER AXS
SMART-APEX diffractometer equipped with CCD area detector
The fourth yellow colored fraction which came out while using
4% hexane/ethylacetate mixture was identified as [
g
5-carbometh-
[k(Mo K
were collected at T = 298 K by
a
) = 0.71073 Å, monochromator: graphite)] [14a]. Frames
, / and 2h-rotation with full quad-
oxycyclopentadienyl][
g
4–1,3-bis(gem-diphenyltrifluoro cyclotri-
x
phosphazenyl)-2,4-diphenylcyclobutadiene]cobalt
(compound 2). Yield: 0.24 g (15%). Mp: 175 °C. IR (m
complex
rant data collection strategy (four domains each with 600 frames)
at 10 s per frame with SAINT [14a,b]. The measured intensities were
reduced to F2 and corrected for absorption with SADABS [14b]. Struc-
ture solution, refinement, and data output were carried out with
the SHELXTL package by direct methods [14c]. Non-hydrogen atoms
were refined anisotropically. All hydrogen atoms were included
in idealized positions, and a riding model was used for the refine-
ment. The crystallographic parameters for compounds 2, 3, and 5
are given in Table 4.
, cmÀ1):
1724s (C@O), 1226vs (P@N), 1092s, 900w, and 814s (P–F). NMR
(CDCl3): 1H NMR: 3.25 (s, 3H, –COOCH3), 4.78 (s, 2H, –CpH), 5.53
(s, 2H, –CpH), 6.88–7.90 (m, 30H, PhH); 13C{1H}, d 51.36 (–CH3),
76.58, 84.83 (C4 ring C), 85.03, 86.32, 86.50, 89.25 (–CpC),
127.19, 127.61, 127.72, 127.85, 127.99, 128.36, 128.44, 128.55,
128.62, 129.23, 129.68, 130.22, 130.36, 130.48, 131.20 (PhC),
1
164.91 (C@O); 31P{1H}, d 1.24 (tm, JP–F = 896 Hz, –PF2), 23.95 (d,
1
1JP–P = 43 Hz, –PPh2), 28.19 (dm, JP–F = 970 Hz, –PF); 19F{1H}, d
1
1
À67.99 (dm, 1F, JP–F = 899 Hz, –PF2), À64.05 (dm, 1F, JP–F
=
1
2.2. Preparation of (b-phenylethynyl)-gem-
diphenyltrifluorocyclotriphosphazene (1)
900 Hz, –PF2), À40.99 (dm, 1F, JP–F = 964 Hz, –PF); MS (ES) [m/z
(species)]: 1076 [M]+; Anal. Calc. for C47H37CoF6N6O2P6: C, 58.31;
H, 3.91; N, 6.28. Found: C, 58.28; H, 3.88; N, 6.25%.
A solution of phenylacetylene (0.16 g, 1.58 mmol) in 20 mL of
anhydrous THF was placed in an oven dried two neck round bot-
tom flask and the solution was cooled to À78 °C. To this 1.6 M solu-
tion of n-BuLi (1.0 mL, 1.58 mmol) was added drop wise. The
reaction mixture was then brought to room temperature and stir-
red for three hours. A solution of N3P3F4Ph2 (0.58 g, 1.58 mmol) in
20 mL of dry THF was added to the above mixture at À78 °C and
the solution was stirred at room temperature for 12 h. Afterwards,
all the solvents were evaporated and the crude product was
chromatographed through a silica gel column. (b-Phenylethynyl)-
gem-diphenyltrifluorocyclotriphosphazene (1) was obtained as a
viscous liquid as the third fraction while using 6% ethylacetate/
The fifth fraction which came out while using 5% ethylacetate/
hexane mixture was identified as another isomer of the cobaltacy-
clopentadienyl metallacycle, (compound 3). Yield: 0.17 g (8%). Mp:
106–110 °C. NMR (CDCl3): 1H, d 3.87 (s, 3H, –COOCH3), 5.29 (s, 1H, –
CpH), 5.31 (s, 1H, –CpH), 5.77 (s, 1H, –CpH), 6.02 (s, 1H, CpH), 6.80–
7.97 (m, 45H, –PhH); 31P{1H}, d 3.38 (tm, 1JP–F = 896 Hz, –PF2), 22.84
(d, 1JP–P = 41 Hz, –PPh2), 29.48 [tm, 1JP–F = 946 Hz, –PF(C)], 54.55 [s,
–PPh3]; 19F{1H}, dÀ67.98 (dm, 1JP–F = 886 Hz, –PF2), –63.95 (dm, 1JP–
1
F = 889 Hz, –PF2), À41.07 [d, JP–F = 945 Hz, –PF(C)]; MS (ES) [m/z
(species)]: 1339 [M]+; Anal. Calc. for C65H52CoF6N6O2P7: C, 52.43;
H, 3.46; N, 7.81. Found: C, 52.41; H, 3.39; N, 7.78%.
The last fraction which came while using 10% ethylacetate/hex-
ane mixture was found to be a spirocyclic phosphazacyclopentadi-
ene compound bound to RCpCo in the g4 mode, (compound 5).
hexane mixture as the eluent. Yield: 0.42 g (60%). IR (m
, cmÀ1):
2192vs (C„C), 1239vs (P@N), 1123s, 905s, 875s and 828s (P–F).
NMR (CDCl3): 1H, d 7.37–7.90 (m, 15H, ArH); 31P{1H}, d 2.12 (tm,
Yield: 0.14 g (8%). Mp: 205–207 °C. IR (m
, cmÀ1): 1720s (C@O),
1
1JP–F = 889 Hz, –PF2), 33.43 (dm, JP–F = 910 Hz, –PF), 22.17 (s, –
1437s, 1225vs (P@N), 1120s, 1028w, 891w, 724s and 694s (P–F).
NMR (CDCl3): 1H NMR: 3.56 (s, 3H, –COOCH3), 5.18 (s, 1H, –
CpH), 5.31 (s, 1H, -CpH), 5.62 (s, 1H, –CpH), 6.03 (s, 1H, –Cp),
6.75–7.88 (m, 31H, PhH, C4P ring H); 13C{1H}, d 52.33 (–CH3),
76.57, 84.83 (C4 ring C), 85.03, 86.32, 86.50, 89.25 (–CpC),
127.62, 127.83, 129.98, 127.85, 127.99, 128.36, 128.44, 128.55,
128.62, 129.23, 129.68, 130.22, 130.36, 130.48, 131.20 (PhC),
1
PPh2); 19F{1H}, d À65.23 (dm, 1F, JP–F = 887 Hz, –PF2), À67.15
1
1
(dm, 1F, JP–F = 885 Hz, –PF2), À38.78 (dm, 1F, JP–F = 907 Hz, –PF).
MS (ES) [m/z (species)]: 448 [M+H]+.
2.3. Preparation of compounds 2, 3, 4 and 5
1
A solution of (b-phenylethynyl)-gem-diphenyltrifluorocyclotri-
phosphazene, compound 1 (1.4 g, 3.1 mmol) and (PPh3)3CoCl
(1.10 g, 1.67 mmol) in 35 mL of toluene was added to a stirred
solution of sodium salt of carbomethoxycyclopentadiene (0.24 g,
1.67 mmol) in 10 mL of THF. The mixture was stirred at room tem-
perature for 15 min, before refluxing for 24 h. Afterwards, all sol-
vents were removed under vacuum, the resulting crude product
chromatographed on a basic alumina column, and eluted with hex-
ane to remove triphenylphosphine and triphenylphosphine oxide
171.22 (–C@O); 31P{1H}, d 3.25 (tm, JP–F = 906 Hz, –PF2), 8.65
1
1
(tm, JP–F = 898 Hz, –PF2), 19.06 (d, JP–P = 42 Hz, –PPh2), 21.31 (d,
1JP–P = 42 Hz, –PPh2), 26.84 (d, JP–P = 39 Hz, Spirocyclic P);
1
19F{1H}, d À70.14 (dm, 1F, JP–F = 909 Hz, –PF2), À65.71 (dm, 1F,
1
1JP–F = 840 Hz, –PF2), À64.31 (dm, 1F, JP–F = 897 Hz, –PF2), À62.47
1
1
1
(dm, 1F, JP–F = 845 Hz, –PF2), À39.19 (dm, 1F, JP–F = 967 Hz,
–PF); MS (ES) [m/z (species)]: 1059 [M]+ 1060 [M+H]+; Anal. Calc.
,
for C47H38CoF5N6O2P6: C, 53.32; H, 3.62; N, 7.94. Found: C, 53.29;
H, 3.58; N, 7.90%.

M.S. Kumar et al. / Inorganica Chimica Acta 372 (2011) 175–182
177
3.2. Reaction of (b-phenylethynyl)-gem-
3. Results and discussion
diphenyltrifluorocyclotriphosphazene with g5
-
[MeOC(O)C5H4]Co(PPh3)2
3.1. Synthesis of (b-phenylethynyl)-gem-
diphenyltrifluorocyclotriphosphazene
The reaction of (b-phenylethynyl)-gem-diphenyltrifluorocyclo-
triphosphazene with in situ generated
g
a
5-[MeOC(O)C5H4]-
CpCo stabilized
Reported multistep methods for the preparation of gem-
diphenyltetrafluorophosphazene involves the highly volatile
N3P3F6 resulting in low yield of the product [15,16]. Recently we
have described a relatively high yielding, less cumbersome method
for the synthesis of gem-diphenyltetrafluorophosphazene by fluo-
rinating gem-diphenyltetrachlorocyclotriphosphazene, which in
turn is prepared by the Friedel–Crafts arylation of hexachlorocyclo-
triphosphazene [17,18]. The (b-phenylethynyl)-gem-diphenyltri-
fluorocyclotriphosphazene, compound 1 has been prepared from
a 1:1 M reaction of gem-diphenyltetrafluorophosphazene with
in situ generated lithiated phenylacetylene (Scheme 1).
Co(PPh3)2 resulted in the formation of
cyclobutadiene complex [
g
5-carbomethoxycyclopentadienyl][g4
-
1,3-bis(gem-diphenyltrifluorocyclotriphosphazenyl)-2,4-diphenyl-
cyclobutadiene]cobalt compound 2, having two gem-diphenyltri-
fluorophosphazene moieties trans to each other in 15% yield and
two structural isomers of the cobaltacyclopentadienyl metallacy-
cles compound 3 and 4 stabilized by PPh3 units in 8 and 19%,
respectively (Scheme 2). In addition, the unprecedented formation
of a novel compound 5, which is best described as a spirocyclic
phosphazacyclopentadiene bound to a RCpCo unit in the
g
4-mode
was also observed in 8% yield. Compounds 2–5 have two stereo-
genic centers and can in principle result in diastereoisomeric mix-
tures. However, we were able to isolate only one isomer from the
reactions in all these cases.
Compound 1 is the first example of gem-diphenyltrifluorocyclo-
triphosphazene based alkyne, obtained in 60% yield as a viscous
liquid at room temperature which solidifies below 0 °C. The com-
pound gave a very strong peak at 2190 cmÀ1 in the IR-spectrum,
One of the isomers of cobaltacyclopentadiene complexes,
which corresponds to the mC„C stretching vibration. The formation
[g
5-carbomethoxycyclopentadienyl](triphenylphosphine)-[(2,5-
of this compound had been further confirmed by using mass
spectrometry and multi-nuclear NMR spectroscopic methods. The
reaction was carried out by taking a slight excess of gem-diphenyl-
tetrafluorophosphazene to avoid the formation of geminally
substituted dialkyne compound. Similar to gem-diphenyltetraflu-
orophosphazene, compound 1 also has been found to be very sta-
ble to air and moisture.
bis(gem-diphenyltrifluorocyclotriphosphazenyl)-3,4-diphenyl-
cobaltacyclopentadiene]cobalt, compound 3 contains two gem-
diphenyltrifluorophosphazene moieties bound to the ring
carbon atoms adjacent to the cobalt center while the other isomer
[g
5-carbomethoxycyclopentadienyl](triphenylphosphine)-[2,4-
bis(gemdiphenyltrifluorocyclotriphosphazenyl-3,5-diphenylcobal-
tacyclopentadiene]cobalt, compound 4 contains one gem-diphe-
nyltrifluorophosphazene moiety adjacent to the cobalt center and
the other away from the cobalt center. Both the compounds were
separated by column chromatography using a basic alumina
column. Compound 3 has been characterized structurally using
X-ray crystallography.
Identity of compound 4 was confirmed by comparing its spec-
tral data with the analogous cobaltacyclopentadienyl metallacycle
having two pentafluorophosphazene moieties present in the 2nd
and 4th positions which has been structurally characterized [10].
P
P
N
P
N
P
n-BuLi
THF
N
P
N
P
H
F
F
F
N
N
F
F
F
F
1
Scheme 1. Synthesis of (b-phenylethynyl)-gem-diphenyltrifluorocyclotriphos-
phazene.
F
F
Na
H3COOC
Ph
P
N
P
N
P
COOCH3
+
F
CoCl(PPh3)3
COOCH3
Ph
+
F
Co
F
+
F
N
P
PPh3
N
F
F
Toluene/THF
Reflux, 24h
F
Ph
N
F
Ph
P
Ph
F
N
Co
F
N
P
P
P
P
Ph
N
P
Ph
P
N
N
P
N
P
N
F
P
N
F
Ph
Ph
N
Ph
Ph
P
Ph
N
F
Ph
Ph
2
3
COOCH3
PPh3
Ph
F
COOCH3
F
P
N
F
Co
F
N
Ph
Ph
Co
P
F
N
F
P
P
Ph
N
P
+
F
P
Ph
N
N
P
Ph
N
P
N
P
N
P
P
F
F
Ph
Ph
Ph
N
N
Ph
F
P
N
Ph
F
Ph
4
5
Scheme 2. Reaction of (b-phenylethynyl)-gem-diphenyltrifluorocyclotriphosphazene with
g
5-(MeOC(O)C5H4)Co(PPh3)2.

178
M.S. Kumar et al. / Inorganica Chimica Acta 372 (2011) 175–182
Its structure was further confirmed by comparing the 19F NMR
spectra of compound 4 and its pentafluorophosphazene analog.
Interestingly, both the compounds gave two different signals for
the –PF moieties, whereas compounds 3 and its pentafluorophosp-
hazenyl analog gave only one signal for the –PF moieties. This dif-
ference, due to the presence of two –PF moieties in different
chemical environment suggests that the two gem-diphenyltriflu-
orophosphazene moieties in compound 4 are present in 2nd and
4th positions similar to the known pentafluorophosphazene
substituted cobaltacyclopentadienyl metallacycle.
precursor for compound 5 cannot be ruled out as a cobaltametalla-
cycle assisted removal of one of the geminal fluorines from a phos-
phazene unit of compound 3 followed by its insertion to form the
phosphazacyclopentadiene can lead to compound 5. An attempted
reaction of cobaltametallacyclic compound 3 with excess of tri-
phenylphosphine and water, however did not result in the forma-
tion of compound 5.
The isolation and characterization of compound 5 prompted us
have a re-look into the reaction of PhC„CP3N3F5 with in situ gen-
erated
g
5-(MeOC(O)C5H4)Co(PPh3)2. In this reaction we have re-
Compound 5 is the first example of phosphazene based spirocy-
ported that a red colored viscous liquid is also formed in the
reaction when carried out for short periods of time (ꢀ8 h) [10].
Although evidence of RCpCo and phosphazenyl moieties was pres-
ent in this compound, it could not be characterized due to the vis-
cous nature of the compound and contamination with other
compounds. In the light of isolation and characterization of com-
clic phosphazacyclopentadiene bound to a CpCo unit in the g4
-
mode and is obtained in 8% yield. It is a rather unusual product
for the reaction of alkyne with in situ generated CpCo(PPh3)2. The
carbonyl inserted cyclopentadienone bound to CpCo unit has al-
ways been found as one of the products from reaction of CpCo(CO)2
with alkynes [19]. However, compound 5 is the first example of an
analogous phosphazene inserted cyclopentadiene bound to a
RCpCo unit. A mechanism was put forward by Rausch et al. for
the formation of the CpCo stabilized cyclopentadienone complex,
which assumes intermediates with one cobalt nucleus. Later it
was suggested that both carbonyl ligands on the metal are ex-
changed in a stepwise fashion by alkyne units followed by oxida-
tive coupling to form the cobaltacyclopentadiene complex [20].
The cobaltacyclopentadiene thus formed, further react with free
carbonyl ligand to form the CpCo stabilized cyclopentadienone
complex (Scheme 3). Recently Gleiter and coworkers have synthe-
sized the CpCo stabilized cyclopentadienone complex from a CpCo
stabilized cyclobutadiene complex as well [21].
pound 5, we repeated the reaction of PhC„CP3N3F5 with
g
5-(MeO-
C(O)C5H4)Co(PPh3)2 for 8 h and isolated the red viscous liquid
which came as a sixth fraction from the column with some con-
tamination of metallacyclic compounds. Mass spectral analysis of
this viscous liquid clearly indicated it to be the pentafluorophos-
phazene derived spirocyclic phosphazacyclopentadiene bound to
a RCpCo unit (m/e 826.91) similar to compound 5. The yield of this
compound was found to be around 20% when the reaction was car-
ried out for 8 h. Though the 31P and 19F NMR spectra of this com-
pound are very complex due to the contamination with
metallacyclic compounds and other impurities, the doublet multi-
plet peak obtained at 26.84 ppm in 31P NMR for the spirocyclic
phosphorus atom of compound 5 was found to be present in this
compound also at 27.24 ppm.
Although repeated reactions have established the reproducibil-
ity and yield of compound 5, the mechanism for its unprecedented
formation has not been clear yet, and is currently being explored.
The possibility of compound 3 with or without its PPh3 unit as a
Thus the nature of most of the compounds obtained from the
reaction of (NPPh2)(NPF2)[NP(F)C„CPh] with
g
5-(MeOC(O)C5H4)-
Co(PPh3)2 was found to be similar to that of the reaction of
R
R
R
R
CO
R
Co
Co
R
Co
Co
-CO
R
Co
-CO
R
R
R
R
OC
CO
CO
R
R
R
R
R
R
R
O
Scheme 3. Proposed mechanism for the formation of CpCo stabilized cyclopentadienone complex.
Fig. 1. X-ray crystal structure of compound 2 (hydrogen atoms have been omitted for clarity).

M.S. Kumar et al. / Inorganica Chimica Acta 372 (2011) 175–182
179
PhC„CP3N3F5. In addition,
cyclopentadiene compound which could not be identified and
characterized from the reaction of PhC„CP3N3F5 with g5
a
novel spirocyclic phosphaza-
The crystal structure of the PPh3 derived cobaltacyclopentadie-
nyl compound 3 is given in Fig. 2. The cobalt-phosphorus (PPh3)
distance [Co1–P3 = 2.218(3), Table 2] is almost the same as that
of pentafluorophosphazene based cobaltametallacyclic compounds
[10]. The Co–P distance is shorter than the values of 2.327(4) Å
found in trans-chlorobis(dimethylglyoximato)(triphenylphos-
phine)cobalt(III) [22], 2.339(1) Å found in bis(dimethylglyoxi-
-
(MeOC(O)C5H4)Co(PPh3)2 earlier was isolated as a crystalline solid
from this reaction and was structurally characterized from this
study as an
g
4-coordinated complex of RCpCo unit.
mato)(tri-n-butylphosphine)(4-pyridyl)cobalt(I)
[23],
and
5-cyclopentadienyl)-1,3-bis(pentafluorophe-
3.3. X-ray studies on compounds 2, 3 and 5
2.234(2) Å in 1-(
g
nyl)-2,4-bis(phenyl)cobalt complex [24]. Unlike the pentafluoro-
phosphazene based cobaltametallacycle, the two C–P distances
connecting the fluorophosphazene units to the metallacycle are
not found to be the same [C11–P6 = 1.768(8) and C8–
P2 = 1.795(7) Å]. The P–F bond distances [P2–F1 = 1.560(6) and
P6–F4 = 1.563(6) Å] which are directly attached to the carbon atom
of the metallacycle were found to be shorter than the P–F bond dis-
tances which are away from the metal center [P4–F2 = 1.582(7)
and P4–F3 = 1.578(6) Å].
The X-ray crystal structure of the CpCo derived cobalt sandwich
compound 2 has been given in Fig. 1. The two gem-diphenylphos-
phazene moieties are present in a trans arrangement, and they are
oriented at angles of 44.12(61)° and 85.22(12)° with respect to the
mean plane containing the cyclobutadiene ring. The two phenyl
rings make angles of 39.24(82)° and 52.23(02)° with the mean
plane containing the central four member ring. The distances of
the P–F bonds which are directly attached to the cyclobutadiene
ring [P1–F1 = 1.554(4) and P4–F4 = 1.547(4) Å] are found to be
longer than the P–F bond distances which are away from the cen-
tral cyclobutadiene ring (Table 1). In compound 2, the two gem-
diphenyltrifluorophosphazene units are present in the gauche form
which is in contrast to the orientation of the two cyclophospha-
zene units of the reported P3N3F5 derived CpCoCb compound
where the two phosphazene units are found to be present in
eclipsed form [10].
The X-ray crystal structure of the spirocyclic CpCo bound phos-
phazacyclopentadiene, compound 5 shows that the cobalt atom is
coordinated to the cyclopentadienyl ring in an
mode, and attached with the phosphazacyclopentadiene ring in
an
4-mode (Fig. 3). The gem-diphenylphosphazene moiety is al-
g
5-coordination
g
most perpendicular to the plane of the four carbon atoms
[C(8),C(9),C(10) and C(11)]. The mean plane of the phosphazene
ring of the gemdiphenylphosphazene moiety is oriented at a dihe-
dral angle of 89.58(11)° to the mean plane of the four C atoms (C8–
C11).
The other gem-diphenylphosphazene moiety which is not in-
volved in five membered ring formation makes an angle of
68.64(82)°, with the mean plane of four carbon atoms (C8–C11).
The phosphorus atoms attached to two phenyl rings in both phos-
phazene units deviate by distances of 0.180(8) and 0.069(7) Å,
respectively, with the mean planes containing the other ring
atoms. The mean planes containing the two phenyl rings make an-
gles of 41.68(92)° and 56.86(52)° with the mean plane containing
the four carbon atoms (C8–C11). The cobalt atom makes distances
of 1.667(3) and 1.604(2) Å with the centroids of cyclopentadiene
and of (C8–C11), respectively. Some of the selected bond distances
and bond angles of compound 5 are given in Table 3.
Table 1
Selected bond lengths and bond angles of compound 2.
Bond lengths (Å)
Co1–C3
P1–F1
P3–F2
P5–F5
P1–N3
P2–C42
P1–C11
C8–C12
2.076(7)
1.554(4)
1.536(4)
1.541(4)
1.591(6)
1.792(6)
1.763(5)
1.485(7)
Co1–C8
P4–F4
P3–F3
P5–F6
P2–C36
P4–C9
N4–P5
1.978(5)
1.547(3)
1.535(4)
1.540(4)
1.807(7)
1.761(5)
1.549(5)
Bond angles (°)
Co1–C8–C12
C3–Co1–C8
O1–C1–O2
131.90(37)
118.31(23)
121.48(67)
106.74(31)
Co1–C9–P4
N1–P1–N3
C36–P2–C42
N3–P1–C11
133.47(27)
118.56(28)
108.30(31)
112.55(27)
The phosphorus atom of the gem-diphenylphosphazene moiety
which is involved in the five membered phosphazacyclopentadiene
ring formation deviate from the mean plane containing the four
C18–P6–C24
Fig. 2. X-ray crystal structure of compound 3 (hydrogen atoms and phenyl rings on triphenylphosphine moiety have been omitted for clarity).

180
M.S. Kumar et al. / Inorganica Chimica Acta 372 (2011) 175–182
carbon atoms (C8–C11) by a distance of 0.572(1) Å. In the case of
CpCo stabilized cyclopentadienone complex, the carbonyl carbon
atom deviate by a distance of only 0.201 Å [21].
The phosphorus atoms attached to two phenyl rings deviate by dis-
tances of 0.023(91) and 0.069(51) Å, respectively, with the mean
planes containing the other ring atoms. In compound 3 both the
phosphazene units deviate very little from the plane and are pres-
ent in slightly puckered forms. In both phosphazene units, the
mean planes containing the three nitrogen atoms make angles of
2.51(32)° and 1.09(52)°, respectively, with the mean planes con-
taining the phosphorus atoms. The phosphorus atoms attached to
two phenyl rings in both phosphazene units deviate by distances
of 0.138(42) and 0.001(02) Å, respectively, with the mean planes
containing the other ring atoms.
X-ray crystal structures of compounds 2, 3 and 5 showed inter-
esting variations in the planarity of phosphazene rings present in
them. In compound 5, the spirocyclic gem-diphenylphosphazene
moiety has been found to be present in a puckered form, and the
other gem-diphenylphosphazene moiety deviates very slightly
from the mean plane. In the spirocyclic gem-diphenylphosphazene
moiety, the mean plane passing through three phosphorus atoms
makes an angle of 7.66(11)° with the mean plane containing the
three nitrogen atoms, and in the case of other gem-diphenylphos-
phazene moiety, the angle is only 2.17(41)°. Unlike compound 5,
the two phosphazene units in compound 2 are almost planar. In
both phosphazene units, the mean planes containing the three
nitrogen atoms make angles of 2.43(31)° and 0.85(32)°, respec-
tively, with the mean planes containing the phosphorus atoms.
3.4. Spectral studies on compounds 1–5
The 31P NMR spectrum of compound 1 gave three different
peaks. The triplet multiplet at 2.12 ppm (JP–F = 915 Hz) corresponds
to the –PF2 moiety, the doublet multiplet at 2.78 ppm (JP–
F = 900 Hz) corresponds to the –PF moiety and the doublet at
22.17 ppm (JP–P = 35 Hz) is assigned to the –PPh2 moiety. Unlike
the 31P NMR spectrum, the 19F NMR spectrum of compound 1 is
slightly complex. The 19F NMR spectrum of compound 1 gave three
different signals. The –PF2 moiety gave two different doublet
Table 2
Selected bond lengths and bond angles of compound 3.
Bond lengths (Å)
Co1–P3
Co1–C8
P2–N1
P5–C12
P6–C42
P8–C36
P4–F2
2.218(3)
1.988(7)
1.606(5)
1.798(8)
1.794(12)
1.815(11)
1.582(6)
1.563(4)
1.553(6)
Co1–C3
Co1–C11
P5–N3
P2–C8
P5–C18
P2–F1
2.074(10)
1.972(7)
1.600(8)
1.795(7)
1.802(9)
1.560(4)
1.578(5)
1.551(6)
multiplets at -67.16 ppm (JP–F = 906 Hz) and at À65.23 ppm (JP–F
=
910 Hz), which suggests that the two fluorine atoms are diastereo-
topic in nature. This kind of observation where the two fluorine
atoms attached to same phosphorus atom giving two different sig-
nals in the 19F NMR spectrum was also observed in fluorophospha-
zene based cobaltametallacyclic compounds [10,11]. The –PF
moiety gave a doublet at À38.78 ppm (JP–F = 906 Hz).
P4–F3
P7–F5
P6–F4
P7–F6
The 31P NMR spectrum of compound 2 shows three different
signals. The triplet multiplet signal at 1.24 ppm (JP–F = 896 Hz)
was assigned to the phosphorus atom attached to two fluorine
atoms. The doublet which appears at 23.95 ppm (JP–P = 43 Hz)
corresponds to the phosphorus atom attached with two phenyl
rings and the doublet multiplet which appears at 28.19 ppm
Bond angles (°)
Co1–C11–C10
C11–Co1–C8
C11–P6–F4
C18–P5–C12
C8–C9-C24
114.14(52)
82.69(29)
102.79(30)
103.99(38)
127.62(60)
Co1–C8–C9
P3–Co1–C11
C8–P2–N1
C36–P8–C42
C11–C10–C30
113.58(46)
95.53(22)
113.42(30)
104.76(52)
126.01(65)
Fig. 3. X-ray crystal structure of compound 5 (hydrogen atoms have been omitted for clarity).

M.S. Kumar et al. / Inorganica Chimica Acta 372 (2011) 175–182
181
Table 3
20.16 ppm (JP–F = 41 Hz). The doublet multiplet signal which oc-
curs at 35.84 ppm (JP–F = 960 Hz) has been assigned for phosphorus
atom attached with single fluorine atom. The singlet peak which
appears at 54.33 ppm is corresponding to the phosphorus atom
of triphenylphosphine attached to the cobalt metal center.
In the 19F NMR spectrum of compound 4 (Fig. 5), the –PF2
groups showed two different doublet multiplet signals at
À70.13 ppm (JP–F = 885 Hz) and À61.45 ppm (JP–F = 902 Hz). Unlike
compound 3, the –PF moiety gave two different signals, both dou-
blets at À32.79 (JP–F = 965 Hz) and À30.40 (JP–F = 972 Hz). This 19F
NMR pattern is in good agreement with the pattern obtained for
pentafluorophosphazene substituted cobaltametallacyclic com-
pound, which contains two pentafluorophosphazene moieties in
the second and fourth positions [10].
Selected bond lengths and bond angles of compound 5.
Bond lengths (Å)
Co1–C3
Co1–C9
P4–N4
P4–C11
P5–C42
P3––C30
Bond angles (°)
2.051(5)
1.986(5)
1.609(5)
1.773(5)
1.810(6)
1.811(6)
Co1–C8
P1–N1
P4–N6
P4–C10
P5–C36
P3–C24
1.999(4)
1.595(4)
1.601(5)
1.802(5)
1.808(6)
1.800(5)
C11–P4–C10
C3–Co1–C11
C42–P5–C36
C24–P3–C30
85.93(21)
112.20(19)
104.13(23)
106.90(23)
C4–Co1–C8
N4–P4–N6
P3–N2–P2
C12–C8–C11
116.16(18)
114.68(21)
121.48(28)
123.49(38)
The 31P and 19F NMR spectra of compound 5 differ considerably
from that of other compounds. This compound gave six different
peaks in the 31P NMR spectrum. More interestingly, the two –PF2
moieties present in the two phosphazene units gave two different
signals, both triplet multiplet signals at 3.25 ppm (JP–F = 906 Hz)
and 8.65 ppm (JP–F = 898 Hz). The doublet multiplet peak obtained
at 26.84 ppm (JP–P = 39 Hz) is assigned to the spirocyclic phospho-
rus atom which is involved in the five membered ring formation
and the multiplicity of this compound results from the coupling
with the other two phosphorus atoms. The two doublet signals at
21.31 ppm (JP–P = 44 Hz) and 19.06 ppm (JP–P = 42 Hz) corresponds
to the two –PPh2 groups. The doublet multiplet at 37.18 ppm
(JP–F = 976 Hz) is assigned to the –PF moiety.
Table 4
Crystal structure parameters of compounds 2, 3 and 5.
Compounds
2
3
5
Empirical
formula
Formula
weight
Space group
a (Å)
C
47H37CoF6N6O2P6 C65H52CoF6N6O2P7 C47H38CoF5N6O2P6
1076.58
1338.85
1058.59
ꢀ
ꢀ
P2(1)/c
9.1382(11)
30.444(4)
17.241(2)
90
P1
P1
10.4213(19)
14.437(3)
23.463(4)
82.327(3)
86.606(3)
74.375(3)
3368.2(11)
2
9.6384(15)
11.0691(17)
22.595(4)
78.071(3)
88.408(3)
81.869(3)
2334.9(6)
2
298(2)
0.71073
1.506
0.640
b (Å)
c (Å)
a
(°)
b (°)
90
90
Similar to 31P NMR spectrum, the 19F NMR spectrum compound
5 also showed interesting features. The two –PF2 moieties present
in two phosphazene units gave four different signals, all doublet
multiplets at À70.14 (JP–F = 909 Hz), À65.71 (JP–F = 840 Hz),
À64.31 (JP–F = 897 Hz) and À62.47 ppm (JP–F = 845 Hz). The occur-
c
(°)
V (Å3)
Z
4796.5(10)
4
T (K)
298(2)
0.71073
1.491
298(2)
0.71073
1.320
0.484
k (Å)
qcalc (g/cm3)
l
(mmÀ1
)
0.628
h Range
R1, wR2
(I > 2
1.34–25.50
0.0750, 0.1574
1.81–21.00
0.0809–0.2200
1.84–25.50
0.0801, 0.1690
r
(I))
(JP–F = 970 Hz) is assigned to phosphorus atom attached to one
fluorine atom. The 19F NMR spectrum of compound 2 shows three
different signals. The two doublet multiplets at À67.99 (1JP–F
=
899 Hz) and À64.05 ppm (1JP–F = 900 Hz), correspond to the –PF2
moiety, which suggest that the two fluorine atoms are diastereo-
topic in nature. The doublet multiplet at À40.99 ppm (1JP–F
=
964 Hz) corresponds to the –PF moiety.
31P NMR spectrum of compound 3 gave four different signals.
The triplet multiplet at 3.38 ppm (JP–F = 896 Hz) corresponds to
the –PF2 group. The phosphorus atom which is attached to two
phenyl rings has appeared as
a doublet at 22.84 ppm (JP–
F = 41 Hz). The doublet multiplet signal which occurs at
29.48 ppm (JP–F = 946 Hz) has been assigned for phosphorus atom
attached to a single fluorine atom. The singlet peak which appears
at 54.55 ppm is corresponding to the triphenylphosphine phospho-
rus atom attached to the cobalt metal center. In 19F NMR spectrum
of compound 3, the –PF2 groups showed two different doublet
multiplet signals at À67.98 ppm (JP–F = 886 Hz) and À63.95 ppm
(JP–F = 889 Hz) and the –PF moiety gave only one doublet at
À41.07 (JP–F = 945 Hz), suggesting that the two –PF moieties are
present in similar chemical environments. This 19F NMR pattern
is in good agreement with the pattern obtained for analogous pen-
tafluorophosphazene substituted cobaltometallacyclic compound
[10].
Fig. 4. 31P{1H} NMR spectra of compound 4.
31P NMR spectrum of compound 4 shows four different signals
(Fig. 4). The triplet multiplet at 3.36 ppm (JP–F = 900 Hz) is due to
the presence of –PF2 group. The phosphorus atom which is at-
tached to two phenyl rings has appeared as
a
doublet at
Fig. 5. 19F{1H} NMR spectra pf compound 4.

182
M.S. Kumar et al. / Inorganica Chimica Acta 372 (2011) 175–182
rence of four different signals for the –PF2 moieties suggests that
all the fluorine atoms are diastereotopic in nature. The doublet
multiplet obtained at À39.19 ppm (JP–F = 967 Hz) has been as-
signed to the –PF group. The difference in the 31P and 19F NMR
spectra of compound 5 shows that the spiro substitution on one
phosphorus atom of one phosphazene unit considerably affects
the electron density and thus chemical shift of the particular phos-
phazene unit. This also suggests that the two phosphazene units
are present in different chemical environments.
associated with this article can be found, in the online version, at
doi:10.1016/j.ica.2011.01.064.
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The first example of a gem-diphenyltrifluorophosphazene de-
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Appendix A. Supplementary material
CCDC 756282, 756283 and 756284 contain the supplementary
crystallographic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif. Supplementary data