Cyclodiphosph(III)azane chemistry - Ylides from the reaction of [(RNH)P-N(t-Bu)]2 [R = t-Bu, i-Pr] with dimethyl maleate and chiral ansa-type derivatives from reaction of [ClP-N(t-Bu)]2 with a substituted BINOL

Article abstract of DOI:10.1016/j.ica.2010.12.072

Use of a simple inorganic ring system with the cyclodiphosph(III)azane skeleton [e.g. [(RNH)P-N(t-Bu)]₂ [R = t-Bu (7), i-Pr (8)] to probe some of the intermediates proposed in phosphine mediated organic reactions is highlighted. Thus the reacti

Full text of DOI:10.1016/j.ica.2010.12.072

Inorganica Chimica Acta 372 (2011) 374–382
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Cyclodiphosph(III)azane chemistry – Ylides from the reaction of
[(RNH)P-N(t-Bu)]2 [R = t-Bu, i-Pr] with dimethyl maleate and chiral ansa-type
derivatives from reaction of [ClP-N(t-Bu)]2 with a substituted BINOL
⇑
K.C. Kumara Swamy , G. Gangadhararao, Venu Srinivas, N.N. Bhuvan Kumar, E. Balaraman,
Manab Chakravarty
School of Chemistry, University of Hyderabad, Hyderabad 500 046, AP, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Available online 11 January 2011
Use of a simple inorganic ring system with the cyclodiphosph(III)azane skeleton [e.g. [(RNH)P-N(t-Bu)]2
[R = t-Bu (7), i-Pr (8)] to probe some of the intermediates proposed in phosphine mediated organic reac-
tions is highlighted. Thus the reaction of 7–8 with the allenylphosphine oxide Ph2P(O)C(Ph)@C@CH2 (9)
Dedicated to Prof. S.S. Krishnamurthy on the
occasion of his 70th birthday.
affords the phosphinimines [(RNH)P(
(11)], while a similar reaction of 7–8 with dimethyl maleate (or dimethyl fumarate) affords the ylides
[(RNH)P( -N-t-Bu)2P(NH-R)@C(CO2Me)-CH2(CO2Me) [R = t-Bu (18), i-Pr (19)]. The implication of such
l-N-t-Bu)2P(@N-R)-C(@CH2)CH(Ph)-P(O)Ph2] [R = t-Bu (10), i-Pr
l
Keywords:
reactions on phosphine mediated organic transformations including Morita–Baylis–Hillman reaction is
mentioned. In a rather rare type of situation, an unusually long phosphoryl (P@O) bond [1.538 (5) Å] as
revealed the X-ray structure of {(R)-6,60-(t-Bu)2-1,10-(C10H5)2-2,20-O2-}{P(O)(N-t-Bu)2-P(Se)} (27) is ratio-
nalized by means of crystallographic disorder in packing after comparing the data with that in the literature
and {1,10-(C10H6)2-2,20-O2}{P(Se)(N-t-Bu)2-P(Se)} (29). X-ray structures of the new compounds 10–11, 18–
19, 27 and 29 are discussed. Compound 10 crystallizes in the chiral space group Pca2(1) with (S)-chirality at
the carbon center [–C(@CH2)CH(Ph)-P] suggesting a case of spontaneous resolution through crystallization.
Ó 2011 Elsevier B.V. All rights reserved.
Phosphine activation
BINOL-substituted derivatives
Ylide
Cyclodiphosphazane
Spontaneous resolution
Allene
1. Introduction
reaction that leads to a diverse number of functionalized and syn-
thetically useful allylic systems [8]. Our interest in this connection
Cyclodiphosph(III)azanes, [ClPNR]n, and their derivatives con-
stitute well-established examples of inorganic ring systems [1].
The synthetic potential of these compounds as highly versatile li-
gands, precursors for macrocycles and more recently, probes to
explore organic reaction pathways, has been exploited by several
groups of workers [2–5]. In addition to these, we have shown that
the partial oxidation of some of these compounds leads to crystals
that exhibit ‘molecular non-stoichiometry’ [6]. In the above cyclo-
diphosph(III)azane precursors, the unshared lone pair on phospho-
rus takes part in the reactions in a majority of cases. We have been
interested in utilizing such a feature in exploring the mechanistic
details of traditional organic reactions such as those shown in
Scheme 1. The primary intermediates in these reactioꢀns are the
phosphonium salts (betaines) depicted as [R0(O)C-C(H) C(@CH2)-
is to identify/isolate compounds analogous to those proposed in
such reactions and in this context, we have utilized the cyclo-
diphosph(III)azane [(t-BuNH)P(
nucleophile. When this P(III) compound was treated with methyl
propiolate, it afforded the tautomeric form (t-Bu-NH)P( -N-t-
l-N-t-Bu)]2, which is an excellent
l
Bu)2P(@N-t-Bu)[CH@CH(CO2Me)] (6) of the expected phospho-
nium salt [7]. Despite the fact that 6 is not a phosphonium salt,
the formation of P–C bond vindicated the involvement of the pos-
tulated intermediates shown in Scheme 1. In the first part of this
paper, we highlight the contrasting reactivity of cyclodiphospha-
zanes 7–8 with an allenylphosphine oxide and dimethyl maleate.
While the former affords a phosphinimine, the latter reaction leads
to a phosphorus ylidic species.
(1), [R0(O)C–C(H)@C(CH2)ꢀ-PR3
]
(2), [(MeO2C)Cꢀ@C
þ
þ
PR3
]
H
MeO2C
(CO2Me)-PR3þ] (3), and [(EWG)CHꢀ-CH2-PR3þ] [EWG @ CN (4),
CO2R (5)] in Scheme 1 [7]. One of the most important reactions
among those shown in Scheme 1 is the Morita–Baylis–Hillman
β
C
α
t-Bu
N
t-Bu
N
C
.
.
.
P
.
.
.
P
P
P
H
N
t-Bu
N
t-Bu
N
NHR
RNH
NH-t-Bu
t-Bu
⇑
Corresponding author. Tel.: +91 40 23134856; fax: +91 40 23012460.
E-mail addresses: kckssc@yahoo.com, kckssc@uohyd.ernet.in (K.C. Kumara
R = t-Bu [7, δ(P) 88.8]
i-Pr [8, δ(P) 90.7]
6 [δ(P): -25.7, 70.0]
Swamy).
0020-1693/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2010.12.072

K.C. K. Swamy et al. / Inorganica Chimica Acta 372 (2011) 374–382
375
2.2. Synthesis of [(i-PrNH)P(l-N-t-Bu)2P(@N-i-Pr)-C(@CH2)CH(Ph)-
P(O)Ph2 (11)
CH2
COR'
COR'
+
+
(a)
(b)
R3P
+
+
COR'
PR3
PR3
1
2
This compound was prepared by following the procedure for
compound 10. Yield: 0.625 g (88%; using 1.12 mmol of 8). Mp:
85–88 °C. IR (KBr, cmꢀ1): 3437, 3256, 3059, 2965, 2866, 1597,
1493, 1439, 1366, 1206, 1028, 873. 1H NMR (400 MHz, CDCl3): d
0.74 and 0.87 (2 s,18H, C(CH3)3), 1.10 (d, 2J(H–H) = 6.4 Hz, 3H,
CHCH3), 1.13 (d, 2J(H–H) = 6.4 Hz, 3H, CHCH3), 1.21 (d, 2J(H–
H) = 6.0 Hz, 3H, CHCH3), 1.31 (d, 2J(H–H) = 6.0 Hz, 3H, CHCH3),
2.01 (d, 2J(P–H) = 8.4 Hz, 1H, NH), 3.47–3.64 (br, 2H, NCH(CH3)2),
5.80 (d, 3J(P–H) ꢁ 26.4 Hz, 1H, @CHAHB cis to P), 6.21 (dd, 2J(P–
H) ꢁ 13.2 Hz, 3J(P–H) ꢁ 6.0 Hz, 1H, P(O)CH), 7.02–8.22 (m, 16H,
Ar–H + @CHAHB trans to P). 13C NMR (100 MHz, CDCl3): d 26.2 and
26.6 (2 s, @NCH(CH3)2), 28.2 (d, 3J(P–C) = 6.2 Hz, NCH(CH3)2), 28.3
(d, 3J(P–C) = 8.0 Hz, NCH(CH3)2), 30.7 and 31.0 (2 s, C(CH3)3), 44.4
(d, 2J(P–C) = 7.2 Hz, C(CH3)3), 46.5 (d, 1J(P–C) ꢁ 63.0 Hz, P(O)C(Ph)),
51.8 (d, 2J(P–C) = 8.5 Hz, C(CH3)3), 126.5, 127.6, 127.8, 128.2, 128.4,
130.5, 130.8, 130.9, 131.3, 132.2, 132.3, 133.1, 133.2, 134.2, 136.2
and 136.3 (2 d, 2J(P–C) ꢁ 13.1 Hz, Ar–C + PC@CH2), 142.5 (d, 1J(P–
C) = 149.1 Hz, PC@CH2). 31P NMR (162 MHz, CDCl3): d ꢀ1.0 (br,
P@N), 32.0 (d, 3J(P–P) ꢁ 24.5 Hz, P@O), 71.9 (br, P-N). LC–MS: m/z
638 [M+1]+. Anal. Calc. for C35H51N4OP3: C, 66.02; H, 8.07; N, 8.80.
Found: C, 66.12; H, 8.15; N, 8.69%.
CO2Me
MeO2C
CO2Me
R3P
+
PR3
MeO2C
3
EWG
EWG
(c)
+
+
R3P
EWG = CN (4), CO2R' (5)
R3P
(Morita-Baylis-Hillman intermediate)
Scheme 1.
In the course of our studies on cyclodiphosphazanes, we have
also made some new observations related to molecular non-
stoichiometry that involves exchange of positions of non-bonded
electron pair (on phosphorus) with phosphoryl oxygen in the crys-
tal lattice of cyclodiphosphazane derivatives [6]. An additional
interest in such compounds was to prepare chiral-BINOL based
cyclodiphosph(V)azanes with a phosphoryl bond for possible use
as chiral auxiliaries [9]. In this paper, we report the synthesis
and X-ray structures of some of these chiral compounds and also
give an example in which there is a rather (unusually) long P@O
bond of 1.538 Å [expected range: 1.445–1.460 Å]. A possible ratio-
nale based on crystal packing effects is also presented.
2.3. Synthesis of (t-Bu-NH)P(l-N-t-Bu)2P(NH-t-Bu)@C(CO2Me)
CH2(CO2Me) (18)
To a solution of 7 (0.531 g, 1.52 mmol) in toluene (15 mL), di-
methyl maleate (0.22 g, 1.52 mmol) was added via syringe at room
temperature, the mixture was stirred for 3 d and the solution con-
centrated in vacuo (ca 1.5 mL) and kept at ꢀ4 °C for 24 h to obtain
the crystals of 18. Yield: 0.66 g (90%). Mp: 138–141 °C. IR (KBr,
cmꢀ1): 3380, 2969, 1752, 1603, 1437, 1368, 1327, 1208. 1H NMR
(400 MHz, CDCl3): d 1.32, 1.42 and 1.55 (3 s, 36H, C(CH3)3), 2.65
(d, 3J(H–H) = 14.4 Hz, 2H, PCCH2), 3.04 (d, 2J(P–H) = 8.0 Hz, 1H,
NH), 3.54 and 3.65 (2 s, 6H, OCH3), 9.08 (d, 2J(P–H) = 8.0 Hz, 1H,
NH). 13C NMR (100 MHz, CDCl3): d 30.9, 31.0, 32.2 and 32.8 (d each,
3J(P–C) = 4.5, 4.5, 3.6 and 9.7 Hz, respectively, C(CH3)3), 31.4 (s,
PCCH2), 45.2 (d, 1J(P–C) = 183.0 Hz, PC), 49.8, 51.0 (2 s, OCH3),
51.5, 51.8 (2 s, C(CH3)3) 52.6 (d, 2J(P–C) = 6 Hz, C(CH3)3), 171.7 (d,
2J(P–C) = 30.0 Hz, CO2Me), 174.9 (d, 3J(P–C) = 10.0 Hz, CO2Me). 31P
NMR (162 MHz, CDCl3): d 23.7, 78.9.
2. Experimental
General experimental conditions are described in a recent paper
[10]. Cyclophosphazane derivatives [(RNH)P(
(7), i-Pr (8)] [1d,5,7], 6,60-di-t-butyl-BINOL [11], the allene
Ph2P(O)C(Ph)@C@CH2 (9) [12] and [ClP( -N-t-Bu)]2 (24) [13] were
l-N-t-Bu)]2 [R = t-Bu
l
prepared by known synthetic routes. Chemicals were procured
from Aldrich or Acros Company. IR spectra were recorded on a
JASCO FT-IR 5400 spectrophotometer. Elemental analyses were
carried out on a Thermo Finnigan EA1112 analyser.
2.1. Synthesis of [(t-BuNH)P(l-N-t-Bu)2P(@N-t-Bu)-C(@CH2)CH(Ph)-
P(O)Ph2 (10)
Cyclodiphosphazane 7 (0.20 g, 0.57 mmol) and allenylphosphine
oxide 9 (0.18 g, 0.57 mmol) were dissolved in dry toluene (5 mL) and
the mixture stirred at room temperature for 15 h. The solution was
concentrated in vacuo (to ca 2 mL) and cooled for 1 d at ꢀ4 °C to ob-
tain crystals of 10. Yield: 0.347 g (91%). Mp: 188–190 °C. IR (KBr,
cmꢀ1): 3358, 2963, 2712, 1887, 1597, 1366, 1308, 1030, 887, 693.
1H NMR (400 MHz, CDCl3): d 0.80, 0.94, 1.23, and 1.46 (4s, 36H,
C(CH3)3), 2.57 (d, 2J(P–H) = 6.8 Hz, 1H, NH), 5.73 (d, 3J(P–
H) ꢁ 27.6 Hz, 1H, @CHAHB cis to P), 6.16 (dd, 3J(P–H) ꢁ 4.8 Hz,
2J(P–H) ꢁ 13.1 Hz, 1H, P(O)CH), 7.00–8.16 (m, 16H, Ar–H + @CHAHB
trans to P). 13C NMR (100 MHz, CDCl3): d 31.1 (d, 3J(P–C) = 17.2 Hz,
C(CH3)3), 32.7 (d, 3J(P–C) = 9.5 Hz, C(CH3)3), 34.4 (d, 3J(P–
C) = 10.9 Hz, C(CH3)3), 47.3 (d, 1J(P–C) ꢁ 63.4 Hz, P(O)C(Ph)), 51.4
(d, 2J(P–C) = 14.6 Hz, C(CH3)3), 52.2 (d, 2J(P–C) ꢁ 6.5 Hz, C(CH3)3),
126.4, 127.6, 127.7, 128.3, 128.4, 129.1, 130.5, 130.8, 130.8, 131.3,
132.1, 132.2, 133.1, 134.4 and 136.2 (d, 2J(P–C) ꢁ 11.2 Hz, (Ar–
C + PC = CH2), 144.5 (d, 1J(P–C) = 159.9 Hz, PC@CH2). 31P NMR
2.4. Synthesis of (i-Pr-NH)P(l-N-t-Bu)2P(NH-i-Pr)@C(CO2Me)CH2
(CO2Me) (19)
The procedure was similar to that for compound 18 using [(i-
PrNH)PN-t-Bu]2 (8) [d(P) 90.7; 0.315 g, 0.98 mmol] and dimethyl
maleate (0.283 g, 0.98 mmol) except that the reaction time was
1 d. Yield: 0.406 g (89%). Mp: 132–136 °C. IR (KBr, cmꢀ1): 3426,
3337, 3100, 2978, 2878, 2288, 2060, 1728, 1609, 1410, 1339,
1277, 1132, 1094, 889. 1H NMR (400 MHz, CDCl3): d 1.14–1.38
(br m, 30H, (C(CH3)2 + C(CH3)3), 2.23 (m, 1H, NH), 2.69 (d, 3J(H–
H) = 14.4 Hz, 2H, PCCH2) 3.18–3.52 (br, 2H, NCH(CH3)2), 3.49 and
3.61 (2s, 6H, OCH3), 8.17–8.23 (m, 1H, @P-NH). 13C NMR
(100 MHz, CDCl3): d 25.6 (d, 3J(P–C) ꢁ 4.6 Hz, NCH(CH3)2), 26.4
(d, 3J(P–C) = 4.6 Hz, NCH(CH3)2), 30.9 (br, C(CH3)3), 31.4 (d, 3J(P–
C) ꢁ 14.2 Hz, C(CH3)3), 41.5 (s, PCCH2), 43.7 (d, 1J(P–
C) ꢁ 182.5 Hz, PC), 44.4 and 44.7 (2s, N–CH(CH3)2), 49.9 and 51.2
(2s, OCH3), 52.8 (d, 2J(P–C) ꢁ 8.4 Hz, C(CH3)3), 171.8 (d, 2J(P–
C) = 31.4 Hz, PC–C(O)), 174.9 (d, 3J(P–C) = 9.2 Hz, PCCH2–C(O)).
31P NMR (162 MHz, CDCl3): d 35.6 (1s, 1P, C@P), 79.9 (1s, 1P,
NH–P). LC–MS: m/z 465 [M+1]+. Anal. Calc. for C20H42N4O4P2: C,
51.71; H, 9.11; N, 12.06. Found: C, 51.62; H, 9.18; N, 12.15%.
(162 MHz, CDCl3):
d
ꢀ19.3 (dd, 3J(P–P) ꢁ 24.9 Hz, 2J(PIII–
PV) ꢁ 8.3 Hz), 31.8 (d, 3J(P–P) ꢁ 24.9 Hz), 69.9 (d, 2J(PIII–
PV) ꢁ 8.3 Hz). LC–MS: m/z 665 [M+1]+. Anal. Calc. for C37H55N4OP3:
C, 66.85; H, 8.34; N, 8.25. Found: C, 66.75; H, 8.30; N, 8.51%.

376
K.C. K. Swamy et al. / Inorganica Chimica Acta 372 (2011) 374–382
2.5. Synthesis of (t-BuNH)P(
l
-N-t-Bu)2P(@N-t-Bu){CH2CH2R}
[M+1]+. Anal. Calc. for C36H46N2O2P2: C, 71.98; H, 7.72; N, 4.66.
[R = CO2Me (20), CO2Et (21), CO2-t-Bu (22), SO2Et (23)]
Found: C, 71.82; H, 7.76; N, 4.55%.
Compound 20: The procedure was the same as that for 18 using
7 (0.74 g, 2.12 mmol) and methyl acrylate (0.18 g, 2.12 mmol)
[reaction time 2 d]. Yield: 0.801 g (87%). Mp: 60–62 °C. IR (KBr,
cmꢀ1): 3390, 2967, 1738, 1329, 1206. 1H NMR (400 MHz, CDCl3):
d 1.31, 1.39 and 1.44 (3 s, 36H, C(CH3)3), 2.20–2.32 (many lines,
4H, PCH2CH2), 2.92 (br, 1H, NH), 3.67 (s, 3H, OCH3). 13C NMR
(100 MHz, CDCl3): d 28.2 (d, 1J(P–C) = 150.0 Hz, PC), 28.5 (s, PCCH2),
31.5–34.2 (many lines, C(CH3)3), 51.3 (s, OCH3), 51.0, 51.7, 52.0,
52.1 (4 lines, C(CH3)3), 173.2 (d, 3J(P–C) = 23.0 Hz, CO2Me). 31P
NMR (162 MHz, CDCl3): d ꢀ6.4, 72.3. LC–MS: m/z 435 [M+1]+.
Compound 21: The procedure was the same as that for 18 using 7
(0.392 g, 1.12 mmol) and ethyl acrylate (0.13 g, 1.12 mmol) [reac-
tion time 2 d]. Yield: 0.466 g (90%). Mp: 68–70 °C. IR (KBr, cmꢀ1):
3356, 2973, 1736, 1464, 1310, 1211. 1H NMR (400 MHz, CDCl3): d
1.24 (t, 3J(H–H) = 6.8 Hz, 3H, OCH2CH3), 1.31, 1.39, 1.44 (3 s, 36H,
C(CH3)3), 2.20–2.31 (many lines, 4H, PCH2CH2), 3.05 (br, 1H, NH),
4.12 (q, 3J(H–H) = 6.8 Hz, 2H, OCH2CH3). 13C NMR (100 MHz, CDCl3):
d 14.2 (s, OCH2CH3), 27.9 (d, 1J(P–C) = 134.0 Hz, PC), 28.6 (s, PCCH2),
31.7 (s, C(CH3)3), 32.8 (d, 3J(P–C) = 10.0 Hz, C(CH3)3), 34.2 (d, 3J(P–
C) = 12.0 Hz, C(CH3)3), 51.1 (d, 2J(P–C) = 13.0 Hz, C(CH3)3), 51.8 (d,
2J(P–C) = 9.5 Hz, C(CH3)3), 52.2 (d, 2J(P–C) = 7.5 Hz, C(CH3)3), 60.4
(s, OCH2), 172.9 (d, 3J(P–C) = 23.0 Hz, CO2Et). 31P NMR (162 MHz,
CDCl3): d ꢀ6.2, 72.8. LC–MS: m/z 449 [M+1]+.
2.7. Synthesis of (R)-[6,60-(t-Bu)2C20H10O2][P(
l-N-t-Bu)2P(O)] (26)
To a solution of 25 (1.81 g, 3.0 mmol) in dry tetrahydrofuran
(5 mL), diisopropyl azodicarboxylate (DIAD) (1.0 mL, 3.0 mmol)
was added. The yellow solution was stirred overnight at 25 °C upon
which it became colorless. Removal of the solvent followed by col-
umn chromatography (ethyl acetate/hexane) afforded a solid that
was crystallized from dichloromethane–hexane mixture (5:2,
7 mL). Yield: 1.56 g (84%). Mp: 240–244 °C(d). IR (KBr, cmꢀ1):
2971, 1622, 1593, 1505, 1385, 1208, 999. 1H NMR (400 MHz,
CDCl3): d 1.05, 1.10, 1.20 and 1.21 (4 s, 36H, t-Bu-H), 6.36 and
6.43 (2 d, 3J(H–H) ꢁ 8.8 Hz, 2H, Ar–H), 7.11–7.13 (m, 2H, Ar–H),
7.40 and 7.46 (2 d, 3J(H–H) ꢁ 8.8 Hz, 2H, Ar–H), 7.62–7.64 (m,
2H, Ar–H), 7.81–7.84 (m, 2H, Ar–H). 13C NMR (100 MHz, CDCl3):
d 30.47, 30.5, 30.6, 31.1, 34.66 and 34.69 (C(CH3)3), 58.3 and 58.8
(2 C(CH3)3), 122.7, 122.8, 122.9, 123.0, 123.3, 123.4, 125.8, 125.9,
126.3, 126.4, 130.0, 130.2, 131.2, 131.3, 148.5, 148.6. 31P NMR
(162 MHz, CDCl3): d 5.3 and 98.9 (2 d, 2J(P–P) = 11.3 Hz each).
LC–MS: m/z 618 [M+1]+. Anal. Calc. for C36H46N2O3P2: C, 70.11; H,
7.52; N, 4.54. Found: C, 70.25; H, 7.47; N, 4.46%. A small amount
(ca 5%) of the bis-oxidized material was also there, but no attempt
was made to purify the compound further.
Compound 22: The procedure was the same as that for 18 using
7 (1.34 g, 3.83 mmol) and t-butyl acrylate (0.13 g, 1.12 mmol)
[reaction time 36 h]. Yield: 1.586 g (87%). Mp: 75–78 °C. IR (KBr,
cmꢀ1): 3356, 2971, 1732, 1364, 1321, 1219. 1H NMR (400 MHz,
CDCl3): d 1.28 (s, 9H, CO2C(CH3)3), 1.37, 1.40 and 1.42 (3 s, 36H,
NC(CH3)3), 2.02–2.12 (m, 2H, PCH2), 2.21–2.32 (m, 2H, PCCH2),
2.95 (br, 1H, NH). 13C NMR (100 MHz, CDCl3): d 28.0 (s, OC(CH3)3),
28.2 (d, 1J(P–C) = 134.0 Hz, PC), 29.9 (br s, PCCH2), 31.7 (s, C(CH3)3),
32.8 (d, 3J(P–C) = 10.0 Hz, NC(CH3)3), 34.3 (d, 3J(P–C) = 12.0 Hz,
NC(CH3)3), 51.1 (d, 2J(P–C) = 15.0 Hz, NC(CH3)3), 51.8 (d, 2J(P–
C) = 10.0 Hz, NC(CH3)3), 52.3 (d, 2J(P–C) = 13.0 Hz, NC(CH3)3), 80.3
(s, OC(CH3)3), 172.3 (d, 3J(P–C) = 23.0 Hz, CO2C(CH3)3). 31P NMR
(162 MHz, CDCl3): d ꢀ3.4, 72.1. LC–MS: m/z 477 [M+1]+.
2.8. Synthesis of(R)-[(6,60-(t-Bu)2C20H10O2][(Se)P(
l-N-t-Bu)2P(O)] (27)
Selenium powder (0.182 g, 2.3 mmol) was added to a solution
of 26 (0.712 g, 1.2 mmol) in dry toluene (15 mL). The solution
was heated under reflux for 24 h. After cooling, excess selenium
was separated by filtration. Toluene was removed in vacuum.
The solid residue thus obtained was crystallized from dichloro-
methane–hexane (1:1) mixture. Yield: 0.61 g (75%). Mp: 154–
156 °C. IR (KBr, cmꢀ1): 2963, 1601, 1470, 1294, 1235, 1197. 1H
NMR (400 MHz, CDCl3): d 1.16 and 1.18 (2 s, 18H, t-Bu-H), 1.32–
1.37 (m, 18H, Nt-Bu-H), 6.46 and 6.53 (2 d, 3J(H–H) ꢁ 8.4 Hz, 2H,
Ar–H), 7.20–7.25 (m, 2H, Ar–H), 7.51 and 7.56 (2 d, 3J(H–
H) ꢁ 8.4 Hz, 2H, Ar–H), 7.75–7.77 (m, 2H, Ar–H), 7.93–7.95 (m,
2H, Ar–H). 13C NMR (100 MHz, CDCl3): d 30.5, 30.58, 30.62, 31.1,
34.7 and 34.8 (C(CH3)3), 58.3 and 58.9 (C(CH3)3), 122.8, 122.9,
123.00, 123.01, 123.40, 123.42, 125.89, 125.93, 126.37, 126.43,
130.0, 130.2, 148.6, 148.7. 31P NMR (162 MHz, CDCl3): d ꢀ1.2 and
36.9 (2 d, 2J(P–P) = 15.1 Hz each). Anal. Calc. for C36H46N2O3P2Se:
C, 62.15; H, 6.66; N, 4.03. Found: C, 61.95; H, 6.71; N, 4.21%. Satel-
lites due to the 77Se atom were not clear probably due to low S/N
ratio. LC–MS (negative mode): m/z 695 [Mꢀ1]+.
Compound 23: The procedure was the same as that for 18 using 7
(0.74 g, 2.12 mmol) and ethylvinylsulfone(0.28 g, 2.34 mmol) [reac-
tiontime2 d]. Yield: 0.82 g (82%). Mp: 92–97 °C. IR(KBr, cmꢀ1):3340,
2969, 1647, 1458, 1364, 1209, 1134. 1H NMR (400 MHz, CDCl3): d
1.28, 1.35 and 1.42 (3 s, 36H, C(CH3)3), 1.36 (br, 3H, CH2CH3), 2.42
(br, 2H, PCH2), 2.95 (br m, 5H, PCH2CH2 + SO2CH2 + NH). 13C NMR
(100 MHz, CDCl3): d 6.6 (s, CH2CH3), 25.8 (d, 1J(P–C) = 128.6 Hz, PC),
31.8 (s, C(CH3)3), 32.8 and 34.2 (d each, 3J(P–C) = 9.7, 12.1 Hz, respec-
tively, C(CH3)3), 46.8 and 47.3 (2 br s, PCH2CH2 + SO2CH2), 51.5 (d,
2J(P–C) = 14.0 Hz, C(CH3)3), 52.1 (d, 2J(P–C) = 8.5 Hz, C(CH3)3), 52.5
(d, 2J(P–C) = 7.3 Hz, C(CH3)3). 31P NMR (162 MHz, CDCl3): d ꢀ10.4,
72.8. Anal. Calc. for C20H46N4O2P2S: C, 51.26; H, 9.89; N, 11.96. Found:
C, 51.26; H, 9.90; N, 11.87%.
2.9. Synthesis of (S)-(C20H10O2)[P(Se)(l-N-t-Bu)2P(Se)] {alternative
formulation: (S)-[(2-O-1-C10H6)2][P(Se)-N-(t-Bu)-P(Se)-N-(t-Bu)]} (29)
Selenium powder (0.152 g, 1.90 mmol) was added to a solution
of 28 [6a] (0.471 g, 0.964 mmol) in dry toluene (10 mL). The solu-
tion was heated under reflux for 24 h. After cooling, excess sele-
nium was separated by filtration. Toluene was removed in
vacuum. The solid residue thus obtained was crystallized from
dichloromethane–hexane (1:1) mixture. Yield: 0.45 g (73%). Mp:
246–248 °C. IR (KBr, cmꢀ1): 2971, 1593, 1505, 1368, 1314, 1186,
2.6. Synthesis of (R)-[6,60-(t-Bu)2C20H10O2][P(
l-N-t-Bu)2P] (25)
This compound was prepared in a manner similar to that for
[(C20H12O2)[P(
l
-N-t-Bu)2P] (28) [6a] using R(ꢀ)-6,60-di-tert-butyl-
1,10-binaphthalene-2,20-diol and [ClP-N(t-Bu)]2 (24). Yield: 4.80 g
(96%, by using 8.3 mmol of 24). Mp: 140–142 °C. IR (KBr, cmꢀ1):
2959, 1618, 1593, 1505, 1366, 1289, 1204, 951. 1H NMR
(400 MHz, CDCl3): d 0.99 and 1.39 (2 s, 36H, t-Bu-H), 6.65 (2 d,
3J(H–H) ꢁ 8.8 Hz, 2H, Ar–H), 7.24–7.33 (m, 4H, Ar–H), 7.77 (s, 2H,
Ar–H), 7.89 (2 d, 3J(H–H) ꢁ 8.8 Hz, 2H, Ar–H). 13C NMR (100 MHz,
CDCl3): d 30.4, 31.1 and 34.7 (C(CH3)3), 58.7 (C(CH3)3), 122.7,
123.5, 123.9, 125.9, 126.2, 129.8, 131.2, 132.9, 148.4, 149.2,
149.4. 31P NMR (162 MHz, CDCl3): d 171.4. LC–MS: m/z 602
1030 cmꢀ1 1H NMR (400 MHz, CDCl3): d 1.25 (s, 18H, t-Bu-H),
.
6.50 (d, 2H), 7.13 (t, 2H) and 7.40 (t, 2H), 7.65 (d, 2H), 7.88 (d,
2H) and 8.06 (d, 2H) (all Ar–H). 13C NMR (100 MHz, CDCl3): d
30.6 (C(CH3)3), 59.5 (C(CH3)3), 123.8, 124.0, 124.2, 125.9, 126.0,
127.3, 127.9, 128.4, 131.3, 134. 31P NMR (162 MHz, CDCl3): d
43.0 (s with broad satellites, 1J(P–Se) = 981.5 Hz); ½a 2D7
= ꢀ8.65
ꢂ
(c = 0.52, CHCl3). X-ray structure was determined for this sample.

K.C. K. Swamy et al. / Inorganica Chimica Acta 372 (2011) 374–382
377
2.10. Synthesis of (R)-[(6,60-(t-Bu)2C20H10O2)[(Se)P (
(30)
l
-N-t-Bu)2P(Se)]
by the attack of P(III) center on the b-carbon atom of the allenyl-
phosphine oxide. Compound 10 exhibits three signals in the 31P
NMR spectrum at d ꢀ19.3 [dd, 2,3J(PP) = 24.9, 8.3 Hz P@N-t-Bu],
31.7 [d, J(PP) = 24.9 Hz, Ph2P(O)–] and 69.9 [d, J(PP) = 8.3 Hz;
P(III)-NH-t-Bu] as expected. However, the 31P NMR signals corre-
sponding to the cyclodiphosphazane ring of compound 11 showed
broad signals at d 72.0 and ꢀ1.0, although the signal for –Ph2P(O)
at d 32.3 (d) was sharp. This behavior (broad peaks in the 31P
NMR spectrum) is probably due to the more pronounced amino-
imino (I–II) tautomerism or phosphinimine (11)-phosphinium salt
(III) equilibrium in compound 11 compared to compound 10. How-
ever, we have not studied this aspect in detail.
Formation of 10 entails the generation of a chiral center. We
have earlier pointed out in an analogous case that it is possible
to observe spontaneous resolution by crystallization [15]. Indeed,
the samples that we checked crystallized in the chiral space group
Pca2(1) with (S)-chirality at the (Ph)(H)C–P carbon center. How-
ever, unlike in the earlier example, the other enantiomer of 10
could not be separated although the solid state CD spectrum sug-
gested that the other enantiomeric form may also be present in
the bulk. In contrast to this, compound 11 crystallized in the cen-
trosymmetric space group P1. The structures of 10 and 11 (Fig. 1)
clearly show the phosphinimine moiety at P(1) with P-N distances
of 1.535(2) and 1.536(2) Å, respectively (cf. Table 2). A comparison
of analogous distances in closely related structures 12–17 (Fig. 2)
reveals that this distance is comparable to those in 12–14, but
longer than that observed in 15–17. Thus it is likely that there is
contribution from the phosphonium ion character (cf. structure
III in Scheme 2) in compounds 10–11 as well as 12–14, a point that
we have not stressed in the earlier work [1d,15,16].
Yield: 0.99 g (70%, by using 1.9 mmol of 25). Mp: 208–212 °C. IR
(KBr, cmꢀ1): 2971, 1620, 1593, 1506, 1368, 1260, 1186, 963, 810.
1H NMR (400 MHz, CDCl3): d 1.17 and 1.19, (2 s, 36H, t-Bu-H),
6.46 (d, 3J(H–H) = 8.8 Hz, 2H, Ar–H), 7.10 (d, 3J(H–H) = 8.8 Hz, 2H,
Ar–H), 7.44 (d, 3J(H–H) = 8.8 Hz, 2H, Ar–H), 7.64 (s, 2H, Ar–H),
7.80 (d, 3J(H–H) = 8.8 Hz, 2H, Ar–H). 13C NMR (100 MHz, CDCl3):
d 30.7, 31.1 and 34.7 (C(CH3)3), 59.5 (C(CH3)3), 122.8, 123.6,
124.1, 126.0, 126.3, 129.9, 131.3, 133.0, 148.6, 149.2, 149.3,
149.4. 31P NMR (162 MHz, CDCl3): d 44.0 (s with satellites, 1,3J(P–
Se) = 991.5 Hz, 3J(P–Se) = 17.8 Hz). LC–MS: m/z 760 [M+1]+. Anal.
Calc. for C36H46N2O2P2Se2: C, 57.00; H, 6.11; N, 3.69. Found: C,
57.12; H, 6.15; N, 3.75%.
2.11. X-ray crystallography
X-ray data for 10–11, 18–19, 27 and 29 were collected on Bru-
ker AXS SMART or OXFORD diffractometer at 296 K using Mo K
a
(k = 0.71073 Å) radiation. The structures were solved by direct
methods [14]; all non-hydrogen atoms were refined anisotropi-
cally. The hydrogen atoms were fixed by geometry or located by
difference Fourier map; subsequently a riding model was used.
Some of the methyl carbon atoms of the t-butyl groups in these
compounds have high thermal parameters, but these do not affect
the overall structure around cyclophosphazane skeleton and hence
we have not tried to model them rigorously. Crystallographic data
are summarized in Table 1. CCDC numbers for compounds 10–11,
18–19, 27 and 29 are (respectively) 797416–797421.
In a second set of reactions, we treated 7–8 with dimethyl male-
ate and obtained the stable ylides 18–19 (Scheme 3). The IR spectra
of 18–19 (also 10–11) showed the m(NH) band in the region 3358–
3. Results and discussion
3427 cmꢀ1. The 31P NMR spectrum of 18 exhibited two peaks at d
23.7 and 78.9, with each one essentially as a singlet. The correspond-
ing signals for 19 appeared at d 35.6 and 79.9, again with negligible
2J(PP) value. In the 13C NMR spectra, the P–C carbon appears at d 43–
45 with a large 1J(P–C) of 182–184 Hz. Notably, the 13C NMR chem-
ical shift value is not in the typical alkenic region perhaps because
the formal double bond is with phosphorus. The corresponding
3.1. Oxidative addition of [(RNH)P(l-N-t-Bu)]2 [R = t-Bu (7), i-Pr (8)]
with allenylphosphine oxide Ph2P(O)C(Ph)@C@CH2 (9) or dimethyl
maleate
Initially, we started with the reaction of cyclodiphosphazanes
7–8 with the allenylphosphine oxide 9. The reaction afforded com-
pound 10 or 11 (Scheme 2) as essentially a single product formed
Table 1
Crystallographic data for compounds 10–11, 18–19, 27 and 29.a
Compound
10b
11
18c
19
27d
29e
Formula
C37H55N4OP3
664.76
orthorhombic
Pca2(1)
C35H51N4OP3
636.71
triclinic
C22H46N4O4P2
492.57
orthorhombic
P2(1)2(1)2(1)
C20H42N4O4P2
464.52
orthorhombic
Pbca
C72H92N4O6P4Se2
1391.30
monoclinic
P2(1)
C28H30N2O2P2Se2
646.40
orthorhombic
P2(1)2(1)2(1)
Formula weightt
Crystal system
space group
P1
a (Å)
b (Å)
c (Å)
18.099(2)
10.038(1)
20.933(2)
90
90
90
9.515(2)
10.152(2)
19.544(3)
79.155(2)
89.058(2)
87.047(2)
1851.7(5)
2
9.002(1)
17.788(1)
18.124(1)
90
90
90
10.354(1)
18.366(2)
27.289(3)
90
90
90
14.838(1)
13.968(1)
23.129(2)
90
96.842(1)
90
10.328(1)
16.448(2)
16.971(2)
90
90
90
a
(o)
b (o)
c
(o)
V (Å3)
Z
3803.1(6)
4
2901.9(3)
4
5189.5(8)
8
4759.5(5)
2
2881.6(5)
4
Dcalcd
l
1.161
0.189
1.142
0.192
1.127
0.181
1.189
0.198
0.971
0.883
1.490
2.705
(mmꢀ1
)
F(0 0 0)
1432
684
1072
2016
1456
1304
Data/restraints/parameters
Goodness-of-fit (GOF) (S)
R1
6685/7/446
1.053
0.0301
0.0779
0.289/ꢀ0.192
6496/0/398
1.044
0.0543
0.1401
0.457/ꢀ0.191
5076/3/306
1.037
0.0744
0.2087
0.465/ꢀ0.217
4563/0/291
1.198
0.0510
0.1085
0.557/ꢀ0.278
16589/1/816
0.960
0.0638
0.1964
0.618/ꢀ0.294
5065/0/331
0.843
0.0379
0.0675
0.575/ꢀ0.336
wR2 (all data)
Max./min. residual electron dens. (e Åꢀ3
)
a
b
c
2
4 0.5
R1
=
R
||Fo| ꢀ |Fc||/
R
|Fo| and wR2 = [
R
w(Fo ꢀ Fc2)2/
R
wFo
]
.
Flack parameter: 0.05(5) chiral at C(19) (S).
Flack parameter: 0.15(18), however chirality is not present at the carbon center.
Flack parameter: 0.020(9).
d
e
Flack parameter: ꢀ0.026(8).

378
K.C. K. Swamy et al. / Inorganica Chimica Acta 372 (2011) 374–382
Ph
Ph
O
t
-Bu
.
.
P
N
.
P
.
H
H
toluene
P
N
C
C
β
C
+
NHR
-Bu
α
γ
t
R-HN
1d, rt
Ph
Yield 90-95%
9, δ(P): 29.0
R =
=
t
i
-Bu 7, δ(P): 88.8
-Pr 8, δ(P): 90.7
H
H
H
H
Ph
O
Ph
Ph
O
t
-Bu
t
-Bu
P
P
+
N
.
.
+
P
N
.
.
Ph
P
P
P
Ph
RHN
N
Ph
RHN
N
NHR
t
-Bu
NHR
t
-Bu
(II)
(I)
H
H
H
H
O
Ph
t
-Bu
O
Ph
Ph
P
N
.
t
-Bu
*
P
.
Ph
P
P
+
N
.
.
*
Ph
H
N
P
P
N
R
NHR
Ph
t
-Bu
H
N
N
NHR
t
-Bu
R
R =
=
t
-Bu 10, δ(P): -19.3 (dd), 31.7 (d),
(III)
69.9 (d) (X-ray)
i
-Pr 11, δ(P): -1.0 (br), 32.3 (d),
72.0(br) (X-ray)
Scheme 2.
Fig. 1. Molecular structures of compounds 10–11; for 10, only one position each for C14–C16 is shown. Hydrogen bonding interactions in compound 11 (Å, Å, Å, o): N(4)–
H(4D)...O(1) 0.80, 2.35, 3.102(3), 156.9; symm. equiv: x, ꢀ1 + y, z.
1J(P–C) values [involving the cyclophosphazane phosphorus] in
compounds 10–11 are in the range 149–160 Hz at d(C) 142–145.
On the basis of our previous studies, it is expected that the 1J(P–C)
values involving an sp2 carbon will be significantly higher than that
involving a sp3 carbon [7,17]. As an example, the 1J(P–C) value in
compound 6 (see above) is 168.9 Hz [7]. Thus in solution, the carbon
attached to the phosphorus of cyclodiphosphazane skeleton in 18–
19 has sp2 character. The up-field chemical shift however, suggests
that it does not involve a C@C (double) bond. Observation of a dou-
blet at d 2.65–2.69 with integrated intensity corresponding to two
protons and with a 3J(P–H) value of 14.4 Hz in the 1H NMR spectra
reveals a P@CCH2 group. All these data are consistent with the struc-
tures shown in Scheme 3, but there could be contribution from the
phosphonium salt structures 180–190. In any case, these are clearly
different from the phosphinimine structures observed in the case of 6
or 10–11. It must also be noted that such ylidic structures were not
proposed in the mechanism for Morita–Baylis–Hillman reaction [8],
but may be involved in specific cases. Further confirmation of the
structures of 18–19 is provided by single crystal X-ray structures
as shown in Fig. 3. The shorter P1–C distances [1.715–1.718 Å] and
the longer P1–N3 distances [1.599–1.616 Å] in 18–19 when com-
pared to the corresponding distances in 10–11 clearly demonstrate
that in compounds 18–19, the P1–C bond is formally a double bond
and the P1–N3 bond is formally a single bond. The presence of intra-
molecular hydrogen bond between N3 and a carbonyl oxygen atom
in both 18 and 19 (Fig. 3) is another proof for the structure as given in
Scheme 3.
In the above context, we also treated [(t-BuNH)P(l-N-t-Bu)]2 (7)
with unsymmetrical activated alkenes CH2@CHR [R = CO2R, SO2Et]
and obtained compounds 20–23 (Scheme 4) that are tautomeric
forms of the expected zwitterionic species 4. Thus these products
are analogous to those with methyl propiolate [cf. compound 6]

K.C. K. Swamy et al. / Inorganica Chimica Acta 372 (2011) 374–382
379
Table 2
t-Bu
H
H
.
toulene, 3 d
.
N
Selected bond distances (Å) with su’s in compounds 10–11 and 18–19.
.
.
P
P
+
N
t-Bu
Compound 10
11
18
19
NHR
rt
MeO2C
CO2Me
RHN
Yield ~90%
P1–N1
P1–N2
P1–N3
P1–C
1.682(2)
1.683(2)
1.669(2)
1.536(2)
1.820(2)
(P1–C15)
1.731(2)
1.740(2)
1.649(2)
1.317(3)
(C15–C16)
1.518(3)
(C15–C17)
1.671(4)
1.654(4)
1.605(5)
1.717(5)
(P1–C17)
1.727(4)
1.749(4)
1.642(5)
1.660(2)
1.664(2)
1.616(2)
1.718(2)
(P1–C15)
1.748(2)
1.753(2)
1.649(2)
R = t-Bu (7), i-Pr (8)
1.688(2)
1.535(2)
1.831(2)
(P1–C17)
1.737(2),
1.736(2),
1.662(2)
1.326(3)
(C17–C18)
1.516(2)
(C17–C19)
H
CO2Me
MeO2C
H
H
CO2Me
MeO2C
t-Bu
N
t-Bu
N
C
C
P2–N1
P2–N2
P2–N4
(P1)C@C
C
C
.
.
.
.
+
P
P
P
P
H
N
t-Bu
N
t-Bu
RHN
NHR
RHN
NHR
18'-19'
18-19
(P1)C–C
1.522(7)
(C17–C18)
1.513(3)
(C15–C16)
[δ(P): 23.7, 78.9]
[δ(P): 35.6, 79.9]
R = t-Bu (18)
i-Pr (19)
Scheme 3.
o
Ref
P=N (A)
H
H
ramidates with other substituents are known to show good chiral
induction in reactions such as asymmetric reduction [9]. In this
direction, we have synthesized a few cyclodiphosphazane com-
pounds bearing a chiral-BINOL residue. The new fairly air-stable chi-
ral cyclodiphosph(III)azane derivative 25 was readily prepared by a
known synthetic route using (R)-6,60-di-t-butyl-BINOL in good
yields [Scheme 6] [6a,11] Analogous derivative 28 using unsubsti-
tuted (S)-BINOL is known [6a]. There was no indication of the pres-
ence of oligomeric products [4a,b] in these reactions. Partial
oxidation of 25 by diisopropyl azodicarboxylate (DIAD) to the
unsymmetrical phosphazane 26, followed by treatment with sele-
nium afforded the compound 27 that has P@O group at one end
and P@Se at the other end.1 The bis-seleno derivatives 29–30 were
readily prepared by treating their respective P(III) precursors 25
and 28 with elemental selenium. The NMR [1H, 13C and 31P] data
for these compounds are consistent with the structures shown in
Scheme 6.
In addition to being chiral, compound 27 is a rare example in
which the two phosphorus atoms of the cyclodiphosphazane are
differently oxidized. In order to understand the effect on structural
parameters, we have determined the X-ray structure of this com-
pound [Fig. 4]. For comparison, we have obtained the X-ray struc-
ture of the diseleno derivative 29 also [Fig. 5]. The ring P-N
distances at the tetracoordinate phosphorus in these are normal
and comparable to those observed in the compounds 10–11 and
18–19 discussed above. The P@Se distances in 27 and 29 are also
nearly the same. However, the P@O distances in 27 [two molecules
in the asymmetric unit; P1–O3 1.538(5), P3–O6 1.495(5) Å] are
unusually long.2 For comparison, in analogous compounds 31–32,
O
Ph
This
R = t-Bu (10) 1.535(2)
= i-Pr (11) 1.536(2)
t-Bu
N
P
.
.
Ph
work
P
P
Ph
H
N
t-Bu
N
R
NHR
H
H
15
O
1.543(3)
(12)
Ar = Ph
O
O
t-Bu
N
P
1(d)
.
4-Me-C6H4 (13) 1.540(2)
.
P
P
N
t-Bu
Ar
N
NH-t-Bu
t-Bu
CH2
t-Bu
N
EtO2C
(14) 1.525(4)
15
.
.
C
P
P
H2
N
N
NH-t-Bu
CO2Et
t-Bu
t-Bu
CO2Et
N
N
H
O
6(b)
(15)
1.464(4)
S
P
O
N
t-Bu
CO2-i-Pr
16(a)
16(b)
X = Cl
(16)
(17)
1.488(3)
1.464(3)
t-Bu
N
N
N
H
CO2-i-Pr
=
N
O
.
.
P
P
N
t-Bu
X
N t-Bu
Fig. 2. The P@N distances in closely related phosphinimines.
[7] but differ from 18–19. The PC signal for compounds 20–23
appears as a doublet at d 25.8–29.0 [1J(P–C) ꢁ 128.6–150.0 Hz] in
the 13C NMR spectra. A compound analogous to 20–23 from the
reaction of acrylonitrile with 7 has been previously characterized
by us before [7] and hence this aspect is not elaborated further.
Formation of both the phosphinimine and the ylidic structures
in the above reactions may be rationalized by reaction sequences
shown in Scheme 5. In the formation of phosphinimine (e.g. 20),
a proton from the –NH-t-Bu group migrates to the b-carbon while
for the formation of ylide (e.g. 18) the CH(CO2Me) proton migrates
to the b-carbon. The presence of an additional electron withdraw-
1
We have also prepared compounds the bis-oxidized and bis-sulfurized deriva-
tives V–VI; X-ray structure of VI has also been determined. The disordered solvent
(toluene) molecules are present in the structure that could not be modeled
satisfactorily. Three molecules are present in the asymmetric unit; only one is shown
in the picture below (hydrogen atoms omitted). This structure has also been
deposited (CCDC 797421). P–S (mean) ꢁ 1.906 Å, P–N (mean) ꢁ 1.677 Å, P–O
(mean) ꢁ 1.607 Å. Further details on V–VI are available as Supplementary informa-
tion.
ing –CO2Me group on the a-carbon is most likely responsible for
the ylidic structure seen in 18–19.
X
(i) m-CPBA (2.4 equiv) for V
or
(ii) or 3 equiv S8 for VI
P
P
O
t-Bu
3.2. Oxidation of P(III) centers in the ansa-type cyclodiphosphazane
derivatives with BINOLs-observation of an unusually long P@O
(phosphoryl) bond
N
Nt-Bu
X
25
toluene
O
110 o
C
X = O V [δ(P): -6.8]
= S VI [δ(P): 49.1]
In a second line of study, we have been interested in the synthesis
of chiral phosphoramidates and related compounds that are based
on a cyclodiphosphazane skeleton [6]. Many chiral cyclic phospho-
2
There were no significant C–HꢃꢃꢃO(@P) interactions in the structure. Also, fairly
long P@O distances are found in 10–11, but these are Ph2P@O distances. The distance
found in 27 is much longer.

380
K.C. K. Swamy et al. / Inorganica Chimica Acta 372 (2011) 374–382
Fig. 3. Molecular structures of compounds 18 and 19; all the non-hydrogen atoms are labeled. Some of the t-butyl carbon atoms are disordered. Only selected bond distances
(Å) are given here. Hydrogen bond parameters in compound 18 (Å, Å, Å, o): N(3)–H(3). . .O(3) 0.71(4), 2.20(5), 2.676(7), 126(5). Hydrogen bond parameters in compound 19 (Å,
o
Å, Å, ): N4–H4D. . .O30 0.83(3), 2.27(3) 3.067(3), 161(2); N3–H3D. . .O1 0.80(3), 2.01(3), 2.718(2), 147(3). Symm equiv: 0.5 ꢀ x, 0.5 + y, z.
t-Bu
R
.
.
N
.
.
toluene, 36-48 h
t-Bu
N
P
P
CH2 CH2
N
+
.
N
t-Bu
.
P
R
rt
P
NH-t-Bu
t-BuNH
N
NH-t-Bu
t-Bu
t-Bu
7
R = CO2Me [20, δ(P): -6.4, 72.3, 87%]
R = CO2Et [21, δ(P): -6.2, 72.8, 90%]
R = CO2-t-Bu [22, δ(P): -3.4, 72.1, 87%]
R = SO2Et
[23, δ(P): -10.4, 72.8, 82%]
Scheme 4.
MeO2C
H
R
H
R
β
α
MeO2C
t-Bu
t-Bu
C
_
C
.
N
.
.
.
+
N
.
.
H
P
P
P
P
H
HN
N
t-Bu
N
t-Bu
HN
NH-t-Bu
NH-t-Bu
t-Bu
t-Bu
7
+
H shift
+
H shift
H
C
CO2Me
MeO2C
H
H
C
H
R
t-Bu
N
MeO2C
C
_
+
t-Bu
N
+
P
.
.
P
H shift
C
+
P
.
.
P
N
t-Bu
_
H
HN
NH-t-Bu
N
t-Bu
NH-t-Bu
t-Bu
N
t-Bu
R = CO2Me (IV)
H
H
MeO2C
H
H
C
t-Bu
N
CO2Me
MeO2C
H
C
C
.
.
t-Bu
N
P
P
C
H
.
N
t-Bu
.
P
P
NH-t-Bu
N
t-Bu
N
t-Bu
HN
t-Bu
NH-t-Bu
(Similarly 19)
18
R = H (20)
(Similarly 21-23)
Scheme 5.

K.C. K. Swamy et al. / Inorganica Chimica Acta 372 (2011) 374–382
381
OH
OH
(R)
.
.
.
.
Cl
P
P
P
O
t-Bu
t-Bu
(a)
N
N
(R)
t-Bu
N
Nt-Bu
O
toluene, Et3N
P
.
.
.
.
Cl
25 [96%, δ(P): 171.4]
24
i-PrO2C-N=N-CO2-i-Pr
(DIAD)
P
O
O
P
P
O
1/8 Se8
O
t-Bu
t-Bu
N
N
(R)
t-Bu
t-Bu
N
N
(R)
O
toluene
110 oC
O
P
.
Se
Fig. 4. Molecular structure of compound 27; only one molecule in the asymmetric
unit is shown. Hydrogen atoms are omitted for clarity. Selected bond distances (Å):
Molecule 1 P1–O1 1.591(4), P1–O3 1.538(5), P1–N1 1.656(5), P1–N2 1.681(5), P2–
O2 1.601(4), P2–N1 1.695(4), P2–N2 1.650(4), P2–Se1 2.046(2). Molecule 2 P3–O4
1.594(4), P3–O6 1.495(5), P3–N3 1.647(6), P3–N4 1.657(5), P4–O5 1.618(5), P4–N4
1.668(6), P4–N3 1.682(6), P4–Se2 2.057(2).
.
27 [75%, δ(P): -1.2(d), 36.9(d)]
26 [ca 84%, δ(P): 5.3(d), 98.9(d)]
[X-ray]
(only spectroscopically
characterized)
.
.
Se
P
P
1/4 Se8
O
O
(b)
t-Bu
t-Bu
N
t-Bu
N
(S)
N
Nt-Bu
(S)
toluene
110 oC
O
O
P
P
.
.
Se
[δ(P): 171.2]
28
29 [73%, δ(P): 43.0; X-ray]
Se
P
P
O
(R)
t-Bu
N
Nt-Bu
Se
O
30 [70%, δ(P): 44.0]
Scheme 6.
the corresponding P@O distances are in the range 1.445–1.460 Å.
Like what was observed before for crystals of species 33 [6], it is
possible that in the crystal there could be exchange of positions
of P@O and P@Se that could make P@O bond look longer crystallo-
graphically, but as of now, we do not have evidence to corroborate
this assertion.
Fig. 5. Molecular structure of compound 29. Selected bond parameters (Å): P1–N1
1.674(3), P1–N2 1.681(3), P1–O1 1.597(3), P1–Se1 2.049(1), P2–N1 1.678(3), P2–N2
1.667(3), P2–O2 1.606(3), P2–Se2 2.061(1).
of these compounds crystallizes in the chiral space group Pca2(1)
with (S)-chirality at a carbon center [–C(@CH2)CH(Ph)-P] suggest-
ing a case of spontaneous resolution through crystallization. New
ansa-type cyclodiphosphazanes with a chiral BINOL residue, that
may be useful as chiral auxiliaries, are synthesized. In one of these,
an unusually long phosphoryl (P@O) bond [1.538(5) Å] is observed.
t-Bu
O
O
O
O
N
O(Se)
P
P
P
P
O
O
P
P
N
t-Bu
O
t-Bu
N
Nt-Bu
O
t-Bu
N
t-BuN
O
O
Se(O)
31 [δ(P): -7.8]
32 [δ(P): -6.0]
33
Acknowledgements
o
P =O (A) 1.456 (2)
1.453 (1)
1.448(2)
1.450(2)
This work was supported by the Department of Science and
Technology (DST), New Delhi. The National Single Crystal Diffrac-
tometer Facility at the University of Hyderabad funded by DST
(New Delhi), and the UPE and the CAS programs of the UGC for
other equipment are gratefully acknowledged. GG, VS, NNBK, EB
and MC thank CSIR for fellowships.
4. Summary
Two structurally different types of products, one a phosphinimine
and the other a phosphorus ylide, respectively, are formed in the
reaction of [(RNH)P-N(t-Bu)]2 (R = t-Bu (7), i-Pr (8)], with the alle-
nylphosphine oxide Ph2P(O)C(Ph)@C@CH2 (9) or dimethyl maleate.
The latter result shows that in addition to the proposed interemdi-
ates in phosphine mediated reactions including Morita–Baylis–
Hillman reaction, other intermediates may also be involved. One
Appendix A. Supplementary material
CCDC 797416, 797417, 797418, 797419, 797420, and 797421
contain the supplementary crystallographic data for 10–11, 18–
19, 27 and 29, respectively. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via

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K.C. K. Swamy et al. / Inorganica Chimica Acta 372 (2011) 374–382
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www.ccdc.cam.ac.uk/data_request/cif. Supplementary data associ-
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(b) M. Chakravarty, R. Rama Suresh, K.C. Kumara Swamy, Inorg. Chem. 46
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