The rearrangement of phosphitohydrazide ligand [(ArO)2P-NPh-NPh-] into iminophosphoranate anion [(PhN{double bond, long}P(OAr)2-NPh-] {(ArO)2P = [CH2(tBuMeC6H2O)2P]} i

Article abstract of DOI:10.1016/j.jorganchem.2009.11.006

The reaction of bromophosphite (ArO)₂PBr {(ArO)₂P = CH₂(6-^tBu-4-Me-C₆H₂O)₂P} with lithium salt of 1,2-diphenylhydrazine gave phosphitohydrazine (ArO)₂P-NPh-NPhH (2) in

Full text of DOI:10.1016/j.jorganchem.2009.11.006

Journal of Organometallic Chemistry 695 (2010) 637–641
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Note
The rearrangement of phosphitohydrazide ligand [(ArO)2P–NPh–NPh–]
into iminophosphoranate anion [(PhN@P(OAr)2–NPh–]
{(ArO)2P = [CH2(tBuMeC6H2O)2P]} in coordination sphere of divalent cobalt
*
Natalia V. Belina, Alexander N. Kornev , Vyacheslav V. Sushev, Georgy K. Fukin, Eugene V. Baranov,
Gleb A. Abakumov
Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences, 49 Tropinin Street, 603950 Nizhny Novgorod, Russia
a r t i c l e i n f o
a b s t r a c t
The reaction of bromophosphite (ArO)2PBr {(ArO)2P = CH2(6-tBu-4-Me-C6H2O)2P} with lithium salt of 1,2-
diphenylhydrazine gave phosphitohydrazine (ArO)2P–NPh–NPhH (2) in 64% yield. The last one reacted
with Co[N(SiMe3)2]2 to afford cobalt(II) iminophosphoranate (PhN@P(OAr)2–NPh–)2Co (3), which is the
result of isomerisation of the phosphitohydrazide ligand in coordination sphere of divalent cobalt.
Ó 2009 Elsevier B.V. All rights reserved.
Article history:
Received 21 September 2009
Received in revised form 3 November 2009
Accepted 8 November 2009
Available online 14 November 2009
Keywords:
Molecular rearrangements
Phosphazanes
Phosphinohydrazines
Amidoimidophosphoranes
Cobalt(II) complexes
X-ray diffraction
1. Introduction
of the M–N r bond, which is usually weaker going from early to
late transition metals. All these factors influence each other, that
complicates prediction of the rearrangement, leaving an intrigue
in research of a new ligands. Here we report the first example
Rearrangements play a key role in phosphorus chemistry being
a practical tool for synthesizing a great variety of useful com-
pounds. Recently it was shown that rearrangements of mono-, bis-
and tris(diphenylphosphino)hydrazide ligands, Ph2P–NPh–NPh–,
(Ph2P)2N–NPh–, (Ph2P)2N–N(PPh2)–, in the coordination sphere of
nickel(II), cobalt(II) and iron(III) result in the formation of metal
complexes of the phosphazene and phosphinoamide type depend-
ing on the starting ligand [1–3] (see Scheme 1).
involving
rearrangement
of
phosphitohydrazide
ligand
{CH2(6-tBu-4-Me-C6H2O)2P–NPh–NPh–} in coordination sphere of
divalent cobalt.
2. Results and discussion
Note, however, that similar phosphinohydrazide complexes,
containing more hindered diisopropylphosphino group, (i-Pr2P–
NPh–NPh)2M (M = Co, Ni), do not undergo rearrangement [4]
whereas lithium salt of bis(diisopropylphosphine)methylhydr-
azine, (i-Pr2P–NMe–NLi–PiPr2) rearranges quickly to iminophos-
phoranate salt i-Pr2P–NMe–PiPr2@NLi [4]. The reason of such
differences still is not clear in details. Nevertheless, it is obvious
that the tendency of the phosphinohydrazide system toward rear-
rangement depends on several factors: (1) the energy of the N–N
bond, which is strongly depended on the nature of the substituents
and a charge on the nitrogen atoms; (2) the energy of the M–P
bond, which is determined by a combination of electronic effects
of direct and back bonding between both atoms; (3) the energy
Starting phosphitohydrazine 2 was prepared in good yield by
the reaction of bromophosphite 1 with an equivalent of monolithi-
um salt of 1,2-diphenylhydrazine:
Ph
Br
NH
Ph
N
t-Bu
P
O
O
t-Bu
t-Bu
P
O
O
t-Bu
+ PhNLi-NHPh
CH3
-LiBr
1
H3C
CH3
64%
2
H3C
ð1Þ
The molecular structure of 2, recorded at 100 K, shows discrete
* Corresponding author. Tel.: +7 831 4627795; fax: +7 831 4627497.
E-mail address: akornev@iomc.ras.ru (A.N. Kornev).
molecular units (Fig. 1).
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.11.006

638
N.V. Belina et al. / Journal of Organometallic Chemistry 695 (2010) 637–641
Compound 2 was found to be quite resistant to oxygen. Bub-
N
bling of O2 through a solution of 2 in THF did not result in forma-
tion of any products during 24 h according 31P NMR analysis.
Phosphitohydrazine 2 was allowed to react with 0.5 equiva-
lent of cobalt(II) bis(trimethylsilyl)amide in toluene. The color
of green solution slowly turned brown–violet. After keeping
the reaction mixture for 3 days at room temperature pink crys-
tals of complex 3 were formed. Crystals suitable for X-ray anal-
ysis were obtained from diethyl ether/toluene mixture. The
molecular structure of 3 with the atom numbering scheme is
shown in Fig. 2. Crystal data and some details of the data col-
lection and refinement for 3 are given in Table 1. The X-ray
investigation reveals formation the spirocyclic complex 3 as
Et2O solvate with central cobalt atom in tetrahedral
environment.
Two nearly planar four-membered metallacycles CoNPN un-
folded relatively to each other to 53.8°. The bond angles N(2A)–
Co(1)–N(1A) 74.0(1)° and N(2B)–Co(1)–N(1B) 74.0(1)° are very
close to that found in similar iminophosphoranate [Ph2P(NC6
H4But)2Co]2 [1]. The P–N bond lengths all lie between the values
1.575(1) Å and 1.596(1) Å, as they occur in phosphazenes [6]. Com-
paring the structural parameters of the compounds 2 and 3 it may
notice that the P–O bonds are shortened going from free ligand
(1.646(2), 1.660(2) Å) to the complex 3 (1.587(1)–1.595(1) Å). Con-
traction of the P–O bonds may be explained by more strong inter-
action of the oxygen atoms with positively charged phosphorus(V)
in 3.
P
P
P
N
N
N
N
M
M
P
N
P
N
P
N
M
M
P
N
P
N
P
N
P
P
N
P
M
M
Scheme 1. Rearrangements of mono-, di- and triphosphinohydrazides in transition
metal coordination sphere (M = Fe3+, Co2+, Ni2+).
Ph
NH
Ph
Ph
N
N
O
Ph
t-Bu
P
P
N
O
0.5 eq. Co[N(TMS)2]2
PhMe, 20oC
O
t-Bu
O
Co
O
N
P
Ph
N
O
Ph
2
4
Ph
Ph
N
O
O
N
O
O
72 h, 20oC
P
Co
P
N
N
Ph
Ph
3
ð2Þ
The IR spectrum of 3 shows an intense absorption bands at
1300 and 1130 cmꢀ1 assigned to the ms and
as(PN) stretching
m
Fig. 1. The molecular structure of 2. Hydrogen atoms except H(2) were omitted for
clarity. Selected bond lengths (Å) and angles (°) for 2: N(1)–N(2) 1.420(3), P(1)–N(1)
1.698(2), P(1)–O(1) 1.660(2), P(1)–O(2) 1.646(2), N(1)–C(24) 1.432(3), N(2)–C(30)
1.407(3), O(2)–P(1)–O(1) 101.30(8), O(1)–P(1)–N(1) 95.79(9), O(2)–P(1)–N(1)
95.95(9), C(1)–O(1)–P(1) 119.3(1), N(2)–N(1)–C(24) 115.6(2), N(2)–N(1)–P(1)
119.1(2), C(24)–N(1)–P(1) 121.8(2), C(30)–N(2)–N(1) 116.7(2), C(6)–C(12)–C(13)
114.8(2).
vibration. The UV–vis spectrum of the solution of 3 in methy-
lene chloride contains two absorptions with kmax 384 and
565 nm. The complex 3 is the single product separated in the
reaction (2). It is appeared impossible to separate the proposed
intermediate(s) 4 during this slow reaction. On the other hand,
in the related reaction of cobalt(II) bromide with lithium salt of
2 in equimolar ratio, the formation of cobalt phosphinohydraz-
ide-monobromide 5 was observed soon after mixing the re-
agents (Eq. (3)). Tentatively we proposed dimeric structure for
5.
In the unit cell, hexane solvate molecules were localized in spe-
cial positions. Table 1 displays the crystal data for 2. The nitrogen
atom N(1) in 2 has a trigonal nearly planar environment (sum of
the angles is 356, 45°). The P(1)–N(1) and N(1)–N(2) bond lengths
in the molecule (1.698(2) and 1.420(3) Å, respectively) are typical
for phosphazanes and phosphinohydrazines [2,5]. Note, however,
the N–N bond distance in 2 is somewhat longer than that found
in monophosphinohydrazine analog PhNH–NPh–PPh2 (1.401(2))
[1]. Eight-membered heterocycle in 2 demonstrates chair-like
conformation.
Ph
O
i. n-BuLi
ii. CoBr2
O
THF, rt
6 days
- CoBr2
N
P
P
N
Br
Br
Ph
Co
3
N
ð3Þ
2
Co
N
Ph
O
O
Ph
5

N.V. Belina et al. / Journal of Organometallic Chemistry 695 (2010) 637–641
639
Table 1
Crystal and structure refinement.
2
3
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
Unit cell dimensions
a (Å)
C38H48N2O2P
595.75
100(2)
Orthorhombic
Pbca
C72H85CoN4O4.5P2
1199.31
100(2)
Triclinic
ꢀ
P1
15.6685(5)
17.1886(6)
24.2235(8)
90
90
90
6523.9(4)
12.8688(5)
15.5278(6)
18.2691(7)
108.3670(10)
91.7030(10)
103.1760(10)
3353.0(2)
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
Volume (Åꢀ3
)
Z
8
2
Density (calculated) (Mg/m3)
Absorption coefficient (mmꢀ1
Crystal size (mm3)
1.213
0.12
1.188
0.354
)
0.30 ꢁ 0.25 ꢁ 0.10
0.85 ꢁ 0.38 ꢁ 0.15
Reflections collected
34226
20158
Independent reflections
Absorption correction
Max./min. transmission
Refinement method
5747 [R(int) = 0.0460]
Semi-empirical from equivalents, SADABS
0.9881/0.9648
13060 [R(int) = 0.0151]
Semi-empirical from equivalents, SADABS
0.9488/0.7529
Full-matrix least-squares on F2
5747/3/552
Full-matrix least-squares on F2
13060/72/823
Data/restraints/parameters
R indices [I > 2
R indices (all data)
Largest diff. peak and hole (e Åꢀ3
r
(I)]
R1 = 0.0548, wR2 = 0.1390
R1 = 0.0730, wR2 = 0.1492
1.074 and ꢀ0.674
R1 = 0.0609, wR2 = 0.1788
R1 = 0.0750, wR2 = 0.1910
1.408 and ꢀ0.606
)
Fig. 2. The molecular structure of 3. The tBu groups at C(6), C(17) and the methyl groups at C(4) and C(15) carbon atoms as well as hydrogen atoms and solvate molecule
(Et2O) were omitted for clarity. Selected bond lengths (Å) and angles (°) for 3: Co(1)–N(2B) 2.012(1), Co(1)–N(2A) 2.021(1), Co(1)–N(1A) 2.025(1), Co(1)–N(1B) 2.032(1),
Co(1)–P(1B) 2.6288(4), Co(1)–P(1A) 2.6357(4), P(1A)–N(1A) 1.584(1), P(1A)–O(2A) 1.587(1), P(1A)–N(2A) 1.593(1), P(1A)–O(1A) 1.595(1), P(1B)–N(1B) 1.575(1), P(1B)–O(1B)
1.589(1), P(1B)–O(2B) 1.592(1), P(1B)–N(2B) 1.596(1); N(2B)–Co(1)–N(2A) 111.6(1), N(2B)–Co(1)–N(1A) 146.3(1), N(2A)–Co(1)–N(1A) 74.0(1), N(2B)–Co(1)–N(1B) 74.1(1),
N(2A)–Co(1)–N(1B) 150.1(1), N(1A)–Co(1)–N(1B) 118.4(1), P(1B)–Co(1)–P(1A) 176.7(1), N(1A)–P(1A)–N(2A) 100.0(1), N(1B)–P(1B)–N(2B) 100.4(1), N(1A)–P(1A)–O(2A)
119.3(1), O(2A)–P(1A)–N(2A) 108.0(1), N(1A)–P(1A)–O(1A) 110.6(1), O(2A)–P(1A)–O(1A) 104.1(1), N(2A)–P(1A)–O(1A) 115.4(1), C(1B)–O(1B)–P(1B) 134.3(1), C(1A)–O(1A)–
P(1A) 127.1(1), P(1A)–N(1A)–Co(1) 93.0(1), P(1B)–N(1B)–Co(1) 92.7(1), P(1B)–N(2B)–Co(1) 92.8(1), P(1A)–N(2A)–Co(1) 92.9(1).
Sparingly soluble brown crystals of 5 have analytical data corre-
sponding to the formula 5 and IR spectrum similar to the starting
ligand 2. Basic hydrolysis of 5 in THF with equimolar amount of
water gave Co-containing precipitate and a solution, containing
phosphitohydrazine 2 according to the 31P NMR spectrum. No
other phosphor-containing products were detected over a period
of 3 h. Unfortunately, we failed in our attempts to obtain crystals
of 5 that were suitable for X-ray crystallography, apparently be-
cause of slow disproportionation and rearrangement of this sub-
stance. Keeping the solution of 5 in THF at room temperature for
about a week gave cobalt bromide and pink crystals of the complex
3 described above in quantitative yield. Formation of the rear-
ranged ligand, containing NPN iminophosphorane system is clearly
seen from IR spectrum. In this case a strong absorption (
mP@N) at
1300 cmꢀ1 occurs.
3. Conclusion
In summary, we have reported the first example of rearrange-
ment of the phosphitohydrazide ligand, (ArO)2P–NPh–NPh–, into

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N.V. Belina et al. / Journal of Organometallic Chemistry 695 (2010) 637–641
iminophosphoranate anion, PhN@P(OAr)2–NPh–, which takes
place in the coordination sphere of Co(II).
Note, that bromophosphite 1 is easily oxidized by dioxygen at
20 °C in solution to give bromophosphate showing a 31P shift at
7.4 ppm.
4. Experimental part
4.4. {CH2(6-tBu-4-Me-C6H2O)2P–NPh–NPhH} (2)
4.1. General
A solution of n-BuLi in hexane (9.0 mL, 1.0 M) was added to a
stirred solution of 1,2-diphenylhydrazine (1.66 g, 9.0 mmol) in
15 mL of toluene at 0 °C. After stirring for 10 min, a solution of
CH2[(t-Bu)MeC6H2O]2PBr (4.04 g, 9.0 mmol) in 20 mL of toluene
was added dropwise. A colorless solution turned orange. The reac-
tion mixture was kept at room temperature for 30 min, the major
part of the solvent was removed in vacuum and 20 mL of hexane
was added. The precipitate (LiBr) was filtered out; the filtrate
was concentrated to 10 mL. A slow crystallization at 20 °C was
completed in about 5 h to leave colorless crystals of 2. Yield:
3.43 g (64%). Anal. Calc. for C38H48N2O2P (2ꢂ½C6H14): C, 76.61; H,
8.12; P, 5.20. Found: C, 76.55; H, 8.20; P, 8.76%. 31P NMR
(80 MHz, CDCl3), ppm: 139.5; 1H NMR (200 MHz, CDCl3): 7.6–6.7
(m,14H), 4.35 (CHaHb dd, 2JH,H = 12 Hz, JH,P = 3 Hz, 1H), 3.35 (CHbHa
d, 2JH,H = 12 Hz, 1H), 2.28 (s, 6H, CH3), 1.23 (s, 18H, tBu), 6.92 (s, 1H,
Solvents were purified following standard methods [7]. Toluene
was thoroughly dried and distilled over sodium prior to use.
Diethyl ether and THF were dried and distilled over Na/benzophe-
none. Cobalt silylamide [Co{N(SiMe3)2}2] [8,9] was prepared
according to a known methods. 2,20-Methylenebis(4-methyl-6-
tert-butylphenol) was purchased from Sigma–Aldrich Chemical
Co. and used as received. All manipulations were performed with
rigorous exclusion of oxygen and moisture, in vacuum or under
an argon atmosphere using standard Schlenk techniques. Hexam-
ethyldisilazane liberated in the course of the metal silylamides
reactions was detected by gas chromatography analyses with a
Tsvet-500 device, equipped with stainless steel columns
0.4 cm ꢁ 200 cm, packed with 5% SE-30 on Chromatone N-Super,
with a thermoconductivity detector and with helium as carrier
gas. Spectrophotometric determination of cobalt in the prepared
compounds was carried out by the methods described in [10].
Infrared spectra were recorded on a Perkin–Elmer 577 spectrome-
ter from 4000 to 400 cm–1 in Nujol on a Perkin–Elmer FT-IR spec-
trometer System 2000 as KBr mulls. NMR spectra were recorded in
CDCl3 or C6D6 solutions using a Bruker DPX-200 spectrometer.
NH). IR (m
, cmꢀ1): 3370w, 1597s, 1290w, 1261w, 1209s, 1114s,
1030w, 932m, 910m, 846s, 832 (sh), 801w, 748m, 693m, 676m,
628ww, 596w, 573w, 528w, 485w, 458w.
Alternatively, phosphitohydrazine 2 may be obtained using
CH2[(t-Bu)MeC6H2O]2PCl [12] instead bromide as a starting mate-
rial in similar yield.
4.2. X-ray crystallography
4.5. Reaction of 2 with Co{N(SiMe3)2}2
X-ray data for 2 and 3 were collected on a Bruker AXS SMART
A solution of Co[N(SiMe3)2]2 (0.49 g, 0.85 mmol) in 5 mL of tol-
uene was added to a solution of the phosphitohydrazine 2 (0.76 g,
1.7 mmol) in the same solvent (10 mL). Green solution slowly
turned reddish brown during reaction time (72 h). The solution
was concentrated at reduced pressure; pink crystals of 3 were
formed after addition of diethyl ether. Yield 0.66 g, 67%.
APEX diffractometer (graphite-monochromator, Mo K
a radiation
(k = 0.71073 Å), /– scan). All structures were solved by direct
x
methods and were refined on F2 using SHELXTL [10] package. All
non-hydrogen atoms were refined anisotropically. H atoms in 2
were refined with mixed treatment: hydrogen atoms in molecule
of 2 were located from Fourier synthesis and refined isotropically,
H atoms of solvate hexane molecule in 2 were included into the
model at geometrically calculated positions and refined using a
riding model. All hydrogen atoms in 3 were placed in calculated
positions and were refined in the riding model. One of t-Bu-groups
in 3 was found to be disordered over two positions and was refined
with a population in each position of 0.5. In crystal of 3 one solvate
Et2O molecule is disordered over two positions so that one part of
Et2O occupies a general position and another part of this one lies in
a special position. SADABS [11] was used to perform absorption cor-
rections. The main crystallographic data and structure refinement
details for 2 and 3 are presented in Table 1.
Anal. Calc. for C72H85CoN4O4.5P2: C, 72.10; H, 7.14; Co, 4.91.
Found: C, 72.30; H, 7.28; Co, 4.86%. IR (m
, cmꢀ1): 1595s, 1300s,
1210s, 1130m, 1050m, 1020m, 925s, 855s, 795m, 750m, 727m,
693s, 629w. UV/vis spectrum (THF): kmax 384, 565 nm.
4.6. Reaction of CoBr2 with lithium salt of 2
A solution of n-butyllithium in hexane (1.6 mL, 0.75 M) was
added slowly to a solution of phosphitohydrazine 2 (0.66 g,
1.2 mmol) in 10 mL of toluene at 0 °C. The reaction mixture was
concentrated under reduced pressure, and 5 mL of THF was added.
The resulted solution of lithium phosphitohydrazide was added to
a homogeneous solution of anhydrous CoBr2 (0.26 g, 1.2 mmol) in
15 mL of THF. The mixture turned dark brown. Brown crystalline
precipitate formed overnight at 0 °C was washed with cold THF
and dried in vacuum. Yield 1.62 g, 98%. Anal. Calc. for
C70H80Br2Co2N4O4P2: C, 60.88; H, 5.84; Br, 11.57; Co, 8.53. Found:
4.3. CH2[(t-Bu)MeC6H2O]2PBr (1)
A mixture of 2,20-methylenebis(4-methyl-6-tert-butylphenol)
(5.0 g, 14.7 mmol) and 1.5 equiv. of tribromophosphine (5.9 g,
22.0 mmol) in 15 mL of chlorobenzene was heated at 135 °C for
3 h in argon atmosphere. Chlorobenzene and excess of PBr3 were
removed under reduced pressure at 50 °C. The residue was dis-
solved in equal amount of toluene; concentrating of the resulted
solution gave colorless crystals (4.12 g, 62%) of 1. Anal. Calc. for
C23H30BrO2P: C, 61.47; H, 6.73; Br, 17.78. Found: C, 61.52; H,
6.69; Br, 17.72%. 1H NMR (200 MHz, CDCl3) 7.3–7.0 (m, 4H), 3.85
(dd, J = 13 Hz, CH2, 2H), 2.3 (s, Me, 6H), 1.4 (s, tBu,18H). 31P NMR
C, 61.03; H, 5.90; Br, 11.49; Co, 8.48%. IR (m
, cmꢀ1): 1592m, 1206m,
1115m, 1026m, 927m, 830s, 744m, 685m, 594w.
5. Supplementary material
CCDC 746205 and 746206 contain the supplementary crystallo-
graphic data for compound 2 and 3. These data can be obtained
free of charge from The Cambridge Crystallographic Data Center
via http://www.ccdc.cam.ac.uk/data_request/cif.
(80 MHz, PhCl), ppm: 174.7. IR (m
, cmꢀ1): 1286w, 1260w, 1202m,
1186m, 1123w, 1098m, 915w, 854sh, 837s, 797w, 775w, 697m,
593m, 552w, 530m, 482m, 452m.

N.V. Belina et al. / Journal of Organometallic Chemistry 695 (2010) 637–641
641
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Acknowledgement
This work was supported by President of RF Grant for the sup-
port of Leading Scientific Schools (Project No. 4182.2008.3).
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