Kinetics of phosphine hydroxymethylation with formaldehyde

Article abstract of DOI:10.1134/S0023158406030062

The kinetics of phosphine hydroxymethylation with formaldehyde is studied. In the absence of a catalyst, phosphine reacts slowly with formaldehyde under normal conditions. Taken separately, amines, hydrochloric acid, and nickel chloride have a low catalytic activity, but the addition of a primary aliphatic amine to nickel chloride effectively increases the hydroxymethylation rate. A probable reaction mechanism is suggested. MAIK Nauka/ Interperiodica 2006.

Full text of DOI:10.1134/S0023158406030062

ISSN 0023-1584, Kinetics and Catalysis, 2006, Vol. 47, No. 3, pp. 358–366. © MAIK “Nauka /Interperiodica” (Russia), 2006.
Original Russian Text © L.I. Grekov, I.A. Novakov, 2006, published in Kinetika i Kataliz, 2006, Vol. 47, No. 3, pp. 364–372.
Kinetics of Phosphine Hydroxymethylation with Formaldehyde
L. I. Grekov and I. A. Novakov
Volgograd State Technical University, Volgograd, 400066 Russia
e-mail: rector@vstu.ru
Received February 16, 2004
Abstract—The kinetics of phosphine hydroxymethylation with formaldehyde is studied. In the absence of a
catalyst, phosphine reacts slowly with formaldehyde under normal conditions. Taken separately, amines, hydro-
chloric acid, and nickel chloride have a low catalytic activity, but the addition of a primary aliphatic amine to
nickel chloride effectively increases the hydroxymethylation rate. A probable reaction mechanism is suggested.
DOI: 10.1134/S0023158406030062
The reaction between PH3 and CH2O in the presence activator were added. The volume of absorbed PH3 was
of transition metal salts (primarily Pt, Pd, and Ni chlo-
rides) affords tris(hydroxymethyl)phosphine (THMP)
continuously determined while shaking the reactor.
In order to change the reaction from diffusion
(mass-transfer) to kinetic control, the number of rock-
ings of the catalytic shaker was set to be 170 per
minute. This critical value for the overall rate of the
process to be determined by chemical reaction
(kinetic control) was determined experimentally. The
deviation of the reaction rate thus measured from the
average value is at most 5%, in agreement with pub-
lished data [4].
PH3 + 3CH2O
P(CH2OH)3,
(I)
which is a valuable intermediate for the synthesis of
polymers, with increased fire resistance [1–4].
There are only a few systematic studies on this reac-
tion. The main difficulty in carrying out this reaction is
the low catalytic activity of the known catalysts and, as
a consequence, an insufficiently high yield of the
desired product [2, 4].
A filter paper impregnated with a 1% solution of
AgNO3 was used as a phosphine leakage indicator in
sealing tests [4]. The PH3 concentration in the liquid
phase was determined by standard procedures [5–8].
In the present work, we studied the kinetics of phos-
phine hydroxymethylation with aqueous formaldehyde
in the presence of nickel chloride activated with pri-
mary aliphatic amines.
After the water and unreacted CH2O were distilled
off under reduced pressure, the reaction products were
characterized by elemental analysis [9]; refractive
EXPERIMENTAL
The kinetics of reaction (I) was studied by a volu-
metric method under unsteady-state conditions in a
closed system. The system consisted of a vigorously
shaken isothermal catalytic reactor and a precalibrated
gas burette filled with a necessary concentration of
phosphine. Concentrated PH3 and PH3–Ar gas mixtures
were used. Phosphine was prepared by the sulfuric acid
decomposition of Zn3P2 and was analyzed on an
LKhM-8 MD chromatograph equipped with a thermal
conductivity detector and a steel column (length 2 m,
diameter 3 mm, Porapak Q packing) at 373 K in a
helium flow (12 ml/min). The chromatograph was cali-
index (n2d0 ) measurements; IR spectroscopy; and 31P,
13C, and 1H NMR [10–14]. NMR spectra were recorded
on a Bruker WP-80 spectrometer operating at
31.44 MHz (31P) or 20.55 MHz (13C). The solvent was
D2O. The 31P NMR spectra, referenced to an external
standard (85% H3PO4), contained signals with chemi-
cal shifts of 24.6 ppm characteristic of THMP. The 13C
NMR spectra exhibited signals with chemical shifts of
57.6 and 54.0 ppm from the carbon atoms of the meth-
ylene groups of organophosphorus compounds. The 1H
brated against iodometric phosphine concentration NMR spectra contained two signals at 4.8 and 4.2 ppm,
data.
indicating the presence of methylene and hydroxyl
hydrogen atoms. IR spectra were recorded on a Specord
IP-75 spectrophotometer. Intense absorption bands char-
acteristic of the O–H (3190 cm–1), C–O (1004 cm–1), and
C–H (2795 cm–1) bonds were observed. The absorption
Kinetic studies were performed as follows. Phos-
phine from the gas burette was passed through a 150-ml
reactor filled with an aqueous solution of formalde-
hyde, the system was sealed, the phosphine content of
the gas mixture was determined, and the catalyst and bands of the P–H and C=O bonds were absent.
358

KINETICS OF PHOSPHINE HYDROXYMETHYLATION WITH FORMALDEHYDE
359
V × 103, l
The molar-ratio spectrophotometric method (SF-46
instrument) was used to elucidate the character of inter-
action between the components of the system [15].
270
220
170
RESULTS AND DISCUSSION
1
The addition of PH3 to CH2O (reaction (I)), which
produces THMP, is unusual. Classical theoretical
chemistry predicts the existence of two reaction mech-
anisms, namely, nucleophilic and electrophilic. The
reaction with phosphine cannot be assigned exactly to
this or another type. This can be explained by the chem-
ical properties of PH3 itself [10, 16], which is called a
“problematic” nucleophilic reagent, such as P–H acids.
At the same time, phosphine cannot be viewed as an
electrophilic reagent. This is the reason why it is diffi-
cult to find a catalyst for the reaction examined.
2
3
4
0
20
40
60
t, min
In the absence of a catalyst, reaction (I) occurs only
under severe conditions, such as an elevated PH3 pres-
sure (40 atm) and a high temperature (373 K) [1, 2]. If
the system does not contain any catalyst or contains an
organic base (N,N,N1,N1-tetramethylethylenediamine),
formaldehyde absorbs phosphine at 293 K very slowly.
Raising the acidity of the CH2O–PH3–H2O system by
adding HCl up to a concentration of 0.44 mol/l acceler-
ates the reaction. However, phosphonium salts rather
than THMP are the final products in reactions catalyzed
by protonic acids [2].
Fig. 1. Kinetics of phosphine hydroxymethylation with
formaldehyde (1) in the absence of a catalyst and in the
presence of (2) 0.22 mol/l N,N,N ,N -tetramethylethylene-
diamine, (3) 0.022 mol/l ethylenediamine, and (4)
1
1
0.44 mol/l HCl. Reaction conditions: 293 K, PPH
=
3
5
0.92 × 10 Pa, [CH O] = 2.71 mol/l.
2
tude lower than the concentration of N,N,N1,N1-tetram-
ethylethylenediamine (see Table 1). It turned out, unex-
pectedly, that the introduction of En into the CH2O–
PH3–NiCl2–H2O system containing nickel chloride
markedly increased the reaction rate (wmax) and the
amount of absorbed phosphine (x) (Table 1) [17]. Since
ethylenediamine was found to activate the NiCl2 cata-
lyst, the main attention in our further investigation was
given to its influence on the mechanism of the reaction.
The rate of phosphine absorption by aqueous CH2O
is a decreasing function of reaction time (Fig. 1), and
the reaction rate is described by the first-order equation
w = kappV,
(1)
where V is the current volume of PH3 and kapp is the
apparent rate constant. The kapp values determined
graphically from the linear anamorphoses lnV – t
(t is the reaction time) are given in Table 1.
In a series of experiments on the effect of different
amines on the catalytic activity of nickel chloride, we
found that the V–t curves are linear and the reaction rate
When 0.022 mol/l of unsubstituted ethylenediamine
(En) is introduced into the CH2O–PH3–H2O system, the
reaction rate increases noticeably (Fig. 1, curve 3),
although the En concentration is one order of magni- is low and is described by Eq. (1) in the presence of
Table 1. Hydroxymethylation of phosphine with formaldehyde in the presence of different catalytic systems at 293 K
Concentration, mol/l
wmax × 103,
PH3
Reaction system
PH3–CH2O
t, min
kapp × 103, min–1
mol l–1 min–1
conversion, %
HCl
En
NiCl2
–
0.44
–
–
–
–
–
60
90
72
54
5.5
18
7
3.2
10.5
3.2
–
16
58
21
28
60
75
70
96
PH3–CH2O–HCl
PH3–CH2O–TEn*
PH3–CH2O–En
–
22 × 10–2
2.2 × 10–2
–
–
18
15
PH3–CH2O–NiCl2
–
2.56 × 10–3 60
–
90
PH3–CH2O–NiCl2–En
–
1.1 × 10–2 2.56 × 10–3 10
110
–
31
1
1
* TEn = N,N,N ,N -tetramethylethylenediamine.
KINETICS AND CATALYSIS Vol. 47 No. 3 2006

360
V × 103, l
GREKOV, NOVAKOV
Indeed, when the desired product (THMP) (0.9 ×
10−2 mol/l) was introduced into the original
CH2O−PH3–NiCl2–En–H2O reaction system, the initial
rate increased and the induction period decreased.
300
200
100
1
2
Being convinced that the reaction is autocatalytic,
we used known procedures [18, 19] proposed for reac-
tions of this type to determine kinetic constants. The
plots of the rate of phosphine absorption by an aqueous
solution of CH2O versus conversion at different
amounts of absorbed (reacted) phosphine were con-
structed (Fig. 3a). Let us assume that the hydroxymeth-
ylation reaction proceeds as follows. At the initial
moment, when the concentration of the product
(THMP) is close to zero, the reaction in the presence of
nickel chloride proceeds at a low rate comparable with
the reaction rate without a catalyst. The presence of an
extremum in the plots in Fig. 3a indicates that the
appearance of THMP in the system accelerates the
reaction. Tertiary phosphines are known to play the key
role in homogeneous catalytic processes using transi-
tion metals, determining the activity and selectivity of
the catalytic system [20, 21]. Therefore, it is quite prob-
able that a catalytically active tris(hydroxyme-
thyl)phosphine complex of nickel chloride or a
[THMP–Ni2+–amine] complex is formed during the
induction period in the ascending branch of the w–x plots.
The reaction rate reaches its highest value and then
decreases because of a decrease in the amount of start-
ing reactants.
4
5
3
0
20
40
60
80
t, min
Fig. 2. Kinetics of phosphine hydroxymethylation with
formaldehyde in the presence of (1) 1 × 10 mol/l
–2
–2
(C H ) N, (2) 0.96 × 10 mol/l (C H ) NH, (3) 1.06 ×
2
−2
5 3
2 5 2
–2
10 mol/l (C H )NH , and (4) 1.09 × 10 mol/l C H
2
5
2
2
4
(NH ) and (5) in the absence of an amine. Reaction condi-
2 2
5
5
tions: 293 K; PPH = 0.92 × 10 (1, 2), 0.91 × 10 (3)
3
5
0.89 × 10 Pa (4, 5); [CH O] = 2.71 mol/l, [NiCl ] =
2
2
–2
0.256 × 10 mol/l.
The experimental data obtained indicate that the rate
of reaction (I) is described by an autocatalysis equation
(taking into account the noncatalytic reaction rate)
[18]:
diethylamine or triethylamine (Fig. 2, curves 1, 2). The
corresponding reaction rate constants (kapp) in the pres-
ence of a secondary or tertiary amine found from the
lnV–t linear anamorphoses are presented in Table 2.
In the absence of an amine or in the presence of a
primary aliphatic amine, the V–t curves are S-shaped
w = kapp,noncat[CH2O*] + kapp,cat [CH2O*][THMP*], (2)
(Fig. 2, curves 3–5) and indicate an induction period where [CH2O*] and [THMP*] are the current concen-
after which the reaction rate increases significantly. A trations of formaldehyde and tris(hydroxyme-
possible explanation for this shape of the curves can be thyl)phosphine, and kapp,noncat and kapp,cat are the appar-
the autocatalytic acceleration of the reaction [18]. ent rate constants of the noncatalytic (min–1) and cat-
Table 2. Hydroxymethylation of phosphine with formaldehyde ([CH2O] = 2.71 mol/l) in the presence of different amines
and 0.256 × 10–2 mol/l NiCl2
wmax × 103,
kapp,cat × 103,
kapp × 103,
Activator concentration
Activator
x, %
×102, mol/l
mol l–1 min–1
l mol–1 min–1
l mol–1 min–1
No catalyst and activator
No activator
NH3
0
5.5
15
–
1.1
5.2
7.7
8.5
13.6
–
3.7
–
6.5
75
0
1.44
1.12
1.06
1.09
0.96
1.08
1.07
37
–
75
CH3NH2
48
–
91
C2H5NH2
En
51
–
93
110
7
–
96
(C2H5)2NH
(CH3)3N
5.3
2.5
3.3
8.1
3.3
4.1
2.4
3
–
(C2H5)3N
–
KINETICS AND CATALYSIS Vol. 47 No. 3 2006

KINETICS OF PHOSPHINE HYDROXYMETHYLATION WITH FORMALDEHYDE
361
ln[CH2O] [mol/l]
w × 103, mol l–1 min–1
120
1.0
(a)
(b)
1
0.5
0
2
80
3
2
–0.5
–1.0
3
40
1
0
20
40
60
80
100
x, %
0
8
16
24
32
40
t, min
–2
Fig. 3. (a) Hydroxymethylation rate versus conversion (1) in the absence of amine and in the presence of (2) 1.06 × 10 mol/l
–2
5
5
ë ç NH and (3) 1.09 × 10 mol/l NH C H NH . Reaction conditions: 293 K; P
= (1, 3) 0.89 × 10 and (2) 0.91 × 10 Pa;
2
5
2
2
2
4
2
PH3
–2
[CH O] = 2.71 mol/l, [NiCl ] = 0.256 × 10 mol/l. (b) Semilogarithmic anamorphoses of the curves in Fig. 3a.
2
2
alytic (l mol–1 min–1) reactions. The solution of Eq. (2) ratios were derived from the plots of the reaction rate
gives the logarithmic expression [18]
versus concentrations of CH2O, NiCl2, and En
(Tables 3–5) [22, 23].
ln[CH2O*]
The plots of the reaction rate versus conversion pass
through maxima at any PH3 pressure in the range
(0.33–0.89) × 105 Pa (Fig. 4). A significant increase in
kapp and wmax (Fig. 5, Table 6) is observed at the PH3
concentration above 50 vol % in the gas mixture
(at pressure above 0.5 × 105 Pa). At a low phosphine
concentration, phosphine absorption almost ceases, and
the amount of absorbed PH3 at low conversions does
not correspond to the stoichiometry of reaction (I). The
substantial effect of the phosphine pressure on the rate
of reaction (I) is probably due to the familiar thermody-
namic dependence of the equilibrium (complexation)
constant on the pressure [24].
[CH2O]([CH2O] + 3kapp, noncat/kapp, cat
)
---------------------------------------------------------------------------------------------
= ln
(3)
3kapp, noncat/kapp, cat
– 1/3kapp, cat([CH2O] + 3kapp, noncat/kapp, cat)t,
where [CH2O*] and [CH2O] are the current and initial
concentrations of formaldehyde, respectively.
The plot of ln[CH2O*] versus t was used to calculate
the apparent rate constants given in Table 2. These plots
look like curves turning into straight lines with a nega-
tive slope equal to 1/3kapp,cat([CH2O] + 3kapp,noncat/kapp,cat
(Fig. 3b) [18].
According to the results presented in Table 2, the
nickel catalyst is most efficiently activated by ethylene-
)
The influence of the addition of the desired product
diamine, primary amines, and ammonia. Secondary on the rate of reaction (I) is illustrated in Table 7. The
amines weakly affect the nickel catalyst, and tertiary addition of THMP substantially increases the initial
amines suppress the catalytic effect of NiCl2. The phos- reaction rate, and this fact was taken into account in the
phine conversion, apparent rate constants, reaction optimization of process parameters for the synthesis of
time, and the optimum reactants : catalyst : activator tris(hydroxymethyl)phosphine.
Table 3. Effect of the formaldehyde concentration on the rate of the reaction of PH3 with CH2O at 293 K, [NiCl2] = 0.128 ×
10–2 mol/l, and [En] = 1.09 × 10–2 mol/l
w × 103, mol l–1 min–1
initial maximum
18 44
kapp × 103,
PPH × 10–5, Pa
[CH2O], mol/l
x, %
l mol–1 min–1
3
0.678
1.356
2.71
0.82
0.80
0.89
0.80
0.82
97
94
95
85
49
115
77
11
1
24
37
29
29
73
92
5.42
110
73
8.14
0.1
KINETICS AND CATALYSIS Vol. 47 No. 3 2006

362
GREKOV, NOVAKOV
Table 4. Effect of the NiCl2 concentration on the rate of the reaction of PH3 with CH2O at 293 K, [CH2O] = 2.71 mol/l, and
[En] = 1.09 × 10–2 mol/l
w × 103, mol l–1 min–1
kapp × 103,
PPH × 10–5, Pa
[NiCl2] × 102, mol/l
x, %
l mol–1 min–1
3
initial
maximum
–
0.89
0.87
0.87
0.89
0.89
20
79
89
95
96
5
18
24
37
44
–
55
73
92
110
–
4.2
6.0
11
0.032
0.064
0.128
0.256
13.6
Table 5. Effect of the En concentration on the reaction rate at 293 K, [CH2O] = 2.71 mol/l, and [NiCl2] = 0.256 × 10–2 mol/l,
and PPH = 0.89 × 105 Pa
3
w × 103, mol l–1 min–1
kapp × 103,
[En] × 102, mol/l
x, %
l mol–1 min–1
initial
maximum
–
75
81
82
96
94
4
18
44
44
37
15
37
1.1
3.1
0.272
0.545
1.09
2.18
73
4.1
110
92
13.6
10.6
The data listed in Table 8 show that the amount of with a larger coordination number prevails at a lower
PH3 absorbed between 293 and 328 K is close to temperature, while the complex with a smaller coordi-
100%, being only 77% at 338 K. The apparent rate nation number predominates at a higher temperature
constants increase between 293 and 318 K and then [24]. It is most likely that, at elevated temperatures,
decrease. The decrease in the reaction rate is most En is displaced from the inner coordination sphere of
likely due to the strong temperature dependence of the
configuration of the nickel complexes: the complex
the catalytic complex, and the rate of reaction (I)
decreases.
w × 103, mol l–1 min–1
120
kapp × 104, l mol–1 min–1
w × 103, mol l–1 min–1
150
150
4
5
90
60
30
100
50
0
100
1
2
2
3
50
3
1
0
20
40
60
80
x, %
0.33
0.52
0.71
0.90
PPH3 × 10–5, Pa
Fig. 4. Hydroxymethylation rate versus conversion at
PPH = (1) 0.33 × 10 , (2) 0.50 × 10 , (3) 0.67 × 10 ,
5
5
5
3
5
5
(4) 0.87 × 10 , and (5) 0.89 × 10 Pa. Reaction conditions:
Fig. 5. (1) Rate constant k , (2) initial hydroxymethyla-
–2
–2
app
293 K; [NiCl ] = 0.256 × 10 mol/l, [En] = 1.09 × 10 mol/l,
2
tion rate constant, and (3) maximum hydroxymethylation
[CH O] = 2.71 mol/l.
2
rate constant versus phosphine pressure.
KINETICS AND CATALYSIS Vol. 47 No. 3 2006

KINETICS OF PHOSPHINE HYDROXYMETHYLATION WITH FORMALDEHYDE
363
Table 6. Effect of the phosphine pressure on the rate of the reaction between phosphine and CH2O at 293 K, [CH2O] =
2.71 mol/l, [NiCl2] = 0.256 × 10–2 mol/l, and [En] = 1.09 × 10–2 mol/l
w × 103, mol l–1 min–1
kapp × 103,
PPH × 10–5, Pa
x, %
l mol–1 min–1
3
initial
maximum
0.33
0.50
0.67
0.87
0.89
24
41
44
93
96
18
18
26
29
44
18
33
0.4
0.5
44
1.4
88
11.2
13.6
110
Table 7. Effect of the THMP concentration on the reaction rate at 293 K, [CH2O] = 2.71 mol/l, [NiCl2] = 0.256 × 10–2 mol/l,
[En] = 1.09 × 10–3 mol/l, and PPH = (0.89–0.92) × 105 Pa
3
w × 103, mol l–1 min–1
[THMP] × 102,
kapp × 103,
x, %
mol/l
l mol–1 min–1
initial
maximum
–
96
99
99
44
73
81
110
103
84
13.6
15.6
15.8
0.18
0.90
Table 8. The effect of temperature on the rate of the reaction of PH3 with CH2O at [CH2O] = 2.71 mol/l, [NiCl2] =
0.256 × 10–2 mol/l, and [En] = 1.09 × 10–2 mol/l
w × 103, mol l–1 min–1
[PH3] × 102,
kapp × 102,
Temperature, K
x, %
mol/l
l mol–1 min–1
initial maximum
293
308
318
328
338
3.55
3.47
3.35
3.24
3.14
96.0
98.7
99.1
98.7
77.2
44
52
57
58
53
110
94
1.4
6.8
117
97
13.5
10.0
1.3
91
with En in the presence of ëç2é (b = 1.66 × 105, ε =
It is difficult to explain the high catalytic activity of
the nickel complexes in the presence of primary amines
in terms of the known models. Therefore, to explain the
synergistic effect of the simultaneous presence of NiCl2
and En, we carried out a chemical simulation of the pro-
cess using published and our spectral data for the reac-
tions in the PH3–CH2O–RNH2–NiCl2–HOH system.
Under the conditions examined, amines do not react
with phosphines. They react only at a high pressure and
523–623 K [25]). Alkaline catalysts are assumed to
activate PH3 by deprotonation, and strong bases and
anhydrous solvents are used for this purpose. Phos-
phine is a weaker acid than water and, hence, cannot
form the PH–2 anion in an aqueous medium [1, 9,
2 l mol–1 cm–1), which were found by using a method
suggested by Bjerrum [29], are close to the values pre-
sented in his monograph. Therefore, CH2O reacts with
the Ni2+ ethylenediamine complex:
2+
NH2
+ 2CH2O
+ 2H2O.
Ni
NH2
(II)
2+
H2C N
Ni
26−28]. Probably, PH3 cannot be activated through the
formation of a complex with nickel chloride, because
we found that phosphine reduces NiCl2 to metal in sev-
eral cases. Nickel chloride forms stable complexes with
H2C N
The inner-sphere condensation of the coordinated
amines. The stability constants of the Ni2+ complexes diamine with CH2O results in Ni2+ ethylenediamine
KINETICS AND CATALYSIS Vol. 47 No. 3 2006

364
GREKOV, NOVAKOV
complexes. Similar products were found for the reac-
tions of the Ni2+, Cu2+, Ru3+, Os3+, and Pt4+ diamine
complexes with acetone, β-diketone, and keto acids
[25, 30]. Numerous experimental data [25, 30] indicate
that Schiff bases, which are unstable in the free state,
are stabilized in these complexes. Condensation reac-
tions (II), which proceed rather readily, are accelerated
by bases [30], which stimulate the acidic dissociation
of ethylenediamine:
2+
NH CH2 PH2
NH CH2 PH2
+ 2H2O
Ni
(VI)
2+
NH2
+ 2H2P(CH2OH)2.
Ni
NH2
2+
NH2
+ 2OH–
In the reaction sequence (II)–(VI), the hydrogen
atom of phosphine is first replaced by a hydroxymethyl
group; the other atoms are replaced more rapidly,
because H2P(CH2OH) and HP(CH2OH)2 are more reac-
tive than PH3 [12]. As a result, THMP appears in the
reaction system. Tetrahydroxymethylphosphine will
not catalyze PH3 hydroxymethylation if a complex
between nickel chloride and a primary amine is not
formed. However, in the presence of phosphine, the sta-
bility of the nickel chloride complexes with En
increases (b = 2.34 × 105, ε= 104 l mol–1 cm–1) and a fast
reaction pathway appears.
Ni
NH2
(III)
0
NH
+ 2H2O.
Ni
NH
The Ni0 diamide reacts with formaldehyde to form
ethylenediimine complexes of Ni2+:
An analysis of the mechanism by the steady-state
concentration method [7, 18] led us to assume that
tris(hydroxymethyl)phosphine can participate in the
following reaction steps:
0
NH
+ 2CH2O
Ni
NH
2+
H2C N
(IV)
+ 2PH3
(CH2OH)3PNi
2+
H2C N
Ni
H2C N
+ 2OH–.
(VII)
2+
H2C N
NH CH2 PH2
NH CH2 PH2
k1
(CH2OH)3PNi
,
We found that nickel was not virtually reduced by
phosphine in the presence of amines and formaldehyde
and, therefore, PH3 reacts with the Ni2+ ethylenedi-
imine complex via an inner-sphere mechanism:
2+
NH CH2 PH2
NH CH2 PH2
2+
H2C N
(CH2OH)3PNi
(CH2OH)3PNi
+ 2PH3
Ni
H2C N
(VIII)
2+
(V)
NH2
k
2+
2
+ 2H2P(CH2OH)2.
NH CH2 PH2
NH CH2 PH2
+2H2O
Ni
NH2
.
The kinetic equation describing the rate of PH3
hydroxymethylation in the presence of the nickel com-
plexes with primary amines was found to be
Since ethylenediaminophosphine, which is formed
in reaction (V), is not detected in the reaction system,
we can assume that it is hydrolyzed to evolve the start-
ing Ni2+ ethylenediamine complex and the reaction
product (hydroxymethylphosphine):
w = k k [CH O][PH ][Ni2+]Σ
1
2
2
3
(4)
× [amine][THMP]/(k2 + k1[CH2O][PH3][amine]).
KINETICS AND CATALYSIS Vol. 47 No. 3 2006

KINETICS OF PHOSPHINE HYDROXYMETHYLATION WITH FORMALDEHYDE
365
Table 9. Rate constants and the thermodynamic and activation parameters of phosphine hydroxymethylation with formalde-
hyde in the presence of NiCl2 and En
Temperature, K
∆E#,
∆H#,
∆S#,
∆G#,
Constant
kJ/mol
kJ/mol
J K–1 mol–1
kJ/mol
298
308
318
328
338
k1 × 10–3, l4 mol–4 s–1
k2, l mol–1 s–1
3.6
7.8
12.8
1.6
12.1
12.1
39.5
18.4
36.4
16.1
–50.9
52.6
77.2
0.87
1.16
1.12
0.86
–192.1
To calculate the k1 and k2 constants and compare the hydroxymethylation with formaldehyde differs radi-
calculated and observed data, the rate equation (4) was cally from the mechanism of the action of other known
converted to
catalysts. The catalytic cycle consists of two key steps,
namely, the interaction of phosphine with the formalde-
hyde–ethylenediamine complex of nickel chloride
(rate-determining step) involving THMP and the
hydrolysis of the resulting complex at the C–N bond
yielding hydroxymethylphosphine and regenerating the
catalyst.
The present study of the regularities of phosphine
hydroxymethylation with formaldehyde made it possible
to determine conditions for the high-selectivity synthesis
of tris(hydroxymethyl)phosphine, which is a valuable
intermediate product of organic synthesis [17, 31].
[CH O][PH ][Ni2+]Σ[amine][THMP]/w
2
3
(5)
= 1/k1 + [CH2O][PH3][amine]/k2.
The experimental data fall close to a straight line in
the coordinates of Eq. (5) (Fig. 6). The value of 1/k2 was
found from the slope of this line, and 1/k1 was found
from the ordinate intercept. At 293 K, k1 × 10–2 = 7.33,
14.83, 23.83, and 35.66 l4 mol–4 s–1 for NH3, CH3NH2,
C2H5NH2, and En, respectively, and k2 = 0.23, 0.39,
0.64, and 0.87 l mol–1 s–1, respectively.
Using similar anamorphoses at five different tem-
peratures in the temperature range 298–338 K, we
found the reaction rate constants in the presence of
NiCl2 activated by ethylenediamine and the activation
energies of steps (VII) and (VIII). These values,
together with the thermodynamic parameters ∆H#, ∆S#,
and ∆G#, are presented in Table 9.
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–2
–2
10 mol/l C H NH , (2) 1.12 × 10 mol/l CH NH ,
2
5
2
3
2
–2
–2
(3) 1.44 × 10 mol/l NH , and (4) 1.09 × 10 mol/l
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PH3
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2
KINETICS AND CATALYSIS Vol. 47 No. 3 2006

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GREKOV, NOVAKOV
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KINETICS AND CATALYSIS Vol. 47 No. 3 2006