Reactivity of functionalised cyclometallated complexes of palladium(II). Crystal and molecular structure of [Pd{3-(CHO)C6H3C(H)=NCy}(Br)(PEtPh2)]

Article abstract of DOI:10.1016/S0022-328X(97)00687-6

Treatment of the cyclometallated complexes [{Pd[3-(CHO)C₆H₃C(H)=NCy}(X)}₂] [X=Cl (1), Br (2), I (3)] with tertiary monophosphines in a complex/phosphine 1:2 or 1:4 molar ratio afforded the halide-bridged cleaved [Pd{3-(CHO)C₆H₃C(H)=NCy}(X)(L)] (6-17) and non-cyclometallated complexes [Pd{3-(CHO)C₆H₃C(H)=NCy}(X)(L)₂] (18-23) (X=Cl, Br or I; L=PPh₃, PEtPh₂, PEt₂Ph or PMePh₂), respectively. Reaction of 6-17 with cyclohexylamine in a complex/amine 1:1 or 1:2 molar ratio gave [Pd{3-(CyC(H)=N)C₆H₃C(H)=NCy}(X)(L)] (24-28) and the non-cyclometallated [Pd{3-(CyC(H)=N)C₆H₃C(H)=NCy}(X)(L)(NH₂Cy)] (29-32) complexes, respectively. Compounds 18, 19 and 22 gave [Pd{3-(CyC(H)=N)C₆H₃C(H)=NCy}(X)(PR₃) ₂] (33-35) with two uncoordinated C=N groups, when treated with cyclohexylamine. Other reaction routes are also discussed. The complexes were characterised by their elemental analysis (C, H, N) and by IR and ³¹P{¹H} and ¹H-NMR data, and [Pd{3-(CHO)(C₆H₃C(H)=NCy}(Br)(PEtPh₂)] (12) was characterised crystallographically.

Full text of DOI:10.1016/S0022-328X(97)00687-6

Journal of Organometallic Chemistry 556 (1998) 31–39
Reactivity of functionalised cyclometallated complexes of
palladium(II). Crystal and molecular structure of
[Pd{3-(CHO)C6H3C(H)ꢀNCy}(Br)(PEtPh2)]
Jose´ M. Vila a,*, M. Teresa Pereira a, Juan M. Ortigueira a, Margarita Lo´pez Torres a,
Alfonso Castin˜eiras a, D. Lata a, Jesu´s J. Ferna´ndez b, Alberto Ferna´ndez b
a Departamento de Qu´ımica Inorga´nica, Uni6ersidad de Santiago de Compostela, 15706 Santiago de Compostela, Spain
b Departamento de Qu´ımica Fundamental e Industrial, Uni6ersidad de La Corun˜a, 15071 La Corun˜a, Spain
Received 5 August 1997
Abstract
Treatment of the cyclometallated complexes [{Pd[3-(CHO)C6H3C(H)ꢀNCy}(X)}2] [X=Cl (1), Br (2), I (3)] with tertiary
monophosphines in complex/phosphine 1:2 or 1:4 molar ratio afforded the halide-bridged cleaved [Pd{3-
a
(CHO)C6H3C(H)ꢀNCy}(X)(L)] (6–17) and non-cyclometallated complexes [Pd{3-(CHO)C6H3C(H)ꢀNCy}(X)(L)2] (18–23) (X=
Cl, Br or I; L=PPh3, PEtPh2, PEt2Ph or PMePh2), respectively. Reaction of 6–17 with cyclohexylamine in a complex/amine 1:1
or 1:2 molar ratio gave [Pd{3-(CyC(H)ꢀN)C6H3C(H)ꢀNCy}(X)(L)] (24–28) and the non-cyclometallated [Pd{3-
(CyC(H)ꢀN)C6H3C(H)ꢀNCy}(X)(L)(NH2Cy)] (29–32) complexes, respectively. Compounds 18, 19 and 22 gave [Pd{3-
(CyC(H)ꢀN)C6H3C(H)ꢀNCy}(X)(PR3)2] (33–35) with two uncoordinated CꢀN groups, when treated with cyclohexylamine. Other
reaction routes are also discussed. The complexes were characterised by their elemental analysis (C, H, N) and by IR and 31P{1H}
1
and H-NMR data, and [Pd{3-(CHO)(C6H3C(H)ꢀNCy}(Br)(PEtPh2)] (12) was characterised crystallographically. © 1998 Elsevier
Science S.A. All rights reserved.
Keywords: Cyclometallated; Palladium; Phosphine complexes
1. Introduction
double bond in the metallation process.
One of the very important reactions of cyclometal-
lated compounds is the cleavage of halide bridged
complexes by neutral or anionic reagents. We have
shown the reactions of halide-bridged complexes
derived from N,N-isophthalylidenebis(cyclohexylamine)
with anionic reagents (thallium acetilacetonate and
thallium cyclopentadienyl) and with cyclohexylamine
[13]. We considered that complexation of tertiary phos-
phines to the palladium atom could be carried out
together with reaction of the dinuclear species with
cyclohexylamine, which should give regeneration of the
CꢀN double bond and/or coordination of the amine
moiety, and this is what we have done. Although we
have previously studied the reactivity of the halide-
bridged complexes derived from a similar ligand (N,N-
Activation of aryl CꢁH bonds to give cyclometallated
complexes is very important in organometallic chem-
istry [1–6]. Bidentate nitrogen-donor ligands may un-
dergo double cyclometallation to produce compounds
with two |MꢁC bonds and with coordination of each
nitrogen atom to one of the metal centres [7–11].
However, we have reported that when the aryl ring is
substituted with two CꢀN double bonds, as in the case
of Schiff bases derived from dialdehydes (e.g. tereph-
thalaldehyde and isophthalaldehyde) mono- or dicy-
clometallated compounds were obtained [12,13]; thus,
the organic ligand may undergo cleavage of one CꢀN
* Corresponding author.
0022-328X/98/$19.00 © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(97)00687-6

32
J.M. Vila et al. / Journal of Organometallic Chemistry 556 (1998) 31–39
Table 1
terephthalylidenebis-cyclohexylamine) with monophos-
phines, no crystallographic evidence was provided for
mononuclear cyclometallated complexes with the
formyl functionality on the metallated aryl ring. We
have now been able to obtain suitable crystals for the
X-ray analysis of one such compound.
Crystal data for compound 12
Empirical formula
Formula weight
Crystal system
C28H31BrNOPPd
614.82
Monoclinic
P21/n
Space group
Unit cell dimensions
˚
a (A)
8.663(1)
12.212(1)
24.954(4)
90
˚
b (A)
˚
2. Results and discussion
c (A)
h (°)
i (°)
93.902(7)
2.1. Crystal structure of
[Pd{3-(CHO)C6H3C(H)ꢀNCy}(Br)(PEtPh2)] (12)
k (°)
90
3
˚
Volume
Z
2634.0 (6) A
4
1.550
2.303
1240
3.05–30.01°
0BhB12, 0BkB17,
−34BlB34
8061
7605 (Rint=0.0772)
7604/0/293
zcalc. (g cm−3
)
Suitable crystals of the title compound were grown
from slowly evaporating a chloroform solution. The
molecular structure is illustrated in Fig. 1. Crystal data
are given in Table 1. Fractional coordinates and
isotropic thermal parameters are listed in Table 2, while
selected bond lengths and bond angles with estimated
standard deviations are listed in Table 3.
Absorption coefficient (mm−1
F(000)
)
q range for data collection
Index ranges
Reflections collected
Independent reflections
Data/restraints/parameters
GOF on F2
Final R indices [I\2|(I)]
R indices (all data)
The molecule comprises a palladium(II) to which is
bonded a chelated N-(3-formylbenzylidene)cyclohexyl-
amine-C2,N group, to a bromine atom and to an
ethyldiphenylphosphine ligand. The palladium atom
1.014
R1=0.0550, wR2=0.1094
R1=0.1366, wR2=0.1373
0.935 and −1.228
Largest difference peak and hole (e
−3
adopts a square-planar geometry as expected for Pd2+
.
˚
A
)
The donor atoms of the chelating Schiff base occupying
cis sites, with somewhat reduced bond angle
a
˚
value of 2.081 A based on the sum of the covalent radii
C(1)ꢁPd(1)ꢁN(1) of 80.9(2)°, consequent upon chela-
tion. This is reflected in the value of the
C(2)ꢁC(1)ꢁPd(1), 132.0(3)°, angle. The sum of angles at
palladium is 360.49°. The PdꢁC bond length
˚
for carbon and palladium, 0.771 and 1.31 A, respec-
tively [14]. This is consistent with those found in related
complexes where partial multiple-bond character of the
PdꢁC bond was assumed [15–17]. The PdꢁN bond
length [Pd(1)ꢁN(1), 2.128(4) A] is longer than the ex-
pected value of 2.01 A calculated from the covalent
˚
[Pd(1)ꢁC(1), 2.017(4) A] is shorter than the expected
˚
˚
˚
2
˚
radii of N(sp ) 0.70 A and palladium 1.31 A. This
lengthening reflects the trans influence of the phosphine
˚
ligand. The PdꢁP bond length Pd(1)ꢁP(1), 2.266 A is
shorter than the sum of the single bond radii for
˚
palladium and phosphorus, 2.41 A [14], as has been
found earlier [16]. The PdꢁBr bond length Pd(1)ꢁBr(1),
˚
2.495 A is somewhat longer than the sum of the cova-
˚
lent radii (2.45 A), consistent with the trans-influence of
the C(phenyl) atom.
The aromatic ring of the Schiff base is planar (r.m.s
˚
0.0033 A) and approximately coplanar (2.7°) with the
adjacent five-membered cyclometallated ring (r.m.s.
˚
0.0179 A). The geometry around the palladium atom is
˚
planar (r.m.s. 0.1134 A), from which the displacement
˚
of palladium is only −0.0635 A.
2.2. Reactions with tertiary monophosphines and
cyclohexylamine
For the convenience of the reader the compounds
and reactions are shown in Scheme 1. The compounds
described in this paper were characterised by elemental
Fig.
1.
Molecular
structure
of
[Pd{3-
(CHO)C6H3C(H)ꢀNCy}(Br)(PEtPh2)] 12.

J.M. Vila et al. / Journal of Organometallic Chemistry 556 (1998) 31–39
33
Table 3
analysis and by IR spectroscopy (data in Section 4) and
˚
Selected bond lengths (A) and angles (°) for 12
by 1H and 31P{1H} (Table 4) and 13C-NMR spec-
troscopy.
˚
Bond lengths (A)
In a previous paper [13] we reported the reactions of
compounds 1–3 with cyclohexylamine, steps i and iii;
however, step ii was not described then, and it has been
included here to further complete Scheme 1. Thus,
treatment of compound 4 (X=Cl) with cyclohexy-
lamine under reflux gave compound 5 (X=Cl), with
regeneration of the CꢀN double bond (for characterisa-
tion of 4 and 5, and for the corresponding bromine and
iodine analogues, for which step ii also could be ef-
fected, see reference [13]).
Treatment of the halide-bridged complexes [{Pd[3-
(CHO)C6H3C(H)ꢀNCy}(X)}2] [X=Cl (1), X=Br (2),
X=I (3)] with tertiary monophosphines in a dimer/
phosphine 1:2 molar ratio gave the cyclometallated
monomer compounds [Pd{3-(CHO)C6H3C(H)ꢀNCy}-
(Cl)(L)] (L: 6, PPh3; 7, PEt2Ph; 8, PEtPh2; 9, PMePh2),
[Pd{3-(CHO)C6H3C(H)ꢀNCy}(Br)(L)] (L: 10, PPh3; 11,
Pd(1)ꢁC(1)
Pd(1)ꢁP(1)
2.017(4)
2.2665(13) Pd(1)ꢁBr(1)
Pd(1)ꢁN(1)
2.128(4)
2.4953(7)
N(1)ꢁC(8)
C(1)ꢁC(6)
C(6)ꢁC(7)
P(1)ꢁC(15)
1.478(6)
1.416(6)
1.449(7)
1.841(5)
N(1)ꢁC(7)
P(1)ꢁC(23)
P(1)ꢁC(17)
1.264(6)
1.821(5)
1.832(5)
Bond angles (°)
C(1)ꢁPd(1)ꢁN(1)
N(1)ꢁPd(1)ꢁP(1)
N(1)ꢁPd(1)ꢁBr(1)
C(23)ꢁP(1)ꢁC(17) 108.4(2)
C(17)ꢁP(1)ꢁC(15) 101.3(2)
C(17)ꢁP(1)ꢁPd(1) 116.4(2)
C(7)ꢁN(1)ꢁC(8)
C(8)ꢁN(1)ꢁPd(1)
C(2)ꢁC(1)ꢁPd(1)
C(5)ꢁC(6)ꢁC(7)
N(1)ꢁC(7)ꢁC(6)
80.9(2)
174.17(11)
93.53(10)
C(1)ꢁPd(1)ꢁP(1)
C(1)ꢁPd(1)ꢁBr(1) 167.79(13)
P(1)ꢁPd(1)ꢁBr(1)
C(23)ꢁP(1)ꢁC(15)
C(23)ꢁP(1)ꢁPd(1) 109.8(2)
C(15)ꢁP(1)ꢁPd(1) 119.4(2)
C(7)ꢁN(1)ꢁPd(1)
C(2)ꢁC(1)ꢁC(6)
C(6)ꢁC(1)ꢁPd(1)
C(1)ꢁC(6)ꢁC(7)
94.13(13)
91.93(4)
99.9(2)
122.0(4)
125.5(3)
132.0(3)
122.0(4)
118.6(4)
112.5(3)
116.3(4)
111.4(3)
116.5(4)
Table 2
PEt2Ph; 12, PEtPh2; 13, PMePh2) and [Pd{3-
(CHO)C6H3C(H)ꢀNCy}(I)(L)] (L: 14, PPh3; 15,
PEt2Ph; 16, PEtPh2; 17, PMePh2), respectively, as pure
air-stable solids, which were fully characterised (see
Section 4 and Table 4).
Atomic coordinates (×104) and equivalent isotropic displacement
2
3
˚
parameters (A ×10 ) for 12
Atom
x
y
z
U (eq)
Pd(1)
Br(1)
P(1)
O(1)
N(1)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
−11(1)
1737(1)
907(1)
−16(1)
1281(1)
1239(1)
1761(1)
1733(1)
−742(2)
755(2)
684(2)
609(2)
168(2)
−225(2)
−162(2)
279(2)
349(2)
870(2)
33(1)
61(1)
34(1)
85(2)
37(1)
31(1)
36(1)
38(1)
41(1)
45(1)
37(1)
41(1)
38(1)
48(1)
71(2)
74(2)
66(2)
51(1)
59(2)
45(1)
68(2)
37(1)
46(1)
60(2)
63(2)
55(2)
47(1)
36(1)
47(1)
59(2)
62(2)
60(2)
47(1)
Reaction of the halide-bridged complexes 1–3 with
tertiary monophosphines in a dimer/phosphine 1:4 mo-
lar ratio gave the non-cyclometallated monomer com-
pounds [Pd{3-(CHO)C6H3C(H)ꢀNCy}(Cl)(L)2] (L: 18,
−1463(1)
−3380(4)
1243(3)
−954(4)
−2083(4)
−2548(4)
−1909(4)
−778(4)
−306(4)
870(4)
2429(4)
3167(4)
4359(5)
4631(5)
3857(5)
2664(4)
−2423(5)
−1217(4)
−760(5)
−2402(4)
−2166(5)
−2844(6)
−3733(6)
−3960(5)
−3313(4)
−2249(4)
−3365(4)
−3884(5)
−3284(6)
−2175(5)
−1666(5)
−3881(6)
−1076(4)
−1181(5)
−1250(5)
−2043(5)
−2822(6)
−2761(6)
−1959(6)
−1855(6)
−978(6)
−1590(7)
−1322(9)
−2125(9)
−1596(8)
−1821(7)
−3720(7)
2142(6)
PPh3;
19,
PMePh2),
[Pd{3-(CHO)C6H3C(H)ꢀ
NCy}(Br)(L)2] (L: 20, PPh3; 21, PMePh2) and [Pd{3-
(CHO)C6H3C(H)ꢀNCy}(I)(PR3)2] (L: 22, PPh3; 23,
PMePh2) respectively, which were fully characterised
(see Section 4 and Table 4). The 31P{1H}-NMR spectra
confirmed the trans geometry of the phosphine ligands,
with a singlet resonance in each case, this is also
confirmed by the weak intensity of the band at 550
cm−1 in the IR spectra [18]. These complexes can also
be obtained by reaction of the appropriate cyclometal-
lated monomer compounds (6–17) with the corre-
sponding monophosphine in a complex/phosphine 1:1
molar ratio. The reactivity of compounds 6–17 was
also tested against cyclohexylamine by refluxing them
with the amine to produce compounds where regenera-
tion of the CꢀN double bond from the formyl group
was achieved: mononuclear cyclometallated complexes
24–28 (complex/cyclohexylamine 1:1 molar ratio)
[Pd{3-(CyC(H)ꢀN)C6H3C(H)ꢀNCy}(Cl)(L)] (L: 24,
PPh3; 25, PEt2Ph; 26, PEtPh2; 27, PMePh2), respec-
C(9)
410(2)
582(3)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
C(27)
C(28)
1080(3)
1539(3)
1365(2)
−677(2)
2351(2)
2818(2)
1976(2)
1892(2)
2115(2)
2412(2)
2495(2)
2276(2)
1350(2)
1243(2)
948(2)
1325(8)
−540(5)
−2111(6)
−3188(7)
−2703(7)
−1160(7)
−82(6)
2240(5)
2128(6)
3238(7)
4428(7)
759(2)
861(2)
1151(2)
tively,
and
[Pd{3-(CyC(H)ꢀN)C6H3C(H)ꢀNCy}-
4544(7)
3457(6)
(I)(PPh3)] (28), and mononuclear non-cyclometallated
complexes 29–32 (monomer/cyclohexylamine 1:2 molar
ratio)
[Pd{3-(CyC(H)ꢀN)C6H3C(H)ꢀNCy}(Cl)(L)-
U(eq) is defined as one third of the trace of the orthogonalised Uij
tensor.
(NH2Cy)] (L: 29, PPh3; 30, PEtPh2; 31, PMePh2), re-

34
J.M. Vila et al. / Journal of Organometallic Chemistry 556 (1998) 31–39
Scheme 1. (i) CyNH2 (2 mol), chloroform, reflux; (ii) CyNH2 (1 mol), chloroform, reflux; (iii) CyNH2 (4 mol), chloroform, reflux; (iv) PR3 (1:2
molar ratio), aqueous acetone, stir at r.t.; (v) PR3 (1:4 molar ratio), aqueous acetone, stir at r.t.; (vi) PR3 (1:1 molar ratio), aqueous acetone, stir
at r.t.; (vii) PR3 (1:1 molar ratio), aqueous acetone, stir at r.t.; (viii) CyNH2 (2 mol), chloroform, reflux; (ix) CyNH2 (1 mol), chloroform, reflux;
(x) CyNH2 (1 mol), chloroform, reflux; (xi) CyNH2 (1 mol), chloroform, reflux; (xii) PR3 (1:1 molar ratio), aqueous acetone, stir at r.t.; (xiii) PR3
(1:1 molar ratio), aqueous acetone, stir at r.t..
spectively, and [Pd{3-(CyC(H)ꢀN)C6H3C(H)ꢀNCy}-
(Br)(PPh3)(NH2Cy)] (32); which also show an uncoordi-
nated CꢀN double bond; the amine cleaves the PdꢁN
bond to give compounds where the palladium atom is
bonded to four different ligands. The HCꢀN and H5
resonances are not coupled to phosphorus, which is
evidence for the twisting of the metallated Schiff base
out of the palladium(II) coordination plane [15]; the
organic ligand is monodentate through the phenyl car-
bon atom. Ring opening of the chelate ring was also
brought about by treating 24–28 with equimolar
amounts of cyclohexylamine; alternatively, type 5 com-
pounds could be treated with equimolar amounts of the
appropriate phosphine to yield compounds 29–32 (see
Section 4).
Treatment of 24–28 with the appropriate phosphine
in a complex/phosphine 1:1 molar ratio gave the
mononuclear non-cyclometallated compounds [Pd{3-
(CyNC(H)C6H3CꢀH)ꢀNCy}(Cl)(L)2] (L: 33, PPh3; 34,
PMePh2) and [Pd{3-(CyNCꢀH)C6H3C(H)ꢀNCy}(I)-
(PPh3)2] (35) with two uncoordinated CꢀN groups each,
and with two mutually trans phosphine ligands which
were fully characterised (see Section 4 and Table 4).
The compounds could also be made from 18–23 by
treatment with equimolar amounts of cyclohexylamine
under reflux, or from 29–32, by reaction with the
corresponding phosphine at room temperature (r.t.)
(see Section 4). Attempts to obtain 33–35 from
6–17 by successive reaction with the amine and
the phosphine in a ‘one pot’ process, were unsuccess-
ful.
3. Conclusions
Although Schiff base cyclometallated palladium(II)
complexes with a phosphine ligand bonded to the metal
atom are known, the structure of compound 12 is the
first example where the metallated ring is functionalised
by a free formyl group. The presence of the formyl
group renders versatile reaction routes; the order with
which the ligands are added to the coordination sphere
of the palladium atom and with which the second CꢀN
double bond is regenerated, may be varied. This gives
different approaches to the synthesis of many of the
compounds described.

J.M. Vila et al. / Journal of Organometallic Chemistry 556 (1998) 31–39
35
Table 4
31P-NMRa and 1H-NMRb datac,d
Compound
31P
Aromatic
Others
6
21.5s
7.71[d, 1H, H2, 1.9e]
9.75[s, 1H, HCꢀO]
6.98[dd, 1H, H4, 8.0f, 1.9e]
6.59[ddd, 1H, H5, 8.0f, 5.9h, 0.9g]
8.24[dd, 1H, HCꢀN, 8.6h, 0.9g]
7
32.5s
34.6s
21.9s
20.4s
32.9s
35.0s
22.0s
20.7s
34.6s
36.2s
22.0s
7.71[d,1H, H2, 1.9e]
9.78[s, 1H, HCꢀO]
7.15[dd, 1H, H4, 8.0f, 1.9e]
6.62[ddd,1H, H5, 8.0f, 5.7h, 1.0g]
8.17[dd, 1H, HCꢀN, 8.2h, 1.0g]
8
7.71[d,1H, H2, 1.9e]
9.76[s, 1H, HCꢀO]
7.05[dd, 1H, H4, 8.0f, 1.9e]
6.66[ddd, 1H, H5, 8.0f, 5.7h, 1.0g]
8.19[dd, 1H, HCꢀN, 8.4h, 1.0g]
9
7.72[d, 1H, H2, 1.8e]
9.76[s, 1H, HCꢀO]
7.05[dd, 1H, H4, 7.9f, 1.8e]
6.59[ddd, 1H, H5, 7.9f, 6.0h, 0.9g]
8.19[dd, 1H, HCꢀN, 8.7h, 0.9g]
10
11
12
13
14
15
16
17
7.71[d, 1H, H2, 1.8e]
9.76[s, 1H, HCꢀO]
7.00[dd, 1H, H4, 8.0f, 1.8e]
6.58[dd, 1H, H5, 8.0f, 6.2h]
8.26[d, 1H, HCꢀN, 8.6h]
7.71[d, 1H, H2, 1.5e]
9.78[s, 1H, HCꢀO]
7.16[dd, 1H, H4, 7.9f, 1.5e]
6.61[dd, 1H, H5, 7.9f, 6.0h]
8.18[d, 1H, HCꢀN, 7.9h]
7.71[d, 1H, H2, 1.8e]
9.76[s, 1H, HCꢀO]
7.05[dd,1H, H4, 8.0f, 1.8e]
6.62[dd, 1H, H5, 8.0f, 6.0h]
8.22[d, 1H, HCꢀN, 8.3h]
7.71[d, 1H, H2, 1.8e]
7.05[dd, 1H, H4, 8.0f, 1.8e]
6.57[d, 1H, H5, 8.0f]
9.76[s, 1H, HCꢀO]
8.21[d, 1H, HCꢀN, 7.9h]
7.71[d, 1H, H2, 1.4e]
9.76[s, 1H, HCꢀO]
7.00[dd, 1H, H4, 7.5f, 1.4e]
6.54[t, 1H, H5, 7.5f, 7.5h]
8.32[d, 1H, HCꢀN, 8.1h]
7.71[d, 1H, H2, 1.9e]
9.79[s, 1H, HCꢀO]
7.18[dd, 1H, H4, 8.0f, 1.9e]
6.61[ddd, 1H, H5, 8.0f, 6.0h, 0.9g]
8.24[dd, 1H, HCꢀN, 8.0h, 0.9g]
7.71[d, 1H, H2, 1.9e]
9.76[s, 1H, HCꢀO]
7.05[dd, 1H, H4, 8.0f, 1.9e]
6.54[ddd, 1H, H5, 8.0f, 6.3h, 1.0g]
8.27[dd, 1H, HCꢀN, 8.2h, 1.0g]
7.71[d, 1H, H2,1.9e]
9.76[s, 1H, HCꢀO]
7.07[dd, 1H, H4, 7.4f, 1.9e]
6.53[dd, 1H, H5,7.4f, 7.0h]
8.27[d, 1H, HCꢀN, 8.0h]
18I
19I
20I
21I
22I
23I
24I
25
22.0s
4.0s
6.98[dd, 1H, H4, 8.0f, 1.9e]
6.62[d, 1H, H5, 8.0f]
9.76[s, 1H, HCꢀO]
8.26[s, 1H, HCꢀN]
7.05[dd,1H, H4, 8.0f, 1.4e]
7.18[d, 1H, H5, 8.0f]
9.70[s, 1H, HCꢀO]
8.42[s, 1H, HCꢀN]
21.5s
3.6s
6.97[dd, 1H, H4, 8.0f, 1.9e]
6.65[d, 1H, H5, 8.0f]
9.74[s, 1H, HCꢀO]
8.33[s, 1H, HCꢀN]
7.05[dd, 1H, H4, 8.0f, 1.8e]
9.68[s, 1H, HCꢀO]
8.43[s, 1H, HCꢀN]
20.8s
2.4s
6.95[dd, 1H, H4, 8.0f, 1.8e]
6.65[d,1H, H5, 8.0f]
9.73[s, 1H, HCꢀO]
8.44[s, 1H, HCꢀN]
7.05[dd, 1H, H4, 7.9f, 1.9e]
9.67[s, 1H, HCꢀO]
8.35[s, 1H, HCꢀN]
40.8s
32.4s
6.80[dd, 1H, H4, 8.0f, 2.0e]
6.45[dd, 1H, H5, 8.0f, 5.7h]
8.19[d, 1H, HCꢀN, 7.8h]
8.08[s, 1H, HCꢀNj]
7.66[d, 1H, H2, 1.8e]
8.13[d, 1H, HCꢀN, 9.4h]
8.11[s, 1H, HCꢀNj]
7.00[dd, 1H, H4, 8.0f, 1.8e]
6.48[dd, 1H, H5, 8.0f, 5.8h]

36
J.M. Vila et al. / Journal of Organometallic Chemistry 556 (1998) 31–39
Table 4 (continued)
Compound
26
31P
Aromatic
Others
34.6s
7.64[d, 1H, H2,1.6e]
8.14[d, 1H, HCꢀN, 8.0h]
8.08[s, 1H, HCꢀNj]
6.87[dd, 1H, H4, 8.0f, 1.6e]
6.51[dd, 1H, H5,8.0f, 5.5h]
27I
28I
29I
30I
31I
32I
33I
34I
35I
22.0s
41.0s
27.2s
34.5s
21.9s
40.7s
27.3s
6.3s
6.90[d, 1H, H4, 8.0f]
8.16[d, 1H, HCꢀN, 7.8h]
8.10[s, 1H, HCꢀNj]
6.47[dd, 1H, H5, 8.0f, 5.6h]
6.81[dd, 1H, H4, 7.9f, 2.0e]
6.38[dd, 1H, H5, 7.9f, 5.8h]
8.25[d, 1H, HCꢀN, 8h]
8.06[s, 1H, HCꢀNj]
6.81[dd, 1H, H4, 8.0f, 2.0e]
6.44[d, 1H, H5, 8.0f]
8.21[s, 1H, HCꢀN]
8.07[s, 1H, HCꢀNj]
6.87[d,1H, H4, 7.9f]
6.51[d, 1H, H5, 7.9f]
8.13[s, 1H, HCꢀN]
8.07[s, 1H, HCꢀNj]
6.88[dd, 1H, H4, 7.9f, 1.9e]
6.45[d, 1H, H5, 7.9f]
8.15[s, 1H, HCꢀN]
8.07[s, 1H, HCꢀNj]
6.81[dd, 1H, H4, 8.0f, 2.0e]
6.42[d, 1H, H5, 8.0f]
8.21[s, 1H, HCꢀN]
8.07[s, 1H, HCꢀNj]
6.80[dd, 1H, H4, 7.9f, 1.9e]
6.43[d, 1H, H5, 7.9f]
8.26[s, 1H, HCꢀN]
8.09[s, 1H, HCꢀNj]
7.11[dd, 1H, H4, 7.9f, 1.9e]
7.00[d, 1H, H5, 7.9f]
8.39[s, 1H, HCꢀN]
8.09[s, 1H, HCꢀNj]
27.4s
6.82[dd,1H, H4, 8.1f, 2.0e]
6.43[d,1H, H5, 8.1f]
8.29[s, 1H, HCꢀN]
8.06[s, 1H, HCꢀNj]
a In CDCl3. Measured at 100.6 MHz (ca. 920°C); chemical shifts (l) in ppm (90.1) to high frequency of 85% H3PO4. b In CDCl3, unless
otherwise stated. Measured at 250 MHz (ca. 920°C); chemical shifts(l) in ppm (90.01) to high frequency of SiMe4. c Coupling constants
in Hz. d s, singlet; d, doublet; dd, doublet of doublets; ddd, doublet of doublets of doublets; t, triplet. e 4J(HH). f 3J(HH). g 5J(HH).
h 4J(PH). i Occluded by the phosphine resonances. j CꢀN group bonded to C3.
4. Experimental details
The mixture was stirred for 4 h at r.t. and the resulting
precipitate was filtered off and the product recrys-
tallised from dichloromethane/hexane as a yellow solid.
Yield 75%. Anal. Found: C, 61.8; H, 5.3; N, 2.1.
C32H31NOPdPCl requires: C, 62.2; H, 5.1; N, 2.3. IR:
4.1. Materials and instrumentation
The synthesis of complexes 1–5 has been reported
previously [13]. Solvents were purified by standard
methods [19]. Chemicals were reagent grade. Cyclo-
hexylamine and the phosphines PPh3, PEtPh2, PEt2Ph
and PMePh2 were purchased from Aldrich. Micro-
analyses were carried out at the Servicio de Ana´lisis
Elemental at the University of Santiago using a Carlo-
Erba Elemental Analyzer, Model 1108. IR spectra were
recorded as KBr or polythene discs on a Perkin-Elmer
1330 and on a Mattson (Servicio de Espectroscop´ıa of
the University of Santiago) spectrophotometers. NMR
spectra were obtained as CDCl3 solutions and refer-
enced to SiMe4 (1H,13C) or 85% H3PO4 (31P{1H}) and
were recorded on Bruker WM-250, AMX-300 and
AMX-500 spectrometers. All chemical shifts were re-
ported downfield from the standards.
w(CꢀN), 1622m cm−1; w(PdꢁCl), 302m cm−1
.
The following compounds were made analogously:
4.2.2. [Pd{3-(CHO)C6H3C(H)ꢀNCy}(Cl)(PEt2Ph)] 7
Yield 75%. Anal. Found: C, 55.2; H, 6.4; N, 2.9.
C24H31NOPdPCl requires: C, 55.2; H, 6.0; N, 2.7. IR:
w(CꢀN), 1620m cm−1; w(PdꢁCl), 302m cm−1
.
4.2.3. [Pd{3-(CHO)C6H3C(H)ꢀNCy}(Cl)(PEtPh2)] 8
Yield 78%. Anal. Found: C, 57.0; H, 5.5; N, 2.5.
C28H31NOPdPCl·0.33 CH2Cl2 requires: C, 56.8; H, 5.3;
N, 2.3. IR: w(CꢀN), 1622m cm−1; w(PdꢁCl), 301m
cm−1
.
4.2. Preparations
4.2.4. [Pd{3-(CHO)C6H3C(H)ꢀNCy}(Cl)(PMePh2)] 9
Yield 75%. Anal. Found: C, 58.3; H, 5.4; N, 2.8.
C27H29NOPdPCl requires: C, 58.3; H, 5.3; N, 2.5. IR:
4.2.1. [Pd{3-(CHO)C6H3C(H)ꢀNCy}(Cl)(PPh3)] 6
A sample of PPh3 (44 mg, 0.17 mmol) was added to
a solution of 1 (60 mg, 0.08 mmol) in acetone (15 cm3).
w(CꢀN), 1615m cm−1; w(PdꢁCl), 299m cm−1
.

J.M. Vila et al. / Journal of Organometallic Chemistry 556 (1998) 31–39
37
4.2.5. [Pd{3-(CHO)C6H3C(H)ꢀNCy}(Br)(PPh3)] 10
Yield 75%. Anal. Found: C, 57.4; H, 4.5; N, 1.9.
C32H31NOPdPBr requires: C, 58.0; H, 4.7; N, 2.1. IR:
4.2.14. [Pd{3-(CHO)C6H3C(H)ꢀNCy}(Cl)(PMePh2)2]
19
Yield 70%. Anal. Found: C, 64.0; H, 6.0; N, 2.0.
w(CꢀN), 1625m cm−1
.
C40H42NOPdP2Cl requires: C, 63.5; H, 5.6; N, 1.9. IR:
4.2.6. [Pd{3-(CHO)C6H3C(H)ꢀNCy}(Br)(PEt2Ph)] 11
Yield 68%. Anal. Found: C, 51.2; H, 5.8; N, 2.0.
C24H31NOPdPBr requires: C, 50.9; H, 5.5; N, 2.5. IR:
w(CꢀN), 1625m cm−1; w(PdꢁCl), 294m cm−1
.
4.2.15. [Pd{3-(CHO)C6H3C(H)ꢀNCy}(Br)(PPh3)2] 20
Yield 65%. Anal. Found: C, 61.4; H, 4.8; N, 1.6.
C50H46NOPdP2Br·0.5CHCl3 requires: C, 61.6; H, 4.8;
w(CꢀN), 1615m cm−1
.
N, 1.4. IR: w(CꢀN), 1625m cm−1
.
4.2.7. [Pd{3-(CHO)C6H3C(H)ꢀNCy}(Br)(PEtPh2)] 12
Yield 75%. Anal. Found: C, 54.3; H, 5.1; N, 2.4.
C28H31NOPdPBr requires: C, 54.7; H, 5.0; N, 2.3. IR:
4.2.16. [Pd{3-(CHO)C6H3C(H)ꢀNCy}(Br)(PMePh2)2]
21
w(CꢀN), 1615m cm−1
.
Yield 65%. Anal. Found: C, 60.5; H, 5.6; N, 1.4.
C40H42NOPdP2Br requires: C, 60.0; H, 5.3; N, 1.8. IR:
w(CꢀN), 1630m cm−1.
4.2.8. [Pd{3-(CHO)C6H3C(H)ꢀNCy}(Br)(PMePh2)] 13
Yield 70%. Anal. Found: C, 54.5; H, 4.8; N, 2.8.
C27H29NOPdPBr requires: C, 54.0; H, 4.9; N, 2.3. IR:
w(CꢀN), 1615m cm−1
.
4.2.17. [Pd{3-(CHO)C6H3C(H)ꢀNCy}(I)(PPh3)2] 22
Yield 60%. Anal. Found: C, 61.8; H, 4.7; N, 1.3.
C50H46NOPdP2I requires: C, 61.8; H, 4.8; N, 1.4. IR:
4.2.9. [Pd{3-(CHO)C6H3C(H)ꢀNCy}(I)(PPh3)] 14
Yield 70%. Anal. Found: C, 54.4; H, 4.8; N, 2.1.
C32H31NOPdPI requires: C, 54.1; H, 4.4; N, 2.0. IR:
w(CꢀN), 1625m cm−1
.
w(CꢀN), 1620m cm−1
.
4.2.18. [Pd{3-(CHO)C6H3C(H)ꢀNCy}(I)(PMePh2)2] 23
Yield 76%. Anal. Found: C, 57.2; H, 5.5; N, 2.0.
C40H42NOPdP2I requires: C, 56.7; H, 5.0; N, 1.7. IR:
4.2.10. [Pd{3-(CHO)C6H3C(H)ꢀNCy}(I)(PEt2Ph)] 15
Yield 70%. Anal. Found: C, 46.8; H, 5.0; N, 2.2.
C24H31NOPdPI requires: C, 47.0; H, 5.1; N, 2.3. IR:
w(CꢀN), 1630m cm−1
.
w(CꢀN), 1618m cm−1
.
4.2.19. [Pd{3-(CyC(H)ꢀN)C6H3C(H)ꢀNCy}(Cl)(PPh3)]
24
4.2.11. [Pd{3-(CHO)C6H3C(H)ꢀNCy}(I)(PEtPh2)] 16
Yield 70%. Anal. Found: C, 50.8; H, 4.7; N, 2.2.
C28H31NOPdPI requires: C, 50.8; H, 4.7; N, 2.1. IR:
A mixture of 6 (50 mg, 0.08 mmol) and cyclohexy-
lamine (9 mg, 0.09 mmol) in chloroform (25 cm3) was
heated under reflux for 8 h in a Dean–Stark apparatus.
After cooling to r.t., the solution was evaporated under
reduced pressure and the required product was isolated
from dichloromethane/hexane as a yellow solid. Yield
88%. Anal. Found: C, 59.2; H, 6.0; N, 3.2.
C38H42N2PdPCl·CH2Cl2 requires: C, 59.7; H, 5.7; N,
3.6. IR: w(CꢀN), 1638h,m, 1620m cm−1; w(PdꢁCl),
w(CꢀN), 1622m cm−1
.
4.2.12. [Pd{3-(CHO)C6H3C(H)ꢀNCy}(I)(PMePh2)] 17
Yield 73%. Anal. Found: C, 48.9; H, 4.4; N, 2.4.
C27H29NOPdPI·0.33CH2Cl2 requires: C, 48.6; H, 4.4;
N, 2.6. IR: w(CꢀN), 1620m cm−1
.
4.2.13. [Pd{3-(CHO)C6H3C(H)ꢀNCy}(Cl)(PPh3)2] 18
275m cm−1
.
The following compounds were made analogously:
4.2.13.1. Method a. The complex was synthesised fol-
lowing a similar procedure to that of 6 but using a
dimer/phosphine 1:4 molar ratio. Yield 68%. Anal.
4.2.20. [Pd{3-(CyC(H)ꢀN)C6H3C(H)ꢀNCy}(Cl)-
(PEt2Ph)] 25
Found:
C,
65.4;
H,
5.5;
N,
1.8.
Yield 83%. Anal. Found: C, 54.7; H, 6.7; N, 3.8.
C30H42N2PdPCl·CHCl3 requires: C, 55.2; H, 6.5; N,
4.2. IR: w(CꢀN), 1640sh,m, 1620sh,m cm−1; w(PdꢁCl),
C50H46NOPdP2Cl·0.5CH2Cl2 requires: C, 65.7; H, 5.1;
N, 1.5. IR: w(CꢀN), 1625m cm−1; w(PdꢁCl), 290m
cm−1
.
275m cm−1
.
4.2.13.2. Method b. A sample of PPh3 (21.2 mg, 0.08
mmol) was added to a solution of 6 (50 mg, 0.08 mmol)
in acetone (15 cm3). The mixture was stirred for 4 h at
r.t. and the resulting precipitate was filtered off and the
product recrystallised from dichloromethane/hexane as
a yellow solid.
4.2.21. [Pd{3-(CyC(H)ꢀN)C6H3C(H)ꢀNCy}(Cl)-
(PEtPh2)] 26
Yield 78%. Anal. Found: C, 59.6; H, 6.3; N, 3.7.
C34H42N2PdPCl·0.5CH2Cl2 requires: C, 60.0; H, 6.2;
N, 4.0. IR: w(CꢀN), 1638m, 1620m cm−1; w(PdꢁCl),
The following compounds were made similarly:
271m cm−1
.

38
J.M. Vila et al. / Journal of Organometallic Chemistry 556 (1998) 31–39
4.2.22. [Pd{3-(CyC(H)ꢀN)C6H3C(H)ꢀNCy}(Cl)-
(PMePh2)] 27
4.2.27. Pd{3-(CyC(H)ꢀN)C6H3C(H)ꢀNCy}(Br)(PPh3)-
(NH2Cy)] 32
Yield 70%. Anal. Found: C, 57.5; H, 6.2; N, 3.8.
C33H40N2PdPCl·0.5CHCl3 requires: C, 57.7; H, 5.9; N,
4.0. IR: w(CꢀN), 1638m, 1620m cm−1; w(PdꢁCl), 271m
Yield 65%. Anal. Found: C, 54.0; H, 5.5 N, 4.0.
C44H55N3PdPBr·1.5CHCl3 requires: C, 54.3; H, 5.7; N,
4.2. IR: w(CꢀN), 1635m, 1618m cm−1
.
cm−1
.
4.2.28. [Pd{3-(CyC(H)ꢀN)C6H3C(H)ꢀNCy}(Cl)-
(PPh3)2] 33
4.2.23. [Pd{3-(CyC(H)ꢀN)C6H3C(H)ꢀNCy}(I)(PPh3)]
28
Yield 80%. Anal. Found: C, 58.0; H, 6.0; N, 4.0.
4.2.28.1. Method a. The complex was synthesised fol-
lowing a similar procedure to that of 24. Yield 70%.
Anal. Found: C, 58.2; H, 5.4; N, 2.4.
C56H57N2PdP2Cl·2CHCl3 requires: C, 58.0; H, 5.0; N,
C38H42N2PdPI requires: C, 57.7; H, 5.4; N, 3.5. IR:
w(CꢀN), 1632m, 1618m cm−1
.
2.3. IR: w(CꢀN), 1637m cm−1; w(PdꢁCl), 291m cm−1
.
4.2.24. [Pd{3-(CyC(H)ꢀN)C6H3C(H)ꢀNCy}(Cl)-
(PPh3)(NH2Cy)] 29
4.2.28.2. Method b. A sample of PPh3 (11.2 mg, 0.04
mmol) was added to a solution of 24 (30 mg, 0.04
mmol) in acetone (15 cm3). The mixture was stirred for
4 h at r.t. and the resulting precipitate was filtered off
and the product recrystallised from chloroform/hexane.
4.2.24.1. Method a. The complex was synthesised
following a similar procedure to that of 24 but using a
monomer/cyclohexylamine 1:2 ratio. Yield 55%. Anal.
Found:
C,
63.3;
H,
6.5;
N,
4.8.
4.2.28.3. Method c. A sample of PPh3 (6.75 mg, 0.025
mmol) was added to a solution of 29 (20 mg, 0.025
mmol) in acetone (15 cm3). The mixture was stirred for
4 h at r.t. and the resulting precipitate was filtered off
and the product recrystallised from chloroform/hexane.
Compounds 34 and 35 were prepared similarly:
C44H55N3PdPCl·0.5CH2Cl2 requires: C, 63.5; H, 6.7;
N, 5.0. IR: w(CꢀN), 1630sh,m, 1620m cm−1; w(PdꢁCl),
273m cm−1
.
4.2.24.2. Method b. To a solution of 24 (30 mg, 0.043
mmol) in CHCl3 CyNH2 (4.3 mg, 0.043 mmol)) was
added in a cyclometallated complex/amine 1:1 molar
ratio. The solution was heated under reflux for 8 h in a
Dean–Stark apparatus. After cooling to r.t., the
solution was evaporated under reduced pressure and
the required product was isolated from dichloro-
methane/hexane.
4.2.29. [Pd{3-(CyC(H)ꢀN)C6H3C(H)ꢀNCy}(Cl)-
(PMePh2)2] 34
Yield 76%. Anal. Found: C, 62.6; H, 6.3; N, 3.3.
C46H53N2PdP2Cl·0.5CHCl3 requires: C, 62.2; H, 6.0;
N, 3.1. IR: w(CꢀN), 1636m cm−1; w(PdꢁCl), 275m
cm−1
.
4.2.30. [Pd{3-(CyC(H)ꢀN)C6H3C(H)ꢀNCy}(I)(PPh3)2]
35
Yield 75%. Anal. Found: C, 63.8; H, 5.7; N, 2.5.
4.2.24.3. Method c. A sample of PPh3 (9.78 mg, 0.04
mmol) was added to a solution of 5 (20 mg, 0.04 mmol)
in acetone (15 cm3). The mixture was stirred for 4 h at
r.t. and the resulting precipitate was filtered off and the
product recrystallised from dichloromethane/hexane.
The following compounds were prepared similarly:
C56H57N2PdP2I requires: C, 63.9; H, 5.5; N, 2.7. IR:
w(CꢀN), 1638sh,m, 1622m cm−1
.
4.3. Single-crystal X-ray diffraction analysis
4.2.25. [Pd{3-(CyC(H)ꢀN)C6H3C(H)ꢀNCy}(Cl)-
(PEtPh2)(NH2Cy)] 30
A prismatic yellow crystal of dimensions 0.15×
0.25×0.40 mm of 12 was mounted on a glass fiber in a
Enraf-Nonius CAD4 diffractometer for data collection.
Unit cell parameters were determined from least-
squares on setting angles of 25 reflections with 8.45B
qB11.90°. Data were collected at r.t. by the ꢀ/2q scan
technique using graphite monochromatised Mo–Kh
Yield 40%. Anal. Found: C, 60.4; H, 6.8; N, 5.0.
C40H55N3PdPCl·0.5CHCl3 requires: C, 60.1; H, 6.8; N,
5.2. IR: w(CꢀN), 1635m, 1618m cm−1; w(PdꢁCl), 272m
cm−1
.
˚
4.2.26. [Pd{3-(CyC(H)ꢀN)C6H3C(H)ꢀNCy}(Cl)-
(PMePh2)(NH2Cy)] 31
(u=0.71093 A) radiation. A total of 8061 reflections
were measured with qmax=30.01°; 7605 unique reflec-
tions; Rint=0.0772; 4260 reflections were considered
observed on the criterion I\2|(I) and corrected for
Lorentz and polarisation effects. An empirical absorp-
tion correction was also made. A summary of the
Yield 60%. Anal. Found: C, 63.0; H, 7.0; N, 5.4.
C39H53N3PdPCl requires: C, 63.6; H, 7.3; N, 5.7. IR:
w(CꢀN), 1635sh,m, 1620m cm−1; w(PdꢁCl), 270m
cm−1
.

J.M. Vila et al. / Journal of Organometallic Chemistry 556 (1998) 31–39
39
Dalton Trans. (1986) 1351.
crystal data, experimental details and refinement results
is shown in Table 1.
[8] G.B. Cayhill, P.J. Steel, J. Organomet. Chem. 395 (1990) 375.
[9] G.B. Cayhill, P.J. Steel, J. Organomet. Chem. 395 (1990) 359.
[10] J.L. Casas, E. Gayoso, J.M. Vila, M.T. Pereira, M. Gayoso,
Synth. React. Inorg. Met. Org. Chem. 21 (1991) 263.
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Ortigueira, M. Thornton-Pett, J. Organomet. Chem. 426 (1992)
267; (b) J.M. Vila, M.T. Pereira, M. Gayoso, M.C. Rodr´ıguez,
J.M. Ortigueira, J.J. Ferna´ndez, M. Lo´pez Torres, J. Organomet.
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Ferna´ndez, A. Ferna´ndez, J.M. Ortigueira, J. Organomet. Chem.
506 (1996) 165.
The structure was solved by direct methods and
2
refined on F by a full-matrix least-squares procedure.
A
weighting scheme w=1/[s2 (Fo2)+(0.0555P)2+
1.3320P] where P=(Fo2 +2F2c)/3 was used in the latter
stages of refinement. Computations were performed by
means of VAX-SDP [20], SHELXS86 [21], and
SCHAKAL [22] programs on a DEX MICROVAXII
computer. Atomic scattering factors and anomalous
dispersion corrections for all atoms were taken from
International Tables for X-ray Crystallography [23].
[14] L. Pauling, The Nature of the Chemical Bond, 3rd ed., Cornell
University Press, New York, 1960.
[15] J.M. Vila, M. Gayoso, M.T. Pereira, A. Romar, J.J. Ferna´ndez,
M. Thornton-Pett, J. Organomet. Chem. 401 (1991) 385 and
references therein.
[16] J.M. Vila, M. Gayoso, M. Lo´pez Torres, et al., J. Organomet.
Chem. 511 (1996) 129.
Acknowledgements
We wish to thank the Ministerio de Educaio´n y
Ciencia (DGICYT) (Proyecto No. PB92-0376) for
financial support.
[17] J. Selbin, K. Abboud, S.F. Watkins, M.A. Gutie´rrez, F.R.
Fronczek, J. Organomet. Chem. 241 (1983) 259.
[18] S. H. Mastin, Inorg. Chem. 13 (1974) 1003.
[19] D.D. Perrin, W.L.F. Armarego, D.P. Perrin, Purification of
Laboratory Chemicals, 2nd ed., Oxford, Pergamon, 1983.
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.