Synthesis of phosphido-bridged dinuclear complexes through sodium reduction of cis-[M{P(C6H11)2H}2Cl2] (M = Ni or Pd)

Article abstract of DOI:10.1039/a607334d

Reduction of cis-[Ni{P(C₆H₁₁)₂H}₂Cl₂] with sodium afforded the dinuclear nickel complex [{Ni(μ-P(C₆H₁₁)₂]-[P(C₆H ₁₁)₂H]}₂]

Full text of DOI:10.1039/a607334d

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Synthesis of phosphido-bridged dinuclear complexes through sodium
reduction of cis-[M{P(C6H11)2H}2Cl2] (M = Ni or Pd)
Roberto Giannandrea,a Piero Mastrorilli,a Cosimo Francesco Nobile*,a and Ulli Englert b
a
Istituto di Chimica del Politecnico and Centro C.N.R.M.I.S.O., trav. 200 Re David, 4 I-70126
Bari, Italy
b Institut für Anorganische Chemie der RWTH Prof. Pirlet Str., 1 D-52074 Aachen, Germany
Reduction of cis-[Ni{P(C6H11)2H}2Cl2] with sodium afforded the dinuclear nickel complex [{Ni[µ-P(C6H11)2]-
[P(C6H11)2H]}2] which, in turn, reacted with CO producing [{Ni[µ-P(C6H11)2](CO)2}2]. The reduction of
cis-[Pd{P(C6H11)2H}2Cl2] occurred in two steps giving first [Pd2{µ-P(C6H11)2}Cl{P(C6H11)2H}3], then
[{Pd[µ-P(C6H11)2][P(C6H11)2H]}2]. The structure of the chloride complex was determined.
Low-valent transition-metal complexes are the foundations for
P(C6H11 2
)
activating small molecules and for achieving organic syntheses
through metal-catalysed reactions. In the framework of our
studies on sodium-promoted reduction of metal complexes,1 we
decided to address the divalent metal dicyclohexylphosphino
complexes of general formula cis-[M{P(C6H11)2H}2Cl2]
(M = Ni or Pd).
[Ni{P(C6H11)2H}2Cl2]
-2 NaCl
[H(C6H11)2P]Ni
2 Na
H
N2
[Ni{P(C6H11)2H}2]
- H2
2 CO
[Ni{P(C6H11)2H}2(CO)2]
1
2
Results and Discussion
Scheme 1 Proposed mechanism of formation of complex 1
The sodium-promoted reduction of [Ni{P(C6H11)2H}2Cl2] in
toluene proceeded with evolution of dihydrogen (revealed by
GC analyses) and resulted in the synthesis of a brown-red com-
pound the elemental analysis and spectroscopic features of
which indicate the formula [{Ni[µ-P(C6H11)2][P(C6H11)2H]}2]
1. This compound shows an UV/VIS spectrum under argon
(or under nitrogen) consisting of three peaks located at 332
C6H
11 C6H11
P
H(C6H11)2P Ni
Ni P(C6H11)2H
C6H11
P
C6H11
(19 500), 370 (14 700) and 510 nm (ε 2800 dm3 molϪ1 cmϪ1
)
whichisverysimilartothat of [{Ni[µ-P(C6H11)2][P(C6H11)2Ph]}2]2
(λmax = 340, 380 and 526 nm). Its IR spectrum shows a sharp
strong band at 2236 cmϪ1 ascribable to the P᎐H stretching of
the co-ordinated dicyclohexylphosphine. The 31P NMR spec-
trum consists of two triplets centred at δ 16 and 118 with a P᎐P
coupling constant of 31.0 Hz. The first is attributable to the co-
ordinated dicyclohexylphosphine whereas the second is
ascribed to a bridging phosphide. The resonance of the latter at
lower fields with respect to the corresponding trisubstituted
phosphine is also a clue to the presence of a three-membered
Ni2P ring,3 thus substantiating the presence of a Ni᎐Ni bond in
the molecule. This is further confirmed by the fact that 1 was
found to be diamagnetic. The structure proposed resembles
therefore those found for [{Ni[µ-P(C6H11)2][P(C6H11)2Ph]}2],2
[{Ni[µ-P(SiMe3)2](PR3)}2] (R = Me, Et or Bun),4 [{Ni(µ-
PBut2)(PR3)}2] (R = Me, Et or OMe)5,6 or [{Ni(µ-PButH)-
(PMe3)}2].7
1
[Ni{P(C6H11)2H}2(CO)2] 2 formed according to Scheme 1.
Complex 2 is white and shows in the IR spectrum two bands at
1984 and 1924 cmϪ1 ascribable to the co-ordinated terminal CO
groups along with a sharp band at 2294 cmϪ1 ascribable to the
co-ordinated P(C6H11)2H. Other spectroscopic features are
reported in the Experimental section.
When a solution of complex 1 was placed under carbon
monoxide at room temperature and atmospheric pressure it
changed rapidly to yellowish brown and the 31P NMR spectrum
recorded after 2 h consisted of three sharp singlets at δ 329.9,
290.3 and Ϫ29. The spectrum of the same solution after 20 h
showed almost complete disappearance of the signal at δ 290.3
and only the two peaks at δ 329.9 and Ϫ29 [the latter ascribable
to free P(C6H11)2H]. The reaction solution afforded, by cooling,
pure [{Ni[µ-P(C6H11)2](CO)2}2]2 3 which when redissolved in
toluene gave a singlet at δ 329.9 in the 31P NMR spectrum. It is
likely that when CO is admitted into a solution containing
complex 1 the first product to be formed is the tricarbonyl spe-
cies [Ni2{µ-P(C6H11)2}2(CO)3] 4 which evolves irreversibly to the
tetracarbonyl complex 3 (Scheme 2). The geometry proposed
for 4 has been observed in [Ni2(µ-PBut2)2(CO)3]6 and that of 3
hasbeen found for [{Ni(µ-PPh2)(CO)2}2].9 Comparison of theIR
spectra in solution of the mixture of complexes 3 and 4 with
that of pure 3 allowed us to assign to [Ni2{µ-P(C6H11)2}2(CO)3]
The stoichiometry of the reduction reaction can be written as
in equation (1). A mechanism similar to that proposed for the
2[Ni{P(C6H11)2H}2Cl2] ϩ 4 Na
[{Ni[µ-P(C6H11)2][P(C6H11)2H]}2] ϩ 4 NaCl ϩ H2 (1)
formation of the dimeric palladium() complex [{Pd(µ-PBut2)-
(PBut2H)}2]8 can be invoked. In this case the sodium can cleave
the two chlorine atoms leading to Ni[P(C6H11)2H]2 which evolves
via intramolecular oxidative addition to [NiH{P(C6H11)2}{P-
(C6H11)2H}]. This latter can easily couple giving rise to H2 and
1. When the reduction of [Ni{P(C6H11)2H}2Cl2] was carried out
under atmospheric pressure of carbon monoxide the expected
the bands at 1997, 1959 and 1934 cmϪ1
.
Sodium reduction of [Pd{P(C6H11)2H}2Cl2] carried out with
a Na :Pd ratio >2:1 and prolonged for about 6 h resulted in the
formation of a complex the elemental analysis and spectro-
J. Chem. Soc., Dalton Trans., 1997, Pages 1355–1358
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C6H11
P
C6H11
C6H11
C6H11
CO
Table 1 Selected bond distances (Å) and angles (Њ) for complex 6 with
estimated standard deviations in parentheses. All C᎐H bond distances
have been idealized to 0.98 Å
P
Ni
OC
OC
CO
Ni
CO
CO
1
OC Ni
Ni
CO
CO
P
P
C6H11
C6H11
C6H11
C6H11
Pd(1)᎐Pd(2)
Pd(1)᎐Cl
Pd(1)᎐P(1)
Pd(1)᎐P(2)
2.819(2)
2.456(5)
2.175(5)
2.281(5)
Pd(2)᎐P(1)
Pd(2)᎐P(3)
Pd(2)᎐P(4)
2.222(5)
2.319(5)
2.339(6)
4
3
Scheme 2 Reaction of complex 1 with CO
Pd(2)᎐Pd(1)᎐Cl
Pd(2)᎐Pd(1)᎐P(1)
Pd(2)᎐Pd(1)᎐P(2)
Cl᎐Pd(1)᎐P(1)
Cl᎐Pd(1)᎐P(2)
P(1)᎐Pd(1)᎐P(2)
Pd(1)᎐Pd(2)᎐P(1)
114.6(1)
50.9(1)
155.7(1)
162.1(2)
89.3(2)
106.4(2)
49.4(1)
Pd(1)᎐Pd(2)᎐P(3)
Pd(1)᎐Pd(2)᎐P(4)
P(1)᎐Pd(2)᎐P(3)
P(1)᎐Pd(2)᎐P(4)
P(3)᎐Pd(2)᎐P(4)
Pd(1)᎐P(1)᎐Pd(2)
94.8(1)
157.6(2)
143.0(2)
108.3(2)
106.8(2)
79.7(2)
C6H
11 C6H11
P
P(C6H11)2H
H(C6H11)2P
Na
[Pd{P(C6H11)2H}2Cl2]
Pd
Pd
Cl
H(C6H11)2P
Fig. 1 Electronic absorption spectra of complexes 5 [4.20 × 10Ϫ5 mol
dm3, (a)] and 6 [5.00 × 10Ϫ5 mol dm3, (b)] in toluene
6
Na
C6H
11 C6H11
P
H(C6H11)2P Pd
Pd P(C6H11)2H
P
C6H11
C6H11
5
Scheme 3 Reduction of cis-[Pd{P(C6H11)2H}2Cl2]
of [Pd{P(C6H11)2H}2Cl2] the formula [Pd2{µ-P(C6H11)2}Cl{P-
(C6H11)2H}3] 6.
The intense IR band at 2298 cmϪ1 can be assigned to the
stretching of the two P3᎐H and P4᎐H bonds whereas that at
2272 cmϪ1 is ascribable to the P2᎐H stretching. The 31P NMR
spectrum of a toluene solution of complex 6 consists of four
signals centred at δ 253.4, 23.9, 4.0 and Ϫ3.4. That at δ 253.4
is a doublet of triplets and belongs to the bridging phosphorus
coupled to the P3 atom with a constant of 166 Hz and to the
other two phosphorus atoms with a coupling constant of about
45 Hz. The P3 resonance is at δ 23.9 and appears as a broad
doublet, the only coupling constant derivable being that to the
bridging P1 atom (166 Hz). The signal at δ 4.0 is a doublet of
triplets with 3J = 248 and 2J = 45 Hz and is attributable to the P4
atom. The larger constant is due to coupling to the P2 atom, the
smaller one to coupling to the other two phosphorus atoms.
The signal at δ Ϫ3.4 is a doublet of doublets of doublets
[J(P2P4) = 248, J(P1P2) = 45, J(P2P3) = 16 Hz] and is ascribable
to the P2 atom coupled to the other three phosphorus atoms.
The structural characterization of this complex was undertaken
by X-ray diffraction and the results (Fig. 2) indicate that it
contains two palladium atoms bridged by a dicyclohexylphos-
phido group; one is bonded to two terminal dicyclohexylphos-
phines and the second to a dicyclohexylphosphine and to a
chlorine atom.
Fig. 2 Molecular structure of complex 6
scopic features of which indicate the formula [{Pd[µ-P(C6H11)2]-
[P(C6H11)2H]}2] 5. This was first prepared by Leoni et. al.10 by
reaction of P(C6H11)2H with either [Pd2{µ-P(C6H11)2}(µ-η3-
C3H5){P(C6H11)2H}2] or [Pd(η3-C3H5)(cp)] (cp = cyclopentadi-
enyl anion). Since no electronic absorption data were available
on phosphide-bridged palladium() complexes we recorded the
UV/VIS spectrum of 5 in toluene solution, revealing three
bands at 411 (13 300), 297 (sh) and 283 nm (ε 30 200 dm3 molϪ1
cmϪ1) (Fig. 1). Care must be taken to prevent the sodium-
promoted decomposition of 5 into metallic palladium: when
the reaction of [Pd{P(C6H11)2H}Cl2] with a large excess of
sodium (Na :Pd ≈ 12:1) was kept overnight with stirring a
greenish suspension was recovered from which no palladium
complex could be isolated.
When the reduction of [Pd{P(C6H11)2H}2Cl2] was stopped
exactly when the initial suspension became an orange solution,
or, alternatively, using a Pd :Na ratio = 2:3, it was possible to
recover an orange solid the elemental analysis of which gave a
P :Pd :Cl ratio of 4:2:1 and the IR spectrum showed the pres-
ence of two absorptions of relative intensity 2:1 in the P᎐H
stretching region at 2298 and 2272 cmϪ1. Moreover the presence
in the 31P NMR spectrum of a signal centred at δ 253.4 attribut-
able to a bridging phosphide involved in a three-membered ring
allows us to assign to the complex obtained by partial reduction
Selected bond distances and angles are given in Table 1. The
Pd(1)᎐Pd(2) distance, 2.819(2) Å, is consistent with a metal–
metal single bond. It is comparable with that found in the cat-
ionic complex [Pd2(µ-PBut2)(PMe3)4]BF4, 2.834(4) Å,11 in which
five ligands surround the two palladium atoms, and longer than
that in the neutral [{Pd(µ-PBut2)(PBut2H)}2], 2.594(1) Å 8 or
[{Pd[µ-P(C6H11)2][P(C6H11)2(OPh)]}2], 2.620(2) Å.3d This length-
ening of the Pd᎐Pd bond is probably due to the steric hindrance
1356
J. Chem. Soc., Dalton Trans., 1997, Pages 1355–1358

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of the eight cyclohexyl groups almost symmetrically distributed
around the Pd᎐µ-P᎐Pd core. The Pd᎐P length is longer in the
terminally bound ligands than in the bridging one and, prob-
ably due to the different trans influences of the phosphine and
the chlorine atom, the Pd(2)᎐P(1) distance is slightly longer
than that of Pd(1)᎐P(1). A complex analogous to 6, of formula
[Pd2{µ-P(C6H11)2}{P(C6H11)2H}3(CO)]ϩ has been recently pro-
posed as one of the isomerization products of [Pd2(µ-
PBut2){P(C6H11)2H}3(CO)]BF4 in [2H6]acetone solution.12
The UV/VIS spectrum of complex 6 is shown in Fig. 1 and
reveals bands at 443 (22 100), 344 (15 900), 290 (sh) and 282 nm
(ε 21 900 dm3 molϪ1 cmϪ1). Complex 6 could be easily reduced
to 5 by reaction with a slight excess of sodium in toluene
(Scheme 3).
(ca. 4 h) it was filtered and the pale yellow filtrate concentrated
to about 4 cm3. Addition of ethanol (20 cm3) and cooling
at Ϫ30 ЊC afforded pure [Ni{P(C6H11)2H}2(CO)2] as white crys-
tals which were washed with cold ethanol and dried in vacuo.
Yield 0.48 g (70%). The compound is quite air stable in the solid
state, but sensitive in solution, and is soluble in aromatic solv-
ents. M.p. = 75–76 ЊC (Found: C, 61.3; H, 9.2; Ni, 11.15; P,
12.0. C26H46NiO2P2 requires C, 61.1; H, 9.05; Ni, 11.5; P,
12.1%). UV/VIS (toluene, 2.28 × 10Ϫ4 mol dmϪ3): λmax/nm (ε/
dm3 molϪ1 cmϪ1) 294 (5200). IR (Nujol mull): νmax/cmϪ1 2294s,
1984vs, 1924vs, 1448s, 1375m, 1340m, 1292m, 1262s, 1191m,
1178m, 1105m, 1040m, 1000w, 905w, 893w, 850s, 829s, 811s,
730m, 509s, 466s, 436m and 384s. δ(31P-{H}) in C6H5Me: 17.2
(s).
Contrary to the case of nickel, neither [{Pd[µ-P(C6H11)2][P-
(C6H11)2H]}2] nor [Pd2{µ-P(C6H11)2}Cl{P(C6H11)2H}3] reacted
with carbon monoxide under ambient conditions.
Tetracarbonylbis(ì-dicyclohexylphosphido)dinickel(I) 3. Car-
bon monoxide was bubbled with stirring into a toluene solution
(0.30g, 0.33mmol, in 6cm3)of [{Ni[µ-P(C6H11)2][P(C6H11)2H]}2]
at room temperature causing a change to red-brown. Concen-
tration, addition of ethanol and cooling to Ϫ20 ЊC afforded
dark red-brown crystals which were filtered off and character-
ized as [{Ni[µ-P(C6H11)2](CO)2}2]2 (0.13 g, 63% yield). δ(31P-
{H}) in C6H5Me: 329.9 (s).
Experimental
Materials and apparatus
All manipulations were carried out under a pure dinitrogen
atmosphere, using freshly distilled and oxygen-free solvents.
Dicyclohexylphosphine was obtained from Strem, cis-[Ni-
{P(C6H11)2H}2Cl2]13 was synthesized by literature methods, and
cis-[Pd{P(C6H11)2H}2Cl2]14 was prepared in quantitative yield
by reaction of [Pd(PhCN)2Cl2] with 2 equivalents dicyclohexyl-
phosphine in toluene at room temperature.
Samples for melting-point determinations were sealed in
capillary tubes under nitrogen. Infrared spectra were recorded
on a Perkin-Elmer 883 spectrometer, UV/VIS spectra in solu-
tion on a Kontron Uvikon 942 spectrophotometer. Elemental
analysis were carried out by using a Carlo Erba model EA 1108
elemental analyser. The gas analyses (H2) were performed using
a Carlo Erba gas chromatograph equipped with a Chromosorb
102 column connected to a Varian 4270 integrator. The NMR
spectra were recorded on a Varian XL200 spectrometer at 297
K, 31P shifts being measured with respect to external 85%
H3PO4. The evolution of hydrogen during reduction reactions
was assessed by a gas burette (50 cm3) connected to the reaction
vessel.
Bis(ì-dicyclohexylphosphido)bis[(dicyclohexylphosphine)
palladium(I)] 5. A suspension of cis-[Pd{P(C6H11)2H}2Cl2] (1.6
g, 2.79 mmol) and sodium sand (0.5 g, 21.7 mmol) in toluene
(30 cm3) was stirred at room temperature until a red-brown
solution was obtained (about 6 h). The metallic sodium in
excess was filtered out and the solution concentrated in vacuo to
about 5 cm3 and cooled to Ϫ30 ЊC. The dark red crystals
formed on standing overnight were filtered off, washed with
cold hexane and dried in vacuo. Yield 0.60 g (43%). The com-
pound is air sensitive, soluble in aromatic solvents and in thf,
slightly soluble in hexane. M.p. = 151 ЊC (Found: P, 11.9; Pd,
20.85. Calc. for C48H90P4Pd2: P, 12.35; Pd, 21.15%). UV/VIS
(toluene, 4.20 × 10Ϫ5 mol dmϪ3): λmax/nm = (ε/dm3 molϪ1 cmϪ1
411 (13 300), 297 (sh) and 283 (30 200). IR (Nujol mull): νmax
/
cmϪ1 2249vs, 1447vs, 1338s, 1291m, 1260m, 1170vs, 1119s,
1108vs, 1069w, 1042m, 1022m, 1000vs, 923s, 905s, 894vs, 852vs,
825vs, 812vs, 784w, 719s, 512s, 454m, 441s, 393s, 363s and 299w.
δ(31P-{H}) in C6H5Me: 10.8 (t, J = 39, 2 Pt) and 234.6 (t, J = 39
Hz, 2 Pµ) [lit.,10 14.2 (t) and 238.0 (t) with J(P᎐P) 39 Hz, in C6D6].
Preparations
Bis(ì-dicyclohexylphosphido)bis[(dicyclohexylphosphine)-
nickel(I)] 1. A suspension of cis-[Ni{P(C6H11)2H}2Cl2] (1.50 g,
2.85 mmol) and sodium sand (0.33 g, 14.2 mmol) in toluene (20
cm3) was stirred at room temperature until a deep red solution
was obtained (about 1 h) and then for 3 h. In the course of the
reaction a stoichiometric amount (H2 :Ni = 0.5:1) of dihydro-
gen was evolved, as revealed by gas chromatographic analysis.
The filtered solution was concentrated in vacuo to about 3 cm3
and, after addition of hexane (10 cm3), cooled to 20 ЊC. The
dark red crystals which formed on standing (about 48 h) were
filtered off, washed with cold hexane and dried in vacuo (0.8 g,
62% yield). The compound is air sensitive, soluble in aromatic
solvents and in tetrahydrofuran (thf), slightly soluble in hexane
and light petroleum (b.p. 30–50 ЊC). M.p. 166–168 ЊC (Found: C,
63.4; H, 10.1; Ni, 12.7; P, 13.21. C48H90Ni2P4 requires C, 63.5;
H, 10.0; Ni, 12.8; P, 13.65%). UV/VIS (toluene, 1.00 × 10Ϫ4 mol
dmϪ3): λmax/nm (ε/dm3 molϪ1 cmϪ1) 332 (19 500), 370 (14 700)
and 510 (2800). IR (Nujol mull): νmax/cmϪ1 2236vs, 1173s,
1110s, 1001s, 895s, 853s, 720m and 511m. δ(31P-{H}) in
C6H5Me: 16 (t, J = 31, 2 Pt) and 118 (t, J = 31 Hz, 2 Pµ).
Chloro(ì-dicyclohexylphosphido)tris(dicyclohexylphosphine)-
dipalladium(I) 6. A suspension of cis-[Pd{P(C6H11)2H}2Cl2]
(1.21 g, 2.11 mmol) and sodium sand (73 mg, 3.17 mmol) in
toluene (30 cm3) was stirred at 0 ЊC (ice-bath) until a red-orange
solution was obtained (about 5 h). The stirring was prolonged
for about 1 h at room temperature. The filtered solution was
concentrated in vacuo to about 5 cm3 and cooled to Ϫ30 ЊC.
The orange crystals formed on standing (about 7 d) were fil-
tered off, washed with cold hexane and dried in vacuo (0.47 g,
43% yield). The compound is air stable in the solid state but
sensitive in solution, soluble in aromatic solvents and in thf,
slightly soluble in hexane. Decomposition at 231 ЊC (Found: Cl,
3.45; P, 12.05; Pd, 19.95. C48H91ClP4Pd2 requires: Cl, 3.4; P,
11.9; Pd, 20.45%). UV/VIS (toluene, 5.00 × 10Ϫ5 mol dmϪ3):
λmax/nm (ε/dm3 molϪ1 cmϪ1 443 (22 100), 344 (15 900), 290 (sh)
and 282 (21 900). IR (Nujol mull): νmax/cmϪ1 2298s, 2272s,
1376m, 1340m, 1292m, 1264s, 1179s, 1103s, 1043m, 1002s,
929m, 915s, 894s, 852vs, 808vs, 728s, 511m, 471s, 440m and
385s. δ(31P-{H}) in C6H5Me: 253.4 [dt, J(P1P3) = 166,
J(P1P2) = J(P1P4) = 45 Hz, P1 ], 23.9 (br d, J = 166, P3), 4.0 [dt,
µ
J(P2P4) = 248, J(P3P4) = J(P2P4) = 45, P4] and Ϫ3.4 [ddd,
Dicarbonylbis(dicyclohexylphosphine)nickel(0) 2. A suspen-
sion of [Ni{P(C6H11)2H}2Cl2] (0.700 g, 1.33 mmol) and sodium
(0.5 g, 21.7 mmol) in toluene (30 cm3) was vigorously stirred at
room temperature under 1 atm (101 325 Pa) carbon monoxide.
As soon as the red suspension turned into a colourless solution
J(P2P1) = 45, J(P4P2) = 248, J(P3P2) = 16 Hz, P2].
Reduction of complex 6 with sodium. A toluene solution of
complex 6 (300 mg in 8 cm3) was treated with sodium sand (55
mg) and stirred at room temperature. After 3 h the originally
J. Chem. Soc., Dalton Trans., 1997, Pages 1355–1358
1357

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verged with 256 parameters using a statistical weighting scheme
w = 1/[σ2(Fo)] at values of R = 0.092 and RЈ = 0.066 with a
goodness of fit of 1.239.
Table 2 Crystal data and parameters of data collection and refine-
ment for 6
Atomic coordinates, thermal parameters, and bond lengths
and angles have been deposited at the Cambridge Crystallo-
graphic Data Centre (CCDC). See Instructions for Authors,
J. Chem. Soc., Dalton Trans., 1997, Issue 1. Any request to the
CCDC for this material should quote the full literature citation
and the reference number 186/399.
Formula
Mr
Crystal system
Space group
a/Å
b/Å
c/Å
α/Њ
C48H91ClP4Pd2
1040.41
Triclinic
¯
P1 (no. 2)
11.000(9)
13.715(9)
17.916(9)
84.91(5)
76.27(7)
76.45(6)
2551(3)
2
Acknowledgements
β/Њ
γ/Њ
Professor G. Pampaloni is gratefully acknowledged for mag-
netic susceptibility measurements. We thank Consiglio Nazion-
ale delle Ricerche and Ministero dell’Università e della Ricerca
Scientifica e Technologica for financial support.
U/Å3
Z
F(000)
1096
1.354
Dc/g cmϪ3
λ(Mo-Kα)/Å
0.710 73
9.02
ω
µ(Mo-Kα)/cmϪ1
Scan type
References
Absorption correction
Transmission (maximum, minimum)
Measured reflections
Independent reflections
Observed reflections [I > 1.0σ(I)]
Refined parameters
Ra
Numerical
0.94–0.90
12 709
7759
3229
256
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167; P. Mastrorilli, G. Moro, C. F. Nobile and M. Latronico, Inorg.
Chim. Acta, 1992, 192, 183.
2 C. F. Nobile, G. Vasapollo, P. Giannoccaro and A. Sacco, Inorg.
Chim. Acta, 1981, 48, 261.
3 (a) P. E. Garrou, Chem. Rev., 1981, 81, 229; (b) A. J. Carty,
S. A. Maclaughlin and D. Nucciarone, in Phosphorus-31 NMR
Spectroscopy in Stereochemical Analysis, eds. J. G. Verkade and
L. D. Quin, VCH, New York, 1987, p. 559; (c) J. Powell, E. Fuchs,
M. R. Gregg, J. Phillips and M. V. R. Steiner, Organometallics, 1990,
9, 387; (d) M. Sommovigo, M. Pasquali, P. Leoni and U. Englert,
Inorg. Chem., 1994, 33, 2686.
4 H. Schäfer, Z. Naturforsch., Teil B, 1979, 34, 1358.
5 R. A. Jones, A. L. Stuart, J. L. Atwood, W. E. Hunter and R. D.
Rogers, Organometallics, 1982, 1, 1721.
0.092
0.066
RЈb
¹
2

R = Σ Fo| Ϫ |Fc /Σ|Fo|. b RЈ = [Σw(|Fo| Ϫ |Fc|) /Σw|Fo| ] .
a
2
²
orange solution turned deep red. After filtration, crystallization
from toluene–hexane afforded pure 5.
Crystallography
6 R. A. Jones, A. L. Stuart, J. L. Atwood and W. E. Hunter,
Organometallics, 1983, 2, 874.
Compound 6 crystallizes in the form of orange coloured rods.
Owing to the small size of the crystals, a redundant data set was
collected. The intensity data were collected with an Enraf-
Nonius CAD4 diffractometer, equipped with a graphite mono-
chromator. On a specimen of dimensions 0.17 × 0.09 × 0.08
mm with well developed and readily indexable faces, 12 709
reflections were collected at Ϫ70 ЊC in the range 3.0 < θ < 24.0Њ
over the whole diffraction sphere (Ϫ12 < h < 12, Ϫ15 < k < 15,
Ϫ20 < l < 20) which resulted in 7759 unique data after merging
and 3229 observed data with I >1.0σ(I). Crystallographic data
are summarized in Table 2. The structure was solved by direct
methods15 and refined on F with the MOLEN system.16 In the
full-matrix least-squares refinement only the Pd, Cl and P
atoms were assigned anisotropic displacement parameters to
avoid an unsatisfactory ratio between observations and vari-
ables. Carbon atoms were refined isotropically, and hydrogen
atoms placed in idealized positions [C᎐H 0.98 Å, B(H) = 1.3
B(C)] and allowed to ride on their C atoms. Refinement con-
7 R. A. Jones, N. C. Norman, M. H. Seeberger, J. L. Atwood and
W. E. Hunter, Organometallics, 1983, 2, 1629.
8 P. Leoni, M. Sommovigo, M. Pasquali, P. Sabatino and D. Braga,
J. Organomet. Chem., 1992, 423, 263.
9 R. G. Hayter, Inorg. Chem., 1964, 3, 711.
10 P. Leoni, M. Pasquali, T. Beringhelli, G. D’Alfonso and A. P.
Minoja, J. Organomet. Chem., 1995, 488, 39.
11 P. Leoni, M. Pasquali, M. Sommovigo, A. Albinati, F. Lianza,
P. S. Pregosin and H. Rüegger, Organometallics, 1994, 13, 4017.
12 P. Leoni, M. Pasquali, M. Sommovigo, A. Albinati, P. S. Pregosin
and H. Rüegger, Organometallics, 1996, 15, 2047.
13 K. Issleib and G. Doll, Z. Anorg. Allg. Chem., 1960, 305, 1.
14 H. Goldwhite and A. S. Hirschon, Transition Met. Chem., 1977, 2,
144.
15 G. M. Sheldrick, SHELXS 86, Program for the solution of crystal
structures, University of Göttingen, 1986.
16 MOLEN, Molecular Structure Solution Procedure, Enraf-Nonius,
Delft, 1990.
Received 28th October 1996; Paper 6/07334D
1358
J. Chem. Soc., Dalton Trans., 1997, Pages 1355–1358