Reactivity of rhodium(III) complexes containing chelating pentachlorophenyl ligands. Molecular structures of fac-[Rh(C6Cl5)3(py)] and mer-[Rh(C6Cl5)3((t)BuNC)3]

Article abstract of DOI:10.1016/S0020-1693(00)00202-4

The reactions of the octahedral rhodium(III) complexes [Rh(C₆Cl₅)₃] and [Rh(C₆Cl₅)₃Cl]- with neutral monodentate ligands have been studied. With pyridine, triethylphosphine or pyrazole, one of the rhodium-o-chloro bonds of the starting materials is broken and complexes of formula [Rh(C₆Cl₅)₃L] and [Rh(C₆Cl₅)₃C1L]^- are obtained. Carbonylation of [Rh(C₆Cl₅)₃] produces the insertion of CO molecules in two of the Rh-C(aryl) bonds giving the diacyl complex [Rh{C(O)C₆Cl₅}₂(C₆Cl₅)(CO)], while the reaction of [Rh(C₆Cl₅)₃] or [Rh(C₆Cl₅)₃Cl]^- with the strong σ-donor ligand (t)BuNC breaks all the rhodium-o-chloro interactions producing the compound mer-[Rh(C₆Cl₅)₃((t)BuNC)₃]. All the complexes are stable to the air and moisture in the solid state and moderately stable in deoxygenated solutions. The compounds have been studied and characterised by IR, NMR and MS. The crystal structures of fac-[Rh(C₆Cl₅)₃(py)] and mer-[Rh(C₆Cl₅)₃((t)BuNC)₃] have been determined by X-ray diffraction methods. They display distorted octahedral metal environments but, while the pyridine complex shows two C₆Cl₅ groups acting as chelate ligands bonded through the ipso-C atom and one of the o-Cl atoms, the isocyanide complex exhibits all the coordinated ligands acting as monodentate groups. (C) 2000 Elsevier Science S.A.

Full text of DOI:10.1016/S0020-1693(00)00202-4

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Inorganica Chimica Acta 308 (2000) 51–58
Reactivity of rhodium(III) complexes containing chelating
pentachlorophenyl ligands. Molecular structures of
fac-[Rh(C6Cl5)3(py)] and mer-[Rh(C6Cl5)3(tBuNC)3]
Mar´ıa P. Garc´ıa a,*, Ana P. Mart´ınez a, M. Victoria Jime´nez a, Carmen Siurana a,
Luis A. Oro a, Fernando J. Lahoz a, Antonio Tiripicchio b
a Departamento de Qu´ımica Inorga´nica, Instituto de Ciencia de Materiales de Arago´n, Uni6ersidad de Zaragoza-C.S.I.C., 50009 Zaragoza, Spain
b Istituto di Chimica Generale ed Inorganica, Uni6ersita` di Parma, Centro di Studio per la Strutturistica Diffrattometrica del CNR,
Viale delle Scienze 78, 43100 Parma, Italy
Received 10 March 2000; accepted 14 June 2000
Abstract
The reactions of the octahedral rhodium(III) complexes [Rh(C6Cl5)3] and [Rh(C6Cl5)3Cl]− with neutral monodentate ligands
have been studied. With pyridine, triethylphosphine or pyrazole, one of the rhodiumꢀo-chloro bonds of the starting materials is
broken and complexes of formula [Rh(C6Cl5)3L] and [Rh(C6Cl5)3ClL]− are obtained. Carbonylation of [Rh(C6Cl5)3] produces the
insertion of CO molecules in two of the RhꢀCaryl bonds giving the diacyl complex [Rh{C(O)C6Cl5}2(C6Cl5)(CO)], while the
t
reaction of [Rh(C6Cl5)3] or [Rh(C6Cl5)3Cl]− with the strong s-donor ligand BuNC breaks all the rhodiumꢀo-chloro interactions
producing the compound mer-[Rh(C6Cl5)3(tBuNC)3]. All the complexes are stable to the air and moisture in the solid state and
moderately stable in deoxygenated solutions. The compounds have been studied and characterised by IR, NMR and MS. The
crystal structures of fac-[Rh(C6Cl5)3(py)] and mer-[Rh(C6Cl5)3(tBuNC)3] have been determined by X-ray diffraction methods.
They display distorted octahedral metal environments but, while the pyridine complex shows two C6Cl5 groups acting as chelate
ligands bonded through the ipso-C atom and one of the o-Cl atoms, the isocyanide complex exhibits all the coordinated ligands
acting as monodentate groups. © 2000 Elsevier Science S.A. All rights reserved.
Keywords: Crystal structures; Rhodium complexes; Pentachlorophenyl complexes
1. Introduction
oxidation reactions [2b,3] giving anionic or neutral
rhodium(III) complexes with only three or four ligands
around the metal but with octahedral environments. A
relevant structural feature observed in several anionic
and neutral rhodium(III) complexes is the capacity of
the pentachlorophenyl group to act as chelate ligand,
through the formation of secondary bonds between the
o-chlorine atoms of the pentachlorophenyl rings and
the metal centres. This situation arises from the fact
that, in these cases, the apparently non-bonded Rh···o-
Cl distances are somewhat longer than the usual octa-
In the context of our investigations on per-
halogenoaryl derivatives of rhodium and iridium we
recently reported the evidence of the potential of the
C6Cl5 group to stabilise the unusual oxidation state (II)
for these metals. So, we have prepared paramagnetic
mononuclear complexes of rhodium(II) [1] and irid-
ium(II) [2] such as the square-planar monoanions
[Rh(C6Cl5)4]2− and [Ir(C6Cl5)4]2− or the neutral com-
pounds [Rh(C6Cl5)2L2] and [Ir(C6Cl5)2(COD)].
The reactivity of the rhodium(II) compounds has
been studied. As expected, they undergo one-electron
,
hedral rhodiumꢀterminal chloride distance, 2.374 A, [4]
but show values well under the sum of the difficult-to-
determine van der Waals radii of these two atoms.
Similar situations have also been reported for other
pentachlorophenyl complexes of rhodium [1b], iridium
* Corresponding author. Tel.: +34-976-761 149; fax: +34-976-
761 187.
E-mail address: pilarg@posta.unizar.es (M.P. Garc´ıa).
0020-1693/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(00)00202-4

52
M.P. Garc´ıa et al. / Inorganica Chimica Acta 308 (2000) 51–58
[2], platinum [5], chromium [6] and silver [7], and in the
closely related pentafluorophenyl derivatives of
rhodium [8] and silver [7]. Other analogous short halo-
gen–metal interactions have also been observed in re-
lated halocarbon transition metal complexes [9].
Trying to get a better understanding of the nature of
the rhodiumꢀortho-chlorine interactions we carried out
a theoretical study [1b] of the molecular orbital distri-
bution using the Extended Hu¨ckel approach [10]. These
calculations showed the existence of Rhꢀo-Cl bonds
due to the presence of a significant electron density
between the metal centre and the ortho-chlorine atoms.
These secondary bonds, although weaker than normal
covalent bonds, are strong enough to be maintained in
solution, at low temperature, or in reactive processes
involving weak donor solvents and/or ligands. How-
ever, these Rhꢀo-Cl bonds can be broken if the appro-
priated ligands are used. In this paper we describe the
reactions of the rhodium(III) complexes [Rh(C6Cl5)3]
and [Rh(C6Cl5)3Cl]− with several neutral N- or P-
donor ligands as well as the treatment of these com-
pounds with unsaturated molecules, such as CO or
tBuNC.
ment formed by the three ipso-C atoms, and three
ortho-Cl atoms of the C6Cl5 rings in 1, or two ortho-Cl
atoms and one terminal chlorine in 2. To check the
relative strength of these Rhꢀo-Cl bonds we have tried
the reaction of these complexes with several neutral
ligands.
One of these Rhꢀo-Cl bonds is easily broken by the
action of neutral N- or P-donor ligands. So, the reac-
tion of 1 with pyridine (py), triethylphosphine (PEt3) or
pyrazole (Hpz) affords neutral complexes whose analyt-
ical and spectroscopic data are in agreement with the
formulation [Rh(C6Cl5)3L] (L=py, 3; PEt3, 4; Hpz, 5)
(Scheme 1). With these ligands it has not been possible
to obtain [Rh(C6Cl5)3L2] or [Rh(C6Cl5)3L3], even work-
ing with a large excess of L. In the same way, the
anionic complex [PBzPh3][Rh(C6Cl5)3Cl] (2), with two
Rhꢀo-Cl secondary bonds, reacts immediately with the
same neutral ligands (1:1 ratio) giving the anionic com-
plexes [Rh(C6Cl5)3ClL]− (L=py, 6; PEt3, 7; Hpz, 8).
Prolonged treatment or the addition of larger amounts
of these neutral ligands to 2 yields mixtures of the
anionic complexes (6–8), the neutral complexes (3–5)
and the [PBzPh3]Cl salt. The conductivity of the com-
plexes 6–8 in acetone solutions are those expected for
the (1:1) electrolytes [11].
2. Results and discussion
An alternative route to the neutral compounds 3–5
implies the reaction of [Rh(C6Cl5)3Cl]− with AgClO4,
filtration of the AgCl and the [PBzPh3]ClO4 formed,
and addition of the neutral ligands to the solution.
The reported X-ray crystal structures of [Rh(C6Cl5)3]
(1) [3] and [Rh(C6Cl5)3Cl]− (2) [1b] show that the
rhodium atoms lie in a distorted octahedral environ-
Scheme 1.

M.P. Garc´ıa et al. / Inorganica Chimica Acta 308 (2000) 51–58
53
the molecular structure of [Rh(C6Cl5)3(py)] (3) (see
below). It shows that the metal centre is six-coordinate.
The rhodium atom is located in a distorted octahedral
environment formed by three RhꢀC s-bonds from the
C6Cl5 groups, one RhꢀN bond of the pyridine ligand
and two Rhꢀo-Cl secondary bonds involving two or-
tho-chlorine atoms of two C6Cl5 groups.
Interestingly, ligands with a greater steric demand
such as PPh3 or AsPh3 do not undergo similar reactions
and the unchanged starting products are recovered.
Complexes [Rh(C6Cl5)3] and [PBzPh3][Rh(C6Cl5)3Cl]
are also recovered unchanged from solutions after
treatment with H2, CO2, SO2 at ambient temperature
and pressure. Treatment of 1 or 2 with CH2N2 led to
decomposition at room temperature; at low tempera-
ture there is no reaction for complex 1, while 2 loses
[PBzPh3]Cl giving complex 1. However, as shown by IR
spectroscopy, a fast reaction of 1 with CO (1 atm,
20°C) occurs affording the insertion product
[Rh{C(O)C6Cl5}2(C6Cl5)(CO)] (9) (Scheme 2).
The yellow diacyl rhodium(III) complex is easily
identified by two intense IR absorptions at 1555 and
1517 cm−1, i.e. in the region expected for rhodium(III)
acyl complexes [13]. The presence of these two acyl
bands suggests that the two acyl groups are not equiva-
lent. The IR spectrum of 9 also displays a sharp w(CO)
absorption at 2112 cm−1 indicating that the complex
also has a terminal CO group. The 13C NMR spectrum
of complex 9 does not give any information about the
complex due to the low solubility of 9 in the usual
solvents. However, according to the stoichiometry and
the IR spectrum, its structure is probably similar to
that of the reported [1b] anion [Rh{C(O)C6Cl5}2-
(C6Cl5)Cl]− with octahedral geometry around the
rhodium atom and the terminal CO group occupying
the position of the terminal chlorine atom of the related
anion.
Scheme 2.
The analytical and spectroscopic data for complexes
3–8 are in accordance with the proposed formulae. All
of them show the IR absorptions assigned to the C6Cl5
rings [12]; complex 5 also exhibits a sharp w(NꢀH) band
at 3380 cm−1, while for compound 8 the w(NꢀH) is a
broad band at 3450 cm−1; complexes 6–8 also exhibit
a w(RhꢀCl) band at about 250 cm−1. The presence of
1
the neutral ligands is confirmed by the H NMR spec-
tra (CDCl3, 20°C) of the complexes. Three resonances
of relative intensities 2:1:2 in the l 7.2–8.8 ppm region
account for the presence of N-bonded pyridine in com-
plexes 3 and 6. Two well-defined signals in the interval
l 1.23–1.94 ppm, with the appropriated multiplicity
and relative intensities, characterise the bonding of PEt3
in 4 and 7. Complex 5 exhibits the NꢀH signal at l 10.4
(br, 1H) ppm, together with those of the Hpz ring at l
7.78 [m, 2H, H(3) and H(5)] and 6.46 [m, 1H, H(4)]
ppm. Compound 8 shows the NꢀH signal as a very
broad band at about 14 ppm, while the protons of the
Hpz ring appear overlapped with that of the [PBzPh3]
cation. The 31P{1H} NMR spectra of 4 and 7 give a
very broad signals at room temperature, while at
−55°C the resonances become doublets at l 3.4 ppm
with a 1J (Rh–P)=88.2 Hz for complex 4 and at l 1.62
Additionally, the reactions of complexes 1 and 2 with
tert-butyl isocyanide have been studied. Organic iso-
cyanides, RNC, are isoelectronic with CO and exhibit
similar bonding capabilities, although they are regarded
as better s-donors and somewhat less efficient p-accep-
tors [14]. Besides, CO and RNC are closely analogous
in their reactions: for instance, both are able to undergo
insertion into MꢀC s bonds. However, this insertion
has not been observed for the reaction of 1 or 2 with
t
the strong s-donor ligand BuNC. In this case, all the
Rhꢀo-Cl and RhꢀCl bonds are broken and the mer-
[Rh(C6Cl5)3(tBuNC)3] (10) complex is obtained. With
complex 2, [PBzPh3]Cl is lost during the reaction. The
IR spectrum of 10 shows two w(CꢁNR) broad bands at
2237 and at 2214 cm−1 typical of terminal isocyanides
[15]. No absorptions in the 1600 cm−1 region charac-
teristic of w(CN) double bond are found, which indi-
cates that the commonly observed insertion [16] of the
isocyanide into the RhꢀC bond to give the iminoacyl
1
ppm with a J (Rh–P)=87.9 Hz for compound 7. This
behaviour suggests that in solution, at low temperature,
there are some dynamic processes, most probably in-
volving the breaking and formation of the secondary
Rhꢀo-Cl bonds. The definitive characterisation of the
spatial distribution of the ligands around the rhodium
atom and their bonding situation in these complexes
have been elucidated by an X-ray structural analysis of

54
M.P. Garc´ıa et al. / Inorganica Chimica Acta 308 (2000) 51–58
Table 1
derivative has not taken place. On the other hand, the
1H NMR of compound 10 [l 1.4, s (18 H) and 1.5, s (9
H) ppm] shows that the isocyanide groups are in a 2:1
ratio so the complex should adopt the mer geometry.
This was confirmed by a single-crystal X-ray structure
analysis of 10.
a
,
Selected bond lengths (A) and angles (°) for [Rh(C6Cl5)3pyl] (3)
RhꢀCl(1)
2.611(7)
3.840(9)
3.491(8)
2.20(3)
2.03(4)
1.80(3)
1.69(3)
2.602(9)
3.887(9)
3.417(7)
1.94(3)
2.09(2)
1.738(8)
2.557(7)
3.857(9)
3.515(8)
2.19(3)
2.01(3)
1.80(2)
1.79(2)
2.613(9)
3.853(8)
3.338(8)
1.99(3)
2.06(3)
1.723(8)
Rh(1)···Cl(5)
Rh(1)···Cl(11)
RhꢀN(1)
RhꢀC(7)
Cl(1)ꢀC(2)
Cl(6)ꢀC(8)
RhꢀCl(6)
Rh(1)···Cl(10)
Rh(1)···Cl(15)
RhꢀC(1)
2.1. Molecular structures of [Rh(C6Cl5)3(py)] (3) and
[Rh(C6Cl5)3(tBuNC)3] (10)
The crystal structures of 3 and 10 have been studied
by single-crystal X-ray crystallography. The respective
molecular structures—including conventional images
of the displacement parameters—are presented in Figs.
1 and 2. Selected bond distances and angles are col-
lected in Tables 1 and 2. As usual in rhodium(III)
chemistry, both complexes exhibit distorted octahedral
RhꢀC(13)
Mean ClꢀC b
Cl(1)ꢀRhꢀCl(6)
Cl(1)ꢀRhꢀN(1)
Cl(1)ꢀRhꢀC(1)
Cl(1)ꢀRhꢀC(7)
Cl(1)ꢀRhꢀC(13)
Cl(6)ꢀRhꢀN(1)
Cl(6)ꢀRhꢀC(1)
Cl(6)ꢀRhꢀC(7)
Cl(6)ꢀRhꢀC(13)
N(l)ꢀRhꢀC(1)
N(1)ꢀRhꢀC(7)
N(1)ꢀRhꢀC(13)
C(1)ꢀRhꢀC(7)
C(1)ꢀRhꢀC(13)
C(7)ꢀRhꢀC(13)
RhꢀCl(1)ꢀC(2)
RhꢀCl(6)ꢀC(8)
RhꢀC(1)ꢀC(2)
RhꢀC(1)ꢀC(6)
RhꢀC(7)ꢀC(8)
RhꢀC(7)ꢀC(12)
RhꢀC(13)ꢀC(14)
RhꢀC(13)ꢀC(18)
99.4(3)
89.0(6)
69.8(9)
81.8(8)
168.6(7)
101.5(7)
166.6(9)
68.7(10)
88.0(8)
86.7(12)
165.1(12)
98.1(10)
101.0(14)
101.5(11)
92.9(11)
74.8(10)
76.5(11)
107(2)
93.9(3)
88.5(7)
69.8(9)
81.4(8)
175.8(9)
106.3(7)
160.0(9)
67.9(8)
88.9(8)
85.4(11)
167.8(10)
93.7(11)
97.3(11)
106.8(12)
96.9(10)
75.2(9)
76.1(9)
105(2)
146(2)
102(2)
145(2)
126(2)
139(2)
107.1(18)
146(2)
123(2)
122(2)
117(2)
a Second value corresponds to the second independent molecule.
b Mean bond distance over all non-coordinated chlorine atoms.
Fig. 1. Molecular structure of one of the two independent molecules
of the complex fac-[Rh(C6Cl5)3(py)] (3) together with the labelling
system.
environments, though they have a different number of
ligands.
Complex 3 has four ligands, with the rhodium atom
in a heavily distorted octahedral environment due to
the chelating bonding mode of two C6Cl5 ligands. The
metal coordination sphere is completed with one
monodentate C6Cl5 group and a pyridine ligand. The
major deviation from a perfect octahedron is caused by
the two four-member metallacycles which exhibit small
bite ClꢀRhꢀC angles (69.3(7)°). The phenyl rings are
tilted to permit the approach of the ortho chlorine
atoms to the metal centre and this fact can be visualised
with the angles around the Cipso atoms (C(1) and
C(7), see Table 1) or with the value of the angles
between the RhꢀCipso and CorthoꢀCpara directions (159–
161(2)°). This chelating coordination mode of the pen-
tachlorophenyl ligands is the origin of the chirality of
the molecule, and has been previously reported for the
rhodium complexes [Rh(C6Cl5)4]−, [Rh(C6Cl5)3Cl]−,
Fig. 2. Molecular representation of complex mer-[Rh(C6Cl5)3-
(tBuNC)3] (10) including the numbering scheme used.

M.P. Garc´ıa et al. / Inorganica Chimica Acta 308 (2000) 51–58
55
[Rh{COC6Cl5}2(C6Cl5)Cl]− [1b] and [Rh(C6Cl5)3] [3].
Both enantiomers are present in the asymmetric part of
the crystal as two independent molecules.
been observed in other related compounds such as
[Rh(C6Cl5)4]2− [1b], [Ir(C6Cl5)4]2− [2b], [Pt(C6Cl5)4]−
[17].
The angles around the isocyanide nitrogen atoms are
in the usual range for sp hybridisation (168.0–
176.8(3)°). The RhꢀC distances are clearly affected by
the structural trans effect: the three pentachlorophenyl
ligands exhibit two similar RhꢀC distances (2.194 and
The lengths Rhꢀo-Cl observed are, as expected, sig-
nificantly longer than the usual terminal Rh(III)ꢀCl
distances, but short enough to be considered secondary
,
bonds (2.584(5) and 2.607(7) A for Cl(1) and Cl(6),
respectively).
,
2.173(3) A), both trans to a phenylic C atom, while the
Complex 10 has three monodentate C6Cl5 and three
third one, trans to the tBuNC, is clearly shorter:
t
terminal BuNC ligands conforming an octahedral co-
,
2.111(3) A.
ordination around the rhodium metal in a mer configu-
ration. The three perhalophenyl rings adopt
a
propeller-like structure to reduce the interatomic repul-
sive interactions between the o-chlorine atoms; the di-
hedral angles between the phenyl rings and the metal
coordination plane including the Cipso carbons are in
the range 47.08(8)–50.37(9)°. This helix disposition has
3. Experimental
C, H and N analyses, and IR spectra (in CH2Cl2
solution or Nujol suspension between polyethylene
sheets) were performed as described elsewhere [1a]. The
NMR measurements were carried out on a Varian
Gemini 2000 spectrometer using commercial probes.
Mass spectra were measured in a VG Autospec double-
focusing mass spectrometer operating in the negative
mode for anionic species and in the positive mode for
neutral complexes. Ions were produced with the stan-
dard Cs+ gun at ca. 30 kV; 3-nitrobenzyl alcohol
(NBA) was used as matrix; high-resolution FAB spec-
tra are in accordance with the simulated isotopic pat-
tern distribution. All reactions were carried out under a
nitrogen or argon atmosphere using standard Schlenk-
line techniques. The starting rhodium(III) compounds
[Rh(C6Cl5)3] and [PBzPh3][Rh(C6Cl5)3Cl] were prepared
as described in the literature [3,16]. Diethyl ether, THF,
CH2Cl2 and hexane were distilled under nitrogen from
the appropriate drying agents.
Table 2
t
,
Selected bond lengths (A) and angles (°) for [Rh(C6Cl5)3( BuNC)3]
(10)
Rh(1)ꢀC(1)
Rh(1)ꢀC(7)
Rh(1)ꢀC(13)
Rh(1)ꢀC(19)
Rh(1)ꢀC(24)
Rh(1)ꢀC(29)
N(1)ꢀC(19)
N(1)ꢀC(20)
N(2)ꢀC(24)
N(2)ꢀC(25)
N(3)ꢀC(29)
N(3)ꢀC(30)
2.194(3)
2.111(3)
2.173(3)
1.989(3)
1.991(3)
2.027(3)
1.139(4)
1.469(4)
1.149(4)
1.469(4)
1.147(4)
1.475(4)
C(1)ꢀRh(1)ꢀC(7)
C(1)ꢀRh(1)ꢀC(13)
C(1)ꢀRh(1)ꢀC(19)
C(1)ꢀRh(1)ꢀC(24)
C(1)ꢀRh(1)ꢀC(29)
C(7)ꢀRh(1)ꢀC(13)
C(7)ꢀRh(1)ꢀC(19)
C(7)ꢀRh(1)ꢀC(24)
C(7)ꢀRh(1)ꢀC(29)
C(13)ꢀRh(1)ꢀC(19)
C(13)ꢀRh(1)ꢀC(24)
C(13)ꢀRh(1)ꢀC(29)
C(19)ꢀRh(1)ꢀC(24)
C(19)ꢀRh(1)ꢀC(29)
C(24)ꢀRh(1)ꢀC(29)
Rh(1)ꢀC(1)ꢀC(2)
Rh(1)ꢀC(1)ꢀC(6)
Rh(1)ꢀC(7)ꢀC(8)
Rh(1)ꢀC(7)ꢀC(10)
Rh(1)ꢀC(13)ꢀC(14)
Rh(1)ꢀC(13)ꢀC(18)
Rh(1)ꢀC(19)ꢀN(1)
Rh(1)ꢀC(24)ꢀN(2)
Rh(1)ꢀC(29)ꢀN(3)
C(19)ꢀN(1)ꢀC(20)
C(24)ꢀN(2)ꢀC(25)
C(29)ꢀN(3)ꢀC(30)
91.29(11)
177.10(12)
97.85(12)
84.11(12)
89.66(12)
91.43(12)
93.56(12)
91.84(12)
178.03(12)
80.98(12)
96.80(12)
87.59(12)
174.20(12)
84.59(12)
89.98(12)
124.1(2)
122.8(2)
124.0(2)
122.6(2)
122.7(2)
124.3(2)
168.0(3)
174.0(3)
175.6(3)
3.1. Preparation of [Rh(C6Cl5)3(L)] (L=py, 3; PEt3, 4;
Hpz, 5)
To dichloromethane (15 ml) solutions of 1 (0.100 g,
0.12 mmol) pyridine (20 ml, 0.25 mmol), triethylphos-
phine (40 ml, 0.27 mmol) and pyrazole (17 mg, 0.25
mmol) were added. The mixtures were stirred for 20
min; partial evaporation of the solvent and addition of
methanol led to the precipitation of compounds 3–5 as
yellow solids which were filtered off, washed with di-
ethyl ether and vacuum dried. Data for 3: Anal. Calc.
for C23H5Cl15NRh: C, 29.70; H, 0.54; N, 1.51. Found:
C, 30.10; H, 0.50; N, 1.53%. IR (Nujol, cm−1):
w(C6Cl5): 1342, 1325, 1313, 1285; 815 (X-sensitive) [12],
678 [w(RhꢀC)]. 1H NMR (20°C, CDCl3), l ppm, 8.8 (m,
2H, o-H), 7.8 (tm, 1H, p-H), 7.4 (m, 2H, m-H). Data
for 4: Anal. Calc. for C24H15Cl15PRh: C, 29.75; H, 1.56.
Found: C, 29.41; H, 1.45%. IR (Nujol, cm−1):
w(C6Cl5): 1340, 1330, 1310, 1305, 1285; 680 [w(RhꢀC)].
1H NMR (20°C, CDCl3), l ppm, 1.54 (m, 6H, CH2),
1.11 (m, 9H, CH3). 31P{1H} NMR (20°C, CDCl3), l
176.8(3)
172.9(3)
176.5(3)

56
M.P. Garc´ıa et al. / Inorganica Chimica Acta 308 (2000) 51–58
1
ppm, 1–5 (br); (−55°C, CDCl3): 3.45 (d, J(P–Rh)=
88.2 Hz). MS (FAB) m/e 968 (M+, 35), 719 (M−
C6Cl5, 18). Data for 5: Anal. Calc. for C21H4Cl15N2Rh:
C, 27.45; H, 0.44; N, 3.05. Found: C, 27.27; H, 0.48, N,
3.22%. IR (Nujol, cm−1): w(NꢀH): 3425; w(C6Cl5):
1340, 1312, 1283; 690 [w(RhꢀC)]. 1H NMR (20°C,
CDCl3), l ppm, 10.4 (br, 1H, NH, Hpz), 7.78 (m, 2H,
H(3) and H(5), Hpz), 6.46 (m, 1H, H(4), Hpz).
ether and vacuum dried. Yield: 90%. Anal. Calc. for
C21Cl15O3Rh: C, 26.98. Found: C, 26.85%. IR (Nujol,
cm−1): w(CO) (cm−1): 2112, 1555, 1517; w(C6Cl5)
(cm−1): 1358, 1337, 1317, 1290, 1273. MS (FAB) m/e
907 (M−CO, 45), 601 [Rh(C6Cl5)2, 100].
3.4. Preparation of [Rh(C6Cl5)3(tBuNC)3] (10)
To a solution of [Rh(C6Cl5)3] (200 mg, 0.235 mmol)
t
3.2. Preparation of (PBzPh3)[Rh(C6Cl5)3Cl(L)] (L=py,
6; PEt3, 7; Hpz, 8)
in CH2Cl2 (15 ml) was added BuNC (80 ml, 0.707
mmol). The mixture was stirred for 30 min. Evapora-
tion to 1 ml and addition of pentane (10 ml) led to a
pale yellow solid which was filtered off, washed with
pentane and vacuum dried. Yield 78%. When
(PBzPh3)[Rh(C6Cl5)3Cl] is used as starting product, the
To orange solutions of (PBzPh3)[Rh(C6Cl5)3Cl] (150
mg, 0.121 mmol) in CH2Cl2 (15 ml) were added the
ligands (py, 0.0097 ml, 0.121 mmol; PEt3, 0.0143 ml,
0.121 mmol; Hpz, 8.23 mg, 0.121 mmol). For L=PEt3
or Hpz the colour of the solutions changed immediately
from orange to yellow. After 30 min stirring, the solu-
tions were concentrated to 1 ml; the addition of light
petroleum ether (5 ml) caused the precipitation of the
complexes as microcrystalline solids, which were filtered
off, washed with pentane and dried. Data for 6: Or-
ange; yield 83%. Anal. Calc. for C48H27Cl16NPRh: C,
43.71; H, 2.06; N, 1.06. Found: C, 43.35; H, 2.13; N,
1.16%. IR (Nujol, cm−1): w(C6Cl5) (cm−1): 1330, 1305,
i
procedure is similar but PrOH is used instead of pen-
tane so the [PBzPh3]Cl remains in solution. Anal. Calc.
for C33H27Cl15N3Rh: C, 36.06; H, 2.47; N, 3.82. Found:
C, 36.77; H, 1.77; N, 3.08%. IR (Nujol, cm−1): w(NꢁC)
(cm−1): 2237 w and 2214 s; w(C6Cl5) (cm−1): 1323,
1317, 1300; 851 and 820 (X-sensitive), 671 [w(RhꢀC)].
1H NMR (20°C, CDCl3), l ppm, 1.4 (s, 18H), 1.5 (s,
9H). MS (FAB) m/e 1064 (M−Cl, 15), 981 (M−Cl−
tBuNC, 10), 767 (Rh(C6Cl5)2(tBuNC)2, 65).
1
1280; 690 [w(RhꢀC)]; w(RhꢀCl): 250. H NMR (20°C,
3.5. Crystal structure determination of complexes
[Rh(C6Cl5)3(py)] (3) and [Rh(C6Cl5)3(tBuNC)3] (10)
CDCl3), l ppm, 8.7 (m, 2H, o-H), 7.5 (tm, 1H, p-H),
7.2 (m, 2H, m-H). \M (acetone, C=5.02×10−4 mol
l
−1): 94 V−1 cm2 mol−1. Data for 7: Yellow; yield
A summary of crystal data and refinement parame-
ters is reported in Table 3. Suitable crystals for the
X-ray diffraction studies were obtained by slow diffu-
sion of hexane into a CH2Cl2 solution of complex 3 and
by slow solvent evaporation of a dichloromethane solu-
tion of 10. In the case of 3, several crystals of different
sizes were checked; all exhibited very weak and broad
reflections and eventually a weak crystal with the
strongest intensities was selected. Diffracted data were
collected on a Philips PW 1100 (3) or a CCD Siemens-
SMART (10) diffractometer equipped with graphite-
monochromated Mo Ka radiation, and using the ꢀ/2q
scan method (3) or ꢀ rotations with narrow frames
(0.3°) (10). Data was collected only to 2q548° for 3 as
no measurable intensities were observed above this
angular value. During data collection instrument and
crystal stability was evaluated from measurement of
equivalent or standard reflections at different measur-
ing times; no important variations were observed. Both
sets of data were corrected for Lorentz and polarisation
effects, and semiempirical [18a] (for 3; transmission
factor 0.642 and 0.817) or empirical absorption correc-
tions [18b] (for 10, min. and max. transmission factor
0.667 and 0.773) were also applied.
73%. Anal. Calc. for C49H37Cl16P2Rh: C, 43.34; H, 2.75.
Found: C, 44.02; H, 2.45%. IR (Nujol, cm−1):
w(C6Cl5): 1335, 1310, 1275; 685, 675 [w(RhꢀC)];
1
w(RhꢀCl): 270. H NMR (20°C, CDCl3), l ppm, 7.8–
2
7.0 (20H, H aromatic), 5.34 (d, 2H, CH2 benzyl, JPH
13 Hz), 1.94 (m, 6H, CH2), 1.23 (m, 9H, CH3). 31P{1H}
NMR (20°C, CDCl3), l ppm, 23.6 (s, 1P, PBzPh3),
2.3–3.1 (br, PEt3); (−55°C, CDCl3): 22.5 (s, 1P,
1
PBzPh3), 1.62 (d, JPRh=87.9 Hz). MS (FAB) m/e 968
[Rh(C6Cl5)3(PEt3), 15], 885 [Rh(C6Cl5)3Cl, 50]. \M (ace-
tone, C=5.0×10−4 mol l−1): 119 V−1 cm2 mol−1
.
Data for 8: Yellow, yield 90%. Anal. Calc. for
C46H26Cl16N2PRh: C, 42.24; H, 2.00; N, 2.14. Found:
C, 43.07; H, 1.86, N, 2.22%. IR (Nujol, cm−1):
w(C6Cl5): 1335, 1320, 1305, 1290; 685 [w(RhꢀC)];
1
w(RhꢀCl): 245. H NMR (20°C, CDCl3), l ppm, 14 (br,
1H, NH, Hpz), 7.8–6.9 (22H, H aromatic, H(3) and
H(5), Hpz), 6.23 (m, 1H, H(4), Hpz), 5.03 (d, 2H, CH2
benzyl, 2JPH 14.3 Hz). \M (acetone, C=5.0×10−4 mol
l
−1): 107 V−1 cm2 mol−1
.
3.3. Preparation of [Rh{C(O)C6Cl5}2(C6Cl5)(CO)] (9)
Through a CH2Cl2 (15 ml) solution of 1 (0.100 g,
0.12 mmol) CO (1atm, room temperature) was bubbled
for 15 min; complex 9 was formed as a yellow solid
which was separated by filtration, washed with diethyl
Both structures were solved by Patterson method
SHELXS-86) [19] and completed by successive difference
Fourier syntheses. Two crystallographically indepen-
dent—but chemically enantiomeric—molecules were
(

M.P. Garc´ıa et al. / Inorganica Chimica Acta 308 (2000) 51–58
57
Table 3
for anomalous dispersion, were used as implemented in
the refinement programs.
Crystallographic data for [Rh(C6Cl5)3py] (3) and [Rh(C6Cl5)3-
(tBuNC)3] (10)
3
10
4. Supplementary material
Empirical
formula
C23H5Cll5NRh
C33H27Cl15N3Rh
Crystallographic data for the structural analysis has
been deposited with the Cambridge Crystallographic
Data Centre, CCDC 145329 and 145330. Copies of this
information may be obtained free of charge from: The
Director, CCDC, 12 Union Road, Cambridge, CB2
1EZ, UK (fax: +44-1223-336033; e-mail: deposit@
ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
Crystal colour
and habit
Crystal size
(mm)
yellow prismatic
block
0.15×0.20×0.25
colourless prismatic
block
0.26×0.22×0.20
Formula weight 930.00
1100.24
Crystal system
Space group
Temperature
(K)
monoclinic
P2l/a (no. 14)
293(1)
monoclinic
P21/n (no. 14)
160(1)
Unit cell dimensions
,
a (A)
18.913(4)
16.971(3)
21.197(5)
115.41(2)
6145(3)
8
2.010
1.881
3–24
−215h521,
05k519,
05l524
10 272
9.8808(7)
11.6928(9)
36.281(3)
93.914(2)
4181.9(5)
4
Acknowledgements
,
b (A)
,
c (A)
i (°)
V (A )
We thank the DGES (Direccion General de Ense-
n˜anza Superior e Investigacion Cientifica, project PB98-
1598) and bilateral CSIC-CNR joint programme for
financial support. We also thank Professor W. Clegg
and Dr A. Edwards for their useful help on X-ray data
collection.
3
,
Z
Dcalc (g cm−3
)
1.747
1.398
v (mm−1
)
2q Range (°)
Index ranges
1.8–28.4
−125h512,
−145k515,
265l546
25 462
Collected
reflections
Unique
References
9615 (Rint=0.0512) 9626 (Rint=0.0286)
reflections
Data/restraints/ 3684/0/481
parameters
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9626/0/479
R1(F)
0.0583
0.0431
[F2\2|(F2)] a
Rw
S
0.0712 b
1.007 d
0.0840 c
1.265 e
a R(F)=S(ꢀFoꢀ−ꢀFcꢀ)/SꢀFoꢀ for 3684 (3) and 8521 (10) observed
reflections.
b Rw=S(w(ꢀFoꢀ−ꢀFcꢀ)2/SwꢀFoꢀ
with
w=0.8981
(|2(Fo)+
2
0.0103(Fo)2)−1
.
c Rw(F)2=(S[w(Fo2−F2c)2]/Sw(F2o)2]1/2 with
(0.0167P)2+6.4483P] (P=(Fo2+2F2c/3).
w
−1=[|2 (Fo)2+
d S=[S(ꢀFoꢀ−ꢀFcꢀ)2) /(n−p)]1/2 for observed data.
e S=[S[w(Fo2−Fc2)2]/(n−p)]1/2 for all data (n=number of reflec-
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atoms in 3 and for all non-hydrogen atoms in 10.
Hydrogen atoms were included in calculated positions
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and displacement parameters. Refinements were carried
out by full-matrix least-squares on F (SHELX-76) [20] (3)
or F2 (SHELXL-97) [21] (10). Final agreement factors are
collected in Table 3. Residual peaks in the final differ-
ence map were 1.17 and −1.02 (3), and 0.51 and
−3
,
−0.63 e A
(10). Atomic scattering factors, corrected

58
M.P. Garc´ıa et al. / Inorganica Chimica Acta 308 (2000) 51–58
Chem. C10 (1993) 455. (d) A. Garc´ıa-Bernabe´, P. Lahuerta,
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.