Diphosphinito-bridged ruthenium(II) and rhodium(III) complexes with stereogenic metal centers

Article abstract of DOI:10.1016/S0020-1693(99)00174-7

The bis-4-phosphinito ligands [(p-Ph₂POC₆H₄)₂X] (X=O, 1; X=CMe₂, 2; X=S, 3) react with [Ru(η⁶-p-cymene)Cl₂]₂ to form the binuclear complexes {[Ru(η⁶-p-cymene)Cl₂]₂[μ-(p-Ph ₂POC₆H₄)₂X]} (X=O, 4; X=CMe₂, 5; X=S, 6) in good yields as red air stable solids. The crystal structures of 4-6 were determined by X-ray analysis. In acetonitrile and in the presence of AgPF₆ (1:1 equiv. with respect to Ru), complexes 4-6 undergo substitution to yield the cationic complexes {[Ru(η⁶-p-cymene)Cl(CH₃CN)] ₂[μ-(p-Ph₂POC₆H₄) ₂X]}[PF₆]₂ (X=O, 7; X=CMe₂, 8; X=S, 9), whose stability in solution is very limited. The acetonitrile ligand in complexes 7-9 can be easily replaced by carbon monoxide; the products {[Ru(η⁶-p-cymene)Cl(CO)]₂[μ-(p-Ph ₂POC₆H₄)₂X]}[PF₆] ₂ (X=O, 10; X=CMe₂, 11; X=S, 12) can only be detected in solution under a CO atmosphere and have limited stability. The reaction of [Rh(η⁵-C₅Me₅)Cl₂]₂ with ligands 1-3 results in the formation of the complexes {[Rh(η⁵-C₅Me₅)Cl₂] ₂[μ-(p-Ph₂POC₆H₄)₂X]} (X=O, 13; X=CMe₂, 14; X=S, 15), which have been isolated as red-orange air stable solids. The cationic complexes {[Rh(η⁵-C₅Me₅)Cl(CH₃CN)] ₂[μ-(p-Ph₂POC₆H₄) ₂X]}[PF₆]₂ (X=O, 16; X=CMe₂, 17; X=S, 18), in which the metal atoms are stereogenic centers, have been obtained from the corresponding complexes 13-15, by treatment in CH₃CN with AgPF₆, and have been characterized only in solution by ³¹P{¹H} NMR spectra and conductivity measurements. On reaction with ligands 1-3, [Rh(η⁵-C₅H₅)(CO)₂] was converted into the binuclear phosphinito-bridged complexes {[Rh(η⁵-C₅H₅)(CO)] ₂[μ-(p-Ph₂POC₆H₄)₂X]} (X=O, 19; X=CMe₂, 20; X=S, 21). The reactions of the binuclear complex {[Rh(η⁵-C₅H₅)(CO)] ₂[μ-(p-Ph₂POC₆H₄)₂S]} (21) with CH₃I, S-(+)-1-bromo-2-methylbutane and racemic PhCH(CH₃)Br were also studied. The products were the corresponding acyl derivatives. The reaction of 21 with neat CH₃I easily afforded the complex {[Rh(η⁵-C₅H₅)(COCH₃)I] ₂[μ-(p-Ph₂POC₆H₄)₂S]} (23), whose structural determination by X-ray analysis is also reported.

Full text of DOI:10.1016/S0020-1693(99)00174-7

www.elsevier.nl/locate/ica
Inorganica Chimica Acta 292 (1999) 84–95
Diphosphinito-bridged ruthenium(II) and rhodium(III) complexes
with stereogenic metal centers
Carmela G. Arena, Daniela Drago, Manuela Panzalorto, Giuseppe Bruno,
Felice Faraone *
Dipartimento di Chimica Inorganica, Chimica Analitica e Chimica Fisica dell’Uni6ersita`, Salita Sperone 31, Villaggio S. Agata,
I-98166 Messina, Italy
Received 10 December 1998; accepted 6 April 1999
Abstract
The bis-4-phosphinito ligands [(p-Ph2POC6H4)2X] (X=O, 1; X=CMe2, 2; X=S, 3) react with [Ru(h6-p-cymene)Cl2]2 to form
the binuclear complexes {[Ru(h6-p-cymene)Cl2]2[m-(p-Ph2POC6H4)2X]} (X=O, 4; X=CMe2, 5; X=S, 6) in good yields as red
air stable solids. The crystal structures of 4–6 were determined by X-ray analysis. In acetonitrile and in the presence of AgPF6
(1:1 equiv. with respect to Ru), complexes 4–6 undergo substitution to yield the cationic complexes {[Ru(h6-p-
cymene)Cl(CH3CN)]2[m-(p-Ph2POC6H4)2X]}[PF6]2 (X=O, 7; X=CMe2, 8; X=S, 9), whose stability in solution is very limited.
The acetonitrile ligand in complexes 7–9 can be easily replaced by carbon monoxide; the products {[Ru(h6-p-cymene)Cl(CO)]2[m-
(p-Ph2POC6H4)2X]}[PF6]2 (X=O, 10; X=CMe2, 11; X=S, 12) can only be detected in solution under a CO atmosphere and
have limited stability. The reaction of [Rh(h5-C5Me5)Cl2]2 with ligands 1–3 results in the formation of the complexes
{[Rh(h5-C5Me5)Cl2]2[m-(p-Ph2POC6H4)2X]} (X=O, 13; X=CMe2, 14; X=S, 15), which have been isolated as red–orange air
stable solids. The cationic complexes {[Rh(h5-C5Me5)Cl(CH3CN)]2[m-(p-Ph2POC6H4)2X]}[PF6]2 (X=O, 16; X=CMe2, 17; X=S,
18), in which the metal atoms are stereogenic centers, have been obtained from the corresponding complexes 13–15, by treatment
in CH3CN with AgPF6, and have been characterized only in solution by 31P{1H} NMR spectra and conductivity measurements.
On reaction with ligands 1–3, [Rh(h5-C5H5)(CO)2] was converted into the binuclear phosphinito-bridged complexes {[Rh(h5-
C5H5)(CO)]2[m-(p-Ph2POC6H4)2X]} (X=O, 19; X=CMe2, 20; X=S, 21). The reactions of the binuclear complex {[Rh(h5-
C5H5)(CO)]2[m-(p-Ph2POC6H4)2S]} (21) with CH3I, S-(+)-1-bromo-2-methylbutane and racemic PhCH(CH3)Br were also
studied. The products were the corresponding acyl derivatives. The reaction of 21 with neat CH3I easily afforded the complex
{[Rh(h5-C5H5)(COCH3)I]2[m-(p-Ph2POC6H4)2S]} (23), whose structural determination by X-ray analysis is also reported. © 1999
Elsevier Science S.A. All rights reserved.
Keywords: Crystal structures; Ruthenium complexes; Rhodium complexes; Diphosphinito-bridged complexes
discussed previously, particularly in arene- and cyclo-
pentadienyl-ruthenium(II) and pentamethylcyclopen-
tadienyl-rhodium(III) complexes. In this context, of
particular relevance are the stereochemical studies per-
formed by Consiglio and Morandini [1] on h5-cyclopen-
tadienylruthenium(II) complexes containing the chiral
1. Introduction
Three-legged piano stool complexes containing a
stereogenic metal are very important species as they
may undergo simple reactions, such as ligand substitu-
tion and migratory insertion, which could provide de-
tailed information regarding the role that metal
stereocenters play in the course of stereoselective trans-
formations. The role of the stereogenic metal has been
ligand
prophos
(prophos=R-1,2-propanediylbis-
(diphenylphosphine)). The chemistry of h6-arene
analogs has been less extensively studied, although
Mashima et al. [2] reported several catalytic studies
using h6-areneruthenium(II) complexes containing the
* Corresponding author. Tel.: +39-090-676 5717; fax: +39-090-
393 756.
binap
(binap=2,2%-bis(diphenylphosphino)-1,1%-bi-
naphthyl) ligand. Several detailed studies, particularly
E-mail address: faraone@chem.unime.it (F. Faraone)
0020-1693/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(99)00174-7

C.G. Arena et al. / Inorganica Chimica Acta 292 (1999) 84–95
85
by Brunner et al. [3], consider the factors which confer
an appreciable configurational stability on the metal
atom.
A literature search reveals that the majority of the
stereochemical investigations on chiral-at-metal half-
sandwich species have concentrated on mononuclear
complexes. Few examples of chiral-at-metal half-sand-
wich binuclear complexes of ruthenium(II) and rhodium-
(III) with one bridging diphosphine ligand have been
reported [4].
2.1.2. (p-Ph2POC6H4)2CMe2 (2)
This compound was obtained by an analogous proce-
dure to 1, as a white solid, starting from 4,4%-isopropyl-
idendiphenol (2.5 g, 10.9 mmol). Yield: 95%. Anal.
Calc. for C39H34O2P2: C, 78.51; H, 5.74. Found: C,
78.72; H, 5.44%. 1H NMR (C6D6): l 1.49 (s, 6H, CH3,),
6.98–7.73 (m, 28H, CH). 31P{1H} NMR (C6D6): l
111.3 (s).
2.1.3. (p-Ph2POC6H4)2S (3)
This work deals with the synthesis of the bis-p-phos-
phinito ligands (p-Ph2POC6H4)2X (X=O, 1; X=
CMe2, 2; X=S, 3), designed to induce a bridging
coordination in transition metal complexes, and their
This compound was obtained by an analogous proce-
dure to 1, as a colorless oil, starting from 4,4%-
1
thiodiphenol (2.00 g, 9.16 mmol). Yield: 88%. H NMR
(C6D6): l 6.9–7.95 (m, 28H, CH). 31P{1H} NMR
(C6D6): l 112.7 (s).
reactions
with
[Ru(h6-p-cymene)Cl2]2,
[Rh(h5-
C5Me5)Cl2]2, and [Rh(h5-C5H5)(CO)2] to give binuclear
complexes. The stereochemical course of some substitu-
tion and oxidative addition reactions is also reported.
The molecular structures of the binuclear complexes
{[Ru(h6-p-cymene)Cl2]2[m-(p-Ph2POC6H4)2X]} (X=O,
CMe2) and of the compound {[Rh2(h5-C5H5)2-
(COCH3)2I2][m-(p-Ph2POC6H4)2S]}, obtained by oxida-
2.2. Preparation of the complexes
2.2.1. {[Ru(p6-p-cymene)Cl2]2[v-(p-Ph2POC6H4)2O]}
(4)
A toluene solution of 1 (0.075 g, 0.131 mmol) was
added to a suspension of [Ru(h6-p-cymene)Cl2]2 (0.080
g, 0.131 mmol) in the same solvent. After 20 min the
suspension disappeared and by stirring for an addi-
tional 15 min a red solid separated. This was isolated
by filtration, washed with toluene (3×5 ml) and dried
in vacuo. Yield: 80%. Anal. Calc. for C56H56Cl4-
O3P2Ru2: C, 56.86; H, 4.77; Cl, 11.99. Found: C, 56.59;
tive
addition
of
{[Rh2(h5-C5H5)2(CO)2][m-(p-
Ph2POC6H4)2S]} with CH3I have been determined by
X-ray diffractometry.
2. Experimental
1
H, 4.89; Cl, 11.73%. H NMR (CDCl3): l 0.80 (d, 12H,
An established method was used to prepare the com-
pound [Rh(h5-C5H5)(CO)2] [5]. All other reagents were
purchased and used as supplied. Solvents were dried by
standard procedures. All experiments were performed
under an atmosphere of purified nitrogen. IR spectra
were obtained as Nujol mulls on KBr plates using a
J(HH)=6.9 Hz, CH3), 1.49 (s, CH3, 6H), 2.48 (sept,
2H, J(HH)=6.9 Hz, CH), 5.21 (m, 8H, CH), 6.9–7.28
(m, 20H, CH), 7.9–7.95 (m, 8H, CH). 31P{1H} NMR
(CDCl3): l 115.0 (s).
2.2.2. {[Ru(p6-p-cymene)Cl2]2[v-(p-Ph2POC6H4)2-
CMe2]} (5)
1
Perkin–Elmer FT-IR 1720 spectrophotometer. H and
31P{1H} NMR spectra were recorded on a Bruker
This compound was obtained by an analogous proce-
dure to 4, as a red solid, starting from [Ru(h6-p-
cymene)Cl2]2 (0.100 g, 0.163 mmol) and 2 (0.097 g,
0.163 mmol). Yield: 85%. Anal. Calc. for
C59H62Cl4O2P2Ru2: C, 58.61; H, 5.17; Cl, 11.73. Found:
1
AMX R300. H NMR spectra were referenced to inter-
nal tetramethylsilane and 31P{1H} spectra to external
85% H3PO4; positive chemical shifts for all nuclei are to
higher frequency. Elemental analyses were performed
by Redox s.n.c., Cologno Monzese, Milan.
1
C, 58.35; H, 4.83; Cl, 11.40%. H NMR (CDCl3): l
0.76 (d, 12H, J(HH)=7.0 Hz, CH3), 1.34 (s, 6H, CH3)
1.47 (s, 6H, CH3) 2.40 (sept, 2H, J(HH)=7.0 Hz, CH),
5.20 (m, 8H, CH), 6.75–7.28 (m, 20H, CH), 7.89–7.93
(m, 8H, CH). 31P{1H} NMR (CDCl3): l 113.5 (s).
2.1. Preparation of the ligands
2.1.1. (p-Ph2POC6H4)2O (1)
A toluene solution of 4,4%-oxydiphenol (2.00 g, 9.89
mmol) and triethylamine (2.5 g, 24.7 mmol) was added
at 0°C dropwise to a stirring solution (40 ml) of PPh2Cl
(4.37 g, 19.8 mmol) in the same solvent (50 ml). The
mixture was allowed to stand at room temperature (r.t.)
and was stirred for an additional 2 h; then was filtered
and the solvent was removed at reduced pressure. The
pure product was obtained as a colorless oil. Yield:
90%. 1H NMR (C6D6): l 6.8–7.85 (m, 28H, CH).
31P{1H} NMR (C6D6): l 113.1(s).
2.2.3. {[Ru(p6-p-cymene)Cl2]2[v-(p-Ph2POC6H4)2S]} (6)
This compound was obtained by an analogous proce-
dure to 4, as a red solid, starting from [Ru(h6-p-
cymene)Cl2]2 (0.090 g, 0.147 mmol) and 3 (0.086 g,
0.147 mmol). Yield: 82%. Anal. Calc. for
C56H56Cl4O2P2SRu2: C, 56.10; H, 4.71; Cl, 11.83.
Found: C, 56.35; H, 4.83; Cl, 11.50%. 1H NMR
(CDCl3): l 0.84 (d, 12H, J(HH)=6.9 Hz, CH3), 1.50
(s, 6H, CH3) 2.52 (sept, 2H, J(HH)=6.9 Hz, CH), 5.27

86
C.G. Arena et al. / Inorganica Chimica Acta 292 (1999) 84–95
(m, 8H, CH), 6.79–7.36 (m, 20H, CH), 7.94–8.00 (m,
was added to a suspension of [(h5-C5Me5)RhCl2]2
(0.160 g, 0.259 mmol) in the same solvent (10 ml). The
mixture was stirred for about 5 h at r.t. during which
time a red solid was formed. The solid was isolated by
filtration and washed with cold toluene (3×3 ml),
hexane (2×5 ml) and dried. Yield: 80%. Anal. Calc. for
C56H58Cl4O3P2Rh2: C, 56.59; H, 4.92; Cl, 11.93. Found:
8H, CH). 31P{1H} NMR (CDCl3): l 115.4 (s).
2.2.4. {[Ru(p6-p-cymene)Cl(CH3CN)]2[v-(p-Ph2-
POC6H4)2O]}[PF6]2 (7)
To a stirring solution of 4 (0.080 g, 0.67 mmol) in
acetonitrile (20 ml) was added solid AgPF6 (0.034 g,
0.134 mmol). After 2 h, the reaction mixture was
filtered and vacuum reduced to ca. 3 ml. A yellow solid
was obtained by addition of diethyl ether (30 ml). This
was separated by filtration, washed with diethyl ether
and dried. Yield: 50%. Due to the instability of complex
7 reliable microanalysis could not be obtained. IR
1
C, 56.71; H, 4.83; Cl, 11.65%. H NMR (CDCl3): l
1.35 (d, 30H, 3J(PH)=3.9 Hz, CH3), 6.8 (d, 4H,
J(HH)=8.8 Hz, C6H4), 7.2 (d, 4H, J(HH)=8.8 Hz,
C6H4), 7.28–7.4 (m, C6H5, 12H) 8.17–8.23 (m, C6H5,
1
8H). 31P{1H} NMR (CDCl3): l 114.1 (d, J(RhP)=
169.6 Hz).
1
(KBr, Nujol) w(PF6−) 840 cm−1, w(CN) 2278 cm−1. H
NMR (CD3CN): l 0.9–1.4 (m, 12H, CH3), 2.53 (m,
6H, CH3CN), 2.14–2.24 (m, 6H, CH3), 2.6–2.9 (m, 2H,
CH), 5.41–5.95 (m, 8H, CH), 6.72–6.95 (m, 8H, C6H4),
7.38–8.92 (m, 20H, C6H5). 31P{1H} NMR (CDCl3): l
125.3 (s), 125.5 (s) (1:1 ratio), −143.8 (sept, J(PF)=
2.2.8. {[Rh(p5-C5Me5)Cl2]2[v-(p-Ph2POC6H4)2CMe2]}
(14)
This compound was obtained similarly to 13 as a red
solid, by reaction of [h5-C5Me5)RhCl2]2 (0.08 g, 0.129
mmol) with 2 (0.077 g, 0.129 mmol). Yield: 85%. Anal.
Calc. for C59H64Cl4O2P2Rh2: C, 58.34; H, 5.31; Cl,
716.8 Hz, PF6−). L (ohm−1 cm2 mol−1) (5×10−4
–
10−3 M, CH3CN) 242.
11.67. Found: C, 58.60; H, 5.60; Cl, 11.95%. H NMR
1
3
(CDCl3): l 1.31 (d, 30H, J(PH)=3.9 Hz, CH3), 1.51
2.2.5. {[Ru(p6-p-cymene)Cl(CH3CN)]2[v-(p-Ph2POC6-
H4)2CMe2]}[PF6]2 (8)
(s, 6H, CH3), 6.5 (d, 4H, J(HH)=8.7 Hz, C6H4), 6.9
(d, 4H, J(HH)=8.7 Hz, C6H4), 7.13–7.28 (m, 12H,
C6H5); 8.03–8.13 (m, 8H, C6H5). 31P{1H} NMR
This compound was obtained similarly to 7, as a
yellow solid, starting from 5 (0.070 g, 0.058 mmol) and
AgPF6 (0.029 g, 0.116 mmol). Yield: 48%. Due to the
instability of complex 8 reliable microanalysis could not
1
(CDCl3): l 113.2 (d, J(RhP)=169.6 Hz).
2.2.9. {[Rh(p5-C5Me5)Cl2]2[v-(p-Ph2POC6H4)2S]} (15)
This compound was obtained similarly to 13, as a red
solid, by reaction between [h5-C5Me5)RhCl2]2 (0.100 g,
0.162 mmol) and 3 (0.095 g, 0.162 mmol). Yield: 78%.
Anal. Calc. for C56H58Cl4O2P2SRh2: C, 55.83; H, 4.85;
be obtained. IR (KBr, Nujol) w(PF6−) 840 cm−1
,
w(CN) 2273 cm−1 1H NMR (CD3CN): l 0.8–1.3
.
(m, 12H, CH3), 1.6 (s, 6H, CH3), 1.8–2 (m, 6H,
CH3CN) 2.5 (m, 6H, CH3), 2.6–2.9 (m, 2H, CH),
5.41–5.95 (m, 8H, CH), 6.72–6.95 (m, 8H, C6H4),
7.38–8.92 (m, 20H, C6H5). 31P{1H} NMR (CD3CN):
l 122.8 (s), 123.5 (s) (1:1 ratio), −143.8 (sept, J(PF)=
1
Cl, 11.77. Found: C, 55.70; H, 4.91; Cl, 11.65%. H
3
NMR (CDCl3): 1.33 (d, 30H, J(PH)=3.9 Hz, CH3),
6.5 (d, 4H, J(HH)=8.7 Hz, C6H4), 7.0 (d, 4H,
J(HH)=8.7 Hz, C6H4), 7.25–7.36 (m, 12H, C6H5);
8.18–8.24 (m, 8H, C6H5). 31P{1H} NMR (CDCl3): l
716.8 Hz, PF6−. L (Ohm−1 cm2 mol−1) (5×10−4
–
10−3 M, CH3CN) 250.
1
114.3 (d, J(RhP)=169.6 Hz).
2.2.6. {[Ru(p6-p-cymene)Cl(CH3CN)]2[v-(p-Ph2POC6-
H4)2S]}[PF6]2 (9)
2.2.10. {[Rh(p5-C5Me5)Cl(CH3CN)]2[v-(p-Ph2POC6-
H4)2O]}[PF6]2 (16)
This compound was obtained similarly to 7, as a
yellow solid, starting from 6 (0.070 g, 0.05 mmol) and
AgPF6 (0.025 g, 0.100 mmol). Yield: 47%. Due to the
instability of complex 9 reliable microanalysis could not
To a stirring solution of 13 (0.050 g, 0.050 mmol) in
acetonitrile (10 ml) was added solid AgPF6 (0.025 g,
0.10 mmol). After 16 h, the reaction mixture was
filtered and vacuum reduced to ca. 3 ml. A yellow–
orange solid was obtained by addition of diethyl ether
(30 ml). This was separated by filtration, washed with
diethyl ether and dried. Yield: 45%. The stability of this
compound is very low in the solid state so it was
characterized only by NMR spectroscopy. 1H NMR
be obtained. IR (KBr, Nujol) w(PF6−) 840 cm−1
,
w(CN) 2275 cm−1 1H NMR (CD3CN): l 0.9–1.3
.
(m, 12H, CH3), 1.8–1.9 (m, 6H, CH3CN), 2.45 (m, 6H,
CH3), 2.6–2.8 (m, 2H, CH), 5.5–6.15 (m, 8H, CH),
6.68–6.87 (m, 8H, C6H4); 7.40–8.90 (m, 20H, C6H5).
31P{1H} NMR (CD3CN):
l 124.4 (s), 125.8 (s)
3
(1:1 ratio), −143.8 (sept, J(PF)=716.8 Hz, PF6−). L
(ohm−1 cm2 mol−1) (5×10−4–10−3 M, CH3CN)
245.
(CD3CN): l 1.4 (d, 30H, J(PH)=3.9 Hz, CH3), 2.4 (s,
6H, CH3CN), 6.3–7.0 (m, 8H, CH), 7.25–7.36 (m,
12H, CH); 8.18–8.24 (m, 8H, CH). 31P{1H} NMR
(CD3CN): l 121.5 (d, 1J(RhP)=169.6 Hz), −143.8
2.2.7. {[Rh(p5-C5Me5)Cl2]2[v-(p-Ph2POC6H4)2O]} (13)
A toluene solution (5 ml) of 1 (0.148 g, 0.259 mmol)
(sept, J(PF)=716.8 Hz, PF6−). L (ohm−1 cm2 mol−1
(5×10−4–10−3 M, CH3CN) 275.
)

C.G. Arena et al. / Inorganica Chimica Acta 292 (1999) 84–95
87
2.2.11. {[Rh(p5-C5Me5)Cl(CH3CN)]2[v-(p-
Ph2POC6H4)2CMe2]}[PF6]2 (17)
[Rh(h5-C5H5)(CO)2] and 2. Yield: 58%. Anal. Calc. for
C51H44O4P2Rh2: C, 61.96; H, 4.49. Found: C, 62.05;
This compound was obtained similarly to 16 starting
from 14 (0.060 g, 0.058 mmol) and AgPF6 (0.029 g,
H, 4.52%. IR (KBr, Nujol) w(CO) 1950 cm−1 1H
.
NMR (CDCl3) l 1.42 (s, CH3, 6H), 5.0 (s, C5H5, 10H),
6.87–6.92 (m, 8H, C6H4), 7.28–7.42 (m, C6H5, 12H),
7.7–7.9 (m, 8H, C6H5). 31P{1H} NMR (CDCl3) l 149.9
1
0.116 mmol).Yield: 47%. H NMR (CD3CN): l 1.5 (d,
3
30 H, J(PH)=3.9 Hz, CH3), 1.61 (s, 6H, CH3), 2.51
(s, 6H, CH3CN), 6.3–7.1 (m, 8H, CH), 7.26–7.36
(m, 12H, CH); 8.18–8.24 (m, 8H, CH). 31P{1H} NMR
(CD3CN): l 120.5 (d, 1J(RhP)=169.6 Hz), −143.8
(d,
1J(RhP)=223.9
Hz).
By
elution
with
dichloromethane/diethyl ether 10:1 no further product,
similar to 22, has been obtained.
(sept, J(PF)=716.8 Hz, PF6−). L (ohm−1 cm2 mol−1
(5×10−4–10−3 M, CH3CN) 270.
)
2.2.15. {[Rh(p5-C5H5)CO]2[v-(p-Ph2POC6H4)2S]} (21)
In a similar manner to the preparation of 19, com-
pound 21 was synthesized by the reaction of [Rh(h5-
C5H5)(CO)2] with 3. Yield: 70%. Anal. Calc. for
C48H38O4SP2Rh2: C, 58.91; H, 3.91. Found: C, 58.71;
2.2.12. {[Rh(p5-C5Me5)Cl(CH3CN)]2[v-(p-
Ph2POC6H4)2S]}[PF6]2 (18)
This compound was obtained similarly to 16 starting
from 15 (0.070 g, 0.068 mmol) and AgPF6 (0.035 g,
H, 3.68%. IR (KBr, Nujol) w(CO) 1950 cm−1
.
1
0.137 mmol). Yield: 43%. H NMR (CD3CN): l 1.5 (d,
1H NMR (CDCl3) l 5.05 (s, C5H5, 10H), 6.85–6.92
(m, C6H4, 8H), 7.25–7.40 (m, C6H5, 12H), 7.7–7.9
(m, C6H5, 8H). 31P{1H} NMR (CDCl3): l 151.1
(d, 1J(RhP)=224.5 Hz). By elution with dichloro-
methane/diethyl ether 10:1 no further product, similar
to 22, has been obtained.
3
30 H, J(PH)=3.9 Hz, CH3), 2.49 (s, 6H, CH3CN),
6.4–7.1 (m, 8H, CH), 7.36–7.46 (m, 12H, CH); 8.18–
8.24 (m, 8H, CH). 31P{1H} NMR (CD3CN): l 121.0 (d,
1J(RhP)=169.5 Hz), −143.8 (sept, J(PF)=716.8 Hz,
PF6−). L (ohm−1 cm2 mol−1) (5×10−4–10−3 M,
CH3CN) 278.
2.2.16. {[Rh(p5-C5H5)(COCH3)I]2[v-(p-
Ph2POC6H4)2S]} (23)
2.2.13. {[Rh(p5-C5H5)CO]2[v-(p-Ph2POC6H4)2O]} (19)
and {Rh(p5-C5H5)[v-(p-Ph2POC6H4)2O]}n (22)
CH3I (2 ml) was added to compound 21 (0.090 g,
0.092 mmol). The resulting mixture was stirred for 1 h
at r.t. On monitoring the reaction by IR spectroscopy,
the disappearance of w(CO) bands of the starting mate-
rial and the appearance of new w(CO) bands were
observed. The volume of the reaction mixture was then
reduced to ca. 3 ml and hexane (20 ml) was added. The
dark red solid obtained was isolated by filtration and
dried. Yield: 82%. Anal. Calc. for C50H44I2O4SP2Rh2:
C, 47.57; H, 3.51. Found: C, 47.69; H, 3.67%. IR (KBr,
[Rh(h5-C5H5)(CO)2] (obtained in heptane from
[Rh(CO)2Cl]2 (0.250 g, 0.643 mmol) and an excess of
Tl(C5H5)) and a slight excess of 1 were refluxed in toluene
(150 ml) for about 5 h. During this time a color change
from yellow to orange occurred. The completion of the
reaction was checked by the disappearance of w(CO)
absorptions for [Rh(h5-C5H5)(CO)2]. The solution was
then concentrated to ca. 30 ml and chromatographed on
a neutral alumina column (2×20 cm) saturated with a
mixture of dichloromethane/diethyl ether 1:1. Elution
with the same solvent mixture and collection of the first
orange band, followed by slow evaporation of the
solvent, gave the product 19 as an orange powder in a
60% yield. Anal. Calc. for C48H38O5P2Rh2: C, 59.89; H,
3.98. Found: C, 60.15; H, 4.08%. IR (KBr, Nujol) w(CO)
1
Nujol) w(CO) 1790 cm−1. H NMR (CDCl3) l 2.64
(s, CH3, 6H), 5.11 (s, C5H5, 10H), 6.99 (d, C6H4,
J(HH)=8.7 Hz, 4H), 7.17 (d, C6H4, J(HH)=8.7 Hz,
4H), 7.25–7.40 (m, C6H5, 12H), 7.9–8.1 (m, C6H5, 8H).
31P{1H} NMR (CDCl3): l 143.8 (d, 1J(RhP)=189.7
Hz).
1
1953 cm−1. H NMR (CDCl3): l 5.02 (s, 10H, C5H5),
6.89–7 (m, 8H, C6H4), 7.3–7.42 (m, 12H, C6H5), 7.7–7.9
(m, 8H C6H5). 31P{1H} NMR (CDCl3): l 150.7 (d,
1J(RhP)=223.7 Hz).
2.3. Crystal data and data collection
Suitable crystals of compounds 4, 5 and 23 were
obtained, respectively, by slow evaporation of diethyl
ether/acetone, diethyl ether/CHCl3 and CH2Cl2/hexane
solutions. Diffraction data were collected at r.t. with a
Siemens R3mV automated four-circle single-crystal dif-
fractometer. Crystals of compounds 5 and 23 were
enveloped by a glue surface to avoid solvent loss during
data collection.
A summary of the crystallographic data and struc-
ture determination is given in Table 1. Reflection in-
tensities were evaluated by profile fitting of a 96-step
peak scan [6] and then corrected for Lorentz and
Elution with dichloromethane/diethyl ether 10:1 gave
the product 22 as an orange powder. Yield: 20%. Anal.
Calc. for C41H33O3P2Rh: C, 66.68; H, 4.5. Found: C,
1
66.59; H, 4.31%. H NMR (CDCl3): l 5.01 (s, 10H,
C5H5), 6.85–6.93 (m, 8H, C6H4), 7.3–7.45 (m, 12H,
C6H5), 7.7–7.8 (m, 8H, C6H5). 31P{1H} NMR (CDCl3):
1
l 151.0 (d, J(RhP)=198.8 Hz).
2.2.14. {[Rh(p5-C5H5)CO]2[v-(p-Ph2POC6H4)2CMe2]}
(20)
In a similar manner to the preparation of 19, the
compound 20 was synthesized by the reaction of

88
C.G. Arena et al. / Inorganica Chimica Acta 292 (1999) 84–95
Table 1
Crystal data and structure determination summary for 4, 5 and 23 a
4
5
23
Formula
Mr
Temperature (K)
Crystal system
Space group
C56H56Cl4O3P2Ru2
1182.89
293
monoclinic
C2
14.446(4)
13.464(2)
26.730(6)
C59H62Cl4O2P2Ru2·1/3[(CH3CO)+2(C2H5)2O]
1268.5
293
C50H60Cl2I2O4P2SRh2·2/3CH2Cl2
1399.9
293
monoclinic
C2/c
35.184(7)
9.541(2)
18.967(4)
triclinic
(
P1
,
a (A)
14.106(5)
14.235(3)
18.173(5)
92.58(2) (2)
94.48(2)
107.84(2)
3453.9(2)
2
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
91.16(2)
116.52(3)
3
,
V (A )
5198(2)
4
5697(2)
4
Z
F(000)
2408
1200
2640
,
u(Mo Ka) (A)
Dcalc (g cm−3
v (mm−1
q Range (°)
0.71073
1.512
0.892
2.19–28.56
6799
6425
4658
594
0.71073
1.221
0.67
2.59–25.05
12209
11410
5222
678
0.943
0.0590
0.1311
0.71073
1.634
1.886
2.23–25.05
5233
5025
2592
329
)
)
Reflections collected
Unique reflections
Reflection (I\4|(I))
No. refined parameters
GOF on F2
0.885
0.0340
0.055
0.725
0.0516
0.0997
R1 (on F, I\4|(I))
wR2 (on F2, all data)
a R1=[ꢀꢁFoꢁ−ꢁFcꢁ]/ꢀꢁFoꢁ. wR2=[ꢀw(ꢁFoꢁ−ꢁFcꢁ)2/ꢀwꢁFoꢁ2]1/2, w=n/(|2(Fo); GOF=[ꢀw(ꢁFoꢁ−ꢁFcꢁ)2/(Nobs−Nparam)]1/2
.
polarization effects. An absorption correction was ap-
For complex 23, during the refinement, it became
apparent that some residual peaks in the difference
Fourier map located next to positions of the acetyl
moiety and of the iodine atom indicated co-crystalliza-
tion of both diastereomers (RR, SS and RS). A cor-
rection for these residuals was introduced by splitting
atoms in two staggered positions having different site
occupancy factors (0.8 and 0.2) and refining acetyl
groups with restrained geometry. In addition, there is
co-crystallized dichloromethane. This CH2Cl2 appeared
disordered over two positions. They were refined with
site occupation factors of 0.3 and with restrained
distances.
plied for 4 by an empirical method [7] using azimuthal
scan data. No absorption corrections were applied for
5 or 23 because of the rapid decay (24% for 5 and
31% for 23) of the crystal under X-ray exposure; and
this reduced the accuracy of the data as can be seen
from crystal data and details of measurement for 5.
The structure of complex 4 was first solved in the
monoclinic space group C2/c, but many systematic
absence violations, related to a glide plane, revealed
the space group C2. Statistical considerations sug-
gested the acentric packing with two half molecules in
special positions, as confirmed by the successful refine-
ment.
The structures were solved by standard Patterson
methods, subsequently completed by a combination of
least-squares technique and Fourier syntheses [8] and
refined by the full-matrix least-squares on F2 [9]. An-
isotropic displacement factors were used for all non-
hydrogen atoms except those that were disordered.
For complex 5, the difference Fourier map of the
crystallographic asymmetric unit revealed signifi-
cant electron density residuals isolated from the
molecule that were interpreted as three co-crystallized
solvent molecules, one of acetone and two of diethyl
ether. Site occupation factors of the solvent groups
were fixed at 0.3 value into the following usual refine-
ment.
Hydrogens were placed at their geometrically calcu-
lated positions and refined ‘riding’ on the correspond-
ing carbon atoms, with fixed isotropic displacement
2
,
parameters (Uiso=0.08 A ). Data reduction, structure
solution and drawings were performed with the
SHELXTL-PLUS [8,9] package and geometrical calcula-
tions with the PARST [10] program. All calculations
were performed on either a m-VAX 3400 or a AXP
DecStation 3000/400.
2.3.1. Computational details
All calculations were accomplished with the AMPAC
(MOPAC) program [11]. Full geometry optimizations of
the ligands were carried out by using the PM3 Hamil-
tonian parameters.

C.G. Arena et al. / Inorganica Chimica Acta 292 (1999) 84–95
89
Table 2
Structural parameters by semi-empirical geometry optimization for 1, 2 and 3
,
,
P···P (A)
P–O (A)
POC (°)
Valence angle (°)
CCXC (°) X=[O, C(CH3)2, S]
1
2
3
11.506
9.848
11.04
1.614
1.613
1.613
122.6
122.8
123.0
115.9
106.9
100.3
125.5–140.6
49.2–51.7
119.5–109.3
formation of the binuclear complexes {[Ru(h6-p-
cymene)Cl2]2[m-(p-Ph2POC6H4)2X]} (X=O, 4; X=
CMe2, 5; X=S, 6), which have been isolated in good
yields as red air stable solids. No other species were
detected even when the reactions were carried out using
a different molar ratio. All the complexes 4–6 are
soluble in chlorinated solvents, benzene, and acetone
and are nonconducting in acetone solution. They have
been characterized by microanalysis, IR, NMR spec-
troscopy and X-ray diffraction studies1 (details are
given in Section 2). The 31P{1H} NMR spectra of
complexes 4–6, in CDCl3 solution, show a single reso-
nance in the range l 113–115 ppm indicating chemical
equivalence of the phosphorus atoms in the coordi-
3. Results and discussion
3.1. Synthesis of ligands
The bis-4-phosphinito ligands 1–3 (Fig. 1) were syn-
thesized in a satisfactory yield by reaction of the corre-
sponding 4,4%-bisphenol with Ph2PCl, in toluene, in the
presence of triethylamine as an acid acceptor. Com-
pounds 1–3 were obtained as colorless oils, except 2,
which is a white solid that is moderately stable in air. In
solution their stability is diminished because formation
of the corresponding oxides occurs easily. In the
31P{1H} NMR spectra of 1–3 a singlet was observed in
the range l 111–113 ppm, consistent with the proposed
structures. These resonances are in the region expected
1
nated ligands. The H NMR spectra are very similar
1
and show resonances for aromatic, isopropyl, and
methyl protons in the correct integration ratio, in ac-
cordance with the proposed structure. The cis or trans
disposition of the h6-p-cymene and h5-cyclopentadienyl
ligands with respect to the metal–metal axis in com-
plexes 4–6, in the solid state, is due to packing effects
and is not a consequence of the requirement of the
bridging ligands. In fact molecular models indicate that
cis–trans interconversion between the isomers should
occur by rotation of 180° around the P–O bond of a
ruthenium atom. The energy required for such a rota-
tion in free ligands was calculated [11] to be about 6.0
kcal mol−1; on this basis, a low rotational barrier value
can also be expected for complexes 4–6.
for phosphinito derivatives. The H NMR spectra of 1
and 3, in C6D6, exhibit resonances for the phenyl
groups together with those for p-substituted aromatic
rings. In the spectrum of compound 2 a singlet at l 1.49
ppm due to the methyl groups is also present.
The geometries of ligands 1–3 were predicted by
semi-empirical calculation [11] (Table 2). All molecular
modeling calculations show that the P–O bond dis-
tances are nearly the same for all the ligands indicating
that the X-group has only a minor influence on the
electronic properties of the phosphorus donor. Interest-
,
ingly the P···P separation ranges from 9.848 A for 2 to
,
11.506 A for 1, indicating that cis or trans chelation to
one metal atom is hindered for these ligands. The
C–X–C angles range from 100.3° for X=S to 115.9°
for X=O and their values are not directly related to
the P···P separation.
The full structural characterization in the solid state
of complexes 4–6 has been undertaken by X-ray
diffraction.
In acetonitrile and in the presence of AgPF6 (1:1
equiv. with respect to Ru), complexes 4–6 undergo a
substitution reaction with CH3CN to produce the
cationic complexes {[Ru(h6-p-cymene)Cl(CH3CN)]2[m-
(p-Ph2POC6H4)2X]}[PF6]2 (X=O, 7; X=CMe2, 8;
X=S, 9). It was also shown that the presence of Ag(I)
3.2. Reactions of ligands 1–3 with
[Ru(p6-p-cymene)Cl2]2
The reaction of [Ru(h6-p-cymene)Cl2]2 with ligands
1–3 in the molar ratio 1:1, in toluene, results in the
1 The crystal structure of 6 was not fully determined owing to
extensive crystal decay. However, the data permit assignment of
a structure with trans disposition of the p-cymene groups with
respect to Ru–Ru axis. Some geometric parameters of 6 will be
considered in the discussion of the structure of 23. Crystal data
(
for 6: C56H56Cl4O2P2SRu2, triclinic, space group P1, a=13.919(5),
,
b=14.311(3), c=17.881(6) A, h=85.98(2), i=89.25(3), k=
Fig. 1. Ligands 1–3.
72.86(2)°.

90
C.G. Arena et al. / Inorganica Chimica Acta 292 (1999) 84–95
Fig. 2. View of the structure of complex 4 with the atom numbering scheme.
does not promote redox reactions. Compounds 7–9 are
yellow solids, soluble in methanol and their stability in
solution is limited very likely owing to CH3CN dissoci-
ation. The lability of the acetonitrile ligands in the
mononuclear cationic complexes [(h6-C6H6)RuCl(CH3-
CN)2]+ and [(h6-C6H6)Ru(PPh3)(CH3CN)Cl]+ has
been clearly demonstrated [12]. In CH3CN solution,
compounds 7–9 are 1:2 electrolytes. In complexes 7–9
both ruthenium atoms become stereogenic centers. In
principle these compounds can give rise to a pair of
enantiomers (RRuRRu and SRuSRu) and the meso form
(RRuSRu, SRuRRu) In some cases 31P{1H} NMR spec-
troscopy allows diastereomers to be distinguished [13].
The 31P{1H} NMR spectra of 7–9, in CDCl3 solution,
show two resonances of comparable intensity in the
range l 122.8–125.5 ppm, indicating the presence in
solution of a pair of enantiomers and the meso form in
equal amounts.
give bi- or tetra-nuclear species failed. Very likely, the
presence of two bridging ligands induces strong repul-
sive interactions between the phenyl groups of the
phosphinito ligands and the isopropyl moiety of the
p-cymene groups and prevents the formation of these
species. Using dppe (dppe=1,2-bis(diphenylphos-
phino)ethane) as a bidentate ligand the complex
[Ru(h6-p-cymene)Cl(dppe)]PF6 [14] was obtained, with
the phosphinito ligands being displaced by the more
basic dppe.
3.3. Description of the crystal structure of
{[Ru(p6-p-cymene)Cl2]2[v-(p-Ph2POC6H4)2O]} (4)
A view of the molecular structure of {[Ru(h6-p-
cymene)Cl2]2[m-(p-Ph2POC6H4)2O]} with the atom-la-
beling scheme is shown in Fig. 2. Selected bond
distances and angles are given in Table 3.
Compounds 7–9 can be very useful starting materials
for the synthesis of complexes in which two [Ru(h6-p-
cymene)] moieties, containing stereogenic ruthenium
atoms, are held together by the bridging phosphinito
ligands 1–3. The acetonitrile ligands in complexes 7–9
can be easily replaced by carbon monoxide. When CO
was bubbled into an acetonitrile solution containing
complexes 7–9 a fast reaction occurs. The progress of
the CH3CN substitution reaction was monitored by IR
spectroscopy. The reaction is complete in about 1 h for
all the substrates.
The geometry around the ruthenium atom is that of
a ‘three legged piano stool’ in which the h6-coordinated
arene ligand occupies the ‘stool’ position, while the Cl
atoms and the P atom occupy the three ‘leg’ positions.
In the binuclear complex the h6-p-cymene planes are
arranged in the cis position with respect to the Ru–Ru
axis, with an angle of 23° to each other. The angle
between the weighted least-squares planes through the
two phenolic rings of the ligand is 77.9°.
The molecule possesses C2 symmetry, and in the
asymmetric unit there are two half molecules with
oxygen atoms in special positions. Both chlorine atoms
are oriented towards the Ru–Ru axis, to minimize the
interaction with the phenyl rings of the ligand. Since
the two half molecules show very similar geometric
parameters, in the following discussion we report only
both values if necessary.
The compounds {[Ru(h6-p-cymene)Cl(CO)]2[m-(p-
Ph2POC6H4)2X]}[PF6]2 (X=O, 10; X=CMe2, 11; X=
S, 12) show one w(CO) band, in CH3CN, in the range
2033–2020 cm−1. Complexes 10–12 can be detected
only in solution, under a CO atmosphere, and have
limited stability. Starting from 7–9 or 10–12, all at-
tempts to obtain complexes in which the ruthenium
centers are bridged by two binucleating 1–3 ligands to
The phosphinito ligand 1 possesses a large valence
angle; in 4 the valence angle C(10)–O(2)–C(10) for

C.G. Arena et al. / Inorganica Chimica Acta 292 (1999) 84–95
91
Table 3
Selected bond lengths (A) and angles (°) for 4
found for areneruthenium(II) complexes. Other signifi-
cant geometric parameters concerning the ruthenium
atom and its coordination sphere include the following:
a
,
,
Bond lengths (A)
Ru(1)–P(1)
Ru(1)–C*
,
,
Ru(1)–CA*r=1.714 A, Ru(1)–P(1)=2.303(3) A,
2.303(3)
1.714
P(1)–C(13)
P(1)–C(1)
1.794(11)
1.815(9)
1.461(12)
1.344(13)
2.287(3)
1.806(11)
1.337(13)
1.445(11)
1.841(13)
,
,
Ru(1)–Cl(1)=2.415(4) A, Ru(1)–Cl=2.416(4)
A
Ru(1)–Cl(1)
Ru(1)–Cl
P(1)–O(1)
Ru(1%)–C*%
Ru(1%)–Cl(1%)
Ru(1%)–Cl(%)
P(1%)–O(1%)
2.415(4)
2.416(4)
1.644(9)
1.716
2.389(4)
2.400(3)
1.627(8)
O(1)–C(7)
which are comparable to those observed for similar
compounds [15].
O(2)–C(10)
Ru(1%)–P(1%)
P(1%)–C(1%)
O(1%)–C(7%)
O(2%)–C(10%)
P(1%)–C(13%)
Also the bond lengths related to the phosphinito
ligand are in good agreement with literature values [16].
3.4. Description of the crystal structure of
Bond angles (°)
C*–Ru(1)–Cl
C*–Ru(1)–Cl(1)
C(13)–P(1)–C(1)
C(7)–O(1)–P(1)
C*%–Ru(1%)–Cl%
C*%–Ru(1%)–P(1%) 127.0
P(1%)–Ru(1%)–Cl(%)
Cl(1%)–Ru(1)–Cl(%) 89.4(1)
{[Ru(p6-p-cymene)Cl2]2[v-(p-Ph2POC6H4)2CMe2]} (5)
124.1
127.2
104.5(5)
121.9(6)
123.8
P(1)–Ru(1)–Cl
C*–Ru(1)–P(1)
P(1)–Ru(1)–Cl(1)
Cl(1)–Ru(1)–Cl
C*%–Ru(1%)–Cl(1%)
C(13%)–P(1%)–C(1%)
P(1%)–Ru(1%)–Cl(1%)
C(7%)–O(1%)–P(1%)
89.1(1)
127.8
86.1(1)
90.0(1)
128.2
112.5(4)
86.8(1)
124.2(6)
A view of the molecular structure of {[Ru(h6-p-
cymene)Cl2]2[m-(p-Ph2POC6H4)2CMe2]} with the atom-
labeling scheme is shown in Fig. 3. Selected bond
distances and angles are given in Table 4.
89.3(1)
{[Ru(h6-p-cymene)Cl2]2[m-(p-Ph2POC6H4)2CMe2]} is
homologous with complex 4, except for the presence of
one methylenic group between the phenolic rings in the
ligand instead of the oxygen atom. In contrast to 4, in 5
the h6-p-cymene groups are in a trans position with
respect to the Ru–Ru axis and lie in two planes nearly
perpendicular with each other; the angle between these
planes is 101.5°. The angle between the weighted least-
squares planes through two phenolic rings is 89.6°.
The nonbonded Ru(1)···Ru(1A) separation is 12.807
a C*, centroid of the six-membered ring of the h6-p-cymene.
both independent molecules is 116.0(12) and 118.4(13)°.
The nonbonded Ru(1)···Ru(1A) separation is 13.09 A,
while P(1)···P(1A) is 10.259 A, this last value being
shorter than that calculated for the ligand (11.51 A) by
,
,
,
semi-empirical calculations [11].
The ruthenium atom is in a pseudo-octahedral envi-
ronment. Considering the h6-p-cymene ring to occupy
three coordination centers, represented by its centroid
(CA*r), the angles formed by it and the other ruthenium
ligands are, respectively: C*Ar–Ru(1)–Cl(1)=127.2°,
,
,
A, while the distance P(1)···P(1A) is 11.714 A, longer
,
than the corresponding value in the free ligand (9.848 A)
as found from the geometry optimization [11]. The
P(1)–O(1)–C(1) angle is 128.5(5)°, and the P(1)–O(1)–
C(1)–C(6) dihedral angle is −170.5(2)°. The valence
angle C(4)–C(1%)–C(4A) is 109.8(7)°, and the dihedral
angle around the methylenic carbon atom C(4)–C(1%)–
C(4A)–C(5A) is 117.8(10)°.
CA*r–Ru(1)–Cl=124.1°,
CA*r–Ru(1)–P(1)=127.8°.
The values of the angles P(1)–Ru(1)–Cl and P(1)–
Ru(1)–Cl(1) are 89.1(1) and 86.1(1)°. The deviations
from the regular arrangement are in the range normally
Fig. 3. View of the structure of complex 5 with the atom numbering scheme.

92
C.G. Arena et al. / Inorganica Chimica Acta 292 (1999) 84–95
3
Table 4
doublet with J(PH)=3.9 Hz.
a
,
Selected bond lengths (A) and angles (°) for 5
The
cationic
complexes
{[Rh(h5-C5Me5)Cl-
(CH3CN)]2[m-(p-Ph2POC6H4)2X]}[PF6]2 (X=O, 16;
X=CMe2, 17; X=S, 18), in which the metal atoms
are stereogenic centers, have been obtained from the
corresponding complexes 13–15 by treatment in
CH3CN with AgPF6, and have been characterized only
in solution by 31P{1H} NMR spectra and conductivity
measurements. The compounds are stable only in
CH3CN solution very likely owing to CH3CN dissocia-
tion. The mechanism of solvent exchange on the half-
sandwich solvento species {[Rh(h5-C5H5)Cl(CH3-
CN)3]2+ provide a model for the reactivity of half-
sandwich compounds [17]. The 31P{1H} NMR spectra
of 16–18, in CH3CN solution, show a doublet centered
at about l 121 ppm (1J(RhP)=169.5). It is not known
whether only one of the two possible diastereomers
(RRhRRh, SRhSRh) and (RRhSRh, SRhRRh) is present or
whether the 31P chemical shifts of the two species are
experimentally indistinguishable. This would seem to
be supported by the line width value of the 31P{1H}
NMR peaks of 34 Hz (9 Hz for 7–9). In the analogous
p-cymeneruthenium(II) complexes 7–9 the 31P{1H}
chemical shifts of the diastereomeric pairs differ only
by 0.2 ppm.
,
Bond lengths (A)
Ru(1)–P(1)
Ru(1)–Cl(1)
Ru(1)–Cl(2)
Ru(1)–C*
2.314(2) Ru(1A)–P(1A)
2.400(2) Ru(1A)–Cl(1A)
2.400(2) Ru(1A)–Cl(2A)
2.313(2)
2.417(2)
2.418(2)
1.719
1.626(5)
1.822(8)
1.815(8)
1.555(11)
1.709
Ru(1A)–C*
P(1)–O(1)
1.618(5) P(1A)–O(1A)
1.796(7) P(1A)–C(16A)
1.817(8) P(1A)–C(10A)
1.532(11) C(4A)–C(1%)
P(1)–C(16)
P(1)–C(10)
C(4)–C(1%)
Bond angles (°)
C*–Ru(1)–P(1)
C*–Ru(1)–Cl(2)
C*–Ru(1)–Cl(1)
P(1)–Ru(1)–Cl(2)
P(1)–Ru(1)–Cl(1)
128.5
125.8
125.1
CA*–Ru(1A)–P(1A)
CA*–Ru(1A)–Cl(2A)
CA*–Ru(1A)–Cl(1A)
127.8
121.9
127.8
94.47(8)
84.11(7)
90.7(1) P(1A)–Ru(1A)–Cl(2A)
86.0(1) P(1A)–Ru(1A)–Cl(1A)
Cl(1)–Ru(1)–Cl(2) 88.2(1) Cl(1A)–Ru(1A)–Cl(2A) 87.25(8)
O(1)–P(1)–C(1)
O(1)–P(1)–Ru(1)
C(4)–C(1%)–C(2%)
128.5(5) C(1A)–O(1A)–P(1A)
114.5(2) O(1A)–P(1A)–Ru(1A)
110.7(8) C(4A)–C(1%)–C(2%)
127.5(5)
115.6(2)
109.9(9)
109.8(7)
C(3%)–C(1%)–C(2%) 107.4(9) C(4)–C(1%)–C(4A)
a C*, centroid of the six-membered ring of the h6-p-cymene.
We carried out the reactions of [Rh(h5-C5H5)(CO)2]
with the ligands 1–3 with the aim of obtaining binuclear
rhodium(I) complexes able to give, by oxidative addi-
tion of alkyl halides, the corresponding rhodium(III)
species containing stereogenic metal centers. The
[Rh(h5-C5H5)(CO)2] was converted into the binuclear
phosphinito-bridged complexes by reaction with ligands
1–3, in toluene, at about 80°C. The reaction was
followed by IR and NMR spectroscopy and it appears
that [Rh(h5-C5H5)(CO)2] is initially transformed into a
carbonyl derivative, although a further compound
was obtained by loss of CO. The reaction was stopped
when the w(CO) bands of the starting material disap-
peared. Spectroscopic IR and NMR data indicated
that the crude product, obtained by evaporation of
the solvents, contains a mixture of two compounds. For
X=O, they have been separated by column chro-
matography on neutral alumina saturated with
dichloromethane–diethyl ether. On the basis of analyt-
ical and spectroscopic data, they have been formulated
as {[Rh(h5-C5H5)(CO)]2[m-(p-Ph2POC6H4)2X]} (X=O,
19; X=CMe2, 20; X=S, 21) and {Rh(h5-C5H5)[m-(p-
Ph2POC6H4)2X]}n, (X=O, 22). In accordance with
their formulation complexes 19–21 show, in the IR
spectrum (Nujol mull), a w(CO) band in the range of
1953–1960 cm−1 and in the 31P{1H} NMR spectrum,
in CDCl3 solution, a doublet in the range l 150–151
As shown in Fig. 2, the usual ‘three-legged piano
stool’ coordination is also observed for 5. The coordi-
nation geometry and the metal–ligand distances are
almost the same as for 4. The values of the angles
formed by the centroid (C* ) of the p-cymene phenyl
Ar
ring and the other ruthenium ligands are: C* –Ru(1)–
Ar
Cl(1)=125.1°, C* –Ru(1)–Cl(2)=125.8°, and CC* –
Ar
Ar
Ru(1)–P(1)=128.5°.
3.5. Reaction of ligands 1–3 with [Rh(p5-C5Me5)Cl2]2
and [Rh(p5-C5H5)(CO)2]
We studied the reaction of [Rh(h5-C5Me5)Cl2]2 with
ligands 1–3 as pentamethylcyclopentadienylrhodi-
um(III) complexes are isoelectronic with arenerutheni-
um(II) complexes. The reaction of [Rh(h5-C5Me5)Cl2]2
with ligands 1–3 in toluene results in the formation, in
a good yield, of the complexes {[Rh(h5-C5Me5)Cl2]2[m-
(p-Ph2POC6H4)2X]} (X=O, 13; X=CMe2, 14; X=S,
15) which have been isolated as red–orange, air-stable
solids, soluble in chlorinated solvents, benzene, and
acetone. They have been characterized by microanaly-
sis, IR and NMR spectroscopy. The 31P{1H} NMR
spectra of 13–15, in CDCl3 solution, show a doublet
centered in the range l 113–114 ppm (1J(RhP)=169.6
1
Hz). The H NMR spectra of 13–15, in CDCl3, show
1
ppm (1J(RhP)=223–228 Hz). In the H NMR spec-
resonances of the protons of the coordinated phos-
phinito ligand together with those of C5Me5 protons in
the correct integration ratio. The latter appear as a
trum, in CDCl3 solution, the cyclopentadienyl protons
resonance appears at l about 5.0 ppm (singlet) to-

C.G. Arena et al. / Inorganica Chimica Acta 292 (1999) 84–95
93
gether with the resonances for the protons of the coor-
dinated ligands in the correct integration ratio. Spectro-
scopic data for 22 are very similar to those for the
corresponding compound 19, except for the lack of the
w(CO) band in the IR spectrum. The very similar values
of the 31P{1H} chemical shifts indicate the same charac-
ter of the Rh–P bond in both types of compounds. For
compound 22 we suggest a structure in which the
Rh(h5-C5H5) moieties are held together by bridged
diphosphinito ligands.
in the reaction mixture of only the starting material and
the acyl derivative. Interestingly, the 31P{1H} NMR
spectrum of the reaction mixture, in CDCl3 solution,
exhibits together with the resonances due to the pres-
ence of 21, two doublets centered at l 150.9 ppm
(1J(RhP)=225.8 Hz) and l 150.1 ppm (1J(RhP)=
225.4 Hz). The complex {[Rh(h5-C5H5)(COCH2-
CH(CH3)C2H5)Br]2[m-(p-Ph2POC6H4)2S]} (24), can give
rise to a pair of diastereoisomers (RRhSCSCRRh and
SRhSCSCSRh) and to the diastereoisomer RRhSCSCSRh
.
The reaction of [Rh(h5-C5H5)(CO)L] (L=tertiary
phosphine, phosphite) with alkyl halides RX have been
extensively studied [18], and shown to proceed by for-
mation of the ionic intermediate [Rh(h5-C5H5)-
(CO)RL]X which affords the neutral final product
[Rh(h5-C5H5)(COR)LX]. Both the ionic intermediate
and the acyl derivative possess a stereogenic rhodi-
um(III) atom.
The existence of two doublets in the 31P{1H} NMR
spectrum supports [12] either the presence of a pair of
diastereoisomers or of the diastereoisomer RRhSCSCSRh
in which the phosphorus atoms are diastereotopic.
On reaction of 21 with racemic PhCH(CH3)Br, in
CHCl3
solution,
the
product
{[Rh(h5-C5H5)-
(COCH(CH3)Ph)Br]2[m-(p-Ph2POC6H4)2S]} (25), was
obtained together with the starting material. In the
31P{1H} NMR spectrum four doublets of different in-
tensity (0.3:0.8:1:1) and with the same 1J(RhP) were
observed instead of those expected for the formation of
all possible diastereoisomers; we were not able to sepa-
rate and fully characterize the diastereoisomers formed
in the reaction and to assign their configurations.
Consiglio and Morandini [19] studied the reactions of
h5-cyclopentadienyl and h5-indenyl rhodium(I) com-
plexes of the type [(h5-C5H5)Rh(P–P*)] and [(in-
denyl)Rh(P–P*)], in which P–P* are chiral C1 and C2
chelating diphosphines, with methyl iodide. The reac-
tion products are the cationic [(h5-C5H5)Rh(P–P*)-
(CH3)]I and [(indenyl)Rh(P–P*)(CH3)]I, in which the
metal is a stereogenic center. The extent of diastereose-
lectivity is complete only with the C1 chiral ligands
prophos and cycphos (prophos=1,2-bis-(diphenyl-
We studied the reactions of the binuclear complex
{[Rh(h5-C5H5)(CO)]2[m-(p-Ph2POC6H4)2S]} (21), with
CH3I, S-(+)-1-bromo-2-methylbutane and racemic
PhCH(CH3)Br. The reaction with CH3I appears to be
irreversible, while those with the other alkyl halides
reach equilibrium conditions. The products were the
acyl derivatives although following the reaction course
by IR and NMR spectroscopy the ionic intermediates
{[Rh(h5-C5H5)(CO)R]2[m-(p-Ph2POC6H4)2S]}[X]2 (X=
Br, I) were detected. The reaction of 21 with neat CH3I
easily affords the complex {[Rh(h5-C5H5)(COCH3)I]2[m-
(p-Ph2POC6H4)2S]} (23), as a red–brown solid, soluble
in chlorinated solvents, benzene, and acetone. Its ace-
tone solutions are not conducting. In accordance with
its formulation the IR spectrum shows a broad w(CO)
1
band at 1690 cm−1 and in the H NMR spectrum, in
CDCl3 solution, a singlet at l 5.11 ppm due to cy-
clopentadienyl protons and a singlet at l 2.64 ppm, due
to the acyl protons, have been evidenced. In the
31P{1H} NMR spectrum, in CDCl3 solution, the com-
pound exhibits only a doublet centered at l 143.8 ppm
(1J(RhP)=189.7 Hz) indicating the presence either of
the meso form (RRhSRh, SRhRRh) or of the pair of
enantiomers RRhRRh and SRhSRh. The structural deter-
mination by X-ray analysis allowed the assignment of
compound 23 as a mixture of both stereoisomeric
(SRhSRh, RRhRRh) and meso forms. We unsuccessfully
checked the mother liquor and the crystallization solu-
tion for the presence of the RRhSRh (meso) form. How-
ever, it could be that the 31P{1H} chemical shifts of the
meso form and of the enantiomeric pair differ very
little; in this case, the meso form would not be
detectable.
phosphino)propane;
cycphos=1,2-bis(diphenylphos-
phino)-1-cyclohexylethane) and seems to be mostly de-
pendent on steric factors due to the diphosphine ligand.
The stereochemical course of the reactions reported
here is more complicated than those reported by Con-
siglio et al. [19], because the formation of the ionic
product is followed by the nucleophilic attack of the
iodide on the rhodium(III) center affording the neutral
acyl-derivative; the last step of the reaction also follows
a stereochemical course. The stereochemical configura-
tions of 23–25 are the result of two processes, each of
which has a stereochemical course.
3.6. Description of the crystal structure of {[Rh(p5-
C5H5)(COMe)I]2[v-(p-Ph2POC6H4)2S]} (23)
The reaction of 21 with neat S-(+)-1-bromo-2-
methylbutane at r.t. is very slow. Raising the tempera-
ture the starting material was still not completely
converted to the acyl derivative. However, after about
12 h, the IR and NMR spectra indicated the presence
A view of the molecular structure of {[(Rh(h5-
C5H5)(COMe)I]2[m-(p-Ph2POC6H4)2S]} with the atom-
labeling scheme is shown in Fig. 4. Selected bond
distances and angles are given in Table 5.

94
C.G. Arena et al. / Inorganica Chimica Acta 292 (1999) 84–95
Fig. 4. View of the structure of complex 23 with the atom numbering scheme.
Table 5
120.2°,
Cp*–Rh(1)–C(19)=129.8°,
Cp*–Rh(1)–
a,b
,
Selected bond lengths (A) and angles (°) for 23
P(1)=125.5°. The distances between the rhodium and
the cyclopentadienyl carbons are in a range from
,
Bond lengths (A)
,
,
Rh(1)–I(1)
Rh(1)–P(1)
S(1)–C(1)
P(1)–C(7)
2.655(1)
2.246(2)
1.774(7)
1.821(7)
Rh(1)–C*
O(1)–C(4)
P(1)–O(1)
P(1)–C(13)
1.955
2.241(6) to 2.34(5) A with a mean value of 2.293(6) A
1.394(8)
1.643(5)
1.813(7)
,
and a Rh-centroid separation of 1.955 A. The Rh(1)–
,
I(1) distance of 2.655(1) A, and Rh(1)–C(acyl) dis-
tance of 2.293(6) A are comparable with the values
,
Bond angles (°)
C*–Rh(1)–P(1)
C*–Rh(1)–I(1)
C*–Rh(1)–C(19)
P(1)–Rh(1)–I(1)
P(1)–Rh(1)–C(19)
I(1)–Rh(1)–C(19)
O(1)–P(1)–C(13)
O(1)–P(1)–Rh(1)
reported for
{(h5-C5H5)Rh[C(O)Me][(S)-(PPh2-
125.5
120.2
129.8
91.30(6)
90.3(5)
90.1(2)
96.8(3)
115.8(2)
C(13)–P(1)–Rh(1)
C(7)–P(1)–Rh(1)
C(1)–S(1)–C(1)*
C(6)–C(1)–S(1)
C(2)–C(1)–S(1)
C(4)–O(1)–P(1)
O(1)–P(1)–C(7)
120.7(2)
116.1(2)
101.9(5)
119.6(6)
121.7(6)
123.2(4)
102.0(3)
NHCH–(Me)Ph]}I [20], the slight differences being
due to positional disorder. The Rh(1)–I(1) bond dis-
tance is shorter than the value reported for the com-
plex {Rh[Ph2P(CH2)3PPh2][C(O)Me]I2} [21]. The
,
Rh(1)–P(1) bond distance (2.246(2) A) is significantly
shorter than that reported for [(h5-C5H5)Rh(PPh3)Cl2]
,
[22] (2.3089(9)) A.
a C*, centroid of the h5-cyclopentadienyl ring.
In the complex the h5-cyclopentadienyl rings are in
the trans position with respect to the metal–metal axis
and lie in two planes which form an angle of 146°
with each other, while the angle between the weighted
least-squares planes through two phenolic rings is
65.72°.
b C(1)*, symmetric atom.
The crystals of {[(Rh(h5-C5H5)(COMe)I]2[m-(p-
Ph2POC6H4)2S]} build up by co-crystallization of the
complex and CH2Cl2 of solvation. Solvent is omitted
in the figure for clarity.
The X-ray analysis shows the existence of 23 in the
solid state as a mixture of (SRhSRh, RRhRRh) and
(RRhSRh, SRhRRh) diastereomers.
,
The Rh(1)···Rh(1A) separation of 8.879 A and the
,
P(1)···P(1A) separation of 9.577 A are shorter than the
,
,
metal–metal (12.55 A) and P···P (11.61 A) separations
found in 6. The P(1)···P(1A) separation is shorter than
,
The asymmetric unit of the cell is represented by a
half discrete molecule of the complex which is consti-
tuted by one Rh(III) atom coordinated to I(1), [m-(p-
Ph2POC6H4)2S] (via the P atom), and a h5-cyclo-
pentadienyl ring. Considering the C5H5-ring to occupy
three coordination sites, the rhodium coordination ge-
ometry might be described as distorted octahedral; the
angles formed by the carbocyclic ring centroid (Cp*)
and the other rhodium ligands are Cp*–Rh(1)–I(1)=
that calculated for the free ligand [11] (11.04 A). The
P(1)–O(1)–C(4) angle is 123.4(4)°, and the dihedral
angle C(1A)–S(1)–C(1)–C(6) is 139.3(7)°. The valence
angle C(1)–S(1)–C(1A) of 101.9(5)° is larger than that
in 6 (101.3)°. This value, as well as the S(1)–C(1)
,
distance of 1.774(7) A, compare well with those re-
,
A reported [23]
for [2,18-diphenyl-1,3,17,19-tetraoxa-10,26-dithia-2,18-
diphospha (3.1.3.1)paracyclophane].
spectively of 103.2° and 1.769

C.G. Arena et al. / Inorganica Chimica Acta 292 (1999) 84–95
95
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Acknowledgements
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Financial support from MURST and the Italian
CNR is gratefully acknowledged.
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