A rhodium(I) complex containing a mixed donor 'P2N' tridentate ligand

Article abstract of DOI:10.1016/S0020-1693(03)00483-3

The reaction of 2-(diphenylphosphino)-N-[2-(diphenylphosphino)benzylidene] benzeneamine (PNCHP) with 0.5 equivalents of [{RhCl(1,5-cyclooctadiene)} ₂] affords the extremely, air-sensitive compound, [RhCl(PNCHP-κ³P,N,P)]. This reacts

Full text of DOI:10.1016/S0020-1693(03)00483-3

Inorganica Chimica Acta 357 (2004) 2379–2384
www.elsevier.com/locate/ica
Note
A rhodium(I) complex containing a mixed donor ‘P2N’
tridentate ligand
1
*
Eric W. Ainscough, Andrew M. Brodie , Anthony K. Burrell , Andreas Derwahl,
Steven K. Taylor
Chemistry – Institute of Fundamental Sciences, Massey University, Private Bag 11-222, Palmerston North, New Zealand
Received 16 July 2003; accepted 19 July 2003
Available online 29 August 2003
Abstract
The reaction of 2-(diphenylphosphino)-N-[2-(diphenylphosphino)benzylidene]benzeneamine (PNCHP) with 0.5 equivalents of
[{RhCl(1,5-cyclooctadiene)}2] affords the extremely, air-sensitive compound, [RhCl(PNCHP-j3P; N; P)]. This reacts with carbon
monoxide to afford [RhCl(CO)(PNCHP-j3P; N; P)] which rearranges in dichloromethane solution to [Rh(CO)(PNCHP-
j3P; N; P)]Cl ꢀ HCl. The single crystal structure of [Rh(CO)(PNCHP-j3P; N; P)]Cl ꢀ HCl shows the Rh to be in a square planar
environment with the HCl molecule held via hydrogen bonding in the lattice. NMR experiments show the coordinated chloride in
[RhCl(PNCHP-j3P; N; P)] can be substituted with tetrahydrofuran, acetonitrile or triphenylphosphine and the complex undergoes
oxidative addition with dichloromethane to yield [Rh(CH2Cl)Cl2(PNCHP-j3P; N; P)].
Ó 2003 Elsevier B.V. All rights reserved.
Keywords: Crystal structure; Rhodium; Phosphorus–nitrogen donor
1. Introduction
above. In addition, polydentate ligands have been
shown to: (i) Offer a more predictable coordination
number and stoichiometry, as the chelate effect mini-
mises the tendency of one or more phosphine groups to
be displaced during a chemical reaction. (ii) Increase the
basicity of the rhodium atom. (iii) Allow more control
on the stereochemistry of the complexes. (iv) Impart
detailed structural and bonding information in the form
of metal–phosphorus and phosphorus–phosphorus
coupling constants [5,6].
Most of the rhodium(I) square planar complexes
undergo oxidative addition reactions yielding octahedral
rhodium(III) complexes [7]. The most common of these
are the [RhX3L3] species, where meridional isomers are
normally the rule [8]. The oxidative addition of carbon
halides to low valent metal complexes is of paramount
interest. It is a key step in a number of industrially im-
portant catalytic processes, such as, carbonylation of
methanol to acetic acid, cross coupling and carbonyla-
tion reactions. It has been found that for oxidative ad-
ditions of carbon halide substrates to complexes of
rhodium(I) (and iridium(I)), the additions are generally
A major aspect of the chemistry of rhodium(I) is the
formation of tertiary phosphine complexes [1]. Of these,
complexes of the type [RhXL3], inspired by Wilkinson’s
compound, where L is a neutral ligand and X can be
virtually any uninegative ion, are the most populous
class. All are 16 electron compounds and are formally
coordinatively unsaturated [2]. Five-coordinate rho-
dium(I) species are commonly produced by addition of
neutral ligands to the four-coordinate species [3]. They
are also the intermediates in substitution reactions of
square planar rhodium(I) complexes, which are often
rapid and proceed by an associative pathway [4].
Generally, the rhodium(I) chemistry of polydentate
ligands is similar to the monodentate case discussed
* Corresponding authors. Tel.: +64-6-356-9099; fax: +64-6-350-5682.
E-mail address: a.brodie@massey.ac.nz (A.M. Brodie).
1
Present address: Actinide, Catalysis and Separations Chemistry, C-
SIC, Mail Stop J514, Los Alamos National Laboratory, Los Alamos,
NM 87545, USA.
0020-1693/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved.
doi:10.1016/S0020-1693(03)00483-3

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enhanced by increasing the electron density on the metal
atom. The activation of dichloromethane requires rela-
tively strong donor ligands, for example, the ligand
2. Results and discussion
2.1. Synthesis and reactivity of [RhCl(PNCHP-j3P;
N; P)] (1)
bis-(dimethylphosphino)ethane
in
the
complex
[Rh{Me2PCH2CH2PMe2}2]Cl [9,10]. Coordination of
ligands with three or four nitrogen donor atoms to
rhodium(I) also gives strong nucleophilic species that
can activate dichloromethane [9]. Whilst the arylphos-
phine moieties of the PNCHP ligand (Scheme 1) are less
basic than the alkylphosphine ligands employed to ac-
tivate carbon halides, the nitrogen donor in combination
with the chelating abilities of the ligand should increase
the basicity of the rhodium atom.
In this study, we have synthesised a Wilkinson’s
compound analogue with a ‘ClNP2’ donor set using the
mixed donor multidentate ligand, 2-(diphenylphos-
phino)-N-[2-(diphenylphosphino)benzylidene]benzene-
Scheme 2 depicts the synthesis and reactions of the
rhodium(I) complex, [RhCl(PNCHP-j3P; N; P)] (1). All
syntheses and manipulations were carried out under
argon due to the air-sensitive nature of the parent
compound 1 and most of the reaction products. The
dark-green (kmax ¼ 651 nm, emax ¼ 2500 Mꢁ1cmꢁ1
,
Rh! pꢂimine
charge
transfer
band)
complex
[RhCl(PNCHP-j3P; N; P)] (1) is prepared by reacting
two equivalents of the PNCHP ligand with the chloro-
bridged dimer [{Rh(COD)Cl}2], in benzene. By con-
trast, the reaction of PNHCH2P, which has the imine
functional group reduced to a secondary amine, with
[{Rh(COD)Cl}2], gives rise to the five-coordinate
[Rh(COD)(PNHCH2P-j3P; N; P)]Cl [12]. In the re-
duced-ligand complex, the PNHCH2P ligand adopts a
facial geometry, unlike PNCHP which prefers a merid-
ional geometry [11]. A solution (e.g., benzene) of 1
changes from dark-green to a rust colour within seconds
when exposed to air. The colour change also occurs in
the solid state but is slower. 31P NMR spectroscopy
shows the reaction is complex, with the formation of
many products, but mass spectrometry suggests one is
amine (PNCHP) [11], and report
investigation into its reactivity.
a preliminary
Scheme 1. The PNCHP ligand.
Scheme 2. Reactivity of [RhCl(PNCHP-j3P; N; P)] (1). aCl ligands in 7 maybe cis.

E.W. Ainscough et al. / Inorganica Chimica Acta 357 (2004) 2379–2384
2381
[{RhCl(PNCHP)O2}2]. The air-sensitivity of 1 is in
contrast to that of the ‘P3’ analogue, [RhCl(PhP-
(CH2CH2CH2PPh2)2-j3P; P; P)], which is stable indefi-
nitely in air [5].
[RhCl(PNCHP-j3P; N; P)] (1) reacts with CO to give
the neutral, five-coordinate, compound [RhCl(CO)-
(PNCHP-j3P; N; P)] (2), as a dark-green precipitate.
The mass spectrum of 2 shows the most intense peak at
m/z 680 (100%), corresponding to the loss of the chloride
ion from the parent. Upon dissolution of 2 in dichlo-
romethane, the coordinated chloride ion is lost and the
orange ionic four-coordinate compound [Rh(CO)-
(PNCHP-j3P; N; P)]Cl ꢀ HCl (3) is obtained, the identity
of which was determined by an X-ray study (see Section
2.2). In the IR, the shift of the m(CO) band from 1959
cmꢁ1 for 2 to 2009 cmꢁ1 for 3 is consistent with the
decrease in the coordination number of the Rh(I) atom
and the formation of a cationic complex. The air-sen-
sitivity of 3 is dramatically diminished compared to the
parent complex 1, with estimated half-lives in solution
(as observed by 31P NMR) of several days (for 3) and
several seconds (for 1).
NMR experiments show acetonitrile (MeCN) will
substitute for the chloride of [RhCl(PNCHP-j3P; N; P)]
(1), with the aid of AgBF4, to give the brown-orange,
cationic complex, [Rh(MeCN)(PNCHP-j3P; N; P)]BF4
(4). The mass spectrum of 4 shows a peak at m/z 653
(100%) which corresponds to the loss of MeCN from the
parent cation although the parent cation [Rh(MeCN)-
(PNCHP-j3P; N; PÞꢃþ is also observed at m/z 693 (87%).
In a similar reaction, the dark-red, tetrahydrofuran
(THF) adduct, [Rh(THF)(PNCHP-j3P; N; P)]BF4 (5), is
prepared by reacting 1 with AgBF4 in THF. The THF
can be readily displaced yielding the yellow, triphenyl-
phosphine complex, [Rh(PPh3)(PNCHP-j3P; N; P)]BF4
(6) which has a peak at m/z 914 (40%) in the mass
spectrum corresponding to the parent cation. When 1 is
dissolved in CH2Cl2 a yellow oxidative-addition product
is obtained which is formulated as [Rh(CH2Cl)-
Cl2(PNCHP-j3P; N; P)] (7) on the basis of its mass
spectrum [the observation of a peak m/z 736 (76%) as-
signable to the [M–Cl]þ ion] and its NMR spectrum (see
Section 2.3).
Fig. 1. An ORTEP diagram of the cation, [Rh(CO)(PNCHP-
j3P; N; PÞꢃþ, of complex 3 showing the numbering system used.
Thermal ellipsoids are at the 50% probability level.
Table 1
ꢀ
Selected bond lengths and angles for complex 3 [A and °] with esti-
mated standard deviations in parentheses
Rh(1)–Cð100Þ
Rh(1)–N
1.802(4)
2.106(4)
2.2864(6) N–Rh(1)–P(1)#1
Cð100Þ–Rh(1)–N
171.34(9)
95.90(2)
Cð100Þ–Rh(1)–P(1)
Rh(1)–P(1)
N–C(1)
N–C(36)
90.05(14)
78.22(15)
168.20(3)
1.283(6)
1.450(8)
1.439(12)
N–Rh(1)–P(1)
P(1)–Rh(1)–P(1)#1
C(1)–C(46)
Symmetry transformations used to generate equivalent atoms: #1,
ꢁx þ 1; y; ꢁz þ 3=2.
by bonding through the two phosphorus atoms [P(1)
and P(1)#1] and the one nitrogen atom (N) with the
fourth site occupied by a carbon monoxide ligand
ꢀ
[Cð100Þ–Oð100Þ]. The Rh(1)–P(1) [2.2864(6) A], Rh(1)–
ꢀ
ꢀ
Cð100Þ [1.802(4) A], Rh(1)–N1 [2.106(4) A] distances are
similar to other rhodium(I)-monocarbonyl cations with
mixed P and N donor sets [13,14]. The P(1)–Rh–P(1)#1
bond angle at 168.20(3)° shows a significant deviation
from the 180° expected for an ideal square-planar ge-
ꢀ
ometry. The N–C(1) imine bond distance at 1.283(6) A
ꢀ
is ꢄ0.02 A longer than the value observed for the un-
coordinated ligand [11b]. Apart from the expected
chloride ion, the asymmetric unit also contains an HCl
molecule (for details see Section 4.3) which appears to
have arisen from the chlorinated solvent used for the
synthesis of the compound. The HCl is held in the lattice
via hydrogen bonds between the chloride and the
PNCHP imine proton, H(1A), one of the aromatic hy-
drogens, H(15A) and as well there is a hydrogen bond
between the two chloride ions (Table 2).
2.2. Single crystal structure of [Rh(CO)(PNCHP-
j3P,N,P)]Cl ꢀ HCl (3)
The X-ray crystal structure of the cation of
[Rh(CO)(PNCHP-j3P; N; P)]Cl ꢀ HCl (3) is shown in
Fig. 1 and selected bond lengths and angles are listed in
Table 1. The cation lies on a twofold rotational axis with
Rh(1), Cð100Þ and Oð100Þ occupying special positions
on that axis and the PNCHP ligand being disordered.
The geometry of the coordination polyhedron about the
rhodium atom is approximately square planar. The
PNCHP ligand occupies three of the coordination sites
2.3. NMR spectroscopy
Proton NMR spectra showed the expected integra-
tion and peak multiplicities. The chemical shifts for the
imino proton (Table 3) ranged from d 10.25 for 3, to

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E.W. Ainscough et al. / Inorganica Chimica Acta 357 (2004) 2379–2384
Table 2
ꢀ
Hydrogen bonds for compound 3 [A and °]
D–Hꢀ ꢀ ꢀA
d(D–H)
d(Hꢀ ꢀ ꢀA)
2.36
d(Dꢀ ꢀ ꢀA)
<(DHA)
C(15)–H(15A)ꢀ ꢀ ꢀCl(1)#2
C(1)–H(1A)ꢀ ꢀ ꢀCl(1)
C(1)–H(1A)ꢀ ꢀ ꢀCl(1)#1
Cl(1)–H(1)ꢀ ꢀ ꢀCl(2)
0.95
0.95
3.307(5)
3.467(7)
3.099(7)
3.305(6)
172.3
130.9
110.0
141(3)
2.77
2.64
0.95
0.93(3)
2.53(4)
Symmetry transformations used to generate equivalent atoms: #1, ꢁx þ 1; y; ꢁz þ 3=2; #2, ꢁx þ 3=2; ꢁy þ 3=2; ꢁz þ 2.
Table 3
31P and 1H NMR data for selected compoundsa
Compound
dP
2J(P,P) (Hz)
1J(Rh,P) (Hz)
dCH @ N
3J(Rh,H) (Hz)
Pa
Pb
Pa
Pb
[RhCl(PNCHP)] (1)
[Rh(CO)(PNCHP)]Cl ꢀ HCl (3)
32.0
44.4
36.6
33.6
44.3
47.1d
40.2
27.1
31.5
30.8
29.7
32.6
408
283
142
123
138
146
143
164
101
148
127
138
148
138
10.25(d)
8.49(d)
2.1
3.7
b
[Rh(MeCN)(PNCHP)]BF4 (4)
c
331
338
[Rh(THF)(PNCHP)]BF4 (5)
c
[Rh(PPh3(PNCHP)]BF4 (6)
296
41, 32
505
[Rh(CH2Cl)Cl2(PNCHP)]e(7)
27.3
103
8.78(d)
3.2
a
31P NMR recorded at 109 MHz, chemical shifts are in ppm relative to 85% H3PO4, solvent CDCl3 unless stated otherwise. 1H NMR recorded at
270 MHz, chemical shifts are in ppm relative to Si(CH3)4, solvent CDCl3 unless stated otherwise.
b
31P data in CH3CN; 1H data in C6D6; Rh-NCCH3 signal at d 2.25(s).
c In THF.
d Rh-PPh3.
e
31P data in CH2Cl2. Rh-CH2Cl signals at d 3.85(m) and 3.46(m).
below the aromatic protons (d > 7:4) for 1. The imino
proton resonance was observed as a doublet for all the
compounds due to coupling with the spin 1/2, 103Rh
nucleus (100%), with the 3J(Rh,H) coupling constants in
the range 2–4 Hz.
most likely caused by the phosphorus atom involved in
the five-membered chelate ring due to the ring
contribution (DR) effect [18,19]. The cloþsely related
complexes [Rh(CO)(PNHCH2P-j3P; N; PÞꢃ and [Rh-
(PPh3)(PNHCH2P-j3P; N; PÞꢃþ, where PNHCH2P is
PNCHP with the imine functional group reduced to a
secondary amine, have similar spectroscopic properties
to the PNCHP compounds above [12]. The product 7 of
the reaction between [RhCl(PNCHP-j3P; N; P)] and
CH2Cl2, displays a relatively large increase in the
2J(P,P) coupling constant and a large reduction of the
1J(P,Rh) coupling constant. This feature is indicative of
a increase in the rhodium oxidation state from +1 to +3
The MeCN complex, 4, displays a singlet at d 2.25,
assignable to the methyl group of the coordinated ace-
tonitrile ligand [15]. Two signals, at d 3.85 and 3.46, with
multiple splitting, are exhibited by the complex
[Rh(CH2Cl)Cl2(PNCHP-j3P; N; P)]BF4 (7) – each of
these have been assigned to one of the –CH2Cl protons.
The observed chemical shift is similar to other Rh(III)–
CH2Cl complexes [9,16], although in those cases, the
methylene protons were magnetically equivalent.
The parent rhodium compound [RhCl(PNCHP-
j3P; N; P)] (1) exhibits an ABX type 31P spectrum re-
sulting from mutual coupling of the two inequivalent
phosphorus nuclei (d 32.0 and 27.1) of the PNCHP li-
gand, and a phosphorus coupling to the 103Rh (100%)
nucleus which has I ¼ 1=2 (Table 2). The coupling
2
[20]. Chemical shifts and the J(P,P) coupling constants
of the product points to the two phosphorus atoms of
PNCHP coordinated in a trans arrangement with the
nitrogen atom also bound.
3. Conclusions
2
constant, J(P,P) is 408 Hz and the coupling constants
1J(P,Rh) are 142 and 148 Hz, respectively. The coupling
constants and chemical shifts are typical of other com-
plexes with nitrogen/phosphorus donor atoms, where
phosphorus atoms of the PPh2 moiety are trans to each
other [17]. For compounds 3 and 6, in which the chlo-
ride in 1 has been replaced by CO or PPh3, one of the
phosphorus resonances of PNCHP has shifted by 12
ppm to higher frequency, while the other exhibits a
much smaller shift. The higher frequency 31P signal is
The enhanced reactivity of [RhCl(PNCHP-j3P; N; P)]
(1) relative to [RhCl(‘P3’)] systems (‘P3’ ¼ mono-, bi- or
tridentate phosphines), can be attributed to the presence
of the coordinated imino nitrogen which has the effect of
increasing the nucleophilicity of the rhodium atom.
Thus the complex rapidly decomposes in air and acti-
vates the halo-carbon bond of dichloromethane. A
comparison of the reactivities of the ‘P3’ ligand complex,
[RhCl(PhP(CH2CH2CH2PPh2)2-j3P; P; P)] [5], and the

E.W. Ainscough et al. / Inorganica Chimica Acta 357 (2004) 2379–2384
2383
‘N3’ ligand complex, [RhCl(2,6-(C(R1) ¼ NR2)2C5H3N-
j3N; N; N)] [9], shows the latter to react in seconds with
CH2Cl2 whereas the ‘P3’ ligand complex does not react.
As expected, the ‘P2N’ complex, 1, lies between these
two extremes, requiring a few hours for the reaction to
go to completion. Exposure to carbon monoxide allows
the formþation of the cation [Rh(CO)PNCHP-
j3P; N; PÞꢃ which does not show the same high
reactivity of the parent [RhCl(PNCHP-j3P; N; P)] (1)
complex, due to the carbon monoxide removing electron
density from the Rh atom.
using THF as solvent. Similarly the PPh3 adduct,
[Rh(PPh3)(PNCHP-j3P; N; P)]BF4 (6), was prepared by
adding the phosphine (in a 1:1 mole ratio) to a THF
solution of 5 and stirring at room temperature. After the
resulting yellow solution was filtered through a plug of
alumina (eluting with THF), the solvent was removed in
vacuo. MS: m/z 914 [M]þ, 652 [M–PPh3]þ.
4.2.2. [RhCl(CO)(PNCHP-j3P,N,P)] (2)
Carbon monoxide was bubbled through a dark-green
solution of 1 (0.154 g, 0.224 mmol) dissolved in 20 mL of
THF for 30 min to give a dark-green precipitate. The
solvent was removed in vacuo, yielding 2 (0.160 g, 79%) as
dark-green microcrystals. Anal. Found: C, 63.10; H, 4.65;
N, 1.82. Calc. for C38H29ClNOP2Rh: C, 63.75; H, 4.08; N,
1.96%; MS: m/z 680 [M–Cl]þ; IR (nujol) 1959 cmꢁ1
[m(CO)]. When compound 2 (0.030 g, 0.042 mmol) was
dissolved in dichloromethane (2 mL), the green colour of
the starting material slowly discharged. n-Hexane vapour
was diffused into the resulting yellow solution to yield
orange crystals of [Rh(CO)(PNCHP-j3P; N; P)]Cl ꢀ HCl
(3) after several days. A single crystal was selected for an
X-ray study. IR (CHCl3) 2009 cmꢁ1 [m(CO)].
4. Experimental
4.1. Materials and instrumentation
NMR measurements were performed on a JEOL
GX270W spectrometer. IR spectra were recorded on a
BIO-RAD FTS-40 instrument. UV–Vis spectra were
recorded using a Shimadzu UV-310PC UV–VIS–NIR
spectrometer. Mass spectra were obtained using a Var-
ian VG70-250S double-focussing magnetic sector spec-
trometer by the method of liquid ion secondary mass
spectroscopy (LSIMS) using m-nitrobenzyl alcohol as
the matrix. Isotope abundance calculations were per-
formed to identify the parent ion. Microanalyses were
performed by the Campbell Microanalytical Labora-
tory, University of Otago. All synthetic work was car-
ried out in an argon atmosphere glove-box, unless stated
otherwise. The complex [{RhCl(COD)}2] [21] and
PNCHP [11a] were prepared as previously reported.
Solvents were dried by standard procedures [22].
4.2.3. [Rh(CH2Cl)Cl2(PNCHP-j3P,N,P)] (7)
Compound 1 (0.030 g, 0.042 mmol) was dissolved in
dichloromethane (2 mL) and allowed to stand until the
green colour of the starting material discharged. n-
Hexane vapour was then slowly diffused into the yellow
solution resulting in the title compound as a yellow
powder. Anal. Found: C, 55.25; H, 3.87; N, 1.65; Cl,
2
18.10. Calc. for C38H31Cl3NP2Rh ꢀ /3CH2Cl2: C, 55.99;
H, 3.92; N, 1.69; Cl, 18.50%; MS: m/z 736 [M–Cl]þ.
4.2. Syntheses
4.3. Determination of the crystal structure of
[Rh(CO)(PNCHP-j3P,N,P)]Cl ꢀ HCl (3)
4.2.1. [RhCl(PNCHP-j3P; N; P)] (1)
A mixture of [{RhCl(COD)}2] (0.239 g, 0.485 mmol)
and PNCHP (0.528 g, 0.961 mmol) in ca. 10 mL of
benzene was stirred at room temperature for 1 h. The
resulting dark-green precipitate of 1 (0.661 g, 100%) was
isolated by filtration and washed with n-pentane. Anal.
Found: C, 64.54; H, 4.29; N, 1.86. Calc. for
C37H29ClNP2Rh: C, 64.60; H, 4.25; N, 2.04%; MS: m/z
687 [M]þ, 652 [M–Cl]þ; UV/Vis: k 651 nm, emax ¼ 2500
Mꢁ1 cmꢁ1. When a dark-green solution of 1 (0.100 g,
0.145 mmol) dissolved in MeCN (4 mL), was combined
with a solution of AgBF4 (0.0283 g, 0.145 mmol) dis-
solved the same solvent (2 mL), a red-brown coloured
solution formed instantaneously. After the solution had
been stirred for 1 h, the white precipitate of AgCl was
removed by filtration to give a rust coloured solution of
[Rh(MeCN)(PNCHP-j3P; N; P)]BF4 (4), which was ta-
ken to dryness in vacuo. MS: m/z 693 [M]þ, 652 [M-
MeCN]þ. The THF adduct, [Rh(THF)(PNCHP-
j3P; N; P)]BF4 (5), was prepared in a similar manner
A single crystal of compound 3, was grown as de-
scribed in the above section and attached to the ends of
a glass fibre with cyanoacrylate glue. Data collection
and refinement were performed as previously described
[23]. The molecule lies on a twofold rotational axis with
the Rh(1), Cð100Þ and Oð100Þ occupying special posi-
tions on that axis and the PNCHP ligand being disor-
dered. The two phenyl rings [C(11) to C(16) and C(21)
to C(26)] and the phosphorus atom P(1) transform quite
well into their symmetry related positions, leading to
larger, but tolerable, temperature factors for the carbon
atoms and were thus refined with site occupation factors
of 1. The oxygen of the CO ligand also shows an elon-
gated parabolloid but a disordered refinement shows no
significant improvement, hence the special position
constraint was left in place. The phenyl-N@CH-phenyl
fragment of the PNCHP ligand was refined as disor-
dered around the C2 axis with site occupation factors
(sof) of 0.5, which gave acceptable bond and tempera-

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[2] G. Wilkinson, R.D. Gillard, J.A. McCleverty (Eds.), Comprehen-
sive Coordination Chemistry: The Synthesis Reactions, Properties
and Applications of Coordination Compounds, vol. 4, Pergamon
Press, Oxford, 1987, p. 913.
ture factors. The temperature factors of related carbon
atom pairs [C(31) C(41), C(32) C(42), etc.] were con-
strained to be equal. The asymmetric unit contains two
chlorine atoms (sof 0.5), which are also disordered
around the C2 axis (pointing to the presence of lattice
[3] F.A. Cotton, G. Wilkinson, C.A. Murillo, M. Bochmann,
Advanced Inorganic Chemistry, sixth ed., Wiley, New York,
1999, p. 1041.
ꢀ
HCl). The atoms, Cl(1) and Cl(2), are 3.305 A apart
indicating a hydrogen bond between the two (the dis-
[4] F.A. Cotton, G. Wilkinson, C.A. Murillo, M. Bochmann,
Advanced Inorganic Chemistry, sixth ed., Wiley, New York,
1999, pp. 1041–1042.
ꢀ
tance of 2.827 A for the symmetry equivalent of Cl(2)
seems too short – published Cl–Hꢀ ꢀ ꢀCl distances lie
[5] T.E. Nappier Jr., D.W. Meek, R.M. Kirchner, J.A. Ibers, J. Am.
Chem. Soc. 95 (1973) 4194.
ꢀ
around 3.2–3.3 A). The most likely position for this
[6] J.A. Tiethof, J.L. Peterson, D.W. Meek, Inorg. Chem. 15 (1976)
1365.
hydrogen was found at the later stages of the refinement
as Q3 and refined labelled H(1). This appears chemically
sensible, however, due to the disorder of the chlorine
atoms, this assignment has to be regarded with caution.
Crystal data for C38H30Cl2NOP2Rh: M ¼ 752:38,
monoclinic, space group C2/c, a ¼ 20:0936ð1Þ; b ¼
[7] F.A. Cotton, G. Wilkinson, C.A. Murillo, M. Bochmann,
Advanced Inorganic Chemistry, sixth ed., Wiley, New York,
1999, p. 1042.
[8] G. Wilkinson, R.D. Gillard, J.A. McCleverty (Eds.), Comprehen-
sive Coordination Chemistry: The Synthesis Reactions, Properties
and Applications of Coordination Compounds, vol. 4, Pergamon
Press, Oxford, 1987, p. 1028.
ꢀ
19:3859ð1Þ, c ¼ 8:9418ð1Þ A, b ¼ 92:227ð1Þ°; V ¼
3
ꢀ
3480:49ð5Þ A , Z ¼ 4; T ¼ 200ð2Þ K, Dcalc ¼ 1:436 g
cmꢁ1, F ¼ 1528, l(Mo Ka) 0.767 mmꢁ1, 10 561 reflec-
tions collected (2:92° < 2h < 54:92°), of which 3804
were unique Rint ¼ 0:0227). Data were corrected for
absorption effects; Tmax ¼ 0:8807; Tmin ¼ 0:7389. The
final R1½I > 2rIÞꢃ ¼ 0:0326; wR2½I > 2rIÞꢃ ¼ 0:0887; R1
(all data) ¼ 0.0385, wR2 (all data) ¼ 0.0922.
[9] H.F. Haarman, J.M. Ernsting,, M. Kranenburg, H. Kooijman, N.
Veldman, A.L. Speck, P.W.N.M. van Leeuwen, K. Vrieze,
Organometallics 16 (1997) 887 (and references therein).
[10] T.B. Marder, W.C. Fultz, J.C. Calabrese, R.L. Harlow, D.
Milstein, J. Chem. Soc., Chem. Commun. (1987) 1543.
[11] (a) E.W. Ainscough, A.M. Brodie, P.D. Buckley, A.K. Burrell,
S.M.F. Kennedy, J.M. Waters, J. Chem. Soc., Dalton Trans.
(2000) 2663;
(b) E.W. Ainscough, A.M. Brodie, A.K. Burrell, X. Fan, M.J.R.
Halstead, S.M.F. Kennedy, J.M. Waters, Polyhedron 19 (2000)
2585;
5. Supplementary material
(c) E.W. Ainscough, A.M. Brodie, A.K. Burrell, S.M.F. Kennedy,
J. Am. Chem. Soc. 123 (2001) 10391;
CCDC 215017 contains the supplementary crystal-
lographic data for this paper. These data can be ob-
tained free of charge via www.ccdc.cam.ac.uk/conts/
retrieving.html (or from the Cambridge Crystallo-
graphic Data Centre, 12, Union Road, Cambridge CB2
1EZ, UK; fax: +44 1223 336033; or E-mail: data_re-
quest@ccdc.cam.ac.uk).
(d) E.W. Ainscough, A.M. Brodie, A.K. Burrell, S.M.F. Kennedy,
J. Organomet. Chem. 609 (2000) 2.
[12] M.L. Edwards, Rhodium(I) complexes of a tridentate hybrid
phosphine-amine ligand: catalytic implications of trans-phospho-
rus geometry, BSc(Hons) Dissertation (1984) University of
Sydney.
[13] M.P. Anderson, C.C. Tso, B.M. Mattson, L.H. Pignolet, Inorg.
Chem. 22 (1983) 3267.
[14] A. Heßler, J. Fischer, S. Kucken, O. Stelzer, Chem. Ber. 127
(1994) 481.
Acknowledgements
[15] C. Hahn, J. Sieler, R. Taube, Polyhedron 17 (1998) 1183.
[16] K. Kashiwabara, A, Morikawa, T. Suzuki, K. Isobe, K. Tatsumi,
J. Chem. Soc., Dalton Trans. (1997) 1075.
We thank Associate Professor C.F. Rickard, Uni-
versity of Auckland for X-ray data collection, Dr. P.A.
Duckworth, University of Sydney for a copy of [12],
Professor G.B. Jameson for useful discussions and the
Massey University Research Fund for financial support.
[17] P. Paul, B. Tyagi, Polyhedron 15 (1996) 675 (and references
therein).
[18] S. Berger, S. Braun, H.-O. Kalinowski, NMR Spectroscopy of the
Non-Metallic Elements, Wiley, Chichester, 1997, p. 837.
[19] G. Dyer, J. Roscoe, Inorg. Chem. 35 (1996) 4098 (and references
therein).
[20] J. Mason (Ed.), Multinuclear NMR, Plenum Press, New York,
1987, p. 394.
References
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[1] F.A. Cotton, G. Wilkinson, C.A. Murillo, M. Bochmann,
Advanced Inorganic Chemistry, sixth ed., Wiley, New York,
1999, 1044.