The complexes: RhCl(P-N)(THP), where P-N is P,N-chelated o-diphenylphosphino-N,N-dimethylaniline and THP is tris(hydroxymethyl)phosphine, and RhCl[(O)P-N][THP(O)] containing O-bonded phosphine oxides

Article abstract of DOI:10.1016/j.ica.2007.11.017

The complex RhCl(P-N)(THP) (1) is synthesized under argon from RhCl(cod)(THP) and P-N, and is structurally characterized; P-N = P,N-chelated o-diphenylphosphino-N,N-dimethylaniline, THP = tris(hydroxymethyl)phosphine, and cod = 1,5-cyclo-octadiene. The co

Full text of DOI:10.1016/j.ica.2007.11.017

Available online at www.sciencedirect.com
Inorganica Chimica Acta 361 (2008) 3199–3204
www.elsevier.com/locate/ica
The complexes: RhCl(P–N)(THP), where P–N is P,N-chelated
o-diphenylphosphino-N,N-dimethylaniline and THP
is tris(hydroxymethyl)phosphine, and RhCl[(O)P–N][THP(O)]
containing O-bonded phosphine oxides
Fabio Lorenzini, Brian O. Patrick, Brian R. James *
Department of Chemistry, The University of British Columbia, Vancouver, BC, Canada V6T 1Z1
Received 24 August 2007; received in revised form 13 November 2007; accepted 14 November 2007
Available online 22 November 2007
Dedicated to Professor Bob Angelici for his lifelong contributions to inorganic and organometallic chemistry; we (Bob and B.R.J.) met almost 40 years
ago when both studying carbonylation of amines.
Abstract
The complex RhCl(P–N)(THP) (1) is synthesized under argon from RhCl(cod)(THP) and P–N, and is structurally characterized; P–
N = P,N-chelated o-diphenylphosphino-N,N-dimethylaniline, THP = tris(hydroxymethyl)phosphine, and cod = 1,5-cyclo-octadiene.
The corresponding synthesis in air yields RhCl[(O)P–N][THP(O)] (2), containing O-bonded phosphine oxide ligands.
Ó 2007 Elsevier B.V. All rights reserved.
Keywords: Rhodium complexes; Phosphines; Phosphine oxides; X-ray structure; Oxidation
1. Introduction
containing a chelated P,P-phosphine-phosphinite ligand
[4]; in such reactions, one of the R groups of the PR3 was con-
verted into the RH hydrocarbon product, the hydrogen
being derived from a THP-hydroxyl group which becomes
the alkoxy group at the residual PR2 moiety (Scheme 1).
We subsequently reacted Ph2P(CH2)2PPh2 (diphos) with
RhCl(cod)(THP) to see whether the –PPh2 moiety of a che-
lated diphosphine (P–P) would undergo a similar cleavage
process with the THP-hydroxyl proton; however, on coordi-
nation, the diphos retained its integrity and no cleavage was
observed [5]. We then tested, for the same reason, reaction of
a P–N ligand with the RhI–THP complex, and the findings
are presented here. Use of the P–N ligand o-diphenylphos-
phino-N,N-dimethylaniline was found to generate
RhCl(P–N)(THP) (1), where the N-donor is trans to the P-
donor of THP as established by spectroscopic and X-ray
crystallographic data, but no subsequent THP-promoted
cleavage was seen. Further, we have recently reported on
the synthesis of the analogous triphenylphosphine complex
We have reported recently the first structurally character-
ized RhI–THP complexes (where THP = P(CH2OH)3,
tris(hydroxymethyl)phosphine) [1], which are water-soluble
and thus of potential interest as precursors for entries into
the areas of aqueous oraqueous/organic two-phase homoge-
neous catalysis (cf. the Ruhrchemie/Rhoˆne-Poulenc propyl-
ene hydroformylation process [2]) and possibly in
biomedical applications using water-soluble drugs [3]. The
unexplored RhI/THP chemistry prompted us to study the
reactivity of RhCl(cod)(THP) with other potential ligands,
including monodentate tertiary phosphines (for example,
PR3), and this led to the discovery of a THP-promoted P–
C bond cleavage of the PR3 to generate a complex of the type
trans- and cis-RhCl(PR3)[P,P-R2POCH2P(CH2OH)2]
*
Corresponding author. Tel.: +1 604 822 6645; fax: +1 604 822 2847.
E-mail address: brj@chem.ubc.ca (B.R. James).
0020-1693/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2007.11.017

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F. Lorenzini et al. / Inorganica Chimica Acta 361 (2008) 3199–3204
R3P
P
Cl
OH
R3P
THP
R3P
R2P
HO
Cl
PR3
Cl
2PR3
-cod
Rh
Rh
+ RH
RhCl(cod)(THP)
Rh
PR2
P
HO
OH
O
O
Scheme 1. Synthesis of trans- and cis-RhCl(PR3)[P,P-R2POCH2P(CH2OH)2]; trans and cis refer to the disposition of the P-atoms with R substituents.
RhCl(P–N)(PPh3) and its ready oxidative addition of O2 to
form a stable, isolable RhIII–peroxide complex [6], and so
we were interested to see if 1 reacted similarly. However, aer-
ial oxidation of 1 yields RhCl[(O)P–N][THP(O)] (2), con-
taining now the O-bonded phosphine oxide ligand
derivatives, as evidenced by spectroscopic data.
4JHH = 1.5, p-H to P of C6H4N), 7.49 (m, 7H, m-H, p-H
3
of PPh; o-H to P of C6H4N), 7.83 (dd, 1H, JHH = 8.5,
4JHH = 3.6, o-H to N of C6H4N), 8.01 (m, 4H, o-H of
1
PPh). 13C{1H} NMR: d 52.61 (d, JCP = 46.38, PCH2),
59.10 (m, N(CH3)2), 123.32 (m, o-C to N of C6H4N „
m-C to P of C6H4N, and CipsoN), 129.52 (s, p-C to N of
C6H4N), 129.75 (m, m- and p-C of Ph), 131.59 (d,
2JCP = 2.15, o-C to P of C6H4N „ m-C to N of C6H4N),
2. Experimental
2
133.60 (s, p-C to P of C6H4N), 135.09 (d, JCP = 12.84,
1
o-C to P of Ph), 136.89 (d, JCP = 47.15, CipsoPPh),
2.1. General considerations
1
138.72 (d, JCP = 39.14, CipsoP of C6H4N). 31P{1H}
1
2
NMR: d 56.81 (dd, JRhP = 193.7, JPP = 48.4, P–N), d
The RhCl(cod)(THP) precursor complex was synthe-
sized by our recently reported method [1], and o-diphenyl-
phosphino-N,N-dimethylaniline, the P–N ligand, was made
according to the literature method [7]. The reactions
between the Rh complex and P–N were carried out under
Ar using standard Schlenk techniques or in a J-Young
NMR-tube. Organic solvents were dried over the appropri-
ate solvents, and were distilled under Ar, while acetone-d6
(Cambridge Isotope Laboratory) was used as received.
1
2
39.54 (dd, JRhP = 161.0, JPP = 48.4, PCH2).
Yellow, X-ray quality, plate crystals of 1 were immedi-
ately obtained by subjecting a 0.027 M acetone solution
of the complex to 1 atm of H2.
2.3. Crystallographic analysis of complex 1
X-ray data for RhCl(P–N)(THP) (1) were collected at
1
31P{1H}, 13C{1H} and H NMR spectra were measured
173 ( 0.1) K on a Bruker X8 APEX diffractometer using
˚
graphite-monochromated Mo Ka radiation (0.71073 A) to
at room temperature (ꢀ300 K) in acetone-d6 on a Bruker
AV400 spectrometer; a residual deuterated solvent proton
(relative to external SiMe4) and external 85% aq H3PO4
were used as references (s = singlet, d = doublet, t = trip-
let, q = quartet, m = multiplet, br = broad; J values given
in Hz). When necessary, atom assignments were made by
means of 1H–13C{1H} (HSQC and HMBC), and
1H–31P{1H} (HSQC and HMBC) NMR correlation spec-
troscopies. Elemental analyses were performed on a Carlo
Erba 1108 analyzer. Mass spectrometry was performed on
a Bruker Esquire electrospray (ESI) ion-trap spectrometer
with samples dissolved in MeOH, with positive ion polarity
scanning from 60 to 1000 m/z.
a maximum 2h value of 55.8°, in a series of / and x scans
in 0.50° oscillations with 5.0 s exposures; the crystal-to-
detector distance was 38.85 mm. Of the 80,413 reflections
collected, 17,162 were unique (Rint = 0.045), equivalent
reflections being merged. Data were collected and inte-
grated using the Bruker SAINT software package [8], and
were corrected for absorption effects using the multi-scan
technique (SADABS) [9], with minimum and maximum trans-
mission coefficients of 0.705 and 0.933, respectively. Data
were corrected for Lorentz and polarization effects, and
the structures were solved by direct methods [10]. Selected
crystallographic data are shown in Table 1, and more
details are provided in the Supporting Information. The
material crystallizes with three molecules in the asymmetric
unit; one CH2OH group of two of the molecules (labelled
Rh1 and Rh2) are disordered, and were each modelled in
two orientations. All non-hydrogen atoms were refined
anisotropically, while all C–H hydrogen atoms were just
included in calculated positions. All O–H hydrogen atoms,
except for those of the disordered CH2OH groups, were
located in difference maps and refined isotropically.
2.2. Synthesis of RhCl(P–N)(THP) (1)
Addition of P–N (9.4 mg, 0.031 mmol) in acetone
(0.3 mL) to an acetone solution (0.7 mL) of
RhCl(cod)(THP) (10.1 mg, 0.027 mmol) at room tempera-
ture under Ar gives immediate formation of a yellow-
orange solution; addition of Et2O (20 mL) yields a yellow
powder that was collected, washed with Et2O (2 ꢁ 5 mL)
and dried under vacuum (13.6 mg; yield 89% on Rh). Anal.
Calc. for C23H29ClNO3P2Rh: C, 48.65; H, 5.15; N, 2.47.
Found: C, 48.96; H, 5.35; N, 2.62%. MS: m/z 532
2.4. Synthesis of RhCl[(O)P–N][THP(O)] (2)
1
2
(MꢂCl+). H NMR: d 3.23 (d, 6H, JHP = 1.4, PCH2),
Addition of P–N (45.8 mg, 0.150 mmol) in acetone
(1.0 mL) to an acetone solution (7.0 mL) of
RhCl(cod)(THP) (50.0 mg, 0.135 mmol) at room tempera-
ture in air immediately gives a yellow-orange solution.
3.82 (s, 3H, NCH3), 3.84 (s, 3H, NCH3), 4.07 (q, 3H,
3JHH = 3JHP = 5.3, PCH2OH), 7.28 (br t, 1H, JHH = 7.7,
3
3
p-H to N of C6H4N), 7.40 (br dt, 1H, JHH = 8.1,

F. Lorenzini et al. / Inorganica Chimica Acta 361 (2008) 3199–3204
3201
Table 1
Crystal data and structure refinements for complex 1
Empirical formula
Mw
C23H29ClNO3P2Rh
567.77
T (K)
173.0 (1)
Crystal system
Crystal size (mm3)
a (A)
monoclinic
0.07 ꢁ 0.30 ꢁ 0.35
˚
14.9929(5)
˚
b (A)
29.2316(9)
16.3870(5)
˚
c (A)
a (°)
b (°)
c (°)
90
90.718(1)
90
7181.3(4)
3
˚
V (A )
Z value
12
1.575
0.984
3480
Dcalc (g cmꢂ3
)
l (mmꢂ1
F(000)
)
Fig. 1. Structure of RhCl(P–N)(THP) (1); ORTEP shows 50% probability
ellipsoids.
Reflections collected
Unique reflections [Rint
Number of variables
Goodness-of-fit on F2
Final R indices (I > 2r(I))
Maximum differential peak/hole (e A
80413
17162 [0.045]
902
1.01
R1 = 0.053a; wR2 = 0.073b
0.58/ꢂ0.49
]
precursor is used in the synthesis, the 31P{1H} NMR spec-
trum of the in situ solution product reveals the doublet sig-
ꢂ3
˚
)
P
P
1
a
nal of RhCl(cod)(THP) [d 17.4 (d, JRhP = 145 Hz)] [1], as
R1 = j(Fo) ꢂ (Fc)j/ (Fo).
P
P
2
2 1=2
b
wR2 ¼ ½ wðF 2o ꢂ F c2Þ = wðF 2oÞ ꢃ
.
well as the signals of complex 1.
Crystals of 1 were surprisingly best obtained by subject-
ing an acetone solution of the complex to an atmosphere of
H2! The observed, immediate precipitation of crystals was a
completely reproducible phenomenon, and was evident
only when using H2. The absence of any 1H NMR hydride
resonance in a CD3OD solution of the crystals and in an
acetone-d6 solution from which they were obtained showed
(disappointingly) that no hydride derivatives were formed;
Addition of Et2O (35 mL) yields 2 as an orange powder
that was filtered off, washed with Et2O (2 ꢁ 5 mL) and
dried under vacuum (66.4 mg; yield 82 % on Rh). Anal.
Calc. for C23H29ClNO5P2Rh: C, 46.06; H, 4.87; N, 2.34.
Found: C, 45.98; H, 5.11; N, 2.46%. MS: m/z 564 (M-
1
3
Cl+). H NMR: d 2.29 (d, 3H, JRhH = 2.8, NCH3), 3.40
3
(d, 3H, JRhH = 2.8, NCH3), d 3.95 (br s, 6H, PCH2),
1
indeed the H and 31P NMR spectra measured in CD3OD
3
7.43 (br t, 1H, JHH = 7.4, p-H to N of C6H4N), 7.49 (br
under H2 were identical to those seen for a CD3OD solu-
tion of 1 under Ar. We speculate that a seeding process
(presumably involving the formation of an undetectable
amount of a hydride derivative) is the likely cause of the
crystallization.
3
4
dt, 1H, JHH = 7.1, JHH = 2.8, p-H to P of C6H4N),
7.54–7.87 (m, 12H, Ph, o-H to P and N of C6H4N).
13C{1H} NMR: d 54.43 (d, JCP = 49.25, PCH2), 60.14
1
(m, N(CH3)2), 121.87–139.73 (m, C6H5, C6H4N). 31P{1H}
2
4
NMR: d 44.44 (dd, JRhP = 145.2, JPP = 29.5, OP–N), d
One of the three closely analogous, independent mole-
cules of RhCl(P–N)(THP) in the asymmetric unit, is shown
in Fig. 1, with selected bond lengths and angles summa-
rized in Table 2. The Rh atoms have the expected square-
planar geometry, with the Rh1, Rh2 and Rh3 atoms being,
2
4
28.83 (dd, JRhP = 118.6, JPP = 29.5, OPCH2).
3. Results and discussion
The RhCl(P–N)(THP) complex 1 was fully character-
ized by elemental analysis, NMR spectroscopy, MS, and
X-ray crystallography (Fig. 1). In the synthesis given in
Section 2 (which involves simple substitution of P–N for
the cod of RhCl(cod)(THP)), a slight excess of P–N was
˚
respectively, 0.0196(6), 0.0320(6) and 0.0008(6) A out of
the mean plane. The chloride is trans to the phosphorus
atom of the chelated P–N ligand, and the THP is trans to
the N-atom; the geometrical parameters shown in Table 2
are unexceptional for those of RhI/THP [1] or RhI/(P–N)
systems [1,12]. In the reported, related structures of
1
used, and the H NMR spectrum of the solution prior to
precipitation of the complex shows free cod, and the
31P{1H} NMR spectrum shows the presence of some P–
N (d ꢂ12.12) and two equal intensity doublets of doublets
at d 39.54 and 56.81 that correspond to the THP and P–N
Table 2
˚
Selected bond lengths (A) and angles (°) in complex 1
1
phosphorus atoms of 1; the magnitude of the JRhP and
Rh(1)–P(1)
Rh(1)–P(2)
Rh(1)–N(1)
Rh(1)–Cl(1)
2.2122(7)
2.1657(6)
2.223(2)
P(1)–Rh(1)–P(2)
P(1)–Rh(1)–N(1)
P(1)–Rh(1)–Cl(1)
P(2)–Rh(1)–N(1)
P(2)–Rh(1)–Cl(1)
N(1)–Rh(1)–Cl(1)
93.71(2)
176.42(6)
93.19(3)
84.08(5)
171.78(3)
89.24(5)
2JPP values are consistent with the presence of cis-phos-
phines [11], as established in the solid state structure (see
below), and the specific assignment to the P-atoms are con-
sistent with the literature data for these two phosphine
ligands coordinated to Rh [1,12]. If a slight excess of the
2.4270(7)

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F. Lorenzini et al. / Inorganica Chimica Acta 361 (2008) 3199–3204
RhCl(P–N)(PPh3) [6] and RhCl(P–N)(CO) [12], the chlo-
ride is also trans to the P-atom of the P–N ligand.
atoms of the (O)P–N and THP(O) ligands. The significant
decreases in the JRhP values (2JRhP for complex 2, and
1JRhP for 1): 145.2 versus 193.7 Hz for the phosphorus
atoms of (O)P–N and P–N, respectively, and 118.6 versus
161.0 Hz for the THP(O) and THP systems, respectively,
are consistent with oxidation at both coordinated phospho-
As in the solid state structure of RhCl(cod)(THP) [1],
there is extensive H-bonding within the asymmetric unit:
there are 11 intermolecular O–H hydrogen bonds in the
˚
1.91–2.68 A range. Associated with the Rh1 molecule,
2
˚
there are 4 such bonds: 1 strong O–H bond (1.91 A)
rus atoms of 1, as is the difference between the JPP and
between one of its hydroxyl-H atoms and an O-atom of
4JPP values for the two complexes (18.9 Hz). As for com-
plex 1, no NMR evidence was seen for hemilabile character
of the (O)P–N ligand.
˚
an Rh2 molecule, 2 strong O–H bonds (1.95, 1.96 A)
between two of its O-atoms and two hydroxyl-H atoms
(one from each of Rh2 and Rh3 molecules), and a marginal
In the convenient, described synthesis of 2, a slight
excess of P–N is essential for the reaction with
RhCl(cod)(THP) in air, since this Rh precursor is also
air-sensitive; use of a less than stoichiometric amount of
P–N gives a more complex product mixture. Similarly,
attempts to synthesize 2 by direct aerial oxidation of com-
plex 1 was problematic in that an uncharacterized brown
co-product was precipitated along with generation of both
free THP(O) and (O)P–N in solution.
˚
O–H bond (2.68 A) between an O-atom of the Rh1 mole-
cule and an H-atom of a THP-methyl of a second Rh2 mol-
ecule. Four intermolecular O–H bonds are displayed by the
˚
Rh2 molecule: 1 strong O–H bond (1.91 A) between one of
its O-atoms and a hydroxyl-H of a second Rh1 molecule, 2
˚
strong O–H bonds (1.95, 2.01 A) between two of its hydro-
xyl-H atoms and two O-atoms (one from each of Rh1 and
˚
Rh3 molecules), and a marginal O–H bond (2.68 A)
between an H-atom of a THP-methyl of an Rh2 molecule
and an O-atom of a second Rh1 molecule. Finally, 3 inter-
molecular O–H bonds are displayed by an Rh3 molecule: 1
The approximate 31P NMR shifts in acetone-d6 solution
for free and RhI-coordinated P–N and THP, and for the
corresponding phosphine oxides, are summarized in Table
3. The data for the free phosphine oxides were acquired by
the in situ reaction of the phosphine with H2O2, a standard
method which can be used also for isolation of the phos-
phine oxides [16]. Although the substituents at the P-atom
are different (alkyl versus aryl), evident are: downfield
shifts of ꢀ65 ppm between free and coordinated phos-
phines, similar upfield shifts between coordinated THP
and THP(O) (11 ppm) and coordinated P–N and (O)P–N
(13 ppm), and the expected downfield shifts on oxidation
of the free phosphine (that for THP being about twice that
for P–N). Of note, the shift differences are in opposite
directions for the free and coordinated phosphine oxides
(17 ppm upfield for the alkyl phosphine and oxide, and
20 ppm downfield for the aryl system): ring contributions
[17] perhaps play a role in the P–N systems.
We are unaware of any literature describing the forma-
tion of a mixed bis(phosphine oxide) complex from a mixed
bis(phosphine) precursor via an aerial oxidation (i.e.
1 ? 2), although such formation of a diphosphine oxide
from a chelated P–P diphosphine has been reported [18a].
The production of a diphosphine monoxide complex from
a diphosphine complex is more common, when either O2 or
OHꢂ may be the source of the oxide [19a]. The mechanism
of the oxidation for the 1 ? 2 conversion has not been
˚
strong O–H bond (1.96 A) between one of its hydroxyl-H
atoms and an O-atom of a second Rh1 molecule, 1 strong
˚
O–H bond (2.01 A) between one of its O-atoms and a
hydroxyl-H of a second Rh2 molecule, and 1 weak H-bond
˚
(2.52 A) between an H-atom of a THP-methyl of an Rh3
molecule and an O-atom of a second Rh3 molecule.
We have found no solution NMR evidence for any
hemilabile behaviour of the P–N ligand, which shows just
its usual chelation to a metal within a 5-membered ring
[12–14], although related o-N,N-dimethylanilinyl substitu-
ents within diphosphine ligands do reveal exchange
between coordinated and free anilinyl rings [15].
The oxidized complex RhCl[(O)P–N][THP(O)] (2),
although we have been unable to grow an X-ray quality
crystal of the material, is well characterized by elemental
analysis, NMR spectroscopy and MS (Fig. 2a). The solu-
tion 31P{1H} NMR spectrum in acetone-d6 shows two dou-
blets of doublets of equal intensity at d 44.44 (2JRhP
=
=
4
4
145.2, JPP = 29.5 Hz) and 28.83 (2JRhP = 118.6 Hz, JPP
29.5 Hz), corresponding, respectively, to the phosphorus
Table 3
NMe2
31P NMR shifts for free and RhI-coordinated phosphines and phosphine
oxidesa
Ph2P
NMe2
Rh
O
Phosphine/phosphine oxide
Free
Coordinated
Ph2P
Rh
O
O
Cl
THP
THP(O)
P–N
(O)P–N
a
ꢂ23
46
40
29
57
44
Cl
OP(CH2OH)3
PPh3
ꢂ12
24
a
b
Approximate dP values in acetone-d6; there is good agreement with
shift data in the literature for these free and coordinated ligands in other
solvents (Refs. [1,13,14]).
Fig. 2. Structure of (a) RhCl[(O)P–N][THP(O)] (2), and (b) RhCl(O2)(P–
N)(PPh3).

F. Lorenzini et al. / Inorganica Chimica Acta 361 (2008) 3199–3204
3203
investigated, but the generally established mechanism for
such O2-oxidations requires the presence of some free phos-
phine, which initially acts as a nucleophile that replaces
coordinated peroxide within a metal-dioxygen intermedi-
ate; the subsequently generated H2O2 and the oxidized
metal turn out to be the actual oxidizing agents of the
phosphine (e.g. RhIII + PR3 + OHꢂ ? RhI + OPR3 + H+)
[6,20]. No evidence has been obtained in our system for for-
mation of a dioxygen intermediate although, as mentioned
in Section 1, the corresponding RhCl(P–N)(PPh3) complex
in toluene reacts rapidly with O2 to give the stable peroxide
complex RhCl(O2)(P–N)(PPh3), where the coordinated
peroxide is trans to the chlorine and P–N phosphorus
atoms (Fig. 2b); at room temperature, no phosphine oxide
complexes are formed in this system, although direct trans-
fer of O-atoms from a peroxide to the two cis-P-atoms
would present a deceptively simple but almost certainly
incorrect mechanism for formation of 2 from 1! The more
basic THP phosphine (versus PPh3) is expected to be more
readily oxidized (as well as being more likely to replace
coordinated peroxide), and its presence appears to promote
oxidation of the P–N ligand; however, further studies are
needed to rationalize this marked difference in behaviour
between the two systems, in particular an investigation of
solvent effects.
Like complex 1, the oxidized complex 2 shows no reac-
tivity toward H2 under mild conditions, and no serendipi-
tous crystallization from its solutions was observed! The
RhCl(P–N)(THP) complex in acetone-d6 does react with
1 atm CO to give a mixture of products, one of which is
judged from 31P NMR data (d = 57.3, d, 1JRhP = 165.1 Hz)
to be the known species RhCl(CO)(P–N) [12]. These reac-
tions with H2 and with CO were carried out as preliminary
studies to investigate potential catalytic activity of 1 (see
Section 1) but the findings, coupled with its insolubility
in aqueous solution (as judged by the lack of a solution col-
our, and any visible dissolution, of a sample of 1 added to
water), are not promising for any activity for hydrogena-
tion or hydroformylation promoted by the presence of
the THP ligand. There is, of course, a vast amount of open
and patent literature on the use of complexes containing
either P–N, P–O, or oxidized phosphine ligands (usually
hemilabile ligand systems) in catalysis [13,18,19,21], espe-
cially carbonylation and hydroformylation systems
[18,19], where there is also an example in which an (O)P–
N ligated system gives a much more active system than
the corresponding P–N system [19b].
of charge from The Cambridge Crystallographic Data Cen-
tre via www.ccdc.cam.ac.uk/data_request/cif. Supplemen-
tary data associated with this article can be found, in the
online version, at doi:10.1016/j.ica.2007.11.017.
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Acknowledgement
We thank NSERC of Canada for financial support via a
Discovery Grant.
Appendix A. Supplementary material
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