Mild intramolecular P–C(sp3) bond cleavage in bridging diphosphine complexes of RuII RhIII and IrIII

Article abstract of DOI:10.1016/j.jorganchem.2021.121704

Three new carboxylic acid functionalised diphosphines, R₂PCH₂N(Ar)CH₂PR₂ [^CyL₁ R = Cy, Ar = (1-CO₂H)(3-OMe)C₆H₃, ^CyL₂ R = Cy, Ar = (1-CO₂H)(3-OH)C₆H₃ and ^PhL₃ R = Ph, Ar = (1-CO₂H)(5-OMe)C₆H₃] have been prepared from condensation of R₂PCH₂OH and the appropriate aromatic amine in MeOH, and isolated as colourless solids (for ^CyL₁, ^CyL₂) in good yield. Reaction of ^CyL₁, ^CyL₂, or ^PhL₃, along with the previously reported diphosphines ^PhL₁, ^PhL₂, and ^PhL₄, and [RuCl(μ-Cl)(η⁶-Me₂CHC₆H₄Me)]₂ in CH₂Cl₂ affords the P/P-bridging dinuclear ruthenium(II) complexes {RuCl₂(η⁶-Me₂CHC₆H₄Me)}₂(μ-^CyL₁?^PhL₄) 1a?f as red/orange solids. Careful monitoring by ³¹P{¹H} NMR spectroscopy of CDCl₃ solutions of 1a?e revealed remarkably clean P?C_sp3 bond cleavage to give Ru^II mononuclear species 2a?e and the known secondary phosphine complexes RuCl₂(η⁶-Me₂CHC₆H₄Me)(PCy₂H) 3 and RuCl₂(η⁶-Me₂CHC₆H₄Me)(PPh₂H) 4. Furthermore, facile P?C_sp³ bond cleavage of ^PhL₁ can be observed using the chloro-bridged dimers [IrCl(μ-Cl)(η⁵-C₅Me₅)]₂ or [RhCl(μ-Cl)(η⁵-C₅Me₅)]₂ instead. Deuterium labelling of ^CyL₁, ^CyL₁, ^PhL₁, and ^PhL₂ enabled the assignment of the methylene protons to be confirmed from ¹H NMR spectroscopy. All new compounds have been characterised using a range of spectroscopic and analytical techniques. Single crystal X-ray structures have been determined for ^CyL₁, 1d·3OEt₂, 1f·2CDCl₃·OEt₂, 2b, 2c, 2d·CDCl₃, 2e·0.5OEt₂ and 6b·1.5CDCl₃. The free phenolic group in ^CyL₁, 1d·3OEt₂, 1f·2CDCl₃·OEt₂, 2b and 2d·CDCl₃ participates in intra- or intermolecular O?H···O hydrogen bonding.

Full text of DOI:10.1016/j.jorganchem.2021.121704

Journal of Organometallic Chemistry 937 (2021) 121704
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Mild intramolecular P–C(sp3) bond cleavage in bridging diphosphine
complexes of RuII RhIII and IrIII ✩
Peter De’Ath, Mark R.J. Elsegood, Christopher A.G. Halliwell, Martin B. Smith∗
Department of Chemistry, Loughborough University, Loughborough, Leics, LE11 3TU, UK
a r t i c l e i n f o
a b s t r a c t
CyL1 R = Cy, Ar = (1-
Article history:
Three new carboxylic acid functionalised diphosphines, R2PCH2N(Ar)CH2PR2
[
Received 30 November 2020
Revised 4 January 2021
Accepted 10 January 2021
Available online 16 January 2021
CO2H)(3-OMe)C6H3, CyL2 R = Cy, Ar = (1-CO2H)(3-OH)C6H3 and PhL3 R = Ph, Ar = (1-CO2H)(5-OMe)C6H3]
have been prepared from condensation of R2PCH2OH and the appropriate aromatic amine in MeOH, and
isolated as colourless solids (for CyL1, CyL2) in good yield. Reaction of CyL1, CyL2, or PhL3, along with the
previously reported diphosphines PhL1, PhL2, and PhL4, and [RuCl(μ-Cl)(η6-Me2CHC6H4Me)]2 in CH2Cl2 af-
fords the P/P-bridging dinuclear ruthenium(II) complexes {RuCl2(η6-Me2CHC6H4Me)}2(μ-CyL1−PhL4) 1a−f
as red/orange solids. Careful monitoring by 31 P{1H} NMR spectroscopy of CDCl3 solutions of 1a−e re-
vealed remarkably clean P−Csp3 bond cleavage to give RuII mononuclear species 2a−e and the known sec-
ondary phosphine complexes RuCl2(η6-Me2CHC6H4Me)(PCy2H) 3 and RuCl2(η6-Me2CHC6H4Me)(PPh2H)
Keywords:
Carboxylic acids
P ligands
Late-transition metals
X-ray crystallography
P−C bond cleavage
3
4. Furthermore, facile P−Csp bond cleavage of PhL1 can be observed using the chloro-bridged dimers
[IrCl(μ-Cl)(η5-C5Me5)]2 or [RhCl(μ-Cl)(η5-C5Me5)]2 instead. Deuterium labelling of CyL1, CyL1, PhL1, and
PhL2 enabled the assignment of the methylene protons to be confirmed from 1H NMR spectroscopy. All
new compounds have been characterised using a range of spectroscopic and analytical techniques. Sin-
gle crystal X-ray structures have been determined for CyL1, 1d·3OEt2, 1f·2CDCl3·OEt2, 2b, 2c, 2d·CDCl3,
2e·0.5OEt2 and 6b·1.5CDCl3. The free phenolic group in CyL1, 1d·3OEt2, 1f·2CDCl3·OEt2, 2b and 2d·CDCl3
participates in intra- or intermolecular O−H···O hydrogen bonding.
© 2021 Elsevier B.V. All rights reserved.
1. Introduction
sation of the P−C−N−C−P framework at either or both Group 15
donor atoms. To the best of our knowledge, only one example of
Tertiary phosphines are routinely used in many disciplines of
inorganic, organic, material, and biological sciences. Their versa-
tility stems from easy manipulation of the chemical structure of
these important ligands, which are often regarded as chemically
robust with respect to decomposition [1,2]. Common degrada-
tion pathways to phosphine ligands include oxidation and P−Caryl
[3] or P−Calkyl [4] bond cleavage reactions. Chelating diphosphines
are widely used in transition metal chemistry and can also be
susceptible to thermal/chemical induced P−C bond activation at
one (or more) metal centres [5]. We [6], and others [7,8], have
been interested for several years in the chemistry of chelating
(aminomethyl)phosphines such as (R2PCH2)2N(R‘) (R = Ph typi-
cally, R‘ = various substituents), a close relative of the widely
used ligand (Ph2PCH2)2CH2 (dppp, Chart 1). Their amenability,
through simple condensation reactions, enables rapid functionali-
P−C bond cleavage at a coordinated P−C−N−C−P ditertiary phos-
phine has been documented [9], whereas Starosta and co-workers
[10] have reported P−C cleavage of a tertiary aminomethylphos-
phine affording an unusual secondary phosphine coordination
complex.
We report here a facile, internal acid-promoted, P−C bond
cleavage within the coordination sphere of a diruthenium cen-
tre and clean formation of two monomeric species bearing either
a bound secondary phosphine [10] or lactone-functionalised P-
monodentate ligand. Bullock et al [11] have extensively used earth-
abundant metal catalysts based on P−C−N−C−P ligand scaffolds
for hydrogen oxidation or production. A crucial step in this process
involves protonation at the pendant nitrogen atom, and this is in-
fluenced by the six-membered chelate ring conformation [11]. The
structures of all new compounds reported in this work, including
dinuclear RuII compounds supported by a bridging P−C−N−C−N
ligand, have been verified by a combination of spectroscopic and
X-ray crystallographic characterisation techniques.
✩
Electronic supplementary information (ESI) available. CCDC 2022153-60. For ESI
and crystallographic data in CIF or other electronic format see DOI.
∗
Corresponding author.
E-mail address: m.b.smith@lboro.ac.uk (M.B. Smith).
https://doi.org/10.1016/j.jorganchem.2021.121704
0022-328X/© 2021 Elsevier B.V. All rights reserved.

P. De’Ath, M.R.J. Elsegood, C.A.G. Halliwell et al.
Journal of Organometallic Chemistry 937 (2021) 121704
2.3.2. Synthesis of Cy2PCH2N(Ar)CH2PCy2
[Ar = C6H3(1-CO2H)(3-OH)] CyL2
3-hydroxyanthranilic acid (0.248 g, 1.62 mmol) and Cy2PCH2OH
(0.731 g, 3.23 mmol) were dissolved in CH3OH (20 mL) and stirred
under reflux for 48 h. The resulting brown solution was evapo-
rated to dryness, suspended in cold, degassed MeOH (5 mL) and
the white solid CyL2 filtered and dried in vacuo. Yield: 0.694 g,
75%. 31P{1H} (CDCl3) δ −12.3 ppm. 1H [(CD3)2SO] δ 17.48 (s, 1H,
COOH), 10.51 (s, 1H, OH), 7.44 (d, JHH 7.6, 1H, arom. H), 7.17 (t, JHH
8.0, 1H, arom. H), 7.03 (d, JHH 8.4, 1H, arom. H), 3.62 (d, JPH 14.4,
Chart 1. PCNCP structural motif and relationship to dppp.
4H, PCH2) 1.71−0.82 (m, 44H, cy. H). FT−IR (KBr): νCO 1634 cm−1
.
Anal. (%) Calcd. for C33H53NO3P2·CH3OH: C, 67.40; H, 9.50; N, 2.31.
Found: C, 67.82; H, 9.06; N, 2.58. The deuterated analogue CyL2
D4
2. Experimental
was similarly prepared from Cy2PCD2OH and used to confirm 1H
NMR methylene assignments in CyL2.
2.1. Materials
The synthesis of ligands PhL1, PhL2, and PhL4 has been reported
previously by us [6e,6f] whilst ligands CyL1, CyL2, and PhL3 were
prepared using standard Schlenk-line techniques under an inert ni-
trogen atmosphere. Ph2PCH2OH was prepared [12] according to a
known procedure and Cy2PCH2OH, Ph2PCD2OH, and Cy2PCD2OH
were likewise prepared similarly, from either Ph2PH or Cy2PH and
(CD2O)n. All coordination reactions were carried out in air, us-
ing reagent grade quality solvents. The compounds [RuCl(μ-Cl)(η6-
Me2CHC6H4Me)]2 [13], [RhCl(μ-Cl)(η5-C5Me5)]2 [14] and [IrCl(μ-
Cl)(η5-C5Me5)]2 [14] were all prepared according to known proce-
dures. All other chemicals were obtained from commercial sources
and used directly without further purification.
2.3.3. Synthesis of Ph2PCH2N(Ar)CH2PPh2
[Ar = C6H3(1-CO2H)(5-OMe)] PhL3
PhL3 was obtained in a similar manner to CyL1/CyL2 from 2-
amino-5-methoxybenzoic acid and Ph2PCH2OH in MeOH. Yield:
0.728 g, 51%. 31P{1H} [(CD3)2SO] δ −24.8 ppm. 1H [(CD3)2SO] δ
15.30 (s, 1H, COOH), 7.75−6.80 (m, 23H, arom. H), 4.15 (s, 4H,
PCH2), 3.70 (s, 3H, OMe). Despite several attempts, an analytically
pure sample for microanalysis could not be obtained.
2.3.4. Synthesis of {RuCl2(η6-Me2CHC6H4Me)}2(CyL1) 1a
[RuCl(μ-Cl)(η6-Me2CHC6H4Me)]2 (0.113 g, 0.184 mmol) and
CyL1 (0.108 g, 0.186 mmol) were dissolved in CH2Cl2 (10 mL) and
stirred for 5 min before reducing in volume to ~2 mL to afford a
dark red solution. Slow addition of diethyl ether (10 mL) produced
an orange precipitate 1a, which was collected by suction filtration
and dried in vacuo. Yield: 0.160 g, 73%. 31P{1H} NMR (CDCl3) δ
2.2. Instrumentation
3
40.0 ppm. 1H (CDCl3) δ 7.27 (d, 1H, JHH 8.0, arom. H), 6.95 (t,
Infrared spectra were recorded as KBr pellets on a Perkin-
Elmer Spectrum 100S (4000−250 cm−1 range) Fourier-Transform
spectrometer. 1H NMR spectra (400 or 500 MHz) were recorded
on a Jeol-ECS-400 FT or Jeol-ECZ-R-500 spectrometer with chem-
ical shifts (δ) in ppm to high frequency of Si(CH3)4 and cou-
pling constants (J) in Hz. 31P{1H} NMR (162 or 202 MHz) spec-
tra were recorded on a Jeol-ECS-400 FT or Jeol-ECZ-R-500 spec-
trometer with chemical shifts (δ) in ppm to high frequency of 85%
H3PO4. NMR spectra were measured in CDCl3, (CD3)2SO or CD3OD
at 298 K. Elemental analyses (Perkin-Elmer 2400 CHN or Exeter
Analytical, Inc. CE-440 Elemental Analyzers) were performed by
the Loughborough University Analytical Service within the Depart-
ment of Chemistry. Single crystal X-ray crystallography was carried
out by the UK National Crystallographic Service at the University of
Southampton or locally by ourselves at Loughborough University.
3
3
1H, JHH 8.0, arom. H), 6.90 (d, 1H, JHH 8.5, arom. H), 5.51 (d,
2
4H, JPH 5.5, CH2P), 5.47−5.29 (m, 8H, Me2CHC6H4Me), 3.89 (s,
3
3H, OMe), 2.73 (sept, 2H, JHH 7.5, Me2CHC6H4Me), 2.14−1.08 (m,
3
44H, Cy. H), 2.02 (s, 6H, Me2CHC6H4Me), 1.21 (d, 12H, JHH 7.0,
Me2CHC6H4Me) ppm. FT−IR (KBr) νCO 1700 cm−1. Anal. (%) Calcd.
for C54H83NO3P2Cl4Ru2·CH2Cl2 requires: C, 51.40; H, 6.70; N, 1.10.
Found: C, 51.00; H, 6.20; N, 1.30.
2.3.5. Synthesis of {RuCl2(η6-Me2CHC6H4Me)}2(CyL2) 1b
[RuCl(μ-Cl)(η6-Me2CHC6H4Me)]2 (0.101 g, 0.165 mmol) and
CyL2 (0.094 g, 0.17 mmol) were dissolved in CH2Cl2 (10 mL) and
stirred for 5 min. The resulting red solution was evaporated to
~2 mL before slow addition of diethyl ether (10 mL) afforded an
orange precipitate 1b, which was collected by suction filtration
and dried in vacuo. Yield: 0.136 g, 70%. 31P{1H} NMR (CDCl3) in-
dicates, in solution, facile conversion to an approx. 1:1 mixture
of 2b and 3. FT−IR (KBr) νCO 1693 cm−1. Anal. (%) Calcd. for
C53H81NO3P2Cl4Ru2 requires: C, 53.70; H, 6.90; N, 1.20. Found: C,
53.90; H, 6.40; N, 0.90.
2.3. Syntheses
2.3.1. Synthesis of Cy2PCH2N(Ar)CH2PCy2
[Ar = C6H3(1-CO2H)(3-OMe)] CyL1
2-amino-3-methoxybenzoic acid (0.345 g, 2.07 mmol) and
Cy2PCH2OH (0.936 g, 4.14 mmol) were dissolved in CH3OH (30 mL)
and stirred under reflux for 24 h. The resulting peach-coloured so-
lution was reduced in volume to ca. 5 mL to afford a white solid,
CyL1, which was collected by suction filtration and dried. Yield:
0.604 g, 50%. 31P{1H} (CDCl3) δ −10.2 ppm. 1H (CDCl3) δ 7.66 (d,
JHH 7.5, 1H, arom. H), 7.18 (t, JHH 8.0, 1H, arom. H), 7.06 (d, JHH
8.5, 1H, arom. H), 5.47 (d, JHH 2.5, 4H, PCH2), 3.44 (s, 3H, OMe),
1.89−1.15 (m, 44H, cy. H). FT−IR (KBr): νCO 1696 cm−1. Anal. (%)
Calcd. for C34H55NO3P2: C, 69.50; H, 9.40; N, 2.40. Found: C, 69.36;
2.3.6. Synthesis of {RuCl2(η6-Me2CHC6H4Me)}2(PhL1) 1c
[RuCl(μ-Cl)(η6-Me2CHC6H4Me)]2 (0.097 g, 0.16 mmol) and PhL1
(0.091 g, 0.16 mmol) were dissolved in CH2Cl2 (10 mL) and the so-
lution stirred for 5 mins. The volume of the solution was reduced
to approx. 2 mL and slow addition of diethyl ether (10 mL) af-
forded an orange precipitate. The solid 1c was collected by suction
filtration and dried in vacuo. Yield: 0.167 g, 89%. Selected data for
1c: 31P{H} (CDCl3) δ 19.2 ppm. 1H (CDCl3) δ 7.88 (t, JHH 7.5, 4H,
arom. H), 7.67 (t, JHH 6.5, 4H, arom. H), 7.41−7.25 (m, 8H, arom.
H), 7.15 (t, JHH 7.5, 4H, arom. H), 7.10 (d, 1H, JHH 7.5, arom. H), 6.67
(t, 1H, JHH 8.0, arom. H), 6.14 (d, 1H, JHH 7.5, arom. H.), 5.19 (d, 2H,
JHH 6.5, Me2CHC6H4Me), 5.06, (d, 2H, JHH 6.5, Me2CHC6H4Me), 4.85
(d, 2H, JPH 16.5, CH2P), 4.78 (d, 2H, JHH 6.5, Me2CHC6H4Me), 4.62
H, 9.27; N, 2.58. The deuterated analogue CyL1 was similarly pre-
pared from Cy2PCD2OH and used to confirm 1H NMR methylene
assignments in CyL1.
D4
2

P. De’Ath, M.R.J. Elsegood, C.A.G. Halliwell et al.
Journal of Organometallic Chemistry 937 (2021) 121704
ca. 50°C, in an NMR tube, for 7 d. Monitoring by 31P{1H} re-
vealed the clean formation of two P-species, 6b, and [IrCl(η5-
C5Me5)(Ph2PH)] 7b. After cooling the solution, fractional crystalli-
sation with petroleum ether gave suitable crystals for X-ray crystal-
lography. Yield: 0.0037 g, 21%. Selected data for 6b: 31P{H} (CDCl3)
δ −1.8 ppm. 1H (CDCl3) δ 7.98 (m, 4H, ArH), 7.40 (m, 7H, ArH), 6.82
(t, 1H, arom. H), 6.64 (dd, 1H, arom. H), 5.26 (d, 2H, CH2N), 4.61
(d, 2H, JHH 6.5, Me2CHC6H4Me), 4.42 (d, 2H, JPH 16.5, CH2P), 3.52
(s, 3H, OMe), 2.37 (sept, 2H, JHH 6.0 Me2CHC6H4Me), 1.64 (s, 6H,
Me2CHC6H4Me), 0.87 (d, 6H, JHH 6.5, Me2CHC6H4Me). FT−IR (KBr):
νCO 1706 cm−1. Anal. (%) Calcd. for C54H59NO3P2Cl4Ru2·CH3OH: C,
54.70; H, 5.30; N, 1.20. Found: C, 54.20; H, 4.90; N, 0.70.
2.3.7. Synthesis of {RuCl2(η6-Me2CHC6H4Me)}2(PhL2) 1d
[RuCl(μ-Cl)(η6-Me2CHC6H4Me)]2 (0.104 g, 0.171 mmol) and
PhL2 (0.0941 g, 0.171 mmol) were dissolved in a mixture of CH2Cl2
(10 mL) and MeOH (5 mL) and stirred for 5 min. The resulting
mixture was evaporated to dryness and the red, crystalline solid
re-dissolved in CH2Cl2 (2 mL). Slow addition of diethyl ether (10
mL) produced an orange-brown precipitate 1d, which was col-
lected by suction filtration and dried in vacuo. Yield: 0.125 g, 63%.
31P{1H} NMR (CDCl3) δ 19.1 ppm. 1H (CDCl3) δ 8.03−6.54 (m,
(s, 2H, CH2P), 3.25 (s, 3H, OMe), 1.33 (d, 15H, JPH 2.0, Cp∗). Anal.
4
(%) Calcd. for C32H35NO3PCl2Ir·1.5CDCl3: C, 42.14; H, 3.86; N, 1.47.
Found: C, 41.97; H, 3.68; N, 1.47. The same procedure was used
for the analogous RhIII compound 6a (Yield: 0.0032 g, 20%). 31P{H}
1
(CDCl3) δ 30.6 ppm, JRhP 140 Hz. 1H (CDCl3) δ 8.06 (m, 4H, ArH),
7.42 (m, 7H, ArH), 6.79 (t, 1H, arom. H), 6.62 (d, 1H, arom. H), 5.27
2
(d, 2H, JPH 4.0, CH2N), 4.65 (s, 2H, CH2P), 3.32 (s, 3H, OMe), 1.30
4
(d, 15H, JPH 3.6, Cp∗).
2
20H, arom. H), 5.47−4.46 (m, 8H, Me2CHC6H4Me), 4.85 (d, 2H, JPH
2
3
16.0, CH2P), 4.57 (d, 2H, JPH 16.0, CH2P), 2.35 (sept, 2H, JHH 7.5,
Me2CHC6H4Me), 2.16−1.73 (m, 6H, Me2CHC6H4Me); 1.27−0.66 (m,
12H, Me2CHC6H4Me) ppm. FT−IR (KBr) νCO 1710 cm−1. Anal. (%)
Calcd. for C53H57NO3P2Cl4Ru2 requires: C, 54.80; H, 4.90; N, 1.20.
Found: C, 54.50; H, 5.20; N, 0.80.
2.4. X-ray crystallography
Suitable crystals of CyL1 were obtained by allowing a MeOH fil-
trate to stand for several days. Suitable crystals of 1d·3OEt2 and
2b were obtained by vapour diffusion of Et2O into a CH2Cl2 solu-
tion. Suitable crystals of 1f·2CDCl3·OEt2, 2c, 2d·CDCl3, 2e·0.5OEt2
and 6b·1.5CDCl3 were obtained by vapour diffusion of Et2O into
a CDCl3 solution. Details of the data collection parameters and
crystal data for CyL1, 1d·3OEt2, 1f·2CDCl3·OEt2, 2b, 2c, 2d·CDCl3,
2e·0.5OEt2 and 6b·1.5CDCl3 are presented in Table 1.
2.3.8. Synthesis of {RuCl2(η6-Me2CHC6H4Me)}2(PhL3) 1e
Compound 1e was prepared in 53% yield following similar
methods to 1a−d. Selected data: 31P{1H} NMR (CDCl3) δ 22.7 ppm.
Anal. (%) Calcd. for C54H59NO3P2Cl4Ru2 requires: C, 55.15; H, 5.07;
N, 1.19. Found: C, 54.47; H, 4.90; N, 1.43.
2.3.9. Synthesis of {RuCl2(η6-Me2CHC6H4Me)}2(PhL4) 1f
[RuCl(μ-Cl)(η6-Me2CHC6H4Me)]2 (0.037 g, 0.060 mmol) and
PhL4 (0.033 g, 0.060 mmol) were dissolved in CDCl3 (1 mL) where-
upon solid 1f deposited after a few minutes. The suspension was
stirred for 2h and diethyl ether (15 mL) added to achieve fur-
ther precipitation. The solid was collected by suction filtration and
dried in vacuo. Yield: 0.063 g, 90%. Selected data: 31P{1H} NMR
(CD3OD) δ 23.0 ppm. FT−IR (KBr) νCO 1662 cm−1. Anal. (%) Calcd.
for C53H57NO3P2Cl4Ru2 requires: C, 54.80; H, 4.90; N, 1.20. Found:
C, 54.81; H, 4.69; N, 0.63.
Measurements for CyL1, 1d3OEt2, 1f·2CDCl3·OEt2, 2b, 2c,
2d·CDCl3, 2e·0.5OEt2, and 6b·1.5CDCl3 were made on modern
diffractometers using X-radiation from a rotating anode or sealed
tube source [15]. Intensities were corrected for Lp effects and semi-
empirically for absorption, based on symmetry-equivalent and re-
peated reflections [15,16]. The structures were solved [17] by di-
rect or dual-space methods and refined on F2 values for all unique
data by full-matrix least squares [18,19]. All non-hydrogen atoms
were refined anisotropically. Carbon-bound hydrogen atoms were
constrained in a riding model with Ueq set to 1.2Ueq of the carrier
atom (1.5 Ueq for methyl hydrogen). For 1d·3OEt2 the CO2H group
showed evidence of disorder, though this was not modelled. De-
spite the use of restraints there is still a rather unreliable pattern
of bond lengths in this group, but the distance from O(4) to the
OEt2 strongly suggests an H-bond, and hence the correct assign-
ment of carbonyl and hydroxyl groups. Restraints were also ap-
plied to the OEt2 group containing O(6). For 1f·2CDCl3·OEt2 the
hydroxyl group at O(3) is positionally disordered at either C(5)
or C(7) with major occupancy of 55.9(16)% on C(7). The atoms of
the Ph ring containing C(22) were modelled as disordered over
two sets of positions with major occupancy 60(3)%. The two Me
groups on the η6-Me2CHC6H4Me ring containing C(51) were also
modelled as two fold disordered with major occupancy 60.5(18)%,
as were the atoms C(54), Cl(5) and Cl(6) in a deuterochloroform
molecule with major occupancy 62(2)%. In 2b the Me groups in
the η6-Me2CHC6H4Me ligand were modelled as 2-fold disordered
with major occupancy 73.8(14)%. For 2d·CDCl3 there is a CDCl3
molecule of crystallisation, modelled as having all bar the C atom
split over two sets of positions with major component 56.2(16)%.
For 2e·0.5OEt2 the OEt2 molecule of crystallisation is disordered
across a symmetry element, so was refined at exactly half weight.
For 6b·1.5CDCl3 the CDCl3 molecule including C(65) was modelled
over two sets of positions with the C atom common to both and
major occupancy 64.0(12)%. That including C(66) was also mod-
elled as disordered over two sets of positions for the H atom and
two of the three chlorines with Cl(10) common to both and major
occupancy of 62(3)%.
2.3.10. Synthesis of 2d and 2e
Typical procedures are illustrated for compounds 2d and
2e. For compound 2d: A dark red solution of [RuCl(μ-Cl)(η6-
Me2CHC6H4Me)]2 (0.032 g, 0.052 mmol) and PhL2 (0.028 g, 0.051
mmol) in CDCl3 (1 mL) was allowed to stand at room temperature
for ca. 5 d. The solid was collected by suction filtration and dried.
Yield: 0.018 g, 51%. Selected data: 31P{1H} NMR (CDCl3/CH3OH)
δ 23.3 ppm. FT−IR (KBr) νCO 1731 cm−1. Anal. (%) Calcd. for
C31H32NO3PCl2Ru·CDCl3 requires: C, 48.71; H, 4.22; N, 1.78. Found:
C, 48.65; H, 4.04; N, 1.56. For compound 2e: A CDCl3 (0.7 ml) so-
lution of 1e (0.0085 g) was allowed to stand at room tempera-
ture for ca. 2d. Fractional crystallisation using diethyl ether gave
a crystalline solid (0.0027 g) which was shown, by 31P{1H} NMR,
to be a mixture of predominantly 2e (δ 26.2, ~80%) and 4 (δ 21.6,
~20%). Other selected data [31P{1H} NMR (CDCl3)] for compounds
2a−2c: δ 32.0 (2a); 32.6 (2b); 23.9 (2c) ppm. For 2c: 1H (CDCl3)
δ 8.02 (t, JHH 7.5, 4H, arom. H), 7.37 (m, 7H, arom. H), 6.78 (t, JHH
5.0, 1H, arom. H), 6.63 (d, 1H, JHH 10.0, arom. H), 5.17 (d, 2H, JHH
5.0, C6H4), 5.11, (d, 2H, JHH 5.0, C6H4), 5.08 (d, 2H, JPH 5.0, CH2P),
4.67 (s, 2H, CH2N), 3.40 (s, 3H, OMe), 2.45 (sept, 1H, JHH 5.0 CH3),
1.74 (s, 3H, CH3), 0.92 (d, 6H, JHH 5.0, CH3). Anal. (%) Calcd. for
C32H34NO3PCl2Ru: C, 56.22; H, 5.02; N, 2.05. Found: C, 55.70; H,
4.88; N, 1.89.
2.3.11. Synthesis of 6b
A CDCl3 (0.7 mL) solution of [IrCl(μ-Cl)(η5-C5Me5)]2 (0.018
g, 0.023 mmol) and PhL1 (0.012 g, 0.021 mmol) was heated to
3

Table 1
Crystallographic data for CyL1, 1d·3OEt2, 1f·2CDCl3·OEt2, 2b, 2c, 2d·CDCl3, 2e·0.5OEt2 and 6b·1.5CDCl3.
Compound
CyL1
1d·3OEt2
1f·2CDCl3·OEt2
53H56Cl4NO3P2
2b
2c
2d·CDCl3
2e·0.5OEt2
6b·1.5CDCl3
32H35Cl2IrNO3P
Empirical formula
C
34H51D4NO3P2
C53H57Cl4NO3P2
Ru2·3(C4H10O)
1384.23
C
C
31H44Cl2NO3PRu
C32H34Cl2NO3PRu
C31H32Cl2NO3PRu·CDCl3
C32H34Cl2NO3PRu·
0.5(C4H10O)
720.60
C
Ru2·2(CDCl3)·C4H10
1475.73
O
·1.5(CDCl3)
956.24
Formula weight
Crystal system
Space group
591.75
681.61
683.54
789.89
Orthorhombic
Pnma
Triclinic
¯
P1
Triclinic
¯
P1
Monoclinic
P21/c
Monoclinic
P21/c
Triclinic
¯
P1
Monoclinic
P21/c
Triclinic
¯
P1
˚
a [A]
12.83918(9)
26.82340(19)
9.60069(6)
90
14.1540(7)
15.0680(8)
15.8022(9)
86.720(4)
74.552(5)
82.143(4)
3217.2(3)
2
11.960(2)
13.769(3)
20.723(4)
82.854(3)
75.466(3)
79.600(3)
3237.8(11)
2
11.1749(3)
19.7445(4)
14.8328(4)
90
11.5086(7)
17.929(1)
15.5634(9)
90
9.591(2)
10.663(3)
17.218(4)
95.816(4)
100.859(4)
104.132(4)
1656.8(7)
2
14.9369(13)
10.3271(9)
21.6601(19)
90
9.6051(3)
12.7278(4)
30.3172(10)
86.0066(5)
87.9905(5)
78.1963(5)
3618.3(2)
4
˚
b [A]
˚
c [A]
α [˚]
β [˚]
γ [˚]
90
110.740(3)
90
109.8956(10)
90
100.4131(14)
90
90
3
˚
Volume [A ]
3306.39(4)
4
3060.67(14)
4
3019.6(3)
4
3286.1(5)
4
Z
λ
T [K]
1.54178
100(2)
1.54178
100(2)
0.71073
150(2)
1.54178
100(2)
0.71073
150(2)
0.71073
150(2)
0.71073
150(2)
0.71073
150(2)
Density (calcd.) [Mg /m3]
1.189
1.429
1.514
1.479
1.504
1.583
1.457
1.755
Absorption coeff. [mm−1
Crystal habit and colour
Crystal size [mm3]
θ Range [°]
]
1.44
6.19
0.97
6.50
0.78
0.96
0.73
4.25
Block, colourless
Block, red
Block, orange
0.20 × 0.16 × 0.11
1.8-25.0
22962
Plate, orange
Block, orange
Block, orange
Plate, orange
0.25 × 0.16 × 0.06
1.9-25.0
22927
Block, orange
0.39 × 0.23 × 0.10
1.7-29.1
32282
0.37 × 0.18 × 0.08 0.15 × 0.10 × 0.05
0.10 × 0.04 × 0.01 0.17 × 0.16 × 0.06 0.20 × 0.14 × 0.07
4.9-68.2
21307
3085
3.3-68.2
52238
11645
0.070
3.9-68.2
27133
5582
1.9-29.1
26627
7335
2.2-26.0
12618
6439
Reflections collected
Independent reflections
Rint
11308
5781
16775
0.019
0.071
0.093
0.056
0.052
0.055
0.021
Reflections with F2 > 2σ(F2)
3031
9491
6537
4915
4761
4800
3995
13893
Number of parameters
305
732
818
376
365
422
410
888
Largest difference peak/hole
0.29, –0.22
2.69, –1.11
2.70, –1.42
1.19, –0.79
0.96, –0.74
2.90, –1.70
2.08, —0.74
1.26, –1.05
−3
˚
[e A
]
b
Final Ra, Rw
0.028, 0.069
0.066, 0.180
0.077, 0.249
0.049, 0.126
0.042, 0.089
0.072, 0.201
0.064, 0.184
0.026, 0.062
a
b
R = ꢀ||Fo| - |Fc||/ꢀ|Fo|. wR2 = [ꢀ[w(Fo2 - Fc2)2]/ꢀ[w(Fo2)2]]1/2
.

P. De’Ath, M.R.J. Elsegood, C.A.G. Halliwell et al.
Journal of Organometallic Chemistry 937 (2021) 121704
Chart 2. Ligands used in this study
Fig. 1. Molecular structure of ligand CyL1. All hydrogen atoms except on O(2) and
the deuterium atoms on C(1) and C(1A) have been omitted for clarity. Selected bond
˚
lengths (A) and angles (°): P(1)−C(1) 1.8661(11), C(1)−N(1) 1.4906(12), C(8)−O(1)
Fig. 2. Molecular structure of 1d•3OEt2. All solvent molecules of crystallisation and
1.218(2), C(8)−O(2) 1.317(2). P(1)−C(1)−N(1) 113.67(7).
hydrogen atoms, except on C(1), C(2), O(2), and O(3), have been omitted for clar-
˚
ity. Selected bond lengths (A) and angles (°): Ru(1)−Cl(1) 2.4175(14), Ru(1)−Cl(2)
2.4084(14), Ru(1)−P(1) 2.3555(15), Ru(2)−Cl(3) 2.4065(15), Ru(2)−Cl(4) 2.4110(16),
Ru(2)−P(2) 2.3476(15), C(9)−O(1) 1.335(11), C(9)−O(2) 1.162(11). Cl(1)−Ru(1)−Cl(2)
88.70(5), Cl(1)−Ru(1)−P(1) 88.77(5), Cl(2)−Ru(1)−P(1) 83.23(5), Cl(3)−Ru(2)−Cl(4)
87.84(5), Cl(3)−Ru(2)−P(2) 86.55(5), Cl(4)−Ru(2)−P(2) 85.73(5).
3. Results and discussion
3.1. Ligand synthesis
Using a well-established Mannich procedure [6] reaction of 1
equiv. of the appropriate amine and 2 equiv. of either Ph2PCH2OH
(for PhL3) or Cy2PCH2OH (CyL1, CyL2) in MeOH afforded the new
carboxylic acid functionalised diphosphines in good yield (Chart 2).
Characterising data (see Experimental section) for PhL3, CyL1, and
CyL2 are in good agreement with the proposed structures. The
31P{1H} NMR spectra show typical singlets at δ(P) −10.2 (CyL1),
−12.3 (CyL2) and −25.6 (PhL3) ppm. The 1H NMR spectra are par-
ticularly diagnostic showing, in addition to the expected reso-
nances for the Ph/Cy groups, resonances at δ(H) 16.3 and 16.0 ppm
(CO2H) and the CH2 protons appear as an AB splitting pattern at
δ(H) 4.18 ppm, consistent with inequivalence of the two methylene
protons, presumably imposed by orientation of the N-bound arene
group which is perpendicular (for PhL1) [6e]. In PhL2 the CH2 pro-
Chart 3. Diruthenium complexes 1a−f prepared in this study.
5

P. De’Ath, M.R.J. Elsegood, C.A.G. Halliwell et al.
Journal of Organometallic Chemistry 937 (2021) 121704
3.2. Dinuclear ruthenium(II) complexes 1a−f
Reaction
of
ligands
CyL1−PhL4
with
[RuCl(μ-Cl)(η6-
Me2CHC6H4Me)]2 (1:1 ratio) in CH2Cl2 gave, after workup, orange
solids 1a−f in 48−89% isolated yields (Chart 3). All compounds
were characterised by NMR spectroscopy whereby 31P{1H} NMR
downfield shifts were consistent with bridging P-coordination of
these ligands. When CDCl3 solutions of 1a−e were monitored over
several days, two major new RuII phosphorus compounds were
observed, both of which have been identified (vide infra).
Whilst diphosphines of this structural motif can P/P-chelate to
ruthenium metal centres [21], the molecular structure of 1d·3OEt2
(Fig. 2) confirms a binuclear arrangement comprising two pseudo-
tetrahedral {RuCl2(η6-Me2CHC6H4Me)} fragments and a bridging
PhL2 ligand [22]. The RuII to ring centroid distances are very
˚
˚
similar at 1.694(2) A at Ru(1), and 1.699(3) A at Ru(2), with a
piano-stool conformation around each Ru metal centre. Unlike CyL1
and PhL1 [6e], the N-arene group torsion angle observed with re-
spect to the C(1)−N(1)−C(2) plane in 1d·3OEt2 is 47.7(3)° whilst
in 1f·2CDCl3·OEt2 this group is essentially parallel [0.8(11)°]. In
1d·3OEt2 both the hydroxyl and carboxylic acid hydrogens act as
H-bond donors to OEt2 molecules of crystallisation (see ESI Fig.
S1).
Fig. 3. Molecular structure of 1f·2CDCl3·OEt2. All solvent molecules of crystalli-
The molecular structure of 1f·2CDCl3·OEt2 (Fig. 3) con-
firms a binuclear arrangement comprising two pseudo-tetrahedral
{RuCl2)(η6-Me2CHC6H4Me} fragments and a bridging PhL3 ligand.
The Ru−P and Ru−Cl bond parameters are as anticipated. Adja-
cent molecules form H-bonded dimers via a classic carboxylic acid
sation and hydrogen atoms, except on C(1), C(2), O(2), and O(3), have been
˚
omitted for clarity. Selected bond lengths (A) and angles (°): Ru(1)−Cl(1)
2.417(3), Ru(1)−Cl(2) 2.403(2), Ru(1)−P(1) 2.344(2), Ru(2)−Cl(3) 2.410(3),
Ru(2)−Cl(4) 2.413(2), Ru(2)−P(2) 2.337(2), C(9)−O(1) 1.272(11), C(9)−O(2) 1.290(11).
Cl(1)−Ru(1)−Cl(2) 87.05(10), Cl(1)−Ru(1)−P(1) 83.50(8), Cl(2)−Ru(1)−P(1) 86.75(8),
Cl(3)−Ru(2)−Cl(4) 88.14(9), Cl(3)−Ru(2)−P(2) 83.67(9), Cl(4)−Ru(2)−P(2) 85.34(8).
˚
head-to-tail arrangement through O(2)−H(2)···O(1A) [2.610(8) A,
123°] hydrogen bonding. At the end of each molecule a CDCl3
molecule of crystallisation forms a bifurcated H-bond to the two
Ru-bound chloride ligands (see ESI Figs. S2 & S3).
tons appear as a singlet at 4.27 ppm [6e]. Deuterium analogues of
CyL1, CyL2, PhL1, and PhL2, labelled with deuterium on the methy-
lene carbons, were similarly prepared [20].
The X-ray structure of CyL1 has been determined and is shown
in Fig. 1. The molecular structure confirms diphosphine forma-
tion and a P−C−N−C−P arrangement with a near perpendicu-
lar N-arene group [torsion angle 88.74(3)°]. The P−C and C−N
bond lengths are similar to those previously reported [6e] for PhL1
3.3. Mononuclear metal complexes 2a−e
Previously, we have shown that ligands PhL1, PhL2 and PhL4
react with the square planar complex [Pd(Me)Cl(η4-cod)] to
form novel Pd6 hexameric compounds via P/P/O-tridentate co-
ordination [6e]. In these complexes, PhL1, PhL2 and PhL4 act
as P/P-chelating ligands to PdII and protonation of the Me
group, by the -CO2H, results in carboxylate formation link-
˚
and there is a strong N(1)···H(2)−O(2) [N(1)···O(2) 2.5201(16) A,
161(2)°] intramolecular H bond. The molecule lies on a mirror
plane.
Chart 4. Chemical structures of 2a-e, 3, and 4.
6

P. De’Ath, M.R.J. Elsegood, C.A.G. Halliwell et al.
Journal of Organometallic Chemistry 937 (2021) 121704
Fig. 4. (upper) 31 P{1H} NMR spectra (in CDCl3) showing P−C(sp3) cleavage of 1c over time. The minor species at around 17 ppm is probably [Ru(η6-
Me2CHC6H4Me)Cl2(Ph2PCH2OH)] [6g]. (lower) 1H NMR spectra (selected region) showing P− C(sp3) cleavage of 1c over time.
ing PdII units into hexamers. In contrast, when CDCl3 solu-
be used to monitor this clean conversion as evidenced by the
Me2CHC6H4Me protons.
Under similar concentrations, monitoring the P−C(sp3) bond
tions of compounds 1a−e were left at r.t. or gently heated,
smooth conversion to two new P-containing RuII compounds
cleavage across the series 1a−e reveals that this process occurs
in approx. 1:1 ratio was observed. These were identified as
2a−e (Chart 4) and either [Ru(η6-Me2CHC6H4Me)Cl2(Cy2PH)] 3
within 1 d (at r.t.) for 1a and slowest (14 d) for 1c, reflecting the
or [Ru(η6-Me2CHC6H4Me)Cl2(Ph2PH)] 4 [23,24]. The progress of
importance of the different electronic effects of Cy and Ph sub-
these reactions was easily monitored by 31P{1H} (Fig. 4, upper)
stituents on P respectively. The N-arene functionality (OMe vs OH)
and 1H NMR (Fig. 4, lower) spectroscopy. The identity of both 3
also plays a significant role, as demonstrated by 1b which under-
went P−C(sp3) bond cleavage completely within 8 h (at r. t.). It
1
and 4 could be confirmed, in CDCl3, by the diagnostic JPH cou-
should also be noted that the overall disposition of substituents
on the N-arene ring may help contribute towards imposing the
dinuclear ruthenium complex into one preferred conformer that
favours P−C(sp3) bond cleavage. C−H activation of a methylene hy-
drogen has previously been reported in two Fe and Mo complexes
bearing a di/triphosphine based on a P−C−N−C−P framework [25].
pling (409 Hz) which was not observed in the known compound
[Ru(η6-Me2CHC6H4Me)Cl2(Ph2POH)], demonstrating that no Ph2PH
dissociation, PIII to PV oxidation and re-coordination as Ph2POH to
the RuII centre had taken place [24]. Furthermore, 1H NMR spec-
tra (Fig. 4, lower), recorded over the same time period, could also
7

P. De’Ath, M.R.J. Elsegood, C.A.G. Halliwell et al.
Journal of Organometallic Chemistry 937 (2021) 121704
Fig. 6. Molecular structure of 2c. All hydrogen atoms except on C(11) and
˚
C(19) have been omitted for clarity. Selected bond lengths (A) and angles (°):
Fig. 5. Molecular structure of 2b. All hydrogen atoms, except on C(11), C(19)
Ru(1)−Cl(1) 2.4227(9), Ru(1)−Cl(2) 2.4152(9), Ru(1)−P(1) 2.3507(10), C(18)−O(1)
1.351(5), C(18)−O(2) 1.209(4), O(1)−C(19) 1.450(4). Cl(1)−Ru(1)−Cl(2) 89.56(3),
Cl(1)−Ru(1)−P(1) 88.09(3), Cl(2)−Ru(1)−P(1) 83.67(3).
˚
and O(3), have been omitted for clarity. Selected bond lengths (A) and an-
gles (°): Ru(1)−Cl(1) 2.4165(10), Ru(1)−Cl(2) 2.4269(10), Ru(1)−P(1) 2.3860(11),
C(18)−O(1) 1.356(5), C(18)−O(2) 1.211(5). O(1)−C(19) 1.462(5), Cl(1)−Ru(1)−Cl(2)
86.51(4), Cl(1)−Ru(1)−P(1) 86.54(3), Cl(2)−Ru(1)−P(1) 86.65(3).
Compounds 2a−e could generally be separated by fractional
crystallisation and the structures of four examples were de-
termined by X-ray crystallography (Figs. 5−8). Important bond
lengths and angles are given in the Fig. captions. Each of
the complexes displays a typical three-legged piano stool struc-
ture with Ru−P and Ru−Cl bond distances broadly as an-
ticipated [6g,23,26]. Suitable crystals of 2b were obtained by
vapour diffusion of Et2O into a CH2Cl2 solution. The molecu-
lar structure of 2b (Fig. 5) confirms a mononuclear arrangement
comprising a piano-stool {RuCl2(η6-Me2CHC6H4Me)} metal frag-
ment and a monodentate P-ligand containing a six membered
N(1)−C(12)−C(13)−C(18)−O(1)−C(19) heterocyclic lactone. The Ru
˚
to ring centroid distance is 1.7098(17) A. Molecules of 2b form H-
bonded dimers via centrosymmetric pairs of head-to-tail O−H···Cl
hydrogen bonds (see ESI Fig. S4).
Compounds 2b and 2c are pseudo-isomorphous, both crys-
tallising in space group P21/c with fairly similar unit cell dimen-
sions. (see Table 1) The molecular structure of 2c (Fig. 6) confirms
a mononuclear arrangement comprising a piano-stool {RuCl2(η6-
Me2CHC6H4Me)} metal fragment and a monodentate P-ligand con-
taining a six-membered N(1)−C(12)−C(13)−C(18)−O(1)−C(19) lac-
tone ring as observed in 2b. The Ru−P and Ru−Cl bond param-
eters are broadly as anticipated. The Ru(1)−Ccentroid distance is
Fig. 7. Molecular structure of 2d·CDCl3. The solvent molecule of crystallisation and
hydrogen atoms, except on C(11), C(19), and O(3), have been omitted for clarity.
˚
Selected bond lengths (A) and angles (°): Ru(1)−Cl(1) 2.4229(16), Ru(1)−Cl(2)
2.4083(16), Ru(1)−P(1) 2.3471(17), C(18)−O(1) 1.353(9), C(18)−O(2) 1.219(8),
O(1)−C(19) 1.460(8). Cl(1)−Ru(1)−Cl(2) 87.31(6), Cl(1)−Ru(1)−P(1) 87.21(5),
Cl(2)−Ru(1)−P(1) 85.00(6).
˚
1.6974(14) A.
The molecular structure of 2d·CDCl3 (Fig. 7) confirms
a
mononuclear arrangement comprising
a
piano-stool {RuCl2(η6-
Me2CHC6H4Me)} metal fragment and a monodentate P-ligand con-
taining a six-membered N(1)−C(12)−C(13)−C(18)−O(1)−C(19) het-
erocyclic lactone as seen for 2b and 2c. The Ru−P and Ru−Cl bond
parameters are broadly as anticipated and the Ru(1)−Ccentroid dis-
and
a
monodentate P-ligand containing
a
six-membered
N(1)−C(12)−C(13)−C(18)−O(1)−C(19) heterocyclic lactone as
seen previously and demonstrating the universality of this trans-
formation. The Ru−P and Ru−Cl bond parameters are broadly as
˚
˚
tance is 1.704(3) A. The hydroxy group forms an intramolecular
anticipated and the Ru(1)−Ccentroid distance is 1.694(3) A, all in
˚
˚
O(3)−H(3)···N(1) [2.846(7) A, 122(8)°A] hydrogen bond which dif-
fers from the intermolecular H-bond interactions seen in 2b.
The molecular structure of 2e·0.5OEt2 (Fig. 8) con-
accord with the previous three Ru structures. Adjacent molecules
form weakly H-bonded centro-symmetric dimer pairs via pairs of
η6-Me2CHC6H4Me (CH)···Cl interactions (see ESI Fig. S5).
ꢀ
firms
a
mononuclear arrangement comprising the famil-
We also briefly explored the scope of this transformation with
iar piano-stool {RuCl2(η6-Me2CHC6H4Me)} metal fragment
other dinuclear chloro-bridged late transition metal centres. Us-
8

P. De’Ath, M.R.J. Elsegood, C.A.G. Halliwell et al.
Journal of Organometallic Chemistry 937 (2021) 121704
Fig. 8. Molecular structure of 2e·0.5OEt2. All solvent molecules of crystalli-
sation and hydrogen atoms, except on C(11) and C(19), have been removed
˚
for clarity. Selected bond lengths (A) and angles (°): Ru(1)−Cl(1) 2.418(2),
Fig. 9. Molecular structure of 6b·1.5CDCl3. All solvent molecules of crystallisation
Ru(1)−Cl(2) 2.4049(19), Ru(1)−P(1) 2.3435(18), C(18)−O(1) 1.409(12), C(18)−O(2)
1.239(11), O(1)−C(19) 1.425(10). Cl(1)−Ru(1)−Cl(2) 88.78(7), Cl(1)−Ru(1)−P(1)
85.47(6), Cl(2)−Ru(1)−P(1) 83.59(6).
and hydrogen atoms, except on C(11) and C(19), have been omitted for clarity. Se-
˚
lected bond lengths (A) and angles (°) (values for second independent molecule
in parenthesis): Ir(1)−Cl(1) 2.4188(8) [2.4150(8)], Ir(1)−Cl(2) 2.4194(8) [2.3995(8)],
Ir(1)−P(1) 2.3043(8) [2.3174(8)], C(18)−O(1) 1.353(4) [1.349(5)], C(18)−O(2) 1.211(4)
[1.219(4)], O(1)−C(19) 1.463(4) [1.465(4)]. Cl(1)−Ir(1)−Cl(2) 89.04(3) [88.89(3)],
Cl(1)−Ir(1)−P(1) 86.96(3) [89.07(3)], Cl(2)−Ir(1)−P(1) 87.81(3) [87.64(3)].
ing PhL1, reaction with [RhCl(μ-Cl)(η5-C5Me5)]2 (1:1) in CH2Cl2,
and precipitation with Et2O/pet. ether (b.p. 60-80 °C), gave a solid
which was analysed by 31P{1H} NMR as a 50:50 mixture of 6a
(Chart 5) [30.2 ppm, JRhP 145 Hz] and [RhCl2(η5-C5Me5)(Ph2PH)]
7a [13.6 ppm, JRhP 141 Hz] [24,27] with no evidence for 5a. When
this reaction was monitored in CDCl3, by 31P{1H} NMR over time
(ca. 4 d, 50 °C), initial formation of the binuclear RhIII complex 5a
[29.4 ppm, JRhP 137 Hz] was observed followed by slow conversion
into 6a [30.7 ppm, JRhP 141 Hz] and 7a [14.0 ppm, JRhP 142 Hz] [27].
Furthermore, when [IrCl(μ-Cl)(η5-C5Me5)]2 and PhL1 (1:1) were
mixed in CDCl3, the binuclear complex 5b [δ(P) −4.2 ppm] was
immediately formed. The 1H NMR spectrum showed a characteris-
tic AX pattern for the P−CH2−N methylene protons [δ(H) 5.09 and
4.58 ppm (JHH 13.2 Hz) indicating significantly different environ-
ments. After standing the NMR solution for ca. 5 d at r.t., two mi-
nor species at δ(P) −2.2 and −10.2 ppm were observed, the latter
assigned as the known [24] compound [IrCl2(η5-C5Me5)(Ph2PH)]
7b. The former we assign to 6b. This process can be accelerated by
heating a solution for 2 d, resulting in clean conversion to 6b:7b in
a 1:1 ratio. Fractional crystallisation afforded suitable orange crys-
tals of 6b for a single crystal X-ray structure analysis and enabled
further characterisation by NMR and elemental analyses.
The molecular structure of 6b·1.5CDCl3 (Fig. 9) confirms
a
mononuclear arrangement comprising
a
piano stool IrCl2(η5-
C5Me5) metal fragment and a monodentate P-ligand containing
a six membered N(1)−C(12)−C(13)−C(18)−O(1)−C(19) heterocyclic
lactone, as previously observed for the RuII examples and demon-
strating cross-transition metal applicability. The Ir−P and Ir−Cl
bond parameters are broadly as anticipated and the Ir(1)−Ccentroid
˚
˚
distance is 1.8205(13) A [Ir(2)−Ccentroid distance is 1.8192(14) A in
a second independent molecule]. There are notable differences be-
tween the two Ir complexes in the asymmetric unit and their in-
tramolecular H-bonds between the C(11/43)H2 group and the Ir-
Chart 5. Chemical structures of compounds 5a/b, 6a/b, and 7a/b.
9

P. De’Ath, M.R.J. Elsegood, C.A.G. Halliwell et al.
Journal of Organometallic Chemistry 937 (2021) 121704
the Cambridge Crystallographic Data Centre, 12 Union Road, Cam-
bridge, CB2 1EZ, UK; fax: (+44) 1223 336 033 or e-mail: de-
posit@ccdc.cam. ac.uk. Additional figures for several of the crystal
structures are also presented.
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Appendix A. Supplementary material
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11