Reactions of trivalent iodine reagents with classic iridium and rhodium complexes

Article abstract of DOI:10.1071/CH17173

In this work, the reactions of iodine(iii) reagents (PhI(L)2: L≤pyridine, acetate (OAc-), triflate (OTf-)) with iridium(i) and rhodium(i) complexes (Vaskas's compound, Wilkinson's catalyst, and bis[bis(diphenylphosphino)ethane]rhodium(i) triflate) are rep

Full text of DOI:10.1071/CH17173

RESEARCH FRONT
CSIRO PUBLISHING
Aust. J. Chem. 2017, 70, 1180–1187
Full Paper
https://doi.org/10.1071/CH17173
Reactions of Trivalent Iodine Reagents with Classic Iridium
and Rhodium Complexes*
A
A B
,
Mohammad Albayer and Jason L. Dutton
A
Department of Chemistry and Physics, La Trobe Institute for Molecular Science,
La Trobe University, Melbourne, Vic. 3086, Australia.
B
Corresponding author. Email: j.dutton@latrobe.edu.au
In this work, the reactions of iodine(III) reagents (PhI(L)2: L ¼ pyridine, acetate (OAcꢀ), triflate (OTfꢀ)) with iridium(I)
and rhodium(I) complexes (Vaskas’s compound, Wilkinson’s catalyst, and bis[bis(diphenylphosphino)ethane]rhodium(I)
triflate) are reported. In all cases, the reactions resulted in two-electron oxidation of the metal complexes. Mixtures of
products were observed in the reactions of IIII reagents with Vaska’s compound and Wilkinson’s catalyst via ligand
exchange and anion scrambling. In the case of reacting IIII reagents with chelating ligand-containing bis[bis(diphenylpho-
sphino)ethane]rhodium(I) triflate, no scrambling was observed.
Manuscript received: 27 March 2017.
Manuscript accepted: 7 July 2017.
Published online: 9 August 2017.
Scheme 3,[12] where the reaction of compound 1 with 2R
resulted in simultaneously oxidizing AuI to AuIII and delivering
pyridine ligands to form compound 6.
Introduction
Iodine(III) reagents with a PhI(L)2 motif (L ¼ ꢀCl, ꢀOAc,
pyridine) have attracted much attention as stoichiometric oxi-
dants owing to their ease of handling, low toxicity, and ability to
act as oxidizing reagents under mild conditions.[1] They have
become a popular way to interrogate higher-oxidation-state
late transition metal complexes.[2] For example, these reagents
have been successfully used in isolating or accessing higher
oxidation states of platinum group metals.[3–10] The Sanford
group has demonstrated the use of these iodine reagents in
investigating C–H bond activation at PdIV centres. The oxida-
tion of compound 1 by either PhICl2 or PhI(OAc)2 resulted in the
isolation and characterization of rare PdIV organometallic
complexes 1Cl and 1OAc (Scheme 1). At elevated tempera-
tures, these compounds undergo reductive elimination, with
C–C, C–Cl, and C–O bond-forming reactions.[3,11]
Our group have been using dicationic IIII reagents [PhI(L)2]
[OTf]2 (L¼ pyridine, 4-dimethylaminopyridine) to explore the
chemistry of the II–IV redox couple for Pd and Pt and the I–III
couple for Au (Schemes 2, 3).[6,12] These reagents were first
synthesized by Weiss in 1994 and later investigated by Zhdan-
kin.[13,14] These dicationic IIII reagents typically simultaneously
oxidize the transition metal and deliver the neutral ligands,
allowing the isolation of charged metal complexes. The oxidation
of compound 1 by [PhI(L)2][OTf]2 (2R) resulted in an unexpected
outcome, as shown in Scheme 2. The reaction is proposed to
proceed through oxidation of PdII to give an unobserved PdIV
intermediate, which undergoes reductive elimination, resulting in
C–C bond formation by linking two 2-phenylpyridine ligands.
Ligand redistribution then gives the observed products 3 and 4.[6]
Our group also reported a new class of tri-cationic gold(III)
complexes using the dicationic IIII reagents, as shown in
Ritter has reported the use of the dicationic IIII reagent 2CN in
the isolation of a PdIV complex (Scheme 4). The oxidation of
compound 7 using 2CN resulted in the formation of PdIV with a
single ligand transfer to give compound 8. This complex was
then used in the formation of a late-stage fluorinating agent via
displacement of pyridine with 18Fꢀ to generate complexes that
have potential to be used in positron emission tomography
(PET) imaging.[15]
Our group has been specifically avoiding phosphine-
containing metal complexes in this chemistry because it was
observed that phosphine ligands react with IIII reagents, resulting
in oxidation of the phosphine.[16] In the present study, we
explored the reactions of selected phosphine-containing IrI and
RhI complexes with IIII reagents containing anionic and neutral
ligands (Fig. 1) and examined if the iodine(III) reagents would be
compatiblewiththese phosphine-containingiridium and rhodium
complexes. A very recent review on the area indicated very little
work has been done examining the reactions of iridium and
rhodium complexes with IIII.[17]
Experimental
Materials and Methods
NMR solvents were purchased from Cambridge Isotope Labora-
tories and dried by stirring for 3 days over CaH2, which was dis-
˚
tilled and stored over3-A molecular sieves in a glovebox. CH2Cl2,
CH3CN, n-hexane, toluene, and chloroform, which were pur-
chased from Caledon Laboratories, were dried usingan Innovative
Technologies solvent purification system. All solvents were
*Jason Dutton is the recipient of the 2016 Alan Sargeson Lectureship.
Journal compilation Ó CSIRO 2017
www.publish.csiro.au/journals/ajc

Hypervalent Iodine Oxidants
1181
N
Cl
Pd
N
N
N
Cl
PhlCl2
N
Heat
Cl
Pd
ϩ
ϪPhl
N
N
1
1Cl
OAc
Pd
N
N
OAc
Phl(OAc)2
N
Heat
OAc
Pd
ϪPhl
N
N
1
1OAc
Scheme 1. Oxidation of compound 1 using PhICl2 and PhI(OAc)2.
R
2ϩ
R
N
N
N
2 OTfϪ
Pd
R
N
2ϩ
N
R
R
N
N
3
2 OTfϪ
Pd
ϩ
ϪPhl
ϩ
N
2ϩ
2 OTfϪ
1
N
N
Pd
R
N
N
2R; R ϭ H, NMe2
4
N
N
N
N
ϭ
Scheme 2. Reaction of compound 1 with dicationic IIII reagents.
ϩ
NMe2
N
R
2ϩ
3ϩ
R
Me2N
N
N
N
N
OTfϪ
2 OTfϪ
I
3 OTfϪ
Au
Au
ϪPhl
N
N
N
R
NMe2
NMe2
R
6
5
2R; R ϭ ϪH, ϪCN, NMe2
Scheme 3. Synthesis of AuIII complex 6.

1182
M. Albayer and J. L. Dutton
2ϩ
CN
N
CN
2ϩ
N
N
I
N
N
N
N
N
N
N
B
N
N
2 OTfϪ
2 OTfϪ
N
B
Pd
Pd
ϩ
N
ϪPhl
N
N
N
N
N
N
N
CN
2CN
7
8
Scheme 4. Reaction of dicationic IIII reagent with PdII.
ϩ
washed with n-hexane (2 ꢁ 10 mL), and dried under reduced
pressure. dP (162 MHz, CDCl3) 2.0 (s), ꢀ1.6 (s), ꢀ9.6 (s), ꢀ10.9
(s), ꢀ12.6, ꢀ13.7 (s). See the Supplementary Material for the
1H NMR. m/z (electrospray ionization mass spectrometry
(ESI-MS)) ([M]nþ) 876.1 [Ir(PPh3)2(CO)(Cl)2(OAc)], 894.1
[Ir(PPh3)2(OAc)3].
Ph
Ph
Ph
Ph
Ph
CO
Ph3P
Cl
PPh3
PPh3
P
P
P
Ph3P
Cl
OTfϪ
Ir
Rh
Rh
PPh3
P
Ph
Ph Ph
Vaska’s complex
Wilkinson’s catalyst
9
10
11
Reaction of 2R with 9
R
2ϩ
A solution of 2R (0.13 mmol) in 5 mL CDCl3 was added drop-
wise to a solution of 9 (100 mg, 0.13 mmol) in 5 mL CDCl3 and
stirred for 3 h at room temperature. A colour change from bright
yellow to light yellow was observed within 30 min. The solvent
was reduced to half under reduced pressure, followed by addi-
tion of 10 mL n-hexane, which resulted in precipitation of a pale
yellow solid. The solid was filtered, washed with n-hexane
(2 ꢁ 10 mL), and dried under reduced pressure. R ¼ NMe2: dP
(162 MHz, CDCl3) ꢀ2.4 (s), ꢀ8.4 (s), ꢀ15.4 (s). See the Sup-
N
I
OTf
I
OAc
I
2 OTfϪ
N
OAc
OAc
2OAc
2OAc.OTf
plementary Material for the 1H NMR. m/z (ESI-MS) ([M]nþ þ
)
R
797.1 [Ir(PPh3)(CO)(Cl)2(DMAP)2]þ, 937.0 [Ir(PPh3)2(CO)
(Cl)2(DMAP)]þ. R ¼ H: dP (162 MHz, CDCl3) 65.9 (s), 26.9 (s),
ꢀ3.9 (s), ꢀ14.6 (s), ꢀ15.2 (s), ꢀ16.4 (s), ꢀ23.1 (s). m/z
(ESI-MS) ([M]nþ) 711.1 [Ir(PPh3)(CO)(Cl)2(Pyr)2]þ, 894.1
[Ir(PPh3)2(CO)(Cl)2(Pyr)]þ.
2R; R ϭ H, NMe2
Fig. 1. Iridium(I), rhodium(I), and iodine(III) reagents used in the present
study.
Reaction of 2OAc.OTf with 9
˚
stored over 3-A molecular sieves in a nitrogen-filled glovebox. All
A mixture of 2OAc (20 mg, 0.064 mmol) and TMS-OTf (23 mL,
0.128 mmol) in 2 mL CDCl3 was added dropwise to a solution of
9 (50 mg, 0.064 mmol) in 2 mL CDCl3. A colour change from
bright yellow to brown was observed in 10 min. An aliquot was
removed for NMR and mass spectrometry analysis. dP
(162 MHz, CDCl3) 14.4 (s), 8.0 (s), 5.3 (s), 2.6 (s), 0.4 (s), ꢀ3.6
(s), ꢀ8.1 (s), ꢀ15.6 (s), ꢀ21.4 (s). m/z (ESI-MS) ([M]nþ) 745.2
[Ir(PPh3)2CO]þ, 753.2 [Ir(PPh3)2Cl]þ, 786.1 [Ir(PPh3)2Cl2]þ,
803.1 [Ir(PPh3)2CO(OAc)]þ, 839.1 [Ir(PPh3)2CO(OAc)Cl]þ.
remaining reagentswere ordered from Sigma–Aldrich and used as
received. Ir(PPh3)2(CO)Cl,[18] Rh(PPh3)3Cl,[19] [Rh(dppe)2][Cl]
(dppe ¼ bis(diphenyl)phosphinoethane),[20] [PhI(Pyr)2][OTf]2
(pyr ¼ pyridine), and [PhI(4-DMAP)2][OTf]2 (DMAP ¼ 4-dime-
thylaminopyridine)[13] were prepared following published pro-
cedures. The metathesis to produce [Rh(dppe)2][OTf] was carried
out by the addition of a 1 : 1 stochiometric ratio of TMS-OTf
(OTf¼ triflate) to a CH2Cl2 solution of [Rh(dppe)2][Cl] followed
by solvent removal at reduced pressure.
CCDC numbers 1539214–1539218 at the Cambridge Crys-
tallographic Data Centre contain the crystallographic data for
this manuscript in .cif format.
Reaction of 2OAc with 10
A solution of 2OAc (35 mg, 0.11 mmol) in 2 mL CDCl3 was
added dropwise to a solution of 10 (100 mg, 0.11 mmol) in
5 mL CDCl3 and stirred for 3 h at room temperature. A colour
change from burgundy to light red was observed. The solvent
was reduced to half under reduced pressure, followed by addi-
tion of 10 mL n-hexane, which resulted in precipitation of a light
orange solid. The solid was filtered, washed with n-hexane
(2 ꢁ 10 mL), and dried under reduced pressure. dP (162 MHz,
CDCl3) 24.5 (d, J 122). dH (400 MHz, CDCl3) 7.43–7.38 (m,
6H), 7.37–7.32 (m, 12H), 7.20–7.17 (m, 12H), 2.08 (s, 3H). dC
Reaction of 2OAc with 9
A solution of 2OAc (42 mg, 0.13 mmol) in 2 mL CDCl3 was
added dropwise to a solution of 9 (100 mg, 0.13 mmol) in
5 mL CDCl3 and stirred for 3 h at room temperature. A colour
change from bright yellow to light yellow was observed within
10 min. The solvent was reduced to half under reduced pressure,
followed by addition of 10 mL n-hexane, which resulted in
precipitation of a pale yellow solid. The solid was filtered,

Hypervalent Iodine Oxidants
1183
(100 MHz, CDCl3) 191.24, 135.61, 130.94, 129.28, 127.71,
25.70. m/z (ESI-MS) ([M]nþ) 721.1 [Rh(PPh3)2(Cl)(OAc)]þ.
Results and Discussion
Treatment of 9 with 2OAc in CDCl3 for 3 h resulted in a
pale yellow solution. The 31P NMR spectrum of the reaction
mixture gave six peaks between 2.0 and ꢀ13.7 ppm, indicating
the presence of a mixture of products. Oxidation of the phos-
phine ligands as inferred from no strongly downfield-shifted
signals was, however, not observed. The cationic ESI mass
spectrum of the reaction mixture indicated the presence of
compounds 12 and 13 at m/z 876.1 and 894.1 (Scheme 5). X-Ray
diffraction studies were done on two single crystals of different
morphologies obtained from vapour diffusion of Et2O into a
concentrated CH2Cl2 solution of the mixture, which showed the
crystals to be IrIII compounds 12 and 13 (Fig. 2). The bond dis-
tances and geometries of the complexes are all typical and
therefore do not warrant any further discussion. The similar
solubility of these products prevented their separation from each
other. Compound 12 gained one chloride and one acetate
whereas compound 13 lost a chloride and a CO, and gained three
acetates. It is obvious that using IIII oxidant with 9 resulted in a
mixture of products, possibly arising from ligand exchange and
anion scrambling. It has been reported that the use of IIII oxidant
in other systems such as AuI/AuIII resulted in significant ligand
and anion scrambling.[12,21,22]
Reaction of 2R with 10
A solution of 2R (0.11 mmol) in 5 mL CDCl3 was added
dropwise to a solution of 10 (100 mg, 0.11 mmol) in 5 mL
CDCl3 and stirred for 3 h at room temperature. A colour change
from burgundy to light red-brown was observed. The solvent
was reduced to half under reduced pressure, followed by
addition of 10 mL n-hexane, which resulted in precipitation of
a light brown solid. The solid was filtered, washed with
n-hexane (2 ꢁ 10 mL), and dried under reduced pressure.
R ¼ NMe2: dP (162 MHz, CH2Cl2) 28.2 (s), 14.1 (d, J 88),
11.9 (d, J 88). m/z (ESI-MS) ([M]nþ) 803.0 [Rh(PPh3)
(Cl)2(DMAP)3]þ, 942.2 [Rh(PPh3)2(Cl)2(DMAP)2]þ. R ¼ H:
dP (162 MHz, CH2Cl2) 65.0 (s), 14.0 (d, J 84), 9.7 (d, J 104).
m/z (ESI-MS) ([M]nþ) 673.6 [Rh(PPh3)(Cl)2(Pyr)3]þ, 854.9
[Rh(PPh3)2(Cl)2(Pyr)2]þ.
Reaction of 2OAc.OTf with 10
A mixture of 2OAc (17 mg, 0.054 mmol) and TMS-OTf (20 mL,
0.108 mmol) in 2 mL CDCl3 was added dropwise to a solution of
10 (50 mg, 0.054 mmol) in 2 mL CDCl3. A colour change from
burgundy to brown was observed in 10 min. An aliquot was
removed for NMR and mass spectrometry analysis. dP
(162 MHz, CDCl3) 61.9 (s), 45.2 (dt, J 135), 23.4 (s), 19.8 (dt,
J 100). m/z (ESI-MS) ([M]nþ) 297.1 [PPh3Cl]þ, 307.1 [RhIPh]þ,
406.0 [RhPPh3NCCH3]þ, 477.0 [RhPPh3Cl2NCCH3]þ, 568.9
[PPh3RhIPh]þ, 627.0 [Rh(PPh3)2]þ, 697.0 [Rh(PPh3)2Cl2]þ.
The reaction of 9 with 2OAc.OTf in a 1 : 1 ratio resulted in a
colour change from bright yellow to brown within 10 min. The
31P NMR of the reaction mixture contained seven peaks between
ꢀ22 and 15 ppm, indicating the presence of seven phosphorus-
containing products. The positive ESI detection mass spectrum
showed a similar scrambling pattern to that found from 2OAc
with 9, with compound 12 being present.
Treatment of 9 with 2NMe2 in CDCl3 at room temperature
for 3 h resulted in a colour change from bright yellow to light
yellow. The 31P NMR spectrum of the isolated solid in CDCl3
gave three peaks at ꢀ2.4, ꢀ8.4, and ꢀ15.4 ppm indicating the
presence of three phosphorus-containing products. Positive
mode ESI-MS detection of a CH3CN solution of the isolated
solid gave fragments that could be identified at [m/z]þ ¼ 797.1
consistent with 14NMe2 and [m/z]þ ¼ 937.1 consistent with
15NMe2 as shown in Scheme 6. The stereochemistry of
14NMe2 cannot be determined from the data. The presence of
one unique P environment in 15NMe2 inferred by the lack of
P–P coupling allows the assignment of PPh3 ligands as trans to
one another, but the configuration of the other ligands relative to
each other cannot be determined.
X-Ray diffraction studies were done on single crystals
obtained from vapour diffusion of Et2O into concentrated
CH2Cl2 solution of the isolated solid, which revealed compound
16. This compound has been synthesized previously by reacting
IrCl(PPh3)3 with chlorine.[23] The use of the IIII oxidant 2H
resulted in a similar outcome, where the ESI-MS spectrum
contained fragments consistent with 14R and 15R. The 31P
NMR spectrum of the isolated solid contained signals between
65.9 and ꢀ23.1 ppm. The signal at 65.9 ppm is consistent with
the formation of the chlorophosphonium cation ([Ph3PCl]þ),[24]
which may occur via reductive elimination from IrIII. Overall,
the reaction of Vaska’s complex 9 with the chosen IIII oxidants
resulted in significant ligand and anion scrambling.
Reaction of 2OAc with 11
A mixture of 2OAc (31 mg, 0.095 mmol) and TMS-OTf (35 mL,
0.19 mmol) in 5 mL CH2Cl2 was added dropwise to a solution of
11 (100 mg, 0.095 mmol) in 5 mL CH2Cl2 and stirred for 1 h at
room temperature. A colour change from bright yellow to yel-
low was observed within 5 min. The solvent was reduced to
half under reduced pressure, followed by addition of 10 mL
n-hexane, which resulted in precipitation of a yellow solid. The
solid was filtered, washed with n-hexane (2 ꢁ 10 mL), and dried
under reduced pressure (84 mg, 70 % yield). dP (162 MHz,
CH2Cl2) 58.6 (dt, J 11, 84), 42.5 (dt, J 11, 115). dH (400 MHz,
CD3CN) 7.81–7.76 (m, 8H), 7.68–7.60 (m, 8H), 7.58–7.56 (m,
12H), 7.39–7.34 (m, 4H), 7.24–7.20 (m, 4H), 7.18–7.15 (m, 4H),
2.68–2.56 (m, 8H), 1.96 (s, 3H). dC (100 MHz, CD3CN) 172.07,
134.55, 134.08, 133.55, 133.25, 130.45, 130.24, 126.05, 125.51,
24.37, 20.22, 16.68. m/z (ESI-MS) ([M]nþ) 479.1 [Rh
(dppe)2(OAc)]2þ
.
Reaction of 2NMe2 with 11
A solution of 2NMe2 (72 mg, 0.095 mmol) in 5 mL CDCl3 was
added dropwise to a solution of 11 (100 mg, 0.095 mmol) in
5 mL CDCl3 and stirred for 3 h at room temperature. A colour
change from bright yellow to yellow was observed. The solvent
was reduced to half under reduced pressure, followed by addi-
tion of 10 mL n-hexane, which resulted in precipitation of a pale
orange solid. The solid was filtered, washed with n-hexane
(2 ꢁ 10 mL), and dried under reduced pressure (80 mg, 53 %
crude yield). dP (162 MHz, CDCl3) 30.8 (s), 40.7 (dt, J 15, 113),
34.5 (dt, 15, 86). dH (400 MHz, CDCl3) 7.98–6.65 (m, 50H),
The reaction of 10 with 2OAc in CDCl3 at room temperature
for 3 h resulted in a colour change to light reddish-brown. The
31P NMR spectrum of the reaction mixture contained two
doublets at 24.5 and 28.3 ppm. The two doublets were taken to
represent two chemically distinct phosphorus atoms coupling
3.19 (s, 12H). m/z (ESI-MS) ([M]nþ
(dppe)2(DMAP)2]3þ, 510.1 [Rh(dppe)2(DMAP)]2þ
)
380.7 [Rh
.

1184
M. Albayer and J. L. Dutton
PPh3
OAc
O
lll
Ir
CO
Ph3P
Cl
O
I
Cl
Ph3P
AcO
III
Ir
Cl
Ir
ϩ
ϩ
AcO
ϪPhl
PPh3
PPh3
CO
OAc
PPh3
12
OAc
9
2OAc
13
Scheme 5. Reaction of 9 with 2OAc products as identified by mass spectrometry and X-ray crystallography.
(a)
(b)
P(2)
Ir(1)
P(2)
Ir(2)
O(4)
O(1)
O(3)
Cl(10)
C(3)
Cl(8)
O(2)
O(11)
P(1)
P(3)
Fig. 2. (a) Solid-state structure of 12. Ellipsoids are depicted at the 50 % probability level, and hydrogen atoms have been
removed for clarity. (b) Solid-state structure of 13. Ellipsoids are depicted at the 50 % probability level, and hydrogen atoms have
been removed for clarity.
R
ϩ
2ϩ
ϩ
R
N
R
N
R
N
Cl
CO
N
Ph3P
Cl
Ph3P
Cl
III
Ir
III
Ir
Ph3P
Cl
OTfϪ
ϩ
l
ϩ
2 OTfϪ
OTfϪ
Ir
ϪPhl
PPh3
PPh3
Cl
CO
CO
N
R
9
14R
15R
PPh3
2R
R ϭ H, NMe2
III
Ir
Cl
Cl
ϩ
Cl
PPh3
16
Scheme 6. Reaction of 9 with 2R products as identified by mass spectrometry and X-ray crystallography.
with 103Rh, which suggests the presence of two compounds,
each with one unique 31P environment.
washed with n-hexane. X-Ray diffraction studies performed on
single crystals obtained from concentrated CH2Cl2 solution of the
isolated solid at ꢀ358C confirmed product 17 as shown in Fig. 3.
The bond distances and geometry are all typical and therefore do
not warrant further discussion. The reaction is proposed to proceed
via oxidation of 10 to give an unobserved intermediate, which is
followed by ligand redistribution and anion scrambling to give the
observed products as shown in Scheme 7.
The most abundant signal in the mass spectrum ([m/z]þ 721.1)
resulted from loss of one chloride from compound 17. A cationic
fragment at [m/z]þ ¼ 745.1 could result from the loss of one
acetate from proposed compound 18. Compound 17 was isolated
by dissolving the solid in a minimum amount of CH2Cl2
and placing at ꢀ358C overnight. The solid then was filtered and

Hypervalent Iodine Oxidants
1185
The dropwise addition of 2NMe2 to 10 at room temperature
in CDCl3 resulted in a colour change from burgundy to light red
over 3 h. The 31P NMR spectrum of the reaction mixture had two
doublets at 14.1 and 11.9 ppm, indicating two phosphorus-
containing products coupling to Rh in the mixture. A singlet at
28.2 ppm could not be identified. The positive ESI-MS detection
of the mixture indicated the presence of 19 and 20 at [m/z]þ
¼ 942.2 and 803.0, which also was consistent with the chlorine
isotope patterns, as shown in Scheme 8. The similar solubilities
of these products prevented their isolation. Using IIII oxidant 2H
resulted in similar Rh products as indicated by mass spectrome-
try and 31P NMR spectroscopy. As with the reaction of 9 with
2H, the 31P NMR also contained a singlet at 65.0 ppm, indicat-
ing the presence of the chlorophosphonium cation [Ph3PCl]þ.
The presence of doublets rather than doublets of doublets
indicates the P atom environments are identical within each of
the two compounds; therefore, the stereochemistry is proposed
to be as depicted for 19R in Scheme 8, although for 20R, this
cannot be ascertained.
The slow addition of 2OAc.OTf to 10 in 1 : 1 ratio resulted in
a colour change from burgundy to brown within 10 min. The
31P NMR of the reaction mixture had four signals between 4 and
62 ppm. The major singlet at 62 ppm represents the chloropho-
sphonium cation [Ph3PCl]þ, which was also observed in the
mass spectrum of the reaction mixture at m/z 297.1. The two
doublets at 45.2 (JP–Rh ¼ 135 Hz) and 19.8 ppm (JP–Rh ¼ 100 Hz)
represent two P–Rh containing products. The cationic ESI mass
spectrum of the reaction mixture contained fragments at m/z ¼
568.9 and 697.1, which were assigned to [Rh(PPh3)(Ph)I]þ and
[Rh(PPh3)2(Cl)2]þ respectively. The former product indicates
that it is possible for the I–Ph fragment of the iodine(III) oxidant to
O(2)
O(1)
Cl(2)
Cl(1)
P(1)
Rh(1)
P(2)
Fig. 3. Solid-state structure of 17. Hydrogen atoms omitted for clarity.
Thermal ellipsoids shown at the 50 % probability level.
OAc
O
OAc
O
III
Rh
PPh3
PPh3
Ph3P
Cl
O
OAc
l
III
O
III
Ph3P
Cl
Cl
Ph3P
AcO
ϩ
ϩ
I
Rh
Rh
PPh3
PPh3
Rh
Ligand
redistribution
ϪPhl
Ph3P
Cl
PPh3
PPh3
OAc
OAc
Proposed
intermediate
10
2OAc
17
18
Scheme 7. Reaction of 10 with 2OAc products as identified by mass spectrometry and X-ray crystallography.
R
N
ϩ
ϩ
2ϩ
R
N
R
N
R
R
PPh3
PPh3
Ph3P
Cl
l
III
N
N
III
Ph3P
Cl
Ph3P
Cl
2 OTfϪ
OTfϪ
Rh
ϩ
OTfϪ
ϩ
Rh
Cl
Rh
ϪPhl
PPh3
N
Cl
N
R
10
19R
20R
R
2R; R ϭ H, NMe2
Scheme 8. Reaction of 10 with 2R products as identified by mass spectrometry.
2ϩ
ϩ
Ph
Ph
P
Ph
Ph
Ph
Ph
Ph
Ph
OAc
I
O
O
P
P
P
P
TMS-OTf
2 OTfϪ
OTfϪ
ϩ
Rh
Rh
Ph
Ph
ϪPhl
P
P
P
Ph
OAc
Ph
Ph
Ph
Ph
Ph
21
11
2OAc
Scheme 9. Reaction of 11 with 2OAc.OTf product as identified by mass spectrometry and X-ray crystallography.

1186
M. Albayer and J. L. Dutton
also become involved in these reactions, which has also been
observed in related chemistry with thiophenes, selenophenes, and
tellurophenes using this family of oxidants.[25–27]
as shown in Scheme 9. Further characterization of compound 21
by X-ray crystallography confirmed that this complex contained
one acetate group bound to the dicationic RhIII in a bidentate
fashion as shown in Fig. 4, with the two dppe ligands retained.
Treatment of compound 11 with 2NMe in CDCl3 at room
temperature for 3 h followed by workup resulted in the isolation
of a yellow solid. The 31P NMR spectrum of the isolated solid
showed two doublets of triplets at 40.7 and 34.5 ppm, which is
consistent with proposed product 22, as well as a singlet at
30.8 ppm. Searching the literature revealed that 1,2-bis(diphe-
nylphosphinyl)ethane (23) has been reported to give an identical
chemical shift to our observation (30.8 ppm).[30] The positive
ESI-MS analysis of the isolated solid shows a major peak at
[m/z]þ ¼ 510.1 with a half-mass-unit peak separation and a
minor peak at [m/z]þ ¼ 380.7 with one-third mass-unit peak
separation, which is in agreement with compound 22 as shown
in Scheme 10.
Compound 23 and related phosphine oxide species have been
observed to be generated from high-oxidation-state phosphorus
triflate species.[16,31] Compounds 22 and 23 were shown to be in
approximate ratio of 4 : 1 by 31P NMR, bearing in mind the
semiquantitative nature of 31P NMR. A battery of efforts to
selectively precipitate 22 to obtain an analytically pure sample
unfortunately failed.
As with Vaska’s complex, the overall result using PhIL2 IIII
oxidants with Wilkinson’s catalyst resulted in significant scram-
bling and overall unproductive reactions.
Treatment of homoleptic bis-dppe chelated RhI compound 11
with 2OAc in CDCl3 at room temperature for 3 h resulted in no
colour change. The 31P NMR spectrum of the reaction mixture
also indicated no reaction had taken place, showing only starting
material. The oxidation of this compound required the use of the
stronger oxidizing reagent 2OAc.OTf reagent, prepared by the
addition of 2 equivalents of TMS-OTf to 2OAc to give 2OAc.
OTf (leaving a free equivalent of TMS-OTf).[16,28,29] The
dropwise addition of a CH2Cl2 solution containing PhI(OAc)
(OTf) and TMS-OTf to compound 11 resulted in a colour change
from bright yellow to yellow and gave a yellow solid after a short
workup. The positive ESI-MS spectrum of the isolated solid
redissolved in CH3CN showed a major peak at [m/z]þ ¼ 479.1
with a half-mass-unit peak separation that is consistent with 21
Conclusion
Reactions of trivalent iodine reagents containing a PhI(L)2 motif
with classic iridium and rhodium complexes have been reported.
The metal complexes under study were successfully oxidized
from þ1 to þ3. Oxidations of Vaska’s compound generally
resulted in a mixture of products via ligand exchange and anion
scrambling. In the case of Wilkinson’s catalyst, the oxidation
also resulted in a mixture of products due to ligand exchange and
anion scrambling. Reactions of trivalent iodine reagents with
homoleptic RhI bound by chelating phosphines (compound 11)
resulted in cleaner oxidation of RhI to RhIII and suggests that
these systems have a better compatibility with IIII reagents. In
most cases, oxidized phosphine was not observed, likely
resulting from reductive elimination from the high-oxidation-
state metal complexes rather than direct oxidation of the phos-
phines, indicating IIII is reasonably compatible with metal-bound
phosphine-containing complexes. However, ligand scrambling
in the oxidized species can clearly present a major problem in
terms of accurately predicting reaction outcomes and isolating
clean products in good yields.
P(1A)
P(1)
P(2)
Rh(1)
P(2A)
O(1A)
O(1)
Fig. 4. Solid-state structure of 21. Hydrogen atoms and triflate counter
ions omitted for clarity. Thermal ellipsoids shown at the 50 % probability
level.
NMe2
3ϩ
2ϩ
NMe2
ϩ
Ph
Ph
Ph
Ph
NMe2
Ph
Ph
Ph
Ph
N
I
N
N
2ϩ
Ph
Ph
P
P
P
P
O
Ph
OTfϪ
ϩ
2 OTfϪ
Rh
P
P
Rh
3 OTfϪ
Ph
ϩ
2 OTfϪ
Ph
Ph
ϪPhl
P
P
P
P
Ph
N
Ph
Ph
23
Ph
11
Ph
Ph
22
NMe2
2NMe2
Scheme 10. Products of the reaction of 11 with 2NMe2 as identified by mass spectrometry.

Hypervalent Iodine Oxidants
1187
Supplementary Material
[13] R. Weiss, J. Seubert, J. Angew. Chem. Int. Ed. Engl. 1994, 33, 891.
doi:10.1002/ANIE.199408911
Experimental details, 1H, 31P NMR spectra, and mass spectra are
available on the Journal’s website.
[14] N. S. Pirkuliyev, V. K. Brel, V. V. Zhdankin, N. S. Zefirov, Russ. J.
Org. Chem. 2002, 38, 1224. doi:10.1023/A:1020990618707
[15] E. Lee, A. S. Kamlet, D. C. Powers, C. N. Neumann, G. B. Boursalian,
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doi:10.1126/SCIENCE.1212625
[16] T. P. Pell, S. A. Couchman, S. Ibrahim, D. J. D. Wilson, B. J. Smith,
P. J. Barnard, J. L. Dutton, Inorg. Chem. 2012, 51, 13034. doi:10.1021/
IC302176F
Conflicts of Interest
The authors declare no conflicts of interest.
Acknowledgements
[17] F. C. Sousa e Silva, A. F. Tierno, S. E. Wengryniuk, Molecules 2017,
22, 780. doi:10.3390/MOLECULES22050780
[18] J. P. Collman, C. T. Sears, M. Kubota, A. Davison, E. T. Shawl, J. R.
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We thank La Trobe University, The Australian Research Council (JLD,
FT16010007) and The Australian Commonwealth (MA, Australian Post-
graduate Award PhD scholarship) for their generous funding of this work.
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