Iridium and rhodium complexes with the hemilabile ligand [2-(1,3-Dioxolane-2-yl)phenyl]diphenylphosphane - Behaviour in solution and structural characterization

Article abstract of DOI:10.1002/ejic.201201188

[MCl(L₂)]₂ (M = Ir, L₂ = 1,5-cyclooctadiene; M = Rh, L₂ = norbornadiene) reacts with [2-(1,3-dioxolane-2-yl)phenyl]diphenylphosphane (1) to afford [MCl(L ₂)(P~O)] (M = Ir, 2; M = Rh, 3), in which the ligand is P-monodentate. Complex 3 reacts with AgClO₄ to give [Rh(Nbd)(PO)]ClO₄ (4), in which the ligand is P,O-bidentate. Complex 2 is static at room temp., whereas 3 and 4 undergo intramolecular exchanges, which are fast at room temperature and slow at 223 K. The conformational changes in 4 are still fast at 223 K. Complexes 2-4 react with CO to afford trans-[MCl(CO)(P~O)₂] (M = Ir, 5; M = Rh, 6) or trans-[Rh(CO) ₂(P~O)₂]ClO₄ (7). Cyclooctadiene complexes react with PPh₂(o-C₆H₄CHO) to afford [MClH(PPh₂(o-C₆H₄CO))(PO] (M = Ir, 8; M = Rh, 9), in which 1 is chelating. Complex 8 contains a single diastereomer, is static in the 303-213 K range and reacts with CO to form [IrClH(PPh ₂(o-C₆H₄CO))(P~O)(CO)] (10). Complex 9 contains two diastereomers 9a/9b in a 95:5 ratio that undergo interconversion, which is slow at low temperature, and reacts with CO to undergo reductive elimination of aldehyde, cleavage of the Rh-O bond and scrambling of phosphanes. A mixture of trans-[RhCl(CO)(κ¹-PPh₂(o-C₆H ₄CHO))(P~O)] (11), 6 and trans-[RhCl(CO)(κ¹-PPh ₂(o-C₆H₄CHO))₂] is formed. Bubbling of nitrogen transforms 11 back into 9. Compound 2 reacts with hydrogen to give the fluxional [IrCl(H)₂(P~O)(PO)] (12) with trans P atoms and cis H atoms, which attains coalescence at 203 K. Complex 12 reacts with mono- or bidentate ligands to afford static [IrCl(H)₂(P~O)₂L] (L = CO, 13; py, 14; nPrNH₂, 15) or [Ir(H)₂(P~O) ₂(en)]BPh₄ (16, en = ethylenediamine). Abstraction of halide from 12 affords [Ir(H)₂(PO)₂]BPh₄ (17), which is fluxional owing to interconversion between only two of the possible four diastereomers, for which ΔH^? = 54.7 ± 0.7 kJ mol^-1 and ΔS^? = 4.7 ± 0.2 J K ^-1 mol^-1. The X-ray structures of 8, 15 and 16 are also reported. [2-(1,3-Dioxolane-2-yl)phenyl]diphenylphosphane (1) coordinates to M^I preferably as a κ¹-P ligand. M^III may afford κ²-P,O coordination in dynamic diastereomers such as A or B. A contains a single diastereomer if M = Ir or two diastereomers in a 95:5 ratio if M = Rh. B contains a mixture of only two diastereomers. Copyright

Full text of DOI:10.1002/ejic.201201188

FULL PAPER
DOI:10.1002/ejic.201201188
Iridium and Rhodium Complexes with the Hemilabile
Ligand [2-(1,3-Dioxolane-2-yl)phenyl]diphenylphosphane –
Behaviour in Solution and Structural Characterization
Montserrat Barquín,[a] Roberto Ciganda,[a] María A. Garralda,*[a]
Lourdes Ibarlucea,[a] Claudio Mendicute-Fierro,[a]
Antonio Rodríguez-Diéguez,[b] and José M. Seco[a]
Keywords: Rhodium / Iridium / Phosphane ligands / Hemilabile ligands / Fluxionality
[MCl(L2)]2 (M = Ir, L2 = 1,5-cyclooctadiene; M = Rh, L2 = nor-
bornadiene) reacts with [2-(1,3-dioxolane-2-yl)phenyl]di-
phenylphosphane (1) to afford [MCl(L2)(P~O)] (M = Ir, 2; M
= Rh, 3), in which the ligand is P-monodentate. Complex 3
undergo interconversion, which is slow at low temperature,
and reacts with CO to undergo reductive elimination of alde-
hyde, cleavage of the Rh–O bond and scrambling of phos-
phanes.
A
mixture
of
trans-[RhCl(CO)(κ1-PPh2(o-
∧
reacts with AgClO4 to give [Rh(Nbd)(P O)]ClO4 (4), in which
C6H4CHO))(P~O)] (11), 6 and trans-[RhCl(CO)(κ1-PPh2(o-
C6H4CHO))2] is formed. Bubbling of nitrogen transforms 11
back into 9. Compound 2 reacts with hydrogen to give the
the ligand is P,O-bidentate. Complex 2 is static at room
temp., whereas 3 and 4 undergo intramolecular exchanges,
which are fast at room temperature and slow at 223 K. The
conformational changes in 4 are still fast at 223 K. Complexes
2–4 react with CO to afford trans-[MCl(CO)(P~O)2] (M = Ir, 5;
M = Rh, 6) or trans-[Rh(CO)2(P~O)2]ClO4 (7). Cyclooctadiene
complexes react with PPh2(o-C6H4CHO) to afford
∧
fluxional [IrCl(H)2(P~O)(P O)] (12) with trans P atoms and
cis H atoms, which attains coalescence at 203 K. Complex 12
reacts with mono- or bidentate ligands to afford static
[IrCl(H)2(P~O)2L] (L = CO, 13; py, 14; nPrNH2, 15) or [Ir(H)2-
(P~O)2(en)]BPh4 (16, en = ethylenediamine). Abstraction of
∧
∧
[MClH(PPh2(o-C6H4CO))(P O] (M = Ir, 8; M = Rh, 9), in
halide from 12 affords [Ir(H)2(P O)2]BPh4 (17), which is flux-
which 1 is chelating. Complex 8 contains a single dia-
stereomer, is static in the 303–213 K range and reacts with
CO to form [IrClH(PPh2(o-C6H4CO))(P~O)(CO)] (10). Com-
plex 9 contains two diastereomers 9a/9b in a 95:5 ratio that
ional owing to interconversion between only two of the pos-
sible four diastereomers, for which ΔH‡ = 54.7Ϯ0.7 kJmol–1
and ΔS‡ = 4.7Ϯ0.2 JK–1 mol–1. The X-ray structures of 8, 15
and 16 are also reported.
hydrogenation or carbonylation.[1,4] They are also useful for
small molecule activation and sensing.[5] Furthermore, they
have also been used as tools in the weak-link approach in
supramolecular chemistry.[6] Palladium complexes of
phenyl-backbone-derived P,O ligands with dioxolane ether
groups have been found to be effective catalysts for cross-
Introduction
Hemilabile ligands contain at least two different types of
donor groups with different bond strengths to metal
centres, which can provide free coordination sites around
the metal atom and stabilise reactive transition metal
centres along the course of a reaction.[1] One type of such
∧
coupling reactions, in which these ligands are P O biden-
hemilabile ligand is the phosphorus–oxygen class of li-
tate.[7,8] Complexes containing [2-(1,3-dioxolane-2-yl)-
phenyl]diphenylphosphane (1) have received less attention
than those with other P,O ligands. Compound 1 includes
two oxygen atoms in addition to the phosphorus atom and
also offers the prospect of chirality due to its enantiotopic
carbon centre. Transition metal complexes of 1 reported in-
clude monodentate coordination in [PdBr(4-tBu-C6H4)-
gands.[2] The ditopic coordination mode, P O (κ -P,O), in
2
∧
which the ligands bind to the metal through both donor
atoms, and P~O (κ1-P) coordination, in which the ligands
bind to the metal in a monodentate fashion through the
phosphorus atom, can give rise to fluxional behaviour.[3]
Complexes formed with these hemilabile ligands are active
catalysts for a variety of homogeneous reactions such as
(P~O)2][7] or [RhCl(Cod)(P~O)] (Cod = 1,5-cycloocta-
[9]
diene),[9] bidentate coordination in [Rh(Cod)(P O)]BF4
∧
[a] Facultad de Química de San Sebastián, Universidad del País
Vasco, UPV/EHU,
or [RuCl2(P O)2],[10] and the formation of cobalt complexes
∧
Apdo. 1072, 20080 San Sebastián, Spain
with four-membered CoCCP metallacycles formed by aryl
C–H activation.[11]
E-mail: mariaangeles.garralda@ehu.es
Homepage: http://www.ehu.es
[b] Facultad de Ciencias, Universidad de Granada,
Avda. Fuenteventura s/n, 18071 Granada, Spain
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201201188.
In this paper, we describe iridium and rhodium com-
plexes of 1 containing κ1-P or κ2-P,O coordinated ether–
phosphane ligand. We have found that their fluxional be-
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haviour involves different intramolecular processes and de- nances at δ = 92.5 and 54.1 ppm, respectively, in the
pends markedly on the metal and on the nature of the co- 13C{1H} NMR spectrum. This indicates the nonequivalence
ligands. X-ray diffraction studies on iridium complexes are of the olefinic bonds trans to the phosphane or chlorine
also reported.
ligands and the equivalence of the two protons within each
double bond. The previously reported rhodium counter-
part, [RhCl(Cod)(P~O)] also shows nonequivalent olefinic
bonds at room temperature.[9]
Results and Discussion
In contrast, the 1H NMR spectrum of [RhCl(Nbd)-
(P~O)] (3) shows only a broad resonance at δ = 4.23 ppm
at room temperature owing to the olefinic protons, which
indicates their fast exchange. A variable temperature study
with CDCl3 and [D8]toluene as solvents was undertaken.
The behaviour of 3 was the same in both solvents. The low
solubility of 3 in CD3OD precluded the corresponding mea-
surements. Coalescence of the olefinic protons resonance
occurs at 263 K. At 223 K, two signals at δ = 5.29 and
3.24 ppm are clearly observed, whereas the other reso-
nances, including the phosphorus resonance, remain unal-
tered. From line-shape analysis[14] of the variable tempera-
Iridium(I) or Rhodium(I) Complexes
The reaction of 1 with diolefinic [MCl(L2)]2 [M = Ir, L2
= Cod; M = Rh, L2 = norbornadiene (Nbd)] complexes
affords compounds [MCl(L2)(P~O)] (2–3, Scheme 1). Nei-
ther the diolefin nor the chlorine atom are displaced when
the reaction is performed with double the stoichiometric
amount of phosphane unlike the case of rhodium with
other PO hemilabile ligands, in which the chlorine atom is
substituted by a second phosphane molecule to afford cat-
ionic species.[12] By halide abstraction from 2 or 3, the for-
mation of cationic species with bidentate coordination of
the hemilabile ligand is expected. The reaction of 3 with
ture 1H NMR spectra the activation parameters ΔH‡
=
39.1Ϯ1.2 kJmol–1 and ΔS‡ = –35.1Ϯ1 JK–1 mol–1 have
been determined. The entropy of activation is relatively
small and falls between 46 and –42 JK–1 mol–1, the accepted
range for intramolecular rearrangement processes.[15] An
associative intermolecular process requires an entropy of
activation lower than –100 JK–1 mol–1.[16] Accordingly, the
observed olefinic exchange can be explained by transient
oxygen coordination to afford a six-membered metallacycle
in a five-coordinate species, followed by pseudorotation. Di-
olefinic pentacoordinate complexes easily undergo ex-
change of the olefinic protons.[17] The low activation barrier
for fluxionality in the norbornadiene complex 3 can be re-
lated to norbornadiene showing a larger π backbonding
than cyclooctadiene[18] and to its higher tendency to afford
neutral pentacoordinate complexes.[19] Fluxional square-
planar chloro(diolefin)rhodium(I) complexes containing 2-
pyridylphosphanes have been reported to undergo such an
associative process allowing pseudorotation that is faster for
norbornadiene complexes than for the corresponding cyclo-
octadiene derivatives.[20]
∧
AgClO4 gave [Rh(Nbd)(P O)]ClO4 (4, Scheme 1, step i),
and attempts to obtain a cationic κ2-P,O derivative from 2
using silver or oxonium salts only resulted in decomposition
products.
Scheme 1. [MCl(diolefin)]2: M = Ir, diolefin = Cod; M = Rh, di-
olefin = Nbd; (i) AgClO4; (ii) CO, requires 1 for all the starting
material to react.
∧
[Rh(Nbd)(P O)]ClO4 (4), also presents fluxional behav-
1
iour in CDCl3 solution. At 223 K, the H NMR spectrum
shows two signals at δ = 5.69 and 3.35 ppm owing to the
According to the spectroscopic evidence, the P,O ligand olefinic protons. Increasing the temperature leads to broad-
is P-monodentate in 2 and 3, whereas in 4 it is bidentate. ening of the resonances of the olefinic protons, which co-
The 31P{1H} NMR spectra show only one resonance, as a alescence at 273 K, and the appearance of a broad reso-
1
singlet for 2 or a doublet for 3 and 4 with JRh,P = 167 and nance at δ = 4.52 ppm at 293 K, whereas the resonances of
168 Hz respectively, in accordance with a phosphorus atom the dioxolane and the phosphorus atom remain unaltered.
trans to the olefin.[13] The spectroscopic features of the di- In the related [Rh(Cod)(P O)]BF4, two resonances are ob-
∧
oxolane ring are similar to those of 1 and show two signals served at room temperature for the olefinic protons.[9] Dif-
in the 4.35–3.90 ppm range owing to the ethylene protons ferent processes must be considered to account for the
and one signal at 6.91, 6.74 and 5.44 ppm for 2, 3 and 4, equilibration of the olefinic protons in the cationic species
respectively, owing to the CHO2 group. The most striking in 4. At room temperature, equilibration of all four olefinic
1
difference between the H NMR spectra of 3 and 4 is the protons occurs. A Berry mechanism in pentacoordinate
1.3 ppm shift of the CHO2 signal towards higher field upon complexes formed by coordination of anions or coordinat-
chelate coordination. The presence of coordinated cyclooc- ing solvents or, alternatively, rapid dissociation and recom-
tadiene in 2 is revealed by two signals at δ = 5.20 and bination of weakly coordinating ligands have been sug-
2.94 ppm in the 1H NMR spectrum that correlate with reso- gested to account for this exchange.[21] From line-shape
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1
analysis of the variable temperature H NMR spectra, the the acyl resonance at δ = 193 ppm as a broad singlet, which
activation parameters ΔH‡ = 50.3Ϯ0.5 kJmol–1 and ΔS‡ = is slightly higher field than in other acyliridium com-
1.6Ϯ0.1 JK–1 mol–1 were obtained. The entropy of acti- plexes.[27] The ethylene protons of the dioxolane group are
vation indicates an intramolecular rearrangement. The split into four multiplets in the 4.29–3.67 ppm range, which
ether oxygen donor atom in hemilabile ligands is frequently indicates O-coordination of the dioxolane moiety.
considered as an intramolecular solvent molecule,[22] there-
fore cleavage of the Rh–O bond and opening of the chelate
ring appears to be responsible for the equilibration of all
the olefinic protons. At 223 K, fast conformational changes
of the nonplanar six-membered chelate, which are fre-
quently found in cationic square-planar complexes contain-
ing such metallacycles,[23] would still equilibrate the protons
of each double bond. Finally, another dynamic process
must be considered to account for the CH2 protons of the
Scheme 2.
dioxolane ring affording only two resonances even at low
temperatures, instead of the four resonances expected for a
The synthesis of 8 can also be achieved by the reaction
of 1 with the known acylhydrido [IrClH(PPh2(o-C6H4CO))-
κ2-P,O coordinated ligand. Fast exchange between the two
possible coordinated O atoms involving loosening of the
Rh–O bond, rotation about the O2HC–phenyl bond and re-
coordination of the formerly free oxygen atom[10,24] would
equilibrate the protons bonded to different carbon atoms
of the dioxolane.
(Cod)],[28] which results in the displacement of the diolefin
to afford 8. This behaviour highlights the higher oxophilic-
ity of IrIII when compared to IrI. The harder IrIII readily
∧
binds the oxygen atom, whereas P O chelation has proved
inaccessible in the IrI complex. Rearrangements of P,O-
hemilabile alkynyl(hydrido)iridium compounds to vinyl-
idene–metal derivatives have also been reported to promote
The diolefinic complexes 2–4 undergo diolefin displace-
ment when they are treated with carbon monoxide. The
presence of one equivalent of 1 is required to afford bis(P-
monodentate) complexes, trans-[MCl(CO)(P~O)2] (5–6) or
trans-[Rh(CO)2(P~O)2]ClO4 (7, Scheme 1, step ii). These
types of compounds appear to be the thermodynamically
more stable products.[25] The IR spectra of 5–7 show single
bands owing to the coordinated CO ligands in the 1993–
1952 cm–1 range. In addition to the disappearance of the
diolefinic resonances, the NMR spectra show a single reso-
nance for the phosphanes and a reduction of the JRh,P cou-
pling constant from 167 to 120 Hz owing to mutually trans
equivalent phosphanes.[26] The 13C{1H} NMR spectrum of
7 contains a doublet owing to Rh-bonded equivalent carb-
onyl groups. The CHO2 resonances are similar to those ob-
served for 2 and 3 and indicate dangling dioxolane groups.
[29]
∧
the opening of the P O chelate.
X-ray diffraction studies on 8 confirm the structure de-
picted in Scheme 2. Selected bond lengths and angles are
listed in Table 1, and Figure 1 shows a molecular perspec-
tive together with the atomic labelling scheme used. The
geometry around the iridium atom is distorted octahedral
with two phosphorus atoms from two bidentate ligands
trans to each other with a P1–Ir–P2 angle of 165.83(6)°. In
addition to the phosphorus atom, one of these ligands
Table 1. Selected bond lengths [Å] and angles [°] for 8, 15 and 16.
8
15
16
Ir–P1
Ir–P2
Ir–H1
Ir–Cl
Ir–O2
Ir–C1
C1–O1
O2–C20
O2–C39
O3–C20
O3–C40
2.281(2)
2.330(2)
1.597(2)
2.452(2)
2.346(4)
1.968(7)
1.215(8)
1.448(7)
1.463(7)
1.398(8)
1.428(9)
Ir1–P1
Ir1–P2
Ir1–H1
Ir1–H2
Ir1–N1
Ir1–Cl1
2.300(3)
2.303(3)
1.58(5)
1.59(4)
2.206(8)
2.488(3)
Ir1–P1
Ir1–P2
2.286(2)
2.282(2)
1.60(5)
Ir1–H1
Ir1–H2
Ir1–N1
Ir1–N2
C43–N1
C44–N2
1.58(7)
2.224(5)
2.214(5)
1.487(8)
1.465(8)
Iridium(III) or Rhodium(III) Complexes
The reaction of [IrCl(Cod)(P~O)] (2) with o-(diphenyl-
phosphane)benzaldehyde (PPh2(o-C6H4CHO)) affords the
∧
acylhydride complex [IrClH(PPh2(o-C6H4CO))(P O)] (8),
in which 1 coordinates through both the phosphorus and
the oxygen atoms (Scheme 2). The reaction involves dis-
placement of the diolefin and chelate-assisted oxidative ad-
dition of the aldehyde to iridium. The resonances observed
in the NMR spectra are sharp in the 303–213 K range and
indicate the presence of a single species in solution. The
hydride resonance appears as a doublet of doublets as a
result of coupling with two nonequivalent phosphorus
atoms at –18.03 ppm (JP,H = 14.8 and 16.5 Hz), which is
characteristic of a hydride ligand trans to a chloride ligand.
The mutually trans (JP,P = 360 Hz) phosphorus atoms ap-
pear in the 31P{1H} NMR spectrum as two doublets at δ =
30.7 and 14.8 ppm, and the 13C{1H} NMR spectrum shows
P1–Ir–P2 165.83(6) P1–Ir1–P2 163.82(9)
P1–Ir1–P2 164.39(7)
P1–Ir1–H1 87(2)
P2–Ir1–H1 84(2)
P1–Ir1–H2 87(2)
P2–Ir1–H2 81(2)
P1–Ir1–N1 98.8(2)
P2–Ir1–N1 92.2(2)
P1–Ir1–N2 93.7(2)
P2–Ir1–N2 99.5(2)
N1–Ir1–N2 77.2(2)
N1–Ir1–H1 170(2)
N1–Ir1–H2 94(2)
N2–Ir1–H1 95(2)
N2–Ir1–H2 171(2)
H2–Ir1–H1 94(3)
H1–Ir–P1 86.63(5)
H1–Ir–P2 79.35(4)
Cl–Ir–C1 95.4(2)
Cl–Ir–P1 95.88(6)
Cl–Ir–O2 83.5(1)
Cl–Ir–P2 98.16(6)
H1–Ir–C1 85.5(2)
H1–Ir–O2 95.6(1)
C1–Ir–P1 85.2(2)
C1–Ir–O2 178.7(2)
C1–Ir–P2 91.5(2)
P1–Ir–O2 95.5(1)
O2–Ir–P2 88.0(1)
P1–Ir1–H1 94(2)
P2–Ir1–H1 79(2)
P1–Ir1–H2 74(2)
P2–Ir1–H2 93(2)
P1–Ir1–N1 96.1(2)
P2–Ir1–N1 96.7(2)
Cl1–Ir1–N1 90.7(2)
Cl1–Ir1–P1 93.18(9)
Cl1–Ir1–P2 96.40(9)
N1–Ir1–H1 79(2)
N1–Ir1–H2 170(2)
Cl1–Ir1–H2 89(2)
Cl1–Ir1–H1 168(2)
Cl–Ir–H1 177.40(5) H1–Ir1–H2 103(3)
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binds to the metal atom through the carbon atom of the velops into a broad doublet of doublet of doublets, whereas
acyl group and the other through one of the oxygen atoms the 31P{1H} NMR spectrum shows the presence of two iso-
of the dioxolane moiety. The acyl group and the other oxy- mers, 9a and 9b, with similar spectroscopic features. At
gen atom are also mutually trans. The coordination sphere 223 K, all the resonances are sharp and the 31P{1H} NMR
is completed with hydride and chloride ligands in trans po- spectrum indicates a 9a/9b ration of 95:5. We believe that
sitions. The Ir–P1 bond [2.281(2) Å] is shorter than the Ir– the fluxional behaviour is due to the interconversion be-
P2 bond [2.330(2) Å], and this may be due to P1 forming tween diastereomers shown in Scheme 3, which is slow at
a five-membered chelate and P2 being in a nonplanar six- low temperature and fast at room temperature. Loosening
membered chelate. The Ir–C1 and the Ir–O2 bond lengths of the Rh–O bond, rotation around the HC–C(aryl) bond
are within the expected ranges,[30] and the C–O distances and re-coordination of the formerly dangling oxygen atom
are in accordance with double or single bonds. When the leads to this exchange.
∧
dioxolane moiety of the P O ligand coordinates, the carbon
atom (C20) of the CHO2 group becomes chiral. The iridium
centre in 8 is also chiral and chelation leads to the possible
formation of two diastereomeric forms. Only one of the
possible diastereomers was detected in the crystal structure,
the one in which the alpha proton of the dioxolane (H20A)
and the hydride ligand (H1) point towards different sides
of the P1C1P2O2 plane.
Scheme 3. Interconversion between diastereomers in 9.
The results obtained show that in solution the oxygen
atom of the hemilabile ligand appears firmly coordinated in
the IrIII derivative 8, whereas in the RhIII complex 9 easy
loosening of the Rh–O bond occurs at room temperature.
We thought it would be interesting to study the reactivity
of 8 and 9 towards CO. Carbon monoxide could cleave the
M–O bond to afford carbonylated MIII derivatives and is
also known to promote the reductive elimination of H2 or
HX from late transition metal hydrides,[33] or of ketones
from alkylacylrhodium complexes.[34]
The reaction of 8 with carbon monoxide does not lead
to reductive elimination of aldehyde. Only the opening of
∧
the P O chelate and coordination of CO occurs to form
[IrClH(PPh2(o-C6H4CO))(P~O)(CO)] (10a) with a dangling
dioxolane and a CO ligand trans to the acyl group as shown
in Scheme 4. A strong absorption band in the IR spectrum
1
indicates the coordination of CO. The H NMR spectrum
shows the expected resonance for a hydride ligand trans to
a chloride ligand (δ = –16.74 ppm), the 31P{1H} NMR
Figure 1. ORTEP view of 8 showing the atomic numbering (20%
probability ellipsoids).
spectrum contains two doublets due to mutually trans phos-
phorus atoms (JP,P = 314 Hz) and the 13C{1H} NMR spec-
The rhodium counterpart of 8, [RhClH(PPh2(o-
trum shows resonances for coordinated acyl and carbonyl
groups. In CDCl3 solution, 10a slowly isomerizes to give
10b, which is responsible for the hydride resonance at δ =
–7.21 ppm. This chemical shift is consistent with a hydride
∧
C6H4CO))(P O)] (9), can be obtained by the reaction of
[RhCl(Cod)]2 with o-(diphenylphosphane)benzaldehyde in
the presence of 1. The NMR spectra of 9 in CDCl3 shows
broad resonances at room temperature, which suggests dy-
namic behaviour in solution. This is in accordance with the
lower oxophilicity of rhodium(III) compared to iridi-
um(III).[31] A related rhodium complex containing a phos-
phane–aldehyde chelate is also highly fluxional.[32] The
31P{1H} NMR spectrum of 9 contains two broad doublets
of doublets owing to the presence of the rhodium atom,
1
and the H NMR spectrum shows four broad resonances
owing to the dioxolane moiety and an extremely broad res-
onance at δ = –14 ppm owing to the hydride. On lowering
the temperature, the resonances due to the dioxolane moi-
ety become sharper. At 273 K, the hydride resonance de- Scheme 4.
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ligand trans to a carbon atom. We propose that in 10b the be seen, and the 31P{1H} NMR spectrum displays a singlet
hydride ligand is trans to the CO ligand in analogy to the at δ = 14.1 ppm. Accordingly, a pentacoordinate structure
related [IrClH(CH=CH2)(PiPr3)2(CO)].[35] Unfortunately, could be envisaged with two monodentate phosphane li-
pure 10b could not be isolated owing to slow decomposition gands mutually trans and two hydride ligands and a chlor-
of the sample, concomitant with the isomerization reaction. ide ligand in the equatorial plane of a trigonal bipyramid,
At variance with 8, the reaction of 9 with CO leads to which resembles some analogues with phosphanes[37] or
the ligand-assisted reductive elimination of aldehyde con- pincer ligands.[38] However, rhodium or iridium dihydrides
comitant with cleavage of the Rh–O bond and the scram- containing phosphane–ether ligands of the [MCl(H)2-
∧
bling of phosphanes to afford a mixture of the new mixed (P~O)(P O)] type have been reported to show fluxional be-
carbonyl trans-[RhCl(CO)(κ1-PPh2(o-C6H4CHO))(P~O)] haviour with very low energy barriers.[31,39] The 31P{1H}
(11), trans-[RhCl(CO)(P~O)2] (6) and the known complex and 1H NMR resonances of 12 broaden when the tempera-
trans-[RhCl(CO)(κ1-PPh2(o-C6H4CHO))2].[32] Complex 11 ture is lowered, which suggests that it is an octahedral spe-
was identified by NMR spectroscopy.[36] Its 31P{1H} NMR cies of the [IrCl(H)2(P~O)(P O)] type that exchanges phos-
∧
spectrum shows an AB system owing to mutually trans phane and also hydride ligands. Coalescence occurs at
1
phosphanes, and according to the H NMR spectrum nei- 203 K and, therefore, thermodynamic parameters could not
ther the aldehyde nor the dioxolane group are coordinated. be obtained. The most accepted mechanism for this behav-
Bubbling of nitrogen through solutions of this mixture iour is the so called “migratory mechanism”,[31,40] which
leads to the slow transformation of 11 into 9, which indi- involves O-dissociation of the coordinated ether–phosphane
cates that the aldehyde reductive elimination concomitant ligand to afford a trigonal bipyramidal intermediate and
with dioxolane de-coordination can be reversed.
O-coordination of the other ether–phosphane ligand. This
Finally, we have studied the reaction of [IrCl(Cod)(P~O)] mechanism allows the chlorine ligand to move from its
(2) prepared in situ with hydrogen, which also leads to an starting position and exchange of hydride ligands. Crystals
oxidative addition reaction and promotes O coordination. of 12 were obtained but were unfortunately of poor quality
As shown in Scheme 5, the presence of one equivalent of 1 and a full X-ray diffraction characterization of the complex
∧
is required to give the dihydride [IrCl(H)2(P O)(P~O)] (12), was precluded. Preliminary studies indicate the presence of
which behaves as a nonelectrolyte in acetone solution.
a phosphane ligand coordinated in a bidentate fashion and
a second one coordinated in a monodentate mode (see Sup-
porting Information). The iridium atom exhibits a distorted
octahedral IrP2OClH2 geometry with the two phosphorus
and two hydride atoms in trans and cis positions, respec-
tively.
Owing to the lability of the Ir–O bonds, the reaction of
12 with monodentate ligands such as CO, pyridine or n-
propylamine or with a bidentate ligand such as ethylenedi-
amine, easily affords neutral [IrCl(H)2(P~O)2L] (13–15) or
cationic [Ir(H)2(P~O)2(en)]BPh4 (16) dihydrides respectively
(Scheme 5). In 13–16, the phosphane ligands are coordi-
nated in a trans P-monodentate fashion, as shown by the
appearance of singlets in the 31P{1H} NMR spectra in the
δ = 23.6–17.4 ppm range for 14–16 or at higher field
(5.2 ppm) for 13 and by the resonances of the ethylene pro-
1
tons of the dioxolane fragment. In their H NMR spectra,
13–15 show doublets of triplets due to two nonequivalent
hydride ligands cis to two equivalent phosphorus atoms,
whereas 16 shows a triplet due to two equivalent hydride
ligands. The chemical shifts for the hydride ligands in 13,
trans to CO or chloride ligands, are –7.39 and –17.94 ppm,
respectively. In 14–16, with hydride ligands trans to a nitro-
gen atom or chloride ligand, the resonances appear between
–21.07 and –23.60 ppm. All these complexes are static on
the NMR time scale at room temperature.
The X-ray structures of 15 and 16 have been determined.
Selected bond lengths and angles are listed in Table 1. Fig-
ures 2 and 3 show molecular drawings for 15 and the cation
in 16 together with the atomic labelling scheme used. The
Scheme 5. (i) L = CO, 13; nPrNH2, 14; py, 15; (ii) L = en, 16; (iii)
NaBPh4.
At room temperature, the NMR spectra in CDCl3 show structures confirm the spectroscopic data and show that in
sharp signals. In the 1H NMR spectrum, only one triplet at both complexes the iridium atom has a distorted octahedral
–26.64 ppm (JP,H = 16.8 Hz) owing to hydride ligands can geometry. The coordination environment is formed by two
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phosphane ligands in trans positions, two hydride ligands
and, finally, one pyridine and one chloride ligand in trans
positions to the hydride ligands H2 and H1, respectively, in
15, or two nitrogen atoms pertaining to one ethylenedi-
amine chelate ligand in 16. The two phosphane ligands are
bent [P1–Ir–P2 163.82(9)° for 15 and 164.39(7)° for 16] to-
ward the smaller hydride ligands. The Ir–P distances com-
pare well with those reported for dihydrides with trans
phosphane ligands.[41] Within each complex, the Ir–P dis-
tances are equal and slightly longer for 15 [2.300(3) Å],
which contains monodentate ligands, than for 16
[2.282(2) Å], which contains ethylenediamine. The Ir–N dis-
tances are in the expected range. In 16, the bite angle of the
ethylenediamine ligand [N1–Ir–N2 77.2(2)°] is similar to
that in [Ir(en)(ppy)2]ClO4.[42] The coordinated ethylenedi-
amine ligand (N1 and N2) is involved in intramolecular hy-
drogen bond interactions with the oxygen atoms O1 and
O3 of two different dioxolane moieties in trans position in-
side the same mononuclear unit. These hydrogen bonds
have values of 3.021(9) and 2.871(9) Å for N1···O1 and
N2···O3, respectively.
Figure 3. ORTEP view of 16 showing the atomic numbering (20%
probability ellipsoids).
ried out (Figure 4). Upon increasing the temperature to
323 K, the hydride resonance becomes sharper and the
phosphorus resonance appears as a singlet owing to faster
interconversion. On lowering the temperature, the reso-
nances broaden further and coalescence occurs at 273 K. At
223 K the hydride region resolves into two sets of signals, a
triplet at δ = –29.43 ppm (JP,H = 15.3 Hz) and a set of two
multiplets at δ = –29.82 and –30.01 ppm (JP,H in the 18–
13 Hz range), respectively. Two sets of resonances due to
coordinated dioxolane groups are also observed. The
31P{1H} NMR spectrum shows a singlet at δ = 10.4 ppm
and an AB system with resonances at δ = 15.6 and
10.1 ppm (JP,P = 320 Hz). This VT NMR study indicates
the presence of two isomers in solution, 17a and 17b. Ac-
cording to the spectroscopic data, both isomers contain hy-
dride ligands trans to oxygen atoms that are equivalent in
17a and nonequivalent in 17b, and therefore two chelating
∧
P O ligands.
1
From line-shape analysis of the variable-temperature H
Figure 2. ORTEP view of 15 showing the atomic numbering (20%
probability ellipsoids).
NMR spectra in the hydride region (Figure 5), the acti-
vation parameters ΔH‡ = 54.7Ϯ0.7 kJmol–1 and ΔS‡
=
4.7Ϯ0.2 JK–1 mol–1 have been determined. The entropy of
Halide abstraction from 12 affords a cationic species that activation indicates an intramolecular rearrangement. The
could be isolated as the tetraphenylborate compound [Ir(H)2- coordination of two dioxolane moieties affords a molecule
∧
(P O)2]BPh4 (17), which behaves as a uni-univalent electro- with three chiral centres, two coordinated CHO2 groups,
lyte in acetone solution. As shown in Scheme 5, in 17 both rendered chiral upon coordination, and the iridium atom.
molecules of 1 coordinate through phosphorus and oxygen Up to four diastereomers could potentially be observed.
atoms. At room temperature, the 1H NMR spectrum in The fluxional behaviour agrees with an interconversion be-
CDCl3 shows a broad hydride resonance at δ = –29.5 ppm, tween only two diastereomers, 17a, which has the same con-
consistent with hydride ligands trans to oxygen atoms, and figuration for the two dioxolane groups, and 17b, which has
very broad signals in the 4.0–3.0 ppm range for the ethylene different configurations for the dioxolane groups. The ex-
protons of the dioxolane moiety. The 31P{1H} NMR spec- change, slow at low temperature and fast at room tempera-
trum also shows a broad signal at δ = 12.7 ppm, which sug- ture, would comprise loosening of the Rh–O bond, rotation
gests that this complex exhibits fluxionality. Variable tem- around the HC–C(aryl) bond and oxygen re-coordination,
perature (VT) 1H and 31P{1H} NMR experiments were car- as indicated for 9.
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1
Figure 4. Variable-temperature H NMR spectra in the hydride region (left) and 31P{1H} NMR spectra (right) of 17 in CDCl3 from 223
to 323 K.
1
Figure 5. Variable-temperature H NMR spectra of 17 in CDCl3, in the hydride region, from 223 to 323 K: (left) calculated and (right)
experimental.
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(ohm–1 cmmol–1): 136 (acetone). 1H NMR (CDCl3, 233 K): δ =
5.69 [s, 2 H, =CH (Nbd)], 5.44 (s, 1 H, HCO2), 4.36 (m, 2 H,
HCHO), 4.25 (m, 2 H, HCHO), 4.07 [s, 2 H, CH (Nbd)], 3.35 [s,
Conclusions
The ligand [2-(1,3-dioxolane-2-yl)phenyl]diphenylphos-
phane coordinates to IrI or RhI preferably as a κ1-P ligand. 2 H, =CH (Nbd)], 1.44 [s, 2 H, CH2 (Nbd)] ppm. 13C{1H} NMR
(CDCl3, 303 K): δ = 103.7 (d, JP,C = 11 Hz, CHO2), 68.6 (CH2O),
64.2 [CH2 (Nbd)], 52.4 [CH (Nbd)] ppm. 31P{1H} NMR (CDCl3):
δ = 24.7 (d, JRh,P = 167 Hz] ppm. C28H27ClO6PRh·0.5(CH2Cl2)
(628.85): calcd. C 50.99, H 4.20; found C 51.10, H 3.95.
In diolefinic complexes, the barriers to exchange of olefinic
protons are lower for norbornadiene derivatives. κ2-P,O co-
ordination is easier with the harder IrIII or RhIII centres and
is more favoured for IrIII than for RhIII. N-Donor ligands
promote the κ1-P coordination mode. κ2-P,O coordination
of 1 in octahedral complexes results in the selective forma-
tion of half of the possible diastereomers. Barriers to in-
terconversion between the diastereomers are low.
trans-[MCl(CO)(P~O)2] (M = Ir, 5; M = Rh, 6): Carbon monoxide
was bubbled through dichloromethane solutions of
2 or 3
(0.053 mmol) at room temperature. After 15 min, addition of a fur-
ther equivalent of 1 (0.053 mmol) led to the immediate precipi-
tation of yellow solids that were decanted, washed with hexane and
dried under vacuum. Data for 5: Yield 65%. IR (KBr): ν = 1952
˜
1
[s, ν(CϵO)] cm–1. H NMR (CDCl3): δ = 6.60 (d, JP,H = 1.9 Hz, 1
Experimental Section
H, HCO2), 4.05 (m, 2 H, HCHO), 3.86 (m, 2 H, HCHO) ppm.
31P{1H}
NMR
(CDCl3):
δ
=
18.9
(s)
ppm.
General Procedures: All reagents were purchased from commercial
sources and used without further purification. The preparation of
the metal complexes was carried out at room temperature under
nitrogen by using standard Schlenk techniques. [IrCl(Cod)]2,
[RhCl(Nbd)]2 and [RhCl(Cod)]2 were prepared according to litera-
ture methods,[43] and so were [2-(1,3-dioxolane-2-yl)phenyl]di-
phenylphosphane (1) and o-(diphenylphosphane)benzaldehyde.[44]
Microanalysis was carried out with a Leco CHNS-932 microana-
lyzer. Conductivities were measured in acetone solution with a
Metrohm 712 conductimeter. IR spectra were recorded with a Nic-
olet FTIR 510 spectrophotometer in the range 4000–400 cm–1
using KBr pellets. NMR spectra were recorded with Bruker Avance
DPX 300 or Bruker Avance 500 spectrometers, 1H, 13C{1H} (TMS
internal standard) and 31P{1H} (H3PO4 external standard) NMR
spectra were measured from CDCl3 or CD2Cl2 solutions.
C43H38ClIrO5P2·0.5(CH2Cl2): calcd. C 54.04, H 4.07; found C
54.10, H 4.53. Data for 6: Yield 43%. IR (KBr): ν = 1963 [s,
˜
1
ν(CϵO)] cm–1. H NMR (CDCl3): δ = 6.97 (m, 1 H, HCO2), 4.03
(m, 2 H, HCHO), 3.74 (m, 2 H, HCHO) ppm. 31P{1H} NMR
(CDCl3):
δ
=
26.4
(d,
JRh,P
=
126 Hz)
ppm.
C43H38ClO5P2Rh·0.5(CH2Cl2): calcd. C 59.54, H 4.48; found C
59.85, H 4.88.
trans-[Rh(CO)2(P~O)2]ClO4 (7): To a dichloromethane solution of
4 (30 mg, 0.045 mmol) was added a further equivalent of 1 (15 mg,
0.045 mmol). Carbon monoxide was then bubbled trough this solu-
tion at room temperature. The addition of diethyl ether afforded a
yellow solid that was collected by filtration, washed with diethyl
ether and dried under vacuum, yield 65%. IR (KBr): ν = 1993
˜
1
[s, ν(CϵO)] cm–1. ΛM (ohm–1 cm2 mol–1): 127 (acetone). H NMR
(CDCl3): δ = 6.43 (s, 1 H, HCO2), 3.77 (m, 2 H, HCHO), 3.30 (m,
2 H, HCHO) ppm. 13C{1H} NMR (CDCl3): δ = 187.2 (d, JRh,C
= 74 Hz, CO), 103.0 (CHO2), 66.4 (CH2O) ppm. 31P{1H} NMR
Warning! Perchlorate salts and perchlorate transition metal com-
plexes may be explosive. Preparations at a larger scale than that
reported herein should be avoided.
(CDCl3):
δ
=
24.3
(d,
JRh,P
=
121 Hz)
ppm.
[MCl(L2)(P~O)] (M = Ir, L2 = Cod, 2; M = Rh, L2 = Nbd, 3): To
a solution of [MCl(L2)]2 (0.045 mmol) in dichloromethane, 1 was
added (0.090 mmol). The resulting orange solution was stirred for
1 h, after which hexane was added to afford orange (2) or yellow
(3) solids that were collected by filtration, washed with hexane and
C44H38ClO10P2Rh·0.5(CH2Cl2): calcd. C 55.13, H 4.06; found C
55.54, H 4.27.
∧
[IrClH(PPh2(o-C6H4CO))(P O)] (8): To a solution of [IrCl(Cod)]2
(30 mg, 0.045 mmol) in dichloromethane, 1 (30 mg, 0.089 mmol)
was added. The resulting orange solution was stirred for 1 h, after
which o-(diphenylphosphane)benzaldehyde (26 mg, 0.089 mmol)
was added. After stirring of the mixture for a further 2 h, the vol-
ume was reduced under vacuum and hexane was added. The re-
sulting orange solid formed was decanted, washed with hexane and
1
dried under vacuum. Data for 2: Yield 30%. H NMR (CDCl3): δ
= 6.91 (d, JP,H = 2.6 Hz, 1 H, HCO2), 5.20 [s, 2 H, =CH (Cod)],
4.19 (m, 2 H, HCHO), 3.90 (m, 2 H, HCHO), 2.94 [s, 2 H, =CH
(Cod)], 2.21 [s, 4 H, (Cod)], 1.88 [s, 2 H, CH2 (Cod)], 1.68 [s, 2 H,
CH2 (Cod)] ppm. 13C{1H} NMR (CDCl3): δ = 102.2 (d, JP,C
=
dried under vacuum, yield 50%. IR (KBr): ν = 2159 [s, ν(Ir–H)],
˜
12 Hz, CHO2), 92.5 [=CH (Cod)], 65.5 (CH2O), 54.1 [=CH (Cod)],
33.5 [CH2 (Cod)], 29.5 [CH2 (Cod)] ppm. 31P{1H} NMR (CDCl3):
δ = 18.1 (s) ppm. C29H31ClIrO2P (670.21): calcd. C 51.97, H 4.66;
1609 [s, ν(C=O)] cm–1. 1H NMR (CDCl3): δ = 6.19 (s, 1 H, HCO2),
4.29, 4.05, 3.85 and 3.67 (m, 1 H, each, HCHO), –18.03 (dd, JP,H
= 14.8 and 16.5 Hz, 1 H, HIr) ppm. 13C{1H} NMR (CDCl3): δ =
193.3 (C=O), 103.7 (d, JP,C = 10 Hz, CHO2), 66.7 and 69.7 (CH2O)
ppm. 31P{1H} NMR (CDCl3): δ = 30.6 (d, JP,P = 360 Hz, PCO),
1
found C 51.85, H 5.14. Data for 3: Yield 70%. H NMR (CDCl3,
233 K): δ = 6.74 (s, 1 H, HCO2), 5.29 [s, 2 H, =CH (Nbd)], 4.21
(m, 2 H, HCHO), 3.97 (m, 2 H, HCHO), 3.81 [s, 2 H, CH (Nbd)],
3.24 [s, 2 H, =CH (Nbd)], 1.41 [s, 2 H, CH2 (Nbd)] ppm. 13C{1H}
NMR (CDCl3, 303 K): δ = 101.6 (d, JP,C = 13 Hz, CHO2), 65.6
(CH2O), 63.7 [CH2 (Nbd)], 50.5 [CH (Nbd)] ppm. 31P{1H} NMR
(CDCl3): δ = 25.6 (d, JRh,P = 168 Hz) ppm. C28H27ClO2PRh
(564.85): calcd. C 59.54, H 4.82; found C 59.57, H 4.70.
∧
∧
15.0 (d, P O) ppm. C40H34ClIrO3P2·0.5(CH2Cl2): calcd. C 54.35,
H 3.94; found C 54.35, H 3.88.
∧
RhClH(PPh2(o-C6H4CO))(P O)] (9): To a solution of [RhCl-
(Cod)]2 (30 mg, 0.061 mmol) in benzene, 1 (41 mg, 0.122 mmol)
was added. The resulting yellow solution was stirred for 15 min.
Upon addition of o-(diphenylphosphane)benzaldehyde (36 mg,
[Rh(Nbd)(P O)]ClO4 (4): To
a dichloromethane solution of
[RhCl(Nbd)]2 (50 mg, 0.108 mmol) was added (72 mg, 0.217 mmol) 0.122 mmol), a yellow precipitate was formed, which was collected
1. The resulting orange solution was stirred for 1 h, after which
AgClO4 (45 mg, 0.217 mmol) was added. The mixture was stirred
for 30 min, and the silver salts were removed by filtration. Hexane
was added to afford a yellow solid that was collected by filtration,
by filtration, washed with benzene and dried under vacuum, yield
1
81%. IR (KBr): ν = 2029 [s, ν(Rh–H)], 1638 [s, ν(C=O)] cm–1. H
˜
NMR (CDCl3, 223 K): δ = 5.98 (s, 1 H, HCO2), 4.22, 4.10, 3.81
and 3.61 (m, each 1 H, HCHO), –14.26 (ddd, JRh,H = 26.3, JP,H
=
washed with hexane and dried under vacuum, yield 75%. ΛM 12.5 and 6.5 Hz, 1 H, HRh) ppm. 13C{1H} NMR (CDCl3, 303 K):
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1
δ = 215.2 (C=O), 103.0 (d, JP,C = 11 Hz, CHO2), 68.4 and 66.0 (KBr): ν = 2206 [s, ν(Ir–H)] cm–1. H NMR (CDCl ): δ = 6.12 (s,
˜
3
(CH2O) ppm. 31P{1H} NMR (CDCl3, 223 K): 9a: δ = 55.0 (dd, 2 H, HCO2), 3.87 (m, 4 H, HCHO), 3.64 (m, 2 H, HCHO), 3.44
∧
JP,P = 364, JRh,P = 138 Hz, PCO), 28.9 (dd, JRh,P = 132 Hz, P O]. (m, 2 H, HCHO), –21.44 (dt, JP,H = 17.7, JH,H = 6.8 Hz, 1 H, HIr),
9b: δ = 58.9 (dd, JP,P = 355, JRh,P = 139 Hz, PCO), 32.6 (dd, JRh,P –22.82 (dt, JP,H = 17.2, JH,H = 6.9 Hz, 1 H, HIr) ppm. 31P{1H}
∧
= 126 Hz, P O) ppm. C40H34ClO3P2Rh·0.5(C6H6): calcd. C 64.39, NMR (CDCl3): δ = 18.2 (s) ppm. C47H45ClIrNO4P2·CH2Cl2: calcd.
H 4.65; found C 64.67, H 4.32.
C 54.27, H 4.46, N 1.32; found C 54.52, H 4.46, N 1.36.
∧
[IrClH(PPh2(o-C6H4CO))(P O)(CO)] (10): Carbon monoxide was
bubbled through
[Ir(H)2(P~O)2(en)]BPh4 (16): To a solution of [IrCl(Cod)]2 (15 mg,
0.024 mmol) in dichloromethane, 1 (30 mg, 0.089 mmol) was
added. The resulting orange solution was stirred for 1 h, after
which hydrogen was bubbled through the solution for 150 min. On
addition of ethylenediamine (4.5 μL, 0.067 mmol), the solution be-
came colourless. The solution was stirred for a further hour, and a
solution of NaBPh4 (15 mg, 0.045 mmol) in methanol was added.
a dichloromethane solution of 8 (40 mg,
0.05 mmol) at room temperature. After 2 h of bubbling, hexane was
added and the resulting solid was decanted and dried under vac-
uum, yield 57%. IR (KBr): ν = 2029 [s, ν(CϵO)], 1624 [s, ν(C=O)]
˜
cm–1. C41H34ClIrO4P2·0.5(CH2Cl2): calcd. C 54.02, H 3.80; found
C 53.30, H 4.42. Data for 10a: 1H NMR (CDCl3): δ = 6.22 (s, 1
H, HCO2), 4.2–3.5 (m, 4 H, HCHO), –16.74 (dd, JP,H = 11.9 and Evaporation of dichloromethane gave an off-white precipitate that
13.7 Hz, 1 H, HIr) ppm. 13C{1H} NMR (CDCl3): δ = 226.9 (dd,
JP,C = 2 and 6 Hz, C=O), 174.3 (t, JP,C = 6 Hz, CϵO), 100.7 (d,
was decanted, washed with methanol and dried under vacuum,
yield 77%. IR (KBr): ν = 3310 (m), 3274 [m, ν(NH )], 2158 [s, ν(Ir–
˜
2
JP,C = 9 Hz, CHO2), 65.3 and 65.4 (CH2O) ppm. 31P{1H} NMR H)] cm–1. ΛM (ohm–1 cm2 mol–1): 77 (acetone). H NMR (CDCl3):
1
(CDCl3): δ = 39.7 (d, JP,P = 314 Hz, PCO), –3.9 (d, P~O) ppm.
δ = 6.20 (s, 1 H, HCO2), 4.25 (m, 2 H, HCHO), 3.86 (m, 2 H,
HCHO), 2.72 (s, 2 H, NH2), 0.87 (m. 2 H, CH2), –21.07 (t, JP,H
1
Data for 10b: H NMR (CDCl3): δ = 6.35 (s, 1 H, HCO2), 4.1–3.6
=
(m, 4 H, HCHO), –7.21 (t, JP,H = 14.8 Hz, 1 H, HIr) ppm. 13C{1H} 17.7 Hz, 1 H, HIr) ppm. 13C{1H} NMR (CDCl3): δ = 100.1
NMR (CDCl3): δ = 202.0 (d, JP,C = 4 Hz, C=O), 174.7 (t, JP,C
=
(CHO2), 65.8 (CH2O), 44.2 (CH2) ppm. 31P{1H} NMR (CDCl3):
6 Hz, CϵO), 100.5 (d, JP,C = 9 Hz, CHO2), 65.1 and 65.5 (CH2O) δ = 17.4 (s) ppm. C68H68BIrN2O4P2·0.25(CH2Cl2): calcd. C 64.88,
ppm. 31P{1H} NMR (CDCl3): δ = 28.6 (d, JP,P = 311 Hz, PCO), H 5.46, N 2.22; found C 64.68, H 5.29, N 2.19.
7.7 (d, P~O) ppm.
∧
[Ir(H)2(P O)2]BPh4 (17): To a solution of [IrCl(Cod)]2 (15 mg,
∧
[IrCl(H)2(P~O)(P O)] (12): To a solution of [IrCl(Cod)]2 (30 mg, 0.024 mmol) in dichloromethane, 1 (30 mg, 0.089 mmol) was
0.045 mmol) in dichloromethane, 1 (60 mg, 0.179 mmol) was
added. The resulting orange solution was stirred for 1 h, after
which hydrogen was bubbled through the solution for 150 min. The
volume of the solution was reduced under vacuum, and hexane was
added to give an orange solid that was decanted, washed with hex-
added. The resulting orange solution was stirred for 1 h, after
which hydrogen was bubbled through the solution for 150 min, and
a solution of NaBPh4 (15 mg, 0.045 mmol) in methanol was added.
Evaporation of dichloromethane gave an off-white precipitate that
was decanted, washed with methanol and dried under vacuum,
ane and dried under vacuum, yield 71%. IR (KBr): ν = 2152 [s,
yield 65%. IR (KBr): ν =
2277 [s, ν(Ir–H)] cm–1. ΛM
˜
˜
ν(Ir–H)] cm–1. 1H NMR (CDCl3): δ = 6.28 (s, 1 H, HCO2), 3.69 (ohm–1 cm2 mol–1): 86 (acetone). H NMR (CDCl3, 223 K): 17a: δ
(m, 2 H, HCHO), 3.53 (m, 2 H, HCHO), –26.64 (t, JP,H = 16.8 Hz, = 6.08 (s, 2 H, HCO2), 3.57, 3.51, 2.95 and 2.55 (m, each 2 H,
1 H, HIr) ppm. 13C{1H} NMR (CDCl3): δ = 101.8 (s, CHO2), 65.5 HCHO), –29.43 (t, JP,H = 15.3 Hz, 1 H, HIr). 17b: 6.04 (s, 1 H,
1
(CH2O) ppm. 31P{1H} NMR (CDCl3):
δ
=
14.1 (s) ppm.
HCO2), 5.64 (s, 1 H, HCO2), 3.40, 2.28, 2.72 and 2.40 (m, each 2
H, HCHO), –29.82 ppm (ddd, JP,H = 17.7 and 13.4; JH,H = 10.0 Hz,
HIr), –30.01 (dt, JP,H = 16.8 Hz, HIr) ppm. 31P{1H} NMR (CDCl3,
223 K): 17a: δ = 10.4 (s). 17b: 15.6 (d, JP,P = 320 Hz], 10.1 (d) ppm.
C66H60BIrO4P2·(CH3OH): calcd. C 66.30, H 5.31; found C 66.10,
H 5.40.
C42H40ClIrO4P2 (898.40): calcd. C 56.15, H 4.49; found C 56.41,
H 4.11.
[IrCl(H)2(P~O)2L] (L = CO, 13; nPrNH2, 14; py, 15): To a solution
of [IrCl(Cod)]2 (15 mg, 0.024 mmol) in dichloromethane, 1 (30 mg,
0.089 mmol) was added. The resulting orange solution was stirred
for 1 h, after which hydrogen was bubbled through the solution for
150 min. CO was bubbled through the solution for a further
120 min (13), or the corresponding ligand (0.112 mmol) was added
(14–15). The volume of the solution was reduced under vacuum,
and hexane was added to give yellow solids that were decanted,
X-ray Structure Determination of 8, 12, 15 and 16: Crystals suitable
for X-ray diffraction were obtained by slow vapour diffusion of
diethyl ether into solutions of 8, 12, 15 and 16. Data were collected
with a Bruker AXS APEX CCD area detector with graphite mono-
chromated Mo-Kα radiation (λ = 0.71073 Å) by applying the ω-
scan method. The data were processed with APEX2[45] and cor-
washed with hexane and dried under vacuum. Data for 13: Yield
1
36%. IR (KBr): ν = 2106 [s, ν(Ir–H)], 1985 [s, ν(CϵO)] cm–1. H rected for absorption by using SADABS.[46] The structures were
˜
NMR (CDCl3): δ = 6.40 (s, 2 H, HCO2), 4.15 (m, 4 H, HCHO),
solved by direct methods by using SIR97,[47] and the positions of
3.82 (m, 4 H, HCHO), –7.39 (dt, JP,H = 18.3, JH,H = 4.5 Hz, 1 H, all non-hydrogen atoms were revealed. These atoms were refined
HIr), –17.94 (dt, JP,H = 15.1, JH,H = 4.6 Hz, 1 H, HIr) ppm.
31P{1H} NMR (CDCl3): δ = 5.2 (s) ppm. C43H40ClIrO5P2 (926.41):
calcd. C 55.75, H 4.35; found C 55.51, H 4.46. Data for 14: Yield
on F2 by a full-matrix least-squares procedure using anisotropic
displacement parameters.[48] All hydrogen atoms were located in
difference Fourier maps and included as fixed contributions riding
on attached atoms with isotropic thermal displacement parameters
61%. IR (KBr): ν = 3310 (m), 3269 [m, ν(NH )], 2200, 2127 [s,
˜
2
ν(Ir–H)] cm–1. 1H NMR (CDCl3): δ = 6.63 (s, 2 H, HCO2), 4.1– 1.2 times those of the respective atom. Final R(F), wR(F2) and
3.9 (m, 6 H, HCHO), 3.55 (m, 2 H, HCHO), 2.87 (br., 2 H, NH2), goodness of fit agreement factors, details on the data collection
1.27 (m, 2 H, CH2N), 0.41 (m, 2 H, CH2), 0.17 (t, JH,H = 7.3 Hz, and analysis for 8, 15 and 16 can be found in Table 2. Attempts to
3 H, CH3), –21.16 (dt, JP,H = 19.2, JH,H = 5.9 Hz, 1 H, HIr), –23.60
(dt, JP,H = 17.2, JH,H = 6.1 Hz, 1 H, HIr) ppm. 13C{1H} NMR new set of F2 (hkl) values with the contribution from solvent mole-
(CDCl3): δ = 99.9 (CHO2), 65.6 and 64.5 (CH2O), 52.8 (CH2N), cules withdrawn was obtained by the SQUEEZE procedure im-
26.5 (CH2), 10.9 (CH3) ppm. 31P{1H} NMR (CDCl3): δ = 23.6 (s) plemented in PLATON-94.[49] Refinement reduced R1 to 0.0589. It
identify the solvent molecules failed in compound 16. Instead, a
ppm. C45H49ClIrNO4P2·0.25(CH2Cl2): calcd. C 55.53, H 5.10, N
1.43; found C 55.76, H 5.23, N 1.48. Data for 15: Yield 68%. IR
should be noted that all crystals undergo a very fast degradation
when they are removed from the mother liquor, which has a high
Eur. J. Inorg. Chem. 2013, 1225–1235
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FULL PAPER
Table 2. Crystal data and structure refinement for compounds 8, 15 and 16.
8
15
16[a]
Empirical formula
Formula weight
Temperature [K]
Crystal system
Space group
a [Å]
b [Å]
C40H34ClIrO3P2
852.26
296(2)
monoclinic
P21
13.2814(7)
13.8731(8)
9.7304(6)
108.500(1)
1700.2(2)
2
C47H43ClIrNO4P2
977.43
120(2)
monoclinic
P21/c
9.185(5)
17.559(5)
25.337(5)
92.907(5)
4081(3)
C68H68BIrN2O4P2
1242.19
120(2)
monoclinic
C2/c
18.664(5)
28.741(5)
25.420(5)
95.355(5)
13576(5)
c [Å]
β [°]
Volume [Å3]
Z
4
8
D(calcd.) [gcm–3]
Absorption coefficient [mm–1]
Scan technique
F(000)
1.665
4.138
ω and φ
844
1.591
3.461
ω and φ
1960
1.215
2.058
ω and φ
5072
Range for data collection [°]
Index ranges
Reflections collected
Independent reflections
Data/restraints/parameters
R[a] (refl. obsd.) [IϾ2σ(I)]
RwF[b](all data)
1.62 to 27.00
–16, –17, –12 to 13, 17, 12
15274
6844[Rint = 0.0405]
6844/1/424
0.0330
1.41 to 25.00
–10, –13, –30 to 10, 20, 28
21530
7167[Rint = 0.0656]
7185/2/513
0.0468
1.30 to 25.00
–14, –32, –30 to 22, 34, 30
36574
11953[Rint = 0.0992]
11953/2/682
0.0589
0.0640
0.1096
0.1204
2
2 2
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Acknowledgments
Partial financial support by Ministerio de Economía y Competitivi-
dad (CTQ2011-24859), Gobierno Vasco, Universidad del País Va-
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Received: October 2, 2012
Published Online: December 19, 2012
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© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim