Rhodium(I), palladium(II) and platinum(II) coordination chemistry of the short-bite chiral ligands (Sc)-N,N-bis(diphenylphosphanyl)-sec- butylamine, (Ra,Ra)-N,N-bis(binaphthylphosphonito) phenylamine and (Ra,Sc)-N-(diphenylphosphanyl)-N- (binaphthylphosphonito)-sec-butylamine

Article abstract of DOI:10.1002/ejic.200300568

The new short-bite chiral ligands (S_c)-N,N- bis(diphenylphosphanyl)-sec-butylamine [(S_c)-1], (R _a,R_a)-N,N-bis(binaphthylphosphonito)phenylamine [(R _a,R_a)-2] and (R_a,S_c)-N- (diphenylphosphanyl)-N-(binaphthylphosphonito)-sec-butylamine [(R _a,S_c)-3] have been treated with rhodium(I), palladium(II) and platinum(II) substrates. The (S_c)-1 ligand reacts with [Pd(C ₆H₅CN)₂Cl₂], [Pt(COD)Cl₂] and [Rh(COD)-(THF)₂]PF₆ to afford the products [Pd(S _c-1)Cl₂] (4), [Pt(S_c-1)Cl₂] (5) and [Rh(COD)(S_c-1)]PF₆ (6), respectively, in high yields. By bubbling CO to a CH₂Cl₂ solution of 6, we formed the dicarbonyl species [Rh(CO)₂(S_c-1)]PF₆ (7), which is stable only in solution under CO. Compounds 4 and 5 were characterized additionally by X-ray diffraction studies. The ligand (R_a,R _a)-2 reacts with [Pd(C₆H₅CN)₂Cl ₂] and [Pt(COD)I₂] to give [Pd(R_a,R _a-2)Cl₂] (8) and [Pt(R_a,R_a-2)I ₂] (9), respectively; the reaction with [Rh(CO)₂Cl] ₂ or [Rh(COD)(THF)₂]PF₆ affords a mixture of mono- and binuclear compounds, in which the ligand is oxidized to the corresponding phosphonate or is partially hydrolysed. The compounds [Pd(R _a,S_c-3)Cl₂] (10) and [Pt(R_a,S _c-3)I₂] (11) were obtained in the analogous reactions using the asymmetric (R_a,S_c)-3 ligand. This ligand reacted with [Rh(CO)₂Cl]₂ in a 2:1 molar ratio in hexane to give a mixture of products in almost equal amounts. The ³¹P{¹H} NMR spectrum recorded in CDCl₃ allowed us to identify the chelate [Rh(R_a,S_c-3)(CO)Cl] (12); the nature of the accompanying dinuclear species 13 is not clear. The catalytic systems formed by [Rh(acac)(CO)₂] and the ligands (R_a,R_a)-2 and (R_a,S_c)-3, at ligand/metal ratios of 1:1 and 1:2, were unstable under the experimental conditions used (CO/H₂ pressure of 50 atm and temperature of 40 °C) for the hydroformylation of styrene; instead, metallic rhodium was afforded together with unidentified decomposition products. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.

Full text of DOI:10.1002/ejic.200300568

FULL PAPER
Rhodium(
I
), Palladium(II) and Platinum(II) Coordination Chemistry of the
Short-Bite Chiral Ligands (Sc)-N,N-Bis(diphenylphosphanyl)-sec-butylamine,
(Ra,Ra)-N,N-Bis(binaphthylphosphonito)phenylamine and (Ra,Sc)-N-
(Diphenylphosphanyl)-N-(binaphthylphosphonito)-sec-butylamine
[a]
[a]
[b]
[a]
`
Gianpiero Calabro, Dario Drommi, Claudia Graiff, Felice Faraone,* and
Antonio Tiripicchio[b]
Keywords: Chiral ligands / Enantioselectivity / Hydroformylation / Palladium / Platinum / Rhodium
The new short-bite chiral ligands (Sc)-N,N-bis(diphenylphos-
the ligand is oxidized to the corresponding phosphonate or
phanyl)-sec-butylamine [(Sc)-1], (Ra,Ra)-N,N-bis(binaphthyl- is partially hydrolysed. The compounds [Pd(Ra,Sc-3)Cl2] (10)
phosphonito)phenylamine [(Ra,Ra)-2] and (Ra,Sc)-N-(di- and [Pt(Ra,Sc-3)I2] (11) were obtained in the analogous reac-
phenylphosphanyl)-N-(binaphthylphosphonito)-sec-butyl-
amine [(Ra,Sc)-3] have been treated with rhodium( ), palla-
tions using the asymmetric (Ra,Sc)-3 ligand. This ligand re-
acted with [Rh(CO)2Cl]2 in a 2:1 molar ratio in hexane to give
a mixture of products in almost equal amounts. The 31P{1H}
NMR spectrum recorded in CDCl3 allowed us to identify the
chelate [Rh(Ra,Sc-3)(CO)Cl] (12); the nature of the accom-
panying dinuclear species 13 is not clear. The catalytic sys-
tems formed by [Rh(acac)(CO)2] and the ligands (Ra,Ra)-2
and (Ra,Sc)-3, at ligand/metal ratios of 1:1 and 1:2, were un-
I
dium(II) and platinum(II) substrates. The (Sc)-1 ligand reacts
with [Pd(C6H5CN)2Cl2], [Pt(COD)Cl2] and [Rh(COD)-
(THF)2]PF6 to afford the products [Pd(Sc-1)Cl2] (4), [Pt(Sc-
1)Cl2] (5) and [Rh(COD)(Sc-1)]PF6 (6), respectively, in high
yields. By bubbling CO to a CH2Cl2 solution of 6, we formed
the dicarbonyl species [Rh(CO)2(Sc-1)]PF6 (7), which is stable
only in solution under CO. Compounds 4 and 5 were charac- stable under the experimental conditions used (CO/H2 pres-
terized additionally by X-ray diffraction studies. The ligand
(Ra,Ra)-2 reacts with [Pd(C6H5CN)2Cl2] and [Pt(COD)I2] to
give [Pd(Ra,Ra-2)Cl2] (8) and [Pt(Ra,Ra-2)I2] (9), respectively;
sure of 50 atm and temperature of 40 °C) for the hydroformyl-
ation of styrene; instead, metallic rhodium was afforded to-
gether with unidentified decomposition products.
the reaction with [Rh(CO)2Cl]2 or [Rh(COD)(THF)2]PF6 af- ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
fords a mixture of mono- and binuclear compounds, in which
Germany, 2004)
Introduction
nobis(diphenylphosphane) (dpppa), but contain atropisom-
eric C2-symmetric binaphthyl moieties bonded to the phos-
phorus donor atoms rather than the phenyl groups. We have
also reported[3] the application of these ligands in pal-
ladiumϪallyl-catalysed reaction of 1,3-diphenylallyl acetate
with dimethylmalonate. Owing to their favourable struc-
tural features, short-bite ligands have been widely used in
organometallic chemistry.[4] These bidentate ligands have
their donor-atoms separated by one spacer atom; their co-
ordination to a metal centre can produce either chelated
mononuclear or bridged dinuclear complexes. In the
mononuclear complexes, the short-bite ligand forms a
strained four-membered ring with a very narrow bite angle;
in the dinuclear complexes, two metal centres are held in
close proximity by the features of the bridging short-bite
ligand and can cooperate to activate a substrate. This prop-
erty of the dinuclear complexes has been found to operate
during homogeneous catalysis.[5]
The design and synthesis of new chiral ligands remains a
significant research subject for the development of tran-
sition metal-catalysed asymmetric syntheses. Satisfactory
enantioselectivities have been obtained when many families
of ligands, with very different features, have been prepared
and applied in asymmetric catalytic reactions.[1] Among
these ligands, the widest range of applications have been
found for those containing atropisomeric C2-symmetric
moieties.[2]
Recently, we began[3] synthesising chiral short-bite li-
gands that resemble the well-known bis(diphenylphosphan-
yl)methane (dppm), phenylpyrophosphite, and phenylami-
[a]
Dipartimento di Chimica Inorganica, Chimica Analitica e
`
Chimica Fisica, Universita di Messina,
Salita Sperone, 31 Vill. S. Agata, 98166 Messina, Italy
Fax: (internat.) ϩ39-090-393756
E-mail: faraone@chem.unime.it
When using short-bite chiral ligands, both coordination
modes (chelated mononuclear or bridged dinuclear com-
plexes) can, in principle, produce beneficial effects during
[b]
Dipartimento di Chimica Generale ed Inorganica, Chimica
`
Analitica, Chimica Fisica, Universita di Parma,
Parco Area delle Scienze 17A, 43100 Parma, Italy
Eur. J. Inorg. Chem. 2004, 1447Ϫ1453
DOI: 10.1002/ejic.200300568
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`
G. Calabro, D. Drommi, C. Graiff, F. Faraone, A. Tiripicchio
FULL PAPER
catalytic enantioselective processes. In fact, the reduced phosphorochloridite derived from (Ra)-binaphthol in a 1:2
number and rigidity of the conformational isomers formed molar ratio in toluene at 0 °C in the presence of an excess
by a strained four-membered metallacycle can induce a of NEt3. Ligands similar to (Sc)-1 have been reported pre-
minor number of processes having different activation ener- viously,[7] but their coordination chemistry has not been ex-
gies. For the bridged dinuclear complexes, novel modes of plored extensively. The ligands (Sc)-1, (Ra,Ra)-2 and
reactivity can be achieved for the activation of a substrate (Ra,Sc)-3 should behave, in principle, either as chelating,
as a consequence of cooperative interactions between the originating, four-membered metallacycles or as bridging li-
metal centres.
gands giving dimetalllic species. Literature reports indicate
As far as we know, only a few chiral, optically pure, that the presence of an alkyl or aryl group on the nitrogen
short-bite ligands have been reported; of these ligands, only atom favours the formation of a four-membered strained
the diphosphane MiniPHOS has been explored as a catalyst ring when the ligand coordinates to a metal centre.[8]
precursor in asymmetric synthesis and it affords excellent
enantioselectivities in representative carbonϪcarbon bond-
formation reactions.[6]
Prior to studying catalytic systems formed from a metal
substrate and a chiral PϪNϪP short-bite ligand in conven-
tional metal-catalysed asymmetric carbonϪcarbon bond
Reactions with Rhodium(
Substrates
i), Palladium(ii) and Platinum(ii)
The reaction of [Pd(C6H5CN)2Cl2] with (Sc)-1 in a 1:1
formation, we explored the coordinating properties of the molar ratio in CH2Cl2 afforded [Pd(Sc-1)Cl2] (4) in high
synthesized (Sc)-N,N-bis(diphenylphosphanyl)-sec-butylam- yield as a yellow orange solid that is stable to air and moist-
ine, (Ra,Ra)-N,N-bis(binaphthylphosphonito)phenylamine ure for a long period of time. This complex was charac-
1
and (Ra,Sc)-N-(diphenylphosphanyl)-N-(binaphthylphos- terized by elemental analysis and H and 31P{1H} NMR
phonito)-sec-butylamine.
spectra; an X-ray diffractometric study established its nat-
ure as a mononuclear complex, with (Sc)-1 chelating to the
palladium() centre. The 31P{1H} NMR spectrum of 4 in
1
CDCl3 displays a singlet at δ ϭ 29.6 ppm; in the H NMR
spectrum, the chiral moiety provides the signals at δ ϭ 0.43
Results and Discussion
3
3
(t, JH,H ϭ 7 Hz, CH3), 0.79 (d, JH,H ϭ 7 Hz, CH3), 1.29
and 0.95 (m, diastereotopic CH2) and 3.28 (m, CH) ppm.
Similarly to [Pd(C6H5CN)2Cl2], [Pt(COD)Cl2] reacted
with an equimolar amount of (Sc)-1 in toluene to give
[Pt(Sc-1)Cl2] (5) as a white microcrystalline solid that is
stable to air for a long time in the solid state and in solu-
tion. An X-ray diffractometric study indicated that 5 is iso-
structural with 4. In its 31P{1H} NMR spectrum in CDCl3,
the phosphorus atom resonance of 5 appears as a singlet at
δ ϭ 15.5 ppm having 195Pt satellites (1JPt,P 3285 Hz); in the
1H NMR spectrum, the pattern of the chiral moiety
CHMeEt is the same as that obtained for 4, except that it
shows additional peaks due to 195Pt satellites.
Ligands
Scheme 1 presents the new short-bite chiral PϪNϪP li-
gands used in the reactions with rhodium(), palladium()
and platinum() substrates.
The addition of a THF solution of (Sc)-1 to an equimolar
solution of [Rh(COD)(THF)2]PF6, obtained in situ from
[Rh(COD)Cl]2 and NH4PF6, in THF, readily gave
[Rh(COD)(Sc-1)]PF6 (6) as an orange solid. Analytical and
conductivity data, together with CO reactivity and NMR
spectroscopic data, support this formulation. In fact, the
31P{1H} NMR spectrum in CDCl3 displays a doublet at
δ ϭ 50.1 ppm (1JRhP ϭ 134 Hz). Upon bubbling CO into a
CH2Cl2 solution of 6, displacement of COD occurs readily
with formation of the dicarbonyl species [Rh(CO)2(Sc-
1)]PF6 (7) [ν˜CO (CH2Cl2) ϭ 2059 and 2098 cmϪ1] together
with small amount of another carbonyl compound, which
is very likely to be the five-coordinate species [Rh(CO)3(Sc-
Scheme 1
These ligands were designed so that we could verify the 1)]PF6; compound 7 requires a CO atmosphere and can be
effects that the position, nature, absolute configuration and handled only in solution.
number of stereogenic centres have on the enantioselective
The ligand (Ra,Ra)-2 reacts in solution with
catalysis. The ligands were synthesized[3] by reacting the [Pd(C6H5CN)2Cl2] and [Pt(COD)I2] to give [Pd(Ra,Ra-
corresponding primary amine RNH2 [R ϭ Ph, (Sc)-(ϩ)-sec- 2)Cl2] (8) and [Pt(Ra,Ra-2)I2] (9), respectively, as yellow-or-
C2H5CHCH3] with the chlorodiphenylphosphane or the ange solids (Scheme 2).
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Rhodium(I), Palladium(II) and Platinum(II) Coordination Chemistry
FULL PAPER
Scheme 2
These formulations are based on analytical and NMR
spectroscopic data. The resonances of the phosphorus
atoms appear in the 31P{1H} NMR spectra, recorded in
CDCl3, as singlets at higher fields than the free ligand, at
δ ϭ 82.1 and 94.5 ppm (1JPt,P ϭ 5296 Hz) for 8 and 9,
respectively. Both 8 and 9 are moderately stable to air and
moisture.
The reaction of (Ra,Ra)-2 with [Rh(CO)2Cl]2 or
[Rh(COD)(THF)2]PF6 leads to the formation of a mixture
of compounds in which the ligand is oxidized to the corre-
sponding phosphonate or is partially hydrolysed. We were
not able to obtain fully characterized products from these
mixtures.
Figure 1. 31P{1H} NMR spectrum in CDCl3 at 298 K: filled black
square: compound 13, filled black circle: compound 12
The asymmetric (Ra,Sc)-3 ligand reacts in CH2Cl2 with
[Pd(C6H5CN)2Cl2] in a 1:1 molar ratio to afford [Pd(Ra,Sc-
3)Cl2] (10) together with small trace amounts of 4. The for-
mation of 4 by NϪPPhosphonite bond cleavage of 10 in the
The formulation of compound 12 as a chelated mononu-
presence of trace amounts of H2O[9] is very unlikely; most clear species is supported by the pattern of the phosphorous
probably the formation of 4 is due to the presence of trace atom resonances in the 31P{1H} NMR spectrum and the
amounts of (Sc)-1 as an impurity in the sample of the 1JRhP values. As expected for the proposed structure, com-
(Ra,Sc)-3 ligand we used. Compound 10 is a yellow solid pound 12 exhibits two doublets of doublets in the 31P{1H}
that is moderately stable in the presence of air or moisture; NMR spectrum, recorded in CDCl3, centred at δ ϭ
1
2
it was isolated in low yield after column chromatography. 103.9 ppm (dd, JRhP ϭ 222, JP,P ϭ 98 Hz) and at δ ϭ
1
2
Its formulation is supported by the presence of two dou- 47.7 ppm (dd, JRhP ϭ 122, JP,P ϭ 98 Hz) for the phos-
blets in the 31P{1H} NMR spectrum recorded in CDCl3 at phonito and phosphino phoshorus atoms, respectively; the
2
δ ϭ 81.8 and 39.9 ppm, with JP,P ϭ 17 Hz, which corre- value of ν˜CO at 1990 cmϪ1 (nujol mull) in the IR spectrum
spond to the phosphonito and phosphino phosphorus supports a structure in which the carbonyl unit is in a trans
atoms, respectively.
position to the higher-trans-influence phosphonito group.
Similarly to [Pd(C6H5CN)2Cl2], [Pt(COD)I2] reacted with As shown in Figure 1 (a), the NMR spectrum of the crude
(Ra,Sc)-3 in a 1:1 molar ratio in toluene to give the product product also indicates, in the region of the phosphonito and
[Pt(Ra,Sc-3)I2] (11) as a white microcrystalline solid that is phosphanyl phoshorus atom resonances, well-resolved sig-
1
2
2
moderately stable to air in the solid state and in solution. nals at δ ϭ 108.0 (ddd, JRhP ϭ 133, JP,P ϭ 46, JP,P
ϭ
Its formulation is supported by the presence of resonances 35 Hz) and 54.4 ppm (ddd, 1JRhP ϭ 124, 2JP,P ϭ 46, 2JP,P ϭ
in the 31P{1H} NMR spectrum, recorded in CDCl3, that 35 Hz) arising from AAЈBBЈXXЈ systems. These spectro-
correspond to phosphonito and phosphino phosphorus scopic data allow us to assign a dinuclear structure to 13,
atoms, together with peaks due to 195Pt satellites.
but they are not sufficient to fully characterize it. On the
The reaction of (Ra,Sc)-3 with [Rh(CO)2Cl]2 in a 2:1 mo- basis the 31P{1H} NMR spectroscopic data, we tentatively
lar ratio in hexane led to a mixture of products in almost propose for 13 the dinuclear head-to-tail structure, 13a (see
equal amounts. The 31P{1H} NMR spectrum of the crude b in Figure 1).[10] The large decrease in the value of JRhP
1
product, recorded in CDCl3 (see a in Figure 1), allows us on proceeding from 12 to 13 can also suggest an oxidation
to identify the chelate [Rh(Ra,Sc-3)(CO)Cl] (12) and a di- process from RhI to RhII and propose an RhIIϪRhII unde-
nuclear species 13, the nature of which we are not able to fined dimer formulation.[11,12] We have ascertained that 12
fully explain.
and 13 do not interconvert; the bulkiness of the binaphthyl
Eur. J. Inorg. Chem. 2004, 1447Ϫ1453
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FULL PAPER
moiety probably prevents the exchange reaction between 12
and 13.
Lists of selected bond lengths and angles of 4 and 5 are
given in Table 1 and 2, respectively.
˚
Crystal and Molecular Structure of [Pd(Sc-1)Cl2] (4) and
[Pt(Sc-1)Cl2] (5)
Table 1. Selected bond lengths [A] and angles [deg] for Molecule A
in 4
Compounds 4 and 5 are isostructural. In the crystals of
4 (and of 5), two crystallographically independent, but very
similar, complexes of [Pd(Sc-1)Cl2] (and of [Pt(Sc-1)Cl2]) are
present. ORTEP views of one of the two molecules of the
complexes 4 and 5 are shown in Figure 2 and 3, respectively.
Pd(1A)ϪP(2A) 2.217(3)
Pd(1A)ϪP(1A) 2.210(3)
Pd(1A)ϪCl(1A) 2.365(3)
Pd(1A)ϪCl(2A) 2.353(3)
P(1A)ϪN(1A) 1.712(7)
P(1A)ϪC(5A) 1.818(9)
Pd(1B)ϪP(1B) 2.212(3)
Pd(1B)ϪP(2B) 2.225(3)
Pd(1B)ϪCl(2B) 2.351(3)
Pd(1B)ϪCl(1B) 2.348(3)
P(1B)ϪN(1B) 1.727(8)
P(1B)ϪC(5B) 1.794(11)
P(1A)ϪC(11A) 1.811(9)
P(1B)ϪC(11B) 1.801(10)
P(1A)ϪP(2A) 2.596(4)
P(1B)ϪP(2B) 2.598(3)
P(2A)ϪN(1A) 1.695(7)
P(2B)ϪN(1B) 1.682(8)
P(2A)ϪC(23A) 1.802(11)
P(2B)ϪC(17B) 1.812(9)
P(2A)ϪC(17A) 1.800(10)
P(2B)ϪC(23B) 1.809(10)
N(1A)ϪC(1A) 1.498(9)
N(1B)ϪC(1B) 1.498(8)
C(1A)ϪC(2A) 1.508(11)
C(1B)ϪC(4B) 1.480(12)
C(1A)ϪC(4A) 1.543(13)
C(1B)ϪC(2B) 1.566(14)
C(2A)ϪC(3A) 1.562(9)
C(2B)ϪC(3B) 1.447(10)
P(2A)ϪPd(1A)ϪP(1A) 71.78(9)
P(2A)ϪPd(1A)ϪCl(1A) 169.25(10)
P(1A)ϪPd(1A)ϪCl(1A) 97.98(10)
P(2A)ϪPd(1A)ϪCl(2A) 95.57(10)
P(1A)ϪPd(1A)ϪCl(2A) 165.45(10)
Cl(1A)ϪPd(1A)ϪCl(2A) 94.99(10)
N(1A)ϪP(1A)ϪPd(1A) 94.1(3)
N(1A)ϪP(2A)ϪPd(1A) 94.3(2)
C(1A)ϪN(1A)ϪP(2A) 132.2(6)
C(1A)ϪN(1A)ϪP(1A) 124.2(6)
P(2A)ϪN(1A)ϪP(1A) 99.3(3)
N(1A)ϪC(1A)ϪC(2A) 111.0(7)
N(1A)ϪC(1A)ϪC(4A) 113.1(7)
C(2A)ϪC(1A)ϪC(4A) 115.0(7)
C(1A)ϪC(2A)ϪC(3A) 111.4(8)
P(1B)ϪPd(1B)ϪP(2B) 71.70(9)
P(1B)ϪPd(1B)ϪCl(2B) 169.49(11)
P(2B)ϪPd(1B)ϪCl(2B) 98.71(11)
P(1B)ϪPd(1B)ϪCl(1B) 95.86(11)
P(2B)ϪPd(1B)ϪCl(1B) 165.18(11)
Cl(2B)ϪPd(1B)ϪCl(1B) 94.23(11)
N(1B)ϪP(1B)ϪPd(1B) 93.9(3)
N(1B)ϪP(2B)ϪPd(1B) 94.7(3)
C(1B)ϪN(1B)ϪP(2B) 126.8(7)
C(1B)ϪN(1B)ϪP(1B) 131.0(7)
P(2B)ϪN(1B)ϪP(1B) 99.3(3)
N(1B)ϪC(1B)ϪC(4B) 113.0(8)
N(1B)ϪC(1B)ϪC(2B) 109.0(7)
C(4B)ϪC(1B)ϪC(2B) 115.6(8)
C(3B)ϪC(2B)ϪC(1B) 110.4(9)
Figure 2. View of one of the two independent molecules of 4, to-
gether with the atomic numbering system. Thermal ellipsoids are
drawn at the 30% probability level
The metal center is in a slightly distorted square-planar
environment, being coordinated by two chlorine atoms and
two phosphorous atoms of the chelating (Sc)-1 ligand. The
chelating ligand forms a four-membered ring with the N1
˚
atom deviating by ca. 0.15 A from the plane formed by
the P1, P2 and Pd1 (or Pt1) atoms. The P1ϪPd1ϪP2 and
P1ϪPtϪP2 bite angles are 71.7 and 72.0° in 4 and 5, respec-
tively. The absolute configuration of the chiral carbon atom
C1 is confirmed to be S.
Catalysis
We used the catalytic systems formed by [Rh(acac)(CO)2]
and ligands (Ra,Ra)-2 and (Ra,Sc)-3, at ligand-to-metal ra-
tios of 1:1 and 1:2, in the hydroformylation of styrene. The
catalytic runs were carried out in benzene solutions using
an equimolar mixture of hydrogen and carbon monoxide
gases. The catalytic systems so formed were unstable under
the experimental conditions (using a CO/H2 pressure of 50
atm and a temperature of 40 °C) and afforded metallic rho-
dium together with unidentified decomposition products.
Thus, the ligands (Ra,Ra)-2 and (Ra,Sc)-3 are unsuitable for
the enantioselective rhodium-catalysed hydroformylation
of styrene.
Figure 3. View of one of the two independent molecules of 5, to-
gether with the atomic numbering system. Thermal ellipsoids are
drawn at the 30% probability level
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Rhodium(I), Palladium(II) and Platinum(II) Coordination Chemistry
FULL PAPER
˚
[Pt(Sc-1)Cl2] (5): Following the same procedure used for the syn-
thesis of 4, compound 5 was obtained as a white crystalline solid
by reacting [Pt(COD)Cl2] (0.50 g, 1.33 mmol) and (Sc)-1 (0.59 g,
1.33 mmol). Yield: 82% (0.777 g, 1.09 mmol). 1H NMR (CDCl3):
δ ؍ 8.00 (m, 10 H, ArϪH), δ ؍ 7.50 (m, 10 H, ArϪH), 3.20 (m,
Table 2. Selected bond lengths [A] and angles [deg] for molecule A
in 5
Pt(1A)ϪP(1A)
Pt(1A)ϪP(2A)
Pt(1A)ϪCl(2A)
Pt(1A)ϪCl(1A)
P(1A)ϪN(1A)
P(1A)ϪC(5A)
P(1A)ϪC(11A)
P(1A)ϪP(2A)
P(2A)ϪN(1A)
P(2A)ϪC(23A)
P(2A)ϪC(17A)
N(1A)ϪC(1A)
C(1A)ϪC(2A)
C(1A)ϪC(4A)
C(2A)ϪC(3A)
P(1A)ϪPt(1A)ϪP(2A)
2.200(2)
Pt(1B)ϪP(1B)
2.201(2)
2.207(2)
2.346(2)
2.355(2)
1.722(6)
1.787(8)
1.810(8)
2.590(3)
1.683(6)
1.811(8)
1.819(8)
1.487(8)
1.542(11)
1.546(12)
1.451(11)
71.97(7)
2.2014(19) Pt(1B)ϪP(2B)
3
2.357(2)
2.360(2)
1.702(6)
1.795(8)
1.807(8)
2.590(3)
1.689(6)
1.795(9)
1.816(8)
1.503(8)
Pt(1B)ϪCl(2B)
Pt(1B)ϪCl(1B)
P(1B)ϪN(1B)
P(1B)ϪC(5B)
P(1B)ϪC(11B)
P(1B)ϪP(2B)
P(2B)ϪN(1B)
P(2B)ϪC(17B)
P(2B)ϪC(23B)
N(1B)ϪC(1B)
1 H, C*H), 1.02 (m, 1 H, CH2), 0.87 (m, 1 H, CH2), 0.77 (d, J ϭ
7 Hz, 3 H, CH3), 0.41 (t, 3J ϭ 7 Hz, 3 H, CH3) ppm. 31P{1H}
1
NMR (CDCl3):
δ
ϭ
15.5 (t, JPt,P
ϭ 3285 Hz) ppm.
C28H29Cl2NP2Pt (707.49): calcd. C 47.54, H 4.13, Cl 10.02, N 1.98;
found C 47.50, H 3.98, Cl 9.94, N 1.89.
[Rh(COD)(Sc-1)]PF6 (6): NH4PF6 (0.260 g, 1.6 mmol) was added
to a solution of [Rh(COD)Cl]2 (0.400 g, 0.8 mmol) in THF (25
mL). The bright-yellow solution was stirred at room temperature
for 30 min. Upon adding the solid ligand (Sc)-1 (0.706 g,
1.6 mmol), an instantaneous change of colour occurred from yel-
low to orange, together with formation of an orange precipitate.
The solvent was evaporated under reduced pressure and the re-
sidual solid was washed three times with hexane to afford the pure
title complex 6 as an orange powder. Yield: 65% (0.830 g,
1.512(10) C(1B)ϪC(4B)
1.523(10) C(1B)ϪC(2B)
1.522(10) C(2B)ϪC(3B)
72.11(8)
P(1B)ϪPt(1B)ϪP(2B)
P(1A)ϪPt(1A)ϪCl(2A) 167.57(8)
P(2A)ϪPt(1A)ϪCl(2A) 97.15(8)
P(1A)ϪPt(1A)ϪCl(1A) 99.35(8)
P(2A)ϪPt(1A)ϪCl(1A) 171.28(8)
Cl(2A)ϪPt(1A)ϪCl(1A) 91.53(8)
P(1B)ϪPt(1B)ϪCl(2B) 171.23(8)
P(2B)ϪPt(1B)ϪCl(2B) 99.77(9)
P(1B)ϪPt(1B)ϪCl(1B) 97.22(9)
P(2B)ϪPt(1B)ϪCl(1B) 167.01(9)
Cl(2B)ϪPt(1B)ϪCl(1B) 91.34(10)
1
1.04 mmol). H NMR (CDCl3): δ ؍ 7.80Ϫ7.40 (m, 32 H, ArϪH),
3.06 (m, 1 H, C*H), 0.82 (m, 1 H, CH2), 0.71 (m, 1 H, CH2), 0.64
(d, 3J ϭ 7 Hz, 3 H, CH3), 0.34 (t, 3J ϭ 6.8 Hz, 3 H, CH3) ppm.
N(1A)ϪP(1A)ϪPt(1A)
N(1A)ϪP(2A)ϪPt(1A)
93.7(2)
94.0(2)
N(1B)ϪP(1B)ϪPt(1B)
N(1B)ϪP(2B)ϪPt(1B)
93.8(2)
94.7(2)
1
31P{1H} NMR (CDCl3): δ ϭ 50.1 (d, JRhP ϭ 134 Hz), Ϫ143.9
(PF6) ppm. C36H41F6NP3Rh (797.55): calcd. C 54.22, H 5.18, F
14.29, N 1.76; found C 53.92, H 5.22, F 14.15, N 1.73.
C(1A)ϪN(1A)ϪP(2A) 133.0(5)
C(1A)ϪN(1A)ϪP(1A) 123.4(5)
C(1B)ϪN(1B)ϪP(2B) 125.3(5)
C(1B)ϪN(1B)ϪP(1B) 131.9(6)
P(2A)ϪN(1A)ϪP(1A)
99.6(3)
P(2B)ϪN(1B)ϪP(1B)
99.0(3)
[Pd(Ra,Ra-2)Cl2] (8): A solution of (Ra,Ra)-2 (0.563 g, 0.78 mmol)
N(1A)ϪC(1A)ϪC(2A) 111.8(6)
N(1A)ϪC(1A)ϪC(4A) 112.3(6)
C(2A)ϪC(1A)ϪC(4A) 113.8(7)
C(1A)ϪC(2A)ϪC(3A) 113.6(7)
N(1B)ϪC(1B)ϪC(4B) 109.8(7)
N(1B)ϪC(1B)ϪC(2B) 112.4(6)
C(4B)ϪC(1B)ϪC(2B) 113.2(7)
C(3B)ϪC(2B)ϪC(1B) 113.4(9)
in toluene (10 mL) was added dropwise to
a solution of
[Pd(PhCN)2Cl2] (0.300 g, 0.78 mmol) in the same solvent (20 mL)
that was cooled in an ice bath. The reaction mixture was stirred
for 30 min; during this time, precipitation of an orange solid oc-
curred. The solid was separated by filtration, washed a few times
with petroleum ether and then dried under reduced pressure to give
the product 8 as an orange solid. Yield: 74% (0.519 g, 0.58 mmol).
1H NMR (CDCl3): δ ؍ 8.33Ϫ7.28 (m, 29 H, ArϪH) ppm. 31P{1H}
NMR (CDCl3): δ ؍ 82.1 (s) ppm. C46H29Cl2NO4P2Pd (899.0):
calcd. C 61.46, H 3.25, Cl 7.89, N 1.56; found C 61.36, H 3.15, Cl
8.02, N 1.50.
Experimental Section
The ligands (Sc)-1, (Ra,Ra)-2 and (Ra,Sc)-3 were prepared as re-
ported in the literature.[3] All other reagents were purchased from
SigmaϪAldrich and Strem and used as supplied. All reactions were
performed under dry nitrogen in a vacuum system or in Schlenk
apparatus. All solvents were purified by conventional procedures
and freshly distilled prior to use. For column chromatography, we
used silica gel 60 (220Ϫ440 mesh) purchased from Fluka. IR spec-
tra were obtained from Nujol mulls on KBr plates using a Per-
[Pt(Ra,Ra-2)I2] (9):
A solution of ligand (Ra,Ra)-2 (0.130 g,
0.18 mmol) in toluene (10 mL) was added dropwise at room tem-
perature to a solution of [Pt(COD)I2] (0.100 g, 0.18 mmol) in the
same solvent (20 mL). After 1 h, the bright-yellow solution was
concentrated under reduced pressure until the volume was ca.
5 mL; after the addition of pentane (30 mL), a deep-yellow solid
precipitated. This solid was crystallized from CH2Cl2/pentane (3:1,
10 mL) to obtain the pure complex 9 as a yellow powder. Yield:
79% (0.166 g, 0.14 mmol). 1H NMR (CDCl3): δ ؍ 8.49 (m, 6 H,
ArϪH), 8.04Ϫ7.95 (m, 11 H, ArϪH), 7.51Ϫ7.31 (m, 4 H, ArϪH),
6.89 (m, 4 H, ArϪH), 6.80Ϫ6.75 (m, 4 H, ArϪH) ppm. 31P{1H}
NMR (CDCl3): δ ؍ 94.5 (1JPt,P ϭ 5296 Hz) ppm. C46H29I2N-
O4P2Pt (1170.59): calcd. C 47.20, H 2.50, I 21.68, N 1.20; found C
46.98, H 2.58, I 21.48, N 1.26.
kinϪElmer FTIR 1720 spectrometer. H and 31P{1H} NMR spec-
1
tra were recorded with a Bruker AMX R300 instrument. 1H NMR
spectra were referenced to internal tetramethylsilane and 31P{1H}
spectra to external 85% H3PO4; positive chemical shifts for all nu-
clei are at relatively higher frequencies. Elemental analyses were
performed by Redox s.n.c., Monza, Milano.
[Pd(Sc-1)Cl2] (4): Solid (Sc)-1 (0.46 g, 1.04 mmol) was added to a
solution of [Pd(PhCN)2Cl2] (0.40 g, 1.04 mmol) in CH2Cl2 (30
mL).The mixture was stirred at room temperature for about 30
min. During this time, the solution became turbid and its colour
switched from dark- to bright-orange. After filtration, evaporation
of the solvent under reduced pressure yielded a solid that was
washed twice with hexane and crystallized from CH2Cl2/petroleum
ether (3:1, 15 mL) to obtain an orange-yellow crystalline solid.
[Pd(Ra,Sc-3)Cl2] (10): A solution of ligand (Ra,Sc)-3 (0.108 g,
0.189 mmol) in CH2Cl2 (10 mL) was added to a solution of
[Pd(PhCN)2Cl2] (0.073 g, 0.189 mmol) in the same solvent (25 mL).
The reaction mixture was stirred for 30 min at room temperature.
The solution was concentrated under reduced pressure until the
Yield: 73% (0.470 g, 0.76 mmol). 1H NMR (CDCl3):
δ ؍
8.02Ϫ7.55 (m, 20 H, ArϪH), 3.28 (m, 1 H, CH), 1.29 (m, 1 H, volume was ca. 5 mL; after the addition of pentane (30 mL), a
3
CH2), 0.95 (m, 1 H, CH2), 0.79 (d, J ϭ 7 Hz, 3 H, CH3), 0.43 (t, yellow solid precipitated. This solid was crystallized from CH2Cl2/
3J ϭ 7 Hz, 3 H, CH3) ppm. 31P{1H} NMR (CDCl3): δ ϭ 29.6 (s)
pentane (3:1, 10 mL), washed twice with petroleum ether and then
ppm. C28H29Cl2NP2Pd (618.80): calcd. C 54.35, H 4.72, Cl 11.46, dried under vacuum to give compound 10. Yield: 68% (0.101 g,
1
N 2.26; found C 54.26, H 4.68, Cl 11.70, N 2.14.
0.13 mmol). H NMR (CDCl3): δ ؍ 8.04Ϫ7.95 (m, 22 H, ArϪH),
Eur. J. Inorg. Chem. 2004, 1447Ϫ1453
www.eurjic.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1451

`
G. Calabro, D. Drommi, C. Graiff, F. Faraone, A. Tiripicchio
FULL PAPER
Table 3. Crystal data and structural refinement for compounds 4 and 5 (R1 ϭ ΣԽԽFoԽ Ϫ ԽFcԽԽ/ΣԽFoԽ, wR2 ϭ {Σ[w(F2c Ϫ F2o)2]/Σ[w(F2o)2]}1/2
)
Compound
4
5
Formula
Formula mass
Wavelength (A)
Crystal system
Space group
Unit cell dimensions (A)
b ϭ 16.891(3)
C28H29Cl2NP2Pd
618.76
0.71073 (Mo-Kα)
orthorhombic
P 212121
a ϭ 14.931(3)
b ϭ 16.966(3)
c ϭ 21.053(5)
5319(2)
C28H29Cl2NP2Pt
707.45
0.71073 (Mo-Kα)
orthorhombic
P 212121
˚
˚
a ϭ 14.951(3)
c ϭ 21.089(5)
3
˚
V (A )
5340(2)
8, 1.760
55.93
2768
Z, density (calcd.) (Mg/m3)
8, 1.545
10.37
2512
Abs. coefficient (cmϪ1
F(000)
)
Crystal size (mm)
θ range (°)
Reflection collected, independent reflections
Obsd. reflections [I Ͼ 2σ(I)]
Data/restraints/parameters
Final R indices [I Ͼ 2σ(I)]
R indices (all data)
0.18 ϫ 0.32 ϫ 0.37
1.54Ϫ28.22
31872, 11746 [R(int) ϭ 0.0788]
5209
11746/0/621
R1 ϭ 0.0433, wR2 ϭ 0.0467
R1 ϭ 0.1310, wR2 ϭ 0.0602
0.22 ϫ 0.21 ϫ 0.22
1.54Ϫ27.98
31436, 11395 [R(int) ϭ 0.0590]
8705
11395/0/621
R1 ϭ 0.0406, wR2 ϭ 0.0916
R1 ϭ 0.0608, wR2 ϭ 0.0991
3.15 (m, 1 H, CH), 1.18 (m, 1 H, CH2), 0.82 (m, 1 H, CH2), 0.73
NMR (CDCl3): δ ؍ 8.04Ϫ6.95 (m, 44 H, ArϪH), 2.90 (m, 2 H,
3
(d, 3J ϭ 7 Hz, 3 H, CH3), 0.41 (t, 3J ϭ 7 Hz, 3 H, CH3) ppm. CH), 1.18 (m, 2 H, CH2), 0.72 (m, 2 H, CH2), 0.78 (d, J ϭ 7 Hz,
2
31P{1H} NMR (CDCl3): δ ؍ 81.8 (d, JP,P ϭ 17 Hz), 39.9 (d, 6 H, CH3), 0.43 (d, 3J ϭ 7 Hz, 6 H, CH3) ppm. 31P{1H} NMR
2JP,P ϭ 17 Hz) ppm. C36H31Cl2NO2P2Pd (784.91): calcd. C 57.74, (CDCl3): δ ؍ 108.0 (ddd, JRhP ϭ 133, JP,P ϭ 46, JP,P ϭ 35 Hz),
1
2
2
1
2
2
H 4.17, Cl 9.47, N 1.87; found C 57.84, H 4.21, Cl 9.62, N 1.77.
54.4 (ddd, JRhP ϭ 124, JP,P ϭ 46, JP,P ϭ 35 Hz) ppm.
[Pt(Ra,Sc-3)I2] (11): Following the same procedure used for the syn-
thesis of 10, compound 11 was obtained as a white solid after re-
acting [Pt(COD)I2] (0.094 g, 0.168 mmol) and solid (Ra,Sc)-3
(0.096 g, 0.168 mmol) in CH2Cl2. Yield: 67% (0.115 g, 0.11 mmol).
1H NMR (CDCl3): δ ؍ 8.04Ϫ7.95 (m, 22 H, ArϪH), 3.08 (m, 1
H, CH), 1.14 (m, 1 H, CH2), 0.75 (m, 1 H, CH2), 0.61 (d, 3J ϭ
7 Hz, 3 H, CH3), 0.35 (t, 3J ϭ 7 Hz, 3 H, CH3) ppm. 31P{1H}
X-ray Data Collection, Structural Solution and Refinement for Com-
pounds 4 and 5: The intensity data of compound 4 and 5 were
collected at room temperature on a Bruker Smart 1000 single-crys-
tal diffractometer. Crystallographic and experimental details for the
structures are summarized in Table 3.
The structures were solved by Patterson and Fourier methods and
refined by full-matrix least-squares procedures (based on F2o)[13]
with anisotropic thermal parameters used in the last cycles of re-
finement for all the non-hydrogen atoms.
2
1
NMR (CDCl3): δ ؍ 98.3 (d, JP,P ϭ 19, JPt,P 4876 Hz), 45.8 (d,
1
2JP,P ϭ 19, JPt,P 3218 Hz) ppm. C36H31Cl2NO2P2Pt (1020.50):
calcd. C 42.37, H 3.06, I 24.87, N 1.37; found C 42.34, H 3.01, I
24.69, N 1.31.
The hydrogen atoms were introduced into geometrically calculated
positions and refined riding on the corresponding parent atoms. In
the final cycles of refinement, we used a weighting scheme: w ϭ 1/
[σ2F2o ϩ (0.0069 P)2] (4, Pd), w ϭ 1/[σ2F2o ϩ (0.0454 P)2] (5, Pt),
where P ϭ (F2o ϩ 2 Fc2)/3.
Reaction of [RhCO)2Cl]2 with (Ra,Sc)-3: Solid (Ra,Sc)-3 (0.320 g,
0.56 mmol) was added at room temperature to a stirred solution of
[Rh(CO)2Cl]2 (0.112 g, 0.288 mmol) in hexane (30 mL). After the
addition, precipitation of a yellow compound was observed. The
mixture was stirred for 30 min at room temperature, and then the
solvent was evaporated under reduced pressure. The solid was
washed with hexane (3 ϫ 10 mL) until the filtered solution was
colourless, i.e., indicating that the excess of [Rh(CO)2Cl]2 had been
separated. The 31P{1H} NMR spectrum of the crude product (Fig-
ure 1), recorded in CDCl3, indicated the presence of both
[Rh(Ra,Sc-3)(CO)Cl] (12) and [Rh(µ-Ra,Sc-3)(CO)Cl]2 (13) together
with other species at very low concentrations. We failed to obtain
compounds 12 and 13 as analytically pure solids, either by using
column chromatographic methods or differences in their solubilit-
ies. The reaction of [RhCO)2Cl]2 with (Ra,Sc)-3 in a 1:2 molar ratio
also afforded a mixture of 12 and 13. Compound [Rh(Ra,Sc-
CCDC-215879 (for 4) and -215878 (for 5 Pt) contain the sup-
plementary crystallographic data for this paper. These data can be
obtained free of charge at www.ccdc.cam.ac.uk/conts/retriev-
ing.html [or from the Cambridge Crystallographic Data Centre, 12
Union Road, Cambridge CB2 1EZ, UK; Fax: (internat.) ϩ 44-
1223-336-033; E-mail: deposit@ccdc.cam.ac.uk].
[1]
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[1a]
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[1b]
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3
1.23 (m, 1 H, CH2), 0.81 (m, 1 H, CH2), 0.49 (d, J ϭ 6 Hz, 1 H,
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2JP,P ϭ 98 Hz) ppm. Compound [Rh(µ-Ra,Sc-3)(CO)Cl]2 (13): 1H
[1h]
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 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2004, 1447Ϫ1453

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