Half-sandwich complexes of osmium containing guanidine-derived ligands

Article abstract of DOI:10.1039/d0dt02713h

Pyridinyl- and phosphano-guanidino complexes of formula [(η6-p-cymene)OsCl(H2L)][SbF6] (cymene = MeC6H4iPr; H2L = N,N′-bis(p-Tolyl)-N′′-(2-pyridinylmethyl)guanidine, H2L1 (1) and N,N′-bis(p-Tolyl)-N′′-(2-diphenylphosphanoethyl)guanidine, H2L2 (2)) have be

Full text of DOI:10.1039/d0dt02713h

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Half-sandwich complexes of osmium containing
guanidine-derived ligands†
Cite this: DOI: 10.1039/d0dt02713h
Amie Parker, Pilar Lamata,* Fernando Viguri, Ricardo Rodríguez, José A. López,
Fernando J. Lahoz,
Pilar García-Orduña and Daniel Carmona
*
6
Pyridinyl- and phosphano-guanidino complexes of formula [(η -p-cymene)OsCl(H
2
L)][SbF
6
] (cymene =
MeC
6
H
4
iPr; H
2
L = N,N’-bis(p-Tolyl)-N’’-(2-pyridinylmethyl)guanidine, H
2
L1 (1) and N,N’-bis(p-Tolyl)-N’’-
6
(2-diphenylphosphanoethyl)guanidine, H
2
L2 (2)) have been prepared from the dimer [{(η -p-cymene)
OsCl}
2
(μ-Cl)
2
] and H
2
L in the presence of NaSbF
6
. Treatment of complex 2 with HCl renders the phos-
6
phano–guanidinium complex [(η -p-cymene)OsCl
AgSbF
2
6
(H )][SbF ] (3). Compounds 1 and 2 react with
3
L
2
6
6
rendering the cationic aqua complexes [(η -p-cymene)Os(H
2
L)(OH
2
)][SbF
6
]
2
2 2
(H L = H L1 (4),
6
H
2
L2 (5)). Addition of monodentate ligands L to compound 4 affords complexes of formula [(η -p-
cymene)Os(H
2
L1)L][SbF
6
]
2
(L = py (6), 4-(NHMe)py (7), CO (8), P(OMe)
3
(9)). Treatment of complexes 4
6
3
and 5 with NaHCO
3
renders the monocationic complexes [(η -p-cymene)Os(κ N,N’,N’’-HL1)][SbF
6
] (10)
6
3
3
and [(η -p-cymene)Os(κ N,N’,P-HL2)][SbF
6
] (11), respectively, in which the HL ligand adopts a fac-κ
coordination mode. The new complexes have been characterised by analytical and spectroscopic means,
including the determination of the crystal structures of the compounds 1–4, 6, 8, and 11, by X-ray diffrac-
tometric methods. The phosphano–guanidino complexes 2 and 5 exhibit a temperature dependent
fluxional process in solution. The new 18 electron complexes 1, 2, 6, and 8–10 are active catalysts for the
Friedel–Crafts reaction between trans-β-nitrostyrene and N-methyl-2-methylindole. Conversions greater
than 90% were obtained. Proton NMR studies support a mechanism involving the Brønsted-acid acti-
vation of trans-β-nitrostyrene through the NH functionalities of the coordinated guanidine ligands.
Received 3rd August 2020,
Accepted 16th September 2020
DOI: 10.1039/d0dt02713h
rsc.li/dalton
5
dro-2H-pyrimido[1,2-a]pyrimidine), the octahedral species [Os
Introduction
6
(
Tpg)
2
(CO)(PPh
3
)], (HTpg = N,N′,N″-triphenylguanidine) and a
6
Guanidines and their derivatives are highly useful compounds family of half-sandwich complexes of formula [(η -p-cymene)
that have found a large variety of applications in fields as OsCl(hpp)] and [(η -p-cymene)OsCl{(C(NR)(NiPr) NHiPr)}]
7
a
6
7b
1
1b,2
diverse as catalysis, coordination chemistry,
materials have been reported so far.
1
f,i,2b,3
2b,4
science
or biological and supramolecular chemistry.
On the other hand, the last decade has witnessed the devel-
In particular, ligands containing the CN3 guanidine moiety opment of organocatalysts based on weakly acidic molecules
have been widely used for the stabilization of different metal capable of acting as electrophile activators through either
8
complexes, taking advantage of their capability of bonding to hydrogen bonding or Brønsted acid catalysis. The H-bond
the metals as neutral, monoanionic or dianionic ligands in a donating ability of these organic catalysts is usually enhanced
1
b,2
variety of coordination modes.
However, osmium com- by means of electron withdrawing substituents. Alternatively,
pounds with this class of ligands remain surprisingly rare. this role has sometimes been played by metallic Lewis acids
Thus, as far as we know, only the dinuclear complexes giving rise to Lewis acid assisted Brønsted acid (LBA) cata-
n
9
[Os
2
Cl
2
(hpp)
2
] , (n = 0, 1; hpp = the anion of 1,3,4,6,7,8-hexahy- lysts. In the context of the present work, the contributions to
this field of Meggers’s and Gladysz’s groups are particularly
relevant. Meggers et al. have reported the application of octa-
hedral 3-aminopyrazolato iridium(III) complexes as “metal-tem-
Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), CSIC – Universidad
de Zaragoza, Departamento de Química Inorgánica, Pedro Cerbuna 12, 50009
Zaragoza, Spain. E-mail: dcarmona@unizar.es, plamata@unizar.es
plated organocatalysts” to highly effective transfer hydrogen-
ations, Friedel–Crafts reactions, sulfa-Michael additions, aza-
†
Electronic supplementary information (ESI) available: Computational details of
10
Henry reactions and α-amination of aldehydes. Gladysz et al.
complexes 1, 2 and 5. Crystallographic data of complexes 4, 6 and 8 H-bond
interactions. NMR spectra of complexes 1–11. CCDC 1983330-1983336. For ESI
and crystallographic data in CIF or other electronic format see DOI: 10.1039/
d0dt02713h
have developed octahedral tris(chelate) cobalt complexes of
ethylenediamines as hydrogen bond donors for promoting
catalytic Michael additions, ring opening polymerization of
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1
1
6
lactide and additions of 1,3-dicarbonyl compounds.
Syntheses of the chlorido complexes [(η -p-cymene)OsCl
Additionally, the latter group has also shown that half-sandwich (H L)][SbF ] (H L = H L1 (1), H L2 (2))
2
6
2
2
2
ruthenium(II) complexes containing 2-guanidinebenzimidazole
The chlorido complexes 1 and 2 were prepared by treating the
ligands are effective hydrogen bond donors that can catalyse the
6
20
dimer [{(η -p-cymene)OsCl} (μ-Cl) ]
with stoichiometric
2
2
1
2
condensation of indoles and trans-β-nitrostyrene,
the ring
amounts of the corresponding ligand in methanol in the pres-
ence of NaSbF (eqn (2)).
6
13
opening polymerization of lactide and the addition of malonate
14
esters to nitroalkenes. Finally, Mirkin et al. have demonstrated
that hydrogen-bond-donating squaramide moieties within a Zr
metal–organic framework and in a heteroligated Pt(II) complex cat-
alyse the Friedel–Crafts reaction between indole and trans-
β-nitrostyrene and that a functionalised biaryl urea group co-
ordinated to Pt(II) catalyse the Diels–Alder reaction between cyclo-
ÂÈÀ
Á
É
Ã
6
1
=2 η ‐p‐cymene OsCl 2ðμ‐ClÞ2 þ H2L
MeOH;NaSbF6 ÂÀ
Á
Ã
ð2Þ
6
ꢀ
ꢀꢀꢀꢀꢀꢀꢀꢀ! η ‐p‐cymene OsClðH2LÞ ½SbF6ꢁ
ꢀ
NaCl
2
H L¼H L1ð1Þ; H L2ð2Þ
2
2
15
pentadiene and methyl vinyl ketone.
In this regard, we have recently reported that water,
The complexes were characterized by analytical and spectro-
scopic means (see Experimental section). Assignment of the NMR
signals was verified by two-dimensional homonuclear and hetero-
1
6
1
7
18
hydroxo-methylpyridine
or phosphano-hydroxo ligands
with an OH functionality coordinated to a Lewis acid metallic nuclear correlations. Coordination of the pyridine nitrogen with
fragment can act as Brønsted acid electrophile activators for the metal in complex 1 is supported by a strong deshielding of the
Friedel–Crafts and Diels–Alder reactions. Coordination to the H6 proton of the pyridine moiety, from 8.25 (free ligand) to
metal enhances the acidity of the OH group of the ligand 8.84 ppm (complex 1). Similarly, a deshielding of about 40 ppm for
giving rise to LBA catalysts. As a continuation of this work, in the phosphorus nucleus indicates the coordination of the phos-
the present paper, we report the preparation of the pyridinyl- phorus atom in complex 2. Additionally, the plausible coordination
and phosphano-guanidine ligands depicted in Scheme 1 with of the iminic nitrogen in both complexes, forming a five-mem-
the aim of (i) studying their coordination chemistry towards bered metallacycle, would render stereogenic the metal centre and
2 2 2
osmium and (ii) applying the resulting complexes as LBA cata- diastereotopic the C–CH –N and P–CH –CH –N methylenes in
lysts, through the NH functionalities present in the guanidine complexes 1 and 2, respectively (see Fig. 1). Indeed, these methyl-
moiety of the ligands, in the Friedel–Crafts reaction between enes are asynchronous giving a pair of signals in each case and,
2
2
trans-β-nitrostyrene and N-methyl-2-dimethylindole.
therefore, supporting κ N,N′ and κ N,P coordination modes for
complexes 1 and 2, respectively.
To unequivocally establish the solid state structure of the
new species, the crystal structure of both compounds was
determined by X-ray diffraction means. A view of the molecular
structure of the cations is depicted in Fig. 1 and relevant
Results and discussion
Synthesis of the ligands
The ligands H L1 and H L2 have been prepared in high yield characteristics of the metal coordination spheres are summar-
2
2
by reacting 1,3-disubstituted-carbodiimides with appropriately ised in Table 1. Both complexes exhibit the so-called “three-
6
functionalised primary amines in dry THF (eqn (1)) following legged piano-stool” geometry. An η -p-cymene group occupies
1
9
literature procedures (see Experimental section).
2
three fac positions and the corresponding ligand, H L1 (1) or
2
H L2 (2), occupies two coordination sites adopting a κ N,N′ or
2
2
κ N,P coordination mode. In both cases, the remaining coordi-
nation position is occupied by a chlorido ligand. The adopted
pseudotetrahedral geometry renders the osmium a stereogenic
centre.
Complex 1 crystallizes in the P ˉ1 centrosymmetric space
group and, therefore, the two enantiomers are present in the
unit cell. However, complex 2 crystallizes in the chiral P2 2 2
1 1
1
ð1Þ
space group as conglomerate and, according to the ligand pri-
2
1
ority sequence, the absolute configuration of the measured
crystal is R at osmium.
From the determined bond distances and angles, there is
no chemically significant difference to be remarked when com-
paring the two related complexes, 1 and 2. Only the electronic
3
situation of the central CN guanidine carbon merits a
comment. In particular, all the C–NH(p-Tolyl) bond distances
are statistically identical (mean value: 1.365(2) Å), indicating a
2
2
slightly partial double bond character for these bonds, while
the C–N bond distance involving the nitrogen coordinated to
the metal atom is found to be comparatively shorter (1.303(4)
Scheme 1 Pyridinyl- and phosphano-guanidine ligands employed.
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Fig. 1 Molecular structure of cation of complexes 1 and 2. For clarity all the hydrogen atoms are omitted, except the N–H protons, and only the
major component of the disordered p-cymene iPr in complex 1 has been displayed.
Table 1 Selected bond lengths (Å) and angles (°) for complexes 1 and 2
Complex 1
Complex 2
Os–Cl
Os–N(1)
Os–N(2)
2.4230(9)
2.092(3)
2.106(3)
1.6759(2)
1.303(4)
1.361(4)
1.372(4)
Cl–Os–N(1)
Cl–Os–N(2)
Cl–Os–Ct
N(1)–Os–N(2)
N(1)–Os–Ct
N(2)–Os–Ct
84.02(9)
86.29(8)
128.12(7)
76.58(12)
132.05(11)
131.47(11)
Os–Cl
Os–P
Os–N(1)
2.4017(7)
2.3289(8)
2.136(3)
1.7208(1)
1.316(4)
1.361(4)
1.365(4)
Cl–Os–P
Cl–Os–N(1)
Cl–Os–Ct
P–Os–N(1)
P–Os–Ct
N(1)–Os–Ct
82.51(3)
82.15(8)
125.26(11)
81.29(8)
134.65(12)
132.11(14)
a
a
a
Os–Ct
Os–Ct
a
C(17)–N(2)
C(17)–N(3)
C(17)–N(4)
C(25)–N(1)
C(25)–N(2)
C(25)–N(3)
a
a
Ct stands for the centroid of the p-cymene ligand.
(
1) and 1.316(4) Å (2)), but always longer than typical NvC hydrogen atom of an NH fragment is involved in N–H⋯F inter-
2
2
bond lengths (1.279(8) A).
actions with a fluorine atom of the counterion (Table 2). This
Analysis of the H-bond donating ability of N–H fragments kind of interaction will be also found in complexes 4, 6 and 8
points out the existence of similar N–H⋯Cl intramolecular (vide infra).
interactions. However, in complex 1, intermolecular N–H⋯Cl
The NMR spectra of complex 1 do not change significantly
1
hydrogen bonds are observed between both enantiomers, from RT to 193 K. However, the H NMR signals of complex 2
2
2
leading to an R (12) graphical set (Fig. 2). In complex 2, the broaden as temperature decreases but no apparent split of
Fig. 2 Intra- and intermolecular interactions in complexes 1 and 2. For clarity all the hydrogen atoms are omitted, except the N–H protons.
Symmetry operations: (i) 2 − x, 2 − y, 1 − z; (ii) −1 + x, y, z.
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Table 2 Geometrical parameters (Å, °) of H-bond interactions of com- nal process. The low temperature limiting spectrum was
plexes 1 and 2
achieved at 183 K and from the equilibration of the phos-
phorus nuclei, the free energy of activation, ΔG , at the
‡
Complex D–H⋯A
D–H
D⋯A
H⋯A
D–H⋯A
coalescence temperature (208 K), for the process has been cal-
‡
−1 23
1
1
2
2
N(3)–H(3N)⋯Cl
0.85(2) 3.233(3) 2.47(2) 148(2)
0.85(3) 3.418(3) 2.62(3) 156(3)
0.84(4) 3.297(3) 2.60(4) 140(3)
culated: ΔG = 9.28 ± 0.12 kcal mol .
N(4)–H(4N)⋯Cl′
N(2)–H(2N)⋯Cl
DFT calculations have been carried out to obtain infor-
mation about the NMR behaviour observed in solution (see
ESI†). First, the structure found in the solid state for com-
pound 2 (Fig. 1) and those of two of its isomers were con-
sidered. In the first isomer, labelled 2a, a tautomer of the
N(3)–H(3N)⋯F(4″) 0.84(4) 3.057(4) 2.27(4) 156(4)
Symmetry code: (′) 2 − x, 2 − y, 1 − z; (″) −1 + x, y, z.
ligand forms a seven-membered metallacycle by adopting a
2
these signals was observed even at 193 K. At this temperature, κ N,P coordination mode, employing the nitrogen atom of one
3
1
1
the P{ H} NMR spectrum of complex 2 showed two broad of the NHp-Tolyl groups; in the second, 2b, the deprotonated
singlets centred at 21.3 and 22.1 ppm, in about 73/27 molar ligand forms two metallacycles, one with five and the other
3
ratio, respectively, which coalesce to one unique sharp singlet with four members, by coordinating κ N,N′,P using its three
at 19.93 ppm, by heating the sample to RT (Fig. 3a). These atoms with coordination capacity (Fig. 3b). DFT calculations
spectroscopic data suggest that complex 2 undergoes a fluxio- established that the most stable isomer is compound 2, the
one found in the solid state and, the calculated relative ener-
gies for 2a and 2b, 13.7 and 22.6 kcal mol− , respectively, are
1
too high to be compatible with the molar ratio observed
in NMR experiments. Then, we considered the δ/λ interconver-
sion of the Os–P–C–C–N five-membered metallacycle. The
calculated activation barrier for the interconversion is
−
1
7
(
.3 kcal mol , smaller than that experimentally found
9.28 kcal mol− ) for the observed fluxional process. More
1
importantly, the δ conformer (the one observed in the solid
state) is 3.9 kcal mol− more stable than the λ conformer and,
therefore, the latter would not be observed in the NMR
spectra. At this point, we realised that in the solid state struc-
1
ture of complexes 1 and 2 (Fig. 1), the NC(NHp-Tolyl)
presents two different dispositions that can be characterized
by the dihedral angle N(2)–C(17)–N(4)–C(25) 49.3(5)°
complex 1) and N(1)–C(25)–N(3)–C(33) = 152.2(3)° (complex 2).
2
moiety
=
(
These two dispositions define two rotamers. We envisaged
that interconversion between the two involved rotamers for 2
(
2 and 2c) could account for the observed NMR behaviour in
this complex. Indeed, according to DFT calculations, 2 is only
1
0
2
.1 kcal mol− less stable than 2c and the activation barrier
−
1
c → 2 was calculated as 9.4 kcal mol in good agreement
with the ΔG determined for the process (9.28 kcal mol−1
‡
)
through NMR experimental data (Fig. 3c). In summary, we
propose that complex 2 undergoes a fluxional process consist-
ing of the interconversion between rotamers 2c and 2.
According to NMR data, this process is free at 283 K and is
frozen at 183 K. The calculated barrier could be related to the
partial double bond character encountered for the C–NH(p-
Tolyl) bond (vide supra).
6
Synthesis of the complex [(η -p-cymene)OsCl (H L2)][SbF ] (3)
2
3
6
When according to eqn (2), complex 2 was isolated in 96%
yield, two minor by-products were detected by NMR spec-
troscopy, each one in about 2% abundance. One of them is
31
1
Fig. 3 (a) Variation with temperature of the P{ H} NMR spectrum of
complex 2 in CD Cl . (b) Relative free energy for compounds 2, 2a and
b. (c) Gibbs free energy profile of the equilibrium between rotamers 2c
complex 11 (see below) in which monodeprotonated H L2
2
2
2
3
adopts a κ P,N,N′ coordination mode with the osmium atom.
2
An alternative preparation and the complete characterization
of complex 11 will be discussed later. The other by-product,
and 2. For clarity, except the NH protons, hydrogen atoms have been
omitted. Free energies are in kcal mol−
1
.
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complex 3, contains the protonated phosphane-guanidine Table 3 Selected bonds lengths (Å) and angles (°) for both independent
molecules of complex 3
H L2 ligand. Complex 3 was independently prepared by treat-
3
ing complex 2 with a stoichiometric amount of HCl (eqn (3),
see Experimental section).
Os(1)–Cl(1)
Os(1)–Cl(2)
Os(1)–P(1)
Os(1)–Ct(1)
C(25)–N(1)
C(25)–N(2)
C(25)–N(3)
Cl(1)–Os(1)–Cl(2)
Cl(1)–Os(1)–P(1)
Cl(1)–Os(1)–Ct(1)
Cl(2)–Os(1)–P(1)
Cl(2)–Os(1)–Ct(1)
P(1)–Os(1)–Ct(1)
2.4288(11)
2.4304(10)
2.3605(10)
1.694(2)
1.330(6)
1.343(7)
1.338(6)
85.29(4)
89.90(4)
125.23(8)
86.67(3)
Os(51)–Cl(51)
Os(51)–Cl(52)
Os(51)–P(51)
Os(51)–Ct(51)
C(75)–N(51)
C(75)–N(52)
C(75)–N(53)
Cl(51)–Os(51)–Cl(52)
Cl(51)–Os(51)–P(51)
Cl(51)–Os(51)–Ct(51)
Cl(52)–Os(51)–P(51)
Cl(52)–Os(51)–Ct(51)
P(51)–Os(51)–Ct(51)
2.4187(10)
2.4302(10)
2.3611(11)
1.6946(16)
1.326(5)
1.339(5)
1.351(5)
86.30(4)
86.67(4)
125.77(7)
85.43(3)
126.91(7)
131.10(7)
a
a
ÂÀ
ꢀ
Á
Ã
6
η ‐p‐cymene OsClðH2L2Þ ½SbF6ꢁ þHCl
2
CH2Cl2 ÂÀ
Á
Ã
6
ꢀꢀꢀꢀꢀ! η ‐p‐cymene OsCl2ðH3L2Þ ½SbF6ꢁ
ð3Þ
3
As a result of the protonation of complex 2, the proton
NMR spectrum of complex 3 shows three singlets at 9.05, 6.77
and 5.88 ppm, which are attributed to the presence of three
different NH protons in the molecule.
126.23(7)
129.77(8)
a
Ct stands for the centroid of the p-cymene ligand.
Notably, the phosphano-guanidino phosphorus nucleus of
complex 3 resonates at −22.85 ppm, 42.78 ppm apart from the
chemical shift observed for the same nucleus in complex 2.
Table 4 Geometrical parameters (Å, °) of the H-bond interactions of
This remarkable difference can be attributed to the “deshield- complex 3
ing ring contribution” originated when a coordinated mono-
dentate phosphane becomes part of a five-membered chelate
N–H
H⋯A
N⋯A
N–H⋯A
2
4
ring.
N(1)–H(1N)⋯F(7)
0.86(3)
0.874(4)
0.86(3)
2.11(4)
2.272(4)
2.59(4)
2.931(6)
3.069(5)
3.386(4)
158(2)
151.6(2)
155(3)
The crystal structure of complex 3 has been determined by N(51)–H(51N)⋯F(4)′
N(53)–H(53N)⋯Cl(52)″
single crystal X-ray diffraction methods. Its asymmetric unit
contains two crystallographically independent but chemically
equivalent molecules; the molecular structure of both cations
is shown in Fig. 4. Excepting the Os–Cl bond lengths, where
statistical small differences are observed, all the rest of bond
distances, in both independent molecules, are identical
(
Table 4). Additionally, one of the independent molecules also
shows a hydrogen bond between one of the NH(p-Tolyl)
protons and one of the chlorido ligands bound to the osmium
(
Fig. 5).
(Table 3). The most interesting feature is the presence of a
planar C(NH ) guanidino carbon (Σ° C(25) = Σ° C(75) = 360.0
3
6
Syntheses of the aqua-complexes [(η -p-cymene)Os(H L)
2
(
1
7)°) with equivalent C–N distances, all in the narrow range
.326 to 1.351(5), confirming a similar partial double bond
character for all the three CN bonds.
In both independent molecules, a hydrogen bond between complexes 1 and 2 was eliminated as AgCl. The presence of
(
OH
2 6 2 2 2 2
)][SbF ] (H L = H L1 (4), H L2 (5)
By treatment with AgSbF in acetone, the chlorido ligand of
6
−
the CH
2
NH proton and the SbF
6
anion was observed trace amounts of water in the solvent allows the isolation of
Fig. 4 Molecular structure of the two independent cations of complex 3. For clarity all the hydrogen atoms are omitted except the NH protons.
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Fig. 5 View of the two independent molecules of complex 3 showing the detected hydrogen bonds. Primed atoms are related to non-primed ones
through x, y − 1, z symmetry operation.
6
the aqua-complexes [(η -p-cymene)Os(H L)(OH )][SbF ] (H L =
2
2
6 2
2
H
2
L1 (4), H
2
L2 (5) in high yield (eqn (4)).
ÂÀ
Á
Ã
6
η ‐p‐cymene OsClðH2LÞ ½SbF6ꢁ
1
; 2
ð4Þ
Acetone;AgSbF6 ÂÀ
Á
Ã
6
ꢀꢀꢀꢀꢀꢀꢀꢀꢀ! η ‐p‐cymene OsðH2LÞðOH2Þ ½SbF6ꢁ
2
ꢀ
AgCl
H2L¼H2L1ð4Þ; H2L2ð5Þ
Complexes 4 and 5 were characterized by analytical and
spectroscopic means (see Experimental section) and by the
determination of the crystal structure of complex 4 by X-ray
diffraction methods. As commented for complex 1, in complex
4
a strong deshielding was also observed for the H6 proton of
the pyridine moiety (δ(H Py) = 9.13 ppm). In both complexes,
6
−
1
broad IR bands above 3100 cm were attributed to the NH
bonds present in the molecule. Fig. 6 shows a view of the
molecular structure of the cation of compound 4 and the most
relevant structural parameters are collected in Table 5.
Fig. 6 Molecular structure of the cation of complex 4. For clarity all the
hydrogen atoms are omitted, except the water and NH protons.
The half-sandwich complex 4 adopts a pseudotetrahedral
piano-stool geometry with the osmium coordinated with the
Table 5 Selected bond lengths (Å) and angles (°) for complex 4
p-cymene ligand, the pyridinic and iminic nitrogens of the Os–O
2.174(7)
2.064(8)
2.090(7)
1.6726(15)
1.313(11)
1.356(13)
1.363(11)
O–Os–N(1)
O–Os–N(2)
O–Os–Ct
N(1)–Os–N(2)
N(1)–Os–Ct
82.7(3)
79.7(3)
131.27(1)
76.8(3)
131.69(1)
133.75(1)
Os–N(1)
guanidine ligand and the oxygen atom of a water molecule.
The osmium atom is a stereogenic centre and complex 4 crys-
tallizes in the P ˉ1 centrosymmetric space group as a racemate. C(17)–N(2)
Geometrical parameters of the metal coordination sphere
agree with those found in complex 1. Proton NH atoms are
only involved in N–H⋯F interactions with one of the counter-
ions (see ESI†).
a
Os–N(2)
Os–Ct
a
a
a
C(17)–N(3)
C(17)–N(4)
N(2)–Os–Ct
a
Ct stands for the centroid of the p-cymene ligand.
At 298 K, the proton and phosphorus NMR spectra of
complex 5 consist of only one set of signals. However, these (Fig. 7a). The low temperature limiting spectrum was achieved
spectra are temperature dependent. In particular, the singlet at 193 K and, from the equilibration of the phosphorus nuclei,
3
1
1
‡
of the P{ H} NMR spectrum at 298 K, upon cooling, broad- the free energy of activation, ΔG , at the coalescence tempera-
‡
ens out, coalesces at about 277 K and splits into two differently ture, for the fluxional process has been calculated: ΔG = 12.22
populated signals (72/28 ratio) below this temperature ± 0.12 kcal mol−
1 23
.
As for complex 2, we suggest that the flux-
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cymene)Os(H
2
L1)(L)][SbF
6
]
2
(L = Py (6), 4-NHMePy (7), CO (8),
P(OMe) (9)) (eqn (5)).
3
ÂÀ
Á
Ã
6
η ‐p‐cymene OsðH2L1ÞðOH2Þ ½SbF6ꢁ þ L
2
4
ꢀ
OH2 ÂÀ
Á
Ã
6
ð5Þ
ꢀꢀꢀꢀꢀꢀ! η ‐p‐cymene OsðH2L1ÞðLÞ ½SbF6ꢁ
2
L¼ Pyð6Þ; 4‐NHMePyð7Þ;
COð8Þ; PðOMeÞ ð9Þ
3
The new compounds have been characterised by analytical
and spectroscopic methods as well as by the determination of
the crystal structure of complexes 6 and 8 by X-ray crystallogra-
phy. Proton NMR data are compatible with a 1/1/1, p-cymene/
H L/L molar ratio. In particular, the IR spectrum of compound
2
−
1
8
shows a band at 2024 cm attributed to the coordinated
3
1
1
carbon monoxide and the P{ H} NMR spectrum of com-
pound 9 consists of a singlet at 74.32 ppm due to the presence
of coordinated trimethylphosphite.
A view of the molecular structure of the cations of com-
pounds 6 and 8 is shown in Fig. 8. Tables 6 lists the most rele-
vant structural features of the complex 6 and those of the two
3
1
1
Fig. 7 (a) Variation with temperature of the P{ H} NMR spectra of
complex 5 in CD Cl
between rotamers 5c and 5. For clarity, except the NH protons, hydro-
. (b) Gibbs free energy profile of the equilibrium independent molecules encountered for complex 8.
2
2
The cationic complexes exhibit “three-legged piano-stool”
gen atoms have been omitted. Free energies are in kcal mol−
1
.
6
geometry. An η -p-cymene group occupies three fac positions
2
and the κ N,N′ chelating H2L1 ligand and the pyridine nitro-
ional behaviour of complex 5 consists of the interconversion
between two rotamers, 5c and 5, that can be characterised by
the values of the dihedral angles involving the NC–(NHp-
Table 6 Selected bond lengths (Å) and angles (°) for complexes 6 and 8
6
8(1)
8(2)
Tolyl)
2
core of the guanidino ligand (Fig. 7b). Indeed, a DFT
Os–N(1)
Os–N(2)
2.102(9)
2.118(9)
2.144(9)
1.701(5)
77.6(3)
78.5(3)
132.5(3)
87.1(3)
132.5(3)
128.9(3)
1.321(14)
1.352(14)
1.363(14)
2.077(8)
2.098(7)
1.890(10)
1.7660(1)
77.1(3)
88.6(4)
127.60(1)
93.3(3)
127.91(1)
127.18(1)
1.311(12)
1.350(15)
1.366(13)
2.083(8)
2.100(7)
1.904(11)
1.7574(1)
76.7(3)
89.6(4)
126.96(1)
92.6(3)
126.88(1)
128.57(1)
1.320(12)
1.346(14)
1.357(12)
−
1
study shows a difference of 0.4 kcal mol between the two
rotamers with an activation barrier of 12.6 kcal mol for the Os–N(5)/C(32)
−1
a
b
Os–Ct
5
c → 5 process, in good agreement with the observed experi-
N(1)–Os–N(2)
N(1)–Os–N(5)/C(32)
N(1)–Os–Ct
N(2)–Os–N(5)/C(32)
N(2)–Os–Ct
N(5)/C(32) –Os–Ct
C(17)–N(2)
mental NMR data (Fig. 7b).
a
a
b
6
b
Syntheses of the cationic complexes [(η -p-cymene)Os(H
2
L1)
a
b
(L)][SbF ] (L = Py (6), 4-NHMePy (7), CO (8), P(OMe) (9))
6
2
3
Substitution of the coordinated water molecule in complex 4 C(17)–N(3)
by monodentate ligands such as, pyridine (Py), 4-methylamine
C(17)–N(4)
pyridine (4-NHMePy), carbon monoxide or trimethylphosphite
a
b
N(5) in complex 6 and C(32) in complex 8. Ct stands for the centroid
6
gives rise to the corresponding cationic complexes [(η -p- of the p-cymene ligand.
Fig. 8 Molecular structure of the cation of complexes 6 and 8. For clarity all the hydrogen atoms are omitted, except the N–H protons.
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1
gen atom (complex 6) or the carbon atom of the CO molecule
H NMR spectra have meant that we did not delve further into
(complex 8) complete the coordination sphere of the metal. this study.
The metal is a stereogenic centre and both complexes crystal-
lize as racemate in the P ˉ1 centrosymmetric space group. Bond Syntheses of the complexes [(η -p-cymene)Os(HL)][SbF
6
]
6
lengths and angles characterising the metal coordination (H
L = H
L1 (10), H L2 (11))
2 2
2
sphere compared well with those reported for complexes with
κ N,N′ coordination modes (compounds 1 and 4). Moreover,
N–H⋯F interactions, similar to those previously commented,
have been found in the crystal packing of complexes 6 and 8
Deprotonation of the H L ligand of complexes 4 and 5 by
2
2
6
NaHCO
Os(HL)][SbF
HL ligand adopts a κ coordination mode.
3
renders the corresponding complexes [(η -p-cymene)
6
] (HL = HL1 (10), HL2 (11)) (eqn (6)) in which the
3
(ESI†).
ÂÀ
Á
Ã
6
η ‐p‐cymene OsðH2LÞðOH2Þ ½SbF6ꢁ þ NaHCO3
2
4;5
Fluxional behaviour of the pyridinyl-guanidino complexes 1, 4,
and 6–9
ꢀCO ;ꢀ2H O
ð6Þ
2
2
ÂÀ
Á
À
ÁÃ
6
3
ꢀ
ꢀꢀꢀꢀꢀ! ꢀ! η ‐p‐cymene Os κ ‐HL ½SbF6ꢁ
ꢀ
NaSbF6
HL¼HL1ð10Þ;HL2ð11Þ
1
The H NMR data recorded for the pyridinyl-guanidino com-
An IR band at 3359 and 3341 cm− for complexes 10 and
1
plexes 1, 4, and 6–9 deserve some comments. As discussed
before, the fluxionality observed for the phosphano-guanidino 11, respectively, and a singlet in the proton NMR spectrum at
complexes 2 and 5 can be rationalised by assuming the 6.15 and 5.76 ppm for 10 and 11, respectively, are attributed to
exchange between two rotamers around the C–NH bond of the the remaining NH functionality. A peak at 23.87 ppm in the
3
1
1
CN moiety of the phosphano-guanidino ligand. Single-crystal
P{ H} NMR spectrum is assigned to the phosphorus nucleus
X-ray data indicated that the double bond character of the of the PPh group of complex 11. As a reflect of the stereogeni-
CH
N–C bond is weakened by delocalization of its electronic city at the metal, the CH N methylene protons of complexes 10
3
2
2
2
charge on the two remaining C–NH bonds of the guanidine and 11 are asynchronous. The molecular structure of complex
group and, as a consequence, the C–NH bond distances reflect 11, determined by X-ray diffraction means (Fig. 9), reveals that
3
a partial double bond character. DFT calculations indicate the ligand HL2 presents a fac κ N,N′,P coordination mode that
that, for complexes 2 and 5, the energy barrier for the rotation probably forces the central N(1) atom to adopt a pyramidal
around the C–NH bond is accessible at room temperature.
On the other hand, the structural data obtained by single- contrasts with the sp hybridization that this nitrogen atom
geometry (Σ angles around N(1) = 331.0(6)°). This geometry
2
2
crystal X-ray methods for the pyridinyl-guanidino compounds presents when the H
2
L ligands coordinate in a chelate κ N,P
1
, 4, 6 and 8 show that the C–NH bonds of the four complexes manner (compound 2). The small N(1)–Os–N(2) and N(1)–C
have a certain double bond character (see Tables 1, 5, and 6). (25)–N(2) angles, 61.85(17) and 109.1(4)°, respectively, far from
Therefore, it can be expected that the guanidine core of complexes the ideal hybridization values, reflect the strain of the four-
1
, 4 and 6–9 also undergo a fluxional process similar to that membered metallacycle Os–N(1)–C(25)–N(2) (Table 7).
described for complexes 2 and 5. Support for this affirmation
stems from the observation, at RT, of one set (complexes 4 and 6,
see Experimental section) or two sets (complexes 1, 8 and 9) of
resonances for the guanidine NH(p-Tolyl) fragments of these com-
plexes in their H NMR spectra. It should be noted that detailed
assignment of the proton NMR spectra is difficult due to the
broadening and overlapping of some of the signals.
Catalytic reactions
Complexes 1, 2, 6 and 8–10 catalyse the Friedel–Crafts (FC)
reaction between N-methyl-2-methylindole and trans-
β-nitrostyrene. The coordinated water molecule of complexes 4
and 5 would be easily displaced by other ligands as it has been
1
In this regard, DFT calculations carried out for complex 1,
indicate that the activation barrier for the interconversion of
two rotamers defined by the N(2)–C(17)–N(4)–C(25) dihedral
angle (−44.5° complex 1, 154.6° complex 1b, see Fig. 1 and
ESI†) is 9.5 kcal mol− , a value similar to that calculated for
1
−1
the phosphano-guanidino complex 2 (9.4 kcal mol , see
above). However, whereas the energy difference between the
−
1
two rotamers of complex 2 is only 0.1 kcal mol the energy
difference between the corresponding rotamers of complex 1 is
.5 kcal mol− (see ESI†). Therefore, the less stable rotamer of
1
2
complex 1 would not be observable by proton NMR.
In summary, it can be anticipated that all the pyridinyl-gua-
nidino complexes, 1, 4 and 6–9, undergo a fluxional process
similar to that described before. The instability at tempera-
tures above room temperature of the involved compounds and
Fig. 9 Molecular structure of the cation of complex 11. For clarity, all
the strong broadening and signal overlapping observed in the the hydrogen atoms are omitted.
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Table 7 Selected bond lengths (Å) and angles (°) for complex 11
Os–P
Os–N(1)
Os–N(2)
2.3302(12)
2.134(4)
2.107(4)
1.703(2)
1.347(7)
1.329(7)
1.363(7)
P–Os–N(1)
P–Os–N(2)
P–Os–Ct
78.27(11)
90.88(12)
133.60(7)
61.85(17)
133.71(14)
131.38(14)
109.1(4)
a
a
Os–Ct
N(1)–Os–N(2)
a
C(25)–N(1)
C(25)–N(2)
C(25)–N(3)
N(1)–Os–Cta
N(2)–Os–Ct
N(1)–C(25)–N(2)
a
Ct stands for the centroid of the p-cymene ligand.
experimentally shown for complex 4 in the preparation of com-
plexes 6–9. To avoid the possible competence of Lewis acid cat-
alysis, these two complexes have not been tested as catalysts in
the FC reaction above mentioned. Table 8 gathers a selection
of the obtained results together with the reaction conditions.
The collected results are the average of at least two comparable
1
Fig. 10 Selected region of the H NMR spectrum of the addition of
trans-β-nitrostyrene to complex 9: trace a, complex 9; traces b, c, d, e,
after the addition of 5, 15, 25 and 30 equiv. of trans-β-nitrostyrene,
respectively.
2 2
reaction runs. Reactions were carried out in CH Cl , at 298 K.
A molar ratio catalyst/nitroalkene/indole of 1/30/20 (5 mol% complexes 6 and 8 are the most active catalysts. After only
catalyst loading) was employed in all cases. Reactions are 6 hours of reaction, conversions of 95 and 96%, respectively,
clean: only the addition product and the remaining unreacted were achieved. Most probably, Brønsted activation of the N–H
reagents were detected in the NMR spectra of the crude reac- bonds becomes more efficient when the charge of the mole-
tion mixture.
cule increases.
All the complexes are active catalysts for the tested reaction.
To shed light on the mechanism of the catalysis, solutions
Whereas, in all cases, conversions greater than 90% have been containing catalyst 9 and trans-β-nitrostyrene were monitored
achieved after several hours of treatment, conversions lower by NMR spectroscopy. Fig. 10 shows the evolution of a selected
1
than 20% were attained after 120 hours of reaction using the region of the H NMR spectrum, by successive addition of
free ligands as catalysts or in blank experiments. Dicationic trans-β-nitrostyrene to a CD Cl solution of 9. All proton reso-
2 2
nances of 9 remain essentially unchanged but those of the NH
protons. These resonances undergo a gradual downfield displace-
ment from 7.27 ppm (H , see eqn (7)) and 7.39 ppm (H ), (trace
a
b
Table 8 Catalytic reaction of N-methyl-2-methylindole with trans-
β-nitrostyrene
a, Fig. 10, δ values in the absence of trans-β-nitrostyrene) to 7.34
and 7.46 ppm, respectively (trace e, 30 equiv. of trans-
β-nitrostyrene added). The NH protons shift can be accounted for
by assuming that trans-β-nitrostyrene does not interact directly
with the metal but an equilibrium between complex 9 and
adduct 9a, in which trans-β-nitrostyrene is hydrogen-bonded to
the NH groups of 9, is established in solution (eqn (7)). This
interaction would be responsible for the activation of the electro-
phile in the FC catalytic reaction studied. Therefore, this process
can be considered as an example of Brønsted-acid catalysis
a
b
Conv.
Entry
Catalyst
t (h)
(%)
1
2
3
4
5
6
7
8
9
—
120
120
120
87
158
6
6
48
48
20
19
19
94
93
95
96
94
90
9
mediated by a Lewis acid assisted Brønsted-acid (LBA) catalyst.
H
H
2
L1
L2
2
6
[(η -p-cymene)OsCl(H
2
L1)][SbF
L2)][SbF
6
] (1)
] (2)
6
[(η -p-cymene)OsCl(H
2
6
6
[(η -p-cymene)Os(H
2
2
2
L1)(Py)][SbF
L1)(CO)][SbF
L1)(P(OMe) )][SbF
] (10)
6
]
6
2
]
(6)
2
6
[(η -p-cymene)Os(H
(8)
6
6
[(η -p-cymene)Os(H
3
]
2
(9)
6
[(η -p-cymene)Os(HL1)][SbF
6
a
Reaction conditions: Catalyst 0.03 mmol, trans-β-nitrostyrene
(0.90 mmol), N-methyl-2-methylindole (0.60 mmol), in 2 mL of
b
CH
2
Cl
2
.
Based on N-methyl-2-methylindole. Determined by NMR. All
ð7Þ
the complexes are active catalysts for the tested reaction. Whereas, in
all cases, conversions greater than 90% have been achieved after
several hours of treatment, comparable reaction runs. Reactions were
2 2
carried out in CH Cl , at 298 K. A molar ratio catalyst/nitroalkene/
Conclusions
indole of 1/30/20 (5 mol% catalyst loading) was employed in all cases.
Reactions are clean: only the addition product and the remaining
unreacted reagents were detected in the NMR spectra of the crude reac-
tion mixture.
2
The pyridinyl- and phosphano-guanidine ligands H L1 and
H L2 can form stable half-sandwich osmium complexes acting
2
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2
2
13
1
as κ N,N′ or κ N,P ligands. The derived phosphano-guanidi- 5.25 (bs, 2H, NH), 4.56 (bs, 2H, CH
2
), 2.30 (s, 6H, Me). C{ H}
1
nium H L2 cation coordinates as a κ P ligand. Notably, the NMR (125.77 MHz, CD Cl , RT): δ = 159.10 (C (Py)), 149.69
3
2
2
2
monodeprotonated guanidinato ligands HL1 and HL2 are able (C
6
(Py)), 149.39 (CvN), 137.47 (C
4
(Py)), 130.65, 123.47 (Ar),
3
3
to form κ N,N′,N″ or κ N,N′,P chelates in which the hybridiz- 122.96 (C (Py)), 122.78 (C
5
3
(Py)), 47.95 (CH
2
), 21.29 (2 × Me).
2
3
ation of the central nitrogen atom has changed from sp to sp
with the concomitant formation of a highly strained four-
membered Os–N–C–N metallacycle. The new complexes cata-
lysed the FC reaction between trans-β-nitrostyrene and
N-methyl-2-methylindole. From spectroscopic data, it can be
inferred that the complexes act as Brønsted-acid catalysts
through the protons of the NH groups of the coordinated H2L
ligands. The findings reported herein may contribute to the
development of new metal-containing Brønsted-acid catalysts
in which the Brønsted acidity relies on M–XH functionalities.
+
H L2. HRMS (μ-TOF), C H N P, [M + H] , calcd: 452.2250,
2
29 30 3
1
found: 452.2264. H NMR (300.10 MHz, CDCl
.45–7.30 (m, 10H, PPh ), 7.08, 6.90 (AB system, J(A,B) = 9.0
Hz, 8H, Ar), 5.63 (bs, 1H, NH), 4.27 (bs, 1H, NH), 3.44 (m, 2H,
3
, RT): δ =
7
2
13
1
NCH
2
), 2.40 (m, 2H, PCH
100.62 MHz, CDCl , RT): δ = 149.70 (CvN), 138.03, 130.22
Ar), 132.86 (d, J(P,C) = 18.8 Hz), 128.87, 128.67 (d, J(P,C) = 6.8
), 39.57 (CH N), 28.70 (d, J(P,C) = 13.2 Hz,
P), 20.88 (2 × Me). P{ H} NMR (202.46 MHz, CDCl , RT):
δ = −20.96 (s).
2
), 2.30 (s, 6H, Me). C{ H} NMR
(
(
3
Experimental
General information
Hz), 128.87 (PPh
CH
2
2
3
1
1
2
3
All preparations have been carried out under argon. All sol-
vents were treated in a PS-400-6 Innovative Technologies
Solvent Purification System (SPS) and degassed prior to use.
Infrared spectra were recorded on PerkinElmer Spectrum-100
6
Preparation of the complexes [(η -p-cymene)OsCl(H L)][SbF ]
2
6
2 2 2
(H L = H L1 (1), H L2 (2)
6
(
ATR mode) FT-IR spectrometer. Carbon, hydrogen and nitro- To a suspension of the dimer [{(η -p-cymene)OsCl} (μ-Cl) ]
2
2
gen analyses were performed using a PerkinElmer 240 B micro- (395.3 mg, 0.5 mmol), in methanol (10 mL), 1.0 mmol of H2L
analyser. H, C and P NMR spectra were recorded on a and 258.7 mg (1.0 mmol) of NaSbF were added. The resulting
1
13
31
6
Bruker AV-300 spectrometer (300.13 MHz), Bruker AV-400 solution was stirred for 5 h and vacuum-evaporated to dryness.
1
(
400.16 MHz) or Bruker AV-500 (500.13 MHz). In both H NMR The residue was extracted with dichloromethane and the solu-
1
3
and C NMR measurements the chemical shifts are expressed tion was concentrated under reduced pressure to ca. 2 mL. The
in ppm downfield from SiMe . The P NMR chemical shifts slow addition of hexane led to the precipitation of a yellow
3
1
4
are relative to 85% H
3
PO
C, P and H correlation spectra were obtained using stan- dried. Crystals of 1 and 2 suitable for X-ray diffraction analysis
dard procedures. Mass spectra were obtained with a Micro Tof- were obtained by crystallisation from CH Cl /methanol (1) or
4
. J values are given in Hz. NOESY and solid which was washed with hexane (3 × 10 mL) and vacuum-
1
3
31
1
2
2
Q Bruker Daltonics spectrometer.
2 2
CH Cl /hexane (2) solutions.
Preparation of the guanidine ligands H L1 and H L2
2
2
At RT, a mixture of 2-pyridinylmethanamine or 2-(diphenyl-
phosphino)ethylamine (1.8 mmol) and 1,3-di-p-toyldicarbodi-
mide (412.8 mg, 1.8 mmol) in dry THF (10 mL) was stirred for
1
5 h. The resulting solution was vacuum-evaporated to
dryness. The residue was washed with hexane (3 × 5 mL).
Evaporation of the solvent under vacuum gave the
guanidine compounds as a white oil. Yield: 85% (H
H L2).
2
L1), 88%
(
2
Complex 1. Yield: 868.6 mg, 94%. Anal. calcd for
ClF OsSb: C, 40.2; H, 3.9; N, 6.05. Found: C, 40.0; H,
C
3
31
H
36
N
4
6
+
.8; N, 6.0. HRMS (μ-TOF), C H N ClF OsSb, [M − SbF ] ,
3
1
36
4
6
6
+
−1
2
22 4
H L1. HRMS (μ-TOF), C21H N , [M + H] , calcd: 331.1917, calcd: 691.2228, found: 691.2253. IR (cm ): 3303 (br), ν(NH);
found: 331.1932. H NMR (500.10 MHz, CD Cl , RT): δ = 8.25 1623 (m), ν(NvC, Py); 1608 (m), ν(NvC); 653 (s), ν(SbF ). H
2 2 6
1
1
(
bd, J(H Py,H Py) = 7.7 Hz, 1H, H Py), 7.68 (t, J(H Py,H Py) ≈ NMR (500.10 MHz, CD Cl , RT): δ = 8.84 (bd, J(H Py,H Py) =
5
6
6
3
4
2
2
5
6
J(H
5
Py,H
4
Py) = 7.7 Hz, 1H, H
4
4 3
Py), 7.30 (d, J(H Py,H Py) = 7.7 Hz, 7.4 Hz, 1H, H
6
Py), 8.34 (s, 1H, NH trans CH
2
), 7.84 (t, J(H
3
Py,
1
H, H
3
Py), 7.20 (bt, J(H
4
Py,H
5
Py) ≈ J(H Py,H
6
5
Py) = 7.7 Hz, 1H,
H
4
Py) ≈ J(H Py,H
5
4
Py) = 7.5 Hz, 1H, H Py), 7.41 (bd, J(H
4
4
Py,
H Py), 7.11 (d), 6.98 (bs) (AB system, J(A,B) = 7.9 Hz, 8H, Ar), H Py) = 7.5 Hz, 1H, H Py), 7.39 (t, J(H Py,H Py) ≈ J(H Py,
5
3
3
4
5
6
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H
5
Py) = 7.4 Hz, 1H, H Py), 7.13 (s, 1H, NH trans Os), 7.02, 6.89 41.2 Hz, 1H, Hpro-R NCH ), 2.96 (m, 1H, Hpro-S NCH ), 2.78 (m,
5 2 2
(
AB system, J(A,B) = 8.3 Hz, 4 H, Ar), 6.99, 6.92 (AB system, J(A,B) 1H, Hpro-R PCH ), 2.34, 2.25 (2 × bs, 6H, Me p-Tol), 2.34–2.10 (2H,
2
=
2
8.3 Hz, 4 H, Ar), 5.95 (d, J(HA′,HB′) = 5.35 Hz, 1H, HB′), 5.81 (d, CH iPr, Hpro-S PCH ), 1.95 (bs, 3H, Me p-cymene), 1.20–0.80 (2 ×
31
1
J(H
.25 (A part of an AB system, J(Hpro-S,Hpro-R) = 17.5 Hz, 1H, Hpro-R
CH ), 4.87 (B part of an AB system, 1H, Hpro-S, CH ), 2.50 (spt,
H, CH iPr), 2.21, 2.20 (2 × s, 6H, Me p-Tol), 2.15 (s, 3H, Me Preparation of the complex [(η -p-cymene)OsCl (H L2)][SbF ] (3)
B
,H
A
) = 5.7 Hz, 1H, H
A
), 5.76 (d, 1H, H
B
), 5.64 (d, 1H, HA′), bs, 6H, Me iPr). P{ H} NMR (202.46 MHz, CD
2 2
Cl , 183 K):
5
,
Major isomer: δ = 21.42 (s); minor isomer: δ = 22.19 (s).
2
2
6
1
2
3
6
13
1
p-cymene), 1.11, 1.09 (2 × d, J(H,H) = 7.0 Hz, 6H, Me iPr). C{ H}
NMR (125.77 MHz, CD Cl , RT): δ = 162.00, 154.63, 140.22,
26.32, 121.43 (Py), 154.37 (CvN), 136.35, 136.19, 134.77, 134.48,
30.93, 130.48, 120.79, 120.06 (Ar), 97.38 (C–Me p-cymene), 91.01
), 75.80 (CHA′), 75.62 (CH ), 73.38
), 32.16 (CH, iPr), 23.48, 22.18 (Me iPr), 21.19
(Me p-Tol), 19.07 (Me p-cymene).
6
To a solution of the complex [(η -p-cymene)OsCl(H L2)][SbF ] (2)
2
6
2
2
(20 mg, 0.019 mmol) in dichloromethane (2 mL), aqueous HCl
1
1
(0.019 mmol) was added. The resulting solution was stirred for 5
days and concentrated under reduced pressure to ca. 0.5 mL. The
slow addition of hexane led to the precipitation of a yellow solid
which was washed with hexane (3 × 1 mL) and vacuum-dried.
Crystals of 3 suitable for X-ray diffraction analysis were obtained
by crystallisation from CH Cl /hexane solutions.
(C–iPr p-cymene), 78.77 (CH
A
B
(CHB′), 61.64 (CH
2
(
2
2
Complex 2. Yield: 1005.3 mg, 96%. Anal. calcd for
C H N ClF OsPSb: C, 44.7; H, 4.2; N, 4.0. Found: C, 44.9; H,
3
9
44
3
6
+
Complex 3. Yield: 12.0 mg, 60%. Anal. calcd for
Cl OsPSb: C, 43.2; H, 4.2; N, 3.9. Found: C, 43.2; H,
4.4; N, 3.7. HRMS (μ-TOF), C39 OsPSb, [M − SbF ] ,
6
4
.2; N, 4.1. HRMS (μ-TOF), C39
H
44
N
3
ClF
6
6
OsPSb, [M − SbF ] ,
−
1
C
39
H
45
N
3
F
2 6
calcd: 812.2562, found: 812.2594. IR (cm ): 3135–3440 (br),
ν(NH); 1608 (m), ν(NvC); 655 (s), ν(SbF6).
+
1
H
45
N
3
Cl
2
F
6
H
NMR
−
1
calcd: 848.2319, found: 848.2355. IR (cm ): 3465–3120 (br),
(500.10 MHz, CD
2
Cl
2
, RT): δ = 8.71 (s, 1H, NH trans CH
2
), 7.22
1
ν(NH); 1632, 1599 (m), ν(NvC); 654 (s), ν(SbF6). H NMR
(s, 1H, NH trans Os), 7.70–7.30 (m, 10H, PPh
2
), 7.04, 6.87 (AB
(
500.10 MHz, CD Cl , RT): δ = 9.05 (bs, 1H, NH), 7.68–7.13 (m,
2 2
system, J(A,B) = 8.3 Hz, 4 H, Ar), 7.00, 6.91 (AB system, J(A,B) =
.3 Hz, 4 H, Ar), 5.81 (d, J(H ,H ) = 5.7 Hz, 1H, H ), 5.77 (d,
J(HA′,HB′) = 5.9 Hz, 1H, HB′), 5.21 (d, 1H, H ), 5.10 (d, 1H, HA′),
.28 (dm, J(P,H) = 40.8 Hz, 1H, Hpro-R NCH ), 3.38 (m, 1H,
2
18H, Ar), 6.77 (bs, 1H, NH), 5.88 (bs, 1H, NHCH ), 5.40 (d,
8
B
A
A
J(H ,H ) = 5.7 Hz, 2H, H ), 5.34 (d, 2H, H ), 3.45 (m, 2H,
B
A
A
B
B
CH N), 3.15 (m, 2H, CH P), 2.35 (bs, 6H, Me p-Tol), 2.30 (spt,
2
2
4
2
1
H, CH iPr), 2.00 (s, 3H, Me p-cymene), 1.04 (d, J(H,H) = 6.9
H
pro-S NCH
2
), 3.03 (m, 1H, Hpro-R PCH
), 2.23, 2.22 (2 × s, 6H, Me p-Tol), 2.05
s, 3H, Me p-cymene), 1.21, 1.06 (2 × d, J(H,H) = 6.9 Hz, 6H,
2
), 2.29 (spt, 1H, CH iPr),
1
3
1
Hz, 6H, Me iPr). C{ H} NMR (125.77 MHz, CD Cl , RT): δ =
2
2
2
.23 (m, 1H, Hpro-S PCH
2
1
54.19 (CvN), 134.00–129.50 (PPh ), 131.87, 127.21 (Ar),
2
(
1
3
1
101.55 (C–iPr), 90.07 (C–Me p-cymene), 82.28 (CH
A
),
Me iPr). C{ H} NMR (125.77 MHz, CD
2
2
Cl , RT): δ = 156.10
8
2
0.18 (CH ), 38.99 (CH N), 30.86 (CH iPr), 26.84 (d, J(P,C) =
B
2
(CvN), 136.61, 136.47, 134.59, 134.21, 131.10, 130.50,
9.7 Hz, CH P), 22.66 (Me iPr), 21.62 (2 × Me, p-Tol), 18.17
2
1
6
20.38, 119.13, 135.90 (d, J(P,C) = 55.11 Hz), 128.42 (d, J(P,C) =
1.74 Hz) (Ar), 103.38 (C–Me, p-cymene), 93.38 (C–iPr,
3
1
1
(
Me p-cymene). P{ H} NMR (202.46 MHz, CD
22.85 (s).
2 2
Cl , RT): δ =
−
p-cymene), 88.56 (CHA′), 81.89 (CH
B
), 81.13 (CH
A
, CHB′), 57.50
(
2
CH N), 31.70 (d, J(P,C) = 33.8 Hz, CH P), 31.16 (CH, iPr),
2
2
6
Preparation of the complexes [(η -p-cymene)Os(H L)
2
3.16, 22.98 (Me iPr), 21.21, 21.18 (2 × Me p-Tol), 18.16
3
1
1
(OH )][SbF ] (H L = H L1 (4), H L2 (5)
2
6 2
2
2
2
(Me, p-cymene). P{ H} NMR (202.46 MHz, CD
2 2
Cl , RT): δ =
1
9.93 (s).
To a solution of the corresponding chlorido complex 1 or 2
, 183 K): Major isomer: δ = 8.40 (0.30 mmol) in acetone (10 mL), 103.1 mg (0.3 mmol) of
), 4.36 (dm, J(P,H) = 41.2 Hz, 1H, Hpro-R AgSbF were added. The resulting suspension was stirred for
NCH ), 3.39 (m, 1H, H NCH ), 3.09 (m, 1H, H PCH2), 2 h. The AgCl formed was separated with cannula and the fil-
1
H NMR (500.10 MHz, CD
2 2
Cl
(s, 1H, NH trans CH
2
6
2
pro-S
2
pro-R
2
2.34–2.10 (2H, CH iPr, Hpro-S PCH ), 2.14, 2.10 (2 × bs, 6H, Me trate was concentrated under reduced pressure to ca. 2 mL.
p-Tol), 1.95 (bs, 3H, Me p-cymene), 1.20–0.80 (2 × bs, 6H, Me iPr). The slow addition of hexane led to the precipitation of a yellow
Minor isomer: δ = 8.63 (s, 1H, NH trans CH ), 3.68 (dm, J(P,H) = solid, which was washed with hexane (3 × 5 mL) and vacuum-
2
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1
3
1
dried. Crystals of 4 suitable for X-ray diffraction analysis were 6H, Me iPr). C{ H} NMR (125.77 MHz, CD
obtained by crystallisation from CH Cl /hexane solutions. 139.46–123.64 (Ar), 95.11 (C–iPr p-cymene), 83.21, 83.17 (CHA,
CH ), 80.32 (CHB′), 78.03 (CHA′), 54.19 (CH N), 31.48 (CH iPr),
5.35 (d, J(P,C) = 32.5, CH P), 23.84, 22.90 (Me iPr), 21.36 (2 ×
Me, p-Tol), 18.25 (Me p-cymene). P{ H} NMR (202.46 MHz,
2 2
Cl , RT): δ =
2
2
B
2
2
2
31
1
1
CD
2 2 2 2
Cl , RT): δ = 22.69 (bs). H NMR (500.10 MHz, CD Cl ,
193 K): Major isomer: δ = 9.97, 8.26 (2 × s, 2H, NH), 7.80–7.27
(
m, 10H, PPh ), 7.27–6.21 (m, 8H, Ar), 6.60, 6.01 (2 × d, J(H ,
2
A
H
B
) = 5.5 Hz, 2H, H
A
, H
B
), 5.66, 5.32 (2 × d, J(HB′,HA′) = 5.5 Hz,
2
2H, HA′, HB′), 4.18 (m, 1H, Hpro-R NCH ), 3.26 (m, 1H, Hpro-S
NCH ), 3.00, 2.53 (2 × m, 2H, PCH ), 2.08, 2.01 (2 × s, 6H, Me
2
2
p-Tol), 1.95 (m, 1H, CH iPr), 1.56 (s, 3H, Me p-cymene), 1.07bs,
.95 (d, J(H,H) = 5.6 Hz) (6H, Me iPr). Minor isomer: δ = 8.65, 8.23
2 × s, 2H, NH), 6.50, 5.90 (2 × d, J(H ,H ) = 6.0 Hz, 2H, H H ),
0
(
A
B
A
B
Complex 4. Yield: 1098.6 mg, 96%. Anal. calcd for
12OOsSb : C, 32.5; H, 3.35; N, 4.9. Found: C, 32.45; H, 3.1;
N, 4.9. HRMS (μ-TOF), C H N F OOsSb , [M − 2SbF − H O −
5.74, 5.58 (2 × d, J(HB′,HA′) = 5.4 Hz, 2H, HA′
HB′), 3.08 (m, 1H,
C
31
H
38
N
4
F
2
Hpro-R NCH ), 2.81 (m, 1H, Hpro-S NCH ), 2.81, 2.45 (2 × m, 2H,
2 2
31
38 4 12
2
6
2
PCH ), 2.40 (m, 1H, CH iPr), 2.31, 2.22 (2 × s, 6H, Me p-Tol), 1.80
2
+
−1
1
3
1
H] , calcd: 655.2480, found: 655.2472. IR (cm ): 3400 (br), ν(NH);
(
(
s, 3H, Me p-cymene), 1.08, 1.03 (2 × bs, 6H, Me iPr). C{ H} NMR
125.77 MHz, CD Cl , 193 K): Major isomer: δ = 153.00 (CvN),
139.90–122.11 (Ar), 102.16, 95.79 (C–Me, C–iPr, p-cymene), 83.09,
2.16 (CH , CH ), 79.26, 74.94 (CHB′, CHA′), 54.24 (CH N), 23.02
CH P), 30.44 (CH, iPr), 23.58, 21.86 (Me, iPr), 20.77, 20.74 (2 × Me,
p-Tol), 17.45 (Me, p-cymene). Minor isomer: δ = 156.71 (CvN),
39.90–122.11 (Ar), 104.39, 93.58 (C–Me, C–iPr, p-cymene), 81.34,
0.84 (CH , CH ), 79.48, 76.94 (CHB′, CHA′), 55.22, 23.86 (CH N,
CH P), 23.58, 21.74 (Me, iPr), 21.10, 21.03 (2 × Me, p-Tol), 17.85
1
3
380 (m), ν(OH); 1610(m), ν(NvC); 653, ν(SbF
6
). H NMR
2
2
(
500.10 MHz, CD Cl , RT): δ = 9.13 (bd, J(H Py,H Py) = 7.7 Hz, 1H,
2
2
5
6
H
(
6
Py), 7.95 (t, J(H
t, J(H Py,H Py) ≈ J(H
H Py) = 7.8 Hz, 1H, H Py), 7.12 (s, 2H, NH), 7.04, 6.97 (AB system,
4
Py,H
5
Py) ≈ J(H
6
Py,H
5
Py) = 7.7 Hz, 1H, H
5
Py), 7.52
8
(
A
B
2
3
4
5
Py,H
4
Py) = 7.8 Hz, 1H, H
4
Py), 7.50 (bd, J(H
4
Py,
2
3
3
J(A,B) = 8.3 Hz, 8H, Ar), 6.12 (m, 4H, H
CH ), 2.35 (spt, 1H, CH iPr), 2.23 (s, 6H, Me p-Tol), 2.15 (s, 3H, Me),
.06 (d, J(HH) = 6.9 Hz, 6H, Me iPr). C{ H} NMR (125.77 MHz,
CD Cl , RT): δ = 163.36, 154.76, 141.82, 127.26, 122.40 (Py), 156.36
CvN), 135.96, 135.45, 130.91, 121.57 (Ar), 94.32, 90.99 (C–Me, C–iPr
p-cymene), 77.37 (CH , CH , CH , CH ), 61.84 (CH ), 32.00 (CH,
A B
, H , HA′, HB′), 5.03 (brs, 2H,
1
8
2
A
B
2
13
1
1
2
3
1
1
2
2
(
2 2
Me, p-cymene). P{ H} NMR (202.46 MHz, CD Cl , 193 K): Major
(
isomer: δ = 22.62 (s). Minor isomer: 25.52 (s).
A
B
A′
B′
2
6
iPr), 23.19, 23.04 (Me iPr), 21.28 (Me p-Tol, Me p-cymene).
Preparation of the complexes [(η -p-cymene)Os(H
2
L1)
(
L)][SbF
6
]
2
(L = Py (6), 4-NHMePy (7)
6
To
a
solution of the complex [(η -p-cymene)Os(H L1)
2
(
OH
2
6 2 2 2
)][SbF ] (4) (185.2 mg, 0.20 mmol) in CH Cl (10 mL),
0.20 mmol of the corresponding pyridine was added. The
resulting solution was stirred for 5 h and concentrated under
reduced pressure to ca. 2 mL. The slow addition of hexane led
the precipitation of a yellow (py) or brown (4-NHMepy) solid,
which was washed with hexane (3 × 5 mL) and vacuum-dried.
Crystals of 6 suitable for X-ray diffraction analysis were
obtained by crystallisation from CH Cl .
2
2
Complex 5. Yield: 1088.3 mg, 86%. Anal. calcd for
C
39
H
46
N
3
F
12OOsPSb
2
: C, 37.0; H, 3.7; N, 3.3. Found: C, 36.9;
12OOsPSb , [M −
SbF − H O − H] , calcd: 776.2833 found: 776.2806. IR
H, 3.6; N, 3.2. HRMS (μ-TOF), C39
2
H
46
N
3
F
2
+
6
−
2
1
(cm ): 3120–3330 (br), ν(NH); 1606 (w), ν(NvC); 654 (s),
1
ν(SbF
6 2 2
). H NMR (500.10 MHz, CD Cl , RT): δ = 8.40 (bs, 1H,
NH trans Os), 8.17 (s, 1H, NH trans CH ), 7.79–7.25 (m, 10H,
2
PPh
2
), 6.97–6.00 (m, 8H, Ar), 6.56 (d, J(H
A B
,H ) = 5.8 Hz, 1H,
H
B
), 5.88 (d, 1H, H
A
), 5.84 (d, J(HB′,HA′) = 5.31 Hz, 1H, HA′),
5
.49 (bs, 1H, H ), 3.90 (bm, 1H, Hpro-R NCH ), 3.23 (m, 1H,
B′
2
H
pro-S NCH
2
), 2.99 (m, 1H, Hpro-R PCH
2
), 2.63 (m, 1H, Hpro-S
PCH
2
), 2.34 (m, 1H, CH iPr), 2.17, 2.15 (2 × s, 6H, Me p-Tol),
Complex 6. Yield: 195.3 mg, 81%. Anal. calcd for
1
.81 (s, 3H, Me p-cymene), 1.20, 1.06 (2 × d, J(H,H) = 6.9 Hz, C H N F OsSb : C, 35.9; H, 3.4; N, 5.8. Found: C, 35.7; H,
3
6
41
5
12
2
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2
3
.2; N, 5.9. HRMS (μ-TOF), C36
H
41
N
5
F
12OsSb
2
, [M − 2SbF
6
− Py − CD
2
Cl
2
, RT): δ = 162.46 (C
2
Py κ N,N′ ligand), 156.63 (C
4
Py), 156.01
+
−1
2
2
H] , calcd: 655.2472, found: 655.2479. IR (cm ): 3378 (br), ν(NH); (CvN), 154.16 (C Py κ N,N′ ligand), 141.26 (C Py κ N,N′ ligand),
6
5
1
2
1
606 (m), ν(NvC); 651 (s), ν(SbF
RT): δ = 9.09 (bd, J(H Py,H Py) = 7.2 Hz, 1H, H
.57 (bd, J(H Py,H Py) = J(H Py,H Py) = 7.1 Hz, 2H, H H Py), 7.97 79.26, 79.22, 78.10, 76.94 (CH CH CH CH ), 61.80 (CH ), 32.12
6
). H NMR (500.10 MHz, CD
2
Cl
2
,
136.16, 135.11, 130.88 (Ar), 127.53 (C
4
Py κ N,N′ ligand), 122.49 (C
3
2
2
5
6
6
Py κ N,N′ ligand), Py κ N,N′ ligand), 121.88 (Ar), 98.36, 93.80 (C–Me p-cymene, C–iPr),
8
3
2
5
6
2
6
A
B
A′
B′
2
(
H
t, J(H
4
Py) ≈ J(H
3
Py,H
4
Py) ≈ J(H
5
Py,H
4
Py) = 7.1 Hz, 1H, H
4
Py), 7.88 (t, J(H
3
Py, (CH iPr), 30.05 (NHMe) 23.78, 22.47 (Me iPr), 21.26 (2 × Me p-Tol),
2
5
Py,H Py) = 7.3 Hz, 1H, H
4
4
Py κ N,N′ ligand), 7.59 (t, (Me p-cymene).
J(H Py,H Py) ≈ J(H Py,H Py) ≈ J(H Py,H Py) ≈ J(H Py,H Py) = 7.1
2
3
4
3
4
5
6
5
6
Hz, 2H, H
3
H
5
Py), 7.48 (t, J(H
Py κ N,N′ ligand), 7.39 (bd, J(H
κ N,N′ ligand), 7.15 (s, 2H, NH), 7.04, 6.97 (AB system, J(A,B) = 7.7
Hz, 8H, Ar), 6.25 (d, J(H ,H ) = 5.8 Hz, 1H, H ), 6.22 (d, J(HA′,HB′) =
.8 Hz, 1H, HB′), 6.12 (d, 1H, H ), 6.01 (d, 1H, HA′), 5.04 (A part of an
4
Py,H
5
Py) ≈ J(H
6
Py,H
5
Py) = 7.2 Hz,
Preparation of the complex [(η -p-cymene)Os(H
2
L1)
2
1
H, H
5
4
Py,H
3 3
Py) = 7.3 Hz, 1H, H Py
(
CO)][SbF ] (8)
6 2
2
After bubbling of carbon monoxide through a dichloromethane/
acetone solution (7 ml, 2.5/1, V/V) of the complex [(η -p-cymene)Os
(H L1)(OH )][SbF ] (4) (228.9 mg, 0.2 mmol) for 30 min, the slow
2 2 6 2
addition of hexane led to the precipitation of a yellow solid which
was washed with hexane (3 × 10 mL) and vacuum-dried. Crystals of
A
B
B
6
5
A
AB system, J(Hpro-R,Hpro-S) = 18.9 Hz, 1H, CHHpro-S), 4.88 (B part of an
AB system, 1H, CHHpro-R), 2.47 (spt, 1H, CH iPr), 2.22 (s, 6H, Me
p-Tol), 2.00 (s, 3H, Me p-cymene), 1.05 (d, J(H,H) = 6.7 Hz, 6H, Me
8
suitable for X-ray diffraction analysis were obtained by crystallisa-
1
3
1
2
iPr). C{ H} NMR (125.77 MHz, CD Cl , RT): δ = 162.90 (C Py κ N,
2
2
2
tion from CH Cl
2
2
.
2
N′ ligand), 157.36 (CvN), 154.20 (C
6
Py κ N,N′ ligand), 153.79 (C
Py κ N,N′ ligand), 141.45 (C Py), 136.62, 134.92,
2
,
2
C
6
Py), 141.60 (C
4
4
2
1
31.06 (Ar), 129.05 (C , C Py), 127.90 (C Py κ N,N′ ligand), 122.59
Py κ N,N′ ligand), 122.10 (Ar), 97.24 (C–Me p-cymene), 97.07 (C–
3
5
5
2
(
C
3
iPr p-cymene), 81.35 (CH ), 80.26 (CHB′), 75.71 (CH ), 75.80 (CHA′),
B
A
6
1.56 (CH ), 32.31 (CH iPr), 23.31, 23.11 (Me iPr), 21.28 (2 × Me
2
p-Tol), 18.23 (Me p-cymene).
Complex 8. Yield: 203.2 mg, 88%. Anal. calcd for C32
OOsSb : C, 33.3; H, 3.1; N, 4.8. Found: C, 33.0; H, 3.0; N, 4.7. HRMS
μ-TOF), C H N F OOsSb , [M − 2SbF − H] , calcd: 683.2421,
36 4 12
H N F
2
+
(
32
36 4 12
2
6
−1
found: 683.2432. IR (cm ): 3379 (br), ν(NH); 2024 (m), ν(CO); 1607
m), ν(NvC); 652 (s), ν(SbF
1
(
6 2 2
). H NMR (300.13 MHz, CD Cl , RT): δ
=
8.86 (bd, J(H Py,H Py) = 7.1 Hz, 1H, H Py), 8.10 (t, J(H Py,H Py) ≈
5
6
6
3
4
J(H
H
3
7
5
Py,H
Py), 7.56 (t, J(H
.55 (s, 1H, NH trans CH ), 6.98 (bs), 6.91(d) (AB system, J(A,B) = 8.2
4
Py) = 7.2 Hz, 1H, H
4
Py), 7.65 (bd, J(H
4
Py,H
3
Py) = 7.2, 1H,
4
Py,H Py) ≈ J(H
5
6
Py,H Py) = 7.1 Hz, 1H, H
5
5
Py),
Complex 7. Yield: 212.6 mg, 84%. Anal. calcd for
2
37 44 6 2
C H N F12OsSb : C, 36.0; H, 3.6; N, 6.8. Found: C, 35.8; H,
A B
Hz, 8H, Ar), 6.67, 6.55 (m, 4H, H H , HA′ HB′), 6.07 (s, 1H, NH trans
3
4
.3; N, 6.9. HRMS (μ-TOF), C H N F OsSb , [M − 2SbF −
-NHMepy − H] , calcd: 655.2472, found: 655.2455. IR (cm ):
3
7
44
6
12
2
6
−1
Os), 5.58 (A part of an AB system, J(Hpro-S,Hpro-R) = 18.7 Hz, 2H,
CHHpro-R), 5.16 (B part of an AB system, 2H, CHHpro-S), 2.48 (spt, 1H,
CH iPr), 2.20, 2.18, 2.12 (3 × s, 9H, Me p-Tol, Me p-cymene), 1.20,
+
3
6
380 (br), ν(NH); 1625 (m), 1608 (m), ν(NvC); 652 (s), ν(SbF ).
1
H NMR (300.13 MHz, CD Cl , RT): δ = 8.91 (bd, J(H Py,H Py)
=
H
2
2
5
6
13
1
1
.12 (2 × d, J(H,H) = 6.9 Hz, 6H, Me iPr). C{ H} NMR
2
7.3, 1H, H
6
Py κ N,N′ ligand), 7.88 (t, J(H
3
Py,H
4
5
Py) ≈ J(H Py,
(
100.62 MHz, (CD ) CO, RT): δ = 174.81 (CO), 163.34 (C Py), 160.52
2
3 2
2
4
Py) = 7.4 Hz, 1H, H
4
Py κ N,N′ ligand), 7.85 (m, 2H, H H
2 6
(
1
CvN), 158.08 (C
28.11 (C Py), 124.02 (C
p-cymene, C–iPr), 94.75, 91.28, 91.13, 90.82 (CH CH CH CHB′),
6
Py), 143.39 (C
4
Py), 137.09, 136.59, 131.40 (Ar),
2
Py), 7.48 (bd, J(H Py,H Py) = 7.4 Hz, 1H, H Py κ N,N′ ligand),
4
3
3
2
5
3
Py), 123.89 (Ar), 120.52, 118.86 (C–Me
7
.42 (t, J(H
6
Py,H
5
Py) = 7.3 Hz, 1H, H
5
Py κ N,N′ ligand), 7.01,
A
B
A′
6
2
.91 (AB system, J(A,B) = 8.3 Hz, 8H, Ar), 6.56 (d, 2H, J(H Py,
6
5.52 (CH
2
), 33.46 (CH iPr), 23.74, 23.27 (Me iPr), 21.49 (2 × Me
H Py) ≈ J(H Py,H Py) = 7.0 Hz, H H Py), 6.12, 6.10, 6.05, 5.96
3
6
5
3
5
p-Tol) 19.99 (Me p-cymene).
(4 × d, J(H
A
,H
B A A′ B
) ≈ J(HA′,HB′) = 6.2 Hz, 4H, H H H HB′), 5.37
(
1
q, 1H, NHMe), 5.23 (A part of an AB system, J(Hpro-S,Hpro-R) =
8.7 Hz, 1H, CHHpro-R), 5.06 (B part of an AB system, 1H,
CHHpro-S), 2.88 (d, J(H,H) = 5.1 Hz, 3H, NHMe), 2.41 (spt, 1H,
CH iPr), 2.20 (s, 6H, Me p-Tol), 2.05 (s, 3H, Me p-cymene), 1.06, 1.00 To
6
Preparation of the complex [(η -p-cymene)Os(H
2
L1)
(
P(OMe) )][SbF ] (9)
3
6 2
6
a
2
solution of the complex [(η -p-cymene)Os(H L1)
13
1
(2 × d, J(H,H) = 6.7, 6H, Me iPr). C{ H} NMR (100.62 MHz, (OH )][SbF ] (4) (185.2 mg, 0.20 mmol) in dichloromethane
2
6 2
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10 mL), 23.6 μL (0.20 mmol) of P(OMe)
Dalton Transactions
(
3
were added. The trated under reduced pressure to ca. 2 mL. The slow addition
resulting solution was stirred for 24 h and concentrated under of hexane led to the precipitation of a yellow solid, which was
reduced pressure to ca. 2 mL. The slow addition of hexane led washed with hexane (3 × 10 mL) and vacuum-dried. Crystals of
the precipitation of a brown solid, which were washed with 11 suitable for X-ray diffraction analysis were obtained by crys-
hexane (3 × 5 mL) and vacuum-dried.
tallisation from CH Cl /hexane solutions.
2 2
Complex 10. Yield: 148.8 mg, 85%. Anal. calcd for
31 35 4 6
C H N F OsSb: C, 41.85; H, 4.0; N, 6.3. Found: C, 42.1; H,
Complex 9. Yield: 217.6 mg, 87%. Anal. calcd for
C H N F O OsPSb : C, 32.7; H, 3.6; N, 4.5. Found: C, 32.7;
3
4
45
4
12
3
2
+
4
.0; N, 6.0. HRMS (μ-TOF), C H N F OsSb, [M − SbF ] ,
3
1
35
4
6
−
6
H, 3.3; N, 4.6. HRMS (μ-TOF), C34
45 4 12 3 2
H N F O OsPSb , [M −
1
+
−1
calcd: 655.2472, found: 655.2495. IR (cm ): 3359 (br), ν(NH);
1
2
(
SbF − H] , calcd: 655.2472, found: 655.2459. IR (cm ): 3341
6
1
6
628 (m), ν(NvC); 654 (s), ν(SbF ). H NMR (500.10 MHz,
br), ν(NH); 1022 (m), ν(PO); 1611 (m), ν(NvC); 651 (s),
1
CD Cl , RT): δ = 9.27 (bd, J(H Py,H Py) = 7.2 Hz, 1H, H Py),
2
2
5
6
6
ν(SbF
6 2 2
). H NMR (500.10 MHz, CD Cl , RT): δ = 8.83 (bd,
7
(
.81 (t, J(H
t, J(H Py,H
J(H Py,H Py) = 7.3 Hz, 1H, H Py), 7.13, 6.92 (AB system, J(A,B)
3
Py,H
4
Py) ≈ J(H
5
Py,H
4
Py) = 7.3 Hz, 1H, H
4
Py), 7.41
J(H Py,H Py) = 8.0 Hz, 1H, H Py), 8.01 (t, J(H Py,H Py) ≈
5
6
6
3
4
4
5
Py) ≈ J(H
6
Py,H
5 5
Py) = 7.2 Hz, 1H, H Py), 7.30 (bd,
J(H Py,H Py) = 7.9 Hz, 1H, H Py), 7.54 (bd, J(H Py,H Py) = 7.9
5
4
4
4
3
4
3
3
Hz, 1H, H
3
Py), 7.53 (t, J(H
4
Py,H
5
Py) ≈ J(H
6
Py,H
5
Py) = 8.0 Hz,
=
8.4 Hz, 4 H, Ar), 7.13, 6.98 (AB system, J(A,B) = 8.4 Hz, 4 H,
Ar), 6.15 (s, 1H, NH), 5.89, 5.88 (2 × d, J(H ,H ) = J(HA′,HB′) =
.1, 2H, H H ), 5.73, 5.71 (2 × d, 2H, H H ), 5.35 (A part of
1
H, H Py), 7.39 (s, 1H, NH trans Os), 7.27 (s, 1H, NH trans
5
A
B
CH ), 7.02, 6.83 (AB system, J(A,B) = 8.3 Hz, 4 H, Ar), 6.95, 6.86
2
5
B
B′
A
A′
(
AB system, J(A,B) = 8.3 Hz, 4 H, Ar), 6.29 (d, J(HA′,HB′) = 5.8
an AB system, J(Hpro-S,Hpro-R) = 17.2, 1H, CHHpro-R), 4.13 (B part
of an AB system, 1H, CHHpro-S), 2.42 (spt, 1H, CH iPr), 2.31,
Hz, 1H, H ), 6.20 (d, J(H ,H ) = 5.7 Hz, 1H, H ), 6.03 (d, 1H,
B′
A
B
A
H ), 5.98 (d, 1H, H ), 5.45 (A part of an AB system, J(Hpro-S,
B
A′
2
×
CD
.30 (s, 6H, Me p-Tol), 2.09 (s, 3H, Me p-cymene), 1.17, 1.14 (2
H
1
1
pro-R) = 18.7 Hz, 1H, CHHpro-R), 5.15 (B part of an AB system,
1
3
1
d, J(HH) = 7.0 Hz, 6H, Me iPr). C{ H} NMR (125.77 MHz,
Cl , RT): δ = 169.61 (CvN), 164.85 (C Py), 155.50 (C Py),
H, CHHpro-S), 3.81 (d, J(PH) = 11.1 Hz, 9H, OMe), 2.32 (spt,
H, CH iPr), 2.20, 2.18 (s, 6H, Me p-Tol), 2.12 (s, 3H, Me
2
2
2
6
1
3
140.35 (C4 Py), 136.28, 135.49, 134.63, 131.13, 130.98 (Ar),
125.93 (C Py), 123.42 (Ar), 122.54 (C Py), 120.26 (Ar), 93.42
p-cymene), 1.17, 0.80 (2 × d, J(H,H) = 7.0 Hz, 6H, Me iPr).
C
1
5
3
{
H} NMR (125.77 MHz, CD Cl , RT): δ = 164.02 (C Py), 156.78
2 2 2
C Py), 156.76 (CvN), 141.58 (C Py), 135.71, 135.50, 135.41,
6 4
35.05, 131.16, 130.43 (Ar), 127.62 (C Py), 122.16 (C Py),
5 3
(
C–Me p-cymene), 90.23 (C–iPr), 74.77 (CH
B
CHB′), 73.58, 73.49
(
(
CH CH ), 59.35 (CH ), 32.47 (CH iPr), 23.58, 23.00 (Me iPr),
A
A′
2
1
1
9
21.40, 21.31 (2 × Me p-Tol), 19.35 (Me p-cymene).
21.64 (d, J(P,C) = 7.5 Hz, C–Me p-cymene), 121.32, 120.76 (Ar),
7.85 (C–iPr p-cymene), 87.76 (CH ), 86.40 (CH ), 85.15 (d, J(P,
A
A′
C) = 11.9 Hz, CHB′), 77.43 (CHA′), 63.39 (CH
2
), 56.22 (d, J(P,C) =
9
2
.2 Hz, OMe), 32.04 (CH iPr), 23.95, 19.92 (Me iPr), 21.22,
1.20 (2 × Me p-Tol), 12.9 (Me p-cymene). P{ H} NMR
3
1
1
(
202.46 MHz, CD
2
Cl
2
, RT, ppm): δ = 74.32 (s).
6
Preparation of the complexes [(η -p-cymene)Os
3
6
(
(
κ N,N′,N″-HL1)][SbF ] (10) and [(η -p-cymene)Os
3
6
6
κ N,N′,P-HL2)][SbF ] (11)
6
To a solution of the corresponding complex [(η -p-cymene)Os
L) (OH )][SbF (H L = H L1 (4), H L2 (5) (0.2 mmol)) in
(
H
2
2
6
]
2
2
2
2
methanol (20 mL), 16.8 mg (0.2 mmol) of solid NaHCO were
3
added. The resulting suspension was stirred for 15 h and then
was vacuum-evaporated to dryness. The residue was extracted
Complex 11. Yield: 192.0 mg, 95%. Anal. calcd for
C H N F POsSb·1/2CH Cl : C, 45.0; H, 4.2; N, 4.0. Found: C,
39 43 3 6 2 2
with dichloromethane and the resulting solution was concen- 44.9; H, 4.0; N, 4.0. HRMS (μ-TOF), C H N F POsSb, [M −
3
9
43 3 6
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+
−1
SbF
6
] , calcd: 776.2806, found: 776.2839. IR (cm ): 3341 (w), electron count agree with the presence of three methanol
1
ν(NH); 1593 (w), ν(NvC); 654 (s), ν(SbF ). H NMR (500.10 MHz, molecules and four dichloromethane molecules in the unit
6
CD
Ar), 6.99, 6.74 (AB system, J(A,B) = 7.8 Hz, 4 H, Ar), 5.76 (s, 1H, into account in the chemical formula, F000 and density.
NH), 5.40, 5.35, 4.80 (3 × bs, 4H, H H H H ), 3.40 (bm, 1H, Compound 6 has been refined as a 2-component twin
NCHHpro-R), 2.98 (bm, 1H, NCHHpro-S), 2.68 (bm, 1H, CH iPr), 2.54 related by a 180 degres rotation around reciprocal b axis. Unit
m, 1H, PCHHpro-S), 2.52 (m, 1H, PCHHpro-R), 2.27 (s, 6H, Me p-Tol), cell and domain orientation matrices were determined with
2 2 2
Cl , RT): δ = 7.76–7.23 (m, 10H, PPh ), 7.02, 6.67 (2 × bs, 4 H, cell of compound 1 and 11, respectively. They have been taken
A
B
A′ B′
(
3
1
2
.25 (s, 3H, Me p-cymene), 1.29 (bd, J(HH) = 7.0 Hz, 3H, Me iPr). Cell Now program. Absorption corrections were performed
1
3
1
32
C{ H} NMR (125.77 MHz, CD
2.16 (CH N), 34.45 (d, J(P,C) = 32.52, CH
2.67 (Me iPr), 21.32, 21.21 (2 × Me p-Tol), 19.40 (Me p-cymene).
2
Cl
2
, RT): δ = 135.60–123.14 (Ar), with Twinabs program. Final structural model refinement
P), 32.63 (CH iPr), 24.17, leads to a 0.289 BASF value.
Crystal structure determination
36ClF OsSb·1.5(CH O); M = 974.10; yellow plate, 0.050 ×
.070 × 0.200 mm ; triclinic P ˉ1 ; a = 10.8413(6) Å, b = 11.1473(6) Å, c
15.2059(6) Å, α = 92.1850(10)°, β = 93.7980(10)°, γ = 110.5430
5
2
2
2
for
complex
1.
3
1
1
P{ H} NMR (202.46 MHz, CD
2
2
Cl , RT): δ = 23.87 (bs).
C
0
31
H
6
N
4
4
r
3
General procedure for the catalytic reaction of N-methyl-2-
methylindole with trans-β-nitrostyrene
=
(
3
−3
−1
c
10)°; V = 1713.31(15) Å , Z = 2, D = 1.888 g cm ; μ = 4.638 cm ;
Catalyst (0.03 mmol), trans-β-nitrostyrene (0.90 mmol) and dry min. and max. absorption correction factors: 0.5093 and 0.6974;
CH Cl (2 mL) were mixed under argon at room temperature 2θmax = 57.24°; 21 006 reflections measured, 7990 unique; Rint
=
2
2
in a Schlenk flask equipped with a magnetic stirrer. The result- 0.0313; number of data/restraint/parameters 7990/2/410; R
1
=
2
ing mixture was stirred for 15 min and then N-methyl-2- 0.0287 [7033 reflections, I > 2σ(I)], wR(F ) = 0.0633 (all data); largest
−3
methylindole (0.60 mmol) was added. The course of the reac- difference peak 1.322 e Å .
tion was monitored by regularly taking samples of ca. 50 μL Crystal structure determination
which, after quenching by addition of Et O, were concentrated 44ClF OsPSb; M = 1047.14; yellow prism, 0.146 × 0.255
under vacuum until dryness. The residue was extracted with × 0.293 mm ; orthorhombic P2 2 2 ; a = 10.9424(4) Å, b =
for
complex
2.
2
C
39
H
6
N
3
3
r
1
1 1
3
Et
dryness, dissolved in CDCl
Conversion values were determined by integration of the
NMR signals of the C3-H proton of the N-methyl-2-methyl- reflections measured, 10 435 unique; Rint = 0.0331; number of
indole (ca. 6.1 ppm) and that of the CHCH NO protons of the data/restraint/parameters 10 435/1/498; R = 0.0175 [10 312
adduct (ca. 5.1 ppm). The collected results are the average of at reflections, I > 2σ(I)], wR(F ) = 0.0411 (all data); largest differ-
2 c
O (4 × 3 mL) and the solution vacuum-evaporated until 13.4216(5) Å, c = 25.9506(10) Å, V = 3811.2(2) Å , Z = 4, D =
1
−3
−1
3
and analysed by H NMR. 1.825 g cm ; μ = 4.214 cm ; min. and max. absorption cor-
1
H
rection factors: 0.3736 and 0.5016; 2θmax = 59.55°; 95 284
2
2
1
2
3
least two comparable reaction runs.
ence peak 1.255 e Å−
Crystal structure determination for complex 3.
C H Cl F N OsPSb)·2(CH Cl )·3/2(C H ); Mr 2466.30;
.
2
X-ray crystallography
(
=
3
9
45
2
6
3
2
2
6
14
3
X-ray diffraction data were collected on a Smart APEX (com- orange prism, 0.160 × 0.200 × 0.224 mm ; triclinic P ˉ1 ; a =
pound 1, 3, 4, 6, 8 and 11) or APEX DUO (complex 2) Bruker 11.0006(6) Å, b = 17.8189(9) Å, c = 26.0251(13) Å, α = 99.1650
3
diffractometers, using graphite-monochromated Mo Kα radi- (10)°, β = 100.6070(10)°, γ = 97.5640(10)°; V = 4881.6(4) Å , Z =
= 1.678 g cm− ; μ = 3.463 cm ; min. and max. absorption
3
−1
ation (λ = 0.71073 Å). Single crystals were mounted on a fiber, 2, D
coated with a protecting perfluoropolyether oil and cooled to correction factors: 0.5077 and 0.6145; 2θmax = 56.81°; 110 689
00(2) K or 120(2) K (in the case of compound 11) with an reflections measured, 23 468 unique; Rint = 0.0432; number of
open-flow nitrogen gas. Data were collected using ω-scans with data/restraint/parameters 23 468/7/1123; R = 0.0363 [19 137
narrow oscillation frame strategy (Δω = 0.3°). Diffracted inten- reflections, I > 2σ(I)], wR(F ) = 0.0989 (all data); largest differ-
c
1
1
2
sities were integrated and corrected of absorption effects by ence peak 2.620 e Å−
3
.
2
5
26
using multi-scan method using SAINT and SADABS pro-
Crystal
structure
determination
for
complex
4.
grams, included in APEX2 package. Structures were solved by
C
31
H
38
F
12
N
4
OOsSb ·2(CH
2
2
Cl ); M = 1314.20; yellow prism,
2
r
2
7
3
direct methods with SHELXS and refined by full-matrix least 0.110 × 0.160 × 0.165 mm ; triclinic P ˉ1 ; a = 8.709(8) Å, b =
2
28
squares on F with SHELXL program included in Wingx 15.2562(14) Å, c = 17.6428(16) Å, α = 110.1590(10)°, β = 92.3050
2
9
3
−3
program system.
(10)°, γ = 98.7480(10)°; V = 2164(2) Å , Z = 2; D
c
= 2.017 g cm
;
Hydrogen atoms have been observed in Fourier difference μ = 4.499 cm− ; min. and max. absorption correction factors:
1
maps. Most of them have been included in the model in calcu- 0.4359 and 0.6240; 2θmax
= 56.31°; 22 268 reflections
lated positions and refined with a riding model. Those of NH measured, 9848 unique; Rint = 0.0627; number of data/
fragments have been included in observed positions, with geo- restraint/parameters 9848/4/531; R = 0.0636 [6988 reflections,
1
2
metrical restraints concerning N–H bond lengths.
I > 2σ(I)], wR(F ) = 0.1383 (all data); largest difference peak
Large solvent accessible voids are observed in the unit cell 2.354 e Å− . Four fluorine atoms of a counterion have been
of compounds 1 and 11. However, the solvent is highly dis- found to be disordered. They have been included in the model
ordered and no attempt to include it in the model lead to ade- in two sets of positions with complementary occupancy factors
3
3
0
quate results. Therefore, Squeeze corrections have been (0.60/0.40(2)). Hydrogen atoms of coordinated water have not
applied. The total potential accessible void volume and the been observed in Fourier difference maps. HFIX 137 instruc-
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tion has been used to calculated their possible positions.
Afterwards, the “three hydrogen atoms” have been refined with
Acknowledgements
a restrain in O–H bond lengths. Their obtained Uiso value have We thank the Ministerio de Ciencia Innovación y Universidades
been used as criteria to select the two most suitable positions.
Crystal structure determination for complex
r
OsSb ; M = 1205.44; yellow prism, 0.060 × 0.095 × Organometálicos Enantioselectivos) for financial support. R. R.
of Spain (CTQ2018-095561-BI00 and CTQ2017-83421-P) and
6. Gobierno de Aragón (Grupo Consolidado: Catalizadores
C
36
H
41
F
12
N
5
2
3
0
=
.100 mm ; triclinic P ˉ1 ; a = 11.5507(13) Å, b = 11.8469(13) Å, c acknowledges the Ministerio de Economía y Competitividad of
15.5684(17) Å, α = 72.5690(10)°, β = 80.2290(10)°, γ = 82.140 Spain for a Ramón y Cajal (RYC-2013-13800) grant. P. G.-O.
3
−3
−1
(
2)°; V = 1994.7(4) Å , Z = 2, D
min. and max. absorption correction factors: 0.5482 and Economía y Competitividad of Spain for a PTA contract.
.7505; 2θmax = 56.576°; 19 485 reflections measured, 13 387
unique; Rint = 0.0774; number of data/restraint/parameters
c
= 2.007 g cm ; μ = 4.612 cm
;
acknowledges CSIC, European Social Fund and Ministerio de
0
2
1
0
3 387/1/518; R
.1352 (all data); largest difference peak 1.590 e Å
Crystal structure determination for complex
OsSb ·1.75(CH Cl ); M = 1302.97; yellow prism,
1
= 0.0608 [9481 reflections, I > 2σ(I)], wR(F ) =
−
3
.
Notes and references
8.
C
32
H
36
F
12
N
4
2
2
3
2
r
1 (a) X.-Y. Cui, C.-H. Tan and D. Leow, Org. Biomol. Chem.,
2019, 17, 4689–4699; (b) J. Francos and V. Cadierno, Dalton
Trans., 2019, 48, 9021–9036; (c) S. Dong, X. Feng and X. Liu,
Chem. Soc. Rev., 2018, 47, 8525–8540; (d) W. Cao, X. Liu and
X. Feng, Chin. Chem. Lett., 2018, 29, 1201–1208; (e) Topics in
Heterocyclic Chemistry, Guanidines as Reagents and Catalysts I
and II, ed. P. Selig, Springer, Cham, Switzerland, 2017;
(f) F. T. Edelmann, Adv. Organomet. Chem., 2013, 1, 55–374;
(g) P. Selig, Synthesis, 2013, 703–718; (h) J. E. Taylor, S. D. Bull
and J. M. J. Williams, Chem. Soc. Rev., 2012, 41, 2109–2121;
(i) F. T. Edelmann, Chem. Soc. Rev., 2012, 41, 7657–7672;
(j) Y. Sohtome and K. Nagasawa, Chem. Commun., 2012, 48,
7777–7789; (k) S. Collins, Coord. Chem. Rev., 2011, 255, 118–
138; (l) X. Fu and C.-H. Tan, Chem. Commun., 2011, 47, 8210–
8222; (m) M. Terada, J. Synth. Org. Chem., Jpn., 2010, 68,
1159–1168; (n) M. P. Coles, Chem. Commun., 2009, 3659–3676;
(o) D. Leow and C.-H. Tan, Chem. – Asian J., 2009, 4, 488–507;
(p) F. T. Edelmann, Chem. Soc. Rev., 2009, 38, 2253–2268.
2 (a) T. Chlupatý and A. Ruzicka, Coord. Chem. Rev., 2016,
314, 103–113; (b) Themed issue: The Chemistry of
Guanidine, Guanidinium, and Guanidinate Compounds,
Aust. J. Chem., 2014, 67(7), https://www.publish.csiro.au/
CH/issue/6955; (c) F. T. Edelmann, Adv. Organomet. Chem.,
0
1
.115 × 0.200 × 0.200 mm ; triclinic P ˉ1 ; a = 16.9772(9) Å, b =
7.1277(9) Å, c = 17.5280(9) Å, α = 84.7380(10)°, β = 66.4340
3
(
10)°, γ = 67.5710(10)°; V = 4307.2(4) Å , Z = 4, D
c
= 2.009 g
cm ; μ = 4.491 cm−1; min. and max. absorption correction
factors: 0.4426 and 0.5750; 2θmax = 56.70°; 64 380 reflections
measured, 20 155 unique; Rint = 0.0424; number of data/
−3
restraint/parameters 20 155/8/1059; R = 0.0690 [14 839 reflec-
1
2
tions, I > 2σ(I)], wR(F ) = 0.2048 (all data); largest difference
peak 8.616 e Å−
3
.
Crystal structure determination for complex 11.
OsPSb·CH Cl ; M = 1095.61; yellow plate, 0.090 ×
.325 × 0.440 mm ; orthorhombic Pna2 ; a = 24.6016(11) Å, b =
0.2764(5) Å, c = 16.4397(8) Å; V = 4156.2(3) Å , Z = 4, D =
C
39
H
43
F
6
N
3
2
2
r
3
0
1
1
1
3
c
.751 g cm− ; μ = 3.931 cm ; min. and max. absorption cor-
3
−1
rection factors: 0.3161 and 0.4546; 2θmax = 57.31°; 53 101
reflections measured, 9956 unique; Rint = 0.0465; number of
data/restraint/parameters 9956/2/469; R
1
= 0.0232 [9428 reflec-
2
tions, I > 2σ(I)], wR(F ) = 0.0572 (all data); largest difference
peak 2.173 e Å−
3
.
Computational details
DFT geometry optimizations and thermochemical calculations
were carried out with the Gaussian 09 program package,
using the B3LYP-D3 hybrid functional. Geometry optimi-
zations were performed in the gas phase with the LanL2TZ(f)
effective core potential basis set for the osmium atoms, and
the 6-311G(d,p) basis set for the remaining ones. All minima
3
3
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Rev., 2001, 214, 91–141.
(no imaginary frequencies) and transition states (one imagin-
3
4
M. K. Kiesewetter, E. J. Shin, J. L. Hedrick and
R. M. Waymouth, Macromolecules, 2010, 43, 2093–2107 and
references therein.
ary frequency) were characterized by calculating the Hessian
matrix. ZPE and gas-phase thermal corrections (entropy and
enthalpy, 298.15 K, 1 atm) from these analyses were calculated.
The nature of the transition states was confirmed by IRC
calculations.
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Conflicts of interest
The authors declare that they have no known competing finan-
cial interests or personal relationships that could have
appeared to influence the work reported in this paper.
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