From tetrahydroborate- to aminoborylvinylidene-osmium complexes via alkynyl-aminoboryl intermediates

Article abstract of DOI:10.1021/ja109691v

The tetrahydroborate OsH(η²-H₂BH ₂)(CO)(PⁱPr₃)₂ (1) reacts with aniline and p-toluidine to give the aminoboryl derivatives Os{B(NHC ₆H₄R)NHCCHCHC(R)CHC}(CO)(PⁱPr₃) ₂ (R = H (2), CH₃ (3)) and four H₂ molecules. Treatment of 2 and 3 with phenylacetylene gives Os{B(NHC₆H ₄R)₂}(C≡CPh)(CO)(PⁱPr₃) ₂ (R = H (4), CH₃ (5)), which react with HBF₄ to afford the amino(fluoro)boryl species Os{BF(NHC₆H ₄R)}(C≡CPh)(CO)(PⁱPr₃)₂ (R = H (6), CH₃ (7)). In contrast to HBF₄, the addition of acetic acid to 4 and 5 induces the release of phenylacetylene and the formation of the six-coordinate derivatives Os{B(NHC₆H₄R) ₂}(K²-O₂CCH₃)(CO)(P ⁱPr₃)₂ (R = H (8), CH₃ (9)). The coordination number six for 4 and 5 can be also achieved by addition of CO. Under this gas Os{B(NHC₆H₄R)₂}(C≡CPh)(CO) ₂(PⁱPr₃)₂ (R = H (10), CH ₃ (11)) are formed. In toluene, these alkynyl-aminoboryl compounds evolve into the aminoborylvinylidenes Os{=C=C(Ph)B(NHC₆H ₄R)₂}(CO)₂(PⁱPr₃) ₂ (R = H (12), CH₃ (13)) via a unimolecular 1,3-boryl migration from the metal to the C_β atom of the alkynyl ligand. Similarly to 4 and 5, complexes 6 and 7 coordinate CO to give Os{BF(NHC ₆H₄R)}(C≡CPh)(CO)₂(PⁱPr ₃)₂ (R = H (15), CH₃ (16)), which evolve to Os{=C=C(Ph)BF(NHC₆H₄R)}(CO)₂(P ⁱPr₃)₂ (R = H (17), CH₃ (18)).

Full text of DOI:10.1021/ja109691v

ARTICLE
pubs.acs.org/JACS
From Tetrahydroborate- to Aminoborylvinylidene-Osmium
Complexes via Alkynyl-Aminoboryl Intermediates
María L. Buil,* Miguel A. Esteruelas,* Karin Garcꢀes, and Enrique O~nate
Departamento de Química Inorgꢀanica, Instituto de Ciencia de Materiales de Aragꢀon, Universidad de Zaragoza-CSIC, 50009 Zaragoza,
Spain
S Supporting Information
b
ABSTRACT: The tetrahydroborate OsH(η2-H2BH2)(CO)-
(PiPr3)2 (1) reacts with aniline and p-toluidine to give the amino-
boryl derivatives Os{B(NHC6H4R)NHCCHCHC(R)CHC}-
jj
j
(CO)(PiPr3)2 (R = H (2), CH3 (3)) and four H2 molecules.
Treatment of 2 and 3 with phenylacetylene gives Os{B-
(NHC6H4R)2}(CtCPh)(CO)(PiPr3)2 (R=H (4), CH3 (5)),
which react with HBF4 to afford the amino(fluoro)boryl species
Os{BF(NHC6H4R)}(CtCPh)(CO)(PiPr3)2 (R=H(6), CH3
(7)). In contrast to HBF4, the addition of acetic acid to 4 and 5 induces the release of phenylacetylene and the formation of the six-
coordinate derivatives Os{B(NHC6H4R)2}(κ2-O2CCH3)(CO)(PiPr3)2 (R = H (8), CH3 (9)). The coordination number six for 4 and 5
can be also achieved by addition of CO. Under this gas Os{B(NHC6H4R)2}(CtCPh)(CO)2(PiPr3)2 (R = H (10), CH3 (11)) are
formed. In toluene, these alkynyl-aminoboryl compounds evolve into the aminoborylvinylidenes Os{dCdC(Ph)B(NHC6H4R)2}-
(CO)2(PiPr3)2 (R = H (12), CH3 (13)) via a unimolecular 1,3-boryl migration from the metal to the Cβ atom of the alkynyl ligand.
Similarly to 4 and 5, complexes 6 and 7 coordinate CO to give Os{BF(NHC6H4R)}(CtCPh)(CO)2(PiPr3)2 (R = H (15), CH3 (16)),
which evolve to Os{dCdC(Ph)BF(NHC6H4R)}(CO)2(PiPr3)2 (R = H (17), CH3 (18)).
’ INTRODUCTION
on η2-coordinated alkynes12 (a) and through oxidative addition
via hydride-alkynyl intermediates evolving either unimolecular
1,3-hydrogen shift13 (b) or deprotonation of the metal center
and subsequent protonation of the alkynyl ligand at Cβ14 (c). A
fourth pathway (d) that may afford vinylidene ligands involves an
R-elimination reaction of a metal-alkenyl group, which may be
obtained through insertion of the alkyne into a metal-hydride
bond.15 Remarkable findings in recent years have shown that
disubstituted vinylidene can be prepared from internal alkynes
through a 1,2-shift similar to that observed in the case of terminal
alkynes. They include heteroatom-substituted alkynes such a silyl-,16
stannyl-,17 thio-,18 and iodoalkynes19 as well as acylalkynes.20 Ishii and
co-workers have demonstrated that, under appropiate conditions, it is
also possible to form vinylidenes from unfunctionalized internal
alkynes.21 Both allenes22 and alkylidenecyclopropanes23 have been
recently employed to prepare ruthenium- and osmium-vinylidene
complexes, respectively.
The chemistry of transition metal complexes of boron is a field
of great current interest1 for its transversal implications including
the functionalization of organic molecules,2 the preparation of
new oligomers and polymers,3 and the reversible dehydrocou-
pling of amineboranes and related compounds.3a,4
Boryl complexes, M-BR2, are the subclass of compounds
with metal-boron bonds exhibiting the strongest potential for
the functionalization of hydrocarbons.5 They allow highly selec-
tive introduction of boryl moieties into organic substrates, which
in turn can be converted into a whole series of other func-
tionalities.6 These species, featuring an electron precise bond
(2c,2e-) between the transition metal and the boron element,7
are commonly prepared by oxidative addition of B-H, B-B, and
B-E bonds (E = main group element) to low-valent transition
metal complexes. Salt elimination reactions between anionic
transition metal compounds and haloboranes or halodiboranes
represent an important alternative synthetic pathway.8 The use of
catecholborane and its derivatives has given access to a large
number of boryl complexes. More recently, boranes with bor-
on-nitrogen bonds have also served as starting compounds for a
few aminoboryl derivatives.9
Complexes containing a tetrahydroborate ligand attached to
the metal through two bridging hydrogen atoms are known for
most of the transition metals.24 NMR studies have pro-
vided evidence of fluxional motion involving the tetrahydrobo-
rate ligand. In the majority of cases, the exchange is simply
between bridging and terminal hydrogen atoms within the
Transition metal-vinylidene complexes10 are intermediates
in a number of synthetically important transformations of
terminal alkynes.11 The alkyne-vinylidene tautomerization
(Scheme 1) has been considered to occur by 1,2-hydrogen shift
Received: October 28, 2010
Published: January 27, 2011
r
2011 American Chemical Society
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Scheme 1
Scheme 2
for other Lewis bases. In contrast to phosphines, phosphites, and
carbon monoxide, which produce the abstraction of BH3 from the
metal center of OsH(η2-H2BH2)(CO)(PiPr3)2 (1), the treat-
28
ment of toluene solutions of this compound with 2.1 equiv of
aniline and p-toluidine leads, after 15 h under reflux, to the amino-
boryl derivatives Os{B(NHC6H4R)NHCCHCHC(R)CHC}-
jj
j
(CO)(PiPr3)2 (R = H (2), CH3 (3)), according to eq 1.
tetrahydroborate ligand. The most generally accepted mechanism
involves the initial breaking of an M-H-B bridge.24e,24f,24h,25
Molecular orbital calculations have indicated that this is the
preferred pathway for exchange of bridging and terminal hydro-
gens in the tetrahydroborate ligand in OsH3(η2-H2BH2)-
(PiPr3)2.26 In agreement with this, most commonly BH3 has
been abstracted from the ligand if the reaction mixture contains
any nucleophile L capable of forming an adduct H3BrL
(Scheme 2).24i,27
Complex OsH(η2-H2BH2)(CO)(PiPr3)2 is a perfect example
of a transition metal tetrahydroborate,28 which strictly follows
the behavior previously metioned.29 As a part of our recent
research program on new insights in transition metal complexes
of boron,30 we have studied its behavior toward anilines and have
discovered that it is an excellent material to generate aminoboryl
derivatives. Interestingly, the formed ligands facilitate the entry
of an alkynyl group into the metal center. The resulting alky-
nyl-aminoboryl intermediates evolve to afford unprecedented
aminoborylvinylidene complexes.
This paper reports (i) the preparation of aminoboryl com-
plexes from a transition metal-tetrahydroborate prototype, (ii)
their conversion into alkynyl-aminoboryl species, (iii) the
transformation of the latter to aminoborylvinylidene derivatives,
and (iv) a mechanistic proposal for the isomerization on the basis
of a kinetic study and DFT calculations.
These reactions, in addition to the formation of the amino-
boryl ligands in the coordination sphere of osmium, produce four
hydrogen molecules per equivalent of starting complex. Five
hydrogen atoms come from 1, the BH4 group, and the hydride
ligand. The amines contribute with one NH-hydrogen atom
each. Furthermore, one of them undergoes ortho-metalation of
the phenyl group and gives an ortho-CH-hydrogen atom. Com-
plexes 2 and 3 are notable not only for the unprecedented
synthetic procedure leading to them but also for the unsaturated
character of the metal center. Most osmium compounds contain-
ing two phosphine ligands are saturated and resist becoming
unsaturated. The presence of at least one π-donor ligand makes
such unsaturated species achievable.29e Complexes 2 and 3 are
rare examples of unsaturated compounds of this type that do not
’ RESULTS AND DISCUSSION
1. Formation of the Aminoboryl Ligands. Arylamines show
a behavior significantly different from that previously observed
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Figure 1. Molecular diagram of 2 (a) and 3 (b). Selected bond lengths (Å) and angles (deg): (a) Os(1)-B(1) 2.072(13), 2.046(16), 2.036(14), and
2.078(14); Os(1)-C(2) 2.161(12), 2.126(12), 2.127(12), and 2.157(11); P(1)-Os(1)-P(2) 165.74(10), 167.49(10), 166.11(11), and 167.73(11);
C(2)-Os-C(13) 167.5(5), 168.5(6), 169.5(5), and 168.9(5). (b) Os(1)-B(1) 2.071(11), 2.038(10), 2.087(11), 2.055(10), 2.055(10), 2.067(11),
2.073(10), and 2.061(11); Os(1)-C(2) 2.154(10), 2.156(9), 2.162(9), 2.161(9), 2.146(9), 2.151(9), 2.146(9), and 2.161(10); P(1)-Os(1)-P(2)
167.97(9), 167.94(8), 168.29(9), 167.08(8), 169.77(8), 167.63(8), 168.53(8), and 167.46(9); C(2)-Os-C(33) 167.8(4), 168.6(4), 170.0(4),
169.5(4), 171.7(3), 170.3(4), 170.3(4), and 168.8(4).
have any π-donor ligand. We note that the reaction of OsCl-
(Bcat)(CO)(PPh3)2 (Bcat = catecholboryl) with o-tolyllithium
leads to Os(o-tolyl)(Bcat)(CO)(PPh3)2. However, attempts to
prepare the phenyl and p-tolyl analogues were not successful.
Thus, the steric protection afforded by the bulkier o-tolyl group
was argued in order to rationalize the stability of this unsaturated
species.31 The alkenyl-alkynyl-carbyne complex Os{(E)-
CHdCHPh}(CtCPh)(tCCH2Ph)(PiPr3)2 is other rare case
of an unsaturated osmium-bisphosphine derivative that does
not contain any π-donor ligand. In contrast to 2 and 3, it is
unstable at temperatures higher than -30 °C, evolving into a
complex mixture of unidentified products.32
respectively. In agreement with the trans disposition of the
phosphine ligands, the 31P{1H} NMR spectra contain singlets
at 29.4 (2) and 29.5 (3) ppm. The chemical shift for the boron
resonances in the 11B NMR spectra, 29 ppm for both com-
pounds, is the expected one for five-coordinate square pyramidal
osmium-boryl derivatives with the boryl ligand trans disposed
to the coordination vacancy.34c,34g
2. Introduction of the Alkynyl Group: Formation of Alky-
nyl-Aminoboryl Derivatives. In spite of the chelate character
of the aminoboryls of 2 and 3, the metalated phenyl group of
these ligands undergoes a σ-bond metathesis reaction with
phenylacetylene. Thus, the treatment of toluene solutions of 2
and 3 with 1.5 equiv of the alkyne for 4 h at room temperature
leads to the alkynyl-aminoboryl derivatives Os{B(NHC6H4-
R)2}(CtCPh)(CO)(PiPr3)2 (R = H (4), CH3 (5)), as a result
of the addition of the C(sp)-H bond of the alkyne to the
Os-Caryl bonds of 2 and 3. Complexes 4 and 5 were isolated as
orange (4) and red (5) solids in 68% and 72% yield, respectively,
according to eq 2.
Complexes 2 and 3 were isolated as orange solids in 91 and
93% yield, respectively, and characterized by X-ray diffraction
analysis. The structure of 2 has four chemically equivalent but
crystallographically independent molecules in the asymmetric
unit, whereas the structure of 3 has eight molecules of the same
type. Figure 1 shows a drawing of a molecule of each complex.
The geometries around the osmium atoms can be rationalized as
square pyramids with the boron atoms in the apex and trans
phosphines (167.73(11)-165.74(10)° for 2 and 169.77(8)-
167.08(8)° for 3).33 The Os-B distances of between 2.078(14)
and 2.036(14) Å (2) and 2.087(11) and 2.038(10) Å (3) support
the osmium-boryl formulation,34 whereas the Os-phenyl bond
lengths of between 2.161(2) and 2.126(12) Å (2) and 2.161(9)
and 2.146(9) Å (3) are typical for Os-Caryl single bonds.35
According to the sp2 hybridization at the boron, the angles
around this atom are between 130.8(12) and 111.6(9)° (2) and
130.6(7) and 111.9(7)° (3).
1
The H, 13C{1H}, 31P{1H}, and 11B NMR spectra of these
compounds in THF-d8 at room temperature are consistent with
1
the structures shown in Figure 1. In the H NMR spectra, the
most noticeable resonances are two singlets at 5.79 and 5.14 ppm
(2) and 5.60 and 5.00 ppm (3), corresponding to the inequiv-
alent NH-hydrogen atoms. The 13C{1H} NMR spectra show the
Os-Cphenyl resonances at 168.5 (2) and 168.6 (3) ppm as
triplets with C-P coupling constants of 11.2 and 11.5 Hz,
Complex 5 has been characterized by X-ray diffraction ana-
lysis. The structure (Figure 2) proves the displacement of the
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metalated phenyl group from the coordination sphere of the
metal by an alkynyl ligand. The geometry around the osmium
atom can be rationalized as a square pyramid, similar to those of 2
and 3, with the boron in the apex, trans phosphines
(P(1)-Os-P(2) = 165.95(5)°),33 and the alkynyl ligand trans
to the carbonyl group (C(1)-Os-C(23) = 173.7(2)°) occupy-
ing the position of the metalated phenyl. The Os-C(1) bond
length of 2.082(5) Å supports an Os-C(sp) single bond14e,35b,36
and indicates a low degree of metal-to-ligand back-bonding.37
The C(1)-C(2) distance and the Os-C(1)-C(2) and C-
(1)-C(2)-C(3) angles are 1.223(7) Å and 176.7(5) and
178.6(7)°, respectively. The Os-B bond length of 2.076(6) Å
agrees well with those of 2 and 3. The angles around the boron
atom, 118.3(5) (N(1)-B-N(2)), 125.7(4) (N(1)-B-Os),
and 115.9(4)° (N(2)-B-Os), are consistent with the sp2
hybridization at this atom.
The 1H, 13C{1H}, 31P{1H}, and 11B NMR spectra of 4 and 5
in benzene-d6 at room temperature are consistent with the
structure shown in Figure 2. In the 1H NMR spectra, the NH-
hydrogen atoms display broad resonances at about 5.5 ppm
for both compounds. The 13C{1H} NMR spectra show at
141.8 (4) and 142.0 (5) ppm triplets with a C-P coupling
constant of 15.4 Hz and at 128.5 (4) and 128.4 (5) ppm
singlets corresponding to the OsCR and Cβ carbon atoms of
the alkynyl ligand. The 31P{1H}NMR spectra contain singlets
at 32.8 (4) and 33.9 (5) ppm. In agreement with 2 and 3, in
the 11B NMR spectra the boron resonances appear at 31 ppm
(4 and 5).
Figure 2. Molecular diagram of 5. Selected bond lengths (Å) and angles
(deg): Os-C(1) 2.082(5), C(1)-C(2) 1.223(7), Os-B 2.076(6),
B-N(1) 1.434(7), B-N(2) 1.467(7); Os-C(1)-C(2) 176.7(5), C-
(1)-C(2)-C(3) 178.6(7), P(1)-Os-P(2) 165.95(5), C(1)-Os-C-
(23) 173.7(2), N(1)-B-N(2) 118.3(5), N(1)-B-Os 125.7(4),
N(2)-B-Os 115.9(4).
Cβ carbon atoms of the alkynyl ligand. The 31P{1H}NMR
spectra contain singlets at 35.6 (6) and 35.5 (7) ppm, whereas
the boron resonances in the 11B NMR spectra are observed at 28
(6) and 30 (7) ppm.
The formation of 6 and 7 involves the addition of HF to one of
the B-N bonds of 4 and 5. In addition to 6 and 7, the process
generates aniline and p-toluidine that are trapped by BF3 to form
One of the amido substituents of the aminoboryl ligands of 4
and 5 can be replaced by fluoride to afford amino(fluoro)boryl
derivatives. Treatment of toluene solutions of 4 and 5 with 1.05
the corresponding RNH2 BF3 adducts (R = Ph, p-tolyl; δ11B, 22;
3
equiv of HBF4 OEt2 for 3 h at room temperature leads to the
δ
19F, -32). Amino(halo)boryl complexes are very scarce.9 Salt
3
alkynyl-amino(halo)boryl complexes Os{BF(NHC6H4R)}-
(CtCPh)(CO)(PiPr3)2 (R = H (6), CH3 (7)), which were
isolated as orange solids in 62% (6) and 56% (7) yield, according
to eq 3.
elimination reactions represent the route of choice to prepare the
greater part of this type of compounds.38 Two exceptions are
the osmium derivative Os{BC1(NHC5H4N)}C1(CO)(PPh3)2,
which is obtained by reaction of Os(BCl2)Cl(CO)(PPh3)2 with
2-aminopyridine,34d and the bis(boryl) complex cis-[(Ph3P)2Pt-
{BCl(NMe2)}2], resulting from the oxidative addition of the
B-B bond of the diborane to Pt(η2-C2H4)(PPh3)2.39 Asym-
metric fluoroboryl compounds are particularly rare. Complex
Os{BF(OC5H4N)}C1(CO)(PPh3)234e and Fe(η5-C5H5){BF-
[Si(SiMe3)3]}(CO)240 have been prepared by halide metathesis
starting from the corresponding chloride counterparts, whereas
the paramagnetic species [Ir{BF(C12H8)}Cl(PMe3)3]þ has
been synthesized by reaction of IrCl(C12H8)(PMe3)3 with
NOBF4 through the formal insertion of BF into a Ir-C bond.41
Alkynyl groups coordinated to late transition metals show a
high nucleophilicity at the Cβ atom. Thus, the addition of HBF4
to alkynyl complexes is a known entry into the synthesis of
vinylidene compounds.10 In this context, the selective prepara-
tion of 6 and 7, according to eq 3, should be pointed out. The
driving force for their formation instead of cationic vinylidene
species appears to be the trend of the [BF4]- anion to release
fluoride in the presence of neutral Lewis bases42 and the high
formation energy of a B-F bond. In agreement with this, in
contrast to HBF4, the addition of acetic acid to toluene solutions
of 4 and 5 affords the six-coordinate derivatives Os{B-
(NHC6H4R)2}(κ2-O2CCH3)(CO)(PiPr3)2 (R = H (8), CH3
(9)), as a result of the protonation of the alkynyl ligand and
its subsequent displacement by the carboxylate group. These
The presence of the fluorine substituent at the boron atom of 6
and 7 is strongly supported by the 1H and 19F NMR spectra of
these compounds in benzene-d6 at room temperature. The H
1
NMR spectra show at 6.62 (6) and 6.52 (7) ppm doublets, with a
H-F coupling constant of 21.9 Hz, whereas the 19F NMR
spectra contain fluoride resonances at -35.7 (6) and -36.5
(7) ppm. The 13C{1H}, 31P{1H}, and 11B NMR spectra agree
well with those of 4 and 5 and are consistent with the structure
shown in Figure 2. The 13C{1H} NMR spectra show at 144.0 (6)
and 144.1 (7) ppm triplets with a C-P coupling constant of 14.7
Hz and at 128.4 (6) and 128.3 (7) ppm singlets due to the CR and
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complexes were isolated as light orange (8) and yellow (9) oils in
86% and 90% yield, respectively, according to eq 4.
separation between the metal center and the carbonyl ligand
trans disposed to the first of them (Os-C(24) = 1.922(3) Å) is
longer (about 0.05 Å) than that between the metal center and the
carbonyl ligand trans disposed to the second one (Os-C(23) =
1.873(3) Å).
The IR, 1H, 13C{1H}, 31P{1H}, and 11B NMR spectra of 10
and 11 are consistent with the structure shown in Figure 3. In
agreement with the cis disposition of the carbonyl groups, the IR
spectra in dichloromethane show two ν(CO) bands at 1979 and
1913 cm-1 (10) and 1978 and 1910 cm-1 (11). The 1H NMR
spectra in benzene-d6 at room temperature contain two NH
resonances at 8.09 and 5.94 ppm (10) and 8.02 and 5.89 ppm
(11), revealing that in solution the boryl ligands do not rotate
around the Os-B bond and the nitrogen atoms of their
substituents lie in the plane perpendicular to the P-Os-P
direction. In the 13C{1H} NMR spectra, the OsCR resonances
of the alkynyl ligands are observed at 104.9 (10) and 105.1 (11)
ppm as triplets with C-P coupling constants of 16.0 and 16.1 Hz,
respectively, whereas the Cβ signals appear at 114.5 ppm for both
compounds. In agreement with equivalent trans phosphines, the
31P{1H} NMR spectra contain singlets at 4.6 (10) and 4.4 (11)
ppm. In the 11B NMR spectra the boron resonances appear at 44
(10) and 43 (11) ppm, shifted by 13 (10) and 12 (11) ppm to
lower field with regard to those of 4 and 5. This is consistent with
the π-donation decrease from the metal to the boron, as a
consequence of the carbonyl coordination, which is not com-
pensated by the amido substituents. In this context, it should be
mentioned thatthe B-N distancesin11of1.433(4) Å (B-N(1))
and 1.446(4) Å (B-N(2)) are statistically identical to those of 5
(B-N(1) = 1.434(7) Å and B-N(2) = 1.467(7) Å).
Complexes 10 and 11 are moderately stable in solution.
In toluene at 80 °C, they evolve into the aminoborylvinylidene
derivatives Os{dCdC(Ph)B(NHC6H4R)2}(CO)2(PiPr3)2 (R =
H (12), CH3 (13)), as a result of the migration of the
aminoboryl ligands from the metal centers to the Cβ atoms of
the alkynyl ligands. The weakening of the Os-B bonds, a con-
sequence of the CO coordination, facilitates the 1,3-boryl shifts.
The transformations are quantitative after 15 min. Complex 12
was isolated as a light yellow solid in 68% yield, whereas complex
13 was obtained as a light orange dry foam in 78% yield.
Complex 12 has been characterized by X-ray diffraction
analysis. The structure (Figure 4) proves the formation of the
unprecedented borylvinylidene ligand. The geometry around the
osmium atom can be described as a distorted trigonal bipyramid
with apical phosphines (P(1)-Os-P(2) = 171.08(4)°) and
inequivalent angles within the Y-shaped equatorial plane
(C(1)-Os-C(21) = 124.60(18)°, C(1)-Os-C(22) = 135.25-
(19)°, and C(21)-Os-C(22) = 100.0(2)°). The vinylidene
ligand is bound to the metal in a nearly linear fashion with an
Os-C(1)-C(2) angle of 176.6(3)°. The Os-C(1) and C-
(1)-C(2) bond lengths of 1.897(4) and 1.341(5) Å, respectively,
compare well with those found in other osmium-vinylidene
complexes and support the vinylidene formulation.14f,23,44
The six-coordinate nature of 8 and 9 is strongly supported by
their IR and 11B NMR spectra. The IR spectra in dichloro-
methane show the νasym(OCO) bands at 1601 (8) and 1613
(9) cm-1 and the νsym(OCO) bands at 1497 (8) and 1514 (9)
cm-1. The values of Δν (Δν = νasym(OCO) - νsym(OCO)) of
104 (8) and 99 (9) cm-1 are consistent with the bidentate
coordination mode of the acetate group.43 As expected for six-
coordinate osmium-boryl compounds,34c the boron resonances
in the 11B NMR spectra in benzene-d6, 37 ppm for 8 and 9,
appear significantly shifted toward lower field (by about 10 ppm)
with regard to those of the related five-coordinate derivatives. A
singlet at 25.2 ppm in the 31P{1H} NMR spectra is also
characteristic of these complexes.
3. Alkynyl-Aminoboryl to Aminoborylvinylidene Trans-
formation. Complexes 4 and 5 are also new examples of five-
coordinate unsaturated complexes that do not contain any
π-donor ligand. The coordination number six for both com-
pounds can be achieved by coordination of carbon monoxide.
Under an atmosphere of this gas, the toluene solutions of 4 and
5 afford the cis-dicarbonyl derivatives Os{B(NHC6H4R)2}-
(CtCPh)(CO)2(PiPr3)2 (R = H (10), CH3 (11)), which were
isolated as white solids in 86% (10) and 93% (11) yield,
according to Scheme 3.
Figure 3 shows a view of the X-ray structure of 11. The
coordination geometry around the osmium atom can be ratio-
nalized as a distorted octahedron with the phosphorus atoms of
the phosphine ligands occupying trans positions (P(1)-Os-
P(2) = 177.59(3)°). The perpendicular plane is formed by the
carbonyl groups cis disposed (C(23)-Os-C(24) = 99.30-
(13)°), the boryl trans disposed to C(24) (B-Os-C(24) =
169.65(12)°), and the alkynyl trans disposed to C(23) (C(1)-
Os-C(23) = 167.88(12)°). The Os-B bond length of 2.256(4)
Å is about 0.2 Å longer than those of 2, 3, and 5. This is consistent
with a decrease of the π-donation from the metal base frontier
orbitals into the empty boron p orbital, as a consequence of the
trans coordination of other π-acidic ligands like carbon mon-
oxide, which weakens the Os-B bond. According to the sp2
hybridization, the angles around the boron atom are between
117.9(2) and 123.4(2)°. The Os-C(1) distance of 2.087(3) Å is
statistically identical with the separation between the metal
center and the alkynyl ligand in 5. In agreement with the latter,
the C(1)-C(2) bond length and Os-C(1)-C(2) and C-
(1)-C(2)-C(3) angles are 1.211(4) Å and 174.1(3) and
178.8(3)°, respectively. As expected for a π-acidic character of
the boryl ligand higher than that of the alkynyl group, the
The 1H, 13C{1H}, 31P{1H}, and 11B NMR spectra of 12 and
13 in benzene-d6 at room temperature are consistent with the
structure shown in Figure 4. The 1H NMR spectra show the NH
resonances at 5.86 (12) and 5.80 (13) ppm. In the 13C{1H}
NMR spectra, the OsCR resonances appear at 297.7 (12) and
298.2 (13) ppm as triplets with C-P coupling constants of 17.2
and 16.9 Hz, respectively. The Cβ signals are observed at 137.0
(12) and 137.1 (13) ppm, also as triplets but with a C-P
coupling constant of 4.3 Hz. In the 31P{1H} NMR spectra, the
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Scheme 3
equivalent phosphines display a singlet at 23.0 ppm for both
compounds. The boron resonances in the 11B NMR spectra are
observed at 27 ppm (12 and 13).
by the same procedure as for 4and 5(Scheme 3). In toluene under a
carbon monoxide atmosphere, complexes 6 and 7 coordinate a
carbonyl group to afford the cis-dicarbonyl-alkynyl-boryl inter-
mediates Os{BF(NHC6H4R)}(CtCPh)(CO)2(PiPr3)2 (R = H
(15), CH3 (16)), which rapidly evolve into the vinylidenes Os-
{dCdC(Ph)BF(NHC6H4R)}(CO)2(PiPr3)2 (R = H (17), CH3
(18)) at room temperature. Complexes 17 and 18 are, however,
much less stable than 12 and 13 toward the deborylation. Traces of
water or of the acid used for the preparation of 6 and 7 prevent their
isolation as pure substances. Thus, amounts of 14 higher than 10%
always contaminate the samples. The alkynyl-boryl species 15 and
16 as well as their borylvinylidene tautomers 17 and 18 were fully
Complexes 12 and 13 react with methanol to give the
previously reported hydride-alkynyl derivative OsH(CtCPh)-
(CO)2(PiPr3)2 (14)36a,45 and CH3OB(NHC6H4R)2 (δ
,
11B
18.6). Its formation most probably takes place via the vinylidene
intermediate Os(dCdCHPh)(CO)2(PiPr3)2 (A), which under-
goes tautomerization. The difference in behavior between A and
the aminoboryl counterparts 12 and 13 is noteworthy. Since the
C-B bond energy is lower than C-H bond energy, the stability
of the aminoboryl-vinylidenes with regard to the corresponding
alkynyl-aminoboryl intermediates appears to be a consequence
of the very weak Os-B bonds in the latter.
1
characterized by H, 13C{1H}, 31P{1H}, 11B, and 19F NMR
spectroscopy.
The alkynyl-amino(fluoro)boryl complexes 6 and 7 can be
transformed into the corresponding amino(fluoro)borylvinylidenes
The NMR spectra of 15 and 16 in benzene-d6 at 12 °C
agree well with those of 10 and 11. The 1H NMR spectra show
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Figure 4. Molecular diagram of 12. Selected bond lengths (Å) and
angles (deg): Os-C(1) 1.897(4), C(1)-C(2) 1.341(5); P(1)-Os-P-
(2) 171.08(4), C(1)-Os-C(21) 124.60(18), C(1)-Os-C(22)
135.25(19), C(21)-Os-C(22) 100.0(2), Os-C(1)-C(2) 176.6(3).
Figure 3. Molecular diagram of 11. Selected bond lengths (Å) and angles
(deg): Os-B 2.256(4), Os-C(1) 2.087(3), C(1)-C(2) 1.211(4),
Os-C(24) 1.922(3), Os-C(23) 1.873(3), B-N(1) 1.433(4), B-N(2)
1.446(4); P(1)-Os-P(2) 177.59(3), C(23)-Os-C(24) 99.30(13),
B-Os-C(24) 169.65(12), C(1)-Os-C(23) 167.88(12), Os-C-
(1)-C(2) 174.1(3), C(1)-C(2)-C(3) 178.8(3), N(1)-B-N(2)
118.4(3), N(1)-B-Os 117.9(2), N(2)-B-Os 123.4(2).
Table 1. Rate Constants for the Alkynyl-Aminoboryl (10) to
Aminoborylvinylidene (12) Transformation
the NH-resonance at 7.94 (15) and 7.83 (16) ppm as doublets
with H-F coupling constants of 26.0 and 26.1 Hz, respectively.
The presence of two carbonyl ligands mutually cis disposed in
these compounds is strongly supported by the 13C{1H} NMR
spectra, which contain two triplets at 187.8 and 184.6 ppm (15)
and 187.9 and 184.7 ppm (16) with C-P coupling constants
between 8.1 and 7.7 Hz. The OsCR resonances of the alkynyl
ligands are observed at 104.3 (15) and 104.5 (16) ppm as triplets
with C-P coupling constants of 14.6 and 14.5 Hz, respectively,
whereas the Cβ resonances appear at 113.0 (15) and 112.9 (16)
ppm. The 31P{1H} NMR spectra show singlets at 6.8 (15) and
6.7 (16) ppm. Broad resonances at 49 (15) and 48 (16) ppm and
at -37.3 (15) and -38.5 (16) ppm in the 11B and 19F spectra,
respectively, are also characteristic of 15 and 16.
T (K)
kobs (ꢁ105 s-1
)
299
310
319
330
340
1.3
4.8
14.8
49.0
142.5
The 1H NMR spectra of 17 and 18 show the NH-resonances
at 6.57 (17) and 6.51 (18) ppm as doublets with a H-F coupling
constant of 20.1 Hz. In the 13C{1H} NMR spectra the OsCR
resonances of the vinylidene ligands appear at 302.3 (17) and
302.1 (18) ppm as triplets with C-P coupling constants of 12.3
and 11.9 Hz, respectively. Singlets at 22.7 (17) and 22.9 (18)
ppm in the 31P{1H} NMR spectra and broad resonances at 29
ppm (17 and 18) and at -107.4 (17) and -108.1 (18) ppm in
the 11B and 19F NMR spectra are also noticeable spectroscopic
features of these vinylidene derivatives.
Figure 5. Eyring plot of kobs for the formation of 12.
4. Mechanism of the Alkynyl-Aminoboryl to Aminoboryl-
vinylidene Transformation. The transformation of 10 to 12
was followed by 31P{1H} NMR spectroscopy. The decrease of 10
(with the corresponding increase of 12) in benzene-d6 is an
exponential function of time, in agreement with a first-order
process. The values obtained for the first-order rate constant kobs
in the temperature range studied are reported in Table 1. The
activation parameters for the tautomerization process were
obtained from the Eyring analysis shown in Figure 5, giving
The slightly negative value of the activation entropy suggests
that the migration of the aminoboryl group from the metal center
to the Cβ atom of the alkynyl ligand is an intramolecular process
that occurs by a mechanism with a geometrically highly oriented
transition state. To obtain information about its nature, we have
also performed DFT calculations (B3PW91) on the tautomer-
ization using PMe3 as model of PiPr3. The changes in free energy
ΔG have been computed at 298.15 K and P = 1 atm. Figure 6
shows the energy profile.
values of ΔHq = 23 ( 1 kcal mol-1 and ΔSq = -5 (
3
2 cal mol-1 K-1
.
3
3
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Figure 6. Energy profile (ΔG (kcal mol-1)) for the tautomerization process.
3
The aminoborylvinylidene complex Os{dCdC(Ph)B-
The procedure used to prepare the key alkynyl-boryl inter-
mediates is simple and unprecedented and should be applicable
to a wide range of transition metals. It starts from a tetrahydro-
borate complex, anilines, and a terminal alkyne. In contrast to
Lewis bases such as phosphines, phosphites, and carbon mon-
oxide, which abstract BH3 from the metal center, we have
discovered that the reactions of the tetrahydroborate complex
with anilines generate aminoboryl derivatives with one of the
amido substituents metalated by the phenyl. This metalated
group undergoes a σ-bond metathesis reaction with the terminal
alkyne to afford the alkynyl-boryl species.
Since fragments containing a C-B bond are established
members of the tools utilized in modern organic synthetic
chemistry47 and vinylidene complexes are intermediates in a
number of synthetically important transformations, one should
expect that borylvinylidene complexes will open routes to
prepare new tools for organic synthesis.
(NHPh)2}(CO)2(PMe3)2 (12t) is 7.0 kcal mol-1 more stable
3
than the alkynyl-aminoboryl tautomer Os{B(NHPh)2}-
(CtCPh)(CO)2(PMe3)2 (10t). The tautomerization takes
place via the transition state TS1, which lies 23.3 kcal mol-1
3
above 10t. The activation enthalpy and entropy of 22.0
kcal mol-1 and -4.4 cal mol-1 K-1, respectively, agree well
3
3
3
with the obtained experimental values. This activation barrier
compares well with those calculated by De Angelis and co-
workers13d and Grotjahn and co-workers13c for the unimolecular
hydride-alkynyl to vinylidene transformations promoted by
RhCl(PiPr3)246 and related rhodium systems.13b,13e
The transition state TS1 can be described as a μ2-η2-alkynyl
species37 where the bent alkynyl ligand (Os-C(1)-C(2) =
168.5° and C(1)-C(2)-C(3) = 165.8°) is σ-bonded to the
osmium atom of the metal fragment Os(CO)2(PMe3)2 (Os-
C(1) = 2.000 Å) and π-coordinated via the carbon-carbon triple
bond C(1)-C(2) (1.258 Å) to the boron atom of the aminoboryl
group. The coordination of the boron is unsymmetrical, the distance
to the R-carbon atom of the alkynyl bridge C(1) (1.731 Å) being
about 0.2 Å shorter than that to the β-carbon atom C(2) (1.940 Å).
’ EXPERIMENTAL SECTION
All reactions were carried out with rigorous exclusion of air using
Schlenk-tube techniques. Solvents were dried by standard procedures
and distilled under argon prior to use or obtained oxygen- and water-free
from MBraun solvent purification apparatus. The starting material
OsH(η2-H2BH2)(CO)(PiPr3)2 (1) was prepared by the published
method.28 Aniline, p-toluidine, and phenylacetylene were obtained from
commercial sources. Aniline and phenylacetylene were purified by
distillation, and p-toluidine was purified by sublimation in a Kugelrohr
distillation oven. 1H, 19F, 11B, 31P{1H}, and 13C{1H} NMR spectra were
recorded on either a Bruker ARX 300, Bruker Avance 300, Bruker
Avance 400, or Bruker Avance 500 MHz instrument. Chemical shifts
(expressed in parts per million) are referenced to residual solvent peaks
(1H, 13C{1H}), external H3PO4 (31P{1H}), BF3(OEt)2 (11B), or CFCl3
’ CONCLUDING REMARKS
This paper shows the discovery of the first transition me-
tal-borylvinylidene complexes and reveals that they can be
formed through alkynyl-boryl intermediates via unimolecular
1,3-boryl migration from the metal center to the Cβ atom of the
alkynyl ligand. Although a similar 1,3-hydrogen shift has been
proposed as the rate-determining step for the alkyne-vinylidene
tautomerization promoted by RhCl(PiPr3)2 and related rhodium
systems, this 1,3-boryl shift is the first process of this type
involving an atom other than hydrogen.
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(19F). Coupling constants, J and N, are given in hertz. Infrared spectra
were run on a Perkin-Elmer 1730 spectrometer as CH2Cl2 solutions. C,
H, N analyses were carried out in a Perkin-Elmer 2400 CHNS/O ana-
lyzer. High-resolution electrospray mass spectra were acquired using a
MicroTOF-Q hybrid quadrupole time-of-flight spectrometer (Bruker
Daltonics, Bremen, Germany). The intensity of the mass relative to
that of the base peak is given in parentheses after the found mass.
methanol (2.5 mL) at 0 °C afforded an orange solid, which was washed
with further portions of cold methanol and dried in vacuo. Yield: 223 mg
(68%). Anal. Calcd for C39H59BN2OOsP2: C, 56.11; H, 7.12; N, 3.36.
Found: C, 56.19; H, 7.26; N, 3.26. IR (CH2Cl2, cm-1):ν(CtC) 2073 (w);
ν(CO) 1875 (s). MS (HR-electrospray): m/z [M] calcd for C39H59-
BN2OOsP2 836.3814, found 836.3821 (4); [M] - [NHC6H5] calcd for
1
C33H53BNOOsP2 744.3312, found 744.3309 (100). H NMR (500.13
MHz, C6D6, 298 K): δ 7.58 (d, JH-H = 7.5, 2H, o-HPh), 7.15 (dd, JH-H
=
=
Preparation of Os{B(NHC6H5)NHCCHCHCHCHC}(CO)(PiP-
JH-H = 7.5, 2H, m-HPh), 6.98 (t, JH-H = 7.5, 1H, p-HPh), 6.95 (dd, JH-H
0
jj
j
r3)2 (2). A solution of OsH(η2-H2BH2)(CO)(PiPr3)2 (1) (230 mg,
0.41 mmol) in 8 mL of toluene was treated with 2.1 equiv of aniline
(79 μL, 0.87 mmol) and heated for 15 h under reflux. After being cooled
to room temperature, the resulting solution was filtered through Celite,
and the solvent was removed in vacuo. The residue was treated with
methanol (1.5 mL) at -78 °C to form an orange solid which was washed
with cold methanol (2 ꢁ 1.5 mL) and dried in vacuo. Yield: 276 mg
(91%). Anal. Calcd for C31H53BN2OOsP2: C, 50.81; H, 7.29; N, 3.82.
Found: C, 50.70; H, 7.19; N, 3.75. IR (CH2Cl2, cm-1): ν(CO) 1865 (s).
MS (HR-electrospray): m/z [M] - [2H] calcd for C31H51BN2OOsP2
0
JH-H = 7.3, 4H, m-Haniline), 6.86 (d, JH-H = 7.3, 4H, o-Haniline), 6.64 (t,
JH-H = 7.3, 2H, p-Haniline), 5.5 (br, 2H, NH), 2.80 (m, 6H, PCHCH3), 1.28
(dvt, N = 13.3, JH-H = 6.8, 18H, PCHCH3), 1.20 (dvt, N = 13.0, JH-H
=
6.5, 18H, PCHCH3). 31P{1H} NMR (202.5 MHz, C6D6, 298 K): δ 32.8
(s). 11B NMR (160.5 MHz, C6D6, 298 K): δ 31 (br). 13C{1H}-APT NMR
plus HMBC and HSQC (125.8 MHz, C6D6, 298 K): δ 196.3 (t, JC-P = 8.7,
CO), 144.0 (br, Cipso-aniline), 141.8 (t, JC-P = 15.4, OsCtC), 130.6 (s, o-
CPh), 129.3 (s, m-Caniline), 129.2 (s, m-CPh), 129.0 (s, Cipso-Ph), 128.5 (s,
OsCtC), 126.4 (s, p-CPh), 119.6 (s, p-Caniline), 119.3 (s, o-Caniline), 26.6
(vt, N = 24.9, PCHCH3), 20.5 and 20.4 (both s, PCHCH3).
Preparation of Os{B(NHC6H4CH3)2}(CtCPh)(CO)(PiPr3)2
(5). An orange solution of 3 (230 mg, 0.30 mmol) in 7 mL of toluene
was treated with 1.5 equiv of phenylacetylene (50.3 μL, 0.45 mmol) and
stirred for 3 h at room temperature. The resulting solution was filtered
through Celite, and the solvent was removed in vacuo. The addition of
methanol (2.5 mL) at 0 °C caused the precipitation of a dark red solid,
which was washed with further portions of cold methanol and dried in
vacuo. Yield: 188 mg (72%). Anal. Calcd for C41H63BN2OOsP2: C,
57.07; H, 7.36; N, 3.25. Found: C, 57.20; H, 7.19; N, 3.38. IR (CH2Cl2,
cm-1): ν(CtC) 2072 (w); ν(CO) 1874 (s). MS (HR-electrospray):
m/z [M] calcd for C41H63BN2OOsP2 864.4127, found 864.4103 (1.5);
[M] - [NHC6H4CH3] calcd for C34H55BNOOsP2 758.3469, found
758.3446 (100). 1H NMR (500.13 MHz, C6D6, 298 K): δ 7.59 (d, JH-H
1
732.3186, found 732.3167 (5). H NMR (500.13 MHz, THF-d8, 298
K): δ 7.28 (d, JH-H = 7.0, 1H, C6H4), 7.12 (dd, JH-H = JH-H = 7.5, 2H,
m-Haniline), 6.86 (d, JH-H = 7.5, 2H, o-Haniline), 6.74 (t, JH-H = 7.5, 1H,
p-Haniline), 6.68 (dd, JH-H = JH-H = 7.0, 1H, C6H4), 6.56 (dd, JH-H
JH-H = 7.0, 1H, C6H4), 6.47 (d, JH-H = 7.0, 1H, C6H4), 5.79 and 5.14
(both s, 2H, NH), 2.54 (m, 6H, PCHCH3), 1.17 (dvt, N = 12.8, JH-H
=
=
7.0, 18H, PCHCH3), 1.15 (dvt, N = 12.8, JH-H = 6.8, 18H, PCHCH3).
31P{1H} NMR (202.5 MHz, THF-d8, 298 K): δ 29.4 (s). 11B NMR
(160.5 MHz, THF-d8, 298 K): δ 29 (br). 13C{1H}-APT NMR plus
HMBC and HSQC (125.8 MHz, THF-d8, 298 K): δ 200.9 (t, JC-P = 8.6,
CO), 168.5 (t, JC-P = 11.2, OsC), 157.6 and 145.7 (both s, Cipso-NH),
139.7 (s, C6H4), 130.0 (s, m-Caniline), 123.6 (s, C6H4), 120.4 (s, p-
Caniline), 120.3 (s, o-Caniline), 119.4 and 111.5 (both s, C6H4), 27.5 (vt,
N = 24.7, PCHCH3), 20.4 (s, PCHCH3).
0
= 7.5, 2H, o-HPh), 7.16 (dd, JH-H = JH-H = 7.5, 2H, m-HPh), 6.99 (t,
JH-H = 7.5, 1H, p-HPh), 6.83 (d, JH-H = 7.3, 4H, o-Htoluidine), 6.79 (d,
Preparation of Os{B(NHC6H4CH3)NHCCHCHC(CH3)CHC}(CO)-
J
H-H = 7.3, 4H, m-Htoluidine), 5.5 (br, 2H, NH), 2.82 (m, 6H, PCHCH3),
jj
j
(PiPr3)2 (3). A solution of OsH(η2-H2BH2)(CO)(PiPr3)2 (1) (197 mg,
0.35 mmol) in 8 mL of toluene was treated with 2.1 equiv of p-toluidine
(80 mg, 0.75 mmol) and heated for 15 h under reflux. During this time the
solution changed from light yellow to orange. After being cooled to room
temperature, the resulting solution was filtered through Celite, and the
solvent was removed in vacuo. The residue was treated with methanol
(1.5 mL) at -78 °C to form an orange solid which was washed with cold
methanol (2 ꢁ 1.5 mL) and dried in vacuo. Yield: 252 mg (93%). Anal.
Calcd for C33H57BN2OOsP2: C, 52.10; H, 7.55; N, 3.68. Found: C, 52.31;
H, 7.48; N, 3.52. IR (CH2Cl2, cm-1): ν(CO) 1863 (s). MS (HR-
electrospray): m/z [M] - [2H] calcd for C33H55BN2OOsP2 760.3499,
found 760.3445 (4). 1H NMR (500.13 MHz, THF-d8, 298 K): δ 7.12 (s,
1H, C6H3), 6.93 (d, JH-H = 7.6, 2H, m-Htoluidine), 6.75 (d, JH-H = 7.6, 2H,
o-Htoluidine), 6.48 (d, JH-H = 7.2, 1H, C6H3), 6.33 (d, JH-H = 7.2, 1H,
C6H3), 5.60 and 5.00 (both s, 2H, NH), 2.53 (m, 6H, PCHCH3), 2.20 (s,
3H, C6H4-CH3), 2.15 (s, 3H, C6H3-CH3), 1.17 (dvt, N = 14.0, JH-H = 7.2,
18H, PCHCH3), 1.15 (dvt, N = 15.2, JH-H = 6.8, 18H, PCHCH3).
31P{1H} NMR (162.0 MHz, THF-d8, 298 K): δ 29.5 (s). 11B NMR (96.3
MHz, THF-d8, 298 K): δ 29 (br). 13C{1H}-APT NMR plus HMBC and
HSQC (100.6 MHz, THF-d8, 298 K): δ200.8 (t, JC-P = 8.6, CO), 168.6 (t,
JC-P = 11.5, OsC), 155.0 and 143.2 (both s, Cipso-NH), 140.8 (s, C6H3),
130.5 (s, m-Ctoluidine), 129.3 (s, C5H4C-CH3), 126.9 (s, C5H3C-CH3),
124.1 (s, C6H3), 120.4 (s, o-Ctoluidine), 111.0 (s, C6H3), 27.6 (vt, N = 24.7,
PCHCH3), 21.9 (s, C6H3-CH3), 20.9 (s, C6H4-CH3), 20.4 (s, PCHCH3).
Preparation of Os{B(NHC6H5)2}(CtCPh)(CO)(PiPr3)2 (4). An
orange solution of 2 (289 mg, 0.39 mmol) in 8 mL of toluene was treated
with 1.5 equiv of phenylacetylene (65.6 μL, 0.59 mmol) and stirred for 4 h
at room temperature. After this time, the mixture was filtered through Celite,
and the filtrate was evaporated to dryness in vacuo. The addition of
1.98 (s, 6H, CH3), 1.30 (dvt, N = 13.5, JH-H = 7.0, 18H, PCHCH3), 1.21
(dvt, N = 13.0, JH-H = 7.0, 18H, PCHCH3). 31P{1H} NMR (162.0
MHz, C6D6, 298 K): δ 33.9 (s). 11B NMR (128.4 MHz, C6D6, 298 K): δ
31 (br). 13C{1H}-APT NMR plus HMBC and HSQC (125.8 MHz,
C6D6, 298 K): δ 196.3 (t, JC-P = 7.0, CO), 142.0 (t, JC-P = 15.4,
OsCtC), 141.8 (s, Cipso-toluidine), 130.6 (s, o-CPh), 129.9 (s, m-
C
toluidine), 129.1 (s, m-CPh), 129.0 (s, Cipso-Ph), 128.4 (s, OsCtC),
128.0 (s, CCH3), 126.3 (s, p-CPh), 119.2 (s, o-Ctoluidine), 26.6 (vt, N =
24.8, PCHCH3), 21.0 (s, CH3), 20.5 and 20.4 (both s, PCHCH3).
Preparation of Os{BF(NHC6H5)}(CtCPh)(CO)(PiPr3)2 (6). An
orange solution of 4 (127 mg, 0.15 mmol) in 6 mL of toluene was treated
with 1.05 equiv of HBF4 OEt2 (21.9 μL, 0.16 mmol) and stirred for 3.30 h
3
at room temperature. The resulting mixture was filtered through Celite, and
the filtrate was evaporated to dryness in vacuo. The addition of an 8:1
pentane/diethyl ether mixture (2 and 0.3 mL) at 0 °C afforded an orange
solid, which was washed with further portions of cold pentane/diethyl ether
mixture (8:1) and dried in vacuo. Yield: 72 mg (62%). Anal. Calcd for
C33H53BFNOOsP2: C, 52.03; H, 7.01; N, 1.84. Found: C, 51.94; H, 6.85;
N, 1.63. IR (CH2Cl2, cm-1): ν(CtC) 2072 (w); ν(CO) 1904 (s). MS
(HR-electrospray):m/z[M] calcd for C33H53BFNOOsP2 763.3296, found
763.3180 (6); [M - H] - [BFNHC6H5] - [C8H5] calcd for C19H41-
OOsP2 539.2242, found 539.2241 (100). 1H NMR (300.13 MHz, C6D6,
298 K): δ 7.57 (d, JH-H = 7.5, 2H, o-HPh), 7.31 (d, JH-H = 7.2, 1H, o-
0
Haniline), 7.30 (d, JH-H = 7.2, 1H, o-Haniline), 7.15 (dd, JH-H = JH-H = 7.5,
4H, m-HPh (2H) þ m-Haniline (2H)), 6.99 (t, JH-H = 7.5, 1H, p-HPh), 6.77
(t, JH-H = 7.2, 1H, p-Haniline), 6.62 (d, JH-F = 21.9, 1H, NH), 2.83 (m, 6H,
PCHCH3), 1.22(dvt, N= 13.5, JH-H = 7.2, 18H, PCHCH3), 1.21(dvt, N=
12.9, JH-H = 6.9, 18H, PCHCH3). 31P{1H} NMR (121.5 MHz, C6D6, 298
K): δ 35.6 (s). 11B NMR (160.5 MHz, C6D6, 298 K): δ 28 (br). 19F NMR
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(282.4 MHz, C6D6, 298 K): δ -35.7 (br). 13C{1H}-APT NMR plus
HMBC and HSQC (75.5 MHz, C6D6, 298 K): δ 194.0 (t, JC-P = 7.8, CO),
144.0 (t, JC-P = 14.7, OsCtC), 144.0 (s, Cipso-aniline, overlapped with
OsCtC), 130.6 (s, o-CPh), 130.0 (s, m-Caniline), 129.2 (s, m-CPh), 128.4 (s,
OsCtC), 128.2 (s, Cipso-Ph), 126.3 (s, p-CPh), 120.2 (s, p-Caniline), 118.8
and 118.7 (both s, o-Caniline), 27.0 (vt, N = 25.4, PCHCH3), 20.4 (s,
PCHCH3).
oil. Yield: 137 mg (90%). Anal. Calcd for C35H61BN2O3OsP2: C, 51.21;
H, 7.49; N, 3.41. Found: C, 51.32; H, 7.41; N, 3.29. IR (CH2Cl2, cm-1):
ν(CO) 1868 (s); νasym(OCO) 1613 (s); νsym(OCO) 1514 (s). MS
(HR-electrospray): m/z [M] - [CH3COO] calcd for C33H58BN2-
OOsP2 763.3734, found 763.3784 (100). 1H NMR (300.13 MHz, C6D6,
298 K): δ 6.88-6.77 (m, 8H, o-Htoluidine þ m-Htoluidine), 6.38 and 5.70
(both s, 2H, NH), 2.48 (m, 6H, PCHCH3), 2.03 and 2.01 (both s, 6H,
CH3 of p-toluidine), 1.73 (s, 3H, CH3), 1.32 (dvt, N = 13.2, JH-H = 6.9,
18H, PCHCH3), 1.20 (dvt, N = 12.9, JH-H = 6.9, 18H, PCHCH3).
31P{1H} NMR (121.5 MHz, C6D6, 298 K): δ 25.2 (s). 11B NMR (96.3
MHz, C6D6, 298 K): δ 37 (br). 13C{1H}-APT NMR plus HMBC and
HSQC (75.5 MHz, C6D6, 298 K): δ 189.7 (t, JC-P = 9.7, CO), 181.6 (s,
CH3COO), 143.5 and 142.3 (both s, Cipso-toluidine), 129.8 and 129.7
(both s, m-Ctoluidine), 128.2 and 127.5 (both s, C-CH3), 119.6 and 119.5
(both s, o-Ctoluidine), 26.9 (vt, N = 23.8, PCHCH3), 26.3 (s, CH3COO),
21.0 (s, CH3), 20.4 and 20.2 (both s, PCHCH3).
Preparation of Os{BF(NHC6H4CH3)}(CtCPh)(CO)(PiPr3)2
(7). A red solution of 5 (139 mg, 0.16 mmol) in 7 mL of toluene was
treated with 1.05 equiv of HBF4 OEt2 (23.2 μL, 0.16 mmol) and stirred
3
for 3 h at room temperature. The red solution was filtered through
Celite, and the solvent was removed in vacuo. The addition of an 8:1
pentane/diethyl ether mixture (2 and 0.3 mL) at 0 °C caused the
precipitation of an orange solid, which was washed with further portions
of cold pentane/diethyl ether mixture (8:1) and dried in vacuo. Yield: 70
mg (56%). Anal. Calcd for C34H55BFNOOsP2: C, 52.64; H, 7.15; N,
1.81. Found: C, 52.53; H, 7.10; N, 1.74. IR (CH2Cl2, cm-1): ν(CtC)
2072 (w); ν(CO) 1902 (s). MS (HR-electrospray): m/z [M þ H] calcd
for C34H56BFNOOsP2 778.3531, found 778.3490 (5); [M - H] -
[BFNHC6H4CH3] - [C8H5] calcd for C19H41OOsP2 539.2242, found
Preparation of Os{B(NHC6H5)2}(CtCPh)(CO)2(PiPr3)2
(10). An orange solution of 4 (125 mg, 0.15 mmol) in 6 mL of toluene
was stirred under carbon monoxide atmosphere for 5 min at room
temperature. Immediately, the solution changed from red to light yellow.
After this time, the solution was concentrated to dryness. The addition of
methanol (2 mL) at -78 °C afforded a white solid, which was washed
with further portions of cold methanol and dried in vacuo. Yield: 111 mg
(86%). Anal. Calcd for C40H59BN2O2OsP2: C, 55.68; H, 6.89; N, 3.25.
Found: C, 55.98; H, 6.92; N, 3.39. IR (CH2Cl2, cm-1): ν(CtC) 2099
(w); ν(CO) 1979 (s), 1913 (s). MS (HR-electrospray): m/z [M þ H]
calcd for C40H60BN2O2OsP2 865.3841, found 865.3810 (13); [MH] -
[PiPr3] calcd for C31H39BN2O2OsP 705.2458, found 705.2447 (100).
1H NMR (300.13 MHz, C6D6, 298 K): δ 8.09 (s, 1H, NH), 7.60 (d,
0
539.2270 (100). 1H NMR(300.13 MHz, C6D6, 298K):δ 7.57(d, JH-H
=
7.5, 2H, o-HPh), 7.24 (d, JH-H = 8.2, 1H, o-Htoluidine), 7.23 (d, JH-H
=
0
8.2, 1H, o-Htoluidine), 7.15 (dd, JH-H = JH-H = 7.5, 2H, m-HPh), 6.98
(t, JH-H = 7.5, 1H, p-HPh), 6.96 (d, JH-H = 8.2, 2H, m-Htoluidine), 6.52
(d, JH-F = 21.9, 1H, NH), 2.83 (m, 6H, PCHCH3), 2.08 (s, 3H, CH3),
1.23 (dvt, N = 13.5, JH-H = 7.2, 18H, PCHCH3), 1.21 (dvt, N = 11.1,
J
H-H = 6.9, 18H, PCHCH3). 31P{1H} NMR (121.5 MHz, C6D6, 298
K): δ 35.5 (s). 11B NMR (96.3 MHz, C6D6, 298 K): δ 30 (br). 19F NMR
(282.4 MHz, C6D6, 298 K): δ -36.5 (br). 13C{1H}-APT NMR plus
HMBC and HSQC (75.5 MHz, C6D6, 298 K): δ 194.0 (t, JC-P = 7.7,
CO), 144.1 (t, JC-P = 14.7, OsCtC), 141.6 (s, Cipso-toluidine), 130.6
(s, o-CPh), 130.4 (s, m-Ctoluidine), 129.1 (s, m-CPh), 128.9 (s, C-CH3),
128.5 (s, Cipso-Ph), 128.3 (s, OsCtC), 126.3 (s, p-CPh), 118.8 and 118.7
(both s, o-Ctoluidine), 27.0 (vt, N = 25.3, PCHCH3), 21.0 (s, CH3), 20.4
(s, PCHCH3).
J
H-H = 7.5, 2H, o-HPh), 7.18 (dd, JH-H = JH-H = 7.5, 2H, m-HPh), 6.99
(t, JH-H = 7.5, 1H, p-HPh), 6.97-6.88 (m, 6H, o-Haniline (2H) þ m-
aniline (4H)), 6.78 (d, JH-H = 7.4, 2H, o-Haniline), 6.67 (t, JH-H = 7.4,
H
2H, p-Haniline), 5.94 (s, 1H, NH), 2.60 (m, 6H, PCHCH3), 1.33 (dvt, N
= 13.7, JH-H = 7.1, 18H, PCHCH3), 1.20 (dvt, N = 13.2, JH-H = 6.9,
18H, PCHCH3). 31P{1H} NMR (121.5 MHz, C6D6, 298 K): δ 4.6 (s).
11B NMR (160.5 MHz, C6D6, 298 K): δ 44 (br). 13C{1H}-APT NMR
Preparation of Os{B(NHC6H5)2}(K2-O2CCH3)(CO)(PiPr3)2
(8). An orange solution of 4 (129 mg, 0.15 mmol) in 7 mL of toluene
was treated with 15 equiv of CH3COOH (132 μL, 2.25 mmol) and
stirred for 2 h at room temperature. The solution was filtered through
Celite, and the solvent was removed in vacuo. Pentane (3 mL) was
added, and the resulting solution was dried in vacuo, giving a light orange
oil. Yield: 106 mg (86%). Anal. Calcd for C33H57BN2O3OsP2: C, 50.00;
H, 7.25; N, 3.53. Found: C, 50.18; H, 7.19; N, 3.45. IR (CH2Cl2, cm-1):
ν(CO) 1868 (s); νasym(OCO) 1601 (s); νsym(OCO) 1497 (s). MS
(HR-electrospray): m/z [M] - [CH3COO] calcd for C31H54BN2-
OOsP2 735.3420, found 735.3488 (100). 1H NMR (300.13 MHz, C6D6,
plus HMBC and HSQC (75.5 MHz, C6D6, 298 K): δ 192.1 (t, JC-P
=
7.7, CO), 183.4 (t, JC-P = 8.2, CO), 146.5 and 146.3 (both s, Cipso
-
aniline), 131.1 (s, o-CPh), 129.8 (s, Cipso-Ph), 129.3 (s, m-CPh), 129.1 (s,
m-Caniline), 126.0 (s, p-CPh), 120.3 and 120.1 (both s, o-Caniline), 120.0
(s, p-Caniline), 114.5 (s, OsCtC), 104.9 (t, JC-P = 16.0, OsCtC), 28.2
(vt, N = 26.9, PCHCH3), 20.6 and 20.0 (both s, PCHCH3).
Preparation of Os{B(NHC6H4CH3)2}(CtCPh)(CO)2(PiPr3)2
(11). A dark red solution of 5 (155 mg, 0.18 mmol) in 6 mL of toluene
was stirred under carbon monoxide atmosphere for 5 min at room
temperature. Immediately, the color of the solution changed from dark
red to light yellow. The resulting solution was then concentrated to
dryness. The addition of methanol (2 mL) at 0 °C afforded a white solid,
which was washed with further portions of cold methanol and dried in
vacuo. Yield: 149 mg (93%). Anal. Calcd for C42H63BN2O2OsP2: C,
56.62; H, 7.13; N, 3.14. Found: C, 56.79; H, 7.02; N, 3.06. IR (CH2-
Cl2, cm-1): ν(CtC) 2099 (w); ν(CO) 1978 (s), 1910 (s). MS (HR-
electrospray): m/z [M þ H] calcd for C42H64BN2O2OsP2 893.4155,
found 893.4123 (15); [MH] - [PiPr3] calcd for C33H42BN2O2OsP2
0
298 K): δ 6.98 (dd, JH-H = JH-H = 7.5, 4H, m-Haniline), 6.88 and 6.84
(both d, JH-H = 7.5, 2H þ 2H, o-Haniline), 6.69 and 6.67 (both t, JH-H
=
7.5, 1H þ 1H, p-Haniline), 6.44 and 5.75 (both s, 2H, NH), 2.46 (m, 6H,
PCHCH3), 1.72 (s, 3H, CH3), 1.29 (dvt, N = 13.4, JH-H = 7.1, 18H,
PCHCH3), 1.17 (dvt, N = 12.6, JH-H = 6.9, 18H, PCHCH3). 31P{1H}
NMR (121.5 MHz, C6D6, 298 K): δ 25.2 (s). 11B NMR (96.3 MHz,
C6D6, 298 K): δ 37 (br). 13C{1H}-APT NMR plus HMBC and HSQC
(75.5 MHz, C6D6, 298 K): δ 189.6 (t, JC-P = 9.7, CO), 181.7 (s,
CH3COO), 145.7 and 144.5 (both s, Cipso-aniline), 129.2 and 129.1
(both s, m-Caniline), 119.7 (s, o-Caniline and p-Caniline), 119.6 (s, o-
Caniline), 119.0 (s, p-Caniline), 26.9 (vt, N = 23.8, PCHCH3), 26.2 (s,
CH3COO), 20.3 and 20.1 (both s, PCHCH3).
1
733.2772, found 733.2789 (100). H NMR (400.16 MHz, C6D6, 298
K): δ 8.02 (s, 1H, NH), 7.60 (d, JH-H = 7.6, 2H, o-HPh), 7.20 (dd, JH-H
0
= JH-H = 7.6, 2H, m-HPh), 7.01 (t, JH-H = 7.6, 1H, p-HPh), 6.89-6.75
(m, 8H, C6H4NH), 5.89 (s, 1H, NH), 2.61 (m, 6H, PCHCH3), 2.01 (s,
6H, CH3), 1.34 (dvt, N = 13.2, JH-H = 6.8, 18H, PCHCH3), 1.22 (dvt, N
= 12.8, JH-H = 6.8, 18H, PCHCH3). 31P{1H} NMR (121.5 MHz, C6D6,
298 K): δ 4.4 (s). 11B NMR (128.4 MHz, C6D6, 298 K): δ 43 (br).
13C{1H}-APT NMR plus HMBC and HSQC (100.6 MHz, C6D6, 298
K): δ 192.2 (t, JC-P = 7.8, CO), 183.5 (t, JC-P = 8.2, CO), 144.3 and
144.0 (both s, Cipso-toluidine), 131.2 (s, o-CPh), 130.0 (s, Cipso-Ph),
Preparation of Os{B(NHC6H4CH3)2}(K2-O2CCH3)(CO)-
(PiPr3)2 (9). A red solution of 5 (160 mg, 0.18 mmol) in 7 mL of
toluene was treated with 15 equiv of CH3COOH (159 μL, 2.70 mmol)
and stirred for 2 h at room temperature. The solution was filtered
through Celite, and the solvent was removed in vacuo. Pentane (3 mL)
was added, and the resulting solution was dried in vacuo, giving a yellow
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129.7 (s, m-Ctoluidine), 129.0 (s, m-CPh), 128.8 and 128.5 (both s,
C-CH3), 125.9 (s, p-CPh), 120.2 and 119.9 (both s, o-Ctoluidine), 114.5
(t, JC-P = 2.3, OsCtC), 105.1 (t, JC-P = 16.1, OsCtC), 28.3 (vt, N =
26.8, PCHCH3), 21.0 and 20.8 (both s, CH3), 20.6 and 20.0 (both s,
PCHCH3).
Preparation of Os{BF(NHC6H5)}(CtCPh)(CO)2(PiPr3)2
(15). A Young cap NMR tube containing 6 (55 mg, 0.07 mmol) in
0.5 mL of C6D6 was sealed under CO atmosphere. The instantaneous
formation of complex 15 was observed in quantitative yield. 1H NMR
(400.13 MHz, C6D6, 285 K): δ 7.94 (d, JH-F = 26.0, 1H, NH), 7.58 (d,
JH-H = 7.6, 2H, o-HPh), 7.50 (d, JH-H = 7.6, 2H, o-Haniline), 7.18 (dd,
0
Preparation of Os{dCdC(Ph)B(NHC6H5)2}(CO)2(PiPr3)2
(12). A solution of 10 (110 mg, 0.13 mmol) in 6 mL of toluene was
heated at 353 K for 10 min. During this time, the color of the solution
changed from colorless to light yellow. The resulting mixture was filtered
through Celite, and the filtrate was evaporated. The residue was treated
with pentane at -78 °C to give a light yellow solid, which was washed
with further portions of cold pentane and dried in vacuo. Yield: 75 mg
(68%). Anal. Calcd for C40H59BN2O2OsP2: C, 55.68; H, 6.89; N, 3.25.
Found: C, 55.75; H, 6.76; N, 3.13. IR (CH2Cl2, cm-1): ν(CO) 1949 (s),
JH-H = JH-H = 7.6, 4H, m-HPh (2H)þ m-Haniline (2H)), 6.99 (t, JH-H
=
7.6, 1H, p-HPh), 6.81 (t, JH-H = 7.6, 1H, p-Haniline), 2.55 (m, 6H,
PCHCH3), 1.27 (dvt, N = 14.0, JH-H = 7.2, 18H, PCHCH3), 1.17 (dvt,
N = 13.4, JH-H = 7.0, 18H, PCHCH3). 31P{1H} NMR (162.0 MHz,
C6D6, 285 K): δ 6.8 (s). 11B NMR (96.3 MHz, C6D6, 285 K): δ 49 (br).
19F NMR (282.4 MHz, C6D6, 285 K): δ -37.3 (br). 13C{1H}-APT
NMR plus HMBC and HSQC (75.5 MHz, C6D6, 285 K): δ 187.8 (t,
JC-P = 7.7, CO), 184.6 (t, JC-P = 8.1, CO), 144.7 (s, Cipso-aniline),
1885 (s). MS (HR-electrospray): m/z [M
C40H60BN2O2OsP2 865.3841, found 865.3807 (0.3); [M] - [BN2C12-
H12] calcd for C28H47O2OsP2 669.2667, found 669.2662 (100). H
þ
H] calcd for
131.1 (s, o-CPh), 130.0 (s, m-Caniline), 129.1 (s, m-CPh), 128.6 (s, Cipso
-
Ph), 125.9 (s, p-CPh), 121.1 (s, p-Caniline), 119.3 and 119.2 (s, o-Caniline),
113.0 (s, OsCtC), 104.3 (t, JC-P = 14.6, OsCtC) 28.1 (vt, N = 27.3,
PCHCH3), 20.4 and 19.7 (both s, PCHCH3).
1
NMR (300.13 MHz, C6D6, 298 K): δ 7.55 (d, JH-H = 7.5, 2H, o-HPh),
0
Preparation of Os{BF(NHC6H4CH3)}(CtCPh)(CO)2(PiPr3)2
(16). This complex was prepared as described for 15, starting from 7
(0.057 mg, 0.07 mmol). 1H NMR (300.13 MHz, C6D6, 285 K): δ 7.83
7.19 (dd, JH-H = JH-H = 7.5, 2H, m-HPh), 7.01-6.95 (m, 5H, p-HPh
(1H) þ m-Haniline (4H)), 6.88 (d, JH-H = 7.4, 4H, o-Haniline), 6.72 (d,
JH-H = 7.4, 2H, p-Haniline), 5.86 (s, 2H, NH), 2.40 (m, 6H, PCHCH3),
1.20 (dvt, N = 13.3, JH-H = 6.9, 18H, PCHCH3), 1.17 (dvt, N = 14.1,
JH-H = 7.2, 18H, PCHCH3). 31P{1H} NMR (121.5 MHz, C6D6, 298
K): δ 23.0 (s). 11B NMR (160.5 MHz, C6D6, 298 K): δ 27 (br).
13C{1H}-APT NMR plus HMBC and HSQC (100.6 MHz, C6D6, 298
K): δ 297.7 (t, JC-P = 17.2, OsdC), 194.6 (t, JC-P = 7.9, CO), 194.3 (t,
JC-P = 8.3, CO), 144.9 (s, Cipso-aniline), 137.0 (t, JC-P = 4.3, OsdCdC),
130.8 (s, Cipso-Ph), 129.3 (s, m-Caniline), 128.9 (s, o-CPh), 128.6 (s, m-
CPh), 124.7 (s, p-CPh), 121.3 (s, o-Caniline), 121.2 (s, p-Caniline), 27.8 (vt,
N = 27.8, PCHCH3), 21.0 and 20.7 (both s, PCHCH3).
(d, JH-F = 26.1, 1H, NH), 7.56 (d, JH-H =7.6, 2H, o-HPh), 7.40 (d, JH-H
=
0
8.1, 2H, o-Htoluidine), 7.18 (dd, JH-H = JH-H = 7.6, 2H, m-HPh), 7.00
(t, JH-H = 7.6, 1H, p-HPh), 6.99 (d, JH-H = 8.1, 2H, p-Htoluidine), 2.58
(m, 6H, PCHCH3), 2.08 (s, 3H, CH3), 1.29 (dvt, N = 13.8, JH-H = 7.2,
18H, PCHCH3), 1.20 (dvt, N = 13.4, JH-H = 7.1, 18H, PCHCH3).
31P{1H} NMR (121.5 MHz, C6D6, 285 K): δ 6.7 (s). 11B NMR (96.3
MHz, C6D6, 285 K): δ 48 (br). 19F NMR (282.4 MHz, C6D6, 285 K):
δ -38.5 (br). 13C{1H}-APT NMR plus HMBC and HSQC (75.5 MHz,
C6D6, 285 K): δ 187.9 (t, JC-P = 7.7, CO), 184.7 (t, JC-P = 8.1, CO),
142.4 (s, Cipso-toluidine), 131.1 (s, o-CPh), 130.6 (s, m-Ctoluidine), 130.2
(s, C-CH3), 129.6 (s, Cipso-Ph), 129.1 (s, m-CPh), 125.9 (s, p-CPh), 119.2
Preparation of Os{dCdC(Ph)B(NHC6H4CH3)2}(CO)2-
(PiPr3)2 (13). A solution of 11 (0.128 mg, 0.14 mmol) in 6 mL of
toluene was heated at 353 K for 15 min. During this time, the solution
changed from colorless to light orange. The resulting mixture was
filtered through Celite, and the filtrate was evaporated. Pentane was
added, and the solvent was removed in vacuo, leading to the formation of
a dry light orange foam. Yield: 100 mg (78%). Anal. Calcd for
C42H63BN2O2OsP2: C, 56.62; H, 7.13; N, 3.14. Found: C, 56.75; H,
7.18; N, 3.21. IR (CH2Cl2, cm-1): ν(CO) 1948 (s), 1876 (s). MS (HR-
electrospray): m/z [M þ H] calcd for C42H64BN2O2OsP2 893.4160,
found 893.4122 (0.8); [M] - [BN2C14H16] calcd for C28H47O2OsP2
and 119.1 (s, o-Ctoluidine), 112.9 (t, JC-P = 2.0, OsCtC), 104.5 (t, JC-P
=
14.5, OsCtC), 28.1 (vt, N = 27.3, PCHCH3), 21.1 (s, CH3), 20.4 and
19.7 (both s, PCHCH3).
Preparation of Os{dCdC(Ph)BF(NHC6H5)}(CO)2(PiPr3)2
(17). The same sample used above in the preparation of the complex
15 was left to evolve in solution at room temperature to give complex 17.
This complex always appears contaminated with the compound OsH-
(CO)(CtCPh)(PiPr3)2 (14). 1H NMR (300.13 MHz, C6D6, 285 K): δ
7.82 (d, JH-H = 7.8, 2H, o-HPh), 7.43 (d, JH-H = 7.8, 2H, o-Haniline), 7.31
1
669.2667, found 669.2659 (100). H NMR (400.13 MHz, C6D6, 298
0
0
(dd, JH-H = JH-H = 7.8, 2H, m-HPh), 7.18 (dd, JH-H = JH-H = 7.8, 2H,
m-Haniline), 7.05 (t, JH-H = 7.8, 1H, p-HPh), 6.85 (t, JH-H = 7.8, 1H, p-
Haniline), 6.57 (d, JH-F = 20.1, 1H, NH), 2.31 (m, 6H, PCHCH3), 1.14
0
K): δ 7.59 (d, JH-H = 7.5, 2H, o-HPh), 7.20 (dd, JH-H = JH-H = 7.5, 2H,
m-HPh), 6.96 (t, JH-H = 7.5, 1H, p-HPh), 6.87 (d, JH-H = 9.4, 4H, o-
Htoluidine), 6.82 (d, JH-H = 9.4, 4H, m-Htoluidine), 5.80 (s, 2H, NH), 2.41
(m, 6H, PCHCH3), 2.04 (s, 6H, CH3), 1.23 (dvt, N = 13.6, JH-H = 7.2,
18H, PCHCH3), 1.18 (dvt, N = 14.0, JH-H = 7.2, 18H, PCHCH3).
31P{1H} NMR (162.0 MHz, C6D6, 298 K): δ 23.0 (s). 11B NMR (128.4
MHz, C6D6, 298 K): δ 27 (br). 13C{1H}-APT NMR plus HMBC and
HSQC (100.6 MHz, C6D6, 298 K): δ 298.2 (t, JC-P = 16.9, OsdC),
(dvt, N = 13.5, JH-H = 7.2, 18H, PCHCH3), 1.12 (dvt, N = 13.5, JH-H
=
7.9, 18H, PCHCH3). 31P{1H} NMR (121.5 MHz, C6D6, 285 K): δ 22.7
(s). 11B NMR (96.3 MHz, C6D6, 285 K): δ 29 (br). 19F NMR (282.4
MHz, C6D6, 285 K): δ -107.4 (br). 13C{1H}-APT NMR plus HMBC
and HSQC (75.5 MHz, C6D6, 285 K): δ 302.3 (t, JC-P = 12.3, OsdC),
194.1 (t, JC-P = 7.9, CO), 193.7 (t, JC-P = 8.3, CO), 143.7 (s, Cipso
-
194.8 (t, JC-P = 8.0, CO), 194.5 (t, JC-P = 8.3, CO), 142.5 (s, Cipso
-
aniline), 135.7 (t, JC-P = 9.1, OsdCdC), 130.0 (s, m-Caniline), 128.6 (s,
m-CPh), 128.4 (s, o-CPh), 128.1 (s, Cipso-Ph), 124.9 (s, p-CPh), 121.8 (s,
p-Caniline), 119.3 and 119.2 (both s, o-Caniline), 27.8 (vt, N = 28.0,
PCHCH3), 20.9 and 20.6 (both s, PCHCH3).
Preparation of Os{dCdC(Ph)BF(NHC6H4CH3)}(CO)2-
(PiPr3)2 (18). The same sample used above in the preparation of the
complex 16 was left to evolve in solution at room temperature to give
complex 18. This complex always appears contaminated with the
compound OsH(CO)(CtCPh)(PiPr3)2 (14). 1H NMR (300.13
toluidine), 137.1 (t, JC-P = 4.3, OsdCdC), 130.8 (s, Cipso-Ph), 130.0
(s, C-CH3), 129.9 (s, m-Ctoluidine), 128.8 (s, o-CPh), 128.6 (s, m-CPh),
124.6 (s, p-CPh), 121.3 (s, o-Ctoluidine), 27.8 (vt, N = 27.7, PCHCH3),
21.1 (s, CH3), 21.0 and 20.8 (both s, PCHCH3).
Reaction of 12 and 13 with Methanol: Formation of OsH-
(CtCPh)(CO)2(PiPr3)2 (14). A solution of 12 (110 mg, 0.13 mmol)
or 13 (115 mg, 0.13 mmol) in 6 mL of toluene was treated with 0.5 mL of
methanol. The mixture was stirred for 2 h at room temperature. After
this time the solution was filtered through Celite, and the solvent was
removed in vacuo. The addition of methanol (1.5 mL) at -78 °C caused
the precipitation of a white solid, which was washed with cold methanol
and dried in vacuo. Yield: 78 mg (92%). The spectroscopic data of the
solid agree well with those previously reported for 14.36a
MHz, C6D6, 285 K): δ 7.83 (d, JH-H = 7.8, 2H, o-HPh), 7.39 (d, JH-H
=
0
8.0, 2H, o-Htoluidine), 7.31 (dd, JH-H = JH-H = 7.8, 2H, m-HPh), 7.00
0
(d, JH-H = JH-H = 8.0, 2H, m-Htoluidine), 6.99 (t, JH-H = 7.8, 1H, p-
HPh), 6.51 (d, JH-F = 20.1, 1H, NH), 2.32 (m, 6H, PCHCH3), 2.11 (s,
3H, CH3), 1.15 (dvt, N = 13.8, JH-H = 6.9, 18H, PCHCH3), 1.12 (dvt,
2260
dx.doi.org/10.1021/ja109691v |J. Am. Chem. Soc. 2011, 133, 2250–2263

Journal of the American Chemical Society
ARTICLE
N = 14.1, JH-H = 7.2, 18H, PCHCH3). 31P{1H} NMR (121.5 MHz,
C6D6, 285 K): δ 22.9 (s). 11B NMR (96.3 MHz, C6D6, 285 K): δ 29
(br). 19F NMR (282.4 MHz, C6D6, 285 K): δ -108.1 (br). 13C{1H}-
APT NMR plus HMBC and HSQC (75.5 MHz, C6D6, 285 K): δ
302.1 (t, JC-P = 11.9, OsdC), 194.2 (t, JC-P = 7.8, CO), 193.8 (t,
JC-P = 8.3, CO), 141.2 (s, Cipso-toluidine), 135.8 (t, JC-P = 8.6,
OsdCdC), 130.6 (s, m-Ctoluidine), 128.7 (s, Cipso-Ph), 128.6 (s, m-
CPh), 128.3 (s, o-CPh), 125.2 (s, p-CPh), 119.4 and 119.3 (both s, o-
Ctoluidine), 27.8 (vt, N = 28.0, PCHCH3), 21.0 (s, CH3), 20.9 and 20.7
(both s, PCHCH3).
Kinetic Analysis for the Alkynyl-Aminoboryl (10) to
Aminoborylvinylidene (12) Transformation. The transforma-
tion of 10 to 12 was followed quantitatively by 31P{1H} NMR spectros-
copy in C6D6. The decrease of the intensity of the phosphorus resonance
was measured automatically at intervals in a Bruker ARX-300 spectro-
meter. Activation parameters ΔHq and ΔSq were obtained by least-
squares fit of the Eyring plot. Errors were computed according to
published methods.48
Computational Details. The theoretical calculations were car-
ried out on the model complexes by optimizing the structure at the
B3PW91-DFT levels with the Gaussian 03 program.49 The basis sets
used were LANL2DZ basis and pseudopotentials for Os, and 6-31G(d,
p) for the rest of the atoms. The transition state has been found by
carrying out potential energy surfaces of the process following the
reaction coordinates, optimizing the maxima, and confirming by fre-
quency calculations. The connections between the starting and final
reactants have been checked by slightly perturbing the TS geometry
toward the minimum geometries and reoptimizing.
Structural Analysis of Complexes 2, 3, 5, 11, and 12. X-ray
data were collected on a Bruker Smart APEX CCD (2, 3, 5, 12) and an
Oxford Diffraction Xcalibur TS (11) instrument using graphite mono-
chromated Mo KR radiation (λ = 0.71073 Å). Data were collected over
the complete sphere and were corrected for absorption by using a
multiscan method applied with the CrisAlys RED package50 for
complex 11 and with SADABS for 2, 3, 5, and 12.51 The structures
were solved by direct methods. Refinement of complexes was
performed by full-matrix least-squares on F2 with SHELXL97,52
including isotropic and subsequently anisotropic displacement param-
eters. The disordered groups observed along all the structures were
refined with two moieties, complementary occupancy factors, and
isotropic thermal parameters.
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’ ASSOCIATED CONTENT
S
Supporting Information. Crystal details for 2, 3, 5, 11,
b
and 12; spectroscopic data for 14; complete ref 49; optimized
coordinates for complexes 10t, TS1, and 12t; and CIF files giving
crystal data for 2, 3, 5, 11, and 12. This material is available free of
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’ AUTHOR INFORMATION
Corresponding Author
maester@unizar.es; mbuil@unizar.es
’ ACKNOWLEDGMENT
(14) (a) de los Ríos, I.; Jimꢀenez-Tenorio, M.; Puerta, M. C.; Valerga,
P. J. Chem. Soc., Chem. Commun. 1995, 1757. (b) de los Ríos, I.; Jimꢀenez-
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Crochet, P.; Esteruelas, M. A.; Gutiꢀerrez-Puebla, E.; Lꢀopez, A. M.;
Dedicated to the memory of Prof. Rafael Suau. Financial
support from the MICINN of Spain (project number
CTQ2008-00810 and Consolider Ingenio 2010 CSD2007-
00006), the Diputaciꢀon General de Aragꢀon (E35), and the
European Social Fund is acknowledged. K.G. thanks the Spanish
MEC for a grant.
2261
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Journal of the American Chemical Society
ARTICLE
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