Reactions of [Re(NO)2(PR3)2][BAr F4] complexes with phenylacetylene

Article abstract of DOI:10.1023/B:RUCB.0000041309.19570.1d

The reaction of [Re(NO)₂(PR₃)₂][BAr ^F₄] (R = cyclo-C₆H₁₃ (1a), Pr ⁱ (1b); [BAr^F₄]^- = [B(3,5-(CF ₃)₂C₆H₃)₄]) with phenylacetylene in the presence of a non-nucleophilic base, like 2,6-bis(tert-butyl)pyridine (BTBP) or Bu^tOK, affords the phenylethynyl complexes [Re(C≡CPh)(NO)₂(PR₃) ₂] (R = cyclo-C₆H₁₃ (2a); Prⁱ (2b)) in moderate yields. In the absence of a base, complexes 1a and 1b are transformed into the compounds [Re(C≡CPh)(CH=C(Ph)ONH)(NO)(PR ₃)₂][BAr^F₄] (3a and 3b, respectively). The structure of complex 3a was confirmed by X-ray diffraction analysis. The latter reaction is proposed to be initiated by deprotonation of the terminal alkyne H atom by the bent nitrosyl ligand followed by the subsequent 1,3-dipolar addition of the ReN(H)O moiety to phenylacetylene.

Full text of DOI:10.1023/B:RUCB.0000041309.19570.1d

1116
Russian Chemical Bulletin, International Edition, Vol. 53, No. 5, pp. 1116—1120, May, 2004
Reactions of [Re(NO)2(PR3)2][BArF ] complexes with phenylacetylene*
4
C. M. Frech, A. Llamazares, M. Alfonso, H. W. Schmalle, and H. Berkeꢀ
Department of Inorganic Chemistry, University of Zurich,
8057 Zurich, Switzerland.
Eꢀmail: chfrech@aci.unizh.ch
–
The reaction of [Re(NO)2(PR3)2][BArF4] (R = cycloꢀC6H13 (1a), Pri (1b); [BArF
]
=
4
[B(3,5ꢀ(CF3)2C6H3)4]) with phenylacetylene in the presence of a nonꢀnucleophilic base, like
2,6ꢀbis(tertꢀbutyl)pyridine (BTBP) or ButOK, affords the phenylethynyl complexes
[Re(C≡CPh)(NO)2(PR3)2] (R = cycloꢀC6H13 (2a); Pri (2b)) in moderate yields. In the
absence of
a base, complexes 1a and 1b are transformed into the compounds
[Re(C≡CPh)(CH=C(Ph)ONH)(NO)(PR3)2][BArF4] (3a and 3b, respectively). The structure
of complex 3a was confirmed by Xꢀray diffraction analysis. The latter reaction is proposed to be
initiated by deprotonation of the terminal alkyne H atom by the bent nitrosyl ligand followed
by the subsequent 1,3ꢀdipolar addition of the ReN(H)O moiety to phenylacetylene.
Key words: rhenium, dinitrosyl complexes, phenylacetylene, alkynyl complexes, 1,3ꢀdipoꢀ
lar addition.
Scheme 1
A common method to prepare alkynyl complexes utiꢀ
lizes the reaction of transition metal complexes with terꢀ
minal acetylenes. After coordination, the acetylenic C—H
bond gets activated through oxidative addition1 or σꢀbond
metathesis2 to afford an alkynylꢀhydride or an alkynyl
complex. The subsequent rearrangement of the alkyne or
the alkynylꢀhydride species into a vinylidene compound
is a very versatile transformation.3 Several catalytic cycles
have been proposed to involve the participation of the
η2ꢀalkyne→η1ꢀvinylidene rearrangement.4 In attempt to
synthesize alkynyl (or vinylidene) complexes of the
[Re(NO)2(PR3)2]+ fragment, these cationic species5 were
treated with phenylacetylene in the absence and presence
of a base leading to different products.
R = cycloꢀC6H13 (a), Pri (b)
B is base
Results and Discussions
the signals of 1a and 1b was observed. Complete converꢀ
sion was achieved in few minutes indicated by a color
change from dark red to orangeꢀyellow. The 1H and
13C{1H} NMR data are consistent with trigonal biꢀ
pyramidal structures of [Re(C≡CPh)(NO)2(PR3)2] comꢀ
plexes with R = cycloꢀC6H13 (2a) and R = Pri (2b). Inꢀ
deed, the 13C{1H} NMR spectra of 2a and 2b in C6D6
show at 20 °C Cα triplets at δ 128.7 for 2a and at 128.9 for
2b and Cβ singlets at δ 118.0 (2a) and 118.2 (2b), in
addition to the resonances assigned to the phenyl subꢀ
stituents of the phenylethynyl ligands (see Scheme 1).
The IR spectra of both compounds exhibit two intense
and characteristic bands at ~1610 and ~1570 cm–1 attribꢀ
utable to vibrations of two nitrosyl ligands. Additionally,
weak bands were observed at ν ≈ 2070 cm–1 for both
Treatment of [Re(NO)2(PR3)2][B(3,5ꢀ(CF3)2C6H3)4]
(R = cycloꢀC6H13 (1a), R = Pri (1b)) with lithium
phenylacetylide resulted in an inseparable mixture of yet
unidentified products. When benzene solutions of comꢀ
plexes 1a and 1b were reacted with a large excess of
phenylacetylene at room temperature in the presence of a
nonꢀnucleophilic base, like 2,6ꢀbis(tertꢀbutyl)pyridine
(BTBP) or ButO–, new 31P NMR signals appeared arising
from the formation of alkynyl complexes (δ 21.7 for 2a
and δ 28.1 for 2b) (Scheme 1). Concomitant decrease of
* Materials were presented at the VII International Conference
on the Chemistry of Carbenes and Related Intermediates
(Kazan, 2003).
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1072—1076, May, 2004.
1066ꢀ5285/04/5305ꢀ1116 © 2004 Plenum Publishing Corporation

Reactions of [Re(NO)2(PR3)2][BArF
]
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 5, May, 2004
1117
4
compounds due to the C≡C moieties.6 Symmetric bondꢀ
stretching vibrations (a1g) are expected to appear as strong
bands in the solid state Raman spectra of the complexes.
Indeed, they revealed an intense and characteristic emisꢀ
sion at ν ≈ 2075 cm–1, which confirms the presence of the
C≡C unit. Alkynyl complexes 2 were isolated by extracꢀ
tion with pentane in moderate yields.
When the alkyne was added to benzene solutions of
complexes 1 in the absence of a base, an unexpected
cyclization reaction occurred involving one of the NO
ligands, which confirms their high reactivity in such sysꢀ
tems (Scheme 2, anions are not shown).*,**,7 After the
addition of the alkyne, a black oily precipitate was slowly
formed. The reaction was completed within 30 min.
olefinic region were observed. The 13C{1H} NMR specꢀ
trum demonstrates for both complexes the presence of
aromatic carbon atoms and the phosphine ligands by adꢀ
ditional triplets at δ 129.8 (3a) and 129.6 (3b), as well as
singlets of very low intensity at δ 115.1 (3a) and 114.9
(3b), which were attributed to the ethynyl C atoms. The
resonances for the three carbon atoms at δ 171.1, 129.6,
and 114.9 correlate in a long range H—C correlation NMR
experiment with the N—H proton of 3b, which indicates
the formation of an unsaturated cyclic (chelating) ligand
including one of the nitrosyl ligands.
The IR spectra of these complexes show an intense
and characteristic band for the remaining nitrosyl ligands
at ν ≈ 1710 cm–1 and another one at ν ≈ 1610 cm–1
attributable to the HNO units and two weak absorptions
at ν ≈ 2240 cm–1 and at ν ≈ 2090 cm–1. The band at lower
wavenumbers might be due to the C≡C moieties, while
those at higher wavenumbers are due to (N—H) vibraꢀ
tions. The solid state Raman spectra of complexes 3a,b
exhibit a weak band at ν ≈ 2090 cm–1 corresponding to an
a1g vibration of the C≡C unit.6
Scheme 2
However, based on these spectroscopic data, the strucꢀ
tures of compounds 3 could not be assigned with certainty
and, therefore, their structures were established by an
exemplary Xꢀray diffraction study on a single crystal of 3a
(Fig. 1). Single crystals were grown by slow evaporation
P(2)
C(10)
H(9)
C(9)
C(2)
C(1)
O(2)
H(2)
N(1)
O(1)
Re(1)
N(2)
P(1)
R = cycloꢀC6H13 (a), Pri (b)
Monitoring the reaction course by 31P NMR spectrosꢀ
copy showed the formation of one major product. Unforꢀ
tunately, attempts to isolate the compound in pure form
Fig. 1. Molecular structure of 3a (20% probability displacement
ellipsoids). Selected bond distances (Å): Re(1)—N(1) 1.809(7),
N(1)—O(1) 1.173(8), Re(1)—C(1) 2.124(6), C(1)—C(2)
1.185(8), Re(1)—C(9) 2.095(7), C(9)—C(10) 1.317(8),
C(10)—O(2) 1.392(8), O(2)—N(2) 1.345(7), Re—N(2) 1.988(5).
Main bond angles (deg): N(1)—Re(1)—N(2) 93.5(3),
N(2)—Re(1)—C(9) 73.5(2), C(9)—Re(1)—C(1) 91.3(3),
N(1)—Re(1)—C(1) 101.7(3), Re(1)—N(1)—O(1) 171.3(5),
Re(1)—N(2)—O(2) 123.0(4), Re(1)—C(9)—C(10) 116.9(5),
C(9)—C(10)—O(2) 116.1(6), Re(1)—C(1)—C(2) 177.0(6).
Counterion [B(3,5ꢀ(CF3)2C6H3]– and H atoms, except H(9)
and H(2), were omitted for clarity.
1
were not successful. The 13C{1H} and H NMR spectroꢀ
scopic investigations in solution allowed structural asꢀ
signments. The 1H NMR spectra of 3a and 3b in THFꢀd8
at 20 °C reveal in addition to the aromatic protons and
those of the phosphine ligands a triplet at δ 8.94 and 9.08
for 3a and 3b, respectively, consistent with an Nꢀprotoꢀ
nated NO moiety.** In addition, small resonances in the
* C. M. Frech and H. Berke, unpublished results.
** A. Llamazares and H. Berke, unpublished results.

1118
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 5, May, 2004
Frech et al.
distilled over Na, and degassed prior to use. All the chemicals
were purchased from Aldrich or Fluka. Unless otherwise stated,
all reagents were used without further purification. Compounds
[Re(NO)2(PR3)2][BArF4] (1) were synthesized according to pubꢀ
lished procedures.5
Elemental analyses were performed on a Leco CHNSꢀ932
analyzer at the University of Zurich, Switzerland. The 1H,
13C{1H} and 31P{1H} NMR spectra were recorded on a Bruker
Avance DRX500 spectrometer. Chemical shifts are expressed in
ppm referenced to C6D6 or THFꢀd8. All chemical shifts for
31P{1H} NMR data are reported downfield in ppm relative to
external 85% H3PO4 at 0.0 ppm. Processing and analyses of the
spectra were done using the Bruker XWINNMR software.
IR spectra were obtained by using KBr pellets with a BioꢀRad
FTSꢀ45 FTIR spectrometer. Raman spectra were recorded on a
of a concentrated benzene solution at 25 °C. The rheꢀ
nium center was found to be in a pseudoꢀoctahedral enviꢀ
ronment with the alkynyl moiety and the remaining niꢀ
trosyl ligand in transꢀarrangement. The C(1)—C(2) and
Re(1)—C(1) distances are typical of an alkynyl moiety
(1.185(8) and 2.124(6) Å, respectively). The C(9)—C(10)
bond distance is 1.373(12) Å, clearly indicating double
bond character and being consistent with the formation
of the σꢀN,C2ꢀ(Oꢀ1ꢀphenylethenylhydroxylamidoꢀC2)yl
ligand. The hydrogen H(2) atom was found in the differꢀ
ence Fourier map and refined isotropically.
The proposed mechanism for these unexpected reacꢀ
tions of 1a and 1b is depicted in Scheme 2. The initial
reaction step is believed to be the formation of alkyne
complexes. Interestingly enough that the following step
requires a nitrosyl ligand to act as a base and thereafter
the formed Re—N(H)—O moiety to act as a 1,3ꢀdipole.
This suggestion gains support from NMR studies of reꢀ
acting compounds 1a and 1b with phenylacetylene at
low temperatures in tolueneꢀd8. These studies reveal
resonances consistent with the formation of πꢀacetylene
intermediates. Raising the temperature to 25 °C afꢀ
forded immediately 3a and 3b without further detectable
intermediates. The reaction is accompanied by a color
change from yellow to black. The increased acidity of the
coordinated terminal alkyne group allows deprotonation
with even weak bases. When no external base is present,
phenylacetylene is deprotonated by a bent and thereꢀ
fore basic nitrosyl ligand, similar to the reaction of
[Re(H)(NO)2(PR3)2] compounds with trifluoromethaneꢀ
sulfonic acid or HBF4.* This HNO complex is then
trapped by a second phenylacetylene molecule. Similarly
to a 1,3ꢀdipolar addition reaction, the Re—N(H)—O moiꢀ
ety adds to the acetylene to yield complexes 3a and 3b
(see Scheme 2).
Renishaw Ramanscope spectrometer (λ = 514 nm).
exc
σꢀPhenylethynyldinitrosoꢀbis[tri(cyclohexyl)phosphine]rheꢀ
nium(I) (2a) and σꢀphenylethynyldinitrosoꢀbis(triisopropylphosꢀ
phine)rhenium(I) (2b). An excess of phenylacetylene was added
to solutions of complexes 1 (80 mg) in benzene (10 mL) conꢀ
taining 1 equiv. of 2,6ꢀbis(tertꢀbutyl)pyridine at 25 °C accompaꢀ
nied by a color change from dark red to orangeꢀyellow. After
stirring the reaction mixture for ~15 min, the solvent was reꢀ
moved under reduced pressure. The product was extracted with
pentane (3×10 mL) followed by filtration. The orangeꢀyellow
solution was dried in vacuo. The products can be recrystallized
from a toluene—pentane mixture at –30 °C. The yields were
20.1 mg (53% for 2a) and 21.2 mg (56% for 2b).
Compound 2a. Found (%): C, 57.81; H, 8.11; N, 2.94.
C
44H71N2O2P2Re. Calculated (%): C, 58.19; H, 7.88; N, 3.08.
IR, ν/cm–1: 1571, 1609 (both s, NO); 2077 (w, C≡C). Raman,
ν/cm–1: 2079 (s, C≡C). 1H NMR (C6D6, 25 °C), δ: 0.97—2.48
(m, 66 H, P(C6H11)3); 6.92—7.49 (m, C≡CPh). 13C{1H} NMR
(C6D6, 25 °C), δ: 26.8, 28.1, 30.3 (all s, P(C6H11)3); 36.5 (t,
P(C6H11), JP,C = 10 Hz); 118.0 (s, C≡CPh); 128.7 (t, C≡CPh,
JP,C = 20 Hz); 125.4, 126.1, 129.8, 135.4 (all s, C≡C(C6H5)).
31P{1H} NMR (C6D6, 25 °C), δ: 21.7 (s, P(C6H11)3).
Compound 2b. Found (%): C, 46.82; H, 7.29; N, 3.92.
C26H47N2O2P2Re. Calculated (%): C, 46.76; H, 7.09; N, 4.19.
IR, ν/cm–1: 1574, 1612 (both s, NO); 2072 (w, C≡C). Raman,
ν/cm–1: 2075 (s, C≡C). 1H NMR (C6D6, 25 °C), δ: 1.25 (m,
36 H, P{CHMe2}3); 2.49 (m, 6 H, P{CHMe2}3); 6.96—7.45
(m, C≡CPh). 13C{1H} NMR (C6D6, 25 °C), δ: 20.1 (s,
P{CH(CH3)2}); 26.8 (t, P{CHMe2}, JP,C = 12 Hz); 118.2
(s, C≡CPh); 128.9 (t, C≡CPh, JP,C = 20 Hz); 125.6, 126.3,
130.0, 135.8 (all s, C≡C(C6H5)). 31P{1H} NMR (C6D6, 25 °C),
δ: 28.1 (s, P{CHMe2}3).
Thus, we have synthesized new rhenium phenylꢀ
ethynyldinitrosylbisphosphine complexes by the addition
of phenylacetylene to the 16ꢀelectron [Re(NO)2(PR3)2]+
cations and deprotonation with a base. In the absence of a
base, the alkyne complexes are deprotonated by one of
the nitrosyl ligands, which initiates a cyclization reaction
including a nitrosyl ligand and a second phenylacetylene
molecule.
2
κ ꢀN,C2ꢀ[Oꢀ(1ꢀPhenylvinyl)hydroxylamidoꢀC2ꢀyl]ꢀσꢀpheꢀ
nylethynylꢀbis[tri(cyclohexyl)phosphine]rhenium(III) tetra[3,5ꢀ
di(trifluoromethyl)phenyl]borate (3a) and κ ꢀN,C2ꢀ[Oꢀ(1ꢀphenylꢀ
2
Experimental
vinyl)hydroxylamidoꢀC2ꢀyl]ꢀσꢀphenylethynylꢀbis[triisopropylꢀ
phosphine]rhenium(III) tetra[3,5ꢀdi(trifluoromethyl)phenyl]borate
(3b). A large excess of phenylacetylene was added to solutions of
complexes 1 (50 mg) in benzene (10 mL), and the mixture was
stirred for 30 min accompanied by the formation of a black oily
precipitate. After removal of the solvent under reduced pressure,
the residue was washed with pentane (3×10 mL) and dried
in vacuo.
All synthetic operations were conducted in ovenꢀdried glassꢀ
ware using a combination of glovebox (MBRAUN 150BꢀGꢀII),
high vacuum, and Schlenk techniques under dinitrogen atmoꢀ
sphere. The solvents were freshly distilled under N2 according to
standard procedures and were degassed by freeze—thaw cycles
prior to use. Deuterobenzene, tolueneꢀd8, and THFꢀd8 were
purchased from Armar, stored in a Schlenk tube (Teflon tap),
Compound 3a. IR, ν/cm–1: 1610 (m, HNO); 1716 (m, NO);
2089 (w, C≡C). Raman, ν/cm–1: 2087 (s, C≡C). 1H NMR
(THFꢀd8, 25 °C), δ: 0.87—2.53 (m, 66 H, P(C6H11)3); 5.06
* A. Llamazares and H. Berke, unpublished results.

Reactions of [Re(NO)2(PR3)2][BArF
]
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 5, May, 2004
1119
4
(br.s, 1 H, CH=C(Ph)ONH); 7.15—7.73 (m, 10 H, C≡C(C6H5),
CHC(C6H5)ONH); 8.94 (t, 1 H, CH=C(Ph)ONH, JP,C = 2 Hz).
13C{1H} NMR (THFꢀd8, 25 °C), δ: 27.0, 28.3, 30.4 (all s,
P(C6H11)3); 36.2 (t, P(C6H11)3, JP,C = 10 Hz); 115.1 (br.s,
CH=C(Ph)ONH); 129.8 (t, C≡CPh, JP,C = 20 Hz); 126.2, 129.0,
129.1, 129.2, 129.3, 130.6, 131.1, 131.7 (all s, C≡C(C6H5),
where it was cooled to 183(2) K using an Oxford Cryogenic
System. The crystalꢀtoꢀimage distance was set to 60 mm
(θmax = 27.99°). The φꢀoscillation scan mode was applied for the
intensity measurement. For the cell parameter refinement,
7998 reflections were selected out of the whole limiting spheres.
A total of 44348 diffraction intensities were collected,8 of which
20377 were independent (Rint = 0.0766) after data reduction.
Numerical absorption correction9 based on 15 crystal faces,
was applied with the FACEitVIDEO and XRED programs.8
The structure was solved by the Patterson method using the
SHELXSꢀ97 program package.10 Interpretation of the differꢀ
ence Fourier maps, preliminary plot generations and checking
for higher symmetry were performed with the PLATON proꢀ
gram11 and the implemented LEPAGE program.12 All heavy
atoms were refined (SHELXLꢀ97)13 using anisotropic displaceꢀ
ment parameters. Positions of H atoms were calculated after
each refinement cycle (riding model). The structural plot (see
Fig. 1) was generated using the ORTEP program.14 Other crysꢀ
tallographic data and the refinement results are presented in
Table 1.
CH=C(C6H5)ONH);
171.7
(s,
CH=C(Ph)ONH).
31P{1H} NMR (THFꢀd8, 25 °C), δ: 39.6 (s, P(C6H11)3).
Compound 3b. IR, ν/cm–1: 1610 (m, HNO); 1712 (m, NO);
2090 (w, C≡C). Raman, ν/cm–1: 2074 (s, C≡C). 1H NMR
(THFꢀd8, 25 °C), δ: 1.43 (m, 36 H, P{CH(CH3)2}3); 2.68 (m,
6 H, P{CHMe2}3); 5.21 (s, 1 H, CH=C(Ph)ONH); 7.08—7.72
(m, 10 H, C≡C(C6H5), CHC(C6H5)ONH); 9.08 (t, 1 H,
CH=C(Ph)ONH, JP,C = 2 Hz). 13C{1H} NMR (THFꢀd8, 25 °C),
δ: 20.1, 20.5 (both s, P{CH(CH3)2}3); 28.4 (т, P{CHMe2}3,
JP,C = 11 Hz); 114.9 (br.s, CH=C(Ph)ONH); 129.6 (br.s,
C≡CPh); 126.6, 129.0, 129.1, 129.2, 130.5, 130.7, 131.1 (all s,
C≡C(C6H5), CH=C(C6H5)ONH). 31P{1H} NMR (THFꢀd8,
25 °C), δ: 43.5 (s, P{CHMe2}3).
Xꢀray diffraction study of complex 3a. A crystal of 3a proꢀ
tected in hydrocarbon oil was selected for an Xꢀray experiment
using a polarizing microscope. The crystal was mounted on a tip
of a glass fiber and immediately transferred to the goniometer of
an imaging plate detector system (Stoe IPDS diffractometer),
Supplementary crystallographic data for compound 3a
can be obtained free of charge via www.ccdc.cam.ac.uk/
conts/retrieving.html or from the Cambridge Crystalloꢀ
graphic Data Centre, 12 Union Road, Cambridge
CB2 1EZ, UK (Fax: (+44) 1223 336033. Eꢀmail:
deposit@ccdc.cam.ac.uk).
Table 1. Crystallographic data and structure refinement paramꢀ
eters for complex 3a
This work was financially supported by the Swiss Naꢀ
tional Science Foundation (SNSF) and the University of
Zurich.
Parameter
Value
Molecular formula
Crystal habitus
C
90H96BF24N2O2P2Re
Plate
Color of crystals
Crystal size/mm3
Red
0.45×0.36×0.16
References
Crystal system
Space group
T/K
a/Å
b/Å
c/Å
α/deg
β/deg
Triclinic
P1
183(2)
–
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12.6853(8)
19.5877(14)
21.0298(15)
103.116(8)
106.323(8)
105.106(8)
4580.4(5)
2
1952.64
1.416
1.457
1984
4.40—55.98
44348
γ/deg
V/Å3
Z
Molecular weight
dcalc/g cm–3
Absorption/mm–1
F(000)
Scan range, 2θ/deg
Number of collected reflections
Number of independent relections
Number of reflections with I > 2σ(I )
Number of restraint parameters
Number of refinement parameters
R1/wR2 (I > 2σ(I ))
R1/wR2 (all data)
Goodness of fit against F 2
Residual electron
20377
9693
48
1037
0.0550/0.1154
0.1226/0.1307
0.769
density/e•Å–3, ρmax/ρ
1.266/1.359
min

1120
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Received February 11, 2004