Preparation of diazoalkane complexes of ruthenium and their cyclization reactions with alkenes and alkynes

Article abstract of DOI:10.1021/om500481d

The diazoalkane complexes [Ru(η⁵-C₅H ₅)(N₂CAr1Ar2)(PPh₃)(L)]BPh₄ (1-5: Ar1 = Ar2 = Ph (a), Ar1 = Ph and Ar2 = p-tolyl (b), Ar1Ar2 = C ₁₂H₈ (c), Ar1 = Ph and Ar2 = PhCO (d); L = PPh₃ (1), P(OMe)₃ (2), P(OEt)₃ (3), PPh(OEt)₂ (4), Bu^tNC (5)) were prepared by allowing the chloro compounds RuCl(η⁵-C₅H₅)(PPh₃)(L) to react with the diazoalkanes Ar1Ar2CN₂ in ethanol. Treatment of complexes 1-5 with ethylene (CH₂=CH₂) under mild conditions (1 atm, room temperature) led not only to the η²-ethylene complexes [Ru(η⁵-C₅H₅)(η²-CH ₂=CH₂)(PPh₃)(L)]BPh₄ (10-14) but also to dipolar (3 + 2) cycloaddition, affording the 4,5-dihydro-3H-pyrazole derivatives [Ru(η⁵-C₅H₅){η¹- N=NC(Ar1Ar2)CH₂CH₂}(PPh₃)(L)]BPh₄ (6-9). Acrylonitrile (CH₂=C(H)CN) reacted with diazoalkane complexes 2 and 3 to give the 1H-pyrazoline derivatives [Ru(η⁵-C ₅H₅){η¹-N=C(CN)CH₂C(Ar1Ar2)NH} (PPh₃)(L)]BPh₄ (19, 20). However, reactions with propylene (CH₂=C(H)CH₃), maleic anhydride (ma, CH=CHCO(O)CO) and dimethyl maleate (dmm, CH₃OCOCH=CHOCOCH₃) led to the η²-alkene complexes [Ru(η⁵-C₅H ₅)(η²-R1CH=CHR2)(PPh₃)(L)]BPh₄ (17-22). Treatment of the diazoalkane complexes 1 and 2 with acetylene CH≡CH under mild conditions (1 atm, room temperature) led to dipolar cycloaddition, affording the 3H-pyrazole complexes [Ru(η⁵-C ₅H₅){η¹-N=NC(Ar1Ar2)CH=CH}(PPh ₃){P(OMe)₃}]BPh₄ (24), whereas reactions with the terminal alkynes PhC≡CH and Bu^tC≡CH gave the vinylidene derivatives [Ru(η⁵-C₅H₅){=C=C(H) R}(PPh₃){P(OMe)₃}]BPh₄ (25, 26). The alkyl propiolates HC≡CCOOR1 (R1 = Me, Et) also reacted with complexes 2 to give the 3H-pyrazole complexes [Ru(η⁵-C₅H ₅){η¹-N=NC(Ar1Ar2)C(COOR1)=CH}(PPh₃){P(OMe) ₃}]BPh₄ (27, 28). The complexes were characterized by spectroscopy and by X-ray crystal structure determinations of [Ru(η⁵-C₅H₅){η¹-N=C(CN) CH₂C(Ph)(p-tolyl)NH}(PPh₃){P(OMe)₃}]BPh ₄ (19b), [Ru(η⁵-C₅H₅) {η²-CH=CHCO(O)CO}(PPh₃){P(OMe)₃}]BPh ₄ (21), and [Ru(η⁵-C₅H₅) {η¹-N=NC(C₁₂H₈)CH=CH}(PPh ₃){P(OMe)₃}]BPh₄ (24c).

Full text of DOI:10.1021/om500481d

Article
pubs.acs.org/Organometallics
Preparation of Diazoalkane Complexes of Ruthenium and Their
Cyclization Reactions with Alkenes and Alkynes
Gabriele Albertin,*,† Stefano Antoniutti,† Alessandra Botter,† Jesus Castro,‡ and Mattia Giacomello†
́
†Dipartimento di Scienze Molecolari e Nanosistemi, Universita
̀
Ca’ Foscari Venezia, Dorsoduro 2137, 30123 Venezia, Italy
‡
́
́
Departamento de Quımica Inorganica, Facultade de Quımica, Edificio de Ciencias Experimentais, Universidade de Vigo, 36310 Vigo,
́
Galicia, Spain
S
* Supporting Information
ABSTRACT: The diazoalkane complexes [Ru(η5-C5H5)-
(N2CAr1Ar2)(PPh3)(L)]BPh4 (1−5: Ar1 = Ar2 = Ph (a),
Ar1 = Ph and Ar2 = p-tolyl (b), Ar1Ar2 = C12H8 (c), Ar1 = Ph
and Ar2 = PhCO (d); L = PPh3 (1), P(OMe)3 (2), P(OEt)3
(3), PPh(OEt)2 (4), ButNC (5)) were prepared by allowing
the chloro compounds RuCl(η5-C5H5)(PPh3)(L) to react with
the diazoalkanes Ar1Ar2CN2 in ethanol. Treatment of com-
plexes 1−5 with ethylene (CH2CH2) under mild conditions
(1 atm, room temperature) led not only to the η2-ethylene
complexes [Ru(η5-C5H5)(η2-CH2CH2)(PPh3)(L)]BPh4
(10−14) but also to dipolar (3 + 2) cycloaddition, affording
the 4,5-dihydro-3H-pyrazole derivatives [Ru(η5-C5H5){η1-N
NC(Ar1Ar2)CH2CH2}(PPh3)(L)]BPh4 (6−9). Acrylonitrile (CH2C(H)CN) reacted with diazoalkane complexes 2 and 3
to give the 1H-pyrazoline derivatives [Ru(η5-C5H5){η1-NC(CN)CH2C(Ar1Ar2)NH}(PPh3)(L)]BPh4 (19, 20). However,
reactions with propylene (CH2C(H)CH3), maleic anhydride (ma, CHCHCO(O)CO) and dimethyl maleate (dmm,
CH3OCOCHCHOCOCH3) led to the η2-alkene complexes [Ru(η5-C5H5)(η2-R1CHCHR2)(PPh3)(L)]BPh4 (17−22).
Treatment of the diazoalkane complexes 1 and 2 with acetylene CHCH under mild conditions (1 atm, room temperature)
led to dipolar cycloaddition, affording the 3H-pyrazole complexes [Ru(η5-C5H5){η1-NNC(Ar1Ar2)CHCH}(PPh3)
{P(OMe)3}]BPh4 (24), whereas reactions with the terminal alkynes PhCCH and ButCCH gave the vinylidene derivatives
[Ru(η5-C5H5){CC(H)R}(PPh3){P(OMe)3}]BPh4 (25, 26). The alkyl propiolates HCCCOOR1 (R1 = Me, Et) also
reacted with complexes 2 to give the 3H-pyrazole complexes [Ru(η5-C5H5){η1-NNC(Ar1Ar2)C(COOR1)CH}(PPh3)-
{P(OMe)3}]BPh4 (27, 28). The complexes were characterized by spectroscopy and by X-ray crystal structure determinations of
[Ru(η5-C5H5){η1-NC(CN)CH2C(Ph)(p-tolyl)NH}(PPh3){P(OMe)3}]BPh4 (19b), [Ru(η5-C5H5){η2-CHCHCO(O)CO}-
(PPh3){P(OMe)3}]BPh4 (21), and [Ru(η5-C5H5){η1-NNC(C12H8)CHCH}(PPh3){P(OMe)3}]BPh4 (24c).
[M]−N2,8f N−N bond cleavage,8k and reduction of the coordi-
INTRODUCTION
■
nated N2CAr1Ar2 ligand.8i However, no example of cyclization
of coordinated diazoalkane had ever been reported until
we found10 that the half-sandwich complexes [Ru(η5-C5H5)-
(N2CAr1Ar2)(PPh3){P(OR)3}]BPh4 can undergo unprece-
dented (3 + 2) cycloaddition of a metal-bonded diazoalkane to
ethylene, yielding 4,5-dihydro-3H-pyrazole derivatives. These
interesting preliminary results prompted us to extend our re-
search and study to activated alkenes and alkynes, as well as to the
influence of ancillary ligands on the cyclization reaction.
The reactivity of diazoalkanes Ar1Ar2CN2 toward transition-
metal complexes has attracted longstanding interest1,2 in the
synthesis of carbene complexes [M]CAr1Ar2,2 often used as
olefin metathesis catalysts.3 The diazoalkane can also cooordi-
nate to the metal center, yielding the metal complexes [M]−
N2CAr1Ar2, which may be of interest as models for under-
standing N2 coordination and functionalization.4,5
A number of diazoalkane complexes of several metals have
been prepared,6−9 displaying a variety of coordination modes, as
shown in Chart 1. In the mononuclear complexes, either the
η1-end-on (type I) or η2-NN side-on (type II) coordination mode
is commonly observed, whereas the two bridging modes III and IV
are reported in dinuclear derivatives. Instead, relatively few
data have been reported on the reactivity of coordinate diazo-
alkane,1,6−9 including the formation of dinitrogen complexes
This paper reports full details of our study of the synthesis of
diazoalkane complexes of ruthenium and the (3 + 2) cycloaddition
Received: May 6, 2014
Published: July 2, 2014
© 2014 American Chemical Society
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Organometallics
Article
4.63 (s, 5H, Cp), 2.42 (s, 3H, CH3); 31P{1H} NMR (CD2Cl2, 20 °C) δ
39.68 (s). Anal. Calcd for C79H67BN2P2Ru (1218.22): C, 77.89; H, 5.54;
N, 2.30. Found: C, 77.68; H, 5.43; N, 2.41. ΛM = 53.6 Ω−1 mol−1 cm2.
[Ru(η5-C5H5)(N2CAr1Ar2)(PPh3)(L)]BPh4 (2−4). In a 25 mL three-
necked round-bottomed flask were placed solid samples of the
appropriate chloro complex RuCl(η5-C5H5)(PPh3)(L) (0.3 mmol), an
excess of the diazoalkane Ar1Ar2CN2 (0.9 mmol), an excess of NaBPh4
(0.6 mmol, 0.205 g), and 10 mL of ethanol. The reaction mixture was
stirred for 24 h, and the solid that formed was filtered and crystallized
from CH2Cl2/EtOH. A further amount of solid complex could be
recovered by concentration of the mother liquor and cooling to −25 °C:
yield ≥70%.
Chart 1. Coordination Modes of Diazoalkane
2a (L = P(OMe)3, Ar1 = Ar2 = Ph): IR (KBr, cm−1) νN2 1967 (m); 1H
NMR (CD2Cl2, 20 °C) δ 7.48−6.87 (m, 45H, Ph), 5.00 (d, 5H, Cp),
3.31 (d, 9H, CH3); 31P{1H} NMR (CD2Cl2, 20 °C) δ AB spin syst, δA
144.47, δB 47.76, JAB = 63.2 Hz. Anal. Calcd for C63H59BN2O3P2Ru
(1065.98): C, 70.98; H, 5.58; N, 2.63. Found: C, 71.17; H, 5.65; N, 2.54.
Λ
M = 54.3 Ω−1 mol−1 cm2.
2b (L = P(OMe)3, Ar1 = Ph, Ar2 = p-tolyl): IR (KBr, cm−1) νN2 1959
(m); 1H NMR (CD2Cl2, 20 °C) δ 7.53−6.86 (m, 44H, Ph), 4.99 (d, 5H,
Cp), 3.32 (d, 9H, CH3 phos), 2.39 (s, 3H, CH3 p-tolyl); 31P{1H} NMR
(CD2Cl2, 20 °C) δ AB, δA 144.7, δB 47.9, JAB = 63.5 Hz. Anal. Calcd for
C64H61BN2O3P2Ru (1080.01): C, 71.17; H, 5.69; N, 2.59. Found: C,
71.30; H, 5.59; N, 2.72. ΛM = 53.2 Ω−1 mol−1 cm2.
of the cooordinate diazoalkane to several alkenes and alkynes,
yielding 3H-pyrazole and 1H-pyrazoline derivatives.
EXPERIMENTAL SECTION
■
General Comments. All synthetic work was carried out under an
appropriate atmosphere (Ar, N2) using standard Schlenk techniques or
in an inert-atmosphere drybox. All solvents were dried over appropriate
drying agents, degassed on a vacuum line, and distilled into vacuum-tight
storage flasks. RuCl3·3H2O was a Pressure Chemical Co. (USA) pro-
duct, phenyldiethoxyphosphine PPh(OEt)2 was prepared by the
method of Rabinowitz and Pellon,11 phosphites P(OMe)3 and P(OEt)3
and tert-butyl isocyanide were Aldrich products used as received,
diazoalkanes were prepared following the known method,12 and other
reagents were purchased from commercial sources in the highest
available purity and used as received. Infrared spectra were recorded on a
Perkin-Elmer Spectrum-One FT-IR spectrophotometer. NMR spectra
(1H, 13C, 31P) were obtained on an Bruker AVANCE 300 spectrometer
at temperatures varying between +20 and −80 °C, unless otherwise
2c (L = P(OMe)3, Ar1Ar2 = C12H8): IR (KBr, cm−1) νN2 1961 (m); 1H
NMR (CD2Cl2, 20 °C) δ 8.00−6.59 (m, 43H, Ph), 5.11 (d, 5H, Cp),
3.45 (d, 9H, CH3); 31P{1H} NMR (CD2Cl2, 20 °C) δ AB, δA 142.0, δB
47.2, JAB = 60.8 Hz. Anal. Calcd for C63H57BN2O3P2Ru (1063.97): C,
71.12; H, 5.40; N, 2.63. Found: C, 71.30; H, 5.51; N, 2.55. ΛM = 55.0
Ω−1 mol−1 cm2.
2d (L = P(OMe)3, Ar1 = Ph, Ar2 = PhCO): IR (KBr, cm−1) νN2 1963
(m), νCO 1614 (s); 1H NMR (CD2Cl2, 20 °C) δ 7.55−6.87 (m, 45H,
Ph), 5.01 (d, 5H, Cp), 3.38 (d, 9H, CH3); 31P{1H} NMR (CD2Cl2,
20 °C) δ AB, δA 139.63, δB 45.66, JAB = 60.4 Hz. Anal. Calcd for
C64H59BN2O4P2Ru (1093.99): C, 70.26; H, 5.44; N, 2.56. Found: C,
70.11; H, 5.36; N, 2.64. ΛM = 52.6 Ω−1 mol−1 cm2.
3a (L = P(OEt)3, Ar1 = Ar2 = Ph): IR (KBr, cm−1) νN2 1961 (m); 1H
NMR (CD2Cl2, 20 °C) δ 7.48−6.87 (m, 45H, Ph), 4.97 (d, 5H, Cp),
3.76 (m, 6H, CH2), 1.09 (t, 9H, CH3); 31P{1H} NMR (CD2Cl2, 20 °C)
δ AB, δA 138.88, δB 47.43, JAB = 63.2 Hz. Anal. Calcd for C66H65-
BN2O3P2Ru (1108.06): C, 71.54; H, 5.91; N, 2.53. Found: C, 71.38; H,
6.00; N, 2.46. ΛM = 56.4 Ω−1 mol−1 cm2.
1
noted. H and 13C spectra are referred to internal tetramethylsilane.
31P{1H} chemical shifts are reported with respect to 85% H3PO4, with
downfield shifts considered positive. COSY, HMQC, and HMBC NMR
experiments were performed with standard programs. The iNMR
software package13 was used to treat NMR data. The conductivity of
10−3 mol dm−3 solutions of the complexes in CH3NO2 at 25 °C was
measured on a Radiometer CDM 83 instrument. Elemental analyses
were determined in the Microanalytical Laboratory of the Dipartimento
di Scienze del Farmaco, University of Padova, Padova, Italy.
3b (L = P(OEt)3, Ar1 = Ph, Ar2 = p-tolyl): IR (KBr, cm−1) νN2 1961
(m); 1H NMR (CD2Cl2, 20 °C) δ 7.50−6.87 (m, 44H, Ph), 4.95 (d, 5H,
Cp), 3.77 (m, 6H, CH2), 2.39 (s, 3H, CH3 p-tolyl), 1.10 (t, 9H, CH3
phos); 31P{1H} NMR (CD2Cl2, 20 °C) δ AB spin syst, δA 139.2, δB 47.6,
JAB = 63.2 Hz; 13C{1H} NMR (CD2Cl2, 20 °C) δ 165−122 (m, Ph), 86.8
(s, Cp), 63.4 (d, CH2), 21.3 (s, CH3 p-tolyl), 16.2 (d, CH3 phos). Anal.
Calcd for C67H67BN2O3P2Ru (1122.09): C, 71.72; H, 6.02; N, 2.50.
Found: C, 71.57; H, 5.91; N, 2.58. ΛM = 53.8 Ω−1 mol−1 cm2.
3c (L = P(OEt)3, Ar1Ar2 = C12H8): IR (KBr, cm−1) νN2 1959 (m); 1H
NMR (CD2Cl2, 20 °C) δ 7.99−6.58 (m, 43H, Ph), 5.09 (s, 5H, Cp),
3.82 (m, 6H, CH2), 1.08 (t, 9H, CH3); 31P{1H} NMR (CD2Cl2, 20 °C)
δ AB spin syst, δA 136.4, δB 46.6, JAB = 60.8 Hz. Anal. Calcd for
C66H63BN2O3P2Ru (1106.05): C, 71.67; H, 5.74; N, 2.53. Found: C,
71.53; H, 5.59; N, 2.46. ΛM = 52.8 Ω−1 mol−1 cm2.
Synthesis of the Complexes. The compounds RuCl(η5-C5H5)-
(PPh3)2 and (RuCl(η5-C5H5)(PPh3)(L) (L = P(OMe)3, P(OEt)3, PPh-
(OEt)2] were prepared following the methods previously reported.14,15
RuCl(η5-C5H5)(PPh3)(ButNC). An equimolar amount of tert-butyl
isocyanide (31 μL, 0.275 mmol) was added to a solution of RuCl-
(η5-C5H5)(PPh3)2 (0.275 mmol, 0.200 g) in benzene (8 mL), and the
reaction mixture was refluxed for 2 h. The solvent was removed under
reduced pressure to give an oil, which was triturated with ethanol
(3 mL). When the resulting solution was cooled to −25 °C, a yellow
solid slowly separated out, which was dried under vacuum: yield ≥85%. IR
(KBr, cm−1) νCN 2109 (s); 1H NMR (CD2Cl2, 20 °C) δ 7.60−7.36 (m,
15H, Ph), 4.56 (s, 5H, Cp), 1.22 (s, 9H, CH3); 31P{1H} NMR (CD2Cl2,
20 °C) δ 53.74 (s). Anal. Calcd for C28H29ClNPRu (547.03): C, 61.48; H,
5.34; Cl, 6.48; N, 2.56. Found: C, 61.31; H, 5.23; Cl, 6.65; N, 2.46.
[Ru(η5-C5H5){N2C(Ph)p-tolyl}(PPh3)2]BPh4 (1b). In a 25 mL three-
necked round-bottomed flask were placed solid samples of RuCl(η5-
C5H5)(PPh3)2 (0.10 g, 0.138 mmol), an excess of (p-tolyl)(Ph)CN2
(0.42 mmol, 87 mg), an excess of NaBPh4 (0.28 mmol, 96 mg), 5 mL of
ethanol, and enough dichloromethane to give a clear solution (2−3 mL).
The reaction mixture was stirred for 6 h and then the solvent removed
under reduced pressure to give an oil, which was triturated with ethanol
(8 mL). A reddish brown solid complex slowly separated out, which was
filtered and crystallized from CH2Cl2/EtOH: yield ≥65%. IR (KBr, cm−1)
νN2 1955 (m); 1H NMR (CD2Cl2, 20 °C) δ 7.45−6.82 (m, 59H, Ph),
3d (L = P(OEt)3, Ar1 = Ph, Ar2 = PhCO): IR (KBr, cm−1) νN2 1964
1
(w), νCO 1612 (s); H NMR (CD2Cl2, 20 °C) δ 7.53−6.87 (m, 45H,
Ph), 4.98 (s, 5H, Cp), 3.68 (m, 6H, CH2), 1.11 (t, 9H, CH3); 31P{1H}
NMR (CD2Cl2, 20 °C) δ AB, δA 133.22, δB 45.10, JAB = 60.8 Hz. Anal.
Calcd for C67H65BN2O4P2Ru (1136.07): C, 70.83; H, 5.77; N, 2.47.
Found: C, 70.63; H, 5.66; N, 2.58. ΛM = 50.9 Ω−1 mol−1 cm2.
4a (L = PPh(OEt)2, Ar1 = Ar2 = Ph): IR (KBr, cm−1) νN2 1942 (m);
1H NMR (CD2Cl2, 20 °C) δ 7.53−6.86 (m, 50H, Ph), 4.74 (s, 5H, Cp),
3.74 (qnt), 3.60, 3.46 (m) (4H, CH2), 1.15, 1.10 (t, 6H, CH3); 31P{1H}
NMR (CD2Cl2, 20 °C) δ AB, δA 164.72, δB 46.25, JAB = 49.8 Hz. Anal.
Calcd for C70H65BN2O2P2Ru (1140.11): C, 73.74; H, 5.75; N, 2.46.
Found: C, 73.52; H, 5.84; N, 2.38. ΛM = 51.6 Ω−1 mol−1 cm2.
4b (L = PPh(OEt)2, Ar1 = Ph, Ar2 = p-tolyl): IR (KBr, cm−1) νN2
1931 (m); 1H NMR (CD2Cl2, 20 °C) δ 7.52−6.87 (m, 49H, Ph), 4.74
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Organometallics
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(s, 5H, Cp), 3.76 (qnt), 3.60, 3.48 (m) (4H, CH2), 2.42 (s, 3H, CH3
p-tolyl), 1.17, 1.02 (t, 6H, CH3 phos); 31P{1H} NMR (CD2Cl2, 20 °C) δ
AB spin syst, δA 165.10, δB 46.45, JAB = 52.0 Hz; 13C{1H} NMR
(CD2Cl2, 20 °C) δ 165−122 (m, Ph), 87.17 (s, Cp), 84.22 (s, CN2),
64.66 (t, CH2), 21.18 (s, CH3 p-tolyl), 16.32 (t, CH3 phos). Anal. Calcd
for C71H67BN2O2P2Ru (1154.13): C, 73.89; H, 5.85; N, 2.43. Found: C,
73.70; H, 5.74; N, 2.38. ΛM = 53.2 Ω−1 mol−1 cm2.
145.46, δB 47.20, JAB = 69.3 Hz. Anal. Calcd for C65H63BN2O3P2Ru
(1094.04): C, 71.36; H, 5.80; N, 2.56. Found: C, 71.44; H, 5.71; N, 2.45.
Λ
M = 54.5 Ω−1 mol−1 cm2.
6b (L = P(OMe)3, Ar1 = Ph, Ar2 = p-tolyl): 1H NMR (CD2Cl2, 20 °C)
δ 7.50−6.75 (m, 44H, Ph), 4.70, 4.69 (s, 5H, Cp), 4.43 (m, 2H, H5),
3.36, 3.34 (d, 9H, CH3 phos), 2.33 (s, 3H, CH3 p-tolyl), 2.22 (m, 2H,
H4); 31P{1H} NMR (CD2Cl2, 20 °C) δ AB, δA 145.5, δB 48.2, JAB = 69.3;
δA 145.6, δB 48.3, JAB = 69.3 Hz; 13C{1H} NMR (CD2Cl2, 20 °C) δ 165−
122 (m, Ph), 97.5 (s, C3), 87.84, 87.79 (s, C5), 84.36, 84.32 (s, Cp),
53.4, 53.1 (s, CH3 phos), 33.99, 33.94 (s, C4), 21.14, 21.11 (s, CH3
p-tolyl). Anal. Calcd for C66H65BN2O3P2Ru (1108.06): C, 71.54; H, 5.91;
N, 2.53. Found: C, 71.67; H, 5.79; N, 2.45. ΛM = 52.5 Ω−1 mol−1 cm2.
4c (L = PPh(OEt)2, Ar1Ar2 = C12H8): IR (KBr, cm−1) νN2 1967 (m);
1H NMR (CD2Cl2, 20 °C) δ 8.00−6.62 (m, 48H, Ph), 4.88 (s, 5H, Cp),
3.96, 3.87, 3.67, 3.51 (m, 4H, CH2), 1.16, 0.90 (t, 6H, CH3); 31P{1H}
NMR (CD2Cl2, 20 °C) δ AB spin syst, δA 162.85, δB 45.90, JAB = 49.8
Hz; 13C{1H} NMR (CD2Cl2, 20 °C) δ 165−120 (m, Ph), 88.39 (s, Cp),
65.29 (t, CH2), 16.32, 16.09 (d, CH3). Anal. Calcd for C70H63BN2-
O2P2Ru (1138.09): C, 73.87; H, 5.58; N, 2.46. Found: C, 73.99; H, 5.46;
N, 2.53. ΛM = 50.4 Ω−1 mol−1 cm2.
1
6c (L = P(OMe)3, Ar1Ar2 = C12H8): H NMR (CD2Cl2, 20 °C) δ
7.77−6.47 (m, 43H, Ph), 4.84 (m, 2H, H5), 4.78 (s, 5H, Cp), 3.40 (d,
9H, CH3), 2.23 (t, 2H, H4); 31P{1H} NMR (CD2Cl2, 20 °C) δ AB, δA
145.5, δB 47.5, JAB = 69.3 Hz; 13C{1H} NMR (CD2Cl2, 20 °C) δ 165−121
(m, Ph), 98.32 (s, C3), 88.95 (s, C5), 84.32 (s, Cp), 53.2 (s, CH3), 30.59
(s, C4). Anal. Calcd for C65H61BN2O3P2Ru (1092.02): C, 71.49; H, 5.63;
N, 2.57. Found: C, 71.32; H, 5.55; N, 2.66. ΛM = 51.9 Ω−1 mol−1 cm2.
7b (L = P(OEt)3, Ar1 = Ph, Ar2 = p-tolyl): 1H NMR (CD2Cl2, 20 °C)
δ 7.50−6.86 (m, 44H, Ph), 4.66, 4.65 (s, 5H, Cp), 4.31 (m, 2H, H5),
3.83 (m, 6H, CH2 phos), 2.35, 2.32 (s, 3H, CH3 p-tolyl), 2.12 (m, 2H,
H4), 1.16, 1.09 (t, 9H, CH3 phos); 31P{1H} NMR (CD2Cl2, 20 °C) δ
AB, δA 140.35, δB 48.50, JAB = 66.8; δA 140.15, δB 48.32, JAB = 66.8 Hz.
Anal. Calcd for C69H71BN2O3P2Ru (1150.14): C, 72.06; H, 6.22; N,
2.44. Found: C, 71.89; H, 6.11; N, 2.46. ΛM = 54.5 Ω−1 mol−1 cm2.
7c (L = P(OEt)3, Ar1Ar2 = C12H8): 1H NMR (CD2Cl2, 20 °C) δ 7.84−
6.32 (m, 43H, Ph), 4.89, 4.88 (t, 2H, H5), 4.75 (s, 5H, Cp), 3.69−3.10
(m, 6H, CH2 phos), 2.20 (t, 2H, H4), 1.03 (t, 9H, CH3); 31P{1H} NMR
(CD2Cl2, 20 °C) δ AB, δA 139.6, δB 47.4, JAB = 68.1 Hz. Anal. Calcd for
C68H67BN2O3P2Ru (1134.10): C, 72.02; H, 5.95; N, 2.47. Found: C,
72.18; H, 5.84; N, 2.40. ΛM = 52.3 Ω−1 mol−1 cm2.
4d (L = PPh(OEt)2, Ar1 = Ph, Ar2 = PhCO): IR (KBr, cm−1) νCO 1609
(s); 1H NMR (CD2Cl2, 20 °C) δ 7.55−6.86 (m, 50H, Ph), 4.75 (s, 5H,
Cp), 3.78, 3.64, 3.48 (m, 4H, CH2), 1.19, 1.07 (t, 6H, CH3); 31P{1H}
NMR (CD2Cl2, 20 °C) δ AB, δA 159.30, δB 44.73, JAB = 49.8 Hz. Anal.
Calcd for C71H65BN2O3P2Ru (1168.12): C, 73.00; H, 5.61; N, 2.40.
Found: C, 72.82; H, 5.54; N, 2.31. ΛM = 53.7 Ω−1 mol−1 cm2.
[Ru(η5-C5H5)(N2CAr1Ar2)(PPh3)(ButNC)]BPh4 (5). In a 25 mL
three-necked round-bottomed flask were placed 55 mg of RuCl(η5-
C5H5)(PPh3)(ButNC) (0.1 mmol), an excess of the appropriate diazo-
alkane Ar1Ar2CN2 (0.3 mmol), an excess of NaBPh4 (0.2 mmol,
68 mg), and 4 mL of ethanol. The reaction mixture was stirred for 24 h,
and then the solvent was removed under reduced pressure to give an oil,
which was triturated with ethanol (2 mL). An orange solid slowly
separated out, which was filtered and crystallized from CH2Cl2/EtOH:
yield ≥55%.
5a (Ar1 = Ar2 = Ph): IR (KBr, cm−1) νCN 2133 (s), νN2 1900 (m); 1H
NMR (CD2Cl2, 20 °C) δ 7.48−6.87 (m, 45H, Ph), 5.04 (s, 5H, Cp),
1.16 (s, 9H, CH3); 31P{1H} NMR (CD2Cl2, 20 °C) δ 51.41(s); 13C{1H}
NMR (CD2Cl2, 20 °C) δ 165−122 (m, Ph), 86.49 (s, Cp), 85.98
(s, CN2), 59.22 (s, C But), 30.46 (s, CH3 But). Anal. Calcd for C65H59-
BN3PRu (1025.04): C, 76.16; H, 5.80; N, 4.10. Found: C, 76.01; H,
5.70; N, 4.18. ΛM = 53.4 Ω−1 mol−1 cm2.
1
8b (L = PPh(OEt)2, Ar1 = Ph, Ar2 = p-tolyl): H NMR (CD2Cl2,
20 °C) δ 7.58−6.87 (m, 49H, Ph), 4.55, 4.35 (m, 2H, H5), 4.49, 4.47 (s,
5H, Cp), 3.67, 3.65 (m, 4H, CH2 phos), 2.38, 2.24 (t, 2H, H4), 2.35, 2.32
(s, 3H, CH3 p-tolyl), 1.23, 1.18, 1.16, 1.01 (t, 6H, CH3 phos); 31P{1H}
NMR (CD2Cl2, 20 °C) δ AB, δA 165.30, δB 46.97, JAB = 55.9; δA 165.20,
δB 46.66, JAB = 57.1 Hz. Anal. Calcd for C73H71BN2O2P2Ru (1182.19):
5b (Ar1 = Ph, Ar2 = p-tolyl): IR (KBr, cm−1) νCN 2130 (s), νN2 1905
(s); 1H NMR (CD2Cl2, 20 °C) δ 7.45−6.87 (m, 44H, Ph), 5.03 (s, 5H,
Cp), 2.40 (s, 3H, CH3 p-tolyl), 1.16 (s, 9H, CH3 But); 31P{1H} NMR
(CD2Cl2, 20 °C) δ 51.51(s); 13C{1H} NMR (CD2Cl2, 20 °C) δ 165−
122 (m, Ph), 86.43 (s, Cp), 85.9 (br, CN2), 59.20 (s, C(CH3)3), 30.48
(s, CH3 But), 21.33 (s, CH3 p-tolyl). Anal. Calcd for C66H61BN3PRu
(1039.07): C, 76.29; H, 5.92; N, 4.04. Found: C, 76.43; H, 5.86; N, 3.96.
C, 74.17; H, 6.05; N, 2.37. Found: C, 74.32; H, 6.00; N, 2.44. ΛM
=
51.5 Ω−1 mol−1 cm2.
1
8c (L = PPh(OEt)2, Ar1Ar2 = C12H8): H NMR (CD2Cl2, 20 °C) δ
9.08−6.88 (m, 48H, Ph), 4.90 (m, 2H, H5), 4.60 (s, 5H, Cp), 3.67, 3.47
(m, 4H, CH2 phos), 2.24, 2.16 (m, 2H, H4), 1.26, 1.16 (t, 6H, CH3
M = 54.7 Ω−1 mol−1 cm2.
phos); 31P{1H} NMR (CD2Cl2, 20 °C) δ AB, δA 165.20, δB 44.65, JAB
=
Λ
5c (Ar1Ar2 = C12H8): IR (KBr, cm−1) νCN 2140 (s), νN2 1939 (s); 1H
54.7 Hz. Anal. Calcd for C72H67BN2O2P2Ru (1166.14): C, 74.16; H, 5.79;
N, 2.40. Found: C, 74.03; H, 5.91; N, 2.33. ΛM = 54.4 Ω−1 mol−1 cm2.
NMR (CD2Cl2, 20 °C) δ 8.20−6.87 (m, 43H, Ph), 5.15 (s, 5H, Cp),
1.17 (s, 9H, CH3); 31P{1H} NMR (CD2Cl2, 20 °C) δ 50.23(s). Anal.
Calcd for C65H57BN3PRu (1023.02): C, 76.31; H, 5.62; N, 4.11. Found:
C, 76.15; H, 5.69; N, 4.03. ΛM = 53.1 Ω−1 mol−1 cm2.
[Ru(η5-C5H5){η1-NNC(Ar1Ar2)CH2CH2}(PPh3)(L)]BPh4 (6−8).
[Ru(η5-C5H5){η1-NNC(Ph)(p-tolyl)CH2CH2}(PPh3)(ButNC)]-
BPh4 (9b). This complex was prepared exactly like the related phos-
phane compounds 6b−8b using a reaction time of 20 h: yield ≥65%; IR
1
(KBr, cm−1) νCN 2123 (s); H NMR (CD2Cl2, 20 °C) δ 7.50−6.86
(m, 44H, Ph), 4.74, 4.72 (s, 5H, Cp), 4.19 (m, 2H, H5), 2.86 (t, 2H, H4),
2.34 (s, 3H, CH3 p-tolyl), 1.29 (s, 9H, CH3 But); 31P{1H} NMR
(CD2Cl2, 20 °C) δ 51.88, 51.69 (s). Anal. Calcd for C68H65BN3PRu
(1067.12): C, 76.54; H, 6.14; N, 3.94. Found: C, 76.36; H, 6.19; N, 4.02.
Λ
M = 50.8 Ω−1 mol−1 cm2.
[Ru(η5-C5H5)(η2-CH2CH2)(PPh3)2]BPh4 (10). In a 25 mL three-
A solution of the appropriate diazoalkane complex [Ru(η5-C5H5)-
(N2CAr1Ar2)(PPh3)(L)]BPh4 (2−4; 0.1 mmol) in CH2Cl2 (10 mL)
was allowed to stand under ethylene (1 atm) for 24 h. The solvent was
removed under reduced pressure to give an oil, which was triturated with
ethanol (2 mL). An orange solid slowly separated out, which was filtered
and fractionally crystallized by diffusion of ethanol into a dichloro-
methane solution of the complex. The first crystals obtained were the
4,5-dihydro-3H-pyrazole complexes 6−8: yield ≥75%.
necked round-bottomed flask were placed a solid sample of the chloro
complex RuCl(η5-C5H5)(PPh3)2 (0.109 g, 0.15 mmol), an excess of
NaBPh4 (0.3 mmol, 0.103 g), and 4 mL of ethanol. The reaction mixture
was stirred under an ethylene atmosphere (1 atm) for 24 h, and then the
pale yellow solid that formed was filtered and crystallized from CH2Cl2
1
and ethanol: yield ≥90%; H NMR (CD2Cl2, 20 °C) δ 7.48−6.81
3
1
31
(m, 50H, Ph), 4.66 (s, 5H, Cp), 2.97 (t, 4H, CH2CH2, J H P = 3.45
Hz); 31P{1H} NMR (CD2Cl2, 20 °C) δ 41.70 (s); 13C{1H} NMR
(CD2Cl2, 20 °C) δ 165−122 (m, Ph), 88.03 (s, Cp), 43.59 (s, CH2
CH2). Anal. Calcd for C67H59BP2Ru (1038.01): C, 77.52; H, 5.73.
Found: C, 77.38; H, 5.80. ΛM = 52.9 Ω−1 mol−1 cm2.
6a (L = P(OMe)3, Ar1 = Ar2 = Ph): 1H NMR (CD2Cl2, 20 °C) δ 7.48−
6.81 (m, 45H, Ph), 4.70 (s, 5H, Cp), 4.45 (m, 2H, H5), 3.35 (d, 9H, CH3
phos), 2.32, 2.19 (m, 2H, H4); 31P{1H} NMR (CD2Cl2, 20 °C) δ AB, δA
3572
dx.doi.org/10.1021/om500481d | Organometallics 2014, 33, 3570−3582

Organometallics
Article
[Ru(η5-C5H5)(η2-CH2CH2)(PPh3)(L)]BPh4 (11−14).
Method 1. A solution of the appropriate diazoalkane complex [Ru(η5-
C5H5)(N2CAr1Ar2)(PPh3)(L)]BPh4 (2, 3; 0.15 mmol) in 10 mL of
CH2Cl2 was placed into an autoclave, which was then pressurized with
propylene (7 atm), and the mixture was stirred at room temperature for
24 h. The solvent was removed under vacuum and the oil obtained
treated with ethanol (3 mL) containing NaBPh4 (0.15 mmol, 51 mg).
A yellow solid slowly separated out, which was filtered and fractionally
crystallized from CH2Cl2 and ethanol: yield ≥40%.
Mixed-ligand compounds were prepared exactly like the related
bis(triphenylphosphine) complex 10: yield ≥85%.
Method 2. In a 25 mL three-necked round-bottomed flask were
placed a solid sample of the chloro complex RuCl(η5-C5H5)(PPh3)(L)
(0.15 mmol), an excess of NaBPh4 (0.3 mmol, 0.103 g), and 4 mL of
ethanol. The reaction mixture was stirred under a propylene atmosphere
(1 atm) for 24 h, and then the solid that formed was filtered and
crystallized from CH2Cl2 and ethanol: yield ≥55%.
11 (L = P(OMe)3): 1H NMR (CD2Cl2, 20 °C) δ 7.52−6.87 (m, 35H,
Ph), 4.85 (s, 5H, Cp), 3.49 (d, 9H, CH3), ABCDXY spin syst (ABCD =
1H, XY = 31P) (4H, CH2CH2), δA, δB 2.99, δC, δD 2.71, JAB = JCD
=
=
12.1, JAC = JBD = 9.0, JAD = JBC = 0.3, JAX = JBX = 5.2, JAY = JBY = 0.2, JCX
JDX = 5.8, JCY = JDY = 0.2 Hz; 31P{1H} NMR (CD2Cl2, 20 °C) δ AB spin
syst, δA 145.4, δB 49.6, JAB = 61.1 Hz; 13C{1H} NMR (CD2Cl2, 20 °C) δ
165−122 (m, Ph), 87.82 (s, Cp), 54.3 (d, CH3), 38.25 (d, CH2CH2).
Anal. Calcd for C52H53BO3P2Ru (899.80): C, 69.41; H, 5.94. Found: C,
69.27; H, 6.05. ΛM = 53.6 Ω−1 mol−1 cm2.
17 (L = P(OMe)3): 1H NMR (CD2Cl2, 20 °C) δ 7.52−6.86 (m, 35H,
Ph), 4.89, 4.82 (d, 5H, Cp), 3.53, 3.50 (d, 9H, CH3 phos), ABCD3XY
1
spin systs (ABCD = H, XY = 31P) (6H, CH3CHCH2), δA 3.47, δB
3.00, δC 2.67, δD 1.54, JAB = 12.7, JAC = 7.7, JAD = 5.8, JAX = 10.7, JAY = 0.1,
JBC = 0.9, JBD = 0.6, JBX = 0.4, JBY = 0.1, JCD = 0.6, JCX = 13.5, JCY = 0.1,
12 (L = P(OEt)3): 1H NMR (CD2Cl2, 20 °C) δ 7.52−6.87 (m, 35H,
Ph), 4.82 (s, 5H, Cp), 3.86 (m, 6H, CH2 phos), ABCDXY spin syst
JDX = 1.0, JDY = 0.1 Hz, δA 3.60, δB 3.38, δC 2.49, δD 1.68, JAB = 10.8, JAC
=
7.6, JAD = 5.4, JAX = 12.8, JAY = 0.1, JBC = 0.3, JBD = 0.4, JBX = 0.2, JBY = 0.1,
JCD = 0.4, JCX = 13.2, JCY = 0.1, JDX = 1.2, JDY = 0.2, JXY = 64.0 Hz; 31P{1H}
NMR (CD2Cl2, 20 °C) δ AB spin systs, δA 144.5, δB 48.4, JAB = 63.0 Hz,
δA 144.6, δB 49.7, JAB = 63.9 Hz; 13C{1H} NMR (CD2Cl2, 20 °C) δ 165−
122 (m, Ph), 88.64, 88.03 (s, Cp), 61.60, 61.42 (s, CH), 54.5 (d, CH3
phos), 44.36 (s), 41.2 (d) (CH2), 24.54, 24.50 (s, CH3 propyl). Anal.
Calcd for C53H55BO3P2Ru (913.83): C, 69.66; H, 6.07. Found: C, 69.82;
H, 6.16. ΛM = 51.6 Ω−1 mol−1 cm2.
(ABCD = 1H, XY = 31P) (4H, CH2CH2), δA, δB 3.01, δC, δD 2.70, JAB
=
JCD = 12.7, JAC = JBD = 0.8, JAD = JBC = 8.5, JAX = JBX = 5.8, JAY = JBY = 0.2,
JCX = JDX = 5.8, JCY = JDY = 0.2 Hz, 1.18 (t, 9H, CH3); 31P{1H} NMR
(CD2Cl2, 20 °C) δ AB spin syst, δA 140.0, δB 49.7, JAB = 60.8 Hz;
13C{1H} NMR (CD2Cl2, 20 °C) δ 165−122 (m, Ph), 88.14 (s, Cp),
63.95 (d, CH2 phos), 38.43 (dd, CH2CH2), 16.16 (d, CH3). Anal.
Calcd for C55H59BO3P2Ru (941.88): C, 70.13; H, 6.31. Found: C, 70.27;
H, 6.44. ΛM = 54.1 Ω−1 mol−1 cm2.
18 (L = P(OEt)3): 1H NMR (CD2Cl2, 20 °C) δ 7.52−6.88 (m, 35H,
Ph), 4.88, 4.87 (s, 5H, Cp), 3.89, 3.82 (m, 6H, CH2 phos), ABCD3XY
13 (L = PPh(OEt)2): 1H NMR (CD2Cl2, 20 °C) δ 7.55−6.86 (m, 40H,
Ph), 4.67 (s, 5H, Cp), 3.85, 3.48 (m, 4H, CH2 phos), ABCDXY spin syst
1
spin systs (ABCD = H, XY = 31P) (6H, CH3CHCH2), δA 3.46, δB
(ABCD = 1H, XY = 31P) (4H, CH2CH2), δA, δB 3.07, δC, δD 2.65, JAB
=
2.99, δC 2.70, δD 1.62, JAB = 12.5, JAC = 7.8, JAD = 6.1, JAX = 10.6, JAY = 0.1,
JCD = 12.9, JAC = JBD = 0.4, JAD = JBC = 8.5, JAX = JBX = 5.4, JAY = JBY = 0.2,
JCX = JDX = 5.4, JCY = JDY = 0.2 Hz, 1.26, 1.16 (t, 6H, CH3); 31P{1H}
NMR (CD2Cl2, 20 °C) δ AB spin syst, δA 164.85, δB 49.56, JAB = 52.6
Hz; 13C{1H} NMR (CD2Cl2, 20 °C) δ 165−122 (m, Ph), 88.87 (s, Cp),
66.74, 66.55 (d, CH2 phos), 40.8 (dd, CH2CH2), 16.62, 16.41
(d, CH3). Anal. Calcd for C59H59BO2P2Ru (973.93): C, 72.76; H, 6.11.
Found: C, 72.61; H, 6.19. ΛM = 55.1 Ω−1 mol−1 cm2.
JBC = 0.9, JBD = 0.6, JBX = −0.1, JBY = 0.1, JCD = 0.6, JCX = 14.0, JCY = JDX
JDY = 0.1 Hz, δA 3.60, δB 3.50, δC 2.52, δD 1.72, JAB = 12.4, JAC = 7.9, JAD
5.9, JAX = 11.3, JAY = 0.1, JBC = 0.2, JBD = 0.1, JBX = −0.1, JBY = 0.1, JCD
=
=
=
0.3, JCX = 13.3, JCY = 0.1, JDX = 1.3, JDY = 0.1 Hz, 1.26, 1.25, 1.20 (t, 9H,
CH3 phos); 31P{1H} NMR (CD2Cl2, 20 °C) δ AB spin systs, δA 139.7, δB
49.8, JAB = 64.0 Hz, δA 139.3, δB 48.3, JAB = 63.0 Hz; 13C{1H} NMR
(CD2Cl2, 20 °C) δ 165−122 (m, Ph), 88.91, 88.17 (s, Cp), 64.35, 64.13
(d, CH2 phos), 61.32, 61.23 (s, CH), 44.38, 44.35 (s, CH2), 24.55,
24.48 (s, CH3 propyl), 16.15, 15.07 (s, CH3 phos). Anal. Calcd for
C56H61BO3P2Ru (955.91): C, 70.36; H, 6.43. Found: C, 70.12; H, 6.35.
14 (L = ButNC): unstable oily product not fully characterized.
Reaction of [Ru(η5-C5H5){η1-NNC(C12H8)CH2CH2}(PPh3){P-
(OMe)3}]BPh4 (6c) with P(OMe)3: Preparation of [Ru(η5-C5H5)-
Λ
M = 52.9 Ω−1 mol−1 cm2.
(PPh3){P(OMe)3}2]BPh4 (15) and C12H8CCH2CH2 (16c). An excess of
trimethyl phosphite (P(OMe)3; 0.3 mmol, 37 μL) was added to a
solution of compound 6c (102 mg, 0.092 mmol) in 1,2-dichloroethane
(12 mL), and the reaction mixture was refluxed for 4 h. The solvent was
removed by evaporation under reduced pressure to give an oil, which
was triturated with ethanol (1 mL). A yellow solid, characterized as
complex 15, slowly separated out from the resulting solution on cooling
to −25 °C, which was filtered and dried under vacuum. The mother
liquor was chromatographed on a silica gel column (50 cm) using a
mixture of petroleum ether (40−60 °C), dichloromethane, and ethanol,
in 20:5:2 ratio, as eluent. The first eluted species was evaporated to
dryness and characterized as compound 16c.
[Ru(η5-C5H5){η1-NC(CN)CH2C(Ar1Ar2)N(H)}(PPh3)(L)]BPh4
(19, 20).
An excess of acrylonitrile (CH2CH(CN); 19 μL, 0.3 mmol) was
added to a solution of the appropriate diazoalkane complex [Ru(η5-
C5H5)(N2CAr1Ar2)(PPh3)(L)]BPh4 (2, 3; 0.1 mmol) in CH2Cl2
(4 mL), and the reaction mixture was stirred for 8 h. The solvent was
removed under reduced pressure to give an oil, which was triturated with
ethanol (2 mL) containing an excess of NaBPh4 (0.2 mmol, 68 mg).
A yellow solid slowly separated out, which was filtered and crystallized
from CH2Cl2/EtOH: yield ≥70%.
1
15: H NMR (CD2Cl2, 20 °C) δ 7.65−6.88 (m, 35H, Ph), 4.87
(s, 5H, Cp), 3.46 (d, 18H, CH3); 31P{1H} NMR (CD2Cl2, 20 °C)
δ A2B spin syst, δA 197.53, δB 99.5, JAB = 51.1 Hz. Anal. Calcd for
C53H58BO6P3Ru (995.83): C, 63.92; H, 5.87. Found: C, 64.05; H, 5.93.
Λ
M = 54.3 Ω−1 mol−1 cm2.
16c: 1H NMR (CD2Cl2, 20 °C) δ 7.85−7.07 (m, 8H, fluorene), 0.89
19b (L = P(OMe)3, Ar1 = Ph, Ar2 = p-tolyl): IR (KBr, cm−1) νCN 2213
(w); 1H NMR (CD2Cl2, 20 °C) δ 7.51−6.61 (m, 44H, Ph), ABC spin
(s, 4H, CH2); MS M+ m/z 192.
[Ru(η5-C5H5)(η2-CH3CHCH2)(PPh3)(L)]BPh4 (17, 18).
syst (3H, H1−H4), δA 7.08, δB 3.61, δC 3.31, JAB = 10.3, JAC = 18.9, JBC
=
−17.5 Hz, 4.74, 4.72 (d, 5H, Cp), 3.39, 3.38 (d, 9H, CH3 phos), 2.37,
2.34 (s, 3H, CH3 p-tolyl); 31P{1H} NMR (CD2Cl2, 20 °C) δ AB, δA
144.09, δB 47.80, JAB = 69.1; δA 143.79, δB 47.88, JAB = 69.1 Hz; 13C{1H}
NMR (CD2Cl2, 20 °C) δ 165−122 (m, Ph), 136.29 (br, C5), 114.10
(s, CN), 83.34 (s br, Cp), 76.29, 76.20 (s, C3), 54.11, 53.97 (d, CH3
phos), 47.95, 47.89 (s, C4), 21.14, 21.10 (s, CH3 p-tolyl). Anal. Calcd for
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Organometallics
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C67H64BN3O3P2Ru (1133.07): C, 71.02; H, 5.69; N, 3.71. Found: C,
71.18; H, 5.61; N, 3.64. ΛM = 55.0 Ω−1 mol−1 cm2.
give an oil, which was triturated with ethanol (3 mL) containing an
excess of NaBPh4 (0.15 mmol, 51 mg). A yellow solid slowly separated
out, which was filtered and crystallized from CH2Cl2/EtOH: yield
≥80%.
19c (L = P(OMe)3, Ar1Ar2 = C12H8): IR (KBr, cm−1) νCN 2207 (w);
1H NMR (CD2Cl2, 20 °C) δ 8.00−6.17 (m, 43H, Ph), 4.99 (s, 5H, Cp),
24b (Ar1 = Ph, Ar2 = p-tolyl): 1H NMR (CD2Cl2, 20 °C) δ 7.49−
6.86 (m, 44H, Ph), 7.36 (m, 1H, H4), 7.24 (m, 1H, H5), 4.76 (dd, 5H,
ABC spin syst (3H, H1−H4), δA 7.09, δB 3.45, δC 3.34, JAB = 10.3, JAC
=
18.9, JBC = −17.5 Hz, 3.32 (d, 9H, CH3); 31P{1H} NMR (CD2Cl2,
20 °C) δ AB, δA 146.87, δB 44.97, JAB = 69.2 Hz; 13C{1H} NMR
(CD2Cl2, 20 °C) δ 165−119 (m, Ph), 133.46 (br, C5), 114.28 (s, CN),
83.77 (s, Cp), 74.61 (s, C3), 53.68 (d, CH3), 46.21 (s, C4). Anal. Calcd
for C66H60BN3O3P2Ru (1117.03): C, 70.97; H, 5.41; N, 3.76. Found: C,
71.16; H, 5.37; N, 3.69. ΛM = 53.3 Ω−1 mol−1 cm2.
3
3
1
1
31
31
Cp, J H P = 1.8, J H P = 0.5 Hz), 3.32 (d, 9H, CH3 phos), 2.31, 2.30
(s, 3H, CH3 p-tolyl); 31P{1H} NMR (CD2Cl2, 20 °C) δ AB spin systs, δA
145.59, δB 47.90, JAB = 68.96, δA 145.55, δB 47.88, JAB = 68.94 Hz;
13C{1H} NMR (CD2Cl2, 20 °C) δ 165−122 (m, Ph), 152.71 (s, C5),
145.55 (s, C4), 104.09 (s, C3), 84.96 (s br, Cp), 53.08 (dd, CH3 phos),
21.12 (s, CH3 p-tolyl). Anal. Calcd for C66H63BN2O3P2Ru (1106.05): C,
71.67; H, 5.74; N, 2.53. Found: C, 71.59; H, 5.68; N, 2.49. ΛM = 53.7
Ω−1 mol−1 cm2.
20b (L = P(OEt)3, Ar1 = Ph, Ar2 = p-tolyl): IR (KBr, cm−1) νCN 2213
(w); 1H NMR (CD2Cl2, 20 °C) δ 7.50−6.85 (m, 44H, Ph), ABC spin
syst (3H, H1−H4), δA 3.31, δB 3.51, δC 7.29 JAB = 10.0, JAC = 20.5, JBC
=
1
24c (Ar1Ar2 = C12H8): H NMR (CD2Cl2, 20 °C) δ 8.71−6.86
−17.9 Hz, 4.70, 4.69 (s, 5H, Cp), 3.92, 3.61 (m, 6H, CH2 phos), 2.38,
2.34 (s, 3H, CH3 p-tolyl), 1.13, 1.12 (s, 9H, CH3 phos); 31P{1H} NMR
(CD2Cl2, 20 °C) δ AB, δA 138.51, δB 48.07, JAB = 69.10; δA 138.22, δB
48.12, JAB = 69.10 Hz; 13C{1H} NMR (CD2Cl2, 20 °C) δ 165−121
(m, Ph), 136.08, 135.90 (br, C5), 114.22, 114.18 (s, CN), 83.37, 83.22
(s, Cp), 76.26, 76.15 (br, C3), 63.64, 62.31 (d, CH2 phos), 48.18, 48.11
(s, C4), 21.10, 21.06 (s, CH3 p-tolyl), 16.18, 16.10 (d, CH3 phos). Anal.
Calcd for C70H70BN3O3P2Ru (1175.15): C, 71.54; H, 6.00; N, 3.58.
Found: C, 71.36; H, 5.95; N, 3.67. ΛM = 52.4 Ω−1 mol−1 cm2.
3
1
1
(m, 43H, Ph), 7.62 (d, 1H, H4), 6.82 (d, 1H, H5, J H H = 3.0 Hz), 4.81
(s, 5H, Cp), 3.48 (d, 9H, CH3); 31P{1H} NMR (CD2Cl2, 20 °C) δ AB
spin syst, δA 143.6, δB 47.5, JAB = 68.2 Hz; 13C{1H} NMR (CD2Cl2,
20 °C) δ 165−119 (m, Ph), 155.24 (s, C5), 141.16 (s, C4), 105.18
(s, C3), 85.21 (t, Cp, 2J P = 2.1 Hz), 53.3 (d, CH3). Anal. Calcd for
13C31
C65H59BN2O3P2Ru (1090.00): C, 71.62; H, 5.46; N, 2.57. Found: C,
71.73; H, 5.53; N, 2.50. ΛM = 51.1 Ω−1 mol−1 cm2.
[Ru(η5-C5H5){CC(H)R}(PPh3){P(OMe)3}]BPh4 (25, 26). An
excess of the appropriate alkyne HCCR (0.14 mmol) was added to a
solution of the diazoalkane complex [Ru(η5-C5H5){N2C(Ph)(p-tolyl)}-
(PPh3){P(OMe)3}]BPh4 (2b; 0.10 g, 0.093 mmol) in 1,2-dichloro-
ethane (10 mL), and the reaction mixture was refluxed for 30 min.
The solvent was removed under reduced pressure to give an oil, which
was triturated with ethanol (2 mL) containing an excess of NaBPh4
(0.15 mmol, 51 mg). A pink solid slowly separated out, which was
filtered and crystallized from CH2Cl2/EtOH: yield ≥60%.
[Ru(η5-C5H5){η2-CHCHC(O)OC(O)}(PPh3){P(OMe)3}]BPh4 (21)
and [Ru(η5-C5H5){η2-CH3OCOC(H)C(H)COOCH3}(PPh3){P-
(OMe)3}]BPh4 (22). In a 25 mL three-necked round-bottomed flask
were placed 0.100 g (0,093 mmol) of the diazoalkane complex [Ru-
(η5-C5H5){N2C(Ph)(p-tolyl)}(PPh3){P(OMe)3}]BPh4 (2b), an excess
(0.3 mmol) of either maleic anhydride (ma; 29 mg) or dimethyl maleate
(dmm; 43 mg), and 5 mL of CH2Cl2. The reaction mixture was stirred
for 24 h and then the solvent removed under reduced pressure to give an
oil, which was triturated with ethanol (2 mL). A yellow solid slowly
separated out, which was filtered and crystallized from CH2Cl2/EtOH:
yield ≥75%.
25 (R = Ph): IR (KBr, cm−1) νRuCC 1653 (m); 1H NMR (CD2Cl2,
20 °C) δ 7.51−6.87 (m, 40H, Ph), 5.57 (m, 1H, CH), 5.36 (s, 5H,
Cp), 3.39 (d, 9H, CH3); 31P{1H} NMR (CD2Cl2, 20 °C) δ AB spin syst,
δA 138.1, δB 47.4, JAB = 48.5 Hz; 13C{1H} NMR (CD2Cl2, 20 °C) δ
21: IR (KBr, cm−1) νCO 1826, 1763 (s); 1H NMR (CD2Cl2, 20 °C) δ
7.65−6.87 (m, 35H, Ph), 5.01 (s, 5H, Cp), ABXY spin syst (X, Y = 1H)
2
2
13C31
P
13C31
P
= 21.9, J
359.28 (dd, Cα, J
= 14.3 Hz), 165−122 (m, Ph),
118.34 (s, Cβ), 93.25 (s, Cp), 54.48 (d, CH3). Anal. Calcd for
(2H, CH), δX 4.23, δY 4.02, JAX = 15.5, JAY = 13.45, JBX = 0.40, JBY
=
0.65, JXY = 4.27 Hz, 3.58 (d, 9H, CH3); 31P{1H} NMR (CD2Cl2, 20 °C)
δ AB spin syst, δA 133.1, δB 41.98, JAB = 55.0 Hz; 13C{1H} NMR
(CD2Cl2, 20 °C) δ 172.76, 171.69 (s, CO), 165−122 (m, Ph), 94.8 (s,
Cp), 56.25 (d, CH3), 46.05, 43.14 (d, CH). Anal. Calcd for
C54H51BO6P2Ru (969.81): C, 66.88; H, 5.30. Found: C, 66.76; H, 5.38.
C58H55BO3P2Ru (973.88): C, 71.53; H, 5.69. Found: C, 71.66; H, 5.61.
Λ
M = 54.0 Ω−1 mol−1 cm2.
1
26 (R = But): IR (KBr, cm−1) νRuCC 1675, 1644 (m); H NMR
(CD2Cl2, 20 °C) δ 7.55−6.87 (m, 35H, Ph), 5.22 (d, 5H, Cp), 4.31 (dd,
1H, CH), 3.99 (d, 9H, CH3 phos), 1.10 (s, 9H, CH3 But); 31P{1H}
M = 52.6 Ω−1 mol−1 cm2.
NMR (CD2Cl2, 20 °C) δ AB spin syst, δA 140.38, δB 47.73, JAB
=
=
Λ
50.7 Hz; C{1H} NMR (CD2Cl2, 20 °C) δ 353.07 (dd, Cα, J
13
2
13C31
P
22: IR (KBr, cm−1) νCO 1746, 1722 (s); 1H NMR (CD2Cl2, 20 °C) δ
20.2, 2J P = 15.3 Hz), 165−122 (m, Ph), 124.86 (s, Cβ), 92.33 (s, Cp),
13C31
7.58−6.87 (m, 35H, Ph), 5.12 (s, 5H, Cp), 3.77, 3.72 (s, 6H, CH3COO),
ABXY spin syst (X, Y = 1H) (2H, CH), δX 3.62, δY 3.32, JAX = 16.6,
JAY = 12.6, JBX = 0.8, JBY = 0.45, JXY = 9.45 Hz, 3.51 (d, 9H, CH3 phos);
54.03 (d, CH3 phos), 32.53 (s, C But), 32.14 (s, CH3 But). Anal. Calcd
for C56H59BO3P2Ru (953.89): C, 70.51; H, 6.23. Found: C, 70.65; H,
6.11. ΛM = 52.8 Ω−1 mol−1 cm2.
31P{1H} NMR (CD2Cl2, 20 °C) δ AB spin syst, δA 138.4, δB 42.70, JAB
=
[Ru(η5-C5H5){η1-NNC(Ar1Ar2)C(H)C(COOMe)}(PPh3){P(OMe)3}]-
58.9 Hz; 13C{1H} NMR (CD2Cl2, 20 °C) δ 173.21, 170.61 (s, CO),
165−122 (m, Ph), 92.15 (s, Cp), 55.87 (d, CH3 phos), 54.08, 46.74
(s, CH), 53.32, 52.62 (s, CH3COO). Anal. Calcd for C56H57BO7P2Ru
(1015.88): C, 66.21; H, 5.66. Found: C, 66.03; H, 5.70. ΛM = 53.5
Ω−1 mol−1 cm2.
BPh4 (27) and [Ru(η5-C5H5){η1-NNC(Ar1Ar2)C(H)C(COOEt)}-
(PPh3){P(OMe)3}]BPh4 (28). An excess of the alkyl propiolate
HCCCOOR (R = Me, Et; 0.30 mmol) was added to a solution of
the appropriate diazoalkane complex [Ru(η5-C5H5)(N2CAr1Ar2)-
(PPh3){P(OMe)3}]BPh4 (2; 0.1 mmol) in dichloromethane (5 mL),
and the reaction mixture was stirred for 48 h. The solvent was removed
under reduced pressure to give an oil, which was triturated with ethanol
(3 mL) containing an excess of NaBPh4 (0.15 mmol, 51 mg). A reddish
brown solid slowly separated out, which was filtered and crystallized
from CH2Cl2/EtOH: yield ≥55%.
Reaction of [Ru(η5-C5H5){η1-NC(CN)CH2C(Ph)(p-tolyl)N(H)}-
(PPh3){P(OMe)3}]BPh4 (19b) with P(OMe)3: Separation of N
C(CN)CH2C(Ph)(p-tolyl)NH (23b). The reaction was carried out
exactly as for the related 4,5-dihydro-3H-pyrazole 6c, but at room tem-
perature for 48 h. The solid which separated out was [Ru(η5-C5H5)
(PPh3){P(OMe)3}2]BPh4 (15), whereas that obtained by chromatog-
raphy of the mother liquor was the free 1H-pyrazoline compound 23b:
27b (Ar1 = Ph, Ar2 = p-tolyl): IR (KBr, cm−1) νCO 1729 (s); 1H NMR
5
1
31
(CD2Cl2, 20 °C) δ 7.62 (d, 1H, CH, H4, J H P = 5.0 Hz), 7.57−6.63
1
IR (KBr, cm−1) νNH 3268 (m), νCN 2213 (w); H NMR (CD2Cl2,
3
1
31
(m, 44H, Ph), 4.81 (d, 5H, Cp, J H P = 2.6 Hz), 3.73 (s, 3H, CH3COO),
3.37 (d, 9H, CH3 phos), 2.34 (s, 3H, CH3 p-tolyl); 31P{1H} NMR
(CD2Cl2, 20 °C) δ AB spin syst, δA 145.15, δB 47.10, JAB = 68.0 Hz;
13C{1H} NMR (CD2Cl2, 20 °C) δ 165−122 (m, Ph), 159.98 (s, CO),
155.95 (s, C4), 147.04 (s, C5), 103.93 (br, C3), 84.77 (s, Cp), 52.59 (d,
CH3 phos), 52.43 (s, CH3COO), 20.46 (s, CH3 p-tolyl). Anal. Calcd for
C68H65BN2O5P2Ru (1164.08): C, 70.16; H, 5.63; N, 2.41. Found: C,
70.29; H, 5.71; N, 2.30. ΛM = 51.4 Ω−1 mol−1 cm2.
20 °C) δ 7.65−6.70 (m, 9H, Ph), AB spin syst (2H, H4), δA 3.74, δB 3.46,
JAB = −11.7 Hz, 2.33 (s, 3H, CH3).
[Ru(η5-C5H5){η1-NNC(Ar1Ar2)CHCH}(PPh3){P(OMe)3}]-
BPh4 (24). A solution of the appropriate diazoalkane complex [Ru(η5-
C5H5)(N2CAr1Ar2)(PPh3){P(OMe)3}]BPh4 (2; 0.11 mmol) in
dichloromethane (10 mL) was stirred under acetlylene (HCCH;
1 atm) for 24 h. The solvent was removed under reduced pressure to
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Article
28b (Ar1 = Ph, Ar2 = p-tolyl): IR (KBr, cm−1) νCO 1721 (s); 1H NMR
a
Scheme 1.
(CD2Cl2, 20 °C) δ 7.62 (s br, 1H, CH, H4), 7.57−6.64 (m, 44H, Ph),
3
1
31
4.83 (d, 5H, Cp, J H P = 3.2 Hz), 4.17, 4.16 (q, 2H, CH2), 3.39 (d, 9H,
CH3 phos), 2.37 (s, 3H, CH3 p-tolyl), 1.20 (t, 3H, CH3 Et); 31P{1H}
NMR (CD2Cl2, 20 °C) δ AB spin syst, δA 145.32, δB 47.10, JAB
=
68.0 Hz; 13C{1H} NMR (CD2Cl2, 20 °C) δ 165−122 (m, Ph), 159.24
(s, CO), 156,57 (s, C4), 148.4 (br, C5), 104.51 (br, C3), 85.62 (d, Cp),
62.69 (s, CH2), 53.32 (d, CH3 phos), 21.29 (s, CH3 p-tolyl), 14.11
(s, CH3 Et). Anal. Calcd for C69H67BN2O5P2Ru (1178.11): C, 70.34; H,
5.73; N, 2.38. Found: C, 70.26; H, 5.64; N, 2.31. ΛM = 51.6 Ω−1 mol−1 cm2.
1
28c (Ar1Ar2 = C12H8): IR (KBr, cm−1) νCO 1715 (s); H NMR
a
Definitions: L = PPh3 (1), P(OMe)3 (2), P(OEt)3 (3), PPh(OEt)2
(4), ButNC (5); Ar1 = Ar2 = Ph (a), Ar1 = Ph, Ar2 = p-tolyl (b),
Ar1Ar2 = C12H8 (c), Ar1 = Ph, Ar2 = PhCO (d).
(CD2Cl2, 20 °C) δ 7.65 (s br, 1H, CH, H4), 8.60−6.24 (m, 43H, Ph),
4.86 (s, 5H, Cp), 4.53 (q, 2H, CH2), 3.49 (d, 9H, CH3 phos), 1.20 (t,
3H, CH3 Et); 31P{1H} NMR (CD2Cl2, 20 °C) δ AB spin syst, δA 145.43,
δB 47.20, JAB = 68.0 Hz. Anal. Calcd for C68H63BN2O5P2Ru (1162.07):
C, 70.28; H, 5.46; N, 2.41. Found: C, 70.40; H, 5.57; N, 2.34. ΛM
=
52.4 Ω−1 mol−1 cm2.
similar to that found in the solid state for 3b. In the spectra
of isocyanide derivatives [Ru(η5-C5H5)(N2CAr1Ar2)(PPh3)-
(ButNC)]BPh4 (5), a strong band at 2140−2130 cm−1 also appears,
due to νCN of the isocyanide.
X-ray Data Collection and Refinement. Crystallographic data for
complexes 21 and 24c were collected on a Bruker Smart 1000 CCD
diffractometer at CACTI (Universidade de Vigo) using graphite-
monochromated Mo Kα radiation (λ = 0.71073 Å), and were corrected
for Lorentz and polarization effects. The software SMART16 was used
for collecting frames of data and indexing reflections, and the deter-
mination of lattice parameters. Crystallographic data for 19b were
collected at room temperature using a Bruker Smart 6000 CCD detector
and Cu Kα radiation (λ = 1.54178 Å) generated by a Incoatec micro-
focus source equipped with Incoatec Quazar MX optics. The software
APEX217 was used for collecting frames of data and indexing reflections
and the determination of lattice parameters. In all cases, the software
SAINT18 was used for integration of the intensity of reflections and
SADABS19 for scaling and empirical absorption correction. The crystal-
lographic treatment was performed with the Oscail program.20 The
structures of 19b and 21 were solved by the Patterson method21 and that
of 24c by using SUPERFLIP.22 Both structures were refined by full-
matrix least squares based on F2.21 Non-hydrogen atoms were refined
with anisotropic displacement parameters. Hydrogen atoms were
included in idealized positions and refined with isotropic displacement
parameters, except those of the maleic anhydride ligand. These were
found in the final density map and refined isotropically. Details of crystal
data and structural refinement are given in the Supporting Information
(Table S1).
Reactions with Ethylene. The reactions of diazoalkane
complexes [Ru(η5-C5H5)(N2CAr1Ar2)(PPh3)(L)]BPh4 (1−5)
with ethylene are shown in Scheme 2.
Although triphenylphosphine complexes [Ru(η5-C5H5)-
(N2CAr1Ar2)(PPh3)2]BPh4 (1) react with CH2CH2 (1 atm)
to give quantitatively the ethylene complex [Ru(η5-C5H5)(η2-
CH2CH2)(PPh3)2]BPh4 (10), the mixed-ligand diazoalkane
derivatives [Ru(η5-C5H5)(N2CAr1Ar2)(PPh3)(L)]BPh4 (2−5)
react with ethylene, under mild conditions (1 atm, room tem-
perature), to give not only small amounts of ethylene complexes
[Ru(η5-C5H5)(η2-CH2CH2)(PPh3)(L)]BPh4 (11−14) but
also the novel derivatives [Ru(η5-C5H5){η1-NNC(Ar1Ar2)-
CH2CH2}(PPh3)(L)]BPh4 (6−9), which contain 4,5-dihydro-
3H-pyrazole as a ligand.
The reaction proceeds with (3 + 2) cycloaddition of the
ethylene to the coordinate diazoalkane giving 4,5-dihydro-3H-
pyrazole derivatives 6−9, in which the novel heterocycle acts as
a ligand. Parallel substitution of the diazoalkane by CH2CH2
also proceeds to a small extent, yielding ethylene complexes
11−14. The two complexes formed by the reaction, [Ru-
(η5-C5H5)-{η1-NNC(Ar1Ar2)CH2CH2}(PPh3)(L)]BPh4
(6−9) and [Ru(η5-C5H5)(η2-CH2CH2)(PPh3)(L)]BPh4
(11−14), were recovered as solids and separated by fractional
crystallization in good yields (70−80% for 6−9, 8−10% for
11−13, traces for 14) as yellow-orange crystalline solids. In
the mother liquor, free diazoalkane Ar1Ar2CN2 forming as a
result of the substitution with CH2CH2 was also detected,
indicating that only the coordinated diazoalkane under-
goes cyclization with ethylene to yield 4,5-dihydro-3H-
pyrazole species.
RESULTS AND DISCUSSION
■
Preparation of Diazoalkane Complexes. Half-sandwich
diazoalkane complexes of the type [Ru(η5-C5H5)(N2CAr1Ar2)-
(PPh3)(L)]BPh4 (1−5) were prepared by reacting the chloro
compounds RuCl(η5-C5H5)(PPh3)(L) with an excess of
diazoalkane in ethanol, in the presence of NaBPh4, as shown in
Scheme 1.
The reaction proceeded with substitution of the chloride
with the Ar1Ar2CN2 group, affording the final diazoalkane
complexes 1−5. Crucial for successful synthesis was the presence
of the NaBPh4 salt which, favoring substitution of the Cl− ligand,
allowed the complexes to separate as orange solids. Both bis-
(triphenylphosphine) [Ru(η5-C5H5)(PPh3)2]+ and mixed-ligand
[Ru(η5-C5H5)(PPh3)(L)]+ fragments (L = phosphites, tert-butyl
isocyanide) are able to stabilize diazoalkane complexes 1−5,
which were isolated as solids stable in air and in solution of polar
organic solvents, where they behave as 1:1 electrolytes.23 Ana-
lytical and spectroscopic data (IR and NMR) confirm the
proposed formulation, which was further supported by an X-ray
crystal structure determination10 of [Ru(η5-C5H5){N2C(Ph)-
(p-tolyl)}(PPh3){P(OEt)3}]BPh4 (3b).
The reaction of free diazoalkane24 with ethylene is very rare25
and needs quite drastic conditions to proceed (11 days, 55 °C).
Coordination with the Ru(η5-C5H5)(PPh3)(L) fragment
activates Ar1Ar2CN2 species toward cyclization, allowing the
formation of 3H-pyrazole species under very mild conditions.
However, only mixed-ligand fragments containing phosphite
or isocyanide can activate diazoalkanes toward cyclization with
CH2CH2, since the bis(triphenylphosphine) complexes
[Ru(η5-C5H5)(N2CAr1Ar2)(PPh3)2]BPh4 (1) give exclusively
substitution reaction with ethylene, affording η2-CH2CH2
derivatives 10. Activation of diazoalkane by coordination was
also observed in imine aziridination catalyzed by ruthenium
complexes,8m but in that case a carbene transfer reaction to imine
occurs.
The IR spectra show a medium-intensity band at 1967−
1900 cm−1, attributed to νCNN of the coordinated diazo-
alkane. Comparison of this value with literature data also suggests
the end-on η1 coordination mode for the Ar1Ar2CN2 group,
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Organometallics
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a
Scheme 2.
a
Definitions: L = P(OMe)3 (6, 11), P(OEt)3 (7, 12), PPh(OEt)2 (8, 13), ButNC (9, 14); Ar1 = Ar2 = Ph (a), Ar1 = Ph, Ar2 = p-tolyl (b), Ar1Ar2 =
C12H8 (c).
determination10 of [Ru(η5-C5H5){η1-NNC(C12H8)CH2CH2}-
The 4,5-dihydro-3H-pyrazole ligand is very stable to substi-
tution in the complexes [Ru(η5-C5H5){η1-NNC(Ar1Ar2)-
(PPh3){P(OMe)3}]BPh4 (6c).
The 4,5-dihydro-3H-pyrazole complexes [Ru(η5-C5H5){η1-
CH2CH2}(PPh3)(L)]BPh4 (6−9) and, at room temperature,
cannot be removed by treatment with excesses of Cl−, phosphine,
NNC(Ph)(p-tolyl)CH2CH2}(PPh3){P(OMe)3}]BPh4 (6b−
9b), containing two different substituents at the C3 carbon atom
of the heterocycle, were obtained as a mixture of two diaste-
reoisomers, owing to the presence of two chiral centers in the
molecule: i.e., the ruthenium atom and the C3 atom of the
carbonyl, or other ligands. Instead, in refluxing dichloroethane,
[Ru(η5-C5H5){η1-NNC(C12H8)CH2CH2}(PPh3){P-
(OMe)3}]BPh4 (6c) does react with an excess of P(OMe)3 with
substitution of the 4,5-dihydro-3H-pyrazole ligand and for-
mation of the phosphine complex [Ru(η5-C5H5)(PPh3)-
{P(OMe)3}2]BPh4 (15) (Scheme 3), which was separated and
characterized.
1
3
heterocyclic ligand. H, P, and 13C NMR spectra confirm the
presence of the two diastereoisomers, showing two sets of signals
for the nuclei of the ligands. In particular, the 31P NMR spectra of
6b−8b show two AB quartets, whereas the proton spectra show
two singlets for the η5-C5H5 protons and two for the CH3 groups
of the p-tolyl substituent at C3 of the 4,5-dihydro-3H-pyrazole.
In addition, two groups of partially overlapping signals were
observed for the H4 and H5 protons of the ligand, fitting the
proposed formulation for the complexes.
Scheme 3. Substitution Reaction
The spectrum of the isocyanide derivative [Ru(η5-C5H5)-
{η1-NNC(Ph)(p-tolyl)CH2CH2}(PPh3)(ButNC)]BPh4 (9b)
also shows two sets of signals, partially overlapping, for both the
1
3P and H nuclei, supporting the presence of two diastereo-
isomers. The IR spectrum also shows a strong band at 2123 cm−1,
due to νCN of ButNC, whereas in the 1H NMR spectrum the signal
of thetert-butylsubstituents appears as a singletat1.29 ppm, fitting
the proposed formulation for 9b.
The 31P NMR spectra of the related complexes [Ru(η5-
Unfortunately, the expected 4,5-dihydro-3H-pyrazole species
C5H5){η1-NNC(C12H8)CH2CH2}(PPh3)(L)]BPh4 (6c−8c)
NNC(C12H8)CH2CH2 could not be obtained by chromato-
graphic separation from the reaction mixture, but only its probable
decomposition product 16c. The formation of such a bicyclic
compound is not surprising, owing to the known thermal26,27 or
photochemical28 decomposition of pyrazolines to give cyclo-
propane. The refluxing conditions used to remove 4,5-dihydro-
3H-pyrazole caused decomposition of the azo species.
Good analytical data were obtained for both 4,5-dihydro-3H-
pyrazole (6−9) and η2-alkene derivatives (10−14), which were
all isolated as yellow or orange solids, stable in air and in solution
of polar organic solvents, where they behave as 1:1 electrolytes.23
Infrared and NMR spectra support the proposed formulations,
which were further confirmed by an X-ray crystal structure
and [Ru(η5-C5H5){η1-NNC(Ph2)CH2CH2}(PPh3)(L)]BPh4
(6a), which contain only one chiral center, show only one AB
quartet, and the 1H and 13C spectra support the presence of the
heterocyclic ligand. In particular, a triplet at 2.32−2.20 ppm
attributed to methylene protons H4 and two triplets at 4.90−
4.45 ppm attributed to methylene hydrogen atoms H5 were
observed in the 1H NMR spectra. The 13C spectrum of 6c shows
two singlets at 88.95 and 30.59 ppm which, in an HMQC
experiment, were correlated with the multiplet at 4.84 ppm and
the triplet at 2.23 ppm, respectively, and attributed to the C5 and
C4 carbon atoms of the 4,5-dihydro-3H-pyrazole ligand. The
singlet at 98.32 ppm was attributed to C3.
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At room temperature, the proton spectra of ethylene com-
plexes [Ru(η5-C5H5)(η2-CH2CH2)(PPh3)(L)]BPh4 (11−13)
show two multiplets at 3.07−2.99 and 2.65−2.71 ppm, but only
one triplet at 2.97 ppm appears for [Ru(η5-C5H5)(η2-CH2
CH2)(PPh3)2]BPh4 (10); they were attributed to the protons of
the coordinated ethylene. Lowering the sample temperature
caused some variations in the spectra, but ethylene peaks were still
broadened even at −90 °C, suggesting that rotation of CH2CH2
still occurred at this temperature. However, the room-temperature
pattern of mixed-ligand complexes 11−13 can be simulated by an
ABCDXY model (X, Y = 31P) with the parameters reported in the
Experimental Section, and the good fit between calculated and
experimental spectra strongly supports the proposed attributions.
In the 13C spectra, CH2CH2 carbon resonances appear as dou-
blets at 38.25−40.80 ppm for 11−13 and as a singlet at 43.59 ppm
for 10, whereas the 31P spectra are AB quartets for 11−13 and one
singlet at 41.70 ppm for 10, fitting the proposed formulation for
complexes 10−13.
4,5-dihydro-3H-pyrazole species. Cyclization with propylene is
probably very slow and requires more drastic conditions, if it is to
proceed.
Styrene is also unreactive toward cyclization with coordinated
diazoalkane, and this result may be attributed to either electronic
or steric factors of the substituent CH3 or C6H5 of the alkene.
However, although the steric requirements of the alkene may be
important in determining the 1,3-dipolar cycloaddition of coor-
dinate diazoalkanes, acrylonitrile (CH2C(H)CN) quickly
reacts with [Ru(η5-C5H5)(N2CAr1Ar2)(PPh3)(L)]BPh4 (2, 3)
to give exclusively the 1H-pyrazoline derivatives [Ru(η5-C5H5)
{η1-NC(CN)CH2C(Ar1Ar2)NH}(PPh3)(L)]BPh4 (19, 20)
in high yields. The reaction proceeds with (3 + 2) cycloaddition
of CH2C(H)CN to the coordinated diazoalkane, giving
3H-pyrazole derivatives [Ru]− η1-NNC(Ar1Ar2)CH2CH(CN)
(A) (Scheme 5), which tautomerize to the final 1H-pyrazoline
derivatives 19 and 20.
Reactions with Substituted Alkenes. The results obtained
with ethylene prompted us to extend our study to the reactivity of
coordinate diazoalkanes toward some electron-rich and electron-
poor alkenes. The results are shown in Scheme 4.
a
Scheme 5.
a
Scheme 4.
a
Definition: [Ru] = [Ru(η5-C5H5)(PPh3)(L)]+.
Tautomerization of the azacycle involves a 1,3-H shift from C
to N and is probably favored by the CN group, making the
CH(CN) hydrogen atom acidic.
The presence of an electron-withdrawing group such as CN
favors cyclization of the alkene rather than substitution, unlike
the case for propylene which, containing the electron-donor
group CH3, exclusively gives η2-CH3CHCH2 derivatives.
In the monosubstituted alkenes CH2CHR, electronic factors
seem to be more important than steric factors in leading the
reaction of coordinated diazoalkane toward cyclization, affording
1H-pyrazoline derivatives.
Surprisingly, the reactions of other activated alkenes, such as
maleic anhydride (CHCHCO(O)CO, ma) and dimethyl
maleate (CH3OCOC(H)C(H)COOCH3, dmm), proceed
with substitution of the coordinated diazoalkane to give almost
quantitatively the η2-alkene complexes [Ru(η5-C5H5){η2-RC-
(H)C(H)R}(PPh3)(L)]BPh4 (21, 22), which were isolated
and characterized. No evidence of the formation of 3H-pyrazole
complexes was obtained from NMR spectra, suggesting that, in
these alkenes, despite the presence of two electron-withdrawing
groups, steric hindrance of substituents prevents the cyclization
reaction, affording only η2-alkene derivatives 21 and 22.
a
Definitions: L = P(OMe)3 (17, 19, 21, 22), P(OEt)3 (18, 20); Ar1 =
Ph, Ar2 = p-tolyl (b), Ar1Ar2 = C12H8 (c); ma = maleic anhydride,
dmm = dimethyl maleate.
Fumaronitrile ((NC)CHCH(CN)) was also reacted with
diazoalkane complexes, but in this case the reaction was very
slow, affording only a mixture of products after 2 days. Although
the NMR spectra suggest the formation of a small amount of the
4,5-dihydro-3H-pyrazole complex, the main species is the
starting diazoalkane complex, which reacts very slowly with the
activated alkene, owing to the presence of two trans CN groups.
Although the number of alkenes used was limited and no
kinetic study was carried out, the results indicate that alkenes
with little steric hindrance (CH2CH2) and/or containing
Under mild conditions (1 atm, room temperature), propylene
(CH3C(H)CH2) does not react with diazolkane complexes
1−5. Instead, under pressure (7 atm, room temperature), substi-
tution of the diazoalkane was observed, with formation of the
propylene complex [Ru(η5-C5H5)(η2-CH3CHCH2)(PPh3)-
(L)]BPh4 (17, 18), but no evidence of a cycloaddition reaction
was detected. In fact, in addition to η2-propylene complexes,
some other unidentified products did form in the reaction
under pressure, but NMR spectra excluded the formation of
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electron-withdrawing groups (CH2CH(CN)) do react with
diazoalkane complexes to give (3 + 2) cycloaddition, whereas
alkenes with either electron-donor groups (CH3CHCH2) or
bulkier substituents only gave substitution of the diazoalkane,
affording η2-alkene derivatives.
Previous studies on the coordinated diazoalkane have shown
that they can give both dinitrogen [M]−N2 and carbene [M]−
CAr1Ar2 complexes.8f N−N bond cleavage has also been ob-
served,8k as well as reduction of the coordinated N2CAr1Ar2
ligand.8i However, an example of the cycloaddition reaction has
been reported for a C-bonded diazoalkane in Rh[η1-C(N2)-
SiMe3][P(OEt)3]3, affording the triazole derivative Rh[CC-
(SiMe3)N2NBut](ButNC)[P(OEt)3] in the reaction with
ButNC.29 Ethene has also been previously reported7j to react
with the diazoalkane complex RhCl(N2CC12H8)(PPri3)2, giving
RhCl(η2-CH2CH2)(PPri3)2 and the fulvalene derivative
CH3CHC(C12H8).
Using the half-sandwich mixed-ligand fragment [Ru(η5-
C5H5)(PPh3)(L)]+ not only allowed coordination of the diazo-
alkane but also led to the unprecedented dipolar (3 + 2) cyclo-
addition of coordinate N2CAr1Ar2 to ethene and acrylonitrile,
affording novel dihydro-3H-pyrazole molecules in one case and
3-cyano-1H-pyrazoline in the other.
Figure 1. ORTEP drawing of the cation of 19b at the 20% probability
level. P(1) represents a PPh3 ligand and P(2) a P(OMe)3 ligand. Only
the hydrogen atoms of the pyrazoline ligand are shown. Selected bond
lengths (Å) are as follows: Ru−CT1, 1.87679(17); Ru−N(1),
2.1151(18); Ru−P(1), 2.3437(5); Ru−P(2), 2.2356(6). Cp ring: Ru−
C(1), 2.228(2); Ru−C(2), 2.259(2); Ru−C(3), 2.238(2); Ru−C(4),
2.198(2); Ru−C(5), 2.199(2); C3N2 ring: N(1)−N(2), 1.379(3);
N(1)−C(5), 1.309(3); N(2)−C(3) 1.502(3); C(4)−C(5), 1.488(4);
C(3)−C(4), 1.556(3); C(6)−N(11), 1.137(3). Selected bond angles
(deg): P(1)−Ru−P(2), 94.48(2); CT1−Ru−P(1), 120.917(15);
CT1−Ru−P(2), 120.888(17); CT1−Ru−N(1), 127.66(5); N(1)−
Ru−P(1), 92.12(5); N(1)−Ru−P(2), 92.21(5). CT1 represents the
centroid of the Cp ligand.
The pyrazoline ligand η1-NC(CN)CH2C(Ar1Ar2)NH is
relatively labile in complexes 19 and 20 and can be substituted at
room temperature by P(OMe)3, yielding [Ru(η5-C5H5)(PPh3)-
{P(OMe)3}2]BPh4 (15) and the free azacycle 23, which can be
separated by chromatography (Scheme 6).
Scheme 6. Substitution Reaction
−
The asymmetric units of 19b and 21 contain a BPh4 anion
(not shown in the figures) and a ruthenium cation complex. In
both cases, the cation complex contains a ruthenium atom in a
half-sandwich piano-stool structure, coordinated by a Cp group,
two phosphane ligands (one PPh3 and one P(OMe)3), and
another ligand completing the octahedral geometry around
ruthenium metal, marked by near-90° values for angles between
the “legs”. The η5 coordination mode of the Cp ligand and the
coordinative behavior of the phosphanes are as expected and do
not need further comments.15,31−33 Noteworthy for 19b is the
new pyrazoline ligand. The 5-phenyl-5-(p-tolyl)-3-cyano-1H-
pyrazoline ligand is bonded to the metal through an sp2 nitrogen
atom labeled N(1), and the geometrical parameters confirm the
proposed formulation as a 1H-pyrazoline ligand and the single-
bond character of the N−N bond. That is, the N−N bond length,
1.379(3) Å, is longer than that expected for a pyrazole ring34 but
much longer than that found in the spiro[fluorene-9,3′-
pyrazoline] ligand,10 at 1.241(4) Å, or in 23c, with a value of
1.260(4) Å (see below). The sp3 N(2) atom is also bonded to
carbon, N(2)−C(3), with a bond length of 1.502(3) Å, a single
bond, and also to a hydrogen atom found clearly out of plane on
the density map. However, the donor sp2 N(1) atom is bonded to
the carbon, N(1)−C(5), with a bond length of 1.309(3) Å, the
expected distance for a delocalized bond.34 The C(5)−C(6)
distance of 1.421(3) Å is only slightly shorter than that expected
for a single bond. The presence of the CN group as a sub-
stituent of the ring explains the electronic delocalization over the
NC−CN−N moiety in the ring (Figure 2).
Unlike 4,5-dihydro-3H-pyrazole in complexes 6−9, the 1H-
pyrazoline molecule 23 can be removed from the complex and
recovered as an oil.
Characterization of Complexes 17−22. 1H-Pyrazoline
derivatives [Ru(η5-C5H5){η1-NC(CN)CH2C(Ar1Ar2)NH}-
(PPh3)(L)]BPh4 (19, 20) and η2-alkene complexes [Ru(η5-
C5H5){η2-RC(H)C(H)R}(PPh3)(L)]BPh4 (17, 18, 21, 22)
were isolated as yellow or orange solids stable in air and in
solution of polar organic solvents, where they behave as 1:1
electrolytes.23 Their characterization has been supported by
analytical and spectroscopic IR and NMR data and by X-ray
crystal structure determinations of [Ru(η5-C5H5)(η2-CH3CH
10
CH2)(PPh3){P(OMe)3}]BPh4 (17), [Ru(η5-C5H5){η1-N
C(CN)CH2C(Ph)(p-tolyl)NH}(PPh3){P(OMe)3}]BPh4
The pyrazoline ring is not planar and has a twisted-envelope
conformation, with puckering parameters Q = 0.213(3) Å and
φ = 249.9(7)°.35 The rms deviation of the five atoms from the
best plane is 0.095 Å, with a maximum of 0.128(2) Å for the atom
(19b), and [Ru(η5-C5H5){η2-CHCHC(O)OC(O)}(PPh3)-
{P(OMe)3}]BPh4 (21), the ORTEP drawings30 of which are
shown in Figures 1, 3, and 4, respectively.
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Figure 2. Atoms involved in the electronic delocalization.
labeled C(3), which is phenyl- and tolyl-substituted. The
ruthenium atom is situated only 0.117(5) Å out of this plane,
and the Ru−N bond forms an angle of only 1.83(15)° with the
plane. The cyanide group also belongs to this plane, with
distances of only 0.083(6) Å for C(6) and 0.116(7) Å for N(11),
confirming the sp2 character of C(5).
Compound 21 contains one η2-maleic anhydride (η2-ma)
ligand as the third leg of the piano-stool structure (Figure 3).
Figure 4. ORTEP view of the cation of 21 showing the disposition of
η2-ma ligand.
(diphenylphosphino)methane),39 Ru(η2-ma)(CO)(CN-p-
tolyl)(PPh3)2,36 and Os(η2-ma)(CO)2(PPh3)2.40 This may
indicate scarce π back-bonding by the metal. However, the
hydrogen atoms deviate by 0.39(6) and 0.35(6) Å out of the
plane with respect to the maleic anhydride ring (C4O) and are
sometimes even much farther: e.g., 0.49 and 0.61 Å in the iron
compound Fe(CO)2(η2-ma)[2-pyridylbis(diphenylphosphino)-
methane].39
To the best of our knowledge,41 the literature only reports one
(η2-ma)ruthenium complex, the Ru(0) species Ru(η2-ma)(CO)-
(CN-p-tolyl)(PPh3)2,36 and a dinuclear compound with the
substituted 2,3-bis(diphenylphosphino)maleic anhydride,
Ru2(CO)6(bma),42 is also known; thus, 21 is the first structurally
characterized (η2-ma)ruthenium(II) complex.
Figure 3. ORTEP view of the cation of 21. P(1) represents a PPh3
ligand, and P(2) represents a P(OMe)3 ligand. Only the hydrogen atoms
of the η2-ma ligand are shown. Selected bond lengths (Å) are as follows:
Ru−CT1, 1.8928(6); Ru−CT2, 2.0675(7); Ru−P(1), 2.3686(18); Ru−
P(2), 2.2824(19); Ru−C(12), 2.182(8); Ru−C(13), 2.179(8). Cp ring:
Ru−C(1), 2.227(6); Ru−C(2), 2.267(7); Ru−C(3), 2.270(6); Ru−
C(4), 2.243(7); Ru−C(5), 2.184(7). Selected bond angles (deg):
P(1)−Ru−P(2), 90.53(6); CT1−Ru−P(1), 119.92(5); CT1−Ru−
P(2), 115.72(5); CT1−Ru−CT2, 129.57(3); CT2−Ru−P(1),
94.95(5); CT2−Ru−P(2), 97.56(6). CT1 represents the centroid of
the Cp ligand; CT2 represents the middle of the C(12)−C(13) bond.
The IR spectra of the 1H-pyrazoline complexes [Ru(η5-
C5H5){η1-NC(CN)CH2C(Ar1Ar2)NH}(PPh3)(L)]BPh4
(19, 20) show weak bands at 2213−2207 cm−1, attributed to νCN
of the azo ligand. Apart from the signals of the ancillary ligands
1
PPh3, P(OR)3, Cp, and BPh4 anion, the H NMR spectra of
19b and 20b, obtained as a mixture of diastereoisomers, show
only one multiplet between 7.29 and 3.31 ppm, which can be
simulated with an ABC model and can be attributed to the
CH2 and NH hydrogen atoms of the 1H-pyrazoline. The 13
C
The η5 coordination mode of the Cp ligand shows Ru−C bond
distances between 2.184(7) and 2.270(6) Å, the shorter one
(C(5) atom) corresponding to that trans to the η2-olefin ligand.
It should be noted that the difference between maximum and
minimum Ru−C bond lengths is almost 0.1 Å. These differences
in related complexes are about 0.05 Å. Coordination of the
maleic anhydride (ma) occurs in such a way that its plane is
almost perpendicular to the Ru−Ct2 bond, with an angle of
105.6°. The planes defined by the metal and the alkene carbon
atoms (metallacyclopropane ring) and by the maleic anhydride
ligand make a dihedral angle of 104.9(3)°, similar to the value of
107° found in the Ru(0) compound Ru(η2-ma)(CO)(CN-p-
tolyl)(PPh3)236 (see Figure 4).
spectra support the presence of the azo ligand, showing two
sets of signals for each carbon resonance C3, C4, C5 and
CN; the 31P NMR spectra display two AB multiplets, match-
ing the proposed formulation. The 1H NMR spectrum of 19c,
which contains fluorene (C12H8) as a substituent, shows the
expected ABC multiplet for the CH2 and NH protons of the
pyrazoline ligand, and the 31P spectrum shows only one AB
multiplet.
The NMR spectra of the propylene derivatives [Ru(η5-
C5H5)(η2-CH3CHCH2)(PPh3)(L)]BPh4 (17, 18) confirm
the presence of two diastereoisomers. In particular, at room tem-
perature, the proton spectra show two sets of signals for the
propylene hydrogen atoms, which were simulated with an
ABCD3XY model (X, Y = 31P) with the parameters reported in
the Experimental Section. The 31P NMR spectra exhibit two AB
multiplets, whereas the 13C spectra show two sets of signals for
the carbon atoms of both ancillary ligands and propylene, fitting a
geometry like those found in the solid state.10
The CC bond length of 1.387(11) Å is only slightly longer
than in the uncoordinated olefin (1.3322(9) Å)37 and clearly
shorter than those usually found for coordinated η2-maleic
anhydride in palladium complexes38 or other zerovalent iron
triad complexes, such as Fe(CO)2(η2-ma)(2-pyridylbis-
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The IR spectrum of maleic anhydride complex [Ru(η5-
C5H5)(η2-ma)(PPh3){P(OMe)3}]BPh4 (21) shows two strong
bands at 1826 and 1763 cm−1, attributed to νCO of the
coordinated anhydride. The 1H NMR spectra confirm the
presence of this ligand, showing two multiplets at 4.23 and 4.02 ppm,
which can be simulated with an ABXY model (A, B = 31P) and
can be attributed to the CH protons of the maleic anhydride.
In the 13C spectra, the carbon resonances of these CH groups
appear as doublets at 46.05 and 43.14 ppm, whereas two singlets
at 172. 76 and 171.69 ppm can be attributed to the carbonyl
groups, fitting the proposed formulation.
Surprisingly, at room temperature, neither phenyl- nor tert-
butylacetylene (HCCR) react with diazoalkane complexes
1−5, and the starting material can be recovered unchanged.
Instead, under reflux conditions, the reaction proceeds to give
vinylidene complexes [Ru(η5-C5H5){CC(H)R}(PPh3){P-
(OMe)3}]BPh4 (25, 26), which were isolated and characterized.
Substitution of the diazoalkane probably gives rise to the η2-alkyne
complex, which undergoes the known tautomerization43−45 of the
coordinated HCCR to yield the final vinylidene derivative.
The absence of cyclization of phenyl- and tert-butylacetylene
prompted us to extend our study to activated alkynes such as
alkyl propiolates HCCCOOR1. In this case, the reaction pro-
Two strong νCO bands at 1746 and 1722 cm−1 appear in the
infrared spectra of the dimethyl maleate complex [Ru(η5-
C5H5){η2-CH3OCOC(H)C(H)COOCH3}(PPh3){P-
(OMe)3}]BPh4 (22), attributed to the two CO groups of the
methyl esters. The 1H NMR spectrum shows two multiplets at
3.62 and 3.32 ppm, which could be simulated with an ABXY
model (A, B = 31P) and can be attributed to the two CH
proton resonances. The spectra also show two singlets at 3.77
and 3.72 ppm of the methyl group of COOMe substituents,
whereas in the 13C spectra both carbonyl and methyl carbon
resonances appear as two singlets at 173.21 and 170.61 ppm and at
52.62 and 53.32 ppm, respectively. Instead, the two olefinic CH
resonances appear as two doublets at 54.08 and 46.74 ppm, although
the 31P spectrum shows an AB quartet, fitting the proposed
formulation for the complex.
ceeds to give 3H-pyrazole derivatives [Ru(η5-C5H5){η1-N
NC(Ar1Ar2)C(H)C(COOR1)}(PPh3){P(OMe)3}]BPh4
(27, 28), formed by dipolar (3 + 2) cycloaddition of the alkyne to
the coordinated diazoalkane.
These results highlight the important influence of substituents
on the terminal alkyne in determining the cyclization reaction,
which proceeds to give 3H-pyrazole derivatives with both
acetylene (HCCH) and alkynes bearing an electron-with-
drawing group, whereas only substitution of the diazoalkane and
formation of vinylidene takes place with alkynes containing bulky
groups (Ph, tBu) with electron-donor properties. Parallel behav-
ior was observed with alkenes, indicating that the coordinated
diazoalkane may easily undergo (3 + 2) cycloaddition under
mild conditions with ethylene, acetylene, and related activated
substrates.
Reactions with Alkynes. The results with alkenes prompted
us to extend study of diazoalkane complexes 2−5 to terminal
alkynes (Scheme 7).
The new 3H-pyrazole complexes [Ru(η5-C5H5){η1-N
a
NC(Ar1Ar2)C(H)C(R)}(PPh3){P(OMe)3}]BPh4 (24, 27,
28) were separated as orange solids stable in air and in solution of
polar organic solvents, where they behave as 1:1 electrolytes.23
Their characterization is supported by analytical and spectro-
scopic (IR, NMR) data and by an X-ray crystal structure deter-
Scheme 7.
mination of the complex [Ru(η5-C5H5){η1-NNC(C12H8)C-
(H)C(H)}(PPh3){P(OMe)3}]BPh4 (24c), whose ORTEP30
plot is shown in Figure 5.
The ruthenium cation complex in 24c also consists of a ruthe-
nium atom coordinated by a Cp group, two phosphane ligands
(one PPh3 and one P(OMe)3), and a new ligand, spiro[fluorene-
9,3′-pyrazole], bound to the Ru center via the nitrogen atom.
This ligand is closely related to a spiro-pyrazoline ligand pre-
viously described by our group10 and also to 19b (see above)
with a 1H-pyrazoline ligand. The most noteworthy characteristic
of the new ligand in 24c is the short N−N bond distance in the
pyrazole ring, 1.260(4) Å, which is slightly longer than that found
in the related pyrazoline ring, 1.241(4) Å,10 but shorter than the
expected value for free pyrazole, 1.366 Å,34 or for other pyrazole
ruthenium complexes [RuCl(p-cymene)(Me2HPz)(PPh2OH)]+,
1.341(4) Å,46 confirming the double-bond character for this bond.
The C−C and C−N bond distances in the pyrazole ring are all in
the normal range for pyrazole rings (in particular, the C(4)−C(5)
bond length (1.313(6) Å) is shorter than that found in the
pyrazoline ring). However, as observed in the spiro[fluorene-9,3′-
pyrazoline] compound,10 the fluorene ring is essentially planar
(rms deviation of 0.0843 Å), with dihedral angles between six-
membered rings and the central five-membered ring of 4.9(3)°.
The pyrazole ring (which this time is planar as expected, with an
rms deviation of 0.0146 Å, quite different from that found in
pyrazoline complexes) is situated almost perpendicular to the
fluorene plane, forming a dihedral angle of 85.9(1)°.
a
Definitions: L = P(OMe)3; Ar1 = Ph and Ar2 = p-tolyl (b), Ar1Ar2 =
C12H8 (c); R = Ph (25), But (26); R1 = Me (27), Et (28).
Under mild conditions (1 atm, room temperature), acetylene
quickly reacts with diazoalkane complexes 2 to give the 3H-pyrazole
complex [Ru(η5-C5H5){η1-NNC(Ar1Ar2)C(H)C(H)}-
(PPh3){P(OMe)3}]BPh4 (24), which was isolated in good
yield and characterized. The reaction proceeds with (3 + 2)
cycloaddition of the acetylene to the coordinate diazoalkane,
giving the 3H-pyrazole derivative 24, in which the heterocycle
acts as a ligand. This reaction parallels that observed with
ethylene, but in this case no substitution was observed, as
cyclization was almost quantitative.
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temperature) and activated alkynes HCCCOOR1, affording
3H-pyrazole complexes, whereas substitution of the diazoalkane
and formation of vinylidene derivatives [Ru]CC(H)R
occur with phenyl- and tert-butylacetylene.
ASSOCIATED CONTENT
* Supporting Information
■
S
Table S1 and CIF files giving crystallographic data for 19b, 21,
and 24c. This material is available free of charge via the Internet
at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*E-mail for G.A.: albertin@unive.it.
■
Figure 5. ORTEP view of the cation of 24c. P(1) represents a PPh3
ligand, and P(2) represents a P(OMe)3 ligand. Only the hydrogen atoms
of the pyrazole ligand are shown. Selected bond lengths (Å) are as
follows. Ru−CT1, 1.8803(9); Ru−N(1), 2.065(3); Ru−P(1),
2.3608(16); Ru−P(2), 2.2216(16). Cp ring: Ru−C(1), 2.209(5);
Ru−C(2), 2.224(4); Ru−C(3), 2.234(5); Ru−C(4), 2.232(4); Ru−
C(5), 2.219(4). C3N2 ring: N(1)−N(2), 1.260(4); N(1)−C(5),
1.452(5); N(2)−C(3), 1.497(5); C(4)−C(5), 1.313(6); C(3)−C(4),
1.473(6). Selected bond angles (deg): P(1)−Ru−P(2), 92.90(5);
CT1−Ru−P(1), 123.88(3); CT1−Ru−P(2), 121.75(5); CT1−Ru−
N(1), 125.90(9); N(1)−Ru−P(2), 89.53(10); N(1)−Ru−P(2),
93.57(10). CT1 represents the centroid of the Cp ligand.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
Thanks go to Mrs. Daniela Baldan, from the Universita
Foscari Venezia, Venezia, Italy, for her technical assistance.
■
̀
Ca’
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and 124.86 ppm (25b) of Cβ. The H NMR spectra show a
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CONCLUSIONS
■
This study reports that diazoalkane molecules coordinated to
the half-sandwich fragment [Ru(η5-C5H5)(PPh3)(L)]+ undergo
unprecedented dipolar (3 + 2) cycloaddition with ethylene
(CH2CH2) under mild conditions (1 atm, room temperature)
to afford dihydro-3H-pyrazole derivatives. Acrylonitrile (CH2
CHCN) also gives cycloaddition to coordinated Ar1Ar2CN2 but
yields 1H-pyrazoline derivatives. Substitution of the diazoalkane
was also observed, yielding η2-alkene complexes. The influence of
the steric and electronic factors of the substituents on the
alkene in leading to cycloaddition vs a substitution process was
partially clarified. Dipolar cycloaddition was also observed with
both acetylene (HCCH) under mild conditions (1 atm, room
3581
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