16-Electron ruthenium(0) complexes containing the Ru(NO)L2+ substructure: Planar RuCH3(NO)L2 vs sawhorse [Ru(NO)(C=C(SiMe3)2)L2]+

Article abstract of DOI:10.1021/om9909892

The synthesis and characterization of RuCl(NO)L₂ (L = PⁱPr₃ and P^tBu₂Me) and RuX-(NO)L₂ (X = F, CH₃, OSO₂CF₃, and H) are reported. All are planar at Ru. Reaction of Ru-(OSO₂CF₃)(NO)L₂ with NaBAr′₄ (Ar′ = C₆H₃(CF₃)₂) in CH₂Cl₂ gives RuCl(CH₂Cl)(NO)L₂⁺, while in C₆H₅F in the presence of Me₃SiC≡CSiMe₃, the vinylidene complex Ru[C=C(SiMe₃)₂]-(NO)L₂⁺ is formed. The latter is a sawhorse structure (i.e., P's trans but NO and C=C-(SiMe₃)₂ cis) and stands in contrast to the oxidative addition isomer Ru(CO)(SiMe₃)(C≡ CSiMe₃)L₂ for the carbonyl analogue. The reason for the thermodynamic reversal for CO vs NO⁺ is discussed on the basis of DFT/(B3PW91) calculations, and the calculated structure shows bending of the nitrosyl, consistent with considerable back-donation.

Full text of DOI:10.1021/om9909892

Organometallics 2000, 19, 1967-1972
1967
16-Electr on Ru th en iu m (0) Com p lexes Con ta in in g th e
+
Ru (NO)L2 Su bstr u ctu r e: P la n a r Ru CH3(NO)L2 vs
Sa w h or se [Ru (NO)(CdC(SiMe3)2)L2]+
Dejian Huang,† William E. Streib,† Odile Eisenstein,*,‡ and
Kenneth G. Caulton*,†
Department of Chemistry, Indiana University, Bloomington, Indiana 47405-7102, and
LSDSMS (UMR 5636), Universite´ de Montpellier 2, 34095 Montpellier Cedex 5, France
Received December 13, 1999
The synthesis and characterization of RuCl(NO)L2 (L ) PiPr3 and PtBu2Me) and RuX-
(NO)L2 (X ) F, CH3, OSO2CF3, and H) are reported. All are planar at Ru. Reaction of Ru-
+
(OSO2CF3)(NO)L2 with NaBAr′4 (Ar′ ) C6H3(CF3)2) in CH2Cl2 gives RuCl(CH2Cl)(NO)L2
,
while in C6H5F in the presence of Me3SiCtCSiMe3, the vinylidene complex Ru[CdC(SiMe3)2]-
(NO)L2 is formed. The latter is a “sawhorse” structure (i.e., P’s trans but NO and CdC-
+
(SiMe3)2 cis) and stands in contrast to the oxidative addition isomer Ru(CO)(SiMe3)(Ct
CSiMe3)L2 for the carbonyl analogue. The reason for the thermodynamic reversal for CO vs
NO+ is discussed on the basis of DFT/(B3PW91) calculations, and the calculated structure
shows bending of the nitrosyl, consistent with considerable back-donation.
according to the literature procedure. 1H, 31P, 19F, and 13C NMR
were recorded on a Varian Gem XL300 or Unity I400 spec-
trometer. Chemical shifts are referenced to residual solvent
peaks (1H, 13C), external H3PO4 (31P), or CFCl3 (19F). Infrared
spectra were recorded on a Nicolet 510P FT-IR spectrometer.
Elemental analysis was performed on a Perkin-Elmer 2400
CHNS/O elemental analyzer at Indiana University. Purity of
those compounds for which elemental analyses are not fur-
nished due to thermolability or partial loss of volatile weak
ligand or lattice solvent is to be ascertained from the spectra
supplied as Supporting Information.
Ru Cl(NO)(P tBu 2Me)2. RuH3Cl(PtBu2Me)2 (200 mg, 0.44
mmol) was dissolved in diethyl ether (5 mL) and to the solution
was slowly added isoamyl nitrite (55 µL, 0.44 mmol). The
solution color immediately changed to green with gas evolu-
tion. The volatiles were evaporated to dryness, and the residue
was washed with pentane and dried to give 0.17 g (80%) of
green crystals. Anal. Calcd for C18H42ClNOP2Ru: C, 44.40; H,
8.70; N, 2.87. Found: C, 44.84; H, 8.65; N, 3.38. 1H NMR (C6D6,
400 MHz, 20 °C): 1.56 (vt, N ) 5.6 Hz, 6H, PCH3), 1.38 (vt,
N ) 12.8 Hz, 36H, PC(CH3)3). 31P{1H} NMR (162 MHz): 44.0
(br, s). IR (C6D6): 1707 (ν(NO)).
In tr od u ction
We report here on synthetic access to the fragment
Ru(NO)L2+, of zerovalent Ru, which allows evaluation
of its reactivity, and (together with DFT (B3PW91)
calculations) the relative thermodynamic stability of
various isomeric products of its reaction with Me3SiCt
CSiMe3. Also accessible is Ru(CH3)(NO)L2, which stands
as a comparison compound (pure σ donor CH3 ligand)
to previously reported1,2 Ru(CO)2L2 and Ru(CO)(NO)-
L2+, whose nonplanar structures seem to contradict the
conventional wisdom that four-coordinate d8 species
should be planar. The full characterization here of the
vinylidene complex Ru(NO)[CC(SiMe3)2]L2+ reveals the
influence of changing the π-acid ligand L′ in Ru(EO)-
L′L2 (E ) C or N+). In particular, the inevitable question
of bending of the M-N-O moiety must also be consid-
ered.
Changing ligands in a systematic manner better
defines those factors that control the structure of four-
coordinate d8 species.
Ru F (NO)(P tBu 2Me)2. RuCl(NO)(PtBu2Me)2 (0.60 g, 1.23
mmol) and CsF (1.4 g, 9.0 mmol) were mixed in acetone (10
mL) and stirred at room temperature for 4 h to give a purple
solution. The volatiles were evaporated, and the residue was
extracted with pentane and filtered through a Celite pad. The
filtrate was concentrated to ca. 5 mL and kept at -40 °C for
12 h. Dark purple crystals were formed, filtered, washed with
pentane at -78 °C, and dried to yield 0.45 g (78%) of product.
Anal. Calcd for C18H42FNOP2Ru: C, 45.95; H, 9.00; N, 3.98.
Exp er im en ta l Section
Gen er a l Com m en ts. All reactions and manipulations were
conducted using standard Schlenk and glovebox techniques.
Solvents were dried and distilled under argon and stored in
airtight solvent bulbs with Teflon closures. Most reagents are
commercially available and degassed or dried before use.
3
4
RuCl3(NO)(PPh3)2 and RuH3Cl(PtBu2Me)2 were prepared
1
Found: C, 46.07; H, 8.68, N, 3.58. H NMR (300 MHz, C6D6,
20 °C): 1.39 (vt, N ) 13 Hz, 36H, PC(CH3)3), 1.30 (dvt, J )
* Corresponding author. E-mail: caulton@indiana.edu.
† Indiana University.
2.4 Hz, N ) 4.8 Hz, 6H, PCH3). 31P{1H} NMR: 48.5 (d, J PF
)
‡ Universite´ de Montpellier 2. E-mail: eisenst@lsd.univ-montp2.fr.
(1) Ogasawara, M.; Macgregor, S. A.; Streib, W. E.; Folting, K.;
Eisenstein, O.; Caulton, K. G. J . Am. Chem. Soc. 1996, 118, 10189.
(2) Ogasawara, M.; Huang, D.; Streib, W. E.; Huffman, J . C.;
Gallego-Planas, N.; Maseras, F.; Eisenstein, O.; Caulton, K. G. J . Am.
Chem. Soc. 1997, 119, 8642.
38 Hz). 19F NMR: -187 (t, J PF ) 36 Hz). IR (C6D6): 1703
(ν(NO)).
Ru (OTf)(NO)(P tBu 2Me)2. RuF(NO)(PtBu2Me)2 (200 mg,
0.43 mmol) was dissolved in 10 mL of C6H6. Me3SiOTf (78 µL,
0.43 mmol) was syringed into the solution, which immediately
turned from purple to green. The mixture was stirred for 5
min, and the volatiles were evaporated to give a green solid,
(3) Fairy, M. B.; Irving, R. J . J . Chem. Soc. (A) 1966, 475.
(4) Oliva´n, M.; Clot, E.; Eisenstein, O.; Caulton, K. G. Organome-
tallics 1998, 17, 3091.
10.1021/om9909892 CCC: $19.00 © 2000 American Chemical Society
Publication on Web 04/08/2000

1968 Organometallics, Vol. 19, No. 10, 2000
Huang et al.
Ta ble 1. Cr ysta llogr a p h ic Da ta for
Ru (CH3)(NO)(P iP r 3)2
which was recrystallized from toluene at -40 °C to give 0.15
g (58%) of dark green crystals. Anal. Calcd for C19H42F3NO4P2-
RuS: C, 38.00; H, 7.05; N, 2.33. Found: C, 38.50; H, 7.02; N,
formula
a, Å
b, Å
c, Å
â, Å
V, Å
Z
C19H45NOP2Ru
1
1.94. H NMR (C6D6, 300 MHz, 20 °C): 1.68 (vt, N ) 5.6 Hz,
7.994(1)
8.946(1)
16.605(2)
92.92(1)
1185.9(5)
2
space group
T, °C
P21/c
6H, PCH3), 1.28 (vt, N ) 13.5 Hz, 36 H, PC(CH3)3). 31P{1H}
NMR (20 °C, 121 MHz): 52.0 (s). 19F NMR (282 MHz, 20 °C):
-79.2 (CF3SO3). IR (C6D6): 1734 (ν(NO)).
-160
0.71069
1.307
8.0
0.0283
0.0319
λ, Å
F
cald, g/cm-3
µ(Mo KR), cm-1
[Ru Cl(CH2Cl)(NO)(P tBu 2Me)2]BAr ′4. Ru(OTf)(NO)(PtBu2-
Me)2 (100 mg, 0.17 mmol) and NaBAr′4 (150 mg, 0.17 mmol)
were mixed with CH2Cl2 (10 mL) and stirred at room temper-
ature for 30 min to give a dark orange solution with precipi-
tates. The mixture was centrifuged and the supernatant
decanted to a flask and concentrated to ca. 3 mL. The solution
was layered with pentane for 2 days to give dark orange
crystals (144 mg, 61%). 1H NMR (CD2Cl2, 400 MHz, 20 °C):
7.73 (s, 8H, ortho-H, of Ar′), 7.56 (s, 4H, para-H of Ar′), 5.96
(t, J PH ) 3.6 Hz, 2H, CH2Cl), 1.67 (vt, N ) 6.0 Hz, 6H, PCH3),
1.46 (vt, N ) 15 Hz, 36H, PC(CH3)3). 31P{1H} NMR (162 MHz,
20 °C): 38.1 (s). 19F NMR (376 MHz, 20 °C): -62.0 (s, CF3 of
Ar′). IR (CD2Cl2): 1840 (ν(NO)).
R
fw
466.59
Rw
a
b
2
R ) ∑||Fo| - Fc||/∑|Fo|. Rw ) [∑w(|Fo| - |Fc|)2/∑w|Fo| ]1/2
where w ) 1/σ2(|Fo|).
hydrogen atoms were obtained from iterations of a least-
squares refinement followed by a difference Fourier calcula-
tion. The ruthenium atom lies on a crystallographic center of
symmetry; consequently the CH3 and NO ligands are disor-
dered, and the disorder places them very near one another.
Nevertheless, they were resolved in the difference Fourier.
Hydrogens were included for the ordered carbons in fixed,
calculated positions with thermal parameters fixed at one plus
the isotropic thermal parameter of the parent carbon. In the
final cycles of refinement, the non-hydrogen atoms were varied
with anisotropic thermal parameters, which, with a scale and
extinction parameter, gave a total of 125 variables. The largest
peak in the final difference map was a ruthenium residual of
0.89, and the deepest hole was -0.04 e/Å3.
[Ru (CdC(SiMe3)2)(NO)(P tBu 2Me)2]BAr ′4. Ru(OTf)(NO)-
(PtBu2Me)2 (100 mg, 0.17 mmol) and NaBAr′4 (150 mg, 0.17
mmol) were mixed in fluorobenzene. To the mixture was
syringed bis(trimethylsilyl)acetylene (40 µL, 0.18 mmol). The
green color turned brown immediately. The mixture was
stirred for 10 min and filtered through a Celite pad. The
filtrate was evaporated to ca. 5 mL and layered with pentane
for two weeks at - 20 °C to give dark orange crystals, which
were filtered, washed with pentane, and dried in vacuo.
Yield: 0.15 g (59%). 1H NMR (400 MHz, 20 °C, in 9:1 (v/v)
mixture of C6H5F and C6D12): 8.33 (s, 8H, ortho-H of Ar′), 7.80
(s, 4H, para-H of Ar′), 1.42 (vt, N ) 5.7 Hz, 6H, PCH3), 1.20
(vt, N ) 13.5 Hz, 18H, P(CH3)3), 1.15 (vt, N ) 14 Hz, 18H,
P(CH3)3), 0.37 (s, 9H, SiMe3), 0.30 (s, 9H, SiMe3). The peaks
at 0.37 and 0.30 ppm broaden and shift toward lower field as
the temperature is raised and finally coalesce to a very broad
peak centered at 0.37 ppm at 80 °C. At this temperature, the
tBu proton peaks (1.20 and 1.15 ppm) also coalesce to one broad
peak at 1.25 ppm. 31P{1H} NMR: 48.2 (s). 13C{1H} NMR
(C6H5F/C6D12 ) 9:1, 100 MHz, 20 °C): 284.1 (t, J PC ) 15 Hz,
RudC), 100.9 (s, RudCdC), 38.1 (vt, NPC ) 18 Hz, P-CMe3),
37.3 (vt, N ) 20 Hz, P-CMe3), 29.8 (s, PC(CH3)3), 28.6 (s, PC-
(CH3)3), 5.2 (vt, NPC ) 24.9 Hz, PCH3), 2.75 (s, SiMe3), 1.88 (s,
SiMe3). IR (C6H5F): 1642 (ν(NO)).
Ru (H)3(NO)(P tBu 2Me)2. Ru(CH3)(NO)(PtBu2Me)2 (10 mg,
0.021 mmol) was dissolved in C6D14 (0.5 mL). The solution was
degassed by freeze-pump-thaw cycles. H2 (1 atm) was
introduced, and the solution was warmed to room temperature.
The green color gave way to pale yellow immediately. NMR
analysis revealed clean formation of Ru(H)3(NO)(PtBu2Me)2
1
and methane (0.22 ppm at -90 °C). H NMR (300 MHz, -90
°C): 1.25 (br, 36H, PC(CH3)3), 1.12 (br, PCH3), -4.26 (dt,
J HH ) 7.3 Hz, 2H, Ru-H), -9.05 (tt, J PH ) 24.3 Hz, J HH ) 7
Hz, Ru-H). 31P{1H} NMR (121 MHz, -90 °C): 76.0 (s). IR
(C6D6): 1676 (ν(NO)). This complex loses H2 readily upon
applying vacuum; therefore no attempts have been made to
isolate it.
Ru H(NO)(P tBu 2Me)2. Ru(CH3)(NO)(PtBu2Me)2 (10 mg,
0.02 mmol) was dissolved in cyclohexane (0.5 mL), degassed,
and reacted with 1 atm H2 at 25 °C to give immediately a pale
yellow solution. The volatiles were removed, and the residue
was subjected to vacuum for 30 min to give a dark brown solid,
which was dissolved in C7D8 for spectral analysis. 1H NMR
(400 MHz): 1.49 (vt, N ) 4.5 Hz, PCH3), 1.18 (vt, N ) 12 Hz,
36H, PC(CH3)3), -9.2 (t, J ) 30 Hz, Ru-H). 31P{1H} NMR (162
MHz): 67.9 (s). IR (C6D6): 1658 (ν(NO)).
Ru (CH3)(NO)(P tBu 2Me)2. RuF(NO)(PtBu2Me)2 (100 mg,
0.21 mmol) was dissolved in pentane. To the solution was
slowly added MeLi (1.4 mol/L, 150 µL). The solution color
changed from purple to green with some precipitate. The
mixture was centrifuged, and the liquid was decanted to a
Schlenk flask, concentrated to ca. 3 mL, and cooled to -40 °C
for 12 h. Dark green crystals were formed, filtered, washed
with tetramethylsilane, and dried. Yield: 80 mg (82%). 1H
NMR (300 MHz, C6D6, 20 °C): 1.37 (vt, N ) 12.4, 36H, PC-
(CH3)3), 1.32 (vt, N ) 5.1, 6H, PCH3), -1.7 (t, J ) 9.7 Hz, 3H,
Ru-CH3). 13C{1H} NMR: 37.0 (vt, N ) 15 Hz, PMe), 30.5 (s,
PCMe3), 9.54 (t, 15 Hz, Ru-CH3). 31P{1H} NMR (121 MHz,
C6D6, 20 °C): 48.4 (s). IR (C6D6): 1661 (ν(NO)). The prepara-
tion for the PiPr3 species proceeded analogously.
X-r ay Str u ctu r e Deter m in ation of Ru (CH3)(NO)(P iP r 3)2.
Crystals were grown from a toluene/pentane mixture. The
crystals were mounted using silicone grease, and they were
then transferred in a nitrogen stream to the goniostat, where
they were cooled to -160 °C for characterization and data
collection (Table 1). A preliminary search for peaks followed
by analysis using programs DIRAX and TRACER revealed a
primitive monoclinic cell. Following intensity data collection,
the conditions l ) 2n for h01 and k ) 2n for 0k0 uniquely
determined space group P21/c. After an analytical correction
for absorption (transmission factors 0.825-0.924), the struc-
ture was solved using the system DIRDIF-96, which revealed
nearly the entire structure. The positions of the remaining non-
Com p u ta tion a l Deta ils
Calculations were carried out with the Gaussian 945 set of
programs within the framework of DFT at the B3PW91 level.6
The Hay-Wadt effective core potential (quasi-relativistic for
the metal center) was used to replace the 28 innermost
electrons of Ru7 and the 10 core electrons of P and Si.8 The
associated double-ú basis sets were used.7,8 They were aug-
mented by d polarization functions for P and Si.9 H, C, O, and
(5) Frisch, M. J .; Trucks, G. W.; Schlegel, H. B.; Gill, P. M. W.;
J ohnson, B. G.; Robb, M. A.; Cheeseman, J . R.; Keith, T.; Petersson,
G. A.; Montgomery, J . A.; Raghavachari, K.; Al-Laham, M. A.;
Zakrzewski, V. G.; Ortiz, J . V.; Foresman, J . B.; Peng, C. Y.; Ayala, P.
Y.; Chen, W.; Wong, M. W.; Andres, J . L.; Replogle, E. S.; Gomperts,
R.; Martin, R. L.; Fox, D. J .; Binkley, J . S.; Defrees, D. J .; Baker, J .;
Stewart, J . P.; Head-Dordon, M.; Gonzalez, C.; Pople, J . A. Gaussian
94, Revision B3; Gaussian, Inc.: Pittsburgh, 1995.
(6) Becke, A. D. J . Chem. Phys. 1993, 98, 5648.
(7) Hay, P. G.; Wadt, W. R. J . Chem. Phys. 1985, 82, 299.
(8) Wadt, W. R.; Hay, P. J . J . Chem. Phys. 1985, 82, 284.
(9) Ho¨llwarth, A. H.; Bo¨hme, M. B.; Dapprich, S.; Ehlers, A. W.;
Gobbi, A.; J onas, V.; Ko¨hler, K. F.; Stegmann, R.; Veldkamp, A.;
Frenking, G. Chem. Phys. Lett. 1993, 208, 237.

16-Electron Ru(0) Complexes
Organometallics, Vol. 19, No. 10, 2000 1969
Sch em e 1a
a
2, 5 L ) PiPr3; others L ) PtBu2Me.
N were represented by a 6-31 G (d,p) basis set.10 Full geometry
optimization was performed without symmetry restriction.
Resu lts
Syn th esis of Ru Cl(NO)L2. RuCl(NO)L2 (1, L )
PtBu2Me; 2, L ) PiPr3) can be synthesized by two
routes: Reduction of RuCl3(NO)(PPh3)2 by Zn/Cu alloy
in hot benzene gives RuCl(NO)(PPh3)2, which undergoes
phosphine exchange to give RuCl(NO)L2 in moderate
yield, a method that is highly dependent on the quality
of Zn/Cu alloy.11 More conveniently, 1 can be obtained
quantitatively by the instantaneous reaction of RuH3-
ClL2 with equimolar isoamyl nitrite (Scheme 1). The
reaction releases H2, as is evidenced by evolution of gas.
This is in agreement with the finding11 that Ru-
Cl(NO)(PiPr3)2 does not react with H2. 2 was synthesized
earlier from RuCl3(NO)(PPh3)2 and reported11 as “ther-
mally unstable” and “can be stored only below -15 °C
for a few days”. In sharp contrast, we found that 1 and
2 are thermally stable up to 80 °C (in benzene) for more
than 5 h, and the solid can be kept under argon
atmosphere for months without any decomposition. The
1H NMR spectrum of 1 shows only one tert-butyl proton
resonance, consistent with a square-planar geometry
similar to 2, which was shown11 by X-ray diffraction as
having a linear NO. The NO stretching frequency of 1
(1707) is close to that of RuCl(NO)(PiPr3)2 (1716 cm-1).
Ru F (NO)L2. Stirring of 1 with excess CsF in acetone
at room temperature (4 h, Scheme 1) gives RuF(NO)L2,
3, cleanly. Compound 3 is isolated as a purple solid,
highly soluble in benzene, but less so in pentane. This
represents a dramatic color change from the green
chloride analogue. The 19F NMR spectrum of 3 is a
triplet at high field (-188 ppm) with relatively large
J PF (33 Hz). Correspondingly, the 31P{1H} NMR signal
is a doublet with the same splitting. Similar to that of
1, there is also only one virtual triplet for the tBu
protons, suggesting the phosphines are mutually trans,
and the complex has a square-planar geometry with a
linear NO. The νNO band at 1703 cm-1 is only slightly
lower that that of the Cl complex, which is surprising
since F is considered a much better π-donating ligand
than chloride.12 However, the strong electronegative
character of F could contribute to a decrease of metal
electron density, an effect that may be important for
F igu r e 1. ORTEP diagram (30% probability ellipsoids) of
RuCH3(NO)(PiPr3)2. Hydrogen atoms are omitted for clar-
ity. Selected bond lengths: Ru1-P2 2.3827(8), Ru(1)-N(13)
1.823(12), Ru(1)-C(12) 2.293(16), O(14)-N(13) 1.059(16)
Å. Selected bond angles: P(2)-Ru(1)-N(13) 90.2(3); P(2)-
Ru(1)-C(12) 89.8(4); N(13)-Ru(1)-C(12) 170.9(7); Ru(1)-
P(2)-C(3) 114.20(11); Ru(1)-P(2)-C(6) 113.28(9); Ru(1)-
P(2)-C(9) 112.68(9)°; Ru(1)-N(13)-O(14) 177.3(10).
Ru(0). Compound 3 is also thermally stable up to 100
°C in toluene solution.
Ru (CH3)(NO)L2. Reaction of 1 and 2 with equimolar
methyllithium (Scheme 1) gives clean formation of
RuMe(NO)L2, 4 and 5, which are isolated as dark green
crystals. The 1H NMR spectrum of 4 also has one virtual
t
triplet for the Bu protons, in agreement with square-
planar geometry. However, the Ru-CH3 proton signal
appears at unusually high field (-1.7 ppm) as a triplet
(J PH ) 9.7 Hz). Although the high-field shift is usually
1
an indication of agostic interactions, the normal J CH
coupling value (127 Hz) in 4 suggests the opposite. We
notice that the methyl (trans to NO) proton resonance
of a saturated complex, [Re(Me)(NO)(PMe3)4][C5H5], also
appears at high field (-1.0 ppm).13 Therefore, the high
chemical shift may derive from CH3 being trans to NO.
The NO stretching frequency (1661 cm-1) of 4 is
significantly lower than that of 1 and 2. Although
methyl is not a π-donating ligand, the strong σ-donating
ability of methyl strongly increases the electron density
of the metal.
Cr ysta l Str u ctu r e of Ru (CH3)(NO)(P iP r 3)2, 5.
While crystals of 4 suffer from severe disorder, Ru-
(CH3)(NO)(PiPr3)2 behaves somewhat better. X-ray qual-
ity crystals were grown from pentane at -40 °C, and
the ORTEP diagram is depicted in Figure 1. The
molecule has a crystallographic center of symmetry,
(10) Hariharan, P. C.; Pople, J . A. Theor. Chim. Acta 1973, 28, 213.
(11) Flu¨gel, R.; Windmu¨ller, B.; Gevert, O.; Werner, H. Chem. Ber.
1996, 129, 1007.
(13) Casey, C. P.; O’Connor, J . M.; Haller, K. J . J . Am. Chem. Soc.
1985, 107, 1241.
(12) Doherty, N. M.; Hoffman, N. W. Chem. Rev. 1991, 91, 553.

1970 Organometallics, Vol. 19, No. 10, 2000
Huang et al.
Sch em e 2
which gives 50/50 disorder of the CH3 and NO ligands.
The disorder could be modeled, but structural param-
eters must be interpreted with caution. The thermal
parameters (Figure 1) of both N and C are longest along
the bonds, a physically unreasonable result symptom-
atic of the close proximity of these atoms. The RuN
distance (1.823(12) Å) is perhaps too long, compared to
an average14 of 1.74 Å, and the Ru-CH3 distance (2.293
Å) is too long compared to an average14 of 2.18 Å. Given
these symptoms, the N-Ru-C angle (170.9(7)°) cannot
confidently be said to deviate significantly (i.e., > 5°)
from linearity.
gives clean formation of Ru(OTf)(NO)L2. The dark green
complex has a higher NO stretching frequency (1734
cm-1) than that of RuF(NO)L2, in agreement with
t
weaker donating power of OTf. The presence of one Bu
1H NMR virtual triplet is in agreement with a planar
geometry.
Rep la cem en t of OTf (Sch em e 2). Salt metathesis
between RuR(OTf)(CO)L2 (L ) PtBu2Me, R ) H, Ph, Me)
and NaBAr′4 has been shown to yield formally 14-
electron Ru(II) complexes [RuR(CO)L2]BAr′4 with two
agostic interactions.16,17 Salt metathesis between Ru-
(OTf)(NO)L2 and NaBAr′4 would thus lead to [Ru(NO)-
L2]BAr′4. Reaction of equimolar NaBAr′4 with Ru(OTf)-
(NO)L2 in CH2Cl2 results in an immediate color change
from green to dark orange. After workup, dark orange
crystals (8) are obtained in good yield. 1H NMR analysis
of product reveals a triplet at 6.0 ppm (J PH ) 3.6 Hz)
with integration of two protons for an Ru-CH2Cl
Ru H(NO)L2 a n d Ru (H)3(NO)L2. Ru(CH3)(NO)L2
reacts with 1 equiv of H2 at room temperature to give
RuH(NO)L2, 6 (Scheme 1). Monitoring the reaction at
-80 °C does not give evidence for any possible primary
products (Ru(H2)(CH3)(NO)L2 or Ru(H)2(CH3)(NO)L2);
instead, only Ru(H)3(NO)L2 and CH4 are observed along
with RuCH3(NO)L2. If the reaction mixture is warmed
to roomtemperature, RuH(NO)L2 is formed and remain-
ing Ru(CH3)(NO)L2 is consumed. This fact itself sug-
gests that RuH(NO)L2 reacts much faster with H2 than
does Ru(CH3)(NO)L2. The hydride of 6 appears at -9.00
ppm as a triplet, and there is also only one virtual triplet
t
functionality. There are also two virtual triplets for Bu
t
protons, indicating diastereotopic Bu groups. The NO
stretching frequency is rather high (1840 cm-1) in
comparison with that of Ru(OTf)(NO)L2 (1734 cm-1), in
agreement with a higher oxidation state of Ru. Accord-
ing to the geometry preference of five-coordinated Ru-
(II) complexes, we conclude that a CH2Cl group occupies
the site trans to the vacant site and Cl is trans to NO,
favoring push-pull stabilization. The fact that this
reaction gives H2ClC-Cl oxidative addition (cf. RuH-
(CO)L2(η2-Cl2CH2)+ for a Ru(II) reagent16,17) supports
t
for the Bu protons, in agreement with a square-planar
geometry. The NO stretching frequency (1658 cm-1) of
6 is close to that of 4. Compound 6 stands as the first
16-electron Ru(0) hydride complex. The hydrides of Ru-
(H)3(NO)L2 appear as a broad peak at -6 ppm at 20
°C, indicating fast exchange among the three H and also
some exchange with added free H2, which appears as
an extremely broad peak at room temperature. At -40
°C (in toluene-d8), the free H2 peak is sharp, suggesting
slow exchange with the hydrides, while the hydride
signals have just started to decoalesce. At lower tem-
perature (-80 °C), the hydride signal decoalesces to two
peaks with 2:1 ratio, at -4.3 ppm (2H) and -9.3 ppm
(1H). The large but identical T1 values (220 ms, -80
°C) of the two hydride signals suggest that 7 is a
trihydride complex, with H exchange fast enough to
average the T1. Detailed hydride exchange dynamics
and mechanism will be published in a separate paper,
along with the chemistry of the Os analogue, Os(H)3-
(NO)L2.15
+
the idea that Ru(NO)L2 is still a reducing species,
despite the strong π-acid nitrosyl ligand.
F ou r -Coor d in a te Ru (0) Vin ylid en e. Combination
of equimolar Ru(OTf)(NO)L2, NaBAr′4, and Me3SiCC-
SiMe3 in fluorobenzene immediately results in a deep
brown solution with a fine precipitate (Scheme 2). After
centrifuging and layering of the liquid with pentane for
2 days, deep brown crystals were obtained. Spectro-
scopic analysis of the crystals support a vinylidene
complex, [Ru(CdC(SiMe3)2)(NO)L2]BAr′4, 9. The 13C-
{1H} NMR spectrum gives a triplet at 284 ppm (J PC
)
15 Hz) and a singlet at 101 ppm for the R- and â-carbon
of vinylidene. Two sets of 13C NMR peaks are also found
for diastereotopic tBu primary and tertiary carbons, and
two singlets at 2.7 and 1.9 ppm are assigned to the
t
Ru (OTf)(NO)L2. Reaction of RuF(NO)L2 with 1 equiv
of Me3SiOTf (OTf ) O3SCF3) in benzene (Scheme 2)
carbons of two SiMe3 groups. Inequivalent Bu groups
(16) Huang, D.; Streib, W. E.; Eisenstein, O.; Caulton, K. G. Angew.
Chem., Int. Ed. Engl. 1997, 36, 2004.
(17) Huang, D.; Huffman, J . C.; Bollinger, J . C.; Eisenstein, O.;
Caulton, K. G. J . Am. Chem. Soc. 1997, 119, 7398.
(14) Orpen, A. G.; Brammer, L.; Allen, F. H.; Kennard, O.; Watson,
D. G.; Taylor, R. J . Chem. Soc., Dalton Trans. 1989, S1.
(15) Yandulov, D.; Caulton, K. G. Inorg. Chem., in press.

16-Electron Ru(0) Complexes
Organometallics, Vol. 19, No. 10, 2000 1971
Me)2+ is higher (19.1 kcal/mol, at 100 °C), as it includes
effects of ion pairing and steric bulkiness of the phos-
phine ligand.2 The two Me3Si proton singlets and the
t
two Bu virtual triplets of [Ru(NO)(CdC(SiMe3)2)L2]+
coalesce to baseline at around 80 °C in fluorobenzene,
which permits evaluation of the barrier for Me3Si group
exchange as 13.3(4) kcal/mol (at 80 °C) and that of tBu
exchange as 13.5(4) kcal/mol. Since these are identical,
a single process effects both site exchanges. We propose
that this process is going to a planar geometry around
Ru (eq 1). While RudCdC(SiMe3)2 rotation itself can
F igu r e 2. Optimized (B3PW91) structure (distances in Å,
angles in deg) for Ru(NO)(CdC(SiH3)2)(PH3)2+. Hydrogens
of PH3 have been removed for clarity.
demand that the Ru coordination geometry is nonpla-
nar. Consistently, two 1H NMR virtual triplets and two
singlets are found for the tBu and SiMe3 groups,
respectively. Inequivalent SiMe3 groups require that the
vinylidene plane be perpendicular to the P-Ru-P axis
interconvert the Me3Si groups, it does not average the
tBu signals, so this rotation alone is not sufficient to
explain the behavior of Ru[CC(SiMe3)2](NO)L2+. This
hypothesis is preferred, although rotational barriers of
vinylidene ligands have been found experimentally to
1
and the C(SiMe3)2 group rotates only slowly on H NMR
time scale. The NO stretching frequency of 9 is low
(1642 cm-1) in comparison with that of [Ru(NO)(CO)-
L2]+ (1709 cm-1), indicating more back-donation from
Ru to NO in the former. On the basis of these data we
propose the complex has a nonplanar geometry with two
phosphines trans to each other and with N and the
vinylidene CR bending toward each other. Two X-ray
data sets both indicated the crystals to be twinned. DFT
be in the range from 7 to 12 kcal‚mol-1 18
exceptions, like [(η5-C5H5)Re(NO)(PPh3)(CCRR′)]+, where
,
with a few
the barrier was found to be around 20 kcal‚mol-1 19
.
Th er m od yn a m ics of Rea ction s of Ru (NO)L2+ vs
Ru (CO)L2. The products of Ru(CO)L2 and Me3SiCt
CSiMe3 appear to have a ground-state structure,20
where oxidative addition of the Si-C(sp) bond has
occurred to give a square-pyramidal Ru(II) product, 11.
+
(B3PW91) optimization of Ru(CC(SiH3)2)(NO)(PH3)2
gives a sawhorse structure (Figure 2) with an N-Ru-C
angle equal to 116°. The NRuCR and CâSi2 units are
coplanar, and the NO ligand is significantly bent (Ru-
N-O ) 144.3°) with O toward the vinylidene ligand.
The PH3 ligands are trans to each other, although the
P-Ru-P angle deviates from linearity (165.5°). This
structure, which fully agrees with the experimental
data, emphasizes the role of the π-acceptor ligands in
the preference for a sawhorse geometry. The vinylidene
orientation permits the empty p carbenoid orbital to
To understand these differences, we have calculated the
products of reaction of HCCH and H3Si-CC-SiH3 with
Ru(NO)(PH3)2+ and Ru(CO)(PH3)2. Three types of prod-
ucts were considered: the alkyne adduct, the vinylidene
product, and the product resulting from the oxidative
addition of the metal to the C-H or C-Si bonds. The
energies relative to the most stable isomer within each
group are given in Table 2.
2
2
overlap with dx -y . (10). Strong electron transfer into
The results show an important dependence of the
relative stabilities of the products with the nature of
the ancillary ligand (CO or NO+) and the alkyne
substituent. For HCCH, the vinylidene product is the
most stable and the alkyne adduct is significantly higher
in energy (6-7 kcal‚mol-1) for both CO and NO ancillary
ligands. The products of oxidative addition are far above
in energy for NO (16.2 kcal‚mol-1) but almost isoener-
getic to the vinylidene complex for CO (0.7 kcal‚mol-1).
π*NO has also occurred, as shown by the RuNO angle.
The angle between the two cis acceptor ligands de-
creases with their π-accepting capability. Thus, in the
isoelectronic Ru(CO)(CC(SiH3)2)(PH3)2 structure, the
C-Ru-C angle is calculated to be 130.7°, which is larger
than with NO (116.0°). The sawhorse structure of this
vinylidene complex is in agreement with that of other
d8 ML4 complexes bearing several π-acceptor ligands.1,2
The nonplanar nature of Ru(CO)2(PtBu2Me)2 and [Ru-
(NO)(CO)L2]+ suggests that inversion at Ru could
control their fluxional behavior. The difference in energy
between the sawhorse and planar structure of Ru(NO)-
(18) (a) Consiglio, G.; Bangerter, F.; Darpin, C.; Morandini, F.;
Lucchini, V. Organometallics 1984, 3, 1446. (b) Consiglio, G.; Moran-
dini, F. Inorg. Chim. Acta 1987, 127, 79. (c) Boland-Lussier, B. E.;
Churchill, M. R.; Hughes, R. P.; Rheingold, A. L. Organometallics 1982,
1, 628. (d) Gamasa, M. P.; Gimeno, J .; Lastra, E.; Martin, B. M.; Anillo,
A.; Tiripicchio, A. Organometallics 1992, 11, 1373. (e) Beddoes, R. L.;
Bitcon, C.; Grime, R. W.; Ricalton, A.; Whiteley, M. W. J . Chem. Soc.,
Dalton Trans. 1995, 2873.
(19) Senn, D. R.; Wong, A.; Patton, A. T.; Marsi, M.; Strouse, C. E.;
Gladysz, J . A. J . Am. Chem. Soc. 1988, 110, 6096
(20) Huang, D.; Heyn, R. H.; Bollinger, J . C.; Caulton, K. G.
Organometallics 1997, 16, 292.
+
(CO)(PH3)2 is calculated to be 13.3 kcal/mol, and the
estimated experimental value of Ru(NO)(CO)(PtBu2-

1972 Organometallics, Vol. 19, No. 10, 2000
Huang et al.
Ta ble 2. DF T En er gies (k ca l‚m ol-1) of P r od u cts of
∆E
Ru(SiH3)(CtCSiH3)(NO)L2+ + HCCH ) +5.2 kcal/mol8
+
a
Ru L′(P H3)2 a n d RCCR, R ) H or SiH3
RuH(CtCH)(NO)L2+ + H3SiCCSiH3
ligand
L′ ) NO+
L′ ) CO
CCH2
HCCH
(H)/(CCH)
CC(SiH3)2
H3SiCCSiH3
(SiH3)/CCSiH3
0
0
This is consistent with SiR3 being a potent electron
donor to electron-deficient Ru.
(3) The competition among vinylidene products favors
H on the coordinated vinylidene and Si on the free
alkyne:
6.8
16.2
0
2.5
6.1
6.0
0.7
11.5
11.2
0
a
The alkyne adducts have a square-planar structure with the
∆E
Ru(NO)(CdCH2)L2+ + H3SiCCSiH3 ) +4.9 kcal/mol8
alkynes perpendicular to the molecular plane. The (H)/(CCH) and
(SiH3)/(CCSiH3) have a square-pyramidal geometry with H or SiH3
at the apical site.
Ru(NO)(CdC(SiH3)2)L2+ + HCCH
All three of these trends also hold for the Ru(CO)L2
analogues.
Going to disilylacetylene decreases the difference in
energy between the vinylidene complex and the alkyne
adduct. However, the most remarkable change concerns
the relative energy of the oxidative addition product.
Con clu sion s
+
The present synthetic sequence M-Cl f M-F f
M-OSO2CF3 f M+ has been effective in several recent
instances of production of high unsaturation. The first
step depends on mass action (excess CsF); the second,
on the strength of the Si-F bond produced. The last step
is a tribute to the high Lewis acidity of sodium in
anhydrous NaBAr′4 when used in a noncoordinating
solvent (here C6H5F) and where the product NaO3SCF3
is presumably insoluble. Since no bond is formed to M+,
and charge separation is also required, it is necessary
that the M-OSO2CF3 bond dissociation energy be small
for this synthetic strategy to succeed.
Ru(NO)(SiH3)(CCSiH3)(PH3)2 is the least stable iso-
meric product of its group, whereas Ru(CO)(SiH3)(CC-
SiH3)(PH3)2 is the most stable isomeric product of its
group. This reversal was already developing in the
HCCH family but has been greatly enhanced by the
presence of the silyl groups.
These results are in good agreement with the experi-
mental observations in the case of disilylalkynes. The
preference for a vinylidene isomer over the η2-alkyne
adduct in the case of NO will contain additional steric
factors for SiMe3 (vs SiH3, Table 2) due to the closer
proximity of the silyl to the phosphine ligands in the
η2-alkyne adduct.
+
The fact that the 14-electron fragment Ru(NO)L2
oxidatively adds the C-Cl bond of CH2Cl2 and isomer-
izes Me3SiCtCSiMe3 to the vinylidene CdC(SiMe3)2 is
consistent with this metal center being more reducing
(π-basic) than electron-deficient (14 valence electrons).
In particular, an η2-alkyne is probably less electron-
withdrawing/oxidizing than either full oxidative addi-
tion of the Si-C bond or the vinylidene ligand. However,
the less electron-withdrawing CO permits “full” oxida-
tive addition (11) in a way that the NO+ analogue does
not.
DFT calculations show a determining influence of the
ancillary ligand and alkyne substituents on the products
of reaction. This is due to the fact that the possible
isomeric structures are reasonably close in energy. This
permits reversal of products to occur by even subtle
change in the nature of reactants.
The remarkable change in products upon the change
of a good π-acceptor ligand (CO) by an even better one
is certainly surprising, and the calculations indicate that
this change could also happen for other alkynes.
The calculations reported here also permit some
conclusions regarding substituent effects (the H/SiH3
transposition) on the η2-alkyne, vinylidene, and oxida-
tive addition isomers:
(1) The alkyne competition reaction is essentially
thermoneutral:
Ack n ow led gm en t. This work was supported by the
ACS-PRF, the University of Montpellier 2, and the
French CNRS.
Su p p or tin g In for m a tion Ava ila ble: Crystallographic
details for Ru(CH3)(NO)(PiPr3)2. Also available are NMR
spectra for five compounds. This material is available free of
charge via the Internet at http://pubs.acs.org.
(2) The competition among oxidative addition prod-
ucts favors H-C and Si-Ru bonds over Si-C and H-Ru
bonds:
OM9909892