Silyl migration of Me3SiCCPh coordinated to [RuH(CO)(P(t)Bu2Me)2]BAr'4 can be reversed: Synthesis and structure of [Ru(CH=C(SiMe3)(Ph))(CO)(P(t)Bu2Me)2]BAr'4

Article abstract of DOI:10.1021/ja991351k

Reaction of 14-electron RuH(CO)L₂⁺ (L = P(t)Bu₂Me, anion = B[C₆H₃(CF₃)₂]₄^-) with Me₃≡SiCCPh gives the silyl-migrated product Ru[CH=C(SiMe₃)Ph](CO)L₂⁺, in which the ortho H on phenyl syn to Ru is agostic to the metal, to give a square-pyramidal coordination geometry augmented by an agostic interaction with a (t)Bu methyl group. These interactions, from X-ray diffraction, persist in solution. Reaction at lower temperature reveals (NMR studies) one detectable species which, however, is unlikely to be an intermediate. Under 1 atm of CO, this cation adds three CO's to give Ru(CO)₂[CO - CH=C(SiMe₃)Ph]L₂⁺, which is shown (¹³CO labeling) to add an additional CO. In the absence of excess CO, this acyl complex forms RuH(CO)₃L₂⁺ with release of Me₃SiC≡CPh; Me₃Si migration is thus reversed.

Full text of DOI:10.1021/ja991351k

10318
J. Am. Chem. Soc. 1999, 121, 10318-10322
Silyl Migration of Me3SiCCPh Coordinated to
[RuH(CO)(PtBu2Me)2]BAr′4 Can Be Reversed: Synthesis and
Structure of [Ru(CHdC(SiMe3)(Ph))(CO)(PtBu2Me)2]BAr′4
Dejian Huang, Kirsten Folting, and Kenneth G. Caulton*
Contribution from the Department of Chemistry and Molecular Structure Center, Indiana UniVersity,
Bloomington, Indiana 47405
ReceiVed April 26, 1999
Abstract: Reaction of 14-electron RuH(CO)L2+ (L ) PtBu2Me, anion ) B[C6H3(CF3)2]4-) with Me3SiCtCPh
gives the silyl-migrated product Ru[CHdC(SiMe3)Ph](CO)L2+, in which the ortho H on phenyl syn to Ru is
agostic to the metal, to give a square-pyramidal coordination geometry augmented by an agostic interaction
t
with a Bu methyl group. These interactions, from X-ray diffraction, persist in solution. Reaction at lower
temperature reveals (NMR studies) one detectable species which, however, is unlikely to be an intermediate.
Under 1 atm of CO, this cation adds three CO’s to give Ru(CO)2[COsCHdC(SiMe3)Ph]L2+, which is shown
+
(13CO labeling) to add an additional CO. In the absence of excess CO, this acyl complex forms RuH(CO)3L2
with release of Me3SiCtCPh; Me3Si migration is thus reversed.
Introduction
an unconventional mechanism, which involves insertion of the
CtC triple bond into the MsH bond to give a metal vinyl
complex as an intermediate. The 14-electron intermediate then
undergoes R-H migration to give the vinylidene complex. The
mechanism is supported by DFT calculations and by a deuterium
labeling study. In sharp contrast, less π-basic but isoelectronic
[RuH(CO)L2]BAr′4 (L ) PtBu2Me) reacts with two molecules
of Me3SiCCH to give, instead of a vinylidene, an alkyne-coupled
η3-butadienyl complex.6 We report here that [RuH(CO)L2]+ also
reacts with an internal silyl alkyne, Me3SiCCPh, to give the
silyl-migrated product, [Ru(CHdC(SiMe3)(Ph))(CO)L2]+. Re-
ported here are the structure and solution spectra of this complex
There is a plethora of reports on isomerization of terminal
alkynes on late transition metal centers to give metal vinylidene
complexes,1 which have found some applications in organic
synthesis.2 Less frequent is the isomerization of silyl alkynes
on 14-electron fragments (i.e., RhClL2, IrClL2, and RuCl2L2; L
) phosphine) to corresponding vinylidenes (eq 1).3 Computa-
and its reaction with CO, which remarkably regenerates
+
tional studies suggested that a 1,2-H (or SiR3) shift is energeti-
cally very costly, and it has been proposed that bimolecular H
transfer is an alternative.4 In contrast, isomerization of terminal
alkynes on unsaturated hydride complexes is not well studied
until recently.5 That report reveals that the 14-electron transient
RuHClL2 reacts with Me3SiCCH to give a vinylidene but by
Me3SiCCPh and RuH(CO)3L2
.
Results
Reaction of [RuH(CO)L2]BAr′4 with Me3SiCCPh. Within
the time of mixing at room temperature, [RuH(CO)L2]BAr′4
reacts with Me3SiCCPh in methylene chloride or fluorobenzene
to give a silyl-migrated product (1) quantitatively (eq 2).
Sterically more demanding Me3SiCCSiMe3, however, does not
(1) (a) Bruce, M. I. Chem. ReV. 1991, 91, 197. (b) Esteruelas, M. A.;
Oro, L. A.; Valero, C. Organometallics 1995, 14, 3596. (c) Touchard, D.;
Haquette, P.; Guesmi, S.; Le Pichon, L.; Daridor, A.; Toupet, L.; Dixneuf,
P. H. Organometallics 1997, 16, 3640. (d) Le Lagadec, R.; Roman, E.;
Toupet, L.; Mu¨ller, U.; Dixneuf, P. H. Organometallics 1994, 13, 5030.
(e) de los Rios, I.; Jime´nez-Tenorio, M.; Puerta, M. C.; Valerga, P. J. Am.
Chem. Soc. 1997, 119, 6529. (f) Bianchini, C.; Peruzzini, M.; Vacca, A.;
Zanobini, F. Organometallics 1991, 10, 3697. (g) Barbaro, P.; Bianchini,
C.; Peruzzini, M.; Polo, A.; Zanobini, F.; Frediani, P. Inorg. Chim. Acta
1994, 220, 5. (h) Antonova, A. B.; Ioganson, A. A. Usp. Khim. 1989, 68,
1197. (i) Wolf, J.; Werner, H.; Serhadli, O.; Ziegler, M. L. Angew. Chem.,
Int. Ed. Engl. 1983, 22, 414. (j) Garc´ıa-Alonso, F. J.; Ho¨hn, A.; Wolf, J.;
Otto, H.; Werner, H. Angew. Chem., Int. Ed. Engl. 1985, 24, 406. (k) Ho¨hn,
A.; Otto, H.; Dziallas, M.; Werner, H. J. Chem. Soc., Chem. Commun. 1987,
852. (l) Werner, H.; Garc´ıa-Alonso, F. J.; Otto, H.; Wolf, J. Z. Naturforsch.
1988, 43b, 722. (m) Werner, H.; Brekau, U. Z. Naturforsch. 1989, 44b,
1438. (n) Ho¨hn, A.; Werner, H. J. Organomet. Chem. 1990, 382, 255. (o)
Werner, H.; Ho¨hn, A.; Schulz, M. J. Chem. Soc., Dalton Trans. 1991, 777.
(p) Rappert, T.; Nu¨rnberg, O.; Mahr, N.; Wolf, J.; Werner, H. Organo-
metallics 1992, 11, 4156. (q) Werner, H.; Baum, M.; Schneider, D.;
Windmu¨ller, B. Organometallics 1994, 13, 1089. (r) Werner, H.; Rappert,
T.; Baum, M.; Stark, A. J. Organomet. Chem. 1993, 459, 319.
(3) (a) Schneider, D.; Werner, H. Angew. Chem., Int. Ed. Engl. 1991,
30, 700. (b) Katayama, H.; Ozawa, F. Organometallics 1998, 17, 5190. (c)
Werner, H.; Baum, M.; Schneider, D.; Windmu¨ller, B. Organometallics
1994, 13, 1089-1097. (d) Katayama, H.; Onitsuka, K.; Ozawa, F.
Organometallics 1996, 15, 4642-4645. (e) Connelly, N. G.; Geiger, W.
E.; Lagunas, M. C.; Metz, B.; Rieger, A. L.; Rieger, P. H.; Shaw, M. J. J.
Am. Chem. Soc. 1995, 117, 12202-12208. (f) Sakurai, H.; Fujii, T.;
Sakamoto, K. Chem. Lett. 1992, 339-342. (g) Naka, A.; Okazaki, S.;
Hayashi, M.; Ishikawa, M. J. Organomet. Chem. 1995, 499, 35-41. (h)
Baum, M.; Windmu¨ller, B.; Werner, H. Z. Naturforsch. 1994, B49, 859. (i)
Baum, M.; Mahr, N.; Werner, H. Chem. Ber. 1994, 127, 1877.
(4) (a) Silvestre, J.; Hoffmann, R. HelV. Chim. Acta 1985, 68, 1461. (b)
Wakatsuki, Y.; Koga, N.; Werner, H.; Morokuma, K. J. Am. Chem. Soc.
1997, 119, 360.
(5) (a) Olivan, M.; Clot, E.; Eisenstein, O.; Caulton, K. G. Organo-
metallics 1998, 17, 3091. (b) Wolf, J.; Stu¨er, W.; Gru¨nwald, C.; Gevert,
O.; Laubender, M.; Werner, H. Eur. J. Inorg. Chem. 1998, 1827.
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(2) Bruneau, C.; Dixneuf, P. H. Acc. Chem. Res. 1999, 32, 311.
10.1021/ja991351k CCC: $18.00 © 1999 American Chemical Society
Published on Web 10/21/1999

Synthesis of [Ru(CHdC(SiMe3)(Ph))(CO)(PtBu2Me)2]BAr′4
J. Am. Chem. Soc., Vol. 121, No. 44, 1999 10319
react; no spectroscopic change is observed on combination of
these reactants. 1 is isolated as red crystals from fluorobenzene/
pentane. The solid-state structure of 1 is determined by X-ray
crystallography (Figure 1). The determination reveals a unit cell
containing two crystallographically independent molecules,
which can represent a distinct advantage since it serves to test
the reality of weak interactions (by their replication or nonrep-
lication). In the present case, a least-squares fit of the two
independent cations shows deviations of less than 0.1 Å, except
for the carbonyl oxygen (0.18 Å), Si (0.25 Å), and the two
phosphine nuclei (0.22 and 0.33 Å); the only major differences
arise from CH3(Si) and CH3(P) orientations. Bond lengths and
angles (Tables 1 and 2) show no significant differences. The
following description deals with features found in both inde-
pendent cations. The structure shows a sawhorse (i.e., nonplanar,
SF4 type) coordination geometry (2P, carbonyl, and vinyl
carbon), augmented by a short ortho agostic donation from the
phenyl C7 hydrogen (Figure 1). A sixth coordination site (trans
to the vinyl carbon C4) is more distantly (i.e., weakly) occupied
Figure 1. ORTEP drawing of [Ru[CHC(SiMe3)(Ph)](CO)(PtBu2Me)2]+
(1). The agostic methyl hydrogens shown are placed in idealized
positions.
Table 1. Crystallographic Data for
[Ru(CHdC(SiMe3)(Ph))(CO)(PtBu2Me)2]BAr′4
t
by one Bu methyl hydrogen. The Ru-C24 distance, 3.049(1)
Å (3.090(13) Å in the second cation), while long, shows a
consistency between independent molecules, suggesting a real
attraction with a well-defined energetic minimum. The ortho
phenyl hydrogen-to-Ru distance is 1.74 Å (1.70), with a Ru-
H-C angle of 131.6° (131.6°). The associated Ru/C distances
are 2.588 and 2.551 Å. The agostic interaction also twists the
Ph ring away from coplanar with the CdC bond. Esteruelas
and co-workers reported the presence of relatively strong agostic
interaction between vinyl C-H and Os(II) in a formally 16-
electron complex, OsH{C6H4-2-(E-CHdCHagosticPh)}(CO)-
(PiPr3)2. This agostic hydrogen is crystallographically located
2.05(7) Å away from Os.7 It is typical of strong C-H metal
interactions that they become nonlinear (i.e., the M-C distance
becomes shorter).8 The reality of the agostic tBu interaction in
8 is supported by the Ru-P-C (quaternary carbon) angle being
formula
a, Å
b, Å
C62H69BF24OP2RuSi space group
P21/c
-168
0.710 69
1.456
17.762(5)
19.337(5)
39.838(10)
97.21(1)
13 574.65 Å3
8
T, °C
λ, Å
c, Å
F
cald, g/cm-3
â, deg
V, Å3
Z
µ(Mo KR), cm-1 a 4.00
Rb
Rw
0.085
0.073
c
formula wt 1488.10
a Graphite monochromator. b R ) ∑||Fo| - |Fc||/∑|Fo|. c Rw
)
[∑w(|Fo| - |Fc |)2/∑w|Fo| ]1/2, where w ) 1/σ2(|Fo|).
2
for only three protons. The other two phenyl protons are located
as a very broad peak (w1/2 ) 300 Hz) at 6.00 ppm, which, upon
cooling to -70 °C, decoalesces to two peaks, a multiplet at
7.65 ppm, and a broad singlet at 3.98 ppm. The higher field
peak is due to the agostic ortho hydrogen. Apparently, the phenyl
group is rotating fast enough to coalesce the two ortho protons
at higher temperatures. Also, at low temperature, decoalescence
of the two meta (Ph) protons is observed, and the 13C{1H} NMR
spectrum of 1 gives six distinct signals for the phenyl carbons
of the cation. Compared to the other phenyl carbon chemical
shifts (128-135 ppm), the agostic carbon resonance is shifted
t
6-9° smaller than that of the corresponding Bu on the
nonagostic PtBu2Me in the same cation and 18-20° smaller
than that of the second tBu within the same (agostic) tBu. Finally,
the Ru-P distance involving the agostic tBu is 0.036 (12 esd’s)
and 0.046 Å (15 esd’s) shorter than that to the “ordinary”
PtBu2Me. This pattern has been seen before.6
Spectroscopic Evidence for Agostic Interactions of 1 in
Solution. Ionic 1 is not soluble in nonpolar solvents such as
benzene or alkanes but is highly soluble in methylene chloride
and fluorobenzene. In either solvent, there is no evidence for
solvent coordination since the CO stretching frequencies remain
the same in both solvents. Therefore, we carried out the
following spectroscopic study of 1 in CD2Cl2. At 20 °C, the 1H
NMR spectrum reveals two virtual triplets for the tBu protons,
indicative of two mutually trans phosphines with diastereotopic
tBu groups. A singlet at 8.35 ppm is found for the R-proton of
the Ru-vinyl group, and the phenyl region shows two multiplets
at 7.75 and 7.43 ppm with an integration ratio of 2:1, accounting
1
to higher field (110 ppm), with J(CH) ) 132 Hz, i.e., much
smaller than the normal J(CH) value of 160-170 Hz for sp2
1
C-H of other phenyl carbons. This is a rare example of agostic
interaction which can be decoalesced on the NMR time scale.
By analyzing the variable-temperature 13C spectra of the phenyl
carbons, we obtained ∆Gq for phenyl rotation of 8.6 kcal‚mol-1
at 273 K. Because the hydrogen exchange is an intramolecular
process, the entropy change should be close to zero. This energy,
however, reflects the upper limit of agostic bond strength since
the barrier has several major contributions: the agostic interac-
tion itself, a steric preference for Ph in the mirror plane, and
the conjugation of Ph π-electrons with the vinyl. The weaker
agostic interaction from the phosphine methyl group of 1 could
not be decoalesced, as was also the case of the formally 16-
electron d6 Re(I) and Mo(0)/W(0) complexes and [RuR(CO)-
L2]BAr′4.9 Nonetheless, the weak agostic interaction with the
(7) Esteruelas, M. A.; Lahoz, F. J.; Onate, E.; Oro, L. A.; Sola, E. J.
Am. Chem. Soc. 1996, 118, 89.
(8) (a) Crabtree, R. H.; Holt, E.; Lavin, M.; Morehouse, S. M. Inorg.
Chem. 1985, 24, 1986. (b) Brookhart, M.; Green, M. L. H.; Wong, L.-L.
Prog. Inorg. Chem. 1988, 36, 1.

10320 J. Am. Chem. Soc., Vol. 121, No. 44, 1999
Huang et al.
Table 2. Selected Geometric Parameters of [Ru(CHdC(SiMe3)(Ph))(CO)(PtBu2Me)2]BAr′4
molecule 1 molecule 2
molecule 1 molecule 2
Bond Lengths (Å)
2.018(9)
molecule 1 molecule 2
Ru(1)-P(16)
Ru(1)-P(26)
Ru(1)-C(2)
2.416(3)
2.452(3)
1.802(10)
2.465(3)
2.419(3)
1.803(10)
Ru(1)-C(4)
Ru(1)-C(7)
O(3)-C(2)
2.026(10)
2.551(8)
1.193(11)
C(4)-C(5)
C(5)-C(6)
C(6)-C(7)
1.376(12)
1.475(13)
1.373(14)
1.343(12)
1.462(12)
1.427(13)
2.588(9)
1.182(10)
Bond Angles (deg)
P(16)-Ru(1)-P(26) 171.31(10) 165.31(10) C(2)-Ru(1)-C(7)
168.5(4)
75.5(3)
163.7(4)
75.7(3)
Ru(1)-C(2)-O(3) 178.6(8)
Ru(1)-C(4)-C(5) 121.2(7)
173.4(8)
120.8(7)
119.6(9)
118.7(8)
124.3(9)
100.3(5)
131.3(7)
P(16)-Ru(1)-C(2) 91.4(3)
P(16)-Ru(1)-C(4) 95.51(28)
P(16)-Ru(1)-C(7) 92.24(24)
P(26)-Ru(1)-C(2) 89.7(3)
P(26)-Ru(1)-C(4) 93.03(28)
P(26)-Ru(1)-C(7) 88.34(23)
87.4(3)
99.3(3)
97.18(22)
91.7(3)
95.3(3)
87.76(22)
88.1(4)
C(4)-Ru(1)-C(7)
Ru(1)-P(16)-C(17) 122.6(4)
Ru(1)-P(16)-C(21) 102.0(4)
Ru(1)-P(16)-C(25) 112.0(4)
Ru(1)-P(26)-C(27) 116.6(4)
Ru(1)-P(26)-C(31) 108.4(4)
Ru(1)-P(26)-C(35) 114.0(4)
118.7(4)
110.6(4)
108.3(4)
121.6(3)
101.4(4)
114.5(3)
C(4)-C(5)-C(6)
C(5)-C(6)-C(7)
117.6(9)
121.5(8)
C(5)-C(6)-C(11) 121.8(10)
Ru(1)-C(7)-C(6) 100.0(6)
Ru(1)-C(7)-C(8) 130.5(7)
C(2)-Ru(1)-C(4)
93.4(4)
Scheme 1a
Scheme 2a
a All the complexes have 1+ charge.
due to either 3a or 3b. η2-Vinyl structures cannot be excluded
for 3. Upon warming to -30 °C, 1 begins to form and after 10
min at room temperature is the only observed product. Because
the structure of 3a(b) is counterproductive for the formation of
1, we propose that the kinetic product 3a(b) reverts to undetected
[RuH(η2-Me3SiCCPh)(CO)L2]+, which then isomerizes to un-
observed 2 before the hydride migrates to give 1. In general,
the striking feature of this reaction is that, due to high mobility
of silyl and hydrogen, thermodynamic product 1 is formed so
readily. Product 1 has the least steric repulsion among the
ligands, and it fills more metal orbitals than does intermediate
3a/b.
a All the complexes have 1+ charge.
CH3 is not likely due to the weaker ligating ability of the C-H
bond of CH3. This is well demonstrated in the formally 14-
electron Ir(III) complex, [IrH2(PtBu2Ph)2]BAr′4,10 in which the
tBu is superior to Ph as an agostic donor.
Search for Reaction Intermediates. Apparently (Scheme
1), formation of 1 goes through a vinylidene intermediate, 2,
formed by 1,2-silyl migration. 2 then undergoes R-H migration
to give 1. To gather spectroscopic evidence for 2, a low-
temperature NMR study was carried out. Combining equimolar
[RuH(CO)L2]BAr′4 and PhCCSiMe3 in a 1:1 mixture of C6H5F
and toluene-d8 at -80 °C causes an immediate color change
from light orange to bright orange. The 31P{1H} NMR spectrum
at this temperature reveals a product with a sharp singlet at 40.6
ppm. Correspondingly, the 1H NMR spectrum shows a peak at
3.65 ppm; no hydride signal is detected. These spectral features
do not support 2, which should have an upfield hydride signal.
The peak at 3.65 ppm is assigned as a vinyl H on a â carbon,
Reaction of 1 with CO. Addition of 1 atm of CO to CD2Cl2
solution of 1 at 25 °C causes an immediate color change from
red to bright yellow. Spectroscopic analysis of the solution
reveals (Scheme 2) formation of [Ru(CO)2[(COsCHdC(SiMe3)-
(Ph)]L2]+ (4). The CdO stretching frequency of 4 is normal
(1645 cm-1) for η1-acyl. The large intensity difference (8:2) of
two CO stretching peaks (1996 and 2087 cm-1) suggests they
are approximately trans. The vinyl proton of 4 is at much higher
field (6.85 ppm) than that of 1, in accord with the CO-inserted
product. Remarkably, at room temperature, the 13C{1H} NMR
shows no resonances for coordinated CO. Below 10 °C, two
broad peaks appear at 203 and 197 ppm with a 1:1 ratio,
indicating that the two metal-bound CO’s are inequivalent at
this temperature. This is likely due to the hindered rotation of
the acyl group, a very common feature for RuXY(CO)(PtBu2-
Me)2 complexes.11 The C(dO) resonance is found at 225 ppm
as a triplet. Moreover, there are two tBu (CH3) chemical shifts,
(9) (a) Heinekey, D. M.; Schomber, B. M.; Radzewich, C. E. J. Am.
Chem. Soc. 1997, 119, 4172. (b) Butts, M. D.; Bryan, J. C.; Luo, X.-L.;
Kubas, G. J. Inorg. Chem. 1997, 36, 3341. (c) Huang, D.; Streib, W. E.;
Eisenstein, O.; Caulton, K. G. Angew. Chem., Int. Ed. Engl. 1997, 36, 2004.
(10) Cooper, A. C.; Streib, W. E.; Eisenstein, O.; Caulton, K. G. J. Am.
Chem. Soc. 1997, 119, 9069.
t
indicating the Bu groups on phosphines are diastereotopic,

Synthesis of [Ru(CHdC(SiMe3)(Ph))(CO)(PtBu2Me)2]BAr′4
J. Am. Chem. Soc., Vol. 121, No. 44, 1999 10321
Scheme 3a
a All the complexes have 1+ charge.
7 is not observed indicates the equilibrium favors 4. Loss of
CO from 7 produces unsaturated 8. R-H migration of 8 gives
vinylidene 9, which isomerizes to alkyne adduct 10. The alkyne
then dissociates, and the 16-electron intermediate [RuH-
(CO)2L2]+ is trapped by CO to form 6. The transformation does
not happen under 1 atm of CO; compound 4 is persistent.
Therefore, CO dissociation from 7 is likely to be the rate-
determining step. The reaction illustrates the high mobility of
silyl and hydride in this complex.
Figure 2. Variable-temperature NMR spectra of 1 + 13CO (excess).
Solvent: CD2Cl2. Peaks labeled A are assigned to 5; peaks marked B
are assigned to 4 (see Scheme 2). The spectrum marked with an asterisk
was recorded after cooling from -10 °C. It is similar to that recorded
at -30 °C, revealing the reversibility of the process.
consistent with slow rotation of the acyl group. If 13CO is used,
similar resonances are observed. It is also evident that 13CO
incorporates to the acyl group, since the integration of the
13C(dO) peak is comparable to that of coordinated CO signals
(Figure 2). Since 4 is a 16-electron complex, it could coordinate
another CO. Indeed, upon cooling (-50 °C) the solution under
excess 13CO, [Ru(13CO)3(13C(O)CHdC(SiMe3)(Ph))L2+] (5) is
formed, and the free CO peak disappears (Figure 2). Strong
evidence for 5 is the 31P{1H} NMR spectrum, which shows an
Discussion
The conversion shown in eq 1 is a very common reaction,
but only for the mobile groups G ) H or SiR3. The rate of
these reactions is highly variable, but, most significantly, there
are no generalizations or predictive principles concerning these
rates. A corollary ignorance is that of mechanism of this
reaction. Often the reaction for G ) H occurs on a cationic
metal center, and the possibility that the conventional mechan-
isms4b might be replaced by base-catalyzed processes (polar
solvent, counterion, or adventitious Brønsted basic impurity)
remains to be clearly evaluated. The fact that silyl groups can
be unexpectedly hydrolyzed off (i.e., R3Si f H)3c emphasizes
the aVailability of potential nucleophilic catalysts. In contrast,
when neutral complexes are involved, base catalysis is less
likely. Indeed, it has been observed recently14 that “The most
remarkable feature is that . . . the metal-assisted isomerization
of HCtCR to CdCHR takes place considerably faster in the
coordination sphere of a four-coordinate cationic than of a
related neutral d8 metal center.” The adduct between (arene)M-
apparent quartet due to the coupling with three 13CO’s (JCP
)
10 Hz; coupling with the acyl 13C is not resolved). It seems
contradictory that five-coordinated 4 shows hindered rotation
and give rise to two different CO’s, while 5 has only two CO
peaks (200.3 and 193.1 ppm). One reason for this may be that
5 has a longer Ru-C(dO) bond (trans to CO) than that (trans
to vacant site) of 4;12 as a consequence, the acyl group in 5 can
rotate faster. At higher temperature (>-10 °C), only 4 and free
13CO are observed.
Isomerization of 4. 4 is not persistent in solution. At 20 °C
and in CD2Cl2, it transforms over 2 h to RuH(CO)3L2+ (6) and
PhCCSiMe3, which is confirmed by comparison of the 1H NMR
data with those of authentic Me3SiCCPh. 6 shows a character-
n
(CO)2 and Me3SiCtCSiMe3 has been shown15 to be an
t
equilibrium mixture of η2-alkyne and vinylidene, CdC(SiMe3)2,
isomers. The equilibrium is established in 1 h when n ) 0 but
essentially instantly for the analogous radical cation (n ) 1+).
The mechanism whereby a Me3Si group can migrate without
the aid of nucleophilic catalysis and in arene solvent is unknown.
In general, we have demonstrated here silyl migration of a
silyl alkyne on the highly electron deficient Ru(II) hydride,
[RuH(CO)L2]+, to give, instead of an 16-electron vinylidene, a
vinyl complex in which two agostic interactions avoid a 14-
electron count. The thermodynamic preference of the product
is in sharp contrast with the reaction product of RuHClL2 with
terminal alkyne, which is a 16-electron vinylidene.5 From this
result, we conclude that less π-basic [RuH(CO)L2]+ cannot
provide enough back-donation to stabilize the unobserved
istic hydride peak at -7.58 ppm and one Bu proton virtual
triplet. To strengthen the assignment, 6 was synthesized
independently from [RuH(CO)L2]+ and excess CO. The X-ray
structure of an analogous complex, [RuH(CO)3(PPh3)2][CH-
(OTf)2], reveals an octahedral geometry around Ru(II).13
Although the transformation from 4 to 6 should involve many
elementary steps, no intermediates are detected by 1H and
31P{1H} NMR spectra. We thus speculate that it goes through
the stepwise transformation depicted in Scheme 3. 4 undergoes
CO deinsertion to give saturated 7. This intramolecular process
should be independent of free CO concentration. The fact that
(11) It is well established that the rotation of Ru-Ph bond in Ru(Ph)-
Cl(CO)(PtBu2Me)2 is slow even at room temperature, so there are five
distinct Ph proton resonances, see: Notheis, J. U.; Heyn, R. H.; Caulton,
K. G. Inorg. Chim. Acta 1995, 229, 187.
(12) Orpen, A. G.; Brammer, L.; Allen, F. H.; Kennard, O.; Watson, D.
G.; Taylor, R. J. Chem. Soc., Dalton Trans. 1989, S1.
(13) Siedle, A. R.; Newmark, N. A.; Gleason, W. B. Inorg. Chem. 1991,
30, 2005.
(14) Windmu¨ller, B.; Nu¨rnberg, O.; Wolf, J.; Werner, H. Eur. J. Inorg.
Chem. 1999, 613.
(15) Bartlett, I. M.; Connelly, N. G.; Martin, A. J.; Orpen, A. G.; Paget,
T. J.; Rieger, A. L.; Rieger, P. H., J. Chem. Soc., Dalton Trans. 1999, 691.

10322 J. Am. Chem. Soc., Vol. 121, No. 44, 1999
Huang et al.
vinylidene, [RuH(dCdCR2)(CO)L2]+, while π-electron-rich
RuHClL2 favors forming a π-acidic vinylidene ligand. Similarly,
RuHClL2 isomerizes ethyl vinyl ether to give a carbene complex
[RuHCl(C(OEt)(CH3))L2],16 while [RuH(CO)L2]+ inserts17 the
CdC bond to give [Ru(η2-CH2CH2OEt)(CO)L2]+. This result
demonstrates that tuning the balance between π-basicity and
Lewis acidity of the unsaturated transition metal complexes can
have a profound effect on the preferred reaction product.
parameters equal to 1.0 plus the isotropic equivalent of the parent atom.
Atoms C(41), C(62), and C(176) failed to converge properly to
anisotropic form, and they were refined with isotropic thermal
parameters, while all other non-hydrogen atoms were refined with
anisotropic thermal parameters. The final difference Fourier was
essentially featureless. The largest peak was 1.08 e/Å3, 0.71 Å from
P(16), and the deepest hole was -0.90 e/Å3.
[Ru(C(O)CHdC(Ph)(SiMe3))(CO)2(PtBu2Me)2]BAr′4 (4). In an
NMR tube, [Ru[CHdC(Ph)(SiMe3)](CO)(PtBu2Me)2]BAr′4 (70 mg,
0.05 mmol) was dissolved in CD2Cl2 (0.5 mL). The solution was
degassed by freeze-pump-thaw cycles three times before CO was
charged. Within the time of mixing, the dark orange color gave way to
bright yellow. To ensure excess CO was added, the same NMR tube
was exposed to CO (1 atm) again. NMR spectral analysis reveals clean
formation of 4. 1H NMR (300 MHz, 20 °C): δ 7.73 (s, 8H, ortho H of
Ar′), 7.57 (s, 4H, para H of Ar′), 7.28 (m, 3H, para and meta H of Ph),
6.85 (s, 1H, Ru(CO)CH), 6.65 (m, 2H, ortho H of Ph), 1.73 (vt, 6H, N
Experimental Section
General Procedures. All reactions and manipulations were con-
ducted using standard Schlenk and glovebox techniques. Solvents were
dried and distilled under argon and stored in airtight solvent bulbs with
Teflon closures. All NMR solvents were dried, vacuum-transferred,
1
and stored in an argon-filled glovebox. H, 31P, and 13C NMR spectra
were recorded on a Varian Gem XL300 or a Unity I400 spectrometer.
Chemical shifts are referenced to solvent peaks (1H, 13C) and external
t
) 5.4 Hz, PCH3), 1.24 (vt, 36 H, N ) 14.4 Hz, Bu), 0.11 (s, 9H,
H3PO4 (31P). Infrared spectra were recorded on a Nicolet 510P FT-IR
Si(CH3)3). 31P{1H} NMR (121 MHz, 20 °C): δ 48.5 (s). IR (CD2Cl2):
2087 (ν(CO)), 1992 (ν(CO)), 1646 (ν(CdO). The volatiles were
removed, and the yellow residue was dissolved in CD2Cl2 to give a
pale yellow solution, which turned to colorless after 2 h. NMR spectra
of the solution revealed clean formation of PhCCSiMe3 and [RuH-
(CO)3(PtBu2Me)2]BAr′4.
18
spectrometer. [RuH(CO)L2]BAr′4
is synthesized by a literature
method. Other chemicals are available from commercial sources.
[Ru(CHdC(Ph)(SiMe3))(CO)(PtBu2Me)2]BAr′4 (1). RuH(OTf)-
(CO)(PtBu2Me)2 (300 mg, 0.50 mmol) and NaBAr′4 (450 mg, 0.50
mmol) were placed in a test tube with a screw cap. Fluorobenzene (10
mL) was added to the test tube, and the mixture was stirred for 10
min. To the mixture was added PhCCSiMe3 (100 µL, 0.51 mmol). The
orange solution immediately turned dark brown. After 5 min, the
mixture was centrifuged, and the solution was decanted to a Schlenk
tube and layered with pentane. Dark orange crystals were obtained after
3 days. The solution was filtered, and the crystals were washed with
pentane to give 350 mg (47%) of product. 1H NMR (300 MHz, CD2Cl2,
20 °C): δ 8.35 (s, 1H, RuCH), 7.77 (m, overlapping with Ar′ ortho
protons, meta H of Ph). 7.73 (s, 8H, ortho H of Ar′), 7.57 (s, 4H, para
H of Ar′), 7.44 (m, 1H, para H of Ph), 6.0 (br, 2H, w1/2 ) 300 MHz,
ortho H of Ph), 1.19 (vt, 18 H, N ) 15 Hz, PtBu), 1.17 (vt, 18 H, N )
15 Hz, PtBu), 0.87 (vt, 6H, N ) 5.7 Hz, PCH3), 0.22 (s, 9H, Si(CH3)3).
31P{1H} NMR (121 MHz, CD2Cl2, 20 °C): δ 41.1 (s). IR (Nujol, cm-1):
2691, 2730 (ν(C-H), agostic), 1968 (ν(CO)). 13C{1H} NMR (100
MHz, -60 °C, CD2Cl2): δ 202.4 (t, JPC ) 13.7 Hz, CO), 170.1 (t, J
) 7.6 Hz, Ru-CH), 161.72 (m, B-C), 150.8 (s, CHdC(SiMe3), 144.8
(s, ipso C of Ph),139.5 (s, meta C of Ph), 134.6 (s, ortho C of Ar′),
133.3 (s, meta C of Ph), 128.7 (q, JCF ) 31 Hz, meta C of Ar′), 128.0
(s, ortho C of Ph), 124.4 (q, JCF ) 270 Hz, CF3), 117.5 (s, para C of
Ar′), 109.6 (s, agostic ortho C of Ph, JCH ) 132 Hz, measured by
J-resolved C,H correlation spectroscopy), 38.2 (vt, N ) 19.8 Hz,
PC(CH3)3), 36.6 (vt, N ) 19.8 Hz, PC(CH3)3), 28.5 (s, PC(CH3)3), 28.1
(s, PC(CH3)3), 4.2 (br s, PCH3), -0.70 (s, SiCH3).
[Ru[13C(O)CHdC(Ph)(SiMe3)](13CO)2(PtBu2Me)2]BAr4′, [Ru(13C-
(O)CHdC(Ph)(SiMe3))(CO)3(PtBu2Me)2]BAr′4, and [RuH(13CO)3-
(PtBu2Me)2]BAr′4. In an NMR tube, [Ru(CHdC(Ph)(SiMe3))(CO)-
(PtBu2Me)2]BAr′4 (70 mg, 0.05 mmol) was dissolved in CD2Cl2 (0.5
mL). The solution was degassed by freeze-pump-thaw cycles three
times before 13CO was charged. Within the time of mixing, the dark
orange color gave way to bright yellow. To ensure excess 13CO was
added, the same NMR tube was exposed to 13CO (1 atm) again.
13C{1H} NMR of [Ru(13C(O)CHdC(Ph)(SiMe3))(13CO)2(PtBu2Me)2]-
BAr′4 (100 MHz, CD2Cl2, -20 °C): δ 225.8 (m, CdO), 203.5 (br,
CO), 197.5 (br, CO). The two CO resonances coalesce to one broad
peak at room temperature at 20 °C at 200 ppm.
When the temperature was cooled to -50 °C, a significant amount
of [Ru(13C(O)CHdC(Ph)(SiMe3))(13CO)3(PtBu2Me)2]BAr′4 was ob-
served. 13C{1H} NMR (100 MHz, -50 °C): δ 242.9 (m, CdO), 200
(m, CO), 193.2 (m, CO). 31P{1H} NMR (162 MHz, -50 °C): δ 52.5
1
(q, JCP ) 10 Hz). H NMR (400 MHz, -50 °C): δ 1.51 (vt, N ) 7
Hz, PCH3), 1.35 (vt, N ) 14 Hz, tBu). This complex was not observed
at 20 °C by NMR spectra.
Removal of volatiles afforded a light yellow residue, which was
dissolved in CD2Cl2 to give a colorless solution of [RuH(13CO)3-
(PtBu2Me)2]BAr′4. 13C{1H} NMR (75 MHz, 20 °C): δ 196.9 (m, 2C,
CO), 194.2 (m, 1C, CO trans to hydride). 1H NMR (300 MHz, 20 °C):
δ 7.73 (s, 8H, ortho H of Ar′), 7.57 (s, 4H, para H of Ar′), 1.68 (vt, N
X-ray Crystal Structure of [Ru(CHdC(Ph)(SiMe3)(CO)(PtBu2Me)2]-
BAr′4. X-ray quality crystals were grown from the solvent mixture of
pentane and fluorobenzene at room temperature. The air- and moisture-
sensitive sample was handled in a nitrogen-filled glovebag. A small
red prismatic crystal was selected and attached to a glass fiber using
silicone grease. The crystal was then transferred to the goniostat, where
it was cooled to -168 °C for characterization and data collection. A
preliminary search for peaks and analysis using the programs DIRAX
and TRACER revealed a monoclinic unit cell. Following complete data
collection to 50° (2θ), the systematic extinctions of 0k0 for k ) 2n +
1 and of h0l for l ) 2n + 1 uniquely identified the space group as
P21/c (No. 14). The subsequent solution and refinement of the structure
confirmed this choice. Details of the data collection are summarized
in Table 1. During the initial data processing and averaging, 25
reflections severely affected by overlap due to the 40 Å axis were
deleted. Attempts were made at locating the hydrogen atoms on C(7)
and C(42), respectively, but none were located. All hydrogen atoms
were then introduced in fixed idealized positions with isotropic thermal
t
) 5.6 Hz, PCH3), 1.37 (vt, N ) 15 Hz, Bu), -7.57 (m, 1H, Ru-H).
31P{1H} NMR (121 MHz, 20 °C): δ 57.6 (m).
Procedure of Low-Temperature NMR Study for Intermediates.
[RuH(CO)(PtBu2Me)2]BAr′4 (20 mg, 0.017 mmol) was covered by
C6H5F and toluene-d8 (1:1) in an NMR tube. Onto the upper wall of
the NMR tube was added PhCCSiMe3 (3.3 µL, 0.017 mmol). The tube
was transferred immediately to a dry ice acetone bath (-78 °C) and
mixed thoroughly. The solution changed color from light orange to
bright yellow. The tube was transferred to a precooled NMR probe for
observation.
Acknowledgment. This work was supported by the National
Science Foundation.
Supporting Information Available: Full crystallographic
details, positional and thermal parameters, and distances and
angles (PDF). This material is available free of charge via the
Internet at http://pubs.acs.org.
(16) Coalter, J. N.; Spivak, G. J.; Ge´rard, H.; Clot, E.; Davidson, E. R.;
Eisenstein, O.; Caulton, K. G. J. Am. Chem. Soc. 1998, 120, 9388.
(17) Huang, D.; Gerard, H.; Clot, E.; Young, V., Jr.; Streib, W. E.;
Eisenstein, O.; Caulton, K. G. Organometallics, in press.
(18) Huang, D.; Huffman, J. C.; Bollinger, J. C.; Eisenstein, O.; Caulton,
K. G. J. Am. Chem. Soc. 1997, 119, 7398.
JA991351K