14-Electron four-coordinate Ru(II) carbyl complexes and their five-coordinate precursors: Synthesis, double agostic interactions, and reactivity

Article abstract of DOI:10.1021/ja990621w

The structure of five-coordinate Ru(II) complexes RuHCl(CO)(PⁱPr₃)₂,1, RuCl₂(CO)(PⁱPr₃)₂, 2, and Ru(Ph)Cl(CO)(P^tBu₂Me)₂, 12, are reported. All three of these complexes have square-based pyramid geometry with the strongest σ-donor ligand trans to the vacant site. These 16-electron complexes do not show bona fide agostic interactions. This is attributed to the strong trans influence ligand (H, CO, and Ph) and π-donation of the Cl, which is further supported by the fact that two agostic interactions are present in the Cl^- removal product of 12, i.e., the four-coordinate [RuPh(CO)L₂]BAr′₄ (L = P^tBu₂Me, Ar′ = 3,5-C₆H₃(CF₃)₂), 16. Structural comparison of 16 and 12 reveals that removal of Cl^- does not change the remaining ligand arrangements but creates two low-lying LUMOs for agostic interactions, which persist in solution as evidenced by IR spectroscopy. Reactions of 16 with E-H (E = B, C(sp)) bonds cleave the Ru-Ph bond and form Ru-E/H bonds by different mechanisms. The reaction with catecholborane gives [RuH(CO)L₂]BAr′₄, which further reacts with catecholborane to give [Ru(BR₂)(CO)L₂]BAr′₄. However, the reaction with Me₃SiCCH undergoes a multistep transformation to give a PhCCSiMe₃- and Me₃SiCCH-coupled product, the mechanism of which is discussed. Reaction of RuCl₂(CO)L₂ with 1 equiv MeLi affords RuMeCl(CO)L₂, 5, which further reacts with MeLi forming RuMe₂(CO)L₂, 7. Variable-temperature ¹³C{¹H} NMR spectra reveal the two methyls in 7 are inequivalent and exchange by overcoming an energy barrier of 6.8 kcal/mol at -30 °C. The chloride of 5 can be removed to give [RuMe(CO)L₂]BAr′₄.

Full text of DOI:10.1021/ja990621w

J. Am. Chem. Soc. 1999, 121, 8087-8097
8087
14-Electron Four-Coordinate Ru(II) Carbyl Complexes and Their
Five-Coordinate Precursors: Synthesis, Double Agostic Interactions,
and Reactivity
Dejian Huang,† William E. Streib,† John C. Bollinger,† Kenneth G. Caulton,*,†
Rainer F. Winter,*,‡ and Thomas Scheiring‡
Contribution from the Department of Chemistry and Molecular Structure Center, Indiana UniVersity,
Bloomington, Indiana 47405-4001, and Institut fu¨r Anorganische Chemie der UniVersita¨t,
Pfaffenwaldring 55, D-70569 Stuttgart, Germany
ReceiVed February 26, 1999
Abstract: The structure of five-coordinate Ru(II) complexes RuHCl(CO)(PiPr3)2, 1, RuCl2(CO)(PiPr3)2, 2, and
Ru(Ph)Cl(CO)(PtBu2Me)2, 12, are reported. All three of these complexes have square-based pyramid geometry
with the strongest σ-donor ligand trans to the vacant site. These 16-electron complexes do not show bona fide
agostic interactions. This is attributed to the strong trans influence ligand (H, CO, and Ph) and π-donation of
the Cl, which is further supported by the fact that two agostic interactions are present in the Cl- removal
product of 12, i.e., the four-coordinate [RuPh(CO)L2]BAr′4 (L ) PtBu2Me, Ar′ ) 3,5-C6H3(CF3)2), 16. Structural
comparison of 16 and 12 reveals that removal of Cl- does not change the remaining ligand arrangements but
creates two low-lying LUMOs for agostic interactions, which persist in solution as evidenced by IR spectroscopy.
Reactions of 16 with E-H (E ) B, C(sp)) bonds cleave the Ru-Ph bond and form Ru-E/H bonds by different
mechanisms. The reaction with catecholborane gives [RuH(CO)L2]BAr′4, which further reacts with catecholbo-
rane to give [Ru(BR2)(CO)L2]BAr′4. However, the reaction with Me3SiCCH undergoes a multistep
transformation to give a PhCCSiMe3- and Me3SiCCH-coupled product, the mechanism of which is discussed.
Reaction of RuCl2(CO)L2 with 1 equiv MeLi affords RuMeCl(CO)L2, 5, which further reacts with MeLi forming
RuMe2(CO)L2, 7. Variable-temperature 13C{1H} NMR spectra reveal the two methyls in 7 are inequivalent
and exchange by overcoming an energy barrier of 6.8 kcal/mol at -30 °C. The chloride of 5 can be removed
to give [RuMe(CO)L2]BAr′4.
Introduction
plexes with a 14-electron count, [Ru(R)(CO)L2]+ (R ) CH3,
Ph, catecholboryl).5 The unusual structural feature of these
complexes is the presence of two agostic interactions.
Coordinatively and electronically unsaturated transition metal
carbyl complexes are key species in promoted reactions such
as olefin polymerization, hydrogenation, hydrosilylation and
hydroboration.1 Particularly, complexes with formally 14-
valence electrons, or 16-electron but bearing an extremely labile
ligand (e.g., agostic bonding, weakly coordinating counterion
or solvent) are recognized as the active catalytic component of
olefin polymerization reactions and are extensively studied, both
on early and late transition metals (III-IVB, Ni, Pd, Pt).2 In
sharp contrast, isolable 14-electron complexes of other transition
metals are rare, although 14-electron species have been proposed
often as active species in organometallic reactions.3 It has been
proposed that a 14-electron complex has the advantage over its
16-electron counterpart since it provides two low-lying empty
orbitals for substrate binding, and group (or atom) migration
and bond formation.4 We wish to report our results on the
synthesis and structure of four-coordinate Ru(II) carbyl com-
The geometry preference of five-coordinate d6 metal com-
plexes has been well studied.6 The diamagnetic Ru or Os
complexes with the general formula, MXY(CO)L2 (X and Y
are univalent ligands, L is usually a phosphine) adopt a square-
based pyramidal geometry with the strongest trans influence
ligand at the apical site so that the LUMO has the highest
possible energy. When the X and Y are significantly different
(e.g., H vs Cl) the geometry of the complex is rather obvious,
but when the X and Y have similar trans influence (e.g., Me vs
H or Ph), predicting the geometry is not straightforward.
Although these complexes are fluxional, the primary reaction
product is usually governed by the ground-state geometry.7 On
the route to 14-electron Ru alkyl complexes, we have synthe-
sized several five-coordinate precursors where X and Y are
carbyls of similar trans influence. Their geometry preferences
* Corresponding author. E-mail: caulton@indiana.edu.
(1) Hegedus, L. S. In ComprehensiVe Organometallic Chemistry II; Abel,
E. W., Stone, F. G. A., Wilkinson, G., Eds.; Pergamon: New York, 1995;
p 1.
(2) (a) Grubbs, R. H.; Coates, G. W. Acc. Chem. Res. 1996, 29, 85. (b)
Brintzinger, H. H.; Fischer, D.; Mulhaupt, R.; Rieger, B.; Waymouth, R.
M. Angew. Chem., Int. Ed. Engl. 1995, 34, 1143 and references therein. (c)
Johnson, L. K.; Kilian, C. M.; Brookhart, M. J. Am. Chem. Soc. 1995, 117,
6414.
(4) Crabtree, R. H. In ActiVation and Functionalization of Methane;
Davies, J. A., Ed.; VCH: New York, 1990; p 69.
(5) A preliminary communication has appeared: Huang, D.; Streib, W.
E.; Eisenstein, O.; Caulton, K. G. Angew. Chem., Int. Ed. Engl. 1997, 36,
2004.
(6) (a) Cundari, T. R. J. Am. Chem. Soc. 1994, 116, 340. (b) Su, M.-D.;
Chu, S.-Y. J. Am. Chem. Soc. 1997, 119, 10178.
(7) (a) Huang, D.; Spivak, G. J.; Caulton, K. G. New. J. Chem. 1998,
22, 1023. (b) Huang, D.; Caulton, K. G. Inorg. Chem. 1996, 35, 7035. (c)
Werner, H.; Stu¨er, W.; Laubender, M.; Lehmann, C.; Herbst-Irmer, R.
Organometallics 1997, 16, 2236.
(3) (a) Wick, D. D.; Goldberg, K. I. J. Am. Chem. Soc. 1997, 119, 10235.
(b) Cooper, A. C.; Caulton, K. G. Inorg. Chim. Acta 1996, 251, 41.
10.1021/ja990621w CCC: $18.00 © 1999 American Chemical Society
Published on Web 08/21/1999

8088 J. Am. Chem. Soc., Vol. 121, No. 35, 1999
Huang et al.
Table 1. Crystallographic Dataa
1
2
12
16
formula
FW
color
space group
T (K)
a (Å)
C19H43ClOP2Ru
485.99
orange
P21/c
173(2)
8.0675(5)
8.9312(7)
16.6316(10)
90
92.492(5)
90
2
1197.2(1)
1.348
0.71073
6.85
C19H42Cl2OP2Ru
520.44
red
C25H47ClOP2Ru
562.12
orange
P1h
C57H59BF24OP2Ru
1389.89
thermochromic
P212121
103
18.176(3)
18.495(3)
18.090(3)
90
90
90
4
6081(46)
1.518
0.71069
4.23
0.062
0.061
Cc
183(2)
21.867(4)
8.648(2)
15.033(2)
90
119.75(1)
90
103
16.680(3)
17.037(4)
10.772(2)
90.81(1)
92.85(1)
112.68(1)
4
2819.10
1.324
0.71069
7.66
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
Z
4
V (Å3)
2468.1(7)
1.401
0.71073
9.88
0.0727
0.0265
F
calc (g/cm3)
λ (Å)
µ (cm-1
wR2
)
0.069
0.0264
0.0464
0.0655
R1
2
a R ) ∑||Fo| - |Fc||/∑|Fo|; Rw ) [∑w(|Fo| - |Fc|)2/∑w|Fo| ]1/2, where w ) 1/σ2(|Fo|).
Table 2. Geometric Parameters of RuHCl(CO)(PiPr3)2
Table 3. Geometric Parameters of RuCl2((CO)(PiPr3)2
Bond Lengths (Å)
Ru-C(3)
Ru-Cl(2)
1.752(6)
2.4219(18) C(3)-O(3)
Ru-P(1)
2.3794(4)
1.164(6)
Ru-C1
Ru-P2
C1-O1
2.358(2)
2.406(3)
2.382(3)
Bond Angles (deg)
P(1)-Ru-P(1)′
P(1)-Ru-Cl(2)
180
89.34(5)
C(12)-P(1)-Ru 112.16(6)
C(3)-Ru-Cl(2)
177.3(2)
90.04(14)
113.62(7)
Bond Angles (deg)
C(3)-Ru(1)-P(1)
C(13)-P(1)-Ru
C1-Ru-Cl1
C1-Ru-P2
C1-Ru-P1
P2-Ru-P1
C18-P1-Ru
C28-P2-Ru
C1-Ru-Cl2
Cl1-Ru-P2
98.0(5)
Cl1-Ru-P1
C15-P1-Ru
C25-P2-Ru
Cl1-Ru-Cl2
Cl2-Ru-P2
Cl2-Ru-P1
C12-P1-Ru
C33-P2-Ru
90.99(9)
114.6(3)
116.8(3)
165.97(3)
90.89(9)
87.66(9)
110.2(3)
106.7(3)
97.7(4)
92.1(4)
C(11)-P(1)-Ru 113.25(6)
Ru(1)-C(3)-O(3) 178.6(8)
170.15(2)
114.7(3)
112.1(3)
96.0(5)
are discussed based on spectroscopic data and X-ray structural
data of related complexes.
88.06(9)
Experimental Section
General Procedures. All reactions and manipulations were con-
ducted using standard Schlenk and argon-filled glovebox techniques.
Solvents were dried according to routine methods, distilled under argon,
and stored in airtight solvent bulbs with Teflon closures. The solvents
were also freshly degassed by freeze-pump-thaw cycles before use.
All NMR solvents were dried, vacuum-transferred, and stored in an
argon-filled glovebox. 1H, 31P, 19F, and 13C NMR spectra were recorded
on a Varian Gem XL300 or Unity I400 spectrometer. Chemical shifts
are referenced to solvent peaks (1H, 13C), or external H3PO4 (31P) and
CFCl3 (19F). Infrared spectra were recorded on a Nicolet 510P FT-IR
spectrometer. Elemental analyses were conducted on the Perkin-Elmer
2400 CHNS/O analyzer at the Department of Chemistry, Indiana
flask and heated at 80 °C for 4 h. The solution color changed from
orange to brown. The volatiles were evaporated in vacuo, and the
residue were extracted with diethyl ether. The diethyl ether solution
was evaporated to a give brown solid, which was recrystallized from
toluene at -40 °C. Yield: 150 mg (70%). Anal. Calcd for C19H42Cl2-
1
OP2Ru: C, 43.84, H, 8.07. Found: C, 44.29, H, 7.78. H NMR (300
MHz, C7D8, 20 °C): δ 2.80 (m, 6H, PCH3) 1.25 (vdt, JHH ) 6.5 Hz,
N ) 14.4 Hz, 36H, PCH(CH3)2). 31P{1H} NMR (145 MHz, C7D8, 20
°C): 44.8 (s). IR(C7D8,cm-1): 1937 (ν(CO)).
X-ray Crystal Structure Determination of RuCl2(CO)(PiPr3)2.
Single crystals were obtained by slow cooling of a hot saturated
methanol solution of the compound. The single crystals were taken
from the mother liquors, separated under Nujol, and sealed in a glass
capillary. The data collection was performed on a Siemens-P4 four-
circle diffractometer. The structure was solved by the Patterson method,
using the SHELXTL-Plus package. The refinement was carried out
with SHELXL-93, employing full-matrix least-squares methods. Aniso-
tropic thermal parameters were refined for all non-hydrogen atoms.
All hydrogen atoms were constrained using a riding model with iso-
tropic thermal parameters fixed at 20% greater than that of the bonded
atom. The structure was refined (227 parameters) on F2 (SHELXL93);
the maximum and the minimum peaks in the final difference Fourier
map corresponded to -0.345/0.839 e/Å3 (Tables1 and 3).
8
9
University. RuHCl(CO)L2 and NaBAr′4 are prepared following
literature procedures. Other chemicals are commercially available and
degassed before use.
X-ray Crystal Structure Determination of RuHCl(CO)(PiPr3)2,
1 (Tables1 and 2). Orange crystals were obtained by slowly cooling
a hot concentrated solution in a 3:1 MeOH/toluene mixture; Siemens
four-circle diffractometer P4. Refinement used 209 parameters without
constraints. Minimum and maximum peak of residual electron density
in the final Fourier map -0.450/0.921 e Å-3. The structure was solved
by direct methods (SHELXTL-Plus) and refined on F2 (SHELXL93).
Due to the special position of the ruthenium atom on a crystallographic
inversion center, the CO and Cl ligand are disordered. The C(3), O(3),
and Cl(2) atoms were refined as “half occupied” (50%). All non-H
atoms were refined with anisotropic thermal parameters. All hydrogen
atoms were introduced at their geometric positions and treated according
to the “riding model” with isotopic thermal parameters fixed at 20%
greater than that of the bonded C-H atom.
Ru(CH3)Cl(CO)(PiPr3)2, 4. RuCl2(CO)(PiPr3)2 (150 mg, 0.3 mmol)
was dissolved in benzene (5 mL). To the solution, MeLi (1.4 mol/L in
diethyl ether, 0.21 mL) was added, and the solution was stirred for 5
h. The solvent was removed, and the residue was extracted with pentane
and filtered. The filtrate was concentrated to 3 mL and cooled to -40
°C for 1 day to give orange crystals. 1H NMR (C6D6, 20 °C): 2.60 (m,
6H, PCH(CH3)2), 1.52 (t, J ) 5 Hz, 3H, Ru-CH3), 1.25 (vtd, N )
13.5 Hz, JHH ) 7 Hz, 18H, PCH(CH3)2), 1.20 (vtd, N ) 13.5 Hz, J )
7 Hz, 18H, PCH(CH3)2). 31P{1H} NMR: 37.7 (s).
RuCl2(CO)(PiPr3)2, 2. RuHCl(CO)(PiPr3)2 (200 mg, 0.41 mmol),
PhCH2Cl (1.0 g, 8.2 mmol), and 10 mL of toluene were mixed in a
(8) Gill, D. F.; Shaw, B. L. Inorg. Chim. Acta 1979, 32, 19. Huang, D.;
Folting, K.; Caulton, K. G. Inorg. Chem. 1996, 35, 7035.
(9) Brookhart, M.; Grant, B.; Volpe, J. Organometallics 1992, 11, 3920.
NMR Study of the Reaction of RuCl2(CO)(PiPr3)2 with MeLi.
RuCl2(CO)(PiPr3)2 (10 mg, 0.019 mmol) was dissolved in C6H6 (0.5

14-Electron Four-Coordinate Ru(II) Carbyl Complexes
J. Am. Chem. Soc., Vol. 121, No. 35, 1999 8089
mL). To the solution, MeLi (1.4 mol/L in diethyl ether, 14 µL) was
added. After 10 min, the 31P{1H} NMR spectrum reveals two products,
Ru(CH3)Cl(CO)(PiPr3)2 and Ru(CH3)2(CO)(PiPr3)2, in equal amounts,
along with starting material. After 3 h, the 31P{1H} NMR spectrum
reveals Ru(CH3)Cl(CO)(PiPr3)2 as the dominant product. To the same
NMR tube, one more equivalent MeLi was added. After 10 min, Ru-
(CH3)2(CO)(PiPr3)2 is the only product based on the 31P{1H} NMR
spectrum. The solvent of the reaction was removed, and to the same
Table 4. Selected Geometric Parameters of
RuPhCl(CO)(PtBu2Me)2
molecule A
molecule B
Bond Lengths (Å)
2.4432(6)
Ru(1)-Cl(2)
Ru(1)-P(3)
Ru(1)-P(13)
Ru(1)-C(23)
Ru(1)-C(29)
O(30)-C(29)
2.4534(6)
2.4178(5)
2.4259(5)
2.0438(4)
1.8129(4)
1.0736(2)
2.4097(5)
2.4296(5)
2.0394(4)
1.8236(4)
1
NMR tube, C6D6 (0.5 mL) was added. H NMR (300 MHz, 20 °C):
2.51 (m, PCH(CH3)2), 1.12 (dvt, J ) 6 Hz, N ) 12.4 Hz, 36H, PCH-
(CH3)2), 0.82 (t, J ) 6 Hz, 6H, Ru-CH3). 31P{1H} NMR: 40.7 (s). IR
(C6D6): 1894 (ν(CO)).
1.0871(2)
Bond Angles (deg)
87.685(14)
Cl2-Ru1-P3
Cl2-Ru1-C23
P3-Ru1-C29
P13-Ru1-C29
Ru1-P3-C9
88.912(14)
90.199(14)
105.167(13)
165.042(5)
173.6980(20)
93.210(18)
90.804(14)
93.044(18)
88.446(14)
89.782(15)
126.188(11)
117.328(15)
179.8500(10)
126.972(10)
Ru(CH3)2(CO)(PtBu2Me)2, 7. RuCl2(CO)(PtBu2Me)2 (150 mg, 0.29
mmol) was dissolved in benzene (5 mL). To the solution, MeLi (1.4
mol/L in diethyl ether, 0.42 mL) was added and stirred for 5 min. The
solvent was removed and residue was extracted with cold tetrameth-
ylsilane and filtered through a Celite pad. The filtrate was concentrated
to 1 mL and cooled to -78 °C for 24 h. Brown crystals were formed,
filtered, and washed with tetramethylsilane. Yield: 66%. 1H NMR (300
MHz, C7D8, 20 °C): 1.28 (vt, N ) 5.4 Hz, 6H, PCH3), 1.07 (vt, N )
11.8 Hz, 36H, PC(CH3)3), 0.52 (t, J ) 6 Hz, Ru-CH3). 31P{1H} NMR
(121 MHz, 20 °C): 43.3 (s) 13C{1H} NMR (100 MHz, 20 °C, C7D8):
201.9 (t, JPC ) 12 Hz, Ru-CO), 36.6 (vt, N ) 15 Hz, PC(CH3)3), 29.7
(s, PC(CH3)3), 2.6 (t, JPC ) 7.1 Hz, Ru-CH3), 1.10 (vt, N ) 5 Hz,
PCH3). -90 °C: 202.5 (t, JPC ) 13 Hz, Ru-CO), 37.2 (vt, N ) 17
Hz, PC(CH3)3), 36.4 (vt, N ) 17 Hz, PC(CH3)3), 29.3 (br, V1/2 ) 56
Hz, PC(CH3)3), 29.6 (br, PC(CH3)3), 17.5 (t, J ) 11 Hz, Ru-CH3),
1.14 (br, P-CH3), -15.7 (t, J ) 7.5 Hz, Ru-CH3). IR (C6D6): 1878
(ν(CO)).
102.948(14)
92.293(14)
86.924(15)
121.222(15)
114.408(13)
110.270(17)
91.457(14)
167.143(4)
92.736(18)
89.874(15)
Ru1-P3-C4
Ru1-P13-C15
Cl2-Ru1-P13
Cl2-Ru1-C29
P13-Ru1-C23
C23-Ru1-C29
Ru1-P3-C5
105.760(17)
112.079(13)
118.831(12)q
Ru1-P13-C14
Ru1-P13-C19
-70 °C, the proton chemical shift of the methyl bound to Ru does not
change much compared to that of 20 °C; therefore, no agostic interaction
from the Ru-CH3 is likely.
Ru(CH3)F(CO)(PtBu2Me)2, 8. Ru(CH3)Cl(CO)(PtBu2Me)2 (0.50 g,
1.0 mmol) and CsF (0.5 g, 3.3 mmol) was mixed with acetone (20
mL) and stirred for 4 h. The volatiles were then removed in vacuo,
and the residue was extracted with pentane and filtered. The filtrate
was concentrated to ca. 5 mL and cooled to -40 °C for 2 days. Brown
crystals were filtered and washed with pentane (-78 °C). Yield: 0.26
g (54%). Anal. Calcd for C20H45FOP2Ru: C, 49.67, H, 9.38. Found:
Ru(Ph)Cl(CO)(PtBu2Me)2, 12. (a) From Ph2Hg. A toluene (40 mL)
solution of RuHCl(CO)(PtBu2Me)2 (2.0 g, 4.1 mmol) and Ph2Hg (2.9
g, 8.0 mmol) was refluxed for 12 h and freed of volatiles.10 The residue
was extracted with pentane (ca. 120 mL), which was evaporated to
dryness to afford a crude product. Recrystallization from methanol gave
1
dark-orange crystals. Yield: 1.92 g (83%). H NMR (C7D8, 20 °C):
8.32 (d, J ) 7.2 Hz, 1H, ortho H of Ph), 7.31 (d, J ) 7.2 Hz, 1H,
ortho H of Ph), 6.78 (m, 1H, para H of Ph), 6.69 (m, 2H, meta H of
Ph), 1.44 (vt, N ) 5.4 Hz, 6H, PMe), 1.04 (vt, N ) 12 Hz, 18H, PtBu),
1.02(vt, N ) 12 Hz, 18H, PtBu). 31P{1H} NMR (C7D8, 20 °C): 34.0
(s). IR (C6D6, cm-1): ν(CO) ) 1902.
1
C, 49.96, H, 9.00. H NMR (400 MHz, C6D6, 20 °C): 1.32 (t, J ) 5
Hz, Ru-CH3), 1.30 (vt, N ) 12.4 Hz, 18H, PC(CH3)3), 1.20 (vt, N )
12.4 Hz, 18H, PC(CH3)3), 1.09 (vt, N ) 5 Hz, P-CH3). 31P{1H}-
NMR: 41.0 (d, JPF ) 22 Hz). 19F NMR: -201 (tq, JPF ) 22 Hz, JFH
) 4 Hz, Ru-F). IR (C6D6): 1887 (ν(CO)).
(b) From RuCl2(CO)(PtBu2Me)2 and PhLi. RuCl2(CO)L2 (100 mg,
0.19 mmol) was dissolved in a 9:1 pentane/toluene mixture (5 mL)
and cooled to -78 °C. PhLi (1.8 M in cyclohexane/ether solution, 160
µL, 0.29 mmol) was added to the mixture. The mixture was stirred
and warmed slowly (over 12 h) to room temperature. The volatiles
were evaporated, and the residue was recrystallized from methanol to
give orange crystals. Yield: 85 mg (79%).
Ru(CH3)(OTf)(CO)(PtBu2Me)2, 9. Ru(CH3)F(CO)(PtBu2Me)2 was
dissolved in diethyl ether (10 mL). To the solution, Me3SiOTf (34 µL)
was added. The mixture was stirred for 10 min and filtered. The filtrate
was concentrated to 2 mL and cooled to -40 °C for 1 day to give
yellow crystals. Yield: 90 mg (70%). Anal. Calcd for C21H45F3O4P2-
RuS: C, 41.10, H, 7.39. Found; C, 41.01, H, 7.43. 1H NMR (300 MHz,
C6D6, 20 °C): 1.49 (vt, N ) 4 Hz, 6H, PCH3), 1.43 (t, J ) 5.2 Hz,
3H, RuCH3), 0.97 (vt, N ) 13 Hz, PC(CH3)3), 0.94 (vt, N ) 13 Hz,
PC(CH3)3). 31P{1H} NMR (121 MHz, 20 °C): 42.4 (s). 19F NMR (282
MHz, 20 °C): -81.0 (s, CF3SO3). IR (C6D6): 1914 (ν(CO)).
Ru(CH3)(BF4)(CO)(PtBu2Me)2, 10. Ru(CH3)F(CO)(PtBu2Me)2 (50
mg, 0.10 mmol) was dissolved in diethyl ether (2 mL). To the solution,
BF3‚OEt2 (13 µL, 0.1 mmol) was added. The mixture was stirred for
1 min and kept undisturbed for 1 h to get orange microcrystals. The
solution was cooled to -78 °C for one more hour, to obtain more
product. The solvent was removed and the crystals were washed with
cold diethyl ether and dried. Yield: 35 mg (63%). 1H NMR (300 MHz,
C6D6, 20 °C): 1.47 (vt, N ) 5.3 Hz, 6H, PCH3), 1.30 (vt, N )12.8 Hz,
18H, PC(CH3)3), 1.22 (vt, N )12.8 Hz, 18H, PC(CH3)3), Ru-CH3
protons are overlapping with tBu proton signals and not assigned. 31P-
{1H} NMR: 43.8 (s), 19F NMR: -210 (br, V1/2 ) 1396 Hz, BF4). IR
(C6D6): 1919 (ν(CO)).
X-ray Crystal Structure Determination of RuPhCl(CO)(PtBu2Me)2
(Tables1 and 4). A small, well-formed crystal was chosen from the
bulk sample and affixed to the tip of a glass fiber with the use of silicone
grease. The mounted sample was then transferred to the goniostat and
cooled to -164 °C for data collection. A systematic search of a limited
hemisphere of reciprocal space located a set of data with no symmetry
or systematic absences, thus indicating a triclinic space group.
Subsequent solution and refinement of the structure confirmed the
choice of the centrosymmetric space group. Data were collected by
the moving crystal, moving detector technique with fixed background
counts at each extreme of the scan. Data were corrected for Lorentz
and polarization effects, and equivalent data were averaged. The
structure was solved by direct methods (SHELXTL) and Fourier
techniques. Hydrogen atoms were placed in calculated positions and
not refined. The final difference electron density map was featureless,
with the highest peak having an intensity of 1.38 e/Å3 and residing
near one Ru atom. There was no detectable disorder, and a least-squares
fit of the coordinates of one independent molecule to those of the other
indicates that the two have a close mirror image relationship. Given
that there are two chemically identical independent molecules in the
triclinic unit cell, one might suspect that a phase change had occurred
[Ru(CH3)(CO)(PtBu2Me)2]BAr′4, 11. Ru(CH3)(BF4)(CO)(PtBu2-
Me)2 (10 mg, 0.018 mmol) and NaBAr′4 (16 mg, 0.018 mmol) were
mixed in 1:2 C6D5F/C7D8 mixture. The solution was stirred for 10 min.
1
Some colorless precipitate forms (NaBF4). H NMR (400 MHz, 20
°C): 8.28 (br, 8H, ortho H of Ar′), 7.64 (br, 4H, para H of Ar′), 1.14,
(br, 3H, Ru-CH3), 1.07 (vt, N ) 5 Hz, 6H, PCH3), 0.91 (vt, N ) 12.8
Hz, 18H, PC(CH3)3), 0.81 (vt, N ) 12.8 Hz, 18H, PC(CH3)3). 31P{1H}
NMR: 41.0 (s). 19F NMR: -62 (s, CF3 of Ar′). IR: 1951 (ν(CO)). At
(10) Rickard, C. E. F.; Roper, W. R.; Taylor, G. E.; Waters, J. M.; Wright,
L. J. J. Organomet. Chem. 1990, 389, 375.

8090 J. Am. Chem. Soc., Vol. 121, No. 35, 1999
Huang et al.
as the crystal was cooled. A check of the unit cell parameters at -55
°C indicated no significant change from those measured at -164 °C
however, so any phase change that may have taken place occurred above
-55 °C.
Table 5. Selected Geometric Parameters of
[RuPh(CO)(PtBu2Me)2]+
Bond Lengths (Å)
Ru1-P10
Ru1-C4
C2-O3
2.3920(22) Ru1-P20
2.058(12) Ru1-C2
1.163(16)
2.3653(28)
1.799(14)
Ru(Ph)F(CO)(PtBu2Me)2, 13. Ru(Ph)Cl(CO)(PtBu2Me)2 (200 mg,
0.36 mmol) and CsF (100 mg, 0.66 mmol) were mixed with acetone
(5 mL) and stirred for 12 h. The mixture was filtered and the residue
was washed with pentane. The combined filtrate was evaporated to
dryness in vacuo. The crude product was recrystallized from pentane
Bond Angles (deg)
P10-Ru1-P20 167.98(14)
P10-Ru1-C2
96.532(28) P20-Ru1-C2
91.5(3) C2-Ru1-C4
93.0
95.5(3)
93.7(8)
P10-Ru1-C4
P20-Ru1-C4
1
(-40 °C). Yield: 150 mg (77%). H NMR (300 MHz, C6D6, 20 °C):
8.44 (d, JHH ) 6.6 Hz, 1H, ortho H of Ph), 7.50 (d, JHH ) 8.1 Hz, 1H,
ortho H of Ph), 6.92 (m, 1H, para H of Ph), 6.90 (m, meta H of Ph),
6.83 (m, meta H of Ph), 1.31 (vt, N ) 5.7 Hz, 6H, PCH3), 1.08 (vt, N
) 13.2 Hz, 18H, PtBu), 0.99 (vt, N ) 12.6 Hz, 18H, PtBu). 31P{1H}
NMR (121 Hz, C6D6, 20 °C): 42.0 (d, JPF ) 24 Hz, Ru-P). 19F NMR
(376 MHz, C6D6, 20 °C): -204.5 (t, J ) 24 Hz, Ru-F). IR (C6D6,
cm-1): ν(CO) ) 1890.
Ru1-P10-C11 98.1(3)
Ru1-P10-C19 109.4(4)
Ru1-P20-C21 121.7(6)
Ru1-P10-DFC15 126.1(4)
Ru1-P20-C29
Ru1-P20-C25
114.6(5)
96.6(3)
temperature. If the crystals were grown at -20 or -40 °C in the same
solvent system, only twinned crystals were obtained. The highly air-
sensitive compound was handled in a nitrogen atmosphere glovebag.
The crystals were mounted using silicone grease and were then
transferred to a goniostat equipped with a nitrogen vapor cold stream
at -170 °C. No decomposition was evident for the crystal at the low
temperature. A preliminary automated search for peaks and then analysis
using programs DIRAX and TRACER revealed a primitive orthor-
hombic cell. Following intensity data collection, the only conditions
observed were h ) 2n for h00, k ) 2n for 0k0, and l ) 2n for 00l
which uniquely determined space group P212121. Data processing
produced a set of 4419 unique intensities and an Rav ) 0.098 for the
averaging of 4109 of these which had been observed more than once.
Four standards measured every 300 data points had considerable random
scatter, but they showed no systematic trends. No correction was made
for absorption (µ ) 4.2 cm-1). The structure was solved using a
combination of direct methods (MULTAN78) and Fourier techniques.
The positions of the Ru atom and the P and C atoms bonded to it were
obtained from an initial E-map. The positions of the remaining non-
hydrogen atoms were obtained from iterations of a least-squares
refinement and difference Fourier calculation. Hydrogens were included
in fixed calculated positions with thermal parameters fixed at one plus
the isotropic thermal parameter of the parent carbon atom. Four of the
carbon atoms, C(24) and C(27) in a tert-butyl group and C(75) and
C(77) in the anion, had thermal parameters that refined to nonpositive
definite anisotropic values. In the final cycles of refinement, these four
atoms were varied with isotropic thermal parameters and the remaining
82 non-hydrogen atoms were varied with anisotropic thermal parameters
to give a final R(F) ) 0.062 for the 756 total variables (Tables1 and
5). The largest peak in the final difference map was 0.95, and the
deepest hole was -1.15 e/Å3.
Ru(Ph)OTf(CO)(PtBu2Me)2, 14. (a) From Ph2Hg. RuH(OTf)(CO)-
(PtBu2Me)2 (0.50 g, 0.83 mmol) and Ph2Hg (0.50 g, 1.4 mmol) were
mixed in toluene (10 mL). The mixture was refluxed for 12 h, during
which time mercury metal precipitates. The solution was cooled to room
temperature and filtered through a Celite pad. The filtrate was
evaporated to dryness. The resulting orange solid was heated in vacuo
at 80 °C to sublime away excess Ph2Hg. The remaining orange solid
was dissolved in diethyl ether and filtered. The filtrate was concentrated
to 3 mL and layered with pentane. Orange crystals were formed over
1 week. Yield: 0.45 g (80%).
(b) From Ru(Ph)F(CO)(PtBu2Me)2 and Me3SiOTf. RuPhF(CO)-
(PtBu2Me)2 (150 mg, 0.28 mmol) was dissolved in cyclohexane (10
mL). To the solution, Me3SiOTf (54 µL, 0.28 mmol) was added. The
mixture was stirred for 10 min and freed of volatiles. Recrystallization
from toluene layered with pentane gave orange crystals. Yield: 110
1
mg (58%). H NMR (300 MHz, C6D6, 20 °C): 8.0 (d, JHH ) 7.8 Hz,
1H, ortho H of Ph), 7.31 (d, JHH ) 7.8 Hz, 1H, ortho H of Ph), 6.90
(t, JHH ) 7.4, 1H, para H of Ph), 6.73 (m, 1H, meta H of Ph), 6.72 (m,
1H, meta H of Ph), 1.50 (br, s, 6H, PCH3), 1.04 (vt, N ) 13.2 Hz,
18H, PtBu), 0.76 (vt, N ) 13.2 Hz, 18H, PtBu). 31P{1H} NMR (121
MHz, C6D6, 20 °C): 40.5 (s, Ru-P). 19F NMR (282 MHz, C6D6, 20
°C): -77.7 (s, O3SCF3). IR (C6D6, cm-1): ν(CO) ) 1921.
Ru(Ph)(CH3)(CO)(PtBu2Me)2, 15. RuPh(OTf)(CO)(PtBu2Me)2 (200
mg, 0.36 mmol) was dissolved in toluene (10 mL). To the solution,
MeLi (1.6 mol/L in diethyl ether, 200 µL, 0.32 mmol) was added. The
mixture was stirred for 5 min, and the volatiles were evaporated to
dryness. The residue was dissolved in tetramethylsilane and filtered.
Removal of the solvent results in a viscous oil, which was recrystallized
from bis(trimethylsilyl) ether to give orange crystals. Yield: 40%. 1H
NMR (300 MHz, C6D6, 20 °C): 7.65 (d, JHH ) 5.7 Hz, 1H ortho H of
Ph), 7.45 (d, JHH ) 5.7 Hz, 1H, ortho H of Ph), 6.72 (m, 3H, meta and
para H of Ph), 1.42 (vt, N ) 12 Hz, 18H, PCCH3), 1.05 (t, JPH ) 4 Hz,
3H, PCH3), 0.99 (vt, N ) 12 Hz, 18H, P(C(CH3)3). 13C{1H} NMR
(C7D8, 100 MHz, 20 °C): 203.7 (t, JPC ) 13 Hz, Ru-CO), 158.5 (s,
Ru-Cipso), 144.0, 139.4, 126.6, 120.4 (s, Ph), 37.5 (vt, N ) 15 Hz,
PC(CH3)3), 36.4 (vt, N ) 16 Hz, PC(CH3)3), 30.0, 29.5 (s, PC(CH3)3),
9.5 (br, Ru-CH3), 5.1 (br, PCH3). IR (C6D6, cm-1): 1883 (ν(CO)).
Anal. Calcd for C26H50OP2Ru: C, 57.64, H, 9.30. Found: C, 57.38,
H, 9.48.
Reaction of [RuPh(CO)(PtBu2Me)2]BAr′4 with C6H4O2B-H.
[RuPh(CO)(PtBu2Me)2]BAr′4 (10 mg, 7.2 × 10-3 mmol) and cat-
echolborane (0.76 µL, 7.2 × 10-3 mmol) were mixed in CD2Cl2 (0.5
mL). After 1 h, NMR analysis of the reaction solution reveals the
formation of [RuH(CO)(PtBu2Me)2]+ and C6H4O2B-Ph, which was
confirmed by comparing the NMR spectra with authentic samples.
Ru(BO2C6H4)(OTf)(CO)(PtBu2Me)2, 17. RuH(OTf)(CO)(PtBu2Me)2
(0.50 g, 8.3 × 10-4 mol) and catecholborane (97 µL, 1.0 × 10-3 mmol)
were mixed with C6H6 (10 mL) and heated at 80 °C for 4 h. The mixture
was evaporated to give a yellow solid, which was recrystallized from
pentane/benzene mixture to give light-yellow crystals. Yield: 0.40 g
(67%). Anal. Calcd for C26H40BF3O6P2RuS; C, 43.50, H, 5.62. Found:
[Ru(Ph)(CO)(PtBu2Me)2]BAr′4, 16. RuPh(OTf)(CO)(PtBu2Me)2
(150 mg, 0.22 mmol) and NaBAr′4 (201 mg, 0.23 mmol) were mixed
in fluorobenzene (5 mL) in a test tube under argon. The mixture was
shaken for 10 min and centrifuged. The liquid was transferred to a
Schlenk flask and layered with pentane. After 2 days, red crystals were
obtained. Yield: 160 mg (52%). Anal. Calcd for C57H59BF24OP2Ru:
1
C, 44.01, H, 6.64. H NMR (300 MHz, C6D6, 20 °C): 7.00 (m, 2H,
O2C6H4), 6.70 (m, 2H, O2C6H4) 1.57 (vt, N ) 5.9 Hz, 6H, PCH3), 1.12
(vt, N ) 13.3 Hz, 18H, PC(CH3)3), 0,85 (vt, N ) 13 Hz, 18H, PC-
(CH3)3). 31P{1H} NMR (C6D6, 20 °C): 53.6 (s, w1/2 ) 194 Hz) 19F
NMR (C6D6, 20 °C): -78.6 (s, CF3). 11B NMR (C6D6, 20 °C): 44.5
(br s). IR (C6D6, cm-1): 1939 (ν(CO)).
1
C, 48.59; H, 4.22. Found: C, 48.61; H, 4.10. H NMR (CD2Cl2, 20
°C): 7.73 (s, 8H, BAr′4), 7.57 (s, 4H, BAr′4), 7.15 (br, s, 2H, Ph), 7.01
(br, s, 2H, Ph), 6.88 (m, 1H, para H of Ph), 1.22 (vt, N ) 4.8 Hz, 6H,
PCH3), 1.18 (vt, N ) 13.2 Hz, 18H, PtBu), 1.12 (vt, N ) 14.4 Hz,
18H, PtBu). 19F NMR (CD2Cl2, 20 °C): -65.2 (s, BAr′4). 31P{1H}
NMR (CD2Cl2, 20 °C): 41.4 (s). IR (CD2Cl2 or fluorobenzene, cm-1):
ν(CO) ) 1958, ν(C-Hagostic) ) 2722, 2672.
[Ru(BO2C6H4)(CO)(PtBu2Me)2], 18. Ru(BO2C6H4)(OTf)(CO)-
(PtBu2Me)2 (10 mg. 0.014 mmol) and NaBAr′4 (12.4 mg, 0.014 mmol)
were mixed in CD2Cl2 to give a yellow solution. NMR analysis of the
mixture revealed clean formation of [Ru(BO2C6H4)(CO)(PtBu2Me)2]-
1
BAr′4. H NMR: 7.73 (s, 8H, ortho H of Ar′), 7.57 (s, 4H, para H of
Crystal Structure of [Ru(Ph)(CO)(PtBu2Me)2]BAr′4. X-ray quality
crystals were grown from a fluorobenzene/pentane mixture at room
Ar′), 7.21 (m, 2H, O2C6H4), 7.05 (2H, O2C6H4), 1.44 (vt, N ) 5.1 Hz,
6H, PCH3), 1.21 (vt, N ) 13.5 Hz, 38H, PC(CH3)3), 1.21 (vt, N )

14-Electron Four-Coordinate Ru(II) Carbyl Complexes
J. Am. Chem. Soc., Vol. 121, No. 35, 1999 8091
13.5 Hz, 18H, PC(CH3)3). 31P{1H} NMR: 43.3 (br s), 19F NMR: -64.1
(s). 11B NMR: 42.8 (br,s). IR: 1981 (ν(CO)).
Reaction of Ru(Ph)(OTf)(CO)(PtBu2Me)2 with Catecholborane.
RuPh(OTf)(CO)(PtBu2Me)2 (10 mg, 0.015 mmol) and catecholborane
(2.0 µL, 0.023 mmol) were mixed in C6D6 (0.5 mL) and heated at 80
°C for 8 h. 1H NMR spectroscopic analysis revealed formation of RuH-
(OTf)(CO)(PtBu2Me)2 and Ru(BO2C6H4)(OTf)(CO)(PtBu2Me)2 with a
ca. 1:1 ratio along with PhBO2C6H4. If one more equivalent of
catecholborane was added and heated for 4 h, only Ru(BO2C6H4)(OTf)-
(CO)L2 was observed.
Reaction of [Ru(Ph)(CO)(PtBu2Me)2]BAr′4 with Me3SiCCH.
When [RuPh(CO)(tBu2Me)2]BAr′4 (10 mg, 7.6 × 10 -3 mmol) and Me3-
SiCCH (1 µL, 7.6 × 10-3 mmol) were dissolved in CD2Cl2, the solution
color changed to red immediately. NMR analysis revealed partial
consumption of [RuPh(CO)(tBu2Me)2]BAr′4 and formation of [Ru((Me3-
SiCHdC-CHdCH(SiMe3)(CO)(PtBu2Me)2]BAr′4 and trace [Ru-
11
(CHdCHSiMe3)(CO)(PtBu2Me)2]BAr′4. 1H NMR (300 MHz, CD2Cl2,
20 °C): 7.71 (s, 8 H, ortho H of Ar′), 7.51 (d, JHH ) 12.3 Hz, 1 H,
RuCH), 5.50 (dt, JHH ) 12.3 Hz, JPH ) 2 Hz, 1 H, RuCHdCH), 1.39
(vt, N ) 4.5 Hz, 6 H, PCH3), 1.28 (vt, N ) 13.2 Hz, 18 H, PtBu), 1.19
(vt, N ) 13.2 Hz, 18 H, PtBu). 0.038 (s, 9 H, SiCH3)3). 31P{1H) NMR
(121 MHz, CD2Cl2, 20 °C): δ 40.8 (s). IR (Nujol, cm-1): 2726, 2677
(ν(C-Hagostic)), 1944 (ν(CO)). If two more equivalents of Me3SiCCH
are added, clean formation of [Ru((Me3SiCHdC-CHdCH(SiMe3)-
(CO)(PtBu2Me)2]BAr′4 was achieved. Analysis of the volatiles revealed
the presence of PhCCSiMe3 as the only product that contains the Ph
group.
General Procedure for Low-Temperature NMR Spectroscopic
Study. [Ru(Ph)(CO)(PtBu2Me)2]BAr′4 (10 mg) was placed in an NMR
tube with Teflon valve closure and carefully covered with CD2Cl2 (0.5
mL) so that the crystals were settled at the bottom of the tube. To the
headspace of the tube, Me3SiCCH (1 µL) was added. The tube was
then promptly taken out of glovebox and placed in a dry ice acetone
bath. The tube was then shaken thoroughly and transferred to a
precooled NMR probe for observation.
Figure 1. ORTEP diagram (50% probability level) of RuHCl(CO)-
(PiPr3)2, 1. Hydrogen atoms are omitted except those bound to Ru.
comment. The structure of 1 is similar with that of Os analogue
OsHCl(CO)(PCy3)2, which also has no agostic interaction.15
Synthesis and X-ray Crystal Structure of RuCl2(CO)L2
(L ) PiPr3), 2. The hydride in 1 is replaced by chloride using
PhCH2Cl (80 °C, 4 h) to give 2 in good yield (eq 1). The
Results and Discussion
Structure of RuHCl(CO)(PiPr3)2, 1. This complex was
originally synthesized by Werner and co-workers.12 The chemi-
cal reactivity has been extensively studied mainly by Esteruelas
and co-workers.13 The rich reactivity ranges from highly
regioselective hydrosilation catalysis to synthesis of cyclopen-
tadienyl complexes such as CpRuCl(CO)(PiPr3). Compounds
with different phosphine ligands (PCy3 and PtBu2Me) have also
been synthesized by a similar method.14 The structure assign-
ment of 1 was based solely on spectroscopic data. These data,
however, do not provide any information on the weak interac-
tions such as agostic bonding. Therefore, we carried out the
X-ray single-crystal structure determination of 1. The ORTEP
plot (Figure 1) shows a square-based pyramidal geometry with
hydride trans to the vacant site and the π-donor (Cl) and the
π-acceptor (CO) ligands trans to each other, benefiting from
push-pull stabilization. Although there is disorder around a
center of symmetry, all three Ru-P-C(methine) angles are
normal (around 113°) and the shortest distance from Ru to (CH3)
carbon (3.5 Å) is too long for agostic interaction. Therefore, 1
is authentically coordinatively unsaturated. Other features of the
structure are normal for Ru(II) complexes and deserve no further
complex has been reported as a byproduct (12% yield) in the
synthesis of 1.16 The method reported here gives a rational
synthesis, which is also a quite specific one, since benzyl
chloride does not transform RuHCl(CO)(PtBu2Me)2 to
RuCl2(CO)(PtBu2Me)2, 3. The latter has been synthesized by
reaction with CHCl3, and the reactivity has been reported.7b The
spectroscopic data of 2 includes only one virtual triplet of
doublets for the methyl group, indicative of the two symmetry
i
elements to make all CH3 of Pr magnetically equivalent.
Moreover, the much higher CO stretching frequency (1937 vs
1908 cm-1 of 1) suggests geometry differences between them.
These results support the geometry with CO trans to the vacant
site, which is proved by X-ray single-crystal structure analysis.
The ORTEP plot of 2 is depicted in Figure 2 and the geometric
parameters are collected in Table 3. Like 1, 2 also adopts a
square-based pyramidal geometry, but with two mutually trans
chlorides and phosphines at the basal and CO at the apical site.
This arrangement is in agreement with the computational
prediction on the geometry preference of five-coordinate d6
metal complexes; the highest trans influence ligand occupies
the apical site, which raises the energy of the LUMO. In 2, the
(11) Huang, D.; Oliva´n, M.; Huffman, J. C.; Eisenstein, O.; Caulton, K.
G. Organometallics 1998, 17, 4700.
(12) Esteruelas, M. A.; Werner, H. J. Organomet. Chem. 1986, 303,
221.
(13) (a) Esteruelas, M. A.; Juana, H.; Oro, L. A. Organometallics 1993,
14, 2377, (b) Esteruelas, M. A.; Gomez, A. V.; Lahoz, F. J.; Ana, M.; Onate,
E.; Oro, L. A. Organometallics 1996, 15, 3423.
(14) Moers, F. G.; Langhout, J. P. Recl. TraV. Chim. Pays-Bas 1972,
91, 591.
(15) Moers, F. G.; Nordik, J. H.; Beurskens, P. T. Cryst. Struct. Comm.
1981, 10, 1149.
(16) Werner H.; Tena, M. A.; Mahr, N.; Peters, K.; von Schnering, H.
G. Chem. Ber. 1995, 128, 41.

8092 J. Am. Chem. Soc., Vol. 121, No. 35, 1999
Huang et al.
thesized independently by treatment of RuHCl(CO)(PtBu2Me)2
with diazomethane, but this reaction fails to convert 1 to 4.7a
The CO stretching frequency (1898 cm-1) of 5 is close to that
of RuHCl(CO)(PtBu2Me)2(1906 cm-1), suggesting that they
have similar geometry. Since methyl has the strongest trans
influence among the ligands, one may reasonably assume that
the complex has a square-based pyramidal geometry with Me
trans to the vacant site. In agreement with this, the carbon
resonance of the Ru-CH3 of 5 appears at unusually high field
(-11.0 ppm). Similarly, the (Os)-CH3 13C{1H} NMR resonance
of Os(CH3)Cl(CO)(PtBu2Me)2 appears at unusually high field
(-38 ppm).7a The high field shift of the hydride has been a
diagnostic feature of five-coordinate Ru and Os complexes with
hydride trans to the vacant site, and perhaps the same is true of
the 13C chemical shift in such a site. The dimethyl complex
RuMe2(CO)(PtBu2Me)2, 7, shows only one ruthenium methyl
proton (or carbon) resonance at room temperature as well as
t
one Bu signal, indicating that the two (Ru)-CH3 and all the
1
tBu methyls are equivalent. However, at -90 °C, two H and
13C{1H} Ru-CH3 signals (13C, -15.7 and 17.5 ppm) are
observed along with two tBu peaks (1H or 13C). Therefore, the
ground-state geometry of the complex has one methyl in the
apical site and the other trans to CO in the basal plane. On the
basis of the decoalescence temperature of the 13C signals of
the Ru-CH3, the energy barrier (∆Gq) of the conversion is
calculated as 6.8 kcal/mol at -30 °C. Since it is an intramo-
lecular process, the entropy change (∆Sq) is expected to be small
such that the ∆Gq value is close to that of ∆Hq. The hydride
site exchange of Ru(H)2(CO)(PtBu2Me)2 has the ∆Hq of 7.6
kcal/mol and ∆Sq of 6.5 eu, so ∆Gq for Ru(H)2(CO)L2 at -30
°C is 6.0 kcal/mol.22 This number compares well to the barrier
of Ru(CH3)2(CO)(PtBu2Me)2, indicating a similar process for
methyl site exchange as that of hydride site exchange of Ru-
(H)2(CO)L2, which is calculated to go through an intermediate
with CO trans to the vacant site and the two hydride trans to
each other (eq 2).
Figure 2. ORTEP diagram (50% probability level) of RuCl2(CO)-
(PiPr3)2, 2. Hydrogen atoms are omitted.
P-Ru-P and Cl-Ru-Cl angles significantly deviate from
180°. A similar structure is adopted by RuCl2(CHR)L2.17 The
bending of Cl-Ru-Cl suppresses filled-filled repulsion be-
tween the Cl lone pair and the metal dπ electron. One iPr group
of phosphine bends toward to the vacant site so that the Ru-
P2-C22 is as much as 10° smaller than that of Ru-P2-C28
(or C25). This may indicate weak agostic interaction, since all
corresponding angles in nonagostic 1 are nearly identical.
However, the long distance of Ru to the nearest CH3 carbon
(3.6 Å) and Ru/H (2.98 Å) speaks against any bonding
interactions. This is in marked contrast with RuCl2(CO)(PCy3)2,
which has an agostic interaction between ortho CH2 of cyclo-
hexyl and Ru(II) (Ru/C is 3.0 Å, and Ru/H is 2.3 Å).18 For
comparison, in Rh(mesityl)3, distances to agostic ortho methyl
groups are Rh/C ) 2.8 Å and Rh/H ) 2.25-2.37 Å.19 The
interplay of steric effects and the trans influence has been
addressed in recent theoretical calculations.20
Ru(Me)Cl(CO)L2 and RuMe2(CO)L2. Addition of 1 equiv
of MeLi to 2 in toluene results in immediate formation of equal
amounts of RuMeCl(CO)(PiPr3)2, 4, and RuMe2(CO)(PiPr3)2,
6, along with some starting materials (Scheme 1). After 3 h, 4
is the dominant product (>90%) with a small amount of starting
material. Apparently, ligand redistribution between 2 and 6
occurs. Ligand scrambling of similar complexes has been
examined before and is considered to be an associative process
even though there are two sterically demanding phosphine
ligands.21 If one more equivalent of MeLi is added, clean
conversion to 6 results. The reaction also succeeds with the
PtBu2Me analogue. RuMeCl(CO)(PtBu2Me)2, 5, has been syn-
Synthesis of RuMeF(CO)L2, RuMe(OTf)(CO)L2, RuMe-
(BF4)(CO)L2, and [RuMe(CO)L2]BAr′4. Halide exchange of
RuMeCl(CO)(PtBu2Me)2 with CsF in acetone for 4 h gives
RuMeF(CO)L2, 8 (Scheme 1), in quantitative yield as judged
by NMR and in 54% isolated yield. The complex is character-
ized by the doublet of the 31P NMR signal (JPF ) 22 Hz) and
a triplet of quartets of the 19F resonance (-201 ppm, JPF ) 22
Hz, JHF ) 4 Hz). The fluoride readily reacts with 1 equiv of
BF3‚OEt2 (in Et2O) to give RuMe(BF4)(CO)L2, 10 (Scheme 1),
which is not soluble in diethyl ether and precipitates from the
reaction solution. However, it is soluble in benzene or toluene,
thus BF4- is likely to be coordinating. Consistent with this, the
19F NMR spectrum of the BF4 is an extremely broad peak (-210
ppm, ω1/2 ) 1396 Hz) at 20 °C, due to exchange of coordinated
BF4-. The CO stretching frequency of 10 is higher than that of
the Ru(Me)Cl(CO)L2 (1919 vs 1898 cm-1). The fluoride in 8
is also readily replaced by trifluoromethane sulfonate (triflate)
using Me3SiOTf (diethyl ether, 10 min) to give RuMe(OTf)-
(CO)L2, 9 (Scheme 1). The CO stretching frequency of this
complex is higher (1914 cm-1) than that of 4, in accordance
(17) Schwab, P.; Grubbs, R. H.; Ziller, J. W. J. Am. Chem. Soc. 1996,
118, 100.
(18) Moers, F. G.; Beurskens, P. T.; Noordik, J. H. Cryst. Struct.
Commun. 1982, 11, 1655.
(19) Hay-Motherwell, R. S.; Koschmieder, S. U.; Wilkinson, G.; Hussain-
Baites, B.; Hursthouse, M. B. J. Chem. Soc., Dalton Trans. 1991, 2821.
(20) Ujaque, G.; Cooper, A. C.; Maseras, F.; Eisenstein, O.; Caulton,
K. G. J. Am. Chem. Soc. 1998, 120, 361.
(21) Poulton, J. T.; Hauger, B. E.; Kuhlman, R.; Caulton, K. G. Inorg.
Chem. 1994, 33, 3325.
(22) Heyn, R. H.; Macgregor, S. A.; Nadasdi, T. T.; Ogasawara, M.;
Eisenstein, O. Caulton, K. G. Inorg. Chim. Acta 1997, 259, 5.

14-Electron Four-Coordinate Ru(II) Carbyl Complexes
J. Am. Chem. Soc., Vol. 121, No. 35, 1999 8093
Figure 3. ORTEP diagrams of Ru(Ph)Cl(CO)(PtBu2Me)2, 12 (a), and [RuPh(CO)(PtBu2Me)2]BAr′4, 16 (b). Hydrogen atoms are omitted.
Scheme 1
t
with the weaker donating ability of OTf than of chloride.
However, OTf cannot be completely replaced by weakly
coordinating BAr′4- (Ar′ ) 3,5-trifluoromethyl phenyl). Thus,
stirring equimolar 9 and NaBAr′4 in CH2Cl2 for 12 h only results
in partial replacement of OTf, as evidenced by IR spectroscopy
to be occupied by C-H bonds from the Bu methyl on the
phosphine ligands.
Synthesis and Structure of Ru(Ph)Cl(CO)(PtBu2Me)2. PhLi
reacts with 3 at low temperature with clean formation of
RuPhCl(CO)L2, 12 (eq 3). Excess PhLi, however, does not cause
to give a solution having two CO bands (1951 and 1914 cm-1
)
with similar intensity. The higher frequency band is assigned
to [RuMe(CO)L2]BAr′4, 11, which was synthesized (Scheme
1) from salt metathesis of NaBAr′4 and 10 (C6H5F, 10 min). 11
is a rare example of a 14-electron four-coordinate Ru(II) alkyl
complex. It might be possible to have two agostic interactions
as we observed for the similar complex [Ru(Ph)(CO)L2]BAr′4
(vide infra). Alternatively, the Ru-methyl group could have
an R-agostic interaction with the metal, which would cause
higher field shift of the methyl proton. However, at 20 °C, this
CH3 proton has a normal chemical shift (1.14 ppm in C6D5F/
C7D8 1:2). This signal does not change position upon cooling
to -70 °C, and therefore, no R-agostic interaction is substanti-
ated. The solvent, C6D5F and toluene-d8, is not likely to be
coordinating to the metal, since [RuH(CO)L2]BAr′4 does not
coordinate these solvents.23 The two vacant sites of 11 are likely
further replacement of the other chloride, probably due to steric
crowding in 12. Reaction of RuH(Ph)(CO)L2 with excess
N-chlorosuccinimide (NCS) also gives 12 in moderate yield.24
Alternatively, refluxing RuHCl(CO)L2 with Ph2Hg in toluene
gives 12 in excellent yield (>80%).24 12 is moderately air stable
and can be recrystallized from methanol (!). The spectroscopic
data of 12 have been reported and discussed before.23 A single
crystal of 12 grown from methanol was chosen for the X-ray
study. The ORTEP drawing of 12 is shown in Figure 3a, and
(23) Huang, D.; Huffman, J. C.; Bollinger, J. C.; Eisenstein, O.; Caulton,
K. G. J. Am. Chem. Soc. 1997, 119, 7398.
(24) Roper, W. R.; Wright, L. J. J. Organomet. Chem. 1977, 142, C1.

8094 J. Am. Chem. Soc., Vol. 121, No. 35, 1999
Huang et al.
Scheme 2
20 °C in benzene within the time of mixing (Scheme 2). In
contrast, substitution of Cl by Me in 12 requires a 10-fold excess
of MeLi and prolonged reaction time (3 days).28 15 (like 6) is
a rare example of a 16-electron Ru(II) complex devoid of
π-basic ligands. Similar to 14, 15 shows five distinct phenyl
proton chemical shifts, revealing the slow rotation of the Ph
1
ring on the H NMR time scale. The Ru-CH3 protons appear
as a triplet at 1.07 ppm (JPH ) 7 Hz). Unlike the high-field 13
C
chemical shifts of methyl of 4 (-11 ppm) and one methyl of 6
(-15 ppm), the methyl 13C chemical shift of 15 is at lower
field (9.5 ppm), in agreement with CH3 trans to CO, not the
vacant site. Although not trans to a π-donor ligand, the CO
stretching frequency is low (1883 cm-1), due probably to the
strong σ-donating powers of CH3 and Ph. 15 contains three
strong trans influencing ligands, Ph, Me, and CO, and they are
all good candidates to occupy the apical site. On the basis of
the NMR spectral data, we conclude that Ph of 15 lies at the
apical site, where it is sterically constrained from rotating easily.
Ru(H)(Ph)(CO)L2, on the other hand, has Ph in the basal plane
since the hydride resonance is at very high field (-28 ppm)
and only three proton chemical shifts for Ph are observed,
indicating fast rotation of the phenyl.23 These results, along with
the geometry of the methyl complexes, permit us to conclude
that the trans influence of the σ-donor ligands has the order of
H > Ph > Me > CO.
16-electron, five-coordinate Ru(II) complexes without π-do-
nor ligands are rare. So far, only one such compound, RuH-
(SiHPh2)(CO)L2, was structurally characterized.29 Similar com-
plexes Ru(H)2(CO)L2 and RuH(Ph)(CO)L2 are not long-lived
species since they tend to eliminate H2 or benzene. In contrast,
15 remains unchanged in toluene for 2 days at 20 °C. Generally,
since metal carbon bonds are weaker than metal hydrogen bonds,
the persistence of 15 should be attributed to the kinetic barrier
for reductive elimination to form a C-C bond.
Synthesis and Structure of [RuPh(CO)L2]BAr′4. Triflate
can be removed from 14 using NaBAr′4 to give [RuPh(CO)-
L2]BAr′4, 16, in either methylene chloride or in fluorobenzene
at room temperature in the time of mixing (Scheme 2). The
highly air-sensitive complex 16 is purified by recrystallization
as orange crystals from a pentane/fluorobenzene mixture with
strict exclusion of air and moisture. At room temperature, the
NMR of the Ph protons show only three peaks, including one
sharp triplet for the para proton and one broad peak for the
meta and one broad peak for the ortho protons. Therefore, the
Ph rotation is faster as compared to 12 with Ph at the apical
site. Upon cooling to -70 °C, each broad peak decoalesces to
two multiplets. The phosphine peak remains a sharp singlet in
the same temperature range; therefore, slow rotation around the
Ru-P bond is not observed, which might have given rise to
two magnetically different phosphines, as is seen for 12.30 Two
virtual triplets for tBu groups reveal the nonplanar arrangement
of the four ligands. The CO stretching frequency is high (1958
cm-1), and two bands with medium strength are also found at
the agostic C-H stretch region (2722 and 2672 cm-1). These
two bands disappear after 16 is saturated with excess CO, which
replaces the agostic interacting C-H bonds (Figure 4). These
agostic interactions are highly fluxional and cannot be frozen
out on the NMR time scale as in the other agostic interactions
between unsaturated metal and the phosphine ligand C-H
bond.31 To gain solid evidence for the structure of 16, an X-ray
the geometric parameters are in Table 4. Similar to 3 and 4, 12
has a square-based pyramidal geometry but with Ph trans to
the vacant site, consistent with the stronger trans influence of
Ph than CO. Moreover, with CO trans to Cl, push-pull
stabilization is maximized. Although two tBu groups on
phosphine ligands point toward the vacant site, the shortest
distance of the phosphine carbon to Ru is 3.24 Å, and the Ru-
P-C(CH3)3 angles do not deviate much from the normal value
of 115°; therefore, there is no agostic interaction. The structure
of the related complex Ru(p-tolyl)Cl(CO)(PPh3)2 shows weak
agostic donations from one ortho phenyl of both phosphines
(Ru/H ) 2.77-2.85 Å Ru/C ) 3.41 Å) to the site trans to the
p-tolyl in a square pyramidal structure.25 Such weak interactions
to PPh3 are absent in RuCl(o-tolyl)(CO)(PPh3)2, where the
o-tolyl methyl appears to form an agostic interaction to Ru
(Ru/H ) 1.9 Å) and o-tolyl is no longer in the apical site of a
square pyramid.10
Halide Replacement of 12. The Cl of 12 can be replaced
with F by salt metathesis with CsF (acetone, 20 °C, 12 h) to
give RuPhF(CO)L2, 13 (Scheme 2). 13 is isolated as orange
crystals from pentane or by sublimation at 140 °C at 5 × 10-2
mmHg. The 31P{1H} NMR of 13 shows a doublet (JPF ) 24
Hz) and, correspondingly, the 19F spectrum is a triplet close
(-204 ppm) to the 19F chemical shift of 8 (-201 ppm). There
are also five distinct phenyl proton resonances, indicative of
slow rotation of Ph around the Ru-C(ipso) bond.
The CO stretching band appears at lower frequency (1890)
than that of 12 (1902) since F is a stronger π-donor than Cl.26
Replacement of F by triflate occurs under mild conditions using
Me3SiOTf (Et2O, 20 °C, immediate reaction) to give Ru(Ph)-
(OTf)(CO)L2, 14, quantitatively. Ligand exchange of Me3Si-X
with metal fluoride has been reported on several occasions.27
Surprisingly, salt metathesis using AgOTf does not give the
same product; instead, decomposition of 12 yields [AgL2]OTf.
14 can also be synthesized in high yield from RuH(OTf)(CO)-
23
L2 and Ph2Hg in refluxing toluene. 14 is soluble in nonpolar
solvents such as benzene and pentane, indicative of coordinated
triflate. Moreover, similar to 12 and 13, 14 also has five distinct
proton NMR signals for Ph, indicative of slow rotation of Ph.
Consistent with weak donation by OTf, the CO stretching
frequency (1921 cm-1) of 14 is higher than those of 12 and 13.
Ru(Ph)(CH3)(CO)L2. As a better leaving group, OTf of 14
is readily replaced by MeLi to give RuPh(Me)(CO)L2, 15, at
(25) The original structure in ref 10 has been better reinterpreted in a
different space group: Marsh, R. E. Acta Crystallogr., Sect. B (Str. Sci.)
1997, 53, 317.
(26) (a) Poulton, J. T.; Folting, K.; Streib, W. E.; Caulton, K. G. Inorg.
Chem. 1992, 31, 3190. (b) Tilset, M.; Hamon, J. R.; Hamon, P. J. Chem.
Soc., Chem. Commun. 1998, 765.
(28) Ogasawara, M. Personal communication.
(27) (a) Doherty, N. M.; Crischlow, S. C. J Am. Chem. Soc. 1987, 109,
7906. (b) Hoffman, N. W.; Prokopuk, N.; Robbins, M. J.; Jones, C. M.;
Doherty, N. M. Inorg. Chem. 1991, 30, 4177. (c) Cooper, A. C.; Huffman,
J. C.; Caulton, K. G. Inorg. Chim. Acta 1998, 270, 261.
(29) Heyn, R. H.; Huffman, J. C.; Caulton, K. G. New J. Chem. 1993,
17, 797.
(30) Notheis, J. U.; Heyn, R. H.; Caulton, K. G. Inorg. Chim. Acta 1995,
229, 187.

14-Electron Four-Coordinate Ru(II) Carbyl Complexes
J. Am. Chem. Soc., Vol. 121, No. 35, 1999 8095
Figure 4. IR spectra of [Ru(Ph)(CO)(PtBu2Me)2]BAr′4, 16 (curve A), and the reaction product of 16 with carbon monoxide (curve B). The bands
due to agostic interactions disappear when 16 is treated with CO.
crystal structure study was carried out. The ORTEP diagram is
shown in Figure 3b and the geometric parameters are in Table
5. Four-coordinate 16 adopts a sawhorse geometry with two
phosphine ligands trans and the Ph and CO cis to each other.
The two vacant sites are occupied by agostic C-H bonds
On the other hand, it shows reactivity of the Ru-Ph with E-H
bonds (E ) boryl, H, and C(sp)).
(A) With Catecholborane, Synthesis of [RuB(C6H4O2)-
(CO)L2]BAr′4. A mixture of 1 equiv catecholborane and 16 in
methylene chloride produces exclusively [RuH(CO)L2]BAr′4
and (C6H4O2)B-Ph in 1 h at room temperature (eq 4). The
t
from two Bu on different phosphines. The Ru/Cagostic dis-
tances are short (2.88 and 2.87 Å, respectively), indicative of
relatively strong interactions. Comparing the structural differ-
ences of 16 and 12 (Figure 3a,b) provides some insight into
the impact of the structural changes upon removal of the X
ligand. Removal of the X ligand does not cause any large
disturbance to the remaining four atoms bound to Ru; they
remain approximately in the same relative position. The
P-Ru-P angles and CO-Ru-C angles are comparable be-
tween 16 and 12. The Ru-P distances are shorter in 16. In sharp
contrast to small movements of atoms directly bound to Ru,
the substituents on phosphine have been disturbed signifi-
cantly. The angle Ru-P3-C5 of 12 is 108°, while it is 10°
smaller in 16. In 12, the angle Ru-P13-C19 is 119°; in
contrast, upon removal of the Cl, this angle decreases to 97°
(Ru-P20-C25). Accordingly, the Ru/Cagostic distances are
shortened by 0.375 and 0.874 Å, respectively, compared to the
corresponding Ru/C distance in 12. Thus, the removal of the
Cl creates two agostic interactions. The absence of agostic
interaction in 12 and the presence of two agostic interactions
in 16 show that agostic interaction is not solely determined by
the nature of the ligand trans to the empty site. If that were the
case, one should have observed an agostic interaction trans to
Ph in 12. Going from a 16e Ru(Ph)Cl(CO)L2 to 14e RuPh-
(CO)L2+ is likely to lower all empty metal orbitals, even those
which in first approximation should not have been influenced
by the presence of the removed ligand (Cl-); there is a general
increase in electrophilicity.
1
products are identified by comparing the H and 31P NMR
spectra with the known values for the two compounds. 14 also
reacts (Scheme 3) with 1 equiv catecholborane, albeit at higher
temperature (80 °C, 4 h), to give RuH(OTf)(CO)L2 (90%), trace
Ru(BR2)(OTf)(CO)L2, 17, and (C6H4O2)B-Ph. If one more
equivalent of catecholborane is added to the reaction mixture,
clean conversion to 17 is achieved. Therefore, the formation of
17 from 14 involves two steps to release (C6H4O2)B-Ph and
H2 separately (Scheme 3). Indeed, reaction of RuH(OTf)(CO)-
L2 with 1 equiv catecholborane cleanly yields 17. 17 has two
tBu virtual triplets and a broad singlet for 31P and 11B (44.5
ppm) signals. The CO stretching band appears at higher
frequency (1939 cm-1) than that of 6, in agreement with the
presence of the π-acidic boryl ligand. The mechanism of this
reaction can be oxidative addition followed by reductive
elimination or σ-bond metathesis. In either mechanism, the
reaction is highly selective for the formation of M-BR2.
Hartwig and co-workers studied the mechanism of the reaction
of saturated CpRu(PPh3)2Me and catecholborane (giving metal
hydride and methylcatecholborane) and concluded that the
reaction proceeds by a four-centered transition state (σ-bond
metathesis), not by oxidative addition.32 Although a similar
mechanism may be operative in eq 4, since the Ru of 16 is
already π-electron deficient and oxidative addition to give aRu-
(IV) species is not favored, highly unsaturated 16 is likely to
coordinate catecholborane before further reaction occurs. Re-
cently, Roper and co-workers reported that the reaction of either
RuHCl(CO)(PPh3)3 or Ru(Ph)Cl(CO)(PPh3)2 with catecholbo-
rane gives Ru(boryl)Cl(CO)(PPh3)2 as the sole product. How-
Reactivity of 16. Surprisingly, this highly electrophilic
complex is thermally robust in solvents such as benzene or
toluene. Upon heating in toluene-d8 (100 °C) for 24 h, no
significant decomposition or reaction is evidenced by NMR
spectroscopy. The 1H NMR spectrum remains unchanged.
Moreover, the two diastereotopic tBu groups do not decoalesce
at 100 °C (toluene-d8), thus there is no phosphine dissociation
or unimolecular inversion through a square-planar intermediate.
(31) Heinekey, D. M.; Radzewich, C. E.; Voges, M. H.; Schember, B.
M. J. Am. Chem. Soc. 1997, 119, 4172.
(32) Hartwig, J. H.; Bhandari, S.; Rablen, P. R. J. Am. Chem. Soc. 1994,
116, 1839.

8096 J. Am. Chem. Soc., Vol. 121, No. 35, 1999
Huang et al.
Scheme 3
ever, no experimental details concerning the reaction of
Ru(Ph)Cl(CO)(PPh3)2 are given. Therefore, it is not clear if the
reaction is also a two-step process, with initial formation of
RuHCl(CO)(PPh3)2, which then further reacts with catecholbo-
rane. In contrast, the Os analogue OsHCl(CO)(PPh3)3 does not
react with catecholborane, while Os(Ph)Cl(CO)(PPh3)2 does, to
give the boryl complex Os(BR2)Cl(CO)(PPh3)2 and benzene.33
Saturated OsHCl(CO)(PPh3)3 may not undergo a ligand dis-
sociation under the reaction conditions, which is a prerequisite
for the reaction to occur, while RuHCl(CO)(PPh3)3 may have a
labile phosphine.
[RuB(O2C6H4)(CO)L2]BAr′4. Salt metathesis of 17 with
NaBAr′4 in methylene chloride or fluorobenzene gives [Ru-
(BR2)(CO)L2]BAr′4, 18, in quantitative yield (Scheme 3). Like
other four-coordinated RuR(CO)L2+, 18 exhibits two virtual
triplets for the tBu groups indicative of nonplanar geometry with
two phosphines mutually trans. Only two proton chemical shifts
are observed for catecholboryl, indicating fast rotation of the
boryl group. 11B NMR and 31P{1H} NMR spectra are broad
singlets probably caused by the quadrupolar 11B. The CO
stretching band of 18 (1981 cm-1) is higher than any other
[RuR(CO)L2]BAr′4 owing to the π-acidic boryl group. To our
knowledge, 18 is the first example of a highly electron-deficient
(14e) Ru(II) boryl complex, the reactivity of which is still under
investigation and will be reported separately.
16 were mixed at -70 °C in an NMR tube in CD2Cl2. At
temperatures below -40 °C, there is no detectable interaction
between 16 and Me3SiCCH. As the temperature rises, one new
product starts to form, which has a characteristic vinyl proton
triplet (JPH ) 2 Hz) at 5.87 ppm. At -5 °C, this product is the
dominant one (>70%, based on 31P NMR integration). 31P NMR
t
of this product is a sharp singlet and two virtual Bu triplets
(1H NMR) are also identified in addition to a singlet for
Me3Si. Therefore, it has two trans phosphines with diastereotopic
tBu groups. On the basis of these data, we propose that the
product has structure 21. The formation of 21 requires that one
Me3SiCCH isomerized to vinylidene before the Ph migratory
insertion occurs. Further warming in the presence of free
Me3SiCCH converts some 21 to PhCCSiMe3, 19 and 20 until
1
all Me3SiCCH is consumed (judging from H NMR). 21 then
isomerizes at room temperature to 22, which has been synthe-
+
sized independently from RuH(CO)L2 and PhCCSiMe3 and
characterized by X-ray diffraction.34 The transformation of 21
to 22 is likely to go through â-hydrogen migration via an
unobserved intermediate, the η2-Ph-CC-SiMe3 adduct 23. The
final reaction mixture gives over 80% 22, and small amounts
of 19 and 20. Although 22 might have been formed via direct
addition of Ru-Ph to the CtC bond, this cannot account for
the complexity of the observed intermediates. Consistently, if
the same reaction is carried out using 3 equiv Me3SiCCH, at
low temperature (<-5 °C), 21 is the dominant product, which
releases PhCCSiMe3 and transforms to 19. No 22 is observed.
The high migrating ability of the silyl, hydrogen, and phenyl
groups makes this reaction complicated and likely leads to the
thermodynamic product.
(B) Reaction with Me3SiCCH. Addition of 1 equiv of Me3-
SiCCH to a methylene chloride solution of 16 at room
temperature gives in the time of mixing partial conversion to
PhCCSiMe3, [Ru{η3-(Me3SiCHdC-CHdCH(SiMe3)}(CO)L2]-
BAr′4, 19, and a trace amount of [Ru(CHdCH(SiMe3)(CO)L2]-
BAr′4, 20 (Scheme 4). If two more equivalents of Me3SiCCH
are added, clean conversion to 19 is observed. 19 can be
Conclusion
+
synthesized independently from RuH(CO)L2 with 2 equiv of
We have demonstrated the synthesis and structural charac-
terization of the 16-electron five-coordinate Ru(II) complexes
and 14-electron four-coordinated Ru(Ph)(CO)L2+, and their
reactivity toward E-H bonds is also examined. On the basis of
the results gathered here, several conclusions can be reached.
(1) Synthesis of the 14-electron four-coordinate complex,
[RuR(CO)L2]BAr′4, is achieved by salt metathesis of its triflate
precursor and NaBAr′4. The cation adopts a sawhorse geometry
with two sterically demanding phosphine ligands trans and the
two strong trans influencing ligands cis to each other so that
the unsaturated metal gains the most steric protection. This also
Me3SiCCH, and its structure has been determined.11 Therefore,
is it likely that the reaction of 16 with Me3SiCCH forms RuH-
(CO)L2+, which further reacts with Me3SiCCH to give 19. The
most straightforward mechanism of the first step is that Me3-
SiCCH and 16 undergo σ-bond metathesis to give Me3SiCCPh
and RuH(CO)L2+, which then reacts with Me3SiCCH to give
19 and 20. Alternatively, oxidative addition of the C(sp)-H
bond to Ru(II) followed by exclusive reductive elimination of
Me3SiCCPh would also account for the first step. To gain more
information on this reaction, a low-temperature NMR spectro-
scopic study was carried out. One equivalent of Me3SiCCH and
(33) Irvine, G. J.; Roper, W. R.; Wright, L. J. Organometallics 1997,
16, 2291.
(34) Huang, D.; Streib, W. E.; Eisenstein, O.; Caulton, K. G. J. Am.
Chem. Soc., in press.

14-Electron Four-Coordinate Ru(II) Carbyl Complexes
J. Am. Chem. Soc., Vol. 121, No. 35, 1999 8097
Scheme 4
+
raises the energy of the empty valence orbitals. The two vacant
sites are occupied by agostic interactions, which is directly
proved, in the case of R ) Ph, by X-ray single-crystal structure
analysis and the solid-state IR spectrum. Structural comparison
of Ru(Ph)(CO)L2+ with its five-coordinated precursor Ru(Ph)-
Cl(CO)L2 reveals that halide removal does not cause a major
geometry change of the remaining fragment; on the other hand,
two agostic interactions are created.
(2) 16-electron Ru(II) carbyl complexes RuR2(CO)L2 without
π-donor ligands are persistent species. This is in sharp con-
trast to the hydride complexes, Ru(H)(Ph)(CO)L2 and RuH-
(Me)(CO)L2, which readily undergo reductive elimination even
at -40°C (RuH(Me)(CO)L2). The persistence of the carbyl
complexes can be attributed to kinetic sluggishness of reductive
elimination.
The sawhorse geometry of Ru(R)(CO)L2 places a vacant
site cis to the M-R bond. In combination with the Lewis acidity
of the metal (as demonstrated by the two agostic interactions),
we can envision some interesting reactivity between an incoming
ligand and M-R. The detailed reactivity study will be pursued
and reported in due course.
Acknowledgment. This work is supported by the National
Science Foundation. We also thank the Deutsche Forschungs-
gemeinschaft and Prof. Dr. W. Kaim for financial support and
Johnson Matthey/Aesar for material support.
Supporting Information Available: Full crystallographic
details, positional and thermal parameters, and distances and
angles on four compounds (PDF). This material is available free
of charge via the Internet at http://pubs.acs.org.
(3) On the basis of the geometry preference of five-coordinate
complexes, the magnitude of trans influence has the following
order: H > Ph > CH3 > CO > Cl.
JA990621W