Effect of Lewis acidity on the synthesis of RuHCl(CO)(phosphine)2: Subtle influence of steric and electronic effects among PiPr3, PiPr2(3,5- (CF3)2C6H3), an

Article abstract of DOI:10.1021/ic000500t

To evaluate the influence of steric, electronic, and synthetic factors, the synthesis of RuHCl(CO)[PⁱPr₂(3,5-(CF₃) ₂C₆H₃)]₂ was carried out, and its Lewis acidity toward Cl^-

Full text of DOI:10.1021/ic000500t

6444
Inorg. Chem. 2001, 40, 6444-6450
Effect of Lewis Acidity on the Synthesis of RuHCl(CO)(phosphine)2: Subtle Influence of
Steric and Electronic Effects among PiPr3, PiPr2(3,5-(CF3)2C6H3), and PiPr2Me
Alexei V. Marchenko,† John C. Huffman,† Pedro Valerga,‡ Manuel Jime´nez Tenorio,‡
Ma Carmen Puerta,*,‡ and Kenneth G. Caulton*,†
Department of Chemistry and Molecular Structure Center, Indiana University,
Bloomington, Indiana 47405-7102, and Departamento de Ciencia de los Materiales e Ingenier´ıa
Metalu´rgica y Quimica Inorga´nica, Facultad de Ciencias, Universidad de Ca´diz, Aptdo. 40,
11510 Puerto Real, Ca´diz, Spain
ReceiVed May 9, 2000
To evaluate the influence of steric, electronic, and synthetic factors, the synthesis of RuHCl(CO)[PiPr2(3,5-
(CF3)2C6H3)]2 was carried out, and its Lewis acidity toward Cl- was compared to that of RuHCl(CO)(PiPr3)2. In
this synthesis, Na2CO3 was shown to be a more effective base than NEt3, because Na+ can better mask the
nucleophilicity of the potential ligand Cl-. An X-ray structure determination of the hydride-free species
RuCl2(CO)(PiPr2Me)2 shows it to be a dimer, and this solid-state structure persists in solution, but as several
different isomers. The synthesis of RuHCl(CO)(PiPr2Me)3 shows that three of this smaller phosphine can crowd
around Ru, but dynamic NMR spectra show one phosphine to be weakly bound. The rate of reaction of
Me3SiCtCH with this molecule is suppressed by added free PiPr2Me, indicating phosphine dissociation to be a
mechanistic component.
Introduction
Scheme 1
A large number of Ru(II) monocarbonyl complexes are
known,1 and they fall into several different classes: five- and
six-coordinate, monomeric RuXCl(CO)(PR3)2 or 3, where X )
H or Cl, and also dimeric [RuCl2(CO)(PR3)2]2. While a broad
range of phosphines have been surveyed, there are no general
principles allowing prediction of whether bis- or tris-phosphine
species will be produced. Certainly, some of the products are
formed under kinetic control, so no conclusion is possible about
how many phosphines can coordinate to one Ru. It is probable,
however, that any monomer/dimer equilibrium is achieved, so
thermodynamic conclusions are possible on this issue. For
example, RuCl2(CO)(PtBu2Me2)2 and RuCl2(CO)(PiPr3)2 are
monomers, but the PMe2Ph analogue is a dimer,4 in a case
probably attributable to steric effects. More subtle steric changes,
and the influence of electronic factors, are beyond our current
ability to predict. These issues are one focus of the present work.
Another focus is the matter of control over formation of
RuHCl vs RuCl2 products. The conversion of RuCl3‚nH2O to
RuHCl(CO)Lm by tertiary phosphine (L) at reflux in alcoholic
solvent rests on a number of critical factors.5 L must be very
bulky if m ) 2 is to be achieved: the synthesis of unsaturated,
2
3
highly reactive, square-pyramidal RuHCl(CO)L2. A monocar-
bonyl product demands a highly limited source of CO ligand
(to avoid formation of saturated RuHCl(CO)2L2), and a primary
alcohol furnishes this by C-C bond cleavage (eq 1).
RCH2OH f RH + CO + 2“H”
(1)
The hydride ligand is furnished concurrently, via the dehydro-
genation of the alcoholic CR. The processes in Scheme 1 (a)
leave the metal oxidation state unchanged and (b) produce
equimolar HCl. Point a shows that beginning with commercially
available RuCl3‚nH2O, that is Ru(III), demands a reducing agent
to arrive at Ru(II). This may well be tertiary phosphine (eq 2),
* Corresponding authors. E-mail M.C.P.: carmen.puerta@uca.es. E-mail
K.G.C.: caulton@indiana.edu.
† Indiana University.
‡ Universidad de Ca´diz.
(1) (a) Chatt, J.; Shaw, B. L.; Field, A. E. J. Chem. Soc. 1964, 3466. (b)
Gill, D. F.; Mann, B. E.; Shaw, B. L. J. Chem. Soc., Dalton Trans.
1973, 311. (c) Jenkins, J. M.; Lupin, M. S.; Shaw, B. L. J. Chem.
Soc. (A) 1966, 1787. (d) Lupin, M. S.; Shaw, B. L. J. Chem. Soc. (A)
1968, 741. (e) Gill, D. F.; Shaw, B. L. Inorg. Chim. Acta 1979, 32,
19. (f) Krassowski, D. W.; Nelson, J. W.; Brower, K. R.; Hauenstein,
D.; Jacobson, R. A. Inorg. Chem. 1988, 27, 4294. (g) Vaska, L.;
DiLuzio, J. W. J. Am. Chem. Soc. 1961, 83, 1262.
(2) Huang, D.; Folting, K.; Caulton, K. G. Inorg. Chem. 1996, 35, 7035.
(3) Huang, D.; Streib, W. E.; Bollinger, J. C.; Caulton, K. G.; Winter, R.
F.; Scheiring, T. J. Am. Chem. Soc. 1999, 121, 8087.
(4) Barnard, C. F. J.; Daniels, J. A.; Jeffery, J.; Mawby, R. J. J. Chem.
Soc., Dalton Trans. 1976, 953.
R3P + 2MCl3 f R3PCl2 + 2MCl2
(2)
but the PV-Cl bonds will be readily hydrolyzed (RuCl3‚nH2O)
to liberate still more HCl, enhancing point b above. In
conclusion, the synthesis requires Brønsted base to scavenge
liberated HCl. If base is not furnished, eq 3 can cause loss of
hydride ligand (as H2) to give a final hydride-free, halide
product.
(5) Kaesz, H. D.; Saillant, R. B. Chem. ReV. 1972, 3, 231.
10.1021/ic000500t CCC: $20.00 © 2001 American Chemical Society
Published on Web 11/07/2001

Effects on the Synthesis of RuHCl(CO)(phosphine)2
Inorganic Chemistry, Vol. 40, No. 25, 2001 6445
(3) even the presence of the strong trans effect ligand hydride
does not prevent binding of three PiPr2Me, forming a six-
coordinate RuHCl(CO)(PiPr2Me)3;
(4) when this RuHCl(CO)(PiPr2Me)3 adds Ru-H across the
triple bond of Me3SiCtCH, the mechanism involves preequi-
librium phosphine loss, and the resulting σ-vinyl ligand prevents
binding of three PiPr2Me in the product; and
(5) comparison of PiPr2(3,5-(CF3)2C6H3) to PiPr3 shows
RuHCl(CO)L2 to be more Lewis acidic for the former toward
Cl-.
Taken together, these results show both the importance of
coordination number 5 for high reactivity of Ru(II) and the
extreme demands on phosphine size which are required to make
unsaturated RuHCl(CO)L2 synthetically accessible.
M-H + HCl f MCl + H2
(3)
A typical example of this is the recent synthesis6 of RuCl2(CO)-
(PiPr2Me)2 from RuCl3‚nH2O + 3PiPr2Me after refluxing for
24 h in MeOC2H4OH. The beneficial influence of Brønsted base
is shown in the recent report7 that RuCl3‚nH2O + 2.5PiPr2Ph
refluxed for 70 h in MeOH gives RuCl2(CO)(PiPr2Ph)2(MeOH).
In contrast, heating RuCl3‚nH2O + 6PiPr2Ph + 2NEt3 in MeOH
for 5 h gave RuHCl(CO)(PiPr2Ph)2. Thus, excess basic phos-
phine (e.g., P(alkyl)3) and added amine gives a hydride, but
the absence of Brønsted bases leads to secondary conversion
of hydride to chloride ligand. This conversion was shown
independently (eq 4).
RuHCl(CO)(PiPr2Ph)2 + HCl MeOH8
Results
RuCl2(CO)(MeOH)(PiPr2Ph)2
(4)
+H2
Synthesis with PiPr2[3,5-(CF3)2C6H3]. This phosphine has
been chosen to be a weaker donor than P(alkyl)3 and thus
perhaps confer greater Lewis acidity on the metal. PiPr2[3,5-
(CF3)2C6H3] was synthesized by reacting PiPr2Cl with previously
prepared 3,5-(CF3)2C6H3MgBr (see hazard note in the Experi-
mental Section) with subsequent quenching with aqueous
NH4Cl solution. This previously unknown phosphine was
isolated as a liquid and characterized by 1H, 31P, and 19F NMR.
1H NMR shows two distinct doublets of doublets for the
isopropyl methyls, which is consistent with the absence of a
symmetry plane relating the two methyls within a given
isopropyl group in the phosphine molecule. Upon exposure to
oxygen, this phosphine oxidizes, leading to the formation of
the phosphine oxide OdPiPr2[3,5-(CF3)2C6H3] (crystalline solid),
This conversion also shows that the smaller (than PiPr3)
phosphine permits binding of a sixth ligand like MeOH.
An equally important aspect of success in this synthesis of
unsaturated molecules is the need to avoid any nucleophile that
might bind to and saturate it. The Lewis acidity of RuHCl-
(CO)(PiPr2Ph)2 (and also the steric accessibility) toward hard
nucleophiles is shown by its reaction with (Ph3PNPPh3)Cl in
benzene to give an anionic adduct, [PPN][RuHCl2(CO)(PiPr2-
Ph)2], A. This behavior illustrates another potential pitfall of
1
which was also characterized by H, 31P, and 19F NMR.
RuHCl(CO)(PiPr2[3,5-(CF3)2C6H3])2. (a) Attempted Use
of the Traditional Synthetic Method. Preparation of RuHCl-
(CO)(PiPr2[3,5-(CF3)2C6H3])2 was attempted using the method
for the synthesis of MHCl(CO)L2 (L ) PiPr3, PtBu2Me, PiPr2-
Ph; M ) Ru, Os): refluxing RuCl3‚3H2O with the phosphine
(1:3 mole ratio) in MeOH or MeOCH2CH2OH in the presence
of NEt3. However, unlike in the previously reported cases,7,11
no precipitation of MHCl(CO)L2 was observed upon cooling
the reaction solution. 31P NMR analysis of the colorless solid
resulting from vacuum removal of solvent revealed the presence
of two products with δ (31P) of 50.6 ppm (major) and 44.8 ppm
[minor, apparently RuCl2(CO)L2, based on the similarity of its
31P chemical shift to that of RuCl2(CO)(PiPr2Ph)2, a known
byproduct in RuHCl(CO)(PiPr2Ph)2 synthesis]. Recrystallization
from toluene-pentane mixture allowed the isolation of the δ
50.6 ppm product, which was identified as [NEt3H][RuHCl2-
(CO)L2]. This is formed by addition of [NEt3H]Cl to RuHCl-
(CO)(PiPr2[3,5-(CF3)2C6H3])2 due to its Lewis acidity caused
by the presence of strongly electron-withdrawing CF3 substit-
uents on the phosphine ligands. The unexpectedly good solubil-
ity of this ammonium “ruthenate” salt in arene solvents (con-
sidering that [Et3NH]Cl has a very poor solubility in these) can
be explained by ion-pairing in solution via hydrogen-bonding
between the N-H proton and chlorides on the ruthenium anion.
A time evolution study during the synthetic reaction by 31P NMR
revealed that the optimal reaction time for the complete
conversion to this product, and minimization of the formation
of byproducts, is 3 h. This ammonium salt shows a hydride
signal at -15.63 ppm (triplet due to coupling to two phospho-
rus), which is significantly downfield from the ∼ -25 ppm
chemical shift for five-coordinate RuHCl(CO)L2 (where there
the synthesis of unsaturated d6 square-pyramidal species: the
formation of a six-coordinate species by coordination of liberated
chloride. For comparison, consider8 the numerous instances
where an attempt to use RLi to convert Cp2MCl to unsaturated
Cp2MR instead produces Cp2MRClLi: chloride is a nucleophile,
not a “leaving group”.
Small variations in phosphine substituent [note that PtBu2-
Me and PiPr3 are isomeric and that PiPr3 and PCy3 (Cy )
cyclohexyl) both have secondary alkyl substituents] and small
variation in reaction conditions thus can have a large conse-
quence on the resulting products from RuCl3‚3H2O + phos-
phine. Because various phosphines have been shown to have a
large and unpredictable influence on the reactivity of their metal
complexes,9,10 we undertook some comparative experiments on
varying phosphine substituent in the hope of deriving some
generally useful principles. These are described below, and they
reveal that
(1) Na2CO3 is superior to NEt3 for scavenging liberated HCl
and rendering Cl- a less-potent ligand for more Lewis acidic
Ru;
(2) PiPr2Me (cf. PiPr3) is small enough to permit dimerization
of RuCl2(CO)L2, and thus reduced Lewis acidity;
(6) Bustelo, E.; Jime´nez-Tenorio, M.; Puerta, M. C.; Valerga, P. J. Chem.
Soc., Dalton Trans. 1999, 2399.
(7) Werner, H.; Stu¨er, W.; Weberndo¨rfer, B.; Wolf, J. Eur. J. Inorg. Chem.
1999, 1707.
(8) “Comprehensive Organometallic Chemistry”, Wilkinson, G.; Stone,
F. G. A.; Abel, E. W., 3, 173, Pergamon Press: Oxford, 1982.
(9) Li, C.; Oliva´n, M.; Nolan, S. P.; Caulton, K. G. Organometallics 1997,
16, 4223.
(10) Huang, D.; Spivak, G. J.; Caulton, K. G. New J. Chem. 1998, 22,
1023.
(11) Esteruelas, M. A.; Werner, H. J. Organomet. Chem. 1986, 203, 221.

6446 Inorganic Chemistry, Vol. 40, No. 25, 2001
Marchenko et al.
is no ligand trans to the hydride) and similar to the previously
reported7 analogous salts [PPN][RuHCl2(CO)L2] and [MePiPr2-
Ph][RuHCl2(CO)L2] (L ) PiPr2Ph). The presence of NEt3H+
in the complex is supported by the observation of a low-field
broad signal for the proton on the nitrogen at 10.47 ppm, as
well as characteristic peaks for the ethyls. Each of the four
i
diastereotopic methyls of the Pr groups shows a doublet of
virtual triplets. The IR spectrum in Nujol shows ν(CO) at
1911 cm-1
.
(b) Use of Na2CO3 as HCl Scavenger. In an attempt to
synthesize RuHCl(CO)L2 and avoid the formation of the
ammonium ruthenate salt, Na2CO3 was used as an HCl
scavenger in place of NEt3. This led to successful synthesis of
RuHCl(CO)(PiPr2[3,5-(CF3)2C6H3])2, isolated as a yellow solid
and identified by H, 31P, and 19F NMR and IR after 3 h of
1
Figure 1. ORTEP view of the nonhydrogen atoms of [RuCl2(CO)(Pi-
Pr2Me)2]2. Primed and unlabeled atoms are related to those indicated
by a crystallographic center of symmetry.
refluxing in MeOH; a 31P NMR time evolution study showed
this to be the optimal reaction time. The hydride chemical shift
of this new complex appears at -24.86 ppm, indicative of the
hydride being trans to the empty site and very close (within
0.5 ppm) to typical values for known RuHCl(CO)L2 examples.
There are also two multiplets, corresponding to two diaste-
reotopic sets of PCH protons of the isopropyl substituents at
2.88 and 2.30 ppm; the methyl region of the 1H NMR spectrum
shows the presence of four diastereotopic CH3 substituents. The
IR spectrum in Nujol shows ν(CO) at 1926 cm-1, which is
significantly higher than that for the complexes with L )
PiPr311 and PtBu2Me12 and indicative of the weaker donor ability
of PiPr2[3,5-(CF3)2C6H3]. This ν(CO) is also higher than for
[NEt3H][RuHCl2(CO)L2], where Cl- lowers ν(CO).
Table 1. Selected Bond Distances (Å) and Angles (deg) for
[RuCl2((CO)(PiPr2Me)2]2
Ru(1)-Cl(2)
Ru(1)-Cl(2)′
Ru(1)-Cl(20)
Ru(1)-Cl(23)
Ru(1)-P(3)
2.4874(9)
2.4943(9)
2.436(3)
2.4377(24) O(21)-C(19)
2.3182(9)
Ru(1)-P(11)
Ru(1)-C(19)
Ru(1)-C(22)
2.3203(10)
1.773(9)
1.898(10)
1.251(9)
1.044(11)
O(24)-C(22)
Cl(2)′ Ru(1)-Cl(2)′ 81.63(3)
Cl(2)-Ru(1)-Cl(20) 90.63(7)
Cl(2)′ Ru(1)-Cl(20) 86.34(7)
Cl(2)-Ru(1)-Cl(23) 85.65(9)
Cl(2)′ Ru(1)-Cl(23) 89.58(9)
Cl(2)-Ru(1)-C(22)
88.1(3)
Cl(2)′ Ru(1)-C(22) 92.6(3)
Cl(20)-Ru(1)-P(3)
93.53(7)
Cl(20)-Ru(1)-P(11) 90.12(7)
Cl(20)-Ru(1)-C(22) 178.5(3)
Cl(2)-Ru(1)-P(3)
Cl(2)′ Ru(1)-P(3)
Cl(2)-Ru(1)-P(11)
91.80(3)
171.99(3)
172.59(3)
Cl(23)-Ru(1)-P(3)
89.74(8)
Na2CO3 is thus seen to be a more effective base than NEt3
in this synthesis. This must relate to the lower solubility of NaCl
than [Et3NH]Cl and especially to rendering the liberated proton
less acidic (by attachment to O2- in the carbonate-derived
products H2O + CO2) than it is in Et3NH+. The ammonium
cation may retain considerable reactivity of the type shown in
eq 3 since it can hydrogen bond to RuHCl(CO)L2 or
RuHCl2(CO)L2-, thus increasing its potential to liberate H2.
(c) Lewis Acidity of RuHCl(CO)(PiPr2[3,5-(CF3)2C6H3])2.
The ability of RuHCl(CO)(PiPr2[3,5-(CF3)2C6H3])2 to add
chloride from its ammonium salts, thus supporting the assign-
ment of [NEt3H][RuHCl2(CO)L2] as the product of the synthesis
in the presence of NEt3, was studied by reacting this five-
coordinate complex with [Bu4N]Cl. When a benzene-d6 solution
of these two reagents in 1:1 ratio was stirred at 20 °C for 10
min, poorly soluble [Bu4N]Cl dissolved by reacting, the color
Cl(23)-Ru(1)-P(11) 93.57(9)
Cl(23)-Ru(1)-C(19) 177.6(3)
Cl(2)′ Ru(1)-P(11) 91.91(3)
P(3)-Ru(1)-P(11)
Ru(1)-Cl(2)-Ru(1)
94.92(3)
98.37(3)
Cl(2)-Ru(1)-C(19)
88.1(3)
Cl(2)′ Ru(1)-C(19) 94.5(3)
Ru(1)-C(19)-O(21) 177.2(9)
Ru(1)-C(22)-O(24) 176.9(11)
NMR signal is seen at 57.0 ppm (vs 57.8 ppm for the five-
coordinate starting material). This indicates only minor conver-
sion to an adduct and rapid exchange between RuHCl(CO)-
(PiPr3)2 and a trace of its chloride adduct. Evidently, the bulkier
and more electron-rich PiPr3 ligands decrease the ability of the
unsaturated metal complex to add nucleophiles such as chloride.
On the basis of these spectral observations, the relative ability
of RuHCl(CO)(PiPr2[3,5-(CF3)2C6H3])2 and RuHCl(CO)(PiPr3)2
to add [Bu4N]Cl was also investigated by internal competition,
1
i.e., mixing these reagents in a 1:1:1 ratio in benzene. H and
31P NMR comparison with the spectral data described above
showed that [Bu4N]Cl adds exclusively to RuHCl(CO)(PiPr2-
[3,5-(CF3)2C6H3])2 while RuHCl(CO)(PiPr3)2 remains intact and
shows no sign of any chloride coordination under these
conditions, thus indicating significantly higher Lewis acidity
of the complex with less electron-rich, smaller phosphine
ligands.
1
changed to nearly colorless, and no precipitate was seen. H
and 31P NMR indicated complete conversion to [Bu4N][RuHCl2-
(CO)L2], spectroscopically analogous to [NEt3H][RuHCl2-
(CO)L2]. The solubility of the complex in toluene can be
explained by ion-pairing. The hydride chemical shift appears
at -14.67 ppm as a triplet, while the 31P{1H} NMR chemical
shift is at 50.6 ppm.
A Still Smaller Phosphine: PiPr2Me. (a) X-ray Structure
and Spectroscopic Characterization of RuCl2(CO)(PiPr2Me)2.
Because of the pale yellow color6 of previously reported
RuCl2(CO)(PiPr2Me)2, which suggests the large HOMO/LUMO
gap of a saturated complex, we evaluated the hypothesis that
the molecule is in fact a dimer. An X-ray structure determination
of crystals grown from EtOH/petroleum ether over a period of
10 days showed definitively (Figure 1 and Tables 1 and 2) that
the molecule is a dimer, and thus, PiPr2Me is small enough that,
in the absence of a strong trans effect hydride ligand, dimer-
ization occurs. The dimer has an equilateral Ru(µ-Cl)2Ru core
(i.e., edge-shared bioctahedron) with the mutually cis phosphines
each trans to the bridging chloride. Each Ru has one terminal
Cl and one terminal CO, mutually trans; because these dimers
To study how size and the absence of electron-withdrawing
phosphine substituents affects the addition of ammonium
chloride salts to RuHCl(CO)L2, the reaction of RuHCl(CO)-
(PiPr3)2 with [Bu4N]Cl was studied. Visually, after 10 min and
after 1 h, the color of a C6D6 solution remained unchanged
1
(yellow) and insoluble colorless solid [Bu4N]Cl remained. H
and 31P NMR indicated only weak equilibrium binding of the
chloride to the metal with only a very low fraction of [Bu4N]-
[RuHCl2(CO)(PiPr3)2] in the solution; the hydride chemical shift
appears at -24.01 ppm as a very broad signal [i.e., only 0.35
ppm downfield from RuHCl(CO)(PiPr3)2], and a broad 31P{1H}
(12) Poulton, J. T.; Folting, K.; Streib, W. E.; Caulton, K. G. Inorg. Chem.
1992, 31, 3190.

Effects on the Synthesis of RuHCl(CO)(phosphine)2
Inorganic Chemistry, Vol. 40, No. 25, 2001 6447
Table 2. Crystallographic Data for [RuCl2((CO)(PiPr2Me)2]2
When the crystalline sample is dissolved in CD3OD at 25
°C, the same two isomers of the Ru dimer are observed. In
addition, a 31P{1H} NMR singlet is seen at 65.5 ppm; this we
attribute to the product of halide bridge splitting by solvent:
RuCl2(CO)(methanol)(PiPr2Me)2. We can be certain that this
signal is not that of monomeric trans-RuCl2(CO)(PiPr2Me)2
formula
color
a, Å
b, Å
c, Å
â, Å
V, Å3
Z
C30H68Cl4O2P4Ru2
yellow
formula weight
space group
T, °C
928.71
C2/c
21.773(1)
16.215(1)
12.545(1)
111.76(0)
4113.33
100
λ, D
0.710 69
1.500
11.75
0.0444
0.0424
F
calcd, g/cm3
µ(Mo KR), cm-1
i
because the Pr methyl proton resonances, best resolved at 20
R
4
Rw
°C, show no virtual triplet character diagnostic of mutually trans
phosphorus nuclei. This signal is broader than those of the dimer,
consistent with dynamic line broadening due to the partial
equilibrium MeOH dissociation. The fact that only dimers are
seen in CD2Cl2 (i.e., 43-47 ppm 31P NMR peaks) indicates
that the 65.5 ppm species is not 5-coordinate RuCl2(CO)-
(PiPr2Me)2 and shows that the dimer is distinctly more stable
than any monomer in CD2Cl2.
2
R ) ∑||Fo| - |Fc||/∑|Fo| Rw ) [∑w(|Fo| - |Fc |)2/∑w|Fo| ]1/2, where
w ) 1/σ2(|Fo|).
are located around a crystallographic center of symmetry, these
Cl and CO are mutually 50/50 disordered, and thus, syn and
anti isomers cannot be distinguished by the X-ray data.
The similarity of all three 31P NMR chemical shifts of the
two dimers shows that the local environment, RuCl3(CO)P2, is
the main determinant of the chemical shift. The modest 31P
NMR chemical shift differences within the AB dimer suggest
that each P is trans to chloride. The same logic suggests that
the AB dimer has structure C, where each P is trans to Cl (not
The compact nature of PiPr2Me is evident from the
P-Ru-P in the dimer: an unexceptional 94.92(3)°. This
contrasts to PiPr3, which are most often mutually trans. In TpRu-
(H2O)(PiPr2Me)2+, the P-Ru-P angle is 98.54(10)°.13
A useful structural comparison compound is monomeric
RuCl2(CO)(PtBu2Me)2,2 B. In this compound, the Ru-Cl
CO). Structure C, a centrosymmetric structure, is preferred on
the basis of avoiding steric congestion between syn-oriented
axial PiPr2Me ligands on two different Ru centers.
Additional evidence for the isomerization of the syn dimer
to C is provided by IR spectroscopy. The IR spectrum of the
original sample used in the X-ray study shows ν(CO) at 1948
cm-1 in Nujol. However, in the IR spectrum taken after the
variable-temperature NMR study (including 30 min at 35 °C),
a new major ν(CO) is observed at 1967 cm-1 in CD2Cl2. This
increase in frequency is indicative of a decrease in the donor
power of the ligand (Cl) trans to the carbonyl and is adequately
explained by the difference in the structure of the syn dimer vs
C: while the syn dimer contains CO trans to terminal Cl, in C
carbonyl is trans to bridging chloride, which decreases the
push-pull interaction between Cl and CO ligands, thereby
increasing ν(CO).
distances [2.358(2) and 2.382(3) Å] are shorter than any in
[RuCl2(CO)(PiPr2Me)2]2, due to the trans influence of the
carbonyl in the dimer. In the monomer, the Ru-P distances
[2.402(3) and 2.406(3) Å] are longer, due to the weaker trans
ligands (i.e., µ-Cl) in the dimer.
Since this dimer structure has equivalent phosphines, it cannot
be the initial product isolated,6 which had an AX 31P{1H} NMR
pattern. We first acted to ascertain the spectroscopic signatures
of the crystals employed in the X-ray study. When a crystalline
sample of [RuCl2(CO)(PiPr2Me)2]2 employed in the X-ray study
is mixed with CD2Cl2 at -70 °C, a partial dissolution of the
solid with the formation of a colorless solution is observed. At
this temperature, 31P{1H} NMR shows only one signal (singlet)
at 45.2 ppm, corresponding to the syn or the anti isomer
described above, in which all phosphine ligands are equivalent.
The 1H NMR spectrum contains two broad methine multiplets
at 2.20 and 2.61 ppm, as well as broad multiplets, corresponding
to methyls of phosphine ligands. No significant spectral changes
are seen upon gradual warming of this solution to 0 °C.
However, upon warming to 20 °C, in addition to the previously
present singlet, 31P{1H} NMR shows the growth of an AB-
pattern at 46.2 and 47.5 ppm (JAB ) 26.0 Hz). The presence of
a new species is also confirmed by the appearance of an
additional methine signal of PiPr2Me ligands at 2.40 ppm in 1H
NMR. The singlet and the AB-dimers are present in the mixture
in 2:1 molar ratio. Heating of the mixture at 35 °C for 30 min
leads to the formation of a homogeneous yellow solution, and
this ratio changes to 3:13.
In summary, RuCl2(CO)(PiPr2Me)2 in noncoordinating sol-
vents appears to exist exclusively, at NMR detection levels, as
dimers, but dimers of several stereochemistries, each of which
has cis phosphines. The rate of equilibration among the isomeric
dimers, as observed in CD2Cl2, is no faster than a time scale of
minutes at 0-25 °C, but this rate is certainly adequate to account
for a low-solution-population isomer to be exclusively the
crystalline product.
(b) A Hydrido-Chloride Incorporating PiPr2Me. To elimi-
nate the loss of a hydride ligand to HCl [i.e., seeking RuHCl-
(CO)(PiPr2Me)2, which could be a monomer], we conducted
the conventional synthetic reaction in methanol with Ru:L ratio
) 1:3.5 in the presence of NEt3. This led to the isolation of a
colorless solid that was identified as the 18-electron tris-
1
phosphine complex D, RuHCl(CO)(PiPr2Me)3, by H and 31P
NMR. 31P{1H}
NMR at 20 °C shows two broad signals at 34.2 (∆ν1/2
)
34.7 Hz) and 11.6 (∆ν1/2 ) 45 Hz) in a 2:1 ratio corresponding
to two mutually trans phosphines and the phosphine trans to
the hydride, respectively. Lack of observable coupling between
phosphorus indicates an equilibrium involving dissociation of
(13) Jime´nez Tenorio, M. A.; Jime´nez Tenorio, M.; Puerta, M. C.; Valerga,
P. J. Chem. Soc., Dalton Trans. 1998, 3601.

6448 Inorganic Chemistry, Vol. 40, No. 25, 2001
Marchenko et al.
presence of the third phosphine ligand trans to the hydride, we
studied the reactivity of saturated RuHCl(CO)(PiPr2Me)3 toward
a variety of small molecules. Addition of two equiv. of H2, C2H4,
or Me3SiH to a solution of RuHCl(CO)(PiPr2Me)3, followed by
mixing for 30 min at room temperature does not lead to any 1H
or 31P NMR spectral change, which is indicative of the absence
of any reactions with these gaseous reagents. These results are
consistent with an analogous behavior of RuHCl(CO)L2 (L )
PtBu2Me,17 PiPr311 which are also completely unreactive toward
these molecules under similar conditions. This lack of reactivity
shows that, although the unsaturated five-coordinate complex
RuHCl(CO)(PiPr2Me)2 is present in solution due to equilibrium
5, binding of σ-donating but bulkier PiPr2Me is preferred over
H2, C2H4 and Me3SiH, despite the steric hindrance created by
the two phosphine ligands in this complex.
the unique phosphine due to the strong trans-influence exerted
by the hydride. The hydride signal appears as a broad doublet
at -8.38 ppm with JHP(trans) ) 108 Hz, which is a typical
trans JPH magnitude for phosphine adducts.14 Cooling to 0 °C
slows the exchange: the hydride peak resolves into a doublet
of triplets [JHP(cis) ) 27 Hz]. The 31P{1H} NMR peaks at this
temperature transform into a doublet and a triplet, respectively,
with JPP′ ) 17 Hz. The consequence of the presence of three
phosphines in the coordination sphere of RuHCl(CO)(PiPr2Me)3
is seen in the IR spectrum: ν(CO) is observed at 1898 cm-1
which is lower than for RuHCl(CO)(PiPr3)2 (1910 cm-1 11
and
RuHCl(CO)(PtBu2Me)2 (1904 cm-1 12
and indicative of the
,
RuHCl(CO)(PiPr2Me)3 h
)
)
RuHCl(CO)(PiPr2Me)2 + PiPr2Me (5)
presence of a donor ligand trans to the hyride. The presence of
three such phosphines in RuHCl(CO)(PiPr2Me)3 provides suf-
ficient donation so that ν(CO) for this complex is lower than
for any known RuHCl(CO)L2.
In contrast, reaction of RuHCl(CO)(PiPr2Me)3 with propyne
is complete in 30 min at +20 °C and leads to the formation
(eq 6) of red five-coordinate vinyl complex Ru(E-CHd
(c) Attempts toward RuHCl(CO)(PiPr2Me)2. In an attempt
to prevent the formation of this tris phosphine adduct, the Ru:L
ratio in the synthesis was changed to 1:2. However, instead of
the expected RuHCl(CO)L2, formation of four major hydride-
containing products was observed, including RuHCl(CO)L3. All
of them had hydride chemical shifts in the -8 to 16 ppm range
and thus none of them could be RuHCl(CO)L2; they are perhaps
Ru2 species. The third phosphine in RuHCl(CO)(PiPr2Me)3 could
not be removed by heating the solid compound under vacuum
at 80 °C after 24 h or by azeotropic distillation with toluene. In
conclusion, PiPr2Me is clearly a phosphine small enough to
destroy unsaturation by binding three phosphines per Ru.
In a “chemical abstraction” attempt to remove the phosphine
ligand trans to the hydride, RuHCl(CO)(PiPr2Me)3 was reacted
with CuBr, a known phosphine-scavenging reagent15 [i.e.,
potentially forming CuBr(PR3)n].16 After 1 h of stirring at 20
°C, the initially colorless solution becomes yellow-orange and
1H and 31P NMR indicates complete conversion to a different
complex, with a broad hydride peak at -15.61 ppm and broad
31P{1H} NMR signals at 35.9, 33.4, and 1.6 ppm. The latter
chemical shift is indicative of phosphine coordination to copper.
Upon cooling to -40 °C, the hydride chemical shift resolves
into four unequally intense triplets (JPH) at -15.22, -15.38,
-16.00, and -16.16 ppm, and the 31P{1H} NMR at this
temperature shows four sharp peaks at 37.0, 35.9, 34.5, and
33.4 ppm, in addition to the unchanged high-field signal for
phosphine on copper. These spectral data imply that, although
the phosphine is “extracted” from ruthenium by copper, the
resulting Cu(PiPr2Me)Br coordinates to the five-coordinate
RuHCl(CO)(PiPr2Me)2 with the formation of a halide-bridged
complex. This is followed by a halide exchange resulting in
four observed hydride complexes of general formula (MeiPr2P)-
CuRuHX2(CO)(PiPr2Me)2, where X ) Cl, Br. Reaction of
RuHCl(CO)(PiPr2Me)3 with CuCl gives the spectral simplifica-
tion expected for elimination of mixed-halide analogues. In
conclusion, phosphine “abstraction” from RuHCl(CO)(PiPr2Me)3
is unsuccessful.
CHCH3)(CO)(Cl)(PiPr2Me)2,which was characterized by 1H and
1
31P NMR. H NMR shows a doublet at 7.06 ppm (JHH(trans)
)
12.0 Hz) and a multiplet at 5.02 ppm, corresponding to the
protons on the CR and Câ atoms of the vinyl fragment. In
addition to the signal of the vinyl complex at 28.6 ppm,
31P{1H} NMR also displays a peak at -10.0 ppm, characteristic
of free PiPr2Me. This result indicates that the absence of a free
coordination site in RuHCl(CO)(PiPr2Me)3 does not prevent the
insertion of the alkyne into the Ru-H bond and that the
methylvinyl ligand has a sufficiently stronger trans effect than
hydride, to give an unsaturated five-coordinate species instead
of a six-coordinate trisphosphine vinyl complex.
Reaction of RuHCl(CO)(PiPr2Me)3 with phenylacetylene also
occurs very fast, resulting within 10 min at room temperature
in complete transformation to Ru(E-CHdCHPh)(CO)(Cl)-
(PiPr2Me)2. The protons on CR and Câ atoms of the vinyl
fragment in this case appear as doublets (JHH(trans) ) 13.7 Hz)
at a significantly lower field (8.95 and 6.52 ppm) than the
propenyl analogue due to the electron-withdrawing effect of the
phenyl substituent. The implied Lewis acidity is also evident
in the 31P{1H} NMR spectrum: unlike in the case of the
methylvinyl complex described above, signals for both the vinyl
complex at 28.2 ppm and the free PiPr2Me are broadened. This
is explained by an equilibrium process involving coordination
and dissociation of the phosphine to the metal center trans to
the more electron-withdrawing phenylvinyl ligand.
Influence of the steric bulk of the substituent on the alkyne
is clearly seen in reaction of RuHCl(CO)(PiPr2Me)3 with
trimethylsilylacetylene. Insertion of acetylene into the Ru-H
bond here occurs at a significantly lower rate: after 1 h at room
temperature, only 20% conversion of the starting material to
(d) Reactivity of RuHCl(CO)(PiPr2Me)3: Does the Sixth
Ligand Poison Reactivity? To understand the effect of the
1
Ru(E-CHdCHSiMe3)(CO)(Cl)(PiPr2Me)2 is found by H and
(14) Poulton, J. T.; Sigalas, M. P.; Folting, K.; Streib, W. E.; Eisenstein,
O.; Caulton, K. G. Inorg. Chem. 1994, 33, 1080.
31P NMR. Even after 120 h at room temperature, only 68%
(15) Dias, E. L.; Grubbs, R. H. Organometallics 1998, 17, 2758.
(16) AdVanced Inorganic Chemistry; Cotton, F. A.; Wilkinson, G., Eds.;
Wiley: New York, 1988; p 757.
(17) Poulton, J. T.; Sigalas, M. P.; Eisenstein, O.; Caulton, K. G. Inorg.
Chem. 1993, 32, 5490.

Effects on the Synthesis of RuHCl(CO)(phosphine)2
Inorganic Chemistry, Vol. 40, No. 25, 2001 6449
(1H), external H3PO4 (31P), or external CF3CO2H (19F). RuHCl(CO)-
(PiPr3)2 was prepared according to a published procedure.10
conversion to the vinyl complex is observed. Unlike in the case
of more Lewis acidic Ru(E-CHdCHPh)(CO)(Cl)(PiPr2Me)2, no
31P NMR line broadening due to the coordination of the third
phosphine is seen in the evolving reaction mixture.
PiPr2[3,5-(CF3)2C6H3]. A dark-brown solution of the Grignard
reagent 3,5-(CF3)2C6H3MgBr in 200 mL of Et2O was prepared using
25 g (0.085 mol) of 3,5-(CF3)2C6H3Br and 2.6 g (0.11 mol) of Mg
according to a published procedure.19 Explosions involving solid
(CF3)2C6H3MgBr have been reported, so the Et2O solution employed
here must not be taken to dryness. A solution of 13 g (0.085 mol) of
PiPr2Cl in 100 mL of Et2O was slowly added dropwise while the flask
was cooled with cold water. The reaction mixture was then gently
refluxed for 20 h. After cooling, the reaction was quenched by addition
of a degassed, saturated NH4Cl solution (30 g in 110 mL H2O) with
ice bath cooling. The Et2O layer was decanted off, and the aqueous
layer was washed with Et2O (2 × 50 mL). The wash was added to the
original Et2O layer and the solution was concentrated at 5 °C. After
concentrating the solution to ∼100 mL, it was dried by stirring with
Na2SO4. After decanting the solution off Na2SO4, Et2O was removed
in vacuo at 5 °C. This resulted in the formation of spectroscopically
The observed order of rates for the alkynes containing
electronically and sterically different substituents with six-coor-
dinate RuHCl(CO)(PiPr2Me)3 (Ph> Me>SiMe3) is similar to
that found in reactions of five-coordinate MHCl(CO)L2 (M )
Os, Ru; L ) PtBu2Me, PiPr3).18 The addition of excess free
PiPr2Me strongly suppresses the rate of the reaction of RuHCl-
(CO)(PiPr2Me)3 with Me3SiCCH. When these two reagents are
reacted in a 1:1 ratio with no added phosphine, 36% conversion
(based on 31P NMR integration) to Ru(CHdCHSiMe3)(CO)(Pi-
Pr2Me)2 is observed after 18 h at 20 °C. If this reaction is
conducted in the presence of a 4-fold excess of free PiPr2Me,
only 5% conversion to the same product is observed after this
time period. This is consistent with eq 5 being crucial to the
alkyne insertion in the Ru-H bond. Apparently it is the more
flexible structure of the square-pyramidal intermediate RuHCl-
(CO)(PiPr2Me)2 (in comparison to octahedral RuHCl(CO)-
(PiPr2Me)3) that allows a direct alkyne attack on the Ru-H
fragment.
1
pure PiPr2[3,5-(CF3)2C6H3] as a viscous liquid (14 g, 50%). H NMR
(C6D6, 20 °C), ppm: 0.59, 0.77 (both dd, JHP ) 11.7 Hz, JHH ) 6.9
Hz, PCHCH3), 1.62 (m, PCH), 7.68 (s, p-hydrogen of 3,5-(CF3)2C6H3),
7.82 (d, JHP ) 4.8 Hz, o-hydrogens of 3,5-(CF3)2C6H3). 31P{1H} NMR
(C6D6, 20 °C): 12.3 (s). 19F{1H} (C6D6, 20 °C): -64.8 (s).
A solution of PiPr2[3,5-(CF3)2C6H3] in C6D6 exposed to air slowly
(∼7 d) oxidizes with the formation of phosphine oxide OdPiPr2[3,5-
(CF3)2C6H3] (observed by NMR). 1H NMR (C6D6, 20 °C), ppm: 0.63,
0.66 (both dd, JHP ) 15.3 Hz, JHH ) 6.9 Hz, PCCH3), 1.69 (m, PCH),
7.88 (d, JHP ) 4.5 Hz, p-3,5-(CF3)2C2H2H), 8.18 (d, JHP ) 8.9 Hz,
o-3,5-(CF3)2C6H2H). 31P{1H} NMR (C6D6, 20 °C), ppm: 48.5. 19F-
{1H} NMR (C6D6, 20 °C), ppm: -64.6.
Conclusions
One conclusion from this work is that, even when L′ ) Cl-,
PiPr2Me, or MeOH binds to a RuHCl(CO)L2 species, the binding
is weak. That is, although the equilibrium position lies to the
left in eq 6,
[NEt3H][RuHCl2(CO)(PiPr2[3,5-(CF3)2C6H3])2]. RuCl3‚3H2O (1.7
g; 6.4 mmol) was mixed with triethylamine (3.4 g; 15 mmol) and Pi-
Pr2[3,5-(CF3)2C6H3] (6.5 g; 20 mmol), and 2-methoxyethanol (60 mL)
was added via cannula. The resulting solution was heated at 120 °C
for 21 h. Volatiles were removed in vacuo, and the residue was
dissolved in a minimum amount of hot toluene. Pentane was added to
the solution, and cooling to -40 °C afforded a colorless precipitate,
which was filtered and washed with 10 mL of pentane. Yield: 3.8 g
(61%). 1H NMR (C6D6, 20 °C), ppm: -15.63 (t, JHP ) 23.1 Hz, RuH),
0.67 (t, JHH ) 6.0 Hz, [N(CH2CH3)3H]), 0.99, 1.11, 1.32, 1.51 (all dvt,
JHH ) 7.5 Hz, N ) 7.8 Hz, PCHCH3), 2.11 (br, m, N(CH2CH3)3H]),
2.55, 3.34 (both m, PCH), 7.81, 9.15 (both s, -3,5-(CF3)2C6H3), 10.47
(br, [Et3NH]). 31P{1H} NMR (C6D6, 20 °C): 50.6 (82%, RuHCl2(CO)(Pi-
Pr2[3,5-(CF3)2C6H3])2-); 44.8 (18%, RuCl2(CO)(PiPr2[3,5-(CF3)2C6H3)])2).
k1
RuHCl(CO)L2L′ y
\
z RuHCl(CO)L2 + L′
(6)
k1 is large enough at 20 °C to let the equilibrium system react
rapidly with substrates (L′′) and to show dynamic NMR
phenomena in the absence of L′′. On the other hand, and highly
dependent on the properties of L, eq 6 can lead to isolation of
six-coordinate products from the traditional synthesis originally
devised for the bulky phosphines PCy3, PiPr3, and PtBu2Me.
The weakness of binding L′ is due to the open coordination
site trans to the (reactive) hydride ligand, but the generally
stronger binding to MHCl(CO)L2 for M ) Os (vs Ru) makes
loss of unsaturation (i.e., the binding of L′) more likely for
osmium.
19F{1H} NMR (C6D6, 20 °C): -64.3. IR (Nujol): ν(CO) ) 1911 cm-1
.
RuHCl(CO)(PiPr2[3,5-(CF3)2C6H3])2. RuCl3‚3H2O (0.5 g; 1.9
mmol) was mixed with PiPr2[3,5-(CF3)2C6H3] (2.1 g; 6 mmol) and Na2-
CO3 (0.2 g; 2 mmol), and methanol (25 mL) was added via cannula.
The resulting solution was refluxed at 70 °C for 8 h. Volatiles were
removed in vacuo, and the resulting solid was dissolved in benzene
and filtered via glass wool. Benzene then was removed in vacuo and
the residue was washed with pentane (2 × 5 mL). This resulted in
yellow-orange solid product. Yield: 1.02 g (65%). 1H NMR (C6D6, 20
°C), ppm: -24.86 (t, JHP ) 18.8 Hz, RuH), 0.66, 0.88, 1.03 (double
intensity), (all m, PCHCH3), 2.30, 2.88 (both m, PCH), 7.71, 8.22
(double intensity) (both s, 3,5-(CF3)2C6H3). 31P{1H} NMR (C6D6, 20
°C): 60.5. 19F{1H} NMR (C6D6, 20 °C): -63.6. IR (Nujol): ν(CO) )
The structural study of the RuCl2(CO)(PiPr2Me)2 species
shows that this phosphine is small enough to permit dimeriza-
tion, with concomitant cis-phosphine stereochemistry. This
emphasizes the narrow range of phosphine steric bulk that
permits isolation of unsaturated RuXCl(CO)L2 species (X ) H
or Cl) using traditional synthetic methods: it is only phosphine
steric bulk that can overcome the Lewis acidity of 16-electron
Ru(II).
The use of a fluorinated aryl group in PiPr2R enables the
synthesis of unsaturated RuHCl(CO)L2 reagents, whose Lewis
acidity shows the transmission of electronic effects from the
3,5-(CF3)2C6H3 group R.
1926 cm-1
.
[Bu4N][RuHCl2(CO)(PiPr2[3,5-(CF3)2C6H3])2]. RuHCl(CO)(PiPr2-
[3,5-(CF3)2C6H3])2 (15 mg; 0.018 mmol) was added to 5 mg (0.018
mmol) of [Bu4N]Cl and dissolved in 0.5 mL of benzene-d6 in an NMR
tube. After mixing for 10 min at 20 °C, the reaction mixture became
Experimental Section
General Considerations. All reactions and manipulations were
conducted using standard Schlenk and glovebox techniques under
prepurified argon. Solvents were dried and distilled under argon and
stored in airtight solvent bulbs with Teflon closures. All NMR solvents
were dried, vacuum-transferred, and stored in a glovebox. 1H, 31P, and
19F spectra were recorded on a Varian Gemini 300 and on a Varian
Inova 400 instruments. Chemical shifts are referenced to residual solvent
homogeneous and the color of the solution changed from yellow-orange
1
to nearly colorless. H NMR (C6D6, 20 °C), ppm: -14.67 (t, JHP
)
22.5 Hz, RuH), 0.90 (t, JHH ) 6.6 Hz, [N(CH2CH2CH2CH3)4]), 1.11,
1.23, 1.35, 1.51 (all m, PCHCH3, [N(CH2CH2CH2CH3)4]), 2.63, 3.28
(m, PCH), 3.11 (t, JHH ) 7.5 Hz), [N(CH2CH2CH2CH3)4]), 7.86, 9.34
(double intensity) (both s, 3,5-(CF3)2C6H3). 31P{1H} NMR (C6D6, 20
°C): 50.6. 19F{1H} NMR (C6D6, 20 °C): -62.4.
(18) Marchenko, A. V.; Gerard, H.; Eisenstein, O.; Caulton, K. G. New J.
Chem. 2001, 25, 1244.
(19) Brookhart, M.; Grant, B.; Volpe, J. Organometallics 1992, 11, 3920.

6450 Inorganic Chemistry, Vol. 40, No. 25, 2001
Marchenko et al.
Reaction of [Bu4N]Cl with RuHCl(CO)(PiPr3)2. RuHCl(CO)-
(PiPr3)2 (15 mg; 0.031 mmol) was added to 8.6 mg (0.031 mmol) of
[Bu4N]Cl and dissolved in 0.5 mL of benzene-d6 in an NMR tube.
After mixing for 10 min or 1 h at 20 °C, the color remains yellow-
orange and the reaction mixture is still heterogeneous due to undissolved
[Bu4N]Cl. NMR indicates the presence of only a very low fraction of
A set of frames from three orthogonal sections of reciprocal space was
used to determine that the crystal possessed monoclinic symmetry with
systematic absences corresponding to either space group C2/c or its
noncentrosymmetric equivalent, Cc. Subsequent solution and refinement
confirmed the centrosymmetric choice, C2/c. The data were collected
using a Bruker-AXS SMART6000 CCD area detector system. A
complete hemisphere of data was collected using 0.3° ω scans. Data
were reduced using the Bruker-AXS SAINT series of programs. The
structure was solved using direct methods (SHELXTL) and Fourier
techniques. There was a disorder involving the terminal chlorine atom
and carbonyl group that was easily modeled. Although hydrogen atoms
were readily located in a difference synthesis, several did not converge
properly. In the final cycles of refinement, all hydrogen atoms were
allowed to vary isotropically except for those associated with C(9),
C(10), and C(15). Hydrogen atoms associated with these three carbons
were placed in fixed, idealized positions. A final difference Fourier
was featureless, the largest peak being 0.55 e/Å3.
Reactions of RuHCl(CO)(PiPr2Me)3 with H2, C2H4, and SiMe3H.
RuHCl(CO)(PiPr2Me)3 (15 mg; 0.027 mmol) was dissolved in 0.5 mL
of benzene-d6 in three NMR tubes. The solutions were freeze-pump-
thaw degassed and H2, C2H4, or SiMe3H was condensed in the tubes
using a vacuum line (gas:Ru molar ratio ) 2:1). After 30 min of mixing
at 20 °C, 1H and 31P NMR showed only the presence of starting
materials in all three cases.
Reaction of RuHCl(CO)(PiPr2Me)3 with Propyne. RuHCl(CO)-
(PiPr2Me)3 (15 mg; 0.027 mmol) was dissolved in 0.5 mL of benzene-
d6 in an NMR tube. The solution was freeze-pump-thaw degassed
and propyne was condensed in the tube using a vacuum line (MeCt
CH:Ru molar ratio ) 2:1). The color of the reaction mixture changed
from colorless to red after mixing for 30 min at 20 °C, and the formation
of Ru(E-CHdCHCH3)(CO)(Cl)(PiPr2Me)2 was observed by NMR. 1H
NMR (C6D6, 20 °C), ppm: 1.03-1.39 (m, PCHCH3, PCH3), 1.84 (d,
JHH ) 6.0 Hz, Ru-CHdCHCH3), 2.73 (m, PCH), 5.02 (m, Ru-CHd
CH-), 7.06 (d, JHH ) 12.0 Hz, Ru-CH)). 31P{1H} NMR (C6D6, 20
°C), ppm: 28.6 (s, Ru(E-CHdCHCH3)(CO)(Cl)(PiPr2Me)2), -10.0 (s,
free PiPr2Me).
Reaction of RuHCl(CO)(PiPr2Me)3 with Phenylacetylene. RuHCl-
(CO)(PiPr2Me)3 (15 mg; 0.027 mmol) was added to 2.6 µL (0.027
mmol) of PhCtCH in 0.5 mL of benzene-d6 in an NMR tube. The
color of reaction mixture changed from colorless to red after mixing
for 10 min at 20 °C and the formation of Ru(E-CHdCHPh)(CO)(Cl)-
(PiPr2Me)2 was observed by NMR. 1H NMR (C6D6, 20 °C), ppm:
1.10-1.31 (m, PCH3, PCHCH3), 2.14, 2.84 (each m, PCH), 6.52 (d,
JHH ) 13.6 Hz, Ru-CHdCH-), 7.08-7.59 (m, Ru-CHdCHPh), 8.95
(d, JHH ) 13.6 Hz, Ru-CH)). 31P{1H} NMR (C6D6, 20 °C), ppm:
28.2 (br, Ru(E-CHdCHPh)(CO)(Cl)(PiPr2Me)2), -10.0 (br, free PiPr2-
Me).
1
[Bu4N][RuHCl2(CO)(PiPr3)2]. H NMR (C6D6, 20 °C), ppm: -24.01
(br, ∆ν1/2 ) 188 Hz, RuH), 0.99 (t, JHH ) 6.6 Hz, [N(CH2CH2-
CH2CH3)4]), 1.22-1.33 (m, PCHCH3, [N(CH2CH2CH2CH3)4]), 2.57 (br,
PCH), 3.19 (br, m, [N(CH2CH2CH2CH3)4]). 31P{1H} NMR (C6D6, 20
°C): 57.0 (br, ∆ν1/2 ) 116 Hz).
Competition Reaction of RuHCl(CO)(PiPr2[3,5-(CF3)2C6H3])2 and
RuHCl(CO)(PiPr3)2 with [Bu4N]Cl. RuHCl(CO)(PiPr3)2 (10.8 mg;
0.022 mmol) was mixed with 18 mg (0.022 mmol) of RuHCl(CO)-
(PiPr2[3,5-(CF3)2C6H3])2 and with 6 mg (0.022 mmol) of [Bu4N]Cl in
0.5 mL of benzene-d6 in an NMR tube. The reaction mixture becomes
heterogeneous (yellow-orange) after mixing for 15 min at 20 °C, and
1H and 31P{1H} NMR indicate the presence of [Bu4N][RuHCl2(CO)-
(PiPr2[3,5-(CF3)2C6H3])2] and unreacted RuHCl(CO)(PiPr3)2.
Variable-Temperature NMR Study of [RuCl2(CO)(PiPr2Me)2]2.
To an NMR tube, cooled to -196 °C and containing 15 mg (0.016
mmol) of crystalline [RuCl2(CO)(PiPr2Me)2]2, was vacuum-transferred
0.5 mL of CD2Cl2. The sample was thawed briefly and then shaken
several times to allow for mixing and inserted into a precooled NMR
probe. The solution at -70 °C was colorless and most of the complex
did not dissolve. 1H NMR (CD2Cl2, -70 °C), ppm: 1.20, (br m, PCH3,
PCHCH3), 2.20, 2.61 (both br m, PCH). 31P{1H} NMR (CD2Cl2, -70
°C): 45.2 (s). No significant spectral changes were observed in the
-70 to 0 °C temperature range. 1H NMR (CD2Cl2, 20 °C), ppm: 1.19-
1.47 (overlapping m, PCH3, PCHCH3), 2.25, 2.40, 2.62 (all m, PCH).
31P{1H} NMR (CD2Cl2, 70 °C) (121.4 Hz): 44.8 (s, 66%), 46.2, 47.5
(AB pattern, JAB ) 26.0 Hz, 34%). After heating for 30 min at 35 °C,
the molar ratio of the singlet and the AB dimers in the mixture is 3:13.
The solution at this temperature is homogeneous and yellow.
RuHCl(CO)(PiPr2Me)3. RuCl3‚3H2O (1.0 g; 3.8 mmol) was mixed
with triethylamine (1.1 g; 10.5 mmol) and PiPr2Me (1.8 g; 13.6 mmol),
and methanol (30 mL) was added via cannula. The resulting solution
was heated at 65 °C for 8 h. Volatiles were removed in vacuo, and the
resulting residue was dissolved in toluene and filtered via a frit. After
toluene was removed by heating at 55 °C for 5 h under vacuum, the
solid was washed with 10 mL of pentane, yielding a mostly colorless
residue. Yield: 1.3 g (62%). 1H NMR (C6D6, 20 °C), ppm: -8.38 (br
d, ∆ν1/2 ) 191 Hz, JHP(trans) ) 108 Hz, RuH), 1.10-1.34, (overlapping
m, PCH3, PCHCH3), 2.02, 2.21, 2.36 (all m, PCH). 31P{1H} NMR
(C6D6, 20 °C): 11.6 (br, ∆ν1/2 ) 45 Hz, RuPiPr2Me trans to the
hydride), 34.2 (br, ∆ν1/2 ) 35 Hz, Ru(PiPr2Me)2 cis to the hydride).
1H NMR (CD2Cl2, 0 °C), ppm: -8.35 (dt, JHP(trans) ) 108 Hz, JHP(cis)
)
27.0 Hz, RuH), 1.15-1.36 (overlapping m, PCH3, PCHCH3), 2.10, 2.25,
2.30 (all m, PCH). 31P{1H} NMR (CD2Cl2, 0 °C): 11.6 (t, JPP ) 17
Hz, RuPiPr2Me trans to the hydride), 34.1 (d, JPP ) 17 Hz, Ru(PiPr2-
Me)2 cis to the hydride).
Reaction of RuHCl(CO)(PiPr2Me)3 with Trimethylsilylacetylene.
RuHCl(CO)(PiPr2Me)3 (15 mg; 0.027 mmol) was added to 3.8 µL
(0.027 mmol) of Me3SiCtCH in 0.5 mL of benzene-d6 in an NMR
tube. No visual changes were observed immediately upon mixing. After
mixing for 1 h at 20 °C, 20% conversion to Ru(E-CHdCHSiMe3)-
Reaction of RuHCl(CO)(PiPr2Me)3 and CuBr. RuHCl(CO)(PiPr2-
Me)3 (15 mg; 0.027 mmol) was added to 10 mg (0.069 mmol) of CuBr
in 0.5 mL of toluene-d6 in an NMR tube. The color of the reaction
mixture changed from colorless to orange after mixing for 1 h at 20
°C. 1H NMR (C7D8, -40 °C), ppm: -16.16, -15.99, -15.38, -15.22
(all t, JHP ) 19.8 Hz, RuH), 0.61-1.73 (overlapping m, PCH3,
PCHCH3), 2.41 (br, PCH). 31P{1H} NMR (C7D8, -40 °C): 1.7 (br,
∆ν1/2 ) 134 Hz, CuPiPr2Me), 33.4, 34.5, 35.9, 37.0 (all s, Ru(PiPr2-
Me)2).
X-ray Diffraction Structure Determination of [RuCl2(CO)-
(PiPr2Me)2]2.1 Single crystals of the dimeric compound suitable for
X-ray structure analysis were obtained directly from the mother liquor,
by concentration of the 2-methoxyethanol solution, diluting with EtOH,
and layering with petroleum ether. Slow diffusion over a period of ca.
10 days at room temperature afforded single crystals of the dimeric
compound (20% yield). The sample consisted of yellow transparent
crystals of varying sizes growing in clumps. One of the larger crystals
was selected, and a well-formed fragment cleaved from a section that
appeared to be flawless. The sample was then affixed to the glass fiber
on a goniometer head and transferred to the goniostat, where it was
cooled to -158 °C for characterization and data collection (Table 2).
1
(CO)(Cl)(PiPr2Me)2 was observed by NMR. H NMR (C6D6, 20 °C),
ppm: 0.11 (-SiMe3), 0.97-1.35 (m, PCH3, PCHCH3), 2.38, 2.84 (each
m, PCH), 5.60 (d, JHH ) 13.2 Hz, Ru-CHdCH-), 8.59 (d, JHH
)
13.2 Hz, Ru-CH)). 31P{1H} NMR (C6D6, 20 °C), ppm: 29.2 (s, Ru-
(E-CHdCHSiMe3)(CO)(Cl)(PiPr2Me)2), -10.2 (s, free PiPr2Me). After
120 h at 20 °C, 31P{1H} NMR shows 68% conversion to Ru(E-CHd
CHSiMe3)(CO)(Cl)(PiPr2Me)2.
Acknowledgment. This work was supported by the U.S.
Department of Energy.
Supporting Information Available: Crystallographic data for
[RuCl2(CO)(PiPr2Me)2]2 in CIF format.This material is available free
of charge via the Internet at http://pubs.acs.org.
IC000500T