Alkyne insertion into the Ru-C bond of a four-membered metallacycle. Insertion rate and reaction pathway

Article abstract of DOI:10.1021/om000649c

The insertion of HOCH₂C≡CH(ha) into the Ru-C bond of Ru^II(RL¹)(PPh₃)₂(CO)Cl, 1, has afforded Ru^II(RL³)(PPh₃)₂(CO)Cl, 3, which has been structurally characterized. Insertion rates in CH₂Cl₂-MeOH for ha as well as for PhC≡CH (pa), which inserts similarly into 1 affording Ru^II(RL²)(PPh₃)₂(CO)Cl, 2, are proportional to the product of the concentrations of alkyne and methanol. The insertion rate of ha is nearly 5 times faster than that of pa, and for a given alkyne the rate increases as R becomes more electron-withdrawing (OMe < Me < Cl). A reaction model implicating the adduct 1·MeOH, which binds and activates the alkyne via displacement of MeOH, is proposed.

Full text of DOI:10.1021/om000649c

Organometallics 2001, 20, 1419-1423
1419
Alk yn e In ser tion in to th e Ru -C Bon d of a
F ou r -Mem ber ed Meta lla cycle. In ser tion Ra te a n d
Rea ction P a th w a y
Kaushik Ghosh, Swarup Chattopadhyay, Sujay Pattanayak, and
Animesh Chakravorty*
Department of Inorganic Chemistry, Indian Association for the Cultivation of Science,
Calcutta 700032, India
Received J uly 28, 2000
The insertion of HOCH2CtCH (ha) into the Ru-C bond of RuII(RL1)(PPh3)2(CO)Cl, 1, has
afforded RuII(RL3)(PPh3)2(CO)Cl, 3, which has been structurally characterized. Insertion rates
in CH2Cl2-MeOH for ha as well as for PhCtCH (pa), which inserts similarly into 1 affording
RuII(RL2)(PPh3)2(CO)Cl, 2, are proportional to the product of the concentrations of alkyne
and methanol. The insertion rate of ha is nearly 5 times faster than that of pa, and for a
given alkyne the rate increases as R becomes more electron-withdrawing (OMe < Me < Cl).
A reaction model implicating the adduct 1‚MeOH, which binds and activates the alkyne via
displacement of MeOH, is proposed.
In tr od u ction
mechanistic model is proposed. The substituents in the
alkyne and the reactive metallacycle have notable
effects on reaction rates. The insertion of hydroxy-
methylacetylene, ha according to eq 1, is being reported
here for the first time, necessitating product character-
ization, which forms a part of the present work.
A few instances of insertion of alkynes into the Ru-C
σ-bond have been documented in the literature,1-6 but
rarely have mechanistic proposals been authenticated
by rate studies.6 The concern of the present work is the
two-carbon metallacycle expansion via insertion of
alkynes generally abbreviated as xa, eq 1. The reaction
Resu lts a n d Discu ssion
Su bstr a tes a n d P r od u cts. The concerned metalla-
cycles, their abbreviations, and numberings are set out
in Figure 1. Three substrates7 of type 1 have been used.
The pa-inserted products of type 2 are already known.1
The reaction of ha with 1 proceeds smoothly in CH2-
Cl2-MeOH mixtures under mild conditions, affording
the type 3 species in virtually quantitative yield. To our
knowledge, this reaction represents the first authentic
example of insertion of ha into the Ru-C bond.
Ch a r a cter iza tion of Ru (RL3)(P P h 3)2(CO)Cl, 3.
Spectral and other physical features of 3 are listed in
the Experimental Section. The N+-H and CdN stretches
occur at ∼3440 and ∼1620 cm-1, respectively, consistent
with the zwitterionic iminium-phenolato function. In
1H NMR, the N+-H and O-H signals occur near δ 12.0
and δ 2.3, respectively (both signals disappear upon
shaking with D2O). The σ-vinyl 10-H proton occurs near
δ 6.3 as a singlet.
was recently authenticated by us via isolation and
structure determination of the expanded cycle in the
case of phenylacetylene, pa (as well as unsubstituted
acetylene).1
Further scrutiny has revealed that the reaction is
suitable for facile rate determination by spectrophoto-
metric methods in the cases of pa and hydroxymethy-
lacetylene, ha. This has provided an opportunity for
probing the reaction pathway. Rates have been mea-
sured in CH2Cl2-MeOH mixtures, revealing that the
four-membered metallacycle itself is not reactive but its
methanol adduct present in equilibrium is. The observed
rate law has been rationalized on this basis, and a
The structure of 3a has been determined (Figure 2,
Table 1). In the distorted octahedral coordination sphere,
the nearly linear P-Ru-P axis lies approximately
perpendicular to the plane (mean deviation of 0.02 Å)
of the RuC2ClO meridian. The hydroxymethyl group is
tilted away from the meridian and lies closer to P2 than
P1, their distances from the O3 atom being 5.176(16)
(1) Ghosh, K.; Pattanayak, S.; Chakravorty, A. Organometallics
1998, 17, 1956 and references therein.
(2) Bruce, M. I.; Catlaw, A.; Cifuentes, M. P.; Snow, M. R.; Tiekink,
E. R. T. J . Organomet. Chem. 1990, 397, 187.
(3) Lutsenko, Z. L.; Aleksandrov, G. G.; Petrovskii, P. V.; Shubina,
E. S.; Andrianov, V. G.; Struchkov, Yu. T.; Rubezhov, A. Z. J .
Organomet. Chem. 1985, 281, 349.
(4) Garn, D.; Knoch, F.; Kish, H. J . Organomet. Chem. 1993, 444,
155.
(5) Barns, R. M.; Hubbard, J . L. J . Am. Chem. Soc. 1994, 116, 9514.
(6) Ferstl, W.; Sakodinskaya, I. K.; Beydoun-Sutter, N.; Borgne, G.
L.; Pfeffer, M.; Ryabov, A. D. Organometallics 1997, 16, 411.
(7) Ghosh, P.; Bag, N.; Chakravorty, A. Organometallics 1996, 15,
3042. (b) Bag, N.; Choudhury, S. B.; Pramanik, A.; Lahiri, G. K.;
Chakravorty, A. Inorg. Chem. 1990, 29, 5013. (c) Bag, N.; Choudhury,
S. B.; Lahiri, G. K.; Chakravorty, A. J . Chem. Soc., Chem. Commun.
1990, 1626.
10.1021/om000649c CCC: $20.00 © 2001 American Chemical Society
Publication on Web 03/09/2001

1420 Organometallics, Vol. 20, No. 7, 2001
Ghosh et al.
Ta ble 1. Selected Bon d Len gth s [Å] a n d An gles
[d eg] for Ru (RL3)(P P h 3)2(CO)Cl, 3A
Distances
Ru-C(11)
Ru-C(10)
Ru-O(1)
Ru-P(1)
Ru-P(2)
N‚‚‚O(1)
1.820(13)
2.020(11)
2.100(7)
2.365(4)
2.376(3)
2.608(12)
Ru-Cl
2.530(3)
O(1)-C(1)
O(2)-C(11)
N-C(8)
1.284(13)
1.153(13)
1.325(14)
1.363(16)
C(9)-C(10)
Angles
C(11)-Ru-C(10)
C(11)-Ru-O(1)
C(10)-Ru-O(1)
C(11)-Ru-P(1)
C(10)-Ru-P(1)
O(1)-Ru-P(1)
C(11)-Ru-P(2)
C(10)-Ru-P(2)
O(1)-Ru-P(2)
91.4(5)
178.1(4)
86.9(4)
89.2(4)
89.4(3)
90.0(2)
92.0(4)
88.1(3)
88.7(2)
P(1)-Ru-P(2)
C(11)-Ru-Cl
C(10)-Ru-Cl
O(1)-Ru-Cl
P(1)-Ru-Cl
177.26(12)
99.6(4)
168.8(4)
82.2(2)
93.08(12)
89.12(11)
131.0(7)
129.8(10)
177.6(11)
P(2)-Ru-Cl
C(1)-O(1)-Ru
C(9)-C(10)-Ru
O(2)-C(11)-Ru
F igu r e 1. Substrates and alkyne-inserted organometallics
of this work.
F igu r e 3. Spectral time evolution in the reaction of 1a
(1.27 × 10-4 M) with ha (9.97 × 10-3 M) in CH2Cl2-MeOH
(8.14 M in MeOH) solution at 308 K.
tures in the presence of a large excess (>10-fold) of xa
over 1a have revealed the rate law of eq 3, the pseudo-
F igu r e 2. ORTEP plot (30% probability ellipsoids) and
atom-labeling scheme for 3a .
rate ) kobs[1a ]
(3)
and 6.275(18) Å, respectively. The chelate ring is nearly
planar (mean deviation of 0.02 Å), and indeed, the
RuRL3 fragment excluding MeC6H5, Me, and CH2OH
groups is approximately planar (mean deviation of 0.04
Å). The Ru-C10 (sp2) bond is ∼0.2 Å longer than Ru-
C11 (sp) bond. The Ru-Cl bond is longer than usual
because of the trans influence of the σ-vinyl site as
observed previously.1
In ser tion Ra tes. These have been determined spec-
trophotometrically in CH2Cl2-MeOH mixtures over a
range of temperature. The two reactions studied in
detail are stated in eq 2. The spectra of the reacting
first-order rate constant kobs being proportional to the
concentration of xa. It was further observed that the
insertion process failed to proceed in pure CH2Cl2. This
prompted us to examine the rate as a function of
methanol concentration at constant xa concentration.
The rate was found to be proportional to the concentra-
tion of methanol. The consolidated concentration de-
pendence of kobs is stated in eq 4 where k′xa is a constant,
vide infra.
kobs ) k′xa[xa][MeOH]
(4)
1a + xa f 2a , 3a
(2)
(8) Chevalier, P.; Sandorfy, C. Can. J . Chem. 1960, 38, 2524. (b)
Bohme, H.; Haake, M. In Advances in Organic Chemistry; Bohme, H.,
Vieche, H. G., Eds.; Interscience: New York, 1976; Part 1, Vol. 9, p 1.
(c) Farvot, J .; Vocelle, D.; Sandorpy, C. Photochem. Photobiol. 1979,
30, 417. (d) Sandorfy, C.; Vocelle, D. Mol. Phys. Chem. Biol. 1989, 4,
195.
solutions (Figure 3, case of ha) are characterized by
multiple isosbestic points, strongly implicating9 that 1a
and the expanded metallacycle are the only stable
absorbing species. Studies in 2:1 CH2Cl2-MeOH mix-

Alkyne Insertion into a Four-Membered Metallacycle
Organometallics, Vol. 20, No. 7, 2001 1421
Ta ble 3. Ra te Da ta for Rea ction of 1a a n d h a in
CH2Cl2-MeOH Mixtu r e
a
T,
K
104[1a ], 103[ha], 103[ha][MeOH], 105kobs
,
103khaK,
M
M
M2
s-1
s-1 M-2
298
1.79
2.82
5.64
8.46
11.28
2.92
5.84
8.76
2.92
5.84
8.76
2.82
5.64
8.46
11.28
0.83
22.95
45.90
68.86
91.82
23.77
47.54
71.31
23.77
47.54
71.31
22.95
45.90
68.86
91.82
2.04
23.0(4)
43.0(3)
56.0(2)
74.0(3)
24.0(3)
52.0(2)
77.0(3)
35.0(1)
67.0(3)
98.0(4)
56.0(3)
108.0(4)
152.0(2)
205.0(4)
5.2(2)
7.2(4)
303
308
313
1.83
1.83
1.79
11.1(4)
13.2(1)
F igu r e 4. Plots of kobs vs [xa][MeOH] at 313 K: (+) ha;
(O) pa.
Ta ble 2. Ra te Da ta for Rea ction of 1a a n d p a in
22.0(3)
CH2Cl2-MeOH Mixtu r e
0.49
a
T,
K
104[1a ], 103[pa], 103[pa][MeOH], 105kobs
,
103kpaK,
6.14
10.24
18.43
16.0(3)
28.0(1)
41.0(3)
M
M
M2
s-1
s-1 M-2
308
1.11
1.32
2.64
3.96
5.28
1.29
2.58
3.87
5.16
0.50
10.74
21.49
32.23
42.98
10.50
21.00
31.50
42.00
1.23
3.3(1)
5.6(4)
2.6(4)
4.2(1)
a
Least-squares deviations are given in parentheses.
7.4(2)
11.9(1)
4.9(2)
9.9(1)
eq 4 is readily derived by combining eqs 3, 6, and 8, the
constant k′xa of eq 4 being related to K and kxa as in eq
9.
313
1.19
0.19
14.8(3)
18.2(3)
0.9(1)
k′xa ) Kkxa
(9)
3.70
1.9(3)
6.17
8.64
3.3(2)
4.8(4)
The value of k′xa increases with increasing tempera-
ture (Tables 2 and 3), and the Eyring equation is obeyed.
The corresponding activation enthalpies (∆H#) are 12.9-
(1.0) and 12.5(1.0) kcal mol-1 and the activation entro-
pies (∆S#) are -28.9(2.9) and -26.7(2.7) eu, respectively,
for the pa and ha insertions. The rate-determining step
is thus associative in nature. We have not succeeded,
however, in determining kxa and K separately, and both
quantities are expected to be temperature-dependent.
This has vitiated estimation of true activation param-
eters, which must relate only to kxa. It is possible,
however, to estimate genuine relative rate constants for
the pa and ha reactions with a given type 1 substrate
by virtue of eq 10, which follows from eq 9. Scrutiny of
1.38
1.10
9.61
1.32
2.64
3.96
5.28
1.29
2.58
3.87
5.16
71.11
10.74
21.49
32.23
42.98
10.50
21.00
31.50
42.00
30.1(1)
6.9(4)
14.7(1)
18.8(2)
27.0(1)
9.6(1)
17.0(3)
24.0(1)
32.0(2)
318
323
6.0(5)
7.1(1)
1.27
a
Least-squares deviations are given in parentheses.
The plots of observed rate constants vs [xa][MeOH]
encompassing large variations in the concentrations of
xa and MeOH are excellently (correlation factor of 0.99)
linear (Figure 4). Rate data are listed in Tables 2 (for
pa) and 3 (for ha).
k′ha kha
Meth a n ol Ad d u ct. The relation of eq 4 is consistent
with the presence of a methanol adduct occurring in
equilibrium, the equilibrium constant being K, eqs 5 and
6. The methanol adduct is taken as the reactive inter-
)
(10)
k′pa kpa
Table 2 reveals that at a given temperature kha ≈ 5kpa.
This is qualitatively reflected in the much higher slope
of the ha line in Figure 4.
1a + MeOH y
\
Kz 1a ‚MeOH
(5)
(6)
Rea ction Mod el. Solutions of 1a in CH2Cl2-MeOH
are nonconducting, and the insertion rate is not affected
by the presence of even large excess of (>10-fold)
chloride (Et4NCl/LiCl) and PPh3 in the reaction me-
dium. These observations militate against possible
displacement of chloride and phosphine ligands by
methanol. On the other hand, the Ru-O(phenolato)
bond in type 1 species is relatively weak and is known
to be readily displaced by Lewis bases.10 It is proposed
that methanol acts as a Lewis base, generating the
reactive adduct stylized as 4. Alkyne π-anchoring and
activation is believed to occur via displacement of
methanol as in 5. Rapid 2 + 2 addition between CtC
and Ru-C (aryl) and reestablishment of the Ru-
[1a ‚MeOH]
[1a ][MeOH]
K )
mediate as in eq 7, which is the rate-determining step
kxa
1a ‚MeOH + xa rds8 2a ,3a + MeOH
(7)
(rds). The corresponding rate law given in eq 8 is
characterized by the rate constant kxa. The relation of
rate ) kxa[1a ‚MeOH][xa]
(8)
(10) Ghosh, P.; Pramanik, A.; Chakravorty, A. Organometallics
1996, 15, 4147. (b) Ghosh, P.; Chakravorty, A. Inorg. Chem. 1997, 36,
64.
(9) Wilkins, R. G. Kinetics and Mechenism of Reactions of Transition
Metal Complexes, 2nd ed.; VCH: New York, 1991; p 156.

1422 Organometallics, Vol. 20, No. 7, 2001
Ghosh et al.
Ta ble 4. Obser ved Ra te Con sta n ts for th e
In ser tion of p a a n d h a in to Ru (RL1)(P P h 3)2(CO)Cl
for Differ en t R a t 313 K in CH2Cl2-MeOH Mixtu r ea
pa insertion
ha insertion
104[1a ], 104[pa], 103kobs
,
104[1a ], 104[ha], 103kobs
,
R
M
M
min-1
M
M
min-1
Me
Cl
OMe
0.15
0.15
0.17
4.1(1)
8.6(1)
3.8(1)
0.45
0.43
0.44
14.3(1)
24.7(3)
12.2(1)
4.68
9.20
a
[MeOH] ) 22.21 M.
of 1, the rate increasing with increasing electron with-
drawal (OMe < Me < Cl).
Exp er im en ta l Section
Ma ter ia ls. The compounds Ru(PPh3)3Cl2 and Ru(RL1)-
12
(PPh3)2(CO)Cl7 were prepared as reported. Phenylacetylene
and hydroxymethylacetylene (propargyl alcohol) were obtained
from Aldrich. The purification of dichloromethane and metha-
nol was done as described before.13 All other chemicals and
solvents were of analytical grade and were used as received.
P h ysica l Mea su r em en ts. Electronic and IR spectra were
recorded with a Shimadzu UV-1601PC spectrophotometer
(thermostated cell compartment) and Perkin-Elmer 783 IR
spectrophotometer. 1H NMR spectra were obtained using a
Bruker 300 MHz FT NMR spectrophotometer (tetramethylsi-
lane internal standard). Microanalyses (C, H, N) were done
by using a Perkin-Elmer 240 C elemental analyzer. Solution
electrical conductivity was measured by a Philips PR 9500
bridge using a platinized conductivity cell with a cell constant
of 1.0.
O(phenolato) bond complete the metallacycle expansion,
affording 2 or 3.
Space-filling models reveal that the 2 + 2 addition
reaction is subject to steric crowding1 from Cl and PPh3
ligands, and this can explain the regiospecificity of the
insertion reaction characterized by the addition of t
CX and tCH fragments, respectively, to the carbon and
metal ends of Ru-C bond.
To our knowledge, the only other reported kinetic
study of alkyne insertion into Ru-C bond concerns
certain orthoruthenated N,N-dimethylbenzylamine spe-
cies6 wherein, unlike in our system, the reaction in-
volves displacement of chloride by methanol.
Effect of Su bstitu en ts. The 2 + 2 addition process
involves nucleophilic attack on the metal. Electron
withdrawal from metal via the Schiff base ligand should
therefore make insertion more facile. The kobs (Table 4)
values for all three type 1 species were determined for
both pa and ha under invariant conditions of temper-
ature (40 °C) and concentrations (alkyne and MeOH).
The R substituents are found to affect kobs significantly,
and it increased with increasing electron withdrawal:
OMe < Me < Cl. Indeed, the plots of log kobs vs Hammett
constants11 of R are found to be linear for both pa and
ha insertions.
Electron-rich alkynes would be expected to insert
more quickly, as ha does compared to pa. The smaller
steric bulk of CH2OH compared to Ph is also an
advantage of ha over pa. The net observed effect is that
ha reacts 5 times faster than pa.
P r ep a r a tion of Com p lexes. Ru(RL3)(PPh3)2(CO)Cl com-
plexes were synthesized in nearly quantitative (∼98%) yield
by reacting Ru(RL1)(PPh3)2(CO)Cl in a CH2Cl2-MeOH mixture
with excess ha. Details of a representative case are given
below. The other compounds were prepared analogously.
[Ru (MeL3)(P P h 3)2(CO)Cl] (3a ). In a round-bottom flask
Ru(MeL1)(PPh3)2(CO)Cl (50 mg, 0.054 mmol) was dissolved in
a 2:1 (by volume) CH2Cl2-MeOH mixture and ha (30 mg, 0.536
mmol) was added to it. The mixture was stirred at 40 °C for
15 min on a magnetic stirrer. The color of the solution changed
from violet to green. When the solution was concentrated and
cooled, a green crystalline solid separated, which was collected,
washed thoroughly with methanol, and dried in vacuo. Yield,
52 mg (98%); mp, 152 °C. Anal. Calcd for RuC55H48NO3P2Cl:
C, 68.14; H, 4.99; N, 1.44. Found: C, 68.19; H, 4.91; N, 1.46.
1H NMR (CDCl3, δ): 6.44 (s, 1H arom), 6.34 (s, 1H, CdCH-
(Ru)), 3.71-3.79 (m, 2H, -CH2-), 2.29 (s, 1H, OH), 12.72 (m,
1H, dN+H), 7.04-7.92 (m, 35 H, arom and -HCdN+), 2.12
(s, 3H, -CH3), 2.29 (s, 3H, -CH3). IR (KBr, cm-1): ν(CdN)
1620; ν(CtO) 1900; ν(N-H, hexachlorobutadiene) 3440. UV-
vis (CH2Cl2, λmax, nm (ꢀ, M-1 cm-1)): 575 (2600), 420 (5070),
320 (8050).
Con clu d in g Rem a r k s
[Ru (ClL3)(P P h 3)2(CO)Cl] (3b). Yield, 51 mg (96%); mp,
155 °C. Anal. Calcd for RuC54H45NO3P2Cl2: C, 65.52; H, 4.58;
N, 1.42. Found: C, 65.57; H, 4.53; N, 1.45. 1H NMR (CDCl3,
δ): 6.43 (s, 1H arom), 6.33 (s, 1H, CdCH(Ru)), 3.71-3.79 (m,
2H, -CH2-), 2.31 (s, 1H, OH), 12.66 (m, 1H, dN+H), 7.11-
7.96 (m, 35 H, arom and -HCdN+), 2.11 (s, 3H, -CH3). IR
(KBr, cm-1): ν(CdN) 1610; ν(CtO) 1890; ν(N-H, hexachlo-
robutadiene) 3440. UV-vis (CH2Cl2, λmax, nm (ꢀ, M-1 cm-1)):
570 (4650), 420 (8850), 320 (14400).
The main finding of this work will now be sum-
marized. The insertion of ha into 1 has afforded the
expanded metallacycle 3 in nearly quantitative yields.
Rate studies in the cases of pa and ha in CH2Cl2-MeOH
mixtures have revealed that the reactive intermediate
is the methanol adduct 1‚MeOH presumably belonging
to structural type 4. The latter anchors and activates
the alkyne via displacement of MeOH as in 5. Sterically
controlled regiospecific 2 + 2 addition between CtC and
Ru-C (aryl) bonds follows, finally affording 2 and 3.
[Ru (MeOL3)(P P h 3)2(CO)Cl] (3c). Yield, 52 mg (98%); mp,
153 °C. Anal. Calcd for RuC55H48NO4P2Cl: C, 67.04; H, 4.91;
N, 1.42. Found: C, 67.01; H, 4.88; N, 1.43. 1H NMR (CDCl3,
Electronic and steric features make ha 5 times more
reactive than pa. The R substituents affect the reactivity
(12) Stephenson, T. A.; Wilkinson, G. J . Inorg. Nucl. Chem. 1966,
28, 945.
(11) Finar, I. L. Organic Chemistry, Vol. 1: Fundamental Principles,
6th ed.; ELBS, Longman Group: Essex, England, 1990; p 605.
(13) Vogel, A. I. Practical Organic Chemistry, 3rd ed.; ELBS and
Longman Group: Harlow, England, 1965; pp 176, 169.

Alkyne Insertion into a Four-Membered Metallacycle
Organometallics, Vol. 20, No. 7, 2001 1423
Ta ble 5. Cr yta l, Da ta Collection , a n d Refin em en t
P a r a m eter s for Ru (RL3)(P P h 3)2(CO)Cl, 3a
δ): 6.44 (s, 1H arom), 6.34 (s, 1H, CdCH(Ru)), 3.71-3.76 (m,
5H, -CH2- and -OMe), 2.31 (s, 1H, OH), 12.71 (m, 1H, d
N+H), 7.13-7.90 (m, 35H, arom and -HCdN+), 2.12 (s, 3H,
-CH3). IR (KBr, cm-1): ν(CdN) 1610; ν(Ct0) 1890; ν(N-H,
hexachlorobutadiene) 3440. UV-vis (CH2Cl2, λmax, nm(ꢀ, M-1
cm-1)): 570 (2460), 420 (4510), 320 (9120).
Ra te Mea su r em en ts. Measurements were carried out in
CH2Cl2-MeOH mixtures by observing the change in absor-
bances at 403 nm for pa and at 408 nm for ha. The kobs values
were calculated from a linear plot of -ln(At - A∞) vs t, where
At and A∞ are the absorbances at time t and at the end of
reaction (48 h), respectively. The activation enthalpy (∆H#) and
entropy (∆S#) were calculated from the variable-temperature
rate constant, using the Eyring equation, eq 11 (kB and h are
the Boltzmann constant and Planck’s constant, respectively).
mol formula
mol wt
cryst syst
space group
a, Å
C55H48ClNO3P2Ru
969.40
monoclinic
P21/c
14.655(8)
15.091(6)
21.949(14)
92.93(5)
4848(5)
4
b, Å
c, Å
â, deg
V, Å3
Z
λ, Å
0.710 73
4.88
1.328
µ, cm-1
D
calcd, g cm-3
Ra, wR2b [I > 2 σ(I)]
7.95, 18.19
R ) ∑|Fo| - |Fc|/∑|Fo|. wR2 ) [∑w(Fo - Fc2)2/∑(Fo2)2]1/2
.
a
b
2
-∆H#
RT
∆S#
R
kBT
k )
exp
exp
(11)
(
)
(
)
]
effects, and an empirical absorption correction14 was done on
the basis of an azimuthal scan of six reflections for the crystal.
The metal atom was located from Patterson maps, and the
rest of the non-hydrogen atoms emerged from successive
Fourier syntheses. The structures were refined by a full-matrix
least-squares procedure on F2. All non-hydrogen atoms were
refined anisotropically. Hydrogen atoms were included at
calculated positions. Calculations were performed using the
SHELXTL, version 5.03,15 program package. Significant crys-
tal data are listed in Table 5.
[
h
1
The plots of -ln[k′xah/(kBT)] vs
/
were satisfactorily linear
T
(correlation factor of 0.98). The curve fit and all other calcula-
tions were done with the Microcal Origin, version 4.0, software
package.
X-r a y Str u ctu r e Deter m in a tion . Single crystals of Ru-
(MeL3)(PPh3)2(CO)Cl, 3a (0.25 × 0.25 × 0.40 mm3) were grown
(at 298 K) by slow diffusion of hexane into dichloromethane
solution followed by evaporation. The crystals were inherently
poor in quality, giving rise to broadened diffraction peaks, and
only moderately good refinement could be achieved. The
thermal parameters are relatively high, especially for one
phenyl ring on the P1 atom. Cell parameters were determined
by a least-squares fit of 30 machine-centered reflections (2θ
) 15-30°). Data were collected with the ω-scan technique in
the range 3° e 2θ e 45° on a Siemens R3m/V four-circle
diffractometer with graphite-monochromated Mo KR radiation
(λ ) 0.710 73 Å). Two check reflections measured after every
198 reflections showed no significant intensity reduction in
any case. All data were corrected for Lorentz polarization
Ack n ow led gm en t. We thank the Department of
Science and Technology, Indian National Science Acad-
emy and the Council of Scientific and Industrial Re-
search, New Delhi, for financial support. Affiliation with
J awaharlal Nehru Centre for Advanced Scientific Re-
search, Bangalore, India, is acknowledged. We are
thankful to Prof. P. Banerjee for helpful discussions.
Su p p or tin g In for m a tion Ava ila ble: X-ray crystallogra-
phy files, in CIF format, for the structure determination of
3a . This material is available free of charge via the Internet
at http://pubs.acs.org.
(14) North, A. C. T.; Phillips, D. C.; Mathews, F. A. Acta Crystallogr.,
Sect. A 1968, 24, 351.
(15) Sheldrick, G. M. SHELXTL, version 5.03; Bruker Analytical
X-ray Systems: Madison, WI, 1994.
OM000649C