Correlation between Structural and Solution Calorimetric Data for Cp*Ru(PR3)2Cl (Cp* = C5Me5) Complexes

Article abstract of DOI:10.1021/om990090k

Single-crystal X-ray diffraction studies were conducted on the following compounds: Cp*Ru(PMe₃)₂Cl (1), Cp*Ru(PPhMe₂)₂Cl (2), Cp*Ru(PMePh₂)₂Cl (3), Cp*Ru(PPh₃)₂Cl (4),

Full text of DOI:10.1021/om990090k

Organometallics 1999, 18, 2357-2361
2357
Cor r ela tion betw een Str u ctu r a l a n d Solu tion
Ca lor im etr ic Da ta for Cp *Ru (P R3)2Cl (Cp * ) C5Me5)
Com p lexes
Dale C. Smith, J r., Christopher M. Haar, Lubin Luo, Chunbang Li,
Miche`le E. Cucullu, Charles H. Mahler,† and Steven P. Nolan*
Department of Chemistry, University of New Orleans, New Orleans, Louisiana 70148
William J . Marshall, Nancy L. J ones,‡ and Paul J . Fagan
Central Research and Development Department, E. I. DuPont de Nemours & Co., Inc.,
Experimental Station, P.O. Box 80328, Wilmington, Delaware 19880-0328
Received February 11, 1999
Single-crystal X-ray diffraction studies were conducted on the following compounds:
Cp*Ru(PMe3)2Cl (1), Cp*Ru(PPhMe2)2Cl (2), Cp*Ru(PMePh2)2Cl (3), Cp*Ru(PPh3)2Cl (4),
Cp*Ru(PEt3)2Cl (5), Cp*Ru(AsEt3)2Cl (6), Cp*Ru(PnBu3)2Cl (7), and Cp*Ru(dmpm)Cl (8).
Structural information obtained from these X-ray studies can be correlated with enthalpies
of ligand substitution previously determined from solution calorimetry. The cone angle of
the phosphine ligand (monodentate) and the Ru-P bond distance were found to be
proportional to the enthalpy of reaction.
In tr od u ction
mochemical studies have determined the enthalpy of
reaction values for a series of organoruthenium species5
formed in the general reaction depicted in eq 1.
Thermochemical measurements have been applied for
some time to the quantitative assessment of metal-
ligand interactions in organometallic systems.1 We have
been investigating the steric and electronic contribu-
tions present in tertiary phosphine and arsine-based
organoruthenium,2 organorhodium,3 and organoiron4
systems by means of solution calorimetry. Recent ther-
Cp*Ru(COD)Cl + 2L f Cp*Ru(L)2Cl + COD (1)
Cp* ) C5(CH3)5; COD ) cyclooctadiene; L ) ER3
(E ) As, P) or L2 ) bidentate phosphine
From this study it was found that the thermochemical
trends in this system can be analyzed in terms of a
predominant contribution from the Tolman cone angle6
of the incoming ligand. We therefore wondered if the
same trends were present in metrical parameters
obtained from single-crystal X-ray diffraction analysis
of the compounds formed in the prior investigation. This
paper discusses the correlation between the enthalpies
of ligand substitution with metrical parameters deter-
mined from single-crystal X-ray diffraction studies of
the following eight complexes: Cp*Ru(PMe3)2Cl (1),
Cp*Ru(PPhMe2)2Cl (2), Cp*Ru(PMePh2)2Cl (3), Cp*Ru-
(PPh3)2Cl (4), Cp*Ru(PEt3)2Cl (5), Cp*Ru(AsEt3)2Cl (6),
Cp*Ru(PnBu3)2Cl (7), and Cp*Ru(dmpm)Cl (8).
* To whom correspondence should be addressed. E-mail: snolan@
uno.edu.
† Permanent address: Lycoming College, Department of Chemistry,
Williamsport, PA 17701.
‡ Permanent address: Lasalle University, Department of Chemistry
and Biochemistry, Philadelphia, PA 19141.
(1) (a) Nolan, S. P. Bonding Energetics of Organometallic Com-
pounds. In Encyclopedia of Inorganic Chemistry; King, R. B., Ed.;
Wiley: New York, 1994. (b) Hoff, C. D. Prog. Inorg. Chem. 1992, 40,
503-561. (c) Martinho Simo˜es, J . A.; Beauchamp, J . L. Chem. Rev.
1990, 90, 629-688. (d) Marks, T. J ., Ed. Bonding Energetics In
Organotransition Metal Compounds; ACS Symp. Ser. 428; American
Chemical Society: Washington, DC, 1990. (e) Marks, T. J ., Ed. Bonding
Energetics In Organotransition Metal Compounds. Polyhedron 1988,
7. (f) Skinner, H. A.; Connor, J . A. In Molecular Stucture and
Energetics; Liebman, J . F., Greenberg, A., Eds.; VCH: New York, 1987;
Vol. 2, Chapter 6.
(2) For organoruthenium systems see: (a) Li, C.; Serron, S.; Nolan,
S. P. Organometallics 1996, 15, 4020-4029. (b) Serron, S. A.; Luo, L.;
Li, C.; Cucullu, M. E.; Nolan, S. P. Organometallics 1995, 14, 5290-
5297. (c) Serron, S. A.; Nolan, S. P. Organometallics 1995, 14, 4611-
4616. (d) Luo, L.; Li, C.; Cucullu, M. E.; Nolan, S. P. Organometallics
1995, 14, 1333-1338. (e) Cucullu, M. E.; Luo, L.; Nolan, S. P.; Fagan,
P. J .; J ones, N. L.; Calabrese, J . C. Organometallics 1995, 14, 289-
296. (f) Luo, L.; Zhu, N.; Zhu, N.-J .; Stevens, E. D.; Nolan, S. P.; Fagan,
P. J . Organometallics 1994, 13, 669-675. (g) Li, C.; Cucullu, M. E.;
McIntyre, R. A.; Stevens, E. D.; Nolan, S. P. Organometallics 1994,
13, 3621-3627. (h) Luo, L.; Nolan, S. P. Organometallics 1994, 13,
4781-4786. (i) Luo, L.; Fagan, P. J .; Nolan, S. P., Organometallics
1993, 12, 4305-4311. (j) Nolan, S. P.; Martin, K. L.; Stevens, E. D.;
Fagan, P. J . Organometallics 1992, 11, 3947-3953.
Resu lts a n d Discu ssion
All Cp*RuCl(L)2 compounds have a central ruthenium
atom coordinated by four groups: Cp*, Cl, and the two
(4) For organorhodium systems see: (a) Haar, C. M.; Huang, J .;
Nolan, S. P. Organometallics 1998, 17, 5018-5024. (b) Huang, J .; Haar,
C. M.; Nolan, S. P.; Marshall, W. J .; Moloy, K. G. J . Am. Chem. Soc.
1998, 120, 7806-7815. (c) Serron, S.; Nolan, S. P.; Moloy, K. G.
Organometallics 1996, 15, 534-539.
(5) Luo, L.; Nolan, S. P.; Fagan, P. J . Organometallics 1993, 12,
4305-4311.
(6) (a) Tolman, C. A. Chem. Rev. 1977, 77, 313-348. (b) Manzer, L.
E.; Tolman, C. A. J . Am Chem. Soc. 1975, 97, 1955-1956. (c) Tolman,
C. A.; Reutter, D. W.; Seidel, W. C. J . Organomet. Chem. 1976, 117,
C30-C33.
(3) For organoiron systems see: (a) Li, C.; Stevens, E. D.; Nolan, S.
P. Organometallics 1995, 14, 3791-3797. (b) Li, C.; Nolan, S. P.
Organometallics 1995, 14, 1327-1331. (c) Luo, L.; Nolan, S. P. Inorg.
Chem. 1993, 32, 2410-2415. (d) Luo, L.; Nolan, S. P. Organometallics
1992, 11, 3947-3951.
10.1021/om990090k CCC: $18.00 © 1999 American Chemical Society
Publication on Web 05/18/1999

2358 Organometallics, Vol. 18, No. 12, 1999
Smith et al.
Ta ble 1. En th a lp ies of Su bstitu tion for
Cp *Ru (COD)Cl + 2L f Cp *Ru (L)2Cl + COD
a
a
∆Hrxn
∆Hrxn
complex
L
(kcal/mol) complex
L
(kcal/mol)
1
2
3
4
PMe3
-32.2(4)
-31.8(3)
-29.4(2)
-22.9(4)
5
6
7
8
PEt3
-27.2(2)
-15.0(2)
-26.0(2)
-33.8(3)
PPhMe2
MePh2
PPh3
AsEt3
PnBu3
dmpm
a
Enthalpy values are provided with 95% confidence limits.
F igu r e 2. ORTEP diagram of Cp*Ru(PPhMe2)2Cl (2) with
ellipsoids drawn at 30% probability.
F igu r e 1. ORTEP diagram of Cp*Ru(PMe3)2)Cl (1) with
ellipsoids drawn at 30% probability.
F igu r e 3. ORTEP diagram of Cp*Ru(PMePh2)2Cl (3) with
ellipsoids drawn at 30% probability.
pnictide atoms (either as two separate monodentate
ligands or as the two coordinating atoms of a bidentate
chelate). Therefore, any variation in structures should
be attributed chiefly to the steric and electronic effects
of the pnictide ligand(s). In each case, the enthalpy of
ligand substitution in the reaction leading to formation
of the product has been reported and is summarized in
Table 1.5
Solid -Sta te Str u ctu r es of Cp *Ru (P Me3)2Cl (1),
Cp*Ru (P P h Me2)2Cl (2), Cp*Ru (P MeP h 2)2Cl (3), an d
Cp *Ru (P (P h )3)2Cl (4). Complexes 1-47 differ only in
the number of phenyl (C6H5) and methyl (CH3) groups
on the phosphine ligands. As expected, complexes 1, 3,
and 4 crystallized in centrosymmetric space groups;
Cp*Ru(PPhMe2)2Cl (2), however, crystallizes in the
acentric space group Cmc21 (No. 36), indicating that the
compound in the crystal is an optically pure enantio-
morph. The absolute configuration of 2 was assigned to
the enantiomorph which yielded the lowest R value
during least-squares refinement (see Experimental Sec-
tion). The ORTEP depictions of 1-4 are respectively
given in Figures 1-4. Bond distances and angles are
given in Table 2.
F igu r e 4. ORTEP diagram of Cp*Ru(PPh3)2Cl (4) with
ellipsoids drawn at 30% probability.
substitution (-32.2, -31.8, -29.4, -22.9 kcal/mol).
However, a dissimilar trend is observed between the
Ru-Cp*(centroid) distances, where 1 < 3 < 4 < 2, and
this trend does not correlate with enthalpy data. As
expected, the P(1)-Ru-P(2) angle is the smallest
(91.08°) in 1 and the largest in 4 (96.8°). Interestingly,
the P(1)-Ru-P(2) angle does not correlate with the cone
angle of the phosphine ligand for 2 and 3. The P(1)-
Ru-P(2) angle is slightly larger in 2 (94.5°) than in 3
(93.0°), even though the cone angle of PMe2Ph (122°) is
much smaller than that of PMePh2 (136°).6
Average Ru-P bond distances increase in the order
1 < 2 < 3 < 4 (2.293, 2.297, 2.310, 2.342 Å), while the
Ru-Cl distances for these complexes are nearly identi-
cal. The Ru-P distances in 1-4 are consistent with the
electron-donor properties of phosphine ligands and
previously determined trends in the enthalpies of ligand
(7) In the course of the revision of this paper we became aware of
the determination of 4 by Professor Paz-Sandoval’s group: Guzei, I.
A.; Paz-Sandoval, M. A.; Torres-Lubian, R.; J uarez-Saavedra, P. Acta
Crystallogr., Sect. C, submitted for publication.

Cp*Ru(PR3)2Cl Complexes
Organometallics, Vol. 18, No. 12, 1999 2359
Ta ble 2. Selected Bon d Len gth s a n d An gles in th e In n er Coor d in a tion Sp h er e of th e Com p lexes
Cp *Ru (L)2Cla
1
2
3
4
5
6b
7
8
Ru-P, Å
2.2923(9)
2.3015(9)
2.4526(8)
1.860(3)
118
91.08(3)
85.30(3)
91.54(3)
127.0(1)
128.0(1)
2.297(1)
2.2986(10)
2.3213(9)
2.4522(9)
1.872(3)
136
93.02(3)
86.8(1)
94.04(3)
129.7(1)
124.9(1)
2.3379(6)
2.3464(5)
2.4583(6)
1.890(3)
145
96.8(1)
87.9(1)
93.4(1)
126.4(1)
125.2(1)
b
2.3097(9)
2.3318(9)
2.4512(8)
1.880(3)
132
2.442(1)
2.449(1)
2.478(2)
1.810(8)
128
98.1(3)
85.4(2)
83.7(2)
127.0(2)
125.7(2)
2.346(1)
2.338(1)
2.456(1)
1.871(4)
132
100.1(2)
86.3(1)
88.6(1)
126.0(1)
124.7(1)
2.2811(9)
2.2865(9)
2.4493(8)
1.837(3)
NA
Ru-Cl, Å
Ru-Cp*, Å
2.451(2)
1.896(5)
122
94.5(2)
89.62(5)
89.62(5)
125.4(2)
125.4(2)
cone angle, deg
P-Ru-P, deg
P(1)-Ru-Cl, deg
P(2)-Ru-Cl, deg
Cp*-Ru-P(1), deg
Cp*-Ru-P(2), deg
a
92.8(1)
70.8(2)
90.5(1)
88.2(1)
125.2(1)
130.8(1)
86.0(1)
86.0(1)
135.9(1)
135.5(1)
Complete structural details are provided as Supporting Information. Parameters referring to P represent As in this complex.
distance is longer in 6 (2.478 Å) than in 5 (2.456 Å).
These structural features reflect the larger size of As
vs P and the greater steric bulk of the triethylarsine
ligand compared to the triethylphosphine ligand. This
increased steric bulk can also be seen in the E-Ru-E
angles of each, with the arsine angle (98.1°) greater than
that of the phosphine (92.8°). Interestingly, the cone
angles for these two ligands, while similar (128° for As,
132° for P), would lead one to predict the opposite trend
for the E-Ru-E angles. Electronic factors must also
be at play here. While the Ru-Cl distance in 5 is 0.022
Å shorter than in 6, the Ru-Cp*(centroid) distances
differ by nearly 0.07 Å, where the phosphine complex 5
displays a longer distance (1.880 Å) than the arsine
complex 6 (1.811 Å). This donor trend is consistent with
the current understanding of electronic contributions
from these ligands.5 Enthalpy measurements reveal
that triethylarsine complex 6 forms a less stable com-
plex (∆Hrxn ) -15.0 kcal/mol vs -27.2 kcal/mol for the
triethylphosphine complex 5). Thus, 6 is a poorer donor,
F igu r e 5. ORTEP diagram of Cp*Ru(PEt3)2Cl (5) with
permitting the Cp* ligand to donate more electron
ellipsoids drawn at 30% probability.
density to the metal, which is consistent with the
shorter Ru-Cp*(centroid) distance found in 6 (1.810 Å)
compared to that found in 5 (1.880 Å). These structural
features are quite similar to those of the analogous
CpRuCl(EEt3)2 complexes that have been previously
reported.8
Solid -Sta te Str u ctu r es of Cp *Ru (P n Bu 3)2Cl (7)
a n d Cp *Ru (d m p m )Cl (8). The organoruthenium com-
plex 7 crystallizes in the monoclinic space group P21/c
(No. 14) and has four molecules per unit cell. The
ORTEP depictions of 7 and 8 are respectively given in
Figures 7 and 8. Complexes 1, 5, and 7 differ in the
n
types of alkyl substituents (Me, Et, Bu). As expected,
comparison of the Ru-P bond lengths of 1, 5, and 7 finds
that the trimethylphosphine ligand in 1 has a shorter
average Ru-P bond length (2.2969 Å) and is thermo-
dynamically more stable (-32.2 kcal/mol) than either
the triethylphosphine complex 5 (2.320 Å and -27.2
kcal/mol) or the tri-n-butylphosphine complex 7 (2.342
F igu r e 6. ORTEP diagram of Cp*Ru(AsEt3)2Cl (6) with
Å and -26.0 kcal/mol). However, a different trend is
ellipsoids drawn at 30% probability.
observed between the Ru-Cp*(centroid) distances, where
Solid -Sta te Str u ctu r es of Cp *Ru (P Et3)2Cl (5) a n d
Cp *Ru (AsEt3)2Cl (6). Compounds 5 and 6 differ only
in the pnictide atom in the EEt3 ligand (E ) As, P). The
structures of 5 and 6 are similar: both are monoclinic
and crystallize in the same space group (No. 14),
although with different settings (P21/c and P21/n, re-
spectively). The ORTEP depictions of 5 and 6 are
respectively given in Figures 5 and 6. As expected, the
average Ru-E distance is longer for E ) As (2.446 Å)
than for E ) P (2.321 Å) and similarly the Ru-Cl
1 < 7 < 5, which does not correlate with enthalpy data.
The P(1)-Ru-P(2) bond angles (91.08° for 1; 92.8° for
5; 100.1° for 7) in this case follow the trends expected
from the cone angles (118° for the smaller PMe3 versus
132° for both the bulkier PEt3 and PnBu3 ligands).6
Cp*Ru(dmpm)Cl (8) crystallizes in the orthorhombic
space group Pbca (No. 61), with one molecule in the
(8) Cucullu, M. E.; Luo, L.; Nolan, S. P.; Fagan, P. J .; J ones, N. L.;
Calabrese, J . C. Organometallics 1995, 14, 289-296.

2360 Organometallics, Vol. 18, No. 12, 1999
Smith et al.
F igu r e 9. Plot of the cone angle (θ) versus the -∆H values
of reaction (kcal/mol) for the Cp*Ru(L)2Cl complexes (slope
-2.42; R ) 0.893).
F igu r e 7. ORTEP diagram of Cp*Ru(PnBu3)2 Cl (7) with
ellipsoids drawn at 30% probability.
F igu r e 10. Plot of the Ru-P bond distance (Å) versus the
-∆H values of reaction (kcal/mol) for the Cp*Ru(L)2Cl
complexes (slope -2.48; R ) 0.971).
can be used to indicate the relative contribution of steric
and electronic effects in these transition-metal systems.
Our previous work has examined a number of systems
involving ruthenium, and we have been able to measure
the enthalpies of reaction for these Cp*Ru(PR3)2Cl
complexes, thereby determining the order of stability
of complexes formed.5 For bond lengths of the inner
coordination sphere of the Cp*Ru(L)2Cl complexes, no
substantial correlation was found between the Ru-Cl
bond lengths and the enthalpy of reaction. In fact, the
Ru-Cl bond distance varies only slightly (2.453 ( 0.002
Å) over the range of P-ligand complexes 1-5, 7, and 8.
Additionally, no correlation was found between the
Ru-Cp* (centroid) distance and the enthalpy of reac-
tion. A straightforward relationship, as illustrated in
Figure 9, appears to exist between the cone angle and
the enthalpy of ligand substitution, with smaller ligands
forming the most stable complexes. As shown in Figure
10, however, a higher degree of correlation exists
between the reaction enthalpies and the Ru-P bond
distances. The Ru-P bond length data used in this and
associated relationships are the average of the two
Ru-P bond lengths found in each complex. The reaction
enthalpies involved in this correlation are directly
related to Ru-P bond dissociation enthalpies, Figure
10 is in fact a bond length-relative bond dissociation
enthalpy correlation.10 It is noteworthy that this rela-
tionship between the reaction enthalpies and the Ru-P
bond distances appears insensitive to substituents and
holds for triaryl, trialkyl, or mixed phosphines, and even
F igu r e 8. ORTEP diagram of Cp*Ru(dmpm)Cl (8) with
ellipsoids drawn at 30% probability.
asymmetric unit and eight in the unit cell. Apparently,
8 is more stable (-33.8 kcal/mol) than Cp*Ru(PMe3)2-
Cl (1) (-32.2 kcal/mol); this greater stability is reflected
in the average Ru-P bond distance in 8 (2.284 Å), which
is shorter than the average Ru-P distance in 1 (2.297
Å). Ring strain reflecting the constricted “bite”9 of the
chelating dmpm is obvious from the distorted P(1)-
C(31)-P(2) angle within the ligand of 91.6° and the
small P(1)-Ru-P(2) angle of 70.8°.
Cor r elation Between Str u ctu r al P ar am eter s an d
Solu t ion Ca lor im et r ic Da t a for Cp *R u (P R 3)2Cl
Com p lexes. We have already seen in organoruthe-
nium,2 organorhodium,3 and organoiron4 tertiary phos-
phine and arsine based systems that steric, electronic,
and structural parameters such as the Tolman6 cone
angle (θ) and electronic parameter (ø) and metal-ligand
bond lengths can be fitted to linear correlations involv-
ing solution thermochemical data. These correlations
(9) Casey, C. P.; Whiteker, G. T.; Campana, C. F.; Powell, D. R.
Inorg. Chem. 1990, 29, 3376-3381.

Cp*Ru(PR3)2Cl Complexes
Organometallics, Vol. 18, No. 12, 1999 2361
Ta ble 3. Cr ysta llogr a p h ic Da ta for th e Com p lexes Cp *Ru (L)2Cl
6b
1
2
3
4
5
7
8
formula
fw
C16H33ClP2Ru C26H37ClP2Ru C36H41ClP2Ru C46H45ClP2Ru C22H45ClP2Ru C22H45ClAs2Ru C34H69ClP2Ru C15H29ClP2Ru
423.94
548.08
672.22
796.37
508.10
595.99
676.43
407.90
color
orange
Pcba (61)
orange
Cmc21 (36)
orange
P21/c (14)
red-orange
P21/c (14)
red-orange
P21/c (14)
orange
P21/n (14)
orange
P21/c (14)
orange
Pcba (61)
space
groupa
a, Å
b, Å
c, Å
15.510(4)
15.634(2)
16.345(3)
90
15.749(3)
12.719(3)
13.080(3)
90
10.254(1)
18.584(2)
17.163(3)
100.73(1)
4
17.166(1)
10.726(1)
20.603(1)
101.64(1)
4
15.252(4)
10.403(3)
15.751(4)
97.73(1)
4
10.683(3)
15.987(4)
15.796(4)
106.91(2)
4
14.588(3)
15.987(4)
16.099(4)
92.40(2)
4
13.933(2)
15.7381(9)
16.678(2)
90
â, deg
formula
8
4
8
units/cell
Rb
0.032
0.031
error of fit 1.14
0.036
0.037
1.39
0.034
0.032
1.05
0.030
0.037
2.11
0.030
0.030
1.13
0.044
0.037
1.16
0.052
0.049
1.60
0.026
0.030
1.24
b
Rw
a
b
The number given in parentheses is the space group number from the International Tables of X-Ray Crystallography. R ) ∑(||Fo|
- |Fc||)/∑|Fo|; Rw ) ∑w(|Fo| - |Fc|)2/∑w|Fo| .
2
less than 1 ppm of oxygen and water. The thermochemical data
have been previously reported.5
for the bidentate phosphine ligand dmpm, despite the
clearly different nature of the latter. The correlation
between crystalline Ru-P distances and solution ther-
mochemical measurements suggests that longer bonds
are associated with less exothermic reactions. This trend
(dmpm > PMe3 > PPhMe2 > PPh2Me > PEt3 > PnBu3
> PPh3) can be explained in terms of the steric and
electronic contributions of the donor P-ligands.6
While there are no other significant correlations
between the enthalpy of reaction and structural param-
eters, as can be expected, there is a correlation between
the P(1)-Ru-P(2) angle and the average P-Ru-Cp*-
(centroid) angle. The P(1)-Ru-P(2) angle can be used
as a measure of the steric bulk of the pnictide ligands,
with a greater angle expected as the ligand occupies
more space. Thus, as the P(1)-Ru-P(2) angle and the
distance between the P atoms increases, the pnictide
ligands move closer to the Cp* group. This in turn
causes the average P-Ru-Cp*(centroid) angle (and the
distance between the pnictide ligands and the Cp*-
(centroid)) to decrease as the Cp* and P-ligands move
closer together.
Complexes 1-8 and Cp*Ru(COD)Cl were synthesized ac-
cording to literature methods.5,12 A general procedure involved
charging a flask with Cp*Ru(COD)Cl, an excess of ligand, and
dry THF as solvent. After the mixture was stirred for about 2
h, the solvent was removed under vacuum. Hexane was
vacuum-transferred to the cooled (-78 °C) flask; the solution
was then warmed to room temperature, stirred, and then
filtered. The solution was then cooled to -78 °C very slowly.
After overnight cooling, cold filtration yielded single crystals
of suitable quality for X-ray diffraction study.
Str u ctu r e Deter m in a tion a n d Cr ysta llogr a p h ic Da ta .
Crystallographic information for all complexes, including cell
dimensions and details of the data collection, are given in Table
3. For each compound, a suitable crystal was mounted on the
glass fiber of a goniometer head in a random orientation and
placed in the cold stream of N2 in an automated diffractometer
using Mo KR radiation. The cell dimensions were determined
in each case from at least 25 centered reflections, and data
were collected. Standard reflections were monitored during
data collection. For complexes 2, 4, 5, and 6 an azimuthal
absorption correction was applied.
The structures were solved by direct methods using either
the SHELXS or MULTAN programs. Each structure was
refined in a full-matrix least-squares refinement on F, using
anomalous terms for Ru, Cl, and As or P, with all non-
hydrogen atoms refined anisotropically. In each case, hydrogen
atoms were located from a Fourier difference map and used
as the basis of H atom positions in the final structure. While
the H atoms in 8 were able to be refined, all the other
structures have idealized and fixed H atoms, after attempts
to refine them proved unsatisfactory. ORTEP diagrams of each
structure are given in Figures 1-8. Selected bond distances
and angles are given in Table 2. Positional and equivalent
isotropic parameters for all non-hydrogen atoms are given as
Supporting Information.
Con clu sion
Single-crystal X-ray diffraction studies of several
Cp*Ru(ER3)2Cl systems have been performed in order
to correlate structural parameters with enthalpies of
ligand substitution. Among this series of complexes,
reaction enthalpies correlate well with Ru-P bond
distances but somewhat weakly with phosphine cone
angle. Other relationships are not as straightforward,
pointing out that various other factors (e.g., electronic
or reorganizational) may also be operative and that they
influence the structural chemistry and thermochemistry
of this system in different ways.11
Ack n ow led gm en t. S.P.N. acknowledges the Na-
tional Science Foundation and DuPont (Educational Aid
Grant) for financial support of this research.
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All manipulations involving
organoruthenium complexes were performed under an inert
atmosphere of argon or nitrogen, using standard high-vacuum
or Schlenk techniques, or in a MBraun glovebox containing
Su p p or tin g In for m a tion Ava ila ble: Details of the crys-
tal structure determinations for complexes 1-8. This material
is available free of charge via the Internet at http://pubs.acs.org.
(10) For the description of such relationships see for example:
Burrow, R. A.; Farrar, D. H.; Hao, J . B.; Lough, A.; Mourad, O.; Poe,
A. J .; Zheng, Y. Polyhedron 1998, 17, 2907-2919 and references cited
therein.
(11) Huang, J .; Haar, C. H.; Nolan, S. P.; Marshall, W. J .; Moloy,
K. G. J . Am. Chem. Soc. 1998, 120, 7806-7815.
OM990090K
(12) Fagan, P. J .; Mahoney, W. S.; Calabrese, J . C.; Williams, I. D.
Organometallics 1990, 9, 1843-1852.