New synthesis of [RuH(CO)(PPh3)2L2][BF4] [L2 = 2py, 2(4-Mepy) or bpy] and X-ray crystal structure of [RuH(CO)(PPh3)2(4-Mepy)2][BF4]

Article abstract of DOI:10.1016/S0020-1693(98)00355-7

The title compounds were prepared by reaction of RuH₂(CO)(PPh₃)₃ with [C₇H₇][BF₄] in the presence of excess pyridine, 4-picoline or 2,2′-bipyridine. The compounds were characterized by IR,

Full text of DOI:10.1016/S0020-1693(98)00355-7

Inorganica Chimica Acta 285 (1999) 318±321
Note
New synthesis of [RuH(CO)(PPh3)2L2][BF4]
[L2 ˆ 2py, 2(4-Mepy) or bpy] and X-ray crystal
structure of [RuH(CO)(PPh3)2(4-Mepy)2][BF4]
Donald F. Mullica, J. Matt Farmer, Jason A. Kautz, Stephen L. Gipson*,
Yohannes F. Belay, Mark S. Windmiller
Department of Chemistry, Baylor University, Waco, TX 76798, USA
Received 27 May 1998; accepted 28 July 1998
Abstract
The title compounds were prepared by reaction of RuH2(CO)(PPh3)3 with [C7H7][BF4] in the presence of excess pyridine, 4-picoline or
1
2,20-bipyridine. The compounds were characterized by IR, H and 31P NMR, and X-ray crystallography (for the 4-Mepy complex). The
spectroscopic data as well as the results of the X-ray crystal structure show that the complexes contain trans-oriented phosphines and cis-
pyridines. Details of the structural content and selected bond distances and angles are internally consistent. # 1999 Elsevier Science S.A.
All rights reserved.
Keywords: Crystal structures; Ruthenium complexes; Hydride complexes; Carbonyl complexes; Pyridine complexes
1. Introduction
drying agents and stored under nitrogen. The complex
RuH2(CO)(PPh3)3 was prepared according to the literature
procedure [5]. IR spectra were obtained using a Mattson
Instruments Cygnus 100 FTIR and 1H and 31P NMR spectra
were obtained on a Bruker AMX 360 NMR spectrometer.
NMR chemical shifts are referenced to residual protons
We recently reported the conversion of OsH2(CO)(PPh3)3
‡
to [OsH(CO)(PPh3)2L2] (L ˆ pyridine or 4-tert-butylpyr-
idine) by means of oxidation, hydride abstraction, and
protonation [1]. The hydride abstraction route proved to
be particularly convenient and we wondered if it might be
applicable to the analogous ruthenium complexes as well.
1
in the solvent (for H) or 85% H3PO4 external standard
(for 31P).
‡
Complexes of the type [RuH(CO)(PR3)2L2] (R ˆ Ph, 4-
MeC6H4; R3 ˆ MePh2; L2 ˆ 2py, 2DMAP, bpy, phen, Cy-
DAB) have been previously prepared by the reaction of
RuHCl(CO)(PR3)3 with the N-donor ligands [2,3]. We
anticipated that our hydride abstraction route might provide
a more convenient synthesis of these hydride complexes
which may ®nd use in catalytic hydrogenation reactions
[2±4].
2.2. Preparation of [RuH(CO)(PPh3)2L2][BF4]
A solution of RuH2(CO)(PPh3)3 (0.15 g, 0.16 mmol) and
pyridine (52 ml, 0.64 mmol) for 1, 4-picoline (62 ml,
0.64 mmol) for 2, or 2,20-bipyridine (0.050 g, 0.32 mmol)
for 3 in 10 ml of freshly distilled THF was prepared under
argon. To this solution [C7H7][BF4] (0.043 g, 0.24 mmol)
was added. The solution was then stirred at room tempera-
ture for a minimum of 6 h, during which time a precipitate
was formed (1, 2 ˆ white; 3 ˆ yellow). The precipitate was
separated by ®ltration and washed with ether. Crude yield:
0.11 g 1; 0.12 g 2; 0.13 g 3. The crude products were
dissolved in CH2Cl2 and ®ltered into a ¯ask containing
THF. CH2Cl2 was removed under reduced pressure to yield
recrystallized products. Yield after recrystallization: 0.093 g
1 (65%); 0.092 g 2 (62%); 0.12 g 3 (81%). Anal. Calc. for
2. Experimental
2.1. Materials and general methods
All syntheses were carried out under argon using Schlenk
techniques. All solvents were distilled from appropriate
*Corresponding author. Tel.: +1-254-710-3311; fax: +1-254-710-2403.
0020-1693/99/$ ± see front matter # 1999 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(98)00355-7

D.F. Mullica et al. / Inorganica Chimica Acta 285 (1999) 318±321
319
Table 1
removal of the check re¯ections, the averaging of duplicate
and equivalent data was carried out (Rint ˆ 0.052). The
remaining intensity data were corrected for Lorentz, polar-
ization and X-ray absorption effects [6] (max., min., trans-
mission factors ˆ 0.9908, and 0.5461). Systematic absences
of 0k0 where k ˆ 2n ‡ 1 and h0l where l ˆ 2n ‡ 1 were
consistent with space group P21/c. A zero moment test (NZ-
test) [7] on the observed data set indicated that it was
centrosymmetric in nature.
Experimental and statistical summary of compound 2
Molecular formula
Formula weight
Crystal system
Space group
C49H45BF4N2OP2Ru
927.7
monoclinic
P21/c (No. 14, C25h
15.395(3)
18.156(4)
17.352(3)
110.53(3)
4542.0(15)
4
)
Ê
a (A)
Ê
b (A)
Ê
c (A)
ꢄ (8)
V (A )
Ê 3
The phase problem was resolved by using the Siemens
SHELXTL PLUS (PC version) [8] which located the heavy atom
(Ru). A series of difference Fourier maps located the atomic
positions of the phosphorous, nitrogen, carbon, and oxygen
atoms. These positions were re®ned isotropically for several
full-matrix least-squares cycles before attempting to locate
the BF4 anion, which was subsequently located by electron
density mapping. Hydrogen atoms at calculated positions
Z
3
Dcalc. (Mg m
Dmeas. (Mg m
)
1.357
3
)
1.351(3)
0.459
1
)
ꢅ (Mo Ka) (mm
F(000) (e )
2ꢂ Range (8)
Á! (8) (!±2ꢂ)
Rint
1904
3.0±40.0
1.15 ‡ 0.34 tan ꢂ
0.052
R (Rw, Rall
)
0.070 (0.091, 0.094)
Ê
(C±H, 0.96 A) on the phenyl rings and the 4-picoline groups
Unique reflections
3131
1.3(9)
560
Extinction correction (e 2)(Â 10
No. variable parameters
Goodness-of-fit
)
4
were allowed to ride on their respective bonding atoms with
3
Ê 2
®xed isotropic thermal parameters, Uiso ˆ 80  10 A .
1.24
Ê
The hydride was also positioned at a distance of 1.78 A (Ru±
3
Ê 2
H, Uiso ˆ 80  10 A ). Several cycles varying the aniso-
C49H45BF4N2OP2RuÁC4H8O (2ÁTHF): C, 63.67; H, 5.34; N,
tropic thermal parameters of all non-hydrogen atoms
and applying a secondary correction to the data yielded
®nal residual index values, R ˆ ÆÁF=ÆFo and Rw ˆ
2.80. Found: C, 63.88; H, 5.61; N, 2.78%. IR (mineral oil):
ꢀ
max (cm 1) (CO) 1 ˆ 1938 (1934 [2]); 2 ˆ 1933; 3 ˆ 1954
2
(1950 [2]). NMR (CD2Cl2): 1 ˆ ꢁH 6.6±7.8 [40H, m, py/
PPh3] and 13.0 [1H, t, JPH 19.8, RuH] ( 12.1, JPH 19.5
[2]); ꢁP 49.8 [s, PPh3]; 2 ˆ ꢁH 6.4±7.6 [38H, m, 4-Mepy/
PPh3], 2.2 [3H, s, Me], 2.1 [3H, s, Me] and 13.0 [1H, t, JPH
20.0, RuH]; ꢁP 49.5 [s, PPh3]; 3 ˆ ꢁH 6.4±8.6 [38H, m, bpy/
PPh3] and 11.3 [1H, t, JPH 19.6, RuH] ( 11.4, JPH 19.2
[2]); ꢁP 48.5 [s, PPh3]. Single crystals for X-ray analysis
were prepared by layering diethyl ether over a solution of 2
in CH2Cl2.
ÆwÁF=ÆwÁFo where ÁF ˆjjFo Fcjj and w ˆ ꢃ
(Fo ), see Table 1. A ®nal difference Fourier map revealed
3
a maximum peak of 1.07 e A in the vicinity of the Ru
Ê
atom which is quite normal in compounds containing heavy
metals. Elsewhere, the map was virtually featureless dis-
playing only a random ¯uctuating background. Atomic
scattering factors and associated anomalous dispersion cor-
rections were obtained from the usual source [9].
3. Results and discussion
2.3. Crystallographic study of 2
3.1. Synthesis and spectroscopy of
[RuH(CO)(PPh3)2L2][BF4]
Conoscopic examination of 2 using crystal rotation
between two crossed polarizers on a Zeiss Photomicroscope
(II) provided evidence that the system was biaxial (aniso-
tropic in nature, birefringent) and optically homogeneous.
Data were collected from a clear colorless parallelepiped-
shaped crystal (0.36 mm  0.08 mm  0.49 mm). An
Enraf-Nonius CAD4-F automated diffractometer equipped
with graphite-monochromated Mo Ka radiation was em-
ployed, see Table 1 for crystal data and solution details. A
least-squares re®nement of 25 well centered high angle
(30.0 ꢀ 2ꢂ ꢀ 50.08) re¯ections yielded ®nal lattice para-
meters. Crystal stability and hardware reliability were ver-
i®ed by monitoring three standard re¯ections as a function
It has been shown previously that OsH2(CO)(PPh3)3 can
‡
be converted to [OsH(CO)(PPh3)2py2] and related com-
plexes by oxidation, hydride abstraction, and protonation,
all performed in CH2Cl2 in the presence of an excess of a
pyridine type ligand [1]. The second pyridine apparently
substitutes for one PPh3 after the ®rst pyridine replaces a
hydride in the oxidation, hydride abstraction, or protonation
step. It was subsequently found that the ruthenium analog,
RuH2(CO)(PPh3)3, reacts similarly with hydride abstractors
in CH2Cl2 in the presence of pyridine type ligands. Upon
further investigation THF proved to be a more convenient
solvent for the reaction since the product, [RuH-
(CO)(PPh3)2L2][BF4], spontaneously precipitates from this
solvent. Tropylium tetra¯uoroborate, [C7H7][BF4], was
more reactive than triphenylcarbenium and so was used
as the hydride abstractor in the present study. As formed, the
Ru±pyridine complexes contain a small amount of an
1
of time (every h). An intensity loss of 0.04% h (1.8%,
total decay) was observed which required a linear decay
correction to the data set (maximum correction of 1.00933,
average 1.00451) using the program DECAY [6]. A total of
4410 intensity measurements were collected of which 4222
were independent and 3131 ®tted F > 6.0ꢃ(F). After the

320
D.F. Mullica et al. / Inorganica Chimica Acta 285 (1999) 318±321
insoluble brown impurity which is easily separated by
recrystallization from CH2Cl2 and THF. When large
excesses of [C7H7][BF4] are used the product also contains
signi®cant amounts of species derived from the reaction of
the tropylium with PPh3 and/or the excess pyridine ligand.
These products are more dif®cult to separate from the
organometallic product and so large excesses of hydride
abstractor should be avoided. The complexes 1 (L ˆ py), 2
(L ˆ 4-Mepy) and 3 (L2 ˆ bpy) are stable in the air for
extended times, but decompose rapidly in solution in the
presence of air.
The infrared spectra of complexes 1, 2 and 3 in mineral oil
mulls display single strong carbonyl stretches at frequencies
close to those previously reported in KBr disks (for com-
plexes 1 and 3 [2]). The 1H NMR spectra of 1 and 3 are also
in agreement with literature reports [2]. All three com-
1
pounds display singlets in their 31Pf Hg NMR spectra,
agreeing with the triplets observed for the Ru±H resonance
1
Fig. 1. The [RuH(CO)(PPh3)2(4-Mepy)2][BF4] molecule with the atom
numbering scheme shown.
in the H NMR and con®rming the chemical equivalency
(trans-orientation) of the PPh3 ligands. The trans-orienta-
tion of the PPh3 ligands and the cis-orientation of the
pyridines are also demonstrated in the X-ray crystal struc-
ture of 2. This is the same geometry proposed for the
osmium complexes through spectroscopic studies alone.
Table 2
Ê
1
Selected interatomic bond lengths (A) and angles (8) for compound 2
Also in agreement with the osmium study, the H NMR
spectrum of the residue remaining after the synthesis of
[RuH(CO)(PPh3)2py2][BF4] displayed resonances attributa-
ble to cycloheptatriene but not bitropyl, con®rming that the
reaction involves hydride abstraction rather than oxidation
followed by deprotonation.
Ru±N(1)
2.195(9)
2.217(7)
1.87(2)
N(1)±C(11)
N(1)±C(15)
C(11)±C(12)
C(12)±C(13)
C(13)±C(14)
C(14)±C(15)
C(13)±C(16)
N(2)±C(21)
N(2)±C(25)
C(21)±C(22)
C(22)±C(23)
C(23)±C(24)
C(24)±C(25)
C(23)±C(26)
C(1A)± O(1A)
1.34(2)
1.35(2)
1.40(2)
1.35(2)
1.35(2)
1.38(2)
1.54(3)
1.35(1)
1.33(1)
1.36(1)
1.35(2)
1.37(2)
1.36(2)
1.49(2)
1.18(2)
Ru±N(2)
Ru±C(1)
Ru±C(1A)
Ru±H(1)
1.83(2)
1.78
Ru±H(1A)
Ru±P(1)
1.79
2.368(3)
2.355(3)
1.831(10)
1.815(11)
1.830(8)
1.843(12)
1.818(10)
1.822(9)
1.17(2)
Ru±P(2)
3.2. Crystal structure of [RuH(CO)(PPh3)2(4-Mepy)2]-
[BF4]
P(1)±C(31)
P(1)±C(41)
P(1)±C(51)
P(2)±C(61)
P(2)±C(71)
P(2)±C(81)
C(1)±O(1)
The resultant data of compound 2 best ®t the centrosym-
metric monoclinic space group P21/c (No. 14). Crystal-
lization occurs with four formula units per unit cell (Z ˆ 4).
The lack of any additional symmetry was veri®ed by the
program MISSYM [10]. The measured density of
N(1)±Ru±N(2)
N(1)±Ru±H(1)
N(1)±Ru±C(1)
N(2)±Ru±C(1)
C(1)±Ru±H(1)
P(1)±Ru±N(1)
P(1)±Ru±N(2)
P(2)±Ru±N(1)
P(2)±Ru±N(2)
P(1)±Ru±P(2)
93.2(3)
85.8(7)
176.5(6)
84.2(5)
97.2(8)
95.5(2)
92.1(2)
90.1(2)
95.5(2)
170.3(1)
Ru±P(1)±C(31)
Ru±P(1)±C(41)
Ru±P(1)±C(51)
Ru±P(2)±C(61)
Ru±P(2)±C(71)
Ru±P(2)±C(81)
Ru±N(1)±C(11)
Ru±N(2)±C(25)
C(16)±C(13)±C(14)
C(26)±C(23)±C(24)
113.5(4)
115.9(3)
117.7(3)
115.1(3)
113.4(3)
116.4(4)
121.4(8)
120.4(7)
119.9(13)
121.3(13)
3
1.351(3) Mg m compares quite well with the calculated
value (Dc ˆ 1.357 Mg m 3). A perspective view of com-
pound 2 (see Fig. 1) shows the crystallographic numbering
scheme. The arrangement of the functional groups about the
Ru atom can be seen as a slightly distorted octahedron
which is evidenced by the involved bond angles found in
Table 2. The cis orientation of the 4-picoline groups and the
trans orientation of the phosphines are in agreement with the
data obtained from solution NMR spectroscopy. An impor-
tant aspect of the structural analysis is that the hydride and
carbonyl ligands are disordered, 50% of the time as seen in
Fig. 1 and 50% in an exchanged orientation. Note, the
occupancies of C(1), O(1) and C(1A), O(1A) were re®ned
to 0.52(4), 0.54(4), 0.49(4), and 0.45(4), respectively. All
bond distances and angles are internally consistent and are
in good agreement with the values found in the Cambridge
Structure Database [11]. Mean Ru±N, Ru±P, P±C, Ru±C and
Ring
Distance (Ph)
Mean
Angle (Ph)
Range
Mean
Range
C(31)±C(36)
C(41)±C(46)
C(51)±C(56)
C(61)±C(66)
C(71)±C(76)
C(81)±C(86)
1.37(5)
1.37(2)
1.38(2)
1.38(4)
1.38(1)
1.38(1)
1.30±1.45
1.35±1.39
1.34±1.41
1.30±1.43
1.37±1.39
1.36±1.40
120(3)
120(1)
120(2)
120(2)
120(1)
120(1)
115.7±125.1
117.3±121.3
117.6±122.0
117.4±123.2
119.0±121.6
117.3±121.1

D.F. Mullica et al. / Inorganica Chimica Acta 285 (1999) 318±321
321
C±O bond lengths are presented in Table 2, 2.20(1),
Ê
2.362(7), 1.827(9), 1.85(2) and 1.17(2) A, respectively.
Acknowledgements
Speci®cally, it is found that the average P±C bond length
is in direct agreement with observed results found in other
structures containing triphenylphosphine groups [12,13]
and in BIDICS [14]. When considering the 4-picoline
groups the mean N±C(sp2), C(sp3)±C(sp2) and C(sp2)±
We thank the Robert A. Welch Foundation (Grants
No. AA-0668 and AA-1083) and Baylor University, in
part, for support of this research. M.S.W. thanks the
National Science Foundation for support through the
REU Program.
2
Ê
C(sp ) bond distances are 1.34(1), 1.52(3) and 1.37(2) A,
respectively. The angles of Ru±P(1, 2) ± C(31, 41, 51, 61,
71, 81) are greater than the ideal tetrahedral geometry
(109.58) and the angles between C(31), C(41), C(51) and
C(61), C(71), C(81) are much less than ideality. However,
the mean bond angles about P(1) and P(2) are 109.58.
Further, the Ru±C>O bond angle associated with the dis-
ordered carbonyl group is 177.7(14)8. This near linear
angular arrangement is an indication of strong directional
bonding related to the interaction of the ruthenium 4d
orbitals and the CO orbitals. The mean C±C bond lengths
and C±C±C bond angles in each phenyl ring can be con-
sidered ideal [15], see Table 2. Planarity of all rings has
been veri®ed by employing a least-squares planes program
MPLN [8]. The mean deviation from planarity for the six
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Ê
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Ê
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Ê
deviation 0.023 A. The dihedral angles between the Ru ring
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150.28, respectively. Finally, the dihedral angle between the
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4. Supplementary material
Structure factors, anisotropic thermal parameters, hydro-
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angles are available from the authors.
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