Synthetic and mechanistic studies on ruthenium dicarbonyl complexes containing PhP(CH2CH2CH2PCy2) 2 (Cyttp) ligand

Article abstract of DOI:10.1016/j.ica.2004.11.049

A synthetic and mechanistic study is reported on ligand substitution and other reactions of six-coordinate ruthenium(II) carbonyl complexes containing tridentate PhP(CH₂CH₂CH₂PCy₂) ₂ (Cyttp). Carbonylation of cis-mer-Ru(OSO₂CF ₃)₂(CO)(Cyttp) (1) affords [cis-mer-Ru(OSO ₂CF₃)(CO)₂(Cyttp)]O₃SCF₃ (2(O₃SCF₃)) and, on longer reaction times, [cis-mer-Ru(solvent)(CO)₂(Cyttp)](O₃SCF₃) ₂ (solvent = acetone, THF, methanol). 2(O₃SCF₃) reacts with each of NaF, LiCl, LiBr, NaI, and LiHBEt₃ to yield [cis-mer-RuX(CO)₂(Cyttp)]⁺ (X = F (3), Cl (4), Br (5), I (6), H (7)), isolated as 3-7(BPh₄). These conversions proceed with high stereospecificity to afford only a single isomer of the product that is assigned a structure in which the Ph group of Cyttp points toward the CO trans to X (anti when X = F, Cl, Br, or I; syn when X = H). Treatment of 2(O ₃SCF₃) with NaOMe and CO generates the methoxycarbonyl complex [cis-mer-Ru(CO₂Me)(CO)₂(Cyttp)]⁺ (8), whereas addition of excess n-BuLi to 2(O₃SCF₃) in THF under CO affords mer-Ru(CO)₂(Cyttp) (9). The two ¹³C isotopomers [cis-mer-Ru(OSO₂CF₃)(CO)(¹³CO) (Cyttp)]O₃SCF₃ (2′(O₃SCF₃): ¹³CO trans to P_C; 2″(O₃SCF₃): ¹³CO cis to all P donors) were synthesized by appropriate adaptations of known transformations and used in mechanistic studies of reactions with each of LiHBEt₃, NaOMe/CO, and n-BuLi. Whereas LiHBEt₃ reacts with 2′(O₃SCF₃) and 2″(O₃SCF ₃) to replace triflate by hydride without any scrambling of the carbonyl ligands, the corresponding reactions of NaOMe-CO are more complex. The methoxide combines with the CO cis to triflate in 2, and the resultant methoxycarbonyl ligand ends up positioned trans to the incoming CO in 8. A mechanism is proposed for this transformation. Finally, treatment of either 2′(O₃SCF₃) or 2″(O₃SCF₃) with an excess of n-BuLi leads to the formation of the same two ruthenium(0) isomers of mer-Ru(CO)(¹³CO)(Cyttp). These products represent, to our knowledge, the first example of a syn-anti pair of isomers of a five-coordinate metal complex.

Full text of DOI:10.1016/j.ica.2004.11.049

Inorganica Chimica Acta 358 (2005) 2341–2348
www.elsevier.com/locate/ica
Synthetic and mechanistic studies on ruthenium dicarbonyl
complexes containing PhP(CH2CH2CH2PCy2)2 (Cyttp) ligand
*
Patrick W. Blosser, Andrew Wojcicki
Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH 43210-1185, USA
Received 4 November 2004; accepted 28 November 2004
Available online 29 January 2005
Dedicated to Professor Fred Basolo, a pioneer of mechanistic inorganic chemistry, with our respect and best wishes on the occasion
of his 85th birthday
Abstract
A synthetic and mechanistic study is reported on ligand substitution and other reactions of six-coordinate ruthenium(II) carbonyl
complexes containing tridentate PhP(CH2CH2CH2PCy2)2 (Cyttp). Carbonylation of cis-mer-Ru(OSO2CF3)2(CO)(Cyttp) (1) affords
[cis-mer-Ru(OSO2CF3)(CO)2(Cyttp)]O3SCF3 (2(O3SCF3)) and, on longer reaction times, [cis-mer-Ru(solvent)(CO)2(Cyttp)]
(O3SCF3)2 (solvent = acetone, THF, methanol). 2(O3SCF3) reacts with each of NaF, LiCl, LiBr, NaI, and LiHBEt3 to yield [cis-
mer-RuX(CO)2(Cyttp)]+ (X = F (3), Cl (4), Br (5), I (6), H (7)), isolated as 3–7(BPh4). These conversions proceed with high stereo-
specificity to afford only a single isomer of the product that is assigned a structure in which the Ph group of Cyttp points toward the
CO trans to X (anti when X = F, Cl, Br, or I; syn when X = H). Treatment of 2(O3SCF3) with NaOMe and CO generates the meth-
oxycarbonyl complex [cis-mer-Ru(CO2Me)(CO)2(Cyttp)]+ (8), whereas addition of excess n-BuLi to 2(O3SCF3) in THF under CO
13
affords mer-Ru(CO)2(Cyttp) (9). The two C isotopomers [cis-mer-Ru(OSO2CF3)(CO)(13CO)(Cyttp)]O3SCF3 (20(O3SCF3): 13CO
trans to PC; 200(O3SCF3): 13CO cis to all P donors) were synthesized by appropriate adaptations of known transformations and used
in mechanistic studies of reactions with each of LiHBEt3, NaOMe/CO, and n-BuLi. Whereas LiHBEt3 reacts with 20(O3SCF3) and
200(O3SCF3) to replace triflate by hydride without any scrambling of the carbonyl ligands, the corresponding reactions of NaOMe–
CO are more complex. The methoxide combines with the CO cis to triflate in 2, and the resultant methoxycarbonyl ligand ends up
positioned trans to the incoming CO in 8. A mechanism is proposed for this transformation. Finally, treatment of either 20(O3SCF3)
or 200(O3SCF3) with an excess of n-BuLi leads to the formation of the same two ruthenium(0) isomers of mer-Ru(CO)(13CO)(Cyttp).
These products represent, to our knowledge, the first example of a syn–anti pair of isomers of a five-coordinate metal complex.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Ruthenium complexes; Carbonyl complexes; Triphosphine complexes; syn–anti Isomerism; Ligand substitution; Isotope effects;
Mechanism
1. Introduction
PhP(CH2CH2CH2PCy2)2 (Cyttpꢀ) and weakly coordi-
ꢀ
nated anions, BF4 or CF3SO3 [1,2]. A number of
We have previously reported synthesis and ligand
substitution reactions of six-coordinate ruthenium(II)
carbonyl complexes containing the tridentate phosphine
these complexes display high configurational stability,
which allows stereochemical studies to be conducted
on ligand substitution and coupling processes. For
example, in this context we recently investigated syn–
anti isomeric behavior of cis-mer-RuX2(CO)(Cyttp)
(X = various monodentate, X2 = various bidentate anio-
nic ligands); this type of geometric isomerism arises as a
*
Corresponding author. Tel.: +1 614 292 4750; fax: +1 614 292
1685.
E-mail address: wojcicki@chemistry.ohio-state.edu (A. Wojcicki).
0020-1693/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2004.11.049

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P.W. Blosser, A. Wojcicki / Inorganica Chimica Acta 358 (2005) 2341–2348
result of the Ph group on the central phosphorus atom
being directed toward either X or CO [2] (cf. I and
NMR spectrum indicated that all of 1 had been con-
verted to product. Solvent was then removed, and the
residue was washed with 25 ml of hexane and dried over-
night under vacuum. Yield of 2(O3SCF3), 0.208 g (95%).
Selected spectroscopic properties. IR (Nujol): m(C„O)
1
II). Here, we describe the preparation of [cis-mer-
Ru(OSO2CF3)(CO)2(Cyttp)]O3SCF3 (2(O3SCF3)) and
its ligand substitution, coupling (migratory insertion)
and reduction reactions.
2060 (s), 1993 (s) cmꢀ1
.
(ppm) 198.6 (q, JPC = 12 Hz, CO cis to 3 P donors),
13C{1H} NMR (acetone-d6): d
2
2
192.2 (dt, JPC = 83, 10 Hz, CO trans to PC). 19F{1H}
NMR (acetone-d6): d (ppm, referenced to internal
CFCl3) ꢀ77.3 (s, RuOSO2CF3), ꢀ79.0 (s, CF3SO3ꢀ).
31P{1H} NMR (acetone-d6):
d
(ppm) 11.4 (d,
2
2JPP = 33.8 Hz, PW (wing P)), ꢀ2.7 (t, JPP = 33.8 Hz,
PC (central P)).
When this reaction was allowed to proceed for ca. 2
weeks, the 19F{1H} resonance at d ꢀ77.3 ppm almost
completely disappeared, and that at d ꢀ79.0 ppm in-
creased in intensity. Also, the 31P{1H} NMR signals of
2(O3SCF3) at d 11.4 and ꢀ2.7 ppm were barely discern-
ible, and new intense signals occurred at d 12.0 ppm (d,
2
2JPP = 33.5 Hz, PW) and ꢀ6.7 ppm (t, JPP = 33.5 Hz,
2. Experimental
PC). The new resonances most likely indicate formation
of [cis-mer-Ru(acetone)(CO)2(Cyttp)](O3SCF3)2. A sim-
ilar behavior of 1 upon carbonylation was observed in
THF or MeOH as indicated by 31P{1H} NMR
spectroscopy.
2.1. General procedures and measurements
Reactions and manipulations of air-sensitive com-
pounds were conducted at room temperature under an
atmosphere of dry argon by use of standard procedures
[4]. Solvents were dried [5], distilled under argon, and
degassed before use. Elemental analyses were carried
out by M–H-W Laboratories, Phoenix, AZ. IR, NMR
(1H, 13C, 19F, and 31P), and mass spectra (FAB-MS)
were obtained as previously described [6,7]. All listed
mass peaks are those of ions containing 102Ru. Relative
peak intensities are given with the assignments.
2.3.2. Preparation of [cis-mer-anti-RuF(CO)2(Cyttp)]-
BPh4 (3(BPh4))
After carbon monoxide had been passed through a
stirred solution of 1 (0.194 g, 0.191 mmol) in 40 ml of
acetone for 1 h, NaF (0.110 g, 2.62 mmol) in 10 ml of
H2O was added, and the mixture was stirred for an addi-
tional hour. All volatiles were removed under vacuum,
MeOH (20 ml) was added to dissolve the residue, and
a solution of NaBPh4 (0.200 g, 0.584 mmol) in 3 ml of
MeOH was introduced with stirring to effect the precip-
itation of a fluffy white solid. The addition of 20 ml of
H2O induced further precipitation. After 5 min of stir-
ring, the white solid was filtered off, washed consecu-
tively with 20 ml of H2O and 2 · 20 ml of hexane, and
dried under vacuum overnight. Yield of 3(BPh4), 0.155
g (85%). The IR and 19F{1H} and 31P{1H} NMR spec-
troscopic properties of the product compare well with
those of 3(BF4), prepared by a different reaction [1].
2.2. Materials
Reagents were procured from various commercial
sources and used as received. 13CO was obtained from
Aldrich Chemical Co. The complexes cis-mer-Ru(O-
SO2CF3)2(CO)(Cyttp) (1) [1] and cis-mer-RuH2(g2-
H2)(Cyttp) [8] were synthesized according to the
literature methods.
2.3. Synthesis of various complexes [cis-mer-RuX(CO)2-
(Cyttp)]+
IR (CH2Cl2): m(C„O) 2048 (s), 1980 (s) cmꢀ1
.
31P{1H} NMR (acetone-d6):
d (ppm) 14.8 (dd,
2
2
2JPP = 36 Hz, JPF = 25 Hz, PW), ꢀ0.8 (dt, JPF = 43
2.3.1. Preparation of [cis-mer-Ru(OSO2CF3)(CO)2-
(Cyttp)]O3SCF3 (2(O3SCF3))
Carbon monoxide was passed through a stirred solu-
tion of cis-mer-Ru(OSO2CF3)2(CO)(Cyttp) (1) (0.213 g,
0.210 mmol) in 15 ml of acetone for 15 min. A 31P{1H}
Hz, JPP = 36 Hz, PC). FAB-MS: m/z 763 (M+, 4), 735
2
(M+ ꢀ CO, 100), 716 (M+ ꢀ CO ꢀ F, 5).
2.3.3. Preparation of [cis-mer-anti-RuCl(CO)2(Cyttp)]-
BPh4 (4(BPh4))
A procedure analogous to that for 3(BPh4) in Section
2.3.2 was followed, using 1 (0.195 g, 0.192 mmol), CO,
and LiCl (0.040 g, 0.94 mmol) in place of NaF, and
employing a shorter reaction time (2 · 30 min instead
1
The designation syn and anti is made in accordance with the
Cahn–Ingold–Prelog priority rules [3] as applied to the two different
ligands that are trans (X and CO in cis-mer-RuX2(CO)(Cyttp)).

P.W. Blosser, A. Wojcicki / Inorganica Chimica Acta 358 (2005) 2341–2348
2343
1
of 2 · 1 h). Yield of 4(BPh4), a white solid, 0.202 g
(96%). Selected spectroscopic properties. IR (CH2Cl2):
1992 (s), m(C@O) 1628 (s), m(C–O) 1027 (m) cmꢀ1. H
NMR (CD2Cl2): d (ppm) 3.54 (s, OMe). 13C{1H}
m(C„O) 2052 (s), 1991 (s) cmꢀ1
.
31P{1H} NMR (ace-
NMR (CD2Cl2): d (ppm) 198.9 (dt, JPC = 13.8, 11.4
2
2
2
Hz, COMe), 198.4 (q, JPC = 9.3 Hz, CO cis to 3 P do-
tone-d6): d (ppm) 10.5 (d, JPP = 35 Hz, PW), ꢀ7.5 (t,
2JPP = 35 Hz, PC). FAB-MS: m/z 779 (M+, 5), 751
(M+ ꢀ CO, 100), 716 (M+ ꢀ CO ꢀ 35Cl, 5).
2
nors), 195.4 (dt, JPC = 76.5, 11.1, Hz, CO trans to PC),
50.6 (s, COMe). 31P{1H} NMR (CD2Cl2): d (ppm) 12.2
2
2
(d, JPP = 37.3 Hz, PW), ꢀ10.1 (t, JPP = 37.3 Hz, PC).
Anal. Calc. for C64H84BO4P3Ru: C, 68.50; H, 7.55.
Found: C, 68.33; H, 7.68%.
2.3.4. Preparation of [cis-mer-anti-RuBr(CO)2(Cyttp)]-
BPh4 (5(BPh4))
The title complex was prepared from 1 (0.163 g, 0.161
mmol), CO, and excess LiBr by a procedure analogous
to that for 4(BPh4) in Section 2.3.3. Yield of 5(BPh4),
0.168 g (91%). The IR and 31P{1H} NMR spectroscopic
properties of the cation match those previously reported
for 5(AsF6) [9]. IR (CH2Cl2): m(C„O) 2052 (s), 1993 (s)
2.4. Reaction of [cis-mer-Ru(OSO2CF3)(CO)2(Cyttp)]-
O3SCF3 (2(O3SCF3)) with n-BuLi
Carbon monoxide was passed through a stirred solu-
tion of 1 (0.053 g, 0.052 mmol) in 10 ml of THF for 30
min, and the contents were treated with n-BuLi in hex-
ane (0.10 ml, 1.6 M, 0.16 mmol). The colorless reaction
mixture turned bright yellow, and a 31P{1H} NMR spec-
trum indicated complete conversion of 2(O3SCF3) to
known [9] mer-Ru(CO)2(Cyttp) (9). Solvent was evapo-
rated, and the residue was extracted with 5 ml of hexane
to remove excess n-BuLi. The remaining solid was
dissolved in 5 ml of benzene, the solution was filtered
cmꢀ1
.
31P{1H} NMR (acetone-d6): d (ppm) 7.4 (d,
2JPP = 35 Hz, PW), ꢀ11.8 (t, JPP = 35 Hz, PC). FAB-
MS: m/z 823 (M+, 8), 795 (M+ ꢀ CO, 100), 716
(M+ ꢀ CO ꢀ Br, 6).
2
2.3.5. Preparation of [cis-mer-anti-RuI(CO)2(Cyttp)]-
BPh4 (6(BPh4))
A procedure analogous to that for 4(BPh4) in Section
2.3.3 was employed, with NaI replacing NaF. Yield of
6(BPh4), 93%. The IR and 31P{1H} NMR spectroscopic
properties of the cation match those previously reported
for 6(I) [9]. IR (CH2Cl2): m(C„O) 2051 (s), 1995 (s)
through a 2-cm pad of Celite, and the yellow
filtrate was evaporated to dryness. Yield of 9, 0.031 g
(80%).
cmꢀ1
.
31P{1H} NMR (acetone-d6): d (ppm) 2.7 (d,
2.5. Synthesis of isomers of [cis-mer-Ru(OSO2CF3)-
(CO)(13CO)(Cyttp)]O3SCF3 (20(O3SCF3)) and
(200(O3SCF3))
2JPP = 35 Hz, PW), ꢀ18.1 (t, JPP = 35 Hz, PC.) FAB-
MS: m/z 871 (M+, 16), 843 (M+ ꢀ CO, 100), 716
(M+ ꢀ CO ꢀ I, 9).
2
2.5.1. Preparation of [cis-mer-Ru(OSO2CF3)(CO)-
(13CO-trans to PC)(Cyttp)] O3SCF3 (20(O3SCF3))
To a partially evacuated Schlenk flask containing a
solution of 1 in the appropriate solvent (acetone,
THF, or MeOH) under argon was introduced gaseous
CO enriched ca. 70% in carbon-13. The flask was closed,
and the contents were stirred for ca. 15 min. The pres-
sure was then returned to 1 atm by introduction of addi-
tional 13CO. This procedure was repeated until 31P{1H}
NMR spectroscopy indicated a complete conversion of
1 to 20(O3SCF3).
2.3.6. Preparation of [cis-mer-syn-RuH(CO)2(Cyttp)]-
BPh4 (7(BPh4))
The title hydrido complex was prepared from 1 (0.088
g, 0.087 mmol), CO, and LiHBEt3 (0.17 ml of 1 M solu-
tion in THF) in 30 ml of THF by a procedure analogous
to that for 4(BPh4) in Section 2.3.3. Yield of 7(BPh4), a
1
white solid, 0.075 g (81%). The IR and H and 31P{1H}
NMR spectroscopic properties of the cation match
those previously reported for 7(BF4) and 7(AsF6) [9].
2.3.7. Preparation of [cis-mer-Ru(CO2Me)(CO)2(Cyttp)]-
BPh4 (8(BPh4))
2.5.2. Preparation of [cis-mer-Ru(OSO2CF3)(CO)-
(13CO-cis to all P donors)(Cyttp)] O3SCF3
A solution of 1 (0.200 g, 0.197 mmol) in 10 ml of
MeOH was treated with gaseous CO for 30 min, and
NaOMe (0.20 mmol) in MeOH was added dropwise.
The contents were stirred for 1 h under CO, and a solu-
tion of NaBPh4 (0.10 g, 0.30 mmol) in ca. 2 ml of MeOH
was added to induce the precipitation of a fluffy white
solid. The volume of the reaction mixture was reduced
to ca. 5 ml, and H2O (10 ml) was introduced with stir-
ring. The white product was filtered off, washed with
two 20-ml portions of hexane, and dried under vacuum
overnight. Yield of 8(BPh4), 0.198 g (90%). Selected
spectroscopic properties. IR (Nujol): m(C„O) 2030 (s),
(200(O3SCF3))
A solution of cis-mer-RuH2(g2-H2)(Cyttp) [8] in hex-
ane was maintained under an atmosphere of 13CO in a
Schlenk flask. Large colorless crystals began to form
on the sides of the flask in ca. 24 h. After 48 h, the crys-
tals were collected on a filter frit, dried, and identified
spectroscopically as cis-mer-syn-RuH2(13CO)(Cyttp)
[8]. Reaction of the isolated carbonyl dihydride with
CF3SO3H according to the literature [1] afforded cis-
mer-Ru(OSO2CF3)2(13CO)(Cyttp) (10) in high yield
(P90%). Complex 10 was converted to 200(O3SCF3) by

2344
P.W. Blosser, A. Wojcicki / Inorganica Chimica Acta 358 (2005) 2341–2348
carbonylation with CO of natural isotopic abundance as
described in Section 2.3.1.
of the resonances at d 11.4 and ꢀ2.7 ppm of
2(O3SCF3). After 2 weeks, the 19F{1H} and 31P{1H}
NMR spectra indicate essentially complete conversion
of 2(O3SCF3) to a new, structurally similar product,
formulated as the solvento complex [cis-mer-Ru
(acetone)(CO)2(Cyttp)](O3SCF3)2 (Scheme 1). Carbon-
ylation of 1 in THF or methanol solution proceeds
similarly.
3. Results and discussion
3.1. Carbonylation of cis-mer-Ru(OSO2CF3)2(CO)-
(Cyttp) (1)
Bubbling carbon monoxide through a solution of 1 in
acetone at room temperature leads to rapid replacement
of the triflate ligand trans to the central phosphorus
atom (PC) of the Cyttp (Scheme 1). This is indicated
by the appearance of a new A2X set of 31P{1H} NMR
signals in which the resonance of PC occurs upfield rela-
tive to that of PW (wing phosphorus), a characteristic of
strong trans-influence ligands opposite PC [10]. After ca.
15 min, the solvent was removed, and the product [cis-
mer-Ru(OSO2CF3)(CO)2(Cyttp)]O3SCF3 (2(O3SCF3))
was isolated in 95% yield. Its assigned structure is sup-
ported by spectroscopic data (cf. Section 2.3.1). The
IR spectrum shows two equal-intensity m(C„O) bands
at 2060 and 1993 cmꢀ1, and the 13C{1H} NMR spec-
trum displays two low-field resonances at d 198.6 ppm
as a quartet (CO cis to three P donors) and d 192.2
ppm as a doublet of triplets (CO trans to PC). The
19F{1H} NMR spectrum consists of two singlets of
approximately equal intensity at d ꢀ77.3 and ꢀ79.0
ppm, in agreement with the presence of one covalent
and one ionic triflate [11].
3.2. Reactions of [cis-mer-Ru(OSO2CF3)(CO)2-
(Cyttp)](O3SCF3) (2(O3SCF3)) with nucleophiles
The presence of weakly coordinating triflate in 2 sug-
gests that this complex should undergo facile substitu-
tion reactions. Indeed, 2(O3SCF3) generated in situ
from 1 and CO reacts readily with each of NaF, LiCl,
LiBr, and NaI to afford the respective [cis-mer-anti-
RuX(CO)2(Cyttp)]+ (3–6) (Scheme 2). Similarly, the hy-
dride [cis-mer-syn-RuH(CO)2(Cyttp)]+ (7) was obtained
from 2(O3SCF3) and LiHBEt3. All of the complexes
ꢀ
3–7 were isolated in 81–96% yield as the BPh4 salts
by anion metathesis in MeOH. Complexes 3 [1] and 5–
7 [9] were reported previously, but their synthesis in-
volved different reactions, mostly oxidation of mer-Ru
(CO)2(Cyttp) (9). For example, 7 was obtained by
When the reaction is allowed to proceed for a longer
time, the 19F{1H} NMR signal at d ꢀ77.3 ppm decreases
in intensity while that at d ꢀ79.0 ppm becomes stronger.
Accompanying this change is the appearance and
growth of a new AX2 set of 31P{1H} resonances at d
2
12.0 and ꢀ6.7 ppm with a JPP similar to that of
2(O3SCF3), and the simultaneous decrease in intensity
Scheme 1.
Scheme 2.

P.W. Blosser, A. Wojcicki / Inorganica Chimica Acta 358 (2005) 2341–2348
2345
treatment of 9 with HBF4 Æ Et2O or HX (X = Cl or Br).
3.3. Mechanistic studies on reactions of 13CO-labeled
[cis-mer-Ru(OSO2CF3)(CO)2(Cyttp)]O3SCF3
1H NMR nOe experiments on 7(BPh4) in which each of
the phenyl resonances (o, m, and p) of the Cyttp ligand
was irradiated show no enhancement of intensity of the
RuH hydride signal. These experiments suggest that the
complex exists as the syn isomer, with the phenyl ring di-
rected away from the hydride ligand and toward the
(20(O3SCF3) and 200(O3SCF3))
To gain insight into mechanistic aspects of some reac-
tions of 2(O3SCF3) presented in Section 3.2, we investi-
gated stereochemical behavior of the 13CO-labeled
20(O3SCF3) and 200(O3SCF3). These two isotopomers
were prepared by stereospecific incorporation of 13CO
into the coordination sphere of ruthenium through use
of known reactions (Scheme 3). Thus, 20(O3SCF3), con-
taining 13CO trans to the PC of Cyttp, was obtained by
carrying out the conversion of 1 to 2(O3SCF3) (cf. Sec-
tion 2.3.1), but with 13CO instead of 12CO. The incom-
ing 13CO ligand ends up exclusively in the
coordination site formerly occupied by the replaced tri-
flate, while the positions of the remaining ligands are not
affected. This is indicated by the splitting patterns and
1
trans CO. Similar H NMR nOe experiments were used
previously to assign structures to syn and anti isomers of
related hydrido metal complexes [9,12]. Since the halide
complexes 3–6 were prepared by analogous ligand sub-
stitution reactions of 2(O3SCF3), and their spectroscopic
properties indicate the presence of only one isomer, they
likewise are assigned structures in which the Cyttp phe-
nyl group is oriented away from the halide and toward
the trans CO (i.e., anti).
The IR m(C„O) values of the complexes 3–6(BPh4)
show little sensitivity to the halide ligand; a similar
behavior has been noted for the series PPN[WX(CO)5]
(PPN = Ph2N; X = F, Cl, Br, I) [13]. In the 31P{1H}
2
relative values of various JPC in the 31P{1H} and
13C{1H} NMR spectra. The former spectrum shows a
doublet of doublets (2JPwC = 9.9 Hz) at d 11.4 ppm for
PW and a doublet (2JPcC = 83 Hz) of triplets at d ꢀ2.7
ppm for PC (2JPP = 33.8 Hz), whereas the latter displays
a strong signal of the trans-to-PC carbonyl carbon as a
doublet of triplets at d 192.2 ppm (cf. Section 3.1).
The isotopomer 200(O3SCF3), containing 13CO in a posi-
tion cis to all three P donors, was synthesized in three
steps starting with cis-mer-RuH2(g2-H2)(Cyttp). Reac-
tion of this polyhydride with 13CO afforded cis-mer-
syn-RuH2(13CO)(Cyttp), the 13CO isotopomer of the
known carbonyl dihydride [8]. The product was in turn
ꢀ
NMR spectra of the BPh4 salts of 3–6, the chemical
shifts of the 31P nuclei move upfield as X varies from F
to I to indicate increased shielding owing to polarizabil-
ity of the halide [14]. A parallel trend has been reported
for the complexes [mer-Re(X)(F)(O)(Cyttp)]BPh4
(X = F, Cl, Br) where X and F are cis [15]. FAB-MS data
for the BPhꢀ salts of 3–6 show similar fragmentation
patterns for the metal complex cation, with [M+ ꢀ CO]
being the most predominant ion detected in each case.
Complex 2(O3SCF3) reacts with NaOMe in methanol
under an atmosphere of CO to form a new methoxycar-
bonyl product, [cis-mer-Ru(CO2Me)(CO)2(Cyttp)]+ (8)
(Scheme 2), which was isolated analytically pure in
excellent yield as 8(BPh4), after anion metathesis using
NaBPh4. The 31P{1H} NMR spectrum of 8(BPh4) (Sec-
tion 2.3.7), an AX2 pattern, is similar to the spectra of
the halide complexes 3–6(BPh4), and the IR spectrum
shows two strong m(C„O) bands at 2030 and 1992
cmꢀ1 to demonstrate a cis structure. The presence of
two inequivalent carbonyl ligands is reflected by the
appearance of 13C{1H} NMR signals at d 198.4 (q,
2
2JPC = 9.3 Hz) and 195.4 (dt, JPC = 76.5, 11.1 Hz).
There is also a O@C resonance of the methoxycarbonyl
group at d 198.9 ppm (dt, 2JPC = 13.8, 11.4 Hz), assigned
from the spectrum of the 13CO-enriched product (cf.
Section 3.3). The angle 2h between the carbonyl ligands
was calculated to be 85ꢁ by use of the equation I(sym)/
I(asym) = cot2h where I(sym)/I(asym) stands for the ra-
tio of the appropriate band intensities [16].
Reaction between 2(O3SCF3) and n-BuLi in excess in
THF solution under CO leads to reduction of the metal
to yield mer-Ru(CO)2(Cyttp) (9) as the only Cyttp-con-
taining product (Scheme 2). Reduction of related ruthe-
nium(II) complexes with RLi, e.g., of [Ru(CO)2(ttp)]2+
(ttp = PhP(CH2CH2CH2PPh2)2) with MeLi, has been
reported [9].
Scheme 3.

2346
P.W. Blosser, A. Wojcicki / Inorganica Chimica Acta 358 (2005) 2341–2348
2
converted to cis-mer-Ru(OSO2CF3)2(13CO)(Cyttp) (10)
by treatment with triflic acid [1]. Finally, carbonylation
of 10 with CO of natural isotopic abundance led to the
substitution of the triflate trans to PC to give
200(O3SCF3). The 31P{1H} NMR spectrum of
200(O3SCF3) shows some similarity to that of 20(O3SCF3)
cis to the three P donors (2JPcC = 9 Hz, JPwC = 6 Hz).
The simplest mechanism that explains these results is di-
rect substitution of ligated triflate by hydride; however,
attack of hydride at the carbonyl cis to the triflate fol-
lowed by replacement of the latter by the formyl hydro-
gen cannot be ruled out.
2
2
but displays nearly equal JPC values of JPwC = 11 Hz
2
The reaction of 20(O3SCF3) with one equivalent of
NaOMe in MeOH under an atmosphere of CO cleanly
produces [cis-mer-Ru(13CO2Me)(CO)2(Cyttp)]+ (80), iso-
lated as 80(BPh4) (Scheme 5). The presence of 13C in the
13CO2Me ligand cis to the three P donor atoms is indi-
cated by 1H, 13C{1H}, and 31P{1H} NMR and IR spec-
troscopy. The 1H NMR spectrum shows the OMe
resonance at d 3.53 ppm as a doublet (3JCH = 3.7 Hz),
and the 13C{1H} NMR spectrum reveals a strong (13C
enrichment) 13CO2Me resonance at d 198.4 ppm as a
doublet of triplets (cf. Section 2.3.7). The 31P{1H}
NMR spectrum resembles that of 8(BPh4), except for
and JPcC = 12 Hz. In the 13C{1H} NMR spectrum,
the strong signal of the 13CO trans to triflate appears
as an approximate quartet (doublet of triplets with
2
2JPcC ꢁ JPwC) at d 198.6 ppm (cf. Section 3.1). All steps
in the formation of 200(O3SCF3) proceed without any ob-
servable ligand scrambling. Also, when 2(O3SCF3) dou-
bly labeled with 13CO was exposed to 12CO for 2 weeks,
no depletion of 13CO was observed by 31P{1H} NMR
spectroscopy to show that the carbonyl ligands are sub-
stitutionally inert at ambient temperature.
Complexes 20(O3SCF3) and 200(O3SCF3) lend them-
selves particularly well to mechanistic studies of reac-
tions with nucleophiles owing to the spectroscopic
handles provided by the 13CO enrichment, the absence
of scrambling between the COꢀs, and the apparent lack
of lability of these two ligands. The fate of each CO
can therefore be determined unambiguously by spectros-
copy after reaction.
an additional, similar doublet splitting of the PC and
.
2
PW resonances owing to comparable values of JPC
The IR m(C„O) bands are unaffected by 13C labeling;
however, the m(C@O) band shifts from 1628 to 1591
cmꢀ1, and the m(C–O) band from 1027 to 1017 cmꢀ1
,
as expected.
When 200(O3SCF3) was treated with a slight excess of
NaOMe under the conditions that mirrored those for
the corresponding reaction of 20(O3SCF3), [cis-mer-Ru
(CO2Me)(CO)(13CO-trans to PC)(Cyttp)]+ (800) and a
small amount of 70 were obtained. The 31P{1H} NMR
spectrum of isolated 800(BPh4) indicates that the 13CO li-
gand has moved from a site cis to PC in 200 to the site
Reactions of 20(O3SCF3) and 200(O3SCF3) with LiH-
BEt3 under CO are given in Scheme 4. Treatment of
20(O3SCF3) with an excess of LiHBEt3 cleanly produces
1
70, isolated as 70(BPh4). The H, 13C{1H} (carbonyl re-
gion), and 31P{1H} NMR spectra of the product in
CDCl3 solution confirm that the 13CO remains trans
to PC (2JPcC = 72 Hz, 2JPwC = 13 Hz, 2JCH = 4 Hz). Sim-
ilarly, reaction of 200(O3SCF3) with LiHBEt3 yields
exclusively 700, isolated as 700(BPh4). The NMR spectra
of this complex indicate that 13CO is still positioned
trans to PC (2JPcC = 76 Hz, JPwC = 11 Hz). Complex
2
70 most likely arises from reaction of 200(O3SCF3) with
NaOH, present as an impurity in NaOMe. This side
reaction may proceed similarly to that of 200(O3SCF3)
Scheme 4.
Scheme 5.

P.W. Blosser, A. Wojcicki / Inorganica Chimica Acta 358 (2005) 2341–2348
2347
with NaOMe (vide infra), with the final step being
decarboxylation of Ru-C(O)OH to Ru-H. Formation
of M–H by reaction of M–CO with OHꢀ is a known
transformation [17].
A possible mechanism of reaction of 2(O3SCF3) (and
its 13C isotopomers) with NaOMe under CO atmosphere
to yield 8(O3SCF3) (and its 13C isotopomers) is presented
in Scheme 6 (the two inequivalent CO ligands in 2 are
8 (or 80 or 800). It is interesting that the ligand C(O)OMe
and the incoming CO occupy trans positions in the prod-
uct. Although migratory insertion reactions of CO and
alkoxide have been little studied [20], in the related inser-
tion involving CO and alkyl, the acyl ligand generated by
coupling and the incoming ligand usually end up mutu-
ally cis [21]. There are, however, exceptions [22].
The reaction of either 20(O3SCF3) or 200(O3SCF3)
with more than two equivalents of n-BuLi in THF under
CO leads to reduction of the metal and formation of
mer-Ru(CO)(13CO)(Cyttp) (Scheme 7). The 31P{1H}
NMR spectrum of the product complexes shows that
three different species were generated: the unlabeled 9
(since 2(O3SCF3) was not 100% enriched in 13CO) and
two isomers of mer-Ru(CO)(13CO)(Cyttp), viz., syn-
9-13CO and anti-9-13CO (90 and 900, with no specific ste-
reochemical assignment). The carbonyl region 13C{1H}
NMR spectrum confirms the presence of 90 and 900.
The appropriate NMR data are presented in Table 1.
Three 31P{1H} NMR sets of signals (a doublet of trip-
lets; two doublets of doublets and triplets of doublets)
occur for the P donor atoms, and two 13C{1H} NMR
doublets of triplets are seen for the 13CO-enriched car-
bonyl ligands.
marked and ¼). Based upon facile ligand substitution
*
reactions of 2 with various nucleophiles Xꢀ and of the re-
lated [mer-Ru(THF)(CO)(P(OMe)3)(Cyttp)]2+ with
OMeꢀ [1], we propose initial coordination of methoxide
to the metal center. The next step would be migration of
OMeꢀ onto the carbonyl cis to it (marked in Scheme
*
6) to give a square-pyramidal intermediate, with the
methoxycarbonyl in an equatorial position. This species
then isomerizes by a Berry pseudorotation (BP) process
[18], in which the C(O)OMe and CO ligands exchange
positions. The driving force for the isomerization is to
generate a more stable intermediate, with the stronger
r-bonding ligand C(O)OMe in an apical site and the
stronger p-bonding ligand CO in an equatorial site [19].
The latter five-coordinate, 16-electron intermediate then
combines with a CO present in the reaction system to yield
Scheme 7.
Table 1
31P{1H} and carbonyl region 13C{1H} NMR data for complexes 9, 90,
a
and 900
Complex
dPC
dPW
2JPP
d13CO
2JPcC
2JPwC
9
3.945
3.938
3.952
37.758
37.758
37.763
47.7
47.8
47.6
90
900
a
222.98
212.97
21.9
15.9
18.9
14.1
d in ppm, J in Hz. Assignment of 90 and 900 is arbitrary.
Scheme 6.

2348
P.W. Blosser, A. Wojcicki / Inorganica Chimica Acta 358 (2005) 2341–2348
The observation of syn and anti isomers appears to be
ucts of each isotopomer of 2. Results of this study sug-
gest that other, related transition-metal Cyttp complexes
may serve as good models for investigations of reaction
mechanisms.
the first for a five-coordinate complex. The isomers 90
and 900 most likely differ by the angles between the 13C
and 31P nuclei [2] caused by the orientation of the Ph
group of Cyttp. The occurrence of separate resonances
in the 31P{1H} NMR spectrum for 9, 90, and 900 is a con-
sequence of slight differences in the shielding of the 31P
nuclei by 12C and 13C [23].
Acknowledgements
The fact that 20(O3SCF3) and 200(O3SCF3) yield the
same mixture of reduction products indicates that nei-
ther carbonyl ligand is lost during the reaction. A path-
way involving attack of n-BuLi at Ru followed by alkyl
migration, and then addition of another n-Buꢀ to Ru fol-
lowed by reductive elimination of 5-nonanone, can there-
fore be excluded. The only reasonable mechanism
appears to be a free radical one. It is possible that reduc-
tion occurs by two one-electron steps, and that the first
step leads to a product that undergoes syn–anti isomeri-
zation, since the starting 20 or 200 exists as a single isomer,
most likely anti [1,2]. However, it cannot be ruled out
that isomerization occurs after the formation of 90 or 900.
Five-coordinate trigonal bipyramidal complexes un-
dergo equatorial and apical ligand scrambling, which
may occur by a so-called 2-for-2 (2 equatorial for 2 api-
cal) exchange process, viz., Berry pseudorotation or the
‘‘turnstile rotation’’ [24]. However, we can find no way
of applying either of these mechanisms to rationalize
syn–anti isomerization of 90/900. Nevertheless, another
intramolecular pathway appears plausible. The molecu-
lar motion effecting this process may be envisaged by
viewing one syn–anti isomer from the equatorial plane.
When the Ru(CO)(13CO) ‘‘wedge’’ is rotated clockwise
by 90ꢁ about the line passing through PC and bisecting
the angle OC–Ru–13CO, while the Cyttp ligand is ro-
tated counterclockwise by 90ꢁ, the other syn–anti isomer
results. This mechanism differs from both Berry pseudo-
rotation and the ‘‘turnstile rotation’’ in that there is no
exchange between equatorial and apical sites.
This study was supported in part by the National Sci-
ence Foundation and The Ohio State University.
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4. Conclusion
The complex [cis-mer-Ru(OSO2CF3)(CO)2(Cyttp)]+,
obtained by carbonylation of the previously prepared
[1] cis-mer-Ru(OSO2CF3)2(CO)(Cyttp), undergoes sub-
stitution of triflate by various monodentate ligands with
high stereospecificity. Its configurationally stable 13C
isotopomers [cis-mer-Ru(OSO2CF3)(CO)(13CO-trans to
PC)(Cyttp)]+ and [cis-mer-Ru(OSO2CF3)(CO)(13CO-cis
to all P donors)(Cyttp)]+ have been selectively synthe-
sized and used to gain mechanistic insight into reactions
with LiHBEt3, NaOMe/CO, and n-BuLi. These reac-
tions proceed, respectively, by: (a) substitution of hy-
dride for triflate without ligand rearrangement, (b)
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and (c) reduction to the same two ruthenium(0) prod-
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