Binding of CO and NH3 at a five-coordinate Ru(ii) centre in the solid state and in solution

Article abstract of DOI:10.1039/c3dt51625c

The known five-coordinate, square-pyramidal, green trans-RuCl ₂(P-N)(PR₃) complexes (P-N = o-diphenylphosphino-N, N′-dimethylaniline; R = Ph (1a), p-tolyl), in the solid state at ambient conditions, or in CDCl₃ solution at low temperatures, coordinate CO (at 1 atm) to form beige-coloured trans-monocarbonyl derivatives. In the solution reactions at room temperature, the PR₃ ligand dissociates and the yellow dicarbonyl complex RuCl₂(CO)₂(P-N) is formed as a mixture of trans,cis- and cis,cis-isomers. With use of ¹³CO, the carbonyls complexes are characterized by variable temperature NMR and IR data, and (for the monocarbonyls) elemental analyses. Similarly, 1a and the dibromo analogue (1b) in the solid state bind NH ₃ to form the beige trans-monoammine species RuX₂(P-N) (PPh₃)(NH₃), trans-4a (X = Cl) and trans-4b (X = Br), with cis P-atoms. The solution NH₃ reactions, however, generate a species, speculatively thought to be the unusual, tight ion-pair, bisammine species [RuX(P-N)(PPh₃)(NH₃)₂...X], 5a (X = Cl) and 5b (X = Br), in which a halide is considered strongly H-bonded to the cis-ammine ligands, although an alternative RuX(P-N)(PPh₃)(NH ₃)₂ formulation with a monodentate P-N ligand cannot be ruled out; dissolution in CDCl₃ of isolated 5a and 5b, which are characterized by NMR, elemental analysis, and conductivity data, results in a partial, reversible loss of NH₃ to form some cis- and trans-4a or -4b, respectively. Treatment of 5a with one mole equivalent of NH ₄PF₆ in acetone solution removes the H-bonded chloride to give [RuCl(P-N)(PPh₃)(NH₃)₂]PF₆ (6), and this is converted by thermal loss of NH₃ to generate the extremely air-sensitive, five-coordinate, ionic species [RuCl(P-N)(PPh ₃)(NH₃)]PF₆ (7). NMR evidence is presented for formation of the tris(ammine) species [Ru(P-N)(PPh₃)(NH ₃)₃](PF₆)₂ (8) via treatment of trans-RuCl₂(P-N)(PPh₃) with an atmosphere of NH ₃ in the presence of 2 mole equivalents of NH₄PF ₆.

Full text of DOI:10.1039/c3dt51625c

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Binding of CO and NH at a five-coordinate Ru(II) centre
3
in the solid state and in solution†
Cite this: Dalton Trans., 2013, 42, 13628
Erin S. F. Ma, Dona C. Mudalige and Brian R. James*
The known five-coordinate, square-pyramidal, green trans-RuCl
phosphino-N,N’-dimethylaniline; R = Ph (1a), p-tolyl), in the solid state at ambient conditions, or in CDCl
solution at low temperatures, coordinate CO (at 1 atm) to form beige-coloured trans-monocarbonyl
derivatives. In the solution reactions at room temperature, the PR ligand dissociates and the yellow dicar-
bonyl complex RuCl (CO) (P–N) is formed as a mixture of trans,cis- and cis,cis-isomers. With use of CO,
the carbonyls complexes are characterized by variable temperature NMR and IR data, and (for the mono-
carbonyls) elemental analyses. Similarly, 1a and the dibromo analogue (1b) in the solid state bind NH to
form the beige trans-monoammine species RuX (P–N)(PPh )(NH ), trans-4a (X = Cl) and trans-4b (X = Br),
with cis P-atoms. The solution NH reactions, however, generate a species, speculatively thought to be
the unusual, tight ion-pair, bisammine species [RuX(P–N)(PPh )(NH ⋯X], 5a (X = Cl) and 5b (X = Br), in
which a halide is considered strongly H-bonded to the cis-ammine ligands, although an alternative RuX-
P–N)(PPh )(NH formulation with a monodentate P–N ligand cannot be ruled out; dissolution in CDCl
of isolated 5a and 5b, which are characterized by NMR, elemental analysis, and conductivity data, results
in a partial, reversible loss of NH to form some cis- and trans-4a or -4b, respectively. Treatment of 5a
with one mole equivalent of NH PF in acetone solution removes the H-bonded chloride to give [RuCl-
P–N)(PPh )(NH ]PF (6), and this is converted by thermal loss of NH to generate the extremely air-
sensitive, five-coordinate, ionic species [RuCl(P–N)(PPh )(NH )]PF (7). NMR evidence is presented for
formation of the tris(ammine) species [Ru(P–N)(PPh )(NH ](PF (8) via treatment of trans-RuCl (P–N)-
(PPh ) with an atmosphere of NH in the presence of 2 mole equivalents of NH PF
2 3
(P–N)(PR ) complexes (P–N = o-diphenyl-
3
3
1
3
2
2
3
2
3
3
3
3
3 2
)
(
3
3
)
2
3
3
4
6
Received 18th June 2013,
Accepted 18th July 2013
(
3
3
)
2
6
3
3
3
6
DOI: 10.1039/c3dt51625c
3
3
)
3
6
)
2
2
www.rsc.org/dalton
3
3
4
6
.
differences in reactivity of 1 in the solid state and in solution,
and an unusual reversible formation of a bisammine complex
Introduction
We reported recently on the reversible binding (in solution from a monoammine species is probably unique. The NH
3
1
2
6
and the solid state) of H S and thiols, H O and alcohols, and work might also find relevance in catalyzed reactions of NH3.
2
2
3
H
2
, to five-coordinate complexes of the type trans-RuX
2
(P–N)-
(
PR ) complex (1), where X is a halogen, R is aryl, and P–N =
3
o-diphenylphosphino-N,N′-dimethylaniline (Chart 1). The pro-
ducts of the S-ligand and H systems are cis-isomers, whereas
the O-donor ligand systems generate trans-products. The
Experimental section
General
2
RuX (P–N)(PR ) species reveal a remarkable range of reactivity: All manipulations were performed under an oxygen-free, Ar
2
3
4
2
we have reported earlier on the similar binding of N , and atmosphere at room temperature (r.t., ∼22 °C) using standard
5
N O to form cis-adducts, and now we report reactivity toward Schlenk techniques. Commercially available compounds were
2
CO and NH . The carbonyl and ammonia systems are more supplied by Aldrich or Fisher, and were used as received
3
complicated than the previously reported systems in that repla- unless stated otherwise. Trans-RuX (P–N)(PPh ) (X = Cl, 1a; Br,
2
3
1
,4
cement of the PR ligand (and perhaps an ancillary chloride) 1b) and trans-RuCl (P–N)(P(p-tolyl) ) (1a′), were prepared by
3
2
3
of the precursor can occur. The findings also reveal major the reported methods, the precursor RuCl ·xH O being
3
2
donated by Colonial Metals, Inc.
Spectral and analytical grade solvents, and deuterated sol-
vents, were purified and stored as described recently. Purified
Department of Chemistry, University of British Columbia, Vancouver,
British Columbia, Canada, V6 T 1Z1. E-mail: brj@chem.ubc.ca
2
3
Ar (H.P.), CO, and NH , were Union Carbide or Matheson Gas
†
Electronic supplementary information (ESI) available: Variable temperature
1
3
1
31
1
1
Co. products, and CO was obtained from Merck Frost
(VT) H NMR and IR spectra of 1a under 1 atm CO; P{ H} and H NMR spectra
3
1
1
of trans-4a and 6, and P{ H} spectrum of 8. See DOI: 10.1039/c3dt51625c
Canada Ltd; Ar was dried by passage through a CaSO column,
4
1
3628 | Dalton Trans., 2013, 42, 13628–13634
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2 3
Chart 1 Reactions of trans-RuX (P–N)(PR ) with various small molecules (L).
whereas the other gases were used as supplied. Gas-tight
Sample-Lok™ syringes (Dynatech) were also used for handling
gaseous reagents; after a syringe was flushed with the gas, a
known quantity (at ambient conditions) was injected into a
septum-sealed reaction vessel or NMR tube. Details on the
2
measurements of NMR and IR spectra were provided recently,
with J values being reported in hertz (Hz), and s = singlet, d =
doublet, m = multiplet, br = broad. Conductivities were
measured using
a Serfass Conductance Bridge Model
RCM15B11 (A. H. Thomas Co. Ltd) connected to a Yellow
Springs Instrument Co. 3403 cell thermostatted at 25 °C, the
−
1
−1
cell constant, σ = 0.001413 ohm cm being determined by
measuring the resistance of a 0.0100 M aq. solution of KCl;
−
3
1
0
M solutions of the complex were prepared using dried
and O -free solvent, and the Λ values are given in units of
cm mol . Microanalyses were performed in this
department on a Carlo Erba 1106 instrument.
RuCl (P–N)(PR )(CO); R = Ph (2a), R = p-tolyl (2a′). A pow-
dered form (0.020 mmol) of the dark green RuCl (P–N)(PR
2
1
M
−
2
−1
ohm
2
3
2
3
)
complexes, R = Ph (1a) or p-tolyl (1a′), was stirred under 1 atm
CO at r.t., the colour attaining a brownish tinge after a few
minutes. After a 6 h treatment, elemental analysis of the solids
corresponded to the monocarbonyl adducts. Yield: 100%.
Anal. Calcd for 2a, C39
2 2
H35NOCl P Ru: C, 61.02; H, 4.60; N,
1
.83. Found: C, 60.4; H, 4.8; N, 1.7. Anal. Calcd for 2a′,
C H NOCl P Ru: C, 62.30; H, 5.10; N, 1.73; Cl, 8.76. Found:
4
2
41
2 2
C, 62.2; H, 5.2; N, 1.7; Cl, 8.9. IR (Nujol): νCO 1962 cm− for
both 2a and 2a′. The olive-green species 2a/2a′ were also
formed in situ when 1 mL of CO gas was added, respectively, to
1
3
1
1
a CDCl
NMR (CDCl
3
solution of 1a/1a′ at low temperatures: for 2a, P{ H}
2
3
, −50 °C): δ 46.09 (d, PPh
3
), 12.97 (d, P–N); JPP
=
1
2
(
(
5.7. H NMR (CDCl , −50 °C): δ 7.7–6.9 (m, ∼29H, Ph), 3.30
s, 6H, NMe
d, PPh ), 12.82 (d, P–N); JPP = 25.2. H NMR (CDCl
3
3
1
1
2 3
); for 2a′, P{ H} NMR (CDCl , −50 °C): δ 44.21
2
1
3
3
, −50 °C):
δ 7.6–6.7 (m, ∼26H, Ph), 2.29 (s, 6H, NMe ), 2.27 (s, 9H, p-tolyl
Me).
RuCl (CO) (P–N) (3). 1 mL of CO gas was injected into a
2 2
2
3
1
1
Fig. 1 Variable temperature P{ H} NMR spectra (CDCl
atm CO.
3
) of 1a or 2a under
1
dark green solution of 1a or 1a′ (0.030 mmol in 0.8 mL CDCl3)
under Ar at r.t. The solution colour became increasingly yellow
over time (see Fig. 1 below). An analytically pure sample of 3
2
13
1
2
was not isolated (see text). The in situ yellow species are 114.9, cis- J
= 14.0). C{ H}: 196.41 (dd, cis- J
= 14,
PC
PC
3
1
1
2
2
2
present as trans,cis- and cis,cis-isomers. For trans,cis-3, P{ H} cis- J = 5.0), 189.60 (m, trans- J = 115, cis- J = 5.8). For
CC
PC
1
CC
1
31
1
NMR (CDCl
−
3
, 20 °C): δ 36.01 (s, P–N). H NMR (CDCl
3
,
cis,cis-3, P{ H}: δ 26.12 (s, P–N); H δ 8.2–6.9 (m, ∼14H, Ph),
3
1
1
31
1
50 °C): δ 7.8–6.9 (m, ∼14H, Ph), 3.25 (s, 6H, NMe ). P{ H} 3.68 (s, 3H, NMe), 2.98 (s, 3H, NMe). P{ H} NMR (CDCl ,
2
3
1
3
2
13
2
2
NMR (CDCl
3
, 20 °C, under CO): δ 36.00 (dd, trans- JPC
=
20 °C, under CO): δ 26.10 (dd, trans- J = 123.5, cis- J
=
PC
PC
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1
3
1
2
2
2
1
1
(
4.0). C{ H}: 194.41 (dd, cis- JPC = 14, cis- JCC = 5.0), 187.9 (d
6
-acetone): δ 58.87 (d, P–N), 51.70 (d, PPh
NMR: δ 8.2–6.2 (m, 29H, Ph), 3.53 (s, 3H, NMe), 3.02 (s, 3H,
) (trans- and cis-4a). Solid 1a NMe), 2.65 (s, 3H, Ru-NH ), 0.53 (s, 3H, Ru-NH ). Λ (acetone,
for 3 h, the in the absence or presence of excess NH ) ∼ 145.
[RuCl(P–N)(PPh )(NH )]PF (7). A 10 mg sample of 6 was
3
); JPP = 31.4. H
2
2
m, trans- J = 124, cis- J = 5.0).
PC CC
trans-RuCl
20 mg, 0.027 mmol) was stirred under 1 atm NH
colour changing from green to beige. Yield: 100%. Anal. Calcd
for 4a, C38 Cl Ru: C, 60.32; H, 5.06; N, 3.70. Found: C, heated in vacuo at 80 °C for 1 h. Yield: 100%. Anal. Calcd for 7,
0.3; H, 5.2; N, 3.7. For trans-4a, P{ H} NMR (CDCl
d, P–N), 50.79 (d, PPh3); JPP = 36.5. H NMR (CDCl ): δ H, 4.9: N, 3.1 (see text). P{ H} NMR (d -acetone): δ 48.6 (br d,
.2–6.2 (m, ∼29H, Ph), 2.72 (s, 6H, NMe
2
(P–N)(PPh
3
)(NH
3
3
3
M
(
3
3
3
3
6
H
38
N
3
2 2
P
3
1
1
6
(
8
3
): δ 53.86
38 38 2 6 3
C H N ClF P Ru: C, 52.69: H, 4.42; N, 3.23. Found: C, 53.8;
2
1
31
1
3
6
2
1
2
), 1.64 (s, 3H, Ru- P–N), 47.8 (br d, PPh ); JPP ∼ 36. H NMR: many overlapping
3
3
1
1
NH
3
). For cis-4a, P{ H}: δ 59.27 (d, P–N), 51.45 (d, PPh
3
), signals in the δ 8.2–6.2 and 3.5–0.5 regions. The dark green
2
1
JPP = 32.3; H δ 8.2–6.2 (m, ∼29H, Ph), 3.61 (s, 3H, NMe), 2.94 solid (7) was extremely air-sensitive, decomposing to a brown
). solid.
(5a). To a solution of 1a (50 mg, [Ru(P–N)(PPh
.068 mmol) in 5 mL C H , 1 atm NH was introduced, and 1a (10 mg, 0.014 mmol) was added 2 equiv. of NH PF
(
s, 3H, NMe), 0.39 (s, 3H, Ru-NH
3
RuCl (P–N)(PPh )(NH
2
3
3
)
2
3 3 3 6 2 6
)(NH ) ](PF ) (8). To a d -acetone solution of
0
6
6
3
4
6
the dark green solution stirred for 1 h at r.t.; addition of (4.5 mg, 0.028 mmol) in the presence of 1 atm NH
hexanes (5 mL) precipitated a blue-green solid that was col- solution over 16 h changed from green to yellow. The NH
lected, washed with hexanes (2 × 5 mL), and dried at r.t. by an was removed by filtration through Celite and the filtrate ana-
3
at r.t.; the
4
Cl
3
1
1
Ar flow. Yield 35 mg, 68%. Anal. Calcd for 5, C38
C, 58.99: H, 5.34; N, 5.43. Found: C, 59.1; H, 5.4: N, 5.2. Λ
acetone, under 1 atm NH ) ∼ 0. Dissolution of 5a in CDCl
H
41
N
3
Cl
2
P
2
Ru: lyzed by NMR spectroscopy. P{ H} NMR (d
6
-acetone): δ 55.26
); JPP = 32.0. H NMR: δ 8.2–6.2 (m,
29H, Ph), 3.21 (s, 6H, NMe ), 3.11(s, 6H, Ru-NH ), 1.10 (s, 3H,
2
1
M
(d, P–N), 51.67 (d, PPh
3
(
3
3
2
3
results in some dissociation of NH
3
3 M 3
and three Ru species (5a, Ru-NH ). Λ (acetone, in the presence of excess NH ) ∼ 290.
3
1
and trans- and cis-4a) are seen in the NMR spectra. For 5a, P-
1
2
1
{
H}: δ 57.20 (d, P–N), 53.24 (d, PPh ), J = 32.0; H δ 8.2–6.2
3 PP
(
3
m, 29H, Ph), 3.72 (s, 3H, Ru-NH
H, Ru-NMe), 1.70 (s, 3H, Ru-NH
data are identical to those given above. A solution of 1a
10 mg, 0.014 mmol) in 0.7 mL CDCl under 1 atm NH
rated in situ solely 5a (see text for plausible structures).
trans-RuBr (P–N)(PPh )(NH ) (trans-4b). This complex was geneous, irreversible reaction of CO with the powdered five-
3
), 3.19 (s, 3H, NMe), 3.00 (s,
). For trans- and cis-4a, NMR
Results and discussion
Carbonyl adducts
3
(
3
3
gene- The monocarbonyl species RuCl
2 3
(P–N)(PR )(CO); R = Ph (2a),
R = p-tolyl (2a′) were isolated in quantitative yields by a hetero-
2
3
3
synthesized in 100% yield via a solid state reaction analogous coordinate precursors, trans-RuCl
to that described for trans-4a, but using RuBr (P–N)(PPh ) (1b) p-tolyl (1a′), and were characterized in the solid state by
as precursor. Anal. Calcd for 4b, C H N Br P Ru: C, 53.98: elemental analysis, and an IR νCO band at 1962 cm . The
2 3
(P–N)(PR ) (R = Ph (1a);
2
3
−
1
3
8
38
3
2 2
3
1
1
H, 4.53; N, 3.31. Found: C, 53.6; H, 4.5: N, 3.1. P{ H} NMR species were also made in situ by a solution reaction at low
CDCl ): δ 55.25 (d, P–N), 50.65 (d, PPh ); JPP = 36.7. H NMR temperature (<−20 °C). The low temperature NMR data, an AX
3 3
CDCl ): δ 8.2–6.2 (m, ∼29H, Ph), 3.01 (s, 6H, NMe ), 1.58 (s, pattern with JPP ∼ 25 Hz in the P{ H} NMR spectrum (Fig. 1,
A–C) and a single H resonance for the NMe
(5b) and cis-4b. These species were Fig. S1, A–C†), are consistent with the trans-dichloro geometry
formed in situ along with trans-4b (see above) in CDCl on as seen for the related aqua and alcohol adducts (see
2
1
(
(
3
3
1
1
3
2
1
H, Ru-NH
RuBr (P–N)(PPh )(NH )
2 3 3 2
3
).
2
protons (e.g.,
3
3
1
1
2
31
1
3
treating 1b with 1 atm NH . For 5b, P{ H}: δ 57.40 (d, P–N), Chart 1). Of note, the more downfield P{ H} shift within the
2
1
5
6.06 (d, PPh
3
), JPP = 31.8; H δ 8.2–6.2 (m, ∼29H, Ph), 3.64 (s, earlier studied cis- and trans-species has been assigned un-
3
H, Ru-NH ), 3.34 (s, 3H, NMe), 2.78 (s, 3H, NMe), 1.75 (s, 3H, ambiguously via a structural vs. δP correlation for the P–N
3
31
1
2
Ru-NH
3
). For cis-4b, P{ H}: δ 62.86 (d, P–N), 51.85 (d, PPh
3
), ligand. However, in 2a and 2a′ the downfield shift (δ
P
∼ 46) is
2
1
J
PP = 31.8; H δ 8.2–6.2 (m, ∼29H, Ph), 3.97 (s, 3H, NMe), 2.74 close to the downfield signal of the PR
3
ligand, and thus the
(
s, 3H, NMe), 0.48 (s, 3H, Ru-NH ). ΛM (under 1 atm NH ) ∼ more upfield signal (δ ∼ 13) is assigned to the P-atom of the
3
3
P
0
. See text for plausible structures of 5b.
aminophosphine, which is trans to the CO ligand. The closest
[
RuCl(P–N)(PPh
3 3 2 6 2
)(NH ) ]PF (6). A 5 mL acetone solution of literature analogue to 2a and 2a′ is trans,mer-RuCl (PNP)CO
NH PF (22 mg, 0.140 mmol) was added to a 10 mL acetone (with νCO = 1955 cm− ) made from a vinylidene precursor, PNP
1
4
6
7
solution of 5a (100 mg, 0.130 mmol). The resulting pale green being the tridentate Me(CH
2
)
2
N[(CH PPh
2
)
2
2 2
] ligand.
solution was stirred under 1 atm NH for 16 h to give a dark The dicarbonyl species RuCl
3
2
(CO) (P–N) (3) is formed as a
2
yellow solution and a suspension of NH Cl, which was mixture of isomers in CHCl3 solution, when 1a or 1a′ is
4
removed by filtration through Celite. Evaporation of the exposed to 1 atm CO at ambient temperature as shown in eqn (1),
3
1
1
acetone yielded a brown residue, which was dissolved in 3 mL the liberated PR
3
being seen in the P{ H} spectrum (e.g.,
CH Cl ; addition of Et O (10 mL) precipitated a yellow solid Fig. 1, C–F); the isomers of 3 are also formed in situ when a
2
2
2
2
that was collected, and washed with Et O (2 × 5 mL). Yield: solution of the monocarbonyl complexes 2a (or 2a′) at low
1
4
4
5 mg, 39%. Anal. Calcd for 6, C38
41 3 6 3
H N ClF P Ru: C, 51.68: H, temperatures is warmed to r.t. under CO (Fig. 1). The in situ H
3
1
1
31
1
.68; N, 4.76. Found: unsatisfactory (see text). P{ H} NMR spectra under 1 atm CO (Fig. S1†), and the in situ P{ H} and
1
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RuCl
2
(CO)
2
(PR
3
)
2
complexes to the cis,cis,trans-isomer has
8,9
been reported to be inhibited at higher CO concentrations.
The corresponding C{ H} NMR spectrum (Fig. 3) shows
doublet of doublet patterns at δ 196.41 and 194.41, each com-
1
3
1
C
2
2
prised of the cis- J value of 14 Hz and a cis- J value of
PC
CC
5.0 Hz – these are assigned to the CO ligand cis to the P-atom
of the P–N ligand in both isomers; the same patterns at δ
C
2
2
1
89.60 (trans- J
= 115, cis- J
= 5.8 Hz) and δC 187.93
CC
PC
2
2
(
trans- JPC = 124, cis- JCC = 5.0 Hz) are due to the CO trans to
31
1
13
this P-atom.
Solution IR spectra over the temperature range 20 to −50 °C
for the in situ formation of 3 from 1a at 1 atm CO (Fig. S2†)
Fig. 2
2 h; ? = unidentified species – the δ 42.5 and 16.5 signals could be those of 2a
see text).
3
P{ H} NMR spectrum (CDCl ) of 1a under 2 atm CO at ∼20 °C after
1
(
also provide evidence for the formation of 2a and the two
isomers of 3; at about −50 °C (Fig. S2,B†), the single ν band
CO
at 1985 cm− corresponds to the monocarbonyl 2a, while the
1
−
1
bands at 2078, 2010 (sh), 1999 and 1967 cm (Fig. S2,F†) cor-
respond to the cis-carbonyls in the two isomers of 3. The spec-
tral pattern with a band in each of the ranges 2100–2000 and
000–1900 cm− agrees well with those observed for analogous
1
2
9
Ru complexes with cis-disposed CO ligands.
Unfortunately, analytically pure forms of 3 could not be iso-
lated from the reaction of 1a with CO. The co-product PPh is
3
clearly a possible impurity, while the NMR spectra (Fig. 1 and
S1†) suggest that some 2a could be present, and the NMR
1
3
spectra measured under CO (Fig. 2 and 3) show other unas-
signed resonances. In Fig. 2, the signals at δ 42.5 and 16.5
could be those of 2a, the values differing by ∼3.5 ppm from
those measured under non-labelled CO, and a signal in Fig. 3
could be due to the CO ligand of 2a. The other unidentified
signals remain problematic; in principle, other carbonyl-
containing compounds might possibly be formed from
1
3
1
Fig. 3
3
C{ H} NMR spectrum (CDCl ) of isomers of 3 formed from 1a under
1
3
2
atm CO at ∼20 °C, eqn (1); A and A’ refer to CO cis to P-atom of P–N ligand,
and B and B’ refer to CO trans to this P-atom; ? = unidentified species (see text).
1
3
gaseous and moisture impurities present in commercial CO,
1
3
1
1,2–4
C{ H} NMR spectra (Fig. 2 and 3) obtained from the r.t. reac- since 1a is reactive toward such impurities.
1
3
tion of 2a with ∼2 atm CO, were used to assign the products
as the cis,cis- and trans,cis-isomers of 3. Fig. S1,A† (the −50 °C tion is shown in Chart 2: dissociation of the PPh ligand from
A reasonable mechanism for the reaction with CO in solu-
3
2 H
spectrum) shows the single NMe resonance of 2a at δ 3.30; the initially formed mono-CO adduct (2a), generates the five-
between −20 °C to r.t., increasing amounts of cis,cis-3 (the coordinate, unobserved intermediate (I), which then binds the
major isomer with two equal intensity signals at δH 3.68 and second CO that can become trans to either a Cl- or N-atom to
2
.98) and trans,cis-3 (a single peak at δ
H
3.25 for the minor give cis,cis-3 or trans,cis-3, respectively. The reaction resembles
3
1
1
isomer) are formed (Fig. S1,B–F†). The P{ H} spectrum that observed between RuCl (PPh ) and CO in solution, where
under CO conditions (Fig. 2) displays two doublets of doub- the initially formed trans,trans,trans-RuCl (CO) (PPh ) species
lets centred at δ 36.00 and 26.10, each showing a trans- JPC isomerizes to the more stable cis,cis,trans-isomer under
P
2
3 3
1
3
2
2
3 2
2
ð1Þ
2
10
value (114.9 and 123.5 Hz, respectively) and a cis- JPC value of ambient conditions. Of note, in contrast to the behaviour of
2
1
4.0 Hz. The
J
PC coupling pattern establishes the cis-(CO)
geometry in the two isomers. Of interest, under 2 atm CO, with CO does liberate PPh and isomers of the dicarbonyl
trans,cis-3 is the major isomer (also evident in the H spec- are formed directly.
trum), whereas this is the minor isomer formed under 1 atm RuCl (CO) (P–N) complex, where P–N is o-(diphenylphos-
CO, the difference resulting from the difference in CO concen- phino)aniline, was made from the six-coordinate precursor
2
2 3 3
solid 1a with CO, reaction of RuCl (PPh ) in the solid state
8
3
1
11
12
A
recently reported,
analogous
2
2
tration. A related isomerization from the all-trans form of RuCl
2
(CO)
3
THF, X-ray data revealing a structure similar to that
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Chart 2 Mechanism for reaction of 1a (R = Ph) with CO to give 2a and the isomers of 3 via I.
of the cis,cis-3 isomer shown in eqn (1) but with the cis-posi-
tions of the P–N interchanged; for this species, IR bands were
−1
seen at 2058 and 1996 cm
.
Ammonia adducts
A green, solid sample of 1a at r.t. readily binds NH (at 1 atm)
3
in the vacant coordination site to form quantitatively trans-
2 3 3
RuCl (P–N)(PPh )(NH ) (trans-4a, cf. Chart 1), as evidenced by
EA (elemental analysis) and the ‘immediate’ NMR data in
3
1
1
CDCl
3
(see Fig. S3 and S4†) – an AX pattern in the P{ H}
1
NMR spectrum and a single H resonance for the NMe
2
protons. However, in this solution, the beige trans-4a isomer
rearranges over time at r.t. to give the more thermodynamically
stable cis-4a, as shown by the NMR spectral changes: inequi-
1
valent NMe groups appear in the H data; and new doublets
2
1
Fig. 4 H NMR spectrum (CDCl
3
) of 5a under 1 atm NH
3
at 20 °C; phenyl
3
1
1
of doublets appear in the P{ H} data (see also Fig. 5B below),
region omitted.
the shifts being close to those found for analogous cis-
1
,3,5
adducts.
species, see below) is also observed in the ‘immediate’ spectra
Fig. S3 and S4†). This must result from some excess NH
It should be noted that some 5a (a bisammine
(
3
being occluded in the solid sample of trans-4a; after 30 min,
the concentrations of 5a and trans-4a diminish significantly as
these species convert to cis-4a.
The formation of the monoammine contrasts with the be-
havior of other five-coordinate species such as RuCl
and RuCl (dppb)(PPh ) (dppb = 1,4-bis(diphenylphosphino)-
butane) which, in solid state or solution reactions with NH ,
2 3 3
(PPh )
2
3
3
1
1a,13
dissociate the PPh
when NH reacts with 1a in C
formed, with the EA of the isolated blue-green complex corres-
ponding to RuCl (P–N)(PPh )(NH (5a). The most obvious
3
to form bisammine species.
However,
3
6 6
H
, a bisammine species is
2
3
3 2
)
formulation is a monochloro Ru-containing cation with an
associated chloride anion; however, the species is non-con-
ducting in acetone or CH Cl solutions, and thus possibilities
2 2
other than a ‘highly unlikely’ seven-coordinate formulation
1
need consideration. The H NMR spectrum for 5a dissolved in
3
1
1
Fig. 5
3 3
P{ H} spectra (20 °C, CDCl ) for 5a: (A) with 1atm NH and (B)
CDCl
NMe
ent with cis-NH groups (free NH is detected at δ 0.50); the
3
under 1 atm NH
3
(Fig. 4) reveals two singlets for Ru-
absence of excess NH
3
.
2
and two singlets for the Ru-(NH
3 2
)
protons, data consist-
3
3
H
resonances for the N-Me groups are sharper than the some- interaction with an NH
what broader ones of the coordinated NH
groups (in all the Me singlet is seen at δ 2.60, whereas in 5a the δ values are 3.19
ammine complexes), and so any equal intensity 3H signals are and 3.00, close to those seen for species with a coordinated
ligand is a possibility. In free P–N, the
3
3
3
1
1
readily assigned. The presence of doublets in the P{ H} spec- NMe
. These data lead to an alternative, highly speculative sug-
trum (Fig. 5A) reveals an AX coupling pattern ( JPP = 32.0 Hz), gestion of the formulation [RuCl(P–N)(PPh )(NH ⋯Cl], a
confirming that the PPh ligand remains coordinated.
strongly associated ion-pair, in which a chloride is H-bonded
A formulation for 5a with a monodentate P–N is plausible, to the NH ligands; such H-bonding would be stronger than in
2
2
3
3 2
)
3
3
but the observed inequivalent N–Me groups would then the ‘dangling’ P–N species. There is an example of such
require restricted rotation of the NMe moiety; an H-bonding second-sphere coordination involving a chloride H-bonded to
2
1
3632 | Dalton Trans., 2013, 42, 13628–13634
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Chart 3 Reversible conversion of 5a/b to 4a/b (R = Ph).
cis-NH3 ligands within structural data for a [Co(NH ) ][Cl]- (H-bonded or coordinated) removed as precipitated NH Cl.
3 6
4
1
4
[
(mesitylenesulfonate)
2
] complex, which consists of alternate Consistent with electronic changes within the coordinated
layers of cations and anions, but we have been unable to find a NH ligands, the two H singlets for the Ru-(NH ) protons in
1
3
3 2
report on such chloride-binding associated with a Ru cation. 6 (vs. values for 5a) are shifted upfield by ∼1.1 ppm (data that
Many unsuccessful attempts were made to grow a crystal of 5a. perhaps favour the ion-pair formulation for 5a); as for 5a, the
Dissolution of 5a in the absence of NH results in partial dis- Me groups of Ru-NMe2 in 6 are magnetically inequivalent
3
sociation of NH over time with formation of some trans- and (Fig. S6†). Several synthesized samples of 6 failed to give satis-
3
3
cis-4a (Fig. 5B); this loss of NH is reversed when the solution factory EA; the N analyses were typically 2% high, perhaps
is re-exposed to 1 atm NH . A mixture of trans- and cis-4a is implying the presence of some tris(ammine) impurity (see 8,
3
3
1
1
also formed when one mole equivalent of NH is added to 1a below). The P{ H} spectrum of solutions of 6 (Fig. S5A†)
3
6 6 3
in C D or CDCl solution. Very similar chemistry was estab- shows an ‘impurity’ doublet signal at δ 55.4, with the other
1
lished for the reaction of NH3 with the bromo analogue required doublet possibly being hidden; the H spectrum
RuBr (P–N)(PPh ) (1b): (i) formation of trans-RuBr (P–N)(PPh )- showed many unidentified resonances in the δ 3.2–0.8 region,
2
3
2
3
(
NH
time to cis-4b, and (iii), formation in solution of 5b, the bromo again, some of these signals likely result from the presence of
analogue of 5a, and its dissociation to trans- and cis-4b. 8 as an impurity (see below). Attempts to dry 6 in vacuo at
3 2
) (4b) in the solid state, (ii) its conversion in solution over as well as signals of Et O that was used in the isolation of 6 –
3
1
1
The changes in the P{ H} spectra over time for both 5a ∼80 °C resulted in a very air-sensitive, dark green solid (7),
and 5b suggest that the overall reversible reactions with NH3 whose elemental analysis for N was consistent with the pres-
occurs via the scheme shown in Chart 3. If 5a/b is an ion-pair, ence of one NH
in the absence of excess NH , the NH trans to the coordinated [RuCl(P–N)(PPh )(NH
X is replaced by the ‘associated X’ to form the trans-4a/4b cation. The P{ H} spectrum of 7 in d -acetone gave ‘new’
3
ligand; this suggests the species might be
3
3
3
3
)]PF containing five-coordinate
6
a
3
1
1
6
2
1
species, which then isomerize to the more stable cis-4a/4b. broad doublets at δ 48.6 and 47.8 ( JPP ∼ 36 Hz), but the H
After 1 week, the solution contains just 5a/b (<10%) and cis-4a/b signals could not be assigned due to overlapping peaks in the
(
>90%), and exposure to 1 atm NH completely regenerates 5a/ 3.5–0.5 region. Complex 7 decomposed in air to a black
3
b. If 5a/b is a dangling P–N species, the NH
by the NMe fragment. We are unaware of any report on revers- a black solid) is consistent with the presence of a vacant
ible formation of a bisammine complex from a monoammine coordination site.
3
would be replaced powder. The reactive nature of 7 (rapid decomposition in air to
2
species.
Of interest, species 6 reacts with NH
mole equivalent of NH PF in d -acetone to generate (after
removal of NH Cl) a further in situ species 8; this shows
3
in the presence of a
4
6
6
Cationic ammine species
4
3
1
1
2
Many attempts were made to characterize thoroughly cationic
P{ H} doublets at δ 55.26 and 51.67 ( JPP = 32 Hz) (see
1
species formed from the neutral complexes noted in the pre- Fig. S7† below) and, in the H spectrum, a singlet δ 3.21 reson-
vious section, by extracting the chloride ligand(s) from such ance for the 6H of the NMe moiety, and coordinated NH
precursors by treatment of the complexes with NH PF . Unfor- resonances at δ 3.11 (6H) and 1.10 (3H). These data show the
2
3
4
6
tunately, isolation of pure mono- or di-cationic complexes has presence of two equivalent and one other NH
3
ligand(s), a
not been accomplished, although the presence of such species PPh , and the P–N ligand and, coupled with a conductivity
3
−
1
2
−1
is proven by NMR and conductivity data.
value of ∼288 ohm cm mol (in the range for a 1 : 2 electro-
1
5
A yellow solid, isolated from the reaction of 5a with NH
4
PF
6
3 3 3 6 2
lyte), 8 is considered to be [Ru(P–N)(PPh )(NH ) ](PF ) . The
3
1
1
in acetone under 1 atm NH
3
, is characterized as [RuCl(P–N)- doublet at δ ∼ 55, which appears in the P{ H} spectrum of 6
PPh )(NH ) ]PF (6). In d -acetone solution, in the absence of (Fig. S5A†), is almost certainly due to 8, the other expected
, the P{ H} spectrum of 6 (Fig. S5A†) shows doublets at δ doublet of 8 (at δ ∼ 52) being hidden. Species 8 was also
8.87 and 51.70 ( JPP = 31.4 Hz), which are very similar to formed in situ in acetone by treating 1a with 1 atm NH
presence of two equivalents of NH
chemistry is outlined in Chart 4.
cm mol , consistent with a 1 : 1 electrolyte. Thus the cation
Of general interest, we have found one other example of a
structure of 6 is pictured as that of 5a with a chloride coordinatively unsaturated complex, namely the H Os (CO)12
(
3
3 2
1
6
6
3
1
NH
5
3
2
in the
3
2
those seen for 5a in this solvent (δ 57.87 and 52.60, JPP
=
4 6
PF (Fig. S7†); the relevant
−
1
3
1.9 Hz; Fig. S5B†), but now the conductivity is ∼146 ohm
2
−1
15
2
3
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Chart 4 Formation of 8 from 6, and from 1a (R = Ph).
cluster, that in the solid state (like 1a) binds CO, NH , and H S
3
2
References
1
6
to form, at least initially, 1 : 1 adducts; this 1994 publication
also gives a useful introduction regarding interest in develop-
ing such solid-state reactions, particularly for their mechanis-
tic details, and for their benefits in synthetic chemistry.
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5 C. B. Pamplin, E. S. F. Ma, N. Safari, S. J. Rettig and
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H and N ) at a five-coordinate Ru(II) centre in complexes of
2 2
2 3
the type RuX (P–N)(PR ) (X = halide; P–N = o-diphenylphos-
phino-N,N′-dimethylaniline; R = Ph, p-tolyl) appeared 20 years
4
ago and, since then, our group has reported on coordination
1
–3,5
of N
2
O, H
2
S, thiols, H
2
O and alcohols.
The systems thus
far reported have simply involved formation (in solid-gas or
solution phase) of 1 : 1 adducts, and have provided data on the
thermodynamics of the binding equilibria. This current paper
8 D. W. Kraasowski, J. H. Nelson, K. R. Brower,
D. Hauenstein and R. A. Jacobson, Inorg. Chem., 1988, 27,
4294.
shows that in the interaction of CO and NH
3
(again in solid-
9 (a) C. F. J. Barnard, J. A. Daniels, J. Jeffery and R. J. Mawby,
J. Chem. Soc., Dalton Trans., 1976, 953; (b) L. M. Wilkes,
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gas or solution phase), more than one molecule of the gas can
become coordinated, and the associated chemistry necessarily
becomes more complicated. Thus, after formation of a mono-
carbonyl from the chloro precursors, a further CO can replace
the monodentate phosphine to form RuCl
mixture of isomers. Within the NH systems, the monoam-
mine adducts, RuX (P–N)(PPh )(NH ), exist as two isomers
that can react further to generate bisammine species, which is
speculatively formulated as containing a non-coordinated
chloride, strongly H-bonded to the coordinated ammines – an
alternative formulation with a dangling P–N ligand is also con-
2 2
(CO)
(P–N) as a 10 (a) T. A. Stephenson and G. Wilkinson, J. Inorg. Nucl.
Chem., 1966, 28, 945; (b) S. Cenini, A. Fusi and
G. Capparella, J. Inorg. Nucl. Chem., 1971, 33, 3576;
(c) B. R. James, L. D. Markham, B. C. Hui and
G. L. Rempel, J. Chem. Soc., Dalton Trans., 1973, 2247;
(d) D. W. Krassowski, K. Reimer, H. E. LeMay and
J. H. Nelson, Inorg. Chem., 1988, 27, 4307.
3
2
3
3
sidered. Reaction of the five-coordinate precursors with NH
3
in 11 (a) K. S. MacFarlane, Ph. D. Dissertation, University of
British Columbia, 1995, ch. 7; (b) F. Porta, C. Tollari,
C. Bianchi and S. Recchia, Inorg. Chim. Acta, 1996, 249, 79.
12 C.-C. Lee, Y.-H. Liu, S.-M. Peng, P.-T. Chou, J.-T. Chen and
S.-T. Liu, Polyhedron, 2012, 35, 23.
the presence of NH PF removes one or two chloride ligand(s)
4
6
to generate cationic Ru(II) species containing two or three
ammine ligands.
The wide range of reactivity of these coordinatively unsatu-
rated Ru(II) complexes is truly remarkable, and practically 13 (a) S. Cenini, F. Porta and M. Pizzotti, J. Mol. Catal., 1982,
limitless!
15, 297; (b) S. L. Queiroz, A. A. Batista, G. Oliva, M. T. do
P. Gambardella, R. H. A. Santos, K. S. MacFarlane,
S. J. Rettig and B. R. James, Inorg. Chim. Acta, 1998, 267,
209.
1
4 R. P. Sharma, R. Bala, R. Sharma, K. N. Singh and
V. Ferretti, J. Mol. Struct., 2006, 784, 117.
Acknowledgements
We thank the Natural Sciences and Engineering Council of 15 W. J. Geary, Coord. Chem. Rev., 1971, 7, 81.
Canada for funding, and Colonial Metals Inc. for a loan of 16 S. Aime, W. Dastru, R. Gobetto and A. J. Arce, Organometal-
RuCl ·xH O.
lics, 1994, 13, 4232.
3
2
1
3634 | Dalton Trans., 2013, 42, 13628–13634
This journal is © The Royal Society of Chemistry 2013