Dioxygen complexes from the reactions of [Cp*RuH2(PP)]+ (PP = dppm, dppe) with air

Article abstract of DOI:10.1021/om990317b

Exposure of [Cp*RuH₂(dppm)]BF₄ in acetone or methanol to air produced a mixture of [Cp*Ru(O₂)(dppm)]BF₄ and [Cp*Ru(O₂)(Ph₂PCH₂P(O)Ph ₂)]BF₄. Reaction of Cp*RuCl(dppm) with NaBPh₄ in methanol in air produced the dioxygen complex [Cp*Ru(O₂)(dppm)]BPh₄, which has been characterized by X-ray diffraction. Reaction of Cp*RuCl(dppm) with H₂O₂ in the presence of NaBPh₄ in air produced [Cp*Ru(O₂)(Ph₂PCH₂P(O)Ph ₂)]BPh₄ and Ph₂P(O)CH₂P(O)PPh₂. Reaction of [Cp*RuH₂(dppe)]BF₄ in acetone or methanol with air also produced a mixture of [Cp*Ru(O₂)(dppe)]BF₄ and [Cp*Ru(O₂)(Ph₂PCH₂CH ₂P(O)Ph₂)]BF₄.

Full text of DOI:10.1021/om990317b

Organometallics 1999, 18, 3597-3602
3597
Dioxygen Com p lexes fr om th e Rea ction s of
[Cp *Ru H2(P P )]+ (P P ) d p p m , d p p e) w ith Air
Guochen J ia,*,† Weng Sang Ng,† Hei Shing Chu,† Wing-Tak Wong,‡
Nai-Teng Yu,† and Ian D. Williams†
Departments of Chemistry, The Hong Kong University of Science and Technology,
Clear Water Bay, Kowloon, Hong Kong, China, and The University of Hong Kong,
Hong Kong, China
Received April 29, 1999
Exposure of [Cp*RuH2(dppm)]BF4 in acetone or methanol to air produced a mixture of
[Cp*Ru(O2)(dppm)]BF4 and [Cp*Ru(O2)(Ph2PCH2P(O)Ph2)]BF4. Reaction of Cp*RuCl(dppm)
with NaBPh4 in methanol in air produced the dioxygen complex [Cp*Ru(O2)(dppm)]BPh4,
which has been characterized by X-ray diffraction. Reaction of Cp*RuCl(dppm) with H2O2
in the presence of NaBPh4 in air produced [Cp*Ru(O2)(Ph2PCH2P(O)Ph2)]BPh4 and Ph2P-
(O)CH2P(O)PPh2. Reaction of [Cp*RuH2(dppe)]BF4 in acetone or methanol with air also
produced a mixture of [Cp*Ru(O2)(dppe)]BF4 and [Cp*Ru(O2)(Ph2PCH2CH2P(O)Ph2)]BF4.
Sch em e 1
In tr od u ction
Reactions of LnM(H2) (e.g. OsHCl(H2)(CO)(P(i-Pr)3)2,1
[OsH(H2)(dppe)2]+,2 [RuH(H2)(dippe)2]+ (dippe ) (i-
Pr)2PCH2CH2P(i-Pr)2)3) or LnMH2 (e.g. RuH2(Ph2PN-
MeNMePPh2)2,4a RuH2(CO)2(PPh3)24b) with oxygen usu-
ally lead to the displacement of the H2 molecule by O2
to give LnM(O2). During the course of investigating the
chemical properties of [Cp*RuH2(dppm)]+, we have
found that reaction of [Cp*RuH2(dppm)]+ with air
produced a mixture of [Cp*Ru(O2)(dppm)]+ and [Cp*Ru-
(O2)(Ph2PCH2P(O)Ph2)]+. Similar results were also ob-
served for the reaction of [Cp*RuH2(dppe)]+ with air.
While the formation of [Cp*Ru(O2)(PP)]+ (PP ) dppm,
dppe) from these reactions is probably not surprising,
as several closely related dioxygen complexes [Cp*Ru-
(O2)(PR3)2]+ have been reported,5-8 production of [Cp*Ru-
(O2)(Ph2PCH2P(O)Ph2)]+ and [Cp*Ru(O2)(Ph2PCH2CH2P-
(O)Ph2)]+ is rather unusual. In this paper, the character-
ization of the new dioxygen complexes and the possible
mechanism for the interesting reactions will be pre-
sented.
Resu lts a n d Discu ssion
Rea ction of [Cp *Ru H2(d p p m )]BF 4 a n d Cp *Ru Cl-
(d p p m ) w ith Air . The complex [Cp*RuH2(dppm)]BF4
(1) is known to exist as a mixture of the dihydride form
trans-[Cp*RuH2(dppm)]BF4 (1a ) and the dihydrogen
form [Cp*Ru(H2)(dppm)]BF4 (1b) in a ratio of 1:2.9,10
Exposure of acetone solutions of 1 to air produced a
brown solution from which complexes [Cp*Ru(O2)-
(dppm)]BF4 ([2]BF 4) and [Cp*Ru(O2)(Ph2PCH2P(O)-
Ph2)]BF4 ([3]BF 4) can be isolated (Scheme 1). An in situ
31P NMR spectrum of the reaction mixture showed that
the major product of the reaction is [3]BF 4. [3]BF 4 is
not formed from further oxidation of [2]BF 4 by air, as
the isolated complex [2]BF 4 did not react further with
air to give [3]BF 4. Similar results were obtained when
pure oxygen gas instead of air was used.
† The Hong Kong University of Science and Technology.
‡ The University of Hong Kong.
(1) Esteruelas, M. A.; Sola, E.; Oro, L. A.; Meyer, U.; Werner, H.
Angew. Chem., Int. Ed. Engl. 1988, 27, 1563.
(2) Bartucz, T. Y.; Golombek, A.; Lough, A. J .; Maltby, P. A.; Morris,
R. H.; Ramachandran, R.; Schlaf, M. Inorg. Chem. 1998, 37, 1555.
(3) (a) J ime´nez-Tenorio, M.; Puerta, M. C.; Valerga, P. Inorg. Chem.
1994, 33, 3515. (b) J ime´nez-Tenorio, M.; Puerta, M. C.; Valerga, P. J .
Am. Chem. Soc. 1993, 115, 9794.
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17, 3875. (b) Porta, F.; Cenini, S.; Giordano, S.; Pizzotti, M. J .
Organomet. Chem. 1978, 150, 261.
(5) (a) Kirchner, K.; Mauthner, K.; Mereiter, K.; Schmid, R. J . Chem.
Soc., Chem. Commun. 1993, 892. (b) Mauthner, K.; Mereiter, K.;
Schmid, R.; Kirchner, K. Inorg. Chim. Acta 1995, 236, 95.
(6) (a) Rios, I. D. L.; J ime´nez-Tenorio, M.; Padilla, J .; Puerta, M.
C.; Valerga, P. J . Chem. Soc., Dalton Trans. 1996, 377. (b) Rios, I. D.
L.; J ime´nez-Tenorio, M.; Padilla, J .; Puerta, M. C.; Valerga, P.
Organometallics 1996, 15, 4565.
(7) Lindner, E.; Haustein, M.; Fawzi, R.; Steimann, M.; Wegner, P.
Organometallics 1994, 13, 5021.
(8) Sato, M.; Asai, M. J . Organomet. Chem. 1996, 508, 121.
[2]BF 4 and [3]BF 4 were also produced when metha-
nol solutions of 1 were exposed to air. However, [2]BF 4
(9) (a) J ia, G.; Morris, R. H. J . Am. Chem. Soc. 1991, 113, 875. (b)
J ia, G.; Lough, A. J .; Morris, R. H. Organometallics 1992, 11, 161.
(10) Klooster, W. T.; Koetzle, T. F.; J ia, G.; Fong, T. P.; Morris, R.
H.; Albinati, A. J . Am. Chem. Soc. 1994, 116, 7677.
10.1021/om990317b CCC: $18.00 © 1999 American Chemical Society
Publication on Web 08/06/1999

3598 Organometallics, Vol. 18, No. 18, 1999
J ia et al.
was produced as the major product in this solvent (the
relative ratio of [2]BF 4 to [3]BF 4 was 4.5:1, as indicated
by an in situ 31P NMR spectrum). Thus, the relative
amounts of [2]BF 4 and [3]BF 4 from the oxidation
reaction appear to be solvent-dependent.
[2]BF 4 could also be obtained cleanly by exposure of
methanol solutions of [Cp*Ru(dppm)]BF4 (generated in
situ from the reaction of AgBF4 and Cp*RuCl(dppm)
(4)9) to air (eq 1). Similarly, stirring a methanol solution
F igu r e 1. Molecular structure of the cation [Cp*Ru(O2)-
(dppm)]+.
of Cp*RuCl(dppm) in the presence of NaBPh4 in air for
3 h produced [Cp*Ru(O2)(dppm)]BPh4 ([2]BP h 4). Ap-
parently O2 from air was absorbed by [Cp*Ru(dppm)]+
to form [2]BF 4 or [2]BP h 4. In principle, N2 and H2O in
air can also react with [Cp*Ru(dppm)]+ to form the
known complexes [Cp*Ru(N2)(dppm)]+ and [Cp*Ru-
(H2O)(dppm)]+.11 However, such complexes were not
detected in our experiments. The dioxygen ligand in
[2]BF 4 or [2]BP h 4 is bound so tightly that it could not
be displaced by N2 or H2.
Complex 2 was characterized by elemental analysis,
IR, MS, and 1H, 13C, and 31P NMR spectroscopy. In
particular, the FAB-MS (NBA matrix) of [2]BF 4 dis-
played peaks at m/z 653 assignable to [Cp*Ru(O2)-
(dppm)]+ and at m/z 621 assignable to [Cp*Ru(dppm)]+.
In the IR spectrum of [2]BF 4, a weak band assignable
to νO-O was observed at 924 cm-1, which is absent in
the IR spectrum of Cp*RuCl(dppm), Cp*RuH(dppm),
and [Cp*RuH2(dppm)]BF4. Similarly, a weak band at
928 cm-1 assignable to νO-O was observed for [2]BP h 4.
The νO-O values are within the range reported for
LnM(O2) complexes.12 The 1H and 31P{1H} NMR data
are fully consistent with the structural assignment. The
structure has been confirmed by an X-ray diffraction
study on [2]BP h 4 (see below).
and at 1120 and 1130 cm-1 for
14a
CH2P(O)Ph2)]SbF6
[Pd(Ph2PCH2P(O)Ph2)2](PF6)2.14b The presence of chelat-
ing Ph2PCH2P(O)PPh2 in [3]BF 4 is further supported
1
1
by its H and 31P NMR data. The H NMR (in acetone-
d6) showed two sets of methylene proton signals at 4.20
and 4.51 ppm, and a Cp* signal at 1.66 ppm which
couples to only one of the phosphorus atoms. The 31P
NMR (in acetone-d6) showed two doublets at 39.7 and
67.5 ppm assignable to P(O)Ph2 and PPh2. The 31P
chemical shifts are significantly downfield compared to
those observed for typical Cp*Ru(η2-dppm) complexes
such as Cp*RuH(dppm) (17.5 ppm),9a [Cp*RuH2(dppm)]-
BF4 (23.4 ppm),9 and [Cp*Ru(L)(dppm)]BF4 (L ) H2, 4.9
ppm;9a CH3CN, 10.48 ppm;11 H2O, 11.2 ppm;11 N2, 3.45
ppm11) but are consistent with the presence of the five-
membered chelating ring15 in [3]BF 4. Ligands of the
type PPh2(CH2)nP(O)Ph2 (n ) 1-3) have been previously
synthesized and used for transition-metal complex-
ation.14,16
Descr ip tion of th e Str u ctu r e of [Cp *Ru (O2)-
(d p p m )]BP h 4. The structure of [Cp*Ru(O2)(dppm)]+
has been confirmed by an X-ray diffraction study on
[Cp*Ru(O2)(dppm)]BPh4. The view of the cationic com-
plex [Cp*Ru(O2)(dppm)]+ is shown in Figure 1. The
crystallographic details and selected bond distances and
angles are given in Tables 1 and 2, respectively.
The structure can be described as a three-legged piano
stool with the O2 and the two PPh2 groups as the legs.
The overall geometry of the complex is very similar to
that observed for the three-legged piano-stool dihydro-
gen complex [Cp*Ru(Η2)(dppm)]BF4.10 For example, in
both cases, the X2 ligands are oriented in such a fashion
to maximize the dπ(Ru)-σ*(H2) and dπ(Ru)-π*(O2)
bonding;17 the O(1)-Ru-O(2) angle (39.9(4)°) in [3]BP h 4
is close to the H-Ru-H angle (38(1)°) in [Cp*Ru(H2)-
(dppm)]BF4.10
Formation of [Cp*Ru(O2)(dppm)]+ provides an ad-
ditional example of metal fragments that can form both
dihydrogen and dioxygen complexes. Reported examples
of such metal fragments include OsHCl(CO)(P(i-Pr)3)2,1
[OsH(dppe)2]+,2 [RuH(dippe)2]+,3 [RuH(dcpe)2]+,3 and
[OsCl(dcpe)2]+.13
Complex [3]BF 4 was characterized by elemental
1
analysis, IR, MS, H, 13C, and 31P NMR spectroscopy.
In particular, the FAB-MS of [3]BF 4 displayed peaks
at m/z 669 corresponding to [Cp*Ru(O2)(Ph2CH2P(O)-
Ph2)]+ and at m/z 637 corresponding to [Cp*Ru(Ph2-
CH2P(O)Ph2)]+. The IR spectrum displayed bands at 928
cm-1 assignable to νO-O and at 1124 cm-1 assignable to
The two PPh2 groups are bonded to ruthenium with
slightly different Ru-P bond distances (Ru-P(1) )
ν
PdO. For comparison, the IR bands for coordinated PdO
were observed at 1127 cm-1 for [Pd(η3-C3H5)(η2-Ph2PCH2-
(14) (a) Mecking, S.; Keim, W. Organometallics 1996, 15, 2650. (b)
Higgins, S. J .; Taylor, R.; Shaw, B. L. J . Organomet. Chem. 1987, 325,
285.
(15) Garrou, P. E. Chem. Rev. 1981, 81, 229.
(16) Bader, A.; Lindner, E. Coord. Chem. Rev. 1991, 108, 27 and
references therein.
(11) Hembre, R. T.; McQueen, S. J . Am. Chem. Soc. 1994, 116, 2141.
(12) See for example: VanAtta, R. B.; Strouse, C. E.; Hanson, L.
K.; Valentine, J . S. J . Am. Chem. Soc. 1987, 109, 1425.
(13) (a) Mezzetti, A.; Zangrando, E.; Zotto, A. D.; Rigo, P. J . Chem.
Soc., Chem. Commun. 1994, 1597. (b) Mezzetti, A.; Zotto, A. D.; Rigo,
P.; Farnetti, E. J . Chem. Soc., Dalton Trans. 1991, 1525.
(17) Schilling, B. E. R.; Hoffmann, R.; Lichtenberger, D. L. J . Am.
Chem. Soc. 1979, 101, 585.

Reactions of [Cp*RuH2(PP)]+ with Air
Organometallics, Vol. 18, No. 18, 1999 3599
Ta ble 1. Cr ysta llogr a p h ic Deta ils for
[Cp *Ru (O2)(d p p m )]BP h 4
Sch em e 2
formula
fw
C59H57BO2Ru
971.93
color, habit
cryst dimens (mm)
cryst syst
space group
a, Å
red, block
0.23 × 0.24 × 0.27
orthorhombic
Pbca (No. 61)
16.628(1)
19.607(2)
30.763(3)
10029(1)
8
b, Å
c, Å
V, Å3
Z
d
calcd, g cm-3
1.287
T (°C)
23.0
F000
4048.00
4.18
45.0
ω-2θ
16.0 (in ω) (up to 4 scans)
0.60 + 0.35 tan θ
7205
2544
286
µ(Mo KR), cm-1
max 2θ, deg
scan type
scan rate, deg min-1
scan width, deg
no. of rflns measd
no. of observns (I > 1.5σ(I))
no. of variables
R, Rw
0.067, 0.055
1.75
+1.11, -0.47
GOF
final max, min ∆F, e Å-3
Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for [Cp *Ru (O2)(d p p m )]BP h 4
O(1)-O(2) 1.37(1) Ru-O(1) 2.003(9) Ru-O(2) 2.002(9)
Ru-P(1)
Ru-C(2)
Ru-C(5)
2.345(4) Ru-P(2)
2.30(1) Ru-C(3)
2.382(4) Ru-C(1)
2.24(1) Ru-C(4)
2.27(1)
2.24(1)
2.22t
C(1)-C(2) 1.43(2) C(1)-C(5) 1.46(2)
C(2)-C(3) 1.39(2) C(3)-C(4) 1.39(2) C(4)-C(5) 1.37(2)
P(1)-Ru-P(2)
P(1)-Ru-O(2)
P(1)-Ru-C(2)
P(1)-Ru-C(4)
P(2)-Ru-O(1)
P(2)-Ru-C(1)
P(2)-Ru-C(3)
P(2)-Ru-C(5)
67.5(1)
103.6(3)
98.8(3)
153.1(4)
119.9(3)
92.4(4)
P(1)-Ru-O(1)
P(1)-Ru-C(1)
P(1)-Ru-C(3)
P(1)-Ru-C(5)
P(2)-Ru-O(2)
P(2)-Ru-C(2)
P(2)-Ru-C(4)
O(1)-Ru-O(2)
86.7(3)
112.0(4)
117.1(4)
149.6(4)
93.3(3)
119.5(3)
135.9(4)
39.9(4)
(dippe)2]BPh43 and [Cp*Ru(O2)(PR3)2)]+ ((PR3)2 ) dppe,5
dippe,6 (P-O)2 (P-O ) (1,3-dioxan-2-ylmethyl)diphen-
ylphosphine,7 and dppf8)). The O-O distance in [2]BP h 4
(1.37(1) Å) is comparable to those of [RuH(O2)(dippe)2]-
BPh4 (1.360(10) Å),3 [Cp*Ru(O2)(dppe)]BF4 (1.398(5) Å),5
[Cp*Ru(O2)(dppf)]BF4 (1.381(11) Å),8 and [Cp*Ru(O2)-
(P-O)2]BPh4 (1.394(9) Å)7 but is shorter than those of
[OsCl(O2)(dcpe)2]BPh4 (1.45(1) Å)13 and [OsH(O2)-
(dppe)2]+ (1.430(5) Å).2
Mech a n ism for th e F or m a tion of [2]BF 4 a n d
[3]BF 4 fr om th e Rea ction of 1 w ith Air . The com-
plex [2]BF 4 is presumably formed by displacement of
the H2 ligand in 1 with O2. Similar reactivity has been
observed for complexes such as OsHCl(H2)(CO)(P(i-
Pr)3)2,1 [RuH(H2)(dppe)2]+,2 [RuH(H2)(dippe)2]+,3 RuH2-
(Ph2PNMeNMePPh2)2,4a and RuH2(CO)2(PPh3)2.4b How-
ever, production of [3]BF 4, a Ph2P(O)CH2PPh2-contain-
ing complex, from the reaction of 1 with air is not
straightforward. It has been reported that reaction of
[CpRu(N2)(dippe)]BPh4 with O2 produced the bis(phos-
phine oxide) (i-Pr)2P(O)CH2CH2P(O)(i-Pr)2 along with
CpRu(η6-C6H5BPh3).6b No intermediate could be ob-
served in the reaction. It was suggested that (i-Pr)2P-
(O)CH2CH2P(O)(i-Pr)2 is probably formed through the
intermediate [CpRu(O2)(i-Pr)2PCH2CH2P(i-Pr)2)]+. In
the case of reaction of [Cp*RuH2(dppm)]+ with air, the
major products are [Cp*Ru(O2)(dppm)]+ and [Cp*Ru-
(O2)(Ph2PCH2P(O)Ph2)]+. We have shown experimen-
tally that [Cp*Ru(O2)(dppm)]+ is unlikely to be the
intermediate for the formation of [Cp*Ru(O2)(Ph2PCH2P-
(O)Ph2)]+.
152.9(4)
102.1(4)
2.345(4) Å; Ru-P(2) ) 2.382(4) Å). The Ru-P bond
distances are longer than those observed for the related
ruthenium complexes [CpRu(η2-dppm)(η1-dppm)]PF6
(2.295(3), 2.325(3), 2.323(2) Å)18 and [Cp*Ru(Η2)(dppm)]-
BF4 (2.297(8), 2.314(9) Å).10 The P(1)-Ru-P(2) angle
(67.5(1)°) is slightly smaller than the corresponding
angles reported for other chelating dppm in complexes
such as [CpRu(η2-dppm)(η1-dppm)]PF6 (70.0(1)°),18
[Cp*Ru(Η2)(η2-dppm)]BF4 (71.4(3)°),10 and CpFePh-
(dppm) (73.8(0)°).19 The Ru-C distances are in the range
2.22(1)-2.30(1) Å, which are very similar to those
reported for related Cp* ruthenium complexes, for
example, [Cp*Ru(O2)(dppe)]+,5 [Cp*Ru(O2)(dippe)]+,6
and [Cp*Ru(H2)(dppm)]+.10
The dioxygen is symmetrically bound to ruthenium
with O(1)-O(2) ) 1.37(1) Å, Ru-O(1) ) 2.003(9) Å, and
Ru-O(2) ) 2.002(9) Å. The O-O distance is longer than
that in the superoxide KO2 (1.28 Å)20 and shorter than
that in H2O2 (1.46 Å).21 The Ru-O bond distances and
O(1)-Ru-O(2) angle are similar to those reported for
other ruthenium dioxygen complexes such as [RuH(O2)-
(18) Bruce, M. I.; Cifuentes, M. P.; Grundy, K. Y.; Liddell, M. J .;
Snow, M. R.; Tiekink, E. R. T. Aust. J . Chem. 1988, 41, 597.
(19) Scott, F.; Kruger, G. J .; Cronje, S.; Lombard, A.; Raubenheimer,
H. G.; Benn, R.; Rufinska, A. Organometallics 1990, 9, 1071.
(20) Valentine, J . S. Chem. Rev. 1973, 73, 235.
(21) Savariault, J . M.; Lehmann, M. S. J . Am. Chem. Soc. 1980,
102, 1298.
A plausible mechanism for the formation of [Cp*Ru-
(O2)(Ph2PCH2P(O)Ph2)]+ is shown in Scheme 2, which
involves the peroxide intermediate (A) formed by reac-

3600 Organometallics, Vol. 18, No. 18, 1999
J ia et al.
tion of 1 with O2. Intramolecular oxygen transfer from
the hydroperoxo ligand to one of the coordinated phos-
phorus atoms would give the peroxophosphine complex
B. Subsequent elimination of H2O would give the
coordinatively unsaturated complex [Cp*Ru(Ph2CH2P-
(O)Ph2)]+ (C), which picks up a O2 molecule to give
[Cp*Ru(O2)(Ph2CH2P(O)Ph2)]+.
oxide intermediate) from the reaction of [Cp*RuH2-
(dppm)]+ with oxygen must be related to the reactivity
of O2 toward the RuH2 or/and Ru(H2) functionality.
Unfortunately, the effect of RuH2 and Ru(H2) function-
alities in the reaction of [Cp*RuH2(dppm)]+ with air is
not clear because the hydride complex exists as a
mixture of the dihydrogen form [Cp*Ru(H2)(dppm)]BF4
and the dihydride form trans-[Cp*RuH2(dppm)]BF4. To
see the effect of RuH2 and Ru(H2) functionalities, we
have investigated the reaction of air with [Cp*RuH2-
(dppe)]BF4 (5), which adopts the dihydride form only.5
Exposure of acetone or methanol solutions of 5 to air
also produced [Cp*Ru(O2)(dppe)]BF4 ([6]BF 4) and
[Cp*Ru(O2)(Ph2PCH2CH2P(O)Ph2)]BF4 ([7]BF 4) (eq 2).
Oxidation of phosphines by hydroperoxides to give
phosphine oxides is one of the typical reactions of
phosphines.24 Hydroperoxide ion has been shown to be
involved in the oxidation of phosphines by oxygen
catalyzed by Pt(PPh3)2(O2).25 Intramolecular O-transfer
from peroxo groups to coordinated phosphines to gener-
ate phosphine oxides has been reported for complexes
such as RhCl(OOH)(acac)(PPh3)226 and RhCl(O4C)(PEt2-
Ph)3.27 Formation of peroxide complexes from the reac-
tions of metal alkyls28 or hydrides29 with O2 and
production of H2O2 from H2 and O2 catalyzed by transi-
tion-metal complexes has been reported.30 In support
of the involvement of the hydroperoxo intermediate in
the formation of [3]BF 4, it was demonstrated that
reaction of Cp*RuCl(dppm) with H2O2 and O2 in the
presence of NaBPh4 produced a mixture of [3]BP h 4 and
dppm oxide (major), whereas the same reaction in the
absence of hydrogen peroxide only gave [2]BP h 4. Reac-
tion of [2]BP h 4 in acetone-d6 with H2O2 produced slowly
an uncharacterized insoluble black precipitate. The
solution only showed 31P signals assignable to [2]BP h 4
and Ph2P(O)CH2P(O)Ph2. This observation again im-
plies that the dioxygen complex [2]BP h 4 is not the
intermediate for the formation of [Cp*Ru(O2)(Ph2PCH2P-
(O)Ph2)]+.
In the proposed mechanism for the formation of
[3]BF 4, water is suggested as the side product. To
confirm the formation of water in the reaction, we have
studied the reaction of air with [Cp*RuD2(dppm)]+,
which was prepared by reaction of [Cp*Ru(dppm)]+ with
D2 gas. Indeed, the 2D NMR spectra of methanol or
acetone solutions of [Cp*RuD2(dppm)]+ after exposure
to air showed signals assignable to D2O.
It is not very clear to us why more [3]BF 4 relative to
[2]BF 4 was produced in acetone but more [2]BF 4
relative to [3]BF 4 was produced in methanol. Possibly,
methanol helped to dissociate the H2 molecule to give
the intermediate [Cp*Ru(dppm)]+ or [Cp*Ru(dppm)-
(MeOH)]+, which facilitates the formation of [2]BF 4.
Rea ction of [Cp *Ru H2(d p p e)]BF 4 w ith Air . For-
mation of [Cp*Ru(O2)(Ph2PCH2P(O)Ph2)]+ (or the per-
The reaction is slower than that of the dppm analogue.
Thus, [Cp*RuH2(dppe)]BF4 is still observable by NMR
after an acetone solution of 5 was exposed to air for 4
h. Like the dppm analogue, the relative amounts of
[6]BF 4 and [7]BF 4 are solvent-dependent. In acetone,
about equal amounts of [6]BF 4 and [7]BF 4 were pro-
duced; in methanol, the dioxygen complex [6]BF 4 is the
major product.
The dioxygen complex [Cp*Ru(O2)(dppe)]+ has been
reported previously and can be prepared easily from the
reaction of [Cp*Ru(dppe)]+ with oxygen.5 The dioxygen
complex [Cp*Ru(O2)(dppe)]+ formed in the oxidation
experiments could be easily identified by comparing the
NMR data to those of authentic samples prepared from
the reaction of [Cp*Ru(dppe)]BF4 with oxygen.5 Unfor-
tunately, we have not been able to obtain pure samples
of [7]BF 4 by either recrystallization or column chroma-
tography. Samples of [7]BF 4 obtained were contami-
nated with the dioxygen complex [6]BF 4. The identity
of [Cp*Ru(O2)(Ph2PCH2CH2P(O)Ph2)]+, however, is
clearly indicated by the NMR, IR, and MS data. In
particular, the FAB-MS of the isolated product displayed
clusters of peaks at m/z 683 corresponding to [Cp*Ru-
(O2)(Ph2CH2CH2P(O)Ph2)]+ and at m/z 651 correspond-
ing to [Cp*Ru(Ph2CH2CH2P(O)Ph2)]+. The IR spectrum
displayed bands at 852 cm-1 assignable to νO-O and at
1056 cm-1 assignable to νPdO. The presence of chelating
Ph2PCH2CH2P(O)PPh2 in [7]BF 4 is further supported
by its 13C and 31P NMR data. The 13C NMR (in CD2Cl2)
showed methylene signals at 18.7 and 22.4 ppm and a
Cp* signal at 8.2 ppm. Consistent with the proposed
structure, the 31P NMR (in CD2Cl2) showed two doublets
at 50.7 and 32.8 ppm assignable to PPh2 and P(O)Ph2,
respectively.
(22) Hembre, R. T.; McQueen, J . C.; Day, V. W. J . Am. Chem. Soc.
1996, 118, 798.
(23) See for example: (a) Brammer, L.; Klooster, W. T.; Lemke, F.
R. Organometallics 1996, 15, 1721. (b) Lemke, F. R.; Brammer, L.
Organometallics 1995, 14, 3980. (c) Conroy-Lewis, F. M.; Simpson, S.
J . J . Chem. Soc., Chem. Commun. 1987, 1675. (d) Chinn, M. S.;
Heinekey, D. M. J . Am. Chem. Soc. 1990, 112, 5166.
(24) Bhattacharya, A. K.; Roy, N. K. In The Chemistry of Organo-
phosphorus Compounds; Hartley, F. R., Ed.; Wiley: New York, 1992;
Vol. 2, p 195.
(25) Sen, A.; Halpern, J . J . Am. Chem. Soc. 1977, 99, 8337.
(26) Suzuki, H.; Matsuura, S.; Moro-Oka, Y.; Ikawa, I. J . Orgnomet.
Chem. 1984, 286, 247.
(27) Aresta, M.; Tommasi, I.; Quaranta, E.; Fragale, C.; Mascetti,
J .; Tranquille, M.; Galan, F.; Fouassier, M. Inorg. Chem. 1996, 35,
4254.
(28) See for example: Lubben, T. V.; Wolczanski, P. T. J . Am. Chem.
Soc. 1987, 109, 424 and references therein.
(29) See for example: Cotton, F. A.; Wilkinson, G. Advanced
Inorganic Chemistry; Wiley: New York, 1988; pp 1104, 1199.
(30) Gamage, S. N.; J ames, B. R. J . Chem. Soc., Chem. Commun.
1989, 1624.
The fact that [Cp*RuH2(dppe)]BF4 (5), which adopts
the dihydride form only, can also reacts with air to give

Reactions of [Cp*RuH2(PP)]+ with Air
Organometallics, Vol. 18, No. 18, 1999 3601
[Cp*Ru(O2)(Ph2CH2CH2P(O)Ph2)]+ may suggest that
formation of [Cp*Ru(O2)(Ph2(CH2)nP(O)Ph2)]+ is related
to the RuH2 functionality. However, the involvement of
the Ru(H2) functionality cannot be excluded completely,
because of the possibility of equilibrium between the
Ru(H2) and RuH2 tautomers.9
Su m m ar y. The reaction of [Cp*RuH2(dppm)]+/[Cp*Ru-
(H2)dppm)]+ in acetone or methanol with air produced
a mixture of [Cp*Ru(O2)(dppm)]BF4 and [Cp*Ru(O2)(Ph2-
PCH2P(O)Ph2)]BF4. Similarly, the reaction of [Cp*RuH2-
(dppe)]+ in acetone or methanol with air also produced
[Cp*Ru(O2)(dppe)]BF4 and [Cp*Ru(O2)(Ph2PCH2CH2P-
(O)Ph2)]BF4. These reactions appear to be solvent-
dependent. Acetone favors the formation of [Cp*Ru(O2)-
(Ph2P(CH2)xP(O)Ph2)]+ (x ) 1, 2); methanol favors the
formation of [Cp*Ru(O2)(Ph2P(CH2)xPPh2)]+ (x ) 1, 2).
[Cp*Ru(O2)(Ph2P(CH2)xP(O)Ph2)]+ species are likely
produced from hydroperoxo intermediates formed by
reaction of O2 with the hydride complexes.
brown solid. The solid was collected by filtration and recrystal-
lized using a minimum amount of acetone to give a reddish
brown microcrystalline solid of [Cp*Ru(O2)(Ph2PCH2P(O)Ph2)]-
BF4. The product was collected by filtration, washed with
ether, and dried under vacuum. Yield: 0.46 g, 43%. IR (KBr,
cm-1): νPdO 1124 (s), νO-O 928 (w). 1H NMR (acetone-d6): δ
1.66 (d, J (PH) ) 1.6 Hz, 15 H, C5(CH3)5), 4.20 (ddd, J (PH) )
13.1, 11.0 Hz, J (HH) ) 14.4 Hz, 1 H, CH2), 4.51 (ddd, J (PH)
) 13.2, 5.6 Hz, J (HH) ) 14.4 Hz, 1 H, CH2), 7.3-8.0 (m, 20 H,
Ph). 31P{1H} NMR (acetone-d6): δ 39.7 (d, J (PP) ) 25.7 Hz),
67.5 (d, J (PP) ) 25.7 Hz). 13C{1H} NMR (CDCl3): δ 8.4 (s, Cp*),
30.6 (dd, J (PC) ) 66.6, 16.4 Hz, CH2), 108.6 (s, Cp*). 128.0-
134.4 (m, Ph). Anal. Calcd for C35H37BF4O3P2Ru: C, 55.64; H,
4.94. Found: C, 55.86; H, 4.90. The filtrate from recrystalli-
zation of [Cp*Ru(O2)(Ph2PCH2P(O)Ph2)]BF4 was passed through
a silica gel column using CH2Cl2/acetone (3:1) as the eluent to
give a brown solution. The eluted solution was concentrated,
and ether was added to give brown crystals of [Cp*Ru(O2)-
(dppm)]BF4. The product was collected by filtration, washed
with ether, and dried under vacuum. Yield: 0.20 g, 19%. For
comparative purposes, the 31P chemical shifts of dppm, dppmO,
and dppmO2 in acetone-d6 were also collected: dppm, δ -23.5
(s); dppmO, δ -28.6 (d, J (PP) ) 50.9 Hz), 26.6 (d, J (PP) )
50.9 Hz); dppmO2, δ 24.6 (s).
Exp er im en ta l Section
Rea ction of Cp *Ru Cl(d p p m ) w ith H2O2. To an NMR
tube (opened to air) containing Cp*RuCl(dppm) and NaBPh4
dissolved in acetone-d6 (0.7 mL) was added ca. 0.10 mL of 30%
H2O2 in water. A 31P NMR spectrum was collected 5 min later.
The 31P NMR showed signals assignable to [Cp*Ru(O2)(Ph2-
PCH2P(O)Ph2)]BF4 and dppm oxide.
All reactions were carried out under a nitrogen atmosphere
using standard Schlenk techniques unless otherwise stated.
Solvents were distilled under nitrogen from sodium-benzo-
phenone (hexane, ether, benzene) or calcium hydride (CH2Cl2).
Microanalyses were performed by M-H-W Laboratories (Phoe-
1
nix, AZ). H and 31P NMR spectra were collected on a J EOL
1
EX-400 spectrometer or a Bruker ARX-300 spectrometer. H
Con fir m a tion of th e F or m a tion of D2O fr om th e Rea c-
tion of [Cp *Ru D2(d p p m )]BF 4 w ith Air . A mixture of 20 mg
(0.03 mmol) of Cp*RuCl(dppm) and 7 mg (0.03 mmol) of AgBF4
dissolved in 0.7 mL of acetone in an NMR tube was sonicated
for 30 min. The reaction mixture was then subjected to 1 atm
of D2 for 1 h to generate [Cp*RuD2(dppm)]BF4 in situ, and then
the mixture was exposed to air and left to stand overnight. A
2D NMR spectrum was collected. 2D NMR (acetone): δ 3.92 (s,
D2O). Formation of D2O in methanol can be confirmed simi-
larly by the observation of the D2O signal at 5.0 ppm.
F or m a t ion of [Cp *R u (O2)(d p p e)]BF 4 ([6]BF 4) a n d
[Cp *Ru (O2)(P h 2P CH2CH2P (O)P h 2)]BF 4 ([7]BF 4) fr om th e
Rea ction of [Cp *Ru H2(d p p e)]BF 4 w ith Air . A 0.52 g (0.70
mmol) portion of [Cp*RuH2(dppe)]BF4 dissolved in 10 mL of
acetone was exposed to air for 5 days to give a brown solution.
The solvent was removed under vacuum to give a brown solid.
The residue showed predominant signals due to [6]BF 4 and
[7]BF 4. Attempts to separate the two compounds by column
chromatography and recrystallization were unsuccessful. [6]BF4
could be obtained cleanly from the reaction of [Cp*Ru(dppe)]-
BF4 with air.5 Selected characterization data for [6]BF 4:
31P{1H} NMR (CD2Cl2) δ 68.5 (s); 1H NMR (CD2Cl2) δ 1.57 (s,
15 H, C5(CH3)5), 2.67 (m, 4 H, CH2), 7.1-7.8 (m, 20 H, Ph);
13C{1H} NMR (CD2Cl2) δ 9.0 (s, Cp*), 26.4 (t, J (PC) ) 38.6
Hz, CH2), 107.2 (s, Cp*), 128.7-133.2 (m, Ph). Selected
characterization data for [7]BF 4: IR (KBr, cm-1) νPdO 1056 (s),
νO-O 852 (w); 1H NMR (CD2Cl2) δ 1.34 (d, J (PH) ) 1.5 Hz,
C5(CH3)5), 1.80-3.36 (m, CH2), 6.95-7.73 (m, Ph); 31P{1H}
NMR (CD2Cl2) δ 32.8 (d, J (PP) ) 15.3 Hz), 50.7 (d, J (PP) )
15.3 Hz); 13C{1H} NMR (CD2Cl2) δ 8.2 (s, Cp*), 18.7, (dd, J (PC)
) 26.8, 5.5 Hz, CH2), 22.4 (t, J (PC) ) 34.0 Hz), 107.3 (s, Cp*),
125.8-133.2 (m, Ph); FAB-MS m/e 685 ([Cp*Ru(O2)(Ph2PCH2-
CH2P(O)Ph2)]+), 651 ([Cp*Ru(Ph2PCH2CH2P(O)Ph2)]+). For
comparative purposes, the 31P chemical shift of dppe, dppeO,
and dppeO2 were collected in acetone-d6: dppe, δ -14.0 (s);
dppeO, δ -13.6 (d, J (PP) ) 47.9 Hz), 29.6 (d, J (PP) ) 47.9
Hz); dppeO2, δ 30.1 (s).
NMR chemical shifts are reported relative to TMS and 31P
NMR chemical shifts relative to 85% H3PO4. IR spectra were
collected on a Perkin-Elmer 1600 spectrometer. Cp*RuCl-
(dppm),9 Cp*RuH(dppm),9 [Cp*RuH2(dppm)]BF4,9 Cp*RuCl-
(dppe),5 [Cp*RuH2(dppe)]BF4,5 and [Cp*Ru(O2)(dppe)]BF4
5
were prepared according to literature methods. All other
reagents were used as purchased from Aldrich.
[Cp*Ru (O2)(dppm )]BP h 4 ([2]BP h 4). A mixture of Cp*RuCl-
(dppm) (0.10 g, 0.15 mmol) and NaBPh4 (0.080 g, 0.23 mmol)
in 10 mL of methanol was stirred under air for 3 h to give a
light brown solid. The solid was collected by filtration, washed
with methanol (5 mL) and ether (10 mL), and then dried under
vacuum. Yield: 0.089 g, 60%. IR (KBr, cm-1): νO-O 928 (w).
1H NMR (acetone-d6): δ 1.63 (t, J (PH) ) 1.4 Hz, 15 H, C5-
(CH3)5), 4.91 (dt, J (PH) ) 11.2 Hz, J (HH) ) 15.1 Hz, 1 H, CH2),
5.20 (dt, J (PH) ) 12.3 Hz, J (HH) ) 15.1 Hz, 1 H, CH2), 6.9-
7.9 (m, 40 H, Ph). 31P{1H} NMR (acetone-d6): δ -11.0 (s). Anal.
Calcd for C59H57BO2P2Ru: C, 72.91; H, 5.91. Found: C, 72.46;
H, 5.86.
[Cp *Ru (O2)(d p p m )]BF 4 ([2]BF 4). A mixture of Cp*RuCl-
(dppm) (0.10 g, 0.15 mmol) and AgBF4 (0.030 g, 0.15 mmol) in
10 mL of methanol was stirred under air for 3 h. The reaction
mixture was filtered through a column of Celite. The filtrate
was concentrated, and ether (10 mL) was added to give light
brown crystals. The product was collected by filtration, washed
with ether, and then dried under vacuum. Yield: 0.090 g, 81%.
IR (KBr, cm-1): νO-O 924 (w). 1H NMR (acetone-d6): δ 1.63 (t,
J (PH) ) 1.4 Hz, 15 H, C5(CH3)5), 4.91 (dt, J (PH) ) 11.2 Hz,
J (HH) ) 15.1 Hz, 1 H, CH2), 5.20 (dt, J (PH) ) 12.3 Hz, J (HH)
) 15.1 Hz, 1 H, CH2), 7.4-7.9 (m, 20 H, Ph). 31P{1H} NMR
(acetone-d6): -11.0 (s). 13C{1H} NMR (CDCl3): δ 8.5 (s, Cp*),
37.2 (t, J (PC) ) 28.1 Hz, CH2), 108.0 (s, Cp*), 126.0-133.2
(m, Ph). Anal. Calcd for C35H37BF4O2P2Ru: C, 56.85; H, 5.04.
Found: C, 56.58; H, 5.02.
F or m a t ion of [Cp *R u (O2)(P h 2P CH2P (O)P h 2)]BF 4-
([3]BF 4) a n d [Cp *Ru (O2)(d p p m )]BF 4 ([2]BF 4) fr om th e
Rea ction of [Cp *Ru H2(d p p m )]BF 4 w ith Air . A 1.0 g (1.4
mmol) portion of [Cp*RuH2(dppm)]BF4 dissolved in 100 mL
of acetone was stirred under air for 20 min to give a brown
solution. The solvent was removed under vacuum to give a
Cr ysta llogr a p h ic An a lysis of [Cp *Ru (O2)(d p p m )]BP h 4.
Suitable crystals for X-ray diffraction study were obtained by
slow diffusion of Et2O into an acetone solution of [Cp*Ru(O2)-
(dppm)]BPh4 at room temperature. A weakly diffracting crystal

3602 Organometallics, Vol. 18, No. 18, 1999
J ia et al.
was mounted on a glass fiber by means of epoxy resin on an
Enraf-Nonius diffractometer using graphite-monochromated
Mo KR radiation (λ ) 0.710 73 Å) for unit-cell determination
and data collection. A summary of crystallographic data and
structure, solution, and refinement details is given in Table
1. Lorentz-polarization and ψ-scan absorption correction31
were applied to all intensity data. The structure was solved
by direct methods (SIR88)32 and subsequently difference
Fourier techniques. Atomic coordinates and thermal param-
eters were refined by full-matrix least-squares analysis with
Ru, P, and O atoms varied anisotropically. Hydrogen atoms
were generated in their ideal positions (d(C-H) ) 0.95 Å). All
calculations were performed on a Silicon Graphics computer
using the program package TEXSAN.33 Selected bond dis-
tances and angles are given in Table 2.
Ack n ow led gm en t. We acknowledge financial sup-
port from the Hong Kong Research Grants Council.
Su p p or tin g In for m a tion Ava ila ble: Tables of all bond
distances and angles, atomic coordinates and thermal param-
eters, and anisotropic displacement coefficients. This material
is available free of charge via the Internet at http://pubs.acs.org.
(31) North, A. C. T.; Philips, D. C.; Mathews, F. S. Acta Crystallogr.,
Sect. A 1968, 24, 351.
(32) Burla, M. C.; Camalli, M.; Cascarano, G.; Giacovazzo, C.;
Polidori, G.; Spagna, R.; Viterbo, D. J . Appl. Crystallogr. 1989, 22, 389.
OM990317B
(33) TEXSAN Crystal Structure Analysis Package; Molecular Struc-
ture Corp., The Woodlands, TX, 1985 and 1982.