Transition metal complexes of the chelating phosphine borane ligand Ph 2PCH2Ph2P·BH3

Article abstract of DOI:10.1039/b413650k

Chromium and ruthenium complexes of the chelating phosphine borane H, B-dppm are reported. Addition of H₃B-dppm to [Cr(CO) ₄(nbd)] (nbd = norbornadiene) affords [Cr(CO)₄(n ¹-H₃B·dppm)] in which the borane is linked to the metal through a single B-H-Cr interaction. Addition of H ₃B·dppm to [CpRu(PR₃)(NCMe)₂]+ (Cp = n⁵-C₅H₅) results in [CpRu(PR ₃)(n¹-H₃B·dppm)][PF₆] (R = Me, OMe) which also show a single B-H-Ru interaction. Reaction with [CpRu(NCMe)₃] only resulted in a mixture of products. In contrast, with [CpRu(NCMe)₃]⁺ (Cp* = n⁵-C ₅Me₅) a single product is isolated in high yield: [Cp*Ru(n²-H₃B-dppm)][PF₆]. This complex shows two B-H-Ru interactions. Reaction with L = PMe₃ or CO breaks one of these and the complexes [Cp*Ru(L)(n¹-H ₃B-dppm)][PF₆,] are formed in good yield. With L = MeCN an equilibrium is established between [Cp*Ru(n²-H ₃B-dppm)][PF₆ and the acetonitrile adduct. [Cp*Ru(n²-H₃B-dppm)][PF₆] can be considered as being operationally unsaturated , effectively acting as a source of 16-electron [Cp*Ru(n²-H ₃B-dppm)][PF₆]. All the new compounds (apart from the CO and MeCN adducts) have been characterised by X-ray crystallography. The solid-state structure of H₃B-dppm is also reported.

Full text of DOI:10.1039/b413650k

View Article Online / Journal Homepage / Table of Contents for this issue
F U L L P A P E R
Transition metal complexes of the chelating phosphine borane ligand
Ph2PCH2Ph2P·BH3
Nicolas Merle, Gabriele Koicok-Ko¨hn, Mary F. Mahon, Christopher G. Frost, Giuseppe D.
Ruggerio, Andrew S. Weller* and Michael C. Willis
Department of Chemistry, University of Bath, Bath, UK, BA2 7AY.
E-mail: a.s.weller@bath.ac.uk
Received 3rd September 2004, Accepted 7th October 2004
First published as an Advance Article on the web 25th October 2004
Chromium and ruthenium complexes of the chelating phosphine borane H3B·dppm are reported. Addition of
1
H3B·dppm to [Cr(CO)4(nbd)] (nbd = norbornadiene) affords [Cr(CO)4(g -H3B·dppm)] in which the borane is linked
5
to the metal through a single B–H–Cr interaction. Addition of H3B·dppm to [CpRu(PR3)(NCMe)2]+ (Cp = g -C5H5)
1
results in [CpRu(PR3)(g -H3B·dppm)][PF6] (R = Me, OMe) which also show a single B–H–Ru interaction. Reaction
5
with [CpRu(NCMe)3]+ only resulted in a mixture of products. In contrast, with [Cp*Ru(NCMe)3]+ (Cp* = g -C5Me5)
2
a single product is isolated in high yield: [Cp*Ru(g -H3B·dppm)][PF6]. This complex shows two B–H–Ru interactions.
1
Reaction with L = PMe3 or CO breaks one of these and the complexes [Cp*Ru(L)(g -H3B·dppm)][PF6] are formed in
2
good yield. With L = MeCN an equilibrium is established between [Cp*Ru(g -H3B·dppm)][PF6] and the acetonitrile
2
adduct. [Cp*Ru(g -H3B·dppm)][PF6] can be considered as being “operationally unsaturated”, effectively acting as a
1
source of 16-electron [Cp*Ru(g -H3B·dppm)][PF6]. All the new compounds (apart from the CO and MeCN adducts)
have been characterised by X-ray crystallography. The solid-state structure of H3B·dppm is also reported.
Although intermolecular metal alkane r-complexes are un-
stable, when the M–HC bond is incorporated into a chelate ring
Introduction
The synthesis of transition metal complexes of the neutral
phosphine boranes, such as H3B·PMe3 and B2H4·(PMe3)2,
has attracted recent interest.1–5 The isoelectronic relationship
between CH3R and H3B·PMe3, coupled with the polarity of
the (d−)H–B(d+) bond means that they are attractive ligands
for the isolation and study of stable analogs of transient
metal–alkane complexes.6,7 A good example of this is given
by the pair of complexes [CpRe(CO)2(cyclo-C5H10)] A8 and
the subsequent intramolecular agostic interaction is significantly
more robust.9 Likewise, chelating phosphine borane ligands such
as H3B·Ph2PCH2PPh2 (H3B·dppm) can stabilise the labile M–
H3B bond towards decomposition or displacement. Examples
of such complexes with this ligand are the rhodium thia- and
2
carba-boranes, exemplified by [(g -H3B·dppm)-nido-RhSB9H10]
2
C
10,11 and [(cod)Rh(g -H3B·dppm)][PF6] (cod = cyclooctadiene),
D.12 These are air-stable crystalline materials analogous to
14-electron late transition metal complexes that are stabilized
by agostic interactions, such as E,13 and in particular those
that contain d-agostic interactions. Other examples of chelating
ligands that show intermolecular [M] · · · H3B interactions are
also known.14,15 Lacking, however, are systematic studies of
synthetic routes to the complexes of these chelating ligands.
Such routes need to be developed if the chemistry of chelate
supported M · · · H3B interactions is to be studied. These are
especially interesting given the inherent stability advantages
that complexes of these ligands show over their monodentate
counterparts coupled with analogy that lies between alkanes and
phosphine boranes: transition metal mediated alkane activation
5
[CpMn(CO)2(H3B·PMe3)] B4 (Cp = g -C5H5) (Scheme 1).
The latter is isolated as a crystalline solid by photolysis of
[CpMn(CO)3] in the presence of H3B·PMe3, while the former has
only been spectroscopically observed at low (−80 ◦C) tempera-
tures for short times (∼30 min), generated by in situ photolysis
of [CpRe(CO)3] in cyclopentane. Both can be considered as r-
complexes with three-centre–two-electron E–H–M bonds (E =
B or C). Even though complexes such as B are significantly
more stable than their alkane analogues, the M · · · H3B bond
is still labile, suffering from spontaneous decomposition3,5 or
displacement by nucleophiles: such as CO liberated in the initial
photochemical synthesis,3 solvent2 or silanes.4
Scheme 1
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 4
T h i s j o u r n a l i s
D a l t o n T r a n s . , 2 0 0 4 , 3 8 8 3 – 3 8 9 2
3 8 8 3
©

View Article Online
being a particularly contemporary topic.7,16 In this paper we
report on synthetic routes to some transition metal complexes
with the chelating ligand H3B·dppm, and their solid and
solution-state structures.
the major organometallic product as judged by 1H and 31P NMR
spectroscopy, Scheme 2. Reaction with the Mo or W congeners
resulted in intractable mixtures. Compound 1 was isolated in
moderate (64%) yield as an analytically pure crystalline solid.
The solid-state structure of 1 is shown in Fig. 2, and selected
bond lengths and angles are given in Table 1.
Results and discussion
The ligand H3B·dppm· is conveniently synthesized as described
by Martin et al. by addition of one equivalent of BH3 (generated
in situ) to dppm.17 Full spectroscopic and structural data for
H3B·dppm were not presented in the original report, and for
the sake of comparison with the metal complexes of this ligand,
we report the solid-state and NMR data here. Fig. 1 shows the
solid-state structure of H3B·dppm, which demonstrates mono-
functionalisation of the dppm ligand. The hydrogen atoms on
the borane were located in the difference map and refined. The
Scheme 2
˚
B–H distances are all the same within error [d(B–H) 1.17(4) A].
˚
The B–P distance is 1.914(3) A.
Fig. 1 Solid-state structure of H3B·dppm. Thermal ellipsoids are
shown at the 50% probability level.
Fig. 2 Solid-state structure of 1. Thermal ellipsoids are shown at the
50% probability level. Hydrogen atoms apart from those associated with
the borane have been omitted for clarity.
1
In the 31P{ H} NMR spectrum of H3B·dppm a doublet [d
−25.5, J(PP) 65 Hz] and a lower-field, broader, signal [d 16.9]
are observed, the latter being assigned to the borane-bound
phosphorus. The 11B NMR spectrum displays a single broad
resonance at d −37.1. In the 1H NMR spectrum the BH3 group
is observed as a quadrupolar broadened, partially collapsed,
quartet centered at d 0.99 [J(BH) 112 Hz]. This sharpens to a
The chromium centre in 1 has approximate octahedral coordi-
nation, surrounded by four carbonyl groups and the H3B·dppm
ligand, which chelates through phosphorus and BH3 groups.
The BH3 hydrogen atoms were located in the final Fourier
difference map and the borane group coordinates to the metal
centre through one Cr–H–B interaction. The {Cr–dppm·BH3}
six membered ring adopts a chair-like conformation, although in
solution it must be fluxional as only one methylene environment
1
11
doublet of doublets in the H{ B} NMR spectrum, showing
coupling to both phosphorus atoms. The methylene protons are
observed as a diagnostic doublet [J(PH) 12 Hz], contrasting with
1
31
dppm in which they resolve only as a singlet. 1H{ P-selective}
is observed in the H NMR spectrum (vide infra). Formation
of the six-membered chelate ring has a small affect on the
H3B·dppm ligand, with the P–C–P and the B–P–C angles being
slightly compressed in 1 compared to free ligand [by 1.5 and
5.5◦, respectively].
experiments demonstrate that it is the boron-bound phosphorus
that shows the appreciable coupling constant with the methylene
protons, with coupling to the other phosphorus negligible.
Addition of the H3B·dppm to suitable precursors from groups
6 and 8 affords complexes of the general type [LnM(H3B·dppm)].
We have previously reported on group 9 adducts.12 Our synthetic
strategy is one that uses metal precursors with weakly bound
ligands (such as olefins and nitriles) which can be displaced
readily by the H3B·dppm ligand. In our hands, more forcing
conditions (modest temperatures, long reactions times) are best
avoided as this invariably leads to decomposition of the ligand,
to form dppm, B2H6, and intractable mixtures of organometallic
products.
˚
The Cr–H(1b) distance [1.78(3) A] lies in between those
Chromium
1
3
˚
measured in [Cr(CO)5(g -H3B·PMe3)] I [1.94(10) A] and the
Addition of H3B·dppm to [Cr(CO)4(nbd)] (nbd = norbornadi-
18
˚
chromium–hydride complex [(CO)5CrH][PPh4] [1.66(5) A]. It
1
ene) results in the formation of [Cr(CO)4(g -H3B·dppm)], 1,† as
is significantly shorter than that found in the related complex
˚
[Cr(CO)3(PCy3)2] II [Cr · · · H 2.240(1) A] that shows a c-
agostic interaction.19 There is a suggestion that the B–H bond
involved in the Cr–H–B interaction is longer than the two
1
† g -H3B·dppm refers to the coordination mode only of the borane part
of the ligand. Implicit is that the phosphorus is also coordinated to the
metal.
˚
˚
terminal B–H bonds [1.23(3) A vs. 1.12(3) A, respectively],
3 8 8 4
D a l t o n T r a n s . , 2 0 0 4 , 3 8 8 3 – 3 8 9 2

View Article Online
◦
˚
Table 1 Selected bond lengths (A) and angles ( ) for H3B·dppm and complexes 1–5
H3B·dppm
P(1)–B
B–H(1C)
1.914(3)
1.14(4)
B–H(1A)
P(1)–C(25)
1.20(3)
1.820(2)
B–H(1B)
1.18(4)
P(1)–B–H(1A)
P(1)–C(25)–P(2)
107.0(16)
112.77(12)
P(1)–B–H(1C)
C(25)–P(1)–B
107.8(18)
113.57(13)
P(1)–B–H(1B)
104.5(19)
Complex 1
Cr–C(26)
Cr–C(29)
Cr–B
1.878(3)
1.856(2)
2.800(2)
1.23(3)
Cr–C(27)
Cr–P(1)
Cr–H(1b)
B–H(1c)
1.835(2)
2.3782(6)
1.78(3)
Cr–C(28)
B–P(2)
B–H(1a)
1.891(3)
1.935(2)
1.12(3)
B–H(1b)
1.12(3)
C(29)–Cr–P(1)
P(2)–C(13)–P(1)
174.94(8)
111.32(11)
P(1)–Cr–C(27)
C(27)–Cr–B
94.55(7)
168.35(8)
Cr–H(1b)–B
C(13)–P(2)–B
136(3)
108.11(10)
Complex 2 (average over two independent molecules in the unit cell)
Ru1–B1
Ru1–H1a
B1–H1b
2.520(4)
1.64(4)
1.13(4)
Ru1–P1
B1–P3
B1–H1c
2.302(1)
1.919(4)
1.18(4)
Ru1–P2
B1–H1a
2.280(1)
1.34(4)
Ru1–H1a–B1
P1–Ru1–B1
116(3)
107.2(1)
P2–C21–P3
P2–Ru1–B1
111.6(1)
81.4(1)
P1–Ru1–P2
B1–P3–C21
93.95(3)
108.9(2)
Complex 3 (average over four independent molecules in the unit cell)
Ru1–B1
Ru1–H1a
B1–H1b
2.499(8)
1.70(6)
1.07(6)
Ru1–P1
B1–P3
B1–H1c
2.226(2)
1.946(7)
1.06(6)
Ru1–P2
B1–H1a
2.286(2)
1.30(6)
Ru1–H1a–B1
P1–Ru1–B1
119(4)
98.3(2)
P2–C9–P3
P2–Ru1–B1
108.7(3)
82.7(2)
P1–Ru1–P2
B1–P3–C9
91.3(1)
111.2(3)
Complex 4
Ru–B
Ru–H(2)
B–H(2)
2.180(4)
1.70(3)
1.35(4)
Ru–P(1)
B–P(2)
B–H(3)
2.3115(10)
1.953(5)
1.14(3)
Ru–H(1)
B–H(1)
1.61(4)
1.29(4)
P(2)–B–H(1)
B–Ru–P(1)
Ru–H(2)–B
106.3(17)
88.48(13)
90(2)
P(1)–B–H(2)
B–Ru–H(1)
Ru–H(3)–B
C(35)–P(2)–B
108.0(14)
36(1)
97(2)
P(2)–B–H(3)
B–Ru–H(2)
Ru–B–H(3)
118.3(17)
38(1)
127.4(18)
P(2)–C(35)–P(1)
108.09(18)
104.40(19)
Complex 5
Ru1–B1
Ru1–H1c
B1–H1b
2.5904(19)
1.76(6)
1.12(6)
Ru1–P1
B1–P2
B1–H1c
2.3127(4)
1.925(2)
1.25(6)
Ru1–P3
B1–H1a
2.2926(4)
1.07(6)
Ru–H1c–B
P1–Ru1–B1
118(1)
100.36(5)
P2–C26–P3
P3–Ru1–B1
112.66(9)
83.41(5)
P1–Ru1–P3
C(26)–P(2)–B(1)
92.142(16)
111.53(8)
although these distances are the same within error, and are not
significantly different to free H3B·dppm. Further similarities
between 1 ◦and I extended to the B–H–M angle [136(1)◦ in 1
I) clearly lies between these two extremes of bonding. This
is consistent with that previously noted for I3,7 (and related
1
compounds5) in that although the g -M–H–B interaction can
˚
and 130(8) in I] and the Cr · · · B distance [2.800(2) A in 1 and
be considered as a three-centre–two-electron bond (on the basis
is reduced B–H coupling constant in the 1H NMR spectrum and
elongated bridging B–H bonds in the solid-state) there is also
significant ionic M(+) · · · (−)HB contribution to the interaction.
The carbonyl ligand trans to the agostic BH3 group in 1
˚
2.873(15) A on I]. These distances and angles are also similar
1
˚
to those measured in [Cr(CO)5{g -B2H4·2PMe3}] [2.876(8) A
◦
and 141(8) ].2 Complexes that show g -borohydride ligands
1
1
such as [(g -BH4)2Cr(py)4], that can be considered as having
˚
an essentially ionic interaction between borane and metal, have
has the shortest Cr–C bond distance [Cr–C(27) 1.835(2) A], as
˚
longer Cr · · · B distances and flatter Cr–H–B angles [viz. 3.309(9)
expected for this weak trans influence group, being ca. 0.045 A
◦
A, 173.9 ].20 However, the Cr–B distance in 1 is much longer than
true r-borane complexes of first row transition metals, such
shorter than the two CO ligands that are mutually trans to
one another. This is also as found for I, [Cr(CO)3(PCy3)2]
II, [W(CO)4(benzophospholide·BH3)], which contains a W–
˚
5
21
˚
as [(g -MeC5H4)Mn(CO)2(HBCy2)] [2.187(3) A] which show
evidence of significant M–B bonding, or those with formal r-
bonds such as the boryl complex [(g -C5Me4Et)Fe(BH2PMe3)]
[2.195(14) A]. The M · · · HB interaction in compound 1 (and
1
1
H–B interaction,14 and [RuH(PMe3)3{g ,g -PMe2CH2RRꢀB(l-
H)}] in which the PMe3 ligand trans to a B–H interaction
has the shortest Ru–P bond.23 Complex 1 is also related to
5
22
˚
D a l t o n T r a n s . , 2 0 0 4 , 3 8 8 3 – 3 8 9 2
3 8 8 5

View Article Online
the spectroscopically characterised d-agostic silane complex
[W(CO)4(Ph2PCH2CH2SiPh2H)].24
in a chemical shift change of the BH3 group in the 11B NMR
spectrum,21,25,26 that there is little change is fully consistent with
the relatively long Cr · · · B interaction observed in the solid-
state. In the infrared spectrum (KBr disc) two B–H stretches
are observed in the region associated with terminal B–H [ca.
2400 cm−1]. The bridging B–H was not identified.
Consideration of the structural metrics of the agostic phos-
phine borane complex 1 compared with the r-complex I show
that the bonding of the borane fragment with the metal centre
can be considered as being very similar in both cases, with
the chelate ring not imposing a significant structural change
of the M–H–B interaction. The presence of a chelate ring
does however have a large impact on stability of the resulting
complex compared with that of the monodentate H3B·PMe3 in I.
Complex I decomposes in C6D6 or under high vacuum liberating
Ruthenium
Ruthenium complexes containing H3B·dppm can be prepared
in a similar manner to 1, this time by displacement of weakly
bound acetonitrile ligands in the complex [CpRu(NCMe)3][PF6],
which has been previously shown to be a useful precur-
1
free H3B·PMe3. The isoelectronic complexes [(CO)4Mn(PR3)(g -
H3B·PMe3)][B(3,5-C6H3(CF3)2)4] are also unstable.5 In contrast
complex 1 is stable in a variety of solvents and under vacuum.
It is not air-stable, however, decomposing on contact to uniden-
tified products.
+
sor to the {CpRu} fragment.27 Addition of H3B·dppm to
[CpRu(NCMe)3][PF6] resulted in a mixture of products, some
1
of which had Ru–H–B interactions (as measured by H NMR
spectroscopy). However, by substituting one of the acetonitrile
ligands with a phosphine (PMe3 or P(OMe)3) to initially form
[CpRu(PR3)(NCMe)2]+,28 stable complexes in good composi-
tional yield could be accessed (Scheme 3). Addition of one
equivalent of PMe3 or P(OMe)3 to [CpRu(NCMe)3][PF6] fol-
The similarity between 1 and I extends to their solution
1
11
spectroscopic data. The H{ B} NMR spectrum of 1 shows
the BH3 group as a doublet [J(PH) 8.4 Hz] at d −2.71, of relative
integral 3H, shifted 3.66 ppm upfield compared to H3B·dppm.
The BH3 group must be rotating rapidly about the B–P axis
on the NMR timescale in solution, exchanging bridging and
terminal hydrogens, as the solid-state structure shows that all
three BH3 protons are inequivalent. This rotation cannot be
frozen out at 190 K in solution, showing that the Cr · · · HB
interaction must be relatively weak. This is also as found for
I, and DG‡ has been estimated for this process to be less than
30 kJ mol−1 and we suggest a similar value for 1. The room-
1
lowed by H3B·dppm resulted in the formation of [CpRu(PR3)(g -
H3B·dppm)][PF6], R = Me 2, R = OMe 3. Both these com-
plexes were isolated as analytically pure crystalline solids in
moderate overall yield (40–50%), although conversion is much
higher (>90%) as measured by NMR spectroscopy of reaction
mixtures. Using bulkier PPh3 resulted in intractable mixtures,
probably due to unfavourable phenyl/phenyl interactions. Com-
pounds 2 and 3 are stable in solution (CD2Cl2) and in the solid
state under an inert atmosphere. The solid-state structures of 2
and 3 are shown in Fig. 3.
1
temperature H NMR spectrum reveals the BH3 signal in 1
as a quadrupolar broadened quartet, with a reduced coupling
constant of ca. 105 Hz compared with BH3·dppm (112 Hz).
From this an estimate of 95 Hz for the value of the J(BH)
for the bridging hydrogen can be obtained, a drop of ca. 15%
compared with free H3B·dppm. A slightly larger drop in J(BH)
was noted for I compared with H3B·PMe3, but both values are
consistent with the description as a three-centre–two-electron B–
H–M interaction. The methylene protons on the dppm ligand
backbone are equivalent in solution, presumably due to rapid
conformation changes of the {Cr · · · dppm·BH3} six-membered
ring in solution, and are observed as a virtual triplet. The
1
13C{ H} NMR spectrum of 1 shows the expected four carbonyl
Scheme 3
environments in the ratio 1 : 1 : 2, all as doublets, in addition
1
to resonances due to the dppm ligand. In the 31P{ H} NMR
Compound
2 crystallises with two independent, well-
spectrum two signals are observed: a doublet at d 59.1 [J(PP
81 Hz)] and a broad signal at d 17.1 assigned to the borane-
bound phosphorus. The 11B NMR spectrum displays a signal at
d −40.7 ppm, which is not appreciably shifted from H3B·dppm.
As a significant Cr–B interaction would be expected to result
separated, ion-pairs in the unit cell. Both the cationic
1
[CpRu(PMe3)(g -H3B·dppm)]+ fragments in the asymmet-
ric unit have similar bond lengths and angles within error, and
the averages are given in Table 1. Usefully, compound 3 also
crystallises with four independent ion-pairs in the unit cell.
Fig. 3 Solid-state structure of the cationic portions of 2 (left) and 3 (right). Details as in Fig. 2.
D a l t o n T r a n s . , 2 0 0 4 , 3 8 8 3 – 3 8 9 2
3 8 8 6

View Article Online
1
Again, bond lengths and angles in each [CpRu(P(OMe)3)(g -
Ru · · · B interaction, in concert with the relatively long Ru–B
distances observed in the solid-state.
H3B·dppm)]+ cationic fragment are essentially the same within
experimental error (3r) and the average values are given. For
both structural refinements the data collection was of sufficient
quality to allow the hydrogen atoms associated with the BH3 to
be located in the final Fourier difference map and freely refined.
In both complexes the H3B·dppm ligand chelates to the metal
centre through one phosphine and a single B–H unit. The change
from r-donating PMe3 in 2 to p-accepting P(OMe)3 in 3 has very
little affect on the Ru–H–B interaction. The Ru–B distances
In contrast to [CpRu(NCMe)3][PF6], addition of H3B·dppm
to [Cp*Ru(NCMe)3][PF6] cleanly resulted in substitution of the
nitrile ligands for the chelating phosphine borane in essentially
quantitative yield (by NMR spectroscopy). Recrystallization
afforded analytically pure material in good yield (94%) that
was characterized by X-ray diffraction and NMR spectroscopy
2
and shown to be [Cp*Ru(g -H3B·dppm)][PF6], 4 (Scheme 4).
Compound 4 is stable in the solid state and solution under an
inert atmosphere, but decomposes slowly (hours) on contact
with air in the solid state and faster in solution.
˚
˚
are the same within error [2.520(4) A 2 and 2.499(8)A 3] as
˚
˚
are the Ru–H distances [1.64(4) A 2 and 1.70(6) A 3], these
being much shorter than observed in [Cp*Ru(dippe)][BArf4]
˚
[d(RuH) 2.262 A] which has a c-agostic interaction. They are
only slightly longer that found in Ru–H hydrides [Ru–H ca.
˚
1.6 A]. The Ru–B distances are considerably longer than found in
the boryl complexes [Cp*Ru(CO)2BH2PMe3]22 [2.243(8) A] and
˚
29
˚
[Ru(Bcat)2(CO)2(PPh3)2] [2.100(3) A], both of which contain
direct Ru–B bonds. They are also significantly longer than Ru–
B distances found in ruthenaborane clusters.30 However they are
shorter than found in [RuH(PMe3)3{g ,g -PMe2CH2RRꢀB(l-
1
1
Scheme 4
H)] that has a single Ru–H–B interaction in a five-membered
chelate ring23 [d(Ru–B) 2.994(1) A; d(RuH) 1.94(2) A]. The B–
H distances around the borane are as expected for B–H bonds,
and while the B–H bond interacting with the ruthenium in each
complex appears to be lengthened slightly compared with the
terminal B–H (Table 1), they are the same within error and are
not significantly different from those in H3B·dppm. The Ru–H–
B angles in 2 and 3 are more compressed than in 1 [116(3), 119(4)
compared with 136(3) in 1] as are the M–B distances, implying
a tighter M–H–B three-centre–two-electron interaction in the
ruthenium complexes.
˚
˚
The solid-state structure of 4 is shown in Fig. 4. Im-
mediately apparent is that only Cp* and H3B·dppm lig-
ands surround the metal. The X-ray data were of sufficient
quality to locate and refine the B–H hydrogen atoms. The
2
H3B·dppm ligand binds to the metal centre g through the
˚
BH3 group [Ru–H1 1.61(4), Ru–H2 1.70(2)A], formally as
two three-centre–two-electron interactions. These distances are
comparable to those found in 2 and 3. However, the Ru–B
distance, 2.180(4) A, is considerably shorter than that found
˚
in compounds 2 and 3 and more like that found complexes
NMR data for complexes 2 and 3 are similar, apart from
differences associated with the phosphine. In the 1H NMR spec-
trum, as well as resonances due to Cp and phenyl, two (integral
1H) methylene environments are observed–demonstrating C1
symmetry in solution consistent with the solid-state structures.
At room temperature the BH3 fragment is rapidly spinning
around the P–B axis as found for 1 and I, exchanging terminal
and bridging hydrogen atoms; with a single B–H environment
integrating to 3 H observed at d −3.41 (2) and d −3.25 (3).
Coupling to 11B is resolved in the former [J(BH) 81 Hz], but not
in the latter, although the signal is broadened significantly. Both
sharpen on decoupling to 11B. The J(11B–1H) coupling constants
are smaller than found in 1, indicative of a stronger M–H–B
interaction, as suggested by the solid-state structure. This is
underscored by the fact that exchange of terminal and bridging
B–H hydrides can be frozen out in 2 and 3, in contrast to 1
and I, so that at 190K three clear environments are observed
that contain Ru–B r bonds such as [Cp*Ru(CO)2BH2PMe3]22
29
˚
˚
[2.243(8) A] and [Ru(Bcat)2(CO)2(PPh3)2] [2.100(3) A]. It
is also similar to ruthenium dihydroborate complexes with
two bridging hydrogens, such as [Cp*Ru(PMe3)(g -BH3Cl)]
2
32
2
˚
[2.122(8) A], [RuH{(g -H)2Bpin}(r-HBpin)(PCy3)2] [2.188(5)
A], [Ru(PMe3)3{g ,g -CH2CHMeCMe2BPh(l-H2)]23 [2.243(3)
33
1
2
˚
˚
2
34
˚
A] and Ru{(g -H)2BC8H14)2(PCy3)} [2.160(2) and 2.085(2) A].
This distance also lies just outside the combined covalent radii
˚
of Ru and B [2.09 A], suggesting a significant Ru–B interaction.
11
in the 1H{ B} NMR spectrum for the BH3 group. Two of
these resonances are in the region associated with terminal B–
H bonds (d 1–3) while the third is to higher field (ca. d −14).
Although this latter chemical shift is significantly to higher-
field than normally observed for ruthenium hydrides (ca. d
−8), it is in the region where three-centre–two-electron Ru–H–B
bridging hydrides are commonly observed in metalloboranes,30
consistent with this description of the Ru–H–B interaction in
the solid state. For both complexes DG‡ for the exchange of
terminal and bridging hydrides is estimated as ∼38 kJ mol−1
which is, as expected, higher than that predicted for 1 and I (less
than 30 kJ mol−1)3 and agostic CH3–M interactions (which are
often highly fluxional),31 but similar to that reported for [(g -
2
H3B·dppm)-nido-RhSB9H10].11 The observation of two terminal
B–H environments at the low-temperature limit is also consistent
with the observed solid-state structure. Other room-temperature
and low-temperature NMR data are as expected. The 11B NMR
spectrum of both 2 and 3 show a single resonance close to that
observed for free H3B·dppm (ca. d −40). That there is virtually
no chemical shift change suggests that there is a negligible
Fig. 4 Solid-state structure of the cationic portion of 4. Details as in
Fig. 1
The hydrogen atoms bridging to the metal appear to be
lengthened when compared with the terminal B–H, although
all are just equivalent within 3r. All can be considered as
being within the B–H bonding distance. The Ru–H–B angles
D a l t o n T r a n s . , 2 0 0 4 , 3 8 8 3 – 3 8 9 2
3 8 8 7

View Article Online
are acute [90(2) and 97(2)◦], and coupled with the short Ru–
B distance, this might implicate a structure with both r-boryl
and hydride ligands. However, the B–Ru–H angles (36–38◦)
are small compared with complexes that are best described as
having such interactions, such as [Cp2W(H)(Bcat)] [78(2)◦]26 or
[Cp2Ta(H)2(Bcat)] [63(2)◦],35 but the same as those described
the B3LYP/DZVP level result are in a good agreement with
the experimentally observed structure (Fig. 5) and inspection of
the Wiberg bond indices from NBO analysis (0.264) indicate a
significant Ru–B interaction.
2
2
for g -BH4 borohydride complexes of ruthenium, e.g. [Ru(H)(g -
BH4)(PMe3)3] [34.5(8)◦].36 This bidentate bonding mode is also
similar to that reported for the spectroscopically characterised
2
complexes [Cp*Ru(PR3)(g -BH4)] (R = e.g., Me, PPh3)37 and
those observed previously in the crystallographically charac-
terised rhodium complexes of H3B·dppm: [(dppm·BH3)-nido-
RhSB9H10]10 and [(cod)Rh(dppm·BH3)][PF6].12 The Ru centre
in 4 is formally 18-electron, although structurally the complex
is more closely related to the 16-electron [Cp*Ru(PMeiPr2)2]+
complexes that also have Cs symmetry.38 These compounds
react readily with donor ligands to form 18-electron complexes
with piano-stool geometries. Likewise, 4 reacts as if a latent 16-
electron complex, adding neutral two-electron ligands such as
1
PMe3 or CO to afford 18-electron complexes, with a g -borane
motif (vide infra).
1
In the H NMR spectrum of 4 (CD2Cl2) resonances due to
Cp* and the dppm·BH3 ligands are observed. In contrast to 2
and 3 the protons on the methylene backbone are equivalent
(observed as a doublet of doublets), indicating Cs symmetry to
the molecule in solution. The bridging B–H protons are observed
as a broad, integral 2 H, resonance at d −8 which sharpens
on decoupling to 11B. The remaining, terminal, BH proton is
shifted far downfield [d 5.12] compared with the position of
terminal B–H groups in the low-temperature limiting spectra of
2 and 3 (d ∼1–3). The chemical shift of this hydride is similar to
that observed in [{Co(CO)3}2(l-CO)(l-BH·PMe3)] which has a
bridging borylene ligand [d 4.59],39 and the chlorotrihydroborato
Fig. 5 DFT calculated structure (B3LYP/DZVP) for 4 (with Me
˚
˚
substituted for Ph). Selected bond lengths (A): Ru–B 2.298A, B–H1
1.273, B–H2 1.272, Ru–H1 1.904, Ru–H2 1.904; B–H1–Ru 90.319,
B–H2–Ru 90.437
Interestingly,
the
phosphine
substituted
boryls
[Cp(CO)3W(BH2·PMe3)],40 [Cp(CO)2Ru(BH2·PMe3)]22 and
[(PR3)Mn(CO)4(BH2·PMe3)]5 only show small upfield chemical
shift changes of Dd 10 compared to the free ligand, considerably
less than for 4 and dihydroborate complexes. This is suggestive
of a smaller interaction between the metal and boron for
these complexes, underscoring the their previous description as
resembling contact-ion pairs: [LnM]− [BH2·PMe3]+.5,40
2
complex [Cp*Ru(PMe3)(g -H3BCl)] [d 6.34]32 but very different
from the r-boryl complexes [Cp(CO)3W(BH2·PMe3)] which
shows a chemical shift in the region associated with terminal
B–H bonds [d 1.92].40 The BH3 group is static on the NMR
timescale over the temperature range 220 K (CD2Cl2) to 340 K
(C2D4Cl2). At this higher temperature compound 4 decomposes
via loss of BH3 (as B2H6) to form, as yet, uncharacterised
As noted, complex 4 bears a structural similarity to 16-
electron [Cp*Ru(P2)]+ complexes which readily add two-electron
ligands.38 Extending this connection further, addition of PMe3
to 4 rapidly results in the displacement of one of the Ru–H–B
linkages and the isolation, in essentially quantitative yield, of
1
products. The 31P{ H} NMR spectrum of 4 is very similar to
1
2 and 3. Only one terminal B–H stretch is observed in the IR
spectrum of 4, at 2454 cm−1, as expected.
the 18-electron complex [Cp*Ru(PMe3)(g -H3B·dppm)][PF6], 5
(Scheme 5). Diagnostic changes in the NMR spectra demon-
2
1
A significant difference in the Ru · · · B bonding between 2
or 3 and complex 4 is indicated by the 11B NMR spectrum,
which shows a single broad resonance at d 15.6, shifted downfield
by ca. 55 ppm compared with both free ligand and complexes
2 and 3. This large chemical shift change is suggestive of a
significant metal–boron interaction in 4.25,26 For example, metal–
boryl complexes show large downfield chemical shifts (Dd ca.
60 ppm) for the three-coordinate boron compared to their
organoborane precursors,21,41 while metallaborane complexes
show marked downfield shifts on removal of a bridging proton
from B–H–M interactions to form strong, direct, M–B bonds.25
Likewise, dihydroborate ligands undergo significant downfield
shifts on coordination to metal centres. For example Li[H-
9-BBN] (9-BBN = 9-borabicyclo[3.3.1]nonane)42 undergoes a
downfield shift in the 11B NMR spectrum when coordinated
strate the change from g to g BH3 coordination of the borane
ligand on coordination of the phosphine. The 11B chemical shift
in 5 and now returns to being more like free ligand [d −40.2], the
high field region of the 1H NMR spectrum shows a single integral
3H resonance at d −3.39, indicating rapid BH3 rotation, while
the Cs symmetry of 5 is lost with two methylene environments
being observed for the CH2 backbone of the dppm ligand. The
rotation of the BH3 group can be slowed, so that at 190 K the
1H NMR spectrum of 5 displays a very broad signal at ∼ d
−14, assigned to the single B–H–M interaction. That the low
temperature limit has not been reached at 190 K shows that this
fluxional process is more facile in 5 than in the Cp congener 2,
for which it can be halted at this temperature.
1
The solid-state structure of 5 confirms the g -BH3 group
(Fig. 6). Despite the change from Cp to Cp* the structural
2
to group V metallocenes such as [Cp2Nb(g -H2BC8H14)]43 and
when incorporated into the, closely related to 4, complex
2
[Ru(g -H2BC8H14)2(PCy3)].34 DFT calculations on this latter
complex indicated delocalization between Ru, boron and bridg-
ing hydrogens with a significant interaction between Ru and
boron. This mirrors the description of the bonding between
[BH4]− and transition metals that also invokes contributions
from both hydrogen and boron,44 and also the bonding in
the paradigmatic molecule B2H6.45 Given the similar chemical
shift change in the 11B NMR spectrum observed in 4 a similar
bonding model is proposed. DFT calculations on 4 (with phenyl
groups replaced with methyl for computational expediency) at
Scheme 5
3 8 8 8
D a l t o n T r a n s . , 2 0 0 4 , 3 8 8 3 – 3 8 9 2

View Article Online
the NMR experiments an estimate of 63(1) kJ mol−1 can be
obtained for the enthalpy associated with breaking one of the
Ru–H–B interactions in 4. Compound 7 shows very similar
NMR spectroscopic data compared with 5 and 6, in particular
1
the diagnostic chemical shift for a g -BH3 group at d −2.70 and
two methylene environments for the dppm ligand backbone. At
190 K thermal decoupling of the quadrupolar boron isotopes
affords a sharp resonance for the boron-bound phosphorus and
1
they are now resolved as a well defined doublets in the 31P{ H}
NMR spectrum.
Conclusions
Complexes of the chelating phosphine borane ligand H3B·dppm
are clearly more stable than those of their monodentate con-
geners, such as H3B·PMe3. All the complexes reported here
are stable at room temperature under an inert atmosphere or
vacuum for weeks, in contrast to complexes of H3B·L.3–5 This
stability no doubt arises from the incorporation of the borane
into a chelate ring and is directly analogous to the relative
stabilities of r-alkane complexes and those with agostic C–H
Fig. 6 Solid-state structure of the cationic portion of 5. Details as in
Fig. 1.
2
interactions. The ability for g -coordination motif of the BH3
1
group in 4 to switch to g can be thought of as providing a
metrics of 5 are similar to 2 (Table 1). The only difference of
latent coordination site at the metal centre, effectively yielding
a 16-electron metal fragment with a chelating phosphine bo-
rane ligand, making them analogous to the Ru(II) complexes
exemplified by [Cp*Ru(PMeiPr2)2]+.38 As pointed out by Marks,
[BH4]− (and thus ligands such as H3B·dppm) can be related
˚
note is that the Ru–B bond distance in 5 [2.5904(19) A] is slightly
˚
longer than in 2 by 0.07 A.
Addition of carbon monoxide to a CH2Cl2 solution of 4 also
2
1
results in a g to g conversion of the H3B·dppm ligand to form of
1
[Cp*Ru(CO)(g -H3B·dppm)][PF6], 6. NMR spectroscopic data
3
to g -allyl ligands in terms of electron donation and frontier
show the diagnostic highfield shift in the 11B NMR spectrum, a
broad, integral 3H signal in the 1H NMR spectrum for the three,
rapidly exchanging, boron hydrides and two methylene environ-
ments consistent with C1 symmetry. The IR spectrum shows
a single, strong, CO stretching band at 1963 cm−1. Complex
6 is closely related to the structurally characterized c-agostic
orbital patterns.44 Complexes with allyl ligands are well-known
3
1
to react via an g to g mechanism (18 EAN to 16 EAN), and
complexes 4 and 5 can be thought of as analogous to these two
coordination modes, respectively. Indeed, Marks coined the term
“gate-keeper” for the borohydride ligand,44 suggesting that the
3
1
g to g change could potentially allow a catalytically reactive site
to be revealed. That any reactivity of the metal bound phosphine
borane is likely to involve coordination of a substrate at the metal
5
silyl complex [(g -C5H4Me)Mn(CO)(Ph2PCH2CH2SiPh2H)].46
2
1
A similar change from g to g bonding mode for the borohydride
2
ligand in the complex [(PMe2Ph)2Ru(H)(CO)(g -BH4)] is also
2
1
first, this g to g structural change of the BH3 unit that retains
the integrity of the phosphine borane and also allows a ligand to
coordinate is an attractive property for the future development
of the transition metal chemistry of these chelating ligands.
observed when an additional phosphine or CO is added.47 How-
1
ever, the resulting complexes, [(PMe2Ph)2Ru(H)(CO)(L’)(g -
BH4)] are unstable at ambient temperature, decomposing via
loss of Lꢀ·BH3. That complexes 5 and 6 are stable is a further
indication of the stability associated with the chelate ring.
Addition of the weaker nucleophile acetontrile to compound
4 does not result in any gross observable change in the chemical
Experimental
11
shifts of room-temperature NMR 1H{ B} NMR spectrum.
General
2
However, close inspection of the signal due to the g -BH3 group
All manipulations were carried out under an atmosphere of
argon, using standard Schlenk-line and glove-box techniques,
unless otherwise stated.9 Glassware were pre-dried in an oven
at 130 ◦C and flamed with a blowtorch under vacuum prior
to use. CH2Cl2, CH3CN and pentane were distilled from
CaH2. Toluene, diethyl ether, THF and hexane were distilled
from sodium benzophenone ketyl. C6D6 was dried over a
potassium mirror; CD2Cl2 and CD3CN were distilled under
vacuum from CaH2. [Cr(CO)4(nbd)],49 [CpRu(NCMe)3][PF6]27
and [Cp*Ru(MeCN)3][PF6]50 were prepared by the published
literature routes. All other chemicals were used as received from
Aldrich or Strem. Microanalyses were performed by Mr Alan
Carver (University of Bath Microanalytical Service).
in 4 reveals an increase in the line width of this signal from
40 to 160 Hz. This suggests that a slow exchange process is
occurring as room temperature. Gradual cooling establishes
a temperature-dependant equilibrium that results at 190 K
in a mixture of two products: 4 and the acetonitrile adduct
1
[Cp*Ru(NCMe)(g -H3B·dppm)][PF6] 7, Keq = 0.73 (Scheme 6).
From a van’t Hoff plot estimates of DH◦ = −19.6(2) kJ mol−1
and DS◦ = 105(1) J mol−1 K−1 can be made for this exchange
process. Nolan has reported the enthalpy of reaction for
addition of acetonitrile to a 16-electron coordinatively unsat-
urated cationic Ru(II) system [(Ph2PNMeNMePPh2)RuCl][BF4]
is −83(1) kJ mol−1.48 Using this figure and DH◦ obtained from
DFT calculations
The Gaussian 98 program was employed with the DZVP
basis set for B3LYP gas-phase geometry optimisations, us-
ing the Berny routine algorithm.51 No symmetry constraints
were imposed, and the nature of each stationary point was
verified through frequency calculations. Wiberg Bond Indices
were obtained by natural population analysis (NPA). Due to
computational time constraints the phenyl groups on 4 where
replaced with methyl.
Scheme 6
D a l t o n T r a n s . , 2 0 0 4 , 3 8 8 3 – 3 8 9 2
3 8 8 9

View Article Online
NMR spectroscopy
J(PH), 12.4 Hz, J(P(BH )H) 12.0 Hz, J(HH), 14.0 Hz], 2.78 [1 H,
3
ddd, CH, J(PH), 7.6 Hz, J(P(BH )H) 14.0 Hz, J(HH), 14.0 Hz],
11
1
1
1H, 1H{ B}, 11B{ H}, 11B and 31P{ H} NMR spectra were
recorded on a Bruker Avance 300 MHz or 400 MHz spec-
trometers at ambient temperature (298 K) unless otherwise
stated. Residual protio solvent was used as reference for 1H and
2.42 (1 H, br, BHt), 1.39 (1 H,3 br, BHt), 0.86 [9 H, d, PMe3,
1
J(PH), 9.2 Hz], −14.85 (1 H, br s, BHb). d(31P{ H}): 61.4 [1 P,
dd, PPh2, J(PPPMe3 ) 42.6 Hz, J(PP) 74.0 Hz], 15.5 (1 P, br, P–B),
2.9 [dd, 1 P, PMe3, J(PPMe3 ) 42.6 Hz, J(PP) 1.3 Hz], −143.09
[heptet, 1 P, J(FP) 710 Hz]. d(11B): −43.7 (1 B, br).
11
1
1H{ B} (CD2Cl2 d = 5.30, CD3CN d = 1.94). 11B and 31P{ H}
NMR spectra were referenced against BF3·OEt2 (external) and
85% H3PO4 (external), respectively. 31C{ H} NMR spectra were
[CpRu{P(OMe)3}(g1-H3B·dppm)][PF6], 3. The ligand
dppm·BH3 (46 mg, 0.116 mmol) was dissolved in
1
referenced to the deuterated solvent. Values are quoted in ppm.
Coupling constants are quoted in Hz. J(PH) coupling constants
were determined from selective decoupling experiments.
10 cm3 CH2Cl2 and added to
a CH2Cl2 solution of
[CpRu{P(OMe)3}(MeCN)2][PF6] (60 mg, 0.116 mmol),
which was generated in situ from [CpRu(NCMe)3][PF6] and
P(OMe)3. The solution was stirred for 16 h at room temperature.
The solvent was removed in vacuo to leave a brown oil. Crystals
suitable for an X-ray diffraction study were grown by dissolving
the oil in minimum CH2Cl2 and layering with pentane to yield
yellow crystals. Mass 0.056 g. Yield 58%. C33H39B F6P4Ru
requires C, 47.56; H, 4.72%. Found: C, 47.30; H, 4.65%. NMR
data (all in CD2Cl2) d(1H): 7.24–7.02 (20 H, m, Ph), 4.85 (5
H, s, Cp), 3.43 [1 H, ddd, CH2, J(PH), 12.4 Hz, J(P(BH )H)
12.4 Hz, J(HH), 14.4 Hz], 3.37 [1 H, ddd, CH2, J(PH), 10.03Hz,
X-Ray crystallography
The crystal structure data for H3B·dppm and compounds 1–5
were collected on a Nonius KappaCCD diffractometer with
details provided in Table 2. Structure solution, followed by
full-matrix least squares refinement was performed using the
SHELX suite of programs throughout.52 Hydrogen atoms were
included at calculated positions throughout apart from those
associated with the borane which were located in the final
Fourier difference map and refined without constraints.
CCDC reference numbers H3B·dppm (249465), 1 (249466), 2
(249467), 3 (249468), 4 (249469), 5 (249470).
J(P(BH )H) 14.4 Hz, J(HH), 14.4 Hz], 3.04 [9 H, d, P(OMe)3,
3
11
J(PH), 11.8 Hz], −3.25 (3 H, br, BH3). d(1H{ B}, 190 K):
7.30–6.78 (20 H, m, Ph), 5.00 (5 H, s, Cp), 3.49–3.32 (2 H, m,
See http://www.rsc.org/suppdata/dt/b4/b413650k/ for cry-
stallographic data in CIF or other electronic format.
CH2), 2.91 [9 H, d, P(OMe)3, J(PH), 11.8 Hz], 2.89 (1H, s,
1
BHt), 1.23 (1H, s, BHt), −14.03 (1 H, s, BHb). d(31P{ H}): 154.1
[1 P, d, P(OMe)3, J(PP) 66.3 Hz], 61.3 [1 P, dd, PPh2, J(PP(OMe)
)
3
Syntheses
66.3 Hz, J(PP(BH )) 69.8 Hz], 14.1 (1 P, br, P–B), −144. 3 [heptet,
3
1 P, J(FP) 710 Hz]. d(11B): − 44.4 (1 B, br).
dppm·BH3. (As synthesised by Martin et al.17): NMR data
(all in CDCl3) d (1H): 7.59–7.11 (20 H, m, Ph), 2.91 [2 H, d,
[Cp*Ru(g2-H3B·dppm)][PF6],
4. [Cp*Ru(MeCN)3][PF6]
CH2, J(HP(BH )) 11.9 Hz], 0.99 [3 H, br q, BH3, J(BH) 112.5 Hz].
(0.150 g, 0.297 mmol) and dppm·BH3 (0.118 g, 0.297 mmol)
were stirred in 20 cm3 of MeCN for 30 min at room temperature.
Solvent was removed in vacuo to leave a red oil. Crystals
suitable for an X-ray diffraction study were grown from a
(1 : 3) CD2Cl2–hexane solution. Mass 0.217 g, yield 94%.
C35H40BF6P3Ru requires C, 53.93; H, 5.17%. Found: C, 53.7;
H, 5.10%. NMR data (all in CD2Cl2) d(1H): 7.76−6.26 (20 H,
m, Ph), 5.12 (1 H, s, BH), 2.90 [2 H, dd, CH, J(PH), 8.9 Hz,
3
11
d(1H{ B}) (selected): 0.99 [3 H, dd, BH3, J(PH) 14.3, 1.5 Hz].
1
d(31P{ H}): 16.9 (1 P, br, PBH3), −25.5 [1 P, d, J(PP) 65.4]. d(11B):
−37.1 (s, 1 B).
[(CO)4Cr(g1-H3B·dppm)], 1. [(CO)4Cr(nbd)] (0.100 g,
0.390 mmol) and dppm·BH3 (0.155 g, 0.390 mmol) were stirred
in 15 cm3 of THF for 16 h at room temperature. The solvent was
removed in vacuo to leave a yellow solid. Crystals suitable for
an X-ray diffraction study were grown by dissolving the solid in
minimum toluene and storage at −70 ◦C for 4 days. Analytically
pure material was obtained by from a toluene–pentane layer.
Mass 0.140 g, yield 64%. C29H25P2O2BCr requires C, 61.95; H,
4.48%. Found: 62.10; H, 4.88%); vmax/cm−1 (CO) 2019, 1923,
1905 and 1870. NMR data (all in C6D6) d(1H): 7.30–6.67 (20 H,
J(P(BH )H) 12.3 Hz], 1.60 (15 H, s, Me3), −9.08 [2 H, br d, BH2].
3
1
d(31P{ H}): 63.3 [1 P, d, PPh2, Hz, J(PP) 98.3 Hz], 18.7 (1 P, br,
P–B), −144.4 [heptet, 1 P, J(FP) 710 Hz]. d(11B): 15.6 (1 B, br).
IR (KBr), m/cm−1: 2454 (m, BH)
[Cp*Ru(PMe3)(g1-H3B·dppm)][PF6], 5. A THF solution of
PMe3 (0.003 g, 0.038) was added to a MeCN solution of
[Cp*Ru(dppmBH3)] (PF6) (0.030 g, 0.038 mmol) and stirred for
5 min to give a yellow solution. Crystals suitable for an X-ray
diffraction study were grown by dissolving the oil in minimum
CH2Cl2 and layering with pentane to yield yellow crystals. Mass
0.026 g, yield 72%). C38H49BF6P4Ru·CH2Cl2 requires C, 49.8;
H, 5.47%. Found: C, 50.1; H, 5.47%. NMR data (all in CD2Cl2)
d(1H): 7.94–6.69 (20 H, m, Ph), 4.06 [1 H, ddd, CH, J(PH),
m, Ph); 2.75 [2 H, dd, CH2, J(PH), 9.0 Hz, J(P(BH )H) 11.9 Hz];
3
−2.84 [3 H, br q, BH3, J(BH) 96 Hz]. d(1H{ B}): −2.71 [3 H,
11
d, BH3, J(PH) 8.4 Hz]. d(13C{ H}): 229.1 [1 C, d, CO, J(PC)
1
11.8 Hz]; 226.0 [1 C, d, CO, J(PC) 4.5 Hz]; 220.5 [2 C, d, J(PC)
13.1 Hz]; 137.7–126.0 (24 C, m, Ph); 30.9 [1C, d, CH2, J(PC)
1
41.7 Hz]. d(31P{ H}): 58.3 [1 P, d, J(PP) 80.7 Hz]; 15.9, (1 P, br s,
P–B); d(11B): −41.5 (1, s). IR (KBr), m/cm−1: 2440 (m, BH), 2393
(m, BH), 2019 (s, CO), 1935 (s, CO), 1899 (vs, CO), 1830 (s, CO).
11.2 Hz, J(P(BH )H) 11.2 Hz, J(HH), 15.2 Hz], 3.12 [1 H, ddd,
3
CH, J(PH), 7.2 Hz, J(P(BH )H) 14.8 Hz, J(HH), 15.2 Hz], 1.50
[CpRu(PMe3)(g1-H3B·dppm)][PF6], 2. dppm·BH3 (91 mg,
0.230 mmol) was dissolved in 10 cm3 of CH2Cl2 and added
to a CH2Cl2 solution of [CpRu(PMe3)(MeCN)2][PF6] (100 mg,
0.230 mmol), [CpRu(NCMe)3][PF6] and PMe3. The resulting
solution was stirred for 16 h at room temperature. The solvent
was removed in vacuo to leave a brown oil. Crystals suitable
for an X-ray diffraction study were grown by dissolving the oil
in minimum CH2Cl2 and layering with pentane to yield yellow
crystals. Mass 0.076 g, yield 42%. C33H39BF6P4Ru requires C,
50.46; H, 5.00%. Found: C, 50.5; H, 4.94%. NMR data (all in
CD2Cl2) d(1H): 7.69−6.77 (20 H, m, Ph), 4.58 (5 H, s, Cp), 3.73
3
(15 H, s, Me), 0.96 [9 H, d, PMe3, J(PH), 8.4 Hz], −3.39 [3 H, br
11
d, BH3, J(BH) 66.4 Hz]. d(1H{ B}) (selected): −3.39 (3 H, br s,
1
BH3). d(31P{ H}): 59.1 [1 P, dd, PPh2, J(PPMe3) 41.7 Hz, J(PP)
67.3 Hz], 10.6 (1 P, br, P–B), −4.3 [1 P, dd, PMe3, J(PMe3P)
42.6 Hz, J(PP) 2.3 Hz], −144.4 [1 P, heptet, J(FP) 710 Hz].
d(11B): −40.2 (1 B, br). IR (KBr), m/cm−1: 2478 (m, BH), 2374
(m, BH).
[Cp*Ru(CO)(g1-H3B·dppm][PF6], 6. A CH2Cl2 solution of
[Cp*Ru(dppmBH3)] (PF6) (0.100 g, 0.128 mmol) was stirred for
15 minutes under a CO atmosphere (1 atm) to give a yellow
solution. Solvent was removed in vacuo to leave a yellow solid.
Mass 0.095 g. Yield 92%. C36H40OBF6P3Ru requires C, 53.55;
H, 4.99%. Found: C, 53.9; H, 5.59%. NMR data (all in CD2Cl2)
d(1H): 7.74–7.02 (20 H, m, Ph), 3.82 [1 H, ddd, CH, J(PH),
[1 H, ddd, CH, J(PH), 11.6 Hz, J(P(BH )H) 11.2 Hz, J(HH),
3
14.8 Hz], 2.92 [1 H, ddd, CH, J(PH), 7.8 Hz, J(P(BH )H) 13.6 Hz,
3
J(HH), 14.8 Hz], 0.97 [9 H, d, PMe3 J(PH), 9.2 Hz], −3.41 [3 H,
11
pcq, BH3, J(BH) 81]. d(1H{ B}, 190 K, 400 MHz): 7.59–6.56
(20 H, m, Ph), 4.53 (5 H, s, Cp), 3.68 [1 H, virtual quartet, CH,
10.4 Hz, J(P(BH )H) 11.4 Hz, J(HH), 15.5 Hz], 3.39 [1 H, ddd,
3
3 8 9 0
D a l t o n T r a n s . , 2 0 0 4 , 3 8 8 3 – 3 8 9 2

View Article Online
D a l t o n T r a n s . , 2 0 0 4 , 3 8 8 3 – 3 8 9 2
3 8 9 1

View Article Online
CH, J(PH), 8.0 Hz, J(P(BH )H) 14.9 Hz, J(HH), 15.5 Hz], 1.66
20 M. Dionne, S. Hao and S. Gambarotta, Can. J. Chem., 1995, 73,
1126.
21 S. Schlecht and J. F. Hartwig, J. Am. Chem. Soc., 2000, 122, 9435.
22 T. Yasue, Y. Kawano and M. Shimoi, Chem. Lett., 2000, 58.
23 R. T. Baker, J. C. Calabrese, S. A. Westcott and T. B. Marder, J. Am.
Chem. Soc., 1995, 117, 8777.
24 U. Schubert and H. Gilges, Organometallics, 1996, 15, 2373.
25 A. S. Weller and T. P. Fehlner, Organometallics, 1999, 18, 447; T. P.
Fehlner and N. P. Rath, J. Am. Chem. Soc., 1987, 109, 5273.
26 J. F. Hartwig and S. R. De Gala, J. Am. Chem. Soc., 1994, 116,
3661.
3
11
(15 H, s, Me), −3.01 [3 H, br d, BH3, J(BH) 50.3 Hz]. d(1H{ B})
1
(selected): −3.01 [3 H, d, BH3, J(PH) 7.9 Hz)]. d(31P{ H}): 51.6
[1 P, d, PPh2, J(PP) 58.0 Hz], 13.5 (1 P, br, P–B), −144.4 [1 P,
heptet, J(FP) 710 Hz]. d(11B): −39.3 (1 B, br). IR (KBr), m/cm−1:
2469 (m br, BH), 2401 (m, br, BH), 1963 (vs, CO)
[Cp*Ru(NCMe)(g1-H3B·dppm)][PF6], 7. Addition of a ten
fold-excess of MeCN to a CD2Cl2 solution of 4 gave little
change in the room-temperature NMR spectra compared with
4 (see text). Gradual cooling resulted in 1H and 31P NMR
spectra that showed the appearance of a new compound,
27 B. M. Trost and C. M. Older, Organometallics, 2002, 21, 2544.
28 E. Ru¨ba, W. Simanko, K. Mauthner, K. M. Soldouzi, C. Slugovc,
K. Mereiter, R. Schmid and K. Kirchner, Organometallics, 1999, 18,
3843; T. P. Gill and K. R. Mann, Organometallics, 1982, 1, 485.
29 C. E. F. Rickard, W. R. Roper, A. Williamson and L. J. Wright,
Organometallics, 2000, 19, 4344.
1
identified as [Cp*Ru(NCMe)(g -H3B·dppm)][PF6] 7. At the
lowest temperature recorded (190 K) the ratio of 4 : 7 was 1 : 0.73.
11
Selected NMR data (all in CD2Cl2, 190 K) d(1H{ B}): 3.65 (1H,
br, vt, CH), 3.20 (1 H, br, vt, CH), 1.36 (15 H, s, Cp*), −2.70
30 X. Lei, M. Shang and T. P. Fehlner, J. Am. Chem. Soc., 1999, 121,
1
(3 H, br, 3H). d(31P{ H}): 51.0 [d, J(PP) 179], 12.8 [br, d, J(PP)
1275.
179]
31 R. H. Crabtree, Angew. Chem., Int. Ed. Engl., 1993, 32, 789.
32 Y. Kawano and M. Shimoi, Chem. Lett., 1998, 935.
33 V. Montiel-Palma, M. Lumbierres, B. Donnadieu, S. Sabo-Etienne
and B. Chaudret, J. Am. Chem. Soc., 2002, 124, 5624.
34 K. Essalah, J. C. Barthelat, V. Montiel, S. Lachaize, B. Donnadieu,
B. Chaudret and S. Sabo-Etienne, J. Organomet. Chem., 2003, 680,
182.
Acknowledgements
The Royal Society (A. S. W.) and EPSRC (N. M.) for funding.
References
35 D. R. Lantero, D. H. Motry, D. L. Ward and M. R. Smith III, J. Am.
1 S. A. Snow, M. Shimoi, C. D. Ostler, B. K. Thompson, G. Kodama
and R. W. Parry, Inorg. Chem., 1984, 23, 511; M. Shimoi, K. Katoh
and H. Ogino, J. Chem. Soc., Chem. Commun., 1990, 23, 811; M.
Shimoi, K. Katoh, H. Tobita and H. Ogino, Inorg. Chem., 1990, 29,
814; M. Hata, Y. Kawano and M. Shimoi, Inorg. Chem., 1998, 37,
4482; W. E. Piers, Angew. Chem., Int. Ed., 2000, 39, 1923.
2 K. Katoh, M. Shimoi and H. Ogino, Inorg. Chem., 1992, 31, 670.
3 M. Shimoi, S. Nagai, M. Ichikawa, Y. Kawano, K. Katoh, M. Uruichi
and H. Ogino, J. Am. Chem. Soc., 1999, 121, 11704.
4 T. Kakizawa, Y. Kawano and M. Shimoi, Organometallics, 2001, 20,
3211.
Chem. Soc., 1994, 116, 10811.
36 J. A. Statler, G. Wilkinson, M. Thornton-Pett and M. B. Hursthouse,
J. Chem. Soc., Dalton Trans., 1984, 1731.
37 H. Suzuki, D. H. Lee, N. Oshima and Y. Morooka, Organometallics,
1987, 6, 1569.
38 M. Jimenez-Tenorio, M. C. Puerta and P. Valerga, Eur. J. Inorg.
´
Chem., 2004, 17.
39 M. Shimoi, S. Ikubo and Y. Kawano, J. Am. Chem. Soc., 1998, 120,
4222.
40 Y. Kawano, T. Yasue and M. Shimoi, J. Am. Chem. Soc., 1999, 121,
11744.
5 T. Yasue, Y. Kawano and M. Shimoi, Angew. Chem., Int. Ed., 2003,
41 S. Aldridge, A. Al-Fawaz, R. J. Calder, A. A. Dickinson, D. J. Willock,
M. E. Light and M. B. Hursthouse, Chem. Commun., 2001, 1986; H.
Braunschweig, Angew. Chem., Int. Ed., 1998, 37, 1786; G. J. Irvine,
M. J. G. Lesley, T. B. Marder, N. C. Norman, C. R. Rice, E. G.
Robins, W. R. Roper, G. R. Whittell and L. J. Wright, Chem. Rev.,
1998, 98, 2685.
42 H. C. Brown, B. Singaram and C. P. Mathew, J. Org. Chem., 1981,
46, 2712.
43 F. C. Liu, C. E. Plecnik, S. M. Liu, J. P. Liu, E. A. Meyers and S. G.
Shore, J. Organomet. Chem., 2001, 627, 109.
42, 1727.
6 M. Shimoi, K. Katoh, Y. Kawano, G. Kodama and H. Ogino,
J. Organomet. Chem., 2002, 659, 102; R. H. Crabtree, Dalton Trans.,
2001, 659, 2437.
7 G. J. Kubas, Metal Dihydrogen and r-Bond Complexes, Kluwer,
Dordrecht, 2001.
8 S. Geftakis and G. E. Ball, J. Am. Chem. Soc., 1998, 120, 9953.
9 M. Brookhart, M. L. H. Green and L. L. Wong, Prog. Inorg. Chem.,
1988, 36, 1; W. Scherer and G. S. McGrady, Angew. Chem., Int. Ed.,
2004, 43, 1782.
10 R. Macias, N. P. Rath and L. Barton, Angew. Chem., Int. Ed., 1999,
38, 162.
44 T. J. Marks and J. R. Kolb, Chem. Rev., 1977, 77, 263.
45 T. A. Albright, J. K. Burdett, and M.-H. Whangbo, Orbital Interac-
tions in Chemistry, Wiley, New York, 1985.
11 O. Volkov, R. Mac´ıas, N. P. Rath and L. Barton, Inorg. Chem., 2002,
41, 5837.
¨
46 U. Schubert, K. Bahr and J. Muller, J. Organomet. Chem., 1987, 327,
357.
12 M. Ingleson, N. J. Patmore, G. D. Ruggiero, C. G. Frost, M. F.
Mahon, M. C. Willis and A. S. Weller, Organometallics, 2001, 20,
4434.
13 W. Baratta, S. Stoccoro, A. Doppiu, E. Herdtweck, A. Zucca and
P. Rigo, Angew. Chem., Int. Ed., 2003, 42, 105; H. Urtel, C. Meier,
F. Eisentra¨ger, F. Rominger, J. P. Joschek and P. Hofmann, Angew.
Chem., Int. Ed., 2001, 40, 781.
47 B. Chamberlain, S. B. Duckett, J. P. Lowe, R. J. Mawby and J. C.
Stott, Dalton Trans., 2003, 2603.
48 J. Shen, C. M. Haar, E. D. Stevens and S. P. Nolan, J. Organomet.
Chem., 1998, 571, 205.
49 M. A. Bennett, L. Pratt and G. Wilkinson, J. Chem. Soc., 1961, 2037.
50 B. Steinmetz and W. A. Schenk, Organometallics, 1999, 18, 943.
51 M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A.
Robb, J. R. Cheeseman, V. G. Zakrzewski, J. A. Montgomery, R. E.
Stratmann, J. C. Burant, S. Dapprich, J. M. Millam, A. D. Daniels,
K. N. Kudin, M. C. Strain, O. Farkas, J. Tomasi, V. Barone, M.
Cossi, R. Cammi, B. Mennucci, C. Pomelli, C. Adamo, S. Cliord,
J. Ochterski, G. A. Petersson, P. Y. Ayala, Q. Cui, K. Morokuma,
D. K. Malick, A. D. Rabuck, K. Raghavachari, J. B. Foresman, J.
Cioslowski, J. V. Ortiz, B. B. Stefanov, G. Liu, A. Liashenko, P.
Piskorz, I. Komaromi, R. Gomperts, R. L. Martin, D. J. Fox, T.
Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayakkara, C. Gonzalez,
M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen, M. W. Wong,
J. L. Andres, C. Gonzalez, M. Head-Gordon, E. S. Replogle, and
J. A. Pople, in Gaussian 98, Pittsburgh, PA, 1998.
14 Z. Bajko, J. Daniels, D. Gudat, S. Ha¨p and M. Nieger,
Organometallics, 2002, 21, 5182.
15 A. Weiss, H. Pritzkow and W. Siebert, Eur. J. Inorg. Chem., 2002,
1607.
16 A. E. Shilov, G. B. Shiul’pin, Activation and Catalytic Reactions of
Saturated Hydrocarbons in the Presence of Metal Complexes, Kluwer,
Dordrecht, 2000.
17 D. R. Martin, C. M. Merkel and J. P. Ruiz, Inorg. Chim. Acta., 1986,
115, L29.
18 M. Y. Darensbourg, R. Bau, M. W. Marks, R. R. Burch, Jr., J. C.
Deaton and S. Slater, J. Am. Chem. Soc., 1982, 104, 6961.
19 K. Zhang, A. A. Gonzalez, S. L. Mukerjee, S.-J. Chou, C. D. Hoff,
K. A. Kubat-Martin, D. Barnhart and G. J. Kubas, J. Am. Chem.
Soc., 1991, 113, 9170.
52 G. M. Sheldrick, SHELX-97: A computer program for refinement of
crystal structures, University of Gottingen, 1997.
¨
3 8 9 2
D a l t o n T r a n s . , 2 0 0 4 , 3 8 8 3 – 3 8 9 2