Cleavage of H-C(sp2) and C(sp2)-X Bonds (X = Alkyl, Aryl, OR, NR2): Facile decarbonylation, isonitrile abstraction, or dehydrogenation of aldehydes, esters, amides, amines, and imines by [RuHCl(PiPr3)2]2

Article abstract of DOI:10.1021/om000390y

The RuHClL₂ fragment (L = PⁱTr₃) reacts at 25 °C with a dozen different G=CHE compounds (G = O, E = R, OR, NR₂; G = NR, E = R) to give π-acid abstraction products, RuHCl(CG)L₂, and E-H. For E-H = C₂H₅OH, alcohol is decarbonylated in a second step to give an additional CO ligand and CH₄. For E-H = HNR(CR′₂H), amine can be dehydrogenated by RuHClL₂ to give RuH(H₂)ClL₂ and CR′₂=NR. X-ray crystallographic studies are presented for the DMF decarbonylation intermediate Ru(H)₂Cl(η²-C(O)NMe₂)L₂, where the strong reducing potential of RuHClL₂ is manifested in the formally Ru(IV) species obtained from oxidative addition of H-C(O)NMe₂. The structure of Ru(H₂)Cl(η²-C₆H₄CH=NMe)L ₂, the product from aryl C-H activation of benzylidenemethylamine, PhHC=NMe, is also presented. This ability to abstract CO, isonitrile, or H₂ is traced to the considerable π-basicity of RuHCl(PⁱPr₃)₂.

Full text of DOI:10.1021/om000390y

Organometallics 2000, 19, 3569-3578
3569
Clea va ge of H-C(sp 2) a n d C(sp 2)-X Bon d s (X ) Alk yl,
Ar yl, OR, NR2): F a cile Deca r bon yla tion , Ison itr ile
Abstr a ction , or Deh yd r ogen a tion of Ald eh yd es, Ester s,
Am id es, Am in es, a n d Im in es by [Ru HCl(P iP r 3)2]2
J oseph N. Coalter, III, J ohn C. Huffman, and Kenneth G. Caulton*
Department of Chemistry, Indiana University, Bloomington, Indiana 47405-7102
Received May 8, 2000
The RuHClL2 fragment (L ) PiPr3) reacts at 25 °C with a dozen different GdCHE
compounds (G ) O, E ) R, OR, NR2; G ) NR, E ) R) to give π-acid abstraction products,
RuHCl(CG)L2, and E-H. For E-H ) C2H5OH, alcohol is decarbonylated in a second step to
give an additional CO ligand and CH4. For E-H ) HNR(CR′2H), amine can be dehydroge-
nated by RuHClL2 to give RuH(H2)ClL2 and CR′2dNR. X-ray crystallographic studies are
presented for the DMF decarbonylation intermediate Ru(H)2Cl(η2-C(O)NMe2)L2, where the
strong reducing potential of RuHClL2 is manifested in the formally Ru(IV) species obtained
from oxidative addition of H-C(O)NMe2. The structure of Ru(H2)Cl(η2-C6H4CHdNMe)L2,
the product from aryl C-H activation of benzylidenemethylamine, PhHCdNMe, is also
presented. This ability to abstract CO, isonitrile, or H2 is traced to the considerable π-basicity
of RuHCl(PiPr3)2.
In tr od u ction
mild conditions in benzene or cyclohexane to liberate
RuHCl(CO)(PiPr3)2 and RH (eq 2). For propionaldehyde
The fragment RuHClL2 (L ) PiPr3), derived from the
dimer [RuHClL2]2,1 has been shown to react with vinyl
ethers by addition of Ru-H across the CdC bond,
followed by R-H migration from the primary product a
to give a heteroatom-stabilized carbene complex.2 We
evaluate here the chemistry of this same electron-rich
Ru fragment with analogous double bonds GdCHE,
where G ) O, NR′ and the group E is an electron donor
(OR, NR2) or even hydrocarbyl R. Reactivity analogous
to that in eq 1 would lead to or proceed through
(R ) Et) as the carbonyl source, the reaction is complete
and quantitative within 30 min, and ethane is observed
1
by H NMR when the reaction is monitored in situ. No
intermediates or liberated ethylene were observed dur-
ing this reaction, and it is presumed to proceed via a
classical, least-motion mechanism initiated by oxidative
addition of aldehydic C-H following initial coordination.
Deinsertion of R from the resulting (H2) or (H)2 acyl
intermediate and subsequent reductive elimination of
alkane completes the process (Scheme 1). A C-H
oxidative process was previously shown to operate for
incorporation of electron-rich enones and enals into the
RuHCl(PiPr3)2 fragment,3 though an alternate initial
path involving addition of Ru-H across CdO cannot be
immediately discounted and has the benefit of main-
taining the preferred (+2) oxidation state of Ru (vs +4)
throughout. Indeed, it may be said that there is some
reluctance to propose oxidative addition to Ru(II), since
this d6 configuration may not be a competent reducing
agent; however, results reported later here will prove
this idea false. From transient Ru-CHR(OH), R-H
L2ClRu-CHE(GH) or L2ClRu-GCH2E species. How-
ever, the results reported here reveal that the ultimate
products are not derived from the Ru-H addition across
the GdC bond but, instead, from reactivity at the keto
or imino C(sp2)-H bond.
Resu lts a n d Discu ssion
Deca r bon yla tion of Ald eh yd es. Dimeric [RuH-
ClL2]2 reacts with aldehydes (HC(O)R, R ) alkyl) under
* To whom correspondence should be addressed. E-mail: caulton@
indiana.edu.
(1) Coalter, J . N., III; Huffman, J . C.; Streib, W. E.; Caulton, K. G.
Inorg. Chem., in press.
(2) Coalter, J . N., III; Bollinger, J . C.; Huffman, J . C.; Werner-
Zwanziger, U.; Caulton, K, G.; Davidson, E. R.; Ge´rard, H.; Clot, E.;
Eisenstein, O. New J . Chem. 2000, 24, 9.
(3) Coalter, J . N., III; Ge´rard, H.; Huffman, J . C.; Bollinger, J . C.;
Davidson, E. R.; Eisenstein, O.; Caulton, K. G. Inorg. Chem., in press.
10.1021/om000390y CCC: $19.00 © 2000 American Chemical Society
Publication on Web 08/02/2000

3570 Organometallics, Vol. 19, No. 18, 2000
Coalter et al.
Sch em e 1
Sch em e 2
H2 to form d would generate the observed product
RuHCl(CO)L2 and isobutylene, a potentially reactive
species (toward RuHClL2), yielding a plausible origin
for the balance (15%) of uncharacterized products
(Scheme 2) from contact with unreacted [RuHClL2]2.
Reaction with 3,3-dimethylbutyraldehyde (R ) CH2-
tBu) offers the opportunity to evaluate the potential for
a â-H elimination of alkene to generate RuHCl(CO)L2,
because here intermediates c and d offer no â-hydro-
gens. In comparison to R ) Et, if the added bulk of R )
t
CH2 Bu (over propionaldehyde) slows the net relative
rate of RH production as with pivaldehyde (vs H2 loss
and â-H elimination), intermediate c (Scheme 2) (or its
H2-loss product, d ) should show longer life (vs R ) tBu),
enabling more complete characterization. However,
after 20 min at room temperature, quantitative conver-
migration forms a hydroxycarbene, where subsequent
tautomeric H transfer yields the acyl intermediate b (eq
3). The first step in this pathway was found to operate
t
sion of RuHClL2 and HC(O)CH2 Bu to RuHCl(CO)L2
t
and neopentane (CH3 Bu, observed) is complete. Thus,
we speculate that the dominant factor in favoring one
path over the other in Scheme 2 (i.e., hydrocarbon vs
H2 elimination) originates from electronic factors (e.g.,
1° vs 3° alkyl) rather than sterics.
In support of this, analogous reaction with benzalde-
hyde (R ) Ph) in C6D6 results in immediate consump-
tion of starting RuHClL2 and 75% conversion to an
intermediate, but no formation of RuHCl(CO)L2 after
30 min at room temperature; free H2 (and 25% RuH-
(H2)ClL2) is also produced. After 48 h at room temper-
ature (in a sealed tube), only 30% conversion to RuHCl-
(CO)L2 and benzene (1H NMR evidence) is achieved, but
heating mildly (60 °C, 12 h) drives the reaction to
completion. The sole kinetic product seen by NMR can
be isolated cleanly by dropwise addition of a [RuHClL2]2
solution to a 5-fold excess (Ru:CdO) of stirred benz-
aldehyde in toluene. The molecule is characterized by
1H NMR (C6D6, 25 °C) by the lack of a high-field (<0
ppm) signal(s), diastereotopic PiPr3 methyl groups, and
three distinct resonances in the aromatic region cen-
in reactions of vinyl ethers and amides with [RuHCl-
(PiPr3)2]2 to generate alkoxy and amido carbenes and is
therefore feasible for the fleeting formation of transient
hydroxycarbenes.
Reaction with the bulky pivaldehyde (R ) tBu) forms
RuHCl(CO)L2 as the primary product (70%), but at a
much slower rate (t1/2 ≈ 15 h). This kinetic sluggishness
increases the occurrence of H2 loss to available RuHClL2
(to rapidly form RuH(H2)ClL2; 15% is observed) from
proposed intermediate c (Scheme 2) to yield unsaturated
Ru(tBu)(CO)ClL2, which will be prone to â-H elimina-
tion. Evidence for such a (H2) or (H)2 alkyl intermediate
(c) was observed after 30 min at room temperature
(C6D6) in the form of a high-field 1H NMR signal (δ
3
3
tered at δ 6.73 (t, J H-H ) 8 Hz, 1H), δ 6.83 (t, J H-H
)
8 Hz, 2H), and δ 7.8 (broad s, w1/2 h ) 90 Hz, 2H) for
the para, meta, and ortho protons of a Ru-C6H5 moiety;
31P{1H} NMR shows only a singlet (δ 36.0). Cooling the
sample to -20 °C (CD2Cl2) results in decoalescence of
the o-C6H5 protons to two broad signals centered at δ
1
7.2 and δ 7.7 by H NMR; two distinct resonances for
2
-9.50, t, J P-H ) 15 Hz, 2H) for the Ru H’s and an
the o-C6H5 carbons at 136.9 and 141.4 ppm and a broad
signal (δ 125.9, w1/2 h ) 116 Hz) for the m-C6H5 carbons
are seen by 13C{1H} NMR. The 13C NMR also shows a
t
upfield-shifted Bu signal (δ 0.72, s, 9H). A correspond-
ing 31P{1H} singlet was also observed (∼50% of total P
intensity), and these signals disappear in concert with
RuHCl(CO)L2 formation. â-H elimination after loss of
2
low-field signal (δ 205.6, t, J P-C ) 14 Hz) for the ipso-
C6H5

Cleavage of H-C(sp2) and C(sp2)-X Bonds
Organometallics, Vol. 19, No. 18, 2000 3571
carbon and νCO ) 1905 cm-1, consistent with the
formulation Ru(Ph)Cl(CO)L2 (e), where a trans Cl-
Sch em e 3
Sch em e 4
Ru-CO benefits from Cl pπfCO π* push-pull stabi-
lization. These data correspond to a structure of Cs
symmetry with transoid phosphines and C6H5 coplanar
with a mirror plane in the ground state, and such a
conformation was seen for the related molecule where
L ) PtBu2Me, whose spectroscopic data resemble those
reported here. However, with L ) PtBu2Me, sharp
signals for the o-C6H5 protons were observed at room
temperature showing slower rotation about Ru-Cipso
,
and consistent with more Cipso pπfRu dπ donation (i.e.,
double-bond character) in these unsaturated molecules
when the less electron donating PtBu2Me is employed.4
Treatment of this aryl complex with 1 atm of H2 in C6D6
results in complete conversion to RuHCl(CO)L2 and
benzene within 12 h at room temperature.
(1:1 Ru:HCO2R) in C6D6, the complex RuH(H2)ClL2 was
detected in addition to anticipated RuHCl(CO)L2 in a
1:2 ratio (31P NMR). Approximately half the starting
ethyl formate remained unreacted, and no free ethanol
was seen.
One explanation for this involves the liberation of free
ethanol (ROH) after the first carbonyl extraction, which
is then rapidly decarbonylated by unreacted [RuHClL2]2
to yield coordinated CO, H2 (scavenged as RuH(H2)-
ClL2), and R′H (Scheme 3). We observe, however, that
[RuHClL2]2 reacts only slowly with ethanol (t1/2 ≈ 12 h)
under identical conditions to liberate equimolar RuHCl-
(CO)L2 and RuH(H2)ClL2. Presumably this proceeds
through alkoxy and η2-aldehydic intermediates, which
have strong precedent in similar decarbonylations,6
though none were detected (Scheme 4). In light of this
slow rate, a more plausible explanation can be formu-
lated where the ethoxy group (R ) CH2Me) generated
from deinsertion of Ru(H2)ClL2(-C(O)OEt) (g) never
leaves Ru as ethanol but is more rapidly converted to
acetaldehyde (R′ ) Me) after release of H2 (scavenged
as RuH(H2)ClL2) and â-H elimination to generate the
product RuHCl(CO)L. The liberated acetaldehyde is
then decarbonylated rapidly to complete the process.
This is illustrated in Scheme 5 (path 1), where the
labilizing effect of a trans CO (in h ) would facilitate H2
loss. One may also reason that the slower reaction of
[RuHClL2]2 with alcohol is due to the lack of this CO in
intermediate f (Scheme 4), in addition to the weaker
bridge-splitting power offered to the dimeric starting
material (vs ester).
The isolation of such a complex shows that although
decarbonylation of aryl aldehydes is effected under mild
conditions, the general trend of slower aryl migrations
and/or reductive eliminations (vs alkyl) results in
complete loss of H2 along path 2 in Scheme 2 to yield
Ru(Ph)Cl(CO)L2. Now, however, Ru-R has no low-
energy mechanism for formation of RuHCl(CO)L2 and
alkene, and any liberation of benzene to form RuHCl-
(CO)L2 from hydrogenolysis of Ru-C6H5 by free H2 is
inhibited by the binding site for H2 in Ru(Ph)Cl(CO)L2
being trans to the phenyl ligand with which it must
react. An example of aryl substituent modification
controlling insertion/deinsertion of C6H4X (incorporated
as M(η2-aroyl) or as M(C6H4X)(CO)) has been recently
demonstrated and shows how a subtle change in elec-
tronics (compared to aryl vs alkyl) can shift the product
outcome dramatically.5
We turned next to substrates with less electrophilic
carbonyl carbons.
Deca r bon yla tion of F or m a tes. The decarbonyla-
tion rate of ethyl formate (R ) CH2R′; R′ ) Me) is
comparable to that of propionaldehyde; within 30 min
no trace of starting [RuHClL2]2 was observed by NMR.
However, the presence of two potential CO units (i.e.,
formyl and OR) in the parent ester results in double
decarbonylation of the ester (for primary alkyls) to two
coordinated CO’s, H2 (scavenged as RuH(H2)ClL2), and
R′H (methane observed for R ) CH2Me) as shown in eq
4. When [RuHClL2]2 and ethyl formate were combined
For further proof of this proposed mechanism, CO
extraction from phenyl formate and tert-butyl formate
(R ) Ph, tBu) were pursued where â-H elimination from
RuOR is precluded, resulting in quantitative formation
of RuHCl(CO)L2 and ROH (observed) over 30 min at
room temperature. Here, path 1 (Scheme 5) is elimi-
nated and formation of Ru(CO) occurs exclusively from
reductive elimination of ROH through path 2 (Scheme
5). Direct reaction of [RuHClL2]2 with free HOPh and
(4) Huang, D.; Streib, W. E.; Bollinger, J . C.; Caulton, K. G.; Winter,
R. F.; Scheiring, T. J . Am. Chem. Soc. 1999, 121, 8087.
(5) Clark, G. R.; Roper, W. R.; Wright, J .; Yap, P. D. Organometallics
1997, 16, 5135.
(6) Chen, Y.; Chan, W. C.; Lau, C. P.; Chu, H. S.; Lee, H. L.
Organometallics 1997, 16, 1241-1246 and references within.

3572 Organometallics, Vol. 19, No. 18, 2000
Coalter et al.
Sch em e 5
HOtBu resulted in no formation of identifiable inter-
mediates proposed in Schemes 4 and 5 after 12 h at
room temperature but, instead, loss of one phosphine
i
and subsequent metalation of Pr to form Ru2H3Cl2L2-
(η2-P(C3H6)iPr2).7
Deca r bon yla tion of F or m a m id es. The decarbon-
ylation of dimethylformamide (DMF, HC(O)NR2; R )
CHR′2; R′ ) H) by [RuHClL2]2 is significantly slower
than that of aldehydes or esters at room temperature
(t1/2 ≈ 2 days) but can be effected in 3 h at 80 °C. Again,
substantial (ca. 20%) formation of RuH(H2)ClL2 is
observed in the product mixture (at 30 h, room temper-
ature), suggesting H2 loss to unreacted [RuHClL2]2 from
a dihydrogen or dihydride intermediate. Indeed, when
1
this reaction is monitored in C6D12 by H and 31P NMR
at room temperature, such an intermediate species is
observed (∼50% of total 31P intensity at 30 h) concur-
rently with starting [RuHClL2]2 and the end product
RuHCl(CO)L2. This intermediate can be prepared in
quantitative yield after 30 min in neat DMF and can
be isolated in 45% yield from a pentane solution
obtained by liquid-liquid extraction of the reaction
products from the DMF solution.
Diagnostic features of the intermediate include
νCO ) 1591 cm-1 and a 13C{1H} signal at 205.1 ppm (t,
J C-P ) 8.2 Hz), consistent with the CO moiety incor-
porated as an η2-carbamoyl ligand,8 and a broad high-
F igu r e 1. Variable-temperature 1H NMR spectra (400
MHz) of the hydride region for Ru(H)2Cl(η2-C(O)NMe2)-
(PiPr3)2 in toluene-d8.
1
field H NMR singlet at -10.4 ppm integrated for 2H
(2J P-H not resolved), identifying them as two hydrides
and not coordinated H2 (Figure 1). The somewhat short
T1 times originate from the geometric constraints of a
pentagonal-bipyramidal geometry (72° is the ideal angle
between equatorial sites) favoring a small H-Ru-H,
(25 °C, C6D6). The methyl groups of the NMe2 unit are
1
inequivalent, resonating at 2.70 and 2.74 ppm; H and
13C{1H} NMR spectra show diastereotopic PiPr3 methyl
groups, and 31P{1H} NMR reveals a singlet at 49.5 ppm.
The inequivalent NMe2 methyl groups exclude N coor-
dination in a structure having transoid phosphines.
Variable-temperature 1H NMR measurements from +20
to -60 °C (C7D8) show the decoalescence of the Ru(H)2
unit to two equal-intensity doublets (broad) centered at
-8.9 and -12.0 ppm (T1(-60 °C, 400 MHz) ) 110 and
125 ms, respectively) with a mutual coupling of 42 Hz
2
though J H-H is rather large, and is consistent with
quantum exchange coupling. Confirmation of the struc-
ture proposed from IR and NMR data was sought
through X-ray crystallography.
The structure determination (Figures 2 and 3) shows
a molecule with a crystallographic mirror plane contain-
ing Ru, Cl, the OCNMe2 groups (thus, the NMe2 group
is planar, with inequivalent methyl groups), and the
hydride(s) (only one hydride was located in the X-ray
data). The trans influence of hydride H1 and of the
(7) Coalter, J . N., III; Huffman, J . C.; Caulton, K. G. Manuscript in
preparation.
(8) Anderson, S.; Hill, A. F.; Ng, Y. T. Organometallics 2000, 19,
15.

Cleavage of H-C(sp2) and C(sp2)-X Bonds
Organometallics, Vol. 19, No. 18, 2000 3573
F igu r e 4. Bonding representations for Ru(H)2Cl(η2-
C(O)NMe2)(PiPr3)2.
Sch em e 6
F igu r e 2. Illustration of the core bond distances and
angles for Ru(H)2Cl(η2-C(O)NMe2)(PiPr3)2.
As with the formate reactions, formation of RuHCl-
(CO)L2 can be accomplished from this species by (1)
deinsertion of the NMe2 group and reductive elimination
of HNR2 (Path 1, Scheme 6) or (2) deinsertion to form
an intermediate Ru“H2” amido complex (2′), which can
then lose H2 to starting [RuHClL2]2 (to form RuH(H2)-
ClL2) and then â-H eliminate CH2dNMe (R′ ) H; path
2, Scheme 6). Monitoring a sample of [RuHClL2]2 and
DMF in C6D6 at 25 °C by NMR showed, in addition to
the only 31P-containing products RuH(H2)ClL2 and
RuHCl(CO)L2, the production of free HNMe2; no CH2d
NMe was observed. This suggests that, at room tem-
perature, the decarbonylation occurs along path 1 and
that path 2 (Scheme 6) is inoperative here, in contrast
to the reactions of formyl esters presented above.
A sample of Ru(H)2Cl(η2-OCNMe2)L2 heated at 80 °C
for 3 h in C6D6 shows complete conversion to RuHCl-
(CO)L2, RuH(H2)ClL2, and RuHCl(CNMe)L2 (2:2:1 mole
ratio), with expulsion of free DMF and HNMe2 (both
observed). These observations suggest that at elevated
temperatures the initial oxidative addition step in DMF
activation is reversible and that back-reaction yields free
DMF and starting [RuHClL2]2, which can then react
with liberated HNMe2 to form the observed isonitrile
complex. Although reaction along path 2 (Scheme 6)
would liberate CH2dNMe, which could potentially lead
to formation of RuHCl(CNMe)L2, the observation of free
DMF requires the loss of it directly from Ru(H)2Cl(η2-
OCNMe2)L2 as can be illustrated in Scheme 7.
F igu r e 3. ORTEP view of Ru(H)2Cl(η2-C(O)NMe2)(PiPr3)2.
The second hydride was not detected in the X-ray study.
hetero carbon C14 is apparently responsible for the long
Ru-Cl2 (2.447 Å) and Ru-O13 (2.338 Å) bonds, but the
carbamoyl group is definitely η2: the N15-C14-Ru
angle is very large (143.65°), to bring the keto oxygen
closer to Ru. The keto carbon has a short (1.955 Å) bond
length to Ru. The one hydride undetected in the X-ray
study is presumably located in the large angle (139°)
between keto C14 and H1. The P-Ru-P (168.5°)
approaches 180°, in contrast to the smaller angles in
truly five-coordinate RuXYZ(PR3)2 square pyramids.
The angles to P from the ligands in the equatorial plane
range from 95.5 to 84.3° (for the small hydride H1).
From the IR, NMR, and X-ray data collected, the best
assignment of this complex places it at a point along
the continuum for the resonance forms shown in Figure
4.
The control reaction of [RuHClL2]2 with HNMe2, and
more detailed spectroscopic characterization of isonitrile
complexes RuHCl(CNR)L2 follows.
Deh yd r ogen a tion of Am in es. Reaction of [RuH-
ClL2]2 with equimolar (N:Ru) HNMe2 in cyclohexane
gives no immediate reaction but after 30 h at at room

3574 Organometallics, Vol. 19, No. 18, 2000
Coalter et al.
formation of free Me2CdNiPr over 24 h at 80 °C.
Likewise, reaction with the bulky HN(SiMe3)2 results
in no direct observation of the intermediates proposed
in eq 5. In all cases, decomposition of RuHClL2 to a
complex mixture of unidentified products was seen.
Sch em e 7
Ison itr ile Abstr a ction fr om Im in es. Unlike decar-
bonylation of the organic carbonyl, which is well known
for aldehydes and has precedent for formyl esters and
amides, the extraction of an isonitrile from a coordinated
imine is unknown.11,12 [RuHClL2]2 reacts with MeHCd
NEt in less than 48 h at room temperature in cyclohex-
ane to generate the new isonitrile complex RuHCl-
(CNEt)L2 and methane in high yield. This complex is
characterized by a high-field hydride at -26.4 ppm (1H,
t, J P-H ) 20 Hz), diastereotopic PiPr3 methyl groups,
and an intact ethyl group by 1H NMR (25 °C, C6D6) and
by a 31P{1H} singlet at 59.0 ppm. The low-field reso-
nance seen by 13C{1H} NMR at 182.0 ppm (t, J C-P ) 12
Hz) and νCN ) 1996 cm-1 are consistent with this
assignment. The bulkier imine MeHCdNtBu, however,
failed to yield any appreciable amount of isonitrile
complex after 5 days at room temperature or after 3 h
temperature results in complete consumption of the Ru
reagent and 75% production of RuH(H2)ClL2, consistent
with â-H elimination from the proposed amido inter-
mediate j (H-N oxidative addition product) to liberate
t
at 60 °C. Since the Bu substituent is somewhat remote
from the C(sp2)-H bond, this observation suggests the
mechanistic necessity of either an η1-N bound species
or an η2-imine species, rather than “direct” attack of Ru
on the C-H bond. Recent work by Bianchini et al. has
shown a base-catalyzed (H2O) path for degradation of
secondary amino carbenes (generated from vinylidene
and primary amine) to coordinated isonitrile and al-
kane,13 and such intermediates could be generated here
by simple addition of Ru-H across MeHCdNEt followed
by R-H migration to Ru (see eq 6). However, we propose
CH2dNMe. No methyl imine was observed in the
reaction mixture, though the isonitrile complex RuHCl-
(CNMe)L2 was found to be the other major 31P-contain-
ing product, which is presumed to be formed from action
of the liberated imine on unreacted [RuHClL2]2. Alter-
natively, it could be formed by analogy to ester double
decarbonylation (see Scheme 4) where the dehydroge-
nated amine (coordinated imine) never dissociates and
is dehydrogenated further to isonitrile concurrent with
a net loss of 2 equiv of H2 (which could be captured by
available RuHClL2). Prominent features of this isonitrile
complex include a high-field hydride (δ -26.0 ppm, t,
1H J P-H ) 19 Hz), a CNMe group (δ 2.6 ppm, s, 3H),
and a 31P{1H} NMR singlet (δ 58.6 ppm). The identifica-
tion of this isonitrile complex was confirmed by com-
parison to an authentic sample generated directly from
[RuHClL2]2 and free CNMe. More thoroughly character-
ized examples of such complexes derived from [RuH-
ClL2]2 and free imine follow.
From these observations, it is clear that â-H elimina-
tion of Ru-NR(CH2R′) to form imine (eq 5) operates in
the dehydrogenation of free secondary amines, though
the liberated imine is more reactive toward RuHClL2
than HNMe2 and, hence, never accumulates to an
observable concentration. This parallels the previously
established trend of aldehydes donating their π-acid
functionality more readily than alcohols. To our knowl-
edge, this is a rare example of secondary amine dehy-
drogenation to imine under mild conditions without
evoking transfer hydrogenation.9,10
a mechanism analogous to that of aldehyde decarbon-
ylation above (eq 2 and Scheme 1), substituting the
isolobal fragment dNR′ for dO for its simplicity,
because of the use here of rigorously anhydrous condi-
tions and because of strong precedent for oxidative
addition reactions of H-C(sp2) in the related molecules
HC(dO)R.
To evaluate the effects of a phenyl substituent, the
corresponding imine, PhHCdNMe, was prepared from
H2NMe and HC(O)Ph. Surprisingly, we find that the
kinetic product from the reaction of [RuHClL2]2 with
PhHCdNMe in toluene is not the anticipated aryl
complex, RuCl(Ph)(CNMe)L2, but retains an H2 unit
instead. This product is characterized in CD2Cl2 by a
Reaction of [RuHClL2]2 with more sterically encum-
bered amines such as HNiPr2, whose resulting imine
should be restricted toward further reaction, shows no
(11) The insertion of isocyanide into Fe-CH3 (reverse reaction of
that reported here) has been recently documented: Bellachiona, G.;
Cardaci, G.; Macchioni, A.; Zuccaccia, C. J . Organomet. Chem., 2000,
594, 119.
(12) J ones, N. D.; MacFarlane, K. S.; Smith, M. B.; Schutte, R. P.;
Rettig, S. J .; J ames, B. R. Inorg. Chem. 1999, 38, 3956.
(13) Bianchini, C.; Masi, D.; Romerosa, A.; Zanobini, F.; Peruzzini,
M. Organometallics 1999, 18, 2376.
(9) Morales-Morales, D.; Chen, W.; J ensen, C. M. Presented at the
218th National Meeting of the American Chemical Society, New
Orleans, LA, 1999. J ensen, C. M. Personal communication.
(10) Catalytic dehydrogenative silylation of amines has recently been
reported: Takaki, K.; Kamata, T.; Miura, Y.; Shishido, T.; Takehira,
K. J . Org. Chem. 1999, 64, 3891.

Cleavage of H-C(sp2) and C(sp2)-X Bonds
Organometallics, Vol. 19, No. 18, 2000 3575
H1-H2 distance of 0.86(5) Å, although these “light
atom” values should be taken as approximate only.
To test the reliability of modern X-ray crystallography
for the location of poorly visible H ligands, this structure
was determined twice, on two different crystals. All
distances and angles involving Ru, C, and N within the
coordination sphere were identical within 1.2 esd’s
between the two determinations. Remarkably, the struc-
tural parameters of the Ru, H1, H2 triangle were also
equal within 1 esd and suggest that both the Ru-H
asymmetry (1.76(3) and 1.47(3) Å to H1 and H2,
respectively) is real and the H1/H2 distance of 0.85(4)
Å from this second determination is real and establishes
this as a compound containing rather unstretched H2.
The minimal lengthening of the H-H distance from that
(0.71 Å) in free H2 can be attributed to the minimal
π-donation from the trans imine nitrogen and the long
Ru-Cl bond (which diminishes the π-donor ability of
chloride). The longer Ru-H1 distance can be attributed
to this H being nearly trans to the imine nitrogen ( N-
Ru-H1 ) 171.2(10)°), while the other H is less so ( N-
Ru-H2 ) 159.4(12)°).
The H2 ligand of Ru(H2)Cl(η2-C6H4CHdNMe)L2 is lost
at elevated temperatures to form unsaturated RuCl(η2-
C6H4CHdNMe)L2. When a sample of Ru(H2)Cl(η2-C6H4-
CHdNMe)L2 is subjected to 80 °C for 12 h in C6D6, the
H2 loss product is formed in 50% yield, as evidenced by
new 1H and 31P NMR signals similar to those of Ru-
(H2)Cl(η2-C6H4CHdNMR)L2, but no corresponding high-
field 1H resonance (<0 ppm). Also observed is 15%
RuH(H2)ClL2 and free PhHCdNMe from the hydroge-
nation of the starting complex’s Ru-C(sp2) bond by the
liberated H2.
F igu r e 5. ORTEP view of Ru(H2)Cl(η2-C6H4CHdNMe)-
(PiPr3)2.
1
room-temperature high-field H NMR signal (δ -9.1, br
2
t, J P-H ) 11 Hz, 2H) whose T1(min) (300 MHz) of 10
ms at -70 °C indicates a dihydrogen ligand. A singlet
(δ 4.13, s, 3H) for NMe and diastereotopic PiPr3 methyls
are seen, and a 31P{1H} NMR singlet is present at δ
38.3. At room temperature, 1H NMR shows four distinct
aryl C-H units and 13C{1H} NMR shows six aromatic
carbons (ipso-C6H4 at δ 172.3, t, 2J C-P ) 3 Hz); a singlet
integrated to one proton and consistent with an imine
XHCdNMe group is also seen by 1H NMR at 8.37 ppm.
Con clu sion s
The reactions reported here illustrate the following
characteristics of [RuHClL2]2.
2
The CdN carbon resonates at δ 190.8 (t, J C-P ) 9 Hz)
and is also consistent with this proposed XHCdNMe
functionality. No strong νCN bands in the region of 2000
cm-1 are found, though the presence of an aryl ring
prohibits concrete assignment of the CdN band. The
observed data indicate the formation of a kinetic product
derived from aryl C-H oxidative addition (rather than
reactivity at H-C(Ph)dNMe) that can be represented
as Ru(H2)Cl(η2-C6H4CHdNMe)L2. Confirmation of this
proposed identity was sought by X-ray crystallography.
(1) This dimer is unsaturated and thus has the
potential to bind even weak donors (although alcohols
themselves, in the absence of base, push the limit on
binding to Ru). The preference to bind π-acidic ligands
is exemplified here, as it was reported that [RuHClL2]2
forms an immediate adduct with the very weakly
σ-donating (but mildly π-accepting) N2 ligand,2 usually
taken to be a much poorer ligand than ROH. The CdG
(G ) O, NR) groups reported here are other examples
of weakly π-acidic ligands.
(2) Halide bridge splitting of the dimeric [RuHClL2]2,
or its adduct with substrates, generates still more
unsaturation, in preparation for “deeper” substrate
transformation.
(3) [RuHClL2]2 and its monomer unit lack any strong
π-acid ligands and, thus, have considerable reducing
power within their d6 configurations. This is most fully
evident in the structure of Ru(H)2Cl[C(O)NMe2]L2,
where the dihydride character indicates the formal
metal oxidation state IV. In the absence of π-acid
ligands, Ru(II) should be seriously considered as a
reducing agent.
The structure determination (Figure 5), carried out
using an area detector, shows a molecule with idealized
Cs symmetry containing a planar C6H4CHdNMe moi-
ety. The angle P12-Ru1-P22 is 164.7°, and the P’s
are bent away from N4. Cl2 is trans to the ipso carbon
C11 (170.7°), and the Ru1-Cl2 distance of 2.53 Å is
substantially lengthened by the strong trans influence
of the coordinated aryl ring. The distances C11-Ru1
and C6-C5 are normal for C(sp2)-Ru and C(sp2)-C(sp2)
bonds at 2.04 and 1.43 Å, respectively, and the C5-N4
distance of 1.29 Å is consistent with a double bond. The
angle C11-Ru1-N4 is a small 78.3(1)° to accom-
modate the five-membered ring and the angles Ru1-
N4-C5 (114.4(2)°) and Ru1-N4-C3 (128.7(2)°) rein-
force sp2 hybridization about N4. The two H atoms of
the coordinated H2 unit were included in the refinement
and found to be approximately trans to N4 at 162 and
168° for N4-Ru1-H2 and N4-Ru1-H1 with an
(4) This reducing power permits oxidative addition of
a broad variety of H-C(sp2)dG bonds, as well as a
phenyl C-H. “Deinsertion” of the resulting Ru[C(G)R]
group is the C-C scission event. In concert with the

3576 Organometallics, Vol. 19, No. 18, 2000
Coalter et al.
added and the tube shaken. The sample was monitored
elimination of H2 or RH, a Ru(II) center is regenerated,
thereby enhancing the Ru(CG) bond.
1
periodically by H and 31P{1H} NMR, and after 24 h at room
temperature, the mixture was found to contain 70% RuHCl-
(5) When OR or NR2 is part of the keto substrate, and
when R is a primary or secondary alkyl, â-hydrogen
migration to Ru of such a hydrogen dehydrogenates the
C-heteroatom single bonds, creating more H2 and a
C-heteroatom double bond. When the heteroatom is
oxygen, the resulting aldehyde can consume a second
mole of ruthenium reagent.
(CO)(PiPr3)2 and 15% RuH(H2)Cl(PiPr3)2.
F r om HC(O)CH2tBu . A 15.0 mg (0.016 mmol) amount of
[RuHCl(PiPr3)2]2 was dissolved in 0.5 mL of C6D6 in an NMR
tube. Via syringe, 2.4 µL (0.032 mmol) of 3,3-dimethylbutyral-
dehyde was added and the tube shaken. 1H and 31P{1H} NMR
taken after 30 min at room temperature showed quantitative
conversion to RuHCl(CO)(PiPr3)2 and neopentane.
Ru (P h )Cl(CO)(P iP r 3)2. A 200 mg (0.218 mmol) amount of
[RuHCl(PiPr3)2]2 in 5 mL of toluene was added dropwise via
syringe to a stirred solution of 225 µL (2.21 mmol) of benz-
aldehyde in 5 mL of toluene at ambient temperature. The
reaction mixture was stirred for 12 h under argon, and the
solvent was removed to yield a red solid. Washing with
pentane (2 × 2 mL) to remove any residual benzaldehyde and
drying in vacuo yielded 160 mg (65%) of the title compound
as a red powder. The yield is quantitative when monitored in
situ by 31P NMR. 1H NMR (400 MHz, C6D6, 20 °C): δ 1.08
(6) (Dihydride)ruthenium(IV) and (dihydrogen)ruthe-
nium(II) complexes mediate these reactions, the hy-
drides can be fluxional, and one example of quantum
exchange coupling between inequivalent but fluxional
hydrides has been observed.
(7) The contrast of dihydride for the carbamoyl vs
dihydrogen for the ortho-metalated phenylimine ligand
may be due in significant part to the larger steric
demand of the metalated phenylimine, which thus
favors the more compact H2 alternative.
(dvt; J P-H ) 3J H-H ) 7 Hz, 18H, P(CHMe2)3), 1.13 (dvt, J P-H
)
3J H-H ) 7 Hz, 18H, P(CHMe2)3), 2.59 (m, 6H, P(CHMe2)3), 6.73
(t, J H-H ) 8 Hz, 1H, p-C6H5), 6.82 (apparent t, J H-H ) 8 Hz,
2H, m-C6H5), 7.8 (vbr s, 2H, o-C6H5). 31P{1H} NMR (162 MHz,
C6D6, 20 °C): δ 36.0 (s). 13C{1H} NMR (101 MHz, C7D8,
-20 °C): δ 19.5 (s, P(CHMe2)3), 19.7 (s, P(CHMe2)3), 24.2 (vt,
J P-C ) 9.1 Hz, P(CHMe2)3), 120.6 (s, p-C6H5), 125.9 (br s,
w1/2 h ) 116 Hz, m-C6H5), 136.9 (br s, w1/2 h ) 90 Hz, o-C6H5),
141.4 (br s, w1/2 h ) 93 Hz, o-C6H5), 155.8 (t, J P-C ) 9.7 Hz,
Thus, while formation of RuRCl(CO)L2 or RuRCl-
(CNR′)L2 (R ) H, Ph) may be a strong thermodynamic
driving force for these reactions, the kinetic facility rests
on the several features of [RuHClL2]2.
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All manipulations were per-
formed using standard Schlenk techniques or in an argon-filled
glovebox unless otherwise noted. Solvents were distilled from
Na, Na/benzophenone, P2O5, or CaH2, degassed prior to use,
and stored over 4 Å molecular sieves in airtight vessels.
Alumina (neutral, activity I, 60-325 mesh) was dried by
i-C6H5), 205.6 (t, J P-C ) 14.0 Hz, Ru(CO)). IR (Nujol): νCO
)
1905 cm-1
.
Ru HCl(CO)(P iP r 3)2. F r om HC(O)OEt. A 15.0 mg (0.016
mmol) amount of [RuHCl(PiPr3)2]2 was dissolved in 0.5 mL of
C6D6 in an NMR tube. Via syringe, 2.6 µL (0.032 mmol) of ethyl
formate was added and the tube shaken. 1H and 31P{1H} NMR
taken after 30 min at room temperature showed clean conver-
sion to RuHCl(CO)(PiPr3)2 and RuH(H2)Cl(PiPr3)2 (2:1), in
addition to half the starting formate and liberated methane.
F r om HC(O)OP h . A 15.0 mg (0.016 mmol) amount of
[RuHCl(PiPr3)2]2 was dissolved in 0.5 mL of C6D6 in an NMR
tube. Via syringe, 3.6 µL (0.032 mmol) of phenyl formate was
added and the tube shaken. 1H and 31P{1H} NMR taken after
30 min at room temperature showed quantitative conversion
to RuHCl(CO)(PiPr3)2 and phenol.
14
heating (250 °C) at 0.003 Torr (48 h). [RuHCl(PiPr3)2]2 and
imines15 (EtNdCHR′) were prepared as previously reported,
and all other reagents were used as received from commercial
vendors after drying and degassing when necessary. In situ
NMR identification of RuHCl(CO)(PiPr3)2,16,17 RuH(H2)Cl-
(PiPr3)2,18,19 and organic products were made by comparison
to literature data and/or authentic samples. 1H NMR chemical
shifts are reported in ppm relative to protio impurities in the
deuterio solvents. 31P NMR spectra are referenced to an
external standard of 85% H3PO4 (0 ppm). NMR spectra were
recorded with either a Varian Gemini 2000 (300 MHz, 1H; 121
MHz, 31P; 75 MHz, 13C) or a Varian Unity Inova instrument
F r om HC(O)OtBu . A 15.0 mg (0.016 mmol) amount of
[RuHCl(PiPr3)2]2 was dissolved in 0.5 mL of C6D6 in an NMR
tube. Via syringe, 3.8 µL (0.032 mmol) of tert-butyl formate
1
(400 MHz, H; 162 MHz, 31P; 101 MHz, 13C). Infrared spectra
1
was added and the tube shaken. H and 31P{1H} NMR taken
were recorded using a Nicolet 510P FT-IR spectrometer.
Ru HCl(CO)(P iP r 3)2. F r om HC(O)Et. A 15.0 mg (0.016
mmol) amount of [RuHCl(PiPr3)2]2 was dissolved in 0.5 mL of
C6D6 in an NMR tube. Via syringe, 2.4 µL (0.032 mmol) of
propionaldehyde was added and the tube shaken. 1H and 31P-
{1H} NMR taken after 30 min at room temperature showed
quantitative conversion to RuHCl(CO)(PiPr3)2 and ethane.
F r om HC(O)tBu . A 15.0 mg (0.016 mmol) amount of
[RuHCl(PiPr3)2]2 was dissolved in 0.5 mL of C6D6 in an NMR
tube. Via syringe, 3.5 µL (0.032 mmol) of pivaldehyde was
after 30 min at room temperature showed quantitative conver-
sion to RuHCl(CO)(PiPr3)2 and tert-butyl alcohol.
[Ru HCl(P iP r 3)2]2 p lu s EtOH. A 15.0 mg (0.016 mmol)
amount of [RuHCl(PiPr3)2]2 was dissolved in 0.5 mL of C6D6
in an NMR tube. Via syringe, 1.9 µL (0.032 mmol) of ethanol
was added and the tube shaken. 1H and 31P{1H} NMR spectra
taken periodically as the sample was allowed to stand at room
temperature showed quantitative conversion to RuHCl(CO)-
(PiPr3)2 and RuH(H2)Cl(PiPr3)2 (1:1) after 3 days (methane was
also observed).
Ru HCl(CO)(P iP r 3)2. F r om HC(O)NMe2. A 15.0 mg (0.016
mmol) amount of [RuHCl(PiPr3)2]2 was dissolved in 0.5 mL of
C6D12 in an NMR tube. Via syringe, 2.5 µL (0.032 mmol) of
(14) [RuHCl(PiPr3)2]2 was prepared by dropwise addition (over 2 h)
of a toluene solution of lithium tetramethylpiperidide to a stirred
suspension of RuH2Cl2(PiPr3)2 in toluene.1-3
(15) Imines were prepared by Schiff base condensation of the
appropriate aldehyde and amine using the method of: Cambell, K.
N.; Sommers, A. H.; Campell, B. K. J . Am. Chem. Soc. 1944, 66, 82-
84. This procedure was modified as detailed in this work for the
preparation of benzylidenemethylamine, PhHCdNMe.
(16) Esteruelas, M. A.; Werner, H. J . Organomet. Chem. 1986, 303,
221.
(17) Huang, D.; Folting, K.; Caulton, K. G. Inorg. Chem. 1996, 35,
7035.
(18) Burrow, T.; Sabo-Etienne, S.; Chaudret, B. Inorg. Chem. 1995,
34(9), 2470.
(19) Wolf, J .; Steuer, W.; Gruenwald, C.; Gevert, O.; Laubender, M.;
Werner, H. Eur. J . Inorg. Chem. 1998, 1827.
1
DMF was added and the tube shaken. H and 31P{1H} NMR
taken after 3 h at 80 °C showed conversion to 80% RuHCl-
(CO)(PiPr3)2 and 15% RuH(H2)Cl(PiPr3)2, with the balance
consisting of RuHCl(CNMe)(PiPr3)2.
Ru (H)2Cl(P iP r 3)2(η2-OCNMe2). A 200 mg (0.218 mmol)
amount of [RuHCl(PiPr3)2]2 was stirred in 3 mL of dry DMF
for 45 min to yield a homogeneous dark orange solution. 31P
NMR assay at this time showed a single resonance (s, 49.8
ppm). In a glovebox, pentane was added (10 × 7 mL), the
mixture was stirred until the pentane layer darkened, and

Cleavage of H-C(sp2) and C(sp2)-X Bonds
Organometallics, Vol. 19, No. 18, 2000 3577
Ta ble 1. Cr ysta llogr a p h ic Da ta a for
Ru (H)2Cl(OCNMe2)(P iP r 3)2
Ta ble 2. Cr ysta llogr a p h ic Da ta a for
Ru (H2)Cl(η2-C6H4CHdNMe)(P iP r 3)2
formula
a, Å
b, Å
c, Å
V, Å3
Z
C21H50NOP2Ru
21.472(1)
8.816(0)
14.015(1)
2653.08 Å3
4
space group
T, °C
Cmc21
-158
formula
a, Å
b, Å
c, Å
â, deg
V, Å3
Z
C26H52ClNP2Ru
39.331(1)
9.075(0)
16.513(1)
99.62(0)
5811.48 Å3
8
space group
T, °C
C2/c
-158
0.710 69
1.319
7.557
0.0242
0.0223
λ, Å
0.710 69
1.330
λ, Å
F
calcd, g/cm-3
F
calcd, g/cm-3
µ(Mo KR), cm-1
8.237
0.0193
0.0184
µ(Mo KR), cm-1
Rb
Rw
Rb
Rw
c
c
fw
531.10
fw
577.18
a
b
Graphite monochromator. R ) ∑||Fo| - |Fc||/∑|Fo|. c Rw
)
Graphite monochromator. R ) ∑||Fo| - |Fc||/∑|Fo|. c Rw
2
a
b
[∑w(|Fo| - |Fc |)2/∑w|Fo| ]1/2, where w ) 1/σ2(|Fo|).
)
[∑w(|Fo| - |Fc|)2/∑w|Fo| ]1/2, where w ) 1/σ2(|Fo|).
2
each pentane layer was removed using a disposable pipet. The
combined pentane extracts (∼70 mL) were reduced to 3 mL
in vacuo with precipitation of a yellow solid and a few
microliters of DMF. After the mixture was cooled overnight
at -20 °C to complete precipitation, the light brown superna-
tant was decanted via cannula, and the yellow solid was
washed with ether (1 × 2 mL) to remove any trace DMF.
Drying in vacuo yielded 105 mg (45%) of the title compound
as a bright yellow powder. 1H NMR (400 MHz, C7D8, -60 °C):
residue was redissolved in C6D6 to show 75% formation of
RuHCl(H2)(PiPr3)2 and 20% production of RuHCl(CNMe)-
1
(PiPr3) by H and 31P{1H} NMR.
Ru HCl(CNEt)(P iP r 3)2. A 400 mg (0.44 mmol) amount of
[RuHCl(PiPr3)2]2 was dissolved in 15 mL of cyclohexane, and
128 µL (1.31 mmol) of ethylideneethylamine (EtNdCHMe) was
added via syringe. After the mixture was stirred at room
temperature for 48 h, the solvent was removed to a liquid N2
trap to yield a viscous red-brown oil. NMR assay at this time
showed >90% conversion to the title compound. The residue
was dissolved in 5 mL of hexane and cooled at -60 °C to
precipitate a small amount of dark solid. The supernatant was
separated via cannula (the precipitate was discarded), and the
filtrate was evaporated to dryness to yield a dark oil. The oil
was taken up in a small amount of hexane and this solution
eluted through a 1.5 in. column of alumina in an argon-filled
glovebox with hexane/EtOAc (50:1). The orange-brown band
was collected, and the solvent was removed in vacuo to yield
the isonitrile complex as an orange-brown, pasty solid (350
mg, 78%). 1H NMR (400 MHz, C6D6, 20 °C): δ -26.4 (t,
2
δ -12.0 (br d, J H-H ) 42 Hz, 1H, Ru H; T1 ) 125 ms), -8.87
2
(br d, J H-H ) 42 Hz, 1H, Ru H; T1 ) 110 ms), 1.07 (br dvt;
3
J P-H ) J H-H ) 7 Hz, 18H, P(CHMe2)3), 1.13 (br dvt, J P-H
)
3J H-H ) 7 Hz, 18H, P(CHMe2)3), 2.10 (m, 6H, P(CHMe2)3), 2.48
(s, 3H, NMe2), δ 2.61 (s, 3H, NMe2). 31P{1H} NMR (162 MHz,
C6D6, 20 °C): δ 49.5 (s). 13C{1H} NMR (101 MHz, C7D8, 0 °C):
δ 19.5 (s, P(CHMe2)3), 19.8 (s, P(CHMe2)3), 25.0 (vt, J P-C
)
9.9 Hz, P(CHMe2)3), 37.0 (s, NMe2), 39.2 (s, NMe2), 205.1 (t,
J P-C ) 8.2 Hz, Ru(η2-OCNMe2)). Variable-temperature 1H
NMR measurements (400 MHz, C7D8) add the following data.
(1) The two hydrides coalesce at -20 °C to yield a broad singlet
at room temperature (δ -10.5, 2H). (2) When the temperature
is increased over the temperature range -60 to 20 °C, ∆δ for
the diastereotopic NMe2 groups decreases from 53 to 8 Hz. IR
3
2J P-H ) 20.0 Hz, Ru H), 0.85 (t, J H-H ) 6.8 Hz, 3H,
Ru(CNCH2CH3)), 1.31 (dvt, J P-H
)
3J H-H ) 6.4 Hz, 18H,
P(CHMe2)3), 1.33 (dvt, J P-H ) 3J H-H ) 6.4 Hz, 18H, P(CHMe2)3),
(Nujol): νCO ) 1591 cm-1
.
3
X-r a y Str u ctu r e of Ru (H)2Cl(P iP r 3)2(η2-OCNMe2). The
crystal was affixed to a glass fiber using silicone grease and
transferred to the goniostat, where it was cooled to -168 °C
using a gas-flow cooling system of local design. Standard inert-
atmosphere techniques were used during the handling and
2.61 (m, 6H, P(CHMe2)3), 3.04 (q, J H-H ) 6.8 Hz, 2H, Ru-
(CNCH2CH3)). 31P{1H} NMR (162 MHz, C6D6, 20 °C): 59.0 (s).
13C{1H} NMR (101 MHz, C6D6, 20 °C): δ 16.3 (s, Ru-
(CNCH2CH3)), 20.1 (s, P(CHMe2)3), 20.8 (s, P(CHMe2)3), 24.9
(vt, J P-C ) 9.9 Hz, P(CHMe2)3), 39.6 (s, Ru(CNCH2CH3)), 182.0
(t, J P-C ) 12.0 Hz, Ru(CNCH2CH3)). IR (Nujol): νCN ) 1996
cm-1. Anal. Calcd for C21H48ClNP2Ru: C, 49.16; H, 9.43.
Found: C, 48.16; H, 9.00.
mounting process. The data were collected on
a Bruker
SMART 6000 CCD diffractometer using 5 s frames with an ω
scan of 0.30°. Data were corrected for Lorentz and polarization
effects and equivalent reflections averaged using the Bruker
SAINT software as well as utility programs from the XTEL
library. An absorption correction was performed using the
SADABS program supplied by Bruker AXS. The structure was
solved using SHELXTL and Fourier techniques. A difference
Fourier phased on the non-hydrogen atoms clearly located all
of the non-hydride hydrogen atoms. After several successive
least squares in which hydrogen atoms were allowed to vary
isotropically, it was possible to locate one of the two metal
hydrides, but not the other. Several additional attempts failed
as well, even though it seems apparent that there is a
satisfactory coordination site available. A final difference
Fourier was essentially featureless. The results are shown in
Tables 1 and 2.
Ru HCl(CNMe)(P iP r 3)2. A 15 mg (0.016 mmol) amount of
[RuHCl(PiPr3)2]2 was dissolved in 0.5 mL of C6D6, and 1.8 µL
(0.33 mmol) of methyl isocyanide was added via syringe. After
3 h at 80 °C, 1H and 31P{1H} NMR showed quantitative
conversion to the title compound. 1H NMR (300 MHz, C6D6,
2
20 °C): δ -26.0 (t, J P-H ) 19 Hz, Ru H), 1.30 (dvt, J P-H
)
3
3J H-H ) 7 Hz, 18H, P(CHMe2)3), 1.33 (dvt, J P-H ) J H-H ) 7
Hz, 18H, P(CHMe2)3), 2.59 (m, 6H, P(CHMe2)3), 2.64 (s, 3H,
Ru(CNCH3)). 31P{1H} NMR (162 MHz, C6D6, 20 °C): δ 58.6.
Immediately after the addition of CNMe at room temperature,
the product mixture was found to be 50% unreacted [RuHCl-
(PiPr3)2]2 and 50% of the bis(isonitrile) complex RuHCl-
(CNMe)2(PiPr3)2. 1H NMR (400 MHz, C6D6, 20 °C): δ -6.90
(t, 2J P-H ) 22 Hz, Ru H), 1.42 (dvt, J P-H ) 3J H-H ) 7 Hz, 18H,
P(CHMe2)3), 1.47 (dvt, J P-H ) 3J H-H ) 7 Hz, 18H, P(CHMe2)3),
2.40 (s, 3H, Ru(CNCH3)), 2.42 (s, 3H, Ru(CNCH3)), 2.68 (m,
6H, P(CHMe2)3). 31P{1H} NMR (162 MHz, C6D6, 20 °C): δ 62.8
(s).
Th er m olysis of Ru (H)2Cl(P iP r 3)2(η2-OCNMe2). A 10.0
mg (0.019 mmol) amount of Ru(H)2Cl(PiPr3)2(η2-OCNMe2) was
1
dissolved in 0.5 mL of C6D6 in an NMR tube. H and 31P{1H}
NMR taken periodically show conversion to RuHCl(CO)(PiPr3)2
(40%), RuH(H2)ClL2 (40%), and RuHCl(CNMe)L2 (20%), with
the liberation of DMF and HNMe2 after 3 h at 80 °C.
P h HCdNMe. Approximately 15 mL (0.34 mol) of anhy-
drous methylamine was condensed under argon at -40 °C in
a thick-walled flask equipped with Solv-Seal joints and a
Teflon stopcock. At this temperature, 20.0 mL (0.20 mol) of
benzaldehyde was added dropwise to the stirred amine so that
no reflux occurred. The vessel was sealed, warmed to room
temperature, and stirred overnight. After recooling to -40 °C,
10 g of crushed KOH was added in portions under a slow argon
purge. The flask was resealed and stirred with warming to
[Ru HCl(P iP r 3)2]2 p lu s HNMe2. A 15.0 mg (0.016 mmol)
amount of [RuHCl(PiPr3)2]2 was dissolved in 0.5 mL of C6D6
in an NMR tube. Using a calibrated bulb, 0.032 mmol of
anhydrous HNMe2 was condensed into the sample after
freezing it with liquid N2, and the tube was tumbled while
being warmed to room temperature. After 30 h at room
temperature, the volatiles were removed in vacuo and the

3578 Organometallics, Vol. 19, No. 18, 2000
Coalter et al.
Ta ble 3. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for Ru (H)2Cl(OCNMe2)(P iP r 3)2
room temperature, resulting in the formation of organic and
aqueous layers. After 1 h, the flask was vented to the air and
the organic layer was washed through Celite with 100 mL of
ether. The solvent was removed on a rotary evaporator, and
the resulting yellow oil was distilled through a Vigreux column
under reduced pressure. After a 1.5 mL forerun, 16.8 g (72%)
of the target imine was collected as a colorless liquid (37-39
Ru(1)-Cl(2)
Ru(1)-P(3)
Ru(1)-O(13)
Ru(1)-C(14)
O(13)-C(14)
2.4474(11)
2.3676(6)
2.3384(22)
1.955(4)
N(15)-C(14)
N(15)-C(16)
N(15)-C(17)
Ru(1)-H(1)
1.327(5)
1.464(5)
1.447(6)
1.49(4)
1.249(6)
1
°C, 0.3 Torr). H NMR (400 MHz, C6D6, 20 °C): δ 3.27 (s, 3H,
Cl(2)-Ru(1)-P(3)
90.46(3)
Ru(1)-C(14)-O(13) 91.04(28)
3
NMe), 7.12 (m, 3H, m,p-C6H5), 7.73 (d, J H-H ) 8 Hz, 2H,
Cl(2)-Ru(1)-O(13) 102.29(14) Ru(1)-C(14)-N(15) 143.7(3)
o-C6H5), 7.90 (s, 1H, PhHCdNMe). 13C{1H} NMR (101 MHz,
C6D6, 20 °C): δ 48.1 (s, NMe), 128.3 (s, C6H5), 128.7 (s, C6H5),
130.4 (s, C6H5), 137.2 (s, i-C6H5), 161.7 (s, PhHCdNMe).
Ru (H2)Cl(η2-C6H4CHdNMe)(P iP r 3)2. A 100 mg (0.108
mmol) amount of [RuHCl(PiPr3)2]2 in 4 mL of cyclohexane was
added dropwise via syringe to a stirred solution of 30 µL (0.243
mmol) of benzylidenemethylamine (PhHCdNMe) in 3 mL of
cyclohexane at ambient temperature. The reaction mixture
was stirred for 4 h under argon (connected to a bubbler), and
the solvent was removed to yield an orange solid. Washing
with cold pentane (2 × 10 mL, -78 °C) to remove any residual
imine and drying in vacuo yielded 95 mg (75%) of the title
compound as a bright orange powder. Product prepared in this
manner contained 10% RuCl(η2-C6H4CHdNMe)(PiPr3)2 as a
byproduct from H2 loss. This side reaction can be eliminated
by conducting the reaction in a sealed vessel, decreasing the
stirring time to 60 min, and drying in vacuo for a maximum
Cl(2)-Ru(1)-C(14) 134.56(12) O(13)-C(14)-N(15) 125.3(4)
P(3)-Ru(1)-P(3)′
P(3)-Ru(1)-O(13)
P(3)-Ru(1)-C(14)
168.51(3)
Cl(2)-Ru(1)-H(1)
86.5(22)
84.31(4)
95.500(14) P(3)-Ru(1)-H(1)
93.762(24) O(13)-Ru(1)-H(1) 171.2(22)
Ru(1)-O(13)-C(14) 56.70(21) C(14)-Ru(1)-H(1) 138.9(22)
Ta ble 4. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for Ru (H)2Cl(OCNMe2)(P iP r 3)2
Ru(1)-P(12)
Ru(1)-P(22)
Ru(1)-N(4)
Ru(1)-C(11)
N(4)-C(3)
2.3799(7)
2.4071(7)
2.1412(21)
2.0403(25)
1.470(4)
N(4)-C(5)
Ru(1)-H(1)
Ru(1)-H(2)
H(1)-H(2)
1.289(3)
1.81(4)
1.48(4)
0.86(5)
P(12)-Ru(1)-P(22) 164.656(26) P(12)-Ru(1)-H(1)
73.0(12)
P(12)-Ru(1)-N(4)
P(12)-Ru(1)-C(11)
P(22)-Ru(1)-N(4)
P(22)-Ru(1)-C(11)
N(4)-Ru(1)-C(11)
Ru(1)-N(4)-C(3)
Ru(1)-N(4)-C(5)
98.40(6)
91.40(7)
96.91(6)
90.69(7)
78.34(9)
P(12)-Ru(1)-H(2)
P(22)-Ru(1)-H(1)
P(22)-Ru(1)-H(2)
83.8(14)
92.0(12)
81.3(14)
N(4)-Ru(1)-H(1) 167.8(13)
of 1 h. The yield is quantitative when monitored in situ by 31
P
N(4)-Ru(1)-H(2) 162.2(14)
1
NMR in a sealed NMR tube. H NMR (400 MHz, CD2Cl2, 20
°C): δ -9.13 (br t; J P-H ) 10.8 Hz, 2H, Ru(H2); T1(20 °C) ) 44
128.74(19) C(11)-Ru(1)-H(1) 110.0(12)
114.37(19) C(11)-Ru(1)-H(2) 83.9(14)
3
Ru(1)-C(11)-C(6) 114.32(19) H(1)-Ru(1)-H(2)
Ru(1)-C(11)-C(10) 130.89(20)
28.3(17)
ms), 1.01 (dvt; J P-H ) J H-H ) 7 Hz, 18H, P(CHMe2)3), 1.07
(dvt, J P-H
)
3J H-H ) 7 Hz, 18H, P(CHMe2)3), 2.14 (m, 6H,
P(CHMe2)3), 4.13 (s, 3H, NMe), 6.77 (m, 2H, C6H4), 7.32 (dd t,
J ) 3 Hz, 8 Hz, 1H, C6H4), 7.69 (d, J ) 6 Hz, 1H, C6H4), 8.37
(s, 1H, C6H4CHdNMe). 31P{1H} NMR (162 MHz, CD2Cl2, 20
°C): δ 38.3 (s). 13C{1H} NMR (101 MHz, CD2Cl2, 20 °C): δ
19.5 (s, P(CHMe2)3), 19.6 (s, P(CHMe2)3), 24.5 (vt, J P-C ) 9.1
Hz, P(CHMe2)3), 47.3 (s, NMe), 119.2, 128.3, 128.4, 144.9, 146.2
difference Fourier was essentially featureless. The results are
shown in Tables 3 and 4.
Ru Cl(η2-C6H4CHdNMe)(P iP r 3)2. A 15.0 mg (0.026 mmol)
amount of Ru(H2)Cl(η2-C6H4CHdNMe)(PiPr3)2 was dissolved
in 0.5 mL of C6D6 in an NMR tube equipped with a Teflon
seal and heated at 80 °C for 12 h. 1H and 31P{1H} NMR showed
50% conversion to RuCl(η2-C6H4CHdNMe)(PiPr3)2 in addition
(s, C6H4), 172.3 (t, J P-C ) 2.8 Hz, ipso-C6H4), 190.8 (t, J P-C
)
9.1 Hz, Ru-C). νCdN was not identified due to overlap with νCd
1
to 15% production of RuH(H2)Cl(PiPr3)2 and PhCHdNMe. H
of C6H5 (Nujol).
C
3
NMR (400 MHz, C6D6, 20 °C): δ 1.11 (dvt; J P-H ) J H-H ) 7
X-r a y Str u ctu r e of Ru (H2)Cl(η2-C6H4CHdNMe)(P iP r 3)2.
A nearly equidimensional sample was affixed to a glass fiber
using silicone grease and transferred to the goniostat, where
it was cooled to -158 °C using a gas-flow cooling system of
local design. Standard inert-atmosphere handling techniques
were used. An initial data set was collected using 5 s frames.
The crystal was then realigned, and the data were collected
using 15 s frames. Data collection and processing followed the
methods cited above. The structure was solved using SHELX-
TL and Fourier techniques. As shown in the figures, the
molecule has near-m symmetry with the Ru atom, H2, and
C8H8N ligand lying approximately on the mirror plane. The
H2 is slightly skewed as shown in the figures. The data for
the 15 s frames were significantly better, allowing integration
to 2θ ) 65°, as opposed to 55° for the 5 s frames. A final
3
Hz, 18H, P(CHMe2)3), 1.14 (dvt, J P-H ) J H-H ) 7 Hz, 18H,
P(CHMe2)3), 2.44 (m, 6H, P(CHMe2)3), 3.49 (s, 3H, NMe), 6.87
(m, 2H, C6H4), 7.29 (t, J ) 3 Hz, 1H, C6H4), 8.93 (d, J ) 8 Hz,
1H, C6H4), δ 7.84 (s, 1H, C6H4CHdNMe). 31P{1H} NMR (162
MHz, C6D6, 20 °C): δ 33.0 (s).
Ack n ow led gm en t. This work was supported by the
National Science Foundation.
Su p p or tin g In for m a tion Ava ila ble: Tables giving full
crystallographic details for Ru(H)2Cl(OCNMe2)(PiPr3)2 and Ru-
(H2)Cl(C6H4CHNMe)(PiPr3)2. This material is available free of
charge via the Internet at http://pubs.acs.org.
OM000390Y