Carbonylhydridonitrosyltris(trimethylphosphine)molybdenum(0): An activated hydride complex

Article abstract of DOI:10.1021/om990945t

The synthesis of the mer-Mo(CO)H(NO)(PMe₃)₃ complex 3 is described, which is obtained from Mo(CO)₄(NO)AlCl₄ via the isolable intermediates MoCl(CO)(NO)(PMe₃)₃ (1) and the borohydride complex Mo(η¹-BH₄)(CO)(NO)(PMe₃)₃ (2). The reactivity of 3 with respect to insertions has been probed. 3 thus reacts with benzaldehyde, benzophenone, acetophenone, and acetone to afford the corresponding alkoxide complexes Mo(CO)(NO)(PMe₃)₃(OCHR′R″) (R′ = H, R″ = Ph (4a); R′, R″ = Ph (4b); R′ = Me, R″ = Ph (4c), and R′, R″ = Me (4d)). A high propensity of 3 to undergo carbonyl insertion was also manifested in its transformations with CO₂ and metal carbonyl compounds. The conversion of 3 with CO₂ leads to the formato-O-complex Mo(CO)(NO)(PMe₃)₃(OCHO) (5), while CO induces PMe₃ substitution with formation of the nonisolable Mo(CO)₂(NO)(PMe₃)₂H compound (6). Fe(CO)₅ readily inserts to yield the dinuclear formyl species (Me₃P)₃(ON)(OC)Mo(μ-OCH)Fe(CO)₄ (7a), and Re₂(CO)₁₀ is transformed to the related μ-formyl complex (Me₃P)₃(ON)(OC)Mo(μ-OCH)Re₂(CO)₉ (7b) in an equilibrium reaction lying far to the formyl side. Temperature-dependent NMR measurements allowed us to derive equilibrium constants and ΔH = -46.5 ± 0.6 kJ/mol and ΔS = -103 ± 2 eu. These values for 7b were approximately reproduced by accurate DFT calculations and investigated further via an incremental analysis of bond dissociation energies. Finally insertion reactions of 3 with various imines were studied. Only in the case of a bisdihydroproline ester did an insertion take place, however, across the ester carbonyl group. Concomitant elimination of a phosphine moiety was observed with formation of the isolable chelate complex traras-Mo[OCH(OCH₃)(C₄H₆N)](CO)(NO)(PMe ₃)₂ (8). The structures of complexes 2, 3, 4b, 7a, 7b, and 8 were studied by X-ray diffraction.

Full text of DOI:10.1021/om990945t

1950
Organometallics 2000, 19, 1950-1962
Ca r bon ylh yd r id on itr osyltr is(tr im eth ylp h osp h in e)m olybd en u m (0):
An Activa ted Hyd r id e Com p lex
Fupei Liang, Heiko J acobsen, Helmut W. Schmalle, Thomas Fox, and
Heinz Berke*
Anorganisch-chemisches Institut, Universita¨t Zu¨rich, Winterthurerstrasse 190,
CH-8057 Zu¨rich, Switzerland
Received December 2, 1999
The synthesis of the mer-Mo(CO)H(NO)(PMe3)3 complex 3 is described, which is obtained
from Mo(CO)4(NO)AlCl4 via the isolable intermediates MoCl(CO)(NO)(PMe3)3 (1) and the
borohydride complex Mo(η1-BH4)(CO)(NO)(PMe3)3 (2). The reactivity of 3 with respect to
insertions has been probed. 3 thus reacts with benzaldehyde, benzophenone, acetophenone,
and acetone to afford the corresponding alkoxide complexes Mo(CO)(NO)(PMe3)3(OCHR′R′′)
(R′ ) H, R′′ ) Ph (4a ); R′, R′′ ) Ph (4b); R′ ) Me, R′′ ) Ph (4c), and R′, R′′ ) Me (4d )). A
high propensity of 3 to undergo carbonyl insertion was also manifested in its transformations
with CO2 and metal carbonyl compounds. The conversion of 3 with CO2 leads to the formato-
O-complex Mo(CO)(NO)(PMe3)3(OCHO) (5), while CO induces PMe3 substitution with
formation of the nonisolable Mo(CO)2(NO)(PMe3)2H compound (6). Fe(CO)5 readily inserts
to yield the dinuclear formyl species (Me3P)3(ON)(OC)Mo(µ-OCH)Fe(CO)4 (7a ), and Re2(CO)10
is transformed to the related µ-formyl complex (Me3P)3(ON)(OC)Mo(µ-OCH)Re2(CO)9 (7b)
in an equilibrium reaction lying far to the formyl side. Temperature-dependent NMR
measurements allowed us to derive equilibrium constants and ∆H ) -46.5 ( 0.6 kJ /mol
and ∆S ) -103 ( 2 eu. These values for 7b were approximately reproduced by accurate
DFT calculations and investigated further via an incremental analysis of bond dissociation
energies. Finally insertion reactions of 3 with various imines were studied. Only in the case
of a bisdihydroproline ester did an insertion take place, however, across the ester carbonyl
group. Concomitant elimination of a phosphine moiety was observed with formation of the
isolable chelate complex trans-Mo[OCH(OCH3)(C4H6N)](CO)(NO)(PMe3)2 (8). The structures
of complexes 2, 3, 4b, 7a , 7b, and 8 were studied by X-ray diffraction.
Earlier it was shown that the strength of
Strongly σ-donating phosphine substituents and an
increasing number of them are expected to enhance this
effect, as demonstrated by a trans-W(CO)2H(NO)(PR3)2
series3b,c and the tris-substituted mer-W(CO)H(NO)-
(PMe3)3 complex.6 Phosphine-dependent hydridicities
have also been traced in a Re(CO)nH(PR3)5-n series.7 On
the basis of the fact that the radius and the electro-
negativity of molybdenum are smaller than those of
tungsten, it can be inferred that the Mo-H bond in
Mo(CO)4-n(H)(NO)(PR3)n (n ) 2-4) complexes will still
be weaker than the W-H bonds in analogous com-
pounds, and therefore it is expected that the former
display higher reactivity. With this background we
decided to approach the synthesis of the tris(strong
phosphine donor)-substituted molybdenum complex Mo-
(CO)H(NO)(PMe3)3 and investigations of its reactivity.
In this work, we succeeded in finding an appropriate
synthetic access to this complex and tested its insertion
behavior toward organic carbonyl groups, CO2, CO,
metal carbonyl moieties, and imines.
LnM-H bonds (M ) transition metal) depends on the
electronegativity of the M center.1 Centers of low
electronegativity cause weaker bonds to hydrogen
and furthermore induce hydridic polarization of this
ligand.2
In particular, our group has demonstrated that
nitrosyl substitution may be used to effect lower orbital
electronegativities2 at various metal centers such as
in the complexes trans-W(CO)2H(NO)(PR3)2,3 Re(CO)-
H2(NO)(PR3)2,4 and Mn,ReH(NO)2(PR3)2,5 thus simu-
lating early transition metal character.
(1) (a) Labinger, J . A.; Bercaw, J . E. Organometallics 1988, 7, 926.
(b) Nolan, S. P.; Stern, D., Marks, T. J . J . Am. Chem. Soc. 1989, 111,
7844. (c) Marks, T. J . Bonding Energetics in Organometallic Com-
pounds; ACS Symposium Series 428; American Chemical Society:
Washington, DC, 1990.
(2) Berke, H.; Burger, P. Comments Inorg. Chem. 1994, 16, 279.
(3) (a) Kundel, P.; Berke, H. J . Organomet. Chem. 1987, 335, 353.
(b) van der Zeijden, A. A. H.; Sontag, C.; Bosch, H. W.; Shklover, V.;
Berke, H.; Nanz, D.; von Philipsborn, W. Helv. Chim. Acta 1991, 74,
1194. (c) van der Zeijden, A. A. H.; Bosch, H. W.; Berke, H. Organo-
metallics 1992, 11, 2051. (d) van der Zeijden, A. A. H.; Berke, H. Helv.
Chim. Acta 1992, 75, 513.
(4) (a) Messmer, A.; J acobsen, H.; Berke, H. Chem. Eur. J . 1999, 5,
3341. (b) J acobsen, H.; Heinze, K.; Llamazares, A.; Schmalle, H. W.;
Artus, G.; Berke, H. J . Chem. Soc. Dalton Trans. 1999, 1717. (c) Gusev,
D. G.; Llamazares, A.; Artus, G.; Berke, H. Organometallics 1999, 18,
75. (d) Nietlispach, D.; Bosch, H. W.; Berke, H. Chem. Ber. 1994, 127,
2403. (e) Nietlispach, D.; Bakhmutov, V. I.; Berke, H. J . Am. Chem.
Soc. 1993, 115, 9191.
(5) (a) Belkova, N. V.; Shubina, E. S.; Ionidis, A. V.; Epstein, L. M.;
J acobsen, H.; Messmer, A.; Berke H. Inorg. Chem. 1997, 36, 1522. (b)
Hund, H. U.; Ruppli, U.; Berke, H. Helv. Chim. Acta 1993, 76, 963.
(6) Ba¨th, F. Ph.D. Thesis, University of Zurich, 1998. Ho¨ck, J .;Fox,
T.; Schmalle, H.; Berke, H. Chimia 1999, 53, 350.
(7) (a) Gusev, D. G.; Nietlispach, D.; Eremenko, I. L.; Berke, H.
Inorg. Chem. 1993, 32, 3628. (b) Nietlispach, D.; Veghini D.; Berke,
H. Helv. Chim. Acta 1994, 77, 2197.
10.1021/om990945t CCC: $19.00 © 2000 American Chemical Society
Publication on Web 04/14/2000

Activated Hydride Complex
Sch em e 1
Organometallics, Vol. 19, No. 10, 2000 1951
pattern can be observed: The 1H NMR (C6D5CD3)
spectrum shows a triplet at δ 1.15 ppm and a doublet
at δ 0.93 ppm, and the 31P NMR displays splitting into
a doublet at δ -10 ppm and a triplet at δ -16.0 ppm
(2J PP ) 28 Hz). The fact that the 11B NMR spectrum
shows a quintet at δ -38.5 ppm (2J HB ) 85 Hz) confirms
the presence of the BH4 unit in the molecule. It has
however to be assumed that all four hydrogen signals
get averaged by a dynamic process fast on the NMR
time scale. The η1 binding of the BH4 moiety has finally
been assured by an X-ray diffraction study.
Treatment of 2 with 15 equiv of PMe3 in toluene at
room temperature yielded the hydride 3. It is note-
worthy that this reaction requires a large excess of PMe3
and a relatively long reaction time of 2 days. It has been
found that when cyclic amines are used for the BH3
scavenging, stoichiometric amounts of the agent may
be sufficient for complete conversion and an even
shorter reaction time may be applied. For instance,
NMR monitoring showed that the conversion of 2 with
quinuclidine or piperidine required only 1 equiv of the
amine and 10 h. However, despite these advantages, it
rendered finally to be very difficult to remove in these
cases the R3N f BH3 byproducts from 3, so that these
routes could not be pursued further.
The 1H NMR spectrum of 3 shows among other
resonances that of the hydride ligand. It appears as a
doublet of triplets at δ -1.92 ppm, a characteristic
pattern of cis-coupling with three meridionally disposed
PMe3 substituents. The structure of 3 has finally
inequivocally been established by an X-ray diffraction
study, which will be discussed later.
In the room-temperature IR spectrum of 3, as well
as in the solid-state Raman spectrum, only one super-
imposed band appears for ν(NO) and ν(MoH). In con-
trast to this, the low-temperature IR spectrum in
hexane taken at -70 °C displays two bands around 1600
cm-1, which are assigned to ν(MoH) (1609 cm-1) and
ν(NO) (1596 cm-1). The position of the ν(MoH) band at
very low vibrational energies allows one to conclude that
the Mo-H bond of 3 is relatively weak, which is also
mirrored in the relatively small calculated BDE given
later.
2. In ser t ion R ea ct ion s of 3. As indicated before,
insertion reactions into a M-H bond naturally depend
on the M-H bond strength, and since we expected the
Mo-H bond of 3 to be on the weak side of the
thermodynamic scale, it was anticipated that 3 would
show an increased tendency to react with aldehydes and
ketones. In fact, it was seen earlier for the presumably
quite strong Ir-H bond that deinsertions of organic
carbonyl compounds are preferred; that is, the corre-
sponding alkoxides decompose at room temperature
with â-H-elimination.12 It should furthermore be noted
that we have experienced earlier that the insertion
reaction of trans,trans-W(CO)2H(NO)(PMe3)2 with benz-
aldehyde afforded an alkoxide. However, this complex
turned out to be unstable with respect to loss of CO due
to the cis-labilizing effect of the alkoxide group.13 In
contrast to this behavior, we expected similar alkoxide
Resu lts a n d Discu ssion s
1. Syn t h esis of m er -Mo(CO)H (NO)(P Me3)3 (3).
Hillhouse et al. have reported the preparation of mer-
Mo(CO)H(NO)(PMePh2)3 via a direct reaction of mer-
Mo(Cl)(CO)(NO)(PMePh2)3 with LiBH4 and PMePh2 in
THF.8 Access to the analogous chloride Mo(Cl)(CO)(NO)-
(PMe3)3 (1) has been achieved by an autoclave reaction
of Mo(AlCl4)(CO)4(NO), prepared according to a litera-
ture procedure.9 Conversion of it with 4 equiv of PMe3
in THF at 80 °C led to 1 in 71% yield. The structure
and composition of 1 have been established by IR, NMR,
1
and elemental analysis. The H NMR in C6D6 shows a
triplet at 1.25 ppm and a doublet at 1.06 ppm, and in
the 31P NMR a doublet at δ ) -10.3 ppm and a triplet
at -17.5 ppm (2J PP ) 30 Hz) were observed. Both
resonance patterns are in accord with the meridional
disposition of three phosphine ligands.
Compound 1 could not directly be transformed into 3
by LiBH4 in Et2O. At room temperature this reaction
produced the borohydride complex Mo(CO)(HBH3)(NO)-
(PMe3)3 (2), instead. Conversion of 2 with PMe3 in
toluene at room temperature then gave the hydride 3
(Scheme 1).
1
The H NMR spectrum of 2 reveals a broad quartet
at δ -1.51 ppm with a characteristic 11B coupling (2J HB
) 86.2 Hz), which was therefore assigned to the protons
of the BH4 group. The spectrum furthermore displays
a triplet at 1.19 ppm (2J HP ) 3.2 Hz) and a broad signal
at 1.03 ppm, both of which belong to the Mephosphine
residues. The broadness of the latter signal can most
likely be attributed to interference of boron quadrupolar
relaxation. A similar picture is obtained by 31P NMR.
In the spectrum one resonance at -17.4 ppm also
appears broadened, again explained on the basis of
boron coupling. This observation is in agreement with
previous ones on related boron-containing compounds.10
The other 31P NMR signal, a singlet at -10.3 ppm, is
assigned to the trans-disposed phosphorus ligands. At
low temperature (-40 °C) further splitting of the signal
(8) Cheng, T.-Y.; Southern, J . S.; Hillhouse, G. L. Organometallics
1997, 16, 2335
(9) Seyferth, K.; Taube, R. J . Organomet. Chem. 1982, 229, 275.
(10) (a) Beall, H.; Bushweller, C. H. Chem. Rev. 1973, 73, 465. (b)
Marks, T. J .; Kolb, J . R. Chem. Rev. 1977, 77, 263.
(11) J acobsen, H.; J onas, V.; Werner, D.; Messmer, A.; Panitz,
J .-C.; Berke, H.; Thiel, W. Helv. Chim. Acta 1999, 82, 297.
(12) Blum, O.; Milstein, D. J . Am. Chem. Soc. 1995, 117, 4582.
(13) Van der Zeijden, A. A. H.; Bosch, H. W.; Berke, H. Organo-
metallics 1992, 11, 2051

1952 Organometallics, Vol. 19, No. 10, 2000
Liang et al.
Sch em e 2
acetone. The phenyl substituent apparently facilitates
these reactions via enhanced electrophilicity of the
Ccarbonyl atom.
In the 1H and 13C NMR spectra of the compounds
4b-d characteristic resonances of the newly formed
-CH- moieties appear. In C6D6 4b displays for this
group a singlet at δ 5.55 ppm (1H NMR) and a doublet
of triplets at δ 87.4 ppm (13C{1H} NMR). The splitting
of the latter signal is assigned to the coupling with the
phosphorus nuclei. In the 1H NMR spectrum of 4c a
quartet appears at δ 4.62 ppm, which results from the
coupling of the methyne proton with those of the methyl
group. Similarily the CH proton of 4d couples with the
two methyl groups, showing a heptet at δ 3.75 ppm
(3J HH ) 6 Hz). In the 13C{1H} NMR spectra of both 4c
and 4d the CH groups are attributed to a doublet of
triplet resonances at δ 79.1 and 70.7 ppm, respectively,
which appear as pseudo-quintets due to partial overlap
of the splitting patterns. It is noteworthy that the trans
phosphine ligands in complex 4c are diastereotopic. This
is caused by the presence of a chiral carbon atom in the
alkoxy residue. Therefore, the 1H NMR spectrum of the
phosphine ligands in 4c consists of three sets of signals
at δ 1.28, 1.11, and 1.03 ppm, respectively. The 31P{1H}
NMR spectrum of 4c does not reflect this diastereotopy.
Comparable to the spectra of 4b and 4d only two groups
of signals are present, a doublet at δ -12.3 and a triplet
at δ -17.5 ppm. In an exemplary way, 4b could be
characterized by an X-ray diffraction study.
derivatives with a reduced content of labile CO to be
quite stable, and indeed the reaction of 3 with PhCHO
produced a stable benzyloxy species 4a (Scheme 2).
The reaction proceeded smoothly at room temperature
in toluene and was completed within a few minutes. 4a
can be isolated in 87% yield as analytically pure yellow
1
crystals. The H NMR spectrum in C6D6 shows, among
other resonances, a characteristic signal at δ 4.91 ppm,
and the 13C{1H}NMR spectrum displays a doublet of
triplets at δ 75.5 ppm, both of which signals correspond
to the resonances of the newly formed CH2 moiety
involving coupling with the three PMe3 ligands. In
unique reaction steps aldehydes and ketones have only
rarely been demonstated to insert into transition metal
hydrogen bonds.3c,d,14 Furthermore, ketones are nor-
mally even more reluctant to undergo these transforma-
tions. Such insertions, however, have been invoked as
key steps in catalytic reduction with transition metal
compounds.15 We therefore tried to explore the possibil-
ity of insertions of 3 with typical simple ketones and
found that these take place with benzophenone, aceto-
phenone, and acetone to afford complexes 4b-d in signi-
ficantly slower reactions than those with benzaldehyde
(Scheme 2). For acetone as the most reluctant reagent
in this series a higher stoichoimetric ratio of 1:2 had to
be applied; in the other cases a 1:1 ratio in toluene
revealed at room temperature somewhat faster rates of
these presumably second-order processes. Under the
given conditions the conversions took approximately 3
h for benzophenone, 7 h for acetophenone, and 10 h for
Insertions of CO2 into a metal hydride bond are of
growing interest, since they are assumed to be the initial
steps in the hydrogenation of CO2.16 Therefore, we
tested whether hydride 3 would be activated enough to
undergo such a transformation.
Indeed, reaction of 3 with 1 bar CO2 in toluene
afforded at room temperature the formato-O-complex
5 (Scheme 2), which can be isolated in 85% yield as
analytically pure yellow crystals after recrystallization
from pentane. In the 1H NMR spectrum 5 shows a
characteristic quartet type signal at δ 8.59 ppm, which
is assigned to the formate proton. Apparently, the three
P nuclei behave in this case as magnetically equivalent.
In the 13C{1H} NMR spectrum the 13C resonance of the
Cformato atom is observed as a multiplet at 167.1 ppm.
1
The other H and 13C NMR resonances of 5 are similar
to those of 3, which suggests closely related carbonyl
and phosphine frameworks for these complexes. The IR
spectrum of 5 in hexane shows a pattern similar to that
of mer-W(OCHO)(CO)(NO)(PMe3)3.6 Among others it
consists of an intense ν(NO) band at 1609 cm-1 and a
3a
ν(OCO) band at 1625 cm-1
.
The expected ν(CO)
absorption is split in the solid-state spectrum, revealing
bands at 1958 and 1931 cm-1
.
(14) Selected references: (a) Grey, R. A.; Pez, G. P.; Wallo, A. J .
Am. Chem. Soc. 1981, 103, 7536. (b) Gaus, P. L.; Kao, S. C.; Youngdahl,
K.; Darensbourg, M. Y. J . Am. Chem. Soc. 1985, 107, 2428. (c) Tooley,
P. A.; Ovalles, C.; Kao, S. C.; Darensbourg, D. J .; Darensbourg, M. Y.
J . Am. Chem. Soc. 1986, 108, 5465. (d) Debad, J . D.; Legzdins, P.;
Lumb, S. A.; Batchelor, R. J .; Einstein, F. W. B. Organometallics 1995,
14, 2543. (e) Van Leeuwen, P. W. N. M.; Roobeek, C. F.; Orpen, A. G.
Organometallics 1990, 9, 2179.
The migratory insertion of CO into a metal-hydride
bond to produce a formyl species has been proposed as
a key step in the homogeneous catalytic hydrogenation
of CO.17 However, the model type isolated insertion step
(15) Selected references: (a) Ponec, V. Catal. Rev.-Sci. Eng. 1978,
18, 151 (b) Costa, L. C. Catal. Rev. Sci. Eng. 1983, 25, 325. (c) Noyori,
R.; Takaya, H. Acc. Chem. Res. 1990, 23, 345. (d) Burk, M. J .; Gross,
M. F.; Harper, T. G. P.; Kalberg, C. S.; Lee, J . R.; Martinez, J . P. Pure
Appl. Chem. 1996, 68, 37. (e) J iang, Q.; J iang, Y.; Xiao, D.; Cao, P.;
Zhang, X. Angew. Chem. 1998, 110, 1203. (f) Nomura, K. J . Mol. Catal.
A: Chem. 1998, 130, 1. (g) Kvintovics, P.; Bakos, J .; Heil, B. J . Mol.
Catal. 1985, 32, 111. (h) Palmer, M. J .; Wills, M. Tetrahedron:
Asymmetry 1999, 10, 2045.
(16) (a) Leitner, W. Angew. Chem., Int. Ed. Engl. 1995, 34, 2207.
(b) Gibson, D. H. Chem. Rev. 1996, 96, 2063. (c) Toyohara, K.; Nagao,
H.; Mizukawa, T.; Tanaka, K. Inorg. Chem. 1995, 34, 5399. (d) Cutler,
A. R.; Hanna, P. K.; Vites, J . C. Chem. Rev. 1988, 88, 1363. (e)
Darensbourg, D. J .; Kudaroski, R. A. Adv. Organomet. Chem. 1983,
22, 129. (f) Darensbourg, D. J .; Ovalles, C. Chemtech 1985, 15, 636.
(g) Darensbourg, D. J .; Ovalles, C. J . Am. Chem. Soc. 1987, 109, 3330.
(h) Darensbourg, D. J .; Darensbourg, M. Y.; Goh, L. Y.; Ludvig, M.;
Wiegreffe, P. J . Am. Chem. Soc. 1987, 109, 7539.

Activated Hydride Complex
Sch em e 3
Organometallics, Vol. 19, No. 10, 2000 1953
Sch em e 4
Treatment of 3 with 1 equiv of Fe(CO)5 indeed
produced at room temperature in toluene the formyl-
bridged complex 7a (Scheme 3), which was isolated as
yellow crystals in 88% yield after recrystallization from
pentane. The bridging formyl group of 7a gives rise to
1
characteristic NMR resonances. In the H NMR spec-
of CO into the M-H bond remains a rarity,18 presum-
ably due to the high bond energy of CO. Considering
the reactivity of 3 and its indicated weaker Mo-H bond,
we set out to investigate the insertion ability of the
Mo-H bond of 3 with regard to CO. At first, the reaction
of 3 with 1 bar CO was studied, which however led
merely to substitution of the unique phosphine ligand
to form complex 6 (Scheme 3). The reaction turned out
to be an equilibrium, which caused reversal of the
reaction during the necessary removal of the solvent in
vacuo, and this thus prevented isolation and full char-
acterization of 6. But the existence of compound 6 can
clearly be deduced from the 1H NMR spectrum, in which
a triplet at -2.73 ppm (2J PH ) 29.6 Hz) corresponding
to the HMo ligand is observed. Another triplet at 1.12
ppm (2J PH ) 3.2 Hz) was assigned to the protons of the
phosphine ligands. In accord with the proposed struc-
ture of 6, the 31P{1H} NMR spectrum revealed a singlet
at -6.5 ppm. The observation that substitution took
place may imply that the direct insertion of CO into the
Mo-H bond is a still thermodynamically unfavorable
process. To possibly overcome any of these factors, we
then attempted reaction of 3 with CO bound in metal
carbonyl compounds, such as Fe(CO)5 and Re2(CO)10.
trum (C6D6) one finds a singlet at 14.09 ppm for the
Hformyl nucleus, and in the 13C{1H} NMR spectrum one
observes a quartet at 306.1 ppm for the Cformyl atom.
The chemical shift of the Hformyl proton appears in the
range of that of [Fe(CO)4CHO]- (15.0 ppm) reported by
Collman et al.19 However, the 13C chemical shift of the
Cformyl atom is observed considerably (about 26.0 ppm)
downfield from that of [Fe(CO)4CHO]-, which is attrib-
uted to an efficient electron withdrawl in the bridging
coordination mode. The IR spectrum of 7a shows,
besides ν(NO) and ν(CO) of the Mo-coordinated ligands
at 1619 and 1931 cm-1, three bands at 2035 (m), 1952
(m), 1925 (s) cm-1, which are assigned to the ν(CO)
vibrations of the Fe(CO)4 unit. This absorption pattern
resembles closely that of the “parent” [Fe(CO)4CHO]-
complex.19
3 can also react with Re2(CO)10 in toluene to generate
the bridging formyl compound 7b (Scheme 4). However,
in contrast to the reaction with Fe(CO)5, the reaction
with Re2(CO)10 is an equilibrium lying at room tem-
perature considerably to the right side (3:Re2(CO)10
)
1:1, 0.051 mol/L, room temperature, K ) 560 L/mol),
as determined by NMR spectroscopy. Despite the equi-
librium situation of its formation, 7b can be isolated
as analytically pure orange crystals in 80% yield
after recrystallization from Et2O. In the 1H NMR
spectrum of 7b the proton resonance of the formyl group
is found at 15.07 ppm, which is close to that of
[Re2(CO)9(CHO)]-.20 The 13C{1H} NMR spectrum also
demonstrates the presence of a Cformyl atom displaying
a pseudo-quartet at 302.3 ppm. The 13C chemical shift
of the bridging formyl carbon atom of 7b is downfield
to that of [Re2(CO)9(CHO)]-.20
The temperature dependence of K allowed the calcu-
lation of ∆H ) -46.5 ( 0.6 kJ /mol and ∆S ) -103 ( 2
eu for the association reaction (see van’t Hoff plot
Figure 1). Apparently the hydride transfer from 3 onto
Re2(CO)10 is moderately exothermic, reflecting a weak
Mo-H bond and the relative strength of the newly
installed C-H and Mo-O bonds (see DFT calculations
vide supra). The significantly negative ∆S is in agree-
ment with the associative character of the process.
It was expected that complexes 7a and 7b would react
further with an excess of 3. We have therefore at-
(17) (a) Miller, R. L.; Toreki, R.; La Pointe, R. E.; Wolczanski, P. T.;
Van Duyne, G. D.; Roe, D. C. J . Am. Chem. Soc. 1993, 115, 5570, and
references therein. (b) Gladysz J . A. Adv. Organomet. Chem. 1982, 20,
1. (c) Burckhardt, U.; Tilley, T. D. J . Am. Chem. Soc. 1999, 121, 6328.
(d) Herrmann, W. A. Angew. Chem., Int. Ed. Engl. 1982, 21, 117. (e)
Blackborow, J . R.; Daroda, R. J .; Wilkinson, G. Coord. Chem. Rev. 1982,
43, 17. (f) Masters, C. Adv. Organomet. Chem. 1979, 17, 61. (g) Klingler,
R. J .; Rathke, J . W. Progr. Inorg. Chem. 1991, 39, 113. (h) Simpson,
M. C.; ColeHamilton, D. J . Coord. Chem. Rev. 1996, 155, 163. (i) Su¨ss-
Fink, G.; Meister, G. Adv. Organomet. Chem. 1993, 35, 41. (k)
Dombeck, B. P. Adv. Catal. 1983, 32, 325. (l) Marko, L. Trans. Met.
Chem. 1992, 17, 474. (m) Ford, P. C. Catalytic Activation of Carbon
Monoxide; ACS Symposium Series 152; American Chemical Society:
Washington, DC, 1981.
(18) (a) Fagan, P. J .; Moloy, K. G.; Marks, T. J . J . Am. Chem. Soc.
1981, 103, 6959. (b) Wayland, B. B.; Woods, B. A. J . Chem. Soc., Chem.
Commun. 1981, 700. (c) Wei M. L.; Wayland B. B. Organometallics
1996, 15, 4681. (d) Wayland, B. B.; Coffin, V. L.; Sherry, A. E.; Brennen,
W. R. ACS Symp. Ser. 1990, 428, 148. (e) Wayland B. B.; Sherry A.
E.; Poszmik G.; Bunn A. G. J . Am. Chem. Soc. 1992, 114, 1673. (f)
Burckhardt U.; Tilley T. D. J . Am. Chem. Soc. 1999, 121, 6328. (g)
Wolczansky P. T.; Threlkel R. S.; Bercaw J . E. J . Am. Chem. Soc. 1978,
101, 218. (h) Labinger J . A.; Wong K. S. ACS Symp. Ser. 1981, 152,
253. (i) Erker, G.; Schmuck, S.; Hoffmann, U. J . Am. Chem. Soc. 1991,
113, 2330. (k) Kropp, K.; Skribbe, V.; Erker, G.; Kru¨ger, C. J . Am.
Chem. Soc. 1983, 105, 3353. (l) Fryzuk, M. D.; Mylvaganam, M.;
Zaworotko, M. J .; MacGillivray, L. R. Organometallics 1996, 15, 1134.
(m) Rappe, A. K. J . Am. Chem. Soc. 1987, 109, 5605, and references
therein.
(19) Collman, J . P.; Winter, S. R. J . Am. Chem. Soc. 1973, 95, 4089.

1954 Organometallics, Vol. 19, No. 10, 2000
Liang et al.
Sch em e 5
respective H and 13C nuclei of the -OC(H)O- group.
The 13C signal of the CdN group is observed at 186.3
ppm, which is shifted considerably downfield with
respect to that of the free imine (∆δ 22.5 ppm). This
can be attributed to the coordination of the Nimine atom.
The two phosphine ligands in 8 are inequivalent due to
the presence of a chiral carbon atom in the molecule,
which is seen from the 1H and 31P resonances of the
phosphine ligands, giving rise to two sets of signals at
1.19 and 1.03 ppm in the 1H NMR and at -6.1 and -6.2
ppm in the 31P NMR spectra.
The reaction according to Scheme 5 was conceived to
proceed via an intermediate. Therefore, a more detailed
NMR study of the reaction was carried out at low
temperature in order to trace such a species. However,
no intermediate was detected and 8 appeared as the sole
product, even at the relatively low temperature of -20
°C where the reaction still proceeded. This suggests that
the displacement reaction of PMe3 takes place practi-
cally simultaneously with the insertion reaction.
Th er m od yn a m ic Con sid er a tion s of th e Meta l
Ca r bon yl In ser tion Rea ction w ith 3 Ap p lyin g DF T
Ca lcu la t ion s. DFT calculations allowed for a parti-
tioning of the equilibrium reaction of Scheme 4 into
respective bond increments. Our computational ap-
proach has been used before in studying the thermo-
dynamic properties of the transition metal hydride
bond,22a and the results were in good agreement with
experimental values.22b These calculations validate the
DFT scheme applied in our analysis. The following
thermodynamic cycle based on homolytic bond cleavage
reactions in the gas phase has been considered to arrive
at a theoretical estimate for the enthalpy of the reaction
of 3 with Re2(CO)10:
1
F igu r e 1. Van’t Hoff plot for the equilibrium reaction of
3 with Re2(CO)10 according to Scheme 4.
tempted their reaction with 3 equiv of 3 under various
conditions, but no further transformation could be
observed.
In view of the high hydride activity of 3, we also
sought to investigate its insertion capability toward
imines. The insertion of imines into transition metal
hydrides is of great general importance, since it is
assumed to be the initial step in catalytic hydrogen-
ations of imines generating amines.15g,21 Imines as
hetero-olefins generally appear to be quite reluctant in
reactions with LnM-H bonds, indicated by the fact that
they require very activated transition metal hydrides
especially in cases when the insertions are observable
as isolated steps.14d,21a
From the series of imines PhNdCHPh, MeNdCHPh,
and Ph2CdNH, the latter two did not react under
various conditions, varying the stoichiometric ratios,
temperatures, and reaction times. Only PhNdCHPh
was found to be converted to a new product at 60 °C,
which unfortunately could not be isolated, and by this
circumstance the structure of this reaction product could
not be assigned.
Considering the lower reactivity of the given imine
series with 3, we turned to applying an activated imine.
The reaction between 3 and a bisdihydroproline deriva-
tive was prototypically investigated (Scheme 5). Inser-
tion indeed occurred, however, not into the CdN double
bond of the imine but rather into the CdO bond of the
ester group and at the same time subsequent loss of a
phosphine ligand took place with formation of an O,N-
chelated product 8 (Scheme 5). Complex 8 was isolated
in 83% yield as analytically pure red crystals and fully
characterized by elemental analysis, NMR, IR, MS, and
an X-ray diffraction study.
3 f [Mo(CO)(NO)(PMe3)3]• + H•
∆H ) 296 kJ /mol (I)
Re2(CO)10 + H• f [Re2(CO)9(CHO)]•
∆H ) -63 kJ /mol (II)
[Mo(CO)(NO)(PMe3)3]• + [Re2(CO)9(CHO)]• f 7b
∆H ) -268 kJ /mol (III)
1
The H NMR spectrum of 8 (C6D6) shows a triplet at
δ 5.41 ppm, and the 13C{1H} NMR spectrum reveals a
The Mo-H bond strength amounts to 296 kJ /mol, and
the H affinity of Re2(CO)10, -62 kJ /mol, is somewhat
lower than that of carbon monoxide (∆H ) -75 kJ /
mol).23 For the insertion reaction into the metal-
hydride bond the reaction sequence affords a value of
∆H ) -34 kJ /mol, which is in fair agreement with the
experimental result.
singlet at 104. 9 ppm, both of which are assigned to the
(20) Casey C. P.; Neumann S. M. J . Am. Chem. Soc. 1978, 100, 2544.
(21) Selected references: (a) Willoughby, C. A.; Buchwald, S. L. J .
Am. Chem. Soc. 1994, 116, 8952. (b) Obora, Y.; Ohta, T.; Stern, C. L.;
Marks, T. J . J . Am. Chem. Soc. 1997, 119, 3745. (c) Christensen, N.
J .; Hunter, A. D.; Legzdins, P.; Sa´nchez, L. Inorg. Chem. 1987, 26,
3344. (d) Kobayashi, S.; Ishitani, H. Chem. Rev. 1999, 99, 1069. (e)
Ringwald, M.; Sturmer, R.; Brintzinger, H. H. J . Am. Chem. Soc. 1999,
121, 1524. (f) J ames, B. R. Catal. Today 1997, 37, 209. (g) Blaser, H.
U.; Spindler, F. Top. Catal. 1997, 4, 275. (h) Schnider, P.; Koch, G.;
Pretot, R.; Wang, G. Z.; Bohnen, F. M.; Kru¨ger, C.; Pfaltz, A. Chem.
Eur. J . 1997, 3, 887.
(22) (a) Folga, E.; Ziegler, T. J . Am. Chem. Soc. 1993, 115, 5169. (b)
Simoes, J . A. M.; Beauchamp, J . L. Chem. Rev. 1990, 90, 629.
(23) Kerr, J . A. Chem. Rev. 1966, 66, 465.

Activated Hydride Complex
Organometallics, Vol. 19, No. 10, 2000 1955
ligand occupying an axial position,24 [Fe(CO)4(CHO)]•
possesses a square pyramidal coordination, with the
HCO ligand occupying one of the basal positions. The
spin density is mainly localized on the metal center. If
this fragment is combined with the [Mo(CO)(NO)-
(PMe3)3]• to form 7a , the iron fragment rearranges to
adapt a trigonal bipyramidal coordination, as shown in
Figure 2. The situation is different when the reaction
with dirhenium decacarbonyl is considered. Although
the most stable geometry we have found for [Re2(CO)9-
(CHO)]• results from hydrogen transfer to a carbonyl
group in axial position, the isomer with equatorial HCO
also represents a local minimum on the energy surface
and is only 17 kJ /mol higher in energy. Its geometry is
closely related to that of the Re fragment in 7b. The
spin density is to a large part localized on the formyl
oxygen atom, which in turn will form the bond to the
Mo radical. If the insertion into the Mo-H bond takes
place via a hydrogen transfer step, the required rear-
rangement of the iron fragment might explain why the
formation of 7a is not an equilibrium reaction. The
dissociation of 7a into the two radical fragments is likely
to have a higher kinetic barrier than the dissociation
of 7b. In the former case, bond breaking does not
directly lead to minimum structures but is associated
with a rearrangement of the formyl radical.
We also considered possible heterolytic bond cleavage
reactions. The key steps, which are associated with the
hydride affinity of the metal carbonyls, are given in VI
and VII.
Re2(CO)10 + H- f [Re2(CO)9(CHO)]-
∆H ) -263 kJ /mol (VI)
Fe(CO)5 + H- f [Fe(CO)4(CHO)]-
∆H ) -260 kJ /mol (VII)
F igu r e 2. Optimized geometries for [Fe(CO)4(CHO)]- and
Mo(CO)(PMe3)3(NO)OCHFe(CO)4 (7a ). The phosphine, the
carbonyl, and the nitrosyl ligands at Mo have been omitted
for clarity.
The hydride affinity HA of Fe(CO)5 is experimentally
known, and our value of 260 kJ /mol comes close to the
upper range of HA ) 234 ( 17 kJ /mol, which Lane and
Squires derived from gas-phase hydride transfer reac-
tions.25 Both metal carbonyls possess a similar hydride
affinity around 260 kJ /mol. The heterolytic bond cleav-
age of 3 in the gas phase, as shown in eq VIII, is
determined by charge separation and is highly endo-
thermic.
We have also considered the reaction of 3 with Fe-
(CO)5, as shown in Scheme 3. Reaction eq I, together
with eqs IV and V, allows the calculation of ∆H for this
conversion:
Fe(CO)5 + H• f [Fe(CO)4(CHO)]•
∆H ) -105 kJ /mol (IV)
[Mo(CO)(NO)(PMe3)3]• + [Fe(CO)4(CHO)]• f 7a
∆H ) -220 kJ /mol (V)
3 f [Mo(CO)(NO)(PMe3)3]+ + H-
∆H ) 610 kJ /mol (VIII)
If we wish to discuss possible reaction mechanisms
involving charged species in solution, it is necessary to
include solvation effects. A rough estimate for solvation
energies can be obtained applying a simple electro-
static continuum model derived by Born and Onsager.26
The energetics for hydride and hydrogen transfer to
Re2(CO)10 and Fe(CO)5 in toluene are compared in eqs
XI and X, and XI and XII, respectively.
For the formation of 7a a reaction enthalpy of ∆H )
-29 kJ /mol is obtained. This value is similar to that of
7b, although the reaction of 3 with Fe(CO)5 is not at
equilibrium at room temperature. The difference be-
tween the formation of 7a and 7b might be understood
when the bond-breaking and bond-making steps are
separately analyzed. It is noticeable that the iron
carbonyl has a much higher hydrogen affinity than the
rhenium carbonyl (compare eqs IV and II). The struc-
ture of this interesting radical resulting from reaction
eq IV is displayed in Figure 2.
(24) Lane, K. R.; Sallans, L.; Squires, R. R. J . Am. Chem. Soc. 1985,
107, 5369.
(25) Lane, K. R.; Squires, R. R. Polyhedron 1988, 7, 1609.
(26) (a) Born, M. Z. Phys. 1920, 1, 45. (b) Onsager, L. J . Am. Chem.
Soc. 1936, 58, 1486. (c) Rashin, A. A.; Honig, B. J . Phys. Chem. 1985,
89, 5588.
Unlike the anion [Fe(CO)4(CHO)]-, which derives its
structure from a trigonal bipyramide with the formyl

1956 Organometallics, Vol. 19, No. 10, 2000
Liang et al.
3 + Re2(CO)10 f [Mo(CO)(NO)(PMe3)3]• +
[Re2(CO)9(CHO)]• ∆H ) 233 kJ /mol (IX)
3 + Re2(CO)10 f [Mo(CO)(NO)(PMe3)3]+ +
[Re2(CO)9(CHO)]- ∆H ) 210 kJ /mol (X)
3 + Fe(CO)5 f [Mo(CO)(NO)(PMe3)3]• +
[Fe(CO)4(CHO)]• ∆H ) 190 kJ /mol (XI)
3 + Fe(CO)5 f [Mo(CO)(NO)(PMe3)3]+ +
[Fe(CO)4(CHO)]- ∆H ) 187 kJ /mol (XII)
Hydride transfer processes to Fe(CO)5 are energeti-
cally favored over those to Re2(CO)10. This is a solvation
effect, since both transition metal carbonyls possess
comparable hydride affinities. We further observe that
in the case of Re2(CO)10, hydride shift is energetically
favored over hydrogen shift, whereas for Fe(CO)5 both
processes are accompanied by comparable changes in
energy. The radical transfer in turn holds an explana-
tion why the reaction between 3 and Fe(CO)5 is not at
equilibrium. The bond formation between [Mo(CO)(NO)-
(PMe3)3]• and [Fe(CO)4(CHO)]• requires a preparation
energy27 of about 85 kJ /mol, which is needed to distort
the iron fragment from its ground-state structure to the
geometric arrangement of the final adduct. This process
thus kinetically stabilizes the bond between the metal
fragments in 7a and inhibits back reaction.
F igu r e 3. ORTEP plot of the structure of 2. Only the
complex of Mo(1) is shown. The thermal ellipsoids are
drawn with 20% probability.
strong trans influence exerted by it. Although the
obtained Mo-HBH distances have to be taken with
4
caution, they seem to be rather long in both molecules
(Table 2) and longer than in 3 (see below), allowing one
to conclude a weak binding of this group and thus
confirming the mentioned strong trans influence of the
NO moiety. The BH4 units furthermore display typical
hinging with Mo-H-B angles of 142.4° and 128.5°; the
wide spread of this angle may indicate a soft energy
surface for the bending at the Mo-bound hydrogen,
which in turn may be taken as a hint that the BH4 unit
is only weakly attached to the metal fragment.
X-r a y Diffr a ction Stu d ies on 2, 3, 4b, 7a , 7b, a n d
8. The structural features of the η1-BH4 complex 2
remain a rarity28 among the versatile bonding modes
found for BH4 units. The examples FeH(η1-BH4)-
(dmpe)2 and FeH(η2-BH4)[MeC(CH2PPh2)3]30 demon-
29
strate that the ancillary ligand sphere may play a
crucial role to determine the coordination mode of the
BH4 moiety. Parallel to this and knowing about the
structures of the related complexes W(CO)(NO)(PR3)2-
(η2-BH4),31 2 also seems to be a case for ligand sphere
enforced η1-binding caused by the phosphine tris-
substitution.
A crystal of 2 suitable for an X-ray analysis was
obtained from a saturated Et2O solution by cooling it
to -30 °C. The X-ray data collection and processing
parameters of 2 are given in Table 1. Figure 3 shows a
structural model of 2.
Complex 3 showed extraordinary hydride reactivity,
which made it interesting to see whether its structure
would reveal unusual geometric parameters. Suitable
crystals were precipitated from hexane solution by
cooling it to -30 °C. The X-ray data collection and
processing parameters of 3 are given in Table 1. Figure
4 shows the structural model of one of the two indepen-
dent molecules of 3 in the unit cell, which both display
octahedral coordination of the molybdenum centers. The
structures of the Mo(CO)(NO)(PMe3)3 fragments are
similar to those in 2; however, they differ in the
equatorial angles. While in the molecule of Mo(1) both
angles of the trans substituents are close to each other
(164.88(2)° and 168.6(1)°), in the molecule of Mo(2)
they differ significantly (153.83(2)° and 178.3(1)°). The
sum of both angles at each Mo center is about the same,
indicating an overall “constant” distortion, i.e., the
leaning over to the hydride ligand.3b It is further-
more noteworthy that the Mo-H bonds are quite long
(1.84(3) and 1.83(3) Å)32 (Table 2). These H atoms were
localized in the difference Fourier maps and could be
refined. Due to the large diffracting volume of the
crystal (Table 1), the reasonable isotropic displacement
parameters of the hydrogens (0.064(10) Å2 for H(1) and
0.049(8) Å2 for H(2)) and R factors of the structure
determination, it is believed that the H positions can
be taken with confidence.
The asymmetric unit of 2 contains two independent
molecules, and in each molecule the Mo center is
pseudo-octahedrally coordinated with three PMe3 ligands
-
in meridional position and the BH4 unit and the
nitrosyl trans to each other. The Mo-N distances are
both on the short side of Mo-NO interactions, indicating
a strongly bound nitrosyl ligand and concomitantly a
(27) J acobsen, H.; Ziegler, T. Inorg. Chem. 1996, 35, 775.
(28) (a) Takusagawa, F.; Fumagalli, A.; Koetzle, T. F.; Shore, S. G.;
Schmitkons, T.; Fratini, A. V.; Morse, K. W.; Wei, C.-Y.; Bau, R. J .
Am. Chem. Soc. 1981, 103, 5165. (b) Ghilardi, C. A.; Midollini, S.;
Orlandini, A. Inorg. Chem. 1982, 21, 4096. (c) Fryzuk, M. D.; Rettig,
S. J .; Westerhaus, A.; Williams, H. D. Inorg. Chem. 1985, 24, 4316.
(d) J ensen, J . A.; Girolami, G. S. J . Am. Chem. Soc. 1988, 110, 4450.
(e) Dionne, M.; Hao, S.; Gambarotta, S. Can. J . Chem. 1995, 73, 1126.
(29) Bau, R.; Yuan, H. S. H.; Baker, M. V.; Field L. D. Inorg. Chim.
Acta 1986, 114, L27.
(30) Ghilardi, C. A.; Innocenti, P.; Midollini, S.; Orlandini, A. J .
Chem. Soc., Dalton Trans. 1985, 605.
(31) Van der Zeijden, A. A. H.; Veghini, D.; Berke, H. Inorg. Chem.
1992, 31, 5106.
The X-ray diffraction study of 4b was carried out
because of its relative uniqueness as an organometallic

Activated Hydride Complex
Organometallics, Vol. 19, No. 10, 2000 1957
Ta ble 1. Su m m a r y of X-r a y Diffr a ction Stu d ies for 2, 3, a n d 4b
2
3
4b
formula
color
C
10H31BMoNO2P3
C10H28MoNO2P3
orange
C26H41MoNO3P3
yellow
orange
cryst dimens (mm)
cryst syst
space group (No.)
a (Å)
b (Å)
c (Å)
â (deg)
V (Å3)
Z
0.48 × 0.28 × 0.18
monoclinic
P21/a (14)
15.9680(12)
9.3075(5)
26.911(2)
96.916(9)
3970.4(5)
8
0.78 × 0.56 × 0.53
orthorhombic
P212121 (19)
14.2303(12)
15.8054(17)
16.4491(16)
0.51× 0.44 × 0.32
momoclinic
P21/c (14)
15.6439(10)
9.8719(4)
19.9105(13)
100.877(8)
3019.6(3)
4
3699.7(6)
8
fw
397.02
1.328
0.898
1648
383.18
1.376
0.962
1584
604.45
1.330
0.619
1260
d(calcd) (g cm-3
abs coeff (mm-1
F(000)
)
)
2θ scan range (deg)
no. of unique data
no. of data obsd [I > 2σ(I )]
abs corr
solution method
no. of params refined
R, wR2 (%) all data
R1 (obsd) (%)a
5.08 < 2θ < 56.06
4.96 < 2θ < 56.08
5.52 < 2θ < 60.66
9526
8731
8964
7077
7856
5950
numerical, 14 crystal faces
Patterson
329
4.79, 9.98
3.38
numerical, 19 cryst. faces
Patterson
315
2.75, 5.50
2.28
numerical, 17 cryst. faces
Patterson
308
5.67, 6.24
3.23
goodness-of-fit
0.972
1.047
1.007
R1 ) ∑(Fo - Fc)/∑Fo; I > 2σ(I); wR2 ) {∑w(Fo - Fc2)2/∑w(Fo2)2}1/2
.
a
2
Ta ble 2. Selected Bon d Len gth s [Å] a n d
Bon d An gles [d eg] of Both Molecu les of 2 a n d 3
2
3
Mo(1)-N(1)
Mo(1)-C(1)
Mo(1)-P(3)
Mo(1)-P(1)
Mo(1)-P(2)
Mo(1)-H(21)
N(1)-O(1)
1.773(3)
2.017(4)
2.4898(9) Mo(1)-P(3)
2.4924(9) Mo(1)-P(1)
2.5159(9) Mo(1)-P(2)
1.9057(3) Mo(1)-H(1)
1.204(4)
1.135(5)
1.781(3)
2.002(3)
2.487(1)
2.501(1)
2.532(1)
Mo(1)-N(1)
Mo(1)-C(1)
1.811(2)
1.988(3)
2.4835(7)
2.4769(7)
2.5172(6)
1.84(3)
1.204(3)
1.153(3)
1.818(2)
1.982(3)
2.4686(7)
2.4536(6)
2.5263(6)
1.83(3)
N(1)-O(2)
C(1)-O(1)
Mo(2)-N(2)
Mo(2)-C(11)
Mo(2)-P(6)
Mo(2)-P(4)
Mo(2)-P(5)
C(1)-O(2)
Mo(2)-N(2)
Mo(2)-C(11)
Mo(2)-P(6)
Mo(2)-P(4)
Mo(2)-P(5)
Mo(2)-H(26)
N(2)-O(3)
2.0748(3) Mo(2)-H(2)
1.206(4)
1.147(4)
N(2)-O(4)
O(3)-C(11)
1.211(3)
1.151(3)
O(4)-C(11)
P(1)-Mo(1)-P(3)
P(2)-Mo(1)-C(1)
167.57(3) P(1)-Mo(1)-P(3)
178.8(1) P(2)-Mo(1)-C(1)
164.88(2)
168.6(1)
N(1)-Mo(1)-H(1) 176(1)
N(1)-Mo(1)-H(21) 167.2(1)
P(4)-Mo(2)-P(6)
164.31(3) P(4)-Mo(2)-P(6) 153.83(2)
F igu r e 4. ORTEP plot of the structure of 3. Only the
complex of Mo(1) is shown. The thermal ellipsoids are
drawn with 20% probability.
P(5)-Mo(2)-C(11) 175.5(1)
N(2)-Mo(2)-H(26) 166.2(1)
Mo(1)-H(26)-B(1) 142.4
Mo(2)-H(26)-B(2) 128.5
P(5)-Mo(2)-C(11) 178.25(8)
N(2)-Mo(2)-H(2) 178.0(9)
of middle transition metal elements and terminal
alkoxide groups have only rarely been structurally
characterized.33b Crystals suitable for X-ray analysis
were obtained by slow cooling of a saturated hexane/
benzene solution (9:1) to -30 °C. Under these conditions
4b crystallizes as a benzene solvate. The unique phos-
phorus ligand displayed rotational disorder in the
methyl groups, which could be refined by an appropriate
occupancy ratio (63/37%). The pseudo-octahedral com-
plex shows a molybdenum environment similar to those
of compounds 2, 3, and 7 (Figure 5). The Mo-O distance,
2.091(1) Å, is on the long side of the scale for Mo-
alkoxide with a metal center in low oxidation state
and the supposed medium strength of the Mo-O bond
indicated by the low values of the presumably
comparable calculated homolytic BDEs of 7a and 7b
and those higher values found in the early transition
metal, lanthanide, and actinide series.1b Such species
(32) Neutron diffraction studies: (a) Schultz, A. J .; Stearley, K. L.;
Williams, J . M.; Mink, R.; Stucky G. D. Inorg. Chem. 1977, 16, 3303.
(b) Brammer, L.; Zhao, D.; Bullock, R. M.; McMullan, R. K. Inorg.
Chem. 1993, 32, 4819. X-ray diffraction studies: (c) Petri, S. H. A.;
Neumann, B.; Stammler, H. G.; J utzi, P. J . Organomet. Chem. 1998,
553, 317. (d) Minato, M.; Sakai, H.; Weng, Z. G.; Zhou, D. Y.;
Kurishima, S., Ito, T.; Yamasaki, M.; Shiro, M.; Tanaka, M.; Osakada,
K. Organometallics 1996, 15, 4863. (e) Luo, X. L.; Kubas, G. J .; Burns,
C. J . Butcher, R. J . Organometallics 1995, 14, 3370. (f) Xu, S. S.; Gong,
J . F.; Zhou, X. Z. Chem. J . Chin. Univ. 1998, 19, 70. (g) Thi, N. P. D.;
Spichiger, S.; Paglia, P.; Bernardinelli, G.; Ku¨ndig, E. P.; Tinns, P. L.
Helv. Chim. Acta 1992, 75, 2593. (h) Dawson, D. M.; Henderson, R.
A.; Hills, A.; Hughes, D. L. J . Chem. Soc., Dalton Trans. 1992, 969.
(33) (a) Brandts, J . A. M.; Boersma, J .; Spek, A. L.; van Koten, G.
Eur. J . Inorg. Chem. 1999, 1727. (b) McQuillan, F. S.; Chen, H. L.;
Hamor, T. A.; J ones, C. J .; J ones, H. A.; Sidebotham, R. P. Inorg. Chem.
1999, 38, 1555. (c) Orpen, A. G.; Brammer, L.; Allen, F. H.; Kennard,
O.; Watson, D. G.; Taylor, R. J . Chem. Soc., Dalton Trans. 1989,
S1, 1.

1958 Organometallics, Vol. 19, No. 10, 2000
Liang et al.
F igu r e 5. ORTEP plot of the structure of 4b. The thermal
ellipsoids are drawn with 50% probability. The benzene
solvate molecule is omitted.
Ta ble 3. Selected Bon d Len gth s [Å] a n d
An gles [d eg] for 4b
Mo(1)-N(1)
Mo(1)-C(1)
Mo(1)-O(3)
Mo(1)-P(2)
Mo(1)-P(1)
Mo(1)-P(3)
N(1)-O(1)
C(1)-O(2)
C(2)-O(3)
1.796(2)
1.997(2)
2.091(1)
2.4964(6)
2.5024(6)
2.5557(7)
1.210(2)
1.144(3)
1.396(2)
N(1)-Mo(1)-C(1)
N(1)-Mo(1)-O(3)
C(1)-Mo(1)-O(3)
N(1)-Mo(1)-P(2)
O(3)-Mo(1)-P(2)
N(1)-Mo(1)-P(1)
P(2)-Mo(1)-P(1)
N(1)-Mo(1)-P(3)
P(2)-Mo(1)-P(3)
P(1)-Mo(1)-P(3)
85.72(8)
177.59(7)
96.08(7)
87.91(6)
90.55(4)
87.59(6)
174.36(2)
97.12(6)
92.92(2)
91.00(2)
F igu r e 6. ORTEP plots of the structures of 7a (above) and
7b (below). The ellipsoids are drawn with 20% probability.
data are listed in Table 4. Selected bond lengths
and angles are given in Table 5. As mentioned before,
insertion of a metal carbonyl unit into a M-H bond
has rarely been seen in transition metal hydride chem-
istry. Consequently, since this represents the major
synthetic access to µ-formyl complexes, such species
have only rarely been subjected to X-ray crystallo-
graphic studies.18g,35
The coordination geometries around the Mo centers
show great similarities with only slight deviations
from an ideal octahedral arrangement (Table 5 and
Figure 6). Only for 7a does one find a more pronounced
bending of the trans-arranged phosphorus ligands
toward the formyl moiety. The iron center of 7a is
pseudo-trigonal bipyramidally coordinated like in the
parent [Fe(CO)4CHO]- anion.19 Also the structure of
the Re2(CO)9CHO unit of 7b is stereochemically related
to that of [Re2(CO)9CHO]-,20 bearing the formyl groups
in equatorial positions. The angles of the µ2-formyl
group at the Cformyl atom are very similar and both
significantly larger than 120°, which is typical of transi-
tion metal µ2-acyl arrangements.18g,34,35 The µ-formyl
C-O distances of 7a and 7b are noticably different, with
a longer separation of the rhenium complex 7b indicat-
ing a stronger π-donating capacity of the Re2(CO)9
Oalkoxide interactions33 (Table 3, compare also structures
of 7 and 8). This effect appears to be caused by a strong
trans influence of the NO group,34 which is mainly a
σ-bonding effect. Concomitantly π donation in the Mo-O
bond is also reduced. It should be mentioned that in
specific cases the σ-type trans influence of the NO
group may be overcompensated by π push-pull effects,
which may lead to unexpectedly short M-(π donor)
distances.34a-c The Mo-O-CHPh2 angle of 4b is rather
wide, 126.2(1)°. For the most part we attribute this to
the steric bulk of the benzhydryl residue.
The structures of 7a and 7b were also determined by
X-ray diffraction studies. Suitable crystals of both
complexes were obtained by slow cooling of saturated
ether solutions to -30 °C. Their structures are displayed
in Figure 6a,b. The crystallographic and refinement
(34) (a) Veghini, D.; Nefedov, S. E.; Schmalle, H.; Berke, H. J .
Organomet. Chem. 1996, 526, 117. (b) Veghini, D.; Berke, H. Inorg.
Chem. 1996, 35, 4770. (c) Lyne, P. D.; Mingos, D. M. P. J . Chem. Soc.,
Dalton Trans. 1995, 1635. (d) Huheey, J . E.; Keiter, E. A.; Keiter, R.
L. Inorganic Chemistry, 4th ed.; Harper Collins College Publisher: New
York, 1993. (e) Richter-Addo, G. B.; Legzdins, P. Metal Nitrosyls;
Oxford University Press: New York, 1992.
(35) (a) Wolczanski, P. T.; Threlkel, R. S.; Santarsiero, B. D. Acta
Crystallogr. Sect. C 1983, 39, 1330. (b) Barger, P. T.; Santarsiero, B.
D.; Armantrout, J .; Bercaw, J . E. J . Am. Chem. Soc. 1984, 106, 5178.

Activated Hydride Complex
Organometallics, Vol. 19, No. 10, 2000 1959
Ta ble 4. Su m m a r y of X-r a y Diffr a ction Stu d ies 7a , 7b, a n d 8
7a
7b
8
formula
color
cryst dimens (mm)
cryst syst
C
15H28FeMoNO7P3
C20H28MoNO12P3Re2
yellow-orange
0.41 × 0.18 × 0.16
monoclinic
P21/n (14)
9.6511(9)
26.513((3)
13.2522(12)
99.96(1)
C13H28MoN2O4P2
red
0.66 × 0.64 × 0.23
orthorhombic
P212121 (19)
10.7371(7)
yellow
0.49 × 0.48 × 0.27
orthorhombic
Pbca (61)
12.6177(6)
13.6232(9)
29.1957(16)
space group (No.)
a (Å)
b (Å)
c (Å)
â (deg)
V (Å3)
Z
16.1098(13)
23.2055(15)
5018.6(5)
8
3339.8(6)
4
4013.9(5)
8
fw
579.08
1.533
1.300
2352
1035.68
2.060
7.795
1952
434.25
1.437
0.828
1792
d(calcd) (g cm-3
abs coeff (mm-1
F(000)
)
)
2θ scan range (deg)
no. of unique data
no. of data obsd [I > 2σ(I )]
abs corr
solution method
no. of params refined
R, wR2 (%) all data
R1, (obsd) (%)a
4.26 < 2θ < 53.52
4.56 < 2θ < 51.76
5.84 < 2θ < 60.68
5287
6130
11 792
4067
4571
9114
numerical, 16 cryst faces
Patterson
257
3.72, 6.45
2.77
numerical, 11 cryst faces
Patterson
356
3.69, 6.58
2.49
numerical, 12 cryst faces
Patterson
397
4.25, 5.61
2.95
goodness-of-fit
1.107
1.050
1.014
R1 ) ∑(Fo - Fc)/∑Fo; I > 2σ(I); wR2 ) {∑w(Fo - Fc2)2/∑w(Fo2)2}1/2
.
a
2
Ta ble 5. Selected Bon d Len gth s [Å] a n d
Bon d An gles [d eg] of 7a a n d 7b
7a
7b
Mo-P(2)
Mo-O(3)
Mo-P(3)
Mo-C(1)
Mo-N(1)
Mo-P(1)
N(1)-O(1)
C(1)-O(2)
C(2)-O(3)
Fe-C(2)
2.5028(7)
2.173(2)
2.5102(7)
2.015(3)
1.774(2)
2.5444(7)
1.210(3)
1.136(3)
1.188(4)
1.917(3)
Mo-P(3)
2.498(2)
2.173(5)
2.528(2)
1.970(7)
1.772(6)
2.556(2)
1.204(8)
1.172(9)
1.265(8)
2.102(7)
Mo-O(3)
Mo-P(1)
Mo-C(1)
Mo-N(1)
Mo-P(2)
N(1)-O(2)
C(1)-O(1)
C(11)-O(3)
Re(1)-C(11)
N(1)-Mo-O(3)
P(2)-Mo-P(3)
C(1)-Mo-P(1)
C(2)-O(3)-Mo
O(3)-C(2)-Fe
178.56(8)
166.06(2)
174.54(8)
143.3(2)
130.7(3)
N(1)-Mo-O(3)
P(3)-Mo-P(1)
C(1)-Mo-P(2)
C(11)-O(3)-Mo
O(3)-C(11)-Re(1)
176.4(2)
175.91(7)
173.9(2)
127.8(5)
127.5(5)
fragment. Both µ-(C-O) bond lengths fall into the
expected range of transition metal bridged acyl com-
pounds.35,36 However, due to their relative shortness,
they do not match with an oxycarbene structure.18g,35
To support the spectroscopically derived structure of
8, an X-ray crystal structure determination was carried
out. Suitable crystals of 8 were grown from pentane by
slow cooling of a solution to -30 °C. The crystallographic
and refinement data are listed in Table 4. The structure
of 8 is displayed in Figure 7 showing only one indepen-
dent molecule of the unit cell. 8 crystallizes in the chiral
space group P212121. Thus, the structure determination
F igu r e 7. ORTEP plot of the structure of 8. Only the
complex of Mo(2) is shown. Thermal ellipsoids are drawn
with 20% probability.
was carried out on an enantiomerically pure crystal of
8 with opposite configuration on C121 and C122 of the
independent molecules. As a consequence of the absence
of a crystallographic mirror plane, both molecules of 8
cannot be mirror images and therefore should deviate
in bonding parameters as given in Table 6 and display
different conformations. The Mo centers of both mole-
cules are pseudo-octahedral with a practically planar
N,O-chelate ring, two almost trans-disposed PMe3 groups,
and the CO and the NO ligands in cis position. There
is no significant difference in the Mo-P bond lengths
(see Table 4). Finally it should be emphasized that the
Mo-O distances of both molecules of 8 are similar to
those of 4b and correspond to elongated values. As for
4b, this is thought to be due to the NO trans influence.
(36) Selected references: J ensen, C. M.; Knobler, C. B.; Kaesz, H.
D. J . Am. Chem. Soc. 1984, 106, 5926. Su¨nkel, K.; Nagel, U.; Beck, W.
J . Organomet. Chem. 1983, 251, 227. J effery, J . C.; Orpen, A. G.; Stone,
F. G. A.; Went, M. J . J . Chem. Soc., Dalton Trans. 1986, 173. Kampe,
C. E.; Broag, N. M.; Kaesz, H. D. J . Mol. Catal. 1983, 21, 297. Kreiter,
C. G.; Franzreb, K.-H.; Sheldrick, W. S. J . Organomet. Chem. 1984,
270, 71. Lenhert, P. G.; Lukehart, C. M.; Warfield, L. T. Inorg. Chem.
1980, 19, 311. Lugan, N.; Lavigne G.; Bonnet J .-J . Inorg. Chem. 1987,
26, 585. Bonnesen, P. V.; Baker, A. T.; Hersh, W. H. J . Am. Chem.
Soc. 1986, 108, 8304. Chen, Y.-J .; Knobler, C. B.; Kaesz, H. D.
Polyhedron 1988, 7, 1891. Longato, B.; Norton, J . R.; Huffmann, J .
C.; Marsella, J . A.; Caulton, K. G. J . Am. Chem. Soc. 1981, 103, 209.
Lippmann, E.; Robl, C.; Berke, H.; Kaesz, H. D.; Beck, W. Chem. Ber.
1993, 126, 933. Xu, D. Q.; Kaesz, H. D.; Khan, S. I. Inorg. Chem. 1991,
30, 1341.

1960 Organometallics, Vol. 19, No. 10, 2000
Liang et al.
PMe3]), 312(80, [M+ - NO - PMe3]), 283 (37, [M+ - CO -
NO - PMe3]), 238 (61, [M+ - CO - 2PMe3]). Anal. Calcd for
Ta ble 6. Selected Bon d Len gth s [Å] a n d
Bon d An gles [d eg] of Both Molecu les of 8
C
10H27ClMoNO2 P3: C 28.75, H 6.53, N 3.35. Found: C 28.88,
Mo(1)-N(11)
Mo(1)-C(11)
Mo(1)-O(31)
Mo(1)-N(21)
Mo(1)-P(2)
1.791(2) Mo(2)-N(12)
1.956(3) Mo(2)-C(12)
2.099(2) Mo(2)-O(32)
2.209(2) Mo(2)-N(22)
2.4870(9) Mo(2)-P(4)
2.5049(9) Mo(2)-P(3)
1.162(4) C(12)-O(12)
1.209(3) N(12)-O(22)
1.280(4) N(22)-C(112)
1.360(4) O(32)-C(122)
1.797(2)
1.971(3)
2.117(2)
2.209(2)
2.4891(8)
2.4910(3)
1.153(4)
1.209(3)
1.276(4)
1.328(3)
H 6.28, N 3.37.
P r ep a r a tion of m er -Mo(HBH3)(CO)(NO)(P Me3)3 (2). A
0.55 g (1.32 mmol) sample of 1 and 0.15 g (6.88 mmol) of LiBH4
were placed in a Schlenk tube, then 20 mL of Et2O was added
via a cannula into the solids at -78 °C, and 0.75 mL (7.28
mmol) of PMe3 was introduced via a syringe. The cold bath
was removed and the reaction mixture was stirred at room
temperature. During this time the yellow suspension changed
to an orange, homogeneous solution. After 2 h (IR monitoring)
the solution was filtered over Celite and the filtrate was dried
in vacuo. The residue was extracted with toluene. Removal of
the toluene in vacuo and recrystallization from Et2O at -30
°C gave orange 2. Yield: 0.39 g (75%). IR (cm-1, THF): 1938
Mo(1)-P(1)
C(11)-O(11)
N(11)-O(21)
N(21)-C(111)
O(31)-C(121)
N(11)-Mo(1)-C(11) 89.6(1)
C(11)-Mo(1)-O(31) 96.3(1)
N(11)-Mo(1)-N(21) 99.7(1)
N(12)-Mo(2)-C(12) 91.4(1)
C(12)-Mo(2)-O(32) 93.1(1)
N(12)-Mo(2)-N(22) 101.4(1)
O(31)-Mo(1)-N(21) 74.42(9) O(2)-Mo(2)-N(22) 74.12(8)
P(2)-Mo(1)-P(1)
176.06(3) P(4)-Mo(2)-P(3)
175.88(3)
1
2
(CO), 1610 (NO). H NMR (C7D8, rt): 1.19 (t, J HP ) 3.2 Hz,
18H, 2PMe3 trans); 1.03 (br, s, 9H, PMe3), -1.51(br, quart.
1J HB ) 86.2 Hz, Mo-HB). 31P{1H} NMR (C7D8, rt): -10.3
(s, 2PMe3 trans), -17.4 (br, s, PMe3). 11B NMR (C7D8, rt): -38.5
Con clu sion s
Our investigations of the Mo(CO)(H)(NO)(PMe3)3
complex (3) revealed an exceptionally high reactivity of
the Mo-H bond. The found high propensity for carbonyl
insertion resembles closely that of metallocene hydride
compounds with early transition metal centers.37 To a
major degree we attribute this to the influence of the
coordinative environment of this compound, specifically
to the effect of the nitrosyl group.2,34 The nitrosyl group
“tunes” the metal center toward lower electronegativity
and furthermore exerts a strong trans influence. H
ligands activated by at least one of these effects should
display lower covalency of the LnM-H bond. As a
consequence, enhanced hydridicity4e and a strong po-
tential for hydride transfer reactions as for 3 and other
complexes38 results.
1
1
2
(quint., J BH ) 85 Hz). H NMR (C7D8, -40 °C): 1.15 (t, J HP
2
) 3.3 Hz, 18H, 2PMe3 trans); 0.93 (d, J HP ) 6.75 Hz, 9H,
PMe3), -1.42 (br, 1H, Mo-HB), 1.20 (br, 3H, BH3). 13C{1H}
2
2
NMR (C7D8, -40 °C): 231(dt, J CPcis ) 10 Hz, J CPtrans ) 49
1
3
Hz, CO); 17.6 (dt, J CP ) 12 Hz, J CP ) 2 Hz, PMe3), 18.0 (td,
1J CP ) 12 Hz, J CP ) 1 Hz, PMe3 trans). 31P{1H} NMR (C7D8,
3
2
2
-40 °C): -10 (d, J PP ) 28 Hz, 2 PMe3 trans), -16 (t, J PP
)
28.1 Hz, PMe3). FAB-MS: 397 (24, M+), 369 (20, [M+ - CO]),
367 (8, [M+ - NO]), 384 (26, [M+ - BH3]), 321 (21, [M+
-
PMe3]), 293 (37, [M+ - CO - PMe3]), 217 (32, [M+ - CO -
2PMe3]). Anal. Calcd for C10H31BMoNO2P3: C 30.25, H 7.89,
N 3.53. Found: C 30.61, H 7.42, N 3.66.
P r ep a r a t ion of m er -Mo(CO)(H)(NO)(P Me3)3 (3). To a
solution of 0.30 g (0.76 mmol) of 2 in 20 mL of toluene placed
in a Schlenk tube was added via syringe 1.20 mL (11.60 mmol)
of PMe3. The mixture was stirred at room temperature for 48
h. After this time the solvent was removed in vacuo. The
remaining residue was extracted with pentane. Concentration
and chilling of the combined solutions to -30 °C gave reddish
crystals of 3. Yield: 0.17 g (58.7%). IR (cm-1, hexane, -70
Exp er im en ta l P a r t
All reactions and manipulations were performed under a
dry N2 atmosphere by conventional Schlenk techniques or in
a glovebox. Solvents were dried by standard methods and
freshly distilled before use. NMR spectra: Varian Gemini-300
instrument; 1H at 300.08 MHz, 13C at 75.46 MHz, 31P at 121.47
MHz, 11B at 96.2 MHz. δ (1H), δ (13C) rel to SiMe4 and δ (31P)
rel to H3PO4, and δ(11B) rel to BF3‚OEt2. IR spectra: Biorad
FTS-45 instrument. Raman spectra: Renishaw Labram Ra-
man microscope. Mass spectra: Finnigan-MAT-8400 spec-
trometer; FAB spectra in 3-nitrobenzyl alcohol matrix.
P r ep a r a tion of m er -Mo(Cl)(CO)(NO)(P Me3)3 (1). To a
stirred solution of 4.50 g (11.1 mmol) of trans-Mo(CO)4(NO)-
(ClAlCl3) in 200 mL of THF, prepared according to a literature
procedure,8 was syringed 5.0 mL (48.5 mmol) of PMe3. The
mixture was vacuum transferred into an autoclave and then
heated to 80 °C. After 48 h (IR monitoring) the mixture was
cooled to room temperature and then cannula transferred into
a frit. After filtration the filtrate was dried in vacuo and the
remaining residue was extracted with Et2O. Removal of Et2O
in vacuo afforded a yellow solid. Yield: 3.30 g (71%). IR (cm-1
°C): 1916, 1900 (CO), 1609 (MoH), 1596 (NO). IR (cm-1
,
hexane rt): 1918 (CO), 1611 (MoH, NO). Raman (cm-1, solid
state): 1883 (CO), 1601 (NO, MoH). 1H NMR (C6D6): 1.27
2
2
(t, J HP ) 3.1 Hz, 18H, 2PMe3 trans); 1.11 (d, J HP ) 6.2 Hz,
2
2
9H, PMe3); -1.92 (dt, J HPtrans ) 27.8 Hz, J HP ) 32.5 Hz, 1H,
Mo-H). 13C{1H} NMR (C6D6): 239.6 (dt, J CPcis ) 11 Hz,
2
2J Cptrans ) 37 Hz, CO); 21 (dt, 1J CP ) 19 Hz, 3J CP ) 3 Hz, PMe3),
21.9 (td, J CP ) 12 Hz, J CP ) 2 Hz, 2PMe3 trans). 31P{1H}
1
3
2
NMR (C6D6): -4.1 (d, J PP ) 29 Hz, 2PMe3 trans), -11.8 (t,
2J PP ) 29 Hz, PMe3). EI-MS: 383 (35, M+), 355 (84, [M+
-
CO]), 353 (78, [M+ - NO]), 325 (20, [M+ - CO - NO]), 279
(86, [M+ - CO - PMe3]), 277 (78, [M+ - NO - PMe3]), 248
(24, M+ - CO - NO - PMe3]), 203 (33, [M+ - CO - 2PMe3]).
Anal. Calcd for C10H28MoNO2P3: C 31.34, H 7.38, N 3.66.
Found: C 31.00, H 7.63, N 3.67.
P r epar ation of mer -Mo(OCH2P h )(CO)(NO)(P Me3)3 (4a).
A 0.0350 g (0.09 mmol) sample of 3 was dissolved in 1 mL of
toluene, and benzaldehyde (9.5 µL, 0.094 mmol) was added.
After a few minutes (NMR monitoring) the solvent was
removed in vacuo and the residue was extracted with pentane.
Concentration and cooling of the combined solutions to -30
°C afforded yellow crystals of 4a . Yield: 0.039 g (87%). IR
THF): 1931 (CO), 1597 (NO). 1H NMR (C6D6): 1.25 (t, 2J HP
)
2
3.2 Hz, 18H, 2PMe3 trans); 1.06 (d, J HP ) 6.4 Hz, 9H, PMe3).
2
2
13C{1H} NMR(C6D6): 230.0 (dt, J CPcis ) 10 Hz, J Cptrans ) 56
1
3
Hz, CO); 17.0 (dt, J CP ) 19 Hz, J CP ) 3 Hz, PMe3, 17.6 (td,
1
(cm-1, hexane): 1922 (CO), 1588 (NO). H NMR (C6D6): 7.40
1J CP ) 11 Hz, 3J CP ) 1 Hz, 2PMe3 trans). 31P{1H} NMR (C6D6):
3
3
(d, J HH ) 7.3 Hz, 2H, Ph), 7.28 (t, J HH ) 7.3 Hz, 2H, Ph),
2
2
-10.3 (d, J PP ) 30 Hz, 2PMe3 trans), -17.5 (t, J PP ) 30 Hz,
PMe3). EI-MS: 418 (7, M+), 390(78, [M+ - CO]), 388 (63,
[M+ - NO]), 360 (8, [M+ - CO - NO]), 314 (100, [M+ - CO -
3
7.11 (t, J HH ) 7.3 Hz, 1H, Ph), 4.91 (s, 2H, CH2O), 1.19 (t,
2J HP ) 3.0 Hz, 18H, 2PMe3 trans); 1.07 (d, J HP ) 6.1 Hz, 9H,
2
PMe3). 13C{1H} NMR (C6D6): 231.6 (dt, 2J CPcis ) 11 Hz, 2J CPtrans
) 56 Hz, CO); 150.0, 127.9, 126.0, 125.6 (4s, Ph), 75.5 (dt,
(37) Erker, G. Acc. Chem. Res. 1984, 17, 103.
3J CPtrans ) 7.3 Hz, J CPtrans ) 1 Hz, CH2O), 17.0 (dt, J CP ) 17
3
1
(38) (a) Rybtchinski, B.; Ben David, Y.; Milstein, D. Organometallics
1997, 16, 3786. (b) Labinger, J . A. In Tranistion Metal Hydrides;
Dedieu, A., Ed.; VCH Publishers Inc.: New York, 1992; p 361.
3
1
3
Hz, J CP ) 3 Hz, PMe3), 17.8 (td, J CP ) 10 Hz, J CP ) 1 Hz,
2PMe3 trans). 31P{1H} NMR (C6D6): -9.9 (d, J PP ) 28 Hz,
2

Activated Hydride Complex
Organometallics, Vol. 19, No. 10, 2000 1961
2
2PMe3 trans), -16.3 (t, J PP ) 28 Hz, PMe3). FAB-MS: 489
Calcd for C13H34MoNO3P3: C 35.38, H 7.78, N 3.17. Found: C
35.02, H 8.23, N 3.17.
(7, M+), 461 (16, [M+ - CO]), 459 (10, [M+ - NO]), 383 (100,
[M+ - PhCHO]), 353 (34, [M+ - CO - PhCH2O]), 307 (18,
[M+ - PhCHO - PMe3]), 278 (44, [M+ - CO - PhCH2O -
PMe3]). Anal. Calcd for C17H34MoNO3P3: C 41.72, H 7.02, N
2.86. Found: C 42.14, H 6.89, N 2.79.
P r ep a r a tion of m er -Mo(OCHO)(CO)(NO)(P Me3)3 (5). A
solution of 0.060 g (0.16 mmol) of 3 in 5 mL of toluene was
stirred at rt under 1 bar CO2 for 1 h. After this time the solvent
was evaporated in vacuo and the residue was extracted with
pentane. Concentration and cooling of the combined solutions
to -30 °C afforded yellow crystals of 5. Yield: 0.057 (85%). IR
P r epar ation of mer -Mo(OCHP h 2)(CO)(NO)(P Me3)3 (4b).
A mixture of 0.040 g (0.1 mmol) of 3 and 0.019 g (0.1 mmol) of
benzophenone in 3 mL of toluene was stirred for 3 h at rt
(NMR monitoring). After this time the solvent was evaporated
in vacuo. The residue was extracted with pentane, and the
combined solutions were concentrated and cooled to -30 °C
1
(cm-1, hexane): 1958, 1931 (CO), 1625 (OCO), 1609 (NO). H
NMR (C6D6): 8.59 (pseudo-quartet, 4J HP ) 1.2 Hz, 1H, OCHO),
2
2
1.23 (t, J HP ) 3.2 Hz 18H, 2PMe3 trans); 1.09 (d, J HP ) 6.9
Hz, 9H, PMe3). 13C{1H} NMR (C6D6): 230.2 (dt, J Cpcis ) 11
2
Hz, 2J CPtrans ) 53 Hz, CO); 167.1 (m, CHO), 17.6 (dt, 1J CP ) 18
to afford yellow 4b. Yield: 0.0480 g (81.4%). IR (cm-1
,
3
1
3
hexane): 1922 (CO), 1588 (NO). 1H NMR (C6D6): 7.44 (d, 3J HH
Hz, J CP ) 3 Hz, PMe3), 17.9 (td, J CP ) 11 Hz, J CP ) 1 Hz,
2
3
2PMe3 trans). 31P{1H} NMR (C6D6): -8.3 (d, J PP ) 28 Hz,
) 7.8 Hz, 2H, Ph), 7.16 (t, J HH ) 7.8 Hz, 2H, Ph), 7.01
(t, J HH ) 7.8 Hz, 1H, Ph), 5.55 (s, 1H, OCH), 1.06 (t, J HP
2
3
1
2PMe3 trans), -15.6 (t, J PP ) 28 Hz, PMe3). EI-MS: 427
)
(8, M+), 399 (25, [M+ - CO]), 397 (13, [M+ - NO]), 353 (42,
[M+ - NO - OCHO], 323 (62, [M+ - CO - PMe3]), 321 (55,
[M+ - NO - PMe3]), 278 (62, [M+ - CO - OCHO - PMe3]).
Anal. Calcd for C11H28MoNO4P3: C 30.92, H 6.62, N 3.28.
Found: C 31.22, H 6.72, N 3.35.
2
2.8 Hz, 18H, PMe3 trans), 1.11 (d, J HP ) 6.0 Hz, 9H, PMe3).
13C{1H} NMR (C6D6): 230.9 (dt, 2J CPcis ) 10 Hz, 2J CPtrans ) 56.7
3
Hz, CO); 152.4, 127.9, 127.1, 125.9 (4s, Ph), 87.4 (dt, J CP ) 6
Hz, 3J CPtrans ) 2 Hz, OCH),17.3 (dt, 1J CP ) 16 Hz, 3J CP ) 3 Hz,
1
3
PMe3), 18.0 (td, J CP ) 10.0 Hz, J CP ) 1.2 Hz, 2PMe3trans).
31P{1H} NMR (C6D6): -12.9 (d, J PP ) 29 Hz, 2PMe3 trans),
2
Rea ction of 3 w ith CO, F or m a tion of Mo(CO)2(H)(NO)-
(P Me3)2 (6). This reaction was carried out in an NMR tube
and monitored by NMR. A 0.0274 g (0.072 mmol) sample of 3
was dissolved in about 0.7 mL of C6D5CD3 in an NMR tube.
The solution was frozen, and the NMR tube was evacuated
and then filled with CO (1 bar). The tube was sealed, the
reaction mixture was allowed to warm to room temperature,
and NMR spectra were recorded frequently. The reaction
reached balance within 2 days. 1H NMR of 6 (C7D8): 1.12
-17.0 (t, J PP ) 29 Hz, PMe3). FAB-MS: 565 (11, M+), 535
2
(12, [M+ - NO]), 507 (11, [M+ - CO - NO]), 383 (84, [M+
Ph2CO]), 354 (48, [M+ - CO - Ph2CHO]), 278 (54, [M+
-
-
CO - Ph2CHO - PMe3]). Anal. Calcd for C23H38MoNO3P3: C
48.85, H 6.79, N 2.48. Found: C 48.82, H 6.99, N 2.47.
P r ep a r a tion of m er -Mo[(OCH(CH3)(P h )](CO)(NO)-
(P Me3)3 (4c). A 0.0350 g (0.09 mmol) sample of 3 was dissolved
in 1 mL of toluene, and 12.0 µL (0.1 mmol) of acetophenone
was added. After 7 h (NMR monitoring) the solvent was
removed in vacuo and the residue was extracted with pentane.
Concentration and cooling to -30 °C of the extracts produced
2
2
(t, J HP ) 3.2 Hz, 18H, 2PMe3); -2.73 (t, J HP ) 29.6 Hz, 1H,
Mo-H). 31P{1H} NMR (C7D8): -6.5 (s).
P r ep a r a t ion of m er -Mo[(µ-OCH )F e(CO)4](CO)(NO)-
(P Me3)3 (7a ). A mixture of 0.065 g (0.17 mmol) of 3 and 23
µL (0.17 mmol) of Fe(CO)5 in 6 mL of toluene was stirred at rt
for 1 h. After this time the solvent was evaporated in vacuo
and the residue was extracted with pentane. Concentration
and chilling of the combined solutions to -30 °C afforded
yellow crystals of 7a . Yield: 0.0862 g (88%). IR (cm-1, THF):
2035, 1952, 1925 (Fe(CO)4), 1931 (Mo(CO)), 1619 (NO). 1H
yellow crystals of 4c. Yield: 0.0420 g (91.3%). IR (cm-1
,
hexane): 1922 (CO), 1584 (NO). 1H NMR (C6D6): 7.36 (d,
3J HH ) 7.4 Hz, 2H, Ph), 7.25 (t, 3J HH ) 7.4 Hz, 2H,Ph), 7.09 (t,
3J HH ) 7.8 Hz, 1H, Ph), 4.62 (quartet, 3J HH ) 6.0 Hz, 1H, OCH),
3
2
1.35 (d, J HH ) 6.5 Hz, 3H, Me), 1.28 (t, J HP ) 2.9 Hz, 9H,
2
PMe3 trans); 1.11 (t, J HP) 2.9 Hz, 9H, PMe3 trans); 1.03 (d,
2J HP ) 5.9 Hz, 9H, PMe3). 13C{1H} NMR (C6D6): 231.4 (dt,
2J CPcis ) 11 Hz, 2J CPtrans ) 57 Hz, CO); 154.1, 127.8, 126.1, 128.5
2
NMR (C6D6): 14.09 (s, 1H, OCH), 1.00 (t, J HP ) 1.6 Hz, 18H,
2PMe3 trans); 1.02 (d, 2J HP ) 2.0 Hz, 9H, PMe3). 13C{1H} NMR
3
3
(4s, Ph), 79.1 (dt, J CP ) 5 Hz, J CPtrans ) 2 Hz, OCH), 30.5
2
2
(C6D6): 228.5 (dt, J CPcis ) 11 Hz, J CPtrans ) 48 Hz, Mo-CO);
1
3
(s, Me), 17.1 (dt, J CP ) 16 Hz, J CP ) 3 Hz, PMe3), 18.2 (td,
306.1 (pseudo-quartet, 3J CP ) 3 Hz, 3J CPtrans ) 2 Hz, -OCH-),
1J CP ) 10 Hz, J CP ) 1 Hz, PMe3 trans), 18.1 (td, J CP ) 10
3
1
1
3
218.2 (s, Fe(CO)4), 16.7 (dt, J CP ) 20 Hz, J CP ) 3 Hz, PMe3),
Hz, J CP ) 1 Hz, PMe3 trans). 31P{1H} NMR (C6D6): -12.3 (d,
3
17.1 (td, J CP ) 12 Hz, J CP ) 1 Hz, 2PMe3 trans). 31P{1H}
1
3
2J PP ) 29 Hz, 2PMe3 trans), -17.5 (t, J PP ) 29 Hz, PMe3).
2
2
NMR (C6D6): -9.9 (d, J PP ) 27 Hz, 2PMe3 trans), -15.6
EI-MS: 503 (12, M+), 475 (100, [M+ - CO]), 473 (58, [M+
-
(t, J PP) 27 Hz, PMe3). EI-MS: 551 (10, [M+ - CO]), 549
2
NO]), 427 (60, [M+ - PMe3]), 399 (58, [M+ - CO - PMe3]),
355 (14, [M+ - CO - PhCOCH3]), 323 (55, [M+ - CO - NO -
PhCH3CHO]). Anal. Calcd for C18H36MoNO3P3: C 42.95, H
7.27, N 2.78. Found: C 43.24, H 7.28, N 2.79.
(10, [M+ - NO]), 503 (24, [M+ - PMe3]), 382 (12, [M+
-
OCHFe(CO)4]), 354 (26, [M+ - CO - OCHFe(CO)4]), 278
(30, [M+ - CO - OCHFe(CO)4 - PMe3]). 196 (100, Fe(CO)5),
168 (100, Fe(CO)4). Anal. Calcd for C15H28FeMoNO7P3:
31.11, H 4.88, N 2.42. Found: C 31.28, H 4.58, N 2.30.
C
P r ep a r a tion of m er -Mo[(OCH(CH3)2](CO)(NO)(P Me3)3
(4d ). A 21.0 µL (0.29 mmol) sample of acetone was added to a
solution of 0.055 g (0.14 mmol) of 3 in 5 mL of toluene. The
mixture was stirred at rt for 10 h (NMR monitoring). After
this time the solvent was removed in vacuo. The residue was
extracted with pentane, and the combined solutions were
concentrated and cooled to -30 °C to afford yellow 4d . Yield:
0.0540 g (85.3%). IR (cm-1, hexane): 1922 (CO), 1580 (NO).
P r ep a r a tion of m er -Mo[(µ-OCH)Re2(CO)9](CO)(NO)-
(P Me3)3 (7b). A mixture of 0.060 g (0.16 mmol) of 3 and 0.105
g (0.16 mmol) of Re2(CO)10 in 10 mL of toluene was stirred for
1 h at rt. After this time the solvent was removed in vacuo.
The residue was extracted with Et2O, and the combined
solutions were concentrated and cooled to -30 °C to afford
orange crystals of 7b. Yield: 0.130 g (80%). IR (cm-1, Nujol):
2094, 2030, 2014, 1984, 1955, 1918, 1908 (Re2(CO)9), 1932
(Mo-CO), 1618 (NO). 1H NMR (C7D8): 15.07 (s, 1H, OCH),
1H NMR (C6D6): 3.75 (hept, J HH ) 6 Hz, 1H, OCH), 1.26 (t,
3
2J HP ) 2.9 Hz, 18H, 2PMe3 trans), 1.03 (d, J HP ) 5.8 Hz, 9H,
2
PMe3), 1.11 (d, J HH ) 5.8 Hz, 6H, 2Me3). 13C{1H} NMR
3
2
2
1.06 (t, J HP ) 3.2 Hz, 18H, 2PMe3 trans); 0.95 (d, J HP ) 7
2
2
Hz, 9H, PMe3). 13C{1H} NMR (C7D8): 288.3 (dt, J CPcis ) 10
Hz, J CPtrans ) 49 Hz, Mo-CO); 302.3 (pseudo-quartet, J CP
4 Hz, OCH), 200.9, 196.5, 191.9 (3s, Re2(CO)9), 16.9 (dt, J CP
2
(C6D6): 232.0 (dt, J CPcis ) 11 Hz, J CPtrans ) 59 Hz, CO), 70.7
(pseudo-quint, J CPtrans ) 5 Hz, J CPtrans ) 2 Hz, OCH), 16.8
3
3
2
3
)
1
3
1
1
(dt, J CP ) 16 Hz, J CP ) 3 Hz, PMe3), 18.1 (td, J CP ) 10 Hz,
3J CP ) 1 Hz, 2PMe3 trans). 31P{1H} NMR (C6D6): -11.8 (d,
3
1
3
) 20 Hz, J CP ) 3 Hz, PMe3, 17.5 (td, J CP ) 12 Hz, J CP ) 1
2J PP ) 29 Hz, 2PMe3 trans), -18.0 (t, J PP ) 29 Hz, PMe3).
2
Hz, 2PMe3 trans). 31P{1H} NMR (C7D8): -11.6 (d, J PP ) 30
2
EI-MS: 441 (10, M+), 413 (63, [M+ - CO]), 355 (20, [M+
CO - Me2CO], 337 (100, [M+ - CO - PMe3]), 335 (100, [M+
-
-
2
Hz, 2PMe3 trans), -16.4 (t, J PP ) 30 Hz, PMe3). EI-MS: 797
(20, [M+ - 2CO - NO - 2PMe3]), 710 (30, [M+ - Re(CO)5]),
633 (38, [M+ - Re(CO)5 - PMe3]), 605 (14, [M+ - Re(CO)5 -
NO - PMe3]), 324 (66, [M+ - CO - NO - Me3CO]). Anal.

1962 Organometallics, Vol. 19, No. 10, 2000
Liang et al.
PMe3 - CO]), 306 (23, [M+ - OCHRe2(CO)10 - PMe3]), 278
(20, [M+ - CO - OCHRe2(CO)10 - PMe3]). Anal. Calcd for
as 92 kJ /mol, as suggested by Baerends et al.44 The reac-
tion enthalpies ∆H were obtained by correcting the reaction
energies ∆E for zero-point energy (ZPE). For reactions I and
VIII, this contribution has been estimated as -10 kJ /mol from
ν(Mo-H) reported for Mo(CO)H(NO)(PMePh2)3,8 for reactions
II, IV, VI, and VII as 20 kJ /mol from the calculated ∆ZPE
between CO and HCO, and for reactions III and V as 4 kJ /
mol from related ν(M-O) values.45
C
20H28MoNO12P3Re2: C 23.19, H 2.73, N 1.35. Found: C 23.32,
H 2.57, N 1.25.
Attem pted Reaction s of 3 with th e Im in es P h NdCHP h ,
MeNdCHP h , a n d P h 2CdNH. All reactions were carried out
in an NMR tube and monitored by NMR. A 0.020 g (0.05 mmol)
sample of 3 and stoichiometric amounts of the imine were
dissolved in about 0.7 mL of C6D5CD3, and the mixture was
transferred into a NMR tube. The 1H NMR and 31P NMR
spectra were recorded revealing no reaction at rt and 60 °C
for MeNdCHPh and Ph2CdNH. The reaction with PhNd
CHPh revealed new resonances with complete transformation,
which however could not be assigned to a unique species.
X-r a y Cr ysta l Str u ctu r e An a lyses on 2, 3, 4b, 7a , 7b,
a n d 8. X-ray diffraction data were collected at 193(1) K using
an imaging plate detector system (STOE IPDS) with graphite-
monochromated Mo KR radiation. A total of 180, 143, 180, 150,
180, and 150 images were exposed at constant times of 1.50,
1.20, 1.70, 2.20, 3.00, and 1.30 min/image for 2, 3, 4b, 7a , 7b,
and 8, respectively. The crystal-to-image distances were set
to 60, 60, 50, 66, 70, and 50 mm (θmax ) 28.03°, 28.04°, 30.35°,
26.85°, 25.88°, and 30.34°). φ-oscillation (7b) or rotation scan
modes (2, 3, 4b, 7a , 8) were selected for the φ increments of
1.0°,1.4°, 1.0°, 1.0°, 1.0°, and 1.0° per exposure in each case.
Total exposure times for the six compounds were 17, 13, 18,
15, 22, and 14 h in the order of the complexes as given above.
The intensities were integrated after using a dynamic peak
profile analysis, and estimated mosaic spread (EMS) check46
was performed to prevent overlapping intensities. A total of
5000 reflections (8000 for 4b) were selected out of the whole
limiting sphere for the cell parameter refinement. A total of
29 126, 33 390, 31 045, 27 597, 22 695, and 30 592 reflections
were collected, of which 9526, 8731, 8964, 5287, 6130, and
11 792 reflections were unique (Rint ) 5.20%, 4.06%, 4.25%
5.65%, 10.88%, and 4.34%); data reduction and numerical
absorption correction used 14, 19, 17, 16, 11, and 12 indexed
crystal faces.46 All six structures were solved by the Patterson
method using an improved version of SHELXS-9747 and refined
with SHELXL 97.48 Absolute configurations were determined
by using Flack’s x-parameter refinement.48,49 The absolute
structure parameter x for compounds 3 and 8 was -0.03(2)
and 0.04(3), respectively. No twinning by merohedry was noted
for both of the non-centrosymmetric structures.
P r epar ation of tr a n s-Mo[OCH(OCH3)(C4H6N)](CO)(NO)-
(P Me3)2 (8). A mixture of 0.050 g (0.13 mmol) of 3 and 22 µL
(0.13 mmol) of (pyrrolidine-2-yl)methyl carboxylate in 5 mL
of toluene was stirred for 2 h at rt. After this time the solvent
was evaporated in vacuo and the residue was extracted with
Et2O. Concentration and chilling of the combined solutions to
-30 °C afforded red crystals of 8. Yield: 0.047 g (83.0%). IR
1
(cm-1, hexane): 1908 (CO), 1592 (NO). H NMR (C6D6): 5.41
4
(t, J HH ) 4.7 Hz, 1H, OCH), 3.56 (br, 2H, pyrrolidine-
H2C(5′)), 3.36 (s, 3H, -OCH3), 2.43 (m,1H, pyrrolidine-
HC(3′)), 2.04 (m, 1H, pyrrolidine-HC(3′)), 1.19 (dd, 4J HP ) 1.9
2
4
2
Hz, J HP ) 4.3 Hz, 9H, PMe3), 1.03 (dd, J HP ) 1.9 Hz, J HP
)
4.3 Hz, 9H, PMe3). 13C{1H} NMR (C6D6): 244.4 (t, J CP ) 10
Hz, CO); 186.3 (t, 3J CP ) 3 Hz, CdN), 104.9 (s, -OCH-), 59.6
(s, -OCH3), 53.7, 32.5, 23.1 (3s, pyrrolidine-C), 15.1 (dd, 1J CP
2
3
1
3
) 13 Hz, J CP ) 8 Hz, PMe3), 14.7 (dd, J CP ) 13 Hz, J CP ) 8
Hz, PMe3). 31P{1H} NMR (C6D6): -6.1 (s, PMe3), -6.2 (s, PMe3).
EI-MS: 434 (30, [M+]), 460 (8, [M+ - CO]), 330 (100, [M+
CO - PMe3]), 328 (100, [M+ - NO - PMe3]), 300 (66, [M+
-
-
PMe3 - CO - NO]), 224 (14, [M+ - NO - CO - 2PMe3]). Anal.
Calcd for C13H28MoN2O4P2: C 35.95, H 6.51, N 6.45. Found:
C 36.26, H 6.03, N 6.46.
Com p u ta tion a l Deta ils. Self-consistent GGA calculations
with gradient corrections due to Becke39 and Perdew40 have
been performed utilizing the Amsterdam Density Functional
package ADF.41 Use was made of the frozen core approxima-
tion. Methyl groups were described using a double-ú STO basis
(ADF database II). For the ns, np, nd, and (n+1)s shells on
the transition metals, and for H, a triple-ú STO basis aug-
mented by one (n+1)p function was employed (ADF database
IV). The valence shell of the remaining main group elements
was described with a double-ú STO basis and one d-STO
polarization function (ADF database III). The numerical
integration grid42 was chosen in a way that significant test
integrals are evaluated with an accuracy of at least four
significant digits. Relativistic effects were included using a
quasi-relativistic approach.43 For systems with an odd electron
count, spin-unrestricted calculations have been performed. The
atomic reference energy for the 2S ground state of H was taken
Ack n ow led gm en t. F.L. would like to thank the
China Scholarship Council and the University of Zurich
for providing an exchange scholarship. H.B. gratefully
acknowledges support from the Swiss National Science
Foundation and from the funds of the University of
Zurich. We furthermore thank Ms. B. Spichtig for MS
analyses.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data and structure refinement parameters, atomic coordinates,
bond lengths, bond angles, anisotropic displacement param-
eters, and hydrogen coordinates of 2, 3, 4b , 7a , 7b , and 8.
Optimized geometries and bonding energies for all calculated
molecules. This material is available free of charge via the
Internet at http://pubs.acs.org.
(39) Becke, A. D. Phys. Rev. A 1988, 38, 3098.
(40) Perdew, J . P. Phys. Rev. B 1986, 33, 8822.
OM990945T
(41) (a) Baerends, E. J .; Be´rces, A.; Bo, C.; Boerrigter, P. M.; Cavallo,
L.; Deng, L.; Dickson, R. M.; Ellis, D. E.; Fan, L.; Fischer, T. H. Fonseca
Guerra, C.; van Gisbergen, S. J . A.; Groeneveld, J . A.; Gritsenko, O.
V.; Harris, F. E.; van den Hoek, P.; J acobsen, H.; van Kessel, G.;
Kootstra, F.; van Lenthe, E.; Osinga, V. P.; Philipsen, P. H. T.; Post,
D.; Pye, C. C.; Ravenek, W.; Ros, P.; Schipper, P. R. T.; Schreckenbach,
G.; Snijders, J . G.; Sola, M.; Swerhone, D.; te Velde, G.; Vernooijs, P.;
Versluis, L.; Visser, O.; van Wezenbeek, E.; Wiesenekker, G.;
Wolff, S. K.; Woo, T. K.; Ziegler, T. ADF Release 1999.01/ 02; SCM:
Amsterdam, 1999. (b) Guerra, C. F.; Snijders, J . G.; te Velde, G.;
Baerends, E. J . Theor. Chem. Acc. 1998, 99, 391.
(44) Baerends, E. J .; Branchadell, V.; Sodupe, M. Chem. Phys. Lett.
1997, 265, 481.
(45) Nakamoto, K. Infrared and Raman Spectra of Inorganic and
Coordination Compounds, 3rd ed.; J ohn Wiley: New York, 1978;
Chapter III-6.
(46) Stoe IPDS software for data collection, cell refinement, and data
reduction, Version 2.87-2.92 (the latter used for 4b); Stoe & Cie,
Darmstadt, Germany, 1997-1999.
(47) SHELXS-97: Sheldrick, G. M. Acta Crystallogr. 1990, 46A, 467.
(48) SHELXL-97: Sheldrick, G. M. Programme for the Refinement
of Crystal Structures; University of Go¨ttingen: Germany, 1997.
(49) Flack, H. D. Acta Crystallogr. 1983, A39, 876.
(50) Bernardinelli, G.; Flack, H. D. Acta Crystallogr. 1985, A41, 500.
(42) te Velde, G.; Baerends, E. J . J . Comput. Phys. 1992, 99, 84.
(43) Ziegler, T.; Tschinke, V.; Baerends, E. J .; Snijders, J . G.;
Ravenek, W. J . Phys. Chem. 1989, 93, 3050.