β-agostic silylamido and silyl-hydrido compounds of molybdenum and tungsten

Article abstract of DOI:10.1021/ic900591e

Reactions of bls(imldo) compounds (RN)₂Mo(PMe₃) _n {n = 2, R = ^tBu; n = 3, R =2,6-dlmethylphenyl (Ar′) and 2,6-dlisopropylphenyl (Ar)) and (RN)₂W(PMe ₃)₃ (R = 2,6-dimethylphenyl a

Full text of DOI:10.1021/ic900591e

Inorg. Chem. 2009, 48, 9605–9622 9605
DOI: 10.1021/ic900591e
β-Agostic Silylamido and Silyl-Hydrido Compounds of Molybdenum and Tungsten†
,
Stanislav K. Ignatov,‡ Andrey Y. Khalimon,§ Nicholas H. Rees, Alexei G. Razuvaev,‡ Philip Mountford, * and
Georgii I. Nikonov§,*
‡Department of Chemistry, Nizhnii Novgorod State University, Gagarin Avenue 23, 603600 Nizhny Novgorod,
Russia, §Department of Chemistry, Brock University, St. Catharines, ON L2S 3A1, Canada, and Chemistry
Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, U.K.
Received March 27, 2009
t
Reactions of bis(imido) compounds (RN)2Mo(PMe3)n (n = 2, R = Bu; n = 3, R =2,6-dimethylphenyl (Ar0) and
2,6-diisopropylphenyl (Ar)) and (RN)2W(PMe3)3 (R = 2,6-dimethylphenyl and 2,6-diisopropylphenyl) with silanes afford
four types of products: the β-agostic silylamido compounds (RN)(η3-RN-SiR02-H )MCl(PMe3)2 (M = Mo and W),
mono(imides) (RN)MCl2(PMe3)3 (M = Mo and W), silyl hydride bis(imido) derivative (ArN)2W(PMe3)(H)(SiMeCl2), and
3 3 3
Si-Cl W bridged product (ArN)(η2-ArN-SiHMeCl-Cl )WCl(PMe3)2. Reactions of molybdenum compounds
3 3 3
3 3 3
(RN)2Mo(PMe3)m (m = 2 or 3)withmono- and dichlorosilanesHSiClnR03-n (R0 = Me, Ph; n = 1,2)afford mainly the agostic
compounds (RN)(η3-RN-SiR02-H )MoCl(PMe3)2, accompanied by small amounts of mono(imido) derivatives (RN)
3 3 3
MoCl2(PMe3)3. In contrast, the latter compounds are the only transition metal products in reactions with HSiCl3, the silicon
co-product being the silanimine dimer (RNSiHCl)2. The reaction of (ArN)2W(PMe3)3 with HSiCl2Me under continuous
removal of PMe3 affords the silyl hydride species (ArN)2W(PMe3)(SiMeCl2)H, characterized by NMR and
X-ray diffraction. This product is stable in the absence of phosphine, but addition of catalytic amounts of PMe3 causes
a fast rearrangement into the Si-Cl W bridged product (ArN)(η2-ArN-SiHMeCl-Cl )WCl(PMe3)2. The
3 3 3
3 3 3
mechanism of silane addition to complexes (RN)2Mo(PMe3)n has been elucidated by means of density functional theory
calculations ofmodelcomplexes(MeN)2Mo(PMe3)n (n = 1-3). Complex (MeN)2Mo(PMe3)2 is foundtobethemoststable
form. It undergoes facile silane-to-imido addition reactions that afford silylamido hydride complexes stabilized by
additional Si H interactions. The easeofthis additionincreases fromHSiMe2Cl toHSiCl3, consistent with experimental
)
3 3 3
observations. The most stable final products of silane addition are the agostic complexes (MeN)(η3-MeN-SiR2-H
3 3 3
MoCl(PMe3)2 (R2 = Me2, MeCl, Cl2) and Cl-bridged silylamido complexes (MeN)(η2-MeN-SiRH-Cl )MoCl(PMe3)2
(R = Me or Cl). In the case of HSiMeCl2 addition the former is the most stable, but for HSiCl3 addition the latter is the preferred
3 3 3
product. In all cases, the isomeric silyl hydride species (MeN)2Mo(PMe3)(H)(SiClR2) are less stable by about 6 kcal mol-1
.
Silane additions to the imido ligand of the tris(phosphine) (MeN)2Mo(PMe3)3 afford octahedral silylamido hydride derivatives.
The different isomers of these addition products are destabilized relative to (MeN)2Mo(PMe3)3 only by 7-24 kcal mol-1 (for
the HSiMe2Cl additions), but since the starting tris(phosphine) is 14.8 kcal mol-1 less stable than (MeN)2Mo(PMe3)2, silane
addition to the latter is a more preferred pathway. A double phosphine dissociation pathway via the species (MeN)2Mo-
(PMe3) was ruled out because this complex is by 24.7 kcal mol-1 less stable than (MeN)2Mo(PMe3)2.
Introduction
silanes, silane alcoholysis, and so forth.1a Among different
types of “arms” linking the agostic Si center to metal, the
nitrogen bridge is one of the best studied.2,3a,4 Agostic
silylamido compounds are usually prepared by salt-elimina-
tion reactions between a silylated amide R0(HR2Si)NM
(M=an alkali metal) and a transition metal halide.2
Transition metal compounds with agostic Si-H
M
3 3 3
interactions1 (1) have attracted significant recent attention,
in part because of their relevance to a wide range of metal-
mediated transformations of organosilicon compounds,
such as hydrosilylation, dehydrogenative polymerization of
(2) (a) Herrmann, W. A.; Huber, N. W.; Behm, J. Chem. Ber. 1992, 125, 1405.
(b) Procopio, L. J.; Carroll, P. J.; Berry, D. H. J. Am. Chem. Soc. 1994, 116, 177.
(c) Herrmann, W. A.; Eppinger, J.; Spiegler, M.; Runte, O.; Anwander, R.
Organometallics 1997, 16, 1813. (d) Nagl, I.; Scherer, W.; Tafipolsky, M.;
Anwander, R. Eur. J. Inorg. Chem. 1999, 1405. (e) Eppinger, J.; Spiegler, M.;
† Dedicated to Prof. Dietmar Seyferth on the occasion of his 80th birthday.
*To whom correspondence should be addressed. E-mail: gnikonov@
brocku.ca. Phone: +1 (905) 6885550, Ext 3350. Fax: +1 (905) 682-9020.
(1) (a) Kubas, G. J. Metal Dihydrogen and σ-Bond Compounds; Kluwer
Academic/Plenum: New York 2001. (b) Crabtree, R. H. Angew. Chem., Int. Ed.
Engl. 1993, 32, 789. (c) Corey, J. Y.; Braddock-Wilking, J. Chem. Rev. 1999, 99,
175. (d) Lin, Z. Chem. Soc. Rev. 2002, 31, 239. (e) Nikonov, G. I. Adv.
Organomet. Chem. 2005, 53, 217.
Hieringer, W.; Herrmann, W. A.; Anwander, R. J. Am. Chem. Soc. 2000, 122,
::
3080. (f ) Klimpel, M. G.; Gorlitzer, H. W.; Tafipolsky, M.; Spiegler, M.; Scherer,
W.; Anwander, R. J. Organomet. Chem. 2002, 647, 236. (g) Rees, W. S.; Just, O.;
Schumann, H.; Weimann, R. Angew. Chem., Int. Ed. Engl. 1996, 35, 419.
r
2009 American Chemical Society
Published on Web 06/08/2009
pubs.acs.org/IC

9606 Inorganic Chemistry, Vol. 48, No. 20, 2009
Ignatov et al.
Scheme 1. Product Diversity in the Reactions of Group 5 Cp/Imido
Compounds with Silanes
(RN)M(PMe3)2. Here we report that such reactions with
hydrochlorosilanes HSiCl3R3-n (n = 1-3) afford a wider
spectrum of silylamido β-Si-H agostic species, and in one
case (for the silane HSiCl3) lead to a productive silane/imido
coupling reaction furnishing an equivalent of silanimine.
A preliminary communication of part of this work has been
published.7
Results and Discussion
Starting Compounds. The reduction of precursors
(RN)2MCl2(DME) (M=Mo, W) has been earlier re-
ported to give several types of compounds. Sodium
amalgam reduction of (ArN)2WCl2(DME) (Ar =
2,6-iPr2C6H3) in the presence of PMe2Ph affords the bis
(phosphine) compound (ArN)2W(PMe2Ph)2.8 Gibson
has reported the X-ray structure of the related compound
(ArN)2Mo(PMe3)2.9 On the other hand, Sundermeyer
et al. provided evidence that for a less bulky imido group
(R =Mes) the tris(phosphine) compound (MesN)2Mo
(PMe3)3 exists in equilibrium with its bis(phosphine) form
and free PMe3.10 In contrast, magnesium reduction
of (tBuN)2MoCl2(DME) was reported to furnish the
imido-bridged dimer [(tBuN)(Me3P)Mo(μ-NtBu)]2.11 In
this work, we found that magnesium reduction of
(RN)2MCl2(DME) (R = Ar or Ar0) in the presence of
excess PMe3 always gives tris(phosphine) compounds
(RN)2M(PMe3)3 (M=Mo, W) existing in solution in
equilibrium with the corresponding bis(phosphine) deri-
vative and free PMe3.
This approach puts severe limitations of the nature of R
groups on silicon, hampering the investigation of substituent
effects of the extent of the Si-H interaction.
We have recently reported an alternative pathway to
β-Si-H silylamido agostic species based on direct coupling
between silanes and reactive transition metal imido com-
pounds.3-5 For Group 5 Cp/imido derivatives Cp(RN)M-
(PMe3)2, their reactions with silanes HSiR03 (R0 = Me, Ph,
Cl, H) afford three types of products: the silyl hydride
compounds Cp(RN)M(PMe3)H(SiR03) (M = V, Nb, Ta),
In the case where R = tBu, the magnesium reduction of
(tBuN)2MoCl2(DME) in the presence of 5 to 7 equiv of
PMe3 affords a mixture of a new bis(phosphine) com-
pound (tBuN)2Mo(PMe3)2 (2a) and the previously
reported dimer [(tBuN)(PMe3)Mo(μ-NtBu)]2. The yield
of 2a increases when more phosphine is used. Addition of
excess PMe3 to [(tBuN)(PMe3)Mo(μ-NtBu)]2 does not
convert it into monomeric 2a, even upon heating to
70 °C for several days. However, we found that very
prolonged heating (3 weeks) of a mixture of (2a) and
[(tBuN)(PMe3)Mo(μ-NtBu)]2 at 70 °C results in selective
decomposition of the latter into insoluble product(s) of
unknown composition, leaving 2a as the single compo-
nent of the solution. Interestingly, there is no formation
of free phosphine during this decomposition, suggesting
that the product is a higher oligomer of {(tBuN)2(PMe3)-
Mo} having the same composition. Furthermore, in
the presence of excess PMe3, degradation of [(tBuN)-
(PMe3)Mo(μ-NtBu)]2 slows significantly, suggesting
that phosphine elimination is the rate determining step.
In summary, the thermolysis of a mixture of 2a and
the agostic compounds Cp(η2-RN-SiR02-H )Nb(PMe3)Cl,
3 3 3
and the silyl chloride compounds Cp(RN)M(PMe3)Cl-
(SiR0HCl) (M = Nb, Ta) (Scheme 1). The formation and
interconversion of these species is determined by the nature of
the metal, M, and the substituents at silicon and nitrogen.4
Taking into account the isolobal relationship between the
imide (RN2-) and cyclopentadienide (Cp-) groups,6 we
became interested in investigating the reactions of hydro-
silanes with Group 6 bis(imido) compounds (RN)2M(PMe3)3
(M =Mo, W), isolobal to Group 5 Cp/imido compounds Cp
(3) (a) Nikonov, G. I.; Mountford, P.; Ignatov, S. K.; Green, J. C.; Cooke,
P. A.; Leech, M. A.; Kuzmina, L. G.; Razuvaev, A. G.; Rees, N. H.; Blake,
A. J.; Howard, J. A. K.; Lemenovskii, D. A. Dalton Trans. 2001, 2903.
(b) Dubberley, S. R.; Ignatov, S. K.; Rees, N. H.; Razuvaev, A. G.;
Mountford, P.; Nikonov, G. I. J. Am. Chem. Soc. 2003, 125, 642.
(c) Nikonov, G. I.; Mountford, P.; Dubberley, S. R. Inorg. Chem. 2003,
42, 258.
(4) Ignatov, S. K.; Merkoulov, A. A.; Rees, N. H.; Dubberley, S. R.;
Razuvaev, A. G.; Mountford, P.; Nikonov, G. I. Chem.;Eur. J. 2008, 14,
296–310.
(5) Silane/imido coupling to give silanimines is also known: Burckhardt,
U.; Casty, G. L.; Tilley, T. D.; Woo, T. W.; Rothlisberger, U. Organo-
metallics 2000, 19, 3830.
(7) (a) Ignatov, S. K.; Rees, N. H.; Dubberley, S. R.; Razuvaev, A. G.;
Mountford, P.; Nikonov, G. I. Chem. Commun. 2004, 952. (b) for related
reactions of (ArN)2Mo(PMe3)3 with H3SiPh see: Khalimon, A. Y.;
Simionescu, R.; Kuzmina, L. G.; Howard, J. A. K; Nikonov, G. I. Angew.
Chem., Int. Ed. 2008, 47, 7701.
(6) (a) Williams, D. S.; Schofield, M. H.; Anhaus, J. T.; Schrock, R. R.
J. Am. Chem. Soc. 1990, 112, 6728. (b) Glueck, D. S.; Green, J. C.;
Michelman, R. I.; Wright, I. N. Organometallics 1992, 11, 4221. (c) Williams,
D. N.; Mitchell, J. P.; Pool, A. D.; Siemeling, U.; Clegg, W.; Hockless, D. C.
R.; O’Neil, P. A.; Gibson, V. C. J. Chem. Soc., Dalton.Trans. 1992, 739. (d)
Sundermeyer, J.; Runge, D. Angew. Chem., Int. Ed. Engl. 1994, 33, 1255. (e)
Gibson, V. C. J. Chem. Soc., Dalton Trans. 1994, 1607. (f) Wigley, D. E.
Prog. Inorg. Chem. 1994, 42, 239.
(8) Williams, D. S.; Schofield, M. H.; Schrock, R. R. Organometallics
1993, 12, 4560.
(9) Dyer, P. W.; Gibson, V. C.; Howard, J. A. K.; Wilson, C.
J. Organomet. Chem. 1993, 462, C15.
(10) Radius, U.; Sundermeyer, J.; Pritzkow, H. Chem. Ber. 1994, 127,
1827.
(11) Dyer, P. W.; Gibson, V. C.; Clegg, W. J. Chem. Soc., Dalton Trans.
1995, 3313.

Article
Inorganic Chemistry, Vol. 48, No. 20, 2009 9607
Scheme 2. Reactions of (RN)2Mo(PMe3)3 with Silanes HSiR02Cl and HSiMeCl2
Table 1. Selected NMR Data for the β-Agostic Silylamido Compounds
compound
δ (1H) Mo-H-Si, ppm [J(P-H), Hz]
δ 29Si, ppm a
1J(Si-H),Hz a
(tBuN)(η2-tBuNSiMe2H)Mo(PMe3)2Cl (3a)
(ArN)(η2-ArNSiMe2H)Mo(PMe3)2Cl (3b)
(Ar0N)(η2-Ar0NSiMe2H)Mo(PMe3)2Cl (3c)
(tBuN)(η2-tBuNSiMePhH)Mo(PMe3)2Cl (4a)
(Ar0N)(η2-Ar0NSiMePhH)Mo(PMe3)2Cl (4b)
(tBuN)(η2-tBuNSiMeClH)Mo(PMe3)2Cl (6a)
(ArN)(η2-ArNSiMeClH)Mo(PMe3)2Cl (6b)
(Ar0N)(η2-Ar0NSiMeClH)Mo(PMe3)2Cl (6c)
1.4b,c
-76.0
-64.9
-63.8f
-79.9
-69.3d
-74.2
-68.7f
-70.1
-70.5f
93
97
0.88 [t, 7.5 ]
1.68f [dd, 3.5, 23.5]
1.83 b,c,e
98f
94
2.14c,d [t, 22]
1.45 [dd, 3.6, 0.9]
1.23b,c,f
98d
123
130f
129
135.6f
2.02g [dd, 4, 20]
a At room temperature unless otherwise stated. b The signal is obscured by other resonances. c Found from 1H-29Si HMQC. d At -40 °C. e At -20 °C.
f At -50 °C. g At -70 °C.
[(tBuN)(PMe3)Mo(μ-NtBu)]2 allows for the production
of pure compound 2a.
[dd, J(P-H) = 3.6 Hz, J(P-H) = 0.9 Hz], two non-
t
equivalent Bu signals at δ 1.54 (imido) and δ 1.15
Reactions of (RN)2Mo(PMe3)n (n = 2,3) with Mono- and
Dichlorosilanes. Molybdenum compounds (RN)2Mo-
(PMe3)n (2; n = 2, R = But (a); n = 3, Ar (b); n = 3, Ar0
(c)) react with mono- and dichlorosilanes to give exclu-
sively the β-Si-H agostic compounds (RN)(η3-RN-
(amido), and the SiMe signal at δ 1.19. The agostic
hydride gives rise to a band at 1851 cm-1 in the IR
spectrum. Compounds 3c, 4a, 4c, 5a, and 6b,c are flux-
ional in solution at room temperature.
The formulation of compound 6a and its congeners as
agostic species is unequivocally supported by the mea-
surements of silicon-hydride coupling constants from the
29Si NMR spectra (Table 1). These values are about half
of those in the parent silanes but significantly larger than
for non-interacting silyl and hydride groups (3-10 Hz).14
Notably, the J(H-Si) of 97 Hz in 3b and 3c is the same as
that observed for the isolobal compound Cp(η3-ArN-
SiR02H )MoCl(PMe3)2 (R02 = Me2 (3a-c), MePh (4a-
3 3 3
c), Ph2 (5a-c), MeCl (6a-c), Scheme 2). The isomeric
silyl hydride compounds (RN)2Mo(SiR02Cl)H(PMe3) were
not observed even when the reactions were monitored
by low temperature NMR.12 The agostic compounds
3-6 are metastable, slowly decomposing in mother
liquor to the thermodynamically stable products (RN)-
MoCl2(PMe3)3 (7, Scheme 2).13 The main silicon co-
product 0 of this reaction is the silanimine dimer
(RNSiR 2)2, whose formation manifests productive
coupling of the imido ligand with the silane. Similar
behavior has been previously observed for silane addi-
tions to the isolobal Group 5 compounds Cp(RN)M-
(PR03)2 (R =Ar or Ar0), for which the initial agostic or
silyl hydride products were found to be intermediates on
the way to dichlorides Cp(RN)MCl2(PR03) and
CpMCl2(PR03)3.4
SiMe2H )NbCl(PMe3).3a Chlorine substitution at sili-
3 3 3
con leads to increased Si-H coupling constants (e.g., 123
Hz in 6a); however, these increased values do not corre-
spond to a stronger Si-H bonding but are instead a result
of rehybridization at the silicon center.7a
The rate of silane addition in Scheme 2 appears to be
controlled by steric factors. The relatively unhindered
compounds 2a and 2c react over a period of several hours.
Compound 2b (bearing a more sterically demanding Ar
group at nitrogen) reacts with silane HSiMe2Cl over-
night, whereas its reaction with the more hindered HSi-
MePhCl takes several days and is accompanied by
significant decomposition to 7b. The bulkiest silane stu-
died, HSiPh2Cl, does not react at all with 2b, even after
several days.
The agostic compounds 3-6 were characterized by
multinuclear NMR, IR, and X-ray structure determina-
tions for compounds 3c and 6c.7 For example, the
1H NMR spectrum of compound 6a exhibits the agostic
Si-H M hydride as a P-coupled signal at δ 1.45
3 3 3
The reaction of (ArN)2Mo(PMe3)3 with HSiMeCl2 was
studied by low temperature NMR in toluene-d8. At
-40 °C, the reaction is 30% complete after 5 min. No
intermediates or byproduct such as (ArN)2Mo(PMe3)H-
(SiMeCl2) or a Si-Cl-Mo bridged compound (ArN)-
(12) In the related Nb chemistry, the silyl hydride Cp(ArN)Nb(PMe3)H-
(SiMe2Cl) is the kinetic product of silane addition to Cp(ArN)Nb(PMe3)2
which has the β-agostic compound Cp(ArNSiMe2-H)Nb(PMe3)Cl as the
thermodynamic product (ref 3a).
(13) (a) Compound (tBuN)MoCl2(PMe3)3 has been previously prepared
by another route: Green, M. L. H.; Konidaris, P. C.; Mountford, P.;
Simpson, S. J. Chem. Commun. 1992, 256. (b) X-ray structure of the related
compound (PhN)WCl2(PPh3)3 is available: Bradley, D. C.; Hursthouse, M.
B.; Malik, K. M. A.; Nielson, A. J.; Short, R. L. J. Chem. Soc., Dalton Trans.
1983, 2651.
(η2-ArNSiClH-Cl )Mo(PMe3)2Cl (vide infra) were
3 3 3
observed, but traces of the decomposition product 7b
were detected in the 31P NMR spectrum. On warming the
(14) Schubert, U. Adv. Organomet. Chem. 1990, 30, 151.

9608 Inorganic Chemistry, Vol. 48, No. 20, 2009
Ignatov et al.
Scheme 3. Degenerate Exchange Equilibrium in Compound 3c (Two
Enantiomers, “A” and “B”)
Table 2. Activation Parameters for the Various Exchange Processes in Com-
pound 3ca
exchanging
groups
ΔH‡
ΔS‡
ΔG‡
(kcal mol-1
)
(cal mol-1 K-1
)
(285 K, kcal mol-1
)
Me1TMe2
Me3TMe4
Me6TMe7
Me8TMe9
10.9(2)
10.8(1)
10.2(3)
9.7(3)
-10(1)
-11(1)
-13(1)
-15(1)
13.9(3)
13.9(2)
13.9(4)
13.9(4)
a See Scheme 3 for numbering scheme.
silicon. Indeed, at -40 °C signals of the second diaster-
eomer were observed by 1H and 31P NMR and coalesced
signals were found at positions corresponding to weighted
average shifts in the major and minor isomers. Unfortu-
nately, the low abundance of the minor diastereomer
(∼5%) hampered quantitative analysis. We, however,
succeeded in measuring the rate constant for phosphine
group exchange at 0 °C (ca. 120 s-1), which is comparable
to the PMe3 exchange for the compound 3c (ca. 78 s-1) and
suggests the occurrence of a similar mechanism.
Reactions of (RN)2Mo(PMe3)3 with HSiCl3. Room
temperature reactions of molybdenum compounds 2a-
c with HSiCl3 afford the corresponding monoimido
compounds 7a-c and the silanimine dimers (-RN-
SiHCl-)2 (eq 1). Some variable amount of the free amine
H2NR was also observed, when the reaction was carried
on the NMR tube scale.
sample to 0 °C for 5 min, a fluxional agostic product 6b
1
forms quantitatively. Its H NMR spectrum at -50 °C
exhibits four nonequivalent signals for the CH protons
of the Ar groups. The Si-H-Mo signal at about δ 1.23
is obscured by other groups, but its chemical shift
could be determined from a 1H-29Si HMQC experiment.
The corresponding 29Si signal is found at δ -68.7 (at
-50 °C). When the reaction was scaled up (diethyl ether,
room temperature for 30 min) the products were
compound 6b and (ArN)Mo(PMe3)3Cl2.
Variable Temperature (VT) NMR Study of 3c and 6c.
As mentioned above, some of the agostic products in
Scheme 2 are fluxional. To gain an understanding of the
dynamic processes involved, VT NMR studies were
performed for compounds 3c and 6c.
The room temperature 1H NMR spectrum of 3c shows
only featureless signals in the aliphatic and aromatic
regions. Lowering the temperature reveals the presence
of only one compound, exhibiting nonequivalent methyl
groups in the amido, imido, and silyl ligands. VT 1H and
31P NMR experiments between -40 and +65 °C revealed
the pairwise methyl group exchange processes Me2 T
Me1, Me7 T Me6, Me8 T Me9, and Me3 T Me4 (see
Scheme 3 for the numbering scheme). This exchange is
degenerate, in the sense that species A and B in Scheme 3
are enantiomers and thus are isoenergetic and indistin-
guishable by NMR. The exchange rates for these four
different processes resulted, within experimental error,
in the same value of the free energy of activation 13.9(3)
kcal mol-1 (Table 2).
The reaction of (ArN)2Mo(PMe3)3 with HSiCl3 at low
temperature was followed by NMR. At -30 °C, the
formation of an initial bis(phopshine) product with two
broad 31P NMR singlets of equal intensity at 20.0 and
-2.6 ppm was observed. This complex shows a downfield
1
SiH signal at 7.10 ppm coupled in H-29Si HSQC with
1
the 29Si NMR signal at -31.8 ppm with J(Si-H) =
1
337.5 Hz (from 29Si INEPT). The large value J(Si-H)
and the fact that neither the SiH signal nor the 29Si NMR
signal are coupled to phosphorus suggest that the SiH
group is not coordinated to metal. These structural
features are consistent with the formation of a silylamido
The coincidence of the exchange rates in the silyl,
amido, imido, and phosphine ligands suggests that there
is a single, highly correlated mechanism of exchange as
summarized in Scheme 4. This appears to proceed via the
complex (ArN)(ArNSiHCl-Cl )Mo(PMe3)2Cl (8b),
3 3 3
partial opening of the Si-H Mo agostic bond, rotation
which presumably has an additional coordination of
one of the Si-bound chlorides to molybdenum, allowing
for the formation of a 18e species. We have no evidence
for the formation of the Si-Cl-Mo bridge, but this
inference is a reasonable alternative to the otherwise
16-electron imido-amido species (ArN)(Ar{Cl2HSi}N)-
Mo(PMe3)2Cl. Further warming the reaction mixture to
-15 °C - 0 °C leads to a slow rearrangement of the initial
product into another bis(phosphine) compound exhibit-
ing a large J(P-P) coupling constant of 223.5 Hz, sug-
gesting the trans arrangement of phosphine ligands. In
the 1H NMR spectrum, this derivative shows a downfield
SiH signal at 6.01 ppm coupled to one of the phos-
phines with the3J(H-P) = 9.0 Hz and also coupled
3 3 3
around the N-Mo bond, and is completed by the ring
closure on the other side of the compound, as shown in
Scheme 4. The ΔSq values (Table 2) are all somewhat
negative which allows us to rule out phosphine dissocia-
tion as a possible step in exchange. The small negative
entropy of activation is consistent with the process shown
in Scheme 4 as it evidently proceeds via a very organized
transition state, highly constrained by steric factors.
The observed fluxionality of the chlorosilyl derivative
6c appears to follow the same mechanism. The quanti-
tative analysis proved more difficult for it involves
exchange between two diastereomers stemming from
the presence of two chiral centers, molybdenum and

Article
Inorganic Chemistry, Vol. 48, No. 20, 2009 9609
Scheme 4. Mechanism of Enantiomer Exchange for 3c
(by 1H-29Si HSQC NMR) to the 29Si signal at -42.4 ppm
(dd, 1J(Si-H) = 327.0 Hz, 2J(Si-P) = 22.1 Hz). The large
value of 1J(Si-H) is consistent with the Si-H bond being
uncoordinate to the metal, whereas the large 2J(Si-P) and
3
small J(SiH-P) constants show that the silicon atom is
directly bound to molybdenum. All together these NMR
features suggest the formation of a silanimine complex
(ArN)(η2-ArN=SiHCl)Mo(PMe3)3Cl2 (9b), which could
be a direct precursor to the compound 7b.15 Consistent
with this description, addition of an equivalent of PMe3 to
this mixture results in immediate formation of 7b.
Reactions of (RN)2W(PMe3)3 with Mono- And Dichlo-
rosilanes. The reactions of the tungsten precursors
(RN)2W(PMe3)3 (R = Ar, Ar0) with silanes are more
complicated and generally less clean than the analogous
reactions of the molybdenum compounds 2a-c. Addition
of HSiMeCl2 to (ArN)2W(PMe3)3 (10b) in pentane, fol-
lowed by the immediate removal of volatiles and recrys-
tallization from diethyl ether, allows for the isolation of
a yellow crystalline compound (ArN)2W(PMe3)H(Si-
MeCl2) (11b). Compound 11b was characterized by
NMR, IR, and X-ray diffraction analysis. In particular,
the W-bound hydride gives rise to a doublet at 10.24 ppm
(J(P-H) = 59.5 Hz) flanked by 183W satellites (J(W-H)=
35.0 Hz) in the 1H NMR. The corresponding
Figure 1. Molecular structure of compound 11b. Hydrogen atoms,
˚
apart from the hydride, are omitted for clarity. Selected distances (A)
and angles (deg): W1-N2 1.779(3), W1-N1 1.789(3), W1-P 2.4778(9),
W1-Si 2.5106(9), W1-H 1.78(4), Si-C28 1.900(3), Si-Cl2 2.0710(14),
Si-Cl1 2.1075(13), N2-W1-N1 121.02(12), N2-W1-P 96.97(8),
N1-W1-P 110.38(8), N2-W1-Si 96.16(8), N1-W1-Si 107.55(8),
P-W1-Si 124.91(3), P-W1-H 66.6(13), Si-W1-H 60.2(13), Cl2-
Si-Cl1 102.38(6), C28-Si-W1 115.28(11), Cl2-Si-W1 115.43(5),
Cl1-Si-W1 113.25(5).
compounds Cp2Ti(PMe3)H(SiClR2)16 and Cp(RN)Ta
(PMe3)H(SiClR2)3b which both exhibit an interligand
hypervalent interaction (IHIs) between the hydride and
silicon centers.4b,17,18
The molecular structure of 11b is shown in Figure 1.
The structure is isolobal with the previously structurally
characterized compounds Cp2Ti(PMe3)H(SiCl2Me)16
and Cp(ArN)Ta(PMe3)H(SiCl2Me).3b Like the latter com-
pounds, the phosphine, hydride, and silyl ligands lie in the
bisecting plane of the pseudometallocene fragment
(ArN)2W.6 The silyl ligand is oriented in such a way that
one of the chloride substituents lies approximately trans
to the hydride. This chloride forms a longer Si-Cl bond
ν(W-H) band in the IR spectrum is seen at 1731 cm-1
.
This hydride is coupled to a 29Si NMR signal at 92.0 ppm
(d, J(P-Si) = 7.5 Hz) with a coupling constant of
-37 Hz. Such an increased magnitude of J(H-Si) com-
pared to values observed in classical silyl hydride com-
plexes (0-10 Hz)1 suggests the presence of nonclassical
Si-H bonding.1e Moreover, the negative sign of this
coupling constant, measured by us in this study, is in
accord with the presence of direct Si-H bonding.16
Analogous negative J(Si-H) values with increased mag-
nitudes have been previously found for the isolobal
˚
of 2.107(2) A compared with the other Si-Cl (Si-Cl(2) =
˚
2.071(2) A). These values correspond well to the Si-Cl
(15) For isolated silaniminecomplexesLnM(η2-RNSiR02) see: (a) Procopio,
L. J.; Carroll, P. J.; Berry, D. H. J. Am. Chem. Soc. 1991, 113, 1870–1872.
(b) Procopio, L. J.; Carroll, P. J.; Berry, D. H. Polyhedron 1995, 14, 45–55.
(c) For a transient silanimine complex see ref 7b.
(16) Ignatov, S. K.; Rees, N. H.; Tyrrell, B. R.; Dubberley, S. R.;
Razuvaev, A. G.; Mountford, P.; Nikonov, G. I. Chem.;Eur. J. 2004, 10,
4991.
(17) Ignatov, S. K.; Rees, N. H.; Merkoulov, A. L.; Dubberley, S. R.;
Razuvaev, A. G.; Mountford, P.; Nikonov, G. I. Organometallics 2008, 27,
5968–5977.
(18) Negative J(H-Si) was calculated for silane σ-complexes Cp(Me3P)Ru-
(Cl)(η2-HSiR3): Osipov, A. L.; Vyboishchikov, S. F.; Dorogov, K. Y.;
Kuzmina, L. G.; Howard, J. A. K.; Lemenovskii, D. A.; Nikonov, G. I.
Chem. Commun. 2005, 3349.

9610 Inorganic Chemistry, Vol. 48, No. 20, 2009
Scheme 5. Preparation of Compounds 11b and 12b
Ignatov et al.
bonds in the related nonclassical compound Cp(ArN)-
˚
NMR spectrum and the observation of three methine
C-H signals in the ratio 1:2:1 in the 1H NMR spectrum
allow us to rule out unequivocally the formation of a
compound such as (ArN)2W(PMe3)Cl(SiMeClH) that
would be isolobal to Cp(ArN)Nb(PMe3)Cl(SiMeClH).3c
The spectroscopic data can best be rationalized in terms
of the formation of a fluxional SiCl-W bridged species
˚
Ta(PMe3)H(SiCl2Me), 2.117(2) A and 2.064(3) A, respec-
tively.3c The W-Si bond length (2.5108(13) A) is rela-
˚
tively short in comparison to other silyl compounds of
tungsten (range 2.533-2.685 A),19 although precise com-
˚
parisons are not possible because none of the latter
contain a dichlorosilyl ligand and/or supporting imido
ligand.20 The short M-Si bond and the elongated Si-Cl
bond trans to the hydride are characteristic features of
(ArN)(η2-ArNSiMeH-Cl )W(PMe3)2Cl (12b), similar
3 3 3
to the Mo compound 8b discussed above.21 Interestingly,
the 29Si NMR spectrum measured at room temperature
overnight showed the presence of a Si-H-W agostic
signal at -90.6 ppm (d, J(H-Si) = 92 Hz) in addition
to other signals. These signals come from the thermal
decomposition of 12b.
IHIs.1e,3,4,16 The W-H bond length of 1.78(6) A lies
˚
within normal ranges. Although the experimentally de-
˚
termined Si-H distance of 2.283 A is too long to suggest
the presence of a significant Si-H interaction, it should
be taken into account that the precise location of a
hydride in a heavy element environment is subject to
significant uncertainty.
These observations are consistent with the reaction
sequence presented in Scheme 5. The silyl hydride com-
pound 11b is formed as a kinetic product, which then
reacts with an equivalent of phosphine to give 12b. The
latter slowly rearranges to (or is in equilibrium with) a β-
Monitoring the reaction between HSiMeCl2 and
(ArN)2W(PMe3)3 by NMR shows that at room tempera-
ture 11b forms within minutes but then decomposes in the
mother liquor over 20-30 min into a new, highly fluxional
bis(phosphine) compound 12b. In contrast, pure 11b is
stable in solution for at least several hours. The salient
Si-H agostic compound (ArN)(η2-ArNSiClMe-H )W-
3 3 3
(PMe3)2Cl (13b). This behavior is reminiscent of the
reactions of the isolobal niobium compounds Cp(RN)-
Nb(PMe3)2 with silanes, where the initially formed com-
pounds Cp(RN)Nb(SiR02Cl)H(PMe3) rearrange into the
1
feature of 12b is that at -40 °C its H NMR spectrum
exhibits a downfield signal for the Si-H bond at 5.78 ppm
(q, J(H-H) = 2.4 Hz) coupled to the Me signal at
0.19 ppm (d, J(H-H) = 2.4 Hz). The large value of
J(H-Si) = 264 Hz clearly establishes that this Si-H
bond is not coordinated to the metal. The corresponding
29Si signal appears at 41.8 ppm. The presence of two
chemically nonequivalent phosphine ligands in the 31P
agostic product Cp(η2-RN-SiR02-H )NbCl(PMe3) (for
3 3 3
R02 = Me2, MePh) or to the silyl chloride compounds Cp-
(RN)Nb(SiMeClH)Cl(PMe3) in the case of R02 = MeCl.
Both of these reactions are catalyzed by PMe3.4 The
rearrangement proceeds via the same Lewis acid-
base adduct/intermediate Cp(RN{fSiMe2-nClnH})Nb-
(PMe3)2 that is formed upon silane addition to the imido
nitrogen of Cp(RN)Nb(PMe3)2.4 The only difference
between this and tungsten chemistry is that a silyl chloride
product of the type (ArN)2W(PMe3)Cl(SiMeClH) is not
formed according to the NMR data.
(19) (a) Sakaba, H.; Hirata, T.; Kabuto, C.; Horino, H. Chem. Lett. 2001,
1078. (b) Sakaba, H.; Tsukamoto, M.; Hirata, T.; Kabuto, C.; Horino, H.
J. Am. Chem. Soc. 2000, 122, 11511. (c) Ueno, K.; Sakai, M.; Ogino, H.
Organometallics 1998, 17, 2138. (d) Figge, L. K.; Carrol, P. J.; Berry, D. H.
Organometallics 1996, 15, 209. (e) Malisch, W.; Schmitzer, S.; Lankat, R.;
Neumayer, M.; Prechtl, F.; Adam, W. Chem. Ber. 1995, 128, 1251.
In accordance with this mechanism, the addition of
PMe3 to a solution of pure (ArN)2W(PMe3)H(SiMeCl2)
(11b) results in immediate color change from yellow to
brown and the formation of a mixture of compounds
composed of 12b, the starting compound (ArN)2W-
(PMe3)3, and the free silane.
(f) Koloski, T. S.; Pestana, D. C.; Carrol, P. J.; Berry, D. H. Organometallics
::
1994, 13, 489. (g) Schmitzer, S.; Weis, U.; Kab, H.; Buchner, W.; Malisch,
W.; Polzer, T.; Posset, U.; Kiefer, W. Inorg. Chem. 1993, 32, 303. (h) H
Sharma, S.; Kapoor, R. N.; Cervantes-Lee, F.; Pannell, K. H. Polyhedron
1991, 10, 1177. (i) Barron, A. R.; Wilkinson, G.; Motevalli, M.; Hursthouse,
M. B. Dalton Trans. 1987, 837. (k) Darensbourg, D. J.; Bauch, C. G.;
Reibenspies, J. H.; Rheingold, A. L. Inorg. Chem. 1988, 27, 4203. (l) Heyn, R.
H.; Tilley, T. D. Inorg. Chem. 1990, 29, 4051. (m) Suzuki, E.; Okazaki, M.;
Tobita, H. Chem. Lett. 2005, 34, 1026. (n) Begum, R.; Komuro, T.; Tobita,
H. Chem.Commun. 2006, 432. (o) Wagner, H.; Baumgartner, J.; Marschner,
C. Organometallics 2005, 24, 4649. (p) Wang, B.; Zhu, B.; Xu, S.; Zhou, X.
Organometallics 2003, 22, 4842. (q) Palitzsch, W.; Beyer, C.; Bohme, U.;
Rittmeister, B.; Roewer, G. Eur. J. Inorg. Chem. 1999, 1813. (r) Mork, B. V.;
Tilley, T. D. J. Am. Chem. Soc. 2004, 126, 4375. (s) Ueno, K.; Asami, S.;
Watanabe, N.; Ogino, H. Organometallics 2002, 21, 1326. (t) Ueno, K.;
Sakai, M.; Ogino, H. Organometallics 1998, 17, 2138.
The reaction between HSiCl2Me and the less hindered
precursor (Ar0N)2W(PMe3)3 affords the agostic com-
pound (Ar0N)(η3-Ar0NSiClMe-H )W(PMe3)2Cl (13c,
3 3 3
eq 2). Compound 13c was isolated in the form of dark
crystals and characterized by NMR and IR spectroscopy.
In contrast to its Mo analogue 6c (Scheme 2), 13c is
non-fluxional at room temperature. Two nonequivalent
(20) There has been described only one silyl derivative of tungsten
supported by the bis(imido) ligand set, (ArN)2W(Si{SiMe3}3)(CH2CH3),
but its structure is not known. In the molybdenum analogue, the Mo-Si bond
is 2.6048(9) A; Casty, G. L.; Tilley, T. D.; Yap, G. P. A.; Rheingold, A. L.
Organometallics 1997, 16, 4746.
(21) Again, as in the case of molybdenum compound (ArN)(ArNSiClH-
Cl )Mo(PMe3)2Cl (8b), we have no direct evidence of the chloride lone
3 3 3
pair donation to tungsten, but the formation of a Si-Cl W bridge appears
3 3 3
˚
to be a good alternative to the otherwise 16e compound (ArN)(ArNSi-
MeHCl)W(PMe3)2Cl.

Article
Inorganic Chemistry, Vol. 48, No. 20, 2009 9611
phosphines give rise to doublets (J(P-P) = 14 Hz) at
-20.7 ppm and -29.9 ppm, flanked by 183W satellites
(J(P-W) = 204 and 168 Hz, respectively). The agostic
(ArN)WCl2(PMe3)3 (15b). Apart from the latter com-
pound, there are also other products formed, but their
identities remain unknown. Similarly, (Ar0N)2W(PMe3)3
(10c) reacts rapidly with HSiCl3 (5 min) to furnish (Ar0N)-
WCl2(PMe3)3 (15c) and (Ar0NSiHCl)2 as the final pro-
ducts.
W
H-Si hydride is seen in the 1H NMR as a multiplet at
3 3 3
2.46 ppm coupled to the Si-Me group and two phos-
phorus atoms (ddq, J(P-H) = 16.7 Hz, J(H-H) = 1.5
Hz, J(P-H) = 0.6 Hz). The corresponding 29Si signal was
found at -77.5 ppm. The H-Si coupling constant of 118
Unlike the related Mo chemistry, when (ArN)2W-
(PMe3)3 reacts with HSiCl3 in the presence of BPh3 at
low temperature, the initial product observed at -20 °C is
the silyl hydride (ArN)2W(H)(SiCl3)(PMe3) (16b). This
compound shows a W-bound hydride at 11.04 ppm
coupled to phosphine (2J(H-P) = 58.8 Hz) and tungsten
(J(W-H) = 31.8 Hz) but only weakly coupled to the 29Si
1
Hz determined from the H-coupled 29Si NMR unequi-
vocally establishes the presence of an agostic W H-Si
3 30 3
interaction. The silyl hydride compound (Ar N)2W-
(PMe3)H(SiMeCl2) and the Si-Cl-W bridged
compound (Ar0N)(η2-Ar0NSiMeH-Cl )W(PMe3)2Cl,
3 3 3
1
which would be analogous to the products 11b and 12b
formed in the corresponding reactions of (ArN)2W-
(PMe3)3 (Scheme 5), were not observed.
signal at 73.8 ppm (the cross-peak in H-29Si HSQC
NMR is observed only when a small J(Si-H) = 7 Hz is
used). These structural features resemble strongly the
pattern observed for the silyl hydride complex 11b. Upon
the increase of temperature to room temperature, this
product decomposes to a mixture of 15b and several
uncharacterized hydride species.
Density Functional Theory (DFT) Calculations. At first
sight, the transformations described above for the
Group 6 (RN)2M(PMe3)n (n = 2,3) systems are similar to
the previously described reactions of Cp(RN)M(PMe3)2
(M = V, Nb, Ta) with silanes.3,4 The significant dif-
ference, however, is that molybdenum compounds
(RN)2Mo(PMe3)n (2; R = Ar, Ar0, But) react with mono-
and dichlorosilanes HSiClnR03-n (n = 1,2) to give exclu-
Addition of HSiClMe2 to a pentane solution of
(Ar0N)2W(PMe3)3 affords a mixture of products, the
predominant component of which is a highly fluxional
agostic compound (Ar0N)(η2-Ar0NSiMe2-H )WCl-
3 3 3
sively the agostic compounds (RN)(η3-RN-SiR02H )-
(PMe3)3 (14c) characterized by its 29Si NMR signal
3 3 3
MoCl(PMe3)2 (R = Ar, Ar0, But), whereas reactions of
their niobium analogues Cp(RN)Nb(PMe3)3 (R = Ar,
Ar0) afford a variety of products, namely Cp(RN)Nb-
at -68.3 ppm coupled to the Si-H W resonance at
3 3 3
2.24 ppm (d, J(P-H) =23.6 Hz, 1J(Si-H) = 87 Hz). The
analogous reaction of (ArN)2W(PMe3)3 with HSiClMe2
gives an even more complicated mixture containing
(PMe3)H(SiR3), Cp(η3-RN-SiR00 -H )Nb(PMe3)Cl,
2
3 3 3
the agostic compound (ArN)(η2-ArNSiMe2-H )WCl
and Cp(RN)Nb(PMe3)Cl(SiRHCl), whose identity de-
pends on the substituents at silicon and reaction condi-
tions. In contrast, the tantalum congener forms only the
silyl hydride derivatives Cp(RN)Ta(PMe3)H(SiR3) and,
in a few cases, silyl chloride compounds Cp(RN)Ta-
(PMe3)Cl(SiRHCl), whereas the reactions of the tungsten
compounds (RN)2W(PMe3)3 (R = Ar, Ar0) with HSi-
Me2Cl and HSiMeCl2 give several silyl hydride and
agostic silylamido products. This difference between the
4d and 5d metals reflects (i) the better ability of the
heavier metals to stabilize higher oxidation states and
(ii) the diminished propensity of Group 6 metals to be in
the highest Group oxidation state (VI) in comparison
with Group 5 metals.
3 3 3
(PMe3)2 (14b), the dichloride (ArN)WCl2(PMe3)3 (15b),
and some other unidentified compounds. Compound
(ArN)(η2-ArNSiMe2-H )WCl(PMe3)2 is fluxional
3 3 3
at room temperature. It was characterized by a 29Si
NMR signal at δ -70 ppm (J(Si-H) = 81 Hz,
J(Si-P) = 9 Hz). Another compound, giving rise to
a
29Si NMR signal at δ -9.8 ppm with the J(Si-H) =
199 Hz, contains a free SiMe2H group but other details of
its structure are not known. Attempted separation of this
mixture by recrystallization afforded only complex 15b
as the final decomposition product.
Our previous studies of the mechanism ofsilaneaddition
to compounds Cp(RN)Nb(PMe3)2 revealed that the reac-
tiongoesvia direct addition of silane to the imido moiety to
give the intermediate Cp(RN)(RNfSiR2ClH )NbCl
(PMe3)2 with a pentacoordinate silicon center, supported
3 3 3
by agostic Si-H Nb bonding rather than via phosphine
3 3 3
dissociation followed by Si-H oxidative addition to the
metal.4 To shed more light on the mechanism of silane
addition to Group 6 bis(imido) compounds and the bond-
ing situation in the various products formed, we carried
out DFT calculations on model compounds featuring
a Me group on the imido center (Scheme 6).
Reactions of HSiCl3 with (RN)2W(PMe3)3. The reac-
tions of (RN)2W(PMe3)3 (R = Ar, Ar0) with HSiCl3
afford the corresponding mono(imido) derivatives (RN)-
WCl2(PMe3)3 (15) as the final products, but are generally
less clean. Addition of HSiCl3 to (ArN)2W(PMe3)3 at
room temperature results in a fast (few minutes) color
change from purple to brown and the formation of a
mixture of compounds, the main component of which is
In accord with our experimental observations, the
most stable product of the addition of HSiMe2Cl to the
model compound (Me)2Mo(PMe3)3 (20) is the agostic
compound (MeN)(η2-MeNSiMe2-H )MoCl(PMe3)2
3 3 3

9612 Inorganic Chemistry, Vol. 48, No. 20, 2009
Ignatov et al.
Scheme 6. Non-Dissociative (with Regard to PMe3) Pathways to Agostic Compound 17a
a Gibbs free energies are expressed in kcal mol-1
.
˚
Table 3. Selected Interatomic Distances (A) of the Mo Structures 17-22
(17, Scheme 6, Table 3). Next comes the silyl hydride
derivative (MeN)2Mo(PMe3)H(SiMe2Cl) (18), having
the chloride trans to the hydride ligand and stabilized
by IHI. A “rotamer” of 18, in which the silyl is rotated in
such a way that chloride is cis to the hydride, cis-(MeN)2Mo-
(PMe3)H(SiMe2Cl) (19), does not have IHI and is further
destabilized by 3.1 kcal/mol. All these compounds are
thermodynamically allowed products.
structures
17
18
19
20
21
22
Mo-Nim 1.773
1.774 1.780, 1.773 1.838, 1.840 1.796 1.767
Mo-
2.097
Nam
Mo-P
2.465, 2.478 2.471
2.520
2.504, 2.508, 2.414 2.435
2.399a
As in our previous studies,4 we considered two mecha-
nisms of silane addition. The “text book” mechanism is
based on phosphine(s) elimination from (MeN)2Mo-
(PMe3)3 to give an unsaturated intermediate(s) that
can add the Si-H bond to the metal center. An alterna-
tive mechanism which we have already described for
related Cp/imido compounds of Group 5 metals4,17 in-
volves addition of the silane as a Lewis acid to the basic
nitrogen center of the imido ligand to give a penta-
coordinate silicon species which then transforms to pro-
ducts via Si-H or Si-Cl activation. Attempts to find an
intermediate or transition state for direct addition of
silane to the metal to give, for example, product 18 were
unsuccessful.
Mo-H
Mo-Si
Mo-Cl
Si-N
1.946
2.664
2.612
1.713
1.621
1.766 1.751
2.503 2.513
Si-H
2.163 2.203
2.145 2.128
Si-Cl
a Central phosphine.
The main difference between the compound (MeN)2-
Mo(PMe3)3 (20) and its Group 5 analogues Cp(MeN)M-
(PMe3)2 (M = Nb, Ta) is that the former has three
phosphine ligands. Therefore, two dissociative and two
associative pathways should be considered. Dissocia-
tion of one PMe3 from 20 to give the bis(phosphine)

Article
Inorganic Chemistry, Vol. 48, No. 20, 2009 9613
Scheme 7. Dissociative (with Regard to PMe3) Pathway to Agostic Compound 17a
a Gibbs free energies are expressed in kcal mol-1
.
(MeN)2Mo(PMe3)2 (21) is a very thermodynamically
profitable process (by 14.8 kcal mol-1, Scheme 7), which
accounts for the observed fluxionality of our starting tris
(phosphines) 2b,c and the fact that the tert-butylimido
compound 2a is a bis(phosphine) compound. In contrast,
further phosphine dissociation from 21 to give a formally
Table 4), that is, have the strongest trans-influence
ligands (imido and hydride) trans to each other. The
Si-H distances are long, primarily as a result of very
opened Mo-N-Si bond angles (139.0, 125.1, and 126.7°,
respectively), which helps to minimize the interligand
repulsion. The compound with an intermediate stability,
24trans, has an acute Mo-N-Si bond angle (110.3°) but
14e species (MeN)2Mo(PMe3) (22) costs 24.7 kcal mol-1
,
˚
which suggests that compound 21 is the most attractive
candidate for silane addition. Nevertheless, in our first set
of calculations we considered addition of HSiClMe2 to
both 20 and 21.
the Si-H distance (2.510 A) is still too long to qualify for
a Si H interaction. It thus appears that the structure of
the initial product of silane addition to 20 is determined
primarily by steric factors.
3 3 3
Addition of HSiClMe2 to the ModN bond of 20
affords a silylamido hydride compound (Scheme 6).
Because this product is pseudo-octahedral, several iso-
mers are possible. To minimize the computational cost,
we assumed that the original cis arrangement of imido
groups is preserved in the product. This assumption leads
to two options: the hydride goes trans to imido to give the
mer-isomer 23 or the hydride adds trans to a phosphine
ligand as in the fac-isomer 24.
For each isomer (23, 24), we considered two possible
rotamers, depending on the orientation of the silyl ligand
(Scheme 6). The trans-rotamers, in which the Si-bound
chloride is trans to the hydride on molybdenum (23trans
and 24trans) are preferred to cis rotamers; and com-
pounds with a trans imido/hydride arrangement are pre-
ferred to trans hydride/phosphines. This selectivity is
hard to rationalize in term of trans-influence because
the most stable compounds 23cis and 23trans and the
least stable compound 24cis are virtually hydride deriva-
Addition of ClSiMe2H to the bis(phosphine) (MeN)2-
Mo(PMe3)2 (21) is much more favorable and affords a
trigonal bipyramidal silylamido hydride species stabilized
by an additional interaction between the hydride and the
silicon atom (Scheme 7). We again considered two ori-
entations for silane addition. Silane attack on the imido
group with the chloride lying cis to the hydride affords a
silane/imido adduct 25cis featuring a penta-coordinate
silicon center with apical N and Cl groups (N-Si-Cl
bond angle equals 155.4°). The hydride is found in the
bridging position, forming elongated bonds to both
˚
˚
molybdenum and silicon (1.838 A and 1.610 A, respec-
tively). This additional agostic Mo H-Si interaction,
also found in related Cp/imido compounds of Nb and
3 3 3
Ta,4,17 helps to stabilize the silane/imido adduct. As a
˚
result of a strong Si-N interaction (1.832 A), the trans
˚
Si-Cl bond is significantly elongated to 2.393 A.
A more favorable isomer, 25trans, lying only 3.8 kcal
mol-1 above the starting bis(phosphine) compound 21, is
formed when silane adds to the imido center, bearing the
chloride trans to the hydride atom. In this case, a more
˚
˚
˚
tives (Mo-H: 1.806 A, 1.837 A, and 1.712 A, respectively;
˚
˚
˚
Si H: 3.347 A, 2.852 A, and 3.088 A, respectively;
3 3 3

9614 Inorganic Chemistry, Vol. 48, No. 20, 2009
Ignatov et al.
˚
Table 4. Selected Interatomic Distances (A) for the Mo Structures 23-25
structures
23cis
23trans
24cis
24trans
25cis
25trans
Mo-Nim
1.792
2.200
2.514a
2.399
2.520a
1.806
3.662
1.706
3.347
2.109
1.791
2.163
2.549 a
2.403
2.549 a
1.837
3.440
1.706
2.852
2.143
1.750
2.131
2.817
2.510
2.514
1.712
3.449
1.723
3.088
2.108
1.748
2.110
2.840
2.529
2.536
1.736
3.050
1.720
2.510
2.164
1.763
1.964
1.753
2.025
Mo-Nam
Mo-P trans to imido
Mo-P trans to amido or vacant site
2.452
2.485
1.838
2.779
1.832
1.610
2.393
2.436
2.549
1.747
Mo-P trans to hydride
Mo-H
Mo-Si
Si-N
Si-H
Si-Cl
1.748
2.114
2.185
a This phopshine is trans to another phosphine.
Scheme 8. Dissociative and Non-Dissociative (with Regard to PMe3) Pathways to Agostic Compound 26a
a Gibbs free energies are expressed in kcal mol-1
.
advanced Si-H activation occurs, leading to a longer Si-
A qualitatively similar picture was observed for the
addition of the dichlorosilane HSiCl2Me (Scheme 8). The
˚
H distance of 2.114 A and a stronger Mo-H bond of
1.747 A (Table 4). The geometry at silicon still can be
˚
most stable product is the Si-H Mo agostic com-
3 3 3
described as penta-coordinate, with the chloride lying
trans to the hydride and forming a H-Si-Cl bond angle
pound 26 which is 3.5 kcal mol-1 more stable than the
Si-Cl Mo bridged isomer 27, which is in turn structu-
3 3 3
˚
of 175.2°. The computed Si-Cl bond length of 2.185 A is
rally analogous to the proposed tungsten compound 12b
(Scheme 5). Structure 26 is also 6 kcal mol-1 more stable
than the silyl hydride compound 28, explaining why we do
not observe this species in the experimental system. Given
that the dissociative (with regard to PMe3) pathway of
silane addition is favorable (see above), we assessed only
one regioisomer of the HSiCl2Me attack on the tris
(phosphine) 20, namely, that having the Si-Cl bond trans
to hydride. This intermediate is the silylamido hydride
elongated relative to experimental Si-Cl bonds in mono-
chloro organosilanes (2.02 A) but is comparable to values
˚
found in compounds where the Si-Cl bond is involved in
hypervalent interactions.22
(22) Corriu, R. J. P.; Young, J. C. In The Chemistry of Organic Silicon
Compounds; Patai, S., Rappoport, Z., Eds.; Wiley: New York, 1989;
Chap. 20.

Article
Inorganic Chemistry, Vol. 48, No. 20, 2009 9615
˚
Table 5. Selected Interatomic Distances (A) for the Mo Structures 26-30
26
27
28
29
30a
30b
Mo-Nim
1.745
2.103
1.748
2.100
1.775, 1.770
1.748
2.135
2.830
2.523
2.526
1.733
3.162
1.752
2.029
1.746
2.029
Mo-Nam
Mo-P trans to imido
Mo-P trans to amido
Mo-P trans to hydride
Mo-H
2.519
2.452
1.982
2.657
2.606
1.671
1.578
2.105
2.524
2.437a
2.533
1.752
2.935
2.434 a
2.537
1.756
2.918
2.482 (trans to silyl)
1.763
Mo-Si
3.056
2.823
1.688
1.494
2.157
Mo-Cl
Si-N
1.692
2.552
2.132, 2.130
(trans to H)
1.728
1.933
2.127, 2.171
(trans to H)
1.729
1.937
2.122, 2.174
(trans to H)
Si-H
Si-Cl
2.107, 2.123
(trans to H)
a This phosphine lies in the MoN2P plane.
derivative 29, closely resembling the monochloride ana-
logue 24trans (Scheme 6). Although the geometry at
silicon can be seen as a highly distorted trigonal bipyr-
amid (the sum of bond angles in the “equatorial plane”
NSiClMe is 342.23°) with a chloride and the hydride in
stable than the silyl hydride 33 (Scheme 9, Table 6), but very
marginally (0.5 kcal mol-1) less stable than the Si-Cl
3 3 3
Mo bridged compound 32. This result is in good accord
with our inability to observe the analogues of 31 and 33
experimentally and is also in accord with the ease of
double SiCl activation in HSiCl3 to give the mono-
imide (RN)MoCl2(PMe3)3 and the silanimine dimer
(RNSiHCl)2. The non-dissociative pathway goes via an
intermediate 34 which is 0.3 kcal mol-1 more stable than
the tris(phosphine) 20. The dissociative pathway, that is, via
silane addition to the bis(phosphine) species 21, goes via the
silylamido compound 35. As in the case of HSiMeCl2
addition discussed above, all attempts to find a rotamer of
compound 35, analogous to the agostic silane adduct 25cis
(Scheme 7), converged to the same compound 35.
˚
the apical positions, the long Si H distance of 2.552 A
3 3 3
indicates the absence of any significant interaction. Also,
there is no difference between the “apical” and “equator-
˚
ial” Si-Cl bonds lengths of 2.130 and 2.132 A, respec-
tively (Table 5). The geometry of this species is evidently
dictated by the steric hindrance of the octahedral Mo
center. This intermediate lies 2.3 kcal mol-1 above the
starting compound 20, which suggests that competitive
HSiMeCl2 addition to the residual tris(phosphine) com-
pound 2 present in the real reaction mixture could be
possible.
Overall, comparing the stability of the intermediates
relative to the starting phosphine compounds, a clear
trend emerges: the introduction of more chlorine groups
at silicon lowers the energy of the intermediates, and also
presumably the energy of the corresponding barriers.
This trend agrees well with the following experimental
order of reactivity (i.e., rates of reaction): HSiMe2Cl <
HSiMeCl2 < HSiCl3. This order correlates with the
increased Lewis acidity of the respective silanes and
qualitatively agrees with our conclusions that the reac-
tions proceed via a donor/acceptor type of interaction
between the Lewis basic imido N atoms and the Lewis
acidic Si centers of the various silanes.
For the more favorable addition of HSiCl2Me to the
bis(phosphine) 21 we again considered two directions of
attack. Attempted optimization of the structural analo-
gue of compound 25cis (Scheme 7), having a chloride
group cis to hydride, resulted in compound 30a
(Scheme 8) which, in fact, is structurally analogous to
the isomeric compound 25trans. This intermediate had a
Si-bound methyl group on the same side of the HMoSiN
plane as the methylimido ligand and is 0.2 kcal mol-1
more stable than the starting compound 21. Another,
more sterically encumbered rotamer 30b, which has the
Si-bound methyl group facing the phosphine ligand lies
above 30a by only 1.6 kcal mol-1. Structurally, both 30a
and 30b are very similar: the Mo-H bond distances are
Comparison of the series of isostructural trigonal-
bipyramidal compounds 25trans (Scheme 7, Table 4),
30a (Scheme 8, Table 5), and 35 (Scheme 9, Table 6)
shows that the Si-H distance progressively contracts
˚
1.752 and 1.756 A, respectively, and the Si-H contacts
˚
are 1.933 and 1.937 A, respectively (Table 5). Compared
with the corresponding parameters in compound 25trans
˚
˚
from 2.114 A in 25trans to 1.745 A in 35, accompanied
˚
˚
˚
(Si-H distance of 2.114 A, Mo-H bond of 1.747 A)
these data indicate stronger Si-H interactions, possibly,
because the more chlorinated fragment MeCl2SiN is a
stronger Lewis acid.
by an elongation of the Mo-H bond from 1.747 A to
1.786 A. This trend can be rationalized in terms of
˚
increased Lewis acidity of the more chlorinated silicon
centers.
Despite the Si-H contact in 30a and 30b being rela-
tively long, the overall geometry at silicon in both rota-
mers can be still described as pseudotrigonal bipyramidal
(the sum of equatorial bond angles is 352.2° and 352.9°,
respectively). The observation of a longer Si-Cl bond for
Interestingly, a similar trend was found for β-Si-H
agostic compounds 17, 26, and 31. The Si-H bond
shortens progressively and the Mo-H bond elongates
as one goes from 17 to the more chlorinated derivative 31.
On the other hand, the Mo-Si distance contracts only
slightly from 2.664 A to 2.656 A along this series. These
trends agree well with our observations that the Si-H
coupling constants in the experimental compounds in-
crease from 3 to 6 and that 3c has a slightly shorter Mo-Si
distance than 6c.7 Note that the strengthening of the
˚
˚
˚
˚
the apical chloride (2.171 A in 30a and 2.174 A in 30b)
˚
than for the equatorial chloride (2.127 A in 30a and
˚
2.122 A 30b) substantiates further this description.
In the case of HSiCl3 addition to 20 and 21, the Si-
3 3 3
H
Mo agostic product 31 is still more thermodynamically

9616 Inorganic Chemistry, Vol. 48, No. 20, 2009
Ignatov et al.
Scheme 9. Dissociative and Non-Dissociative (with Regard to PMe3) Pathways to Agostic Compound 31a
a Gibbs free energies are expressed in kcal mol-1
˚
.
Table 6. Selected Interatomic Distances (A) for the Mo Structures 31-35
31
32
33
34
35
Mo-Nim
1.747
2.125
1.745
2.118
1.771
1.7420
2.160
2.816
2.509
2.528
1.728
3.197
1.748
2.020
Mo-Nam
Mo-P trans to imido
Mo-P trans to amido
Mo-P trans to hydride
Mo-H
2.442
2.518
2.058
2.656
2.564
1.655
1.551
2.084, 2.068
2.518
2.443 (equatorial phosphine)
2.479 (trans to silyl)
1.761
2.471
2.512
1.786
2.826
Mo-Si
3.082
2.858
1.669
1.482
2.120
Mo-Cl
Si-N
1.676
2.615
2.097, 2.103, 2.085
1.724
1.745
2.124, 2.116, 2.155
Si-H
2.165
2.090, 2.102 (trans to H), 2.090
Si-Cl
Si-H interaction from 17 to 31 contradicts the usual
expectation that introduction of more electron-with-
drawing groups at silicon should promote oxidative
addition of the Si-H bond to the metal because of
increased back-donation to the Si-H antibonding orbi-
tal.1 An explanation of this abnormality in terms of
interplay of the decreased direct donation and increased
back-donation has been offered in a previous work.7
It appears that the reason for the increased relative
with silanes R02SiClH have some similarities and also some
important differences in comparison with the reactions of the
isolobal Cp(RN)Nb(PMe3)2 systems. Thus: (i) mono- and
dichlorosilanes give only agostic compounds (RN)(η2-RN-
SiR02H )MoCl(PMe3)2; (ii) in no case are silyl hydride
3 3 3
products (RN)2Mo(PMe3)H(SiR02Cl) observed, even transi-
ently when the reactions are followed by low temperature
NMR; (iii) the reaction with HSiCl3 affords a silanimine
dimer and the dichloride compound (RN)MoCl2(PMe3)3;
(iv) the mechanism of silane addition involves Si attack on an
imido nitrogen of the bis(phosphine) compound (RN)2Mo-
(PMe3)2, which initially either exists as a bis(phosphine)
species for R=tBu or is easily formed from the tris(phos-
phine) precursor for R=Ar or Ar0.
stability of HSi-Cl M bridged compounds in compar-
ison to their ClSiH M β-agostic isomers is the de-
3 3 3
3 3 3
creased donor ability of the Si-H bond in the more
chlorinated systems.
Conclusions
The related reactions of the tungsten compounds (RN)2W-
(PMe3)3 (R=Ar or Ar0) proceed in a similar way with one
notable exception: in the case of the reaction between
The reactions of molybdenum compounds (RN)2Mo
t
(PMe3)n (R = Ar or Ar0 for n = 3; R = Bu for n = 2)

Article
Inorganic Chemistry, Vol. 48, No. 20, 2009 9617
(ArN)2W(PMe3)3 (10b) and HSiMeCl2 we were able to
intercept the silyl hydride oxidative addition intermediate
(ArN)2W(PMe3)(H)(SiMeCl2). This compound is thermally
stable in the absence of free phosphine, but like its isolobal
analogue Cp(ArN)Nb(PMe3)(H)(SiMe2Cl), instantaneously
rearranges into a silylamido species upon addition of PMe3.
In contrast to our expectations, the first silylamido product of
(bd, J(H-H) = 7.2 Hz, m-Ar0), 6.68 (t, J(H-H) = 7.2 Hz,
p-Ar0), 2.32 (bs, 12, Me/Ar), 0.93 (bs, 27, PMe3). 31P NMR
(121.4 MHz, toluene-d8, 25 °C): δ 31.4 (bs, 1, PMe3), -8.4 (bs, 2,
PMe3). 1H NMR (300 MHz, toluene-d8, at -10 °C): δ 7.23
(bs, 2, m-Ar0), 7.13 (bs, 2, m-Ar0), 6.74 (t, J(H-H) = 5.7 Hz, 2,
p-Ar0), 2.43 (bs, 6, Me/Ar), 2.29 (bs, 6, Me/Ar), 1.27 (d,
J(P-H) = 6.6 Hz, 9, PMe3), 0.80 (bs, 18, PMe3). 13C NMR
(75.4 MHz, toluene-d8, at -10 °C): δ 158.7 (i-Ar0), 125.6, 123.3,
116.4 (all Ar0), 25.0 (Me/Ar), 24.7 (Me/Ar), 22.0 (PMe3), 17.1
(2 PMe3). 31P NMR (121.4 MHz, toluene-d8, at -10 °C): δ 31.7
(s, 1, PMe3), -8.1 (s, 2, PMe3).
this rearrangement is not a Si-H W agostic compound,
3 3 3
according to NMR. In the absence of structural data, we
tentatively assign this product the Si-Cl W bridged struc-
3 3 3
ture (ArN)(η2-ArNSiMeH-Cl )W(PMe3)2Cl. DFT calcu-
(ArN)2W(PMe3)3 (10b). Compound 10b is fluxional at room
3 3 3
1
temperature. H NMR (300 MHz, C6D6): δ 7.7 (bs, Ar), 2.34
lations for model Mo compounds do indeed find such a
Cl-bridged form. This is 3.5 kcal mol-1 less stable than the
alternative β-Si-H agostic isomer in the case of HSiCl2Me
addition, but is the global minimum for the addition of
HSiCl3. This result is in good accord with our inability to
observe agostic products in reactions of Mo and W phos-
(bs, Ar0), 3.7 (bs, CH), 1.30 (bs, Ar), 1.1 (bs, PMe3). 31P NMR
(121.4 MHz, C6D6): δ -14.1 (bs, 1, PMe3), -24.0 (bs, 2,
PMe3). 1H NMR (300 MHz, toluene-d8, at -20 °C): δ 7.00
(d, J(H-H) = 7.5, 1, p- Ar), 6.90 (t J(H-H) = 7.5, 1, m- Ar),
3.83 (sept, J(H-H) = 6.6 Hz, 2, CH), 3.51 (sept, J(H-H) =
6.9 Hz, 2, CH), 1.46 (d, J(P-H) = 8.1 Hz, 8, PMe3), 1.41 (d,
J(P-H) = 6.6 Hz, Ar), 1.25 (d, J(P-H) = 6.6 Hz, Ar), 1.08 (vt,
J(P-H) = 2.2 Hz, 18, PMe3). 13C NMR (75.4 MHz, toluene-d8,
at -20 °C): δ 128.6, 127.8, 31.6 (CH), 30.8 (CH), 32.7 (PMe3),
31.1 (Me/Ar), 31.1 (Me/Ar), 29.2 (PMe3). 31P NMR (121.4
MHz, toluene-d8, at -20 °C): δ -7.9 (t, J(P-P) = 18.2 Hz,
J(W-P) = 461 Hz, 1, PMe3), -17.7 (d, J(P-P) = 18.2 Hz,
J(W-P) = 316 Hz, 2, PMe3).
phine compounds with HSiCl3. The Si-Cl M bridged
3 3 3
structure also appears to be a reasonable intermediate in
the course of formation of the monoimide product (RN)-
MCl2(PMe3)3 stemming from elimination of the silanimine
RNdSiHCl from (RN)(η2-ArNSiClH-Cl )M(PMe3)2Cl.
3 3 3
Experimental Section
(Ar0N)2W(PMe3)3 (10c). Compound 10c is fluxional at room
temperature. 1H NMR (300 MHz, C6D6): δ 7.22 (bs, Ar0), 2.34
(bs, Ar0), 1.46 (bs, 1PMe3), 0.94 (bs, 2PMe3). 31P NMR (121.4
MHz, C6D6): -11.9 (bs, 1, PMe3), -26.5 (bs, 2, PMe3).
All manipulations were carried out using conventional
Schlenk techniques. Solvents were dried over sodium or
sodium benzophenone ketyl and distilled into the reaction
vessel by high vacuum gas phase transfer. NMR spectra were
recorded on a Varian Mercury-vx (1H 300 MHz, 31P 121.4
MHz, 13C 75.4 MHz, 29Si 59.6 MHz) and Unity-plus (1H, 500
MHz; 31P 202.4 MHz, 13C 125.7 MHz) spectrometers. IR
spectra were obtained as Nujol mulls with a FTIR Perkin-
Elmer 1600 series spectrometer. Silanes were obtained from
Sigma-Aldrich, apart from HSiClMePh, which was pur-
chased from Lancaster.
(tBuN)(tBuNSiMe2-H )Mo(PMe3)2Cl (3a). To a solution
3 3 3
of (tBuN)2Mo(PMe3)2 (0.654 g, 1.68 mmol) in 25 mL of pentane
was added HSiClMe2 (0.20 mL, 1.80 mmol). The mixture was
stirred for an hour at room temperature during which time the
color changed to gray. All volatiles were removed in vacuo, and
the residue was extracted by pentane (2 ꢀ 15 mL), filtered, and
dried in vacuo. Yield: 0.49 g. (1.01 mmol, 60%) of a brown oily
compound. The compound does not crystallize from pentane
1
upon cooling to -30 °C. IR (Nujol): νSi-H = 1992 cm-1. H
Precursor Phosphine Compounds. Starting phosphine com-
pounds (RN)2M(PMe3)n (M = Mo, W; n = 2,3) were prepared
analogously to the literature method.9 Correct elemental ana-
lyses were not obtained because these compounds are highly
sensitive to air and for n = 3 easily loose the phosphine.
(tBuN)2Mo(PMe3)2 (1a). 1H NMR (300 MHz, toluene-d8, at
25 °C): 1.49 (s, 18, tBu), 1.31 (broad d, J(P-H) = 7.5 Hz, 18,
PMe3). 31P NMR (121.4 MHz, toluene-d8, at 20 °C): 38.5
(bs, PMe3).
NMR (300 MHz, C6D6): δ 1.54 (s, 9, But), 1.47 (d, J(P-H) =
7.5 Hz, 9, PMe3), 1.40 (d, J(P-H) = 6.6 Hz, 9, PMe3), ∼1.4
(found by 1H-29Si HMQC, Mo-H), 1.02 (s, 9, But), 1.27
(d, J(P-H) = 8.5, 0.81 (d, J(P-H) = 1.8 Hz, 3, SiMe2), 0.55
(d, J(P-H) = 2.4 Hz, 3, SiMe2). 13C NMR (75.4 MHz, C6D6):
δ 68.5 (s, CMe3), 55.7 (s, CMe3), 36.0 (s, CMe3), 31.5 (s, CMe3),
23.2 (d, J(P-C) = 23.6 Hz), 22.8 (d, J(P-C) = 21.1 Hz), 3.4
(s, SiMe), 0.9 (s, SiMe). 31P NMR (121.4 MHz, C6D6): δ 6.9
(d, J(P-P) = 12 Hz, 1P), 5.0 (d, J(P-P) = 12 Hz, 1P). 29Si
NMR (59.6 MHz, 25 °C, C6D6): -76 (J(Si-H) = 93.2 Hz). C,
H,N analysis (%) calcd for C16H34MoN2P2SiCl (484.63): C
39.63, H 8.94, N 5.78; found: C 38.46, H 8.03, N 5.78.
1H NMR (300 MHz, toluene-d8, at -50 °C): 1.60 (s, 18, tBu),
1.28 (d, J(P-H) = 7.8 Hz, 18, PMe3). 13C NMR (75.4 MHz,
t
toluene-d8, at -50 °C): 64.5 (CMe3), 34.7 (s, Me of Bu), 25.3
(d, J(P-C) = 24.0 Hz). 31P NMR (121.4 MHz, toluene-d8, at
-50 °C): 39.5 (bs, PMe3).
(ArN)2Mo(PMe3)3 (1b). Compound 1b is fluxional at room
(tBuN)(tBuNSiPhMe-H )Mo(PMe3)Cl (4a). HSiPhMeCl
3 3 3
(0.17 mL, 1.12 mmol) was added to a solution of (tBuN)2Mo-
(PMe3)2 (0.523 g, 1.34 mmol) in 20 mL of pentane. The mixture
was left to stand at room temperature for an hour to give a dark-
brown solution. Then the solution was filtered and dried in
vacuo to give brown oil. According to the 1H and 31P NMR, a
mixture of two isomers of (tBuN)(tBuNSiPhMeH)Mo(PMe3)Cl
(4a) contaminated with (tBuN)MoCl2(PMe3)3 (6a, about 30%
of the mixture) is formed. The content of 6a in the solution
increases with time because of decomposition of the initial
product. All attempts to purify 4a from 6a failed because of
close solubility of both products. Yield: 0.61 g. NMR spectra
at room temperature show the presence of a fluxional com-
1
temperature. H NMR (300 MHz, C6D6, at 25 °C): δ 7.16 (d,
J(H-H) = 7.5 Hz, 4, m-Ar), 6.92 (t, J(H-H) = 7.5 Hz, 2,
p-Ar), 3.77 (sept, J(H-H) = 6.9 Hz, 4, CH), 1.32 (d, J(H-H) =
6.9 Hz, 24, Me/Ar), 1.03 (bs, 27, PMe3). 31P NMR (121.4 MHz,
C6D6): δ (bs, PMe3). 1H NMR (300 MHz, toluene-d8, at
-40 °C): δ 7.18 (d, J(H-H) = 7.5, 2, m-Ar), 7.09 (d, J(H-H)
= 7.5, 2, m-Ar), 6.90 (t, J(H-H) = 7.5, 2, p Ar), 3.81 (sept,
J(H-H) = 6.9 Hz, 2, CH), 3.66 (sept, J(H-H) = 6.9 Hz, 2,
CH), 1.42 (d, J(P-H) = 6.9 Hz, 12, Ar), 1.29 (d, J(P-H) =
6.9 Hz, 12, Ar), 1.21 (d, J(P-H) = 7.5 Hz, 9, PMe3), 0.89 (vt,
J(P-H) = 2.3 Hz, 18, PMe3). 13C NMR (toluene-d8, at -40 °C):
δ 128.9, 127.9, 31.7 (CH), 31.2 (CH), 31.4 (Me/Ar), 29.6 (Me/
Ar), 28.8 (PMe3), 23.3 (PMe3). 31P NMR (121.4 MHz, toluene-
d8, at -20 °C): δ -29.9 (s, 1, PMe3), -5.0 (s, 2, PMe3).
pound. IR (Nujol): νSi-H = 2121 cm-1 29Si NMR (59.6 MHz,
.
25 °C, C6D6): δ -79.9 (J(Si-H) = 94 Hz, J(Si-H) = 3.1 Hz,
J(Si-P) = 5.6 Hz).
Major Isomer of 4a. 1H NMR (300 MHz, toluene-d8, -20 °C):
δ 7.92 (d, J(H-H) = 7.8 Hz, o-Ph), 7.23 (m, m-Ph), 7.14
(Ar0N)2Mo(PMe3)3 (1c). Compound 1c is fluxional at room
1
temperature. H NMR (300 MHz, toluene-d8, 25 °C): δ 7.12

9618 Inorganic Chemistry, Vol. 48, No. 20, 2009
Ignatov et al.
1
(0.225 g, 0.48 mmol, 11%) of the same compound. H NMR
(m, p-Ph), 1.64 (m, Mo-H, found from 1H-29Si HMQC
experiment), 1.70 (s, But), 1.44 (d, J(P-H)=8.1 Hz, 9, PMe3),
(300 MHz, C6D6): δ 1.43 (vt, J = 3.6 Hz, 18, trans PMe3), 1.25
(d, J(P-H) = 7.6 Hz, 9, cis PMe3), 1.01 (s, 9, But). 31P NMR
(121.4 MHz, C6D6): δ 7.3 (bs, 1, cis PMe3), -5.9 (bs, trans
PMe3), agrees with the literature data (ref 14a).
t
1.37 (d, J(P-H) = 6.9 Hz, 9, PMe3), 0.72 (s, Bu). 13C NMR
(75.4 MHz, toluene-d8, -20 °C): δ 140.3 (s, o-Ph), 133.4
t
(s, p-Ph), 133.0 (s, m-Ph), 55.1 (s, Bu), 40.8 (s, But), 27.5 (s,
t
PMe3), 27.1 (s, PMe3), 35.5 (s, Bu). 31P NMR (121.4 MHz,
NMR Tube Preparation of (ArN)(ArNSiMe2-H )Mo-
3 3 3
toluene-d8, -20 °C): δ 12.2 (d, J(P-P) = 12.7 Hz, 1, PMe3), 1.4
(d, J(P-P) = 12.7 Hz, 1, PMe3).
(PMe3)2Cl (3b). To 0.0248 g (0.037 mmol) of (ArN)2Mo-
(PMe3)3 in 1 mL of ether was added 0.004 mL (0.037 mmol) of
HSiClMe2. The mixture was left overnight at room temperature.
All volatiles were removed in vacuo, and the residue was
redissolved in 0.6 mL of C6D6. NMR spectra showed clean
formation of 3b. This product is not fluxional at room tempera-
ture. Scaling up the reaction resulted in a non-separable mixture
of 3b and (ArN)MoCl2(PMe3)3 (7b). IR (Nujol): νSi-H = 1943,
cm-1. 1H NMR (300 MHz, C6D6): δ 7.23 (t, J(H-H) = 4.5 Hz,
1), 7.07 (d, J(H-H) = 4 Hz, 2), 6.95 (pseudo t, J(H-H) = 3 Hz,
2), 6.84 (dd, J(H-H) = 3 Hz, J(H-H) = 6 Hz, 1), 4.33 (sept,
J(H-H) = 6.6 Hz, 1, CH), 3.78 (sept, J(H-H) = 6.6 Hz, 1,
CH), 3.45 (sept, J(H-H) = 6.8 Hz, 1, CH), 3.11 (sept,
J(H-H) = 6.7 Hz, 1, CH), 1.52 (d, J(H-H) = 6.5 Hz, 3, Pri),
1.28 (d, J(H-P) = 6 Hz, 9, PMe), 1.25 (d, J(H-P) = 7.0 Hz, 3,
Pri), 1.23 (d, J(H-H) = 6 Hz, 3, Pri), 1.22 (d, J(H-H) = 6.5 Hz,
3, Pri), 1.12 (d, J=7.5, 9, PMe), 1.05 (d, J(H-H) = 6.5 Hz, 3,
Pri), 1.02 (d, J(H-H) = 7 Hz, 3, Pri), 1.00 (d, J(H-H) = 7 Hz, 3,
Pri), 0.98 (s, 3, SiMe2), 0.93 (d, J(H-H) = 7 Hz, 3, Pri), 0.876
(t, J(P-H) = 7.5 Hz, 1, MoHSi), 0.65 (s, 3, SiMe2). 13C NMR
(75.4 MHz, C6D6): δ 155.0 (s, i-Ar), 153.2 (s, i-Ar), 145.9 (s,
o-Ar), 144.6 (s, o-Ar), 142.2 (s, o-Ar), 140.0 (s, o-Ar), 123.7,
123.5, 122.5, 121.9, 29.6 (s, Me-Pri), 27.6 (s, CH), 27.5 (s, CH),
27.3 (s, Me-Pri), 26.5 (s, 2CH), 24.6 (s, Me- Pri), 24.5 (s, Me Pri),
24.9 (s, Me Pri), 23.9 (s, Me-Pri), 23.2 (s, Me-Pri), 22.5 (s,
Me-Pri), 21.5 (d, J(P-C) = 21.3 Hz, PMe), 20.3 (d, PMe), 2.8
(s, SiMe2), -0.036 (s, SiMe2). 31P NMR (121.4 MHz, C6D6):
δ 4.7 (d, J(P-P) =7 Hz), -6.8 (d, J(P-P) = 8 Hz). 29Si NMR
(59.6 MHz, 25 °C, C6D6): δ -64.9 (1J(Si-H) = 97 Hz,
2J(Si-H) = 3.1 Hz).
Minor Isomer of 4a. 1H NMR (300 MHz, toluene-d8, -20 °C):
δ 8.36 (d, J(H-H) = 7.8 Hz, o-Ph), 7.39 (m, m-Ph), 7.21(m,
p-Ph), 1.95 (s, But), 1.83 (Mo-H, found from the 1H-29Si
HMQC experiment), 1.46 (d, J(P-H) = 6.9 Hz, 9, PMe3),
t
1.26 (d, J(P-H) = 7.2 Hz, 9, PMe3), 1.05 (s, Bu). 13C NMR
(75.4 MHz, toluene-d8, -20 °C): δ 142.8 (s, o-Ph), 140.2 (s,
m-Ph), 134.6 (s, p-Ph), 43.0 (s, But), 27.5 (s, PMe3), 27.0 (s,
PMe3), 36.4 (s, tBu). 31P NMR (121.4 MHz, toluene-d8,
-20 °C): δ 12.3 (d, J(P-P) = 13.5 Hz, 1, PMe3), -0.3 (d,
J(P-P) = 13.5 Hz, 1, PMe3).
(tBuN)(tBuNSiPh2-H )Mo(PMe3)2Cl (5a). HSiPh2Cl (0.3
3 3 3
mL, 1.40 mmol) was added to a solution of (tBuN)2Mo(PMe3)2
(0.546 g, 1.40 mmol) in 25 mL of pentane. The mixture was left at
room temperature for 4 days. Then the solution was filtered and
dried in vacuo to give a brown powder. The yield is quantitative
1
according to H NMR. Yield: 0.806 g. (1.32 mmol, 94%). IR
(Nujol): νSi-H = 1950 cm-1. 1H NMR (300 MHz, C6D6): δ 8.38
(dd, J(P-H) = 1.6 Hz, J(P-H) = 8.1 Hz, 2, o-Ph), 7.96 (dd,
J(P-H) = 2.0 Hz, J(P-H) = 7.6 Hz, 2, o-Ph), 7.26-7.08 (m,
6, m,p-Ph), 2.32 (dd, J(P-H) = 25.9 Hz, J(P-H) = 9.2 Hz, 1,
Mo-H), 1.67 (s, 9, But), 1.47 (d, J(P-H) = 7.7 Hz, 9, PMe3),
1.37 (d, J(P-H) = 7.3 Hz, 9, PMe3), 1.15 (s, 9, But), 0.66 (s, 9,
But). 13C NMR (75.4 MHz, C6D6): δ 138.7, 135.9, 129.7, 129.3,
128.5 (all Ph), 69.0 (s, CMe3), 55.5 (s, CMe3), 36.8 (s, CMe3),
31.0 (s, CMe3), 23.3 (d, J(P-C) = 23.9 Hz, PMe3), 22.9 (d, J(P-
C) = 21.3 Hz, PMe3). 31P NMR (121.4 MHz, C6D6): δ 5.7 (d,
J(P-H) = 13.4 Hz, 1), -5.3 (d, J(P-H) = 13.4 Hz, 1). 29Si
NMR (59.6 MHz, 25 °C, C6D6): δ -87.4 (J(Si-H) = 103.3 Hz).
C,H,N analysis (%): calcd for C26H47N2MoClSiP2 (609.10):
51.10, H 8.08, N 4.58; found: C 50.10, H 8.03, N 4.56.
NMR Tube Preparation of (ArN)(ArNSiMePh-H )Mo-
3 3 3
(PMe3)2Cl (4b). To 0.0254 g (0.039 mmol) of (ArN)2Mo-
(PMe3)3 in 0.6 mL of C6D6 was added an equivalent of HSi-
MePhCl. NMR monitoring showed slow formation of 3b over
a period of several days, accompanied by significant decom-
position to (ArN)MoCl2(PMe3)3 (7b). 31P NMR (121.4 MHz,
C6D6): δ 3.40 (b), -6.24 (b).
(tBuN)(tBuNSiMeCl-H )Mo(PMe3)2Cl (6a). HSiCl2Me
3 3 3
(0.25 mL, 2.40 mmol) was added to a solution of (tBuN)2Mo
(PMe3)2 (0.75 g, 1.92 mmol) in 15 mL of ether. The mixture was
stirred for 10 min, filtered, and dried in vacuo to give brown oil.
1
The yield is quantitative according to H NMR. The oil was
(ArN)(ArNSiMeCl-H )Mo(PMe3)2Cl (6b). To 0.135 g
extracted by 40 mL of hexane, filtered, and cooled to -30 °C for
a month to produce dark-brown crystals. The cold solution was
decanted, and the residue was quickly washed by 5 mL of
pentane and dried. Yield: 0.30 g. (0.59 mmol, 31%). IR (Nujol):
3 3 3
(0.20 mmol) of 1b in 50 mL of pentane was added 0.1 mL of
silane HSiMeCl2. Within few minutes the initial dark-green
color changes to yellow-brown. All volatiles were removed in
vacuo, affording a brown oil, which was shown by NMR to be a
mixture of 6b and 7b. Attempts to recrystallize the mixture to
isolate pure 6b failed. The only crystalline material isolated from
different solvents and under different regimes was 7b. NMR
scale preparation of 6b showed the quick (within 7 s) formation
of highly fluxional 6b which then decomposes in solution to 7b.
IR (Nujol): νSi-H = 1919 cm-1. 1H NMR (300 MHz, toluene-
d8, -50 °C): δ 4.27 (sept, J(H-H) = 6.6 Hz, 1, CH), 4.19 (sept,
J(H-H) = 6.6 Hz, 1, CH), 3.74 (sept, J(H-H) = 6.3 Hz, 1,
CH), 2.92 (sept, J(H-H) = 6.3 Hz, 1, CH), 1.50 (d, J(H-H) =
6.6 Hz, 3, CH3), 1.47 (d, J(H-H) = 6.6 Hz, 3, CH3), 1.45 (s, 3,
SiMe), 1.39 (d, J(H-H) = 6.3 Hz, 3, CH3), 1.28 (d, J(H-H) =
6.0 Hz, 3, CH3), 1.23 (Mo-H-Si obscured by a PMe3 signal but
determined from 29Si-1H HMQC at -50 °C), 1.17 (multiplet of
the Ar signal obscured by PMe3, 6, CH3), 1.16 (d, J(H-P) = 7.5
Hz, 9, PMe3), 0.99 (doublet of the Ar signal obscured by PMe3,
3, CH3), 0.98 (d, J(H-P) = 8.7 Hz, 9, PMe3), 0.89 (d,
J(H-H) = 6.6 Hz, 3, CH3). 13C NMR (75.4 MHz, toluene-d8,
-50 °C): δ 152.6 (s, i-Ar), 151.4 (s, i-Ar), 145.1 (s, o-Ar), 144.9 (s,
o-Ar), 143.9 (s, o-Ar), 140.0 (s, o-Ar), 124.0, 123.9, 123.5, 122.4,
122.3, 29.3 (Me-Ar), 28.4 (Me-Ar), 27.7 (CH), 27.4 (CH), 26.58
(CH), 26.27 (CH), 25.5 (Me-Ar), 24.6 (Me-Ar), 24.5 (Me-Ar),
ν
Si-H = 1851 cm-1
.
1H NMR (300 MHz, C6D6): δ 1.54 (s, 9, But), 1.43 (dd, J(P-
H) = 3.6 Hz, J(P-H) = 0.9 Hz, Mo-H), 1.35 (d, J = 8.0 Hz, 9,
PMe3), 1.28 (d, J(P-H) = 7.1 Hz, 9, PMe3), 1.19 (s, 3, SiMeCl),
1.15 (s, 9, But). 13C NMR (75.4 MHz, C6D6): δ 69.7 (s, CMe3),
54.9 (s, CMe3), 35.2 (s, CMe3), 31.1 (s, CMe3), 22.5 (dd,
J(P-C) = 2.5 Hz, J(P-C) = 24.8 Hz, PMe3), 22.2 (d, J(P-
C) = 22.0 Hz, PMe3), 3.2 (SiMe). 31P NMR (121.4 MHz, C6D6):
δ 9.8 (d, J(P-P) = 11.8 Hz, 1), -3.7 (d, J(P-P) = 11.8 Hz, 1).
29Si NMR (59.6 MHz, 25 °C, C6D6): δ -74.2 (J(Si-H) =
123 Hz, J(Si-P) = 9 Hz). C,H,N analysis (%): calcd for
C15H40N2MoCl2SiP2 (505.37): 35.65, H 7.98, N 5.54; found: C
34.44, H 7.71, N 5.43.
(ButN)Mo(PMe3)3Cl213a (7a). To 25 mL of ether solution of
(ButN)2Mo(PMe3)2 (1.70 g, 4.35 mmol) was added an equiva-
lent of PMe3 followed by 0.7 mL of HSiCl3 (6.94 mmol).
Instantaneous reaction occurs, resulting in the formation of a
brown precipitate. The mixture was cooled to -30 °C overnight.
The cold solution was filtered off, and the residue was washed
by 3 mL of ether and dried to give 1.11 g (2.39 mmol, 55%) of
a light-amber powder of 6a. Keeping the mother liquor at
-30 °C over the period of 4 days afforded the second crop

Article
Inorganic Chemistry, Vol. 48, No. 20, 2009 9619
24.3 (Me-Ar), 23.7 (Me-Ar), 22.1 (Me-Ar), 20.7 (PMe3, ob-
scured by toluene), 19.6 (PMe3, obscured by toluene), 5.6
(SiMe). 31P NMR (121.4 MHz, toluene-d8, -50 °C): δ 10.5
(d, J(P-P) = 8.7 Hz, 1 PMe3), -3.8 (d, J(P-P) = 8.7 Hz, 1
PMe3). 31P NMR (121.4 MHz, C6D6, 25 °C): δ 8.7 (bs), -4.5
(bs). 29Si NMR (119.2 MHz, toluene-d8, -50 °C): δ -68.5
(1J(Si-H) = 130 Hz, 2J(Si-P) = 16.2 Hz).
CH3, NAr), 1.39 (bs, 6H, 2CH3, NAr), 1.23 (bs, 3H, CH3, NAr),
1.07 (bs, 3H, CH3, NAr), 1.19 (bs, 9H, PMe3), 0.63 (bs, 9H,
PMe3). 31P NMR (243 MHz, toluene-d8, -50 °C) δ: -8.6 (d,
2
2J(P-P) = 223.5 Hz, PMe3), -17.1 (d, J(P-P) = 223.5 Hz,
PMe3). 29Si INEPT+ NMR (119.2 MHz, toluene-d8, -50 °C,
J(Si-H)= 200Hz) δ: -42.4 (dd, 1J(Si-H) = 327.0 Hz, 2J(Si-P)
1
= 22.1 Hz, Si-H). H-13C HSQC NMR (J(H-C) = 145 Hz,
-30 °C, toluene-d8) δ: 127.8, 124.8, 124.7 124.3, 123.6 (m-C and
p-C of NAr), 28.4, 28.2, 27.2, 26.7 (CH, NAr), 30.5, 27.3, 25.9,
25.8, 24.8, 24.7, 24.5, 23.8 (CH3, NAr), 16.8, 15.3 (PMe3).
(ArN)Mo(PMe3)3Cl2 (7b). A 0.2 mL portion (1.98 mmol) of
HSiCl3 was added to 15 mL of pentane solution of (ArN)2Mo-
(PMe3)3 (0.274 g, 0.424 mmol). Within 10 min the color changed
from dark-green to yellow-brown. The mixture was left at room
temperature for 20 h. The solution was filtered off, and the
residue was washed by 3 mL of cold pentane and dried. Yield
0.11 g (0.193 mmol, 42%), green crystals. Volatiles were re-
moved from the mother liquor to give oil. According to NMR
this product was mainly (ArNSiClH-)2.
7b. 1H NMR (300 MHz, C6D6): δ 7.01 (t, J = 7.7 Hz, 1, p-Ar),
6.87 (d, J = 7.7 Hz, 1, m-Ar), 4.12 (sept, J(H-H) = 6.8 Hz, 2,
CH), 1.40 (vt, J(H-P) = 2.4 Hz, 18, PMe3), 1.27 (d, J(P-H) =
8.4 Hz, 9, PMe3), 1.17 (d, J(H-H) = 6.6 Hz, 12, CH3). 13C
NMR (75.4 MHz, toluene-d8, -50 °C): δ 146.8, 126.7 (p-Ar),
123.9 (m-Ar), 27.1 9s, CH), 25.4 (CH3), 23.1 (d, J(P-C) = 23.0
Hz, 1 PMe3), 17.1 (vt, J(P-C) = 11.5 Hz, 1 PMe3). 31P NMR
(121.4 MHz, C6D6): δ 3.6 (t, J(P-P) = 16.7 Hz, 1 PMe3), -7.8
(d, J(P-P) = 16.7 Hz, 1 PMe3). C,H,N analysis (%): calcd for
C21H44NMoP3Cl2 (570.354): C 44.22, H 7.78, N 2.46; found: C
43.23, H 7.78, N 2.46.
(Ar0N)(Ar0NSiMe2-H )Mo(PMe3)2Cl (3c). To a solution
3 3 3
of (Ar0N)2Mo(PMe3)3 (0.381 g, 0.677 mmol) in 40 mL of ether
was added HSiClMe2 (0.25 mL, 2.25 mmol). In 5 min the color
changed from dark-green to dark-brown. The solution concen-
trated to 15 mL, and 15 mL of hexane was added; the mixture
was placed in a freezer (-30 °C) overnight to give dark well-
defined crystals, which were isolated by filtration and drying
in vacuo. Yield: 0.100 g. Two more crops were obtained
by concentrating the solution and cooling to -30 °C. Total
yield: 0.277 g (0.477 mmol, 70%). IR (Nujol): νSi-H =1910
cm-1(weak). 1H NMR (500 MHz, -40 °C, toluene-d8): δ 7.24
(d, J (H-H) = 7.4 Hz, 1, m-Ar0NSi), 7.10 (d, J (H-H) = 7.5 Hz,
1, m-Ar0NSi), 7.00 (t, J(H-H) = 7.4 Hz, 1, p-Ar0NSi), 6.83 (d,
J(H-H) = 7.53 Hz, 1, m-Ar0N), 6.78 (t, J(H-H) = 7.4 Hz, 1,
p-Ar0N), 6.75 (d, J(H-H) = 7.6 Hz, 1, m-Ar0N), 2.85 (s, 3, Me-
Ar0NSi), 2.49 (s, 3, Me-Ar0N), 2.07 (s, 3, Me-Ar0NSi), 2.06 (s, 3,
Me-Ar0N), 1.68 (dqq, J = 2.2 Hz, J = 1.7 Hz, J = 23.3 Hz, 1,
MoH), 1.23 (d, J(P-H) = 7.1 Hz, 9, PMe3), 0.98 (d, J (P-H) =
8.5 Hz, 9, PMe3), 0.71 (d, J = 1.7 Hz, 3, SiMe), 0.25 (d, J = 2.2
Hz, 3. SiMe). 13C NMR (125.7 MHz, -40 °C, toluene-d8): δ
158.2 (d, J (P-C) = 2.0 Hz, i-Ar0NSi), 154.5 (d, J (P-C) = 5.6
Hz, i-Ar0N), 135.4 (d, J (P-C) = 2.1 Hz, o-Ar0NSi), 133.7 (d,
J(P-C) = 1.6 Hz, o-Ar0NSi), 131.3 (d, J(P-C) = 1.8 Hz,
o-Ar0N), 128.8 (s, m-Ar0N), 128.5 (s, m-Ar0NSi), 128.3 (s,
m-Ar0N), 128.1 (s, m-Ar0NSi), 128.0 (s, o-Ar0N), 123.3 (s,
p-Ar0N), 121.0 (s, p-Ar0NSi), 21.6 (s, Me-Ar0NSi), 20.4 (s, Me-
Ar0N), 20.0 (s, Me-Ar0NSi), 19.9 (s, Me-Ar0N), 19.5 (d, J(P-
C) = 21.2 Hz, PMe3), 18.6 (dd, J(P-C) = 25.0 Hz, J(P-C) =
0.8, PMe3), 31P NMR (121.4 MHz, -40 °C, toluene-d8): δ 6.4 (d,
J(P-P) = 9 Hz, 1, PMe3), -7.0 (d, J(P-P) = 9 Hz, 1, PMe3).
29Si NMR (119.2 MHz, -50 °C, toluene-d8): δ -63.8 (1J(Si-
H) = 98 Hz, 2J(Si-Me) = 7.2 Hz, J(Si-P) = 21.5 Hz). C,H,N
analysis (%): calcd for C24H43N2MoP2SiCl (581.045): C 49.63,
H 7.46, N 4.82; found: C 48.99, H 6.92, N 4.82.
(ArNSiClH)2. 1H NMR (300 MHz, C6D6): δ 7.03-6.90 (m),
5.48 (s) 3.40 (sept, J(H-H) = 6.6 Hz, 2, CH), 1.41 (d, J(H-H) =
6.6 Hz, 12, CH3). 29Si-1H HMQC NMR (59.6 MHz, C6D6,
25 °C): δ 37.3.
NMR Reaction of (ArN)2Mo(PMe3)3 with HSiCl3 in the
Presence of BPh3. A solution of HSiCl3 (4.0 μL, 0.04 mmol)
and BPh3 (9.5 mg, 0.04 mmol) in 0.3 mL of toluene-d8 was added
to an NMR tube containing a frozen solution of (ArN)2Mo-
(PMe3)3 (26.5 mg, 0.04 mmol) in 0.4 mL of toluene-d8. The
mixture was placed to 600 MHz NMR spectrometer pre-cooled
to -20 °C and was cooled down to -70 °C. The mixture was
slowly warmed up, and the course of the reaction was monitored
by NMR. At -30 °C, the formation of an initial product with the
suggested structure (ArN)(ArNSiHCl-Cl )Mo(PMe3)2Cl (8b)
3 3 3
was observed. Warming the mixture up to -15 °C - 0 °C leads to
a slow rearrangement of the initial product into another com-
pound, whose NMR features are consistent with the structure
(ArN)(η2-ArN=SiHCl)Mo(PMe3)3Cl2 (9b). Further increase of
the temperature to >0 °C leads to fast decomposition to a
mixture of (ArNSiHCl)2 and (ArN)MoCl2(PMe3)3 (7b).
(Ar0N)(Ar0NSiMePh-H )Mo(PMe3)2Cl (4c). To a dark-
3 3 3
green solution of (Ar0N)2Mo(PMe3)3 (0.267 g, 0.475 mmol) in
40 mL of ether was added HSiCl2Me (0.1 mL, 0.67 mmol). The
resultant solution was kept at room temperature for 2 h,
developing brown color. The solution filtered from small
amount of gray deposit and concentrated to 10 mL, and the
mixture placed in a freezer (-30 °C) overnight to give a dark
crystalline deposit. The cold solution was filtered off, and the
product was washed by 5 mL of hexane and dried in vacuo.
Yield: 0.186 g. (0.289 mmol, 61%). IR (Nujol): νSi-H = 1906
cm-1(weak). 1H NMR (300 MHz, -40 °C, toluene-d8): δ 8.15
(d, J(H-H) = 7.8 Hz, 4H,), 7.52 (d, J(H-H) = 6.9 Hz, 4H,),
7.23-6.93 (m,), 6.78 (m, 4H,), 2.64 (s, 3, C6H4Me2), 2.69 (s, 3,
C6H4Me2), 2.45 (s, 3, C6H4Me2), 2.29 (s, 3, C6H4Me2), 2.24 (s, 3,
C6H4Me2), 2.19 (s, 3, C6H4Me2), 2.17 (s, 3, C6H4Me2), 2.14 (t,
J(P-H) = 22 Hz, 2, Mo-H), 2.10 (s, 3, C6H4Me2), 1.24 (d,
J(P-H) = 7.0 Hz, 9, PMe3), 1.23 (d, J(P-H) =7.0 Hz, 9,
PMe3), 1.15 (d, J(P-H) =1.8 Hz, 3, SiMe), 1.00 (d, J(P-H)=8.5
Hz, 9, PMe3), 0.99 (d, J(P-H) = 8.5 Hz, 9, PMe3), 0.58 (d,
J(P-H) = 1.8 Hz, 3, SiMe). 13C NMR (75.4 MHz, -40 °C,
toluene-d8): δ 157.5, 154.9, 154.4, 136.6, 136.0, 135.5, 135.1,
134.2, 133.3, 132.4, 131.4, 129.9, 127.2, 123.7, 123.6, 121.2, 21.9,
21.5, 20.8, 20.3, 30.0, 19.4 (d, J(P-C) = 21.0 PMe3), 19.3
(d, J(P-C) = 216 PMe3), 18.7 (d, J(P-C) = 25.2, PMe3),
18.6 (d, J(P-C) = 25.1 PMe3), 1.0 (SiMe), -3.4 (SiMe). 31P
1
(ArN)(ArNSiHCl-Cl )Mo(PMe3)2Cl (8b). H NMR (600
3 3 3
MHz, -30 °C, toluene-d8) δ: 7.44 (bm, 1H, NAr), 7.33 (bm, 1H,
NAr), 6.92-7.19 (multiplet overlapping with the residual
toluene-d8 resonances, 4H, NAr), 7.10 (1H, Si-H, found by
1H-29Si HSQC), 4.85 (bs, 1H, CH, NAr), 4.70 (bs, 1H, CH,
NAr), 3.98 (bs, 1H, CH, NAr), 2.79 (bs, 1H, CH, NAr), 1.60 (bs,
6H, CH3, NAr), 1.49 (bs, 3H, CH3, NAr), 1.37 (bs, 6H, 2CH3,
NAr), 1.04 (bs, 9H, PMe3), 0.94 (bs, 9H, PMe3), 0.90 (bs, 3H,
CH3, NAr), 0.77 (bs, 3H, CH3, NAr). 31P NMR (243 MHz,
-30 °C, toluene-d8) δ: 20.0 (bs, PMe3), -2.6 (bs, PMe3). 29Si
INEPT+ NMR (119.2 MHz, -30 °C, toluene-d8, J(Si-H) =
200 Hz) δ: -31.8 (d, 1J(Si-H) = 337.5 Hz, Si-H). 1H-13C
HSQC NMR (J(H-C) = 145 Hz, -30 °C, toluene-d8) δ: 130.9,
125.1, 124.9, 124.7 124.1 (m-C and p-C of NAr), 28.5, 27.9, 26.5,
25.7 (CH, NAr), 30.5, 27.3, 26.4, 24.7, 23.8, 22.4 (CH3, NAr),
20.6, 18.8 (PMe3).
1
(ArN)(η2-ArN=SiHCl)Mo(PMe3)3Cl2 (9b). H NMR (600
MHz, toluene-d8, -50 °C) δ: 6.81-7.38 (multiplet overlapp-
ing with the residual toluene-d8 resonances, 6H, NAr), 6.01 (bd,
3J(H-P) = 9.0 Hz, 1H, Si-H), 4.41 (bs, 1H, CH, NAr), 4.11 (bs,
1H, CH, NAr), 3.70 (bs, 1H, CH, NAr), 3.11 (bs, 1H, CH, NAr),
1.60 (bs, 6H, 2CH3, NAr), 1.53 (bs, 3H, CH3, NAr), 1.49 (bs, 3H,

9620 Inorganic Chemistry, Vol. 48, No. 20, 2009
Ignatov et al.
NMR (121.4 MHz, 25 °C, toluene-d8): δ 5.5 (bs), -7.9 (bs). 29Si
NMR (59.6 MHz, 25 °C, C6D6): -74.0 (J = 100 Hz). 29Si NMR
(59.6 MHz, -40 °C, C6D6): -69.3 (J = 98 Hz). C,H,N analysis
(%) calcd for C24H43N2MoP2SiCl (643.116): 54.16, H 7.05, N
4.36; found: C 54.03, H 7.06, N 4.43.
washed by 1 mL of pentane. The crystals were dried to afford
0.048 g of 11b. The combined fractions were concentrated to
3 mL and cooled first to -30 °C and then to -80 °C to give the
second crop. Total yield: 0.0655 g (0.90 mmol, 27%). IR (Nujol):
1731 cm-1. 1H NMR (300 MHz, 23 °C, C6D6): δ 11.24 (dd, J(P-
H) = 59.5 Hz, J(W-H) = 35.0 Hz, J(Si-H) = 30.0 Hz 1, WH),
7.07 (m, 4, m- Ar), 7.03 (m, 2, p- Ar), 3.99 (sept, J(H-H) =
6.9 Hz, 2, CH), 3.66 (sept, J(H-H) = 6.9 Hz, 2, CH), 1.51 (s, 3,
SiMe), 1.23 (d, J(H-H) = 6.6 Hz, 24, Ar), 1.15 (d, J(P-H) =
10.2 Hz, 9, PMe3). 13C NMR (75.4 MHz, 25 °C, C6D6): δ 153.5
(i-Ar), 143.1 (o-Ar), 125.4 (p-Ar), 122.7 (m-Ar), 28.0 (s, CH),
24.1 (s, Me/Ar), 23.9 (s, Me/Ar), 20.4 (SiMe), 19.0 (d, J(P-C) =
35.9 Hz, PMe3). 31P NMR (121.4 MHz, 23 °C, C6D6):
δ 1.22 (J(P-W) = 316 Hz). 29Si NMR (59.6 MHz, 23 °C,
C6D6): δ 92.1 (J(Si-W) = 36.7 Hz). C,H,N analysis (%): calcd
for C28H47N2WPSiCl2 (725.49): C 46.36, H 6.53, N 3.86; found:
C 45.57, H 6.94, N 3.77.
(Ar0N)(Ar0NSiMeCl-H )Mo(PMe3)2Cl (6c). To a solution
3 3 3
of (Ar0N)2Mo(PMe3)3 (0.326 g, 0.580 mmol) in 40 mL of ether
was added HSiCl2Me (0.15 mL, 1.37 mmol). In 3-4 min the color
changed from dark-green to dark-brown. The solution filtered
from small amount of gray deposit and concentrated to 10 mL, 10
mL of hexane was accurately added, and the mixture was placed
overnight in a freezer (-30 °C) to give dark, well-defined crystals.
The cold solution was filtered off, and the product was dried in
vacuo. Yield: 0.150 g. (0.249 mmol, 43%). IR (Nujol): νSi-H
=
1
1920 cm-1 (weak). H NMR (300 MHz, -10 °C, toluene-d8):
δ 7.07 (bd, J(H-H) = 7.6 Hz, 1, m-Ar0), 6.98 (bd, J(H-H) = 7.5
Hz, 1, m-Ar0), 6.87 (vt, J(H-H) = 7.5 Hz, 1, p-Ar0), 6.87 (bs, 3, m
+p-Ar0), 2.60 (bs, 3, Me-Ar0), 2.39 (bs, 3, Me-Ar0), 2.37 (bs, 6,
Me-Ar0), 1.76 (dq, J(H-P) = 18 Hz, J(H-H) = 1.5 Hz, 1,
MoH), 1.18 (d, J(P-H) = 7.4 Hz, 9, PMe3), 0.99 (d, J(P-H) =
8.5 Hz, 9, PMe3), 0.97 (d, J(H-H) = 1.5 Hz, 3, SiMe). 13C NMR
(75.4 MHz, -10 °C, toluene-d8): δ 154.9 (d, J(P-C) = 1.8 Hz,
i-Ar0), 154.5 (dd, J(P-C) = 1.8, 3.5 Hz, i-Ar0), 134.6 (s, o-Ar0),
128.5 (s, m-Ar0), 128.4 (s, m-Ar0), 124.3 (s, p-Ar0), 121.7 (s, p-Ar0),
21.1 (s, Me-Ar0), 20.4 (s, Me-Ar0), 19.3 (d, J(P-C) = 22.8 Hz,
PMe3), 18.6 (d, J(P-C) = 25.8 Hz, PMe3), 1.8 (s, SiMe). 31P
NMR (121.4 MHz, -60 °C, toluene-d8):δ 10.2 (bd, J(P-P)= 6.5
Hz, 1, PMe3), -5.0 (bd, J(P-P) = 6.5 Hz, 1, PMe3). 29Si NMR
(59.6 MHz, 25 °C, C6D6): -70.1 (J(Si-H) = 129 Hz, J(Si-P) =
7.2 Hz). 29Si NMR (119.2 MHz, -50 °C, toluene-d8): -70.5
(J(Si-H) = 135.6 Hz, J(Si-P) = 20.6 Hz). C,H,N analysis (%)
calcd for C23H40N2MoP2SiCl2 (601.353): C 45.93, H 6.70, N 4.66;
found: C 46.23, H 6.93, N 4.74.
Reaction of (ArN)2W(PMe3)H(SiCl2Me) (11b) with PMe3.
To a sample of 11b in C6D6 were added 6 equiv of PMe3. Imme-
diate color change from yellow to brown-green occurred. NMR
spectra revealed a mixture of the starting compound 11b and the
agostic (ArN)(ArNSiMeHCl )W(PMe3)2Cl (12b) contami-
nated by some (ArN)2W(PMe3)3 and HSiCl2Me. At room tem-
3 3 3
perature, the system converts to 12b. 12b: IR (Nujol): 2180 cm-1
.
1H NMR (300 MHz, -40 °C, toluene-d8): δ 7.25 (d, J(H-H) =
7.9 Hz, m-Ar), 7.22 (d, J(H-H) =8.4 Hz, m-Ar), 6.99 (m obscured
by toluene, m-Ar), 6.93 (m, p-Ar), 5.78 (badly resolved quartet,
J(H-H) = 2.4 Hz, J(Si-H) = 263.8 Hz, 1H, SiH), 4.39 (q,
J(H-H) =6.6 Hz, 1 CH), 3.97 (q, J(H-H) =6.9 Hz, 2 CH), 3.65 (q,
J(H-H) =6.6 Hz, 1 CH), 1.58 (d, J(H-H) =6.6 Hz, 3, Ar), 1.54
(d, J(P-H) =8.7 Hz, 9, PMe3), 1.51 (d, J(H-H) = 6.6 Hz, 3, Ar),
1.48 (d, J(H-H) =6.3 Hz, 3 Ar), 1.39 (d, J(H-H) =6.9 Hz, 6, Ar),
1.31 (d, J(H-H) =6.9 Hz, 6, Ar), 1.26 (d, J(P-H) =8.4 Hz, 9,
PMe3), 1.18 (d, J(H-H) = 6.6 Hz, 3, Ar), 1.10 (d, J(H-H) =
6.6 Hz, 3, Ar), 0.19 (d, J(H-H) = 1.0 Hz, 3H, SiMe). 13C NMR
(75.4 MHz, -40 °C, toluene-d8): δ 150.6 (i-Ar), 149.0 (i-Ar), 143.6
(o-Ar), 142.2 (o-Ar), 141.7 (o-Ar), 125.7 (m-Ar), 124.2 (m-Ar), 123.8
(p-Ar), 123.5 (m-Ar), 123.2 (m-Ar), 29.8 (CH), 28.8 (CH), 28.2 (CH),
27.1 (CH), 26.5 (Me-Ar), 25.8 (Me-Ar), 25.5 (Me-Ar), 25.4 (Me-Ar),
25.2 (Me-Ar), 25.1 (Me-Ar), 24.8 (d, J(P-C) =21.0 Hz PMe3), 23.9
(s, PMe3). 13P NMR (121.4 MHz, -40 °C, toluene-d8): δ -8.8 (d,
J(P-P) =9.6 Hz, -22.6 (d, J(P-P) =9.6 Hz. 13P NMR
(121.4 MHz, 25 °C, toluene-d8): δ -12.4 (bs, 1P), -24.8 (bs, 1P).
29Si HMQC: δ 41.8.
(Ar0N)Mo(PMe3)3Cl2 (7c). A 0.2 mL portion (1.98 mmol) of
HSiCl3 was added by syringe to 15 mL of an ether/pentane (1:2)
solution of (Ar0N)2Mo(PMe3)3 (0.380 g, 0.675 mmol). Within a
minute the color changed from dark-green to yellow-brown, and a
small amount of gray precipitate was formed. In 30 min the
solution was filtered, cooled to -78 °C, and slowly concentrated
in vacuo to 2 mL. The cold solution was filtered, the residue
washed by 1 mL of cold pentane, and volatiles removed in an
analogous fashion from the combined fractions to give a yellow-
brown oil and green solid. Yield of (Ar0N)Mo(PMe3)3Cl2: 0.237 g
(0.461 mmol, 68%). The volatiles were removed from mother
liquor to give 0.237 g of a yellow-brown oil, which mostly con-
sisted of (Ar0NSiClH)2 contaminated by (Ar0N)Mo(PMe3)3Cl2.
7c. 1H NMR (300 MHz, C6D6): δ 6.84 (pt, J(H-H) = 7.35
Hz, 1, p- Ar0), 6.70 (d, J(H-H) = 7.5 Hz, 1, m-Ar0), 2.42 (s, 6,
Me), 1.23 (d, J(P-H) = 7.1 Hz, 9, PMe3), 1.38 (vt, J(P-H) =
3.45 Hz, 18, trans PMe3), 1.24 (d, J(P-H) = 7.5 Hz, cis PMe3).
13C NMR (75.4 MHz, C6D6): δ 135.2 (s, o-Ar0), 128.6 (s, m-Ar0),
125.5 (s, p-Ar0), 20.1 (s, Me), 22.2 (d, J(P-H) = 23.3 Hz, cis
PMe3), 17.1 (vt, J (P-H) = 11.5 Hz, trans PMe3). 31P NMR
(121.4 MHz, C6D6): δ 3.69 (t, J(P-P) = 17.0, 1 trans P), -7.9 (d,
J (P-P) = 17.0, 2 cis P). C,H,N analysis (%): calcd for (514.24):
C 39.71, H 7.06, N 2.72; found: C 40.70, H 6.84, N 3.28.
(Ar0N)(ArN’SiMeCl-H )W(PMe3)2Cl (13c). To 0.284 g
3 3 3
(0.437 mmol) of (Ar0N)2W(PMe3)3 dissolved in 10 mL of
pentane:toluene mixture (10:1) C6D6 was added by syringe
0.15 mL (1.37 mmol) of HSiMeCl2. The color quickly changes
from deep-purple to dark-brown. The reaction was allowed to
proceed at room temperature for 1.5 h and then the reaction
mixture was cooled to -30 °C. Dark crystals were formed
during several days. The cold solution was decanted and the
crystals were washed by small amount of cold pentane and
dried. Yield: 0.112 g (0.112 g, 37%). IR (Nujol): 1914 cm-1. 1H
NMR (300 MHz, C6D6): δ 7.11(d, J = 7.2 Hz,1, m-Ar0), 7.06 (d,
J = 7.2 Hz, 1, m-Ar0), 6.91 (t, J = 7.7 Hz, 1, p-Ar0), 6.85 (t. J =
6.2 Hz, 1, p-Ar0), 6.85 (d, J = 6 Hz, 2, m-Ar0), 2.56 (s, Ar0NSi, 3),
2.51 (s, Ar0NSi, 3), 2.46 (ddq, J(P-H) = 16.7 Hz, J(H-H) =
1.5 Hz, J(P-H) = 0.6 Hz, 1, Si-H-W), 2.33 (s, Ar0, 6), 1.34 (d,
J = 7.8 Hz, PMe), 1.14 (d, 8.7 Hz, PMe), 1.08 (d, J = 1.5 Hz, 3
SiMe), 0.87 (t, J(P-H) = 7.1 Hz, 1, W-H). 13C NMR (75.4
MHz, C6D6): δ 156.4 (i, Ar0), 155.3 (i, Ar0), 135.1 (o, Ar0), 134.4
(o, Ar0), 128.5 (m, Ar0), 128.2 (m, Ar0), 127.9 (m, Ar0), 123.2
(p, Ar0), 122.2 (p, Ar0), 22.7 (d, J(P-C) = 27.1 Hz, PMe), 21.6
(d, J(P-C) = 29.6 Hz, PMe), 21.0 (C6H3Me), 20.8 (C6H3Me),
20.5 (C6H3Me), -1.2 (SiMe). 13P NMR (121.4 MHz, C6D6):
δ 20.7 (d+d, J(P-P) = 14 Hz, J(31P-183W) = 204.0 Hz 1, P),
-29.9 (d+d, J(P-P) = 14 Hz, J(31P-183W) = 168.2 Hz). 29Si
NMR (59.6 MHz, C6D6): δ -77.6 (1J(Si-H) = 118 Hz). C,H,N
1
[(Ar0N)HClSi-]2: IR (Nujol). νSi-H = 2240 cm-1. H NMR
(300 MHz, C6D6): δ 6.82 (m, 3, m+p- Ar0), 5.44 (s+d, J (H-Si)
= 337 Hz, 1, Si-H), 2.19 (s, 6, Me). 13C NMR (75.4 MHz,
C6D6): δ 137.4 (s, o-Ar0), 129.7 (s, m-Ar0), 127.8 (p-Ar0), 19.9 (s,
Me). 29Si NMR (59.6 MHz, C6D6): δ - 20.9 (s). EI-HRMS: m/z
found (calcd. for C16H20Cl2N2Si2) 366.0540 (366.0542).
(ArN)2W(PMe3)H(SiCl2Me) (11b). A 0.15 mL portion (1.37
mmol) of HSiCl2Me were added to 10 mL of pentane solution of
(ArN)2W(PMe3)3 (0.259 g, 0.34 mmol) causing the color change
from deep-purple to brown. In 10 s all volatiles were pumped off
to give a purple residue. This was extracted with 5 mL of ether,
filtered, and cooled to -30 °C. Yellow crystals were produced
overnight. The cold solution was decanted, and the crystals were

Article
Inorganic Chemistry, Vol. 48, No. 20, 2009 9621
analysis (%): calcd for C23H40N2WP2SiCl2 (689.365): C 40.07,
H 5.85, N 4.06; found: C 40.87, H 6.10, N 3.91.
NMR Tube Preparation of (ArN)(ArNSiMe2-H )W-
Table 7. X-ray Diffraction Crystal Data and Structure Refinement for 11b
compound
formula
FW
11b
C28H47Cl2N2PSiW
725.49
3 3 3
(PMe3)2Cl (14b). To 0.069 g (0.090 mmol) of (ArN)2W-
(PMe3)3 in 0.6 mL of C6D6 was added by syringe 0.011 mL
(0.099 mmol) of HSiMe2Cl. The course of the reaction was
monitored by NMR. The reaction gave a mixture of com-
pounds, the main component of which was highly fluxional at
room temperature. The 29Si NMR experiment (59.6 MHz,
C6D6) revealed three products with a direct Si-H bond, one
of which was assigned the agostic structure 14b (δ -70 ppm,
J(Si-H) = 81 Hz, J(Si-P) = 9 Hz).
color, habit
cryst size, mm
cryst sys
yellow, block
0.15 ꢀ 0.20 ꢀ 0.20
monoclinic
P21/n
10.0467 (2)
32.2846 (3)
10.5529 (2)
107.754(5)
2149.51(12)
4
150
1.478
1464
Mo
3.812
space group
˚
a, A
˚
b, A
˚
c, A
β, deg
3
˚
V, A
(Ar0N)(Ar0NSiMe2-H )W(PMe3)2Cl (14c). A 0.185 g por-
Z
T, K
3 3 3
tion (0.284 mmol) of (Ar\N)2W(PMe3)3 dissolved in 30 mL of
pentane was added 0.15 mL of silane HSiMe2Cl. The mixture
was stirred at room temperature for an hour, during which time
the color changes from purple to dark-brown. Volatiles
were removed in vacuo to give a green solid. Yield: 0.121 g
(0.182 mmol, 64%). IR (Nujol): νSi-H = 1908 cm-1, 1770 cm-1
(impurity). 1H NMR (500 MHz, -50 °C, toluene-d8): δ 7.21 (d,
J(H-H) = 6.3 Hz, 1, Ar0), 7.09 (m, Ar0), 6.83 (d, J(H-H) = 7.5
Hz, 2, Ar0), 6.93 (m, Ar0), 6.82 (m, Ar0), 2.84 (s, 3, Me), 2.39 (s, 3,
Me), 2.21 (m, J(P-H) = 23.6 Hz, W-H), 2.14 (s, 3, Me), 2.09 (s,
3, Me), 1.41 (d, J(P-H) = 7.2 Hz, 9, PMe3), 1.12 (d, J(P-H) =
8.7 Hz, 9, PMe3), 0.82 (s, 3, SiMe), 0.40 (s, 3. SiMe). 13C NMR
(125.7 MHz, -50 °C, toluene-d8): δ 129.4, 128.9, 128.4. 125.8,
22.5 (d, J(P-C) = 25.8 Hz, PMe3), 21.6 (s, Me), 21.1 (s, Me),
20.0 (s, Me), 0.44 (s, SiMe), -3.5 (s, SiMe). 31P NMR (121.4
MHz, -50 °C, toluene-d8): δ 13.1 (1J(P-P) = 15.1 Hz), -27.1
(1J(P-P) = 15.1 Hz). 29Si NMR (59.6 MHz, 25 °C, toluene-d8):
δ -68.3 (1J(Si-H) = 87 Hz).
F
calc, g/cm3
F(000)
radiation
μ, mm-1
transmission factors
2θmax, deg
total no. of reflns
no. of unique reflns
Rmerge
0.466 - 0.583
54.96
14107
7401
0.02
no. with I g nθ(I)
no. of variables
R
6229 (n = 2)
324
0.0295
Rw
GOF
max Δ/σ
0.0616
1.047
0.001
reaction was monitored by NMR. At -20 °C, the selective
formation of an initial product with the suggested structure
(ArN)2W(H)(SiCl3)(PMe3) (16b) was observed. Warming the
mixture up to -10 °C leads to a slow rearrangement of the initial
product into other hydride species, which do not contain a
coordinated PMe3 ligand. Addition of excess PMe3 and warming
the mixture to room temperature results in fast formation of
(ArNSiHCl)2 and (ArN)WCl2(PMe3)3 (15b).
(Ar0N)W(PMe3)3Cl2 (15c). A 0.0012 mL portion of HSiCl3
(0.012 mmol) was added to 5 mL of hexane solution of
(Ar0N)2W(PMe3)3 (0.077 g, 0.012 mmol). In 20 s all volatiles
were removed in vacuo to give a dark-green solid. NMR showed
the formation of a mixture of compounds, the main compo-
nent of which is (Ar0N)W(PMe3)3Cl2. IR(Nujol) 2274, 2167,
1778 cm-1 (silane and hydride impurities). 1H NMR (300 MHz,
23 °C, toluene-d8): δ 6.84 (m, 1, p-Ar), 6.78 (d, J(H-H) = 7.8
Hz, 2, m-Ar), 2.37 (s, 6, Me), 1.44 (vt, J(P-H) = 4.5 Hz, 18,
trans-PMe3), 1.42 (d, J(P-H) = 7.5 Hz, 9, cis-PMe3). 13C NMR
(125.7 MHz, 23 °C, toluene-d8): δ 169.0 (i), 142.2 (o), 129.0 (m),
128.1 (p), 26.5 (d, J(P-C) = 27.3 Hz, cis PMe3), 20.4 (s, Me-Ar),
18.0 (vt, J(P-C) = 13.5 Hz, trans PMe3). 31P NMR (121.4
MHz, 23 °C, toluene-d8): δ -23.0 (s), -24.1 (s).
1
(ArN)2W(H)(SiCl3)(PMe3) (16b). H NMR (600 MHz, to-
2
luene-d8, 226 K) δ: 11.04 (d, J(H-P) = 58.8 Hz, 1H, W-H),
7.00-7.26 (multiplet overlapping with the residual toluene-d8
resonances, 6H, NAr), 4.01 (bs, 2H, 2CH, NAr), 3.91 (bs, 1H,
CH, NAr), 3.56 (bs, 1H, CH, NAr), 1.50 (bs, 6H, 2CH3, NAr),
1.42 (bs, 3H, CH3, NAr), 1.31 (m, 12H, 4CH3, NAr), 1.19 (bs,
2
1
3H, CH3, NAr), 1.05 (d, J(H-P) = 7.8 Hz, 9H, PMe3). H-
{31P} NMR (600 MHz, toluene-d8, 224 K) δ: 11.04 (bs, 1H, W-
H), 1.05 (s, 9H, PMe3). 31P NMR (243 MHz, toluene-d8, 223 K)
δ: 3.01 (s+sat, 1J(P-W) = 328.0 Hz, PMe3). 1H-29Si HSQC
NMR (J(Si-H) = 7 Hz, toluene-d8, 253 K) δ: 73.8 (SiCl3).
1H-13C HSQC NMR (J(H-C) = 145 Hz, -30 °C, toluene-d8)
δ: 127.4, 126.4, 123.9, 123.4, 123.3, 121.9 (m-C and p-C of NAr),
27.8, 27.6, 21.7 (CH, NAr), 26.5, 25.9, 25.2, 24.8, 24.0, 23.5, 21.1
(CH3, NAr), 18.03 (PMe3).
(ArN)W(PMe3)3Cl2 (15b). A 0.15 mL portion (1.47 mmol) of
HSiCl3 was added to 10 mL of ether solution of (ArN)2W-
(PMe3)3 (0.152 g, 0.20 mmol) at 0 °C. The mixture was stirred for
20 s, and then all volatiles were removed in vacuo to give brown
oil. This oil was dissolved in 5 mL of ether and charged with
pentane, causing precipitation of a brown solid. The solution
was filtered off, and the residue was washed with pentane and
1
DFT Calculations. The unconstrained geometry optimi-
zation was carried out for all the considered structures with
the Gaussian 03 program package,23 using DFT and apply-
ing Becke three parameter hybrid exchange functional in
dried. H NMR (300 MHz, 23 °C, C6D6): δ 7.13(m, 1, p-Ar),
6.92 (d, J(H-H) = 8.4 Hz, 2, m-Ar), 4.02 (sept, J(H-H) = 7.0
Hz, 2, CH), 4.01 (sept, J(H-H) = 6.3 Hz, 2, CH), 1.45 (vt, J(P-
H) = 4.2 Hz, 18, trans-PMe3), 1.44 (d, J(P-H) = 7.1 Hz, 9, cis-
PMe3), 1.18 (d, J(H-H) =7.2 Hz, 12, ArMe). 13C NMR (125.7
MHz, 23 °C, C6D6): δ 151.5, 145.1, 125.5 (p-Ar), 123.7 (m-Ar),
27.4 (d, J(P-C) = 27.3 (CH), 27.6 Hz, cis-PMe3), 25.3 (s, Ar-
Me), 18.0 4 (vt, J(P-C) = 13.4 Hz, cis-PMe3). 31P NMR (121.4
MHz, 23 °C, C6D6): δ -27.8 (s, 2P), -28.8 (s, 1P).
(23) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Zakrzewski, V. G.; Montgomery, Jr., J. A.;
Stratmann, R. E.; Burant, J. C.; Dapprich, S.; Millam, J. M.; Daniels, A.
D.; Kudin, K. N.; Strain, M. C.; Farkas, O.; Tomasi, J.; Barone, V.; Cossi,
M.; Cammi, R.; Mennucci, B.; Pomelli, C.; Adamo, C.; Clifford, S.;
Ochterski, J.; Petersson, G. A.; Ayala, P. Y.; Cui, Q.; Morokuma, K.;
Malick, D. K.; Rabuck, A. D.; Raghavachari, K.; Foresman, J. B.;
Cioslowski, J.; Ortiz, J. V.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz,
P.; Komaromi, I.; Gomperts, R.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-
Laham, M. A.; Peng, C. Y.; Nanayakkara, A.; Gonzalez, C.; Challacombe,
M.; Gill, P. M. W.; Johnson, B.; Chen, W.; Wong, M. W.; Andres, J. L.;
Gonzalez, C.; Head-Gordon, M.; Replogle, E. S.; Pople, J. A. Gaussian 03;
Gaussian, Inc.: Wallingford, CT, 2004.
NMR Reaction of (ArN)2W(PMe3)3 with HSiCl3 in the Pre-
sence of BPh3. A solution of HSiCl3 (4.2 μL, 0.041 mmol) and
BPh3 (10.0 mg, 0.041 mmol) in 0.4 mL of toluene-d8 was added at
-80 °C to a solution of (ArN)2W(PMe3)3 (10b) (31.5 mg, 0.041
mmol) in 0.4 mL of toluene-d8 in an NMR tube. The mixture was
immediately frozen by liquid nitrogen and placed to a 600 MHz
NMR spectrometer pre-cooled to -30 °C, and cooled down to
-70 °C. The mixture was slowly warmed up, and the course of the

9622 Inorganic Chemistry, Vol. 48, No. 20, 2009
Ignatov et al.
conjunction with gradient-corrected nonlocal correlation
functional of Perdew and Wang (B3PW91).24 The 6-31G(d,p)
basis set was used for the H, C, N, Si, P and Cl atoms. The
Hay-Wadt effective core potentials (ECP) and the corre-
sponding VDZ basis sets were used for the Mo atoms.25 The
same level of theory was used in the frequency calculations
performed at the located stationary points. The thermody-
namic parameters were calculated in the rigid rotor-harmonic
oscillator approximation.
squares procedures (Table 7).26 All non-hydrogen atoms were
refined anisotropically, the hydrogen atoms except the hydride
(which was located from Fourier difference synthesis and posi-
tionally refined isotropically) were placed in calculated positions
and refined in a “riding” model.
Acknowledgment. G.I.N. and P.M. thank the Royal Society
(London) for a joint research grant. This research was further
supported by the Royal Society of Chemistry award to Inter-
national Authors and by a grant from Petroleum Research
Funds administered by the ACS (to G.I.N.). S.K.I. is grateful
to the Russian Fund for Basic Research for a research grant. We
thank Dr. A. R. Cowley for collecting the X-ray data.
Crystal Structure Determinations for 11b. The crystals of 11b
were grown from diethyl ether by cooling to -30 °C. The
crystals were mounted in a film of perfluoropolyether oil on a
glass fiber and transferred to a Siemens three-circle diffract-
ometer with a CCD detector (SMART system). The data were
corrected for Lorentz and polarization effects. The structure
was solved by direct methods and refined by full-matrix least-
Supporting Information Available: VT NMR spectra for
compound 3c and X-ray data in CIF format for compound
11b. This material is available free of charge via the Internet at
http://pubs.acs.org.
(24) (a) Becke, A. D. J. Chem. Phys. 1993, 98, 5648. (b) Perdew, J. P.;
Burke, K.; Wang, Y. Phys. Rev. B 1996, 54, 16533.
(25) Hay and, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 299.
(26) SHELXTL-Plus, Release 5.10; Bruker AXS Inc.: Madison, WI, 1997.