Synthesis of Chelate-Supported Dialkyl and Alkylidene Complexes of Molybdenum (VI)

Article abstract of DOI:10.1021/om990124o

The use of chelating diamide [o-(Me₃SiN)₂C₆H₄]^2- as a coligand for high-oxidation early transition metal complexes has been investigated. Reaction of Mo(NPh)₂Cl₂DME with Li₂[o-(Me₃SiN)₂C₆H₄] afforded green microcrystals of [Mo(NPh)(μ-NPh)(o-(Me₃SiN)₂C₆H ₄)]2 (1), while reaction of Mo(NPh)₂Cl₂DME with H₂[o-(Me₃SiN)₂C₆H₄] gave Mo(NPh)Cl₂(o-(Me₃-SiN)₂C₆H ₄)(NH₂Ph) (2). Two derivatives of 2 are reported, Mo(NPh)Cl₂(o-(Me₃SiN)₂C₆H ₄)-(PMe₃) (3) and Mo(NPh)Cl₂(o-(Me₃SiN)₂C₆H ₄)(THF) (4). Structural studies of 3 are reported. Reaction of 3 or 4 with RMgX (X = Cl or Br) gave Mo(NPh)R₂(o-(Me₃SiN)₂C₆H ₄) (R = Me 5, Ph 6, CH₂CMe₃ 7, CH₂Ph 8, CH₂SiMe₃ 9). Reaction of 2 with RMgCl (R = CH₂CMe₃) CH₂-SiMe₃) gave mixtures of Mo(NPh)R₂(o-(Me₃SiN)₂C₆H ₄) and Mo(NPh)₂R₂. Both Mo(NPh)₂-(CH₂CMe₃)2 (10) and Mo(NPh)₂(CH₂SiMe₃)₂ (11) were isolated form the reaction of Mo(NPh)₂Cl₂DME and RMgCl (R = CH₂CMe₃, CH₂SiMe₃). The alkylidene, Mo(NPh)(C(H)-CMe₃)(o-(Me₃SiN)₂C ₆H₄)(PMe₃) (13), was isolated from the reaction of 7 and an excess of PMe₃ at 80 ^°C, while Mo(NPh)(C(H)SiMe₃)(o-(Me₃SiN)₂C ₆H₄)(PMe₃) (14) was only observed by 1 H NMR under similar conditions.

Full text of DOI:10.1021/om990124o

Organometallics 1999, 18, 4253-4260
4253
Articles
Syn th esis of Ch ela te-Su p p or ted Dia lk yl a n d Alk ylid en e
Com p lexes of Molybd en u m (VI)
Carlos G. Ortiz, Khalil A. Abboud, and J ames M. Boncella*
Department of Chemistry and Center for Catalysis, University of Florida,
Gainesville, Florida 32611-7200
Received February 22, 1999
The use of chelating diamide [o-(Me3SiN)2C6H4]2- as a coligand for high-oxidation early
transition metal complexes has been investigated. Reaction of Mo(NPh)2Cl2DME with Li2[o-
(Me3SiN)2C6H4] afforded green microcrystals of [Mo(NPh)(µ-NPh)(o-(Me3SiN)2C6H4)]2 (1),
while reaction of Mo(NPh)2Cl2DME with H2[o-(Me3SiN)2C6H4] gave Mo(NPh)Cl2(o-(Me3-
SiN)2C6H4)(NH2Ph) (2). Two derivatives of 2 are reported, Mo(NPh)Cl2(o-(Me3SiN)2C6H4)-
(PMe3) (3) and Mo(NPh)Cl2(o-(Me3SiN)2C6H4)(THF) (4). Structural studies of 3 are reported.
Reaction of 3 or 4 with RMgX (X ) Cl or Br) gave Mo(NPh)R2(o-(Me3SiN)2C6H4) (R ) Me 5,
Ph 6, CH2CMe3 7, CH2Ph 8, CH2SiMe3 9). Reaction of 2 with RMgCl (R ) CH2CMe3, CH2-
SiMe3) gave mixtures of Mo(NPh)R2(o-(Me3SiN)2C6H4) and Mo(NPh)2R2. Both Mo(NPh)2-
(CH2CMe3)2 (10) and Mo(NPh)2(CH2SiMe3)2 (11) were isolated form the reaction of
Mo(NPh)2Cl2DME and RMgCl (R ) CH2CMe3, CH2SiMe3). The alkylidene, Mo(NPh)(C(H)-
CMe3)(o-(Me3SiN)2C6H4)(PMe3) (13), was isolated from the reaction of 7 and an excess of
PMe3 at 80 °C, while Mo(NPh)(C(H)SiMe3)(o-(Me3SiN)2C6H4)(PMe3) (14) was only observed
1
by H NMR under similar conditions.
In tr od u ction
lidene compounds supported by ligands derived from
N,N′-bis(trimethylsilyl)-o-phenylenediamine (H2-o-(Me3-
SiN)2C6H4).6 By using this chelating ligand, we achieved
the syntheses of thermally stable, coordinatively un-
saturated dialkyl species.7 These complexes display
insertion chemistry with alkyl isocyanides8 and undergo
â-hydride abstraction in the presence of Lewis bases.9
In addition, the thermally stable neopentylidene com-
For several decades the study of high oxidation state,
early transition metal compounds and their derivatives
has been the focus of intense research due to their use
in organic synthesis and in catalysis.1 Among the most
studied derivatives of high oxidation state early transi-
tion metal compounds are metal alkyls and alkylidenes.
High oxidation state alkyls have been extensively used
as catalysts for the polymerization of olefins, as exem-
plified by the large number of reports using group 4
metallocene type systems.2 Likewise, the importance of
alkylidenes is demonstrated by the comprehensive study
of the olefin metathesis reactions that they are able to
catalyze.3,4 Through this reaction, alkylidenes have been
shown to catalyze the polymerization of strained olefinic
ring systems in ring opening metathesis polymerization
(ROMP) and the polymerization of acyclic dienes (AD-
MET).5
(4) (a) Schrock, R. R. Acc. Chem. Res. 1990, 23, 158. (b) Schrock, R.
R.; DePue, R. T.; Feldman, J .; Schaveren, C. J .; Dewan, J . C.; Liu, A.
H. J . Am. Chem. Soc. 1987, 109, 1423. (c) Nguyen, S. T.; Grubbs, R.
H.; Ziller, J . W. J . Am. Chem. Soc. 1993, 115, 9858. (d) McConville, D.
H.; Wolf, J . R.; Schrock, R. R. J . Am. Chem. Soc. 1993, 115, 4413. (e)
Oskam, J . H.; Schrock, R. R. J . Am. Chem. Soc. 1993, 115, 11831. (f)
O’Dell, R.; McConville, D. H.; Hofmeister, G. E.; Schrock, R. R. J . Am.
Chem. Soc. 1994, 116, 3414. (g) Schrock, R. R. Polyhedron 1995, 14,
3177. (h) Feldman, J .; Davis, W. M.; Thomas, J . K.; Schrock, R. R.
Organometallics 1990, 9, 2535. (i) Schrock, R. R.; Luo, S.; Lee, J . C.;
Zanetti, N. C.; Davis, W. M. J . Am. Chem. Soc. 1996, 118, 3883. (j)
Schrock, R. R.; Murdzek, J . S.; Bazan, G. C.; Robbins, J .; DiMare, M.;
O’Regan, M. J . Am. Chem. Soc. 1990, 112, 3875. (k) Fox, H. H.; Lee,
J . K.; Park, L. Y.; Schrock, R. R. Organometallics 1993, 12, 759. (l)
Schrock, R. R.; Weinstock, I. A.; Horton, A. D.; Liu, A. H.; Schoefield,
M. H. J . Am. Chem. Soc. 1988, 110, 2686. (m) Edwards, D. S.; Schrock,
R. R. J . Am. Chem. Soc. 1982, 104, 6806. (n) Wengrovius, J . H.;
Schrock, R. R. Organometallics 1982, 1, 148. (o) Rocklage, S. M.;
Schrock, R. R.; Churchill, M. R.; Wasserman, H. J . Organometallics
1982, 1, 1332. (p) Schrock, R. R.; De Pue, R. T.; Feldman, J .; Yap, K.
B.; Yang, D. C.; Davis, W. M.; Park, L.; Di Mare, M.; Schoefield, M.;
Anhaus, J .; Walborsky, E.; Evitt, E.; Kru¨ger, C.; Betz, P. Organome-
tallics 1990, 9, 2262. (q) Pedersen, S. F.; Schrock, R. R. J . Am. Chem.
Soc. 1982, 104, 7483.
Previous reports from our group have focused on the
chemistry of W(VI) imido dichloride, dialkyl, and alky-
(1) Collman, J . P.; Hegedus, L. S.; Norton, J . R.; Finke, R. G.
Principles and Applications of Organotransition Metal Chemistry;
University Science Books: Mill Valley, CA, 1987.
(2) (a) Ciardelli, F.; Carlini, C. In Comprehensive Polymer Science;
Pergamon: New York, 1992; 1st suppl, Chapter 4. (b) Coates, G. W.;
Waymouth, R. M. In Comprehensive Organometallic Chemistry II;
Pergamon: New York, 1995; Vol. 12, Chapter 12.1.
(3) (a) Ivin, K. J . Olefin Metathesis; Academic Press: London, 1983.
(b) Feldman, J .; Schrock, R. R. Prog. Inorg. Chem. 1991, 39, 1. (c)
Moore, J . S. In Comprehensive Organometallic Chemistry II; Perga-
mon: New York, 1995; Vol. 12, Chapter 12.2.
(5) Wagener, K. B.; Boncella, J . M.; Nel, J . G.; Duttweiler, R. P.;
Hillmyer, M. A. Makromol. Chem. 1990, 191, 365.
(6) (a) Vanderlende, D. D.; Abboud, K. A.; Boncella, J . M. Polym.
Prepr. 1994, 35, 691. (b) Vanderlende, D. D.; Abboud, K. A.; Boncella,
J . M. Organometallics 1994, 13, 3378.
10.1021/om990124o CCC: $18.00 © 1999 American Chemical Society
Publication on Web 09/23/1999

4254 Organometallics, Vol. 18, No. 21, 1999
Ortiz et al.
plex W(NPh)(C(H)CMe3)(o-(Me3SiN)2C6H4)(PMe3) was
shown to catalyze the ROMP of norbornene and cy-
clooctene and catalyze the ADMET oligomerization of
1,9-decadiene.10
nylimido ortho-protons were observed as two doublets
at 6.55 ppm (4H) and 6.74 ppm, which arise from the
inequivalent phenylimido groups. This inequivalency
was also confirmed by the observation of a triplet at 6.87
ppm (2H) and a triplet overlapping with the doublet at
6.74 ppm (together integrating to 6H), with both triplets
corresponding to the para-phenylimido hydrogens. A
triplet for a meta-phenyl imido hydrogen was observed
at 7.00 ppm, with its inequivalent counterpart overlap-
ping with one of the pda-ring resonances from 7.07 to
7.12 ppm. The other pda-ring resonance was clearly
observed at 7.26 ppm (4H).
Further proof of the formulation of 1 was obtained
from a single-crystal X-ray diffraction study. Unfortu-
nately, a structure refinement suitable for publication
was not obtained. However, the data were sufficient to
confirm the identity of 1 as an imido-bridged dimer
supported by the chelating-diamide group. Efforts to
grow higher quality single crystals for X-ray diffraction
are continuing. It is noted that several examples of
imido-bridged dimers have been reported; thus the
structure of 1 is precedented.14
For some time, we have been interested in using N,N′-
disubstituted-o-phenylenediamides (o-pda) as ancillary
ligands for other high oxidation state early transition
metal systems. While disubstituted-pda compounds
have already been reported for Zr(IV), Ti(IV),11 and
recently Ta(V),12 our efforts with other members of
group 6 have, until now, been unsuccessful. We now
wish to report the syntheses and characterization of Mo-
(VI) complexes supported by imido and chelating-
diamide coligands. Included in this work are the syn-
theses of dichloride and dialkyl species, the synthesis
of alkylidene species, and the isolation of a dimeric Mo-
(VI) complex.
Resu lts a n d Discu ssion
Syn th esis of Im id o-Br id ged Dim er . Since our
bidentate diamide ligand was bound to W(VI) through
the reaction of dilithiated Li2-o-(Me3SiN)2C6H4 with
W(NPh)Cl4(OEt2),6 the reaction of Li2-o-(Me3SiN)2C6H4
with Mo(NPh)2Cl2DME13 was investigated.
Syn th esis of Ch ela te-Su p p or ted Dich lor id e Sp e-
cies. When a suspension of brick-red Mo(NPh)2Cl2DME
in hexanes was mixed with a hexanes solution contain-
ing 2 equiv of H2-o-(Me3SiN)2C6H4 and stirred overnight,
a slow reaction occurred giving a dark green solution
along with the formation of a blue precipitate. Filtration
of the reaction mixture gave a nearly quantitative yield
of a hexanes-insoluble blue-purple powder, 2.
When Li2-o-(Me3SiN)2C6H4 was prepared in situ in
Et2O, cooled to -78 °C, and then added to an -78 °C
Et2O solution of Mo(NPh)2Cl2DME, a rapid color change
from orange to green occurred as the reaction mixture
returned to room temperature. Filtration of the reaction
mixture followed by extraction of the remaining solids
with toluene and removal of the solvent in vacuo
produced low yields of forest-green, microcrystalline
[Mo(NPh)(µ-NPh)(o-(Me3SiN)2C6H4)]2 (1).
The NMR spectra of 2 were consistent with the
structure shown in eq 2. Proton NMR (C6D6) spectra of
1
The H NMR spectra are consistent with the dimeric
structure shown in eq 1. A sharp singlet was observed
2 displayed one resonance due to equivalent Me3Si
groups at 0.40 ppm (18H) and a broad singlet at 3.92
ppm (2H) corresponding to the coordinated aniline N-H
at -0.04 ppm (36H) and is assigned to equivalent Me3-
1
protons. Although the aromatic region in the H NMR
Si methyl groups. Signals corresponding to the phe-
of 2 was rather complex (three different phenyl rings),
the presence of the o-phenylenediamide ring was con-
(7) Boncella, J . M.; Wang, S. Y.; Vanderlende, D. D.; Huff, R. L.;
Vaughan, W. M.; Abboud, K. A. J . Organomet. Chem. 1996, 530, 59.
(8) Huff, R. L.; Wang, S. Y.; Abboud, K. A.; Boncella, J . M. Abboud,
K. A. Organometallics 1997, 16, 1779.
(9) (a) Wang, S. Y. S.; Abboud, K. A.; Boncella, J . M. J . Am. Chem.
Soc. 1997, 119, 11990. (b) Wang, S. Y. S.; Vanderlende, D. D.; Abboud,
K. A.; Boncella, J . M. Organometallics 1998, 17, 2628.
(10) Vaughan, W. M.; Abboud, K. A.; Boncella, J . M. J . Am. Chem.
Soc. 1995, 117, 11015.
(11) Aoyagi, K.; Kalai, K.; Gantzel, P. K.; Tilley, T. D. Organome-
tallics 1996, 15, 923.
(12) (a) Aoyagi, K.; Kalai, K.; Gantzel, P. K.; Tilley, T. D. Polyhedron
1996, 15, 4299. (b) Pinad, G. J .; Thornton-Pett, M.; Bochmann, M. J .
Chem. Soc., Dalton Trans. 1998, 393.
(14) (a) Nugent, W. A. Inorg. Chem. 1983, 22, 965. (b) Amor, F.;
Sal, P. G.; de J esus, E.; Martin, A.; Perez, A. I.; Royo, P.; Vazquez, A.
Organometallics 1996, 15, 2103. (c) Nugent, W. A.; Harlow, R. L. J .
Am. Chem. Soc. 1980, 102, 1759. (d) Leung, W. H.; Danopoulos, A. A.;
Wilkinson, G.; Bates, B. H.; Hursthouse, M. B. J . Chem. Soc., Dalton
Trans. 1991, 2051. (e) Walsh, P. J .; Hollander, F, J .; Bergman, R. G.
J . Am. Chem. Soc. 1988, 110, 8729. (f) Chisholm, M. H.; Folting, K.;
Huffman, J . C.; Ratermann, A. L. Inorg. Chem. 1982, 21, 978. (g)
Thorn, D. L.; Nugent, W. A.; Harlow, R. L. J . Am. Chem. Soc. 1981,
103, 357. (h) Danopoulos, A. A.; Wilkinson, G. Polyhedron 1990, 9,
1009. (i) Nugent, W. A.; Harlow, R. L. Inorg. Chem. 1979, 18, 2030. (j)
Dyer, P. W.; Gibson, V. C.; Clegg, W. J . Chem. Soc., Dalton Trans.
1995, 3313. (k) Sullivan, A. C.; Wilkinson, G.; Moteralli, M.; Hurst-
house, M. B. J . Chem. Soc., Dalton Trans. 1988, 53.
(13) Fox, H. H.; Yap, K. B.; Robbins, J .; Cai, S.; Schrock, R. R. Inorg.
Chem. 1992, 31, 2287.

Dialkyl and Alkylidene Complexes of Mo(VI)
Organometallics, Vol. 18, No. 21, 1999 4255
Ta ble 1. Cr ysta l Da ta a n d Str u ctu r e Refin em en t
for 3
firmed by its two distinct resonances centered at 6.6
ppm (m, 4H). Slightly lower yields of 2 were obtained
by refluxing Mo(NPh)2Cl2DME and 1 equiv of H2-o-(Me3-
SiN)2C6H4 in hexanes for 7 h followed by cooling to room
temperature and filtration. Alternatively, 2 was also
isolated by stirring equimolar quantities of starting
materials in hexanes at room temperature for 2 days.
A possible pathway for the formation of 2 involves loss
of DME from the starting material followed by coordi-
nation of the Mo atom to H2-o-(Me3SiN)2C6H4. Diamine
protons are then either both transferred to an imido
nitrogen or form a dianilide complex followed by R
abstraction of an NH proton by one of the anilide groups.
These types of proton-transfer reactions have been
postulated to be part of the formation of multiply bonded
ligands in related complexes.15 For example, Wilkinson
et al.16 reported that the reaction of Cr(NBut)2Cl2 and
excess NH2But resulted in the formation of Cr(NBut)2-
(NHBut)Cl with loss of ButNH3Cl. Nugent and Chan17
have reported that W(N-t-Bu)2(HN-t-Bu)2 reacts with
substituted vicinal diols to form chelated-glycolate
compounds W(N-t-Bu)2(X)(NH2-t-Bu) (X ) pinacolate,
benzopinacolate, and perfluoropinacolate) with loss of
aniline. In addition, Wigley et al. have reported that
[Mo(NAr)3Cl]- is converted to Mo(NAr)2(NH2Ar)2 in the
presence of NH2Ar.18
empirical formula
fw
C25H46Cl2MoN3OPSi2
658.64
temperature
wavelength
crystal system
space group
unit cell dimens
173(2) K
0.71073 Å
monoclinic
P2(1)/c
a ) 9.7269(2) Å, R ) 90°
b ) 17.7600(4) Å, â ) 94.237(1)°
c ) 18.9629(4) Å, γ ) 90°
3266.88(12) Å3, 4
1.339 Mg/m3
volume, Z
density (calcd)
abs coeff
0.709 mm-1
F(000)
1376
crystal size
θ range for data collection
limiting indices
0.28 × 0.16 × 0.14 mm
2.10-27.50°
-12e h e 11, -21e k e 22,
-22 e l e 24
21565
7435 [R(int) ) 0.0308]
empirical
no. of reflns collected
no. of indep reflns
abs corr
max. and min. transmn
refinement method
0.928 and 0.712
full-matrix least-squares on F2
no. of data/restraints/params 7435/0/461
goodness-of-fit on F2
final R indices [I > 2σ(I)]
R indices (all data)
extinction coeff
largest diff peak and hole
1.027
R1 ) 0.0283, wR2 ) 0.0676 [6045]
R1 ) 0.0409, wR2 ) 0.0734
0.0010(2)
0.492 and -0.702 e Å-3
Because of possible side reactions with coordinated
aniline during alkylation reactions, species of the type
Mo(NPh)Cl2(o-(Me3SiN)2C6H4)L (L ) PMe3 3, THF 4)
were prepared from 2. Compound 3 was prepared by
NMR spectra in C6D6 confirmed the presence of coor-
dinated THF as two multiplets at 1.06 ppm (4H) and
3.56 ppm (4H). In addition, the singlet at 0.44 ppm
corresponding to the equivalent Me3Si methyl groups
was consistent with octahedral coordination geometry.
Crystals of 3 were obtained by cooling a concentrated
Et2O solution to -20 °C for several days. Data collection
and refinement parameters are listed in Table 1. As
Figure 1 shows, 3 has a distorted octahedral geometry
with the PMe3 and phenylimido ligands in mutually
trans positions. The molybdenum metal center is raised
0.307(1) Å above the plane containing the chloride and
amido N atoms. A long Mo-P(1) bond length of 2.7240(6)
Å19,20 is indicative of a weak interaction between the
metal center and the phosphorus atom. The Mo-N3
bond length of 1.745(2) Å is consistent with a MotN
triple bond.21 The Mo-N1 [2.018(2) Å] and Mo-N2
[2.017(2) Å] bond lengths are within normal values for
Mo-N single bonds as are the Mo-Cl1 and Mo-Cl2
distances.
dissolving 2 in Et2O at room temperature followed by
addition of excess PMe3 with stirring. Blue-purple
microcrystals of 3 were obtained by concentrating the
reaction mixture and cooling to -78 °C. Proton and 13C
NMR spectra suggest that 3 has pseudo-octahedral
coordination geometry, with the phenylimido and PMe3
ligands occupying mutually trans positions. Proton
NMR spectra showed equivalent Me3Si groups, which
give rise to one resonance at 0.44 ppm (18H). A doublet
centered at 0.73 ppm (9H, J PH ) 8.7 Hz) was assigned
to the PMe3 methyl groups. The pda ligand showed its
characteristic set of resonances centered around 6.90
ppm (m, 4H). In addition, two triplets and a doublet
corresponding to the imido ligand were also observed
(6.77 ppm (t), 7.04 ppm (t), and 7.83 ppm (d)).
(19) (a) Galindo, A.; Gutierrez, E.; Monge, A.; Paneque, M.; Pastor,
A.; Perez, P. J .; Rogers, R. D.; Carmona, E. J . Chem. Soc., Dalton Trans.
1995, 3801. (b) Green, M. L. H.; Konidis, P. C.; Mountford, P. J . Chem.
Soc., Dalton Trans. 1994, 2851. (c) Goedheijt, M. S.; Akkerman, O. S.;
Bickelhaupt, F.; can Leeuwen, P. W. N. M.; Veldman, N.; Spek, A. L.
Organometallics 1994, 13, 2931. (d) Borgmann, C.; Limberg, C.; Driess,
A. J . Organomet. Chem. 1997, 541, 367. (e) Dilworth, J . R.; Gibson, V.
C.; Lu, C.; Miller, J . R.; Redshaw, C.; Zheng, Y. J . Chem. Soc., Dalton
Trans. 1997, 269. (f) Limberg, C.; Buchner, M.; Heinze, K.; Walter, O.
Inorg. Chem. 1997, 36, 872. (g) Yooh, K.; Parkin, G.; Rheingold, A. L.
J . Am. Chem. Soc. 1992, 114, 2210.
(20) A search of the Cambridge Database (October, 1998 release)
revealed that 3 has a Mo-P bond that is more that 0.2 Å longer than
the average Mo-P bond in six-coordinate molecules (2.507 Å). Allen,
F. H.; Kennard, O. Chem. Des. Automation News 1993, 8, 31.
(21) (a) Chou, C. Y.; Huffman, J . C.; Maatta, E. A. J . Chem. Soc.,
Chem. Commun. 1984, 1184. (b) Vaughan, W. M.; Abboud, K. A.;
Boncella, J . M. Organometallics 1995, 14, 1567. (c) Schrock, R. R.;
Murdzek, J . S.; Bazan, G. C.; Robbins, J .; DiMare, M.; O’Regan, M. J .
Am. Chem. Soc. 1990, 112, 3875. (d) Casty, G. L.; Tilley, T. D.; Yap,
G. P. A.; Rheingold, A. L. Organometallics 1997, 16, 4746. (e) Dyer, P.
W.; Gibson, V. C.; Howard, J . A. K.; Whittle, B.; Wilson, C. J . Chem
Soc., Chem. Commun. 1992, 1666. (f) Dyer, P. W.; Gibson, V. C.;
Howard, J . A. K.; Wilson, C. J . Organomet. Chem. 1993, 462, C15.
The THF adduct Mo(NPh)Cl2(o-(Me3SiN)2C6H4)THF,
4, was prepared by stirring 2 in THF for 1 h followed
by precipitation with pentane and filtration. Proton
(15) (a) Nugent, W. A.; Mayer, J . M. Metal-Ligand Multiple Bonds:
Wiley-Interscience: New York, 1988; Chapter 3. (b) Wigley, D. E. Prog.
Inorg. Chem. 1994, 42, 239.
(16) Danopoulos, A. A.; Leung, W. H.; Wilkinson, G.; Battes, B. H.;
Hursthouse, M. B. Polyhedron 1990, 9, 2625.
(17) Chan, D. M. T.; Fultz, W. C.; Nugent, W. A.; Roe, D. C.; Tulip,
T. H. J . Am. Chem. Soc. 1985, 107, 251.
(18) Morrison, D. L.; Wigley, D. E. Inorg. Chem. 1995, 34, 2610.

4256 Organometallics, Vol. 18, No. 21, 1999
Ortiz et al.
shown in eq 4. There are two triplets in a 2:1 ratio at
6.82 ppm (2H) and 6.90 ppm (1H), which were assigned
to the phenyl group hydrogens para to the metal center
and para to the imido nitrogen, respectively. Another
set of resonances that confirmed the identity of 6 are
two doublets in a 4:2 ratio at 7.40 and 7.61 ppm, which
are assigned to the phenyl group protons ortho to the
metal center and ortho to the imido nitrogen, respec-
tively. One of the resonances attributed to the pda-ring
protons was observed, but it is partially overlapping
with the doublet at 7.40 ppm. However, these two
resonances integrate to six total hydrogens.
The 1H spectra of 7-9 are similar in that they display
resonances that are assigned to equivalent Me3Si groups
as well as doublets (or in the case of 8 an AB quartet)
for the methylene protons of the alkyl groups. Although
these spectra are consistent with a square pyramidal
structure, they are also consistent with rapidly equili-
brating square pyramidal and trigonal bipyramidal
structures at room temperature. Given that the solid-
state structure of W(NPh)(CH2CMe3)2(o-(Me3SiN)2C6H4)
is a trigonal bipyramid7 and that the compound is
F igu r e 1. Thermal ellipsoid drawing of 3. Thermal el-
lipsoids are drawn to 40% probability.
1
fluxional at room temperature, we investigated the H
Syn th esis of Dia lk yl Com p lexes. The reaction of
4 with 2 equiv of RMgCl (R ) Me 5, R ) Me3CCH2 7,
PhCH2 8, Me3SiCH2 9) in Et2O at -78 °C gave orange-
red mixtures within 1 h, and the reaction of 4 with 2
equiv of RMgBr (R ) Ph 6) produced a purple mixture
within 1 h. Removal of the solvent followed by extraction
with pentane or toluene separated the desired dialkyl
products Mo(NPh)R2(o-(Me3SiN)2C6H4) from the mag-
nesium salts. Complexes 5, 7, and 9 were crystallized
by cooling concentrated acetonitrile solutions to 0 °C,
while compounds 6 and 8 were recrystallized from
toluene and pentane solutions cooled to -78 °C, respec-
tively.
spectra of 7-9 at low temperatures.
1
Variable-temperature H NMR studies showed that
7 and 9 are fluxional in solution and that decoalescence
of the Me3Si peak occurs at -18 and -30 °C, respec-
tively. The two-site exchange approximation gives ∆Gq
) 12.6 kcal/mol for this process for 7 and ∆Gq ) 11.9
kcal/mol for 9.23 Thus, the NMR spectra of both 7 and
9 are consistent with trigonal bipyramidal structures
in which the imido group and one Me3SiN group occupy
the axial positions. It appears that this geometry is
preferred over the square pyramid with an apical imido
group for steric reasons. The 1H NMR spectrum of 8 was
invariant from room temperature to -78 °C.
Rea ctivity of 2 w ith Alk yla tin g Agen ts. When 2
was allowed to react with 2 equiv of RMgCl (R ) Me3-
CCH2 or Me3SiCH2) in diethyl ether at -78 °C, an
unexpected mixture of products was obtained. The
mixture contained 7 and 9 as well as the bis-imido
species of the type Mo(NPh)2R2 (10, and 11, respec-
tively). Formation of dimeric 1 was not observed.
Proton NMR spectra of 5 in C6D6 revealed the
presence of two methyl groups as a singlet at 1.13 ppm
(6H). Both the methyl and Me3Si groups, respectively,
were equivalent at room temperature. This suggests
that the coordination geometry of this compound is
square pyramidal with the phenylimido group occupying
the apical position (eq 4). Carbon-13 NMR spectra in
Mo(NPh)Cl2(o-(SiMe3N)2C6H4)(NH2Ph) +
Et2O, -78 °C
Mo(NPh)R2(o-(SiMe3N)2C6H4)
2RMgCl
8
R ) CH2CMe3, 7 and 10
CH2SiMe3, 9 and 11
+ Mo(NPh)2R2 (5)
We have independently prepared 10 and 11 by reac-
tion of Mo(NPh)2Cl2DME with 2 equiv of RMgCl (R )
(22) For review of agostic interactions: Brookhart, M.; Green, M.
L. H.; Wang, L. Prog. Inorg. Chem. 1988, 36, 1. More recent ex-
amples: (a) Coles, M. P.; Gibson, V. C.; Clegg, W.; Elsewood, M. R. J .
Polyhedron 1998, 17, 2483. (b) J affart, J .; Mathier, R.; Etienne, M.;
McGrady, J . E.; Eisenstein, O.; Maseras, F. J . Chem. Soc., Chem.
Commun. 1998, 2011. (c) Cole, J . M.; Gibson, V. C.; Howard, J . A. K.;
McIntyre, G. J .; Walker, G. L. P. J . Chem. Soc., Chem. Commun. 1998,
1829. (d) Rietveld, M. H. P.; Teunissen, W.; Hagen, H.; van de Water,
L.; Grove, D. M.; van der Schaaf, P. A.; Mu¨hlebach, A. L.; van Koten,
G. Organomentallics 1997, 16, 1674. (e) Haaland, A.; Scherer, W.;
Ruud, K.; McGarrady, G. C.; Downs, A. J .; Swang, O. J . Am. Chem.
Soc. 1998, 120, 3762. (f) J ordan, R. F.; Bradley, P. K.; Baenziger, N.
C.; LaPointe, R. E. J . Am. Chem. Soc. 1990, 112, 1289.
CDCl3 show the methyl carbons to be at 31.28 ppm with
1
a coupling constant of J CH ) 126.4 Hz. This coupling
constant indicates that agostic interactions22 between
the methyl hydrogens and the metal center in 5 are
unlikely, at least at room temperature, despite the 16e-
formal electron count at the metal center.
Proton NMR spectra of 6 in C6D6 solution showed
equivalent Me3Si groups at 0.11 ppm (18H), which
suggested the symmetric square pyramidal structure
(23) Sandstro¨m, J . Dynamic NMR Spectroscopy; Academic Press:
New York, 1982.

Dialkyl and Alkylidene Complexes of Mo(VI)
Organometallics, Vol. 18, No. 21, 1999 4257
Sch em e 1
d8) do not show evidence for proton exchange even when
cooled to -85 °C.
Syn th esis of Ch ela te-Su p p or ted Alk ylid en es.
The alkylidene complex 13 was obtained when a toluene
solution of 7 was heated to 80 °C for 0.5 h in the
presence of excess PMe3. Proton NMR spectra of this
purple solid revealed a singlet at 0.37 ppm (18H)
assigned to Me3Si methyl groups, a broadened doublet
at 0.85 ppm corresponding to coordinated PMe3, and a
singlet at 1.32 ppm (9H), which was assigned to the
alkylidene tert-butyl group. A small, broad singlet was
observed at 12.13 ppm (1H) and is assigned to the
alkylidene hydrogen.
Me3CCH2 and Me3SiCH2) in Et2O at -78 °C. Both 10
and 11 were obtained in high yields and purity in this
manner. Similar compounds have been reported by
Schrock24 and Osborn25 as intermediates in the synthe-
ses of molybdenum(VI) alkylidenes with alkoxide or
triflate ancillary ligands. However, they did not report
these complexes (presumably because of the unexpected
insolubility of 10 and 11 in aliphatic hydrocarbon
solvents). Proton NMR (C6D6) spectra of 10 showed the
neopentyl methyl resonance as a sharp singlet at 1.19
ppm (18H) and the methylene protons as a singlet at
2.06 ppm (4H). Proton NMR (C6D6) of 11 showed a sharp
singlet at 0.17 ppm (18H) corresponding to the Me3Si
methyl protons and a singlet at 1.58 ppm (4H) for the
methylene protons. The aromatic region showed the
normal resonances for equivalent phenyl imido groups.
Alkylidene 13 demonstrated fluxional behavior while
in solution. A coalesced resonance was observed at room
temperature for the Me3Si groups, which decoalesced
at -37 °C (∆Gq ) 12.51 kcal/mol). The mechanism for
this equilibration is proposed to involve the reversible
dissociation of phosphine from the metal center. The
dissociation induces a plane of symmetry in the mol-
ecule, which makes the Me3Si groups equivalent. A
similar mechanism is observed in the analogous tung-
sten complex.6b
In a similar reaction, when bis(trimethylsilylmethyl)
9 was heated to 85 °C in toluene-d8 in the presence of
excess PMe3, formation of the corresponding alkylidene
was observed. The formation of alkylidene 14 was
confirmed by a singlet at 13.62 ppm attributed to the
alkylidene proton and a singlet near 0.0 ppm for TMS.
This alkylidene, however, has proven difficult to isolate
in pure form.
P olym er iza tion Rea ction s. The activity of several
of the compounds described above toward olefin polym-
erization was examined. Dimethyl 5 was added to an
ethylene-saturated MAO solution in toluene. After 10
min no polyethylene was obtained. However, the po-
lymerization of norbornene was achieved by preparing
alkylidenes in situ. In separate experiments, small
samples of the dialkyls 7, 8, and 9 were heated to 85 °C
in toluene for 0.5 h. To these reaction mixtures, toluene
solutions of freshly sublimed norbornene were added
and stirred without heat for 1 h. Moderate quantities
of polynorbornene were isolated in both cases as white
solids. Further study of these polymerization reactions
One possible explanation for the reactivity observed
in the reaction of 2 with alkylating agents is shown in
Scheme 1. If 2 is equilibrating with 12, alkylation of 12
would lead to 10 and 11, while alkylation of 2 would
give 7 and 9. In separate NMR-scale experiments,
samples of 7 and 10 were combined with aniline and
H2-o-(Me3SiN)2C6H4, respectively. No reaction was ob-
served in either case. This eliminates the possibility that
in the presence of aniline or H2-o-(Me3SiN)2C6H4 the
dialkyl species interconvert. We were, however, unable
to detect further evidence for the equilibrium between
12 and 2 other than the reactivity observed with the
alkylating agents. Proton NMR samples of 2 (toluene-
(24) Oskam, J . H.; Fox, H. H.; Yap, K. B.; Mcconville, D. H.; O’Dell,
R.; Lichtenstein, B. J .; Schrock, R. R. J . Organomet. Chem. 1993, 459,
185.
(25) Schoettel, G.; Kress, J .; Osborn, J . A. J . Chem Soc., Chem.
Commun. 1989, 1962.

4258 Organometallics, Vol. 18, No. 21, 1999
Ortiz et al.
6.54-6.80 (m, 8H, aromatic), 6.98 (t, 2H, aromatic), 7.82 (d,
2H, aromatic). 13C NMR (CDCl3): δ 1.28, 119.75, 120.99,
122.93, 125.08, 126.91, 128.49, 128.56, 129.47, 140.57, 146.03,
155.63.
Usin g 1 equ iv of Dia m in e. The above procedure was
repeated using 0.5 g (1.13 mmol) of Mo(NPh)2Cl2(DME) and
0.287 g (1.13 mmol) of bis(trimethylsylil)-o-phenylenediamine.
The reaction mixture was allowed to stir for ca. 2 days at room
temperature or refluxed in hexanes for 7 h. From either
procedure blue-purple Mo(NPh)Cl2(o-(Me3SiN)2C6H4)(NH2Ph)
was obtained in high yield and purity.
and of the isolated polymers is underway and will be
reported in the future.
Exp er im en ta l Section
Gen er a l Meth od s. All reactions were conducted under a
dry argon atmosphere using standard Schlenk techniques, and
all compounds were handled in
a nitrogen-filled drybox.
Diethyl ether, dimethoxyethane, tetrahydrofuran, toluene,
pentane, hexane, and hexamethyldisiloxane were distilled
under nitrogen from sodium or sodium benzophenone ketyl
and degassed prior to use. Acetonitrile was dried over P2O5,
vacuum-transferred into a storage flask, and stored over
molecular sieves prior to use.
NMR spectra were obtained on a Varian Gemini 300 or VXR
300 instrument in C6D6 or CDCl3 solutions, referenced to
residual solvent peaks, and reported relative to TMS. 31P NMR
spectra were referenced to external H3PO4.
The compounds Mo(NPh)2Cl2DME13 and bis(trimethylsilyl)-
o-phenylenediamine6,26 were prepared according to literature
procedures. All other reagents were obtained from Aldrich
Chemicals and used as received.
Elemental analyses were performed by Atlantic Microlab,
Inc., Norcross, GA. Despite repeated recrystallizations, we
were unable to obtain satisfactory elemental analyses for
compounds 5-13, with the results usually being 1-2% low in
carbon with satisfactory results for N and H. Given the
propensity for Mo alkyls to form metal carbides on pyrolysis,
this is not unexpected.
Mo(NP h )Cl2(o-(Me3SiN)2C6H4)(P Me3), 3. A sample of 2
(3.0 g, 4.98 mmol) was slurried in diethyl ether (25 mL) and
stirred at room temperature. A small excess of PMe3 (0.417 g,
5.48 mmol) was added via syringe. The reaction mixture
immediately formed a royal blue solution, which was stirred
for 1 h. Concentration (ca. 15 mL) followed by cooling (-78
°C) and filtration gave 2.7 g of microcrystalline 3 (92%).
Recrystallization of 3 from diethyl ether provided analytically
pure compound. Anal. Calcd for C21H36Si2N3Cl2PMo: C, 43.15;
1
H, 6.21; N, 7.19. Found: C, 43.03; H, 6.14; N, 7.23. H NMR
(C6D6): δ 0.44 (s, 18H, NSiMe3), 0.74 (d, 9H, J P-H ) 8.7 Hz,
PMe3), 6.77 (t, 1H, phenylimido para-proton), 6.83 (m, 2H,
diamine ring meta-protons), 6.99 (m, 2H, diamine ring ortho-
protons), 7.04 (t, 2H, phenylimido meta-protons), 7.83 (m, 2H,
phenylimido ortho-protons). 13C NMR (CDCl3): δ 1.41, 11.50
(d, 18.17 Hz), 120.70, 125.55, 128.34, 128.77, 129.11, 129.47.
31P NMR (C6D6): δ -22.48.
Mo(NP h )Cl2(o-(Me3SiN)2C6H4)(THF ), 4. At room temper-
ature a sample (5.0 g, 8.31 mmol) of 2 was dissolved in
tetrahydrofuran (30 mL) and stirred for 1 h. Upon addition of
THF, the reaction mixture acquired a royal blue color. Con-
centration (ca. 20 mL) followed by addition of pentane (ca. 150
mL) caused precipitation of 4, which was isolated by filtration
and dried in vacuo (5.21 g, 76%). Analytically pure 4 was
obtained after washing the product with cold pentane (ca. 20
mL) three times. Anal. Calcd for C22H35ON3Si2Cl2Mo: C, 45.51;
High-resolution mass spectra were obtained in FAB mode
on samples of the compounds dissolved in NPOE (para-
nitrophenyl octyl ether) and were performed in the Mass
Spectrometry Laboratory at the Department of Chemistry,
University of Florida.
[Mo(NP h )2(o-(Me3SiN)2C6H4)]2, 1. A sample of bis(trim-
ethylsilyl)-o-phenylenediamine (0.574 g, 2.27 mmol) was dis-
solved in 20 mL of diethyl ether and cooled to -78 °C. With
stirring, 2 equiv of n-BuLi (1.82 mL, 4.55 mmol) was added.
The yellow solution was stirred at -78 °C for 20 min and then
at room temperature for 30 min. This yellow solution was then
combined with a slurry of Mo(NPh)2Cl2(DME) (1.0 g, 2.27
mmol) in Et2O (20 mL) at -78 °C. The reaction mixture turned
to a forest-green color within a few minutes and was then
stirred at room temperature for 1 h. The solution was then
filtered and the precipitate dried under reduced pressure.
Extraction with toluene (30 mL) produced a green solution that
was then pumped to dryness, giving 1 as green microcrystals
in low yield (0.27 g, 23% yield). Washing the product four times
with cold ether and twice with pentane provided analytically
pure 1. Anal. Calcd for C48H64N8Si4Mo2: C, 54.52; H, 6.10; N,
1
H, 6.08; N, 7.24. Found: C, 45.53; H, 6.10; N, 7.18. H NMR
(C6D6): δ 0.44 (s, 18H, NSiMe3), 1.07 (m, 4H, -OCH2CH2CH2-
CH2-), 3.56 (m, 4H, -OCH2CH2CH2CH2-), 6.74 (t, 1H,
phenylimido para-proton), 6.82 (m, 2H, diamine ring meta-
protons), 6.94 (t, 2H, phenylimido meta-protons), 7.01 (m, 2H,
diamine ring ortho-protons), 7.73 (d, 2H, phenylimido ortho-
protons). 13C NMR (CDCl3): δ 1.18, 25.34, 68.58, 120.07,
120.92, 125.02, 127.26, 128.41, 128.59, 129.44.
Mo(NP h )Me2(o-(Me3SiN)2C6H4), 5. A diethyl ether solu-
tion (25 mL) of 4 (1.0 g, 1.72 mmol) was cooled to -78 °C. Two
equivalents of 3.0 M MeMgCl (1.15 mL, 3.45 mol) in Et2O was
added in a dropwise fashion, and the mixture was allowed to
warm to room temperature. The blue solution quickly turned
to an orange-red solution. After 1 h of stirring, the mixture
was pumped to dryness and extracted with pentane once (50
mL). The volume of the filtrate was then reduced ca. 10 mL.
Acetonitrile was then added (30 mL) to precipitate the product,
which was isolated by filtration at 0 °C (0.59 g, 74%). Further
purification of 5 was attained by recrystallization (five times)
from concentrated pentane/acetonitrile (20:80) solutions cooled
to 0 °C. Melting point: 96-100 °C. Anal. Calcd for C20H33N3-
Si2Mo: C, 51.36; H, 7.11; N, 8.98. Found: C, 49.11; H, 7.02;
N, 8.34. 1H NMR (C6D6): δ 0.36 (s, 18H, NSiMe3), 1.14 (s, 6H,
MoMe2), 6.84 (t, 1H, phenylimido para-proton), 6.98 (m, 2H,
diamine ring meta-protons), 7.02 (t, 2H, phenylimido meta-
protons), 7.34 (m, 2H, diamine ring ortho-protons), 7.42 (d, 2H,
phenylimido ortho-protons). 13C NMR (CDCl3): δ 1.22, 31.29
(s, Mo-Me2, J C-H ) 126.4 Hz), 122.05, 124.38, 124.83, 124.91,
128.45, 134.77, 156.45. MS Calcd for [M - CH3]+: 454.1035
m/e. Found (FAB): 454.1096 m/e.
1
10.60. Found: C, 54.37; H, 6.16; N, 10.44. H NMR (C6D6): δ
-0.04 (s, 36H, NSiMe3), 6.55 (d, 4H, aromatic), 6.75 (m, 6H,
aromatic), 6.87 (t, 2H, aromatic), 7.01 (t, 4H, aromatic), 7.1
(m, 8H, aromatic), 7.26 (m, 4H, aromatic). 13C NMR (CDCl3):
δ 1.273, 122.03, 122.27, 122.53, 123.71, 124.20, 125.67, 128.22,
128.84, 141.76, 156.28, 171.96.
Mo(NP h )Cl2(o-(Me3SiN)2C6H4)(NH2P h ), 2. Usin g 2 equ iv
of Dia m in e. A hexanes solution (30 mL) of bis(trimethylsilyl)-
o-phenylenediamine (5.74 g, 22.7 mmol) was added to a slurry
of Mo(NPh)2Cl2(DME) (5.0 g, 11.3 mmol) in hexanes (40 mL).
The dark red mixture was stirred for 24 h and filtered, giving
a blue-purple powder. Washing the powder twice with hexanes
(20 mL) followed by washing with cold diethyl ether (20 mL)
gave pure compound in 91% yield (6.23 g). Analytically pure
2 was obtained by washing twice with cold diethyl ether. Anal.
Calcd for C24H34Si2N4Cl2Mo: C, 47.91; H, 5.69; N, 9.31.
1
Found: C, 47.89; H, 5.66; N, 9.24. H NMR (C6D6): δ 0.39 (s,
Mo(NP h )P h 2(o-(Me3SiN)2C6H4), 6. A diethyl ether solu-
tion (25 mL) of 4 (0.5 g, 0.862 mmol) was cooled to -78 °C
and charged with 2 equiv of PhMgBr in Et2O (0.86 mL, 1.72
mmol). After 1 h of stirring at room temperature the mixture
18H, NSiMe3), 3.95 (s, 2H, NH2Ph), 6.24 (m, 2H, aromatic),
(26) Birkofer, L.; Kuhlthau, H. P.; Ritter, A. Chem. Ber. 1960, 93,
2810.

Dialkyl and Alkylidene Complexes of Mo(VI)
Organometallics, Vol. 18, No. 21, 1999 4259
was stripped of solvent and dried (in vacuo). Extraction with
toluene (25 mL) followed by concentration (10 mL) and cooling
(-78 °C) produced red-purple microcrystals in good yield (0.35
g, 70%). Further purification of the product was attained after
washing the crude product with cold pentane three times. The
compound may be recrystallized from Et2O at -78 °C. Melting
point: 114-117 °C. Anal. Calcd for C30H37N3Si2Mo: C, 60.89;
3.73, 58.01, 118.83, 126.81, 127.60, 128.72, 154.50.
Rea ction of 2 w ith Alk yla tin g Agen ts. To a diethyl ether
(30 mL) solution of 2 (0.45 g, 0.758 mmol) cooled to -78 °C
was added 2 equiv of 0.54 M neopentylmagnesium chloride in
Et2O (2.80 mL, 1.51 mmol) with stirring. The solution was then
allowed to stir at room temperature for 1 h. The solvent was
removed in vacuo and pentane used to extract the product.
The pentane was then removed in vacuo and the solid dried.
Proton NMR spectra showed a mixture of 7 and 10 in a 1.18:1
ratio.
1
H, 6.30; N, 7.10. Found: C, 58.54; H, 6.33; N, 6.87. H NMR
(C6D6): δ 0.12 (s, 18H, NSiMe3), 6.78-6.98 (m, aromatics),
7.06-7.12 (m, aromatics), 7.34-7.43(m, 6H, aromatics), 7.60
(d, 2H, phenylimido ortho-protons). 13C NMR (CDCl3): δ 0.46,
123.23-134.784 (aromatic, overlapping). MS Calcd for [M +
H]+: 594.1664 m/e. Found (FAB): 594.1669 m/e.
The 0.45 g of 2 was reacted with a 1.28 M solution of
trimethylsilylmethylmagnesium chloride (1.18 mL, 1.51 mmol)
following the same reaction procedure as described above.
Proton NMR spectra revealed a 1.09:1 mixture of 9 and 11.
Mo(NP h )(CH2CMe3)2(o-(Me3SiN)2C6H4), 7. A diethyl ether
(40 mL) solution of 4 (0.5 g, 0.862 mmol) was cooled to -78
°C. Two equivalents of 0.54 M neopentylmagnesium chloride
(3.19 mL, 1.72 mmol) in Et2O was added in a dropwise fashion,
and the reaction mixture was allowed to warm to room
temperature. The blue solution quickly turned to a red-brown
solution. After 1 h of stirring, the mixture was pumped to
dryness and extracted with pentane (50 mL). The filtrate was
stripped of solvent in vacuo, and 7 was isolated as a viscous
oil. Recrystallization from acetonitrile (15 mL) at 0 °C yielded
7 as a red solid in high yield (0.41 g, 79%). Further recrystal-
lization from acetonitrile gave red crystals. Anal. Calcd for
Mo(NP h )2(CH2CMe3)2, 10. Two equivalents of 0.54 M
neopentylmagnesium chloride in Et2O (8.43 mL, 4.55 mmol)
was added to a stirring slurry of Mo(NPh)2Cl2DME (1.0 g, 2.27
mmol) in Et2O (40 mL) at -78 °C and stirred for 2 h at room
temperature. The solvent was removed in vacuo and then
toluene (30 mL) added to extract a light orange solution. After
removal of the solvent in vacuo crystalline 10 was isolated in
good yield (0.81 g, 85%) and high purity. Recrystallization from
toluene/pentane gave crystals suitable for elemental analysis.
Anal. Calcd for C22H32N2Mo: C, 62.84; H, 7.67; N, 6.66.
1
Found: C, 61.63; H, 7.54; N, 6.56. H NMR (C6D6): δ 1.19 (s,
36H, CH2CMe3), 2.04 (s, 4H, CH2CMe3), 6.80 (t, 2H, phe-
nylimido para-proton), 6.99 (t, 4H, phenylimido meta-protons),
7.28 (d, 4H, phenylimido ortho-protons). 13C NMR (C6D6): δ
33.79, 81.99, 123.75, 125.24, 128.96, 157.20.
C
28H49N3Si2Mo: C, 58.00; H, 8.52; N, 7.25. Found: C, 57.10;
H, 8.61; N, 7.17. 1H NMR (C6D6): δ 0.56 (s, 18H, NSiMe3),
0.95 (s, 18H, CH2CMe3), 2.57 (d, 2H, CH2CMe3), 2.77 (d, 2H,
CH2CMe3), 6.90 (t, 1H, phenylimido para-proton), 6.96 (m, 2H,
diamine ring meta-protons), 7.09 (t, 2H, phenylimido meta-
protons), 7.30 (m, 2H, diamine ring ortho-protons), 7.75 (d, 2H,
phenylimido ortho-protons). 13C NMR (CDCl3): δ 4.17, 33.66,
38.58, 82.52, 117.97, 126.43, 128.60, 145.17, 154.44.
Mo(NP h )2(CH2SiMe3)2, 11. Two equivalents of 1.28 M
trimethylsilylmethylmagnesium chloride in diethyl ether (2.54
mL, 3.26 mmol) was added to a stirring slurry of Mo(NPh)2Cl2-
DME (0.72 g, 1.63 mmol) in Et2O (40 mL) at -78 °C and stirred
for 2 h at room temperature. The solvent was removed in
vacuo, and then pentane (ca. 25 mL) was added to extract a
dark orange solution, which after filtration and removal of the
pentane in vacuo yielded crystalline 11 as a red solid in good
yield (0.62 g, 84%). Recrystallization from pentane gave
crystals suitable for analysis. Anal. Calcd for C20H32N2Si2Mo:
C, 53.07; H, 7.12; N, 6.19. Found: C, 51.45; H, 7.10; N, 6.05.
1H NMR (C6D6): δ 0.05 (s, 36H, CH2SiMe3), 1.62 (s, 4H, CH2-
SiMe3), 7.06 (t, 2H, phenylimido para-proton), 7.13 (d, 4H,
phenylimido meta-protons), 7.24 (t, 4H, phenylimido ortho-
protons). 13C NMR (CDCl3): δ 1.96, 56.52, 123.58, 124.89,
128.54, 156.34.
Mo(NP h )(CH2P h )2(o-(Me3SiN)2C6H4), 8. Two equivalents
of a 1 M benzylmagnesium chloride solution in THF (1.72 mL,
1.72 mmol) was added to a stirring diethyl ether (30 mL)
solution of 4 (0.5 g, 0.862 mmol) at -78 °C. After 1 h of stirring
at room temperature, the mixture was pumped to dryness and
extracted with pentane (50 mL). The filtrate was then con-
centrated (ca. 10 mL), cooled to -78 °C, and filtered, giving
red-orange crystals of 8 (0.37 g, 69%). Further purification of
8 was attained by recrystallization (five times) from concen-
trated pentane solutions cooled to -78 °C. Melting point: 112-
116 °C. Anal. Calcd for C32H41N3Si2Mo: C, 62.01; H, 6.67; N,
6.78. Found: C, 61.17; H, 6.59; N, 6.63. 1H NMR (C6D6): δ
0.09 (s, 18H, NSiMe3), 2.87 (m, 4H, CH2Ph), 6.86 (m, 3H,
aromatics), 7.07 (m, 4H, aromatics), 7.09 (m, 8H, aromatics),
7.35 (m, 4H, aromatics). 13C NMR (CDCl3): δ 1.083, 54.43,
122.32, 123.34, 125.56, 126.47, 127.53, 127.80, 128.57, 134.31,
152.79, 156.33. MS Calcd for [M + H]+: 622.1995 m/e. Found
(FAB): 622.2 m/e.
Mo(NP h )(C(H)C(CH3)3)(o-(Me3SiN)2C6H4)(P Me3), 13. In
a resealable ampule a toluene (30 mL) solution of 7 (1.12 g,
1.92 mmol) was combined with an excess of trimethylphos-
phine (1.46 g, 19.2 mmol) and heated to 80 °C for 0.5 h. The
color of the solution changed form red-orange to a dark purple
color. The toluene was removed in vacuo. Microcrystals of 13
were obtained from a concentrated pentane (ca. 5 mL) solution.
Compound 13 was recrystallized three times from pentane (ca.
5 mL) at -78 °C. Isolated yield: 0.70 g (63%). Anal. Calcd for
Mo(NP h )(CH2SiMe3)2(o-(Me3SiN)2C6H4), 9. A diethyl ether
solution (30 mL) of 4 (0.5 g, 0.862 mmol) was cooled to -78 °C
with stirring. Two equivalents of 1.28 M trimethylsilylmeth-
ylmagnesium chloride (1.34 mL, 1.72 mmol) in Et2O was added
in a dropwise fashion, and the reaction mixture was allowed
to warm to room temperature. The blue solution quickly turned
to a red-orange solution. After 1 h of stirring, the mixture was
pumped to dryness and extracted with pentane (40 mL). The
pentane filtrate was then pumped to dryness to yield 9 as a
green solid in good yield (0.42 g, 80%). The compound may be
purified by recrystallization from acetonitrile (0 °C). Anal.
Calcd for C26H49N3Si4Mo: C, 51.03; H, 8.07; N, 6.87. Found:
C, 49.95; H, 7.91; N, 6.82. 1H NMR (C6D6): δ 0.03 (s, 18H,
CH2SiMe3), 0.47 (s, 18H, NSiMe3), 1.82 (d, 2H, CH2SiMe3), 2.19
(br, 2H, CH2SiMe3), 6.87 (t, 1H, phenylimido para-proton), 6.81
(m, 2H, diamine ring meta-protons), 7.08 (t, 2H, phenylimido
meta-protons), 7.27 (m, 2H, diamine ring ortho-protons), 7.71
(d, 2H, phenylimido ortho-protons). 13C NMR (CDCl3): δ 2.27,
C
26H46N3Si2PMo: C, 53.49; H, 7.94; N, 7.19. Found: C, 51.11;
H, 7.66; N, 7.23. 1H NMR (C6D6): δ 0.378 (s, 18H, NSiMe3),
0.871 (d, 9H, J P-H ) 8.1 Hz, PMe3) 1.32 (s, 9H, C(CH3)3), 6.6-
7.2 (m, aromatic), 12.14 (s, 1H, C(H)C(CH3)3). 13C NMR
(C6D6): δ 4.0, 17.5, 35.7, 43.4, 116.2, 120.8, 123.0, 124.6, 125.9,
128.6, 148.6, 275.3.
Mo(NP h )(CHSi(CH3)3)(o-(Me3SiN)2C6H4)(P Me3), 14. In
an NMR tube a toluene-d8 solution of 9 was charged with an
excess of PMe3 and heated to 80 °C for 12 h. Formation of 14
was observed by NMR. Efforts to isolate this compound have
proven difficult.
X-r a y Exp er im en ta l. Suitable crystals of 3 were obtained
by cooling a concentrated Et2O solution to -20 °C for several
days. Data were collected at 173 K on a Siemens SMART
PLATFORM equipped with
a CCD area detector and a
graphite monochromator utilizing Mo KR radiation (λ )

4260 Organometallics, Vol. 18, No. 21, 1999
Ortiz et al.
0.71073 Å). Cell parameters were refined using 8192 reflec-
tions. A hemisphere of data (1381 frames) was collected using
the ω-scan method (0.3° frame width). The first 50 frames were
remeasured at the end of data collection to monitor instrument
and crystal stability (maximum correction on I was < 1%).
ψ-scan absorption corrections were applied based on the entire
data set.
The structure was solved by the direct methods in SHELXL-
972727 and refined using full-matrix least squares. The non-H
atoms were treated anisotropically, whereas the hydrogen
atoms were calculated in ideal positions and were riding on
their respective carbon atoms. A total of 461 parameters were
refined in the final cycle of refinement using 6045 reflections
with I > 2σ(I) to yield R1 and wR2 of 2.83% and 6.76%,
respectively. Refinement was done using F2.
Ack n ow led gm en t. We wish to acknowledge the
National Science Foundation (CHE-9523279) for the
support of this work. K.A.A. wishes to acknowledge the
National Science Foundation for funding of the purchase
of the X-ray equipment.
Su p p or tin g In for m a tion Ava ila ble: Tables of bond
lengths and angles and positional and thermal parameters.
This material is available free of charge via the Internet at
http://pubs.acs.org.
(27) Sheldrick, G. M. SHELXL-97, Program for the refinement of
crystal structures; University of Gottingen: Germany, 1997.
OM990124O