Formation of a 1-azaallenylidene ligand by reaction of an amido complex with tetracyanoethylene

Article abstract of DOI:10.1021/ic025665b

Amido complexes of Mo(II) allyl carbonyl fragments containing monodentate amido ligands, prepared by reaction of suitable chloro precursors with potassium amides, react (for the N(H)(p-tolyl) derivative) with tetracyanoethylene to give a 1-azaallenylidene complex.

Full text of DOI:10.1021/ic025665b

Inorg. Chem. 2002, 41, 4111−4113
Formation of a 1-Azaallenylidene Ligand by Reaction of an Amido
Complex with Tetracyanoethylene
,†
Dolores Morales,† Julio Pe´rez,* Luc´ıa Riera,† V´ıctor Riera,† and Daniel Miguel‡
Departamento de Qu´ımica Orga´nica e Inorga´nica/IUQOEM Facultad de Qu´ımica,
UniVersidad de OViedo-CSIC, 33071, OViedo, Spain, and Departamento de Qu´ımica Inorga´nica,
Facultad de Ciencias, UniVersidad de Valladolid, 44071 Valladolid, Spain
Received April 23, 2002
Scheme 1
Amido complexes of Mo(II) allyl carbonyl fragments containing
monodentate amido ligands, prepared by reaction of suitable chloro
precursors with potassium amides, react (for the N(H)(p-tolyl)
derivative) with tetracyanoethylene to give a 1-azaallenylidene
complex.
The strong electrophile tetracyanoethylene (TCNE) reacts
NaOMe affords stable yet highly reactive alkoxo complexes,5
and we thought that a similar route could be used to prepare
amido derivatives. Here we report the synthesis and structure
of new amido complexes [Mo(N(p-tolyl)R)(η3-C3H4-Me-2)-
(CO)2(phen)] (R) H or p-tolyl) and their reactivity toward
TCNE.
The reactions of [MoCl(η3-C3H4-Me-2)(CO)2(phen)] (1)
with K[NR(p-tol)] (R ) H or p-tolyl) afforded the amido
complexes [Mo(N(p-tol)R)(η3-C3H4Me-2)(CO)2(phen)]6 (R
) H, 2; p-tolyl, 3) (Scheme 1), which were characterized
by IR and NMR spectroscopy and, for 3, by X-ray diffraction
(Figure 1).7
with organic amines undergoing the sequential replacement
of two CN groups to afford 1,1-diamino-2,2-dicyanoethyl-
enes.1 The reactivity of TCNE toward N-metalated amines,
i.e., amido complexes, has not been studied. Coordination
compounds containing polycyanoethylene moieties, which
could be envisaged as products, have attracted considerable
attention.2 Amido complexes may show an enhanced reactiv-
ity compared with free amines as a result of π conflict
between the nitrogen lone pair of the amido ligand and filled
metal d orbitals.3 However, in most stable amido compounds,
this reactivity is mitigated by π donation from the amido
nitrogen to empty d orbitals, by steric hindrance due to bulky
ancillary ligands, or by both factors.4
We recently found that the reaction of [MoCl(η3-allyl)-
(CO)2(phen)] (phen ) 1,10-phenanthroline) complexes with
(5) Hevia, E.; Pe´rez, J.; Riera, L.; Riera, V.; Miguel, D. Organometallics
2002, 21, 1750.
(6) Synthesis of 2: K[N(H)(p-tol)] (0.26 mmol) in THF (10 mL) was
added to a solution of 1 (100 mg, 0.24 mmol) in THF (10 mL) at
-78 °C. After stirring for 10 min, in vacuo solvent evaporation,
extraction of the residue (CH2Cl2, 2 × 5 mL), filtration (Celite), in
vacuo concentration to 5 mL, layering with hexane (20 mL), and
standing at -20 °C, red crystals were obtained. Yield: 107 mg, 92%.
Anal. Calcd for C25H23MoN3O2: C, 60.86; H, 4.70; N, 8.52. Found:
C, 60.71; H, 4.97; N, 8.55. IR (νCO) (CH2Cl2): 1926, 1839. 1H NMR
(CD2Cl2): 8.94 [dd (JH2,3 ) JH9,8 ) 5.0, JH2,4 ) JH7,9 ) 1.3), 2H,
* Author to whom correspondence should be addressed. E-mail: japm@
sauron.quimica.uniovi.es. Fax: 0034985103446.
† Universidad de Oviedo-CSIC.
‡ Universidad de Valladolid.
(1) (a) Fatiadi, A. J. Synthesis 1986, 249. (b) Dhar, D. N. Chem. ReV.
1967, 67, 611. (c) Cairns, T. L.; McKusick, B. C. Angew. Chem. 1961,
73, 520.
(2) (a) Hartmann, H.; Kaim, W.; Hartenbach, I.; Schleid, T.; Wanner, M.;
Fiedler, J. Angew. Chem., Int. Ed. 2001, 40, 2842. (b) Nemykin, V.
N.; Kobayashi, N. Chem. Commun. 2001, 165. (c) Gordon, D. C.;
Deakin, L.; Arif, A. M.; Miller, J. S. J. Am. Chem. Soc. 2000, 122,
290. (d) Pokhodnya, K. I.; Epstein, A. J.; Miller, J. S. AdV. Mater.
2000, 12, 410. (e) Hoshino, H.; Iida, K.; Kawamoto, T.; Mori, T. Inorg.
Chem. 1999, 38, 4229.
(3) (a) Jayaprakash, K. N.; Gillepsie, A. M.; Gunnoe, T. B.; White, D. P.
Chem. Commun. 2002, 372. (b) Caulton, K. G. New J. Chem. 1994,
18, 25. (c) Mayer, J. M. Comments Inorg. Chem. 1988, 8, 125.
(4) (a) Mindiola, D. J.; Hillhouse, G. L. J. Am. Chem. Soc. 2001, 123,
4623. (b) Jayaprakash, K. N.; Conner, D.; Gunnoe, T. B. Organome-
tallics 2001, 20, 5254. (c) Flood, T. C.; Lim, J. K.; Deming, M. A.;
Keung, W. Organometallics 2000, 19, 1166. (d) Cummins, C. C.
Chem. Commun. 1998, 1777. (e) Gunnoe, T. B.; White, P. S.;
Templeton, J. L. J. Am. Chem. Soc. 1996, 118, 6916. (f) Francisco,
L. W.; White, P. S.; Templeton, J. L. Organometallics 1996, 15, 5127.
H2,9], 8.45 [dd (JH4,3 ) JH7,8 ) 8.6 Hz), 2H, H4,7], 7.99 [s, 2H, H5,6],
7.76 [dd, 2H, H3,8], 6.69, 6.66, 6.60 and 6.57 [AA′BB′, 4H, C6H4],
3.90 [s br, 1H, N-H], 3.00 [s, 2H, Hs], 2.08 [s, 3H, C6H4-CH3],
1.48 [s, 2H, Ha], 0.64 [s, 3H, η3-C3H4(CH3)-2]. 13C{1H} NMR (CD2-
Cl2): 231.4 [CO], 158.8, 151.7, 144.5, 137.4, 130.6, 129.4, 127.7,
125.3, 121.7 and 115.8 [phen and C6H4], 87.8 [C2, η3-C3H4(CH3)],
68.1 [C1 and C3, η3-C3H4(CH3)-2], 26.0 [C6H4-CH3], 20.1 [η3-C3H4-
(CH3)-2].
(7) Crystal data for 3: C32H29MoN3O2, M ) 583.52, monoclinic, space
group P21/n, a ) 13.194(4) Å, b ) 12.113(3) Å, c ) 17.992(5) Å, â
) 105.471(4)°, V ) 2771.1(13) Å3, T ) 293 K, Z ) 4, Dcalcd ) 1.399
Mg/m3, F(000) ) 1200, µ(Mo KR) ) 0.507 mm-1, reflections
collected/unique ) 11944/3978 (Rint ) 0.0828); parameters, 346; final
R1 ) 0.0789, wR2 ) 0.1178 (all data), GOF) 1.010, max/min residual
electron density 0.698/-0.715 e Å-3, solution and refinement using
SHELXL.20
10.1021/ic025665b CCC: $22.00 © 2002 American Chemical Society
Published on Web 07/13/2002
Inorganic Chemistry, Vol. 41, No. 16, 2002 4111

COMMUNICATION
Figure 1. Molecular structure and numbering scheme of 3 with hydrogen
atoms omitted for clarity.
As in previous reactions of chloro complexes such as 1
with carbanions8 and alkoxides,5 the amide anion gives the
stereospecific Cl- substitution, in contrast with the well-
known allylic alkylation observed with malonate or other
resonance stabilized anions.9 Thus, in the molecule of the
product, the allyl and amido groups are on opposite sides of
the plane defined by the phen nitrogens and the two
carbonyls.
Figure 2. Molecular structure and numbering scheme of 4 with hydrogen
atoms omitted for clarity.
Scheme 2
The νCO IR bands of 2 and 3 are even lower than those of
related alkoxo derivatives,5 reflecting the strongly donating
properties of the amido groups.
The 1H NMR spectra of 2 between 25 and -80 °C include
a set of four phen signals, consistent either with free rotation
around the Mo-N bond or with a single rotamer possessing
a mirror plane. Since in the solid state structure of 3 (Figure
1) the two p-tolyl groups are inequivalent, but only one set
Strong electrophiles attack selectively the amido ligand
of 2. Thus, reactions with HOTf and MeI afforded [Mo(η3-
C3H4-Me-2)(NH2(p-tol))(CO)2(phen)]OTf and [MoI(η3-C3H4-
Me-2)(CO)2(phen)], respectively. The better ligating prop-
erties of I- compared with OTf- explain the different types
of products.
The tolylamido complex 2 reacts with TCNE to give [Mo-
{NdCdC(CN)C(CN)(CdN(p-tol))}(η3-C3H4-Me-2)(CO)2-
(phen)]15 (4) (Scheme 2), characterized by spectroscopy and
X-ray diffraction (Figure 2).16
In 4 a {Mo(η3-C3H4-Me-2)(CO)2(phen)} fragment (whose
geometry is like that of the precursor 2) is bound to a
1
of p-tolyl signals is seen in the H NMR between 25 and
-80 °C, free rotation around the Mo-N seems more
plausible. On the other hand, free rotation can be expected
for complexes that, like 2 and 3, are electron precise
considering single Mo-N(amido) bonds, and lack any steric
hindrance.10 The amido group of 3 is planar at nitrogen, a
feature of most structurally characterized amido complexes.11
For electron-precise compounds such as 2 and 3, this fact is
interpreted as due to electron delocalization involving the
substituents of the amido ligand. In fact, lowering the
temperature causes the broadening of the AA′BB′ signal of
the p-tolyl groups of 2 and 3, indicating that the rotation
around the N-(p-tolyl) bonds is being frozen, in accord with
delocalization of the lone pair on the amido nitrogen over
the aryl groups.
(14) Mo(II) or W(II) amido complexes: (a) Caldarelli, J. L.; White, P. S.;
Templeton, J. L. J. Am. Chem. Soc. 1992, 114, 10097. (b) Powell, K.
R.; Pe´rez, P. J.; Luan, L.; Feng, S. G.; White, P. S.; Brookhart, M.;
Templeton, J. L. Organometallics 1994, 13, 1851. Considering single
M-N bonds; i.e., not counting π donation from N to M, these are 16
electron compounds. Using the same counting scheme, the amido
complexes reported in the present paper are 18 electron species.
(15) Synthesis of 4: TCNE (16 mg, 0.12 mmol) was added to 2 (50 mg,
0.10 mmol) in THF (20 mL). CAUTION! The HCN byproduct is
extremely toxic! Workup as for 2 gave red crystals. Yield: 56 mg,
94%. Anal. Calcd for C30H22MoN6O2: C, 60.61; H, 3.73; N, 14.14.
Found: C, 60.32; H, 4.01; N, 14.37. IR (CH2Cl2): 2206 (νCtN), 2167
(νCdN), 1961, 1881 (νCO).1H NMR (CD2Cl2): 9.17 [dd (JH2,3 ) JH9,8
) 5.0, JH2,4 ) JH7,9 ) 1.3), 2H, H2,9], 8.48 [dd (JH4,3 ) JH7,8 ) 8.1),
2H, H4,7], 7.89 [s, 2H, H5,6], 7.02 [dd, 2H, H3,8], 6.48 [s broad, 4H,
C6H4], 3.26 [s, 2H, Hs], 2.30 [s, 3H, C6H4-CH3], 1.70 [s, 2H, Ha],
0.70 [s, 3H, η3-C3H4(CH3)-2]. 13C{1H} NMR (CD2Cl2): 224.2 [CO],
152.2, 148.7, 145.2, 139.1, 134.2, 131.0, 129.4, 127.9, 125.5 and 120.9
[phen and C6H4], 85.5 [C2, η3-C3H4(CH3)], 56.8 [C1 and C3, η3-C3H4-
(CH3)-2], 21.0 [C6H4-CH3], 18.8 [η3-C3H4(CH3)-2].
The chemistry of Mo(II) carbonyl complexes has been
extensively studied;12 nevertheless, amido complexes of this
type are rare. Lack of selectivity in the synthetic reactions
and the CO-labilizing effect of the amido group13 can explain
this paucity of derivatives.14
(8) Pe´rez, J.; Riera, L.; Riera, V.; Garc´ıa-Granda, S.; Garc´ıa-Rodr´ıguez,
E. J. Am. Chem. Soc. 2001, 123, 7469.
(9) Trost, B. M.; Lautens, M. J. Am. Chem. Soc. 1982, 104, 5543.
(10) A similar behavior has been recently found for amido complexes [Re-
(NRR′)(CO)3(N-N)]; see: Hevia, E.; Pe´rez, J.; Riera, V.; Miguel, D.
Organometallics 2002, 21, 1966.
(11) The only exceptions: (a) Dewey, M. A.; Arif, A. M.; Gladysz, J. A.
J. Chem. Soc., Chem. Commun. 1991, 712. (b) Dewey, M. A.; Stark,
G. A.; Gladysz, J. A. Organometallics 1996, 15, 4798. (c) Jayaprakash,
K. N.; Gunnoe, T. B.; Boyle, P. D. Inorg. Chem. 2001, 40, 6481.
(12) Baker, P. K. AdV. Organomet. Chem. 1995, 40, 45.
(13) Darensbourg, D. J.; Klausmeyer, K. K.; Reibenspies, J. H. Inorg. Chem.
1996, 35, 1535.
(16) Crystal data for 4: C31H24Cl2MoN6O2, M ) 679.40, monoclinic, space
group P21/n, a ) 8.602(3) Å, b ) 17.697(5) Å, c ) 20.147(6) Å, â
) 90.000(6)°, V ) 3066.8(16) Å3, T ) 293 K, Z ) 4, Dcalcd ) 1.471
Mg/m3, F(000) ) 1376, µ(Mo KR) ) 0.640 mm-1, reflections
collected/unique ) 13599/4475 (Rint ) 0.0279); parameters, 382; final
R1 ) 0.0491, wR2 ) 0.1125 (all data), GOF ) 1.038, max/min
residual electron density 1.175/-0.862 e Å-3, solution and refinement
using SHELXL.20
4112 Inorganic Chemistry, Vol. 41, No. 16, 2002

COMMUNICATION
Scheme 3
The Mo-N-C-C grouping is linear (N(3)-C(32)-C(33)
) 178.5(5)°, Mo(1)-N(3)-C(32) ) 178.8(4)°). This can
be explained assuming some multiple character for the bonds
involved. The angles about C(33)18 and C(35)18 are close to
120°, suggesting sp2 character of these carbons.
Although some complexes with related keteniminato
ligands are known,19 their preparation from amido complexes
is unprecedented. The reactivity of 2 and 3 toward different
electrophiles is under investigation.
Acknowledgment. We thank Prof. Agust´ın Galindo for
insight, and Ministerio de Ciencia y Tecnolog´ıa (Projects
MCT-00-BQU2000-0220, PB97-0470-C02-01) and FICYT
(PR-01-GE-7) for support and for predoctoral (L.R.) and
postdoctoral (D.M.) fellowships.
Supporting Information Available: Crystal data for 3 and 4
and experimental details for all of the new compounds. This material
is available free of charge via the Internet at http://pubs.acs.org.
keteniminato (1-azaallenylidene) ligand trans to the allyl
group.
The formation of this ligand can be rationalized consider-
ing TCNE insertion into the N-H bond17 of 2, giving a
tricyanovinylamine group, followed by 1,2-elimination of
HCN1 and intramolecular metal shift (Scheme 3).
IC025665B
(18) C(32)-C(33)-C(34) ) 118.7(4)°, C(32)-C(33)-C(35) ) 120.7(4)°,
C(34)-C(33)-C(35) ) 120.6(4)°; C(33)-C(35)-C(36) ) 115.2(4)°,
N(6)-C(35)-C(36) ) 121.8(4)°, N(6)-C(35)-C(33) ) 123.0(4)°.
(19) (a) Bruce, M. I.; Wallis, R. C.; Skelton, B. W.; White, A. H. J. Chem.
Soc., Dalton Trans. 1981, 2205. (b) Ricci, J. S.; Ibers, J. A. J. Am.
Chem. Soc. 1971, 93, 2391. (c) Sacher, W.; Nagel, U.; Beck, W. Chem.
Ber. 1987, 120, 895. (d) Fulton, J. R.; Bouwkamp, M. W.; Bergman,
R. G. J. Am. Chem. Soc. 2000, 122, 8799.
(17) Insertion of unsaturated electrophiles into N-H bonds of amido
complexes: (a) Glueck, D. S.; Winslow, L. J. N.; Bergman, R. G.
Organometallics 1991, 10, 1462. (b) VanderLende, D. D.; Abboud,
K. A.; Boncella, J. M. Inorg. Chem. 1995, 34, 5319.
(20) Sheldrick, G. M. SHELXTL, An integrated system for solVing, refining,
and displaying crystal structures from diffraction data, version 5.1;
Bruker AXS, Inc.: Madison, WI, 1998.
Inorganic Chemistry, Vol. 41, No. 16, 2002 4113