A monomeric samarium bis(iminophosphorano) chelate complex with a Sm=C bond [8]

Full text of DOI:10.1021/ja9936114

726
J. Am. Chem. Soc. 2000, 122, 726-727
Scheme 1
A Monomeric Samarium Bis(Iminophosphorano)
Chelate Complex with a SmdC Bond
Kasani Aparna, Michael Ferguson,† and Ronald G. Cavell*
Contribution from the Department of Chemistry
UniVersity of Alberta, Edmonton, AB, Canada T6G 2G2
ReceiVed October 8, 1999
new samarium complex represents the first example of a lan-
thanide metal bound to the dianionic methandiide ligand environ-
ment provided by the bis(iminophosphorano)methane system.
Complex 2, [Sm{C(Ph2PdNSiMe3)2-κ3C,N,N′}(NCy2)(THF)],
a yellow air-sensitive crystalline solid, was obtained when 1 equiv
of H2C(Ph2PdNSiMe3)2 113 was added to a toluene solution of
samarium tris(dicyclohexylamide)14 under an argon atmosphere
(Scheme 1). Both of the methylene protons are removed and
dicyclohexylamine is eliminated,15 in parallel to our results with
the Group 4 metals.8 A few examples of the double deprotonation
of the P-CH2-P backbone have been structurally established in
related P-C-P systems;16-20 with the group 10 and 13 metals,
however, these complexes are bi- and trimetallic bridged com-
plexes in contrast to the present monomeric samarium complex.
The complex is paramagnetic, so the NMR resonances are
broad as expected; the 31P NMR spectrum for 2 consisted of one
broad singlet at 43.3 ppm which is downfield shifted by 48.7
ppm with respect to the free ligand value. The proton NMR for
complex 2 did not show a methylene resonance for the P-CH2-P
backbone, indicating that the ligand has been doubly deprotonated.
No 13C{1H} NMR signal was observed for the quaternary P-C-P
carbon atom despite trials with long acquisition periods, possibly
because the signal is broadened due to the presence of paramag-
netic samarium nuclei. Complex 2 is stable under an argon
atmosphere at room temperature in aromatic solvents for extended
periods of time; however, it decomposes upon thermolysis
(toluene solvent at 120 °C) to give intractable compounds.
The molecular structure of [Sm{C(Ph2PdNSiMe3)2-κ3C,N,N′}-
(NCy2)(THF)] 221 was confirmed by X-ray crystallography. Two
Lanthanide chemistry is one of the most rapidly developing
areas of organometallic chemistry because of its potential
relevance to catalysis.1 Lanthanide alkyls and hydrides have
recently attracted considerable interest as single-component olefin
polymerization catalysts and reagents for organic synthesis.2 Most
of these complexes are stabilized by cyclopentadienyl and related
ligands. The only known carbene complexes of lanthanide metals
are the adducts of the neutral carbene ligands,3-5 whereas
extensive transition metal carbene chemistry is known.6 We report
herein a novel, non-Cp, samarium compound containing a metal-
carbon multiple bond that was obtained by the facile deprotonation
of the methylene backbone of the bis(iminophosphorano)methane
ligand. This extension to the lanthanide group continues our
study7-12 of metal bis(iminophosphorano)methane complexes. The
† X-ray Structure Determination Laboratory.
* To whom correspondence should be addressed. Telephone 780-492-5310.
FAX 780-492-8231. E-mail: Ron.Cavell@Ualberta.ca.
(1) (a) Gun’ko, Y. K.; Edelmann, F. T. Comments Inorg. Chem. 1997, 19,
153-184. (b) Ephritikhine, M. Chem. ReV. 1997, 97, 2193-2242. (c)
Anwander, R.; Herrmann, W. A. Top. Curr. Chem. 1996, 179, 1-32. (d)
Edelmann, F. T. Top. Curr. Chem. 1996, 179, 247-276. (e) Schumann, H.;
Meese-Marktscheffel, J. A.; Esser, L. Chem. ReV. 1995, 95, 865-986. (f)
Edelmann, F. T. Angew. Chem., Int. Ed. Engl. 1995, 34, 2466-2488. (g)
Edelmann, F. T., Scandium, Yttrium, and the Lanthanide and Actinide
elements, Excluding their Zero Oxidation State Complexes. In ComprehensiVe
Organometallic Chemistry (II); Abel, E. W., Stone, F. G. A., Wilkinson, G.,
Eds.; Pergamon: Oxford, 1995; Vol. 4, Chapter 2, p 155. (h) Schaverien, C.
J. AdV. Organomet. Chem. 1994, 36, 283-363.
(2) (a) Hultzsch, K. C.; Spaniol, T. P.; Okuda, J. Angew. Chem., Int. Ed.
1999, 38, 227-230. (b) Shapiro, P. J.; Cotter, W. D.; Schaefer, W. P.;
Labinger, J. A.; Bercaw, J. E. J. Am. Chem. Soc. 1994, 116, 4623-4640. (c)
Coughlin, E. B.; Bercaw, J. E. J. Am. Chem. Soc. 1992, 114, 7606-7607. (d)
Shapiro, P. J.; Bunel, E.; Schaefer, W. P.; Bercaw, J. E. Organometallics
1990, 9, 867-869. (e) Yasuda, H.; Yamamoto, H.; Yokota, K.; Miyake, S.;
Nakamura, A. J. Am. Chem. Soc. 1992, 114, 4908-4910. (f) Schaverien, C.
J. Organometallics 1994, 13, 69-82. (g) Jeske, G.; Lauke, H.; Mauermann,
H.; Swepston, P. N.; Schumann, H.; Marks, T. J. J. Am. Chem. Soc. 1985,
107, 8091-8103. (h) Jeske, G.; Schock, L. E.; Swepston, P. N.; Schumann,
H.; Marks, T. J. J. Am. Chem. Soc. 1985, 107, 8103-8110. (i) Jeske, G.;
Lauke, H.; Mauermann, H.; Schumann, H.; Marks, T. J. J. Am. Chem. Soc.
1985, 107, 8111-8118. (j) Arredondo, V. M.; Tian, S.; McDonald, F. T.;
Marks, T. J. J. Am. Chem. Soc. 1999, 121, 3633-3639. (k) Arredondo, V.
M.; McDonald, F. T.; Marks, T. J. Organometallics 1999, 18, 1949-1960.
(3) Herrmann, W. A.; Munck, F. C.; Artus, G. R. J.; Runte, O.; Anwander,
R. Organometallics 1997, 16, 682-688.
(12) Kasani, A.; McDonald, R.; Cavell, R. G. J. Chem. Soc., Chem.
Commun. 1999, 1993-1994.
(13) Appel, R.; Ruppert, I. Z. Anorg. Allg. Chem. 1974, 406, 131-144.
(14) Minhas, R. K.; Ma, Y.; Song, J.-I.; Gambarotta, S. Inorg. Chem. 1996,
35, 1866-1873.
(15) Preparation of [Sm{C(Ph2PdNSiMe3)2-κ3C,N,N′ }(NCy2)(THF)] 2: All
experimental manipulations were performed under rigorously anaerobic
conditions using Schlenk techniques or an argon-filled glovebox. To a toluene
(4 mL) solution of [Sm(NCy2)3(THF)]14 (0.205 g, 0.268 mmol), was added
H2C(Ph2PdNSiMe3)2 (0.15 g, 0.268 mmol) with stirring at room temperature.
The reaction mixture was stirred at room temperature for a day and heated at
80 °C for 20min. Bright yellow crystals were obtained upon allowing the
flask to stand at room temperature for 2 days. The product was filtered and
dried under vacuum. Yield 0.14 g, 54.4%. IR data (Nujol mull): 1435s, 1341w,
1243s, 1177w, 1146m, 1107s, 1086s, 1065s, 1026s, 948m, 917w, 886m, 834s,
763s, 749s, 729m, 713s, 699s, 678w, 659m, 648m, 608s, 548s, 521s, 511s,
480s. 1H NMR (C6D6): δ 9.80 (br s, phenyl), 7.78 (br s, phenyl), 6.65 (br s,
phenyl), 6.40 (br s, phenyl), 5.78 (br s, phenyl), 2.80 (br s, THF), 1.95 (br s,
Cy), 1.34 (br s, Cy), 1.10 (s, CH3Si), 0.94 (m, Cy), 0.36 (m, THF), -1.54 (br
s, Cy), -1.85 (br s, Cy), -2.21 (br s, Cy). 13C {1H} NMR (C6D6): 133.1 (br
s, phenyl), 130.0 (br s, phenyl), 129.3 (br s, phenyl), 126.8 (br s, phenyl),
69.3 (s, CH-Cy), 62.7 (s, CH2-THF), 36.2 (s, CH2-Cy), 26.6 (s, CH2-
Cy), 26.4 (s, CH2-THF), 20.4 (s, CH2-Cy), 5.5 (s, CH3Si), 31P{1H} NMR
(C6D6): δ 43.3 (br s). Anal. Calcd for desolvated crystals of C47H68N3OP2-
Si2Sm.: C, 58.83; H, 7.14; N, 4.38. Found: C, 59.39; H, 7.25; N, 4.40.
(16) Al-Resayes, S. I.; Hitchcock, P. B.; Nixon, J. F. J. Chem. Soc., Chem.
Commun. 1986, 1710-1711.
(4) Schumann, H.; Glanz, M.; Winterfeld, J.; Hemling, H.; Kuhn, N.; Kratz,
T. Angew. Chem., Int. Ed. Engl. 1994, 33, 1733-1734.
(5) Arduengo, A. J., III; Tamm, M.; McLain, S. J.; Calabrese, J. C.;
Davidson, F.; Marshall, W. J. J. Am. Chem. Soc. 1994, 116, 7927-7928.
(6) See for example: (a) 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; pp 475 (b) Doyle, M. P.;
Forbes, D. C. Chem. ReV. 1998, 98, 911-935. (c) Vyboishchikov, S. F.;
Frenking, G. Chem. Eur. J. 1998, 4, 1428-1438. (d) Brothers, P. J.; Roper,
W. R. Chem. ReV. 1988, 88, 1293-1326. (e) Erker, G. Angew. Chem., Int.
Ed. Engl. 1989, 28, 397-412. (f) Feldman, J.; Schrock, R. R. Prog. Inorg.
Chem. 1991, 39, 1-74. (g) Wulff, W. D. Organometallics 1998, 17, 3116-
3134. (h) Brookhart, M.; Studabaker, W. B. Chem. ReV. 1987, 87, 411-432.
(7) Cavell, R. G.; Kamalesh Babu, R. P.; Kasani, A.; McDonald, R. J.
Am. Chem. Soc. 1999, 121, 5805-5806.
(8) Kamalesh Babu, R. P.; McDonald, R.; Decker, S. A.; Klobukowski,
M.; Cavell, R. G. Organometallics 1999, 18, 4226-4229.
(17) Browning, J.; Dixon, K. R.; Hilts, R. W. Organometallics 1989, 8,
552-554.
(9) Kasani, A.; McDonald, R.; Cavell, R. G. Organometallics 1999, 18,
3775-3777.
(18) Robinson, G. H.; Lee, B.; Pennington, W. T.; Sangokoya, S. A. J.
Am. Chem. Soc. 1988, 110, 6260-6261.
(10) Kasani, A.; Kamalesh Babu, R. P.; McDonald, R.; Cavell, R. G. Angew.
Chem., Int. Ed. Engl. 1999, 38, 1483-1484.
(19) Lee, B.; Sangokoya, S. A.; Pennington, W. T.; Robinson, G. H. J.
Coord. Chem. 1990, 21, 99-105.
(11) Aparna, K.; Ferguson, M.; McDonald, R.; Cavell, R. G. Organome-
tallics 1999, 18, 4241-4243.
(20) Robinson, G. H.; Self, M. F.; Pennington, W. T.; Sangokoya, S. A.
Organometallics 1988, 7, 2424-2426.
10.1021/ja9936114 CCC: $19.00 © 2000 American Chemical Society
Published on Web 01/13/2000

Communications to the Editor
J. Am. Chem. Soc., Vol. 122, No. 4, 2000 727
Figure 2.
Figure 1. (a) An ORTEP22 view of [Sm{C(Ph2PdNSiMe3)2-κ3C,N,N′}-
(NCy2)(THF)] 2 showing the atom labeling scheme. The hydrogen atoms
have been removed for clarity and the remaining atoms are represented
by Gaussian ellipsoids at the 20% probability level. Selected interatomic
distances [Å] and angles [deg] are as follows: Sm-C(1) ) 2.467(4),
Sm-N(1) ) 2.409(4), Sm-N(2) ) 2.449(4), Sm-N(3) ) 2.216(4),
Sm-O ) 2.479(3), N(1)-P(1) ) 1.632(4), P(1)-C(1) ) 1.671(4), P(2)-
C(1) ) 1.666(4), P(2)-N(2) ) 1.626(4), N(1)-Sm-N(2) ) 120.6(1),
N(1)-Sm-C(1) ) 66.2(1), N(2)-Sm-C(1) ) 65.8(1), P(1)-C(1)-P(2)
) 138.0(3), N(1)-P(1)-C(1) ) 107.5(2). (b) A side view of the central
plane of 2.
well as other lanthanides. The Sm-N bond distances to the
phosphinimine nitrogen atoms are longer than the Sm-N bond
distance to the nitrogen atom of the dicyclohexylamido group
indicating that the imine groups are best described as neutral donor
substituents.
The bond distances within the ligand framework in complex 2
are considerably altered in comparison with the related values in
free bis(iminophosphorano)methane ligands;24,25 the PdN bond
distances are elongated and the endocyclic P-C bond distances
are significantly shorter; however, the exocyclic P-C distances
are unaffected. The P-C-P bond angle 138.0(3)° is considerably
widened compared to the corresponding values in CH3CH{Ph2Pd
N(p-tolyl)}2 (112.39(19°))24 as well as in H2C{Cy2PdNSiMe3}2
(117.41(12)°).25 These factors suggest that there is a delocalization
of π electron density within each four-membered metallocylic
ring, arising from conjugation of SmdC and PdN bonds which
can be represented as shown in Figure 2.
ORTEP22 views of complex 2 along with selected bond lengths
and bond angles are shown in Figure 1. The core structure consists
of two nearly planar, fused four-membered rings with a Sm-
C(1) shared edge. The two four-membered rings form an open
book with a dihedral angle of 37.7(1)°. Intramolecular chelation
of two trimethylsilyliminophosphorane units completes the co-
ordination around the samarium. The samarium to carbon bond
distance {Sm-C(1) ) 2.467(4) Å} is considerably shorter (10%)
than the average Sm-carbon distances23 {average 2.743 Å,
median 2.738 Å}, which indicates multiple bond character
between the samarium and carbon atom and hence this species
could be formulated as a carbene. This Sm-carbene distance is
also shorter than the related distances in neutral carbene ligand
complexes3-5 of samarium5 (Sm-C ) 2.837(7), 2.845(7) Å) as
The bis(iminophosphorano)methandiide ligand generated in situ
by amine elimination yields a stable complex with samarium with
a carbene structure. This complex represents the first example of
a lanthanide bound to a dianionic carbene ligand system. Further
study of this complex is underway.
Acknowledgment. We thank the Natural Sciences and Engineering
Research Council of Canada, NOVA Chemicals Corp, and the University
of Alberta for financial support.
Supporting Information Available: Tables of crystallographic
experimental details, atomic coordinates, selected interatomic distances
and angles, torsion angles, anisotropic displacement parameters, and
derived atomic coordinates (PDF). This material is available free of charge
via the Internet at http://pubs.acs.org
(21) Crystal Data for [Sm{C(Ph2PdNSiMe3)2-κ3C,N,N′}(NCy2)(THF)]‚0.5
toluene 2 : Triclinic, P1h (No. 2), a ) 10.7169(6) Å, b ) 11.3464(6) Å, c )
21.699(1) Å, R ) 81.095(1)°, â ) 82.152(1)°, γ ) 84.774(1)°, V ) 2575.7-
(2) Å3, Z ) 2. The structure was solved by direct methods and refined by
full-matrix least-squares procedures: R1 ) 0.0457 (wR2 ) 0.1220) for 8085
2
2
JA9936114
reflections with Fo g 2σ(Fo ).
(22) Johnson, C. K.; ORTEP, Report ORNL No. 5138, Oak Ridge National
Labs, Oak Ridge, TN, 1976.
(24) Avis, M. W.; Elsevier: C. J.; Veldman, N.; Kooijman, H.; Spek, A.
L. Inorg. Chem. 1996, 35, 1518-1528.
(25) Crystal Structure of CH2{PCy2dNSiMe3}2: Kamalesh Babu, R. P.;
Cavell, R. G.; McDonald, R., University of Alberta Structure Determination
Laboratory, Report RGC 9802.
(23) Allen, F. H.; Davies, J. E.; Galloy, J. J.; Johnson, O.; Kennard, O.;
Macrae, C. F.; Mitchell, E. M.; Mitchell, G. F.; Smith, J. M.; Watson, D. G.
J. Chem. Inf. Comput. Sci. 1991, 31, 187-204. The values were calculated
from the data retrieved from the Cambridge Crystallographic Data Base.