C-H versus O-H bond cleavage reactions of Bis(2-hydroxyphenyl)phenylamine, PhN(o-C6H4OH)2: Synthesis and structural characterization of mononuclear and dinuclear tungsten aryloxide complexes which exhibit bidentate, tridentate, and tetradentate coordination modes

Article abstract of DOI:10.1021/om060732l

The phenylimino-bridged diphenol PhN(o-C₆H₄OH) ₂ reacts with W(PMe₃)₄(η²- CH₂PMe₂)H to yield a variety of mononuclear and dinuclear complexes that include [κ²-PhN(C₆H ₄-OH)(C₆H₃O)]W(PMe₃) ₄H₂, [μ-κ²,κ²- PhN(C₆H₃O)₂]{W-(PMe₃) ₄H₂}₂, [κ³-PhN(C ₆H₄O)₂]W(PMe₃)₃H ₂, [κ⁴-N(C₆H₄)-(C ₆H₄O)₂]W(PMe₃)₃H, and [κ²-PhN(C₆H₄O)₂] ₂W(PMe₃)₂ via O-H and C-H bond activation reactions. Structural characterization of these compounds by X-ray diffraction demonstrates that the derived alkoxide ligand is structurally flexible and can adopt bidentate, tridentate, and tetradentate coordination modes.

Full text of DOI:10.1021/om060732l

Organometallics 2006, 25, 5839-5842
5839
C-H versus O-H Bond Cleavage Reactions of
Bis(2-hydroxyphenyl)phenylamine, PhN(o-C6H4OH)2: Synthesis and
Structural Characterization of Mononuclear and Dinuclear
Tungsten Aryloxide Complexes Which Exhibit Bidentate,
Τridentate, and Tetradentate Coordination Modes
Bryte V. Kelly, Joseph M. Tanski, Kevin E. Janak, and Gerard Parkin*
Department of Chemistry, Columbia UniVersity, New York, New York 10027
ReceiVed August 11, 2006
12,13
Summary: The phenylimino-bridged diphenol PhN(o-C6H4OH)2
reacts with W(PMe3)4(η2-CH2PMe2)H to yield a Variety of
mononuclear and dinuclear complexes that include [κ2-PhN(C6H4-
diphenol PhN(o-C6H4OH)2
towards W(PMe3)4(η2-CH2-
PMe2)H, thereby resulting in a series of O-H and C-H bond
activation reactions to give products that feature (i) bidentate
κ2-O2 and κ2-OC, (ii) tridentate κ3-O2N, and (iii) tetradentate
κ4-O2CN coordination modes.
Whereas the tris(phenol) N(o-C6H4OH)3 has been used to
prepare a variety of transition-metal derivatives,14 counterparts
of the structurally related diphenol PhN(o-C6H4OH)2 have not
previously been reported.15 It is, therefore, noteworthy that an
array of tungsten complexes may be obtained via treatment of
OH)(C6H3O)]W(PMe3)4H2,
[µ-κ2,κ2-PhN(C6H3O)2]{W-
(PMe3)4H2}2, [κ3-PhN(C6H4O)2]W(PMe3)3H2, [κ4-N(C6H4)-
(C6H4O)2]W(PMe3)3H, and [κ2-PhN(C6H4O)2]2W(PMe3)2 Via
O-H and C-H bond actiVation reactions. Structural charac-
terization of these compounds by X-ray diffraction demonstrates
that the deriVed alkoxide ligand is structurally flexible and can
adopt bidentate, tridentate, and tetradentate coordination modes.
(6) For recent examples, see: (a) Tsang, W. C. P.; Jamieson, J. Y.; Aeilts,
S. L.; Hultzsch, K. C.; Schrock, R. R.; Hoveyda, A. H. Organometallics
2004, 23, 1997-2007. (b) Schrock, R. R.; Jamieson, J. Y.; Dolman, S. J.;
Miller, S. A.; Bonitatebus, P. J., Jr.; Hoveyda, A. H. Organometallics 2002,
21, 409-417. (c) Waltz, K. M.; Carroll, P. J.; Walsh, P. J. Organometallics
2004, 23, 127-134. (d) Chisholm, M. H.; Lin, C.-C.; Gallucci, J. C.; Ko,
B.-T. Dalton Trans. 2003, 406-412. (e) Damrau, H.-R. H.; Royo, E.; Obert,
S.; Schaper, F.; Weeber, A.; Brintzinger, H.-H. Organometallics 2001, 20,
5258-5265. (f) Lehtonen, A.; Sillanpa¨a¨, R. Inorg. Chem. Commun. 2001,
4, 108-110. (g) Eilerts, N. W.; Heppert, J. A. Polyhedron 1995, 14, 3255-
3271. (h) Ru Son, A. J.; Schweiger, S. W.; Thorn, M. G.; Moses, J. E.;
Fanwick, P. E.; Rothwell, I. P. Dalton Trans. 2003, 1620-1627.
(7) For CH2 and CHR linkers, see: (a) Hagenau, U.; Heck, J.; Kaminsky,
W.; Schauwienold, A. M. Z. Anorg. Allg. Chem. 2000, 626, 1814-1821.
(b) Mulford, D. R.; Fanwick, P. E.; Rothwell, I. P. Polyhedron 2000, 19,
35-42. (c) Okuda, J.; Fokken, S.; Kang, H.-C.; Massa, W. Chem. Ber.
1995, 128, 221-227. (d) Lehtonen, A.; Sillanpa¨a¨, R. Polyhedron 2003,
22, 2755-2760. (e) Gonza´lez-Maupoey, M.; Cuenca, T.; Frutos, L. M.;
Castan˜o, O.; Herdtweck, E. Organometallics 2003, 22, 2694-2704. (f)
Toscano, P. J.; Schermerhorn, E. J.; Barren, E.; Liu, S. C.; Zubieta, J. J.
Coord. Chem. 1998, 43, 169-185.
(8) For S linkers, see: (a) Amor, F.; Fokken, S.; Kleinhenn, T.; Spaniol,
T. P.; Okuda, J. J. Organomet. Chem. 2001, 621, 3-9. (b) Janas, Z.;
Jerzykiewicz, L. B.; Przybylak, K.; Sobota, P.; Szczegot, K. Eur. J. Inorg.
Chem. 2004, 1639-1645. (c) Takashima, Y.; Nakayama, Y.; Hirao, T.;
Yasuda, H.; Harada, A. J. Organomet. Chem. 2004, 689, 612-619. (d)
Fokken, S.; Reichwald, F.; Spaniol, T. P.; Okuda, J. J. Organomet. Chem.
2002, 663, 158-163. (e) Porri, L.; Ripa, A.; Colombo, P.; Miano, E.;
Capelli, S.; Meille, S. V. J. Organomet. Chem. 1996, 514, 213-217. (f)
Nakayama, Y.; Saito, H.; Ueyama, N.; Nakamura, A. Organometallics 1999,
18, 3149-3158. (g) Miyatake, T.; Mizunuma, K.; Kakugo, M. Makromol.
Chem., Macromol. Symp. 1993, 66, 203-214. (h) Natrajan, L. S.; Hall, J.
J.; Blake, A. J.; Wilson, C.; Arnold, P. L. J. Solid State Chem. 2003, 171,
90-100. (i) Arnold, P. L.; Natrajan, L. S.; Hall, J. J.; Bird, S. J.; Wilson,
C. J. Organomet. Chem. 2002, 647, 205-215. (j) Kakugo, M.; Miyatake,
T.; Mizunuma, K. Chem. Express 1987, 2, 445-448. (k) Takashima, Y.;
Nakayama, Y.; Yasuda, H.; Harada, A. J. Organomet. Chem. 2002, 651,
114-123.
Introduction
Alkoxide (OR) and aryloxide (OAr) ligands have been
employed extensively in organometallic chemistry,1 with ap-
plications in areas as diverse as olefin and acetylene metathesis2
and materials chemistry.3 The widespread use of these ligands
is commonly associated with their ability to stabilize a variety
of coordination environments. Specifically, alkoxide and ary-
loxide ligands are electronically versatile due to the availability
of two lone pairs on the oxygen atom that allow them to function
as one-electron (X), three-electron (LX), or five-electron (L2X)
donors4 depending upon the electronic needs of the metal center.
Furthermore, the steric demands of alkoxide and aryloxide
ligands may also be readily modified, as exemplified by the
very bulky OCBut3 ligand.5 In addition to mono(aryloxide)
ligands, considerable attention has been given to the application
of bis- and poly(aryloxide) ligands. With respect to bis-
(aryloxide) ligands, the majority of studies have been devoted
to biphenolate or binaphtholate derivatives in which the two
aryloxide moieties are directly linked together,6 but more
recently attention has been given to derivatives in which the
aryloxide groups are attached by a linker.7-10 Since the nature
of the linker modifies the chemistry of the system,11 we are
interested in developing the application of bis(aryloxide) ligands
that feature a nitrogen bridge, with particular emphasis being
given to the chemistry of the early transition metals. In this
paper, we describe the reactivity of the phenylimino-bridged
* To whom correspondence should be addressed. E-mail: parkin@
columbia.edu.
(9) For [CH2N(R)CH2] linkers, see: (a) Tshuva, E. Y.; Groysman, S.;
Goldberg, I.; Kol, M.; Goldschmidt, Z. Organometallics 2002, 21, 662-
670. (b) Tshuva, E. Y.; Goldberg, I.; Kol, M.; Goldschmidt, Z. Organo-
metallics 2001, 20, 3017-3028. (c) Tshuva, E. Y.; Versano, M.; Goldberg,
I.; Kol, M.; Weitman, H.; Goldschmidt, Z. Inorg. Chem. Commun. 1999,
2, 371-373. (d) Toupance, T.; Dubberley, S. R.; Rees, N. H.; Tyrrell, B.
R.; Mountford, P. Organometallics 2002, 21, 1367-1382. (e) Alcazar-
Roman, L. M.; O’Keefe, B. J.; Hillmyer, M. A.; Tolman, W. B. Dalton
Trans. 2003, 3082-3087. (f) Groysman, S.; Goldberg, I.; Kol, M.; Genizi,
E.; Goldschmidt, Z. Inorg. Chim. Acta 2003, 345, 137-144.
(1) (a) Bradley, D. C.; Mehrotra, R. C.; Rothwell, I. P.; Singh, A. Alkoxo
and Aryloxo DeriVatiVes of Metals; Academic Press: San Diego, CA, 2001.
(b) Chisholm, M. H. Chemtracts: Inorg. Chem. 1992, 4, 273-301.
(2) Schrock, R. R. Polyhedron 1995, 14, 3177-3195.
(3) Hubert-Pfalzgraf, L.G. Coord. Chem. ReV. 1998, 178-180, 967-
997.
(4) Green, M. L. H. J. Organomet. Chem. 1995, 500, 127-148.
(5) Wolczanski, P. T. Polyhedron 1995, 14, 3335-3362.
10.1021/om060732l CCC: $33.50 © 2006 American Chemical Society
Publication on Web 11/10/2006

5840 Organometallics, Vol. 25, No. 25, 2006
Communications
Scheme 1
W(PMe3)4(η2-CH2PMe2)H with PhN(o-C6H4OH)2, with the
nature of the product being critically dependent on stoichiometry
(Scheme 1). For example, W(PMe3)4(η2-CH2PMe2)H reacts with
PhN(o-C6H4OH)2 in a 1:2 molar ratio to yield the octahedral
bis(diphenolate) complex [κ2-PhN(C6H4O)2]2W(PMe3)2 (1) via
reaction with the O-H bonds of two PhN(o-C6H4OH)2 mol-
ecules.16 In contrast, the corresponding reaction with a 1:1 molar
ratio results in both O-H and C-H bond activation, yielding
[κ2-PhN(C6H4OH)(C6H3O)]W(PMe3)4H2 (2) (Scheme 1), in
which one of the O-H bonds remains intact and participates
in a O-H‚‚‚O hydrogen-bonding interaction with the oxygen
atom of the aryloxide moiety (Figure 1). Despite the hydrogen-
bonding interaction, the O-H bond in [κ2-PhN(C6H4OH)-
(C6H3O)]W(PMe3)4H2 (2) is reactive and treatment with
W(PMe3)4(η2-CH2PMe2)H results in the formation of the
dinuclear complex [µ-κ2,κ2-PhN(C6H3O)2]{W(PMe3)4H2}2 (3),
which corresponds to an overall 2:1 stoichiometry.
The formation of [κ2-PhN(C6H4OH)(C6H3O)]W(PMe3)4H2 (2)
in the 1:1 reaction is of particular note, because the bidentate
κ2-O,C coordination mode demonstrates that oxidative addition
of the C-H bond of the aryloxy ligand is favored over oxidative
addition of the second O-H bond. In this regard, we have
previously demonstrated that ortho C-H bond activation to give
four-membered oxametallacycles is a common feature of the
reactions of W(PMe3)4(η2-CH2PMe2)H with phenols and have
established that this preference is kinetic in origin.17,18 Sup-
porting this notion, the C-H bond cleavage reaction is reversible
and [κ2-PhN(C6H4OH)(C6H3O)]W(PMe3)4H2 (2) converts to [κ3-
PhN(C6H4O)2]W(PMe3)3H2 (4) upon heating at ca. 60 °C
(Scheme 2).19 The molecular structure of [κ3-PhN(C6H4O)2]W-
(PMe3)3H2 (4) has been determined by X-ray diffraction (Figure
2), thereby demonstrating that, in contrast to [κ2-PhN-
(C6H4O)2]2W(PMe3)2 (2), the nitrogen atom also coordinates
to the metal center;20 as such, the ligand adopts a tridentate
κ3-O2N mode.
(10) Other linkers include Te,10a S(O),10b S2,10c SCH2CH2S,10d CH2CH2,10e
and N(H)C(O)C(O)NH:10f (a) Nakayama, T.; Watanabe, K.; Ueyama, N.;
Nakamura, A.; Harada, A.; Okuda, J. Organometallics 2000, 19, 2498-
2503. (b) Okuda, J.; Fokken, S.; Kang, H.-C.; Massa, W. Polyhedron 1998,
17, 943-946. (c) Okuda, J.; Fokken, S.; Kleinhenn, T.; Spaniol, T. P. Eur.
J. Inorg. Chem. 2000, 1321-1326. (d) Capacchione, C.; Proto, A.; Ebeling,
H.; Mu¨lhaupt, R.; Mo¨ller, K.; Manivannan, R.; Spaniol, T. P.; Okuda, J. J.
Mol. Catal. A: Chem. 2004, 213, 137-140. (e) Fokken, S.; Spaniol, T. P.;
Okuda, J.; Sernetz, F. G.; Mu¨lhaupt, R. Organometallics 1997, 16, 4240-
4242. (f) Jimenez-Pe´rez, V. M.; Camacho-Camacho, C.; Gu¨izado-Rodr´ıguez,
M.; No¨th, H.; Contreras, R. J. Organomet. Chem. 2000, 614-615, 283-
293.
(11) For example, sulfur-bridged bis(aryloxide) ligands create more
active titanium olefin polymerization catalysts than the corresponding
methylene-bridged derivatives. See: Miyatake, T.; Mizunuma, K.; Kakugo,
M. Makromol. Chem., Macromol. Symp. 1993, 66, 203-214.
(12) Kelly, B. V.; Tanski, J. M.; Anzovino, M. B.; Parkin, G. J. Chem.
Crystallogr. 2005, 35, 969-981.
(13) Flad, G.; Demerseman, P.; Royer, R. Bull. Soc. Chim. Fr. 1976,
1823-1824.
(14) For titanium, niobium, and tantalum complexes, see: Michalczyk,
L.; de Gala, S.; Bruno, J. W. Organometallics 2001, 20, 5547-5556.
(15) For antimony complexes of this ligand, see: Tanski, J. M.; Kelly,
B. V.; Parkin, G. Dalton Trans. 2005, 2442-2447.
(16) The structurally related molybdenum complex Mo(PMe3)2(OPh)4
has been reported. See: (a) Hascall, T.; Murphy, V. J.; Parkin, G.
Organometallics 1996, 15, 3910-3912. (b) Hascall, T.; Murphy, V. J.;
Janak, K. E.; Parkin, G. J. Organomet. Chem. 2002, 652, 37-49.
Figure 1. Molecular structure of [κ2-PhN(C6H4OH)(C6H3O)]W-
(PMe3)4H2 (2).

Communications
Organometallics, Vol. 25, No. 25, 2006 5841
Scheme 2
Figure 2. Molecular structure of [κ3-PhN(C6H4O)2]W(PMe3)3H2
(4).
A further example of the structural versatility of this system
is provided by the observation that [κ3-PhN(C6H4O)2]W-
(PMe3)3H2 (4) reductively eliminates H2 at ca. 80 °C to give
[κ4-N(C6H4)(C6H4O)2]W(PMe3)3H (5) via oxidative addition of
the ortho C-H bond of the phenyl substituent, thereby generat-
ing a tetradentate tripodal ligand. [κ4-N(C6H4)(C6H4O)2]W-
(PMe3)3H (5) has been structurally characterized by X-ray
diffraction (Figure 3), and the W-N bond length (2.271(8) Å)
is substantially shorter than that in the κ3 precursor, [κ3-PhN-
(C6H4O)2]W(PMe3)3H2 (4) (2.451(4) Å), an observation that
may be associated with the geometrical constraint imposed by
formation of the W-C bond. The formation of [κ4-N(C6H4)-
Figure 3. Molecular structure of [κ4-N(C6H4)(C6H4O)2]W(PMe3)3H
(5).
(C6H4O)2]W(PMe3)3H (5) is reversible, and treatment with H2
(1 atm) regenerates [κ3-PhN(C6H4O)2]W(PMe3)3H2 (4) (K ≈
103 M-1 at 80 °C).
The interconversion of [κ3-PhN(C6H4O)2]W(PMe3)3H2 (4)
and [κ4-N(C6H4)(C6H4O)2]W(PMe3)3H (5) presumably proceeds
via the 16-electron intermediate {[κ3-PhN(C6H4O)2]W(PMe3)3}.
Evidence in support of this statement is provided by the
observation that [κ3-PhN(C6H4O)2]W(PMe3)3H2 (4) reacts with
CO and C2H4 to give the bis(carbonyl) and bis(ethylene)
complexes [κ3-PhN(C6H4O)2]W(PMe3)2(CO)2 (6) and [κ3-PhN-
(C6H4O)2]W(PMe3)(C2H4)2 (7), which may be viewed as
derivatives of {[κ3-PhN(C6H4O)2]W(PMe3)3}. While the car-
bonyl complex is an 18-electron derivative, the ethylene complex
is formally a 16-electron compound; closely related precedents
are, nevertheless, provided by W(PMe3)2(C2H4)2Cl2 and
W(PMe3)2(C2H4)2(Me)(ClAlMe2Cl).21
(17) For example, of the monosubstituted phenols 2-RC6H4OH (R )
Me, Et, Pri, But) for which a variety of potential C-H bond activation
reactions are possible, leading to the formation of four-, five- or six-
membered oxametallacycles, only 2-methylphenol gives the five-membered
oxametallacycle W(PMe3)4[κ2-OC6H3(CH2)]H2, with all other derivatives
giving the four-membered ortho-metalated alternative W(PMe3)4[κ2-OC6H3R]-
H2. See: (a) Rabinovich, D.; Zelman, R.; Parkin, G. J. Am. Chem. Soc.
1990, 112, 9632-9633. (b) Rabinovich, D.; Zelman, R.; Parkin, G. J. Am.
Chem. Soc. 1992, 114, 4611-4621.
(18) For other examples of structurally characterized compounds with
four-membered ortho-metalated aryloxide ligands, see: (a) Bag, N.;
Choudhury, S. B.; Lahiri, G. K.; Chakravorty, A. J. Chem. Soc., Chem.
Commun. 1990, 1626-1627. (b) Bag, N.; Choudhury, S. B.; Lahiri, G. K.;
Chakravorty, A. Inorg. Chem. 1990, 29, 5013-5014. (c) Aneetha, H.; Rao,
C. R. K.; Rao, K. M.; Zacharias, P. S.; Feng, X.; Mak, T. C. W.; Srinivas,
B.; Chiang, M. Y. Dalton Trans. 1997, 1697-1703.
In summary, the diphenol PhN(o-C6H4OH)2 has proven to
be a useful reagent for preparing a variety of tungsten aryloxide
compounds. Structural characterization of these compounds by
X-ray diffraction demonstrates that the derived alkoxide ligand
is structurally flexible and can adopt bidentate, tridentate, and
tetradentate coordination modes and can also link two metal
centers together. The ability to synthesize the dinuclear complex
[µ-κ2κ2-PhN(C6H3O)2]{W(PMe3)4H2}2 (3) suggests that the
reactivity of the O-H bond in [κ2-PhN(C6H4OH)(C6H3O)]W-
(19) An interesting aspect of the conversion of [κ2-PhN(C6H4OH)-
(C6H3O)]W(PMe3)4H2 to [κ3-PhN(C6H4O)2]W(PMe3)3H2 is that the overall
oxidative addition of the second O-H bond is inhibited by PMe3 and
catalyzed by H2.
(20) The W-N bond length in W(PMe3)3[κ3-N(C6H4O)2(Ph)]H2 is 2.451-
(4) Å. For comparison, the average W-NR3 bond length for compounds
listed in the Cambridge Structural Database is 2.31 Å (Cambridge Structural
Database, Version 5.27). Allen, F. H.; Kennard, O. 3D Search and Research
Using the Cambridge Structural Database. Chemical Design Automation
News 1993, 8(1), 1, 31-37.
(21) Sharp, P. R. Organometallics 1984, 3, 1217-1223.

5842 Organometallics, Vol. 25, No. 25, 2006
Communications
Supporting Information Available: Text, figures, and tables
giving experimental details and CIF files giving crystallographic
data. This material is available free of charge via the Internet at
http://pubs.acs.org.
(PMe3)4H2 (2) may enable the synthesis of heterobimetallic
complexes, an area that is currently being investigated.
Acknowledgment. We thank the U.S. Department of
Energy, Office of Basic Energy Sciences (Contract No. DE-
FG02-93ER14339), for support of this research.
OM060732L