A novel trisamidophosphine ligand and its Group(IV) metal complexes

Article abstract of DOI:10.1021/om401018f

A novel trisamidophosphine ligand scaffold has been synthesized and employed to coordinate all of the group(IV) metals. The resulting complexes feature closed half-cage geometries with the phosphorus donor and all three amides binding to the metal. Out of nine complexes of the type [PN ₃]MX (M = Ti, Zr, Hf; X = NMe₂, OTf, CH₃), the zirconium derivatives have been studied by X-ray diffraction and shown to exhibit metal-phosphorus distances that are well in range of a coordinative bond. In contrast to its heavier homologues, the titanium methyl species [PN₃]TiMe is prone to thermally induced ligand CH activation with concomitant loss of methane.

Full text of DOI:10.1021/om401018f

Communication
pubs.acs.org/Organometallics
A Novel Trisamidophosphine Ligand and Its Group(IV) Metal
Complexes
Malte Sietzen, Hubert Wadepohl, and Joachim Ballmann*
Anorganisch-Chemisches Institut, Universitat Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
̈
S
* Supporting Information
ABSTRACT: A novel trisamidophosphine ligand scaffold has been
synthesized and employed to coordinate all of the group(IV) metals.
The resulting complexes feature closed half-cage geometries with the
phosphorus donor and all three amides binding to the metal. Out of
nine complexes of the type [PN3]MX (M = Ti, Zr, Hf; X = NMe2, OTf,
CH3), the zirconium derivatives have been studied by X-ray diffraction
and shown to exhibit metal−phosphorus distances that are well in range
of a coordinative bond. In contrast to its heavier homologues, the
titanium methyl species [PN3]TiMe is prone to thermally induced
ligand CH activation with concomitant loss of methane.
igands combining hard and soft donor functionalities (so-
while the interaction between the phosphine and the amido-
Lcalled hybrid ligands) are frequently used in cases that coordinated metal ion is limited substantially.6
Trisaminophosphines with ethylene or phenylene NP linkers
require a high degree of electronic flexibility at the coordinated
metal ion. Amidophosphines are certainly among the most
prominent hybrid ligand systems and have been widely applied,
inter alia, to support metal-catalyzed hydrosilylations, (de)-
hydrogenations, and polymerizations as well as numerous
noncatalytic transformations.1 The amidophosphine ligand
family is commonly categorized by the ligands’ number of N-
and P-donor sites, and the resulting subclasses are then
abbreviated as [NP],2 [NPN],3 [PNP],4 and [P2N2].5 While all
of the former NP combinations have been well explored, [PN3]-
based systems are fairly underdeveloped, with coordination
compounds of only one tris-anionic trisamidophosphine ligand
scaffold reported so far (complexes A; see Scheme 1).6 A closer
look, however, reveals that the central metal of the latter
methylene-linked system A is coordinated by three amides only
with the phosphine lone pair pointing away from the metal (exo-
P configuration). Thus, polynuclear species are formed easily,
are known as well (B with R = H, SiMe3 and C; see Scheme 1),7
but no coordination compounds of these ligands have been
reported so far.8 In case of B (R = SiMe3), it is documented that
attempts to prepare molybdenum complexes led to the
formation of insoluble materials instead of well-defined
complexes.7a A possible explanation for this finding is that the
hypothetical coordination of all four donor atoms might generate
highly strained cages, which in turn favors the formation of exo-P-
configured and polynuclear systems. This hypothesis is
supported by a computational study on sila-[PN3] cages, which
predicts the exo-P configuration to be lower in energy in the case
of ligand B (R = H). The latter study finally arrived at the
conclusion that the cage configuration (exo-P vs endo-P) is
mainly dependent on the linkage between the phosphine and the
amido donor atoms.9 As these sila-[PN3] cages are predicted to
favor the desired endo configuration in case of C3 linkages
(propylene or benzylene spacers), we turned our attention to the
benzylene-linked trisaminophosphine 1 (see Scheme 2), bearing
in mind that related neutral trisamino [PN3] derivatives have
been studied earlier.10 The targeted protio ligand H3[PN3] (1)
was synthesized starting from the corresponding trisaldehyde11
Scheme 1. Known Methylene-Linked Trisamidophosphine
Complexes A and the C2-Linked Trisaminophosphine
Ligands B and C
Scheme 2. Synthesis of H3[PN3] (1; Ar = 3,5-Xylyl)
Received: October 18, 2013
Published: January 24, 2014
© 2014 American Chemical Society
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Scheme 3. Syntheses of Complexes 2−10 (M = Ti, Zr, Hf, Ar = 3,5-Xylyl)
via reductive amination. A method described by Tajbakhsh and
co-workers12 employing sodium borohydride in 2,2,2-trifluor-
oethanol was utilized for this purpose, and the protio ligand 1 was
obtained in acceptable yield (51%) and high purity after
recrystallization from ethanol (see Scheme 2).
metal in place. The configuration at the phosphorus atom is
revealed to be endo with a Zr−P distance of 2.824(1) Å, which is
in the range of those of comparable amidophosphine
complexes.13 The trigonal-bipyramidal coordination sphere is
completed by the remaining apical dimethylamido ligand, which
is positioned trans with respect to the phosphine (N4−Zr−P
173.13(5)°). To confirm that the observed endo configuration is
maintained in solution, variable-temperature NMR spectro-
scopic studies were performed, but no differences between the
Complexes of titanium, zirconium, and hafnium were obtained
by the reaction of 1 with the corresponding tetrakis-
(dimethylamido) precursors of the group(IV) metals. These
conversions proceeded cleanly to afford the corresponding
dimethylamido complexes [PN3]M(NMe2) (M = Ti (2), Zr (3),
Hf (4)) in good yields (70−85%) (Scheme 3). Interestingly, 3
and 4 are formed within 2 h at 75 °C, while the respective
titanium complex (2) requires higher temperatures (120 °C in
toluene) and prolonged reaction times (3 days) to reach full
conversion. In each case, the reaction can be monitored by 31P
NMR spectroscopy, as the formation of the dimethylamido
complexes is indicated by the emergence of new signals at −46.0
(2), −46.5 (3), and −51.0 ppm (4) and a decreasing intensity of
the signal of 1 (−36.5 ppm). The 1H and 13C NMR spectra of 2−
4 are indicative of C3-symmetric complexes, with only one
resonance each observed for the equivalent sets of atoms of the
individual side arms. The resonance for the six methylene
protons is broadened, possibly due to the dimethylamido group,
which disrupts the global symmetry to some extent. The
observed upfield shift of the 31P NMR signals upon complex
formation is rather counterintuitive,6d as the coordination of the
phosphorus lone pair to a metal center is usually accompanied by
a deshielding of the phosphorus nucleus. To elucidate this
phenomenon, the molecular structure of 4 was determined in the
solid state by means of single-crystal X-ray diffraction. Suitable
crystals for this purpose were grown by slow diffusion of pentane
into a solution of the complex in toluene at −40 °C (see Figure
1). In accordance with the NMR data, X-ray analysis overall
confirms the expected approximate C3-symmetric half-cage
structure, with the three amido moieties holding the central
1
31P and H spectra were recognized upon comparison of the
room-temperature spectra to those taken at −80 °C. Thus, we
propose that the structures in the solid state and solution are
fairly equivalent. DFT studies of complexes 2−4 (including NBO
calculations and second-order perturbation analyses in NBO
basis) indicate the presence of donor−acceptor interactions
between filled phosphorus-centered and virtual metal-centered
orbitals. Wiberg bond indices of approximately 0.5 were
determined for the metal−phosphine interaction in 2 - 4 (see
the Supporting Information).
In order to convert the dimethylamido complexes 2−4 to the
corresponding halides [PN3]M(Hal), reactions with trimethyl-
silyl halides were studied. Upon treatment of 4 with trimethylsilyl
chloride (Me3SiCl) in toluene, incomplete conversion with
concomitant formation of several unidentified side products was
observed. Employing a slight excess of Me3SiCl or heating the
former mixture resulted in extensive decomposition. In some
cases, purification of the reaction mixture via crystallization was
pursued (see the Supporting Information for the X-ray structure
of [PN3]ZrCl); however, the exchange of the dimethylamido
groups for halides seemed to be unreliable and hardly
reproducible in general. This is not the case when triethylsilyl
trifluoromethanesulfonate is used instead. Thus, the dimethyla-
mido complexes 2−4 were cleanly converted into the
corresponding triflates [PN3]MOTf (M = Ti (5), Zr (6), Hf
(7)) in good yields (60−80%) and under mild conditions.
Similar to the case for 2−4, the 1H NMR spectra of 5−7 reveal a
3-fold symmetry, indicating either free rotation of the
coordinated triflates or the presence of noncoordinating triflato
anions in solution. The 31P NMR shifts (−31.8 ppm (5), −43.1
ppm (6), −34.9 ppm (7)) suggest these complexes to have a
stronger P−M interaction than the dimethylamido compounds,
which is consistent with weakly coordinating or noncoordinating
triflates. To further elucidate the nature of the M−OTf
interaction, single crystals of 6 were grown by slowly cooling a
saturated solution of the complex in toluene to −40 °C. In 6, the
ligand coordinates in the expected fashion, forming a half-cage
complex (see Figure 2). The coordinated ancillary triflato anion
completes the trigonal-bipyramidal coordination geometry,
which resembles the binding situation found in 3.14 In
comparison to 3, the metal−N (approximately 2.06 Å) and
metal−P (2.720(7) Å) bond lengths are slightly shorter in 6,
suggesting a stronger zirconium−ligand interaction. The
stronger metal−phosphine interactions in 5−7 have also been
confirmed by DFT studies. NBO analysis indicates the presence
Figure 1. ORTEP diagram of 3 (solvent molecules and protons omitted
for clarity, ellipsoids set at 50% probability). Selected bond lengths (Å)
and angles (deg): Zr−N4 2.050(2), Zr−N1 2.088(2), Zr−N2 2.099(2),
Zr−N3 2.129(2), Zr−P 2.824(1); N4−Zr−N1 105.67(6), N4−Zr−N2
102.96(6), N1−Zr−N2 108.93(6), N4−Zr−N3 96.35(6), N1−Zr−N3
124.14(6), N2−Zr−N3 115.10(7), N4−Zr−P 173.13(5), N1−Zr−P
79.65(5), N2−Zr−P 78.97(5), N3−Zr−P 76.93(5).
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Figure 3. ORTEP diagram of 9 (solvent molecules and protons omitted
for clarity, ellipsoids set at 50% probability). Selected bond lengths (Å)
and angles (deg): Zr−N2 2.085(3), Zr−N1 2.092(3), Zr−N3 2.095(3),
Zr−C46 2.286(3), Zr−P 2.807(8); N2−Zr−N1 118.0(1), N2−Zr−N3
114.7(1), N1−Zr−N3 115.9(1), N2−Zr−C46 100.0(1), N1−Zr−C46
99.5(1), N3−Zr−C46 104.6(1), N2−Zr−P 77.88(7), N1−Zr−P
78.64(7), N3−Zr−P 79.40(7), C46−Zr−P 176.0(1).
Figure 2. ORTEP diagram of 6 (solvent molecules and protons omitted
for clarity, ellipsoids set at 50% probability). Selected bond lengths (Å)
and angles (deg): Zr−P 2.7199(7), Zr−O1 2.148(2), Zr−N1 2.062(2),
Zr−N2 2.065(2), Zr−N3 2.066(2); O1−Zr−P 178.14(5), N1−Zr−P
81.05(6), N1−Zr−O1 99.22(8), N1−Zr−N2 119.05(8), N1−Zr−N3
113.96(8), N2−Zr−P 80.47(6), N2−Zr−O1 97.82(8), N2−Zr−N3
119.79(8), N3−Zr−P 81.55(6), N3−Zr−O1 99.99(8).
Scheme 4. Synthesis of 11 Starting from 8 (Ar = 3,5-Xylyl)
of polarized metal−phosphorus bonds (approximately 80% P
centered and 20% metal centered) with Wiberg bond indices of
approximately 0.6 (see the Supporting Information).
Treatment of the triflato complexes 5−7 with a solution of
methyllithium at −78 °C in toluene afforded the corresponding
methyl complexes [PN3]MCH3 (M = Ti (8), Zr (9), Hf (10)) in
acceptable yields (50−60%). The 1H NMR spectra again indicate
the presence of C3-symmetric species in solution, with only one
set of side arm signals present. The protons of the methyl groups
resonate at 1.93 ppm (8), 0.40 ppm (9), and 0.22 ppm (10),
respectively, and the 31P NMR spectra exhibit singlets in all cases
(−58.0 ppm (8), −58.5 ppm (9), and −54.7 ppm (10)). The
observed upfield shift of the 31P NMR resonances once more
supports that the phosphine is actually coordinated in solution.
NBO calculations including second-order perturbation analyses
on 8−10 suggest the presence of donor−acceptor interactions
between the individual lone pairs at phosphorus and metal-
centered virtual orbitals. In case of 8, electron delocalization
involves an antibonding Ti−Me orbital (see the Supporting
Information). Wiberg bond indices for the metal−phosphine
interactions in 8−10 (approximately 0.5) are roughly equivalent
to the respective indices determined for 2−4 (see the Supporting
Information, Table S4). Single crystals of the zirconium methyl
complex 9 were generated by cooling a freshly prepared solution
of 9 in dichloromethane to −40 °C (see Figure 3). X-ray
diffraction analysis of these crystals revealed that the molecular
structure of 9 compares well to the structures of 3 and 6, as all
species exhibit trigonal-bipyramidal coordination spheres with
local C3 symmetry at the central metals. With respect to the
[PN3]Zr fragment, the metric parameters of the dimethylamido
(3) and methyl (9) species are fairly similar, with the Zr−P bond
length being slightly shorter (2.807(8) Å) in the case of 9. In
comparison to other zirconium methyl complexes, the Zr−C
bond length (2.286(3) Å) in 9 is found within the usual
boundaries.13
reactivity between 8 and both heavier homologues might very
well be explained by the aforementioned electron delocalization,
which involves a σ*Ti−Me orbital in the case of 8. As single crystals
of 11 suitable for X-ray diffraction could not be obtained, careful
analysis by 31P, 1H, and 13C and various two-dimensional NMR
techniques (see the Supporting Information) was employed to
establish the proposed structure of 11. What is evident from the
1H NMR spectrum of 11 is that the overall C3 symmetry is lost
and that only five protons for the ligand’s benzylic positions are
observed. One of these benzylic signals (singlet at 4.17 ppm) is
coupled to no other proton (according to 1H,1H−COSY) but is
found in coupling range to the 31P nucleus (1H,31P-HMBC cross
peak) and therefore assigned to the CH-activated methyne
position. A matching 13C resonance was found at 83.9 ppm, and
the assignment was ascertained by HSQC spectroscopy. APT
and DEPT spectra confirmed that this 13C signal indeed
corresponds to a methyne group.
Particularly interesting is the observed 31P resonance of 11 at
+46.1 ppm (singlet), as it experienced a downfield shift of over
100 ppm in comparison to the signal for 8 (−58.0 ppm). This
observation is in accordance with DFT calculations on 11, which
suggest a rather strong coordination of the central phosphine
(Ti−Pcalcd 2.425 Å) with a Wiberg bond index of approximately
0.74 (bonding interaction indicated by NBO analysis; see the
Supporting Information). Thus, the experimentally and
computationally obtained results are both in agreement with
the proposed structure of 11.
In conclusion, we synthesized a tripodal trisamidophosphine
ligand and explored its coordination chemistry with the
group(IV) metals. Nine complexes of the type [PN3]MX (M =
Ti, Zr, Hf, X = NMe2, OTf, CH3; 2−10) and the CH-activated
species 11 have been prepared and the molecular structures of
the zirconium derivatives elucidated by X-ray diffraction. To the
best of our knowledge, 1 is the first example of a tris-anionic
trisamidophosphine ligand that coordinates in a tetradentate
fashion. Studies directed toward the application of 11, for
Both the zirconium and hafnium methyl species (9 and 10) are
temperature-sensitive and decompose in an nonspecific manner
upon heating, while no signs of hydrides were evident upon
addition of gaseous H2 (10 bar). The titanium system (8),
however, is cleanly converted upon heating (75 °C for 2 h) to
afford the CH-activated product 11 shown in Scheme 4 along
with methane (detected by 1H NMR). The difference in
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example in dehydrocoupling reactions,15 are currently under way
in our laboratories.
Ferreira, M. J.; Patrick, B. O.; Fryzuk, M. D. Inorg. Chem. 2008, 47,
1319−1323. (d) Fryzuk, M. D.; Love, J. B.; Rettig, S. J.; Young, V. G.
Science 1997, 275, 1445−1447.
(6) (a) Raturi, R.; Lefebvre, J.; Leznoff, D. B.; McGarvey, B. R.;
Johnson, S. A. Chem. Eur. J. 2008, 14, 721−730. (b) Keen, A. L.; Doster,
M.; Han, H.; Johnson, S. A. Chem. Commun. 2006, 1221−1223. (c) Han,
H.; Johnson, S. A. Eur. J. Inorg. Chem. 2008, 471−482. (d) Han, H.;
Elsmaili, M.; Johnson, S. A. Inorg. Chem. 2006, 45, 7435−7445.
(e) Hatnean, J. A.; Raturi, R.; Lefebvre, J.; Leznoff, D. B.; Lawes, G.;
Johnson, S. A. J. Am. Chem. Soc. 2006, 128, 14992−14999. (f) Han, H.;
Johnson, S. A. Organometallics 2006, 25, 5594−5602.
(7) (a) Smythe, N. C. Ph.D. Dissertation; Massachusetts Institute of
Technology, Cambridge, MA, 2006 (available via the Internet at http://
hdl.handle.net/1721.1/37838). (b) Fryzuk, M. D. Personal communica-
tion.
ASSOCIATED CONTENT
* Supporting Information
■
S
Text, figures, tables, and CIF files giving experimental procedures
and characterization data for the preparation of 1−11, including
1H and 31P NMR spectra, X-ray characterization data for 2, 6, 9,
and [PN3]ZrCl, and computational results and Cartesian
coordinates for 1−11. This material is available free of charge
via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*J.B.: e-mail, joachim.ballmann@uni-heidelberg.de; tel, (+49)
6221 548596.
■
(8) Similarly, [PO3] ligand scaffolds are known, but no complexes with
tetradentate [PO3] moieties have been reported so far. See: (a) Krezel,
A.; Latajka, R.-l.; Bujacz, G. D.; Bal, W. Inorg. Chem. 2003, 42, 1994−
2003. (b) Kasak
48, 5665−5668.
́
, P.; Arion, V. B.; Widhalm, M. Tetrahedron Lett. 2007,
Notes
The authors declare no competing financial interest.
(9) Sidorkin, V. F.; Doronina, E. P. Organometallics 2009, 28, 5305−
5315.
ACKNOWLEDGMENTS
■
(10) (a) Chandrasekaran, A.; Timosheva, N. V.; Day, R. O.; Holmes, R.
R. Inorg. Chem. 2002, 41, 5235−5240. (b) Leschke, M.; Lang, H.;
Melter, M.; Rheinwald, G.; Weber, C.; Mayer, H. A.; Pritzkow, H.;
Zsolnai, L.; Driess, A.; Huttner, G. Z. Anorg. Allg. Chem. 2002, 628, 349−
356. (c) Leschke, M.; Melter, M.; Walfort, B.; Driess, A.; Huttner, G.;
Lang, H. Z. Anorg. Allg. Chem. 2004, 630, 2022−2030. (d) Zeng, X.;
Hucher, N.; Reinaud, O.; Jabin, I. J. Org. Chem. 2004, 69, 6886−6889.
(e) Over, D.; de la Lande, A.; Zeng, X.; Parisel, O.; Reinaud, O. Inorg.
Chem. 2009, 48, 4317−4330.
(11) Whitnall, M. R.; Hii, K. K.; Thornton-Pett, M.; Kee, T. P. J.
Organomet. Chem. 1997, 529, 35−50.
(12) Tajbakhsh, M.; Hosseinzadeh, R.; Alinezhad, H.; Ghahari, S.;
Heydari, A.; Khaksar, S. Synthesis 2011, 490−496.
(13) (a) Kasani, A.; Gambarotta, S.; Bensimon, C. Can. J. Chem. 1997,
75, 1494−1499. (b) Schrock, R. R.; Casado, A. L.; Goodman, J. T.;
Liang, L.-C.; Bonitatebus, P. J., Jr.; Davis, W. M. Organometallics 2000,
19, 5325−5341. (c) Mehrkhodavandi, P.; Schrock, R. R.; Bonitatebus, P.
J., Jr. Organometallics 2002, 21, 5785−5798. (d) Turculet, L.; Tilley, T.
D. Organometallics 2002, 21, 3961−3972. (e) Weng, W.; Yang, L.;
Foxman, B. M.; Ozerov, O. V. Organometallics 2004, 23, 4700−4705.
(f) Lee, W.-Y.; Liang, L.-C. Inorg. Chem. 2008, 47, 3298−3306.
(g) Frazier, K. A.; Froese, R. D.; He, Y.-Y.; Klosin, J.; Theriault, C. N.;
Vosejpka, P. C.; Zhou, Z.; Abboud, K. A. Organometallics 2011, 30,
3318−3329. (h) Liang, L.-C.; Chien, P.-S.; Hsiao, Y.-C.; Li, C.-W.;
Chang, C.-H. J. Organomet. Chem. 2011, 696, 3961−3965.
(14) Similar group(IV) triflates with tren-based ligand systems have
been reported earlier: (a) Schubart, M.; O’Dwyer, L.; Gade, L. H.; Li,
W.-S.; McPartlin, M. Inorg. Chem. 1994, 33, 3893−3898. (b) Schrock, R.
R.; Cummins, C. C.; Wilhelm, T.; Lin, S.; Reid, S. M.; Kol, M.; Davis, W.
M. Organometallics 1996, 15, 1470−1476.
This work was funded by the Fond der Chemischen Industrie
(Liebig-Stipenium for J.B. and FCI-Doktorandenstipendium for
M.S.) The authors thank Prof. L. H. Gade for generous support
and helpful discussions and S. Batke as well as C. Blasius for
experimental assistance. We are grateful to an unknown reviewer
who brought ref 7a to our attention.
REFERENCES
■
(1) (a) Whited, M. T.; Grubbs, R. H. Organometallics 2008, 27, 5737−
5740. (b) Seidel, W. W.; Summerscales, O. T.; Patrick, B. O.; Fryzuk, M.
D. Angew. Chem., Int. Ed. 2009, 48, 115−117. (c) Tran, B. L.; Pink, M.;
Mindiola, D. J. Organometallics 2009, 28, 2234−2243. (d) Thapa, I.;
Gambarotta, S.; Korobkov, I.; Duchateau, R.; Kulangara, S. V.;
Chevalier, R. Organometallics 2010, 29, 4080−4089. (e) Wang, L.;
Cui, D.; Hou, Z.; Li, W.; Li, Y. Organometallics 2011, 30, 760−767.
(f) Ballmann, J.; Pick, F.; Castro, L.; Fryzuk, M. D.; Maron, L. Inorg.
Chem. 2013, 52, 1685−1687. (g) Crestani, M. G.; Hickey, A. K.; Gao, X.;
Pinter, B.; Cavaliere, V. N.; Ito, J.-I.; Chen, C.-H.; Mindiola, D. J. J. Am.
Chem. Soc. 2013, 135, 14754−14767. (h) Marquard, S. L.; Bezpalko, M.
W.; Foxman, B. M.; Thomas, C. M. J. Am. Chem. Soc. 2013, 135, 6018−
6021. (i) Smith, D. A.; Herbert, D. E.; Walensky, J. R.; Ozerov, O. V.
Organometallics 2013, 32, 2050−2058.
(2) (a) Liang, L.-C.; Lee, W.-Y.; Hung, C.-H. Inorg. Chem. 2003, 42,
5471−5473. (b) Liang, L.-C.; Lee, W.-Y.; Yin, C.-C. Organometallics
2004, 23, 3538−3547. (c) Miller, A. J. M.; Dempsey, J. L.; Peters, J. C.
Inorg. Chem. 2007, 46, 7244−7246. (d) Wei, M.-M.; Garcia-Melchor,
M.; Daran, J.-C.; Audin, C.; Lledos, A.; Poli, R.; Deydier, E.; Manoury, E.
Organometallics 2012, 31, 6669−6680.
(3) (a) Fryzuk, M. D.; Johnson, S. A.; Patrick, B. O.; Albinati, A.;
Mason, S. A.; Koetzle, T. F. J. Am. Chem. Soc. 2001, 123, 3960−3973.
(b) Fryzuk, M. D.; Petrella, M. J.; Patrick, B. O. Organometallics 2005,
24, 5440−5454. (c) MacLachlan, E. A.; Fryzuk, M. D. Organometallics
2005, 24, 1112−1118. (d) Zhu, T.; Wambach, T. C.; Fryzuk, M. D.
Inorg. Chem. 2013, 50, 11212−11221.
(15) (a) Waterman, R. Chem. Soc. Rev. 2013, 42, 5629−5641.
(b) Waterman, R. Curr. Org. Chem. 2012, 16, 1313−1331. (c) Ghebreab,
M. B.; Newsham, D. K.; Waterman, R. Dalton Trans. 2011, 40, 7683−
7685. (d) Roering, A. J.; Leshinski, S. E.; Chan, S. M.; Shalumova, T.;
MacMillan, S. N.; Tanski, J. M.; Waterman, R. Organometallics 2010, 29,
2557−2565.
(4) (a) Fan, L.; Foxman, B. M.; Ozerov, O. V. Organometallics 2004, 23,
326−328. (b) Fafard, C. M.; Adhikari, D.; Foxman, B. M.; Mindiola, D.
J.; Ozerov, O. V. J. Am. Chem. Soc. 2007, 129, 10318−10319. (c) Kilgore,
U. J.; Sengelaub, C. A.; Pink, M.; Fout, A. R.; Mindiola, D. J. Angew.
Chem., Int. Ed. 2008, 47, 3769−3772. (d) Askevold, B.; Khusniyarov, M.
M.; Herdtweck, E.; Meyer, K.; Schneider, S. Angew. Chem., Int. Ed. 2010,
49, 7566−7569. (e) Grueger, N.; Wadepohl, H.; Gade, L. H. Dalton
Trans. 2012, 41, 14028−14030. (f) Venkanna, G. T.; Ramos, T. V. M;
Arman, H. D.; Tonzetich, Z. J. Inorg. Chem. 2012, 51, 12789−12795.
(5) (a) Fryzuk, M. D.; Johnson, S. A.; Rettig, S. J. J. Am. Chem. Soc.
2001, 123, 1602−1612. (b) Morello, L.; Love, J. B.; Patrick, B. O.;
Fryzuk, M. D. J. Am. Chem. Soc. 2004, 126, 9480−9481. (c) Morello, L.;
615
dx.doi.org/10.1021/om401018f | Organometallics 2014, 33, 612−615