Electronic factors affecting metal-metal interactions in early/late heterobimetallics: Substituent effects in zirconium/platinum bis(phosphinoamide) complexes

Article abstract of DOI:10.1021/om100356a

The bidentate metalloligand (NMe₂)₂Zr( ⁱPrNPPh₂)₂ (1) has been synthesized and treated with (COD)PtMe₂ to generate the heterobimetallic Zr/Pt species (NMe₂)₂Zr(ⁱPrNPPh₂) ₂PtMe₂ (2). Complex 2 can be treated with TMSCl to generate the dichloride species Cl₂Zr(ⁱPrNPPh ₂)₂PtMe₂ (3), a useful precursor for generating a range of Zr/Pt complexes featuring different Zr substituents. Upon treatment with lithio or Grignard reagents, Cl(Me₃SiCH₂)Zr( ⁱPrNPPh₂)₂PtMe₂ (4), (Me ₃SiCH₂)₂Zr(ⁱPrNPPh₂) ₂PtMe₂ (5), and Me₂Zr(ⁱPrNPPh ₂)₂PtMe₂ (6) have been synthesized. Complexes 1-6 have been characterized using X-ray crystallography, revealing an unmistakable trend in Pt-Zr distance as a function of the electron-releasing ability of the Zr-bound X-type ligands. In addition, the solid-state structure of 6 reveals isomerization of the chelating metalloligand from a cis to a trans configuration about Pt and an unusual anagostic interaction between one of the Pt-bound Me groups and the electron-deficient Zr center. This isomerization is accompanied by a thermoneutral methyl group exchange process between Zr and Pt.

Full text of DOI:10.1021/om100356a

Organometallics 2010, 29, 5179–5186 5179
DOI: 10.1021/om100356a
Electronic Factors Affecting Metal-Metal Interactions in Early/Late
Heterobimetallics: Substituent Effects in Zirconium/Platinum
Bis(phosphinoamide) Complexes†
Benjamin G. Cooper, Claudia M. Fafard, Bruce M. Foxman, and Christine M. Thomas*
Department of Chemistry, Brandeis University, 415 South Street, Waltham, Massachusetts 02454
Received April 27, 2010
The bidentate metalloligand (NMe2)2Zr(iPrNPPh2)2 (1) has been synthesized and treated with
(COD)PtMe2 to generate the heterobimetallic Zr/Pt species (NMe2)2Zr(iPrNPPh2)2PtMe2 (2).
Complex 2 can be treated with TMSCl to generate the dichloride species Cl2Zr(iPrNPPh2)2PtMe2
(3), a useful precursor for generating a range of Zr/Pt complexes featuring different Zr substituents.
Upon treatment with lithio or Grignard reagents, Cl(Me3SiCH2)Zr(iPrNPPh2)2PtMe2 (4),
(Me3SiCH2)2Zr(iPrNPPh2)2PtMe2 (5), and Me2Zr(iPrNPPh2)2PtMe2 (6) have been synthesized.
Complexes 1-6 have been characterized using X-ray crystallography, revealing an unmistakable
trend in Pt-Zr distance as a function of the electron-releasing ability of the Zr-bound X-type ligands.
In addition, the solid-state structure of 6 reveals isomerization of the chelating metalloligand from a
cis to a trans configuration about Pt and an unusual anagostic interaction between one of the Pt-
bound Me groups and the electron-deficient Zr center. This isomerization is accompanied by a
thermoneutral methyl group exchange process between Zr and Pt.
Chart 1
Introduction
Over the last several decades, dinuclear transition-metal
complexes that incorporate two intrinsically different transi-
tion-metal centers have received increasing interest.1,2 Investiga-
tions of these so-called early/late heterobimetallic complexes
have led to a greater understanding of the nature of the highly
polar metal-metal bonds in these species and how the disparity
between the electronic properties of each metal fragment leads
to enhanced reactivity patterns.3 Of particular interest is the
cooperative reactivity of the Lewis acidity of the early transition
metal and the Lewis basicity of the late transition metal in
σ-bond activation reactions.3-8 Wolczanski and co-workers ex-
amined a variety of early/late heterobimetallic complexes linked
by LX-type alkoxyphosphines and uncovered several examples
of cooperative reactivity between the two metal centers,9-12
including methyl group exchange between Zr and Pt in Cp*Zr-
Me(μ-OCH2PPh2)2PtMe2 (Chart 1).13
Inspired by Nagashima’s report of the usage of tris(phosphino-
amide)zirconium fragments as metalloligands for Mo and Cu,14
we have recently investigated this class of ligands as a method for
tuning redox potentials and supporting unusual coordination
geometries in early/late heterobimetallic Zr/Co complexes.15,16 In
our studies, we have found that substituents on both the phos-
phorus and nitrogen moieties of the phosphinoamide ligands
† Part of the Dietmar Seyferth Festschrift.
*To whom correspondence should be addressed. E-mail: thomasc@
brandeis.edu.
(1) Wheatley, N.; Kalck, P. Chem. Rev. 1999, 99, 3379–3420.
(2) Stephan, D. W. Coord. Chem. Rev. 1989, 95, 41–107.
(3) Gade, L. H. Angew. Chem., Int. Ed. 2000, 39, 2658–2678.
(4) Oishi, M.; Kato, T.; Nakagawa, M.; Suzuki, H. Organometallics
2008, 27, 6046–6049.
(5) Baranger, A. M.; Bergman, R. G. J. Am. Chem. Soc. 1994, 116,
3822–3835.
(6) Baranger, A. M.; Hollander, F. J.; Bergman, R. G. J. Am. Chem.
(11) Ferguson, G. S.; Wolczanski, P. T.; Parkanyi, L.; Zonnevylle,
M. C. Organometallics 1988, 7, 1967–1979.
Soc. 1993, 115, 7890–7891.
(7) Fulton, J. R.; Hanna, T. A.; Bergman, R. G. Organometallics
2000, 19, 602–614.
(12) Slaughter, L. M.; Wolczanski, P. T. Chem. Commun. 1997, 2109–
2110.
(13) Baxter, S. M.; Ferguson, G. S.; Wolczanski, P. T. J. Am. Chem.
(8) Gade, L. H.; Memmler, H.; Kauper, U.; Schneider, A.; Fabre, S.;
Bezougli, I.; Lutz, M.; Galka, C.; Scowen, I. J.; McPartlin, M. Chem.
Eur. J. 2000, 6, 692–708.
(9) Ferguson, G. S.; Wolczanski, P. T. Organometallics 1985, 4, 1601–
1605.
(10) Ferguson, G. S.; Wolczanski, P. T. J. Am. Chem. Soc. 1986, 108,
8293–8295.
Soc. 1988, 110, 4231–4241.
(14) Sue, T.; Sunada, Y.; Nagashima, H. Eur. J. Inorg. Chem. 2007,
2007, 2897–2908.
(15) Greenwood, B. P.; Forman, S. I.; Rowe, G. T.; Chen, C.-H.;
Foxman, B. M.; Thomas, C. M. Inorg. Chem. 2009, 48, 6251–6260.
(16) Greenwood, B. P.; Rowe, G. T.; Chen, C.-H.; Foxman, B. M.;
Thomas, C. M. J. Am. Chem. Soc. 2009, 132, 44–45.
r
2010 American Chemical Society
Published on Web 08/03/2010
pubs.acs.org/Organometallics

5180 Organometallics, Vol. 29, No. 21, 2010
Cooper et al.
Scheme 1
have a substantial effect on the reactivity of the resulting hetero-
bimetallic complexes. We anticipated that modification of the
ancillary halide ligands would also have a dramatic effect on
metal-metal interactions and reactivity; however, the limited
synthetic accessibility and the paramagnetic nature of such halide
substitution products renders them less than ideal for such a
comparative study.
Zr(NMe2)4 was pursued. Indeed, treatment of Zr(NMe2)4
i
with 2 equiv of the phosphinoamine PrNHPPh2 results in
clean formation of (NMe2)2Zr(iPrNPPh2)2 (1) with conco-
mitant evolution of gaseous HNMe2 (Scheme 1). Complex 1
is characterized by a singlet at 3.7 ppm in its 31P{1H} NMR
spectrum, implying at least some degree of phosphine co-
ordination to Zr in solution on the basis of an upfield shift of
∼30 ppm relative to the free ligand. The phosphines are, in
fact, both coordinated to Zr in the solid state (vide infra).
As shown in Scheme 1, treatment of metalloligand 1 with
(COD)PtMe2 at elevated temperature (80 °C) results in forma-
tion of the heterobimetallic Zr/Pt complex (NMe2)2Zr(iPrNP-
Ph2)2PtMe2 (2), as evidenced by a single 31P{1H} NMR signal
with 195Pt satellites at 36.9 ppm (1JPt-P = 1650 Hz). Similar to
Nagashima’s report with the tridentate metalloligand ClZr-
(iPrNPPh2)3,14 synthesis of an analogue of 2 via treatment of 1
with (COD)PtCl2 is complicated by ligand rearrangement via
In addition to tridentate tris(phosphinoamide)zirconium me-
talloligands, Nagashima has also investigated bidentate tita-
nium bis(phosphinoamide) derivatives of these ligands and their
coordination chemistry toward late transition metals.17-19 In
the series of compounds Cl2Ti(tBuNPPh2)2Pt(X)(Y) (X=Y =
Cl; X=Cl, Y=Me; X=Cl, Y=p-tolyl; X=Y=Me), it was
found that as the substituents on Pt imparted more electron
density on the Pt center, as evidenced by a decrease in 1JPt-P, the
PtfTi interaction was strengthened (Chart 1).17 Moreover,
Nagashima et al. coordinated Cl2Ti(tBuNPPh2)2 to Ni, Pt,
and Pd allyl fragments, finding that the proximity of these
late-transition-metal centers to the electron-deficient Ti center
leads to enhanced reactivity toward nucleophilic attack at the
allyl ligand.19 Interestingly, the zirconium bis(phosphinoamide)
analogues have not been studied, ostensibly because these metal-
loligands are inaccessible via treatment of ZrCl4 with 2 equiv of
Li(Ph2PNR); only trisubstituted (Ph2PNR)3ZrCl is isolated.14
Herein we report a facile route to a bidentate zirconium bis-
(phosphinoamide) metalloligand, (NMe2)2Zr(iPrNPPh2)2, its
coordination to the PtMe2 fragment, and a comparative study
examining the effects of varying the ancillary ligands on the Zr
center on metal-metal interactions.
1
halide transfer from Pt to Zr. In the H NMR spectrum of 2,
equivalent resonances for all four isopropyl methyl groups indi-
cate that the two phosphinoamide ligands are equivalent, as
expected, but also that the two methyl groups in each isopropyl
group are equivalent with each other. Given the π-donating
ability of the phosphinoamide nitrogen atom, free rotation
of the isopropyl group around the N-C bond is likely not
possible; therefore, a boat-chair-boatringflipmustbeoccur-
ring on the NMR time scale to render each isopropyl methyl
group equivalent.17
Interestingly, the reactivity of complex 2 appears to be
centered at the Zr(NMe2)2 fragment. For example, treatment
of 2with 2 molar equiv of TMSCl at room temperature results in
clean conversion to Cl2Zr(iPrNPPh2)2PtMe2 (3). Complex 3,
which is far less soluble in organic solvents than 2, is character-
Results
Synthesis of Zr Metalloligand and Zr/Pt Complexes. Given
the apparent inaccessibility of the Zr bis(phosphinoamides)
from ZrCl4, a route to these bidentate metalloligands via
ized by a broad singlet at 11.4 ppm with 195Pt satellites (1JPt-P
=
1450 Hz) in its 31P{1H} NMR spectrum. The 1H NMR spec-
trum of 3, however, is indicative of inequivalent phosphinoa-
mide ligands; two signals are observed for the isopropyl methyl
groups on the phosphinoamide nitrogen, and two inequivalent
types of phenyl resonances are observed. Furthermore, the
resonance for each of the ligands’ isopropyl methyl groups is a
broad singlet rather than the expected doublet; this indicates
(17) Nagashima, H.; Sue, T.; Oda, T.; Kanemitsu, A.; Matsumoto,
T.; Motoyama, Y.; Sunada, Y. Organometallics 2006, 25, 1987–1994.
(18) Sunada, Y.; Sue, T.; Matsumoto, T.; Nagashima, H. J. Organo-
met. Chem. 2006, 691, 3176–3182.
(19) Tsutsumi, H.; Sunada, Y.; Shiota, Y.; Yoshizawa, K.; Nagashima,
H. Organometallics 2009, 28, 1988–1991.

Article
Organometallics, Vol. 29, No. 21, 2010 5181
Table 1. Selected Interatomic Distances and Angles of 2-6 As Determined via X-ray Crystallography
2
3
4
5
6
Pt-Zr, A
Pt-P, A
3.2343(3)
2.2895(8)
2.2993(8)
2.108(3)
2.115(3)
2.126(3)
2.130(3)
2.028(3)
2.060(3)
162.87(11)
164.65(10)
105.43(3)
117.1
2.7761(5)
2.3448(11)
2.3328(11)
2.104(5)
2.100(5)
2.105(4)
2.158(4)
2.5146(12)
2.4076(12)
164.33(14)
173.48(14)
97.90(4)
2.9006(2)
2.3181(5)
2.3298(5)
2.101(2)
3.1411(2)
2.3044(4)
2.3173(4)
2.1046(16)
2.1015(15)
2.0928(12)
2.0832(12)
2.2225(17)
2.2359(16)
171.07(5)
166.72(5)
100.303(14)
115.2
2.7082(4)
2.2758(11)
2.2773(11)
2.174(4)
2.108(4)
2.184(3)
2.174(3)
2.240(4)
2.232(4)
N/A
Pt-C, A
2.100(2)
Zr-N, A
2.0733(18)
2.0983(18)
2.3919(6)
2.243(2)
163.91(7)
166.83(7)
105.317(19)
117.4
Zr-X, A
P-Pt-Ctrans, deg
P-Pt-P, deg
154.77(4)
av N-Zr-N/N-Zr-X,a deg
89.9
a Average of three (2, 4-6) or four (3) angles that form the pseudo-equatorial plane about Zr.
diastereotopic behavior within the isopropyl group, but it causes
only minor separation in 1H NMR resonances compared to that
resulting from the two inequivalent phosphinoamide ligands.
For these two types of inequivalencies to exist, there must be no
boat-chair-boat ring flip occurring—the result of a stronger
PtfZr interaction. A shorter metal-metal distance in 3 (vide
infra) supports this claim. While the elemental analysis of sam-
ples of 3 dried extensively in vacuo is indicative of the empirical
formula Cl2Zr(iPrNPPh2)2PtMe2 and no well-separated reso-
nances for coordinated THF are present in the 1H NMR (in d8-
THF) spectrum of 3, one THF molecule per molecule of
complex 3 is detectable by 1H NMR in benzene, and the solid-
state structure of 3 shows a six-coordinate Zr center with one
bound THF molecule (vide infra). Such a structure in solution
Figure 1. Displacement ellipsoid representation (50%) of 1. Hy-
drogen atoms have been omitted for clarity. Relevant interatomic
distances (A) and angles (deg): Zr1-P1, 2.8178(3); Zr1-N1,
2.118(8); Zr1-N2, 2.0653(9); N1-Zr1-N2, 105.43(4); N1-Zr1-
N1, 117.68(5); N2-Zr-N1, 113.43(3); N2-Zr1-N2, 100.24(6);
sum of angles about N2, 359.99.
would account for the inequivalence of the phosphinoamide
ligands, and the lability of the THF molecule in solution would
explain both (i) the ability of the bound THF to be removed in
vacuo and (ii) the absence of distinct resonances for bound THF
due to rapid exchange of THF molecules in d8-THF.
The ability to exchange Cl- ligands with lithio or Grignard
reagents renders complex 3 a useful precursor to examine the
effects of Zr substitution on metal-metal interactions between
Zr and Pt. Indeed, treatment of 3 with 1 equiv of Me3SiCH2-
MgCl leads to quantitative formation of the monosubstituted
complex Cl(Me3SiCH2)Zr(iPrNPPh2)2PtMe2 (4). The 31P{1H}
NMR spectrum of complex 4 has a characteristic singlet with
coupling to 195Pt at 23.2 ppm (1JPt-P = 1570 Hz). As a result of
the configuration of chloro and alkyl substituents at the Zr
center, the 1H NMR spectrum shows diastereotopic behavior,
with two independent resonances for each isopropyl methyl
group and two sets of phenyl resonances. Similar to the case for
3, complex 4 does not undergo a ring flip, but in this compound
the two ligands are equivalent. In an analogous procedure, the
disubstituted product (Me3SiCH2)2Zr(iPrNPPh2)2PtMe2 (5)
can be synthesized via treatment of 3 with 2 equiv of solid
Me3SiCH2Li. Lacking a halide in an ancillary position, the
zirconium center in 5 has more electron density than in 3 or 4,
decreasing the PtfZr donation and increasing the metal-metal
distance (vide infra), rendering the boat-chair-boat ring flip
possible. The equivalence of the phosphinoamide substitutents
ligands are equivalent; however, the 31P NMR resonance is
shifted downfield significantly more (67.6 ppm) and the 1JPt-P
value is significantly larger (2480Hz) than thatobservedin the
31P NMR spectra of 2-5. Such a large coupling constant
indicates that, in contrast to 2-5, the phosphines in 6 adopt a
trans configuration; this is confirmed by the solid-state struc-
ture (vide infra).
Structural Characterization of Zr/Pt Complexes. Single
crystals of complexes 1-6 were characterized by X-ray diffrac-
tion, and relevant interatomic distances and angles are sum-
marized in Table 1. The solid-state structure of the bidentate
zirconium metalloligand 1 confirms that in the solid state the
phosphinoamide ligand coordinates to the Zr center through
both the amide and phosphine donors (Figure 1). However, the
weakness of the phosphine-zirconium interaction is evident in
the long Zr-P distance (2.8178(3) A; both ligands are equiva-
lent by symmetry). As expected for a complex of an electron-
poor d0 metal, the geometry about all four amido nitrogen
atoms is planar. Taking into account only the ligated nitrogen
atoms, the Zr center adopts a pseudo-tetrahedral geometry.
The solid-state structure of 2 (Figure 2) confirms that the
Zr metalloligand 1 coordinates to the PtMe2 fragment in a
bidentate cis configuration. In the cis complexes 2-5, the six-
membered metallacyclohexane ring formed by the two phos-
phinoamide ligands and two metal centers adopts a boat
configuration with Zr and Pt at the bow and stern, allowing
the metals to be in close proximity to each other and permitting
a potential PtfZr interaction. The Pt-Zr interatomic distance
1
in the H NMR spectrum of complex 5 is indeed indicative
of a fluxional product on the NMR time scale (at room tempera-
ture), and the 31P{1H} NMR spectrum possesses a singlet at
26.9 ppm with coupling to 195Pt (1JPt-P = 1690 Hz).
When 3 is treated with 2 equiv of MeLi, a Zr dimethyl
complex, Me2Zr(iPrNPPh2)2PtMe2 (6), with distinctly dif-
ferent spectroscopic properties, is observed. The 31P{1H} and
1H NMR spectra of 6 indicate that both phosphinoamide

5182 Organometallics, Vol. 29, No. 21, 2010
Cooper et al.
two phosphinoamide ligands in the 1H NMR spectrum, as one
amide is trans to a Cl- ligand while the other is trans to THF.
The solid-state structures of monosubstituted and disubsti-
-
tuted Me3SiCH2 complexes (4 and 5, respectively; Figure 4)
show gradually increasing Pt-Zr distances as electron-rich
Me3SiCH2 alkyl groups are added to Zr (2.9006(2) and
-
3.1411(2) A, respectively). The geometry about Zr in complex
4 is moderately more distorted toward trigonal bipyramidal
(average N-Zr-N and N-Zr-C31 angles 117.4°) than in
complex 5 (average N-Zr-N and N-Zr-C37 angles 115.2°),
consistent with the more pronounced PtfZr interaction in the
former complex. As in complex 3, the structures of both 4 and 5
feature one methyl group distorted from the square plane about
Pt by 11 and 9°, respectively.
As indicated by the vastly different spectroscopic parameters
observed for complex 6, the X-ray crystal structure of this
methyl-substituted species shows that the bidentate phos-
phine metalloligand coordinates to Pt in a trans configuration
(Figure 5). This geometry enforces the shortest Pt-Zr distance
in this series of bimetallics: 2.7082(4) A. Another unusual feature
observed in the solid-state structure of 6 is the orientation of the
C34-Pt1-C33 vector such that one Pt-bound methyl group
appears to be weakly coordinating to the Zr center. While the
distance from the methyl carbon to Zr is 2.868(4) A, one of the
methyl hydrogen atoms is well within range to interact with Zr
(2.710 A). ThisC-H distance is too elongated to be indicative of
a bona fide agostic, three-center-two-electron Zr-C-H
interaction;21 however, the interaction can certainly be classi-
fied as “anagostic”, a term first introduced by Lippard to des-
cribe M-C-H interactions which are more electrostatic in
nature.22,23 Low-temperature 1H NMR was performed on
complex 6 in attempts to see an inequivalent bridging proton;
however, all six Pt-methyl protons appear equivalent at all
temperatures investigated (room temperature to -67 °C). This
Zr-C-H interaction likely results from the inherent disparity in
the electronic nature of the two metal centers and the electron-
poor, Lewis acidic nature of the Zr center.
Figure 2. Displacement ellipsoid representation (50%) of 2.
Hydrogen atoms have been omitted for clarity.
Figure 3. Displacement ellipsoid representation (50%) of 3. Hydro-
gen atoms and a THF solvate molecule have been omitted for clarity.
Discussion
of 3.2343(3) A in 2, however, is relatively long in comparison to
the sum of the van der Waals radii (2.749 A),20 suggesting that
there is little or no interaction between the two metal centers.
The geometry about Zr in 2 is pseudo-tetrahedral, and the d8 Pt
center adopts a square-planar configuration.
Structural and Spectroscopic Trends. While no other ex-
amples of Pt-Zr (or Pt-Hf) interactions have been struc-
turally characterized to date,24 the intermetallic distances in
complexes 2-6 can be compared with reported distances in
Ti/Pt heterobimetallics. The Ti-Pt distances in Nagashima’s
aforementioned bis(phosphinoamide) Ti/Pt complexes, Cl2Ti-
(tBuNPPh2)2Pt(X)(Y), range from 2.69 to 2.84 A.17 Thus, the
distances ranging from 2.71 to 3.23 A observed in 2-6 are
certainly comparable, given the (i) smaller covalent radius of
Ti compared to Zr (1.324 vs 1.454 A, respectively) and (ii) the
presence of less basic chloride ligands on Ti in all four
complexes. Three additional examples of Ti-Pt interactions
have been reported to date, including Cp2Ti(μ-CtCtBu)2Pt-
(PPh3),25 Cp2Ti(μ-O(PhCdCH)PPh2)Pt(O(PhCdCH)PPh2),26
The structure of complex 3 (Figure 3) features a much more
prominent PtfZr interaction. Upon replacement of the electron-
releasing NMe2- groups in 2 with less basic Cl- ligands in
complex 3, the Zr center becomes more electrophilic, binding
one THF solvent molecule (observable in both the crystal struc-
ture and the 1H NMR spectrum in C6D6) and withdrawing elec-
tron density from the nearby d8 Pt center. Thus, the Pt-Zr dis-
tance in 3 is 2.7761(5) A, significantly shorter than that in 2.
While this distance is nearly equivalent to the sum of the van der
Waals radii of Pt and Zr,20 the geometry about Zr is unequi-
vocally distorted octahedral with O1, Cl1, N2, and N1 in the
equatorial plane (average angles ∼90°) and the Pt center and Cl2
in the axial positions. Such a geometry would only be adopted in
the presence of PtfZr donation. The geometry about Pt in 3 is
square-planar, although it is considerably more distorted than
in complex 2, with one of the two methyl groups bent out of
the square plane by 13°. The asymmetry imparted by THF
coordination explains the aforementioned inequivalence of the
(21) Brookhart, M.; Green, M. L. H.; Parkin, G. Proc. Natl. Acad.
Sci. U.S.A. 2007, 104, 6908–6914.
(22) Braga, D.; Grepioni, F.; Tedesco, E.; Biradha, K.; Desiraju,
G. R. Organometallics 1997, 16, 1846–1856.
(23) Sundquist, W. I.; Bancroft, D. P.; Lippard, S. J. J. Am. Chem.
Soc. 1990, 112, 1590–1596.
(24) On the basis of a 2010 search of the Cambridge Structural
Database.
(25) Berenguer, J. R.; Fornies, J.; Lalinde, E.; Martın, A. Angew.
´
ꢀ
Chem., Int. Ed. Engl. 1994, 33, 2083–2085.
(26) Braunstein, P.; Morise, X.; Benard, M.; Rohmer, M.-M.; Welter,
(20) Pauling, L. The Nature of the Chemical Bond, 3rd ed.; Cornell
University Press: Ithaca, NY, 1960.
R. Chem. Commun. 2003, 610–611.

Article
Organometallics, Vol. 29, No. 21, 2010 5183
Figure 4. Displacement ellipsoid representation (50%) of 4 and 5. Hydrogen atoms have been omitted for clarity.
The 31P NMR data, both chemical shifts and 1JP-Pt values,
also follow a distinct trend as the anionic ligands on Zr are
1
varied. The JP-Pt coupling constant increases in the order
ZrCl2<ZrCl(CH2SiMe3)<Zr(CH2SiMe3)2, Zr(NMe2)2, im-
plicating that the Pt-P bond strength decreases in the oppo-
site order of strength of the Zr-Pt interaction. While at first
this may seem counterintuitive solely on the basis of electron
withdrawal from the Pt center by Zr, the trend can be ex-
plained in terms of the electron withdrawal through the phos-
phinoamide ligand itself. Thus, as the Zr center becomes more
electron poor, the phosphinoamide ligand becomes a poorer
electron donor to Pt, weakening the P-Pt bond. Interestingly,
the 31P chemical shifts for complexes 2-5 appear to follow a
similar trend.
1
1
Variable-Temperature H NMR of Complex 5. H NMR
spectra of 5 in d8-THF were obtained at 10 °C intervals from
20 °C to -60 °C. At 20, 10, and 0 °C, just one resonance is
present for the four silyl methylene protons in one molecule of 5,
indicative of the occurrence of a boat-chair-boat ring-flip that
renders the two ancillary (trimethylsilyl)methyl groups equiva-
lent. At -10 °C, however, two adjacent singlets of equal inten-
sity replace the lone singlet that was observed at higher tempera-
tures, indicating an inequivalence in the two types of silyl
methylene protons that would only be caused by a cessation of
fluxional ring-flip behavior (Scheme 2). This phenomenon is also
observed for the isopropyl resonances. At room temperature,
just one peak is observed for both the pseudo-axial and pseudo-
equatorial isopropyl methyl groups (equivalent due to the pre-
sence of the boat-chair-boat fluxionality), but at -10 °C, two
peaks are present instead of one, indicating diastereotopicity bet-
ween the pseudo-axial and pseudo-equatorial isopropyl methyl
groups due to the inability of the ring flip to occur at this lower
temperature.
Cis/Trans Isomerization and Methyl Group Exchange in
Complex 6. Two aspects of complex 6 warrant further discus-
sion: (1) the unusual anagostic interaction between the Zr center
and the Pt-bound methyl group observed in the solid state and
(2) the mechanism by which the isomerization of the Pt-bound
phosphines from a cis to a trans configuration occurs. With
respect to observation 1, the geometry of complex 6 is reminis-
cent of proposed intermediates in intermetallic ligand ex-
change processes. Examples of these bimetallic processes include
the aforementioned methyl group exchange between Zr and
Pt in Cp*ZrMe(μ-OCH2Ph2P)2PtMe213 and CO-promoted mi-
gration of a silyl group from Fe to Pt in phosphido-bridged
Figure 5. Displacement ellipsoid representation (50%) of 6.
Hydrogen atoms and a toluene solvate molecule have been
omitted for clarity.
and Cp2Ti(μ-CH2)(μ-X)PtMe(PMe2Ph) (X = Me or Cl),27
whose Pt-Ti distances are also comparable to those observed
in 2-6 (2.787, 2.721(2), 2.776(1), and 2.962(2) A, respectively).
Of particular interest is a comparison of the Pt-Zr intera-
1
tomic distances, 31P NMR shifts, and JP-Pt coupling con-
stants as a function of Zr substituents, X and Y (Table 2). With
the exception of complex 6, whose trans configuration prevents
a direct comparison with 2-5, there is a distinct trend in the
electron-releasing nature of the X and Y substituents on Zr and
the structural and spectroscopic properties in this series of
compounds. Differences in the electronic nature of X and Y
suggest that the electron density on Zr should decrease in the
order Zr(NMe2)2 > Zr(CH2SiMe3)2 > ZrCl(CH2SiMe3) >
ZrCl2. As the Zr center becomes more electron-poor, the dative
PtfZr interaction should strengthen. Indeed, the Pt-Zr dis-
tance in 2-5 decreases in this order (Table 2). For example,
complex 3 has the least electron-releasing substituents (Cl-) on
Zr and thus the shortest interatomic Pt-Zr distance among
2-5, 2.7761(5) A. This trend in PtfM distance complements
the trend in PtfTi distance observed by Nagashima et al., who
demonstrated that as the electron density on Pt is increased, the
PtfTi interaction strengthens.17
(27) Ozawa, F.; Park, J. W.; Mackenzie, P. B.; Schaefer, W. P.;
Henling, L. M.; Grubbs, R. H. J. Am. Chem. Soc. 1989, 111, 1319–1327.

5184 Organometallics, Vol. 29, No. 21, 2010
Cooper et al.
Table 2. Pt-Zr Interatomic Distances Determined by X-ray Crystallography and 31P{1H} Chemical Shifts and 1JP-Pt Coupling Constants
As Zr Substituents in (X)(Y)Zr(iPrNPPh2)2Pt(Me)2 Complexes Are Varied
complex
X
Y
Pt-Zr dist, A
31P{1H} shift, ppm
1JP-Pt, Hz
-
-
2
3
4
5
6
NMe2
NMe2
Cl-
3.2343(3)
2.7761(5)
2.9006(2)
3.1411(2)
2.7082(4)
37.5
11.4
23.2
26.9
67.6
1650
1450
1570
1690
2480
Cl-
Cl-
-
CH2SiMe3-
CH2SiMe3
Me-
-
CH2SiMe3
Me-
Scheme 2. Boat-Chair-Boat Fluxionality in Complex 5a
a In the presence of this fluxionality at room temperature, the silyl methylene protons labeled in both red and blue as well as the isopropyl methyl
protons labeled A and B appear equivalent by 1H NMR. In the absence of this fluxionality at -10 °C and below, pseudo-axial (“blue” and “A”) protons
appear inequivalent with their pseudo-equatorial (“red” and “B”) counterparts.
and 0.72 ppm (Pt bound) in equal intensities, and while the iPr
methyl/Zr methyl/Pt methyl ratio observed in 6 is 12/6/6, that
observed in the d3-MeLi addition product is 12/3/3 (Figure 6).
These integration data are consistent with previously reported,
well-understood methyl exchange processes, but further inves-
tigation is required to assign a definitive mechanistic process by
which the exchange occurs.
Conclusion
In summary, we have found that the substituents on the Lewis
acidic Zr center in early/late heterobimetallic Zr/Pt complexes
have a well-defined and dramatic effect on the strength of the
PtfZr interaction. These differences are manifested in the
crystallographically determined Pt-Zr interatomic distances,
which are substantially shorter when Zr is bound by less electron
releasing X-type ligands and substantially longer when Zr is
bound by electron-rich X- or LX-type ligands. These funda-
mental effects have implications toward surface-supported cat-
alysis, suggesting that strong metal support interactions (SMSI)
between late transition metals and early-metal oxide supports
may be stronger (and, thus, have a greater effect on reactivity)
when the early-metal oxide framework is more Lewis acidic. A
scrambling of methyl groups between Zr and Pt has also been
Figure 6. 1H NMR spectra of complex 6 (top) and the product
of addition of d3-MeLi to 3 (bottom), showing evidence for CD3
exchange into methyl positions on both Pt and Zr.
observed; while ligand exchange processes between metal centers
have been studied extensively,30 this particular example is inter-
esting, since identical ligands are exchanging, discounting a
thermodynamically driven process. Future work will focus on
the mechanism of this unique methyl exchange process and its
potential relevance to reactions involving C-C bond formation
or cleavage.
complexes: (CO)3(SiR3)Fe(μ-PR2)Pt(CO)(L) þ CO f (CO)4-
Fe(μ-PR2)Pt(L)(SiR3).28,29 With this in mind, we sought to
investigate whether a similar exchange of methyl groups between
Zr and Pt was occurring during the formation of complex 6.
Indeed, treatment of Cl2Zr(iPrNPPh2)2PtMe2 (3) with2equivof
Experimental Section
d3-MeLi did not lead exclusively to (CD3)2Zr(iPrNPPh2)2PtMe2
but rather to a mixture of isotopically labeled products in which
CD3- moieties were apparently present in positions on both Zr
and Pt. The 1H NMR spectrum of this d3-MeLi addition pro-
duct shows resonances for CH3- at both 1.09 ppm (Zr bound)
General Considerations. All syntheses reported were carried
out using standard glovebox and Schlenk techniques in the
absence of water and dioxygen, unless otherwise noted. Pentane,
benzene, diethyl ether, toluene, and tetrahydrofuran were de-
gassed and dried by sparging with N2 gas followed by passage
through an activated alumina column. All solvents were stored
(28) Braunstein, P.; Knorr, M.; Hirle, B.; Reinhard, G.; Schubert, U.
Angew. Chem., Int. Ed. Engl. 1992, 31, 1583–1585.
(29) Messaoudi, A.; Deglmann, P.; Braunstein, P.; Hofmann, P.
(30) Garrou, P. E.; Stone, F. G. A.; Robert, W. Adv. Organomet.
Chem. 1984, 23, 95–129.
Inorg. Chem. 2007, 46, 7899–7909.

Article
Organometallics, Vol. 29, No. 21, 2010 5185
Table 3. X-ray Diffraction Experimental Details for (NMe2)2Zr(iPrNPPh2)2 (1), (NMe2)2Zr(iPrNPPh2)2Pt(Me)2 (2),
(THF)Cl2Zr(iPrNPPh2)2Pt(Me)2 THF (3 THF), and Cl(Me3SiCH2)Zr(iPrNPPh2)2Pt(Me)2 (4), (Me3SiCH2)2Zr(iPrNPPh2)2Pt(Me)2
3
3
(5), and (Me)2Zr(iPrNPPh2)2Pt(Me)2 (6)
1
2
3 THF
3
4
5
6 (toluene)
3
chem formula
fw
T (°C)
λ (A)
a (A)
C34H46N4P2Zr C36H52N4P2PtZr C40H56Cl2N2O2P2PtZr C36H51ClN2P2PtSiZr C40H62N2P2PtSi2Zr C41H54N2P2PtZr
975.37
663.93
-153
889.09
1016.06
-153
923.61
923.15
-153
-80
-153
-153
0.71073
16.5830(9)
27.4822(15)
10.0945(5)
90
123.198(2)
90
3849.6(4)
C12/c1
4
0.71073
11.5577(6)
12.2179(6)
13.2809(7)
100.145(2)
92.754(2)
96.693(2)
1828.99(16)
P1
0.71073
9.3496(4)
34.5901(15)
13.6659(5)
90
90.455(2)
90
4419.5(3)
P121/c1
4
1.527
3.624
0.0234, 0.0491
P
0.71073
11.0436(3)
12.4138(3)
18.0560(4)
78.7040(10)
84.2540 (10)
75.9310(10)
2351.00(10)
P1
0.71073
11.1953(6)
20.0505(11)
19.8404(11)
90
0.71073
19.3441(5)
9.7686(3)
20.5726(6)
90
b (A)
c (A)
R (deg)
β (deg)
γ (deg)
V (A3)
space group
Z
104.257(2)
90
4316.4(4)
P121/c1
4
1.501
3.637
0.0154, 0.0368
95.5730(10)
90
3869.12(19)
P121/n1
4
1.585
3.994
0.0362, 0.0748
2
1.614
4.223
2
1.305
3.366
0.0227, 0.0496
Dcalcd (g/cm3)
1.146
0.394
μ (cm-1
)
R1, wR2a (I > 2σ(I)) 0.0219, 0.0584 0.0349, 0.0984
P
P
P
a R1 = ||Fo| - |Fo||/ |Fo|; wR2 = { [w(Fo2 - Fc2)2]/ [w(Fo2)2]}1/2
.
over 3 A molecular sieves. Deuterated benzene and toluene were
purchased from Cambridge Isotope Laboratories, Inc., de-
gassed via repeated freeze-pump-thaw cycles, and dried over
3 A molecular sieves. d8-THF was dried over Na, vacuum
transferred, and degassed via repeated freeze-pump-thaw
cycles. Solvents were frequently tested using a standard solution
of sodium benzophenone ketyl in tetrahydrofuran to confirm
the absence of oxygen and moisture. Ph2PNHiPr31,32 and
(400 MHz, C6D6): δ 7.56 (m, 8 H, Ar H), 6.98 (m, 12 H, Ar H), 3.63
(m, 2 H, NCHMe2), 3.19 (s, 12 H, NMe2), 1.12 (d, J = 6.4 Hz, 12
H, NCHMe2), 1.04 (dd, 3JP-H = 6.4, 8.8 Hz, 2JPt-H=66 Hz, 6 H,
PtMe2,). 13C{1H} NMR (100.5 MHz, C6D6):δ 137.0 (d, 1JP-C=47
Hz, ipso-Ph), 134.0 (d, 2JP-C=10 Hz, 3JPt-C=11 Hz, ortho-Ph),
3
129.5 (s, para-Ph), 127.8 (d, JC-P = 10 Hz, meta-Ph), 54.5 (d,
2JC-P=11 Hz, CHMe2), 45.2 (s, NMe2), 27.3 (s, CHMe2), 15.5
(dd, PtMe2, did not observe Pt satellites, JP-C =8 and 89 Hz).
Anal. Calcd for C6H52N4P2PtZr: C, 48.63; H, 5.90; N, 6.30. Found:
C, 48.52; H, 5.89; N, 6.17.
33
(COD)PtMe2 were synthesized using literature procedures.
TMSCl was degassed via repeated freeze-pump-thaw cycles.
All other chemicals were purchased from Aldrich, Strem, or
Alfa Aesar and used without further purification. NMR spectra
were recorded at ambient temperature unless otherwise stated
on a Varian Inova 400 MHz instrument. 1H and 13C NMR
chemical shifts were referenced to residual solvent. 31P NMR
chemical shifts were referenced to 85% H3PO4. Elemental
microanalyses were performed by Complete Analysis Labora-
tories, Inc., Parsippany, NJ.
Cl2Zr(iPrNPPh2)2PtMe2 (3). To a stirred solution of 2 (376
mg, 0.423 mmol) in a 1/1 mixture of THF (3 mL) and Et2O (3
mL) was added Me3SiCl (113 μL, 0.889 mmol). The resulting
solution was stirred for ca. 72 h. Volatiles were removed in
vacuo, and the remaining residue was washed with pentane (2 ꢀ
5 mL) and then dried under vacuum to afford 3 as a light yellow
solid (317 mg, 86% yield). Crystals suitable for X-ray diffraction
were grown via layering a concentrated THF solution of 3 with
pentane at -35 °C. 31P{1H} NMR (161.8 MHz, d8-THF): δ 11.4
(1JP-Pt = 1450 Hz). 1H NMR (d8-THF): δ 7.55 (d, 2 H, J = 6.8
Hz, Ar H), 7.23-7.44 (overlapping br m, 16 H, Ar H), 6.95 (br
m, 2 H, Ar H), 3.63 (m, 2 H, NCHMe2), 1.63 (br s, 6 H,
NCHMe2), 1.10 (br s, 6 H, NCHMe2), 0.92 (m, 6 H, PtMe2,
2JH-Pt = 67 Hz). 13C{1H} NMR (100.5 MHz, d8-THF): δ 134.7
(ortho-Ph), 133.7 (ipso-Ph), 133.2 (ipso-Ph), 131.4 (ortho-Ph),
129.6 (para-Ph), 127.7 (meta-Ph), 127.0 (meta-Ph), 54.1 (s,
CHMe2), 26.1 (s, CHMe2) 17.1 (m, PtMe2, did not observe Pt
satellites). Anal. Calcd for C32H40N2P2Cl2PtZr: C, 44.08; H,
4.62; N, 3.21. Found: C, 43.94; H, 4.78; N, 3.47.
(NMe2)2Zr(iPrNPPh2)2 (1). Solid iPrNHPPh2 (2.0 g, 8.2 mmol)
and Zr(NMe2)4 (1.0 g, 3.7 mmol) were combined in pentane (20
mL). The resulting yellow solution was stirred overnight, and
volatiles were then removed under vacuum. The remaining oily
residue was dissolved in a minimum amount of pentane and stored
at -35 °C to precipitate 1 as a light yellow solid (2.3 g, 96% yield).
Crystals suitable for X-ray diffraction were grown from a concen-
trated pentane solution of 1 at -35 °C. 31P{1H} NMR (161.8 MHz,
C6D6): δ 3.7. 1H NMR (400 MHz, C6D6): δ 7.58 (m, 8 H, Ar H),
7.08 (m, 12 H, Ar H), 3.79 (m, 2 H, NCHMe2), 3.33 (s, 12 H,
NMe2), 1.16 (d, J = 6.4 Hz, 12 H, NCHMe2). 13C{1H} NMR
(100.5 MHz, C6D6): δ 139.6 (s, Ar), 133.6 (d, J = 16.7 Hz, Ar),
129.2 (s, Ar), 128.7 (s, Ar), 53.7 (m, CHMe2), 46.4 (t, J = 4.6 Hz,
NMe2), 28.0 (s, CHMe2). Anal. Calcd for C34H46N4P2Zr: C, 61.51;
H, 6.98; N, 8.44. Found: C, 61.41; H, 6.87; N, 8.35.
Cl(Me3SiCH2)Zr(iPrNPPh2)2PtMe2 (4). Solid 3 (53.7 mg,
0.062 mmol) was dissolved in C6D6 (∼2 mL), and Me3-
SiCH2MgCl (1.0 M in diethyl ether, 62 μL, 0.062 mmol) was
added. After 7 min, the resulting solution was filtered through
Celite and volatiles were removed from the filtrate in vacuo. The
resulting solids were washed with pentane (5 mL) and dried to
afford an analytically pure sample of 4 (39.6 mg, 71% yield).
Crystals suitable for X-ray diffraction were grown via diffusion of
pentane into a concentrated toluene solution of 4 at -35 °C.
31P{1H} NMR (161.8 MHz, C6D6): δ 23.2 (1JP-Pt = 1570 Hz). 1H
(400 MHz, C6D6): δ 7.54 (m, 4 H, ortho-Ar), 7.28 (m, 4 H, ortho-
Ar), 7.08 (m, 4 H, meta-Ar), 7.00 (m, 2 H, para-Ar), 6.85 (m, 2 H,
para-Ar), 6.69 (m, 4 H, meta-Ar), 3.54 (m, 2 H, NCHMe2), 1.96 (s,
2 H, CH2SiMe3), 1.48 (d, J = 6.4 Hz, 12 H, NCHMe2, 1.36 (m,
3JPt-H = 65 Hz, 6 H, PtMe2), 0.56 (s, 9 H, SiMe3). 13C{1H} NMR
(100.5 MHz, C6D6): δ 138.0 (m, ipso-Ph), 134.2 (m, ortho-Ph),
130.5 (s, para-Ph), 128.3 (overlapping with C6D6, meta-Ph), 54.1 (s,
CHMe2), 27.2 (s, CHMe2) 26.7 (s, CHMe2), 26.1 (s, CH2SiMe3),
16.8 (m, PtMe2, did not observe Pt satellites), 3.7 (s, SiMe3). Anal.
(NMe2)2Zr(iPrNPPh2)2PtMe2 (2). Solid 1 (950 mg, 1.43 mmol)
and (COD)PtMe2 (435 mg, 1.30 mmol) were dissolved in THF (9
mL), and the solution was transferred to a sealed Schlenk tube and
heated overnight at 80 °C. Volatiles were removed from the result-
ing solution under vacuum. The remaining residue was washed with
pentane (2 ꢀ 5 mL) and dried in vacuo to give 2 as a light yellow
powder (748 mg, 65% yield). Crystals suitable for X-ray diffraction
were grown from a pentane/THF mixture at -35 °C. 31P{1H}
NMR (161.8 MHz, C6D6): δ 36.9 (1JP-Pt = 1650 Hz). 1H NMR
(31) Sisler, H.; Smith, N. J. Org. Chem. 1961, 26, 611–613.
(32) Poetschke, N.; Nieger, M.; Khan, M. A.; Niecke, E.; Ashby,
M. T. Inorg. Chem. 1997, 36, 4087–4093.
(33) Bassan, R.; Bryars, K. H.; Judd, L.; Platt, A. W. G.; Pringle,
P. G. Inorg. Chim. Acta 1986, 121, L41–L42.

5186 Organometallics, Vol. 29, No. 21, 2010
Cooper et al.
Calcd for C36H51N2SiP2ClPtZr: C, 46.82; H, 5.57; N, 3.03. Found:
C, 46.73; H, 5.37; N, 2.88.
X-ray Crystallography Procedures. All operations were per-
formed on a Bruker-Nonius Kappa Apex2 diffractometer, using
graphite-monochromated Mo KR radiation. All diffractometer
manipulations, including data collection, integration, scaling,
and absorption corrections, were carried out using the Bruker
Apex2 software.34 Preliminary cell constants were obtained
from 3 sets of 12 frames. Structures were solved using
SIR92,35 and refinements (full-matrix-least-squares) were car-
ried out using the Oxford University Crystals for Windows
program.36 All non-hydrogen atoms were refined using aniso-
tropic displacement parameters. Experimental details are pro-
vided in Table 3, and data collection, solution, and refinement
details are supplied in the Supporting Information.
(Me3SiCH2)2Zr(iPrNPPh2)2PtMe2 (5). Solid 3 (56.8 mg,
0.065 mmol) was suspended in C6H6 (2 mL), and to this
suspension was added solid Me3SiCH2Li (12.3 mg, 0.131 mmol).
The resulting solution was stirred for approximately 15 min and
then filtered through Celite. Volatiles were removed from the
filtrate under vacuum. The resulting solids were washed with
pentane (5 mL) and dried to afford an analytically pure sample
of 5 (23.1 mg, 36% yield). Crystals suitable for X-ray diffraction
were grown via diffusion of pentane into a concentrated toluene
solution of 5 at -35 °C. 31P{1H} NMR (161.8 MHz, C6D6): δ
26.9 (1JP-Pt = 1690 Hz). 1H NMR (400 MHz, C6D6): δ 7.47 (m,
8 H, Ar H), 6.94 (12 H, Ar H), 3.55 (m, 2 H, NCHMe2), 1.69 (br
s, 4 H, CH2SiMe3), 1.28 (m, 2JH-Pt = 66 Hz, 6 H, PtMe2), 1.18
(d, J = 6.4 Hz, 12 H, NCHMe2), 0.48 (s, 18 H, SiMe3). 13C{1H}
NMR (100.5 MHz, C6D6): δ 135.3 (d, 1JP-C = 52 Hz, ipso-Ph),
133.23 (m, ortho-Ph), 129.8 (s, para-Ph), 128.2 (overlapping with
C6D6, meta-Ph), 53.9 (s, CHMe2), 26.1 (s, CH2SiMe3), 27.9 (s,
Acknowledgment. This material is based upon work
supported by the Department of Energy under Award
No. DE-SC0004019.37 We also acknowledge Chun-Hsing
Chen and Bennett Greenwood for assistance with X-ray
crystallography and Brandeis University for funding.
2
CHMe2), 14.0 (d, JP-C = 90 Hz, PtMe2, did not observe Pt
satellites), 4.4 (s, SiMe3). Anal. Calcd for C40H62N2Si2P2PtZr:
C, 49.26; H, 6.41; N, 2.87. Found: C, 48.92; H, 6.35; N, 2.92.
Me2Zr(iPrNPPh2)2PtMe2 (6). Solid 3 (135 mg, 0.155 mmol)
was dissolved in diethyl ether (2 mL), and to this solution was added
MeLi (1.6 M in diethyl ether, 195 μL, 0.312 mmol). The resulting
solution was stirred for 1.5 h and then filtered through Celite.
Volatiles were removed from the filtrate under vacuum, and the
residue was washed with pentane (2 ꢀ 2 mL) and then dried under
vacuum to give 6 as a light tan solid (81 mg, 63% yield). Crystals
suitable for X-ray diffraction were grown via vapor diffusion of pen-
tane into a concentrated toluene solution of 6 at -35 °C. 31P{1H}
Supporting Information Available: Text, figures, and CIF files
giving crystallographic data for complexes 1-6. This material is
available free of charge via the Internet at http://pubs.acs.org.
(34) Apex 2, Version 2 User Manual, M86-E01078; Bruker Analytical
X-ray Systems: Madison, WI, 2006.
(35) Altomare, A.; Cascarano, G.; Giacovazzo, G.; Guagliardi, A.;
Burla, M. C. J. Appl. Crystallogr. 1994, 27.
(36) Betteridge, P. W.; Carruthers, J. R.; Cooper, R. I.; Prout, K.;
Watkin, D. J. J. Appl. Crystallogr. 2003, 36, 1487.
(37) This report was prepared as an account of work sponsored by an
agency of the United States Government. Neither the United States
Government nor any agency thereof, nor any of their employees, makes
any warranty, express or implied, or assumes any legal liability or
responsibility for the accuracy, completeness, or usefulness of any
information, apparatus, product, or process disclosed, or represents
that its use would not infringe privately owned rights. Reference herein
to any specific commercial product, process, or service by trade name,
trademark, manufacturer, or otherwise does not necessarily constitute
or imply its endorsement, recommendation, or favoring by the United
States Government or any agency thereof. The views and opinions of
authors expressed herein do not necessarily state or reflect those of the
United States Government or any agency thereof.
1
NMR (161.8 MHz, C6D6): δ 67.6 ppm (1JP-Pt = 2480 Hz). H
NMR (400 MHz, C6D6): δ 7.68 (m, 8 H, Ar H), 7.09 (m, 12 H, Ar
H), 3.70 (m, 2 H, NCHMe2), 1.41 (d, J = 6.4 Hz, 12 H, NCHMe2),
2
1.09 (s, 6 H, ZrMe2), 0.71 (m, JH-Pt = 45 Hz, 6 H, PtMe2).
13C{1H} NMR (100.5 MHz, C6D6): δ 138.0 (m, ipso-Ph), 134.2 (m,
ortho-Ph), 130.5 (s, para-Ph), 128.3 (overlapping with C6D6, meta-
Ph), 52.3 (s, CHMe2), 47.1 (s, ZrMe2) 27.4 (s, CHMe2), 8.8 (dd,
PtMe2, did not observe Pt satellites, JP-C = 8 and 89 Hz). Anal.
Calcd for C34H46N2P2PtZr: C, 49.14; H, 5.58; N, 3.37. Found: C,
48.96; H, 5.53; N, 3.17.