Improved one-pot synthesis of mixed methyl - aryl platinum(II) diimine complexes

Article abstract of DOI:10.1021/om050899z

A general one-pot synthetic route for mixed methyl-aryl Pt(II) diimine complexes is described. Performing the alkylation in neat Me₂S instead of ether or THF greatly reduces the amount of comproportionation products otherwise formed, diminishes separation problems, and improves yields. Treatment of the intermediate methyl - aryl complexes (Me₂S) ₂Pt(Me)(Ar) with diimines (N-N) furnishes the methyl - aryl Pt(II) diimine complexes (N-N)Pt(Me)(Ar) in 76-84% yields. The Pt methylphenyl complex [p-Tol-N=C(Me)C(Me)=N-p-Tol]Pt(Me)(Ph) has been characterized by X-ray diffraction.

Full text of DOI:10.1021/om050899z

Organometallics 2006, 25, 1055-1058
1055
Improved One-Pot Synthesis of Mixed Methyl-Aryl Platinum(II)
Diimine Complexes
Martin Lersch,† Bjørn Dalhus,† John E. Bercaw,‡ Jay Labinger,‡ and Mats Tilset*,†
Department of Chemistry, UniVersity of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo, Norway, and
Arnold and Mabel Beckman Laboratories of Chemical Synthesis, California Institute of Technology,
Pasadena, California 91125
ReceiVed October 18, 2005
Summary: A general one-pot synthetic route for mixed methyl-
aryl Pt(II) diimine complexes is described. Performing the
alkylation in neat Me2S instead of ether or THF greatly reduces
the amount of comproportionation products otherwise formed,
diminishes separation problems, and improVes yields. Treatment
of the intermediate methyl-aryl complexes (Me2S)2Pt(Me)(Ar)
with diimines (N-N) furnishes the methyl-aryl Pt(II) diimine
complexes (N-N)Pt(Me)(Ar) in 76-84% yields. The Pt methyl-
phenyl complex [p-Tol-NdC(Me)C(Me)dN-p-Tol]Pt(Me)(Ph)
has been characterized by X-ray diffraction.
therefore not easily displaced by diimine ligands, rendering these
compounds less suitable as intermediates in the synthesis of
mixed Pt(II) alkyl-aryl diimine complexes.
One such compound, (N-N)Pt(Me)(Ph) (where N-N ) Ar-
NdC(Me)-C(Me)dNAr (1), Ar ) 2,6-Me2C6H3 (1a)) has been
synthesized by making use of a more labile ligand, dimethyl
sulfide, allowing for facile introduction of the desired diimine
ligand. (Me2S)2Pt(Me)(Ph) was prepared by reacting phenyl-
lithium with (Me2S)2Pt(Me)(Cl) in ether at -20 °C. This resulted
in a complex mixture (most likely due to the presence of dinu-
clear Me2S-bridged species in addition to the desired product).
Subsequent reaction of this mixture with the diimine 1a in tol-
uene furnished the desired methyl-phenyl product (N-N)Pt-
(Me)(Ph) (2a) in 31% overall yield after separation from the
diphenyl byproduct (N-N)PtPh2 (3a) by flash chromatogra-
phy.17 However, attempts to synthesize analogous compounds
with other diimine ligands yielded significant amounts of the
undesired dimethyl and diphenyl byproducts, the latter being
particularly difficult to separate from the desired product. In
this work we show that a variety of methyl-phenyl and meth-
yl-tolyl Pt(II) diimine complexes can be synthesized in a one-
pot procedure by performing the arylation step in dimethyl
sulfide as solvent, followed by addition of the diimine ligand.
The formation of byproducts due to disproportionation of the
intermediates (Scheme 1) is greatly suppressed in the presence
of a large excess of dimethyl sulfide.
Introduction
The development of methods for direct, selective conversion
of hydrocarbons to value-added products remains a challenge.1-4
Seminal work by Garnett and Shilov demonstrated that Pt salts
are able to activate otherwise unreactive aromatic and aliphatic
C-H bonds and to mediate the hydrocarbon functionalization.5-7
Studies on the aqueous K2PtCl4 system and on model systems
have provided considerable mechanistic understanding of the
process; our groups have made particularly effective use of mod-
el complexes (N-N)PtR2, where N-N is a diimine ligand.8,9
Both aliphatic and aromatic C-H activations by cationic
Pt(II) complexes have been studied extensively. A good deal
of the mechanistic insight is obtained from studies on the reverse
reaction, protonolysis of Pt hydrocarbyls. Hence, a convenient
synthetic route to mixed alkyl-aryl Pt(II) model complexes
would provide a valuable tool for comparisons of aliphatic and
aromatic C-H activation reactivity. A substantial number of
syntheses of mixed L2Pt(R′)(R′′) compounds have previously
been attempted,10-14 primarily to study competition between
cleavage of alkyl vs aryl bonds in reactions with electrophiles15
or in thermal decomposition.16 A common feature of successful
syntheses is that the ligand L used in the alkylation or arylation
step (typically COD and PR3) is not particularly labile and
Results and Discussion
Preparations. A closer examination of the synthesis of 2a
revealed that the reaction yields significant amounts of the
Pt(II) diphenyl (3a) and dimethyl (4a) byproducts. Furthermore,
varying reaction conditions and the ligand used showed that
the product distribution largely depends on reaction times,
workup procedure, and diimine ligand.18 The chromatographic
separation of the methyl-phenyl product from the dimethyl and
diphenyl byproducts is not always trivial, depending on the
ligand used. Because of these problems, a method was sought
to reduce the formation of byproducts in the first place.
It is a possibility that the byproducts 3a and 4a are formed
by disproportionation of the (Me2S)2Pt(Me)(Ph) intermediate
prior to coordination of the diimine. If so, it is expected that
* To whom correspondence should be addressed. E-mail:
mats.tilset@kjemi.uio.no.
† University of Oslo.
‡ California Institute of Technology.
(1) Labinger, J. A.; Bercaw, J. E. Nature 2002, 417, 507-514.
(2) Shilov, A. E. ActiVation and Catalytic Reactions of Saturated
Hydrocarbons in the Presence of Metal Complexes; Kluwer Academic:
Dordrecht, The Netherlands, 2000.
(3) Arndtsen, B. A.; Bergman, R. G.; Mobley, T. A.; Peterson, T. H.
Acc. Chem. Res. 1995, 28, 154-162.
(4) Crabtree, R. H. Dalton Trans. 2001, 2437-2450.
(5) Garnett, J. L.; Hodges, R. J. J. Am. Chem. Soc. 1967, 89, 4546-
4547.
(6) Gol’dshleger, N. F.; Shteinman, A. A.; Shilov, A. E.; Eskova, V. V.
Zh. Fiz. Khim. 1972, 46, 1353.
(7) Gol’dshleger, N. F.; Tyabin, M. B.; Shilov, A. E.; Shteinman, A. A.
Zh. Fiz. Khim. 1969, 43, 2174-2175.
(12) Glockling, F.; McBride, T.; Pollock, R. J. I. Inorg. Chim. Acta 1974,
8, 77-79.
(13) Alibrandi, G.; Minniti, D.; Scolaro, L. M.; Romeo, R. Inorg. Chem.
1988, 27, 318-324.
(14) Pantcheva, I.; Nishihara, Y.; Osakada, K. Organometallics 2005,
24, 3815-3817.
(15) Jawad, J. K.; Puddephatt, R. J. J. Chem. Soc., Chem. Commun. 1977,
892-893.
(8) Lersch, M.; Tilset, M. Chem. ReV. 2005, 105, 2471-2526.
(9) Fekl, U.; Goldberg, K. I. AdV. Inorg. Chem. 2003, 54, 259-320.
(10) Jawad, J. K.; Puddephatt, R. J.; Stalteri, M. A. Inorg. Chem. 1982,
21, 332-337.
(16) Komiya, S.; Yamamoto, A.; Yamamoto, T. Chem. Lett. 1978, 1273-
1276.
(17) Johansson, L.; Tilset, M.; Labinger, J. A.; Bercaw, J. E. J. Am. Chem.
Soc. 2000, 122, 10846-10855.
(11) Milstein, D.; Stille, J. K. J. Am. Chem. Soc. 1979, 101, 4981-4991.
10.1021/om050899z CCC: $33.50 © 2006 American Chemical Society
Publication on Web 01/17/2006

1056 Organometallics, Vol. 25, No. 4, 2006
Notes
Table 2. 1H NMR Product Distribution in Isolated
Compounds
Scheme 1
isolated yield (%)
product distribn (%)
2a:3a:4a
2b:3b:4b
2c:3c:4c
5d:6d:4d
78
84
80
76
99:1:0
99:1:0
99:1:0
97:2:1
Table 1. 1H NMR Product Distribution of 2a, 3a, and 4a in
Test Reactionsa
Scheme 3
temp (°C)
solvent
product distribn 2a:3a:4a (%)
-20
-20
-20
-78
Et2O
70:12:18
77:10:14
90:4:6
Et2O, 10 equiv Me2S
Me2S
Me2S
99:1:0
a See experimental part for details.
Scheme 2
on the column can by minimized by addition of 1% triethyl-
amine to the eluent. However, the separation is rather poor and
any separation obtained might just as well be a result of the
solubility trends in the eluent: 5d > 6d > 4d.20
A possible mechanism for the intermolecular transfer of
methyl and phenyl ligands between the two Pt centers would
be a metathesis-type reaction (intermolecular transfer of a methyl
and/or phenyl group), with or without accompanying dissocia-
tion of Me2S. Some examples of comproportionation and
disproportionation of Pt(II) complexes are already known.
Suzaki et al. report disproportionation of (COD)Pt(Ph)(CH2-
COMe) and comproportionation of (COD)Pt(CH2COMe)2 and
(COD)PtPh2, which supposedly proceed via an intermediate with
bridging phenyl and acetonyl ligands.21 Scott and Puddephatt
investigated the comproportionation of (Me2S)2PtCl2 and (Me2S)2-
PtMe2.22 This reaction proceeds by dissociation of Me2S, leaving
the coordinatively unsaturated intermediate (Me2S)PtMe2 (often
referred to as a T-shaped, three-coordinate species). Two major
pathways are outlined, involving either a bridging Me2S or a
bridging Cl followed by an oxidative addition/reductive elimina-
tion sequence or an SE2 type reaction.
The observed inhibition of disproportionation of (Me2S)2Pt-
(Me)(Ph) by Me2S suggests that the major pathway of dispro-
portionation involves dissociation of Me2S, leading to a three-
coordinate species as suggested by Scott and Puddephatt,
followed by disproportionation, leading to the formation of Pt2-
Me4(µ-SMe2)2 and (Me2S)2PtPh2. The fact that small amounts
of Pt(II) dimethyl and diaryl byproducts are formed even when
the reaction is performed in neat Me2S might indicate that there
also exists a nondissociative pathway for the disproportionation
of (Me2S)2Pt(Me)(Ph) and(Me2S)2Pt(Me)(p-Tol), but this path-
way must be less favorable energetically compared to the
dissociative one.
comproportionation of Pt2Me4(µ-SMe2)2 and (Me2S)2PtPh2 will
produce (Me2S)2Pt(Me)(Ph) (Scheme 1). To test this, Pt2Me4-
(µ-SMe2)2 and (Me2S)2PtPh2 were added to an NMR tube and
dissolved in CD2Cl2. An immediate reaction took place, yielding
a mixture of dimethyl, diphenyl, and methyl-phenyl complexes.
NMR spectra recorded 20 h later showed virtually no change
in the product distribution. A similar experiment was performed,
but this time Me2S was added to the CD2Cl2 before the reactants
1
were dissolved. The H NMR spectrum recorded immediately
after mixing showed that, in the tube containing Me2S, the
dinuclear Pt2Me4(µ-SMe2)2 was split up to form the correspond-
ing mononuclear species (Me2S)2PtMe2 and, most important,
no comproportionation products were observed. These observa-
tions suggest that the comproportionation mechanism involves
dissociation of Me2S and that the disproportionation of (Me2S)2-
Pt(Me)(Ph) could hence be inhibited by the addition of Me2S.
These results encouraged us to see what effect added Me2S
could have in the arylation of (Me2S)2Pt(Me)(Cl). The best
yields of the desired mixed alkyl-aryl products relative to the
dimethyl and diaryl products were obtained by performing the
reaction in neat Me2S at -78 °C, as summarized in Table 1.
Preparative-scale reactions were tested for a range of diimine
ligands (Scheme 2). Excess lithium reagents were quenched by
addition of tert-butyl bromide. A dichloromethane solution of
the diimine ligand was added before the reaction mixture was
warmed to room temperature and solvents were removed. The
residue was redissolved in dichloromethane, filtered through
Celite, and stirred for 4 h. Final workup involved rapid filtration
through a short pad of basic alumina to remove traces of LiCl.19
The mixed alkyl-aryl complexes 2a-c and 5d,e were obtained
Compound 2e, a partially deuterated (at the diimine aryl
groups) analogue of 2d, was also prepared. The deuterated
ligand 1e was obtained from a deuterated aniline precursor
which was prepared by heating 3,5-di-tert-butylaniline with DCl
in D2O (Scheme 3).23 CD3OD was added to increase the
solubility of the formed anilinium chloride. Aqueous basic
workup afforded the deuterated aniline.
Characterization. All new compounds were characterized
by 1H NMR and 13C NMR. The 1H NMR spectra of the mixed
alkyl-aryl complexes show a double set of signals from the
1
in 97-99% purity by H NMR and in isolated yields of 76-
84% (Scheme 2, Table 2). Chromatography was attempted with
both basic alumina and silica gel. Decomposition of the products
(20) The Rf values from a TLC plate eluted with 1:2 Et2O/hexane were
all around 0.43-0.46 for 5d, 6d, and 4d.
(21) Suzaki, Y.; Yagyu, T.; Yamamura, Y.; Mori, A.; Osakada, K.
Organometallics 2002, 21, 5254-5258.
(18) It should be noted that if (Me2S)2Pt(Me)(Cl) contains impurities of
(Me2S)2PtCl2, this will yield the corresponding (Me2S)2PtAr2 after arylation.
(19) LiCl has a considerable solubility in methylene chloride. This is
evidenced by yields in excess of 100% after evaporation only.
(22) Scott, J. D.; Puddephatt, R. J. Organometallics 1983, 2, 1643-
1648.
(23) Aurich, H. G. Chem. Ber. 1968, 101, 1761-1769.

Notes
Organometallics, Vol. 25, No. 4, 2006 1057
1
Table 3. Selected H NMR Data for the Pt(II) Methyl-Aryl
Compounds
1H NMR, δa
compd
Pt-Me (2J(195Pt-H))
NdCMe
Ar Me or Ar CMe3
2ab
2b
2c
0.75 (87.8)
0.92 (87.5)
0.94 (87.6)
0.92 (86)
1.41, 1.52
1.66, 1.72
1.63, 1.71
1.67, 1.72
2.10, 2.25
2.11, 2.39
2.27, 2.44
1.19, 1.38
5d
a Dichloromethane-d2. b Data from ref 17.
Table 4. CrystalDataandStructureRefinementDetailsfor 2c
empirical formula
formula wt
temp
wavelength
cryst syst
C25H25N2Pt
548.56
105(2) K
0.71073
Figure 1. ORTEP drawing of compound 2c (molecule A) with
50% probability ellipsoids. Hydrogen atoms have been omitted for
clarity.
monoclinic
space group
unit cell dimens
P21/c
a ) 26.9672(7) Å
b ) 8.8779(2) Å
79-88°, respectively, for complexes without and with methyl
groups in the 2,6-positions of the diimine N-aryl rings).24 The
upfield shift of Pt-Me and NdCMe in 2a compared to the
signals in 2b,c and 5d could be a result of different conforma-
tional preferences and consequential interligand aromatic ring-
current effects of the 2,6-substituted ligand (2a) compared with
the 3,5- and 4-substituted ligands.
Conclusion. Mixed diimine Pt(II) alkyl-aryl complexes have
been synthesized in a convenient one-pot procedure by perform-
ing the arylation at low temperature with Me2S as the solvent.
This procedure suppresses the formation of dimethyl and
diphenyl byproducts.
c ) 18.9608(5) Å
â ) 107.046(1)°
vol, Z
density (calcd)
abs coeff
F(000)
cryst size
4340.0(2) Å3
1.679 Mg/m3
6.478 mm-1
2136
0.25 × 0.20 × 0.15 mm
θ range for data
no. of rflns collected
no. of indep rflns
refinement method
data/param ratio
goodness of fit on F2
final R indices (I > 2σ(I))
R indices (all data)
∆F(max)
2.15-35.02°
86 453
19 007
least-squares against F2 using all rflns
37
1.19
0.050
0.062
4.4
∆F(min)
-3.8
Experimental Section
General Considerations. Me2S was dried by stirring with a Na
dispersion in mineral oil (Aldrich), vacuum-distilled, and stored
over activated 4 Å molecular sieves.25 All other reagents were used
as received. Phenyllithium in cyclohexane/ether was purchased from
Aldrich and standardized by titration with 1,3-diphenyl-2-propanone
tosylhydrazone.26 Basic alumina was purchased from Panreac. cis/
trans-(Me2S)2Pt(Me)(Cl)27 and the diimine ligands28 1a-d were
synthesized as previously described.
NMR spectra were recorded on Bruker 300 and 500 instruments
(300.13 and 500.13 MHz for 1H). Chemical shifts (δ) are reported
in ppm relative to CHDCl2 at δ 5.32, CHCl3 at δ 7.24, or C6HD5
at δ 7.15 for 1H and relative to CD2Cl2 at δ 53.8 for 13C. Elemental
analyses were performed by Ilse Beetz Mikroanalytisches Labo-
ratorium (Kronach, Germany).
Table 5. Selected Bond Lengths (Å) and Angles (deg) for
Molecule A of the Crystal Structure of 2c
Distances
Pt(1A)-N(1A)
Pt(1A)-N(2A)
Pt(1A)-C(19A)
Pt(1A)-C(20A)
2.085
2.122
2.043
2.012
N(1A)-C(1A)
N(1A)-C(5A)
N(2A)-C(2A)
N(2A)-C(12A)
1.300
1.439
1.303
1.425
Angles
Pt(1A)-N(1A)-C(1A)
Pt(1A)-N(1A)-C(5A)
Pt(1A)-N(2A)-C(2A)
Pt(1A)-N(2A)-C(12A)
117.86
124.12
116.25
124.69
N(1A)-Pt(1A)-N(2A)
C(19A)-Pt(1A)-N(1A)
C(20A)-Pt(1A)-N(2A)
C(19A)-Pt(1A)-C(20A)
75.96
96.37
99.86
87.85
nonequivalent halves of the diimine ligand (selected data are
shown in Table 3).
X-ray-quality crystals of 2c were grown by slow evaporation
from an ether solution. Details of the structure determination
are given in the Experimental Section. Table 4 lists experimental
and crystallographic data, and selected bond distances and angles
for molecule A are given in Table 5. The asymmetric unit
contained the two nearly identical molecules A and B. Figure
1 shows an ORTEP drawing of molecule A of 2c. The diimine
N-aryl rings are twisted relative to the coordination plane by
Pt-N-C(ipso)-C(ortho) dihedral angles of 60.5/81.7° and 68.5/
80.3° for A and B, respectively. The chelate rings in A and B
are almost perfectly planar, the sum of the four cis L-Pt-L′
angles around Pt being 360.0 and 360.3°, respectively. The Pt-
(1)-N(2) bond trans to Pt-Me is 0.03 Å (average) longer than
the Pt(1)-N(1) bond trans to Pt-Ph, presumably reflecting a
slightly greater trans influence of the methyl group compared
to the phenyl group. Although the diimine N-aryl rings are
twisted out of the coordination plane in the solid state for 2c,
the aryl rings presumably rotate freely in solution for 2b,c and
5d. However, the methyl groups in the 2,6-positions of the
N-aryl groups in 2a would present a barrier toward this rotation.
The angles between the coordination plane and the aryl rings
in 2c (61-82°) span a greater range than the corresponding
angles in related (N-N)PtII diphenyl complexes (66-71 and
Test Reactions: [ArNdC(Me)C(Me)dNAr]Pt(Me)(Ph), Ar )
2,6-Me2C6H3 (2a). Small-scale test reactions were done to deter-
mine relative product distributions. In a typical reaction, (Me2S)2-
Pt(Me)(Cl) (40 µmol) and a stirring bar were added to a 5 mL
round-bottomed flask, which was fitted with a septum and flushed
with nitrogen. Dry solvent was added, and the flask was cooled
(see Table 1 for details). PhLi (40 µmol) was added by dropwise
addition to the stirred suspension. After 20 min a few drops of
aqueous 2 M NH4Cl were added to quench excess lithium reagents.
Diimine ligand 1a (40 µmol) dissolved in toluene (4 mL) was added,
and the reaction mixture was gradually warmed to room temperature
and stirred overnight. Evaporation yielded a residue which was
1
dissolved in CD2Cl2 and analyzed by H NMR.
Preparative Scale: [ArNdC(Me)C(Me)dNAr]Pt(Me)(Ph),
Ar ) 3,5-Me2C6H3 (2b). In a typical reaction, (Me2S)2Pt(Me)(Cl)
(24) Wik, B. J.; Lersch, M.; Krivokapic, A.; Tilset, M. Submitted for
publication.
(25) Attemps to store Me2S over Na/benzophenone resulted in slow
formation of gas bubbles. These were not analyzed further.
(26) Lipton, M. F.; Sorensen, C. M.; Sadler, A. C.; Shapiro, R. H. J.
Organomet. Chem. 1980, 186, 155-158.
(27) Hill, G. S.; Irwin, M. J.; Levy, C. J.; Rendina, L. M.; Puddephatt,
R. J. Inorg. Synth. 1998, 32, 149-153.
(28) Stamp, L.; Tom Dieck, H. Inorg. Chim. Acta 1987, 129, 107-114.

1058 Organometallics, Vol. 25, No. 4, 2006
Notes
(202.1 mg, 0.546 mmol) and a magnetic stirring bar was added to
a 25 mL round-bottomed flask fitted with a septum and flushed
with nitrogen. Dry Me2S (4 mL) was added with a syringe and the
mixture cooled to -78 °C, causing the starting material to form a
fine precipitate. PhLi (0.469 mL, 1.34 M, 0.628 mmol, 1.15 equiv)
was added by dropwise addition to the stirred suspension. After
the complete addition of PhLi the formed precipitate disappeared,
leaving a clear solution. The solution was stirred overnight and
excess lithium reagent quenched by addition of tert-butyl bromide
(127 µL, 1.092 mmol, 2 equiv). The diimine ligand 1b (159.0 mg,
0.546 mmol) dissolved in CH2Cl2 (3 mL) was added, the mixture
was taken up to room temperature, and all solvents were evaporated
on a vacuum line with a cold trap (stench! glassware cleaned with
household bleach). The residue was dissolved in CH2Cl2, upon
which a deep red complex immediately was formed, filtered through
a short pad of Celite, and stirred for 4 h at room temperature.
Filtration through a plug of basic alumina and evaporation of the
solvent yielded a deep purple residue which was washed several
times with pentane. Drying under vacuum yielded 2b (265.0 mg,
) 3.4 Hz). 1H NMR (300 MHz, C6D6): δ 0.81 (3H, s, NdCCH3),
0.88 (3H, s, NdCCH3), 1.27 (18H, s, C(CH3)3), 1.32 (18H, s,
C(CH3)3), 2.04 (3H, s, JPt-H ) 87 Hz), 2.27 (3H, s, (C6H4)CH3),
2
6.78-6.83 (4H, m), 7.06 (2H, d, J ) 1.7 Hz), 7.25-7.46 (4H, m).
13C NMR (75 MHz, CD2Cl2): δ -10.6 (JPt-C ) 807 Hz), 20.7,
21.11, 21.14, 31.3, 31.5, 35.0, 35.4, 116.5, 116.9, 120.3, 120.5,
127.0 (JPt-C ) 78 Hz), 129.7, 137.5 (JPt-C ) 30 Hz), 140.5, 147.0,
147.2, 151.3, 152.0, 170.4, 173.2. Anal. Calcd for C40H58N2Pt: C,
63.05; H, 7.67; N, 3.68. Found: C, 63.44; H, 7.61; N, 3.68.
3,5-Di-tert-butyl-2,4,6-trideuterioaniline. The following is a
modification of a published procedure.23 A glass bomb was fitted
with a magnetic stirring bar, filled with 3,5-di-tert-butylaniline
(0.530 g, 2.584 mmol), DCl (0.5 mL), D2O (1.0 mL), and CD3OD
(0.5 mL), frozen, and evacuated on a vacuum line. The bomb was
heated to 105 °C for 3 days. All solvents were evaporated, and
new DCl (0.5 mL), D2O (1.0 mL) and CD3OD (0.5 mL) were added.
After freezing and evacuation the bomb was heated for another 5
days. After evaporation the process was repeated one more time
with heating for another 5 days. The reaction mixture was quenched
by addition of 2 M NH4OH to pH 10 and extracted with diethyl
ether (3 × 20 mL). The organic phase was washed with water and
dried with MgSO4. Evaporation yielded the product (0.509 g, 95%)
1
84% yield) as a deep purple powder. H NMR (500 MHz, CD2-
Cl2): δ 0.92 (s, 3H, Pt-CH3, 2JPt-H ) 87.5 Hz), 1.66 (s, 3H, Nd
CCH3), 1.72 (s, 3H, NdCCH3), 2.12 (s, 6H, Ar CH3), 2.39 (s, 6H,
Ar CH3), 6.33 (br s, 2H, Ar H), 6.68 (br s, 3H, Ar H), 6.50-6.83
(m, 5H, Pt-(C6H5)), 6.96 (br s, 1H, Ar H). 13C NMR (75 MHz):
1
as an off-white solid. The degree of deuteration by H NMR was
∼98% in both para and ortho positions. 1H NMR (200 MHz,
1
CDCl3): δ 1.27 (18H, s), 3.56 (2H, br s).
δ -11.9 (Pt-CH3, JPt-C ) 807 Hz), 20.8 (overlapping Ar Me
and NdCCH3), 21.17 (NdCCH3), 119.2 (6 Hz), 120.2 (7 Hz), 120.8
[ArNdC(Me)C(Me)dNAr]Pt(Me)(p-Tol), Ar ) 3,5-tBu2C6D3
(5e). 5e was synthesized as described above from p-tolyllithium,
(Me2S)2Pt(Me)(Cl) (193 mg, 0.5224 mmol), and diimine 1e (243.8
mg, 0.5224 mmol), yielding 5e (282.1 mg, 70%) as a deep purple
3
(12 Hz), 125.5 (Roth H, JPt-H ) 78 Hz), 127.3, 127.9, 137.4 (31
Hz), 137.9 (Ar CH3), 138.8 (Ar CH3), 145.8 (ipso), 146.6 (ipso),
147.3 (ipso), 170.1 (NdCCH3), 173.1 (NdCCH3). Anal. Calcd for
C27H32N2Pt: C, 55.95; H, 5.56; N, 4.83. Found: C, 56.09; H, 5.26;
N, 4.92.
1
2
solid. H NMR (500 MHz, CD2Cl2): δ 0.92 (3H, s, JPt-H ) 87
Hz, Pt-CH3), 1.19 (18H, s, C(CH3)3), 1.38 (18H, s, C(CH3)3), 1.67
(3H, s, NdCCH3), 1.72 (3H, s, NdCCH3), 2.04 (3H, s, (C6H4)-
[ArNdC(Me)C(Me)dNAr]Pt(Me)(Ph), Ar ) 2,6-Me2C6H3
(2a). 2a was synthesized and worked up in a manner similar to
that for 2b (see above) from (Me2S)2Pt(Me)(Cl) (52.6 mg, 0.142
mmol, 1 equiv) and 1a (41.5 mg, 0.142 mmol, 1 equiv), yielding
2a (64.6 mg, 78% yield) as a deep purple powder. The recorded
1H NMR spectrum was in accordance with published data.10
3
3
CH3), 6.39 (2H, “d”, JH-H ) 8.1 Hz, m-H), 6.52 (2H, “d”, JH-H
) 8.1 Hz, 3JPt-H ) 65 Hz, o-H); due to incomplete deuteration of
the ligand peaks are also seen at δ 6.89 (s), 7.11 (s), and 7.35 (s).
X-ray Crystallographic Structure Determination of 2c. Crys-
tals of 2c were grown by slow evaporation from a diethyl ether
solution. Single-crystal X-ray data were collected at 105 K with a
Bruker Smart 1k CCD diffractometer, integrated, and processed
with Saint.29 Analytical absorption correction was carried out using
Xprep29 followed by Sadabs.30 The structure was solved in space
group P21/c with two crystallographically independent molecules
in the asymmetric unit and refined with Shelxtl31 to a final R factor
of 0.05 with data (>99% completeness) extending to 2θ ) 70°
(Mo KR radiation). All non-hydrogen atoms were refined aniso-
tropically, while all H atoms were kept in idealized positions,
refining a single C-H distance for all H atoms connected to the
same C atom. Uiso values for the H atoms were fixed at 1.2Ueq
(-CH- and -CH2-) and 1.5Ueq (-CH3) of the parent C atom.
Experimental data, crystal data, and refinement results are sum-
marized in Table 4.
[ArNdC(Me)C(Me)dNAr]Pt(Me)(Ph), Ar ) 4-MeC6H4 (2c).
2c was synthesized and worked up in a similar manner from
(Me2S)2Pt(Me)(Cl) (53.5 mg, 0.144 mmol) and 1c (38.2 mg, 0.144
mmol), yielding 2c (63.8 mg, 80%) as a deep purple powder. X-ray-
quality crystals were grown by slow evaporation from a diethyl
1
ether solution. H NMR (300 MHz, CD2Cl2): δ 0.94 (s, 3H, Pt-
1
CH3, JPt-H ) 87.6 Hz), 1.63 (s, 3H, NdCCH3), 1.71 (s, 3H, Nd
CCH3), 2.29 (s, 3H, Ar CH3), 2.45 (s, 3H, Ar CH3), 6.51-6.86
(m, 7H), 6.67 (d, 4H, 3J ) 8.2 Hz), 7.34 (d, 2H, 3J ) 8.0 Hz). 13
C
NMR (75 MHz): δ -10.7 (Pt-CH3, 1JPt-C ) 810 Hz), 21.0, 21.12,
21.14, 21.2, 121.0, 121.8, 122.4, 126.0 (JPt-H ) 82 Hz), 128.8,
129.7, 136.2, 136.5, 138.0 (JPt-C ) 32 Hz), 145.0, 145.2, 145.4,
171.0, 173.8. Anal. Calcd for C25H28N2Pt: C, 54.44; H, 5.12; N,
5.08. Found: C, 54.51; H, 5.10; N, 5.08.
[ArNdC(Me)C(Me)dNAr]Pt(Me)(p-Tol), Ar ) 3,5-tBu2C6H3
(5d). Butyllithium (103.3 µL, 1.6 M in hexane, 0.165 mmol, 1.15
equiv) was added by dropwise addition to 4-iodotoluene (37.6 mg,
0.172 mmol, 1.2 equiv) dissolved in 1 mL of anhydrous Me2S under
nitrogen, and the mixture was stirred for 15 min at -78 °C and
then for 15 min at ambient temperature. The solution of p-
tolyllithium was cooled to -78 °C again and transferred via cannula
to 4 (53.2 mg, 0.143 mmol, 1 equiv) dissolved in 1 mL of anhydrous
Me2S, and this mixture was stirred overnight at -78 °C. Quenching,
reaction with diimine ligand 1c (66.2 mg, 0.143 mmol), and workup
as described above yielded 5d (100.3 mg, 76%) as a deep purple
powder. 1H NMR (500 MHz, CD2Cl2): δ 0.92 (3H, s, 2JPt-H ) 86
Hz), 1.19 (18H, s, C(CH3)3), 1.38 (18H, s, C(CH3)3), 1.67 (3H, s,
NdCCH3), 1.72 (3H, s, NdCCH3), 2.04 (3H, s, (C6H4)CH3), 6.38-
Acknowledgment. M.L. thanks the Norwegian Research
Council (NFR) for generous funding and the U.S.-Norway
Fulbright Foundation for a grant allowing him to spend 7 months
at the California Institute of Technology.
Supporting Information Available: Crystal structure data for
2c as a CIF file. This material is available free of charge via the
Internet at http://pubs.acs.org.
OM050899Z
(29) SMART and SAINT Area-detector Control and Integration Software;
Siemens Analytical X-ray Instruments Inc., Madison, WI.
(30) Sheldrick, G. M. SADABS, Program for Absorption Correction;
University of Go¨ttingen, Go¨ttingen, Germany, 1996.
(31) Sheldrick, G. M. SHELXTL, Version 5; Siemens Analytical X-ray
Instruments Inc., Madison, WI.
3
6.40 (2H, m), 6.44-6.60 (4H, m (incl JPt-H,ortho ) 65 Hz), 6.89
(2H, d, J ) 1.7 Hz), 7.11 (1H, br t, J ) 3.4 Hz), 7.35 (1H, br t, J