New building blocks for the noncovalent assembly of homo- and hetero-multinuclear metallodendrimers

Article abstract of DOI:10.1021/om970424a

Ligands 5 and 8, derived from the coupling of [3,5-bis[(diphenylphosphinyl)methyl]phenyl]-oxy groups to bi- and trifunctional spacers, respectively, were cyclometalated with Pd[CH₃-CN]₄(BF₄)₂, cis-[PtCl₂

Full text of DOI:10.1021/om970424a

Organometallics 1997, 16, 4287-4291
4287
New Bu ild in g Block s for th e Non cova len t Assem bly of
h om o- a n d h eter o-Mu ltin u clea r Meta llod en d r im er s
Wilhelm T. S. Huck, Bianca Snellink-Rue¨l, Frank C. J . M. van Veggel,* and
David N. Reinhoudt*
Laboratory of Supramolecular Chemistry and Technology and MESA Research Institute,
University of Twente, P.O. Box 217, NL-7500 AE Enschede, The Netherlands
Received May 21, 1997X
Ligands 5 and 8, derived from the coupling of [3,5-bis[(diphenylphosphinyl)methyl]phenyl]-
oxy groups to bi- and trifunctional spacers, respectively, were cyclometalated with Pd[CH3-
CN]4(BF4)2, cis-[PtCl2(PPh3)2], or NiCl2‚6H2O. The cationic Pd and Pt complexes were
converted into overall neutral Pd-Cl and Pt-Cl complexes. The resulting pincer complexes
can be used as building blocks for the controlled assembly of both homo- and hetero-
multinuclear metallodendrimers. The 31P NMR spectra of the pincer complexes exhibit
different shifts for chloride, H2O, or nitrile occupying the fourth coordination site, making
the 31P chemical shift an excellent diagnostic tool for the assembly process.
In tr od u ction
introduction of a variety of transition metals is possible.7
The synthesis and characterization of (metallo)dendrim-
ers incorporating phosphorus ligands has been reported
in literature.8 The use of PCP ligands as metalloden-
drimer building blocks should make it possible to
assemble nanosize assemblies containing a variety of
(e.g., catalytically active) transition metals.9
There is an increasing interest in the development of
new strategies to synthesize well-defined nanosize
structures. Noncovalent synthesis can be used to
construct nanostructures in an efficient way.1 The
branched architecture and large, spherical dimensions
combined with high molecular masses make dendrimers
ideal model compounds to test noncovalent synthesis
routes. Metallodendrimers containing transition metals
in every generation have been reported in the litera-
ture.2 In previous articles, we have described “con-
trolled assembly” as a new approach to build metallo-
dendrimers of nanometer dimensions.3 The building
blocks BB-Cl and G0 for controlled assembly contain
SCS Pd-pincer complexes that are coupled via branched
spacers (Chart 1).4 The coordination of the nitrile ligand
of BB-Cl to coordinatively unsaturated Pd centers was
exploited to assemble the dendrimer building blocks via
noncovalent interactions.5
Resu lts a n d Discu ssion
The synthesis leading to the pincer ligands 5 and 8
is summarized in Schemes 1 and 2. An excess of
K+-PPh2 was added to the previously described bis-
(chloride) 110 to give the corresponding bis(diphenylphos-
phine). The reaction was performed under the exclusion
of air using standard Schlenk techniques. To facilitate
the experimental conditions in the following steps, the
diphenylphosphines were oxidized to the corresponding
phosphine oxides with H2O2. After the deprotection of
the phenol group using CsF, the phosphine oxide 2 was
obtained in 60% yield. The 1H NMR spectrum of 2
clearly shows a doublet (J ) 13.8 Hz) at δ 3.49 ppm
which corresponds to the CH2P(O) protons.
The synthesis of PCP pincer ligands 5 and 8 is shown
in Scheme 2. Phenol 2 was coupled to spacers 3 or 6
with K2CO3 in CH3CN. Compounds 4 and 7 were
isolated in rather poor yields, as they slowly decomposed
during column chromatography. Prior to cyclometala-
tion, the phosphine oxide groups in 4 and 7 were
reduced with trichlorosilane and triethylamine in m-
xylene11 to give the phosphine ligands 5 and 8, respec-
tively. The reduction was quantitative after 12 h, as
To broaden the scope of this controlled assembly
strategy, it is desirable to introduce different transition
metals in such building blocks, but the SCS pincer
ligands (e.g., as in G0 and BB-Cl) cannot be used
because cyclometalation is only possible with Pd(II).6
However, with PCP instead of SCS pincer ligands, the
X Abstract published in Advance ACS Abstracts, August 15, 1997.
(1) Philp, D.; Stoddart, J . F. Angew. Chem., Int. Ed. Engl. 1996, 35,
1154.
(2) Serroni, S.; Denti, G.; Campagna, S.; J uris, A.; Ciamo, M.;
Balzani, V. Angew. Chem., Int. Ed. Engl. 1992, 31, 1493. Campagna,
S.; Denti, G.; Serroni, S.; J uris, A.; Venturi, M.; Ricevuto, V.; Balzani,
V. Chem. Eur. J . 1995, 1, 211. Achar, S.; Puddephatt, R. J . Angew.
Chem., Int. Ed. Engl. 1994, 33, 847. Achar, S.; Puddephatt, R. J . J .
Chem. Soc., Chem. Commun. 1994, 1895.
(3) Huck, W. T. S.; van Veggel, F. C. J . M.; Reinhoudt, D. N. Angew.
Chem., Int. Ed. Engl. 1996, 35, 1213. Huck, W. T. S.; Hulst, A. J . R.
L.; Timmerman, P.; van Veggel, F. C. J . M.; Reinhoudt, D. N. Angew.
Chem., Int. Ed. Engl. 1997, 36, 1006.
(4) Similar complexes containing NCN pincer ligands have recently
been reported, see: Davies, P. J .; Grove, D. M.; van Koten, G.
Organometallics 1997, 16, 800.
(7) Moulton, C. J .; Shaw, B. L. J . Chem. Soc., Dalton Trans. 1976,
1020. Gorla, F.; Venanzi, L. M.; Albinati, A. Organometallics 1994,
13, 1607. Weisman, A.; Gozin, M.; Kraatz, H.-B.; Milstein, D. Inorg.
Chem. 1996, 35, 1792 and references cited therein.
(8) Slany, M.; Bardaji, M.; Casanove, M.-J .; Caminade, A.-M.;
Majoral, J .-P.; Chaudret, B. J . Am. Chem. Soc. 1995, 117, 9764. Slany,
M.; Bardaji, M.; Caminade, A.-M.; Chaudret, B.; Majoral, J .-P. Inorg.
Chem. 1997, 36, 1939. Herring, A. M.; Steffey, B. D.; Miedaner, A.;
Wander, S. A.; DuBois, D. L. Inorg. Chem. 1995, 34, 1100. Lange, P.;
Schier, A.; Schmidbauer, H. Inorg. Chem. 1996, 35, 637.
(5) Huck, W. T. S.; van Veggel, F. C. J . M.; Kropman, B. L.; Blank,
D. H. A.; Keim, E. G.; Smithers, M. M. A.; Reinhoudt, D. N. J . Am.
Chem. Soc. 1995, 117, 8293. Huck, W. T. S.; Snellink-Rue¨l, B. A.; van
Veggel, F. C. J . M.; Lichtenbelt, J . W. Th.; Reinhoudt, D. N. Chem.
Commun. 1997, 9.
(9) For catalytically active dendrimers, see: Knapen, J . W.; van der
Made, A. W.; de Wilde, J . C.; van Leeuwen, P. W. N. M.; Wijkens, P.;
Grove, D. M.; van Koten, G. Nature 1994, 372, 659.
(6) Errington, J .; McDonald, W. S.; Shaw, B. L. J . Chem. Soc., Dalton
Trans. 1980, 2313.
(10) Huck, W. T. S.; van Veggel, F. C. J . M.; Reinhoudt, D. N. J .
Mater. Chem. 1997, 1213.
S0276-7333(97)00424-X CCC: $14.00 © 1997 American Chemical Society

4288 Organometallics, Vol. 16, No. 20, 1997
Huck et al.
Ch a r t 1
Sch em e 1
ppm. This is in accordance with the chemical shifts
reported for similar complexes.14 The FAB-MS spec-
trum for G0,P d shows a signal at m/ z 1971.3 corre-
sponding to [G0,P d - Cl]+ (calcd 1971.6). The FAB-MS
spectrum of BBP d -Cl shows signals at m/ z 1402.9 and
1367.2 corresponding to M+ (calcd 1402.9) and [BBP d
Cl - Cl]+ (calcd 1367.4), respectively.
-
Nickel was introduced by stirring ligands 5 and 8 with
NiCl2‚6H2O and (i-Pr)2EtN (Hu¨nig’s base). Initially, a
red complex is formed which led to the light yellow
PCPNi-Cl complex after the addition of base. This was
isolated in fairly low and variable yields because the
complex is rather sensitive toward oxidation in solution.
The complexes were purified by repeated precipitation
1
confirmed by H NMR spectroscopy. The doublet at δ
3.49 ppm for the CH2P(O) protons had disappeared, and
a singlet at δ 3.21 ppm was observed for the CH2P
protons. The FAB-MS spectrum of 8 shows a very small
signal at m/ z 1587.6 (M+, calcd 1587.0). Large signals
are present which can be assigned to the oxidized ligand.
Oxidation probably takes place inside the mass spec-
trometer. The ligands 5 and 8 were not purified further
prior to cyclometalation.
1
from a solution in CH2Cl2 with diethyl ether. The H
NMR spectra of G0,Ni and BBNi-Cl were similar to the
spectra of the analogous Pd compounds. The 31P NMR
spectra for both G0,Ni and BBNi-Cl show one signal at
δ 34.6 ppm. The FAB-MS spectra confirmed the forma-
tion of the Ni complexes. The spectrum of G0,Ni shows
signals at m/ z 1864.4 and 1828.3 corresponding to M+
(calcd 1864.2) and [GNi-Cl - Cl]+ (calcd 1828.3),
respectively. The FAB-MS spectrum of BBNi-Cl shows
a signal at m/ z 1272.7 corresponding to [BBNi-Cl -
Cl]+ (calcd 1272.2).
Cycloplatination was achieved by reaction of the
phosphine ligands 5 and 8 with cis-[PtCl2(PPh3)2].15 The
initial complex contained one molecule of coordinated
PPh3 at the fourth coordination site and was in equi-
librium with the desired chloride adduct. To obtain the
Pt-Cl complex, the PPh3 was removed by stirring with
elemental sulfur and KCl. Subsequently, the complexes
were triturated with MeOH and toluene to remove any
residual PPh3.16 The Pt complexes were characterized
by 1H and 31P NMR spectroscopy and FAB-MS. The 1H
NMR spectra of G0,P t and BBP t-Cl do not differ
significantly from the analogous Ni and Pd complexes.
The signal for the proton between the two donor arms
at δ 6.49 has disappeared completely, indicating com-
plete cyclometalation. The signal for the CH2P protons
The cyclometalation of ligands 5 and 8 using the
appropriate metal complexes is summarized in Scheme
3.12 Palladium was introduced in good yields using
Pd[CH3CN]4(BF4)2 in CH3CN.13 The characteristic color
change from orange to light yellow was a clear indica-
tion of cyclopalladation. The initial cationic complexes
were converted to the Pd-Cl complexes by stirring with
brine. The Pd complexes G0,P d and BBP d -Cl were
obtained in 50-70% yield after purification by precipi-
1
tation from CH2Cl2 with diethyl ether. The H NMR
spectrum of BBP d -Cl shows complete cyclopalladation
as the signal at δ 6.49 ppm for the aryl proton between
the two donor arms has disappeared completely. The
signal for the CH2P protons has shifted from δ 3.21 to
3.91 ppm. The absence of a doublet at δ 3.52 ppm shows
that no oxidation has taken place. The 31P NMR spectra
for both G0,P d and BBP d -Cl show one signal at δ 33.4
(11) Hattori, T.; Sakamoto, J .; Hayashizaka, N.; Miyano, S. Syn-
thesis 1994, 199.
(12) It should be possible to introduce Rh(I) and Ir(I) in PCP ligands.
See ref 7 and Gupta, M.; Hagen, C.; Flesher, R. J .; Kaska, W. C.;
J ensen, C. M. J . Chem. Soc., Chem. Commun. 1996, 2083. However,
reaction of 5 with HRh(PPh3)4 or [RhCl(cod)]2 (cod ) 1,5-cyclooctadiene)
did not give any cyclometalated products. The only difference with the
ligands used in the literature is that ligands 5 and 8 all have para
ether functions. Apparently, the electron-donating properties of this
substituent deactivate the C-H bond toward insertion by the transition
metal.
(14) Kraatz, H.-B.; Milstein, D. J . Organomet. Chem. 1995, 488, 223.
(15) Gorla, F.; Venanzi, L. M.; Albinati, A. Organometallics 1994,
13, 43.
(16) According to the literature procedures, reaction with [Pt2(µ-
Cl)2(η3-CH2C(CH3)CH2)2] should lead in one step to the desired Pt-Cl
complex. However, no reaction took place even after refluxing for 48
h. Anklin, C. G.; Pregosin, P. S.; Wombacher, F. J .; Ru¨egg, H. J .
Organometallics 1990, 9, 1953.
(13) Loeb, S. J .; Shimizu, G. K. H. J . Chem. Soc., Chem. Commun.
1993, 1395.

homo- and hetero-Multinuclear Metallodendrimers
Organometallics, Vol. 16, No. 20, 1997 4289
Sch em e 2
Sch em e 3
is broad and slightly shifted to δ 3.86 ppm. The 31P
NMR spectra of both G0,P t and BBP t-Cl show one
singlet at δ 32.3 ppm with two corresponding 195Pt
satellites. The P-Pt coupling constant is 1481 Hz, close
to the value obtained from the 195Pt NMR (1467 Hz)
results. One singlet with two satellites is visible in the
195Pt NMR of G0,P t at δ -4286.1 ppm, which confirms
the formation of a PCP Pt-Cl complex. The FAB-MS
spectra of G0,P t and BBP t-Cl show signals at m/ z
2237.0 and 1545.8 corresponding to [G0,P t - Cl]+ (calcd
2237.8), and [BBP t-Cl - Cl]+ (calcd 1545.3), respec-
tively.
31P NMR spectroscopy can be a powerful tool in
characterizing the internal structure of homo- and
hetero-nuclear metallodendrimers. Small changes in
the chemical shifts caused by a shielding of the inner
generation by the outer layers might be visible in the
31P spectrum as the chemical shift values are very

4290 Organometallics, Vol. 16, No. 20, 1997
Huck et al.
Ta ble 1. 31P NMR Ch em ica l Sh ift Va lu esa for
determined with a Reichert melting point apparatus and are
uncorrected. 1H and 13C NMR spectra were recorded in CDCl3
(unless indicated otherwise) with Me4Si as the internal
standard on a Bruker AC 250 spectrometer. 31P NMR spectra
were recorded on a Varian 400WB spectrometer with H3PO4
as the internal standard. Both 13C and 31P NMR spectra were
recorded in the 1H-decoupled mode. FAB-MS spectra were
recorded with a Finnigan MAT 90 spectrometer using m-NBA
as a matrix. THF was freshly distilled from Na/benzophenone
and CH2Cl2 from K2CO3. Other chemicals were of reagent
grade and used as received. Column chromatography was
performed with silica gel 60H (0.005-0.040 mm) from Merck.
Pd[CH3CN](BF4)2,19 cis-[PtCl2(PPh3)2],16 R,R′,R′′-tribromo-
mesitylene,20 and compounds 110 and 310 were prepared
according to literature procedures.
b
BBM-Cl a n d G0,M
Ni
Pd
Pt
-Cl
34.6
37.0
45.0
33.4; 31.8c
36.1c
32.3
39.6
d
-BF4-/H2O
-BF4-/CH3CN
39.1; 38.6c
a
b
Samples measured in CDCl3; except c. Identical values for
d
BBM-Cl and G0,M.
c CD3NO2/CD2Cl2 (1:1). Not measured.
sensitive toward small changes in the microenvironment
around the metal center.17 A series of 31P NMR
measurements were conducted to determine the chemi-
cal shift of the P atoms in the various complexes. As
discussed above, all BBM-Cl and G0,M complexes (M )
Pd, Pt, Ni) gave one single signal in CDCl3 (Table 1).
As expected, the signals exhibit solvent dependence, as
demonstrated by the shift from δ 33.4 ppm in CDCl3 to
δ 31.8 ppm in CD3NO2/CD2Cl2 (1:1) for the Pd complexes
(Table 1).
When a solution of AgBF4 in water was added to a
solution of G0,Ni in CDCl3, an immediate and complete
shift from δ 34.6 to 37.0 ppm was observed, which was
assigned to the cationic aqua complex. The shift was
not caused by changes in solvent polarity, as a drop of
water without AgBF4 did not result in any significant
change in the 31P NMR spectrum. Subsequent addition
of a small amount of CD3CN resulted in the instanta-
neous formation of the acetonitrile complex, which was
clear from the shift of the 31P NMR signal to δ 45.0 ppm.
The results concerning the other metal centers are also
summarized in Table 1. These model experiments gave
a qualitative idea about the controlled assembly strat-
egy.3 It indicates that activation of the M-Cl complexes
and coordination of the nitrile ligands are very fast and
quantitative reactions. The equilibrium between the
different complexes is completely shifted to the complex
with the strongest coordinating ligand occupying the
fourth coordination site.
3,5-Bis[(diph en ylph osph in yl)m eth yl]ph en ol (2). Dichlo-
ride 1 (4 g, 13.1 mmol) was dissolved in THF (150 mL), and
the solution was put under an argon atmosphere using a
freeze-thaw cycle. Subsequently, potassium diphenylphos-
phide (79 mL, 39.3 mmol, 0.5 N solution in THF) was added
via a syringe at room temperature. The reaction mixture was
refluxed for 1 h, during which the color of the reaction mixture
changed from bright red to dark yellow. After the reaction
mixture was cooled to room temperature, the solvent was
evaporated in vacuo and the residue dissolved in CH2Cl2. To
this solution a 10% aqueous solution of H2O2 (100 mL) was
added, and the mixture was stirred vigorously for 1 h. After
separation of the layers, the organic phase was washed with
brine (250 mL) and H2O (100 mL) and dried over Na2SO4. After
evaporation of the solvent, the residue was dissolved in THF
(200 mL) and solid CsF (2.19 g, 14.4 mmol) was added. After
the reaction mixture was heated to reflux and stirred overnight
at room temperature, the THF was evaporated in vacuo. The
residue was dissolved in CH2Cl2 (200 mL), washed with water
(200 mL), and dried over Na2SO4. After purification by column
chromatography (silica, eluent CH2Cl2/MeOH 99:1 to 97:3), 2
was obtained pure as a white solid. Yield: 2.1 g (31%). Mp:
118-120 °C. 1H NMR: δ 7.83-7.21 (m, 20H, PPh2), 6.72 (s,
2H, ArH), 6.43 (s, 1H, ArH), 3.49 (d, 4H, J ) 13.8 Hz, CH2P).
FAB-MS: m/ z 523.2 ((M + H)+, calcd 523.2). Anal. Calcd
for C32H28O3P2: C, 73.56; H, 5.40. Found: C, 73.90; H, 5.42.
r,r′-Bis[[3,5-bis[(d ip h en ylp h osp h in yl)m eth yl]p h en yl]-
oxy]-r′′-cya n om esitylen e (4). Pincer ligand 2 (2.00 g, 3.90
mmol) and K2CO3 (0.54 g, 3.90 mmol) were stirred in CH3CN
(50 mL) for 1 h at room temperature. Subsequently, R,R′-
dibromo-R′′-cyanomesitylene (0.42 g, 1.18 mmol) was added,
and the reaction mixture was stirred for 4 days at 40 °C. TLC
showed complete conversion, and the solvent was evaporated.
The residue was dissolved in CH2Cl2 (100 mL) and washed
with brine (100 mL) and water (100 mL), and the organic
phase was dried over Na2SO4. After concentration under
reduced pressure, the crude product was purified by column
chromatography (SiO2, CH2Cl2/Et3N 95:5). Et3N was removed
by washing the column fraction with 1 N HCl (100 mL) and
brine (100 mL), and after drying over Na2SO4, pure 4 was
obtained as a white solid. Yield: 0.70 g (35%). Mp: 120-
122 °C. 1H NMR: δ 7.68-5.59 (m, 16H, PPh2), 7.51-7.37 (m,
24H, PPh2), 7.23 (s, 2H, ArH), 7.19 (s, 1H, ArH), 6.66 (s, 2H,
ArH), 6.58 (s, 4H, ArH), 4.72 (s, 4H, CH2O), 3.76 (s, 2H, CH2-
CN), 3.52 (d, 8H, J ) 13.7 Hz, CH2P). 13C NMR: δ 158.2,
138.3, 133.0, 132.7, 131.8-125.9, 115.2, 69.0, 46.1, 37.4. 31P
NMR: δ 29.5. FAB-MS: m/ z 1186.3 (M+, calcd 1186.2),
The use of the building blocks described above in the
controlled assembly of both homo- and hetero-multi-
nuclear metallodendrimers is in progress.18
Con clu sion s
To broaden the scope of the controlled assembly
process, a number of building blocks containing Ni(II),
Pd(II), and Pt(II) centers have been synthesized. 31P
NMR spectroscopy was used to study the reactions
which are needed in the controlled assembly process at
the fourth coordination site. The exchange of the
chloride ligands with neutral solvent molecules via
reaction with AgBF4 is a fast and quantitative reaction.
Exp er im en ta l Section
Syntheses were carried out using standard Schlenk tech-
niques under an atmosphere of argon. Melting points were
1208.5 ((M + Na)+, calcd 1209.2). Anal. Calcd for C74H63
-
(17) Launay, N.; Caminade, A.-M.; Lahana, R.; Majoral, J .-P. Angew.
Chem., Int. Ed. Engl. 1994, 33, 1589. Galliot, C.; Pre´vote´, D.; Cami-
nade, A.-M.; Majoral, J .-P. J . Am. Chem. Soc. 1995, 117, 5470.
(18) Preliminary MALDI-TOF MS experiments revealed that it is
possible to synthesize metallodendrimers containing either Pd or Ni.
In addition to the signals for the (oxidized) building block, the MALDI-
TOF mass spectrum of G1,P d P d shows a signal at m/ z 6115 correspond-
ing to [M - 3BF4]+ (calcd 6111). A signal at m/ z 5687 corresponding
to [M - 3BF4]+ (calcd 5682) is present in the MALDI-TOF mass
spectrum of G1,NiNi. The complexes are sensitive toward oxidation in
solution, and future experiments will be carried out under rigorous
exclusion of air during the assembly process.
NO6P4‚NaCl: C, 71.41; H, 5.10; N, 1.12. Found: C, 71.90; H,
5.36; N, 1.09.21
(19) Sen, A.; Ta-Wang, L. J . Am. Chem. Soc. 1981, 103, 4627.
(20) Vo¨gtle, F.; Zuber, M.; Lichtenhaler, R. Chem. Ber. 1973, 106,
717.
(21) The phosphine oxide ligands easily complex NaCl, which can
also be seen in the FAB-MS spectrum (M + Na)+. Apparently, the
ligand was not washed sufficiently with water to remove all of the
NaCl. However, this did not hamper further reactions.

homo- and hetero-Multinuclear Metallodendrimers
Organometallics, Vol. 16, No. 20, 1997 4291
r,r′,r′′-Tr is[[3,5-b is[(d ip h e n ylp h osp h in yl)m e t h yl]-
p h en yl]oxy]m esitylen e (7). The experimental conditions
are similar to those described for 4; white solid. Yield: 0.45
g (43%). Mp: 135-138 °C. 1H NMR: δ 7.68-7.61 (m, 24H,
PPh2), 7.47-7.40 (m, 36H, PPh2), 7.18 (s, 3H, ArH), 6.69 (s,
3H, ArH), 6.57 (s, 6H, ArH), 4.69 (s, 6H, CH2), 3.52 (d, 12H, J
) 13.8 Hz, CH2P). 13C NMR: δ 158.9, 137.7, 133.6, 131.8,
130.0, 129.4, 128.5, 115.3, 69.4, 38.4. 31P NMR: δ 29.5. FAB-
MS: m/ z 1681.8 (M+, calcd 1681.7). Anal. Calcd for
and a red solution formed. To this red solution Hu¨nig’s base
(0.07, 0.42 mmol) was added, and the reaction mixture was
heated to reflux. The color changed to light yellow in 0.5 h,
and the mixture was stirred at room temperature overnight.
The solvent was evaporated under reduced pressure, and the
residue was dissolved in CH2Cl2 (50 mL). The excess amount
of NiCl2 was filtered off. The organic phase was washed with
water, and G0Ni was obtained as a pale yellow solid by
precipitation with diethyl ether. Yield: 40 mg (24%). Mp:
167-170 °C. 1H NMR: δ 7.80-7.76 (m, 24H, PPh2), 7.42-
7.29 (m, 39H, PPh2 + ArH), 6.63 (s, 6H, ArNiH), 4.90 (s, 6H,
CH2O), 3.73 (bs, 12H, CH2P). 31P NMR: δ 34.2. FAB-MS:
m/ z 1864.2 (M+, calcd 1864.2), 1828.3 ((M - Cl)+, calcd
1828.7). Anal. Calcd for C105H87O3P6Ni3Cl3‚2.25NiCl2: C,
58.47; H, 4.16. Found: C, 58.20; H, 4.00.
C
105H90O9P6: C, 74.99; H, 5.39. Found: C, 74.71; H, 5.20.
r,r′-Bis[[3,5-bis[(d ip h en ylp h osp h in o)m eth yl]p h en yl]-
oxy]-r′′-cya n om esitylen e (5). Phosphine oxide 4 (0.1 g, 0.06
mmol) was suspended in m-xylene, which was flushed with
argon. HSiCl3 (0.14 mL, 1.43 mmol) and degassed Et3N were
added via a syringe. The reaction flask was closed, heated to
120 °C, and stirred overnight. After the mixture was cooled
to room temperature, the clear solution was poured into
degassed 2 N NaOH (100 mL). The white suspension which
formed was extracted with toluene (2 × 50 mL) and concen-
trated in vacuo. 1H NMR spectroscopy of the crude product
showed complete reduction of the phosphine oxide groups. The
colorless oil was used directly for the cyclometalation. 1H
NMR: δ 7.28-7.15 (m, 43H, ArH), 6.45 (s, 2H, ArH), 6.32 (s,
4H, ArH), 4.66 (s, 4H, CH2O), 3.67 (s, 2H, CH2CN), 3.18 (s,
8H, CH2P).
BBNi-Cl. The experimental conditions are similar to those
described for G0,Ni; pale yellow solid. Yield: 24 mg (14%).
Mp: 162-164 °C. 1H NMR: δ 7.91-7.85 (m, 16H, PPh2),
7.45-7.35 (m, 25H, PPh2 + ArH), 7.32 (s, 2H, ArH), 6.77 (s,
4H, ArNiH), 5.22 (s, 1H, CH2Cl2), 4.98 (s, 4H, CH2O), 3.85 (bs,
8H, CH2P), 3.72 (s, 2H, CH2CN). 31P NMR: δ 34.6. FAB-
MS: m/ z 1272.7 ((M - Cl)+, calcd 1272.2). Anal. Calcd for
C
74H61NO2P4Ni2Cl2‚0.5CH2Cl2: C, 66.24; H, 4.63; N, 1.04.
Found: C, 66.37; H, 4.45; N, 1.21.
G0,P t Reduced ligand 5 (0.084 mmol) was dissolved in
.
r,r′,r′′-Tr is[[3,5-b is[(d ip h e n ylp h osp h in yl)m e t h yl]-
p h en yl]oxy]m esitylen e (8). The experimental conditions
are similar to those described for the reduction of 7; colorless
oil. 1H NMR: δ 7.35-7.10 (m, 63H, ArH), 6.49 (s, 3H, ArH),
6.33 (s, 6H, ArH), 4.62 (s, 6H, CH2O), 3.21 (s, 12H, CH2P).
FAB-MS: m/ z 1587.6 (M+, calcd for C105H90O3P6 1587.0).
degassed CHCl3 (25 mL), and 2 equiv of cis-[PtCl2(PPh3)2] (0.13
g, 0.168 mmol) was added. The mixture was heated to reflux
and stirred for 20 h, during which a white precipitate formed.
After the reaction mixture was cooled to room temperature,
the volume was reduced in vacuo to 10 mL and elemental
sulfur (0.04 g, 0.164 mmol), KCl (0.01 g, 0.164 mmol), and
acetone (4 mL) were added. The resulting suspension was
stirred for 5 h at 50 °C, whereupon the reaction mixture was
evaporated to dryness. Repeated crystallization from CH2Cl2/
diethyl ether and washing with cold toluene (10 mL) gave G0,P t
as a white solid. Yield: 80 mg (60%). Mp: 181-183 °C. 1H
NMR: δ 7.89-7.82 (m, 24H, PPh2), 7.40-7.31 (m, 39H, PPh2
+ ArH), 6.77 (s, 6H, ArPtH), 4.98 (s, 6H, CH2O), 3.84 (bs, 12H,
CH2P). 31P NMR: δ 32.3 (J PPt ) 1481 Hz). 195Pt NMR: δ
-4286 (J PtP ) 1467 Hz). FAB-MS: m/ z 2237.0 ((M - Cl)+,
G
0,P d . The freshly reduced ligand 8 (95.1 mg, 0.060 mmol)
was dissolved in CH3CN (25 mL), and Pd[CH3CN]4(BF4)2 (80.0
mg, 0.18 mmol) was added in one portion. After 15 min of
stirring at room temperature, the pale yellow solution was
evaporated to dryness. The residue was dissolved in CH2Cl2
(25 mL) and stirred overnight with brine (25 mL). The layers
were separated, and the organic solvent was evaporated under
reduced pressure. After crystallization from CH2Cl2/diethyl
ether, pure G0,P d was obtained as a pale yellow solid. Yield:
80 mg (67%). Mp: 137-138 °C. 1H NMR: δ 7.78-7.70 (m,
24H, PPh2), 7.38-7.31 (m, 39H, PPh2 + ArH), 6.72 (s, 6H,
ArPdH), 5.22 (s, 4H, CH2Cl2), 4.93 (s, 6H, CH2O), 3.84 (bs, 12H,
CH2P). 31P NMR: δ 33.0. FAB-MS: m/ z 1971.3 ((M - Cl)+,
calcd 1972.6). Anal. Calcd for C105H87O3P6Pd3Cl3‚2.25CH2-
Cl2: C, 58.57; H, 4.19. Found: C, 58.05; H, 4.09.
BBP d -Cl. The experimental conditions are similar to those
described for G0,P d ; pale yellow solid. Yield: 72 mg (55%).
Mp: 157-158 °C. 1H NMR: δ 7.90-7.78 (m, 16H, PPh2),
7.42-7.36 (m, 24H, PPh2), 7.35 (s, 1H, ArH), 7.32 (s, 2H, ArH),
6.68 (s, 4H, ArPdH), 5.22 (s, 3H, CH2Cl2), 4.95 (s, 4H, CH2O),
3.91 (bs, 8H, CH2P), 3.75 (s, 2H, CH2CN). 31P NMR: δ 33.4.
FAB-MS: m/ z 1369.0 ([M - Cl]+, calcd 1368.4). Anal. Calcd
for C74H61P4NO2Pd2Cl2‚1.5CH2Cl2: C, 59.69; H, 4.16; N, 0.90.
Found: C, 59.41; H, 4.15; N, 0.99.
calcd 2237.8). Anal. Calcd for
C105H87O3P6Pt3Cl3‚0.5S8‚
2C7H8: C, 55.68; H, 4.40; S, 4.44. Found C, 55.25; H, 4.01; S,
4.96.
BBP t-Cl. The experimental conditions are similar to those
described for G0,P t; white solid. Yield: 0.06 g (40%). Mp: 178-
179 °C. 1H NMR: δ 7.95-7.81 (m, 16H, ArH), 7.49-7.39 (m,
25H, ArH), 7.33 (s, 2H, ArH), 6.77 (s, 4H, ArPtH), 4.99 (s, 4H,
CH2O), 3.86 (bs, 8H, CH2P), 3.84 (s, 2H, CH2CN). 31P NMR:
δ 32.3 (J PPt ) 1467 Hz). 195Pt NMR: δ -4286 (J PtP ) 1467
Hz). FAB-MS: m/ z 1546.2 ((M - Cl)+, calcd 1545.8). Anal.
Calcd for C74H61NO2P4Pt2Cl2: C, 56.21; H, 3.89; N, 0.89.
Found: C, 56.44; H, 3.92; N, 0.94.
Ack n ow led gm en t. We thank the Dutch Foundation
for Chemical Research (SON) for financial support and
R. Fokkens and Prof. N. Nibbering for the MALDI-TOF
MS and FAB-MS measurements.
G
0,Ni. The freshly reduced ligand 8 (95.1 mg, 0.060 mmol)
was dissolved in a mixture of CH2Cl2/EtOH 3:1 (50 mL), and
6 equiv of NiCl2‚6H2O (0.09 g, 0.36 mmol) was added in one
portion. The reaction mixture was stirred for 1 h at 60 °C,
OM970424A