Organometallic Oligomers Based on 1,8-Diisocyano-p-menthane (dmb): Syntheses and Characterization of the {[M(diphos)(dmb)]BF4} n and {[Pd2(diphos)2(dmb)](ClO 4)2}n Materials (M = Cu, Ag; diphos = dppe, dppp)

Article abstract of DOI:10.1021/ic034780z

A new strategy to synthesize organometallic oligomers is presented and consists of using the title diisocyanide and chelated metal fragments with bis(diphenylphosphine)alkanes. The title materials are synthesized by reacting the [M(dppe)(BF₄)] and [M₂(dppp)₂](BF ₄)₂ complexes (M = Cu, Ag; dppe = bis(diphenylphosphino)ethane, dppp = bis(diphenylphosphino)propane) with dmb and the Pd₂-bonded d⁹-d⁹ Pd ₂(dmb)₂Cl₂ dimer with dppe or dppp. The model compounds [M(diphos)(CN-t-Bu)₂]BF₄ (M = Cu, Ag) and [Pd₂(diphos)₂(CN-t-Bu)₂](ClO₄) ₂ (diphos = dppe, dppp) have been prepared and characterized as well for comparison purposes. Three of the model compounds were also characterized by X-ray crystallography to establish the diphosphine chelating behavior. The materials are amorphous and have been characterized from the measurements of the intrinsic viscosity, DSC, TGA, and XRD, as well as their capacity for making stand-alone films. The intrinsic viscosity data indicate that the Cu and Pd₂ materials are oligomeric in solution (～8-9 units), while the Ag materials are smaller. For {[Cu(dppe)(dmb)]-BF₄}_n, a glass transition is reproducibly observed at about 82 °C (ΔC _p = 0.43 J/(g deg)), which suggests that these materials are polymeric in the solid state. The Cu and Ag species are luminescent in the solid state at room temperature exhibiting λ_max and τ _e (emission lifetime) around 480-550 nm and 18-48 μs, respectively, while the Pd₂ species are not luminescent under these conditions. During the course of this study, the unsaturated [M ₂-(dppp)₂](BF₄)₂ starting materials (M = Cu, Ag) were prepared, one of which (M = Ag) was characterized by crystallography. The bridging behavior of the dppp ligand in this case contrasts with the chelating behavior seen for the saturated [Cu(dppp)(CN-t-Bu)₂]BF₄ complex.

Full text of DOI:10.1021/ic034780z

Inorg. Chem. 2004, 43, 1491−1501
Organometallic Oligomers Based on 1,8-Diisocyano-p-menthane (dmb):
Syntheses and Characterization of the {[M(diphos)(dmb)]BF4}n and
{[Pd2(diphos)2(dmb)](ClO ) } Materials
4 2 n
(M ) Cu, Ag; diphos ) dppe, dppp)
,1a
Eric Fournier,1a Ste´phanie Sicard,1a Andreas Decken,1b and Pierre D. Harvey*
De´partement de chimie, UniVersite´ de Sherbrooke, Sherbrooke, PQ, Canada J1K 2R1, and the
Department of Chemistry, UniVersity of New Brunswick,
Fredericton, New Brunswick, Canada E3B 6E2
Received July 7, 2003
A new strategy to synthesize organometallic oligomers is presented and consists of using the title diisocyanide and
chelated metal fragments with bis(diphenylphosphine)alkanes. The title materials are synthesized by reacting the
[M(dppe)(BF )] and [M (dppp)2](BF ) complexes (M ) Cu, Ag; dppe ) bis(diphenylphosphino)ethane, dppp )
4
2
4 2
bis(diphenylphosphino)propane) with dmb and the Pd2-bonded d9−d9 Pd2(dmb)2Cl2 dimer with dppe or dppp. The
model compounds [M(diphos)(CN-t-Bu)2]BF (M ) Cu, Ag) and [Pd2(diphos)2(CN-t-Bu)2](ClO ) (diphos ) dppe,
4
4 2
dppp) have been prepared and characterized as well for comparison purposes. Three of the model compounds
were also characterized by X-ray crystallography to establish the diphosphine chelating behavior. The materials
are amorphous and have been characterized from the measurements of the intrinsic viscosity, DSC, TGA, and
XRD, as well as their capacity for making stand-alone films. The intrinsic viscosity data indicate that the Cu and
Pd2 materials are oligomeric in solution (∼8−9 units), while the Ag materials are smaller. For {[Cu(dppe)(dmb)]-
BF }n, a glass transition is reproducibly observed at about 82 °C (∆C ) 0.43 J/(g deg)), which suggests that
4
p
these materials are polymeric in the solid state. The Cu and Ag species are luminescent in the solid state at room
temperature exhibiting λmax and τe (emission lifetime) around 480−550 nm and 18−48 µs, respectively, while the
Pd2 species are not luminescent under these conditions. During the course of this study, the unsaturated [M -
2
(dppp)2](BF ) starting materials (M ) Cu, Ag) were prepared, one of which (M ) Ag) was characterized by
4 2
crystallography. The bridging behavior of the dppp ligand in this case contrasts with the chelating behavior seen
for the saturated [Cu(dppp)(CN-t-Bu)2]BF complex.
4
Chart 1
Introduction
The title bridging ligand (Chart 1) has become a highly
versatile assembling building block over the past 30 years.2
Indeed, this ligand is well-known for the synthesis of
binuclear complexes, although some examples of tri- and
tetranuclear dmb-containing species have also been reported.3
by X-ray diffraction techniques and molecular weight
measurements (Mn and Mw). Applications in the areas of
semi- and photoconductivity and photovoltaic cells were
reported as well.4d
Recently, this ligand was used for the first time in the
+
synthesis of the organometallic polymers {M(dmb)2 }n (M
) Cu, Ag; Chart 2),4 which have been fully characterized
The uniqueness of these new materials is that they keep
their polymeric, or at least oligomeric, nature in solution4b,e
and can use both the U- and Z-conformations for dmb to
form various isomeric 1-D polymers.4c On the other hand,
the related and more flexible diisocyanide ligand tmb (2,5-
* To whom correspondence should be addressed. E-mail: p.harvey@
Usherbrooke.ca. Tel: (819) 821-7092 or (819) 821-8000 ext 8000, ext 2005.
Fax: (819) 821-8017.
(1) (a) Universite´ de Sherbrooke. (b) University of New Brunswick.
(2) Harvey, P. D. Coord. Chem. ReV. 2001, 219, 17, and references therein.
10.1021/ic034780z CCC: $27.50 © 2004 American Chemical Society
Published on Web 01/13/2004
Inorganic Chemistry, Vol. 43, No. 4, 2004 1491

Fournier et al.
Chart 2
Chart 3
Chart 4
dimethyl-2′,5′-diisocyanohexane) produces 2- or 3-D polymer
structures, as reported for polymers of the type {Ag(tmb)+}n
and {Ag2(tmb)32+}n.5 The two strategies for the synthesis of
1-D materials that retain their oligomeric or polymeric nature
in solution are the use of two dmb bridges between
the metallic fragments (such as fragment ) M+ 4 and
M2(dppm)22+ 6 with M ) Cu, Ag; dppm ) bis(diphenylphos-
phino)methane; Chart 3) and of axially functionalizable
metallic fragments exhibiting strong (and not so labile)
M-Laxial bonding (such as Pd-CNR and Pd-P; Chart 4).3a,b
In the examples illustrated below, M4 species are bridged
together by dmb (Z-conformer), or by flexible diphosphine
ligands, leading to crystalline and amorphous materials,
respectively.7
We now wish to report the synthesis and characterization
of a series of new oligomers built upon chelated diphosphine
metallic fragments, such as “M(diphos)+” and “Pd2(diphos)22+
”
(M ) Cu, Ag; diphos ) dppe, dppp), and the bridging dmb
ligands. This approach is novel and is based on the
intramolecular steric hindrance and ring stress that prevent
the dimer formation. The materials are characterized from
the measurements of the intrinsic viscosity, DSC, TGA,
XRD, luminescence spectroscopy, and the capacity of
forming stand-alone film and compared to model compounds
such as the mononuclear complexes [M(dppe)(CN-t-Bu)2]-
BF4 (M ) Cu, Ag) and [M(dppp)(CN-t-Bu)2]BF4 and Pd2-
bonded dimers [Pd2(diphos)2(CN-t-Bu)2](ClO4)2 (diphos )
dppe, dppp). In the area of coordination polymers and
(3) (a) Zhang, T.; Drouin, M.; Harvey, P. D. Inorg. Chem. 1999, 38, 1305.
(b) Zhang, T.; Drouin, M.; Harvey, P. D. Inorg. Chem. 1999, 38, 957.
(c) Fortin, D.; Drouin, M.; Harvey, P. D.; Herring, F. G.; Summers,
D. A.; Thompson, R. C. Inorg. Chem. 1999, 38, 1253. (d) Zhang, T.;
Drouin, M.; Harvey, P. D. Inorg. Chem. 1999, 38, 4928. (e) Sykes,
A. G.; Mann, K. R. Inorg. Chem. 1990, 29, 4449. (f) Sykes, A. G.;
Mann, K. R. J. Am. Chem. Soc. 1988, 110, 8252. (g) Sykes, A. G.;
Mann, K. R. J. Am. Chem. Soc. 1990, 112, 7247. (h) Harvey, P. D.;
Drouin, M.; Michel, A.; Perreault, D. J. Chem. Soc., Dalton Trans.
1993, 1365.
(4) (a) Perreault, D.; Drouin, M.; Michel, A.; Harvey, P. D. Inorg. Chem.
1992, 31, 3688. (b) Fortin, D.; Drouin, M.; Turcotte, M.; Harvey, P.
D. J. Am. Chem. Soc. 1997, 119, 531. (c) Fortin, D.; Drouin, M.;
Harvey, P. D. J. Am. Chem. Soc. 1998, 120, 5351. (d) Fortin, D.;
Drouin, M.; Harvey, P. D. Inorg. Chem. 2000, 39, 2758. (e) Turcotte,
M.; Harvey, P. D. Inorg. Chem. 2002, 41, 2971.
(5) (a) Guitard, A.; Mari, A.; Beauchamp, A. L.; Dartiguenave, Y.;
Dartiguenave, M. Inorg. Chem. 1983, 22, 1603. (b) Dartiguenave, M.;
Dartiguenave, A.; Mari, A.; Guitard, A.; Olivier, M.-J.; Beauchamp,
A. L. Can. J. Chem. 1988, 66, 2386.
(6) (a) Fournier, E.; Lebrun, F.; Decken, A.; Harvey, P. D. Submitted for
publication. (b) Lebrun, F. M.Sc. Dissertation, Universite´ de Sher-
brooke, 2001.
(7) Examples of of diphosphine-linked cluster units have been reported.
See for instance: (a) Ferguson, G.; Hourintane, R.; Spalding, T. R.
Acta Crystallogr., Sect. C 1991, 47, 544. (b) Tanase, T.; Horiuchi,
T.; Yamamoto, Y.; Kobayashi, K. J. Organomet. Chem. 1992, 440,
1. (c) Hattersley, A. D.; Housecroft, C. E.; Rheingold, A. L. Inorg.
Chim. Acta 1999, 289, 149. (d) Ferrer, M.; Rosell, O.; Seco, M.; Soler,
M.; Font-Bardia, M.; Solans, X.; de Montauzon, D. J. Organomet.
Chem. 2000, 598, 215.
1492 Inorganic Chemistry, Vol. 43, No. 4, 2004

Organometallic Oligomers Based on dmb
Table 1. Numbering of the Investigated Compounds
(4.38 mmol) volume of t-BuNC was added dropwise using a
microsyringe. The solution was stirred for 1 h and then evaporated.
The white powder was dissolved in a minimum amount of
dichloromethane prior to adding 100 mL of diethyl ether to
precipitate a white solid, which was filtered out and dried in vacuo.
Yield: 60% (470 mg). 1H NMR (CD2Cl2): δ 7.57-7.42 (m, 20H,
Ph), 2.43 (m, 4H, CH2), 1.38 (s, 18H, CH3). 31P{1H} NMR
(CD2Cl2): δ -7.58. 13C{1H} NMR (CD2Cl2): δ 132.7, 132.6,
131.0, 57.7, 30.1, 26.0. IR (KBr): ν 1059 (BF4), 2170 cm-1 (CtN).
Raman (neat solid): ν 2172 cm-1 (CtN). UV-vis (CH3CN): 222
(44 500), 272 nm (27 500 M-1 cm-1).
compd
no.
[M(dppe)(CN-t-Bu)2]BF4
[Cu(dppp)(CN-t-Bu)2]BF4
[Pd2(dppe)2(CN-t-Bu)2](ClO4)2
[Pd2(dppp)2(CN-t-Bu)2](ClO4)2
{[M(dppe)(dmb)]BF4}n
{[M(dppp)(dmb)]BF4}n
{[Pd2(dppe)2(dmb)](ClO4)2}n
{[Pd2(dppp)2(dmb)](ClO4)2}n
M ) Cu, 1; M ) Ag, 2
3
4
5
M ) Cu, 6; M ) Ag, 7
M ) Cu, 8; M ) Ag, 9
10
11
oligomers of Cu(I) and Ag(I) exhibiting luminescence, only
a few examples have been reported so far.8 A compound
numbering is provided in Table 1.
[Ag(dppe)(CN-t-Bu)2]BF4 (2). [Ag(dppe)(BF4)] (1.16 g, 1.96
mmol) was dissolved in 100 mL of degassed acetone. A 442 µL
(3.91 mmol) volume of t-BuNC was added dropwise using a
microsyringe. The solution was stirred for 2 h and then reduced to
20 mL volume in vacuo. A 150 mL volume of diethyl ether was
added to precipitate the product, which was filtered out and dried.
Experimental Section
Materials. dmb, Pd2(CN-t-Bu)4Cl2, Pd2(dmb)2Cl2, and [Cu-
(NCMe)4]BF4 were synthesized according to literature procedures.9
The [M(dppe)(BF4)] starting materials (M ) Cu, Ag) were prepared
in the same way as [Ag(dppe)(ClO4)],10 except that AgClO4 was
replaced by either AgBF4 or [Cu(CNMe)4]BF4. The [M2(dppp)2]-
(BF4)2 dimers were synthesized in the same manner as the
complexes [Cu2(dppp)2](ClO4)211 and [Ag2(dppb)2](NO3)212 (dppb
) bis(diphenylphosphino)butane), except that dppp was used instead
of dppb, [Cu(NCMe)4]BF4 instead of [Cu(NCMe)4]ClO4, and
AgBF4 instead of AgNO3. The identity of the [M2(dppp)2](BF4)2
starting materials was confirmed by X-ray structure determination
methods for M ) Ag (see below and the Supporting Information).
Cu(BF4)2‚H2O, AgBF4, t-BuNC, dppe, and dppp were purchased
from Aldrich and were used as received. The solvents acetone
(Fisher), acetonitrile (Anachemia), dichloromethane (ACP), diethyl
ether (ACP), and butyronitrile (Aldrich) were purified according
to published procedures.13 The Cu and Ag compounds and Pd2
1
Yield: 88% (1.49 g). H NMR (CD2Cl2): δ 7.49-7.36 (m, 20H,
Ph), 2.43 (m, 4H, CH2P), 1.48 (s, 18H, CH3). 31P{1H} NMR
(CD2Cl2): δ 3.38. 13C{1H} NMR (CD2Cl2): δ 141.2, 132.7, 130.8,
129.3, 57.4, 30.0, 24.9. IR (KBr): ν 2183 (CtN), 1057 cm-1 (BF4).
Raman (neat solid): ν 2184 cm-1 (CtN). UV-vis (CH3CN): 222
(44 500), 270 nm (30 300 M-1 cm-1).
[Cu(dppp)(CN-t-Bu)2]BF4 (3). [Cu2(dppp)2](BF4)2 (301 mg,
0.263 mmol) was dissolved in 100 mL of degassed acetone. A 150
µL (1.33 mmol) volume of t-BuNC was added dropwise using a
microsyringe. The solution was stirred for 1 h and then evaporated.
The white powder was dissolved in a minimum amount of
dichloromethane prior to addition of 100 mL of diethyl ether to
precipitate a white solid. The solid was filtered out and dried in
vacuo. Yield: 77% (301.6 mg). 1H NMR (CD2Cl2): δ 7.49-7.36
(m, 20H, Ph), 2.40 (m, 4H, CH2P), 1.93 (m, 2H, CCH2C) 1.35 (s,
18H, CH3). 31P{1H} NMR (CD2Cl2): δ -8.21. 13C{1H} NMR
(CD2Cl2): δ 132.6, 130.8, 129.1, 30.1, 27.8, 19.1, 18.0. IR (KBr):
ν 1061 (BF4), 2172 cm-1 (CtN). Raman (neat solid): ν 2171 cm-1
(CtN). UV-vis (CH3CN): 222 (43 900), 274 nm (27 200 M-1
cm-1).
-
-
species were prepared as BF4 and ClO4 salts, respectively. The
-
Pd2 species were originally prepared as BF4 salts, but the use of
ClO4- ion gave better chemical analysis. The handling of perchlo-
rate salts of organometallic cations represents a potential explosiVe
hazard. The use of small amounts is recommended.
{[Cu(dppe)(dmb)]BF4}n (6). [Cu(dppe)(BF4)] (609 mg, 1.11
mmol) was dissolved in 70 mL of degassed acetone. A 425 mg
(2.22 mmol) amount of dmb was dissolved in 200 mL of degassed
acetone in another flask. Both solutions were cooled to 0 °C, and
the dmb solution was added dropwise to the dimer solution. The
mixture was stirred for 2 h and then reduced to 15 mL volume in
vacuo. A 150 mL volume of diethyl ether was added to precipitate
the product, which was filtered out and dried. Yield: 57.5% (472
mg). 1H NMR (CD2Cl2): δ 7.50-7.40 (m, 20H, Ph), 2.42 (m, 4H,
CH2P), 1.83-1.11 (m, 18H, for 1.04 dmb). 31P{1H} NMR
(CD2Cl2): δ 7.68. 13C{1H} NMR (CD2Cl2): δ 141.5, 132.6, 131.0,
129.5, 62.8, 60.5, 44.9, 37.3, 29.3, 26.5, 25.6, 22.8. IR (KBr): ν
2174 (CtN), 1070 cm-1 (BF4). Raman (neat solid): ν 2173 cm-1
(CtN). Anal. Calcd for C38H42N2P2BF4Cu + 0.04 dmb: C, 62.53;
H, 5.82; N, 3.94. Found: C, 62.70; H, 6.19; N, 3.92. UV-vis
(CH3CN): 222 (43 600), 270 nm (27 900 M-1 cm-1).
{[Ag(dppe)(dmb)]BF4}n (7). [Ag(dppe)(BF4)] (272 mg, 0.230
mmol) was dissolved in 70 mL of degassed acetone. A 86.8 mg
(4.56 mmol) amount of dmb was dissolved in 200 mL of degassed
acetone in another flask. Both solutions were cooled to 0 °C, and
the dmb solution was added dropwise to the dimer solution. The
mixture was stirred for 2 h and then reduced to 15 mL volume in
vacuo. A 150 mL volume of diethyl ether was added to precipitate
the product, which was filtered out and dried. Yield: 90% (323
mg). 1H NMR (CD2Cl2): δ 7.47-7.32 (m, 20H, Ph), 2.41 (m, 4H,
CH2P), 2.00-1.81 (m, 6H, dmb) 1.54-1.28 (m, 12H, for 1.21 dmb).
[Cu(dppe)(CN-t-Bu)2]BF4 (1). [Cu(dppe)(BF4)] (601.3 mg, 1.09
mmol) was dissolved in 150 mL of degassed acetone. A 496 µL
(8) (a) Zhang, J.; Xiong, R. G.; Chen, X. T.; Che, C.-M.; Xue, Z.; You,
X.-Z. Organometallics 2001, 20, 4118. (b) Liu, Q.-X.; Xu, F.-B.; Li,
Q.-S.; Zang, X.-B.; Leng, Y. L.; Chou, Z.-Z. Zhang, Organometallics
2003, 22, 309. (c) Zhang, J.; Xiong, R.-G.; Chen, X.-T.; Xue, Z.; Peng,
S.-M.; You, X.-Z. Organometallics 2002, 21, 235. (d) Sun, D.; Cao,
R.; Weng, J.; Hong, M.; Liang, Y. J. Chem. Soc., Dalton Trans. 2002,
291. (e) Tong, M.-L.; Shi, X.-M. Chen, New. J. Chem. 2002, 26, 814.
(f) Zheng, S.-L.; Tong, M.-L.; Tan, S.-D.; Wang, Y.; Shi, J.-X.; Tong,
Y.-X.; Lee, H. K.; Chen, X.-M. Organometallics 2001, 20, 5319. (g)
Henary, M.; Wootton, J. L.; Khan, S. I.; Zink, J. I. Inorg. Chem. 1997,
36, 796.
(9) (a) For Pd2(CN-t-Bu)2Cl2, see: Yamamoto, Y.; Yamazaki, H. Bull.
Chem. Soc. Jpn. 1985, 58, 1843. Otsuka, S.; Tatsuno, Y.; Ataka, K.
J. Am. Chem. Soc. 1971, 93, 6705. (b) For dmb see: Weber, W. D.;
Gokel, G. W.; Ugi, I. K. Angew. Chem., Int. Ed. Engl. 1972, 11, 530.
(c) For Pd2(dmb)2Cl2 see: Perreault, D.; Drouin, M.; Michel, A.;
Harvey, P. D. Inorg. Chem. 1992, 31, 2740. (d) For [Cu(NCMe)4]-
BF4 see: Diez, J.; Gamasa, M. P.; Gimeno, J.; Tiripicchio, A.;
Tiripicchio Camellini, M. J. Chem. Soc., Dalton Trans. 1987, 1275.
(10) Coronas, J. M.; Rossel, O.; Sales, J. J. Organomet. Chem. 1976, 121,
265.
(11) Kitagawa, S.; Kondo, M.; Katawa, S.; Wada, S.; Mackawa, M.;
Munakata, M. Inorg. Chem. 1995, 34, 1455.
(12) Ruina, Y.; Yimin, H.; Baoyu, X.; Dongmei, W.; Douman, J. Transition
Met. Chem. 1996, 21, 28.
(13) (a) Perrin, D. D.; Armarego, W. L. F.; Perrin, D. R. Purification of
laboratory Chemicals Pergamon: Oxford, U.K., 1966. (b) Gordon,
A. J.; Ford, R. A. The Chemist’s Companion, a Handbook of Practical
Data, Techniques, and References Wiley: New York, 1972; p 436.
Inorganic Chemistry, Vol. 43, No. 4, 2004 1493

Fournier et al.
31P{1H} NMR (CD2Cl2): δ 4.49. 13C{1H} (CD2Cl2): δ 143.8,
143.3, 132.7, 131.0, 129.5, 63.2, 60.7, 44.1, 36.91, 29.0, 27.0, 25.1,
22.7. IR (KBr): ν 2180, 2133 (CtN), 1058 cm-1 (BF4). Raman
(neat solid): ν 2178 cm-1 (CtN). Anal. Calcd for C38H42N2P2-
BF4Ag + 0.21 dmb: C, 59.11; H, 5.60; N, 4.12. Found: C, 59.14;
H, 5.61; N, 4.08. UV-vis (CH3CN): 222 (38 600), 270 nm (32 200
M-1 cm-1).
{[Cu(dppp)(dmb)]BF4}n (8). ([Cu2(dppp)2](BF4)2) (312 mg,
0.227 mmol) was dissolved in 70 mL of degassed acetone. A 109.3
mg (5.68 mmol) amount of dmb was dissolved in 150 mL of
degassed acetone in another flask. Both solutions were cooled to 0
°C, and the dmb solution was added dropwise to the dimer solution.
The mixture was stirred for 1 h and then reduced to 20 mL volume
in vacuo. Then 150 mL of diethyl ether was added to precipitate
the product, which was filtered out and dried. Yield: 92% (385
mg). 1H NMR (CD2Cl2): δ 7.40-7.40 (m, 20H, Ph), 2.41 (m, 4H,
CH2P), 1.86-1.81 (m, 4H, dmb + CCH2C dppp) 1.63-1.05 (m,
16H, for 1.13 dmb). 31P{1H} NMR (CD2Cl2): δ -8.17. 13C{1H}
NMR (CD2Cl2): δ 133.8, 132.5, 130.7, 129.2, 63.4, 61.0, 45.5,
37.2, 29.2, 27.8, 22.8, 18.9. IR (KBr): ν 2168 (CtN), 1057 cm-1
(BF4). Raman (neat solid): ν 2171 cm-1 (CtN). Anal. Calcd for
C39H44N2P2BF4Cu + 0.13 dmb: C, 62.20; H, 6.29; N, 3.72.
Found: C, 62.65; H, 6.29; N, 3.67. UV-vis (CH3CN): 222
(38 900), 270 nm (23 400 M-1 cm-1).
{[Ag(dppp)(dmb)]BF4}n (9). The dimer [Ag2(dppp)2](BF4)2 (572
mg, 0.492 mmol) was dissolved in 100 mL of degassed acetone. A
280 mg (1.48 mmol) amount of dmb was dissolved in 200 mL of
degassed acetone in another flask. Both solutions were cooled to 0
°C, and the dmb solution was added dropwise to the dimer solution.
The mixture was stirred for 2 h and then reduced to 30 mL volume
in vacuo. A 150 mL volume of diethyl ether was added to precipitate
the product, which was filtered out and dried. Yield: 96% (758
mg). 1H NMR (CD2Cl2): δ 7.39-7.23 (m, 20H, Ph), 2.41 (m, 4H,
CH2P), 2.03-1.91 (m, 4H, for 1.1 dmb) 1.68-1.48 (m, 18H, dmb
+ CCH2C dppp). 31P{1H} NMR (CD2Cl2): δ -1.30. 13C{1H} NMR
(CD2Cl2): δ 144.2, 143.5, 133.5, 132.6, 130.7, 129.3, 63.3, 60.6,
43.9, 36.9, 28.8, 27.1, 22.6, 18.9. IR (KBr): ν 2185, 2130 (CtN),
1055 cm-1 (BF4). Raman (neat solid): ν 2188 cm-1 (CtN). Anal.
Calcd for C39H44N2P2BF4Ag + 0.1 dmb: C, 59.14; H, 5.65; N,
3.77. Found: C, 59.14; H, 5.61; N, 4.08. UV-vis (CH3CN): 222
(40 300), 272 nm (33 700 M-1 cm-1).
added dropwise to the dimer solution. The mixture was stirred for
2 h and then reduced to 10 mL volume in vacuo. A 100 mL volume
of diethyl ether was added to precipitate the product, which was
filtered out and dried. N.B.: This compound must be prepared fresh
prior to each analysis; it is unstable, even under inert atmosphere
1
in the dark. Yield: 92% (32.3 mg). H NMR (CD3CN): δ 7.85-
7.01 (m, 40H, Ph), 2.55 (m, 8H, CH2P), 1.77 (m, 4H, CH2CH2P),
1.61 (s, 18H, CH3). 31P{1H} NMR (CD3CN): δ -5.62 (d, J )
∼28), 10.25 (d, J ) ∼28). 13C{1H} NMR (CD3CN): δ 141.8, 131.5,
129.5, 128.9, 57.5, 28.9, 27.6, 18.3. IR (KBr): ν 2179 cm-1 (CtN).
Mass spec FAB (m/z): 1038 (Pd2(dppp)2; 1037.7), 1120 (Pd2-
(dppp)2(CN-t-Bu); 1120.9), 1303 ((Pd2(dppp)2(CN-t-Bu)(ClO4);
1303.4). UV-vis (CH3CN): 414 nm (26 000 M-1 cm-1).
{[Pd2(dppe)2(dmb)](ClO4)2}n (10). Under inert atmosphere in
the dark, [Pd2(dmb)2Cl2] (19 mg, 0.029 mmol) and 9.8 mg (0.092
mmol) of LiClO4 were dissolved in 50 mL of acetonitrile. The
solution was stirred for 1 h. A 22.8 mg (0.057 mmol) amount of
dppe was dissolved in 50 mL of acetonitrile in another flask. The
dppe solution was added dropwise to the dimer solution. The
mixture was stirred for 2 h and then reduced to 10 mL volume in
vacuo. A 100 mL volume of diethyl ether were added to precipitate
the product, which was filtered out and dried. Yield: 79% (32.0
mg). 1H NMR (CD3CN): δ 7.56-6.98 (m, 40H, Ph), 2.65 (m, 8H,
CH2P), 2.05-1.15 (m, 18H, dmb). 31P{1H} NMR (CD3CN): δ -5
(d), 10 (d). 13C{1H} NMR (CD3CN): δ 148.5, 142.2, 131.5, 131.8,
128.5, 65.2, 63.7, 44.2, 35.3, 27.8, 26.5, 24.9, 21.6. IR (KBr): ν
2170 cm-1 (CtN). Mass spec FAB (m/z): 1010 (Pd2(dppe)2;
1009.7), 1199 (Pd2(dppp)2(dmb); 1199.9). Anal. Calcd for C64H66N2-
Pd2P4Cl2O8: C, 54.95; H 4.76; N 2.00. Found: C, 52.67; H 4.76;
N 2.06. UV-vis (CH3CN): 412 nm (28 000 M-1 cm-1).
{[Pd2(dppp)2(dmb)](ClO4)2}n (11). Under inert atmosphere in
the dark, [Pd2(dmb)2Cl2] (29 mg, 0.044 mmol) and 6.3 mg (0.059
mmol) of LiClO4 were dissolved in 50 mL of acetonitrile. The
solution was stirred 1 h. A 36.0 mg (0.087 mmol) amount of dppp
was dissolved in 50 mL of acetonitrile in another flask. The dppp
solution was added dropwise to the dimer solution. The mixture
was stirred for 2 h and then reduced to 10 mL volume in vacuo. A
100 mL volume of diethyl ether was added to precipitate the
product, which was filtered out and dried in the dark. Yield: 86%
1
(53.6 mg). H NMR (CD3CN): δ 7.53-7.03 (m, 40H, Ph), 2.58
(m, 8H, CH2P), 2.10 (m, 4H, CH2CH2P), 201-0.98 (m, 18H, dmb).
31P{1H}: -5.72 (d, J ) ∼25 Hz), 10.38 (d, J ) ∼25 Hz). 13C{1H}
NMR (CD3CN): δ 148.5, 142.2, 131.5, 131.8, 128.5, 65.2, 63.7,
61.9, 44.9, 37.6, 28.2, 27.7, 23.8, 17.9. IR (KBr): ν 2170 cm-1
(CtN). Mass spec FAB (m/z): 1038 (Pd2(dppp)2; 1037.9), 1227.3
(Pd2(dppp)2(dmb); 1227.2). Anal. Calcd for C66H70N2Pd2Cl2O8: C,
55.56; H 4.94; N 1.96. Found: C, 52.12; H 5.14; N 2.08. UV-vis
(CH3CN): 414 nm (25 700 M-1 cm-1).
{[Pd2(dppe)2(CN-t-Bu)2](ClO4)2}n (4). [Pd2(CN-t-Bu)4Cl2] (37
mg, 0.06 mmol) was dissolved in 50 mL of acetonitrile in the dark
under N2 atmosphere, and 13 mg (0.13 mmol) of LiClO4 was added
to the mixture. A 48 mg (0.12 mmol) amount of dppe was dissolved
in 50 mL of acetonitrile in another flask. The dppe solution was
added dropwise to the dimer solution. The mixture was stirred for
2 h and then reduced to 10 mL volume in vacuo. A 100 mL volume
of diethyl ether was added to precipitate the product, which was
filtered out and dried. N.B.: This compound must be prepared fresh
prior to each analysis; it is unstable, even under inert atmosphere
Apparatus. All NMR spectra were acquired with a Bruker AC-
300 spectrometer (1H 300.15 MHz, 13C 75.48 MHz, 31P 121.50
MHz) using the solvent as chemical shift standard, except in 31P
NMR, where the chemical shifts are relative to D3PO4 85% in D2O.
All chemical shifts (δ) and coupling constants (J) are given in ppm
and hertz, respectively. The IR spectra were acquired on a Bomem
FT-IR MB series spectrometer equipped with a baseline-diffused
reflectance. The emission spectra were measured on a Spex
Fluorolog II spectrofluorometer using a HgXe excitation lamp. The
emission lifetimes were measured with a nanosecond N2 laser
system from PTI model GL-3300 pumping a dye laser model GL-
302. The glass transition temperatures (Tg) were measured using a
Perkin-Elmer 5A DSC7 instrument equipped with a thermal
controller 5B TAC 7/DS. Calibration standards were water and
indium. The FT-Raman spectra were acquired on a Bruker RFS
1
in the dark. Yield: 78% (64.2 mg). H NMR (CD3CN): δ 7.59-
7.16 (m, 40H, Ph), 2.53 (m, 8H, CH2P), 1.68 (s, 18H, CH3). 13C{1H}
NMR (CD2Cl2): δ 148.2, 131.7, 130.7, 129.2, 56.4, 30.0, 23.9.
31P{1H}: 44.6 (d, J ) ∼0) 57.0 (d, J ) ∼0). IR (KBr): ν 2179
cm-1 (CtN). Mass spec FAB (m/z): 1010 (Pd2(dppe)2; 1009.7),
1093 (Pd2(dppe)2(CN-t-Bu); 1092.8). UV-vis (CH3CN): 420 nm
(28 600 M-1 cm-1).
{[Pd2(dppp)2(CN-t-Bu)2](ClO4)2}n (5). Under inert atmosphere
in the dark, {[Pd2(CN-t-Bu)4Cl2] (15 mg, 0.024 mmol) was
dissolved in 50 mL of acetonitrile and 5.4 mg (0.051 mmol) of
LiClO4. A 21.1 mg (0.051 mmol) amount of dppp was dissolved
in 50 mL of acetonitrile in another flask. The dppp solution was
1494 Inorganic Chemistry, Vol. 43, No. 4, 2004

Organometallic Oligomers Based on dmb
Chart 5
100/S spectrometer. XRD (X-ray powder diffraction) data were
acquired on a Rigaku/USA Inc. diffractometer with a copper anode
operating under a 30 mA current and a 40 kV tension. TGA were
acquired on a TGA 7 of Perkin-Elmer instrument between 50 and
650 °C at 3°/min under nitrogen atmosphere.
Crystallography. All thee crystals were grown by vapor
diffusion using acetone-tert-butyl methyl ether at 23 °C. Single
crystals were coated with Paratone-N oil, mounted using a glass
fiber, and frozen in the cold nitrogen stream of the goniometer. A
hemisphere of data was collected on a Bruker AXS P4/SMART
1000 diffractometer located at the University of New Brunswick
using ω and θ scans with a scan width of 0.3° and using expo-
sure times of 30 s for [Cu(dppe)(CN-t-Bu)2]BF4 (1), 10 s for
[Ag(dppe)(CN-t-Bu)2]BF4 (2) and [Cu(dppp)(CN-t-Bu)2]BF4 (3),
and 25 s for [Ag2(dppp)2](BF4)2. The CCD detector distance was
5 cm. The data were reduced (SAINT)14 and corrected for
absorption (SADABS).15 The structures were solved by direct
methods and refined by full-matrix least squares on F (SHELX-
TL).15,16 For [Cu(dppe)(CN-t-Bu)2]BF4 (1), one of the tert-butyl
groups was disordered and the site occupancy determined using
an isotropic model as 0.75 (C(34)-C(36)) and 0.25 (C(34A)-
C(36A)) and fixed in subsequent refinement cycles. All non-
hydrogen atoms were refined anisotropically. Hydrogen atoms were
found in Fourier difference maps and refined isotropically with the
exception of the hydrogen atoms in the disordered group. Hydrogen
atoms of the major component were included in calculated positions
and refined as a riding model C(34)-C(36). Hydrogen atoms at
C(34A)-C(36A) were omitted. A rigid model does exist and means
the x, y, z, and U are not refined. A riding model means the x, y,
and z change as x, y, and z of the atom they are bonded to change
and U is taken as 1.2-1.5 (depending on type) of Ueq of the atom
it rides on. The hydrogen atoms of the major component were
treated as a rigid model. So the hydrogen atoms at C(34)-C(36)
were included in calculated positions and refined (using a rigid
model), but the hydrogen atoms at C(34A)-C(36A) were omitted.
For [Ag(dppe)(CN-t-Bu)2]BF4 (2), one of the t-Bu groups was
disordered and the site occupancy determined using an isotropic
model as 0.33 (C(8)-C(10)), 0.33 (C(8A)-C(10A), and 0.33
(C(8B)-C(10B)) and fixed in subsequent refinement cycles. All
non-hydrogen atoms were refined anisotropically with the exception
of the disordered t-Bu group. Hydrogen atoms were located in
Fourier difference maps and refined isotropically with the exception
of the methyl hydrogens at C(8)-C(10), C(8A)-C(10A) and
C(8B)-C(10B), which were omitted. For [Cu(dppp)(CN-t-Bu)2]-
BF4 (3), the BF4 anion and one of the t-Bu group was disordered
and the site occupancy was determined using an isotropic model
as 0.75 (F(1)-F(3)), 0.25 (F(1A)-F(3A), 0.7 (C(10)-C(12)), and
0.3 (C(10A)-C(12A)) and was fixed in the subsequent refinement
cycles. All non-hydrogen atoms were refined anisotropically.
Hydrogen atoms were located in Fourier difference maps and
refined isotropically with the exception of the methyl hydrogens
at C(6) which were included in calculated positions and refined
using a riding model. Hydrogen atoms at C(10A)-C(12A) were
omitted. For [Ag2(dppp)2](BF4)2, the BF4 anion was disordered and
the site occupancy determined using an isotropic model as 0.75
(F(2)-F(4)) and 0.25 (F(2A)-F(4A) and fixed in subsequent
refinement cycles. All non-hydrogen atoms were refined anisotro-
pically. Hydrogen atoms were located in Fourier difference maps
and refined isotropically.
Intrinsic Viscosity. The oligomeric nature of the materials in
solution was qualitatively established from the measurements of
the intrinsic viscosity using the universal standard polymethyl
methacrylate from Aldrich (Mn ) 12 000, 15 000, 120 000, and
320 000). All measurements were repeated 5 times for greater
accuracy. Although the results were checked against the known
oligomer {[Ag(dmb)2]BF4}n (Mn ) 4000),4e the results are still at
the lower end of the method’s accuracy. Only an approximate value
of number of units can be obtained.
Computer Modeling. The calculations were performed using
the commercially available PC model from Serena Software (version
7.0), which uses the MMX empirical model. No constraint on bond
distances and angles was applied to ensure that deviations from
normal geometry were depicted. The program sets by default a N+
for any tetravalent nitrogen, and unrealistic intramolecular N+‚‚‚
N+ repulsions are computed. The isocyanide group behaves as a
neutral fragment. To overcome this problem, CtN-R was replaced
by the CtC-R group. These fragments exhibit relatively the same
dimension. The method was checked against X-ray data for
[M(dppe)(CN-t-Bu)2]+ (M ) Cu, Ag) and [Cu(dppp)(CN-t-Bu)2]+
(see text).
Results and Discussion
Model Compounds. The dppe17 and dppp11,18 ligands can
act either as chelates or bridging species on both Cu(I) and
Ag(I) ions according to the literature. Because no crystal
suitable for X-ray diffraction studies has been obtained for
the reported oligomers in this work and no data on complexes
of the type [M(diphos)(CNR)]+ are reported in the Cam-
bridge Databank, the “chelate vs bridging” behavior has been
addressed by synthesizing and characterizing the model
mononuclear compounds [M(dppe)(CN-t-Bu)2]BF4 (M ) Cu
(1), Ag (2)) and [Cu(dppp)(CN-t-Bu)2]BF4 (3). This mono-
dentate CN-t-Bu ligand can adequately mimic both the
electronic density and steric behavior of dmb (Chart 5).The
syntheses proceed from a 1:2 (M/t-BuNC) stoichiometric
reaction between the starting materials [M(dppe)(BF4)] or
19
[M2(dppp)2](BF4)2 and the isocyanide. These compounds
crystallize easily and have been characterized by X-ray
crystallography (Tables 2 and 3; Figures 1 and 2). The chelate
form for these diphosphines is observed, where the 5- and
6-membered rings for the dppe and dppp species exhibit
puckered and chair structures, respectively. The t-BuNC
(17) (a) Albano, V. C.; Bellon, P. L.; Ciani, G. J. Chem. Soc., Dalton Trans.
1972, 1938. (b) Chi-Chang, L.; Yong-Shou, L.; Li, L. Jiegou Huaxue
1993, 12, 286 (also Cambridge Structural Database). (c) Saravanab-
harathi, D.; Monika; Venugopalan, P.; Samuelson, A. G. Polyhedron
2002, 21, 2433. (d) Semmelmann, M., Ph.D. Dissertation, Universita¨t
Karlsruhe, 1997; p 35.
(18) (a) Affandi, D.; Berners-Price, S. J.; Effendy, Harvey, P. J.; Healy, P.
C.; Ruch, B. E.; White, A. H. J. Chem. Soc., Dalton Trans. 1997,
1411. (b) Tiekink, E. R. T. Acta Crystallogr. 1990, 46c, 1933. (c)
Brandys, M.-C.; Puddephatt, R. J. Chem. Commun. 2001, 1508. (d)
Xie, W.-G.; Wang, R.-W.; Xiong, Y.-F.; Yang, R.-N.; Wang, D.-M.;
Jin, D.-M.; Chen, L.-R.; Luo, B.-S. Jiegou Huaxue 1997, 16, 293.
See also the Cambridge Databank. (e) Ferrer, M.; Rossel, O.; Seco,
M.; Soler, M.; Font-Bardia, M.; Solans, X.; de Montauzon, D. J.
Organomet. Chem. 2000, 598, 215.
(14) SAINT 6.02; Bruker AXS, Inc.: Madison, WI, 1997-1999.
(15) Sheldrick, G. SADABS; Bruker AXS, Inc.: Madison, WI, 1999.
(16) Sheldrick, G. SHELXTL 5.1; Bruker AXS, Inc.: Madison, WI, 1997.
Inorganic Chemistry, Vol. 43, No. 4, 2004 1495

Fournier et al.
Table 2. Crystallographic Data for 1-3
[Cu(dppe)(CN-t-Bu)2](BF4) (1)
[Cu(dppp)(CN-t-Bu)2](BF4) (3)
[Ag(dppe)(CN-t-Bu)2](BF4) (2)
formula
fw
C36H42BCuF4N2P2
715.01
C37H44BCuF4N2P2
729.03
C36H42AgBF4N2P2
759.34
cryst size
lattice
space group
0.28 × 0.45 × 0.50
monoclinic
P21/n
0.25 × 0.30 × 0.40
monoclinic
P21/c
0.40 × 0.45 × 0.45
monoclinic
P21/n
a, Å
b, Å
c, Å
14.0252(15)
10.2034(11)
25.515(2)
90
103.765(2)
90
3546.4(6)
4
1.339
1488
0.755
198(1)
0.0289
15.5433(9)
11.2094(6)
21.4362(12)
90
92.483(1)
90
3731.3(4)
4
1.298
1520
0.719
173(1)
0.0327
14.1130(8)
10.2075(6)
25.8175(16)
90
103.381(1)
90
3618.3(4)
4
1.394
1560
0.693
173(1)
0.0292
R, deg
â, deg
γ, deg
V, Å3
Z
F(calcd), g cm-3
F(000)
µ(Mo KR), mm-1
temp, K
R1a
wR2b
0.0785
0.0976
0.0828
no. of observns (I > 2.00σ(I))
no. of variables
6101
577
8479
642
8217
556
a R1 ) ∑||Fo| - |Fc||/∑|Fo|. b wR2 ) (∑[w(Fo Fc )2]/∑[Fo ])1/2. Weight for 1 ) 1/[σ2(Fo ) + (0.0463P)2 + (1.7267P)], weight for 2 ) 1/[σ2(Fo ) +
2 -
2
4
2
2
(0.0498P)2 + (1.9892P)], and weight for 3 ) 1/[σ2(Fo ) + (0.0569P)2 + (0.6494P)], where P ) (max(Fo , 0) + 2Fc )/3.
2
2
2
Figure 1. Molecular structure for [Ag(dppe)(CN-t-Bu)2]BF4 (2). The
ellipsoids are shown at 30% probability. The H atoms and BF4 ion are
not shown for clarity. The compound is isostructural to [Cu(dppe)(CN-t-
Bu)2]BF4 (1) (see Supporting Information).
Figure 2. Molecular structure for [Cu(dppp)(CN-t-Bu)2]BF4 (3). The
ellipsoids are shown at 30% probability. The H atoms and the BF4 ion
are not shown for clarity.
-
-
ligands coordinate the two remaining tetrahedral positions
of the M atoms, and the M-P, M-C, and CtN distances
are normal (Table 3). Some deviations from linearity of the
MCN angles, which are on average 173 and 169° for M )
Cu and Ag in the [M(dppe)(CN-t-Bu)2]BF4 complexes,
respectively, and 172° for [Cu(dppp)(CN-t-Bu)2]BF4, are
observed. The PMP and CMC angles are smaller and greater,
respectively, than the ideal tetrahedral angle, due to the
smaller bite angle of the chelating diphos ligand.
Other related d9-d9 Pd2 dimers have been reported in the
literature including the M2(diphos)2(CNR)22+ complexes and
the Pd2(dppp)22+ species, where M ) Pd or Pt and R ) Me,
2,4,6-Me3C6H2, and 2,6-Me2C6H3.20 Their structures consist
of an unsupported Pd-Pd bond with two square planar Pd
fragments forming angles of 84-88°.20 The two diphosphine
ligands are chelating each of the Pd atoms via one of the
equatorial and the axial positions. The remaining equatorial
coordination sites are occupied by the isocyanide ligands.
No crystal suitable for X-ray analysis was obtained for
the dimers in this work. The 31P NMR spectra exhibit 2
resonances associated with P atoms coordinated at the axial
and equatorial positions. The 2J(P, P) values are very small,
The model compounds [Pd2(diphos)2(CN-t-Bu)2](ClO4)2
(diphos ) dppe (4), dppp (5)) were prepared in one step
from the starting Pd2(CN-t-Bu)4Cl2 complex (Scheme 1).
2+
(19) The dication is isostructural to Au2(dppp)2
: Brandys, M.-C.;
Puddephatt, R. J. Chem. Commun. 2001, 1280. Moreover, a distinctive
difference is noticed in Ag-P distances (2.3797(4) and 2.3890(4) Å)
between the unsaturated Ag2(dppp)22+ cation (shorter than 0.1 Å) and
the saturated Ag(dppe)(CN-t-Bu)2 species. An electronic effect is
likely to be at the origin for this difference. In addition, the PAgP
(20) (a) Tanase, T.; Kawahara, Ukaji, H.; Kobayashi, K.; Yamazaki, H.;
Yamamoto, Y. Inorg. Chem. 1993, 32, 3682. (b) Tanase, T.; Ukaji,
H.; Kudo, Y.; Ohno, M.; Kobayashi, K.; Yamamoto, Y. Organome-
tallics 1994, 13, 1374. (c) Lindsay, C. H.; Benner, L. S.; Balch, A. L.
Inorg. Chem. 1980, 19, 3503. (d) Budzelaar, P. H. M.; van Leeuwen,
P. W. N. M.; Roobeek, C. F. Organometallics 1992, 11, 23.
+
angle (159°) strongly deviates from linearity, witnessing the important
-
Ag+‚‚‚F-BF3 interactions.
1496 Inorganic Chemistry, Vol. 43, No. 4, 2004

Organometallic Oligomers Based on dmb
Table 3. Selected Bond Distances (Å) and Angles (deg) for 1-3
[Cu(dppe)(CN-t-Bu)2]BF4 (1)
[Ag(dppe)(CN-t-Bu)2]BF4 (2)
[Cu(dppp)(CN-t-Bu)2]BF4 (3)
d(MP)
d(MC)
d(CtN)
2.2979(5)
2.3038(5)
1.9245(18)
1.9306(18)
1.144(2)
2.4939(5)
2.4982(5)
2.145(2)
2.1719(19)
1.141(3)
1.139(3)
2.2636(4)
2.2898(5)
1.9176(18)
1.935(2)
1.142(2)
1.132(3)
1.145(2)
PMP
CMC
CMP
89.088(17)
120.19(1)
112.39(5)
108.35(5)
116.61(5)
105.69(5)
175.55(16)
170.33(16)
84.504(16)
119.67(8)
114.21(6)
108.57(6)
118.28(5)
106.01(6)
174.96(18)
163.54(18)
98.737(17)
113.54(8)
118.98(5)
110.63(6)
108.61(5)
104.22(6)
170.86(15)
172.85(18)
MCN
Scheme 1
which are consistent with two interacting 31P nuclei forming
a PPdP angle of ∼90°. The UV-visible spectra also exhibit
a strong absorption at ∼414 nm, characteristic of the presence
of a Pd-Pd bond (discussed below).
dmb Oligomers. The colorless Cu and Ag materials are
obtained by reacting the corresponding starting [M(dppe)-
(BF4)] or [M2(dppp)2](BF4)2 materials with dmb in excess.
The yellow Pd2 polymers are obtained differently by reacting
the d9-d9 dimer Pd2(dmb)2Cl2 with 2 equiv of dppe or dppp
according to
Pd2(dmb)2Cl2 + 2diphos f
(1/n)Pd2(diphos)2(dmb)2+n + dmb + 2Cl- (1)
where diphos is dppe (10; 79% yield) or dppp (11; 86%
yield). The close similarity in the 31P NMR, IR, and UV-
vis spectra between the model compounds and the oligomers
suggests that the “Pd2(diphos)2(CNR)22+” unit is present in
the materials, including the chelate structure of the “Pd-
(diphos)” fragment.
All investigated dmb-containing materials are amorphous
according to the XRD patterns (see examples in the Sup-
porting Information), and no crystal suitable for single-crystal
X-ray studies was obtained despite numerous attempts.
The TGA traces for both the t-BuNC model compounds
and dmb-containing materials indicate two thermal events.
The low-temperature event corresponds to the loss of the
isocyanides, and the higher temperature event, to the loss of
the diphosphines and counteranion (see Supporting Informa-
tion for details). The weight losses are consistent with the
isocyanide/diphosphine/counterion ratio, taking into account
the uncertainties. The comparison between the t-BuNC model
compounds and dmb-containing materials indicates that the
t-BuNC ligand is generally lost at a lower temperature with
Figure 3. TGA traces for [Cu(dppe)(CN-t-Bu)2]BF4 (1, up) and {[Cu-
(dppe)(dmb)]BF4}n (6, down). The broken line is the first derivative of the
TGA traces.
respect to the dmb analogues (see Figure 3 as an example,
Supporting Information). For instance, the first weight loss
for [Cu(dppe)(CN-t-Bu)2]BF4 (3) occurs in the 160-224 °C
window, while it occurs at 178-334 °C for {[Cu(dppe)-
(dmb)]BF4}n (6). The first derivative traces exhibit inflection
points at 201.4 and 211.6 °C for [Cu(dppe)(CN-t-Bu)2]BF4
(3) and {[Cu(dppe)(dmb)]BF4}n (6), respectively.
The intrinsic viscosity measurements indicate that the Mn
values for {[Pd2(dppe)2(dmb)](ClO4)2}n and {[Pd2(dppp)2-
(dmb)](ClO4)2}n are 11 800 and 12 200 ((200), respectively.
The average number of Pd2 units is ∼8-9. Similarly, the
{[Cu(diphos)(dmb)]BF4}n materials exhibit Mn of (dppe, 6;
Inorganic Chemistry, Vol. 43, No. 4, 2004 1497

Fournier et al.
Chart 6
Chart 7
6570) and (dppp, 8; 6870), which also indicate the presence
of oligomers. Conversely, the Ag materials dissolve far more
rapidly than those of Cu and Pd2 species, and their corre-
sponding acetonitrile solutions exhibit no time difference with
the pure solvent. This result indicates the presence of
extensively dissociated materials in solution. All in all, the
data are consistent with the formulation shown in Chart 6
for these new materials.
a degree of reliability of the method employed. These
complexes are the three model Cu and Ag complexes
9c
described above and the X-raycharacterized Pd2(dmb)2Cl4
4+
and [Pd(dppe)(dmb)]2 (Chart 7).22
The comparison between MMX and X-ray data for the
+
M(diphos)(CN-t-Bu)2 complexes is presented in Table 4.
The computations give satisfactory results in M-P distances
(the largest difference is 0.07 Å, 2.8%) and skeleton angles
(the largest difference is ∼5°, but usually it is ∼1°) for the
Cu complexes, but worse comparisons are noticed for the
Ag species. The M-C and CtN distances are respectively
under- and overestimated. Their sums, however, provide a
better comparison. Similar observations are made for the
The chemical analysis and the integration of the 1H NMR
signals are consistent with the 1:1.x diphos/dmb stoichiom-
etries for the {M(diphos)(dmb)+}n (M ) Cu, Ag) oligomers,
where x is a small number (∼1-2) and is due to the presence
of dmb acting as end-of-chain units. The presence of weak
IR peaks associated with uncoordinated CtNR groups
(∼2130 cm-1) is noted for the Ag-containing oligomers in
the solid state, which is consistent with end-of-chain
dmb units. For the {Cu(diphos)(dmb)+}n (6 and 8)
and {Pd2(diphos)2(dmb)2+}n materials (10 and 11), there is
no evidence for such an IR peak in the solid state, suggesting
that the signal may be weak or the oligomers may be cyclic.
Using the spin-coating technique, or by simply evaporating
an acetonitrile solution, these 6 materials form clear films
with no sign of a heterogeneous area under the microscope.
While the films formed by the Ag oligomers are found to
be brittle, stand-alone films are obtained for the Cu and Pd2
materials. In one case, {[Cu(dppe)(dmb)]BF4}n (6), a glass
transition at Tg ) 81.5 °C (∆Cp ) 0.43 J/(g deg)) is
reproducibly observed in the DSC traces.
4+
Pd2(dmb)2Cl4 and [Pd2(dppe)(dmb)]2 complexes,22 where
bond lengths and angles are well reproduced in the calcula-
tions, except that the Pd-P distance is somewhat off. The
distance is longer by about 0.1 Å.
2+
The structures for the chiral Pd2(diphos)2(CN-t-Bu)2
complexes (diphos ) dppe (4), dppp (5)) have been modeled
as well (see Figure 4 for example). The computed Pd-Pd
(2.66), Pd-Pax (2.36), Pd-Peq (2.36), and Pd-C (1.89 Å)
distances compare reasonably well with those found experi-
mentally for the corresponding aryl species (2.60-2.62,
2.32-2.36, 2.30-2.33, 1.96-1.97 Å, respectively).20 The
computed structures exhibit a twisted geometry where the
dihedral angle (CPdPdC) is about 77-78°, an angle that is
smaller than those seen for the above compounds (86°).20
This difference reflects the presence of greater steric
hindrance for the tert-butyl groups in comparison with the
diphos-phenyl fragments. Full rotation about the Pd-Pd bond
is severely hindered, so inversion of configuration is impos-
sible.
The Pd2 materials belong to a broader family of organo-
metallic oligomers, which contains unsupported M2 bonds
in the backbone. The number of examples is still somewhat
limited,21 but the incorporation of a Pd2 bond is, to our
knowledge, unprecedented.
The replacement of the two t-BuNC groups in these
computed models by one dmb bridging ligand generates the
dinuclear “Pd2(diphos)2(dmb)2+” complex, where the Pd-
Pd bond is now supported by a dmb ligand (Figure 5). While
most distances remained unchanged, significant changes are
noted in PdCN (158-169°), and dihedral angles (∼73°),
witnessing significant ring stress. In addition, the PPdPdP
axis now exhibits a pronounced arch where the PPdPd angles
are in the range of 160°. This structure is not favored.
Similarly, the tetranuclear structure for “[Pd2(diphos)2-
(dmb)]24+” exhibits a macrocycle composed of two Pd-Pd-
(Z-dmb) units where the two Pd-Pd axes are placed parallel
to each other (Figure 6). Although no major distortions are
noted in the structure, the dmb ligand is found quasi-
Computer Modeling. Modeling is used to qualitatively
address two issues. The first one concerns why oligomer
structures are favored in this work, while, in other related
complexes, dimer species are observed. The second one
concerns what we can extract from the computed structures
in terms of predicted properties. The first series of computa-
tions deals with the comparison between computed and X-ray
structures of related Cu, Ag, and Pd2 complexes, providing
(21) (a) Tenhaeff, S. C.; Tyler, D. R. Organometallics 1991, 10, 473. (b)
Tenhaeff, S. C.; Tyler, D. R. J. Chem. Soc., Chem. Commun. 1989,
1459. (c) Tenhaeff, S. C.; Tyler, D. R. Organometallics 1992, 11,
1466. (d) Tenhaeff, S. C.; Tyler, D. R. Organometallics 1991, 10,
1116. (e) Male, J. L.; Lindsfors, B. E.; Covert, J.; Tyler, D. R.
Macromolecules 1997, 30, 6404. (f) Nieckarz, G. F.; Tyler, D. R.
Inorg. Chim. Acta 1996, 242, 303. (g) Male, J. L.; Yoon, M.; Glenn,
A, G.; Weakly, T. J. R.; Tyler, D. R. Macromolecules 1999, 32, 3898.
(h) Nieckarz, G. F.; Litty, J. J.; Tyler, D. R. J. Organomet. Chem.
1998, 554, 19.
(22) The X-ray structure for [Pd(dppe)(dmb)]2(PF6)4 will be reported
elsewhere: Fortin, J.-F.; Harvey, P. D. To be published.
1498 Inorganic Chemistry, Vol. 43, No. 4, 2004

Organometallic Oligomers Based on dmb
Table 4. Comparison of MMX and X-ray Data for 1-3, Pd2(dmb)2Cl4, and [Pd(diphos)(dmb)]2 Complexesa
4+
Cu(dppe)(CN-t-Bu)2+ (1)
Cu(dppp)(CN-t-Bu)2+ (3)
Ag(dppe)(CN-t-Bu)2+ (2)
d(M-P), Å
d(M-C), Å
d(CtN), Å
2.27 (2.30)
1.82 (1.93)
1.19 (1.15)
2.27 (2.28)
1.82 (1.92)
1.19 (1.14)
2.43 (2.50)
1.99 (2.16)
1.18 (1.14)
(PMP), deg
(CMC), deg
(MCN), deg
(PMC), deg
85.2 (89.1)
121.4 (120.2)
171.6 (172.8)
110.7 (110.8)
93.7 (98.7)
118.6 (119.7)
172.5 (171.9)
110.9 (110.9)
79.4 (84.5)
122.0 (119.7)
171.7 (169.3)
108.0 (118.8)
b
4+ c
4+
Pd2(dmb)2Cl4
[Pd(dppe)(dmb)]2
[Pd(dppp)(dmb)]2
d(Pd-P), Å
d(Pd-C), Å
d(CtN), Å
2.38 (2.27)
1.93 (2.02)
1.20 (1.13)
2.38
1.93
1.20
1.93 (1.97)
1.14 (1.13)
(PPdP), deg
(CPdC), deg
(PdCN), deg
(PPdC), degd
78.9 (82.7)
92.5 (90.6)
174.3 (176.0)
94.3 (93.4)
82.7
94.2
174.0
91.6
178.0 (178.6)
177.5 (178.6)
a The X-ray data are placed in parentheses and are from this work unless stated otherwise. b From ref a. c From ref b. d Only the angles approaching 90°
of the square planar geometry are provided.
2+
-
Figure 4. Computer model for Pd2(dppp)2(CN-t-Bu)2 (5). The ClO4
ion is not shown.
Figure 5. Computer modeling of a fictitious dimer Pd2(dppp)2(dmb)2+
The stress in the “Pd2(dmb)” ring makes this structure improbable.
.
encapsulated between the four diphos chelates pressed
between the phenyl groups. Numerous C-H‚‚‚H-C contacts
(2.257, 2.268 and 2.408 Å, for the structure shown in Figure
6) are noted indicating the presence of some steric interac-
tions. These interactions are also felt by a small increase in
calculated Pd-Pax distances (from 2.38 to 2.39-2.40 Å) and
a small deviation of the PdPdPax angles (∼169° in compari-
son with ∼174° calculated for the model compounds
Pd2(diphos)2(CN-t-Bu)22+; Figure 4).
On the other hand, the computed models for the
{Pd2(diphos)2(dmb)2+}n oligomers (see Figure 7 as an
example) exhibit dmb ligands in their gauche conformation
that are significantly less encapsulated than the above dimer
and phenyl groups with no or a few close C-H‚‚‚H-C
contacts. For instance, the shortest C-H‚‚‚H-C distance is
2.487 Å in this case. The average computed PdCN angles
are ∼176.5°. In addition, multiple conformations (relative
orientation of Pd2 units with respect to each other) are
possible, where the Pd-Pd bonds are never found parallel
to each other. Computations performed on 3 identical (same
stereoisomer) or different units (both enantiomers) show that
stereoregularity seems impossible at least for short fragments.
This result may explain the amorphous morphology observed
(XRD) for the solid material.
The structure of a cyclic “Cu2(diphos)2(dmb)22+” dimer
has also been examined and consists of a similar geometry
4+
to the [Pd(dppe)(dmb)]2 discussed above. The difference
is that the CMC angle is tetrahedral instead of 90°. This
macrocycle exhibits some ring stress (see Supporting Infor-
mation). For instance, the computed PdCN angles range from
165 to 171° in comparison with computed angles of 172.5°
for the mononuclear Cu(dppp)(CN-t-Bu)2+ (3) (Table 4). This
result contrasts greatly with the d8-d8 compound [Pd(dppe)-
(dmb)]24+ and suggests that a simple increase in CMC angle
from 90 to 109.5° is enough to create a ring stress and to
drive the oligomer formation.23
Electronic Spectra. The {[M(diphos)(dmb)]BF4}n and
[M(diphos)(CN-t-Bu)2]BF4 species (M ) Cu, Ag; diphos )
(23) The computed segments for {Cu(dppp)(dmb)+}n exhibit an average
PdCN angle of 175° indicating the absence of stress in the chain.
Inorganic Chemistry, Vol. 43, No. 4, 2004 1499

Fournier et al.
Figure 9. Comparison of the UV-vis spectra of {[Pd2(dppe)2(dmb)]-
(ClO4)2}n (10) in PrCN at 298 (s) and 77 K (---).
NR and PPh2 groups. This assignment is based on the recent
theoretical findings (EHMO and DFT) and spectroscopic
experimental data for the mixed-ligand related dimer complex
[Cu2(dppm)2(O2CMe)]+ 24 and the monomer [M(CN-t-
Bu)4]+.4b
The electronic absorption spectra for the Pd2(diphos)2(CN-
t-Bu)22+ model compounds and the {Pd2(diphos)2(dmb)2+}n
polymers in PrCN exhibit narrow featureless absorptions at
293 K at 420 (4) and 414 nm (5) for the dimers and at 428
(10) and 416 nm (11) for the polymers with diphos ) dppe
and dppp, respectively (see Figure 9 as an example). These
values are slightly blue-shifted with respect to the starting
material Pd2(dmb)2Cl2 (444 nm) but compare favorably with
that of the related d9-d9 dimer Pd2(dppm)2Cl2 (418 nm).26
This absorption is easily assigned to dσ f dσ* as previously
demonstrated by Sourisseau and co-workers for Pd2(dppm)2-
Cl2 (by resonance Raman spectroscopy),25 and by this group
for Pd2(dmb)2Cl2 (EHMO,26 DFT,27 and FT-Raman spec-
troscopy second moment band analysis26). The electronic
bands associated with dσ f dσ* electronic transitions for
M2-bonded species generally exhibit low energy, high
intensity (ꢀ > 25 000 M-1 cm-1; Table 5), and small fwhm
(full width at half-maximum; 2200 < fwhm < 2700 cm-1
at 293 K), as seen for these two materials (2540 and 2670
cm-1 for the dppe and dppp species, respectively). Upon
cooling of the {Pd2(diphos)2(dmb)2+}n-containing solution
from 293 to 77 K, the λmax and fwhm of the dσ f dσ* bands
decrease slightly down to 424 and 406 nm and 2500 and
2300 cm-1 for dppe (10) and dppp (11), respectively.
Figure 6. Top and side view of a computer model for the fictitious
[Pd2(diphos)2(dmb)]24+ complex. This structure exhibits close C-H‚‚‚H-C
contacts.
Figure 7. Computer model for a fragment of the {Pd2(dppp)2(dmb)2+
}
n
oligomer (10). This is one possible conformation and one pair of the same
-
enantiomer. Other combinations exist. The ClO4 ion is not shown.
+
Solid-State Luminescence. The M(diphos)(CN-t-Bu)2
model compounds (1-3) and {M(diphos)(dmb)+}n polymers
(M ) Cu, Ag; diphos ) dppe, dppp; 6-9) exhibit broad
luminescence found between ∼480 and 550 nm in the solid
state (Figure 8). The Stokes shift is very large (>17 000
cm-1), and the emission lifetimes range in the microsecond
time scale (18 < τe < 48 µs; see detail in Table 6). This
experimental evidence indicates that the emission is phos-
phorescence. These emission maxima and lifetimes compare
Figure 8. UV-vis spectra (left-hand side) for {[Ag(dppe)(dmb)]BF4}n
(7) in acetonitrile at 298 K and solid-state emission spectra (right-hand side)
for the same material at 298 K.
dppe, dppp; 1-3, 6-9) exhibit a structureless low-energy
absorption at 272 ( 2 nm, with absorptivities ranging from
23 000 to 34 000 M-1 cm-1(see Experimental Section for
data and Figure 8 as an example). This electronic band is
assigned to a metal-to-ligand charge transfer (MLCT), where
the ligand manifold comprises both the π-systems of the Ct
(24) Harvey, P. D.; Drouin, M.; Zhang, T. Inorg. Chem. 1997, 36, 4998.
(25) Alves, O. L.; Virtoge, M.-C.; Sourisseau, C. NouV. J. Chim. 1983, 7,
231.
(26) Harvey, P. D.; Murtaza, Z. Inorg. Chem. 1993, 32, 4721.
(27) Provencher, R.; Harvey, P. D. Inorg. Chem. 1996, 35, 2113.
1500 Inorganic Chemistry, Vol. 43, No. 4, 2004

Organometallic Oligomers Based on dmb
Table 5. UV-Vis Data for 4, 5, 10, and 11
ACN/293 K
ꢀ (M-1 cm-1
PrCN/293 K
PrCN/77 K
fwhm (cm-1
)
compds
λmax (nm)
)
λ
max (nm)
fwhm (cm-1
)
λ
max (nm)
[Pd2(dppe)2(CN-t-Bu)2](ClO4)2 (4)
[Pd2(dppp)2(CN-t-Bu)2](ClO4)2 (5)
{[Pd2(dppe)2(dmb)](ClO4)2}n (10)
{[Pd2(dppp)2(dmb)](ClO4)2}n (11)
420
416
418
414
28 600
26 000
28 000
26 100
422
418
420
416
2200
2100
2700
2500
416
410
424
406
1800
1900
2500
2300
+
Table 6. Solid-State Emission Data for the M(diphos)(CN-t-Bu)2
Model Compounds and {M(diphos)(dmb)+}n Oligomers
Concluding Remarks. The bridging ligand dmb exhibits
a very strong tendency to assemble metallic fragments to
provide organometallic oligomeric materials. This observa-
tion greatly conflicts with most works reported on this ligand
in the literature, where dimeric species are frequently
observed.1 The fact that many of these materials are
amorphous renders their reliable characterization very dif-
ficult and contributes to the lower number of literature reports
on dmb-containing materials with respect to the dimer
counterparts. This paper reports another strategy for the
synthesis of dmb-based organometallic polymers, which
consists of using bulky metallic fragments such as the
Pd2(diphos)2 units. Steric hindrance prevents dmb from
bridging the Pd2 bond (presumably due to a large unfavorable
twist CPdPdC angle) and also from making the unobserved
dimer [Pd2(diphos)2(dmb)+2]2.
compds
λ
max emission (nm)
τe (µs)
[Cu(dppe)(CN-t-Bu)2](BF4) (1)
[Ag(dppe)(CN-t-Bu)2](BF4) (2)
[Cu(dppp)(CN-t-Bu)2](BF4) (3)
{[Cu(dppe)(dmb)](BF4)}n (6)
{[Ag(dppe)(dmb)](BF4)}n (7)
{[Cu(dppp)(dmb)](BF4)}n (8)
{[Ag(dppp)(dmb)](BF4)}n (9)
540
515
478
480
548
500
480
42 ( 4
21 ( 4
18 ( 3
38 ( 5
27 ( 2
22 ( 4
48 ( 4
favorably to those of other tetravalent mononuclear,4b,28
dinuclear,29,30 trinuclear,29,31 and polynuclear species.29,32 The
emissive excited state responsible for the emission in these
3
cases is assigned to a MLCT as described above.
2+
Conversely, the Pd2(diphos)2(CN-t-Bu)2 (4 and 5) and
{Pd2(diphos)2(dmb)2+}n (10 and 11) species are found to be
nonluminescent at 293 K in the solid state. This lack of
luminescence has also been observed for other d9-d9 dimers
such as Pd2(dppm)2Cl2 and Pd2(dmb)2Cl2, for example.33 This
behavior has been discussed previously in terms of an
efficient photoinduced homolytic Pd-Pd bond cleavage,
followed by a diradical recombination.26
Acknowledgment. This research was supported by the
Natural Sciences and Engineering Research Council of
Canada (NSERC).
Supporting Information Available: Pictures showing the
4+
computed structures for the fictitious [Pd2(diphos)2(dmb)]2
4+
and [Pd2(diphos)2(dmb)]2 complexes, XRD patterns for the
{[Ag(diphos)(dmb)]BF4}n polymers (diphos ) dppe, dppp), a table
gathering the TGA data, and X-ray crystallographic files for
[M(dppe)(CN-t-Bu)2]BF4 (M ) Cu (1), Ag (2)) and [Cu(dppp)-
(CN-t-Bu)2]BF4 (3) in CIF format. This material is available free
of charge via the Internet at http://pubs.acs.org.
(28) (a) Simon, J. A.; Palke, W. E.; Ford, P. C. Inorg. Chem. 1996, 35,
6413. (b) Crane, D. R.; DiBenedetto, J.; Palmer, C. E. A.; McMillin,
D. R.; Ford, P. C. Inorg. Chem. 1988, 27, 3698.
(29) Ford, P. C.; Cariati, E.; Bourassa, J. Chem. ReV. 1999, 99, 3625 and
the references therein.
(30) Piche´, D.; Harvey, P. D. Can J. Chem. 1994, 72, 705.
(31) Wang, C.-F.; Peng, S.-M.; Chan, C.-K.; Che, C.-M. Polyhedron 1996,
15, 1853.
IC034780Z
(32) (a) Cariati, E.; Roberto, D.; Ugo, R.; Ford, P. C.; Galli, S.; Sironi, A.
Chem. Mater. 2002, 14, 5116. (b) Herary, M.; Wootton, J. L.; Khan,
S. I.; Zink, J. I. Inorg. Chem. 1997, 36, 796. (c) Lai, D. C.; Zink, J.
I. Inorg. Chem. 1993, 32, 2594. (d) Henary, M.; Zink, J. I. Inorg.
Chem. 1991, 30, 3111.
(33) The Pd2(dmb)2Cl2 complex weakly luminesces in solution at 77 K
(λmax ) 625 nm; τe ) 71 ( 6 ns).23 The Pd2(diphos)2(CN-t-Bu)2+
and {Pd2(diphos)2(dmb)2+}n species also show some luminescence in
solution at 77 K between 510 and 560 nm with τe in the nanosecond
time scale as well.
Inorganic Chemistry, Vol. 43, No. 4, 2004 1501