Generation and insertion reactivity of cationic palladium complexes that contain halogenated alkyl ligands

Article abstract of DOI:10.1021/om034211z

The generation of cationic palladium complexes that contain halogenated alkyl ligands (R^X) and their reactivity with vinyl chloride, ethylene, and CO are described. {(ⁿHex)HC-(mim)₂}Pd(CHCl₂)Cl (1; ⁿHex = n-hexyl, mim = N-methylimidazol-2-yl) reacts with 0.5 equiv of [Li(Et₂O)_2.8][B(C₆F₅)₄] to form [{{(ⁿHex)HC(mim)₂}Pd(CHCl₂)}₂(μ- Cl)][B(C₆F₅)₄] as a 1:1 mixture of diastereomer (3a,b). 3a,b do not react with vinyl chloride. The reaction of 1 with 1 equiv of [Li(Et₂O)_2.8][B(C₆F₅)₄] in the presence of ethylene or CO yields [{(ⁿHex)HC-(mim)₂}Pd(CHCl₂)(L)][B(C₆ F₅)₄] adducts (L = ethylene (4), CO (5)). The reaction of (dppp)-Pd(ⁿC₃F₇)Me (7; dppp = 1,3-bis(diphenylphosphino)propane) with [HNMePh₂][B(C₆F₅)₄] yields [(dppp)Pd(ⁿC₃F₇)(NMePh₂)][B (C₆F₅)₄] (8). 8 does not react with vinyl chloride or ethylene but does react with CO to form [(dppp)Pd(ⁿC₃F₇)(CO)][B(C₆ F₅)₄] (9). 4, 5, and 9 do not undergo insertion under mild conditions. The reaction of (^tBu₂bipy)Pd(CH₂Cl)Cl (10; ^tBu₂bipy = 4,4′-di-tert-butyl-2,2′-bipyridine) with 0.5 equiv of [Li(Et₂O)_2.8][B(C₆F₅)₄] yields [{(^tBu₂bipy)Pd-(CH₂Cl)}₂(μ-Cl)][B (C₆F₅)₄] (11). In the presence of one equiv of [Li(Et₂O)_2.8][B(C₆F₅)₄], 11 reacts with vinyl chloride by net 1,2-insertion and β-Cl elimination to generate Pd-Cl⁺ species and allyl chloride and with CO at -78°C to form [(^tBu₂bipy)Pd(CH₂Cl)(CO)] [B(C₆F₅)₄] (12). At 20°C, 12 undergoes slow CO insertion followed by β-Cl elimination to generate Pd-Cl⁺ species and ketene. The reaction of (α-diimine)Pd(CH₂Cl)Cl (13; α-diimine = (2,6-ⁱPr₂-C₆H₃)N=CMeCMe= N(2,6-ⁱPr₂-C₆H₃)) with 1 equiv of [Li(Et₂O)_2.8][B(C₆F₅)₄] in the presence of vinyl chloride yields Pd-Cl⁺ species and allyl chloride, most likely via net 1,2-insertion and β-Cl elimination of a (α-diimine)Pd(CH₂Cl)(CH₂=CHCl)⁺ intermediate. In general, L₂Pd(R^X)(substrate)⁺ species undergo slower insertion than non-halogen-substituted L₂Pd(R)-(substrate)⁺ analogues.

Full text of DOI:10.1021/om034211z

600
Organometallics 2004, 23, 600-609
Gen er a tion a n d In ser tion Rea ctivity of Ca tion ic
P a lla d iu m Com p lexes Th a t Con ta in Ha logen a ted Alk yl
Liga n d s
Stephen R. Foley, Han Shen, Umair A. Qadeer, and Richard F. J ordan*
Department of Chemistry, The University of Chicago, 5735 South Ellis Avenue,
Chicago, Illinois 60637
Received October 1, 2003
The generation of cationic palladium complexes that contain halogenated alkyl ligands
(RX) and their reactivity with vinyl chloride, ethylene, and CO are described. {(nHex)HC-
(mim)2}Pd(CHCl2)Cl (1; nHex ) n-hexyl, mim ) N-methylimidazol-2-yl) reacts with 0.5 equiv
of [Li(Et2O)2.8][B(C6F5)4] to form [{{(nHex)HC(mim)2}Pd(CHCl2)}2(µ-Cl)][B(C6F5)4] as a 1:1
mixture of diastereomers (3a ,b). 3a ,b do not react with vinyl chloride. The reaction of 1
with 1 equiv of [Li(Et2O)2.8][B(C6F5)4] in the presence of ethylene or CO yields [{(nHex)HC-
(mim)2}Pd(CHCl2)(L)][B(C6F5)4] adducts (L ) ethylene (4), CO (5)). The reaction of (dppp)-
Pd(nC3F7)Me (7; dppp ) 1,3-bis(diphenylphosphino)propane) with [HNMePh2][B(C6F5)4] yields
[(dppp)Pd(nC3F7)(NMePh2)][B(C6F5)4] (8). 8 does not react with vinyl chloride or ethylene
but does react with CO to form [(dppp)Pd(nC3F7)(CO)][B(C6F5)4] (9). 4, 5, and 9 do not undergo
insertion under mild conditions. The reaction of (tBu2bipy)Pd(CH2Cl)Cl (10; tBu2bipy ) 4,4′-
di-tert-butyl-2,2′-bipyridine) with 0.5 equiv of [Li(Et2O)2.8][B(C6F5)4] yields [{(tBu2bipy)Pd-
(CH2Cl)}2(µ-Cl)][B(C6F5)4] (11). In the presence of one equiv of [Li(Et2O)2.8][B(C6F5)4], 11 reacts
with vinyl chloride by net 1,2-insertion and â-Cl elimination to generate Pd-Cl+ species
and allyl chloride and with CO at -78 °C to form [(tBu2bipy)Pd(CH2Cl)(CO)][B(C6F5)4] (12).
At 20 °C, 12 undergoes slow CO insertion followed by â-Cl elimination to generate Pd-Cl+
species and ketene. The reaction of (R-diimine)Pd(CH2Cl)Cl (13; R-diimine ) (2,6-iPr2-
C6H3)NdCMeCMedN(2,6-iPr2-C6H3)) with 1 equiv of [Li(Et2O)2.8][B(C6F5)4] in the presence
of vinyl chloride yields Pd-Cl+ species and allyl chloride, most likely via net 1,2-insertion
and â-Cl elimination of a (R-diimine)Pd(CH2Cl)(CH2dCHCl)+ intermediate. In general, L2-
Pd(RX)(substrate)+ species undergo slower insertion than non-halogen-substituted L2Pd(R)-
(substrate)+ analogues.
In tr od u ction
bipyridine (tBu2bipy), 1,3-bis(diphenylphosphino)pro-
pane (dppp), 1,2-bis(dimethylphosphino)ethane) by 2,1-
insertion to yield robust O-chelated L2Pd{CHClCH2C(d
O)Me}+ complexes. The VC 2,1-insertion regiochemistry
is favored in part because the alternative L2Pd{CH2-
CHClC(dO)Me}+ 1,2-insertion products would be de-
stabilized by placement of the electron-withdrawing Cl
and acyl substituents on the same carbon. However, L2-
Pd{CHClCH2C(dO)Me}+ species do not undergo chelate
ring opening or insertion reactions with VC, ethylene,
or CO.
The observation of VC 2,1-insertion of L2Pd{C(dO)-
Me}+ species suggests that it may be possible to direct
a 2,1-insertion polymerization of VC by using a head-
group (RX) that contains an electron-withdrawing halo-
gen substituent, which should be a weaker chelator than
an acyl group (Scheme 1). In this strategy, it is envi-
sioned that the L2Pd(RX)+ initiator would undergo an
electronically driven VC 2,1-insertion to yield L2Pd-
(CHClCH2RX)+, which is trapped by VC coordination
rather than by chelation. The electron-withdrawing R-Cl
substituent of the resulting L2Pd(CHClCH2RX)(VC)+
species would direct 2,1-insertion, leading to chain
growth.
The development of metal-catalyzed insertion polym-
erization reactions of vinyl halides is a challenging goal.1
Previously we showed that single-site olefin polymeri-
zation catalysts based on early or late transition metals
undergo net 1,2-insertion of vinyl chloride (VC), but the
resulting LnMCH2CHRCl species undergo â-Cl elimina-
tion to form LnMCl products and CH2dCHR olefins,
which precludes insertion polymerization.1a-c Similar
1,2-insertion/â-X elimination reactions of CH2dCHX
substrates (X ) F, Cl, Br) have been reported by other
groups.2 In an effort to circumvent â-Cl elimination, we
investigated the reaction of VC with cationic metal acyl
complexes.3 VC reacts with L2Pd{C(dO)Me}+ species
(L2 ) 4,4′-dimethyl-2,2′-bipyridine, 4,4′-di-tert-butyl-2,2′-
(1) (a) Stockland, R. A., J r.; J ordan, R. F. J . Am. Chem. Soc. 2000,
122, 6315. (b) Foley, S. R.; Stockland, R. A., J r.; Shen, H.; J ordan, R.
F. J . Am. Chem. Soc. 2003, 125, 4350. (c) Stockland, R. A., J r.; Foley,
S. R.; J ordan, R. F. J . Am. Chem. Soc. 2003, 125, 796. (d) Boffa, L. S.;
Novak, B. M. Chem. Rev. 2000, 100, 1479.
(2) (a) Strazisar, S. A.; Wolczanski, P. T. J . Am. Chem. Soc. 2001,
123, 4728. (b) Watson, L. A.; Yandulov, D. V.; Caulton, K. G. J . Am.
Chem. Soc. 2001, 123, 603. (c) Boone, H.; Athey, P. S.; Mullins, M. J .;
Philipp, D.; Muller, R.; Goddard, W. A. J . Am. Chem. Soc. 2002, 124,
8790. (d) Kang, M.; Sen, A.; Zakharov, L.; Rheingold, A. L. J . Am.
Chem. Soc. 2002, 124, 12080.
(3) Shen, H.; J ordan, R. F. Organometallics 2003, 22, 1878.
Metal alkyls containing R-halogen substituents are
10.1021/om034211z CCC: $27.50 © 2004 American Chemical Society
Publication on Web 12/31/2003

Pd Complexes with Halogenated Alkyl Ligands
Organometallics, Vol. 23, No. 3, 2004 601
Sch em e 1
Ch a r t 1a
a
Ar ) 2,6-iPr2-C6H3.
To probe the feasibility of Scheme 1 and how halogen
substituents on the alkyl ligand influence the reactivity
of late-metal olefin polymerization catalysts, we have
studied the generation and insertion chemistry of a set
of cationic LnPd(RX)+ complexes that contain haloge-
nated alkyl ligands (Chart 1). The complexes used for
this study were chosen for synthetic accessibility and
because the insertion reactivity of the corresponding Ln-
PdMe+ cations has been studied previously. The (nHex)-
HC(mim)2 (nHex ) n-hexyl; mim ) N-methylimidazol-
2-yl) ligand (A) was chosen because {(nHex)HC(mim)2}-
PdMe+ is an ethylene dimerization catalyst and Pd-
CHCl2 species are easily accessible in this system.11 The
dppp ligand (B) was chosen because (dppp)PdMe+ is
among the most active catalysts known for CO/ethylene
copolymerization.12 The tBu2bipy and R-diimine (R-
diimine ) (2,6-iPr2-C6H3)NdCMeCMedN(2,6-iPr2-C6H3))
ligands (C, D) were selected because (R2bipy)PdMe+ and
(R-diimine)PdMe+ are active for olefin dimerization and
polymerization, respectively, and the reactivity of these
species with VC has been studied in detail.1,13
quite common.4-6 However, MCHClCH2R species are
susceptible to nucleophilic displacement of the R-chlo-
ride7 and in some cases undergo R-Cl elimination to
generate carbene complexes.8 Additionally, the R-Cl
substituent is expected to decrease the nucleophilic
character and migratory aptitude of the MCHClCH2R
group, inhibiting subsequent insertions.9 Nevertheless,
reversible CO insertion of Co(CO)3(L)CH2Cl (L ) CO,
PPh3) has been observed.10
(4) For reviews see: (a) Friedrich, H.; Moss, J . R. Adv. Organomet.
Chem. 1991, 33, 235. (b) Morrison, J . A. Adv. Organomet. Chem. 1993,
35, 211.
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Sneddon, D. W. J . Chem. Soc,. Dalton Trans. 1989, 761. (b) McCrindle,
R.; Arsenault, G. J .; Farwaha, R.; Hampden-Smith, M. J .; Rice, R. E.;
McAlees, A. J . Chem. Soc., Dalton Trans. 1988, 1773. (c) McCrindle,
R.; Arsenault, G. J .; Gupta, A.; Hampden-Smith, M. J .; Rice, R. E.;
McAlees, A. J . J . Chem. Soc., Dalton Trans. 1991, 949. (d) Ferguson,
G.; Li, Y.; McAlees, A. J .; McCrindle, R.; Xiang, K. Organometallics
1999, 18, 2428. (e) Ferguson, G.; Gallagher, J . F.; McAlees, A. J .;
McCrindle, R. Organometallics 1997, 16, 1053.
(6) (a) Hubbard, J . L.; Morneau, A.; Burns, R. M.; Nadeau, O. W. J .
Am. Chem. Soc. 1991, 113, 9180. (b) Ogino, H.; Shoji, M.; Abe, Y.;
Shimura, M.; Shioni, M. Inorg. Chem. 1987, 26, 2542. (c) Friedrich,
H. B.; Moss, J . R. J . Organomet. Chem. 1993, 453, 85. (d) Moss, J . R.;
Niven, M. L.; Stretch, P. M. Inorg. Chim. Acta 1986, 119, 177. (e)
Haarman, H. F.; Ernsting, J . M.; Kranenburg, M.; Kooijman, H.;
Veldman, N.; Spek, A. L.; van Leeuwen, P. W. N. M.; Vrieze, K.
Organometallics 1997, 16, 887. (f) Bergamini, P.; Bortolini, O.; Costa,
E.; Pringle, O. G. Inorg. Chim. Acta 1996, 252, 33. (g) Bradd, K. J .;
Heaton, B. T.; J acob, C.; Sampanthar, J . T.; Steiner, A. J . Chem. Soc.,
Dalton Trans. 1999, 1109. (h) Leoni, P. Organometallics 1993, 12, 2431.
(i) Leoni, P.; Marchetti, F.; Paoletti, M. Organometallics 1997, 16, 2146.
(j) Mashima, K.; Fukumoto, A.; Nakano, H.; Kaneda, Y.; Tani, K.;
Nakamura, A. J . Am. Chem. Soc. 1998, 120, 12151. (k) Do¨hring, A.;
Goddard, R.; Hopp, G.; J olly, P. W.; Kokel, N.; Kru¨ger, C. Inorg. Chim.
Acta 1994, 222, 179.
(7) (a) McCrindle, R.; Ferguson, G.; McAlees, A. J .; Arsenault, G.
J .; Gupta, A.; J ennings, M. C. Organometallics 1995, 14, 2741. (b)
Hubbard, J . L.; McVicar, W. K. J . Organomet. Chem. 1992, 429, 369.
(c) Werner, H.; Wilfried, P.; Feser, R.; Zolk, R.; Thometzek, P. Chem.
Ber. 1985, 118, 261. (d) Hubbard, J . L.; McVicar, W. K. Organometallics
1990, 9, 2683.
(8) (a) Wilhelm, T. E.; Belderrain, T. R.; Brown, S. N.; Grubbs, R.
H. Organometallics 1997, 16, 3867. (b) Belderrain, T.; Grubbs, R. H.
Organometallics 1997, 16, 4001. (c) Goldman, A. S.; Tyler, D. R.
Organometallics 1984, 3, 449. (d) Yang, M. X.; Sarkar, S.; Bent, B. E.;
Bare, S. R.; Holbrook, M. T. Langmuir 1997, 13, 229.
Resu lts
Activation of {(n Hex)HC(m im )2}P d(CHCl2)Cl. The
dichloromethyl complex {(nHex)HC(mim)2}Pd(CHCl2)-
Cl (1) is prepared by exposure of {(nHex)HC(mim)2}Pd-
(Me)Cl (2) to ambient room light in CH2Cl2.11 The
reaction of 1 with [Li(Et2O)2.8][B(C6F5)4] at -40 °C yields
the dinuclear complex [{{(nHex)HC(mim)2}Pd(CHCl2)}2-
(µ-Cl)][B(C6F5)4] (3a ,b) as a 1:1 mixture of diastereomers
(Scheme 2). Complexes 3a ,b form by initial chloride
abstraction from 1 to yield {(nHex)HC(mim)2}Pd-
(CHCl2)+, which is trapped by 1. The remaining 0.5
equiv of [Li(Et2O)2.8][B(C6F5)4] does not react. Complexes
3a ,b decompose above 0 °C; the decomposition products
were not identified.
The structures of 3a ,b were established by NMR, ESI-
MS, stoichiometry, and derivatization experiments. The
1H NMR spectra of 3a ,b contain two sets of resonances
of equal intensity corresponding to the two diastereo-
mers. The spectra show that, for each isomer, the two
(nHex)HC(mim)2 ligands are equivalent but the two mim
(9) (a) Axe, F. U.; Marynick, D. S. J . Am. Chem. Soc. 1988, 110,
3728. (b) Cotton, J . D.; Markwell, R. D. J . Organomet. Chem. 1990,
388, 123. (c) Cotton, J . D.; Crisp, G. T.; Daly, V. A. Inorg. Chim. Acta
1981, 47, 165. (d) Cross, R. J .; Gemmill, J . J . Chem. Soc., Dalton Trans.
1981, 2317. (e) Cawse, J . N.; Fiato, R. A.; Pruett, R. L. J . Organomet.
Chem. 1979, 172, 405. (f) Anderson, G. K.; Cross, R. J . Acc. Chem.
Res. 1984, 17, 67. (g) Kuhlmann, E. J .; Alexander, J . J . Coord. Chem.
Rev. 1980, 33, 195. (h) Calderazzo, F.; Noack, K. Coord. Chem. Rev.
1966, 1, 118. (i) Koga, N.; Morokuma, K. J . Am. Chem. Soc. 1986, 108,
6136.
(11) (a) Burns, C. T.; Shen, H.; J ordan, R. F. J . Organomet. Chem.
2003, 638, 240. (b) Burns, C. T.; J ordan, R. F. Abstr. Pap., Am. Chem.
Soc. 2001, 222, 310-INOR.
(12) Drent, E.; Budzelaar, P. H. M. Chem. Rev. 1996, 96, 663.
(13) (a) Brookhart, M.; Rix, F. C.; DeSimone, J . M.; Barborak, J . C.
J . Am. Chem. Soc. 1992, 114, 5894. (b) Tempel, D. J .; J ohnson, L. K.;
Huff, R. L.; White, P. S.; Brookhart, M. J . Am. Chem. Soc. 2000, 122,
6686.
(10) Galamb, V.; Pa´lyi, G.; Boese, R.; Schmid, G. Organometallics
1987, 6, 861.

602 Organometallics, Vol. 23, No. 3, 2004
Foley et al.
Sch em e 2
of excess ethylene at -40 °C quantitatively yields
{(nHex)HC(mim)2}Pd(CHCl2)(CH2dCH2)+ (4; Scheme
3). The 1H NMR spectrum of 4 contains two broad
ethylene resonances (δ 5.34, 5.17 at 20 °C) that are
shifted from the free ethylene position (δ 5.38). This
result is consistent with the AA′BB′ pattern expected
for a structure in which the CdC bond is perpendicular
to the Pd square plane and olefin rotation is fast on the
NMR time scale.14 Complex 4 does not insert CH2dCH2
at 23 °C. For comparison, {(nHex)HC(mim)2}Pd(Me)-
(C2H4)+ inserts ethylene rapidly above -10 °C, leading
to catalytic ethylene dimerization.11 Complex 4 slowly
decomposes at 23 °C (ca. 31% after 19 h); the decom-
position products are the same as those from the
thermal decomposition of 3a ,b in the absence of ethyl-
ene.
Rea ction of 3a ,b w ith CO. As CO is potentially
more reactive for insertion than ethylene, the reactivity
of 3a ,b with CO was investigated. The reaction of 1 and
[Li(Et2O)2.8][B(C6F5)4] in the presence of excess CO (1
atm) at -78 °C yields {(nHex)HC(mim)2}Pd(CHCl2)-
(CO)+ (5) quantitatively (Scheme 3). The NMR spectra
1
of 5 contain characteristic H NMR (δ 5.85) and 13C
Sch em e 3
NMR (δ 61.0) resonances for the Pd-CHCl2 unit. The
Pd-CO 13C resonance appears at δ 172.0, which is
similar to the corresponding value for {H2C(mim)2}Pd-
{C(dO)Me}(CO)+ (δ 173.8). The IR vCO value for 5 in
CD2Cl2 solution is 2144 cm-1, which is slightly higher
than the free CO value (2139 cm-1 in CD2Cl2), indicating
that 5 is a “nonclassical” CO complex, in which d-π*
back-bonding is minimal.15-17 For comparison, the vCO
value of {H2C(mim)2}Pd{C(dO)Me}(CO)+ is 2121 cm-1 11b
.
Complex 5 does not undergo CO insertion up to 70
°C under 1 atm of CO. Above this temperature, 5
decomposes. In contrast, {H2C(mim)2}Pd(Me)(CO)+
readily inserts CO at -78 °C and 1 atm.11b
Ca tion ic P d (n C3F 7) Com p lexes. Hughes reported
the synthesis of (tmeda)Pd(nC3F7)Me (6; tmeda )
N,N,N′,N′-tetramethylenediamine),18 which is a poten-
tial precursor to L2Pd(n-C3F7)+ species via ligand sub-
stitution and methide abstraction. The reaction of 6 with
dppp yields (dppp)Pd(nC3F7)Me (7) quantitatively
(Scheme 4).19 The 31P NMR spectrum of 7 contains two
doublets of triplets at δ 13.9 and -0.4, due to the J PP
and J PF coupling. The 19F NMR spectrum contains
resonances at δ -79.9, -92.6, and -117.6 for the n-C3F7
group.
rings at a given Pd center are inequivalent, consistent
with the Ci symmetry of 3a and the C2 symmetry of 3b.
The Pd-CHCl2 units of 3a ,b are identified by 1H (δ 6.34,
6.08) and 13C (δ 61.6, 61.2) resonances which are similar
to those of 1 (δ 6.34, δ 62.1). The positive ion ESI mass
spectrum contains a parent ion pattern which matches
the calculated isotope distribution. Additionally, the 1H
NMR spectra are the same for 2:1 and 1:1 mixtures of
1 and [Li(Et2O)2.8][B(C6F5)4] in CD2Cl2, which confirms
the stoichiometry in Scheme 2.
Rea ction of 3a ,b w ith CH2dCHCl. The reaction of
1 and 1 equiv of [Li(Et2O)2.8][B(C6F5)4] in the presence
of VC in CD2Cl2 yields 3a ,b (Scheme 3). Above 0 °C,
thermal decomposition of 3a ,b occurs in the same
manner as in the absence of VC. These results show that
VC does not displace 1 from 3.
(14) The 1H NMR spectrum of 4 in the presence of excess free
ethylene at -10 °C contains separate resonances for free and coordi-
nated ethylene that are not significantly broadened, indicating that
exchange of free and coordinated ethylene is slow on the NMR time
scale. In contrast, {(nHex)HC(mim)2}Pd(Me)(CH2dCH2)+ undergoes
fast exchange with free ethylene under these conditions. As ethylene
exchange occurs by an associative mechanism, the additional steric
crowding due to the -CHCl2 group of 4 apparently inhibits this process.
(15) Lupinetti, A. J .; Strauss, S. H.; Frenking, G. Prog. Inorg. Chem.
2001, 49, 1.
(16) Goldman, A. S.; Krogh-J espersen, K. J . Am. Chem. Soc. 1996,
118, 12159.
(17) (a) Guo, Z.; Swenson, D. C.; Guram, A. S.; J ordan, R. F.
Organometallics 1994, 13, 766. (b) Shen, H.; J ordan, R. F. Organome-
tallics 2003, 22, 2080. (c) Guram, A. S.; Swenson, D. C.; J ordan, R. F.
J . Am. Chem. Soc. 1992, 114, 8991.
(18) Hughes, R. P.; Sweetser, J . T.; Tawa, M. D.; Williamson, A.;
Incarvito, C. D.; Rhatigan, B.; Rheingold, A. L.; Rossi, G. Organome-
tallics 2001, 20, 3800.
(19) Complex 6 does not react with ArNdCMeCMedNAr (Ar ) 2,6-
iPr2-C6H3) even after 10 days at 75 °C, under which conditions 6
gradually decomposes.
Rea ction of 3a ,b w ith CH2dCH2. As ethylene
coordinates more strongly than VC to L2PdR+ species,1b
the reaction of 3a ,b with ethylene was investigated. The
reaction of 1 with [Li(Et2O)2.8][B(C6F5)4] in the presence

Pd Complexes with Halogenated Alkyl Ligands
Organometallics, Vol. 23, No. 3, 2004 603
Sch em e 4
Sch em e 7
Sch em e 5
Sch em e 6
Complex 7 reacts with [HNMePh2][B(C6F5)4] at -70
°C in CD2Cl2 to form (dppp)Pd(nC3F7)(NMePh2)+ (8)
1
quantitatively (Scheme 5). The N-Me H and 13C NMR
resonances of 8 are slightly shifted from the free amine
values, consistent with coordination of the NMePh2
ligand.20 Complex 8 does not react with VC or ethylene
up to 23 °C, at which temperature it decomposes.
However, 8 does react with CO (1 atm) at -78 °C to
yield (dppp)Pd(nC3F7)(CO)+ (9) quantitatively. The vCO
value for 9 is 2162 cm-1 (CD2Cl2), which indicates that
this species is also a nonclassical carbonyl complex.
Complex 9 is stable in CD2Cl2 at 23 °C for days in the
presence of excess CO (1 atm). In contrast, (dppp)Pd-
(Me)(CO)+ (vCO 2132 cm-1) readily inserts CO under
these conditions to yield (dppp)Pd{C(dO)Me}(CO)+ (vCO
2130 cm-1).3,21
Syn th esis of P d CH2Cl Com p lexes. The results
described above show that L2Pd(CHCl2)+ and L2Pd-
(nC3F7)+ species are very resistant to insertion reactions.
However, these species may be poor models for the L2-
Pd(CHClR)+ species in Scheme 1, due to the presence
of multiple R-halogen substituents. Therefore, we in-
vestigated the chemistry of several L2Pd(CH2Cl)+ spe-
cies. McCrindle reported the synthesis of L2Pd(CH2Cl)Cl
complexes by the reaction of (cod)PdCl2 (cod ) cyclooc-
tadiene) with CH2N2 followed by displacement of cod
by bidentate dinitrogen and diphosphine ligands.5a We
prepared (tBu2bipy)Pd(CH2Cl)Cl (10) and (R-diimine)-
Pd(CH2Cl)Cl (11) by this route (Scheme 6).
t
contains six bipy resonances and two Bu resonances,
t
which confirms that the two rings of a given Bu2bipy
ligand are inequivalent. The positive ion ESI mass
spectrum of 11 contains a parent ion peak envelope
which matches the calculated isotope distribution.
Additionally, the H NMR spectra are the same for 2/1
and 1/1 mixtures of 10 and [Li(Et2O)2.8][B(C6F5)4]
1
in CD2Cl2, which confirms the stoichiometry in Scheme
7.
Complex 11 decomposes at 20 °C over 12 h in the
presence of 1 equiv of [Li(Et2O)2.8][B(C6F5)4] to a mixture
of Pd0 and three soluble (tBu2bipy)Pd species (Scheme
7). The first two soluble species, [(tBu2bipy)2Pd][B(C6F5)4]2
(11 mol % vs starting 10) and [{(tBu2bipy)Pd(µ-Cl)}2]-
[B(C6F5)4]2 (10 mol % vs 10), were identified straight-
forwardly by NMR, ESI-MS, and independent synthesis.
The third soluble Pd species is formed in 29 mol % yield
versus 10. The 1H NMR spectrum of this species
contains one set of bipy resonances at δ 8.83 (d, J ) 6
Hz, 4H), 7.96 (d, J ) 2 Hz, 4H) and 7.61 (dd, J ) 6, 2
Hz, 4H), characteristic of effective C2 (or higher) sym-
metry at Pd. The positive ion ESI mass spectrum of this
species contains a prominent peak envelope at m/z 857.0
which matches the calculated isotope distribution for
{(tBu2bipy)PdCl}2(µ-Cl)+. A species with a very similar
NMR spectrum and an identical ESI mass spectrum is
generated by the reaction of (tBu2bipy)PdCl2 and [Li-
(Et2O)2.8][B(C6F5)4] in CD2Cl2 or by mixture of [{(tBu2-
bipy)Pd(µ-Cl)}2][B(C6F5)4]2 and (tBu2bipy)PdCl2 in CD2-
Cl2. Therefore, the third species is assigned as [{(tBu2-
bipy)PdCl}2(µ-Cl)][B(C6F5)4].22,23 The fate of the Pd-
CH2Cl group in Scheme 7 was not determined.24
Gen er ation an d Stability of (tBu 2bipy)P d(CH2Cl)+
Sp ecies. The reaction of 10 with [Li(Et2O)2.8][B(C6F5)4]
at -78 °C in CD2Cl2 yields the dinuclear complex
[{(tBu2bipy)Pd(CH2Cl)}2(µ-Cl)][B(C6F5)4] (11; Scheme 7).
The 1H NMR spectrum of 11 contains a singlet at δ 4.00
for the PdCH2Cl unit. The 1H NMR spectrum also
(20) Casey, C. P.; Carpenetti, D. W., II; Sakurai, H. Organometallics
2001, 20, 4262.
(21) Shultz, C. S.; Ledford, J .; DeSimone, J . M.; Brookhart, M. J .
Am. Chem. Soc. 2000, 122, 6351.

604 Organometallics, Vol. 23, No. 3, 2004
Foley et al.
Sch em e 8
Sch em e 9
R ea ct ion of [{(t Bu 2b ip y)P d (CH 2Cl)}2(µ-Cl)][B-
(C6F 5)4] a n d VC. The reaction of 10 and 1 equiv of [Li-
(Et2O)2.8][B(C6F5)4] in the presence of VC (32 equiv) at
-78 °C in CD2Cl2 yields 11. No reaction with VC was
observed up to 0 °C. However, 11 does react with VC
slowly (10 h) at 20 °C to yield allyl chloride (45 mol %
vs 10), [{(tBu2bipy)Pd(µ-Cl)}2][B(C6F5)4]2 (16 mol % vs
10), and [{(tBu2bipy)PdCl}2(µ-Cl)][B(C6F5)4] (34 mol %
vs 10).23 No Pd0 is observed. These observations are
consistent with generation of (tBu2bipy)Pd(CH2Cl)(VC)+,
net 1,2-VC insertion into the Pd-CH2Cl bond, and â-Cl
elimination (Scheme 8). The yield of allyl chloride is
lower than expected because the thermal decomposition
of 11 (see Scheme 7) competes with VC insertion.
R ea ct ion of [{(t Bu 2b ip y)P d (CH 2Cl)}2(µ-Cl)][B-
(C6F 5)4] w ith CO. The presumed intermediate VC
adduct in Scheme 8, (tBu2bipy)Pd(CH2Cl)(VC)+, was not
detected, and therefore it was not possible to compare
the insertion rate of this species to that of (R2bipy)Pd-
(Me)(VC)+ species.1b To probe the migratory aptitude
of the Pd-CH2Cl group, the reaction of 11 with CO was
studied. The reaction of 10 and [Li(Et2O)2.8][B(C6F5)4]
in the presence of excess CO at -78 °C yields [(tBu2-
bipy)Pd(CH2Cl)(CO)][B(C6F5)4] (12, Scheme 9). Complex
12 is stable up to 20 °C, at which point it slowly reacts.
1
In H NMR monitoring experiments, after 20 min at 20
°C, 50% of 12 had reacted and resonances for diketene
[-CH2C(dCH2)OC(dO)-] were observed. After 2 h at
20 °C, the consumption of 12 was complete. The 1H
NMR spectrum of the product mixture contains three
sets of (tBu2bipy)Pd resonances which correspond to [(t-
Bu2bipy)2Pd][B(C6F5)4]2 (6 mol % vs 10), [{(tBu2bipy)-
PdCl}2(µ-Cl)][B(C6F5)4] (28 mol % vs 10), and a third
species assigned as [(tBu2bipy)Pd(Cl)(CO)][B(C6F5)4] (31
mol % vs 10). The formation of Pd(0) was also ob-
served.23 The carbonyl adduct [(tBu2bipy)Pd(Cl)(CO)]-
[B(C6F5)4] was converted to [{(tBu2bipy)Pd(µ-Cl)}2]-
[B(C6F5)4]2 by removing the volatiles under vacuum and
dissolving the residue in CD2Cl2.
(22) The chemical shift and line width of the δ 8.83 1H NMR
resonance of [{(tBu2bipy)PdCl}2(µ-Cl)][B(C6F5)4] varies slightly as the
ratio of precursors is varied. The effective C2 symmetry of {(tBu2bipy)-
PdCl}2(µ-Cl)+ and the broadening of the δ 8.83 resonance of this species
likely arise from bridge/terminal Cl exchange or exchange of free (t-
Bu2bipy)PdCl2 with {(tBu2bipy)PdCl}2(µ-Cl)+.
(23) The combined yields of [(tBu2bipy)2Pd][B(C6F5)4]2, [{(tBu2bipy)-
Pd(µ-Cl)}2][B(C6F5)4]2, and [{(tBu2bipy)PdCl}2(µ-Cl)][B(C6F5)4] total
100% based on the tBu2bipy ligand of starting 10 and 89% based on
the Pd of starting 10. The Pd0 accounts for the remaining Pd from 10.
The combined chlorine content of [{(tBu2bipy)Pd(µ-Cl)}2][B(C6F5)4]2 and
[{(tBu2bipy)PdCl}2(µ-Cl)][B(C6F5)4] corresponds to 1 equiv of Cl from
10. Similarly, for Schemes 8-10, excellent mass balance of the ancillary
ligand (tBu2bipy or R-diimine) was observed. In some cases, the Cl
content of the products exceeds the expected value, which is ascribed
to reactions of the Pd byproducts with LiCl.
These observations are consistent with CO insertion
of 12 followed by â-Cl elimination to yield PdCl+ species
and ketene, as illustrated in Scheme 9. It is well
established that ketene readily dimerizes to diketene.25
The diketene formed in Scheme 9 is consumed, although
(24) No ethylene, allyl chloride, CH2Cl2, or CH2ClCH2Cl was ob-
served in the decomposition of 11.
(25) Clemens, R. J . Chem. Rev. 1986, 86, 241.

Pd Complexes with Halogenated Alkyl Ligands
Organometallics, Vol. 23, No. 3, 2004 605
Sch em e 10a
Discu ssion
The studies described above probe how the reactivity
of L2Pd(RX)+ species is influenced by the presence of
R-halogen substituents on the alkyl ligand. Several
interesting points emerge from this work. First, while
the electron-withdrawing power of a RX group may
enhance the electrophilic character of a L2Pd(RX)+
species, it also decreases the back-bonding ability of the
metal center and therefore inhibits coordination of
π-acceptor substrates such as VC and ethylene. For
example, VC does not displace {(nHex)HC(mim)2}Pd-
(CHCl2)Cl from the dinuclear cation 3a ,b and, perhaps
more strikingly, neither VC nor ethylene displaces
NMePh2 from 8. The weak back-bonding in L2Pd(RX)+
species is manifested by the high νCO values of the
carbonyl complexes {(nHex)HC(mim)2}Pd(CHCl2)(CO)+
(5, 2144 cm-1) and (dppp)Pd(nC3F7)(CO)+ (9, 2162 cm-1).
In fact, the νCO value for 9 is in the same range as the
values for the “O-inside” isomers of the d0 carbonyls
(C5R5)2Zr{C(dO)Me}(CO)+ (R ) Me, 2152 cm-1; R ) H,
2176 cm-1), in which conventional back-bonding is
absent.17
A second general observation is that L2Pd(RX)-
(substrate)+ species undergo much slower insertion than
the corresponding L2Pd(Me)(substrate)+ complexes.
Among the carbonyl adducts studied, neither 5 nor 9
undergo insertion, and 12 undergoes only very slow
insertion, under conditions where the corresponding L2-
Pd(Me)(CO)+ species insert rapidly. Similarly, ethylene
complex 4 does not undergo insertion under conditions
where related {RHC(mim)2}Pd(Me)+ derivatives insert
rapidly. These results are in line with previous studies
of CO insertion into M-R bonds, which have shown
that, almost invariably, electron-releasing substituents
on the migrating R group promote migration and
stabilize the insertion product, while electron-withdraw-
ing substituents have the opposite effects.9 This trend
has been ascribed to differences in bond strengths (M-
RX > M-R) and differences in the basicity/nucleophi-
licity of the migrating group (R > RX). It is also possible
that steric crowding associated with the -CHCl2 inhib-
its insertion of 4 and 5.14
a
Ar ) 2,6-iPr2-C6H3.
its fate is unknown. The formation of ketene was
confirmed by a trapping experiment. Addition of excess
EtOD (6 equiv) to a CD2Cl2 solution of [(tBu2bipy)Pd-
(CH2Cl)(13CO)][B(C6F5)4] (12-13C1) at -78 °C, followed
by warming to room temperature for 3 h, produced the
labeled ethyl acetate, H2DC(13CdO)OCH2CH3, derived
from trapping of H2Cd13CdO by EtOD, in 65% yield.26
Several other examples of â-Cl elimination of chloro-
acetyl complexes have been reported previously. For
example, (C5H5)M(CO)3{(CdO)CH2Cl} species (M ) Mo,
W) undergo â-Cl elimination to generate (C5H5)M(CO)3-
Cl and ketene.27 Additionally, CO insertion into a Rh-
CH2I bond followed by â-I elimination has been pro-
posed.28
These results show that 12 inserts CO very slowly
(hours) at 20 °C. For comparison, (tBu2bipy)Pd(Me)-
(CO)+ inserts CO (1 atm) at -78 °C to yield (tBu2bipy)-
Pd{C(dO)Me}(CO)+ within 5 min.3
Rea ction of “(r-d iim in e)P d (CH2Cl)+” a n d VC.
The results described above show that “(tBu2bipy)Pd-
(CH2Cl)+” reacts with VC by net 1,2-insertion followed
by â-Cl elimination. To determine if L2PdCH2Cl+ species
that are analogous to highly active L2PdR+ olefin
polymerization catalysts exhibit similar chemistry, we
briefly investigated the reactivity of (R-diimine)Pd(CH2-
Cl)Cl (13, Scheme 6). As shown in Scheme 10, the
reaction of 13 and [Li(Et2O)2.8][B(C6F5)4] in the presence
of VC (78 equiv) for 10 h at 20 °C yields [{(R-diimine)-
Pd(µ-Cl)}2][B(C6F5)4]2 (14 mol % vs 13), (R-diimine)PdCl2
(72 mol % vs 13),1b Pd0, and free allyl chloride (80 mol
% vs 13).23 These observations are consistent with
generation of (R-diimine)Pd(CH2Cl)(VC)+ (not observed),
net VC 1,2-insertion into the Pd-CH2Cl bond, and â-Cl
elimination.
A third key observation is that L2Pd(CH2Cl)+ species
t
(L2 ) Bu2bipy, R-diimine) react with VC to yield allyl
chloride and products derived from L2Pd-Cl+ in high
yield. The most direct route to these products is forma-
tion of a L2Pd(CH2Cl)(VC)+ adduct, 1,2-VC insertion to
produce a L2Pd(CH2CHClCH2Cl)+ intermediate, and
â-Cl elimination. Alternatively, the initial insertion
could occur with 2,1-regiochemistry to produce L2Pd-
(CHClCH2CH2Cl)+, which undergoes chain walking via
a L2Pd(H)(CHCldCHCH2Cl)+ intermediate (E) to form
L2Pd{CH(CH2Cl)CH2Cl)+, followed by â-Cl elimination.
The available evidence is insufficient to distinguish
these pathways. However, the sterically crowded, elec-
tron-poor CHCldCHCH2Cl ligand of intermediate E
should be easily displaced by VC (which is present in
excess in Schemes 8 and 10) or allyl chloride. The
absence of CHCldCHCH2Cl in the products of Schemes
8 and 10 argues against the 2,1-insertion pathway.
Further studies will be necessary to understand the
regioselectivity of VC insertion into Pd-RX and Pd-R
bonds.29
(26) (a) Weston, W. S.; Cole-Hamilton, D. J . Inorg. Chim. Acta 1998,
280, 99. (b) Hommeltoft, S. I.; Baird, M. C. J . Am. Chem. Soc. 1985,
107, 2548.
(27) Dilgassa, M.; Curtis, M. D. J . Organomet. Chem. 1979, 172,
177.
(28) (a) Weston, W. S.; Lightfoot, P.; Cole-Hamilton, D. J . J .
Organomet. Chem. 1998, 553, 473. (b) The reaction of (Cy3P)2Pd(CH2-
Cl)Cl with 30 atm of CO yields (Cy3P)2PdCl2 and diketene, presumably
by CO insertion and â-Cl elimination. Huser, M.; Francois, M.; Osborn,
J . Fr. Patent 2637281, 1990.

606 Organometallics, Vol. 23, No. 3, 2004
Foley et al.
Finally, it is interesting to note that (tBu2bipy)Pd-
{C(dO)CH2Cl}+ undergoes fast â-Cl elimination to form
products derived from (tBu2bipy)PdCl+ (Scheme 9),
despite the fact that the high-energy species ketene is
produced. As noted above, L2Pd{C(dO)Me}+ species
undergo 2,1-insertion of VC to yield O-chelated L2Pd-
{CHClCH2C(dO)Me}+ complexes.3 However, L2Pd-
{CHClCH2C(dO)Me}+ complexes do not undergo che-
late ring opening or insertion with CO, which precludes
VC/CO copolymerization. The present results suggest
that even if these chelate complexes did insert CO, VC/
CO copolymerization would be thwarted by â-Cl elimi-
nation of the resulting L2Pd{C(dO)CHClCH2C(dO)-
Me}+ complexes.
prepared by literature procedures. (cod)Pd(CH2Cl) was pre-
pared by the literature procedure, with the exception that
CH2N2 was added at -78 °C.5a [Pd(MeCN)4][BF4]2 was pur-
chased from Strem and used as received. All other chemicals
were purchased from Aldrich and used as received. Elemental
analyses were performed by Midwest Microlab or Galbraith
Laboratories, Inc.
NMR spectra were recorded on Bruker DMX-500 or DRX-
400 spectrometers in Teflon-valved tubes at 23 °C unless
1
otherwise indicated. H and 13C chemical shifts are reported
versus SiMe4 and were determined by reference to residual
1H and 13C solvent signals. Coupling constants are reported
in Hz.
The NMR spectra of cationic complexes contained signals
for the free B(C6F5)4 anion, which are as follows: 13C{1H}
-
NMR (CD2Cl2) δ 148.5 (d, J ) 242), 137.0 (d, J ) 247), 135.6
(d, J ) 244), 123.1 (br, Cipso); 19F NMR (CD2Cl2) δ -132.1 (d,
J ) 6, 8F, Fortho), -161.3 (t, J ) 20, 4F, Fpara), -165.2 (t, J )
18, 8F, Fmeta); 19F NMR (CD2Cl2, -70 °C) δ -132.5 (d, J ) 5,
8F, Fortho), -161.7 (t, J ) 20, 4F, Fpara), -164.9 (t, J ) 18, 8F,
Con clu sion s
This study shows that L2Pd(CHCl2)+, L2Pd(nC3F7)+,
and L2Pd(CH2Cl)+ complexes can be generated by
methods used to generate analogous L2Pd(Me)+ species.
In general, L2Pd(RX)+ species are much less reactive for
olefin or CO insertion compared to corresponding L2-
Pd(R)+ alkyl species. The chloromethyl complexes, L2-
Pd(CH2Cl)+, do coordinate and insert vinyl chloride, but
the insertion occurs with net 1,2-regiochemistry and is
followed by fast â-Cl elimination to produce allyl chlo-
ride and products derived from L2PdCl+. Thus, while
VC polymerization via repetitive 2,1-insertion (as in
Scheme 1) may be feasible, the presence of the R-Cl
substituent in the putative MCHClCH2R+ chain carry-
ing active species will probably be insufficient by itself
to direct a subsequent 2,1-insertion of VC. Other,
presumably ligand-based strategies will be required to
achieve a 2,1-insertion polymerization of VC.
F
meta); 11B NMR (CD2Cl2) δ -16.1 (br s); 11B NMR (CD2Cl2,
-70 °C) δ -15.8 (br s).
Unless otherwise noted, Et2O does not coordinate to the Pd
species described here. Data for free Et2O are as follows: 1H
NMR (CD2Cl2, -70 °C) δ 3.35 (q, J ) 7, 4H), 1.09 (t, J ) 7,
6H); 13C{1H} NMR (CD2Cl2, -70 °C) δ 65.7, 15.2; 1H NMR
(CD2Cl2) δ 3.43 (q, J ) 7, 4H), 1.15 (t, J ) 7, 6H); 13C{1H}
NMR (CD2Cl2) δ 66.0, 15.5.
Electrospray mass spectra (ESI-MS) were recorded on
freshly prepared samples (ca. 1 mg/mL in CH2Cl2) using an
Agilent 1100 LC-MSD spectrometer incorporating a quadru-
pole mass filter with an m/z range of 0-3000. A 5 µL sample
was injected by flow injection using an autosampler. Purified
nitrogen was used as the nebulizing and drying gas. Typical
instrumental parameters: drying gas temperature 350 °C,
nebulizer pressure 35 psi, drying gas flow 12.0 L/min, frag-
mentor voltage 0 or 70 V. In all cases where assignments are
given, observed isotope patterns closely matched calculated
isotope patterns. The listed m/z value corresponds to the most
intense peak in the isotope pattern.
Exp er im en ta l Section
Gen er a tion of [{{(n Hex)HC(m im )2}P d (CHCl2)}2(µ-Cl)]-
[B(C6F 5)4] (3a ,b). A valved NMR tube was charged with
{(nHex)HC(mim)2}Pd(CHCl2)Cl (10.0 mg, 0.0206 mmol) and
[Li(Et2O)2.8][B(C6F5)4] (18.4 mg, 0.0206 mmol), and CD2Cl2 (0.5
mL) was added by vacuum transfer at -196 °C. The tube was
warmed to -40 °C and vigorously shaken. A slurry of a white
solid in a pale yellow supernatant formed within ca. 3 h at
-40 °C. The free Et2O and LiCl coproducts were not removed.
The tube was maintained at -78 °C until further character-
ization and reactions were carried out. The 1H NMR spectrum
established that 3a ,b had formed quantitatively. 1H NMR
(CD2Cl2, -40 °C): δ 7.65 (d, J ) 1, 1H), 7.61 (d, J ) 1, 1H),
7.17 (s, 2H), 7.01 (d, J ) 1, 1H), 6.99 (d, J ) 1, 1H), 6.93 (d, J
) 1, 1H), 6.85 (d, J ) 1, 1H), 6.34 (s, 1H, PdCHCl2), 6.08 (s,
1H, PdCHCl2), 4.20 (m, 2H, coincidental (nHex)CH), 3.75 (s,
3H), 3.74 (s, 3H), 3.71 (s, 3H), 3.69 (s, 3H), 3.56 (q, J ) 7,
22.4H, free and Li+-coordinated Et2O), 2.65 (m, 2H, CHCHH),
2.35 (m, 2H, CHCHH), 1.29 (m, 16H, (CH2)4), 1.18 (t, J ) 7,
33.6H, free and Li+-coordinated Et2O), 0.80 (m, 6H, CH2CH3).
13C{1H} NMR (CD2Cl2, -40 °C): δ 144.8, 144.6, 144.2 (2
coincidental imidazole C), 126.9, 126.8, 126.5, 126.4, 121.8,
121.6, 121.3, 121.2, 66.0 (free and coordinated Et2O), 61.6
(PdCHCl2), 61.2 (PdCHCl2), 38.4 (CH2), 38.1 (CH2), 34.4 (2
coincidental CH2CH), 34.0 (Me), 33.9 (Me), 33.9 (Me), 33.8 (Me),
31.6 (CH2), 31.5 (CH2), 29.1(CH2), 29.0 (CH2), 27.6 (CH2), 27.4
(CH2), 22.6 (2 coincidental CH2), 14.6 (free and coordinated
Et2O), 14.0 (CH2CH3), 13.9 (CH2CH3). Positive ion ESI-MS:
m/z 936.8, {(nHex)HC(mim)2}Pd(CHCl2)}2(µ-Cl)+.
Gen er a l P r oced u r es. All manipulations were performed
using drybox or Schlenk techniques under an N2 atmosphere,
or on a high-vacuum line, unless otherwise indicated. Nitrogen
was purified by passage through columns containing activated
molecular sieves and Q-5 oxygen scavenger. CH2Cl2 was
distilled from CaH2 and degassed prior to use. CD2Cl2 was
distilled from P4O10 and degassed prior to use. Pentane was
purified by passage through columns of activated alumina and
BASF R3-11 oxygen removal catalyst. {(nHex)HC(mim)2}Pd-
(CHCl2)Cl was prepared as described elsewhere and contains
ca. 5% {(nHex)HC(mim)2}PdCl2, which does not interfere in
the reactions reported in this paper, as shown by NMR.11 [Li-
(Et2O)2.8][B(C6F5)4] was provided by Boulder Scientific and used
as received. The Et2O content was determined by 1H NMR with
C6Me6 as an internal standard. [HNMePh2][B(C6F5)4,30 (tmeda)-
Pd(nC3F7)Me,18 tBu2bipy,31 (cod)Pd(Me)Cl,32 and CH2N233 were
(29) For discussions of the factors that may influence insertion
regioselectivity, see ref 3 and: (a) Michalak, A.; Ziegler, T. J . Am.
Chem. Soc. 2001, 123, 12266. (b) Michalak, A.; Ziegler, T. Organome-
tallics 1999, 18, 3998. (c) Michalak, A.; Ziegler, T. Organometallics
2000, 19, 1850. (d) Deubel, D. V.; Ziegler, T. Organometallics 2002,
21, 4432. (e) Deubel, D. V.; Ziegler, T. Organometallics 2002, 21, 1603.
(f) Philipp, D. M.; Muller, R. P.; Goddard, W. A., III; Storer, J .; McAdon,
M.; Mullins, M. J . Am. Chem. Soc. 2002, 124, 10198. (g) von Schenck,
H.; Stro¨mberg, S.; Zetterberg, K.; Ludwig, M.; Åkermark, B.; Svensson,
M. Organometallics 2001, 20, 2813.
(30) Tjaden, E. B.; Swenson, D. C.; J ordan, R. F. Organometallics
1995, 14, 371.
(31) Belser, P.; Zelewsky, A. Helv. Chim. Acta 1980, 63, 1675.
(32) Drew, D.; Doyle, J . R. Inorg. Synth. 1990, 28, 346.
(33) (a) Black, T. H. Aldrichim. Acta 1983, 16, 3. (b) Aldrich
Technical Bulletin AL-180; Aldrich Chemical Co.: Milwaukee, WI,
2003, p 1 and references therein.
Gen er a tion of [{(n Hex)HC(m im )2}P d (CHCl2)(C2H4)]-
[B(C6F 5)4] (4). A valved NMR tube containing a CD2Cl2
solution of 1:1 mixture of 3a ,b and [Li(Et2O)2.8][B(C6F5)4]

Pd Complexes with Halogenated Alkyl Ligands
Organometallics, Vol. 23, No. 3, 2004 607
generated as described above was frozen at -196 °C, and
ethylene (5 equiv) was added by vacuum transfer from a
calibrated gas bulb. The tube was warmed to -10 °C and
maintained at -10 °C for 10 min, and the volatiles were
removed under vacuum. CD2Cl2 was added by vacuum transfer
at -196 °C. The tube was warmed to -78 °C, and a slurry of
a fine white solid in a pale yellow supernatant was obtained.
The tube was maintained at -78 °C until further character-
ization and reactions were carried out. The 1H NMR spectrum
(PCH2CH2); the C3F7 resonances were not observed. 31P{1H}
NMR (CD2Cl2, -70 °C): δ 29.5 (dt, J ) 53, 30), -3.2 (dt, J )
53, 42). 19F{1H} NMR (CD2Cl2, -70 °C): δ -80.4 (s), -89.9
(br s), -117.6 (s).
Gen er a tion of [(d p p p )P d (n C3F 7)(CO)][B(C6F 5)4] (9). A
valved NMR tube containing a CD2Cl2 solution of 8 generated
as described above was exposed to CO (1 atm) for 5 min at
-78 °C. A clear pale yellow solution was obtained. The free
NMePh2 was not removed. The 1H NMR spectrum established
that 9 had formed quantitatively. Methane was also present.
1H NMR (CD2Cl2): δ 7.70-7.44 (m, 20H), 7.28 (t, J ) 8, 4H,
NPh), 7.03 (d, J ) 8, 4H, NPh), 6.98 (t, J ) 8, 2H, NPh), 2.61
(m, 4H), 2.15 (m, 2H). 13C{1H} NMR (CD2Cl2): δ 149.5 (NPh),
133.8, 133.6, 133.4 (d, J ) 11), 132.5 (d, J ) 11), 130.8 (d, J )
11), 130.1 (d, J ) 11), 129.5 (NPh), 127.4 (d, J ) 50), 125.4 (d,
J ) 57), 121.5 (NPh), 120.7 (NPh), 26.0 (dd, J ) 35, 12, PCH2),
23.3 (dd, J ) 28, 5, PCH2), 18.3 (PCH2CH2); the assignment
of the Pd-CO resonance was achieved using 13CO, giving δ
174.3 (d, J ) 104, PdCO); the C3F7 resonances were not
observed. 31P{1H} NMR (CD2Cl2): δ 11.3 (dt, J ) 56, 44), -5.4
(dt, J ) 56, 33). 19F{1H} NMR (CD2Cl2): δ -79.8 (t, J ) 13),
1
established that 4 had formed quantitatively. H NMR (CD2-
Cl2, -10 °C): δ 7.58 (d, J ) 2, 1H), 7.07 (d, J ) 2, 1H), 6.97 (d,
J ) 2, 1H), 6.71 (d, J ) 2, 1H) 5.35 (s, 1H, CHCl2), 5.31 (m,
coordinated ethylene and CDHCl2), 5.13 (m, 2H, coordinated
ethylene), 4.29 (dd, J ) 8, 7, 1H, (nHex)CH), 3.78 (s, 3H, Me),
3.72 (s, 3H, Me), 2.47-2.36 (m, 1H, CHCHH), 2.32-2.23 (m,
1H, CHCHH), 1.38-1.17 (m, 8H, CH2), 0.83 (t, J ) 8, 3H,
CH2CH3). 13C{1H} NMR (CD2Cl2, -10 °C): δ 144.8, 144.7,
125.5, 124.4, 123.4, 122.2, 95.5 (coordinated ethylene), 64.0
(CHCl2), 39.2 (CH2), 34.7 (Me), 34.3 (Me), 34.1 (CH2CH), 31.6
(CH2), 29.0 (CH2), 27.4 (CH2), 22.6 (CH2), 14.0 (CH2CH3).
Gen er a tion of [{(n Hex)HC(m im )2}P d (CHCl2)(CO)][B-
(C6F 5)4] (5). A valved NMR tube containing a CD2Cl2 solution
of 1:1 mixture of 3a ,b and [Li(Et2O)2.8][B(C6F5)4] generated as
described above was exposed to CO (1 atm) for 5 min at -78
°C. The tube was warmed to 23 °C. A slurry of a fine white
solid in a pale yellow supernatant was obtained. The tube was
maintained at -78 °C until further characterization and
reactions were carried out. The 1H NMR spectrum established
that 5 had formed quantitatively. 1H NMR (CD2Cl2): δ 7.22
(d, J ) 2, 1H), 7.10 (d, J ) 2, 1H), 7.03 (d, J ) 2, 1H), 6.96 (d,
J ) 2, 1H), 5.85 (s, 1H, PdCHCl2), 4.34 (t, J ) 8, 1H, (nHex)-
CH), 3.80 (s, 3H, Me), 3.77 (s, 3H, Me), 2.33-2.20 (m, 2H,
CHCH2), 1.35-1.21 (m, 8H, (CH2)4), 0.86 (t, J ) 7, 3H,
CH2CH3). 13C{1H} NMR (CD2Cl2): δ 172.0 (Pd-CO), 145.7,
144.8, 128.7, 125.8, 123.7, 123.4, 61.0 (PdCHCl2), 39.1 (CH2),
35.0 (Me), 34.6 (Me), 34.5 (CH2CH), 31.6 (CH2), 29.0 (CH2),
27.5 (CH2), 22.8 (CH2), 14.0 (CH2CH3). IR (CD2Cl2): vCO 2144
-80.6 (t, J ) 35), -133 (s). IR (CD2Cl2): vCO 2162 cm-1
.
(tBu 2bip y)P d (CH2Cl)Cl (10). A flask was charged with
t
(cod)Pd(CH2Cl)Cl (64 mg, 0.21 mmol), Bu2bipy (57 mg, 0.21
mmol), and CH2Cl2 (5 mL). The resulting clear yellow solution
was stirred for 10 min and filtered, and the volatiles were
removed under vacuum. The resulting brown powder was
washed with hexanes (4 × 10 mL), dried under vacuum, and
dissolved in CH2Cl2 (2 mL). Hexanes (10 mL) were added,
resulting in the precipitation of (tBu2bipy)Pd(CH2Cl)Cl as a
pale yellow powder (64 mg, 65%). 1H NMR (CD2Cl2): δ 9.01
(d, J ) 6, 1H), 8.76 (d, J ) 6, 1H), 8.05 (d, J ) 2, 1H), 7.99 (d,
J ) 2, 1H), 7.64 (dd, J ) 6, 2, 1H), 7.55 (dd, J ) 6, 2, 1H), 4.00
(s, 2H, PdCH2Cl), 1.45 (s, 9H), 1.41 (s, 9H). 13C{1H} NMR (CD2-
Cl2): δ 164.4 (2C), 156.7 (2C), 149.6 (2C), 124.5, 124.0, 119.5,
118.5, 33.8 (PdCH2Cl), 35.9 (2C, CMe3), 30.4 (CMe3), 30.3
(CMe3). Anal. Calcd for C19H26N2PdCl2: C, 49.64; H, 5.70; N,
6.09. Found: C, 49.87; H, 5.70; N 6.13.
cm-1
.
Gen er a tion of [{(tBu 2bip y)P d (CH2Cl)}2(µ-Cl)][B(C6F 5)4]
(11). A valved NMR tube was charged with (tBu2bipy)Pd(CH2-
Cl)Cl (9.7 mg, 0.022 mmol) and [Li(Et2O)2.8][B(C6F5)4] (9.6 mg,
0.011 mmol), and CD2Cl2 (0.5 mL) was added by vacuum
transfer at -196 °C. The tube was warmed to -78 °C and
transferred to a precooled NMR probe, and NMR spectra were
recorded. 1H NMR (CD2Cl2, -70 °C): δ 8.82 (d, J ) 6, 2H),
8.59 (d, J ) 6, 2H), 8.07 (s, 2H), 8.03 (s, 2H), 7.66 (br d, J )
6, 2H), 7.58 (br d, J ) 6, 2H), 4.00 (s, 4H, PdCH2Cl), 1.39 (s,
18H), 1.35 (s, 18H). Positive ion ESI-MS: m/z 885.0, {(tBu2-
bipy)Pd(CH2Cl)}2(µ-Cl)+.
(d p p p )P d (nC3F 7)Me (7). A flask was charged with (tmeda)-
Pd(nC3F7)Me (200 mg, 0.492 mmol) and dppp (202 mg, 0.492
mmol), and CH2Cl2 (25 mL) was added by cannula. A clear
yellow solution formed rapidly. The mixture was stirred at 23
°C for 2 h, and the volatiles were removed under vacuum. The
solid was dissolved in CH2Cl2 (10 mL), and the volatiles were
removed under vacuum. This procedure was repeated twice
to yield (dppp)Pd(nC3F7)Me as a pale yellow solid (290 mg,
1
84%). H NMR (CD2Cl2): δ 7.58-7.31 (m, 20H), 2.39 (m, 4H),
1.74 (m 2H), 0.24 (t, J ) 7, 3H). 13C{1H} NMR (CD2Cl2): δ
134.4 (d, J ) 34), 133.7 (d, J ) 4), 133.6 (d, J ) 3), 131.7 (d,
J ) 42), 130.7, 130.2, 128.9 (d, J ) 10), 128.5 (d, J ) 10), 29.7
(dd, J ) 20, 5, PCH2), 27.8 (dd, J ) 24, 6, PCH2), 19.4
(PCH2CH2), 5.7 (d, J ) 86, PdMe); the C3F7 resonances were
not observed. 31P{1H} NMR (CD2Cl2): δ 13.9 (dt, J ) 41, 30),
-0.4 (dt, J ) 41, 38). 19F{1H} NMR (CD2Cl2): δ -79.9 (t, J )
9), -92.6 (br t), -117.6 (br). Anal. Calcd for C31H29F7P2Pd: C,
52.97; H, 4.16. Found: C, 52.59; H, 4.17.
(tBu 2bip y)P d Cl2. A flask was charged with (cod)PdCl2 (100
mg, 0.351 mmol) and tBu2bipy (94.1 mg, 0.351 mmol), and CH2-
Cl2 (25 mL) was added by cannula. The resulting clear yellow
solution was stirred for 1 h at 23 °C, and the volatiles were
removed under vacuum. (tBu2bipy)PdCl2 was obtained as a
1
pale yellow solid (138 mg, 89%). H NMR (CD2Cl2): δ 9.13 (d,
J ) 6, 2H), 7.93 (d, J ) 2, 2H), 7.57 (dd, J ) 6, 2, 2H), 1.43 (s,
18H). 13C{1H} NMR (CD2Cl2): δ 165.6, 156.5, 150.5, 124.3,
119.7, 36.1 (CMe3), 30.3 (CMe3). Anal. Calcd for C18H24N2-
PdCl2: C, 48.51; H, 5.43; N, 6.29. Found: C, 48.31; H, 5.37;
N, 6.29.
Gen er a tion of [(d p p p )P d (n C3F 7)(NMeP h 2)][B(C6F 5)4]
(8). A valved NMR tube was charged with 7 (10.0 mg, 0.0142
mmol) and [HNMePh2][B(C6F5)4] (12.3 mg, 0.0142 mmol), and
CD2Cl2 (0.5 mL) was added by vacuum transfer at -196 °C.
The tube was warmed to -78 °C and vigorously shaken to yield
[{(tBu 2bip y)P d (µ-Cl)}2][B(C6F 5)4]2. A flask was charged
with (tBu2bipy)PdCl2 (150 mg, 0.34 mmol), AgPF6 (85 mg, 0.34
mmol), and CH2Cl2 (10 mL). The mixture was stirred at room
temperature for 15 min, yielding a yellow slurry. Solid [Li-
(Et2O)2.8][B(C6F5)4] (307 mg, 0.34 mmol) was added, and the
suspension was stirred for 30 min. The mixture was filtered
to remove the white precipitate, yielding a clear yellow
solution. The solution was condensed to 3 mL under vacuum
1
a clear greenish yellow solution. The H and 31P NMR spectra
established that 8 had formed quantitatively. Methane was
also present. 1H NMR (CD2Cl2, -70 °C): δ 7.75-7.15 (m, 20H,
PPh), 7.25 (t, J ) 8, 4H, NPh), 7.01 (d, J ) 8, 4H, NPh), 6.94
(t, J ) 8, 2H, NPh), 3.29 (s, 3H, NMe), 2.60 (br s, 2H), 2.48 (br
s, 2H), 1.94 (br s, 2H). 13C{1H} NMR (CD2Cl2, -70 °C): δ 147.2
(NPh), 132.9 (d, J ) 11), 132.8, 132.6 (d, J ) 10), 132.5, 129.7
(d, J ) 11), 129.1 (d, J ) 12), 129.0 (NPh), 125.4 (d, J ) 10),
125.0 (d, J ) 24), 121.8 (NPh), 119.8 (NPh), 40.7 (NMe), 27.3
(d, J ) 37, 14, PCH2), 22.8 (dd, J ) 34, 5, PCH2), 17.2
and placed in
a
-30 °C freezer. [{(tBu2bipy)Pd(µ-Cl)}2]-
[B(C6F5)4]2 precipitated overnight as a yellow powder, which
was isolated by filtration and dried under vacuum (0.280 g,

608 Organometallics, Vol. 23, No. 3, 2004
Foley et al.
1
75%). H NMR (CD2Cl2): δ 8.16 (d, J ) 6, 4H), 8.01 (d, J ) 2,
by 1H NMR. 1H NMR of [-CH213C(dCH2)O13C(dO)-] (CD2-
4H), 7.61 (dd, J ) 6, 2, 4H), 1.43 (s, Bu, 36H). 13C{1H} NMR
Cl2): δ 4.93 (ddtd, J CH ) 7.1, J HH ) 4.5, J HH ) 1.9, J CH )
t
2
2
4
4
(CD2Cl2): δ 169.6, 156.6, 149.9, 126.0, 121.7, 36.7 (CMe3), 30.0
(CMe3). Positive ion ESI-MS: m/z 411.0, [{(tBu2bipy)Pd(µ-
Cl)}2]2+. Anal. Calcd for C84H48N4Pd2Cl2B2F40: C, 46.31; H,
2.22; N, 2.57. Found: C, 46.11; H, 2.37; N, 2.22.
0.6, 1H, dCH2), 4.59 (ddtd, 2J CH ) 5.9, 2J HH ) 4.5, 4J HH ) 1.6,
4J CH ) 0.8, 1H, dCH2), 3.95 (dddd, 2J CH ) 6.9, 2J CH ) 5.4, 4J HH
4
) 1.9, J HH ) 1.6, 2H, C-CH2). Coupling constant determina-
tions were made by visually and iteratively fitting simulated
spectra to experimental spectra. Simulations were performed
using gNMR.34 After 2 h, (tBu2bipy)Pd(CH2Cl)(13CO)+ had
reacted completely to give [{(tBu2bipy)PdCl}2(µ-Cl)][B(C6F5)4]
(28 mol % vs 10), [(tBu2bipy)Pd(Cl)(13CO)][B(C6F5)4] (31 mol
% vs 10), and [(tBu2bipy)2Pd][B(C6F5)4]2 (6 mol % vs 10). Pd(0)
was also observed. No further reaction was observed after 2
days. Data for [(tBu2bipy)Pd(Cl)(13CO)][B(C6F5)4] are as fol-
lows: 1H NMR (CD2Cl2) δ 9.11 (dd, J ) 6, 2, 1H), 8.38 (dd, J
) 6, 2, 1H), 8.12 (d, J ) 2, 1H), 8.07 (d, J ) 2, 1H), 7.79 (dd,
J ) 6, 2, 1H), 7.69 (d, J ) 6, 2, 1H), 4.08 (s, 2H, PdCH2Cl),
1.50 (s, 9H), 1.48 (s, 9H); positive ion ESI-MS m/z 437.9, [(t-
Bu2bipy)Pd(Cl)(13CO)]+; 13C{1H} NMR (CD2Cl2) δ 172.3 (Pd-
13CO). The solvent was removed under vacuum, and the
residue was redissolved in CD2Cl2, resulting in the complete
conversion of [(tBu2bipy)Pd(Cl)(13CO)][B(C6F5)4] to [{(tBu2bipy)-
Pd(µ-Cl)}2][B(C6F5)4]2.
Gen er a tion of [{(tBu 2bip y)P d Cl}2(µ-Cl)][B(C6F 5)4]. A
valved NMR tube was charged with (tBu2bipy)PdCl2 (9.7 mg,
0.022 mmol), [Li(Et2O)2.8][B(C6F5)4] (19.2 mg, 0.022 mmol), and
CD2Cl2 (0.6 mL), yielding a slurry of a white precipitate in a
pale yellow solution. NMR spectra showed that the reaction
was complete after 15 min and no further reaction was
observed after 3 days at room temperature. 1H NMR (CD2-
Cl2): δ 8.83 (br d, J ) 6, 4H), 7.96 (d, J ) 2, 4H), 7.60 (dd, J
) 6, 2, 4H), 1.44 (s, tBu, 36H). 13C{1H} NMR (CD2Cl2): δ 166.9,
156.6, 150.5, 124.9, 120.1, 36.2 (CMe3), 30.2 (CMe3). Positive
ion ESI-MS: m/z 857.0, [{(tBu2bipy)PdCl}2(µ-Cl)}]+.
[{(tBu2bipy)PdCl}2(µ-Cl)][B(C6F5)4] can also be generated by
a mixture of [{(tBu2bipy)Pd(µ-Cl)}2][B(C6F5)4]2 (0.007 mmol)
and (tBu2bipy)PdCl2 (0.014 mmol) in CD2Cl2 (0.6 mL), which
results in a very similar NMR spectrum and an identical ESI
mass spectrum.
[(tBu 2bip y)2P d ][B(C6F 5)4]2. An NMR tube was charged
with Bu2bipy (11.4 mg, 0.042 mmol) and [Pd(MeCN)4][BF4]2
(9.4 mg, 0.021 mmol), and CD2Cl2 (0.5 mL) was added by
vacuum transfer at -196 °C. The tube was heated to 50 °C
for 18 h, by which time the reactants had dissolved. The
volatiles were removed under vacuum, and [Li(Et2O)2.8]-
[B(C6F5)4] (39.0 mg, 0.044 mmol) was added. The tube was
opened under air, and CH2Cl2 was added. The tube was shaken
vigorously, and a white precipitate formed immediately. The
tube was allowed to stand at room temperature for 30 min.
The mixture was filtered through a Celite plug, and the filtrate
was placed in a -80 °C bath. Yellow block crystals formed
overnight. The crystals were collected, washed with CH2Cl2,
Tr a p p in g of Keten e fr om th e Rea ction of [{(tBu 2bip y)-
P d (CH2Cl)}2(µ-Cl)][B(C6F 5)4] a n d 13CO. A CD2Cl2 solution
of [(tBu2bipy)Pd(CH2Cl)(13CO)][B(C6F5)4] was generated in a
valved NMR tube at -78 °C as described above. Excess CH3-
CH2OD (6 equiv) was added at -78 °C, and the tube was
t
1
warmed to room temperature for 3 h. The H NMR spectrum
showed that H2DC(13CdO)OCH2CH3 had formed in 65% yield.
Analysis of volatiles from the tube showed that this labeled
1
ethyl acetate was the only major species present. H NMR of
H2DC(13CdO)OCH2CH3 (CD2Cl2): δ 4.08 (d of q, J ) 7, 3, 2H),
1.99 (d of t, J ) 7, 4, 2H), 1.26 (t, J ) 7, 3H).
(r-d iim in e)P d (CH2Cl)Cl (13). A flask was charged with
(cod)Pd(CH2Cl)Cl (43.2 mg, 0.144 mmol), R-diimine (58.3 mg,
0.144 mmol), and CH2Cl2 (4 mL). The resulting clear orange
solution was maintained at room temperature for 30 min.
Pentane (20 mL) was added, resulting in precipitation of a deep
yellow powder. The product was collected by filtration, washed
with pentane (2 × 10 mL), and dried under vacuum, yielding
a yellow powder (66 mg, 77%). This material was further
purified by precipitation from a CH2Cl2 solution layered with
pentane, which yielded 13‚0.25 CH2Cl2; the presence of solvent
was confirmed by NMR and elemental analysis. Anal. Calcd
for C29H42N2PdCl2‚0.25 CH2Cl2: C, 56.92; H, 6.94; N, 4.54.
Found: C, 56.53; H, 6.84; N, 4.79. 1H NMR (CD2Cl2): δ 7.45-
7.25 (m, 6H, Ar), 3.19 (s, 2H, PdCH2Cl), 3.09 (sept, J ) 7, 2H,
CHMe2), 2.94 (sept, J ) 7, 2H, CHMe2), 2.11 (s, 3H, NdCMe),
2.08 (s, 3H, NdCMe), 1.41 (d, J ) 7, 6H, CHMe2), 1.36 (d, J )
7, 6H, CHMe2), 1.17 (d, J ) 7, 12H, CHMe2). 13C{1H} NMR
(CD2Cl2): δ 175.6 (NdC), 174.5 (NdC), 139.3 (2C, Ar Cipso),
138.4 (4C, Ar Cortho), 128.5 (Ar Cpara), 127.6 (Ar Cpara), 124.7
(2C, Ar Cmeta), 123.7 (2C, Ar Cmeta), 36.8 (Pd-CH2Cl), 29.4
(CHMe2), 29.0 (CHMe2), 24.1 (CHMe2), 23.7 (CHMe2), 23.5 (2
CHMe2), 21.9 (NdCMe), 20.2 (NdCMe). Positive ion ESI-MS:
1
and dried under vacuum. H NMR (CD2Cl2): δ 8.31 (d, J ) 6,
4H, H6), 8.22 (d, J ) 2, 4H, H3), 7.86 (dd, J ) 6, 2, 4H, H5),
1.48 (s, 18H, Bu). 13C{1H} NMR (CD2Cl2): δ 170.2, 156.9,
t
149.6, 126.8, 122.1, 36.8, 30.0. Positive ion ESI-MS: m/z 321.1,
[(tBu2bipy)2Pd]2+. Anal. Calcd for C84H48B2F40N4Pd: C, 50.41;
H, 2.42; N, 2.80. Found: C, 50.29; H, 2.60; N, 2.73.
Rea ction of [{(tBu 2bip y)P d (CH2Cl)}2(µ-Cl)][B(C6F 5)4]
a n d Vin yl Ch lor id e. A valved NMR tube was charged with
(tBu2bipy)Pd(CH2Cl)Cl (10, 5.0 mg, 0.011 mmol) and [Li-
(Et2O)2.8][B(C6F5)4] (9.7 mg, 0.011 mmol), and CD2Cl2 (0.6 mL)
and vinyl chloride (32 equiv) were added by vacuum transfer
at -196 °C. The tube was warmed to -78 °C and transferred
to a precooled NMR probe, and NMR spectra were recorded.
No reaction was observed until 20 °C. After 10 h at 20 °C, the
1H NMR spectrum showed that [{(tBu2bipy)PdCl}2(µ-Cl)]-
[B(C6F5)4] (34 mol % vs 10), [{(tBu2bipy)Pd(µ-Cl)}2][B(C6F5)4]2
(16 mol % vs 10), and free allyl chloride (45 mol % vs 10) were
present. No Pd(0) was observed.
Rea ction of [{(tBu 2bip y)P d (CH2Cl)}2(µ-Cl)][B(C6F 5)4]
a n d 13CO. A valved NMR tube was charged with (tBu2bipy)-
Pd(CH2Cl)Cl (10, 5.0 mg, 0.011 mmol) and [Li(Et2O)2.8]-
[B(C6F5)4] (9.7 mg, 0.011 mmol), and CD2Cl2 (0.6 mL) and 13CO
(40 equiv) were added by vacuum transfer at -196 °C. The
tube was warmed to -78 °C and transferred to a precooled
NMR probe, and NMR spectra were recorded. At -78 °C, the
only product observed was [(tBu2bipy)Pd(CH2Cl)(13CO)][B-
(C6F5)4]. Data for [(tBu2bipy)Pd(CH2Cl)(13CO)][B(C6F5)4] are as
follows: 1H NMR (CD2Cl2, -70 °C) δ 8.60 (d, J ) 6, 1H), 8.41
(d, J ) 6, 1H), 8.12 (s, 1H), 8.10 (s, 1H), 7.78 (br d, J ) 6, 1H),
7.63 (d, J ) 6, 1H), 4.08 (s, 2H, PdCH2Cl), 1.37 (s, 9H), 1.33
(s, 9H); 13C{1H} NMR (CD2Cl2, -70 °C) δ 172.1 (Pd-13CO),
165.0 (2C), 156.8 (2C), 150.3 (2C), 125.9, 125.1, 121.2, 120.3,
33.6 (PdCH2Cl), 36.1 (2C, CMe3), 30.2 (CMe3), 30.0 (CMe3). No
further reaction was observed until 20 °C. After 20 min at 20
°C, 50% of the Pd-CH2Cl had reacted and resonances for 13C-
labeled diketene [-CH213C(dCH2)O13C(dO)-] were observed
m/z 561.2, [(R-diimine)Pd(CH2Cl)] +
.
R ea ct ion of (r-d iim in e)P d (CH2Cl)Cl/[Li(E t2O)2.8][B-
(C6F 5)4] a n d VC. A valved NMR tube was charged with (R-
diimine)Pd(CH2Cl)Cl (7.0 mg, 0.012 mmol) and [Li(Et2O)2.8]-
[B(C6F5)4] (10.4 mg, 0.012 mmol), and CD2Cl2 (0.6 mL) and
VC (78 equiv) were added by vacuum transfer at -196 °C. The
tube was warmed to 20 °C, and NMR spectra were recorded
periodically. After 10 h at 20 °C, [{(R-diimine)Pd(µ-Cl)}2]-
[B(C6F5)4]2 (14 mol % vs 13) and (R-diimine)PdCl2 (72 mol %
vs 13) were the only organometallic species observed by 1H
NMR.1b Allyl chloride (80 mol % vs 13) was also present. Pd-
(0) was observed in the reaction tube. NMR and GC-MS
analyses of volatiles showed that allyl chloride was the only
major volatile species present.
(34) gNMR, version 4.1.2; Adept Scientific, Letchworth, U.K., 2000.

Pd Complexes with Halogenated Alkyl Ligands
Organometallics, Vol. 23, No. 3, 2004 609
Ack n ow led gm en t. We thank Dr. J in Qin for as-
sistance with ESI-MS experiments and Edward Stoe-
benau for assistance with NMR spectra simulations.
This work was supported by the Edison Polymer In-
novation Corp. and the Department of Energy (Contract
No. DE-FG02-00ER15036).
OM034211Z