Insertion of unsaturated hydrocarbons into the palladium-carbon bond of complexes (N?N)Pd(C(=N-2,6-Me2Ph)Me)X (N?N = bpy, phen; X = Cl, Br, I, BF4): A structural and mechanistic study

Article abstract of DOI:10.1021/om9701940

The reactivity of Pd-carboimine complexes toward unsaturated hydrocarbon bonds has been studied. Insertion of norbornadiene and norbornene into the Pd-C bond of the neutral complexes (N?N)Pd(C(=N-2,6-Me₂C₆H₃)Me)X (X = Cl (1), Br (2), I (3); N?N = 2,2′-bipyridine (bpy, a), 1,10-phenanthroline (phen, b)) afforded quantitatively the novel and stable complexes [(N?N)Pd(C₇H₈C(=NR)Me)]X and [(N?N)Pd(C₇H₁₀C(=NR)Me)]X (R = 2,6-Me₂C₆H₃). Insertion reactions of the unstrained unsaturated hydrocarbons ethylene, propylene, 3-methyl-1,2-butadiene, and acetylene with the cationic complexes [(N?N)Pd-(C(=NR)Me)]X (N?N = bpy, phen; R = 2,6-Me₂C₆H₃; X = BF₄) provided the complexes [(N?N)-Pd(C₂H₄C(=NR)Me)]X, [(N?N)Pd(C₃H₆C(=NR)Me)]X, [(N?N)Pd(C₅H₈C(=NR)Me)]X, and [(bpy)Pd(C₂H₂C(=NR)Me)]X. The remarkable stability of these products is caused by the strong coordination of the carboimine nitrogen to the palladium center. Reaction of 1a and 1b with HC≡CCOOMe gave, instead of an insertion product, the Michael addition product (N?N)Pd[C(=CH₂)N(2,6-Me₂C₆H ₃)(CH=CHCOOMe)]Cl. Kinetic measurements carried out on the norbornadiene insertion reactions with 1a,b, 2a, and 3a revealed that the reactions are first order in the palladium concentration and occur via a norbornadiene concentration-independent and dependent pathway.

Full text of DOI:10.1021/om9701940

4150
Organometallics 1997, 16, 4150-4160
In ser tion of Un sa tu r a ted Hyd r oca r bon s in to th e
P a lla d iu m -Ca r bon Bon d of Com p lexes
(NkN)P d (C(dN-2,6-Me2P h )Me)X (NkN = bp y, p h en ; X ) Cl,
Br , I, BF 4): A Str u ctu r a l a n d Mech a n istic Stu d y
J ohannes G. P. Delis, Peter G. Aubel, Kees Vrieze,* and
Piet W. N. M. van Leeuwen
Anorganisch Chemisch Laboratorium, J . H. van’t Hoff Research Instituut, Universiteit van
Amsterdam, Nieuwe Achtergracht 166, NL-1018 WV Amsterdam, The Netherlands
Nora Veldman and Anthony L. Spek†
Bijvoet Center for Biomolecular Research, Vakgroep Kristal-en Structuurchemie,
Universiteit Utrecht, Padualaan 8, NL-3584 CH Utrecht, The Netherlands
Received March 10, 1997X
The reactivity of Pd-carboimine complexes toward unsaturated hydrocarbon bonds has
been studied. Insertion of norbornadiene and norbornene into the Pd-C bond of the neutral
complexes (NkN)Pd(C(dN-2,6-Me2C6H3)Me)X (X ) Cl (1), Br (2), I (3); NkN = 2,2′-bipyridine
(bpy, a ), 1,10-phenanthroline (phen, b)) afforded quantitatively the novel and stable
complexes [(NkN)Pd(C7H8C(dNR)Me)]X and [(NkN)Pd(C7H10C(dNR)Me)]X (R ) 2,6-
Me2C6H3). Insertion reactions of the unstrained unsaturated hydrocarbons ethylene,
propylene, 3-methyl-1,2-butadiene, and acetylene with the cationic complexes [(NkN)Pd-
(C(dNR)Me)]X (NkN = bpy, phen; R = 2,6-Me2C6H3; X ) BF4) provided the complexes [(NkN)-
Pd(C2H4C(dNR)Me)]X, [(NkN)Pd(C3H6C(dNR)Me)]X, [(NkN)Pd(C5H8C(dNR)Me)]X, and
[(bpy)Pd(C2H2C(dNR)Me)]X. The remarkable stability of these products is caused by the
strong coordination of the carboimine nitrogen to the palladium center. Reaction of 1a and
1b with HCtCCOOMe gave, instead of an insertion product, the Michael addition product
(NkN)Pd[C(dCH2)N(2,6-Me2C6H3)(CHdCHCOOMe)]Cl. Kinetic measurements carried out
on the norbornadiene insertion reactions with 1a ,b, 2a , and 3a revealed that the reactions
are first order in the palladium concentration and occur via a norbornadiene concentration-
independent and dependent pathway.
In tr od u ction
involves X or L displacement by the alkene, affording a
four-coordinate intermediate, followed by migratory
insertion, and one in which the alkene adds to the
complex to give a five-coordinate alkene adduct followed
by migratory insertion. Ab initio calculations carried
out by Thorn and Hoffmann on ethylene insertion into
the Pt-H bond demonstrated that insertion from a four-
coordinate intermediate is preferred.14 Experimental
studies on these reactions supported the calculations
and showed that, particularly when X is a weakly bound
ligand, the insertion occurs via a four-coordinate
intermediate.15-18 Insertion of alkenes into Pd-C bonds
has also been demonstrated to occur via four-coordinate
intermediates, such as the intramolecular alkene inser-
tion reaction of (PPh3)2Pd(CO2(CH2)2CHdCH2)Cl19 and
The insertion of unsaturated hydrocarbons like olefins
and acetylenes into metal-carbon bonds is a very
important reaction in many homogeneously catalyzed
processes.1-4 An example of such a process is the
palladium-catalyzed copolymerization of CO and al-
kenes leading to the formation of polyketones,2,3,5-10
which involves successive insertions of CO and al-
kene.4,11-13
The insertion of an alkene into L2M(R)X complexes
(M ) Pd, Pt) can follow two possible routes: one that
* To whom correspondence should be addressed.
† To whom correspondence concerning crystallographic data should
be addressed.
X Abstract published in Advance ACS Abstracts, August 15, 1997.
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S0276-7333(97)00194-5 CCC: $14.00 © 1997 American Chemical Society

Unsaturated Hydrocarbon Insertion into Pd-C Bonds
Organometallics, Vol. 16, No. 19, 1997 4151
SX/SX102A four-sector mass spectrometer coupled to a J EOL
MS-MP 7000 data system. IR spectra were recorded on a Bio-
Rad FTS-7. Synthesis of the complexes (bpy)Pd(C(dN-2,6-
Me2C6H3)Me)Cl and (phen)Pd(C(dN-2,6-Me2C6H3)Me)Cl has
been described before.29
alkene insertion into [(phen)Pd(R)L]BAr4 (R ) H, CH3,
C(O)CH3; L ) OEt2).13 On the other hand, it has been
proposed that five-coordinate intermediates are involved
in the insertion of ethylene into the Pt-H bond of the
L2PtH(SnCl3) complex20 and in the intramolecular
insertion reaction of the (Ph2POHOPPh2)PtH(Ph2P(CH2)n-
CHdCH2) complex.21
Examples of insertion of unsaturated hydrocarbons
into Pd-acyl bonds are relatively scarce. Some studies
are known for complexes containing phosphine lig-
ands,19,22-24 bidentate11-13,25,26 and terdentate nitrogen
ligands,27 and NkO ligands,28 of which a few deal with
kinetic measurements. Sen et al. carried out a kinetic
study on insertion of the strained alkene norbornadiene
into the Pd-acyl bond of the complexes [(PPh3)2Pd(CH3-
CN)(C(O)R)]BF4.23 However, dissociation of the phos-
phine ligands resulted in complex kinetics.
Recently, we performed a detailed kinetic study on
insertion reactions of norbornadiene and allenes with
the neutral complexes (Ar-BIAN)Pd(C(O)R)X and (NkN)-
Pd(C(O)R)X, respectively (NkN = 8-(2-pyridyl)quinoline,
Ar-BIAN, R-DAB),25,29 which indicated that Pd-N bond
breaking rather than Pd-X bond breaking is involved
in the insertion reaction. Lately, we reported the first
isocyanide insertion reaction in (NkN)Pd(Me)Cl com-
plexes (NkN = 2,2′-bipyridine (bpy), 1,10-phenanthroline
(phen), 2,2′-bipyrimidine (bpm)) leading to the car-
boimine products (NkN)Pd(C(dNR)Me)Cl (R ) 2,6-
Me2C6H3, t-Bu, CH2tosyl).29,30 We were interested in
whether the carboimine products would allow insertion
of unsaturated hydrocarbons and if so whether the
reactivity would be similar to the analogous (NkN)Pd-
(C(O)Me)Cl complexes. Moreover, the direct synthesis
of the polyimine analogue of polyketone via subsequent
alternating insertion of isocyanides and alkenes would
be of great interest.
Syn th esis of (bp y)P d (C(dN-2,6-Me2C6H3)Me)Br (2a ).
The complex (bpy)Pd(C(dN-2,6-Me2C6H3)Me)Cl (100 mg; 0.23
mmol) and KBr (164 mg; 1.4 mmol) were dissolved in a mixture
of dichloromethane (60 mL) and acetone (40 mL) and stirred
for 2 h. The solvent was evaporated, and the residue was
washed twice with dichloromethane. The volume of the
solvent was concentrated and hexane (30 mL) was added,
providing a yellow crystalline material, which was collected
by centrifugation. Yield: 101 mg; 0.21 mmol; 90%. 1H NMR
3
data (300 MHz, CDCl3) δ: 9.31 (d, J ) 4.4 Hz, 1H, H6), 9.05
3
(d, J ) 4.4 Hz, 1H, H6′), 8.11 (br, 2H, H3, H3′), 8.02 (t, 8.1
Hz, 1H, H4), 7.97 (t, 8.0 Hz, 1H, H4′), 7.60 (m, 1H, H5), 7.51
3
3
(t, J ) 6.5 Hz, 1H, H5′), 6.97 (d, J ) 7.2 Hz, 2H, Hmeta), 6.84
3
(t, J ) 7.2 Hz, 1H, Hpara), 2.34 (s, 3H, C(dNR)CH3), 2.26 (s,
6H, (CH3)2Ph). IR ν(CdN) (KBr): 1623 cm-1
. A
13C NMR
spectrum could not be obtained because of the low solubility.
FAB MS found (calcd for C20H20N3PdBr): 488 (488).
Syn th esis of (bp y)P d (C(dN-2,6-Me2C6H3)Me)I (3a ). The
synthesis was carried out according to the procedure followed
above for 2a , yielding a dark yellow crystalline material (112
mg; 0.19 mmol; 85%). 1H NMR data (300 MHz, CDCl3) δ: 9.47
3
3
(d, J ) 4.9 Hz, 1H, H6), 8.94 (d, J ) 4.9 Hz, 1H, H6′), 8.12
3
(d, J ) 4.1 Hz, 2H, H3, H3′), 8.04 (t, 7.9 Hz, 1H, H4), 7.70 (t,
7.7 Hz, 1H, H4′), 7.63 (m, 1H, H5), 7.48 (m, 1H, H5′), 6.96 (d,
3
3J ) 7.1 Hz, 2H, Hmeta), 6.85 (t, J ) 6.9 Hz, 1H, Hpara), 2.43
(s, 3H, C(dNR)CH3), 2.26 (s, 6H, (CH3)2Ph). IR ν(CdN)
(KBr): 1635 cm-1. A 13C NMR spectrum could not be obtained
because of the low solubility. FAB MS found (calcd for C20
H20N3PdI): 535 (535).
-
Gen er a l P r oced u r e for In ser tion of Nor bor n a d ien e
a n d Nor bor n en e in Com p lexes (NkN)P d (C(dN-2,6-Me2-
C6H3)Me)X (NkN = bp y (a ), p h en (b)) p r ovid in g com -
p lexes 4a ,b (X ) Cl), 5a (X ) Br ), 6a (X ) I) (In ser tion of
Nor bor n a d ien e), a n d 7a ,b (In ser tion of Nor bor n en e).
The complex (NkN)Pd(C(dN-2,6-Me2C6H3)Me)Cl (40 mg; 0.090
mmol) and the appropriate alkene (5.0 equiv; 0.45 mmol; 41
mg) were dissolved in dichloromethane (20 mL) and stirred
for 2 h for reaction with norbornadiene and 24 h for reaction
with norbornene. The volume of the solution was concentrated
to 5 mL, and diethyl ether (30 mL) was added. The crystalline
material was collected by centrifugation.
Exp er im en ta l Section
Ma ter ia l a n d Ap p a r a tu s. All manipulations have been
carried out in an atmosphere of purified, dry nitrogen using
standard Schlenk techniques. Solvents were dried and stored
under nitrogen. 1H NMR and 13C NMR spectra were recorded
on a Bruker AMX 300 and DRX 300 (300.13 and 75.48 MHz
respectively). Elemental analyses were carried out in our
institute. Mass spectrometry was carried out on a J EOL J MS
Atom labeling schemes for the complexes 4a ,b, 5a , 6a , and
7a ,b are as follows.
(19) Samsel, E. G.; Norton, J . R. J . Am. Chem. Soc. 1984, 106, 5505-
5512.
(20) Clark, H. C.; J ablonski, C. R.; Halpern, J .; Mantovani, A.; Weil,
T. A. Inorg. Chem. 1974, 13, 1541-1543.
(21) van Leeuwen, P. W. N. M.; Roobeek, C. F.; Frijns, J . H. G.; Guy
Orpen, A. Organometallics 1990, 9, 1211-1222.
(22) Dekker, G. P. C. M.; Elsevier, C. J .; Vrieze, K.; van Leeuwen,
P. W. N. M.; Roobeek, C. F. J . Organomet. Chem. 1992, 430, 357-
372.
(23) Brumbaugh, J . S.; Whittle, R. R.; Parvez, M.; Sen, A. Organo-
metallics 1990, 9, 1735-1747.
(24) Ozawa, F.; Hayashi, T.; Koide, H.; Yamamoto, A. J . Chem. Soc.,
Chem. Commun. 1991, 1469-1470.
(25) Groen, J . H.; Delis, J . G. P.; van Leeuwen, P. W. N. M.; Vrieze,
K. Organometallics 1997, 16, 68-77.
(26) Delis, J . G. P.; Groen, J . H.; van Leeuwen, P. W. N. M.; Vrieze,
K.; Veldman, N.; Spek, A. L. Organometallics 1997, 16, 551-562.
(27) Ru¨lke, R. E.; Kaasjager, V. E.; Kliphuis, D.; Elsevier, C. J .; van
Leeuwen, P. W. N. M.; Vrieze, K.; Goubitz, K. Organometallics 1996,
15, 668-677.
(28) Green, M. J .; Britovsek, G. J . P.; Cavell, K. J .; Skelton, B. W.;
White, A. H. J . Chem. Soc., Chem. Commun. 1996, 1563-1564.
(29) Delis, J . G. P.; Aubel, P. G.; van Leeuwen, P. W. N. M.; Vrieze,
K.; Veldman, N.; Spek, A. L. Organometallics, 1997, 16, 2948-2957.
(30) Delis, J . G. P.; Aubel, P. G.; van Leeuwen, P. W. N. M.; Vrieze,
K.; Veldman, N.; Spek, A. L. J . Chem. Soc., Chem. Commun. 1995,
2233-2234.
[(bp y)P d (C7H8C(dN-2,6-Me2C6H3)Me)]Cl (4a ). Yield: 43
mg; 0.086 mmol; 95%. 1H NMR data (300 MHz, CDCl3) δ: 9.13
3
3
(d, J ) 8.0 Hz, 1H, H3), 9.00 (d, J ) 8.1 Hz, 1H, H3′), 8.56
3
(d, 3J ) 5.0 Hz, 1H, H6), 8.37 (t, J ) 7.8 Hz, 1H, H4), 8.08 (t,
3
3J ) 7.8 Hz, 1H, H4′), 7.73 (t, J ) 6.1 Hz, 1H, H5), 7.28 (m,
3
3
3H, H11, H12), 6.97 (t, J ) 6.1 Hz, 1H, H5′), 6.35 (dd, J )
3
3
3
5.5 Hz, J ) 2.8 Hz, 1H, H17), 6.24 (dd, J ) 5.5 Hz, J ) 2.8
Hz, 1H, H18), 5.69 (d, 3J ) 4.4 Hz, 1H, H6′), 3.11 (s, 1H, H16),

4152 Organometallics, Vol. 16, No. 19, 1997
Delis et al.
3.06 (s, 1H, H19), 2.65 (dd, 3J ) 6.3 Hz, 3J ) 3.3 Hz, 1H, H15),
1H, H5), 7.23 (m, 3H, H11, H12), 6.96 (t, 3J ) 6.3 Hz, 1H,
3
3
3
3
2.59 (d, J ) 6.2 Hz, 1H, H20), 2.30 (s, 3H, H10), 2.21 (s, 3H,
H5′), 5.64 (d, J ) 4.7 Hz, 1H, H6′), 3.06 (dd, J ) 6.5 Hz, J
) 1.8 Hz, 1H, H16), 2.78 (d, 3J ) 6.5 Hz, 1H, H19), 2.48 (d, 3J
) 3.8 Hz, 1H, H15), 2.41 (d, 3J ) 3.8 Hz, 1H, H20), 2.26 (s,
3H, H10), 2.24 (s, 3H, H10), 2.13 (d, 3J ) 13 Hz, 1H, H21),
1.83 (s, 3H, H14), 1.50 (d, 3J ) 13 Hz, 1H, H21), 1.62-1.50
(m, 4H, Hnbn). 13C NMR data (75.48 MHz, CDCl3) δ: 199.1
(C13), 156.6 (C2), 153.7 (C2′), 149.3 (C6), 147.0 (C6′), 141.4
(C4), 140.6 (C4′), 127.2 (C3), 126.3 (C3′), 125.7 (C5), 124.8 (C5′),
144.4, 130.6, 130.3, 129.6, 128.0 (CPh), 65.7, 57.1, 43.8, 42.2,
36.2, 30.5, 29.9 (Cnbn) 18.9, 18.4, 19.0 (CMe). FAB MS found
(calcd for C27H30N3PdCl - Cl): 502 (502).
3
H10), 2.10 (d, J ) 8.7 Hz, 1H, H21), 1.94 (s, 3H, H14), 1.58
(d, 3J ) 8.7 Hz, 1H, H21). 13C NMR data (75.48 MHz, CDCl3)
δ: 197.4 (C13), 156.7 (C2), 153.7 (C2′), 148.9 (C6), 147.1 (C6′),
141.5 (C4), 140.7 (C4′), 136.5 (C3), 134.4 (C3′), 144.2, 130.6,
130.5, 130.1, 129.7, 128.2, 125.7, 124.8 (CPh, CdCnbd), 127.4
(C5), 126.5 (C5′), 58.6, 51.4, 48.6, 47.3, 45.6 (Cnbd), 19.0, 18.7,
19.2 (CMe). Elemental analysis found (calcd for C27H28N3Pd-
Cl‚CH2Cl2): C, 53.88 (54.13); H, 5.15 (4.87); N, 6.72 (6.76). FAB
MS found (calcd for C27H28N3PdCl - Cl): 500 (500).
[(bp y)P d (C7H8C(dN-2,6-Me2C6H3)Me)]Br (5a ): Yield: 47
mg; 0.086 mmol; 95%. 1H NMR data (300 MHz, CDCl3) δ: 9.03
[(p h en )P d (C7H10C(dN-2,6-Me2C6H3)Me)]Cl (7b): Yield:
3
3
(d, J ) 8.1 Hz, 1H, H3), 8.92 (d, J ) 8.1 Hz, 1H, H3′), 8.59
45 mg; 0.085 mmol; 95%. 1H NMR data (300 MHz, CDCl3) δ:
(d, 3J ) 5.4 Hz, 1H, H6), 8.35 (t, J ) 7.8 Hz, 1H, H4), 8.08 (t,
9.03 (d, J ) 7.3 Hz, 1H, H4), 8.99 (d, J ) 5.2 Hz, 1H, H6),
3 4 3
3
3
3
3J ) 7.8 Hz, 1H, H4′), 7.76 (t, J ) 6.7 Hz, 1H, H5), 7.28 (m,
8.68 (dd, J ) 8.2 Hz, J ) 1.3 Hz, 1H, H4′), 2.27 (d, J ) 8.8
3 3
3
3H, H11, H12), 7.00 (t, 3J ) 6.7 Hz, 1H, H5), 6.38 (dd, 3J )
Hz, 1H, H7), 8.22 (dd, J ) 8.2 Hz, J ) 5.0 Hz, 1H, H5), 8.20
(d, 3J ) 8.8 Hz, 1H, H7′), 7.43 (d, 3J ) 8.2 Hz, 5.0 Hz, 1H,
3
3
3
5.4 Hz, J ) 3.0 Hz, 1H, H17), 6.24 (dd, J ) 5.4 Hz, J ) 2.9
Hz, 1H, H18), 5.70 (d, 3J ) 5.2 Hz, 1H, H6′), 3.11 (s, 1H, H16),
3.06 (s, 1H, H19), 2.67 (dd, 3J ) 6.3 Hz, 3J ) 2.1 Hz, 1H, H15),
2.60 (d, J ) 6.2 Hz, 1H, H20), 2.30 (s, 3H, H10), 2.21 (s, 3H,
H10), 2.10 (d, J ) 8.8 Hz, 1H, H21), 1.94 (s, 3H, H14), 1.58
3
4
H5′), 7.34 (m, 3H, H11, H12), 5.97 (dd, J ) 5.0 Hz, J ) 1.3
Hz, 1H, H6′), 3.38 (dd, 3J ) 6.5 hz, 3J ) 2.1 Hz, 1H, H16),
2.91 (d, 3J ) 6.5 Hz, 1H, H19), 2.55 (s, 2H, H15, H20), 2.34 (s,
3H, H10), 2.31 (s, 3H, H10), 2.21 (d, 3J ) 10 Hz, 1H, H21),
3
3
(d, 3J ) 8.7 Hz, 1H, H21). 13C NMR data (75.48 MHz, CDCl3)
δ: 197.0 (C13), 156.2 (C2), 153.2 (C2′), 148.6 (C6), 146.7 (C6′),
140.9 (C4), 140.2 (C4′), 143.8, 136.0, 133.8, 130.2, 130.1, 129.6,
129.2, 124.3 (CPh, CdCnbd), 127.7 (C3), 127.0 (C3′), 125.9 (C5),
125.2 (C5′), 58.2, 50.9, 48.1, 46.9, 45.1 (Cnbd), 18.7, 18.5, 18.1
(CMe). FAB MS found (calcd for C27H28N3PdBr - Br): 500
(500).
1.88-1.53 (m, 4H, Hnbn), 1.43 (d, J ) 10 Hz, 1H, H21). 13C
3
NMR data (75.48 MHz, CDCl3) δ: 198.6 (C13), 149.6 (C6),
147.4 (C6′), 146.3 (C2), 144.1 (C2′), 140.1 (C4), 139.1 (C4′),
125.9 (C7), 125.0 (C7′), 130.4, 130.2, 129.9, 129.8, 129.6, 129.3,
127.9, 127.7, 127.4 (CPh, Cphen), 65.5, 56.5, 43.6, 41.8, 35.8, 30.1,
29.4 (Cnbn), 18.6, 18.5, 18.0 (CMe). Elemental analysis found
(calcd for C29H30N3PdCl‚CH2Cl2): C, 55.66 (55.66); H, 5.09
(4.99); N, 6.44 (6.49). FAB MS found (calcd for C29H30N3PdCl
- Cl): 526 (526).
Gen er a l P r oced u r e for In ser tion of Eth ylen e, P r op yl-
en e, 3-Meth yl-1,2-bu ta d ien e, a n d Acetylen e in Com -
p lexes (NkN)P d (C(dN-2,6-Me2C6H3)Me)Cl (NkN = bp y
(1a ), p h en (1b)) P r ovid in g Com p lexes 9a ,b (In ser tion of
Eth ylen e), 10a ,b (In ser tion of P r op ylen e), 11a ,b (In ser -
t ion of 3-Met h yl-1,2-b u t a d ien e), a n d 12 (In ser t ion of
Acetylen e). The complex (NkN)Pd(C(dN-2,6-Me2C6H3)Me)-
Cl (40 mg, 0.090 mmol) and AgBF4 (1.2 eq; 0.1 mmol; 21 mg)
were dissolved in a mixture of dichloromethane and acetoni-
trile (5:1) and stirred for 5 min. The suspension was filtered,
after which, the alkene, acetylene, or allene was added by a
microsyringe in the case of a liquid reagent or by bubbling
through the solution in the case of a gaseous reagent. The
solution was stirred until it changed from yellow to almost
colorless. The solvent was evaporated and the residue dis-
solved in dichloromethane. The solution was filtered, after
which, ether was added to the solution to result in the
formation of a crystalline material.
[(bp y)P d (C7H8C(dN-2,6-Me2C6H3)Me)]I (6a ): Yield: 51
mg; 0.081 mmol; 90%. 1H NMR data (300 MHz, CDCl3) δ: 8.94
3
3
(d, J ) 8.2 Hz, 1H, H3), 8.84 (d, J ) 8.0 Hz, 1H, H3′), 8.61
(d, 3J ) 5.3 Hz, 1H, H6), 8.36 (t, J ) 7.5 Hz, 1H, H4), 8.08 (t,
3
3J ) 7.3 Hz, 1H, H4′), 7.77 (t, J ) 6.4 Hz, 1H, H5), 7.28 (m,
3
3
3
3H, H11, H12), 7.02 (t, J ) 6.6 Hz, 1H, H5′), 6.40 (dd, J )
3
3
3
5.5 Hz, J ) 2.9 Hz, 1H, H17), 6.26 (dd, J ) 5.5 Hz, J ) 2.8
Hz, 1H, H18), 5.71 (d, 3J ) 4.6 Hz, 1H, H6′), 3.12 (s, 1H, H16),
3.08 (s, 1H, H19), 2.70 (dd, 3J ) 6.3 Hz, 3J ) 2.3 Hz, 1H, H15),
3
2.61 (d, J ) 6.3 Hz, 1H, H20), 2.32 (s, 3H, H10), 2.23 (s, 3H,
H10), 2.13 (d, J ) 8.9 Hz, 1H, H21), 1.95 (s, 3H, H14), 1.60
3
(d, 3J ) 8.7 Hz, 1H, H21). 13C NMR data (75.48 MHz, CDCl3)
δ: 197.7 (C13), 156.6 (C2), 153.4 (C2′), 149.4 (C6), 147.4 (C6′),
141.4 (C4), 140.7 (C4′), 144.4, 136.7, 134.5, 130.8, 130.7, 130.2,
129.8, 124.6 (CPh, CdCnbd), 128.3 (C3), 127.8 (C3′), 126.6 (C5),
125.5 (C5′), 58.8, 51.7, 48.8, 47.5, 45.7 (Cnbd), 19.4, 19.1, 18.8
(CMe). FAB MS found (calcd for C27H28N3PdI - I): 500 (500).
[(p h en )P d (C7H8C(dN-2,6-Me2C6H3)Me)]Cl (4b): Yield:
46 mg; 0.088 mmol; 98%. 1H NMR data (300 MHz, CDCl3) δ:
3
3
9.06 (m, 1H, H6), 9.04 (d, J ) 4.6 Hz, 1H, H4), 8.70 (dd, J )
4
3
3
8.0 Hz, J ) 2.2 Hz, 1H, H4′), 8.29 (dd, J ) 8.2 Hz, J ) 5.3
[(bp y)P d (C2H4C(dN-2,6-Me2C6H3)Me)]BF 4 (9a ): Yield:
3
3
Hz, 1H, H5), 8.26 (d, J ) 8.2 Hz, 1H, H7), 8.19 (d, J ) 8.2
22 mg; 0.051 mmol; 57%. 1H NMR data (300 MHz, CDCl3) δ:
Hz, 1H, H7′), 7.44 (dd, 3J ) 8.0 Hz, 3J ) 5.3 Hz, 1H, H5′),
8.43 (m, 2H, H3, H3′), 8.38 (d, J ) 4.8 Hz, 1H, H6), 8.20 (dd,
3
3
4
3
4
7.35 (m, 2H, H11), 7.30 (dd, J ) 2.1 Hz, 1H, H12), 6.50 (dd,
3J ) 7.8 Hz, J ) 1.4 Hz, 1H, H4), 8.01 (dd, J ) 7.8 Hz, J )
3J ) 5.6 Hz, J ) 3.0 Hz, 1H, H17), 6.29 (dd, J ) 5.5 Hz, J
1.4 Hz, 1H, H4′), 7.61 (dt, J ) 6.3 Hz, 4J ) 1.0 Hz, H, H5),
3
3
3
3
) 3.0 Hz, 1H, H18), 6.00 (dd, 3J ) 5.0 Hz, 4J ) 1.0 Hz, 1H,
7.27 (m, 3H, H11, H12), 7.08 (t, 3J ) 6.3 Hz, 1H, H5′), 5.84 (d,
3
3
3
H6′), 3.17 (d, J ) 1.9 Hz, 2H, H16, H19), 2.96 (dd, J ) 6.2
Hz, 3J ) 2.2 Hz, 2H, H15, H20), 2.34, (s, 3H, H10), 2.29 (s,
3H, H10), 2.17 (d, 3J ) 8.8 Hz, 1H, H21), 2.01 (s, 3H, H14),
1.62 (d, 3J ) 8.8 Hz, 1H, H21). 13C NMR data (75.48 MHz,
CDCl3) δ: 197.7 (C13), 149.8 (C6), 148.0 (C6′), 146.8 (C2), 144.6
(C2′), 140.6 (C4), 139.6 (C4′), 136.6 (C7), 134.3 (C7′), 144.6 (C3),
144.4 (C3′), 128.2 (C5), 127.8 (C5′), 130.8, 130.6, 130.1, 129.7,
128.4, 126.5, 125.5 (CPh, CdCnbd), 58.8, 51.1, 48.8, 47.3, 45.5
(Cnbd) 19.1, 18.6, 19.0 (CMe). Elemental analysis found (calcd
for C29H28N3PdCl.CH2Cl2): C, 55.53 (55.83); H, 5.04 (4.96); N,
6.38 (6.51). FAB MS found (calcd for C29H28N3PdCl - Cl): 524
(524).
3J ) 4.8 Hz, 1H, H6′), 2.95 (t, J ) 6.3 Hz, 2H, CH2), 2.81 (t,
3J ) 6.3 Hz, 2H, CH2), 2.27 (s, 6H, H10), 1.88 (s, 3H, H14).
13C NMR data (75.48 MHz, CDCl3) δ: 198.8 (C13), 156.1 (C2),
153.2 (C2′), 149.2 (C6), 148.7 (C6′), 140.6 (C4), 140.0 (C4′),
124.0 (C3), 123.1 (C3′), 126.8 (C5), 126.1 (C5′), 45.1 (C15), 27.1
(C20), 143.7, 130.3, 129.2, 127.6 (CPh), 17.7, 18.6 (CMe).
Elemental analysis found (calcd for C22H24N3PdBF4‚1/2C4H8O):
C, 50.61 (51.50); H, 5.15 (5.05); N, 7.44 (7.51). FAB MS found
(calcd for C22H24N3PdBF4 - BF4): 436 (436).
[(p h en )P d (C2H4C(dN-2,6-Me2C6H3)Me)]BF 4 (9b): Yield:
25 mg; 0.054 mmol; 60%. 1H NMR data (300 MHz, CDCl3) δ:
3
3
8.85 (d, J ) 5.1 Hz, 1H, H6), 8.69, (d, J ) 7.4 Hz, 1H, H7),
3
3
[(bp y)P d (C7H10C(dN-2,6-Me2C6H3)Me)]Cl (7a ): Yield: 42
8.53 (d, J ) 8.1 Hz, 1H, H7′), 8.01 (d, J ) 5.3 Hz, 1H, H4),
3 3
mg; 0.084 mmol; 93%. 1H NMR data (300 MHz, CDCl3) δ: 9.00
7.98 (d, J ) 5.3 Hz, 1H, H4′), 7.46 (d, J ) 5.1 Hz, 1H, H5),
3
3
3
(d, J ) 8.1 Hz, 1H, H3), 8.88 (d, J ) 8.2 Hz, 1H, H3′), 8.52
(d, 3J ) 5.6 Hz, 1H, H6), 8.32 (t, 3J ) 7.8 Hz, 1H, H4), 8.05
7.45 (d, J ) 5.1 Hz, 1H, H5′), 7.30 (m, 3H, H11, H12), 6.11
(d, 3J ) 4.8 Hz, 1H, H6′), 3.03 (m, 4H, CH2), 1.93 (s, 3H, H14),
2.31 (s, 6H, H10). 13C NMR data (75.48 MHz, CDCl3) δ: 197.0
3
4
3
(dt, J ) 7.7 Hz, J ) 1.2 Hz, 1H, H4′), 7.67 (t, J ) 6.3 Hz,

Unsaturated Hydrocarbon Insertion into Pd-C Bonds
Organometallics, Vol. 16, No. 19, 1997 4153
(C13), 144.3 (C2), 141.9 (C2′), 147.8 (C6), 145.3 (C6′), 137.5
(C4), 136.8 (C4′), 128.3 (C3), 127.8 (C3′), 125.6 (C5), 125.1 (C5′),
123.5 (C7), 123.0 (C7′), 142.2 128.3, 127.2, 125.6 (CPh), 43.3
(C15), 24.9 (C20), 15.8, 16.6 (CMe). Elemental analysis found
(calcd for C24H24N3PdBF4): C, 52.12 (52.63); H, 4.45 (4.42); N,
7.63 (7.67). FAB MS found (calcd for C24H24N3PdBF4 - BF4):
460 (460).
6.9 Hz, 1H, dCH), 7.32 (m, 3H, H11, H12), 7.08 (t, 3J ) 6.4
Hz, 1H, H5′), 6.30 (d, 3J ) 6.8 Hz, 1H, dCH), 5.91 (d, 3J ) 5.2
Hz, 1H, H6′), 2.26 (s, 6H, H10), 2.02 (s, 3H, H14). 13C NMR
data (75.48 MHz, CDCl3) δ: C13 not observed, 155.8 (C2),
154.0 (C2′), 148.7 (C6), 147.2 (C6′), 141.6 (C4), 141.2 (C4′),
127.4 (C5), 126.2 (C5′), 124.7 (C3), 123.8 (C3′), 143.0, 131.5,
129.0, 128.0 (CPh), 108.6 (C15), 107.7 (C20), 17.8, 17.8, (CMe).
Rea ction of Meth yl P r op iola te w ith (NkN)P d (C(dN-
2,6-Me2C6H3)Me)Cl (NkN = bp y (1a ), p h en (1b)) P r ovid in g
Com plexes 13a,b. The complex (NkN)Pd(C(dN-2,6-Me2C6H3)-
Me)Cl (40 mg, 0.090 mmol) and methylpropiolate (2 equiv; 0.18
mmol; 0.18 mg) were dissolved in dichloromethane and stirred
for 2 h. The volume of the solution was concentrated to 5 mL,
and diethyl ether (30 mL) was added. The crystalline material
was collected by centrifugation.
[(bp y)P d (C3H6C(dN-2,6-Me2C6H3)Me)]BF 4 (10a ): Yield:
28 mg; 0.061 mmol; 68%. 1H NMR data (300 MHz, CDCl3) δ:
3
3
8.58 (d, J ) 5.7 Hz, 1H, H6), 8.50 (d, J ) 7.9 Hz, 1H, H3′),
3
3
4
8.41 (d, J ) 8.1 Hz, 1H, H3), 8.24 (dt, J ) 7.8 Hz, J ) 1.4
3
4
Hz, 1H, H4), 8.00 (dt, J ) 7.8 Hz, J ) 1.4 Hz, 1H, H4′), 7.70
(dt, 3J ) 7.2 Hz, 4J ) 1.4 Hz, 1H, H5), 7.26 (m, 3H, H11, H12),
3
4
3
7.02 (dd, J ) 7.8 Hz, J ) 1.0 Hz, 1H, H5′), 5.87 (d, J ) 5.3
Hz, 1H, H6′), 3.53 (dd, 2J ) 19.2 Hz, 3J ) 7.5 Hz, 1H, Hpropenyl),
3
2.84 (t, J ) 7.2 Hz, 1H, Hpropenyl), 2.44 (s, 3H, H10), 2.13 (s,
(b p y)P d [C(dCH2)N(2,6-Me2C6H 3)(CHdCH COOMe)]Cl
(13a ): Yield: 47 mg; 0.088 mmol; 98%. 1H NMR data (300
MHz, CDCl3) δ: 9.57 (d, 3J ) 13.0 Hz, dCH), 9.30 (d, 3J ) 5.0
3H, H10), 1.95 (s, 3H, H14), 1.25 (d, 3J ) 7.2 Hz, 3H,
CH3propenyl). 13C NMR data (75.48 MHz, CDCl3) δ: 196.8 (C13),
155.9 (C2), 153.0 (C2′), 149.0 (C6), 146.9 (C6′), 140.5 (C4), 140.0
(C4′), 127.2 (C5), 126.3 (C5′), 124.0 (C3), 123.1 (C3′), 143.7,
130.3, 130.3, 129.5, 128.9, 127.6 (CPh), 42.1 (C15), 53.1 (C20),
24.1, 19.4, 18.3, 17.5 (CMe). FAB MS found (calcd for C23H26N3-
PdBF4 - BF4): 450 (450).
3
Hz, 1H, H6′), 9.20 (d, J ) 5.5 Hz, 1H, H6), 8.12 (m, 4H, H4,
3
3
H4′, H3, H3′), 7.61 (t, J ) 5.5 Hz, 1H, H5), 7.52 (t, J ) 5.9
3
3
Hz, 1H, H5′), 7.15 (d, J ) 5.4 Hz, 2H, H11), 7.10 (t, J ) 4.6
3
3
Hz, 1H, H12), 4.24 (d, J ) 13.0 Hz, 1H, dCH), 4.16 (d, J )
3
2.0 Hz, 1H, dCH2), 3.81 (d, J ) 2.0 Hz, 1H, dCH2), 3.50 (s,
3H, OMe), 2.18 (s, 6H, H10, 2.30 (s, 6H, H10). 13C NMR data
(75.48 MHz, CDCl3) δ: 170.0 (CdO), 156.0 (C2′), 154.6 (C2),
151.9 (C6), 149.4 (C6′), 139.1 (C4), 139.3 (C4′), 127.9 (C5), 127.6
(C5′), 129.3 (C3), 122.5 (C3′), 153.2 (Pd-Cd), 152.2 (dCH-
(COOMe), 138.0, 136.8, 134.4, 126.4, 126.3 (CPh), 93.4 (H2Cd),
87.4 (CHd), 50.2 (COOMe), 17.7, 17.5 (CMe). FAB MS found
(calcd for C24H24N3O2PdCl): 528 (528).
[(ph en )P d(C3H6C(dN-2,6-Me2C6H3)Me)]BF4 (10b): Yield:
29 mg; 0.062 mmol; 69%. 1H NMR data (300 MHz, CDCl3) δ:
3
3
8.73 (d, J ) 8.3 Hz, 1H, H4), 9.00 (d, J ) 5.3 Hz, 1H, H6),
3
3
3
8.51 (d, J ) 8.1 Hz, 1H, H4′), 8.10 (dd, J ) 8.3 Hz, J ) 5.3
3
3
Hz, 1H, H5), 8.07 (d, J ) 8.8 Hz, 1H, H7), 8.02 (d, J ) 8.8
Hz, 1H, H7′), 7.42 (dd, 3J ) 8.2 Hz, 3J ) 5.3 Hz, 1H, H5′),
3
7.32 (m, 3H, H11, H12), 6.16 (d, J ) 5.0 Hz, 1H, H6′), 3.63
2
3
(p h en )P d [C(dCH 2)N(2,6-Me2C6H 3)(CH dCH COOMe)]-
(dd, J ) 19.3 Hz, J ) 7.6 hz, 1H, Hpropenyl) 3.11 (m, Hpropenyl),
Cl (13b): Yield: 47 mg; 0.085 mmol; 95%. 1H NMR data (300
3
2.41 (s, 3H, H14), 2.24 (d, J ) 19.3 hz, 1H, Hpropenyl), 2.00 (s,
3
3
3H, H14), 2.22 (s, 6H, H10), 1.43 (d, 3J ) 7.2 Hz, 3H,
CH3propenyl). 13C NMR data (75.48 MHz, CDCl3) δ: 195.0 (C13),
147.7 (C6), 145.6 (C6′), 144.2 (C2), 142.1 (C2′), 137.6 (C4), 136.8
(C4′), 128.3 (C3), 127.8 (C3′), 125.6 (C5), 125.2 (C5′), 123.9 (C7),
123.0 (C7′), 141.9, 128.4, 128.4, 127.5, 127.0, 125.7 (CPh), 51.3
(C15), 40.2 (C20), 22.4, 17.3, 16.3, 15.6 (CMe). FAB MS found
(calcd for C25H26N3PdBF4 - BF4): 474 (474).
MHz, CDCl3) δ: 9.67 (d, J ) 13.0 Hz, 1H, dCH), 9.56 (dd, J
) 4.9 Hz, 4J ) 1.5 Hz, 1H, H6), 9.46 (dd, 3J ) 5.2 Hz, 4J ) 1.2
3
Hz, 1H, H6′), 8.57 (m,, 2H, H4, H4′), 8.05 (d, J ) 8.8 Hz, 1H,
H7), 8.00 (d, 3J ) 8.8 Hz, 1H, H7′), 7.94 (dd, 3J ) 8.2 Hz, 3J )
4.8 Hz, 1H, H5), 7.86 (dd, 3J ) 8.2, 3J ) 4.8 Hz, 1H, H5′), 7.17
3
3
(d, J ) 5.4 Hz, 2H, H11), 7.12 (t, J ) 5.4 Hz, 1H, H12), 4.28
3
3
(d, J ) 13.0 Hz, 1H, dCH), 4.25 (d, J ) 2.0 Hz, 1H, dCH2),
3.88 (d, 3J ) 2.0 Hz, 1H, dCH2), 3.50 (s, 3H, OMe), 2.34 (s,
6H, H10), 2.24 (s, 6H, H10). A 13C NMR spectrum could not
be obtained because of solubility problems. Elemental analysis
found (calcd for C26H24N3O2PdCl‚1/2CH2Cl2): C, 54.11 (53.51);
[(bp y)P d (C5H8C(dN-2,6-Me2C6H3)Me)]BF 4 (11a ): Yield:
28 mg; 0.059 mmol; 65%. 1H NMR data (300 MHz, CDCl3) δ:
3
3
8.58 (d, J ) 4.8 Hz, 1H, H6), 8.50 (d, J ) 8.0 Hz, 1H, H3′),
3
3
4
8.44 (d, J ) 8.2 Hz, 1H, H3), 8.24 (dt, J ) 7.9 Hz, J ) 1.3
3
4
H, 4.55 (4.24); N, 6.86 (7.06). FAB MS found (calcd for C26
24N3O2PdCl): 552 (552).
Cr ysta l Str u ctu r e Deter m in a tion a n d Refin em en t of
-
Hz, 1H, H4), 8.03 (dt, J ) 7.8 Hz, J ) 1.3 Hz, 1H, H4′), 7.66
(dt, 3J ) 6.6 Hz, 4J ) 1.3 Hz, 1H, H5), 7.28 (m, 3H, H11, H12),
H
3
4
3
7.07 (dt, J ) 6.0 Hz, J ) 1.3 Hz, 1H, H5′), 6.00 (d, J ) 5.5
Hz, 1H, H6′), 3.39 (s, 2H, Pd-CH2), 2.30 (s, 6H, H10), 2.15 (s,
6H, dC(CH3)2), 2.02 (s, 3H, H14). 13C NMR data (75.48 MHz,
CDCl3) δ: 186.3 (C13), 155.9 (C2), 153.3 (C2′), 149.5 (C6), 147.0
(C6′), 140.6 (C4), 140.0 (C4′), 127.0 (C5), 126.5 (C5′), 124.0 (C3),
123.1 (C3′), 141.9, 130.1, 129.2, 127.6 (CPh), 34.6 (C15), 143.6
()CMe2), 18.1, 21.3 (CMe). Elemental analysis found (calcd for
C25H28N3PdBF4): C, 53.05 (53.26); H, 5.04 (5.01); N, 7.41 (7.45).
FAB MS found (calcd for C25H28N3PdBF4 - BF4): 476 (476).
[(ph en )P d(C5H8C(dN-2,6-Me2C6H3)Me)]BF4 (11b): Yield:
27 mg; 0.054 mmol; 60%. 1H NMR data (300 MHz, CDCl3) δ:
10b a n d 13a . Crystals of 10b and 13a were mounted on a
Lindemann glass capillary and transferred into the cold
nitrogen stream on an Enraf-Nonius CAD4-Turbo diffractom-
eter on a rotating anode. Accurate unit cell parameters and
an orientation matrix were determined by least-squares fitting
of the setting angles of 25 well-centered reflections (set 4)31 in
the range 11.52° < θ < 14.04° and 5.47° < θ < 15.47°, for 10b
and 13a , respectively. Reduced cell calculations did not
indicate higher lattice symmetry.32 Crystal data and details
on data collection and refinement are given in Table 1. Data
were corrected for Lp effects and the observed linear decay.
Data were not corrected for absorption for 10b. An empirical
absorption/extinction correction was applied (DIFABS33 as
implemented in PLATON)34 to 13a (transmission range 0.145-
1.000).
3
3
9.03 (d, J ) 5.1 Hz, 1H, H6), 8.71 (d, J ) 8.1 Hz, 1H, H4),
3
3
3
8.53 (d, J ) 8.0 Hz, 1H, H4′), 8.08 (dd, J ) 8.2 Hz, J ) 5.1
3
3
Hz, 1H, H5), 8.03 (s, 2H, H7, H7′), 7.46 (dd, J ) 8.1 Hz, J )
5.1 Hz, 1H, H5′), 7.33 (m, 3H, H11, H12), 6.24 (d, 3J ) 5.0 Hz,
1H, H6′), 3.62 (s, 2H, Pd-CH2), 2.33 (s, 6H, H10), 2.11 (s, 3H,
)C(CH3)2), 2.07 (s, 3H, )C(CH3)2), 2.04 (s, 3H, H14). 13C NMR
data (75.48 MHz, CDCl3) δ: 150.5 (C6), 148.1 (C6′), 144.8 (C2),
144.2 (C2′), 140.0 (C4), 139.4 (C4′), 130.8 (C3), 130.3 (C3′),
128.1 (C5), 127.6 (C5′), 126.3 (C7), 125.4 (C7′), 142.1, 130.8,
129.8, 128.1 (CPh), 34.7 (C15). FAB MS found (calcd for
The structure was solved by automated Patterson methods
and subsequent difference Fourier techniques (DIRDIF-92).35
Refinement on F2 was carried out by full-matrix least-squares
techniques (SHELXL-93);36 no observance criterion was ap-
plied during refinement. Hydrogen atoms were included in
the refinement on calculated positions riding on their carrier
C
27H28N3PdBF4 - BF4): 500 (500).
[(bp y)P d (C2H2C(dN-2,6-Me2C6H3)Me)]BF 4 (12): 1H NMR
3
(31) de Boer, J . L.; Duisenberg, A. J . M. Acta Crystallogr. 1984, A40,
C410.
(32) Spek, A. L. J . Appl. Crystallogr. 1988, 21, 578.
(33) Walker, N.; Stuart, D. Acta Crystallogr. 1983, A39, 158.
(34) Spek, A. L. Acta Crystallogr. 1990, A46, C34.
data (300 MHz, CDCl3) δ: 8.99, (d, J ) 5.2 Hz, 1H, H6), 8.66
3
3
(d, J ) 8.0 Hz, 1H, H3), 8.57 (d, J ) 8.0 Hz, 1H, H3′), 8.33
(dt, 3J ) 7.9 Hz, 4J ) 1.1 Hz, 1H, H4), 8.10 (dt, 3J ) 7.9 Hz, 4J
) 1.3 Hz, 1H, H4′), 7.76 (t, 3J ) 6.4 Hz, 1H, H5), 7.66 (d, 3J )

4154 Organometallics, Vol. 16, No. 19, 1997
Delis et al.
Ta ble 1. Cr ysta l a n d Refin em en t Da ta for [(p h en )P d (C3H6C(dN-2,6-Me2C6H3)Me)]BF 4 (10b) a n d
(bp y)P d [C(dCH2)N(2,6-Me2C6H3)(CHdCHCOOMe)]Cl (13a )
10a
13b
Crystal Data
C25H26N3Pd‚BF4‚CH2Cl2
646.66
orthorhombic
Pbca (No. 61)
11.6278(9)
formula
mol wt
crystal system
space group
a, Å
C24H24ClN3O2Pd
528.35
triclinic
P1h (No. 2)
8.659(4)
9.098(8)
15.137(14)
92.74(8)
102.33(5)
104.12(6)
1123.5(15)
1.562
b, Å
c, Å
20.978(2)
21.768(2)
R, deg
â, deg
γ, deg
V, Å3
5309.9(7)
1.618
8
D
Z
calc, g cm-3
2
F (000)
2608
9.5
0.15 × 0.45 × 0.50
536
9.7
µ, cm-1
crystal size, mm
0.05 × 0.20 × 0.30
Data Collection
T, K
150
150
θ
min, θmax deg
1.9, 27.5
0.710 73
graphite monochromator
1.4, 23.0
0.710 73
graphite monochromator
wavelength (Mo KR) Å
scan type
∆ω, deg
ω
ω
0.66 + 0.35 tan θ
0.90 + 0.35 tan θ
Hor, vert aperture, mm
X-ray exposure time, h
linear decay, %
reference reflections
data set (hkl)
no. of total data
no. of total unique data
Rint
2.18 + 1.09 tan θ, 4.00
17.9
2
1h 2h 6h, 1h 5h 2, 2h 1h 5
-15:0, -27:25, 0:28
10627
6072
0.0470
3.00, 4.00
17.9
1
4h 1 1
-9:0, -9:9, -16:16
3355
3112
0.1536
DIFABS transm. range
0.145-1.000
Refinement
338
0.1391
No. of refined parameters
279
0.2620
wR2a
Rb
0.0558 [for 3845 Fo > 4σ(Fo)]
0.0945 [for 1783 Fo > 4σ(Fo)]
S
1.06
1.03
w-1c
σ2(F2) + (0.0608P)2
0.000, 0.000
σ2(F2) + (0.1000P)2
0.001, 0.000
(∆/σ)av, (∆/σ)max
min and max F, e Å-3
-0.62, 1.15 (near Pd)
-1.22, 1.50 (near Pd)
a
2
b
wR2 ) [∑[w(Fo - Fc2)2]/∑[w(Fo2)2]]0.5
.
R ) ∑(||Fo| - |Fc||)/∑|Fo|. c P ) (max(Fo2, 0) + 2Fc2)/3.
atoms. All non-hydrogen atoms were refined with anisotropic
thermal parameters. The hydrogen atoms were refined with
a fixed isotropic displacement parameter related to the value
of the equivalent isotropic displacement parameter of their
carrier atoms by a factor of 1.5 for the methyl hydrogen atoms
and 1.2 for the other hydrogen atoms, respectively. Weights
were introduced in the final refinement cycles for 10b but not
13a . Neutral atom scattering factors and anomalous disper-
sion corrections were taken from ref 37. Geometrical calcula-
tions and illustrations were performed with PLATON.34 All
calculations were performed on a DECstation 5000/133.
Kin etic Mea su r em en ts. The reaction rates were obtained
spectrophotometrically by repetitive scanning of the spectrum
at that wavelength, at which the difference in absorbance of
product and educt was largest. Norbornadiene was added to
a prethermostated solution of the palladium complex in the
appropriate solvent in a 1 cm quartz cell. The UV spectra were
recorded on a Perkin-Elmer Lambda 5 spectrometer, and the
solution was thermostated by a MGW Lauda K4R electronic
with a temperature accuracy of 0.5 °C.
Resu lts a n d Discu ssion
In ser tion of Alk en es in to P d -C(dNR)Me Bon d s.
Reaction of the neutral carboimine complexes (NkN)-
Pd(C(dN-2,6-Me2C6H3)Me)X (1a , NkN = 2,2′-bipyridine
(bpy), X ) Cl; 1b, NkN = 1,10-phenanthroline (phen),
X = Cl; 2a , NkN = bpy, X = Br, 3a : NkN = bpy; X = I)
with excess norbornadiene afforded the insertion prod-
ucts [(NkN)Pd(C7H8C(dN-2,6-Me2C6H3)Me)]X (4a , NkN
= bpy, X ) Cl; 4b, NkN = phen, X = Cl; 5a , NkN = bpy,
X = Br; 6a , NkN = bpy, X = I) (see eq 1).
(35) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
Garc´ıa-Granda, S.; Gould, R. O.; Smits, J . M. M.; Smykalla, C. The
DIRDIFF program system, Technical report of the Crystallography
Laboratory, University of Nijmegen, The Netherlands 1992.
(36) Sheldrick, G. M. SHELXL-93 Program for crystal structure
refinement. University of Go¨ttingen, Germany 1993.
(37) Wilson, A. J . C. International Tables for Crystallography;
Kluwer Academic Publishers: Dordrecht, The Netherlands, 1992; Vol.
C.

Unsaturated Hydrocarbon Insertion into Pd-C Bonds
Organometallics, Vol. 16, No. 19, 1997 4155
Sch em e 1
The conversion of the complexes 1a , 1b, 2a , and 3a
to the products 4a , 4b, 5a , and 6a was quantitative
within 30 min for 1a , 2a , and 3a and 16 h for 1b at 293
K, when 5 equiv of the alkene was added to a solution
of the starting complex in dichloromethane. The inser-
tion goes to completion upon addition of 1 equiv of
norbornadiene, but the reaction rate is much lower.
Insertion of norbornadiene into the Pd-C bond of
complex (NkN)Pd(C(dN-t-Bu)Me)Cl (NkN ) bpy, phen)
led to the formation of several uncharacterized side
products beside the expected insertion product, while
complex (NkN)Pd(C(dNCH2tosyl)Me)Cl (NkN ) bpy,
phen) did not react with norbornadiene even after
several days in dichloromethane.
In complexes 4a , 4b, 5a , and 6a , the nitrogen atom
of the carboimine group is coordinated to the palladium
forming a five-membered palladacycle, as could be
inferred from the high equivalent conductance mea-
sured in acetonitrile for the mentioned complexes of
about 140 Ω-1 cm2 mol-1, when compared to the
conductance for (bpy)Pd(Me)Cl of 4 Ω-1 cm2 mol-1 and
for 1a of 3 Ω-1 cm2 mol-1. The products 4a b, 5a , and
6a are very stable when compared to the acetyl ana-
logues [(bpy)Pd(C7H8C(O)Me)]Cl12 and [(Ar-BIAN)Pd-
(C7H8(C(O)Me)]Cl,11 which can be ascribed to the strong
coordination of the imine nitrogen to the palladium
center, preventing decomposition of the complex via â-H
elimination.
with [(bpy)Pd(C(O)Me)(CH3CN)]OTf.12 Therefore, the
products 9a ,b and 10a ,b can be considered as very rare
examples of isolable products resulting from insertion
of ethylene and propylene.13,28
Insertion of isocyanide into the Pd-C bond of the
complexes 4a ,b, 5a , and 6a would be the next step in a
co-oligomerization of isocyanides and alkenes. However,
addition of the isocyanide DIC to these complexes in
dichloromethane or in acetonitrile results in immediate
substitution of the bidentate nitrogen ligand by the
isocyanide. Insertion of an isocyanide needs initial
precoordination to the palladium center, which is in-
hibited by the strongly coordinated imine nitrogen.
Ch a r a cter iza tion of th e P r od u cts Obta in ed by
Alk en e In ser tion . The products 4a ,b, 5a , 6a , 7a ,b,
9a ,b, and 10a ,b have been characterized by 1H and 13C
NMR spectroscopy, mass spectroscopy, and/or elemental
analyses, while an X-ray structure determination has
been carried out for complex 10b. The 1H NMR spectra
of the complexes 4a ,b, 5a , 6a , and 7a ,b showed the
formation of only one isomer, viz. the cis addition of
Pd-(C(dNR)Me) to the exo face of the alkene, as could
An interesting reaction is the insertion of norbornene
into the Pd-C bond of the neutral complexes 1a and
1b in dichloromethane leading to a quantitative forma-
tion of the complexes [(NkN)Pd(C7H10C(dN-2,6-Me2C6-
H3)Me)]Cl (NkN = bpy (7a ), phen (7b)). Insertion of
norbornene is much slower than insertion of norborna-
diene and goes to completion within 16 h and several
days for complexes 1a and 1b, respectively, while the
reaction of (bpy)Pd(C(O)Me)Cl with norbornene resulted
in only 16% conversion of the starting complex.12 Prob-
ably, the coordination of the imine nitrogen to the
palladium center of the products 7a and 7b causes the
reaction to go to completion.
The complexes 1a and 1b did not react with ethylene
and propylene in dichloromethane. However, the ionic
complexes [(bpy)Pd(C(dN-2,6-Me2C6H3)Me)(NCMe)]BF4
(8a ) and [(phen)Pd(C(dN-2,6-Me2C6H3)Me)(NCMe)]BF4
(8b ), prepared in situ by reaction with AgBF4 in the
presence of acetonitrile, readily underwent insertion of
ethylene and propylene to form the insertion products
as shown in Scheme 1.
3
be concluded from the coupling constants J (H15-H20)
1
which are around 6.2 Hz.11,12,23,38 The H NMR spectra
of the complexes 4a ,b, 5a , and 6a showed a well-defined
pattern for the inserted alkene with the remaining
alkene protons H17 and H18 of the inserted norborna-
diene at around 6.3 ppm.
The insertion products [(NkN)Pd(C2H4C(dN-2,6-
Me2C6H3)Me)]BF4 (NkN = bpy (9a ), phen (9b)) and
[(NkN)Pd(C3H6C(dN-2,6-Me2C6H3)Me)]BF4 (NkN = bpy
(10a ), phen (10b)) are formed within 1-3 h, when
stirred under alkene atmosphere in 57-69% yield. The
insertion of ethylene appeared to be about twice as fast
as the insertion of propylene. Remarkable is that the
products 9a ,b and 10,b are stable for several days in
solution at low temperature (273 K) and for several days
in crystalline form at room temperature.
1
A remarkable aspect of the H NMR spectrum of the
products 4a ,b, 5a , 6a , 7a ,b, 9a ,b, and 10a ,b is the high-
field shift of the ortho proton H6′ adjacent to the
nitrogen of the bpy and phen ligands, which can be
observed at 5.8 ppm for bpy and at 6.0 ppm for phen,
while normally these signals appear around 8.5 ppm.
This high-field shift can be explained by the close
proximity of the Me2C6H3 group to the ortho proton H6′
caused by the coordination of the carboimine group to
the palladium center, as is also clear from the molecular
structure of [(phen)Pd(C3H6C(dN-2,6-Me2C6H3)Me)]BF4
It is known that insertions of unactivated alkenes like
ethylene and propylene do not occur in neutral com-
plexes such as (LkL)Pd(R)X (X = halide), while in ionic
complexes (X ) solvent) where they do occur the
products are susceptible to â-hydrogen elimination, as
was shown for insertion reactions of unstrained alkenes
(38) Groen, J . H.; Elsevier, C. J .; Vrieze, K.; Smeets, W. J . J .; Spek,
A. L. Organometallics 1996, 15, 3445-3455.

4156 Organometallics, Vol. 16, No. 19, 1997
Delis et al.
C(13) has a larger trans influence than N(3) of the imine
group. The Pd-C(13) bond distance of 2.024(4) Å is
comparable to other Pd-C(sp3) bond distances trans to
a Pd-N(sp2) bond.12,39-41 The bite angle N(1)-Pd-N(2)
is 79.80(15)°, which is normal for (NkN)Pd(II) complexes
containing bpy or phen ligands.11,12,29,42
It is clear from the molecular structure that propylene
exclusively inserts via a 2,1-insertion. Hydrocarbony-
lation reactions of propylene3 catalyzed by (R2P(CH2)3-
PR2)Pd(II) complexes and a study on enantioselective
copolymerization of propylene and CO,43 however, dem-
onstrated that insertion of propylene into the Pd-acyl
bond in these cases is preferentially 1,2 and larger R
groups on the phosphine enhance this preference. The
2,1-insertion reaction of propylene with complexes 8a ,b
might therefore be rationalized by the low steric bulk
of the bpy and phen ligands and the large steric bulk of
the C(dN-2,6-Me2C6H3)Me group.
F igu r e 1. ORTEP plot34 at 50% probability level of
complex [(phen)Pd(C3H6C(dN-2,6-Me2C6H3)Me)]BF4 (10b).
In ser tion of Allen es in to P d -C(dNR)Me Bon d s.
Upon reaction of 3-methyl-1,2-butadiene with the neu-
tral complexes 1a and 1b in dichloromethane, several
uncharacterized products were obtained. Reaction of
3-methyl-1,2-butadiene with the ionic complexes 8a and
8b, however, resulted in the quantitative formation of
[(bpy)Pd(C5H8C(dN-2,6-Me2C6H3)Me)]BF4 (11a ), and
[(phen)Pd(C5H8C(dN-2,6-Me2C6H3)Me)]BF4 (11b) re-
spectively, as shown in eq 2.
Ta ble 2. Selected Bon d Dista n ces (Å) a n d Bon d
An gles (d eg) for
[(p h en )P d (C3H6C(dN-2,6-Me2C6H3)Me)]BF 4 (10b)a
bond distances (Å)
bond angles (deg)
Pd-N(1)
2.177(4)
2.053(4)
2.049(4)
2.024(4)
1.276(6)
1.433(6)
1.513(9)
1.515(7)
1.493(7)
1.493(8)
N(1)-Pd-N(2)
79.80(15)
103.66(15)
95.95(18)
80.75(19)
115.5(3)
106.1(3)
115.6(4)
125.1(5)
122.7(4)
111.0(4)
110.2(4)
119.3(4)
Pd-N(2)
N(1)-Pd-N(3)
Pd-N(3)
Pd-C(13)
N(2)-Pd-C(13)
N(3)-Pd-C(13)
Pd-N(3)-C(16)
Pd-C(13)-C(15)
N(3)-C(16)-C(15)
N(3)-C(16)-C(17)
C(16)-N(3)-C(18)
Pd-C(13)-C(14)
C(13)-C(15)-C(16)
C(15)-C(16)-C(17)
N(3)-C(16)
N(3)-C(18)
C(13)-C(14)
C(13)-C(15)
C(15)-C(16)
C(16)-C(17)
a
Esd’s in parentheses.
(10b) (vide infra). Coordination of the carboimine group
could not be inferred from IR spectrometry since the
CdN stretch frequencies of the alkene insertion prod-
ucts were obscured by those of the bidentate nitrogen
ligand. The CdN 13C signal of the products 4a ,b, 5a ,
6a , 7a ,b, 9a ,b, and 10a ,b can be observed at around
198 ppm, which is, as expected,11,12,38 about 15 ppm
higher than that of the starting complexes 1a and 1b.
The 1H NMR spectrum of the propylene insertion
products 10a and 10b exhibited the formation of only
one isomer (see Scheme 1).
Molecu la r Str u ctu r e of [(p h en )P d (C3H6C(dN-2,6-
Me2C6H3)Me)]BF 4 (10b). Crystals of complex 10b
suitable for an X-ray structure determination were
obtained from slow diffusion of hexane in a solution of
the complex in dichloromethane. The molecular struc-
ture is presented in Figure 1, and selected bond lengths
and bond angles are collected in Table 2.
The structure of complex 10b shows bidentate coor-
dination of phenanthroline to the square planar pal-
ladium center with N(3) of the imine group and the
chiral carbon atom C(13) of the secondary alkyl group
completing the coordination plane. Due to coordination
of N(3) (Pd-N(3) ) 2.049(4) Å), the Me2C6H3 group is
in close proximity of C(1) of phenanthroline. The plane
of the Me2C6H3 group is orientated orthogonally to the
coordination plane of palladium.
These products are stable for several days in solution
and can be stored under an atmosphere of nitrogen in
crystalline form for several weeks without decomposi-
tion. They were characterized by 1H and 13C NMR and
mass spectroscopy and/or by elemental analysis.
Analogous to the alkene-inserted products 4a ,b, 5a ,
6a , 7a ,b, 9a ,b, and 10a ,b, the nitrogen of the car-
boimine group is coordinated to the metal center, which
could be concluded from the high-field shift of the ortho
proton H6′ of bpy and phen.
Rea ction s of Ca r boim in e Com p lexes w ith Al-
k yn es. Acetylene does not react with the neutral
complexes 1a and 1b, but a very fast mono insertion
into the Pd-C bond of the ionic complex 8a occurs in
dichloromethane leading to [(bpy)Pd(C2H2C(dN-2,6-
Me2C6H3)Me)]BF4 (12a ) (see eq 3). In several cases,
double insertion of alkynes prevails over monoin-
sertion.44-46 We may explain the monoinsertion by the
strong coordination of the imine nitrogen atom to the
(39) Ru¨lke, R. E.; Han, I. M.; Elsevier, C. J .; Vrieze, K.; van
Leeuwen, P. W. N. M.; Roobeek, C. F.; Zoutberg, M. C.; Wang, Y. F.;
Stam, C. H. Inorg. Chim. Acta 1990, 169, 5-8.
(40) Markies, B. A.; Rietveld, M. H. P.; Boersma, J .; Spek, A. L.;
van Koten, G. J . Organomet. Chem. 1992, 424, C12-C16.
(41) Byers, P. K.; Canty, A. Organometallics 1990, 9, 210-220.
(42) Ru¨lke, R. E.; Delis, J . G. P.; Groot, A. M.; Elsevier, C. J .; van
Leeuwen, P. W. N. M.; Vrieze, K.; Goubitz, K.; Schenk, H. J .
Organomet. Chem. 1996, 508, 109-120.
Both enantiomers are present in the crystal (lattice
group Pbca).
The Pd-N(1) bond distance of 2.177(4) Å is longer
than the Pd-N(2) distance of 2.053(4) Å, showing that
(43) Nozaki, K.; Sato, N.; Takaya, H. J . Am. Chem. Soc. 1995, 117,
9911-9912.
(44) Ryabov, A. D.; van Eldik, R.; Le Borgne, G.; Pfeffer, M.
Organometallics 1993, 12, 1386-1393.
(45) Pfeffer, M. Recl. Trav. Chim. Pays-Bas 1990, 109, 567-576.

Unsaturated Hydrocarbon Insertion into Pd-C Bonds
Organometallics, Vol. 16, No. 19, 1997 4157
palladium center preventing precoordination of another
equivalent of acetylene.
Unfortunately, the product 12a is relatively unstable
as compared to the alkene and allene insertion products
mentioned above. Decomposition of the complex occurs
within several hours in solution. Therefore, complex
12a could be characterized by 1H NMR spectroscopy
only, showing two doublets for the alkenyl fragment at
7.66 and 6.30 ppm with a coupling constant of 3J H-H
)
F igu r e 2. ORTEP plot34 at 50% probability level of
complex (bpy)Pd[C(dCH2)N(2,6-Me2C6H3)(CHdCHCOOMe)]-
Cl (13a ).
6.8 Hz between the two olefinic protons, characteristic
of a cis configuration of the alkenyl fragment. It should
be mentioned that reaction of acetylene with the cationic
complex 8b containing phenanthroline did not lead to
formation of any stable or characterizable product.
Unexpectedly, the neutral complexes 1a and 1b
reacted with methylpropiolate to give (bpy)Pd[C(dCH2)N-
(2,6-Me2C6H3)(CHdCHCOOMe)]Cl (13a ) and (phen)Pd-
[C(dCH2)N(2,6-Me2C6H3)(CHdCHCOOMe)]Cl (13b )
within 1 h, as shown in eq 4, instead of giving insertion
Sch em e 2
products.
close to the imine complex. We have obtained proof for
the tautomerism in complex 1a in a reaction with D2O,
since, when 1a was stirred in acetone with excess D2O,
the methyl group on the imine carbon was quantita-
tively deuterated within 1 h (see eq 5).
These compounds are very stable and could be ana-
lyzed by 1H and 13C NMR, mass spectroscopy and/or
elemental analysis, while an X-ray structure determi-
nation has been carried out for complex 13a . The H
NMR spectrum showed the hydrogen atoms of the
1
NCHdCHCOO fragment around 9.6 and 4.3 ppm with
3
a coupling constant of J H-H ) 13.1 Hz between the
olefinic protons characteristic of a trans configuration
of the olefin. The bpy and phen proton signals appear
at values normally observed for (NkN)Pd(II) com-
plexes.29,41,42 Reaction of 1a ,b with MeO2CCO2Me (DM-
DCA) and 8a ,b with methylpropiolate and DMDCA
resulted in formation of several uncharacterizable prod-
ucts.
The formation of complexes 13a and 13b can be
explained by a mechanism involving initial imine-
enamine tautomerism followed by a Michael addition
of N-H to the R,â-unsaturated ester methylpropiolate
(see Scheme 2).
Such an imine-enamine tautomerism also occurs in
a reaction of trans-Pd(C(dN-C6H4-p-Me)Me)Cl(PEt3)2
with MeO2CtCO2Me (DMDCA).47 Since we do not see
any signal of the enamine complexes in the 1H NMR
spectrum of 1a and 1b, we may conclude that the
equilibrium of the imine-enamine tautomerism lies
Molecu la r Str u ctu r e of (bp y)P d [C(dCH2)N(2,6-
Me2C6H3)(CHdCHCOOMe)]Cl (13a). Crystals of com-
plex 13a suitable for X-ray structure determination
were obtained by slow diffusion of hexane into a solution
of the complex in dichloromethane. The molecular
structure of complex 13a is presented in Figure 2, while
selected bond lengths and bond angles have been
collected in Table 3.
This structure displays a square planar surrounding
of the palladium atom by a bidentate coordinated bpy
ligand, the chloride atom and by carbon C(11). The Pd-
N(1) distance of 2.125(14) Å is longer than the Pd-N(2)
distance of 2.023(15) Å because of the higher trans
influence of carbon C(11) with respect to the chloride
atom.48 The Pd-C(11) distance of 1.990(18) Å is com-
parable to other Pd-C(sp2) bond distances of (NkN)-
Pd(II) complexes.42
(46) Clark, H. C.; Milne, C. R. C.; Wong, C. S. J . Organomet. Chem.
1977, 136, 265-279.
(47) Clark, H. C.; Milne, C. R. C.; Payne, N. C. J . Am. Chem. Soc.
1978, 100, 1164-1169.

4158 Organometallics, Vol. 16, No. 19, 1997
Delis et al.
Ta ble 4. Ra te Con sta n ts k1 a n d k2 a n d th e
En th a lp y a n d En tr op y of Activa tion for Rea ction
of Com p lexes (NkN)P d (C(dN-2,6-Me2C6H3)Me)Cl
w ith Nor bor n a d ien e
Ta ble 3. Selected Bon d Dista n ces (Å) a n d Bon d
An gles (d eg) for
(bp y)P d [C(dCH2)N(2,6-Me2C6H3)-
(CHdCHCOOMe)]Cl (13a )a
T
k1 × 102 k2 × 102
∆Hq
∆Sq
bond distances (Å)
bond angles (deg)
NkN
X
(K)
(s-1
)
(M-1 s-1
1.68(8)
)
(kJ mol-1
)
(J K-1 mol-1
)
Pd-Cl
2.309(5)
2.125(14)
2.023(15)
1.990(18)
1.32(2)
1.40(2)
1.47(2)
1.36(2)
1.34(2)
Cl-Pd-N(1)
96.6(5)
87.9(5)
78.1(6)
bpy (1a ) Cl 293.0 0.07(2)
298.0 0.10(4)
302.0 0.11(3)
304.0 0.20(7)
phen (1b) Cl 304.0 0.02(1)
bpy (2a ) Br 304.0 0.94(9)
Pd-N(1)
Cl-Pd-C(11)
2.58(18) k1 70.2(6.2) k1 -66(21)
3.30(14) k2 56.8(3.8) k2 -85(13)
4.18(31)
0.56(4)
7.89(42)
Pd-N(2)
Pd-C(11)
C(11)-C(12)
N(3)-C(11)
N(3)-C(13)
N(3)-C(21)
C(21)-C(22)
N(1)-Pd-N(2)
N(2)-Pd-C(11)
C(12)-C(11)-N(3)
C(11)-N(3)-C(21)
N(3)-C(21)-C(22)
C(21)-C(22)-C(23)
96.7(7)
119.6(16)
123.9(15)
130.0(16)
122.1(17)
bpy (3a )
I
304.0 1.58(23) 15.8(10)
a
Esd’s in parentheses. Conditions: acetonitrile solvent; [Pd] )
0.375 mM.
aEsd’s in Parentheses.
F igu r e 4. Effect of the concentration of excess bpy on the
rate constant k1 of the reaction of norbornadiene with 1a
in CH3CN at 304 K ([Pd] ) 0.375 mM).
F igu r e 3. Dependence of the pseudo-first-order rate
constants kobs on the norbornadiene concentration for the
reaction of complexes 1a and 1b with norbornadiene in
CH3CN at 304 K ([Pd] ) 0.375 mM).
Kin etic Mea su r em en ts of Nor bor n a d ien e In ser -
tion . The kinetics of the norbornadiene insertion into
the Pd-C bond of 1a , 1b, 2a , and 3a as shown in eq 1
were studied by monitoring the absorption in the range
of 360-620 nm as a function of time in a UV-visible
spectrometer. All reactions were carried out with a
large excess (at least 10-fold) of norbornadiene as
compared to the metal complex, i.e., under pseudo-first-
order conditions. The conversion of the starting com-
plexes is quantitative under these conditions, and in all
cases, isosbestic points were obtained. The reaction
rates kobs (s-1) were calculated from the slope of the plots
ln{(At - A∞)/A0 - A∞)} vs time. All reactions were found
to be first order in the concentration of the metal
complex for at least three half-lifes when the reaction
was performed in acetonitrile, while, unfortunately, in
dichloromethane no straight lines were obtained in a
first-order plot. In fact, the rate of the reaction in
dichloromethane increases during the reaction time,
which may be ascribed to an increase of the polarity of
the reaction mixture caused by formation of ionic
insertion products. It should be mentioned that the
reaction in the polar solvent acetonitrile is faster than
in dichloromethane.
F igu r e 5. Effect of the concentration of excess bpy on the
rate constant k2 of the reaction of norbornadiene with 1a
in CH3CN at 304 K ([Pd] ) 0.375 mM).
(Figure 3). Therefore, we have only carried out kinetic
measurements for the reaction of complex 1b with nbd
at 304 K. The rate constants k1 and k2 for reactions of
the complexes 1a , 1b, 2a , and 3a , along with the values
of the parameters of activation ∆Hq and ∆Sq for reaction
of complex 1a , determined from the values of k1 and k2
measured in the temperature range of 293-304 K, have
been collected in Table 4.
In flu en ce of th e X Liga n d . The value for k1 and
k2 for the reaction of (bpy)Pd(C(dN-2,6-Me2C6H3)X (X
) Cl (1a ), Br (2a ), I (3a )) with norbornadiene measured
at 31 °C in acetonitrile increases in the order X ) Cl <
Br < I. However, the variations in the values for both
k1 and k2 are relatively small.
The pseudo-first-order rate constants kobs gave straight
lines when plotted against the concentration of norbor-
nadiene with a nonzero intercept with the y-axis (see
Figure 3), indicating that the usual25,26 rate eq kobs
)
k1 + k2[nbd] is obeyed. The reaction of norbornadiene
with complex 1b containing phen appeared to be much
slower than the reaction with complex 1a containing bpy
In flu en ce of Excess F r ee Bid en ta te Nitr ogen
Liga n d a n d Ch lor id e. In Figures 4 and 5, the
influence of addition of excess free bpy to 1a on the value
of k1 and k2, respectively, is displayed. Interestingly,
(48) Appleton, T. G.; Clark, H. C.; Manzer, L. E. Coord. Chem. Rev.
1973, 10, 335.

Unsaturated Hydrocarbon Insertion into Pd-C Bonds
Organometallics, Vol. 16, No. 19, 1997 4159
Sch em e 3. P ossible Rou tes for th e
Sch em e 4. P ossible Rou tes for th e
Nor bor n a d ien e-In d ep en d en t k1 P a th w a y
Nor bor n a d ien e-Dep en d en t k2 P a th w a y
I, IV, or V by free ligand, providing a species containing
two nitrogen ligands coordinated in a monodentate way.
Actually, we have observed the formation of a new
complex in the 1H NMR spectrum of a mixture of
complex 1a or 1b and 1 equiv of free bpy or phen,
respectively, in CDCl3 at 230 K, which is most likely
species VIII containing two nitrogen ligands (eq 6).
the norbornadiene-independent pathway with rate con-
stant k1 is strongly retarded by addition of excess bpy.
The value for k1 decreases from 0.20 × 10-2 s-1 without
excess ligand to 0.0064 × 10-2 s-1 with 1.5 equiv of
excess ligand. This result is comparable to that ob-
tained for the reaction of norbornadiene with (p-An-
BIAN)Pd(C(O)Me)Cl.25 Unexpectedly, the norbornadiene-
dependent pathway with a rate constant k2 is also
retarded by excess ligand. The value for k2 decreases
from 0.042 M-1 s-1 without excess ligand to 0.015 M-1
s-1 with 1.5 equiv of excess ligand. It should be noted
that the value of k2 in the case of reaction of (p-An-
BIAN)Pd(C(O)Me)Cl with norbornadiene appeared to be
hardly affected by excess ligand.25
Since substitution of one of these ligands by norborna-
diene in species VIII can be expected to be more difficult
than substitution of a solvent molecule of species I, IV,
or V, an apparent decrease of the value of k1 might be
observed.
Alk en e-Dep en d en t k2 P a th w a y. The alkene-de-
pendent k2 pathway might occur either via an initial
alkene association affording a square-pyramidal inter-
mediate XIII (Scheme 4, pathway E), as we have
previously reported for the norbornadiene insertion
reaction in (Ar-BIAN)Pd(C(O)R)X25 complexes, or via
initial nitrogen dissociation (intermediate IX, pathway
D), as we have recently proposed for the allene insertion
reaction with (NkN)Pd(R)X complexes.26
Pathway D for the insertion into the Pd-carboimine
bond seems most likely, since nitrogen donor atom site
exchange in (NkN)Pd(C(dNR)Me)Cl complexes (NkN
= bpy, phen, 2,2′-bipyrimidine; R ) t-Bu, tosylmethyl)
also involves Pd-N bond breaking.29 Furthermore,
kinetic measurements29 showed that the exchange
process is much faster (kobs is ca. 0.5 s-1 at 303 K) than
the norbornadiene insertion (kobs ) 1.18 × 10-2 s-1 at
304 K, [nbd] ) 0.216 M, 1a ). A mechanism involving
Pd-X bond breaking before or during the rate-deter-
mining step is not likely, since the difference in the
value for k2 of complexes 1a (X ) Cl), 2a (X ) Br), and
3a (X ) I) is not very large. Moreover, no mass law
retardation upon addition of free halide is observed.
The retardation of the k2 pathway upon addition of
excess free ligand might be explained by coordination
of the extra ligand instead of norbornadiene on the
vacant site of intermediate IX or X leading to less
reactive species. The observation that (NkN)Pd(C(dN-
CH2tosyl)Me)Cl (NkN = bpy, phen) does not react with
Addition of excess Cl- in the form of NEt4Cl, while
the ionic strength is maintained constant by addition
of NEt4OTf, influenced neither the value for k1 nor for
k2. This has also been observed for the reaction of (p-
An-BIAN)Pd(C(O)Me)Cl with norbornadiene.25
Mech a n ism of th e Nor bor n a d ien e In ser tion .
From the kinetic measurements, it is clear that the
norbornadiene insertion reaction with 1a , 1b, 2a , and
3a proceeds via two pathways: one that is independent
of the norbornadiene concentration with a rate constant
k1 and one that is linearly dependent on the norborna-
diene concentration with a rate constant k2.
Alk en e-In d ep en d en t k1 P a th w a y. For the reaction
of (Ar-BIAN)Pd(C(O)R)X with norbornadiene we have
recently reported the possible pathways A, B, and C (see
Scheme 3),25 involving a rate determining Pd-solvent
bond-making reaction, which is more important than
Pd-X bond breaking (pathway A) or Pd-N bond break-
ing (pathways B and C).
Pathways A, B, and C are in agreement with the
absence of mass law retardation by halide ions and the
small influence of the nature of the coordinated halide
on the reaction rate.
The retardation of the k1 pathway upon addition of
free ligand may be explained by substitution of the
weakly coordinating solvent molecule in intermediate

4160 Organometallics, Vol. 16, No. 19, 1997
Delis et al.
norbornadiene is consistent with a rate-determining
migratory insertion step, as has also been proposed for
the allene29 and norbornadiene25 insertion reactions. It
is known that electron-withdrawing groups on a migrat-
ing R group (in this case the tosylmethyl group) retard
migration, while electron-donating groups accelerate
migration.25,26,49-52
In this study, we were able to study the influence of
the flexibility of the ligand on the rate of norbornadiene
insertion, while we have previously employed only the
very rigid Ar-BIAN ligand.25 From the results it is clear
that the value for k2 of complex 1a (4.18(31) × 10-2 M-1
s-1) containing the flexible ligand bpy is much larger
Pd-C bond29 and alkene insertion into the Pd-car-
boimine bond. Further insertions on the road to poly-
imine fragments do not occur owing to the strong
coordination of the carboimine nitrogen to the metal
center.
A kinetic study on the norbornadiene insertion reac-
tion in (NkN)Pd(C(dNR)Me)X complexes showed that
the reaction involves two pathways, one of which is
independent and one dependent on the norbornadiene
concentration. The alkene concentration-independent
pathway may proceed via a rate-determining solvent-
assisted halide or nitrogen dissociation, followed by
alkene association and migratory insertion, while the
alkene concentration-dependent pathway may occur via
initial dissociation of a nitrogen donor followed by
alkene association and a rate-determining migratory
insertion.
than that of complex 1b (0.56(4) × 10-2 M-1 s-1
)
containing the very rigid ligand phenanthroline. One
may imagine that the intermediates containing mono-
dentate ligands such as IX, X, and XI are more readily
formed for flexible ligands such as bpy than for rigid
ligands such as phen, for which the dissociated nitrogen
must stay in close proximity of the metal center.
Ack n ow led gm en t. Professor Dr E. Drent and Dr
W. P. Mul (Koninklijke/Shell-Laboratorium, Amster-
dam) are acknowledged for their helpful discussions and
Shell Research BV for financial support. This work was
supported in part (N.V. and A.L.S.) by the Netherlands
Foundation of Chemical Research (SON) with financial
aid from the Netherlands Organization for Scientific
Research (NWO). We thank J .-M. Ernsting for NMR
spectroscopy assistance and R. H. Fokkens and J . W.
H. Peeters for mass spectroscopy.
Con clu sion
The neutral and cationic (NkN)Pd(C(dNR)Me)X com-
plexes undergo facile and quantitative insertion of
strained and unstrained alkenes, allenes, and alkynes
to give in most cases remarkably stable products.
Unfortunately, we have not succeeded in direct forma-
tion of the polyimine analogue of polyketone. Nonethe-
less, we have been able to demonstrate the existence of
the first two steps, i.e., isocyanide insertion into the
Su p p or tin g In for m a tion Ava ila ble: Further details of
the structure determinations, including tables of atomic
coordinates, bond lengths and angles, and thermal parameters
for 10b and 13a and the measured kobs’s of all the kinetic
reactions (17 pages). Ordering information is given on any
current masthead page.
(49) Anderson, G. K.; Cross, R. J . Acc. Chem. Res. 1984, 17, 67-74.
(50) Cross, R. J .; Gemmill, J . J . Chem. Soc., Dalton Trans. 1981,
2317-2320.
(51) Axe, F. U.; Marynick, D. S. J . Am. Chem. Soc. 1988, 110, 3728-
3734.
(52) Koga, N.; Morokuma, K. J . Am. Chem. Soc. 1986, 108, 6136-
6144.
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