Reactivity of a Nickel Fluoride Complex: Preparation of New Tetrafluoropyridyl Derivatives

Article abstract of DOI:10.1021/om980935c

Treatment of trans-[NiF(2-C₅F₄N)(PEt₃)₂] (1), obtained by reaction of Ni(COD)₂ with PEt₃ and pentafluoropyridine, with Me₃SiOTf effects the formation of the air-stable inflate co

Full text of DOI:10.1021/om980935c

1710
Organometallics 1999, 18, 1710-1716
Rea ctivity of a Nick el F lu or id e Com p lex: P r ep a r a tion of
New Tetr a flu or op yr id yl Der iva tives†
Thomas Braun,‡ Simon Parsons,§ Robin N. Perutz,*,‡ and Matthias Voith‡
Departments of Chemistry, University of York, Heslington, York YO10 5DD, U.K., and
University of Edinburgh, West Mains Road, Edinburgh EH9 3J J , U.K.
Received November 17, 1998
Treatment of trans-[NiF(2-C5F4N)(PEt3)2] (1), obtained by reaction of Ni(COD)2 with PEt3
and pentafluoropyridine, with Me3SiOTf effects the formation of the air-stable triflate complex
trans-[Ni(OTf)(2-C5F4N)(PEt3)2] (2). The X-ray crystal structure reveals a molecular complex
with approximately square-planar coordination at nickel, a Ni-O distance of 1.957(2) Å,
and a Ni-C distance of 1.851(3) Å. The reaction of 2 with NaOPh yields the phenoxy complex
trans-[Ni(OPh)(2-C5F4N)(PEt3)2] (3). The crystal structure of 3 was determined. The Ni-O
and Ni-C distances are 1.894(4) and 1.861(6) Å, respectively. The complexes trans-[NiPh-
(2-C5F4N)(PEt3)2] (5) and trans-[NiMe(2-C5F4N)(PEt3)2] (6) were obtained on treatment of 1
with PhLi and Me2Zn, respectively. Treatment of 6 with CO yielded 2-acetyltetrafluoropy-
ridine, while reaction with air yielded 2-methyltetrafluoropyridine. The studies reported in
this paper demonstrate the synthesis of nickel derivatives of tetrafluoropyridine with the
metal in a 2-position as well as the preparation of new 2-substituted tetrafluoropyridines
by C-C coupling reactions.
In tr od u ction
The ease of synthesis of 1 offered new opportunities for
investigating the reactivity of the Ni-F bond in a
molecular system. The replacement of the metal-bound
fluorine in 1 by a new anionic ligand would provide an
entry to compounds of the general structure trans-[NiR-
(2-C5F4N)(PEt3)2]. Although several nickel pentafluo-
rophenyl derivatives of the type trans-[NiX(C6F5)L2]8,9
and trans-[Ni(C6F5)2L2]8 have been reported, to the best
of our knowledge no other transition-metal compound
with a 2-tetrafluoropyridyl ligand is known. In this
paper we describe the synthesis and molecular struc-
tures of (2-tetrafluoropyridyl)nickel derivatives with
triflate, phenoxide, phenyl, and methyl ligands as well
as the preparation of new 2-substituted tetrafluoro-
pyridines by C-C coupling reactions.
Several methods have recently been reported for
activating carbon-fluorine bonds of fluoroaromatic and
fluoroaliphatic compounds by reaction at appropriate
transition-metal centers.1-5 One of the most striking
reactions we have encountered is the fast oxidative
addition of pentafluoropyridine at a nickel center,
yielding trans-[NiF(2-C5F4N)(PEt3)2] (1).5 The special
properties of the transition-metal-fluorine bonds are
increasingly being recognized,3,6 as is the role of carbon-
metal-fluorine fragments in synthesis and catalysis.1-3,7
† Dedicated to Prof. Helmut Werner on the occasion of his 65th
birthday.
‡ University of York.
§ University of Edinburgh.
(1) Burdeniuc, J .; J edlicka, B.; Crabtree, R. H. Chem. Ber./ Recl.
1997, 130, 145 and references therein.
(2) Kiplinger, J . L.; Richmond, T. G.; Osterberg, C. E. Chem. Rev.
1994, 94, 373 and references therein.
Resu lts
Syn th esis of tr a n s-[Ni(OTf)(2-C5F 4N)(P Et3)2] (2).
The complex trans-[NiF(2-C5F4N)(PEt3)2] (1) reacts im-
mediately with Me3SiOTf to give the air-stable triflate
complex trans-[Ni(OTf)(2-C5F4N)(PEt3)2] (2) in 83%
yield. An additional pathway to 2 is the stepwise
treatment of a hexane solution of [Ni(PEt3)2(COD)] with
C5F5N and Me3SiOTf without isolation of 1. The struc-
(3) Murphy, E. F.; Murugavel, R.; Roesky, H. W. Chem. Rev. 1997,
97, 3425 and references therein.
(4) Edelbach, B. L.; J ones, W. D. J . Am. Chem. Soc. 1997, 119, 7734.
(5) Cronin, L.; Higgitt, C. L.; Karch, R.; Perutz, R. N. Organome-
tallics 1997, 16, 4920.
(6) Inter alia: (a) Doherty, N. M.; Hoffman, N. W. Chem. Rev.
1991, 91, 553. (b) Caulton, K. G. New J . Chem. 1994, 18, 25. (c)
Whittlesey, M. K.; Perutz, R. N.; Greener, B.; Moore, M. H. J . Chem.
Soc., Chem. Commun. 1997, 187. (d) Murphy, V. J .; Hascall, T.; Chen,
J . Y.; Parkin, G. J . Am. Chem. Soc. 1996, 118, 7428. (e) Poulton, J . T.;
Sigalas, M. P.; Folting, K.; Streib, W. E.; Eisenstein, O.; Caulton, K.
G. Inorg. Chem. 1994, 33, 1476. (f) Cooper, A. C.; Huffman, J . C.;
Caulton, K. G. Inorg. Chim. Acta 1998, 270, 261. (g) Pilon, M. C.;
Grushin, V. V. Organometallics 1998, 17, 1774. (h) Cooper, A. C.;
Folting, K.; Huffman, J . C.; Caulton, K. G. Organometallics 1997, 16,
505. (i) Murphy, V. C.; Rabinovich, D.; Hascall, T.; Klooster, W. T.;
Koetzle, T. F.; Parkin, G. J . Am. Chem. Soc. 1998, 120, 4372. (j) Tilset,
M.; Hamon, J .-R.; Hamon, P. J . Chem. Soc., Chem. Commun. 1998,
765.
1
ture proposed for 2 (Scheme 1) is supported by the H,
31P, 19F, and 13C NMR data (Table 1). The presence of
the triflate ligand is indicated by a quartet at δ 121.2
in the 13C NMR spectrum at 233 K and a broad singlet
(8) (a) J olly, P. W. In Comprehensive Organometallic Chemistry I;
Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon: Oxford,
U.K., 1982; Vol. 6, Chapter 37.4. (b) Kubiak, C. P. In Comprehensive
Organometallic Chemistry II; Abel, E. W., Stone, F. G. A., Wilkinson,
G., Eds.; Pergamon: Oxford, U.K., 1995; Vol. 9, Chapter 2.4.
(9) See also: (a) Ceder, R. M.; Granell, J .; Muller, G. J . Chem. Soc.,
Dalton Trans. 1998, 1047. (b) Ceder, R. M.; Granell, J .; Muller, G.;
Font-Bard´ıa, M.; Solans, X. Organometallics 1995, 14, 5544.
(7) (a) Aizenberg, M.; Milstein, D. Science 1994, 265, 359. (b)
Aizenberg, M.; Milstein, D. J . Am. Chem. Soc. 1995, 177, 8674. (c)
Kiplinger, J . L.; Richmond, T. G. J . Chem. Soc., Chem. Commun. 1996,
1115. (d) Kiplinger, J . L.; Richmond, T. G. J . Am. Chem. Soc. 1996,
118, 1805.
10.1021/om980935c CCC: $18.00 © 1999 American Chemical Society
Publication on Web 04/01/1999

Nickel Derivatives of Tetrafluoropyridine
Organometallics, Vol. 18, No. 9, 1999 1711
Ta ble 1. NMR Da ta a t 298 K (δ (J /Hz))
31P{1H} 19Fa
complex
1H
13C{1H}
2 (THF-d8) 1.11 (m, 12H, CH2),
11.9 (s) -77.82 (s, 3F, CF3), -84.90 (dt,
J (FF) ) 15.3, J (FF) ) 26.7, 1F,
F6), -131.79 (t, J (FF) ) 26.7, 1F,
F3), -148.60 (m, 1F, F4), -171.45
(m, 1F, F5)c
151.1 (m, Cipso of C5F4N), 148.3 (dm, J (CF) )
237.1, CF), 148.1 (dm, J (CF) ) 230.9, CF),
145.4 (dm, J (CF) ) 269.1, CF), 132.1 (dm,
J (CF) ) 259.9, CF), 121.2 (s, br,d CF3), 14.6 (t,
J (PC) ) 12.5, CH2), 8.7 (s, CH3)
170.1 (s, Cipso of C6H5), 165.6 (m, Cipso of
C5F4N), 149.5 (tm, J (CF) ) 237.1, CF), 145.2
(dm, J (CF) ) 289.2, CF), 130.4, 121.7, 114.8
(all s, CH), 14.9 (t, J (PC) ) 11.8, CH2), 8.9 (s,
CH3)e,f
0.90 (m,b 18H, CH3)
3 (C6D6)
7.52 (d, J (HH) ) 7.7,
2H, Hortho), 7.31 (t,
J (HH) ) 7.7, 2H,
11.8 (s) -85.19 (m, 1F, F6), -132.52 (t,
J (FF) ) 26.6, 1F, F3), -150.66
(m, 1F, F4), -172.62 (m, 1F, F5)
H
meta), 6.73 (t, J (HH)
) 7.2, 1H, Hpara), 1.01
(m, 12H, CH2), 0.90
(m, 18H, CH3)
4 (C6D6)
8 (s, OH), 7.64-6.69
(m, 10H, Ph), 1.00 (m,
12H, CH2), 0.90 (m,
18H, CH3)g
11.2 (s)f -85.07 (m, 1F, F6), -132.22 (t,
J (FF) ) 27.7, 1F, F3), -150.24
169.9 (s, Cipso of C6H5), 165.5 (m, Cipso of
C5F4N), 159.9 (s, Cipso of C6H5), 149.5 (tm,
J (CF) ) 227.9, CF), 145.2 (dm, J (CF) ) 268.1,
CF), 131.1, 130.4, 121.7, 120.8, 117.3, 114.9
(all s, CH), 14.8 (t, J (PC) ) 12.0, CH2), 8.9 (s,
CH3)e-g
184.3 (m, Cipso of C5F4N), 165.9 (t, J (CP) )
30.2, Cipso of C6H5), 150.4-147.0 (m, CF),
143.8 (t, J (CF) ) 267.2, CF), 137.9 (t, J (CF) )
3.0, CH), 137.2 (t, J (CF) ) 3.0, CH), 126.7 (t,
J (CF) ) 2.4, CH), 126.4 (t, J (CF) ) 2.3, CH),
121.9 (t, J (CF) ) 2.1, CH), 14.2 (t, J (PC) )
12.5, CH2), 7.9 (s, CH3)h
(m, 1F, F4), -172.22 (m, 1F, F5)g
5 (C6D6)
7.70 (m, 1H, Hortho),
7.52 (m, 1H, Hortho),
7.12 (t, J (HH) ) 7.5,
2H, Hmeta), 6.73 (m,
1H, Hpara), 0.88 (m,
30H, CH2CH3)
14.0 (s)f -85.47 (m, 1F, F6), -132.89 (t,
J (FF) ) 29.9, 1F, F3), -152.33 (m,
1F, F4), -173.62 (m, 1F, F5)
6 (THF-d8) 1.38 (m, 12H, CH2),
1.09 (m, 18H,
20.1 (s) -91.59 (m, 1F, F6), -138.25 (t,
J (FF) ) 30.5, 1F, F3), -159.00
198.0 (m, Cipso of C5F4N), 150.6 (dm, J (CF) )
223.0, CF), 149.0 (dm, J (CF) ) 270.9, CF),
132.0-129.6 (m, CF), 16.1 (t, J (PC) ) 12.3,
CH2), 9.5 (s, CH2CH3), -8.5 (t, J (PC) ) 25.4,
NiCH3)
CH2CH3), -0.89 (t,
J (PH) ) 9.0, 3H,
NiCH3)
(m, 1F, F4), -180.81 (m, 1F, F5)
7 (C6D6)
8 (C6D6)
1.84 (dm, J (HF) ) 2.2,
-85.29 (m, 1F), -141.53 (m, 1F),
-146.63 (m, 1F), -161.71 (m, 1F)
-83.00 (m, 1F), -137.13 (m, 1F),
-141.16 (m, 1F), -149.92 (m, 1F)
CH3)
2.16 (s, CH3)
a
b
d
Numbering of fluorine atoms as in Scheme 1. t in 1H{31P}, J (HH) ) 7.5 Hz. c In C6D6. At 233 K: q, J (CF) ) 338.6. e In THF-d8.
f One CF resonance is masked by the signal at δ 130.4. The δ values can be slightly shifted, depending on the phenol concentration.
One CF resonance is masked by the solvent.
g
h
(PEt3)2] (1), which are based on 19F-19F decoupling
Sch em e 1. Rea ction s of Nick el Tetr a flu or op yr id yl
experiments.5 The trans geometry is indicated by the
Com p lexes
equivalence of the 31P nuclei in the 31P NMR spectrum.
The structure of 2 was also determined by X-ray
crystallography.
Cr ysta l Str u ctu r e of tr a n s-[Ni(OTf)(2-C5F 4N)-
(P Et3)2] (2). The triflate complex 2 was crystallized
from hexane at -20 °C. An ORTEP diagram of the
crystal structure is shown in Figure 1. The principal
bond lengths and angles are summarized in Table 2.
Despite a rotational disorder about the Ni-C(2)-C(50)
axis the structure provides useful data. The angles
between the adjacent ligands at nickel vary from
86.8(1) to 92.90(8)°. The dihedral angle between the
nickel coordination plane and the plane of the aryl ring
is 87.8°. The Ni-C distance of 1.851(3) Å differs little
from the values found for trans-[NiF(2-C5F3HN)(PEt3)2]
(1.869(4) Å)5 or for the dimeric pyridyl complex [NiCl-
(PEt3){µ-κ2(C,N)-(2-C5ClH3N)}]2 (1.866(10), 1.867(9) Å).11
The triflate anion is monodentate oxygen-bonded with
at δ -77.82 in the 19F NMR spectrum. The observation
a Ni-O bond length of 1.957(2) Å, which is longer than
of the asymmetric sulfonyl stretching frequency at 1314
the mean value of Ni-O distances of four-coordinate
cm-1 is consistent with a metal-bonded triflate group
Ni(II) aryloxy complexes of 1.865 Å.12 It is, however,
with the assumed η1-coordination mode.10 The assign-
significantly shorter than the Ni-O bond lengths in
ment of 2 as the 2-pyridyl isomer is based on the
the octahedral complex [Ni(bipy)2(OTf)2] (2.148(4),
chemical shifts of four further fluorine resonances at δ
2.135(5) Å).13
-84.90, -131.79, -148.60, and -171.45 for the aromatic
fluorine atoms. The assignments were made by com-
parison with the data found for trans-[NiF(2-C5F4N)-
(11) Bennett, M. A.; Hockless, D. C. R.; Wenger, E. Polyhedron 1995,
14, 2637.
(12) Orpen, A. G.; Brammer, L.; Allen, F. H.; Kennard, O.; Watson,
D. G.; Taylor, R. J . Chem. Soc., Dalton Trans. 1989, S.1.
(10) Lawrance, G. A. Chem. Rev. 1986, 86, 17.

1712 Organometallics, Vol. 18, No. 9, 1999
Braun et al.
equivalence of the two ortho and two meta protons on
the NMR time scale. The most characteristic feature in
the 13C NMR spectrum is the low-field position of the
ipso carbon signal of the phenyl group at δ 170.1.14,15
The 19F NMR spectrum reveals only the four signals in
the aromatic region at δ -85.19, -132.52, -150.66, and
-172.62, which appear at almost the same chemical
shifts as those found for 2.
The 19F and 31P NMR signals of 3 are slightly shifted
in the presence of phenol by an amount which depends
on the phenol concentration. The signals in the 1H NMR
spectrum for the aromatic hydrogen atoms together with
the eight resonances in the 13C NMR spectrum for the
carbon atoms are consistent with the presence of two
chemically inequivalent aromatic rings. The 13C NMR
spectrum now reveals two resonances for quaternary
ipso carbon atoms at δ 170 and 160. We therefore
assume that the phenol adduct trans-[Ni(OPh)(2-C5F4N)-
(PEt3)2]‚HOPh (4) is formed, in which a phenol molecule
is bound to the phenoxide ligand via an O-H‚‚‚O bond
in a way similar to that for the complex trans-[NiMe-
(OPh)(PMe3)2]‚HOPh.15 The presence of the hydrogen
1
bonding is also indicated in the H NMR spectra. The
resonance at about δ 8 is due to the OH hydrogen, which
is at considerably lower field than the OH resonance at
ca. δ 5.5 of free phenol.14c,15 Crystallization of 4 from a
hexane solution regenerates compound 3.
Cr ysta l Str u ctu r e of tr a n s-[Ni(OP h )(2-C5F 4N)-
(P Et3)2] (3). The phenoxy complex 3 was crystallized
from hexane at -20 °C. An ORTEP diagram of the
crystal structure is shown in Figure 2. Selected bond
lengths and angles are summarized in Table 3. Com-
pound 3 exhibits a square-planar geometry with the
pyridyl group coordinated trans to the phenoxy ligand.
The angles about the nickel atom are distorted from an
ideal square-planar geometry and vary from 85.3(2) to
93.6(1)°. Both the phenyl plane of the phenoxy ligand
and the plane defined by the pyridyl ring are nearly
perpendicular to the coordination plane. The dihedral
angle between the nickel coordination plane and the
plane of the fluorinated aryl ring is 94.4°, while the
angle between the nickel coordination plane and the
phenyl plane is 102.9°. The angle between the nickel
coordination plane and the plane defined by Ni(1)-
O(19)-C(19) is 97.2°. The Ni-O-C angle (123.1(4)°) is
somewhat smaller than the one found in trans-[NiMe-
(OPh)(PMe3)2]‚HOPh (127.1°)15 but almost the same as
the equivalent angle in trans-[NiH(OPh)(PBz3)2]‚HOPh
(123.4(4)°),16 where a phenol moiety is also associated
with the phenoxy ligand through O-H‚‚‚O hydrogen
bonding. As a consequence of the lack of hydrogen
bonding the Ni-O bond in 3 of 1.894(4) Å is shorter
than the distances in trans-[NiMe(OPh)(PMe3)2]‚HOPh
(1.932(5) Å)15 and trans-[NiH(OPh)(PBz3)2]‚HOPh
(1.949(7) Å)16 but longer than the one found in trans-
[Ni{O-(o,o-C6tBuMeH3)}2(PMe3)2] (1.861(3) Å).14a It is
also significantly shorter than the equivalent bond
F igu r e 1. ORTEP36 diagram of the structure of trans-[Ni-
(OTf)(2-C5F4N)(PEt3)2] (2) with ellipsoids shown at the 30%
level. Note that the rotational disorder about Ni-C2-C50
leads to averaging of the locations across the pyridyl ring.
Ta ble 2. P r in cip a l Bon d Len gth s (Å) a n d
An gles (d eg) of On e Rota m er of
tr a n s-[Ni(OTf)(2-C5F 4N)(P Et3)2] (2)a
Ni(1)-O(1)
Ni(1)-C(2)
Ni(1)-P(1)
Ni(1)-P(2)
O(1)-S(1)
S(1)-C(19)
C(30)-F(30)
C(40)-F(40)
1.957(2)
1.851(3)
2.224(1)
2.229(1)
1.455(2)
1.803(5)
1.340(9)
1.339(8)
C(50)-F(50)
C(60)-F(60)
N(10)-C(2)
N(10)-C(60)
C(2)-C(30)
C(30)-C(40)
C(40)-C(50)
C(50)-C(60)
1.343(8)
1.339(8)
1.38(1)
1.29(3)
1.37(1)
1.42(2)
1.36(2)
1.37(2)
P(1)-Ni(1)-P(2)
P(1)-Ni(1)-O(1)
P(2)-Ni(1)-O(1)
P(1)-Ni(1)-C(2)
P(2)-Ni(1)-C(2)
171.14(4)
92.43(8)
92.90(8)
86.8(1)
O(1)-Ni(1)-C(2)
Ni(1)-C(2)-C(30)
Ni(1)-C(2)-N(10)
Ni(1)-O(1)-S(1)
170.7(1)
130.6(7)
113.9(7)
151.1(2)
89.0(1)
a
The two rotamers have nearly identical bond distances. Any
differences are less than 2σ, except for N(10)-C(60) (4σ).
Syn th esis of tr a n s-[Ni(OP h )(2-C5F 4N)(P Et3)2] (3)
an d tr a n s-[Ni(OP h )(2-C5F4N)(P Et3)2]‚HOP h (4). The
preparation of trans-[Ni(OPh)(2-C5F4N)(PEt3)2] (3) pro-
ceeds by a metathesis reaction involving 2 and NaOPh.
The resulting yellow crystals are moderately air-stable.
The reaction of 1 with NaOPh, which was monitored
by NMR, also yields the phenoxy complex 3. No reaction
is observed between 1 and phenol. The 1H NMR
spectrum of 3 shows three well-resolved resonances of
the ortho, meta, and para protons of the phenoxy ligand
at δ 7.52, 7.31, and 6.77. This is consistent with a rapid
rotation around the C-O bond, which causes the
(14) (a) Klein, H. F.; Dal, A.; J ung, T.; Braun, S.; Ro¨hr, C.; Flo¨rke,
U.; Haupt, H.-J . Eur. J . Inorg. Chem. 1998, 621. (b) Alsters, P. L.;
Baesjou, P. J .; J amssen, M. D.; Kooijman, H.; Sicherer-Roetman, A.;
Spek, A. L.; van Koten, G. Organometallics 1992, 11, 4124. (c) Holland,
P. L.; Andersen, R. A.; Bergman, R. G.; Huang, J .; Nolan, S. P. J . Am.
Chem. Soc. 1997, 119, 12800.
(15) Kim, Y.-J .; Osakada, K.; Takenaka, A.; Yamamoto, A. J . Am.
Chem. Soc. 1990, 112, 1096.
(13) Aizawa, S.; Yagyk, T.; Kato, K.; Funahashi, S. Anal. Sci. 1995,
11, 557.
(16) Seligson, A. L.; Cowan, R. L.; Trogler, W. C. Inorg. Chem. 1991,
30, 3371.

Nickel Derivatives of Tetrafluoropyridine
Organometallics, Vol. 18, No. 9, 1999 1713
Sch em e 2. Rea ctivity of 6
NMR spectroscopic data. The 13C NMR spectrum dis-
plays a triplet at δ 165.9 with a coupling of J (PC) ) 30
Hz for the ipso carbon atom of the phenyl group, which
is consistent with a metal-bonded phenyl group. The
restricted rotation of the phenyl group around the
Ni-C bond causes inequivalence of the carbon atoms
on the NMR time scale. All five resonances appear as
triplets (Table 1). This is in sharp contrast to the 13C
NMR data found for the compound trans-[NiBr(Ph)-
(PMe3)2], which is fluxional at room temperature and
where only the signal for the ipso carbon atom appears
as a triplet.18 The resonance for the ipso carbon atom
of the tetrafluoropyridyl group is found at rather low
field, δ 184.3. The 1H NMR spectrum reveals four
different signals for the five inequivalent aromatic
protons (Table 1).
F igu r e 2. ORTEP36 diagram of the structure of trans-[Ni-
(OPh)(2-C5F4N)(PEt3)2] (3) with ellipsoids shown at the 30%
level.
Ta ble 3. P r in cip a l Bon d Len gth s (Å) a n d
An gles (d eg) of tr a n s-[Ni(OP h )(2-C5F 4N)(P Et3)2] (3)
Ni(1)-O(1)
Ni(1)-C(2)
Ni(1)-P(1)
Ni(1)-P(2)
O(1)-C(19)
C(3)-F(3)
C(4)-F(4)
C(5)-F(5)
1.894(4)
1.861(6)
2.215(2)
2.202(2)
1.322(7)
1.358(7)
1.351(8)
1.325(8)
C(6)-F(6)
N(1)-C(2)
N(1)-C(6)
C(2)-C(3)
C(3)-C(4)
C(4)-C(5)
C(5)-C(6)
1.348(8)
1.367(8)
1.319(9)
1.381(8)
1.356(9)
1.36(1)
Syn th esis of tr a n s-[NiMe(2-C5F 4N)(P Et3)2] (6).
The reaction of 2 with MeLi proceeds in a way similar
to that with PhLi, and the methyl complex trans-[NiMe-
(2-C5F4N)(PEt3)2] (6) is obtained in moderate yield as a
yellow solid. However, 6 is more conveniently prepared
from trans-[NiF(2-C5F4N)(PEt3)2] (1) and Me2Zn in 87%
1.36(1)
1
yield. The H NMR spectrum of 6 displays a triplet at δ
P(1)-Ni(1)-P(2)
P(1)-Ni(1)-O(1)
P(2)-Ni(1)-O(1)
P(1)-Ni(1)-C(2)
P(2)-Ni(1)-C(2)
O(1)-Ni(1)-C(2)
172.44(8)
93.6(1)
85.2(1)
89.3(2)
91.4(2)
175.7(2)
Ni(1)-O(1)-C(19)
O(1)-C(19)-C(24)
O(1)-C(19)-C(20)
Ni(1)-C(2)-N(1)
Ni(1)-C(2)-C(3)
123.1(4)
123.1(6)
119.2(6)
120.2(5)
123.1(5)
-0.89 (J (PH) ) 9.0 Hz), indicating that the methyl
group is bound to the metal. This structure is also
supported by the 13C NMR spectrum, which shows a
triplet at δ -8.5 (J (PC) ) 25.4 Hz). The resonance for
the ipso carbon atom of the pyridyl ligand appears at δ
198.0, a rather higher chemical shift than for 2 and 3.
R ea ct ivit y of tr a n s-[NiMe(2-C5F 4N)(P E t3)2] (6).
Preliminary investigations on the reactivity of 6 reveal
C-C coupling reactions of the organic ligands (Scheme
2). On admission of air to a solution of 6 the reductive-
elimination product 2-C5MeF4N (7) is formed. Treat-
ment of 6 with CO affords the corresponding ketone
2-C5(COMe)F4N (8) and [Ni(CO)2(PEt3)2]. The proposed
structures for both tetrafluoropyridines are supported
length found in trans-[Ni(OTf)(2-C5F4N)(PEt3)2] (2). The
Ni-C distance of 1.861(6) Å is almost the same as the
value found for 2.
Syn th esis of tr a n s-[NiP h (2-C5F 4N)(P Et3)2] (5).
After we had shown that we can replace the triflate
ligand in 1 or 2 by using a phenoxide anion as nucleo-
phile, we became interested in extending these studies
to reactions with carbon nucleophiles. On treatment of
a hexane solution of 1 with excess PhLi at -78 °C and
subsequent addition of methanol the phenyl complex 5
is obtained, which was crystallized at -20 °C. The very
low yield of 14% is probably due to the extreme solubil-
ity of the product. However, it is necessary to recrystal-
lize 5 in order to get a pure complex. Attempts to
displace the triflate ligand of 2 using PhLi or PhMgCl
were less successful. In the latter case, the chloro
derivative trans-[NiCl(2-C5F4N)(PEt3)2]17 is formed in-
stead. The proposed structure of 5 is based mainly on
1
by the H and 19F NMR and mass spectrometric data.
The IR spectrum of 8 displays an absorption at 1713
cm-1, which is assigned to the vibration of the CdO
bond.
Discu ssion
The syntheses of compounds of the general type trans-
[NiR(2-C5F4N)(PEt3)2] (R ) F, OTf, OPh, Ph, Me) are
(18) Carmona, E.; Paneque, M.; Poveda, M. L. Polyhedron 1989, 8,
285.
(17) Braun, T.; Perutz, R. N., unpublished results.

1714 Organometallics, Vol. 18, No. 9, 1999
Braun et al.
summarized in Scheme 1. The reactions reported rep-
resent two ways of substituting a fluorine ligand by a
new anionic group. One approach is fluoride abstraction
using Me3SiOTf, which leads to the air-stable complex
trans-[Ni(OTf)(2-C5F4N)(PEt3)2] (2) and Me3SiF (identi-
fied by 1H and 19F NMR spectroscopy). Similar reactions
were recently described by Caulton et al., who generated
the complexes [RuPh(OTf)(CO)(PtBu2Me)2] and [Ir(H)2-
(OTf)(PtBu2Ph)2] from the corresponding fluorides.6f,19
So far there has been only one square-planar nickel
triflate compound in the literature.20 Compound 2 is an
excellent starting material for the synthesis of trans-
[Ni(OPh)(2-C5F4N)(PEt3)2] (3) by a salt metathesis reac-
tion. Complex 3 is air-stable over weeks, in contrast to
trans-[NiMe(OPh)(PEt3)2],21 which is very unstable, or
trans-[NiMe(OPh)(PMe3)2],15 which could only be iso-
lated as a phenol adduct. However, a phenol adduct of
3, trans-[Ni(OPh)(2-C5F4N)(PEt3)2]‚HOPh (4), was ob-
served in solution.
Compounds bearing the tetrafluoropyridyl and a
second carbon ligand may be synthesized by nucleophilic
substitution reactions of the fluoride in 1 or the triflate
in 2 by a phenyl or methyl group. Although penta-
fluoropyridine itself undergoes nucleophilic substitution
at the para position, there is no sign of substitution on
the perfluorinated ring in these reactions.22 The air-
sensitive methyl compound 6 is more easily prepared
from 1 and an excess of ZnMe2. In contrast to the nickel
complexes trans-[NiR(4-C5H4F)(PEt3)2] (R ) Ph, Me)23
and trans-[NiPh2(PEt3)2],24 5 and 6 are stable in solution
over a few days. However, the complexes trans-[NiMe-
(C6F5)(PPh2Me)2]25 and trans-[NiPh(2-C6H4Cl)(PEt3)2]26
are also of remarkable stability. This stability could be
due to a strong π-back-bonding from the nickel center
to the perfluorinated aromatic ring.25,27,28 The high
chemical shift of the signal for the ipso carbon at δ 198.0
of the pyridyl ligand in 6 may also be an indicator of
back-bonding.
or CO, respectively. It is known that O2 can act as a
phosphine scavenger by either complexation or oxida-
tion, which can lead to the observed pyridine.26 Since 1
does not react with CO, we assume that the incorpora-
tion of CO occurs via an insertion-migration process
of CO into the M-CH3 bond. The C-C coupling reaction
is then induced by a second CO molecule, and the final
products are formed.
Con clu sion s
Nickel-pyridyl complexes are uncommon and, when
they do occur, are often dimeric species.11,30 Compounds
with a perfluorinated pyridyl ligand in the 2-position
were unknown until we reported the C-F activation of
pentafluoropyridine on a nickel center.5 This paper
details the preparation of the monomeric pentafluoro-
pyridyl complexes trans-[NiR(2-C5F4N)(PEt3)2] (R )
OTf, OPh, Ph, Me) by using trans-[NiF(2-C5F4N)(PEt3)2]
(1) or trans-[Ni(OTf)(2-C5F4N)(PEt3)2] (2) as precursor.
The X-ray structures of 2 and trans-[Ni(OPh)(2-C5F4N)-
(PEt3)2] (3) have been determined.
Since it is very difficult to prepare tetrafluoropy-
ridines substituted in the 2-position (2-XC5F4N) by
either electrophilic or nucleophilic substitution, very few
are known.22,31 There are no magnesium, lithium,
copper, or other derivatives of tetrafluoropyridine with
a metal in the 2-position.22 Not only do the nickel
compounds 1-6 represent some rare examples of metal
tetrafluoropyridyl complexes28,32 but also they are the
first derivatives where the tetrafluoropyridine is coor-
dinated to the metal in the 2-position. This is of special
interest as the compounds 3, trans-[NiPh(2-C5F4N)-
(PEt3)2] (5), and trans-[NiMe(2-C5F4N)(PEt3)2] (6) pro-
vide an opportunity to synthesize new 3,4,5,6-tetra-
fluoropyridines. Preliminary investigations show that
on treatment of 6 with air or CO the pyridines 2-C5-
MeF4N (7) and 2-C5(COMe)F4N (8) are formed, respec-
tively. We have found no previous descriptions of these
compounds.
According to CSD only a few Ni-O bond lengths are
known in square-planar nickel phosphine complexes.29
The X-ray structures of 2 and 3 are therefore of
particular interest. Probably because of the more weakly
bonded triflate ligand the Ni-O distance of 1.957(2) Å
in 2 is clearly larger than the value found for 3
(1.894(4) Å). There is not much difference in the Ni-C
bond lengths between 2, 3, and trans-[NiF(2-C5F3HN)-
(PEt3)2].5
Exp er im en ta l Section
Gen er a l Meth od s. Most of the synthetic work was carried
out on a Schlenk line or in an argon-filled glovebox with oxygen
levels below 10 ppm. All solvents (AR grade) were dried over
sodium benzophenone ketyl and distilled under argon before
use. Benzene-d6 and THF-d8 (Apollo Scientific Ltd) were dried
by stirring over potassium and then transferred under vacuum
into NMR tubes fitted with Young stopcocks. The lithium and
zinc reagents were obtained from Aldrich. Sodium phenoxide
was prepared by adding sodium hydride to a solution of phenol
in toluene. Pentafluoropyridine was obtained from Fluorochem
Ltd and was dried over molecular sieves (4 Å). Ni(COD)2
(Strem Chemicals) was used as received. Complex 1 was
prepared as described in the literature.5
The C-C coupling products 2-C5MeF4N (7) and 2-C5-
(COMe)F4N (8) are observed on treatment of 6 with air
(19) (a) Huang, D.; Streib, W. E.; Eisenstein, O.; Caulton, K. G.
Angew. Chem., Int. Ed. Engl. 1997, 36, 2004. See also: (b) Veltheer,
J . E.; Burger, P.; Bergman, R. G. J . Am. Chem. Soc. 1995, 117, 12478.
(c) Huang, D.; Caulton, K. G. J . Am. Chem. Soc. 1997, 119, 3185.
(20) Grove, D. M.; van Koten, G.; Ubbels, H. J . C.; Zoet, R.; Spek,
A. L. Organometallics 1984, 3, 1003.
(21) Yamamoto, T.; Kohara, T.; Yamamoto, A. Bull. Chem. Soc. J pn.
1981, 54, 2010.
(30) Crociani, B.; Di Bianca, F.; Giovenco, A. Berton, A. J . Orga-
nomet. Chem. 1987, 323, 123.
(22) Brooke, G. M., J . Fluorine Chem. 1997, 86, 1.
(23) Parshall, G. W. J . Am. Chem. Soc. 1974, 96, 2360.
(24) Chatt, J .; Shaw, B. L. J . Chem. Soc. 1960, 1718.
(25) Rausch, M. D.; Tibbetts, F. E. Inorg. Chem. 1970, 9, 512.
(26) Coronas, J . M.; Muller, G.; Rocamora, M.; Miravittles, C.;
Solans, X. J . Chem. Soc., Dalton Trans. 1985, 2333.
(27) (a) Isobe, K.; Nakamura, Y.; Kawaguchi, S. Bull. Chem. Soc.
J pn. 1980, 53, 139. (b) Isobe, K.; Kawaguchi, S. Heterocycles 1981, 16,
1603.
(28) Chukwu, R.; Hunter, A. D.; Sautersiero, B. D. Organometallics
1991, 10, 2141.
(29) Fletcher, D. A.; McMeeking, R. F.; Parkin, D. J . J . Chem. Inf.
Comput. Sci. 1996, 36, 746.
(31) Inter alia: (a) Banks, R. E.; J ondi, W.; Tipping, A. E. J . Chem.
Soc., Chem. Commun. 1989, 1268. (b) Anderson, L. P.; Feast, W. J .;
Musgrave, W. K. R. J . Chem. Soc. C 1969, 2559. (c) Chambers, R. D.;
Waterhouse, J . S.; Williams, D. L. H. J . Chem. Soc., Perkin Trans. 2
1977, 585. (d) Banks, R. E.; Haszeldine, R. N.; Legge, K. H.; Rickett,
F. E. J . Chem. Soc., Perkin Trans. 1 1974, 2367. (e) Banks, R. E.; J ondi,
W. J .; Tipping, A. E. J . Fluorine Chem. 1996, 99, 87.
(32) (a) Cooke, J .; Green, M.; Stone, F. G. A. J . Chem. Soc. A 1968,
173. (b) Blackmore, T.; Bruce, M. I.; Stone, F. G. A. J . Chem. Soc. A
1968, 2158. (c) Green, M.; Taunton-Rigby, A.; Stone, F. G. A. J . Chem.
Soc. A 1968, 2762. (d) Artamkina, G. A.; Mil’chenko, A. Y.; Beletskaya,
I. P.; Reutov, O. A. J . Organomet. Chem. 1986, 311, 199.

Nickel Derivatives of Tetrafluoropyridine
Organometallics, Vol. 18, No. 9, 1999 1715
Ta ble 4. Cr ysta l Str u ctu r e Da ta for Com p lexes 2 a n d 3
2
3
empirical formula
Mr
C
18H30F7NNiO3P2S
C23H35F4NNiOP2
538.19
594.14
radiation
wavelength/Å
temp/K
Cu KR
Mo KR
1.541 80
0.710 73
220
220
cryst size/mm3
color, habit
cryst syst
space group
lattice params
a/ Å
0.54 × 0.47 × 0.35
orange block
orthorhombic
Pbca
0.50 × 0.25 × 0.08
yellow lath developed in (001)
monoclinic
P21/n
16.068(3)
16.551(5)
b/ Å
15.342(3)
9.1992(18)
c/ Å
21.406(3)
18.253(5)
â/deg
90
5276.92
104.55(2)
2689.95
V/ Å3
Z
D
8
1.50
3.60
2438.85
4
1.33
0.88
1130.16
calcd/g cm-3
abs coeff/mm-1
F(000)
scan type
θ range/deg
index ranges
no of rflns measd
no of indep rflns
Rint
ω-θ
ω-θ
2.75-70.26
2.51-24.99
0 e h e 19, 0 e k e 18, -26 e l e 0
5247
4723
0.00
-19 e h e 19, -1 e k e 10, 0 e l e 21
6909
4740
0.20
abs cor
ψ-scans (Tmin ) 0.061, Tmax ) 0.176)
numerical (Tmin ) 0.632, Tmax ) 0.799)
no. of data/params
goodness of fit on F2
residuals R
3292/380
2369/290
1.1780
1.1273
0.0446
0.0576
Rw
0.0484
0.0521
observn criterion
final max δ/σ
weighting scheme
max peak in final diff map/e Å-3
min peak in final diff map/e Å-3
>2σ(I)
>2σ(I)
0.19
0.0019
Chebychev polynomial
0.36
-0.20
Chebychev polynomial
0.61
-0.49
The NMR spectra were recorded with a Bruker AMX 500
spectrometer. The 1H NMR chemical shifts were referenced
to residual C6D5H at δ 7.15 or THF-d7 at δ 1.8. The 13C{1H}
spectra were referenced to C6D6 at δ 128.0 and THF at δ 26.7.
The 19F NMR spectra were referenced either to internal C6F6
at δ 162.9 or to external CFCl3 at δ 0, and the 31P{1H} NMR
spectra were referenced externally to H3PO4 at δ 0. Mass
spectra were recorded on a VG Autospec. Infrared spectra were
recorded on a Mattson-Unicam RS spectrometer fitted with a
CsI beam splitter. NMR data are listed in Table 1.
tr a n s-[Ni(OTf)(2-C5F 4N)(P Et3)2] (2). (a) A solution of 1
(64 mg, 0.14 mmol) in 5 mL of toluene was treated with Me3-
SiOTf (25 µL, 0.14 mmol) at -78 °C. After the reaction mixture
had been warmed to room temperature, the solvent was
removed under vacuum. The residue was washed with hexane
(10 mL) and extracted with ether (20 mL). The extract was
filtered through a cannula, and the resulting solution was
concentrated to 10 mL. A yellow powder precipitated at -20
°C, which was separated from the mother liquor and dried in
vacuo. Yield: 68 mg (83%).
(b) Ni(COD)2 (651 mg, 2.4 mmol) was suspended in 5 mL of
hexane, and PEt3 (744 µL, 5.0 mmol) was added, giving a
yellow solution. After addition of C5F5N (307 µL, 2.8 mmol)
the reaction mixture was cooled to 0 °C and Me3SiOTf (516
µL, 2.8 mmol) was added. The solution was stirred for 30 min
at room temperature, and the volatiles were removed under
vacuum. The remaining yellow solid was dissolved in ether (5
mL), and the solution was filtered through a cannula. Addition
of hexane (5 mL) afforded a yellow precipitate, which was
filtered off and dried in vacuo. Yield: 114 mg (80%). Anal.
Calcd for C18H30F7NNiO3P2S: C, 36.39; H, 5.09; N, 2.36.
Found: C, 36.39; H, 5.24; N, 2.32. IR (Nujol, cm-1): 1620 (vw),
1590 (w), 1489 (s), 1413 (vs), 1386 (w), 1314 (s), 1300 (w), 1234
(s), 1215 (s), 1175 (s), 1095 (m), 1034 (vs), 997 (s), 812 (m).
tr a n s-[Ni(OP h )(2-C5F 4N)(P Et3)2] (3). A solution of 2 (94
mg, 0.16 mmol) in 5 mL of THF was treated with NaOPh (745
mg, 0.64 mmol) and stirred for 30 min at room temperature.
After the solvent was removed under vacuum, the yellow
residue was extracted with hexane (5 mL). The extract was
then filtered through a cannula, and the filtrate was concen-
trated to about 2 mL in vacuo. Yellow crystals precipitated at
-20 °C, which were separated from the mother liquor and
dried in vacuo. Yield 58 mg (68%). Anal. Calcd for C23H35F4-
NNiOP2: C, 51.33; H, 6.56; N, 2.60. Found: C, 51.43; H, 6.36;
N, 2.44. IR (Nujol, cm-1): 1620 (w), 1586 (s), 1482 (vs, br),
1450 (s), 1405 (vs), 1385 (m), 1315 (m), 1300 (vs), 1273 (m,
br), 1250 (m, br), 1159 (m, br), 1087 (s), 1037 (s), 994 (s), 806
(s), 763 (s), 726 (m), 692 (m).
tr a n s-[NiP h (2-C5F 4N)(P Et3)2] (5). A solution of 1 (190 mg,
0.40 mmol) in hexane (5 mL) was treated at -78 °C with a
solution of PhLi in cyclohexane/ether (70:30, 1.13 mL, 1.82
mmol). After the reaction mixture had been warmed to room
temperature, methanol (1 mL) was added and the volatiles
were removed under vacuum. The residue was then extracted
with hexane (10 mL), the extract was filtered, and the filtrate
was reduced to 1 mL in vacuo. A yellow powder was obtained
at -20 °C, which was separated from the mother liquor and
dried in vacuo. Yield: 30 mg (14%). Anal. Calcd for C23H35F4-
NNiP2: C, 52.91; H, 6.76; N, 2.68. Found: C, 53.04; H, 7.14;
N, 2.47. IR (Nujol, cm-1): 1617 (vw), 1597 (vw), 1583 (w), 1482
(s), 1436 (m), 1406 (s), 1387 (m), 1366 (m), 1291 (w), 1259 (w),
1248 (w), 1089 (br, m), 1034 (br, m), 994 (m), 809 (br, m), 763
(m), 735 (vw), 530 (w), 501 (w).
tr a n s-[NiMe(2-C5F 4N)(P Et3)2] (6). (a) A solution of 2 (134
mg, 0.22 mmol) in 5 mL of toluene was treated at -78 °C with
a solution of MeLi in cumene/THF (90:10, 247 µL, 0.25 mmol).
After the reaction mixture had been warmed to room temper-
ature, the solvents were removed under vacuum. The resulting
residue was extracted with hexane (5 mL), the extract was
filtered through Celite, and the filtrate was concentrated to
about 2 mL in vacuo. A yellow powder precipitated at -20 °C,

1716 Organometallics, Vol. 18, No. 9, 1999
Braun et al.
which was separated from the mother liquor and dried in
vacuo. Yield: 24 mg (24%).
was refined in which all the ring sites were assigned full-
weight atoms, those ortho to the metal atom being modeled
with composite scattering factors (0.5N + 0.5C) with half-
weight F atoms attached. All other F atoms were full-weight.
This refinement converges to R ) 4.47% for 309 parameters.
All bonds and angles adopted normal values except the bond
lengths to the partial-weight F atoms, which were 1.202(5) and
1.278(5) Åsi.e., rather too short. The anisotropic displacement
parameters (adp’s) suggested that a more chemically reason-
able model would be to allow small displacement between the
two alternative ring orientations in addition to the 180°
rotation, with all atoms except the pivot atom, C(2), split over
two sites with equal weight. Refinement of this model natu-
rally suffered from correlation effects, and it was at first
necessary to refine two intersecting rigid bodies with common
Uiso’s for nearby atomic sites. Later it was possible to relax
these constraints and refine the positions of all atoms freely,
the least-squares parameters being constructed of linear
combinations of parameters anticipated to be closely correlated
(e.g. N1(x) ( C30(x), where N(1) is the equivalent of N(10) in
Figure 1 after rotation about Ni(1)-C(2)). The adp’s of the F
atoms were refined freely, while common adp’s were refined
for C and N sites within 1 Å of each other. The bond lengths
to C(2) and C-F bond lengths were respectively made subject
to similarity restraints. All other non-H atoms were refined
freely with apd’s. R for this model was 4.46% for 380
parameters, and though this does not statistically improve the
data fitting over the first model described, it is chemically more
realistic, and for this reason it is presented here.
(b) A solution of 1 (80 mg, 0.17 mmol) in hexane (5 mL) was
treated at -78 °C with a solution of Me2Zn in toluene (431
µL, 0.85 mmol). After the reaction mixture had been stirred
for 4 h at room temperature, methanol (1 mL) was added. The
solution was stirred for 1 h, and the volatiles were removed
under vacuum. The resulting residue was then extracted with
hexane (10 mL), the extract was filtered through Celite, and
the solvent was removed under vacuum. A yellow powder was
obtained, which was dried in vacuo. Yield: 68 mg (87%). Anal.
Calcd for C18H33F4NNiP2: C, 46.99; H, 7.23; N, 3.04. Found:
C, 46.30; H, 7.22; N, 2.82. IR (Nujol, cm-1): 1617 (vw), 1588
(vw), 1579 (w), 1477 (vs), 1396 (s), 1381 (m), 1279 (w), 1259
(br, w), 1243 (w), 1224 (vw), 1176 (vw), 1161 (br, w), 1081 (m),
1063 (vw) 1033 (s), 989 (s).
Tr ea tm en t of 6 w ith Air . A solution of 6 in C6D6 was
saturated with air. The volatiles were transferred under
vacuum into an NMR tube. 19F and 1H NMR spectra demon-
strated that this distillate consisted of a solution of 7 in C6D6.
High-resolution mass spectrum (EI, m/z): calcd for C6H3F4N,
165.020 16; found, 165.020 26.
Rea ction of 6 w ith CO. A solution of 6 in C6D6 was
saturated with CO. The volatiles were transferred under
vacuum into an NMR tube. 19F and 1H NMR spectra demon-
strated that this distillate consisted of a solution of 8 in C6D6.
Mass spectrum (EI, m/z, relative intensity): 193 (22%) [C5-
(COMe)F4N]+, 178 (12%) [C5(CO)F4N]+, 150 (29%) [C5F4N]+,
43 (100%) [COMe]+.
X-r a y Cr ysta llogr a p h ic Stu d ies of 2 a n d 3. Crystals of
2 and 3 were grown at -20 °C from hexane solutions. Data
were collected on a Stoe Stadi-4 diffractometer equipped with
an Oxford Cryosystems low-temperature device.33 Intensities
were measured in the ω-θ mode with Cu KR radiation for 2
and Mo KR radiation for 3. Following data reduction both
structures were solved by Patterson methods (DIRDIF)34 and
Refinement of the crystal structure of 3 proceeded normally;
Rint is rather high because the majority of the contributing
data are quite weak and lie between 45 and 50° in 2θ.
Full details of atomic coordinates, anisotropic displacement
parameters, and other details of the refinements are given in
the Supporting Information.
refined by full-matrix least squares against F (Crystals).35
H
Ack n ow led gm en t. Our thanks go to Dr. C. L.
Higgitt for assistance with the NMR experiments and
for helpful discussions. We acknowledge the EPSRC for
financial support.
atoms were placed in calculated positions. Other relevant
crystal data are given in Table 4.
In 2 the C5NF4 ring is disordered via a 180° rotation about
the Ni(1)-C(2) axis. An approximate model for this disorder
(33) Cosier, J .; Glazer, A. M. J . Appl. Crystallogr. 1986, 19, 105.
(34) Beurskens, P. T.; Beurskens, G.; Bosman, W. P.; de Gelder, R.;
Garc`ıa-Granda, S.; Gould, R. O.; Israe¨l, R.; Smits, J . M. M. DIRDIF-
96; Crystallography Laboratory, University of Nijmegen, Nijmegen,
The Netherlands, 1996.
(35) Watkin, D. J .; Prout, C. K.; Carruthers, J . R.; Betteridge, P.
W. CRYSTALS, Issue 10; Chemical Crystallography Laboratory,
University of Oxford, Oxford, U.K., 1996.
Su p p or tin g In for m a tion Ava ila ble: X-ray crystallo-
graphic data for 2 and 3, including tables of atomic coordinates,
bond lengths and angles, anisotropic displacement parameters,
and hydrogen coordinates and Ueq values and ORTEP dia-
grams. This material is available free of charge via the Internet
at http://pubs.acs.org.
(36) J ohnson, C. K., ORTEP; Report ORNL-5138; Oak Ridge Na-
tional Laboratory: Oak Ridge, TN, 1976.
OM980935C