Synthesis, structures, characterization, dynamic behavior, and reactions of novel late transition metal(II) 1-azaallyls

Article abstract of DOI:10.1021/om0498955

The preparation of homoleptic late transition metal (II) 1-azaallyl compounds by reactions with anhydrous late transition metal halides with the appropriate lithium or potassium 1-azallyl KL(1) was described. Single-crystal X-ray analysis of showed that the 1-azaallyl was bounded to the metal center in an η³-NCC mode in the mononuclear compounds. The diagramatic group 10 metal 1-azaallyl compounds were fully characterized by multinuclear NMR sepctroscopy and were found to be mixture of isomers. The results of the variable-temperature and variable-temperature saturation transfer NMR spectroscopic experiments show that the isomers of each of the compounds are to be involved in a dynamic process.

Full text of DOI:10.1021/om0498955

Organometallics 2004, 23, 2591-2600
2591
Syn th esis, Str u ctu r es, Ch a r a cter iza tion , Dyn a m ic
Beh a vior , a n d Rea ction s of Novel La te Tr a n sition
Meta l(II) 1-Aza a llyls
Anthony G. Avent, Peter B. Hitchcock, Michael F. Lappert,* Rafae¨l Sablong, and
J ohn R. Severn
The Chemistry Department, University of Sussex, Brighton, BN1 9QJ , U.K.
Received February 9, 2004
A series of homoleptic late transition metal(II) 1-azaallyl compounds ([M(L)2] {L ) η3-
N(SiMe3)C(tBu)CH(C6H4Me-4), M ) Fe (5), Co (6), or Ni (7)}, [M(L1)2] {L1 ) η3-N(SiMe3)C-
(Ph)CH(SiMe3), M ) Ni (8) or Pd (9)}, [M(L2)2] {L2 ) η3-N(SiMe3)C(tBu)CH(SiMe3), M ) Fe
(10) or Co (11)}, or [M(L3)2] {L3 ) η1-N(SiMe3)C(tBu)CH(C10H7-1), M ) Fe (12)} have been
prepared by reactions of anhydrous late transition metal halides {MX2 ) FeBr2, CoCl2, [NiBr2-
(dme)], or [PdCl2(cod)]} with the appropriate lithium or potassium 1-azallyl KL (1), [LiL1(thf)]2
(2), [LiL2]2 (3), or KL3 (4) in a 1:2 molar ratio. The heteroleptic 1-azallylnickel(II) complex
Ni(η3-C3H5)(L3) (13) was prepared from [{Ni(η3-C3H5)(µ-Br)}2] with a stoichiometric amount
of the 1-azaallylpotassium reagent KL3 (4). Single-crystal X-ray analysis revealed the
1-azaallyl to be bonded to the metal center in an η3-NCC mode in the mononuclear compounds
5-8 and 10, whereas in 12 the 1-azallyl is N-bound in the κ1-enamido fashion. The iron(II)
(5, 10, and 12) and cobalt(II) (6 and 11) compounds are paramagnetic and have magnetic
moments in the range 5.01-5.61 µB and 2.73-3.01 µB, respectively, characteristic of a high-
spin d6 and low-spin d7 electronic configuration, respectively. The diamagnetic group 10 metal
1-azaallyl compounds (7-9 and 13) were fully characterized by multinuclear NMR
spectroscopy and were found to be a mixture of isomers. Several NOE, two-dimensional,
and saturation transfer NMR spectroscopic experiments were used to elucidate the nature
of the three isomers. Variable-temperature and variable-temperature saturation transfer
NMR spectroscopic experiments showed the isomers of each of compounds 7-9 to be involved
in a dynamic process. Electrochemical and oxidation studies on compounds 5 and 6 are
reported, as are R-olefin oligomerization reactions catalyzed by 13 with MAO or B(C6F5)3.
In tr od u ction
to be excellent synthons for the formation of hetero-
cycles,5 as have 3-halo-1-azaallyllithium compounds.6
This contribution is part of our ongoing study into the
diversity of ligating possibilities of the 1-azaallyl ligand
system. In a series of papers we have shown that a
variety of coordinated N-silyl-1-azaallyl anions can be
formed via the interaction of an R-hydrogen-free nitrile
with a trimethylsilylmethyllithium reagent Li[CH3-nRn]
The 1-azaallyl anions belong to the large class of
anions of the general formula [X ) Y-Z or X ) Y ) Z]-
and are part of a family of ligands which includes7
neutral 1-azaallyls (e.g., N,N′-dialkyl-1,4-diazabuta-1,3-
dienes),8 1-azaallyl dianions (as in [{Ru(CO)3}2{µ-C(iPr)C-
(R ) SiMe3 and n ) 1, 2, or 3),1a Li[CH(SiMe3){SiMe3-n
-
(OMe)n}] (n ) 1 or 2),1b or Li[CH(SiMe2OMe)2].1b The
lithium 1-azaallyls1a were excellent ligand transfer
reagents, producing various metal-1-azaallyl complexes
with intriguing coordination chemistry.2 The majority
of attention paid to the chemistry of 1-aza-allylmetal
complexes has been their use as reagents in carbon-
carbon bond formation,3 as in controlled aldol condensa-
tion reactions or regioselective R-functionalization of
ketones.3,4 N-Silyl-1-azaallyl anions (formed via inser-
tion of a nitrile into a lithium alkyl bond) have proved
(4) (a) Wittig, G.; Frommeld, H. D.; Suchanek, P. Angew. Chem.,
Int. Ed. Engl. 1963, 2, 683. (b) Wittig, G.; Reiff, H. Angew. Chem., Int.
Ed. Engl. 1968, 7, 7. (c) Stork, G.; Dowd, S. R. J . Am. Chem. Soc. 1963,
85, 2178.
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1241. (b) Konakahara, T.; Takagi, Y. Heterocycles 1980, 14, 393. (c)
Konakahara, T.; Kurosaki, J . J . Chem. Res. 1989, (S) 130, (M) 1068.
(d) Konakahara, T.; Sugama, N.; Sato, K. Heterocycles 1992, 33, 157.
(e) Konakahara, T.; Hojahmat, M.; Sujimoto, K. Heterocycles 1997, 45,
271. (f) Konakahara, T.; Watanabe, A.; Sato, K. Heterocycles 1985, 23,
383. (g) Konakahara, T.; Watanabe, A.; Maehara, K.; Nagata, M.;
Hojahmat, H. Heterocycles 1993, 35, 1171. (h) Konakahara, T.; Sato,
M.; Haruyama, T.; Sato, K. Nippon Kagaku Kaishi 1990, 466. (i)
Konakahara, T.; Hojahmat, M.; Tamura, S. J . Chem. Soc., Perkin
Trans. 1 1999, 2803. (j) Konakahara, T.; Sugama, N.; Yamada, A.;
Kakehi, A.; Sakai, N. Heterocycles 2001, 55, 313. (k) Konakahara, T.;
Ogawa, R.; Tamura, S.; Kakehi, A.; Sakai, N. Heterocycles 2001, 55,
1737.
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Ed. Engl. 1985, 24, 881. (b) Aelterman, W.; De Kimpe, N.; Tyvorskii,
V.; Kulinkovich O. J . Org. Chem. 2001, 66, 53.
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metallics 2002, 21, 2422. (b) Hitchcock, P. B.; Lappert, M. F.; Layh,
M. J . Chem. Soc., Dalton Trans. 2001, 2409.
(1) (a) Hitchcock, P. B.; Lappert, M. F.; Layh, M.; Liu, D.-S.; Sablong,
R.; Shun, T. J . Chem. Soc., Dalton Trans. 2000, 2301, and references
therein. (b) Hitchcock, P. B.; Lappert, M. F.; Wei, X.-H. J . Organomet.
Chem. 2003, 683, 83.
(2) Caro, C. F.; Lappert, M. F.; Merle, P. G. Coord. Chem. Rev. 2001,
219-221, 605.
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10.1021/om0498955 CCC: $27.50 © 2004 American Chemical Society
Publication on Web 04/21/2004

2592 Organometallics, Vol. 23, No. 11, 2004
Avent et al.
Sch em e 1. Va r ia tion in Bon d in g Mod es of th e
(iPr)N(tBu)C(O)}]9h),9 imidoyls (as in [Pd(Br){C(NtBu)-
CH2C6H4Br-4}(PMe3)2]10k),10 and the 2-pyridylalkyls (as
in [Li{µ-CR2(C5H4N-2)}]2).11 The coordination chemistry
of transition metal 1-azaallyl complexes is similar to
that of the extensively studied class of ligands: 1-ox-
aallyls (or enolates),12 η3-1-phosphaallyls,13 2-azaallyls,14
1,3-diphosphaallyls,15 1-aza-3-phosphaallyls,16 or metal-
1,3-diazaallyls including benzamidinates.17 They can
bind to a metal in one of six bonding modes A-F
(Scheme 1), depending on the nature of the substituent
groups on the ligand and the presence or absence of
neutral coligand(s). The most common bonding modes
are A, B, and C, with bonding mode A predominantly
found in metal 2-pyridylalkyl complexes. Bonding mode
D is shown with a bridging hydrogen.
1-Aza a llyl Moieties
This paper deals with Fe(II), Co(II), Ni(II), and Pd-
(II) complexes. Published data on this theme relate to
various 2-pyridylalkyls of Fe, Co, and Ni.2 Exceptions
are [M{η3-N(R)C(tBu)C(H)R}I(L)] (M ) Ni, Pd; L )
(8) (a) de Lange, P. P. M.; Fru¨hauf, H.-W.; van Wijnkoop, M.; Vrieze,
K.; Wang, Y.; van Heijdenrijk, D.; Stam, C. H. Organometallics 1990,
9, 1691. (b) De Lange, P. P. M.; Van Wijnkoop, M.; Fru¨hauf, H.-W.;
Vrieze, K.; Goubitz, K. Organometallics 1993, 12, 428. (c) Meca, L.;
C´ısarˇova´, I.; Dvorˇa´k, D. Organometallics 2003, 22, 3703.
PPh3, or absent) and [Ni{η3-N(C6H3Me2-2,6)C(R)C(H)R}-
(tmeda)] (R ) SiMe3);18 these were prepared from [Ni-
(cod)2] or [Pd(dba)2] and RNdC(tBu)C(H)(R)I and the
1:1 adducts + PPh3, or [Li{η3-N(C6H3Me2-2,6)C(R)C-
(H)R}(tmeda)] with [NiBr2(dme)]. The compound [Ni-
{η3-N(R)C(tBu)C(H)R}I(PPh3)] was X-ray characterized,
and the PPh3-free Ni(II) or Pd(II) iodides were shown
to be mixtures of isomers in solution.
In a preliminary communication, we drew attention
to the five compounds [M{η3-N(R)C(tBu)C(H)R1}2] (M
) Fe, Co; R1 ) R, C6H4Me-4; M ) Ni, R1 ) C6H4Me-4)
and [Fe{N(R)C(tBu)dC(H)C10H7-1}2].19 We now describe
the synthesis, characterization, and fluxional processes
of these and four other 1-azaallylmetal(II) (Fe, Co, Ni,
Pd) complexes, including the X-ray structures of six of
them; some of these data were alluded to in a review.2
(9) (a) Nakamura, Y.; Bachmann, K.; Heimgartner, H.; Schmid, H.;
Daly, J . J . Helv. Chim. Acta 1978, 61, 589. (b) Song, J .-S.; Han, S.-H.
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1990, 9, 2386. (c) Mirkin, C. A.; Lu, K.-L.; Geoffroy, G. L.; Rheingold,
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(g) Mul, W. P.; Elsevier, C. J .; Polm, L. H.; Vrieze, K.; Zoutberg, M. C.;
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O. C. P.; Delis, J . G. P.; Mul, W. P.; Vrieze, K.; Elsevier, C. J .; Smeets,
W. J . J .; Spek, A. L. Inorg. Chem. 1993, 32, 3640. (i) Elsevier, C. J .;
Mul, W. P.; Vrieze, K. Inorg. Chim. Acta 1992, 200, 689. (j) Polm, L.
H.; Elsevier, C. J .; Mul, W. P.; Vrieze, C. J .; Christophersen, M. J . N.;
Muller, F.; Stam, C. H. Polyhedron 1988, 7, 2521. (k) Polm, L. H.; van
Koten, G.; Vrieze, K.; Stam, C. H.; van Tunen, W. C. J . J . Chem. Soc.,
Chem. Commun. 1983, 1177.
(10) (a) Durfee, L. D.; Rothwell, I. A. Chem. Rev. 1988, 88, 1059,
and references therein. (b) Seyferth, D.; Hoke, J . B. Organometallics
1988, 7, 524. (c) Carmona, E.; Palma, P.; Paneque, M.; Poveda, M. L.
Organometallics 1990, 9, 583. (d) O’Connor, J . M.; Uhrhammer, R.;
Rheingold, A. L.; Roddick, D. M. J . Am. Chem. Soc. 1991, 113, 4530.
(e) Henderson, W.; Kemmitt, R. D. W.; Prouse, L. J . S.; Russell, D. R.
J . Chem. Soc., Dalton Trans. 1990, 781. (f) Henderson, W.; McKenna,
P.; Prouse, L. J . S.; Russell, D. R. J . Chem. Soc., Dalton Trans. 1989,
345. (g) Al´ıas, F. M.; Belderra´ın, T. R.; Paneque, M.; Poveda, M. L.;
Carmona, E.; Valerga, P. Organometallics 1997, 16, 301. (h) Veya, P.;
Floriani, C.; Chiesi-Villa, A.; Rizzoli, L. Organometallics 1993, 12, 4899.
(i) Al´ıas, F. M.; Belderra´ın, T. R.; Paneque, M.; Poveda, M. L.; Carmona,
E.; Valerga, P. Organometallics 1998, 17, 5620. (j) Ca´mpora, J .;
Hudson, S. A.; Carmona, E. Organometallics 1995, 14, 2151. (k) Delis,
J . G. P.; Aubel, P. G.; Vrieze, K.; van Leeuwen, P. W. N. M.; Veldman,
N.; Spek, A. L.; van Neer, F. J . R. Organometallics 1997, 16, 2948. (l)
Ca´mpora, J .; Hudson, S. A.; Massiot, P.; Maya, C. M.; Palma, P.;
Carmona, E.; Mart´ınez-Cruz, L. A.; Vegas, A. Organometallics 1999,
18, 5225.
(11) Papasergio, R. I.; Raston, C. L.; White, A. H. J . Chem. Soc.,
Chem Commun. 1983, 1419.
(12) For example: Burkhardt, E. R.; Doney, J . J .; Bergman, R. G.;
Heathcock, C. H. J . Am. Chem. Soc. 1987, 109, 2022.
(13) (a) Mercier, F.; Fischer, J .; Mathey, F. Angew. Chem., Int. Ed.
Engl. 1986, 25, 357. (b) Mercier, F.; Hugel-Le Goff, C.; Mathey, F.
Organometallics 1988, 7, 955. (c) Hugel-Le Goff, C.; Mercier, F.; Ricard,
L.; Mathey, F. J . Organomet. Chem. 1989, 363, 325. (d) Mercier, F.;
Mathey, F. Organometallics 1990, 9, 863.
Resu lts a n d Discu ssion
Syn th esis a n d Ch a r a cter iza tion of 1-Aza a llyl
Gr ou p 8-11 Tr a n sition Meta l Com p lexes. The
starting potassium or lithium 1-azaallyls KL (1),20
[LiL1(thf)]2 (2),1a [LiL2]2 (3),1a and KL3 (4)21 were
prepared by literature procedures [L ) {N(R)C(tBu)CH-
(C6H4Me-4)}, L1 ) {N(R)C(Ph)CH(R)}, L2 ) {N(R)-
C(tBu)CH(R)}, L3 ) {N(R)C(tBu)CH(C10H7-1)}; R )
SiMe3].
Reaction of 2 equiv of the appropriate lithium or
potassium 1-azaallyl with the anhydrous metal(II)
halide (FeBr2, CoCl2, [NiBr2(dme)], or [PdCl2(cod)]) in
tetrahydrofuran at ambient temperatures afforded the
crystalline, colored, monomeric transition metal(II)
1-azaallyls 5-12 in good yields (Scheme 2). Each of
5-12 was soluble in diethyl ether, but much less so in
hydrocarbon solvents (except for 5), and surprisingly air-
and moisture-stable in the solid. The allylnickel(II)
(14) (a) Keable, H. R.; Kilner, M. J . Chem. Soc., Dalton Trans. 1972,
153. (b) Andrews, P. C.; Armstrong, D. R.; Clegg, W.; Craig, F. J .;
Dunbar, L.; Mulvey, R. E. J . Chem. Soc., Chem. Commun. 1997, 319.
(15) Appel, R.; Schuhn, W.; Nieger, M. Angew. Chem., Int. Ed. Engl.
1988, 27, 416.
(16) (a) Wang, Z.-X.; Wang, D.-Q.; Dou, J .-M. J . Organomet. Chem.
2003, 665, 205. (b) Hitchcock, P. B.; Lappert, M. F.; Uiterweerd, P. G.
H.; Wang, Z.-X. J . Chem. Soc., Dalton Trans. 1999, 3413.
(18) Hitchcock, P. B.; Lappert, M. F.; Layh, M. Z. Anorg. Allg. Chem.
2000, 626, 1081.
(19) Danie´le, S.; Deelman, B.-J .; Hitchcock, P. B.; Hu, J .; Lappert,
M. F.; Layh, M.; Liu, D.-S.; Sablong, R.; Severn, J . R. Education in
Advanced Chemistry; Marcinie´c, B., Ed.; Wydawnictwo Poznanskie:
Pozna´n-Wroclaw, 1999; Vol. 6, Chapter 12.
(20) Lappert, M. F.; Liu, D.-S. Neth. Pat. Appl. 9500085, 1995.
(21) Hitchcock, P. B.; Lappert, M. F.; Liu, D.-S. J . Chem. Soc., Chem.
Commun. 1994, 2637.
(17) See: (a) Barker, J .; Kilner, M. Coord. Chem. Rev. 1994, 133,
219. (b) Edelmann, F. T. Coord. Chem. Rev. 1994, 137, 403.

Novel Late Transition Metal(II) 1-Azaallyls
Organometallics, Vol. 23, No. 11, 2004 2593
magnetic moment.29 A value of ca. 6 µB on such a
complex has been recorded, but the possibility of a trace
of an Fe(III) impurity could not be discounted.30 In
contrast to the above high-spin Fe(II) 1-azaallyls, the
d7 Co(II) complexes 6 and 11 are clearly of low spin (both
at ambient temperature). Observed magnetic moments
for low-spin Co(II) complexes have generally exceeded
the spin-only value of 1.73 µB, usually being in the range
2.2-3.2 µB,28 due to a large orbital contribution. Despite
the precedents on the related Fe(II) and Co(II) 2-pyridyl-
alkyls (Table 1), it is the d7 rather than the d6 analogue
that is of low spin at ambient temperature. Measure-
ments on a wider temperature range would be useful
to determine whether spin-crossover was readily acces-
sible.
Sch em e 2. Rou tes to Com p ou n d s 5-14
Attempted oxidation of 5 or 6 was carried out with
TCNE, Ag[BF4], Ag[SbF6], or p-benzoquinone. For the
Fe complex 5 there was in each case rapid precipitation
of metal even at -78 °C. For the Co complex 6, the
solution changed from a deep orange to dark green,
which persisted at <-30 °C, whereafter the color
reverted to deep orange. The resultant filtrate contained
approximately half of unreacted 5 or 6 and the C-C
ligand-coupled product [N(R)dC(tBu){C(H)(C6H4Me-
4)}]2. Consistent with these observations, the CV of 5
and 6 (Table 1) showed ready irreversible oxidation.
Cr ysta l Str u ctu r es. The molecular structures of the
isomorphous complexes 5-7, with atom-numbering
schemes, are exemplified in Figure 1 for the case of the
iron(II) 1-azaallyl 5; an alternative view illustrated for
the Ni(II) analogue 7 is in Figure 2. Figures 3-5 show
the molecular structures for complexes 8, 10, and 12,
respectively. Selective bond distances and the NC1C2
angle for each of the monomeric crystalline complexes
5-8, 10, and 12 are represented schematically in
Scheme 3 and more extensively with comparative data
on [Ni{η3-N(R)C(tBu)CH(R)}I(PPh3] and Fe(II) and Co-
(II) 2-pyridylalkyls in Table 2. In 5-8 and 10 the metal
is sandwiched between the two staggered η3-1-azaallyl
ligands, the metal being the centroid of a distorted
octahedron. An alternative description places the metal
at the center of an NC2N′C2′ or C1C2C1′C2′ square
with a pendant η-alkene or η-imine (cf. ref 31), respec-
tively. In each of these metal(II) complexes 5-8 and 10
the substituents on the two 1-azaallyl ligands are
arranged in a mutually transoid fashion. In the cen-
trosymmetric 5-7 and 10 each ligand has the anti-
conformation, while for 8 it is syn. The Ni(II) complex
8 also differs from 5-7 and 10 in not being centrosym-
metric, the N-M′-N′ bond angle of 163.1(2)0 diverging
from the linear arrangement found in the other four.
This is probably a general feature of the L1 ligand,
complex [Ni(L3)(η3-CH2CHCH2)] (13) was obtained from
[{Ni(η3-CH2CHCH2)(µ-Cl)}2] and KL3.
An attempt to synthesize a Cu(II) analogue from
anhydrous CuCl2 with 1 equiv of [LiL2]2 in diethyl ether
led instead to the C-C ligand-coupled product22 and the
(1-azaallyl)copper(I) dimer23 (Scheme 2).
Each of the complexes 5-13 was characterized by
1
microanalyses and mass spectra, with H and 13C NMR
spectroscopic data for the diamagnetic Ni(II) (7, 8, 13)
and Pd(II) (9) complexes, and single-crystal X-ray
structures for 5, 6, 7, 8, 10, and 12. The ambient-
temperature NMR spectroscopic data revealed that in
solution 7, 8, 9, and 13 existed as a mixture of isomers.
For the paramagnetic Fe(II) (5, 10, 12) and Co(II) (6,
11) complexes, further measurements were of (a) mag-
netic moments in benzene at 298 K, recorded using
Evans’ method24 (with diamagnetic corrections25,26), and
(b) irreversible oxidation potentials (relative to the
FeCp2+/FeCp2 couple), by cyclic voltammetry on 5 and
6 (in thf as solvent; [NnBu4][BF4] as supporting elec-
trolyte, at a scan rate of 200 mV s-1). These data, as
well as yields and colors, are shown in Table 1, with
corresponding information on some 2-pyridylalkyl ana-
logues.27,28
While the magnetic moments for the homoleptic d6
Fe(II) 1-azaallyls 5, 6, and 12 are significantly larger
than those of the cited 2-pyridylalkyl analogues (for
which µeff is in one case close to the calculated spin-
only high-spin value of 4.90 µB), they are in line with
much data in the literature. Thus, for various tetra-
hedral salen-type Fe(II) complexes, µeff was generally
around 5.2 µB, attributed to orbital contributions to the
t
having a Ph rather than a Bu substituent at C1. The
other geometric parameters for each of 5-8 and 10 are
unexceptional (Table 2) and clearly demonstrate the η3-
(29) Holm, R. H.; Everett, G. W.; Chakravorty, A. Prog. Inorg. Chem.
1966, 7, 83.
(22) Hitchcock, P. B.; Lappert, M. F.; Tian, S. J . Organomet. Chem.
1997, 549, 1.
(23) Hitchcock, P. B.; Lappert, M. F.; Layh, M. J . Chem. Soc., Dalton
Trans. 1998, 1619.
(30) Calvin, M.; Bailes, R. H. J . Am. Chem. Soc. 1946, 68, 949.
(31) (a) Owen, G. R.; Vilar, R.; White, A. J . P.; Williams, D. J .
Organometallics 2003, 22, 3025. (b) Karsch, H. H.; Leithe, A. W.;
Reisky, M.; Witt, E. Organometallics 1999, 18, 90. (c) Hoberg, H.; Go¨tz,
V.; Kru¨ger, C.; Tsay, Y.-H. J . Organomet. Chem. 1979, 169, 209. (d)
Gabor, B.; Kru¨ger, C.; Marczinke, B.; Mynott, R.; Wilke, G. Angew.
Chem., Int. Ed. Engl. 1991, 30, 1666. (e) Butler, G.; Eaborn, C.; Pidcock,
A. J . Organomet. Chem. 1980, 185, 367. (f) Clemens, J .; Green, M.;
Stone, F. G. A. J . Chem. Soc., Dalton Trans. 1973, 1620. (g) Mukhed-
kar, V. A.; Mukhedkar, A. J . J . Inorg. Nucl. Chem. 1981, 43, 2801.
(24) Evans, D. F. J . Chem. Soc. 1959, 2003.
(25) O’Connor, C. J . Prog. Inorg. Chem. 1982, 29, 203.
(26) See Supporting Information for general procedure.
(27) Leung, W.-P.; Lee, H.-K.; Weng, L.-H.; Luo, B.-S.; Zhou, Z.-Y.;
Mak, T. C. W. Organometallics 1996, 15, 1785.
(28) Leung, W.-P.; Lee, H.-K.; Weng, L.-H.; Zhou, Z.-Y.; Mak, T. C.
W. J . Chem. Soc., Dalton Trans. 1997, 779.

2594 Organometallics, Vol. 23, No. 11, 2004
Avent et al.
Ta ble 1. Yield s a n d Selected P r op er ties of th e F e(II) a n d Co(II) 1-Aza a llyls a n d Som e Com p a r a tive Da ta
Ox
compounda
yield (%)
color
mp (°C)
µ
eff (µB)
Ep (V)
5 [FeL2]
79
91
78
80
52
89
86
63
70
red
red
red
yellow
red
orange
orange
red
163-165
5.27
5.61
5.01
4.24
4.92
3.01
2.73
3.11
2.31
0.22
10 [FeL2
12 [FeL3
]
]
135-138
2
2
>60 dec
110-112
[Fe{CR2(C5H4N-2)}2]27
[Fe{CPh(R)(C5H4N-2)}2]27
6 [CoL2]
0.85
0.64
0.7
118-120 dec
128-130 dec
120-123
11 [CoL2
]
2
[Co{CR2(C5H4N-2)}2]28
116-118
183-185 dec
0.86
[Co{CPh(R)(C5H4N-2)}2]28
red
a
L ) {N(R)C(tBu)CH(C6H4Me-4)}; L2 ) {N(R)C(tBu)CH(R)}, L3 ) {N(R)C(tBu)CH(C10H7-1)}; R ) SiMe3.
Sch em e 3. Sch em a tic Rep r esen ta tion of th e
Molecu la r Str u ctu r es of Com p ou n d s 5-8, 10, a n d
12, w ith Selected Bon d Len gth s (Å) a n d An gles
(d eg) w ith th e Atom -La belin g Sch em e
F igu r e 1. Molecular structures of the isomorphous com-
pounds 5-7, illustrated for the iron compound 5.
N-C1 and shorter C1-C2 bonds in 12 than in the other
five complexes, which may be compared with the N-C1
and C1-C2 bond lengths of 1.435(4) or 1.38(1) Å and
1.349(5) or 1.35(1) Å in the tin(II) Sn[N(R)C(tBu)dC(H)-
C6H3Me2-2,5]232 or the copper(I) [Cu{N(R)C(tBu)dC(H)R}-
(PPh3)]33 complex, respectively. A significant feature is
the deviation in 12 of N-Fe-N′ from linearity (the iron
is disordered across the inversion center), although
there are ample precedents in other crystalline two-
coordinate Fe(II) complexes FeX2 [X2 ) (NSiMe3-nPhn)2
F igu r e 2. Alternative view of the molecular structures of
compounds 5-7, illustrated for the nickel compound 7.
(n ) 134 or 235) or (C6H2 Bu3-2,4,6)2:36,37 172.1(1)°, 169.0-
t
1-azaallyl bonding mode B to the metal; in each of the
isoleptic complexes 5-7, the central M-C bond is
slightly shorter than the terminal M-C, whereas the
reverse is the case for 8 and 10.
The structure of the centrosymmetric crystalline Fe-
(II) complex 12 is unique within the present series of
homoleptic metal(II) 1-azaallyls in that it is an enami-
dometal complex; that is, the bonding mode is C.
Consistent with that view are the significantly longer
(32) Hitchcock, P. B.; Hu, J .; Lappert, M. F.; Layh, M. Severn, J . R.
J . Chem. Soc., Chem. Commun. 1997, 1189.
(33) Hitchcock, P. B.; Lappert, M. F.; Layh, M. J . Chem. Soc., Dalton
Trans. 1998, 1619.
(34) Chen, H.; Bartlett, R. A.; Dias, H. V. R.; Olmstead, M. M.;
Power, P. P. J . Am. Chem. Soc. 1989, 111, 4338.
(35) Bartlett, R. A.; Power P. P. J . Am. Chem. Soc. 1987, 109, 7563.
(36) Wehmschulte, R. J .; Power, P. P. Organometallics 1995, 14,
3264.
(37) Mu¨ller, H.; Seidel, W.; Go¨rls, H. Angew. Chem., Int. Ed. Engl.
1995, 34, 325.

Novel Late Transition Metal(II) 1-Azaallyls
Organometallics, Vol. 23, No. 11, 2004 2595
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles (d eg) for 5, 6, 7, 8, 10, a n d 12 a n d Som e Com p a r a tive Da ta
compounda
5 [FeL2]
M-N
M-C1
M-C2
N-C1
C1-C2
N-M-N′ N-C1-C2 N-M-C2 N′-M-C2
1.916(4) 2.086(5) 2.105(5) 1.364(6)
1.880(4) 2.041(4) 2.092(5) 1.359(6)
1.915(2) 2.030(3) 2.063(3) 1.341(4)
1.884(3) 2.097(4) 2.016(4) 1.347(5)
1.914(3) 2.139(3) 2.074(3) 1.347(4)
1.881(6) n.a.
1.987(6)
2.135(5) n.a.
2.139(5)
1.405(6)
1.403(6)
1.422(4)
1.411(6)
1.433(5)
1.349(8)
180
180
180
163.1(2)
180
115.1(4)
115.0(4)
116.0(3)
113.1(4)
111.7(3)
121.4(5)
70.9(2)
71.6(2)
72.1(1)
72.2(2)
70.3(1)
n.a.
109.1(2)
108.4(2)
108.0(1)
110.2(2)
109.7(1)
n.a.
6 [CoL2]
7 [NiL2]
8 [NiL1
]
2
2
10 [FeL2
12 [FeL3
]
]
n.a.
1.403(8)
153.6(1)
2
[Fe{CR2(C5H4N-2)}2]27
2.154(0) 1.347(10) 1.489(9)
180
112.7(6)
113.6(9)
107.6(1)
108.8(1)
111.4(1)
66.8(2)
67.2(3)
68.5(2)
69.3(2)
70.7(2)
2.131(7) 1.341(6)
2.071(3) 1.358(5)
2.092(6) 1.345(8)
1.469(6)
1.484(5)
1.482(7)
1.409(9)
[Co{CPh(R)(C5H4N-2)}2]28 1.897(3)
/
/
180.0(1)
180
[Co{CR2(C5H4N-2)}2]28
1.923(4)
[NiL2(I)(PPh3)]18
1.932(5) 2.139(7) 1.982(6) 1.334(8)
a
L ) {N(R)C(tBu)CH(C6H4Me-4)}; L1 ) {N(R)C(Ph)CH(R)}, L2 ) {N(R)C(tBu)CH(R)}, L3 ) {N(R)C(tBu)CH(C10H7-1)}; R ) SiMe3.
F igu r e 5. Molecular structure of compound 12.
F igu r e 3. Molecular structure of compound 8.
F igu r e 6. Isomers of complexes 7 and 8.
F igu r e 4. Molecular structure of compound 10.
the three isomers of 7 were shown to be present in
relative proportions 40 (7a ):7 (7b):3 (7c). The experi-
(1)°, 157.9(2)°, or 158.9(3)°, respectively]. The N-Fe-
ments relating to 7 are described below.
N′ bond angle in gaseous [Fe(NR2)2] is, however, 180°.38
Each of the isomers 7a , 7b, and 7c showed NOEs
NMR Sp ectr oscop ic Ch a r a cter iza tion of th e Iso-
between the trimethylsilyl proton (Ha) and the tert-butyl
m er s of [Ni{η3-N(R)C(tBu )CH(C6H4Me-4)}2] (7). The
proton (Hc) and between the methine proton (Hb) and
three isomers of each of the Ni(II) complexes [NiL2] (7)
both the tert-butyl (Hc) and ortho-aryl protons (Hd). This
and [NiL1 ] (8) are designated as a , b, and c in Figure
2
is consistent with the 1-azaallyl ligand adopting the
6; assignments for 7 and 8, based on nuclear Overhauser
least sterically hindered anti-conformation for each
(NOE) experiments in toluene-d8 at ambient tempera-
isomer.
ture, are summarized in Table 3. Under these conditions
The molecular structure of crystalline 7 corresponds
to that of 7a . The observation that isomer 7b did not
(38) Andersen, R. A.; Faegri, K.; Green, J . C.; Haaland, A.; Lappert,
M. F.; Leung, W.-P.; Rypdal, K. Inorg. Chem. 1988, 27, 1782.
show NOEs between the trimethylsilyl and methine

2596 Organometallics, Vol. 23, No. 11, 2004
Avent et al.
Ta ble 3. 1H NMR NOE Da ta of th e Isom er s of 7
carbon trans to nitrogen, whereas in a and c they are
arranged in a cis fashion.
a n d 8 (in tolu en e-d 8 a t 298 K, 500 MHz)a
F lu xion a l P r ocesses. Variable-temperature (VT) 1H
NMR spectroscopic experiments were performed on 7
and 8 in toluene-d8. When the temperature of the
solution of 7 was raised to 358 K, the resonances for 7b
and 7c broadened; at 373 K, those of 7b and 7c
disappeared only to reappear on cooling to 298 K. Line
shape analysis of 7a showed no observable change. For
8, however, no change in the ratio of the three isomers
was observed (298-383 K). A very minor new species
appeared at δ 4.5, probably from decomposition/hydroly-
sis of the ligand; its concentration remained very low
(∼2%). At 373 K, the three methine signals became
broad and broadened further at 383 K. For complex 13,
a VT-NMR spectroscopic experiment (C6D6) showed that
broadening of the signals, particularly those attributed
to the methine protons (both allyl and azaallyl) and to
the trimethylsilyls, began already at 313 K. At 333 K,
only a single species was observed (but the signals of
both methines remained broad; they became sharp at
353 K). By cooling to 298 K, the two isomers were once
more observed in the same relative ratio, 2.7:1.
Variable-temperature saturation transfer (VTST) 1H
NMR spectroscopic experiments in toluene-d8 were
performed on complexes 7 and 8. Irradiation of the
methine singlet Hb of isomer 7b at δ 4.53 reduced the
intensity by 5% of its methine singlet Hb, at δ 5.22, but
had no effect on the methine singlet Hb at δ 5.51 of 7a ;
the latter had shown NOEs for the aryl (Hd) and tert-
butyl (Hc) signals of isomer 7b. The second VTST
experiment, at 328 K, involved irradiation of Hb for 7b
at δ 4.53, which greatly reduced the intensity (60%) of
Hb at δ 5.22 of 7c, with Hb (δ 5.51) of 7a unaffected.
Irradiation of the C-trimethylsilyl (Hc1) singlet of 8a at
δ -0.08 reduced strongly the intensity of the Hc1 of 8b
and 8c at δ 0.11 and 0.24, respectively. Similar irradia-
tion of the N-trimethylsilyl (Ha1) protons at δ 0.44 also
significantly decreased the corresponding signals of 8b
and 8c at δ 0.08 and 0.35, respectively, indicating a
dynamic exchange between the three species.
irradiated
affected peaks (δ) and increased intensity (%)
peak
isomer
(δ, Hx)
(δ)
%
(δ)
%
(δ)
%
7a
0.34 (Ha)
5.51 (Hb)
0.44 (Ha)
4.53 (Hb)
0.25 (Ha)
5.22 (Hb)
5.51 (Hb)
0.34 (Ha)
7.30 (Hd)
0.88 (Ha)
5.22 (Hb)
0.25 (Ha)
3.36 (Hb1
3.36 (Hb1
4.0 7.36 (Hd) 8.1
0.6 1.0 (Hc)
5.0
1.0 7.36 (Hd) 6.8
7b
7c
8a
1.1 7.30 (Hd) 8.2
4.6 7.45 (Hd) 7.1
0.4 1.10 (Hc) 1.2 7.45 (Hd) 6.2
10.3 7.32 (Hd1) 5.2
4.0 7.32 (Hd1) 1.3
0.6 0.44 (Ha1) 0.4 7.32 (Hd1) 3.3
0.8 0.44 (Ha1) 0.3 3.36 (Hb1) 7.9
5.2
-0.08 (Hc1
)
)
)
)
)
)
)
0.44 (Ha1
)
3.36 (Hb1) -0.08 (Hc1
7.32 (Hd1) -0.08 (Hc1
8b
0.08 (Ha1
0.24 (Hc1
)
7.68 (Hd1
2.20 (Hb1
)
8.6 7.68 (Hd1) 3.4
2.20 (Hb1
7.68 (Hd1
)
)
0.24 (Hc1
0.08 (Hc1
)
)
0.8 7.68 (Hd1) 4.5
0.7 0.24 (Hc1
) 0.8 2.20 (Hb1) 9.1
8c
0.11 (Hc1
)
3.36 (Hb1) 3.3
3.36 (Hb1 5.4
0.35 (Ha1
)
)
a
For Hx abbreviations, see inset of Figure 6.
protons is consistent with 7b having the two 1-azaallyl
ligands in an anti-conformation but with a trans-
configuration with eclipsed nitrogens. The final isomer,
7c, showed NOEs attributed to the trimethylsilyl (Ha)
and methine (Hb) protons. This, and the fact that isomer
7c contains the 1-azaallyl ligand in the anti-conforma-
tion, points to isomer 7c existing in the cis-configura-
tion.
NMR Ch a r a cter iza tion of th e Isom er s of [Ni{η3-
N(R)C(P h )CH(R)}2] (8). NMR spectroscopy showed
that compound 8 existed in solution as three isomers,
a , b, and c in relative ratios 15.8:8.3:1, respectively.
1
Indeed, the H NMR spectrum (298 K, C6D6) revealed
three sets of two inequivalent SiMe3 signals, at δ -0.08
(CHSiMe3) and 0.44 (NSiMe3) (a ), δ 0.05 (NSiMe3) and
0.24 (CHSiMe3) (b), and δ 0.08 (CHSiMe3) and 0.32
(NSiMe3) (c). Three signals were also noticed for the
protons in the 2-position of the phenyl ring, at δ 7.41
(a ), 7.75 (b), and 7.85 (c). Only two methine proton
resonances were present at δ 2.28 (b) and 3.45 (a and
c); the latter signal split at 263 K in toluene-d8 into δ
3.36 (c) and 3.39 (a ). The 13C{1H} NMR spectrum
showed four SiMe3 [at δ 2.3 and 2.6 (a ), 1.9 and 3.3 (b)]
and two methine carbon [at δ 55.9 (a ) and 44.3 (b)]
resonances. Signals corresponding to the minor isomer
c were either hidden or not observed. Nevertheless, the
three species were distinguishable by the 29Si{1H} NMR
spectroscopic INEPT technique at 263 K, with NSiMe3
at δ -4.1 (a ), -3.7 (b), and -3.4 (c) and SiMe3 signals
at δ 0.8 (b), 1.0 (c), and 3.3 (a ). The N-trimethylsilyl
resonances were assigned unambiguously to their cor-
responding isomers by 2D 29Si{1H}/1H correlation.
NOE studies similar to those performed on complex
7 were carried out on solutions of crystalline 8 in C6D6
at 298 K. The N-trimethylsilyl (Ha1), methine (Hb1),
C-trimethylsilyl (Hc1), and aryl (Hd1) proton signal
(Figure 6) of each of the three isomers was irradiated
in turn, and the effects on the rest of the spectrum were
noted, as summarized in Table 3.
The VT and VTST 1H NMR spectroscopic experiments
for compound 7 indicate that each of the isomers 7b and
7c was involved in a dynamic exchange process with
the other, but not with 7a . In contrast, for 8 all three
isomers (8a -c) were interconverting. Several dynamic
processes have been described for complexes containing
1-azaallyl or 2-pyridylalkyl moieties: (i) for conversion
of 1-azaallyl anions (Li,39 Mg,40 Al,40 and Zn40) having
the kinetically controlled E-configuration into the ther-
modynamically stable Z-configuration; and (ii) the
fluxional behavior of the tin(II) 2-pyridylalkyls [Sn{η2-
CR2C5H4N-2}2], [Sn{η2-CR2C5H4N-2}Cl], and [Sn{η2-
CR2C5H4N-2}N(R)2].41 As for (ii), the significant varia-
tion of δ[119Sn{1H}] with temperature for the three
compounds was attributed to a weak dative pyridyl-N-
1
Sn bond. The H NMR spectrum of [Sn{CR2C5H4N-2}-
Cl] at 193 K showed two distinct SiMe3 signals, which
merged at 220 K. The proposed mechanism41 for the
An interesting feature of complexes 7 and 8 is the fact
that the signal for the methine proton for 7b (δ 4.53) or
8b (δ 2.28) appeared at much lower frequency than
those assigned to the other isomers: 7a (δ 5.51), 7c (δ
5.22), 8a (δ 3.39), and 8c (δ 3.36). This is attributed to
a trans-influence, as only in isomer b is the methine
(39) (a) Knorr, R.; Lo¨w, P. J . Am. Chem. Soc. 1980, 102, 3241. (b)
Knorr, R.; Weiss, A.; Lo¨w, P. J .; Ra¨pple, E. Chem. Ber. 1980, 113, 2462.
(40) (a) Lalonde, J . J .; Bergbreiter, D. E.; Newcomb, M. J . Org.
Chem. 1986, 51, 1369.
(41) Engelhardt, L. M.; J olly, B. S.; Lappert, M. F.; Raston, C. L.;
White, A. H. J . Chem. Soc., Chem. Commun. 1988, 336.

Novel Late Transition Metal(II) 1-Azaallyls
Organometallics, Vol. 23, No. 11, 2004 2597
Sch em e 4. P r op osed Mech a n ism for Dyn a m ic P r ocesses in Com p ou n d s 7 a n d 8
interconversion involved η2-κ1-slippage and rotation
around the terminal tin-carbon bond. A similar mech-
anism had been postulated to explain the fluxional
behavior of a series of (η3-1-azaallyl)di(carbonyl)nitrosyl-
iron complexes, which at ambient temperature showed
interconversion of the syn and anti methine protons of
the terminal carbon;42 the proposed mechanism was via
an η3-κ1 slippage, followed by rotation around the
terminal carbon. The single-crystal X-ray diffraction
study of [Sn{η3-N(R)C(Ph)CR2}{N(R)C(Ph)dCR2}]
showed it to exist in the crystalline state as a mixed
step I or R1 in step VI) about the N-C(tBu) or Ni-N
bond, respectively, due to the two sets of C(tBu)dCH-
(C6H4Me-4) moieties; a possible corollary is that 7a may
not undergo η3 f κ1 slippage (I in Scheme 4). For 8, the
exchange between each of the three isomers is accounted
for in the case of 8a T 8b (from 8a ) by the successive
steps IV and I; the barrier R2 for steps I is lower,
involving two sets of sterically less encumbered C(tBu)d
CH(SiMe3) moieties. The variation in the relative pro-
portions (e.g., the greater prominence of isomer b for 8
rather than 7) may be due to steric effects.
(iminoalkyl)(enamido) complex.36 VT H and 13C NMR
An alternative to the η3 f κ1 f (η3)′ mechanism is
the η3 f (η3)′, involving rotation about one of the Ni-
centroid axes. For example, isomer 7a does not undergo
such a rotation (VII in Scheme 4) to generate 7d ,
because the latter would have the sterically unfavorable
cis-configuration with eclipsed nitrogen atoms. In vari-
ous η3-allyl-metal systems, the η3 f (η3)′ process has
been confirmed spectroscopically, as in selected com-
plexes of Mo, W, Ru, Rh, and Pt,43a such as [Mo(η3-
C3H5)(CO)3(diphos)]+,43b and has also been proposed to
account for the observed equivalence of the allyl groups
in [Ru(η3-C3H5)2(CO)2].44 For [M(η3-C3H5)2] (M ) Ni, Pt),
however, a qualitative MO treatment indicated that
simple rotation about the allyl-metal axis was sym-
metry-forbidden and hence a high-energy process.45
Both mechanisms have been put forward for [Ni(η3-1-
1
spectroscopic experiments on crystalline [Sn{η3-N(R)C-
(Ph)CR2}{N(R)C(Ph)dCR2}] showed the two ligands to
be equivalent in solution down to 183 K, indicating that
there was a rapid exchange between the κ1- and η3-
coordinated ligands.33
On the basis of our experiments on the isomers of 7
and 8 and the above literature precedents, the proposed
mechanism of the exchange processes is summarized in
Scheme 4 (the isomers shown in parentheses are
intermediates or transition states); the failure to observe
an isomer 7d or 8d is attributed to the excessively high
barrier for the possible rearrangement III, V, or VI. The
7b T 7c exchange is suggested to involve from 7b
successive (I and II in Scheme 4) C-Ni dissociation (η3
f κ1 slippage) followed by a 180° rotation about the
Ni-N bond. The lack of exchange between 7a and 7b
or 7c is attributed to possible restricted rotation (R2 in
(43) (a) Faller, J . W. Adv. Organomet. Chem. 1978, 16, 211. (b)
Faller, J . W.; Haitko, D. A. J . Organomet. Chem. 1978, 149, C19.
(44) Cooke, M.; Goodfellow, R. J .; Green, M.; Parker, G. J . Chem.
Soc (A) 1971, 16.
(42) Nakanishi, S.; Masuzaki, K.; Takata, T. Inorg. Chem. Commun.
2000, 3, 469.
(45) Ro¨sch, N.; Hoffmann, R. Inorg. Chem. 1974, 13, 2656.

2598 Organometallics, Vol. 23, No. 11, 2004
Avent et al.
stored over a potassium mirror (thf-d8, C6D6, and toluene-d8)
or A4 molecular sieve (CDCl3).
MeC3H4)2], in which a total of 12 isomers, due to syn-
or anti-methyl groups, is possible; spectroscopic studies,
however, showed the complex to exist as a mixture of
four isomers, detected in both the 13C and 1H NMR
spectra at -20 °C and shown, by analysis of the proton-
proton coupling constants, to contain exclusively syn-
substituted η3-allyl groups.46 These four isomers under-
went fluxional processes with one another, but with
retention of the syn-configuration, suggesting that any
η3 f κ1 ligand slippage occurred at the CH2 carbon.
P olym er iza tion Exp er im en ts. Compounds 8 and
13 were used as catalyst precursors for ethylene polym-
erization. The reactions were carried in toluene at ca.
298 K under 1.4 bar of ethylene, in the presence of MAO
(500 equiv/Ni) or B(C6F5)3 (1.5 equiv/Ni). Limited
amounts of oligomer were obtained (but not analyzed)
with 8/B(C6F5)3. No poly-(oligo-)merization was observed
for the other experiments.
Elemental analyses were performed on a CEC 240 XA
analyzer by Medac Ltd, Brunel University (the %C reported
for 5 and 13 were lower than calculated, a feature we have
noted previously on Si-containing compounds examined by
Medac). EI-MS data were recorded using VG Autospec or
Kratos MS 80 RF instruments at 70 eV. The carrier gas was
helium, at a flow rate 2 cm3 min-1. Melting points were
determined under argon in sealed capillaries on an electro-
thermal apparatus and were uncorrected.
NMR spectra were recorded using a Bruker AC-P250 (1H,
250.1; 13C, 62.9 MHz), DPX-300 (1H, 300.1; 13C, 75.5 MHz),
AMX-400 (1H, 400.1; 13C 100.6 MHz), or AMX-500 (1H, 500.1;
13C, 125.7; 29Si, 99.3 MHz) spectrometer and referenced
internally (1H, 13C) to residual solvent. The 29Si spectra were
referenced externally to SiMe4. Unless otherwise stated, all
NMR spectra other than 1H were proton-decoupled and
recorded at ambient probe temperature. IR spectra were
recorded either as Nujol mulls between KBr plates or as KBr
pellets using a Perkin-Elmer 1720 FT spectrometer.
Compounds KL (1),20 [LiL1(thf)]2 (2),1a LiL2 (3),1a KL3 (4),21
[NiBr2(dme)],47 [{Ni(η3-C3H5)(µ-Br}2],48 and [PdCl2(cod)]49 were
synthesized according to published procedures, while FeBr2
(Aldrich) was purchased and used without further purification.
CoCl2 (BDH) was dried using refluxing trimethylsilyl chloride
and then heated at 140 °C in vacuo.
Con clu sion s
Nine crystalline 1-azaallylmetal(II) complexes have
been prepared in good yield from the appropriate
potassium or lithium 1-azaallyl and the metal(II) halide
MX2 or [{Ni{η3-C3H5)(µ-Cl)}2]: [FeL2] (5), [CoL2] (6),
[NiL2] (7), [NiL1 ] (8), [PdL1 ] (9), [FeL2 ] (10), [CoL2 ]
[F e{η3-N(SiMe3)C(tBu )CH(C6H4Me-4)}2] (5). A solution
of KL (1) (1.20 g, 4 equiv) in thf (ca. 40 cm3) was slowly added
to a stirred suspension of FeBr2 (0.43 g, 2 mmol) in thf (ca. 10
cm3) at -78 °C. The suspension was allowed to warm to room
temperature and stirred for a further 16 h. The resultant dark
red solution, with a fluffy white precipitate (KBr), was filtered.
The solvent was removed from the filtrate in vacuo to afford
a dark red microcrystalline solid, which was washed with light
petroleum (bp 30-40 °C, ca. 20 cm-3). The residue was
dissolved in CH2Cl2 (ca. 30 cm3) and filtered to remove further
KBr. The filtrate was concentrated to ca. 10 cm3 and cooled at
-30 °C, yielding complex 5 (0.91 g, 79%), as bright red single
crystals, mp 163-5 °C. MS: m/e (%, assignments), 576 (37),
[M]+; 420 (27, [M - N(SiMe3)C(tBu)]+); 316 (68, [M - L]+); 261
(54, [L + 1]+); 246 (13, [L - Me]+); 204 (30, [L - tBu]+). Anal.
Calcd for C32H52FeN2Si2: C, 66.6; H, 9.11; N, 4.85. Found: C,
65. 8; H, 9.09; N, 4.91.
2
2
2
2
(11), [FeL3 ] (12), and [Ni{η3-C3H5)(L3)] (13) (L ) {N-
2
(R)C(tBu)CH(C6H4Me-4)}, L1 ) {N(R)C(Ph)CH(R)}, L2
) {N(R)C(tBu)CH(R)}, L3 ) {N(R)C(tBu)CH(C10H7-1)};
R ) SiMe3; MX2 ) FeBr2, CoCl2, [NiBr2(dme)], [PdCl2-
(cod)]). X-ray structures show that (i) the complexes 5,
6, and 7 are isomorphous, and (ii) in each of 5-8 and
10 the staggered pair of 1-azaallyl ligands binds to the
pseudooctahedral metal ion in an η3-fashion, whereas
the two-coordinate Fe(II) complex 12 has the ligands
bound in the κ1-enamido mode. Remarkably, although
the Fe(II) 1-azaallyls 5, 10, and 12 are high-spin d6
complexes with magnetic moments (in solution at ambi-
ent temperature) in the range 5.01-5.61 µB, the cobalt-
(II) analogues 6 and 11 are low-spin d7 complexes, with
µeff ) 2.73-3.01 µB. The diamagnetic Ni(II) (7, 8, 13)
and Pd(II) (9) 1-azaallyls exist as a mixture of three (7,
8, 9) or two (13) isomers in C6D6 or toluene-d8 at 298
K; their structures have been elucidated from NOE, 2D,
and saturation transfer NMR spectroscopic data. Dy-
namic processes in toluene-d8 have been revealed by
further variable-temperature NMR spectral data and
mechanisms suggested in terms of η3 f κ1 f (η3)′ Ni-C
dissociative/associative processes.
[Co{η3-N(SiMe3)C(tBu )CH(C6H4Me-4)}2] (6). A solution
of KL (1) (1.61 g, 5 equiv) in thf (ca. 40 cm3) was slowly added
to a stirred suspension of CoCl2 (0.34 g, 3 mmol) in thf (ca. 10
cm3) at -78 °C. After warming to room temperature and
stirring for a further 12 h, a dark red solution was obtained.
Tetrahydrofuran was removed in vacuo; the residual red solid
was heated at ca. 70 °C for 3 h. The residue was washed with
light petroleum (bp 60-80 °C, ca. 10 cm3) and extracted with
CH2Cl2 (ca. 30 cm3). The dark orange extract was filtered and
the solvent was removed from the filtrate in vacuo to afford
an orange crystalline solid, which was redissolved in Et2O (ca.
40 cm3), concentrated to ca. 15 cm3, and cooled at -30 °C to
yield bright orange single crystals of complex 6 (1.36 g, 89%),
mp >130 °C dec. MS: m/e (%, assignments), 580 (17, [M]+);
522 (10, [M - tBu]+); 423 (18); 320 (31, [M - L]+); 261 (51, [L
Exp er im en ta l Section
Gen er a l P r oced u r es. All experiments were performed
under an atmosphere of pure argon using Schlenk apparatus
and a vacuum line, unless otherwise stated. The solvents used
were of reagent grade or better and were freshly distilled under
dry dinitrogen and freeze/thaw degassed prior to use. The
drying agents employed were (i) sodium benzophenone (ben-
zene, diethyl ether, thf, toluene, and dme), (ii) sodium-
potassium alloy (light petroleum, bp 30-40 and 60-80 °C),
and (iii) phosphorus(V) oxide (dichloromethane). Reaction
solvents and deuterated solvents for NMR spectroscopy were
t
+ 1]+), 246 (15, [L - Me]+); 204 (32, [L - Bu]+). Anal. Calcd
for C32H52CoN: C, 66.3; H, 9.10; N, 4.83. Found: C, 66.3; H,
9.16; N, 4.73.
[Ni{η3-N(SiMe3)C(tBu )CH(C6H4Me-4)}2] (7). A solution of
KL (1) (0.98 g, 3 equiv) in thf (ca. 40 cm3) was slowly added to
a stirred suspension of [NiBr2(dme)] (0.5 g, 1.6 mmol) in thf
(ca. 10 cm3) at -78 °C. The suspension was allowed to warm
to room temperature and was stirred for a further 12 h,
(46) Henc, B.; J olly, P. W.; Salz, R.; Wilke, G.; Benn, R.; Hoffmann,
E. G.; Mynott, R.; Schroth, G.; Seevogel, K.; Sekutowski, J . C.; Kru¨ger,
C. J . Organomet. Chem. 1980, 191, 425.
(47) Ward, L. G. D. Inorg. Synth. 1972, 13, 162.
(48) Fischer, E. O.; Bu¨rger, G. Z. Naturforsch. 1961, 16b, 77.
(49) Drew, D.; Doyle, J . R. Inorg. Synth. 1972, 13, 52.

Novel Late Transition Metal(II) 1-Azaallyls
Organometallics, Vol. 23, No. 11, 2004 2599
yielding a dark red solution. Tetrahydrofuran was removed
in vacuo. The residue was washed with light petroleum (bp
60-80 °C, ca. 15 cm3) and was extracted with Et2O (ca. 20
cm3). The extract was filtered. The solvent was removed from
the filtrate in vacuo to afford a red crystalline solid, which
was redissolved in warm benzene (ca. 30 cm3) and concentrated
to ca. 10 cm3 to afford bright red single crystals of complex 7
(0.55 g, 57%), mp 174-8 °C. In toluene-d8 at 298 K, three
isomers of relative intensities 80% (7a ), 14% (7b), and 6% (7c)
CH, 9b), 3.49 (s, CH, 9c), 3.67 (s, CH, 9a ), 7.00-7.11 (m, Ph),
7.34-7.39 (m, Ph), 7.55-7.61 (m, Ph), 7.68 (m, Ph). 13C{1H}
NMR (75.5 MHz): δ 2.4, 2.5, 2.8, and 3.3 (s, Si(CH3)3 and NSi-
(CH3)3), 42.0 (s, CH, 9b), 48.5 (s, CH, 9c), 58.1 (s, CH, 9a ),
128.0, 128.1, 128.3, 128.5, 128.7, 129.5, 130.1, and 130.4 (s,
Ph o-, m-, and p-CH), 141.3 (9c), 142.5 (9a ), and 142.6 (9b, s,
Ph Cipso), 167.5 (9a ) and 175.0 (9b, s, CN). MS: m/e (%,
assignments), 630 (60, [M - H]+); 616 (10, [M - Me]+); 557
(13, [M - H - SiMe3]); 544 (10, [M - CHSiMe3]); 354 (47, [M
- L1 - Me]+); 262 (89, [L1]+); 247 (75, [L1 - Me]+); 185 (29,
[L1 - Ph]+); 176 (56, [L1 - NSiMe3]+); 73 (100, [SiMe3]+). Anal.
Calcd for C28H48N2PdSi4: C, 53.3; H, 7.66; N, 4.44. Found: C,
53.8; H, 7.62; N, 4.44.
1
were identified by H NMR (500 MHz): δ 7.46 (d, Ar o-H, 7c),
7.36 (d, Ar o-H, 7a ), 7.30 (d, Ar o-H, 7b), 6.78 (d, Ar m-H, 7a ),
6.72 (d, Ar m-H, 7c), 5.51 (s, 4-MeC6H4CHC(tBu), 7a ), 5.22 (s,
4-MeC6H4CHC(tBu), 7c), 4.53 (s, 4-MeC6H4CHC(tBu), 7b), 2.00
(s, 4-CH3C6H4, 7c), 1.98, (s, 4-CH3C6H4, 7b), 1.95 (s, 4-CH3C6H4,
7a ), 1.15 (s, C(CH3)3, 7c), 1.10 (s, C(CH3)3, 7b), 1.00 (s, C(CH3)3,
7a ), 0.45 (s, NSi(CH3)3, 7b), 0.34 (s, NSi(CH3)3, 7a ), 0.25 (s,
NSi(CH3)3, 7c). 13C{1H} NMR (75.46 MHz): δ 151.90 (s, C(t-
Bu)NSi), 137.65 (Cipso), 133.83 (Cipso), 128.88 (CH), 126.93 (CH),
64.47 (s, CHC(tBu)), 39.44 (s, C(CH3)3), 29.39 (s, 4-CH3C6H4),
4.34 (s, NSi(CH3)3). MS: m/e (%, assignments), 580 (17, [M]+);
[F e{η3-N(R)C(tBu )CH(R)}2] (10). A solution of [LiL2]2 (3)
(0.8 g, 3 mmol) in Et2O (ca. 10 cm3) was slowly added to a
stirred suspension of FeBr2 (0.35 g, 1.6 mol) in Et2O (ca. 50
cm3) at -78 °C. The suspension was allowed to warm to room
temperature and was stirred for 4 h. The mixture was filtered
and solvent removed from the dark red filtrate in vacuo. The
residual orange solid was heated at ca. 80 °C in vacuo for 4 h,
then extracted with light petroleum (bp 60-80 °C, ca. 40 cm3).
Crystallization was affected by concentrating to ca. 20 cm3 and
cooling to -30 °C, affording deep red single crystals of complex
10 (1.47 g, 91%), mp 135-8 °C. MS: m/e (%, assignment), 540
t
522 (10, [M - Bu]+); 423 (18, [M - N(SiMe3)C(tBu)]+); 320
(31, [M - L]+); 261 (48, [L + 1]+); 246 (17, [L - Me]+); 204
t
(28, [L - Bu]+). Anal. Calcd for C32H52NiN2Si2: C, 66.3; H,
9.10; N, 4.83. Found: C, 66.6; H, 9.08; N, 4.89.
t
(47, [M]+); 483 (38, [M - Bu]+); 298 (9, [M - L2]+); 186 (16,
[Ni{η3-N(R)C(P h )CH(R)}2] (8). [LiL1(thf)]2 (1.52 g, 2.23
mmol) in thf (15 cm3) was added dropwise to a solution of
[NiBr2(dme)] (0.69 g, 2.23 mmol) in thf (20 cm3) at ca. 0 °C.
The resulting deep purple mixture was set aside for ca. 15 min
at 0 °C and then 2 h at ca. 20 °C. The solvent was removed in
vacuo, and the residue was “stripped” with light petroleum
(bp 30-40 °C, 3 × 10 cm3; this procedure refers to adding the
solvent and then removing it in vacuo) and then extracted into
light petroleum (bp 30-40 °C, 20 cm3). The extract was
filtered. The filtrate was concentrated to ca. 3-4 cm3 and
cooled to -30 °C, yielding deep purple crystals of 8 (0.78 g,
59%), mp 95-8 °C. As for 7, three isomers in C6D6 at 298 K of
relative intensities 63 (8a ), 33 (8b), and 4% (8c) were identified
by 1H NMR (300.1): δ -0.08 (s, Si(CH3)3, 8a ), 0.05 (s, NSi-
(CH3)3, 8b), 0.08 (s, Si(CH3)3, 8c), 0.24 (s, Si(CH3)3, 8c), 0.32
(s, NSi(CH3)3, 8c), 0.44 (s, NSi(CH3)3, 8a ), 2.28 (s, 1 H, CH,
t
[L2 - Bu]+); 170 (13, [L - N(tBu)]+). Anal. Calcd for C24H56
-
FeN2Si4: C, 53.3; H, 10.5; N, 5.18. Found: C, 53.1; H, 10.6;
N, 5.12.
Co{N(R)C(tBu )CH(R)}2 (11). A solution of [LiL2]2 (3) (1.0
g, 4 mmol) was slowly added to a stirred suspension of CoCl2
(0.26 g, 2 mmol) in Et2O (ca. 30 cm3) at -78 °C. The dark
orange suspension was allowed to warm to room temperature
and was stirred for 4 h. Diethyl ether was removed in vacuo
and the residual orange solid heated at ca. 80 °C in vacuo for
4 h, then extracted with light petroleum (bp 30-40 °C, ca. 40
cm3), and crystallized by concentrating to ca. 10 cm3 and
cooling at -30 °C to yield bright orange single crystals of
complex 11 (0.95 g, 86%), mp 120-3 °C. MS: m/e (%,
t
assignment), 543 (100, [M]+); 486 (27, [M - Bu]+); 429 (12,
[M - N(SiMe3)C(tBu)]+). Anal. Calcd for C24H56CoN2Si4: C,
53.0; H, 10.3; N, 5.16. Found: C, 53.1; H, 10.2; N, 5.07.
[F e{N(R)C(tBu )dCH(C10H7-1)}2] (12). A solution of KL3
(4) (2.0 g, 6 mmol) in thf (ca. 50 cm3) was added to FeBr2 (0.64
g, 3 mmol) suspended in thf (ca. 10 cm3) at -78 °C. The
suspension was allowed to warm to room temperature and
stirred for a further 12 h, a dark red solution being obtained.
Tetrahydrofuran was removed in vacuo, and the residual red
solid was washed with light petroleum (bp 60-80 °C, ca. 20
cm3) and diethyl ether (ca. 25 cm3), then extracted with toluene
(ca. 50 cm3). The extract was filtered, and the filtrate was
concentrated to ca. 10 cm3 and cooled at -30 °C to give bright
red single crystals of complex 12 (1.5 g, 78%), mp >60 °C dec.
MS: m/e (%, assignment), 647 (28, [M]+); 591 (41, [M - tBu]+);
492 (18, [M - N(SiMe3)C(tBu)]+); 352 (10, [M - L3]+). Anal.
Calcd for C38H52FeN2Si2: C, 70.3; H, 8.09; N, 4.31. Found: C,
70.2; H, 8.11; N, 4.29.
3
8b), 3.45 (s, CH, 8a and 8b), 7.05 (m, Ph m-H), 7.41 (d, J HH
) 7 Hz, Ph o-H), 7.75 (m, Ph p-H, 8a and 8c), 7.85 (m, Ph
p-CH, 8b). 13C{1H} NMR (75.5 MHz): δ 1.9, 2.3, 2.6, and 3.3
(s, Si(CH3)3 and NSi(CH3)3), 44.3 (s, CH, 8b), 55.9 (s, CH, 8a ),
128.0, 128.2, 129.0, 129.8, and 130.5 (s, Ph o-, m-, and p-CH),
142.8 and 143.6 (s, Ph Cipso), 160.3 and 163.2 (s, CN). 29Si NMR
(99.3 MHz): δ -4.1 (s, NSi(CH3)3, 8b), -3.7 (s, NSi(CH3)3, 8a ),
-3.4 (s, NSi(CH3)3, 8c), 0.8 (s, Si(CH3)3, 8b), 1.0 (s, Si(CH3)3,
8c) and 3.3 (s, NSi(CH3)3, 8a ). MS: m/e (%, assignments), 582
(13, [M - H]+); 483 (71, [M - CHNSiMe3]+); 263 (56, [L1
-
H]+); 248 (17, [L1 - H - Me]+); 185 (25, [L1 - Ph]+); 176 (72,
[L1 - NSiMe3]+); 147 (100) and 73 (85, [SiMe3]+). Anal. Calcd
for C28H48N2NiSi4: C, 57.6; H, 8.36; N, 4.80. Found: C, 57.7;
H, 8.36; N, 4.69.
[P d {η3-N(R)C(P h )CH(R)}2] (9). [LiL1(thf)]2 (2.24 g, 3.28
mmol) in thf (20 cm3) was added dropwise to a suspension of
[PdCl2(cod)] (0.94 g, 3.29 mmol) in thf (20 cm3) at ca. 20 °C.
The resulting deep brown mixture was stirred for 20 min, the
solvent was removed in vacuo, and the residue was “stripped”
with light petroleum (bp 60-80 °C, 3 × 20 cm3) and then
extracted into light petroleum (bp 30-40 °C, 20 cm3). The
extract was filtered. Volatiles were removed form the filtrate
in vacuo, affording a deep red-brown oil. The latter was covered
with light petroleum (bp 30-40 °C, 15 cm3). Cooling to -20
°C gave yellow-orange crystals of 9 (1.00 g, 52%), mp 73-5
°C. As for 7, three isomers of 9 in C6D6 at 298 K of relative
intensities 51 (9a ), 30 (9b), and 19% (9c) were identified by
1H NMR (300.1 MHz): δ 0.07 (s, Si(CH3)3 or NSi(CH3)3, 9a ),
0.19 (s, Si(CH3)3 or NSi(CH3)3, 9b), 0.22 (s, Si(CH3)3 or NSi-
(CH3)3, 9c), 0.32 (s, Si(CH3)3 or NSi(CH3)3, 9b), 0.39 (s, Si(CH3)3
or NSi(CH3)3, 9c), 0.49 (9a , s, Si(CH3)3 or NSi(CH3)3), 2.69 (s,
[Ni{η3-C3H5}{N(R)C(tBu )dCH(C10H7-1)}2] (13). KL3 (4)
(0.93 g, 2.77 mmol) in thf (ca. 25 cm3) was added dropwise to
a cooled (0 °C) solution of [{Ni(η3-C3H5)(µ-Br}2] (0.56 g, 1.56
mmol) in thf (30 cm3). The resulting mixture was warmed to
ca. 25 °C and stirred for 3 h. The solvent was removed in vacuo
and “stripped” with pentane (30 cm3). The dark red residue
was extracted with pentane (45 cm3). The extract was filtered;
the filtrate was concentrated to 3-4 cm3 and cooled at -20
°C, affording deep red and sticky crystals, which upon recrys-
tallization yielded 13 (0.55 g, 50%), mp 92-4 °C. Two isomers
of 13 in C6D6 at 298 K of relative intensities 73 (13a ) and 27%
(13b) were identified by 1H NMR (300.1 MHz): δ 0.41 (s, NSi-
(CH3)3, 13a ), 0.42 (s, NSi(CH3)3, 13b), 1.05 (s, C(CH3)3, 13b),
1.31 (s, C(CH3)3, 13a ), 1.19 (d, 3J HH ) 13 Hz, CH2CHCH2, 13b),
3
3
1.53 (d, J HH ) 13 Hz, CH2CHCH2, 13a ), 1.70 (d, J HH ) 13

2600 Organometallics, Vol. 23, No. 11, 2004
Avent et al.
Ta ble 4. Exp er im en ta l Da ta for th e Str u ctu r e Deter m in a tion of th e Cr ysta llin e Com p lexes 5-8, 10, a n d 12
5
6
7
8
10
12
empirical formula
M
C
576.8
32H52FeN2Si2
C32H52CoN2Si2
579.9
C32H52N2NiSi2
579.7
C28H48N2NiSi4
583.7
C24H56FeN2Si4
540.9
C38H52FeN2Si2
648.9
cryst syst
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
orthorhombic
Pbca (No. 61)
17.949(7)
8.668(2)
20.850(4)
90
90
90
3244(2)
4
0.56
orthorhombic
Pbca (No. 61)
20.706(4)
18.326(3)
8.849(4)
90
90
90
3358(2)
4
0.60
orthorhombic
Pbca (No. 61)
20.690(3)
18.295(2)
8.856(1)
90
monoclinic
P21/n (No. 14)
11.919(7)
16.414(13)
17.285(9)
90
91.55(5)
90
3380(4)
4
monoclinic
C2/c (No. 15)
15.865(1)
11.671(2)
17.936(2)
90
91.02(1)
90
3320.5(7)
4
triclinic
P1h (No. 2)
9.152(5)
9.982(8)
10.990(10)
75.39(8)
73.74(7)
66.10(5)
870.1(12)
1
90
90
3352.2(7)
4
0.672
30
293(2)
4882
Z
µ
abs coeff(Mo KR) (mm-1
)
0.73
0.61
0.53
θmax for data colln (deg)
temperature (K)
no. of indep reflns
Rint
25
173(2)
2840
25
293(2)
2955
173(2)
5933
0.09
293(2)
2919
0.03
173(2)
3051
no. of reflns with I > 2σ(I)
no. of data/restraints/
params
1526
2840/0/169
1609
2955/0/169
2674
4881/0/169
4426
5933/0/324
2173
2919/0/146
2010
3051/0/199
R1 (I > 2σ(I))
wR2 (all data)
0.062
0.145
0.063
0.149
0.058
0.153
0.061
0.174
0.047
0.138
0.107
0.313
Hz, CH2CHCH2, 13a ), 1.87 (d, 3J HH ) 13 Hz, CH2CHCH2, 13b),
hydrogen atoms were included in the riding mode with Uiso-
3
3.12 (m, CH2CHCH2, 13a ), 3.27 (d, J HH ) 7 Hz, CH2CHCH2,
(H) ) 1.2Ueq(C) or 1.5Ueq(C) for Me groups. Details of the data
collection and refinement are given in Table 4. The C9 methyl
group of 5 was included as disordered over two orientations
related by a 60° rotation about C6-C9. The p-CH3 group of 6
was assumed to be disordered over two likely orientations. The
iron atom of 12 was disordered across the inversion center;
the high R factor for 12 is due to weak diffraction from the
crystal; there was no indication of solvent electron density in
the difference map.
13b), 4.29 (m, 3J HH ) 6 Hz, CH2CHCH2, 13a ), 4.52 (m, 3J HH
)
7 Hz, CH2CHCH2, 13b), 5.88 (s, ArCHCtBu, 13b) and 6.19 (s,
ArCHCtBu, 13a ), 7.13-8.37 (Ar). 13C{1H} NMR (75.5 MHz):
δ 3.9 (s, NSi(CH3)3, 13a and 13b), 29.3 (s, C(CH3)3, 13b), 29.6
(s, C(CH3)3, 13a ), 39.4 (s, C(CH3)3, 13a and 13b), 49.2 (s, CH2-
CHCH2, 13a ), 51.4 (s, CH2CHCH2, 13a and 13b), 53.0 (s, CH2-
CHCH2, 13b), 61.7 (CH2CHCH2, 13b), 62.4 (s, CH2CHCH2,
10a ), 108.4 (s, ArCHCtBu, 13a ), 109.4 (s, ArCHCtBu, 13b),
123.5-135.0 (s, C10H7-), 149.8 (s, ArCHCtBu, 13a ) and 150.7
(s, ArCHtBu, 13 b). MS: m/e (%, assignments), 395 (32, [M -
H]+); 338 (20, [M - H - tBu]+); 297 (89, [L3H]+); 282 (40, [L3H
- Me]+); 240 (67, [L3H - tBu]); 141 (64, [Ni(C3H5)2]+); 127 (21,
[Ni(C3H5)2-CH2]+); 100 (35, [M - L3]+), 74 (87, [SiMe3]+). Anal.
Calcd for C22H31NNiSi: C, 66.7; H, 7.88; N, 3.53; Found: C,
65.6; H, 7.90; N, 3.45.
Ack n ow led gm en t. We thank Dr. R. Wife (SPECS
and BioSPECS) and the EPSRC for a case award for
J .R.S., the European Commission for a Marie Curie
Fellowship for R.S., and Prof. C. J . Pickett of the J ohn
Innes Centre, Norwich, UK, for cyclic voltammetry
studies.
X-r a y Cr ysta llogr a p h ic Str u ctu r e Deter m in a tion s of
Com p ou n d s 5-8, 10, a n d 12. Single crystals of each of 5, 8,
and 12 were removed from the Schlenk tube under a stream
of argon and rapidly covered with a layer of hydrocarbon oil.
A suitable crystal was selected, attached to a glass fiber, and
immediately placed in the low-temperature nitrogen stream.
Single crystals of each of 6, 7, and 10 were sealed under argon
in Lindemann capillaries; data for these were collected at 293-
(2) K and for 5, 8, and 12 at 173(2) K on an Enraf-Nonius
CAD4 diffractometer using monochromated Mo KR (λ )
0.70173 Å) radiation. The crystal structures were solved by
direct methods (SHELXS-86)50 and refined by full-matrix least-
squares procedures (SHELXL-93),51 with absorption correction
by ψ-scans. All non-hydrogen atoms were anisotropic, and
Su p p or tin g In for m a tion Ava ila ble: Full listings of X-ray
crystallographic data, atomic coordinates, thermal parameters,
bond distances and bond angles, and hydrogen parameters for
5, 6, 7, 8, 10, and 12; magnetic moment calculations for 5, 6,
10, 11, and 12; and cyclic voltammograms for 5 and 6. This
material is available free of charge via the Internet at
http://pubs.acs.org.
OM0498955
(50) Sheldrick, G. M. In Crystallographic Computing 3; Sheldrick,
G. M., Kru¨ger, C., Goddard, R., Eds.; Oxford University Press: Oxford,
1985; pp 175-189.
(51) Sheldrick, G. M. SHELXL-93, A Program for Structure Refine-
ment; University of Go¨ttingen: Germany, 1993.