A Paramagnetic Organometallic Nickel(II) Complex
J. Am. Chem. Soc., Vol. 118, No. 24, 1996 5691
Van Koten et al. demonstrated that the [(2,6-Me2NCH2)-
C6H3]- ligand stabilized the unique organometallic Ni(III)
complex.1c-e The remarkably low NiII/NiIII redox potentials1c-e,k
of {[(2,6-Me2NCH2)C6H3]NiII}X originate catalytic reactivity
in the Kharasch addition reaction, i.e., the 1:1 addition of
polyhalogenated alkanes to alkenes with formation of new C-C
and C-X bonds. Homogenous catalysts related to heteroge-
neous ones based on soluble polymeric supports1j or silane
dendrimers11 functionalized with pendant arylnickel(II) com-
plexes have been explored as well.
Chart 1
Organometallic chemistry of nickel is of current interest in
connection with mechanism of reactions of metalloenzymes
which contain the nickel ion, e.g., methyl-S-coenzyme-M
reductase and carbon monoxide dehydrogenase.5-9 Organo-
nickel complexes have been included as crucial intermediates
in both enzymatic cycles. In general organonickel(II) complexes
are diamagnetic including uncommon derivatives of nickel(II)
porphyrins.10 Paramagnetic organonickel(II) compounds are
extremely rare and for a very long period of time have been
exemplified by (σ-methyl)nickel(II)[(R,R,S,S)-N,N′,N′′,N′′′-tet-
ramethylcyclam].11 Recently a paramagnetic σ-methyl deriva-
tive of F430 (a nickel(II) tetrapyrrole whose structure corre-
sponds to that of hydrocorphin) was prepared by in situ
methylation.12 In the same time the axial coordination of
σ-phenyl to nickel(II) to produce paramagnetic complexes with
21-thiaporphyrin or 21-N-methylporphyrin as equatorial ligands
were demonstrated as well.13
In the context of organometallic chemistry of nickel(II)
facilitated by the appropriate construction of the polydentate
macrocycle, we have focused on porphyrin-related ligands, i.e.,
2-aza-5,10,15,20-tetraphenyl-21-carbaporphyrin and 2-N-methyl-
5,10,15,20-tetraphenyl-21-carbaporphyrin. These ligands are
isomers of their regular counterparts, i.e., of 5,10,15,20-
tetraphenylporphyrin and 5,10,15,20-tetraphenyl-21-N-meth-
ylporphyrin and are formed formally by an inversion of pyrrole
or N-methylated pyrrole rings.14-16 With the replacement of
the pyrrolenine nitrogen by a methine group, a carbaporphyrin
molecule retains coordination properties as demonstrated re-
cently by the formation of diamagnetic nickel(II) complexes,
i.e., (CTPP)NiII and (2-NCH3CTPP)NiII.14,16 CTPPH2 and
2-NCH3CTPPH are geometrically similar to TPPH2 and poten-
tially offer a suitable fit to a variety of metal ions. The structural
constraints typical for metalloporphyrins may be instrumental
in stabilization of their metallocarbaporphyrin counterparts
resulting in a peculiar stabilization of a σ-metal-carbon
bond.14,16 The unusual lability of the inner C-H bond is a
prerequisite of the 21-carbaporphyrin coordination to produce
the relatively robust NiII-C bond.
(1) (a) de Koster, A.; Kanters, J. A.; Spek, A. L.; van der Zeijden, A. A.
H.; van Koten, G.; Vrieze, K. Acta Crystallogr. 1985, C41, 893. (b) Grove,
D. M.; van Koten, G.; Ubbels, H. J. C.; Zoet, R.; Spek, A. L. Organome-
tallics 1984, 3, 1003. (c) Grove, D. M.; van Koten, G.; Zoet, R.; Murrall,
N. W.; Welch, A. J. J. Am. Chem. Soc. 1983, 105, 1379. (d) Grove, D.
M.; van Koten, G.; Mul, P.; Zoet, R.; van der Linden, J. G. M.; Legters, J.;
Schmitz, J. E. J.; Murrall, N. W.; Welch, A. J. Inorg. Chem. 1988, 27,
2466. (e) Grove, D. M.; van Koten, G.; Mul, W. P.; van der Zejden, A. A.
H.; Terheiden, J.; Zoutberg, M. C.; Stam, C. H. Organometallics 1986, 5,
322. (f) Grove, D. M.; van Koten, G.; Louwen, J. N.; Noltes, J. G.; Spek,
A. L.; Ubbels, H. J. C. J. Am. Chem. Soc. 1982, 104, 6609. (g) Abbenhuis,
H. C. L.; Feiken, N.; Haarman, H. F.; Grove, D. M.; Horn, E.; Kooijman,
H.; Spek, A. L.; van Koten, G. Angew. Chem., Int. Ed. Engl. 1991, 30,
996. (h) Grove, D. M.; van Koten, G.; Verschuuren, A. H. M. J. Mol.
Catal. 1988, 45, 169. (i) Grove, D. M.; Verschuuren, A. H. M.; van Koten,
G.; van Beek, J. A. M. J. Organomet. Chem. 1989, 372, C1. (j) van de
Kuil, L. A.; Grove, D. M.; Zwikker, J. W.; Jenneskens, L. W.; Drenth, W.;
van Koten, G. Chem. Mater. 1994, 8, 1675. (k) van de Kuil, L. A.; Luitjes,
H.; Grove, D. M.; Zwikker, J. W.; van der Linden, J. G. M.; Roelofsen, A.
M.; Jenneskens, L. W.; Drenth, W.; van Koten, G. Organometallics 1994,
13, 468. (l) Knapen, J. W. J.; van der Made, A. W.; de Wilde, J. C.; van
Leeuwen, P. W. N. M.; Wijkens, P.; Grove, D. M.; van Koten, G. Nature
1994, 372, 659. (m) Terheijden, J.; van Koten, G.; Vinke, I. C.; Spek, A.
L. J. Am. Chem. Soc. 1985, 107, 2891.
In the course of the mild methylation of CTPPH2 we have
identified the derivative methylated exclusively at the ligand
periphery.16 Here we have sought to extend our investigation
from the methylation of 21-carbaporphyrin to its nickel(II)
complex.
(2) (a) Moulton, C. J.; Saw, B. L. J. Chem. Soc., Dalton Trans. 1976,
1020. (b) Rimml, H.; Venanzi, L. M. J. Organomet. Chem. 1983, 259,
C6. (c) Nemeh, S.; Jensen, C.; Binamira-Soriaga, E.; Kaska, W. C.
Organometallics 1983, 2, 1422. (d) Gozin, M.; Weisman, A.; Ben-David,
Y.; Milstein, D. Nature 1993, 364, 699. (e) Liou, S.-Y.; Gozin, M.; Milstein,
D. J. Chem. Soc., Chem. Commun. 1995, 1965.
(3) Newkome, G. R.; Puckett, W. E.; Gupta, V. K.; Kiefer, G. E. Chem.
ReV. 1986, 86, 451.
(4) Giesbrecht, G. R.; Hanan, G. S.; Kickham, J. E.; Loeb, S. J. Inorg.
Chem. 1992, 31, 3286.
As a part of our continuing program of investigating the
general relationship between the isotropic shift pattern and the
molecular and electronic structures of paramagnetic nickel(II)
porphyrins13,17-19 we now report on the synthesis and charac-
terization of mono- and dimethylated nickel(II) carbaporphyrins.
In particular this work demonstrates that it is conceivable to
stabilize high-spin organonickel(II) macrocyclic complex with
(5) Jaun, B. HelV. Chim. Acta. 1990, 73, 2209.
(13) Chmielewski, P. J.; Latos-Graz˘yn´ski, L. Inorg. Chem. 1992, 31,
5231.
(6) Lu, W. P.; Harder, S. R.; Ragsdale, S. W. Biochemistry 1990, 265,
3124.
(14) (a) First reported by Chmielewski, P. J. and Latos-Graz˘yn´ski, L. at
12th Summer School on Coordination Chemistry, Karpacz, Poland 1993.
(b) Chmielewski, P. J.; Latos-Graz˘yn´ski, L.; Rachlewicz, K.; Głowiak, T.
Angew. Chem., Int. Ed. Engl. 1994, 33, 779.
(15) Furuta, H.; Asano, T.; Ogawa, T. J. Am. Chem. Soc. 1994, 116,
767.
(7) Halcrow, M. A.; Christou, G. Chem. ReV. 1994, 94, 2421.
(8) (a) Pfaltz, A. In The Bioinorganic Chemistry of Nickel; Lancaster, J.
R., Jr.; Ed., VCH Publishers, Inc.: New York, 1988; p 275. (b) Jaun, B.
In Metal Ions in Biological Systems; Sigel, H., Sigel, A., Eds.; Marcel
Dekker, Inc.: New York, 1993; Vol. 29, p 287.
(9) Stavropoulos, P.; Muetterties, M. C.; Carrie´, Holm, R. H. J. Am.
Chem. Soc. 1991, 113, 8485.
(10) (a) Chevrier, B.; Weiss, R. J. Am. Chem. Soc. 1976, 98, 2985. (b)
Callot, H. J.; Chevrier, B.; Weiss, R. J. Am. Chem. Soc. 1978, 100, 4773.
(11) D’Aniello, M. J., Jr.; Barefield, E. K. J. Am. Chem. Soc. 1976, 98,
1610.
(16) Chmielewski, P. J.; Latos-Graz˘yn´ski, L. J. Chem. Soc., Perkin Trans.
2 1995, 503.
(17) Latos-Graz˘yn´ski, L. Inorg. Chem. 1985, 24, 1681.
(18) (a) Lisowski, J.; Latos-Graz˘yn´ski, L.; Szterenberg, L. Inorg. Chem.
1992, 31, 933.
(19) Chmielewski, P. J.; Latos-Graz˘yn´ski, L.; Pacholska, E. Inorg. Chem.
1994, 33, 1992.
(12) Lin, S.-K.; Jaun, B. HelV. Chim. Acta. 1991, 74, 1725.