Inor anic 'homiei
:Communication
A T-Shaped Three-Coordinate Nickel(I) Carbonyl Complex and the
Geometric Preferences of Three-Coordinate d9 Complexes
Nathan A. Eckert,t Adriana Dinescu,* Thomas R. Cundari,*,* and Patrick L. Holland*,t
Department of Chemistry, University of Rochester, Rochester, New York 14267, and Department
of Chemistry, University of North Texas, Denton, Texas 76203
Received June 22, 2005
A three-coordinate diketiminate-nickel(I) complex with a carbonyl
ligand has been characterized using EPR and IR spectroscopies
and X-ray crystallography. The T geometry (bending from the
sterically favored C2v structure) contrasts with that of isosteric d9
copper(ll) complexes. DFT calculations on a truncated model
reproduce experimental geometries, implying that the geometric
differences are electronic in nature. Analysis of the charge
distribution in the complexes shows that the geometry of the three-
coordinate d9 complexes is affected by differential charge donation
of the ligands to the metal center.
Three-coordinate complexes of transition metals with
partially filled d shells have received attention because of
their unusual reactivity and electronic structure.' The pre-
dominant geometry in crystallographically characterized
three-coordinate complexes is trigonal-planar, with the
ligands symmetrically distributed to minimize steric effects.
The main exception to this generalization is with low-spin
d8 systems, which clearly favor a T-shaped geometry.2
In recent papers, we described the synthesis and electronic
structure of a series of three-coordinate complexes with d6,
d7, d8, and d9 electronic configurations at the metal center.3,4
A bulky /3-diketiminate ligand ("L") was used, and a
sterically favored Y geometry was evident at the metal in
each case. In the Y geometry, the nickel coordination
environment is idealized C2v, with the non-diketiminate
ligand on both mirror planes. The d9 example, LtBuNi(THF)
(Figure 1, left), is notable because there are few examples
of isolable three-coordinate nickel(I) complexes,5 one series
of three-coordinate copper(II) complexes,6 and no three-
coordinate d9 complexes of heavier metals. Understanding
* To whom correspondence should be addressed. E-mail: tomc@unt.edu
(T.R.C.), holland@chem.rochester.edu (P.L.H.).
t University of Rochester.
I University of North Texas.
(1) Cummins, C. C. Prog. Inorg. Chem. 1998, 47, 685.
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(3) Smith, J. M.; Lachicotte, R. J.; Holland, P. L. Chem. Commun. 2001,
1542.
(4) Holland, P. L.; Cundari, T. R.; Perez, L. L.; Eckert, N. A.; Lachicotte,
R. J. J. Am. Chem. Soc. 2002, 124, 14416.
7702 Inorganic Chemistry, Vol. 44, No. 22, 2005
Ni N o .
/ 0
N 'r
LtBuNi(THF) LMeNi(CO)
Y geometry T geometry
idealized C2v idealized Cs
Figure 1. Synthesis and thermal-ellipsoid plots of LtBuNi(THF)4 and LMe-
Ni(CO). Ellipsoids are at 50% probability, and hydrogen atoms are omitted
for clarity.
of three-coordinate nickel(I) complexes is also biologically
relevant because three-coordination is potentially accessible
in the low-coordinate "proximal" nickel site of acetyl-
coenzyme A synthase (where methylcobalamin, CO, and
coenzyme A are transformed into acetyl-coenzyme A).7
Below, we use synthetic, crystallographic, and theoretical
studies to show that the first three-coordinate nickel(I)
carbonyl complex prefers a T geometry. We compare it to
relevant nickel(I) and copper(II) complexes to arrive at new
(5) (a) Bradley, D. C.; Hursthouse, M. B.; Smallwood, R. J.; Welch, A.
J. J. Chem. Soc., Chem. Commun. 1972, 872. (b) Nilges, M. J.;
Barefield, E. K.; Belford, R. L.; Davis, P. H. J. Am. Chem. Soc. 1977,
99, 755. (c) Ellis, D. D.; Spek, A. L. Acta Crystallogr. 2000, C56,
1067. (d) Eaborn, C.; Hill, M. S.; Hitchcock, P. B.; Smith, J. D. Chem.
Commun. 2000, 691. (e) Mindiola, D. J.; Hillhouse, G. L. J. Am. Chem.
Soc. 2001, 123, 4623. (f) Melenkivitz, R.; Mindiola, D. J.; Hillhouse,
G. L. J. Am. Chem. Soc. 2002, 124, 3846. (g) Kitiachvili, K. D.;
Mindiola, D. J.; Hillhouse, G. L. J. Am. Chem. Soc. 2004, 126, 10554.
(h) Kogut, E.; Wiencko, H. L.; Zhang, L.; Cordeau, D. E.; Warren, T.
H. J. Am. Chem. Soc. 2005, 127, 11248.
(6) (a) Holland, P. L.; Tolman, W. B. J. Am. Chem. Soc. 1999, 121, 7270.
(b) Holland, P. L.; Tolman, W. B. J. Am. Chem. Soc. 2000, 122, 6331.
(c) Randall, D. W.; DeBeer George, S.; Holland, P. L.; Hedman, B.;
Hodgson, K. O.; Tolman, W. B.; Solomon, E. I. J. Am. Chem. Soc.
2000, 122, 11632. (d) Jazdzewski, B. A.; Holland, P. L.; Pink, M.;
Young, V. G., Jr.; Spencer, D. J. E.; Tolman, W. B. Inorg. Chem.
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10.1021/ic0510213 CCC: $30.25 2005 American Chemical Society
Published on Web 10/05/2005
