Acta Crystallographica Section B

Structural Science

Volume 63, Part 4 (August 2007)

research papers

Acta Cryst. (2007). B63, 603-611 [ doi:10.1107/S0108768107027024 ]

Ligand and coordination-plane distortions in platinum(II) complexes of isomers of dimethyl-2,2'-bipyridine

V. Maheshwari, M. Carlone, F. R. Fronczek and L. G. Marzilli

Abstract: Pseudo-square-planar platinum(II) complexes containing 4,4' (4,4'-Me₂bipy), 5,5' (5,5'-Me₂bipy) and 6,6' (6,6'-Me₂bipy) isomers of dimethyl-2,2'-bipyridine (Me₂bipy) were synthesized and structurally characterized to assess the effects of methyl-group position on structure. The Pt-N distances in (Me₂bipy)PtCl₂ complexes fall in the typical range [2.017 (3)-2.032 (3) Å]. Only minor distortions such as 2.4 and 5.5° twisting of the two pyridyl rings in (4,4'-Me₂bipy)PtCl₂ (I) and (5,5'-Me₂bipy)PtCl₂ (II), respectively, occur. However, (6,6'-Me₂bipy)PtCl₂ (III) is highly distorted: the two pyridyl rings in (III) have a large bowing angle ( [theta] _B) of 19.2°. The presence of distortions in (III), but not in (I) and (II), is attributed to repulsions between the 6,6'-methyl groups and the cis chloro ligands. [(4,4'-Me₂bipy)₂Pt](BF₄)₂ (IV) undergoes a bow-incline deformation having a large [theta] _B value (24.2°), and the ligands are inclined relative to the coordination plane by 18.80 (13)°. Complex (IV) joins a small list of distorted bis-bipyridine complexes; this finding can be attributed to the unfavorable repulsions between the 6,6' hydrogen substituents of opposing ligands. Some of these complexes exhibit canting rather than bow-incline distortion, a trend suggesting that subtle solid-state effects determine the nature of the distortion.

Keywords: repulsive interligand interactions; methyl-group position; solid-state effects.


	Structure factor file (CIF format) (359.8 kbytes) [ doi:10.1107/S0108768107027024/bk5058Isup2.fcf ] Contains datablock I

	Structure factor file (CIF format) (124.5 kbytes) [ doi:10.1107/S0108768107027024/bk5058IIsup3.fcf ] Contains datablock CompoundII

	Structure factor file (CIF format) (305.3 kbytes) [ doi:10.1107/S0108768107027024/bk5058IIIsup4.fcf ] Contains datablock CompoundIII

	Structure factor file (CIF format) (338.1 kbytes) [ doi:10.1107/S0108768107027024/bk5058IVsup5.fcf ] Contains datablock CompoundIV

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