The stereochemistry of β -diketo complexes with trimethylplatinum iv. III. The crystal structure of trimethyl (acetylacetonyl-) 2:2'-bipyridyl platinum

Abstract

The results of an X -ray crystal structure analysis of the crystalline complex, (CH 3 ) 3 Pt(CH 3 . CO . CH . CO . CH 3 )C 10 H 8 N 2 , formed by trimethylplatinum with acetylacetone and 2:2'-bipyridyl are presented. There are four monomeric molecules in a monoclinic unit cell having a = 14.863, b = 8.480, c = 13.749 Å, β = 99° 24' at 110±10 °K and space group P 2 1 / c . The atomic positions have been determined by three-dimensional analysis from observations collected at 100 to 120 °K. Refinement, including allowance for anisotropic thermal motion, was carried out by the method of least squares until the value of the residual R was 0.084. The platinum atom is octahedrally co-ordinated to three methyl groups in the cis configuration (Pt—C = 2.05 Å), to the two nitrogen atoms of the bipyridyl (Pt—N = 2.15 Å) and to the central or ‘active methylene’ carbon atom of acetylacetone (Pt—C = 2.36 Å). The oxygen atoms of the acetylacetone take no part in the co-ordination; this is the first example of a β -diketone acting as an unidentate ligand solely through a carbon atom. Comparison of the bond lengths in this and in the dimeric trimethyl 4:6-dioxononyl platinum suggests that in both compounds the β -diketone is in the keto and not the enol form; in the present compound the oxygen atoms are not chelated and the C=0 bonds are not parallel.