Crystal and molecular structures of the title compounds have been determined from three dimensional
X-ray diffraction data recorded on a four-circle diffractometer. Crystals of the acetyl complex,
trans-PtCl(COMe)(PMePh2)2,(1), are monoclinic, space group P2,1/c, with a 12.9709(5), b 11.1024(5),
c 277535(9) Ǻ, β 94.75(1)° and Z 6. Crystals of the trifluoroacetyl complex, trans-PtCl(COCF3)-
(PMePh2)2, (2), are monoclinic, space group P21/n (non-standard setting of P21c), with a 11.4246(7),
b 15.5750(7), c 15.4200(8) Ǻ, β 90.54(1)° and Z 4. For (I), with Z 6, the unit cell contains one set
of four equivalent molecules in the general equipoint and one set of two equivalent (disordered)
molecules located at inversion centres. The four molecules in (2) comprise a single equivalent set
in the general equipoint. Least-squares analyses converge with R 0.042 for (1) (5696 unique data)
and R 0.025 for (2) (3933 unique data). Molecules of both complexes exhibit small deformations
from planar towards tetrahedral platinum geometry; the acyl and coordination planes are approximately
orthogonal. The phosphine substituents in (2) and in the 'general' molecules in (1) are
approximately eclipsed, and approximately eclipse the Pt-C (acetyl) bonds. In the 'special' molecules
in (1) the phosphines are constrained to adopt the mutually staggered conformation found in the
alkyl analogues trans-PtClR(PMePhM2)2 (R = Me, CF3, C2F2). Important comparative lengths
in (1) (general molecule) and in (2) (in square brackets) are: Pt-C 2.028(6) [1.960(4)] A, Pt-Cl
2.430(2) [2.390(1)] Ǻ, Pt-P 2.301(2), 2.297(2) [2.316(1), 2.321(1)] A, C-O 1.182(8) [1.210(5)] 8,
and C C (acetyl) 1.488(10) [1.547(6)] A. The trifluoroacetyl ligand forms a shorter and presumably
stronger bond with platinum, and exerts a larger cis- and a smaller trans-influence than the acyl
ligand. The smaller trans-influence of the trifluoroacetyl ligand is consistent with the expectation
from platinum-chlorine stretching frequencies (v(Pt-Cl)).
