Comparison of σ-acyl and σ-perfluoroacyl groups as ligands: Crystal and molecular structures of the platinum(II) complexes trans-PtCl(COR)(PMePh2)2 (R = Me,CF3)

Abstract

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)).

Terminal Platinum(II) Perfluoroacyl Phosphido Complexes: Synthesis and Dynamic Processes

“…The crystal structure of 3 shows the expected square planar geometry at platinum; the angles around the metal center range from 89.70(6)° to 90.6(2)°. The structure is similar to that of the related complex trans -Pt(PPh 2 Me) 2 (COCF 3 )(Cl) . The Pt−Cl, Pt−C(O), and carbonyl bond lengths for 3 (2.402(2), 1.990(7), and 1.191(9) Å, respectively) are the same within experimental error as those in the trifluoroacyl complex (2.390(1), 2.028(6), and 1.210(5) Å).…”

Comparison of the Thermal and Reductive Decarbonylation of a Rhodium Trifluoroacetyl Diphosphine Complex

“…The major difference, as expected, is in the Rh−C bond length, with the acyl complex having the shorter bond (1.946 vs 2.014 Å). This trend is in agreement with two previously reported pairs of perfluoroacyl and perfluoroalkyl complexes of rhodium and platinum − but is in contrast to our results with cobalt, where the Co−C bond length of the trifluoromethyl complex was shorter than that of the trifluoroacetyl complex . On the other hand, the Rh−C bond length for the acetyl complex reported by Moloy and Petersen (1.981 Å) is, as expected, significantly longer than the trifluoroacetyl bond length of 1 .…”