Molecular structures of mixed-ligand palladium(II) and platinum(II) alkyl complexes, including three isomorphous compounds

The crystal structures of the complexes [PdMe(β-dik)(PPh3)][β-dik = acetylacetonate (acac) or monothioacetylacetonate (sacac)] and [PtEt(β-dik)(PPh3)] have been determined. All four complexes crystallize inthe triclinic space group P with two molecules in the unit cell. They have a slightly distorted square-planar geometry. For the pair of acac complexes O(1)–Pd–O(2) 88.8(2), O(1)–Pt–O(2) 89.2(2), C(O)–Pd–P 88.3(2) and C(O)–Pt–P 92.7(2)°; Pd-C 2.003(9), Pt–C 2.013(9), Pd-P 2.209(2) and Pt–P 2.182(2)Å. for the two sacac complexes, S(1)–Pd–O(2) 91.35(9), S(1)–Pt–O(2) 91.59(9), C(O)–Pd–S(1) 86.4(2) and C(O)–Pt–S(1) 86.8(1)°; Pd-C 2.033(7), Pt–C 2.058(6)Å, Pd-P 2.274(1)Å. Comparison of the M–C bonds in the structures shows a slight lengthening in complexes containing the sacac ligand, consistent with the previously observed enhanced carbonylation activity of the platinum sacac complex over that of the analogus acac compound. A comparison of M–P bonds reveals that those of Pt are consistently shorter than those of Pd, in agreement with proposed relative and bond strength.