Structural trends in [Rh(PhCOCHCO(CH₂)_nCH ₃)(CO)(PPh₃)] (n = 0-3) and related complexes: Crystal structure of [Rh(PhCOCHCO(CH₂)₂CH₃)(CO) (PPh₃)]

The [Rh(PhCOCHCO(CH₂)₂CH₃)(CO)(PPh ₃)], 3, complex was characterized by means of solid-state X-ray crystallography. It was shown by means of statistical averages and histograms that the bond lengths and angles of 3 are in the typical range for [Rh(PhCOCHCO(CH₂)_nCH₃)(CO)(PPh₃)] (n = 0-3) and [Rh(β-diketonato)(CO)(PPh₃)] complexes. DFT calculations on the preferred orientation of PPh₃ in 3 show that the size of the Ph and (CH₂)₂CH₃ side groups on the β-diketonato ligand of 3 does not influence the preferred orientation of PPh₃ in this complex. Complexes 1 and 2 (with alkyl chain length of n = 0, 1, respectively) show π-π stacking in the solid crystalline state, whereas complexes 3 and 4 (with n = 2, 3, respectively) do not. This results in different packing arrangements across the series, ranging from both isomers present (50:50) at independent positions for complexes 1 and 2 (with n = 0, 1), to one isomer disordered for complex 3 (with n = 2), and an 89.7:10.3 isomer distribution in the same space in the unit cell for complex 4 (with n = 3). It is postulated that in the solid crystalline state, the increasing alkyl chain length disrupts the supramolecular complementarity between pairs of the same isomer and that the increasing length of the alkyl chain starts to interact with the PPh₃. The orientation of PPh₃ in complexes 1-4 is in agreement with the preferred minimum energy orientation of PPh₃ in experimental crystal structures of [Rh(β-diketonato)(CO)(PPh₃)] complexes. Graphical Abstract: The structure and structural parameters of [Rh(PhCOCHCO(CH₂)₂CH₃)(CO)(PPh₃)] are compared with related [Rh(β-diketonato)(CO)(PR₃)] complexes.[Figure not available: see fulltext.]