Computational Descriptors for Chelating P,P- and P,N-Donor Ligands¹

Abstract

The ligand knowledge base approach has been extended to capture the properties of 108 bidentate P,P- and P,N-donor ligands. This contribution describes the design of the ligand set and a range of DFT-calculated descriptors, capturing ligand properties in a variety of chemical environments. New challenges arising from ligand conformational flexibility and donor asymmetry are discussed, and descriptors are related to other parameters, such as the ligand bite angle. A novel map of bidentate ligand space, potentially useful in catalyst design and discovery, has been derived from principal component analysis of the resulting LKB-PP descriptors. In addition, a range of multiple linear regression models have been derived for both experimental and calculated data, considering ligand bite angles in square-planar palladium complexes and ligand dissociation energies from octahedral chromium complexes, respectively. These data sets were fitted with models based on LKB descriptors to explore the transferability of descriptors to different coordination environments and to illustrate potential applications of such models in catalyst design, allowing predictions about novel or untested ligands.

Synthesis and spectroelectrochemistry of transition metal carbonyls with 1,1′-bis(phosphino)metallocene ligands

“…The [Cr(CO)4(P X P)] complexes of dppf, dipf and dcpf have been optimized as described previously [9], using the standard BeckeePerdew (BP86) functional [21e25] in Jaguar [26] and the 6-31G* basis set for all atom apart from Cr and Fe, for which the Los Alamos ECP basis set (LACV3P) was used. Optimizations were run with "loose" convergence criteria (5 times larger than default) on isolated molecules and vibrational frequencies were not computed; energetic corrections for zero-point energies are likely to be small and optimization to saddle points appears unlikely for these large complexes.…”

“…The catalytic activity of [Ru(CO) 2Àn (CNR) n (dippf)X 2 ] (n ¼ 0, 1; X ¼ Cl, Br; R ¼ CH 2 C 6 H 5 , Cy, t Bu, 2,6-C 6 H 3 Me 2 , S-(À)-C(H)MePh) for transfer hydrogenation was found to be poorer than related isocyanide compounds, however, these carbonyl compounds were very efficient cycloisomerization catalysts [8]. Finally, computational studies have been performed on [Cr(CO) 4 (dippf)] and [Cr(CO) 4 (dcpf)] [9].…”

Molybdenum Nitrosyl Complexes and Their Application in Catalytic Imine Hydrogenation Reactions

“…The lowest rate of hydrogenation was found for 2d (initial TOF = 50 h -1 ), presumably due to the high steric congestion of the cyclohexyl substituent of the dcype ligand, which prevents a facile approach of the PhCH=N(α-naphthyl) substrate to the metal centre. Complexes 2a-2c showed a strong dependence of the diphosphane bite angle [40] on the rate of hydrogenation. Complex 2c with the largest bite angle in this series demonstrated the lowest activity (initial TOF = 68 h -1 ), whereas the hydrides 2a and 2b exhibited significantly higher rates of hydrogenation (initial TOF values: 106 h -1 for 2a, 123 h -1 for 2b).…”

Isomeric Preference in Complexes of Palladium(II) with Chelating P,N‐Donor Ligands

“…[2][3][4][5][6][7][8] The properties of a number of P,P-and P,N-donor ligands in a variety of chemical environments have been recently studied, building a map of bidentate ligand space that has potential applications in predictions about novel or untested ligands. [9] The coordination of P,N-donor chelating ligands to synthesize four-coordinate complexes can give rise to different isomers when the ancillary ligands are different. This isomeric possibility can be important in catalytic processes, as the activity of each isomer could not be the same.…”