Steric effects of phosphorus ligands in organometallic chemistry and homogeneous catalysis

Rhodium(I) Complexes of the Conformationally Rigid IBioxMe4Ligand: Preparation of Mono-, Bis-, and Tris-ligated NHC Complexes

“…Complexes of the formulation cis-[M(NHC)(CO) 2 Cl] (M = Rh, Ir) have been widely used to probe the electronic and steric characteristics of NHC ligands (Table 1). 22 In particular, these complexes allow the determination of the Tolman electronic parameter (TEP) 23 for the NHC ligand from the carbonyl stretching frequencies of cis-[M(NHC)(CO) 2 Cl], avoiding the need to prepare toxic nickel adducts. 24,25 Using this approach the calculated TEP for IBioxMe 4 using 4 (2053 cm -1 ) is in good agreement with that determined using the previously reported iridium analogue cis-[Ir(IBioxMe 4 )(CO) 2 Cl] (2052 cm -1 ) 11 and both are marginally larger in magnitude than those of (13); 5 -Rh1-Cl2, 2.3642(15); Rh1-C3, 2.048(6); Rh1-C18, 2.197(6); Rh1-C19, 2.182(6); Rh1-C21, 2.098(6); Rh1-C22, 2.105(6); Θ NHC (@C3), 177.2 (4).…”

Synthesis, characterization, dynamics and reactivity toward amination of η3-allyl palladium complexes bearing mixed ancillary ligands. evaluation of the electronic characteristics of the ligands from kinetic data

“…Remarkably, the dimethyl bis-substituted allyl terminus is trans to NHC ligand as observed in solution by 1 H NMR technique. The metal environment is almost regular square planar, as the dihedral angle between the planes defined by the atoms C (22), Pd,C(24) and P, Pd, C(1) is 9.4 • , and that between the planes defined by the atoms P, Pd, C(1) and C(22A), Pd, C(24) is 4.8 • . In both cases, the sum of the bond angles about Pd equals almost exactly 360 • .…”

“…In both cases, the sum of the bond angles about Pd equals almost exactly 360 • . The 1,1-dimethylallyl residue again binds Pd in the h 3 mode and the atoms in the coordination sphere, that is, P, C(1), C (22) and C(24), deviate from the best mean plane by 0.06, 0,10, 0.12 and 0.11 Å , respectively (Pd off by 0.05 Å ). In the alternate arrangement with C(22A) in place of C(22) all the atoms, including Pd, are coplanar within 0.06 Å .…”

Structural and Photophysical Properties of (Phosphane)gold(I)‐Decorated 4,4′‐Diethynyl‐2,2′‐bipyridine Ligands

“…In the light of the structure of compound 4 (see below), the lack of Au...Au interactions cannot simply be attributed to the steric demands of the triarylphosphine units (Tolman cone angles for PPh 3 and P(4-Tol) 3 = 145 o ). [50] Fig. 1 Molecular structure of compound 1 in 2{1} .…”

“…In each solid state structure, each gold atom has two neighbouring gold atoms, one at a separation of <3.4 Å and a second at just over twice this distance (7.389 Å in 3 and 8.654 Å in 4). The difference in the Tolman cone angle of the phosphine (PEt 3 , 132 o and P i Pr 3 , 160 o ), [50] appears to be sufficient to tune the packing so that the dominant aurophilic interactions are between spatially distinct pairs of gold atoms resulting in the different chain assemblies shown in Figure 7. …”