Conformational analysis of triphenylphosphine in square planar organometallic complexes: [(PPh3)(ML1L2L3)] and [M(acac)(L′)(PPh3)]

The conformation analysis of free PPh3 and PPh3 coordinated to tetrahedral, trigonal-bipyramidal, octahedral or square planar achiral metal centres is discussed. Results from ADF calculations, in agreement with experimental structures, show that favoured degenerate conformations of complex-bound PPh3 in square planar [(PPh3)((MLLL3)-L-1-L-2)] and [M(acac)(L')(PPh3)] complexes can be obtained by applying the following principles (P helicity, view along P-M axis), (i) superimpose C-ortho of the vertical ring A onto the nadir plane perpendicular to the square plane and allow ring A to tilt towards the smallest ligand, (ii) allow ring B to tilt in the space below the smallest ligand in the quadrant between the nadir plane below the complex and a horizontal plane through the SQP of the complex, (iii) tilt ring C over the largest ligand and (iv) allow correlated tilting of rings A, B and C to minimize inter ring-ring and inter ring-ligand interactions.