Structure and dynamics of P,N-containing heterocycles and their metal complexes in solution.

Conformations and dynamics of 1,5-diaza-3,7-diphosphacyclooctane (1) with chiral l-menthyl substituents on the phosphorus atoms and several metal complexes thereof were investigated by a variety of DNMR methods. In solution 1 adopts a C(2) symmetrical "crown"-like conformation (CW) and the conformational preference and dynamics of the complexes depend on the type of metal: for the Cu complex the CW form is preferred, whereas the Pd, Pt, or Mo complexes exist in an equilibrium of two "chair-boat"-like conformations (CB/CB*). The barriers of interconversion between these two conformations for the Pd and Pt complexes are about 2 times higher than for the Mo complex. Quantum chemical calculations (B3LYP/6-31G(d)) are in agreement with experimental findings.

First representative of optically active P-L-menthyl-substituted (aminomethyl)phosphine and its borane and metal complexes.

The first representative of 1,5-diaza-3,7-diphosphacyclooctanes (1) with chiral L-menthyl substituents on the phosphorus atoms was obtained by condensation of L-menthylphosphine with formaldehyde and p-toluidine. This optically active cyclic bisphosphine readily forms a stable P,P-complex with borane (2) and P,P-chelate complexes with platinum(II) (3) and palladium(II) dichloride (4). The structure of the bisphosphine 1 in solution was elucidated by employing a variety of 1D/2D NMR correlation experiments, and the molecular structure of complex 3 was studied by X-ray crystallography.