Through-Space J(P,P) and J(P,F) Spin-Spin Coupling in C1-Symmetric Biaryl Diphosphanes

The first simultaneous P-31, P-31 and P-31, F-19 solution-phase through-space nuclear spin-spin coupling in biphenyl derivatives is reported. The magnitudes of the coupling constants are in the range 5.3-28.7 and 2.3-5.1 Hz, respectively. Their observation became possible through access to a recently developed class of C-1-symmetric biphenyl diphosphanes. We used this to prepare a series of model compounds for the study of the through-space couplings. Various 1D and 2D techniques [COSY, NOESY, heteronuclear single quantum coherence (HSQC), HMBC, HSCQ-TOCSY, selective H-1{P-31}-decoupling and iterative bandshape analysis] were applied to assign the H-1, C-13, F-19 and P-31 NMR spectra as completely as possible. X-ray structure determinations confirmed the structural assignments and afforded P center dot center dot center dot P distances and torsion angles in the solid state. No simple correlation was found between the experimental J(P-31,P-31) values in solution and the relevant geometric parameters (P center dot center dot center dot P distance and torsional angle between the phosphorus lone pairs) in the solid state.