On the Synthesis and Coordination Properties of N ‐Aryl‐substituted 1, 3, 2‐Diazaphospholidine‐4, 5‐diimines

New 1, 3, 2‐diazaphospholidine‐4, 5‐diimines were synthesized by condensation of lithiated oxalamidines with PCl 3 or PhPCl 2 , and characterized by spectral and analytic data. The products react selectively with [(nbd)W(CO) 4 ], [Mo(CO) 6 ], or [(PhCN) 2 PdCl 2 ] to give stable complexes, in which the heterocycle binds as chelating, bidentate ligand through the nitrogen atoms of the diimine unit. Formation of P ‐bound or dinuclear complexes was not observed. Reaction with PCl 3 or AsCl 3 in the presence of SnCl 2 as reducing agent was unspecific. Evidence for the formation of bicyclic products arising from formal [4+1] cycloaddition between the diimine unit and a transient pnictogen(I) species was not obtained, and only a diimine complex of SnCl 4 was isolated in moderate yield. Single‐crystal X‐ray diffraction studies reveal that coordination of the diimine unit induces a substantial structural distortion of the ligand framework, which allows to explain the occurrence of substantial 31 P coordination shifts despite the absence of a direct metal‐phosphorus bond.