Synthesis and coordination properties of new σ2,λ3-P/N switchable chelator based on [1,2,3]-diazaphosphole

Novel hybrid ligands based on [1,2,3]-diazaphosphole (dap) were prepared and their coordination behaviour toward selected transition metals has been studied. The syntheses and spectroscopic properties of polydentate bis(5-t-butyl-[1,2,3]-diazaphosphol-2-yl)-dimethylsilane (BdapsH,tBu) and bis(4-methyl-5-ethyl-[1,2,3]-diazaphosphol-2-yl)-dimethylsilane (BdapsMe,Et) are reported. In zerovalent compounds of the type [M(CO)4(κ2-P,P’-BdapsR1,R2)] (R1 = Me, R2 = Et, M = Cr, Mo and W; R1 = H, R2 = t-Bu, M = W) and [Ni(κ2-P,P’-BdapsH,tBu)2] the ligand serves as P,P‘-donor giving rigid six-membered chelate rings. BdapsMe,Et is also capable to behave as N,N’-chelator as confirmed by an isolation of high-spin chelate complex [CoBr2(κ2-N,N’-BdapsMe,Et)]. The reaction of parent 2H-4-methyl-5-ethyl-[1,2,3]-diazaphosphole with NiBr2∙DME yielded paramagnetic compound [NiBr2(κ-N-dap)2], where dap heterocycle bonds nickel(II) centre via 1-nitrogen donor atoms in distorted tetrahedral environment. All studied complexes showing different coordination modes of new ligands were fully characterized including single-crystal X-ray diffraction analysis.