Contrasting connectivity of amidine and phosphaamidine (1,3-P,N) Cu(I) complexes

Article abstract of DOI:10.1016/j.ica.2016.02.024

Aprotic acetamidine {Me₂N-C(Me)=N(R)(CuBr)}₂ {R = ⁱPr (2a), Cy (2b), Ph (2c)} and neutral 1,3-P,N phosphaamidine copper bromide complexes {(CuBr)(Ph₂PC(Ph)=NPh)}₄ (6a), {(CuBr)₄(Ph₂PC(Ph)=NⁱPr)₂}·{2CH₂Cl₂} (6b), (CuBr)₄(ⁱPr₂PC(Ph)=NPh)₂} (7a) and {(CuBr)₄(ⁱPr₂PC(Ph)=NⁱPr)₂} (7b) are prepared by direct combination of corresponding amidine and phosphaamidine with CuBr(DMS). X-ray crystallographic analysis of the acetamidine complexes reveal monodentate N_imine coordination to copper with significant degree of delocalization about the N-C=N framework and a relatively short Cu-Cu interaction of 2.5758(8) ? in 2c compared to (2.9801)(10) ? 2a. The phosphaamidine ligands are never η¹-N_imine bound; instead they are η¹-P bound in the cubane complex 6a or η²-bound in the step cluster complexes 6b, 7a and 7b.