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

•Aprotic acetamidine ligands coordinate to Cu through solely the Nimine.•A bulky phosphaamidine coordinates η1–P to Cu, leaving the Nimine basic site dangling.•Less bulky phosphaamidines coordinate η2–P,N to Cu.

Aprotic acetamidine {Me2NC(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 Nimine coordination to copper with significant degree of delocalization about the NCN framework and a relatively short Cu–Cu interaction of 2.5758(8) Å in 2c compared to (2.9801)(10) Å 2a. The phosphaamidine ligands are never η1–Nimine bound; instead they are η1–P bound in the cubane complex 6a or η2-bound in the step cluster complexes 6b, 7a and 7b.

Graphical abstractCoordination geometries of uncharged and aprotic amidines and 1,3-(P,N) phosphaamidines on Cu(I) centers.Figure optionsDownload full-size imageDownload as PowerPoint slide