Paper

Dalton Trans., 2008, 1043 – 1054, DOI: 10.1039/b715736c

N-Phosphino-amidines and -guanidines: synthesis, structure and P,N-chelate chemistry

Lise Baiget, Andrei S. Batsanov, Philip W. Dyer, Mark A. Fox, Martin J. Hanton, Judith A. K. Howard, Philip K. Lane and Sophia A. Solomon

The syntheses of the cyclic N-phosphino-amidines and -guanidines Ph₂PN(Prⁱ)C(NPrⁱ₂)N(Prⁱ) (1) and Ph₂PN(c-Hex)C(R)N(c-Hex) [R = piperazino (2), morpholino (3), Me (4), and Ph (5)] are reported. DFT studies have identified the preferred structures for compounds 1–5 with the E-configuration being the most stable form for the N-phosphino-amidines, while the Z-conformation is preferred for the N-phosphino-guanidines something that highlights the potential of such systems to act as k²-P,N-chelates. The differences in donor characteristics of 2–5 have been probed through the study of their corresponding P(V) selenide derivatives (6–9) and their complexes with the cis-RhCl(CO) (10–12) and cis-PdCl₂ (13–17) fragments. In line with the DFT studies both the amidines and guanidines are found to coordinate as k²-P,N-chelates, with the latter being moderately weaker donor ligands. The molecular structures of compounds 3 and 4, together with those of the Rh and Pd complexes 10 and 15, respectively, have been determined in the solid state by X-ray crystallography, the latter confirming bidentate k²-P,N-chelation.

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