Flexible Bonding of the Phosph(V)azane Dianions [S(E)P(μ-NtBu)] 2 2 .

Oxidation of the PIII dianion [S-P(μ-NtBu)]2 2- (1) with elemental sulphur, selenium and tellurium gives the PV dianions [(S)(E)P(μ-NtBu)]2 2- (E = S (6 a), Se (6 b), Te (6 c)). Although 6 c proves to be too unstable, the S,S-dianion 6 a and ambidentate S,Se-dianion 6 b are readily transferred intact to main group and transition metal elements, producing a range of new cage and coordination compounds. While their coordination characteristics are in many ways similar to closely-related isoelectronic phosph(V)azane anions [(E)(RN=)P(μ-NtBu)]2 2- , the sterically unhindered nature of 6 introduces an expanded range of coordination modes, that is, facial S,S- and Se,Se-bonding as well as side-on S,Se-coordination. All of these bonding modes are observed for the amibidentate S,Se dianion 6 b.