Abstract Triply coordinated trivalent nitrogen atoms are known to lose most or all of their Lewis donor capacity when bonded to a third or higher row element. It is shown here, in the case of P-bonded nitrogen atoms, that structural constraints which maintain the nitrogen atom in a pyramidal configuration can contribute much in preserving their basicity and/or nucleophilic character. In particular, nitrogen atoms apically bonded to 5-coordinated formally penta- or trivalent phosphorus atoms can display definite basicity. Examples of metal- and base-induced opening and closing of P[sbnd]N bonds are also presented. The following unusual coordination modes and/or reaction issues are exemplified: where A can be-depending on the case-H+, CH3 +, BH3, BF3 or a transition metal moiety, as for example CpMo(CO)2Cl or CpMo(CO)2, etc. The factors that affect the rather variable P[sbnd]N bond length are discussed.