η(3)‐Coordination and Functionalization of the 2‐Phosphaethynthiolate Anion at Lanthanum(III)

We present the η(3)‐coordination of the 2‐phosphaethynthiolate anion in the complex (PN)(2)La(SCP) (2) [PN=N‐(2‐(diisopropylphosphanyl)‐4‐methylphenyl)‐2,4,6‐trimethylanilide)]. Structural comparison with dinuclear thiocyanate‐bridged (PN)(2)La(μ‐1,3‐SCN)(2)La(PN)(2) (3) and azide‐bridged (PN)(2)La(μ‐1,3‐N(3))(2)La(PN)(2) (4) complexes indicates that the [SCP](−) coordination mode is mainly governed by electronic, rather than steric factors. Quantum mechanical investigations reveal large contributions of the antibonding π*‐orbital of the [SCP](−) ligand to the LUMO of complex 2, rendering it the ideal precursor for the first functionalization of the [SCP](−) anion. Complex 2 was therefore reacted with CAACs which induced a selective rearrangement of the [SCP](−) ligand to form the first CAAC stabilized group 15–group 16 fulminate‐type complexes (PN)(2)La{SPC((R)CAAC)} (5 a,b, R=Ad, Me). A detailed reaction mechanism for the SCP‐to‐SPC isomerization is proposed based on DFT calculations.