Unprecedented η3-Coordination and Functionalization of the 2-Phosphaethynthiolate Anion at Lanthanum(III)


We present the unprecedented η3-coordination of the 2-phosphaethynthiolate anion in the complex (PN)2La(SCP) (2) [PN = N-(2-(diisopropylphosphanyl)-4-methylphenyl)-2,4,6-trimethylanilide)]. Structural comparison with dinuclear thiocyanate bridged (PN)2La(μ-1,3-SCN)2La(PN)2 (3) and azide bridged (PN)2La(μ-1,3-N3)2La(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)2La{SPC(RCAAC)} (5a,b) (R = Ad, Me). A detailed reaction mechanism for the SCP to SPC isomerization is proposed based on DFT calculations.

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