Access to new Janus head ligands: linking sulfur diimides and phosphanes for hemilabile tripodal scorpionates

Abstract

Reactions of lithium dialkyl/phenyl phosphanylmethylides, RR′PCH(X)Li (R, R′ = Me, Et, Ph and R = Me, R′ = Ph; X = H or Me), with sulfur diimides S(NR′′)₂ (R′′ = ^tBu or SiMe₃) in an equimolar ratio yielded Janus head complexes with the structural motif [Li{RR′PCH(X)S(NR′′)₂}]₂ (R′′ = ^tBu, SiMe₃). The basic core of these dimeric complexes is composed of a (LiN)₂ four-membered ring containing two four-coordinated lithium atoms. A lithium complex of the new Janus head ligand with another structural motif [TMEDA·Li{Ph₂PCH₂S(NSiMe₃)₂}] (6) could be isolated from the reaction of [Ph₂PCH₂Li·TMEDA] with S(NSiMe₃)₂. Two monomeric complexes [Mg{Me₂PCH₂S(NR′′)₂}₂] (7, 8) were synthesised by a straightforward reaction of [Li{Me₂PCH₂S(NR′′)₂}₂] with MgCl₂ in pentane. The magnesium atom is chelated by one phosphorus atom and two nitrogen atoms of each unit of the hemilabile ligand in a tripodal manner, leading to octahedral geometry around the magnesium cation. A complete analysis of [Ph₂PCH₂(SNSiMe₃)(HNSiMe₃)] (9) is also described in which one nitrogen atom of the imido moiety is protonated.