Aminocarbyne coupling reactions at M(Ph2PCH2CH2PPh2)2(M = Mo or W) sites. Synthesis and properties of the diaminoacetylene complexes trans-[MX(η2-MeHNCCNHMe)-(Ph2PCH2CH2PPh2)2]A (X = F, Cl or ClO4; A = BF4′ PF6′ HCl2 or ClO4) and of their di(aminocarbyne)-type precursors

Abstract

Treatment of trans-[M(CNMe)₂(dppe)₂]1(M = Mo or W, dppe = Ph₂PCH₂CH₂PPh₂) in CH₂Cl₂ with HA (A = BF_4′ PF_6′ Cl or ClO₄) gives the diaminoacetylene complexes trans-[MX(η²-MeHNCCNHMe)(dppe)₂]A 2(X = F, Cl or ClO₄; A = BF_4′ PF_6′ HCl₂ or ClO₄). The crystal structure of trans-[MoF(η²-MeHNCCNHMe)(dppe)₂][BF₄] has been determined. A key intermediate in the reaction, trans-[M(CNHMe)₂(dppe)₂]A₂3(A = HCl₂ or ClO₄), has also been isolated and shown to be best viewed as a ‘iminomethylenium’ species CNHMe. The acetylenic CC triple bond in 2 undergoes base-induced cleavage (e.g., by LiBuⁿ) to form the parent complex 1.