Group 1 Bis(iminophosphorano)methanides, Part 1: N-Alkyl and Silyl Derivatives of the Sterically Demanding Methanes H2C(PPh2NR)2 (R = Adamantyl and Trimethylsilyl)

Treatment of [Li{HC(PPh2NSiMe3)2}]2 with 2 equiv of [MOR] (M = Rb, Cs; OR = 2-ethylhexoxide) afforded the heavy group 1 methanides [Rb{HC(PPh2NSiMe3)2}(THF)2] (1) and [Cs{HC(PPh2NSiMe3)2}(DME)2] (2), which do not exhibit methanide C···M contacts in the solid state. Following a literature procedure, H2C(PPh2)2 was reacted with 2 equiv of AdN3 (Ad = adamantyl) to give H2C(PPh2NAd)2 (3). Reaction of 3 with 1 equiv of ButLi in toluene afforded dimeric [Li{HC(PPh2NAd)2}]2 (4). Treatment of 3 with 1 equiv of [M(Bn)] (M = Na, K; Bn = CH2C6H5) in THF gave the Lewis base adducts [M{HC(PPh2NAd)2}(THF)2] [M = Na (5), K (6)]. The heavy group 1 methanides [Rb{HC(PPh2NAd)2}(THF)2] (7) and [Cs{HC(PPh2NAd)2}(DME)2] (8) were prepared by the reaction of [MOR] (M = Rb, Cs; OR = 2-ethylhexoxide) with 4 or reaction of [Cs(Bn)] with 3. The synthetic utility of these group 1 transfer agents has been demonstrated by the preparation of [La{HC(PPh2NR)2}(I)2(THF)] [R = SiMe3 (9), Ad (10)] from [La(I)3(THF)4], employing a salt metathesis methodology. Complexes 1–10 have been characterized by X-ray crystallography, multielement NMR spectroscopy, FTIR spectroscopy, and CHN microanalyses.