Amino-functionalised diarylphosphide complexes of the alkali metals and lanthanum

Abstract

The secondary phosphines Ar(C₆H₄-2-CH₂NMe₂)PH [Ar = mes (3), Tripp (4)] may be isolated in good yields from reactions between Li(C₆H₄-2-CH₂NMe₂) and the respective dichlorophosphine, followed by reduction with LiAlH₄ [mes = 2,4,6-Me₃C₆H₂, Tripp = 2,4,6-Prⁱ₃C₆H₂]. Metalation of either 3 or 4 with BuⁿLi gives the corresponding lithium compound; the lithium derivative of 3 was isolated as the separated ion pair complex [Li(12-crown-4)₂][(mes)(C₆H₄-2-CH₂NMe₂)P]·THF (5). The lithium complexes Ar(C₆H₄-2-CH₂NMe₂)PLi undergo metathesis reactions with either NaOBu^t or KOBu^t to give the heavier alkali metal phosphides {Ar(C₆H₄-2-CH₂NMe₂)P}M·1/2OEt₂ [Ar = mes, M = Na (8), K (9); Ar = Tripp, M = K (10)]. Metathesis reactions between 9 and LaI₃(THF)₄ give only intractable products; in contrast, a metathesis reaction between 10 and LaI₃(THF)₄ yields the heteroleptic complex {(Tripp)(C₆H₄-2-CH₂NMe₂)P}₂LaI (11). Compound 11 reacts cleanly with K{N(SiMe₃)₂} to give {(Tripp)(C₆H₄-2-CH₂NMe₂)P}₂La{N(SiMe₃)₂} (14). Compounds 3–5, 8–11 and 14 have been characterised by multi-element NMR spectroscopy; in addition, compounds 5, 11 and 14 have been studied by X-ray crystallography.