Synthesis and crystal structure of the heteroleptic lanthanum(III) bis-diphosphinomethanide complex [La{CH(PPh2)2}2(I)(THF)2]

Treatment of CH2(PPh2)2 with n-BuLi/t-BuOK in diethyl ether affords the potassium diphosphinomethanide complex [K{CH(PPh2)2}(OEt2)0.5] (1) in high yield. Metathesis of two equivalents of 1 with LaI3(THF)4 yields the heteroleptic bis-diphosphinomethanide complex [La{CH(PPh2)2}2(I)(THF)2] (2). X-ray crystallography shows the diphosphinomethanide ligands in 2 adopt different coordination modes in the solid state; one adopts a κ2-PP mode with no La–C contact, and the other adopts an η3-PCP mode, thus giving an eight-coordinate lanthanum centre.