Bis(phosphinimino)methanide borohydride complexes of neodymium and scandium

Bis(phosphinimino)methanide rare earth metal bis(borohydrides) [{(Me3SiNPPh2)2CH}Nd(BH4)2(THF)] (1) and [{(Me3SiNPPh2)2CH}Sc(BH4)2] (2) were prepared by reaction of [Ln(BH4)3(THF)n] and K{CH(PPh2NSiMe3)2}. All new compounds have been characterized by standard analytical/spectroscopic techniques, and the solid state structures were established by single crystal X-ray diffraction. In compound 1 both BH4− groups are η3-coordinated, whereas an η3- and an η2-coordination mode is observed for compound 2 at 200 K. Interestingly, a second conformational polymorph of 2 exists, in which both BH4− groups show an η3-coordination mode.