Monoarsenic, diarsenic and mixed phosphorus-arsenic substituted niobocenes

Arsenic monobromides BrAsR 2 (R = Me, Et) insert easily into the Nb-H bond of [Cp 2 NbH 3 ] affording the ionic complexes [Cp 2 NbH 2 (HAsR 2 )]Br (R = Et ( 1a ), Me ( 1b )). Deprotonation of 1a produces the dihydridarsenido derivative [Cp 2 NbH 2 (AsEt 2 )] ( 2a ) cleanly and in high yield (93%), whereas deprotonation of 1b gives the expected [Cp 2 NbH 2 (AsMe 2 )] ( 2b ) together with a considerable amount of [Cp 2 NbH 3 ]. Reaction of (AsEt 2 ) 2 with [Cp 2 NbBH 4 ] in the presence of NEt 3 results in the formation of complexes [Cp 2 Nb(HAsEt 2 )(BH 3 AsEt 2 )] ( 6 ) and [Cp 2 NbH 2 (BH 3 AsEt 2 )] ( 7 ). It was found that NEt 3 is a catalyst of this reaction. The orange complex [Cp 2 Nb(HAsEt 2 )(HP i− Pr 2 )]Br ( 9 ) was prepared by the reaction of BrAsEt 2 with [Cp 2 NbH(HP i− Pr 2 )]. Deprotonation of 9 affords the phosphinoarsenido complex [Cp 2 Nb(AsEt 2 )(HPPr 2 −i )] ( 10 ). The molecular structure of 6 was found from an X-ray structure determination.