This paper deals with the preparation and structural investigation of asymmetric bis(silyl) niobocene hydrides, Cp
2Nb(SiHMe
2)(H)(SiXMe
2) (
2; X = F (
a), Cl (
b), Br (
c), I (
d)) and Cp
2Nb(SiXMe
2)(H)(SiYMe
2) (X,Y= F-I; X
Y).Complexes
2a-d were prepared by selective electrophilic activation of the Si-H bond in Cp
2Nb(SiHMe
2)
2(H). TheCp
2Nb(SiXMe
2)(H)(SiYMe
2) complexes were prepared by electrophilic activation of the Si-H bond in
2a-
d and, insome cases, by electrophilic exchange of the X halides in Cp
2Nb(SiXMe
2)
2(H) (
1) for other halides, Y. The structuresof complexes
2b and
2c have been studied by X-ray and neutron diffraction (ND). The ND results unequivocallyestablished that the hydride ligand in
2c is shifted toward the SiBrMe
2 ligand and that in
2b is positioned symmetricallybetween two nonequivalent silyl groups, with the H···SiClMe
2 distance being shorter because of the shorter Nb-SiClMe
2 bond length. Analysis of the X-ray structures of complexes
2a-
d and complexes Cp
2Nb(SiXMe
2)(H)(SiYMe
2) shows that the largest structural distortions are observed for the silyl groups substituted by heavy halogenatoms. These trends are rationalized in terms of stronger interligand hypervalent interactions (IHI) Nb-H···Si-Xfor heavy atoms X from Group 7.