Post on 31-Dec-2015
description
SSCr Meeting, Bern, 2006 J-N. Chotard, Y. Filinchuk, K. Yvon
La2MgNi2H8, the first mixed polyanionic
transition metal hydride
J-N. Chotard, Y. Filinchuk, K. Yvon
Introduction
Complex metal hydrides
~ 80 compounds containing ~ 30 different
transition metal hydride complexes:
almost all of them are mononuclear
1st polynuclear hydride complexes based on 3d-metal
[Ni2H7]7- & [Ni4H12]12-
SSCr Meeting, Bern, 2006 J-N. Chotard, Y. Filinchuk, K. Yvon
Synthesis and structure determ.
• La2MgNi2: arc-melting La and Ni, sintering the product with Mg
• La2MgNi2H8: hydrogenation/deuteration in an autoclave:30 bar, 100°C
High-resolution synchrotron powder diffraction (SNBL at ESRF):indexing, metal structure (FOX), Rietveld
High-resolution neutron powder diffraction (HRPT, SINQ, PSI):16 deuterium atom positions (FOX), Rietveld
SSCr Meeting, Bern, 2006 J-N. Chotard, Y. Filinchuk, K. Yvon
Structure of La2MgNi2H8
Metal atom shifts < 0.65 Å
11.84 7.8211.96 Å92.78 °
7.643.94 Å
Tetragonal Monoclinic
SSCr Meeting, Bern, 2006 J-N. Chotard, Y. Filinchuk, K. Yvon
La2MgNi2 La2MgNi2H8
Two types of D-atom positionsLa2MgNi2
La2MgNi2H8
SSCr Meeting, Bern, 2006 J-N. Chotard, Y. Filinchuk, K. Yvon
Bonding :18 electron rule
34 electrons 64 electrons
La3+, Mg2+ [Ni2H7]7-, [Ni4H12]12-, H-
This concept is supported by observed changes in physical properties
SSCr Meeting, Bern, 2006 J-N. Chotard, Y. Filinchuk, K. Yvon