Early lanthanide organometallic hydrides: electronic and steric control of the stability

Steric and electronic effects on the stability of early lanthanide, neodymium and samarium, organometallic hydrides are discussed. The instability of (tmp)(2)SmH (tmp = tetramethylphospholyl) is attributed to electronic factors and the low stability of ((BuC5H4)-Bu-t)(2)SmH is related to steric reasons. The analogous neodymium hydride ((BuC5H4)-Bu-t)(2)NdH, could not be obtained, whereas the more hindered triethylborohydride was formed. Access tea bisphospholyl bridged heterobimetallic ruthenium-lanthanide hydrides is also related to the size of the lanthanide atom. The bimetallic structures are accessible for lanthanides of ionic radii smaller than 1 Angstrom. The role of organometallic hydrides versus alkyls as catalysts for olefin or diene polymerization is discussed, a first and unique example of hex-1-ene and isoprene copolymerization is presented. (C) 2000 Elsevier Science S.A. All rights reserved.