PRASEODYMIUM ALKOXIDE CHEMISTRY - SYNTHESIS AND MOLECULAR-STRUCTURE OF 2)(MU,ETA(2)-OR)(4)(MU,ETA(L)-OR)(OR)(OPME(3))](2) (R=C(2)H(4)OME) AND [Y4PR(MU(5)-O)(MU(3)-OR)(4)(MU-OR)(4)(OR)(5)] (R=PR-I)

Various routes to praseodymium alkoxide shave been investigated. Compo unds such as Pr5O(OR)(13) [R = Pr-i (1), Am-1], [Pr4O2(ONp)(8)](m) (Np = neopentyl), [Pr(OC(2)H(4)NMe(2))(3)](3) were obtained by reaction o f praseodymium turnings with the corresponding alcohols. Alcoholysis r eactions of the bis-trimethylsilylamide afford [Pr4O(ONp)(10)](m), [Pr 4O2(ONp)(8)](m), Pr-3(OR)(9)(ROH)(2) [R = Bu(t), Am-t] and [Pr4O2(OC(2 )H(4)OMe)(8)](m) (2a), the latter derivatives illustrating the trend f or the formation of oxo species. The compounds were characterized by e lemental analysis, FT-IR and NMR. Their reactivity has been investigat ed, the mixed-metal species Pr4TiO(OPri)(14) and Y4PrO(OPri)(13) were obtained. Ligand exchange reactions afforded [Pr4O2(OR)(3)(OR')(5)](m) species (R = Pr-i, R' = C(2)H(4)NMe(2)' R = SiMe(3), R' = Pr-i) and [ Pr(OC(2)H(4)NMe(2))(thd)(2)](2). X-ray structure analysis of the adduc t obtained by reaction of [Pr4O2(OC(2)H(4)OMe)(8)](m) with trimethylph osphine oxide reveals a centrosymmetric framework 2)(mu,eta(2)-OR)(4)( mu,eta(1)-OR)(OR)(OPMe(3))](2) (2b) of eight octa-coordinated praseody mium atoms, assembled by tetrahedral and square-planar oxo ligands. Th e M-O bond lengths spread over the range 2.246(6)-2.762(6) Angstrom an d to follow the order Pr-OR (terminal) < mu,eta(2)-Pr-OR < mu(3),eta(2 )-Pr-OR < Pr-O(ether). The Y4PrO(OPri)(13) species corresponds to a pe ntanuclear oxo aggregate similar to that of the parent homometallic sp ecies. Copyright (C) 1997 Elsevier Science Ltd.