Bent vs Linear Metallocenes Involving C5Me5 vs C8H8 Ligands: Synthesis, Structure, and Reactivity of the Triple-Decked (C5Me5)(THF)xSm(C8H8)Sm(THF)x(C5Me5) (x = 0, 1) Complexes Including a Formal Two-Electron Oxidative Addition to a Single Lanthanide Metal Center1

Abstract

A new series of bimetallic triple-decked organometallic sandwich complexes involving Sm(II) can be prepared by reacting [(C5Me4R)Sm(μ-I)(THF)2]2 with 1 equiv of K2C8H8 in toluene to form [(C5Me4R)Sm(THF)]2(μ-η8:η8-C8H8) (R = Me, 1; R = Et, 2). The diglyme ([MeOCH2CH2]2O) adduct of 1, {[(C5Me5)Sm(diglyme)]2(μ-η8:η8-C8H8)}(THF)2 (3) crystallizes from THF with a bridging (C8H8)2- dianion sandwiched between two [(C5Me5)Sm(diglyme)]+ cations with a 137.6° (C5Me5 ring centroid)−Sm−(C8H8 ring centroid) angle. This bent triple-decked metallocene has 2.91(2) A Sm−C(C5Me5) and 2.96(5) A Sm−C(C8H8) average distances. 1 and 2 can be desolvated at 30−50 °C under high vacuum over several hours to yield [(C5Me4R)Sm]2(μ-η8:η8-C8H8) (R = Me, 4; R = Et, 5). It was of interest to determine if 4 and 5 had triple-decked metallocene structures with three parallel rings since previously characterized bis(cyclooctatetraenyl) lanthanide and actinide complexes such as uranocene, (C8H8)2U, and [(C8H8)2Ce]- have parallel rings where...