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 center

A new series of bimetallic triple-decked organometallic sandwich complexes involving Sm(II) can be prepared by reacting [(C5Me4R)Sm(mu-I)(THF)(2)](2) with 1 equiv of K2C8H8 in toluene to form [(C5Me4R)-Sm(THF)](2)(mu-eta(8):eta(8)-C8H8) (R = Me, 1; R = Et, 2). The diglyme ([MeOCH2CH2](2)O) adduct of 1, {[(C5Me5)-Sm(diglyme)](2)(mu-eta(8):eta(8)-C8H8)} (THF)(2) (3) crystallizes from THF with a bridging (C8H8)(2-) dianion sandwiched between two [(C5Me5)Sm(diglyme)](+) cations with a 137.6 degrees (C5Me5 ring centroid)-Sm-(C8H8 ring centroid) angle. This bent triple-decked metallocene has 2.91(2) Angstrom Sm-C(C5Me5) and 2.96(5) Angstrom Sm-C(C8H8) average distances. 1 and 2 can be desolvated at 30-50 degrees C under high vacuum over several hours to yield [(C5Me4R)-Sm](2)(mu-eta(8):eta(8)C(8)H(8)) (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)(2)U, and [(C8H8)(2)Ce](-) have parallel rings whereas (C5Me5)(2)-Sm is bent. Complex 4 is found to crystallize from toluene with a structure that retains the bent geometry of 3 with 149.3 degrees and 148.9 degrees (C5Me5 ring centroid)-Sm-(C8H8 ring centroid) angles. 5 crystallizes from toluene with a similar bent triple-decked metallocene structure with 157.6 degrees (C5Me5 ring centroid)-Sm-(C8H8 ring centroid) angles. The ethyl groups in 5 are oriented toward the metal center with 3.40 Angstrom Sm ... C(CH2CH3) distances. Complexes 1 and 2 each do two-electron reductions of 1,3,5,7-C8H8 to form (C5Me4R)Sm(C8H8)-(THF); 4 and 5 react similarly with 1,3,5,7-C8H8 to form (C5Me4R)Sm(C8H8). A two-electron reduction of C5Me5Cl by 1 generates (C5Me5)Sm(C8H8)(THF) and (C5Me5)(2)SmCl(THF), a product in which C5Me5Cl has been added to a single (C5Me5)Sm(THF) unit in 1.