Synthesis and reactivity of mono(pentamethylcyclopentadienyl) tetraphenylborate lanthanide complexes of ytterbium and samarium: Tris(ring) precursors to (C5Me5)Ln moieties

摘要

The synthesis of unsolvated (C5Me5)Ln(BPh4) complexes (Ln = Sm, Yb) has been investigated to determine if the productive chemistry of the metallocene tetraphenylborate complexes, (C5Me5)(2)Ln(mu-Ph)(2)BPh2, can be expanded to mono(pentamethylcyclopentadienyl) systems. Precursors (C5Me5)(2)Yb, 1, and (C5Me5)(2)Sm, 2, were both prepared by desolvation of (C5Me5)(2)Ln(THF)(2) under high vacuum in near quantitative yields. Compounds 1 and 2 react with [Et3NH][BPh4] to form divalent (C5Me5)Ln(mu-eta(6):eta(1)-Ph)(2)BPh2 (3, Yb; 4, Sm) complexes in which two of the phenyl rings of the tetraphenylborate counteranion coordinate eta(6) to the lanthanide to generate a three-ring coordination geometry involving cyclopentadienyl and arene coordination. In contrast to the expected trigonal plane defined by the three-ring centroids in 3, the structure of 4 is pyramidal with Sm 0.41 A out of the plane of the three-ring centroids. Complex 3 reacts with THF to make the polysolvated complex, [(C5Me5)Yb(THF)(4)][BPh4], 5, which can also be obtained from (C5Me5)(2)Yb(THF)(2) and [Et3NH][BPh4]. With 4, a monosolvated complex, (C5Me5)Sm[(mu-eta(6):eta(1)-Ph)(mu-eta(2):eta(1)-Ph)BPh2](THF), 6, can be isolated that retains eta(6) coordination by one aryl ring and displays eta(2) coordination with the other aryl ring. Reaction of phenazine with 3 and 4 is accompanied by ligand redistribution to form the trivalent bis(pentamethylcyclopentadienyl) products, [(C5Me5)(2)Ln](2)[mu-eta(3):eta(3)-C12H8N2], (Yb, 7; Sm, 8). Reduction of azobenzene by 4 generates a mono(pentamethylcyclopentadienyl)tetraphenylborate complex, (C5Me5)Sm[(mu-eta(6):eta(1)-Ph)BPh3](N2Ph2), 9, that contains an eta(6) coordinated phenyl ring and an azobenzene radical anion.