Ligand-based reduction chemistry of f element complexes: Synthesis, characterization, and reactivity studies of lanthanide and actinide metallocenes

This dissertation involves the examination of new methods of lanthanide and actinide reduction chemistry. Specifically, the research has examined how ligand-based reduction can be combined with metal-based reduction to achieve multi-electron reduction. This research has resulted in the discovery of not only new lanthanide and actinide reduction systems, but also unusual insertion, metalation, and sigma-bond metathesis reactivity for f-elements. In addition, the first crystallographically characterizable examples of (O2CEPh) 1 (E = S, Se) ligands were identified.; Chapter 1 compares the ligand-based reduction chemistry of (EPh) 1- (E = S, Se, Te) ligands in a metallocene environment to the sterically induced reduction chemistry of the (C5Me5)1- ligands in (C5Me5)3Sm. The use of both Sm1+ and Sm3+ starting materials have allowed for the synthesis and characterization of new trivalent samarocene benzene chalcogenolate complexes for the evaluation of (EPh)1- ligand-based reductions. Chapter 2 describes how CO2 insertion reactions can be used to derivatize aryl chalcogenide ligands and provide the first crystallographically characterizable (O2CEPh)1- complexes, [(C5 Me5)2Sm(O2CEPh)]2 (E = S, Se).; In Chapter 3, the reductive reactivity of the (BPh4) 1- ligand in [(C5Me5)2U][(mu-eta 2:eta1-Ph)2BPh2], was compared with that of the tetramethyl analog, [(C5Me4H) 2U][mu-eta6:eta1-Ph)(mu-eta 1:eta1-Ph)BPh2], using PhSSPh as a probe to determine if the mode of (BPh4)1- bonding affected the reduction. A much improved synthesis of [(C5Me5) 2U][(mu-eta2:eta1-Ph)2BPh 2] from [(C5Me5)2UH]2, and [Et3NH][BPh4] is also described as well as its reaction with MeCN that provides another route to the unusual, parallel-ring, uranium metallocene [(C5Me5)2U(NCMe)5][BPh 4]2.; In Chapter 4, the reductive chemistry of [(C5Me5) 2UH]2 and [(C5Me5)2UH 2]2 was examined to determine if the H1- ligands would act as reductants. These actinide hydrides can act as 4-, 6-, and 8-electron reductants depending on the substrate with H2 as the byproduct of a H1- → e1- + 1/2 H2 redox couple. This hydride reduction chemistry allows complexes of redox inactive Th4+ such as [(C5Me5)2ThH 2]2 to be 4 and 6 electron reductants.; Chapter 5 describes how actinide hydrides, [(C5Me5) 2UH]2 and [(C5Me5)2ThH 2]2, can deliver a cascade of reactions involving not only reduction, but also insertion and metalation to assemble complicated products from their reaction with acetonitrile. In each case, a six carbon chain product is generated from acetonitrile to form [(C5Me5) 2An(CH3-C(NH)=CH-C(NH)=CH=CN]2 (An = U, Th). The cyanopentadienyl dianion, (C6N3H7) 2-, that bridges the two metalocene units is formed from three molecules of acetonitrile with loss of six hydrogen atoms in the case of the uranium complex and eight hydrogen atoms in the case of the thorium analog.; Chapter 6 describes the synthesis of an unusual uranium tuck-in/tuck-over complex. (C5Me5)U[mu-eta5:eta 1:eta1-C5Me3(CH2) 2](mu-H)2U(C5Me5)2 from [(C5Me5)2UH]2. This is the first crystallographically characterized example of a tuck-in and tuck-over structure, in the same complex.; In Chapter 7, studies with (C5Me5)2UMe 2 as a multi-electron reductant were examined to determine if other actinide complexes with normal bond distances could function as multi-electron reductants. However, no reductive reactivity was observed. Instead, (C 5Me5)2UMe2 participates in a different type of reaction that appears to involve sigma-bond metathesis with one and two equivalents of PhEEPh (E = S, Se, Te) to form (C5Me 5)2U(EPh)Me (E = S, Se) and (C5Me5) 2U(EPh)2 (E = S, Se, Te), respectively, with concomitant formation of MeEPh. In the case of one equivalent of PhTeTePh, C-H activation of the aryl ring occurred to form (C5Me5)2U(eta 2-TeC6H4) along with MeTePh and CH4.; Chapter 8 describes how atmospheric pressure chemical ionization mass spectrometry (APCI-MS) has been used to characterize the air sensitive paramagnetic organouranium...