The complexes [Ce(tmtaa)2], [Ce(tmtaa)(tmtaaH)] and [Ce2(tmtaa)3(thf)2] are obtained from Ce[N(SiMe3)2]3 and tmtaaH2, the macrocyclic ligand 6,8,15,17-tetramethyldibenzotetraaza[14]-annulene, depending on the stoichiometry, solvent and temperature. The crystal structure of Ce(tmtaa)2 is isostructural with Zr(tmtaa)2, however magnetic susceptibility measurements in the range 5-300 K show that Ce(tmtaa)2 is not diamagnetic, but is a temperature-independent paramagnet (TIP), similar to Ce(cot)2, cerocene.

Group 3 and lanthanide alkyl complexes supported by PNP-pincer ligands were prepared to investigate the sigma-bond metathesis reaction. These complexes were found to effectively carry out this reaction. Alkylidene complexes were prepared by sigma-bond metathesis with gamma-hydrogens of neopentyl groups to generate metallacyclobutanes which undergo a retro-[2+2] reaction. These complexes were also competent hydrogenation, semihydrogenation, hydrosilation, semihydosilation, and cross-dehydocoupling (amines and silanes) catalysts. The mechanisms of these catalytic reactions as well as the sigma-bond metathesis reaction in general were thoroughly studied by computational techniques. The sigma-bond metathesis reaction was probed by energy decomposition analysis to reveal that polarizability of the metal complex is key to promoting efficient metathesis. A new energy decomposition analysis was developed to treat these bonds in unbiased ways. Work towards the preparation of 1,3-dilithiopropane, a useful molecule for possible preparation of alkylidene complexes, was reported.

The paramagnetic 1:1 coordination complexes of (C5Me5)2Yb with a series of 4,4'-disubstituted bipyridines, bipy-X, where X is Me, tert-Bu, OMe, Ph, CO2Me, and CO2Et have been prepared. All of the complexes are paramagnetic and the values of the magnetic susceptibility as a function of temperature show that these values are less than expected for the cation, [(C5Me5)2Yb(III)(bipy-X)]+, which have been isolated as the cation-anion ion-pairs [(C5Me5)2Yb(III)(bipy-X)]+[(C5Me5)2YbI2]f fnfn where X is CO2Et, OMe and Me. The 1H NMR chemical shifts (293 K) for the methine resonances located at the 6,6' site in the bipy-X ring show a linear relationship with the values of chiT (300 K) for the neutral complexes which illustrates that the molecular behavior does not depend upon the phase with one exception, viz., (C5Me5)2Yb(bipy-Me). Single crystals of the 4,4'-dimethylbipyridine complex undergo an irreversible, abrupt first order phase change at 228 K that shatters the single crystals. The magnetic susceptibility, represented in a delta vs. T plot, on this complex, in polycrystalline form undergoes reversible abrupt changes in the temperature regime 205 - 212 K, which is suggested to be due to the way the individual molec ular units pack in the unit cell. A qualitative model is proposed that accounts for the sub-normal magnetic moments in these ytterbocene-bipyridine complexes.