| The olefin complex (silox)3Nb(η2- trans-1-phenyl-2-vinylcyclopropane) (2-PhVicPr, silox = tBu3SiO) was synthesized as a means of testing the existence a hypothesized biradical transition state for olefin dissociation. The binding of the olefin to (silox)3NbPMe3 (2-PMe 3) produces two diastereomeric complexes (2-maj and 2-min) that undergo cyclopropane ring-cleavage and α-H atom abstraction to yield isomeric alkylidene-ene products cis/trans-(silox)3Nb=CH-CH=CH-CH 2CH2Ph (cis-2-alk and trans-2-alk) upon thermolysis. The two diastereomers rearranged at different rates and kinetic models suggest that trans-2-alk converts to cis-2-alk prior to ring cleavage and rearrangement. Phenomenological kinetic isotope effects were consistent with the kinetic models.;Efforts were undertaken to synthesize [(silox)3Ta]2N 2 in order to circumvent the apparent kinetic barrier to dinitrogen activation by (silox)3Ta (1). N-aminoazidirines reacted with (silox) 3Ta to produce the parent imide (silox)3TaNH (1=NH) and with (silox)3Ta=CH2 to produce alkyl hydrazide complexes. The methyl hydrazide (silox)3Ta(CH3)NHNH 2 (3-NHNH2) thermally degraded to the tetraaza-bimetallacycle [(CH3)(silox)2Ta](μ-NH-N)(μ-NHNH)[(CH3)(silox) 2Ta]•2tBu3SiOH (4•2tBu 3SiOH) with concomitant evolution of CH4. The dinitrogen complex [(silox)2Ta(Cl)]2N2 could be prepared via salt metathesis and methylated to produce [(silox)2Ta(CH 3)]2N2. Attempts to oxidatively couple 1=NH or (silox)3TaNLi resulted only in decomposition or production of 1=NH. White phosphorus (P4) was found to react with 1 (at −78° C) and 2-PMe3 (at room temperature) to produce [(silox)3M] 2(η1,η2:μ2)P 2 (M = Nb, Ta). When 2-PMe3 was treated with P4 at −78° C for 16 h the novel complex [(silox)3Nb( cP3)]2 was formed.;Attempts to create new ligands containing the 2-aza-allyl anion resulted in CC-coupling chemistry that produced interesting organic frameworks. Both 3- and 5- membered rings and [4.4.0]-bicyclic systems could be constructed from the same precursor ligand, (CH3)2C(CHNCH2 Py)2, upon treatment with different metal complexes. Chromium, cobalt and nickel bis(amide) complexes produced unique metal-metal bonded species as a result of the triple CC-coupling reaction that produces 4,4,8,8-tetramethyl-2,6-di(pyridin-2-yl)-3,7-bis((E)-(pyridin-2-ylmethylene)amino)-octahydro-1,5-naphthyridine (14) as an octadentate ligand. |
