Studies In Orbital Symmetry Constraints Of The Reactivity Of Group (V) Tri-Tert-Butyl Siloxide Compounds And In The Ephemeral Existence Of Destabilized 2-Aza-Allyl Anionic Ligands

摘要

The olefin complex (silox)3Nb(2-trans-1-phenyl-2-vinylcyclopropane) (2PhVicPr, 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-PMe3) produces two diastereomeric complexes (2-maj and 2min) that undergo cyclopropane ring-cleavage and -H atom abstraction to yield isomeric alkylidene-ene products cis/trans-(silox)3Nb=CH-CH=CH-CH2CH2Ph (cis-2alk 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]2N2 in order to circumvent the apparent kinetic barrier to dinitrogen activation by (silox)3Ta (1). Naminoazidirines 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)NHNH2 (3-NHNH2) thermally degraded to the tetraazabimetallacycle [(CH3)(silox)2Ta](-NH-N)(-NHNH)[(CH3)(silox)2Ta]•2tBu3SiOH (4●2tBu3SiOH) with concomitant evolution of CH4. The dinitrogen complex [(silox)2Ta(Cl)]2N2 could be prepared via salt metathesis and methylated to produce [(silox)2Ta(CH3)]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(1,1:2)P2 (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 CCcoupling chemistry that produced interesting organic frameworks. Both 3- and 5membered rings and [4.4.0]-bicyclic systems could be constructed from the same precursor ligand, (CH3)2C(CHNCH2Py)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.