C-C Bond Formation and Related Reactions at the CNC Backbone in (smif)FeX (smif=1,3-Di-(2-pyridyl)-2-azaallyl): Dimerizations, 3+2 Cyclization, and Nucleophilic Attack; Transfer Hydrogenations and Alkyne Trimerization (X = N(TMS)2, dpma = (Di-(2-pyridyl-methyl)-amide))

Molecular orbital analysis depicts the CNCnb backbone of the smif (1,3-di-(2-pyridy1)-2-azaally1) ligand as having singlet diradical and/or ionic character where electrophilic or nucleophilic attack is plausible. Reversible dimerization of (smif)Fe{N(SiMe3)(2)} (1) to [{(Me3Si)(2)N}Fe](2)(mu-K-3,K-3-N,py(2)-smif,smif) (2) may be construed as diradical coupling. A proton transfer within the backbone-methylated, and o-pyridine-methylated smif of putative ((b)Me(2)(0)Me(2)smif)Fe-N(SiMe3)(2) (8) provides a route to [{(Me3Si)(2)N}Fe](2)(mu-K-4,K-4-N,py(2),C-(Me-b,(CH2)-C-b,Me-0(2)(smif)H))(2) (9). A 3 + 2 cyclization of ditolyl-acetylene occurs with 1, leading to the dimer [{2,5-di(pyridin-2-yl)-3,4-di-(p-tolyl-2,5-dihydropyrrol-1-ide)}FeN-(SiMe3)(2))(2) (11), and the collateral discovery of allcyne cyclotrimerization led to a brief study that identified Fe(N(SiMe3)(2)(THF) as an effective catalyst. Nucleophilic attack by (smif)(2)Fe (13) on 'BuNCO and (2,6-Pr2C6H3)NCO afforded (RNHCO-smif)(2)Fe (14a, R = 'Bu; 14b, 2,6-' PrC6H3). Calculations suggested that (dpma)(2)Fe (15) would favorably lose dihydrogen to afford (smif)(2)Fe (13). H-2-transfer to allcynes, olefins, imines, PhN=NPh, and ketones was explored, but only stoichiometric reactions were affected. Some physical properties of the compounds were examined, and X-ray structural studies on several dinuclear species were conducted.