Hydrazido-, diazenido-, and amido-derivatives of lithium: a theoretical study related to nitrogen fixation reactions

Molecular orbital analysis of the metal–hydrazide(2−) bonding in co-ordination chemistry †

“…Previous ab initio studies on isodiazene NNH 2 have shown that the energy difference between the singlet state (1b 1 ) 2 (2b 2 ) 0 and the triplet state (1b 1 ) 1 (2b 2 ) 1 is small. 107, 108 This reflects the relatively low energy of the π* NN (2b 2 ) orbital. Our MP2 calculations found the singlet state more stable than the triplet state by 13.1 kcal mol Ϫ1 .…”

“…It should be noted that a similar structure was found for the isoelectronic [B(NNH 2 )] ϩ model. 108 These results suggest that co-ordinated NNR 2 ligands are reluctant to accept more than one electron in their π* NN orbital, i.e. to fully break the NN double bond and significantly pyramidalize N β .…”

“…q and [Li(NNH 2 )] q (q ‫؍‬ ؉1, 0 or ؊1) models Following a previous approach 108 we have modelled a η 1bonded metal atom first by a proton, which is a simple σ acceptor, and secondly by Li ϩ which has both σand π-accepting properties. The ligands considered were NNH 2 , [NNH 2 ] Ϫ and [NNH 2 ] 2Ϫ .…”

The chemistry of dinitrogen residues. Part 1. Diazenido-complexes of titanium, and some substituted analogues. X-Ray crystal structures of [Ti(C5H5)Cl2(NNPh)], [Ti(C5H5)Cl2(NCBunBut)], and [Ti(C5H5)Cl2(NPPh3)]

“…The TiNC linkage is almost linear [ 17 1.3( 4)"], but the TiN separation, at 1.872(4) A, is very short, certainly shorter than a formal TiN single bond. 14 The NC bond length is 1.267(6) A, a typical double bond, somewhat shorter than in LiN=CBu', (1.30 A)21 and essentially equal to the NC bond in [Zr(C,H,),(N=CHPh)] [ 1.259 (7) The ketimido-group can act as a bridging three-electron donor as in [{Fe(CO),(N=CR,)),] (R = C,H,Me-4).23 Each nitrogen atom bridges between two irons. This does not occur in our case, possibly due to the steric influence of the two butyl groups.…”

“…13.73(1), b = 12.85(5), c = 14.567(7) A, p = 109.85(5)", U = R = qF0ll ~c l ~/ w o l ~ -R' = [ W l F o I -I~c1)2/~wl~o1211f[Ti(C,H,)C1,(NCBu"But)]. The compound was prepared as described below.…”