Bridged nitrogen structure

Dialkylzinc compounds have a tendency to form colored, and sometimes paramagnetic, adducts with 7r-acceptor ligands. The potentially bridging nitrogen donor pyrazine (and 4,4 -bipyridine) formed dinuclear complexes, Scheme 31, while the chelating 2,2 - bipyridine formed mononuclear adducts with diisopropylzinc.78 In the bis(diisopropylzinc)-pyrazine adduct 33, the presence of an unpaired electron was detected, but the resolution of the ESR spectra was insufficient for an unambiguous structural assignment. 

Despite the capability of anionic amide groups to form aggregates with metals via bridging nitrogen atoms, most of the monoorganomagnesium amides that have been structurally characterized in the solid state have a discrete monomeric structure. 

The solid-state structure of the species DMG = CH2NMe2 is a tetramer in which each Li atom is associated with three carbanion carbons and one nitrogen atom. Similar analysis of N,N-diisopropylbenzamide and 1-naphthamide shows that in the solid state the bulky amide substituent, being unable to bridge the amide carbonyl O with ortho-C via a single Li atom, escapes into bridged dimer structures in which one Li is planar with the amide and the other is planar with the aromatic ring. 

Sn—N = 2.33 A.557 The structures of triorganotin succinimides, phthalimides, and hexahydrophthalimides have been investigated by Mossbauer spectroscopy. Structures involving five-co-ordinate tin and bridging nitrogen were proposed.55 ... 

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