The compound [Ph2Sn(2-OC6H4C(CH3)NCH2COO)], 1, shows a distorted trigonal-bipyramidal geometry in the solid state. Reaction of 1 with Ph3SnCl yields a 1:1 adduct in which the two tin atoms are joined via the carbonyl atom of the ligand in 1 to form a mixed diorgano/triorgano species. NMR data indicate that the 1:1 adduct dissociates in noncoordinating solvent. Similarly, [ t Bu2Sn(2-OC6H4C(CH3)NCH2COO)· t Bu2SnCl2], which has been characterized crystallographically in the solid state, is dissociated in solution. In contrast to the above behavior, monomeric [Vin2Sn(2-OC6H4C(CH3)NCH2COO)] forms an adduct with a water molecule to yield [Vin2Sn(2-OC6H4C(CH3)NCH2COO)OH2] in the solid state.

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The synthesis of the o-phenylene-bridged ditin species o-C 6 H 4 (SnXMe 2 ) 2 (2, X ) Cl; 4, X ) F) and o-C 6 H 4 (SnCl 2 Me) 2 (3) is reported and the crystal structures of [o-C 6 H 4 (SnClMe 2 ) 2 ‚ Cl] -[(Ph 3 N) 2 P] + (5) and [o-C 6 H 4 (SnClMe 2 ) 2 ‚F] -[K‚C 20 H 24 O 6 ] + (7) are described. Variabletemperature 119 Sn and 19 F NMR studies indicate that 2 and 4 act as bidentate Lewis acids toward chloride and fluoride ions exclusively forming the stable anionic 1:1 complexes 5, 7, and [o-C 6 H 4 (SnFMe 2 ) 2 ‚F] -[Et 4 N] + ( 8). No formation of dianionic 1:2 adducts was observed even with excess of halide ions. The affinity of 2 toward fluoride is greater than toward chloride. Reaction of 2 with HMPA gives the neutral complex o-C 6 H 4 (SnClMe 2 ) 2 ‚(Me 2 N) 3 PO (10), the crystal structure of which is also described.

Structural investigations, i.e. solid-state (X-ray), solution ( 1 H NMR) and gas-phase (theoretical), on molecules with the general formula MeOC(LS)N(H)C 6 H 4 -4-Y: Y 5 H (1), NO 2 (2), C(LO)Me (3), Cl (4) have shown a general preference for the adoption of an E-conformation about the central C-N bond. Such a conformation allows for the formation of a dimeric hydrogen-bonded { … H-N-CLS} 2 synthon as the building block. In the cases of 1-3, additional C-H … O interactions give rise to the formation of tapes of varying topology. A theoretical analysis shows that the preference for the E-conformation is about the same as the crystal packing stabilisation energy and consistent with this, the compound with Y 5 C(LO)OMe, (5), adopts a Z-conformation in the solid-state that facilitates the formation of N-H … O, C-H … O and C-H … S interactions, leading to a layer structure. Global crystal packing considerations are shown to be imperative in dictating the conformational form of molecules 1-5.

Si NMR spectroscopy, IR spectroscopy and electrospray mass spectrometry, and in the case of 4 and 6 also by X-ray diffraction. The key feature of the crystal structures is the incorporation of tert-butoxy groups into the hydrogen bonding. The results obtained are discussed in relation to the sol±gel process.