A monomeric selenium(iv) diimide and a dimeric seleninylamine

Abstract

The selenium(IV) diimide AdN=Se=NAd (Ad = 1-adamantyl) adopts a monomeric structure with a Z,E configuration in the solid state whereas the seleninylamine OSe(mu-NBut)2SeO crystallizes as the cis-dimer.

Experimental and Theoretical Investigations of Structural Trends for Selenium(IV) Imides and Oxides: X-ray Structure of Se3(NAd)2

“…9 Consistently, density functional calculations on the model systems E(NMe)2 (E = S, Se, Te) predict that the dimerization is highly exothermic for E = Te and endothermic for E = S, in agreement with experimental observations, but approximately thermoneutral for E = Se. 10 In a preliminary communication we showed by X-ray crystallography that Se(NAd)2 (1b, Ad = 1-adamantyl) is a syn,anti-monomer in the solid state, 11 in agreement with the conclusions of solution NMR studies of 1a. 8 Interestingly, the hybrid imido-oxo system (seleninyl amine) OSe(-N t Bu)2SeO (2a) first reported by Herberhold in 1986, 12 forms a dimer with the oxo ligands in a cis configuration in the solid state.…”

“…The structures of Se(NAd)2 (1b) and cis-OSe(-N t Bu)2SeO (2a) were reported in a preliminary communication. 11 It is informative to consider the structural trends within the isoelectronic series, 1b, 2a and 3 in the context of the isovalent analogues formed by the other chalcogens (see Scheme 2). The sulfur(IV) analogues of 1, 2 and 3 are, without exception, monomers.…”

“…1-3) can be compared with the experimental values 11,14 and with the molecular parameters that have been observed for monomeric sulfur 49 and selenium diimides. 11 The calculated parameters are found to be close to the experimental values, where available:…”

“…56 This is consistent with the experimental observations that 1a and 1b are monomeric species. 8,11 It has recently been shown that the difference in reaction energies for sulfur and selenium diimides can be ascribed to the lower -bond energies of Se=N bonds which makes the coupling of the two fragments energetically more preferable. 10 Figure 3 shows that the cyclodimerization and cycloaddition energies are rather independent of the identity of the R group (H, Me and t Bu derivatives).…”

“…8 Interestingly, the hybrid imido-oxo system (seleninyl amine) OSe(-N t Bu)2SeO (2a) first reported by Herberhold in 1986, 12 forms a dimer with the oxo ligands in a cis configuration in the solid state. 11 The third member of this isoelectronic series, (SeO2)∞ (3), has a polymeric chain structure. 13 The unsymmetrical imido-oxo species t BuNSe(-N t Bu)2SeO (4a) has a cyclic structure similar to that of 2a.…”