Because of their similar cationic radii, potassium and thallium(I) compounds are usually regarded as closely related. Homologous molecular species containing either K(+) or Tl(+) are very rare, however. We have synthesized potassium and thallium salts MN3RR' derived from the biphenyl- or terphenyl-substituted triazenes Tph2N3H (1a), Dmp(Mph)N3H (1b), Dmp(Tph)N3H (1c), and (Me4Ter)2N3H (1d) (Dmp=2,6-Mes 2C6H3 with Mes=2,4,6-Me3C6H2; Me4Ter=2,6-(3,5-Me2C6H3)2C6H3; Mph=2-MesC6H4; Tph=2-TripC6H4 with Trip=2,4,6-(i)Pr3C6H2). The potassium complexes 2a- d were obtained in almost quantitative yield from the reaction of 1a- d with potassium metal in n-heptane. Metalation of 1a- d with TlOEt afforded the thallium triazenides 3a- d in high yields. All new compounds have been characterized by (1)H and (13)C NMR spectroscopy, elemental analysis, and X-ray crystallography and for selected species by melting point (not 3b), IR spectroscopy (2a, 2d, 3a, 3c, 3d), and mass spectrometry (2a, 3c). In the solid-state structures of monomeric 2a and 3a, quasi-monomeric 2b, 3b, 2c, and 3c, and dimeric 2d and 3d additional metal-eta (n)-pi-arene-interactions to the flanking arms of the biphenyl- and terphenyl groups in the triazenide ligands of decreasing hapticity n are observed. Remarkably, all homologous potassium and thallium complexes crystallize in isomorphous cells. For 2a and 3a, the nature of the M-N and M...C(arene) bonding was studied by density functional theory calculations.

Diphosphanes with polarised P–P bonds react readily with Lewis acids like borane, gallium trichloride, or with elemental selenium, to give products arising from electrophilic attack at the more basic phosphorus atom and consecutive bond cleavage. Spectroscopic studies proved that the initial reaction with borane proceeds under preservation of the P–P bond to give a transient phosphane–borane which rearranged below ambient temperature. The results suggest that Lewis acid coordination decisively enhances the weakening of the polarised P–P bond. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Using monoanionic triazenide ligands derived from biphenyl and m-terphenyl substituted triazenes Dmp(Tph)N 3 H (1a), (Me 4 Ter) 2 N 3 H (1b) or Dmp(Mph)N 3 H (1c) (Dmp = 2,6-Mes 2 C 6 H 3 with Mes = 2,4,6-Me 3 C 6 H 2 ; Me 4 Ter = 2,6-(3,5-Me 2 C 6 H 3 ) 2 C 6 H 3 ; Mph = 2-MesC 6 H 4 ; Tph = 2-TripC 6 H 4 with Trip = 2,4,6-i-Pr 3 C 6 H 2 ), several magnesium triazenides were synthesized. Heteroleptic complexes [Mg(N 3 Ar 2 )I(OEt 2 )] (Ar 2 = Dmp/Tph (2a), (Me 4 Ter) 2 (2b) were obtained from metalation of the corresponding triazenes with di-n-butylmagnesium followed by reaction with iodine in diethyl ether as the solvent in high yields. Replacing diethyl ether by n-heptane afforded trinuclear compounds [Mg 3 (N 3 Ar 2 ) 2 I 4 ] (3a, 3b) in low yields in which a central MgI 2 fragment is coordinated by two iodomagnesium triazenide moieties. Two unsolvated homoleptic magnesium compounds [Mg(N 3 Ar 2 ) 2 ] (4b, 4c) were obtained from di-n-butylmagnesium and triazenes 1b or 1c in a 1:2 ratio. Depending on the nature of the substituents, the magnesium center either shows the expected tetrahedral or a rather unusual square planar coordination.