We report the synthesis and structural characterization of the new monomeric borane complex H3B·hppH (hppH = 1,3,4,6,7,8‐hexahydro‐2H‐pyrimido[1,2‐a]pyrimidine), which represents the first example of a structurally characterized 1:1 complex between hppH and a group 13 element hydride. Significant intramolecular and, in the crystalline phase, intermolecular H···H contacts are established in this complex. It is shown that the complex can be used as a precursor to new dinuclear boron(II) compounds featuring a B–B single bond. Thus H2 elimination followed by dimerization of H3B·hppH leads to [(hpp)BH]2 with two bridging hpp units. The structural details derived from X‐ray diffraction measurements are reported.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

The tripodnickel(0) species [tripod 4 Ni 3 ] (1) {tripod = CH 3 C(CH 2 PPPh 2 ) 3 } is shown to undergo oxidative addition with disulfides or diselenides REER (E = S, Se, R = tBu, Ph) to produce [tripodNi(ER)] (2). Compounds 2 show pseudo tetrahedral coordination. They are paramagnetic with one unpaired electron per molecule. Their magnetic behaviour is almost that of an ideal Curie-type magnet down to temperatures of 2 K. They undergo reversible one electron oxidation to the 16 valence electron species [tripodNi(ER)] + . The isoelectronic pseudo tetrahedral 16 valence electron cobalt species [tripodCo(ER)] (3) are obtained by reduction of CoCl 2 with KC 8 in the presence of tripod and subsequent reaction with REER (E = S, Se; R = tBu, Ph). They are paramagnetic with two unpaired electrons per molecule. They can be reversibly oxidised to the 15 valence electron compounds [tripodCo(ER)] + while their reduction to the 17 valence electron species [tripodCo(ER)] -, which would be isoelectronic to the stable compounds 2, is not observed. Under appropriate conditions the reactions with REER do not result in the formation of 3 but yield [tripodCoECotripod] (4) by extrusion of sulfur and selenium from the substrate. Compounds 4 show a linear Co-E-Co framework with very short Co-E bonds (E = S: 205 pm; E = Se: 216 pm). They are members of a family of dimetallaheterocumulenic compounds [L n MEML n ] (E =