A variable-temperature study of 1,2-bis(dimethylamino)-1,2-bis(2,6-dimethylanilino)diborane.

The title compound, C(20)H(32)B(2)N(4), is monoclinic at ambient temperature but triclinic (pseudo-monoclinic) below 150 K. The structures of the two phases, determined at 200 and 120 K, respectively, are very similar, the molecular symmetry being crystallographic C(2) and approximate (local) C(2), respectively. There is significant π conjugation within each N-B-N moiety, but none between them or between the N-B-N and arene moieties.

A new cyclic borazine species B(8)(NH)(4)(NMe(2))(8) containing a twelve-membered B(8)N(4) ring.

The reaction between B(2)(NMe(2))(4) and two equivalents of [NH(4)][PF(6)] in thf at room temperature affords the new cyclic borazine B(8)(NH)(4)(NMe(2))(8) containing a non-planar twelve-membered ring with alternating B(2)(NMe(2))(2) and NH units.

Synthesis and characterisation of the persistent radical [BCl2(bipy)]*.

The persistent radical, [BCl(2)(bipy)](*) (bipy = 2,2'-bipyridyl), has been prepared and characterised by X-ray crystallography, ESR and DFT calculations. The structure is compared with that of the cation, [BCl(2)(bipy)](+).

Unusual chalcogen-boron ring compounds: the gas-phase structures of 1,4-B4S2(NMe2)4 and related molecules.

The structure of 1,4-B4S2(NMe2)4 has been determined by gas-phase electron diffraction and quantum chemical calculations and is compared with the known solid-state structure. While these structures are similar, with a twisted ring geometry [the dihedral angle S-B-B-S from electron diffraction is 75.4(16) degrees], they are strikingly different to the solid-state structure of 1,4-B4O2(OH)4, which is planar. Using quantum chemical calculations, the combinations of O or S in the ring and OH or NMe2 as the substituent have been studied and it has been shown that there are two separate causes of the twisted ring. Since the calculated (and observed) structure of 1,4-B4O2(OH)4 is planar but that of 1,4-B4S2(OH)4 is twisted, it is concluded that the inclusion of sulfur in the ring twists the structure by approximately 40 degrees. By comparing the structures of 1,4-B4S2(OH)4 and 1,4-B4S2(NMe2)4 it has been determined that the twist caused by the NMe2 groups is around 30 degrees.

Synthesis and reactivity of cobalt boryl complexes.

The reaction between [Co(PMe3)4] and B2(4-Mecat)2 (4-Mecat = 1,2-O2-4-MeC6H3) or between [Co(PMe2Ph)4] and B2(cat)2 (cat = 1,2-O2C6H4) affords the paramagnetic Co(II) bisboryl complexes [Co(PMe3)3[B(4-Mecat)]2] and [Co(PMe2Ph)3{B(cat)]2] respectively, both of which have been structurally characterised. ESR data and preliminary diboration and boryl transfer reactivity studies are also presented. The reaction between [CoMe(PMe3)4] and B2(cat)2 affords the Co(I) monoboryl complex [Co(PMe3)4[B(cat)]].