Synthesis and structure of two new (guanidinate)boron dichlorides and their attempted conversion to boron(i) derivatives

To test the feasibility of the guanidinate architecture for the support of boron(i) carbene analogues the energy gap between the singlet and triplet states of the model compound, [Me 2 NC{N(Ph)} 2 B:] (7), has been probed by both DFT and second order Møller-Plesset (MP2) methods. The singlet state is calculated to be more stable than the triplet state by between 6.0 and 10.1 kcal mol -1 . The new (guanidinate)boron dichlorides [Ph 2 NC{N(Mes) 2 ]BCl 2 (14) and [Ph 2 NC{N(Dipp) 2 ]BCl 2 (15) have been prepared and characterized by single-crystal X-ray diffraction. Attempts to reduce 14 and 15 to the corresponding boron(i) species were not successful. © 2008 The Royal Society of Chemistry.