New guanidine-borane adducts: An experimental and theoretical approach

[Display omitted] •New arylguanidines and [HB(C6F5)2] adducts have been synthesized and characterized.•Guanidines coordinate to borane in a neutral monohapto coordination mode.•The difference in the coordination site between the different compounds was justified by theoretical studies. We report here a series of new adducts incorporating arylguanidines Ar*NC(NiPrH)2 (Ar* = C6H5, (p-CN-C6H4), (p-CF3-C6H4) and (2,4,6-(CH3)3-C6H2)) bearing donor or acceptor substituents in the phenyl rings, and bispentafluorophenylborane [HB(C6F5)2]. The spectroscopic and structural features of the new compounds [(C6F5)2HBNAr*C(NiPrH)2] (Ar* = C6H51, (2,4,6-(CH3)3-C6H2) 2, (p-CN-C6H4) 3 and (p-CF3-C6H4) 4) have been studied by multinuclear NMR and X-ray diffraction techniques. The structural differences between 1 and 2–4 compounds have been explained using electronic structure descriptors based on DFT calculations at the B3LYP/6–31 + G(d,p) level in the gas phase.