Structures and bonding of homoleptic bis(2,3-dihydro-1,3-diborole) complexes of nickel and platinum

Abstract Homoleptic metal complexes of the boron heterocycle 2,3-dihydro-1,3-diborole {(R 1 C) 2 (R 2 B) 2 R 3 (H)C} 1 are described. X-Ray crystal structure determinations of two nickel and platinum derivatives are presented. In the nickel complex [Ni( 1d ) 2 ] 6d (R 1  = R 2  = R 3  = Et) the essentially coplanar heterocycles attain a pentahapto coordination mode with a gauche orientation with respect to one another. An 18 VE count is attained. In contrast, in the 14 VE platinum complex [Pt( 1a ) 2 ] 4a (R 1  = R 2  = Et, R 3  = Me) the ligands are strongly folded and adopt a tetrahapto coordination. The molecule is centrosymmetric in the crystalline state. DFT MO calculations are presented to establish the relative stabilities of these coordination modes for nickel and platinum, respectively.