Polymeric [dihydrobis(pyrazol-1-yl)borato]potassium(I) and three dihydrobis(pyrazol-1-yl)borate–magnesium(I) compounds obtained by disproportionation of the Grignard reagent

Abstract

Reaction of the Grignard reagent with polydentate nitrogen-donor ligands yields new species with rare magnesium coordination and possible catalytic activity. In the first of the title compounds, poly[[mu4-dihydrobis(pyrazol-1-yl)borato-kappa2N,N']potassium(I)], [K(C6H8BN4)]n, (I), polymeric chains form a two-dimensional network in the [100] plane. Each potassium ion is coordinated by four N atoms of pyrazolyl ligands, while weak (mu-BH)...K+ interactions additionally stabilize the structure. The K and B atoms both lie on a mirror plane. In three new structures obtained by disproportionation of the Grignard reagent, each Mg atom is bound to a kappa2N,N'-type ligand, forming the basal plane, and tetrahydrofuran molecules occupy the axial positions. Di-mu-chlorido-bis[dihydridobis(pyrazol-1-yl)borato]tris(tetrahydrofuran)dimagnesium(II), [Mg2(C6H8BN4)2Cl2(C4H8O)3], (II), adopts a dimeric structure with mu-Cl-Mg interactions. One of the Mg atoms has an octahedral coordination, while the other has a distorted square-pyramidal environment. However, in the bis-chelate compounds bis[dihydridobis(pyrazol-1-yl)borato-kappa2N,N'](tetrahydrofuran-kappaO)magnesium(II), [Mg(C6H8BN4)2(C4H8O)], (III), and bis[dihydridobis(pyrazol-1-yl)borato-kappa2N,N']bis(tetrahydrofuran-kappaO)magnesium(II), [Mg(C6H8BN4)2(C4H8O)2], (IV), the Mg atoms have square-pyramidal and octahedral environments, respectively. The Mg atom in (IV) lies on an inversion centre.