Anionic bidentate pyrazolate

In 1994, the ab initio X-ray crystal stucture determination from powder diffraction data of [Cu(pz)] and [Ag(pz)] were reported (13). During these studies it was ascertained that copper(I) and silver(I) pyrazolates, depending on the synthetic method used, each appear in two distinct crystalline phases. The a-[Cu(pz)] , 2a, and /3-[Cu(pz)] , 2b, consist of infinite chains of linearly coordinated copper atoms, bridged by exo-bidentate pyrazolate anions (Fig. 2). The two phases differ mainly in the interchain Cu- -Cu contacts, which are 3.34 A in a-[Cu(pz)] and 2.97 A in 3-[Cu(pz)] . 

In 1981, the synthesis and the first stmcture analysis of a compound with an endo-bidentate pyrazolate anion, [U(C5H5)3(r 2-pz)], 251, were reported (186). 

The compound UCp3(C3H3N2) (C3H3N2 = pyrazolate anion) was synthesized (30) with the expectation of forming a dimeric organo-uranium derivative. This was based on the known coordination behavior of the ligand in transition metal chemistry where it is almost exclusively exo-bidentate. The structure of the molecule is shown in Fig. 10 and reveals a novel n -endo-bidentate bonding mode for the... 

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