Tris(pyrazolyl)methane ligands: The neutral analogs of tris(pyrazolyl)borate ligands

Despite the widespread use of tris(pyrazolyl)borate ligands, their isoelect ronic, neutral analogs, tris(pyrazolyl)methane Ligands, have not been exten sively studied. By use of appropriate starting materials, such as [Cu(NCMe) (4)]PF6 or [Cd-2(thf)(5)](BF4)(4), stable cationic complexes of the ligands HC(3,5-Me(2)pz)(3), HC(3-Phpz)(3) and HC(3-Bu(t)pz)(3) can be prepared wit h the metals copper(I), silver(I), cadmium(ll), lead(II) and thallium(I). I n many cases isoelectronic groups of complexes, such as [HB(3,5-Me(2)pz)(3) ](2)Cd, {[HC(3,5-Me(2)pz)(3)]Cd[HB(3,5-Me(2)pz)(3)]}(+), and {[HC(3,5-Me(2) pz)(3)](2)Cd}(2+), have been prepared and shown to have very similar struct ures. The Cd-113 NMR chemical shifts of the three complexes are also very s imilar. The isoelectronic complexes {[HC(pz)(3)](2)Pb}(2+) and [HB(pz)(3)]( 2)Pb have similar distorted six-coordinate structures. The isoelectronic pa ir {[HC(3,5-Me(2)pz)(3)](2)Pb}(2+) and [HB(3,5-Me(2)pz)(3)](2)Pb have very similar octahedral structures in which the lone pair on the lead(ll) is ste reochemically inactive. Thus, for most cases the tris(pyrazolyl)methane and tris(pyrazolyl)borate ligands bond to these metals in a similar fashion.