Rhenium(V) Dioxo Complexes with Dihydrobis(pyrazolyl)borates: Synthesis and Reactivity toward Electrophilic Substrates

The compounds trans,trans-[ReO2(py)4][ReO2{H2B(pz*)2}2] (pz* = pz (1), 3,5-Me2pz (2)) have been prepared
by reacting trans-[ReO2(py)4]Cl with the corresponding dihydrobis(pyrazolyl)borate. Compounds 1 and 2 react
with electrophilic substrates, such as ClXMe3 (X = Si, Sn), leading to the neutral monoxo derivatives [ReO(OSiMe3){H2B(pz*)2}2] (pz* = pz (3), 3,5-Me2pz (4)) and [ReO(OSnMe3){H2B(pz)2}2] (5) and regenerating
trans-[ReO2(py)4]Cl. Compounds 1 and 3 crystallize from dichloromethane/n-hexane as yellow crystals, with
one molecule of solvated CH2Cl2 in the case of 1. Crystallographic data:  1, triclinic space group P1̄, a = 9.419(1)
Å, b = 9.584(1) Å, c = 12.652(1) Å, α = 89.03(1)°, β = 82.41(1)°, γ = 72.75(1)°, V = 1080.9(2) Å3, Z = 2;
3, monoclinic space group P21/n, a = 10.785(2) Å, b = 17.680(2) Å, c = 11.971(2) Å, β = 98.67(1)°, V =
2256.5(6) Å3, Z = 4.