Unusual fluxional and T1 properties for [ReH4(CO)(PMe2Ph)3]+: a polyhydride with classical and nonclassical tautomers

Abstract

NMR studies show that [ReH₄(CO)(PMe₂Ph)₃]BF₄ exists as a tautomeric mixture (ΔH 1.1 kcal mol^–1)(1 cal = 4.184 J) of the classical tetrahydride [T₁(min., 250 MHz) 80 ms](3a)(major) and the nonclassical d⁴ tautomer [T₁(min., 250 MHz) 8 ms for the (H₂) peak](3b)[Re(H₂)H₂(CO)(PMe₂Ph)₃]⁺(minor), the HD analogue of which has J_H,D 34 Hz; the fluxional processes in the system lead to an unusual temperature dependence of the T₁ values.