Competition between NH···HIr Intramolecular Proton−Hydride Interactions and NH···FBF3-or NH···O Intermolecular Hydrogen Bonds Involving [IrH(2-thiazolidinethione)4(PCy3)](BF4)2and Related Complexes

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Abstract
The reaction of IrH5(PCy3)2 in acetone with 2 equiv of HBF4 results in the formation of the air-stable complex [Ir(H)2(PCy3)2(acetone)2]BF4, 1. The reaction of 1 with an excess of 2-thiazolidinethione or 2-benzothiazolethione in the presence of 2 equiv of HBF4 gives the complexes [Ir(H)(PCy3)(L)4](BF4)2 (2a, L = 2-thiazolidinethione; 2b, L = 2-benzothiazolethione). Complex 2a has an intramolecular NH···H(Ir)···HN interaction both in the crystalline solid as determined by X-ray diffraction and in a CD2Cl2 solution as determined by the T1 method. The dHH were determined to be 2.2 ± 0.1 Å in the solid state and 1.9 ± 0.1 Å in solution. The NH···H(Ir)···HN interactions and NH···F···HN hydrogen bonds which involve FBF3- form a four-member ring in a butterfly conformation. The nOe effect of the hydride on the NH proton is around 10%. A crystal of 2a is in the triclinic space group P1̄ with a = 11.426(3), b = 11.922(3), c = 19.734(4) Å, α = 87.05(1)°, β = 88.23(1)°, γ = 75.50(1)°, V = 2599(1) Å3, and Z = 2 at T = 173 K; full-matrix least-squares refinement on F2 was performed for 10 198 independent reflections; R[F2>2σ(F2)] = 0.0480, Rw(F2) = 0.099. The formation of the NH···HIr proton−hydride interaction is as favorable as the formation of intermolecular hydrogen bonds NH···FBF3- or NH···O hydrogen bonds with OPPh3 or H2O in CD2Cl2. A similar NH···HIr interaction also has been observed in the complexes [Ir(H)2(PCy3)2(L)2]BF4 (3a, L = 2-thiazolidinethione; 3b, L = 2-benzothiazolethione) but not in the complexes with L = NH2NH2 (3c) and L = NH3 (3d). Both the NH and IrH protons are deuterated when a solution of 2 or 3 in C6D6 is exposed to 1 atm of D2 gas or D2O.