Dirhodium Formamidinate Compounds with Bidentate Nitrogen Chelating Ligands

The reactions of [Rh2(DTolF)2(CH3CN)6][BF4]2 (1) (DTolF = N,N‘-di-p-tolylformamidinate) with 2,2‘-bipyridine (bpy)
and 1,10-phenanthroline (phen) proceed with substitution of CH3CN molecules to give products with the N−N
ligands chelating in an equatorial−equatorial (eq−eq) fashion. Compound 1 reacts with 1 equiv of bpy to yield a
mixture of [Rh2(DTolF)2(bpy)(CH3CN)3][BF4]2·(CH3)2CO (2a) and [Rh2(DTolF)2(bpy)(CH3CN)4][BF4]2 (2b). Compound
2a crystallizes in the monoclinic space group P21/n with a = 13.5856(2) Å, b = 18.0402(2) Å, c = 21.4791(3) Å;
α = 90°, β = 101.044(1)°, γ = 90°; V = 5167.27(12) Å3, Z = 4, R = 0.0531, and Rw = 0.0948. Compound
2b crystallizes in the monoclinic space group P21/n with a = 10.9339(2) Å, b = 24.4858(1) Å, c = 19.4874(3) Å;
α = 90°, β = 94.329(1)°, γ = 90°; V = 5202.38(13) Å3, Z = 4, R = 0.0459, and Rw = 0.1140. The reaction
of compound 1 with 2 equiv of bpy affords [Rh2(DTolF)2(bpy)2(CH3CN)][BF4]2 (3) which crystallizes in the monoclinic
space group P21/a with a = 19.4534(4) Å, b = 13.8298(3) Å, c = 19.8218(5) Å; α = 90°, β = 109.189(1)°, γ
= 90°; V = 5036.5(2) Å3, Z = 4, R = 0.0589, and Rw = 0.0860. Compound 1 reacts with 1 equiv of phen to form
[Rh2(DTolF)2(phen)(CH3CN)3][BF4]2·2C2H5OC2H5 (4) which crystallizes in the triclinic space group P1̄ with
a = 12.6346(2) Å, b = 13.5872(2) Å, c = 19.0597(3) Å; α = 71.948(1)°, β = 73.631(1)°, γ = 71.380(1)°; V =
2886.70(8) Å3, Z = 2, R = 0.0445, and Rw = 0.1207. A notable feature of the cations in 2a, 3, and 4 is the
presence of only one axial (ax) CH3CN ligand, a fact that can be attributed to the steric effect of the formamidinate
bridging ligands. Compounds 2a, 2b, 3, and 4 were fully characterized by X-ray crystallography and 1H NMR
spectroscopy, whereas [Rh2(DTolF)2(phen)2(CH3CN)2][BF4]2 (5) was characterized by 1H NMR spectroscopy.