The synthesis and characterization of products from reactions of Rh2(form)2(O2CCF3)2(CH3CN)2 (form = N,N‘-p-ditolylformamidinate, N,N‘-diphenylformamidinate) and the partially solvated [Rh2(DTolF)2(CH3CN)6][BF4]2 (DtolF = N,N‘-p-ditolylformamidinate) with the DNA purine analogues, 9-ethylguanine, and 9-ethyladenine are described. X-ray crystallography was used to characterize Rh2(DTolF)2(O2CCF3)2(CH3CN)2 (1) which crystallizes in the space group P21/n with a = 10.849 (3) Å, b = 21.435 (6) Å, c = 18.677 (3) Å, V = 4340 Å3, Z = 4, R = 0.0451, and R w = 0.0904. The two rhodium centers are bridged by four O2CCF3 - ligands with a Rh−Rh distance of 2.24743(5) Å. Compound 1 reacts with 9-ethylguanine to form Rh2(DTolF)2(9-EtGH)2(O2CCF3)2 (3) which exists as two isomers, namely head-to-head and head-to-tail as confirmed by 1H NMR spectroscopy. [Rh2(DTolF)2(CH3CN)6][BF4]2 (5) crystallizes in the Pbca space group with a = 21.646 (3) Å, b = 31.272 (3) Å, c = 14.561(4) Å, V = 9857 Å3, Z = 8, R = 0.046, and R w = 0.063. The Rh−Rh bond distance is 2.5594 (8) Å. The partially solvated compound 5 reacts with 9-ethyladenine and 9-ethylguanine to form [Rh2(DTolF)2(9-EtAH)2(CH3CN)][BF4]2 (6) and [Rh2(DTolF)2(9-EtGH)2(CH3CN)][BF4]2 (7), respectively. Compound 6 was characterized by X-ray crystallography as well as by variable temperature 1H NMR spectroscopy. [Rh2(DTolF)2(9-EtAH)2(CH3CN)][BF4]2 crystallizes in the P21/c space group with a = 15.648(8) Å, b = 16.575(5) Å, c = 20.026(8) Å, β = 105.17(4)°, V = 4994 Å3, Z = 4, R = 0.063, and R w = 0.073. This compound contains two bridging DTolF- ligands as well as two 9-ethyladenine ligands bridging through the N7 and exocyclic N6 positions in a head-to-tail fashion. 1H NMR studies performed on 6 revealed that the N6 position is in the imino (NH-) form.

The new cationic complex cis-Rh2(μ-DTolF)2(CH3CN)6][BF4]2 (1) was prepared and reacted with the purine 9-ethyladenine to afford the novel compound cis-[Rh2(μ-DTolF)2(μ-9-EtAH)2(CH3CN)][BF4]2 (2) with two bridging 9-EtAH ligands. The solid-state and solution structures of 1 and 2 have been determined by X-ray crystallography and 1H NMR spectroscopy. Compound 2 represents the first reported dirhodium compound with bridging adenines rather than the expected axially coordinated form.

The reactions of [Rh(2)(DTolF)(2)(CH(3)CN)(6)][BF(4)](2) (1) (DTolF = N,N'-di-p-tolylformamidinate) with 2,2'-bipyridine (bpy) and 1,10-phenanthroline (phen) proceed with substitution of CH(3)CN 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 [Rh(2)(DTolF)(2)(bpy)(CH(3)CN)(3)][BF(4)](2).(CH(3))(2)CO (2a) and [Rh(2)(DTolF)(2)(bpy)(CH(3)CN)(4)][BF(4)](2) (2b). Compound 2a crystallizes in the monoclinic space group P2(1)/n with a = 13.5856(2) A, b = 18.0402(2) A, c = 21.4791(3) A; alpha = 90 degrees, beta = 101.044(1) degrees, gamma = 90 degrees; V = 5167.27(12) A(3), Z = 4, R = 0.0531, and R(w) = 0.0948. Compound 2b crystallizes in the monoclinic space group P2(1)/n with a = 10.9339(2) A, b = 24.4858(1) A, c = 19.4874(3) A; alpha = 90 degrees, beta = 94.329(1) degrees, gamma = 90 degrees; V = 5202.38(13) A(3), Z = 4, R = 0.0459, and R(w) = 0.1140. The reaction of compound 1 with 2 equiv of bpy affords [Rh(2)(DTolF)(2)(bpy)(2)(CH(3)CN)][BF(4)](2) (3) which crystallizes in the monoclinic space group P2(1)/a with a = 19.4534(4) A, b = 13.8298(3) A, c = 19.8218(5) A; alpha = 90 degrees, beta = 109.189(1) degrees, gamma = 90 degrees; V = 5036.5(2) A(3), Z = 4, R = 0.0589, and R(w) = 0.0860. Compound 1 reacts with 1 equiv of phen to form [Rh(2)(DTolF)(2)(phen)(CH(3)CN)(3)][BF(4)](2).2C(2)H(5)OC(2)H(5) (4) which crystallizes in the triclinic space group P1macro with a = 12.6346(2) A, b = 13.5872(2) A, c = 19.0597(3) A; alpha = 71.948(1) degrees, beta = 73.631(1) degrees, gamma = 71.380(1) degrees; V = 2886.70(8) A(3), Z = 2, R = 0.0445, and R(w) = 0.1207. A notable feature of the cations in 2a, 3, and 4 is the presence of only one axial (ax) CH(3)CN 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 (1)H NMR spectroscopy, whereas [Rh(2)(DTolF)(2)(phen)(2)(CH(3)CN)(2)][BF(4)](2) (5) was characterized by (1)H NMR spectroscopy.