THE NITROSYL LIGAND AND THE RHENIUM-TRIFLATE BOND IN RHENIUM(I) COMPLEXES

The reaction of ReCl(2)L(2)(CO)(NO) (L = P(OMe)(3) (1a), PEt(3) (1b)) with excess silver trifluoromethanesulfonate (AgOTf) in boiling aceton itrile led to an isomeric mixture of [ReCl(CH3CN)(2)L(CO)(NO)][OTf] (L = P(OMe)(3) (2a) PEt(3) (2b)) (approximately 2:1 ratio) with the chlo ride ligands trans to CO or NO. The isomers of 2a and 2b could not be separated, except for a few yellow prisms of the trans Cl, NO compound of 2b, the structure of which was established by an X-ray diffraction study. The cation of 2b contains an octahedral Re atom bearing one ph osphine ligand trans to one acetonitrile molecule (Re-N3 2.144(6) Angs trom). A second acetonitrile ligand (Re-N2 2.143(6) Angstrom) is locat ed trans to the CO ligand (Re-Cl 1.928(8) Angstrom, C1-O2 1.142(10) An gstrom) and the chlorine substituent is arranged trans to the NO group (Re-N1 1.810(3) Angstrom, N1-O1 1.190(11) Angstrom). The Cl-Re-NO moi ety was found to be positionally disordered. For further characterizat ion of these isomers by chemical means, 2a and 2b were reacted with bp y to yield stable [ReCl(bpy)(CO)L(NO)][OTf] derivatives (L = P(OMe)(3) (3a), PEt(3) (3b)). The solid state IR spectrum supports the assumpti on that the isomers of 3a and 3b co-crystallize in the same crystal fr amework. This apparently prevented separation by crystallization. The reaction of 1 with 1 or 2 equiv of AgOTf in boiling toluene allowed th e preparation of the mono- and disubstituted complexes ReCl(OTf)L(2)(C O)(NO) (L = P(OMe)(3) (4a), PEt(3) (4b)) and Re(OTf)(2)L(2)(CO)(NO) (L = P(OMe)(3) (5a), PEt(3) (5b)). The replacement of the triflate ligan ds in 5a and 5b by acetonitrile are slow reactions (approximately 5d f or 5a and 15h for 5b at room temperature), which proceed with retentio n of the geometry. They result in the formation of the ionic [Re(CH3CN )(2)L(2)(CO)(NO)][OTf](2) products (L = P(OMe)(3) (6a), PEt(3) (6b)). The structure of 6a was confirmed by an X-ray diffraction study. IR an d P-31 NMR investigations of the acetonitrile monosubstituted intermed iates of this reaction indicated a somewhat faster replacement of the triflate ligand disposed trans to the carbonyl group. In the presence of bpy, 5a underwent in boiling toluene an Arbuzov-like phosphite deal kylation, producing a dinuclear [Re(CO)(bpy)(NO)[P(O)(OMe)(2)]](2)[OTf ](2) (7) complex in which the two Re fragments are linked by two phosp honite moieties, forming a planar six-membered ring. The reaction of 5 b with bpy gave only decomposition products. By analogy, Re(OTf)(CO)(3 )(PEt(3))(2) (8) was prepared and reacted with bpy under the same cond itions as for 5b. In this case [Re(CO)(2)(bpy)(PEt(3))(2)][OTf] (9) wa s isolated demonstrating that the presence of the nitrosyl ligand sign ificantly influences the reactivity of Re-1 complexes. The compounds 2 b, 5b, 6a, 7, and 8 were characterized by X-ray analyses. Crystal data follow. C12H21CIF3N3O5PReS (2b): monoclinic, space group P2(1)/c, a = 13.581(6) Angstrom, b = 13.063(5) Angstrom, c = 12.608(5) Angstrom, b eta = 93.48(2)degrees, V = 2232.6(16) Angstrom(3), Z = 4. The structur e was solved by the Patterson method and refined by full-matrix least squares procedures to R = 0.0441, R(w) = 0.0699 for 4239 observed refl ections with \F-o\ greater than or equal to 4 sigma(\F-o\). C14H24F6N3 O14P2ReS2 (6a): monoclinic, space group C2/c, a 15.610(4) Angstrom, b = 11.159(3) Angstrom, c = 17.006(4) Angstrom, beta = 91.50(2)degrees, V = 2961.3(12) Angstrom(3), Z = 4. The structure was solved by the Pat terson method and refined by full-matrix least squares procedures to R = 0.0541, R(w) = 0.0892 for 3222 observed reflections with \F-o\ grea ter than or equal to 4 sigma(\F-o\). 5b: triclinic, space group <P(1)o ver bar>, a = 9.066(2) Angstrom, b = 12.161(3) Angstrom, c = 12.759(3) Angstrom, alpha = 88.01(2)degrees, beta = 82.83(2)degrees, gamma = 86 .53(2)degrees, V = 1392.6(6) Angstrom(3), Z = 2. 7: triclinic, space g roup <P(1)over bar>, a = 9.158(3) Angstrom, b = 10.319(2) Angstrom, c = 14.641(4) Angstrom, alpha = 103.54(2)degrees, beta = 94.16(2)degrees , gamma = 115.75(2)degrees, V = 1187.3(5) Angstrom(3), Z = 1. 8: tricl inic, space group <(P)1over bar>, a = 8.287(3) Angstrom, b = 9.672(3) Angstrom, c = 16.429(6) Angstrom, alpha = 94.86(3)degrees, beta = 90.2 3(3)degrees, gamma = 112.20(2)degrees, V = 1214.0(7) Angstrom(3), Z = 2.