Cationic Arylmanganese(ii) Derivatives Occurring In Ion-pair Forms With Tetraphenylborate Anions - Synthetic, Structural, and Magnetic Studies

We report a class of cationic manganese(II) aryl compounds stabilized by weak donor solvents or by interactions with the counteranion BPh(4)(-) to form ion-pair species. The parent compound used was Mn(3)Mes(6) (1; Mes = 2,4,6-Me(3)C(6)H(2)), which can be synthesized on a large scale by a conventional method and conveniently used as starting material. Reaction of 1 with BPh(3) in Et(2)O gave the cationic derivative [MesMn(OEt(2))(3)](+)BPh(4)(-) (2), containing a single Mn-C bond and three weakly bonded Et(2)O molecules. In order to avoid coordinating solvent, the reaction between 1 and BPh(3) was then carried out in toluene. This reaction gave, depending on the reaction time and the BPh(3)/Mn ratio, the monomeric [MesMn(eta(3)-Ph)(2)BPh(2)] (3) and the dimeric [Ph(2)B(eta(2)-Ph)(2)(mu-MnPh)(2)(eta(2)-Ph)(2)BPh(2)] (4) ion pairs. Temperature-dependent magnetic measurements showed that for 1 and 4 a strong antiferromagnetic coupling exists between the d(5) ions brought about by the bridging aryl groups and/or the short Mn...Mn distance (2.851(2) Angstrom, 1; 2.796(1) Angstrom, 4). Such a coupling, much greater than that observed in several Mn(II)-Mn(II) dimers, has J values of 55.4 cm(-1) (complex 4) and 40.4 cm(-1) (complex 1). Crystallographic details: 1 is triclinic, space group P ($) over bar 1, with a = 12.850(3) Angstrom, b = 20.327(4) Angstrom, c = 11.407(3) Angstrom, alpha = 95.11(2)degrees, beta = 114.00(2)degrees, gamma = 98.77(2)degrees, Z = 2, and R = 0.052; 2 is triclinic, space group P ($) over bar 1, with a = 11.237(2) Angstrom, b = 19.035(2) Angstrom, c = 10.991(1) Angstrom, alpha = 99.30(1)degrees, beta = 106.66(1)degrees, gamma = 104.58(1)degrees, Z = 2, and R = 0.070; 3 is monoclinic, space group P2(1)/n, with a = 10.070(1) Angstrom, b = 15.901(1) Angstrom, c = 20.876(2) Angstrom, beta = 101.94(1)degrees, Z = 4, and R = 0.054; 4 is monoclinic, space group P2(1)/c, with a = 15.074(4) Angstrom, b = 13.289(4) Angstrom, c = 20.139(5) Angstrom, beta = 98.39(2)degrees, Z = 4, and R = 0.055.