Efficient methods for the preparation of bromine-containing exo-nido- and closo-ruthenacarborane clusters

An efficient method for the synthesis of bromine-containing exo-nido-clusters of a general formula exo-5,6,10-[Br(Ph3P)(2)Ru]-5,6,10-(mu-H)(3)-10-H-7,8-R-2-nido-7,8-C2B9H6 (R = H, Me) was developed using the reactions of RuBr2(PPh3)(3) with [K][7,8-R-2-7,8-nido-C2B9H10]. Replacement of the phosphine ligands in the starting exo-nido-cluster (R = H) with the diphosphine ones afforded a series of diamagnetic (18-electron) closo-bromoruthenacarboranes, 3-Br-3,3-[kappa(2)-Ph2P(CH2)(n) PPh2]-3-H-closo-3,1,2-RuC2B9H11 (n = 3-5). A mild thermal method of the halide ligands exchange (Cl -> Br) upon heating of diamagnetic chlorine-containing complexes 3,3-[kappa(2)-Ph2P(CH2)(n) PPh2]-3-H-3-Cl-closo-3,1,2-RuC2B9H11 (n = 3-5) with excess of CBr4 in benzene (70-80 A degrees C) was suggested for the synthesis of paramagnetic (17-electron) bromine-containing ruthenacarboranes, 3-Br-3,3-[kappa(2)-Ph2P(CH2) (n) PPh2]-closo-3,1,2-RuC2B9H11 (n = 3, 4) or 3-Br-3,3,8-[kappa(2)-Ph-2(CH2)(5)PPh]-mu-(C6H4-0)-closo-3,1,2-RuC2B H-9(10). Paramagnetic chlorine-containing clusters 3-Cl-3,3-[kappa(2)-Ph2P(CH2)(n) PPh2]-closo-3,1,2-RuC2B9H11 (n = 2-4) were alternatively used as the starting compounds in the exchange reaction. Complexes with dppp and dppb (dppp is 1,3-bis(diphenylphosphino)propane, dppb is 1,4-bis(diphenylphosphino)butane) were used as examples to study the thermal reactions (toluene, 110 A degrees C) leading in the presence of CBr4 to paramagnetic mono(P-o-phenylene)- and bis(P,P-o-phenylene)cycloboronated clusters, 3-Br-3,3,8-[kappa(2)-Ph-2(CH2) (n) PPh]-mu- -(C6H4-0)-closo-3,1,2-RuC2B H-9(10) and 3-Br-3,3,4,8-[kappa(2)-Ph-2(CH2)(n) P]-mu- -(C6H4-0)-closo-3,1,2-RuC2B H-9(9) (n = 3, 4). The compounds obtained were characterized by NMR spectroscopy (in the case of diamagnetic complexes), ESR spectroscopy and mass spectrometry (in the case of paramagnetic compounds). X-ray diffraction experiments were carried out for two cycloboronated paramagnetic complexes.