Synthesis and crystal structures of nickel(II) and palladium(II) complexes with o-carboranyl amidine ligands

A number of new nido-carboranyl amidines 10-R(CH2)(n)NHC(Et)=HN-7,8-C2B9H11 (n = 2, R = OH, OMe, and NMe2; n = 3, R = OH) were synthesized by the nucleophilic addition of amino alcohols and N,N-dimethylethylenediamine to the highly activated -C N+- triple bond of the 10-propionitrilium derivative of nido-carborane. A similar reaction of 10-EtCuN-7,8-C2B9H11 with ethylenediamine unexpectedly resulted in the cleavage of the C N bond to form the ammonium derivative 10-H3N-7,8-C2B9H11. The complexation of the synthesized carboranyl amidines 10-MeO(CH2)(2)NHC(Et)vHN-7,8-C2B9H11 and 10-Me2N(CH2)(2)NHC(Et)vHN-7,8-C2B9H11 with nickel and palladium phosphine complexes [(Ph3P)(2)MCl2] (M = Ni, Pd) was studied. The reactions with 10-MeO(CH2)(2)NHC(Et)vHN-7,8-C2B9H11 result in half-sandwiched metallacarborane complexes with the retention of one triphenylphosphine ligand [3-Ph3P-3-(8MeOCH(2)CH(2)N=C(E t)NH)-3,1,2-MC2B9H10], while the reactions with 10-Me2N(CH2)(2)NHC(Et)vHN-7,8-C2B9H11 proceed with the complete loss of the phosphine ligands and lead to the formation of complexes with the eta(5):kappa(2)(N,N')-coordinated carboranyl amidine ligand [3,3-(8-Me2NCH2CH2N=C(Et)NH)-3,1,2-MC2B9H10]. The crystal molecular structures of the synthesized complexes were determined by single crystal X-ray diffraction.