Regioselective nucleophilic addition of triphenylphosphine to the nitrosylruthenium alkynyl complexes having a hydrotris(pyrazol-1-yl)borate: formation of phosphonio-alkenyl, alkynyl, and allenyl species

A nitrosylruthenium alkynyl complex of TpRuCl(C=CPh)(NO) (1a) was reacted with PPh3 in the presence of HBF4.Et2O at room temperature to give a beta-phosphonio-alkenyl complex (E)-[TpRuCl{CH=C(PPh3)Ph}(NO)]BF4 (2.BF4). On the other hand, for gamma-hydroxyalkynyl complexes TpRuCl{C=CC(R)(2)OH}(NO) (R = Me (1b), Ph (1c), H (1d)), similar treatments with PPh3 were found to give gamma-phosphonio-alkynyl [TpRuCl{C=CC(Me)(2)PPh3} (NO)]BF4 (3.BF4), alpha-phosphonio-allenyl [TpRuCl{C(PPh3)=C=CPh2}(NO)]BF4 (4.BF4), and a novel product of gamma-hydroxy-beta-phosphonio-alkenyl (E)-[TpRuCl{CH=C(PPh3)CH2OH} (NO)]BF4 (5.BF4), respectively. Dominant factors for the selectivity in affording 3-5 were associated with the steric congestion and electronic properties at the c - carbons, along with those around the metal fragment. From the bis(alkynyl) complex TpRu(CCPh)(2)(NO) (6), a bis(b-phosphonioalkenyl) (E,E)-[TpRu{CH=C(PPh3)Ph}(2)(NO)](BF4)(2) {7.(BF4)(2)} was produced at room temperature. However, similar reactions at 0degreesC gave an alkynyl beta-phosphonio-alkenyl complex (E)-[TpRu(C=CPh){CH=C(PPh3)Ph}-(NO)]BF4 (8.BF4) as a sole product, of which additional hydration in the presence of HB4.Et2O afforded a beta-phosphonio-alkenyl ketonyl (E)-[TpRu{CH2C(O)Ph}{CH=C(PPh3)Ph}(NO)]BF4 (9.BF4). Five complexes, 2-5 and 7 were crystallographically characterized.