Novel single or double insertion of alkynes into rhodium– and iridium–oxygen or –phosphorus atom bonds and transannular addition of 1-alkynes between the rhodium atom and the ipso-carbon atom of the phosphorus ligand

Abstract

Reactions of Cp*MCl(MDMPP-P,O) (1a: M = Rh; 1b: M = Ir; MDMPP-P,O = PPh2(C6H3-2-MeO-6-O)) or Cp*MCl(BDMPP-P,O) (2a: M = Rh; 2b: M = Ir; BDMPP-P,O = PPh(C6H3-2,6-(MeO)2)(C6H3-2-(MeO)-6-O)) with 1-alkynes were carried out in the presence of KPF6. Complex 1a reacted with HCCR (R = Ph, p-tolyl) to give [Cp*Rh{PPh2(C6H3-2-(MeO)-6-(O-CRCHCHCR))}](PF6) 5 bearing the (P,O,C) tridentate ligand derived from a head-to-head dimerization of 1-alkynes, whereas reaction with nBuCCH gave a head-to-tail double insertion complex 6, however the reactiones of 1b in MeOH gave carbene complexes [Cp*Ir{PPh2(C6H3-2-(MeO)-6-O)(C(OMe)CH2R)}](PF6) 13 and a carbonyl complex [Cp*Ir(CO){PPh2(C6H3-2-(MeO)-6-O)}](PF6) 14. Rhodium complexes 1a and 2a afforded [Cp*Rh(CO){PPh2(C6H3-2-(MeO)-6-(OCHC(COOR)))}](PF6) 8 or [Cp*Rh(CO){PPh(C6H3-2,6-(MeO)2)(C6H3-2-(MeO)-6-(OCHC(COOR)))}](PF6) 11 on treatment with HCCCOOR (R = Me, Et). Reactions of 1a, 1b, 2a or 2b with ROOCCCCOOR (R = Me, Et) gave [Cp*MCl{PPh2(C6H3-2-(MeO)-6-(OC(COOR)C(COOR)))}] (9: M = Rh, 17: M = Ir) and [Cp*MCl{PPh(C6H3-2,6-(MeO)2)(C6H3-2-(MeO)-6-(OC(COOR)C(COOR)))}] (12: M = Rh, 18: M = Ir), respectively. Reactions of 1a or 1b with HCCC6H4-4-COOMe bearing an electron-withdrawing substituent gave the head-to-head double insertion products (5c: M = Rh; 16: M = Ir) and Cp*MCl2[PPh2{CHC(C6H3-4-COOMe)(C6H3-2-(MeO)-6-(OH))}] (7: R = Rh; 15: R = Ir), and resulted in a cis-insertion into the P–C bond of the phosphine ligand and a cleavage of the Rh–O bond. Reaction with 2a afforded 10a, derived from a transannular addition of 1-alkyne between the Rh atom and the ipso-carbon atom of the phosphine ligand. Reactions of 9 with CO or isocyanides (L) in the presence of KPF6 or Ag(CF3SO3) gave [Cp*Rh(L){PPh2(C6H3-2-(MeO)-6-(OC(COOR)C(COOR)))}]X (L = XylNC, MesNC, CO; X = PF6, CF3SO3). Structural data for some complexes obtained here are described. The reaction mechanism is discussed.