PREPARATION, STRUCTURE, AND REACTIVITY OF NEW BIS(ACETYLIDE) AND ACETYLIDE-VINYLIDENE RUTHENIUM(II) COMPLEXES STABILIZED BY PHOSPHITE LIGANDS

Bis(alkynyl) complexes Ru(C=CR)(2)P-4 (1-3) (R = Ph, p-tolyl, (t)Bu; P = P(OMe)(3) (1), P(OEt)(3) (2), PPh(OEt)(2) (3)) were prepared by reacting RuCl2P4 with excess Li+ RC=C-, and a trans geometry was established both in solids (X-ray) and in solution. The reaction of these alkynyls (1-3) with electrophilic reagent depends on the nature of the phosphite ligand. Vinylidene-acetylide derivatives [Ru(C=CR){=C=C(R(1))R}P-4](+) (R(1) = H (4, 5), CH3 (7, 8), ArN=N (10), I (12), 2,3-(NO2)(2)C6H3S (14)) were prepared with P(OMe)(3) and P(OEt)(3) ligand by treatment of 1 and 2 with HBF4, CF(3)SO(3)Me, ArN2+BF4-, I-2, and 2,3-(NO2)(2)C6H3SCl, respectively. Instead, only the diazo- and iodovinylidenes [Ru(C=CR){=C=C(R(1))R}P-4](+) (R(1) = p-tolN=N (11), I (13)) were obtained with the PPh(OEt)(2) phosphite ligand. These vinylidene compounds were fully characterized by IR, H-1, P-31, and C-13 NMR spectra, and a single-crystal X-ray structure determination of complex [Ru(C=CPh){=C=C(Me)Ph)-{P(OEt)(3)}(4)]CF3SO3 (8a) is reported. The alkynyl-vinylidene [Ru(C=CR){=C=C(H)R}P-4](+) cations (4, 5) rearrange in solution to enynyl [Ru(eta(3)-RC(3)CHR)P-4](+) derivatives, and the reaction is inhibited by the presence of free alkyne. Kinetic data support a mechanism involving a pentacoordinate intermediate formed by loss of the vinylidene ligand. Substitution of the =C=C(H)R ligand by phosphite, isocyanide, and nitrile is easy in 4 and 5 and leads to [Ru(C=CPh){P(OMe)(3)}P-4](+) (17), [Ru(C=CPh)(p-tolNC)P-4](+) (18), and [Ru(p-tolCN)(2)P-4](2+) (19) (P = P(OEt)(3)), derivatives. Deprotonation with a base of the vinylidene ligand in 4 and 5, giving Ru(C=CR)(2)P-4, was also detected.