Ruthenocenyl ruthenium bimetallic complexes: Electrospray mass spectrometric study of [RuX(η5-C5H5)(η2-dppr)] n+ (dppr=1,1′-bis(diphenylphosphino)ruthenocene) (X=Cl, n=0; X=CO, CH3CN, C=CHPh, n=1) and the X-ray crystal and molecular structure of [Ru(η5-C5H5)(CO)(η 2-dppr)]PF6

Abstract

[RuCl(Cp)(PPh3)2] (Cp=η5-C5H5) reacts with dppr in refluxing benzene to give [RuCl(Cp)(dppr)], 1, {dppr=[Ru(η5-C5H4PPh2) 2]} in 91% yield. Complex 1 ionizes in boiling acetonitrile in the presence of excess NH4PF6 to give [Ru(Cp)(CH3CN)(dppr)]PF6, 2, in 76% yield. Under CO at 60°C, 1 converts to [Ru(Cp)(CO)(dppr)]Cl, 3a, whose derivative [Ru(Cp)(CO)(dppr)]PF6, 3b, can also be obtained from 2 in 86% with CO. With HCCPh, 2 instantaneously gives a vinylidene complex, [Ru(C=CHPh)(Cp)(dppr)]PF6, 4, quantitatively (98%). The kinetic stability of the η2-coordinated dppr ring is evident in these reactions. The X-ray molecular structure of 3b [space group P21/c, a=9.990(2), b=19.498(4), c=19.113(4) Å and β=96.21(3)°] reveals a pseudo-octahedral Ru(II) structure with a η5-Cp, a chelated dppr, a terminal CO and an uncoordinated PF6 - anion. It is the first piano-stool dppr structure characterized by X-ray single-crystal diffractometry. The dppr chelate has a large bite (100.5(1)°) and there is no direct interaction between the two Ru(II) centers (Ru(1)Ru(2) 4.389 Å). The electrospray mass spectra (ESMS) of 2-4 generally give peaks due to the intact cations at low cone voltages. As the cone voltage increases, fragmentation commences which inevitably gives [Ru(Cp)(dppr)]+ as the primary fragment ion. In-situ doping of dppr with AgNO3 gives [Ag(dppr)]+ as the major species plus [Ag(dppr)2]+ (m/z 1307) and other oxidized by-products. Similar treatment of 4 gives an acetylide complex [Ag{Ru(Cp)(CCPh)(dppr)}2]+ (m/z 1843) at 20 V which ejects one Ru metalloligand to give [Ag{Ru(Cp)(CCPh)(dppr)}]+ (m/z 975) at higher voltages. Complex 4 is hydrogenated with H2 gas to give ethylbenzene in 55% yield after 4 h in refluxing THF. It also catalyzes the hydrogenation of HCCPh to give 52% of ethylbenzene in 5 h at 5 mol.% catalyst level. © 1999 Elsevier Science S.A.