Molecular hydrogen complexes: the effect of steric factors on the protonation of the monohydrides [(η⁵-C₅H₅)Ru(Ph₂P(CH₂)_nPPh₂)H](n= 1–3)

Abstract

Protonation of the title complexes leads to either (q*-H2) or trans-dihydride monocations depending on the length of the chain connecting the two phosphine atoms; TI and JHD measurements are used to support these structures.We reported recently1 that protonation of [(q5-C5H5)Ru(PPh3)(ButNC)H] gave the (q2-H2) cation, [(775-

New, Highly Efficient Catalyst Precursors for Kharasch Additions − [RuCl(Cp*)(PPh3)2] and [RuCl(Ind)(PPh3)2]

“…CO) with the Cp* analogue. [16] Interestingly enough, [RuCl(Cp)(CO) 2 ] and [RuCl(Cp*)(CO) 2 ] were inactive for Kharasch addition under the reaction conditions shown in Table 1. The high activity of complex 2 might thus result from an increase in both the electron density and the steric congestion at the ruthenium center provided by the Cp* ligand, which would allow some stabilization of the 16-electron intermediate.…”

“…[15] It is known that the 18-electron complexes 1Ϫ3, containing two triphenylphosphanes, can exchange at least one of these ligands for another ligand (carbon monoxide, isonitriles, phosphanes, ...), by way of an unsaturated 16-electron transient species, under more or less forcing conditions, depending on the nature of the η 5ligand linked to the metal center. [16,17] The unsubstituted Cp ring allows one PPh 3 to be exchanged for one CO under rather forcing conditions (150 atm CO), whereas smooth substitution proceeds under mild conditions (2 atm. CO) with the Cp* analogue.…”

Protonation of Cp*M(dppe)H Hydrides: Peculiarities of the Osmium Congener

“…[21] Protonation of the ruthenium congener was reported only at room temperature to yield a 1:2 mixture of [CpRu(η 2 -H 2 )(dppe)] + and trans-[CpRuH 2 (dppe)] + . [26] For the recently studied series of Group 8 Cp*M(dppe)-H complexes (M = Fe, [15,27,28] Ru, [29] Os [23] ), the low-temperature protonation by strong acids (195 K, CD 2 Cl 2 ) yields (η 2 -H 2 ) (Fe, Ru) or cis-(H) 2 (Os) complexes as kinetic products of syn protonation. For all three metals they convert into the corresponding trans-dihydrides upon warming.…”

[(2,3,5,6-η)-Bicyclo[2.2.1]hepta-2,5-diene]chloro[(1,2,3,4,5-η)-1,2,3,4,5-pentamethyl-2,4-cyclopentadien-1-yl]ruthenium

“…Stable cationic Ru II complexes can be obtained in good yield if a monodentate ligand is also present in the reaction mixture (eq 3). 3 In addition to Me 3 P, CO and cyclic arsines have been incorporated into Cp*Ru(NBD) complexes using this procedure. 3, 8 Stepwise substitution of the chloride ligand has been performed by treatment of 1 with AgBF 4 in EtOH.…”