Unexpected effect of the ring on the extent of Si⋯H interligand interactions in half-sandwich silyl hydrides of ruthenium

Abstract

This paper reports preparation of new silyl hydride complexes of ruthenium supported by the Cp/PR(3) ligand set. It is shown that the easiest and most general route to these complexes is provided by the thermal reaction of [RuCp(PR(3))(H)(3)] with hydrosilanes. Complexes [RuCp(PR(3))(H)(2)(SiMe(2)Cl)] exhibit Interligand Hypervalent Interactions (IHI) between the hydride and silyl ligands. Comparison of the X-ray structures of complexes [RuCp(PPr(i)(3))(H)(2)(SiMe(2)Cl)], [RuCp(PPhPr(i)(2))(H)(2)(SiMe(2)Cl)], and [RuCp(PPh(3))(H)(2)(SiMe(2)Cl)] shows that the IHI weakens with the decreasing electron-releasing ability of the phosphine. Comparison of the X-ray structure of [RuCp(PPh(3))(H)(2)(SiMe(2)Cl)] with the structure of the previously reported complex [RuCp*(PPh(3))(H)(2)(SiMe(2)Cl)] reveals that the lack of IHI in the latter compound is due to unfavourable steric interactions between the bulkier Cp* ring and the SiMe(2)Cl group.

Polyhydrides of Platinum Group Metals: Nonclassical Interactions and σ-Bond Activation Reactions

“…The related compounds RuH 2 (SiMe 2 Cl)­(η 5 -C 5 H 5 )­(PR 3 ) (PR 3 = P i Pr 2 Me ( 242 ), PMe 2 Ph ( 243 )) have been also prepared, starting from the corresponding chloride complexes RuCl­(η 5 -C 5 H 5 )­(PR 3 ) 2 (PR 3 = P i Pr 2 Me ( 244 ), PMe 2 Ph ( 245 )). These ruthenium­(IV) dihydride-silyl species exhibit hydride–silicon hypervalent interactions, whose strength decreases with the decreasing basicity of the phosphine coligand . The reactions of the NHC-supported trihydride RuH 3 (η 5 -C 5 H 5 )­(IPr) ( 94 ) with hydrosilanes HSiR 3 afford the dihydride-silyl complexes RuH 2 (SiR 3 )­(η 5 -C 5 H 5 )­(IPr) (SiR 3 = SiCl 3 ( 246 ), SiMeCl 2 ( 247 ), SiMe 2 Cl ( 248 ), SiH 2 Ph ( 249 ), SiHMePh ( 250 ), SiMe 2 Ph ( 251 )) with nonclassical Si···H interligand interactions (Scheme ).…”

Two-Silicon Cycle for Carbonyl Hydrosilylation with Nikonov’s Cationic Ruthenium(II) Catalyst

“…To identify the actual hydride donor in Nikonov’s carbonyl hydrosilylation, we initially targeted the preparation of the postulated neutral ruthenium­(II) monohydride 8 (Scheme , top), but its independent synthesis failed. However, we were able to access the ruthenium­(IV) silyl dihydride 13a (Scheme , bottom) which can be regarded as the oxidative-addition complex of hydrosilane 5a added to the coordinatively unsaturated ruthenium­(II) monohydride 12 ; 12 , in turn, could be available from 8 by acetonitrile dissociation (Scheme , top) . That silyl dihydride 13a is exactly what, in analogy to Brookhart’s case, we imagined to be the hydride source in a two-silicon cycle.…”

Steric and Electronic Effects in Half-Sandwich Ruthenium Silane σ-Complexes with Si−H and Si−Cl Interligand Interactions

“…In particular, the silyl group occupies the position between the chloride and hydride ligands, with the Si-bound chloride lying trans to the Ru-bound chloride (the angle RuCl−Si−Cl is 164.06(4)° in 4b and 162.50(9)° in 4c ; the dihedral angles Cl−Ru−Si−Cl are 179.7 and 179.2°, respectively). Both structures revealed Ru−Si bonds elongated in comparison with those in related half-sandwich silyl complexes of ruthenium (Table ): 2.3564(7) Å in 4b versus the range 2.2950(5)−2.3099(9) Å for complexes Cp*Ru(R 3 P)H 2 SiMeCl 2 and 2.4035(2) Å in 4c versus the range 2.302(3)−2.364(2) Å for Ru complexes with the SiR 2 Cl ligands. , The Ru−Si bond in 4c is somewhat longer than the Ru−Si bond in the related silane σ-complex 2c (2.3982(7) Å), consistent with a stronger silane σ-complex character of 4c . The most remarkable feature of 4b , c is the presence of a short RuCl···SiCl contact.…”

“…How ancillary ligands affect the strength of simultaneous Si−H and Si−Cl interactions in these species still remains to be determined. As part of our broad research program on studying the role of nonclassical interligand interactions in metal complexes, ,− we became interested in investigating the effect of ancillary ligands on Si−H interactions supported by the Cp′(Pr i 3 P)Ru platform (where Cp′ is Cp or substituted Cp). For the dihydride silyl complexes Cp′(Pr i 3 P)RuH 2 (SiR 3 ) with interligand hypervalent interactions (IHI) we found an unexpected interplay of steric and electronic factors .…”

“…As part of our broad research program on studying the role of nonclassical interligand interactions in metal complexes, ,− we became interested in investigating the effect of ancillary ligands on Si−H interactions supported by the Cp′(Pr i 3 P)Ru platform (where Cp′ is Cp or substituted Cp). For the dihydride silyl complexes Cp′(Pr i 3 P)RuH 2 (SiR 3 ) with interligand hypervalent interactions (IHI) we found an unexpected interplay of steric and electronic factors . Here we report the effect of changing the Cp* ring in the silane σ-complexes Cp*(Pr i 3 P)RuCl(η 2 -HSiR 3 ) ( 2 ) for an unsubstituted Cp ring and its consequences for the Si−H and Cl···Si interactions.…”