Modulation of reactivity and stereochemistry of substrate binding by the group X in RuHX(CO)(P-tert-Bu2Me)2

Abstract

and give RuH(C2Ph)(CO)P2. The CO stretching frequency of this product shows evidence of ir donation from acetylide. The large downfield 13C chemical shift of Ca in this compound may have the same cause. A labeling study shows that the proton eliminated in HX is that of the PhC2H. Reaction of RuHF(CO)P2 with HSiMe3 yields FSiMe3 and RuH"(SiMe3)(CO)P2 (n = 1 and 3). Reaction of RuH(C2Ph)(CO)P2 with equimolar PhC2H gives products of Ru-H addition with both regiochemistries. Reaction with excess PhC2H gives Ru(C2Ph)2(CO)P2, whose structure is proposed on the basis of variable-temperature 31P and 13C NMR studies. Reaction of these Ru-H bonds with D2 or alkyne must occur cis to H (i.e., between H and X). Such attack stereochemistry is made easier when the opening of the HRuX angle is energetically facile. Ab initio SCF calculations show that the opening of the HRuX angle is easier for a heavier halide, which accounts for the higher reactivity observed for the iodide derivative. An internal competition experiment shows that PhC2H reacts faster with RuHX(CO)P2 when X = C2Ph than when X = Cl. Underlying this complex reactivity is the fact that RuHX(CO)P2 is a multifunctional reagent.

C–H Activation on Co,O Sites: Isolated Surface Sites versus Molecular Analogs

“…In the limit of high [ 5 - d 1 ], this full rate law simplifies to a rate law that is equal to the one we determined experimentally (eq ). This mechanism is consistent with previous studies on molecular complexes: HRu­(OSiPh 3 )­(P t Bu 3 ) 2 (CO) reacts with PhCCH through C–H activation on Ru-OSiPh 3 to produce HRu­(CCPh)­(P t Bu 3 ) 2 (CO) and HOSiPh 3 , and similar mechanisms have been proposed for benzene C–H activation by Ir–OR, , Ru–OR, and Pd–OR complexes as well as for activation of indene by Rh–OH complexes…”

“…In the limit of high [5-d 1 ], this full rate law simplifies to a rate law that is equal to the one we determined experimentally (eq 10). This mechanism is consistent with previous studies on molecular complexes: HRu(OSiPh 3 )(PtBu 3 ) 2 (CO) reacts with PhCCH through C−H activation on Ru-OSiPh 3 to produce HRu(CCPh)(PtBu 3 ) 2 (CO) and HOSiPh 3 , 25 and similar mechanisms have been proposed for benzene C−H activation by Ir−OR, 5c,d Ru−OR, 26 and Pd− OR complexes 27 as well as for activation of indene by Rh−OH complexes 28 However, alternative mechanisms have been proposed, involving metallacycle intermediates or stepwise processes. For instance, in the C−H activation of a variety of C−H bonds to imido Zr species 7, 29 the rate of addition of t-butylacetylene to 7 was much faster than any other C−H bond and involved an inverse H/D kinetic isotope effect (KIE) of 0.8, while the others possessed large KIEs of 5−8.…”

Coinage Metal Hydrides: Synthesis, Characterization, and Reactivity

“…The neutral silver­(I) fluorides LAgF (L = 6Dipp or 7Dipp) also activate dihydrogen, cleanly forming the hydride-bridged disilver cations and the [HF 2 ] − anion after several days (Scheme ). This overall heterolysis of dihydrogen by two silver fluorides, reminiscent of the hydrogenolysis of ruthenium­(II) fluorides, − displays a first-order rate dependence on both silver and dihydrogen concentration. Although other sequences cannot be ruled out, this profile is consistent with initial rate-limiting heterolysis by a single LAgF molecule, with rapid subsequent formation of a hydride bridge and bifluoride …”

Alkoxy/siloxy group exchange in the system vinyltrialkoxysilane–iridium(i) siloxide complex

“…1 The composite (s + p) electron donor ability of the group X in, for example, the complex of formula [RuH(X)(CO)(P-Bu 2 Me) 2 ], determined by Caulton et al using spectroscopic data, increased in the sequence OSiPh 3 < OSiMe 3 < OEt. 3,4 The stereoelectronic properties of the siloxy groups, particularly in metal siloxides, can be effectively exploited in molecular catalysis, either by using the above groups as ancillary ligands of early-TM complexes (see comprehensive studies by Wolczanski et al 1,[4][5][6] and Feher et al 7,8 ) or by exploiting their ability to form bridging structures in a low oxidation state of the late-TM complexes (e.g. Rh(I) [9][10][11] and Ir(I) 12 ).…”