Thermal Si−C Bond Cleavage of LRhH(SiAr₃)(μ-H)(μ-Cl)RhH(SiAr₃)L (Ar = C₆H₅, C₆H₄F-p; L = P(i-Pr)₃) To Give LRhH(μ-SiAr₃)(μ-SiAr₂)(μ-Cl)RhHL Containing Symmetrically Bridging Triarylsilyl and Diarylsilylene Ligands

Abstract

The reaction of dinuclear rhodium complex LRhH(SiPh 3 )(µ-H)(µ-Cl)RhH(SiPh 3 )L (1; L ) P(i-Pr) 3 ) with excess HSi(C 6 H 4 F-p) 3 leads to replacement of the SiPh 3 ligands with the Si- 4), respectively. Heating of benzene or toluene solution of 1 and 2 at 60 °C results in Si-C bond cleavage of a triarylsilyl ligand and affords LRhH(µ-SiAr 3 )(µ-SiAr 2 )-(µ-Cl)RhHL (7, Ar ) Ph; 8, Ar ) C 6 H 4 F-p) accompanied by liberation of benzene and fluorobenzene, respectively. The NMR ( 1 H and 31 P) spectra of 7 and 8 indicate symmetrical coordination of the bridging triarylsilyl and diarylsilylene groups to two Rh centers. The reaction of 1 to form 7 at 55-70 °C obeys first-order kinetics with the kinetic parameters: ∆G q ) 112 kJ mol -1 , ∆H q )129 kJ mol -1 , and ∆S q ) 58 J mol -1 deg -1 at 298 K. Complexes 2-4 also undergo thermal Si-C bond cleavage of a triarylsilyl ligand to liberate fluorobenzene as the organic product. The rate constants of the reaction increase in the order 2 < 4 < 3 < 1.

Rhodium Phosphines Partnered with the Carborane Monoanions [CB11H6Y6]- (Y = H, Br). Synthesis and Evaluation as Alkene Hydrogenation Catalysts

“…This makes each metal center formally Rh 3+ , consistent with the observed diamagnetism. The Rh−Rh distance is in the range associated with dinuclear rhodium complexes with a metal−metal bond. − The two chloride ligands do not span the Rh−Rh vector symmetrically, one Rh−Cl distance in each Rh−Cl−Rh unit being significantly longer than the other: viz., Rh(2)−Cl(1) = 2.538(3) Å and Rh(1)−Cl(1) = 2.416(3) Å. This difference can be traced back to the approximate trans orientation of the terminal hydrides with respect to the chloride ligands (H(2)−Rh(2)-Cl(1) = 168(4)° and H(1)−Rh(1)−Cl(2) = 163(3)°), meaning that each bridging chloride is approximately trans to both a phosphine and a hydride, with a resulting differential in the observed Rh−Cl bond lengths.…”

Nickel-Catalyzed Cyclopolymerization of Hexyl- and Phenylsilanes

“…Tanaka reported that the dinickel complexes with bridging silylene and silyl ligands have a Si···Si interaction between the ligands . σ-Bond metathesis is not usually suggested as the valid mechanism for the Si–Si bond formation by late transition metals, although it is discussed as a mechanism of the Si–H bond activation in dinuclear Rh complexes with Si ligands . In this paper, we present polycondensation of primary silanes using Ni catalysts to form the cyclic oligosilanes selectively.…”

“…10 bond activation in dinuclear Rh complexes with Si ligands. 11 In this paper, we present polycondensation of primary silanes using Ni catalysts to form the cyclic oligosilanes selectively.…”

Reactions of Hydrosilanes with Transition Metal Complexes and Characterization of the Products

“… 227 Additional derivatives with Ar 3− n Ph n SiH: n = 1 or 2, Ar = C 6 H 4 - p -F; n = 0, Ar = C 6 H 4 - p -CF 3 and Ar = C 6 H 4 -4-CH 3 (not isolated). When [L(H)RhSiPh 3 ] 2 (μ-H)(μ-Cl) was treated with 4 equiv of HSiAr 3 (Ar = C 6 H 4 Me- p ), [L(H)RhSiAr 3 ] 2 ( μ -H)(μ-Cl) (12 pts) and [L(H)SiAr 3 Rh](μ-H)(μ- Cl)[RhH(SiPh 3 )L] (44 pts) and 3-216 (44 pts) formed 228 X-ray structure of [L(H)RhSiPh 3 ] 2 (μ-H)(μ-Cl) (L = P( i Pr) 3 ) reported in ref . 229 AAA′ part of AA′MM'XX′ pattern …”