Carbenerhodium Complexes of the Half-Sandwich-Type: Synthesis, Substitution, and Addition Reactions

Abstract

A series of carbenerhodium(I) complexes of the general composition [(eta5-C5H5)Rh(=CRR')(L)] (2a-2i) with R = R'= aryl and L = SbiPr3 or PR3 has been prepared from the square-planar precursors trans-[RhCl(=CRR')(L)2] and NaC5H5 in excellent yields. Reaction of the triisopropylsibane derivative 2a. which contains a rather labile Rh-Sb bond, with CO, PMe3, and CNR (R = Me, CH2Ph, tBu) leads to the displacement of the SbiPr3 ligand and affords the substitution products [(eta5-C5H5)Rh(=CPh2)(L)] (3-7). In contrast, treatment of the triisopropylphosphane compound 2c with CO and CNtBu leads to the cleavage of the Rh=CPh2 bond and gives besides [(eta5-C5H5)Rh(PiPr3)(L)] (10, 12) by metal-assisted C-C coupling diphenylketene Ph2C=C=O (11) or the corresponding imine Ph2C=C=NtBu (13). While the reaction of 2a, c with C2H4 yields [(eta5-C5H5)Rh(C2H4)(L)] (14, 15) and the trisubstituted olefin Ph2C=CHCH3 (16), treatment of 2a, c with RN3 leads to the cleavage of both the Rh-EiPr3 and Rh=CPh2 bonds and gives the chelate complexes [(eta5-C5H5)Rh(kappa2-RNNNNR)] (19, 20). The substitution products 3 (L=CO) and 4 (L= PMe3) react with an equimolar amount of sulfur or selenium by addition of the chalcogen to the Rh=CPh2 bond to generate the complexes [(eta5-C5H5)Rh(kappa2-ECPh2)(L)] (21-24) with thio- or selenobenzophenone as ligand. Similarly, treatment of 3 with CuCl affords the unusual 1:2 adduct [(eta5-C5H5)(CO)Rh(mu-CPh2)(CuCl)2] (25), which reacts with NaC5H5 to form [(eta5-C5H5)(CO)Rh(muCPh2)Cu(eta5-C5H5)] (26). The molecular structures of 3 and 22 have been determined by X-ray crystallography.

Half‐Sandwich Benzylidene Ruthenium Complexes Bearing Phosphanyl‐Pyridine Ligands: Reactivity towards Nucleophiles and Electrophiles

“…Complexes [Ru(C 5 H 5 )Cl(=CHPh)(PPh 3 )] and [Ru(C 5 Me 5 )Cl(=CHPh)(PPh 3 )] have been already prepared by using their respective labile ethylene complexes as precursors 25. In the same way, similar compounds that contain rhodium27 or iridium28 have been synthesized. Nevertheless, the related osmium compound [Os(C 5 H 5 )Cl(P i Pr 3 )(=CHPh)] has been obtained by direct reaction between [Os(C 5 H 5 )Cl(P i Pr 3 ) 2 ] and phenyldiazomethane 29…”

Electronic structure and electrophilic reactivity of discrete copper diphenylcarbenes

“…As this Fischer copper carbene com-plex is prepared via transmetallation from (CO) 5 Cr@ CR 1 (OR 2 ), it is reasonable to expect bimetallic [M](l-CRR 0 ) [Cu] species as intermediates [16]. In fact, spectroscopic data have been reported for two coppercontaining bimetallic carbenes Cp(CO)Ru(l-CPh 2 )-(CuCl) 2 and Cp(CO)Ru(l-CPh 2 )CuCp prepared by addition of CuCl to Cp(CO)Rh@CPh 2 followed by treatment with NaCp [17].…”

Synthesis, Molecular Structure, and CC Coupling Reactions of Carbeneruthenium(II) Complexes with C5H5Ru(CRR′) and C5Me5Ru(CRR′) as Molecular Units

“…[8] These compounds are not only the first rhodium(i) complexes bearing a carbene unit that is not stabilized by linkage of the carbene carbon atom to a heteroatom such as O, S, or N, [9] but they are also remarkable insofar as they react with olefins not to give cyclopropanes but mono-or trisubstituted ethene derivatives instead. [8,10] The rich chemistry offered by the rhodium carbenes trans-[RhCl(CRR')(L) 2 ] [10] and [(h 5 -C 5 H 5 )Rh(CRR')(L)] [11] prompted us to extend the diazoalkane route to the prepa- Scheme complex [(h 5 -C 5 Me 5 )RuCl(PiPr 3 )] is violet. [13] Treating a suspension of 3 or 4 in dichloromethane with CO affords the monocarbonyl compounds 5 and 6, which have previously been prepared by other routes.…”

“…Therefore, 10 has only been characterized by 1 H, 13 C, and 31 P NMR spectroscopy. Typical features of 10 and 11 are the two multiplets at d 3.53 and 3.03 ppm (10) and d 2.86 and 2.56 ppm (11) due to the ethene protons in the 1 H NMR spectra, and the singlet at d 46.2 ppm (10) and d 47.4 ppm (11) due to the olefinic carbon atoms in the 13 C NMR spectra. The chemical shift difference of about 76 ± 77 ppm between the 13 C NMR resonances of coordinated and free ethene indicates that in 10 and 11 the degree of back-bonding from Ru to C 2 H 4 is moderate; [17] it is possibly less than that in [(h 5 -C 5 H 5 )RuH(C 2 H 4 )(PPh 3 )] [18] or [(h 5 -C 5 H 5 )Ru(C 2 H 4 )-(PPh 3 ) 2 ]BF 4 .…”

“…While halfsandwich-type rhodium compounds [(h 5 -C 5 H 5 )Rh(CR 2 )(PR' 3 )] have hitherto only been prepared with R aryl, [11] related ruthenium complexes are also accessible with CHPh and CHSiMe 3 as carbene ligands. The synthetic routes are summarized in Scheme 6.…”