Formation of Osmium− and Ruthenium−Cyclobutylidene Complexes by Ring Expansion of Alkylidenecyclopropanes

Abstract

Alkylidenecyclopropanes containing a chelation assistant at the terminal carbon atom of the olefinic moiety undergo an Os- or Ru-promoted ring expansion reaction to afford metal cyclobutylidene derivatives. The process occurs through a novel mechanism that implies a 1,2-migration of a CH(2) group of the three-membered ring from an olefinic carbon atom to the other one. It takes place, without direct participation of the metal, on a metallaheterocyclopentene intermediate which is generated from an eta(2)-methylenecyclopropane species stabilized by coordination of the chelation assistant.

Gold‐Catalyzed Intermolecular Anti‐Markovnikov Hydroamination of Alkylidenecyclopropanes

“…[27] To evaluate this hypothesis, we generated the thermally unstable gold p-ACP complex [(P1)Au(h 2 -1 a)] + SbF 6 À (6 a) as an equilibrium mixture (~25:1) of trans/cis isomers from reaction of 1 a with a 1:1 mixture of AgSbF 6 and (P1)AuCl at À80 8C to À40 8C [Eq. (1)].…”

“…Regarding the anti-Markovnikov regioselectivity of goldcatalyzed ACP hydroamination, we initially considered that the gold p-ACP bond might be polarized toward a cyclopropylcarbinyl cation-like structure (structures c and d, Figure 1), as has been invoked to account for Pt II - [25] or Pd IIcatalyzed [26] ACP-to-cyclobutene isomerization and for the stoichiometric conversion of ACPs into Ru and Os cyclobutylidene complexes. [27] To evaluate this hypothesis, we generated the thermally unstable gold p-ACP complex [(P1)Au(h 2 -1 a)] + SbF 6 À (6 a) as an equilibrium mixture (~25:1) of trans/cis isomers from reaction of 1 a with a 1:1 mixture of AgSbF 6 and (P1)AuCl at À80 8C to À40 8C [Eq. (1)].…”

Synthesis of Nitrogen-Substituted Methylenecyclopropanes by Strain-Driven Overman Rearrangement of Cyclopropenylmethyl Trichloroacetimidates

“…[1][2][3][4] Typically, these highly strained systems are susceptible to ring-opening reactions [5][6][7][8][9][10][11][12][13][14][15][16][17], cycloaddition reactions [18][19][20][21][22][23] and ring-expansion reactions [23][24][25][26][27][28]. They have also proved to be precursors for densely functionalized cyclopropanes via ringretaining C-C [29][30][31][32][33][34][35][36][37] and C-heteroatom bond forming reactions to their exocyclic double bond.…”

Syntheses, structures and electrochemical properties of homoleptic ruthenium(III) and osmium(III) complexes bearing two tris(carbene)borate ligands

“…It is surprising that no ruthenium and osmium complex with the Ph[B(R-ImH) 3 ] ligand has been reported yet. In comparison, the chemistry of Ru and Os complexes with tris(pyrazolyl)borate (Tp) ligand (C, Chart 1) has been extensively studied [27][28][29][30][31][32][33][34].Herein we report the synthesis, structure, X-ray photoelectronic spectroscopy (XPS), and electrochemical properties of ruthenium(III) and osmium(III) complexes [PhB(ImMe) 3 ] 2 M(OTf) (M = Ru, 1a; M = Os, 1b) with two tris(carbene)borate ligands. To our knowledge, 1b is the first Os(III)-NHC complex and 1a is among a limited number of Ru(III)-NHC complexes reported in the literature [35].…”

“…It is surprising that no ruthenium and osmium complex with the Ph[B(R-ImH) 3 ] ligand has been reported yet. In comparison, the chemistry of Ru and Os complexes with tris(pyrazolyl)borate (Tp) ligand (C, Chart 1) has been extensively studied [27][28][29][30][31][32][33][34].…”