Metallorganische Lewis-Säuren

A Cyclopropenylidene Approach to Tricarbide Complexes: Synthesis and Structure of [M(CO)5{μ2-C3(OCH2CH3)}Fe(CO)2(Cp)] (M = Cr, Mo, W)

“…An X-ray crystal structure determination shows that 4 has a scalene C 3 ring with a chromium center, iron center, and ethoxide bound to the vertices (Figure ). The Cr−C ring distance, 2.066(3) Å, falls within the range of known chromium cyclopropenylidene complexes. ,, This bond length is appreciably shorter than a bond between Cr and a sp 2 -hybridized carbon (2.21 Å) and longer than those in most Fischer carbenes. Specifically, the Cr−C bond is longer than that in [Cr{C 3 (OCH 2 CH 3 ) 2 }(CO) 5 ] ( 1 , 2.010(7) Å) 18 but about the same as those in the less electron-rich complexes 7 and 8 (2.05(1) and 2.071(8) Å). , The trans Cr−CO bond is shorter than the cis Cr−CO bonds, thus indicating that the cyclopropenylidene group is a poor π-acceptor but a good σ-donor as seen in similar Fischer carbene complexes with strongly electron-donating substituents on the carbene ligand.…”

Carbon–Carbon Bond Formation at a Neutral Terminal Carbido Ligand: Generation of Cyclopropenylidene and Vinylidene Complexes

“…[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] [Ru(C)(H 2 IMes)(PCy 3 )Cl 2 ] (4; H 2 IMes = 4,5-dihydro-1,3-bis(mesityl)imidazol-2-ylidene) reacts similarly with DMAD, but the reaction is not clean since the product reacts further with DMAD before all of 4 has been consumed. Although 2 does not react with a variety of alkenes and alkynes (see the Supporting Information), it reacts cleanly with MeO 2 CC CCO 2 Me (dimethyl acetylenedicarboxylate, DMAD) over 4 h in C 6 H 6 .…”

“…[24] Figure 1 depicts a thermal ellipsoid plot of one of the two chemically equivalent but crystallographically independent molecules of 3 in the crystal. [9,[14][15][16][17][18][19][20][21][22][23] The formation of 3 from 2 is interesting because the cyclopropylidene complex [Ru{ = CC 2 H 2 (CO 2 Me) 2 }-(PCy 3 ) 2 Cl 2 ] (6) is not observed as an intermediate when 2 is formed from 1 by reaction with Feists ester. The cyclopropenylidene ring lies in the Cl-Ru-Cl plane.…”

“…The structure shows significant bond localization in the cyclopropenylidene fragment. [14][15][16][17][18][19][20][21][22][23] Unlike 1, 3 does not react appreciably with common olefins or alkynes, although under some conditions small amounts of 2 are formed, suggesting reversibility of the 2!3 transformation (see the Supporting Information). [9,[14][15][16][17][18][19][20][21][22][23] The formation of 3 from 2 is interesting because the cyclopropylidene complex [Ru{ = CC 2 H 2 (CO 2 Me) 2 }-(PCy 3 ) 2 Cl 2 ] (6) is not observed as an intermediate when 2 is formed from 1 by reaction with Feists ester.…”

Low-valent Organorhenium Compounds

“…Oxidation o f(87) with AgPF6 gives the dicationic butatrienediylidene complexes(89) 205. Dicarbide-carbonylrhenium complexes [(CO)5 Re-C=C-Re(CO)5 ] are not accessible f r o m [M 2 C 2 ] (M = Na, Li) and [Re(CO) 5 (FBF 3 )], and diiodoethyne and [Re(CO) 5 ]" gives only [ReI(CO) 5 ] and [Re 2 I 2 (CO) 8 ].…”