The First Structurally Characterized Metal Complex with the Molecular Unit M=C=C=C=CR2

Ruthenium−Aminoallenylidene Complexes from Butatrienylidene Intermediates via an Aza-Cope Rearrangement: Synthetic, Spectroscopic, Electrochemical, Spectroelectrochemical, and Computational Studies

“…The first consists of the activation of terminal alkynyl keto complexes {M}-CtCC(O)CHRR′ (or enol ethers thereof) with a formally OH-abstracting agent such as trifluoroacetic acid anhydride. 9,10 This method, as originally introduced by Selegue, 10 has ultimately rendered Cl(P i Pr 3 ) 2 IrdCdCdCdCPh 2 as the first stable butatrienylidene complex that also lends itself to structural characterization by X-ray methods. 9 This compound owes its stability to protection of the terminal sp 2 carbon by aryl substituents, which is also the key to stable pentatetraenylidene complexes.…”

“…9,10 This method, as originally introduced by Selegue, 10 has ultimately rendered Cl(P i Pr 3 ) 2 IrdCdCdCdCPh 2 as the first stable butatrienylidene complex that also lends itself to structural characterization by X-ray methods. 9 This compound owes its stability to protection of the terminal sp 2 carbon by aryl substituents, which is also the key to stable pentatetraenylidene complexes. 11 A more direct access route consists of the activation of terminal diynes by coordinatively unsaturated yet electron-rich transition-metal fragments.…”

“…In contrast, a secondary butatrienylidene complex derived from phenylbutadiyne is deprotonated by NEt 3 to give the phenylbutadiynyl complex, 14 while the tertiary butatrienylidene complex Cl(P i Pr 3 ) 2 IrdCdCdCdCPh 2 adds trifluoroacetic acid to the internal C 2 -C 3 double bond. 9 The high synthetic potential of the primary butatrienylidene intermediates is highlighted by their cycloaddition/cycloreversion sequences with aromatic imines, yielding 4-ethynylquinolidine or vinyl-substituted 1-azabuta-1,3-diene complexes, depending on the substituents on the imine. 12c,d We have already communicated an instance where the transient butenynyl complexes [Cl-(L 2 ) 2 Ru-CtCC(NMe 2 allyl)dCH 2 ] + , derived from amine addition to the respective butatrienylidene precursors (L 2 ) Ph 2 PCH 2 Ph 2 (dppm), Et 2 PC 2 H 4 PEt 2 (depe)), rearrange under very mild conditions via an Aza-Cope type process to the aminoallenylidene isomers [Cl(L 2 ) 2 Rud CdCdC(NMe 2 )C 4 H 7 ] + .…”

Closing the Gap between MC3 and MC5 Metallacumulenes: The Chemistry of the First Structurally Characterized Transition-Metal Complex with MdCdCdCdCR2 as the Molecular Unit

“…The unsuccessful attempts: Preparation of alkynyl(hydrido)-iridium(iii) and vinylideneiridium(i) complexes: Taking the structural analogy between the target molecule trans-[IrCl-(CCCCPh 2 )(PiPr 3 ) 2 ] (8) and the corresponding iridium allenylidenes trans-[IrCl(CCCR 2 )(PiPr 3 ) 2 ] into consideration, we initially attempted to prepare the IrC 4 complex by using the same methodology developed for the IrC 3 relatives. Since the C 3 ligand of the iridium allenylidenes was formed from propargylic alcohols HC CCR 2 (OH), for the synthesis of a compound with a homologous C 4 unit we had to find a starting material with an additional carbon atom in the C n chain.…”

Iridium(I)- und Iridium(III)-Komplexe mit Triisopropylarsan als Ligand

“…In den letzten Jahren haben wir in einer Reihe von Arbeiten gezeigt, dass das Moleku È lfragment [IrCl(PiPr 3 ) 2 ] ein ausgezeichnetes ¹Stu È tzkorsettª fu È r die Koordination so unterschiedlicher Liganden wie C 2 H 2 [1], C 2 H 4 [2], CPh 2 [3], C=CR 2 [4], C=C=CPh 2 [5], C=C=C=CPh 2 [6], C=C=C=C=CPh 2 [7] und N 2 [8] ist. Wir hatten in ju È ngster Zeit ebenfalls darauf hingewiesen, dass es Unterschiede in der Koordinationsfa È higkeit von PiPr 3 und SbiPr 3 In Abb.…”