Bis(metallaethynyl) Ketones: Synthesis and Structure of {(Ph₃P)AuC≡C}₂CO and Attempted Transmetalation: Formation and Structure of [1,3-{Ru(dppe)Cp}₂{c-COC(OMe)CHCCH}]PF₆

Abstract

The bis(metallaethynyl) ketone {(Ph 3 P)AuCtC} 2 CO (1), obtained from (Me 3 SiCtC) 2 CO, AuCl(PPh 3 ), and NaOMe, forms an Au 3 3 3 Au-bonded dimer in the solid state (Au 3 3 3 Au = 2.9825(3) Å). The ES-MS contains ions [2M + X] + (X = Na, K, Au), but the lack of the ion [2M] + and NMR evidence suggest that the dimeric structure is not preserved in solution. Compound 1 reacts with RuCl(dppe)Cp to afford the unusual dimetal-substituted pyrylium complex [1,3-{Ru(dppe)Cp} 2 {c-COC(OMe)CHCCH}]PF 6 (2). The molecular structure of 2 is also reported, together with a proposed route for its formation.

Preparation of pyranylidene complexes of ruthenium

“…19 The pyran-2-ylidene ligand is bonded to the ruthenium metal with a Ru-C distance of 2.018(3) Å. This is shorter than the usual range for Ru-C(sp 2 ) single bonds [2.03-2.11 Å] 20,21 although slightly longer than that found for other Fischer-type carbene complexes. 22 The pyran-2-ylidene ring is essentially planar (rms of 0.016 Å).…”

Some Ruthenium Derivatives of Penta-1,4-diyn-3-one

“…It is likely that the presence of the electron-withdrawing ketone function deactivates the deprotected (HCC) 2 CO (which is also unstable under these reaction conditions) toward metalation. Transmetalation of (PPh 3 AuCC) 2 CO with RuCl(dppe)Cp was also examined, but this led to the formation of an unusual dimetal-substituted pyrylium complex, [1,3-{Ru(dppe)Cp} 2 { c -COC(OMe)CHCCH}]PF 6 , rather than the desired bimetallic complex {[Cp(dppe)Ru]CC} 2 CO.…”

“…The latter step is often achieved with K 2 Cr 2 O 7 or MnO 2 , exemplified in the syntheses of (Me 3 SiC≡C) 2 CO 2 and (FcC≡C) 2 CO. 3,4 Alternative approaches include reaction of an alkynoic chloride, RC≡CC(O)Cl with Me 3 SiC≡CC≡CSiMe 3 under Friedel-Crafts conditions to give RC≡CC(O)C≡CC≡CSiMe 3 , for example. [3][4][5] However, to the best of our knowledge, there are only three derivatives of the 'skipped diyne' penta-1,4-diyne-3-one which contain transition metals, namely FcC≡CC(O)C≡CSiPr i 3 , 2 (FcC≡C) 2 CO 3,4 and {(Ph 3 P)AuC≡C} 2 CO. 5 The range of complexes in which two metal-ligand fragments are linked by unsaturated bridges, particularly -(C≡C) x -chains, 6 has recently been expanded to include compounds in which other groups, including a third metal-ligand moiety, such as ferrocene and biferrocene, 7,8 Ru(dppe) 2 , 9 Ru 2 (DMBA) 4 (DMBA = N,N'-dimethylbenzamidinate), 10 C 2 Co 2 (CO) 2 (dppm), 11 Pd(PEt 3 ) 2 , 12 and Hg, 13 and also transition metal clusters, 14 have been inserted into the -conjugated pathway. There is much current interest in the electronic structures of these complexes, and both experimental and computational results suggest that the inserted group may act as an insulator or an amplifier, with respect to the extent of -conjugation between the metal end-groups.…”

“…A variety of synthetic routes to this material and derivatives are now known, with one common approach to bis(alkynyl) ketones involving reactions of a formic ester with alkynyllithium reagents, followed by oxidation of the resulting alcohols, (RCC) 2 CH(OH). The latter step is often achieved with K 2 Cr 2 O 7 or MnO 2 , exemplified in the syntheses of (Me 3 SiCC) 2 CO and (FcCC) 2 CO. , Alternative approaches include reaction of an alkynoic chloride, RCCC(O)Cl, with Me 3 SiCCCCSiMe 3 under Friedel–Crafts conditions to give RCCC(O)CCCCSiMe 3 , for example. − However, to the best of our knowledge, there are only three derivatives of the “skipped diyne” penta-1,4-diyn-3-one that contain transition metals, namely, FcCCC(O)CCSiPr i 3 , (FcCC) 2 CO, , and {(Ph 3 P)AuCC} 2 CO …”

Sonogashira-Like Coupling Reactions with Phosphine–Gold(I) Alkynyl Complexes

“…15 A protodesilylation of its trimethylsilyl-protected precursor 18 (shown in Scheme 8) followed by treatment with iodobenzene (19) under Sonogashira conditions has been carried out in the author's laboratory, but none of the desired Sonogashira coupling product was obtained. 16 However, converting 18 into the gold species 20 (isolated in high yield) 16,17 and employing this compound as a substrate in the Sonogashira coupling with 19 gave the desired product 21 (Scheme 8). Although the product is formed in only moderate yield (31% when using THF and Et 3 N as the solvent; 37% when using CH 2 Cl 2 as the solvent), this example shows the advantage of turning to gold(I) complexes when the terminal alkyne precursors are difficult to handle.…”