Carbon-chalcogen wires: alkynyltellurolatocarbynes

The reactions of [W(CBr)(CO)2(Tp*)] (Tp* = tris(dimethylpyrazolyl)borate) with LiTeCCR (R = SiMe3, SiiPr3, iPr, nBu, tBu, Ph, C6H4Me-4, methylimidazol-2-yl) afford the first alkynyltellurolatocarbynes [W(CTeCCR)(CO)2(Tp*)]. Both the WC and CC multiple bonds are prone to metal addition as exemplified by treatment with [MCl(SMe2)] (M = Cu, Au) to afford the hexametallic complex [W2Cu4(μ-CTeCCSiiPr3)2Cl4(CO)4(Tp*)2] and [WAu(μ-CTeCCSiMe3)Cl(CO)2-(Tp*)] which evolves to the unusual hypervalent [WAu(μ-CTeCl4)(SMe2)(CO)2(Tp*)].

Triiron Complex with N-Ferrocenyl Aminocarbyne Ligand Bridging a Diiron Core: DFT, Electrochemical, and Biological Insights

The first N-ferrocenyl aminocarbyne complex, [Fe2Cp2(CO)2(μ-CO){μ-CN(Me)(Fc)}]CF3SO3 ([2]CF3SO3), was synthesized with an 88% yield from [Fe2Cp2(CO)4], isocyanoferrocene (CNFc), and methyl triflate. The synthesis proceeded through the intermediate formation of [Fe2Cp2(CO)3(CNFc)], 1. Multinuclear NMR experiments revealed the presence of cis and trans isomers for [2]CF3SO3 in organic solvents, in agreement with DFT outcomes. Electrochemical and spectroelectrochemical studies demonstrated one reduction process occurring prevalently at the diiron core and one oxidation involving the ferrocenyl substituent. The oxidation process is expected to favor the redox activation of [2]+ in a biological environment. Both [2]CF3SO3 and its phenyl analogue [Fe2Cp2(CO)2(μ-CO){μ-CN(Me)(Ph)}]CF3SO3 ([3]CF3SO3), prepared for comparison, exerted moderate antiproliferative activity against the human cancer cell lines A431, HCT-15, PSN-1, 2008, and U1285. However, [2]CF3SO3 exhibited a higher cytotoxicity than [3]CF3SO3, showed a substantial ability to induce intracellular ROS production, and outperformed cisplatin in a three-dimensional SCLC cell model.

Poly(imidazolyliden-yl)borato Complexes of Tungsten: Mapping Steric vs. Electronic Features of Facially Coordinating Ligands

A convenient synthesis of [HB(HImMe)3](PF6)2 (ImMe = N-methylimidazolyl) is decribed. This salt serves in situ as a precursor to the tris(imidazolylidenyl)borate Li[HB(ImMe)3] pro-ligand upon deprotonation with nBuLi. Reaction with [W(≡CC6H4Me-4)(CO)2(pic)2(Br)] (pic = 4-picoline) affords the carbyne complex [W(≡CC6H4Me-4)(CO)2{HB(ImMe)3}]. Interrogation of experimental and computational data for this compound allow a ranking of familiar tripodal and facially coordinating ligands according to steric (percentage buried volume) and electronic (νCO) properties. The reaction of [W(≡CC6H4Me-4)(CO)2{HB(ImMe)3}] with [AuCl(SMe2)] affords the heterobimetallic semi-bridging carbyne complex [WAu(μ-CC6H4Me-4)(CO)2(Cl){HB(ImMe)3}].

Isonitrile μ2-carbido complexes

The μ-carbido complex [WPt(μ-C)Br(CO)2(PPh3)2(Tp*)] (Tp = hydrotris(dimethylpyrazolyl)borate) undergoes substitution of one phosphine ligand with isonitriles to afford complexes [WPt(μ-C)Br(CNR)(CO)2(PPh3)(Tp*)] (R = tBu, C6H3Me2-2,6, C6H2Me3-2,4,6). For aryl but not alkyl isocyanides disubstitution follows to afford [WPt(μ-C)Br(CNR)2(CO)2(Tp*)] (R = C6H2Me2-2,6, C6H2Me3-2,4,6). The bis(isonitrile) derivatives, including [WPt(μ-C)Br(CNtBu)2(CO)2(Tp*)], may also be prepared from the reactions of triangulo-[Pt3(CNR)6] with [W(CBr)(CO)2(Tp*)]. Bis- and tris(dimethylpyrazolyl)borate pro-ligand salts replace the bromide and one phosphine in [WPt(μ-C)Br(CNC6H2Me3)(CO)2(PPh3)(Tp*)] or the bromide and one isonitrile in [WPt(μ-C)Br(CNC6H2Me3)2(CO)2(Tp*)] to afford [WPt(μ-C)(CNC6H2Me3)(CO)2(Tp*)(L)] (L = κ2-Tp*, dihydrobis(pyrazolyl)borate). Structural, spectroscopic and computational data for the complexes are discussed to interrogate the nature of the WC-Pt carbido bridge by analogy with a range of other sp-C1 and sp-B1 ligands (CN, CCH, CP, CAs, CSb, CNO, BO, BNH and BCH2).

Heterobimetallic μ2-Halocarbyne complexes

The halocarbyne complexes [M(≡CX)(CO)2(Tp*)] (M = Mo, W; X = Cl, Br; Tp* = hydrotris(dimethylpyrazolyl)borate) react with [AuCl(SMe2)], [Pt(-H2C=CH2)(PPh3)2] or [Pt(nbe)3] (nbe = norbornene) to furnish rare examples of μ2-halocarbyne...

Symmetric and non-symmetric anthracen-diyl bis(alkylidynes)

Three examples of 9-bromo-10-(alkylidynyl)anthracenes, [W{CC(C₆H₄)₂CBr}(CO)₂(L)] (L = hydrotris(dimethylpyrazol-1-yl)borate Tp*, hydrotris(pyrazol-1-yl)borate Tp, hydrotris(2-mercapto-N-methylimidazol-1-yl)borate Tm) were prepared via modified Fischer-Mayr acyl oxide-abstraction protocols. With a sufficiently bulky ancillary ligand (L = Tp*) the aryl bromide is ammenable to cross-coupling reactions that enable more elaborate derivatives to be prepared. These including symmetric bis(alkylidynyl)anthracenes as well as non-palindromic examples bearing disparate metals and/or co-ligands. In contrast, these couplings fail for smaller ligands (L = Tp, Tm) where it was found that Pd⁰ or Pt⁰ were instead able to coordinate across two WC bonds to give trimetallic bow-tie complexes, [W₂M{μ-CC(C₆H₄)₂CBr}₂(CO)₄(L)₂] (M = Pd, Pt; L = Tp, Tm).

Tetrel and pnictogen functionalised propargylidynes

The reaction of [W([triple bond, length as m-dash]CC[triple bond, length as m-dash]CSiMe₃)(CO)₂(Tp*)] (Tp* = tris(dimethylpyrazolyl)borate) with AgNO₃ affords {[W([triple bond, length as m-dash]CC[triple bond, length as m-dash]CAg)-(CO)₂(Tp*)][AgNO₃]}_n while [Hg{C[triple bond, length as m-dash]CC[triple bond, length as m-dash]W(CO)₂(Tp*)}₂] with ⁿBuLi affords [W([triple bond, length as m-dash]CC[triple bond, length as m-dash]CLi)(CO)₂(Tp*)]. These anhydrous reagents allow the installation of main group elements (e.g., Si, Sn, Pb, P, As) as propargylidyne termini.

Heterobimetallic μ2-carbido complexes of platinum and tungsten

The tungsten–platinum μ-carbido complex [WPt(μ-C)Br(CO)₂(PPh₃)₂(Tp*)] (Tp* = hydrotris(dimethylpyrazol-1-yl)borate) undergoes facile substitution of both bromide and phosphine ligands to afford a diverse library of μ-carbido complexes.

Carbyne decorated porphyrins

Porphyrins peripherally decorated with four transition-metal carbynes substituents are obtained in one step via a Pd⁰/Au^I transmetallation shuttle beginning with a stannyl carbyne.

Metal coordination of phosphoniocarbynes

Heterobi- and tetrametallic phosphoniocarbyne bridged complexes arise from the reactions of the terminal phosphoniocarbyne [W(CPMe₂Ph)(CO)₂(Tp*)]PF₆ with unsaturated metal centres.

The significance of phosphoniocarbynes in halocarbyne cross-coupling reactions

Competent intermediates as well as productive and non-productive tangents have been identified in the catalytic cycle for palladium(0)–copper(i) mediated synthesis of propargylidynes via cross coupling reactions of bromocarbyne complexes with alkynes.