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}].

Fluorocarbyne complexes via electrophilic fluorination of carbido ligands.

The new fluorocarbynes [M([triple bond, length as m-dash]CF)(CO)2(Tp*)] (M = Mo, W; Tp* = tris(dimethylpyrazolyl)borate) arise from electrophilic fluorination of the lithiocarbynes [M([triple bond, length as m-dash]CLi)(CO)2(Tp*)] with FN(SO2Ph)2. The reactions of [W([triple bond, length as m-dash]CF)(CO)2(Tp*)] with [AuCl(SMe2)] and PhICl2 afford the first µ2-fluorocarbyne complex [WAu(µ-CF)Cl(CO)2(Tp*)] and the first high oxidation state fluorocarbyne [W([triple bond, length as m-dash]CF)Cl2(Tp*)], respectively.

Access to and Reactivity of Fe0 , Fe-I , FeI , and FeII PCcarbene P Pincer Complexes.

Despite their promising metal-ligand cooperative reactivity, PCcarbene P pincer ligands are rarely reported for first-row transition-metal centres. Using a dehydration methodology, we report access to an Fe0 PCcarbene P pincer complex (1) that proceeds via an isolated α-hydroxylalkyl hydrido complex (3). Reversible carbonyl migration to the carbene position in 1 is found to allow coordination chemistry and E-H bond addition (E=H, B, Cl) across the iron-carbene linkage, representing a unique mechanism for metal-ligand cooperativity. The PCcarbene P pincer ligand is also found to stabilize formal FeII , FeI , and Fe-I oxidation states, as demonstrated with synthesis and characterization of the complexes [11-X][BArF 20 ] (X=Br, I), 12, and K[13]. Compound K[13] is found to be highly reactive, and abstracts hydrogen from a range of aliphatic C-H sources. Computational analysis by DFT suggests that the formal FeI and Fe-I complexes contain significant carbene radical character. The ability of the PCcarbene P ligand scaffold to partake in metal-ligand cooperativity and to support a range of iron oxidation states renders it as potentially useful in many catalytic applications.

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.

The significance of phosphoniocarbynes in halocarbyne cross-coupling reactions.

Competent intermediates in palladium(0)-copper(i) mediated catalytic cross coupling reactions of the bromocarbyne complex [W([triple bond, length as m-dash]CBr)(CO)2(Tp*)] (Tp* = hydrotris(dimethylpyrazolyl)borate) have been isolated however heterobimetallic phosphoniocarbyne complexes [WPd(µ-CPPh3)Br(CO)2(PPh3)x(Tp*)] are identified as productive (x = 1) or non-productive (x = 0) tangents to the catalytic cycle.

Dimetallapoly-yn-diylidynes: Ln M≡C-(C≡C)x -C≡MLn (x=0-4).

Synthetic routes to dimetallated Cx carbon wires in which two metals are separated by a linear carbon chain involving terminal metal-carbon triple bonds are described for the complexes [(Tp*)(CO)2 W≡C-(C≡C)n -C≡W(CO)2 (Tp*)] (Tp*=hydrotris(dimethylpyrazolyl)borate) where n=1, 3 or 4, joining the previously known examples with n=0, 1 and 2 to complete the series as models for linear carbyne C∞ .

Pentadiynylidyne and Pentacarbido Complexes.

The reaction of the halocarbyne [W(≡CBr)(CO)2 (Tp*)] (Tp*=hydrotris(3,5-dimethylpyrazol-1-yl)borate) with trimethylsilyl-butadiyne, mediated by [Pd(PPh3 )4 ] and CuI, affords the first pentadiynylidyne complex [W(≡CC≡CC≡CSiMe3 )(CO)2 (Tp*)]. Desilylation provides a general route to heterobimetallic pentacarbido complexes, including [(Tp*)(CO)2 W(µ-C5 )(PPh3 )2 Ru(η-C5 H5 )] and [(Ph3 P)2 (CO)HIr{(µ-C5 )W(CO)2 (Tp*)}2 ].

A [C1 + C2] route to propargylidyne complexes.

The reactions of [W([triple bond, length as m-dash]CBr)(CO)2(Tp*)] (Tp* = hydrotris(dimethylpyrazolyl)borate) with a range of terminal alkynes (RC[triple bond, length as m-dash]CH), mediated by [Pd(PPh3)4] and CuI, afford new proparylidynes [W([triple bond, length as m-dash]C-C[triple bond, length as m-dash]CR)(CO)2(Tp*)] [R = tBu, C6H4X (X = H, NH2, NO2), ferrocenyl, APh3 (A = C, Si, Ge), B(O2CCH2)2NMe]. Similar treatment of [W([triple bond, length as m-dash]CBr)(CO)2(Tp*)] with Ph2Si(C[triple bond, length as m-dash]CH)2 affords the ditungstaoctatetrayne [W2(µ-C6)(CO)4(Tp*)2] while the bimetallic complex [W2{µ-([triple bond, length as m-dash]CC[triple bond, length as m-dash]C)2SiPh2}(CO)4(Tp*)2], which is obtained from [W([triple bond, length as m-dash]CBr)(CO)2(Tp*)] and Ph2Si(C[triple bond, length as m-dash]CSnPh3)2, reacts with [AuCl(THT)] (THT = tetrahydrothiophene) to provide the tetrametallic complex [W2Au2{µ-([triple bond, length as m-dash]CC[triple bond, length as m-dash]C)2SiPh2}Cl2(CO)4(Tp*)2].

Confluence of disparate carbido chemistries: [WRuAu2(µ-C)2Cl2(CO)2(PCy3)2(Tp*)].

The reaction of [Ru(CAuCl)Cl2(PCy3)2] with [W([triple bond, length as m-dash]CSnnBu3)(CO)2(Tp*)] (obtained from [W([triple bond, length as m-dash]CBr)(CO)2(Tp*)], nBuLi and ClSnnBu3) affords the heterotetrametallic bis(carbido) complex [WRuAu2(µ-C)2Cl3(CO)2(PCy3)2(Tp*)] in which the two distinct µ-carbido ligands adopt linear and T-shaped geometry at carbon.

Synthesis and reactivity of selenium functionalised allylidynes and propargylidynes.

The reactions of the trimethylsilylpropargylidyne [W([triple bond, length as m-dash]CC[triple bond, length as m-dash]CSiMe3)(CO)2(Tp*)] (1: Tp* = hydrotris(dimethylpyrazolyl)borate) towards selenium centred reagents when treated with tetrabutylammonium fluoride (TBAF) were explored in order to prepare alkynylselenolato propargylidynes, e.g., [W([triple bond, length as m-dash]CC[triple bond, length as m-dash]CSePh)(CO)2(Tp*)]. Treating 1 with TBAF and PhSeSePh resulted in E and Z isomers of the vinylcarbyne (allylidyne) complex [W{[triple bond, length as m-dash]CC(SePh)[double bond, length as m-dash]CHSePh}(CO)2(Tp*)] in addition to traces of the trisubstituted derivative [W{[triple bond, length as m-dash]CC(SePh)[double bond, length as m-dash]C(SePh)2}(CO)2(Tp*)]. Reactions with PhSeCl resulted in the isolation of bimetallic bis-substituted allylidyne complex [(Tp*)(CO)2W[triple bond, length as m-dash]CC(SePh)[double bond, length as m-dash]C(SePh)C[triple bond, length as m-dash]CC[triple bond, length as m-dash]W(CO)2(CO)2(Tp*)] as well as the desired selenolatopropargylidyne [W([triple bond, length as m-dash]CC[triple bond, length as m-dash]CSePh)(CO)2(Tp*)].

Synthesis and reactivity of an anionic allenylidene complex.

The reaction of [W([triple bond, length as m-dash]CC[triple bond, length as m-dash]CSiMe3)(CO)2(Tp*)] (Tp* = hydrotris(dimethylpyrazolyl)borate) with MeLi generates the first example of an anionic allenylidene complex Li[W([double bond, length as m-dash]C[double bond, length as m-dash]C[double bond, length as m-dash]CMeSiMe3)(CO)2(Tp*)] which reacts with electrophiles (H+, Me+) at the ß-carbon to afford vinylcarbyne (allylidyne) complexes [W([triple bond, length as m-dash]CCE[double bond, length as m-dash]CMeSiMe3)(CO)2(Tp*)] (E = H, Me), and with bromine provides the unprecedented binuclear bis(carbyne) complex {C([double bond, length as m-dash]CMeSiMe3)C[triple bond, length as m-dash]W(CO)2(Tp*)}2via oxidative C-C coupling at the ß-carbon.

Bis(alkylidynyl)tellurides and ditellurides.

The tellurocarbonylates [M(CTe)(CO)2(Tp*)]- (M = Mo, W; obtained from [M([triple bond, length as m-dash]CBr)(CO)2(Tp*)] and Li2Te or [M([triple bond, length as m-dash]CLi)(CO)2(Tp*)] and Te) react with an additional equivalent of [M([triple bond, length as m-dash]CBr)(CO)2(Tp*)] to give bis(alkylidynyl)tellurides, [M2(µ-CTeC)(CO)4(Tp*)2], whilst oxidation with [Fe(η-C5H5)2]PF6 affords the corresponding ditellurides [M2(µ-CTe2C)(CO)4(Tp*)2]. The unprecedented M[triple bond, length as m-dash]CTeC[triple bond, length as m-dash]M and M[triple bond, length as m-dash]CTe2C[triple bond, length as m-dash]M bridges are discussed with reference to more conventional but rare alkylidynyltelluroethers [M([triple bond, length as m-dash]CTeR)(CO)2(Tp*)] (R = Me, nBu, Ph).