Reactions of cyano(alkynyl)ethenes with some alkynyl- and diynyl-ruthenium complexes

Reactions of Ru(CCPh)(PPh₃)₂Cp with (NC)₂CCR¹R² (R¹ = H, R² = CCSiPrⁱ₃8; R¹ = R² = CCPh 9) have given η³-butadienyl complexes Ru{η³-C[C(CN)₂]CPhCR¹R²}(PPh₃)Cp (11, 12), respectively, by formal [2 + 2]-cycloaddition of the alkynyl and alkene, followed by ring-opening of the resulting cyclobutenyl (not detected) and displacement of a PPh₃ ligand. Deprotection (tbaf) of 11 and subsequent reactions with RuCl(dppe)Cp and AuCl(PPh₃) afforded binuclear derivatives Ru{η³-C[C(CN)₂]CPhCHCC[ML_n]}(PPh₃)Cp [ML_n = Ru(dppe)Cp 19, Au(PPh₃) 20]. Reactions between 8 and Ru(CCCCR)(PP)Cp [PP = (PPh₃)₂, R = Ph, SiMe₃, SiPrⁱ₃; PP = dppe, R = Ph] gave η¹-dienynyl complexes Ru{CCC[C(CN)₂]CRCH[CC(SiPrⁱ₃)]}(PP)Cp (15-18), respectively, in reactions not involving phosphine ligand displacement. The phthalodinitrile C₆H(CCSiMe₃)(CN)₂(NH₂)(SiMe₃) 10 was obtained serendipitously from (Me₃SiCC)₂CO and CH₂(CN)₂, as shown by an XRD structure determination. The XRD structures of precursor 7 and adducts 11, 12 and 17 are also reported.     

Synthesis of di-, tri- and tetranuclear platinum(II) and copper(I) acetylide complexes

Heterobimetallic {cis-[Pt](μ-σ,π-CCPh)₂}[Cu(NCMe)]BF₄ (3a: [Pt] = (bipy)Pt, bipy = 2,2′-bipyridine; 3b: [Pt] = (bipy′)Pt, bipy′ = 4,4′-dimethyl-2,2′-bipyridine) is accessible by the reaction of cis-[Pt](CCPh)₂ (1a: [Pt] = (bipy)Pt, 1b: [Pt] = (bipy′)Pt]) with [Cu(NCMe)₄]BF₄ (2). Substitution of NCMe by PPh₃ (4) can be realized by the reaction of 3a with 4, whereby [{cis-[Pt](μ-σ,π-CCPh)₂}Cu(PPh₃)]BF₄ (5) is formed. On prolonged stirring of 3 and 5, respectively, NCMe and PPh₃ are eliminated and tetrametallic {[{cis-[Pt](η²-CCPh)₂}Cu]₂}(BF₄)₂ (6) is produced. Addition of an excess of NCMe to 6 gives heterobimetallic 3a.When instead of NCMe or PPh₃ chelating molecules such as bipy (7) are reacted with 3a then the heterobimetallic π-tweezer molecule [{cis-[Pt](μ-σ,π-CCPh)₂}Cu(bipy)]BF₄ (8) is formed. Treatment of 8 with another equivalent of 7 produced [Cu(bipy₂)]BF₄ (9) along with [Pt](CCPh)₂. However, when 3b is reacted with 1b in a 1:1 molar ratio then 10 and 11 of general composition [{[Pt](CCPh)₂}₂Cu]BF₄ are formed. These species are isomers and only differ in the binding of the PhCC units to copper(I). A possible mechanism for the formation of 10 and 11 is presented.The solid state structures of 6, 10 and 11 are reported. In 11 the [{cis-[Pt](μ-σ,π-CCPh)₂}₂Cu]⁺ building block is set-up by two nearly orthogonal positioned bis(alkynyl) platinum units which are connected by a Cu(I) ion, whereby the four carbon-carbon triple bonds are unsymmetrical coordinated to Cu(I). In trimetallic 10 two cis-[Pt](CCPh)₂ units are bridged by a copper(I) center, however, only one of the two PhCC ligands of individual cis-[Pt](CCPh)₂ fragments is η²-coordinated to Cu(I) giving rise to the formation of a [(η²-CCPh)₂Cu]⁺ moiety with a linear alkyne-copper-alkyne arrangement (alkyne = midpoint of the CC triple bond). In 6 two almost parallel oriented [Pt](CCPh)₂ planes are linked by two copper(I) ions, whereby two individual PhCC units, one associated with each Pt building block, are symmetrically π-coordinated to Cu.     

Some complexes containing carbon chains end-capped by M(CO)2Tp′ [M = Mo, W; Tp′ = HB(pz)3, HB(dmpz)3] groups

Complexes M(CCCSiMe₃)(CO)₂Tp′ (Tp′ = Tp [HB(pz)₃], M = Mo 2, W 4; Tp′ = Tp^∗ [HB(dmpz)₃], M = Mo 3) are obtained from M(CCCSiMe₃)(O₂CCF₃)(CO)₂(tmeda) (1) and K[Tp′].Reactions of 2 or 4 with AuCl(PPh₃)/K₂CO₃ in MeOH afforded M{CCCAu(PPh₃)}(CO)₂Tp′ (M = Mo 5, W 6) containing C₃ chains linking the Group 6 metal and gold centres.In turn, the gold complexes react with Co₃(μ₃-CBr)(μ-dppm)(CO)₇ to give the C₄-bridged {Tp(OC)₂M}CCCC{Co₃(μ-dppm)(CO)₇} (M = Mo 7, W 8), while Mo(CBr)(CO)₂Tp^∗ and Co₃{μ₃-C(CC)₂Au(PPh₃)}(μ-dppm)(CO)₇ give {Tp^∗(OC)₂Mo}C(CC)₂C{Co₃(μ-dppm)(CO)₇} (9) via a phosphine-gold(I) halide elimination reaction. The C₃ complexes Tp′(OC)₂MCCCRu(dppe)Cp^∗ (Tp′ = Tp, M = Mo 10, W 11; Tp′ = Tp^∗, M = Mo 12) were obtained from 2-4 and RuCl(dppe)Cp^∗ via KF-induced metalla-desilylation reactions. Reactions between Mo(CBr)(CO)₂Tp^∗ and Ru{(CC)_nAu(PPh₃)}(dppe)Cp^∗ (n = 2, 3) afforded {Tp^∗(OC)₂Mo}C(CC)_n{Ru(dppe)Cp^∗} (n = 2 13, 3 14), containing C₅ and C₇ chains, respectively. Single-crystal X-ray structure determinations of 1, 2, 7, 8, 9 and 12 are reported.     

Preparation of imine complexes of ruthenium and osmium stabilised by [MCl(η -p-cymene)(PR3)] fragments

Imine complexes [MCl(η ⁶-p-cymene){η¹-NHC(H)Ar}(PR₃)]BPh₄ (1-3) [M = Ru, Os; PR₃ = PPh(OEt)₂, PPh₂OEt; Ar = Ph, p-tolyl] were prepared by reacting MCl₂(η ⁶-p-cymene)(PR₃) precursors with benzyl azide ArCH₂N₃ in the presence of NaBPh₄. Benzophenone-imine complexes [MCl(η ⁶-p-cymene){η¹-NHCPh₂}(PR₃)]BPh₄ (4-6) [M = Ru, Os; PR₃ = PPh(OEt)₂, PPh₂OEt] were also prepared by allowing MCl₂(η ⁶-p-cymene)(PR₃) to react with Ph₂CNH in the presence of NaBPh₄. The complexes were characterised spectroscopically (IR, ¹H, ¹³C, ³¹P, ¹⁵N NMR) and by X-ray crystal structure determination of [RuCl(η ⁶-p-cymene){η¹-NHC(H)-p-tolyl}{PPh(OEt)₂}]BPh₄ (1b).     

Syntheses and molecular structures of some compounds containing many-atom chains end-capped by tricobalt carbonyl clusters

Several complexes containing Co₃ carbonyl clusters end-capping carbon chains of various lengths are described. Pd(0)/Cu(I)-catalysed reactions between {Co₃{μ₃-C(CC)₂Au(PPh₃)}(μ-dppm)(CO)₇ and I(CC)₂SiMe₃ or FcCCI gave {Co₃{μ₃-C(CC)_xR}(μ-dppm)(CO)₇ [x = 4, R = SiMe₃3; x = 3, R = Fc 8]; treatment of 3 with NaOMe and AuCl(PPh₃) gave 4 [x = 4, R = Au(PPh₃)]. Related preparations of Co₃{μ₃-C(CC)₂[Ru(PP)Cp′]}(μ-dppm)_n(CO)_9−2n [PP = (PPh₃)₂, Cp’ = Cp, n = 1, 5; PP = dppe, Cp′ = Cp^∗, n = 1, 6; 0, 7] are also described. Syntheses of bis-cluster complexes {Co₃(μ-dppm)(CO)₇}₂(μ-C_x) (x = 14, 12; 16, 9; 18, 11; 26, 10) - the latter being the longest cluster-capped C_x chains so far described - and the mercury-bridged compounds Hg{(CC)_xC[Co₃(μ-dppm)(CO)₇]}₂ (x = 1, 13; 2, 14) are reported. The molecular structures of 7, 12, 13 and 14, as well as of Co₃(μ₃-CCCSiMe₃)(μ-dppm)(CO)₆(PPh₃) (15) and Co₃{μ₃-CC(O)OEt}(μ-dppm)(CO)₇ (16), are reported.     

Some ruthenium complexes containing cyanocarbon ligands: syntheses, structures and extent of electronic communication in binuclear systems

The preparation of several ruthenium complexes containing cyanocarbon anions is reported. Deprotonation (KOBu^t) of [Ru(NCCH₂CN)(PPh₃)₂Cp]PF₆ (1) gives Ru{NCCH(CN)}(PPh₃)₂Cp (2), which adds a second [Ru(PPh₃)₂Cp]⁺ unit to give [{Ru(PPh₃)₂Cp}₂(μ-NCCHCN)]⁺ (3). Attempted deprotonation of the latter to give the μ-NCCCN complex was unsuccessful. Similar chemistry with tricyanomethanide anion gives Ru{NCC(CN)₂}(PPh₃)₂Cp (4) and [{Ru(PPh₃)₂Cp}₂{μ-NCC(CN)CN}]PF₆ (5), and with pentacyanopropenide, Ru{NCC(CN)C(CN)C(CN)₂}(PPh₃)₂Cp (6) and [{Ru(PPh₃)₂Cp}₂{μ-NCC(CN)C(CN)C(CN)CN}]PF₆ (7). The Ru(dppe)Cp* analogues of 6 and 7 (8 and 9) were also prepared. Thermolysis of 6 (refluxing toluene, 12 h) results in loss of PPh₃ and formation of the binuclear cyclic complex {Ru(PPh₃)Cp[μ-NC{C(CN)C(CN)₂}CN]}₂ (10). The solid-state structures of 2-4 and 8-10 have been determined and the nature of the isomers shown to be present in solutions of the binuclear cations 7 and 9 by NMR studies has been probed using Hartree-Fock and density functional theory.     

On the reactivity of [IrCl(N2)(PPh3)2] with alkynylsilanes - A new route to vinylidene iridium(I) complexes

The iridium dinitrogen complex [IrCl(N₂)(PPh₃)₂] (1) was found to react with alkynylsilanes to form the vinylidene iridium(I) complexes trans- (R/R′ = Ph/Me, 2; Me/Me, 3; Bn/Me, 4; SiMe₃/Me, 5; SiEt₃/Et, 6; ⁱPr/Me, 7) and with Me₃SiCCC(O)R to yield the iridium η²-alkyne complexes trans-[IrCl{η²-Me₃SiCCC(O)R}(PPh₃)₂] (R = OEt, 9; Me, 11). Complex 9 was found to isomerize upon heating or upon UV irradiation yielding the vinylidene complex trans-[IrCl{CC(SiMe₃)CO₂Et}(PPh₃)₂] (10). The reaction of 1 with Me₃SiCCCCSiMe₃ yielded the complex trans-[IrCl{CC(SiMe₃)CCSiMe₃}(PPh₃)₂] (8), whereas with MeO₂CCCCO₂Me the iridacyclopentadiene complex [Ir{C₄(CO₂Me)₄}Cl(PPh₃)₂] (13) was formed. The complexes were characterized by means of ¹H, ¹³C and ³¹P NMR spectroscopy as well as by IR spectroscopy and microanalysis.     

Nickel(II) bis(diphenylphosphino)amide: Redox-coupling of dppa ligands in coordination sphere of Ni and some other properties

The reactions of Ni^II[(PPh₂)₂N]₂ (2) with various reagents are described. Addition of two moles of carbon monoxide to 2, at 20 °C and atmospheric pressure leads to the redox coupling of dppa ligands and formation of zero-valent nickel complex (CO)₂Ni(Ph₂PNPPh₂PPh₂NPPh₂) (4). The nickel atom in 4 has a tetrahedral coordination and is incorporated into the NiP₄N₂ ring adopting a distorted chair conformation with phosphorus-phosphorus bond length 2.2777(5) Å. Contrary to CO, sulphur dioxide reacts with 2 to form simple adduct (SO₂)Ni^II[(PPh₂)₂N]₂. The reaction of 2 with allyl bromide runs as alkylation of dppa ligand to form All-N(PPh₂)₂NiBr₂. The reduction of 2 with metallic sodium in THF gives Ni(0) complex, HN(PPh₂)₂Ni(Ph₃P)₂ (7). The electrochemical reduction of 2 in CH₂Cl₂ takes place in two steps: reversible one-electron and quasi-reversible three-electron step.     

The synthesis and single-crystal X-ray structures of palladium(II) and platinum(II) complexes of the difluorovinyl and 1-chloro-2-fluorovinyl-substituted phosphines, PPh2(Z-CFCFH) and PPh2(E-CClCFH)

The coordination chemistry of the fluorovinyl substituted phosphines PPh₂(Z-CFCFH) and PPh₂(E-CClCFH) with K₂MX₄ (M = Pd, Pt; X = Cl, Br, and I) salts has been investigated resulting in the first reported palladium(II) and platinum(II) complexes of phosphines containing partially fluorinated vinyl groups. The complexes have been characterised by a combination of multinuclear [¹H, ¹³C{¹H}, ¹⁹F, ³¹P{¹H}] NMR spectroscopy, and IR/Raman spectroscopy. The single-crystal X-ray structures of trans-[PdX₂{PPh₂(CFCFH)}₂], X = Cl (1), Br (2), I (3), trans-[PdCl₂{PPh₂(CClCFH)}₂] (4), cis-[PtX₂{PPh₂(CFCFH)}₂], X = Cl (5), Br (6), trans-[PtI₂{PPh₂(CFCFH)}₂] (7), and both cis- and trans-[PtCl₂{PPh₂(CClCFH)}₂] (8), have been determined. Results obtained from spectroscopic and crystallographic data suggest that replacement of a β-fluorine by hydrogen, whilst reducing the steric demand of the ligand, has little effect on the electronic character of the ligand. The presence of a proton in the vinyl group results in short proton-halide secondary interactions in the solid state (d(H?X) = 2.72(3) for 1, and 2.92(5) Å for 2) forming an infinite chain ribbon motif.     

Syntheses and molecular structures of some phosphine-gold(I) derivatives of 1,3-diynes

The syntheses of several diynylgold(I) phosphine complexes, including Au(CCCCH){P(tol)₃} (1), Au(CCCCSiMe₃)(PR₃) (R = Ph 2-Ph, tol 2-tol), Au(CCCCFc)(PPh₃) (3), {(tol)₃P}Au(CC)_nAu{P(tol)₃} [n = 2 (4), 3 (6), 4 (7)], {(Ph₃P)Au}CCCC{Au[P(tol)₃]} (5), [ppn][Au{CCCCAu[P(tol)₃]}₂] (8), [Au₂(μ-I)(μ-dppm)₂][Au(CCCCSiMe₃)₂] (9), Hg{CCCCAu(PR₃)}₂ (R = Ph 10-Ph, tol 10-tol) and {(triphos)Cu}CCCC{Au[P(tol)₃]} (11) are described. Of these, the X-ray molecular structures of 1, 2-tol, 3, 4 and 9 have been determined.     

Heterotrimetallic and heterotetrametallic transition metal complexes

The synthesis of the ruthenium σ-acetylides (η⁵-C₅H₅)L₂Ru-CC-bipy (4a, L = PPh₃; 4b, L₂ = dppf; bipy = 2,2′-bipyridine-5-yl; dppf = 1,1′-bis(diphenylphosphino)ferrocene) is possible by the reaction of [(η⁵-C₅H₅)L₂RuCl] (1) with 5-ethynyl-2,2′-bipyridine (2a) in the presence of NH₄PF₆ followed by deprotonation with DBU. Heterobimetallic Fc-CC-NCN-Pt-CC-R (10a, R = bipy; 10b, R = C₅H₄N-4; Fc = (η⁵-C₅H₅)(η⁵-C₅H₄)Fe; NCN = [1,4-C₆H₂(CH₂NMe₂)₂-2,6]⁻) is accessible by the metathesis of Fc-CC-NCN-PtCl (9) with lithium acetylides LiCC-R (2a, R = bipy; 2b, R = C₅H₄N-4).The complexation behavior of 4a and 4b was investigated.Treatment of these molecules with [MnBr(CO)₅] (13) and {[Ti](μ-σ,π-CCSiMe₃)₂}MX (15a, MX = Cu(NCMe)PF₆; 15b, MX = Cu(NCMe)BF₄; 16, MX = AgOClO₃; [Ti] = (η⁵-C₅H₄SiMe₃)₂Ti), respectively, gave the heteromultimetallic transition metal complexes (η⁵- C₅H₅)L₂Ru-CC-bipy[Mn(CO)₃Br] (14a: L = PPh₃; 14b: L₂ = dppf) and [(η⁵-C₅H₅)L₂Ru-CC-bipy{[Ti](μ-σ,π-CCSiMe₃)₂}M]X (17a: L = PPh₃, M = Cu, X = BF₄; 17b: L₂ = dppf, M = Cu, X = PF₆; 18a: L = PPh₃, M = Ag, X = ClO₄; 18b: L₂ = dppf, M = Ag, X = ClO₄) in which the appropriate transition metals are bridged by carbon-rich connectivities.The solid-state structures of 4b, 10b, 12 and 17b are reported. The main structural feature of 10b is the square-planar-surrounded platinum(II) ion and its linear arrangement. In complex 12 the N-atom of the pendant pyridine unit coordinates to a [mer,trans-(NN′N)RuCl₂] (NN′N = 2,6-bis-[(dimethylamino)methyl]pyridine) complex fragment, resulting in a distorted octahedral environment at the Ru(II) centre. In 4b a 1,1′-bis(diphenylphosphino)ferrocene building block is coordinated to a cyclopentadienylruthenium-σ-acetylide fragment. Heterotetrametallic 17b contains a (η⁵-C₅H₅)(dppf)Ru-CC-bipy unit, the bipyridine entity of which is chelate-bonded to [{[Ti](μ-σ,π-CCSiMe₃)₂}Cu]⁺. Within this arrangement copper(I) is tetra-coordinated and hence, possesses a pseudo-tetrahedral coordination sphere.The electrochemical behavior of 4, 10b, 12, 17 and 18 is discussed. As typical for these molecules, reversible oxidation processes are found for the iron(II) and ruthenium(II) ions. The attachment of copper(I) or silver(I) building blocks at the bipyridine moiety as given in complexes 17 and 18 complicates the oxidation of ruthenium and consequently the reduction of the group-11 metals is made more difficult, indicating an interaction over the organic bridging units.The above described complexes add to the so far only less investigated class of compounds of heteromultimetallic carbon-rich transition metal compounds.     

Linear homobimetallic palladium complexes

The oxidative addition of C₆H₄-1,4-I₂ (1) to Pd(PPh₃)₄ (2) gives mononuclear trans-(Ph₃P)₂Pd(C₆H₄-4-I)(I) (3), which can be converted to trans-(Ph₃P)₂Pd(C₆H₄-4-I)(OTf) (5) by its reaction with [AgOTf] (4). Complex 5 can be used in the high-yield preparation of a series of unique cationic mono- and dinuclear palladium complexes of structural type [trans-(Ph₃P)₂Pd(C₆H₄-4-I)(L)]⁺ (7, L = C₄H₄N₂; 9a, L = C₅H₄N-4-CN; 9b, L = NC-4-C₅H₄N) and [trans-(C₆H₄-4-I)(Ph₃P)₂Pd ← N^∩N → Pd(PPh₃)₂(C₆H₄-4-I)]²⁺ (14a, N^∩N = C₆H₄-1,4-(CN)₂; 14b, N^∩N = (C₆H₄-4-CN)₂; 14c, N^∩N = 4,4′-bipyridine (=bipy)). Complexes 7, 9 and 14 rearrange in solution to give [trans-(Ph₃P)₂Pd(C₆H₄-4-PPh₃)(L)]²⁺ (10, L = C₄H₄N₂; 12a, L = C₅H₄N-4-CN; 12b, L = NC-4-C₅H₄N) and [trans-(C₆H₄-4-PPh₃)(Ph₃P)₂Pd ← N^∩N → Pd(PPh₃)₂(C₆H₄-4-PPh₃)]⁴⁺ (15a, N^∩N = C₆H₄-1,4-(CN)₂; 15b, N^∩N = (C₆H₄-4-CN)₂) along with {[(Ph₃P)₂(Ph₃P-4-C₆H₄)Pd(μ-I)]₂}²⁺ (11).The solid state structures of 3, 9a, 10, 11 and 15b are reported. Most characteristic for all complexes is the square-planar coordination geometry of palladium with trans-positioned PPh₃ ligands. In 3 the iodide and the 4-iodo-benzene are linear oriented laying with the palladium atom on a crystallographic C₂ axes. In 9a this symmetry is broken by steric interactions of the PPh₃ ligands with the 4-cyanopyridine and 4-iodobenzene groups. Compound 11 contains two μ-bridging iodides with different Pd-I separations showing that the ligand induces a stronger trans-influence than PPh₃. In 15b, the Ph₃PC₆H₄Pd ← NCC₆H₄C₆H₄CN → PdC₆H₄PPh₃ building block is rigid-rod structured with the C₆H₄ units perpendicular oriented to the Pd coordination plane, while the biphenylene connecting moiety is in-plane bound.     

Dimerisation and reactivity of HCCCCFc at ruthenium centres

In contrast to the simple diynyl complexes formed in reactions between HCCCCFc and MCl(dppe)Cp∗; (M = Fe, Ru), an analogous reaction with RuCl(PPh₃)₂Cp∗; in the presence of KPF₆ and dbu resulted in dimerisation of the diyne at the Ru centre to afford a mixture of [Ru{η¹,η²-C(CCFc)C(L)CHCCCHFc}(PPh₃)Cp∗]PF₆ (L = dbu 1, PPh₃2). Similar reactions with RuCl(PR₃)₂L gave [Ru{η¹,η²-C(CCFc)C(dbu)CHCCCHFc}(PR₃)L]PF₆ (L = Cp, R = Ph 3, m-tol 4; L = η⁵-C₉H₇, R = Ph 5). The reaction between 3 and I₂, followed by crystallization of the paramagnetic product from MeOH, afforded the dicationic [Ru{C(CCFc)C(dbu)CHC(OMe)C(OMe)CHFc}(PPh₃)Cp](I₃)₂6. The molecular structures of 2·2CH₂Cl₂ and 6.S (S = 2CH₂Cl₂, C₆H₆) were determined by single-crystal XRD studies.     

Reaction of metal carbonyl anions with electrophilic alkynes: Synthesis of isomeric η-acryloyl and σ-vinyl complexes

Treatment of the metal carbonylate anions [CpMo(CO)₂(L)]⁻ (Cp = η-C₅H₅; L = PPh₂Me, PPh₂Et) with the electrophilic alkynes methyl propiolate or DMAD (RCCCO₂Me, where R = H or CO₂Me, respectively) followed by protonation affords the η³-acryloyl (1-oxoallyl) complexes [CpMo(η³-COCRCHCO₂Me)(CO)(L)] (3a-d) as the major products, together with the isomeric vinyl complexes trans-[CpMo(CRCHCO₂Me)(CO)₂(L)] (4a-d). On the basis of the regioselectivity of the reaction, it is proposed that nucleophilic attack of the carbonylate anion occurs at the alkyne carbon bearing R; migration of the anionic vinyl ligand to a CO followed by protonation gives 3, whereas protonation without insertion gives 4. The X-ray structures of the acryloyl complex [CpMo(η³-COCHCHCO₂Me)(CO)(PPh₂Me)] (3b) and its vinyl isomer [CpMo(σ-CHCHCO₂Me)(CO)₂(PPh₂Me)] (4b) have been determined.     

Cyclometallated thiosemicarbazone palladium(II) compounds: The first crystal and molecular structures of mononuclear complexes with a η-diphosphine ligand

Treatment of the thiosemicarbazones 2-XC₆H₄C(Me)NN(H)C(S)NHR (R = Me, X = F, a; R = Et, X = F, b; R = Me, X = Cl, c; R = Et, X = Br, d) with potassium tetrachloropalladate(II) in ethanol, lithium tetrachloropalladate(II) in methanol or palladium(II) acetate in acetic acid, as appropriate, gave the tetranuclear cyclometallated complexes [Pd{2-XC₆H₃C(Me)NNC(S)NHR}]₄ (1a-1d). Reaction of 1a-1d with the diphosphines Ph₂PCH₂PPh₂ (dppm), Ph₂P(CH₂)₂PPh₂ (dppe), Ph₂P(CH₂)₃PPh₂ (dppp) or trans-Ph₂PCHCHPPh₂ (trans-dpe) in 1:2 molar ratio gave the dinuclear cyclometallated complexes [{Pd[2-XC₆H₃C(Me)NNC(S)-NHR]}₂(μ-diphosphine-P,P)] (2a-5a, 3b, 3d, 4c, 5c). Reaction of 1a, 1b with the short-bite or long-bite diphosphines, dppm or cis-dpe, in a 1:4 molar ratio gave the mononuclear cyclometallated complexes [Pd{2-XC₆H₃C(Me)NNC(S)NHR}(diphosphine-P)] (6a, 6b, 7a). The molecular structure of ligand a and of complexes 1a, 3d, 5a, 5c, 6a, 6b and 7a have been determined by X-ray diffraction analysis. The structure of complex 7a shows that the long-bite cis-bis(diphenylphosphino)ethene phosphine appears as monodentate with an uncoordinated phosphorus donor atom.     

Luminescent rhenium(I)-gold(I) hetero organometallics linked by ethynylphenanthrolines

The first luminescent rhenium(I)-gold(I) hetero organometallics, Re{phenAu(PPh₃)}(CO)₃Cl (3) and Re{(PPh₃)AuphenAu(PPh₃)}(CO)₃Cl (4), have been prepared using the gold(I) complex AuCl(PPh₃) (PPh₃ = triphenylphosphine) and the novel rhenium(I) complexes Re(phenH)(CO)₃Cl (5) (phenH = 3-ethynyl-1,10-phenanthroline) or Re(HphenH)(CO)₃Cl (6) (HphenH = 3,8-bis(ethynyl)-1,10-phenanthroline). All the present rhenium(I) complexes 3-6 were revealed to possess a facial configuration (fac-isomer) with respect to the three carbonyl ligands. The main frameworks for these new gold(I) organometallics were constructed by the Au-C σ-bonding (with the η¹-type coordination) between the ethynylphenanthrolines and the Au(I) phosphine unit. Re(I)-Au(I) heterometallics 3 and 4 have shown single phosphorescence from the ³MLCT excited state and this observation can be interpreted in terms of the efficient intramolecular energy transfer from the Au(I) unit to the Re(I) unit.     

The reactions of some σ-alkynylnickel complexes with 7,7,8,8-tetracyanoquinodimethane

The σ-alkynyl complexes Ni(η⁵-C₅H₅)(PPh₃)-CC-R (1), Ni(η⁵-C₅H₅)(PPh₃)-CC-X-CCH (2) and Ni(η⁵-C₅H₅)(PPh₃)-CC-X-CC-Ni(η⁵-C₅H₅)(PPh₃) (3), reactwith 7,7,8,8-tetracyanoquinodimethane, TCNQ, at 30 °C by insertion of the alkyne CC into a CC(CN)₂ bond to give Ni(η⁵-C₅H₅)(PPh₃)-C{C₆H₄C(CN)₂}-C{C(CN)₂}-R (4), from 1, Ni(η⁵-C₅H₅)(PPh₃)-C{C₆H₄C(CN)₂}-C{C(CN)₂}-X-CCH (5), from 2, and Ni(η⁵-C₅H₅)(PPh₃)-C{C₆H₄C(CN)₂}-C{C(CN)₂}-X-CC-Ni(η⁵-C₅H₅)(PPh₃) (6),and Ni(η⁵-C₅H₅)(PPh₃)-C{C₆H₄C(CN)₂}- C{C(CN)₂}-X-C{C(CN)₂}-C{C₆H₄C(CN)₂}-Ni(η⁵-C₅H₅)(PPh₃) (7),from 3 {R = (a) C₆H₅, (b) 4-PhC₆H₄, (c) 4-Me₂NC₆H₄, (d) 1-C₁₀H₇ (1-naphthyl), (e) 2-C₁₀H₇ (2-naphthyl), (f) 9-C₁₄H₉ (9-phenanthryl), (g) 9-C₁₄H₉ (9-anthryl), (h) 3-C₁₆H₉ (3-pyrenyl), (i) 1-C₂₀H₁₁ (1-perylenyl), (j) 2-C₄H₃S (2-thienyl), (k) C₁₀H₉Fe (ferrocenyl = Fc) and (l) H; X = (a) nothing, (b) 1,4-C₆H₄, (c) 1,3-C₆H₄ and (d) 4,4′-C₆H₄-C₆H₄}. The reaction is regiospecificand the other possible insertion product, R-C{C₆H₄C(CN)₂}-C{C(CN)₂}-Ni(η⁵-C₅H₅)(PPh₃) etc., is not formed. Under the same conditions, there is no evidencefor the reaction of TCNQ with the -CCH of 2, PhCCH, 1,4-C₆H₄(CCH)₂ or FcCCH, or for the reaction of more than one CC(CN)₂ of TCNQ with a Ni-alkynyl moiety. Complexes 4-7 are all air-stable, purple solids which have been characterised by elemental analysis and spectroscopy (IR, UV-Vis, ¹H NMR and ¹³C NMR),and by X-ray diffraction for 4a, 4b and 4l. The UV-Vis spectra of 4-7 are very similar. This implies that all contain the same active chromophore which, it is suggested, is Ni-C(5)C₆H₄C(CN)₂ and not R-C(4)C(CN)₂. This isconsistent with the molecular structures of 4a, 4b and 4l which show that the first of these potentially chromophoric fragments is planar or close to it with an in-built potential for delocalisation, whilst in the second the aryl group R is almost orthogonal to the CC(CN)₂ plane. The molecular structures of 4a, 4b and 4l also reveal a short Ni?C(4) separation, indicative of a Ni → C(4) donor-acceptor interaction. The electrochemistry of 4a shows aquasi reversible oxidation at ca. 1 V and complicated reduction processes. It is typical of most 4, but 4l is different in that it shows the same quasi reversible oxidation at ca. 1 V but two reversible reductions at −0.26 and −0.47 V (vs. [Fe(η⁵-C₅Me₅)₂]^+/0 0.0 V).     

Reactivity of silyl-substituted heterobimetallic iron-platinum hydride complexes towards unsaturated molecules: Part II. Insertion of trifluoropropyne and hexafluorobutyne into the platinum-hydride bond

Insertion of hexafluorobutyne into the Pt-H bond of the heterobimetallic complexes [(OC)₃Fe{Si(OMe)₃}(μ-Ph₂PXPPh₂)Pt(H)(PPh₃)] (1a X = CH₂; 1b X = NH) yields the σ-alkenyl complexes [(OC)₃Fe{μ-Si(OMe)₂(OMe)}(μ-Ph₂PXPPh₂)Pt{C(CF₃)C(H)CF₃}] (3a X = CH₂; 3b X = NH). This insertion reaction is accompanied by dissociation of the platinum bound PPh₃ ligand and saturation of the vacant coordination site by a dative μ−η²-Si-O → Pt interaction. Addition of the Pt-H bond of 1a across the triple bond of 3,3,3-trifluoropropyne affords in a regiospecific manner [(OC)₃Fe{μ-Si(OMe)₂(OMe)}(μ-dppm)Pt{C(CF₃)CH₂}] (2) having the trifluoromethyl substituent on the α-carbon. Addition of RNC to 3 affords the isocyanide adducts [(OC)₃Fe{Si(OMe)₃}(μ-Ph₂PXPPh₂)Pt(CNR){C(CF₃)C(H)CF₃}] (4a R = t-Bu, X = CH₂; 4b R = 2,6-xylyl, X = CH₂; 4c R = 2,6-xylyl, X = NH). In dichloromethane solution 3a is gradually transformed into the C₄F₆-bridged compound [(OC)₃Fe(μ-dppm)(μ-CF₃CCCF₃)Pt(CO)] 5. The Pt-bound carbonyl ligand of 5 is displaced by xylylisocyanide or trimethylphosphite affording the derivatives [(OC)₃Fe(μ-dppm)(μ-CF₃CCCF₃)Pt(CNxylyl)] 6 and [(OC)₃Fe(μ-dppm)(μ-CF₃CCCF₃)Pt{P(OMe)₃}] 7. The molecular structures of 4a, 5 and 6 have been determined by X-ray diffraction studies.     

1,1-Insertion of substituted alkynes into the Ir-O bond of η-carboxylato iridium complexes

Alkyl-carbonyl-iridium [Ir(CH₃)(CO)(η²-O₂CR′)(PPh₃)₂]⁺ (1, R′ = CH₃, Ph, p-C₆H₄CH₃) react with alkynes (RCCH; R = Ph, p-C₆H₄CH₃) in the presence of NEt₃ to give acyl-alkynyl-iridium Ir(C(O)CH₃)(-CCR)(η²-O₂CR′)(PPh₃)₂ (4) which further react with RCCH to give alkyl-carbonyl-cis-bis(alkynyl) iridium Ir(CH₃)(CO)(CCR)₂(PPh₃)₂ (5). cis-Bis(alkenyl)iridium complexes, Ir(-CHCH₂)₂(η²-O₂CCH₃)(PPh₃)₂ (6) and (η²-O₂CCH₃)(PPh₃)₂ (7) react with substituted alkynes RCCH (R = Ph, p-C₆H₄CH₃, cyclohex-1-enyl) to give cis-bis(alkynyl) Ir(CCR)₂(η²-O₂CCH₃)(PPh₃)₂ (9) that further react with RCCH to undergo the alkyne insertion reaction into the Ir-O bond to produce iridacycles containing vinyl acetate ligands, (-CCR)₂(PPh₃)₂ (8).